Bridging Interparticle Li⁺ Conduction in a Soft Ceramic Oxide Electrolyte

TLDR

Li⁺‑conductive ceramic oxides such as garnet‑structured Li₇La₃Zr₂O₁₂ are promising for high‑energy solid‑state Li‑metal batteries, yet their high‑temperature sintered pellets are brittle and suffer from poor interparticle Li⁺ conduction, limiting thin‑film electrolyte fabrication and battery performance. Solid‑state NMR revealed that a uniform conjugated polymer nanocoating on ceramic oxide particles creates continuous Li⁺ pathways between adjacent particles in unsintered ceramics. The resulting tape‑cast thin‑film electrolyte (<10 µm) exhibits high ionic conductivity, a high Li⁺ transference number, and a broad electrochemical window, enabling stable cycling of symmetric Li/Li cells and all‑solid‑state Li‑metal cells.

Abstract

Li+-conductive ceramic oxide electrolytes, such as garnet-structured Li7La3Zr2O12, have been considered as promising candidates for realizing the next-generation solid-state Li-metal batteries with high energy density. Practically, the ceramic pellets sintered at elevated temperatures are often provided with high stiffness yet low fracture toughness, making them too brittle for the manufacture of thin-film electrolytes and strain-involved operation of solid-state batteries. The ceramic powder, though provided with ductility, does not yield satisfactorily high Li+ conductivity due to poor ion conduction at the boundaries of ceramic particles. Here we show, with solid-state nuclear magnetic resonance, that a uniform conjugated polymer nanocoating formed on the surface of ceramic oxide particles builds pathways for Li+ conduction between adjacent particles in the unsintered ceramics. A tape-casted thin-film electrolyte (thickness: <10 μm), prepared from the polymer-coated ceramic particles, exhibits sufficient ionic conductivity, a high Li+ transference number, and a broad electrochemical window to enable stable cycling of symmetric Li/Li cells and all-solid-state rechargeable Li-metal cells.