Process for preparing particles of sulfide solid material comprising li, p, s and x elements

Abstract

The present disclosure relates to a process for preparing particles of a sulfide solid material (M) comprising at least Li, P, S and X elements, comprising the step of providing a powder of lithium sulfide (Li2S) comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and having a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH. It also relates to particles obtained by said process and their use for the preparation of an electrode, of an electrolyte layer of an electrode or of a separator.

Description

DescriptionPROCESS FOR PREPARING PARTICLES OF SULFIDE SOLID MATERIAL COMPRISING Li, P, S AND X ELEMENTSCross-reference to related application

[0001] This application claims priority to European application No. 24315299.8 filed on June 19, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present disclosure relates to a process for preparing particles of a sulfide solid material (M) comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and having a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH, b) mixing at least Li2S of step a), P2S5 and LiX, where X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof, optionally in the presence of a solvent (S) to obtain a composition (C); c) optionally removing at least a portion of the solvent (S) from the composition (C) obtained on step b) so that to obtain a sulfide solid material precursor (P); d) optionally pressing the sulfide solid material precursor (P) of step c) into pellets; e) heating the composition (C) or the precursor (P) obtained in step c) e.g. in the form of pellets, to a temperature in the range of from 350°C to 580°C, under an inert atmosphere, for a time period ranging from 1 to 12 hours, thereby forming the sulfide solid material particles; andf) optionally treating the sulfide solid material particles obtained in step e) to obtain a desired particle size.

[0003] It also relates to particles obtained by said process and their use for the preparation of an electrode, of an electrolyte layer of an electrode or of a separator.Background

[0004] 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.

[0005] Because the solvent used as an electrolyte is flammable, all-solid-state lithium ion batteries not using organic solvent are very attractive. Such all-solid-state lithium ion batteries are formed by solidifying the whole battery using a solid electrolyte, for example containing Li, P, S, and optionally a halogen.

[0006] One of the starting materials to prepare such a sulfide solid electrolyte (SSE) is lithium sulfide (Li2S), generally available as a powder. Although it is well known that purity of lithium sulfide (Li2S) powder is crucial to obtain a high purity sulfide solid electrolyte, less is known about the influence of some specific impurities contained in this starting material onto the properties of the resulting SSE.

[0007] Different methods have been disclosed in the art for the manufacture of Li2S generally involving raw materials such as LiOH or Li2COs as lithium source and H2S as sulfur source.

[0008] In some examples the manufacture of Li2S is performed in solution, e.g. in an organic solvent, and is therefore a gas-liquid reaction between gaseous H2S stream and LiOH or Li2COs in solution. However, it appears to be advantageous, environmentally and economically, to perform a gas-solid reaction between gaseous H2S stream and LiOH or Li2COs solid particles at least because it requires less effluent management.

[0009] The overall equilibrated reaction between LiOH and H2S can be represented by the following reaction scheme 1 :(scheme 1 )

[0010] Sulfide solid electrolytes (SSE) are typically synthetized by a solid phase reaction (mechanosynthesis) involving different raw materials such as l_i2S, P2S5 and optionally LiX, wherein X is an halogen or a pseudo-halogen. Mechanosynthesis conditions and raw materials can impact basic properties of SSE such as phase purity, ionic conductivity and particle size.

[0011] Among them, phase purity is a key property since it will determine the final ionic conductivity of the SSE as well as the cycling performance of batteries containing it.

[0012] Therefore, the control of the purity of raw materials involved in the synthesis of SSE, of l_i2S in particular, is important to get enhanced performing products in battery applications.

[0013] Particle size is another key property since it will ultimately determine the final thickness of the separator layer and the compactness of the catholyte electrode. When a proper particle size is not achieved during the synthesis of the SSE, post-milling or post-grinding is performed. However, this posttreatment step is generally responsible for ionic conductivity loss due to deterioration of the final SSE surface. It is thus important to obtain SSE of small particle size involving post-milling or post-grinding without imparing ionic conductivity properties.

[0014] 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.

[0015] JP2019102412 A2 discloses a process of reduction of the size of coarse particles of sulfide through an atomization process.

[0016] Therefore, there is a need for a process of manufacturing sulfide solid electrolytes powder having particle size distribution after synthesis and further milling that does not impair ionic conductivity properties.

[0017] There is also a need for a process of manufacturing sulfide solid electrolytes powder having high phase purity.

[0018] Finally, there is a need for a process of manufacturing sulfide solid electrolytes powder having high ionic conductivity.Summary

[0019] All these needs and more are fulfilled by a first aspect of the invention which relates to a process for preparing particles of a sulfide solid material (M) comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and having a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH, b) mixing at least Li2S of step a), P2S5 and LiX, where X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof, optionally in the presence of a solvent (S) to obtain a composition (C); c) optionally removing at least a portion of the solvent (S) from the composition (C) obtained on step b) so that to obtain a sulfide solid material precursor (P); d) optionally pressing the sulfide solid material precursor (P) of step c) into pellets; e) heating the composition (C) or the precursor (P) obtained in step c) e.g. in the form of pellets, to a temperature in the range of from 350°C to 580°C, under an inert atmosphere, for a time period ranging from 1 to 12 hours, thereby forming the sulfide solid material particles; and f) optionally treating the sulfide solid material particles obtained in step e) to obtain a desired particle size distribution.

[0020] Another object of the present invention is particles of sulfide solid material (M) comprising at least Li, P, S and X elements, obtained by the process according to the invention, characterized in that:- they have a D50-value ranging from 0.5 pm to 8 pm and a D90-value less than or equal to 25 pm as measured by laser diffraction after milling; and- they have a (PS4)3’ content of at least 99 %, a (P2S?)4’ content of less than 0.6 % and a (PCk)3’ content of less than 0.4 % as determined by solid31P NMR.

