SULFIDIC SOLID ELECTROYLYTE AND ITS PRECURSOR II

Abstract

The present invention relates to a solid electrolyte, its precursor, methods for producing the same as well as its use, e.g. in electrochemical cells and capacitors, fuel cells, batteries and sensors.

Claims

1. A solid electrolyte precursor represented by the following formula (I):
Li.sub.(2a-n)Y.sup.n+S.sub.a  (I) wherein Y is independently selected from P, As, Ge, Sn, B, Si, Al, Ga, and Sb, 4≤n≤5, and 4≤a≤6, preferably 4.8≤a≤5.2, in particular being selected from Li.sub.5PS.sub.5, Li.sub.5AsS.sub.5, Li.sub.4GeS.sub.4, Li.sub.4SiS.sub.4, Li.sub.3BS.sub.3, Li.sub.4SnS.sub.4, Li.sub.3GaS.sub.3, Li.sub.3AlS.sub.3, Li.sub.5SbS.sub.5 or mixtures thereof, such as physical mixtures, mixed crystals and/or solid solutions.

2. The precursor according to claim 1, further comprising at least one dopant, such as Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, O, Sb, B, Ga, Se, O, Te, Mg, Na, Ca or a mixture thereof in their respective oxidation state.

3. A method for producing a solid electrolyte precursor according to claim 1, comprising the steps of: (i) providing a lithium salt, preferably LiOH, Li.sub.2CO.sub.3, Li.sub.2SO.sub.4, Li.sub.2O, Li.sub.2O.sub.2 or a mixture thereof in a reaction vessel, (ii) contacting a sulfur-containing reaction gas, such as H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof, with the lithium salt of step (i) at elevated temperatures, such as 90-250° C., (iii) contacting a Y-containing component, such as P.sub.2S.sub.5, As.sub.2S.sub.5, GeS.sub.2, SiS.sub.2, B.sub.2S.sub.3, SnS.sub.2, Ga.sub.2S.sub.3, Al.sub.2S.sub.3, Sb.sub.2S.sub.5 or a mixture thereof, with the product obtained in step (ii) at elevated temperatures, such as 288-1200° C., and (iv) optionally discharging the product obtained in step (iii), wherein the Y-containing component is at least partially present in a gaseous phase.

4. The method according to claim 3, wherein in step (ii) the molar ratio of S in sulfur-containing reaction gas, particularly H.sub.2S, to Li in lithium salt provided in step (i) is 1:1-1:10, preferably 1:1-1:5, more preferably about 1:2.

5. The method according to claim 3, wherein in step (iii) the molar ratio of Y in Y-containing component, particularly P.sub.2S.sub.5, to Li in lithium salt provided in step (i) is 1:1-1:10, preferably 1:3-1:6, more preferably about 1:5.

6. The method according to claim 3, wherein step (ii) and/or step (iii) is performed at a total gas flow of 0.1-1000 m.sup.3/h, preferably 5-500 m.sup.3/h, more preferably 10-50 m.sup.3/h.

7. Use of a solid electrolyte precursor according to claim 1, for preparing a solid electrolyte, in particular a sulfidic solid electrolyte, in particular represented by the following formula (II):
Li.sub.(2b+c-m)Y.sup.m+S.sub.bX.sub.c  (II) wherein X is independently selected from group 17 elements, such as Cl, Br and I, Y is independently selected from P, As, Ge, Sn, B, Si, Al, Ga, and Sb, 4≤m≤5, 4≤b≤6, and 0≤c≤2, or represented by the following formula (III):
Li.sub.(8-q*(1-t)-r*t)Y′.sup.q+.sub.1-tY″.sup.r+.sub.tS.sub.4  (III) wherein Y′ is independently selected from Si, and Ge, Y″ is independently selected from P, Al, Sn, Ga, and Sb, 3≤q≤5 2≤r≤6 0≤t<≤1.

8. The use according to claim 7, wherein the solid electrolyte is Li.sub.3PS.sub.4, Li.sub.7P.sub.3S.sub.11, or Li.sub.10YP.sub.2S.sub.12, wherein Y is independently selected from Si, Sn, and Ge.

