Superior Electrochemical Performance For Supercapacitors Research Articles

Design and regulation of FeCo2S4 nanoneedles deposited on carbon felt as binder-free electrodes for high-performance hybrid supercapacitor

Hybrid supercapacitors have drawn much attention since they possess both high energy density and power density. Carbon felt (CF) is chosen as the substrate in this work due to its 3D porous structure, good conductivity, and excellent flexibility. FeCo2S4 nanoneedles are uniformly deposited on CF via hydrothermal, annealing and sulfidation processes, forming the binder-free FeCo2S4 @CF electrode. The morphology of FeCo2S4 deposited on the CF can be designed and regulated by controlling the hydrothermal reaction time. The electrode with unique features is beneficial to the exposure of electroactive sites and the rapid transport of electrons/ions, showing a high specific capacitance of 847.8 mF cm−2 and outstanding rate performance. The hybrid supercapacitor assembled by FeCo2S4 @CF electrode and activated carbon felt exhibits the maximum specific capacitance of 309.7 mF cm−2, energy density of 110.1 μWh cm−2 and power density of 562.4 μW cm−2. Besides, the capacitance retention of the device reaches 98.5% after 10,000 charge-discharge cycles and 87.2% after 3000 bending cycles respectively, revealing its great cycling stability and flexibility. Therefore, this work provides an effective and feasible strategy for the morphology regulation of binary transition metal sulfides with superior electrochemical performance for supercapacitors.

Fabrication of ionic liquid based D-Ti3C2/MoO3 hybrid electrode system for efficient energy storage applications

Recently, Ti3C2 MXene with facile physicochemical properties is a fascinating candidate material for energy storage applications. Herein, solvothermal method was employed to fabricate the novel d-Ti3C2/MoO3@IL by incorporation of imidazolium based ionic liquid to MoO3 nanorods (MoO3@IL); which was intimately anchored onto the surface of d-Ti3C2 MXene. Additionally, this d-Ti3C2 MXene acts as a promising conductive substrate not only to maintain structural stability, but maintains the electrophilicity of electroactive centers as well. Similarly, MoO3@IL improves electrical conductivity due to ionic liquid, and improves reaction kinetics by supplying effective channel for charge transport system with improved pseudocapacitance. Owing to the intimate interaction, the d-Ti3C2/MoO3@IL electrode exhibited exceptional electrochemical performances with specific capacitance of 1680 F g–1 at 1 A g–1, outstanding rate performance, and excellent cyclic stability. Moreover, the symmetric supercapacitor (SSC) device from d-Ti3C2/MoO3@IL demonstrated excellent energy densities of 41 Wh kg–1 and 9.6 Wh kg–1 at power densities of 990 W kg–1 and 3456 W kg–1 respectively. We have employed this novel hybrid electrode material for SSC device application for the first time. The results proved that d-Ti3C2/MoO3@IL is an advanced electrode material, and this scheme provides the valuable method to fabricate MXene and ionic liquid based electrodes with superior electrochemical performance for supercapacitors.

N-doped hollow carbon nanoplates with mesoporous thin shells towards high-performance supercapacitors

Integrating hollow structures and ordered mesopores in carbon materials is critical for electrochemical devices to facilitate fast ion-transport pathways and large ion-accessible surface areas. In this work, a self-templating method is used to prepare hollow ordered mesoporous carbon (HOMC) materials by self-assembling resol-F127 composite micelles on the surface of two-dimensional (2D) metal-organic-framework (MOF) nanoplates, followed by polymerization and carbonization. During the hydrothermal reaction, MOF nanoplates act as a 2D template to assemble resol-F127 composite micelles, leading to hollow ordered mesostructured polymer (HOMP). At the same time, N-containing species are released from the dissolved MOF nanoplates, resulting in N-doped HOMC after carbonization. Benefiting from the structural advantages (e.g., high surface area, hierarchical porous architecture composed of hollow interiors and thin mesoporous shells) and the high amount of N-doping, the as-prepared HOMC exhibits superior electrochemical performance for supercapacitors, demonstrated by a high specific capacitance of 271 F g−1 at a current density of 0.5 A g−1, excellent rate capability, and high capacitance retention of 98.1% after 20,000 cycles. The strategy can provide a new avenue for designing and constructing hollow carbon materials for various applications in electrochemical energy storage devices.

