Solution synthesis method of lithium argyrodite particles

Abstract

The present invention relates to a method for synthesizing lithium argyrodite particles of formula Li7-(a+b)PS6-(a+b+c)OcXaQb with X and Q two distinct halogenated elements chosen from F, Cl, Br, I; O the oxygen atom, with 1≤a+b<2, c between 0 and 0.25, limits included, a and b not being simultaneously zero, from a lithium reagent Li2Sx with x between 1 and 8, a phosphorus reagent Rp chosen from P2S5, P4S10, P4S9 and P4S9+n with n between 0 and 1, and a halogenated compound chosen from LiX and PSX3; and an optional phosphorus or halogenated oxygenated reagent selected from P2O5, LiClO4, LiBrO4, LiIO4, by formation of a solvato-complex intermediate compound Li3PS4 solvent, centrifugation, redispersion of the centrifuged phase in an anhydrous solvent, then filtration and washing of said intermediate compound; drying and heat treatment. Figure 4 to be published

Description

Title of the invention: Method for the synthesis in solution of lithium argyrodite particles Technical field

[0001] The present invention relates to the field of electrochemical energy storage via lithium batteries, more particularly all-solid-state batteries using an inorganic phase of argyrodite type as solid electrolyte. The invention relates more particularly to the preparation in solution of argyrodite phases and aims to propose a relevant method in terms of product quality, preparation time and industrial extrapolation. Prior art

[0002] The development of industrializable methods for the preparation of argyrodite phases having good ionic conduction properties is essential for the development of all-solid-state batteries. Furthermore, in order to be viable, these preparation methods must be able to be extrapolated to the industrial scale at an acceptable cost.

[0003] Initially, the argyrodite phases were obtained by solid-state preparation methods by fusion-quenching, as described for example in patent applications and patents US 20170222257A1, US8075865 BB, US09899701 B2. The latter are time-consuming and difficult to extrapolate to the industrial scale. More recently, preparation methods by mechanosynthesis have been described and generally make it possible to obtain smaller micrometric particles than by fusion-quenching methods with good conductivity. These methods are now the majority and involve grinding sequences lasting several days, followed by high-temperature heat treatment, as described in particular in patent applications and patents US 11264642 BB, CN113097560 A, US 11245131 BB, US11699809 B2, as well as in the publication Phys. Status Solidi A208, No. 8 (2011).

[0004] Liquid grinding methods are also described and make it possible to reduce the grinding time and the particle size, as described in patent applications WO2022162085 A, CN113410513 A, CN109638347 A, US 11258057 BB. Mechanosynthesis techniques require equipment, for example planetary mills, which cannot be extrapolated to an industrial scale.

[0005] Alternative preparation methods in solution have also been described. For example, the authors of ACS Energy Lett. 2019, 4, 265-270 describe the method for preparing lithium argyrodite (LiPSX) via the formation of an intermediate compound Li3PS4-2THF in a tetrahydrofuran THF solvent (24h at room temperature). ambient) and then adding a solution comprising LiX (I, Br and Cl) and Li2S in ethanol. After stirring overnight, the solution is evaporated under reduced pressure and then dried under reduced pressure at 140°C for 20 hours. Finally, the powder is densified by pressing and annealed at 550°C / 6 hours under reduced pressure.

[0006] Other patents and patent applications describe the preparation of argyrodites via reaction of Li2S, P2S5 and LiX in a polar solvent at room temperature (US10777846 BB; US20210242493 A1, CN114455613 A, US10777846 BB). The solvents may be, for example, alcohols, carbonates, esters, ethers, nitriles or mixtures. After evaporation under reduced pressure of the solvent (25-50°C for 1 to 3 hours), a powder is recovered and preferably dried under reduced pressure (several drying sequences may be used). This is then heat treated between 350°C and 550°C for 1 to 5 hours.

