ULTRA FINE SOLID SULFIDE PARTICLES COMPRISING Li, P AND S ELEMENTS

Abstract

The present invention relates to a process for manufacturing a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements comprising the steps of: (a) providing a powder (P1) comprising particles of the solid sulfide material (M), an organic solvent (S) and an ester compound (E) to obtain a suspension (S1); (b) submitting the suspension (S1) to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2); (c) removing by evaporation under stirring, the organic solvent (S) and the ester (E) from the suspension (S2) to recover a powder (P2); (d) drying under stirring the powder (P2) until a constant weight of the desired powder (P) is recovered. It also relates to the powder (P) obtained by the process and its use as solid electrolyte.

Description

ULTRA FINE SOLID SULFIDE PARTICLES COMPRISING Li, P AND S ELEMENTSCross-reference to related application

[0001] This application claims priority to European application No. 24315330.1 filed on July 05, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0002] The present invention relates to a process for manufacturing a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements comprising the steps of:(a) providing a powder (P1 ) comprising particles of the solid sulfide material, at least one organic solvent (S) and at least one ester (E) of carboxylic acid compound different from (S) to obtain a suspension (S1 ), wherein the boiling point (bpE) of the ester compound (E) is at least 30°C higher than the boiling point (bps) of the organic solvent (S), preferably 60°C higher;(b) submitting the suspension (S1 ) obtained in (a) to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2);(c) removing by evaporation under stirring, at a temperature (T) not exceeding bpE - 30°C, at least partially the organic solvent (S) and the ester (E) from the suspension (S2) to recover a powder (P2);(d) drying under stirring at a temperature (T) not exceeding bpE - 30°C the powder (P2) obtained in (c) until a constant weight of the desired powder (P) is recovered.It also relates to the powder (P) obtained by the process and its use as solid electrolyte.Background

[0003] Lithium ion batteries are widely used as power supplies notably for appliances. In such secondary batteries, an organic solvent is used as an organic liquid electrolyte and lithium ions migrate from one electrode to the other, depending on whether the battery is charging or discharging.

[0004] Because the solvent used as an electrolyte is flammable, all-solid-state lithium ion battery not using organic solvent are very attractive. Such all-solid-state lithium ion batteries are formed by solidifying the whole battery using components which are all solid, that-is-to-say the cathode, the anode and the electrolyte. Because all the components of the solid-state batteries are solid, including the electrolyte, all-solid-state batteries have a large electrical resistance and provide a small output current, in comparison to a battery using a liquid electrolyte. This means that there is a need for solid electrolytes having a high conductivity, as well as an aptitude to maintain this high conductivity over time. Sulfide solid electrolytes (SSE) containing Li, P, S, and optionally a halogen are good candidates.

[0005] Sulfide solid electrolytes (SSE) are typically synthetized by a solid phase reaction (mechanosynthesis) involving different raw materials such as Li2S, P2S5 and optionally LiX, wherein X is a halogen or a pseudo-halogen. Mechanosynthesis conditions can impact basic properties of SSE such as phase purity, particle size and ionic conductivity.

[0006] Among them, particle size is a key property since it will ultimately determine the final thickness of the separator layer and the compactness of the catholyte electrode made from the SSE. It is also sought for the SSE material to be able to be easily formulated with electrochemically active materials, binder materials and / or electro conductive materials to be able to be easily coated and without leading to defects, such as, for example, "streaked" films.

[0007] When a proper particle size is not achieved during the synthesis of the SSE, milling is performed. However, this post-treatment step is generally responsible for ionic conductivity loss due to deterioration of the final SSE surface.

[0008] Therefore, there is a need for milling post-treatment conditions suitable to reduce the particle size of the SSE powder without impairing ionic conductivity.

[0009] For example, EP2732451 B1 discloses a method for producing a sulfide solid electrolyte material, comprising a step of adding an ether compound to a coarse-grained material of a sulfide solid electrolyte material and microparticulating the coarse-grained material by a pulverization treatment.

[0010] JP2019102412 A2 discloses a process of reduction of the size of coarse particles of sulfide through an atomization process.

[0011] US 2022 / 0173428 A1 relates to a method for producing a lithium-ion conductive sulfide solid electrolyte material such as Li5.4PS4.4Clo.8Bro.8 or Li5.8PS4.8d1 2; the method including a step of wet-pulverizing a slurry containing the lithium-ion conductive sulfide, an organic solvent and an ester compound, wherein the ester compound is an ester of a carboxylic acid and an alcohol. Some examples are provided with toluene, heptane or decane as the solvent and butyl acetate, ethyl pivalate as the ester. The sulfide solid electrolyte is recovered by solid-liquid separation with no further details. After drying, the resulting solid sulfide presents at least one peak observed in a chemical shift range of 3.4 ppm to 4 8 ppm in a spectrum obtained by1H-NMR measurement. It is stated that a solid-state battery that is obtained using a sulfide solid electrolyte having a1H NMR peak in this range has improved cycle characteristics. Nothing is said about the particle size of the recovered sulfide solid electrolyte except that it is passed through a sieve with an aperture size of 75 pm.

