HK1173560A - Coated positive electrode materials for lithium ion batteries - Google Patents

Description

Coated positive electrode materials for lithium ion batteries

Technical Field

The present invention relates to coated positive electrode active materials for lithium ion batteries, and in particular to lithium rich positive electrode active materials with inert coatings. The invention further relates to batteries having improved performance attributes due to selected coatings of positive electrode active materials.

Background

Lithium batteries are widely used in consumer electronic devices due to their relatively high energy density. Rechargeable batteries are also referred to as secondary batteries, and lithium ion secondary batteries generally have a negative electrode material that can incorporate lithium when the battery is charged. For some existing commercial batteries, the negative electrode material may be graphite and the positive electrode material may include lithium cobalt oxide (LiCoO)₂). In practice, only a moderate portion of the positive electrode active material theoretical capacity can generally be used. At least two other positive electrode active materials based on lithium are currently also used on the market. The two materials are LiMn with a spinel structure₂O₄And LiFePO having an olivine structure₄. The other materials do not provide any significant improvement in energy density.

Lithium ion batteries are generally classified into two types according to their applications. The first category relates to high power batteries, where lithium ion battery cells are designed to deliver high current (amps) in applications such as power tools and Hybrid Electric Vehicles (HEVs). However, such designs result in a reduction in the cell energy, since designs that provide high current typically reduce the total energy that can be delivered from the battery. A second class of designs involves high energy batteries, where lithium ion battery cells are designed to deliver low to medium current (amps) and deliver higher total capacity in applications such as cellular phones, laptop computers, Electric Vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs).

Disclosure of Invention

In a first aspect, the invention relates to a lithium ion battery positive electrode material comprising a lithium ion battery positive electrode material consisting of Li of the formula_1+xM_1-xO₂Active compositions represented by wherein M is a metal element or a combination thereof and 0.01. ltoreq. x.ltoreq.0.3An inorganic coating composition, wherein the coating composition comprises a metal/metalloid fluoride.

In yet another aspect, the invention relates to a lithium ion battery comprising a positive electrode, a negative electrode comprising a lithium incorporation composition, a separator between the positive electrode and the negative electrode, and an electrolyte comprising lithium ions. Typically, the positive electrode comprises an active material, a different conductive powder, and a polymer binder, wherein the positive electrode active material comprises an active composition coated with an inorganic coating composition. The positive electrode active material can have a specific discharge capacity of at least about 190mAh/g at room temperature at a discharge rate of 2C from 4.6 volts to 2.0 volts during the fifteenth charge/discharge cycle. In some embodiments, the active composition may be approximated by the formula Li_1+xM_1-xO₂Wherein M is a metal element or a combination thereof and 0.01. ltoreq. x.ltoreq.0.3, said active composition being coated with an inorganic coating composition.

In another aspect, the invention relates to a lithium ion battery comprising a positive electrode, a negative electrode comprising a lithium incorporation composition, and a separator between the positive electrode and the negative electrode, wherein the positive electrode comprises an active material having an active composition coated with an inorganic composition, a different conductive powder, and a polymeric binder. The positive electrode active material can have a specific discharge capacity of at least about 245mAh/g at room temperature at a discharge rate of C/3 from 4.6 volts to 2.0 volts, an average voltage of at least about 3.55 volts, and a capacity at 40 cycles of at least about 90% of the capacity at 10 cycles.

Drawings

Fig. 1 is a schematic view of a battery structure separated from a container.

FIG. 2 is a graph of uncoated high capacity cathodic lithium oxide material at (a)100 micron and (b)20 micron resolution, respectively, relative to a reference bar as shown in the legend of the distance scale, and at (c) relative to a reference bar as shown in the legend of the distance scale, respectivelyAlF at 100 micron and (d)20 micron resolution₃A set of SEM micrographs of the coated high capacity cathodic lithium metal oxide material.

FIG. 3 is a sample of uncoated (untreated) high capacity cathode lithium metal oxide material and AlF of varying thicknesses₃Curve of X-ray diffraction spectrum of the coated sample.

Fig. 4 is a set of (two) curves of cell voltage versus capacity for an uncoated high specific capacity cathodic lithium metal oxide material cycled (a) at a charge/discharge rate of 0.1C in the first cycle and (b) at a charge/discharge rate of 1/3C in the voltage range of 2.0V to 4.6V in the seventh cycle.

Fig. 5 is a plot of specific discharge capacity versus cycle number for uncoated high capacity cathode lithium metal oxide materials cycled at 0.1C in the first three cycles, 0.2C in the 4 th through 6 th cycles, and 0.33C in the 7 th through 40 th cycles.

FIG. 6 shows (a) uncoated and (b) 7nm AlF₃Coating and (c) passing through 25nm AlF₃A set of TEM micrographs of the coated high specific capacity cathodic lithium metal oxide material.

Fig. 7 is a graph showing differential scanning calorimetry data for high capacity positive electrode active materials (uncoated samples and 4 coated samples).

Fig. 8 is a plot of the electrochemical impedance spectroscopy results for an electrode formed from the positive electrode active material (5 samples of coated material).

FIG. 9 is a 3nm AlF cycled (a) at a charge/discharge rate of 0.1C in the first cycle and (b) at a charge/discharge rate of 1/3C in the voltage range of 2.0V to 4.6V in the seventh cycle₃A set of (two) curves of cell voltage versus specific discharge capacity for coated high capacity cathode lithium metal oxide materials.

FIG. 10 is a 3nm AlF₃Specific discharge capacity versus cycle times for coated high specific capacity cathode lithium metal oxide materialsA plot of numbers that cycles at 0.1C in the first three cycles, 0.2C in the 4 th to 6 th cycles, and 0.33C in the 7 th to 40 th cycles.

FIG. 11 is a graph of 22nm AlF cycled (a) at a discharge rate of 0.1C in the first cycle and (b) at a discharge rate of 1/3C in the voltage range of 2.0V to 4.6V in the seventh cycle₃A set of (two) curves of cell voltage versus specific discharge capacity for coated high specific capacity cathodic lithium metal oxide materials.

FIG. 12 is a22 nm AlF₃A plot of specific discharge capacity versus cycle number for the coated high specific capacity cathodic lithium metal oxide material cycled at 0.1C in the first three cycles, 0.2C in the 4 th to 6 th cycles, and 0.33C in the 7 th to 40 th cycles.

FIG. 13 is uncoated and has 5 different AlFs₃A set of comparative curves of specific discharge capacity versus cycle number for coating thickness of high specific capacity cathodic lithium metal oxide materials cycled at 0.1C in the first three cycles, 0.2C in the 4 th to 6 th cycles, and 0.33C in the 7 th to 40 th cycles.

FIG. 14 shows (a) irreversible capacity loss (IRCL)% versus AlF for high specific capacity cathode materials₃Coating thickness and (b) specific IRCL vs AlF₃Set (two) curves of coating thickness.

FIG. 15 is (a) average voltage vs. AlF for high specific capacity cathode materials₃Coating thickness and (b) average voltage reduction% vs. AlF₃Set (two) curves of coating thickness.

FIG. 16 is a graph of coulombic efficiency versus AlF for high specific capacity cathode materials between the first and 34 th cycles at 0.33C cycle₃Curve of coating thickness.

FIG. 17 is a plot of the x-ray diffraction pattern of lithium metal oxide with one of 4 different metal difluoride coatings.

FIG. 18 shows a display (A)MgF with an average thickness of about 3nm₂A coating and (B) SrF having an average thickness of about 2nm₂A set of transmission electron micrographs of the coating.

Fig. 19 is a plot of cell voltage versus capacity for a first charge and discharge cycle at a rate of C/10 for a battery formed from an uncoated high capacity positive electrode active material.

FIG. 20 is a graph of MgF-mediated pathways₂Cell voltage versus capacity curves for the first charge and discharge cycle at a rate of C/10 for cells formed from the coated high capacity positive electrode active material.

FIG. 21 shows a graph of SrF₂Cell voltage versus capacity curves for the first charge and discharge cycle at a rate of C/10 for cells formed from the coated high capacity positive electrode active material.

FIG. 22 shows a schematic diagram of a filter formed by a filter formed of BaF₂Cell voltage versus capacity curves for the first charge and discharge cycle at a rate of C/10 for cells formed from the coated high capacity positive electrode active material.

FIG. 23 shows a schematic representation of a warp CaF₂Cell voltage versus capacity curves for the first charge and discharge cycle at a rate of C/10 for cells formed from the coated high capacity positive electrode active material.

FIG. 24 is a graph of a positive electrode active material coated with no positive electrode active material or MgF coated with positive electrode active material₂、SrF₂、BaF₂Or CaF₂Curves of specific discharge capacity as a function of cycle number for 5 batteries formed with the coated positive electrode active material.

FIG. 25 is a graph formed from a negative electrode comprising graphite and AlF having an uncoated or specified average thickness₃Positive electrodes of coated high capacity active materials form a graph of specific discharge capacity as a function of cycle number for button cells.

FIG. 26 is a graph showing AlF on a second lithium-rich active material having an average thickness of about 3nm (A) and about 17nm (B)₃One set (two) of transmission electron micrographs of the coating.

Fig. 27 is a plot of cell voltage versus capacity for a first charge and discharge cycle at a rate of C/10 cycling between 2.0V and 4.3V for a battery formed from an alternative positive electrode active material.

FIG. 28 is a schematic diagram showing a structure consisting of AlF₃The coated alternative positive electrode active material forms a cell voltage versus capacity curve for the first charge and discharge cycle at a rate of C/10 cycling between 2.0V and 4.3V.

Fig. 29 is a plot of cell voltage versus capacity for a first charge and discharge cycle at a rate of C/10 cycling between 2.0V and 4.5V for a battery formed from an alternative positive electrode active material.

FIG. 30 is a schematic diagram of a liquid crystal display device composed of a substrate having AlF₃The coated alternative positive electrode active material forms a cell voltage versus capacity curve for the first charge and discharge cycle at a rate of C/10 cycling between 2.0V and 4.5V.

FIG. 31 is uncoated and has 5 different AlFs₃A set of comparative curves of specific discharge capacity versus cycle number for the coating thickness of the replacement positive active material cycled at 0.1C in the first two cycles and 0.33C in the 3 rd to 18 th cycles.