[0007] Other methods of preparation in solution have been developed to attempt to accelerate the reaction kinetics, in particular by varying the operating conditions, such as temperature, pressure, stirring method and solvent combination, see in particular patent application WO2021 / 099625 which proposes cooling to -80°C, or patent US 10879559 which combines two solvents: a polar solvent and a saturated or unsaturated hydrocarbon. Summary of the invention

[0008] Surprisingly, the Applicant discovered that it was possible to prepare lithium argyrodite particles in solution according to a particular method not involving expensive equipment or steps, with short reaction times, therefore extrapolable to the industrial scale.

[0009] The invention relates to a method for synthesizing lithium argyrodite particles of formula Li7_(a+b)PS6-(a+b+c)OcXaQb with X and Q two distinct halogenated elements chosen from F, Cl, Br, I; O the oxygen atom, with l <a+b<2, c compris entre 0 et 0,25, bornes incluses, a et b n’étant pas simultanément nuis, à partir d’un réactif lithium Li2Sx avec x compris entre 1 et 8, un réactif phosphore Rp choisi parmi P2S5, P4S10, P4S9 et P4S9+n avec n compris entre 0 et 1, et un composé halogéné choisi parmi LiX et PSX3; et un éventuel réactif oxygéné phosphoré ou halogéné choisi parmi P2O5 LiC104, LiBrO4, LiIO4comprenant au moins les étapes suivantes sous atmosphère inerte : A) Contacting the lithium reagent and the halogenated compound and the optional halogenated oxygenated reagent, previously suspended in at least one first polar solvent (solvent 1), with a suspension containing at least the phosphorus reagent and the optional phosphorus oxygenated reagent in at least one second polar solvent (solvent 2, of identical or different nature) at a temperature between 50 and 150°C and formation in suspension under reflux of an intermediate compound in the form of a solvato-complex Li3PS4-solvent in mixture with the other solid reagents Li2 Sx and LiX and the possible oxygenated reagent, the volume ratio solvent 1 / solvent 2 being between 1 and 4, preferably between 0.5 and 1.5, the relative proportions of the different reagents being chosen stoichiometrically with respect to the formula Li7_(a+b)PS6-(a+b+c)OcXaQb of the final compound in the form of lithium argyrodite particles; B) Centrifugation, redispersion of the centrifuged phase in a third anhydrous solvent, of the same or different nature as that of said first and second solvents, then filtration and washing of said intermediate compound; C) Drying at a temperature between 25°C and 150°C for a period of between 1 hour and 10 hours. D) Heat treatment at a temperature between 300 and 600°C and a duration between 1 and 10 hours.

[0010] According to a first embodiment, in step A):

[0011] Al) the lithium reagent Li2Sx, preferably Li2, can be dispersed under stirring. S, the halogenated compound (LiX or PSX3, preferably LiX) and the optional halogenated oxygenated reagent in a first polar solvent (solvent 1) at a mass concentration of lithium reagent Li2Sx in the solvent of between 10 g / L and 100 g / L, preferably between 30 g / L and 70 g / l and a mass concentration of halogenated compound LiX or PSX3 in the solvent of between 1 g / L and 100 g / L, preferably between 5 g / L and 80 g / L, and a mass concentration of halogenated oxygenated reagent of between 0.1 and 10 g / L, and the suspension obtained can be heated between 25°C and 50°C, preferably between 30°C and 40°C;

[0012] A2) then the phosphorus reagent Rp can be dispersed under stirring in a second polar solvent (solvent 2), at a mass concentration of phosphorus reagent in the solvent of between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L, the suspension obtained being heated between 50°C and 150°C, preferably between 90°C and 110°C;

[0013] A3) the lithium reagent solution and compound can be gradually added halogenated, preferably Li2S and LiX, in the suspension of phosphorus reagent, preferably P2S5, activated at temperature for a period of between 1 min and 6 min, preferably between 2 and 4 min and the resulting suspension is kept stirring at reflux for a period of between 1 and 24 hours, preferably between 2 and 8 hours under an inert atmosphere.

