Asymmetric Hybrid Supercapacitor Research Articles

Sea urchin-like CoNi2S4 materials derived from nickel hexamyanocobaltate for high-performance asymmetric hybrid supercapacitor

In this work, a mild chemical precipitation method and simple hydrothermal treatment of the nickel hexamyanocobaltate precursor strategy are developed to prepare a sea urchin-like CoNi2S4 compound with remarkable specific capacity and excellent cycling stability. The prepared CoNi2S4 has an outstanding specific capacity of 149.1 mA h g−1 at 1 A g−1 and an initial capacity of 83.1% after 3000 cycles at 10 A g−1. Moreover, the porous carbon nanospheres (PCNs) with exhibit cycling stability (94.7% of initial specific capacity after 10 000 cycles at 10 A g−1) are selected as negative electrode to match CoNi2S4 positive electrode for assembly of CoNi2S4//PCNs asymmetric supercapacitor (ASC). Satisfactorily, the as-assembled CoNi2S4//PCNs ASC exhibits an impressive energy density of 41.6 Wh kg−1 at 797 W kg−1, as well as the suitable capacity retention of 82.8% after 10 000 cycles. The superior properties of the device demonstrated that the as-prepared material is potential energy storage material.

One-step superficial electrodeposition of nickel-cobalt-sulfide for high-energy hybrid asymmetric supercapacitor

A cathodic electrodeposition (ED) technique is adopted to grow multi-component nickel–cobalt-sulfide (NCS) nanosheet arrays on highly conducting nickel foam substrate. The chronoamperometry (CA) deposited electrode has shown exceptional electrochemical activity in terms of specific capacity, rate capability and excellent redox reversibility than the cyclic voltammetry (CV) deposited electrode. Having the benefit of highly conductive nanosheet arrays and three-dimensional open framework of the nanostructure, the binary metal sulfide exhibits high specific capacity of 820 C g−1 at 2 A g−1. When the NCS electrodes were combined with boron-doped graphene oxide to form an asymmetric hybrid supercapacitor, it delivered a high energy density of 83 Wh g−1 and high-power density of 9619 W kg−1.

Mesoporous nanohybrids of 2D layered Cu–Cr phosphate and rGO for high-performance asymmetric hybrid supercapacitors

Asymmetric hybrid supercapacitors (AHSs) with wide operating voltage windows can be developed by effectively combining electric double-layer capacitor- and battery-type electrodes while maintaining their excellent cycling stabilities. In this study, the hybridization of two-dimensional Cu–Cr phosphate (CCP) with layered reduced graphene oxide (rGO) is achieved to develop a high-performance AHS. CCP and rGO are combined into CCP/rGO (CCPG) nanohybrids by a simple and inexpensive single-step chemical method. The CCPG nanohybrids prepared with an optimal amount of rGO exhibit mesoporosity with high surface areas (40 m2/g) and fast charge transfer kinetics. The optimized CCPG delivers a higher specific capacity of 1620 C/g than CCP (694 C/g) in a three-electrode configuration at a current density of 1 A/g. When fabricated using the CCPG and rGO, the AHS exhibits a high specific capacity of 177 C/g, high specific energy of 65.14 Wh/kg, high specific power of 826 W/kg at 1 A/g, and outstanding cyclic stability (94%) within the widened potential window (1.6 V) in aqueous electrolyte. This study suggests that conducting rGO plays a crucial role in the formation of high-performance CCPG nanohybrids, and consequently, the resulting CCPG electrode demonstrates considerably enhanced physiochemical and electrochemical properties, compared with the CCP electrode. Through this hybridization approach, various nanohybrids of other metal dichalcogenide phosphates and rGO can also be developed.

Effects of various molarities of nickel oxide on the aggregate 1D–3D structure and its electrochemical activity

The effect of concentration on the charge storage of supercapacitors is one of the crucial parameters. In the current work, we have successfully deposited the 1D–3D aggregate structure of the nickel oxide (NiO) with its various content concentration of the nickel nitrate precursor on stainless steel (SS) via the simplest hydrothermal technique. The influence of the molarities of the NiO on the nanostructures as well as electrochemically charge storage applications has been studied. The X-Ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR were used for structural, and morphological analysis of the nickel oxide. Here, we observed the cubic structure with the Fm-3 m space group of NiO nanomaterials. SEM images depict the 1D-columnar flakes along with aggregate 1D–3D morphology. The flakes like NiO nanomaterials exhibit a highly electrochemically charge storage pseudocapacitive nature. The optimized 0.40 M of NiO nanomaterial electrode shows the highest specific capacitance value is 639.3 Fg−1 at 5 mVsec−1 in aqueous 1 M KOH in an aqueous electrolyte. The observed maximum specific energy (SE) and specific power (SP) are 74.13 Whkg−1 and 2.07 KWkg−1. The optimized NiO//reduced Graphene Oxide (rGO) based asymmetric hybrid supercapacitor device (AsHSD) shows an excellent specific capacitance value is 34.8 Fg−1 with the highest charging-discharging capability of 83 % up to 100 cycles.

