NEW SOLID SULFIDE ELECTROLYTES

Abstract

The present invention concerns a new solid material according to general formula (I) as follows: Li.sub.4−2xZn.sub.xP.sub.2S.sub.6 (I) wherein 0<x≤1. The invention also refers to a method for producing a solid material comprising at least bringing at least lithium sulfide, phosphorous sulfide, and a zinc compound, optionally in one or more solvents. The invention also refers to said solid materials and their use as solid electrolytes notably for electrochemical devices.

Claims

1. A solid material comprising Li, Zn, P and S elements and exhibiting at least peaks at position of: 13.4°+/−0.5°, 16.9°+/−0.5°, 27.1°+/−0.5°, 32.1°+/−0.5°, 32.6°+/−0.5° when analyzed by x-ray diffraction using CuKα radiation at 25° C.

2. (canceled)

3. The solid material according to claim 1 wherein the solid material is of general formula (I) as follows:
Li.sub.4−2xZn.sub.xP.sub.2S.sub.6  (I) wherein 0<x≤1.

4. The solid material according to claim 1 wherein x is chosen from 0.33 to 0.5.

5. The solid material according to claim 1 wherein it is in powder form with a distribution of particle diameters having a D50 comprised between 0.05 μm and 10 μm.

6. The solid material according to claim 1 wherein the solid is selected from a group consisting of: Li.sub.3.8Zn.sub.0.1P.sub.2S.sub.6, Li.sub.3.6Zn.sub.0.2P.sub.2S.sub.6, Li.sub.3.5Zn.sub.0.25P.sub.2S.sub.6, Li.sub.3.33Zn.sub.0.33P.sub.2S.sub.6, Li.sub.3.2Zn.sub.0.4P.sub.2S.sub.6, Li.sub.3Zn.sub.0.5P.sub.2S.sub.6, and Li.sub.2.666Zn.sub.0.666P.sub.2S.sub.6.

7. A method for producing the solid material according to claim 1 comprising at least bringing at least lithium sulfide, phosphorous sulfide and zinc compound, optionally in one or more solvents, then proceeding with a heat treatment at a temperature in the range of from 375° C. to 900° C., under an inert atmosphere, thereby forming the solid material.

8. A process for the preparation of a solid material comprising Li, Zn, P and S elements and exhibiting at least peaks at position of: 13.4°+/−0.5°, 16.9°+/−0.5°, 27.1°+/−0.5°, 32.1°+/−0.5°, 32.6°+/−0.5° when analyzed by x-ray diffraction using CuKα radiation at 25° C., said process comprising at least the process steps of: a) obtaining a composition by admixing stoichiometric amounts of lithium sulfide, phosphorous sulfide, and a zinc compound, optionally in one or more solvents, under an inert atmosphere; b) applying a mechanical treatment to the composition obtained in step a); c) optionally removing at least a portion of the one or more solvents from the composition obtained on step b), so that to obtain a solid residue; d) heating the obtained residue obtained in step c) at a temperature in the range of from 370° C. to 900° C., under an inert atmosphere, thereby forming the solid material; and e) optionally treating the solid material obtained in step d) to the desired particle size distribution.

9. A process for the preparation of a solid material according to general formula (I) as follows:
Li.sub.4−2xZn.sub.xP.sub.2S.sub.6  (I) wherein 0<x≤1, preferably x is chosen from 0.2 to 0.7; said process comprising at least the process steps of: a) obtaining a composition by admixing stoichiometric amounts of lithium sulfide, phosphorous sulfide, and a zinc compound in order to obtain Li.sub.4−2xZn.sub.xP.sub.2S.sub.7, optionally in one or more solvents, under an inert atmosphere; b) applying a mechanical treatment to the composition obtained in step a); c) optionally removing at least a portion of the one or more solvents from the composition obtained on step b), so that to obtain a solid residue; d) heating the obtained residue obtained in step c) at a temperature in the range of from 375° C. to 900° C., under an inert atmosphere, thereby forming the solid material; and e) optionally treating the solid material obtained in step d) to the desired particle size distribution.

10. The process according to claim 8 wherein the zinc compound is chosen in the group consisting of ZnS and Zn.

11. The process according to claim 8 wherein lithium sulfide is Li2S, phosphorous sulfide is P2S5, and zinc compound is ZnS.

