Robust Polymer Electrolyte Membranes with High Ambient-Temperature Lithium Ion Conductivity via Polymerization-Induced Microphase Separation

Robust polymer electrolyte membranes (PEMs) exhibiting high conductivity under ambient conditions are vital for designing next-generation electrochemical devices. We present the in-situ preparation of mechanically robust PEMs via polymerization-induced microphase separation, and incorporation of lithium salt into one of the microphase separated domains. The facile design strategy involves controlled growth of polystyrene from a poly(ethylene oxide) macro-chain transfer agent (PEO-CTA) and simultaneous chemical cross-linking by divinylbenzene in the presence of lithium (Li) salt and succinonitrile. Small angle X-ray scattering and transmission electron microscopy confirmed the formation of a disordered structure with bicontinuous morphology and a characteristic domain size of order 13 nm. The long-range continuity of the PEO/Li salt conducting nanochannels and the plasticization of the PEO polymer chains by succinonitrile facilitated outstanding conductivities (~ 0.35 mS/cm) at 30 °C. Concurrently, the mechanical robustness of the hybrid material (modulus E′ ~ 0.3 GPa at 30 °C) was ensured by a densely cross-linked polystyrene framework.