Binder-free Supercapacitor Electrode Research Articles

Copper nanoparticles incorporated porous carbon nanofibers as a freestanding binder-free electrode for symmetric supercapacitor with enhanced electrochemical performance

A freestanding and binder free copper/porous carbon nanofibers (Cu/PCNFs) composite has been synthesized by a simple and cost effective electrospinning technique. The synthesized composite exhibits a unique morphology with high surface area of about 330.48 m2g−1 and high conductivity of 767.95 Sm−1. In a three electrodes system, the resultant Cu/PCNFs electrodes show a specific capacitance of 333.5 Fg−1 at a current density of 1 Ag−1 in 1 M of H2SO4 aqueous electrolyte. The assembled quasi-solid state symmetric supercapacitor (q-SSSC) exhibits a high specific capacitance value of 177.01 Fg−1 at a current density of 1.5 Ag−1 in PVA/H2SO4 polymer gel electrolyte with 95.8% capacitance retention up to 10 000 cycles. This q-SSSC can effectively deliver a high energy density of 24.53 Wh kg−1 at a power density of 1500 W kg−1. Thus, the synthesized Cu/PCNFs composites could be useful as an effective electrode material for next-generation high performance flexible supercapacitors.

Electrochemical energy storage properties of solvothermally driven ZnFe2O4 microspheres

Herein, a facile solvothermal technique was employed to produce ZnFe2O4 microspheres. The physico-chemical properties of these microspheres were probed by various techniques such as XRD, SEM and TEM. Furthermore, these microspheres were utilized to design a cost-effective, binder-free supercapacitor electrode. The obtained noticeable specific capacitance (175 F g−1 at a current density of 5 A g−1) and rate performance with good cycling stability were assigned to the large surface area and unique porosity of ZnFe2O4 microspheres, which allows faster ion-diffusion across the electrode and buffer volume changes during rapid charging-discharging. Electrochemical impedance spectroscopy analysis further verifies the observed phenomena as noted in voltammetric and charge-discharge studies. The work opens up an avenue to consider crystalline, porous and high surface area enabled hetero-metallic oxides to be promising candidates for high-performing supercapacitors.

Porous polyaniline arrays oriented on functionalized carbon cloth as binder-free electrode for flexible supercapacitors

Flexible supercapacitor (FSC), thanks to light weight, efficient power delivery and high safety, holds great potential in potable/wearable electronics, whose development would be accelerated by ideal electrode materials. Herein, we report a flexible binder-free electrode composed of polyaniline (PANI) nanofiber-lapped arrays in-situ grown on the molecular-modified carbon cloth (fCC) by a facile one-spot protocol. After optimization, PANI/fCC-2 electrode affords a high specific capacitance of 517.3 F g−1 at 1 A g−1, benefited from highly pseudocapacitive PANI and open channels favorable for rapid ion/electron transfer. Using this novel electrode, flexible quasi-solid-state SC with PVA/H2SO4 gel electrolyte displays a high energy density of 9.03 Wh kg−1 at a power density of 82.9 W kg−1 and is retained at 6.11 Wh kg−1 at 2784.3 W kg−1, with excellent rate capability (97.4% capacitance retention from 0.5 to 20 A g−1) and good cycling stability (79.5% retention over 10,000 cycles). Besides, such four devices in series can light up a light-emitting diode (LED) indicator as a proof of concept in real applications. Our research would provide a promising avenue to develop flexible integrated electrode for next-generation high-performance devices.

