EP4659291A1

EP4659291A1 - Low pressure all-solid-state batteries

Info

Publication number: EP4659291A1
Application number: EP23821991.9A
Authority: EP
Inventors: Thomas MARCHANDIER; Vladimir Ouspenski; Jean-Marie Tarascon; Benjamin HANNEQUART
Original assignee: Centre National de la Recherche Scientifique CNRS; Sorbonne Universite; College de France; Saint Gobain Ceramics and Plastics Inc
Current assignee: Centre National de la Recherche Scientifique CNRS; Sorbonne Universite; College de France; Saint Gobain Ceramics and Plastics Inc
Priority date: 2023-02-03
Filing date: 2023-12-11
Publication date: 2025-12-10
Also published as: EP4411864A1; JP2026504462A; KR20250162529A; WO2024160428A1; CN120917576A

Abstract

The present invention relates to an all-solid-state-battery (ASSB) comprising successively: an anode comprising lithium in the metallic state, at least one solid electrolyte layer comprising a solid electrolyte material, and a cathode composite comprising a cathode active material and a halide solid electrolyte, wherein the all- solid-state-battery is submitted to a pressure comprised from 0.05 MPa to 30 MPa. The invention further pertains to a process of making said ASSB comprising assembling a cell comprising the ASSB and applying a pressure ranging from 0.05 MPa to 30 MPa onto the assembled cell.

Description

Description Title: Low pressure All-Solid-State Batteries Technical field [1] The present invention belongs to the field of all-solid-state rechargeable batteries (ASSB) and in particular relates to the optimization of their cycling. Technical background [2] ASSBs are of particular interest as a substitute to traditional Li-Ion batteries, especially since they raise fewer safety concerns and have higher energy densities, thus higher capacities. By design, ASSBs were supposed to have anodes composed of lithium in the metallic state which would allow their energy density to increase by up to 50% compared to Li- ion batteries. [3] To obtain an ASSB, a solid electrolyte is used instead of the liquid electrolytes found in Li-Ion batteries. ASSBs also use high energy NMC cathode particles, said particles being incorporated into the solid state electrolyte. [4] Such solid electrolyte is for example chosen from oxides, sulphides and halides solid electrolytes. Amongst the sulphides solid electrolytes, the following examples are the most common: lithium thiophosphate (β-Li3PS4, LPS), argyrodite (Li6PS5Cl) such as described in H.J. Deiseroth, et al. “Li⁶PS⁵X: a class of crystalline Li-rich solids with an unusually high Li+ mobility.” Angew. Chem. Int. Ed., 47 (2008), pp.755-758. Finally, halides are usually represented by the formula Li3MX6 wherein M is a rare earth and X at least one halide, for example Li³InCl⁶, such as described in X. Li et al. “Air-stable Li3InCl6 electrolyte with high voltage compatibility for all- solid-state batteries.” Energy Environ. Sci., 2019,12, pp. 2665-2667; Schmidt, M. O. et al. “Zur Kristallstruktur von Li3InCl6.” Zeitschrift für Anorg. und Allg. Chemie 1999, 625 (4), 539–540; and G.Meyer, et al. “Handbook on the Physics & Chemistry of Rare Earths”, V.28, chapter 177, 2000 Elsevier Sci. [5] Amongst the above-mentioned solid electrolytes, each presents its advantages and drawbacks. [6] The oxides, in particular the garnet type LLZO, have a good stability in oxidation and reduction but present relatively low ionic conductivity. The 5 sulphides present relatively high ionic conductivity and are stable towards the anode but suffer from a low stability at high potential and form a toxic gas (H2S) when exposed to humidity. Finally, the halides present a relatively good ionic conductivity and a good stability in oxidation but react at the interface with the negative electrode. 10 [7] Another feature of ASSBs, is that they require, by their design, to have high pressure applied on them. This pressure is required since, obviously, ASSBs are made of solid materials, and it is needed to maintain good contact between the active material and the solid electrolyte. A usual pressure for ASSBs is about 100 MPa. 15 [8] However, this high pressure leads to further issues, namely mechanical extrusion of lithium through the solid electrolyte, lithium creep and dendrites formation at the anode. [9] All of the above-mentioned (electro)chemical stability issues have led so far to replace the lithium metal anode supposed to be present in ASSBs 20 by, for example, graphite, lithium alloys such as LiIn, or even silicon. While these anode materials yield interesting results, they exchange performance for stability. However, the increase in energy density promised with ASSBs will only be possible by stably incorporating a lithium metal anode. 25 [10] A recent study (Gao et al., “Solid-state lithium battery cathodes operating at low pressure”, Joule 6, 636-646, March 16, 2022) demonstrated that, in specific condition, a similar capacity retention to that obtained at higher pressure was possible by reducing the volume expansion of the cathode active material. To achieve this goal, this document teaches to use NMC 30 811 as a cathode active material, most importantly in a reduced voltage range and at 80 °C, against a LiIn anode and with Li3InCl6 as a catholyte, while the cell is submitted to a 2 MPa pressure. [11] However, this document still does not teach how to implement an anode made from lithium in the metallic state in a normal voltage range (up to 4.4 V). of the invention 5 Technical problem [12] The invention thus offers to solve the technical problem of providing a high capacity ASSB wherein the anode is made of lithium in the metallic state, which is stable in normal use conditions. Solution to the technical problem 10 [13] The inventors surprisingly found that implementing a halide solid electrolyte as the catholyte allowed to obtain ASSBs comprising an anode made of lithium in the metallic state that is stable at low pressure. [14] Thus, according to a first aspect, the present invention relates to an all- solid-state-battery comprising successively: 15 - an anode comprising lithium in the metallic state, - at least one solid electrolyte layer comprising a solid electrolyte material, and - a cathode composite comprising a cathode active material and a halide solid electrolyte, 20 wherein the all-solid-state-battery is submitted to a pressure comprised from 0.05 MPa to 30 MPa. [15] An all-solid-state battery (ASSB) according to the invention allows to provide ASSBs with a high energy capacity and a better retention of their capacity. 