[0021] Still another object of the present invention relates to the use of the particles of sulfide solid material (M) according to the invention for the preparation of a composition (C’) comprising (i) the sulfide solid material (M) and (ii) at least one polymeric material (P).

[0022] The present invention also relates to the use of the particles of sulfide solid material (M) according to the invention for the preparation of an electrolyte layer of an electrode or of a separator.Disclosure of the invention

[0023] At the present time, the influence of the features of the raw materials engaged into the synthesis on final SSE properties is neither well understood nor well reported in literature.

[0024] The inventors have found that l_i2S powder comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and less than 0.005 wt %, expressed in equivalent LiOH, of the compound (I) to which is assigned the peak signal at -2.0 ± 0.2 ppm in solid state proton NMR allows to prepare sulfide solid material (M) having small particle size, higher level of phase purity and thus enhanced ionic conductivity properties when compared to sulfide solid material prepared from Li2S powder which does not possess this level of purity.

[0025] Indeed, the Li2S powder of the invention has a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt %, preferably less than 0.003 wt %, more preferably less than 0.002 wt % of equivalent LiOH.

[0026] However, the peak signal at -2.0 ± 0.2 ppm cannot be assigned to LiOH.

[0027] Without being bound to any theory it is assumed that the compound (I) is LiSH

[0028] The inventors have found that other properties of Li2S powder, which are specicific surface area and particle size, allows to prepare sulfide solid material (M) with enhanced properties.

[0029] Advantageously, the inventors have found that the process according to the invention allows preparing particles of sulfide solid material (M) having low particle size after milling or grinding.

[0030] Without being bound to any theory, this result may be attributed to a higher reactivity of the l_i2S due to higher purity.

[0031] Advantageously, the inventors have found that the process according to the invention allows preparing particles of sulfide solid material (M) having high phase purity .

[0032] Again this result may be attributed to a higher purity of the l_i2S raw material.

[0033] Therefore, the process according to the present invention is process for preparing particles of a sulfide solid material (M) comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and having a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH, b) mixing at least Li2S of step a), P2S5 and LiX, where X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof, optionally in the presence of a solvent (S) to obtain a composition (C); c) optionally removing at least a portion of the solvent (S) from the composition (C) obtained on step b) so that to obtain a sulfide solid material precursor (P); d) optionally pressing the sulfide solid material precursor (P) of step c) into pellets; e) heating the composition (C) or the precursor (P) obtained in step c) e.g. in the form of pellets, to a temperature in the range of from 350°C to 580°C, under an inert atmosphere, for a time period ranging from 1 to 12 hours, thereby forming the sulfide solid material particles; and f) optionally treating the sulfide solid material particles obtained in step e) to obtain a desired particle size.

[0034] The l_i2S powder used in the present invention is a highly pure raw material.

[0035] The l_i2S powder generally comprises less than 0.2 wt %, preferably less than 0.15 wt % of residual LiOH as measured by solid state proton NMR and has a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH, preferably less than 0.003 wt % of equivalent LiOH.

[0036] Moreover, the Li2S powder used in the present invention may exhibit a purity of more than 99 wt % as measured by XRD.

[0037] Finally, the Li2S powder used in the present invention may contain less than 0.08 wt % of carbon residues as measured by C / S elemental analysis,

[0038] The Li2S powder used in the present invention has generally a specific surface area equal or more than 2 m2 / g; preferably equal or more than 3 m2 / g. Good results were obtained with Li2S powder presenting a specific surface area of 3.5 m2 / g. The specific surface area is determined by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method.

[0039] The Li2S powder used in the present invention has a specific surface area generally not exceeding 20 m2 / g, for example not exceeding 15 m2 / g sometimes not exceeding 10 m2 / g.

[0040] The Li2S powder used in the present invention generally has a specific surface area ranging from 2 m2 / g to 20 m2 / g, sometimes ranging from 3 m2 / g to 15 m2 / g.

[0041] The Li2S powder used in the present invention has generally a D50-value ranging from 20 pm to 500 pm; sometimes ranging from 100 pm to 500 pm; often ranging from 200 pm to 500 pm; typically ranging from 250 pm to 450 pm.

[0042] For example, Li2S powder of step a) may have a particle size distribution presenting a D50-value ranging from 20 pm to 400 pm.

[0043] The Li2S powder used in the present invention has generally a D90-value of less than 1000 pm, sometimes of less than 700 pm.

[0044] The particle size distribution can be measured by laser diffraction from a dispersion of the powder in para-xylene.

[0045] 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.

[0046] According to the above, l_i2S powder used in the present invention is further characterized in that it exhibits at least one, preferably all, of the following features: it has a purity of more than 99 wt % as measured by XRD, it contains less than 0.08 wt % of carbon residues as measured by C / S elemental analysis, it has a specific surface area ranging from 2 to 20 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, it has a d50-value ranging from 20 pm to 500 pm, as measured by laser diffraction in para-xylene, it has a d90-value of less than 1000 pm, as measured by laser diffraction in para-xylene.

[0047] The l_i2S powder used in the present invention generally presents an amount of H2S release of less than 400 ml / g when exposed to a relative humidity of 35- 40% at 23°C during 60 minutes. This is particularly advantageous since it appears that l_i2S powder of the present invention is stable during storage or transportation.

[0048] The l_i2S powder used in the present invention can be obtained via gas-liquid reaction between gaseous H2S stream and LiOH or Li2COs in solution, or in gas phase. However, it appears to be advantageous to manufacture l_i2S powder by a method comprising the steps of: i) providing a powder of lithium hydroxide (LiOH powder A), or a powder of lithium carbonate (Li2COs powder A’) presenting a residual water content below 5 wt %;ii) reacting such LiOH powder A or U2CO3 powder A’ with H2S present in a reagent gas (RG1 ) to obtain l_i2S powder, optionally carbon dioxide and water vapor, wherein reagent gas (RG1 ) comprises H2S, a gas (G) selected from the list consisting of H2, CH4, C2H6, CsHs, and mixtures thereof and optionally an inert carrier gas (CG) different from (G); wherein reacting LiOH powder A or Li2COs powder A’ with H2S present in the reagent gas (RG1 ) is performed in at least one fixed bed reactor, at least one fluidized bed reactor, at least one stirred reactor or at least one mobile bed reactor.

