Composition comprising sulfide solid material comprising alkali metal, p, s and halogen elements

Abstract

The present disclosure relates to a composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and further comprising cerium oxide (CeO2) in an amount ranging from 0.05 to 10 % by weight based on the weight of solid sulfide material. It also relates to a process for preparing the composition (C). Finally, the present disclosure pertains to solid electrolyte, secondary battery, electrode and separator comprising the composition (C).

Description

DescriptionCOMPOSITION COMPRISING SULFIDE SOLID MATERIAL COMPRISING ALKALI METAL, P, S AND HALOGEN ELEMENTSThis application claims priority to European patent application No. 23307246.1 filed on December 18, 2023, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0001] The present disclosure relates to a composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and further comprising cerium oxide (CeO2) in an amount ranging from 0.05 to 10 % by weight based on the weight of solid sulfide material. It also relates to a process for preparing the composition (C). Finally, the present disclosure pertains to solid electrolyte, secondary battery, electrode and separator comprising the composition (C).Background

[0002] 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.

[0003] 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 sulfide electrolyte, for example containing Li, P, S, and a halogen.

[0004] Solid sulfide electrolyte are highly hygroscopic materials, and likely to hydrolyze in the presence of water from ambient air giving gaseous H2S as the main product. H2S is highly toxic and corrosive therefore representing a threat to people and equipment.

[0005] Strategies to mitigate the risk of H2S release are of the greatest importance to ensure the commercial success of the technology. Active strategies, which consist in modifying the material, for example by doping, results in modification of the crystalline structure that can be accompanied by an improvement of the chemical stability of solid sulfide electrolyte. Passive strategies where the material is not modified, and for example, where H2S release in the atmosphere is avoided using H2O or H2S trap can be an alternative.

[0006] Whatever the strategy used, it has to have a minimized impact onto the performance of the solid sulfide electrolyte such as ionic conductivity.

[0007] In the present invention, a passive strategy is considered as a feasible and cost effective way to mitigate H2S release in the atmosphere in case of accident, faulty packaging or handling and during cycling. Several scientific teams have used such passive strategy previously.

[0008] For example, US 2013 / 0011746 A1 relates to the provision of a solid sulfide electrolyte material for an all solid-state lithium secondary battery comprising Fe, Zn or Bi oxides such as Fe2O3, ZnO or Bi2Os, capable of preventing generation of hydrogen sulfide to the outside. ZnO and Bi2Os are found to be the most efficient to decrease the amount of H2S generation, when the solid sulfide electrolyte material wherein they are included is exposed to air. Due to Bi2Os restricted electrochemical stability, ZnO is better to maintain a high ionic conductivity of said solid sulfide electrolyte material. However, ionic conductivity is divided by 2 or more through introducing ZnO into the sulfide. The same results are published in Journal of Materials Chemistry A, 2013, 1, 6320-6326

[0009] JP2020061260 A, pertains to the provision of a solid electrolyte for all-solid lithium ion battery containing l_i2S and P2S5, which does not generate H2S while keeping good ionic conductivity. For this purpose, the solid sulfide electrolyte of the invention comprises PbO2 or SnO2 and comparative example are solid sulfide electrolyte comprising no oxide or comprising ZrO2 or TiO2. This technical solution suffers from the drawback of involving materials containing hazardous metals, such as Pb or Sn. Moreover, if the addition of those oxidesto solid sulfide electrolyte moderately decreases the amount of H2S generation, it also results in a significant decrease of ionic conductivity, which is divided by 2 and up to 5.

[0010] Journal of Non-Crystalline Solids, 364 (2013), 57-61 discloses that addition of Li2O in a Li2S-P2Ss glass reduces H2S gas generation, while a relatively high ionic conductivity of said glass sulfide electrolyte material is maintained. However, ionic conductivity is divided by 3 or more through introducing U2O into the sulfide glass.

[0011] Finally, JP2017120728 A2 pertains to the use of U2O to reduce H2S gas generation in an argyrodite electrolyte material of formula LiePSsCI, while the ionic conductivity of said argyrodite electrolyte material is maintained. However, the amount of U2O which is added is so low (< 1.5 wt %) that the effect of reducing the H2S generation amount is not clearly observed.Summary

[0012] The Applicant is aware that solid sulfide electrolyte containing Li, P, S, and halogen suffers from poor stability during storage, especially when exposed to ambient moisture.

[0013] The Applicant is aware that solid sulfide electrolyte containing Li, P, S, and halogen may generate H2S release during storage, especially when exposed to ambient moisture, during accident, faulty packaging or handling and during cycling.

[0014] There is a need for solid sulfide electrolyte powder containing Li, P, S, and halogen which remains stable and does not generate H2S release when exposed to moisture during storage or transportation.

[0015] There is a need for solid sulfide electrolyte powder containing Li, P, S, and halogen which remains stable and does not generate H2S release when present in a battery submitted to cycling.

