<scp> Amino‐functionalized SiO ₂ </scp> modified porous polyetherimide separator for high performance <scp>Li‐S</scp> batteries

Abstract

As one of the most promising energy storage systems, the application of lithium sulfur battery is hindered by low ionic conductivity, poor thermal stability, and a serious shuttle effect of polysulfide species of commercial polyolefin separators. Herein, a kind of novel porous polyetherimide (PEI) based separator (IAPEI-4) with excellent heat resistance and electrochemical properties was prepared. Briefly, by grafting amino group (–NH2) onto the surface of SiO2, highly dispersed amino-functionalized SiO2 (A-SiO2) were synthesized as fillers to blend PEI matrix. Based on physical characterizations of the representative IAPEI-4 separator, abundant micropores and mesopores exist in the separator, and A-SiO2 nanoparticles are uniformly distributed in the PEI matrix. The ameliorated Li+ transport channels and the uniform distribution of A-SiO2 nanoparticles endow IAPEI-4 separator with higher ionic conductivity (1.60 mS cm−1) and Li+ transfer number (0.63). Besides, the IAPEI-4 separator exhibits good electrochemical stability and excellent thermal stability (no shrinkage at 200°C). The Li-S cells with the IAPEI separator also show greatly enhanced electrochemical performances. After 100 cycles, its specific discharge capacity can reach 695.4 mAh g−1 at 0.2 C and its capacity retention rate is 84.8%. This simple and effective separator modification method can provide a general strategy to achieve high-performance Li-S batteries.