Process for preparing particles of sulfide solid material

Abstract

The present disclosure relates to a process for preparing particles of sulfide solid material comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) having a D50-value ranging from 20 µm to 500 µm as measured by laser diffraction in para-xylene, a specific surface area equal or more than 5 m² / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, b) reacting Li2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles; wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof. 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 MATERIALCross-reference to related patent applications

[0001] This application claims priority filed on 10 March 2023 in Europe with Nr. 23305326.3, 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 sulfide solid material comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) having a D50-value ranging from 20 pm to 500 pm as measured by laser diffraction in para-xylene, a specific surface area equal or more than 5 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, b) reacting Li2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles, wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.

[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 battery 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 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 ot the particle size and the porosity of such starting material onto the properties of the resulting SSE. 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 sulur source.

[0007] 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, environementally 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.

[0008] The overall equilibrated reaction between LiOH and H2S can be represented by the following reaction scheme 1 :2 LiOH + H2SLi2S + 2 H2O , . „ ,2 2 2(scheme 1 )

[0009] 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 an halogen or a pseudo-halogen. Mechanosynthesis conditions can impact basic properties of SSE such as phase purity, particle size and ionic conductivity.

[0010] 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. When a proper particle size is not achieved during the synthesis of the SSE, post-milling is performed. However, this posttreatment step isgenerally responsible for ionic conductivity loss due to deterioration of the final SSE surface. Moreover, it represents an additional cost to the overall process for manufacturing separators or electrodes.

[0011] 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.

[0012] JP2019102412 A2 discloses a process of reduction of the size of particles of coarse particles of sulfide through an atomization process.

[0013] Therefore, there is a need for a process of manufacturing sulfide solid electrolytes powder having particles size distribution after synthesis that would not require post-milling.

[0014] There is also a need for a process of manufacturing sulfide solid electrolytes powder having high phase purity.

[0015] Finally, there is a need for a process of manufacturing sulfide solid electrolytes powder having high ionic conductivity.Summary

[0016] All these needs and more are fulfilled by a first aspect of the invention which relates to a process for preparing particles of sufide solid material comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) having a D50-value ranging from 20 pm to 500 pm as measured by laser diffraction in para-xylene, a specific surface area equal or more than 5 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, b) reacting Li2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles, wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.

[0017] Another object of the present invention is particles of sulfide solid material 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 0.5pm to 8 pm and a D90-value less than or equal to 20 pm as measured by analytical centrifuge analysis after deagglomeration.

[0018] Another object of the present invention relates to the use of the sulfide solid material particles according to the invention for the preparation of a composition (C) comprising (i) the sulfide solid material and (ii) at least one polymeric material (P).

[0019] The present invention also relates to the use of the sulfide solid material particles according to the invention for the preparation of an electrolyte layer of an electrode or of a separator.Disclosure of the invention

[0020] 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.

[0021] The inventors have found that key properties for l_i2S powder, produced by a solid-gas reaction, which are specicific surface area and particle size, when acquired allow to prepare sulfide solid material having lower particle size while keeping the same level of phase purity and excellent ionic conductivity properties when compared to sulfide solid material prepared from l_i2S powder which does not possess said property.

[0022] Advantageously, the inventors have found that the process according to the invention allows preparing particles of sulfide solid material having low particle size, which can be achieved merely by deagglomeration of the powder obtained and not by further milling or grinding.

[0023] By deagglomeration is meant, a size reduction process in which weakly bonded cluster of particles (agglomerates) of powders or crystals are broken apart without further disintegration of the powder or crystal particles themselves.

[0024] Without being bound to any theory, this result may be attributed to a higher reactivity of the l_i2S due to higher specific surface area.

[0025] Surprisingly, powder of lithium sulfide (l_i2S) having relatively large particle size, for example a D50-value ranging from 20 pm to 500 pm, has been found to be favorable to the preparation of sulfide solid material having low particle size.

