Implementing reliable battery systems with long cycle life, high power output and low cost are of great importance. High performance dual-graphite battery (DGB) is one of promising candidates. Herein, we develop a novel high concentration electrolyte (HCE), 2 M LiPF6- ethyl-methyl carbonate/sulfolane, which can endow the DGB with a high ceiling voltage of 5.3 V, an elongated cycle life (94.7% of capacity retention after 1000 cycles at 5 C rate) and simultaneously fast charging/discharging kinetics (91.0 mAh g−1 even at 20 C rate). Combinational experiments are conducted to investigate the mechanism of this HCE on the improvement of the electrochemical performance. It is found that this HCE could suppress the graphite cathode from structural collapse owing to the increased proportion of contact ion pairs and ion aggregates. Besides, it prompts the formation of a dense and uniform SEI layer, leading to highly reversible Li+ intercalation/deintercalation. This would promote the development of DGB with high rate performance and excellent cycleability.