25 [16] According to a second aspect, the present invention also concerns a process of making the all-solid-state-battery according to the preceding invention, comprising the following steps: - assembling a cell comprising the all-solid-state-battery, and - applying a pressure ranging from 0.05 MPa to 30 MPa, notably from 30 0.075 MPa to 20 MPa, in particular from 0.08 MPa to 10 MPa, preferably from 0.1 MPa to 2 MPa and even more preferably from 0.2 MPa to 1 MPa onto the assembled cell. of the invention [17] As demonstrated herein after, the present invention allows to implement a 5 metallic lithium anode in a stable ASSB system at room temperature, in normal use conditions. [18] As mentioned herein above, an ASSB implementing a metallic lithium anode yields a high energy density. Brief description of the drawings 10 [19] Figs 1, 3 and 4 represent the electrochemical performances of cells, or all- solid-state batteries, respectively according to the examples 1, 2 and 3 of the invention at C/20 at room temperature, namely the first galvanostatic cycle of the battery. [20] Fig 2 represents the electrochemical performances of cells, or all-solid- 15 state-batteries according to the comparative examples below at C/20 at room temperature, namely the first galvanostatic cycles of the batteries [21] Figs 5 and 6 are a graphical representation of the charge and discharge capacities in milliampere hours per grams (mAh/g) versus cycle number, respectively for the cells of the examples 2 and 3 of the invention, 20 illustrating the capacity retention of the cell. Fig 6 further illustrates the pressure applied to the cell at each cycle. Detailed description of embodiments [22] An all-solid-state-battery according to the invention comprises a halide solid electrolyte in its cathode composite. 25 [23] Without being bound by any theory, the inventors surprisingly discovered that the use of a halide solid electrolyte in a cathode composite of an ASSB allowed to obtain a functional ASSB, retaining its capacity even at low pressures. [24] In particular, the ASSB according to the invention retains its capacity even 30 when being cycled at low pressures, such as the pressures listed below. [25] Accordingly, an ASSB according to the invention may be submitted to a pressure comprised from 0.075 MPa to 20 MPa, in particular from 0.08 MPa to 10 MPa, preferably from 0.1 MPa to 2 MPa and even more preferably from 0.2 MPa to 1 MPa. 5 [26] An all-solid-state-battery according to the invention also comprises at least one solid electrolyte layer comprising a solid electrolyte material. [27] In a particular embodiment of the invention, the solid electrolyte material is chosen from oxide solid electrolytes, sulphide solid electrolytes and halide solid electrolytes, in particular chosen from sulphide solid electrolytes and 10 halide solid electrolytes, preferably the solid electrolyte material is a sulphide solid electrolyte. [28] Said halide solid electrolytes, sulphide solid electrolytes and oxide solid electrolytes are detailed herein after. Halide solid electrolytes 15 [29] In an ASSB according to the invention, a halide solid electrolyte is at least comprised in the cathode composite. It may also be comprised as a solid electrolyte material in at least one solid electrolyte layer. [30] Halide solid electrolytes may be represented by the following chemical formula 20 M3-z(Me^k+)fX3-z+k*f wherein -3≤z≤3, k is the valence of Me and 2≤k<6, 0≤f≤1; - M comprises an alkali metal element, in particular including Li; 25 - Me comprises a metal other than an alkali metal, and - X is a halogen. [31] In a particular embodiment, f is different from zero. [32] In a particular embodiment, Me comprises more than one metal element and k may be the average of the total of the valence of each metal 30 element. For example, when Me includes a trivalent element and a tetravalent element in equal molar quantity, k=(3+4)/2=3.5. In particular, k may be 2, 3, 4 or 5. [33] It is understood that atomic vacancy can be present inside the unit cell of the halide solid electrolyte. In this case, atomic vacancy can be noted in 5 the formula of the solid halide electrolyte as M^3-z(Me^k+)^f●yX^3-z+k*f wherein ● represents atomic vacancy inside the unit cell and y is the number of vacant atomic positions. In a particular embodiment, y can be f*(k-1). [34] In a particular embodiment, M can include Li, Na, K, Rb, Cs, or any combination thereof. For example, M can include at least one of Li and Na, 10 or a combination thereof. In a further aspect, M can consist of at least one alkali metal element. For example, M can consist essentially of at least one alkali metal element chosen from the group consisting of Li, Na, K, Rb and Cs. In another example, M can consist of Li. In yet another example, M can consist of a combination of Li and at least one of Na, K, Rb and Cs. 15 In still another example, M can consist of Na and at least one of Cs and Rb. In another example, M can consist of at least