The preparation and electrochemical performances of the composite materials of CeO_2 and ZnO as anode material for Ni-Zn secondary batteries

摘要

The composite materials of CeO_2 and ZnO (CeO_2/ZnO) were prepared by one step hydrothermal method. The X-ray diffraction (XRD) patterns reveal that CeO_2 does not enter the lattice of ZnO and no new phase is generated. The energy dispersive spectrometer (EDS) spectra of CeO_2/ZnO demonstrates that the elemental composition on the surface of CeO_2/ZnO is Ce, Zn, O. The scanning electron microscopy (SEM) images of CeO_2/ZnO and pure ZnO show that the grain sizes of CeO_2/ZnO significantly increased after compositing and part of CeO_2 coating on the surface of ZnO. Tafel plot, cyclic voltammetry (CV), electrochemical impedance spectroscope (EIS) and galvanostatic charge-discharge measurements were utilized to examine the electrochemical performances of CeO_2/ZnO. Compared with pure ZnO and ZnO physical mixed with CeO_2 (ZMC), the CeO_2/ZnO have a more positive corrosion potential in the zinc electrodes which indicates the CeO_2/ZnO has a good anticorrosion ability. A lower charge platform and a flatter discharge platform of CeO_2/ZnO indicate that the CeO_2/ZnO have a better charge/discharge performance as anodic material for Ni/Zn cells. Most important of all, the CeO_2/ZnO anodes show much more stable cycle stability. At the 50th cycle, the discharge capacity of pure ZnO anode reduces to 358.4 mAhg~(-1) at 1 C with the capacity retention ratio of 68%, while the capacity retention ratio of CeO_2/ZnO anodes are 96.7%, 99.1% and 95.2%, respectively.