Journal
CERAMICS INTERNATIONAL
Volume 47, Issue 6, Pages 8290-8299Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2020.11.190
Keywords
Bi2O3; Pseudo-capacitance; Vacancy defects; Electrochemical performance
Categories
Funding
- National Key R&D Program of China [2019YFA0210003]
- National Natural Science Foundation of China [12075172, 11875209, 11705029]
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This study investigated the impact of vacancy defects on the physical-chemical properties of Bi2O3 powders used as supercapacitor electrodes. It was found that the h-Bi2O3 sample with more V'''BiVO++V'''(Bi) defects exhibited better cycle stability and rate performance, attributed to the insertion/extraction process of K+ ions in the surface defects. Furthermore, the high concentration of V'''BiVO++V'''(Bi) defects in the h-Bi2O3 electrode led to improved conductivity and higher specific energy density in an asymmetric supercapacitor configuration.
Vacancy defects have important impacts on the physical-chemical properties of metal oxides. In the present work, two types of Bi2O3 powders with different morphologies were synthesized for supercapacitor electrodes by calcination (denoted as c-Bi2O3) and two-step hydrothermal methods (donated as h-Bi2O3). Vacancy clusters of V'BiVO++V'''(Bi) with different concentrations were observed in these two samples by positron annihilation lifetime spectroscopy. The results of electrochemistry revealed that the charge storage behavior of h-Bi2O3 with more V'''BiVO++V'''(Bi) defects obeyed both semi-infinite diffusion-controlled battery-type mechanism and surface-controlled pseudo-capacitance mechanism, while that of the calcined c-Bi2O3 electrode with a lower concentration of V'''BiVO++V'''(Bi) defects followed only the semi-infinite diffusion-controlled battery-type mechanism. The pseudocapacitance of h-Bi2O3 could be attributed to the insertion/extraction process of more K+ ions in the V'''BiVO++V'''(Bi) Bi surface defects. Due to the partial pseudo-capacitance and improved conductivity caused by more V'''BiVO++V'''(Bi) defects, the h-Bi2O3 electrode had a larger capacitance (1043 F g(-1) at 1 A g(-1)), a higher rate performance (560 F g(-1) at 60 A g(-1)), and better cycle stability (93% retention at 50 A g(-1) after 2000 cycles). Furthermore, because of the high-concentration of V'''BiVO++V'''(Bi) defects, the Ni/Co-MOF//h-Bi2O3 asymmetric supercapacitor delivered a relatively higher specific energy density of 47 Wh kg(-1) at 1125 W kg(-1). Taken together, these results indicate that surface vacancy clusters play an important role in boosting the electrochemical performance of metal oxide electrodes.
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