one of Na and Cs. [35] In a particular embodiment, Me can include an alkaline earth metal element, a rare earth element, a 3d transition metal, an element chosen from Zr, Ti, Sn, Th, Ge, Ta, Nb, Mo, W, Sb, Te, In Bi, Al, Ga, and any 20 combination thereof. For example, Me can include an alkaline earth metal including Ba, Mg, Ca and Sr, or any combination thereof. In another example, Me can include a rare earth element, in particular Me can consist of at least one rare earth element. The rare earth element may be chosen from Y, Sc, Ce, Gd, Er, La, Yb and their combinations. In a further 25 example, Me can include a 3d transition metal, in particular chosen from Zn, Cu, V and any combination thereof. In still another example, Me can include an element chosen from Zr, Ti, Sn, Th, Ge, Ta, Nb, Mo, W, Sb, Te, In Bi, Al, Ga and any of their combinations. [36] In a particular embodiment, X can include a halogen, in particular chosen 30 from Cl, Br, I and any combination thereof. In an example, X can include at least one of Cl and Br. Preferably, X can consist of Cl, Br or any combination thereof. [37] Accordingly, in an embodiment of the present invention, at least the halide solid electrolyte comprised in the cathode composite, is of the formula M3-z(Me^k+)fX3-z+k*f wherein -3≤z≤3, 2≤k<6, 0≤f≤1; - M comprises an alkali metal element, in particular including Li; - Me comprises a divalent, trivalent, tetravalent, pentavalent or hexavalent metal element or any combination thereof, in particular Me is chosen from: i. alkaline earth metals, including Ba, Mg, Ca, Sr, ii. rare earth elements such as Y, Sc, Ce, Gd, Er, La, Yb and their combinations, iii. a 3d transition metal such as Zn, Cu, V, and iv. an element chosen from Zr, Ti, Sn, Th, Ge, Ta, Nb, Mo, W, Sb, Te, In Bi, Al, Ga, and v. any combination thereof, and - X is a halogen, in particular chosen from Cl, Br, I and any combination thereof; preferably the halide solid electrolyte is Li3In(Cl,Br)6, and in particular is Li3InCl6, optionally, the solid electrolyte material comprised in the solid electrolyte layer is independently chosen from the formula (I), in particular from Li³In(Cl,Br)⁶ and preferably is Li³InCl⁶. [38] In a particular embodiment, the halide solid electrolyte can be represented by Li3-zMe^k+X3-z+k. When z is not 0, the complex metal halide can be non- stoichiometric. When z is 0, the complex metal halide can be stoichiometric. For example, -0.95≤z≤0.95. In another example, Me includes Y, Gd, Yb, In, Sc, Zn, Mg, Ca, Ba, Sn or a combination thereof, and X is Cl, Br or a combination thereof. [39] In a particular embodiment, the solid halide electrolyte can be represented by Li3MeBr6. In another particular embodiment, the solid halide electrolyte can be represented by Li3MeCl6. In these embodiments, Me can consist of at least one of the above-mentioned metal elements, having a valence of 3. Me can include at least one of the above-mentioned metal elements, wherein the average valence of the at least one metal element is 3. [40] In another particular embodiment, the solid halide electrolyte can consist of Li, Y, and at least one of Cl and Br. For example, the solid halide electrolyte can consist of Li, Y and Cl. In another example, the solid halide electrolyte can consist of Li, Y and Br. In still another example, the solid halide electrolyte can consist of Li, Y, Cl and Br. In a particular example, the solid halide electrolyte can be represented by Li3xY1-xCl3 or Li3xY1-xBr3, wherein 0<x≤0.5. [41] In another particular embodiment, the solid halide electrolyte can consist of Li, Gd and at least one of Cl and Br. For example, the solid halide electrolyte can consist of Li, Gd and Cl. In another example, the solid halide electrolyte can consist of Li, Gd and Br. In still another example, the solid halide electrolyte can consist of Li, Gd, Cl and Br. In a particular example, the solid halide electrolyte can be represented by Li3xGd1-xCl3 or Li3xGd1-xBr3, wherein 0.01≤x<1. [42] In another particular embodiment, the solid halide electrolyte can consist of Li, In, and at least one of Cl and Br. For example, the solid halide electrolyte can consist of Li, In and Cl. In another example, the solid halide electrolyte can consist of Li, In and Br. In still another example, the solid halide electrolyte can consist of Li, In, Cl and Br. In a particular example, the solid halide electrolyte can be represented by Li3xIn1-xCl3 or Li3xIn1-xBr3, wherein 0≤x<0.5. [43] The solid halide electrolyte may be chosen from Li3InCl6, Li3InBr6, Li3YCl6, Li3YBr6, Li2.7Y0.7Zr0.3Cl6, Li2.8Y0.8Sn0.2Cl6, Li3.2Y0.8Zn0.2Cl6, Li3.2Y0.8Mg0.2Cl6, Li3Y1/3Zr1/3Mg1/3Cl6, Li3Y1/3Sn1/3Mg1/3Cl6, Li3Y1/3Zr1/3Zn1/3Cl6, Li2.95Na0.05YBr6, Li2.95K0.05YBr6, Li2.95Cs0.05YBr6, Li3Y0.7Gd0.3Br6, Li3Y0.8Yb0.2Br6, Li3Y0.9La0.1Br6, Li2.9Y0.9Ce0.1Br6, Li3In0.5Y0.5Cl6 or Li3Y(Cl,Br)6. [44] Sulphide solid electrolytes suitable for the present invention may include, for example, lithium sulphide, silicon sulphide, phosphorous sulphide, boron sulphide or a combination thereof. [45] In a preferred embodiment of the invention, the solid electrolyte material comprised in the at least one solid electrolyte layer of the ASSB according to the invention is a sulphide solid electrolyte. [46] Examples of sulphide solid electrolytes may include at least one of Li2S— P2S5, Li2S—P2S5—LiX (where X is a halogen element), Li2S—P2S5—Li2O, Li2S—P2S5—Li2O—LiI, Li2S—SiS2, Li2S—SiS2—LiI, Li2S—SiS2—LiBr, Li2S—SiS2—LiCl, Li2S—SiS2—B2S3—LiI, Li2S—SiS2—P2S5—LiI, Li2S— B²S³, Li²S—P²S⁵—Z^mSⁿ (where m and n each are a positive number, Z represents any of Ge, Zn, and Ga), Li2S—GeS2, Li2S—SiS2—Li3PO4, Li2S—SiS2—LipMOq (where p and q each are a positive number, M represents at least one of P, Si, Ge, B, Al, Ga, or In). [47] The