A rigid-flexible gel interlayer with Li+-conducting/e−-insulating properties for dendrite-free solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) have garnered significant attention due to their high energy density. However, the development of these batteries is hindered by the problematic growth of lithium dendrites, posing safety concerns. This study addresses this issue by introducing an organic–inorganic gel interlayer (GI) between garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) and Li metal using a simple, cost-effective, and scalable in-situ thermal polymerization method. The GI features a three-dimensional cross-linked network and LLZTO particles, enhancing interfacial ionic contact and facilitating Li⁺ migration and diffusion at the interface. The electron-insulating nature of the GI prevents the growth of Li dendrites toward solid-state electrolytes and accommodates changes in Li volume during the plating and stripping process. Additionally, the electrochemical cycling forms a LiF-rich interphase, promoting uniform Li deposition. Consequently, Li symmetric cells exhibit a high critical current density of 1.9 mA cm⁻² and an extended cycling life of 600 h at 1.5 mA cm⁻². SSLMBs, when coupled with LiFePO₄, LiNi_0.5Co_0.2Mn_0.3O₂, and carbon fluoride (CF) cathodes, showcase outstanding electrochemical performance. The insights gained into interface properties and the demonstrated facile strategy in this work have the potential to accelerate the development of artificial interlayers for SSLMBs, ultimately leading to batteries with superior electrochemical performance.