High‐Energy‐Density All‐V ₂ O ₅ Battery

Abstract Symmetrical batteries hold great promise as cost‐effective and safe candidates for future battery technology. However, they realistically suffer low energy density due to the challenge in integrating high specific capacity with high voltage plateau from the limited choice of bipolar electrodes. Herein, a high‐voltage all‐V ₂ O ₅ symmetrical battery with clear voltage plateau is conceptualized by decoupling the cathodic/anodic redox reactions based upon the episteme of V ₂ O ₅ intercalation chemistry. As the proof‐of‐concept, a hierarchical V ₂ O ₅ ‐carboncomposite (VO‐C) bipolar electrode with boosted electron/ion transport kinetics is fabricated, which shows high performance as both cathode and anode in their precisely clamped working potential windows. Accordingly, the symmetrical full‐battery exhibits a high capacity of 174 mAh g ⁻¹ along with peak voltage output of above 2.9 V at 0.5C, remarkable capacity retention of 81% from 0.5C to 10C, and good cycling stability of 70% capacity retention after 300 cycles at 5C. Notably, its energy density reaches 429 Wh kg ⁻¹ at 0.5C estimated by the cathode mass, which outperforms most of the existing Li/Na/K‐based symmetrical batteries. This study leaps forward the performance of symmetrical battery and provides guidance to extend the scope of future battery designs.