HK1197850A - Nanostructured materials for electrochemical conversion reactions - Google Patents

Description

Nanostructured materials for electrochemical conversion reactions

Technical Field

The present disclosure relates to a battery system.

Background

In recent years, both public and private sectors have invested a great deal of valuable resources into clean energy technology due to the shortage of fossil fuel-based energy and the adverse environmental impact from fossil fuel consumption. An important aspect of clean energy technology is energy storage, or simply battery systems. In the past, many battery types were developed and used, which have their own advantages and disadvantages. Due to the chemistry of lithium materials, including high charge densities, lithium materials have been used in various components of batteries. For example, in rechargeable lithium ion batteries, lithium ions move from the negative electrode to the positive electrode during discharge. In the basic operation of a lithium battery, the conversion material undergoes a conversion reaction with lithium, and the performance of the conversion material is an important aspect of the battery.

Disclosure of Invention

One aspect of the present disclosure relates to cathode materials that may be characterized as particles or nano-domains having a median characteristic dimension of about 20nm or less. These particles or nano-domains include (i) particles or nano-domains of a metal selected from iron, cobalt, manganese, copper, nickel, bismuth, and alloys thereof, and (ii) particles or nano-domains of a fluoride of lithium.

In some embodiments, the individual particles additionally comprise metal fluorides. In some cases, the cathode material additionally comprises a fluoride of iron, such as iron fluoride. For example, the metal may be iron, and the particles or nano-domains further comprise iron fluoride.

In some embodiments, some particles or nano-domains contain only metal and other particles or nano-domains contain only fluoride of lithium. In some embodiments, individual particles of cathode material comprise both metal and fluoride of lithium. In one example, the fluoride of lithium comprises lithium oxyfluoride.

In some embodiments, the cathode material additionally comprises (iii) a conductive additive. In some cases, the conductive additive is a mixed ionic-electronic conductor. In some cases, the conductive additive is a lithium ion conductor. In some embodiments, the lithium ion conductor is or comprises thio-LiSICON, garnet, lithium sulfide, FeS₂Copper sulfide, titanium sulfide, Li₂S-P₂S₅Lithium iron sulfide, Li₂S-SiS₂、Li₂S-SiS₂-LiI、Li₂S-SiS₂-Al₂S₃、Li₂S-SiS₂-GeS₂、Li₂S-SiS₂-P₂S₅、Li₂S-P₂S₅、Li₂S-GeS₂-Ga₂S₃Or Li₁₀GeP₂S₁₂。

In some embodiments, the median characteristic dimension of the particle or nano-domain is about 5nm or less. In some materials, the metal in the particles is present as metal nano-domains having a median characteristic dimension of less than about 20 nm. In some materials, the particles or nano-domains are at about 1000nm³Is substantially uniform within the volume of (a).

Another aspect of the present disclosure relates to a glass transition material for a cathode. Such materials may be characterized by metals, one or more oxidizing species, and reducing cations mixed at a size of less than 1 nm. In addition, the glass transition material is at 1000nm³Is substantially uniform within the volume of (a). In some embodiments, the cation comprises lithium, sodium, or magnesium. In some embodiments, the glass transition material is substantially free of volume greater than 125nm³Of a single metal species or an oxidic species.

Another aspect relates to a cathode, which may be characterized by the following features: (a) a current collector; and (b) an electrochemically active material in electrical communication with the current collector. The electrochemically active material comprises (i) a metal component, and (ii) a lithium compound component mixed with the metal component over a distance dimension of about 20nm or less. In addition, the electrochemically active material has a reversible specific capacity of about 350mAh/g or greater when discharged with lithium ions at a rate of at least about 200mA/g when fully charged with the compound forming the metal component and an anion of the lithium compound.

In some cases, the cathode additionally comprises a conductivity enhancer, such as an electronic conductor component and/or an ionic conductor component. Some cathodes contain mixed ionic-electronic conductor components. In some cases, the mixed ionic-electronic conductor component comprises less than 30 wt% of the cathode. Examples of mixed ionic-electronic conductor components include thio-LiSICON, garnet, lithium sulfide, FeS₂Copper sulfide, titanium sulfide, Li₂S-P₂S₅Lithium iron sulfide, Li₂S-SiS₂、Li₂S-SiS₂-LiI、Li₂S-SiS₂-Al₂S₃、Li₂S-SiS₂-GeS₂、Li₂S-SiS₂-P₂S₅、Li₂S-P₂S₅、Li₂S-GeS₂-Ga₂S₃And Li₁₀GeP₂S₁₂。

In some cathodes, the metal component is a transition metal, aluminum, bismuth, or an alloy of any of these metals. In some cases, the metal component is copper, manganese, cobalt, iron, or an alloy of any of these metals. For example, the metal component may be an alloy of iron with cobalt and/or manganese. In some cathodes, the metal component comprises metal grains having a median characteristic length of about 5nm or less.

In some embodiments, the lithium compound component is selected from the group consisting of lithium halides, lithium sulfides, lithium thiohalides, lithium oxides, lithium nitrides, lithium phosphides, and lithium selenides. In one example, the lithium compound component is a fluoride of lithium. In another example, the lithium compound component is a fluoride of lithium and the metal component is manganese, cobalt, copper, iron, or an alloy of any of these metals. In some cathodes, the lithium compound component contains particles or nano-domains having a median characteristic length dimension of about 5nm or less. In some embodiments, the lithium compound component comprises an anion that forms a metal compound with the metal upon charging, the metal compound and lithium ion undergo a reaction to form the metal and lithium compound component, and the gibbs free energy of the reaction is at least about 500 kJ/mole.

Another aspect of the disclosure relates to a solid state energy storage device characterized by the following characteristics: (i) an anode, (ii) a solid-state electrolyte, and (iii) a cathode comprising (a) a current collector, (b) an electrochemically active material in electrical communication with the current collector. The electrochemically active material comprises (i) a metal component, and (ii) a lithium compound component mixed with the metal component over a distance dimension of about 20nm or less. Additionally, the electrochemically active material has a reversible specific capacity of about 600mAh/g or greater when discharged with lithium ions at 50 ℃ at a rate of at least about 200mA/g versus Li between 1 and 4V.

In some energy storage devices, the anode, solid-state electrolyte, and cathode together provide a stack having a thickness of about 1 μm to 10 μm. In some designs, the electrochemically active material is provided in a layer having a thickness of about 10nm to 300 μm.

In some energy storage devices, the electrochemically active material has a reversible specific capacity of about 700mAh/g or greater when discharged with lithium ions at a rate of at least about 200 mA/g. In some designs, the device has an average voltage hysteresis of less than about 1V when cycled at 100 ℃ and at a charge rate of about 200mAh/g of cathode active material.

Various other features of the solid state energy storage device are the same as those just identified for the cathode. These other characteristics include the composition of the cathode, etc.

Another aspect of the present disclosure relates to a battery cell characterized by the following features: (a) an electrolyte; (b) an anode; and (c) a solid-state conversion material having an interface with the electrolyte, the solid-state conversion material in a discharged state comprising a metal, one or more oxidizing species, and a reducing cation mixed at a size of less than 1 nm. In some embodiments, the conversion material is substantially glassy. The metal may be a transition metal material, such as a cobalt, copper, nickel, manganese, and/or iron material. The cation may be a lithium, sodium and/or magnesium material.

In another aspect, the present disclosure relates to a battery device characterized by the following features: (a) an anode region comprising lithium; (b) an electrolyte region; (c) a cathode region comprising a thickness of fluoride material configured as amorphous lithium; and (d) a plurality of iron metal particulate matter spatially disposed within the interior region of the thickness of the fluoride of lithium to form a lithiated conversion material. Additionally, the battery device has an energy density characterizing the cathode region that is greater than about 80% of a theoretical energy density of the cathode region. In some embodiments, the first plurality of iron metal species is characterized by a diameter of about 5nm to 0.2 nm. In some embodiments, the thickness of the fluoride material of lithium is characterized by a thickness of 30nm to 0.2 nm. In some cases, the thickness of the fluoride material of lithium is uniform. In some embodiments, the cathode region is characterized by an iron to fluorine to lithium ratio of about 1:3: 3. In some embodiments, the cathode region is characterized by an iron to fluorine to lithium ratio of from about 1:1.5:1.5 to 1:4.5: 4.5.

Another aspect of the present disclosure relates to a method of forming a conversion material, which may be characterized by the following operations: (i) providing a first precursor material, the first precursor material comprising a metallic material; (ii) providing a second precursor material, the second precursor material containing a reducing cationic material; (iii) vaporizing the first precursor material and the second precursor material to a vapor state; (iv) mixing the first and second precursor materials in a vapor state within a vacuum chamber to form a mixed material within the chamber, the mixed material containing the first and second precursor materials mixed at a length dimension of less than about 20 nm; and (v) collecting the mixed material. In some embodiments, the first precursor material and the second precursor material are characterized by a tendency to phase separate. In some embodiments, the evaporation is performed using a thermal evaporation method, an electron beam method, or a flash evaporation method. In some embodiments, the method additionally includes the operation of cooling the mixed material at a rate of at least about 10 kelvin per second.

Another aspect of the present disclosure relates to a method of forming a conversion material, the method characterized by the operations of: (i) providing a first precursor material comprising a metallic material; (ii) providing a second precursor material comprising a reducing cationic material; (iii) melting the first precursor material and the second precursor material to a liquid state; (iv) injecting the first and second precursor materials into a cooling environment in which the first and second precursor materials form a mixed material that cools at a rate of at least about 100 kelvin per second to produce shaped particles; and (v) collecting the shaped particles. In some embodiments, the first precursor material and the second precursor material are characterized by a tendency to phase separate. In some embodiments, the shaped particles comprise a first precursor material and a second precursor material mixed at a length dimension of less than about 20 nm.

In some embodiments, the cooling environment is a cooling chamber. The cooling chamber may comprise a cooling surface. The cooling surface may be characterized by a high thermal conductivity. In some cases, cooling includes exposing the mixed material to a cryogenic gaseous substance.

In some embodiments, the method additionally comprises the operations of: injecting a first precursor material from a first nozzle into a common region of a cooling chamber; a second precursor material is injected from a second nozzle into a common region of the cooling chamber.

In some embodiments, the method additionally comprises the operations of: combining the first precursor material and the second precursor material to form a combined material; the combined materials are sprayed into a cooling chamber.

The melting of the first precursor material may be performed separately from the melting of the second precursor material. The melting may be performed at different temperatures for the first precursor material and the second precursor material.

Another aspect of the present disclosure relates to forming a battery cell by: (i) receiving a layer of cathode current collector; (ii) forming a cathode region comprising a nanostructure switching material comprising formed nano-domains of iron and nano-domains of fluoride of lithium; (iii) forming a solid electrolyte layer covering the cathode region; and (iv) forming an anode and/or an anode current collector overlying the solid electrolyte layer. The nanostructure conversion material may be atomically mixed. In some embodiments, the method includes the additional operation of forming electrical contact with the cathode current collector and the anode and/or anode current collector.

Drawings

Fig. 1A shows a solid state energy storage device comprising an anode and a cathode separated and separated by a solid state electrolyte.

Fig. 1B shows a solid state energy storage device having an anode current collector adjacent to the anode and a cathode current collector adjacent to the cathode.

Fig. 2A shows five examples of switching materials with various nano-domain and particle forms.

Fig. 2B shows additional examples of particles and nano-domain structures that may be used in ferric fluoride and related switching materials.

Fig. 3 schematically depicts a matrix material provided as a continuous layer embedding separate particles or nano-domains of a conductivity enhancer and an active material.

Fig. 4 shows a graph of cell performance as measured by cathode volumetric energy density versus LiF in a layered structure.

FIG. 5 shows a graph of the constant current charge discharge of a 66nm 3LiF + Fe cathode at 120 ℃.

FIG. 6 shows a graph of the constant current charge discharge of a 129nm 3LiF + Fe cathode at 120 ℃.

FIG. 7 shows the cathode at 134nm (3LiF + Fe + S)_0.14) A graph of constant current discharge of the battery of (1).

