Electrochemical Performance Of Asymmetric Supercapacitor Research Articles

The Impact of Formate-Based Electrolytes on The Electrochemical Performance of Asymmetric Supercapacitors Containing Activated Carbon and MnO2 as Electrode Materials

In this work we report on the properties of three novel aqueous electrolytes containing 1 m (mol kg−1) of lithium formate, sodium formate and potassium formate in H2O. We show that these cheap and environmentally friendly electrolytes display high conductivity and low viscosity from 0 °C to 80 °C. When used in asymmetric supercapacitors (SCs) containing Manganese dioxide (MnO2) as active material in the positive electrode and activated carbon (AC) as active material in the negative electrode, these electrolytes allow the design of devices with operating voltage up to 1.7 V. Asymmetric SC containing these novel electrolytes display good capacity (19 mAh g−1, 18 mAh g−1 and 13 mAh g−1 in 1 m HCOOK in H2O, 1 m HCOOLi in H2O and 1 m HCOONa in H2O, respectively). The capacity retention after 10,000 cycles of the devices containing 1 m HCOOLi in H2O, 1 m HCOONa in H2O and 1 m HCOOK in H2O are all higher than 85%.

NiCoZn-LDH grown with NiMoO4 nanoneedles as a high-performance electrode for supercapacitors

One of the key obstacles in preparing high-performance supercapacitors is designing advanced structures with excellent electrochemical capacitance properties. This paper proposes a simple and fast hydrothermal synthesis method for synthesizing high-performance flower-shaped NiCoZn layered hydroxides (NiCoZn-LDH) on a foam nickel substrate with a heterostructure of NiMoO4 (NMO) nanoneedles, and further forming a heterostructure with NiCoZn-LDH nanoflowers. The electrode material synthesized by this method has significantly improved electrochemical performance. Its specific capacitance reached 3030 mF/cm2 (863C/g) at 4 mA/cm2 and 2317 mF/cm2 (662C/g) at 10 mA/cm2. In addition, an asymmetric supercapacitor (ASC) constructs with NiCoZn-LDH@NMO@NF as the positive electrode material and activated carbon as the negative electrode material achieves an energy density of 0.222 mWh/cm2 at a power density of 0.08 W/cm2. Experimental studies shown that the heterostructure of NiCoZn-LDH@NMO plays a crucial role in improving the electrochemical performance of asymmetric supercapacitors. This provides new insights for the design of next-generation ASC active materials and is beneficial for the development of new energy storage devices.

Electrochemical performance of asymmetric supercapacitors based on NiCo(OH)4/Cu2(OH)3NO3 electrode

Copper salt metal compounds are widely used in the field of supercapacitor electrode material due to their rich ionic groups. In this paper, NiCo(OH)4/Cu2(OH)3NO3 electrode material is prepared by the solvothermal method by doping NiCo-based hydroxide with copper salt metal compounds (Cu2(OH)3NO3). NiCo(OH)4/Cu2(OH)3NO3 electrode material with different morphologies and sizes is prepared by adjusting the concentration of metal salts. When the metal salt concentration is 2 M, the prepared circular sheet NiCo(OH)4/Cu2(OH)3NO3 electrode material with a diameter of 3 μm and a thickness of 150 nm exhibits excellent specific capacitance (1335 C g−1 at 1 A g−1) and capacitance retention (after 5000 cycles, the capacitance retention rate is 71.7 %). Furthermore, the NiCo(OH)4/Cu2(OH)3NO3//AC asymmetric supercapacitor is prepared, which exhibited an energy density is 83.78 Wh kg−1 at a power density of 800 W kg−1. The capacitance retention rate of the asymmetric supercapacitor is 65.2 % (after 5000 cycles at 10 A g−1). We used copper salt metal compounds (Cu2(OH)3NO3) to improve the electrochemical performance of NiCo-based hydroxide electrode material. This idea has certain reference significance for improving the performance of NiCo-based hydroxide electrode material.