sulphide solid electrolyte may also be an argyrodite of the general formula Li7-xPS6-xXx (where 0≤x≤2 and X is a halogen element). Preferably, the sulphide solid electrolyte is the argyrodite of formula Li6PS5Cl. [48] The sulphide solid electrolyte may also be a thiophosphate such as a thio- LISICON, for example chosen from (Li)4-xGe1-xPxS4, wherein x ranges from 0 to 1, Li7P2S8I and Li2S-P2S5. [49] For example, the sulphide solid electrolyte may include Li²S and P²S⁵. When a sulphide-based solid electrolyte material constituting the sulphide- based solid electrolyte includes Li2S—P2S5, a molar ratio of Li2S and P2S5 may, for example, range from 50:50 to 90:10. [50] Accordingly, in an embodiment of the present invention, the solid electrolyte material may be a sulphide solid electrolyte, in particular chosen from the group consisting of thiophosphates and argyrodites of the formula Li7-xPS6-xXx wherein 0≤x≤2 and X is a halide, notably chosen from Cl, Br and I, and preferably the sulphide solid electrolyte is chosen from argyrodites and even more preferably is Li6PS5Cl. Oxide solid electrolytes [51] Lithium oxide solid electrolytes, or simply oxide solid electrolytes, suitable for the present invention may include, for example, NASICON, perovskites, LISICON, garnets or a combination thereof. [52] In a particular embodiment of the invention, the solid electrolyte material comprised in the at least one solid electrolyte layer of the ASSB according to the invention is an oxide solid electrolyte. [53] Accordingly, in an embodiment of the present invention, the solid electrolyte material may be an oxide solid electrolyte, in particular chosen from the group consisting of a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li⁷La³Zr²O¹², preferably the oxide solid electrolyte is a garnet, and even more preferably the oxide solid electrolyte is Li7La3Zr2O12. Anode [54] In an all-solid-state battery according to the invention, the anode comprises lithium in the metallic state. [55] Accordingly, the anode of an ASSB according to the invention may be a doped and/or surface-treated lithium metal anode. [56] Preferably, in the all-solid-state-battery according to the invention, the anode consists in lithium in the metallic state. [57] The thickness of the anode in an ASSB or an assembly according to the invention may range from 10 µm to 500 µm. [58] A buffer layer may be deposited on the anode of an ASSB according to the invention. In particular, said buffer layer may comprises, preferably consists in, a buffer material chosen from a lithium phosphate such as Li3PO4 or lithium phosphorus oxynitrides; a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li7La3Zr2O12; preferably the buffer layer comprises, in particular consists in, Li3PO4. Cathode [59] In an all-solid-state battery according to the invention, the cathode composite comprises a cathode active material and a halide solid electrolyte as described herein above. In particular, the cathode may 5 comprise particles comprising, preferably consisting in, the halide solid electrolyte. [60] The cathode active material is a material capable of storing and releasing metal ions, in particular alkali metal ions such as Li or Na ions. [61] As cathode active materials transition metal fluorides, polyanionic 10 materials, fluorinated polyanionic materials, transition metal sulphides, transition metal oxyfluorides, transition metal oxysulphides, transition metal oxynitrides and lithium-containing transition metal oxide, doped or not, coated or not may be used. In particular, the cathode active material may be a transition metal oxide such as a lithium-cobalt oxide, a lithium- 15 nickel-cobalt-aluminium oxide or a lithium-nickel-manganese-cobalt-oxide. Transition metal oxides suitable for use as a cathode active material may be, for example, LiNi0.6Mn0.2Co0.2O2, Li(NiCoAl)O2 and LiCoO2. Preferably, the cathode active material is the transition metal oxide of the formula LiNi0.6Mn0.2Co0.2O2. 20 [62] The cathode active material may be present in an ASSB according to the invention, in the form of particles. The median diameter of the anode active material particles may range from 0.1 µm to 100 µm. Preferably, the median diameter of the anode active material particles is larger than the median diameter of the halide solid electrolyte particles. 25 [63] The cathode composite may comprise - from 55 to 75 % wt., in particular from 60 to 70 % wt., and preferably 66.5 % wt. of cathode active material, - from 20 to 40 % wt., in particular from 25 to 30 % wt., and preferably 28.5 % wt. of halide solid electrolyte, and optionally 30 - from 1 to 10 % wt., in particular from 2 to 7 % wt., and preferably 5 % wt. of an electron conducting carbon compound. [64] The thickness of the cathode in an ASSB according to the invention may range from 10 µm to 500 µm. [65] A buffer layer may be deposited on the cathode of an ASSB according to the invention. In particular, the buffer layer deposited on the cathode assembly according to the invention comprises, preferably consists in, a buffer material chosen from a lithium phosphate such as Li3PO4 or lithium phosphorus oxynitrides; lithium nitride; a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; and a garnet such as Li7La3Zr2O12; preferably the buffer layer comprises, in particular consists in, Li3PO4. [66] The cathode composite may comprise an electron conductor compound chosen from natural or artificial graphite, graphene, carbon nano-tubes, acetylene black, Ketjen black, activated carbon, carbon fluoride, metal powders, conductive whiskers, conductive metal oxides, conductive polymers, metal fibres or carbon fibres, preferably the electron conductor is vapour grown carbon fibres. Buffer layer [67] An ASSB according