[0026] Therefore, the process according to the present invention is a process for preparing particles of sufide solid material comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) having a D50-value ranging from 20 pm to 500 pm, as measured by laser diffraction in para-xylene, a specific surface area equal or more than 5 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, b) reacting Li2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles, wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.

[0027] The Li2S powder used in the present invention has generally a specific surface area equal or more than 5 m2 / g; preferably equal or more than 7 m2 / g. Good results were obtained with L i2S powder presenting a specific surface area of 8 m2 / g. The specific surface area is determined by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method.

[0028] The Li2S powder used in the present invention has a specific surface area generally not exceeding 50 m2 / g, for example not exceeding 20 m2 / g sometimes not exceeding 15 m2 / g.

[0029] The Li2S powder used in the present invention has generally a specific surface area ranging from 5 m2 / g to 20 m2 / g, sometimes ranging from 7 m2 / g to 15 m2 / g.

[0030] The Li2S powder used in the present invention has generally a D50-value ranging from 20 pm to 500 pm; sometimes ranging from 50 pm to 500 pm; often ranging from 100 pm to 500 pm; typically ranging from 250 pm to 450 pm.

[0031] For example, U2S powder of step a) may have a particle size distribution presenting a D50-value ranging from 20 pm to 400 pm or from 50 pm to 400 pm.

[0032] The Li2S powder used in the present invention has generally a D90-value of less than 1000 pm, sometimes of less than 700 pm.

[0033] The particle size distribution can be measured by laser diffraction from a dispersion of the powder in para-xylene.

[0034] 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.

[0035] High reactivity of l_i2S powder can be evaluated in view of its reactivity versus moisture. Therefore, the l_i2S powder used in the present invention generally presents an amount of H2S release of more than 200 ml / g when exposed to a relative humidity of 30-40% at 23°C during 60 minutes; preferably of more than 350 ml / g; more preferably of more than 500 ml / g. Besides, the H2S release generally does not exceed 700 ml / g.

[0036] In some embodiments, the l_i2S powder used in the present invention has a D50-value ranging from 20 pm to 500pm, a specific surface area equal or more than 5 m2 / g and presents an amount of H2S release of more than 200 ml / g when exposed to a relative humidity of 30-40% at 23°C during 60 minutes.

[0037] In some other embodiments, the l_i2S powder used in the present invention has a D50-value ranging from 20 pm to 400pm, a specific surface area equal or more than 5 m2 / g, and presents an amount of H2S release of more than 200 ml / g when exposed to a relative humidity of 30-40% at 23°C during 60 minutes.

[0038] The l_i2S powder used in the present invention can be obtained by any synthetic pathway. For example, via gas-liquid reaction between gaseous H2S stream and LiOH or Li2COs in solution. However, it appears to be advantageous to perform a gas-solid reaction between gaseous H2S stream and LiOH or Li2COs solid particles at least because it requires less effluent management. Generally, gas-solid reaction between gaseous H2S and LiOH is preferred.

[0039] The process according to the invention comprises a step b) which consists in reacting U2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles.

[0040] Preferably, phosphorous sulfide (P2S5) is in the form of powder which has 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.

[0041] Generally, 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.

[0042] In some preferred embodiments, X is is selected from the list consisting of F, Cl, I, Br and mixture thereof.

[0043] Generally step b) of the process according to the present invention comprises the following steps of: i) obtaining a composition by admixing at least l_i2S of step a) P2S5 and LiX, optionally in one or more solvents; ii) applying a mechanical treatment to the composition obtained in step i); iii) optionally removing at least a portion of the one or more solvents from the composition obtained on step ii), so that to obtain a sulfide solid material precursor; iv) optionally pressing the sulfide solid material precursor of step iii) into pellets; v) heating the obtained precursor obtained in step iii) 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 vi) optionally treating the sulfide solid material obtained in step v) to the desired particle size distribution.

[0044] In some embodiments step i) is performed under an inert atmosphere. Inert atmosphere as used in step i) 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 thecontext 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.

