Polymer electrodes in solid-state metal-ion batteries: An in-depth review on recent advances, challenges, and future prospects

The pursuit of next-generation rechargeable batteries that are lightweight, intrinsically safe, sustainable, and mechanically flexible has accelerated interest in all organic solid-state battery concepts based on conducting and redox-active polymers as electrode materials. While many redox polymers exhibit intrinsically low electronic conductivity, conducting polymers can provide substantial electronic transport, highlighting the need for a more nuanced understanding of structure–property relationships in polymer-based electrodes. The key challenges instead arise from polymer swelling in liquid or quasi-solid electrolytes, limited ionic/electronic percolation, and interfacial instabilities at polymer–electrolyte and polymer–current-collector interfaces. This review synthesizes fundamental principles of polymer electrochemistry, including charge transport, redox kinetics, and the evolution of conductivity in electrochemical environments. We critically evaluate major classes of polymer electrode materials, outlining their advantages, limitations, and the design strategies used to enhance performance through molecular engineering, cross-linking, composite formation, and interface modification. Special emphasis is placed on the transition from liquid to solid and quasi-solid electrolytes as a route to mitigate swelling, enhance safety, and stabilize interfacial chemistry. We outline the overarching vision for all-organic solid-state batteries that unite sustainability (bio-derived and recyclable components), intrinsic safety (non-flammable solid electrolytes), mechanical flexibility, and compatibility with low-energy manufacturing. By accurately framing the key challenges and highlighting the transformative potential of polymer-based electrochemical systems, this review provides a roadmap toward practical and scalable all-organic solid-state battery technologies.