Evaluation of properties and performance of nanoscopic materials in vanadium diboride/air batteries

The unique eleven electron per molecule electrochemical oxidation of vanadium diboride (VB2) combined with an air cathode provides VB2/air batteries that have extremely high theoretical energy densities. Testing of VB2/air cells at various discharge times showed that VB2/air batteries containing nanoscopic VB2 anodes provide higher capacities and voltages than cells containing macroscopic VB2 anodes. The structure and properties of nanoscopic VB2 were compared with those of macroscopic VB2 to provide further insight into the enhanced electrochemical performance of the nanomaterial. From nitrogen physisorption and electrical conductivity measurements, we determined that the higher performance of the nanoscopic VB2 material compared with the macroscopic VB2 material may result from the combination of the nanomaterial's higher surface area and higher electronic conductivity. The thickness of the zirconia layer applied to prevent corrosion in alkaline electrolyte was shown by transmission electron microscopy and energy dispersive X-ray spectroscopy to be ca. 3-40 nm which may allow rapid discharge through the coating. Electrochemical impedance spectroscopy results showed that for cells containing both the macroscopic and the nanoscopic materials the resistance associated with charge transfer increases during the discharge process. The results provide a basis for further development of high energy and power density VB2/air batteries.