The Strategy to Tune Li Stripping/Plating Behavior in Li Alloy Anode

Abstract

Li metal anode is the most promising anode for high-energy-density batteries due to its high specific capacity (3860 mAh/g) and highest oxidation potential. However, the high reactivity of Li metal with electrolytes and the resultant formation of Li dendrites restrict its practical applications. To tune the reactivity and Li deposition behavior, Li alloys were widely studied and demonstrated to perform better than Li in Li metal batteries.1-4 Here, we studied the electrochemical behavior of one solid-solution phase Li alloy. In this work, the phase transition in the Li stripping process and phase separation after Li plating were observed, which can be attributed to the sluggish Li diffusion in the solid-solution phase of the alloy. To unlock the Li stripping capacity without phase transition, we designed a bi-phase Li composite anode by introducing Li+ conductive materials. Due to the reduced diffusion length, Li can diffuse into the Li solid-solution phase after plating back on the bi-phase Li composite anode, resulting in uniform Li deposition morphology. Accordingly, the bi-phase Li composite anodes showed much better rate performance than the Li alloy or pristine Li. With these findings, it is expected that the new bi-phase Li composite anodes are a promising direction for long-life, high-power, and high-energy Li metal batteries, including Li-S batteries.