12. The process according to claim 8 wherein the solvent is selected in the group consisting of alkanols, notably having 1 to 6 carbon atoms, such as methanol, ethanol, propanol and butanol; carbonates, such as dimethyl carbonate; acetates, such as ethyl acetate; ethers, such as dimethyl ether, tetrahydrofuran; organic nitriles, such as acetonitrile; aliphatic hydrocarbons, such as hexane, pentane, 2-ethylhexane, heptane, decane, and cyclohexane; and aromatic hydrocarbons, such as xylene and toluene.

13. The process according to claim 8 wherein in step b) the mechanical treatment is performed by wet or dry milling.

14. The process according to claim 8 wherein the heat treatment is carried out in step d) at a temperature in the range of from 400° C. to 700° C.

15. (canceled)

16. The solid electrolyte of claim 17, wherein the solid material is of formula (I) as follows:
Li.sub.4−2xZn.sub.xP.sub.2S.sub.6  (I) wherein 0<x≤1.

17. A solid electrolyte comprising at least the solid material of claim 1.

18. An electrochemical device comprising at least a solid electrolyte comprising at least the solid material of claim 1.

19. A solid state battery comprising at least a solid electrolyte comprising at least the solid material of claim 1.

20. A vehicle comprising at least a solid state battery comprising at least a solid electrolyte comprising at least the solid material of claim 1.

21. An electrode comprising at least: a metal substrate; directly adhered onto said metal substrate, at least one layer made of a composition comprising: (i) the solid material according to claim 1; (ii) at least one electro-active compound (EAC); (iii) optionally at least one lithium ion-conducting material (LiCM) other than the solid material of the invention; (iv) optionally at least one electro-conductive material (ECM); (v) optionally a lithium salt (LIS); and (vi) optionally at least one polymeric binding material (P).

22. A separator comprising at least: the solid material according to claim 1; optionally at least one polymeric binding material (P); optionally at least one metal salt, notably a lithium salt; and optionally at least one plasticizer.

Description

FIGURES

[0131] FIG. 1: powder XRD pattern of samples of Examples 1˜4 and 6. Circle highlight ZnS contribution in Example 4.

[0132] FIG. 2: powder XRD pattern of samples of Example 2 and Example 5. Stars indicate diffraction peaks of LiZnPS.sub.4-type phase in Example 5.

EXPERIMENTAL PART

[0133] The examples below serve to illustrate the invention, but have no limiting character.

[0134] X-Ray Diffraction

[0135] X-Ray Diffraction of the samples were collected using a Bruker D8 diffractometer with Cu Kα radiation at RT (except example 1 that was collected with Co Kα radiation at 25° C.) The samples were sealed in a Be-equipped sample holder in an Ar filled glovebox prior to the experiment. The diffractions were collected in 28 range of 10° to 100° in 13 hours. The lattice parameters were determined by fitting the diffraction profiles using Full-Prof Suite.

[0136] Conductivity & Electrochemical Impedance Spectroscopy (EIS)

[0137] Before the impedance spectroscopy measurements, powder samples were cold-pressed at 530 MPa in an Ar filled glovebox. The pellets were then sandwiched between pre-dried carbon paper electrodes, and then loaded into air-tight sample holders. The AC impedance spectra were collected by using Biologic MTZ-35 frequency response analyser. During the measurements, the AC potential for excitation was set at 50 mV for all the samples. The frequency range of the measurement of the Example 1 was 0.01 Hz to 30 MHz, whereas a range of 0.1 Hz to 30 MHz was applied in the measurements of the Example 2, the Example 3, the Example 4 and the Counter Example 5. The impedance measurements took place at stabilized temperatures between 20° C. and 60° C. for the Example 1, −10° C. and 80° C. for the Example 2, −10° C. and 70° C. for the Example 3, 0° C. and 50° C. for the Example 4 and 0° C. and 80° C. for the Example 5, in steps of 10° C. The ionic conductivity values were obtained by fitting the data into equivalent circuit models using ZView software. The slopes of the σT versus 1/T plots were used to determine activation energy values.

[0138] Moisture Stability

[0139] Moisture stability was measured using a H.sub.2S sensor (Sensorcon Industrial Pro from Molex). H.sub.2S liberation kinetic was measured at 23° C. with 30 mg of each sample in a 10 L desiccator filled with ambient non-dried air (relative humidity between 70% and 90%, non-controlled). Values showed (in ppm) by the sensor are recorded every 20 seconds for 15 minutes and converted in number of moles of H.sub.2S generated per liter of ambient air and gram of sample.