FIG. 8 shows the cathode at 134nm (3LiF + Fe + S)_0.53) A graph of constant current discharge of the battery of (1).

Fig. 9 provides a graph of cell performance as measured by cathode volumetric energy density versus length dimension of LiF material in a layered structure.

Fig. 10 is a graph of cell performance as measured by cathode volumetric energy density versus the length dimension of Fe in the layered structure.

Fig. 11 provides a cross-sectional view of a nanostructured conversion material at a size of about 5 nm.

Fig. 12 provides a cross-sectional view of a nanostructured conversion material at a size of about 2 nm.

Fig. 13 provides a cross-sectional view of a nanostructured conversion material at a size of about 2 nm.

Fig. 14 is a graph illustrating an example of nanostructured conversion materials and the benefits of maintaining compositional uniformity.

Fig. 15 shows the theoretical energy density of a lithiated conversion cathode material relative to a standard Li anode.

Fig. 16 shows the theoretical specific energy of a lithiated conversion cathode material relative to a standard Li anode.

Fig. 17 shows a plot of initial 5 charge/discharge cycles (voltage (measured against a standard lithium electrode) versus cathode material active capacity) for a copper fluoride sample.

Fig. 18 shows the discharge energy of samples containing some of the transition metal alloys used in the conversion material.

Fig. 19 is a graph of the capacity and hysteresis statistics provided by the following samples of switching material: FeCo + LiF, FeMn + LiF, Fe₃Co + LiF and the control sample Fe + LiF.

Detailed Description

Introduction to the design reside in

The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. The disclosed embodiments relate to cathodes containing high capacity materials that reversibly undergo redox reactions at high rates after multiple charge-discharge cycles. Such materials are sometimes referred to herein as "conversion" materials.

Typically, embedding and/or converting materials may be used in the battery system. For example, the cathode material may be used for lithium intercalation or conversion. Intercalation materials that can be prepared at macroscopic or nano-scale are typically used and generally have lower energy densities (e.g., less than about 800Wh/kg active material). Conversely, the conversion material may provide a much higher energy density (e.g., about 1000-.

In some embodiments, the conversion material comprises an oxidizing species, a reducing cationic species, and a metal species. These materials are sometimes referred to herein as ingredients or components. The oxidizing substance is typically a strongly electronegative element, compound or anion. Examples of oxidizing species anions include halides (fluorides, chlorides, bromides, and iodides), oxides, and sulfides, and the like. The reducing cationic species is typically an electropositive element or cation, such as lithium, sodium, potassium or magnesium and ions thereof. The electropositivity of metal species is generally weaker than that of reducing cationic species. Transition metals are sometimes used as the metal species. Examples include cobalt, copper, nickel, manganese and iron. The conversion material may contain two or more oxidizing species, two or more reducing cationic species, and/or two or more metal species.

As understood in the art, batteries and their electrodes undergo electrochemical transformation during discharge and during charging in the case of secondary or rechargeable batteries. The charge and discharge states of the specific conversion material will now be described.

And (3) discharging state: in the discharged state, the metal species is generally more reduced than in the charged state. For example, the metal species is in an elemental state or a lower oxidation state or positive valence (e.g., +2 rather than + 3). In addition, during discharge, the oxidizing species can pair with the reducing cationic species and de-pair from the metallic species. Further, during discharge, the reducing cation species tends to migrate into the cathode where it is oxidized by pairing with the oxidizing species. Pairing typically occurs through the formation of chemical bonds, such as covalent or ionic bonds.

According to this embodiment, in the discharge state, the conversion material may comprise an elemental metal material, one or more oxidizing species, and a reductive cation material. As an example, the discharge state may include at least one elemental metal, such as iron, and a reducing cation halide, such as a fluoride of lithium. The components of the discharge conversion material may be thoroughly dispersed with each other in the discharge material. As described more fully below, these materials may be intermixed or dispersed at a size of about 20nm or less.

It is understood that cathodes of the type described herein can exist in a variety of states of charge. In some cases, the battery is designed or operated such that full discharge is never achieved. Thus, for example, if the fully charged conversion material is ferric fluoride, the cathode of a "full" discharge may contain a mixture of elemental iron, lithium fluoride and some ferric fluoride and possibly some ferrous fluoride. The use of "discharged" or "discharged state" herein is a relative term, referring only to the state of the switching material that is more discharged than the charged state of the material. Likewise, the use of "charged" or "charged state" herein refers to a state of a switching material that is more charged than the corresponding discharged state of the material.

The charging state is as follows: in the charged state, the metal species tends to pair with the oxidizing species, usually forming compounds. During charging, oxidizing species tend to unpair from reducing cationic species and pair with metal species. The reducing cationic species tend to migrate out of the cathode and migrate and/or diffuse to the negative electrode where they exist in a more strongly reduced state (e.g., lithium as elemental metal, such as lithium metal, or intercalated matrix, such as carbon or silicon).

As an example, during charging, elemental iron may pair with fluoride anions to form ferric fluoride and/or ferrous fluoride. At the same time, the fluoride anion can be unpaired from reducing cation fluorides such as lithium fluoride. The now free lithium cation migrates and/or diffuses to the cathode where it is reduced to metallic lithium or lithium intercalation material.

The size of the components in the switching material, whether in the charged or discharged state, affects the relevant electrochemical properties of the material. It has been found that conversion materials whose components or compositions are separated by very small distances (sometimes on the order of atomic dimensions) can have particular performance benefits compared to conversion materials whose components are separated by larger distances. In some embodiments, the components are separated by a distance of no greater than about 20 nm. These conversion materials have been found to provide various benefits such as increased cycle life, improved efficiency, improved energy density, improved power density, and improved low temperature performance. The term "nanostructured" is sometimes used to refer to switching materials in either a charged or discharged state, where the constituent materials are separated from each other by a dimension of about 20nm or less.

In some embodiments, in the discharged state, the switching material contains dispersed domains of the elemental metal (or alloy thereof) and the lithium compound. In some embodiments, the dispersed grains of the metal or alloy are embedded in a continuous matrix of the lithium compound. In other embodiments, the metal or alloy and the lithium compound are present as small particles or other dispersed structures. In each case, the various components of the switching material may be mixed and/or otherwise present in nanostructure sizes. The single domain may be a nano-domain. The nano-domains may have an average or median characteristic dimension of about 20nm or less, or about 10nm or less, or about 5nm or less. Using ferric fluoride as an example switching material, the nano-domains may be primarily ferric and lithium fluoride in the discharged state. In the charged state, the nano-domains are predominantly ferric fluoride. In both charge states, the nano-domains may be crystalline or amorphous/glassy. The domains may be compositionally uniform (e.g., containing only metallic species) or non-uniform (e.g., consisting of a combination of metallic species, oxidizing species, and reducing cationic species).

In various embodiments, the conversion material is formed or mixed such that its components are spaced apart in a dimension of about 1nm or less. Some such materials may be glassy or amorphous in character. Glassy materials can be viewed as being substantially glassyAmorphous, substantially homogeneous in composition and substantially lacking long range order. In some examples, the glass transition material is at 1000nm³Is substantially homogeneous (compositionally and/or morphologically) within the volume of (a).

The switching material is structured at the nanometer level (e.g., less than 20nm in length). In one example, FeF in a charged conversion material₃The molecules may be characterized by a glassy or amorphous structure and be substantially homogeneous. In some examples, the switching material may include a glassy compound of lithium, sodium, and/or magnesium in the discharge state. Such glassy or amorphous structures may be provided as particles, layers, and the like. Within these particles or layers, the constituent metals, oxidizing species, and reducing cationic species are, on average, spaced apart from one another by a distance no greater than the noted length dimension. In some cases, particles having a glassy or amorphous state are substantially free of agglomeration. In other cases, at least some of the particles form agglomerates.

According to this embodiment, in the discharge state, the conversion material may comprise metallic materials, one or more oxidizing species, and a reducing cationic material spaced apart in a dimension of less than about 20 nm. More specifically, the conversion material is at about 1000nm³Or substantially uniform within a smaller volume. In one example, the molecules comprising the metal, the oxidizing species, and the reducing cation are structured on a nanometer scale. As presented in the above examples, the discharge material may contain an elemental form of a metal substance and a compound of a reducing metal cation and an anion of an oxidizing substance.

In the charged state, the conversion material contains a compound of a metal. In some embodiments, the electrochemical charge-discharge reaction at the cathode can be represented by the following formula regardless of the stoichiometric ratio:

wherein M is a metal species and X is an oxidizing species; for example, elements such as halogens, oxygen, sulfur, phosphorus, nitrogen, selenium, or combinations of these elements. In a specific example, the oxidizing species is a combination of halide ions and chalcogen ions (e.g., fluoride and sulfide). In certain variations of the above chemical reaction formulas, lithium is replaced by sodium, potassium, magnesium, or other electropositive metal ions.

The discharge path of the metal compound MX present in the charged cathode material according to the above formula should react with lithium ions. Typically, when considering the complete battery reaction Li + MX → LiX + M, the discharge reaction is associated with a suitably large gibbs free energy. Gibbs free energy through Δ G_rxn= E n F corresponds to the cell voltage of the reaction, where E is the voltage, n is the number of electrons reacted and F is the faraday constant. In some embodiments, the gibbs free energy of reaction is at least about 500 kJ/mole or at least about 750 kJ/mole or at least about 1 MJ/mole.

In some embodiments, the voltage of the fully charged cathode is at least about 2.0V with respect to the lithium metal electrode, or at least about 3.0V with respect to the lithium metal electrode, or at least about 4.0V with respect to the lithium metal electrode, or at least about 4.5V with respect to the lithium metal electrode.

In the charged state, the cathodic switching material may retain the general morphological characteristics present in the discharged state. These characteristics include component separation distance (e.g., grain or crystal size), matrix structure (e.g., glassy state), and the like. In some cases, the material may expand in the discharged state. The volume change may be about 5% or more, or about 10% or more, depending on the material.

Examples of suitable metal species M include transition metals, aluminum, and bismuth. In some cases, the metal is selected from the first row transition metals. Specific examples of transition metals that may be used include vanadium, chromium, copper, iron, cobalt, manganese, nickel, ruthenium, titanium, silver, and tungsten. Alloys of these metals may also be used. Examples of these alloys include alloys of iron with cobalt and alloys of iron with manganese. Examples of suitable oxidant anions X include O, S, N, P, F, Se, Cl, I, and combinations thereof.

Examples of suitable state-of-charge cathode materials include sulfides, oxides, halides, phosphides, nitrides, chalcogenides, oxysulfides, oxyfluorides, sulfur-fluorides, and sulfur-oxyfluorides. In various embodiments, the charged conversion material includes one or more of the following: AgF; AlF₃；BiF₃；B₂O₃；Co₃O₄；CoO；CoS₂；Co_0.92S；Co₃S₄；Co₉S₈；CoN；Co₃N；CoP₃；CoF₂；CoF₃；Cr₂O₃；Cr₃O₄；CrS；CrN；CrF₃；CuO；Cu₂O；CuS；Cu₂S；CuP₂；Cu₃P；CuF₂；Fe₂O₃；FeO；FeOF；FeS₂；FeS；Fe₂S₂F₃；Fe₃N；FeP；FeF₂、FeF₃；FeOF；Ga₂O₃；GeO₂；MnO₂；Mn₂O₃；Mn₂O₅；MnO；MnS；MnS₂；MnP₄；MnF₂、MnF₃、MnF₄、MoO₃；MoO₂；MoS₂；Nb₂O₅；NiO；NiS₂；NiS；Ni₃S₂；Ni₃N；NiP₃；NiP₂；Ni₃P；NiF₂；PbO；RuO₂；Sb₂O₃；SnF₂；SnO₂；SrO₂；TiS₂；TiF₃；V₂O₃；V₂O₅；VF₃；WS₂；ZnF₂(ii) a Andcombinations thereof.

