Superior Capacitive Performance Research Articles

Superior capacitive performance achieved in wide HOMO–LUMO gap cyanoethyl cellulose nanocomposites via forming a built-in electric field

The nanocomposite film exhibited superior energy storage density, which is by far the highest energy storage performance of core–shell nanocomposites reported to date.

Lamellar Hierarchical Porous Carbon Prepared from Coal Tar Pitch through a Lamellar Hard Template Combined with the Precarbonization and Activation Method for Supercapacitors

The lamellar porous carbon favors the diffusion and penetration of electrolyte ions and presents a fantastic advantage as an energy storage electrode material. In this work, the lamellar Mg5(OH)4(CO3)2·4H2O template is synthesized via a simple precipitation method in the low-temperature hydrothermal condition. Lamellar hierarchical porous carbon (LHPC) is successfully synthesized through the Mg5(OH)4(CO3)2·4H2O hard template and the KOH activation method using coal tar pitch (CTP) as the carbon source. The effects of activation temperature and activator dosage on the morphology, microstructure, and supercapacitor performance are researched at length. LHPCs-1–700 displays a good lamellar structure and an abundant mesoporous structure, so as to exhibit superior capacitive performance compared with other carbon electrodes. The specific capacitance for LHPCs-1–700 reaches 298 F g–1 at 1 A g–1 and still maintains 234 F g–1 at 50 A g–1 with a high capacitance retention of 78.5% in the three-electrode system. The kinetic behavior of the LHPCs-1–700 electrode was also analyzed according to the CV data obtained at different scan rates, and it was found that the fast kinetic capacitance contribution was up to 87% at 200 mV s–1. The assembled LHPCs-1–700 symmetric supercapacitor delivered an energy density of 16.73 W h kg–1 with a power density of 859.4 W kg–1 in 1 M Na2SO4 solution. Besides, the specific capacitance retention rate could still reach 95.8% after 8000 cycles.

Biochar for Supercapacitor Application: A Comparative Study.

Biochar is a carbon-rich solid that can be prepared through heat treatment of biomass under an inert atmosphere. In the present work, biochar prepared from different feedstocks, namely, Litchi chinensis (Litchi) seeds, Syzygium cumini (Jamun) seeds, and pine cone, were evaluated for charge storage in the form of supercapacitors. The physicochemical and electrochemical properties of the biochar were highly dependent on the preparation temperature and the choice of feedstock. Among the three feedstocks, Litchi seed-derived biochar showed the highest specific capacitance of 190 F g-1 at 1 A g-1 in a symmetric cell configuration. N and O heteroatom functionalities in the Litchi seed-derived biochar, higher specific surface area, and pore volume for electrolyte adsorption were responsible for its superior capacitive performance as compared to Jamun seeds and pine cone biochar.

Superior capacitive performance of spherical MnV2O6·2H2O-graphene nanosheet hybrid as electrode material for asymmetric supercapacitor

The evolution of advanced supercapacitors depends highly on the design and synthesis of electrodes with rational morphology and structure. In this paper, a facile methanol-assisted solvothermal method is reported for the synthesis of spherical hydrated manganese vanadate (MnV2O6·2H2O)-reduced graphene oxide (rGO) nanosheets hybrid. In particular, the utilization of methanol can not only change the isotropy growth of MnV2O6 but also suppresses the phase-transformation process (from orthorhombic to monoclinic) by preventing the deintercalation of crystal water. Remarkably, the MnV2O6·2H2O exhibits a superior specific capacity of 1678.5 F g−1 which is nearly four times more than that of MnV2O6 (410.2 F g−1) at 2 A g−1. After integrating with graphene, MnV2O6·2H2O spheres are uniformly encapsulated by graphene sheets with a size reduction from 1 μm to 200 nm. And a “GO-assisted Ostwald ripen-splitting” mechanism is proposed to explain the formation of MnV2O6·2H2O-rGO. Consequently, the MnV2O6·2H2O-rGO hybrid exhibits significantly improved conductivity, enhanced specific capacity (1976.3 F g−1 at 2 A g−1) and good rate capability (1422.5 F g−1 at 10 A g−1 and 1155.5 F g−1 at 20 A g−1) as well as excellent cycling stability (94.2% capacitance retention after 10,000 cycles). Moreover, the assembled asymmetric supercapacitor using MnV2O6·2H2O-rGO (the positive electrode) and activated carbon (the negative electrode) shows a superior energy density of 51.5 Wh⋅kg−1 at the power density of 849.2 W kg−1.

