Transition metal nitrides: Unveiling active site engineering in bifunctional materials for next-generation energy storage

Transition metal nitrides (TMNs) hold great promise for use as electrodes in advanced electrochemical energy storage, thanks to their superior electrical conductivity, outstanding chemical stability, and favorable catalytic performance. Despite growing research interest, a systematic overview exploring the role of TMNs in supercapacitors (SCs) and lithium‑sulfur (Li S) batteries remains scarce. This review comprehensively summarizes recent progress in the design and application of TMNs for high-performance SCs and Li S batteries. We first categorize typical structural configurations and synthetic methods of TMNs. Then, we discuss in detail the electrochemical functions and the functionality of key TMNs (MₓN, where M = V, Ti, Mo, Nb, W) in these two energy storage systems, with emphasis on charge storage mechanisms and material engineering strategies, particularly active site engineering. Notably, while supercapacitors rely on pseudocapacitive surface processes and Li S batteries depend on adsorption-catalysis bifunctional sites, reflecting distinct energy storage mechanisms and active centers, TMNs serve as “electronic superhighways” in both systems, efficiently overcoming their respective conductivity limitations. To conclude, the key challenges and future opportunities for TMN-based electrodes are outlined. This work is devoted to establishing a fundamental framework and practical guidelines for the rational development of TMN materials toward next-generation energy storage technologies with high efficiency, long-term stability, and scalability.