FIG. 32 is uncoated and has 5 different AlFs₃A set of comparative curves of specific discharge capacity versus cycle number for coating thickness replacement positive electrode active materials cycled at 0.1C in the first two cycles and 0.33C in the 3 rd to 18 th cycles between 2.0V and 4.5V.

Detailed Description

It has been found that lithium rich metal oxides can be effectively coated with a metal fluoride coating at relatively small thicknesses to significantly improve the performance of the resulting lithium ion battery. Lithium rich metal oxides can be stably charged to high voltages, resulting in higher discharge capacities relative to some lower voltage materials. The coating can improve a range of properties of the resulting battery. In particular, the coated material may exhibit a high average voltage, which may provide a more consistent voltage over a wide range of battery capacities. The materials can be efficiently synthesized using techniques that can be readily scaled for commercial production. In addition, the materials can be synthesized at high tap densities so that the resulting batteries can exhibit high effective capacities for a given battery volume. In addition, the battery exhibits high specific capacity and excellent cycling when charged and discharged at moderate rates. The inert metal oxide or metal phosphate coating may also provide desired performance attributes to the resulting battery formed from the material. Therefore, the material can be effectively used for commercial applications involving medium discharge capacity (rate capability), such as plug-in hybrid electric vehicles.

The lithium ion batteries described herein have achieved improved cycling performance while exhibiting high specific capacity and high overall capacity. Suitable synthesis techniques for lithium-rich metal oxides include, for example, coprecipitation or sol-gel synthesis. The use of a metal fluoride coating, metal oxide coating, or other suitable coating may provide enhanced cycling performance. The positive electrode material also exhibits a high average voltage over the discharge cycle so that the battery has a high power output and a high specific capacity. The materials can also exhibit high specific capacities at surprisingly high rates (e.g., 2C discharge rates). The battery continues to exhibit high total capacity when cycled due to relatively high tap density and excellent cycling performance. In addition, the positive electrode material exhibits a reduced amount of irreversible capacity loss during the first charge and discharge cycle of the battery so that the negative electrode material can be reduced accordingly. The combination of excellent cycling performance, high specific capacity, and high overall capacity makes the resulting lithium ion battery an improved power source, particularly for high energy applications such as electric vehicles, plug-in hybrid vehicles, and the like.

The battery described herein is a lithium ion battery in which the non-aqueous electrolyte solution contains lithium ions. For secondary lithium ion batteries, lithium ions are released from the negative electrode during discharge so that the negative electrode functions as an anode during discharge, while electrons are generated from oxidation of lithium after the lithium ions are released from the electrode. Accordingly, the positive electrode absorbs lithium ions during discharge through intercalation or the like so that the positive electrode serves as a cathode that consumes electrons during discharge. Upon recharging of the secondary battery, the flow of lithium ions is reversed through the battery, while the negative electrode takes up lithium and the positive electrode releases lithium as lithium ions. Typically, batteries are formed to have lithium ions in the positive electrode material such that initial charging of the battery transfers a substantial portion of the lithium from the positive electrode material to the negative electrode material in preparation for discharging the battery.

The word "element" is used herein in its conventional manner and refers to a member of the periodic table, wherein the element has the appropriate oxidation state if the element is in the composition, and wherein the element is in its elemental form M only when the element is indicated as being in its elemental form⁰. Thus, the metallic element is usually in the metallic state only in its elemental form or in the corresponding alloy in the form of the metallic element. In other words, the metal oxide or other metal composition is generally not a metal other than a metal alloy.

In some embodiments, lithium ion batteries can use positive electrode active materials that are lithium rich relative to a reference homologous electroactive lithium metal oxide composition. In some embodiments, LiMO may be compared to the composition₂Excess lithium is mentioned, where M is one or more metals having an average oxidation state of + 3. The additional lithium in the initial cathode material provides corresponding additional lithium that can be transferred to the negative electrode during charging so that the battery capacity for a given weight of cathode active material can be increased. In some embodiments, the other lithium is obtained at a higher voltage, such that the initial charging occurs at the higher voltage to obtain other capacities represented by the other lithium of the positive electrode.

Lithium-rich lithium metal oxides formed in a suitable manner are believed to have a composite crystal structure in which excess lithium helps to form another crystalline phase. For example, in some embodiments of lithium rich materials, Li₂MnO₃The material can be mixed with layered LiMnO₂From other transition metals having appropriate oxidation states for the component or manganese cationSimilar composite compositions that are cationically substituted are structurally integrated. In some embodiments, the positive electrode material can be represented by two-component notation as Li₂M′O₃·(1-x)LiMO₂Wherein M is one or more metal cations having an average valence of +3, wherein at least one cation is a Mn ion or a Ni ion and wherein M' is one or more metal cations having an average valence of + 4. The compositions are further described, for example, in U.S. patent No. 6,680,143 entitled Lithium Metal Oxide Electrodes for Lithium Cells and batteries issued to sakura (Thackeray) et al, which is incorporated herein by reference. A particularly interesting positive electrode active material has the formula Li_1+xNi_αMn_βCo_γA_δO₂Wherein x is between about 0.05 and about 0.3, α is between about 0.1 and about 0.4, β is between about 0.3 and about 0.65, γ is between about 0 and about 0.4 and δ is between about 0 and about 0.15, and wherein A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof.

Furthermore, Li [ Li ]_0.2Ni_0.175Co_0.10Mn_0.525]O₂Surprisingly large capacities have been achieved as shown in co-pending U.S. patent application 12/332,735 (the' 735 application) entitled "Positive Electrode material for High Specific Discharge Capacity Lithium Ion Batteries," issued to Lopez (Lopez) et al, which is incorporated herein by reference. The materials in the' 735 application were synthesized using a carbonate co-precipitation process. Furthermore, compositions obtained using hydroxide coprecipitation and sol-gel synthesis means achieve extremely High Specific capacities, as in the title "Positive electrode Material for Lithium Ion Batteries with High Specific Discharge Capacity and Process for synthesizing said Material (Positive electrode Material for Lithium Ion Batteries with High Specific Discharge)Capacity and Process for the Synthesis of the Materials) "U.S. application No. 12/246,814 (' 814 application), which is incorporated herein by reference. The composition has a lower risk of combustion relative to some other high capacity cathode materials due to the specific composition having a layered structure and reduced amounts of nickel, thereby improving safety. The compositions use lower amounts of environmentally desirable fewer elements and can be made from starting materials that are cost-appropriate for commercial scale production.

A carbonate co-precipitation process has been performed on desired lithium-rich metal oxide materials having nickel, cobalt, and magnesium cations in the compositions described herein and exhibiting high specific capacity performance. In addition to high specific capacity, the materials also exhibit excellent tap density, allowing the materials to have high overall capacity in fixed volume applications. As shown in the examples below, lithium rich metal oxide materials formed using a carbonate co-precipitation process have improved performance properties. In particular, the particular lithium-rich compositions of the previous paragraph formed by the carbonate co-precipitation process can be used in coated form to obtain the results in the examples below.

The intercalation and deintercalation of lithium ions may induce lattice changes of the electroactive material when using a corresponding battery with an intercalation-based positive electrode active material. As long as the change is substantially reversible, the capacity of the material does not change significantly with cycling. However, it has been found that the capacity of the active material decreases to varying degrees with cycling. Thus, after a number of cycles, the performance of the battery falls below an acceptable value and the battery needs to be replaced. In addition, at the first cycle of the battery, there is typically an irreversible capacity loss that is significantly greater than the capacity loss of each cycle in subsequent cycles. The irreversible capacity loss is equal to the difference between the charge capacity and the first discharge capacity of the new battery. To compensate for this first cycle irreversible capacity loss, additional electroactive material can be incorporated into the negative electrode so that the battery can be fully charged even when this lost capacity is not available during most of the life of the battery. The negative electrode material is substantially consumed due to the inclusion of other negative electrode active materials to compensate for the irreversible capacity loss. Irreversible capacity loss is generally attributable to changes during the initial charge-discharge cycle of the battery material, which changes can be substantially maintained during subsequent cycles of the battery. Some of the irreversible capacity loss can be attributed to the positive electrode active material, and the coated materials described herein provide a reduction in the irreversible capacity loss of the battery.

Suitable coating materials can both improve the long-term cycling performance of the material and reduce the first cycle irreversible capacity loss. While not wishing to be bound by theory, the coating may stabilize the crystal lattice of the positive electrode active material during the absorption and release of lithium ions such that irreversible changes in the crystal lattice are significantly reduced. In particular, metal fluoride compositions can be used as effective coatings. Metal fluoride composition as cathode active material (particularly LiCoO)₂And LiMn₂O₄) The general use of the coating of (a) is described in published PCT application WO2006/109930a entitled "fluoride Compound Coated Cathode Active Material for Lithium secondary batteries and Method for Preparing the Same" to Sun et al, which is incorporated herein by reference.

It has been found that metal fluoride coatings can significantly improve lithium rich layered positive electrode active materials. Specifically, AlF₃May be a desirable coating material due to moderate material costs and relatively low environmental issues associated with lithium ions, but other metal fluorides are also suitable. The performance improvements associated with coating materials can generally involve significantly reducing capacity fade for long-term cycling, significantly reducing first-cycle irreversible capacity loss, and improving capacity. Since the coating material is not believed to function in a unit cycle, it is surprising that the coating material can increase the active material specific capacity. The amount of coating material can be selected to enhance the performance improvement observed. Improvements in lithium rich positive electrode active materials are further describedIn the '735 application and the' 814 application.

The materials described herein also exhibit large tap densities. In general, a higher tap density of positive electrode material results in a higher overall capacity battery when the specific capacity is comparable. Active materials with high tap densities also allow for batteries with greater specific energy and specific power. Generally, batteries with larger capacities may provide longer discharge times for particular applications. Thus, the battery may exhibit significantly improved performance. It is useful to note that during charge/discharge measurements, the specific capacity of the material depends on the discharge rate. The maximum specific capacity of a particular material is measured at an extremely slow discharge rate. In actual use, the actual specific capacity is less than maximum due to discharge at a faster rate. During actual use, a more practical specific capacity can be measured using an appropriate discharge rate that is more similar to the rate during actual use. For low to medium rate applications, a suitable test rate involves discharging the battery over 3 hours. In conventional notation, this is written as C/3 or 0.33C. Faster or lower discharge rates may be used, as desired.

