Composite electrode with uniform deposition behavior

Abstract

This invention relates to a composite electrode for an electrochemical solid-state battery, comprising: at least one substantially non-porous solid electrolyte layer comprising at least one first solid electrolyte; at least one porous solid electrolyte layer comprising at least one second solid electrolyte; and at least one current collector layer, the porous solid electrolyte layer disposed on at least one surface of the current collector layer and disposed between the substantially non-porous solid electrolyte layer and the current collector layer; at least a portion of the surface of the micropores of the porous solid electrolyte layer has been modified by a coating having at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium; and the thickness of the coating on the surface of the micropores of the porous solid electrolyte layer decreases with increasing spacing between the respective micropore surface and the current collector layer. The invention also relates to methods of manufacturing such a composite electrode, its applications, and electrochemical solid-state batteries comprising such a composite electrode.

Description

Technical Field

[0001] This invention relates to a composite electrode comprising at least one porous solid electrolyte layer, which exhibits uniform deposition behavior when used as a negative electrode in an electrochemical solid-state battery, during the deposition of elemental lithium. The invention also relates to methods for manufacturing such a composite electrode and its applications. Background Technology

[0002] Battery packs store electrical energy. They convert the energy from chemical reactions into electrical energy. In this context, a distinction is made between primary and secondary battery packs. A primary battery pack is capable of functioning only once, while a secondary battery pack, also known as a rechargeable battery, is rechargeable. A battery pack here comprises one or more battery cells.

[0003] Lithium-ion battery packs are particularly used in storage batteries. They are especially outstanding for their high energy density, thermal stability, and exceptionally low self-discharge. Lithium-ion battery packs are used particularly in motor vehicles, especially electric vehicles.

[0004] Lithium-ion battery packs typically include a positive electrode and a negative electrode, where the positive electrode is called the cathode and the negative electrode is called the anode. Each electrode includes at least one current collector and at least one active material. A recent development focus is on the application of solid electrolytes. These can prevent the deposition of dendritic crystals of elemental lithium and thus improve safety when using metallic lithium as the active material. Metallic lithium is preferably used as the anode active material due to its higher achievable energy density. The dense (kompakt) electrode composed of metallic lithium has a small interface with the separator and therefore leads to high current density and consequently, damage mechanisms such as dendritic growth during the operation of the electrochemical solid-state battery.

[0005] ED Wachsman and researchers from the University of Maryland have proposed an application of a porous lithium metal anode in lithium-sulfur battery packs (https: / / ecs.confex.com / ecs / 232 / webprogram / Paper103639.html).

[0006] US 2017 / 187063 discloses an electrolyte material comprising lithium-conducting ceramic particles distributed in a matrix consisting of a lithium-conducting solid polymer, an electrolyte salt, and chemical additives to form a ceramic-polymer composite material, wherein the chemical additives are configured to reduce the ionic resistance at the interface between the ceramic particles and the ion-conducting solid polymer.

[0007] JP2017-117672 discloses a method for manufacturing an all-solid-state energy storage device, comprising the steps of: forming a positive electrode current collector on a first insulating substrate; forming a positive electrode layer on the positive electrode current collector; forming a first solid electrolyte layer on the positive electrode layer; forming a negative electrode current collector on a second insulating substrate; forming a negative electrode layer on the negative electrode current collector; forming a second solid electrolyte layer on the negative electrode layer; forming an attached solid electrolyte layer on at least one of the first and second solid electrolyte layers; and connecting the first solid electrolyte layer and the second solid electrolyte layer to each other by the attached solid electrolyte layer. Summary of the Invention

[0008] The subject of this invention is a composite electrode for electrochemical solid-state batteries, comprising:

[0009] At least one substantially non-porous solid electrolyte layer, the substantially non-porous solid electrolyte layer comprising at least one first solid electrolyte;

[0010] At least one porous solid electrolyte layer, said porous solid electrolyte layer comprising at least one second solid electrolyte; and

[0011] At least one current collector layer,

[0012] in

[0013] The porous solid electrolyte layer is disposed on at least one surface of the current collector layer and is disposed between the substantially non-porous solid electrolyte layer and the current collector layer.

[0014] At least a portion of the surface of the micropores in the porous solid electrolyte layer has been modified by a coating, wherein the coating has at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium; and

[0015] The thickness of the coating on the surface of the micropores of the porous solid electrolyte layer decreases as the distance between the corresponding micropore surface and the current collector layer increases, wherein the coating has at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium.

[0016] The composite electrode according to the invention comprises at least one substantially non-porous solid electrolyte layer. It is preferentially used as a separator in the composite electrode according to the invention and is therefore preferably non-conductive, while possessing good ionic conductivity, especially relative to lithium ions.

[0017] The substantially non-porous solid electrolyte layer has a first surface and a second surface and includes at least one solid electrolyte and optionally at least one binder and / or, if necessary, at least one conductive salt for improving ionic conductivity.

[0018] Preferably, the solid electrolyte in the substantially non-porous solid electrolyte layer is at least one inorganic solid electrolyte, particularly selected from sintered inorganic ionic conductors and / or unsintered inorganic ionic conductors. Suitable inorganic solid electrolytes are known to those skilled in the art.

[0019] Sintered inorganic ionic conductors possess exceptionally high mechanical strength. Suitable sintered inorganic ionic conductors, especially those containing oxides, include:

[0020] a) Garnet with the general molecular formula (I):

[0021] Li y A3B2O 12 (I)

[0022] Wherein, A is at least one element selected from the group consisting of La, K, Mg, Ca, Sr and Ba, and B is at least one element selected from the group consisting of Zr, Hf, Nb, Ta, W, In, Sn, Sb, Bi and Te, where 3 ≤ y ≤ 7.