Construction of vertically aligned Ni-Co-Mo hybrid oxides nanosheet array for high-performance hybrid supercapacitors

Multi-metal oxide materials have gained increasing attention due to their superior electrochemical performance for supercapacitors. In this work, Ni-Co-Mo oxides composite materials (NiCoMo/NF) are synthesized and anchored on Ni foam in the form of vertically aligned nanosheet arrays using a two-step hydrothermal method. It has confirmed that good electrochemical performance stems from a synergic interaction effect between the hybrid Ni-Co-Mo composite materials and the co-existence of Ni-Co and Co-Mo oxide, which can be attributed to a unique nanostructure in the hybrid Ni-Co-Mo composite materials and Ni-Co/Co-Mo oxide intersections with each other. The NiCoMo/NF binder-free electrode shows an enhanced specific capacitance of 1837.7 F g−1(3.31 F cm−2) at a current density of 1 A g−1 and maintains capacitance retention of 81.2% after 6000 cycles at 5 A g−1. Meanwhile, the fabricated hybrid capacitor achieves high specific energy of 41.1 W h kg−1. The results indicate that NiCoMo/NF has the potential for application in supercapacitors. Moreover, our work provides a practical approach for fabrication of multi-metal oxide materials and hold promise for high-power energy storage devices.

Phosphidated Ni-Mn layered double hydroxide–based electrode material with superior electrochemical performance for supercapacitors

Layered double hydroxides (LDHs) exhibit excellent electrochemical performance in alkali solutions. However, their low conductivity and poor cycle stability limit their application. In this work, Ni-Mn LDH was grown on activated carbon nanofibers (ACNFs) and then phosphidated to obtain an electrode material with a three-dimensional core–shell structure (ACNFs@Ni-Mn-P). This composite combines the electrochemical activity of the two-dimensional phosphidated nanosheets with the structural stability of the one-dimensional nanofibers. The resulting ACNFs@Ni-Mn-P electrode exhibits a high specific capacitance of 1077 F g−1 at 1 A g−1, which is 4.9 times higher than that of a non-phosphidated ACNFs@Ni-Mn LDH electrode, and retains stability of 88.53% at a high current density of 10 A g−1 even after 5000 cycles. Moreover, an asymmetrical supercapacitor featuring an ACNFs@Ni-Mn-P positive electrode achieves comparatively prominent specific energy of 56.25 Wh kg−1 at 806.13 W kg−1, respectively. Therefore, ACNFs@Ni-Mn-P as electrode material has great potential for application in supercapacitors.

Nacre-inspired surface-engineered MXene/nanocellulose composite film for high-performance supercapacitors and zinc-ion capacitors

Ti3C2Tx is a promising electrode material for supercapacitors, whereas it suffers from the re-stacking problem and fluorine-rich functional groups, thereby restricting its electrochemical performance. Herein, delaminated Ti3C2Tx flakes are modified by alkalization and post-annealing treatments to considerably decrease –F and –OH functional groups. In addition, inspired by the architecture of nacres, the modified Ti3C2Tx is combined with soybean stalk-derived nanofibrillated cellulose, which can improve mechanical properties, prevent dense packing of Ti3C2Tx, and facilitate the transport of electrolyte ions. Therefore, the optimized composite film exhibits large tensile strength (53.9 MPa), high electrical conductivity (24930 S m−1), and superior electrochemical performance for supercapacitors and zinc-ion capacitors. In particular, the composite film under quasi-solid-state supercapacitor configuration delivers high capacitances of 303.1 and 211.4 F g−1 at 1 and 10 mA cm−2, respectively, excellent cyclability (92.84% capacitance retention over 10,000 cycles), and great affordability to bending deformations. This work offers an efficient way to construct high-performance flexible electrodes for high-power applications.