The conversion material can be discharged by cations that react exothermically with the conversion material. Cations are generally low cost and light weight (smaller atomic weight). Specific examples include Mg, Na and Li. As an example, for FeF₃A switching material and Li cations, the switching material being approximately Li when manufactured or in a discharged state₃FeF₃An amorphous mixture of lithium, iron and fluorine in the proportions indicated. In some embodiments, the three elements are thoroughly mixed in atomic size. In various embodiments, the conversion material is characterized by an iron to fluorine to lithium ratio of about 1:1.5:1.5 to 1:4.5: 4.5.

Certain disclosed embodiments relate to the use of redox reactions of lithium ions with metal fluorides as energy sources in cathode materials. By way of example, in the charged state, a suitable cathode material is very small particles of ferric fluoride, which may be quantum dot sized (e.g., about 5nm in the smallest cross-section) or glassy or amorphous. In some embodiments, electrodes made of metal fluoride redox materials are used in batteries with solid electrolytes, such as inorganic electrolytes. A specific example of such an electrolyte is LiPON.

In some embodiments, the discharge of the cathode is accompanied by the reaction of iron fluoride or other transition metal fluoride with lithium ions that migrate or intercalate into the iron fluoride matrix and react there to form lithium fluoride and elemental iron. The large gibbs free energy associated with this reaction provides a very high available energy for the cell. This energy can be compared to the energy of standard lithium insertion (or lithium intercalation depending on the electrode matrix) cathode materials used in conventional lithium ion batteries, such as lithium cobalt oxide, lithium manganese oxide, lithium titanate, and the like. The materials disclosed herein incorporate a large number of lithium atoms per transition metal during discharge. During charging, the intercalation reaction involves up to one lithium atom per transition metal (e.g., when lithium is derived from Li)⁺Reduction to Li⁰When cobalt is derived from Co³⁺Oxidation to Co⁴⁺) In the conversion reactionE.g. to form FeF₃In those reactions, each transition metal reacts with three lithium atoms. In fact, most insertion compounds react half a lithium atom per transition metal because the electrode structure becomes unstable if more than 1/2 lithium is extracted. This is that the transition metal electrode materials disclosed herein provide more than traditional electrode materials (e.g., LiCoO)₂140 mAh/g) of the capacity of the battery, and a significantly higher capacity (e.g., 700mAh/g or greater). This capacity can be achieved even at high rates and after multiple cycles when the electrodes have suitably high ionic and electronic conductivities as disclosed herein.

The challenge associated with this technology is slow mass transfer of lithium ions through the iron fluoride or lithium fluoride matrix (which may be in particulate form). As a result, the full capacity of the material is not achieved because many reaction sites are difficult to reach within the time period required for charging or discharging the battery in many applications. In addition, the rate performance of the material is relatively poor due to the too long diffusion and migration time of lithium ions through the matrix. Still further, significant mass transfer overpotentials accompany the charging and discharging of these materials. This overpotential results in lower energy delivered to the application, more heat generation that can lead to problems at the system level, and lower efficiency that increases user costs. The challenge may also exist in batteries employing switching materials having non-ferrous metal species, non-fluoride oxidizing species, and/or reducing cation species other than lithium ions, as described above.

To address the challenge of slow mass transfer, cathode materials containing elemental metals or alloys and lithium compounds (in the discharged state) or metal compounds (in the charged state) can be provided in the form of very small particles or nano-domains. In some embodiments, the particles or domains have a median characteristic dimension of about 20nm or less, or about 10nm or less. In some aspects, the particles or domains have a median characteristic dimension of about 5nm or less. In some cases, the conversion material may be a glassy or amorphous material. In some embodiments, of the cathodeThe particles or domains have a very tight distribution, e.g., a standard deviation of about 50% or less. In some embodiments, at least about 90% of the particles or domains in the electrode have a characteristic dimension of about 1 to 5 nm. In some embodiments, the particle feature size has a d of about 20nm or less, or about 10nm or less, or about 5nm or less₅₀The value is obtained. d₅₀Defined as the characteristic size of 50% of the particles smaller than it. The particles or domains may be present at these dimensions at any point in the lifetime of the cathode. In some examples, particles or domains are present at these sizes in the fabricated cathode. In some examples, the particles or domains are present at these sizes after the first discharge of the cathode or after the first full charge/discharge cycle of the cathode. In some embodiments, the characteristic size of the average size of the particles or domains of the cathode does not change by more than about 500% or about 100% after multiple cycles (e.g., 10 cycles, 50 cycles, 100 cycles, or 500 cycles).

The very small separation distance of the components described herein provides a shorter diffusion path for lithium or other electropositive ions to move from the outside of the particle or domain to the reactive metal compound sites within the particle/domain (discharge) or from the lithium compound within the particle/domain to the surface of the particle/domain (charge). For example, during charging, lithium ions must dissociate from the lithium fluoride and transport to the outside of the particle/domain where they contact the electrolyte. After disengaging the particles/domains, the lithium ions may have to contact some other ion conducting matrix in the electrode before reaching the electrolyte. Conversely, during discharge, lithium ions traverse a path from the electrolyte into the electrode body where they must travel a distance before reaching the target particle/domain, where they enter and penetrate the particle/domain and then find the site of the reactive metal compound. Only after this multi-stage transport does the lithium ions take part in the redox reaction to generate electrochemical energy (discharge). During charging, the reverse path is reversed. The use of a small active material separation distance allows the cathode to operate at improved rate performance, which has not previously been available.

An additional benefit derived from the very small component separation distance is the relatively shorter diffusion distance between the metal atoms and the anions. Since metal and anion atoms are large and heavy, they generally transport more slowly than lithium. The provided nanostructures place the metal atoms in close proximity to the anion, reducing the distance they must diffuse.

An additional challenge to achieve the potential benefits of switching materials arises from the high surface area to mass ratio of very small particles. The large surface area (as a function of the mass of the reactive material) results in a larger portion of the active material being converted into a Solid Electrolyte Interface (SEI) layer, which abstracts much of the available lithium and makes it exist in an unstable form. Thus, it also results in a shorter cycle life, since the SEI layer can continue to grow for several cycles. The SEI formed around particles that undergo significant volume changes during cycling can sometimes break up, providing a fresh surface that must be covered by the SEI. The grown SEI contains species that do not contribute to the energy stored in the battery and may form a barrier to lithium transport, reducing the rate performance of the battery.

In some embodiments, the second challenge is addressed by using a solid electrolyte. The solid electrolyte provides an ion-conducting medium in the formation of the SEI layer without consuming significant amounts of active materials. Thus, the cathode material is able to retain its inherently high reversible capacity. It is to be understood, however, that in other embodiments, the cathodes described herein are used with liquid and gel phase electrolytes.

Many types of solid electrolyte layers can be used. In some cases, the electrolyte material has a relatively high lithium ion conductivity, e.g., at least about 10^-6Siemens per centimeter or at least about 10^-3Siemens per centimeter. Examples of inorganic materials that can be used as the sole electrolyte layer include LiPON and similar lithium ion conductors.

Fig. 1A illustrates one form of the solid state energy storage device described herein. The device (100) includes an anode (140) and a cathode (150) spaced apart and a solid state electrolyte (130) disposed between the anode and the cathode.

Fig. 1B illustrates one form of a solid state energy storage device having an anode current collector (110) adjacent to the anode and a cathode current collector (120) adjacent to the cathode. Generally, the current collector is a solid conductive matrix in intimate contact with the electrochemically active material of the electrode. Forms of the current collector include sheets, foils, foams, meshes, perforated sheets, and the like. The current collector should be made of a conductive material that is electrochemically compatible with the cathode material. Examples include copper, aluminum, nickel, tungsten, titanium, tantalum, molybdenum, tantalum nitride and titanium nitride, steel, stainless steel, and alloys or mixtures thereof.

As used herein, a solid state energy storage device means an energy storage device comprising a solid state anode, a solid state cathode, a solid state electrolyte, and other optional components, but does not comprise any non-solid components as an anode, cathode, or electrolyte.

Capacity of electrode

In some embodiments, the cathode conversion material as fabricated has a specific capacity of at least about 600mAhr/g of fully charged cathode material. In some embodiments, the cathode material maintains this fully charged capacity after multiple cycles. The fully charged material is the stoichiometric metal compound MX. Examples of such compounds include the above-mentioned sulfides, fluorides, phosphides, selenides, nitrides, oxides, chalcogenides, oxysulfides, oxyfluorides, sulfur-fluorides, sulfur-oxyfluorides, and chlorides.

In some embodiments, the cathodic conversion material is capable of maintaining this high capacity upon high rate discharge after multiple cycles. For example, the cathode material can retain a capacity of at least about 600mAh/g when discharged at a rate of at least about 200mA/g of the fully charged cathode material. In some embodiments, the material maintains this capacity at a higher discharge rate of at least about 600mA/g of fully charged cathode material. In some embodiments, the material maintains this capacity at discharge rates of up to about 6000mA/g of fully charged cathode material. The discharge rate can be maintainedIs a constant value or can be changed during discharge without dropping below 200 mA/g. In some embodiments, the cathode material maintains a high capacity at high speed (e.g., 600mAh/g at 200 mA/g) after subsequent charging. In some cases, the electrode material is capable of maintaining such a high rate capacity for 10 or more cycles. Typically it is capable of maintaining this high rate capacity for even longer, for example about 20 or more cycles, or about 50 or more cycles, or about 100 or more cycles, or about 500 or more cycles. The cathode material discharged a full charge of 600mAh/g in each cycle. The cycling can be performed such that the voltage of the cathode is in a range relative to Li/Li⁺Between 4V and 1V. In some embodiments, the charge rate may be greater than 200mA/g, greater than 600mA/g, or greater than 6000mA/g, and the material retains a capacity of about at least 600 mAh/g.

High capacity performance can be achieved when cycling through a range of temperatures, for example, from about 0 degrees Celsius to 100 degrees Celsius or from about 20 degrees Celsius to 100 degrees Celsius.

In one aspect, the switching material provides a capacity of greater than about 350mAh/g of active material when cycled between 1 and 4V at a charge/discharge rate of 200mA/g at about 100 degrees celsius relative to a lithium metal negative electrode. In other aspects, the electrode material provides a capacity of greater than about 500mAh/g, or greater than about 600mAh/g, or greater than about 700mAh/g, in each case with capacity values for the active material cycling at a charge/discharge rate of 200mA/g at about 100 degrees celsius in a voltage range between 1 and 4V versus the lithium metal negative electrode. In another aspect, the electrode materials described herein provide a capacity of about 350mAh/g to 750mAh/g when cycled between 1 and 4V at about 100 degrees Celsius at a charge/discharge rate of 200mA/g relative to a lithium metal negative electrode. In another embodiment, the electrode is made at a rate of 400mA/g and at a temperature of 120 ℃ relative to a standard lithium metal electrode (Li/Li)⁺) Or between 1 and 4.5V relative to Li at a rate greater than 1C and at a temperature above 50℃, the electrode material may be discharged between 1.5 and 4V relative to LiHas a specific capacity of greater than about 400 mAh/g.

In some cases, cathodes made from such materials have a high average discharge voltage of greater than about 2V when discharged under the above conditions. The high performance cathode materials disclosed herein maintain their good performance (e.g., high specific capacity, high energy density, high average discharge voltage, and low hysteresis) even when discharged at high rates.

In another aspect, a device employing the cathode materials described herein provides an average voltage hysteresis of less than 1V at a charge/discharge rate of 200mA/g over a voltage range between 1 and 4V relative to a lithium metal electrode at about 100 degrees celsius. In another aspect, such devices provide an average voltage hysteresis of less than 0.7V when cycled between 1 and 4V at a charge/discharge rate of 200mA/g at about 100 degrees celsius relative to a lithium metal electrode. In one embodiment, the device provides an average voltage hysteresis of less than about 1V when cycled between 1 to 4V at a charge/discharge rate of 600mA/g at about 100 degrees celsius relative to a lithium metal electrode. In one embodiment, the device provides an average voltage hysteresis of less than about 1V when cycled between 1.5 to 4V at a charge/discharge rate of 200mA/g at about 50 degrees celsius relative to a lithium metal electrode. The hysteresis level may be maintained for at least 10 cycles or at least 30 cycles or at least 50 cycles or at least 100 cycles.

