Electrode Material For Storage Research Articles

Synergetic Coupling of Redox-Active Sites on Organic Electrode Material for Robust and High-Performance Sodium-Ion Storage.

Organic electrode materials (OEMs), valued for their sustainability and structural tunability, have been attracting increasing attention for wide application in sodium-ion batteries (SIBs) and other rechargeable batteries. However, most OEMs are plagued with insufficient specific capacity or poor cycling stability. Therefore, it's imperative to enhance their specific capacity and cycling stability through molecular design. Herein, we designed and synthesized a heteroaromatic molecule 2,3,8,9,14,15-hexanol hexaazatrinaphthalene (HATN-6OH) by the synergetic coupling of catechol (the precursor of ortho-quinone)/ortho-quinone functional groups and HATN conjugated core structures. The abundance of catechol/ortho-quinone and imine redox-active moieties delivers a high specific capacity of nine-electron transfer for SIBs. Most notably, the π-π interactions and intermolecular hydrogen bond forces among HATN-6OH molecules secure the stable long-term cycling performance of SIBs. Consequently, the as-prepared HATN-6OH electrode exhibited a high specific capacity (554 mAh g-1 at 0.1 A g-1 ), excellent rate capability (202 mAh g-1 at 10 A g-1 ), and stable long-term cycling performance (73 % after 3000 cycles at 10 A g-1 ) in SIBs. Additionally, the nine-electron transfer mechanism is confirmed by systematic density functional theory (DFT) calculation, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Raman analysis. The achievement of the synergetic coupling of the redox-active sites on OEMs could be an important key to the enhancement of SIBs and other metal-ion batteries.

Multi-walled carbon nanotube decorated SnS2 microsphere and its supercapacitive properties

The present study leads to the investigation of high performance energy storage electrode material employing the simple and adoptable hydrothermal technique. The typical synthesis and characterization of SnS2 microspheres are reported. Furthermore, the supercapacitive performance of SnS2 microspheres is performed and 58 mAh g−1 of specific capacity is observed at the current density of 1 A g−1. Further, the specific capacity of sole SnS2 microspheres is enhanced by adding the modest amount of MWCNTs and improved specific capacity of 110 mAh g−1 is observed from MWCNT/SnS2 electrode material. Furthermore, due to the high specific capacity of composite, aqueous asymmetric supercapacitor (ASC) is designed with MWCNT/SnS2 as positive (+ve) electrode and activated carbon (AC) as negative (−ve) electrode. The high energy density of 37.14 W h kg−1 is delivered with the power density of 725 W kg−1 by MWCNT/SnS2//AC. In addition, for the electronic application, two parallel connected yellow color light emitted diodes (LEDs) are also lit by series connected two MWCNT/SnS2//AC devices.

The oxygen-doped self-supporting functional carbon nanotube sponge realized the synergistic enhancement of lithium ion transport and lithium polysulfide reaction

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage systems, in which the severe shuttle effect causes the loss of the sulfur active species and unacceptable capacity and cycling stability. Here, a self-supporting functional carbon nanotube sponge (FCNTS), electrostatically repelling polysulfide anions and allowing Li+ to pass through, is synthesized by etching channels and introducing enriched anions on CNTs based on the “Donnan effect”. The experimental results confirmed that FCNTS accelerated the Li-ion transport, that is, the Li+ transfer rates of the FCNTS materials were 8.226 (Li2S4 reduction) and 3.627 times (Li2S oxidation) that of the CNTs blank samples, respectively. Meanwhile, defects and O-group modified FCNTS regulated the local charge density of carbon-based materials, which enriched the reduction current response of the soluble Li2S4 and the oxidation current of Li2S2/Li2S around the cathode more than 1.9 and 1.6 times that of the CNTs blank samples, respectively. This significantly improved the kinetics and suppressed the overpotential. Thus, the cells assembled by S@FCNTS achieved a high-rate performance (866.9 mAh∙g−1 at 2 C), excellent stability (fading rate of only 0.035% per cycle after 500 cycles at 2 C), and a high area capacity of 13.2 mAh∙cm−2 at a high sulfur load of 10.9 mA∙cm−2. This work demonstrates a dynamic polysulfide-interception strategy to facilitate the utilization of polysulfides and provides a promising idea for the design of multi-functional sulfur storage electrode materials for high-load LSBs.

