Next-generation Supercapacitors Research Articles

Design and Fabrication of Highly Porous 2D Bimetallic Sulfide ZnS/FeS Composite Nanosheets as an Advanced Negative Electrode Material for Supercapacitors

Metal sulfides delivered much better electrochemical performance over metal oxides due to the extended potential window with high conductivity and therefore are much investigated in the field of energy storage applications. Herein, binder-free two-dimensional bimetallic (ZnS/FeS) interconnected composite nanosheet arrays are synthesized on carbon cloth (2D-ZFS@CC) as an innovative negative electrode material for supercapacitors. The 2D-ZFS@CC exhibits improved capacitance (1367.5 F g–1/1641 C g–1 at 3 A g–1), rate-capability (58.5% at 10-fold high current density), and capacitance retention (87%) over bimetallic oxide (ZnFe2O4). This is accomplished by intelligently regulating the morphology to generate numerous pores with a wide accessible surface area and high porosity, which favors high capacitance, whereas the binder-free nature of the active material promotes fast charge transfer characteristics. Moreover, the kinetic analysis suggested that the 2D-ZFS@CC electrode stored charge based on the hybrid charge storage mechanism with b values of 0.70 and 0.72 for anodic and cathodic peaks, respectively. These results demonstrate the significant potential application of 2D-ZFS@CC as a negative electrode material for next-generation supercapacitor electrodes.

Novel electrochemical deposition of Co(CO3)0.5(OH)∙0.11H2O nano-needles with folded umbrella-like architecture onto nickel foam for supercapacitors

Here, we developed a novel anodic hydrothermal electrochemical deposition technology capable of directly growing a film of Co(CO3)0.5(OH)∙0.11H2O∙0.11H2O onto nickel foam for supercapacitors. The resultant film exhibited a morphology of nano-needles with folded umbrella-like architecture, different from the smooth needle-like morphology in reported articles, and could deliver a specific capacitance of 2.455 F·cm−2 (1227F·g−1) at 5 mA∙cm−2, a rate capability of 58.9% after a 6 fold increase in the charge/discharge current density and a capacity retention of 93.7% after 10,000 cycles in a three-electrode electrolytic cell. When packaged as a two-electrode asymmetric supercapacitor (ASC) device with the Co(CO3)0.5(OH)∙0.11H2O film electrode as the positive electrode and active‑carbon as the positive electrode, the ASC device exhibited specific capacitances of 1.46(112.3), 1.38(106.2), 1.36(104.6), 1.25(96.2) and 1.11 F·cm−2 (85.4 F·g−1) at 5, 8, 10, 20 and 30 mA∙cm−2, and the capacitance retention rate of 72.9% after 10,000 cycles at 8 mA∙cm−2. The results demonstrate the potential of anodic hydrothermal electrochemical deposition in fabricating the film of active electrode materials on conductive substrates for next-generation supercapacitor with high performance.

Facile synthesis of layered NiCo2S4/NiO/nickel foam nanoarchitecture as a sophisticated efficient electrode for next-generation supercapacitors

The current study demonstrates the layered nanospheres of NiCo2S4/NiO/NF that were synthesized using the facile and economical chemical bath deposition that was employed as a potential electrode for supercapacitors. Various electrochemical analyses were made using cyclic voltammetry, galvanostatic charge-discharge, potentiostatic electron impedance spectroscopy. The structure, phase, morphology, and chemical composition were examined by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The as-synthesized precursors of electroactive material behavior were illustrated by the three-electrode setup where 3 M KOH was deployed as an electrolyte. The peculiar and unique structural features of the nanoparticles enable and deliver effective pathways for swift electronic and ionic diffusion. Hence, as-synthesized binder-free NCS/NiO/NF showed a dominant specific capacity of 188.03 mA h g−1 at a current density of 1 A g−1, the enhanced rate capability of 80.63%, and the predominant cycling stability of 92.56% over 4000 cycles which are considered an appreciable value than the independent NCS/NF and NiO/NF electrodes. The results in this study portray the fact that the nanocomposite of NCS/NiO/NF establishes an excellent energy storage performance for next-generation supercapacitor applications.

Three-Dimensional Hierarchical Core/shell Electrodes Using Highly Conformal TiO2 and Co3O4 Thin Films for High-Performance Supercapattery Devices.