Flexible solid-state supercapacitor integrated by methanesulfonic acid/polyvinyl acetate hydrogel and Ti3C2Tx

MXenes, as a rapidly developing family of materials, have achieved promising results as solid-state supercapacitor (SSS) electrode. Investigations of optimizing MXene-based SSSs concentrate on electrode recently. However, the state-of-the-art MXene-based SSSs present inferior rate performances compared to aqueous devices. Herein, we optimize the performance of MXene-based SSS by introducing a green, low temperature resistant and highly ionic conductive methanesulfonic acid/polyvinyl acetate (MSA/PVA) hydrogel as electrolyte. The assembled SSS (FT-SSS) outperforms the one fabricated by the usual liquid electrolyte casting method, showing high areal capacitance (1719 mF cm−2), long cycle life (92%, 80,000 cycles), low-temperature resistance (-30°C) and flexibility. More importantly, FT-SSS presents superior capacitance and rate performance that exceeds the corresponding aqueous supercapacitor (AQS). The areal capacitance increases by 127% at 1000 mV s−1 compared with AQS. Energy dispersive spectroscopy maps, X-ray diffraction and X-ray photoelectron spectroscopy analysis reveal that MSA pre-intercalate into Ti3C2Tx, forming electrodes with a wrinkled and porous structure, which reduces MXene stacking effect and enhances electrolyte accessibility. -OH and H2O (physisorbed to -OH) content in Ti3C2Tx rise, too, further improving MXene pseudocapacitive performance.

Simultaneously tuning the hierarchical porous structure and graphitization degree of biomass derived carbon for supercapacitors

In this study, a series of biomass derived carbon with tunable hierachical porous structure and graphitization degree are prepared through biomass dehydration treatment combined with a one-step activation-graphitization process. Studies have shown that when the mass ratio of activator, graphitizing agent and dehydration precursor is 1:0.5:1, the derived carbon (GHPPC1-0.5) has an excellent hierarchical porous structure and a suitable graphitization degree. This unique microstructure brings it outstanding electrochemical performance, typically, the GHPPC1-0.5 possesses the superior specific capacitance (434 F g−1) and rate performance (74% capacitance retention at 20 A g−1) in three-electrode systems. The GHPPC1–0.5 based symmetric supercapacitors are assembled in aqueous electrolyte and organic electrolyte, respectively, and they both exhibit excellent energy density (28.8 and 70.5 Wh kg−1) and acceptable cycling stability (7.8 and 14.4% loss over 5000 cycles). The above positive results herald the superiority of the biomass derived carbon preparation strategy proposed in this study.

Sodium alginate-derived micropore dominated carbon 3D architectures through dual template engineering for high-performance Zn-ion hybrid capacitors

Zinc-ion hybrid capacitors (ZIHCs) represent a new generation of high-performance energy conversion equipment for their excellent energy and power densities and environmental friendliness. However, the high cost and complicated preparation process limit the application of carbon-based materials in ZIHCs, so it is advisable to design a simple strategy to fabricate advanced carbon-based electrodes. Herein, we developed sodium alginate-derived micropore dominated porous carbon (DSPCs) through a dual-template strategy. This dual-template method includes the etching of the carbon skeleton by its own sodium salt and the activation of the carbon materials by KCl. Through this strategy, the accessible surface area can be effectively increased and the pore structure can be controlled, so that DSPCs exhibit superior capacitive performance. As expected, the energy densities of the symmetric supercapacitors based on DSPCs are 10.17 and 3.8 Wh kg−1 (power densities of 150 and 6000 W kg−1), respectively. The constructed ZIHCs device preform an outstanding energy density of 99.22 Wh kg−1 (200 W kg−1) at an operating voltage of 0–1.8 V. Even the power density reaches up to 40 kW kg−1 and the energy density maintain at 5.11 Wh kg−1. This work developed a new avenue for the application of high-performance porous carbon materials in ZIHCs.

