Fluoroalkyl ether electrolyte with redefined in-cell ion affinity upgrades rate performances of lithium ion batteries

Lithium ion batteries have profound impact on every corner of human life. However, strong solvation of Li+ and rough interfacial ion transfer associated with conventional electrolytes limit the long cycle, high-rate battery operation of lithium ion batteries. Herein we design an electrolyte system based on fluoroalkyl ether 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether (THE) and ether electrolytes to effectively upgrade the long-cycle rate performances of electrodes in general. With THE rich in fluoroalkyl groups adjacent to oxygen atoms, the electrolyte owns an ultra-high polarity, enabling solvation-free Li+ transfer with an energy barrier of 0.11 eV, only 1/7 of that for conventional ether electrolytes, and 10-times enhancement in Li+ transference at electrolyte/anode interface. In addition, the uniform adsorption of fluorine-rich THE on anode and subsequent LiF formation suppress dendrite formation and stabilize the solid electrolyte interphase layer. With the electrolyte, LiFePO4 cathodes deliver unprecedented cyclic performances with only 0.0012% capacity loss cycle-1 over 5000 cycles at 10 C, along with upgraded rate performances as observed for other mainstream electrodes including LiCoO2, LiNi0.5Mn0.3Co0.2O2 and Li4Ti5O12.