2D-2D nanohybrids of Ni–Cr-layered double hydroxide and graphene oxide nanosheets: Electrode for hybrid asymmetric supercapacitors

• 2D graphene oxide (GO) nanosheets are employed to improve the electrode performance of layer double hydroxide (LDH). • Nanohybrids of Ni–Cr-LDH and GO nanosheets (NCG) are prepared via electrostatic self-assembly method. • NCG nanohybrids enables self-assembly with high surface area, mesoporous morphology, high electrical conductivity, and high charge transfer kinetics. • The aqueous hybrid supercapacitors device displays high energy density (ED) of 51.85 Wh kg –1 and power density (PD) of 1.34 kW kg –1 . • All-solid-state hybrid supercapacitor displays exceptional ED of 38.51 Wh kg–1 and PD of 1.33 kW kg –1 Nanohybrids of 2D Ni–Cr-layered double hydroxide (Ni–Cr-LDH) and graphene oxide (GO) nanosheets (Ni–Cr-LDH–GO) are prepared by electrostatic self-assembly between cationic Ni–Cr-LDH nanosheets and anionic GO nanosheets. Anionic GO nanosheets provide charge-transporting conducting channels leading to remarkably improved electrochemical activity of Ni–Cr-LDH–GO nanohybrid. The unique Ni–Cr-LDH–GO nanohybrid electrodes enable stable electrochemical structure, abundant active electrochemical sites, and fast electron-transporting channels, which play a crucial role in improving the specific capacities, cycle stability, and rate capacity. As a result, Ni–Cr-LDH–GO nanohybrid electrodes demonstrate excellent electrochemical performance with a specific capacity of 815 C g –1 at 1 A g –1 , superior to pristine Ni–Cr-LDH (354 C g –1 ). An aqueous hybrid supercapacitor (AHS) device displays outstanding electrochemical performance with improved energy density (ED) of 51.85 Wh kg –1 and power density (PD) of 1.34 kW kg –1 . An all-solid-state hybrid supercapacitor (ASSHS) displays ED of 38.51 Wh kg –1 and PD of 1.33 kW kg –1 . Furthermore, AHS and ASSHS show excellent cycling stability of 89% and 86% capacitance retention after 10,000 galvanostatic charge/discharge (GCD) cycles, respectively. The present exfoliation-restacking strategy provides a useful method for developing a 2D-2D Ni–Cr-LDH–GO structure for a highly active hybrid-type supercapacitor structure. Exfoliation-reassembly strategy is use to synthesize 2D-2D Ni–Cr-LDH–GO nanohybrids. Owing to the high surface area and high electrical conductivity, Ni–Cr-LDH–GO nanohybrids demonstrated excellent electrochemical performance as a redox electrode in hybrid asymmetric supercapacitor.

Hierarchical polygon Co3O4 flakes/N,O-dual doped porous carbon frameworks for flexible hybrid supercapacitors

The core idea of green chemistry is using or converting renewable materials to exploit higher performance. Biomass materials, as low-cost, abundant, eco-friendly, and renewable organic materials, are regarded as ideal and encouraging candidates in various fields. Noteworthy, carbon nanomaterials derived from biomass materials are proposed as promising and potential alternatives for energy materials for their high conductivity, hierarchical porosity and excellent stability. Herein, all biomass-based flexible electrode is designed and prepared, in which kelp and bacterial cellulose (BC) are used as carbon energy resources and flexible substrate, respectively. The design idea is converting two biomass materials into high-performance flexible electrode components. The aqueous hybrid asymmetric supercapacitor reveals high flexibility, excellent stability and considerable electrochemical performance with high energy density and power density of 0.39 mWh cm −2 (31.8 Wh kg –1 , 6.5 mWh cm −3 ) and 21.7 mW cm −2 (1768.5 W kg –1 , 361.7 mW cm −3 ), respectively, along with 94.5% capacitance retention after 10,000 cycles, revealing great potential in flexible devices.