[0014] In a second embodiment, in step A): Al) a first part of the lithium reagent Li2Sx, preferably Li2S, and the phosphorus reagent, preferably P2S5>, can be dispersed under stirring in a first polar solvent (solvent 1) at a mass concentration of lithium reagent (preferably Li2 S) in the solvent of between 3 g / L and 30 g / L, preferably between 5 g / L and 20 g / l and a mass concentration of phosphorus reagent (preferably P2S5) in the solvent of between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L, and the suspension obtained can be heated between 25°C and 50°C, preferably between 30°C and 40°C, to form a solution; A2) a second part of the lithium reagent Li2Sx and the halogenated compound LiX or PSX3 can be dispersed with stirring in a second polar solvent (solvent 2) at a mass concentration of lithium reagent Li2Sx in the solvent of between 10 g / L and 80 g / L, preferably between 5 g / L and 70 g / L and a mass concentration of halogenated compound LiX or PSX3 of between 1 g / L and 100 g / L, preferably between 5 g / L and 80 g / L and the suspension obtained can be heated between 50°C and 150°C, preferably between 90°C and 110°C; A3) then the solution of lithium reagent and phosphorus reagent (preferably Li2S and P2S5) can be gradually added to the suspension of lithium reagent and halogenated compound (preferably Li2S + LiX), for a period of between 1 min and 6 min, preferably between 2 and 4 min and the resulting suspension can be kept stirring at reflux for a period of between 1 and 24 h, preferably between 2 and 8 h under an inert atmosphere.

[0015] Said intermediate compound in the form of a solvato-complex can be recovered in the form of a wet powder by centrifugation at a speed of between 1000 and 10,000 rpm for a period of between 5 and 30 min, redispersion in a third anhydrous solvent, then washing on a frit with an identical or different anhydrous solvent.

[0016] The drying of step C) can be carried out under reduced pressure of between 102 and 103 mbar at a temperature of between 40°C and 80°C for a period of between 2 h and 6 h.

[0017] The drying of step C) can be followed by a step D) of heat treatment carried out in a crossed bed reactor under a flow of inert gas or under reduced pressure of between 102 and 103 mbar.

[0018] The inert gas may be argon or nitrogen or a mixture of the two and the gas flow rate may be between 1 L / g / h and 15 L / g / h, preferably between 8 and 12 L / h / g.

[0019] The Li2Sx reagent can be pretreated before suspension by mechanical grinding in a dry process or in solution, by dissolution-precipitation in a solvent.

[0020] The polar solvent, whether the first solvent (solvent 1) or the second solvent (solvent 2), can be chosen from cyclic or linear ethers, esters, nitriles, alcohols, thiols.

[0021] The synthesis process according to the invention in which X=C1, a =1, b=0, c=0 makes it possible to obtain an argyrodite phase Li6PS5Cl.

[0022] The synthesis process according to the invention in which X=C1, a =1.5, b=0, c=0 makes it possible to obtain an argyrodite phase Li5j5PS4,5Clij5.

[0023] The synthesis process according to the invention in which X=C1 Q=Br, a =0.5, b=0.5, c=0 makes it possible to obtain an argyrodite phase LigPSsClo.sBro^. List of figures [Fig 1]

[0024] [Fig.l] represents a block diagram of the synthesis steps according to the invention. [Fig 2]

[0025] [Fig.2] represents the Raman spectrum of the Li6PS5Cl phase obtained in example 1. [Fig 3]

[0026] [Fig.3] represents the diffractogram of the Li6PS5Cl phase obtained in example 1. [Fig 4]

[0027] [Fig.4] represents the SEM image of the Li6PS5Cl particles obtained in example 1. Description of the embodiments

[0028] The present invention relates to a new method for preparing argyrodite phases of formula Li7_(a+b)PS6-(a+b+C)OcXaQb with X and Q two distinct halogenated elements chosen from F, Cl, Br, I; O the oxygen atom, with l <a+b<2, c compris entre 0 et 0,25, bornes incluses, a b n’étant pas simultanément nuis, ladite méthode de synthèse permettant des temps réaction courts la possibilité d’être extrapolée à échelle industrielle.

[0029] When c=0 the argyrodite phase is of formula Li7 (.,+bJPS6 (.,+bJ XaQb Reagents#

[0030] The reagents used in the process for synthesizing argyrodites according to the invention are as follows.

