Poly(vinylidene fluoride) Modified Commercial Paper as a Separator with Enhanced Thermal Stability and Electrolyte Affinity for Lithium‐ion Battery
Ze Zhang, Meiling Zhou, Ji Yu, Jianxin Cai, Zhenyu Yang
Abstract
Commercial paper is of great potential as a ready‐made substrate to make battery separator due to superior electrolyte affinity of cellulose. Nevertheless, the direct utilization of commercial paper as a separator is impracticable because of its micro‐sized holes between coarse cellulose fibers, which might induce short circuits. Herein, a novel reinforced composite separator is proposed by modifying commercial paper (CP) with high‐dielectric polymer poly(vinylidene fluoride) (PVDF) via a vacuum filtration method. The paper substrate enables excellent electrolyte wettability and high ionic conductivity of the CP‐PVDF composite separator due to the superior electrolyte affinity of cellulose molecule. Meanwhile, the strong hydrogen bonds between F atoms in PVDF and H atoms in the ‐OH groups of cellulose endow the separator with high thermal stability and mechanical strength. Moreover, the CP‐PVDF exhibits outstanding interfacial compatibility toward Li metal anode and guarantees the prominent cycle durability of symmetric Li/Li cells up to 600 h. As a result, the LiFePO 4 /Li cells assembled with CP‐PVDF separator show dramatic rate performance with high discharge capacity of 113.7 mAh g −1 , and prolonged cycle life at 5 C. This work indicates that the paper‐based composite membranes possess great potential for high‐safety and electrochemical performance batteries.