[0045] It is preferred that stirring be conducted in step i) when the raw materials are brought into contact with each other under an atmosphere of an inert gas such as nitrogen or argon. 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 0.5 MPa.

[0046] Preferably in step i), 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).

[0047] 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 LisPS4 can be obtained from 3 moles of Li2S and 1 mole of P2S5. Similarly, 2 moles of LiyPsSn can be obtained from 7 moles of Li2S and 3 moles of P2S5. Still similarly, 2 moles of LiePSsCI can be obtained from 5 moles of Li2S, 1 mole of P2S5 and 2 moles of LiCI.

[0048] The solvent of step i), 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 and any other compound that might be introduced in step i). Said solvent may also substantially suspend, dissolve or otherwise admix the above described components, e.g., lithium sulfide, phosphorus sulfide and any other compound that might be introduced in step i).

[0049] Solvent of the invention then constitutes in step i) a continuous phase with dispersion of one or more of the above described components.

[0050] Depending on the components and the solvent, 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).

[0051] In certain preferred aspects, the solvent may suitably be a polar solvent. Solvents are preferably polar solvents 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.

[0052] It is understood that references herein to “a solvent” include one or more mixed solvents.

[0053] An amount of about 1 wt% to 80 wt% of the powders mixture and an amount of about 20 wt% to 99 wt% of the solvent, based on the total weight of the powders mixture and the solvent, may be mixed. Preferably, an amount of about 25 wt% to 75 wt% of the powders mixture and an amount of 25 wt% to 75 wt% of the solvent, based on the total weight of the powders mixture and the solvent, may be mixed. Particularly, an amount of about 40 wt% to 60 wt% of the powders mixture and an amount of about 40 wt% to 60 wt% of the solvent, based on the total weight of the powders mixture and the solvent, may be mixed.

[0054] The temperature of step i) in presence of solvent 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 found between solvent and admixed compounds. Preferably step i) is done between -20°C and 40°C and more preferably between 15°C and 40°C. In absence of solvent step i) is done at a temperature between -20°C and 200°C and preferably between 15°C and 40°C.

[0055] Duration of step i) is preferably between 1 minute and 1 hour.

[0056] Mechanical treatment to the composition in step ii) may be performed by wet or dry milling; notably be performed by adding the powders mixture to a solvent and then 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.

[0057] Said milling is also known as reactive-milling in the conventional synthesis of lithium argyrodites.

[0058] The mechanical milling method also 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.

[0059] In such a condition, lithium sulfide, phosphorous sulfide, LiX and any other compound that might be introduced in step i) are allowed to react optionally in a solvent for a predetermined period of time.

[0060] The temperature of step ii) in presence of solvent is between the fusion temperature of the selected solvent and ebullition temperature of the selected solvent at a temperature where no unwanted reactivity is found between solvent and compounds. Preferably step ii) is done at a temperature between -20°C and 80°C and more preferably between 15°C and 40°C. In absence of solvent step a) is done between -20°C and 200°C and preferably between 15°C and 40°C.

[0061] Mechanical treatment to the composition in step ii) may also be performed by stirring, notably by using well known techniques in the art, such as by using standard powder or slurry mixers.

[0062] Usually a paste or a blend of paste and liquid solvent may be obtained at the end of step ii).

[0063] In step iii), 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.

[0064] The temperature in step iii) is selected to allow removal of solvent. Preferably when drying is selected as method for solvent removal, temperature is selected below ebullition temperature and as a function of vapor partial pressure of the selected solvent.

[0065] Duration of step iii) 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.

[0066] It is preferred that step iii) 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.

[0067] The sulfide solid material precursor of step iii) generally comprises at least 85 mol % of P species under the form of glassy (PS4)3’ entities; preferably at least 88 mol %; as dertermined by31P NMR.

[0068] In step iv) the sulfide solid material precursor of step iii) 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

[0069] In step v) the heating, or thermal treatment, of the precursor obtained in step iii) e.g. in the form of pellets, may notably allow to convert the amorphized powder mixture (glass) obtained above into a sulfide solid material crystalline or mixture of glass and crystalline (glass ceramics).

