Unveiling dendrite-suppressing potential of alkali metal-based alloys in lithium metal batteries

Abstract

We reveal a concept of adding K and Na to dual-cation systems and investigate their effects on dendrite growth morphology and electrolyte decomposition reactivity in lithium metal batteries (LMBs). We analyze the effects of Li/K- and Li/Na-alloyed surfaces on Li ion diffusion along the deposition direction, as well as the reactivity of the electrolytes and the composition of the solid electrolyte interface (SEI) resulting from electrolyte decomposition. Compared with the Li/K system, the Li/Na-alloyed surface can significantly reduce Li diffusion along the z-direction and effectively prevent the formation of dendrite-like morphologies. Furthermore, the Li/Na-alloyed surface substantially mitigates the reactivity of the bis(fluorosulfonyl)imide (FSI−) anion and fluorinated ether (TTE) solvent, thus inhibiting the generation of excessive SEI species. Additionally, the regulated and simplified components of a hybrid LiF/NaF SEI layer in the Li/Na system are observed. This hybrid layer is expected to promote the uniform deposition of Li and exhibit excellent electrical insulating properties, thereby effectively preventing electron transfer to the electrolytes and enhancing the Coulombic efficiency of LMBs. This study presents new insights into the dendrite-suppressing potential of alkali-metal alloys for improving the stability and safety of LMBs.