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.