Binder-free Supercapacitor Electrode Research Articles

Facile preparation of flexible binder-free graphene electrodes for high-performance supercapacitors.

A facile two-step strategy to prepare flexible graphene electrodes has been developed for supercapacitors using thermal reduction of graphene oxide (GO) and thermally reduced graphene oxide (TRGO) composite films. The tunable porous structure of the GO/TRGO film provided channels to release the high pressure generated by CO2 gas. The graphene electrode obtained from reduced-GO/TRGO (1 : 1 in mass ratio) film showed great flexibility and high film density (0.52 g cm−3). Using the EMI-BF4 electrolyte with a working voltage of 3.7 V, the as-fabricated free-standing reduced-GO/TRGO (1 : 1) film achieved a great gravimetric capacitance of 180 F g−1 (delivering a gravimetric energy density of 85.6 W h kg−1), a volumetric capacitance of 94 F cm−3 (delivering a volumetric energy density of 44.7 W h L−1), and a 92% retention after 10 000 charge/discharge cycles. In addition, the solid state flexible supercapacitor with the free-standing reduced-GO/TRGO (1 : 1) film as the electrodes and the EMI-BF4/poly (vinylidene fluoride hexafluopropylene) (PVDF-HFP) gel as the electrolyte also demonstrated a high gravimetric capacitance of 146 F g−1 with excellent mechanical flexibility, bending stability, and electrochemical stability. The strategy developed in this study provides great potentials for the synthesis of flexible graphene electrodes for supercapacitors.

Carbon dots decorated zinc cobaltite nanowires-assembled hierarchical arrays supported on nickel foam as binder-free electrodes for high performance supercapacitors

Hierarchical and binder-free electrode materials with large electroactive sites and low contact resistance are benefit for electrochemical capacitors. Herein, this paper reports the binder-free and hierarchical ZnCo 2 O 4 arrays decorated with carbon dots (CDs/ZnCo 2 O 4 ) on nickel foam by hydrothermal route. The CDs/ZnCo 2 O 4 arrays exhibit the nanowires-assembled hierarchical grass-like structure. The outward directed nanowires yield high surface-to-volume ratio. The nanowires exhibit the average length of 1 μm and diameter of 50 nm. The specific capacitance of the CDs/ZnCo 2 O 4 can reach 1937 F/g higher than the 1192 F/g of bare ZnCo 2 O 4 at 1 A/g. And 78.5% capacitance retention rate is achieved while the current density increases from 0.5 to 8 A/g. 90% of the capacitance retention over 5000 charge-discharge cycles at 15 A/g indicates high cycling stability. These boosted electrochemical performances are attributed to the structural feature with exposed electroactive sites, high electrical conductivity assisted by CDs, and opened interspaces for electrolyte ion diffusion. Asymmetric two-electrode system assembled with CDs/ZnCo 2 O 4 and activated carbon delivers a high-energy density of 54.94 W h/kg at 425.3 W/kg and retains an energy density of 13.23 W h/kg at 6804 W/kg. This study provides a new approach to design high-performance electrode materials for supercapacitors. • Hierarchical ZnCo 2 O 4 arrays were decorated with carbon dots (CDs). • CDs/ZnCo 2 O 4 electrode exhibited 1937 F/g at 1 A/g higher than bare ZnCo 2 O 4 . • Assembled two-electrode system delivered 54.94 W h/kg at 425.3 W/kg.

Fabrication of three-dimensional WO3 nanotube bundles on carbon cloth as a binder-free electrode for high-performance supercapacitors

The WO3 nanotube bundles are fabricated on carbon cloth, exhibiting high specific capacitance, low charge transfer resistance, and excellent stability.