Boosting the electrochemical performance of NiFe2O4/Carbon composite materials by nitrogen doping for supercapacitors application

The development of high-performance anode materials is of great importance for improving the electrochemical performance of asymmetric supercapacitors. Here, nickel ferrite/porous carbon composite is synthesized via hydrothermal approach and the electrochemical properties are improved by nitrogen doping process. As the surface nitrogen content of the porous carbon precursor increased from 2.40 at.% to 9.53 at.%, the nickel ferrite/porous carbon composite exhibited substantial improvement in specific capacitance (increased from 136.4 to 201.4 F g−1 at 1 A g−1) in an alkaline aqueous electrolyte. The energy density of the assembled asymmetric supercapacitor was increased from 17.7 W h kg−1 to 11.2 W h kg−1, and the cycle retention rate after 10,000 cycles at 2 A g−1 was increased from 16.5 % to 85.7 %. Nitrogen atoms on the carbon surface provide active sites for the growth of nickel ferrite nanoparticles and enhance the interfacial effect between nickel ferrite nanoparticles and porous carbon materials, enhancing the charge transfer and preventing particle aggregation during charge and discharge processes. The fabricated nickel ferrite/nitrogen-doped porous carbon composite exhibits excellent capacitance and cycling stability, providing a new option for asymmetric supercapacitor anode materials.

Sonochemically produced ternary metallic sulfides to enhance the electrochemical performance of asymmetric supercapacitors

Designing compositions of transition metal alloys alongside their nanostructures remains pivotal in the creation of electrochemical energy storage devices. Supercapacitors, renowned for their remarkable electrochemical capabilities, have garnered substantial interest. Nonetheless, there persists a need for electrode materials exhibiting enhanced charge storage characteristics. In this respect, the simple sonochemical method was used to easily synthesize various magnesium, silver, and copper sulfide composites. In a three-electrode setup, the electrode material Mg25Ag50Cu25S (MACS) exhibits outstanding electrochemical properties. MACS enabled the attainment of an outstanding specific capacity of 825 C/g at 1.0 A/g, showcasing its remarkable performance in this regard. Asymmetric supercapacitors were also made with the MACS. This assembly allowed the charge-storing ability to be further examined in two electrode setup. The MACS//AC device showed an outstanding energy density of 45 Wh/kg having an 850 W/kg power density thus demonstrating exceptional energy-storing ability. Cyclic stability of 73% after 5000 GCD cycles was also shown by this MACS//AC device. The developed ternary metal sulfides exhibit outstanding properties when assessed against previously published literature, offering an effective and preferred component in future storage technologies.

Alkali-Etched NiCoAl-LDH with Improved Electrochemical Performance for Asymmetric Supercapacitors

Hydrotalcite, first found in natural ores, has important applications in supercapacitors. NiCoAl-LDH, as a hydrotalcite-like compound with good crystallinity, is commonly synthesized by a hydrothermal method. Al3+ plays an important role in the crystallization of hydrotalcite and can provide stable trivalent cations, which is conducive to the formation of hydrotalcite. However, aluminum and its hydroxides are unstable in a strong alkaline electrolyte; therefore, a secondary alkali treatment is proposed in this work to produce cation vacancies. The hydrophilicity of the NiCoAl-OH surface with cation vacancy has been greatly improved, which is conducive to the wetting and infiltration of electrolyte in water-based supercapacitors. At the same time, cation vacancies generate a large number of defects as active sites for energy storage. As a result, the specific capacity of the NiCoAl-OH electrode after 10,000 cycles can be maintained at 94.1%, which is much better than the NiCoAl-LDH material of 74%.

Facile Access to Ni/Co-Based Nanoscale Coordination Polymers for the Boosted Electrochemical Performance of Asymmetric Supercapacitors

Nanoscale coordination polymers (nCPs) have obtained significant attention as cutting-edge materials for energy storage equipment. Nevertheless, monometallic nCPs are often challenging in terms of high capacitance, tunable electrochemical activity, and high conductivity. Herein, an available strategy for boosting the electroconductibility and structure stability of Ni-based nCPs is presented by partially substituting Ni2+ with proper level Co2+ stoichiometry. Co2+ has a beneficial effect on the electrochemical behavior of Ni/Co-nCPs. The bimetallic Ni/Co-nCPs with an appropriate ratio of Ni/Co being 4 has a high Cs of 1160.2 F g–1, which is about 1.47-fold that of Ni-nCPs. When Ni/Co-nCPs are applied as the anode in an asymmetric supercapacitor, the device gives rise to an exceptional energy density of 43.7 W h kg–1 at a power density of 594.9 W kg–1 and a remarkable capacitance retention over 7000 cycles. The strategy established in this work paves a pathway for the rational design and facile preparation of bimetallic Ni/Co-nCPs for energy storage devices with boosting electrochemical properties.

