KR20200093467A - Method for producing a cathode for a solid-state battery - Google Patents

Abstract

The present invention relates to a method for producing a cathode for a solid-state battery to manufacture a cathode easy to handle and usable to a solid-state battery. According to the present invention, the method comprises the following steps of: (30) manufacturing a mixture (6) compressing a cathode active material (2) and at least one different component (4); (32) to manufacture a macro porous cathode material (10), mixing the mixture (6) with an electron conductive oxide (8); (34) forming a cross-linked bond (18) of the cathode active material (2) by a heating process; and (36) to manufacture a fine porous cathode material (14), mixing the macro porous cathode material (10) with a solid electrolyte material (12).

Description

Method for manufacturing cathode for solid battery {METHOD FOR PRODUCING A CATHODE FOR A SOLID-STATE BATTERY}

The present invention relates to a method for manufacturing a cathode of a solid state battery and a cathode for a solid state battery.

Methods for manufacturing cathodes for solid state batteries are known from the prior art. However, the cathode composition of today's solid state batteries manufactured through known methods lacks performance for various reasons. The reasons here include, in particular, insufficient contact between the active material and the solid electrolyte material and degradation leading to high interfacial resistance. In addition, conventionally prepared composite cathodes often have high porosity because it is difficult to perform efficient compression. In the case of a high performance cathode, it must be ensured that there are both sufficient ionic conduction paths and sufficient electron conduction paths within the cathode, which require the materials to be joined as closely as possible to one another.

Approaches known from the prior art to solve the problems mentioned propose a solution-based preparation of a cathode composition in particular, wherein the active material, solid electrolyte and conductive additive are dissolved with a polymer binder, placed on a substrate and then dried. . Likewise, dry production of electrodes by pressing is known, where the components are mechanically mixed and then compressed to form a complex without the use of a binder. It is also known that instead of a binder, a conductive polymer such as polyethylene oxide (PEO) is used with the conductive salt.

Publication No. US 9,325,001 B2 relates to a composite active material, comprising a coating layer for coating the composite active material, wherein the coating is formed in such a way that the coating does not break or separate when the composite active material is kneaded (kneading), It is applied on the composite active material.

Publication EP 1 347 524 B1 relates to an active material in which lithium can be reversibly inserted and removed, and a secondary battery comprising such an active material. The task of the public publication mentioned above here is to propose a new active material which is formed through the step of mixing a complex oxide of lithium and a transition metal and provides a new battery element structure with a non-aqueous electrolyte.

The publicly known solutions described above have proven to be disadvantageous as well in many respects. On the one hand, for example, solution-based fabrication does not provide a useful possibility to subsequently adjust the porosity of the electrode produced on the substrate. In addition, the electrodes presented so far can only be loaded with a very small amount of active material, thus providing only a low energy density. Further, unless it is maintained in a pressurized form, the dry electrode compressed in one form is difficult to handle after the pressing process. The approach comprising a conductive polymer is also not a promising approach due to the low ionic conductivity of the polymer at room temperature, because the rate capability of the electrode is always limited by the polymer. In addition,-as used in all conventional approaches known from the prior art-the inorganic solid electrolyte in contact with the carbon-based conductive additive reacts during the filling step, and in this way the performance of the corresponding composite cathode is strongly limited. Is known. Finally, the use of the binder should also be evaluated critically, as it will likewise reduce the performance of the cathode by blocking the conduction path.

Accordingly, the object of the present invention is to at least partially eliminate the disadvantages described above, and in particular the object of the present invention is to manufacture a cathode that is easy to handle and as efficient as possible for use in a solid-state battery in a simple and possibly cost-effective manner. It is to provide a method for manufacturing a cathode for a solid-state battery, which makes it possible.

The object is achieved by a method having the features of claim 1 and by a cathode according to claim 11. Additional features and details of the invention will become apparent from the dependent claims, description and drawings.

