Poly(vinylidene fluoride) Modified Commercial Paper as a Separator with Enhanced Thermal Stability and Electrolyte Affinity for Lithium-ion Battery

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 LiFePO4/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.