Method of forming CoOOH and NiOOH in a NiMH electrochemical cell and an electrochemical cell formed thereby
US6270535A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 4, 1998 |
| Grant date | Aug 7, 2001 |
| Priority date | — |
| Expiry date | Sep 4, 2018 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T29/49108
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A formation procedure for a NiMH electrochemical cell is disclosed that significantly shortens the time required to fully form such a cell. The formation procedure includes a first step during which the cell is charged at a constant voltage of preferably 1.0 volt for approximately three hours. A second charging step is performed by applying either a constant charge current at a predetermined rate of C/3 for five hours or applying a constant voltage of 1.45 to 1.5 volts for five to nine hours. A third step may optionally be used whereby the cell is charged at a constant current of C/10 for about two hours. NiMH cells subjected to this formation procedure have a much greater percentage of the starting cobalt material in the positive electrode converted to CoOOH thereby improving the conductive matrix formed about the Ni(OH).sub.2 /NiOOH particles, which constitute the active material of the positive electrode. The disclosed inventive formation procedures result in higher utilization, higher cell capacities following long-term storage, or storage at high temperatures as well as improved capacity recovery following deep discharge.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.