The technical features disclosed for the method according to the invention, here also apply in relation to the cathode according to the invention, and vice versa, are always interchangeably referred to in connection with the disclosure of the individual aspects of the invention. Or can be referred to. Advantageous embodiments of the invention are described in the dependent claims.

The method for manufacturing the cathode of a solid-state battery can preferably serve to produce a stand-alone cathode, where the stand-alone cathode is used directly in the battery, especially due to its self-supporting, ie mechanical strength and high flexibility. It is understood to be a cathode, which may and may not need to be additionally attached to the conductive substrate.

Cathodes that can be produced by the method can be used here, preferably in solid batteries, which can be used in particular for use in electric or hybrid vehicles.

Here, the method according to the present invention for manufacturing a cathode of a solid state battery comprises the steps of preparing a mixture consisting of a cathode active material and at least one other component, in order to prepare a macro porous cathode material, the mixture with an electron conductive oxide Mixing, forming a crosslink of the cathode active material by a heating process, and mixing the macroporous cathode material with a solid electrolyte material to produce a microporous cathode material.

In this case, the mixture prepared according to the first step of the present method may include, in addition to the cathode active material, preferably an additive formed in the form of an organic oxide as another component, particularly polyethylene oxide as another component. The mixture can here be formed, for example, at least partially in the form of a flowable solution, in particular in the form of a viscous slurry. Further, the step of mixing the mixture with the electron-conducting oxide, provided according to the second step of the method according to the invention, can be carried out, for example, in such a way that the mixture is provided in a solution with the electron-conducting oxide. The electron-conducting oxide can advantageously be present here, preferably in the form of nanoparticles dispersed and/or suspended in solution. However, an alternative sol-gel approach can also be considered, which can only be formed of the corresponding oxides in subsequent heating processes. The macroporous cathode material prepared through the step of mixing the mixture with the electron conductive oxide already has electronic conductivity, but not yet ionic conductivity. A specific third step of the process according to the invention for forming the crosslinking of the cathode active material, provided in the form of a heating process, is preferably in the presence of oxygen, especially under pure oxygen atmosphere, but also at defined oxygen partial pressures, It can be carried out, for example, in CO/CO ₂ or a saturated gas of water vapor. The step of mixing the macroporous cathode material with the solid electrolyte material, provided according to the fourth step of the method according to the invention, can likewise be carried out in such a way that the macroporous cathode material is provided in a solution with a solid electrolyte material. . In this case, the solid electrolyte material may be present, for example, in the form of nanoparticles. Alternatively, it is also conceivable that dissolved extracts are used which react to the solid electrolyte, for example in a further subsequent heating step. The microporous cathode material produced through the step of mixing the macroporous cathode material with the solid electrolyte material now has both electronic conductivity and ionic conductivity.

In this case, the term macroporous cathode material in the context of the present invention is understood to be a cathode material that contains intimate and intimate linkage of individual components, in particular in the way that electronic conductivity is provided, but ionic conductivity is not present. On the other hand, the term microporous cathode material is understood to be a cathode material comprising intimate and intimate connections of the individual components, in particular in a manner that ensures both electronic conductivity and ionic conductivity according to the invention. Electronic conductivity in the context of the present invention is understood to mean the transport of charge through an electrode. On the other hand, ionic conductivity is understood according to the invention to mean material transport, in particular charge transport associated with the movement of charged ions.

By macroporous cathode material, for example, the pores contain a volume of at least 5% on average, preferably at least 10%, especially at least 20%, relative to the particle ratio, and/or the average pore size exceeds the nanometer range It can be understood to be a phosphorus substance. Microporous cathode material also means that the pores contain, on average, a volume of at least less than 20%, preferably less than 10%, especially less than 5%, relative to the particle ratio, and/or have an average pore size in the micrometer range. It can be understood to be less than a substance.

