Electrochemical Capacitive Performance Research Articles

Hierarchical NiCo2O4@NiCo2S4 Nanocomposite on Ni Foam as an Electrode for Hybrid Supercapacitors.

In this work, NiCo2O4@NiCo2S4 nanocomposite with a hierarchical structure is prepared by a multistep process. First, NiCo2O4 nanowires array on Ni foam is prepared by a hydrothermal and a subsequent calcination process. Then, the NiCo2O4 nanowires array is converted to NiCo2O4@NiCo2S4 nanocomposite through a vapor-phase hydrothermal process. The NiCo2O4@NiCo2S4/Ni foam electrode exhibits a specific capacitance of 1872 F g–1 at 1 A g–1, a capacitance retention of 70.5% at 10 A g–1, and a retention ratio of 65% after 4000 charge–discharge cycles. The capacitance of NiCo2O4@NiCo2S4 nanocomposite is much higher than that of the NiCo2O4 nanowires array. The excellent electrochemical capacitive performances of the NiCo2O4@NiCo2S4 nanocomposite can be attributed to the hierarchical nanostructure, which can provide large surface areas and short diffusion pathways for electrons and ions. By using the NiCo2O4@NiCo2S4/Ni foam as the positive electrode and activated carbon/Ni foam as the negative electrode, a hybrid supercapacitor device is fabricated. The device achieves an energy density of 35.6 W h kg–1 and a power density of 1.5 kW kg–1 at 2 A g–1.

In-depth study of electrochemical capacitor performance of MnO2 during phase transition from Ramsdellite-MnO2 to Birnessite-MnO2

In this work, we report a birnessite-MnO2/ramsdellite-MnO2/F_SnO2 (FTO) composite planar electrode with 3D peony-like micro-structure for micro-supercapacitors (m-SCs), which is prepared via an original series resistor electrochemical deposition (SRED) of MnO2 and subsequent secondary-growth. The composite electrode achieves an excellent specific capacitance of 1261 F g-1 at 10 A g−1 and extraordinary cycling stability with a significant 304% capacity retention after 10000 GCD cycles. Different from conventional cases, even though it is Mn+4, the MnO2 prepared by the SRED would undergo a secondary-growth with phase transition process during the GCD cycling, which could dramatically improve the pseudocapacitance performance by surface/inner-surface and diffusion-controlled insertion capacity aspects. The mechanism is in-depth discovered by deconvolution of double-layer and Faradaic insertion capacity at different stages of the phase transition, and first principle calculation based on density functional theory (DFT). The secondary-growth process also offers a fabulous self-repairing feature of the SC electrode materials, which caters the maintenance-free and long-life requirement of the m-SCs application. Scan rate dependency of the bulk and the surface/near-surface pseudocapacitance is confirmed via de-convoluted the total capacities and the redox peaks of CV curves with different scan rates.

An all-in-one material with excellent electrical double-layer capacitance and pseudocapacitance performances for supercapacitor

3D porous nitrogen-doped graphene nanosheets (PNGs) are facilely prepared via a simple one-step segmented thermal annealing method, using graphene oxide (GO) as carbon source, urea as nitrogen source and pore generator. During the pyrolysis process at 300 °C, urea and oxygenous groups on GO sheets can release large amounts of gas such as NH3, HCNO and H2O, which act as pore generators to tear and strike GO nanosheets to form 3D porous nanostructured material. When the temperature is increased up to 800 °C, a large amount of nitrogen-containing gas can react with the functional groups on GO. Consequently, the pore forming and nitrogen doping processes of GO are successfully realized and 3D PNGs are prepared. The research results show that the PNGs with an optimal N-doping content of 6.9% display a high surface area of 490.2 m2 g−1 and excellent electrochemical capacitive performance. The outstanding electrical double-layer capacitance and the increasing pseudocapacitance are attributed to the large specific surface area and the high nitrogen content, respectively. In 1 M H2SO4 electrolyte, the PNGs exhibit a specific capacitance of 337.0 F g−1 and a low capacitance loss of 2.4% after 5000 cycles. Moreover, a symmetric supercapacitor with a cell voltage of 1.3 V is assembled, which displays both high energy density and high power density of 19.9 W h kg−1 and 650 W kg−1, respectively. The all-in-one material with excellent electrical double-layer capacitance and pseudocapacitance is promising in supercapacitor.

