In this work, we report a high-performance and self-standing supercapacitor electrode composed of a Co and Mn layered double hydroxide (CoMn-LDH) nanostructure on Ni foam (NF) prepared by one-step electrochemical deposition. The CoMn-LDH electrode delivers a high capacitance of-2673.6 F g(-1) at 1 A g(-1), with the excellent rate performance (-1488.0 F g(-1) at 60 A g(-1)) and good cycle stability (-86.7% capacitance retention after 5000 cycles at 12 A g(-1)). The asymmetric supercapacitors assembled using the cathode of CoMn-LDH, the anode of activated carbon on carbon cloth and the electrolyte of 2.0 M KOH yield an energy density of-97.5 W h kg(-1) at 800.0 W kg(-1), good cycling performance of-89.2% capacitance retention after 5000 cycles at 5 A g(-1) with the Columbic efficiency around 100%. These results indicate that the CoMn-LDH nanostructure on NF is a promising electrode for high-performance energy storage applications.

In this paper, a superior independent electrode of reef-like Co(OH)2-coated FeCo2S4 (FeCo2S4@Co(OH)2) prepared on Ni foam by two-step hydrothermal synthesis (FeCo2S4) and electrodeposition (Co(OH)2) is reported. A higher capacitor of 6169.2 mF cm -2 is produced at 1 mA cm -2 . The aqueous asymmetric supercapacitors (AASCs) exhibit an energy density of 0.377 mWh cm -2 at 0.8 mW cm -2 and maintain capacity retention of 80.56% even after the 20000 cycles at 10 mA cm -2 . In view of its good properties and superficial formulation, we conceive that this research could render valuable exploration for the development of high-performance self-supporting electrodes applicable in AASCs.

In this work, we report a high-performance self-standing electrode of Mn(OH)(2)-coated Ni3S2 (Ni3S2@Mn(OH)(2)) nanosheets on Ni foam by hydrothermally growing the Ni3S2 nanosheets and electrodepositing Mn(OH)(2) around Ni3S2. The structure of the Ni3S2 nanosheets grown by the hydrothermal method is more stable, and the electrodeposition method is easier to synthesize Mn(OH)(2) without using any binder. The electrochemical characterization demonstrates that combining the Ni3S2 nanosheet with the Mn(OH)(2) coating is an effective way to improving the charge storage performance because of the synergetic effects of both materials/structures. The electrode possesses a high area-specific capacitance of 6430.2 mF cm(-2) at 1 mA cm(-2) and good cycle stability with similar to 80.9% capacitance retention after 9000 cycles at 8 mA cm(-2). The aqueous asymmetric supercapacitors assembled with the Ni3S2@Mn(OH)(2) cathode, the activated carbon anode and 1 M KOH electrolyte delivers an energy density of 0.371 mWh cm(-2) at 0.799 mW cm(-2), as well as good cycle stability with similar to 86.3% capacity retention after 10,000 cycles at 20 mA cm(-2). Given the high performance and relatively simple preparation, this work provides a valuable exploration of developing high-performance cathodes for aqueous supercapacitors.

Rechargeable zinc-ion (Zn2+) batteries are emerging as a promising alternative for lithium-ion batteries. However, the reported cathodes normally suffer from sluggish Zn2+ diffusion kinetics, leading to poor rate performance and inadequate cycle life. Introducing additives is a frequently adopted solution. In this work, poly(3,4- ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) is introduced as the additive into V2O5 center dot 3H(2)O (P-VO) during its one-step hydrothermal growth. Structural characterization indicates that the introduction of PEDOT:PSS not only expands the interlayer spacing of V2O5, thus facilitating Zn2+ diffusion in V2O5, but also increases the ratio of V4+ to V5+, leading to more O vacancies and improved electrochemical activity accordingly. As a result, the aqueous Zn2+ battery with a P-VO electrode exhibits a high capacity (424.3 mAh g(-1) at 0.2 A g(-1)) and long-term cycle stability of up to 2000 cycles with a capacity retention of 89.4% at 5.0 A g(-1).

