WO2025079070A1

WO2025079070A1 - Preparation of lithium bromide and li-argyrodite

Info

Publication number: WO2025079070A1
Application number: PCT/IL2024/050987
Authority: WO
Inventors: Ran Elazari; Mohamad Masarwa; Igor KOMPANIETS; Yishay Diamant; Elizabeta SHANDALOV
Original assignee: Bromine Compounds Ltd
Current assignee: Bromine Compounds Ltd
Priority date: 2023-10-11
Filing date: 2024-10-09
Publication date: 2025-04-17
Anticipated expiration: 2026-04-11

Abstract

The invention provides a process for preparing anhydrous lithium bromide, comprising the steps of converting an aqueous suspension of lithium carbonate with hydrobromic acid into a solution of lithium bromide; removing residual carbon dioxide from the solution by gas-stripping, wherein the solution has acidic pH; neutrali zing the acidic lithium bromide solution by addition of lithium hydroxide to form lithium bromide brine with a nearly neutral pH; and recovering anhydrous lithium bromide from the brine. The so- formed anhydrous lithium bromide is used as a starting material in the mechanochemical synthesis of bromide-containing Li-argyrodite, which is useful in the fabrication of all-solid-state battery.

Description

Preparation of lithium bromide and Li-argyrodite

Background of the invention

There is a growing demand for lithium-ion containing compounds, as starting materials for lithium-ion battery technologies and other energy related fields. Lithium bromide (LiBr) is one of them and it has a significant role in the synthesis of Li-ion conductor/solid electrolytes used in the battery industry.

One important solid electrolyte that can serve in all-solid- state Li-ion batteries is Li-argyrodite with the formula of

Li₆PS₅Br. It can be prepared by stepwise ball-milling, followed by a solid-state sintering method (e.g., ball milling of a powder blend consisting of Li2S, P2S5 and LiBr, to obtain a uniform precursor powder blend, followed by thermal treatment (e.g., at ~500°C, heating rate 3°/min, in continuous Argon flow) ) to produce the Li-argyrodite (Li₆PS₅Br) in a pure crystalline form. However, the conditions of the synthesis process strongly influence the properties of Li-argyrodite (Li₆PS₅Br) solid electrolytes (See A. Gautam, M. Sadowski, N. Prinz, H. Eickhoff, N. Minafra, M. Ghidiu, S. P. Culver, K. Able, T. F. Fassler, M. Zobel, W. G. Aeier Chem. Mater. 2019, 31, 10178) .

Lithium bromide usually exists in anhydrous (LiBr) and hydrated forms, e.g., as a monohydrate (LiBr-H2O) . Only the anhydrous form can be used in the synthesis of Li₆PS₅Br. Lithium bromide is prepared industrially by neutralizing lithium carbonate or lithium hydroxide with hydrobromic acid, i.e., in water. But the recovery of the anhydrous LiBr from an aqueous solution is not straightforward: concentrating the lithium bromide aqueous solution by evaporation followed by filtration of the precipitated salt yields the hydrated form. Dehydration of the monohydrate to produce the anhydrous form is difficult to achieve, as the monohydrate does not release its water molecule easily .

There are a few reports on the preparation of high purity anhydrous lithium bromide. Synthesis of alkali metal halides in the form of very fine particulates is described in US 3,839,546, by the reaction of in-situ prepared alkali metal alkoxide and dry hydrogen halide gas. Efforts to obtain high purity lithium bromides from a suspension of lithium carbonate in water were also reported in old Soviet patents SU 929557 and SU 1038282. But in the Soviet patents, instead of feeding hydrobromic acid prepared beforehand to a suspension of lithium carbonate, the hydrobromic acid was produced in situ by reducing elemental bromine with, e.g., ammonia. Eventually lithium bromide was collected by evaporating the solution at 170 °C. Purity level of 99.5 wt . % was reported. US 6,582,832 is about a method of producing highly pure lithium salts suitable for use in lithium secondary cells, but only synthesis of lithium fluoride was exemplified. JP 2016-175786 shows that the average particle size of lithium bromide could be lowered down to <50 μm without using milling or similar pulverization methods, but rather by dissolution of the anhydrous lithium bromide in an organic solvent and recrystallization with the aid of an antisolvent. Preparation of lithium bromide by contacting lithium carbonate with hydrogen bromide gas (>200°C) was shown in WO 2024/038429. Anhydrous lithium bromide grades of >99% or > 99.5% purity are available in the marketplace from a few manufacturers.

The invention

We introduced some modifications into the synthesis of anhydrous lithium bromide from lithium carbonate and hydrobromic acid, i.e., the synthesis shown by reaction equation (1) :

Li₂CO₃ + 2HBr 2LiBr + CO₂ + H₂O (1) The X-ray powder diffraction pattern of the anhydrous lithium bromide prepared by our modified synthesis method indicates a high crystalline phase purity with only a trace amount of the monohydrate present. Data shown below further indicates that the as-formed anhydrous lithium bromide possesses a reduced particle size distribution as compared to commercially available s amp les.

We have found that the resultant anhydrous lithium bromide is well suited as a starting material in the solid-state synthesis of bromine-containing Li-argyrodite, e.g., Li₆PS₅Br (or a mixed bromide/halide Li-argyrodite, e.g., Li₆PS₅BrxCli-x) . For

Li₆PS₅Br, the reaction equation is the following:

5Li₂S + P2S5 + 2LiBr 2Li₆PS₅Br (2)

It appears that the Li₆PS₅Br formed by the solid-state synthesis method is influenced by the lithium bromide starting material. For example, it is not uncommon for solid state formation reactions of Li₆PS₅Br to afford an impure product with a remnant of unreacted starting materials (Li₂S, P₂Ss and LiBr) . But X-ray powder diffraction patterns of Li₆PS₅Br that was prepared with the aid of our modified anhydrous lithium bromide did not show any significant peaks assigned to the starting materials, indicating that the reaction had essentially gone to completion to give Li₆PS₅Br in a highly pure form. The Li₆PS₅Br obtained by the solid-state reaction possesses acceptable room temperature ionic conductivity, e.g., around 2 x 10^-3 S/cm (at 35°C, the ionic conductivity of Li₆PS₅Br was about 3.7 x 10^-3 S/cm) . When the Li₆PS₅Br is used as a solid electrolyte, the assembled solid- state batteries show good electrochemical performance, i.e., good discharge behavior, especially when the batteries operated at a relatively low stack pressure (e.g., ~150 MPa) . For example, in the experimental work reported below, a cell consisting of a solid electrolyte Li₆PS₅Br layer interposed between a cathode based on LiNi_xMn_yCo_zO₂ (NMC811) and lithium anode was tested (labeled LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li-In (x + y + z = 1) ) and was shown to give good results; Li-In means lithium metal pressed against indium mesh.