Unveiling the charge storage mechanisms of perovskite fluoride KMnF3 in neutral aqueous electrolyte

Perovskite fluorides (ABF3) have attracted much attention as an emerging and promising electrode material for electrochemical energy storage. However, to reveal the charge storage mechanisms of ABF3 in neutral media and further facilitate their energy storage utilizations remains very challenging. Herein, we have, for the first time, elucidated the charge storage mechanisms of KMnF3 in neutral aqueous electrolyte (1 M Na2SO4) via diverse ex/in situ physicochemical/electrochemical techniques, showing the dominated conversion reactions along with partial insertion/extraction reactions and adsorption during the charging/discharging processes. Specifically, the KMnF3 nanocrystals transform into amorphous MnOOH/(hydrated)MnO2 nanosheets via adsorption and conversion mechanisms by formation/oxidation of [Mn-OH] intermediates and Mn2+ accompanying with partial H+ extraction of MnOOH to MnO2 in the first charging period, while the partial Na+ and H+ insert into the MnO2 to form Na0.5MnO2 and MnOOH and further (hydrated)MnO2 and MnOOH convert into Mn3O4 and/or Mn2+ in the discharging period. The as-constructed aqueous electrochemical capacitors (ECs) by matching KMnF3 positive electrode with activated carbon (AC) negative electrode exhibit good energy/power density and spectacular cycling behavior. Overall, this work addresses an in-depth understanding of charge storage mechanisms of KMnF3 in neutral media and plays a milestone-like role in developing state-of-the-art ABF3 in aqueous storage systems.

In‐Built Polaronic States Self‐Regulation for Boosting Potassium‐Ion Diffusion Kinetics

AbstractPotassium ion batteries (PIBs) have attracted enormous attention due to their low cost and high abundance of potassium resources. Here, self‐hybridized BiOBr0.5I0.5 with a flower‐like structure composed of 2D nanosheets is assembled and used as PIBs anode. According to the systematic theoretical calculations, the unbalanced charge distribution between Br and I atoms induces an intensified internal electric field and a wide van der Waals gap; while the decreasing of electron polarons caused by the hybridized structure improves the stability and electronic conductivity of the system. Moreover, the K+ ion uptake induces an energetic evolution in polaronic states in the BiOBr0.5I0.5 crystal skeleton, whereby the dynamic K+ ion‐halogen atoms correlation in situ forms hole‐like polarons, which substantially promotes K+ ion diffusion kinetics and the corresponding reaction kinetics during charge/discharge processes, imparting significant implications for the design of high‐performance energy storage electrode materials by engineering the interface interaction and electronic structure. Therefore, with this atomic orbital self‐hybridized structure, the K+ ion diffusion kinetics and the corresponding reaction kinetics during the charge/discharge process are both enhanced remarkably, thus enabling a high electrochemical performance of 155 mAh g−1 at 1000 mA g−1 over 4000 cycles in PIBs with the BiOBr0.5I0.5 as the anode.

Constructing highly stable and biomimetic supercapacitor materials of 2D MoS2 coupled with NiCoLDH @chitosan carbon microsphere

Due to the growing demand for clean and renewable energy, the effective utilization of renewable resources in energy storage and has been concerned. And high specific capacitance and stable electrochemistry for energy storage devices are challenging to develop. Learning from unique structure of goniastrea coral, we design to construct three-dimensional layered conductive electrodes material made of MoS2@chitosan carbon spheres (MNCCS) composite. The NiCoLDH nanosheets construct on the surface of conductive chitosan carbon spheres to effectively form open permeable channels and rich conductive networks, improves the efficient energy storage and electrochemical stability. MoS2 is strongly coupled with NiCoLDH nanosheets through heterointerface, which resembles tentacles on the surface of coral, exposing more active sites to efficiently trap ions. Besides, the obtained material possesses favorable heterojunction interface and defects, which provide sufficient available electroactive sites and numerous storage charge area. Hence, The MNCCS presents an outstanding specific capacitance of 2605.9 F g−1 at 1 A g−1. Notably, a supercapacitor fitted with MNCCS electrode and CCS electrode achieves high specific capacitance (234.4 F g−1 at 1 A g−1), the maximum energy density of 77.0W h kg−1 at highest power density of 667.4W kg−1, along with the excellent cycling stability of 90.8% retention over 10,000 cycles. This work provides a new perspective for fabricating high-performance and stable supercapacitors electrode material for clean energy storage.

