Influence of surface modification with Sn6O4(OH)4 on electrochemical performance of ZnO in Zn/Ni secondary cells

The surface-modified ZnO by Sn6O4(OH)4 was prepared by a simple hydrolyzation process and the influence of Sn6O4(OH)4 on electrochemical performance of ZnO was investigated by charge/discharge cycling test, slow rate cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with the unmodified ZnO, the Sn6O4(OH)4-modified ZnO showed improved electrochemical properties, such as superior electrochemical cycle stability, higher discharge capacity and utilization ratio. The surface modification could suppress the dissolution of ZnO in the alkaline electrolyte and maintain the electrochemical activity of ZnO. When the Sn6O4(OH)4 content reached 27 wt.%, the discharge capacity of the modified ZnO hardly declined over 80 cycling test, the average utilization ratio could reach 98.5%, and the modified ZnO electrodes had no obvious weight loss after the cycling tests. However, the charge/discharge plateau voltage with the Sn6O4(OH)4-modified ZnO slightly decreased. For the modified ZnO electrodes, two anodic peaks occurred in the CV curves, and the charge transfer resistance increased from the EIS results, both of which were ascribed to the suppressive effect of surface modification on the electrochemical reactions.