[0070] 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 orfrom 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.

[0071] Preferably in step v), 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.

[0072] 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.

[0073] In step vi), it is possible to treat the sulfide solid material to the desired particle size distribution. Indeed, the sulfide solid material 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.

[0074] By deagglomeration is meant, a size reduction process in which weakly bonded cluster of particles (agglomerates) of powders or crystals are broken apart without further disintegration of the powder or crystal particles themselves.

[0075] In some preferred embodiments, step vi) consists of the deagglomeration of the sulfide solid material obtained in step v) to the desired particle size distribution.

[0076] 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 6 pm, more preferably from 1 pm to 5 pm, as determined by means of analytical centrifuge analysis.

[0077] Generally, said powder has a D90 value of the particle size distribution of less than or equal to 20 pm, preferably less than or equal to 15 pm, more preferably less than or equal to 10 pm, as determined by means of analytical centrifuge analysis.

[0078] 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 1.5 pm, as determined by means of analytical centrifuge analysis.

[0079] In some embodiments, step b) comprises the following steps of: i') obtaining a solution by admixing at least l_i2S of step a) P2S5 and LiX, in one or more solvents under inert atmosphere; ii') removing at least a portion of the one or more solvents from the composition obtained on step i’), so that to obtain a sulfide solid material precursor; iii') optionally pressing the sulfide solid material precursor of step ii’) into pellets; iv') heating the obtained precursor obtained in step ii’) 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 v')optionally treating the sulfide solid material particles obtained in step iv’) to the desired particle size distribution.

[0080] Various features of step i’) are basically similar to those of step i), such as for instance with respect to l_i2S, P2S5, LiX, any other compound that might be introduced in step i) and solvent. Preferably temperature in step i’) ranges from -200°C to 100°C, preferably from -200°C to 10°C.

[0081] In some embodiments during step i’), a solution of Li2S, P2S5 and LiX is obtained before any other compound is introduced and further solubilized.

[0082] Features in the removal of solvent as mentioned in step ii’) may be similar to those ones as expressed in step iii). Preferably in step ii’), temperature is in the range of from 30°C to 200°C, under an inert atmosphere, and preferably under a pressure 0.0001 Pa to 100 MPa.

[0083] The sulfide solid material precursor of step ii’) generally comprises at least 85 mol % of P species under the form of glassy (PS4)3’ entities; preferably at least 88 mol %; as dertermined by31P NMR.

[0084] In step iii’) the sulfide solid material precursor of step ii’) may be pressed into pellets as expressed in step iv).

[0085] Heating of step iv’) may be carried out with features as expressed in step v). Preferably at a temperature in the range of from 350°C to 580°C, under an inert atmosphere and preferably under a pressure 0.0001 Pa to 100 MPa.

[0086] Features of treating the sulfide solid material as mentioned in step v’) may be similar to those ones as expressed in step vi).

[0087] In some embodiments, the sulfide solid material 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.

[0088] Thus, step b) is reacting l_i2S powder of step a) with at least P2S5 and LiX; wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.

[0089] Similarly, step i) is obtaining a composition by admixing at least l_i2S of step a), P2S5 and LiX, optionally in one or more solvents; and step i’) is obtaining a solution by admixing at least L i2S of step a), P2S5 and LiX, in one or more solvents under inert atmosphere.

[0090] Therefore, the composition ratio of each element can be controlled by adjusting the amount of the Li2S, 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 elements Li, P, S and X, which is obtainable from the applied amounts of the precursorsunder 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.

[0091] In some preferred embodiments, X is is selected from the list consisting of F, Cl, I, Br and mixture thereof.

[0092] Preferably, phosphorous 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.

[0093] 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.

[0094] Therefore in some embodiments, the sulfide solid material obtained by the process according to the invention responds to the formula (II):Li?-2x-yMxPS6-yXy (II) wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof; wherein M is an alkaline earth metal element selected from Sr, Ca, Mg and Ba; wherein x is a number such as 0.01 < y < 0.5; 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.

