GAS RECOMBINATION IN SEALED NI-MH2 CELLS

This paper focuses on investigation of gas recombination in a positive -limited-sealed Ni-MHx cell. The positive electrodes were prepared by electrochemical impregnation of fibrous nickel plaques. The metal hydr ide negative electrodes were made by pasting the mixture of rare-earth hydrogen storage alloy powders, conducting and binding agents on foam ed nickel substrates. The measurement of the positive capacity at diff erent charge times was used to estimate the partial current for oxygen evolution at the same time. The effects of charge rate, electrolyte s aturation level and initial state of charge of the positive electrodes on the recombination were investigated in sealed Ni-MHx cells. By det ermining the differential capacity of nickel hydroxide electrodes, an improved mathematical model was used to evaluate the gas recombination parameters during charge, overcharge, rest and discharge of the posit ive-limited-sealed Ni-MHx cell. The gas recombination during rest, dis charge and overdischarge was also examined. The oxygen recombination o n the nickel hydroxide electrodes can be neglected due to the consumpt ion of water when the nickel hydroxide electrodes were discharged. The longer overdischarge produced an increase in cell pressure for the se aled Ni-MHx cell at an electrolyte unsaturated level and the evolving gas can be recombined by a following recharge operation.