Investigation of Zn-to-Co Chemometric Ratio in Zinc
Cobaltite Spinel as Battery-Type Superior Redox-Active Electrodes
for Hybrid Supercapacitors: Density Functional Theory Analysis
posted on 2024-01-23, 22:17authored byAdesh Prasad, Mohit Dilip Borse, Gutturu Rajasekhara Reddy, Mohammad Asif, Sang Woo Joo, Gowra Raghupathy Dillip
Engineering
nonstoichiometric metal ions in the binary metal oxides
is gaining importance in electrochemical energy storage and conversion
devices. Zinc cobaltite (ZnCo2O4), a p-type spinel structure, has been stringently applied in
these fields. In this work, the chemometric ratios of metal ions (Zn
and Co) are varied, and the impact of this nonstoichiometry on the
electronic structure-modified ZnCo2O4 and its
effect on the electrochemical properties are studied in detail. The
experiment uses the microwave-assisted hydrothermal method to vary
the metal precursor to get the desired nonstoichiometry between Zn
and Co in the ZnCo2O4 binary metal oxides. A
set of four different samples is prepared by varying the Zn–Co
precursor stoichiometric concentrations as 0.5–4, 1.0–4,
1.5–4, and 2.0–4, respectively. These four ZCO samples
are first confirmed by X-ray diffraction analysis, followed by refining
the structures to determine the nonstoichiometries of the elements
and supported by X-ray photoelectron spectroscopy. Density functional
theory is applied to determine the electronic structure of ZnCo2O4 with fully stoichiometric (bulk or no vacancy),
three different, single-atom (Zn–, O−)- and dual atom
(Zn– and O−)-deficient ZnCo2O4 and compared. Among four samples, ZCO-1.5–4 and ZCO-2.0–4
are constructed in a hybrid supercapacitor device for practical application.
The optimum ZCO-1.5–4 with Zn- and O-deficiency electrodes
has shown better specific capacity (312.5 C g–1 at
1 A g–1), energy density (49.4 W h kg–1), and power density (10.168 kW kg–1) than other
electrodes. Therefore, the work will provide a database for constructing
various chemometric ratios of binary metal oxides for achieving optimized
nonstoichiometry for the enhanced electrochemical performance of the
practical device.