Facile fabrication of PMIA composite separator with bi-functional sodium-alginate coating layer for synergistically increasing performance of lithium-ion batteries

Abstract

Lack of safety and unenough electrochemical performance have been known as a fundamental obstacle limiting the extensive application of lithium-ion batteries (LIBs). It is really preferable but challenging to fabricate thermal-response separator with shutdown function for high-performance LIBs. Herein, a thermal-response sodium-alginate modified PMIA (Na-Alg/PMIA) composite separator with shutdown function was designed and prepared by non-solvent phase induced separation (NIPs). PMIA and Na-Alg are combined by hydrogen bonding. While Na-Alg increases polar groups and makes Li+ easy to be transported, a small amount of Na+ can provide Li+ active sites, accelerate Li+ deposition coating and effectively inhibit the formation of Li dendrites. The as-prepared Na-Alg/PMIA composite separators can close pores at 200 °C and maintain dimensional integrity without obvious thermal shrinkage. In addition, the Na-Alg/PMIA composite separators has excellent wettability and ionic conductivity, resulting in high specific capacity and retention during the charge–discharge cycles. After 50 cycles, the capacity retention of cells with the Na-Alg/PMIA-20 composite separator is 84.3 %. At 2 C, cells with the Na-Alg/PMIA-20 composite separators still held 101.1 mAh g−1. This facile yet effective method improves the electrochemical performance while ensuring the safety of the LIBs, which provides ideas for the commercial application of PMIA separators.