The characterization of new type of alkaline fuel cell based on oxidation of chemical hydride has been studied. The chemical hydride can be used as a new fuel source in a fuel cell system. As a result, we have discovered that the electrochemical reaction rate is higher at a normal temperature compared with cells containing other hydrogen fuels where a hydrogen-releasing agent, NaBH4, is added to an aqueous alkaline solution of electrolyte as hydrogen fuel. That is, the fuel can be supplied very simply for the cell. If air is supplied to the oxygen cathode made of highly dispersed platinum particles supported in high-surface-area carbon paper, and the hydrogen releasing agent is fed to the alkaline solution of electrolyte at the side of metal hydride anode false(ZrCr0.8Ni1.2 alloy), the cell can produce electric current continuously. Also it can be operated at a normal temperature and produce a large amount of energy due to its high energy density of 6,000 Ah/kg or more (for NaBH4 or KBH4false). Therefore, the developed cell has higher electrochemical reaction rate and energy density than the conventional fuel cells using other hydrogen sources. © 2002 The Electrochemical Society. All rights reserved.

For the purpose of developing a Zr-based Laves phase alloy with higher capacity and better performance for electrochemical application, extensive work has been carried out. After careful alloy design of ZrMn 2 -based hydrogen storage alloys through varying their stoichiometry by means of substituting or adding alloying elements, the Zr 0.9 Ti 0.1 (Mn 0.7 V 0.5 Ni 1.4 ) 0.92 with high capacity (392 mAh/g at the 0.25C) and improved performance (comparable to that of commercialized AB 5 type alloy) was developed. Another endeavor was made to improve the poor activation property and the low rate capability of the developed Zr-based Laves phase alloy for commercialization. The combination method of hot-immersion and slow-charging was introduced. It was found that electrode activation was greatly improved after hot immersion at 80 o C for 12 h followed by charging at 0.05C. The effects of this method are discussed in comparison with other activation methods. The combination method was successfully applied to the formation process of 80 Ah Ni/MH cells. A series of systematic investigations has been rendered to analyze the inner cell pressure characteristics of a sealed type Ni-MH battery. It was found that the increase of inner cell pressure in the sealed type Ni/MH battery of the above-mentioned Zr-Ti-Mn-V-Ni alloy was mainly due to the accumulation of oxygen gas during charge/discharge cycling. The fact identified that the surface catalytic activity was affected more dominantly by the oxygen recombination reaction than the reaction surface area was also identified. In order to improve the surface catalytic activity of a Zr¯Ti¯Mn¯V¯Ni alloy, which is closely related to the inner pressure behavior in a sealed cell, the electrode was fabricated by mixing the alloy with Cu powder and a filamentary type of Ni and replacing 75% of the carbon black with them; thus, the inner cell pressure rarely increases with cycles due to the active gas recombination reaction. Measurements of the surface area of the electrode and the surface catalytic activity showed that the surface catalytic activity for the oxygen recombination reaction was greatly improved by the addition of Cu powder and the filamentary type of Ni. Finally, we have collaborated with Hyundai Motors Company on fabrication of the 80Ah cells for Electric Vehicles and evaluated the cell performance.

The effect of manganese addition on hydrogen storage performance of vanadium-based BCC alloys was investigated by measuring mainly pressure-composition (P-C) isotherms at 303K. Annealing heat-treatment was also considered in selected cases. The XRD patterns showed BCC single phase in all the alloys. With increasing Mn content, the lattice parameters decreased linearly, thus resulting in an increase in plateau pressure and a reverse effect on maximum hydrogen storage capacity. However, an effective hydrogen storage capacity as high as 1.92 wt.% was achieved at x = 0.075. V-Ti-Mn alloys showed a surprisingly flat desorption plateau, but lots of absorbed hydrogen cannot desorb at ambient temperature. Although V 0.44 Ti 0.20 Cr 0.12 Mn 0.12 Fe 0.12 alloy did not show the first plateau, both the maximum and effective hydrogen storage capacities were very low.