DE102018203466A1 - Metal-ion battery and method for producing a metal electrode with an intermediate layer for a metal-ion battery - Google Patents

Abstract

A metal-ion battery (10) is proposed, comprising a cathode (50), a separator (40), and a metal electrode (20) as an anode, characterized by an intermediate layer (30) which is arranged between the metal electrode (20). and the separator (40) and directly contacting the metal electrode (20), the intermediate layer (30) - for metal ions of the metal electrode (20) having a transfer coefficient of at least about 0.8, preferably at least about 0.9 preferably at least about 0.99, - is formed electrically insulating, and- has a dielectric strength of at least 1 kV / mm, in particular at least 5 kV / mm, preferably at least 10 kV / mm.

Description

Field of the invention

The invention relates to a metal-ion battery and a method for producing a metal electrode with an intermediate layer for a metal-ion battery.

State of the art

A variety of metal-ion batteries, in particular lithium-ion cells, is known. For lithium-ion batteries, for example, the cathode has a metal oxide as the active material, while the anode has graphite, amorphous carbon, silicon or lithium titanate as the active material. Recent developments are aimed at using lithium metal as the anode in combination with a solid electrolyte. The solid electrolyte is necessary to sufficiently mechanically support the lithium metal electrode, particularly when depositing lithium (i.e., charging the battery), so that lithium grows flat rather than dendritically.

In previously known lithium-ion cells, the lithium electrode or the lithium foil may not have a clearly defined surface. The surface which later forms the interface to the solid electrolyte or separator, under unfavorable circumstances, comprises lithium foil production and / or storage reaction products, eg reactions with the lubricant (typically hydrocarbons) for rolling the lithium foil and reactions with the atmosphere (in the Film production and / or storage). Reactions with the atmosphere lead to reaction products such as Li ₂ O (reaction with O ₂ ), Li ₂ CO ₃ (reaction with CO ₂ ), Li ₃ N (reaction with N ₂ ) and / or LiOH (reaction with water). The same applies to alkali and / or alkaline earth metal electrodes. The reaction products usually have a low electrical conductivity, for example in the range 10 ^-8 S / cm to 10 ^-9 S / cm.

Under unfavorable conditions, the current densities which can be achieved in particular in the charging direction (ie with high cycle stability) with metal electrodes, in particular with lithium metal electrodes, are low owing to these reaction products. For example, the maximum current density is less than 0.5 mA / cm ² .

Disclosure of the invention

Advantages of the invention

Embodiments of the present invention can advantageously make it possible to provide a metal-ion battery or a method for producing a metal electrode with an intermediate layer for a metal-ion battery, which enables high current densities with simultaneously high cycle stability or by means of a metal electrode can be produced with an intermediate layer for a battery, which allows high current densities with high cycle stability.

• - für Metallionen der Metallelektrode eine Überführungszahl von mindestens ca. 0,8, vorzugsweise mindestens ca. 0,9, besonders vorzugsweise mindestens ca. 0,99, aufweist,
• - elektrisch isolierend ausgebildet ist, und
• - eine Durchschlagsfestigkeit von mindestens 1 kV/mm, insbesondere mindestens 5 kV/mm, vorzugsweise mindestens 10 kV/mm, aufweist.

According to a first aspect of the invention, there is proposed a metal-ion battery comprising a cathode, a separator, and a metal electrode as an anode, characterized by an intermediate layer disposed between the metal electrode and the separator and directly contacting the metal electrode, wherein the interlayer

• - For metal ions of the metal electrode has a transfer coefficient of at least about 0.8, preferably at least about 0.9, particularly preferably at least about 0.99,
• - Is electrically insulated, and
• - Has a dielectric strength of at least 1 kV / mm, in particular at least 5 kV / mm, preferably at least 10 kV / mm.