[0016] The Applicant noticed that existing solutions for preparing solid sulfide electrolyte containing Li, P, S, and halogen, which remains stable and does not generate H2S release, through adding metal oxide therein require the use ofhazardous metal and / or are detrimental to the ionic conductivity of said solid sulfide electrolyte.

[0017] There is a need for solid sulfide electrolytes powder containing Li, P, S, and a halogen which remains stable when exposed to moisture during storage or transportation and having high ionic conductivity and low activation energy.

[0018] There is a need for new solid sulfide electrolyte containing Li, P, S, and halogen comprising metal oxide that will confer increased stability toward air moisture and will avoid generation of H2S release while maintaining high ionic conductivity and low activation energy.

[0019] There is a need for a process for preparing new solid sulfide electrolyte containing Li, P, S, and halogen comprising said metal oxide.

[0020] Hence, the Applicant faced the problem of providing solid sulfide electrolyte containing Li, P, S, and halogen that can fulfill the above-mentioned needs.

[0021] The present invention relates to a composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and further comprising cerium oxide (CeO2) in an amount ranging from 0.05 to 10 %, preferably from 0.2 to 6 %, more preferably from 0.4 to 4 % and even more preferably from 0.5 to 2 % by weight based on the weight of solid sulfide material.

[0022] The present invention also relates to processes for preparing the composition (C).

[0023] The present invention also relates to a solid electrolyte comprising the composition (C) according to the invention.

[0024] The present invention also relates to a secondary battery comprising the solid electrolyte according to the invention, more particularly to a lithium secondary battery.

[0025] The present invention also relates to an electrode comprising the composition (C) according to the invention.

[0026] The present invention also relates to a separator comprising the composition (C) according to the invention.Disclosure of the invention

[0027] The present invention relates to a composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and further comprising cerium oxide (CeO2) in an amount ranging from 0.05 to 10 % by weight based on the weight of solid sulfide material.

[0028] The inventors have surprisingly found that such composition presents increased stability toward air moisture while keeping high conductivity and low activation energy.

[0029] The reaction between gaseous H2S and metal oxide is generally described as represented in scheme 1 below:rnnoniMxOy+yH2S - ► MxSy+yH2OI / / / J

[0031] Without being bound to any theory, this reaction is reaction is thought to be irreversible and responsible for the efficient H2S trapping.

[0032] The composition (C) generally comprises cerium oxide (CeC ) in an amount ranging from 0.05 to 10 %, preferably from 0.2 to 6 %, more preferably from 0.4 to 4 % and even more preferably from 0.5 to 2 % by weight based on the weight of solid sulfide material.

[0033] The composition (C) generally comprises at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen.

[0034] In some preferred embodiments, the alkali metal is Li. Accordingly, the at least one solid sulfide material comprises Li, P and S and at least one halogen.

[0035] In some embodiments, the solid sulfide material responds to formula (I): Li7-yPS6-yXy (I) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .0 < y < 1.6.Good results were obtained with X is Cl and y is equal to 1 , therefore with LiePSsCI.

[0036] In some other embodiments, the solid sulfide material responds to formula (II):Li7-2x-yAxPS6-yXy (I I) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein A 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; wherein y is a number such as 0.5 < y < 2; preferably such as 1.0 < y < 1.8; more preferably such as 1 .0 < y < 1 .6.

[0037] Still, in some other embodiments, the solid sulfide material responds to formula (III):Li7-x -yA’x’PS6-yXy (III) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein A’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < x’ < 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 .0 < y < 1 .6.

[0038] The solid sulfide materials of formulae (l)-(lll) can be either crystalline or glassy materials.

[0039] The solid sulfide materials may be any commercially available material of formula (l)-(lll)

[0040] Any method, well known by the person of ordinary skill in the art, can be used to prepare the solid sulfide materials of formulae (l)-(lll).

[0041] For example, the particles of solid sulfide materials of formulae (l)-(lll) can be prepared by a method comprising the steps of i) obtaining a composition by admixing the starting materials, 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 solid precursor; iv) optionally pressing the solid precursor from 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 300°C to 700°C, under an inert atmosphere, for a time period ranging from 1 to 12 hours, thereby forming the solid sulfide material particles; and vi) optionally treating the solid sulfide material obtained in step v) to the desired particle size distribution.

[0042] The starting materials of step i) are introduced in relative amounts suitable to obtain the solid sulfide material of targeted stoichiometry.

[0043] For example, when preparing the solid sulfide material of formula (I), the starting materials of step i) may comprise lithium sulfide (l_i2S), phosphorus sulfide (P2S5) and a compound of formula LiX wherein X represents at least one halogen element.

[0044] Still as matter of example, when preparing the solid sulfide material of formula(II), the starting materials of step i) may comprise lithium sulfide (l_i2S), phosphorus sulfide (P2S5), a compound of formula LiX and at least one alkaline earth metal element compound such as BeS, SrS, CaS, MgS, BaS, BeX2, SrX2, CaX2, MgX2, and BaX2, wherein X represents at least one halogen element.

