Suppressing Second‐Order Jahn–Teller Distortion in VO ₂ (B): A Dissolution‐Resistant Electrode for Durable Aqueous Energy Storage

Abstract The development of robust, high‐performance electrode materials constitutes a critical research frontier in aqueous energy storage systems. Vanadium oxides (VO _x )‐based compounds, particularly VO ₂ (B), stand out as promising candidates owing to their multivalent redox chemistry and structural diversity. However, their practical implementation frequently encounters obstacles such as dissolution. The corresponding dissolution issue originates from the second‐order Jahn–Teller (SOJT) distortion of VO ₆ octahedra, coupled with parasitic reactions involving water molecules. This dissolution pathway results in rapid capacitance fading during the cycling process. Herein, poly‐anionic group modification, specifically utilizing phosphate groups, is employed to reinforce the robustness of VO ₆ octahedra against OH ^– attack and enhance the stability of VO ₂ (B) electrode (denoted as PM‐VO). During redox cycling in the PM‐VO electrode, the V─O bonds within the VO ₆ octahedra are stabilized, effectively mitigating structural distortions caused by the SOJT effect. The PM‐VO electrodes exhibit remarkable cycling stability, retaining 83.6% of initial capacitance after 20 000 charge‐discharge cycles at 20 mA cm ⁻² . This surface engineering protocol provides a foundational framework for developing robust transition metal oxide‐based electrodes in aqueous battery systems.