Localized concentrated high-concentration electrolyte enhanced stability and safety for high voltage Li-ion batteries

The stability of electrolyte at high voltage is important to the development of Li-ion battery that required by the high energy density and high security. However, the decomposition of commercial electrolyte at high voltage limits its practical application. Herein, we introduce a “localized concentrated high-concentration electrolyte” which indicates underlying prospect in high voltage batteries. The “localized concentrated high-concentration electrolyte” can be achieved by adding 1,1,1,3,3,3-hexafluoroisopropyl methyl ether into traditional dimethyl carbonate and fluoroethylene carbonate solvents. The electrolyte (3 mol L−1 LiPF6 DMC/FEC/HFPM 6/1/3) exhibits excellent flame retardant, low viscosity, wide electrochemical window and superior wettability. The Li‖LiNi0.5Mn1.5O4 and Li‖Li1.144Mn0.544Ni0.136Co0.136O2 coin cells with this electrolyte display splendid discharge capacity of 122.2 mAh g−1 after 400 cycles and 221.0 mAh g−1 after 100 cycles at 0.5 C, respectively. While 100.1 mAh g−1 after 35 cycles and 194.8 mAh g−1 after 100 cycles are obtained in commercial electrolyte, respectively. Further analysis shows that stability of high voltage cathodes is mainly contributed to the fluoride protective layer. This method offers a novel pathway for high-concentration electrolyte to improve the performance of Li-ion batteries.