Mitigating Jahn–Teller Effects by Fast Electrode Kinetics Inducing Charge Redistribution

Abstract

Manganese hexacyanomanganates have attracted significant attention as promising cathode materials for sodium‐ion batteries owing to the high theoretical capacity and low cost of Mn resources. Because of the strong Jahn–Teller effect, causing unstable local phase transition and distortion, the redox reactions of the high‐spin state of Mn(III) are considered to be a conundrum. Herein, it is reported that the charge‐redistribution mechanism of low‐spin MnIII + high‐spin MnIII → low‐spin MnII + high‐spin MnIV in manganese hexacyanomanganates can decrease unstable high‐spin MnIII, leading to the mitigation of Jahn–Teller distortion. X‐ray absorption near‐edge spectroscopy and X‐ray photoelectron spectroscopy suggest that the fast reaction rate activates charge redistribution. Moreover, different crystal structures, reported using post‐mortem synchrotron X‐ray diffraction analysis, confirm a large orthorhombic structure, thus verifying the presence of charge redistribution based on the superexchange rule. These results demonstrate that manganese hexacyanomanganate in an aqueous electrolyte can achieve long‐term cyclability, thus paving the way for high‐performance batteries.

Defect Engineering in Prussian Blue Analogs for High‐Performance Sodium‐Ion Batteries

“…However, researchers gradually realized that MnHCF had the Jahn-Teller effect and Mn 3+ was extremely easy to dissolve into the electrolyte, so they began to seek strategies to alleviate the unstable local phase transitions and distortions caused by Jahn-Teller effect. [13,[63][64][65] By doping multiple metal elements in the N-coordinated M A centers, the deficiency tuning of PBAs can be a strategy to improve their electrochemical properties. For example, FeHCFs and MnHCFs have a high capacity but an unsatisfactory cycling life and high-rate performance.…”

Solid-state synthesis of β-NaAlO2 nanoflakes as an anode material for high-performance sodium-ion batteries

“…The redox activity of Al 3+ /Al 4+ may also be accompanied by a phase transition driven by a Jahn-Teller effect induced by the sodiation and desodiation mechanism, where the symmetry reduces with geometric distortion. 18,19 Besides, the CV curve illustrates the electrochemical characteristics of the SIB with respect to the number of cycles. The voltammograms were observed with good stability and profile retention after the first cycle.…”

Investigating the role of interstitial water molecules in copper hexacyanoferrate for sodium-ion battery cathodes

“…PBAs have garnered signicant attention as cathode materials for aqueous Na-ion batteries because their redox potentials are within the electrochemically stable voltage window for aqueous electrolytes. 20,21 In addition, the open frame structure of PBAs [22][23][24][25][26] that has large channels (∼3.2 Å) and interstitial sites (∼4.6 Å) 27 not only facilitates reversible Na + -ion diffusion within the structure, but also enables the accommodation of Na + ions without the dehydration of water molecules, resulting in lower activation energy for charge transfer in aqueous electrolytes (5.1 kJ mol −1 ), which is a ten-fold decrease compared to that of an organic electrolyte system (51 kJ mol −1 ). 28 These unique properties make PBAs a promising choice for cathode materials in aqueous Na + -ion batteries.…”