Anodic electrochemical mechanism and performance dominant factors of the VB2-air battery

Abstract

The vanadium diboride air battery (VB2-air battery) is a primary battery with the highest intrinsic anode capacity of 4060 mAh g−1 and a theoretical open circuit potential of 1.55 V. So far, the studies of the battery are particularly limited by the elusive anodic electrochemical mechanism. In this work, the following new mechanism for the charge transfer reaction of the anode is proposed: VB2+12OH-→VO2++2BOH4-+2H2O+11e-. From the possible reactions of the anode, we conclude that the surface of the VB2 is not passivated during the battery's standing and discharging processes, which is further verified by specially designed experiments. The surface density of the active substance, the direct contact area of the active substance with the electrolyte, and the hydroxide ion concentration are considered as the dominant factors of the battery's discharge voltage and discharge capacity. A series of measurements on pouch cells have been conducted to ensure the direct proportion between the evolution tendency of charge transfer reaction and the concentration of the hydroxide ions.