Performance Improvement of NiMH-Based Fuel Cell/Battery (FCB) with α-Ni(OH)2

概要

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In a NiMH-based Fuel Cell/Battery (FCB) system, the performance of the positive electrode composed of a mixture of α-Ni(OH)2 and MnO2 was compared with that of another electrode composed of a mixture of β-Ni(OH)2 and MnO2. When Al-doped α-Ni(OH)2 was used to replace β-Ni(OH)2 for the active material of the positive electrode, more stable operation of Fuel Cell/Battery (FCB) system was achieved. Cyclic voltammetry (CV) results for the Al-doped α-Ni(OH)2 positive electrode showed that the electron transfer number of α-Ni(OH)2 was 1.5 times larger than that of β-Ni(OH)2, which led to an improved discharge capacity. Furthermore, the plateau voltage in the second working voltage for α-Ni(OH)2/MnO2 was more stable compared to that for β-Ni(OH)2/MnO2 in the fuel cell reaction when the cell was overcharged to an SOC of 300%. In addition, the plateau voltage in the first working voltage was higher than that of β-Ni(OH)2 by 0.2 V, which could be attributed to better contact between the polymer gel electrolyte and the electrode in the case of Al-doped α-Ni(OH)2 due to the negligible volume change of Al-doped α-Ni(OH)2 during the overcharge/discharge.