High Ionic-Conductivity of Poly(vinyl alcohol)/Cellulose Porous Composite Separators Prepared via Hydrogen-Bond Reconstruction for Lithium Metal Batteries

Cellulose-based membranes are promising alternatives to polyolefin separators due to their thermal stability, porous structure, and biocompatibility, but the dense structure, caused by strong hydrogen bonding and van der Waals forces between cellulose fibers, hinders ion transport and electrochemical performance. Herein, a kind of excellent porous structure with superior electrolyte wettability composite separator based on the poly(vinyl alcohol) (PVA) and cellulose was rationally designed and successfully prepared by using a blending method via hydrogen-bond reconstruction between the PVA molecular chains and cellulose. The three-dimensional (3D) porous structure and superior electrolyte wettability of the PVA/cellulose (PAC) composite separator could hinder the transport of anions and promote the migration of Li+, resulting in an excellent ionic conductivity and a transference number of up to 2.36 mS·cm–1 and 0.832, respectively. These characteristics effectively suppressed Li dendrite growth and formed a stable fluorine-rich solid electrolyte interphase (SEI) layer on the Li-metal surface. Consequently, the lithium metal battery assembled with the PAC separator showed a stable cycling performance and rate performance with discharge-specific capacities of 127 mAh·g–1 at 1 C, while the Li|PAC|Li symmetric lithium metal battery showed a stable polarized voltage of about 51 mV at 400 h. This study proposes a modification strategy for the cellulose membrane-based lithium metal battery separators to achieve high-rate capabilities.