Accordingly, a first aspect of the invention is a process of preparing anhydrous lithium bromide, comprising the steps of: converting an aqueous suspension of lithium carbonate with hydrobromic acid into a solution of lithium bromide; removing residual carbon dioxide from the solution by gas- stripping, wherein the solution has acidic pH; neutralizing the acidic lithium bromide solution by addition of lithium hydroxide to form lithium bromide brine with a nearly neutral pH; and recovering anhydrous lithium bromide from the brine.

Another aspect of the invention is a mechanochemical process of preparing bromide-containing Li-argyrodite, such as Li₆PS₅Br or LisPSsClyBri-y (e.g., 0.1<y<0.9) , comprising mechanical milling of Li2S, P2S5 and anhydrous LiBr powders (and optionally, a second lithium halide powder) to obtain a milled phase and annealing the milled phase to afford an essentially pure bromide-containing Li-argyrodite, wherein the anhydrous LiBr used as a starting material is characterized in that:

A) it consists of a powder possessing a particle size distribution (determined by laser diffraction particle size analysis, e.g., with Malvern, Mastersizer 3000) showing: D10 15 μm, e.g., 5 < D10 10 μm;

D50 30 μm, e.g., 15 < D50 25 μm; and

D90 d 100 μm, e.g., 25 < D90 d 75 μm or 30 < D90 d 50 μm; and a BET specific surface area of not less than 0.7 m²/g, e.g., from 0.75 to 1.0 m²/g, e.g., from 0.8 to 0.9 m²/g (determined e.g., with Quantochrome Instrument) ; and/or

B) it consists of a powder that was recovered from a neutral or nearly neutral lithium, bromide solution that was formed by reaction of lithium carbonate with hydrobromic acid, during which reaction residual carbon dioxide was expelled from an acidic lithium bromide solution, followed by neutralizing the acidic lithium bromide solution with the aid of lithium hydroxide, wherein the powder is preferably a spray-dried powder .

The starting materials for the lithium bromide formation reaction (hydrobromic acid and lithium carbonate) are preferably of high purity.

Commercial hydrobromic acid with the desired strength (~48-49 wt . % HBr) and purity is available from various manufacturers, for example, I CL- IP [https : //www. icl-ip. com/product/hbr/ ], with a density of not less than 1.488 g/ml (at 20°C) , free bromine of less than 10 pμm and free chlorides of less than 100 pμm .

HBr can be made by several methods described in, e . g. , http : //www. weizmann. ac. il/sci-tea/Brombook/pdf/ chapter5.pdf and US 10, 626, 015 ( in the latter, by a reaction of elemental bromine with sulfur dioxide in water, to form HBr and H2SO4, separation by distillation of the HBr/water azeotropic mixture and eventually the recovery of 48 wt . % HBr with very low concentrations of sulfate and chloride) .

Battery-grade lithium carbonate suitable for use in the invention is available on the marketplace, e . g. , with £99.0%,

£99.3%, £99.5%, £99.8% purity from manufacturers such as

Albemarle Corporation ( formerly Rockwood Lithium) . Technical grade lithium carbonate can be treated to reach an acceptable purity level to qualify as battery-grade lithium carbonate by the method described in US 6, 592, 832 (bubbling CO2 through Li2COa suspension, to convert L12CO3 into a water soluble lithium bicarbonate, filtering the lithium bicarbonate solution, passing the filtrate through an ion-exchange resin to remove metal impurities, decomposing the lithium bicarbonate under heating to precipitate L12CO3 and collecting L12CO3 with a high purity) ; or by the method described by Xu et al. in Metals 2021, 11, 1490 (where, instead of passing the lithium bicarbonate - containing filtrate through an ion-exchange resin, the solution is evaporated to crystallize lithium carbonate followed by air- stream pulverization) ; or by the method shown in US 6,048,507.

High purity hydrobromic acid and lithium carbonate are combined in a reaction vessel. The order of addition is not critical, e.g., either lithium carbonate (e.g., as a solid, or suspended in water) is slowly added to a reaction vessel that was previously charged with ~48% HBr solution, or vice versa, ~48% HBr solution is slowly introduced into a reaction vessel that was previously charged with a suspension of lithium carbonate in water. Hydrobromic acid of a lower strength is workable but is less desired because the recovery of the product requires evaporation of water/drying the solution; the lower the volume of hydrobromic acid supplied to the reaction, the more efficient the evaporation/drying step (e.g., reduced energy requirements) .

The rate of feeding of the last-added reactant to the reactor is adjusted to control the foaming that occurs due to carbon dioxide evolution. Yet, it was observed that foaming is not a significant problem when a reactor with a sufficiently large capacity is used, such that about 50 to 70% of the volume of the reactor (e.g., a stirred batch reactor) is filled with the added reactants. The rate of adding the HBr solution (or L12CO3) should match the capability of the reactor to remove the evolved CO₂. Residual CO2, which was not expelled from the reactor, remains dissolved in the resultant lithium bromide. The removal of the residual CO2 from the solution, by way of gas-stripping, takes place in an acidic environment, created by the hydrobromic acid. When carbon dioxide dissolves in water, some of it reacts to form carbonic acid. A suitable acidic environment, e.g., a pH in the range from 1 to 3, shifts the equilibrium from the product (carbonic acid) to the reactants (CO2 and H2O) , enabling the removal of CO2 from the solution by a stream of inert gas that is passed through the reactor. The desired acidic environment can be generated by charging the reactor with hydrobromic acid, followed by addition of less than the equivalent amount of the lithium carbonate, say, from 80 to 98% of the equivalent amount, e.g., from 90 to 95%. After the conversion of the lithium carbonate to lithium bromide, the excess of unreacted hydrobromic acid present in the lithium bromide solution will set the pH in the desired acidic range. The same effect could be achieved by adding hydrobromic acid in a slight molar excess (say, 5 to 10 molar%) to a reactor that was previously charged with lithium carbonate suspension.

