a capacitor-type electrode as the power source is the trend to enhance the energy density of SCs by extending the operating voltage on the premise of advantages retention. [3,4] In addition, exporation of battery-type electrode materials with novel architectures owning large surface area, high conductivity, appropriate porosity, and excellent mechanical stability can improve the specific capacity and thus leads to a noticeable increase in energy density. [5] Transition metal oxides/hydroxides as battery-type electrode materials for HSCs are extensively developed because of their hypotoxicity, cost effectiveness, and high theoretical capacity. [6][7][8][9] Nevertheless, their inferior electron conductivity and structure stability lead to compromised rate capability and cycling stability. [10] Recently, transition metal sulfides (TMS), especially ternary TMS such as NiCo 2 S 4 , are considered as notable battery-type electrode candidates for HSCs due to their enhanced electrical conductivity, more flexible structure, and richer redox sites than that of the corresponding oxide counterparts and monometal sulfides. [11][12][13][14][15] Various morphologies of NiCo 2 S 4 nanostructures such as nanotubes, [16] nanoplates, [17] nanourchins, [18] nanoflowers, [19] and nanoonions [20] have been successfully constructed, and their electrochemical properties were investigated. However, it is noteworthy that coatings of NiCo 2 S 4 and active carbon (AC) using polymer binders and conductive additives usually have unsatisfactory electrochemical performance owing to increased contact resistance. [21] Direct growth of NiCo 2 S 4 with numerous shapes like 1D nanofibers, [22] nanotubes, [22,23] and hollow nanoneedles, [22] 2D nanosheets, [24] and 3D nanocaterpillars [25] on 3D conductive backbones as binder-free electrode is an appropriate choice to maximize electrode material loading and supply approachability to electrolyte ions, resulting in enhanced electrochemical reaction kinetics. 1D nanostructure arrays, especially hollow tube-like structures, possess many superiorities over solid rod-like structures because they can provide more efficient routes for the transfer of electrons and ions. [22,23] 2D nanostructure arrays with large specific surface area can narrow the ion transport distance and expand the contact area with electrolyte. [24,26] Unfortunately, free-standing 1D/2D nanostructure arrays often suffer from mechanical instability during A significant development in the design of a NiCo 2 S 4 3D hierarchical hollow nanoarrow arrays (HNA)-based supercapacitor binder free electrode assembled by 1D hollow nanoneedles and 2D nanosheets on a Ni foam collector through controlling ionic liquid 1-octyl-3-methylimidazolium chloride ([OMIm]Cl) concentration is reported. The unique NiCo 2 S 4 -HNA electrode acquires high specific capacity (1297 C g −1 at 1 A g −1 , 2.59 C cm −2 at 2 mA cm −2 ), excellent rate capability (maintaining 73.0% at 20 A g −1 ), and long operational life (maintaining 92.4% after 10 000 cycles at 5 A g −1 ...

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We have developed a simple solvothermal–calcination strategy to synthesize continuous graphitic carbon coated hollow CuO (H–CuO@GC) spheres with excellent electrochemical performance. The H–CuO@GC spheres exhibit a high specific surface area (106.6 m2 g–1), penetrated mesochannels (∼5–15 nm), a large pore volume (0.313 cm3 g–1), a robust hollow structure, and an integral graphitic carbon layer. The H–CuO@GC sphere electrode presents high capacitance, good rate capability, and outstanding cycling ability in supercapacitors. In addition, the asymmetric supercapacitor (ASC) assembled by this structure exhibits a good rate capability (retain 75.7% at 10 A g–1) and an excellent cycling stability (90.2% capacitance retention after 10000 cycles), as well as a high energy density (38.6 W h kg–1 at a power density of 1.018 kW kg–1). This work represents a novel design strategy for the improvement of low-conductive nanomaterials applied in many fields, especially in energy applications.

Mesoporous carbon nano grape skins have been fabricated via a facile hydrothermal method. The resulting carbon nano grape skins showed excellent performance when used as supercapacitor electrode.