11-Electron transfer vanadium diboride employed as an anode of air batteries: status, progress, and challenges

Metal–air batteries have garnered significant research interest due to their superior energy density compared to advanced lithium-ion batteries. Specifically, vanadium diboride (VB₂)–air batteries stand out because of the high theoretical specific capacity of the VB₂ material, which facilitates 11 electron transfers per molecule during oxidation when air acts as the anode in these batteries. This remarkable theoretical specific capacity (4060 mA h g⁻¹) and its potential applications in energy storage and new energy vehicles have spurred considerable enthusiasm. Nevertheless, numerous scientific challenges remain, which must be resolved prior to their commercial viability. This paper provides a comprehensive overview of recent advancements in vanadium diboride materials for metal–air batteries, focusing on key components such as air cathodes, metal anodes, and electrolytes. It highlights several strategies that significantly enhance the stability and efficiency of VB₂–air batteries. These include the development of highly efficient air cathodes incorporating robust and stable oxygen reduction reaction (ORR) catalysts, as well as the surface modification of anode materials. For instance, surface treatments using ZrO₂ and polydopamine (PDA) have been shown to effectively improve the stability and discharge efficiency of VB₂–air batteries. Additionally, the paper discusses the primary challenges impeding further improvements in the performance and longevity of VB₂–air batteries. It concludes by proposing potential research directions to address these challenges, offering insights into the development of next-generation VB₂-based energy storage systems.