3D lithium metal anodes hosted in asymmetric garnet frameworks toward high energy density batteries

Abstract Solid-state electrolytes (SSEs) have been widely studied to enable applications of high-energy Li metal anodes in batteries with high safety and stable performance. However, integration of SSEs into batteries is hindered by the infinite volume change of Li metal anodes upon cycling, the unstable resistance between Li and SSE, and low battery energy densities. To address these challenges, we developed a porous-dense bilayer structured garnet SSE as a 3D ionic framework for Li metal. The framework consists of one porous layer as a volume-stable host of Li metal with a large contact area, and one dense layer as a solid-state separator preventing short-circuits. The flatness of the dense layer enables simple battery manufacturing by laying a pre-made cathode on top of the bilayer framework. The thicknesses of the porous and dense layers are well controlled at 50 and 20 µm, respectively, to improve the battery energy density. Based on the bilayer garnet framework and highly loaded Li(Ni0.5Mn0.3Co0.2)O2 (NMC) cathodes (32 mg/cm2), we developed solid-state Li-NMC batteries with energy densities (329 W h/kg and 972 W h/L) significantly higher than all of the state-of-art garnet-based Li metal batteries. The bilayer framework design provides a promising strategy towards solid-state Li metal batteries with high energy densities because of its well-optimized thickness, stable cycling performance, and feasibility to be integrated with high-energy cathodes.