Facile stepwise hydrothermal synthesis of hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays: A promising binder-free positive electrode for high-performance asymmetric supercapacitors

In this study, we have fabricated a flexible supercapacitor with outstanding pseudocapacitive performance using hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays. The dandelion-like CoMoO4/CoMoO4 nanostructure electrode yields a high specific capacitance (1548 F g−1 at a current density of 1 A g−1) and superior cycling stability performance (94% capability retention after 5000 cycles at 8 A g−1) in the 3 mol L–1 KOH solution. Furthermore, a flexible asymmetric supercapacitor device was assembled based on nickel foam/CoMoO4/CoMoO4 dandelion-like as positive electrode and activated carbon (AC) as negative electrode. The CoMoO4/CoMoO4 nanostructure//AC asymmetric supercapacitor device represents remarkable electrochemical performance such as good specific capacitance of 152 F g−1 and maximum energy and power densities of 54.04 Wh kg−1 and 8.83 kW kg−1, respectively. These encouraging results depict great potential in developing energy storage devices by making heterostructure nanomaterials.

Urchin-like hierarchical ruthenium cobalt oxide nanosheets on Ti3C2Tx MXene as a binder-free bifunctional electrode for overall water splitting and supercapacitors.

Synthesizing efficient electrode materials for water splitting and supercapacitors is essential for developing clean electrochemical energy conversion/storage devices. In the present work, we report the construction of a ruthenium cobalt oxide (RuCo2O4)/Ti3C2Tx MXene hybrid by electrophoretic deposition of Ti3C2Tx MXene on nickel foam (NF) followed by RuCo2O4 nanostructure growth through an electrodeposition process. Owing to the strong interactions between RuCo2O4 and Ti3C2Tx sheets, which are verified by density functional theory (DFT)-based simulations, RuCo2O4/Ti3C2Tx MXene@NF can serve as a bifunctional electrode for both water splitting and supercapacitor applications. This electrode exhibits outstanding electrocatalytic activity with low overpotentials of 170 and 68 mV at 100 A m-2 toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The RuCo2O4/Ti3C2Tx MXene@NF-based alkaline water-splitting cell only requires 1.62 V to achieve a current density of 100 A m-2, which is much better than that of RuO2@NF and Pt/C@NF-assembled cells (1.75 V@100 A m-2). The symmetric supercapacitor (SSC)-assembled electrode displays a high specific capacitance of 229 F g-1 at 3 A g-1. The experimental results, complemented with theoretical insights, provide an effective strategy to prepare multifunctional materials for electrocatalysis and energy storage applications.

Cobalt-Based Metal-Organic Framework Electrodeposited on Nickel Foam as a Binder-Free Electrode for High-Performance Supercapacitors

Cobalt-Based Metal-Organic Framework Electrodeposited on Nickel Foam as a Binder-Free Electrode for High-Performance Supercapacitors

A cobalt-based metal–organic framework electrodeposited on nickel foam as a binder-free electrode for high-performance supercapacitors

Co-MOF/NF has been prepared by cathodic electrodeposition using highly active cobalt as a surface modifier, and shows improved capacitance performances.

Fabrication of Nico Layered Double Hydroxide on Carbon Fiber Paper as High Performance Binder-Free Electrode for Supercapacitors

Fabrication of Nico Layered Double Hydroxide on Carbon Fiber Paper as High Performance Binder-Free Electrode for Supercapacitors

Manganese-doped tungsten disulfide microcones as binder-free electrode for high performance asymmetric supercapacitor

Manganese-doped tungstate sulfide (Mn-WS2) microcones were developed with varying levels of Mn, grown directly on electrically conductive Ni foam, and used as binder-free electrode material for supercapacitors. The experimental research indicates that Mn-WS2 microcones has significantly improved electrochemical activity and cyclic stability compared with pure WS2 due to additional ion diffusion channels. A strong synergy between the transitional metal ions in Mn-WS2 remarkably improved the redox activity, rate capability, and cycling stability. The Mn-WS2 microcones had a high specific capacitance of 107.79 mA h g−1 at 1 A g−1, a high rate capability of 75.18% at 20 A g−1, and 96.1% capacitance retention after 10,000 charge–discharge cycles. The effect of Mn ions on the electrochemical performance of WS2 microcones was also studied in detail. The enhanced electrochemical performance of the electrode can be attributed to the unique structural features of WS2 microcones arrays grown in Ni foam, which allow the surface of WS2 to be highly accessible to electrolyte ions. Furthermore, an all solid state asymmetric supercapacitor (ASCs) assembled with Mn-WS2 microcones as anode and GO/Fe3O4 cathode (Mn-WS2//PVA-KOH// GO/Fe3O4) delivered high specific energy of 70.65 W h kg−1 at 997.41 W kg−1. These results confirm that Mn-WS2 with outstanding electrochemical properties could be a promising electrode material for practical application in electrochemical energy storage field.