Mechanochemistry coupled with MgCO3 one-step activation to prepare coal-based hierarchical porous carbon for supercapacitors

Fabricating functional porous carbon materials for supercapacitors (SC) without using alkali/acid activation is a big challenge. Here, we present a green mechanochemistry coupled with MgCO3 one-step activation to transform low-rank coal into high-quality porous carbon materials. Under the action of ball milling, the high-energy CO2 sputtering effect from MgCO3 leads to an instantaneous explosion inside the precursor. In the activation stage, the structure of the precursor becomes loose and a large number of fresh active sites is created, which increases the defects and forms a pore structure to couple heteroatoms. Meanwhile, the generated MgO nanocrystals can be used as a template for subsequent activation. The experimental results and density functional theory calculation indicate that the obtained coal-based hierarchical porous carbon (CHPC) has a large specific surface area (SSSA), abundant micro-mesopores, optimized pore size distribution, high graphitization, O/N doping and high adsorption energy (Ead), possessing superior electrochemical performance for SC. Optimized CHPC possesses a high specific capacitance (C) of 328 F g−1 at 0.5 A g−1. CHPC symmetric SC achieves an energy density of 10.17 Wh kg−1 at 125 W kg−1 and 7.5 Wh kg−1 under 5000 W kg−1. This work provides an easy and inexpensive approach for SC development.

A facile synthesis of Ni0.85Se@Cu2-xSe nanorods as high-performance supercapacitor electrode materials.

Transition-metal selenides are regarded as promising electrode materials due to their superior electrochemical performances for supercapacitors. In this study, a nanorod-like hybrid of Ni0.85Se@Cu2-xSe on a Ni-foam substrate is successfully synthesized via a facile one-step route. The Ni0.85Se@Cu2-xSe nanorods are found to be deposited uniformly on the Ni-form substrates. When used as a battery-type electrode in a supercapacitor, the as-deposited Ni0.85Se@Cu2-xSe electrode exhibits a high specific capacity of 1831 F g-1 at 1 A g-1 and 78.4% of capacitance retention after 8000 cycles at 10 A g-1. Moreover, the assembled Ni0.85Se@Cu2-xSe//AC asymmetric supercapacitor (ASC) exhibits an energy density of 63.2 W h kg-1 at a power density of 800.1 W kg-1, as well as good cycling stability (92.1% capacitance retention after 5000 cycles).

Ultrathin N-doped Ti3C2-MXene decorated with NiCo2S4 nanosheets as advanced electrodes for supercapacitors

An integrated system of heterostructure composites which can protect and optimize the structure and performance of single composition shows the positive signal of being interested in energy storage and conversion field. Recently, MXenes with versatile physicochemical properties are intriguing candidate materials for energy storage. Herein, by in situ nucleation and ion-exchange reaction, open NiCo2S4 nanosheets were intimately anchored onto the surfaces of ultrathin nitrogen-doped Ti3C2-MXene nanosheets (N-Ti3C2) to form the novel hierarchical N-Ti3C2/NiCo2S4 nanosheets. Furthermore, ultrathin N-Ti3C2 serves as a favorable conductive substrate not only to maintain structural stability, but also to afford the electrophilicity of electroactive centers and harmonize the electrochemical properties in multi-composition systems. On the other hand, NiCo2S4 nanosheets supply the effective channel for charge transport resulting in improved reaction kinetics and offer higher pseudocapacitance. Owing to the unique heterostructure and friendly interfacial interaction, the N-Ti3C2/NiCo2S4 electrode exhibits outstanding electrochemical performances with specific capacitance of 1849 F g−1 at 2 mV s−1, low internal resistance, excellent rate performance, and stable cycle life, which is much better than that of Ti3C2-MXene electrode. The results demonstrate that the heterostructure N-Ti3C2/NiCo2S4 was an advanced electrode, and this strategy provide the useful method to design MXenes-based electrode with superior electrochemical performance for supercapacitors.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo2S4 polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo2S4 electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg−1 at 1Ag−1 and an excellent rate capability of ~80.4% at 20Ag−1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo2S4 as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg−1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