to the invention may comprise at least one buffer layer, preferably one or two buffer layer(s). Said buffer layer(s) may be in contact with a surface of the solid electrolyte material. When an ASSB according to the invention comprises two buffer layers, these layers are in contact with two opposing faces of the solid electrolyte layer. [68] Said buffer layer, or separation layer, is intended to prevent a direct electrochemical or chemical reaction between two components of an ASSB according to the present invention. Accordingly, the buffer layer can prevent such reactions between: the sulphide and the halide solid electrolytes, the halide solid electrolyte and the anode and/or the sulphide solid electrolyte and the cathode. [69] Therefore, in a preferred embodiment of the invention, a buffer layer is located in between: a sulphide and a halide solid electrolytes, a halide solid electrolyte and the anode and/or a sulphide solid electrolyte and the cathode. [70] As described above, both sulphide and halide solid electrolytes, alone or in combination, may be present in an ASSB according to the invention as a solid electrolyte material comprised in a solid electrolyte layer; halide solid electrolytes are further present in the cathode composite of an ASSB according to the invention. [71] In an ASSB according to the invention, the buffer layer may thus be located at the interface between: the cathode composite and a solid electrolyte layer, two electrolytes layers, and/or the anode and a solid electrolyte layer. [72] Preferably, a buffer layer as defined herein is located at the interface between: the cathode composite and a solid electrolyte layer comprising a sulphide solid electrolyte, two electrolyte layers respectively comprising a halide solid electrolyte and a sulphide solid electrolyte, and/or the anode and a solid electrolyte layer comprising a halide solid electrolyte. [73] In order to fulfil the requirement of preventing the above-listed reactions, the buffer layer needs to have a good electrochemical stability both towards lithium metal anodes and solid electrolytes, in particular halide solid electrolytes, sulphide solid electrolytes and lithium oxide solid electrolytes. [74] Thus, the buffer layer may comprise an oxide-based or fluoride-based compound which is chemically inert for halide, sulphide and/or lithium oxide solid electrolytes. [75] In a particular embodiment of the invention, the buffer layer comprises a metal oxide such as Al2O3, ZnO, ZrO2, TiO2, preferably, the buffer layer comprises Al²O³. [76] In another embodiment of the invention, the buffer layer comprises an ionic conductor chosen from a lithium phosphate such as Li3PO4 or lithium phosphorus oxynitrides; lithium nitride; a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li7La3Zr2O12; and LiAlO2. [77] Accordingly, an ASSB according to the invention may comprise at least one buffer layer, preferably one or two buffer layer(s), in contact with a surface of the solid electrolyte material, said buffer layer may comprise, in particular consists, in a buffer material chosen from a lithium phosphate such as Li3PO4 or lithium phosphorus oxynitrides; lithium nitride; a NASICON such as LiTi²(PO⁴)³; a perovskite such as (LaLi)TiO³; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li7La3Zr2O12; and Al2O3, more particularly the buffer layer comprises, in particular consists in, Li³PO⁴ or Al²O³; preferably, the buffer layer comprises, in particular consists in, Li3PO4. [78] Li3PO4 is preferred as a buffer material due to its good compatibility with both sulphide and halide solid electrolytes and acceptable ionic conductivity of Li⁺. [79] Furthermore, while the ionic conductivity of the buffer layer may be acceptable, it is still lower than the one of either a sulphide or halide solid electrolyte. [80] However, limiting the thickness of the buffer layer to less than 10 nm allows to still prevent reactions as mentioned herein above, while also mitigating the limiting aspect of the ionic conductivity of the buffer layer. [81] In other words, a buffer layer that is at least 10 nm thick yields an ASSB with poorer electrochemical properties. [82] On the other hand, a buffer layer that is finer than 0.5 nm does not sufficiently prevent the herein mentioned reactions between two components of an ASSB. [83] Accordingly, in an ASSB according to the invention, the buffer layer may have a thickness ranging from 0.5 to less than 10 nm, in particular from 0.75 to 5 nm, and preferably from 1 to 2 nm. [84] In order to meet the thickness requirement for a buffer layer in an ASSB according to the present invention, the buffer layer may be deposited onto a surface by a vapor deposition based method. [85] Such vapor deposition based methods are for example, Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD). [86] The buffer layer may also be deposited by Atomic Layer Deposition (ALD). ALD allows a particularly fine tuning of the thickness of the buffer layer. [87] The buffer layer may be deposited onto a powder substrate or onto a densified substrate. [88] Accordingly, the powder substrate may be a component of an ASSB according to the invention before its densification. Hence, the powder substrate may be the solid electrolyte, the anode and/or the cathode composite. [89] When the buffer material is deposited onto a powder substrate, a coated powder substrate is obtained. Once said coated powder substrate is densified, the buffer material constitutes a buffer layer on at least one surface of the obtained densified material. [90] In order to provide lithium in the buffer layer, for example when the buffer layer is Li3PO4, a precursor of the formula LiOR wherein R is a C1-C6 alkyl may be used as a precursor, preferably lithium tert-butoxide