Multiscale-structured polyvinylidene fluoride/polyacrylonitrile/ vermiculite nanosheets fibrous membrane with uniform Li+ flux distribution for lithium metal battery

Abstract

Preparing a separator regulating Li+ flux is considered to be a promising method to solve the Li dendrite problem of lithium metal battery (LMB). Herein, for the first time, the multiscale-structured polyvinylidene fluoride/polyacrylonitrile/vermiculite nanosheets (PVdF/PAN/VNs) fibrous membranes are obtained via a one-step electrospinning method. As-prepared PVdF/PAN/VNs fibrous membrane display the multiscale-structure with VNs embedded into the PVdF/PAN fibers accompanied by high porosity and interpenetrated pore, facilitating in homogenizing Li+ flux distribution at the separator/electrode interface, and thus inhibiting the Li dendrite formation and growth. Meanwhile, because of synergistic effect of PAN and VNs with liquid electrolyte, as-prepared PVdF/PAN/VNs fibrous membrane demonstrates good wettability, high ionic conductivity, strong tensile strength, excellent thermal stability and enhanced electrochemical stability, guaranteeing the improvement of battery performance and safety of LMB. More importantly, compared to the Celgard membrane based cell, as-prepared PVdF/PAN/VNs membrane based Li/Li4Ti5O12 cell shows better rate capability with a discharge capacity of 139.3 mA h g−1 at 10C rate, and the PVdF/PAN/VNs membrane based Li/Li cell displays stable lithium plating/stripping behavior with lower overpotential. This work provides a new strategy of regulating Li+ flux distribution for promoting the practical application of LMBs.