Insights into the electrochemistry of layered double hydroxide containing cobalt and aluminum elements in lithium hydroxide aqueous solution

The electrochemical capacitive behavior of layered double hydroxide containing cobalt and aluminum (Co–Al LDH), synthesized by a “memory effect” route, was in detail evaluated by cyclic voltammetry (CV) and chronopotentiometry in 1 M LiOH aqueous electrolyte. A specific capacitance of 187 F g−1 was obtained even after 1000 cycles at a current of 2 A g−1. Moreover, it was found that Co–Al LDH undergoes two independent electrode processes in LiOH aqueous solution, involving the simultaneous intercalation of an ion-pair, i.e. lithium cation and hydroxyl group, which is different from the mechanisms in NaOH and KOH aqueous solutions. The possible reason is thought to be the selective intercalation into Co–Al LDH for alkali metal ions due to their respective ionic radius. Only the cation with appropriate size is suited for inserting into [Co(OH)6] or [Al(OH)6] octahedral vacancies.