9. A method for preparing a solid electrolyte, comprising the steps of: (a) providing a solid electrolyte precursor according to claim 1, in a reaction vessel, (b) contacting at least one X-containing and/or S-containing lithium salt and/or Y-containing sulfide with the solid electrolyte precursor of step (a) at elevated temperatures, such as 90-700° C., and (c) optionally discharging the product obtained in step (b).

10. The method according to claim 9, wherein the X-containing lithium salt is a halide, such as LiCl, LiBr, LiI or a mixture thereof, preferably LiCl or LiBr, and/or wherein the S-containing lithium salt is preferably Li.sub.2S, and/or wherein the Y-containing sulfide is preferably P.sub.2S.sub.5.

11. The method according to claim 9, wherein in step (b) the molar ratio of X in X-containing lithium salt or of S in the S-containing lithium salt to solid electrolyte precursor provided in step (a) is 0.01:1-3:1.

12. The method according to claim 9, further comprising a step (b.1) of adding to the product obtained in step (b) at least one doping agent, e.g. an anionic or cationic doping agent, preferably in the form of a salt.

13. A solid electrolyte obtainable by a method according to claim 9.

14. An electrochemical cell comprising the solid electrolyte according to claim 13.

Description

[0106] FIG. 1: XRD pattern of Li.sub.6PS.sub.5Cl measured with CuKα radiation in a 20 range of 5-90° and displayed as relative intensity I.sub.rel. Peaks marked with # originate from the sample holder.

EXAMPLE 1

[0107] 100.0 g of LiOH.H.sub.2O having a total water content of 42 wt. % were heated at 150° C. for 1 h in a fluidized bed reactor. Subsequently, the pre-dried lithium salt was contacted with a reaction gas, comprising P.sub.2S.sub.5 and H.sub.2S in a molar ratio of 1:5, as well as nitrogen as a carrier gas in a content of 95 vol. % with respect to the total amount of gas, at a total gas flow of 18 m.sup.3/h for 1 h at 150° C., yielding the solid electrolyte precursor.

[0108] Then, the solid electrolyte precursor was contacted with solid lithium chloride salt at 400° C., wherein the molar ratio of LiCl to solid electrolyte precursor was 1:1.

[0109] The solid electrolyte obtained has a stoichiometric composition of Li:P:S:Cl of 6:1:5:1 and an ionic conductivity of 4.5 mS/cm at room temperature, measured under inert gas atmosphere with electrochemical impedance spectroscopy on an Metrohm Autolab in a frequency range from 1 MHz to 100 Hz. The sample pellet was prepared by grinding the solid electrolyte powder and filled into a pressurized sample cell with a diameter of 13 mm with stainless steel electrodes. The applied pressure during measurement was p=3t.

[0110] An X-ray powder diffraction analysis was conducted on a Bruker D2 phaser diffractometer with CuK.sub.α radiation in a 2θ range of 5-90° with a step width of 0.020°.

[0111] The respective powder pattern is illustrated in FIG. 1 and showed characteristic reflections at a 2θ angle [° ]: 25.53, 30.04, and 31.41, and no reflections at a 2θ angle [° ]: 17.53, 18.05, 32.52, 34.88, 44.81, 46.66, 50.17, and 53.10.

[0112] The present invention comprises the following aspects: [0113] 1. A solid electrolyte precursor represented by the following formula (I):