The rational design and development of novel electrode materials with promising nanostructures is an effective technique to improve their supercapacitive performance. This work presents high-performance core/shell electrodes based on three-dimensional hierarchical nanostructures coated with conformal thin transition-metal oxide layers using atomic layer deposition (ALD). This effective interface engineering creates disorder in the electronic structure and coordination environment at the interface of the heteronanostructure, which provides many more reaction sites and rapid ion diffusion. At 3 A g-1, the positive CuCo2O4/Ni4Mo/MoO2@ALD-Co3O4 electrode introduced here exhibits a specific capacity of 1029.1 C g-1, and the fabricated negative Fe3O4@ALD-TiO2 electrode significantly outperforms conventional carbon-based electrodes, with a maximum specific capacity of 372.6 C g-1. The supercapattery cell assembled from these two interface- and surface-tailored electrodes exhibits a very high energy density of 110.4 W h kg-1 with exceptional capacity retention over 20,000 cycles, demonstrating the immense potential of ALD for the next generation of supercapacitors.

Graphene's Role in Emerging Trends of Capacitive Energy Storage.

Technological breakthroughs in energy storage are being driven by the development of next-generation supercapacitors with favorable features besides high-power density and cycling stability. In this innovation, graphene and its derived materials play an active role. Here, the research status of graphene supercapacitors is analyzed. Recent progress is outlined in graphene assembly, exfoliation, and processing techniques. In addition, electrochemical and electrical attributes that are increasingly valued in next-generation supercapacitors are highlighted along with a summary of the latest research addressing chemical modification of graphene and its derivatives for future supercapacitors. The challenges and solutions discussed in the review hopefully will shed light on the commercialization of graphene and a broader genre of 2D materials in energy storage applications.

Mn3-x Fex O4 Hollow Nanostructures for High-Performance Asymmetric Supercapacitor Applications.

Design of hollow nanostructure and controllable phase of mixed metal oxides for improving performance in supercapacitor applications is highly desirable. Here we demonstrate the rational design and synthesis of Mn3-x Fex O4 hollow nanostructures for supercapacitor applications. Owing to high porosity and the specific surface area that provides more active sites for electrochemical reactions, the electrochemical performance of Mn3-x Fex O4 hollow nanostructure substantially enhanced comparing with pristine Mn3 O4 . Particularly, in 1.0 M KOH electrolyte, Mn0.16 Fe2.84 O4 with a typical diameter of 20 nm exhibits excellent specific capacitance of 2675, 2320, 1662, 987 F g-1 at current densities of 1, 2, 5, 10 A g-1 , respectively, which is significantly superior to those of other transition metal oxides. Besides, an asymmetric supercapacitor is assembled by using Mn0.16 Fe2.84 O4 and activated carbon as a positive and a negative electrode, respectively. Electrochemical results indicate a high energy density of 42 Wh kg-1 at a power density of 0.75 kW kg-1 , which makes this hollow nanostructure a highly promising electrode for achieving high-performance next-generation supercapacitors.

Ionic Liquids for Supercapacitive Energy Storage: A Mini-Review

Ionic liquids (ILs), composed of bulky organic cations and versatile anions, have sustainably found widespread utilizations in promising energy-storage systems. Supercapacitors, as competitive high-power devices, have drawn tremendous attention due to high-rate energy harvesting and long-term durability. The electric energy of supercapacitors is stored through the ion dynamics and physicochemical interactions at the electrolyte/electrode interface. To satisfy the high-energy request for building better supercapacitors, ILs stand out by virtue of the characteristic negligible vapor pressure and molecular designability, coupled with several fascinating features including a highly ionized environment, good thermal/chemical stability, and universal solubility/affinity. This mini-review offers an overview of recent IL utilizations in both electrolyte exploitation and electrode synthesis for supercapacitors. On the role of IL-based electrolyte components, three representative types (i.e., neat IL electrolytes, IL mixtures, and IL (quasi-)solid-state electrolytes) are applied to put aside the water-splitting roadblock, thus affording high charge storage under wide electrochemical stability potentials. On the other hand, the involvement of ILs in material science is described as microstructure-directing agents, heteroatom dopants, and carbon precursors, respectively, for the purpose of boosting the interfacial physicochemical interactions toward superior electrode capacitances. Finally, current challenges and future outlooks associated with IL media/materials are summarized for next-generation supercapacitor applications.

