A SULFIDIC SOLID ELECTROYLYTE AND ITS PRECURSOR

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 or capacitors, fuel cells, batteries, and sensors.

Claims

1. A solid electrolyte precursor represented by the following formula (I):
Li.sub.(2a+b)S.sub.aX.sub.b  (I) wherein X is independently selected from group 17 elements, preferably Cl, Br, and I, 2≤a≤3, preferably 2.4≤a≤2.6, and 0<b≤2, preferably 0.8≤b≤1.2.

2. The precursor according to claim 1, being selected from Li.sub.6S.sub.2.5Cl, Li.sub.6S.sub.2.5Br and Li.sub.6S.sub.2.5I.

3. The precursor according to claim 1, further comprising at least one dopant selected from the group consisting of Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, Se, O, Te, Mg, Na, Ca, Sb, B, Ga and a mixture thereof.

4. A method for producing a solid electrolyte precursor according to claim 1, comprising the steps of: (i) providing a lithium salt in a reaction vessel, (ii) contacting at least one first reaction gas and at least one second reaction gas with the lithium salt of step (i) at elevated temperatures such as above 80° C., preferably at 90-250° C., and (iii) optionally discharging the product obtained in step (ii), wherein one of the first and the second reaction gas is a sulfur-containing gas and the other reaction gas is a X-containing gas.

5. The method according to claim 4, 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.

6. The method according to claim 4, wherein the at least one first reaction gas is a hydrogen halide, such as HCl, HBr, HI or a mixture thereof, and, preferably, the at least one second reaction gas is a sulfur source selected from the group consisting of H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof, or wherein the at least one first reaction gas is a sulfur source selected from the group consisting of H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof, and, preferably, the at least one second reaction gas is a hydrogen halide, such as HCl, HBr, HI or a mixture thereof.

7. The method according to claim 4, wherein the molar ratio of S in S-containing reaction gas to X in X-containing reaction gas is 10:1-1:1, preferably 3:1-1.5:1, more preferably 2.6:1-2.4:1.

8. Use of a solid electrolyte precursor according to claim 1, for preparing a solid electrolyte.

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 a Y-containing component with the solid electrolyte precursor of step (a), and (c) optionally discharging the product obtained in step (b), wherein step (b) is performed at elevated temperatures, such as above 285° C., preferably at 288-900° C., wherein Y is independently selected from P, As, Ge, Si, B, Sn, Ga, Al and Sb, and wherein the Y-containing component is at least partially present in a gaseous phase in step (b).

10. The method according to claim 9, wherein the Y-containing component is selected from the group consisting of P.sub.2S.sub.5, As.sub.2S.sub.5, GeS.sub.2, SiS.sub.2, B.sub.2S.sub.3, SnS, Ga.sub.2S.sub.3, Al.sub.2S.sub.3, Sb.sub.2S.sub.5 and a mixture thereof.

11. The method according to claim 9, wherein in step (b) the molar ratio of Y in Y-containing component to solid electrolyte precursor provided in step (a) is 0.2:1-2:1, preferably 0.5:1-1:1.

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

13. A solid electrolyte represented by the following formula (II):
Li.sub.(2c+d−n)Y.sup.n+S.sub.cX.sub.d  (II) wherein X is independently selected from group 17 elements, preferably Cl, Br and I, Y is independently selected from P, As, Ge, Si, B, Sn, Ga, Al, and Sb, 4≤n≤5, 4≤c≤6, and 0<d≤2, being substantially free from reflections in a X-ray powder diffractogram using CuK.sub.a radiation at a 2θ angle [°]:17.5, 18.0, 32.5, 34.9, 44.8, 46.7, 50.2 and/or 53.1.

14. The solid electrolyte according to claim 13, further comprising at least one dopant, such as Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, Se, O, Te, Mg, Na, Ca, Sb, B, Ga or a mixture thereof.

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

Description

[0096] The present invention shall be further illustrated in more detail but not limited by the following FIGURE and example.

[0097] 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

[0098] 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 HCl and H.sub.2S in a molar ratio of 1:2.5, 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.

[0099] Then, the solid electrolyte precursor was contacted with gaseous P.sub.2S.sub.5 at 288° C. at a total gas flow of 18 m.sup.3/h (including nitrogen as a carrier gas in a content of 95 vol. % with respect to the total amount of gas) for 1 h, wherein the molar ratio of P.sub.2S.sub.5 to solid electrolyte precursor was 0.5:1.

[0100] 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. 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°.

[0101] The respective powder pattern 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 (see FIG. 1).

