A 3D hierarchically porous nanoscale ZnO anode for high-energy rechargeable zinc-air batteries

Abstract

The successful future development of electrically rechargeable zinc-air batteries (ZABs) is hampered by the insufficient zinc anode stability upon reversible cycling. The reversible oxidation and reduction of the entire zinc species with respect to full cyclability plays a key role for the success of ZABs. Herein we devise fabrication and use of a porous carbon matrix containing finely dispersed ZnO nanoparticles as anode in a zinc-air cell showing full rechargeability. The hybrid anode material allows for an improved zinc utilization in a newly devised cell set up and an unprecedented cyclability upon deep discharge reported so far for ZABs. Investigations on the ZnO conversion reaction by cyclic voltammetry, postmortem X-ray diffraction and postmortem TEM have revealed its reversibility by solving problems of zinc anode degradation. Galvanostatic cycling of the full cell shows that the charging time impacts the discharge capacity while the coulombic efficiency is only slightly affected. At a lower current density, a high mean discharge capacity of 207 mAh/g is received whereas a high current density facilitates a comparable high overall coulombic efficiency of 83%. To the best of our knowledge the herein reported cell represents a rare example of a prototypical Zn-air cell with full recyclability.