Excellent Energy Storage Capability Research Articles

Strategies for Advanced Supercapacitors Based on 2D Transition Metal Dichalcogenides: From Material Design to Device Setup.

Recently, the development of new materials and devices has become the main research focus in the field of energy. Supercapacitors (SCs) have attracted significant attention due to their high power density, fast charge/discharge rate, and excellent cycling stability. With a lamellar structure, 2D transition metal dichalcogenides (2D TMDs) emerge as electrode materials for SCs. Although many 2D TMDs with excellent energy storage capability have been reported, further optimization of electrode materials and devices is still needed for competitive electrochemical performance. Previous reviews have focused on the performance of 2D TMDs as electrode materials in SCs, especially on their modification. Herein, the effects of element doping, morphology, structure and phase, composite, hybrid configuration, and electrolyte are emphatically discussed on the overall performance of 2D TMDs-based SCs from the perspective of device optimization. Finally, the opportunities and challenges of 2D TMDs-based SCs in the field are highlighted, and personal perspectives on methods and ideas for high-performance energy storage devices are provided.

A structured phase change material integrated by MXene/AgNWs modified dual-network and polyethylene glycol for energy storage and thermal management

Phase change materials (PCMs) present promising potential in the application of thermal management. Nevertheless, low thermal conductivity and risk of liquid leakage hindered the development of PCMs with broad adoption. Here, we fabricate a shape-stable composite phase change material by encapsulating polyethylene glycol (PEG) into a dual-network hydrogel, which was modified using Ti3C2Tx MXenes and silver nanowires (AgNWs). With the synergistic effect of MXene nanosheets and AgNWs, the composite material that was prepared demonstrates a significant increase in thermal conductivity, reaching a value of 0.64 (W/m·K) and also exhibits a suitable photo-thermal conversion efficiency (88.9%). Moreover, the resulting composite PCM with high-level of PEG loading (90.1%) deliver a remarkable phase change enthalpy (124.8 J/g), highlighting its excellent energy storage capability. Additionally, the final composite displays reliable structural stability and exceptional thermal management performance by reducing the operational temperature of a typical lithium-ion battery by over 12 °C during a 3C discharge process. We demonstrate a promising approach for developing composite PCM for thermal management.

Ni6Se5, an unexplored transition metal chalcogenide of formula M(n+1)Xn(2≤n≤8), for high-performance hybrid supercapacitor and Li-ion battery application.

This work reports an in-situ, one-step hydrothermal preparation procedure of a binder-free electrode growth of Ni6Se5on nickel foam (Ni6Se5/NF) with a rod-like structure. Ni6Se5is an enveloped transition metal chalcogenides of formula M(n+1)Xn(where 2≤n≤8, M is a transition metal and X is chalcogen) of the nickel selenide family. The Ni6Se5/NF electrode described here demonstrates an exceptional lifetime of 81% capacitance retention over 20000 cycles and a high specific capacitance of 473.5 Fg-1at a current density of 4 Ag-1. The Ni6Se5/NF/activated carbon asymmetric supercapacitor exhibits a remarkable 97.3 Whkg-1energy density and a 2325 Wkg-1power density. Ni6Se5served as an active electrode material in supercapacitor applications and offered exceptional power density and long cycle life. Ni6Se5/NF, used as an anode for Li-ion batteries (LIB), has a lithium storage capacity of 939.7 mAhg-1at 100 mAg-1current density. Ni6Se5active electrode material's excellent energy storage capability, which was previously unreported, is particularly beneficial for electrochemical energy storage device applications.