Network-like FeNb2O6 nanostructures on flexible carbon cloth as a binder-free electrode for aqueous supercapacitors

Because of their multiple chemical valence states, multi-element transition metal oxides can undergo reversible redox reactions between the different valence states during charging and discharging. However, the low electrical conductivity of transition metal oxides limits the rate of electron transfer. The combination of transition metal oxides with three-dimensional carbon substrate is a promising but extremely challenging strategy to prepare high specific capacitance, stable and environmentally friendly supercapacitor electrode materials. Here we report a facile one-step vapor deposition synthesis of network-like FeNb2O6 nanostructures directly growing on flexible carbon cloth (CC). The as-prepared FeNb2O6/CC composite has good electrical conductivity, and the network-like structure also makes it have large specific surface area. Resultantly, the composite exhibits an high specific capacity of 365.9 mAh g−1 at a current density of 2.5 A g−1. And at the current density of 25 A g−1, a specific capacity of 75.9 mAh g−1 can still be maintained.

Embellishing hierarchical 3D core-shell nanosheet arrays of ZnFe2O4@NiMoO4 onto rGO-Ni foam as a binder-free electrode for asymmetric supercapacitors with excellent electrochemical performance

Tailoring hierarchical hybrid core-shell electrodes with impartial microstructural features and excellent electroactive constituents is crucial for the design of high-performance supercapacitors (SCs). Herein, for the first time, we fabricate uniformly aligned porous ZnFe2O4 (ZFO) nanosheet arrays onto reduced graphene oxide-garnished conductive Ni foam (rGO-NF) substrates and subsequently embellish the first layer of ZFO nanosheets with morphology-controlled secondary NiMoO4 nanosheets to achieve a hierarchical 3D core-shell structure of ZnFe2O4@NiMoO4 nanosheet arrays (NSAs) onto rGO-NF for SC applications. Improving the synergistic effect of the core-shell nanoarchitecture with a conductive rGO-NF substrate, the hierarchical 3D ZFO@NMO NSAs tend to have superb electronic conductivity, tailoribility, effective nanoporous channels, and appropriate roadways for rapid ion/electron transfer, which are required for rapid reversible redox reactions, thus reflecting the excellent electrochemical features, including the excellent specific capacitance, good rate performance, and prolonged cyclic performance of the three electrode assemblies for SCs. An asymmetric supercapacitor (ASC) device composed of ZFO@NMO NSAs@rGO-NF as the cathode and MOF-derived hollow porous carbon (MDHPC) as the anode exhibits a high energy density of 58.6 Wh kg-1 at a power density of 799 W kg-1 with prolonged cyclic durability (89.6 % after 7000 cycles), thus indicating its potential applicability towards advanced hybrid SCs.

Highly hydrophilic electrodeposited NiS/Ni3S2 interlaced nanosheets with surface-enriched Ni3+ sites as binder-free flexible cathodes for high-rate hybrid supercapacitors

In this study, nanostructured nickel sulfides (NiS, Ni3S2 and NiS/Ni3S2) were fabricated directly on the surface of flexible carbon fiber cloths by simply modifying the deposition parameters of pulse-reversal (PR) electrodeposition method and utilized as binder-free flexible electrodes for aqueous hybrid supercapacitors (SCs). X-ray photoelectron spectroscopy and contact angle measurement studies verifies that the surface of heterostructure NiS/Ni3S2 electrode has enriched Ni3+ sites and highly hydrophilic nature. Consequently, the heterostructure NiS/Ni3S2 electrode demonstrated superior rate capability than that of both single phase NiS and Ni3S2 electrodes. Additionally, the hybrid SC device based on the flexible NiS/Ni3S2 electrode delivered a capacity of 40.4 mAh g−1 at a current density of 2 A g−1 and representing a maximum energy density of 32.3 Wh kg−1 at an impressive power density of 1.6 kW kg−1. Furthermore, the device provided excellent electrochemical stability with a capacity retention of 86.2%, even after a 120-h floating test. Hence, the heterostructure NiS/Ni3S2 with interlaced nanosheets morphology should be considered as promising binder-free flexible electrode materials for next-generation energy storage applications.

