Advanced Supercapacitor Electrodes Research Articles

Two-dimensional hierarchical MoS2 lamella inserted in CoS2 flake as an advanced supercapacitor electrode

The two-dimensional hierarchical structure has a positive effect on improving the stability of the electrode materials for supercapacitors. In this work, an exquisite hierarchical structure of CoS2 flake with the two-dimensional MoS2 lamella (MoS2@CoS2) was constructed using flake-like ZIF-67 as a precursor through multiple calcination and one-step sulfuration. The CoS2 nanosheets composed of CoS2 nanoparticles anchored on the carbon skeleton could provide a stable structure for subsequent reactions. Moreover, the inserted 2D cross-linked MoS2 multilayers could effectively prevent the interlayer expansion and structural collapse, and especially ensure the electrochemical performance and morphological stability of the transition metal sulfides. As a result, MoS2@CoS2 exhibits an extraordinary specific capacitance (950 F g−1 at 1 A g−1) and an appreciable cycle life with a capacitance retention of 94.6% (10, 000 cycles at 10 A g−1). Meanwhile, the MoS2@CoS2//reduced graphene oxide (RGO) asymmetric supercapacitor shows an energy density of 33.94 Wh kg−1 at a power density of 1040 W kg−1. Such excellent performance benefits from more electrochemically active sites and the rapid kinetics reaction which was ascribed to the rational design of two-dimensional hierarchical structure.

CoS/Nitrogen-doped carbon composites derived from Zeolitic imidazolate frameworks-67 as advanced electrodes for supercapacitors

Using ZIF-67 as precursor, CoS/Nitrogen-doped carbon (CoS/NC) composites are successfully prepared by applying chemical vapor deposition (CVD) treatment at three different curing temperatures. The results show that the optimal curing temperature is 700 °C, and CoS/NC-700 is a hollow cage-like polyhedron structure formed by the combination of CoS nanosheets and nitrogen doped carbon skeleton. The specific capacitance is 789 F g−1 at 1 A g−1 current density and a rate capacity of 80.2% under a 20 A g−1 of current density. The CoS/NC-700//AC capacitor has the highest energy density of 32.8 Wh kg−1 when the power density is 620.0 W kg−1 and the capacitor remains 89.2% of initial capacitance after 10,000 charge-discharge cycles at current density of 5 A g−1.

Oxygen vacancy-engineered ultrathin NiCo2O4 nanosheet arrays derived from MOFs as an advanced electrode for supercapacitors.

To overcome the poor electronic conductivity and slow ion transport of NiCo2O4, ultrathin nanosheet arrays with oxygen vacancies are constructed by a facile NaBH4 reduction method using a bimetallic MOF as the precursor. Benefiting from the advantages of highly exposed surface area and short paths for charge transport of ultrathin 2D nanosheets, as well as the improved electronic conductivity arising from oxygen vacancies, the optimal 0.1-Ov-NiCo2O4/NF electrode shows excellent electrochemical performance, largely outperforming pristine NiCo2O4/NF.

Crumpled graphene microspheres anchored on NiCo2O4 nanoparticles as an advanced composite electrode for asymmetric supercapacitors with ultralong cycling life.

The rational design of composite electrodes that may take full advantage of pseudocapacitive metal oxides and graphene is still challenging. Herein, nickel cobaltate (NiCo2O4) nanoparticle-anchored crumpled graphene microspheres (CGMs) were fabricated through a simple spray-assisted self-assembly process and used as a composite electrode for aqueous supercapacitors. Due to the porous spherical architecture and well-dispersed NiCo2O4 nanoparticles on graphene, the NiCo2O4/CGM electrode displays ideal electrochemical performance, including a specific capacitance of 369.8 F g-1 (at 1 A g-1), good rate performance of 85% capacitance retention even at 10 A g-1 and intriguing cycling stability. An aqueous asymmetric supercapacitor (ASC) with an operating voltage of 1.6 V was then assembled using the NiCo2O4/CGM composite and nitrogen-doped CGM (N-CGM) as the positive and negative electrodes in KOH electrolyte, respectively. The ASC device exhibited an excellent energy density of 24.7 W h kg-1 at a power density of 799.6 W kg-1, and an ultralong cycling life with a capacitance retention of 85% after 50 000 cycles. The satisfactory electrochemical performance and ultralong cycling stability indicate that the NiCo2O4/CGM electrode has promising applications in advanced supercapacitors.