Graphitic carbon nitride nanomaterials for high‐performance supercapacitors

AbstractGraphitic carbon nitride is a promising material as an electrode material for advanced electrochemical energy storage devices because of its controllable structure, physicochemical properties, and abundant active sites. However, its intrinsic properties as electrode materials can not be fully expressed owing to limited electrical properties, which impede charge transfer and material exchange inside devices. During the past decade, the challenge has been addressed through material engineering strategies, such as exfoliation and composition, and then advanced energy devices, such as supercapacitors, have been assembled. In this regard, a timely review of graphitic carbon nitride for high‐performance supercapacitors requires to be put forward for summarizing past studies and inspiring future research works as well. This review article summarizes recent progress in material synthesis and property regulation of graphitic carbon nitride nanomaterials and their application in assembling advanced supercapacitors with high energy density and superior working stability. Finally, based on existing research and our experimental experience, a perspective for directing future research has been presented concerning material synthesis and electrochemical application of graphitic carbon nitride.

Boosting capacitive deionization of monovalent and hardness ions using Ti3C2Tx MXene as an intercalation-type pseudocapacitive electrode

MXene is a promising electrode material for energy storage and capacitive deionization (CDI) applications. In this study, a viable approach was developed to synthesize Ti3C2Tx at different LiF/Ti3AlC2 mass ratios of 0.5 – 2.0 for the enhanced CDI to remove different cations including hardness (Mg2+ and Ca2+), salt (Na+), and ammonium (NH4+) ions. The Ti3C2Tx was fabricated using the hydrothermal method in the presence of LiF and HCl. The optimal mass ratio of 1.0 results in the formation of hydrophilic and well-delaminated nanosheets. Moreover, the Ti3C2Tx-1 shows an interconnected meso-macroporous structure with a specific surface area of 48.4 m2/g. The Ti3C2Tx MXene exhibits an exceptional electrochemical performance with a specific capacitance of 540 F g−1 at 5 mV s−1 in the presence of 1 M H2SO4. A remarkable desalination performance with the salt adsorption capacity (SAC) of 39.7 mg g−1 is obtained. The well-suited lattice fringe and inter-connected porous structure of the Ti3C2Tx nanosheets accelerate the electron transport, which can maintain the cyclability over 50 cycles. This enhanced electron transport leads to an improved deionization capability during the CDI process. Moreover, the Ti3C2Tx-based CDI device exhibits prominent selectivity for hardness ions with SACs of 43.8 and 39.5 mg g−1 for Ca2+ and Mg2+, respectively. The SAC of NH4+ can also be up of 39.7 mg g−1 at 1000 mg L−1. Results in this study clearly elaborate the promising potentiality for the utilization of MXene as an effective electrode material for desalination and other electrochemical applications.

Morphology induced symmetrical supercapacitive performance of the 3D interconnected Ni(OH)2 framework

The rational design of electrode materials for energy storage applications is a key element of resolving the energy crisis. Herein, nickel hydroxide (NHO) nanostructures with different morphologies, such as platelet (Platelets-NHO), three-dimensional flower (3DF-NHO), and flake-like (Flakes-NHO) morphologies, were synthesized using different solvents inside the hydrothermal reactor during the reaction process. The fabricated electrode materials of the NHO nanostructure were further characterized using different types of microscopic and spectroscopic techniques, and their electrochemical performance was further studied in a three-electrode assembly cell to explore the morphological effect on the supercapacitive performance. The 3DF-NHO displayed a significantly enhanced capacitance value (1112.5 F g−1) than Platelets-NHO (820.0 F g−1) and Flakes-NHO (850.0 F g−1) at the same current load (1 A g−1). The electrochemical supercapacitive performance of 3DF-NHO, Platelet-NHO, and Flakes-NHO revealed that the morphology played an important role in enhancing the electrode chemical performance of the electrode material. The symmetric assembly cell of 3DF-NHO was also assembled, and cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and cyclic stability tests were recorded, revealing excellent performance for potential applications in the field of energy storage devices. Among the materials, the excellent performance of 3DF-NHO is credited to the three-dimensional structures and interconnected petals, which provide a better surface and suitable space for the electrolytes during the electrochemical reaction. These results suggest that the rational design of the electrode material using an appropriate solvent could help to fabricate a large number of different morphologies of NHO, which may be a potential candidate for energy storage electrode materials.

