The alkaline solid polymer electrolyte system with the conductivity of (8.5±0.2) × 10−4 Scm−1 composes of polyvinyl alcohol (PVA) and potassium hydroxide (KOH) have been used in fabrication of Mg2Ni/Ni(OH)2 nickel metal hydride cell. The self-dehydriding of the cell during storage was presented by open circuit voltage study. Cell degradation after charge-discharge cycling is characterized by means of X-ray diffraction and scanning electron microscopic analyses. The failure of the cell can be ascribed by a small formation of Mg(OH)2 oxide layer and surface resistance between electrode-electrolyte.