Generally, the improvement in performance attributes of a battery is not entirely related to its coating thickness. The properties will be studied in more detail below and the corresponding results will be given in the examples. In summary, the reduction in irreversible capacity loss tends to plateau at coating thicknesses of about 10 nanometers (nm). In terms of average voltage, the coating helps to reduce the average voltage, but the average voltage does not decrease significantly when the coating is thinner. In terms of specific capacity, as the coating thickness increases, the specific capacity first increases and then decreases. And the specific capacity results vary with cycling and discharge rates.

One set of results presented in the examples below provides information that can be used to evaluate an appropriate coating thickness to achieve desired battery performance for a high voltage battery with appropriate long-term cycling properties. It has been found that irreversible capacity loss is significantly reduced for thicker metal fluoride coatings having a thickness of about 20nm or more. The material with the thick coating also showed good cycling after 34 charge-discharge cycles at a rate of C/3. However, the material showed a significant drop in average voltage. The materials with thicker coatings also exhibit reduced specific capacity relative to thinner coatings. The decrease in specific capacity of materials with thicker coatings is more pronounced at higher rates, which may indicate that the thicker coating prevents lithium ions from moving through the thicker coating.

With a moderate metal fluoride coating thickness between about 8nm and about 20nm, the material exhibits nearly the same reduction in irreversible capacity loss as observed with materials having larger coating thicknesses. Furthermore, the average voltage is greater than that obtained with thicker coatings. In addition, the specific capacity of the material is also greater than its active composition with a greater coating thickness. However, positive electrode active materials with moderate coating thicknesses can have significantly poorer coulombic efficiencies relative to materials with greater coating thicknesses. In other words, the specific capacity of materials with greater coating thickness decays more rapidly with cycling. Thus, if the results are extrapolated to more cycles, it is expected that positive electrode active materials with intermediate thickness metal fluoride coatings will have undesirably poor cycling properties in most applications.

Surprisingly, positive electrode active materials with thinner metal fluoride coatings exhibit surprisingly desirable results. Thus, positive electrode active materials having a metal fluoride coating with a coating thickness of about 0.5nm to about 12nm have desirable and surprisingly good properties when incorporated into a battery. The material exhibits less irreversible capacity loss reduction. The irreversible capacity loss in the context of long-term cycling is not the most important property of the material. Positive electrode active materials with thinner metal fluoride coatings have larger average voltages comparable to the average voltage of the uncoated material. The material may have a high initial specific capacity, and the material may exhibit desirable coulombic efficiency such that decay with cycling is low at moderate rates at least to 40 cycles.

Rechargeable batteries have various uses, such as mobile communication devices (e.g., telephones), mobile entertainment devices (e.g., MP3 players and televisions), portable computers, combinations of such devices with a wide range of applications, and transportation devices (e.g., automobiles and forklifts). Most batteries used in such electronic devices have a fixed volume. It is therefore highly desirable that the positive electrode materials used in such batteries have a high tap density so that there is substantially more chargeable material in the positive electrode to achieve a higher overall capacity of the battery. The batteries described herein, incorporating positive electrode active materials that are improved in specific capacity, tap density, and cycling, can provide improved performance to consumers, particularly in medium current applications.

The batteries described herein are suitable for vehicular applications. In particular, the batteries may be used in battery packs for hybrid, plug-in hybrid, and electric vehicles. The vehicle typically has a battery pack selected to balance weight, volume, and capacity. Although larger batteries may provide a greater range of electrical operation, larger batteries take up more space, making them difficult to use for other purposes, and have a greater weight that can degrade performance. Thus, due to the high capacity of the cells described herein, batteries that produce the desired amount of total power can be prepared in an appropriate volume, and can accordingly achieve excellent cycling performance as described herein.

Battery structure

Referring to fig. 1, a battery 100 is schematically shown having a negative electrode 102, a positive electrode 104, and a separator 106 between the negative electrode 102 and the positive electrode 104. The cell may comprise a plurality of positive electrodes and a plurality of negative electrodes (e.g., in a stack) and appropriately placed separators. The electrolyte in contact with the electrodes provides ionic conductivity through the separator between the electrodes of opposite polarity. The cell typically includes current collectors 108, 110 connected to the negative electrode 102 and the positive electrode 104, respectively.

Lithium has been used in both primary and secondary batteries. An attractive feature of lithium metal is its light weight and the fact that it is the most electropositive metal, and lithium ion batteries can also advantageously utilize various aspects of that feature. Certain forms of metals, metal oxides, and carbon materials are known to incorporate lithium ions into their structures by intercalation, alloying, or similar mechanisms. It is further described herein that desirable mixed metal oxides can be used as electroactive materials for positive electrodes in secondary lithium ion batteries. A lithium ion battery refers to a battery in which the negative electrode active material is a material that absorbs lithium during charging and releases lithium during discharging. If lithium metal is used as the anode itself, the resulting battery may be generally referred to as a lithium battery.

The nature of the negative electrode intercalation material affects the voltage of the resulting cell because the voltage is the difference between the half-cell potentials of the cathode and anode. Suitable negative electrode lithium intercalation compositions can include, for example, graphite, synthetic graphite, coke, fullerene, niobium pentoxide, tin alloys, silicon, titanium oxide, tin oxide, and lithium titanium oxide, such as Li_xTiO₂(x is more than 0.5 and less than or equal to 1) or Li_1+xTi_2-xO₄(x is more than or equal to 0 and less than or equal to 1/3). Other Negative Electrode materials are described in co-pending U.S. patent application No. 2010/0119942 entitled "Composite Compositions, Negative electrodes with Composite Compositions, and Corresponding Batteries to komar (Kumar), and U.S. patent application No. 2009/0305131 entitled" Lithium Ion Batteries with particulate Negative Electrode Compositions "to komar et al, both of which are incorporated herein by reference.

The positive and negative electrode active compositions are typically powder compositions that are held together in the respective electrodes with a polymeric binder. The binder may provide ionic conductivity to the active particles when in contact with the electrolyte. Suitable polymeric binders include, for example, polyvinylidene fluoride, polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylate, rubber (e.g., ethylene-propylene-diene monomer (EPDM) rubber or Styrene Butadiene Rubber (SBR)), copolymers thereof, or mixtures thereof. The particulate loading in the binder may be greater, for example greater than about 80 wt%. To form the electrode, the powder may be blended with the polymer in a suitable liquid (e.g., a solvent for the polymer). The resulting paste can be pressed into an electrode structure. In some embodiments, the battery may be constructed based on the method described in co-pending U.S. patent application No. 2009/0263707 entitled High Energy Lithium Ion Secondary battery (High Energy Lithium Ion Secondary Batteries) to Buckley et al, which is incorporated herein by reference.

The positive electrode composition and possibly the negative electrode composition also typically include a conductive powder that is different from the electroactive composition. Suitable supplemental conductive powders include, for example, graphite, carbon black, metal powders (e.g., silver powders), metal fibers (e.g., stainless steel fibers), and the like and combinations thereof. Typically, the positive electrode can include about 1 wt% to about 25 wt%, and in other embodiments about 2 wt% to about 15 wt% of the different conductive powders. Those skilled in the art will recognize that other ranges of conductive powder amounts falling within the explicit ranges above are also encompassed by the present disclosure and are within the present disclosure.

The electrodes are typically connected to a conductive current collector to facilitate the flow of electrons between the electrodes and an external circuit. The current collector may comprise a metal, such as a metal foil or a metal grid. In some embodiments, the current collector may be formed from nickel, aluminum, stainless steel, copper, or the like. The electrode material is cast as a thin film on the current collector. The electrode material and current collector may then be dried, for example in an oven, to remove the solvent from the electrode. In some embodiments, about 2kg/cm of dry electrode material may be applied in contact with the current collector foil or other structure²To about 10kg/cm²(kg/cm) pressure.

The separator is located between the positive electrode and the negative electrode. The separator is electrically insulating while providing at least a selected ionic conductivity between the two electrodes. Various materials may be used as the spacer. Commercially available separator materials are typically formed from polymers such as polyethylene and/or polypropyleneThe polymer is a porous plate that can provide ionic conductivity. Commercially available polymeric separators include, for example, Hilded from Herschel Selaginese, Charlotte, N.CA series of spacer materials. Meanwhile, ceramic-polymer composite materials have been developed for spacer applications. The composite separator may be stable at higher temperatures, and the composite material may significantly reduce the risk of combustion. Polymer-ceramic composites for Separator materials are further described in U.S. patent application No. 2005/0031942 entitled "electrical Separator, Method for Producing the Same, and use thereof" issued to hennig (hennig) et al, which is incorporated herein by reference. The polymer-ceramic composite for lithium ion battery separators is sold under the trademark Sapalin: () Sold by the winning Industries (Evonik Industries), germany.

A solution containing solvated ions is referred to as an electrolyte, and an ionic composition that dissolves in an appropriate liquid to form solvated ions is referred to as an electrolyte salt. Electrolytes for lithium ion batteries can include one or more selected lithium salts. Suitable lithium salts generally have an inert anion. Suitable lithium salts include, for example, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl imide), lithium trifluoromethanesulfonate, lithium tris (trifluoromethylsulfonyl) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride, lithium difluorooxalato borate, and combinations thereof. Traditionally, the electrolyte contains a 1M concentration of lithium salt, although greater or lesser concentrations may be used.

For lithium ion batteries of interest, a non-aqueous liquid is typically used to dissolve the lithium salt. The solvent typically does not dissolve the electroactive material. Suitable solvents include, for example, propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyltetrahydrofuran, dioxolane, tetrahydrofuran, methyl ethyl carbonate, γ -butyrolactone, dimethyl sulfoxide, acetonitrile, formamide, dimethylformamide, triglyme (tri (ethylene glycol) dimethyl ether), diglyme (diethylene glycol dimethyl ether), DME (glyme or 1, 2-dimethoxyethane or ethylene glycol dimethyl ether), nitromethane and mixtures thereof.