Designed formation of 2D/2D hierarchical V2CTx MXene/NiV layered double hydroxide heterostructure with boosted electrochemical performance for asymmetric supercapacitors

Designing exceptional hierarchical structure of nanocomposites has far-reaching significance for improving the electrochemical performance. Herein, a new 2D/2D hierarchical structure of V2CTx MXene/NiV layered double hydroxide (V2CTx/NiV-LDH) composite was successfully constructed by in-situ synthesis method. The introduction of V2CTx MXene with high electrical conductivity can suppress the aggregation of NiV-LDH nanosheets and relieve the volume change, which significantly improves the electrical conductivity of the composites and provides more active sites. The synergistic effect of NiV-LDH and V2CTx effectively enhances the charge storage capacity. The specific capacitance of V2CTx/NiV-LDH-10 electrode at 1 A g−1 is 1658.19 F g−1. Meanwhile, V2CTx/NiV-LDH-10 exhibits excellent stability with 80.95 % capacity retention after 10,000 cycles. Moreover, the asymmetric supercapacitor based on V2CTx/NiV-LDH-10 (positive electrode) and AC (negative electrode) assembled achieves a maximum energy density of 54.19 Wh kg−1 at a power density of 750 W kg−1. The results show that V2CTx/NiV-LDH-10 is a promising electrode candidate material for green energy storage.

Electrochemical performance of asymmetric supercapacitor with binder-free CoxMn3-xSe4 and radish-derived carbon electrodes using K3[Fe(CN)6] additive in electrolyte

For the development of high-energy portable electronic devices with long cycling life, herein, we provide an effective strategy of using a small quantity of K3[Fe(CN)6] as a redox additive in aqueous KOH solution as the electrolyte, which greatly enhances the energy storage performance of positive electrode via faradaic transitions of redox pair at the electrode–electrolyte interface. Construction of nanoarchitectured CoxMn3-xSe4 arrays on conductive carbon cloth (CC) substrate (CC/CMS arrays) by a facile one-step potentiostatic electrodeposition (chronoamperometry) process and their structural, morphological, and electrochemical characterizations are successfully demonstrated. The allied electron transport mechanism of K3[Fe(CN)6] further enhancing the electrochemical performance of optimized CC/CMS array positive electrode in the KOH + K3[Fe(CN)6] electrolyte is discussed in detail. Moreover, the novel CC/CMS-based asymmetric supercapacitor (ASC) device is assembled employing biomass-derived radish carbon (Radish-C) negative electrode (i.e., CC/CMS//Radish-C ASC) and separately evaluated in the electrolytes with and without redox additive. In the redox additive KOH + K3[Fe(CN)6] electrolyte, the ASC device delivers higher specific capacity (85.7 mAh g−1), energy density (64.3 Wh kg−1), and long-term charge–discharge lifespan (98.8% retention after 10,000 cycles) than that in the pristine KOH electrolyte. The practicality of CC/CMS//Radish-C ASC device in the redox additive electrolyte is also established in this work.

Co2P decorated Co3O4 nanocomposites supported on carbon cloth with enhanced electrochemical performance for asymmetric supercapacitors

An effective strategy is demonstrated to promote electrochemical performance by the combination of Co3O4 with Co2P to form a composite electrode.

