Method for Preparing Lithium Thiolate

Abstract

The present invention relates to a new process for preparing lithium thiophosphates as well as to the products obtainable by said process and their use, in particular as solid electrolytes.

Description

Technical Field

[0001] The present invention relates to a method for preparing lithium thiophosphate, and to lithium thiophosphate obtained thereby, and to the use of the aforementioned product, in particular as a solid electrolyte.

Background Art

[0002] Lithium batteries are used to power portable electronic devices and electric vehicles because of their high energy and power density. Conventional lithium batteries utilize a liquid electrolyte composed of a lithium salt dissolved in an organic solvent. Since the organic solvent is flammable, safety problems occur in the aforementioned systems. When lithium dendrites are formed and pass through the liquid electrolyte medium, a short circuit occurs, heat is generated, and an accident that can lead to serious injury may occur.

[0003] Solid sulfide electrolytes are advantageous for use in lithium batteries because of their high ionic conductivity and mechanical properties. Since these electrolytes can be pelletized by cold pressing and attached to the electrode material, a high-temperature assembly process is not required. Eliminating the high-temperature sintering process removes one of the problems associated with using a lithium metal anode in a lithium battery.

[0004] Argyrodite has been known since ancient times and was first described in 1886 by C. Winkler in argyrodite Ag 8 GeS 6 which led to the discovery of germanium by its analysis. The family of argyrodites consists of over 100 crystalline solids and includes, for example, solid compounds in which silver is replaced by copper, germanium is replaced by gallium or phosphorus, and sulfur is replaced by selenium. Thus, Nitsche, Kuhs, Krebs, Evain, Boucher, Pfitzner, and Nilges have, inter alia, studied Cu 9 GaS 6 Ag 7 PSe 6 and Cu 8 GaS 5Compounds such as Cl are described, and these solid structures are derived from argillodite.

[0005] Therefore, a complete solution route for preparing sulfide-based solid electrolytes is required.

[0006] Invention An object of the present invention is to provide LiPS to a sulfide-based solid electrolyte, which is prepared by a synthetic route that can be preferably set up faster and more easily compared to the methods described above.

[0007] An object of the present invention is to provide a new process for the preparation of LiPS materials in solution, which preferably improves productivity and enables control of the morphology of the resulting product.

[0008] An object of the present invention is also to provide a method for preparing halogen-free argillodite Li 7 PS 6 with improved transport properties.

[0009] Therefore, the present invention relates to a method for preparing lithium thiophosphate, comprising at least one step of preparing a solution S1 at a temperature T1 comprising -200 °C to 10 °C, preferably -110 °C to 0 °C, wherein the aforementioned solution S1 comprises a solvent and at least one P species in the form of (PS 4 ) 3- , at least one Li species in the form of Li + , and residual sulfur in the form of polysulfides, and then a step of removing at least a part of the solvent from the aforementioned solution to obtain lithium thiophosphate.

[0010] The present invention also relates to lithium thiophosphate that can be easily obtained by the method of the present invention. The present invention also relates to the use of such lithium thiophosphate as a solid electrolyte. The present invention also refers to a solid electrolyte containing such lithium thiophosphate, and an electrochemical device containing lithium thiophosphate according to the present invention, in particular, a solid electrolyte containing lithium thiophosphate according to the present invention. The present invention also relates to a solid battery containing the solid electrolyte of the present invention, and a vehicle containing the solid battery.

[0011] Definitions Throughout this specification, unless the context requires otherwise, the word "comprise" or variations thereof, such as "comprises", "comprising", "includes", "including", are understood to mean that they include the stated element or method step or group of elements or method steps, but do not exclude any other element or method step or group of elements or method steps. According to a preferred embodiment, the words "comprise" and "include" and their variations mean "consist exclusively of".

[0012] As used herein, the singular forms "a", "an", and "the" include plural aspects unless the context clearly indicates otherwise. The term "and / or" includes the meanings of "and", "or", and also all other possible combinations of the elements related to this term.

[0013] The term "between" should be understood to include the limit points.

