SOLVENT FOR ELECTROLYTIC SOLUTION, ELECTROLYTIC SOLUTION, AND GEL-LIKE ELECTROLYTE

The invention provides a solvent for an electrolyte solution, an electrolyte solution, and a gel-like electrolyte superior in oxidation resistance and flame resistance. A solvent for an electrolyte solution comprising at least one boric ester represented by the following formula (I), and a boric ester represented by the following formula (II): B(ORf) 3 (I); B(OCH 2 CH 2 CN) 3 (II) wherein, in formula (I), each Rf independently represents CH 2 (CF 2 ) n CF 3 or CH(CF 3 ) 2 , n is an integer from 0 to 6, and at least a part of each of -ORf and -OCH 2 CH 2 CN included in the boric esters is transesterified.