[0031] For the lithium reagent, the reagents are preferably Li2S, Li2Sx with x between 2 and 8. Throughout the description, for the sake of simplification, the lithium reagent is designated by Li2Sx with x between 1 and 8.

[0032] For the phosphorus reagent, the reagents are preferably P2S5, P4Si0, P4S9 and P4S 9+n with n between 0 and 1.

[0033] For the phosphorus oxygenated reagent, the reagent is preferably P2O5.

[0034] For the halogenated compound type reagent, the reagents are preferably LiX with X= F, Cl, Br and I and / or PSX3 with X= F, Cl, Br and I.

[0035] For the halogenated oxygenated reagent, the reagents are preferably LiClO4, LiBrO4 and LiIO4.

[0036] All the preparation methods for obtaining the reagents described in the present application are suitable for the method of preparing the argyrodite phases according to the invention.

[0037] Advantageously, the Li2Sx reagent can be pretreated.

[0038] In the case of Li2S, the pre-treatment may be mechanical (planetary) grinding in a dry or solution process or dissolution-precipitation in ethanol, or any other method known to those skilled in the art.

[0039] Polar solvents are used for the dispersion and / or activation of the reagents. Advantageously, one or more solvents may be used in combination for the dispersion and activation of the reagents, in particular: - for the dispersion of the lithium reagent and the halogenated compound, preferably Li2S and LiX (solvent 1): cyclic or linear ethers (e.g. THF and dimethoxyethane (DME)), esters (alkyl acetate, for example: butyl acetate), nitriles (e.g. acetonitrile), alcohols (e.g. methanol), thiols (e.g. propanethiol). - for the activation of the phosphorus reagent, e.g. P2S5 (Solvent 2): cyclic or linear ethers (e.g. THF and dimethoxyethane), esters (alkyl acetate, e.g. butyl acetate; isobutylisobutyrate, dimethyl glutarate, diethyl glutarate), nitriles (e.g. acetonitrile), alcohols (e.g. methanol), thiols (e.g. propanethiol).

[0040] All solvents are anhydrous.

[0041] The preparation method comprises at least four steps. All manipulations are carried out under an inert atmosphere. • A step of formation in suspension under reflux of the intermediate compound Li3PS4-solvent (solvato-complex) in the presence of other solid reagents (for example Li2S and LiX). • A washing step by centrifugation and filtration • A drying step preferably under reduced pressure • A heat treatment step,

[0042] The relative proportions of the different reagents are chosen by a person skilled in the art in a stoichiometric manner, depending on the formula of the final argyrodite compound targeted. Advantageously, for each reagent:

[0043] the mass concentration of Li2Sx in the solvent can be between 30 g / L and 70 g / L,

[0044] the mass concentration of the phosphorus reagent, for example P2S5 in the solvent can be between 35 g / L and 70 g / L,

[0045] the mass concentration of LiCl in the solvent can be between 5 g / L and 30 g / L,

[0046] the mass concentration of LiBr in the solvent can be between 15 g / L and 55 g / L,

[0047] the mass concentration of Lil in the solvent can be between 30 g / L and 80 g / L,

[0048] the mass concentration of PSC13 in the solvent can be between 1 g / L and 20 g / L,

[0049] the mass concentration of LiClO4 in the solvent can be between 0.1 g / L and 5 g / L,

[0050] the mass concentration of LiBrO4 in the solvent can be between 0.1 g / L and 5 g / L,

[0051] the mass concentration of LiIO4 in the solvent can be between 0.5 g / L and 10 g / L,

[0052] the mass concentration of P2O5 in the solvent can be between 0.1 g / L and 5 g / L.

[0053] Without limitation, the method is described below for Li2S and LiX reagents, as well as P2S5.

[0054] First step: The first step can be done in two alternative ways.

[0055] [Fig. 1] above shows the different stages of formation of the compound of the argyrodite phase according to the first embodiment.

[0056] [Fig. 1] below shows the different stages of formation of the compound of the argyrodite phase according to a second embodiment.