[0045] Still as matter of example, when preparing the solid sulfide material of formula(III), the starting materials of step i) may comprise lithium sulfide (Li2S), phosphorus sulfide (P2S5), a compound of formula LiX and at least one compound such as Na2S, K2S, CS2S, CU2S, Ag2S, NaX, KX, CsX, CuX and AgX, wherein X represents at least one halogen element.

[0046] Just for the matter of example, the solvent of step i) can be selected among aliphatic hydrocarbons (for instance hexane, heptane, octane or nonane, preferably heptane) and aromatic hydrocarbons (for instance benzene, toluene, ethylbenzene, xylenes or liquid naphthenes, preferably xylenes). For example, the solvent can be selected from the group consisting of xylene, paraxylene, heptane, octane, and mixtures thereof.

[0047] Cerium oxide which has the chemical formula CeO2 can be obtained for example by calcination of cerium oxalate, cerium carbonate or cerium hydroxide. Alternatively, cerium oxide may be obtained through theprecipitation reaction of Ce(NO3)3, 6H2O solution promoted by the addition of NaOH.Furthermore, cerium oxide can be prepared as described in US2010072417A2. Alternatively, commercially available cerium oxide may be used.

[0048] Generally, the solid sulfide material and the cerium oxide are present in the composition (C) under the form of particles.

[0049] Hence, the composition (C) according to the invention is a powder composition comprising solid sulfide material and cerium oxide (CeC ) under the form of particles.

[0050] Generally, the solid sulfide material is present under the form of particles having a median particle size (D50) being higher than the median particle size (D50) of cerium oxide particles.

[0051] Generally, the solid sulfide material is present under the form of particles having a median particle size (D50) in the range of from about 0.5 to about 40 pm; sometimes in the range of from about 1 to about 20 pm; often in the range of from about 5 to about 15 pm.

[0052] Generally, the cerium oxide particles is present under the form of particles having a median particle size (D50) in the range of from about 1 to about 3,000 nm, sometimes in the range of from about 5 to about 2,000 nm, often in the range of from about 10 to about 700 nm, even more often in the range of from about 50 to about 500 nm, such as in the range of from about 100 to about 400 nm.

[0053] Dn corresponds to the diameter of the particles for which n% of the particles have a diameter which is less than Dn. D50 (median) is defined as the size value corresponding to the cumulative distribution at 50%. The D50-value corresponds to the median particle size of the distribution.

[0054] These parameters are usually determined from a distribution in volume of the diameters of a dispersion of the particles of the solid material in a solution, obtained with a laser diffractometer, using the standard procedure predetermined by the instrument software. The laser diffractometer uses the technique of laser diffraction to measure the size of the particles by measuringthe intensity of light diffracted as a laser beam passes through a dispersed particulate sample. The laser diffractometer may be the Mastersizer 3000 manufactured by Malvern for instance.

[0055] The measurement of the particle size distribution (PSD), e.g. D50-value, D10- value and D90-value, may be performed by laser diffraction e.g. in para-xylene or isomeric xylene. Data can be treated with the optical model of Fraunhofer.

[0056] In some other embodiments, the composition (C) according to the invention is an agglomerated powder comprising solid sulfide material and cerium oxide under the form of particles and a polymeric binding material (P).

[0057] The composition (C) is characterized by a low emission of H2S in given conditions. Indeed, when the composition is exposed for 60 minutes to an atmosphere composed of humid air with a relative humidity of 35%, the release r of H2S is lower than 90 mL / g of composition, the measurement being performed at a temperature of 23°C. Thus, r is determined by a simple test which consists in exposing the composition to a humid atmosphere and in measuring the quantity of H2S released during the first 60 minutes at which the composition is in contact with said atmosphere. The relative humidity is well known to the person skilled in the art. It corresponds to the ratio of the partial pressure of water vapor in an atmosphere air I water to the equilibrium vapor pressure of water at a given temperature, r may be lower than 75 mL / g. r is generally higher than 1 mL / g.

[0058] Under the same experimental conditions, it is also possible to determine the rate of emission of H2S expressed in mL FhS / g / h. This rate is lower than 90 mL H2S / g / h.

[0059] The composition (C) generally exhibits an ionic conductivity measured at 23°C on pressed (500 MPa) pellets by impedance spectroscopy, higher than 0.5 mS / cm, preferentially higher than 1.0 mS / cm, preferentially higher than 2.0 mS / cm. The ionic conductivity is generally less than 12 mS / cm, more particularly less than 10 mS / cm.

[0060] The measurement of the ionic conductivity (o) can be performed on a pressed pellet. Typically, a pressed pellet is manufactured using a uniaxial or isostaticpressure. 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.

[0061] The ionic conductivity values (o) can be obtained at different temperature. The slopes of the oT versus 1 / T plots are used to determine activation energy values. The composition (C) generally exhibits a low activation energy value.

[0062] Therefore, the inventors have found that the composition (C) according to the invention is particularly suitable to be used as solid electrolyte for secondary batteries.

[0063] Another object of the present invention relates to a process for preparing a composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and further comprising cerium oxide (CeO2) in an amount ranging from 0.05 to 10 % by weight based on the weight of solid sulfide material.