[0049] The gas (G) can be selected from the list consisting of H2, CH4, C2H6, CsHs, and mixtures thereof. For example the gas (G) is H2.

[0050] The inert carrier gas (CG) can be nitrogen, argon or mixtures thereof. For example, the inert carrier gas (CG) is nitrogen.

[0051] Generally, the reagent gas (RG1 ) comprises H2S in an amount ranging from 30 % to 99.9 % in volume and the gas (G) in an amount ranging from 0.1 % to 20 % in volume with regard to the total of the volume of the reagent gas (RG1 ).

[0052] For example, the reagent gas (RG1 ) may consist of 60 % in volume of H2S, 10 % in volume of gas (G) and 30 % in volume of inert carrier gas (CG).

[0053] Still for example, the reagent gas (RG1 ) may consist of 60 % in volume of H2S, 5 % in volume of gas (G) and 35 % in volume of inert carrier gas (CG).

[0054] When LiOH powder A is used as raw material, step ii) can take place at a temperature ranging from 100 to 400°C., for example at 200°C.

[0055] When Li2COs powder A’ is used as raw material, step ii) can take place at a temperature ranging from 200 to 700°C.

[0056] The reaction of step ii) can take place at a pressure below 10 bars (1 MPa), for example at a pressure of 1 bar (0.1 Mpa).

[0057] The process according to the invention comprises step b) which consists in mixing at least Li2S powder of step a), P2S5 and LiX, optionally in the presence of a solvent (S) to obtain a composition (C).

[0058] In some embodiments step b) is performed under an inert atmosphere. Inert atmosphere as used in step b) refers to the use of an inert gas; ie. a gas that does not undergo detrimental chemical reactions under conditions of the reaction. Inert gases are used generally to avoid unwanted chemical reactions from taking place, such as oxidation and hydrolysis reactions with the oxygen and moisture in air. Hence inert gas means gas that does not chemically react with the other reagents present in a particular chemical reaction. Within the context of this disclosure the term “inert gas” means a gas that does not react with the sulfide solid material precursors. Examples of an “inert gas” include, but are not limited to, nitrogen, helium, argon, neon, xenon, with less than 1000 ppm of liquid and airborne forms of water, including condensation. The gas can also be pressurized.

[0059] Preferably in step b), the inert atmosphere comprises an inert gas such as H2S, dry N2, dry Argon or dry air (dry may refer to a gas with less than 800ppm of liquid and airborne forms of water, including condensation).

[0060] The composition ratio of each element can be controlled by adjusting the amount of the l_i2S, P2S5 and LiX when the sulfide solid material is produced. The raw materials including l_i2S, P2S5 and LiX and their molar ratio 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 precursors 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.

[0061] Preferably, phosphorus sulfide (P2S5) and halogen or pseudo halogen containg compounds (LiX) are in the form of powder which have an average particle diameter comprised between 0.5 pm and 400 pm. The particle size can be evaluated with SEM image analysis or laser diffraction analysis.

[0062] The solvent (S) of step b), when present, may suitably be selected from one or more of polar or non-polar solvents that may substantially dissolve at least one compound selected from: lithium sulfide, phosphorus sulfide, LiX and any othercompound that might be introduced in step b). Said solvent (S) may also substantially suspend, dissolve or otherwise admix the above described components, e.g., lithium sulfide, phosphorus sulfide, LiX and any other compound that might be introduced in step b).

[0063] Solvent (S) of the invention then constitutes in step b) a continuous phase with dispersion of one or more of the above described components.

[0064] Depending on the components and the solvent (S), some of the components are then rather dissolved, partially dissolved or under a form of a slurry.(ie. component(s) is / are not dissolved and forming then a slurry with the solvent).

[0065] In certain preferred aspects, the solvent (S) may suitably be a polar solvent. Solvents are preferably selected in the group consisting of alkanols, notably having 1 to 6 carbon atoms, such as methanol, ethanol, propanol and butanol; carbonates, such as dimethyl carbonate; acetates, such as ethyl acetate; ethers, such as dimethyl ether; organic nitriles, such as acetonitrile; aliphatic hydrocarbons, such as hexane, pentane, 2-ethylhexane, heptane, decane, and cyclohexane; and aromatic hydrocarbons, such as tetrahydrofuran, xylenes and toluene.

[0066] It is understood that references herein to solvent (S) include one or more mixed solvents.

[0067] An amount of about 1 wt% to 80 wt% of the powders and an amount of about 20 wt% to 99 wt% of the solvent (S), based on the total weight of the powders and the solvent (S), may be mixed. Preferably, an amount of about 25 wt% to 75 wt% of the powders and an amount of 25 wt% to 75 wt% of the solvent (S), based on the total weight of the powders and the solvent (S), may be mixed. Particularly, an amount of about 40 wt% to 60 wt% of the powders and an amount of about 40 wt% to 60 wt% of the solvent (S), based on the total weight of the powders and the solvent (S), may be mixed.

[0068] The temperature of step b) in presence of solvent (S) is preferably between the fusion temperature of the selected solvent and ebullition temperature of the selected solvent at a temperature where no unwanted reactivity is foundbetween solvent and admixed powders. Preferably step b) is done between - 20°C and 40°C and more preferably between 15°C and 40°C.

[0069] In absence of solvent step b) is done at a temperature between -20°C and 200°C and preferably between 15°C and 40°C.

[0070] Mixing to obtain the composition (C) in step b) may be performed by dry or wet milling; notably be performed by adding the powders to a solvent (S) and then wet milling at about 100 rpm to 1000 rpm, notably for a duration from 10 minutes to 80 hours more preferably for about 4 hours to 40 hours.

