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 as candidate power sources for electric vehicles and large-scale energy storage systems due to their intrinsic safety, high energy density and wide range of operating temperature. However, the poor wettability at the interface of garnet/Li metal anode, high interfacial impedance, and the uncontrollable growth of Li dendrites during the repeated cycling processes limit the practical applications of SSMLBs. In this work, SnCl2 layer has been prepared on surface of Li6.5La3Zr1.5Ta0.5O12 (LLZTO) solid-state electrolyte by a convenient wet-chemistry method. Then the Li-Sn/LiCl hybrid ionic/electronic conducting layer can be in-situ formed through the conversion reaction between molten Li and SnCl2. This hybrid conducting layer can significantly reduce the interfacial impedance, ensure the close contact between the Li and garnet interface, and inhibit the growth of Li dendrites. As a result, the 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 can work stably over 6000 h at a current density of 0.2 mA cm-2 without the formation of dendritic Li growth and interfacial contact failure. Moreover, the hybrid conducting layer can enable the full cell assembled with LiFePO4 cathode to deliver a greatly improved long-term cycle stability and rate performance. This simple wet-chemistry strategy as well as the excellent electrochemical performances in this work demonstrate a potential strategy to develop high-performance garnet-based solid-state lithium metal batteries.