The electrodes described herein can be incorporated into various commercial battery designs. For example, the cathode composition can be used in prismatic cells, wound cylindrical cells, button cells, or other suitable cell shapes. The test in each example was performed using a button-type unit cell. The cell may comprise a single cathode structure or a plurality of cathode structures assembled in parallel and/or series electrical connection. While positive electrode active materials can be used in primary batteries or in single charge applications, the resulting batteries typically have desirable cycling properties for secondary battery applications over multiple cycles of the battery.

In some embodiments, the positive and negative electrodes and the separator therebetween can be stacked, and the resulting stacked structure can be rolled into a cylindrical or prismatic configuration to form a battery structure. An appropriate conductive tab may be welded (or the like) to the current collector and the resulting jellyroll structure may be placed in a metal can or polymer can with the negative and positive tabs welded to appropriate external contacts. Electrolyte is added to the cartridge and the cartridge is sealed to complete the cell. Some rechargeable commercially available batteries currently in use include, for example, cylindrical 18650 batteries (18 mm in diameter and 65mm in length) and 26700 batteries (26 mm in diameter and 70mm in length), although other battery sizes may be used.

Positive electrode active material

The positive electrode active material comprises a lithium intercalated metal oxide composition. In some embodiments, the lithium metal oxide composition can comprise a composition enriched in lithium relative to a reference composition. In general, LiMO may be mixed₂Taken as a reference composition, and the lithium-rich composition can be approximated by the formula Li_1+xM_1-yO₂Mention is made of where M represents one or more metals and y is related to x on the basis of the average valence of the metals. In some embodiments, it is generally believed that the lithium-rich composition can form a layered composite crystal structure, and for the embodiments, x is approximately equal to y. In some embodiments, the composition comprises Ni, Co and Mn ions and optionally comprises one or more other metal ion dopants. It has surprisingly been found that dopants can improve the performance of the resulting composition with respect to capacity after cycling. Furthermore, for the coated samples, it was also found that doping can increase the average voltage and reduce irreversible capacity loss to some extent. The desired electrode active material can be synthesized using the synthesis approaches described herein.

Lithium-rich composition Li_1+xM_1-yO₂Other lithium is provided that can be used to contribute to the capacity of the battery. The battery can operate at higher voltages due to additional lithium loading to the negative electrode during charging. Thus, the materials provide desirable high voltage materials with higher specific capacities.

In some particularly interesting compositions, the composition may be prepared from compounds of formula Li_1+xNi_αMn_βCo_γA_δO₂Described, wherein x is between about 0.01 and about 0.3, α is between about 0.1 and about 0.4, β is between about 0.3 and about 0.65, γ is between about 0 and about 0.4, δ is between about 0 (or 0.001 if not zero) and about 0.15, and wherein A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof. In some embodiments, the sum of x + α + β + γ + δ in the positive electrode active material is approximately equal to 1.0. A when present in small amounts may be considered a dopant element. Those skilled in the art will recognize that the present disclosure encompasses and is within the present disclosure other ranges of parameter values falling within the explicit ranges set forth above. Coatings for such materials are further described below.

For some embodiments of the materials described herein, sakurane and coworkers have proposed composite crystal structures of some lithium-rich metal oxide compositions, where Li₂M′O₃Composition and LiMO₂The components are structurally integrated into a layered structure. The electrode material can be represented by the two-component notation as b Li₂M′O₃·(1-b)LiMO₂Wherein M is one or more metal elements having an average valence of +3 and wherein at least one element is Mn or Ni and M' is a metal element having an average valence of +4 and 0 < b < 1, and in some embodiments 0.03. ltoreq. b.ltoreq.0.9. For example, M may be Ni⁺²、Co⁺³And Mn + 4. The general formula of the composition can be written as Li_1+b/(2+b)M′_2b/(2+b)M_2(1-b)/(2+b)O₂. This equation conforms to the sum of x + α + β + γ + δ in the equation of the previous paragraph (where x ═ b/(2+ b)) is equal to 1. It has been found that batteries formed from such materials are comparable to the use of the corresponding LiMO₂The composition forms a battery that can be cycled at higher voltages and has higher capacity. Such materials are generally set forth in U.S. patent 6,680,143 entitled "lithium metal oxide electrode for lithium cells and batteries" issued to saxorey et al and U.S. patent 6,677,082 entitled "lithium metal oxide electrode for lithium cells and batteries" issued to saxorey et al, both of which are incorporated herein by reference. Sakrey confirmed that Mn, Ti and Zr were particularly useful as M' and Mn and Ni as M.

The structure of some specific layered structures is further described in saxaley et al "for lithium rich Li for lithium batteries_1+xM_1-xO₂Review of the structural complexity of electrodes (M ═ Mn, Ni, Co) (Comments on the structural complexity of lithium-rich Li_1+xM_1-xO₂Electrochemistry (M ═ Mn, Ni, Co) for lithium batteries) ", electrochemical Communications (Electrochemistry Communications)8(2006), 1531-1538, which are incorporated herein by reference. The study reported in this article illustrates a study having the formula Li_1+x[Mn_0.5Ni_0.5]_1-xO₂And Li_1+x[Mn_0.333Ni_0.333Co_0.333]_1-xO₂The composition of (1). This article also illustrates the structural complexity of the layered material.

Recently, Kang (Kang) and co-workers have described having the formula Li for use in secondary batteries_1+xNi_αMn_βCo_γM′_δO_2-zF_zWherein M' ═ Mg, Zn, Al, Ga, B, Zr, Ti, x is between about 0 and 0.3, α is between about 0.2 and 0.6, β is between about 0.2 and 0.6, γ is between about 0 and 0.3, δ is between about 0 and 0.15 and z is between about 0 and 0.2. The metal range and fluorine are proposed to improve the cell capacity and stability of the resulting layered structure during electrochemical cycling. See U.S. patent 7,205,072 entitled Layered cathode materials for lithium ion rechargeable batteries (' 072 patent) to health et al, which is incorporated herein by reference. This reference reports cathode materials with capacities below 250mAh/g (milliamp hour/gram) after cycling at room temperature 10 times at unspecified rates that are assumed to increase performance values. Kang et al examined the inclusion of Li_1.2Ni_0.15Mn_0.55Co_0.10O₂Similar to the compositions tested in the examples below.

The results obtained in the' 072 patent relate to the solid state synthesis of materials that do not achieve comparable cycling capacities to batteries formed using cathode active materials formed using a co-precipitation process. The improved properties of materials formed by co-precipitation are further described in the '814 and' 735 applications described above. The co-precipitation process for the dopant materials described herein is further described below.

The performance of the positive electrode active material is affected by many factors. It has been found that thin metal fluoride coatings or other inorganic coatings can significantly improve many important performance parameters. Further, the average particle diameter and the particle diameter distribution are two of the basic properties characterizing the positive electrode active material, and the properties affect the discharge capacity and tap density of the material. Since batteries have a fixed volume, it is desirable for the materials used in the positive electrode of the battery to have a high tap density if the specific capacity of the material can be maintained at a desirably high value. Thus, the total capacity of the battery may be higher due to the presence of more chargeable material in the positive electrode. Coatings may be added when forming the materials described herein using the described processes, while still obtaining good tap density. In general, tap densities of at least about 1.3 grams per milliliter (g/mL), in other embodiments at least about 1.6g/mL, and in some embodiments at least about 2.0g/mL, can be obtained using a commercially available tap densitometer using appropriate tap parameters to obtain tap densities. Those skilled in the art will recognize that the present disclosure encompasses and falls within the scope of other tap densities within the specific ranges set forth above.

Synthesis method

The synthesis approaches described herein can be used to form lithium-rich cathode active materials with improved specific capacity and high tap density upon cycling. The synthesis method has been applied to the synthesis of compounds having the formula Li_1+xNi_αMn_βCo_γA_δO₂The composition of (a), wherein x is between about 0.01 and about 0.3, a is between about 0.1 and about 0.4, β is between about 0.3 and about 0.65, γ is between about 0 and about 0.4, δ is between about 0 and about 0.1, and wherein a is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof. In some embodiments, the sum of x + α + β + γ + δ in the positive electrode active material is approximately equal to 1.0, and for such embodiments, a layered crystalline structure may be formed as described above. The synthesis is also suitable for commercial scale. In particular, a co-precipitation process can be used to synthesize the desired positive electrode material that is lithium-rich with desirable results. Further, the material having the metal fluoride may be coated using a solution-assisted precipitation method discussed in detail below.

In the coprecipitation process, the metal salt is added as requiredThe molar ratio is dissolved in an aqueous solvent (e.g., purified water). Suitable metal salts include, for example, metal acetates, metal sulfates, metal nitrates, and combinations thereof. The solution concentration is generally chosen to be between 1M and 3M. The relative molar amounts of the metal salts can be selected according to the desired formula of the product material. Likewise, dopant elements as well as other metal salts may be introduced in appropriate molar amounts to incorporate the dopant into the precipitation material. May then be added, for example, by adding Na₂C0₃And/or ammonium hydroxide to adjust the pH of the solution to precipitate the metal hydroxide or carbonate with the desired amount of the metal element. Typically, the pH may be adjusted to a value between about 6.0 to about 9.0. The solution may be heated and stirred to promote precipitation of the hydroxide or carbonate. The precipitated metal hydroxide or carbonate may then be separated from the solution, washed and dried to form a powder, followed by further processing. For example, drying may be performed in an oven at about 110 ℃ for about 4 hours to about 12 hours. Those skilled in the art will recognize that the present disclosure encompasses and is within the scope of the present disclosure other process parameters within the explicit ranges set forth above.

The collected metal hydroxide or carbonate powder can then be subjected to a heat treatment to convert the hydroxide or carbonate composition to a corresponding oxide composition while removing water or carbon dioxide. Typically, the heat treatment may be performed in an oven, furnace, or the like. The heat treatment may be performed in an inert atmosphere or an atmosphere in which oxygen is present. In some embodiments, the material may be heated to a temperature of at least about 350 ℃ and in some embodiments from about 400 ℃ to about 800 ℃ to convert the hydroxide or carbonate to an oxide. The heat treatment may generally be performed for at least about 15 minutes, in other embodiments from about 30 minutes to 24 hours or more, and in other embodiments from about 45 minutes to about 15 hours. A heat treatment may additionally be performed to improve the crystallinity of the product material. This calcination step for forming the crystalline product is typically performed at a temperature of at least about 650 ℃, and in some embodiments from about 700 ℃ to about 1200 ℃, and in other embodiments from about 700 ℃ to about 1100 ℃. The calcination step to modify the structural properties of the powder may generally be performed for at least about 15 minutes, in other embodiments from about 20 minutes to about 30 hours or more, and in other embodiments from about 1 hour to about 36 hours. The heating step may be combined with an appropriate temperature ramp-up to produce the desired material, as desired. It will be recognized by those skilled in the art that other temperature and time ranges within the explicit ranges above are also contemplated and are within the present disclosure.