Voltage hysteresis is the difference between the discharge voltage and the charge voltage, both of which vary with the state of charge. It represents the low efficiency of the cell (energy lost to heat), usually caused by the stagnation of ion transport or reaction. Therefore, an overvoltage is required to drive the reaction, which results in a discharge voltage lower than the open circuit voltage and a charge voltage higher than the open circuit voltage. Low hysteresis indicates that the battery is efficient.

In the following discussion, various cathode compositions are described. In each of these compositions, the shape and size of the particles/domains may vary as discussed. As examples, the particles/domains of active material in the cathode have a size of about 20nm or less, or are largeA median feature size of about 10nm or less, or about 5nm or less. In some embodiments, the material is glassy or amorphous. In some embodiments, the particles/domains of the material have a standard deviation of about 50% or less. In some embodiments, the characteristic dimension of the particles/domains has a d of about 20nm or less, or about 10nm or less, or about 5nm or less₅₀The value is obtained.

Cathode active component-metal component and lithium compound component

In one aspect of the foregoing device, the cathode comprises an active component (switching material) comprising a metal or alloy component in elemental form and a lithium compound component when the device is in a discharge state.

In general, the metal component may be any metal, or a mixture or alloy of metals. In one embodiment, the metal component is a transition metal, or a mixture or alloy of transition metals. In one embodiment, the metal component is selected from Bi, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, and Ru, or mixtures or alloys of the foregoing metals. In one embodiment, the metal component is selected from the group consisting of Fe, Cu, Mn, and Co. In one embodiment, the metal component is Fe. In one embodiment, the metal component is Cu. In one embodiment, the metal component is Co. In one aspect, the metal component is an alloy of iron with another metal, such as Co or Mn.

In one embodiment, the metal component comprises a mixture or alloy of a first metal and a second metal. In one version of the mixed metal component, the metal component comprises separate nano-domains of the first metal and the second metal. In another aspect, the metal component comprises nano-domains of a mixture or alloy of the first and second metals. In one embodiment, the first metal is Fe and the second metal is Cu. In general, the lithium compound component is any lithium compound that produces (i) lithium ions that migrate to the anode and (ii) an anion that reacts with the metal component to provide the metal compound component upon charging of the device. Thus, in the charged state, the cathode material comprises a metal compound component. The anion in the lithium compound may generally be any anion that forms a lithium compound in the discharged state and a metal compound in the charged state. In one embodiment, the lithium compound is a lithium halide, lithium oxide, lithium sulfide, lithium nitride, lithium phosphide, lithium thio-halide, lithium hydride, or a mixture thereof. In one embodiment, the lithium compound is a lithium halide. In one embodiment, the lithium compound is a fluoride of lithium.

In one arrangement, the "conversion reaction" may be written as:

the left-hand side of equation 1 represents a cathode active material in a discharge state, wherein the cathode active material contains a metal component M and a lithium compound component Li_nAnd (4) X. c is the formal oxidation state of the anion X.

The right hand side of equation 1 represents the state of chargeWherein the cathode active material has been converted into a metal compound component M_aX_bAnd provides Li ions for diffusion through the electrolyte to the anode and provides electrons to an external circuit.

X is generally a stable compound Li which forms separately from the lithium and the metal M_nX and M_aX_bAny anionic species of (a). M may generally be any metal. In one embodiment, M is a transition metal. In one embodiment, M is selected from Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, and Ru. In one embodiment, M is selected from Fe, Co and Cu. In one embodiment, M is Cu. In one embodiment, M is Fe. In one embodiment, M is Co.

Metal compounds M which can be used_aX_bSpecific examples of (a) include, but are not limited to, the following compounds:

in some embodiments, the materials described herein are provided in particulate form (containing a series of discrete, unconnected particles). In some embodiments, the material is provided in the form of one or more continuous layers having a matrix of nano-domains or regions embedded with a metal component and/or a lithium compound component, such as a lithium compound or ion conductor. In some embodiments, the individual particles contain a mixture of a metal component and a lithium compound component. In some embodiments, some particles contain only a metal component. In some embodiments, some particles contain only a lithium compound component.

Fig. 2A shows four examples of electrode forms. This diagram is merely an example, which should not unreasonably limit the scope of the claims. One of ordinary skill in the art would recognize many alternatives, substitutions, and modifications. It is to be understood that the above-described particles or domains are nanostructured (e.g., separated from each other by a length dimension of less than about 20 nm), and that these particles or domains may combine to form the primary and secondary particle structures shown in examples 1-4.

Example 1 (top left of fig. 2A) shows an embodiment in which the electrode active material comprises unencapsulated nano-domains of lithium fluoride, elemental metal, and metal fluoride. Such materials may exist in any state of charge, but most typically exist in a fully discharged or near fully discharged state. Example 2 (top right) shows an electrode form in which metal fluoride nanoparticles and lithium fluoride nanoparticles are encapsulated in an elemental matrix. In each encapsulation example, the encapsulation units may be present as individual particles or as a continuous layer. Example 3 (bottom left) illustrates a form in which a metal fluoride matrix encapsulates lithium fluoride nano-domains and elemental metal nano-domains. Example 4 (bottom right) shows a form in which lithium fluoride encapsulates metal fluoride particles or nano-domains and elemental metal particles or nano-domains.

Fig. 2B shows additional examples of particles and nano-domain structures that may be used in ferric fluoride and related switching materials. In the example of fig. 2B, the structure at the upper left side is a primary particle 211, which can be found in a discharge cathode. The primary particles 211 comprise dispersed nano-domains of iron metal 213 and lithium fluoride 215. Typically, the characteristic cross-sectional dimension of the primary particles is about 100nm or less. As mentioned, the cross-sectional size of the nano-domains constituting the primary particle is about 20nm or less (e.g., about 5nm or less). In some cases, the nano-domains are compositionally uniform.

The upper right structure in fig. 2B shows the discharged secondary particles 217 of the ferric fluoride conversion material (not drawn to scale). The secondary particles are composed of particles of primary particles 211 such as those represented in the upper left structure and possibly of an ion-conductive material and/or an electron-conductive material 219. The secondary particles may be agglomerates or agglomerates of the primary particles and optionally particles of the ionically/electronically conductive material. In some embodiments, the secondary particles are present in the form of a slurry for covering the current collector when forming the cathode. In some embodiments, the secondary particles have a cross-sectional dimension of about 0.1 to 5 microns. All sizes appearing in the discussion of fig. 2B are median.

The lower left and lower right structures presented in fig. 2B represent the primary particles 221 and the secondary particles 223, respectively, of the fully charged ferric fluoride conversion material. Other conversion materials may be substituted for the ferric fluoride and its discharge products in the structure shown in fig. 2B.

The relative amounts of the lithium compound component and the metal component can vary widely, but should be suitable for use in a battery cell. In other words, the components should be provided in relative amounts that do not introduce significant amounts of unused materials that do not contribute to electrochemical energy conversion or enhance conductivity. In some embodiments, iron is employed as the metal component, and the molar ratio of iron to lithium in the cathode active material is about 2 to 8, or about 3 to 8. In some embodiments, with a divalent metal, such as copper, the molar ratio of metal to lithium in the cathode active material is about 1 to 5. In various embodiments, the cathode material is characterized by an iron to fluorine to lithium ratio of about 1:3:3 or from about 1:1.5:1.5 to 1:4.5: 4.5.

It should be understood that although fig. 2A and 2B illustrate LiF and metal-F materials, other types of materials as explained above are possible. For example, lithium fluoride may be replaced by a combination of lithium fluoride and lithium sulfide. In such an example, the metal fluoride may be replaced by a metal fluoride/sulfide combination.

Cathode active component-lithium metal compound component

In another aspect of the device, at some point during the electrode charging state, the cathode comprises an active component comprising a lithium metal compound component. Generally, the lithium metal compound component is any compound that contains lithium, a non-lithium metal, and an anion and produces lithium ions and metal compounds that migrate to the anode when the device is charged.

In one approach, such a reaction can be written as:

the left-hand side of equation 2 represents the cathode active material in a discharge state, in which the cathode active material contains a lithium metal component Li_dM_eX_fThe right hand side of equation 2 represents a system in a charged state in which the cathode active material has been converted to a metal compound component M_eX_fAnd provides lithium ions for diffusion through the electrolyte to the anode and provides electrons to an external circuit. In reaction 2, all lithium in the lithium metal compound is converted into lithium ions. In another aspect, less than all of the lithium in the lithium metal compound is converted to lithium ions. One scheme for such a reaction is given in equation 3

Wherein g is<d. According to Li_d-gM_eX_fThermodynamic and kinetic stability of compounds, such compounds being able to act as Li_d-gM_eX_fExist, or may be disproportionated into a mixture of one or more lithium compounds, metal compounds, and lithium metal compounds.

In one embodiment, the lithium metal compound component is a lithium metal oxide, lithium metal sulfide, lithium metal nitride, lithium metal phosphide, lithium metal halide, or lithium metal hydride, or a mixture thereof. In one embodiment, the lithium metal compound component is a lithium metal halide. In one embodiment, the lithium metal compound component is a lithium metal fluoride. In one embodiment, the lithium metal compound component is lithium iron fluoride. In one embodiment, the lithium metal compound component is lithium copper fluoride. In one embodiment, the lithium metal compound component is lithium cobalt fluoride.

Cathode active component-metal component, lithium compound component and lithium metal compound component

In another aspect of the device, at some point in the electrode charge state, the cathode comprises an active component comprising a metal component, a lithium compound component, and a lithium metal compound component. The metal component, the lithium compound component, and the lithium metal compound component may be as described above. In aspects of the device, the metal, lithium, metal compound, and/or lithium compound can have a median characteristic dimension of 30nm or less, or 20nm or less, or 10nm or less, or 5nm or less. In some cases, the components are mixed in individual particles or layers and are separated from each other by the indicated length dimension and/or are present together in a glassy or amorphous state within these particles or layers.

Cathode active component-metal compound component

As can be seen from the above equations 1, 2 and 3, in a charged state, the cathode active component includes a metal compound component containing a metal and an anion. In one embodiment, the metal compound component is an oxide, nitride, sulfide, phosphide, halide, sulfur-halide or hydride of a metal selected from the group consisting of Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W and Ru. In one embodiment, the metal compound component is a fluoride of a metal selected from the group consisting of Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, and Ru. In one embodiment, the metal compound component is a fluoride of a metal selected from Fe, Cu or Co. In one embodiment, the metal compound component is FeF₃、FeF₂、CuF₂、CoF₂Or CoF₃. In one embodiment, the metal compound component is FeF_xWherein x is 1 to 3. In one embodiment, the metal compound component is CuF_xWherein x is 1 to 3. In one embodiment, the metal compound component is CoF_xWherein x is 1 to 3.

Cathode MEIC, electron conductor and ion conductor

In one version of the device, the cathode comprises a mixed electron-ion conducting component ("MEIC component") together with the active component described above. The MEIC component may generally be made of any material that is compatible with the other materials of the device and allows electron and lithium ion transport sufficient for operation of the device. In one embodiment, the MEIC component is a polymer having a 10 deg.f at the operating temperature of the device^-7An electron conductivity of S/cm or more. In one embodiment, the MEIC component is a polymer having a 10 deg.f at the operating temperature of the device^-7A lithium ion conductivity material of S/cm or more. Examples of materials that may be used as components of the MEIC include, but are not limited to, lithium titanates, lithium iron phosphates, vanadium oxides, cobalt oxides, manganese oxides, lithium sulfides, molybdenum sulfides, iron sulfides, LiPON, MoO₃，V₂O₅Carbon, copper oxides, lithium insertion compounds, e.g. LiCoO₂、Li(CoMn)O₂、LiMn₂O₄、Li(CoNiMn)O₂、Li(NiCoAl)O₂Or other materials having a high lithium ion conductivity. In one aspect, the MEIC component is made of the same material as the solid electrolyte. In one aspect, the MEIC component is made of a different material than the solid electrolyte. The MEIC component itself may be electrochemically active (e.g., MoO)₃Or V₂O₅) Or may not exhibit electrochemical activity (e.g., LiPON). In one aspect, the MEIC is LiPON.