One advantage of this is that the battery usually has a high current density with high cycle stability, inter alia, since there is no further layer between the metal electrode and the intermediate layer. The intermediate layer directly or directly contacts the metal electrode (or lithium electrode). The battery usually allows fast charging at the metal anode or metal electrode at technically relevant cathode loadings of about 1.0 mAh / cm ² . In particular, a C-rate> 0.5 is achieved, wherein the C-rate refers to the nominal capacity of the battery in ampere hours (Ah) related charging or discharging. The intermediate layer usually conducts substantially only metal ions of the metal electrode (in English: single ion conductor), is electrically insulating and has a high dielectric strength between the metal electrode and the separator. The intermediate layer is usually thermodynamically stable in contact with the metal electrode or lithium electrode and / or forms at the first contact (in the production of the battery) with the metal or lithium reaction products that are thermodynamically stable to the metal or lithium and the have the properties of the remaining intermediate layer or similar properties in terms of transfer coefficient, electrical insulation and dielectric strength.

The transference number, t (also Hittorf transference number called) are usually the fraction of the total electric current I of which by a particular type of ion (here, metal ions of the metal electrode) i is transported: t _i = I _iMetallionen / I _Total

Thus, the transfer coefficient of the intermediate metal ion layer of the metal electrode generally indicates how large the mobility of the metal ions in the intermediate layer is relative to the mobility of the counterions (anions) in the intermediate layer. The mobility of the counterions or anions is low to very low or negligible at a large or very large value of the transfer coefficient for the metal ions of the metal electrode. The transfer number can be determined, for example, by the Hittorf method.

The intermediate layer is generally electrically insulating, i. it has a low electron conductivity and is at the same time a very good ion conductor for the ions of the metal electrode, e.g. Lithium ions.

The dielectric strength usually indicates up to which current densities no electron breakdown (avalanche breakdown) takes place. The dielectric strength is usually greater than the highest expected electric field strength to which the intermediate layer is exposed, ie in particular at least the following inequality between the dielectric strength and the ionic conductivity of the intermediate layer can be met: dielectric strength ≥ i _{M +, max} / σ _{M +,} where i _{M +, max is} the maximum area current density of the metal ions through the intermediate layer and σ _{M + is} the ionic conductivity of the metal ion intermediate layer of the metal electrode. Preferably, the dielectric strength of the intermediate layer is ten times, in particular one hundred times, the minimum value determined by the stated inequality. Example: If the dielectric strength is in the range of technically relevant insulators, ie in the range of approx. 10 kV / mm (eg an insulator made of Al ₂ O ₃ , Teflon or the like), a preferred surface current density of 10 mA / cm ² results Minimum conductivity of the intermediate layer for metal ions of at least 1 * 10 ^-7 S / cm, in particular 1 * 10 ^-6 S / cm, preferably 1 * 10 ^-5 S / cm. For typical ceramic or glassy ionic conductors, such as LiPON, Li ₃ N, LLTO, garnets, eg LLZO, sulfidic solid ion conductors, antiperware kites (eg Li ₃ OCl, which may be doped with divalent ions such as Ba, Mg) can be estimated for breakdown strength be lower than for typical technical isolators (eg Al ₂ O ₃ or PTFE). The dielectric strength of typical ceramic or glassy ion conductors as an intermediate layer is usually in the range of about 1 kV / mm to about 5 kV / mm. Thus, the ionic conductivity of the intermediate layer is usually at a current density of 10 mA / cm ² at least 1 * 10 ^-6 S / cm, preferably at least 1 * 10 ^-5 S / cm, more preferably at least 1 * 10 ^-4 S / cm ,

In particular, the intermediate layer may be formed such that the intermediate layer is compact, i. that no percolating porosity (pores connecting one side of the intermediate layer to the other side) is present. Closed nanopores are usually undesirable, but generally can be present.

According to a second aspect of the invention, a method for producing a metal electrode with an intermediate layer for a metal-ion battery, in particular as described above, is proposed, wherein the intermediate layer is designed to contact a separator of the metal-ion battery, the method the steps of arranging an intermediate layer directly on a metal electrode, in particular a lithium metal electrode, or arranging a metal electrode, in particular a lithium metal electrode, directly on an intermediate layer. The intermediate layer has a transfer coefficient of at least about 0.8, preferably at least about 0.9, particularly preferably at least about 0.99, for metal ions of the metal electrode, is electrically insulating, and has a dielectric strength of at least 1 kV /. mm, in particular at least 5 kV / mm, preferably at least 10 kV / mm, on.

