Polypropylene Separators with Robust Mussel-inspired Coatings for High Lithium-ion Battery Performances

Abstract

The performances of lithium-ion batteries (LIBs) are dependent on the wettability and stability of porous separators. Musselinspired coatings seem to be useful to improve the surface wettability of commercialized polyolefin separators. However, it is still a challenge to guarantee their stability under polar electrolytes. Herein, we report a facile and versatile way to enhance the wettability and stability of polypropylene separators by constructing robust polydopamine (PDA) coatings triggered with CuSO4/H2O2. These coatings were conveniently deposited on the polypropylene separator surfaces and the PDA-coated separators exhibited the improved surface wettability and thermal stability. The electrolyte uptake increased nearly two folds from the pristine separator to the modified ones. Correspondingly, the ionic conductivity also rose from 0.82 mS·cm-1 to 1.30 mS·cm-1. Most importantly, the CuSO4/H2O2-triggered PDA coatings were very stable under strong polar electrolytes, endowing the cells with excellent cycle performance and enhanced C-rate capacity. Overall, the results unequivocally demonstrate that application of PDA coatings on polyolefin separator triggered by CuSO4/H2O2 is a facile and efficient method for improving the wettability and stability of separators for high LIBs performance.