Porous biochars with nitrogen defects prepared from hydrogel template-modified food waste for high-performance supercapacitors

The complex composition and heterogeneous nature of food waste limit the application of biochar materials derived from it in supercapacitors. In this study, biochar was prepared from simulated food waste using a hydrogel template and employed to fabricate supercapacitor electrodes. Food waste was first transformed into a soluble state through an advanced oxidation process (potassium persulfate/heat). Small-molecule polymerization was then performed to generate a structurally uniform food waste hydrogel (FWH). Urea was added during the synthesis of FWH to achieve the uniform incorporation of nitrogen into its structure. FWH biochar (FWHB) was obtained from FWH via pyrolysis at different temperatures (500, 700, and 900 °C). Then, we evaluated the physicochemical properties and electrochemical performances of the obtained FWHB samples. The FWHB pyrolyzed at 700 °C (FWHB700) exhibited a unique sponge-like microstructure with a high specific surface area of 693 m2∙g−1, which was 20 times that of untreated food waste biochar. FWHB700 also showed excellent energy storage performance, with a specific capacitance of up to 461 F∙g−1 at a current density of 1 A∙g−1. Based on physicochemical analysis and density functional theory calculations, the energy storage capacity of FWHB700 was found to be related to its high specific surface area, developed pore structure, as well as abundant nitrogen defects and heteroatom active sites. The symmetric FWHB700//FWHB700 supercapacitor delivered a high energy density of 9.99 Wh∙kg−1 at a power density of 125 W∙kg−1, with 88.2 % capacitance retention after 10,000 charge–discharge cycles. In summary, this study introduces a promising electrode material for energy storage and provides a new approach for the efficient utilization of food waste resources.

Graphene modification with chrysin molecules as a high performance electrode material for supercapacitor

In this study, chrysin (CHY) molecules are immobilized on the surfaces of graphene oxide (GO) via π-π interactions to obtain organic molecular-modified reduced graphene oxide (RGO) composite electrode material (CHY/RGO) by one-step hydrothermal. On one hand, CHY molecules can contribute to capacitance through faradic reactions. On the other hand, they act as spacers that impede the accumulation of graphene nanosheets and promote electrolyte ion migration. As a result, CHY/RGO exhibits excellent capacitance performance. The specific capacitance is up to 707F g−1 (1 A g−1), and the capacitance remains 100% after 10 000 circles. In addition, the symmetrical supercapacitor (CHY/RGO//CHY/RGO) displays excellent energy storage performance, achieving an energy density of 38 Wh kg−1 at a power density of 800 W kg−1. Two CHY/RGO//CHY/RGO devices in series is capable of lighting 50 LEDs. Density functional theory (DFT) calculations show that CHY molecules are adsorbed parallel to the RGO by the π-π stacking. The DFT calculations also indicate that the modification of CHY molecules alters the charge distribution on the surface of RGO. Therefore, CHY/RGO composites offer a higher capacitance and superior cycle stability, making them a promising choice for future energy storage electrode materials.

Ni2P2O7 Thin Film Electrode for High Performance Supercapacitor Applications

Abstract: The electrochemical performances of the supercapacitor essentially rely on electrode materials. The transition metal phosphates have been attracted as electrode material for energy storage in supercapacitor. A valley-like Ni2P2O7 thin film electrode is synthesized by economic and reproducible chemical bath deposition technique. The high specific capacitance of Ni2P2O7 is obtained as 548 F/g at current density 1 A/g. The electrode delivered enhanced energy density of 14.47 Wh k/g at a power density 0.16 kW k/g. The results indicate that Ni2P2O7 is an exemplary supercapacitor candidate and it would lead to productive research in future energy storage applications.

