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

preprint
revised on 16.04.2020 and posted on 20.04.2020 by Xianghui Zhang, Cody B. Cockreham, Esra Yilmaz, Gengnan Li, Nan Li, Su Ha, Liangjie Fu, Jianqing Qi, Hongwu Xu, Di Wu

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.

History

Email Address of Submitting Author

d.wu@wsu.edu

Institution

Washington State University

Country

United States

ORCID For Submitting Author

0000-0001-6879-321X

Declaration of Conflict of Interest

N/A

Exports