[0064] Therefore, another object of the invention is a process for preparing the composition (C) according to the invention, comprising mixing particles of sulfide solid material with particles of cerium oxide (CeC ), as previously described.

[0065] The process for preparing the composition (C) according to the invention can be either a dry process i.e. wherein the mixing involves solid particles only, or a wet process wherein particles are mixed in the presence of a liquid medium.

[0066] The dry process is generally performed at a temperature ranging from -20°C to 60°C; preferably at a temperature ranging from -10°C to 50°C; more preferably at a temperature ranging from 0°C to 40°C. Good results were obtained at room temperature.

[0067] Mixing can be conducted using any equipment well known by the person skilled in the art to be suitable to mix solid particles and powders composed of solid particles, optionally in the presence of a liquid medium.

[0068] Just for the sake of example, the mixing of particles of sulfide solid material with particles of cerium oxide can be conducted in a ploughshare blender, avertical ribbon blender, a vertical conical screw blender, a double cone blender, a V shape blender or a horizontal ribbon blender.

[0069] In some embodiments, the mixing is conducted as high-energy mixing. For example, high energy mixing can be performed in a ball mill e.g. a planetary ball mill.

[0070] Good results were obtained by mixing the powders manually using mortar and pestle.

[0071] When the process for preparing the composition (C) according to the invention is a wet process, it comprises the steps of a) mixing particles of at least one sulfide solid material as previously described with particles of cerium oxide (CeC ) or of cerium oxide precursor in the presence of a liquid medium to obtain a composition (O’); b) removing the liquid medium from the composition (O’) obtained on step a), so that to obtain the composition (C).

[0072] Step a) can be performed using any equipment well known by the person skilled in the art, for example as described above.

[0073] In some embodiments, in step a) particles of sulfide solid material and particles of cerium oxide (CeC ) are in suspension in the liquid medium.

[0074] Therefore, the liquid medium is composed of one or more solvent wherein sulfide solid material and cerium oxide (CeC ) are substantially not solubilized or totally not solubilized. By substantially not soluble is meant that less than 5 wt%, preferably less than 1 wt % of sulfide solid material and cerium oxide (CeO2) are solubilized.

[0075] Thus, the liquid medium generally comprises at least one solvent selected from aliphatic hydrocarbons (for instance hexane, heptane, octane or nonane, preferably heptane) and aromatic hydrocarbons (for instance benzene, toluene, ethylbenzene, xylenes or liquid naphthenes, preferably xylenes). For example, the liquid medium comprises or is composed of solvent that can be selected from the group consisting of xylene, para-xylene, heptane, octane, and mixtures thereof.

[0076] In some other embodiments, in step a) particles of sulfide solid material are in suspension in the liquid medium and particles of cerium oxide (CeC ) are partially solubilized or completely solubilized in the liquid medium.

[0077] Therefore the liquid medium is composed of one or more solvent wherein sulfide solid material is substantially not solubilized or totally not solubilized while cerium oxide (CeO2) is partially or completely solubilized. By substantially not soluble is meant that less than 5 wt%, preferably less than 1 wt % of sulfide solid material are solubilized. By partially solubilized is meant that at least 5 wt%, preferably at least 15 wt% of cerium oxide are solubilized.

[0078] Still, in some other embodiments, in step a) particles of sulfide solid material are in suspension in the liquid medium and particles of precursor of cerium oxide (CeO2) are partially solubilized or completely solubilized in the liquid medium. In that embodiment, step b) generally further comprises a step of formation of cerium oxide (CeC ) from the precursor before finally obtaining composition (C).

[0079] In the embodiments where cerium oxide (CeC ) or precursor of cerium oxide (CeO2) is partially or completely solubilized, the liquid medium generally comprises at least one solvent selected from aliphatic alcohols (for instance methanol, ethanol, or propanol), and optionally one or more solvent selected from aliphatic hydrocarbons (for instance hexane, heptane, octane or nonane, preferably heptane) and aromatic hydrocarbons (for instance benzene, toluene, ethylbenzene, xylenes or liquid naphthenes, preferably xylenes). For example, the liquid medium comprises or is composed of ethanol and optionally a solvent that can be selected from the group consisting of xylene, para-xylene, heptane, octane, and mixtures thereof.

[0080] The wet process to prepare the composition (C), where cerium oxide (CeC ) or precursor of cerium oxide (CeC ) is partially or completely solubilized, is therefore an efficient mixing similar to impregnation or incipient wetness impregnation, which are well-known methods for dispersing nanoparticles (here cerium oxide) on the surface of a support (here the sulfide solid material).

[0081] The precursor of cerium oxide (CeC ), can be for example CeCh or Ce(NO3)3.

[0082] In the wet process step a) is generally performed at a temperature preferably between the fusion temperature of the selected liquid medium and ebullition temperature of the selected liquid medium.

[0083] In the wet process step a) is generally performed at a temperature ranging from -10°C to 60°C; preferably at a temperature ranging from 0°C to 50°C; more preferably at a temperature ranging from 10°C to 40°C. Good results can be obtained at room temperature.