Temperature dependence for high electrical performance of Mn-doped high surface area activated carbon (HSAC) as additives for hybrid capacitor

Herein, we manufactured the positive and negative electrodes for the hybrid capacitor. The Mn-doped High surface area of Activated carbon composite used for the positive electrode and as-prepared composite was calcined at 600 °C and 800 °C. The morphological structures and pore-size distributions of MnYP-600HTT and MnYP-800HTT were characterized by means of XRD, SEM, EDAX, TEM, and BET. According to the BET specific surface-area evaluation, MnYP-600HTT and MnYP-800HTT were 1272.6 and 1388.1 m2/g, respectively. Total pore volumes were 0.627 and 0.687 cm3/g, which is beneficial for forming ion-transport channels in electrochemical reactions. The MnYP-600HTT electrode had a high specific capacity of 177.2 mAh/g at 20C, and the capacity retention was 64.8%. During the entire cycling, MnYP-600HTT had excellent cyclic stability in 500 cycles along with high efficiency. The robust design of the MnYP-600HTT and MnYP-800HTT cathode materials introduced in this work pave the way for designing next-generation supercapacitors operating at ultra-high C rates. The Mn-doped high surface of activated carbon had stable energy density and superior cycling stability that were demonstrated in supercapacitor systems.

Building next-generation supercapacitors with battery type Ni(OH)2

This review exclusively elaborates the unnoticed vision into the design, fabrication, mechanism, and investigation of fascinating Ni(OH)2-based supercapacitors in an asymmetric fashion.

Role of electrolytes on the electrochemical characteristics of Fe3O4/MXene/RGO composites for supercapacitor applications

This study aims at developing hybrid composite materials consisting of iron oxide (Fe3O4) /MXene /reduced graphene oxide (RGO) without any impurities using optimized experimental parameters to be utilized in next-generation supercapacitor applications and the searching of suitable electrolyte for the developed hybrid electrode materials. We have generated Fe3O4-decorated MXene nanosheets on RGO by a simple chemical oxidation method. The initial grain size of Fe3O4 of about 43 nm is further reduced to 30 nm when prepared with MXene nanosheets. The as-prepared samples are used as a negative electrode material and their capacitive performance is analyzed in potassium hydroxide (KOH), sodium sulphate (Na2SO4) and lithium chloride (LiCl) electrolytes. Fe3O4/MXene/RGO nanocomposites showed the best performance. Regarding the electrolytes, the following order has been obtained 5 M LiCl > 1 M Na2SO4 > 1 M KOH, which matches well with the bare ion size order. Moreover, Fe3O4/MXene/RGO electrode exhibits an 82.1% of cyclic stability up to 5000 charge/discharge cycles at a current density of 5 A g-1 demonstrating the best performance.

A Bottom‐up In‐situ Preparation of Graphene‐like Porous Carbon for Ultrahigh Surface Area Specific Capacitance Supercapacitors

AbstractNitrogen‐doped porous carbon is an ideal electrode material for supercapacitors, and the development of efficient and inexpensive graphene‐based porous carbon is of great significance to promote its application. In this study, a bottom‐up in‐situ method is developed to grow nitrogen‐doped 3D graphene‐like porous carbon (Cu‐GL‐NPC) with Cu as a catalyst. The Cu‐GL‐NPC possessed the high nitrogen content of 7.64% and the high ratio of pyrrolic nitrogen, along with open three‐dimensional porous structure, which led to the smooth transfer of electrolyte. Consequently, the Cu‐GL‐NPC delivered an extremely high surface area specific capacitance of 49.2 μF cm−2 at a current density of 1 A g−1. This study provides an insight for better understanding the effect of catalysts on the formation of porous carbon, which is beneficial for the design of new nanocarbon materials with different structures and different nitrogen doping types, and would offer ideas for the development of carbon materials for the next generation of supercapacitors.

