Pseudocapacitive Performance Research Articles

Synthesis of Co3 O4 /Carbon Heteroaerogels with Ultrahigh Capacitance via Polyethyleneimine Intercalation of Co2 BIM4 Nanosheets.

The development of metal-organic frameworks (MOFs)-based supercapacitors have attracted intense concentration in recent years due to their regularly arranged porous and tunable pore sizes. However, the performance of the MOFs-derived supercapacitors is also low because of their poor electrical conductivity and rarely accessible active sites. In the present work, we developed a Co-MOF (namely Co2 BIM4 , BIM=benzimidazole) nanosheets derived Co3 O4 /nitrogen-doped carbon (Co2 BIM4 -Co3 O4 /NC) heteroaerogel as a novel supercapacitor electrode. The 3D Co2 BIM4 -Co3 O4 /NC heteroaerogels were obtained by directly intercalating polyethyleneimine (PEI) into the interlayers of Co2 BIM4 nanosheets and following by carbonizing the resulting Co2 BIM4 /PEI composite. The Co2 BIM4 -Co3 O4 /NC electrode possessed 3D conductive framework with an overlapped hetero-interface and expanded interlayers, leading to fast and stable charge transfer/diffusion and an enhanced pseudocapacitance performance. Therefore, the Co2 BIM4 -Co3 O4 /NC electrode showed ultrahigh capacitance of 2568 F g-1 at 1 A g-1 , 1747 F g-1 at 10 A g-1 , and excellent long cycling time with a capacitance preservation of 92.7 % following 10000 cycles at 10 A g-1 , which is very promising for applications in supercapacitors and other energy storage devices.

Two-step polyaniline loading in polyelectrolyte complex membranes for improved pseudo-capacitor electrodes

AbstractA two-step polyaniline (PANI) loading procedure has been developed to produce polyelectrolyte complex composite membranes (CPECs) to be used as supercapacitor electrodes. In the first step, CPECs were prepared by co-precipitation of poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) mixed with various amounts of PANI as a filler. CPECs were formed by compression molding into 100 micron membranes using NaCl as a plasticizer and characterized for their electrochemical properties. In the second step, the highest capacitance CPEC membranes with 60% PANI loading were further modified and doped by crossflow polymerization of aniline through the composite membranes. By using a two-compartment crossflow reactor containing aniline and ammonium persulfate on each side, the PANI content of the composite membrane was further increased. Cyclic voltammetry showed a doubling in the capacitance of the membranes after the crossflow polymerization. The resulting electrodes were flexible with high capacitance and could be used to improve pseudocapacitor performance.

Lignin-derived carbon as a high efficient active material for enhancing pseudocapacitance performance of p-type conductive polymer

As first research work, lignin derived carbon (LDC) was chemically synthesized, then studied its effects on the supercapacitive properties of the POAP/ LDC composite, as an active martial, and then characterized by FE-SEM and BET methods. For significantly increasing the volumetric capacitance and achieving a synergistic effect, poly ortho aminophenol (POAP) was injected into the channels of LDC. POAP could be uniformly dispersed within the channels due to their high pore volume and surface area. Moreover, in addition to active pseudocapacitive function and facilitating energy storage, POAP could act as a proton transport media and promoter of protonation/deprotonation processes during the redox reactions in the channels. The values of 485 F/g at 1.0 A/g current density and 86% (as a good cycle stability) after 3000 cycles are obtained as the specific capacitance (Cs) and the retention rate of the initial capacity.

Influence of calcination temperature on structural, morphological, and electrochemical properties of Zn2P2O7 nanostructure