If the cathode comprises a MEIC component, the minimum amount of MEIC component will generally be that amount which allows for lithium ion and electron transport sufficient to operate the device. The maximum amount is the amount of MEIC that provides the required specific capacity or other electrical characteristic for the electrochemically active cathode material when operating at the required rate, voltage range, and state of charge. In one version of the device comprising the MEIC, the minimum amount of MEIC is about 1% by weight of the cathode material. In one version of the device comprising the MEIC, the minimum amount of MEIC is about 5% by weight of the cathode material. In one version of the device comprising the MEIC, the maximum amount of MEIC is about 50% by weight of the cathode material. In one version of the device comprising the MEIC, the maximum amount of MEIC is about 25% by weight of the cathode material.

The MEIC material may be provided in various forms in the electrodes. In one example, small particles of MEIC are mixed with electrochemically active particles and compressed. In another example, the MEIC covers the active material particles. In yet another example, the MEICs are arranged in a vertical line. The MEIC may be constructed of at least two materials, one having high electronic conductivity and the other having high ionic conductivity.

In some versions of the device, the cathode includes a dispersed electron conductor to increase the electron conductivity of the electrode. In various aspects, the component has a molecular weight of greater than 10^-7Electron conductivity of S/cm. In some embodiments, the method comprisesThe compound may be carbon or a metal compound. Examples of forms of carbon that may be employed include graphite, activated carbon, nanotubes, nanofibers, nanowires, graphene oxide, and the like. When present, the electron conductor may be present in an amount of about 20% by weight or less, or about 10% by weight or less, of the active material in the cathode. For example, the material may be provided as nanowires, nanoparticles, nanocrystals, and may be oriented in the direction of the electrode to the electrolyte, or may be randomly dispersed. In some embodiments, the material forms a percolating network throughout the cathode.

In some aspects of the device, the cathode comprises dispersed Li⁺An ion conductor to increase the ionic conductivity of the electrode. For example, the material may be provided in the form of nanowires, nanoparticles, nanocrystals, and may be oriented in the direction of the electrode to the electrolyte, or may be randomly dispersed. The ionic material may be formed as a coating around the active material particles. In some embodiments, the material forms a percolating network throughout the cathode. In certain aspects, the material has a temperature of at least 10 at the operating temperature of the device^-7Ion conductivity of S/cm. In some cases, the material has at least 10^-5S/cm, or the material has an ionic conductivity of greater than 10^-4Ion conductivity of S/cm. Having the Li⁺Conductive materials are known in the art; a non-limiting list includes lithium iron phosphate, carbon, Li₂O-SiO₂-ZrO₂、Li-Al-Ti-P-O-N、LiMO₂、Li₁₀GeP₂S₁₂、Li_1.5Al_0.5Ge_1.5(PO₄)₃、Li₇La₃Zr₂O₁₂、Li₉SiAlO₈、Li₃Nd₃Te₂O₁₂、Li₅La₃M₂O₁₂(M=Nb,Ta)、Li_5+xM_xLa_3-xTa₂O₁₂(M = Ca, Sr, Ba), LiPON, lithium sulfide, lithium iron sulfide, lithium phosphate, Lisicon, thio-Lisicon, glassy structure, lanthanum titanateLithium, garnet structure, beta '' alumina, and lithium solid electrolyte. In aspects, the ionic conductivity of the material is at least greater than the ionic conductivity of the electrolyte. The ionic conductor is preferably present in an amount of about 20 weight percent or less, or more preferably about 10 weight percent or less, of the active material in the cathode.

Morphology of the cathode

In one embodiment of the device, the cathode is a thin film comprising an active component and optionally a MEIC component. Any of the above active components and MEIC components may be used. The film may be a continuous layer, such as a sputtered deposited layer. Alternatively, the film may be a layer comprising particles and/or nano-domains, and optionally held together by a binder. In one aspect, the thin film cathode has a thickness of about 2.5 to 500 nm. In another aspect, the thin film cathode has a thickness of between about 5 and 300 nm. In another aspect, the thin film cathode has a thickness of about 200nm or greater. In some cases, the components of the cathode material (conversion material) are intermixed with each other in individual particles or layers and are separated from each other in the above-indicated length dimensions and/or are present together in the glassy or amorphous state within these particles or layers. In some cases, the component is provided as a nano-domain.

Cathode morphology-metal compound particles/nano-domains

For devices comprising a metal compound component and optionally a MEIC therein, in one aspect, the cathode comprises particles/nano-domains of the optional MEIC and the metal compound component. The particles or nano-domains containing the metal compound component may generally be of any shape and size. In one aspect, at least some of the particles or nano-domains containing the metal component are approximately spherical. However, they may also be other shapes, such as rods, wires, pillows, polygons, flakes, and combinations of any of these shapes, including or not including spheres. As used herein, "close to spherical" means that none of the three linear dimensions of the particle has a characteristic length that exceeds twice the characteristic length of one of the other two dimensions. It is to be understood that the nearly spherical particles or nano-domains described below may be replaced by non-spherical particles or nano-domains. In such cases, the term "diameter" may be considered as the characteristic dimension of the particle, which is the shortest path across the particle or nano-domain.

In one embodiment, at least some of the particles or nano-domains containing the metal compound component are approximately spherical and such particles have a median diameter between about 1 and 20 nm. In one embodiment, at least some of the particles or nano-domains containing the metal compound component are approximately spherical, and such particles or nano-domains have a median diameter of between about 3 and 10nm, or between about 1 and 5 nm. The diameter of the particles or nano-domains can be measured by methods known to those skilled in the art; methods include visual inspection of SEM and TEM micrographs, dynamic light scattering, laser diffraction, and the like. In one aspect, the metal compound component comprises particles or nano-domains of iron-containing fluoride. In one aspect, the metal compound component comprises particles or nano-domains of iron fluoride (ferric and/or ferrous fluoride), copper fluoride, cobalt fluoride, or manganese fluoride, at least some of which are approximately spherical, and such spherical particles or nano-domains have a median diameter of between about 1 to 20 nm. In one aspect, the metal compound component comprises particles or nano-domains of iron fluoride, copper fluoride, cobalt fluoride, or manganese fluoride, at least some of which are approximately spherical, and such spherical particles or nano-domains have a median diameter of between about 3 to 10nm, or between about 1 to 5 nm. In some cases, the components of the cathode material (conversion material) are mixed in individual particles as described herein, and within these particles, they are separated from each other by the length dimension indicated above and/or exist together in a glassy or amorphous state.

In one aspect, the cathode comprises a MEIC component and particles of a metal compound component embedded in a matrix of the MEIC component. The particles or nano-domains of the metal compound component may be as described above.

Cathode morphology-metal particles/nano-domains and lithium compound particles/nano-domains

For devices in which the cathode active material comprises a metal component, a lithium compound component, and an optional MEIC at some states of charge, in one aspect, the cathode comprises particles or nano-domains of the optional MEIC and metal component and particles or nano-domains of the lithium compound component. The particles of the metal component and the particles of the lithium compound component can generally be of any shape and size. Such active materials may comprise some particles or nano-domains containing only the metal and other particles or nano-domains containing only the lithium compound (rather than particles containing both the metal and the lithium compound). In other embodiments, some or all of the particles contain both a metal and a lithium compound. Unless otherwise specified herein, particles can be homogeneous (containing only metal, lithium compound, or other material) or heterogeneous (e.g., containing both metal and lithium compound in a particle) containing two or more materials in a single particle. When they are heterogeneous, the components of the cathode material (conversion material) are mixed in individual particles and within these particles they are separated from each other by the length dimensions indicated above and/or exist together in a glassy or amorphous state.

In one aspect, the particles or nano-domains of at least some of the metal components are approximately spherical. In one aspect, the particles or nano-domains of at least some of the metal components are approximately spherical and such particles or nano-domains have a median diameter of 1 to 20 nm. In one aspect, the particles or nano-domains of at least some of the metal components are approximately spherical and such particles or nano-domains have a median diameter of about 3 to 10 nm. In one aspect, the metal component comprises particles or nano-domains of iron, copper, cobalt or manganese. In one aspect, the metal component comprises particles or nano-domains of iron, copper, cobalt, or manganese, at least some of which are approximately spherical, and such spherical particles or nano-domains have a median diameter of about 1 to 20nm, or about 3 to 10nm, or about 1 to 5 nm.

Cathode morphology-lithium metal compound particles or nano-domains

For devices in which the cathode comprises a lithium metal compound component and optionally a MEIC in some states of charge, in one aspect, the electrode comprises particles or nano-domains of the optional MEIC and the lithium metal compound component. The particles or nano-domains of the lithium metal compound component may generally be of any shape and size, including those described above for the other components.

Solid electrolyte

The solid-state electrolyte may generally be made of any material that is compatible with the other materials of the device, has a sufficiently large lithium ion conductivity to allow passage of lithium ions for operation of the device, and has a sufficiently small electronic conductivity for operation of the device. In one aspect, the solid state electrolyte has a temperature greater than 10 at 100 degrees celsius^-7And S/cm lithium ion conductivity. Preferably, the material has at least 10 at 100 degrees celsius^-5S/cm, even more preferably, the material has an ionic conductivity of greater than 10^-4Ion conductivity of S/cm. In one aspect, the solid state electrolyte has less than 10 at 100 degrees celsius^-10Electron conductivity of S/cm. In one embodiment, the solid electrolyte is selected from LiPON, lithium aluminum fluoride, Li₂O-SiO₂-ZrO₂、Li-Al-Ti-P-O-N、Li_3xLa_2/3-xTiO₃、Li₁₀GeP₂S₁₂、Li_1.5Al_0.5Ge_1.5(PO₄)₃、Li₇La₃Zr₂O₁₂、Li₉SiAlO₈、Li₃Nd₃Te₂O₁₂、Li₅La₃M₂O₁₂(M=Nb、Ta)、Li_5+xM_xLa_3-xTa₂O₁₂(M = Ca, Sr, Ba), LiPON, lithium phosphate, Lisicon, thio-LiSICON, Li₂S-X(X=SiS₂、GeS₂、P₂S₅、B₂S₃、As₂S₃)、Li_aAl_bGa_cB_dS_e(PO₄)_f、Li_aAl_bGa_cB_dS_e(BO₃)_f、Li_aGe_bSi_cS_d(PO₄)_e、Li_aGe_bSi_cS_d(BO₃)_eAnti-perovskite hydrates, glassy structures, lanthanum lithium titanate, garnet structures, beta' alumina and other lithium solid electrolytes. In one aspect, the solid electrolyte is LiPON. In one embodiment, the solid electrolyte is lithium aluminum fluoride. In one embodiment, the solid electrolyte is LiAlF₄. In some embodiments, a liquid or gel electrolyte is used without a solid electrolyte. Such electrolytes may be of any type used with conventional lithium ion batteries.

Anode material

The negative electrode may generally be made of any material that is compatible with the other materials of the device, and may store lithium atoms or ions when the device is in a charged state and may provide lithium ions for intercalation into the cathode when the device is in a discharged state. In one aspect of the device, the negative active material is lithium metal. In one aspect of the device, the negative electrode material is lithium silicide, Li-Sn, or other high capacity, low voltage material alloyed with lithium. In one aspect of the device, the negative active material is lithium intercalated into a carbon component, such as graphite. In some cases, the anode active material is a material capable of inserting lithium ions with a higher reversible capacity than carbon. Such materials include tin, magnesium, germanium, silicon, oxides of these materials, and the like.

In one aspect of the device, the negative electrode material is a porous material that allows lithium plating into the pores, thereby relieving the expansion pressure that would otherwise act on the electrolyte through cathode expansion due to lithium plating. In one aspect, the pores are carbon nanotubes, carbon buckyballs, carbon fibers, activated carbon, graphite, porous silicon, aerogels, zeolites, xerogels, and the like.