[0057] The steps below are described with reference to [Fig.l].

[0058] Step 1: formation in suspension (reflux) of the intermediate compound

[0059] The synthesis method according to the invention makes it possible to overcome the kinetic limitation of the formation of the intermediate compound by activating the phosphorus reagent, for example P2S5. Indeed, this is in the form of an adamantate cage P4Si0, limiting the reaction with Li2S. The activation of the P2S5 reagent consists of heating the adamantate cage to dedimerize it. In order to promote a rapid reaction, the lithium and halogenated compound reagents, here Li2S and LiX, previously suspended, are added hot to the suspension containing the phosphorus reagent P2S5. • Step 1.1

[0060] The first phase makes it possible to disperse the lithium reagent Li2S and the halogenated compound LiX in a first polar solvent (solvent 1), for example in a Schlenck type flask, to form a suspension. The dispersion is advantageously carried out in an ultrasonic bath between 25°C and 50°C, preferably between 30°C and 40°C for a period of between 1 min and 120 min, preferably between 10 and 50 min. The mass concentration of Li2S in the solvent is between 10 g / L and 100 g / L, preferably between 30 g / L and 70 g / L. The mass concentration of LiX is between 1 g / and 100 g / L, preferably between 5 g / L and 35 g / L when X= Cl, preferably between 10 g / L and 60 g / L when X= Br and preferably between 20 g / L and 80 g / L when X= I. • Step 1.2

[0061] The second phase makes it possible to disperse the P2S5 reagent in a second polar solvent (solvent 2, which may be of the same nature as solvent 1) in a three-necked flask equipped with a water cooler. The suspension is heated between 50°C and 150°C, preferably between 90°C and 110°C with stirring. The mass concentration of P2S5 in the solvent is between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L. • Step 1.3

[0062] The suspension of Li2S + LiX is advantageously transferred into a device allowing the gradual addition of activated P2S5 into the suspension, for example a dropping funnel, to be added drop by drop into the temperature-activated P2S5 suspension. The time for adding the suspension is between 1 min and 6 min, preferably between 2 and 4 min.

[0063] The resulting suspension is maintained at reflux at a temperature between 50 and 150°C (preferably at 100°C) for a time between 1 and 24 hours, preferably between 2 and 8 hours, under an inert atmosphere. The inert atmosphere may be dynamic (constant flow) or static and the nature of the gas may be argon or nitrogen or a mixture of the two. The molar ratio Li2S / P2S5 is between 3 and 6, preferably between 4 and 5. The molar ratio LiX / P2S5 is between 0.5 and 3.5, preferably between 1 and 3. The volume ratio solvent 1 / solvent 2 is between 0.1 and 4, preferably between 0.5 and 1.5.

[0064] According to the second embodiment of step 1, which is described with reference to [Fig.l] below, as an example for reagents Li2S and LiX, as well as P2S5: • Alternative step 1.1

[0065] The first sub-step makes it possible to disperse a first part of the lithium reagent Li2 S and the phosphorus reagent P2S5 in a first polar solvent, preferably aprotic (solvent 1), for example in a Schlenck type flask, to form a solution. The mass concentration of Li2S in the solvent is between 3 g / L and 30 g / L, preferably between 5 g / L and 20 g / L. The mass concentration of P2S5 in the solvent is between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L. • Alternative step 1.2

[0066] The second sub-step makes it possible to disperse a second part of the lithium reagent Li2S and the halogenated compound LiX in a second polar solvent (solvent 2, which may be of the same nature as solvent 1), for example in a three-necked flask equipped with a water cooler, to form a suspension. The suspension is heated between 50°C and 150°C, preferably between 90°C and 110°C, with stirring. The mass concentration of Li2S in the solvent is between 10 g / L and 80 g / L, preferably between 20 g / L and 70 g / L. The mass concentration of LiX is between 1 g / L and 100 g / L, preferably 5 g / L and 35 g / L when X= Cl, preferably between 10 g / L and 60 g / L when X= Br, and preferably between 20 g / L and 80 g / L when X= I. • Alternative step 1.3

