| abstract |
The disclosure provides an electrolyte solution that enables a lithium ion secondary battery to have reduced initial resistance, a small increase in resistance at high-temperature cycles, and reduced gas generation at high temperature. The electrolyte solution for a lithium ion secondary battery contains lithium difluorophosphate, an oxalic acid ion, and a compound (1) represented by the following formula (1): n n n n n n n n n n wherein R 1 and R 2 are each independently a methyl group, an ethyl group, a propyl group, or a butyl group. |