[0014] Ratios, concentrations, amounts, and other numerical data may be presented in a range format in this specification. Such range formats are used merely for convenience and brevity and are to be construed flexibly as including not only the numerical values explicitly listed as the limits of the range, but also all individual numerical values or sub-ranges that are included within that range as if each were explicitly listed. For example, a temperature range of about 120°C to about 150°C includes not only the explicitly listed limits of about 120°C to about 150°C, but also sub-ranges such as 125°C to 145°C, 130°C to 150°C, etc., and individual amounts within the stated range such as, for example, 122.2°C, 140.6°C, and 141.3°C, etc., including small quantities.

[0015] The term "electrolyte" specifically refers to a material that allows ions, for example, Li + to move through it, but does not allow electrons to conduct through it. An electrolyte serves to electrically insulate the cathode and anode of a battery while allowing ions, for example, Li + to permeate the electrolyte. The "solid electrolyte" according to the present invention specifically means any type of material in which ions, for example, Li + can move around while the material is in a solid state.

[0016] The term "electrochemical device" specifically refers to a device that generates and / or stores electrical energy by, for example, electrochemical and / or electrostatic processes. Electrochemical devices may include electrochemical cells such as batteries, particularly solid-state batteries. A battery can be a primary (i.e., single-use or "disposable") battery or a secondary (i.e., rechargeable) battery.

[0017] As used herein, the term "vehicle" or "vehicular" or other similar terms includes passenger cars, buses, trucks, various commercial vehicles such as general motor vehicles including sports utility vehicles (SUVs), ships including various boats and vessels, aircraft, etc., and is understood to include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels obtained from resources other than petroleum). As mentioned herein, a hybrid vehicle is a vehicle having two or more different power sources, e.g., both a gasoline-powered vehicle and an electric-powered vehicle.

[0018] Detailed Description of the Invention The method of the present invention is based on the preparation of a homogeneous solution containing ionic species. Thus, it is not accompanied by a suspension.

[0019] Thus, all species involved in the preparation of lithium thiophosphate are dissolved in the solvent and are in the form of ionic species as described above.

[0020] An essential feature of the method of the present invention is the temperature T1 defined above. Thus, the method of the present invention is carried out at a low temperature, especially to dissolve all species and thus obtain solution S1 at the required temperature.

[0021] Once solution S1 is prepared, a step for removing at least a part of the solvent is then carried out. Then, lithium thiosulfate is obtained as a solid, preferably as a powder.

[0022] Preferably, the term "at least a part of the solvent" refers to at least 50% by weight of the aforementioned solvent, preferably at least 60% by weight of the aforementioned solvent.

[0023] (PS 4 ) 3- The P species in the form of 2 S 5 P 4 S 10 P 4 S 9 and P 4 S 9+xIt is preferably obtained from a precursor selected from the group consisting of (0 < x < 1).

[0024] Li + The Li species in the form of is Li 2 It is preferably obtained from a precursor selected from the group consisting of S and LiHS.

[0025] The residual sulfur in the form of polysulfide is P 2 S 5 P 4 S 10 P 4 S 9 P 4 S 9+x (0 < x < 1), Li 2 S, It is preferably obtained from a precursor selected from the group consisting of S and LiHS.

[0026] According to one embodiment, the solution S1 is obtained by mixing lithium sulfide and phosphorus sulfide in a solvent at a temperature in the range of -200°C to 10°C, preferably -110°C to 0°C.

[0027] According to this embodiment, all reactants are advantageously added together to the solvent at temperature T1.

[0028] According to another embodiment, the solution S1 defined above is obtained by performing the following steps: - A step of mixing lithium sulfide in a solvent to obtain a precursor solution, and - A step of adding phosphorus sulfide to the aforementioned precursor solution at a temperature including -200°C to 10°C, preferably -110°C to 0°C, to obtain the aforementioned solution S1.

[0029] According to this embodiment, the solution S1 is prepared in two steps.

[0030] Preferably, the step for removing at least a part of the solvent from the solution S1 is carried out at a temperature including 30°C to 200°C, preferably 30°C to 100°C. According to one embodiment, this temperature can include 35°C to 65°C.

[0031] The step for removing the solvent can be carried out by implementing conventional means, particularly by solvent evaporation.

[0032] This preferred temperature range for solvent removal is advantageous in that secondary reactions are not promoted at such temperature values.

[0033] The preparation of solution S1 can be carried out in an inert atmosphere, under vacuum or under a stream of H 2 S.

