We prepared a lithium bis(fluorosulfonyl)imide (LiFSI)-based low ethylene carbonate (EC) content electrolyte as a new electrolyte. LiFSI enough dissociates in mixed solvents containing only a small amount of EC and the LiFSI-based low EC content electrolyte shows a high ionic conductivity comparable to that of a conventional LiPF6-based high EC content electrolyte. In addition, the LiFSI-based low EC content electrolyte has an unusual solvation state of Li ion and we consider that the desolvation process from Li ion in our new electrolyte system is different from that in the conventional high EC content systems. A graphite half-cell assembled with our new electrolyte shows a quite low Li ion transfer resistance and outstanding charge and discharge rate performance compared to the conventional high EC content systems. A graphite/LiNi1/3Mn1/3Co1/3O2 cell assembled with our new electrolyte also shows superior charge and discharge rate performance and excellent long cycle stability.