[0071] Said milling is also known as reactive-milling in the conventional synthesis of lithium argyrodites.

[0072] The mechanical milling method has an advantage that, simultaneously with the production of a glass mixture, pulverization occurs. In the mechanical milling method, various methods such as a rotation ball mill, a tumbling ball mill, a vibration ball mill and a planetary ball mill or the like can be used. Mechanical milling may be made with or without balls such as ZrO2.

[0073] Mixing to obtain the composition (C) in step b) may also be performed by stirring, notably by using well known techniques in the art, such as by using standard powder or slurry mixers.

[0074] Usually a paste or a blend of paste and liquid solvent (S) may be obtained at the end of step b).

[0075] In some embodiments during step b), a solution in the solvent (S) of l_i2S, P2S5, LiX and of any other compound that might be introduced in step b) is obtained as the composition (C).

[0076] In such conditions, lithium sulfide, phosphorous sulfide, LiX and any other compound that might be introduced in step b) are allowed to react optionally in a solvent for a predetermined period of time.

[0077] During step b) the pressure may be from 0.0001 Pa to 100 MPa, preferably from 0.001 Pa to 20 MPa, more preferably from 0.01 Pa to 0.5 MPa.

[0078] The process according to the invention comprises a step c) which consists in removing at least a portion of the solvent (S) from the composition (C) obtained on step b) so that to obtain a sulfide solid material precursor (P).

[0079] In step c), at least a portion of the solvent is removed notably means to remove at least about 30%, 40%, 50%, 60%, 70%, 80%, 90% 95% or 100%, of the total weight of a solvent used, or any ranges comprised between these values. Solvent removal may be carried out by known methods used in the art, such as decantation, filtration, centrifugation, drying or a combination thereof.

[0080] The temperature in step c) is selected to allow removal of solvent. Preferably when drying is selected as a method for solvent removal, temperature is selected below ebullition temperature and as a function of vapor partial pressure of the selected solvent.

[0081] Duration of step c) is between 1 second and 100 hours, preferably between 1 hour and 20 hours. Such a low duration may be obtained for instance by using a flash evaporation, such as by spray drying.

[0082] It is preferred that step c) be conducted under an atmosphere of an inert gas such as nitrogen or argon. The dew point of an inert gas is preferably -20°C or less, particularly preferably -40°C or less. The pressure may be from 0.0001 Pa to 100 MPa, preferably from 0.001 Pa to 20 MPa, preferably from 0.01 Pa to 20 MPa. Notably the pressure may range from 0.0001 Pa to 0.001 Pa, notably by using ultravacuum techniques. Notably the pressure may range from 0.01 Pa to 0.1 MPa by using primary vacuum techniques.

[0083] It is understood that in the case where the composition (C) obtained on step b) does not contain any solvent (S) then composition (C) and precursor (P) are the same.

[0084] In step d) the sulfide solid material precursor of step c) may be pressed into pellets. For example, the sulfide solid material precursor may be pressed in a mold to form the pellet. Molding can be performed with equipment well known by the person skilled in the art. For the sake of example, molding can be run using uniaxial press or single punch tableting machines.

[0085] In step e) the heating, or thermal treatment, of the precursor obtained in step c) e.g. in the form of pellets, may notably allow to convert the amorphizedpowder mixture (glass) obtained above into a sulfide solid material crystalline or mixture of glass and crystalline (glass ceramics).

[0086] Heat treatment is carried out at a temperature in the range of from 350°C to 580°C, for example from 370°C to 550°C or from 390°C to 530°C, notably for a duration of 1 hour to 12 hours, more particularly from 2 hours to 10 hours or from 3 hours to 7 hours. Heat treatment may start directly at high temperature or via a ramp of temperature at a rate comprised between 1 °C / min to 20°C / min. Heat treatment may finish with quenching or via natural cooling from the heating temperature or via a controlled ramp of temperature at a rate comprised between 1 °C / min to 20°C / min.

[0087] Preferably in step e), the inert atmosphere comprises an inter gas such as dry N2, or dry Argon (dry may refer to a gas with less than 800 ppm of liquid and airborne forms of water, including condensation). Preferably in step e) the inert atmosphere is a protective gas atmosphere used in order to minimize, preferably exclude access of oxygen and moisture.

[0088] The pressure at the time of heating may be at normal pressure or under reduced pressure. The atmosphere may be inert gas, such as nitrogen and argon. The dew point of the inert gas is preferably -20°C or less, with -40°C or less being particularly preferable. The pressure may be from 0.0001 Pa to 100 MPa, preferably from 0.001 Pa to 20 MPa, preferably from 0.01 Pa to 20 MPa. Notably the pressure may range from 0.0001 Pa to 0.001 Pa, notably by using ultravacuum techniques. Notably the pressure may range from 0.01 Pa to 0.1 MPa by using primary vacuum techniques.

[0089] In step f), it is possible to treat the sulfide solid material (M) to the desired particle size distribution. Indeed, the sulfide solid material (M) obtained by the process according to the invention as described above may comprise agglomerates that can be reduced into a powder of desired particle size distribution by deagglomeration. By deagglomeration is meant, a size reduction process in which weakly bonded clusters of particles (agglomerates) ofpowders or crystals are broken apart without further disintegration of the powder or crystal particles themselves.

[0090] Further size reduction can be obtained by milling or grinding using equipments well known by the person having ordinary skills in the art. For example, the sulfide solid material (M) can be submitted to a final dry milling step in a pin mill grinder.

[0091] In some preferred embodiments, step f) consists of the deagglomeration of the sulfide solid material (M) obtained in step e) to the desired particle size distribution.

[0092] Generally, said powder has a D50 value of the particle size distribution ranging from 0.5 pm to 8 pm, preferably from 1 pm to 7 pm, more preferably from 1 pm to 6 pm, as determined by means of laser diffraction .