Plasma-tuneable oxygen functionalization of vertical graphenes enhance electrochemical capacitor performance

Vertical Graphene Nanosheets (VGN) is one of the most promising energy storage materials in particular for electrochemical capacitor electrode applications. Yet, the intrinsic hydrophobic nature of VGN impedes electrode-electrolyte interaction and necessitates VGN surfaces to be hydrophilic to enhance the charge storage performance. This work not only demonstrates the improved effectiveness of surface modification through oxygen plasma exposure to transform the inherent hydrophobic VGN surfaces into super-hydrophilic ones, but also fills the existing knowledge gap about the specific oxygenated functionalities that cause this transition. Here we use an innovative combination of ex-situ or in-situ exposures to reveal and quantify the specific oxygenated functionalities on VGN surfaces. In particular, a preferential increase in hydroxyl and carbonyl type functional groups is demonstrated at higher plasma powers. In this way, the super-hydrophilic VGN electrodes reveal a ten times increase in the areal capacitance over the inherent hydrophobic ones. Moreover, a significant difference in capacitance amongst the samples treated in ex-situ and in-situ manner under the same plasma power is also demonstrated. The observed variation in the capacitance is related to the type and relative presence of the oxygenated functional groups. This simple and scalable approach elucidates the critical role of surface chemistry and the possibility of decorating VGN structures with preferential functional groups to achieve superior specific capacitance.

Optimizing the preparation conditions of polypyrrole electrodes for enhanced electrochemical capacitive performances

Here, we put forward an optimum proposal to prepare high-performance polypyrrole (PPy) electrodes for supercapacitor applications. A detailed study regarding the effects of different preparation conditions including electropolymerized mode, parameter, and current collector on the electrochemical capacitive performances of PPy electrodes is carried out. Fourier transform infrared spectroscopy and X-ray diffraction tests indicate the above preparation conditions have no effect on the component and crystal structure of PPy prepared. Electrochemical measurements manifest a significant effect of current collector on supercapacitive properties of PPy electrodes. Graphite foil as the current collector with low resistance shows remarkably superior capacitive performances compared with FTO-conducting glass and ITO conductive plastic. SEM characterizations show galvanostatically polymerized PPy particles have obviously smaller aggregation degree than potentiostatically polymerized PPy particles, which results in better electrochemical properties for former. Among different preparation conditions, the PPy deposited on graphite foil under galvanostatic mode with 2 mA cm−2 shows the best electrochemical capacitive properties. The optimized PPy/graphite electrodes show a high specific capacitance of 173.0 mF cm−2 at 0.2 mA cm−2, superior rate capability, and outstanding cycling stability (retaining 90.5% of initial capacitance for 5000 cycles).

Application of Water Lettuce (Pistia S.) as Conductive Carbon in Electrochemical Capacitor

A conductive carbon material from Water Lettuce (Pistia S.) powder has been prepared for use in Electrochemical Capacitor (EC) device. The features on surface functionality, morphology, and crystallography were analysed based on Boehm titration / FTIR, SEM and XRD instrumentations. The performance of ECs was studied by using impedance spectroscopy method,in which capacitances were calculated from the data. The surface features measurement showed that surface area (S), volume (Vm), and total volume (Vt) were 1238 m2 g-1, 5.98 cm2 g-1 and 1.99 cm3 g-1. FTIR spectrogram shows the functionality on the surface of carbon, -OH (3,800 – 4,000 cm-1), C-C, C-O, C-N (500 – 1,500 cm-1) and C=C, C=O, C=N (1,050, 1,500, 2,300 – 2,400 cm-1). XRD analysis showed that carbon sample has sharp peaks indicating crystallite of carbon and sylvite. SEM analyses indicated the existence of micro pores in the carbon samples. The higher impedances were come from electrodes with high content (70 %) of WL carbon, range from 100 to 120 ohm. Low content carbon (30 %) electrode has impedance range from 80 to 100 ohm. Critical point to capacitance – resistance character of EC for the asymmetric and symmetric ECs was 5 and 114 Hz. Capacitance analysis plots of ECs showed convergence of the values and reached minimum in frequency near 500 Hz. The maximum value of capacitance is about 0.401 F.