[0023] The most preferred representative is garnet with the molecular formula (I) and a predominantly cubic crystal structure, especially with the molecular formula Li7La3Zr2O. 12 Lithium-lanthanum-zirconate and molecular formula Li5La3Ta2O 12 Lithium-lanthanum-tantalate (LLTa) and LLZO doped with niobium or tantalum.

[0024] b) Perovskites of the general molecular formula (II):

[0025] Li 3x La 2 / 3-x TiO3(LLTO)(II)

[0026] Where 2 / 3 ≥ x ≥ 0.

[0027] The preferred example is Li 0.35 La 0.55 TiO3 perovskite.

[0028] c) NASICON-type glass ceramics and / or glasses, represented by the general molecular formula (III):

[0029] Li 1+x R x M 2-x (PO4)3 (III)

[0030] Where M is selected from at least one element in the group Ti, Ge and Hf.

[0031] R is selected from at least one element of the group Al, B, Sn and Ge, where 0 ≤ x < 2.

[0032] Preferred examples are lithium-aluminum-titanium phosphates (LATP, especially Li...). 1.4 Al 0.4 Ti 1.6 (PO4)3) and lithium-aluminum-germanium-phosphate (LAGP, especially Li) 1.5 Al 0.5 Ge 1.5 (PO4)3).

[0033] d) LiSICON-type glass ceramics and / or glasses, represented by the general molecular formula (IV):

[0034] Li 2+2x Zn 1−x GeO4 (IV)

[0035] Where x relates to the corresponding share in mole percentage and 0 ≤ x < 1;

[0036] The preferred example is Li2ZnGeO4.

[0037] Suitable unsintered inorganic ionic conductors, especially those including sulfurized solid electrolytes, such as:

[0038] a) Sulfide glasses and / or glass ceramics of the general molecular formula (V):

[0039] (1-a) [x (Li2S) y (P2S5) z (M n S m )] · a [LiX] (V)

[0040] Where M n S mIt has the meaning of SnS2, GeS2, B2S3 or SiS2.

[0041] X can represent Cl, Br, or I.

[0042] x, y, and z can each take values ​​from 0 to 1 independently of each other, provided that x + y + z = 1, and

[0043] a has values ​​from 0 to 0.5, especially from 0 to 0.35;

[0044] The preferred representative is Li 10 GeP2S 12 Li 9.6 P3S 12 and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 .

[0045] b) Sulfide glasses and / or glass ceramics of molecular formula (VI):

[0046] Li3PS4 (VI).

[0047] c) Sulfide glasses and / or glass ceramics of formula (VII):

[0048] x [Li2S] · (1-x) [P2S5] (VII)

[0049] Where 0 < x < 1.

[0050] Preferred compositions are 0.67[Li2S]·0.33[P2S5], 0.7[Li2S]·0.3[P2S5], and 0.75[Li2S]·0.25[P2S5].

[0051] d) Sulfide glasses and / or glass ceramics of molecular formula (VIII):

[0052] (1 − y) (0.7 · Li2S ·0.3 · P2S5) · y LiX (VIII)

[0053] Where X can have the meanings of F, Cl, Br and / or I, and 0 ≤ y ≤ 0.2; and

[0054] The preferred representatives are 0.9 (0.7 · Li₂S · 0.3 · P₂S₅) · 0.1 LiI and

[0055] 0.9 (0.7 · Li2S · 0.3 · P2S5) · 0.1 LiCl.

[0056] e) Australite with molecular formula (IX):

[0057] Li y PS5X (IX)

[0058] Where y has the value 7 and X has the meaning of S, or

[0059] Where y has a value of 6 and X can be selected from Cl, Br and I and mixtures thereof.

[0060] The preferred representatives are Li7PS6, Li6PS5Cl and Li6PS5I.

[0061] The substantially non-porous solid electrolyte layer further includes at least one binder. This is possible when sintering of the ionic conductor can be omitted (this applies to sulfurized ionic conductors). Suitable binders include at least one organic polymer. Here, all binders commonly used in solid electrolyte composites can be used. Suitable binders are known to those skilled in the art and include not only binders that merely contribute to improving the stability of the composite membrane (which are also referred to herein as polymer binders) but also binders that perform other functions, such as polymer electrolytes. The binder may therefore include other components besides the at least one polymer, particularly conductive salts for improving ionic conductivity.

[0062] Suitable polymer binders include, in particular, carboxymethyl cellulose (CMC), styrene-butadiene copolymer (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), and ethylene-propylene-diene terpolymer (EPDM).

[0063] Polymer electrolytes include at least one polymer and at least one conductive salt, especially lithium salt.

[0064] Suitable polymers for the polymeric electrolytes mentioned herein are particularly emphasized as follows: polyalkylene oxide derivatives of polyethylene oxide, polypropylene oxide, etc., or polymers including: polyalkylene oxide derivatives; derivatives of polyvinylidene fluoride (PVDF), polyhexafluoropropylene, polycarbonate, polyacrylate, polyphosphate, polyalkylimide, polyacrylonitrile, poly(meth)acrylate, polyphosphazene, polyurethane, polyamide, polyester, polysiloxane, polymalonate, etc. Derivatives that are particularly emphasized are fluorinated or partially fluorinated derivatives of the polymers mentioned above. Similarly, block and brush copolymers of different representatives of the polymer classes mentioned above are suitable. They may also include mechanically robust polymer blocks, such as polystyrene or polyimide. Also included are: transversely crosslinked polymers and oligomers (i.e., polymers having >2 and < 20 repeating units of monomers in the sense of this invention), wherein the polymer is constructed from said oligomers. Polymers having ≥ 20 repeating units are referred to herein as polymers. Preferred polymer compounds are those having an olefin oxide structure, a urethane structure, or a carbonate structure in molecular form. For example, polyolefin oxides, polyurethanes, and polycarbonates are preferred due to their good electrochemical stability. Furthermore, polymers belonging to the fluorocarbon family are preferred. Polyvinylidene fluoride and polyhexafluoropropylene are preferred due to their stability. The number of repeating units in such olefin oxides, urethanes, carbonates, and / or fluorocarbon units is preferably in the range of 1 to 1000, more strongly preferably in the range of 5 to 100. Polyalkylene oxides, such as polyethylene oxide and polypropylene oxide, having 1 to 1000, more strongly preferably 5 to 100 repeating units are particularly preferred.