[0034] According to one embodiment, the method of the present invention includes a further step after the step for removing the solvent. Preferably, after removing the solvent, lithium thiophosphate is then heat-treated at a temperature including 150°C to 700°C.

[0035] Such a step consists of the heat treatment of solid lithium thiosulfate obtained after the step for removing the solvent.

[0036] Preferably, the solvent used in the method of the present invention can dissolve lithium thiophosphate, lithium sulfide and phosphorus sulfide. Thus, as described above, this solvent gives a homogeneous solution S1 as defined above.

[0037] According to a preferred embodiment, the solvent is an aliphatic alcohol. Most preferably, the solvent is selected from the group consisting of ethanol, methanol and mixtures thereof.

[0038] According to a preferred embodiment, temperature T1 includes -110°C to 0°C, preferably -110°C to -10°C, most preferably -100°C to -50°C, particularly -90°C to -70°C. For example, T1 is about -80°C.

[0039] According to a specific embodiment, the temperature used during the step of removing at least a part of the solvent from solution S1 includes 35°C to 65°C, and temperature T1 includes -110°C to -10°C, preferably -100°C to -50°C.

[0040] In particular, during the preparation of solution S1, the temperature T1 remains constant.

[0041] Advantageously, the method according to the invention allows for much less, and even no, global and local deviation with respect to stoichiometry.

[0042] According to one embodiment, the lithium thiophosphate is Li 3 PS 4 、Li 7 PS 6 、Li 7 P 3 S 11 and Li 9.6 P 3 S 12 selected from the group consisting of.

[0043] Lithium sulfide is generally a compound containing one or more sulfur atoms and one or more lithium atoms, or one or more sulfur-containing ionic groups and one or more lithium-containing ionic groups. In certain preferred embodiments, lithium sulfide can consist of sulfur atoms and lithium atoms.

[0044] Phosphorus sulfide is generally a compound containing one or more sulfur atoms and one or more phosphorus atoms, or one or more sulfur-containing ionic groups and one or more phosphorus-containing ionic groups. In certain preferred embodiments, phosphorus sulfide can consist of sulfur atoms and phosphorus atoms. Examples of phosphorus sulfide include, but are not limited to, P 2 S 5 、P 4 S 3 、P 4 S 10 、P 4 S 4 、P 4 S 5 、P 4 S 6 、P 4 S 7 、P 4 S 8 and P 4 S 9 can include.

[0045] Preferably, lithium sulfide contains or is lithium sulfide Li 2 S, and phosphorus sulfide may contain or be phosphorus pentasulfide P 2 S 5 .

[0046] Solution S1 may contain at least 50 mol% of Li species in the form of Li+, preferably at least 80 mol% of Li species in the form of Li+, more preferably at least 95 mol% of Li species in the form of Li+ with respect to the total amount in moles of lithium sulfide added to the solvent.

[0047] Solution S1 may contain at least P species in the form of (PS 4 ) 3- and (P 2 S 7 ). 4-

[0048] Solution S1 contains, with respect to the total amount in moles of phosphorus sulfide added to the solvent, at least 50 mol% of P species in the form of (PS 4 ), preferably at least 80 mol% of P species in the form of (PS 3- ), more preferably at least 95 mol% of P species in the form of (PS 4 ), or at least 99 mol% of P species in the form of (PS 3- ). 4 ) 3- 4 ) 3-

[0049] The present invention also relates to lithium thiophosphate that can be easily obtained by the method defined above.

[0050] The present invention also relates to the use of lithium thiophosphate defined above as a solid electrolyte.

[0051] The present invention also relates to a solid electrolyte containing lithium thiophosphate defined above, particularly a sulfide-based solid electrolyte for a lithium ion battery.

[0052] ​​​ The present invention also relates to an electrochemical device containing lithium thiophosphate defined above. The present invention also refers to a solid battery such as an all-solid-state lithium secondary battery containing the solid electrolyte defined above, and a vehicle containing the solid battery defined above.

[0053] Typically, a lithium solid 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 contains a solid electrolyte containing lithium thiophosphate as defined above.

Brief Description of the Drawings

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Example

[0055] The following examples are useful for illustrating the present invention but have no limiting features.

