NON-AQUEOUS ELECTROLYTE FOR POWER STORAGE ELEMENT, NON-AQUEOUS ELECTROLYTE POWER STORAGE ELEMENT, AND METHOD FOR PRODUCING NON-AQUEOUS ELECTROLYTE POWER STORAGE ELEMENT

A nonaqueous electrolyte for an energy storage device according to an aspect of the present invention includes an imide salt (a), a salt (b) in which a charge center element of an anion is boron and which has an oxalato group, and a difluorophosphate (c), in which a content of the imide salt (a) is 3 or more in terms of molar ratio with respect to a total content of the salt (b) in which the charge center element of the anion is boron and which has the oxalato group and the difluorophosphate (c). A nonaqueous electrolyte for an energy storage device according to another embodiment of the present invention includes an imide salt (a), a salt (b) in which a charge center element of an anion is boron and which has an oxalato group, and a difluorophosphate (c), in which a content of the imide salt (a) is 25 mol% or more with respect to a total content of all ionic compounds.