[0012] US 2022 / 0263122 A1 discloses a sulfide solid electrolyte having a very small particle size and a low specific surface area. According to the authors, these features contribute reducing the viscosity of sulfide solid electrolyte slurry, and thus to reduce the amount of solvent required to prepare slurry suitable for manufacturing batteries. The median diameter D50 is of 0.10 pm or more and 2.0 pm or less; D10 is of 0.10 pm or more and 1.0 pm or less and D95 is of 0.70 pm or more and 3.0 pm or less. Sulfide solid electrolyte is obtained by wet-pulverizing a slurry containing the lithium-ion conductive sulfide, an organic solvent and an ester compound such as toluene and butyl acetate. The sulfide solid electrolyte is recovered by solid-liquid separation with no further details. Nothing is said about the ionic conductivity of the sulfide solid electrolyte with such a small particle size and low specific surface area. Recovered sulfide solid electrolyte is passed through a sieve with an aperture size of 53 pm.

[0013] According to the above, there is a need for milling post-treatment conditions suitable to reduce the particle size of the SEE powder without impairing ionic conductivity.

[0014] There is a need for milling post-treatment conditions suitable to reduce the particle size of the SEE powder without formation of coarse particles that would need to be eliminated by further sieving.

[0015] There is a need for milling post-treatment conditions suitable to reduce the particle size of the SEE powder and to enhance the specific surface area of the particles, allowing better interaction with the binder when used in battery applications.

[0016] There is a need for these milling post-treatment in wet conditions suitable to reduce the particle size of the SEE powder and to manage solvent removal without impairing ionic conductivity.

[0017] There is a need for these milling post-treatment in wet conditions suitable to reduce the particle size of the SEE powder and to manage solvent removal without formation of coarse particles that would need to be eliminated by further sieving.

[0018] There is a need for milling post-treatment in wet conditions suitable to reduce the particle size of the SEE powder and to enhance the specific surface area of the particles, allowing better interaction with the binder when used in battery applications.

[0019] Summary of the invention

[0020] All these needs and more are fulfilled by a first aspect of the invention which relates to a process for manufacturing a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements comprising the steps of:(a) providing a powder (P1 ) comprising particles of the solid sulfide material (M), at least one organic solvent (S) and at least one ester (E) of carboxylic acid compound different from (S) to obtain a suspension (S1 ), wherein the boiling point (bp ) of the ester compound (E) is at least 30°C higher than the boiling point (bps) of the organic solvent (S), preferably 60°C higher;(b) submitting the suspension (S1 ) obtained in (a) to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2);(c) removing by evaporation under stirring, at a temperature (T) not exceeding bpE - 30°C, at least partially the organic solvent (S) and the ester (E) from the suspension (S2) to recover a powder (P2);(d) drying under stirring at a temperature (T) not exceeding bpE - 30°C the powder (P2) obtained in (c) until a constant weight of the desired powder (P) is recovered. It also relates to the powder (P) obtained by the process and its use as solid electrolyte.

[0021] Another object of the present invention is a powder (P) obtainable by the process according to the invention comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements , wherein the particle size distribution of the powder (P) is such that the mean diameter D50 ranges from 0.2 to 5 pm and the span (D90-D10) / D50 is at most equal to 3.0 as measured by laser diffraction analysis in xylene; wherein the IR spectrum of the powder (P) reveals a peak with a maximum at a wavelength between 1650 cm-1and 1730 cm-1assigned to the C=O group of an organic compound (C) grafted onto the particles.

[0022] Still another aspect of the invention is the use of the powder (P) according to the invention as a solid electrolyte.

[0023] Finally, other aspects of the invention relate to an electrode or a separator comprising the powder (P) according to the invention.Detailed description

[0024] Advantageously, the inventors have found that the process according to the invention allows preparing powder (P) comprising particles of sulfide solid material (M) having low average particle size, narrow particle size distribution and high ionic conductivity.

[0025] Moreover, the process according to the invention allows preparing particles of sulfide solid material (M) onto which a compound (C) bearing a carbonyl group (C=O group) is grafted.

[0026] Without being bound to any theory, this grafted organic compound (C) is assumed to be responsible for protecting the surface of the particle from moisture, and / or carbon dioxide from air and for avoiding agglomeration during and after the process. It is assumed that organic compound (C) is derived from the ester (E) involved in the process according to the invention.

[0027] Therefore, the process according to the invention is a process for manufacturing a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements comprising the steps of:(a) providing a powder (P1 ) comprising of particles of the solid sulfide material (M), at least one organic solvent (S) and at least one ester (E) of carboxylic acid compound different from (S) to obtain a suspension (S1 ), wherein the boiling point (bp ) of the ester compound (E) is at least 30°C higher than the boiling point (bps) of the organic solvent (S), preferably 60°C higher;(b) submitting the suspension (S1 ) obtained in (a) to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2);(c) removing by evaporation under stirring, at a temperature (T) not exceeding bpE - 30°C, at least partially the organic solvent (S) and the ester (E) from the suspension (S2) to recover a powder (P2);

[0028] (d) drying under stirring at a temperature (T) not exceeding bpE - 30°C the powder (P2) obtained in (c) until a constant weight of the desired powder (P) is recovered.

[0029] (P1 ) comprising particles of the solid sulfide material (M), means that (P1 ) may contain some impurities or raw material inherent to the synthesis of the solid sulfide material (M).

[0030] In some embodiments the powder (P1 ) consists or essentially consists of particles of the solid sulfide material (M). By essentially consists is meant that powder (P1 ) contains less than 5 wt %, preferably less than 3 wt % and more preferably less than 1 wt % of material which is different from particles of at least one sulfide solid material (M).

[0031] The solid sulfide material (M) can be any solid sulfide material comprising Li, P and S elements.

