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Key Words:Bismuth compounds;Capacitance - Doping (additives) - Electrochemical electrodes - Electrolytes - Graphene - Nanoparticles - Nanosheets - Nanotubes - Nickel compounds - Oxygen vacancies - Supercapacitor

Abstract:In this paper, we constructed oxygen vacancy-containing Bi<inf>2</inf>O<inf>3</inf> nanosheet arrays (OV-Bi<inf>2</inf>O<inf>3</inf> NSAs) with typical mesoporous structures and CoNi<inf>2</inf>S<inf>4</inf> nanoparticles (CoNi<inf>2</inf>S<inf>4</inf> NPs) grown on N-doped graphene nanotubes (N-GNTs) through facile approaches. The as-fabricated OV-Bi<inf>2</inf>O<inf>3</inf> NSAs and CoNi<inf>2</inf>S<inf>4</inf> NPs were specifically used as advanced freestanding negative and positive electrodes, respectively, for application in asymmetric supercapacitors (ASCs). The introduction of ample vacancies to Bi<inf>2</inf>O<inf>3</inf> NSAs can not only enhance their electronic conductivity and donor density but also ameliorate their surface features, which greatly enables the transport of electrolyte ions and electrons, giving rise to rapid redox processes at the Bi<inf>2</inf>O<inf>3</inf>/electrolyte interfaces. Benefiting from the introduction of the oxygen vacancies and the particular morphologies, as well as the synergistic contributions of various components in the nanohybrid electrode, the N-GNTs@OV-Bi<inf>2</inf>O<inf>3</inf> NSA electrode delivers a substantially appreciable specific capacitance of 643 F g⁻¹ at 1 A g⁻¹ coupled with exceptional rate capability. Moreover, the as-synthesized N-GNTs@CoNi<inf>2</inf>S<inf>4</inf> NP electrode also presents an ultrahigh specific capacitance of 2142 F g⁻¹ at 2.5 A g⁻¹. More importantly, the assembled N-GNTs@OV-Bi<inf>2</inf>O<inf>3</inf> NSAs//N-GNTs@CoNi<inf>2</inf>S<inf>4</inf> NP asymmetric supercapacitor with an expanded operation voltage of 1.6 V yields a maximum specific energy density of 86.6 W h kg⁻¹ at a power density of 1.6 kW kg⁻¹ and outstanding cycling characteristics (85% capacitance retention after 10 000 cycles). This study underscores the potential significance of both incorporating oxygen vacancies into metal compounds and integrating the conductive skeleton with the active materials as a strategy for augmenting the electrochemical performances of the electrode materials.<br/> © The Royal Society of Chemistry.

Volume:7

Issue:13

Translation or Not:no

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