Keiji Koyama

Development of long life lithium ion battery for power storage

Abstract With the aim of developing lithium ion batteries with a long life and high efficiency for power storage, we experimentally evaluated combinations of cathode and anode active materials, in which batteries are able to obtain over 4000 cycles or 10 years of life. An acceleration method was evaluated using coin cells. We found that changing the current density was effective for evaluating battery life, since the logarithm of the cycle life showed a linear relationship to current density. Based on the current density increasing method, various combinations of cathode and anode active materials were tested. The cell system of LiCoO2/Li4/3Ti5/3O4 clearly showed a long life of about 4000 cycles. The energy density of the cell using the Li4/3Ti5/3O4 anode is obviously smaller than that using a graphite anode, the cell with Li4/3Ti5/3O4 anode was thought to have some merit especially in the large-scale-layer-built type battery by the applicability of the Al anode collector and a light weight battery case.

Electroless pure nickel plating process with continuous electrolytic regeneration system

Abstract We have developed an electroless nickel plating solution in which titanium ion redox system, Ti 3+ →Ti 4+ +e − , was used as a reducing agent. The stability of the solution has been improved by the selection of chelating agents and their ratio to nickel and titanium ion, and by the addition of an amino acid and a sulfur-containing compound. A pure nickel film containing no phosphorus was obtained from the new electroless plating solution. Any other elements except nickel were not detected by inductively coupled plasma analysis. Electrolytic regeneration system of the solution has been also developed. Continuous running test for more than 100 h has been achieved in a pilot plant and the bath is believed to be stable enough to apply to a commercial production line.