The lithium element may be incorporated into the material at one or more selected steps of the process. For example, the lithium salt may be incorporated into the solution by adding a hydrated lithium salt before or after performing the precipitation step. In this way, the lithium species are incorporated into the hydroxide or carbonate material in the same manner as other metals. Additionally, due to the nature of lithium, lithium elements can be incorporated into the material in a solid state reaction without adversely affecting the resulting properties of the product composition. Thus, for example, a suitable amount of a lithium source (e.g., LiOH H), typically a powder, can be added₂O、LiOH、Li₂CO₃Or a combination thereof) with the precipitated metal carbonate or metal hydroxide. The powder mixture is then subjected to a further heating step to form an oxide and then a crystalline end product material.

Additional details of the hydroxide co-precipitation process are set forth in the above-referenced' 814 application. Additional details of the carbonate co-precipitation process are set forth in the above-mentioned' 735 application.

Coating and method of forming coating

It has been found that inert inorganic coatings (e.g., metal fluoride coatings) can significantly improve the performance of the lithium rich layered positive electrode active materials described herein. However, there is a trade-off in the variation of the resulting battery properties with coating thickness. The effect of the coating on battery performance was evaluated against a matrix of important battery performance parameters, as described herein. Evaluating performance using coating thickness yields a relatively complex relationship. It has been surprisingly found that a thin coating (no more than about 8nm thick) can achieve the best overall performance improvement. The improvement of the battery properties is described in detail in the following section.

The coatings can improve the performance of the lithium-rich high capacity compositions described herein in lithium ion secondary batteries. Generally, selected metal fluorides or metalloid fluorides can be used as the coating. Also, fluoride coatings with combinations of metal and/or metalloid elements can be used. Metal/metalloid fluoride coatings have been proposed for stabilizing the performance of positive electrode active materials for lithium secondary batteries. Suitable metal and metalloid elements for fluoride coatings include, for example, Al, Bi, Ga, Ge, In, Mg, Pb, Si, Sn, Ti, Tl, Zn, Zr, and combinations thereof. Aluminum fluoride can be a desirable coating material because it is reasonably cost effective and considered environmentally benign. The metal fluoride coating is outlined in PCT published application WO2006/109930a entitled "fluoride compound coated cathode active material for lithium secondary batteries and method of making the same" to grandson et al, which is incorporated herein by reference. The published patent application provides information on LiF, ZnF₂Or AlF₃Coated LiCoO₂The result of (1). The above-mentioned grandchild PCT application specifically relates to the following fluorochemical compositions: CsF, KF, LiF, NaF, RbF, TiF, AgF₂、BaF₂、CaF₂、CuF₂、CdF₂、FeF₂、HgF₂、Hg₂F₂、MnF₂、MgF₂、NiF₂、PbF₂、SnF₂、SrF₂、XeF₂、ZnF₂、AlF₃、BF₃、BiF₃、CeF₃、CrF₃、DyF₃、EuF₃、GaF₃、GdF₃、FeF₃、HoF₃、InF₃、LaF₃、LuF₃、MnF₃、NdF₃、VOF₃、PrF₃、SbF₃、ScF₃、SmF₃、TbF₃、TiF₃、TmF₃、YF₃、YbF₃、TlF₃、CeF₄、GeF₄、HfF₄、SiF₄、SnF₄、TiF₄、VF₄、ZrF₄、NbF₅、SbF₅、TaF₅、BiF₅、MoF₆、ReF₆、SF₆And WF₆。

AlF₃Coating pair LiN_1/3Co_1/3Mn_1/3O₂The effect of the cycle characteristics of (1) is further described in the article of Sunzen et al for improving Li [ Ni ] for lithium secondary batteries_1/3Co_1/3Mn_1/3]O₂AlF for high voltage cycling performance of cathode materials₃Coating (AlF)₃-Coating to Improve High Voltage Cycling Performance of Li[Ni_1/3Co_1/3Mn_1/3]O₂Cathodal Materials for Lithium Secondary Batteries ", journal of the electrochemical Society, 154(3), a168-a172 (2007). In addition, AlF₃Coating pair LiNi_0.8Co_0.1Mn_0.1O₂The influence of the cycling performance of (D) is further described in the article "AlF by AlF" by Wu (Woo) et al₃Coated Li [ Ni ]_0.8Co_0.1Mn_0.1]O₂Significant Improvement of electrochemical Performance of cathode material (Significant Improvement of electrochemical Performance of AlF)₃-Coated Li[Ni_0.8Co_0.1Mn_0.1]O₂Cathode Materials) ", journal of the electrochemical society, 154(11) a1005-a1009(2007), which article is incorporated herein by reference. Using Al₂O₃Coatings to increase capacity and reduce irreversible capacity loss can be found in Wu (Wu) et al, "high capacity, surface modified Li with Low irreversible capacity loss [ Li_(1-x)/3Mn_(2-x)/3Ni_x/3Co_x/3]O₂Layered cathode (High Capacity, Surface-Modified Layered Li [ Li ]_(1-x)/3Mn_(2-x)/3Ni_x/3Co_x/3]O₂Cathodods with Low IrversibleCapacity Low) ", Electrochemical and Solid State Letters, 9(5) A221-A224(2006), which is incorporated herein by reference. Improved metal oxide coatings are described in the issued VancattChalan et al, entitled "Metal oxide Coated Positive Electrode Materials for Lithium Ion Batteries," is incorporated herein by reference in co-pending U.S. provisional patent application No. 61/253,286. Using LiNiPO₄The improved cycle performance of the coating is described in the article by Li-Ni-PO₄Treatment to enhance high capacity xLi₂MnO₃(1-x)LiMO₂(M ═ Mn, Ni, Co) discharge capability of electrode (Enhancing the rate capability of high capacity xLi)₂MnO₃(1-x)LiMO₂(M＝Mn，Ni，Co)electrodes by Li-Ni-PO₄"electrochemical communication 11, 748-.

It has been found that metal/metalloid fluoride coatings can significantly improve the performance of lithium rich layered compositions for lithium ion secondary batteries. See, for example, the above-referenced '814 and' 735 applications. In particular, the coating can improve battery capacity. However, the coating itself is not electrochemically active. When the specific capacity loss due to the amount of coating added to the sample exceeds a certain level, where the benefits of adding the coating are offset by its electrochemical inertness, a decrease in battery capacity can be expected. In general, the amount of coating can be selected to strike a balance between the beneficial stability due to the coating and the specific capacity loss due to the weight of coating material that generally does not directly contribute to the high specific capacity of the material.

However, it has been found that the variation of the battery properties with the coating thickness is complex. In particular, the coating also affects other properties of the active material, such as average voltage, irreversible capacity loss, coulombic efficiency, and impedance. The desired coating thickness can be selected based on an evaluation of the overall range of battery properties observed for a particular coating thickness. In general, the coating may have a thickness of about 0.05nm to about 50 nm. However, as further described below, it has been surprisingly found that thinner coatings can provide the best overall performance for a wide range of cycling secondary lithium ion batteriesA performance parameter. In some particularly interesting embodiments, the coating has a thickness of about 0.5nm to about 12nm, in other embodiments about 1nm to about 10nm, in other embodiments 1.25nm to about 9nm, and in other embodiments about 1.5nm to about 8 nm. Those skilled in the art will recognize that the present disclosure also encompasses and falls within the scope of other coating materials that fall within the scope of the aforementioned definitions. Through AlF₃AlF in coated metal oxide materials effective to improve uncoated material capacity₃The amount is related to the particle size and surface area of the uncoated material. Generally, the amount of coating material is between about 0.01 mole% to about 10 mole%, in other embodiments about 0.05 mole% to about 7 mole%, in other embodiments about 0.1 mole% to about 5 mole%, and in other embodiments about 0.2 mole% to about 4 mole% relative to the total metal content of the particle. Those skilled in the art will recognize that the present disclosure also encompasses and falls within the scope of other coating materials that fall within the scope of the aforementioned definitions.

The fluoride coating may be deposited using solution-based precipitation. The powder of the positive electrode material may be mixed in a suitable solvent (e.g., an aqueous solvent). The soluble composition of the desired metal/metalloid can be dissolved in a solvent. NH4F may then be gradually added to the dispersion/solution to precipitate the metal fluoride. The total amount of coating reactants can be selected to form a desired amount of coating, and the ratio of coating reactants can be based on the stoichiometry of the coating material. Specifically, a coating of a desired thickness can be formed by adding appropriate amounts of coating reactants. The choice of the amount of coating material can be verified by examining the product particles using electron microscopy as described in the examples below. The coating mixture may be heated to an appropriate temperature (e.g., in the range of about 60 ℃ to about 100 ℃ for an aqueous solution) and held for about 20 minutes to about 48 hours during the coating process to facilitate the coating process. After removing the coated electroactive material from the solution, the material may be dried and heated to a temperature of typically about 250 ℃ to about 600 ℃ for about 20 minutes to about 48 hours to complete the formation of the coated material. Heating may be in a nitrogen atmosphereOr other substantially oxygen-free atmosphere. For forming AlF₃、MgF₂、CaF₂、SrF₂And BaF₂The specific procedure for coating is described in the examples below. Inert metal oxide coating (e.g. Al)₂O₂And Li-Ni-PO₄Coating) is described in the article cited above.

Performance of battery

Batteries formed from the coated positive electrode active materials described herein exhibit excellent performance under practical discharge conditions in medium current applications. In particular, the active materials have shown high specific capacity at moderate discharge rates upon cycling of the battery. In addition, some coated positive electrode active materials have shown improved cycling, thereby expecting multiple cycles. It has been surprisingly found that thinner coatings can provide more desirable overall performance characteristics as compared to batteries formed from positive electrode active materials having thicker coatings. In particular, thinner coatings have improved cycling and larger average discharge voltages. Although active materials with thinner coatings provide less reduction in irreversible capacity loss for a battery, the thin coatings can be used to form batteries with somewhat reduced irreversible capacity loss, and other improved properties of batteries formed from materials with thinner coatings are more important than differences in irreversible capacity loss. Thus, it has been found that coatings having an average thickness of from about 0.5nm to about 8nm provide, among other things, the desired balance to achieve superior performance characteristics.