Rational design and synthesis of nickel-cobalt-manganese trimetallic hydroxides with micro-flower like for high-performance asymmetric supercapacitors

The construction of high energy density and porous micro-nano structure is suitable for fast electron/ion transport, which motivates us to design electrode materials with hierarchical structures. However, the synthesis route of multi-metal hydroxides is still restricted due to the complexity and high cost. Herein, we use a rational design constructing nickel-cobalt-manganese hydroxides (Ni–Co–Mn–OH) micro-flower structure by using the one-pot hydrothermal. The Ni–Co–Mn–OH is consisting of ultrathin stacking nanosheets with a three-dimensional multi-order micro-flower structure. And its internal nanoporous channels can stimulate electron/ion transfer. Toward the application in supercapacitor, when the molar ratio of Ni and Mn is 9.69:1, the prepared electrode presented superior capacitance performance (1135 F g−1 at 1 A g−1) and excellent rate performance 97% retention at 20 A g−1) in the three electrode system. Moreover, the asymmetric supercapacitor was also fabricated, exhibiting excellent capacitance of 115 F g−1 at 1 A g−1, high energy density of 54.375 Wh·kg−1 at a power density of 0.3758 kW kg−1. And the maximum power density could reach 7.5 kW kg−1 and the energy density at this time was 12.08 Wh·kg−1.

Copper doped CoSx@Co(OH)2 hierarchical mesoporous nanosheet arrays as binder-free electrodes for superior supercapacitors

Heteroatom doping is an effective route to boost the capacitance performance of metal sulfides-based electrode materials. Herein, an array of hierarchical 3D mesoporous Cu doped CoS x @Co(OH) 2 nanosheets (namely Cu/CoS x @Co(OH) 2 ) is successfully prepared on Ni foam through a metal-organic-framework (MOF) mediated approach. The combination of compositional merits and tuned electronic properties induced by copper doping leads to superior capacitance performance. The optimal Cu doped electrode (Cu/CoS x @Co(OH) 2 -2) displays an ultrahigh specific capacitance and outstanding rate capability, which outperforms the best values obtained on other transition metal sulfide (TMS) electrodes. And the Cu/CoS x @Co(OH) 2 -2//activated carbon (AC) asymmetric two-electrode supercapacitor device exhibits a favorable energy density of 39.25 Wh kg −1 and outstanding cycle life. X-ray photoelectron spectroscopy (XPS) results reveal that the greatly decreased binding energy barriers of two redox pairs (Co 2+ /Co 3+ and Cu + /Cu 2+ ) are beneficial to higher electrochemical performance. Density function theory (DFT) results further disclose the Cu-doping effect and the benefit of nanocomposite formation on the energy storage performance. The results provide an inspiration to the optimization of TMS-based electrodes for high performance electrochemical energy storage systems. • MOF-engaged strategy is employed to prepare Cu doped CoS x @Co(OH) 2 nanosheets. • Improved conductivity and facilitated reaction kinetics are induced by doping • Greatly decreased energy barrier between Cu + /Cu 2+ and Co 2+ /Co 3+ redox pairs. • DFT calculations disclose the doping effect and the superior capacitance. • Ultrahigh capacitance, outstanding stability and high energy density are obtained.

