Comparative structural and electrochemical study of spherical ZnO with different tap density and morphology as anode materials for Ni/Zn secondary batteries

Abstract

In this work, we compare the behavior of five kinds of high-density spherical ZnO with different surface morphology as anode materials for nickel/zinc rechargeable batteries to investigate the effects of microstructure and surface properties of ZnO on the electrochemical performance of zinc anodes. For the first time, five spherical ZnO samples with tap densities of 1.62, 2.00, 2.38, 2.83, and 3.12 g cm−3 have been successfully developed via a complexing co-precipitation method by adjusting the composition of alkaline solution and pH value. It is discovered that an enhanced volume specific capacity and more stable cycling performance can be achieved for the anode with spherical ZnO (3.12 g cm−3). Nevertheless, the as-obtained ZnO sample with higher tap density shows slightly worse high-rate performance and lower discharge capacity. Interestingly, as confirmed by the CV and Tafel polarization test, with the increase of ZnO’s tap density, the zinc anodes exhibit better reversibility and higher corrosion resistance. Consequently, the denser solid spherical structure of spherical ZnO is beneficial to effectively adjust its “dissolution-deposition” process, significantly suppressing the outward growth of zinc dendrites and enhancing the batteries’ cycling stability.