Decorating carbon nanosheets with copper oxide nanoparticles for boosting the electrochemical performance of symmetric coin cell supercapacitor with different electrolytes

The synergetic combination of double-layer capacitor carbon nanosheets and pseudocapacitive CuO particles with enhanced electrochemical properties had been proposed. Herein, CuO/carbon nanosheets electrode material with outstanding electrochemistry performance was successfully synthesized via a low-cost and controllable strategy. Such rational architecture integrates high-conductivity carbon nanosheets with rich-chemical-activity CuO particles. The surface-functional carbon nanosheets serve as a conductive substrate, provide an efficient pathway and accelerate the fast diffusion of electrons. This electrode material depicts high specific capacitance up to 183.9 and 371.1 F g−1 at 1 A g−1 in Na2SO4 and KOH electrolyte using three-electrode tests, respectively. Moreover, two symmetric devices using this CuO/carbon nanosheets electrode material were assembled with different electrolytes. The as-fabricated device with KOH electrolyte delivers remarkable energy density of 19.36 W h kg−1 at power density of 355.6 W kg−1 and still maintains 12.06 W h kg−1 at 1750.7 W kg−1. The as-fabricated device with Na2SO4 electrolyte achieves the maximum energy density of 12.46 W h kg−1 at 355.6 W kg−1. The capacitance retention rate is maintained at 94.4% after 2000 cycles in the as-fabricated coin cell supercapacitor with Na2SO4 electrolyte, showing outstanding long-cycling life. Herein, the strategic integration of CuO particles with two-dimensional functional carbon nanosheets as the electrode material provides superior electrochemical performance for supercapacitors.

Environment-benign synthesis of rGO/MnOx nanocomposites with superior electrochemical performance for supercapacitors

Chemical oxidation synthesis of graphene oxide (GO) through modified Hummers methods has been widely employed for producing graphene- or reduced GO (rGO)-based advanced functional materials such as rGO/MnOx nanocomposites. However, the manganese species in GO colloids are usually washed out during GO synthesis through modified Hummers methods, causing manganese waste and environmental risk. In this paper, we report preparation of rGO/MnOx nanocomposites, in which MnOx is composed of Mn2O3, Mn3O4, and MnO2 components, through anneal treatment of the precursor counterparts obtained by simple pH tuning of GO colloids. The rGO/MnOx nanocomposites exhibit superior electrochemical performance for supercapacitors. rGO/MnOx-5, derived from GO colloids with pH 5, exhibits a high gravimetric discharge capacitance (Cdis) of 191 F g−1 at 20 A g−1 and a high capacitance retention (82.9%) relative to Cdis at 1 A g−1. Furthermore, typical symmetric supercapacitor cells made from rGO/MnOx-5 show a high areal capacitance (172 mF cm−2) and excellent capacitance retention (96.6%) at 2 A g−1 (10 mA cm−2) for 20,000 cycles, holding great potential for practical applications. The superior electrochemical performance of rGO/MnOx nanocomposites is attributed to multiple charge storage mechanisms in association with the coexistence of mixed-valent manganese oxides.

Honeycomb-Like Interconnected Network of Nickel Phosphide Heteronanoparticles with Superior Electrochemical Performance for Supercapacitors.

