US Patent 7709157 Non-aqueous electrolyte secondary battery and electrolyte for the same

The present invention provides a safe non-aqueous electrolyte secondary battery with characteristics analogous to those of a conventional battery by minimizing battery expansion that causes damage to a device during high temperature exposure or storage. The non-aqueous electrolyte secondary battery comprises: (a) a chargeable and dischargeable positive electrode; (b) a negative electrode capable of absorbing and desorbing lithium; (c) a separator for preventing direct electron transfer between the positive electrode and the negative electrode; and (d) an non-aqueous electrolyte; the non-aqueous electrolyte comprising a non-aqueous solvent and a solute, the non-aqueous solvent comprising a lactone, the solute comprising lithium bis(fluorosulfonyl)imide represented by the formula (1):(F—O2S—N—SO2—F)Li.