As described above, the irreversible capacity loss is the difference between the first charge specific capacity and the first discharge specific capacity. For the values described herein, irreversible capacity loss was evaluated against a lithium metal negative electrode against a positive electrode active material background. It is desirable to reduce irreversible capacity loss so that no additional negative electrode active material is required to balance the final, non-cycled positive electrode active material. In some embodiments, the irreversible capacity loss is no more than about 60mAh/g, in other embodiments no more than about 55mAh/g, and in other embodiments from about 30mAh/g to about 50 mAh/g. The irreversible capacity loss can be between about 40mAh/g to about 60mAh/g with respect to a balance of various cell parameters. Also, in some embodiments, the irreversible capacity loss is no more than about 19% and in other embodiments no more than about 18% of the first cycle specific charge capacity. Those skilled in the art will recognize that the present disclosure encompasses and falls within other irreversible capacity loss ranges.

For some applications, the average voltage may be an important parameter of the battery. The average voltage may be related to the capacity available above a certain voltage. Therefore, in addition to having a high specific capacity, it is desirable for the positive electrode active material to cycle at a high average voltage. For materials described herein that cycle between 4.6V and 2.0V, the average voltage may be at least about 3.475V, in other embodiments at least about 3.5V, in other embodiments at least about 3.525V, and in other embodiments from about 3.55V to about 3.65V. Those skilled in the art will recognize that the present disclosure encompasses and is within the present disclosure other average voltage ranges within the explicit ranges set forth above.

In general, various similar test procedures can be used to evaluate the capacity performance of a battery positive electrode material. Some specific test procedures are set forth to evaluate the performance values described herein. Suitable test procedures are described in more detail in the examples below. Specifically, the battery can be cycled between 4.6 volts and 2.0 volts at room temperature, although other ranges can be used and different results obtained accordingly. In addition, the specific capacity is extremely dependent on the discharge rate. Likewise, notation C/x indicates that the cell was discharged at a rate such that the cell was sufficiently discharged to the selected voltage minimum within x hours.

In some embodiments, the positive electrode active material has a specific capacity of at least about 245 milliamp hours per gram (mAh/g) during the tenth cycle at a discharge rate of C/3, in other embodiments at least about 250mAh/g, and in other embodiments from about 255mAh/g to about 265 mAh/g. Further, the 40 th cycle discharge capacity of the material cycled at a discharge rate of C/3 is at least about 94%, and in other embodiments at least about 95% of the 7 th cycle discharge capacity. The remaining amount of specific capacity at 40 cycles relative to the specific capacity at the seventh cycle may also be referred to as coulombic efficiency, as further described in the examples. Furthermore, the coated material may exhibit surprisingly good discharge capability. In particular, a material discharged at a rate of 2C from 4.6V to 2.0V at room temperature at the 15 th charge/discharge cycle may have a specific discharge capacity of at least about 190mAh/g, in other embodiments at least about 195 mAh/and in other embodiments at least about 200 mAh/g. One skilled in the art will recognize that other specific capacity ranges are contemplated and are within the present disclosure.

In general, the results herein show that a balance of factors allows for particularly desirable battery performance for a thin coating on the positive electrode active material. The results in the examples show that thicker coatings can result in greater impedance, which can contribute to the observed capacity and voltage performance. Excellent specific capacity, coulombic efficiency and average voltage can be obtained by using a proper thin coating.

Examples of the invention

Examples include data obtained using a button-type cell and other data obtained from a cylindrical cell. The formation of a button cell using a lithium foil negative electrode is summarized in the introduction to the present invention, and the formation of a button cell using a carbon-based electrode is described in example 5 below. The button cell cells tested in examples 1, 3 and 4 were manufactured according to the procedure outlined herein. Mixing Lithium Metal Oxide (LMO) powder with acetylene black (SpubeutTM (SuperP)^TM) From Timcal, Inc., Switzerland) and graphite (KS 6)^TMAvailable from temka ltd) to form a homogeneous powder mixture. PVDF (KF 1300) of polyvinylidene difluoride alone^TMPurchased from wuyu (Kureha) corporation, japan) was mixed with N-methyl-pyrrolidone NMP (Honeywell-Riedel-de-Haen) and stirred overnight to form a PVDF-NMP solution. The homogeneous powder mixture was then added to the PVDF-NMP solution and mixed for about 2 hours to form a homogeneous slurry. Will be provided withThe slurry was applied to an aluminum foil current collector to form a wet film.

The positive electrode material was formed by drying the aluminum foil current collector with the wet film in a vacuum oven at 110 ℃ for about 2 hours to remove NMP. The positive electrode material is pressed between the rolls of the plate mill to obtain a positive electrode having the desired thickness. An example of a positive electrode composition produced using the above process and having a ratio of LMO: acetylene black: graphite: PVDF of 80: 5: 10 is shown below.

The positive electrode was placed in an argon-filled glove box to make a button-type cell. Lithium foil (FMC lithium) with a thickness of 150 microns was used as the negative electrode. The electrolyte is 1M LiPF₆A solution by mixing LiPF₆The salt was formed by dissolving in a 1: 1 volume ratio mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate (available from Ferro corporation, Ohio, USA). A three-layer (polypropylene/polyethylene/polypropylene) microporous separator (2320, available from hilgard, LLC, NC, usa) impregnated with electrolyte was placed between the positive and negative electrodes. A few more drops of electrolyte were added between the electrodes. The electrodes were then sealed in 2032 button cell hardware (baohquan (Hohsen) inc., japan) using a crimping process to form button cell batteries. The resulting button-type unit cells were tested using a makerr (Maccor) cycle tester to obtain a charge-discharge curve and cycle stability after several cycles. All electrochemical data contained herein were obtained at three rates with successive cycles (first three cycles at 0.1C (C/10), 4 th to 6 th at 0.2C (C/5), or seventh and further cycles at 0.33C (C/3)).

Example 1 Metal sulfate with Na ₂ CO ₃ /NH ₄ OH reaction for carbonate coprecipitation

This example demonstrates the use of a carbonate co-precipitation process toForming the desired cathode active material. Adding stoichiometric amount of metal sulfate (NiSO)₄·xH₂O、CoSO₄·xH₂O and MnSO₄·xH₂O) is dissolved in distilled water to form an aqueous metal sulfate solution. Separately preparing a solution containing Na₂CO₃And NH₄An aqueous solution of OH. To form a sample, the two solutions were gradually added to the reaction vessel to form a metal carbonate precipitate. The reaction mixture is stirred and kept at a temperature between room temperature and 80 ℃ for 2-24 hours. The pH of the reaction mixture is between 6 and 9. Generally, the aqueous metal sulfate solution has a concentration of 1M to 3M, and Na₂CO₃/NH₄The aqueous OH solution has 1M to 4M Na₂CO₃Concentration and 0.2M to 2M NH₄The OH concentration. The metal carbonate precipitate was filtered off, washed several times with distilled water, and dried at 110 ℃ for about 16 hours to form a metal carbonate powder. Specific ranges of reaction conditions used to prepare the samples are further listed in table 1.

TABLE 1

Reaction process conditions	Value of
		Reaction pH	6.0-9.0
Reaction time	2-24 hours
		Reactor type	Intermittent type formula
Reactor agitation speed	200-1400rpm
		Reaction temperature	Room temperature to 80 deg.C
Concentration of metal salt	1-3M
		Na2CO3(precipitant) concentration	1-4M
NH4OH (chelating agent) concentration	0.2-2M
		Flow rate of metal salt	1-100mL/min
Na2CO3And NH4Flow rate of OH	1-100mL/min

Mixing an appropriate amount of Li₂CO₃The powder is combined with a dry metal carbonate powder and thoroughly mixed by a pot mill, a double planetary mixer, or a dry powder rotary mixer to form a homogeneous powder mixture. A portion (e.g., 5 grams) of the homogeneous powder is calcined, followed by additional mixing steps to further homogenize the resulting powder. The further homogenized powder is again calcined to form a lithium composite oxide. The product composition was determined to be Li_1.2Ni_0.175Co_0.10Mn_0.525O₂. The specific range of the calcination conditionsAre shown in Table 2.

TABLE 2

Scanning Electron Microscope (SEM) micrographs of the lithium composite oxide at different magnifications are shown in fig. 2a and 2b, which confirm that the formed particles have a substantially spherical shape and are relatively uniform in size. The x-ray diffraction pattern of the untreated composite powder is shown in fig. 3, which shows the characteristics of the rock-salt type structure.

The composition was used to form a button cell according to the procedure outlined above. The button-type unit cells were tested and the voltage versus capacity curves for the first cycle at a discharge rate of 0.1C and the voltage versus capacity curves for the seventh cycle at a discharge rate of 0.33C are shown in fig. 4(a) and (b), respectively. The first cycle specific capacity of the cell at a discharge rate of 0.1C was about 245 mAh/g. The seventh cycle specific capacity of the cell was about 220mAh/g at a discharge rate of 0.33C. The specific capacity versus cycle life of the button cell battery was also tested and the results are shown in fig. 5. The first three cycles were measured at a discharge rate of 0.1C. The three subsequent cycles were measured at a rate of 0.2C. Subsequent cycles were all measured at a rate of 0.33C. After 40 cycles of charge and discharge, the battery maintained a specific capacity of 90% or more relative to the 7 th cycle.

