Thickness regulation of electric double layer via electronegative separator to realize High-Performance Lithium-Metal batteries

Abstract

Lithium metal anode is considered as a promising electrode material for next-generation energy storage systems due to their high theoretical capacity and a low redox potential. However, the uncontrollable growth of Li dendrites severely hindered its practical application. Separators, a vital component in batteries, offer a promising solution to this issue, which can regulate the transport of lithium ions (Li+) and guide the homogenous deposition of Li+. In this study, a three-dimensional porous structure coating layer is constructed on the surface of the commercial polyethylene separator by polymer-induced phase separation (PIPS) and UV-induced cross-linking reactions. The incorporation of synthetized sulfonated SiO2 particles (S-SiO2) enable the successful construction of a negatively charged separator (PE@S-SiO2) based on negatively charged moieties on the surface, which compresses the thickness of the electric double layer (EDL) to optimize the Li+ transport dynamics and suppress dendritic growth. The resulting PE@S-SiO2 separator displays superior electrolyte wettability, much higher thermal resistance, high lithium transference number (0.86), and ionic conductivity (1.15 mS/cm). Consequently, when assembled into lithium metal batteries, the negatively charged separator endows stable cycling over 800 h at a current density of 1 mA cm−2.