[0084] Step b) can be performed using any means well known by the person skilled in the art to remove a liquid medium comprising one or more solvents from a composition. Liquid removal may be carried out by known methods, such as decantation, filtration, centrifugation, drying or a combination thereof.

[0085] The temperature in step b) can be selected to allow removal of the liquid medium. Preferably, when drying is selected as method for liquid removal, temperature is selected below ebullition temperature and as a function of vapor partial pressure of the selected liquid medium.

[0086] In step b), removing the liquid medium means removing at least about 97%, 98%, 99% or 100%, of the total weight of the liquid medium used, or any ranges comprised between these values.

[0087] The composition (C) of the present invention may be used to manufacture a solid electrolyte.

[0088] The present invention also includes a solid electrolyte comprising the composition (C) described herein.

[0089] The solid electrolyte according to the invention comprises then the composition (C) and optionally at least one lithium ion-conducting material (LiCM) other than the solid solid sulfide material of composition (C), like lithium conducting oxides such as lithium stuffed garnets Li?La3Zr20i2 (LLZO).

[0090] The solid electrolyte according to the invention may also optionally comprise polymers such as styrene butadiene rubbers, organic or inorganic stabilizers such as SiO2 or dispersants.

[0091] The present invention also includes an electrochemical device comprising the solid electrolyte described herein.

[0092] Preferably in the electrochemical device, particularly a rechargeable electrochemical device, the solid electrolyte is a component of a solid structure for an electrochemical device selected from the group consisting of cathode, anode and separator.

[0093] The present invention also relates to a solid state battery, more preferably to an alkali metal battery, in particular to a lithium battery, comprising the solid electrolyte described herein.

[0094] The present invention also relates to a solid state secondary battery, more preferably to an alkali metal battery, in particular to a lithium battery, comprising at least one inventive electrochemical device, for example two or more.

[0095] Typically, a lithium solid-state battery includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. At least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer includes a solid electrolyte as defined above.

[0096] The present invention also relates to an electrode comprising:- a metal substrate;- directly adhered onto said metal substrate, at least one layer made of a composition (C”) comprising:(i) the composition (C) of the present invention;(ii) at least one electro-active compound (EAC);(iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid sulfide material of composition (C);(iv) optionally at least one electro-conductive material (ECM);(v) optionally a lithium salt (LIS) other than the lithium ionconducting material (LiCM) and other than the solid sulfide material of composition (C);(vi) optionally at least one polymeric binding material (P).

[0097] The electro-active compound (EAC) denotes a compound which is able to incorporate or insert into its structure and to release lithium ions during the charging phase and the discharging phase of an electrochemical device. An EAC may be a compound which is able to intercalate and deintercalate into its structure lithium ions. For a positive electrode (cathode), the EAC may be a composite metal chalcogenide of formula LiMeCte wherein:- Me is at least one metal selected in the group consisting of Co, Ni, Fe, Mn, Cr, Al and V;- Q is a chalcogen such as 0 or S.

[0098] The EAC may more particularly be of formula LiMeC . Preferred examples of EAC include LiCoC , LiNiC>2, LiMnC , LiNixCoi-xO2 (0 < x < 1 ), LiNixCoyMnzC (0 < x, y, z < 1 and x+y+z=1 ) for instance LiNii / 3Mm / 3Coi / 3O2, LiNio.6Mno.2Coo.2O2, LiNio.8Mno.1 Coo.1 O2, Li(NixCoyAlz)O2 (x+y+z=1 ) and spinel- structured LiMn2O4 and Li (Nio.5Mm.5)04.

[0099] The EAC may also be a lithiated or partially lithiated transition metal oxyanion- based electro-active material of formula MiM2(JO4)fEi-f, wherein:- Mi is lithium, which may be partially substituted by another alkali metal representing less that 20% of Mi ;- M2 is a transition metal at the oxidation level of +2 selected from Fe, Co, Mn, Ni or mixtures thereof, which may be partially substituted by one or more additional metals at oxidation levels between +1 and +5 and representing less than 35% of the M2 metals, including 0;- JO4 is any oxyanion wherein J is either P, S, V, Si, Nb, Mo or a combination thereof;- E is a fluoride, hydroxide or chloride anion;- f is the molar fraction of the JO4 oxyanion, generally comprised between 0.75 and 1.The MiM2(JO4)fEi-f electro-active material as defined above is preferably phosphate-based. It may exhibit an ordered or modified olivine structure.

[0100] For a positive electrode, the EAC may also be sulfur or Li2S.

[0101] For a positive electrode, the EAC may also be a conversion-type materials such as FeS2 or FeF2 or FeF3.

[0102] For a negative electrode, the EAC may be selected in the group consisting of graphitic carbons able to intercalate lithium. More details about this type of EAC may be found in Carbon 2000, 38, 1031-1041. This type of EAC typically exist in the form of powders, flakes, fibers or spheres (e.g. mesocarbon microbeads).