[0032] In some embodiments the solid sulfide material (M) responds to the formula (I): Li7-xPS6-xXx (I) wherein:- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0033] Generally, the solid sulfide material (M) responding to the formula (I) is prepared by well-known methods involving Li2S, P2S5 and LiX as raw materials. The molar ratio of the raw materials are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elements Li, P, S and X, which is obtainable from the applied amounts of the raw materials under the condition of complete conversion without side reactions and other losses. Just for the sake of example 2 moles of LiePSsCI can be obtained from 5 moles of Li2S, 1 mole of P2S5 and 2 moles of LiCI.

[0034] In some other embodiments the solid sulfide material (M) responds to the formula (II):Li7-2y-xMyPS6-xXx (II) wherein:- M is an alkaline earth metal element selected from Sr, Ca, Mg and Ba;- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- y is a positive number such as 0.01 < y < 0.5; preferably such as 0.01 < y < 0.1 ;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0035] Generally, the solid sulfide material (M) responding to the formula (II) is prepared by well-known methods involving Li2S, P2S5, LiX and MX2, MS ormixture thereof as raw materials. The molar ratio of the raw materials are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elements Li, P, S, M and X, which is obtainable from the applied amounts of the raw materials under the condition of complete conversion without side reactions and other losses.

[0036] Still in some other embodiments the solid sulfide material (M) responds to the formula (III):Li7-y’-xM’y’PS6-xXx (III) wherein:- M’ is selected from Na, K, Rb, Cs, Cu and Ag;- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- y’ is a positive number such as 0.01 < y’ < 0.5; preferably such as 0.01 < y’ < 0.1 ;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0037] Generally, the solid sulfide material (M) responding to the formula (II) is prepared by well-known methods involving Li2S, P2S5, LiX and M’X, M’2S or mixture thereof as raw materials. The molar ratio of the raw materials are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elements Li, P, S, M’ and X, which is obtainable from the applied amounts of the raw materials under the condition of complete conversion without side reactions and other losses.

[0038] Whether the solid sulfide material (M) responds to the formula (I), (II) or (III), X is preferably selected from the list consisting of F, Cl, I, Br and mixture thereof; more preferably from the list consisting of Cl, I, Br and mixture thereof; even more preferably from the list consisting of Cl, Br and mixture thereof.

[0039] There is no limitation regarding the powder P1. It is merely composed of coarser particles than the particles of the desired powder (P).

[0040] The organic solvent (S) can be selected from the group consisting of aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof. Aliphatic hydrocarbons are for instance hexane, heptane, octane or nonane. Cycloaliphatic hydrocarbons are for instance cyclohexane, cyclopentane or cycloheptane. Aromatic hydrocarbons are for instance benzene, toluene, ethylbenzene, xylenes or liquid naphthenes.

[0041] Good results were obtained using a xylene mixture of isomers.

[0042] The ester (E) of carboxylic acid compound is different from the solvent (S) and the boiling point (bp ) of the ester compound (E) is at least 30°C higher than the boiling point (bps) of the organic solvent (S); preferably at least 60°C higher; more preferably at least 70°C higher.

[0043] The inventors have experienced that, surprisingly if the difference between the boiling point (bp ) of the ester compound (E) and the boiling point (bps) of the organic solvent (S) is not sufficient, it is not possible to get small enough particle size for the sulfide solid material (M) to be suitable for further use in battery applications.

[0044] By boiling point (bpE) of the ester compound (E) and boiling point (bps) of the organic solvent (S) is meant boiling point measured under standard ambient temperature and pressure.

[0045] The ester (E) of carboxylic acid compound is generally at least one compound responding to formula R-C(=O)-O-R’ wherein R is a C1-C4, optionally branched, alkyl group and R’ is a C6-C12, optionally branched or cyclic, alkyl group.

[0046] Good results were obtained using a xylene mixture of isomers and octyl acetate. Under standard ambient temperature and pressure, the boiling point of the xylene mixture of isomers is 138.5°C, while the boiling point of octyl acetate is 211 °C.

[0047] Other possibilities are xylene mixture of isomers and hexyl acetate. Under standard ambient temperature and pressure, the boiling point of the xylene mixture of isomers is 138.5°C, while the boiling point of hexyl acetate is 171.5°C.

[0048] In some embodiments, the couple organic solvent (S) I ester (E) is selected from the list consisting of xylene mixture of isomers / octyl acetate, xylene mixture of isomers / hexyl acetate, ethyl benzene / hexyl acetate, ethyl benzene / octyl acetate, toluene / hexyl acetate, toluene / octyl acetate, heptane / octyl acetate, heptane / hexyl acetate, hexane / octyl acetate, hexane / hexyl acetate, cyclohexane / octyl acetate and cyclohexane / hexyl acetate.

[0049] Suspension (S1 ) is obtained in step (a) by admixing powder (P1 ), solvent (S) and the ester (E). There is no particular influence of the order of addition.

[0050] Generally, the suspension (S1 ) comprises a weight ratio of powder (P1 ) and organic solvent (S) ranging from 0.01 to 0.5, preferably from 0.05 to 0.3 and the amount of ester compound (E) represents from 0.01 wt % to 10 wt %, preferably from 0.02 wt % to 5 wt %, of the total weight of the powder (P1 ) and of the organic solvent (S).

[0051] Good results were obtained with a weight ratio of powder (P1 ) and organic solvent (S) of 0.26 and 1 .4 wt % of ester compound (E) with regard to the total weight of the powder (P1 ) and of the organic solvent (S).

[0052] Good results were also obtained with a weight ratio of powder (P1 ) and organic solvent (S) of 0.1 and 0.024 wt % of ester compound (E) with regard to the total weight of the powder (P1 ) and of the organic solvent (S).