On an industrial scale, it may be more convenient to add alternate portions of lithium carbonate and hydrobromic acid to the reactor or employ a mixed order of addition. For example, to produce 100 kg of dry anhydrous lithium bromide, a reactor is charged with 15 to 25 kg of water (or an equal amount of lithium bromide solution from a previous run) , then ~ 48% hydrobromic acid (about 20 to 30% of the total, e.g., from 40 to 60 kg of ~48% HBr) , followed by an equivalent amount of lithium carbonate. When the evolution of CO2 ceases or only moderate foaming is observed, the remainder of lithium carbonate is added, e.g., from 70 to 80% of the total, forming a suspension with about 25 to 35% solid content based on the total weight of the reaction mixture. Next, ~48 % hydrobromic acid is added slowly under pH measurement control to reach the equivalent point and further lower the pH to create the fairly strong acidic environment needed to convert carbonate to CO2 and its removal by gas-stripping, e.g., by adjusting the pH in the range from 1 to 3.

Thus, the invention provides a process comprising charging a reactor with water (or lithium bromide solution from a previous run) , a portion of the hydrobromic acid and about (±10%) an equivalent amount of lithium carbonate, and when the evolution of CO2 ceases or only moderate foaming is observed, adding the remainder of lithium carbonate thereby forming a suspension, slowly adding hydrobromic acid under pH measurement control to reach the equivalent point, further lowering the pH to adjust the pH in the acidic range needed to convert carbonate to CO2 and its removal by gas-stripping.

Gas-stripping is performed by bubbling a gas, e.g., an inert gas such as nitrogen (air could also be used) through the lithium bromide solution, sweeping away the carbon dioxide. By way of example, for the production scale described above, nitrogen is injected into the reactor over about 10 to 60 minutes at a rate suitable to remove CO2, with the aid of a diffuser or a sparging unit installed at the bottom of the reactor below the level of the solution, through which the incoming nitrogen stream is passed and breaks up into bubbles, or by means of any other equivalent design that enables removal of dissolved carbon dioxide from the solution by injected nitrogen .

Next, lithium hydroxide is added to the CO2-free (or nearly free) acidic lithium bromide solution to react with and neutralize excess hydrobromic acid. Lithium hydroxide with an acceptable purity (>%99) is available, e.g., from Sigma- Aldrich. Because this is a titration reaction of a strong acid with a strong base, pH =7, i.e., neutrality is reached when an amount of lithium hydroxide has been added that is exactly equivalent to the amount of hydrogen bromide present. Deviation from neutral pH necessitates correction, by addition of either hydrobromic acid or lithium hydroxide. Still, some slight deviation is acceptable as it would not impair the final product, namely a slightly alkaline pH of 7-8.

The concentration of the lithium bromide solution obtained is usually from 20 to 50 wt.%, that is, a concentrated brine. The anhydrous salt is recovered from the brine, starting with filtration to remove insoluble impurities, followed by evaporation of the water to dryness and subjecting the solids to thermal drying, or by spray drying of the brine to obtain the anhydrous solid.

As pointed out above, concentration of the brine by partial evaporation to exceed the saturation limit and produce a slurry, and then separation of the crystals from the mother liquor by filtration or centrifugation, e.g., at room temperature, would yield the hydrate form of lithium bromide. It would still be possible to dehydrate the isolated crystals, e.g., by thermal- vacuum drying, to obtain the anhydrous form. However, such an approach is considered less efficient. Preferred methods of recovering anhydrous lithium bromide from the brine, are now described .

The brine is evaporated to dryness at a sufficiently high temperature to generate the anhydrous form, rather than lithium bromide monohydrate (or dihydrate) , e.g., by heating the brine to a temperature of not less than 120°C, preferably to a temperature from 140 to 180°C, under vacuum. A dry vacuum pump with a maximum vacuum capability of less than 5 millibars can be used, such as, for example, an Edwards dry vacuum pump.

A drying method that is suited to the isolation of anhydrous lithium bromide from the brine solution is spray drying. The brine solution - optionally preheated to a temperature of about 50 to 100 °C - is sprayed as fine droplets into a hot gas stream. The temperature of the incoming hot air stream is from 150 to 250°C. The outgoing air stream which exits the drier is at a temperature of 100 to 160 °C. The brine solution is injected into the drier through an atomizer nozzle at a flow rate adjusted to sustain the abovementioned temperature of the outgoing air stream, where the droplets are brought into contact with the hot air stream supplied at a flow rate adjusted to serve the same goal. The dry solid collected at the bottom of the drier is rapidly discharged from the solid outlet port of the drier, preferably under nitrogen blanket to minimize the contact with moisture in the air, which may result in wetting and/or rehydrating the powder and packed under proper storage conditions (exclusion of humidity) .

The crystalline anhydrous lithium bromide collected (i.e., a fresh sample, before storage and exposure to air moisture) is essentially free from the monohydrate impurity, as indicated by the X-ray powder diffraction pattern of the LiBr (CuKa radiation) , exhibiting strong peaks at 28.2°, 32.6° and 46.8° 20 (±0.2) , wherein the X-ray powder diffraction pattern is essentially devoid of peaks at positions 22.2° ,31.6° and 39.0 20 (±0.2) , assigned to the monohydrate.

The anhydrous lithium bromide of the invention is also free of the corresponding carbonate, i.e., with a carbonate content of not more than 100 pμm, e.g., not more than 60 pμm, e.g., <50 pμm, from 30 to 50 pμm (determined by acid-base titration with hydrochloric acid as a titrant) . For example, the anhydrous lithium bromide has a purity level >99.8% on a dry basis.

For example, laser diffraction particle size analysis (Mastersizer 3000, Malvern) of spray-dried lithium bromide provides a full particle size distribution (PSD) showing: D10 15 μm, e.g., 5 < D10 10 μm;

D50 30 μm, e.g., 15 < D50 25 μm; and

D90 100 μm, e.g., 25 < D90 75 μm or 30 < D90 50 μm; a preferred PSD lies in the ranges of 5 < D10 10 μm;

15 < D50 25μm and 30 < D90 50μm.

The anhydrous lithium bromide obtained by the method of the invention possesses a BET specific surface area of not less than 0.7 m²/g, e.g., from 0.75 to 1.0 m²/g, e.g., from 0.8 to 0.9 m²/g. Moisture measurement in spray dried samples by Karl Fischer titration showed less than 500 pμm water (limit of quantification) .

It is noted that the powder sized by the laser diffraction technique is a "reaction-derived anhydrous lithium bromide powder", namely, one that was not subjected to downstream operations to reduce particle size.