Rapid synthesis of porous manganese cobalt sulfide grown on Ni foam by microwave method for high performance supercapacitors

Abstract In this paper, a simple, low-cost and fast microwave technology of growing vertically cross-linked manganese cobalt sulfide (MCS) on Ni foam (NF) is successfully developed for the first time. As a binder-free electrode for supercapacitors and delivers high capacitance of 2084 F g−1 at 1 A g−1, excellent rate performance (1200 F g−1 at 100 A g−1) and good cycling stability (80.6% capacitance retention after 5000 cycles). In addition, a asymmetric supercapacitor (ASC) is composed of MCS/NF as positive electrode and activated carbon (AC) as negative electrode. The asymmetric supercapacitor achieves a remarkable performance with a specific capacitance of 134.6 F g−1, an energy density of 48 Wh kg−1, and a power density of 11.8 kW kg−1, which is able to light up a light-emitting diode. This work not only provides a green and rapid synthesis method for preparing electrode materials, but also provides an innovative idea.

Hierarchically Porous Nanostructured Nickel Phosphide with Carbon Particles Embedded by Dielectric Barrier Discharge Plasma Deposition as a Binder-Free Electrode for Hybrid Supercapacitors

Three-dimensional (3D) metal phosphides are promising superior electrode components for supercapacitors. In this study, 3D porous nickel phosphide nanoarrays are successfully enrooted on the surface of nickel foam (Ni2P/NF) by low-temperature hydrothermal treatment. Subsequently, a nanocarbon was embedded over Ni2P@NF by efficient utilization of the environmental pollutant ethylene gas via a dielectric barrier discharge plasma reactor. This nanocarbon was deposited on porous Ni2P/NF nanoarrays (Ni2P-C/NF) as a positive electrode sandwiched with peanut shell-derived porous activated carbon (PNS-AC) as a negative electrode for the fabrication of a hybrid supercapacitor device. The hybrid supercapacitor device (Ni2P-C/NF//PNS-AC) delivers an enormous amount of areal and gravimetric capacities values at a 1 A g–1 current density of 318.8 μAh cm–2 and 106.2 mAh g–1, respectively. Moreover, the hybrid supercapacitor device achieved outstanding energy and power density with excellent cyclic durability (90.1%) even after 5000 cycles at 7 A g–1, which are 108.1 Wh kg–1 at 1 A g–1 and 14,370.4 W kg–1 at 15 A g–1, respectively. These results evidenced that the novel nanostructured Ni2P/NF with embedded carbon nanoparticles has excellent potential as the supercapacitor electrode material.

Ni,Zn-codoped MgCo2O4 electrodes for aqueous asymmetric supercapacitor and rechargeable Zn battery

Ni,Zn-codoped spinel MgCo2O4 is in-situ grown on Co foam through a simple one-pot hydrothermal process, which acts as binder-free electrodes for supercapacitor and aqueous rechargeable Zn battery. As-prepared Ni,Zn-codoped MgCo2O4 electrode exhibits enhanced capacitance (14.43 F cm−2 or 1500 F g−1) and cycling stability (no decay of its initial capacitance after 20000 cycles), and its asymmetric supercapacitor with AC as negative electrode delivers ultrahigh rate capability, good energy density and excellent cycling durability. In addition, aqueous rechargeable Zn battery consisting of this Ni,Zn-codoped MgCo2O4 cathode and Zn anode presents ultrahigh capacity (1.93 mA h cm−2) and excellent cycling durability (no decay of its initial capacitance after 30000 cycles). This work supplies a new strategy in designing and constructing high-performance and binder-free spinel type electrode for supercapacitor and aqueous rechargeable Zn battery.

Nanoporous structure synthesized by selective phase dissolution of AlCoCrFeNi high entropy alloy and its electrochemical properties as supercapacitor electrode

Fabrication of nanoporous metal core/oxide shell structure using equiatomic AlCoCrFeNi high entropy alloy (HEA) and its electrochemical property as supercapacitor electrode have been investigated in the present study. As-cast AlCoCrFeNi HEA consists of interconnected Al–Ni rich and Cr–Fe rich phases by spinodal phase separation. Nanoporous structure can be obtained by selectively dissolving the Al–Ni rich phase and retaining the remaining Cr–Fe rich phase by passivation in sulfuric acid solution at 313 K. In particular, the scale of nanoporous structure in the present study is predictable since it only depends on the scale of original spinodal-decomposed microstructure in as-cast state. When used as a binder free electrode for supercapacitor, Cr–Fe rich nanoporous structure exhibits high volumetric capacitance of 700 F cm−3 and excellent cycling stability of over 3000 cycle. As the microstructural scale in as-cast state becomes finer, the nanoporous structure exhibits better capacitance properties. The present result shows that Cr–Fe rich nanoporous metal core/oxide shell has a good potential for application as supercapacitor electrode.