[0053] Generally step (a) is performed at a temperature not exceeding 120°C. Good results were obtained at room temperature.

[0054] In some embodiments step (a) is performed under an inert atmosphere. Inert atmosphere can be composed of nitrogen, argon or mixtures thereof.

[0055] In step (b) the suspension (S1 ) obtained in (a) is submitted to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2).

[0056] The mechanical treatment is generally performed at a temperature not exceeding 120°C. Good results were obtained at room temperature.

[0057] In some embodiments step (b) is performed under an inert atmosphere. Inert atmosphere can be composed of nitrogen, argon or mixtures thereof.

[0058] The mechanical treatment can be performed using a rotation ball mill, a tumbling ball mill, a vibration ball mill and a planetary ball mill or the like. Mechanical milling may be made with or without balls such as ZrO2 balls.

[0059] Mechanical treatment may also be performed by stirring, notably by using well known techniques in the art, such as by using standard powder or slurry mixers.

[0060] In some preferred embodiments step (b) is conducted by wet ball milling.

[0061] Mechanical treatment of (S1 ) in step (b) may be performed by milling at about 500 rpm to 5000 rpm, notably for a duration from 10 minutes to 10 hours; preferably for about 30 minutes to 5 hours.

[0062] Mechanical treatment of (S1 ) in step (b) may be performed in a bead milling device with a peripheral speed ranging from 5 L / h to of 50 L / h.

[0063] Good results were obtained using the bead mill MicroCer® manufactured by Netzsch.

[0064] In step (c) the organic solvent (S) and the ester compound (E) are at least partially removed from suspension (S2) by evaporation under stirring, at a temperature (T) not exceeding bpE - 30°C, to recover a powder (P2).

[0065] For example, a temperature (T) not exceeding bpE - 30°C means not exceeding 181 °C in the case of octyl acetate which boiling point is 211 °C.

[0066] In some embodiments, in step (c) the organic solvent (S) and the ester compound (E) are at least partially removed from suspension (S2) by evaporation under stirring, at a temperature (T) not exceeding bpE - 60°C, to recover the powder (P2).

[0067] Evaporation can be performed at ambient pressure or under vacuum.

[0068] The temperature (T) of step (c) is between the fusion temperature of the solvent (S) and ebullition temperature (bps) of the solvent (S). Preferably step (c) is done at a temperature between -20°C and 200°C and more preferably between 40°C and 200°C.

[0069] In some embodiments, step (c) is conducted through evaporation of the solvent (S) and of the ester (E) under stirring optionally under reduced pressure at a temperature ranging from 40°C to 200°C.

[0070] In step (c), at least a portion of the solvent (S) and of the ester compound (E) is removed notably means to remove at least about 30%, 40%, 50%, 60%, 70%, 80%, 90% 95% or 98%, of the total weight of the solvent (S) and the ester (E) used, or any ranges comprised between these values.

[0071] Evaluation of this portion can be made by condensation of the solvent (S) and the ester (E) removed and by comparing weight condensed to weight introduced.

[0072] The inventors have found that vigorous stirring is required during evaporation of the organic solvent (S) and the ester compound (E) to avoid any agglomeration and formation of coarse particles in addition to small particles.

[0073] Therefore vigorous stirring is required during evaporation of the organic solvent (S) and the ester compound (E) to obtain small particle size and narrow particle size distribution.

[0074] Particle size distribution can be characterized by laser diffraction using xylene dispersion of the powder. D10, D50 and D90 are obtained from the volumebased particle size distribution of the powder. Dx-value denotes the value which is determined with regard to the distribution by volume of the sizes of the particles for which x% of the particles have a size less than or equal to this value Dx. Thus, for example, with respect to D10, 10% of the particles have a size which is less than D10. For example again, with respect to D90, 90% of the particles have a size which is less than D90. D50 corresponds to the median value of the distribution by volume.

[0075] The inventors have experienced that, solvent removal by well-known solidliquid separation methods such as decantation, filtration, centrifugation, drying or a combination thereof does not lead to small enough particle size for the sulfide solid material (M) to be suitable for further use in battery applications.

[0076] Without being bound to any theory, it is assumed that the difference between the boiling point (bp ) of the ester compound (E) and the boiling point (bps) of the organic solvent (S) allows complete or substantially complete removal of solvent (S) while ester compound (E) plays the role of dispersing agent and isfinally probably the origin of the compound (C) grafted onto the particles thus preventing reagglomeration.

[0077] Stirring is meant to indicate the use of a device comprising at least two parts, each part having a relative speed versus the others. For example, evaporation under stirring can be conducted in a reactor equipped with an impeller, a blade or a turbine rotating at high speed. Besides, evaporation under stirring can indicate the use of a stirring equipment suitable to generate a vortex in the presence of the suspension (S2).

[0078] A powder (P2) is recovered after step (c). The powder (P2) may contain traces of solvent (S) and / or of the ester compound (E). Therefore a step (d) of drying of the powder (P2) is generally required in the process according to the invention.

[0079] Step (d) is conducted under stirring at a temperature (T) not exceeding bpE - 30°C. It can be conducted in the same equipment as for step (c). It can also be conducted in an equipment more adapted for the drying of powders like a rotary kiln or a paddle dryer.

[0080] In some embodiments, in step (d) is conducted under stirring at a temperature (T) not exceeding bpE - 60°C.

[0081] The temperature (T) of step (d) is between the fusion temperature of the solvent (S) and ebullition temperature of the solvent (S). Preferably step (d) is done at a temperature between -20°C and 200°C and more preferably between 40°C and 200°C.