is used as a precursor to provide lithium. [91] In order to provide phosphate in the buffer layer, for example when the buffer layer is Li3PO4, a precursor of the formula OP(OR)3 wherein R is a C¹-C³ alkyl may be used as a precursor, preferably OP(OCH³)³ is used as a precursor. [92] In order to provide aluminium in the buffer layer, for example when the buffer layer is Al2O3, a precursor of the formula AlR3 wherein R is a C1-C3 alkyl may be used as a precursor, preferably Al(CH3)3 is used as a precursor. [93] In order to provide oxygen in the buffer layer, for example when the buffer layer is Al²O³, ozone may be used as a precursor. [94] In a particular embodiment of the invention, the buffer layer is deposited by Atomic Layer Deposition and the Atomic Layer Deposition reactor is set at a temperature: - ranging from 85 °C to 185 °C, in particular from 100 °C to 170 °C, and preferably at 150 °C, or - ranging from 200 °C to 400 °C, in particular from 250 °C to 350 °C, and preferably at 300 °C. [95] The present invention further relates to a process of making the all-solid- state-battery according to the invention, comprising the following steps: - assembling a cell comprising the all-solid-state-battery, and 5 - applying a pressure ranging from 0.05 MPa to 30 MPa, notably from 0.075 MPa to 20 MPa, in particular from 0.08 MPa to 10 MPa, preferably from 0.1 MPa to 2 MPa and even more preferably from 0.2 MPa to 1 MPa onto the assembled cell. [96] In a particular embodiment of the invention, said pressure is applied and 10 then a constant volume is maintained for the battery cell. [97] In other words, the process of the invention may comprise a further step of maintaining the volume of the all-solid-state-battery, in particular while said ASSB is cycling. [98] In another embodiment of the invention, said pressure is applied and 15 maintained regardless of the volume of the battery cell. [99] In other words, the process of the invention may comprise a further step of maintaining the pressure applied of the all-solid-state-battery, in particular while said ASSB is cycling. [100] The pressure evolution within the cell may be monitored by positioning the 20 cell in a frame equipped with: - a mean for applying a pressure, such as a screw, for example at the top of the cell, and - a force sensor at the opposite end of the cell, for example at the bottom. 25 [101] The force sensor measures a data representing the pressure applied to the cell by the mean for applying a pressure. [102] A control unit may be provided which is configured for determining the applied pressure according to the force measured from the force sensor and for controlling the mean for applying a pressure. Said control unit is 30 configured to control the mean for applying a pressure in function of the measured data representing the pressure applied to the cell. Said control unit is for example configured to memorize a predetermined data representing a predetermined pressure. Said control unit may be configured to compare said predetermined memorized data with the data representing the pressure applied to the cell. The control unit may memorize a command law of the mean for applying a pressure comprising the comparison of the predetermined data with the data representing the pressure applied to the cell. When both data are different, said control unit is configured to control the mean for applying a pressure to adjust the pressure applied to the cell. [103] The electrodes and electrolytes of an ASSB according to the invention are prepared according to processes known by the person skilled in the art and illustrated in the examples below. to the invention [104] Li6PS5Cl was synthesized by the annealing of stoichiometric mixture of Li2S, P2S5, and LiCl in an Al2O3 crucible. [105] The powder mixture was placed in the crucible and sealed under vacuum in a quartz tube, and finally annealed at 550 °C at a heating rate of 5 °C/min for 72 hours followed by natural cooling to room temperature. [106] A Li⁶PS⁵Cl solid electrolyte pellet was obtained. [107] Li3InCl6 was prepared by dissolution of InCl3 and LiCl in distilled water. The precursors were left stirring overnight continuously at room temperature and the obtained clear solution was naturally dried at 100 °C. [108] A white powder was obtained and subsequently dried firstly at 100 °C for 24 hours and then at 200 °C for 24 hours under dynamic vacuum (P < 1 mbar) followed by natural cooling to room temperature. [109] A cathode composite was prepared by hand-ground mixture of LiNi0.6Mn0.2Co0.2O2(NMC622):Li3InCl6:VGCF (66.5:28.5:5 in weight ratio). [110] The battery assembly was carried out in a cell consisting of a cylindrical polyetherimide (PEI) cell body and two stainless steel pistons of 8 mm diameter. [111] The assembling procedure was carried out under argon atmosphere in a glove box ([O2] < 1 ppm, [H2O] < 1 ppm). [112] The two-electrode cell was assembled as follows. [113] 35 mg of Li3InCl6 were spread and cold pressed at 100 MPa, then 15 mg of Li⁶PS⁵Cl were formed on the anode side in the same conditions. [114] 6 to 7 mg/cm² of cathode composite (NMC622/Li3InCl6/VGCF) was spread on the Li3InCl6 surface at the cathode side and the whole stack was further densified at 400 MPa for 15 minutes. [115] After the densification, an 80 to 100 µm thick metallic Li disk was placed on the anode side and a pressure of 1 MPa was applied on the fully assembled cell for electrochemical studies. Example 2 according to the invention [116] The same procedure than for example 1 according to the invention was followed but a pressure of 9 MPa was applied on the fully assembled cell for the electrochemical studies. Example 3 according to the invention [117] The same procedure than for example 1 according