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 parallel to LiNi0.5Mn1.5O4 and Li parallel to 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. (C) 2019 Elsevier Ltd. All rights reserved.