Nobuaki Matsumoto

A Nickel Electrode with Ni-Coated 3D Steel Sheet for Hybrid Electric Vehicle Applications

A Ni-coated 3D steel sheet, at a quarter of the cost of conventional Ni foam, was designed as a substrate for the positive electrode of a nickel/metal hydride battery. A new thin positive electrode was developed using this substrate, and the electrochemical properties were investigated. The thin positive electrode using the Ni-coated 3D sheet and polystyrene acrylic acid ester (PSA) as a binder maintained a discharge capacity of more than 80% of initial capacity even after 1000 cycles in cycle test under 25°C, which was comparable to the Ni foam electrode. However, the electrode showed capacity fade after 180 cycles in cycle test under 45°C, because of the decomposition of PSA. The results of Fourier transform IR analysis indicated that styrene-maleic acid resin (SMA) had high stability in alkaline solution at high temperatures and was more suitable as a binder than PSA. A new battery for hybrid electric vehicles (HEVs) was developed using the thin positive electrode with the Ni-coated 3D sheet and SMA. The power density of the new battery achieved 1055 W/kg, compared with 480 W/kg for the conventional one. In the HEV mode cycle test, both the capacity and the power output of the cell remained at more than 80% of the initial value even after 25,000 cycles.