As pointed out above, the anhydrous lithium bromide obtained by the present invention is useful as a starting material in the mechanochemical synthesis of Li₆PS₅Br - a solid electrolyte in 'all-solid-state Li-ion batteries' . In its most general form, an all-solid-state battery consists of three distinct layers:

(1) a positive electrode layer that contains (i) an active cathode material (consisting of lithium transition metal oxides e.g., LixM_yO_z, where M stands for one or more transition metal; (ii) a solid electrolyte and (iii) a conductive additive, e.g., carbon nano fibers;

(2) a pure argyrodite solid electrolyte; and

(3) a negative electrode (Li metal or Li/In composite/alloys ) .

The argyrodite solid electrolyte is located in between the cathode and anode. Ni foam and Cu foil are usually used as current collectors for cathode and anode respectively.

In a conventional design for commercial use, individual cells as described above are assembled (in series and/or parallel) into modules, which in turn are packed under pressure (stack pressure) , to attain the desired output voltage and capacity, e.g., a pack for use in electric vehicles and energy storage devices .

Thus, the invention provides the use of the anhydrous LiBr formed by the reaction of lithium carbonate with hydrobromic acid as described above, as a starting material in the mechanochemical synthesis of a bromide-containing Li-argyrodite solid electrolyte.

The mechanochemical synthesis of the bromide-containing Li- argyrodite consists of two major steps.

The first step of the mechanochemical synthesis of Li₆PS₅Br or Li₆PS₅ClyBr_1-y (e.g., 0.1<y<0.9) involves the mixing and size reduction (e.g., by mechanical milling) of a powder blend consisting of stoichiometric amounts of Li2S, P2S5 and LiBr (or a suitably proportioned mixture of LiBr/LiCl instead of LiBr alone) . Ball milling is the method of choice for the mixing and size reduction; the conditions, namely, time, applied energy, and size, hardness and density of the grinding media used for Li-argyrodite synthesis are generally known (e.g., Boulineau et al. [Solid State Ionics 221 (2012) (1-5) ] ) - For example, balls with a diameter from 1 to 20 mm, made from zirconia, agate, alumina, or stainless steel, may be considered, with a preference to zirconia balls, owing to their high density. The weight ratio between the grinding media (e.g., ZrO₂ balls) and the powder blend is not less than 3:1, e.g., from 4:1 to 50:1, for example, 5:1. Ball milling of the Li2S, P2S5 and LiBr takes place in a powerful rotatable milling apparatus with a rotation speed of not less than 450 rμm (planetary ball mill, e.g., a rotation speed of 600 rμm can be used for lab scale preparation) . The ball milling is run under inert atmosphere .

The powder blend consisting of the starting materials (Li2S, P2S5 and LiBr or LiBr/LiCl) is subjected to ball milling over at least 1 hour. For example, a continuous process consisting of repeated cycles of energetic milling, with each cycle involving from 15 to 25 minutes of milling, e.g., 20 minutes, at the rotation speed mentioned above, followed by an intermission (from 5 to 15 minutes) . The total number of cycles may be from 5 to 10, e.g., 6, such that the ball milling could last 120 to 300 minutes.

The second step of the synthesis is the annealing/calcining of the ball-milled solid phase in a suitable furnace/calcination oven under an inert atmosphere, for example, by heating the ball-milled solid phase in a tube furnace under an argon atmosphere at a temperature of not less than 450°C, e.g., from 480 to 600°C, for example, from 500 to 550°C, over a few hours. The heating rate and argon flow rate are adjusted according to the furnace design; on a laboratory scale tube furnace, a heating rate of 1-5 degree/min and an argon supply of 150 sccm were found satisfactory. The sample is collected, allowed to cool down with optional post-annealing grinding, to form a finely divided powder.

Accordingly, another aspect of the invention is a process comprising a mechanochemical synthesis of a bromide-containing Li-argyrodite, which process comprises the steps of: a) mixing and size reduction of a powder blend consisting of stoichiometric amounts of Li2S, P2S5 and anhydrous LiBr as previously described, and optionally also LiCl, to form a milled solid phase; b) annealing the milled solid phase to afford a crystalline bromide-containing Li-argyrodite; and c) optionally grinding the bromide-containing Li-argyrodite.

The annealed (optionally ground) phase consists of the bromide- containing Li-argyrodite, e.g., Li₆PS₅Br, in a substantially pure form. That is, X-ray powder diffraction analysis (CuKa radiation) shows only the characteristic peaks of Li₆PS₅Br (e.g., at positions 25.2, 29.7, 31.1 and 51.9 20) and no diffraction lines, or insignificant diffraction lines, assigned to the starting materials, i.e., Li2S and LiBr (such as at 27.1 and 53.2 20 for Li2S and 28.2 and 32.6 for LiBr) .

The mechanochemically synthesized Li₆PS₅Br of the invention has been shown to possess an acceptable ionic conductivity, e.g., not less than ~2.0x10^-3 S/cm (the powder was pressed into a pellet using a hydraulic press and attached to electrodes as described in the experimental section below; the conductivity was calculated by the formula

where d is the thickness of the pellet, S is the area of the pellet and R_e is the resistance determined by electrochemical impedance spectroscopy) . Accordingly, another aspect of the invention is a mechanochemically synthesized bromide-containing Li-argyrodite obtainable from the anhydrous lithium bromide as described above, characterized by one or more of the following: a) X-ray powder diffraction pattern essentially devoid of peaks assigned to Li2S and/or LiBr starting materials; b) ionic conductivity at room temperature > 2.0x10^-3 S/cm.

Full cells incorporating the mechanochemically synthesized

Li₆PS₅Br of the invention as a solid electrolyte (cells such as LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li-In) show good electrochemical performance. These cells, when discharged for example at 0.1C rate (1^st cycle) , showed discharge capacities of nearly 200 mAhg-¹, higher than the capacities measured for corresponding cells assembled with the comparative Li₆PS₅Br (the one made from a commercially available anhydrous LiBr) . LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li-In cells with the solid electrolyte of the invention were also studied to determine the effect of stack pressure applied during battery operation, by conducting cycling tests at different constant pressures. At low-moderate operating stack pressure, e.g., < 200 MPa, such as from 120 to 180 MPa, e.g., from 140 to 160 MPa, the cells showed good electrochemical behavior, even at high discharge rates (e.g., 4C) . For example, cells operating at a stack pressure of 113 and 150 MPa maintained discharge capacities of 100 mAhg^-1 and 120 mAhg-¹ at a rate of 4C, respectively.