[0065] To improve ionic conductivity, at least one conductive salt is typically added to at least one polymer of the polymer electrolyte. Suitable conductive salts are, in particular, lithium salts. This conductive salt can be selected, for example, from the group consisting of: lithium halides (LiCl, LiBr, LiI, LiF), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium nitrate (LiNO3), lithium tetrafluoromethanesulfonate ((LiSO3CF3), lithium bis(fluorosulfonyl)imide (Li[N(SO2F)2], LiFSI), lithium bis(tetrafluoromethanesulfonyl)imide (Li[N(SO2(CF3))2], LiTFSI), lithium bis(pentafluoromethanesulfonyl)imide (LiN(SO2C2F5)2, LiBETI), lithium bis(oxalatoborate)borate (LiB(C2O4)). 2,Lithium difluorooxalate borate (Li[BF2(C2O4)], LiDFOB), lithium tris(pentafluoromethyl)difluorophosphate (LiPF2(C2F5)3), and combinations thereof are particularly preferred. The conductive salts are selected from lithium iodide (LiI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (Li[N(SO2F)2], LiFSI), and lithium bis(tetrafluoromethylsulfonyl)imide (Li[N(SO2(CF3))2], LiTFSI), and combinations thereof. The conductive salts can be used individually or in combination.

[0066] Preferably, the total amount of at least one conductive salt comprises 1 to 50% by weight, particularly 2 to 40% by weight, of the total weight of the polymer electrolyte.

[0067] The composition of the composite membrane (Kompositfolie) may optionally include other components, but preferably does not include conductive additives.

[0068] Essentially, a non-porous solid electrolyte layer is essentially devoid of micropores. This means that a essentially non-porous solid electrolyte layer has a free micropore volume of less than 5 vol%, strongly preferably less than 2 vol%, and especially less than 1 vol% with respect to the total volume of the solid electrolyte layer.

[0069] The substantially non-porous solid electrolyte layer preferably has a layer thickness of 0.1 to 500 μm, especially 1 to 100 μm.

[0070] The composite electrode according to the invention includes at least one current collector layer. This facilitates the electrical contact of the composite electrode. The at least one current collector layer comprises at least one conductive material, particularly a metal. Particularly preferred metals are copper, lithium, nickel, aluminum, and alloys of these metals with each other or with other metals. The at least one current collector layer has at least one first surface and at least one second surface and preferably has a layer thickness of 10 to 500 μm, particularly 50 to 300 μm.

[0071] The composite electrode according to the invention comprises at least one porous solid electrolyte layer. The microporous surface of the porous solid electrolyte layer facilitates the deposition of truly active material, i.e., elemental lithium. The at least one porous solid electrolyte layer is therefore capable of conducting ions and, in particular, exhibits good conductivity with respect to lithium ions.

[0072] The at least one porous solid electrolyte layer has at least one first surface and at least one second surface. The at least one porous solid electrolyte layer is disposed on at least the first surface of the current collector layer. Preferably, the at least one porous solid electrolyte layer is disposed directly on at least the first surface of the current collector layer, i.e., there is no other material between the at least one porous solid electrolyte layer and the current collector layer, and the first surface of the current collector layer is in direct contact with the first surface of the porous solid electrolyte layer. In an alternative embodiment, a cladding made of another metal is disposed between the current collector layer and the porous solid electrolyte layer to improve the contact between the current collector layer and the porous solid electrolyte layer.

[0073] The at least one porous solid electrolyte layer is further disposed between the substantially non-porous solid electrolyte layer and the current collector layer. Preferably, the substantially non-porous solid electrolyte layer is disposed directly on the surface of the at least one porous solid electrolyte layer opposite to the current collector layer, i.e., without any other intermediate layer. The substantially non-porous solid electrolyte layer is disposed on the second surface of the porous solid electrolyte layer. Preferably, the first surface of the substantially non-porous solid electrolyte layer is in direct contact with the second surface of the porous solid electrolyte layer.

[0074] The porous solid electrolyte layer includes at least one solid electrolyte and optionally at least one binder and / or, if necessary, at least one conductive salt for improving ionic conductivity and / or at least one conductive additive for improving electrical conductivity.

[0075] Preferably, the solid electrolyte in the porous solid electrolyte layer is at least one inorganic solid electrolyte, particularly selected from: sintered inorganic ionic conductors and / or unsintered inorganic ionic conductors. Suitable inorganic solid electrolytes particularly include: the sintered inorganic ionic conductors and / or unsintered inorganic ionic conductors described above. The porous solid electrolyte layer and the substantially non-porous solid electrolyte layer may comprise entirely or partially the same inorganic solid electrolyte. However, the inorganic solid electrolytes in the porous solid electrolyte layer and the substantially non-porous solid electrolyte layer may also be different from each other.

[0076] The porous solid electrolyte layer may also optionally include at least one binder and / or, if necessary, at least one conductive salt. Both are preferably selected from the binders and conductive salts mentioned above and may be the same as or different from the conductive salts and / or binders of the substantially porous solid electrolyte layer.

[0077] The porous solid electrolyte layer may also optionally include at least one conductive additive. Suitable conductive additives include conductive carbon black, graphite, and carbon nanotubes. The application of conductive additives is generally possible if sintered ionic conductors can be abandoned (this is particularly suitable for sulfurized ionic conductors).