Growing Co–Ni–Se nanosheets on 3D carbon frameworks as advanced dual functional electrodes for supercapacitors and sodium ion batteries

The reasonable design of electrode materials is crucial for tuning the electrochemical performances of advanced energy storage systems.

MOF-derived carbon coated Cu3P with Ni doping as advanced supercapacitor electrode materials

Metal phosphide materials have drawn much attention due to their high supercapacitive activity.

Co9S8 quasi-hexagonal nanoparticles coupled with WS2 nanoring anchored on 3D sulfur, nitrogen Co-doped carbon nanotubes@graphene oxide cross-linking architecture for high performance asymmetric supercapacitor

Designing advanced hybrid supercapacitors (SCs) electrode materials with 3D cross-linking hierarchical porous architecture has desirable structural advantages, which can facilitate ion transport and provide excellent reaction site. Herein, a unique nanostructure consisting of Co9S8 quasi-hexagonal nanoparticles coupled with WS2 nanoring anchored on 3D sulfur, nitrogen Co-doped carbon nanotubes@graphene oxide (Co9S8@WS2-NS-15mlGO@CNTs) was obtained using a facile solvothermal strategy. This cross-linking and hierarchical porous nanostructure can maximize the electrical conductivity of entirety, which provides a favorable transport and permeability for the ions and electrons of the electrolyte environment. Benefiting from the structural compositional advantages and full play of the synergetic coupling effect, the as-prepared Co9S8@WS2-NS-15mlGO@CNTs electrode material exhibits absolutely the topmost specific capacitance of 1820.8 F g−1 at a current density of 1 A g−1 and outstanding cycle stability with a capacitance retention of 90.2% after 10000 cycles at 30 A g−1. Moreover, an asymmetric supercapacitor (ASC) fabricated by Co9S8@WS2-NS-15mlGO@CNTs (positive electrode) and NS-15mlGO@CNTs (negative electrode) presents an ultra-high energy density of 95.3 Wh kg−1 at a power density of 600 W kg−1, and long cycle life with 86.7% specific capacity retention at a current density of 20 A g−1 after 10000 cycles. It is believed that the presented work may open a new perspective to fabricate future competitive high-performance energy storage devices.

High-capacity CoP-Mn3P nanoclusters heterostructures derived by Co2MnO4 as advanced electrodes for supercapacitors

Although transition metal oxides (TMOs) have attracted enormous attention owing to their high performance in supercapacitors, it still remains challenging issues in terms of the poor electrical conductivity, sluggish redox kinetics and insufficient electrochemical active sites. Herein, the high-capacity CoP-Mn3P nanoclusters featuring the heterogeneous interfaces have been successfully synthesized through hydrothermal method followed by annealing. The heterojunction formed between CoP and Mn3P redistributes the charge at the interface between them, generating the built-in electric field to accelerate electron transfer, and thus the conductivity of the electrode is enhanced. Moreover, the unique morphology of nanoclusters composed of flake structures is beneficial to provide more electrochemical active sites. Consequently, the resultant CoP-Mn3P nanoclusters electrode delivers an exceptional gravimetric specific capacity (2714 F g−1 at 1 A g−1) as well as a long cycle lifespan (83.1% of capacitance retention after 10,000 cycles). An asymmetric supercapacitor (ASC) device assembling with employing CoP/Mn3P electrode presents an ultrahigh energy density value of 46.4 Wh kg−1 at a power density of 800.0 W kg−1 and a super capacitance retention of 86.2% after 30,000 cycles. This work paves an effective way for the investigation on the charge transfer kinetics of electrode materials.

NiCo2S4 nanosheets decorated on nitrogen-doped hollow carbon nanospheres as advanced electrodes for high-performance asymmetric supercapacitors

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCo2S4 nanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCo2S4/NHCS composite with a core–shell structure. This three-dimensionally confined growth of NiCo2S4 can effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCo2S4/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10 000 cycles, outstanding specific capacitance of 902 F g−1 at 1 A g−1, and it retained 90.6% of the capacitance at 20 A g−1. Moreover, an asymmetric supercapacitor composed of NiCo2S4/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kg−1 at 750 W kg−1), excellent power density (15003 W kg−1 at 21.88 Wh kg−1), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCo2S4 shell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCo2S4/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.

