The development of high-performance supercapacitors (SCs) often faces some contradictory and competing requirements such as excellent rate capability, long cycling life, and high energy density. One ...effective strategy is to explore electrode materials of high capacitance, electrode architectures of fast charge and mass transfer, and electrolytes of wide voltage window. Here we report a facile and readily scalable strategy to produce high-performance N-doped graphene with a high specific capacitance (∼390 F g−1). A symmetric SC device with a wide voltage window of 3.5 V is also successfully fabricated based on the N-doped graphene electrode. More importantly, the as-assembled symmetric SC delivers a high energy density of 55 Wh kg−1 at a power density of 1800 W kg−1 while maintaining superior cycling life (retaining 96.6% of the initial capacitance after 20,000 cycles). Even at a power density as high as 8800 W kg−1, it still retains an energy density of 29 Wh kg−1, higher than those of previously reported graphene-based symmetric SCs.
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•N-doped graphene with 3D porous architecture was successfully prepared.•The electrode delivered high specific capacitance and excellent cycling stability.•The symmetrical supercapacitor achieved a remarkable energy and power density.
Battery-supercapacitor hybrid (BSH) device is one of the most promising candidates for next advanced energy storage systems because it can bridge the performance gap between lithium ion batteries and ...conventional capacitors. Herein, we report a novel porous core-shell structured Fe2O3@Fe3C@C nanochains and urchin-like Ni–Co carbonate hydroxide hybridized (denoted as NiCo–CHH) microspheres for advanced battery-type supercapacitors. The as-obtained Fe2O3@Fe3C@C anode shows high specific capacity (611 C g−1) and good rate capability. The fabricated NiCo–CHH cathode delivers high specific capacity (814 C g−1) and excellent cycling stability. When assembled into a battery-type supercapacitor, the NiCo–CHH//Fe2O3@Fe3C@C device delivers a high energy density (95.2 Wh kg−1) and excellent cycling stability. Moreover, In situ Raman spectroscopy proves the reversibility of the NiCo–CHH electrode, and the synergistic effects of Ni and Co ions, further revealing its energy storage mechanism. These findings provide a novel insight on high-performance battery-type supercapacitors.
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•The Fe2O3@Fe3C@C nanochains are successfully constructed, exhibiting high capacity.•The NiCo–CHH electrode exhibits outstanding electrochemical performance.•The charge storage behaviour of NiCo–CHH is probed by in situ Raman spectroscopy.•The battery-type supercapacitor demonstrates high energy storage capability.
Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique ...nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoO x ) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoO x /NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon–graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.
Aqueous rechargeable batteries present desired properties of considerable energy density, low-cost and high safety for large-scale energy storage systems. However, the scarcity of available negative ...electrode materials with high capacity and satisfying cycling life still hinders their development. Here, we report a novel tunnel structured KCu7S4 negative electrode material for aqueous rechargeable batteries. The structural evolution and charge storage mechanism of the KCu7S4 is successfully studied by using ex-situ XPS and XRD. The charge storage can be attributed to the deep oxidation of Cu+ into Cu2+/Cu3+ and the good reversible reaction. The electrochemical induced irreversible phase transformation of Cu7S4 into Cu1.96S is mainly responsible for the capacity degradation of the KCu7S4 electrode. Fortunately, the optimized KCu7S4/rGO composite electrode shows good electrochemical performance and the fabricated full cell delivers good energy storage capability. These findings can broaden the horizon of negative elctrode materials and endow new opportunities for the fabrication of advanced rechargeable batteries.
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•The structural evolution and energy storage mechanism of KCu7S4 are successfully understood.•The KCu7S4/rGO composite delivers high capacity and good rate capability.•The fabricated Ni(OH)2//KCu7S4/rGO battery exhibits good energy storage capability.