In this paper, we report a high-performance self-supported supercapacitor electrode composed of a cracked bark-shaped Ni-Co-Mn ternary metallic sulfide (NiCoMnS4) nanostructure on carbon cloth prepared by a simple one-step hydrothermal process and subsequent electrochemical treatment. The electrode delivers a high specific discharge capacity of up to 2470.4 F g−1 at 1 A g−1 and high rate performances of 1635.6 F g−1 at 10 A g−1 and 910.2 F g−1 even at 32 A g−1. Cycling tests indicate that NiCoMnS4 could maintain >91.1% of its initial capacity and nearly 100% Coulombic efficiency over 10,000 cycles at 8 A g−1. An aqueous asymmetric supercapacitor assembled with NiCoMnS4 as the cathode, activated carbon as the anode, and 1 mol L−1 KOH as the electrolyte delivers an energy density of 68.2 W h kg−1 at 850.1 W kg−1 and capacity retention of 92.5% after 10,000 cycles at 4 A g−1. Given the excellent performance and simple material preparation of our proposed device, this study provides a valuable foundation for the development of self-supported metallic sulfide based electrodes with high electrochemical properties for potential application in aqueous asymmetric supercapacitors.

In this paper, we report a self-supported flexible electrode consisting of NiCoMnS4 nanosheets on NiCo2O4 nanowires, denoted as NiCo2O4@NiCoMnS4 (NCO@NCMS) prepared by the hydrothermal growth (NiCo2O4) and the following electrodeposition (NiCoMnS4) on a carbon cloth (CC) substrate. The electrode delivers a high specific capacity of 4836 mF cm(-2) at 1 mA cm(-2) and excellent rate performance, i.e., 3820 mF cm(-2) at 10 mA cm(-2) and 2820 mF cm(-2) even at 60 mA cm(-2). An aqueous asymmetric supercapacitor (AASC) assembled using NCO@NCMS on CC as the cathode, activated carbon on CC as the anode and 2 M KOH as the electrolyte delivers a high energy density of 0.399 mWh cm(-2) at 0.85 mW cm(-2) and excellent cycle stability with similar to 81.2% capacity retention after 20 0 0 0 cycles at a high current density of 20 mA cm(-2). In view of the excellent performance and facile preparation, this study is believed to provide a valuable exploration of developing high-performance electrodes and AASCs. (C) 2021 Elsevier Ltd. All rights reserved.

Herein, a high-performance supercapacitor cathode composed of carbon nanotubes (CNTs)@Ni3V2O8@NiCo2S4 nanosheets (CNTs@NVO@NCS) on Ni foam (NF) is reported, in which the composite nanoparticles of CNTs and Ni3V2O8 (CNTs@NVO) and the NiCo2S4 (NCS) nanosheets around CNTs@NVO are synthesized by hydrothermal growth and electrodeposition, respectively. A high specific capacitance of 8722.0 mF cm(-2) at 1 mA cm(-2) together with good rate performance, i.e., 7337.6 mF cm(-2) at 16 mA cm(-2) and 4560.0 mF cm(-2) even at 60 mA cm(-2) is delivered by the electrode. Cycling test indicates that similar to 81.8% of its initial capacitance and similar to 100% Coulombic efficiency over 10,000 cycles at 10 mA cm(-2) can be maintained. An aqueous asymmetric supercapacitor assembled using CNTs@NVO@NCS on NF as the cathode, the activated carbon on carbon cloth as the anode and the 2 M KOH aqueous electrolyte delivers good cycle performance with similar to 14.1% total capacitance decay after 10,000 cycles at 20 mA cm(-2) and an energy density as high as 0.414 mWh cm(-2) at 0.800 mW cm(-2). In view of facile preparation and excellent performance, this research provides a meaningful and valuable exploration for designing and fabricating high-performance cathodes and the related energy storage devices.