[0095] Thus step b) is reacting l_i2S powder of step a) with at least P2S5, LiX and a compound selected from MX2, MS and mixture thereof.

[0096] Similarly, step i) is obtaining a composition by admixing at least U2S of step a), P2S5, LiX and a compound selected from MX2, MS and mixture thereof, optionally in one or more solvents; and step i’) is obtaining a solution by admixing at least Li2S of step a), P2S5 , LiX and a compound selected from MX2, MS and mixture thereof, in one or more solvents under inert atmosphere.

[0097] Therefore, the composition ratio of each element can be controlled by adjusting the amount of the U2S, P2S5, LiX and MX2, MS or mixture thereof in step b). The raw materials including Li2S, P2S5, LiX and MX2, MS or mixture thereof andtheir 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.

[0098] Preferably, phosphorous 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.

[0099] 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.

[0100] Therefore in some embodiments, the sulfide solid material 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 N3, or a combination thereof; wherein M’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < y < 0.5; 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.

[0101] Thus, step b) is reacting Li2S powder of step a) with at least P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof.

[0102] Similarly, step i) is obtaining a composition by admixing at least U2S of step a), P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof, optionally in one or more solvents; and step i’) is obtaining a solution by admixing at least Li2S of step a), P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof, in one or more solvents under inert atmosphere.

[0103] 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 thereofand 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.

[0104] Preferably, lithium sulfide, phosphorous sulfide (P2S5), halogen or pseudo halogen compounds (LiX), and Na, K, Rb, Cs, Cu and Ag compound (M’X or M’2S) are in the form of powders which have an average particle diameter comprised between 0.5 pm and 400 pm.

[0105] Another object of the present invention is related to particles of sulfide solid material comprising at least Li, P, S and X elements, obtained 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 analytical centrifuge analysis after deagglomeration.

[0106] Accordingly, the present invention is also related to particles of sulfide solid material responding to the formula (I), (II) or (III) as above described.

[0107] Another object of the present invention is related to the use of the particles according to the invention for the preparation of a composition (C) comprising(i) the sulfide solid material of formula (I), (II) or (III) and (ii) at least one polymeric material (P).

[0108] The composition (C) of the invention may be used for the preparation of an electrode. The composition (C) 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 (C) of the invention may also be used for the preparation of a separator.

[0109] The composition (C) more particularly comprises:(i) a sulfide solid material 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).

[0110] Another object of the present invention is related to the use of the particles according to the invention for the preparation of an electrode or for the preparation of an electrolyte layer of an electrode.

[0111] Still another object of the present invention is related to the use of the particles according to the invention for the preparation of a separator.

[0112] 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.Figure

[0113] Figure 1 : Solid state31P NMR spectrum of argyrodite precursor after step a). Examples

[0114] XRD Analysis

[0115] 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 dry room.

[0116] Solid-state31P NMR

[0117] Solid-State NMR spectra were recorded on a Bruker Avance 400 spectrometer equipped with a high-speed DVT4 probe.31P measurements were performed by magic-angle-spinning (MAS) at a speed of 10 kHz, in single-pulse mode with a relaxation time D1 = 60s. Reference for31P NMR was 85% H3PO4.

[0118] Particle Size Distribution measurement

[0119] 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 filtered on a 800 pm sieve and introduced in a Malvern Mastersizer 3000. Data was treated with the optical model of Fraunhofer.

[0120] A second methodology to measure particle size distribution was used for sulfide solid electrolyte (SSE) powders of formula LiePSsCI. For this purpose, analytical centrifuge LUMiSizer® (LUM) equipment and air-tight quartz tubes were used. At first, the powder was deagglomerated in a 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 powde was deagglomerated at 6000 rpm for 29 min. When the deagglomeration step was finished, a small aliquot was sampled under gentle stirring and introduced into the air-tight quartz tubes. The sample was then analyzed and particle size distribution are determined using the Rosin-Rammler-Sperling-Bennet model.