[0093] Generally, said powder has a D90 value of the particle size distribution of less than or equal to 25 pm, preferably less than or equal to 21 pm, as determined by means of laser diffraction .

[0094] Generally, said powder has a D10 value of the particle size distribution of less than or equal to 2 pm, preferably less than or equal to 1.8 pm, as determined by means of laser diffraction .

[0095] In some embodiments, the sulfide solid material (M) obtained by the process according to the invention responds to the formula (I):Li7-yPS6-yXy (I) wherein y is a number such as 0.5 < y < 2; preferably such as 1.0 < y < 1.8; more preferably such as 1 .2 < y < 1 .6.

[0096] Thus, step b) is mixing l_i2S powder of step a) with P2S5 and LiX; wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof, optionally in the presence of a solvent (S) to obtain a composition (C).

[0097] Therefore, the composition ratio of each element can be controlled by adjusting the amount of the l_i2S, P2S5 and LiX in step b). The raw materials including Li2S, P2S5 and LiX and their molar ratio are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elementsLi, P, S and X, which is obtainable from the applied amounts of the precursors 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.

[0098] In some preferred embodiments, X is selected from the list consisting of F, Cl, I, Br and mixture thereof.

[0099] Preferably, phosphorus sulfide (P2S5), halogen or pseudo halogen compounds (LiX) are in the form of powders which have an average particle diameter comprised between 0.5 pm and 400 pm.

[0100] Sometimes, the sulfide solid material obtained by the process according to the invention which responds to the formula (I) can be doped by an alkaline earth metal element.

[0101] Therefore in some embodiments, the sulfide solid material obtained by the process according to the invention responds to the formula (II):Li7-2x-yMxPS6-yXy (II) wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof; wherein M is an alkaline earth metal element selected from Be, Sr, Ca, Mg and Ba; wherein x is a number such as 0.01 < x < 0.5; preferably such as 0.01 < x < 0.1 ; wherein y is a number such as 0.5 < y < 2; preferably such as 1.0 < y < 1.8; more preferably such as 1 .2 < y < 1 .6.

[0102] Thus step b) is mixing Li2S powder of step a) with P2S5, LiX and a compound selected from MX2, MS and mixture thereof, optionally in the presence of a solvent (S) to obtain a composition (C).

[0103] Therefore, the composition ratio of each element can be controlled by adjusting the amount of the Li2S, P2S5, LiX and MX2, MS or mixture thereof in step b). The raw materials including Li2S, P2S5, LiX and MX2, MS or mixture thereof and their molar ratio are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elements Li, P, S, X and M, whichis obtainable from the applied amounts of the precursors under the condition of complete conversion without side reactions and other losses.

[0104] Preferably, phosphorus sulfide (P2S5), halogen or pseudo halogen compounds (LiX), and alkaline earth metal compound (MX2 or MS) are in the form of powders which have an average particle diameter comprised between 0.5 pm and 400 pm.

[0105] Sometimes, the sulfide solid material obtained by the process according to the invention which responds to the formula (I) can be doped by an element selected from Na, K, Rb, Cs, Cu and Ag.

[0106] Therefore in some embodiments, the sulfide solid material (M) obtained by the process according to the invention responds to the formula (III):Li7-x-yM’x’PS6-yXy (III) wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof; wherein M’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < x’ < 0.5; preferably such as 0.01 < x’ < 0.1 ; wherein y is a number such as 0.5 < y < 2; preferably such as 1.0 < y < 1.8; more preferably such as 1 .2 < y < 1 .6.

[0107] Thus, step b) is mixing l_i2S powder of step a) with P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof, optionally in the presence of a solvent (S) to obtain a composition (C).

[0108] Therefore, the composition ratio of each element can be controlled by adjusting the amount of the Li2S, P2S5, LiX and M’CI, M’2S or mixture thereof in step b). The raw materials including Li2S, P2S5, LiX and M’CI, M’2S or mixture thereof and their molar ratio are selected according to the target stoichiometry. The target stoichiometry defines the ratio between the elements Li, P, S, X and M’, which is obtainable from the applied amounts of the precursors under the condition of complete conversion without side reactions and other losses.

[0109] Preferably, lithium sulfide, phosphorus sulfide (P2S5), halogen or pseudo halogen compounds (LiX), and Na, K, Rb, Cs, Cu and Ag compound (M’X orM’2S) are in the form of powders which have an average particle diameter comprised between 0.5 pm and 400 pm.

[0110] Another object of the present invention is related to particles of sulfide solid material (M) comprising at least Li, P, S and X elements, obtainable by the process according to the invention, having a D50-value ranging from 0.5 pm to 8 pm and a D90-value less than or equal to 20 pm (as measured by laser diffraction ) after milling; and having a (PS4)3’ content of at least 99 %, a (P2S?)4’ content of less than 0.6 % and a (PCk)3-content of less than 0.4 % as determined by solid31P NMR.

[0111] Generally, the particles of sulfide solid material (M) have a ionic conductivity measured at 23°C on pellets pressed at 500 MPa by impedance spectroscopy of at least 2.4 mS / cm and an activation energy equal or less than 0.4eV between -20°C and 60°C.

[0112] The measurement of the ionic conductivity is performed on a pressed pellet. Typically, a pressed pellet is manufactured using a uniaxial or isostatic pressure. When uniaxial pressure is applied to form the pellet, a pressure above 100 MPa, preferentially above 300 MPa, is applied for a duration of at least 30 seconds. The measurement is done under uniaxial pressure typically between 2 MPa and 200 MPa.

[0113] Accordingly, the present invention is also related to particles of sulfide solid material (M) responding to the formula (I), (II) or (III) exhibiting the features as above described.

