Mitigated reaction kinetics between lithium metal anodes and electrolytes by alloying lithium metal with low-content magnesium

Abstract

Lithium (Li) metal is regarded as a promising anode candidate for high-energy-density rechargeable batteries. Nevertheless, Li metal is highly reactive against electrolytes, leading to rapid decay of active Li metal reservoir. Here, alloying Li metal with low-content magnesium (Mg) is proposed to mitigate the reaction kinetics between Li metal anodes and electrolytes. Mg atoms enter the lattice of Li atoms, forming solid solution due to the low amount (5 wt%) of Mg. Mg atoms mainly concentrate near the surface of Mg-alloyed Li metal anodes. The reactivity of Mg-alloyed Li metal is mitigated kinetically, which results from the electron transfer from Li to Mg atoms due to the electronegativity difference. Based on quantitative experimental analysis, the consumption rate of active Li and electrolytes is decreased by using Mg-alloyed Li metal anodes, which increases the cycle life of Li metal batteries under demanding conditions. Further, a pouch cell (1.25 Ah) with Mg-alloyed Li metal anodes delivers an energy density of 340 Wh kg−1 and a cycle life of 100 cycles. This work inspires the strategy of modifying Li metal anodes to kinetically mitigate the side reactions with electrolytes.