3D carboxyl and hydroxyl co-enriched graphene hydrogels as binder-free electrodes for symmetric supercapacitors

At present, amino acids are often used as the source of heteroatom functional groups for the preparation of doped graphene materials. However, a large amount of amino acids will be used as reaction precursors in the preparation process, which will lead to increased cost, reduced efficiency and waste of resources. Herein, a very small amount of neutral l-alanine is employed to synthesize 3D carboxyl and hydroxyl co-enriched graphene hydrogels (CHGHs) by a one-pot hydrothermal method. The CHGHs contain copious carboxyl and hydroxyl groups, and a small amount of nitrogen-containing functional groups. In addition, the CHGHs also present large specific surface areas and 3D porous structures. Therefore, the CHGH-20 binder-free electrode displays a high specific capacitance of 262.8 F g−1 at 0.3 A g−1, and this value still maintains 84.3% (221.6 F g−1) at 10 A g−1 in a two-electrode system in 6 M KOH. Furthermore, the CHGH-20 electrode also displays outstanding cycle stability with 103.6% of its initial capacitance after 10,000 cycles at 10 Ag−1. Therefore, the CHGHs samples prepared by a very small amount of neutral l-alanine have great significance for the practical application of supercapacitors.

Hierarchical zinc cobalt sulfide flowers grown on nickel foam as binder-free electrodes for high-performance asymmetric supercapacitors

In this work, hierarchical zinc cobalt sulfide flowers on nickel foam (f-Zn0.76Co0.24S/Ni foam) are fabricated by a facile two-step hydrothermal method. The obtained f-Zn0.76Co0.24S/Ni foam are directly used as the binder-free electrodes for high-performance supercapacitors. The as-prepared f-Zn0.76Co0.24S/Ni foam exhibite a high specific capacitance of 1906 F g−1 at a current density of 1 A g−1 and good rate performance. The excellent electrochemical performance can be attributed to the unique interconnected flower structure, which provides a path for the rapid diffusion of electrolyte ions. Moreover, the f-Zn0.76Co0.24S/Ni foam//Fe2O3@rGO asymmetric supercapacitor is assembled. It can achieve a high energy density of 75.7 Wh kg−1 at a power density of 700.5 W kg−1 and display superior cycling stability with 86.7% retention after 8000 cycles.

Ni-Bi-S nanosheets/Ni foam as a binder-free high-performance electrode for asymmetric supercapacitors

Supercapacitors are attracting tremendous interests in electrochemical energy storage and binary metal sulfides are attracting increasing attention due to higher electrochemical activities over their monometal counterparts. In this report, we show a novel Ni-Bi-S nanosheets/Ni foam electrode with superior performance for supercapacitors. In the synthetic process, Ni foam is utilized as current collector as well as Ni source for the Ni-Bi-S. Bi source plays a crucial role to achieve desired morphology for the Ni-Bi-S and uniform nanosheets network can be obtained by controlling the amount of the Bi (NO3)2. The Ni-Bi-S nanosheets/Ni electrode demonstrates a high specific capacitance of 4.81 F/cm2 at 5 mA/cm2 and an outstanding cycling performance. After 3000 cycles, 97.6% of the initial capacitance can be retained at 20 mA/cm2 and the retention is still as high as 83.4% even after 6500 cycles. An asymmetric supercapacitor constructed with Ni-Bi-S cathode and commercial conductive cloth (CC) anode demonstrates with a high energy density of 2.96 mWh/cm3 and a good retention rate after 2000 cycles.