Synthesis of nickel iron sulfides used as electrode materials for supercapacitors

Herein, hydroxides of nickel and iron as well as sulfide of nickel and iron were synthesized by hydrothermal method. Structure, elemental composition and morphology of the samples were characterized by XRD, EDX and SEM. Electrochemical properties of the electrodes were studied by cyclic voltammetry (CV). The results indicate that, Ni/NF, Fe/NF and NiFe/NF show pseudocapacitor behavior while NiS/NF, FeS/NF and NiFeS/NF are likely to be hybrid asymmetric supercapacitors. The synergistic effect of bimetallic nickel and iron ions of the hydroxides and sulfides provides better electrochemical performance of the electrode materials. NiFeS/NF exhibits the highest specific capacitance, 2079 F g-1.

Embedding Metal–Organic Frameworks for the Design of Flexible Hybrid Supercapacitors by Electrospinning: Synthesis of Highly Graphitized Carbon Nanofibers Containing Metal Oxide Nanoparticles

Electrospun carbonaceous fibers have emerged as promising electrode materials for application in energy storage devices. However, their relatively poor electrical conductivity (due to their amorphous carbon structures) and low capacitive performance lead to poor prospects for their further application. Herein, a universal synthesis of highly graphitized carbon nanofibers, containing various metal oxide nanoparticles (e.g., Fe2O3, NiO), by the pyrolysis of metal–organic framework (MOF)‐embedded electrospun nanofibers, is reported. The resulting carbon nanofibers exhibit large mesopore volumes, contain large quantities of Faradic metal oxide nanoparticles, and are highly graphitized. The fibers also have excellent mechanical flexibility, provide fast ion transfer characteristics, and a large pseudocapacitance combined with excellent electrical conductivity, leading to large specific capacitances. Consequently, asymmetric flexible hybrid supercapacitors assembled from Fe2O3‐embedded highly graphitized carbon nanofibers (FOCNF) and NiO‐embedded highly graphitized carbon nanofibers (NOCNF) exhibit a high energy density of 43.1 Wh kg−1 at a power density of 412.5 W kg−1 and possess excellent flexibility (capacitance retention of 94.4% at 180° bending and 96.2% at 30° twisting) with superior cycling stability. This strategy provides a new MOF‐based approach for the design and synthesis of multifunctional flexible carbonaceous materials and might lead to their further application in flexible energy storage devices.

Comparison of the Properties of Ni–Mn Hydroxides/Oxides with Ni–Mn Phosphates for the Purpose of Hybrid Supercapacitors

This study aims to quantify the synergistic effect of Ni2+ and Mn2+ ions on the capacitive performance of oxide, hydroxide and phosphate electrodes in alkaline electrolytes. Three types of phases containing both nickel and manganese in a ratio of one-to-one were selected due to their stability in alkaline media: oxides with ilmenite and spinel structures (NiMnO3 and Ni1.5Mn1.5O4); hydroxides with layered structures (β-Ni1/2Mn1/2(OH)2); and phosphates with olivine and maricite structures (LiNi1/2Mn1/2PO4 and NaNi1/2Mn1/2PO4). In the mixed hydroxides and phosphates, Ni2+ and Mn2+ ions randomly occupied one crystallographic site, whereas in the ilmenite oxide, a common face was shared by the Ni2+ and Mn4+ ions. The electrochemical parameters of the Ni–Mn compositions were evaluated in asymmetric hybrid supercapacitor cells working with alkaline electrolytes and activated carbon as a negative electrode. A comparative analysis of oxides, hydroxides and phosphates enabled us to differentiate the effects of nickel and manganese ions, structures and morphologies on their capacitive performance. Thus, the best performed electrode was predicted. The electrode composition should simultaneously contain Ni and Mn ions, and their morphologies should comprise spherical aggregates. This was an ilmenite NiMnO3, which delivers high energy and power density (i.e., 65 W h kg−1 at 3200 W kg−1) and exhibits a good cycling stability (i.e., around 96% after 5000 cycles at a current load of 240 mA g−1).