[0103] The EAC may also be: lithium metal; lithium alloy compositions (e.g. those described in US 6,203,944 and in WO 00 / 03444); lithium titanates, generally represented by formula Li4TisOi 2; these compounds are generally considered as “zero-strain” insertion materials, having low level of physical expansion upon taking up the mobile ions, i.e. Li+; lithium-silicon alloys, generally known as lithium silicides with high Li / Si ratios, in particular lithium silicides of formula Li4.4Si and lithium-germanium alloys, including crystalline phases of formula Li4.4Ge. EAC may also be composite materials based on carbonaceous material with silicon and / or silicon oxide, notably graphite carbon / silicon and graphite / silicon oxide, wherein the graphite carbon is composed of one or several carbons able to intercalate lithium.

[0104] The lithium ion-conducting material (LiCM) other than the solid solid sulfide material of composition (C) can be lithium conducting oxides such as lithium stuffed garnets Li?La3Zr20i2 (LLZO).

[0105] The electro-conductive material (ECM) is typically selected in the group consisting of electro-conductive carbonaceous materials and metal powders or fibers. The electron-conductive carbonaceous materials may for instance be selected in the group consisting of carbon blacks, carbon nanotubes, graphite, graphene and graphite fibers and combinations thereof. Examples of carbon blacks include ketjen black and acetylene black. The metal powders or fibers include nickel and aluminum powders or fibers.

[0106] The lithium salt (LIS) may be selected in the group consisting of LiPFe, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, LiB(C2O4)2, LiAsFe, LiCICU, LiBF4, LiAICU, LiNO3, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2,LiC(SO2CF3)3, LiN(SO3CF3)2, LiC4F9SO3, IJCF3SO3, LiAICk, LiSbFe, LiF, LiBr, LiCI, LiOH and lithium 2-trifluoromethyl-4,5-dicyanoimidazole.

[0107] The function of the polymeric binding material (P) is to hold together the components of the composition (C”). The polymeric binding material is usually inert. It preferably should be also chemically stable and facilitate the electronic and ionic transport. The polymeric binding material is well known in the art. Non-limitative examples of polymeric materials (P) include notably: (1 ) VDF or TFE based polymers, notably in the form of copolymers, block copolymers or graft copolymers; (2) hydrogenated or non-hydrogenated diene-based rubber polymers, notably in the form of block copolymers and graft polymers such as polyisobutylene (PIB), styrene-butadiene rubber (SBR), (hydrogenated) acrylonitrile butadiene rubber ((h)NBR), styrene- ethylene-butylene-styrene (SEBS) and the like; (3) polymers comprising at least one alkyl (meth)acrylate, notably in the form of copolymers, block copolymers and graft copolymers, such as polymethylmethacrylate (PMMA), polybutylacrylate (BA), styrene-butylacrylate (ST-BA), styrene methylacrylate (ST-MA), butylacrylate-acrylonitrile (BA-CN) and the like; (4) polysaccharide based polymers, copolymers, block copolymers and graft copolymers such as carboxymethylcellulose (CMC), guar and the like; (5) polymers based on acrylonitrile, notably in the form of copolymers block copolymers and graft polymers such as poly(acrylonitrile) (PAN), acrylonitrile-methylacrylate (PANMA), styrene-acrylonitrile (SAN) acrylonitrile-styrene-acrylate (ASA) and the like; (6) polyamideimide (PAI) polymers, copolymers, block copolymers and graft polymers.

[0108] The polymeric material (P) may be selected in the list consisting of vinylidenefluoride (VDF)-based (co)polymers. The polymeric material (P) may more particularly be a copolymer comprising or consisting of units of VDF and hexafluoropropylene (HFP).

[0109] The polymeric material (P) may be selected in the list consisting of the optionally hydrogenated thermoplastic elastomers based on styrene. Thepolymeric material (P) may more particularly be a styrene-butadiene rubber (SBR) or a styrene-ethylene-butylene-styrene (SEBS).

[0110] The polymeric material (P) may be selected in the list consisting of polymers comprising units of acrylonitrile. The polymeric material (P) may more particularly be a copolymer of acrylonitrile, butadiene and / or butyl acrylate.

[0111] The proportion of the composition (C) of the invention in the composition (C”) may be between 0.1 wt% to 80 wt%, based on the total weight of the composition (C”). In particular, this proportion may be between 1.0 wt% to 60 wt%, more particularly between 5 wt% to 30 wt%. The thickness of the electrode is not particularly limited and should be adapted with respect to the energy and power required in the application. For example, the thickness of the electrode may be between 0.01 mm to 1 ,000 mm.

[0112] A separator is an ionically permeable membrane placed between the anode and the cathode of a battery. Its function is to be permeable to the lithium ions while blocking electrons and assuring the physical separation between the electrodes.

[0113] The present invention also relates to a separator comprising:- the composition (C) of the present invention;- optionally at least one polymeric binding material (P);- optionally at least one metal salt, notably a lithium salt (LIS) other than the solid sulfide material of composition (C);- optionally at least one plasticizer.