One-step hydrothermal growth of reduced graphene oxide/nickel hexacyanoferrate nanocomposite on Ni foam for binder-free supercapacitor electrode

The in-situ growth of nickel hexacyanoferrate/reduced graphene oxide nanocomposite (Ni-HCF/rGO) on Ni foam was successfully achieved with a facile one-step hydrothermal method. Ni foam was not only used as the current collector but also the nickel source. By simply heating Ni foam in the aqueous solution containing graphene oxide (GO), potassium ferricyanide and P-toluenesulfonic acid (TSA), Ni-HCF/rGO nanocube arrays were synthesized on Ni foam. X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron miscroscopy (SEM) and Raman spectroscopy were used to characterize the Ni-HCF/rGO. As the supercapacitor electrode, Ni-HCF/rGO/Ni foam exhibits high capacity, long cycling life and good rate capability in 2.0 M KOH aqueous solution. An asymmetrical supercapacitor device (ASC) was assembled with Ni-HCF/rGO/Ni foam and activated carbon (AC) as the positive and negative electrodes, respectively. The fabricated ASC presents a maximum energy density of 4.38 W h m−2 at power density of 34 W m−2, suggesting its potential in practical applications.

ZnO Nano-Flowers Assembled on Carbon Fiber Textile for High-Performance Supercapacitor’s Electrode

Herein, a crystalline nano-flowers structured zinc oxide (ZnO) was directly grown on carbon fiber textile (CFT) substrate via a simple hydrothermal process and fabricated with a binder-free electrode (denoted as ZnO@CFT) for supercapacitor (SC) utilization. The ZnO@CFT electrode revealed a 201 F·g−1 specific capacitance at 1 A·g−1 with admirable stability of >90% maintained after 3000 cycles at 10 A·g−1. These impressive findings are responsible for the exceedingly open channels for well-organized and efficient diffusion of effective electrolytic conduction via ZnO and CFT. Consequently, accurate and consistent structural and morphological manufacturing engineering is well regarded when increasing electrode materials’ effective surface area and intrinsic electrical conduction capability. The crystalline structure of ZnO nano-flowers could pave the way for low-cost supercapacitors.

In-situ evolution of the NiO nanosheets on 3D-Ni-foam as a self-supported electrode for energy storage device applications

This report shows the inexpensive synthesis of in-situ evolution of NiO nanosheets on 3D-Ni-foam as an outstanding binder-free and self-supported electrode for supercapacitors. The NiO//NiO supercapacitor shows a high specific capacitance (159.3F g−1) at 6.7 A g−1, energy density (22.1 W h kg−1), and excellent power density (15250 W kg−1). It unfolds superb stability (93.9%) after 10,000 GCD cycles and (95.4%) after 14 h voltage holding tests (VHTs). Also, it shows a low leakage current of 0.09 mA during 2 h VHTs.

A new hierarchically porous Cu-MOF composited with rGO as an efficient hybrid supercapacitor electrode material

Exploring new materials for efficient energy storage is imperative to derive uninterrupted energy supply from non-conventional sustainable sources. The present paper reports on the synthesis of a new Cu-MOF (HMRL-1), involving the reaction of a tetracarboxylic linker and Cu2+ salt under solvothermal conditions. Using a simple ultrasonication approach, the as-synthesized MOF has been further used to fabricate a composite with reduced graphene oxide (rGO) (R). The resulting composite (HMRL-1/R) has been explored as a binder-free supercapacitor electrode material for deriving enhanced charge storage capacity. The supercapacitor performance of the composite material has been investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The electrochemical investigations reveal that HMRL-1/R composite exhibits hybrid capacitive features with a specific capacitance (CS) of 366.6 Fg−1 at 1 Ag−1 and excellent cyclic stability and performance retention, which is much higher than that of pristine HMRL-1 and R due to their synergistic effect. All the findings suggest that as-prepared material is a promising candidate for an electrode material in supercapacitor applications.