Uniform MgCo2O4 porous nanoflakes and nanowires with superior electrochemical performance for asymmetric supercapacitors

In this work, MgCo2O4 nanoflakes (NFs) and nanowires (NWs) on stainless steel foil (SSF) were hydrothermally prepared followed with an additional annealing conversion of the precursors. These MgCo2O4 nanomaterials possessed mesoporous structures and electrochemical tests demonstrated their battery-like feature. The MgCo2O4 were peeled off the SSF, and the NF-based powders exhibited a high specific capacity of 424.98 C g−1 at 1 A g−1, while the NW powders delivered 351.17 C g−1. An asymmetric supercapacitor (ASC) was assembled with MgCo2O4 as cathode and AC as anode, respectively, and the MgCo2O4 NFs//AC ASC possessed an excellent electrochemical performance such as a capacity up to 146.10 C g−1, a long-life cycling stability with 108.28% capacity retention over 5000 cycles at 6 A g−1, and an high energy density of 41.10 W h kg−1 at a power density of 1012.80 W kg−1. In contrast, the MgCo2O4 NWs//AC ASC exhibited a similar cycling durability and an inferior energy density of 36.97 W h kg−1. Such impressive results indicate that the mesoporous MgCo2O4 NFs and NWs may serve as promising battery-like cathode materials for the next-generation advanced supercapacitors. Besides, the present method can provide some merits including simple and cost-effective synthesis, large production, and especially the shape of MgCo2O4 is uniform and can be easily tuned by changing the reaction parameters. The current method can be extended for the preparation of other transition metal oxides (TMOs)-based electrode materials with superior performances.

3D interconnected Fe-Co-S nanosheets network directly grown on graphene coated nickel foam with enhanced electrochemical performance for asymmetric supercapacitors

Boosting practical capacitance of anodes is one of keys to the development of aqueous asymmetric supercapacitors (ASCs). Herein, 3D interconnected Fe-Co-S nanosheets network with plenty of wrinkles grown on graphene coated Ni foam (GNF) is obtained by rationally controlling the micro-morphology of Fe-Co-S. Such a unique structure forms abundant pores and creates large accessible surface area and high porosity to favor high capacitance while the wrinkles netting with each other is favorable for charge transfer in the active materials. Meanwhile, energy storage mechanism of the Fe-Co-S anode reveals that both Fe and Co elements contribute capacitance via Fe0/Fe2+/Fe3+ and Co0/Co2+ reversible redox reactions during charging and discharging processes. As a result, the prepared Fe-Co-S/GNF delivers a high specific capacitance of 1.7 F/cm2 (850 F/g) at a current density of 1 mA/cm2. Coupled with a Ni-Bi-S/NF cathode, a specific capacitance of 7.54 F/cm3 and a remarkable energy density of 2.68 mWh/cm3 at a high current density of 16.67 mA/cm2 are obtained for the Ni-Bi-S/NF//Fe-Co-S/GNF aqueous ASC. Even at a super-high current density of 83.33 mA/cm2, those values still keep at 2.99 F/cm3 and 1.06 mWh/cm3, respectively. These findings display the huge application potential of the Fe-Co-S/GNF anode for ASCs.

Reduced CoNi2S4 nanosheets decorated by sulfur vacancies with enhanced electrochemical performance for asymmetric supercapacitors

Nowadays, it is a matter of great concern to design electrode materials with excellent electrochemical performance for supercapacitors by a safe, efficient and simple method. And these characteristics are usually related to the vacancies and impurities in the electrode. To investigate the effect of the vacancies on the electrochemical properties of the supercapacitor cathode material, the uniform reduced CoNi2S4 (r-CoNi2S4) nanosheets with sulfur vacancies have been successfully prepared by a one-step hydrothermal method. And the formation of sulfur vacancies are characterized by Raman, X-ray photoelectron spectroscopy and other means. As the electrode for supercapacitor, the r-CoNi2S4 nanosheet electrode delivers a high capacity of 1918.9 F g−1 at a current density of 1 A g−1, superior rate capability (87.9% retention at a current density of 20 A g−1) and extraordinary cycling stability. Compared with the original CoNi2S4 nanosheet electrode (1226 F g−1 at current density of 1 A g−1), the r-CoNi2S4 nanosheet electrode shows a great improvement. The asymmetric supercapacitor based on the r-CoNi2S4 positive electrode and activated carbon negative electrode exhibits a high energy density of 30.3 W h kg−1 at a power density of 802.1 W kg−1, as well as excellent long-term cycling stability. The feasibility and great potential of the device in practical applications have been successfully proved by lightening the light emitting diodes of three different colors.

