PEI-SiO2 composite membranes with high thermal stability: Synthesis by self-assembled in situ growth and application in lithium-ion batteries

To improve the safety of lithium-ion batteries (LIBs), a polyether amide–silica (PEI-SiO 2 ) composite membrane was developed by the in situ hydrolysis of tetraethylorthosilicate (TEOS) and its subsequent self-assembly on the surface of PEI fibers. Because of the presence of the SiO 2 shell, the PEI-SiO 2 composite membrane exhibited good thermal stability at high temperatures. The composite membrane did not change its color and size after heating at 200°C for 1 h as well as exhibited excellent flame retardancy. Moreover, the membrane maintained its high porosity even after the introduction of shell layers. The electrolyte is completely absorbed in the membrane within 0.5 s. The electrolyte uptake was up to 625%, and the ionic conductivity was up to 1.9 mS/cm at room temperature. Compared to the polyolefin membrane and the pure PEI membrane, the PEI-SiO 2 composite membrane showed higher electrochemical stability, with an electrochemical window of up to 5.5 V. The battery assembled with the composite membrane showed excellent cycle stability, and the capacity retention rate was as high as 98.6% after 50 cycles. The LIBs based on the PEI-SiO 2 composite membrane exhibited safe operation and high electrochemical performance, thus highlighting the applicability of the composite membrane in high-power batteries.