[0078] The porous solid electrolyte layer has an open, porous structure. Preferably, the open micropore volume of the porous solid electrolyte layer is at least 40 vol%, preferably at least 50 vol%, and especially at least 60 vol%, with respect to the total volume of the porous solid electrolyte layer. The open micropore volume can be determined using more common methods known to those skilled in the art. Suitable methods highlighted are the BET method (DIN ISO 9277) and the mercury porosity method (DIN ISO 66139).

[0079] In one embodiment of the present invention, the total volume of the porous solid electrolyte layer is constant.

[0080] In an alternative implementation, the porosity, i.e. the proportion of the volume of open micropores in the porous solid electrolyte layer with respect to the total volume of the porous solid electrolyte layer, decreases with increasing distance from the surface of the current collector layer.

[0081] The porous solid electrolyte layer preferably has a layer thickness of 1 to 500 μm, especially 10 to 100 μm.

[0082] The porous solid electrolyte layer is further characterized in that the micropore surfaces of the open micropores of the porous solid electrolyte layer are at least partially equipped with a coating. The coating herein comprises at least one material suitable for reducing the interfacial resistance between the second solid electrolyte and elemental lithium.

[0083] Modification of the free microporous surface of the porous solid electrolyte layer is preferably carried out in coordination with the specific properties of the corresponding solid electrolyte. Reduction of the interfacial resistance between the second solid electrolyte and elemental lithium is preferably achieved by a coating having a material that enhances the dielectric constant (dielectric conductivity) and / or electrical conductivity of the microporous surface.

[0084] According to the invention, the increased electrical conductivity is preferably achieved through a coating comprising at least one conductive material. Suitable materials include, in particular, conductive carbon variants, metals and alloys, inorganic semiconductors, and conductive polymers. Conductive carbon variants are particularly emphasized as conductive carbon black, graphite, and carbon nanotubes. Suitable metals include, in particular, gold, platinum, copper, silver, and lithium. Gold-lithium alloys are particularly emphasized as alloys. Inorganic semiconductors include, in particular, Si, GaN, and CdTe, which can also be p-doped or n-doped if necessary. Suitable conductive polymers are particularly characterized by conjugated double bonds along the polymer backbone. Polypyrrole, polythiophene, polyaniline, polyacetylene, and poly-p-phenylene should be emphasized.

[0085] According to the present invention, the increase in dielectric constant (dielectric conductivity) is preferably achieved through a coating having at least one dielectric material with a high dielectric constant. Suitable materials include, in particular, BaTiO3, SrTiO3, barium-strontium titanate, and CaCu3Ti4O3. 12 TiO2 and Al2O3. Furthermore, the following composite materials are suitable, which are particles composed of the previously mentioned conductive materials (carbon variants, such as conductive carbon black, graphite, carbon nanotubes; metals, such as Au, Pt, Cu, Ag, Li; alloys, such as Li / Au; inorganic semiconductors, such as Si, GaN, CdTe, which may optionally be p-doped or n-doped; and conductive polymers) having an insulating shell, particularly in the form of a shell made of a non-conductive polymer (e.g., polyolefin).

[0086] Conductive and / or dielectric materials are applied in the form of a coating onto at least a portion of the micropore surface of the open micropore volume of the porous solid electrolyte layer.

[0087] A coating having an open microporous surface of a porous solid electrolyte layer with at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium is particularly advantageous: the coating has a layer thickness and / or coverage that decreases with increasing spacing between the respective microporous surface and the current collector layer. The coating preferably has a layer thickness of at least 1 nm (close to the current collector layer), preferably at least 1.5 nm, and a maximum of 500 nm (close to a substantially non-porous solid electrolyte layer), preferably a maximum of 400 nm. In the case of a partial coating, the coverage is preferably at least 1% (close to the current collector layer) and a maximum of 100% (close to a substantially non-porous solid electrolyte layer).

[0088] The coating is preferably selected based on the coating material used, the coating thickness and coverage, the coating composition, and the porosity and composition of the porous solid electrolyte layer, such that the reduction of the interfacial resistance Z between the second solid electrolyte and elemental lithium follows a functional relationship:

[0089]

[0090] in, It is the volume-specific active surface area of ​​the porous solid electrolyte layer. is the effective ionic resistance of the second solid electrolyte; and x is the distance between the corresponding microporous surface and the surface of the current collector layer.

[0091] The selection of materials for the coating, porous solid electrolyte layer, and especially for the second solid electrolyte and the coating material, is preferably made such that the activation energy of the interfacial resistance at the micropore surface of the porous solid electrolyte layer is as similar as possible to the activation energy of the ionic resistance of the second solid electrolyte. This ensures that uniform deposition behavior for lithium ions is maintained over the widest possible temperature range, regardless of the spacing from the current collector layer.

[0092] Alternatively, the interfacial resistance profile for the preferred charging temperature of the electrochemical solid-state battery is optimized to minimize aging of the porous solid electrolyte layer, wherein a composite electrode should be used in the electrochemical solid-state battery.

[0093] In one embodiment of the invention, the open micropore volume of the porous solid electrolyte layer is not filled (i.e., apart from the coating according to the invention).

[0094] In an alternative embodiment of the invention, the open micropore volume of the porous solid electrolyte layer is further (i.e., in addition to the coating according to the invention) completely or partially filled with atomic lithium.

[0095] The subject of this invention is also a method for manufacturing a composite electrode according to the invention, the method comprising at least the following steps:

[0096] (a) Providing a first composite material, the first composite material comprising at least one first solid electrolyte and, if necessary, at least one first binder;

[0097] (b) Provide at least one substantially non-porous layer on the surface of a substrate, the substantially non-porous layer being composed of a first composite material, so as to form a substantially non-porous solid electrolyte layer having a first surface and a second surface.

