Elucidating the crucial role of configuration entropy in governing the Jahn-Teller effect, Na+ diffusion kinetics, and conductivity within cobalt-free Mn-based Prussian blue cathode materials

Co-free manganese-based Prussian blue analogues (Mn-PBAs) have emerged as exceptionally promising cathode materials for sodium-ion batteries (SIBs), offering low cost and high specific capacity. However, the detrimental Jahn-Teller effect, compounded by sluggish Na + diffusion kinetics and inherently poor electrical conductivity, severely undermines structural stability and cycling performance. Herein, we pioneer a novel Co-free entropy regulation strategy to overcome these formidable challenges. Four distinct Co-free PBAs with precisely controlled (configuration entropy (Δ S conf ) were meticulously synthesized via a straightforward co-precipitation method. Comprehensive electrochemical diagnostics combined with rigorous density functional theory (DFT) simulations unequivocally reveal that elevating Δ S conf demonstrably accelerates Na + diffusion, significantly enhances electrical conductivity, and effectively suppresses Jahn-Teller distortion. In situ X-ray diffraction (XRD) and in situ Raman spectroscopy analyses vividly characterized the structural transitions occurring during sodiation/desodiation, demonstrating markedly improved structural reversibility with increasing Δ S conf . Consequently, the Co-free high-entropy (HE) PBA cathode delivers truly remarkable cycling stability, (retaining 62.3 % capacity after an astounding 10 000 cycles at 5 000 mA g −1 , alongside exceptional rate capability of 75.1 mAh g −1 at 5 000 mA g −1 ). These groundbreaking findings provide profound insight for designing future high-performance cathode materials from abundant, environmentally friendly elements for next-generation SIBs.