Accordingly, the invention also relates to an all-solid-state battery, comprising: a cathode, wherein the cathode active material is lithium transition metal oxide, optionally in admixture with a solid electrolyte material and conductive additive (s) ; an anode; and a solid electrolyte layer interposed between the cathode and anode, comprising the bromide-containing Li-argyrodite as previously described, such as Li₆PS₅Br.

The cathode material generally has the formula Li_aM_bO_c, where M stands for one or more transition metals. The lithium transition metal oxides that are most widely used include lithium cobalt oxide (LiCoO₂ or LCO) , lithium manganese oxide (LiMn₂O4 or LMO) , lithium manganese nickel oxide (Li₂Mn3NiOs or LMNO) , lithium nickel manganese cobalt oxide (LiNixMn_yCo_zO₂ or NMC; x+y+z=l) and lithium nickel cobalt aluminum oxide (LiNixCo_yAl_zO₂ or NCA; x+y+z=l) . Another type of cathode material worth mentioning is LiFePO₄ (LFP) .

Conductive additive (s) included in the carbon material are carbon forms selected from various types of carbon black commonly used in lithium batteries, such as carbon fibers, Super P, Ketjen black, acetylene black, carbon nanotubes (CNT, e.g., MWCNT) and vapor grown carbon fibers (VGCF) .

The cathode material is therefore a suitably proportioned blend consisting of the lithium transition metal oxide, bromide- containing Li-argyrodite and conductive additives, e.g., proportioned by weight 55-75:25-35:0-10.

The anode is generally a lithium metal, e.g., a lithium foil, or Li-In (lithium metal pressed against indium mesh) , or any other lithium-hos ting material. Alloys are available in various forms including foils and powders.

Exemplary all-solid-state batteries have the following designs: LiCoO|₂ Li₆PS₅Br | Li

LiCoO|₂ Li₆PS₅Br | Li-In

LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li, x+y+z=l, e.g., LiNio. ₈Mno.₁CO₀.₁O₂

LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li-In, x+y+z=l, e.g., LiNio.₈Mno.₁CO₀.₁O₂ LiNi_xCo_yAl_zO₂ | Li₆PS₅Br | Li, x+y+z=l, e.g. , LiNio.8Coo.15Alo.05O2

LiNi_xCo_yAl_zO₂ | Li₆PS₅Br | Li-In, x+y+z=l, e.g. , LiNio.8Coo.15Alo.05O2

Processing of the electrodes and solid electrolyte includes the steps of forming the powders into 0.5-1.0 mm, e.g., 0.7 mm thick pellets by application of very high fabrication pressure; the fabrication pressure may vary from 350 to 400 MPa (e.g., ~370 MPa) , 120 to 180 MPa (e. g., ~150 MPa) and 120 to 180 MPa (e.g., ~150 MPa) for pressing the cathode powder blend, the Li₆PS₅Br solid electrolyte and the Li/In anode, respectively (stack pressure, as opposed to fabrication pressure, is the external pressure subsequently applied during operation (cycling) ) . For battery assembly and battery finishing, individual cells are stacked together, e.g., to create a bipolar configuration, contact tabs are joined to outer current collectors and the battery is placed in an electrically insulated package.

In the drawings

Figure 1 shows XRD patterns of a sample of anhydrous LiBr of the invention and a commercial sample.

Figures 2a-2c show SEM images of a commercial anhydrous LiBr powder .

Figures 3a-3c show SEM images of anhydrous LiBr powder of the invention .

Figure 4 is a schematic diagram of the spray drying system used to dry lithium bromide.

Figure 5 shows XRD patterns of samples of Li₆PS₅Br prepared from anhydrous LiBr of the invention and from a commercial LiBr powder .

Figures 6a-6c show SEM images of Li₆PS₅Br prepared by mechanochemical synthesis from a commercial anhydrous LiBr powder . 18

Figures 7a-7c show SEM images of Li₆PS₅Br prepared by a mechanochemical synthesis from anhydrous LiBr powder of the invention.

Figures 8A-8D show an experimental set-up used to measure the electrochemical performance of LiNi_xMn_yCo_zO₂| Li₆PS₅Br | Li-In cell .

Figures 9A-9B show the charge/discharge curves of

LiNixMn_yCo_zO₂| Li₆PS₅Br | Li-In cells (discharged at rate of 0.1C) , when the solid electrolyte was Li₆PS₅Br prepared by mechanochemical synthesis from a commercial anhydrous LiBr powder .

Figure 9C-9D show the charge/discharge curves of

LiNixMn_yCo_zO₂| Li₆PS₅Br | Li-In cells (discharged at rate of 0.1C) , when the solid electrolyte was Li₆PS₅Br prepared by mechanochemical synthesis from anhydrous LiBr of the invention.

Figures 10A-10D show the results of cycling tests recorded for

LiNixMn_yCo_zO₂| Li₆PS₅Br | Li-In cells under varying stack pressure

(discharge capacity versus cycle number plots) ; the solid electrolyte was Li₆PS₅Br prepared by mechanochemical synthesis from anhydrous LiBr powder of the invention.

Examples

Materials

High purity HBr was received from ICL IP. Pure Li2CO3 powder was purchased from Albemarle (formerly Rockwood Lithium) . LiOH, Li2S and P₂S₅ were purchased from Sigma Aldrich. Anhydrous LiBr (used in the comparative study) was purchased from Sigma Aldrich.

Methods

X-ray powder diffraction patterns were recorded by a Bruker XRD diffractometer, model D8 Advance. XRD patterns from 10° to 80° 20 were recorded at room temperature using CuKa radiation with the following measurement conditions: tube voltage of 40 kV, tube current of 40 mA, at steps of 0.0194 °/min. Because the samples are sensitive to air and moisture, they were placed in a special kind of specimen holder from Bruker AXS . Samples were packed inside the glovebox prior to analysis (moisture and oxygen levels < 0.1%) .

High-resolution SEM images were obtained by a FEI, Magellan 400L high-resolution scanning electron microscope (FEI Company, USA) equipped with an EDX spectroscopy attachment.

Particle size distribution was determined by laser diffraction particle size analysis on a Mastersizer 3000, Malvern, which measures the intensity of light scattered as a laser beam passes through a dispersed particulate sample. LiBr sample was prepared by adding 0.5gr of LiBr to 10 ml of isooctane, followed by the addition of two or three drops of lecithin and thorough mixing. The sample is placed in the measurement cell of the Malvern instrument US-10% 2 min before measurement and off during measurement; stirrer operating at 1000rpm.

BET specific surface area was measured by Quantachrome Nova 1200e. Carbonate content of the anhydrous lithium bromide was determined by acid/base titration using hydrochloric acid as titrant ( calculated as carbonate and/or bicarbonate ) .

