Lithium anode in carbonate-based electrolyte: High-performance by self-protected solid-electrolyte-interphase

Abstract

Lithium metal is considered as the ultimate negative electrode for future high-energy batteries because of its lowest electrode potential and very high theoretical capacity. However, its practical application is severely plagued by the hazardous lithium dendritic growth upon charge and low coulombic efficiency resulting from the inhomogeneous mass and charge transfers across the Li/electrolyte interface. Herein we report an economical and effective approach to step out of this dilemma, using self-protected Solid electrolyte interphase (SEI) in carbonate-based electrolyte with Vinylethylene carbonate (VEC) additive. VEC as a sacrificing material can prevent the Li salts and solvent decomposition, and further free radical reaction of VEC decomposition products in-situ form self-protected highly uniform and mechanical strength SEI layer on Li metal surface. The versatile effects of this unique SEI layer are demonstrated by the uniform lithium plating/stripping and very high Coulombic efficiency (up to 96% after 150 cycles at 1 mA cm−2 with 1 mAh cm−2). Lithium metal batteries, employing the self-protected Li metal negative electrode coupled with LiFePO4, exhibit excellent performance in both cycling stability and rate capability. Even the anode free cell Cu|NMC811, an impressive high initial coulombic efficiency of 92.5% and promising improvement of cycling performance are achieved.