Synthesis of ternary CoZnAl layered double hydroxide and Co-embedded N-doped carbon nanotube hollow polyhedron nanocomposite as a bifunctional material for ORR electrocatalyst and supercapacitor electrode

The construction of non-precious and high-performance nanomaterial is the current hotspot in oxygen reduction reaction and supercapacitor applications. Herein, a novel composite consisting of a three-metal layered double hydroxide (CoZnAl-LDH) and a ZIF-derived carbon base (Co/NCNHP) is proposed, which is fabricated by the hydrothermal synthesis of CoZnAl-LDH and the in situ loading of Co/NCNHP in different ratios of 10, 20, and 30 %. The synthesized nanomaterials were evaluated by various physical and electrochemical tests. The results manifest that the addition of Co/NCNHP with a carbon nanotube hollow polyhedron morphology to the flower-like CoZnAl-LDH had a remarkable impact on its morphology and properties, such that it elevates the surface area, enhances mass and electron transfer, and improves electrical conductivity of the final product. Based on the results, the CoZnAl-LDH@Co/NCNHP 20 % indicated better electrochemical performance than other synthesized samples. This composite offered excellent ORR catalytic activity with an onset potential of −0.043 V vs. Ag/AgCl in alkaline electrolyte, 4-electrons path selectivity (average electron transfer number = 3.69), and high durability. Furthermore, it exhibited a superior capacitance performance of 869.6 F.g−1 at a current density of 1 A.g−1 and superior cycling stability (92.7 % capacitance retention at 2 A.g−1 after 1000 cycles). Therefore, according to the test results, the final as-prepared nanocomposite possesses a desirable electrochemical performance in both ORR and supercapacitor applications.

Facile fabrication of flower-like γ-Fe2O3 @PPy from iron rust for high-performing asymmetric supercapacitors

Flower-like rust with porous structure can be obtained on the Fe plate by accelerated corrosion in the marine atmosphere. A core-shell structure of γ-Fe2O3 @PPy was developed through annealing and in situ chemical polymerization of pyrrole. The dehydroxylation after annealing enriches the inherent pore structure of rust. The conductive PPy layer with the capacitive properties were found to improve the stability of iron-based anodes while enhancing the charge storage performance. The rust-based composite exhibited superior capacitance performance over the original rust. By matching with a cathode from nickel-cobalt layered double hydroxide (NiCoLDH) based porous Ni network, the asymmetric device delivered a high volumetric energy density of 7.9 mWh cm–3 at a power density of 14.99 mW cm–3, and favorable cycle stability (capacitance retention of 90.1% after 8000 cycles). Most importantly, the energy storage mechanism of rust-based electrodes with flower-like structures was discussed in detail. The recycling and reuse of rust resources were successfully realized by the direct utilization of rusted steel as anode materials for supercapacitor applications.

Capacitive Properties of Chlorine Doped Graphene Quantum Dots Anchored into Reduced Graphene Oxide

In this study, Cl-GQDs anchored into pure reduced graphene oxide (Cl-GQDs/rGO) hybrid materials were hydrothermally fabricated and characterized by various analyses. Meanwhile, P-GQDs, S-GQDs and N-GQDs were also fabricated and anchored into rGO as controls. The AFM images of Cl-GQDs, P-GQDs, N-GQDs and S-GQDs displayed the average height of 1–3 nm, 1–1.5 nm, 1.5–2.0 nm and 4.0–4.5 nm, respectively. Moreover, the absorbance and fluorescence spectra of Cl-GQDs were different from those of other doped graphene quantum dots. Cyclic voltammetry and galvanostatic charge-discharge curves were employed to analyze the capacitive performances of doped-GQDs/rGO. At the current density of 2 A g−1, the capacitance of Cl-GQDs/rGO achieved 316 F g−1, which was about 3 times, 2 times and 1.5 times as high as that of rGO, S or N-GQDs/rGO and P-GQDs/rGO, respectively. At the power density of 1.1−3.3 KW Kg−1, Cl-GQDs/rGO reached the energy density of 53.2 − 32.1 Wh Kg−1. Electrochemical impedance spectroscopy clearly indicated that Cl-GQDs could improve the conductivity of rGO in the electrochemical reaction, resulting in superior capacitive performances.

Efficient Metal-Oriented Electrodeposition of a Co-Based Metal-Organic Framework with Superior Capacitive Performance.

