Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

Hybrid ceramic–polymer membranes have emerged as solid-state electrolytes (SSEs) promising high ionic conductivity, strong mechanical strength, and easy processing. However, the inherent incompatibility between inorganic ceramics and organic polymers remains a great challenge for their applications. In this work, we investigated the interaction of polydopamine (PDA)-based polymer with both inorganic garnet-type Li7La3Zr2O12 (LLZO) ceramic and organic poly(ethylene oxide) (PEO) electrolytes to enhance their interfacial binding in both cast membrane from mixed composite slurry and multilayered electrolyte setups. For the LLZO-PEO cast composite membrane, the polymerization of dopamine directly on the LLZO particle surfaces was explored. PDA-coated LLZO powders can mix well with PEO into a homogeneous composite slurry to considerably improve the processability and smoothness of the resulting cast membrane. For the introduction of PDA-co-PEO polymer as an interfacial layer for the multilayered solid electrolyte setup, substantial improvement in the wettability between the LLZO surface and PEO was observed, suggesting that intimate interfacial contact facilitated by PDA-co-PEO copolymer could be achieved. Most importantly, the introduction of the PDA-based interfacial layer can lead to significant increase of the lithium-ion conductivity to meet the current industrial benchmark of 10–4 S cm–1 at room temperature, promising the development of future all-solid-state electrolytes for battery applications.