Counter Example 1: Li4P2S6 Synthesized Via Solid State Route

[0140] Li.sub.2S and P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%), were used as starting materials, mixed with mortar and pestle in an Ar filled glovebox. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 750° C. for 60 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0141] The XRD pattern shows a well-crystalline material, with XRD peaks (28 position with Cu alpha wavelength): at 16.8°, 27°, 32°, 32.4°. Indexation in the trigonal space group P-31m is possible and cell parameters are a=b=6.08 Å and c=6.60 Å and the volume per formula atom is 211 Å.sup.3/f.u.

[0142] Ionic conductivity at 60° C. is 9*10.sup.−9 S/cm with an activation energy of 0.61 eV. Ionic conductivity at room temperature was too low to be measured directly, around 10.sup.−9 S/cm.

[0143] H.sub.2S generation after 12 minutes was 54 μmol/L.sub.air/g.sub.sample.

Example 2: Li.SUB.3.33.Zn.SUB.0.33.P.SUB.2.S.SUB.6

[0144] Li.sub.2S, P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%), and ZnS (produced by Alfa Aesar 99%) were used as starting materials. 2 g of total powder at the desired molar ratio were put in a 45 mL ZrO.sub.2 jar with 15 ZrO.sub.2 balls (3 g/ball, 10 mm diameter) in an Ar filled glovebox. The jar was sealed with scotch and parafilm to prevent air exposure, then was taken out of the glovebox and was placed in Fritzch Planetary Micro Mill Pulverisette 7. It was ball-milled with 510 RPM rotating speed for 38 hours while employing 15 minute breaks in every 15 minutes of milling, in order to prevent excessive heating of the jar. The jar was then moved in an Ar filled glovebox to collect the powder. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet was vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 600° C. for 36 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0145] The XRD pattern shows a well-crystalline material, with XRD peaks at (28 position with Cu alpha wavelength): 13.4°, 16.9°, 27.1°, 32.1°, 32.6°. Indexation in the trigonal space group P-31m is possible, cell parameters are a=b=6.06 A and c=6.59 A and the volume per formula atom is 209 Å.sup.3/f.u.

[0146] No extra phase is detected, proving that Zn is inserted in the structure.

Ionic conductivity at 25° C. is 1.Math.10.sup.−6 S/cm with an activation energy of 0.51 eV.

[0147] H.sub.2S generation after 12 minutes was 14 μmol/L.sub.air/g.sub.sample.

Example 3: Li.SUB.3.Zn.SUB.0.5.P.SUB.2.S.SUB.6

[0148] Li.sub.2S, P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%) and ZnS (produced by Alfa Aesar 99%) were used as starting materials. 2 g of total powder at the desired molar ratio were put in a 45 mL ZrO.sub.2 jar with 12 ZrO.sub.2 balls (3 g/ball, 10 mm diameter) in an Ar filled glovebox. The jar was sealed with scotch and parafilm to prevent air exposure, then was taken out of the glovebox and was placed in Fritsch Planetary Micro Mill Pulverisette 7. It was ball-milled with 510 RPM rotating speed for 38 hours while employing 15 minute breaks in every 15 minutes of milling, in order to prevent excessive heating of the jar. The jar was then moved in an Ar filled glovebox to collect the powder. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 600° C. for 36 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0149] The XRD pattern shows a well-crystalline material, with XRD peaks at (28 position with Cu alpha wavelength): 13.4°, 16.9°, 27°, 32°, 32.5°. Indexation in the trigonal space group P-31m is possible, cell parameters are a=b=6.06 A and c=6.59 A and the volume per formula atom is 210 Å.sup.3/f.u.

[0150] No extra phase is detected, proving that Zn is inserted in the new structure.

[0151] Ionic conductivity at 20° C. is 3.Math.10.sup.−7 S/cm with an activation energy of 0.51 eV.

[0152] H.sub.2S generation after 12 minutes was 1 μmol/L.sub.air/g.sub.sample.