[0056] X-ray diffraction: The XRD diffraction pattern of the powder was obtained using a Cu X-ray tube (Cu Kalpha with a wavelength of 1.5406 Å) on an XRD goniometer with Bragg Brentano geometry. The setup can be used in various optical configurations, i.e., using variable or fixed divergence slits, or solar slits. Primary filtering devices such as a Panalytical monochromator or Bragg Brentano HD optics can also be used. When a variable divergence slit is used, the typical illuminated area is 10 mm × 10 mm. The sample holder is mounted on a spinner, and during acquisition, the rotation speed is typically 60 rpm. The tube settings were operated at 40 kV / 30 mA for variable slit acquisition and 45 kV / 40 mA for fixed slit acquisition using the incident Bragg Brentano HD optics. The acquisition step was 0.017° per step. The angular range was typically 5° to 90° with 2 theta or more. The total acquisition time was typically 30 minutes or more.

[0057] The powder is covered with Kapton film to prevent reaction with moisture in the air.

[0058] Conductivity measurement: The conductivity was obtained for pellets made using a uniaxial press operating at 500 MPa.

[0059] The measurement was carried out under a load of 40 MPa, and two carbon paper foils were used as current collectors in the pressure cell (BATTE-CELL-0067 EQ-PSC-15-P) of MTI.

[0060] The impedance spectrum was obtained with a Biologic VMP3 device, and the temperature control was verified by a Binder climatic chamber. The period of 2 hours was set so that the temperature could equilibrate between two measurements.

[0061] The impedance spectroscopy was obtained in the PEIS mode with an amplitude of 10 mV and a frequency range of 1 MHz to 1 kHz (25 points per decade, 50 measurements on average per frequency point).

[0062] Liquid NMR 31 The NMR spectrum of the P solution was recorded on a Bruker 300 MHz spectrometer equipped with a QNP Z-GRD Z8352 / 107 probe. The relaxation time was 7 seconds. The spectrum was 1 decoupled from H.

[0063] Solid NMR The solid NMR spectrum was recorded on a Bruker Avance 400 spectrometer equipped with a high-speed DVT4 probe. 31 P and 6 the measurement of Li was performed by magic angle spinning (MAS) at a speed of 10 kHz in the single pulse mode of relaxation time D1 according to the experiment (see the following example). 7 The measurement of Li was performed in the static single pulse mode with a relaxation time D1 = 120 s. 31 The reference for P NMR was 6 in Li NMR, 85% H 3 PO 4 , 5 mol L -1 aqueous LiCl solution.

[0064] Example 1 - Li7 PS 6 Preparation Li 2 S (724 mg, Albemarle) was weighed in a 100 mL Schlenk flask filled with Ar with both oxygen and moisture levels below 1 ppm in a glove box. 30 mL of anhydrous ethanol (VWR, moisture content less than 50 ppm) was added to the flask. Then, the flask was taken out of the glove box and connected to an N 2 / vacuum line. The resulting mixture was stirred for 20 minutes under an inert atmosphere (dry nitrogen).

[0065] P 2 S 5 S (574 mg, BK Giulini) was weighed in a 100 mL three-necked flask. It was cooled to -80 °C for 30 minutes using a dry ice / acetone bath, and then the above Li 2 S solution was quickly transferred to the flask using a Teflon cannula. Then, the solution was stirred for 5 hours while maintaining the temperature at -80 °C. No further changes were observed. Then, the solvent was removed slowly under primary vacuum, first at room temperature, and then when the temperature was raised to 50 °C and the solution was concentrated to about 60% of its initial volume, it was left overnight at this value. The resulting product was a pale yellow powder. This was characterized by powder X-ray diffraction, solid 31 P and 6 Li MAS NMR (D1 = 60 s for both nuclei), and solid 7 Li static NMR. The XRD powder pattern shows the predominance of the Li 7 PS 6 phase in its high-temperature polymorph (space group F-43m). 31 The P solid NMR spectrum is consistent with the presence of PS 4 3- entities in the solid.

[0066] The conductivity was measured by impedance spectroscopy of pellets of the material and was σ = 6×10 -7 S.cm -1 at room temperature.