Moisture was determined by the Karl Fischer technique using a titration system consisting of 870 KF Titrino plus and 860 KF Thermoprep instruments . With the aid of tightly sealed sample vials , the samples are moved into the oven of the 860 KF Thermoprep . As the LiBr powder is heated up to 200°C, 15min, hydrated water is removed and channeled into the titration cell by a stream of pure nitrogen . The water content of the sample is then determined with the 870 KF Titrino plus ( LOQ of the method 0 . 05% ) .

Example 1

Preparation of anhydrous LiBr including vacuum drying

The quantities of the raw materials were calculated to give 1000 g of dry LiBr .

A 2-liter reactor equipped with a mechanical stirrer and a pH electrode was charged with 1930 gr of 48 % HBr solution . Nearly an equivalent amount of lithium carbonate ( 426 gr . ) was added slowly, by small portions , while the reaction mixture was stirred . During the reaction CO2 evolved; the rate of addition of lithium carbonate was adj usted to prevent overflow of the reaction mixture .

After addition of nearly 95% of the total equivalent amount of lithium carbonate , pH measurement was started . Addition of lithium carbonate was stopped at pH « 1 -2 . The reaction mixture was stirred (without further addition of lithium carbonate ) , to ensure that the pH was stabili zed within the acidic region of l<pH<3 . I f pH>3 is measured, then HBr would be added to adj ust the pH to the range of l<pH<3 . Next, nitrogen was introduced to the reactor via a nozzle and bubbled through the solution for 15 minutes while agitating. Then, the acidic solution was neutralized by slow addition of lithium hydroxide, raising the pH from the range of l<pH<3 to pH=7-8. The reaction mixture was cooled to room temperature. The solution was filtered on a 1 μm filter to remove insoluble impurities. The filtrate was placed in a rotary evaporator flask and dried under a vacuum of <5 millibars at a temperature of 150°C for 2 hours to obtain anhydrous lithium bromide.

Figure 1 shows X-ray powder diffraction patterns of anhydrous lithium bromide of the invention and commercial product from Sigma Aldrich. The patterns are labeled "LiBr-ICL" and "LiBr- Sigma"; lower (orange) and upper (red) patterns, respectively. The two samples exhibited similar diffraction lines, namely, the three most intense diffraction peaks of anhydrous lithium bromide were at 28.2°, 32.6° and 46.8° 20 (±0.2) . Both samples contained minute amounts of lithium bromide monohydrate impurity; the weak peaks at positions 22.2°, 31.6° and 39.0 20 (±0.2) are assigned to the monohydrate. The diffraction lines measured for the commercial anhydrous LiBr sample are slightly stronger as compared to the anhydrous LiBr of the invention, suggesting that the LiBr-ICL powder consisted of particles of a smaller size.

Figures 2a-2c and 3a-3c show SEM images of a commercial LiBr powder from Sigma Aldrich and LiBr powder of the invention, respectively (2a/3a: xlOO magnification, scale bar=400 μm; 2b/3b: x200 magnification, scale bar=200 μm; 2c/3c: x5000 magnification; scale bar=5 μm) . It is seen that both powders consisted of particles that are non-uniform in size with random morphology. It appears that the LiBr-ICL powder possessed a smaller particle size as compared to the commercial sample LiBr, in agreement with the XRD results. The observations made above were confirmed by laser diffraction particle size analysis of the anhydrous lithium bromide of the invention and the commercial product from Sigma Aldrich. The particle size distribution (by volume) is tabulated in Table 1.

Table 1

Example 2

Preparation of anhydrous LiBr including spray drying

Lithium bromide was synthesized by the method of Example 1, but the recovery of the powder took place in a spray dryer, with the aid of the experimental set-up as shown in Figure 4.

The LiBr-containing filtrate obtained at the end of the synthesis was mixed with acetone (300 g filtrate/140 g acetone) . The solution was supplied at a feed rate of 110 ml per hour to the top of a drying chamber and was broken up into droplets by means of a nozzle using compressed nitrogen gas. A stream of hot gas was introduced laterally to the drying chamber (nozzle temperature was 170°C) . The solvent (water/acetone mixture) underwent evaporation; solid particles were recovered from the exhaust gas using a cyclone separator and collected in a vessel. The powder collected was discharged from the vessel under a nitrogen blanket and was dried in a vacuum drying oven (200°C, 30-60 millitorr) for twelve hours. The powder was subjected to analysis to determine BET surface area, particle size distribution and moisture.

The results are set out in Table 2. Table 2

Example 3

Preparation of anhydrous LiBr (large scale, vacuum drying)

The quantities of the raw materials were calculated to give 100 kg of dry lithium bromide.

A 250-liter glass lined reactor was charged with 19.27 kg of deionized water. 50.15 kg of 48.5% hydrobromic acid was added under stirring. Lithium carbonate (11.2 kg) was added by small portions. The reaction was accompanied by the evolution of CO2, and foaming occurred in the reactor.

Next, 31.7 kg of lithium carbonate was added to the reactor, to obtain a slurry of 30% solids in the reaction mixture, followed by the slow addition of 141.9 kg of 48.5% hydrobromic acid, over four hours .

After the addition of the acid was completed, nitrogen was bubbled through the reaction mixture for one hour to remove residual CO2. At the end of the stripping of CO2, the pH of the reaction mixture was acidic. Small amounts of lithium hydroxide were added to neutralize the reaction mixture, reaching a pH of 7 - 8.

The lithium bromide solution was filtered through a 1 μm filter to remove insoluble impurities. The water was evaporated to dryness, at a temperature of 170 °C under maximal vacuum (P<20 mbar at the end of evaporation) . The product was rapidly discharged under a nitrogen atmosphere and packed under conditions suitable for air/moisture-sensitive samples.

Examples 4 (of the invention) and 5 (comparative) Mechanochemical synthesis of Li₆PS₅Br and characterization

Li2S powder (2.2975 g, 0.05 mol; from Sigma Aldrich) , P2S5 powder (2.227 g, 0.01 mol; from Sigma Aldrich) and LiBr powder (1.737 g, 0.02 mol; either of Example 1 or from Sigma Aldrich, in Examples 4 and 5, respectively) were ball milled using 12 zirconia balls of 10 mm diameter (weight proportion balls: powder was 5:1) . The milling was carried out in an 80 ml Planetary ball mill inside a glovebox. Six milling cycles were performed, each cycle consisting of twenty minutes of rotating the balls at 600 rpm, and a ten-minute break. During ball milling, the reagents became stuck on the inner wall of the jar. So, after a while, the material was scraped down from the wall to the bottom of the jar, and milling resumed.