Ammonium zinc phosphate hydrates (NH4ZnPO4: NZPO) precursor powder was synthesized by a facile hydrothermal method at 200°C for 8 h. Effect of calcination temperature on structure, morphology and electrochemical properties of zinc pyrophosphate nanostructure (Zn2P2O7: ZPO Nstr) was studied by calcination NZPO precursor powder at 500 (ZPO5), 600 (ZPO6), 700 (ZPO7) and 800 (ZPO8) °C under argon flow for 1 h. Calcination temperature significantly affect structure of samples, since the X-ray diffraction (XRD) analysis confirmed a monoclinic phase with space group P21/n (Z = 4) in NZPO precursor powder, an orthorhombic phase of γ-Zn2P2O7 with space group Pbcm in ZPO5 Nstr, and a monoclinic phase of space group I2/c (Z = 12) in ZPO6, ZPO7 and ZPO8 Nstr. Moreover, the crystallite size of calcined ZPO Nstr increased with increasing calcination temperature. The micrographs of all ZPO Nstr revealed by scanning electron microscope (SEM) indicated the dependence of morphology on calcination temperature i.e. a dense agglomeration of perfect rectangular bars of smooth surface with irregular size intercalated by small incomplete grown crystals with small cracked fractures spread on their surfaces was observed in ZPO5 Nstr. For ZPO6 and ZPO7 Nstr, similar morphology was observed with a less dense agglomeration. Selected area electron diffraction (SAED) patterns of all samples obtained by transmission electron microscope (TEM) confirmed their crystal structures. The analyzed data of X-ray absorption near edge spectroscopy (XANES) indicated the presence of Zn2+ cations in all ZPO Nstr samples. Electrochemical properties of all active ZPO Nstr working electrodes studied by the cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectrum (EIS) using a three–electrode system in a 3 M KOH electrolyte displayed the pseudo-capacitor performance correlated with Faradaic redox reaction. In addition, the specific capacitance (Cs) was found to decrease at higher calcination temperature. The highest Cs of 102.9 F g−1 at 1 A g−1 with 81.58% retention of cycling stability after 1000 cycle test was achieved in ZPO5 Nstr electrode.

Pseudocapacitance multiporous vanadyl phosphate/graphene thin film electrode for high performance electrochemical capacitors

Supercapacitors are being considered as promising electricity storage devices with green sustainable energy conversion. To efficiently develop and optimize pseudocapacitive material of vanadyl phosphate, herein, multiporous vanadyl phosphate/graphene (denoted as MP-VOPO4@rGO) is fabricated for the first time with phytic acid as a phosphorus source by extremely simple sol-gel and drop coating methods, and used as the free binder thin film electrode of supercapacitors. The smart combination of honeycomb-like architecture and graphene incorporation results in more active sites and low internal resistance, significantly improving energy storage performance. The effect of introducting polystyrene (denoted as PS) template and rGO on the performance of the nanocomposite is systematically analyzed by comparing the performance of the corresponding thin film electrodes. The MP-VOPO4@rGO thin film electrode delivers superior pseudocapacitive performance of 672 F g−1 at 1 A g−1 as well as a remarkable rate capability of 552 F g−1 at 5 A g−1, and it presents a remarkable longterm cycling stability, with a capacitance retention of 83.5% after 5000 cycles. Very interestingly, the results of surface capacitance contribution dominance clearly demonstrates its rapid capacitive response. In addition, based on MP-VOPO4@rGO thin film as positive and negative electrodes, the corresponding assembled symmetric supercapacitors exihibits outstanding energy density of 26.3 Wh kg−1 at power density of 249.9 W kg−1. This investigation can not only provide a versatile strategy to design other thin film electrode materials but also open up a new insight into the development of polyanion phosphate composites for next-generation high performance energy storage systems.

Highly porous niobium oxide/carbon matrix materials with distinct pseudocapacitive performances in aqueous electrolytes

NbO2/porous carbon matrix composite material for supercapacitor application is prepared by a facile sugar blowing method. Owing to the unique porous and intergrowth structure, this material possesses effective electron-ion-conductive-network. Thus, it delivers an impressive capacitance of 261 Fg−1 (686 F cm-3) at 1 A g−1 and 175 Fg−1 (460 F cm−3) at 50 A g−1 in 1 M H2SO4. With a wide potential window of 1.8 V in 1 M Li2SO4, it achieves 184 Fg−1 (484 F cm−3) at 1 A g−1 and 130 Fg−1 (342 F cm−3) at 50 A g−1, respectively. Remarkably, a symmetric two-electrode-cell with this material using 1 M Li2SO4 retains its operating voltage of 1.8 V, delivering 18.2 Wh kg−1 (47.9 Wh l−1) at 810 W kg−1 (2130.3 W l−1), and 10.5 Wh kg−1 (27.6 Wh l−1) at 81000 W kg−1 (213030 W l−1), as well as excellent cyclic capability (>10000 cycles). These interesting performance reveals the significant prospect of this material to be utilized in supercapacitors and other electrochemical devices.

MOF derived TiO2 with reversible magnesium pseudocapacitance for ultralong-life Mg metal batteries

• An ultralong-life cathode in Mg metal battery was obtained. • Surface redox and pseudocapacitive mechanism for Mg storage are demonstrated. • The high ion migration on TiO 2 -UN@C interface is revealed. Magnesium metal batteries have attracted much attention due to the good safety, low cost of magnesium and high theoretical volumetric capacity. However, developing magnesium metal batteries is restricted by large polarization and sluggish kinetics during Mg insertion/deinsertion process. Herein, TiO 2 ultrafine nanocrystals derived from Ti-metal–organic-framework (Ti-MOF) are applied as the cathodes in magnesium metal batteries. Remarkably, an ultralong life of the Mg(s) || TiO 2 battery can be obtained during cycling (capacity retention of 75% after 1000 cycles). On the basis of in-situ XRD characterization and cyclic voltammetry analysis, a high pseudocapacitive performance is found, which results in the high kinetics. Moreover, according to Arrhenius behavior, carbon skeleton in TiO 2 cathode can facilitate ion migration and Faraday reaction, thus improving the magnesium storage performance.

