Method for producing lithium difluorophosphate

The A method of producing lithium difluorophosphate, the method comprising:

• obtaining a first raw material mixture by mixing lithium hexafluorophosphate, at least one selected from the group consisting of an oxide of phosphorus (A) and a lithium salt of a phosphoric acid (B), and at least one hydrocarbon solvent selected from the group consisting of tetralin, toluene, hexane and cyclohexane, a content of the hydrocarbon solvent contained in the first raw material mixture being 50% by mass or more with respect to an entirety of the first raw material mixture;
• obtaining a second raw material mixture in a form of a wet cake by removing at least a part of the hydrocarbon solvent contained in the obtained first raw material mixture;
• and
• producing a crude product containing lithium difluorophosphate by reacting the second raw material mixture at a temperature of from 100° C. to 350° C., wherein producing the crude product includes producing the crude product by reacting lithium hexafluorophosphate with at least one selected from the group consisting of an oxide of phosphorus (A) and a lithium salt of a phosphoric acid (B) according to the following reaction formula:
• Reaction formula:
• x(LiPF6)+y(oxide of phosphorus (A))+z(lithium salt of phosphoric acid (B)) n(LiPO2F2)
• wherein, in the reaction formula, x, y, z, and n represent stoichiometric coefficients, each of x and n independently represents an integer of 1 or more, and each of y and z independently represents an integer of 0 or 1 or more, provided that, x, y, z, and n satisfy the following formulae (1) to (4):
• x+number of Li atoms in (B)×z=n;
• Formula (1):
• x+number of P atoms in (A)×y+number of P atoms in (B)×z=n;
• Formula (2):
• number of O atoms in (A)×y+number of O atoms in (B)×z=2n;
• and Formula (3):
• 6x=2n. Formula (4):

A method of producing lithium difluorophosphate, the method comprising:

• obtaining a first raw material mixture by mixing lithium hexafluorophosphate, at least one selected from the group consisting of an oxide of phosphorus (A) and a lithium salt of a phosphoric acid (B), and a hydrocarbon solvent having from 6 to 12 carbon atoms, a content of the hydrocarbon solvent contained in the first raw material mixture being 50% by mass or more with respect to an entirety of the first raw material mixture;
• obtaining a second raw material mixture in a form of a wet cake by removing at least a part of the hydrocarbon solvent contained in the obtained first raw material mixture;
• producing a crude product containing lithium difluorophosphate by reacting the second raw material mixture at a temperature of from 100° C. to 350° C.;
• obtaining a solution by dissolving the crude product in a purification solvent;
• and
• extracting lithium difluorophosphate from the solution.