ZnO-assisted synthesis of lignin-based ultra-fine microporous carbon nanofibers for supercapacitors

Reducing the material size could be an effective approach to enhance the electrochemical performance of porous carbons for supercapacitors. In this work, ultra-fine porous carbon nanofibers are prepared by electrospinning using lignin/ polyvinylpyrrolidone as carbon precursor and zinc nitrate hexahydrate (ZNH) as an additive, followed by pre-oxidation, carbonization, and pickling processes. Assisted by the ZnO template, the pyrolytic product of ZNH, abundant micropores are yielded, leading to the formation of microporous carbon nanofibers with specific surface area (SSA) up to 1363 m2 g−1. The average diameter of the lignin-based ultra-fine porous carbon nanofibers (LUPCFs) is effectively controlled from 209 to 83 nm through adjusting the ZNH content. With good flexibility and self-standing nature, the LUPCFs could be directly cut into electrodes for use in supercapacitors. High accessible surface, enriched surface N/O groups, and reduced fiber diameters endow the LUPCFs-based electrodes with an excellent specific capacitance of 289 F g−1. The reduction of fiber diameters remarkably improves the rate performance of the LUPCFs and leads to a low relaxation time constant of 0.37 s. The high specific capacitance of 162 F g−1 is maintained when the current density is increased from 0.1 to 20 A g−1. Besides, the fabricated LUPCFs show exceptional cycling stability in symmetrical supercapacitors, manifesting a promising application prospect in the next generation of supercapacitors.

A facile synthesis of boron nitride supported zinc cobalt sulfide nano hybrid as high-performance pseudocapacitive electrode material for asymmetric supercapacitors

High specific energy, extended working potential, and elevated cyclic stability are the major issues regarding supercapacitor technology. To fabricate a competent hybrid supercapacitor electrode, it is necessary to combine both pseudocapacitive and electric double-layer capacitor (EDLC)-type materials smartly. The prime objective of this work is to develop a high-performance asymmetric supercapacitor (ASC) device with long-term cycling stability and extended working potential. Accordingly, an ASC device was fabricated by using sphere-like pseudocapacitive Zinc Cobalt sulfide (ZCS) in combination with other pseudocapacitive [Boron Nitride (BN) and Polypyrrole (PPY)] and EDLC-type [CNT] materials. The synthesized quaternary composite exhibited maximum specific capacitance (Csc) of 534 and 785 F/g in aqueous (1 M KCl) and organic [(1 M TEABF4 in acetonitrile (ACN)] electrolytes, respectively. Moreover, it also exhibited excellent cycling stability (capacitance retention of 106% after 10,000 charge/discharge cycles) in aqueous electrolyte. Apart from this, a theoretical study has been exposed to determine the EDLC and pseudocapacitive contribution of the electrode materials. Further, the ASC device exhibited an extended working potential (worked up to 1.8 V) with high specific energy of 49.6 Wh/kg in organic electrolyte. With these promising electrochemical performance, this mixed metal chalcogenide based ASC is considered as potential candidate for next-generation supercapacitors.

Current Research of Graphene-Based Nanocomposites and Their Application for Supercapacitors.

This review acmes the latest developments of composites of metal oxides/sulfide comprising of graphene and its analogues as electrode materials in the construction of the next generation of supercapacitors (SCs). SCs have become an indispensable device of energy-storage modes. A prompt increase in the number of scientific accomplishments in this field, including publications, patents, and device fabrication, has evidenced the immense attention they have attracted from scientific communities. These efforts have resulted in rapid advancements in the field of SCs, focusing on the development of electrode materials with features of high performance, economic viability, and robustness. It has been demonstrated that carbon-based electrode materials mixed with metal oxides and sulfoxides can perform extremely well in terms of energy density, durability, and exceptional cyclic stability. Herein, the state-of-the-art technologies relevant to the fabrication, characterization, and property assessment of graphene-based SCs are discussed in detail, especially for the composite forms when mixing with metal sulfide, metal oxides, metal foams, and nanohybrids. Effective synthetic methodologies for the nanocomposite fabrications via intercalation, coating, wrapping, and covalent interactions will be reviewed. We will first introduce some fundamental aspects of SCs, and briefly highlight the impact of graphene-based nanostructures on the basic principle of SCs, and then the recent progress in graphene-based electrodes, electrolytes, and all-solid-state SCs will be covered. The important surface properties of the metal oxides/sulfides electrode materials (nickel oxide, nickel sulfide, molybdenum oxide, ruthenium oxides, stannous oxide, nickel-cobalt sulfide manganese oxides, multiferroic materials like BaMnF, core-shell materials, etc.) will be described in each section as per requirement. Finally, we will show that composites of graphene-based electrodes are promising for the construction of the next generation of high performance, robust SCs that hold the prospects for practical applications.