By means of the method according to the invention, it is possible to provide very low porosity and particularly high performance cathodes, without the addition of a binder material or a carbon-based conductive additive, in particular by using an electron conductive oxide. In this case, the electron-conducting oxide provided according to the present invention can be responsible for both the function of the binder and the function of the conductive additive, and additionally has electron conductivity for crosslinking properties. By replacing the carbon-based conductive additive, deterioration of the solid electrolyte material can also be prevented. In addition, the handling of cathodes produced by the method according to the invention is simplified compared to cathodes manufactured according to the standard, which enables scalable production of solid batteries with higher performance.

It can be provided according to the invention that the mixture is provided on the substrate for drying, especially before the step of mixing the mixture with the electron-conducting oxide, particularly with regard to simple and accurately meterable mixing. In this case, the mixture can preferably be cast on a substrate, where the substrate can be formed, for example, in the form of an organic substrate, in particular a polyester substrate. In this case, the mass ratio between the cathode active material and at least one other component can be set in particular to create a defined surface load on the substrate. The mixture here is preferably dried in such a way that a separable solid structure is formed. After the mixture is dried on the substrate, the mixture can be converted, for example, into a preferred form, and preferably stamped into a preferred form. Here, the substrate can be specifically removed in a heating step other than the present invention for crosslinking the cathode active material by releasing a corresponding gas such as CO ₂ and the like.

In addition, with regard to the advantageous selection of the active material, it can be provided according to the invention that the active material is formed in the form of lithium cobalt oxide (LCO) and/or lithium nickel cobalt manganese oxide (NMC). Here, LCO is particularly suitable due to its high resistance to heat. On the other hand, NMC is also particularly suitable due to its high performance, current and capacity. Alternatively, designs in which the active material is formed in the form of a mixture with various cathode materials, in particular additives in the form of LFP or HV-spinel, can also be considered. Here, the active material may advantageously be provided with a protective coating, for example a coating formed in the form of LiNbO ₃ , which is particularly suitable when NCM is used as the active material.

According to the invention, it can also be provided that the electron-conducting oxide comprises an electron conductivity of at least 10 ² S/m under standard conditions in order to ensure always high enough conductivity of the present cathode in various applicability. The electron-conducting oxide is preferably formed of a material having electrical conductivity in the range of the electrical conductivity of the metal. In this case, the electron conductive oxide comprises a conductivity of at least 10 ² S/m, preferably at least 10 ⁴ S/m, especially at least 10 ⁶ S/m under standard conditions. The electron-conducting oxide is, for example, ReO ₃ and/or TiO and/or CrO ₂ and/or Ti ₂ O ₃ and/or VO and/or V ₂ O ₃ and/or ReO and/or Fe ₃ O ₄ and/or NbO and/or MnO ₂ .

With regard to the structurally simple possibility of making a stand-alone cathode, according to the present invention, after the step of mixing the macroporous cathode material with a solid electrolyte to produce a microporous cathode material, the microporous cathode material is applied on a solid electrolyte membrane. It may be provided that the steps are performed. Here, the microporous cathode material can be dried or still wet, preferably applied onto a solid electrolyte membrane which has already been prepared. The solid electrolyte membrane can be formed of the same or different solid electrolyte from the cathode material here. Here, a solid adhesive bond between the microporous cathode material and the solid electrolyte membrane can be formed, in particular, through mechanical pressure and/or heating, where temperature on the one hand ultimately dries the cathode, and on the other hand the solid electrolyte By increasing its fluidity, it involves a stronger connection with other components.

With regard to the understanding of a cell stack comprising a cathode according to the invention for a solid-state battery, it can be provided according to the invention that the step of applying the anode layer is provided, especially in the context of a particularly compact arrangement of the solid-state battery. The anode layer here can preferably be formed in the form of a metal foil, in particular in the form of a lithium foil, which can be pressed on the side of the solid electrolyte membrane which is positioned opposite the cathode, for example for closing the cell configuration.