One-step synthesis of self-supported NixP nanowires/Ni hybrid foam as battery-like electrode for high-performance supercapacitors

The search of low-cost, earth-abundant and high electro-capacitive electrode materials is significant for the practical application of supercapacitors. Here we introduce a simple and cost-effective strategy for one-step synthesis of self-supported NixP nanowires/Ni hybrid foam electrodes from commercially available Ni foams via low-temperature thermal phosphorization. This electrode exhibits superior electrochemical capacitive performance featured by an ultrahigh-rate performance (0.36 C cm−2 at 100 mA cm−2) and long cycling stability (a stable capacitance of 0.74 C cm−2 at 20 mA cm−2 for 5000 cycles), which benefits from the good electrical conductivity of NixP nanowires active materials on Ni foam and one-dimensional structure for NixP. This work demonstrates a facile and effective avenue to prepare a cheap and efficient super-capacitive electrode for the practical application of supercapacitors.

Carbon Capsules of Ionic Liquid for Enhanced Performance of Electrochemical Double-Layer Capacitors.

Ion accessibility, large surface area, and complete wetting of a carbonaceous electrode by the electrolyte are crucial for high-performance electrochemical double-layer capacitors. Herein, we report a facile and scalable method to prepare electrode-electrolyte hybrid materials, where an ionic liquid (IL) electrolyte is encapsulated within a shell of reduced graphene oxide (rGO) nanosheets as the active electrode material (called rGO-IL capsules). These structures were templated using a Pickering emulsion consisting of a dispersed phase of 1-methyl-3-butylimidazolium hexafluorophosphate ([bmim][PF6]) and a continuous water phase; graphene oxide nanosheets were used as the surfactant, and interfacial polymerization yielded polyurea that bound the nanosheets together to form the capsule shell. This method prevents the aggregation and restacking of GO nanosheets and allows wetting of the materials by IL. The chemical composition, thermal properties, morphology, and electrochemical behavior of these new hybrid architectures are fully characterized. Specific capacitances of 80 F g-1 at 18 °C and 127 F g-1 at 60 °C were achieved at a scan rate of 10 mV s-1 for symmetric coin cells of rGO-IL capsules. These architected materials have higher capacitance at low temperature (18 °C) across many scan rates (10-500 mV s-1) compared with analogous cells with the porous carbon YP-50. These results demonstrate a distinct and important methodology to enhance the performance of electrochemical double-layer capacitors by incorporating electrolyte and carbon material together during synthesis.

Decorating Graphene Oxide with Ionic Liquid Nanodroplets: An Approach Leading to Energy Dense, High Voltage Supercapacitors

