LITHIUM DIFLUOROPHOSPHATE, ELECTROLYTIC SOLUTION CONTAINING LITHIUM DIFLUOROPHOSPHATE, PROCESS FOR PRODUCING LITHIUM DIFLUOROPHOSPHATE, PROCESS FOR PRODUCING NONAQUEOUS ELECTROLYTIC SOLUTION, NONAQUEOUS ELECTROLYTIC SOLUTION, AND NONAQUEOUS-ELECTROLYTIC-SOLUTION SECONDARY CELL EMPLOYING THE SAME

摘要

A difluorophosphate salt, which is expensive and not readily available, can be produced with a high purity readily and efficiently from inexpensive and readily available materials. A nonaqueous electrolyte secondary battery that exhibits low-temperature discharge and heavy-current discharge characteristics and high-temperature preservation and cycle characteristics without impairing the battery safety. A hexafluorophosphate salt is reacted with a compound having a bond represented by the following formula (1) in the molecule: €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒSi-O-Si€ƒ€ƒ€ƒ€ƒ€ƒ(1) A nonaqueous electrolyte used for nonaqueous electrolyte secondary batteries including a negative electrode and a positive electrode that can occlude and discharge ions, and a nonaqueous electrolyte is prepared from a mixture obtained by mixing at least one nonaqueous solvent, a hexafluorophosphate salt and a compound having a bond represented by the following formula (1), and removing low-boiling compounds newly formed in the system, the low-boiling compounds having a lower boiling point than that of the compound having the bond represented by the formula (1): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒSi-O-Si€ƒ€ƒ€ƒ€ƒ€ƒ(1)