In the course of carrying out the method according to the invention, in order to ensure as flexible and finely measurable mixing as possible, the electron conductive oxide is mixed with the mixture and/or the solid electrolyte material is mixed with the macroporous cathode material. It may be particularly specifically provided that they are each previously suspended in a solvent. For the suspension of electron-conducting oxides and/or solid electrolyte materials, high volatility non-protonic solvents such as, for example, THF, cyclohexane, methyl acetate, chloroform, dichloromethane, diethyl ether, acetonitrile, etc. are suitable. , Where the electron-conducting oxide and/or solid electrolyte material is particularly soluble in a solvent in the form of nanoparticles, and may be present in a suspended or dispersed state.

With regard to definable and controllable reactivity and conversion as far as possible, it is also conceivable that a supply of inert gas is provided in the course of carrying out the method according to the invention. The inert gas can be formed here in the form of an inert gas, for example argon, helium, and the like. In addition, nitrogen or other gases or certain gas mixtures can also be used.

It can also be provided in accordance with the invention that LLZO (garnet) and/or NASICON are used as solid electrolyte materials to provide the widest possible electrochemical stability window of the cathode material. Likewise, in addition to these two solid electrolyte materials mentioned, other materials with particularly similar electrochemical stability windows may also be used.

Considering the high bonding potential between the electron conductive oxide and the mixture and between the solid electrolyte material and the macroporous cathode material, the electron conductive oxide and/or solid electrolyte material is present in a size of 2 to 5 nm before the mixing step. It can also be provided according to the method according to the invention. In this case, the electron-conducting oxide and solid electrolyte material can preferably be pulverized or otherwise processed before being added to the solvent, particularly through a mechanical-physical manufacturing process such as a milling process or the like. Here, with respect to the size of the solid electrolyte material and/or electron-conducting oxide, they are preferably pulverized or prepared to a size of less than 10 nm, preferably of less than 5 nm, in particular of less than 3 nm. Can.

Likewise, the subject of the invention is also a cathode for a solid-state battery, which can be produced through the method according to claim 1. Here, the cathode comprises an active material, an electron-conducting oxide and a solid electrolyte, wherein the cathode is formed in the form of a stand-alone cathode and includes electron conductivity and ion conductivity. Thus, the cathode according to the invention for a solid-state battery comprises the same advantages as already described in detail in connection with the method according to the invention. The present cathode for a solid state battery can be formed here particularly in the form of a high performance composite cathode. The stand-alone cathode compartment can be understood here to be a cathode which can be used directly in batteries, in particular because of its self-supporting, ie mechanical strength and high flexibility, and which need not be additionally attached on a conductive substrate. It should be understood that a standalone cathode may alternatively also be disposed on an electronically conductive substrate.

Other advantages, features and details of the present invention will become apparent from the following description in which embodiments of the present invention are described in detail with reference to the drawings. The features recited in the claims and detailed description herein may each be essential to the invention, either individually or in any combination.

1 shows a schematic view of the individual steps of a method according to the invention for manufacturing a cathode of a solid-state battery.

The same reference numbers are used for the same technical features in the drawings.

1 shows a schematic view of the individual steps of a method according to the invention for manufacturing a cathode of a solid-state battery. Here, according to the method according to the invention presented herein, first in the preceding first step of the method according to the invention, to prepare a mixture 6 consisting of the cathode active material 2 and at least one other component 4 Step 30 is performed.

In this case, the other components may preferably be formed in the form of an organic oxide, in particular in the form of a polyethylene oxide. The mixture 6 can also be formed, for example, in the form of at least partially flowable solutions, in particular in the form of viscous slurries or the like. The mixture 6 is, after its manufacture, cast on the substrate 16 for drying in this case, where the substrate 16 is formed in the form of a polyester substrate in this case. The mass ratio between the cathode active material 2 and the at least one other component 4 can be set here in particular to generate a defined surface load on the substrate 16. According to the invention, the mixture 6 is dried here preferably in such a way that a separable solid structure is formed. After the mixture 6 is dried on the present substrate 16, the mixture 6 can be stamped, for example, into a desired shape. The substrate 16 can be removed here again from the mixture, for example in a subsequent heating step or the like. In this case, the active material can be formed in the form of LCO and/or NMC. However, alternatively, designs in which the active material is formed in the form of a mixture with various cathode materials, in particular additives in the form of LFP or HV-spinel, can also be considered. Here the active material may advantageously also be provided with a protective coating, for example a coating formed in the form of LiNbO ₃ .