An efficient cathodic electrodeposition method is developed for coating Co‐based metal‐organic frameworks (Co‐MOF) on carbon fiber cloth (CFC), a widely used substrate in energy fields. The use of a highly active Co metal surface enables nucleation and growth of Co‐MOF in 3D rodlike crystal bundles. When used as a binder‐free electrode (Co‐MOF/CFC) for supercapacitors, it shows a high areal capacitance of 1784 mF cm−2 at 1 mA cm−2, good cycling stability and excellent rate capability. The assembled asymmetric all‐solid‐state supercapacitor device (Co‐MOF/CFC//AC) delivers a high energy density and power density. This work may open up an effective approach to realize the electrosynthesis of MOF films, promoting use in energy storage and conversion fields.

Enhancing high-temperature capacitor performance of polymer nanocomposites by adjusting the energy level structure in the micro-/meso-scopic interface region

The interface plays a major role in the conduction and breakdown behaviors of dielectric materials. Enhancing interface compatibility and Schottky barrier to reduce conduction loss and enhance breakdown strength of nanocomposites has been widely studied. Nevertheless, there are few reports on the effect of the energy level structure in filler/polymer and electrode/dielectric interface region on the breakdown strength and high-temperature energy storage performances. Herein, the polyimide (PI) films sandwiched by Al2O3 layers and filled with SiO2 shell-coated high-K BaTiO3 nanofibers were prepared. Our results reveal that the wide bandgap oxide layer can regulate the energy level structure of the interface region, introduce deep traps in the nanocomposites and increase the Schottky barrier at the electrode/dielectric interface to impede charge injection and transport. Moreover, the nanocomposites combine the advantages of anisotropic dielectric properties from the Al2O3 layer, SiO2 shell, and BaTiO3 core, enhancing dielectric constants of the nanocomposites. The optimal nanocomposites show greatly enhanced discharge energy density and breakdown strength at 150 °C, which are 370% and 38% higher than those of PI, respectively. This work provides more insight into the mechanism of electrical conduction and breakdown in polymer nanocomposites and offers an effective strategy for developing polymer nanocomposites with superior capacitive performance at elevated temperatures.

MOF-derived molybdenum selenide on Ti3C2Tx with superior capacitive performance for lithium-ion capacitors

MOF-derived molybdenum selenide on Ti3C2Tx with superior capacitive performance for lithium-ion capacitors

Superior capacitive performance of micropore-dominant porous carbon derived from biomass wastes

A series of porous carbon materials with rich O-containing groups are facilely fabricated from the poplar catkin biomass wastes. The optimal KAPC-700-2, which is prepared under the conditions of calcination temperature 700 °C and a mass ratio of 1:2 for the pre-carbonized carbon to activation agent (K2CO3), possesses a micropore-dominant porous network. Benefitting from the hierarchical porous network with a large specific surface area (1410 m2 g−1) and high O-doping amount (11.99 at.%), KAPC-700-2 displays excellent capacitive performance. The corresponding specific capacitance is 278.0 F g−1 at 1.0 A g−1 in the three-electrode system, as well as remarkable rate capability. The energy density in the assembled symmetrical devices (40.5 Wh kg−1 at 0.27 kW kg−1) is superior to many previous results. Other than that, KAPC-700-2 exhibits high cycling stability with a 105.8% capacitance retention in the 30,000th charge/discharge cycle at 1.0 A g−1. Our work offers a good strategy to produce porous carbon from annoying bio-wastes for advanced electrochemical energy storage devices.

