Energy Density Hybrid Supercapacitor Research Articles

High energy density hybrid supercapacitors derived from novel Ni3Se2 nanowires in situ constructed on porous nickel foam

A novel Ni3Se2 nanowires are synthesized in situ on the surface of nickel foam through a one-step hydrothermal reaction under the reaction time of 24 h, and it demonstrates excellent energy storage performance for hybrid supercapacitors.

High energy density hybrid supercapacitor based on cobalt-doped nickel sulfide flower-like hierarchitectures deposited with nitrogen-doped carbon dots

The exploration of advanced electrode materials with outstanding electrochemical properties is of considerable importance for hybrid supercapacitors but challenging. In this paper, an effective two-step solvothermal route is demonstrated to synthesize nitrogen-doped carbon dots (NCDs) decorated cobalt-doped nickel sulfide (Co-NiS) flower-like hierarchitectures. Because of the modification with NCDs and doping by cobalt atoms, the resulting Co-NiS/NCDs hierarchitectures exhibit an ultrahigh specific capacity up to 1240 C g-1 (2480 F g-1) at 1 A g-1 and a remarkable rate capability of 790.8 C g-1 (1581.6 F g-1) even at 20 A g-1 when used as advanced electrodes for supercapacitors. More significantly, coupling with ap-phenylenediamine (PPD) modified reduced graphene oxide (rGO) anode, a hybrid supercapacitor device is successfully constructed, which possesses an impressive energy density of 71.6 W h kg-1 at 712.0 W kg-1 and a decent cyclic stability with 78.3% retention after 12 000 cycles at 5 A g-1. The dual improvement strategy may provide insight to rational engineering of novel electrode materials with multi-components for high-performance hybrid supercapacitors.

An unexpected phase-transformation of cobalt–vanadium layered double hydroxides toward high energy density hybrid supercapacitor

Vanadium-based active materials have attracted attention due to their superior characteristics such as multivalent oxidation state and low cost. Here, we report a cobalt-vanadium layered double hydroxide that can be used in a high energy density hybrid supercapacitor electrode. The molar ratio of the cobalt and vanadium is controlled to enhance the charge storage performance of the proposed cathode material. The cobalt-vanadium layered double hydroxide exhibits a high specific capacitance of 1579 F g−1 at 1 A g−1 current density. We determine that this high performance is attributed to an unexpected phase transform occurring in the layered double hydroxide, which is not observed in mono metal hydroxides, during the electrochemical charging process using soft X-ray-based advanced analysis. An aqueous hybrid supercapacitor based on our cathode material shows a maximum energy density of 75.71 Wh kg−1 at a power density of 1043.72 W kg−1 with superior cycle stability (82% after 10000 cycles).

Ultra-High Energy Density Hybrid Supercapacitors Using MnO2/Reduced Graphene Oxide Hybrid Nanoscrolls.

Manganese oxide (MnO2) is a promising material for supercapacitor applications, with a theoretical ultra-high energy density of 308 Wh/kg. However, such ultra-high energy density has not been achieved experimentally in MnO2-based supercapacitors because of several practical issues, such as low electrical conductivity of MnO2, incomplete utilization of MnO2, and dissolution of MnO2. The present study investigates the potential of MnO2/reduced graphene oxide (rGO) hybrid nanoscroll (GMS) structures as electrode material for overcoming the difficulties and for developing ultra-high-energy storage systems. A hybrid supercapacitor, comprising MnO2/rGO nanoscrolls as anode material and activated carbon (AC) as a cathode, is fabricated. The GMS/AC hybrid supercapacitor exhibited enhanced energy density, superior rate performance, and promising Li storage capability that bridged the energy–density gap between conventional Li-ion batteries (LIBs) and supercapacitors. The fabricated GMS/AC hybrid supercapacitor demonstrates an ultra-high lithium discharge capacity of 2040 mAh/g. The GMS/AC cell delivered a maximum energy density of 105.3 Wh/kg and a corresponding power density of 308.1 W/kg. It also delivered an energy density of 42.77 Wh/kg at a power density as high as 30,800 W/kg. Our GMS/AC cell’s energy density values are very high compared with those of other reported values of graphene-based hybrid structures. The GMS structures offer significant potential as an electrode material for energy-storage systems and can also enhance the performance of the other electrode materials for LIBs and hybrid supercapacitors.

A systematic approach to achieve high energy density hybrid supercapacitors based on Ni–Co–Fe hydroxide

Recently, ternary metal compounds have received substantial attention owing to their remarkable characteristics such as multiple valence states and a high electrochemical activity. Herein, we propose and validate a nickel–cobalt–iron (NCF) hydroxide cathode material for use in high energy density hybrid supercapacitors. The molar ratio of the NCF compounds was controlled and systematically studied to improve the electrochemical performance of the proposed cathode material. A high nickel ratio can enhance the specific capacitance of the metal hydroxide, and cobalt increases the rate capability. High nickel-based NCF hydroxide exhibits a high specific capacitance of 1321 F g−1 at a current density of 1 A g−1 with 57.7% capacitance retention observed at 20 A g−1. An aqueous HSC based on NCF hydroxide and activated carbon exhibits a high energy density (73.07 Wh kg−1) at a power density of 1.07 kW kg−1 with remarkable cycle stability (75.5% after 50,000 cycles).