[0098] (c) Providing a second composite material, the second composite material comprising at least one second solid electrolyte and, if necessary, at least one second binder;

[0099] (d) Applying at least a porous layer composed of a second composite material to at least a portion of a first surface of a substantially non-porous solid electrolyte layer to form a porous solid electrolyte layer, wherein the porous solid electrolyte layer has a first surface and a second surface, wherein the second surface of the porous solid electrolyte layer faces the first surface of the substantially non-porous solid electrolyte layer.

[0100] (e) Coating at least a portion of the microporous surface of the micropores of the second composite material with at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium, wherein the layer thickness and / or coverage of the coating decreases with increasing spacing between the corresponding microporous surface and the first surface of the porous solid electrolyte layer.

[0101] (f) Applying at least one current collector layer to the first surface of a porous solid electrolyte layer; and

[0102] (g) Fill the micropores of the first composite material completely or partially with elemental lithium, if necessary.

[0103] In method step (a), a first composite material is provided, comprising at least one first solid electrolyte and at least one first binder, and, if necessary, a conductive salt. Suitable materials have been previously described. Preferably, the first composite material is provided in such a manner that the binder is at least partially plasticized and at least one first solid electrolyte and, if necessary, the conductive salt are added to the plasticized binder using a mixer and / or agitator. The plasticization can be carried out by transferring heat and / or by adding a solvent. A suitable solvent is one capable of at least partially dissolving the binder used.

[0104] In method step (b), at least one substantially non-porous layer composed of a first composite material is applied to the substrate surface to form a substantially non-porous solid electrolyte layer having a first surface and a second surface. The second surface faces the substrate surface. The first surface faces away from the substrate surface and is freely accessible.

[0105] In this regard, the plasticized composite material obtained in step (a) is applied to the substrate surface. Various methods are familiar to those skilled in the art. Suitable methods for manufacturing are particularly emphasized as follows: doctor blade coating, offset printing, screen printing, inkjet printing, spin coating, roll-to-roll processes using a carrier film, stacking processes using a carrier film, and extrusion / dry coating. These methods can be performed by melt or with a suitable solvent. Preferably, the plasticized composite material obtained from step (a) is used directly. In a preferred embodiment, a solvent is used. When a solvent is used, it is preferably removed again after the method steps are performed under reduced pressure and / or increased temperature. The porosity can be reduced by subsequent extrusion, rolling, or calendering. In particular, in the case of oxidized ionic conductors, the substantially non-porous solid electrolyte layer applied to the substrate surface is sintered, in which organic additives (Zusatz), such as binders, are decomposed.

[0106] In method step (c), a second composite material is provided, consisting of at least one second solid electrolyte, at least one second binder, and, if necessary, a conductive salt and / or a conductive additive. Suitable materials have already been described previously. Preferably, the second composite material is provided by at least partially plasticizing the binder and adding the at least one second solid electrolyte and, if necessary, the conductive salt to the plasticized binder using a mixer and / or agitator. The plasticization can be carried out by applying heat and / or by adding a solvent. A suitable solvent is one capable of at least partially dissolving the binder used.

[0107] In method step (d), at least one porous layer composed of a second composite material is applied to at least a portion of the first surface of a substantially non-porous solid electrolyte layer to form a porous solid electrolyte layer, wherein the porous solid electrolyte layer has first and second surfaces, wherein the second surface of the porous solid electrolyte layer faces the first surface of the substantially non-porous solid electrolyte layer.

[0108] Therefore, the plasticized second composite material obtained in step (c) is applied to at least a portion of the first surface of the substantially non-porous solid electrolyte layer. Various methods are familiar to those skilled in the art for this purpose. Suitable methods for manufacturing are particularly emphasized as follows: doctor blade coating, offset printing, screen printing, inkjet printing, spin coating, roll-to-roll processes using a carrier film, stacking processes using a carrier film, and extrusion / dry coating. These methods can be performed by melt or with a suitable solvent. Preferably, the plasticized composite material as obtained from step (c) is used directly.

[0109] Preferably, a solvent is used. By subsequently removing the solvent, the desired porosity of the porous layer is simultaneously adjusted. Solvent removal is preferably performed at an increased temperature and / or a reduced pressure.

[0110] If the plasticized second composite material obtained from step (c) is used to provide a porous layer without the addition of a solvent, a volatile additive (e.g., CO2) can be added to adjust the porosity of the porous layer. In this case, the removal of the solvent is omitted. However, a reduction in ambient pressure can be advantageous in order to regulate the formation of micropores.

[0111] Alternatively, additives that can be selectively removed, for example, by pore-forming particles of a polymer (e.g., PMMA) that preferably have a decomposition temperature below that of the binder used, can be added to the porous layer. In particular, in the case of oxidized ionic conductors, the resulting layer composite is sintered, in which the organic additives, such as the binder, and the pore-forming particles decompose.

[0112] In the next method step (e), at least a portion of the microporous surface of the porous solid electrolyte layer is coated with at least one material for reducing the interfacial resistance between the second solid electrolyte and elemental lithium, wherein the layer thickness and / or coverage of the coating decreases with increasing spacing between the respective microporous surface and the first surface of the porous solid electrolyte layer. Suitable materials have been previously described.

[0113] Suitable methods for coating the surface or interface of porous solid electrolyte layers preferably include chemical vapor deposition (CVD), particularly in atomic layer deposition (ALD) embodiments; physical vapor deposition (PVD), particularly sputtering and evaporation; wetting of micropores by coating with a suspension containing a suitable solvent and / or suspending agent, for example by means of a doctor blade or inkjet printing and subsequent drying; and electrodeposition methods.