[0067] Finally, the solution of Li2S and P2S5 is advantageously transferred into a device allowing the gradual addition of Li2S and LiX into the suspension, for example in a dropping funnel, to be added dropwise into the suspension of Li2S + LiX. The time for adding the solution of Li2S and P2S5 is between 1 min and 6 min, preferably between 2 and 4 min. The resulting suspension is maintained at reflux at a temperature between 50 and 150°C (preferably 100°C) for a time between 1 and 24 h, preferably between 2 and 8 h under an inert atmosphere. The inert atmosphere can be dynamic (constant flow) or static and the nature of the gas can be argon or nitrogen or a mixture of the two. The molar ratio Li2S / P2S5 is between 3 and 6, preferably between 4 and 5. The molar ratio LiX / P2S5 is between 0.5 and 3.5, preferably between 1 and 3.The solvent 1 / solvent 2 volume ratio is between 0.1 and 4, preferably between 0.5 and 1.5.

[0068] Step 2: washing of the intermediate compound (solvato-complex)

[0069] At the end of the reaction, the intermediate compound, which is a mixture of a solvato-complex Li3PS4-solvent with the other solid reagents Li2Sx and LiX and the optional oxygenated reagent, is in the form of a suspension in the mixture of solvents. Said intermediate compound is recovered by centrifugation, advantageously at a speed of between 1000 and 10000 rpm for a duration of between 5 and 30 min (here 10000 rpm for 20 min) and redispersed in a third anhydrous solvent (of the same nature as previously or different) before being washed, advantageously on a frit with an identical or different anhydrous solvent, to obtain a wet powder. Step 3#: Drying

[0070] The powder obtained is dried, preferably under reduced pressure (typically between 102 and 103 mbar), at a temperature between 25°C and 150°C, preferably between 40°C and 80°C for a period of 1 h to 10 h, preferably between 2 h and 6 h. Step 4#: Heat treatment

[0071] A heat treatment is carried out, preferably in a crossed bed reactor under inert gas flow or under reduced pressure (typically between 102 and 103 mbar). The nature of the inert gas can be argon or nitrogen or a mixture of the two. The gas flow rate is between 1 L / g / h and 15 L / g / h, preferably between 8 and 12 L / h / g. This configuration allows efficient removal of the solvent. The treatment temperature is advantageously between 300°C and 600°C for a duration of between 1 hour and 10 hours. The treatment conditions depend on the nature of the phase to be treated. Characterization techniques

[0072] The SEM images are taken with a scanning electron microscope (SEM) (Supra 40 model sold by Zeiss®). The acceleration voltage is 2kV.

[0073] RAMAN analysis is useful for determining the phases present by observing, in particular, the RAMAN absorption wavelengths of the PS43 tetrahedra, which are at the origin of the good ionic conductivity of the thiophosphates. The acquisition of the Raman spectra is carried out on a Renishaw spectrometer equipped with a confocal lens and a 532 nm laser. The sample is previously conditioned in sealed cells. The spectra were acquired with the following parameters: power 3.9 mW and time 100 s.

[0074] DRX analysis allows to control the obtaining of the characteristic crystalline structure of argyrodites. The acquisition of the diffractograms is carried out on a D4 Brucker diffractometer (40 kV, 40 mA) with a copper anode (Kal = 1.54060 Å; Ka2 = 1.54439 Å). The sample is previously conditioned between two Kapton sheets sealed with vacuum grease.