[0114] Another object of the present invention is related to the use of the particles of sulfide solid material (M) according to the invention for the preparation of a composition (O’) comprising (i) the sulfide solid material (M) of formula (I), (II) or (III) and (ii) at least one polymeric material (P).

[0115] The composition (O’) of the invention may be used for the preparation of an electrode. The composition (O’) of the invention may also be used for the preparation of an electrolyte layer of an electrode. The electrode may be a positive electrode or a negative electrode. The composition (O’) of the invention may also be used for the preparation of a separator.

[0116] The composition (C’) more particularly comprises:(i) a sulfide solid material (M) according to formula (I), (II) or (II);(ii) at least one polymeric material (P);(iii) optionally at least one electro-active compound (EAC);(iv) optionally at least one lithium ion-conducting material (LiCM) other than the sulfide solid material of the invention;(v) optionally at least one electro-conductive material (ECM); and(vi) optionally a lithium salt (LIS).

[0117] Another object of the present invention is related to the use of the particles of sulfide solid material (M) according to the invention for the preparation of an electrode or for the preparation of an electrolyte layer of an electrode.

[0118] Still another object of the present invention is related to the use of the particles of sulfide solid material (M) according to the invention for the preparation of a separator.Figures

[0119] Figure 1 : solid state1H NMR spectrum of Li2S used in the process according to the invention

[0120] 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.

[0121] 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.Examples

[0122] Materials

[0123] LiOH-H2O was obtained from Altichem (dso = 300-350 pm).H2S was obtained from Air Liquide (purity > 99.5 vol.%).Li2S was provided by Lorad Chemical Corporation.

[0124] LiCI and P2S5 were respectively provided from Altichem and Italmatch, purity>99%.

[0125] Preparation of Li2S according to the present invention

[0126] Approximately 126 grams of LiOH, 1 H2O obtained from Altichem were weighted and introduced into a quartz fixed bed reactor equipped with a heating system. The powder was exposed to a N2 flow and the temperature was raised up to 200 °C to remove water. H2O was recovered as a condensate downstream. Once there was no more H2O collected, the temperature was raised up to 400 °C. After the temperature was stabilized, the reagent gas composition comprising H2S, N2 and in some experiments H2 was introduced in the reactor via an inlet pipe and the gas hour space velocity (GHSV) was kept at 300 IT1. The gas flows were controlled by mass flow controllers. The sulfidation reaction started as soon as H2S gets in contact with the LiOH powder. The sulfidation reaction was followed by weighting condensed water collected after unreacted gas and formed water vapor were extracted via an outlet pipe. Furthermore, the endothermic reaction was followed by measuring the temperature in the bed powder. The sulfidation reaction was stopped when no more H2O or no more endotherm icity was detected. Finally, the reactor was cooled down under N2 flow and the Li2S powder recovered. Characteristics of the different samples are reported in table 2.

[0127] The reagent gas composition was 60 vol % of H2S, 2 vol % of H2 and 38 vol % of N2for Li2S 0, 60 vol % of H2S, 5 vol % of H2 and 35 vol % of N2 for Li2S 1 , and 60 vol % of H2S, 10 vol % of H2 and 30 vol % of N2 for Li2S 2.

[0128] The reagent gas composition was 100 vol % of H2S for Li2S 3 (comparative).

[0129] Preparation of sulfide solid electrolyte of formula LiePSsCI (argyrodite)

[0130] step a) : 21 g of LiCI; 56 g of P2S5 and 58 g of Li2S 1 were successively weighed and added in a glass container. The powders were homogenized by gentle manual mixing. They were then added to a zirconia bowl (Across) containing 529 g of ZrO2 balls (10 mm, Across). 136 g of xylene isomeric (Carlo Erba, purity>99% , dry) was then added and used to rinse the powder from the glass container directly inside the zirconia bowl. The bowl was rapidly sealed to prevent any xylene isomeric evaporation. Wet-ball milling was conducted witha Retsch™ PM400 planetary ball-mill. After 14 h of effective milling at 350 rpm, a pale yellow / beige paste was obtained.

[0131] Prior to drying, the milling balls were separated from the light beige paste through sieving at 4 mm. The paste was then transferred in a glass balloon. Isomeric xylene can be added in these steps in order to fluidize the slurry. The drying takes place in a rotative evaporator under dynamic vacuum at 60°C to remove the xylene. The xylene was condensed by ice water and the drying was continued until no xylene was recovered. The total time of drying was approximately 3 hours.

[0132] step b) : the dried mixture was charged under dry air (dew point < - 40°C) in an alumina crucible that was covered with a lid. The reactor is then inserted in a tubular oven and the product is crystallized at 490°C during 6 hours (heating ramp 5°C / min) under N2flow (30 L / h). It is allowed to cool down to room temperature (20-30 °C) under the same N2flow. The final product is submitted to a final dry milling step in a pin mill grinder (21000 rpm and speed injection of 10 rpm) to give the sulfide solid electrolyte of formula l_i6PS5CI with properties reported in table 3. Similar procedure was used to prepare argyrodites 0-4 from Li2S 0, Li2S 2, Li2S 3 and Li2S 4.

[0133] Evaluation of LiOH content in Li2S by solid state1H NMR

[0134] 1H NMR spectrum was recorded on Li2S samples to determine H containing impurities. The Avance spectrometer 400 from Broker was used with a high speed probe with a magic-angle spinning of 10 kHz and in one pulse sequence (D1 = 600 s). The calibration standard is H2O (5=4.8ppm).

[0135] Different peaks were attributed to different species as reported in Table 1 .Table 1 : Chemical species identified by solid state1H NMR* It is assumed that compound (I) is LiSH.