Supercapacitors, also known as electric double-layer capacitors (EDLCs), are able to store energy rapidly and reversibly through the formation of a double-layer of electronic and ionic charge, closely spaced, at the electrode/electrolyte interface.[1-2] Due to the combination of various advantageous properties, such as efficient operation at high power density, long cycle life and improved safety compared to Li-ion batteries,[3,4] supercapacitors are being increasingly used as alternative power sources to rechargeable batteries. However, the implementation of supercapacitors in practical application is still restricted by the limited energy density, typically 5-8 Wh/L,[5] which is much lower than that of lead-acid batteries which can achieve ~50-90 Wh/L.[6] Considering a symmetric configuration, the volumetric energy density (E V) of a supercapacitor is directly proportional to the volumetric capacitance (C V) of a single electrode and the square of operating voltage (U) following the equation, Ev = 1/8(C V·U 2). Therefore, in such a system, there are two ways to improve energy density: boosting capacitance and extending cell voltage window. The operating voltage of EDLCs is typically limited by the stability of electrolyte and thus room temperature ionic liquids (ILs) with large electrochemical stability windows (> 3-4 V) have become promising next-generation electrolytes. However, the relatively high viscosity of ILs results in lower ionic conductivity compared to traditional aqueous or organic electrolytes and also leads to challenges with pore wetting. On the electrode side, materials with a high intrinsic capacitance (C DL) per area and a large ion-accessible surface area (SSA) are needed to achieve high gravimetric capacitance (C G) since C G = C DL·SSA. The potentially high electrical conductivity, surface area, and chemical stability of graphene-based materials make them promising candidate electrode.[7,8] Theoretically, single layer graphene can exhibit SSA as high as 2675 m2/g. While pristine graphene is limited by its low quantum capacitance leading to C DL ~3-4 mF/cm2, more defective and functionalized graphene produced by the chemical or thermal reduction of graphene oxide (GO) have been shown to exhibit C DL > 17 mF/cm2 in non-aqueous electrolyte leading to theoretical gravimetric capacitance, C G,theoretical > 450 F/g if all of graphene’s surface area could be made ion-accessible. To prevent aggregation and restacking of graphene-based materials into lower SSA structures, we demonstrated an IL microemulsion system (Figure 1) that spontaneously assembles on the surface of GO, placing nanometer-sized droplets of a high-performance, hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) directly onto the available surface of well-dispersed single GO layers. We first demonstrate that a common non-ionic surfactant, Tween 20 is capable of forming a stable microemulsion with EMImTFSI with a particle size on the order of several nanometers. These surfactant stabilized nano-droplets (microemulsion particles) spontaneously adsorb to GO sheets yielding a dispersion which can be cast directly onto current collectors leading to a dense nanocomposite of GO/IL/Tween 20. Tween 20 is then removed by evaporation, while the GO is thermally reduced leading to what we refer to as layered IL-mediated reduced GO (IM-rGO) electrodes. The approach is found to yield high ion-accessible SSA as evidenced by one of the highest C G ever reported (302 F/g) when the composite contains 80 wt% IL. These results indicate that the microemulsion particles formed were better able to deploy IL as a spacer to prevent rGO sheets from restacking. Reducing the IL content to 60 wt%, resulted in dense electrodes that exhibited a C V = 218 F/cm3, which is the highest value reported to date among all graphene-based supercapacitors leading to exceptional volumetric energy density. Reference (1) Conway, B. E. Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications. Springer Science & Business Media 2013. (2) Miller, J. R.; Simon, P. Electrochemical capacitors for energy management. Science 2008, 321, 651. (3) Du Pasquier, A.; Plitz, I.; Menocal, S.; Amatucci, G. A comparative study of Li-ion battery, supercapacitor and nonaqueous asymmetric hybrid devices for automotive applications. J. Power Sources 2003, 115, 171. (4) Khaligh, A.; Li, Z. Battery, ultracapacitor, fuel cell, and hybrid energy storage systems for electric, hybrid electric, fuel cell, and plug-in hybrid electric vehicles: State of the art. IEEE transactions on Vehicular Technology 2010, 59, 2806. (5) Burke, A. R&D considerations for the performance and application of electrochemical capacitors. Electrochim. Acta 2007, 53, 1083. (6) Linden, D. Handbook of batteries. Fuel and Energy s 1995, 265. (7) Pope, M. A.; Aksay, I. A. Four-Fold Increase in the Intrinsic Capacitance of Graphene through Functionalization and Lattice Disorder. J. Phys. Chem. C 2015, 119, 20369. (8) Stoller, M. D.; Park, S.; Ruoff, R. S. Graphene-based ultracapacitors. Nano Lett. 2008, 8, 3498. Figure 1

