Regulating Li transport in Li-magnesium alloy for dendrite free Li metal anode

Li metal has become a strong candidate for anode due to its high theoretical specific capacity and lowest electrochemical potential. However, the poor reversibility caused by continuous chemical and electrochemical degradation hinders the practical application of Li metal. Solid-solution-based metal alloy phases have been proposed as hosts for regulating the non-dendrite electrodeposition, but the fundamental understanding remains unclear due to the drastically different deposition behaviors of Li on them. Here we found the difference in the diffusion coefficient of Li atoms on solid-solution-based metal alloy phases (Li−Mg and Li−Ag alloys) was a major contributor to the different deposition behaviors. The low Li atom diffusion coefficient of Li−Mg alloy showed a preferential Li accumulation on the upper surface rather than the inward-growth plating of Li atoms into alloy foil in Li−Ag alloy. By the process of secondary recrystallization, we improved the diffusion coefficient of Li atoms in Li−Mg alloy that facilitates the inward transfer rather than surface plating of Li atoms. In this case, the recrystallized Li−Mg alloy underwent a solid-solution phase change in the delithiation-lithiation cycles which yielded a high Coulombic efficiency of 99.3% with a reversible gravimetric capacity of 2,874 mAh·g−1 and superior cycling stability over 5,000 h without dendrite growth.