In the second step of the method according to the invention, in order to produce the macroporous cathode material 10 in this case, the step 32 of mixing the mixture 6 with the electron-conducting oxide 8 can be performed. The step 32 of mixing the mixture 6 according to the invention with the electron-conducting oxide 8 is performed in this case by providing the mixture 6 with a solution having the electron-conducting oxide 8. Here, the electron-conducting oxide 8 is present in the solvent in a suspended state in the form of nanoparticles in this case. As a suitable solvent here, a volatile non-protonic solvent is particularly suitable. The macroporous cathode material 10 prepared through the step 32 of mixing the mixture 6 with the electron-conducting oxide 8 already has an electron conductivity, but not yet an ionic conductivity. The electron-conducting oxide 8 here preferably has an electrical conductivity in the range of the electrical conductivity of the metal, for example at least 10 ² S/m, preferably at least 10 ⁴ S/m, in particular at least 10 ⁶ S/m It is formed of a material containing the conductivity of. The electron-conducting oxide 8 is here specifically ReO ₃ and/or TiO and/or CrO ₂ and/or Ti ₂ O ₃ and/or VO and/or V ₂ O ₃ and/or ReO and/or Fe ₃ O ₄ and And/or in the form of NbO and/or MnO ₂ .

In a subsequent third step of the method according to the invention, the step 34 of subsequently forming the crosslinking 18 of the cathode active material 2 by a heating process is carried out. A specific third step of the process according to the invention can be carried out here preferably in the presence of oxygen, especially under a pure oxygen atmosphere, but also at defined oxygen partial pressures, for example in CO/CO ₂ or a saturated vapor of water vapor. have. In addition to the use of oxygen gas, an inert gas may alternatively or additionally also be provided in the above method step or in another method step to control reactivity and conversion.

According to the fourth step of the method according to the invention, the step 36 of mixing the macroporous cathode material 10 with the solid electrolyte material 12 is finally performed to produce the microporous cathode material 14. . The step 36 of mixing the macroporous cathode material 10 with the solid electrolyte material 12 is performed by providing the macroporous cathode material 10 in a solution with the solid electrolyte material 12, as in the present case. The solid electrolyte material 12 can likewise be present in the form of nanoparticles suspended in a solvent. Here, LLZO (garnet) and/or NASICON can be used as a solid electrolyte material. In addition to the solid electrolyte materials mentioned as well, other materials with similar similar electrochemical stability windows can also be used. The microporous cathode material 14 produced through the step of mixing the macroporous cathode material 10 with the solid electrolyte material 12 now has both electron conductivity and ionic conductivity. The term macroporous cathode material 10 here is understood to be a cathode material comprising intimate and intimate connections of the individual components in a manner in which in the context of the present invention, in particular, electron conductivity is guaranteed, but ionic conductivity is not permitted. . Microporous cathode material here is understood in the context of the present invention to be a cathode material comprising a close and intimate connection of the individual components, in a way in which both electronic conductivity and ionic conductivity are guaranteed.

In a further optional step of the method according to the invention, after the step 36 of mixing the macroporous material 10 with the solid electrolyte 12 to produce the microporous cathode material 14, the microporous cathode material ( Step 38 of applying 14) onto the solid electrolyte membrane 20 may be performed. Here, the microporous cathode material 14 may be dried or still wet, preferably applied on a solid electrolyte membrane 20 which has already been prepared. The solid electrolyte membrane 20 can be formed of the same or different solid electrolyte from the solid electrolyte 12 from the cathode material here. Here, a solid adhesive bond between the microporous cathode material 14 and the solid electrolyte membrane 20 can be formed, particularly through mechanical pressure and/or heat.

