Effect of crystallinity on the electrochemical performance of nanometer Al-stabilized a-nickel hydroxide

摘要

Nanometer Al-stabilized a-Ni(0H)2, synthesized by urea decomposition, was tested to have better crystallinity from Ni(NO_3)_2-6H_2O and A1(NO_3)_3-9H_2O (Sample A) than that from NiSO_4-6H_2O and A1_2(SO_4)_3-18H_2O (Sample B), and more agglomeration was found for the badly crystallized Sample B as shown by TEM. XPS spectra determined that the positively charged part for Sample A and B was [Ni_(0.78) Al_(0.22)(OH)_2]~((0.22+) and [Ni_(0.95)Al_(0.05)(OH)_2]~(0.05+), respectively. TG and DSC showed that the thermal processes of the two samples are different, where Sample B decomposed at a higher temperature. Cyclic voltammetry (CV) test showed that Sample A had better reversibility, and anodic oxidation peak of Sample B disappeared with the increase in scanning rate. Sample A had smaller electrochemical resistance as shown by electrochemical impedance spectroscopy (EIS), and electrode reaction of Sample A is mostly controlled by proton diffusion, while that of Sample B is a mixed controlled electrode process. Sample B also has poorer electrochemical discharge and cycle life performance.