One advantage of this is that a metal electrode with an intermediate layer for a metal-ion battery can usually be manufactured in a technically simple manner, the battery usually having a high current density with simultaneously high cycle stability, i.a. since there is no further layer between the metal electrode and the intermediate layer. The intermediate layer generally contacts directly the metal electrode (or lithium electrode).

Ideas for embodiments of the present invention may be considered, inter alia, as being based on the thoughts and findings described below.

In one embodiment, the metal electrode is a lithium metal electrode and the metal ions are Li ⁺ ions. An advantage of this is that the metal-ion battery generally has a particularly high capacity or capacity at low volume, ie has a high energy or power density.

In one embodiment, the metal electrode is an alkali metal and / or alkaline earth metal electrode. The advantage of this is that the metal-ion battery is usually very inexpensive to produce and technically simple.

According to one embodiment / the intermediate layer comprises Li _x PO _y N _z, Li ₂ N, Li _3x La _{2 / 3x} TiO _3, and or shell, for example, Li ₇ La ₃ Zr ₃ O _12th As a result, the intermediate layer can usually be constructed in a technically simple and cost-effective manner and at the same time have a high dielectric strength. For Li _x PO _y N _z , x, y and z may each be integer values. For Li _3x La _2/3-x TiO ₃ , x can usually be ⅓ or ⅔.

According to one embodiment, the intermediate layer comprises a sulfide ion conductor comprising lithium, sulfur and phosphorus, in particular comprising lithium, sulfur and phosphorus in combination with silicon, germanium, tin, chlorine, bromine and / or iodine, and / or an antiperowskite, eg Li ₃ OCI , in particular an antiperowskite doped with divalent ions, for example barium and / or magnesium. Preferably, the intermediate layer may comprise a sulfidic glass comprising Li2S and P2S5 and / or a glass-ceramic / glass-ceramic comprising Li2S and P2S5, or crystalline materials from the LGPS class, e.g. Li10GeP2S12, Li10SnP2S12, Li9.54Si1.74P1.44S11.7CI0.3, Li9.6P3S12, or argyrodites such as Li7PS6, Li6PS5CI, Li6PS5Br, or each consist thereof. An advantage of this is that the intermediate layer usually has a particularly high dielectric strength.

According to one embodiment, the intermediate layer has a thickness of approximately 1 nm to approximately 20 μm, in particular approximately 1 nm to approximately 5 μm, preferably approximately 1 nm to approximately 10 nm. An advantage of this is that the metal-ion battery can usually have a particularly low volume.

According to one embodiment, the electron conductivity σ _{e of} the intermediate layer is less than or equal to the following value, in particular less than 1/10 of the following value, preferably less than 1/100 of the following value: σ _{M +} * a / L / 2, where a is the smallest atomic distance is the intermediate layer, where L is a maximum thickness of the intermediate layer, and where σ _{M + is} a conductivity of the metal ion intermediate layer of the metal electrode. As a result, a particularly good electrical insulation between separator and metal electrode is usually achieved.

According to an embodiment of the method, before the step of arranging the intermediate layer directly on the metal layer or the step of arranging the metal layer on the intermediate layer, a passivation layer is removed from the metal layer, in particular by plasma etching and / or chemical etching, in an inert atmosphere the step of arranging the intermediate layer or arranging the metal layer is performed in an inert atmosphere. As a result, it is generally technically easily ensured that no further layer (for example, of reaction products of the metal layer with air, water, lubricating oil or the like) exists between the intermediate layer and the metal layer. Thus, the electrical resistance between the intermediate layer and the metal layer is usually particularly low.

According to one embodiment, in the step of disposing the intermediate layer on the metal layer, the intermediate layer is applied to the metal layer by physical vapor deposition, chemical vapor deposition and / or atomic layer deposition. As a result, the intermediate layer can usually be applied to the metal layer in a technically simple and secure manner without a further layer between the intermediate layer and the metal layer.

The battery may be a primary battery or a secondary battery.

The properties or values with regard to the electrical insulation, the dielectric strength and the transfer coefficient can also be higher in each case for the operating temperature of the battery (typically room temperature (eg about 20 ° C. or about 22 ° C.) or for solid-state battery cells based on polymer electrolytes Temperatures, typically in the range 40 ° C - 80 ° C) apply.