[0082] In some embodiments, step (d) is conducted through evaporation of the solvent and of the ester (E) under stirring optionally under reduced pressure at a temperature ranging from 40°C to 200°C.

[0083] In step (d) the powder (P2) obtained in (c) is dried under stirring at a temperature (T) not exceeding bpE - 30°C, in some embodiments not exceeding bpE - 60°C, until a constant weight of the desired powder (P) is recovered. Until a constant weight of the desired powder (P) is recovered means that the drying is conducted until the weight loss of the powder measured, in an interval of 1 h in the set conditions of temperature, pressureand stirring, represents less than 0.1 wt % of the total weight of powder (P), preferably less than 0.05 wt %, more preferably less than 0.01 wt %.

[0084] Another object of the present invention is a process for manufacturing a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements, wherein the particle size distribution of the powder (P) is such that the mean diameter D50 ranges from 0.2 to 5 pm and the span (D90- D10) / D50 is at most equal to 3.0 as measured by laser diffraction analysis in xylene; and wherein the IR spectrum of the powder (P) reveals a peak with a maximum at a wavelength comprised between 1650 cm-1and 1730 cm-1assigned to the C=O group of an organic compound (C) grafted onto the particles.

[0085] Generally the amount of organic compound (C) bearing C=O group grafted onto the particles of sulfide solid material (M) ranges from 0.01 wt% to 2 wt%; preferably from 0.1 wt% to 1 wt% with regards to the total weight of the powder (P) comprising those particles.

[0086] The amount of organic compound (C) bearing C=O group grafted onto the particles can be determined by e.g. thermogravimetric analysis (TGA).

[0087] Some evidence were found by TGA that the grafted compound (C) is derived from the ester (E) involved in the process according to the invention.

[0088] Still another object of the invention is a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements obtained by the process according to the invention as previously disclosed.

[0089] In some embodiments powder (P) consists or essentially consists of particles of at least one sulfide solid material (M) and of grafted organic compound (C). By essentially consists is meant that powder (P) contains less than 5 wt %, preferably less than 3 wt % and more preferably less than 1 wt % of material which is different from particles of at least one sulfide solid material (M) and of grafted organic compound (C).

[0090] The present invention also relates to a powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements , wherein the particle size distribution of the powder (P) is such that the mean diameterD50 ranges from 0.2 to 5 pm and the span (D90-D10) / D50 is at most equal to 3.0 as measured by laser diffraction analysis in xylene; and wherein the IR spectrum of the powder (P) reveals a peak a peak with a maximum at a wavelength comprised between 1650 cm’1and 1730 cm’1assigned to the C=O group of an organic compound (C) grafted onto the particles.

[0091] The mean diameter D50 of the powder (P) according to the invention generally ranges from 0.2 to 5 pm; sometimes ranges from 0.5 to 5 pm; for example from 1.1 to 5 pm.

[0092] The span (D90-D10) / D50 of the powder (P) according to the invention is at most equal to 3.0; sometimes at most equal to 2.7.

[0093] Generally, the powder (P) according to the present invention is such that the solid state1H NMR spectrum of said powder (P) does not show any signal in the range of 3 ppm to 5 ppm.

[0094] Generally, the powder (P) according to the present invention exhibits an ionic conductivity of at least 1 mS / cm as measured at 200 MPa by impedance spectroscopy at 23°C on pellets pressed at 500 MPa.

[0095] Generally, the powder (P) according to the present invention exhibits a specific surface area of the particles measured Brunauer-Emmet-Teller (BET) method ranging 5 m2 / g to 40 m2 / g; preferably from 7 m2 / g to 30 m2 / g.

[0096] Generally, the powder (P) according to the present invention exhibits a BET C factor related to the affinity of the solid with the adsorbate of less than 30; preferably of less than 25, more preferably of less than 20.

[0097] In some embodiments, the powder (P) according to the invention responds to the formula (I):Li7-xPS6-xXx (I) wherein:- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0098] In some embodiments, the powder (P) according to the invention responds to the formula (II):Li7-2y-xMyPS6-xXx (II) wherein:- M is an alkaline earth metal element selected from Sr, Ca, Mg and Ba;- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- y is a positive number such as 0.01 < y < 0.5; preferably such as 0.01 < y < 0.1 ;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0099] In some embodiments, the powder (P) according to the invention responds to the formula (III):Li7-y-xM’y’PS6-xXx (III) wherein:- M’ is selected from Na, K, Rb, Cs, Cu and Ag;- x is a positive number such as 0.5 < x < 2; preferably such as 1 .0 < x < 1 .8; more preferably such as 1 .2 < x < 1 .6;- y’ is a positive number such as 0.01 < y’ < 0.5; preferably such as 0.01 < y’ < 0.1 ;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.

[0100] Another aspect of the present invention is the use of the powder (P) according to the invention as a solid electrolyte.

[0101] Still another aspect of the present invention is a solid electrolyte comprising at least the powder (P) according to the invention.

[0102] The present invention also pertains to an electrode comprising at least:- a metal substrate;- directly adhered onto said metal substrate, at least one layer made of a composition comprising:(i) the powder (P) according to the invention;(ii) at least one electro-active compound (EAC);(iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid material of the invention;(iv) optionally at least one electro-conductive material (ECM);(v) optionally a lithium salt (LIS);(vi) optionally at least one polymeric binding material (P).

[0103] The present invention also pertains to a separator comprising at least:- the powder (P) according to the invention;- optionally at least one polymeric binding material (P);- optionally at least one metal salt, notably a lithium salt;- optionally at least one plasticizer.