Nanowire-assembled Co3O4@NiS core–shell hierarchical with enhanced electrochemical performance for asymmetric supercapacitors

In this study, a three-dimensional (3D) hierarchical Co3O4@NiS core–shell heterostructure supported on nickel foam (NF) has been constructed. This Co3O4@NiS/NF can directly serve as a binder-free electrode for a pseudocapacitor, which could achieve a high specific capacitance of 1395.3 F g−1 at a current density of 1 A g−1 in 6 M KOH electrolyte, and an ideal rate capability of 711 F g−1 at a current density of 10 A g−1. Additionally, the electrode has a high capacitance retention of 89.9% after 5000 cycles. The asymmetric supercapacitor exhibits the maximum energy density of 61.34 W h kg−1 at a power density of 800 W kg−1, as well as an excellent cycling life of 89.3% capacitance retention. The enhanced electrochemical performance can be mainly ascribed to the special 3D core–shell nanowire arrays nanostructure with great conductivity, enlarged surface area, abundant accessible active sites and intrinsic stability. We anticipate that the present Co3O4@NiS/NF could be a promising electrode material for energy storage applications.

Controllable synthesis of NiSe/MoSe2/MoO2 3D hierarchical hollow microspheres with enhanced performance for asymmetric supercapacitors

The application of hybrid materials with well-designed composition and morphology is an effective approach towards enhanced electrochemical performance of asymmetric supercapacitors (ASCs). Here a facile two-step growth-annealing strategy to construct a NiSe/MoSe2/MoO2 three-dimensional (3D) hierarchical hollow architecture comprising two-dimensional (2D) thin nanoflakes is reported. The reaction time and Ni/Mo mole ratio of precursor are crucial for the construction of NiSe/MoSe2/MoO2 3D hierarchical hollow microsphere (HHM). The as-synthesized NiSe/MoSe2/MoO2 3D HHM with large specific surface area and well-developed mesoporous can increase contact area between active material and electrolyte, and shorten the path and time for electrolyte ions transport, thereby achieving outstanding electrochemical performance. The NiSe/MoSe2/MoO2 3D HHM shows a high specific capacitance of 1061 F g−1 at a current density of 2 A g−1, exceptional rate capability (maintaining 57% of its initial capacitance at 20 A g−1) and stable long-term cycling performance (retaining 93.9% of its initial capacitance after 10,000 cycles at 3 A g−1). Moreover, the NiSe/MoSe2/MoO2 3D HHM-based ASC provides a high energy density of 48.1 Wh kg−1 at a power density of 428 W kg−1, and still maintains 20.4 Wh kg−1 even at a high power density of 7.3 kW kg−1, suggesting its great potential in superior-performance ASCs.

Fabrication of Solid-State Asymmetric Supercapacitors Based on Aniline Oligomers and Graphene Electrodes with Enhanced Electrochemical Performances.

This work describes solid-state asymmetric supercapacitors (ASCs), composed of aniline oligomers as a cathode, nonoxidative graphene sheet as an anode, and polyvinyl alcohol–potassium hydroxide gel as an electrolyte. The synergistic effects resulting from the combination of aniline oligomer and graphene sheet have greatly enhanced the electrical and electrochemical performance of ASCs. The electrical and electrochemical properties of ASCs were highly dependent on the protonation levels of aniline oligomers including aniline tetramer, aniline trimer, and aniline dimer. The aniline tetramer with an appropriate chain length provided higher carrier transport within the anode compared to that of the aniline dimer and trimer. The water-dispersible graphene (WDG) sheets greatly enhanced structural stability and cycle life of aniline tetramers by alleviating swelling, chain scission, and shrinking of the aniline tetramers. The ASC composed of aniline tetramer/WDG sheet exhibited high areal capacitance (62.2 mF/cm2), volumetric capacitance (207.4 F/cm3), and good cycling stability (97.2% after 2000 cycles and 90.4% after 10 000 cycles). The strategy presented in this work is simple and facile, which would give an insight into efficient ways for applying aniline tetramers and graphene sheet for state-of-art electronic applications.

