Microcalorimetry study of Ni/H/sub 2/ battery self-discharge mechanism

Self‐Discharge of the Nickel Electrode in the Presence of Hydrogen: I. Textural Study

“…In short, these experiments demonstrate (i) that water-dissolved hydrogen can interact directly with the nickel electrode in its charged state at elevated temperature (60ЊC) and very low hydrogen pressure (3 bars), (ii) that increasing hydrogen pressure results in an increase in the reduction rate (e.g., increased self-discharge) in agreement with previous reports, 4 and (iii) that a bare nickel metal substrate is not necessary to promote the ␤(III) r ␤(II) or ␥ r ␤(II) transformations.…”

“…It should be recalled that the hydrogen pressure can reach about 70-80 bars when the cell is fully charged and ready to be used. It has been clearly demonstrated by microcalorimetry studies [4][5][6][7][8] that the self-discharge rate increases with the hydrogen pressure. A typical Ni/H 2 cell can lose up to 50% of its initial capacity in approximately 10 days at 50 atm and 20ЊC.…”

Self‐Discharge of the Nickel Electrode in Presence of Hydrogen: II. Electrochemical Approach

“…Finally, among the most likely mechanisms are (ii) the direct chemical reaction between hydrogen and NiOOH 2-7 and/or (iii) an electrochemical oxidation of hydrogen at the positive electrode with the rate partially limited by a diffusion process. [2][3][4]6,7 However, from the empirical plots of the cell pressure vs. time, none of the above mechanisms has been fully confirmed. 2 The above literature survey dealing with Ni/H 2 self-discharge kinetics simply reflects the complexity of the issue, most likely due to the complicated nickel hydroxide electrode chemistry that is a function of the cell state of charge.…”