Samples were annealed in quartz tubes that were placed in a tube furnace. The quartz tubes were sealed to avoid exposure to air. Annealing was carried over 5 hours at 500°C under an argon atmosphere (heating rate: 3 degree/ min; argon flow: 150 sccm) .

Annealed samples were removed from the quartz tubes (inside the glovebox) and ground in a mortar over thirty minutes to get a fine powder.

Figure 5 shows X-ray powder diffraction patterns of Li₆PS₅Br of Examples 4 (obtained from the anhydrous LiBr of Example 1) and 5 (obtained from LiBr from Sigma Aldrich) . The patterns are labeled "Li₆PS₅Br from ICL LiBr" and "Li₆PS₅Br from Sigma LiBr"; see lower (orange) and upper (brown) patterns, respectively. XRD Patterns indicate a high degree of crystallinity (the hump in the low angle region is due to the XRD holder) . For both samples, all diffraction peaks in the XRD are assigned to

Li₆PS₅Br. Diffraction peaks belonging to the starting materials (Li2S, P2S5 and LiBr) were not observed or insignificant, indicating that the reactants were consumed essentially completely and Li₆PS₅Br formation reaction went to completion in both cases.

Figures 6a-6c and 7a-7c show SEM images of Li₆PS₅Br prepared from the commercial LiBr powder from Sigma Aldrich and LiBr powder of the invention, respectively (6a/7a: x200 magnification, scale bar=200 μm; 6b/7b: x500 magnification, scale bar=50 μm; 5c/6c: x5000 magnification; scale bar=5 μm) . Agglomerated particles with porous structure are seen in both samples. The SEM images also show that the particle size of the solid electrolyte derived from lithium bromide of the invention is smaller as compared to the electrolyte derived from commercial LiBr. This is consistent with the XRD results, where diffraction lines of lower intensity were observed for the "Li₆PS₅Br from Sigma LiBr" pattern as compared to the "Li₆PS₅Br from ICL LiBr" .

The ionic conductivity of Li₆PS₅Br from ICL LiBr was studied using a Pressure Controlled & Airtight Split Cell. Three pellets with a diameter of 5 mm were prepared, i.e., with an area (S) of 0.785 cm². Each pellet was prepared by placing 80 mg of the solid electrolyte inside the cell and pressing at 150 MPa. The thickness of the pellet usually depends on the pressure applied; at 150 MPa, the average pellet thickness (d) was around 0.07 cm. Steel current collectors (cell parts) were used for the conductivity measurements, which were conducted at two different temperatures: 25 and 35°C by electrochemical impedance spectroscopy (EIS) . EIS was performed over a frequency range of 1 MHz to 5 MHz with an applied amplitude of 10 mV by an electrochemical working station (Biologic VMP-300) , to determine resistance (R_e) . Ionic conductivities were then calculated by the formula:

The geometrical features of the three pellets (S and d) , resistance (R_e) measured in the corresponding cells at T=25°C and 35°C, and calculated ionic conductivities are tabulated in

Table 3.

Table 3

The average ionic conductivity measured at RT and 35°C were 2.08x10^-3 S/cm and 3.66x10^-3 S/cm, respectively. The ionic conductivity of the Li₆PS₅Br prepared from the LiBr powder of the invention is therefore within the conductivity range acceptable for Li₆PS₅Br solid electrolyte, i.e., above the threshold of 2x10^-3 S/cm.

Example 6 Electrochemical performance of all solid-state cells with

Li₆PS₅Br solid electrolyte

Cells consisting of LiNio.₈Mno.₁CO₀.₁O₂-Li₆PS₅Br/Li₆PS₅Br/Li-In were tested in the study, using a typical Pressure Controlled & Airtight Split Cell. 60-80 mg of the solid electrolyte (either Li₆PS₅Br from ICL LiBr of Example 4 or Li₆PS₅Br from Sigma LiBr of Example 5) were first inserted into the cell and pressed to form a disc-shaped pellet using a hydraulic press at a fabrication pressure of 150 MPa. Next, a cathode powder blend consisting of LiNio. ₈Mno.₁CO₀.1O2,

Li₆PS₅Br (either Li₆PS₅Br from ICL LiBr or Li₆PS₅Br from Sigma LiBr) and carbon fibers was prepared. The blend (proportioned 65:30:5 by weight) was mixed for thirty minutes. 10 mg of the cathode blend was inserted inside the cell and spread uniformly on the surface of the solid electrolyte. Ni-foam was placed as a current collector and 370 Mpa pressure was applied. As an anode, Li/In and Cu foil were positioned in the cell and 150 MPa pressure was applied by the hydraulic press.

The cells were transferred to a steel jacket and varied external pressure was applied in the range of 113-250 MPa (stack pressure) on the cell assembly, to determine the effect of stack pressure on cell performance.

The study consisted of two parts, A and B.

Part A: Discharge and charge behavior and capacity testing

The goal of Part A was to determine the discharge and charge behavior of LiNio.₈Mno.₁CO₀.₁O₂-Li₆PS₅Br/Li₆PS₅Br/Li-In cells and the capacities obtained from discharge curves (voltage versus capacity) , to compare between the different solid electrolytes (Li₆PS₅Br from ICL LiBr according to Example 4 versus Li₆PS₅Br from Sigma LiBr of Example 5) .

The tested cells were closed at a pressure of 150 MPa and measurements were carried out at room temperature. The cells were discharged (3.7 V to 2.0 V vs. Li/In) at a rate of 0.1C. The charge/discharge curves (1^st cycle) are shown in Figures 9A- 9B and 9C-9D, for Li₆PS₅Br from ICL LiBr and Li₆PS₅Br from Sigma LiBr, respectively (in duplicate, i.e., two cells were fabricated for each type of solid electrolyte) . The results are tabulated in Table 4.

Table 4

Both types of cells show typical discharge curves. But the cell that was fabricated from the solid electrolyte of the invention exhibits a higher discharge capacity at a rate of 0.1C (1^st cycle) .

The comparison was conducted on a larger scale (ten cells of each type, discharged (2 V-3.7 V vs. Li/In) at a rate of 0.1C) and the results (discharge capacity, 1^st cycle) are tabulated in Table 5.