[0114] The electrode and the separator may be prepared using methods well-known to the skilled person. This usually comprises mixing the components in an appropriate solvent and removing the solvent. For instance, the electrode may be prepared by the process which comprises the following steps:- a slurry comprising the components of composition (C”) and at least one solvent is applied onto the metal substrate;- the solvent is removed.

[0115] Usual techniques known to the skilled person are the following ones: coating and calendaring, dry and wet extrusion, 3D printing, sintering of porous foamfollowed by impregnation. Usual techniques of preparation of the electrode and of the separator are provided in Journal of Power Sources, 2018 382, 160- 175. Other techniques such as extrusion, paste extrusion, (electro)spray coating, kneading followed by calendaring may be used.

[0116] The electrochemical devices, notably batteries such as solid state batteries described herein, can be used for making or operating cars, computers, personal digital assistants, mobile telephones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communication equipment or remote car locks, and stationary applications such as energy storage devices for power plants.

[0117] The electrochemical devices, notably batteries such as solid state batteries described herein, can notably be used in motor vehicles, bicycles operated by electric motor, robots, aircraft (for example unmanned aerial vehicles including drones), ships or stationary energy storages. Preferred are mobile devices such as are vehicles, for example automobiles, bicycles, aircraft, or water vehicles such as boats or ships. Other examples of mobile devices are those which are portable, for example computers, especially laptops, telephones or electrical power tools, for example from the construction sector, especially drills, battery-driven screwdrivers or battery-driven tackers.

[0118] 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.

[0119] Examples

[0120] Materials

[0121] l_i2S was obtained from Lorad (purity 99.9%, 100% screened to less than 75 pm).P2S5 (purity> 99%) and LiCI (purity> 99%) were obtained from Sigma Aldrich. ZnO nanopowder (< 100 nm particle size) was obtained from Sigma Aldrich. CeO2 nanopowder (< 25 nm particle size) was obtained from Sigma Aldrich.

[0122] XRD Analysis

[0123] 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 at dew points between -43°C and - 47 °C.

[0124] Particle Size Distribution measurement

[0125] The Particle Size Distribution (PSD) of the powders was evaluated using laser diffraction measurement. For this purpose, the powder was stirred in isomeric xylene (Carlo Erba). The solvent was dried with molecular sieves in order to ensure no traces of water. Prior to measurement, a suspension of 0.3 wt. % of sulfide was prepared and agitated in an ultraturrax with rotor stator (IKA) at 3000 r.p.m. for 30 min. Then, an aliquot of the suspension was sampled and introduced in the analytical device (Malvern Mastersizer 3000). Data was treated with the optical model of Fraunhofer.

[0126] Example 1 : preparation of LiePSsCI

[0127] step a) : 22.7 g of LiCI (Sigma-Aldrich, purity> 99%); 59.5 g of P2S5 (Sigma- Aldrich, purity>99%) and 61.5 g of l_i2S (Lorad, 100%, 200 mesh) are successively weighed and added in a glass container. The powders are homogenized by gentle manual mixing. They are then added to a 500 mL zirconia bowl (Across) containing 480 g of ZrO2 balls (5 mm, Across). 106.3 g of para-xylene (Sigma-Aldrich, purity>99%, dry) is then added and used to rinse the powder from the glass container directly inside the zirconia bowl. The bowl is rapidly sealed to prevent any para-xylene evaporation. Wet-ball milling is conducted with a Across PQ-N2 planetary ball-mill. After 65 h of milling at 580 rpm, a pale yellow / beige paste is obtained.

[0128] The paste is transferred in a dry alumina crucible and dried under dynamic vacuum at 130°C to remove the para-xylene. The para-xylene is condensed by ice water and the drying is continued until the volume of condensed xylene equals the volume introduced at the wet ball-milling step. After 5 hours of drying, the milling balls are separated from the light beige powder through sieving at 4 mm

[0129] step b) : the dried mixture is charged under dry air (dew point < - 15°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 the same N2 flow and rotation. The final product is grinded to obtain a powder. Argyrodite crystalline phase is confirmed by XRD.Particle size distribution is such that 5pm < D50 < 10pm and D90 < 30pm.

[0130] Example 2: preparation of LiePSsCI / Cet compositions

[0131] CeO2 powder is thermally treated at 80°C under vacuum during 5 hours i.e. until constant weight is measured. Resulting dry CeO2 and LiePSsCI of example 1 powders are mixed manually by mortar and pestle for 5 min until homogeneous mixture is created. Composition of the mixtures is given in table 1.XRD confirms the presence of both compounds i.e. CeO2 additive and argyrodite phase.

[0132] Comparative Example 1 : preparation of LiePSsCI / ZnO compositions

[0133] ZnO powder is thermally treated at 80°C under vacuum during 5 hours i.e. until constant weight is measured. Resulting dry ZnO and LiePSsCI of example 1 powders are mixed manually by mortar and pestle for 5 min until homogeneous mixture is created. Composition of the mixtures is given in table 1.XRD confirms the presence of both compounds i.e. ZnO additive and argyrodite phase.