Designing of ultra-long-life hybrid supercapacitor based on advanced battery-type electrochemical performance from porous nanostructured nickel-doped bimetallic spinel electrodes

Engineering novel hierarchical nanostructure-based electrode materials with higher surface area remains a great challenge in energy storage field to achieve higher energy density hybrid supercapacitor for portable electronic applications. Herein, mono or mixed/bimetallic Co3O4, ZnCo2O4 and nickel (Ni) ions incorporated ZnCo2O4 (Ni0·05Zn0·95Co2O4) spinels with porous nanostructures were prepared via a simple eco-benign novel wet-chemical approach, followed by calcination. The Ni0·05Zn0·95Co2O4 composite revealed the hierarchical hollow nanospindles with a high specific surface area, and it has the ability to supply more electroactive sites for the diffusion of aqueous electrolyte ions, further assisting the electron transportation in electrochemical analysis. In particular, the Ni0·05Zn0·95Co2O4@Ni foam (NF) electrode revealed a battery-like electrochemical feature and exhibited the specific capacity of ∼138 mA h g−1 which is dramatically higher than the ZnCo2O4@NF (∼56 mA h g−1) and Co3O4@NF (∼34 mA h g−1) electrodes at 1 A g−1 due to the strong synergistic effect of Ni and Co ions and rapid reaction kinetics. Additionally, a pouch-type Ni0·05Zn0·95Co2O4@NF//commercial activated carbon@NF hybrid supercapacitor device showed maximum energy and power densities of ∼54.9 W h kg−1 and ∼6105 W kg−1, respectively. Impressively, the fabricated device further exhibited an ultra-long cycling life (114% capacitance retention after 15000 cycles) and successfully demonstrated its real-time portable electronic applications.

One-step deposition of a Ni(OH)2-graphene hybrid prepared by vacuum kinetic spray for high energy density hybrid supercapacitor

Hybrid supercapacitors (HSCs) that use the nickel hydroxide-graphene hybrid (NGH) as an anode material and reduced graphene oxide (rGO) as a cathode material are a promising HSC structure. The NGH electrode is synthesized by one-step, binder-free deposition of a micro-size hydroxide powder and graphite powder mixture on nickel foam by the nanoparticle deposition system (NPDS). The NPDS is classified as a vacuum kinetic spraying approach. The electrochemical performance of the NGH-10 electrode in a 3-electrode cell demonstrates a specific capacitance of 3408 F/g at 1 A/g. The NGH-10//rGO HSC displays a specific capacitance of 180 F/g at 1 mA/cm2 in a high operating potential from 0 V to 1.6 V. The NGH-10//rGO HSC has an energy density of 64 Wh/kg @ 411 W/kg, and still 20 Wh/kg @ 8230 W/kg.

Synergistic Effects of Cobalt Molybdate@Phosphate Core-Shell Architectures with Ultrahigh Capacity for Rechargeable Hybrid Supercapacitors.

Designing binder-free and core-shell-like electrode materials with synergistic effects has attracted widespread attention for the development of high energy density hybrid supercapacitors (HSCs). Herein, binder-free cobalt molybdate nanosheet-laminated cobalt phosphate micropetals on nickel foam (CoM NS@CoP/NF) were facilely prepared for use as an effective battery-type electrode in HSCs. With the multifunctional features, the rationally combined core-shell-like CoM NS@CoP/NF electrode exhibited a maximum capacity of 886.8 μA h/cm2 at a current density of 5 mA/cm2 with a good rate capability of 64.2% and cycling stability of 87.4% (after 10 000 cycles). The high electrochemical performance of the hybrid composite could be attributed to the synergistic effects of hierarchical architectures and large accessible electroactive area, which facilitates the fast electron/transportation within the active material and accelerates the redox chemistry process. Utilizing the superior energy-storage properties, a pouch-type HSC was fabricated with core-shell-like CoM NS@CoP-6 h architectures as a battery-type electrode and activated carbon as a capacitive-type electrode in an aqueous alkaline electrolyte. The miniature hybrid device exhibited maximum energy and power densities of 0.44 mW h/cm2 and 40.35 mW/cm2, respectively, with good cycling stability. Moreover, the HSCs can energize various portable electronic equipments, which demonstrates their suitability for real-time applications.

Hierarchical CoGa layered double hydroxides grown on nickel foam as high energy density hybrid supercapacitor

Hierarchical cobalt gallium layered double hydroxide microns flower and sheet was in situ gown on Ni foam via a facile and one-step hydrothermal method. The capacity of preparing Co-Ga-layered double hydroxides (Co-Ga-LDH), as supercapacitor electrode, was evaluated via three electrode system. And different feeding ration of cobalt and gallium was attempted to optimize the better capacity performance. The as-obtained Co-Ga (1:1)-LDH hybrid shows the enhanced the specific capacity 1431.5 C/g at current density of 1 A/g and approximately 74% initial capacity at current density of 20 A/g. A hybrid supercapacitor was assembled consisting of Co-Ga-LDH and reduced graphene (rGO), which show the high energy density 68.07 Wh/kg at power density 825 W/kg. To our best knowledge, it is the first time that cobalt gallium layered double hydroxides was prepared and studied in energy storage field.

