Energetic Cost for Being "Redox-Site-Rich" in Pseudocapacitive Energy Storage with Nickel-Aluminum Layered Double Hydroxide Materials.

Author(s) Zhang, X.; Cockreham, C.B.; Yılmaz, E.; Li, G.; Li, N.; Ha, S.; Fu, L.; Qi, J.; Xu, H.; Wu, D.
Journal J Phys Chem Lett
Date Published 2020 May 07

Defining the energetic landscape of pseudocapacitive materials such as transition metal layered double hydroxides (LDHs) upon redox-site enrichment is essential to harnessing their power for effective energy storage. Here, coupling acid solution calorimetry, XRD, and DRIFTS, we demonstrate that as the Ni/Al ratio increases, both as-made (hydrated) and dehydrated NiAl-LDH samples are less stable as evidenced by their enthalpies of formation. Moreover, the higher specific capacity at an intermediate Ni/Al ratio of 3 is enabled by effective water-LDH interactions, which energetically stabilize the excessive near-surface Ni redox sites, solvate intercalated carbonate ions, and fill the expanded vdW gap, paying for the "energetic cost" of being "redox-site-rich". Thus, from a thermodynamic perspective, engineering molecule/solid-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.

DOI 10.1021/acs.jpclett.0c00865
ISSN 1948-7185
Citation J Phys Chem Lett. 2020;11(9):37453753.

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