Investigation of graphene based NiS nanocomposite by solvothermal method for energy storage application

Fabrication of electrode with graphene-based material has received widespread interest in the specialization of energy-related devices. Especially in supercapacitors, engineering electrode material with graphene shows promising performance with enhanced energy and power density. In this work, graphene-nickel sulphide (G-NiS) hybrid nanocomposite was synthesized successfully by solvothermal method. The phase purity of the materials were determined from XRD studies. SEM image reveals deposition of NiS nanoparticles over the surface of graphene oxide layer forming a flower-like structure. The G-NiS nanocomposite electrode shows an excellent specific capacitance of 409.2F/g at low current density of 5 A/g in the three electrode cell. A symmetric supercapacitor based on G-NiS nanocomposite exhibited a high specific capacitance of 136.2F/g at 5 A/g and excellent cycling stability with coulombic efficiency of 98.1% after 1000 cycles. The high performance of the nanocomposite is mainly attributed to the presence of the NiS nanoparticles deposited on the graphene surface which readily produce more active sites for electron transport. Thus, the as prepared G-NiS nanocomposite could be an advanced supercapacitor electrode material.

Rational design of hierarchically sulfide and MXene-reinforced porous carbon nanofibers as advanced electrode for high energy density flexible supercapacitors

In this study, in-situ carbon coating technology was used to embed the sulfide-loaded MXene in the carbon nanofibers through electrospinning to improve the sulfide conductivity and ion transfer rate. Polyacrylonitrile (PAN) with a high carbon conversion rate was used as carbon nanofiber, while polyvinylpyrrolidone (PVP) with a low carbon conversion rate was used as a pore-forming sacrificial agent . PAN–PVP-based porous carbon nanofibers (PCNF) with good meso/macropore structure were prepared via a thermally induced phase separation process. FeCo 2 S 4 nanoparticles and ultra-thin Ti 3 C 2 T x MXene were uniformly fixed in PCNF in situ, and a flexible hybrid film was prepared as the electrode material of supercapacitors (FeCo 2 S 4 /MXene/PCNF). The FeCo 2 S 4 /MXene/PCNF hybrid membrane inherits a three-dimensional pore structure and hierarchical PCNF nanostructure . It can provide continuous channels for the rapid electrolyte diffusion, thereby obtaining electrochemically active FeCo 2 S 4 nanoparticles. Moreover, carbon nanofibers can act as a conductive core for providing effective electron transport for the rapid Faraday redox reaction of the FeCo 2 S 4 sheath or as a buffer matrix for reducing local volume expansion/contraction during long-term cycling. Therefore, the optimized FeCo 2 S 4 /MXene/PCNF hybrid membrane has excellent cyclic stability, which fundamentally solves the problems of poor sulfide conductivity and cyclic stability.

Hierarchical MCo2O4@Ni(OH)2 (M = Zn or Mn) core@shell architectures as electrode materials for asymmetric solid-state supercapacitors

In this study, the self-assembled Ni(OH)2-nanosheet-adorned hierarchical MCo2O4@Ni(OH)2 (M = Zn or Mn) core@shell heterostructures are prepared by a three-step process, via tuning the core-compositions, as advanced electrodes for supercapacitors (SCs). The tuning of the core composition makes a significant impact on the physicochemical properties, morphology, and electrochemical performance. Among the MCo2O4@Ni(OH)2 materials, the nanopine forest-like ZnCo2O4@Ni(OH)2 optimal architecture exhibits superior supercapacitive performance (areal/specific capacity, 1.34 mA h cm−2/432.6 mA h g−1 at 3 mA cm−2 current density and a ∼90% cycling stability upto 5000 cycles). Meanwhile, 3D porous nitrogen-doped carbon (PNC) with perfect rhombic dodecahedral morphology is used as negative electrode material with high surface area (1600 m2 g−1), excellent capacity (49.2 mA h g−1 at 2 mA cm−2) and rate performance (∼55% at 50 mA cm−2). The solid-state asymmetric device comprising ZnCo2O4@Ni(OH)2 (positive electrode) and hierarchical PNC (negative electrode) affords a high cell capacity of 97.8 mA hg−1 at 4 mA cm−2, with 86% cycle stability after 10,000 cycles. Moreover, the device exhibits 78.2 W h kg–1 of energy density at a power density of 451 W kg−1 and 40.4 W h kg−1 of energy density at 4691.0 W kg−1 of power density. This study provides insight into electro-active material design and construction of heteronanostructures for high-performance SCs.

