A novel type of flexible fiber/wearable supercapacitor that is composed of two fiber electrodes - a helical spacer wire and an electrolyte - is demonstrated. In the carbon-based fiber supercapacitor (FSC), which has high capacitance performance, commercial pen ink is directly utilized as the electrochemical material. FSCs have potential benefits in the pursuit of low-cost, large-scale, and efficient flexible/wearable energy storage systems.

Nanohoneycomb-like strongly coupled CoMoO4 -3D graphene hybird electrodes are synthesized for supercapacitors which exhibit excellent specific capacitance and superior long-term cycle stability. The supercapacitor device can power a 5 mm-diameter LED efficiently for more than 3 min with a charging time of only 2 s, and shows high energy densities and good cycle stability.

Potassium‐ion batteries (PIBs) have attracted considerable attention due to the low redox potential, low price, and abundance, in comparison to lithium and sodium. Herein, a novel potassium MoSe2/N‐C battery with a new electrolyte, 1 m potassium bis(fluoro‐slufonyl)imide in ethyl methyl carbonate, is reported. The MoSe2/N‐C composite, which consists of carbon‐coated MoSe2 nanosheets, is synthesized through solvothermal and annealing method. As an anode material for PIBs, it exhibits an outstanding rate performance and long cycling stability. Meanwhile, a reversible capacity of 258.02 mA h g−1 is achieved after 300 cycles at 100 mA g−1, obtaining a Coulombic efficiency close to 100%. Even at a high current density, it can maintain 218 and 197 mA h g−1 at 500 and 1000 mA g−1, respectively. The charge/discharge mechanism of MoSe2/N‐C as the anode material for PIBs is investigated. These results reveal that the insertion and the extraction of K+ will lead to a phase transition of MoSe2. During the charge process, a part of the MoSe2 will transform to Mo15Se19 and the major final discharge product is K5Se3.

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