Hierarchical nanosheets-anchored-on-microsheets FeCo2S4 arrays as binder-free electrode for high-performance hybrid supercapacitor

The binary transition metal sulfides are highly desirable electrode materials for high-performance supercapacitors, thanks for their excellent electrochemical activity and electrical conductivity. Herein, the hierarchical FeCo2S4 arrays are designed and constructed on Ni foam, which consists of microsheets anchored nanosheets. The FeCo2S4 hierarchical structure provides high conductivity and abundant electroactive sites as well as facial and short ion transport paths. Therefore, the FeCo2S4 electrode achieves an excellent specific capacitance of 2488.50 F g−1 (7.66 F cm−2) at 5 mA cm−2, and a high level of cycle stability of 95.67% retention after 5000 cycles. The FeCo2S4//activated carbon (AC) device delivers the maximal energy density of 44.89 W h kg−1 and the maximal power density of 4015.56 W kg−1. The impressive electrochemical properties of hierarchical FeCo2S4 arrays make it a promising high-performance electrode for hybrid supercapacitors.

In situ Growth of Cu2O/CuO Nanosheets on Cu Coating Carbon Cloths as a Binder-Free Electrode for Asymmetric Supercapacitors.

Cu2O/CuO nanosheets in-situ grown on Cu-Carbon cloths (Cu-CCs), namely Cu2O/CuO@Cu-CCs, are constructed by a simple strategy with electroless copper plating, chemical etching, and thermal dehydration. The as-prepared material is directly used as binder-free electrodes for supercapacitors (SCs). CCs coated with Cu, as the current collector, can effectively promote the charge collection and electron transfer, while the hierarchical Cu2O/CuO nanosheets provide massive active sites for fast faradic reactions. The composite electrode exhibits high specific capacitance [1.71 F cm−2, equivalent to 835.2 F g−1, at the current density of 10 mA cm−2 (3.57 A g−1)]. The asymmetric supercapacitor device using Cu2O/CuO@Cu-CCs as the positive electrode and activated carbon as the negative electrode, achieves a superior energy density up to 60.26 Wh kg−1 at a power density of 299.73 W kg−1 and an excellent long-term cycling stability (9.65% loss of its initial capacitance after 5,000 cycles). The excellent electrochemical performance is mainly ascribed to the unique hierarchical structure of Cu2O/CuO@Cu-CCs, making it attractive as a potential electrode material for high performance SCs.

Ethanol interfacial assembly of Na0.44MnO2 nanorod/active carbon toward the fabrication of high-density hybrid films for binder-free supercapacitor electrode

There is an intense interest for utilization of self-assembly to fabricate high-density hybrid films for practical energy storage. In this paper, high-density (1.5 mg/cm2) hybrid Na0.44MnO2 nanorod (average diameter 70 nm and average aspect ratio 10)/active carbon films (with area of 9 cm2) were fabricated by direct toluene/water interfacial assembly, achieving the binder-free supercapacitor electrode with advanced electrochemical performance. The density of interfacial films can be precisely controlled by regulating the dosage of assembled nano-units. We showed that the hybrid films can be easily transferred onto a Ni foam and subsequently use as binder-free supercapacitor electrode. The electrochemical testing of film electrode exhibited a high specific capacitance of 189.6 F/g and good capacitance retention at high charge-discharge rates as well as cycling stability. It is suggested that this direct interfacial assembly approach paves the way for the fabrication of 2D functional nanomaterials, particularly useful in practical applications, such as advanced supercapacitor electrode.

