Eco‐Degradable and Flexible Solid‐State Ionic Conductors by Clay‐Nanoconfined DMSO Composites

Abstract Solid‐state electrolytes can alleviate the safety issues of electrochemical energy systems related to chemical and thermal instabilities of liquid electrolytes. While a liquid provides seamless ionic transport with almost perfect wettability between electrodes, a solid‐state electrolyte needs to demonstrate at least comparable electrochemical performance to liquid electrolytes as well as mechanical robustness and flexibility. Here, the facile preparation of montmorillonite (MMT)/dimethyl sulfoxide (DMSO) nanocomposites is reported, which show high ionic conductivities, mechanical strengths, and thermal stabilities by forming nacre‐mimetic “brick‐and‐mortar” structures. The molecularly confined structures of DMSO are confirmed by X‐ray diffraction peaks with d‐spacings of interplanar spacing that are slightly larger than MMTs. The MMT/DMSO composites have mechanical strengths and toughnesses of 55.3 ± 4.8 MPa and 210.2 ± 32.6 kJ m⁻², respectively. The ionic conductivity is ≈2 × 10⁻⁴ S cm⁻¹ at room temperature, and their thermal stability is in the range of −100 to 120 °C. The optical translucency, on‐demand eco‐degradability, and solution processability together make the MMT/DMSO composites unique materials with a wide range of solid‐state electrochemical applications including batteries.