Enhanced pseudocapacitive performance of MoS2 by introduction of both N-GQDs and HCNT for flexible supercapacitors

In this work, we report a strategy for enhancing the pseudocapacitive performance of MoS2 materials by the introduction of nitrogen-doped graphene quantum dots (N-GQDs) and helical carbon tubes (HCNT). By a simple hydrothermal process, the hybrid composite (MoS2, N-GQDs and HCNT) were coated on the carbon cloth (CC) without any binders, which can be directly used as advanced electrode material for high-performance solid-state flexible supercapacitors. In this hybrid structure, N-GQDs are inserted between the layers of MoS2 nanosheets, which induce and expose more active sites for pseudocapacitance contributions in MoS2 electrode materials. Meanwhile, HCNT acts as electrically conducting bridge for enhancing the electrical conductivity of MoS2 nanosheets and speeding up transport of electronic. As results, the hybrid composite (MoS2, N-GQDs and HCNT) show higher capacitive performance than pure MoS2. The specific capacitance of hybrid composite is high up to 3360 mF cm−2. Further, the assembled solid-state flexible supercapacitor shows high specific capacitance of 1893 mF cm−2, outstanding cycle life (capacitance retention of 86% after 2500 cycles), good mechanical stability and great flexibility. Our work provides a reference for the preparation of MoS2 composites with high supercapacitive performance.

Rational construction of NiCo2O4@Fe2O3 core-shell nanowire arrays for high-performance supercapacitors

Fe2O3 electrode materials exhibit excellent electrochemical performance in electrochemical energy storage system. However, its poor electrical conductivity limits its future practical application. The binder-free NiCo2O4@Fe2O3 composites was reasonably designed and fabricated on carbon fiber paper with NiCo2O4 nanowires as conductive scaffold in the present investigation. The three-dimensional nanostructure of the porous Fe2O3 nanorods coated the NiCo2O4 nanowire arrays showed the fascinating electrochemical performance, including high specific capacitance of 262 ​mF/cm2 at a current density of 1 ​mA/cm2, and remarkable cycle stability with ~74.2% capacitance retention after 4000 cycles. The excellent pseudocapacitance performance of NiCo2O4@Fe2O3 composite materials is due to synergistic effect between NiCo2O4 and Fe2O3. The results of the present work show that NiCo2O4@Fe2O3 core-shell composite electrode is expected to exhibit excellent performance in the field of supercapacitors.

Defect-rich CeO2 in a hollow carbon matrix engineered from a microporous organic platform: a hydroxide-assisted high performance pseudocapacitive material.

A microporous organic polymer (MOP) was utilized for the engineering of nanoparticulate CeO2 in a hollow carbon matrix (H-C/CeO2). After CeO2 nanoparticles were incorporated into a hollow MOP platform (H-MOP) through the decomposition of cerium acetate, successive carbonization produced H-C/CeO2. The redox feature of defective CeO2 in a conductive carbon matrix induced promising pseudocapacitive behavior. In particular, the H-C/CeO2 showed excellent electrochemical performance in an alkaline electrolyte (KOH), due to the hydroxide ion-assisted redox behavior of defective CeO2. H-C/CeO2-3 with an optimized amount of CeO2 showed specific capacitances of up to 527 (@0.5 A g-1) and 493 F g-1 (@1 A g-1). Even at high current densities of 10 and 20 A g-1, the H-C/CeO2-3 maintained high capacitances of 458 and 440 F g-1, respectively. After 10 000 cycling tests, the H-C/CeO2-3 retained the 94-95% capacitance of the first cycle.

Carbon black nanoparticle trapping: a strategy to realize the true energy storage potential of redox-active conjugated microporous polymers

The pseudocapacitive performance of redox-active conjugated microporous polymers was enhanced through the trapping of carbon black nanoparticles.

Hierarchical porous CeO2 micro rice-supported Ni foam binder-free electrode and its enhanced pseudocapacitor performance by a redox additive electrolyte

A hierarchical porous CeO2 micro rice/NF binder free electrode was fabricated via a facile hydrothermal method and the electrochemical performances were enhanced by the addition of 0.2 M K4[Fe(CN)6] redox additive in a 3 M KOH electrolyte.

