The influence of the memory effect on X-ray diffraction, X-ray photoelectron spectroscopy and Raman scattering in the positive electrodes of the nickel metal hydride batteries were investigated. The obtained data of X-ray diffraction, X-ray photoelectron spectroscopy and Raman scattering in the samples shown the memory effect are hardly affected during the charge-discharge processes. The peak intensity of the Raman mode due to the defect of the crystal structure in the samples shown the memory effect is larger than those in the normal and reconditioned samples. These results suggest that the samples shown the memory effect involve more disorder and/or proton vacancy than the normal and reconditioned samples. Consequently, the redox mechanism of the nickel oxide electrode based on the reversible insertion-deinsertion of protons and electrons is deteriorated. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.040212jes} All rights reserved.