[0136] The quantification of LiOH was made by the integration of the whole1H signal i.e. from -34 ppm to 34 ppm after substraction of the probe signal, thereby giving an LiOH equivalent content. In this regard, other H impurities might be present and the value of LiOH can be overestimated. A calibration plot was prepared by analyzing different mixtures of LiOH (Sigma Aldrich) and LiCI (Sigma Aldrich). LiCI was chosen as an inert sample in order to avoid the presence of residual LiOH in the sample. For this purpose, 0.5, 1 , 2, 5 and 10 wt. % LiOH in LiCI mixtures were prepared in a glovebox (moisture level < 5 ppm, O2 level < 5 ppm). Then, for each mixture the whole1H signal was integrated after substraction of the probe signal and the calibration plot was obtained as a straight line passing through the origin. All the signals are normalized by the sample mass introduced in the NMR rotor. This way, the technique can be considered as semi-quantitative. Results regarding residual LiOH contents are reported in table 2.

[0137] Evaluation of compound (I) content by solid state1H NMR

[0138] The quantification of the compound (I) was made by the integration of the1H peak signal assigned to the compound (I) at -2.0 ppm. For this purpose the integration was made from the chemical shift of the peak + 0.5 ppm to the chemical shift of the peak - 0.5 ppm, i.e. from -1.5 ppm to -2.5 ppm as represented on figure I. No deconvolution was applied. Compound (I) content was calculated as LiOH equivalent using the calibration plot described above. Results are reported in table 2.

[0139] Table 2: Characteristics of Li2S powders prepared using different reagent gas compositions and of commercially available Li2SIt is clear from the results presented in table 2 that the residual LiOH present in the l_i2S used in the process according to the invention (l_i2S 1 or 2), i.e. manufactured using a reagent gas composition comprising H2S and H2, is reduced when compared with l_i2S manufactured by a process using a reagent gas composition comprising H2S but no H2 (l_i2S 3 or 4). The same trend is observed for the compound (I) content expressed in wt % of equivalent LiOH.

[0140] XRD Analysis

[0141] 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 sample holder 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.

[0142] Solid-state31P NMR

[0143] Solid-State NMR spectra were recorded on a Broker Avance 400 spectrometer equipped with a high-speed probe.31P measurements were performed by magic-angle-spinning (MAS) at a speed of 14 kHz, in single-pulse mode with arelaxation time D1 = 500s. Reference for31P NMR was 85% H3PO4 (6=0ppm). The integration of the31P spectra was performed with NMRnotebook software.

[0144] Composition of the different argyrodites (LiePSsCI) as measured by31P NMR is provided in table 3. In31P NMR technique, (PS4)3’ entities are responsible for a broad signal with a maximum at around 84.7 ppm chemical shift and spread from 78 ppm to 90 ppm. (P2S?)4’ entities are responsible for a signal spread from 90 ppm to 95 ppm. (PCM)3-entities are responsible for signal spread from 9 ppm to 10 ppm. Integration of the different signals gave the atomic percentage of the different entities.

[0145] Particle Size Distribution measurement

[0146] The Particle Size Distribution (PSD) of the l_i2S powders was evaluated using laser diffraction measurement. For this purpose, the powder was stirred in para-xylene. The solution was introduced in a Malvern Mastersizer 3000. Data was treated with the optical model of Fraunhofer.

[0147] The same instrument was used to measure particle size distribution for sulfide solid electrolyte (SSE) powders of formula LiePSsCI. A different methodology for powder dispersion was used. At first, the powder was deagglomerated in an Ultra-Turrax® Tube Drive P (IKA) using Tubes ST-20 (IKA). The tubes were filled with 45 mg of SSE powder. Then, 15 grams p-xylene, which was previously dried with a molecular sieve, were added to the tube. The tubes were then inserted into the Ultra-Turrax® tool and SSE powder was deagglomerated at 6000 rpm for 30 min. When the deagglomeration step was finished, a small aliquot was sampled under gentle stirring and introduced into the malvern analytical module. Data was treated with the optical model of Fraunhofer.

[0148] Specific surface area of the particles by BET method

[0149] 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 160 °C for 2 hours prior to analysis. The specificsurface area was calculated by considering the P / P° range between 0.05 and 0.2. At least 6 points were selected within this range of P / P° in order to obtain a good correlation coefficient.

[0150] Determination of H2S emission

[0151] The preparation of the sample is carried out in a dry Ar glove-box (moisture level < 5 ppm, O2 level < 5 ppm). The sample, 100 mg of powder, is placed in an open circular holder with a circular surface of 7.02 cm2. Then, the holder is placed on a zirconia pot where it can be isolated from the atmosphere. The zirconia pot is transferred from the dry-argon glove box to a room air operated one that is used for the H2S quantification test. The dew point is set at 6.2 °C which corresponds to a relative humidity between 35 - 40 % at room temperature (23°C). Humidity is measured by a Dew Point probe from Mitchell Instruments (EA2-TX-100). Humidity within the glove-box can be controlled by the inlet of pre-dried compressed air. The atmosphere within the glove-box is homogenized by means of two fans. Once the atmosphere is stable, the zirconia pot is opened, exposing the sample to the controlled humid atmosphere. H2S quantification is carried out by a Sensorcon sensor (Industrial Pro - H2S Pro). The experiment is carried out for 60 minutes at the end of which the zirconia pot is again closed.

[0152] Conductivity & Electrochemical Impedance Spectroscopy (EIS)

[0153] Preparation of the samples and measurements were conducted in a dry room. Before the impedance spectroscopy measurements, powder samples were cold-pressed at 500 MPa. The conductivity was acquired on pellets done using a uniaxial press operated at 500 MPa. Pelletizing was done using a lab scale uniaxial press. Two carbon paper foils (Papyex soft graphite N998 Ref: 496300120050000, 0.2mm thick from Mersen) are used as the current collector. Pellets with their carbon electrodes attached are then loaded into airtight sample holders and a pressure of 80 MPa is applied on the sample holder for the 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 different temperatures. Each spectrum isacquired after 2 hours of stabilization at the target temperature. The temperature range goes from -20°C to 60°C by steps of 10°C. Impedance spectroscopy is acquired in PEIS mode with an amplitude of 20m V and a range of frequencies from 1 MHz to 1 kHz (25 points per decade and a mean of 50 measurements per frequency point).