Transition-metal-based heteronanoparticles are attracting extensive attention in electrode material design for supercapacitors owing to their large surface-to-volume ratios and inherent synergies of individual components; however, they still suffer from limited interior capacity and cycling stability due to simple geometric configurations, low electrochemical activity of the surface, and poor structural integrity. Developing an elaborate architecture that endows a larger surface area, high conductivity, and mechanically robust structure is a pressing need to tackle the existing challenges of electrode materials. This work presents a supercapacitor electrode consisting of honeycomb-like biphasic Ni5P4-Ni2P (NixPy) nanosheets, which are interleaved by large quantities of nanoparticles. The optimized NixPy delivers an ultrahigh specific capacity of 1272 C g-1 at a current density of 2 A g-1, high rate capability, and stability. An asymmetric supercapacitor employing as-synthesized NixPy as the positive electrode and activated carbon as the negative electrode exhibits significantly high power and energy densities (67.2 W h kg-1 at 0.75 kW kg-1; 20.4 W h kg-1 at 15 kW kg-1). These results demonstrate that the novel nanostructured NixPy can be potentially applied in high-performance supercapacitors.

Bi2S3 nanoparticles anchored on graphene nanosheets with superior electrochemical performance for supercapacitors

Great progress has been made in developing nanostructured metal oxides and metal sulfides as electrode materials for supercapacitors. Poor electrical conductivities of these materials, however, limit their supercapacitive performance. In this work, a facile synthesis strategy is developed to prepare Bi2S3/graphene composites with Bi2S3 nanoparticles anchored on graphene nanosheets. The Bi2S3/graphene composite electrodes exhibit promising electrochemical performance in a negative potential window of −0.9–0V (vs. Ag/AgCl) in 1M Na2SO4 electrolyte. A large specific capacitance of about 400F/g can be achieved by the Bi2S3/graphene composite electrode with good rate capability and cycle performance. The present work indicates that the Bi2S3/graphene composites are promising anode materials for developing high-performance asymmetric supercapacitors.

Manganese dioxide nanoflakes anchored on reduced graphene oxide with superior electrochemical performance for supercapacitors

Nanostructured manganese dioxide (MnO2)/reduced graphene oxide (RGO) composite is fabricated via a simple hydrothermal process. The MnO2/RGO composite is used to construct supercapacitors as electrodes with high loading mass of active materials. The electrochemical properties of constructed supercapacitors are tested by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements demonstrate that MnO2/RGO electrode exhibits a high specific capacity of 316 F·g−1 at a current density of 200 mA·g−1 and good long-term cycling stability with capacitance retention of 93% at 500 mA·g−1 after 1000 cycles. The superior electrochemical performance of as-prepared composite could be mainly attributed to its unique structure, which is composed of MnO2 nanoflakes well-integrated on the surfaces of RGO.

Template-assisted synthesis of NiP@CoAl-LDH nanotube arrays with superior electrochemical performance for supercapacitors

A novel NiP@CoAl-LDH nanotube arrays (NiP@CoAl-LDH NTAs) are successfully designed on Ni foam via template-assisted electrodeposition process. The unique nanotube arrays can provide a short diffusion path for electrolyte ions and a high utilization rate for electrode materials. As a consequence, the obtained NiP@CoAl-LDH NTAs electrode presented the superior electrochemical performances, which demonstrated an areal specific capacity of 0.67Ccm−2 (556Cg−1) at 1mAcm−2 and a high capacity retention of 74.1% at 20mAcm−2, much higher than that of NiP NTAs and CoAl-LDH electrodes. The asymmetric supercapacitor device (ACS device) also displayed predominant electrochemical properties, such as high specific capacity of 156.1Cg−1 at 2mAcm−2 and energy density of 37.18Whkg−1 at a power density of 0.45kWkg−1. Besides, the specific capacity of ACS device maintained 95.50% of the initial specific capacity at 6mAcm−2 after 4000 cycles, indicating its potential applications in long-term cycle life supercapacitor. These results illustrate the promise of NiP@CoAl-LDH NTAs as electrode for supercapacitor.