[0134] Determination of H2S emission

[0135] 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 inan 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 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. Relative humidity is set at 30- 35% at room temperature (25°C) (corresponding to a Dew Point of 6.2°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 predried 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. The release r of H2S is expressed in ml of H2S per g of composition (ml / g).

[0136] Conductivity measurements

[0137] The conductivity is acquired on pellets done using a uniaxial press operated at 500 MPa. The measurement is performed under a loading of 40 MPa and two carbon paper foils are used as current collector in a pressure cell from MTI (BATTE-CELL-0067 EQ-PSC-15-P). The impedance spectra are acquired on a Biologic VMP3 device at room temperature (i.e. 23 °C) and the control of temperature is ensured by a Binder climatic chamber. Duration of two hours is set to allow the temperature to be equilibrated between two measurements.

[0138] Impedance spectroscopy is acquired in PEIS mode with an amplitude of 10mV and a range of frequencies from 1 MHz to 1 kHz (25 points per decade and a mean of 50 measurements per frequency point).

[0139] The conductivity o at 23°C of the reference material LiePSsCI is normalized as equal to 100, therefore o loss at 23°C (%) of Example 1 is 0%. The value of o loss at 23°C (%) of Comparative Example 1 is -5 % with regards to the conductivity o at 23°C of the reference material LiePSsCI.

[0140] Table 1 :

[0141] Results presented in table 1 show that the presence of CeO2 in the sulfide LiePSsCI decreases the H2S generation in a much more effective way than ZnO does, while maintaining a higher ionic conductivity of said sulfide. Accordingly, cerium oxide is suitable for obtaining a good tradeoff between control of H2S release and ionic conductivity of sulfides such as LiePSsCI.

Claims

ClaimsClaim 1 . Composition (C) comprising at least one solid sulfide material comprising, at least one alkali metal selected from Li and Na, elements P and S and at least one halogen, and comprising cerium oxide (CeC ) in an amount ranging from 0.05 to 10 % by weight based on the weight of solid sulfide material.Claim 2. The composition (C) according to claim 1 , wherein the alkali metal is Li.Claim 3. The composition (C) according to claim 2, wherein the solid sulfide material responds to formula (I):Li7-yPS6-yXy (I) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .0 < y < 1 .6.Claim 4. The composition (C) according to claim 2, wherein the sulfide solid material responds to formula (II):Li?-2x-yAxPS6-yXy (II) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein A 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; wherein y is a number such as 0.5 < y < 2; preferably such as 1 .0 < y < 1 .8; more preferably such as 1 .0 < y < 1 .6.Claim 5. The composition (C) according to claim 2, wherein the sulfide solid material responds to formula (III):Li7-x-yA’x’PS6-yXy (III) wherein X is selected from the list consisting of F, Cl, I, Br, or a combination thereof; wherein A’ is selected from Na, K, Rb, Cs, Cu and Ag; wherein x’ is a number such as 0.01 < x’ < 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 1.0 < y < 1 .6.Claim 6. The composition (C) according to any one of the preceding claims, wherein the sulfide solid material is present under the form of particles having a median particle size obtained from the distribution in volume being higher than the median particle size of the cerium oxide particles as measured by laser diffraction in para-xylene.Claim 7. The composition (C) according to any one of the preceding claims, wherein the sulfide solid material is present under the form of particles having a median particle size obtained from the distribution in volume in the range of from about 0.5 to about 40 pm as measured by laser diffraction in para-xylene.Claim 8. Process for preparing the composition (C) according to any one of claims 1 to 7, comprising mixing particles of sulfide solid material with particles of cerium oxide (CeO2).Claim 9. Process for preparing the composition (C) according to any one of claims 1 to 7, comprising the steps of: a) mixing particles of at least one sulfide solid material with particles of cerium oxide (CeO2) or of cerium oxide (CeO2) precursor in the presence of a liquid medium to obtain a composition (C’); b) removing the liquid medium from the composition (C’) obtained on step a), so that to obtain the composition (C).Claim 10. The process according to claim 8 or claim 9, wherein the mixing is conducted as high-energy mixing.Claim 11. A solid electrolyte comprising the composition (C) according to any one of claims 1 to 7.Claim 12. An electrochemical device comprising the solid electrolyte according to claim 11.Claim 13. A solid state secondary battery comprising the composition (C) according to any one of claims 1 to 7.Claim 14. An electrode comprising:- a metal substrate;- directly adhered onto said metal substrate, at least one layer made of a composition (C”) comprising:(i) the composition (C) according to claims 1 to 7;(ii) at least one electro-active compound (EAC);(iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid sulfide material of composition (C);(iv) optionally at least one electro-conductive material (ECM);(v) optionally a lithium salt (LIS) other than the lithium ionconducting material (LiCM) and other than the solid sulfide material of composition (C);(vi) optionally at least one polymeric binding material (P)Claim 15. A separator comprising:- the composition (C) according to claims 1 to 7;- optionally at least one polymeric binding material (P);- optionally at least one metal salt, notably a lithium salt (LIS) other than the solid sulfide material of composition (C);- optionally at least one plasticizer.

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