Hierarchical coating of MnO2 nanosheets on ZnCo2O4 nanoflakes for enhanced electrochemical performance of asymmetric supercapacitors

The design of heterostructured pseudo-capacitive materials plays a key role in fabricating asymmetric supercapacitors (ASCs) with high energy density and electrochemical cycle life for the evolution of next-generation energy storage devices. Use of ZnCo2O4 nanoflakes covered with MnO2 nanosheets led to a synergistic effect that produced a larger electroactive surface area for charge storage than that provided by bare ZnCo2O4 nanoflakes or MnO2 nanosheets. The ZnCo2O4 nanoflakes served as the backbone for the growth of the MnO2 nanosheets. The ZnCo2O4-MnO2 heterostructure was synthesized on Ni foam using a combined binder-free electrodeposition and hydrothermal method. The electrode formed using this unique method showed a maximum specific capacitance of 2057 F g−1 at a current density of 1 A g−1 with a rate capability of 65% even after a 15-fold increase in current density. Moreover, the electrode showed a cycling stability of 96.5% after 5000 successive cycles at a current density of 15 A g−1. An ASC formed using ZnCo2O4-MnO2 as the positive electrode and activated carbon as the negative electrode delivered a maximum energy density of 69 W h kg-1 with 93.5% capacity retention after 5000 cycles. Further, an experiment to investigate the commercial application of ASCs was conducted.

Ultra-high-rate, ultra-long-life asymmetric supercapacitors based on few-crystalline, porous NiCo2O4 nanosheet composites

A few-crystalline, porous NiCo2O4 nanosheet composite (FCP-NiCo2O4/RGO/CNTs) has been synthesized and it exhibits superior electrochemical performance for asymmetric supercapacitors, especially in terms of ultra-high-rate and ultra-long cycle life.

Advanced binder-free electrodes based on CoMn2O4@Co3O4 core/shell nanostructures for high-performance supercapacitors.

Three-dimensional (3D) hierarchical CoMn2O4@Co3O4 core/shell nanoneedle/nanosheet arrays for high-performance supercapacitors were designed and synthesized on Ni foam by a two-step hydrothermal route. The hybrid nanostructure exhibits much more excellent capacitive behavior compared with either the pristine CoMn2O4 nanoneedle arrays alone or Co3O4 nanosheets alone. The formation of an interconnected pore hybrid system is quite beneficial for the facile electrolyte penetration and fast electron transport. The CoMn2O4@Co3O4 electrode can achieve a high specific capacitance of 1627 F g−1 at 1 A g−1 and 1376 F g−1 at 10 A g−1. In addition, an asymmetric supercapacitor (ASC) was assembled by using the CoMn2O4@Co3O4 core/shell hybrid nanostructure arrays on Ni foam as a positive electrode and activated carbon as a negative electrode in an aqueous 3 M KOH electrolyte. A specific capacitance of 125.8 F g−1 at 1 A g−1 (89.2% retention after 5000 charge/discharge cycles at a current density of 2 A g−1) and a high energy density of 44.8 W h kg−1 was obtained. The results indicate that the obtained unique integrated CoMn2O4@Co3O4 nanoarchitecture may show great promise as ASC electrodes for potential applications in energy storage.

Energy storage performance of hybrid aqueous supercapacitor based on nano-Li2MnSiO4 and activated carbon

Novel asymmetric supercapacitor (ASC) composed of nanocrystalline Li2MnSiO4 (LMS) and activated carbon (AC) in aqueous electrolyte is investigated. ASC is tested in three different electrolytes, viz. 2 M KOH, 2 M LiOH, and 2 M Li2SO4. The aqueous solution of 2 M KOH is found to be an appropriate electrolyte in terms of better capacitance, cyclability, and rate capability probably due to a smaller hydration sphere radius and larger ionic conductivity of K+ ions. The electrochemical performance of ASC is examined using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) cycling, and results are complimented with electrochemical impedance spectroscopy (EIS). Novel ASC exhibits the specific capacitance of 60 (±5) F g−1 at 3 mV s−1 in 2 M KOH. The excellent cyclability (till 5000 cycles) is also observed. The improved supercapacitive properties are mainly ascribed to the unique morphology of LMS (surface area ∼30 m2 g−1 and homogenous meso-pore distribution) which provides easy percolation of electrolytic ions to provide better formation of electric double layer with minor redox behavior. The ex situ X-ray diffraction (XRD) measurement was carried out on a cycled electrode to support the plausible reaction mechanism.