Table 5

The results tabulated above indicate that cells utilizing

Li₆PS₅Br of the invention as the solid electrolyte show high 1^st discharge capacity (at a rate of 0.1C) , nearly 200 mAhg^-1. The comparative cells, that contain Li₆PS₅Br made from commercial LiBr, exhibit lower discharge capacity. The dataset of discharge capacities measured for cells with the Li₆PS₅Br of the invention show lower variability as compared to the comparative dataset.

Part B: Effect of stack pressure on performance of cells incorporating Li₆PS₅Br from ICL LiBr as solid electrolyte

The electrochemical performance of all solid-state cells consisting of LiNio.₈Mno.₁CO₀.₁O₂-Li₆PS₅Br/Li₆PS₅Br/Li-In was studied with variation of the operating stack pressure over the range of ~100 to 250 MPa, using the assembly shown in Figures 8A-8D. The LiNi ₈oM. no.₁CO₀.₁O₂-Li₆PS₅Br/Li₆PS₅Br/Li-In cell (with Li₆PS₅Br of Example 4) was embedded inside a tubular mold made of polyether ether ketone, PEEK. The stack pressure applied on the tested cell was varied by tightening the nuts on the three bolts of a sample holder, in which the tubular mold is placed.

The cells were cycled at four different constant stack pressures (113 MPa, 150 MPa, 225 MPa and 250 MPa at a temperature of 35°C) . Cycling behavior (plots of discharge capacity at different rates versus cycle number are shown in Figures 10A-10D, respectively; the results represent the average of measurements taken with two cells) . Cells were cycled at 0.1C rate for the cycles 1-3, at 0.2C rate for the cycles 4-6, at 0.3C rate for the cycles 7-9, at 0.5C rate for the cycles 10-12, at 1C rate for the cycles 13- 15, at 2C rate for the cycles 16-18, at 4C rate for the cycles 19-21 and at 0.1C rate for the cycles 22-26.

The results indicate that cells operating at stack pressures of 113 and 150 MPa exhibit initial discharge capacities of 180 and 220 mAhg^-1, respectively, and fairly good discharge behavior at a high discharge rate , maintaining discharge capacities of 100 mAhg-¹ and 120 mAhg^-1 at a rate of 4C , respectively . Inferior discharge behavior is observed for cells operating at higher stack pressures , namely, in the >200 MPa range ; such cells show a capacity loss < 100 mAhg^-1. In summary, the cell operating at a stack pressure of 150 MPa emerged victorious from the experimental work reported herein, showing a high initial discharge capacity and excellent capacity retention .

Claims

1 ) A process for preparing anhydrous lithium bromide , comprising the steps of : converting an aqueous suspension of lithium carbonate with hydrobromic acid into a solution of lithium bromide ; removing residual carbon dioxide from the solution by gas- stripping, wherein the solution has acidic pH; neutrali zing the acidic lithium bromide solution by addition of lithium hydroxide to form lithium bromide brine with a nearly neutral pH; and recovering anhydrous lithium bromide from the brine .

2 ) A process according to claim 1 , comprising charging a reactor with water, a portion of the hydrobromic acid and about an equivalent amount of lithium carbonate , and when the evolution of CO2 ceases or only moderate foaming is observed, adding the remainder of lithium carbonate thereby forming a suspension, slowly adding hydrobromic acid under pH measurement control to reach the equivalent point , further lowering the pH to adj ust the pH in the acidic range needed to convert carbonate to CO2 and its removal by gas-stripping .

3 ) A process according to claim 1 or 2 , wherein the gas- stripping is performed by bubbling an inert gas or air through the lithium bromide solution, sweeping away the carbon dioxide .

4 ) A process according to any one of claims 1 to 3 , wherein the anhydrous lithium bromide is recovered by evaporation of the water to dryness under vacuum .

5 ) A process according to any one of claims 1 to 3 , wherein the anhydrous lithium bromide is recovered by spray drying the brine . 6) Anhydrous lithium bromide obtainable by the process of claims 1 to 5, characterized by one or more of the following: a) X-ray powder diffraction pattern exhibiting peaks at 28.2°, 32.6° and 46.8° 20 (±0.2) and essentially devoid of peaks at positions 22.2° ,31.6° and 39.0 20 (±0.2) , assigned to the monohydrate ; b) carbonate content of less than 100 pμm; c) particle size distribution determined by laser diffraction showingD10 15μm, D50 30μm and D90 100μm; and d) BET specific surface area of not less than 0.7 m²/g.

7) Use of the anhydrous LiBr of claim 6 as a starting material in the mechanochemical synthesis of a bromide-containing Li- argyrodite solid electrolyte.

8) A process comprising the mechanochemical synthesis of bromide-containing Li-argyrodite, wherein the synthesis includes the steps of: a) mixing and size reduction of a powder blend consisting of stoichiometric amounts of Li₂S, P₂S₅ and anhydrous LiBr as defined in claim 6, or a suitably proportioned mixture of LiBr/LiCl, to form a milled solid phase; b) annealing the milled solid phase to afford a crystalline bromide-containing Li-argyrodite; and c) optionally grinding the bromide-containing Li- argyrodite .

9) Bromide-containing Li-argyrodite obtainable by the process of claim 8, characterized by one or more of the following: a) X-ray powder diffraction pattern essentially devoid of peaks assigned to Li2S and/or LiBr starting materials; and b) ionic conductivity at room temperature > 2.0x10^-3

S/cm. 10) Bromide-containing Li-argyrodite according to claim 9, which is Li₆PS₅Br.

11) All-solid-state battery comprising: a cathode comprising lithium transition metal oxide (s) , optionally in admixture with a solid electrolyte material and conductive additive (s) ; an anode; and a solid electrolyte layer interposed between the electrodes, the solid electrolyte comprises the bromide-containing Li- argyrodite of any one of claim 9 and 10.

12) An all-solid-state battery according to claim 11, comprising

Li₆PS₅Br as the solid electrolyte.

13) An all-solid-state battery according to claim 12, selected from the group consisting of:

LiCoO₂ | Li₆PS₅Br | Li

LiCoO|₂ Li₆PS₅Br | Li-In

LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li, x+y+z=l

LiNi_xMn_yCo_zO₂ | Li₆PS₅Br | Li-In, x+y+z=l

LiNi_xCo_yAl_zO₂ | Li₆PS₅Br | Li, x+y+z=l

LiNi_xCo_yAl_zO₂ | Li₆PS₅Br | Li-In, x+y+z=l

14) An all-solid-state battery according to any one of claims 11 to 13, wherein the applied stack pressure is in the range of 100 to 180 MPa.