[0075] The ionic conductivity of the samples is measured by electrochemical impedance spectroscopy between two blocking electrodes in a thermostated cell (ASC-T model sold by Sphere Energy®). The solid electrolyte is directly densified to 4 ton / cm2 between the two electrodes. The impedance measurement is carried out with a Biologie® MTZ-35 impedance meter between 30 MHz and 1 Hz with an amplitude of 10 mV relative to a voltage of 0 V and a temperature of 30 °C. Examples

[0076] Example 1: Preparation of the Li6PS5Cl phase according to the invention

[0077] In a Schlenck tube, 0.45 g of Li2S and 2.17 g of P2S5 are dispersed in 50 mL of tetrahydrofuran THF. The tube is then placed under ultrasound for 30 min at 35°C and then the resulting solution is transferred into a dropping funnel. In a three-necked flask, 1.70 g of Li2S and 0.85 g of LiCl are weighed and dispersed in 50 mL of butyl acetate BA. The suspension of Li2S and LiCl is heated to 100°C in a reflux assembly. The solution of Li2S and P2S5 is then added dropwise over 3 min to the solution of Li2S and LiCl. After stirring for 4 hours at a temperature maintained at 100°C, the flask is allowed to cool to room temperature. The suspension is then centrifuged at 10,000 rpm for 20 min. The precipitate is redispersed in tetrahydrofuran (THF) before being washed on a frit with THF, resulting in a wet white powder. This is then dried under reduced pressure at 50°C for 5 h.The powder obtained is then annealed at 550°C for 4 h under an argon flow rate of 10 L / h / g.

[0078] The obtained powder is characterized by Raman spectroscopy ([Fig.2]), X-ray diffraction ([Fig.3]), scanning electron microscopy ([Fig.4]) and impedance spectroscopy. [Fig.2] shows the Raman spectrum of the obtained phase with the vibration peak at 424 cm 1 characteristic of the PS43 units of the Li6PS5Cl phase. [Fig.3] confirms that the crystalline structure of the obtained phase corresponds mainly to Li6PS5 Cl. [Fig.4] shows the Li6PS5Cl particles obtained before heat treatment. The measured ionic conductivity is 2.94 xlO 4S / cm at 30°C.

Claims

1. Claims Process for the synthesis of lithium argyrodite particles of formula Li7 Ia+b)PS6 (.l+b +c )OcXaQb with X and Q two distinct halogenated elements chosen from F, Cl, Br, I; O the oxygen atom, with l ​A. Contacting the lithium reagent and the halogenated compound and the optional halogenated oxygenated reagent, previously suspended in at least one first polar solvent (solvent 1), with a suspension containing at least the phosphorus reagent and the optional phosphorus oxygenated reagent in at least one second polar solvent (solvent 2), of identical or different nature at a temperature between 50 and 150°C and formation in suspension under reflux of an intermediate compound in the form of a solvato-complex Li3PS4-solvent in mixture with the other solid reagents Li2Sx and LiX and the optional oxygenated reagent, the volume ratio solvent 1 / solvent 2 being between 0.1 and 4, preferably between 0.5 and 1.5, the relative proportions of the different reagents being chosen stoichiometrically with respect to the formula Li- (.,+bJPS6 +b+c)OcXaQb of the final compound in the form of lithium argyrodite particles; B. Centrifugation, redispersion of the centrifuged phase in a third anhydrous solvent, of the same or different nature as that of said first and second solvents, then filtration and washing of said intermediate compound; C. Drying preferably under reduced pressure, at a temperature between 25°C and 150°C for a period of between 1 hour and 10 hours. D. Heat treatment at a temperature between 300 and 600°C and a duration between 1 and 10 hours.

2. Process for the synthesis of argyrodite particles according to claim 1, wherein in step A): Al) the lithium reagent Li2Sx, preferably Li2S, the halogenated compound LiX or PSX3, preferably LiX, and the optional halogenated oxygenated reagent are dispersed with stirring in a first polar solvent (solvent 1) at a mass concentration of lithium reagent Li2Sx in the solvent of between 10 g / L and 100 g / L, preferably between 30 g / L and 70 g / L and a mass concentration of halogenated compound LiX or PSX3 in the solvent of between 1 g / L and 100 g / L, preferably between 5 g / L and 80 g / L, and a mass concentration of halogenated oxygenated reagent of between 0.1 and 10 g / L, and the suspension obtained is heated between 25°C and 50°C, preferably between 30°C and 40°C;A2) then the phosphorus reagent Rp is dispersed with stirring in a second polar solvent (solvent 2), at a mass concentration of phosphorus reagent in the solvent of between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L, the suspension obtained being heated between 50°C and 150°C, preferably between 90°C and 110°C; A3) the solution of lithium reagent and halogenated compound, preferably Li2S and LiX, is gradually added to the suspension of phosphorus reagent, preferably P2S5, activated at temperature for a period of between 1 min and 6 min, preferably between 2 and 4 min and the resulting suspension is kept stirring at reflux for a period of between 1 and 24 h, preferably between 2 and 8 h under an inert atmosphere.;