Example 2 formation of AlF ₃ Coated metal oxide materials

Utilization of aluminum fluoride (AlF) using a solution-based process₃) A thin layer was applied to the metal oxide particles prepared in the examples above. For a selected amount of aluminum fluoride coating, an appropriate amount of a saturated solution of aluminum nitrate is prepared in an aqueous solvent. The metal oxide particles are then added to the aluminum nitrate solutionTo form a mixture. The mixture was mixed vigorously for a period of time to achieve homogenization. The length of mixing time depends on the volume of the mixture. After homogenization, a stoichiometric amount of ammonium fluoride is added to the homogenized mixture to form an aluminum fluoride precipitate while retaining the fluorine source. After precipitation was complete, the mixture was stirred at 80 ℃ for 5 h. The mixture was then filtered and the solid obtained was washed repeatedly to remove any unreacted material. Calcining the solid at 400 ℃ for 5 hours in a nitrogen atmosphere to form AlF₃A coated metal oxide material. Representative Via AlF₃SEM micrographs of the coated lithium composite oxide at different magnifications are shown in fig. 2c and 2d, which indicate that the formed particles have a substantially spherical shape and are relatively uniform in size.

Samples of Lithium Metal Oxide (LMO) particles synthesized as described in example 1 were coated with different selected amounts of aluminum fluoride using the process described in this example. Evaluation of the resulting AlF Using Transmission Electron microscopy₃The thickness of the coating. For example, fig. 6a shows a Transmission Electron Micrograph (TEM) of uncoated lithium composite oxide particles, and fig. 6b shows AlF having a thickness of about 7nm₃TEM micrograph of the coated LMO particles, and FIG. 6c shows AlF with about 25nm₃TEM micrograph of the coated LMO particles. The thickness of the coating on the particle surface is approximately constant. The x-ray diffraction patterns of the aluminum fluoride-coated LMO samples with coating thicknesses of 3nm, 6nm, 11nm, 22nm, and 40nm, and the diffraction patterns of the untreated (i.e., uncoated) samples are shown in fig. 3. All x-ray diffraction patterns showed the characteristics of rock salt type structure as the uncoated LMO sample. The aluminum fluoride coated LMO was then used to form a button cell according to the procedure shown above. The button cell was tested as described in the examples below.

Differential Scanning Calorimetry (DSC) was used to investigate the stability of the cathode active material. DSC results for uncoated LMO particles and particles with 4 different coating thicknesses are shown in figure 7. The change in the peak in the heat flow with temperature indicates a phase change or the like of the material. As can be seen from fig. 7, all coating thicknesses stabilized the material relative to the low temperature active phase, but greater coating thicknesses further increased stability. Thus, if a coated LMO material is used in the positive electrode, it is expected that a battery formed from the material will exhibit greater temperature stability at higher temperatures.

Example 3 AlF ₃ Cell capacity of coated samples

This example demonstrates the cell performance versus coating thickness (for a range of AlF's)₃Coating thickness and various battery performance parameters).

Electrochemical Impedance Spectroscopy (EIS) was used to check the impedance of the positive electrode. This data provides information on the interfacial properties of the coated material. The electrodes are disturbed by a current in the form of a sine wave. A plot of the EIS results is given in fig. 8. The results show thicker AlF₃The coating may result in a greater charge transfer resistance.

The button-type unit cells were formed from the synthesized material as described in example 2 using the process and button-type unit structure described above. The cells were cycled to evaluate their performance. The first three cycles were measured at a charge/discharge rate of 0.1C. The three subsequent cycles were measured at a charge/discharge rate of 0.2C. Subsequent cycles were measured at a charge/discharge rate of 0.33C.

The voltage versus capacity curves for the first cycle at a charge/discharge rate of 0.1C and the seventh cycle at a charge/discharge rate of 0.33C for a button cell formed from 3nm aluminum fluoride coated LMO material are shown in fig. 9(a) and 9 (b). The first cycle specific capacity of the cell at a discharge rate of 0.1C was about 265 mAh/g. The first cycle specific capacity of the cell at a discharge rate of 0.33C was about 250 mAh/g. The specific capacity versus cycling of the button cell was also tested and the results are shown in fig. 10. After 40 cycles of charge and discharge, the positive electrode active material of the battery maintains a specific capacity of 95% or more relative to the specific capacity at cycle 7 (first C/3 cycle).

The voltage versus capacity curves for the first cycle at a discharge rate of 0.1C and the seventh cycle at a discharge rate of C/3 for a button cell formed from 22nm aluminum fluoride coated LMO material are shown in fig. 11(a) and 11 (b). The first cycle specific capacity of the cell at a discharge rate of 0.1C was about 260 mAh/g. The seventh cycle specific capacity of the cell at a discharge rate of 0.33C was about 235 mAh/g. The specific capacity versus cycling of the button cell was also tested and the results are shown in fig. 12. After 40 charge and discharge cycles, the battery maintained approximately 98% specific capacity relative to the seventh cycle specific capacity.

Button cells formed from uncoated, 3nm, 6nm, 11nm, 22nm, and 40nm aluminum fluoride coated LMO material were tested for specific capacity versus cycling and the results are shown in fig. 13. Batteries with coated LMO materials show a complex relationship between specific capacity performance as a function of coating thickness. The cells utilizing LMO material with 6nm aluminum fluoride coating had the highest specific capacity at low cycle times, while the cells utilizing LMO material with 4nm aluminum fluoride coating had the highest capacity at 40 cycles. The battery utilizing LMO material with a 40nm coating had the lowest specific capacity, which was lower than the battery utilizing uncoated material, but this battery showed a slight increase in capacity with cycling.

The first cycle irreversible capacity loss (IRCL) was measured for cells with uncoated, 3nm, 6nm, 11nm, 22nm, and 40nm aluminum fluoride coated LMO materials. The results of the percent total capacity versus coating thickness are shown in fig. 14a, and the results of the specific capacity change versus coating thickness are shown in fig. 14 b. The IRCL results show a stable reduction in IRCL for cells with a coating thickness of about 10nm, and the IRCL for cells with 11nm, 22nm, and 40nm aluminum fluoride coated LMO material is approximately stable.

The average voltage of the cells was measured for cells with positive electrodes containing uncoated, 3nm, 6nm, 11nm, 22nm, and 40nm aluminum fluoride coated LMO materials. The average voltage was taken from 4.6V discharge to 2.0V. The plot of average voltage versus coating thickness is shown in fig. 15a, and the plot of percent voltage reduction versus coating thickness versus uncoated material performance is shown in fig. 15 b. The average voltage generally shows a decrease with increasing aluminum fluoride coating thickness on the LMO material, but for coatings of 6nm or less, the decrease in average voltage is smaller.

In addition, the coulombic efficiency of cells with uncoated, 3nm, 6nm, 11nm, 22nm, and 40nm aluminum fluoride coated LMO materials was measured. As used herein, coulombic efficiency was evaluated as the percentage of the specific capacity at cycle 40 to the specific capacity at cycle 7, with the first cycle being performed at a rate of C/3. In other words, the coulombic efficiency was 100 × (specific capacity at cycle 40)/(specific capacity at cycle 7). The curve of coulombic efficiency as a function of coating thickness is shown in fig. 16. The coulomb efficiency increases by about 2% when the coating thickness increases from 0 to 3 nm. The coulomb efficiency decreases significantly as the coating thickness increases from 3nm to 6nm and 11 nm. The coulombic efficiency of the cells formed with the positive electrode active material increased dramatically when the coating thickness was 22nm and 40 nm.

Example 4-Material with Metal difluoride coating and corresponding Battery

This example illustrates the formation of MgF on lithium rich metal oxides₂、CaF₂、BaF₂And SrF₂The coating, and the corresponding button cell data presented indicate improved performance of the coated material.

A sample of Lithium Metal Oxide (LMO) particles synthesized as described in example 1 was sampled with 1-4nm MgF₂、CaF₂、BaF₂And SrF₂And (4) coating. A stoichiometric amount of the selected metal nitrate (e.g., magnesium nitrate) is dissolved in water and mixed with a corresponding amount of lithium metal oxide under constant stirring. Then, ammonium fluoride was slowly added to the mixture while continuing stirring. After the addition of excess ammonium fluoride, the mixture was heated to about 80 ℃ for about 5 hours. After the deposition was complete, the mixture was filtered and calcined at 450 ℃ for 5 hours under nitrogen atmosphere. Warp beamThe x-ray diffraction pattern of the metal difluoride-coated LMO sample and the diffraction pattern of the corresponding untreated (i.e., uncoated) sample are shown in fig. 17. All x-ray diffraction patterns showed the characteristics of rock salt type structure as the uncoated LMO sample. By MgF₂(A) Coated samples and SrF₂(B) Transmission electron micrographs of the coated samples are shown in fig. 18A and 18B.

The button cell was formed using the metal difluoride coated LMO according to the procedure outlined above. The voltage of the first cycle of the uncoated material (from 4.6V to 2.0V) versus specific charge and discharge capacity at a rate of C/10 is shown in fig. 19. The LMO material of this batch had a slightly greater specific capacity than the uncoated material used to obtain figure 4 a. MgF at C/10 rate₂、SrF₂、BaF₂And CaF₂The corresponding voltage versus specific charge and discharge capacity curves for (a) are given in figures 20-23, respectively. The four first cycle curves for cells using positive electroactive materials with different metal difluoride coatings show similar first cycle performance with MgF₂The material of the coating showed a slightly higher specific discharge capacity. The unit was subjected to 16 cycles, with 1 st and 2 nd cycles at a rate of C/10, 3 rd and 4 th cycles at a rate of C/5, 5 th and 6 th cycles at a rate of C/3, 7 th to 11 th cycles at a rate of 1C and 12 th to 16 th cycles at a rate of 2C. The cycling results are given in figure 24. All batteries made from the coated samples exhibited significantly greater specific discharge capacity at all rates relative to batteries formed from the uncoated composition. With SrF₂、BaF₂And CaF₂The coated materials all exhibited similar performance, while the cells formed from MgF₂The coated positive electrode active material formed cells exhibited slightly greater specific discharge capacity at all rates.

Example 5-from AlF ₃ Button form of the coated compositionUnit cell

The examples use graphite as the negative electrode active material to study the cell performance of button cell batteries.

Lithium Metal Oxide (LMO) powder produced as described in example 1 was thoroughly mixed with conductive carbon (e.g., a mixture of acetylene black and graphite) to form a homogeneous powder mixture comprising 10-20 wt% conductive carbon. Separately, polyvinylidene fluoride (PVDF) was mixed with N-methyl-pyrrolidone (NMP) and dried overnight to form a PVDF-NMP solution. The homogeneous powder mixture was then added to the PVDF-NMP solution and mixed for 2-6 hours to form a homogeneous slurry. The slurry was applied to an aluminum foil current collector using a commercially available coater to form a wet film.