[0104] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0105] The invention will be now described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.Experimental section

[0106] Samples preparation

[0107] Example 1 (Reference)

[0108] Stoichiometric argyrodite of formula LiePSsCI is obtained as described in W02023062011A1

[0109] Characterization of the product is reported in table 1.

[0110] Example 2 (According to the invention)

[0111] 68g of solid electrolyte LiePSsCI of example 1 , 3.4g of octyl acetate, 259g of dehydrated xylene (mixture of isomer) and 192g of 0.6-0.8mm diameter zirconia beads are placed in the grinding chamber of a bead mill MicroCer® manufactured by Netzsch and milled at 2500RPM for 45minutes with a peripheral speed of 18.4L / h.

[0112] The resulting suspension is then subjected to liquid-beads separation and transferred in a reactor equipped with a paravisc-shape paddle. Agitation is set at 200 RPM and the reactor is inerted by 3 cycles of vacuum and nitrogen. Then, evaporation and drying is conducted at 60°C and 20 mbar for 3 hours i.e. until constant weight is obtained. The reactor is kept under vacuum and transferred in an Ar filled glovebox to retrieve the final powder.

[0113] Example 3 (According to the invention)

[0114] 22g of solid electrolyte LiePSsCI of example 1 , 0.06g of octylacetate, 222g of dehydrated xylene (mixture of isomer) and 322g of 1 .0mm diameter zirconia beads are placed in the grinding chamber of a planetary ball mill PM100 manufactured by Retsch and milled at rotation speed of 200RPM for 4h.

[0115] The resulting suspension is then treated as the suspension of example 2.

[0116] Example 4 (Comparative)

[0117] 22g of solid electrolyte LiePSsCI of example 1 , 0.06g of octylacetate, 222g of dehydrated xylene (mixture of isomer) and 322g of 1 .0mm diameter zirconia beads are treated as in example 3.

[0118] The resulting suspension is then subjected to liquid-beads separation, and solid-liquid separation. Solid-liquid separation is performed by filtration over 0.45 pm filter. The recovered wet solid is further dried at 60°C at 20mbar to retrieve the final powder.

[0119] Example 5 (Comparative)

[0120] 22g of solid electrolyte Li6PS5CI of example 1 , 0.06g of octylacetate, 222g of dehydrated xylene (mixture of isomer) and 322g of 1 .0mm diameter zirconia beads are placed in the grinding chamber of a planetary ball mill PM100 manufactured by Retsch and milled at rotation speed of 200RPM for 4h.

[0121] The resulting suspension is then subjected to liquid-beads separation and transferred to a 500m L round bottomed flask. Distillation and drying is then conducted in a rotative evaporator manufactured by IKA at 80°C and 35mbar for 3 hours to retrieve the final powder.

[0122] Example 6 (Comparative)

[0123] 68g of solid electrolyte LiePSsCI of example 1 , 3.4g of octylacetate, 259g of dehydrated xylene (mixture of isomer) and 192g of 0.6-0.8mm diameter zirconia beads are treated as in example 2.

[0124] The resulting suspension is then subjected to liquid-beads separation and transferred to a 500m L round bottomed flask. Distillation and drying is then conducted in a rotative evaporator manufactured by IKA at 80°C and 35mbar for 3 hours. The flask is kept under vacuum and transferred in an Ar filled glovebox to retrieve the final powder.

[0125] Example 7 (Comparative)

[0126] Example 7 is conducted in the same way as example 3 but in the absence of octyl acetate.

[0127] 22g of solid electrolyte LiePSsCI of example 1 , 222g of dehydrated xylene (mixture of isomer) and 322g of 1 .0mm diameter zirconia beads are treated as in example 3.

[0128] The resulting suspension is then treated as the suspensions of example 2 and example 3.

[0129] Example 8 (Comparative)

[0130] Example 8 is conducted in the same way as example 3 but replacing octyl acetate (Bp=211 °C) by butyl acetate (Bp=126°C).

[0131] 22g of solid electrolyte LiePSsCI of example 1 , 0.06g of butyl acetate, 222g of dehydrated xylene (mixture of isomer) and 322g of 1 .0mm diameter zirconia beads are treated as in example 3.

[0132] The resulting suspension is then treated as the suspensions of example 2 and example 3.

[0133] Particle Size Distribution (PSD)

[0134] The PSD of the powder is measured by laser diffraction using xylene in a Malvern Panalytical Mastersizer 3000. D10, D50 and D90 are obtained from the volume-based particle size distribution of the powder. The powder is predisperse at 6000 RPM for 30min in a solution at 0.3wt%. Measurements are done in anhydrous xylene dried with 3A molecular sieve. Molecular sieve is previously activated by a thermal treatment under air at 350°C for 12 hours.The measurement time is 10 seconds, the measurements are performed 10 times. D10, D50 and D90 given in Table 1 are the average of the 10 measurements. The model used is Mie with a refractive index of the material is 1 .88, the shape is “non-spherical” and the refractive index of the media is 1.496.

[0135] I R spectroscopy

[0136] Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra were recorded in an Ar filled glovebox on an Alpha II spectrometer manufactured by Bruker. Spectra are acquired with 24 scans and a resolution of 4 cm-1between 4000 and 400 cm-1. Before the measurement, the background is set with a gold mirror.