Constructing N, Se co-doped carbon nanofibers encapsulated with hollow FeSe2 nanospheres as electrodes for energy storage

Iron selenide (FeSe2), a p-type narrow band gap (1.0 eV) semiconductor, has been considered as a potential electrode material for electrochemical energy storage owing to its many benefits, including quick electron transfer, excellent electrical conductivity and exceptional theoretical specific capacity. Nevertheless, the volumetric expansion, agglomeration, low ion-diffusion capacity and other inadequacies in the process of discharging and charging. Therefore, FeSe2 is far short of high initial coulomb efficiency, long-cycle stability, and excellent rate performance. The greatest obstacle to the practical use of energy storage systems is these drawbacks. Herein, the electrospinning and a thermally-induced selenization route are adopted to encapsulate the FeSe2 hollow nanospheres into the intertwined Se, N co-doped carbon nanofibers (Se, N-FeSe2CNFs). Density functional theory calculation delivers that Se, N-FeSe2CNFs nanocomposite presents extremely low bandgap and high density of states at the Femi level, demonstrating significantly increased conductivity. When assembling into the all-solid-state symmetric supercapacitors (ASSSCs), the Se, N-FeSe2CNFs ASSSCs provide a remarkable specific capacity of 330.2 F g−1 and maintain 92.0% after 5000 cycles at 2 A g−1. Meanwhile, the resistance of charge transfer decreases from 0.73 Ω (FeSe2) to 0.28 Ω (Se, N-FeSe2CNFs). Moreover, the Se, N-FeSe2CNFs ASSSCs deliver 128.6 Wh kg−1 (energy density) at about 800 W kg−1 (power density). Additionally, the Se, N-FeSe2CNFs anodes also have outstanding reversible capacity (549.5 mAh g−1 at 0.1 A g−1) and stability of long-circulation (481.3 mAh g−1 after 100 circles and 480.9 mAh g−1 after 200 circles at 0.1 A g−1) for sodium-ion batteries (SIBs). The superb property of energy storage can be due to the encapsulated structure that can maintain the integrity of structures for electrodes during electrochemical reactions and the Se, N heteroatoms doped CNFs that can conducive to ions/charges transport and storage. The designed encapsulated structure and synthesis approach have broad application prospects in electrochemical energy storage.

Breaking the barriers: Engineering the crystalline-amorphous interface of Fe3O4@Fe electrode material for unparalleled energy storage and water splitting efficiency

Innovatively regulating the crystalline-amorphous (c-a) interface of electrode materials is critical for enhancing supercapacitor and electrochemical water splitting performance. In this research, an oxygen defect-rich Fe3O4@Fe electrode material with a unique and tunable c-a interface was synthesized using prussian blue (PB) as a template. The resulting interface facilitates electron transport and ion diffusion, increases the charge storage active sites, and enhances energy storage capacity. Density functional theory (DFT) simulations demonstrated that oxygen defects can effectively enhance ionic conductivity and facilitate electrochemical water splitting. The optimal Fe3O4@Fe electrode exhibits remarkable specific capacitance (1526.766 mF cm−2 at 1 mA cm−2) and exceptional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance, with overpotential values of 231 and 359 mV at 10 mA cm−2, respectively. Furthermore, as an overall water splitting electrocatalyst, the optimal Fe3O4@Fe can reach 10 mA cm−2 at a battery voltage of 1.645 V, demonstrating its tremendous potential as a highly efficient electrocatalyst.

Highly efficient and stable layered AgZnS@WS2 nanocomposite electrode as superior charge transfer and active redox sites for energy harvesting device