In one aspect of the device, the anode is formed in situ during the first charge cycle of the cell. If the device is manufactured in the discharged state (using a lithiated cathode), a first charge cycle will extract lithium from the cathode and deposit it on the anode side. In the case where the anode is a lithium metal anode, the anode is thus formed in situ by plating on an anode current collector. In this case, preferably, the anode current collector is a metal that does not form an alloy with lithium or react with lithium; a non-limiting list of possible choices of anode current collector metals includes TaN, TiN, Cu, Fe, stainless steel, W, Ni, Mo, or alloys thereof. In one aspect, there is excess lithium on the cathode side in the fabricated device. In another aspect, there may be an excess of lithium in the anode current collector on the anode side in the fabricated device. Excess lithium is desirable to extend the cycle life of the battery, as some lithium is inevitably lost due to side reactions, alloying with the current collector, or reacting with air and/or water leaking into the device.

In one aspect of the device, there is an encapsulation that substantially prevents air and water from entering the active material. The encapsulation may be LiPON, an oxide, a nitride, an oxynitride, a resin, an epoxy, a polymer, parylene, a metal (e.g., Ti or Al), or a multi-layer combination thereof. Moisture and oxygen barriers are known in food packaging, semiconductor packaging, and the like.

Current collector

The devices described herein include optional positive and/or negative current collectors. The current collector may generally be made of any material capable of transporting electrons from or to an external circuit to or from the anode or cathode. In one aspect, the device does not include a cathode current collector, with electrons being transferred directly to and from the cathode to an external circuit. In one aspect, the device does not include an anode current collector, with electrons being transferred directly to and from the anode to an external circuit. In one aspect, the device includes neither a cathode current collector nor an anode current collector. In one aspect, the negative current collector is a metal, such as copper. In one aspect, the negative current collector is a copper alloy. In one aspect, the negative current collector is an alloy of copper with a metal selected from the group consisting of nickel, zinc, and aluminum, or copper coated on a metal or polymer foil. In one aspect, the current collector is copper and further comprises a non-copper metal layer disposed between the copper and the cathode or anode material. In one aspect, the positive current collector is a metal, such as copper, and further includes a layer of nickel, zinc, or aluminum interposed between the copper and the anode material. In one aspect, the positive current collector is aluminum. In one aspect, the positive current collector is aluminum or an aluminum alloy. In one aspect, the positive current collector is aluminum and further includes a non-aluminum metal layer disposed between the aluminum and the cathode or anode material. In one aspect, the current collector is steel or stainless steel. In one aspect, the current collector is steel or stainless steel, and further includes a non-steel metal layer disposed between the steel and the cathode or anode material. The cathode current collector and the anode current collector may be different materials selected from the materials listed above or conversely the same materials.

Energy density

In one aspect, the devices described herein have an energy density of at least about 50Whr/kg or about 50 to 1000Whr/kg when cycled between 1 and 4V versus Li at 100 degrees celsius and measured at a current rate of at least about 200mAh/g of cathode active material. In another aspect, the devices described herein have an energy density of about 100 to 750 Whr/kg. In another aspect, the devices described herein have an energy density of about 250 to 650 Whr/kg. In another aspect, the devices described herein have an energy density of greater than about 250 Whr/kg. As used herein, energy density is the energy density at the device level; i.e., the total energy stored in the device divided by the mass of the device, including the mass of the anode, cathode, electrolyte, current collector, and packaging of the device. From a volumetric standpoint, in some embodiments, the device has an energy density of at least about 600Wh/L under the conditions described above.

In one aspect, the cathodes described herein have an electrode energy density of about 500 to 2500Whr/kg when measured at a temperature of 100 degrees. In another aspect, the cathodes described herein have an electrode energy density of about 800 to 1750 Whr/kg. In another aspect, the cathodes described herein have an energy density of about 1000 to 1600 Whr/kg. In another aspect, the cathodes described herein have an energy density of greater than about 1000 Whr/kg. As used herein, electrode energy density is the energy density at the electrode level; i.e., the total energy stored in the device divided by the mass of the cathode in the discharged state, wherein the mass of the electrode includes the mass of electrochemically active material, lithium, positive current collector, and any electrochemically inactive components (e.g., ionic or electronic conductor additives) in the cathode.

Mixed fluoride/sulfide cathode

In one aspect, at some point in the state of charge, the cathode includes a metal component and a lithium compound component containing lithium, fluorine, and sulfur. In one embodiment, the lithium compound component comprises a mixture of lithium fluoride and lithium sulfide. In one embodiment, the lithium compound component comprises a sulfur fluoride of lithium. In one embodiment, the cathode contains lithium, fluorine, sulfur and a metal component selected from iron, copper, cobalt, manganese, bismuth or alloys of these metals. In one embodiment, the cathode contains a compound comprising lithium, fluorine, sulfur, and iron. In one embodiment, the cathode contains lithium fluoride, lithium sulfide and a metal component selected from iron, copper, cobalt, manganese, bismuth or an alloy of any of these metals. In one embodiment, the cathode comprises lithium fluoride, lithium sulfide, and iron. In one embodiment, the cathode contains about 30 to 80 wt% lithium fluoride (3LiF + Fe would be 58wt% LiF), about 1 to 20 wt% lithium sulfide, and a metal component. In one embodiment, the cathode contains between about 40 and 70 weight percent lithium fluoride, between about 2 and 15 weight percent lithium sulfide, and between about 30 and 60 weight percent iron. In one embodiment, the cathode contains about 50 to 70 weight percent lithium fluoride, about 0 to 20 weight percent lithium sulfide, and about 20 to 50 weight percent iron. In one aspect, the cathode contains lithium fluoride, lithium sulfide and a metal component when the electrochemical cell is in a relatively discharged state, and contains a metal fluoride and lithium sulfide and optionally lithium fluoride and a metal component when in a more charged state.In such an arrangement, the cathode is substantially free of metal sulfide in the more charged state. In one aspect, the cathode contains lithium fluoride, lithium sulfide and iron when the electrochemical cell is in a relatively discharged state, and iron fluoride and lithium sulfide and optionally lithium fluoride and iron components when in a more charged state. In such an arrangement, the cathode is substantially free of metal sulfide in the more charged state. In one aspect, the cathode contains lithium fluoride, lithium sulfide and a metal component when the electrochemical cell is in a relatively discharged state, and a metal fluoride and a metal sulfide and optionally lithium fluoride, lithium sulfide and a metal component when in a more charged state. In one aspect, the cathode contains lithium fluoride, lithium sulfide and iron when the electrochemical cell is in a relatively discharged state, and iron fluoride and iron sulfide and optionally lithium fluoride, lithium sulfide and iron components when in a more charged state. In other embodiments, the sulfide component may be iron sulfide (FeS or FeS)₂) Iron sulfate, copper sulfide, lithium sulfide (Li)_xS) and/or solid sulfur. FeS, FeS have been found₂And Li₂S is a significantly higher lithium conducting oxide than other known lithium conducting oxides such as LiPON, MoO_x、VO_x、LiFePO₄And lithium titanate, the better lithium ion conductors.

In some embodiments, a battery containing a cathode with a sulfide or other conductivity enhancer is cycled in a range where the conductivity enhancer is not reactive. Iron sulfide is known to convert to elemental iron and sulfur at a voltage of about 1.7 volts versus lithium/lithium ion. It is believed that elemental sulfur can damage certain solid electrolytes (particularly oxide-type solid electrolytes), so it may be desirable to prevent the formation of sulfur during normal cycling. To prevent the electrochemical reduction of sulfide to sulfur, the device is configured by using a battery management circuit or other control mechanism to prevent the cathode from reaching 1.7 volts during discharge. In summary, the "off" voltage is selected such that the desired electrochemical reaction occurs completely or near completely (conversion of all or most of the electrochemically active material in the electrode occurs) while the conductivity enhancing component does not react. In the case of the iron sulfide-iron sulfide system, a discharge voltage of between about 1.8 and 2.2 volts (e.g., about 2 volts) versus the lithium/lithium ion pair is generally suitable.

In some embodiments, the device comprises an intermediate layer disposed between the cathode and the electrolyte. Such an interlayer may prevent sulfur or other species from migrating to and damaging the electrolyte. The intermediate layer should also be conductive to lithium ions, and stable at the cathode operating voltage and with respect to the cathode material and electrolyte material,

in some embodiments, a matrix or other strong binder is used to keep the conductivity enhancing material and cathode active material in close proximity over repeated cycles. It has been observed that the conductivity enhancing material (e.g., iron sulfide) and the cathode active material can separate over time during normal cycling. If this occurs, the electrode performance suffers. The conductivity enhancing material should be very close (typically on the order of nanometers) to the electrochemically active material. This very close relationship can be established during the manufacturing process and then maintained through the use of a matrix during cycling. The matrix is an ionic and electronic conductor. Examples of suitable matrix materials include LiF, AlF₃、LiAlF₄、SiO₂、Al₂O₃、MoO₃、MoS₂、LiFePO₄、VO_xAnd LiTiO_x。

In certain aspects, the matrix material is provided as a continuous layer embedded with separate particles or nano-domains of the conductivity enhancer and the active material. Two examples are shown in figure 3. For example, when the cathode is in the discharged state, the matrix intercalates (i) iron sulfide and (ii) separate particles or nano-domains of elemental iron and lithium fluoride. In another example, the matrix is intercalated with (i) iron sulfide and (ii) elemental iron and (iii) separate particles or nano-domains of lithium fluoride when the cathode is in a discharged state. In some embodiments, the conductivity enhancer is provided in a core-shell arrangement with the active material (e.g., iron and/or lithium fluoride) covered by the conductivity enhancer (e.g., iron sulfide). Such core-shell particles may be embedded in a matrix as described above. In certain aspects, the matrix, active material, and conductivity enhancer are provided in the same small particle. For example, the matrix material may encapsulate two or more small particles or nano-domains, at least one of which is an active material, at least another of which is a conductivity enhancer. In some embodiments, the composite particles may have a median characteristic dimension of about 5nm to 100 nm.

Cathode/electrolyte interlayer

In one aspect, the cathode in the discharged state comprises a metal component and an intermediate layer disposed between the cathode and the electrolyte, the intermediate layer being substantially impermeable to the metal component. In some embodiments, the intermediate layer improves cycling performance by preventing migration and/or reaction of the cathode material with the electrolyte. In one aspect, the intermediate layer comprises one or more of the following: lithium fluoride, silicon dioxide, aluminum phosphate, aluminum fluoride, aluminum oxide, and molybdenum oxide. In one aspect, the intermediate layer is lithium fluoride. In one aspect, the intermediate layer is silicon dioxide. In one embodiment, the cathode contains iron and the interlayer is lithium fluoride. In one embodiment, the electrode comprises iron and the intermediate layer is silicon dioxide. In one aspect, the thickness of the intermediate layer is between about 2 and 50 nm. In one embodiment, the cathode contains iron and the intermediate layer is lithium fluoride having a thickness of between about 2 and 50 nm. In one embodiment, the cathode contains iron and the intermediate layer is silicon dioxide having a thickness of between about 2 and 50 nm. In one embodiment, the electrolyte is LiPON, the cathode contains iron, and the intermediate layer is lithium fluoride. In one embodiment, the cathode contains iron and the intermediate layer is silicon dioxide. In one embodiment, the cathode contains iron and the intermediate layer is lithium fluoride having a thickness of between about 2 and 50 nm. In one embodiment, the cathode contains iron and the intermediate layer is silicon dioxide having a thickness of between about 2 and 50 nm.

Small excess of lithium

Conventional lithium ion batteries are manufactured to typically contain a large excess of lithium in excess of that required to fully charge and discharge the battery. In particular, solid state and/or thin film lithium ion batteries contain a large excess of lithium in excess of that required for complete discharge of the battery. The volume of the negative electrode having a large excess of lithium does not vary in a large proportional amount. For example, a 4-fold excess of lithium is typically used. In operation, the cell cycles to only about 20% of the anode lithium, so the volume change is only 20%.

In one aspect of the batteries described herein, a small excess of lithium is present. In one embodiment, less than 25 wt% excess lithium is present. Without mitigation, an excess of only 25 wt% lithium would result in a change in the volume of the negative electrode of about 500%, which would place more stress on the electrolyte.

