Production method for solid electrolyte and electrolyte precursor

1 . A production method of a solid electrolyte containing a lithium element, a sulfur element, a phosphorous element, and a halogen element, the method comprising:

mixing a complexing agent having an ester group and also having at least one branch with a solid electrolyte raw material, and drying to obtain an electrolyte precursor comprising the complexing agent, a lithium element, a sulfur element, a phosphorus element, and a halogen element;

heating the electrolyte precursor to obtain an amorphous solid electrolyte; and

heating the amorphous solid electrolyte in an inert gas atmosphere or a reduced pressure atmosphere to obtain a crystalline solid electrolyte,

wherein the crystalline solid electrolyte is in a form of particles, and

wherein the halogen element comprises bromine and iodine.

2 . The production method of a solid electrolyte according to claim 1 , wherein the solid electrolyte contains a PS 4 3− skeleton.

3 . The production method of a solid electrolyte according to claim 1 , wherein the solid electrolyte contains a thio-LISICON Region II-type crystal structure.

4 . The production method of a solid electrolyte according to claim 3 , wherein the solid electrolyte does not have diffraction peaks at 2θ=17.5° and 26.1° in the X-ray diffractometry using a CuKα ray.

5 . The production method of a solid electrolyte according to claim 1 , wherein a boiling point of the complexing agent is 100° C. or higher.

6 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent is a compound represented by the following general formula (I):

R 11 —X 11 —R 12 —X 12 —R 13   (1)

wherein X 11 and X 12 are each independently a single bond, an ester group, or an ether group, and at least one of X 11 and X 12 is an ester group; R 11 and R 13 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms; R 12 is a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms; and at least one of R 11 , R 12 , and R 13 has a branch.

7 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent has an ester group and at least one selected from an ester group and an ether group, with a total of these groups being two or more.

8 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent has a methyl ether group.

9 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent is propylene glycol monomethyl ether acetate.

10 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent has a 2-propyl group in at least one end thereof.

11 . The production method of a solid electrolyte according to claim 1 , wherein the complexing agent is isobutyl isobutyrate.

12 . The production method of a solid electrolyte according to claim 1 , wherein the solid electrolyte raw material contains lithium sulfide and diphosphorus pentasulfide as raw materials.

13 . The production method of a solid electrolyte according to claim 1 , wherein the solid electrolyte raw material contains amorphous Li 3 PS 4 or crystalline Li 3 PS 4 as a raw material.

14 . The production method of a solid electrolyte according to claim 1 , comprising mixing the solid electrolyte raw material, the complexing agent, and a solvent that does not dissolve the electrolyte precursor.

15 . The production method of a solid electrolyte according to claim 14 , wherein the solvent is at least one solvent selected from an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent, and an ether-based solvent.

16 . A production method of a solid electrolyte containing a lithium element, a sulfur element, a phosphorous element, and a halogen element, the method comprising:

mixing a complexing agent having an ester group and also having at least one branch with a solid electrolyte raw material, and drying to obtain an electrolyte precursor comprising the complexing agent, a lithium element, a sulfur element, a phosphorus element, and a halogen element;

heating the electrolyte precursor to obtain an amorphous solid electrolyte; and

heating the amorphous solid electrolyte at a temperature of 130° C. to 300° C. in an inert gas atmosphere or a reduced pressure atmosphere to obtain a crystalline solid electrolyte,

wherein the halogen element comprises bromine and iodine.

17 . A production method of a solid electrolyte containing a lithium element, a sulfur element, a phosphorous element, and a halogen element, the method comprising:

mixing a complexing agent having an ester group and also having at least one branch with a solid electrolyte raw material, and drying to obtain an electrolyte precursor comprising the complexing agent, a lithium element, a sulfur element, a phosphorus element, and a halogen element, wherein a content of the solid electrolyte raw material is 5 g to 300 g relative to an amount of one liter of the complexing agent;

heating the electrolyte precursor to obtain an amorphous solid electrolyte; and

heating the amorphous solid electrolyte in an inert gas atmosphere or a reduced pressure atmosphere to obtain a crystalline solid electrolyte,

wherein the halogen element comprises bromine and iodine.

18 . The production method of a solid electrolyte according to claim 1 , wherein the mixing is performed at a temperature of −10° C. to 50° C.