Superior capacitive performance of nitrogen-doping three-dimensional hydrangea-like porous carbons derived from oxidized coal tar pitch polymerized p-phenylenediamine

Nitrogen-doping three-dimensional hydrangea-like porous carbons (NHPCs) were prepared by coal tar pitch oxidized by KMnO4 (OCTP) as carbon precursor and p-phenylenediamine (pPDA) as nitrogen source. The terminal amine group on the pPDA and the oxygen-containing functional group on the OCTP were grafted together by chemical oxidative polymerization. Not only successfully achieved nitrogen-doping, but also the benzene ring in pPDA could occupy the branching space of polycyclic aromatic hydrocarbons in OCTP and reduce its irreversible accumulation. The as-prepared NHPCs showed a unique three-dimensional hydrangea-like structure, which could provide large specific surface area (2237 m2 g−1), abundant micro/mesopores and high nitrogen content (3.7%). Remarkably, NHPC-600 exhibited excellent electrochemical performance as the electrode material of supercapacitors, such as a high specific capacitance up to 423 F g−1 at 0.1 A g−1 and long cycle stability (maintaining 94.3% of the initial capacitance after 10,000 cycles) in 6 M KOH. Simultaneously, NHPC-600 achieved a higher working voltage (3.6 V) in EMIMBF4 electrolyte, thereby obtaining a high energy density (56.4 Wh kg−1).

Enhanced hydrogen storage and superior capacitive performances of ball milled PMMA/h-BN core–shell nanocomposite

Enhanced hydrogen storage and superior capacitive performances of ball milled PMMA/h-BN core–shell nanocomposite

Triple capacitance via the dehydration of saturated water from carboxylated chitosan bearing zwitterion electrolytes

BackgroundIn the solid-state polymer electrolyte, the saturated water plays an role in increasing ionic conductivity but decreasing the electrochemical window. The water retention effect on zwitterionic polymer electrolyte is investigated in this study. MethodsCarboxylated chitosan (CCS) was subjected to oxa-Michael addition with sulfobetaine methacrylate (SBMA) to produce CCS-SBMA. Its structure was investigated by IR and 1H NMR and used the raman spectrum to observe three different types of water. CCS-SBMA electrolyte and carbon electrode were assembled into supercapacitor for electrochemical testing. Significant findingsCCS-SBMA was grafted 45.7% of sulfobetaine group via Nuclear Magnetic Resonance (NMR) spectra. During dehydration of saturated water from CCS-SBMA polymer electrolyte to 90% retention, the free water proportion decreased, and the bound water proportion increased via Raman spectra analysis. Accordingly, the electrochemical window increased from 1.6V to 2.05V with 10% dehydration of saturated water. Surprisingly, the supercapacitor performance with 90% water retention showed triple specific capacitance of 414.3F/g in comparison with 138.6F/g evaluated from galvanostatic charge-discharge analysis. In this study, CCS-SBMA bearing zwitterion was designed as polymer electrolyte to remain bound water proportion and enhance ion-dissociation during dehydration of saturated water for superior capacitance performance of solid-state supercapacitor.

High-voltage and wide temperature aqueous supercapacitors aided by deep eutectic solvents

• DES can expand the voltage and operating temperature range of aqueous supercapacitors; • DFT is applied for electrolyte design, optimization and theoretical calculation; • Adjusting the molar ratio of DES and water can influence on the structure and performance of electrolyte; • DES exhibits important potential for high-performance aqueous supercapacitors. For water supercapacitors, how to realize high voltage and wide temperature range operation is of great theoretical and practical significance. In this work, introducing a deep eutectic solvent (DES) composed of choline chloride (ChCl, as hydrogen bond acceptor) and ethylene glycol (EG, as hydrogen bond donor) into H 2 O (as co-hydrogen bond donor) produces DES-H 2 O electrolyte. Furthermore, density functional theory (DFT) can design and verify the DES system. The experimental results show that the molar ratio of DES plays a decisive role in the solvent structure and supercapacitor performance. When the molar ratio of ChCl, EG and H 2 O is 1:2:2, the DES structure is the most stable, the total energy is the largest (49.93 eV), also exhibiting the high voltage window of 2.4 V, and the wide temperature range of − 40 to 80 °C. In the meanwhile, superior capacitive performance also occurs with specific capacity of 202 F g −1 , energy density of 40.3 Wh kg −1 and cyclability (98.51% after 10,000 cycles) The present DES-H 2 O electrolyte has the advantages of low price, easy synthesis, good water resistance and high electrochemical performance, which makes it have large application potential in the field of supercapacitors.