Nitrogen plasma activation of cactus-like MnO2 grown on carbon cloth for high-mass loading asymmetric supercapacitors

The electrochemical performance of high theoretical capacitance MnO2 is usually restricted to low mass loading electrode due to the slower electron/ion diffusion kinetics in dense electrodes. Defect engineering has been supposed to an effective way to improve the capacitive performance of transition metal oxides. Herein, cactus-like structure MnO2 was grown on carbon cloth (CC) and treated with N2-plasma to obtain the N-MnO2 electrode with high mass loading of 12 mg cm−2. Benefiting from the hierarchical structure and rich oxygen vacancies, the as-prepared N-MnO2 electrode delivered a high mass specific capacitance of 443F g−1 and a high areal capacitance of 5320 mF cm−2. Furthermore, the N-MnO2 electrode released an excellent rate capability with 71.8% capacitance retention at 20 mA cm−2 as well as gratifying cycling life with 96 % capacitance retention after 8 000 cycles at 20 mA cm−2. Moreover, an asymmetrical supercapacitor device assembled by N-MnO2 and activated CC can achieve a high energy density of 0.56 mWh cm−2 (46 Wh kg−1) at the power density of 5.14 mW cm−2 (420 W kg−1) with good cycle stability. Such facile N2-plasma treatment for defect engineering shows great potential in the rational design for advanced supercapacitor electrodes with high mass loading.

Rational design of ZIF-8 assimilated hierarchical porous carbon nanofibers as binder-free electrodes for supercapacitors

Recently, tremendous attention has been paid to carbon-based fibers, particularly porous carbon fibers (PCFs), because of their great potential as electrodes for advanced supercapacitors (SCs). However, the relatively complex preparation and monotonous pore structure are still the most important challenge that PCFs needs to counter. In this work, an eco-friendly yet facile approach has been applied to synthesis PCFs with tunable multi-level pores and satisfactory electrochemical performance. By using the combinations of electrospinning technology, hard-template method and carbonization process, nanofibers with interconnected multi-level pores can be achieved. It is demonstrated that the pore engineered PCF possesses enhanced electrochemical performance. For instance, the PCF electrode possesses a high capacitance of 211 F g−1 in 6 mol L−1 KOH at a density of 0.5 A g−1 together with excellent rate capability. Meanwhile, a high areal capacitance of 1.2 F cm−2 also can be achieved at a mass loading of 10 mg cm−2. Additionally, symmetrical supercapacitor assembled by PCF electrodes exhibits good capacitance of 101.9 F g−1 at the current density of 0.5 A g−1, such device also can deliver an energy density up to 60.1 Wh kg−1 with ionic liquid electrolyte.

Dual-Redox-Sites Enable Two-Dimensional Conjugated Metal-Organic Frameworks with Large Pseudocapacitance and Wide Potential Window.

Advanced supercapacitor electrodes require the development of materials with dense redox sites embedded into conductive and porous skeletons. Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) are attractive supercapacitor electrode materials due to their high intrinsic electrical conductivities, large specific surface areas, and quasi-one-dimensional aligned pore arrays. However, the reported 2D c-MOFs still suffer from unsatisfying specific capacitances and narrow potential windows because large and redox-inactive building blocks lead to low redox-site densities of 2D c-MOFs. Herein, we demonstrate the dual-redox-site 2D c-MOFs with copper phthalocyanine building blocks linked by metal-bis(iminobenzosemiquinoid) (M2[CuPc(NH)8], M = Ni or Cu), which depict both large specific capacitances and wide potential windows. Experimental results accompanied by theoretical calculations verify that phthalocyanine monomers and metal-bis(iminobenzosemiquinoid) linkages serve as respective redox sites for pseudocapacitive cation (Na+) and anion (SO42-) storage, enabling the continuous Faradaic reactions of M2[CuPc(NH)8] occurring in a large potential window of -0.8 to 0.8 V vs Ag/AgCl (3 M KCl). The decent conductivity (0.8 S m-1) and high active-site density further endow the Ni2[CuPc(NH)8] with a remarkable specific capacitance (400 F g-1 at 0.5 A g-1) and excellent rate capability (183 F g-1 at 20 A g-1). Quasi-solid-state symmetric supercapacitors are further assembled to demonstrate the practical application of Ni2[CuPc(NH)8] electrode, which deliver a state-of-the-art energy density of 51.6 Wh kg-1 and a peak power density of 32.1 kW kg-1.

