Electrolyte design for high power dual-ion battery with graphite cathode for low temperature applications

The design of electrolyte suitable for low-temperature use is of great significance to expand the applications of energy storage devices. Dual-ion battery (DIB) with fast ion transport kinetics is expected to be a nascent battery system that can deliver high power density both at room temperature and low temperatures. In this work, we design a 4.8 M lithium bis(fluorosulfonyl)imide in 2,2,2-trifluoroethyl acetate/dimethyl carbonate (LiFSI FEA/DMC) + 1 % LiPF6 electrolyte with a low melting point of about −93 °C, enabling graphite cathode in a DIB to achieve excellent fast charge/discharge capability with a high capacity of about 108 mAh g−1 and 80 mAh g−1 at 10 C at 25 °C and 0 °C, respectively. Even at −30 °C, the graphite cathode can still give a capacity of 69.2 mAh g−1 at 0.5 C. The graphite||Li DIB with 4.8 M LiFSI FEA/DMC + 1 % LiPF6 electrolyte also exhibits a stable cycle life with a capacity retention of 91.5 % at 5 C after 2000 cycles at 25 °C. The electrolyte forms a uniform cathode electrolyte interface film on the graphite surface, as confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy, which enables the outstanding electrochemical performance of the graphite cathode in a wide working temperature range from −30 °C to 25 °C.