[0102] The present invention covers the following items: [0103] 1. A solid electrolyte precursor represented by the following formula (I):

Li.sub.(2a+b)S.sub.aX.sub.b  (I)

wherein X is independently selected from group 17 elements, [0104] 2≤a≤3, and

[0105] 0<b≤2. [0106] 2. The precursor according to item 1, wherein X is independently selected from the group consisting of Cl, Br and I. [0107] 3. The precursor according to any of the preceding items, wherein 0.8≤b≤1.2. [0108] 4. The precursor according to any of the preceding items, wherein 2.4≤a≤2.6. [0109] 5. The precursor according to any of the preceding items, being selected from Li.sub.6S.sub.2.5Cl, Li.sub.6S.sub.2.5Br and Li.sub.6S.sub.2.5I. [0110] 6. The precursor according to any of the preceding items, further comprising at least one dopant. [0111] 7. The precursor according to item 6, wherein the dopant is selected from Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, Se, O, Te, Mg, Na, Ca, Sb, B, Ga or a mixture thereof in their respective oxidation state. [0112] 8. The precursor according to any of items 6-7, 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. [0113] 9. The precursor according to any of the preceding items, being in a crystalline state, preferably in the form of a pure phase. [0114] 10. A method for producing a solid electrolyte precursor according to any of items 1-9, comprising the steps of: [0115] (i) providing a lithium salt in a reaction vessel, [0116] (ii) contacting at least one first reaction gas and at least one second reaction gas with the lithium salt of step (i) at elevated temperatures, and [0117] (iii) optionally discharging the product obtained in step (ii), [0118] wherein one of the first and the second reaction gas is a sulfur-containing gas and the other reaction gas is a X-containing gas. [0119] 11. The method according to item 10, wherein the lithium salt has a water content of 0-50 wt. %, preferably 0-10 wt. %.

[0120] 12. The method according to any of items 10-11, 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. [0121] 13. The method according to any of items 10-12, 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. [0122] 14. The method according to any of items 10-13, wherein step (i) and/or step (ii) is carried out in dry air or an inert gas atmosphere, such as N.sub.2, He or Ar atmosphere. [0123] 15. The method according to item 14, wherein the inert gas or dry air is substantially free from water. [0124] 16. The method according to any of items 10-15, wherein step (ii) is performed at temperatures above 80° C., preferably at 90-250° C. [0125] 17. The method according to any of items 10-16, wherein the at least one first reaction gas is a hydrogen halide, such as HCl, HBr, HI or a mixture thereof, and, preferably, the at least one second reaction gas is a sulfur source selected from H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof. [0126] 18. The method according to any of items 10-17, wherein the at least one first reaction gas is a sulfur source selected from H.sub.2S, S.sub.8, CS.sub.2, mercaptanes or a mixture thereof, and, preferably, the at least one second reaction gas is a hydrogen halide, such as HCl, HBr, HI or a mixture thereof. [0127] 19. The method according to any of items 10-18, wherein in step (ii) the first and the second reaction gas are provided sequentially or simultaneously. [0128] 20. The method according to any of items 10-19, wherein the at least one first reaction gas and the at least one second reaction gas are contacted prior to step (ii). [0129] 21. The method according to any of items 10-20, wherein the at least one first reaction gas and the at least one second reaction gas are substantially free from water. [0130] 22. The method according to any of items 10-21, wherein the molar ratio of S in S-containing reaction gas to X in X-containing reaction gas is 10:1-1:1, preferably 3:1-1.5:1, more preferably 2.6:1-2.4:1. [0131] 23. The method according to any of items 10-22, wherein the at least one first reaction gas further comprises a carrier gas. [0132] 24. The method according to any of items 10-23, wherein the at least one second reaction gas further comprises a carrier gas. [0133] 25. The method according to any of items 10-24, 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 even more preferably about 20 m.sup.3/h. [0134] 26. The method according to any of items 10-25, further comprising a step of adding to the product obtained in step (ii) at least one doping agent, e.g. comprising Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, O, Se, Te, Mg, Na, Ca, Sb, B, Ga or a mixture thereof in their respective oxidation state as a dopant. [0135] 27. The method according to item 26, wherein the at least one doping agent is an anionic or cationic doping agent, in particular provided in the form of a salt. [0136] 28. Use of a solid electrolyte precursor according to any of items 1-9 for preparing a solid electrolyte. [0137] 29. The use according to item 28, wherein the solid electrolyte is represented by the following formula (II):

