A Superior Stable Interlayer for Dendrite-free Solid-state Lithium Metal Batteries

Abstract Garnet-type solid-state electrolyte (SSE) has emerged as a potential candidate for high-energy-density lithium (Li) metal batteries owing to its preferable Li-ion conductivity and non-flammability. However, the unexpected dendrite propagation restricts its practical application. Herein, we design a bifunctional Co3O4 layer on garnet-type Li6.5La3Zr1.5Ta0.5O12 (LLZTO) pellets by simply magnetron sputtering to suppress the Li dendrite growth. Small free energy change ΔG between Li and Co3O4 decreases the interfacial impedance (from 975 to 75 Ω∙cm−2). In-situ formed Co/Li2O layer effectively improves critical current density up to 4.8 mA∙cm–2 through homogenizing the electric-field distribution, blocking electron conduction, and providing mechanical protection for SSEs. As a result, the Li/Co3O4-SSE-Co3O4/Li symmetric cell shows extremely stable cycling performance (600 h at a current density of 1 mA∙cm−2 without short circuit), and Li/Co3O4-SSE/LFP full cell exhibits good electrochemical performance, comparable to that of equipped with liquid electrolyte. Specially, the cyclic voltammetry (CV) curves of the symmetric cell have been proposed to study the interface reaction. This work provides new thinking for designing bifunctional layer for high stable garnet-based solid-state lithium metal batteries.