Holey Graphene for Energy Storage

Graphene, owing to its large specific surface area (SSA) and excellent electronic conductivity has been a focus of research as an electrode material in electrochemical capacitors (EC). However, van der Wall’s attraction between the individual graphene sheets results in stacking of sheets while fabricating electrodes. This phenomenon decreases the SSA and restricts electrolyte diffusion pathways thereby deteriorating the performance of EC. Another challenge is that bulk manufacturing of graphene with a low cost process does not exist. These challenges can be resolved by using reduced graphene oxide (RGO) which is structurally similar to graphene with few oxygen functional groups and defects. Solution based process to synthesize RGO are indeed facile. Furthermore, previous studies indicate that modified RGO morphologies can be used as potential electrode material for electrochemical capacitors (EC). By creating nanopores within the RGO sheets, the specific surface area of electrode and diffusion of electroactive species can be improved. Here, we present a simple solution based process to manufacture holey graphene from graphene oxide (GO) via microwave (MW) radiations. GO aqueous dispersion prepared by modified Hummer’s method can be converted to RGO via thermal, chemical or photochemical methods. Then, RGO in presence of hydrogen peroxide is irradiated with microwaves. The application of MW radiation generates OH free radicals, which etch the carbon atoms present at the active defective sites on RGO. This creates a carbon vacancy on RGO sheet, consequently extending to form the nanopores. This holey graphene is characterized using TEM, XPS, BET, Raman & FTIR. Next, holey graphene is utilized to build an electrochemical capacitor and tested to show improved diffusion of electrolyte and higher energy density. The fundamental knowledge gained from this study can also be applied in the fields of batteries, hydrogen storage and catalysis.

Fabrication of Metal Organic Framework Flexible All Solid State Supercapacitors By Electrophoretic Deposition

Two-dimensional (2D) materials exhibit remarkable properties that suggest many possibilities for electronic applications. Metal organic frameworks (MOFs) are 2D nanosheets materials, which are good candidates for applications in various electrochemical applications such as fuel cells, batteries, and supercapacitors. Herein we report the fabrication of Ni3(2,3,6,7,10,11-hexaaminotriphenylene)2 (Ni3(HITP)2) flexible all solid-state supercapacitors by electrophoretic deposition (EPD). The Ni3(HITP)2 films were electrophoretically deposited in a layer-by-layer fashion onto targeted substrates. The electrodes’ surface morphology characterized by SEM shows a porous surface, and a honeycomb morphology known for improving the capacitive performance. TEM pictures confirmed the ultrathin two-dimensional structure of the (Ni3 (HITP)2) electrodes. The electrochemical capacitive performance of the obtained symmetric Ni3(HITP)2 supercapacitor has been characterized using cyclic voltammetry measurements and galvanostatic charge-discharge tests. This work demonstrates an exciting potential of EPD for the fabrication of high performance MOFs for flexible solid state energy storage systems.

Polyaniline/graphene nanocomposites towards high-performance supercapacitors: A review

Abstract Among frequently investigated advanced electrode materials for supercapacitors, polyaniline (PANI) is considered as an ideal electrode material due to its high theoretical capacitance, desirable chemical stability, easy synthesis and low cost. However, neat PANI electrodes are lack of long-term stability and high power density due to their low surface area, large volume changes during release/doping of ions and low conductivity. The composition of PANI with carbon materials especially conductive and high-surface-area graphene provides an effective approach to solve these problems. This review presents an overview of recent advances in the design, synthesis and applications of PANI/graphene nanocomposites as high-performance electrode materials for supercapacitors. The PANI/graphene nanocomposites can combine the advantages of both electrical double-layer capacitances of graphene and pseudocapacitances of PANI, which therefore exhibit long cycle life and large energy density. Various strategies for the synthesis of PANI/graphene nanocomposites are briefly introduced, and several main factors influencing electrochemical capacitive performances of PANI/graphene nanocomposites are presented and discussed. Finally, the future research directions for the PANI/graphene nanocomposites for supercapacitors are also summarized and discussed.