[0114] Here, the preferred gradual variation of the coating thickness within the porous solid electrolyte layer is controlled in the aforementioned vapor deposition technique by appropriately selecting deposition conditions (vacuum chamber pressure, temperature, amount or concentration of the applied substance) and application duration or pulse duration and frequency. If the coating is applied using a suspension method, the gradual variation of the coating thickness within the porous solid electrolyte layer can be controlled by the amount and concentration of the applied substance and drying conditions.

[0115] In step (g), at least one current collector layer is applied to the first surface of the porous solid electrolyte layer. This can be done in a roll-to-roll process in the form of a pre-prepared current collector film. Alternatively, other methods are also possible, such as coating methods, such as physical vapor deposition (PVD) techniques, especially sputtering and evaporation.

[0116] It will be apparent to those skilled in the art that the described order of method steps (a) through (g) is merely exemplary and does not necessarily correspond to the actual chronological order in which the method steps are performed. For example, alternatively, method steps (a) and (b) may be performed regardless of method steps (c), (d), (e), and / or (f), and the at least one porous solid electrolyte layer (including a current collector layer if necessary) and at least one substantially non-porous solid electrolyte layer are connected to each other only after their completion.

[0117] The micropores of the porous solid electrolyte layer of the obtained composite electrode can optionally be completely or partially filled with elemental lithium in further process steps. This is particularly necessary if the composite electrode is to be used as a negative electrode in an electrochemical solid-state battery, wherein the active material of the composite electrode as a positive electrode includes initially completely delithiated active materials (e.g., conversion materials, such as SPAN, V2O5). Filling the micropores with atomic lithium can be performed by chemical vapor deposition (CVD), especially in atomic layer deposition (ALD) embodiments; by physical vapor deposition (PVD), especially sputtering and evaporation; by electrodeposition methods; and / or by wetting the micropores with fluid (molten) lithium metal. The amount of lithium used must here correspond at least to the capacity of the initially completely delithiated active material of the positive electrode. Additionally, less excess lithium can be applied to compensate for lithium loss during operation of the electrochemical solid-state battery. This approach is also advantageous when active material is applied at the positive electrode, where the positive electrode is not completely delithiated. In a preferred embodiment, the micropores of the porous solid electrolyte layer of the resulting composite electrode are thus at least partially filled with atomic lithium. This filling is preferably carried out uniformly across the overall open micropore volume of the composite electrode.

[0118] The subject of this invention is also the application of the composite electrode according to the invention or the composite electrode obtained according to the method of the invention, wherein the composite electrode is used as a negative electrode (anode) in electrochemical solid batteries, especially in lithium-ion battery packs.

[0119] The subject of this invention is also correspondingly an electrochemical solid-state battery comprising at least one composite electrode, or a composite electrode obtained according to the method of this invention, as a negative electrode (anode). Because the substantially non-porous solid electrolyte layer of the composite electrode according to this invention in such an electrochemical solid-state battery can also function as a separator and electrolyte, other separators and / or electrolytes can, in principle, be omitted.

[0120] The electrochemical solid-state battery according to the invention therefore includes at least one composite electrode according to the invention and at least one positive electrode (cathode), wherein the composite electrode according to the invention is arranged such that the second surface of the at least one substantially non-porous solid electrolyte layer faces the positive electrode and preferably makes direct contact with it.

[0121] The positive electrode includes at least one active material composite, which includes at least one active material, at least one binder, and, if necessary, conductive additives and a solid electrolyte.

[0122] Suitable active materials for positive electrodes are layer oxides, such as lithium-nickel-cobalt-aluminum oxides (NCA; e.g., LiNi). 0.8 Co 0.15 Al 0.05 O2), lithium-nickel-cobalt-manganese oxides (NCM; e.g., LiNi), 0.8 Mn 0.1 Co 0.1 O2 (NMC(811)), LiNi 0.33 Mn 0.33 Co 0.33 O2 (NMC (111)), LiNi 0.6 Mn 0.2 Co 0.2 O2 (NMC (622)), LiNi 0.5 Mn 0.3 Co 0.2 O2 (NMC (532)) or LiNi 0.4 Mn 0.3 Co 0.3 O2 (NMC (433), generally n(Li2MnO3)· 1-n (LiMO2) overlithiated layer oxides, where M = Co, Ni, Mn, Cr, and 0 ≤ n ≤ 1; spinel generally n(Li2MnO3)· 1-n (LiM2O4), where M = Co, Ni, Mn, Cr, and 0 ≤ n ≤ 1. Furthermore, especially those with the molecular formula LiM x Mn 2-x Spinel compounds of O4, where M = Ni, Co, Cu, Cr, Fe (e.g., LiMn2O4, LiNi). 0.5 Mn 1.5 O4); olivine compounds with the molecular formula LiMPO4, where M = Mn, Ni, Co, Cu, Cr, Fe (e.g., LiFePO4, LiMnPO4, LiCoPO4); silicate compounds with the molecular formula Li2MSiO4, where M = Ni, Co, Cu, Cr, Fe, Mn (e.g., Li2FeSiO4); Tavorit compounds (e.g., LiVPO4F), Li2MnO3, Li 1.17 Ni 0.17 Co 0.1 Mn 0.56O2, LiNiO2, Li2MO2F (where M=V, Cr), Li3V2(PO4)3, conversion materials such as FeF3, V2O5 and / or sulfur-containing materials such as SPAN.

[0123] Suitable binders, conductive additives, and solid electrolytes can be selected from those mentioned above.

[0124] In one embodiment of the invention, the electrochemical solid-state battery includes a positive electrode comprising an active material that is initially completely delithiated and wherein the micropores of a porous solid electrolyte layer of the composite electrode according to the invention are completely or partially filled with elemental lithium.