Controllable preparation of N-doped porous carbons with enhanced porosity and energy storage capacity using high internal phase emulsion template

In this work, a series of N-doped porous carbons (NPCs) are prepared via high internal phase emulsion (HIPE) template, followed by growing polyaniline (PANI) arrays and subsequent carbonization/activation. As evidenced by SEM and N2 absorption/desorption results, the NPCs have interconnected hierarchical porous structures with abundant micropores and mesopores inside. The morphology and porous structures of NPCs can be tuned by changing aniline concentration and polymerization time, respectively. With the increase of aniline concentration or polymerization time, the porous structure of NPC becomes more and more serried, however too high aniline concentration (>0.75 M) makes the porous structure become sparse, which is because excess PANI will nucleate itself and make it detach from the surface of NPC. As a result, the specific surface area (SSA) of NPCs first increases to 1769 m2/g and then decreases. Electrochemical performances of the obtained NPCs are evaluated in detail. The test results indicate that both aniline concentration and polymerization time have notable influence on the specific capacitance of NPCs. The specific capacitance of NPC obtained under optimized conditions reaches up to 241 F/g at 1 A/g with a retention ratio of 97.8% after 10, 000 cycles at a high current density, proving its excellent energy storage capability and cycling stability. In two-electrode system, the NPC provides an energy density of 27 Wh/kg at a power density of 400 W/kg and remains a high energy density of 19 Wh/kg at a high power density of 10002 W/kg.

High-Entropy Oxides Prepared by Dealloying Method for Supercapacitors

High-entropy oxides (HEOs) are materials with a multielement mixture and a stable structure, which are widely used in energy storage due to their electrochemical properties. For application to supercapacitors, the method of preparation of HEOs needs to be improved, and the energy storage mechanism of the material needs to be investigated. In this experiment, 3 M NaOH was used to etch the FeCoNiCrMnAl95 alloy, and then (FeCoNiCrMn)3O4 was successfully produced by a facile oxidation treatment. HRTEM images show that the materials have a porous structure, and EDS mapping suggests that the individual elements are evenly distributed. The XRD and SAED patterns indicate that it has a stable crystal structure. The HEOs prepared by dealloying exhibited excellent supercapacitor characteristics, with a specific capacitance of 639 F/g at 1 A/g and retention of 80.77% at 10 A/g. Density functional theory (DFT) simulations back up this excellent energy storage capability. This work offers a novel method for manufacturing HEOs and a solid option for supercapacitor anode materials.

Carbon Nanotube@Nickel Hydroxide Nanosheets Core–Shell Nanostructures Enabling Thermally Assisted 3D‐Printed Solid‐State Microsupercapacitors

Microsupercapacitors have picked up a remarkable reputation as prospective micropower sources for compact electronics. Unfortunately, the fabricating complexity of electrode structures and preparing sophistication of electrode materials have prevented their practical deployment. Herein, a one‐step low‐temperature precipitation method is applied to straightforwardly self‐assemble porous Ni(OH)2 nanosheets on the surface of carbon nanotubes (CNTs) surface beneath electrostatic interaction. The developed core–shell 1D CNTs@Ni(OH)2 nanosheets nanostructures exhibit high electron and ion conductivity, a sign of excellent energy storage capability. In this vein, a thermally assisted 3D printing process is intelligently regulated to enable the fabrication of 3D interdigital electrodes from as‐obtained materials. The ultimate solid‐state microsupercapacitors of CNTs@Ni(OH)2 nanosheets core–shell nanostructures in this way exhibit excellent cycle stability and offer an exceptional areal capacitance of 39.6 mF cm−2, approximately a size of or two higher than that of C‐based partners. A strong foundation for high‐quality microsupercapacitors is laid by the high specific capacity of CNTs@Ni(OH)2 nanosheets core–shell nanostructures and the ability to fabricate 3D interdigital electrodes using a thermally assisted 3D printing process.

Electrochemical performance of polyaniline-coated γ-MnO2 on carbon cloth as flexible electrode for supercapacitor

