Structure Modification and Change of Electrochemical Activity of Nickel Hydroxides

Abstract

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 ---, ~-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 CoHQ structure embedded into the crystalline lattice, which leads to the inhibition effects during the transition phase ~-Ni(OH)2--~ ~-NiOOH and to some certain types of the crystalline lattice disorder facilitating the reverse transition to the ~-Ni(OH)2 structure during NHE discharging. It has been shown that the ~-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 ~-Ni(OH)~ structure forming H-bonds with the layers of the nickel hydroxide crystalline lattice.

Anionic carbonate activation of layered (α+β) nickel hydroxide

“…Cobalt compounds in the form salts, oxides or hydroxide are added to the active mass. As structural activators, soluble salts of zinc or aluminum are added during the synthesis stage of hydroxide [49,50]. This leads to coprecipitation with the formation of double hydroxides and LDH.…”

Co-doped NiO nanoflake array films with enhanced electrochromic properties

“…Obviously, the addition of CoSO 4 in the CBD solution exerts an effect on the growth of NiO lm. This phenomenon can be explained by the fact that CoSO 4 inhibits the transition from b-Ni(OH) 2 to g-NiOOH, 45 while This journal is © The Royal Society of Chemistry 2014 g-NiOOH with a higher valence state is conducive to the growth of NiO lm. 39 In addition, the electrochemically accessible surface area of NiO lm with an appropriate amount of Co doping should be greater than that of undoped NiO lm because of the existence of small pores.…”

The electrocatalytic behaviour of electroless Ni–P alloys

“…Another contribution may arise from the phosphorous oxidation since amorphous phosphates (or other compounds) once deposited in the electrode surface hinder the observation of possible crystalline phases. The difficulty in the detection of the new surface phases can also be related with their amorphous nature, particularly recognized when a-Ni(OH) 2 is present [94]. Nickel oxides prepared by anodic deposition have been described as aggregates consisting of Ni 2+ , Ni 3+ OH À , H 2 O with a non-stoichiometric nature [76].…”