Construction of LiCl/LiF/LiZn hybrid SEI interface achieving high-performance sulfide-based all-solid-state lithium metal batteries

This study is led by Prof. Chuang Yu (School of Electrical and Electronic Engineering, Huazhong University of Science and Technology).

Compared with traditional lithium-ion batteries, all-solid-state lithium metal batteries have attracted extensive attention due to their higher safety and energy density. The chlorine-rich lithium-sulfur-silver-germanium electrolyte Li_5.5PS_4.5Cl_1.5 has been widely developed due to its high ionic conductivity, low grain boundary resistance, and good mechanical properties. However, its poor chemical/electrochemical stability with the lithium metal anode leads to high interface impedance, which leads to uneven deposition/stripping of lithium ions at the interface, and induces the growth of lithium dendrites into the solid electrolyte, which greatly limits its application in all-solid-state lithium metal batteries.

Recently, Professor Yu Chuang designed a composite lithium metal anode Li-10% ZnF₂ through a simple conversion reaction between lithium and metal fluoride. The experimental results show that the composite lithium metal anode comprises Li, LiF, and Li-Zn phases. Interestingly, the in-situ growth of dense and uniform LiCl interface phase is simultaneously induced at the anode/electrolyte interface, and LiCl/LiF/Li-Zn forms a hybrid SEI interface phase. Among them, the LiCl and LiF interface phases with high interface energy effectively induce the uniform deposition of Li⁺ and reduce the overpotential of Li⁺ deposition, while the LiZn alloy interface phase accelerates the diffusion of lithium ions. The synergistic effect of the above functional interface phases inhibits the growth of lithium dendrites and constructs a more stable lithium anode/electrolyte interface. In addition, DFT calculations based on first-principles calculations show that the hybrid SEI (LiCl/LiF/Li-Zn) has higher interface energy with lithium compared to the single SEI (LiCl), which can effectively inhibit the growth of lithium dendrites. The experimental and computational results reported in this paper not only clarify the role of mixed SEI in all-solid-state lithium metal batteries but also provide effective ideas for constructing a stable Li/SE interface.

The first author of this paper is Dr. Wei Chaochao of Huazhong University of Science and Technology, and the corresponding author is Professor Yu Chuang of Huazhong University of Science and Technology.