First-Principles Theory of Electrochemical Capacitance of Nanostructured Materials: Dipole-Assisted Subsurface Intercalation of Lithium in Pseudocapacitive TiO2 Anatase Nanosheets

Joongoo Kang, Su Huai Wei, Kai Zhu, Yong Hyun Kim

Research output: Contribution to journalArticlepeer-review

54 Scopus Citations

Abstract

As the size of the material decreases to the nanoscale, the distinction between batteries and electrochemical capacitors becomes obscured. Here, a first-principles approach is developed to calculate electrochemical capacitance of nanomaterials. Using TiO2 anatase nanosheets interfaced with lithium ion-containing electrolytes as an example, we reveal a microscopic mechanism for lithium intercalation in this system. We demonstrate that a TiO2 nanosheet is a hybrid of supercapacitor and battery, possessing characteristics of both depending on electrode potential. At positive electrode potential above 2.2 V versus Li/Li+, the system behaves as capacitor with the formation of electric double layers at the surface. As the electrode potential decreases below the threshold, lithium intercalation into the interior takes place, assisted by the surface electric dipole field. Our findings provide a coherent picture of how a transition from pure capacitors to batteries or pseudocapacitors occurs in these nanostructured materials.

Original languageAmerican English
Pages (from-to)4909-4915
Number of pages7
JournalJournal of Physical Chemistry C
Volume115
Issue number11
DOIs
StatePublished - 2011

NREL Publication Number

  • NREL/JA-5900-50346

Keywords

  • nanostructured materials

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