Kazuki Okuno

Nickel Substrate Having Three-Dimensional Micronetwork Structure for High-Power Nickel/Metal-Hydride Battery

A low-cost substrate for the positive electrode of nickel/metal-hydride battery was developed by using a nonwoven cloth with a three-dimensional micronetwork structure, in which the amount of plated nickel was less than half compared with the conventional foam-type substrate. The substrate was designed to have a finer structure than the foam-type substrate. The cylindrical sealed cell using the substrate exhibited superior high-rate discharging capability to the cell using the foam-type substrate, despite the reduction of plated nickel. The characteristic microporous structure of the substrate presumably contributes to the improvement of high-rate discharge performance.

High-capacity electric double layer capacitor using three-dimensional porous current collector

A three-dimensional porous current collector made of a nickel-chromium alloy was developed based on foamed polyurethane. The foam-type substrate exhibited a high tolerance at high voltages in nonaqueous electrochemical systems. The electric double layer capacitor (EDLC) using the foam-type substrate exhibited stable charge/discharge behavior and showed a superior high-rate discharge capability as compared to an EDLC using the conventional aluminum foil. Furthermore, impedance analysis revealed an improved current collecting ability for the foam-type substrate. To improve the performance of EDLCs, a methodology that uses a three-dimensional current collector was described.

Influence of Nickel Foam Pore Structure on the High-Rate Capability of Nickel/Metal-Hydride Batteries

The influence of nickel foam pore structure on the high-rate capability of nickel/metal-hydride (Ni/MH) batteries was studied to develop a substrate suitable for high-power use. Three types of nickel foam substrates with different pore structures were used for preparing the sealed cells. Among the three prepared sealed cells, the cell using the substrate with a smallest pore diameter and largest surface area exhibited the best high-rate discharging performance. The electrochemical impedance measurement also showed a close relationship between the charge-transfer resistance and the pore structure of the substrate. The contact area between the current collector and the active material is considered to significantly affect the contact resistance and the charge-transfer resistance. The pore-size reduction and the enlargement of the surface area of the substrate were revealed to be effective in improving the high-rate performance of Ni/MH batteries.