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‖LiNi_0.5Mn_1.5O₄ and Li‖Li_1.144Mn_0.544Ni_0.136Co_0.136O₂ 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.