3. Process for the synthesis of argyrodite particles according to claim 1, wherein in step A): Al) a first part of the lithium reagent Li2Sx, preferably Li2S, and the phosphorus reagent, preferably P2S5, are dispersed with stirring in a first polar solvent (solvent 1) at a mass concentration of lithium reagent, preferably Li2S, in the solvent of between 3 g / L and 30 g / L, preferably between 5 g / L and 20 g / L and a mass concentration of reagent phosphorus, preferably P2S5, in the solvent between 10 g / L and 100 g / L, preferably between 30 g / L and 80 g / L, even more preferably between 35 g / L and 70 g / L, and the suspension obtained is heated between 25°C and 50°C, preferably between 30°C and 40°C, to form a solution; A2) a second part of the lithium reagent Li2Sx and the halogenated compound LiX or PSX3 are dispersed with stirring in a second polar solvent (solvent 2) at a mass concentration of lithium reagent Li2Sx in the solvent of between 10 g / L and 80 g / L, preferably between 5 g / L and 70 g / L and a mass concentration of halogenated compound LiX or PSX3 of between 1 g / L and 100 g / L, preferably between 5 g / L and 80 g / L and the suspension obtained is heated between 50°C and 150°C, preferably between 90°C and 110°C;A3) then the solution of lithium reagent and phosphorus reagent, preferably Li2S and P2S5, is gradually added to the suspension of lithium reagent and halogenated compound, preferably Li2S + LiX, for a period of between 1 min and 6 min, preferably between 2 and 4 min, and the resulting suspension is kept stirring at reflux for a period of between 1 and 24 h, preferably between 2 and 8 h, under an inert atmosphere.;

4. Synthesis process according to one of claims 1 to 3, in which said intermediate compound in solvato-complex form is recovered in the form of wet powder by centrifugation at a speed of between 1000 and 10,000 rpm for a period of between 5 and 30 min, redispersion in an anhydrous solvent, then washing on a frit with an identical or different anhydrous solvent.

5. Synthesis process according to any one of claims 1 to 4, in which the drying of step C) is carried out under reduced pressure of between 102 and 103 mbar at a temperature of between 40°C and 80°C for a duration of between 2 h and 6 h.

6. Synthesis process according to one of claims 1 to 5, in which the drying of step C) is followed by a step D) of heat treatment carried out in a crossed-bed reactor under a flow of inert gas or under reduced pressure of between 102 and 103 mbar.

7. A synthesis method according to claim 6, wherein the inert gas is argon or nitrogen or a mixture of both, and the flow rate gas is between 1 L / g / h and 15 L / g / h, preferably between 8 and 12 L / h / g.

8. Synthesis process according to one of the preceding claims, in which the Li2Sx reagent is pretreated before suspension by mechanical grinding in a dry process or in solution, by dissolution-precipitation in a solvent.

9. Synthesis process according to one of the preceding claims, in which the polar solvent, whether the first solvent (solvent 1) or the second solvent (solvent 2), is chosen from cyclic or linear ethers, esters, nitriles, alcohols, thiols.

10. Synthesis process according to one of claims 1 to 9, in which X=C1, a =1, b=0, c=0 and an argyrodite phase Li6PS5Cl is obtained.

11. Synthesis process according to one of claims 1 to 9, in which X=C1, a =1.5, b=0, c=0 and an argyrodite phase Li5>5PS4.5Cl is obtained.

12. 1.5- Synthesis process according to one of claims 1 to 9, in which X=C1 Q=Br, a =0.5, b=0.5, c=0 and an argyrodite phase Li gPSsClo^Bro^ is obtained.

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