[0121] Specific surface area of the particles by BET method

[0122] 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 200 °C for 2 hours prior to analysis. The specific surface 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.

[0123] Determination of H2S emission

[0124] The preparation of the sample is carried out in a dry Ar glove-box (moisture level < 5 ppm, O2 level < 5 ppm). The sample (between 350 and 700 mg of powder) is placed in an open circular holder with a circular surface of 4.02 cm2. Then, the holder is placed on a zirconia pot where it can be isolated from theatmosphere. 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. Relative humidity is set at 35% at room temperature (23°C) (corresponding to a Dew Point of 6.7°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.

[0125] Conductivity & Electrochemical Impedance Spectroscopy (EIS)

[0126] 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 500MPa. 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 current collector. Pellets with their carbon electrodes attached are then loaded into air-tight sample holders and a pressure of 40 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 is acquired 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 20mV and a range of frequencies from 1 MHz to 1 kHz (25 points per decade and a mean of 50 measurements per frequency point).

[0127] Materials

[0128] Dry LiOH was obtained from Supelco and LiOH-H2O from Chengdu.Dry H2S was obtained from Air Liquide (purity > 99.5 vol.%).l_i2S Lorad 200 and 40 were provided by Lorad Chemical Corporation.

[0129] Li2S preparation

[0130] Sulfidation set-up

[0131] The reaction was performed in a 200 mL stirred quartz reactor that can operate under an inert atmosphere and at high temperature.The reactor was equipped with gas inlet and outlet, an agitator and counterblades. The reactor was equiped with a system allowing heating the reactor and the lid of the reactor. The temperature was measured by a probe placed in the powder introduced in the reactor. A pump connected to the reactor made possible the introduction of the reagent gas by an inlet pipe. An outlet pipe was connected to a Dean-Starck apparatus to recover water generated by the reaction and further to a scrubber containing NaOH to neutralize unreacted H2S. The reactor was inerted with nitrogen, applying cycles of purge under vacuum followed by refill with nitrogen.

[0132] Drying of LiOH

[0133] LiOH-hLO was placed in the reactor at a temperature set at 200 °C under a flow of dry nitrogen during 3 h. The mechanical stirring was set at 100 r.p.m.

[0134] Preparation of Li2S powder (A)

[0135] 3 moles of dried LiOH powder were placed into the reactor. The reactor was inerted with 3 cycles of purge under vacuum followed by refill with nitrogen. Then, mechanical stiring was set at 100 r.p.m. and temperature at 200°C.Dry H2S, after passing through molecular sieves, was introduced in the reactor via an inlet pipe at a flow rate of 10NL / h until reaching 2.5 equivalent with regards to LiOH present.Unreacted H2S and formed water vapor were extracted via an outlet pipe and condensed water was collected via a Dean-Starck apparatus while H2S was neutralized in a scrubber containing NaOH.

[0136] Preparation of Li2S powder (B)

[0137] 3 moles of dry LiOH powder were placed into the reactor. The reactor was inerted with 3 cycles of purge under vacuum followed by refill with nitrogen. Then, mechanical stiring was set at 100 r.p.m. and temperature at 240°C.Dry H2S, after passing through molecular sieves, was introduced in the reactor via an inlet pipe at a flow rate of 20NL / h until reaching 2.0 equivalent with regards to LiOH present.Unreacted H2S and formed water vapor were extracted via an outlet pipe and condensed water was collected via a Dean-Starck apparatus while H2S was neutralized in a scrubber containing NaOH.

[0138] l_i2S powder having the characteristics described in table 1 was used as raw material.

[0139] Table 1 : l_i2S powder characteristicsAs can be seen from table 1 , the l_i2S powders present a high reactivity towards water vapor as illustrated by the high amount of H2S released during exposure to moisture.

[0140] LiCI and P2S5 were respectively provided from Altichem and Italmatch, purity>99%.