Anion and cation substitution is an effective way in modulating electrochemical properties of electrode materials to achieve enhanced performance. Herein, we report our finding in the fabrication of ...advanced binder-free supercapacitor electrodes of hierarchical anion- (phosphorus-) and cation- (zinc- and nickel-) substituted cobalt oxides (denoted as ZnNiCo-P) architectures assembled from nanosheets grown directly on Ni foam. In contrast to the reference Co-P systems, the as-prepared electrode manifests a markedly improved electrochemical performance with a high specific capacity of ~ 958 C g−1 at 1 A g−1 and an outstanding rate capability (787 C g−1 at 20 A g−1) due to its compositional and structural advantages. Density functional theory calculations confirm that the Co species partially replaced by Zn/Ni and O species by P can simultaneously improve the charge transfer behavior and facilitate the OH- adsorption and deprotonation/protonation reaction process. Moreover, an aqueous hybrid supercapacitor based on self-supported ZnNiCo-P nanosheet electrode demonstrates a high energy density of 60.1 Wh kg−1 at a power density of 960 W kg−1, along with a superior cycling performance (89% of initial specific capacitance after 8000 cycles at 10 A g−1 is retained). These findings offer insights into the rational design of transition metal compounds with multi-components and favorable architectures by manipulating the cations and anions of metal compounds for high-performance supercapacitors.
A high-performance mix-metal phosphide nanosheet electrode enables excellent capacity, rate capability, and cycle stability of hybrid supercapacitors. The electrode is composed of hierarchical Zn and Ni co-substituted Co phosphide nanosheet arrays grown on porous Ni foam. Display omitted
•Hierarchical ZnNiCo-P nanosheet arrays grown directly on Ni foam are constructed for the first time.•The resultant binder-free electrodes manifest outstanding electrochemical performances.•The synergetic contribution and structural features together contribute to outstanding electrochemical performance.•The assembled ZnNiCo-P//PPD-rGOs hybrid supercapacitor achieved a high energy density of 60.1 W h kg−1 at a power density of 960 W kg−1.
In situ Raman spectroscopy is a powerful technique for probing the structure and phase composition of the electrode materials that are undergoing charge-discharge process. Herein, the charge storage ...mechanism of as-prepared Ni(HCO3)2 nanomaterial is successfully studied by using the in situ Raman spectroscopy. The charge storage can be attributed to the deep oxidation of Ni2+ into Ni3+, and the irreversible phase transformation of γ-NiOOH into disordered β-Ni(OH)2 damages the crystal structure of Ni(HCO3)2, arousing the capacity loss of the electrode during the long-term cycling process. Under the guidance of the experimental investigations, a porous Ni(HCO3)2/reduced graphene oxide (rGO) nanocomposite is designed and synthesized, exhibiting ultrahigh specific capacity (846 C g−1) and excellent rate capability (618 C g−1 at 20 A g−1). When coupled with an negative electrode based on rGO, the resulting hybrid supercapacitor shows an ultrahigh energy density of 66 Wh kg−1 at power density of 1.9 kW kg−1 and good cycling stability. These findings provide important insight into the mechanism of charge storage, and scientific basis for design of high-performance energy storage materials.
A porous Ni(HCO3)2/rGO nanocomposite used as a positive electrode for hybrid supercapacitor delivers high energy density, superior rate capability and good cycling stability. The energy storage behavior and structural evolution of the Ni(HCO3)2 nanomaterial are carefully investigated using in situ Raman spectroscopy. Display omitted
•The Ni(HCO3)2/rGO nanocomposite was successfully prepared, demonstrating high capacity and excellent rate performance.•The energy storage mechanism of the Ni(HCO3)2 is investigated by using in situ Raman spectroscopy.•The hybrid supercapacitor demonstrates ultrafast energy storage capability.