to the invention was followed but an initial pressure of 10 MPa was applied on the fully assembled cell for the first cycle of the electrochemical studies. The cell was cycled for 30 cycles. While the first 5 cycles were obtained at a pressure of 10 MPa, the 5 next were at 5 MPa. Every 5 cycles, the pressure applied to the cell was reduced to: 2 MPa, then 1 MPa, then 0.5 MPa and finally 0.2 MPa. Solid example 1: Catholyte an argyrodite obtained by ceramic route [118] Li6PS5Cl was synthesized accordingly to the Example 1 according to the invention. [119] The battery obtained with this compound is herein after referenced as “(SS)Li6PS5Cl”. route [120] Li6PS5Cl was obtained by first homogenising stoichiometric amounts of Li2S, P2S5 and LiCl in a mortar. Then, 1 g of the resulting powder was transferred to a 45 mL zirconia jar with 12 zirconia balls of 10 mm in diameter and was grinded at 600 rpm for 14 h in a Fritsch P7 Pulverisette. [121] The cell obtained with this compound is herein after referenced as “(BM)Li6PS5Cl”. a commercial argyrodite [122] Li6PS5Cl with a particle size of 1 µm, sold under the reference Fine LPSCl, was purchased from NEI Corporation. [123] The battery obtained with this compound is herein after referenced as “(NEI)Li6PS5Cl”. obtained by ceramic [124] Li6PS5Cl was prepared from 140 mg of Li6PS5Cl obtained according to the comparative example 1, wet ground in 1.5 mL of xylene for 30 min using a SPEX apparatus and 1 stainless steel ball of 10 mm in diameter. [125] The battery obtained with this compound is herein after referenced as “(SS-BM)Li⁶PS⁵Cl”. Batteries assembly [126] The batteries assembly was carried out in cells consisting of a cylindrical polyetherimide (PEI) cell body and two stainless steel pistons of 8 mm diameter. [127] The assembling procedure was carried out under argon atmosphere in a glove box ([O2] < 1 ppm, [H2O] < 1 ppm). [128] The two-electrode cells were assembled as follows. [129] 50 mg of Li6PS5Cl from the comparative example 1, 2, 3 or 4 were spread and cold pressed at 100 MPa. [130] 6 to 7 mg/cm² of cathode composite (NMC622/ Li⁶PS⁵Cl/VGCF) was spread on the Li6PS5Cl surface at the cathode side, next a mixture of Li0.5In and Li6PS5Cl (in a 60:40 weight ratio) was added on the Li6PS5Cl at the anode side. Finally, the whole stack was further densified at 400 MPa for 15 minutes. [131] After the densification, a pressure of 9 MPa was applied on the fully assembled cell for electrochemical studies. Electrochemical testing [132] For all of the examples, the electrochemical testing were carried out in a cell consisting of a cylindrical polyetherimide (PEI) cell body and two stainless steel pistons of 8 mm diameter. [133] All the electrochemical cycling procedures were carried out under argon atmosphere in a glove box ([O²] < 1 ppm, [H²O] < 1 ppm) at room temperature unless specified otherwise. Galvanostatic cycling [134] Galvanostatic cycling studies were carried out at room temperature at C/20 (C correspond to 1 mole of Li exchanged between the two electrodes of the battery per mole of active material in 1 h) in the voltage range of 2.7-4.2 V versus Li/Li⁺ (also referenced as Li⁰/Li⁺) for the examples according to the invention and in the voltage range of 2.1-3.6 V versus LiIn/In for the comparative examples, the voltage difference between 5 Li⁰/Li⁺ and LiIn/Li being 0.6 V the two voltage range are in fact equivalentAll electrochemical measurements were conducted with a VMP3 potentiostat/galvanostat (BioLogic) controlled with EC-Lab software. [135] The pressure evolution within the cells during the galvanostatic cycling was controlled and monitored by positioning the cell in a stainless steel 10 frame equipped with a screw on top and a force sensor at the bottom. [136] Figs. 1, 3 and 4 depict the cycling performances of the cell stack of the examples, respectively 1, 2 and 3, according to the invention, between 2.7 and 4.2 V vs. Li⁺/Li, in particular the first cycle curve. These figures demonstrate low irreversible capacity and low polarization after the initial 15 cycle. [137] Figs.5 and 6 further illustrate the cycling performances of the cell stacks of the examples 2 and 3 according to the invention, in the same conditions but for 30 cycles. These figures demonstrate a stable capacity retention over cycling of an ASSB according to the invention. In particular Fig. 6 20 demonstrates a good capacity retention even at a pressure as low as 0.2 MPa. [138] By comparison, Fig 2. depicts the cycling performance of the cell stacks of the comparative examples, between 2.1 and 3.6 V vs. LiIn/In (corresponding to 2.7-4.2 V vs. Li⁺/Li), in particular the first cycle curve. 25 This figure demonstrates an important irreversible capacity (> 50 mAh/g) after the initial cycle for each of the tested sulphide solid electrolytes incorporated in the cathode of the batteries. [139] Therefore, the examples detailed herein above demonstrate that an ASSB according to the invention, i.e. wherein the cathode comprises a halide 30 solid electrolyte and the anode comprises lithium in the metallic state, can operate at low pressure (9 MPa), and even at very low pressures (1 MPa, 0.5 MPa, 0.2 MPa), without the expected drawbacks of ASSBs implementing such an anode such as mechanical extrusion of lithium through the solid electrolyte, lithium creep and dendrites formation at the anode. These drawbacks are alleviated while still obtaining an ASSB with a stable capacity over its lifespan. 5

Claims

