| abstract |
A thiophosphate flame retardant represented by (R 1 S) 3 P═O, wherein R 1 is aryl, alkaryl, or aralkyl, is added to a non-aqueous solvent to the extent of approximately 1/10-1/100 of a carbonate type solvent which is the main component of an electrolyte, to provide a lithium ion secondary cell solvent offering improved fire-retarding properties without much change of electrolyte composition. In this way, the boiling point can be raised and flame retarding properties can be conferred with almost no increase in the viscosity of the electrolyte. |