Carbon cloth (CC) based supercapacitor is considered as one of the most promising electrode materials for flexible supercapacitor due to their excellent flexibility and electrochemical properties. In this paper, a low-cost ternary hybrid material polyaniline-coated γ-MnO2/carbon cloth (PANI@γ-MnO2/CC) is synthesized via facile hydrothermal and in-situ electrochemical polymerization reactions for superior supercapacitor electrode materials. Flexible conductive CC can not only be used as a scaffold for the growth of γ-MnO2 and PANI but also can be used as a carbon source for generation γ-MnO2. The structure and electrochemical properties of PANI@γ-MnO2/CC composite are investigated via different testing techniques. The coating PANI layer on the surface of γ-MnO2@CC with a three-dimensional hierarchical structure provides high electroactive surface area and accelerates the ion diffusion and electron transfer. Due to synergistic effects between the components, the flexible PANI@γ-MnO2/CC composite displays a high specific capacitance of 1105 mF cm−2 (371.4 C g−1) at a current density of 1 mA cm−2 in 0.5 M H2SO4 aqueous electrolyte and long cycle stability for 2000 cycles with 86.35%, as well as good rate performance 72.3% capacitance retention from 1 to 10 mA cm−2. Furthermore, flexible asymmetric supercapacitor (FASCs) based on PANI@γ-MnO2/CC and PVA-H2SO4 gel electrolyte have been fabricated and it has shown the energy density of 10.4 mW cm−3 at a power density of 1.5 mWh cm−3. The ease of preparation and excellent energy storage capability indicates that the PANI@γ-MnO2/CC composite could be a promising electrode material for supercapacitor application.

High sodium ionic conductivity in PEO/PVP solid polymer electrolytes with InAs nanowire fillers

Solid-state sodium ion batteries are frequently referred to as the most promising technology for next-generation energy storage applications. However, developing a suitable solid electrolyte with high ionic conductivity, excellent electrolyte–electrode interfaces, and a wide electrochemical stability window, remains a major challenge. Although solid-polymer electrolytes have attracted great interest due to their low cost, low density and very good processability, they generally have significantly lower ionic conductivity and poor mechanical strength. Here, we report on the development of a low-cost composite solid polymer electrolyte comprised of poly(ethylene oxide), poly(vinylpyrrolidone) and sodium hexafluorophosphate, mixed with indium arsenide nanowires. We show that the addition of 1.0% by weight of indium arsenide nanowires increases the sodium ion conductivity in the polymer to 1.50 × 10−4 Scm−1 at 40 °C. In order to explain this remarkable characteristic, we propose a new transport model in which sodium ions hop between close-spaced defect sites present on the surface of the nanowires, forming an effective complex conductive percolation network. Our work represents a significant advance in the development of novel solid polymer electrolytes with embedded engineered ultrafast 1D percolation networks for near-future generations of low-cost, high-performance batteries with excellent energy storage capabilities.

The Ni/Ni3S2 nanocomposite derived from Ni-ZIF with superior energy storage performance as cathodes for asymmetric supercapacitor and rechargeable aqueous zinc ion battery

The design of cathode material with unique structure and excellent electrochemical property is critical for the development of energy storage device. We report herein the synthesis of a nanocomposite with heterostructure of metallic nickel (Ni) and nickel sulfide (Ni3S2) through a facile solid-gas state reaction method, using Ni-ZIF MOFs and sulfur as precursors. The electrochemical energy storage capabilities of the synthesized composite as cathodes for both supercapacitor and zinc ion batteries have been investigated. Owing to the good conductivity of metallic Ni and superior pseudocapacitive behavior of the Ni3S2, the Ni/Ni3S2 nanocomposite exhibit excellent energy storage capability in both supercapacitor and zinc ion batteries. It was revealed that the Ni/Ni3S2 nanocomposite exhibit an excellent specific capacity of 2228 F g−1 at a current density of 4 A g−1. A high capacity of 1496 F g−1 is remained even at a high current density of 12 A g−1, demonstrating good rate capability of the electrode material. When the Ni/Ni3S2 was used as the cathode material for zinc ion battery, the assembled Ni/Ni3S2//Zn aqueous zinc ion battery can provide a high energy density of 379 Wh kg−1 at power density of 0.34 kW kg−1. The battery also exhibits long-term cyclic stability with capacity retention ratio of 84.1% after 1000 cycles and good rate performance. Our work proposed a facile route to produce transition metal sulfide nanocomposite with excellent capacitive properties as cathode material for the supercapacitor and aqueous zinc ion batteries in green energy storage application.