In situ synthesis of hierarchical NiCo-MOF@Ni1-xCox(OH)2 heterostructures for enhanced pseudocapacitor and oxygen evolution reaction performances.

Integrating the merits of different components to construct heterostructures for energy storage and conversion has attracted intensive attention. Herein, taking advantage of bimetallic MOFs and transition bimetal hydroxide, we have successfully used nanoflower-like Ni1-xCox(OH)2 as both the precursor and template to in situ construct three dimensional (3D) NiCo-MOF@Ni1-xCox(OH)2 (denoted as MOF@TMH) hierarchical heterostructures. Benefiting from the optimized composition with hierarchical heterostructures assembled by ultrathin nanosheets, MOF@TMH-2 possesses rich effective active sites and high electrochemical reactivity, delivering superior pseudocapacitor performance with a specific capacitance of 1855.3 F g-1 at 2 A g-1 and good rate performance. Besides, MOF@TMH-2 also exhibits excellent OER activity with small overpotentials of 193 mV and 310 mV at 10 and 100 mA cm-2, respectively.

Effect of Vinylene Carbonate Electrolyte Additive on the Surface Chemistry and Pseudocapacitive Sodium-Ion Storage of TiO2 Nanosheet Anodes

Although titanium dioxide has gained much attention as a sodium-ion battery anode material, obtaining high specific capacity and cycling stability remains a challenge. Herein, we report significantly improved surface chemistry and pseudocapacitive Na-ion storage performance of TiO2 nanosheet anode in vinylene carbonate (VC)-containing electrolyte solution. In addition to the excellent pseudocapacitance (~87%), the TiO2 anodes also exhibited increased high-specific capacity (219 mAh/g), rate performance (40 mAh/g @ 1 A/g), coulombic efficiency (~100%), and cycling stability (~90% after 750 cycles). Spectroscopic and microscopic studies confirmed polycarbonate based solid electrolyte interface (SEI) formation in VC-containing electrolyte solution. The superior electrochemical performance of the TiO2 nanosheet anode in VC-containing electrolyte solution is credited to the improved pseudocapacitive Na-ion diffusion through the polycarbonate based SEI (coefficients of 1.65 × 10−14 for PC-VC vs. 6.42 × 10−16 for PC). This study emphasizes the crucial role of the electrolyte solution and electrode–electrolyte interfaces in the improved pseudocapacitive Na-ion storage performance of TiO2 anodes.

Influence of nanostructured VO-acetylacetonate coordination system with 2-(pyridin-4-ylmethylene) hydrazine-1-carbothioamide in pseudocapacitance performance of p-type conductive polymer composite film

ABSTRACT In this work, first, VO-acetylacetonate coordination system with 2-(pyridin-4-ylmethylene) hydrazine-1-carbothioamide (VO(acac)2L) was synthesised via sonochemical routes. Then POAP/VO(acac)2L films were fabricated through electropolymerization of poly ortho aminophenol (POAP) in the presence of VO(acac)2L and used as the active electrode of an electrochemical supercapacitor (SC) with a significant electrochemical properties improvement. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) was applied to characterise the structural state of the prepared samples. Also, some electrochemical methods such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) were carried out for the system performance investigation. This work may open an avenue to develop efficient and robust nanocomposite materials for an energy storage device in an acidic medium.

Boosting pseudocapacitive energy storage performance via both phosphorus vacancy defect and charge injection technique over the CoP electrode

It is an indisputable fact that electrochemical performance is always ameliorated by introducing proper phosphorus vacancy defect into electrode materials. In this work, the lattice-like CoP grown on the nickel foam with appropriate concentration of vacancies is fabricated successfully. The specific capacitance of 1865 F g−1 is improved by 1.7 times compared with the pristine CoP of 1125 F g−1 at the current density of 1 A g−1. Meanwhile, the deliberately designed electrode also possesses great stability of retention rate up to 90% after 5000 cycles. Before the electrode is assembled into the asymmetric supercapacitor, the potential window is altered by electrode potential blend technique in order to utilize capacitances of anode and cathode efficiently. Subsequently, the supercapacitor is studied in the electrochemistry systematically. The results show that power density is up to 737 W kg−1 as energy density is 31 W h kg−1. Meanwhile, the capacitance retention rate remains 88% after 5000 cycles. It is a meaningful guide for exploring efficient energy storage equipment that appropriate vacancies are injected into electrode materials, and optimal potential windows are obtained via electrode potential blend technology.