It should be noted that some of the possible features and advantages of the invention are described herein with respect to different embodiments of the metal-ion battery and the method of manufacturing a metal electrode with an intermediate layer for a metal-ion battery. A person skilled in the art will recognize that the features can be suitably combined, adapted or replaced in order to arrive at further embodiments of the invention.

list of figures

• 1 zeigt eine Querschnittsansicht einer Ausführungsform der erfindungsgemäßen Metall-Ionen-Batterie.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention.

• 1 shows a cross-sectional view of an embodiment of the metal-ion battery according to the invention.

The figure is merely schematic and not to scale.

Embodiments of the invention

1 shows a cross-sectional view of an embodiment of the metal according to the invention Ion battery 10 , The metal-ion battery 10 may in particular be a lithium-ion battery.

The metal-ion battery 10 includes a metal electrode 20 , an intermediate layer 30 , a separator 40 , a cathode 50 and a cathode current collector 60 , The intermediate layer 30 is between the separator 40 and the metal electrode 20 arranged. On the interlayer 30 opposite side of the metal electrode 20 An anode current collector can be arranged. The metal electrode 20 may be a lithium electrode and the metal ions may be lithium ions.

The intermediate layer 30 is directly or directly on the metal electrode 20 or the metal layer of the metal electrode 20 (where the metal ions originate from the metal layer), ie between the metal electrode 20 or the metal layer of the metal electrode 20 there is no additional layer In particular, no further layer in the form of reaction products of the metal layer with the air, water or oils is present. For a lithium metal electrode, the possible reaction products would be, for example, LiO ₂ , Li ₂ CO ₃ , Li ₃ N, LiOH. In particular, there is no layer between the intermediate layer 30 and the metal electrode 20 or the metal layer of the metal electrode 20 in the range of nanometers or sub-nanometers. Ie that no layer between the interlayer 30 and the metal electrode 20 or the metal layer of the metal electrode 20 is present, which has a thickness in 1 from top to bottom, in the range of nanometers or even lower values.

The intermediate layer 30 is electrically insulating, has a high dielectric strength and is a good conductor especially for the metal ions of the metal electrode 20 (single ion conductor), eg Li ⁺ ions.

In particular, electrically insulating may mean that the following inequality is satisfied, where σ _{e is} the electron conductivity of the intermediate layer 30 , σ _{M +} the metal ion conductivity of the intermediate layer 30 is, a the smallest atomic distance of the intermediate layer 30 or within the intermediate layer 30 and L is the largest thickness of the intermediate layer 30 is (where the thickness of the intermediate layer 30 from the metal electrode 20 in the direction of the separator 40 extends or vice versa): ${\mathrm{\sigma }}_e\le \frac{a}{\frac{L}{2}}*\mathrm{\sigma }{\text{M}}_{+},$

In particular, the electron conductivity σe is less than 1/10, preferably less than 1/100, more preferably less than 1/1000, the value to the right of the specified inequality. For example, if the intermediate layer 30 a LiPON layer is (LixPOyNz where x, y and z are each integer values) and the operating temperature is room temperature (eg 20 ° C or 22 ° C), the intermediate view is a metal ion conductivity σM +, in particular a lithium ion conductivity σL +, of 1.2 * 10 ^-6 S / cm and have an electronic conductivity σe of 8 * 10 ^-14 S / cm. Since LiPON is an amorphous material and a smallest lattice spacing can not be given directly, it is conservatively estimated to be 100 pm. Thus, the above inequality for layer thicknesses of the intermediate layer is ≦ 750 μm, in particular ≦ 75 μm, preferably ≦ 7.5 μm, particularly preferably ≦ 750 nm.

In particular, the electron conductivity is at least so small that the penetration depth of the electrons is smaller than half the smallest atomic distance a within the intermediate layer 30 ,

The metal-ion battery 10 has a high cycle stability, ie that the capacity of the battery is substantially equal or unchanged even after more than 200 cycles, in particular more than 1000 cycles, preferably more than 3000 cycles. In addition, high deposition rates or current densities of more than 0.5 mA / cm ² , in particular more than 2 mA / cm ² , preferably more than 5 mA / cm ² , more preferably more than 10 mA / cm ² , more preferably more than 15 mA / cm ² , possible.

