Small-molecule organic electrode materials for rechargeable batteries

Small-molecule organic electrode materials (SMOEMs) have shown tremendous potential as cathodes or anodes for various rechargeable batteries including lithium and sodium batteries, due to their easy material availability, high structure designability, attractive theoretical capacity, and wide adaptability to counterions. However, they suffer from the severe dissolution problem and the subsequent shuttle effect in nonaqueous electrolytes, which cause the poor cycling stability and Coulombic efficiency. To satisfy the demands on the energy density and cycling stability simultaneously, the molecular structures of SMOEMs need to be rationally designed, and extrinsic approaches including electrode engineering and electrolyte optimizations can be further conducted. In this review, we summarize the fundamental knowledge about SMOEMs, including their working principles and applications, structure classifications, molecular structure design methods, and extrinsic optimization strategies. Moreover, we also provide some original insights aiming at guiding the research and development of SMOEMs in a more scientific and practical way. In brief, SMOEMs are facing huge opportunities and challenges as candidates to enable the next-generation of efficient, sustainable, and green rechargeable batteries.