| Abstract Scope |
Compositional modification by increasing concentration of redox site is effective to tune the energy density and enhance the performance of pseudocapacitive materials. Here, I report our recent study on the structure-energetics-performance relationships of nickel–aluminum layered double hydroxides (NiAl-LDHs) as a function of Ni/Al ratio. Specifically, increase of Ni/Al ratio results in expanded van der Waals gap, which leads to fast charge–discharge kinetics, degraded crystallinity, and high cycling stability. In addition, using acid solution calorimetry, in situ XRD, and in situ DRIFTS, we figure out that increase of Ni/Al ratio leads to energetically less stable as-made (hydrated) and dehydrated NiAl-LDHs, supported by experimentally measured formation enthalpies. Moreover, the highest specific capacity observed, 2128 F/g at 1 A/g, is owing to effective hydration that energetically stabilizes the Ni redox sites, solvates carbonate ions, and fills interlayer space, in other words, paying for the “energetic cost” of being “redox site rich”. |