Comprehensive Guide for the Rational Design of High‐Entropy Layered Transition Metal Oxide Cathodes for Sodium‐Ion Batteries

Abstract Sodium‐ion batteries (SIBs) have emerged as a cost‐effective alternative to lithium‐ion batteries due to the natural abundance and wide geographic distribution of sodium resources, which mitigate concerns over the scarcity and price volatility of lithium. However, the larger ionic radius of Na + (1.02 Å) compared to Li + (0.76 Å) produces inferior diffusion kinetics and structural stability. Therefore, layered transitional metal oxide cathode materials have extensively utilized high entropy doping to suppress undesirable phase transitions, improve kinetic performance, and enhance cationic and oxygen redox reversibility. Although the compositional tunability of high entropy doping offers considerable potential, it also introduces significant structural and chemical complexity. This necessitates the precise selection and optimization of dopant elements to target specific limitations observed in conventional low entropy systems. Accordingly, this review comprehensively evaluates the impact of dopant strategies and configurational entropy on the performance of compositionally proximate high entropy materials. It offers a systematic guide for rationally tailoring high entropy techniques to overcome interconnected performance‐limiting obstacles across diverse undoped systems. The review clarifies the definitional controversy surrounding the term “high entropy” and elucidates the theoretical limitations that hinder the accurate prediction of high entropy materials before concluding with an outline of prospective research directions.