[0141] Preparation of sulfide solid electrolyte of formula LIGPSSCI (argyrodite)

[0142] step a) : 7.7 g of LiCI; 20.1 g of P2S5 and 20.8 g of Li2S 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 440 g of ZrO2 balls (5 mm, Across). 113.5 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 wasconducted with a Retsch™ PM400 planetary ball-mill. After 14 h of milling at 350 rpm , a pale yellow / beige paste was obtained.

[0143] The paste was transferred in a dry alumina crucible and dried under dynamic vacuum at 130°C to remove the xylene. The xylene was condensed by ice water and the drying was continued until no xylene was recovered. After 5 hours of drying, the milling balls were separated from the light beige powder through sieving at 4 mm.

[0144] The powder obtained after step a), which corresponds to the sulfide solid electrolyte precursor, comprises high amount of glassy (PS4)3’ species as measured by solid state31P NMR. This fact reflects the high advancement of the reaction leading to the desired sulfide solid electrolyte.

[0145] Composition of the precursor as measured by31P NMR is provided in table 2. In31P NMR technique, glassy (PS4)3’ entities are responsible for massif peak centered at around 84 ppm chemical shift. This peak might not be symmetric due to the existence of crystal (PS4)3’ entities which are responsible for peak centered at around 86.4 ppm. When needed, the deconvolution of the peak can help provide the relative proportion of each of the (PS4)3’ species. Furthermore, other entities such as (P2S7)4’ and (P2S6)2’ can be found at 94 and 106 ppm (see figure 1 ).

[0146] Table 2: Argyrodite precursor composition after step a)

[0147] The inventors have observed that precursor obtained from l_i2S according to the invention generally comprises more glassy (PS4)3’ moities than, or a same amount of glassy (PS4)3’ moities as, precursor obtained from l_i2S e.g. having a D50 below 20 pm and / or having specific surface area below 5 m2 / g. Therefore, the reaction involving l_i2S according to the invention is more advanced or equally advanced at this stage.

[0148] step b) : the dried mixture was charged under dry air (dew point < - 40°C) in a quartz reactor. The reactor is then inserted in a rotative oven and the product is crystallized at 490°C during 12 hours (heating ramp 1.5°C / min) with a rotation of 9 rpm under N2 flow (30 L / h). It is allowed to cool down to 50°C under same N2 flow and rotation. The final product is submitted to a slight deagglomeration to give the sulfide solid electrolyte of formula LiePSsCI with properties reported in table 3.

[0149] Table 3: Argyrodite properties

[0150] As can be seen from table 3, the argyrodite powder obtained from l_i2S of the invention has small particle size, smaller than particle size of argyrodite powder obtained from l_i2S e.g. having a D50 below 20 pm and / or having specific surface area below 5 m2 / g. Accordingly, argyrodite powders obtained from l_i2S Powder (A) and l_i2S Powder (B) have a D50 of respectively 4.7 pm and 6 pm, while argyrodite powders obtained from l_i2S Powder Lorad 40 and U2S PowderLorad 200 have a D50 of respectively 8.6 pm and 7.4 pm. Moreover, argyrodite powders obtained from Li2S Powder (A) and U2S Powder (B) have a D90 of respectively 9.7 pm and 12 pm, while argyrodite powders obtained from Li2S Powder Lorad 40 and Li2S Powder Lorad 200 have a D90 of respectively 15.9 pm and 15.3 pm.

[0151] This reduction of particle size is not detrimental to the ionic conductivity of the resulting argyrodite which is higher than or close to 3 mS / cm at 30°C. This is advantageous, since SSE particles properties and particularly SSE particles size will determine the difficulty to manufacture thin separator and compact catholyte electrode. SSE particles of small size can be used to manufacture separator and catholyte without milling which generally impairs the ionic conductivity of the material.