High-performance hierarchical MnO2/CNT electrode for multifunctional supercapacitors

Supercapacitors possessing multiple functions other than storing energy, such as bearing mechanical loads, are a promising technology for a wide range of applications. However, achieving both energy storage efficiency and mechanical strength/stiffness requires structurally strong electrolytes and high-capacitance electrodes. Herein, we report a novel method of synthesizing a high-mass loading of MnO2 on carbon nanotube (CNT) mats to create nanocomposite electrodes of high capacitance and mechanical properties. With CNTs acting as structural reinforcement for the pseudocapacitive MnO2 matrix, the resulting nanocomposite electrodes exhibited an ultrahigh areal capacitance of 2579 mF/cm2 at a current density of 1 mA/cm2 and excellent mechanical properties. These electrodes were then used to fabricate flexible and mechanically strong structural supercapacitors by infusing with a PVA gel electrolyte and a PEGDGE solid electrolyte, respectively. The resulting flexible supercapacitors yielded a high areal capacitance of 947 mF/cm2 while the structural supercapacitors gave a high tensile modulus of 6.1 GPa. These results demonstrated that the hierarchical MnO2/CNT electrodes could provide both excellent energy storage capability and structural stiffness and strength, expanding their applications beyond mono-functional supercapacitors.

Interface engineering for enhancing performance of additive-free NiTe@NiCoSe2 core/shell nanostructure for asymmetric supercapacitors

Interface engineering of electro-active materials for supercapacitor (SC) is an effective strategy to adjust their corresponding physic-chemical properties. In this article, the core/shell structured NiTe@NiCoSe2 composite with a 3D hierarchical architecture has been reasonably defined by coating large theoretical capacity NiCoSe2 on NiTe nanorods using a simple hydrothermal method followed by electrodeposition process. Density functional theory (DFT) calculations indicate that the NiTe@NiCoSe2 sample has an enhanced density of state (DOS) near the Fermi level, which provide additional theoretical assistance for the improved electrochemical performance. Thanks to the well-designed core/shell architecture and high-efficient synergistic effects among multi-components, the prepared NiTe@NiCoSe2 electrode exhibits excellent energy storage capability. In addition, the NiTe@NiCoSe2//AC asymmetric supercapacitor (ASC) delivers a maximum energy density of 59.8 Wh kg−1 at 800 W kg−1. Importantly, the outstanding durableness with 96.6% capacitance retention after 10000 cycles manifests the good stability of the core/shell structure of the NiTe@NiCoSe2 electrode. These superior electrochemical performances show that the current composite materials are comparable to the most Se/Te-based electrodes for supercapacitors.

Electrospinning synthesis of NiCo2O4 embedded N-doped carbon for high-performance supercapacitors

Transition metal oxides play an important role in energy storage. However, their wide applications suffer from low conductivity and poor stability. In this study, a NiCo2O4 embedded N-doped carbon (NC) composite (NiCo2O4@NC) was synthesized using a novel strategy that combines electrospinning and thermal treatment. NC provides an excellent microenvironment for the Faradic reaction of NiCo2O4, while NiCo2O4 endows an ultrahigh specific capacitance to the composite. The obtained NiCo2O4@NC electrode exhibited a high specific capacitance of 2000.6 F g−1 at 1 A g−1. Furthermore, an asymmetric cell based on NiCo2O4@NC shown excellent energy storage capability, exhibiting a high specific energy of 61.2 Wh kg−1 at 548.6 W kg−1. The superior electrochemical performance of the cell is attributed to the material properties of the components and the unique heterostructure of the composite. The results demonstrate that NiCo2O4@NC is a promising electrode material for supercapacitors.

Superior capacitive energy storage capability in polymer composites induced by polydopamine-coated paraelectric platelets

Dielectric nanocomposites with excellent energy storage capabilities have great potential applications in film energy storage capacitors. However, limited energy storage density (Ue) and poor efficiency (η) of nanocomposites based on the incorporation of the high dielectric constant (er) fillers restrict their practical energy storage application due to low breakdown strengths (Eb) and electric displacement difference (Dmax-Drem) value. Herein, paraelectric SrTiO3 (ST) plates have been successfully synthesized through three-step molten salt process and modified by polydopamine (PDA) nanolayer. The moderate dielectric constant ST has the advantage for increasing the breakdown strength of poly(vinylidene fluoride) (PVDF)-based composites owing to the mitigation of electric field distortion. The ST@PDA platelets bring the highest Dmax-Drem (8.65 μC/cm2) together with enhanced Eb (350 MV/m) to the composites on account of the strong microscopic barrier layers. Consequently, the composite film filled with optimized ST@PDA platelets content (2.5 vol%) endows the maximum Ue of 12.45 J cm−3 at 350 MV/m, which presents the best result when compared to the neat PVDF and dielectric nanocomposites added with diverse ST morphologies including nanoparticles, nanowires, and nanofibers reported previously. This work offers an efficiency strategy utilizing high insulating paraelectric fillers with a plate structure to maximize the improvement in capacitive energy storage performance for dielectric composites.

