Binder-free Electrode For High-performance Supercapacitors Research Articles

Three-dimensional nanostructured NiO–Co3(VO4)2 compound on nickel foam as pseudocapacitive electrodes for electrochemical capacitors

An advanced binder-free electrode for high-performance supercapacitors has been designed by growing 3D nanostructured NiO–Co3(VO4)2 compound on nickel foam. Such unique nanocomposite combined separately the advantages of the perfect cycling stability and rate capability of Co3(VO4)2 and the high specific capacitances of NiO. Furthermore, the nanostructure of NiO–Co3(VO4)2 could provide higher specific surface area and more active sites. As a result, this electrode exhibited remarkable specific capacitances of 1166Fg−1 at a current density 0.5Ag−1, perfect cycle stability of cycle efficiency 99.4% after 5000 cycles and excellent electrochemical performance than the single oxide electrodes. To enhance energy density, the asymmetric supercapacitor was assembled where NiO–Co3(VO4)2 and activated carbon acted as the positive and negative electrodes, respectively. The maximum specific capacitance of 109Fg−1 and the specific energy of 38.8Whkg−1 are demonstrated for a cell voltage between 0 and 1.6V, exhibiting a high energy density and stable power characteristics. And this work also demonstrates the feasibility of rational design of advanced integrated compound electrode for high-performance supercapacitors.

Facile synthesis of ultrathin manganese dioxide nanosheets arrays on nickel foam as advanced binder-free supercapacitor electrodes

Ultrathin MnO2 nanosheets arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the binder-free electrode for high-performance supercapacitors. This unique well-designed binder-free electrode exhibits a high specific capacitance (595.2 F g−1 at a current density of 0.5 A g−1), good rate capability (64.1% retention), and excellent cycling stability (89% capacitance retention after 3000 cycles). Moreover, an asymmetric supercapacitor is constructed using the as-prepared MnO2 nanosheets arrays as the positive electrode and activated microwave exfoliated graphite oxide (MEGO) as the negative electrode. The optimized asymmetric supercapacitor displays excellent electrochemical performance with an energy density of 25.8 Wh kg−1 and a maximum power density of 223.2 kW kg−1. These impressive performances suggest that the MnO2 nanosheet array is a promising electrode material for supercapacitors.

Facile synthesis of ultrathin nickel hydroxides nanoflakes on nickel foam for high-performance supercapacitors

Ultrathin Ni(OH)2 nanoflakes grown on nickel foam have been prepared via a facile hydrothermal route without adding any additional nickel sources and further investigated as a binder-free electrode for high-performance supercapacitors. Benefiting from high conductivity and enough spaces between the nanoflakes in combination with high surface area, the Ni(OH)2 nanoflakes show high-capacitance performance with a specific capacitance of 2342Fg−1 at a charge and discharge current density of 2mAcm−2 and 1100Fg−1 at 8mAcm−2 with a good cycling ability (80.4% of the initial specific capacitance remains after 2000 cycles). These results show that Ni(OH)2 nanoflakes with this cost-effective synthesis route and distinguished electrochemical performance combined with the flexible nickel foam substrate are very promising for the next generation of high-performance supercapacitors.

Mass production of multi-channeled porous carbon nanofibers and their application as binder-free electrodes for high-performance supercapacitors.

A unique class of multi-channeled porous carbon nanofibers (MCPCNFs) are designed with dual-pathway ion transport capability via a modified electrospinning approach. Combined with other features including high conductivity and numerous functional groups for facilitating the formation of electric double-layer charges, the MCPCNFs exhibit excellent supercapacitive performance, holding great potential for high-performance supercapacitor electrode materials.

Facile synthesis of single-crystalline NiO nanosheet arrays on Ni foam for high-performance supercapacitors

Single-crystalline NiO nanosheet arrays on Ni foam as a binder-free electrode for high-performance supercapacitors, fabricated by a facile and cost-effective hydrothermal approach, exhibit a high specific capacitance, good rate capability, and excellent cycling stability.

Facile fabrication and perfect cycle stability of 3D NiO@CoMoO4 nanocomposite on Ni foam for supercapacitors

An advanced binder-free electrode for high-performance supercapacitors has been designed by growing a three-dimensional (3D) NiO@CoMoO4 nanocomposite on Ni foam. Such a unique nanocomposite combined separately the advantages of the perfect cycling stability and rate capability of CoMoO4 and the high specific capacitance of NiO. Furthermore, the nanostructure of NiO@CoMoO4 could serve as an “ion reservoir” to store ions of the electrolyte, and give it a higher specific surface area and more active sites. As a result, this electrode exhibited remarkable specific capacitances (848 F g−1 at a current density of 0.5 A g−1), perfect cycle stability (100% of cycle efficiency after 3000 cycles) and excellent electrochemical performance compared to single oxide electrodes. And this work also demonstrates the feasibility of rational design of advanced integrated nanocomposite electrodes for high-performance supercapacitors.

Free-standing and mechanically flexible mats consisting of electrospun carbon nanofibers made from a natural product of alkali lignin as binder-free electrodes for high-performance supercapacitors

Mechanically flexible mats consisting of electrospun carbon nanofibers (ECNFs) were prepared by first electrospinning aqueous mixtures containing a natural product of alkali lignin together with polyvinyl alcohol (PVA) into composite nanofiber mats followed by stabilization in air and carbonization in an inert environment. Morphological and structural properties, as well as specific surface area, total pore volume, average pore size, and pore size distribution, of the lignin-based ECNF mats were characterized; and their electrochemical performances (i.e., capacitive behaviors) were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The lignin-based ECNF mats exhibited outstanding performance as free-standing and/or binder-free electrodes of supercapacitors. For example, the ECNFs made from the composite nanofibers with mass ratio of lignin/PVA being 70/30 (i.e., ECNFs (70/30)) had the average diameter of ∼100 nm and the Brunauer–Emmett–Teller (BET) specific surface area of ∼583 m2 g−1. The gravimetric capacitance of ECNFs (70/30) electrode in 6 M KOH aqueous electrolyte exhibited 64 F g−1 at current density of 400 mA g−1 and 50 F g−1 at 2000 mA g−1. The ECNFs (70/30) electrode also exhibited excellent cycling durability/stability, and the gravimetric capacitance merely reduced by ∼10% after 6000 cycles of charge/discharge.

Single-crystalline NiCo2O4 nanoneedle arrays grown on conductive substrates as binder-free electrodes for high-performance supercapacitors

In this work, we have successfully grown single-crystalline nanoneedle arrays of NiCo2O4 on conductive substrates such as Ni foam and Ti foil through a simple solution method together with a post-annealing treatment. Remarkably, the NiCo2O4–Ni foam binder-free electrode exhibits greatly improved electrochemical performance with very high capacitance and excellent cycling stability.