Self-supported ultrathin NiCo-LDH nanosheet array/Ag nanowire binder-free composite electrode for high-performance supercapacitor

The supercapacitor (SC) based on nickel cobalt layered double hydroxide (NiCo-LDH) has aroused great interest in the field of energy storage. However, the agglomeration and low electrical conductivity are unfavorable for electrochemical performance. Herein, Ag nanowires (Ag NWs) was first dip-coated on nickel foam (NF) to form a conductive substrate, on which the NiCo-LDH nanosheet array in-situ grew to construct an efficient three-dimensional (3D) self-supported hierarchical structure NiCo-LDH/Ag NWs/NF electrode. The presence of Ag NWs inhibits aggregation of LDH nanosheets and accelerates the electron transfer. Electrochemical studies exhibit that NiCo-LDH/Ag/NF hybrid electrode possesses the higher specific capacitance of 2920.6 F g−1 at a current density of 5 A g−1 and excellent cycling stability (89.8% after 2000 cycles) compared with the electrode without Ag NWs. The asymmetric supercapacitor (ASC) with the NiCo-LDH/Ag/NF heterostructure as the positive electrode and active carbon (AC) as the negative electrode displays a high energy density of 42.9 Wh kg−1 at a power density of 800 W kg−1. When two aqueous ASCs were assembled in series and charged for only 1 min, the stored energy was capable of powering two green light-emitting-diodes (LEDs) for more than 3 min, indicating NiCo-LDH/Ag/NF electrode material shows great potential application in supercapacitor.

Ultrathin nanosheet-assembled hollow microplate CoMoO4 array derived from metal-organic framework for supercapacitor with ultrahigh areal capacitance

The rational control of metal-organic frameworks derived hollow nanomaterials with rapid mass transport and multiple active metal sites are desirable for emerging energy storage. Herein, CoMoO4 hollow microplate array on Ni foam is prepared via a facile self-sacrificing templated strategy from ion-exchange of cobalt-organic framework microplate array. Benefiting from hollow microplate structure constructed by ultrathin nanosheets, CoMoO4 as binder-free electrode for supercapacitor delivers ultrahigh areal capacitance/capacity (12.2 F cm−2/6120 C cm−2 at 2 mA cm−2), superior rate property (82.2% at high current density of 50 mA cm−2) and excellent cycling stability (90.5% retention after 5000 cycles). Moreover, an asymmetric supercapacitor device is assembled by using CoMoO4 as positive electrode and activated carbon as negative electrode, achieving high energy density of 0.321 mWh cm−2 at power density of 1.7 mW cm−2 and superior capacitance retention of 96.0% over 5000 cycles. Importantly, a blue light-emitting diode can be illuminated 2 min, indicating a great potential for practical applications. These excellent results demonstrate that this efficient strategy can extend to prepare various bimetallic oxides arrays with hollow and hierarchical microstructure for high-performance supercapacitors.

Facile Fabrication of MCo2S4(M = Mn, Ni) Nanotube Arrays for High-Performance Supercapacitors

MCo2S4(M = Mn, Ni) nanomaterials are attracting considerable attention because of their unique nanostructure, good redox properties, excellent theoretical capacitance, low cost and easy preparation. Herein, MCo2S4(M = Mn, Ni) nanotube arrays have been fabricated by a one-pot hydrothermal method and could be used as conductive additive and binder-free electrodes for supercapacitors. The results show that the specific capacitance of MCo2S4(M = Mn or Ni) nanotube arrays could reach as high as 2667 and 1623 F/g at the current density of 10 A/g, respectively, indicating high rate performance. Furthermore, the MnCo2S4 nanotube arrays exhibited excellent cycling stability (68% of initial specific capacitance after 1800 cycles). These excellent electrochemical properties benefit from the synergistic effects of unique tubular microstructure and high conductivity of the samples. Schematic illustration of formation of MCo2S4(M = Mn, Ni)

MnO2 nanowires electrodeposited on freestanding graphenated carbon nanotubes as binder-free electrodes with enhanced supercapacitor performance

MnO2 nanowires/graphenated carbon nanotubes (CNTs) have been fabricated on stainless steel (SS) substrate through chemical vaporous deposition (CVD) and electrodeposition method as binder-free supercapacitor electrodes. The MnO2 nanowires/graphenated CNTs nanocomposites have high areal capacitance of 492.5 mF/cm2 (615.6 F/g) at the current density of 0.5 mA/cm2 and outstanding energy density of 985 Wh/m2 with power density of 2.98 kW/m2. After 5000 cycles at 0.5 mA/cm2, the capacity retention of the MnO2/graphenated CNTs is still maintained 95% of the initial capacitance, suggesting exceptional capacitance retention and superior stability. The predominant electrochemical performance of the MnO2/graphenated CNTs is contributed to the synergistic effects of high conductivity of graphenated CNTs and high pseudocapacitance of MnO2 nanowires.

