Comparing additive containing electrolytes to the pure KOH and pure salt electrolytes, significant
changes in degradation and discharge capacity were observed. For salts in Area 1 of Figure 3 (i.e.,
degradation 100%), a synergistic effect between the salt additives and KOH
electrolyte is presumed to explain the improvement in electro-performance. The synergistic effect
can be explained by the following inferences: (1) a solid film forms on the surface of both electrodes.
As shown in Figure 14, all the anions in Area 1 were able to react with Mg2+ and Ni2+ on the surface of
MgNi metal hydride particles and Ni2+ on the surface of β-Ni(OH)2 particles to form a solid deposit [20,21].
In this research, discharge capacity is closely related to the amount of MgNi metal hydride in
negative electrodes. This solid film over the MgNi metal hydride particles could physically protect the
electrode from electrolyte corrosion; (2) H-transfer is promoted in aqueous electrolyte. The salt
additives’ effects were considered from the aspects of the anions and cations