Claims Claim 1. An all-solid-state-battery comprising successively: - an anode comprising lithium in the metallic state, - at least one solid electrolyte layer comprising a solid electrolyte 5 material, and - a cathode composite comprising a cathode active material and a halide solid electrolyte, wherein the all-solid-state-battery is submitted to a pressure comprised from 0.05 MPa to 30 MPa. 0 Claim 2. The all-solid-state-battery according to the preceding claim, wherein the pressure is comprised from 0.075 MPa to 20 MPa, in particular from 0.08 MPa to 10 MPa, preferably from 0.1 MPa to 2 MPa, even more preferably from 0.2 MPa to 1 MPa. Claim 3. The all-solid-state-battery according to any of the preceding claims,5 wherein the solid electrolyte material is chosen from oxide solid electrolytes, sulphide solid electrolytes and halide solid electrolytes, in particular chosen from sulphide solid electrolytes and halide solid electrolytes, preferably the solid electrolyte material is a sulphide solid electrolyte. Claim 4. The all-solid-state-battery according to any of the preceding claims,0 wherein the anode consists in lithium in the metallic state. Claim 5. The all-solid-state-battery according to any of the preceding claims, wherein the cathode active material is chosen from transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulphides, transition metal oxyfluorides, transition metal oxysulphides,5 transition metal oxynitrides and lithium-containing transition metal oxide, doped or not, coated or not, in particular the cathode active material is a transition metal oxide such as a lithium-cobalt oxide, a lithium-nickel-cobalt- aluminium oxide or a lithium-nickel-manganese-cobalt-oxide, preferably of the formula LiNi0.6Mn0.2Co0.2O2. 0 Claim 6. The all-solid-state-battery according to any of the preceding claims, wherein the cathode composite comprises: - from 55 to 75 % wt., in particular from 60 to 70 % wt., and preferably 66.5 % wt. of cathode active material, - from 20 to 40 % wt., in particular from 25 to 30 % wt., and preferably 28.5 % wt. of halide solid electrolyte, and optionally - from 1 to 10 % wt., in particular from 2 to 7 % wt., and preferably 5 % wt. of an electron conducting carbon compound. Claim 7. The all-solid-state-battery according to any of the preceding claims, wherein the cathode composite comprises an electron conductor compound chosen from metal powders, conductive whiskers, conductive metal oxides, conductive polymers, metal fibres or electron conducting carbon compound such as natural or artificial graphite, graphene, carbon nano-tubes, acetylene black, Ketjen black, activated carbon, carbon fluoride and carbon fibres, preferably the electron conductor is vapour grown carbon fibres. Claim 8. The all-solid-state-battery according to any of the preceding claims, wherein at least the halide solid electrolyte comprised in the cathode composite is of the formula (I) M^3-z(Me^k+)^fX^3-z+k*f (I) wherein -3≤z≤3, 2≤k<6, 0≤f≤1; - M comprises an alkali metal element, in particular including Li; - Me comprises a divalent, trivalent, tetravalent, pentavalent or hexavalent metal element or any combination thereof, in particular Me is chosen from: i. alkaline earth metals, including Ba, Mg, Ca, Sr, ii. rare earth elements such as Y, Sc, Ce, Gd, Er, La, Yb and their combinations, iii. a 3d transition metal such as Zn, Cu, V, and iv. an element chosen from Zr, Ti, Sn, Th, Ge, Ta, Nb, Mo, W, Sb, Te, In Bi, Al, Ga, and v. any combination thereof, and - X is a halogen, in particular chosen from Cl, Br, I and any combination thereof; in particular the halide solid electrolyte is Li3In(Cl,Br)6, and in particular is Li3InCl6, optionally, the solid electrolyte material comprised in the solid electrolyte layer is independently chosen from the formula (I), in particular from Li3In(Cl,Br)6 and preferably is Li3InCl6. Claim 9. The all-solid-state-battery according to any of the preceding claims, wherein the solid electrolyte material is a sulphide solid electrolyte, in particular chosen from the group consisting of thiophosphates and argyrodites of the formula Li7-xPS6-xXx wherein 0≤x≤2 and X is a halide, notably chosen from Cl, Br and I, and preferably the sulphide solid electrolyte is chosen from argyrodites and even more preferably is Li6PS5Cl. Claim 10. The all-solid-state-battery according to any of the preceding claims, wherein the solid electrolyte material is an oxide solid electrolyte, in particular chosen from the group consisting of a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li7La3Zr2O12, preferably the oxide solid electrolyte is a garnet, and even more preferably the oxide solid electrolyte is Li7La3Zr2O12. Claim 11. The all-solid-state-battery according to any of the preceding claims, comprising at least one buffer layer, preferably one or two buffer layer(s), in contact with a surface of the solid electrolyte material wherein the buffer layer comprises, in particular consists in, a buffer material chosen from a lithium phosphate such as Li3PO4 or lithium phosphorus oxynitrides; lithium nitride; a NASICON such as LiTi2(PO4)3; a perovskite such as (LaLi)TiO3; a LISICON such as Li14ZnGe4O16, Li4SiO4 or LiGeO4; a garnet such as Li7La3Zr2O12; and Al2O3, more particularly the buffer layer comprises, in particular consists in, Li³PO⁴ or Al²O³; preferably, the buffer layer comprises, in particular consists in, Li3PO4. Claim 12. The all-solid-state-battery according to the preceding claim, wherein the buffer layer has a thickness ranging from 0.5 nm to less than 10 nm, in particular from 0.75 to 5 nm, and preferably from 1 to 2 nm. Claim 13. A process of making the all-solid-state-battery according to any of the preceding claims, comprising the following steps: - assembling a cell comprising the all-solid-state-battery, and - applying a pressure ranging from 0.05 MPa to 30 MPa, notably from 0.075 MPa to 20 MPa, in particular from 0.08 MPa to 10 MPa, preferably from 0.1 MPa to 2 MPa and even more preferably from 0.2 to 1 MPa onto the assembled cell.