A fast and low-cost interface modification method to achieve high-performance garnet-based solid-state lithium metal batteries

Garnet-based solid-state lithium metal batteries (SSLMBs) are considered to be the candidate power sources for electric vehicles and large-scale energy storage systems due to their high energy density, wide operating temperature and high safety. However, poor wettability of garnet/Li metal anode interface, large interfacial impedance and penetrating lithium dendrite growth during cycling limit the practical application of SSLMBs. In this paper, SnS2 ultra-thin film is fabricated on the surface of solid-state Li6.75La3Zr1.75Ta0.25O12 (LLZTO) electrolyte by a rapid (ca. 5 min) liquid-phase deposition method. Then, a Li2S/LixSn mixed ionic/electronic conductive layer is in-situ constructed through the conversion reaction between molten Li and SnS2. This mixed conductive layer can significantly reduce interfacial impedance, ensure intimate contact at the Li/garnet interface and inhibit growth of lithium dendrites. Thus, the resulting Li symmetric cell with Li2S/LixSn modification layer exhibits a low interface resistance of 47 Ω cm2 and a long lifespan over 1000 cycles. Moreover, using this Li/garnet interface, the full cell assembled with LiFePO4 cathode shows both excellent cycling and rate performance. These results demonstrate the feasibility of the proposed modification strategy for solid-state garnet electrolyte, and pave the way for the development of high-performance solid-state batteries.