[0125] In an alternative embodiment of the invention, the electrochemical solid-state battery includes a positive electrode comprising an active material that is initially not completely delithiated and wherein the micropores of the porous solid electrolyte layer of the composite electrode according to the invention are partially filled with elemental lithium in order to compensate for lithium loss.

[0126] The electrochemical solid-state battery according to the invention can be advantageously used, for example, in electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), tools, or consumer electronics products. Tools are particularly understood here as household tools and garden tools. Consumer electronics products are particularly understood as mobile phones, tablet PCs, or laptops. In the future, due to the high energy density of the electrochemical solid-state battery according to the invention, its use in electrically powered flight equipment is also conceivable.

[0127] Advantages of the present invention

[0128] The composite electrode according to the invention provides a porous electrode for depositing elemental lithium as an active material in an electrochemical solid-state battery with a large surface area. In the open micropores of the porous solid electrolyte layer of the composite electrode, the coating according to the invention allows for uniform deposition of metallic lithium during charging of the electrochemical solid-state battery and subsequent decomposition during discharge. Conversely, in the absence of the coating according to the invention, lithium is deposited unevenly within the porous solid electrolyte layer (i.e., preferably near the separator). The micropores are thus filled more rapidly than the rest. This results in localized high mechanical stress, which can damage the electrochemical solid-state battery, up to and including the cracking of the solid electrolyte, potentially leading to reduced electrochemical power or complete battery failure. The invention addresses this problem by specifically coating the microporous surface of the porous solid electrolyte layer, thereby selectively and unevenly adjusting the interfacial resistance between the solid electrolyte and lithium. Increased current density and damage near the reinforced separator, as well as the resulting impact on the lifespan of the electrochemical solid-state battery, are avoided.

[0129] Therefore, compared to conventional porous electrodes used for depositing lithium metal, the composite electrode is superior in terms of uniform deposition behavior in porous composite electrodes, and thus superior in terms of smaller maximum local current intensity and significantly reduced aging or increased lifespan of electrochemical solid-state batteries, because high local mechanical stress and the resulting extrusion of lithium metal within the porous anode are avoided as much as possible.

[0130] As long as the local mechanical stress that occurs after the micropores are completely filled with metallic lithium is above the fracture strength of the porous solid electrolyte layer, in the absence of the coating according to the invention on the surface of the micropores of the porous solid electrolyte layer, only a small portion of the anode capacity can be fully utilized, thus making the use of the invention necessary for the function of the corresponding high-energy battery pack.

[0131] Furthermore, the present invention simplifies the battery pack management system because the porous solid electrolyte layer has a constant total resistance during charging and discharging and does not exhibit the hysteresis that should be observed in common porous electrodes. Attached Figure Description

[0132] Embodiments of the present invention are further described with reference to the accompanying drawings and the following description:

[0133] Figure 1 A schematic diagram of the composite electrode according to the present invention is shown;

[0134] Figure 2aFigures 1 and 2 show simulations of lithium deposition behavior in conventional porous electrodes; and Figures 3 and 4 show simulations of lithium deposition behavior in conventional porous electrodes.

[0135] Figure 3a Figures 1 and 2 show a simulation of the deposition behavior of lithium in the composite electrode according to the invention. Detailed Implementation

[0136] Figure 1 A schematic diagram of a composite electrode 1 according to the invention is shown, comprising a substantially non-porous solid electrolyte layer 2, a porous electrolyte layer 3, and a current collector layer 4. The substantially non-porous solid electrolyte layer 2 has a first surface 21 and a second surface 22. The porous electrolyte layer 3 has a first surface 31 and a second surface 32. The current collector layer 4 has a first surface 41 and a second surface 42. The substantially non-porous solid electrolyte layer 2 comprises at least one first solid electrolyte, such as LLZO, and optionally at least one binder, such as PVDF. The porous solid electrolyte layer 3 is disposed directly on the first surface 21 of the substantially non-porous solid electrolyte layer 2 via the second surface 32. The porous solid electrolyte layer 3 comprises at least one second solid electrolyte 7, such as LLZO, and optionally at least one binder, such as PVDF, and a large number of open micropores 6 distributed over the total volume of the porous solid electrolyte layer 3. The micropore surface is equipped with a coating 5 according to the invention, the coating comprising a material for reducing the interfacial resistance Z between the second solid electrolyte 7 and elemental lithium. The current collector layer 4 is disposed directly on the first surface 31 of the porous solid electrolyte layer 3 with its first surface 41. The current collector layer 4 is made of, for example, copper. The thickness and / or coverage of the coating 5 decreases with increasing spacing x between the microporous surface and the first surface 41 of the current collector layer 4 or the first surface 31 of the porous solid electrolyte layer 3.

[0137] exist Figure 2a Figures 1 and 2b illustrate a simulation of the deposition behavior of elemental lithium in a conventional porous composite electrode. Figure 2a In the diagram, the distance x between the surface of the current collector layer 4 and the interface resistance Z is plotted on the horizontal axis and the vertical axis. Clearly, the interface resistance Z is constant across the total distance x (curve 50). Figure 2b In the figure, the distance x from the surface of the current collector layer 4 is plotted on the horizontal axis, and the volume fraction V of metallic lithium is plotted on the vertical axis. It should be noted that lithium deposition is preferably performed in regions having a large distance x from the surface of the current collector layer 4 (curve 52). Only when a larger amount of lithium has been deposited, lithium is also deposited on microporous surfaces having a smaller distance x from the surface of the current collector layer 4 (curve 51). Curve 53 shows the degree of filling of the micropores 6 with lithium at the start of deposition.