Synthesis of cobalt-nickel pyrophosphates/N-doped graphene composites with high rate capability for asymmetric supercapacitor

Transition metal pyrophosphates have recently shown great potential applications in the field of supercapacitor due to their high capacitance and stable structure. However, the poor electric conductivity of these materials has seriously restricted the rate performance of supercapacitor. Here we report a simple synthesis of Co0.4Ni1.6P2O7/N-doped graphene (NG) composites, which possess fine conductive network and satisfied mesopore structure for improving the electrochemical capacitance performances. By this method, the graphene nanosheets could be simultaneously N-doped by the released NH3 gases during the transformation of the precursor Co0.2Ni0.8NH4PO4·H2O to Co0.4Ni1.6P2O7, without introducing any other N-containing resources. The effects of N-doped graphene content on the morphology and the electrochemical properties of the obtained Co0.4Ni1.6P2O7/NG materials were studied. With the increase of N-doped graphene content, the morphology of the composites could be changed from sheet-like agglomerate to flower-like clusters. The optimized composite showed much higher specific capacitance and remarkable rate capability (1473 F g-1 at 1 A g−1 and 1443 F g-1 at 15 A g−1) compared with pure pyrophosphates. By further using the as-prepared material for positive electrode, we assembled a robust asymmetric supercapacitor with excellent energy density and power density as well as long cycling life, which demonstrate its great potential to be used in supercapacitor application.

Core-shell structured Ni3S2@Co(OH)2 nano-wires grown on Ni foam as binder-free electrode for asymmetric supercapacitors

Core-shell structured Ni3S2@Co(OH)2 nano-wires directly grown on Ni foam as a binder-free electrode for asymmetric supercapacitors are synthesized though a facile two-step process. This unique core–shell architecture consisting of ultrathin Co(OH)2 nano-sheets and Ni3S2 nano-wires exhibits significantly enhanced electrochemical capacitive performance. The Ni3S2@Co(OH)2 electrode demonstrates high specific capacitance of 2139.4 F g−1 at the current density of 2 mA cm−2, and retains capacitance of 1139.4 F g−1 at a much higher current density of 40 mA cm−2. An asymmetric supercapacitor using Ni3S2@Co(OH)2 as cathode and active carbon as anode is successfully assembled in a coin cell. The as-prepared cell delivers high-power density as high as 18.27 kW kg−1 at the energy density of 74.79 Wh kg−1 with good cycling stability, which shows its feasibility for many practical applications for energy storage. These results indicate that the newly developed core-shell architecture is an efficient way towards improve the electrochemical performance in various promising energy storage applications.

High electrochemical capacitor performance of oxygen and nitrogen enriched activated carbon derived from the pyrolysis and activation of squid gladius chitin

Activated carbon containing nitrogen functionalities exhibits excellent electrochemical property which is more interesting for several renewable energy storage and catalytic applications. Here, we report the synthesis of microporous oxygen and nitrogen doped activated carbon utilizing chitin from the gladius of squid fish. The activated carbon has large surface area of 1129 m2 g−1 with microporous network and possess ∼4.04% of nitrogen content in the form of pyridinic/pyrrolic-N, graphitic-N and N-oxide groups along with oxygen and carbon species. The microporous oxygen/nitrogen doped activated carbon is utilize for the fabrication of aqueous and flexible supercapacitor electrodes, which presents excellent electrochemical performance with maximum specific capacitance of 204 Fg−1 in 1 M H2SO4 electrolyte and 197 Fg−1 as a flexible supercapacitor. Moreover, the device displays 100% of specific capacitance retention after 25,000 subsequent charge/discharge cycles in 1 M H2SO4 electrolyte.

Cactus‐Like NiCoP/NiCo‐OH 3D Architecture with Tunable Composition for High‐Performance Electrochemical Capacitors

AbstractTo effectively enhance the energy density and overall performance of electrochemical capacitors (ECs), a new strategy is demonstrated to increase both the intrinsic activity of the reaction sites and their density. Herein, nickel cobalt phosphides (NiCoP) with high activity and nickel cobalt hydroxides (NiCo‐OH) with good stability are purposely combined in a hierarchical cactus‐like structure. The hierarchical electrode integrates the advantages of 1D nanospines for effective charge transport, 2D nanoflakes for mechanical stability, and 3D carbon cloth substrate for flexibility. The NiCoP/NiCo‐OH 3D electrode delivers a high specific capacitance of ≈1100 F g−1, which is around seven times higher than that of bare NiCo‐OH. It also possesses ≈90% capacitance retention after 1000 charge–discharge cycles. An asymmetric supercapacitor composed of NiCoP/NiCo‐OH cathode and metal–organic framework‐derived porous carbon anode achieves a specific capacitance of ≈100 F g−1, high energy density of ≈34 Wh kg−1, and excellent cycling stability. The cactus‐like NiCoP/NiCo‐OH 3D electrode presents a great potential for ECs and is promising for other functional applications such as catalysts and batteries.

