Thermally stable and high electrochemical performance ultra-high molecular weight polyethylene/poly(4-methyl-1-pentene) blend film used as Li-ion battery separator

The advances in Li-ion batteries (LIBs) for energy storage continuously face major challenges like acquiring high performance, stability and safety. A separator plays major role for safety and performance of batteries through its porous structure and interaction with electrolyte. In this work, a suitable microporous structure of ultra-high molecular weight polyethylene/poly(4-methyl-1-pentene) (UHMWPE/PMP) blend film via sequential biaxial stretching is achieved by tuning PMP content. The incorporation of PMP leads to high porosity and wettability enabling a significant increase of air permeability, electrolyte uptake and ionic conductivity. A low shrinkage, of 0.7% in transverse direction and 1.6% in machine direction, is observed after exposing PM2 (the film with 7.5 wt% of PMP) at 120 degrees C for 1 h indicating the high thermal stability. Most importantly, a cell containing PM2 presents an excellent electrochemical performance. The discharge capacity reaching 172.8 mAh/g and efficient stable cycling with 99.89% as coulombic efficiency during 100 cycles are obtained at 0.1 and 1 C-rate, respectively. Apart from existing blend separators, current work provides an alternative of using UHMWPE/PMP blend films and deepens the understanding of the role of porous structure for the design of LIBs with best performance in future. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study achieved a suitable microporous structure of UHMWPE/PMP blend film by tuning PMP content, leading to increased electrolyte uptake and ionic conductivity while maintaining high thermal stability. The film exhibited excellent electrochemical performance with high discharge capacity and stable cycling, providing a promising alternative for designing LIBs with best performance in the future.