Li.sub.(2a-n)Y.sup.n+S.sub.a  (I) [0114] wherein Y is independently selected from P, As, Ge, Sn, B, Si, Al, Ga, [0115] and Sb, [0116] 3≤n≤5, preferably 4≤n≤5, and [0117] 3≤a≤6, preferably 4≤a≤6. [0118] 2. The precursor according to item 1, wherein 4.8≤a≤5.2. [0119] 3. The precursor according to any of the preceding items, wherein Y.sup.n+ is independently selected from P.sup.5+, As.sup.5+, Ge.sup.4+, Si.sup.4+, B.sup.3+, Sn.sup.4+, Ga.sup.3+, Al.sup.3+ and Sb.sup.5+. [0120] 4. The precursor according to any of the preceding items, being selected from Li.sub.5PS.sub.5, Li.sub.5AsS.sub.5, Li.sub.4GeS.sub.4, Li.sub.4SiS.sub.4, Li.sub.3BS.sub.3, Li.sub.4SnS.sub.4, Li.sub.3GaS.sub.3, Li.sub.3AlS.sub.3, Li.sub.5SbS.sub.5 or mixtures thereof, such as physical mixtures, mixed crystals and/or solid solutions. [0121] 5. The precursor according to any of the preceding items, further comprising at least one dopant. [0122] 6. The precursor according to item 5, wherein the dopant is selected from Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, O, Sb, B, Ga, Se, O, Te, Mg, Na, Ca or a mixture thereof in their respective oxidation state. [0123] 7. The precursor according to any of items 5-6, wherein the dopant is present in an amount of less than 10 wt. %, preferably 0.01-9.0 wt. %, more preferably 0.10-5.0 wt. %, with reference to the total weight of the precursor. [0124] 8. The precursor according to any of the preceding items, being in a crystalline or partially crystalline state, more preferably in the form of a pure phase. [0125] 9. A method for producing a solid electrolyte precursor according to any of items 1-8, comprising the steps of: [0126] (i) providing a lithium salt in a reaction vessel, [0127] (ii) contacting a sulfur-containing reaction gas with the lithium salt of step (i) at elevated temperatures, [0128] (iii) contacting a Y-containing component with the product obtained in step (ii) at elevated temperatures, and [0129] (iv) optionally discharging the product obtained in step (iii), [0130] wherein the Y-containing component is at least partially present in a gaseous phase. [0131] 10. The method according to item 9, wherein the lithium salt has a water content of 0-50 wt. %, preferably 0-10 wt. %. [0132] 11. The method according to any of items 9-10, wherein step (i) is preceded by a step of pre-drying the lithium salt at an elevated temperature, such as at least 80° C., preferably 90-250° C., optionally at reduced pressure. [0133] 12. The method according to any of items 9-11, wherein the lithium salt in step (i) is LiOH, Li.sub.2CO.sub.3, Li.sub.2SO.sub.4, Li.sub.2O, Li.sub.2O.sub.2 or a mixture thereof. [0134] 13. The method according to any of items 9-12, wherein step (i) and/or step (ii) and/or step (iii) is carried out in dry air or an inert gas atmosphere, such as N.sub.2, He or Ar atmosphere. [0135] 14. The method according to item 13, wherein the inert gas or dry air is substantially free from water. [0136] 15. The method according to any of items 9-14, wherein step (ii) is performed at temperatures above 80° C., preferably at 90-250° C. [0137] 16. The method according to any of items 9-15, wherein the sulfur-containing reaction gas is selected from H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof. [0138] 17. The method according to any of items 9-16, wherein step (iii) is performed at temperatures above 285° C., preferably at 288-1200° C. [0139] 18. The method according to any of items 9-17, wherein the Y-containing component is selected from P.sub.2S.sub.5, As.sub.2S.sub.5, GeS.sub.2, SiS.sub.2, B.sub.2S.sub.3, SnS.sub.2, Ga.sub.2S.sub.3, Al.sub.2S.sub.3, Sb.sub.2S.sub.5 or a mixture thereof. [0140] 19. The method according to any of items 9-18, wherein the sulfur-containing reaction gas and the Y-containing component are substantially free from water. [0141] 20. The method according to any of items 9-19, wherein in step (ii) the molar ratio of S in sulfur-containing reaction gas, particularly H.sub.2S, to Li in lithium salt provided in step (i) is 1:1-1:10, preferably 1:1-1:5, more preferably about 1:2. [0142] 21. The method according to any of items 9-20, wherein in step (iii) the molar ratio of Y in Y-containing component, particularly P.sub.2S.sub.5, to Li in lithium salt provided in step (i) is 1:1-1:10, preferably 1:3-1:6, more preferably about 1:5. [0143] 22. The method according to any of items 9-21, wherein the sulfur-containing reaction gas further comprises a carrier gas. [0144] 23. The method according to any of items 9-22, wherein the Y-containing component further comprises a carrier gas. [0145] 24. The method according to any of items 9-23, wherein step (ii) is performed at a total gas flow of 0.1-1000 m.sup.3/h, preferably 5-500 m.sup.3/h, more preferably 10-50 m.sup.3/h. [0146] 25. The method according to any of items 9-24, wherein step (iii) is performed at a total gas flow of 0.1-1000 m.sup.3/h, preferably 5-500 m.sup.3/h, more preferably 10-50 m.sup.3/h. [0147] 26. The method according to any of items 9-25, further comprising a step (ii.1), prior to step (iii), of adding to the product obtained in step (ii) at least one doping agent, e.g. an anionic or cationic doping agent. [0148] 27. The method according to any of items 9-26, further comprising a step (iii.1) of adding to the product obtained in step (iii) at least one doping agent, e.g. an anionic or cationic doping agent. [0149] 28. The method according to any of items 26-27, wherein the at least one doping agent is provided in the form of a salt. [0150] 29. Use of a solid electrolyte precursor according to any of items 1-8 for preparing a solid electrolyte, in particular a sulfidic solid electrolyte. [0151] 30. The use according to item 29, wherein the solid electrolyte is represented by the following formula (II):