Synthesis and Characterization of CuO-NiO Nanocomposites for Electrochemical Supercapacitors

The CuO nanostructures and CuO-NiO nanocomposites of various compositions were successfully synthesized by simple hydrothermal method followed by calcination for investigation of their pseudocapacitive performances. The UV-vis spectroscopy, x-ray diffraction, field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy were used to characterize the as-synthesized electrode materials. Among these different CuO-NiO nanocomposites, CuO(x)NiO(100 − x), that’s with equal mole ratio, CuO(50)NiO(50) exhibits the highest specific capacitance of 35.63 F g−1 at current density of 0.3 A g−1. In addition, it shows excellent cycling stability with capacity retention of 85.7% at 1000th cycle at current density of 10 A g−1. The morphology of CuO(50)NiO(50) nanostructures as determined by FESEM and HRTEM studies, revealed aggregated three-dimensional (3D) hierarchical networks due to aggregation of various parallel 2D thin nanosheets. The supercapacitive activity of the synthesized CuO and CuO-NiO nanomaterials was found to follow the order: CuO(50)NiO(50) > CuO(20)NiO(80) > CuO(100) > CuO(80)NiO(20).

MoO2 nanoparticles confined in N,P-codoped graphene aerogels with excellent pseudocapacitance performance

In this work, MoO2@NPGA nanocomposites were successfully prepared via a simple hydrothermal and calcination route. The as-prepared MoO2@NPGA composites exhibit a synergistic effect between MoO2 and N,P-codoped graphene aerogels, which can significantly improve the electrochemical performance of the MoO2@NPGA electrodes. Moreover, the results also proved that the mass loading of MoO2 has a huge effect on the electrochemical properties of MoO2@NPGA composites. With an appropriate amount of MoO2, the MoO2@NPGA composite shows a high specific capacitance (335 F g−1 at 1 A g−1) and excellent cycle stability (capacitance remains at 88% after 6000 cycles). Furthermore, the assembled symmetric supercapacitor displays a high energy density of 23.75 W h kg−1 at a power density of 300 W kg−1 and can maintain an energy density of 17.1 W h kg−1 when the power density reaches up to 6005 W kg−1.

Improvement of the Pseudocapacitive Performance of Cobalt Oxide-Based Electrodes for Electrochemical Capacitors

Cobalt oxide nanopowders are synthesized by the pyrolysis of aerosol particles of water solution of cobalt acetate. Cobalt nanopowder is obtained by subsequent reduction of obtained cobalt oxide by annealing under a hydrogen atmosphere. The average crystallite size of the synthesized porous particles ranged from 7 to 30 nm, depending on the synthesis temperature. The electrochemical characteristics of electrodes based on synthesized cobalt oxide and reduced cobalt oxide are investigated in an electrochemical cell using a 3.5 M KOH solution as the electrolyte. The results of electrochemical measurements show that the electrode based on reduced cobalt oxide (Re-Co3O4) exhibits significantly higher capacity, and lower Faradaic charge–transfer and ion diffusion resistances when compared to the electrodes based on the initial cobalt oxide Co3O4. This observed effect is mainly due to a wide range of reversible redox transitions such as Co(II) ↔ Co(III) and Co(III) ↔ Co(IV) associated with different cobalt oxide/hydroxide species formed on the surface of metal particles during the cell operation; the small thickness of the oxide/hydroxide layer providing a high reaction rate, and also the presence of a metal skeleton leading to a low series resistance of the electrode.

Synthesis of Co3O4/reduced graphene oxide by one step-hydrothermal and calcination method for high-performance supercapacitors

In this work, a simple and environmental one step-hydrothermal and calcination method was used to prepare Co3O4/reduced graphene oxide (rGO) composite. The result shows that tiny Co3O4 nanoparticles are dispersed on rGO sheets to form a three-dimensional structure, which provides more active sites than Co3O4 nanowires structure. When acting as an electrochemical supercapacitor, structure optimized Co3O4/rGO-120-12 electrode exhibits high specific capacitance of 1152 F/g at 1 A/g in 6 M KOH electrolyte. As an assemble device, Co3O4/rGO reveals higher specific capacitance (about 85 F/g) than Co3O4 (about 36 F/g) at current density of 1 A/g and excellent stability with 89.1% after 5000 cycles. The device exhibits a relatively high energy density of 57.26 Wh/kg at a power density of 2240.68 W/kg. Hence, the superior pseudocapacitive performance of Co3O4/rGO can be ascribed to the synergy between rGO and Co3O4 as well as the excellent three-dimensional structure obtained by changing the hydrothermal conditions.