[0067] Next, inside a glove box filled with Ar, 325 mg of this solid was manually ground in an agate mortar and transferred to a quartz tube (length 250 mm, inner diameter 10 mm, wall thickness 1.1 mm) sealed at one end. The quartz tube was taken out of the glove box and quickly connected to a vacuum line equipped with a pressure gauge via a PVC vacuum tube. When the pressure measured inside the system became less than 1 millibar, the quartz tube was sealed using a torch fueled by propane and oxygen. The sealed quartz tube was heated to 550 °C in a muffle furnace according to a ramp of 2 °C / min, and this temperature was maintained at this value for 5 hours. When the furnace was cooled to 30 °C, the quartz tube was returned inside the glove box, cut with a tungsten carbide cutter, and the dark brown solid inside was collected. This solid was characterized by powder X-ray diffraction, 31 P and 6 Li solid-state MAS NMR (D1 = 500 s and 3000 s, respectively), and impedance spectroscopy. The Li 7 PS 6 phase is shown in its high-temperature polymorph (space group F-43m) together with the impurities of LiCl, Li 2 S and Li 3 PO 4 . The conductivity of the sample at room temperature reaches 1.03 mS·cm -1 with an activation energy of 0.47 eV between -20 °C and 60 °C, which is the highest ever reported for this type of material.

Claims

1. At least one step for preparing a solution S1 at a temperature T1 including -200°C to 10°C, wherein the solution S1 comprises a solvent and at least (PS ４ ) ３－ P species in the form of, Li ＋ Li species in the form of, and at least one step including residual sulfur in the form of polysulfides, and then a step for removing at least a part of the solvent from the solution S1 to obtain lithium thiophosphate. A method for preparing lithium thiophosphate.

2. The method according to claim 1, wherein the solution S1 is obtained by mixing lithium sulfide and phosphorus sulfide in the solvent at a temperature including -200°C to 10°C.

3. The solution S1 is obtained by the following steps: - A step of mixing lithium sulfide in the solvent to obtain a precursor solution, and - A step of adding phosphorus sulfide to the precursor solution at a temperature including -200°C to 10°C to obtain the solution S1, according to the method of claim 1.

4. The step for removing at least a part of the solvent from the solution S1 is carried out at a temperature including 30°C to 200°C, according to the method of any one of claims 1 to 3.

5. The preparation of the solution S1 is carried out in an inert atmosphere, under vacuum or under a stream of H ２ S according to any one of claims 1 to 4, wherein the preparation is carried out under a stream of S.

6. Lithium thiophosphate is then heat-treated at a temperature including 150°C to 700°C, according to the method of any one of claims 1 to 5.

7. The solvent can dissolve lithium thiophosphate, lithium sulfide, and phosphorus sulfide, according to the method of any one of claims 1 to 6.

8. The solvent is an aliphatic alcohol, according to the method of any one of claims 1 to 7.

9. The solvent is selected from the group consisting of ethanol, methanol, and mixtures thereof, according to the method of any one of claims 1 to 8.

10. The temperature T1 includes -110°C to 0°C, preferably -110°C to -10°C, particularly -100°C to -50°C, according to the method of any one of claims 1 to 9.

11. The lithium thiophosphate is Li ３ PS ４ , Li ７ PS ６ , Li ７ P ３ S １１ , and Li ９．６ P ３ S １２ The method according to any one of claims 1 to 10, selected from the group consisting of.

12. The solution S1 contains Li species in the form of Li+ of at least 50 mol%, preferably at least 80 mol%, more preferably at least 95 mol% based on the total amount in moles of lithium sulfide added to the solvent, according to the method of any one of claims 1 to 11.

13. The solution S1 contains, in terms of moles of phosphorus sulfide added to the solvent, at least 50 mol% of P species in the form of (PS ４ ), ３－ preferably at least 80 mol% of P species in the form of (PS ４ ), ３－ more preferably at least 95 mol% of P species in the form of (PS ４ ), ３－ The method according to any one of claims 1 to 12.

14. The temperature T1 includes -100°C to -50°C, and the step for removing at least a part of the solvent from the solution S1 is carried out at a temperature including 35°C to 65°C, according to the method of any one of claims 1 to 12.

15. Use of lithium thiophosphate obtainable by the method according to any one of claims 1 to 14 as a solid electrolyte.

16. A method for preparing a solid electrolyte, including the method according to any one of claims 1 to 14.

17. A method for manufacturing an electrochemical device, including the method according to claim 16.

18. A method for manufacturing a solid-state battery, comprising the method according to Claim 17.

19. A method for manufacturing a vehicle, comprising the method according to Claim 18.

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