Manganese oxides are regarded as promising cathode materials for aqueous zinc ion batteries (ZIBs) due to their low cost and high theoretical capacity. However, their practical application is ...seriously hindered because of the inferior electronic conductivity, sluggish diffusion kinetics and structural instability. Herein, we develop a new K-preintercalated MnO2 (K0.19MnO2·0.56H2O, KMO) nanosheet by a facile hydrothermal method. Preintercalation of K+ ions into the MnO2 crystal layers with structural reconstruction can activate more active sites, strengthen the crystal structural stability and facilitate the insertion/extraction of Zn2+ ions. The charge shielding effect of crystal water promotes the diffusion kinetics of Zn2+ ions. The obtained KMO electrode delivers high specific capacity (107 mAh g−1) and good cycling stability (~87.5% capacity retention after 2000 cycles), revealing its potential application for aqueous ZIBs.
Currently, energy storage systems are of great importance in daily life due to our dependence on portable electronic devices and hybrid electric vehicles. Among these energy storage systems, hybrid ...supercapacitor devices, constructed from a battery-type positive electrode and a capacitor-type negative electrode, have attracted widespread interest due to their potential applications. In general, they have a high energy density, a long cycling life, high safety, and environmental friendliness. This review first addresses the recent developments in state-of-the-art electrode materials, the structural design of electrodes, and the optimization of electrode performance. Then we summarize the possible classification of hybrid supercapacitor devices, and their potential applications. Finally, the fundamental theoretical aspects, charge-storage mechanism, and future developing trends are discussed. This review is intended to provide future research directions for the next generation of high-performance energy storage devices.
Supercapacitors are promising devices for highly efficient energy storage and power management. A notable improvement in performance has been achieved through recent advances in understanding charge ...storage mechanism and the development of advanced nanostructured materials. Here, by combining experimental and theoretical investigations, we have unveiled the detailed charge storage mechanism of KCu7S4 wires based on a flexible all-solid-state supercapacitor. KCu7S4 with a unique double-tunnel structure and excellent conductivity exhibits outstanding properties as an electrode material in supercapacitors. Both electrochemical experiments and DFT calculations show that the stable energy storage process is mainly contributed by potassium ions׳ insertion/extraction, where potassium ions are proved to have been more active than lithium ions in the redox reactions on the KCu7S4 electrodes. The flexible supercapacitor based on the KCu7S4/Graphene paper is low-cost, easy to fabricate and environmentally friendly. The understanding for the charge storage presented in this work would guide the improvement on supercapacitor and exploration of new electrode materials.
KCu7S4 with unique double-tunnel structure and excellent conductivity exhibits outstanding properties as a redox active material in supercapacitors. The diffusion paths of K+, Li+ and H+ in the KCu7S4 tunnels are reported based on the density functional theory, thermodynamic analysis and nudged elastic band method.
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•KCu7S4 with unique double-tunnel structure and excellent conductivity exhibits outstanding electrochemical properties.•The diffusion paths of K+, Li+ and H+ in the KCu7S4 tunnels are reported based on the theoretical analysis.•A highly flexible all-solid-state supercapacitor is fabricated based on the KCu7S4/Graphene paper electrodes.
The electrochemical performance of the electrode material for supercapacitor is influenced by several factors and could be facilitated by a particular morphology. A reasonable morphology can provide ...more active sites and larger specific surface area, and increase the ion transport rate. Herein, NiCo
2
Se
4
with hollow nanobamboo shoot (NBS) structure is prepared by a two-step hydrothermal process and the formation of hollow structure is due to the Kirkendall effect. The NiCo
2
Se
4
synthesized with optimal conditions achieves a high specific capacitance of 6.21 F cm
−2
at a current density of 1 mA cm
−2
, and the cycling stability of NiCo
2
Se
4
is as high as 76% after 5000 cycles at 20 mA cm
−2
. The designed NiCo
2
Se
4
//AC supercapacitor can achieve an energy density of 24.9 Wh kg
−1
at a power density of 537.04 W kg
−1
. All of the above demonstrate that NiCo
2
Se
4
bamboo shoot-like structure has a promising application in supercapacitor.
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