Three-dimensional microsphere-like cobalt-glycerolate strutted nickel hydroxidenitrate nanoflakes grown by hydrothermal method for asymmetric hybrid supercapacitors

The core-shell structure is always a greatly effective structure in asymmetric hybrid supercapacitor, duo to a high specific surface area and porosity that can accommodate partial expansion during the redox reaction. Herein, a cobalt-glycerolate@nickel hydroxidenitrate microsphere (CoG@Ni3(NO3)2·(OH)4) with core-shell structure is prepared by a simple two-step hydrothermal method. The as-produced CoG@Ni3(NO3)2·(OH)4 possesses extremely high specific capacity (265.9 mA h g−1 at 1 A g−1) and an excellent rate capability (with 75.5% of initial capacity at 10 A g−1). In addition, as an cathode material, flower-sphere-like Bi-Bi2Se3 materials is selected to match a new CoG@Ni3(NO3)2·(OH)4//Bi-Bi2Se3 asymmetric supercapacitor. It exhibits a specific capacity (125.1 mA h g−1 at 1 A g−1) and an impressive rate property (with 77.6% of initial capacity at 10 A g−1). Satisfactorily, the asymmetric supercapacitor device, which cleverly assembles by the above two electrode materials, achieves impressive specific energy of 54 Wh kg−1 at 760 W kg−1, and a capacitance retention rate of 80% after 4000 cycles. The excellent performance of the asymmetric supercapacitor proves that the materials possess great potential in the energy storage field.

Controlled preparation of NiCo-LDH@CuCo2O4/Ti3C2 core−shell structure for high performance asymmetric supercapacitor

ABSTRACT In this work, NiCo-LDH@CuCo2O4/Ti3C2 core–shell structured electrode materials are grown on Ni foam by hydrothermal routes. The as-prepared electrode exhibited an ultra-high gravimetric capacitance of 3480 mF cm−2 with good reversibility. The excellent performances can be attributed to the unique heterogenous structure. An asymmetric hybrid supercapacitor is assembled by using NiCo-LDH@CuCo2O4/Ti3C2 as the positive electrode and activated carbon as the negative electrode. The ASC presents high energy density (0.72 mW h cm−3 at a power density of 57.6 mW cm−3) and a capacity retention of 99.5% after 6000 cycles.

Controlled Growth of 3D Interpenetrated Networks by NiCo2O4 and Graphdiyne for High-Performance Supercapacitor.

In this paper, the 2D all-carbon graphdiyne, which possesses superior 2D strength and high mixed conductivities for both electrons and ions, is used to protect nickel cobalt oxide nanostructures with multidimensions. The in situ grown graphdiyne seamlessly wraps on nanostructures to form 3D interpenetrating networks, leading to significant improvement in the conductivity and avoidance of the structural degradation. The assembled hybrid asymmetric supercapacitor showed a high specific capacitance of 200.9 F g-1 at 1 A g-1 with an energy density of 62.8 Wh kg-1 and a power density of 747.9 W kg-1. The device also showed a preeminent rate capability (86.4% capacitance retention, while the current density was increased from 1 to 20 A g-1) and an ultrastable long-term cycling performance (the capacitance retention is about 97.7% after 10 000 cycles at a high current density of 20 A g-1).

Heteroatom-doped reduced graphene oxide integrated with nickel-cobalt phosphide for high-performance asymmetric hybrid supercapacitors

The increasing energy demand and lack of sustainable energy storage systems have attracted considerable attention towards electrochemical capacitors. Transition metal phosphides have emerged as excellent electrode materials for electrochemical capacitors because of their highly metalloid characteristics and low cost. This paper reports the synthesis of binder-free nickel-cobalt phosphide nano horns wrapped with phosphorus-doped reduced graphene oxide by a hydrothermal reaction followed by phosphorization. The nickel-cobalt phosphide nano horns are formed by the Kirkendall effect due to differences in the diffusion rates of phosphorus ions and metal sources. The as-prepared electrode delivers a high specific capacity of 264.9 mAh g−1 (2384 F g−1) at 1 A g−1 and a high rate capability of 72 % at 15 A g−1. The asymmetric hybrid supercapacitor consisted of nickel-cobalt phosphide wrapped with phosphorus-doped reduced graphene as the anode, and activated carbon as the cathode yields a good energy density of 39.7 Wh kg−1 and a high power-density of 8.82 kW kg−1 with high cycling stability of 90 % after 10,000 charge–discharge cycles. The excellent pseudocapacitive properties of the as-prepared binary metal phosphide confirms its value for widespread practical applications in electrochemical supercapacitors.