Nitrogen and sulfur codoped porous carbon microsphere: a high performance electrode in supercapacitor

Abtract Nitrogen and sulfur codoped porous carbon microspheres (NS-PCMSs) with superior electrochemical performance for supercapacitors were successfully fabricated using sublimed sulfur, thiourea and TMTD as different sulfur source by a solvothermal method. The transmission electron microscopy(TEM), scanning electron microscopy (SEM) and Raman spectroscopy indicate the obtained NS-PCMSs have uniform morphology and partially graphitic structure. The N2 adsorption-desorption analysis reveal that all the NS-PCMSs have the hierarchical pore structure and relatively lower specific surface area (397.4–413.8 m2 g-1). The results of the X-ray photoelectron spectroscopy (XPS) demonstrated that the nitrogen and sulfur successfully incorporated into the carbon frameworks. Electrochemical tests show NS-PCMSs present the superior specific capacitance (242–295 Fg-1 at 0.1 A g-1), outstanding rate capability (the specific capacitance at 10 A g-1 were 216–247 F g-1,respectively) and excellent cyclic stability (almost no attenuation after 10000 cycles). This study provides that the NS-PCMSs have huge application potential to be one of the splendid supercapacitor electrode materials.

Design of three dimensional hybrid Co3O4@NiMoO4 core/shell arrays grown on carbon cloth as high-performance supercapacitors

Electrodes with rationally designed hybrid nanostructure composites can have superior electrochemical performance for supercapacitors to single structured materials.

Amorphous FeOOH Quantum Dots Assembled Mesoporous Film Anchored on Graphene Nanosheets with Superior Electrochemical Performance for Supercapacitors

Previous research on iron oxides/hydroxides has focused on the crystalline rather than the amorphous phase, despite that the latter could have superior electrochemical activity due to the disordered structure. In this work, a simple and scalable synthesis route is developed to prepare amorphous FeOOH quantum dots (QDs) and FeOOH QDs/graphene hybrid nanosheets. The hybrid nanosheets possess a unique heterostructure, comprising a continuous mesoporous FeOOH nanofilm tightly anchored on the graphene surface. The amorphous FeOOH/graphene hybrid nanosheets exhibit superior pseudocapacitive performance, which largely outperforms the crystalline iron oxides/hydroxides‐based materials. In the voltage range between −0.8 and 0 V versus Ag/AgCl, the amorphous FeOOH/graphene composite electrode exhibits a large specific capacitance of about 365 F g−1, outstanding cycle performance (89.7% capacitance retention after 20 000 cycles), and excellent rate capability (189 F g−1 at a current density of 128 A g−1). When the lower cutoff voltage is extended to −1.0 and −1.25 V, the specific capacitance of the amorphous FeOOH/graphene composite electrode can be increased to 403 and 1243 F g−1, respectively, which, however, compromises the rate capability and cycle performance. This work brings new opportunities to design high‐performance electrode materials for supercapacitors, especially for amorphous oxides/hydroxides‐based materials.

Co3O4@MWCNT Nanocable as Cathode with Superior Electrochemical Performance for Supercapacitors

Using a simple hydrothermal procedure, cobalt oxide (Co3O4) with preferred orientation along (220) planes is in situ prepared and coated on MWCNT. The prepared Co3O4@MWCNT nanocable shows superior electrochemical performance as cathode material for aqueous supercapacitors in 0.5 M KOH solution. Its redox peaks retain the well-defined shapes even when the scan rate increases to 200 mV/s. Its specific capacitance is high, 590 F/g at 15 A/g and 510 F/g even at 100 A/g within the potential range from -0.2 to 0.58 V (vs SCE). There is no capacitance fading after 2000 full cycles. This excellent performance is superior to the pristine and the reported Co3O4, which is ascribed to the unique nanocable structure with orientation.