Co-electrophoretic deposition of Mn2O3/activated carbon on CuO nanowire array growth on copper foam as a binder-free electrode for high-performance supercapacitors

Co-electrophoretic deposition of Mn2O3/activated carbon on CuO nanowire array growth on copper foam as a binder-free electrode for high-performance supercapacitors

Flexible and porous Co3O4-carbon nanofibers as binder-free electrodes for supercapacitors

Flexible and porous Co3O4-carbon nanofibers as binder-free electrodes for supercapacitors

MnMoO4 nanorods-encapsulated carbon nanofibers hybrid mat as binder-free electrode for flexible asymmetric supercapacitors

In this work, the in-situ formation of MnMoO4 nanoparticles and simultaneous encapsulation within the porous carbon nanofiber (CNF) matrix through electrospinning-carbonization-thermal annealing processes were carried out. The results of various spectroscopic and morphological analyses confirmed the successful formation of rectangular-shaped MnMoO4 nanorods within the CNF matrix. The MnMoO4@CNF hybrid yielded a maximum specific capacitance of 389.7 F/g at 0.1 A/g, which is 3-folds more than that of CNF (123.4 F/g). The MnMoO4@CNF symmetric cell with an aqueous KOH electrolyte possessed a maximum energy density of 54.12 Wh/kg at a power density of 10 W/kg. The excellent capacitive performances of as-prepared MnMoO4@CNF nanofibers could be ascribed to their high specific surface area (229.35 m2/g) with wide mesoporous distribution (3–13 nm) and enhanced reactivity of the nano-sized MnMoO4 nanoparticles. The hybrid electrode demonstrated excellent cyclic stability with capacitance retention of 92.1% after 5000 cycles, suggesting restricted extrication of metal oxide from the CNF matrix during the charge-discharge process. A flexible solid-state asymmetric supercapacitor was assembled by using MnMoO4@CNF hybrid mat as a positive electrode and activated carbon cloth as a negative electrode. The polymer gel electrolyte (PVA + KOH) was used as electrolyte-cum-separator. The as-prepared MnMoO4@CNF//AC cell yielded a highest energy density of 37.46 Wh/kg and an equivalent power density of 278 W/kg. The present investigation could open new horizons in developing next-generation flexible solid-state supercapacitors for wearable electronics.

Capillary enhanced hydrophilic block carbon material for binder-free supercapacitor electrode

Excellent wettability of electrode materials is an important prerequisite for high-efficiency energy storage devices. Inspired by the capillarity, we design a new type of block carbon material with vertical channel array that can generate capillary tension and then enhance the hydrophilicity in aqueous liquid. When applied to supercapacitors, this electrode not only exhibits an excellent affinity ( e.g., 0°) for aqueous electrolyte, but also can be directly utilized as an electrode without any additions. Electrochemical measurements demonstrate that this novel hydrophilic and binder-free electrode enjoys satisfactory performances including high capacitance ( e.g., 2452 mF cm −2 at 5 mA cm −2 ), long cycling life in coin-type device ( e.g., 100% after 10 000 cycles). Furthermore, the pure carbon-assembled quasi-solid-state supercapacitor could deliver an appealing energy density up to 5.49 mWh cm −2 at a power density of 50.0 mW cm −2 . This work presents the strategy of hydrophilic conversion of materials through rational structural construction for the first time, and demonstrates an ultra-facile supercapacitor electrode which is full of practical application value. • Block carbon material with vertical channels was designed. • Capillary effect caused by channels optimized the transport of electrolyte. • The electrode exhibited better electrochemical performance in supercapacitors.