Lattice engineering exfoliation-restacking route for 2D layered double hydroxide hybridized with 0D polyoxotungstate anions: Cathode for hybrid asymmetric supercapacitors

A lattice engineering exfoliation-reassembling route is used to prepare porous layer-by-layer self-assembled nanohybrids of cobalt-chromium-layered double hydroxide (Co-Cr-LDH) intercalated with 0D polyoxotungstate anions (CCW). The CCW nanohybrids provide interconnected nanosheets morphology, highly porous stacking structure, flexible chemical composition, and exceptional electrochemical activity. The self-assembled CCW nanohybrids display a high specific capacity of 1303 C g–1 with a capacity retention of 85.43 % over 5000 cycles. An aqueous hybrid asymmetric supercapacitor (AHAS) and all-solid-state hybrid asymmetric supercapacitor (ASHAS) devices are fabricated using CCW nanohybrids and reduced graphene oxide (rGO) as cathode and anode, respectively. The AHAS device demonstrates a high specific capacitance of 167 F g–1 at 0.8 A g–1 and specific energy (SE) of 59.37 Wh kg−1 at specific power (SP) of 640 W kg−1 with capacitance retention of 91 % after 10,000 cycles. Moreover, the ASHAS device delivers high specific capacitance of 126 F g–1 at 1.92 A g–1 and SE of 44.58 Wh kg–1 at SP of 1536 W kg–1 with capacitance retention of 87 % over 10,000 cycles. The POW intercalative hybridization significantly improves the electrode activity of the CCW nanohybrids, representing an effective method for developing LDH-based nanohybrid materials.

Mesoporous nanohybrids of 2–D Cobalt–Chromium layered double hydroxide and polyoxovanadate anions for high performance hybrid asymmetric supercapacitors

An exfoliation-reassembling process is utilized to develop mesoporous intercalative nanohybrids of cationic 2-D cobalt-chromium-layered double hydroxide (Co–Cr-LDH) nanosheets and polyoxovanadate (POV) anions (Co–Cr-LDH-POV nanohybrids). The Co–Cr-LDH-POV nanohybrid displays a maximum specific capacity (SC) of 732 C g−1 at 1 A g−1, attributed to the layer-by-layer porous structures with expanded gallery height. An aqueous and solid-state hybrid asymmetric supercapacitor devices are fabricated by Co–Cr-LDH-POV nanohybrid as cathode and rGO nanosheets as an anode. An aqueous hybrid asymmetric supercapacitor (AHAS) device delivers an SC of 238.72 C g−1 at 0.8 A g−1 with a specific energy (SE) of 53.04 Wh kg−1 at 512 W kg−1 specific power (SP) and capacity retention of 85% over 10,000 cycles. Moreover, a solid-state hybrid asymmetric supercapacitor (SHAS) device displays a high SC of 148 C g−1 at 2.4 A g−1 with a SE of 27.59 Wh kg−1 at 2560 W kg−1 SP and capacity retention of 90.23% over 5000 cycles. Nevertheless, the obtained results suggest that such a new type of porous LDH-polyoxometalate (LDH-POM) based nanohybrids are useful as cathode for next-generation energy storage applications.

Facile synthesis of novel Zn5Mo2O11·5H2O nanoflowers with excellent rate capability in supercapacitors

Metal oxides are considered as promising pseudocapacitive materials with high theoretical capacitance. However, the low electric conductivity and low rate capability of metal oxides limit their practical applications in supercapacitors. Therefore, high rate capability electrode materials are highly desirable in energy storage system. In this work, a facile method has been demonstrated to synthesize novel Zn5Mo2O11·5H2O nanoflowers. Benefiting from the synergistic effects of nanoflower structure with abundant active sites and the hydrous feature with improved ion diffusion and electron transfer, the Zn5Mo2O11·5H2O nanoflowers electrode shows a capacitance of 347.3 F g−1 at a current density of 1.0 A g−1 and a state-of-the-art capacitance retention of ∼85.0% when the current density increases by 20 times (20.0 A g−1). The assembled asymmetric hybrid supercapacitor using the Zn5Mo2O11·5H2O nanoflowers electrode and active carbon electrode shows a maximum energy density of 26.7 Wh kg−1, a high power density of 15.0 kW kg−1 and a long cycling life (81.4% capacitance retention after 5000 cycles). This study sheds light on the synthesis and practical application of hydrous metal oxides with high rate capability in supercapacitors.