In-situ synthesis of V2O5 hollow spheres coated Ni-foam as binder-free electrode for high-performance symmetrical supercapacitor

V2O5 hollow spheres coated Ni-foam (VO-HS/NF) is hydrothermally synthesized by an in-situ strategy. Diameter of VO-HS ranges from 300 nm to 500 nm, and the shell thickness is about 40 nm on average. The electrochemical properties of VO-HS/NF electrode demonstrate that it chemically stores charges by redox via the intercalation pseudocapacitance. The symmetrical supercapacitor (SSC) device is assembled using VO-HS/NF as the binder-free electrode and its electrochemical performance is studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). VO-HS/NF SSC device exhibits the pseudocapacitive behavior with specific capacitance of 135 mF·cm−2 at 0.5 mA·cm−2 and energy density of 356 mW·h·m−2 at 3.5 W·m−2 owing to the good ion response and high-quality contact between VO-HS and NF. This work provides an effective and facile strategy for synthesizing additive-free VO-HS/NF as high-performance electrodes for energy storage devices.

Rationally design of 2D branched Ni(OH)2/MnO2 hybrid hierarchical architecture on Ni foam for high performance supercapacitors

As electrode materials for supercapacitors, nanostructured hybrids always show better performance compared to corresponding single material. In this work, Ni(OH)2 flakes/MnO2 nanosheets hybrid hierarchical architecture (Ni(OH)2/MnO2 HHA) was constructed on Ni foam (NF) through a two-step hydrothermal reaction. Interestingly, MnO2 nanosheets are vertically grown on the both sides of Ni(OH)2 flakes, forming a highly porous structure with large specific surface area and amounts of diffusion channels. As a binder-free electrode for supercapacitors, Ni(OH)2/MnO2 HHA/NF exhibits a high specific capacity of 253.6 mAh g−1 at 2 A g−1, which is much higher than the individual Ni(OH)2 and MnO2. The excellent electrochemical performance can be attributed to the highly porous architecture, two-dimensional (2D) feature and synergistic effect between Ni(OH)2 and MnO2. The asymmetric hybrid supercapacitor was assembled using Ni(OH)2/MnO2 HHA/NF (24 h) as positive electrode and activated carbon (AC) as negative electrode in 3 M KOH. The hybrid supercapacitor cell can be cycled in the voltage window of 0–1.9 V and exhibits a maximum specific energy of 29.9 Wh kg−1 at 1900 W kg−1. The results indicate that the Ni(OH)2/MnO2 HHA/NF electrode shows great potential in design of high-performance energy storage devices. The construction of this 2D branched hierarchical architecture provides an effective method to obtain excellent electrode materials for energy storage.

A facile two-step method for the fabrication of carbon coated manganese oxide nanostructure as a binder-free supercapacitor electrode

In this work, a facile two-step strategy had been developed to synthesize carbon coated manganese oxide for the fabrication of high performance supercapacitor. First, MnO2 nanoflakes were synthesized on Ni foam by a simple chemical deposition method. Then a thin layer of alginate sodium (NaAlg) coated the nanoflakes by electrophoretic deposition (EPD) and was calcined to carbon, which could increase the conductivity and prevent the crystal from dissolving. As a result, the carbon coated manganese oxide displayed an enhanced capacitance of 412 F g−1 at a current density of 1 A g−1 and the capacitance retention maintained 95.7% after 10,000 cycles of charge/discharge, indicating that the binder-free process provided low internal resistance and reversible charge storage behavior.