High energy density hybrid supercapacitor based on 3D mesoporous cuboidal Mn2O3 and MOF-derived porous carbon polyhedrons

Nowadays, it is highly desired to design and fabricate efficient and cost-effective electrode materials for energy conversion and storage devices. Manganese oxides are remarkable electrode material for pseudocapacitors due to their ideal capacitive behaviour, low cost and environmental friendliness. However, low conductivity and poor cycling stability remain major challenges for their commercialization. Herein, we demonstrate the direct growth of mesoporous cuboidal Mn2O3 via a one-step hydrothermal approach on the highly conductive surface of nickel foam (Mn2O3@NF) as a high-performance binder-free electrode material for supercapacitors(SCs). The as-prepared cuboidal Mn2O3 possesses high specific surface area and mesoporous feature which lead to larger number of active sites and improve the electrochemical storage activity. As a result, excellent pseudocapacitive performance is achieved with remarkably enhanced capacitance of 791 Fg-1 at 5 mVs-1 and good cycling stability is observed with retaining 92.5% of its initial capacitance after 5000 continuous charging-discharging cycles. Furthermore, a hybrid SC has been fabricated using Mn2O3@NF as a positive electrode and metal-organic framework (MOF) derived mesoporous carbon as a negative electrode. The hybrid Mn2O3@NF//MC device can operate with a large working potential window of 0.0–1.6 V, which leads to a specific energy density of 112.82 Wh kg−1 at a moderate power density of 320 W kg−1 and also exhibits excellent cycling capability with retaining 86.73% of the original capacitance after 5000 cycles, which is comparable than most of previously reported manganese oxide based SCs. The experimental results show that the Mn2O3@NF can offer great potential for practical energy storage applications.

High Volumetric Energy Density Hybrid Supercapacitors Based on Reduced Graphene Oxide Scrolls.

The low volumetric energy density of reduced graphene oxide (rGO)-based electrodes limits its application in commercial electrochemical energy storage devices that require high-performance energy storage capacities in small volumes. The volumetric energy density of rGO-based electrode materials is very low due to their low packing density. A supercapacitor with enhanced packing density and high volumetric energy density is fabricated using doped rGO scrolls (GFNSs) as the electrode material. The restacking of rGO sheets is successfully controlled through synthesizing the doped scroll structures while increasing the packing density. The fabricated cell exhibits an ultrahigh volumetric energy density of 49.66 Wh/L with excellent cycling stability (>10 000 cycles). This unique design strategy for the electrode material has significant potential for the future supercapacitors with high volumetric energy densities.

A Mn/Co-oxide electrode for potential use in high energy density hybrid supercapacitors

A simple and inexpensive thermal pyrolysis method was used at the laboratory-scale to produce a high charge-storage Mn/Co-oxide electrode for hybrid supercapacitors. The material was investigated using galvanostatic charge-discharge (GCD), SEM, EDX, XPS and XRD. The Mn/Co-oxide exhibited a highly porous and intricate microstructure which allowed for high charge storage (capacitance). NaOH, LiOH, NaClO4 and LiClO4 electrolytes were employed and it was concluded that the pH, the type of anion and the size of cation played a large role in the resulting charge storage capability of the material. The highest capacitance of 4500 ± 60 mF cm−2 (1.38 mAh cm−2) was observed in 1.0 M LiOH at a current density of 0.4 mA cm−2. The high apparent capacitance was due to intercalation of cations (Na+ or Li+) into the crystalline structure of the Mn0.5Co0.5-oxide phase, rendering the electrochemical behavior of the metal-oxide closer to that of Li-ion battery electrodes than to pure supercapacitors.

High Energy Density Hybrid Supercapacitor: In-Situ Functionalization of Vanadium-Based Colloidal Cathode.

A novel and creative in-situ electrochemical activation method to transform vanadium ions to highly electroactive colloidal cathode in KOH solution under electric field has been designed. After undergoing electrochemical reaction, the in-situ-functionalized vanadium-based colloidal cathode can adapt their geometrical structure to the high pseudocapacitive activity. The vanadium-based colloids//activated carbon asymmetric supercapcitor displays a high energy density of 50.4 Wh/kg at a power density of 250 W/kg, which is higher than most reported vanadium-based supercapacitors. The main advantage of this system is that the materials synthesis and the device operation are performed in the same reactive environment. The obtained vanadium-based colloids can display high V3+ cation utilization ratios of about 100% for one-electron redox reactions. The present results highlight a new area of research on in-situ formation of reactive electrode materials under realistic environments, which can bring new chemistry and new structures of materials that are only present under the current in-situ reactive conditions.