Li.sub.(2c+d−n)Y.sup.n+S.sub.cX.sub.d  (II) [0138] wherein X is independently selected from group 17 elements, preferably Cl, Br and I, [0139] Y is independently selected from P, As, Ge, Si, B, Sn, Ga, Al and Sb, [0140] 4≤n≤5, [0141] 4≤c≤6, and [0142] 0<d≤2. [0143] 30. A method for preparing a solid electrolyte, comprising the steps of: [0144] (a) providing a solid electrolyte precursor according to any of items 1-9 in a reaction vessel, [0145] (b) contacting a Y-containing component with the solid electrolyte precursor of step (a), and [0146] (c) optionally discharging the product obtained in step (b), [0147] wherein step (b) is performed at elevated temperatures, [0148] wherein Y is independently selected from P, As, Ge, Si, B, Sn, Ga, Al and Sb, and [0149] wherein the Y-containing component is at least partially present in a gaseous phase in step (b). [0150] 31. The method according to item 30, 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. [0151] 32. The method according to item 31, wherein the inert gas or dry air is substantially free from water. [0152] 33. The method according to any of items 30-32, wherein step (b) is performed at temperatures above 285° C., preferably at 288-900° C. [0153] 34. The method according to any of items 30-33, 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, Ga.sub.2S.sub.3, Al.sub.2S.sub.3, Sb.sub.2S.sub.5 or a mixture thereof. [0154] 35. The method according to any of items 30-34, wherein in step (b) the molar ratio of [0155] Y in Y-containing component to solid electrolyte precursor provided in step (a) is 0.2:1-2:1, preferably 0.5:1-1:1. [0156] 36. The method according to any of items 30-35, wherein the Y-containing component is substantially free from water. [0157] 37. The method according to any of items 30-36, wherein the Y-containing component further comprises a carrier gas. [0158] 38. The method according to any of items 30-37, wherein step (b) 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, even more preferably about 20 m.sup.3/h. [0159] 39. The method according to any of items 30-38, further comprising a step of adding to the product obtained in step (b) at least one doping agent, e.g. a cationic or anionic doping agent. [0160] 40. The method according to item 39, wherein the at least one cationic doping agent comprises Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, O, Se, Te, Mg, Na, Ca, Sb, B, Ga or a mixture thereof in their respective oxidation and/or the anionic doping agent comprises O.sup.2− S.sup.2−, Se.sup.2−, or Te.sup.2−. [0161] 41. A solid electrolyte obtainable by a method according to any of items 30-40. [0162] 42. A solid electrolyte represented by the following formula (II):

Li.sub.(2c+d−n)Y.sup.n+S.sub.cX.sub.d  (II) [0163] wherein X is independently selected from group 17 elements, [0164] Y is independently selected from P, As, Ge, Si, B, Sn, Ga, Al and Sb, [0165] 4≤n≤5, [0166] 4≤c≤6, and [0167] 0<d≤2, [0168] being substantially free from reflections in a X-ray powder diffractogram using CuK.sub.α radiation at a 2θ angle [°]:17.5, 18.0, 32.5, 34.9, 44.8, 46.7, 50.2 and/or 53.1. [0169] 43. The solid electrolyte according to item 42, being substantially free from reflections in a X-ray powder diffractogram using CuK.sub.α radiation at a 2θ angle [°]:17.5, 18.0, 32.5, 34.9, 44.8, 46.7, 50.2 and 53.1. [0170] 44. The solid electrolyte according to any of items 42-43, having characteristic reflections in a X-ray powder diffractogram using CuK.sub.α radiation at a 2θ angle [°]:25.2, 25.5, 29.6, 30.0, 31.0 and/or 31.4. [0171] 45. The solid electrolyte according to any of items 42-44, further comprising at least one dopant. [0172] 46. The solid electrolyte according to item 45, wherein the dopant is selected from Mn, Ge, Sn, V, Ni, Cr, Si, Al, As, Se, O, Te, Mg, Na, Ca, Sb, B, Ga or a mixture thereof in their respective oxidation state. [0173] 47. The solid electrolyte according to any of items 45-46, 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 solid electrolyte. [0174] 48. The solid electrolyte according to any of items 42-47, having an ionic conductivity of 0.01-500 mS/cm, preferably 1-100 mS/cm at 20° C. [0175] 49. The solid electrolyte according to any of items 42-48, wherein X is independently selected from Cl, Br and I. [0176] 50. The solid electrolyte according to any of items 42-49, wherein 0.8≤d≤1.2. [0177] 51. The solid electrolyte according to any of items 42-50, wherein 4.5≤c≤5.5. [0178] 52. The solid electrolyte according to any of items 42-41, 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+. [0179] 53. The solid electrolyte according to any of items 42-52, wherein Y.sup.n+ is P.sup.5+. [0180] 54. The solid electrolyte according to any of items 42-53, being selected from Li.sub.6PS.sub.5Cl, Li.sub.6PS.sub.5Br and Li.sub.6PS.sub.5I. [0181] 55. An electrochemical cell comprising the solid electrolyte according to any of items 42-53. [0182] 56. Use of a solid electrolyte according to any of items 42-53 in an electrochemical cell or capacitor, a fuel cell, a battery, or a sensor.