The metal electrode 20 with the intermediate layer 30 can be made in different ways:

A metal electrode 20 or metal foil, in particular a lithium metal foil, is initially provided. On the metal electrode 20 or metal foil, in particular lithium metal foil, or its surface, a native passivation layer of reaction products of the metal of the metal foil with the air, water, etc. is present. The native passivation layer is removed in an inert atmosphere (eg high vacuum or argon atmosphere), for example by plasma etching and / or chemical etching. Subsequently, the intermediate layer 30 from an inert solution (ie that the solvent of the solution is thermodynamically stable to the metal of the metal foil) in an inert atmosphere on the metal foil or metal electrode 20 applied. Finally, the solution is dried. Now you have an intermediate layer 30 that directly or directly (ie without further layer between them) on the metal foil or metal electrode 20 is arranged (and connected to it).

Another alternative way to make the metal electrode 20 with the intermediate layer 30 is: removing the native passivation layer from the metal foil or metal electrode 20 in a high vacuum by plasma etching and subsequent application of the intermediate layer 30 on the metal foil or metal electrode 20 by physical vapor deposition (English PVD), preferably in a high vacuum, and / or chemical vapor deposition (English chemical vapor deposition, CVD short) and / or atomic layer deposition (abbreviated ALD). Now you have an intermediate layer 30 directly or directly on the metal foil or metal electrode 20 is arranged and with the metal foil or metal electrode 20 connected is. Alternatively, the metal electrode 20 by means of PVD, CVD and / or ALD on the intermediate layer 30 be deposited.

As an alternative to the method described in the last paragraph, the production of a thin metal layer, in particular a thin lithium layer, on an electronically conductive substrate (eg copper or nickel foil) by physical vapor deposition (English physical vapor deposition, PVD short) in a high vacuum (or in a Noble gas atmosphere) for forming a metal electrode 20 and applying the intermediate layer 30 on the metal layer of the metal electrode 20 while the metal layer continues to be in a high vacuum (or in a noble gas atmosphere) (eg in the same system).

Another way to make the metal electrode 20 with the intermediate layer 30 is to carry out the entire production of the metal electrode 20 with the intermediate layer 30 in an inert atmosphere. That is, the ingot production and the rolling process for producing the metal electrode 20 in an inert atmosphere (eg high purity argon) is carried out and then the intermediate layer 30 by means of an inert solution (see above), which is subsequently dried, or by means of physical vapor deposition, chemical vapor deposition and / or atomic layer deposition on the metal electrode 20 is applied.

The metal layer or metal electrode 20 can on the interlayer 30 For example, be applied by means of PVD CVD and / or ALD, wherein the intermediate layer 30 may be a free-standing layer or may be arranged on an inert support. It is also conceivable that the intermediate layer 30 already on the separator 40 is arranged, wherein the separator 40 may be detached or already with the cathode 50 and the cathode current collector 60 connected is. In this case, therefore, the metal, for example lithium, on a finished composite consisting of separator 40 , Cathode 50 and cathode current collector 60 applied.

Another possibility is that the metal electrode 20 , in particular the lithium metal electrode, between the intermediate layer 30 and an anode current collector, for example a thin metal foil, in particular of copper, is electrodeposited. This means that first the interlayer 30 is arranged directly or directly on the anode current collector. Then, for example, when first loading the metal-ion battery 10 , a metal layer or the metal electrode 20 between the intermediate layer 30 and the anode current collector. This can be in-situ, ie in the otherwise finished metal-ion battery 10 , or ex-situ, for example, in a galvanic standard process performed. Also, this galvanic deposition of the lithium electrode between the intermediate layer 30 and the anode current collector is an arrangement of the metal electrode 20 or the lithium electrode on the intermediate layer 30 ,

The electrolyte of the separator 40 and / or the cathode 50 may comprise or consist of a liquid electrolyte, a gel electrolyte, a dry polymer electrolyte and / or a ceramic and / or vitreous electrolyte.