Ultrahigh energy storage density at low operating field strength achieved in multicomponent polymer dielectrics with hierarchical structure

Dielectric composites with excellent capacitive energy storage capabilities have great potential applications in energy storage capacitors operating efficiently at relatively low field strengths. Herein, unlike the traditional methods via the introduction of fillers including randomly distributed ceramic nanofibers and aligned nanowires arrays into the monolayer films are simply to increase the energy storage density (Ue), both Ue and charge–discharge efficiency (η) at low electric field strengths have been improved in tri-layered all-polymer films owing to the synergistic effect of multiple interbedded interfaces and deliberately modulation of linear dielectric poly(methyl methacrylate) (PMMA) contents. The effects of film structure on the energy storage capabilities have been comparatively discussed. Consequently, an ultrahigh Ue of 15 J cm−3 accompanied with great η of 76.5% has been delivered in the resulting tri-layered film via optimizing the PMMA content (30 wt%) of out layers at 350 MV m−1, surpassing the energy storage upper limits of the reported polymer dielectrics that show the Ue of ~12 J cm−3 and η of ~70% at comparable electric fields of 310–380 MV m−1. Along with high pulsed power density, multicomponent polymer dielectrics with hierarchically structure provide an effective paradigm for achieving the low operating field strength applications of capacitive energy storage devices with excellent energy storage capability.

Tailoring specific properties of polymer-based composites by using graphene and its associated compounds

ABSTRACT Graphene and its associated compounds have been identified as extraordinary structural nano-fillers that can tailor the properties of new polymer-based composites with specific functionalities. Graphene possesses perfect 2D atomic architecture and has a large surface area that enhances the bonding, with tailored functional groups on its surface with polymer chains to form high strength composites. Recently, a lot of research has focused on developing composites with high specific strength, high electrical and thermal conductivities, high impact resistance, excellent energy storage capability and ability to maintain their strength at low-temperature environments by using graphene, graphene oxide (GO), reduced graphene oxide (rGO) or carbon nanotube/graphene. Ultimate goals are to design composites that can meet specific requirements for different engineering applications. In this paper, the discussion on all aspects in relation to the use of graphene and its associated compounds for advanced composites will be given in detail. The potentiality of using these materials for high-tech applications will be explored. Up to date, it has been proved that the use of graphene-based nanofillers does improve the mechanical, interfacial bonding, electrical, thermal and electromagnetic interference shield properties of polymer-based materials. Appropriately adding a small amount of these nanofillers do make a big difference to the properties of host materials.

Synthesis of MnO2/NiCo-Layered Double Hydroxide Hybrid as Electrode Materials for Supercapacitor

MnO2 nanosheets decorated with NiCo-LDH nanoplates were developed for high-performance supercapacitors. The construction strategy involved a facile two-step method including hydrothermal step and co-precipitation step. The samples were characterized by TEM, XRD, XPS, BET, and FT-IR. The prepared MnO2/NiCo-LDH composites with a large specific surface area and a certain active sites, realized the excellent energy storage capability in supercapacitors, due to the proper integration and optimization of the advantages of both MnO2 and LDH. Consequently, MnO2/NiCo-LDH shows a specific capacitance 555.6 F/g at current density of 1 A/g in 6 M KOH electrolyte, which is much higher than that of pure MnO2. Besides, MnO2/NiCo-LDH still can keep good cycling stability after 1000 cycles. This study indicates that MnO2/NiCo-LDH composite may have great potential as electrode material for supercapacitors.