Example 4: Li.SUB.2.666.Zn.SUB.0.666.P.SUB.2.S.SUB.6

[0153] Li.sub.2S, P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%) and ZnS (produced by Alfa Aesar 99%) were used as starting materials. 2 g of total powder at the desired molar ratio were put in a 45 mL ZrO.sub.2 jar with 15 ZrO.sub.2 balls (3 g/ball, 10 mm diameter) in an Ar filled glovebox. The jar was sealed with scotch and parafilm to prevent air exposure, then was taken out of the glovebox and was placed in Fritsch Planetary Micro Mill Pulverisette 7. It was ball-milled with 510 RPM rotating speed for 38 hours while employing 15 minute breaks in every 15 minutes of milling, in order to prevent excessive heating of the jar. The jar was then moved in an Ar filled glovebox to collect the powder. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 600° C. for 36 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0154] The XRD pattern shows a well-crystalline material, with XRD peaks at (28 position with Cu alpha wavelength): 13.4°, 16.9°, 27°, 32.1°. 32.5°. Indexation in the trigonal space group P-31m is possible, cell parameters are a=b=6.06 A and c=6.59 A and the volume per formula atom is 209 Å.sup.3/f.u.

[0155] Small amount of ZnS extra phase is detected, proving that large part of Zn is inserted in the structure but that solubility limit is probably reached.

[0156] Ionic conductivity at 20° C. is 5.Math.10.sup.−7 S/cm with an activation energy of 0.56 eV.

[0157] H.sub.2S generation after 12 minutes was 0 μmol/L.sub.air/g.sub.sample.

Counter Example 5: Li.SUB.3.33.Zn.SUB.0.33.P.SUB.2.S.SUB.6 .at 350° C.

[0158] Li.sub.2S, P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%?) and ZnS (produced by Alfa Aesar) were used as starting materials. 2 g of total powder at the desired molar ratio were put in a 45 mL ZrO.sub.2 jar with 15 ZrO.sub.2 balls (3 g/ball, 10 mm diameter) in an Ar filled glovebox. The jar was sealed with scotch and parafilm to prevent air exposure, then was taken out of the glovebox and was placed in Fritsch Planetary Micro Mill Pulverisette 7. It was ball-milled with 510 RPM rotating speed for 38 hours while employing 15 minute breaks in every 15 minutes of milling, in order to prevent excessive heating of the jar. The jar was then moved in an Ar filled glovebox to collect the powder. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 350° C. for 36 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0159] The XRD pattern shows well-crystalline materials, with XRD peaks at (28 position with Cu alpha wavelength): 13.4°, 16.9°, 18.3°, 27°, 29.7°, 32.1°, 32.5°.

[0160] This set of diffraction peaks can be indexed as the combination of a Zn doped Li.sub.4P.sub.2S.sub.6 phase and a LiZnPS4-type phase. The peaks around 18.3° and 29.7° point to the presence of LiZnPS4-type phase.

[0161] Ionic conductivity at 20° C. is 3.Math.10.sup.−7 S/cm with an activation energy of 0.56 eV.

[0162] H.sub.2S generation after 12 minutes was 19 μmol/L.sub.air/g.sub.sample.

Counter Example 6: Li.SUB.4.P.SUB.2.S.SUB.6 .Synthesized Via Ball Milling at 350° C.

[0163] Li.sub.2S, P.sub.2S.sub.5 (both produced by Sigma Aldrich, ≥99%) were used as starting materials. 5 g of total powder at the desired molar ratio were put in a 45 mL ZrO2 jar with 15 ZrO2 balls (3 g/ball, 10 mm diameter) in an Ar filled glovebox. The jar was sealed with scotch and parafilm to prevent air exposure, then was taken out of the glovebox and was placed in Fritsch Planetary Micro Mill Pulverisette 7. It was ball-milled with 510 RPM rotating speed for 64 hours while employing 15 minute breaks in every 15 minutes of milling, in order to prevent excessive heating of the jar. The jar was then moved in an Ar filled glovebox to collect the powder. The resulting powder was pelletized at 530 MPa with a 6 mm diameter die. The pellet vacuum sealed in a carbon coated quartz tube, then the tube was annealed at 350° C. for 36 hours. After the annealing step, the tube was slowly cooled down to 25° C., and it was opened in an Ar filled glovebox.

[0164] The XRD pattern shows a well-crystalline material, with XRD peaks (28 position with Cu alpha wavelength): at 16.8°, 27°, 32°, 32.4°. Indexation in the trigonal space group P-31m is possible and cell parameters are a=b=6.08 Å and c=6.61 Å and the volume per formula atom is 211 Å.sup.3/f.u.

[0165] Ionic conductivity at was too low to be measured directly, so estimated 10.sup.−10 S/cm at 25° C.

[0166] H.sub.2S generation after 12 minutes was 126 μmol/L.sub.air/g.sub.sample.