In another optional step of the method according to the invention, the step 40 of applying the anode layer 22 may also be provided, which anode layer is in particular in the form of a metal foil, in particular lithium, especially with regard to a compact arrangement. It can be formed in the form of a foil and can be pressed on the side of the solid electrolyte membrane 20 which is positioned opposite the cathode, for example to close the cell configuration.

By means of the method according to the invention, it is possible to provide very low porosity and particularly high performance cathodes, without the addition of a binder material or a carbon-based conductive additive, in particular by using an electron conductive oxide. By replacing the carbon-based conductive additive, deterioration of the solid electrolyte material can also be prevented. In addition, the handling of composite cathodes produced by the method according to the invention is also simplified compared to cathodes manufactured according to the standard, which enables scalable production of solid batteries with higher performance.

2 cathode active material
4 different ingredients
6 mixture
8 electron conductive oxide
10 Macro Porous Cathode Material
12 solid electrolyte material
14 microporous cathode material
16 substrates
18 crosslinking
20 solid electrolyte membrane
22 anode layer
30 steps to prepare a mixture
32 Mixing the mixture
34 forming a crosslink
36 Mixing macroporous cathode material
38 Applying the microporous cathode material
40 Applying Anode Layer

Claims (11)

A method for manufacturing a cathode of a solid state battery,
-Preparing a mixture (6) consisting of a cathode active material (2) and at least one other component (4) (30),
-Mixing (32) the mixture (6) with an electron-conducting oxide (8) to produce a macro-porous (macro porous) cathode material (10),
-Forming (34) the crosslinking (18) of the cathode active material (2) by a heating process,
Mixing the macroporous cathode material 10 with the solid electrolyte material 12 to produce a microporous cathode material 14 (36)
Method for manufacturing a cathode of a solid-state battery comprising a. According to claim 1,
The mixture (6) is provided on the substrate for drying, prior to the step (32) of mixing with the electron conductive oxide (8). The method according to claim 1 or 2,
The cathode active material (2) is characterized in that it is formed in at least one form of lithium cobalt oxide (LCO) and lithium nickel cobalt manganese oxide (NMC). The method according to claim 1 or 2,
The method according to claim 1, wherein the electron conductive oxide (8) comprises a conductivity of at least 10 ² S/m under standard conditions. The method according to claim 1 or 2,
To prepare the microporous cathode material 14, after the step 36 of mixing the macroporous cathode material 10 with the solid electrolyte 12, the microporous cathode material 14 is replaced with a solid electrolyte membrane 20 ) Applying onto (38) is performed. The method according to claim 1 or 2,
A method characterized in that a step 40 of applying the anode layer 22 is provided. The method according to claim 1 or 2,
At least one of the solid electrolyte material 12 prior to mixing 36 with the electron conductive oxide 8 and the macroporous cathode material 10 prior to mixing 32 with the mixture 6 is a solvent, respectively. Method characterized in that it is present in a suspended state. The method according to claim 1 or 2,
A method characterized in that a supply of inert gas is provided. The method according to claim 1 or 2,
A method characterized in that at least one of LLZO (garnet) and NASICON is used as the solid electrolyte material 12. The method according to claim 1 or 2,
A method characterized in that at least one of the electron conductive oxide (8) and the solid electrolyte material (12) is present in a size of 2 to 5 nm before mixing (32, 36). As a cathode for a solid battery,
A solid, which may be prepared through the method according to claim 1 or 2, comprising an active material, an electron-conducting oxide and a solid electrolyte, the cathode being formed in the form of a stand-alone cathode, comprising electron conductivity and ion conductivity. Battery cathode.

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