One way to address this challenge is to control the volume change by changing the electrode structure. In addition, glassy electrolytes can withstand bending due to volume changes in the negative electrode on the order of 100%. In some embodiments, excess lithium is plated into the open pores (typically in the negative electrode), which mitigates the expansive forces on the electrolyte. In various embodiments, the pores occupy the same volume whether they are filled with lithium or empty. Examples of materials that can provide suitable pores include nanotubes (e.g., carbon nanotubes), carbon buckyballs, carbon fibers, activated carbon, graphite, porous silicon, aerogels, zeolites, xerogels, and the like.

Another way to deal with the volume expansion associated with limited excess lithium in the cell involves the use of a "multi-stack" cell structure comprising relatively thinner layers. Each stack includes an anode layer, an electrolyte layer, and a cathode layer. All lithium in a "one stack" cell (conventional) is in one anode at least 50-200 μm thick, and the volume change of the anode can result in 50-200 μm expansion that the cell cannot withstand. However, if the cell contains tens (or hundreds, or thousands) of stacks in a single cell, each of which is, for example, 100 nanometers thick, the system will better match between the shrinkage of the anode to the expansion of the cathode. In some examples, a multi-stack configuration would use, for example, 100 layers of anode/electrolyte/cathode, each layer corresponding to 1/100 of conventional thickness.

In some embodiments, some or all of the excess lithium in the cell is provided in the fabricated cathode. In some embodiments, the cathode material has an amount of elemental lithium and other components described above (e.g., metal and lithium compound particles or nano-domains). In some examples, the lithium metal is present in the cathode active material at a level of less than about 50 wt.% or less than about 30 wt.%.

Application for a device

The devices described herein may generally be used in any application where energy storage is desired. The device may be particularly well suited for applications such as electric vehicles, hybrid vehicles, consumer electronics, medical electronics, and grid storage and conditioning.

Electrode manufacturing process

The cathodes described herein can be made by a number of different methods. The following is a list of manufacturing options, including material synthesis and methods of coating on a substrate.

Vacuum processes including sputtering, evaporation, reactive evaporation, vapor deposition, CVD, PECVD, MOCVD, ALD, PEALD, MBE, IBAD and PLD.

Wet synthesis, including CBD, electroplating, spray and in situ formation, Langmuir blodgett, layer-by-layer formation, electrostatic spray deposition, ultrasonic spray deposition, aerosol spray pyrolysis, sol gel synthesis, one pot synthesis, and other bottom-up methods.

Dry synthesis, including pressing, hot pressing, cold pressing, isostatic pressing, sintering, spark plasma sintering, flame pyrolysis, combustion synthesis, plasma synthesis, atomization and melt spinning.

Top-down methods, such as jet milling, wet/dry milling, planetary milling, and high energy milling.

Coating methods such as slot die, spin coating, dip coating, doctor blade, metering rod (metering rod), slot casting, screen printing, ink jet printing, aerosol jet, roll blade, comma coating, reverse comma coating, tape casting, slip casting, gravure coating and microgravure coating.

Methods only used for material synthesis include sol-gel synthesis, one-pot synthesis, bottom-up synthesis, melt spinning. Methods used only for particle size reduction include wet grinding, dry grinding, planetary grinding, high energy grinding, jet grinding. Methods used only for coating include slit, spin coating, dip coating, doctor blade, metering bar, slot casting, screen printing, inkjet printing, aerosol jet, roll blade, comma coating, reverse comma coating, tape casting, slip casting, gravure coating, microgravure coating. All other listed methods are some mix of synthesis/deposition.

In some embodiments, the cathode material is produced using sputtering, PVD, ALD, or CBD. In one version, the device is fabricated by sequential deposition of an anode current collector, an anode, an electrolyte, a cathode, and a cathode current collector on a substrate. In one version, there is no separate substrate, and the anode, electrolyte, cathode, and cathode current collectors are deposited directly on the anode current collector. In one version, the cathode, electrolyte, anode and anode current collectors are deposited directly on the cathode current collector without a separate substrate.

In some embodiments, the conversion material for the cathode is prepared using a method in which one or more precursors or reactants are contacted in a solid phase. Many such methods may be used. They are collectively referred to as solid phase synthesis. Examples include hot pressing, cold pressing, isostatic pressing, sintering, calcining, spark plasma sintering, flame pyrolysis, combustion synthesis, plasma synthesis, atomization, and melt spinning. Some solid phase syntheses involve milling and mixing of bulk precursor materials. The bulk materials are ground to very small sizes, then combined or mixed and reacted as necessary to form the desired composition. Milling can be carried out by jet milling, cryogenic milling, planetary milling (Netzsch, Fritsch), high energy milling (Spex), and other milling techniques known to those skilled in the art. In some embodiments, the milled and mixed particles are calcined. In some embodiments, the milling device produces particles or nano-domains having a median characteristic dimension on the order of about 20nm or less. In various embodiments, one reactant comprises iron and the other reactant comprises fluorine. For example, one reactant may be an iron compound containing an anion such as nitrate or nitrite and the other reactant may be a fluoride of hydrogen, such as ammonium bifluoride.

In a specific embodiment, the nanostructured conversion material is formed by mixing precursor materials at their liquid atomic level. More specifically, a method of providing a nanostructured switching material is implemented. The method includes providing a first precursor material comprising a metal-containing material. For example, the metalliferous material includes iron and/or other metallic materials. A second precursor material is also provided. The second precursor material comprises an oxidizing anionic material, such as a fluoride material. The first precursor material and the second precursor material are characterized by a tendency to phase separate. The phase separation material has a positive enthalpy of mixing. In their steady state, the phase separated materials separate to form separate regions composed primarily of each single material. It is understood that it is difficult to fabricate a nanostructured glass transition material from two precursor materials without the use of the methods described herein because the two precursor materials have a tendency to phase separate.

In the atomization process, two precursor materials are separately melted into liquid states and injected into a cooling chamber that quenches the materials into an unstable or metastable state. For example, the first precursor material and the second precursor material have different melting temperatures and thus may melt separately or together at a temperature above the melting point. Mixing and spraying the two precursor materials may be performed in different orders, depending on the particular embodiment. In a particular embodiment, the two precursor materials are placed together as late as possible during the pre-injection process. The two precursor materials are then ejected into the cooling chamber through a single nozzle while being placed together in their liquid state. For example, the nozzle forces the two precursor materials into small-sized particles or nano-domains, which allows mixing to occur at the atomic level, with rapid quenching of the materials to "freeze" in the mixed state.

Alternatively, the two precursor materials may be sprayed separately through two or more nozzles into the cooling chamber, with mixing occurring only within the cooling chamber. In the cooling chamber, the two precursor materials mix at a size of less than about 20nm to become shaped particles consisting of a nanostructured mixture of the two precursors. Since the two precursor materials have a tendency to phase separate, the shaped particles or nano-domains need to be cooled rapidly to stay in a mixed and nano-structured state. In various embodiments, the shaped particles or nano-domains cool at a rate of at least about 100 kelvin per second. In one particular embodiment, the cooling rate is approximately 10000 kelvin per second. For example, the shaped particles or nano-domains cool to room temperature and are sufficiently stable in the nano-structured and mixed state. Cooling can be performed in a variety of ways. In one implementation, the cooling is performed by injecting cold inert gas into the cooling chamber. In another embodiment, the cooling is performed by a cooling surface such as a cold bronze drum or anvil. The formed particles or nano-domains are then collected. For example, another method is implemented to use the formed particles or nano-domains as a switching material in a battery cell.

It is to be understood that the conversion material may be processed using different techniques according to various embodiments of the present invention. For example, instead of using a cooling chamber, a cooled surface may be used to create the formed particles or nano-domains. In a particular embodiment, a rotating cooling surface is provided, and the formed particles or nano-domains cool rapidly due to direct contact with the cooling surface.

As mentioned, the nanostructured conversion material may be formed by an evaporation method. In many evaporation techniques, the precursor material is heated to a temperature at which it has a significant vapor pressure, and then allowed to deposit on the substrate to a thickness of nanometer dimensions. Such techniques include thermal evaporation, electron beam evaporation, vapor deposition, close space sublimation, and the like. Depending on the application, the precursor material may or may not have a tendency to phase separate. In their respective gaseous states, the two precursor materials mix within the chamber to form a mixed material within the chamber, the mixed material being characterized by a length dimension of less than about 20 nm. Cooling may occur naturally or by contact with a cold surface or cold gas. The mixed material was then collected.

To deposit the iron fluoride compounds as described herein, co-evaporation of the iron and fluorine containing materials may be carried out such that the two major components of the matrix are mixed in the vapor phase and then deposited onto a substrate to form nano-domains or particles having length dimensions of about 20nm or less. In another embodiment, the source of each individual component of the composition is separately evaporated and deposited onto the substrate such that the components form separate layers. By keeping these layers to have sufficiently thin dimensions and an appropriate mass ratio, the desired compound is formed. Typically, each layer is very thin, typically on the order of nanometers or less. The mass ratios are selected to produce active compounds or mixtures having molar or stoichiometric ratios as described elsewhere herein.

One example of a suitable evaporation technique is vapor transport deposition or flash evaporation. Which provides for the continuous deposition of the desired film material by saturating the carrier gas with vapor from the sublimation source. The saturated mixture is directed onto the substrate at a lower temperature, causing supersaturation and subsequent film growth. In one embodiment, the reactor employs separate powder sources of fluorine and iron. A helium source blows hot helium into the powder that sublimes and is transported into the reactor where the components mix in the gas phase before being deposited on the cold substrate. In a properly designed apparatus, each powder is provided through a separate tube, and during transport through the tube, the powder is vaporized by hot helium or other carrier gas. A non-limiting list of evaporation sources may include LiF, FeF₃、FeF₂、LiFeF₃Fe and Li. The vaporized source material may be exposed to a fluorine-containing material such as F₂、CF₄、SF₆、NF₃Etc. produced byReaction processes in plasma or ambient gas. For FeLi_aF_bSuitable precursors for the compounds may include iron nanoparticles, fluorides of iron (II), fluorides of iron (III), stainless steel, lithium metal, lithium fluoride or gas phase precursors, such as F₂、CF₄、SF₆And NF₃。

Battery structure

The above disclosure describes various elements of a battery comprising a current collector, an anode, a cathode, and an electrolyte. Conventional forms of cell design may be used. These include both cylindrical and prismatic configurations, such as those used in consumer electronics, electric vehicles, medical equipment, uninterruptible power supplies, and the like. The size and footprint of these cells may be similar to conventional forms of cells such as a, AA, AAA, C, 18650, and the like.

Although the description focuses primarily on solid electrolytes, it should be understood that the cathodes disclosed herein may also be used in batteries using liquid or gel electrolytes. A small multi-stack cell configuration may be used.

In various embodiments, the device has a battery maintenance or battery controller device, such as a battery charger and associated circuitry for controlling discharge and/or charge parameters such as cutoff voltage, cutoff capacity, current, and temperature, among others.

Results of the experiment

FIG. 4: a plot of cell performance as measured by cathode volumetric energy density versus small length size LiF material in a layered structure. Energy density was measured by constant current discharge between 1 and 4V at a rate of 10C and 120 ℃; all cells have equal total thickness (e.g., a cell with a length dimension of 35nm has twice the number of layers as a cell with a length dimension of 70 nm). The cell was constructed by sputtering 30nm Ti and 40nm TiN on a Si wafer, followed by a cathode layer, followed by sputtering 200nm LiPON electrolyte. The area of the punched Li foil with the thickness of 100 mu m is 0.3cm²And pressed to define a cell area. Make TiThe N and Li foil electrical contacts were used for measurements on a hot plate held at 120 ℃.

The stack was fabricated by fabricating successive layers of Fe and LiF at a thickness ratio of 1:7, which produced a discharge cell with a stoichiometric ratio of approximately Fe +3 LiF. As the length dimension increases, the cathode performance degrades, showing the benefits of nanostructured cathodes (or cathode particles) down to less than 10 nm.

Tables summarizing the data in fig. 7-10 are as follows. It is useful to note that the appropriate amount of sulfur in the cathode significantly improves the mass loading capability of the electrode.

