Analysis of the Memory Effect in Positive Electrode of Ni-MH Batteries by Scanning Electron Microscopy/Energy Dispersive X-ray Mapping and Transmission Electron Microscopy

摘要

The influence of the memory effect on scanning electron microscopy/energy dispersive X-ray mapping and transmission electron microscopy in the positive electrodes of the nickel metal hydride batteries were investigated. Nickel and aluminum are reversed distribution of oxygen for all the samples. Yttrium mapping in the normal and reconditioned samples are hardly affected during the charge-discharge processes. On the contrary, yttrium was aggregated in the samples shown the memory effect. The rosette-shaped and the tube-shaped precipitates were observed in the surface of the sample shown the memory effect by transmission electron microscopy images. The rosette-like precipitates were mainly composed of metallic nickel and β-Ni(OH)2 crystal, and the tube-shaped precipitates were mainly composed of metallic yttrium. These precipitates disappeared in a reversible manner by the reconditioning of the memory effect.