Superspreading-Based Fabrication of Thermostable Nanoporous Polyimide Membranes for High Safety Separators of Lithium-Ion Batteries

The development of thermally stable separators is a promising approach to address the safety issues of lithium-ion batteries (LIBs) owing to the serious shrinkage of commercial polyolefin separators at elevated temperatures. However, achieving controlled nanopores with a uniform size distribution in thermostable polymeric separators and high electrochemical performance is still a great challenge. In this study, nanoporous polyimide (PI) membranes with excellent thermal stability as high-safety separators is developed for LIBs using a superspreading strategy. The superspreading of polyamic acid solutions enables the generation of thin and uniform liquid layers, facilitating the formation of thin PI membranes with controllable and uniform nanopores with narrow size distribution ranging from 121 +/- 5 nm to 86 +/- 6 nm. Such nanoporous PI membranes display excellent structural stability at elevated temperatures up to 300 degrees C for at least 1 h. LIBs assembled with nanoporous PI membranes as separators show high specific capacity and Coulombic efficiency and can work normally after transient treatment at a high temperature (150 degrees C for 20 min) and high ambient temperature, indicating their promising application as high-safety separators for rechargeable batteries. Superspreading strategy is utilized to continuously fabricate nanoporous polyimide (PI) membranes with controlled pore sizes and narrow pore size distribution for high-safety separators. The prepared nanoporous PI membranes exhibit excellent thermal stability and high electrochemical performance. Lithium-ion batteries assembled with nanoporous PI membranes as separators show excellent capacity retention and coulomb efficiency with reliable safety performance at high temperatures.image