Li.sub.(2b+c-m)Y.sup.m+S.sub.bX.sub.c  (II) [0152] wherein X is independently selected from group 17 elements, such as Cl, Br and I, [0153] Y is independently selected from P, As, Ge, Sn, B, Si, Al, Ga, and Sb, [0154] 3≤m≤5, preferably 4≤m≤5, [0155] 3≤b≤6, preferably 4≤b≤6, and [0156] 0≤c≤2. [0157] 31. The use according to item 29, wherein the solid electrolyte is represented by the following formula (III):

Li.sub.(8-q*(1-t)-r*t)Y′.sup.q+.sub.1-tY′.sup.r+.sub.tS.sub.4  (III) [0158] wherein Y″ is independently selected from Si, and Ge, [0159] Y″ is independently selected from P, Al, Sn, Ga, and Sb, [0160] 3≤q≤5 [0161] 2≤r≤6 [0162] 0≤t<≤1 [0163] 32. The use according to item 29, wherein the solid electrolyte is Li.sub.3PS.sub.4, Li.sub.7P.sub.3S.sub.11, or Li.sub.10YP.sub.2S.sub.12, wherein Y is independently selected from Si, Sn, and Ge. [0164] 33. A method for preparing a solid electrolyte, comprising the steps of: [0165] (a) providing a solid electrolyte precursor according to any of items 1-8 in a reaction vessel, [0166] (b) contacting at least one X-containing and/or S-containing lithium salt and/or Y-containing sulfide with the solid electrolyte precursor of step (a) at elevated temperatures, and [0167] (c) optionally discharging the product obtained in step (b). [0168] 34. The method according to item 33, wherein step (a) and/or step (b) is carried out in dry air or an inert gas atmosphere, such as N.sub.2, He or Ar atmosphere. [0169] 35. The method according to item 34, wherein the inert gas is substantially free from water. [0170] 36. The method according to any of items 33-35, wherein step (b) is performed at temperatures above 80° C., preferably at 90-700° C. [0171] 37. The method according to any of items 33-36, wherein the X-containing lithium salt is a halide, such as LiCl, LiBr, LiI or a mixture thereof, preferably LiCl or LiBr, and/or wherein the S-containing lithium salt is preferably Li.sub.2S, and/or wherein the Y-containing sulfide is preferably P.sub.2S.sub.5. [0172] 38. The method according to any of items 33-37, wherein in step (b) the molar ratio of X in X-containing lithium salt or of S in the S-containing lithium salt to solid electrolyte precursor provided in step (a) is 0.01:1-3:1. [0173] 39. The method according to any of items 33-38, wherein the X-containing lithium salt is substantially free from water. [0174] 40. The method according to any of items 33-39, further comprising a step (b.1) of adding to the product obtained in step (b) at least one doping agent, e.g. an anionic or cationic doping agent. [0175] 41. The method according to item 40, wherein the at least one doping agent is provided in the form of a salt. [0176] 42. A solid electrolyte obtainable by a method according to any of items 33-41. [0177] 43. An electrochemical cell comprising the solid electrolyte according to item 42.