[0137] NMR Spectrometry

[0138] Solid-State NMR spectra were recorded on a Neo Avance 400Mhz spectrometer manufactured by Bruker with a high-speed DVT4 probe.1H measurements were performed in single pulse mode, with a pulse of 90° and a rotation speed of 10 kHz. The relaxation time D1 was set at 10s and 32 measurements were made. The analysis was made at room temperature. The reference used for the indexation of chemical shifts is a water rotor with a chemical shift fixed at 4.8ppm. Measurements are made between -10ppm and 10ppm.

[0139] Samples from example 2 and example 3 according to the invention do not show any signal in the spectral region ranging from 3 to 5ppm.

[0140] Specific surface area of the particles by BET method

[0141] Specific surface area of the particles was measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method described in “The Journal of the American Chemical Society”, vol. 60, page 309, February 1938.The instrument used was a Micromeritics® TriStar 3000. The samples were pretreated in vacuum at 120 °C for 2 hours prior to analysis. The specific surface area was calculated by considering the P / P° range between 0.05 and 0.25. At least 6 points were selected within this range of P / P° in order to obtain a good correlation coefficient.

[0142] The BET C factor is related to the affinity of the solid with the adsorbate which is here the N2 molecules, and so to the heat of adsorption. The higher the value of C, the higher the interaction between solid and adsorbate.

[0143] Thermogravimetric analysis (TGA)

[0144] TGA of powder was made with a thermobalance TGA / DSC3+LF100 manufactured by Mettler. It was coupled to an infrared spectrometer Tensor 27 from Broker and a mass spectrometer Thermostar® GSD 350 from Pfeiffer Vacuum (MCD mode). The connection is made at the gas outlet with a T- shape PTFE pipe heated at 110°C. The heating ramp is 5°C from 25°C to 600°C and the measurement is made under a nitrogen flux of 50mL / min.

[0145] Conductivity & Electrochemical Impedance Spectroscopy (EIS)

[0146] The ionic conductivity of the sulfide solid electrolytes is measured according to the following method, in an Ar filled glove box. 150mg of powder is introduced between 2 stainless steel current collectors in an airtight PEEK pressure cell (15.5mm diameter), densified and pelletized in a uniaxial press at 9.6t (500MPa) for 1 minute. Pressure is released and set back at 3.85t (200MPa) for ionic conductivity measurement. The impedance spectra are acquired on a Biologic VMP3 device. The samples are placed in a Binder thermostatic chamber to perform the impedance measurements at 23°C. Impedance spectroscopy is acquired after 2 hours equilibration time; in PEIS mode with an amplitude of 20mV, no bias and a range of frequencies from 500kHz to 5kHz with 25 measurements per decade and 10 measurements for each frequency. The pellet is then extracted in glovebox from the cell and its thickness is measured.

[0147] XRD Analysis

[0148] The XRD d iff ractog rams of the powders were acquired on a XRD goniometer (Malvern-Panalytical Aeris) in the Bragg Brentano geometry, with a Cu X Ray tube (Cu Kalpha wavelength of 1 .5406 A). Tube settings were operating at 40 kV / 15 mA, 600 W). The setup was used with fixed slits and Soller slits of 0.02 rad. A filtering device on the primary side may also be used, like a nickel filter, a monochromator or a Bragg Brentano HD optics from Panalytical. The sampleholder was loaded on a spinner; rotation speed was typically 60 rpm during the acquisition. Acquisition step was 0.0108° per step. Angular range was typically 10° to 90° in two theta or larger. Total acquisition time was typically 30 min or longer. Measurements were made in a dry room.

[0149] B value reported in table 3 below is the crystallographic density of the material. It is determined by le Bail refinement of the XRD diagram of the products acquired with Cu wavelength. All the XRD diagrams were fitted using a cubic F-43m space group.

[0150] Table 1 : D10, D50 and D90 and ionic conductivity at 23°C for solid sulfide electrolytes of examples 1 to 8*no ester; **butyl acetate (Bp=126°C) I xylene mixed (Bp=137°C) n.d. stands for not determined.

[0151] According to all these results, the inventors have demonstrated that the process according to the invention is suitable to manufacture a solid sulfide material with a good compromise regarding particle size distribution (i.e. small size particles with a narrow span) and ionic conductivity.

[0152] Table 2: IR peak in the 1650-1850 cm-1region assigned to (C=O) containing compound

[0153] The maximum of the peak assigned to the carbonyl group of the organic compound (C) is observed at lower wavelength (1715 cm-1) than the maximum of the peak assigned to the carbonyl group of octyl acetate (1740 cm’1).

[0154] According to results of table 2, the inventors have demonstrated that the process according to the invention is suitable to manufacture a solid sulfide powder having an organic compound (C) containing a carbonyl group grafted on the surface of the particles. It has been found that surprisingly this grafted sulfide material is a free flowing material with no tendency to agglomerate during drying.

[0155] Thermogravimetric analysis (TGA) of the powder of Example 2, revealed 1 wt % of ester grafted onto the surface of the particles. Indeed, TGA equipment coupled to an infrared spectrometer and a mass spectrometer revealed the departure of 1 wt % of products, identified as octanol, thioacetone and compound comprising C, O and S elements, between 180°c and 405°C.

[0156] Thermogravimetric analysis made with same equipment coupled to an infrared spectrometer and a mass spectrometer of a physical mixture of powder of Example 2, revealed departure of the “free” octyl acetate at a temperature below 180°C.

[0157] Table 3: Specific surface area, C parameter, density and CS for solid sulfide electrolytes of examples 1 to 8*no ester; **butyl acetate (Bp=126°C) / xylene mixed (Bp=137°C)

[0158] As previously mentioned BET C factor is related to the affinity of the solid with the N2 molecules. The higher the value of C, the higher the interaction. Accordingly, in the example according to the invention the interaction with N2 is significantly lowered with regard to the reference but also with the comparative examples. It is assumed that this is due to the presence of the organic compound (C) containing a carbonyl group grafted on the surface of the particles.