FIG. 5: graph of constant current charge and discharge of a 66nm 3LiF + Fe cathode at 120 ℃. The cell was constructed as described above and measurements were made at C-rates of 10C (dashed line) and 1C (solid line). The energy density at 10C was as high as 88% at 1C, and the voltage hysteresis was 0.89V at 1C and 0.91V at 10C. The performance of 66nm 3Li + Fe cathodes was significantly degraded with C-rate.

FIG. 6: graph of constant current charge and discharge of a 129nm 3LiF + Fe cathode at 120 ℃. The cell was constructed as described above and measurements were made at C-rates of 10C (dashed line) and 1C (solid line). The energy density at 10C was as great as 58% at 1C, and the voltage hysteresis was 0.92V at 10C and 0.72V at 1C. As the cathode became thicker, the degradation in performance with rate was even more pronounced, indicating that performance was mass transfer limited.

FIG. 7: the cathode is 134nm (3LiF + Fe + S)_0.14) A graph of constant current discharge of the battery of (1). The cell was constructed as described above and at 10C (dashed line) and 1C (solid line)) Is measured at the C-rate of (a). The energy density at 10C was 83% of that at 1C, the voltage hysteresis was 0.72V at 1C, and 0.88V at 10C. The cathode has much better rate performance than the cathode of similar thickness and no sulfur content in fig. 3, showing significant benefit from 2% S content.

FIG. 8: the cathode is 134nm (3LiF + Fe + S)_0.53) A graph of constant current discharge of the battery of (1). The cell was constructed as described above and measurements were made at C-rates of 10C (dashed line) and 1C (solid line). The data at 10C showed 106% higher energy density than at 1C, 0.61V capacity-averaged voltage hysteresis, 0.75V at 1C, and 74% energy efficiency, 64% at 1C. Within statistical fluctuations, there was virtually no degradation in performance at 10C versus 1C, indicating that 7% sulfide loading substantially improved cell mass transfer.

As described above, according to the embodiments of the present invention, the cathode energy density is improved by the nano-structured conversion material. Fig. 9 provides a graph of cell performance as measured by cathode volumetric energy density versus length dimension of LiF material in a layered structure. The energy density was measured by constant current discharge between 1 and 4V versus Li at a rate of 10C and 120 ℃. The figure is based on all measured cells having essentially the same total thickness (e.g. a cell with a length dimension of 35nm has twice the number of layers as a cell with a length dimension of 70 nm). As shown in fig. 9, when the length dimension of LiF is less than 40nm and the length dimension of Fe is about 5nm, the cathode energy density is about 1500Wh/L or more. When the length dimension of LiF is less than 20nm and the length dimension of Fe is less than about 5nm, the cathode energy density is about 2500Wh/L or greater. It is understood that high energy densities can be achieved due to the nano-structuring of the particles. As described above, according to embodiments of the present invention, the nanostructure may be formed in various ways.

Fig. 10 is a graph of cell performance as measured by cathode volumetric energy density versus F material in the small length dimension of the layered structure. Energy density was determined by running the cell at a rate of 10C and 120 ℃ in a complete cell configurationMeasurements were made with respect to a constant current discharge between 1 and 4V of Li. For measurement purposes, the cells were fabricated by coating on Si/SiO₂50nm of Pt was sputtered onto the wafer, followed by a cathode layer, followed by 200nm of LiPON electrolyte. A top electrode of Fe is sputtered in a defined area and during charging Li is plated onto the Fe surface, creating an anode in situ. Pt and Fe were electrically contacted for measurement on a hot plate maintained at 120 ℃. As described above, the laminate was manufactured by manufacturing successive layers of Fe and LiF at a thickness ratio of 1:3, which manufactured a discharge cell having a stoichiometric ratio of about Fe +3 LiF. As the length dimension increases, the cathode performance deteriorates, showing the benefit of nanostructured cathode morphology down to less than 2 nm. More specifically, as shown in fig. 10, the cathode energy density versus layer structure graph shows: as the length dimension decreases, the energy density per volume increases. On the x-axis, "20X 0.5" indicates 20 layers (0.5nm Fe +1.5nm LiF), "20X 1" indicates 20 layers (1nm Fe +3nm LiF) and "10X 2" indicates 10 layers (2nm Fe +6nm LiF).

Fig. 11 provides a cross-sectional view of a nanostructured conversion material at a size of about 5 nm. As can be seen from fig. 3 described above, the length dimension of about 5nm does not perform as well as nanostructured switching materials at smaller dimensions (low performance means less than ideal material structure). For example, the diagrams shown in fig. 13-15 are part of the cell structure shown in fig. 1A and B.

Fig. 12 provides a cross-sectional view of a nanostructured conversion material at a size of about 2 nm. At the smaller dimensions compared to fig. 11, the nanostructured switching material performs better than the microstructure shown in fig. 11.

Fig. 13 provides a cross-sectional view of a nanostructured conversion material at a size of about 2 nm.

Fig. 14 is a graph illustrating an example of nanostructured switching material and the benefits of maintaining compositional uniformity. For example, a model is created to calculate the number of reactions within a certain distance from any given atom. It is assumed that the reaction, for example Li + F + Fe → FeLiF, is a multistep FeF₃In conversion lithiation reactionsOne step, the model then calculates the distances L1 and L2, where L1 is the distance between F and Li and L2 is the distance between F and Fe. As can be seen by the calculations, when considering the almost exact stoichiometric ratios F/Fe =3 and F/Fe =2.5, the larger part of the reaction can be completed within a shorter distance. This results in a battery with higher performance: higher efficiency, greater charge/discharge rates, and higher delivered energy. Thus, a glassy/amorphous transition material should be prepared in such a way that the near ideal stoichiometric ratio is maintained throughout the material.

Fig. 15 shows the theoretical energy density of lithiated conversion cathode materials relative to a standard Li anode. The overpotential is assumed to be 0.7V, taking into account mass transfer losses, activation losses at reasonable voltages, and the hysteresis inherent in the shift reaction. Fig. 16 shows the theoretical specific energy of lithiated conversion cathode materials relative to standard Li anodes. Again, the overpotential is assumed to be 0.7V, taking into account mass transfer losses, activation losses at reasonable voltages, and the inherent hysteresis of the shift reaction. Since the values shown are theoretical values, the complete conversion at thermodynamic potential is assumed.

Fig. 17 shows a plot of the initial 5 charge/discharge cycles (voltage (measured against a standard lithium electrode) versus cathode material active capacity) for the copper fluoride sample. As shown, the cathode active material showed reversibility, only moderate hysteresis, high average voltage and near full capacity.

Fig. 18 shows the discharge energy of a sample containing a specific transition metal alloy for the conversion material. Specifically, the conversion material comprises FeCo + LiF, FeMn + LiF and Fe₃Co + LiF and the control sample Fe + LiF. The discharge rate was 10C and the discharge voltage limit was 4 to 1V relative to a standard lithium metal electrode. The sample had a nominal thickness ratio of 7LiF to 1M, where M is a metal, which in the non-control case is an alloy. In each sample, ten layers of metal (in the composition) were formed, with ten layers of LiF alternately interposed between the metal layers. As can be seen, the 50% Fe-50% Co and 50% Fe-50% Mn samples provide particularly high specific capacities.

In fig. 19, capacity and hysteresis statistics are provided for the following conversion material samples: FeCo + LiF, FeMn + LiF, Fe₃Co + LiF and the control sample Fe + LiF. The samples were discharged at the rates given for C/3, 1C, 10C (C/3 is white, 1C is gray, and 10C is black) for the different color representations, with a voltage range of 4 to 1V versus the lithium metal electrode.

Claims (27)

1. A cathode material comprising:

particles or nano-domains having a median characteristic dimension of about 20nm or less,

wherein the particles or nano-domains comprise (i) particles or nano-domains of a metal selected from iron, cobalt, manganese, copper, nickel, bismuth, and alloys thereof, and (ii) particles or nano-domains of a fluoride of lithium.

2. The cathode material of claim 1, wherein the metal is iron, manganese or cobalt and the molar ratio of metal to lithium fluoride is about 2 to 8.

3. The cathode material of claim 1, wherein the metal is copper or nickel and the molar ratio of metal to lithium fluoride is about 1 to 5.

4. The cathode material of claim 1, wherein the metal is iron and the particles or nano-domains further comprise iron fluoride.

5. The cathode material of claim 1, wherein the cathode material further comprises (iii) a conductive additive.

6. The cathode material of claim 1, wherein the median characteristic dimension of the particles or nano-domains is about 5nm or less.

7. The cathode material of claim 1, wherein the particles or nano-domains are at about 1000nm³Is substantially uniform within the volume of (a).

8. A cathode, comprising:

(a) a current collector having a plurality of current collector elements,

(b) an electrochemically active material in electrical communication with the current collector and comprising: (i) a metal component, and (ii) a lithium compound component mixed with the metal component in a distance dimension of about 20nm or less,

wherein, when fully charged with the compound forming the metal component and the anion of the lithium compound, the electrochemically active material has a reversible specific capacity of about 350mAh/g or greater when discharged at a rate of at least about 200mA/g with lithium ions.

9. The cathode of claim 8, wherein the cathode further comprises a mixed ionic-electronic conductor component.

10. The cathode of claim 8, wherein the mixed ion-electron conductor component has a glassy structure.

11. The cathode of claim 8, wherein the metal component is a transition metal, aluminum, bismuth, or an alloy of any of these metals.

12. The cathode of claim 8, wherein the metal component comprises metal grains having a median characteristic length of about 5nm or less.

13. The cathode of claim 8, wherein the lithium compound component is a fluoride of lithium.

14. The cathode of claim 8, wherein the lithium compound component comprises particles or nano-domains having a median characteristic length dimension of about 5nm or less.

15. The cathode of claim 8, wherein the electrochemically active material is provided in a layer having a thickness of about 10nm to 300 μm.

16. The cathode of claim 8, wherein, when fully charged, the electrochemically active material has a reversible specific capacity of about 300mAh/g or greater when discharged by lithium ions at a rate of at least about 6000 mA/g.

17. The cathode of claim 8, wherein the cathode exhibits an average voltage hysteresis of less than about 1V when cycled between 1V to 4V versus Li at a temperature of 100 ℃ and discharged at a rate of about 200mAh/g cathode active material.

18. A method of manufacturing a battery, the method comprising:

(a) providing a cathode comprising an electrochemically active material in electrical communication with a current collector and comprising: (i) a metal component, and (ii) a lithium compound component mixed with the metal component over a distance dimension of about 20nm or less, wherein the electrochemically active material, when fully charged with a compound forming the metal component and an anion of the lithium compound, has a reversible specific capacity of about 350mAh/g or greater when discharged with lithium ions at a rate of at least about 200 mA/g; and

(b) combining a cathode with an anode and a solid state electrolyte to form the battery.

19. The method of claim 18, further comprising preparing the electrochemically active material by solid state synthesis.

20. The method of claim 19, wherein the solid phase synthesis comprises mixing and milling precursors or reactants of the electrochemically active material.

21. The method of claim 19, wherein the solid phase synthesis comprises reacting an iron-containing compound and a fluoride.

22. The method of claim 18, further comprising preparing the electrochemically active material by evaporation of one or more precursors of the electrochemically active material.

23. The method of claim 22, wherein the evaporating comprises evaporating a material selected from the group consisting of LiF, FeF₃、FeF₂、LiFeF₃Fe and Li precursors are evaporated.

24. The method of claim 22, wherein said evaporating comprises evaporating a liquid comprising a solvent selected from the group consisting of F₂、CF₄、SF₆And NF₃In the gaseous environment of (2) to react the vaporized precursorShould be used.

25. The method of claim 18, further comprising preparing the electrochemically active material by:

melting one or more precursors of the electrochemically active material;

atomizing the molten precursor into particles; and

cooling the particles to mix the metal component and the lithium compound component at a length dimension of about 20nm or less.

26. The method of claim 25, wherein the cooling is at a rate of at least about 100 kelvin per second.

27. The method of claim 25, wherein the cooling is performed by contacting the particles with a rotating cooling surface.