Transition metal dichalcogenides (TMDs) are considered to be excellent candidates in energy storage applications because of their 2D structure and astonishing electrochemical features. Still, the poor stability of these materials limits their way to becoming perfect supercapattery electrode materials. Therefore, researchers are synthesizing their hybrids with other electrode materials to minimize these drawbacks. Herein, the tungsten disulfide (WS2) nanosheets were combined with hydrothermally synthesized silver zinc sulfide (AgZnS) nanostructures to design a hybrid electrode material for high-performance energy storage devices with superior charge transfer and abundant active redox sites. The highly porous structure of AgZnS@WS2 was analyzed by BET which confirmed the enhancement in ion diffusion and the reversible redox mechanism. The composite was analyzed using SEM, XRD, RAMAN, and XPS to study its morphological, structural, and compositional properties. The effect of different electrolytes was studied to estimate the electrochemical characteristics. The AgZnS electrode, upon characterization in 1 M KOH, revealed the maximum specific capacity (Qs) of 1209.06 Cg−1 at 1.8 Ag−1. While the AgZnS@WS2 hybrid electrode exhibited the Qs of 2516.58 Cg−1 at the same current density (js) benefitting from the features of both materials. The AgZnS@WS2 hybrid electrode employed in a supercapattery revealed a maximum Qs of 388.8 Cg−1 at 1.2 Ag−1. The device delivered a maximum energy density of 86.4 Wh kg−1 and a notable power density of 4987.6 W kg−1. The superb 95 % cycle stability and strong electrochemical performance of AgZnS@WS2 are the results of the highly conductive structure and synergistic effect of hybrid material for high surface area with quick ion diffusion. The astonishing features of hybrid material are suitable and encouraging for its industrial applications as supercapattery electrode material.

Synergistic effect for improving the hydrogen storage capability and electrochemical performance of AB2 Laves phase alloys

The structure of a series AB2 Laves-type metal hydride alloys, in which Ce was doped into Ti0.24Zr0.76Ni1.15Mn0.7V0.15 and annealed the alloys, was studied and correlated to hydrogen storage properties and electrochemical performances. X-ray diffraction, scanning electron microscope, and energy-dispersive spectroscopy results revealed that Ce formed a CeNi3 secondary phase instead of entering the Laves phases. The synergistic effect of the CeNi3 and (Ti,Zr)Ni phase improved the hydrogen storage and electrochemical discharge properties of the Ce-doped (Ce0.02) alloy. Especially, the secondary phases could decrease the hydrogen absorption plateau, reduce the hysteresis phenomenon, and increase the hydrogen storage capacity (from 0.9 wt% to 1.4 wt% at 25 ℃). The formation of CeNi3Hx hydride on the surfaces of alloy electrodes led to a higher discharge capacity (∼500 mAh/g) and a faster activation rate. The Ce0.02 alloy also showed a good cyclic stability ∼82.08%, after 500 charge-discharge cycling, which could be ascribed to the good corrosion resistance of the CeNi3 phase on the surface of alloy. In addition, annealing treatment promoted the depletion of (Ti,Zr)Ni secondary phase and the transformation from the C14 to C15 phase. The Ce-doped AB2 alloy can be used as a hydrogen storage and hydride battery electrode material.

Sol-gel method preparation and high-rate energy storage of high-entropy ceramic (FeCoCrMnNi)C porous powder

Among the existing electrochemical capacitive energy storage electrode materials, the (TiNbTaZrHf)C, (VCrNbMoZr)2N, (CoCrFeMnNi)3O4, (FeCoCrMnMg)3O4 and (FeCoCrMnCuZn)3O4 all have excellent capacitive performance, but the energy density is limited due to the narrow potential window. In order to solve the problem of low energy density of electrochemical supercapacitor, a kind of high-entropy carbides (HEMCs) with broad potential window is designed from generalized analysis of electrochemical window of active elements. This high-entropy carbide contains five active elements of Fe, Co, Cr, Mn and Ni. The prepared HEMC-3 has abundant pores and a specific surface area of 417.8 m2 g−1. The large specific surface area makes the HEMCs have high-rate energy storage performance. Electrochemical tests show that the HEMC-3 presents a potential window of [-1.0, 0.6] versus Hg/HgO, and can obtain a specific capacitance of 169.7 F g−1 at a current density of 0.5 A g−1. Due to the designed wide potential window of the prepared HEMCs, the energy density has been greatly improved, which shows a new strategy for developing of electrochemical supercapacitor electrode materials.

