STRUCTURE MODIFICATION AND CHANGE OF ELECTROCHEMICAL ACTIVITY OF NICKEL HYDROXIDES

Questions concerning the interrelationship between the structure of nickel hydroxides used in alkaline batteries and their electrochemical activity are discussed. A great role in the nickel hydroxide electrode (NHE) activation played by the increase of the depth of the transition higher nickel hydroxides --> beta-Ni(OH)2 during NHE discharging is shown. The latter can be achieved by modifying the higher nickel hydroxide structure. In particular, the cobalt(II) hydroxide additive enables this modification during NHE charging forming the fragments of the CoHO2 structure embedded into the crystalline lattice, which leads to the inhibition effects during the transition phase beta-Ni(OH)2 --> gamma-NiOOH and to some certain types of the crystalline lattice disorder facilitating the reverse transition to the beta-Ni(OH)2 structure during NHE discharging. It has been shown that the gamma-NiOOH structure modification can be achieved by various means. In particular, some positive effects increasing the NHE reversibility are observed in the presence of the inert zinc hydroxide additive, as well as some portion of stable anions incorporated into the beta-Ni(OH)2 structure forming H-bonds with the layers of the nickel hydroxide crystalline lattice.