Artificial interface engineering to achieve high-performance garnet-based solid-state lithium metal batteries

Abstract

Garnet-based solid-state lithium metal batteries (SSMLBs) are considered one of the candidates that could realise the future application of lithium metal anodes owing to their inherent safety, high energy density and wide operating temperature range. However, the poor wettability and high impedance of the garnet/Li-metal anode interface limit the practical application of SSMLBs. In this work, an SnCl₂ layer was prepared on the surface of an Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) solid-state electrolyte via a convenient wet-chemistry method. Next, the Li–Sn/LiCl hybrid ionic/electronic conducting layer was in situ formed through the conversion reaction between molten Li and SnCl₂. This hybrid conducting layer can significantly reduce interfacial impedance, ensure the close contact between Li and the garnet interface, and inhibit the growth of Li dendrites. As a result, interfacial impedance was reduced from 293.9 Ω to 9.4 Ω, and the critical current density (CCD) of LLZTO was increased from 0.5 mA cm⁻² to 0.8 mA cm⁻². Besides, the Li/Li symmetric cell could work stably over 6000 h at a current density of 0.2 mA cm⁻² without the formation of dendritic Li and interfacial contact failure. Furthermore, the hybrid conductive layer enables the full cell assembled with LFP or NCM622 to show greatly improved long-term cycle stability and rate performance. This simple wet-chemistry strategy and the excellent electrochemical performances in this work demonstrate a potential strategy to develop high-performance garnet-based solid-state lithium metal batteries.