[0138] exist Figure 3aFigures b and c illustrate a simulation of the deposition behavior of elemental lithium in the composite electrode 1 according to the invention. Figure 3a In the diagram, the distance x between the surface of the current collector layer 4 and the surface is plotted on the horizontal axis, and the interfacial resistance Z is plotted on the vertical axis. Clearly, the interfacial resistance Z increases continuously with increasing distance x (curve 60). Figure 3b In the figure, the distance x from the surface of the current collector layer 4 is plotted on the horizontal axis, and the volume fraction V of metallic lithium is plotted on the vertical axis. It should be seen that lithium is deposited uniformly through the total volume of the porous solid electrolyte layer 3 (curves 61, 62). Curve 63 shows the degree of filling of the micropores 6 with lithium at the beginning of deposition.

Claims

1. A composite electrode (1) for a solid-state battery for electrochemistry, the composite electrode comprising: At least one substantially non-porous solid electrolyte layer (2), the substantially non-porous solid electrolyte layer comprising at least one first solid electrolyte; At least one porous solid electrolyte layer (3), the porous solid electrolyte layer comprising at least one second solid electrolyte (7); and At least one current collector layer (4). in The substantially non-porous solid electrolyte layer has a free micropore volume of less than 5 vol% with respect to the total volume of the solid electrolyte layer, and the porous solid electrolyte layer (3) is disposed on at least one surface (41, 42) of the current collector layer (4) and is disposed between the substantially non-porous solid electrolyte layer (2) and the current collector layer (4). At least a portion of the surface of the micropores (6) of the porous solid electrolyte layer (3) has been modified by a coating (5), wherein the coating has at least one material for reducing the interfacial resistance Z between the second solid electrolyte (7) and elemental lithium; and The thickness and / or coverage of the coating (5) on the surface of the micropores (6) of the porous solid electrolyte layer (3) decreases with increasing spacing x between the corresponding micropore surface and the current collector layer (4), wherein the coating has at least one material for reducing the interfacial resistance Z between the second solid electrolyte (7) and elemental lithium, wherein the materials of the second solid electrolyte and the coating are selected such that the activation energy of the interfacial resistance at the micropore surface of the micropores of the porous solid electrolyte layer and the activation energy of the ionic resistance of the second solid electrolyte are as similar as possible.

2. The composite electrode (1) according to claim 1, wherein, The at least one substantially non-porous solid electrolyte layer (2) and the at least one porous solid electrolyte layer (3) comprise at least one sintered or unsintered inorganic solid electrolyte.

3. The composite electrode (1) according to claim 1 or 2, wherein, The micropores (6) of the porous solid electrolyte layer (3) are completely or partially filled with elemental lithium.

4. The composite electrode (1) according to claim 1 or 2, wherein, The decrease in the interfacial resistance Z between the second solid electrolyte (7) and elemental lithium follows a functional relationship: in, It is the volume-specific active surface of the porous solid electrolyte layer (3); It is the effective ionic resistance of the second solid electrolyte (7); and x is the distance between the corresponding microporous surface and the surface of the current collector layer (4).

5. The composite electrode (1) according to claim 1 or 2, wherein, The coating (5) on the micropore surface of the micropores (6) of the porous solid electrolyte layer (3) includes at least one material that helps to improve the dielectric constant and / or electrical conductivity of the micropore surface.

6. A method for manufacturing the composite electrode (1) according to any one of claims 1 to 5, wherein the method comprises the method steps: (a) Providing a first composite material, the first composite material being composed of at least one first solid electrolyte; (b) Provide at least one substantially non-porous layer on the surface of a substrate, the substantially non-porous layer being composed of a first composite material, so as to form a substantially non-porous solid electrolyte layer (2) having a first surface (21) and a second surface (22). (c) Providing a second composite material, the second composite material being composed of at least one second solid electrolyte (7); (d) Apply at least one porous layer composed of the second composite material to at least a portion of the first surface (21) of the substantially non-porous solid electrolyte layer (2) to form a porous solid electrolyte layer (3), wherein the porous solid electrolyte layer has a first surface (31) and a second surface (32), wherein the second surface (32) of the porous solid electrolyte layer (3) faces the first surface (21) of the substantially non-porous solid electrolyte layer (2). (e) Coating at least a portion of the micropore surface of the micropores (6) of the second composite material with at least one material for reducing the interfacial resistance Z between the second solid electrolyte (7) and elemental lithium, wherein the layer thickness and / or coverage of the coating (5) decreases with increasing spacing between the corresponding micropore surface and the first surface (31) of the porous solid electrolyte layer (3), wherein the materials of the second solid electrolyte and the coating are selected such that the activation energy of the interfacial resistance at the micropore surface of the porous solid electrolyte layer and the activation energy of the ionic resistance of the second solid electrolyte are as similar as possible; (f) Apply at least one current collector layer (4) to the first surface (31) of the porous solid electrolyte layer (3).

7. The method of claim 6, wherein at least a portion of the microporous surface of the first composite material is coated using a chemical vapor deposition method, a physical vapor deposition method, and / or a wetting method.

8. The method according to claim 6, wherein the method further comprises the following method steps: (g) The micropores (6) of the first composite material are completely or partially filled with elemental lithium.

9. The application of the composite electrode (1) according to any one of claims 1 to 5 or the composite electrode (1) manufactured according to any one of claims 6 to 8, wherein the composite electrode is used as a negative electrode in a lithium-ion battery pack.

10. An electrochemical solid-state battery comprising at least one composite electrode (1) according to any one of claims 1 to 5 or a composite electrode (1) manufactured according to any one of claims 6 to 8 as a negative electrode.

11. The electrochemical solid-state battery according to claim 10, wherein the electrochemical solid-state battery comprises a positive electrode containing an initially completely delithiated active material, and wherein the micropores (6) of the porous solid electrolyte layer (3) of the composite electrode (1) are completely or partially filled with elemental lithium.

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