High-entropy Mn–Prussian blue analogues enable long-term cycling in aqueous sodium-ion batteries through synergistic redox and ion diffusion enhancements

Manganese-based Prussian blue analogues (Mn-PBA) have garnered significant attention due to their exceptionally high specific capacity in aqueous sodium-ion batteries (ASIBs). However, the dissolution of Mn²⁺ ions during the charge/discharge process leads to structural degradation, adversely affecting cycle life and limiting practical applications. In this work, a high-entropy strategy is employed to overcome this limitation. The resulting high-entropy Mn-PBA (HE-Mn-PBA), synthesized via a simple co-precipitation method, benefits from entropy stabilization and synergistic effects among multiple metal components, enabling excellent structural integrity during prolonged cycling. As a cathode material, HE-Mn-PBA achieves nearly 100 % capacity retention (116.07 mAh g^-1) after 200 cycles at 1 A g^-1, along with stable performance over 10,000 cycles. In situ Raman spectroscopy confirms the formation of enhanced and reversible redox-active centers, while kinetic analyses reveal significantly improved Na⁺ diffusion kinetics. Furthermore, a full cell assembled with a polyimide anode delivers a high energy density of 56.11 Wh kg^-1. This high-entropy engineering approach offers a promising pathway to address the stability challenges of Mn-based materials in ASIBs.