A Janus-faced, perovskite nanofiber framework reinforced composite electrolyte for high-voltage solid lithium-metal batteries

High-voltage solid lithium-metal batteries (HVSLMBs) are not only energy denser but also safer than state-of-the-art lithium-ion batteries. However, the narrow electrochemical stability windows and low ionic conductivities of polymer solid electrolytes severely hinder the practical application of this type of battery. To simultaneously address these issues, we propose and fabricate a thin yet mechanically strong composite solid electrolyte by forming a layer of a reduction-tolerant polyethylene glycol diacrylate (PEGDA) and oxidation-resistant poly(vinylidene fluoride) (PVDF) within the perovskite nanofiber framework. The unique Janus-faced design enables stable and intimate contact with the lithium metal anode and high-voltage cathode, while the perovskite inorganic electrolyte Li_0.33La_0.557TiO₃ (LLTO) nanofiber framework endows the membrane with a high ionic conductivity of 0.1 mS cm⁻¹ at room temperature (25 °C) and excellent mechanical strength with the thickness of as low as 24 μm. When paired with a high-voltage LiNi_0.8Co_0.1Mn_0.1O₂ cathode, the solid lithium battery can deliver a reversible discharge capacity of as high as 176 mAh g⁻¹ at 0.2C at room temperature. This work offers a novel, effective strategy to develop high-performance solid electrolytes for next-generation high-voltage lithium batteries.