Tailoring the Electronic Conductivity of Coating Layer on the Composite Separator for Li Metal Anode

Abstract

Protection of lithium (Li) metal anodes is essential for the high performance of lithium metal batteries. Although the SnO₂ coating layer on the composite separator can provide protection for the Li metal anode, the effect diminishes over time as Li is plated on the coating surface, which can be attributed to the increased electronic conductivity of the reduced SnO₂ artificial solid electrolyte interfacial layer. Here, poly(vinylidene fluoride) (PVDF) is blended with SnO₂ to form an insulated SnO₂/PVDF hybrid coating layer. The SnO₂/PVDF hybrid coating layer significantly mitigates initial capacity loss and enhances the Coulombic efficiency of Cu||Li batteries. Adjustments to electronic conductivity of coating layer result in the deposition of large grain size Li beneath the hybrid coating layer. The SnO₂/PVDF (=7/3) (S₇P₃) layer can stabilize the freshly deposited Li and improve the cycling performance of the Cu@Li/S₇P₃ electrode. The S₇P₃@PE composite separator can significantly increase the cycle performance of LiFePO₄ (LFP)||Li batteries under low-temperature conditions. Furthermore, the S₇P₃ layer can provide substantial advantages to LFP batteries with limited Li capacity, as well as to lithium-free anodes. Our approach to regulating Li deposition behavior by tailoring the electronic conductivity of the coating layer facilitates the long-term stability of the Li metal anode.