A Practical High-Energy Alkaline Aqueous Battery and Strategies to Suppress Its Hydrogen Evolution

Aqueous VB₂-air batteries with high mass and volume specific energy and high safety have attracted an increasing amount of attention due to the multielectron reactions of VB₂. However, the existing VB₂-based batteries have many shortcomings, such as alkaline electrolyte volatilization and carbonation due to the half-open structure of air cathode and hydrogen evolution corrosion of the VB₂ anode. Thus, it is crucial to identify a cathode material with a stable structure, high energy density, and suitability for VB₂-based batteries. In this work, four crystallographic structures of MnO₂ (α-, β-, γ-, and δ-) were selected as the cathode to construct a closed VB₂-based alkaline battery. The results of galvanostatic discharge tests show that the γ-MnO₂ cathode has the highest discharge specific capacity of 280 mAh g^-1 with utilization reaching 90.9%. XRD and in situ Raman analyses indicate that the cathode mainly undergoes a proton-embedded transition-type reaction. Additionally, V₂O₅ was adopted as an anode additive to suppress hydrogen evolution corrosion. The closed VB₂-MnO₂ aqueous battery with a designed capacity of 30-35 mAh cm^-2 can achieve a discharge specific capacity of 2385 mAh g^-1 at a current density of 800 mA g^-1, which is 1080 mAh g^-1 higher than that without additives, indicating that such an optimized VB₂-MnO₂ aqueous battery has high practical potential.