Energetic Cost for Being “Redox-Site-Rich” in Pseudocapacitive Energy Storage with Nickel – Aluminum Layered Double Hydroxide Materials

20 April 2020, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


Defining the energetic landscape of pseudocapacitive materials such as transition metal layered double hydroxides (LDHs) upon redox site enrichment is essential to harness their power for effective energy storage. Here, coupling acid solution calorimetry, in situ XRD, and in situ DRIFTS, we demonstrate that as the Ni/Al ratio increases, both as-made (hydrated) and dehydrated NiAl-LDH samples are less stable evidenced by their enthalpies of formation. Moreover, the higher specific capacity at intermediate Ni/Al ratio of 3 is enabled by effective water – LDH interactions, which energetically stabilizes the excessive near-surface Ni redox sites, solvates intercalated carbonate ions, and fills the expanded vdW gap, paying for the “energetic cost” of being “redox site rich”. Thus, from a thermodynamic perspective, engineering molecule/solids – LDH interactions on the nanoscale with confined guest species other than water, which energetically impose stronger stabilization, may help us to achieve their specific capacitance potential.


Energetics-Structure-Performance Relationships
Layered Double Hydroxides
Hydration Energetics
Enthalpy of Formation
in situ XRD & DRIFTS

Supplementary materials

Revised SI 04-16-2020


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