Preparation and electrochemical capacitive performance of phenolated calcium lignosulfonate-based phenol formaldehyde resin porous carbon

Abstract

Specific capacitance, energy and power density coherence in electrochemically synthesized polyaniline-nickel oxide hybrid electrode

Abstract In the present manuscript, polyaniline (PAni), nickel oxide (NiO), and a fine nanosheet-type network of PAni-NiO hybrid film electrodes are prepared using electrodeposition technique and envisaged as electrode materials in electrochemical capacitor application. Furthermore, these film electrodes are characterized for their structural and morphological studies with the help of X-ray diffraction and scanning electron microscopy measurements, respectively. Atomic force microscopy revelation affords the roughnesses of electrode surfaces. Contact angle elucidation explodes the hydrophilic nature of PAni, NiO and PAni-NiO hybrid electrode surfaces. Electrochemical measurements confirm that the PAni-NiO hybrid electrode shows synergic effect as its specific capacitance measured at a scan rate of 5 mV/s in 1 M Na 2 SO 4 electrolyte is noticeably higher (936.36 F/g) than the PAni and NiO electrodes (601 and 263.5 F/g). All these electrodes exhibit remarkable capacity retention performance after 2000 cycles. The nanosheet network of PAni-NiO hybrid electrode offer a great reaction surface area for rapid ion and electron transfer with good stability as well, which all are advantageous for enhancing the electrochemical capacitance performance.

Preparation and electrochemical capacitive performance of hollow urchin-like Ni2P/CoP bimetallic phosphides for high-performance supercapacitors

In this paper, the preparation and electrochemical capacitive performance of hollow urchin-like Ni2P/CoP (HU Ni2P/CoP) bimetallic phosphides have been reported. Electrochemical measurements deliver a high specific capacity of 1038 F g−1 at a current density of 1 A g−1, and achieve the good capacitance retention of 91% after 3000 cycles at 20 A g−1, indicating HU Ni2P/CoP bimetallic phosphides can be used as the novel electrode materials for supercapacitor applications.

Unusual carbon nanomesh constructed by interconnected carbon nanocages for ionic liquid-based supercapacitor with superior rate capability

The exploration of various porous nanocarbon materials with an extraordinary electrochemical capacitive performance in ionic liquid (IL) electrolytes is urgently needed for development of the next-generation energy storage devices. Significant improvements in energy density have been achieved, however, supercapacitors with IL electrolytes usually suffer from issues related to low power density and large IR drop. Herein, we report an unprecedented carbon nanomesh that is made up of interconnected densely-packed carbon nanocages with ultrathin partially graphitic shells. The large specific surface area and well-developed mesopores combined with its unique structural features, make it a very competitive material for high-performance supercapacitor in IL electrolyte. Notably, this unique nanosheets morphology with lots of in-plane nanopores on their surface can provide fast cross-plane ion diffusion pathways, and meanwhile, the carbon nanocages with partially graphitic shells ensure the rapid electron transfer. The supercapacitor assembled with the optimized sample can deliver a high specific capacitance (up to 194 F/g at 1 A/g), superior rate capability (68% capacitance retention at 70 A/g), low IR drop (0.685 V at 70 A/g). Moreover, benefiting from the wide working voltage and high-rate capability, the energy densities can maintain at 56.1 Wh/kg even at an ultrahigh power density of 61.250 kW/kg. Strikingly, the as-assembled supercapacitor can successfully power a light-emitting diodes (LED, 2.2 V) module with 53 red LED lights demonstrating its great potential for practical applications in energy storage devices.