[0159] The ratio AB / CS of the product according to the invention is slightly reduced with regard to the value obtained for the reference sample.

[0160] Moreover the specific surface area measured by the BET method of the product according to the invention is enhanced when compared to the SSA of the reference and thus better interaction with e.g. a polymeric binder is expected in battery applications.

Claims

ClaimsClaim 1 . A process for manufacturing a powder (P) comprising particles of at least one sulfide solid material comprising Li, P and S elements comprising the steps of:(a) providing a powder (P1 ) comprising particles of the solid sulfide material, at least one organic solvent (S) and at least one ester compound (E) different from (S) to obtain a suspension (S1 ), wherein the boiling point (bp ) of the ester compound (E) is at least 30°C higher than the boiling point (bps) of the organic solvent (S), preferably 60°C higher;(b) submitting the suspension (S1 ) obtained in (a) to a mechanical treatment thereby reducing the size of the particles of the solid sulfide material (M) and obtaining a suspension (S2);(c) removing by evaporation under stirring, at a temperature (T) not exceeding bpE - 30°C, at least partially the organic solvent (S) and the ester (E) from the suspension (S2) to recover a powder (P2);(d) drying under stirring at a temperature (T) not exceeding bpE - 30°C the powder (P2) obtained in (c) until a constant weight of the desired powder (P) is recovered.Claim 2. The process according to claim 1 , wherein the ester (E) of carboxylic acid compound is at least one compound responding to formula R-C(=O)-O-R’ wherein R is a C1-C4, optionally branched, alkyl group and R’ is a C6-C12, optionally branched or cyclic, alkyl group; and wherein the organic solvent (S) is selected from the group consisting of aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof.Claim 3. The process according to claim 1 or 2, wherein in step (a) the suspension (S1 ) comprises a weight ratio of powder (P1 ) and organic solvent (S) ranging from 0.01 to 0.5, preferably from 0.05 to 0.3 and the amount of ester compound (E) represents from 0.01 wt % to 10 wt %, preferably from 0.02 wt % to 5 wt % of the total weight of the powder (P1 ) and of the organic solvent (S).Claim 4. The process according to any one of claims 1 to 3, wherein step (b) is conducted by wet ball milling.Claim 5. The process according to any one of claims 1 to 4, wherein step (c) is conducted through evaporation of the solvent (S) and of the ester (E) under stirring optionally under reduced pressure at a temperature ranging from 40°C to 200°C.Claim 6. The process according to any one of claims 1 to 5, wherein step (d) is conducted under stirring optionally under reduced pressure at a temperature ranging from 40°C to 200°C.Claim 7. The process according to any one of claims 1 to 6, wherein the particle size distribution of the powder (P) is such that the mean diameter D50 ranges from 0.2 to 5 pm and the span (D90-D10) / D50 is at most equal to 3.0 as measured by laser diffraction analysis in xylene; and wherein the IR spectrum of the powder (P) reveals a peak with a maximum at a wavelength comprised between 1650 cm’1and 1730 cm’1assigned to the C=O group of an organic compound (C) grafted onto the particles.Claim 8. A powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements obtained by the process according to any one of claims 1 to 7.Claim 9. A powder (P) comprising particles of at least one sulfide solid material (M) comprising Li, P and S elements, wherein the particle size distribution of the powder (P) is such that the mean diameter D50 ranges from 0.2 to 5 pm and the span (D90-D10) / D50 is at most equal to 3.0 as measured by laser diffraction analysis in xylene; and wherein the IR spectrum of the powder (P) reveals a peak with a maximum at a wavelength between 1650 cm’1and 1730 cm’1assigned to the C=O group of an organic compound (C) grafted onto the particles.Claim 10. The powder (P) according to claim 8 or 9, wherein the solid state1H NMR spectrum of the powder (P) does not show any signal in the range of 3 ppm to 5 ppm.Claim 11 . The powder (P) according to any one of claims 8 to 10 exhibiting an ionic conductivity of at least 1 mS / cm as measured at 200 MPa by impedance spectroscopy at 23°C on pellets pressed at 500 MPa.Claim 12. The powder (P) according to any one of claims 8 to 11 exhibiting a BET C factor of less than 30.Claim 13. The powder (P) according to any one of claims 8 to 12 wherein the sulfide solid material (M) comprising Li, P and S elements responds to the formula (I):Li7-xPS6-xXx (I) wherein:- x is a positive number such as 0.5 < x < 2;- X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, and NCS, or a combination thereof.Claim 14. Use of the powder (P) according to any one of claims 8 to 13 as a solid electrolyte.Claim 15. A solid electrolyte comprising at least the powder (P) according to any one of claims 8 to 13.Claim 16. An electrode comprising at least:- a metal substrate;- directly adhered onto said metal substrate, at least one layer made of a composition comprising:(i) the powder (P) according to any one of claims 8 to 13;(ii) at least one electro-active compound (EAC);(iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid material of the invention;(iv) optionally at least one electro-conductive material (ECM);(v) optionally a lithium salt (LIS);(vi) optionally at least one polymeric binding material (P).Claim 17. An separator comprising at least:- the powder (P) according to any one of claims 8 to 13;- optionally at least one polymeric binding material (P);- optionally at least one metal salt, notably a lithium salt;- optionally at least one plasticizer.

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