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Biomass carbon-based MnO electrode materials were synthesized using ramie as the biomass precursor of carbon and potassium permanganate as the precursor of MnO. The ramie-activated carbon/manganese monoxide (RAC/MnO) composite electrodes exhibited a specific capacitance of 720 F/g at a current density of 0.5 A/g. A symmetric cell assembled using the composite electrodes showed a specific capacitance of 45 F/g at 0.5 A/g and an energy density of 12.25 Wh/kg at a power density of 350 W/kg. The excellent electrochemical performance was analyzed by characterizing the electrodes' chemical composition, microstructure, crystal orientation, specific surface area, and pore distribution. Because of the large overpotential of MnO, the composite electrode's working voltage reached 1.4 V, which is 40% higher than 1.0 V of traditional carbon electrodes. As such, supercapacitors can have higher energy density and power density with the RAC/MnO composite electrodes. The experimental equipment for synthesizing the electrodes is very simple and is promising for large-scale commercialization. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we report a nanostructured CMK-3/NiCo 2 S 4 electrode material for supercapacitors. Owing to the introduction of CMK-3, the CMK-3/NiCo 2 S 4 electrode exhibits a novel nanostructure of nanorods, and has a great improvement in conductivity. The CMK-3/NiCo 2 S 4 electrode demonstrates a high specific capacitance (1843.1 F g−1 at 1 A g−1, 3.89 F cm−2 at 2 mA cm−2) and excellent cycling stability (94.2% over 2000 cycles at 10 A g−1). Moreover, an asymmetric supercapacitor (ASC) device is assembled with CMK-3/NiCo 2 S 4 and activated carbon (AC) as positive and negative electrode, respectively, to characterize the electrodes' electrochemical performance. The ASC device achieves a high energy density (34.9 Wh/kg at 357 W/kg) and a high power density (7300 W/kg at 15.3 Wh/kg), suggesting that the composite is a superior electrode material for high-performance supercapacitors. Graphical abstract Image 1 Highlights • CMK-3/NiCo 2 S 4 nanostructured films have been successfully grown by facile methods. • Ultrahigh specific capacitance with superior rate performance has been achieved. • An asymmetric supercapacitor with high energy density was successfully assembled. [ABSTRACT FROM AUTHOR]

Activated biomass carbons (ABC) produced from bamboo by carbonization and activation have high specific surface areas and mesoporous structures. The specific surface area, total pore volume, and average pore size of the activated biomass carbon are controlled by adjusting the activation temperature from 700 to 1000 °C. The carbon materials activated at 900 °C have an optimal mesoporous structure with a high specific surface area (2221.1 m 2  g −1 ), the highest capacitance (293 F g −1 at 0.5 A g −1 in 3 M KOH aqueous electrolyte) and excellent rate capability (193.8 F g −1 at 20 A g −1 ). Symmetric supercapacitors made of the optimal electrodes exhibit a high energy density of 10.9 Wh kg −1 (18.2 Wh L −1 ) at a power density of 63 W kg −1 (105 W L −1 ) and outstanding capacitance retention of 91.8% over 10,000 cycles. The high electrochemical performance of the mesoporous ABCs show that they are highly promising for energy-storage applications with further optimization. [ABSTRACT FROM AUTHOR]

NiCoS-based nanostructured films have been grown directly onto nickel foams by a facile two-step method, involving the growth of NiCo-precursor and subsequent conversion into NiCoS via a sulfidation process, with the aid of sodium dodecyl surfactant (SDS). This synthesis method enables the fabrication of binder- and conductive additive-free electrodes for supercapacitors. The influence of the surfactant on the crystal structure, morphology, and electrochemical performance of the electrodes has been investigated. The NiCoS-SDS films exhibit a complex cellular and hierarchical porous structure, which are different from NiCoS-pure films with nanotube arrays structure. Moreover, the electrochemical tests show that the NiCoS-SDS nanostructured electrode exhibits an ultrahigh specific capacitance of 2519 F g at 0.5 A g, which doubles that of the NiCoS-pure nanotube arrays electrode. In addition, the NiCoS-SDS electrode exhibits excellent cycling stability with 90.7 % capacitance retention at 10 A g after 8000 cycles. In view of the low cost and superior electrochemical performance, the NiCoS-SDS electrodes are promising electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]