Ternary lithium-salt organic ionic plastic crystal polymer composite electrolytes for high voltage, all-solid-state batteries

Organic ionic plastic crystals (OIPCs) are a promising class of solid electrolyte material and recent reports of high concentration Li-containing OIPCs are drawing attention due to their enhanced performance. In this report, nano-sized poly(vinylidene difluoride) (PVdF) particles were incorporated with 1:1 (mole ratio) LiFSI : [C2mpyr][FSI], (C2mpyr = N-ethyl-N-methylpyrrolidinium, FSI = bis(fluorosulfonyl)imide) in a ternary composite, and developed as free-standing solid electrolytes using a facile powder pressing strategy. The electrolytes exhibited relatively high ionic conductivity, up to 10-4 S cm-1 at 30 °C, resulting from an interphase consisting of the OIPC-LiFSI coating the individual, closely packed PVdF particles. The Li+ transference number was 0.44±0.02 at 50 °C, the highest value reported so far for a plastic crystal based electrolyte. Li | LiNi1/3Mn1/3Co1/3O2 cells charged to 4.6 V sustained up to 1300 charge-discharge cycles at 50 °C, highlighting the exceptional stability of these electrolytes. The cells exhibited better capacity retention than a comparative liquid LP30 electrolyte (1 M LiPF6 in ethylene carbonate : dimethyl carbonate (vol. 1:1)) when cycled at a rate of 1 C at 50 °C.