Organic Mixed Ionic-Electronic Conductors for Solid-State Batteries

Solid-state batteries (SSBs) are considered as the next-generation battery technology, poised to deliver both high energy and enhanced safety. Nonetheless, their transition from laboratory to market is impeded by several critical challenges. Among these, the solid-solid interfaces within SSBs represent a bottleneck, characterized by issues such as poor physical contact, side reactions, temporal separation, and sluggish charge carrier transfer. Developing key materials to construct the efficient solid-solid interface is critical for building high-performance SSBs. Organic mixed ionic-electronic conductors (OMIECs) have emerged as a promising alternative to conventional conductors in addressing the abovementioned issues owing to their intrinsic properties, including the capability of conducting both ions and electrons, mechanical flexibility, and structural designability. This review will first elucidate the necessity of the integration of OMIECs in SSBs. Next, a comprehensive exploration of the composition, preparation methods, key advantages, and basic characterizations of OMIECs is presented. This review then delves into recent research progress on OMIECs in SSBs, with a special focus on their application in cathode coating layers, the creation of a 3D mixed conductive framework for Li hosting, and their integration as inner layers in Li anodes. Conclusively, potential future applications and innovative designs of OMIECs are discussed.