A binder-free facile synthetic approach for amorphous, hydrous nickel copper phosphate thin film electrode preparation and its application as a highly stable cathode for hybrid asymmetric supercapacitors

A facile and binder-free synthesis of amorphous nickel–copper phosphate thin film electrodes with nickel: copper variation by SILAR method for application as a cathode in hybrid supercapacitors.

High-Energy Asymmetric Supercapacitor Based on the Nickel Cobalt Oxide (NiCo2O4) Nanostructure Material and Activated Carbon Derived from Cocoa Pods

Nickel cobalt oxide (NiCo2O4) nanoagglomerates were effectively synthesized through a simplistic low-temperature co-precipitation technique. The obtained material was further calcined to enhance its morphological properties and reduce the size of its individual particle of agglomerates. The as-synthesized NiCo2O4 agglomerates were characterized through the employment of various techniques, which include scanning/transmission electron microscopies (SEM/TEM), X-ray diffraction, Raman spectroscopy and X-ray fluorescence spectroscopy (XRF), and thermogravimetric analysis (TGA). Electrochemical performances of the as-synthesized electrode materials evaluated in a three-electrode configuration could deliver an optimized specific capacity of 95.6 mA h g–1 at a 0.5 A g–1 specific current. A fabricated hybrid asymmetric supercapacitor (SC) composed of NiCo2O4 and the activated carbon obtained from cocoa pods (Cocoa AC-700) as the positive and negative electrodes (NiCo2O4//AC cocoa-700), respectively, delivered a specific capacity of around 168.7 mA h g–1 at 0.5 A g–1 and a corresponding specific energy and power of 47.7 W h kg–1 and 430.0 W kg–1, respectively. The SC exhibited a substantial cycling stability, resulting in a Coulombic efficiency of 97.2% with a related capacity retention of 96.6% recorded after a cycling test of over 11,000 cycles at 5 A g–1.

Sr- and Fe-substituted LaMnO3 Perovskite: Fundamental insight and possible use in asymmetric hybrid supercapacitor

The symmetry or structural stability of ABO3-type perovskite oxides depends largely on the size of ‘A’ and ‘B’ cations, which determines the material properties. The partial substitution of these cations may be used to tune these properties. The ionic sizes and valence states of the cations play an important role in improving the properties of perovskite. In this study, the substitution of La3+ with Sr2+ with a larger ionic radius and Mn3+ with Fe3+with a similar ionic radius favored both the crystal symmetry and the mixed ionic–electronic conductivity of the perovskite. Electrodes based on La0.7Sr0.3Mn0.5Fe0.5O3 (LSMFO55) exhibited a faradaic behavior with a specific capacity of 330 C g−1 (92 mAh g−1) at 12C rate, while this electrode maintained a capacity of 259 C g−1 at 240C (charge or discharge in 15 s). Additionally, exohedral carbon nano-onions (CNO) were introduced as a negative electrode to design an asymmetric hybrid supercapacitor (AHS) with a widened cell voltage. The use of CNO as a negative electrode in the AHS improved the rate capability drastically compared to the use of rGO. This device maintained a good energy density even at an extra-high charging rate (600C) owing to its outstanding rate capability. The high-rate performance of the LSMFO55//CNO AHS can be elucidated by successful fabrication with a mixed ionic–electronic conductive positive electrode and a CNO negative electrode. Tuning the electronic and ionic conductivities by cationic substitution and adopting an appropriate carbon-derived negative electrode (such as CNO) can provide a practical high-rate hybrid device using various perovskites.

Facile One-Step Microwave-Assisted Method to Synthesize Nickel Selenide Nanosheets for High-Performance Hybrid Supercapacitor

Nanosheets structures can be employed as the most promising electrode material to enhance electrochemical performance for supercapacitors. Nickel Selenide (Ni0.85Se) nanosheets are synthesized using a rapid microwave synthesis method in a single step. The Ni0.85Se nanosheets possess a high surface area (125 m2g−1) with a hexagonal crystalline structure. It shows magnificent electrochemical properties, such as splendid specific capacitance (2530 Fg-1 at 0.5 Ag−1). An asymmetric hybrid supercapacitor is fabricated with nickel selenide nanosheets as a positive electrode and activated carbon as a negative electrode. The assembled hybrid supercapacitor displays a high energy density of 63.5 WhKg−1 at a power density of 404 WKg−1, and after 8000 cycles, only 5% capacitance is lost along with the better voltage window at 0–1.6 V.