Sulfur source-inspired synthesis of β-NiS with high specific capacity and tunable morphologies for hybrid supercapacitor

A novel β-NiS active material with tunable morphologies is synthesized through a facile one-step hydrothermal approach by choosing a special substance 2-mercaptopropionic acid as sulfur source. It is found that the introduced sulfur source has a great influence on phase structure and morphology of nickel sulfides. Benefiting from the selection of an excellent sulfur source, pure β-NiS was obtained and the morphology modification from microsphere to microflower and then to urchin-like structure was successfully achieved. More remarkably, the products at all morphologies indicate excellent energy storage capability, among which a highest specific capacity of 313.1 mAh g−1 is attained. In addition, the fabricated asymmetric supercapacitor indicates an attractive energy density of 49 W h kg−1 at a power density of 399 kW kg−1 and a good capacitance retention rate of 98 % after 5000 cycles. Our work opens another avenue for phase-controlled synthesis of pure nickel sulfide with tunable morphologies for various applications.

EDTA-Fe(III) sodium complex–derived bubble-like nitrogen-enriched highly graphitic carbon nanospheres as anodes with high specific capacity for lithium-ion batteries

Bubble-like nitrogen-enriched graphitic carbon was prepared using EDTA-Fe(III) sodium complex (ethylenediaminetetraacetic acid ferric sodium salt) as the precursor. The complex was carbonized at 700 °C for 2 h in argon atmosphere, and then, the product was washed with diluted hydrochloric acid and distilled water to remove iron and iron compounds so as to achieve the hollow carbon nanospheres. The as-prepared bubble-like carbon material exhibits excellent energy storage capability as the anode for lithium-ion batteries. A maximal reversible specific capacity of about 505 mAh g−1 can be achieved at a current density of 100 mA g−1, and 150 mAh g−1 can still be retained at a high current density of 1600 mA g−1, demonstrating superior cycling performance and excellent rate capability mainly due to the unique porous architecture and improved conductivity.

Simultaneously enhanced discharge energy density and efficiency in nanocomposite film capacitors utilizing two-dimensional NaNbO3@Al2O3 platelets.

With rapid developments in the consumer electronics market, electrostatic capacitors need to store as much energy as possible within a rather restricted space. In this work, nanocomposite films combining two-dimensional core-shell NaNbO3@Al2O3 platelets (2D NN@AO Ps) and poly(vinylidene-fluoride hexafluoropropylene) (P(VDF-HFP)), featuring excellent energy storage capability, high efficiency, and ultrafast discharge performance, are designed and fabricated. Both the experimental results and finite element simulations confirm the superiority of these 2D NN@AO Ps nanocomposite films in improving the breakdown strength (Eb) and energy storage capability. In particular, the introduction of 3 vol% 2D NN@AO Ps results in much enhanced discharge energy density of 14.59 J cm-3 and outstanding discharge efficiency of 70.1% in NN@AO Ps/P(VDF-HFP) nanocomposite films, which is much greater than that of pure P(VDF-HFP) (7.74 J cm-3). The corresponding nanocomposite films exhibit excellent reliability in energy storage performance under consecutive cycling. Therefore, this research could reveal a new chapter in the study and application of polymer nanocomposites in energy-storage dielectric capacitors.

2D Metal Chalcogenides Incorporated into Carbon and their Assembly for Energy Storage Applications.

2D metal chalcogenides have become a popular focus in the energy storage field because of their unique properties caused by their single-atom thicknesses. However, their high surface energy and van der Waals attraction easily cause serious stacking and restacking, leading to the generation of more inaccessible active sites with rapid capacity fading. The hybridization of 2D metal chalcogenides with highly conductive materials, particularly, incorporating ultrasmall and few-layered metal chalcogenides into carbon frameworks, can not only maximize the exposure of active sites but also effectively avoid their stacking and aggregation during the electrochemical reaction process. Therefore, a satisfactory specific capacity will be achieved with a long cycle life. In this Concept, the representative progress on such intriguing nanohybrids and their applications in energy storage devices are mainly summarized. Finally, an outlook of the future development and challenges of such nanohybrids for achieving an excellent energy storage capability is also provided.