Zephyranthes-like Co2NiSe4 arrays grown on 3D porous carbon frame-work as electrodes for advanced supercapacitors and sodium-ion batteries

Zephyranthes-like Co2NiSe4 arrays grown on 3D porous carbon frame-work as electrodes for advanced supercapacitors and sodium-ion batteries

Three-dimensional polypyrrole-enhanced flower-like ZnCo2S4 nanoclusters used as advanced electrodes for supercapacitors

Confinement transition metal compounds with conducting polymer is an effectively to inhibit the volume change during the Faradic reaction. In this work, three-dimensional flower-like polypyrrole-wrapped ZnCo2S4 (ZnCo2S4@PPy) core-shell nanoclusters were successfully prepared by two-step hydrothermal and electrochemical deposition methods. The obtained ZnCo2S4@PPy composite exhibited remarkable electrochemical performance corresponding to a specific capacitance of 1486 F g−1 at 1 A g−1, which suggested its potential use as a supercapacitor electrode material. Furthermore, the asymmetric supercapacitor containing a ZnCo2S4@PPy positive electrode demonstrated a high specific energy of 33.78 Wh kg−1 at 800.05 W kg−1 and relatively long cycle life (90% capacitance retention after 5000 cycles). The excellent electrochemical performance of ZnCo2S4@PPy can be attributed to the synergistic effect of its main components and unique flower-like core-shell structure. The results reveal that the ZnCo2S4@PPy core-shell nanocluster array is a promising electrode material for future energy-storage devices.

Bimetallic Co0.4Ni1.6P derived from cobalt functionalized a new nickel metal-organic-framework as an advanced electrode for high-performance supercapacitors

A new nickel metal organic framework (MOF) based on 4-cyan-5-acidamide-bisimidazole were fabricated using hydrothermal method. The Co@Ni-MOFwasprepared by doping Ni-MOF with Co2+through post-synthetic modification method. The bimetallic Co0.4Ni1.6P was obtained through phosphorization of Co@Ni-MOF and showed high specific capacity 330F/g at 1 A/g and capacity retention was 96% over 5000 cycles. The supercapacitor device was prepared (Co0.4Ni1.6P//AC) and demonstrated specific energy of 30.9 Wh/kg at power of 806 W/kg. These results provided a new way to design bimetallic phosphide (MOF-based materials) for supercapacitor application.

Core−shell coaxially structured NiCo2S4@TiO2 nanorod arrays as advanced electrode for solid-state asymmetric supercapacitors

An integrated electrode of core–shell coaxially structured NiCo2S4@TiO2 nanorod arrays/carbon cloth (NiCo2S4@TiO2@CC) have been fabricated, via a two-step hydrothermal method. Comprehensive structural and compositional analyzes are performed to understand the effects of the NiCo2S4 shell on the TiO2 core. Such core–shell arrays structure can significantly provide abundant electroactive sites for redox reactions, convenient ion transport paths, and favorable structure stability. The NiCo2S4@TiO2@CC electrode represents a splendid specific capacitance (650 F g−1 at 1 A g−1) and enhanced cycling stability (capacitance retention of 97% over 10 000 cycles at 5 A g−1). Additionally, the assembled NiCo2S4@TiO2@CC//CNT@CC solid-state asymmetric supercapacitors exhibit a maximal energy density of 0.6 mWh cm−3 at 32.4 W cm−3, and topping cycling stability (85% capacitance retention after 5000 cycles at 5 mA cm−2). The results demonstrate that the well-designed NiCo2S4@TiO2@CC presented in this work are applicable for the development of electrode materials in energy storage devices.

Assembling Co3O4 Nanoparticles into MXene with Enhanced electrochemical performance for advanced asymmetric supercapacitors

MXenes with unique 2D open structure, large surface-area-to-volume ratios, high pseudo-capacitance, and conductivity are attractive for advanced supercapacitor electrodes. However, the restacking issue of MXenes hinders ion accessibility, resulting in the reduction of volume performance, mass load, and speed capability. To address these issues, a facile hydrothermal synthesis strategy is proposed to fabricate Co3O4 nanoparticles-MXene (Co-MXene) composite by the self-assembly process. Co3O4 nanoparticles, introduced in the MXene matrix, effectively prevent self-restacking and shorten ion/electron transport paths. Consequently, the obtained Co-MXene electrode delivers the high-performance of 1081F g−1 at a current density of 0.5 A g−1, surpassing the pristine MXene electrode (89F g−1 at 0.5 A g−1). Being assembled into asymmetric supercapacitors (ASC), a high energy density of 26.06 Wh kg−1 at 700 W kg−1 was realized. After 8000 cycles, the ASC device maintains 83% of initial specific capacitance at 2 A g−1. This work highlights a simple and efficient method for developing high-performance MXene-based electrodes for supercapacitors.