Microstructural study of sonochemical synthesized belt-like Zr(MoO4)2/MoO3 composites for efficient energy storage

It is currently being widely explored as an electrode material for future storage devices that transition metal oxides can provide a synergistic effect during electrochemical reactions. We synthesized composites of Zr(MoO4)2/MoO3 with belt-like morphologies using ligand assisted Ultrasonics. Compared to other methods of synthesis, ultrasonic synthesis is less costly and easier to use, and it has the advantage of speeding up the formation process. It is possible that the duration of the sonication process can have an impact on the microstructural properties of the sample. As a result, Zr(MoO4)2/MoO3 composites were synthesized under ultrasonic probes for five, ten, and fifteen minutes, respectively. The achieved sample serves as an active material in an electrochemical energy storage system comprised of a three-electrode cell and an electrolyte containing KOH. Depending on the current density, the kinetics of the electrochemical reaction and the stability of the materials in the working electrode are affected. Nevertheless, the capacity of Zr(MoO4)2/MoO3 composites was studied at different currents of 0.5, 1, 2 and 3 mA in order to identify optimal parameters. The results indicate an increase in discharge capacity at 2 mA from the first cycle to the thirteenth cycle, from 200 to 750 mAhg−1. In contrast, applying a current of 3 mA results in a decrease in capacity and structural damage. Conversely, using lower currents of 0.5 and 1 mA results in lower capacity compared to 2 mA. In this way, belt-like Zr(MoO4)2/MoO3 composites can be utilized as potential active materials in energy storage systems, such as hydrogen storage.

High mass loading paper-based electrode material with cellulose fibers under coordination of zirconium oxyhydroxide nanoparticles and sulfosalicylic acid

With the rapid expansion of the flexible electronics market, it is critical to develop high-performance flexible energy storage electrode materials. Cellulose fibers, which are sustainable, low cost, and flexible, fully meet the requirements of flexible electrode materials, but they are electrically insulating and cause a decrease in energy density. In this study, high-performance paper-based flexible electrode materials (PANI:SSA/Zr-CFs) were prepared with cellulose fibers and polyaniline. A high mass loading of polyaniline was wrapped on zirconia hydroxide-modified cellulose fibers under metal-organic acid coordination through a facile in situ chemical polymerization process. The increase in mass loading of PANI on cellulose fibers not only improves the electrical conductivity but also enhances the area-specific capacitance of the flexible electrodes. The results of electrochemical tests show that the area specific capacitance of the PANI:SSA/Zr-CFs electrode is 4181 mF/cm2 at 1 mA/cm2, which is more than two times higher than that of the electrode with PANI on pristine CFs. This work provides a new strategy for the design and manufacture of high-performance flexible electronic electrodes based on cellulose fibers.

2D/2D nanoarchitecture of Ni/NiCo2O4 deposited onto reduced graphene oxide for high-performance hybrid supercapacitor applications

The advanced energy storage electrode materials should mainly be focused on nanoarchitecture, multiple redox states, large surface area, and plenty of surface-active sites. Thereby, designing well-defined nanostructured electrode materials and tailoring them with a suitable supporting material is a prime requirement for supercapacitor application. Herein, we report the facile solvothermal synthesis of Ni/NiCo2O4 nanosheets directly decorated onto reduced graphene oxide (rGO) followed by thermal treatment. The porous 2D/2D Ni/NiCo2O4@rGO framework could enable easier ion diffusion to the electroactive site with reduced resistance for charge and mass transportation. In addition, a 2D/2D nanoarchitecture with strong face-to-face contacts can provide an extremely coupling interface that exhibits to have tremendous potential for energy storage performance. Interestingly, the resulting Ni/NiCo2O4@rGO nanoarchitecture electrode exhibits a higher specific capacitance of 1110 F g−1 at a specific current of 1 A g−1, which is much higher than those of Ni/NiO@rGO (500 F g−1) and CoO/Co3O4@rGO (425 F g−1) electrodes under the similar condition. Besides, the Ni/NiCo2O4@rGO nanoarchitecture electrode shown considerably high specific capacitance (574 F g−1) even though the specific current increased to 20 A g−1, demonstrating that the nanoarchitecture electrode preserves good rate capability. Further, a hybrid supercapacitor was constructed using the Ni/NiCo2O4@rGO nanoarchitecture electrode, and it delivered a high specific capacitance of 127 F g−1, with a high energy density of 40.63 Wh kg−1 for a power density of 854.81 W kg−1. As well as the hybrid supercapacitor exhibited excellent long-term cyclability with 90.1 % retention over 20,000 charge-discharge cycles.