In-situ hydrothermal synthesis of δ-MnO2/soybean pod carbon and its high performance application on supercapacitor

Manganese dioxide, with large theoretical capacitance, is a promising electrode material of supercapacitors, while the poor cyclic stability limits its practical application. Traditional carbon loading using graphene or carbon nanotube is still unsatisfactory due to high cost. In this study, renewable waste of soybean pod was utilized as the precursor of carbon matrix. The MnO2/soybean pod carbon composite material was synthesized by a one-step in-situ hydrothermal method. The composite material displayed natural tube structure, and its surface was sheathed with numerous δ-MnO2 nanorods. After carbon loading, the MnO2/soybean pod carbon delivered a superior specific capacitance of 530 F g–1 in Na2SO4 electrolyte as the three-electrode system, 46% higher than 362 F g–1 of pristine MnO2. Using the symmetrical two-electrode system, such the composite electrode further revealed high capacitance retention of 91% and reversible capacitance of 189 F g–1 after 6000 charge/discharge cycles. It demonstrates that this work develops a scalable strategy to obtain high-performance and cost-effective electrode material of next-generation supercapacitors.

Fabrication of Boron-Doped Activated Carbon for Zinc-Ion Hybrid Supercapacitors

Zinc-ion hybrid supercapacitors (ZICs) have recently been spotlighted as energy storage devices due to their high energy and high power densities. However, despite these merits, ZICs face many challenges related to their cathode materials, activated carbon (AC). AC as a cathode material has restrictive electrical conductivity, which leads to low capacity and lifetime at high current densities. To overcome this demerit, a novel boron (B) doped AC is suggested herein with improved electrical conductivity thanks to B-doping effect. Especially, in order to optimize B-doped AC, amounts of precursors are regulated. The optimized B-doped AC electrode shows a good charge-transfer process and superior electrochemical performance, including high specific capacity of 157.4 mAh g−1 at current density of 0.5 A g−1, high-rate performance with 66.6 mAh g−1 at a current density of 10 A g−1, and remarkable, ultrafast cycling stability (90.7 % after 10,000 cycles at a current density of 5 A g−1). The superior energy storage performance is attributed to the B-doping effect, which leads to an excellent charge-transfer process of the AC cathode. Thus, our strategy can provide a rational design for ultrafast cycling stability of next-generation supercapacitors in the near future.

Synthesis of rGO/CuO/Ag Ternary Nanocomposites Via Hydrothermal Approach for Opto-electronics and Supercapacitor Applications

The present investigation deals with the synthesis of reduced graphene oxide (rGO)/copper oxide (CuO)/silver (Ag) ternary nanocomposites (NCs) by hydrothermal method to improve the electrical behavior. In typical synthesis, ammonia was used as a reducing agent at room temperature. The powder X-ray diffraction (PXRD) pattern revealed the existence of single-phase monoclinic structure and face-centered cubic (FCC) phase of CuO and Ag. Other phase impurities were also observed from the prepared rGO/CuO/Ag NCs. The surface morphology of rGO/CuO/Ag NCs was investigated by SEM and TEM analysis. The surface elemental composition of the prepared material was investigated by the EDAX analysis. The dielectric response of the materials was studied by dielectric constant, dielectric loss, and AC conductivity studies. The lesser amount of activation energy was attained from the synthesized rGO/CuO/Ag NCs, and it was proved that this type of material is the most emerging candidate for various opto-electronics application. The electrochemical behavior was studied by the cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. From this study, ideal capacitance behavior with high capacitance of about 575 F/g was achieved respectively for rGO/CuO/Ag NCs at the current density of 1 Ag−1in 0.5 M K2SO4 electrolyte solution. These superior electrochemical features demonstrated that the prepared rGO/CuO/Ag NCs are a potential candidate for next-generation supercapacitor systems.