[0154] Table 3: Argyrodite properties: partice size and conductivity

[0155] As can be seen from table 3, the argyrodite powders obtained from l_i2S of the invention have small particle size. This small particle size is not detrimental to the ionic conductivity of these argyrodites which is higher than or equal to 2.4 mS / cm at 23°C. This is advantageous, since SSE particles properties and particularly SSE particles size will determine the difficulty to manufacture thin separators and compact catholyte electrodes.

[0156] Table 4: Argyrodite properties: PS4, P2S7 and PCM contentAs can be seen from table 4, the argyrodite powders obtained from l_i2S of the invention have higher (PS4)3’ expressed in atomic percentage and measured by solid31P NMR spectroscopy than argyrodite powders obtained from other Li2S. This higher purity is accompanied with higher conductivity and equal or lower energy of activation. This higher purity may also enhance the cyclability of batteries comprising these argyrodite powders.

Claims

ClaimsClaim 1 . A process for preparing particles of a sulfide solid material (M) comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) comprising less than 0.2 wt % of residual LiOH as measured by solid state proton NMR and having a solid state proton NMR spectrum showing a peak signal at -2.0 ± 0.2 ppm that corresponds to less than 0.005 wt % of equivalent LiOH, b) mixing at least Li2S of step a), P2S5 and LiX, where X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof, optionally in the presence of a solvent (S) to obtain a composition (C); c) optionally removing at least a portion of the solvent (S) from the composition (C) obtained on step b) so that to obtain a sulfide solid material precursor (P); d) optionally pressing the sulfide solid material precursor (P) of step c) into pellets; e) heating the composition (C) or the precursor (P) obtained in step c) e.g. in the form of pellets, to a temperature in the range of from 350°C to 580°C, under an inert atmosphere, for a time period ranging from 1 to 12 hours, thereby forming the sulfide solid material (M) particles; and f) optionally treating the sulfide solid material particles obtained in step e) to obtain a desired particle size distribution.Claim 2. The process of claim 1 , wherein Li2S powder is further characterized in that it exhibits at least one, preferably all, of the following features:- it has a purity of more than 99 wt % as measured by XRD,- it contains less than 0.08 wt % of carbon residues as measured by C / S elemental analysis,- it has a specific surface area ranging from 2 to 20 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method,- it has a d50-value ranging from 20 pm to 500 pm, as measured by laser diffraction in para-xylene,- it has a d90-value of less than 1000 pm, as measured by laser diffraction in para-xylene.Claim 3. The process of claim 1 or 2, wherein the sulfide solid material (M) responds to the formula (I):Li7-yPS6-yXy (I) wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .2 < y < 1 .6.Claim 4. The process of claim 1 or 2, wherein the sulfide solid material (M) responds to the formula (II):Li?-2x-yMxPS6-yXy (II) wherein M is an alkaline earth metal element selected from Be, Sr, Ca, Mg and Ba; wherein x is a number such as 0.01 < x < 0.5; preferably such as 0.01 < x < 0.1 ; wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .2 < y < 1 .6; wherein in step b) the composition (C) is obtained by mixing, optionally in the presence of a solvent (S), l_i2S powder of step a) P2S5, LiX and a compound selected from MX2, MS and mixture thereof; and wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof.Claim 5. The process of claim 1 or 2, wherein the sulfide solid material (M) responds to the formula (III)Li7-x-yM’x’PS6-yXy (III) wherein M’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < x’ < 0.5; preferably such as 0.01 < x’ < 0.1 ; wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .2 < y < 1 .6;wherein in step b) the composition (C) is obtained by mixing, optionally in the presence of a solvent (S), l_i2S powder of step a) with P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof; and wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and combinations thereof.Claim 6. The process of any one of claims 1 to 5, wherein in step b) mixing is performed by dry or wet milling.Claim 7. The process of any one of claims 1 to 5, wherein in step b) composition (C) is a solution of at least l_i2S of step a) and P2S5 in the solvent (S).Claim 8. The process of any one of the preceding claims, wherein the particles of sulfide solid material (M) obtained have:- a D50-value ranging from 0.5 pm to 8 pm and a D90-value less than or equal to 25 pm as measured by laser diffraction after milling; and- a (PS4)3' content of at least 99 %, a (P2S?)4’ content of less than 0.6 % and a (PCM)3’ content of less than 0.4 % as determined by solid31P NMR.Claim 9. Particles of sulfide solid material (M) comprising at least Li, P, S and X elements obtainable by the process according to anyone of claims 1 to 8 characterized in that :- they have a D50-value ranging from 0.5 pm to 8 pm and a D90-value less than or equal to 25 pm as measured by laser diffraction after milling; and- they have a (PS4)3’ content of at least 99 %, a (P2S?)4’ content of less than 0.6 % and a (PCM)3’ content of less than 0.4 % as determined by solid31P NMR.Claim 10. The particles according to claim 9, characterized in that they have an ionic conductivity measured at 23°C on pellets pressed at 500 MPa by impedancespectroscopy of at least 2.4 mS / cm and an activation energy equal or less than 0.4eV between -20°C and 60°C.Claim 11 . The particles according to claim 9 or 10 wherein the sulfide solid material (M) responds to the formula (I), (II) or (III).Claim 12. Use of the particles of sulfide solid material (M) according to claims 9 to 11 for the preparation of a composition (C’) comprising (i) the sulfide solid material (M) of formula (I), (II) or (III) and (ii) at least one polymeric material (P).Claim 13. Use of the particles of sulfide solid material (M) according to claims 9 to 11 for the preparation of an electrode or for the preparation of an electrolyte layer of an electrode.Claim 14. Use of the particles of sulfide solid material (M) according to claims 9 to 11 for the preparation of a separator.

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