The positive electrode structure was formed by drying the aluminum foil current collector with the wet film electrode to remove NMP. The positive electrode and current collector are pressed together between the rolls of a plate mill to obtain a positive electrode of the desired thickness connected to a foil current collector.

A blend of graphite, optionally conductive carbon, and a binder is used as the negative electrode, with about 80-99 wt% graphite. The negative electrode composition was coated on a copper foil current collector and dried. A three-layer (polypropylene/polyethylene/polypropylene) microporous separator (2320, available from hilgard, LLC, NC, usa) impregnated with electrolyte was placed between the positive and negative electrodes. A few more drops of electrolyte were added between the electrodes. An electrode stack having a positive electrode-separator-negative electrode was placed within a button cell. The electrolyte is 1M LiPF₆A solution by mixing LiPF₆The salt was formed by dissolving a mixture of ethylene carbonate, diethyl carbonate and dimethyl carbonate (available from Fisher-Tropsch, Ohio, USA) in a volume ratio of 1: 1. An electrolyte is placed in the cell with the electrode stack and the button cell is sealed.

The resulting cells were tested using a makerr cycle tester to obtain a charge-discharge curve and cycle stability over several cycles. The first cycle is performed at a rate of C/10, and the second to 50 th cyclesThe loop is performed at a rate of C/3. Uncoated (i.e., untreated) samples and samples with 5 different alfs₃The results for the coating thickness samples with respect to specific capacity as a function of cycle are plotted in fig. 25. After the first few cycles, the reaction mixture was made of AlF with a thickness of 3nm₃The batteries formed with the coatings exhibit significantly greater specific capacities.

Example 6-with AlF ₃ Alternative positive-charge active compositions for coatings and corresponding batteries

This example demonstrates having selected amounts of AlF₃Battery performance results of the positive electrode of the coating composition with an alternative electroactive material.

The positive electrode active material was synthesized as described in example 1. However, the product composition for the battery positive electrode in this example was Li_1.07Ni_0.31Co_0.31Mn_0.31O₂. With AlF as described in example 2₃Particles of the product composition are coated. To obtain AlF with different amounts₃Samples of the coating composition. Representative transmission electron micrographs given in fig. 26A and 26B show average coating thicknesses of about 3nm (a) and about 17nm (B).

The button-type unit cell is formed using the above-described process and the button-type unit structure. The cells were cycled to evaluate their performance. The first two cycles were measured at a charge/discharge rate of 0.1C. Subsequent 3 rd to 18 th cycles were measured at a charge/discharge rate of 0.33C. One set of samples was cycled between 2.0V and 4.3V, while the other set of samples was cycled between 2.0V to 4.5V.

Cycling between 2.0V and 4.3V with uncoated active material (FIG. 27) or AlF of about 3nm thickness₃The voltage versus specific capacity for the uncoated positive electrode active material and the positive electrode active material of the coating (fig. 28) is depicted in fig. 27 and 28. The cells formed from the coated samples exhibited greater discharge capacity and a corresponding reduction in irreversible capacity loss. Cycling between 2.0V and 4.5V gave similar results. At 2.0V anduncoated (FIG. 29) or with AlF at about 3nm cycling between 4.45V₃The positive electrode active material voltage versus specific capacity curves for the coating (fig. 30) are given in fig. 29 and 30, respectively. As expected, the charge and discharge capacity was greater when cycling to higher voltages.

Button cells formed from uncoated, 3nm, 8nm, 17nm, 22nm, and 47nm aluminum fluoride coated LMO materials were tested for specific capacity versus cycling between 2.0V and 4.3V and cycling from 2.0V to 4.5V. The specific discharge capacity as a function of cycling between 2.0V and 4.3V is shown in fig. 31, and the specific discharge capacity as a function of cycling between 2.0V and 4.5V is shown in fig. 32. Batteries with the coated LMO materials of the invention showed reduced specific capacity performance with increasing coating thickness, but certain materials with different coating thicknesses had substantially the same specific capacity results, as seen in fig. 31 and 32. The material with the thickest coating consistently has a lower specific capacity than the uncoated material, while the remaining coated material exhibits a greater specific capacity relative to the uncoated material. The results are qualitatively consistent with the results in fig. 13 and 25, with a thick coating having a lower specific capacity than the uncoated sample and a thin coating achieving the best specific capacity performance upon cycling.

The above-described embodiments are intended to be illustrative, not limiting. Other embodiments are within the claims. Additionally, although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Any incorporation by reference of documents above is limited so as not to incorporate subject matter that is contrary to the explicit disclosure herein.

Claims (25)

1. A positive electrode material of lithium ion battery contains Li_1+xM_1-xO₂A reactive composition represented by wherein M is a metal element or combination thereof and 0.01 ≦ x ≦ 0.3, the material being coated with an inorganic coating composition, wherein the coating composition comprises a metal/metalloid fluoride.

2. The positive electrode material of claim 1 wherein the coating composition comprises AlF₃、MgF₂、CaF₂、SrF₂Or BaF₂。

3. The positive electrode material of claim 1 wherein the coating has an average thickness of about 0.5 nanometers (nm) to about 12 nm.

4. The positive electrode material of claim 1 wherein the coating has an average thickness of about 1nm to about 8 nm.

5. The positive electrode material of claim 1 wherein the active composition can be approximated by the formula bLiM' O₂·(1-b)Li₂M″O₃Wherein M 'represents one or more metal ions having an average valence of +3 and M' represents one or more metal ions having an average valence of +4 and 0 < b < 1.

6. The positive electrode material of claim 1 wherein the active composition is proximately represented by the formula Li_1+xNi_αMn_βCo_γA_δO₂Representative, wherein x is between about 0.05 to about 0.25, α is between about 0.1 to about 0.4, β is between about 0.4 to about 0.65, γ is between about 0 to about 0.3, and δ is between about 0 to about 0.1, and wherein A is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof.

7. The positive electrode material of claim 1 wherein the active composition is proximately represented by the formula Li_1+xNi_αMn_βCo_γO₂Representative thereof, wherein x is between about 0.05 and about 0.25, α is between about 0.1 and about 0.4, β is between about 0.3 and about 0.65, and γ is between about 0.05 and about 0.4.

8. The positive electrode material of claim 1 having a specific capacity of at least about 245mAh/g when discharged from 4.6V to 2.0V at room temperature at a discharge rate of C/3.

9. A battery comprising the positive electrode material of claim 1 and a non-aqueous electrolyte comprising lithium ions.

10. A lithium ion battery comprising a positive electrode, a negative electrode comprising a lithium inclusion composition, a separator between the positive electrode and the negative electrode, and an electrolyte comprising lithium ions, wherein the positive electrode comprises an active material, a different conductive powder, and a polymer binder, wherein the positive electrode active material comprises an active composition coated with an inorganic coating composition, and the positive electrode active material has a specific discharge capacity of at least about 190mAh/g at room temperature at a discharge rate of 2C from 4.6 volts to 2.0 volts in a fifteenth charge/discharge cycle.

11. The lithium ion battery of claim 10 wherein the negative electrode comprises elemental carbon.

12. The lithium ion battery of claim 10, wherein the inert inorganic composition comprises a metal/metalloid fluoride.

13. The lithium ion battery of claim 12, wherein the coating composition has an average thickness of from about 0.5nm to about 12 nm.

14. The lithium ion battery of claim 10, wherein the inert inorganic coating composition comprises a metal/metalloid oxide.

15. The lithium ion battery of claim 10 wherein the active composition is approximately represented by the formula Li_1+xM_1-xO₂Wherein M is a metal element or a combination thereof and 0.01. ltoreq. x.ltoreq.0.3.

16. The lithium ion battery of claim 10 wherein the active composition is proximately represented by the formula Li_1+xNi_αMn_βCo_γM”_δO₂Representative, wherein x is between about 0.05 to about 0.25, α is between about 0.1 to about 0.4, β is between about 0.4 to about 0.65, γ is between about 0 to about 0.3, and δ is between about 0 to about 0.1, and wherein M "is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof.

17. The lithium ion battery of claim 10, wherein the irreversible capacity loss is reduced by at least about 10% relative to the irreversible capacity loss of an equivalent battery formed with an uncoated positive electrode active material.

18. The lithium ion battery of claim 10, wherein the active composition has a tap density of at least about 1.3 g/mL.

19. A lithium ion battery comprising a positive electrode, a negative electrode comprising a lithium inclusion composition, and a separator between the positive electrode and the negative electrode, wherein the positive electrode comprises an active material having an active composition coated with an inorganic composition, a different conductive powder, and a polymer binder, the positive electrode active material has a specific discharge capacity of at least about 245mAh/g at a discharge rate of C/3 from 4.6 volts to 2.0 volts at room temperature, an average voltage of at least about 3.55 volts, and a capacity at 40 cycles of at least about 90% of the capacity at 10 cycles.

20. The lithium ion battery of claim 19 wherein the positive electrode active material has a specific capacity of at least about 250mAh/g at a discharge rate of C/3 from 4.6 volts to 2.0 volts at room temperature.

21. The lithium ion battery of claim 19 wherein the capacity at 40 cycles at room temperature at a discharge rate of C/3 from 4.6 volts to 2.0 volts is at least about 95% of the capacity at 10 cycles.

22. The lithium ion battery of claim 19 wherein the inorganic composition coating the positive electrode active composition comprises a metal/metalloid fluoride.

23. The lithium ion battery of claim 19 wherein the positive electrode active composition comprises a positive electrode active material that consists essentially of Li_1+xM_1-xO₂A compound represented by the formula, wherein M is one or more metal elements and x is 0.01. ltoreq. x.ltoreq.0.3.

24. The lithium ion battery of claim 23 wherein the positive electrode active composition comprises a positive electrode active composition of the formula Li_1+xNi_αMn_βCo_γM”_δO₂Representative compositions wherein x is between about 0.05 and about 0.25, α is between about 0.1 and about 0.4, β is between about 0.4 and about 0.65, γ is between about 0 and about 0.3, and δ is between about 0 and about 0.1, and wherein M "is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof.

25. The lithium ion battery of claim 19 wherein the negative electrode comprises elemental carbon.