Claims

ClaimsClaim 1 . A process for preparing particles of a sulfide solid material comprising at least Li, P, S and X elements, comprising the steps of: a) providing a powder of lithium sulfide (Li2S) having a D50-value ranging from 20 pm to 500 pm as measured by laser diffraction in para-xylene, a specific surface area equal or more than 5 m2 / g as measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method, b) reacting Li2S powder of step a) with at least P2S5 and LiX, to obtain the Li, P, S and X containing sulfide solid material particles, wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.Claim 2. The process of claim 1 , wherein the powder of lithium sulfide (Li2S) of step a) presents an amount of H2S release of more than 200 ml / g when exposed to a relative humidity of 30-40% at 23°C during 60 minutes.Claim 3. The process of claim 1 or 2, wherein step b) comprises the following steps of: i) obtaining a composition by admixing at least Li2S of step a) P2S5 and LiX, optionally in one or more solvents; ii) applying a mechanical treatment to the composition obtained in step i); iii) optionally removing at least a portion of the one or more solvents from the composition obtained on step ii), so that to obtain a sulfide solid material precursor; iv) optionally pressing the sulfide solid material precursor of step iii) into pellets; v) heating the obtained precursor obtained in step iii) 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; andvi) optionally treating the sulfide solid material particles obtained in step v) to the desired particle size distribution.Claim 4. The process of claim 3, wherein in step ii) the mechanical treatment is performed by wet or dry milling.Claim 5. The process of claim 1 or 2, wherein step b) comprises the following steps of: i') obtaining a solution by admixing at least l_i2S of step a) P2S5 and LiX, in one or more solvents under inert atmosphere; ii') removing at least a portion of the one or more solvents from the composition obtained on step i’), so that to obtain a sulfide solid material precursor; iii') optionally pressing the sulfide solid material precursor of step ii’) into pellets; iv') heating the obtained precursor obtained in step ii’) 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 v') optionally treating the sulfide solid material particles obtained in step iv’) to the desired particle size distribution.Claim 6. The process of any one of claims 3 to 5, wherein the sulfide solid material precursor of step iii) or step ii’) comprises at least 85 mol % of P species under the form glassy (PS4)3’ entities as dertermined by31P NMR.Claim 7. The process of any one of claims 1 to 6, wherein the sulfide solid material 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; wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and N3, or a combination thereof.Claim 8. The process of any one of claims 1 to 7, wherein the sulfide solid material further comprises an alkaline earth metal element and responds to the formula (II):Li?-2x-yMxPS6-yXy (II) wherein X is selected from the list consisting of F, Cl, I, Br, CN, NC, OCN, NCO, SCN, NCS and Ns, or a combination 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 < y < 0.5; 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; and wherein step b) is reacting l_i2S powder of step a) with at least P2S5, LiX and a compound selected from MX2, MS and mixture thereof.Claim 9. The process of any one of claims 1 to 7, wherein the sulfide solid material further comprises an element selected from Na, K, Rb, Cs, Cu and Ag and 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 N3, or a combination thereof; wherein M’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < y < 0.5; 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; and wherein step b) is reacting l_i2S powder of step a) with at least P2S5, LiX and a compound selected from M’X, M’2S and mixture thereof.Claim 10. The process of any one of the preceding claims, wherein the sulfide solid material particles have 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 analytical centrifuge analysis.Claim 11. Particles of sulfide solid material comprising at least Li, P, S and X elements, obtained by the process according to anyone of claims 1 to 10 characterized in that it has 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 analytical centrifuge analysis after deagglomeration.Claim 12. The particles according to claim 11 wherein the sulfide solid material responds to the formula (I), (II) or (III).Claim 13. Use of the sulfide solid material particles according to claim 11 or 12 for the preparation of a composition (C) comprising (i) the product of formula (I), (II) or (II) and (ii) at least one polymeric material (P).Claim 14. Use of the sulfide solid material particles according to claim 11 or 12 for the preparation of an electrode or for the preparation of an electrolyte layer of an electrode.Claim 15. Use of the sulfide solid material particles according to claim 11 or 12 for the preparation of a separator.

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