Comparative Study of the Supercapacitive Performance of Three Ferrocene-Based Structures: Targeted Design of a Conductive Ferrocene-Functionalized Coordination Polymer as a Supercapacitor Electrode.

As redox-active based supercapacitors are known as highly desirable next-generation supercapacitor electrodes, the targeted design of two ferrocene-functionalized (Fc(COOH)2 ) clusters based on coinage metals, [(PPh3 )2 AgO2 CFcCO2 Ag(PPh3 )2 ]2 ⋅7 CH3 OH (SC1 : super capacitor) and [(PPh3 )3 CuO2 CFcCO2 Cu(PPh3 )3 ]⋅3 CH3 OH (SC2 ), is reported. Both structures are fully characterized by various techniques. The structures are utilized as energy storage electrode materials, giving 130 F g-1 and 210 F g-1 specific capacitance at 1.5 A g-1 in Na2 SO4 electrolyte, respectively. The obtained results show that the presence of CuI instead of AgI improves the supercapacitive performance of the cluster. Further, to improve the conductivity, the PSC2 ([(PPh3 )2 CuO2 CFcCO2 ]∞ ), a polymeric structure of SC2 , was synthesized and used as an energy storage electrode. PSC2 displays high conductivity and gives 455 F g-1 capacitance at 3 A g-1 . The PSC2 as a supercapacitor electrode presents a high power density (2416 W kg-1 ), high energy density (161 Wh kg-1 ), and long cycle life over 4000 cycles (93 %). These results could lead to the amplification of high-performance supercapacitors in new areas to develop real applications and stimulate the use of the targeted design of coordination polymers without hybridization or compositions with additive materials.

Ultrafast long-life zinc-ion hybrid supercapacitors constructed from mesoporous structured activated carbon

Zinc-ion hybrid supercapacitors (ZICs) with high capacity and long life provide an intelligent solution that will expand the scope of energy storage applications in the future. Nevertheless, activated carbon (AC) as a cathode material still encounters serious challenges because of the low ionic diffusion and transport ability due to its microporous structure and poor wettability during cycling, which leads to rapid capacity and life fading at high current densities. In this paper, we present an engineered surface of AC with a mesoporous structure and an improved wettability using a dehydrogenation process of polyvinylpyrrolidone for ultrafast long-life ZICs. The developed ZIC exhibits an excellent energy storage performance with a high specific capacity of 176 mAh g−1 at a current density of 0.5 A g−1 and an outstanding high-rate performance of 72 mAh g−1 at 10 A g−1, in addition to a robust ultrafast long life of over 40,000 cycles and a 78% capacity retention. The superior energy storage characteristics are strongly attributed to unique mesopores on the surface and an improved wettability that provide enlarged surface areas and facile ionic diffusion/transport capability of the AC cathode, demonstrating the promising potential of ZICs as next-generation supercapacitors.

Non-peripheral octamethyl-substituted copper (II) phthalocyanine nanorods with MXene sheets: An excellent electrode material for symmetric supercapacitor with enhanced electrochemical performance

MXene based composites are promising candidates with a broad range of potential applications, especially in electrochemical energy storage and conversion devices. In this work, we demonstrate the preparation of a novel MXene/N–CuMe2Pc (non-peripheral octamethyl-substituted copper (II) phthalocyanine) based composite as the electrode material in supercapacitors. The integration of highly redox-active N–CuMe2Pc into MXene leads to the large surface area, which enhances the active sites for electrochemical redox reactions. For instance, composite prepared with a weight ratio of 1:0.2 of MXene:N–CuMe2Pc (M10P2) exhibits remarkable maximum specific capacitance of 786.1 F g−1. The enhanced capacitance performance is attributed to the synergistic effect of water intercalated MXene layers and N–CuMe2Pc. The constructed M10P2 based symmetric supercapacitor shows excellent performance with a maximum energy density of 8.84 Wh kg−1 with a power density of 112.3 W kg−1. Additionally, the symmetric device exhibits outstanding cyclic stability (92.3%) even after 20,000 cycles with satisfactory Coulombic efficiency. This work proves the new insight of preparation of MXene/N–CuMe2Pc composites for high-performance next-generation supercapacitor sectors in the near future.