The transfer number of the intermediate layer 30 is at least about 0.8, preferably at least about 0.9, more preferably at least about 0.99, even more preferably substantially 1 ,

The term "approx." May in particular mean a deviation of ± 5%, preferably ± 3%, of the respectively indicated value.

Finally, it should be noted that terms such as "comprising," "comprising," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a multitude. Reference signs in the claims are not to be considered as limiting.

Claims (10)

A metal-ion battery (10) comprising a cathode (50), a separator (40), and a metal electrode (20) as an anode, characterized by an intermediate layer (30) arranged between the metal electrode (20) and the separator (40 ) and the metal electrode (20) directly contacted, wherein the intermediate layer (30) - for metal ions of the metal electrode (20) has a transfer coefficient of at least about 0.8, preferably at least about 0.9, more preferably at least about 0th , 99, - is formed electrically insulating, and - has a dielectric strength of at least 1 kV / mm, in particular at least 5 kV / mm, preferably at least 10 kV / mm. Metal ion battery (10) after Claim 1 wherein the metal electrode (20) is a lithium metal electrode and the metal ions are Li ⁺ ions. Metal ion battery (10) after Claim 1 wherein the metal electrode (20) is an alkali metal and / or alkaline earth metal electrode. Metal ion battery (10) according to one of the preceding claims, wherein the intermediate layer (30) Li _x PO _y N _z , Li ₂ N, Li _3x La _2/3-x TiO ₃ , and / or garnets, eg Li ₇ La ₃ Zr ₃ O ₁₂ . A metal-ion battery (10) according to any one of the preceding claims, wherein the intermediate layer (30) comprises a sulfide ion conductor comprising lithium, sulfur and phosphorus, in particular comprising lithium, sulfur and phosphorus in combination with silicon, germanium, tin, chlorine, bromine and phosphorus / or iodine, and / or an antiperowskite, for example Li ₃ OCI, in particular an antiperowskite doped with divalent ions, for example barium and / or magnesium. Metal ion battery (10) according to any one of the preceding claims, wherein the intermediate layer (30) has a thickness of about 1 nm to about 20 microns, in particular about 1 nm to about 5 microns, preferably about 1 nm to about 10 nm. Metal-ion battery (10) according to one of the preceding claims, wherein the electron conductivity σ _{e of} the intermediate layer (30) is less than or equal to the following value, in particular less than 1/10 of the following value, preferably less than 1/100 of the following value, is: σ _{M +} * a / L / 2, where a is the smallest atomic distance of the intermediate layer (30), where I is a largest thickness of the intermediate layer (30), and where σ _{M + is} a conductivity of the metal ion intermediate layer (30) (20) is. Method for producing a metal electrode (20) having an intermediate layer (30) for a metal-ion battery (10), in particular according to one of the preceding claims, wherein the intermediate layer (30) for contacting a separator (40) of the metal-ion battery Battery (10) is formed, wherein the method comprises the following steps: Arranging an intermediate layer (30) directly on a metal electrode (20), in particular a lithium metal electrode, or arranging a metal electrode (20), in particular a lithium metal electrode, directly on an intermediate layer (30), wherein the intermediate layer (30) - For metal ions of the metal electrode (20) has a transfer coefficient of at least about 0.8, preferably at least about 0.9, more preferably at least about 0.99, - Is electrically insulated, and - Has a dielectric strength of at least 1 kV / mm, in particular at least 5 kV / mm, preferably at least 10 kV / mm. Method according to Claim 8 wherein, before the step of disposing the intermediate layer (30) directly on the metal electrode (20) or the step of arranging the metal electrode (20) on the intermediate layer (30), a passivation layer of the metal electrode (20), in particular by plasma etching and or chemical etching, in an inert atmosphere, and the step of disposing the interlayer (30) or disposing the metal electrode (20) in an inert atmosphere is performed. Method according to Claim 8 or 9 wherein, in the step of disposing the intermediate layer (30) on the metal electrode (20), the intermediate layer (30) is applied to the metal electrode (20) by physical vapor deposition, chemical vapor deposition and / or atomic layer deposition or in the step of disposing the metal electrode (20) 20) on the intermediate layer (30) the metal electrode (20) by means of physical vapor deposition, chemical vapor deposition and / or atomic layer deposition on the intermediate layer (30) is applied.

Images