Highlighting Charge Redistribution Phenomenon in Mn-Based Prussian Blue Analogues for Enhancing Redox Stability

Abstract

The development of sodium-ion batteries is increasingly critical due to the limited availability and rising cost of lithium resources, positioning a promising alternative to lithium-ion batteries. Conventional Mn-based cathode materials often suffer from the strong Jahn-Teller effect of MnIII, leading to structural instability and capacity fading. Herein, it is demonstrated that activating charge redistribution between adjacent transition metals in Mn-based Prussian blue analogues, driven by tuning electronic conductivity, plays a crucial role in mitigating the Jahn-Teller effect. X-ray absorption spectroscopy reveals the electronic interaction between Mn and Fe under charge redistribution by demonstrating their complementary redox behavior. Computational analysis attributes this charge redistribution to the structural framework of Prussian blue analogues, where the energy barrier for charge transfer across Fe-C-N-Mn bonds is modulated by electrode-level conductivity. This strategy demonstrates the enhanced cycle stability by mitigating Jahn-Teller effect while effectively maintains Mn redox activity beyond the trivalent state. Consequently, this presents a distinct advantage in terms of energy density, and these findings suggest that with optimized electronic conductivity, Mn-based Prussian blue analogues can be positioned as promising cathode materials for next-generation sodium-ion batteries with high energy density and enhanced cycling performance.