Researchers from the University of Michigan and Osaka University in Japan propose in a paper in the Journal of Power Sources a high-temperature, rechargeable metal-air battery that relies on Ti or Zr metal as the anode and the shuttling of oxygen anions between the cathode and the anode through a solid-oxide ion-conducting electrolyte.
Theoretical capacities for these batteries are as high as 840 mAh g−1 for Ti- and 500 mAh g−1 for Zr-based metal-air batteries.
The use of intercalation compounds as electrodes in Li-ion batteries has proven crucial to the success of these electrochemical storage devices, enabling high charge and discharge rate capabilities as well as high cycle lifetimes. Li-intercalation compounds used as electrodes in Li-ion batteries consist of an electronically conducting host structure that can undergo large variations in Li concentration without significant crystallographic modifications.
A drawback of intercalation compounds, however, is their limited capacity, both by weight and volume. Alternative electrode reaction mechanisms are, therefore, actively investigated. One such mechanism, inspired by the Li-air battery, is to dispense of the host structure altogether and to let the shuttled ion react with oxygen in ambient air, thereby forming a metal oxide at the cathode (i.e. Li2O2 or Li2O in the Li-air battery). Although the theoretical capacity of a Li-air battery is substantially higher than can be achieved with intercalation compounds, it nevertheless suffers from sluggish kinetics and large hysteresis between charge and discharge. This poor kinetics has its origin in part due to the formation of the electronically insulating and poorly conducting oxide reaction product on the current collector.
The Li-air battery has nevertheless sparked interest in other metal-air battery concepts. The challenge there, however, is the difficulty in finding electrolytes that conduct multivalent metal cations. Here we propose a high-temperature metal-air battery that has much in common with the intercalation processes, relying on pure Ti or Zr as the anode.—Van der Ven et al.
Key for the proposed battery is the use of Ti or Zr as the anode as these metals are unique in their ability to dissolve oxygen up to concentrations of 33% with minimal structural and volumetric changes, the researchers said. The cathode has much in common with solid-oxide fuel cells.
Anton Van der Ven, Brian Puchala, Takeshi Nagase (2013) Ti- and Zr-based metal-air batteries. Journal of Power Sources, Volume 242, Pages 400-404 doi: 10.1016/j.jpowsour.2013.05.074