Active and passive high-entropy shell enabling high rate and durable sodium manganese hexacyanoferrate cathode for sodium ion batteries

Sodium manganese hexacyanoferrate (MnHCF) is a promising cathode material for sodium-ion batteries (SIBs) due to its high theoretical capacity, low cost, and ease of preparation. However, MnHCF typically suffer from poor rate performance and limited cycling stability, primarily due to low electrical conductivity and undesired Jahn-Teller distortions during sodiation and desodiation process. In this study, we successfully employ a co-precipitation method to coat MnHCF with a structurally stable high-entropy hexacyanoferrate (HE-HCF), forming a core-shell structured HE-MnHCF. The high-entropy shell enhances the diffusion kinetics of Na⁺, maintains high capacity even at high current, and significantly improves structural stability by mitigating the Jahn-Teller effect. As a result, HE-MnHCF demonstrates a high reversible capacity of 119.5 mAh g⁻¹ at 0.01 A g⁻¹ and excellent cycling stability, retaining 64.3 % of its capacity after 1000 cycles at 0.5 A g⁻¹. This approach offers a novel strategy for stabilizing electrode materials through high-entropy coatings, paving the way for the advancement of cathode materials in SIBs.