Electrode Material For Storage Research Articles

Ag doped ZnSnO3 nanocubes: Promotion on the charge storage mechanism for supercapacitors

Morphology optimization with noble elements doping is yet a critical, promising advance to develop an electrochemical energy storage capacity of the prepared materials for supercapacitors. With this, we have synthesized Ag element doped low-cost ZnSnO3 nanocubes via facile co-precipitation method for electrochemical energy storage application. With the compact particle size, nanoporous nature, high surface area and high adsorption properties, 20% Ag supported ZnSnO3nanocubes outperforms than other controlled electrodes. The maximum 517 and 258 F/g capacitance was achieved from cyclic voltammogram (CV) at 10 mV/s and galvanostatic charging/discharging (GCD) profiles at 1 A/g respectively. The capacitive retention of 87.06% was achieved after 5000 cycles for the same electrode. This work will give an interesting outlook for the preparation of novel energy storage electrode materials in diverse morphology for future portable electronic devices sector.

Anomalous increase in specific capacitance in MXene during galvanostatic cycling studies

Layered Ti3C2 is attracting much attention as a promising electrode material for energy storage devices due to its excellent electrical conductivity and electrochemical properties due to its surface functional groups. Though various methods have been used to etch Ti3AlC2, the energy storage performance of Ti3C2 mainly depends on exfoliation of aluminium, surface functional groups and intercalation of potassium. Hence, the optimization of Ti3AlC2 etching process has been done by hydrothermal, stirring, and ultra-sonication methods which exhibits a different specific capacitance of 8.7 F g−1, 23.75 F g-1, and 141.45 F g−1 respectively in 3 M KOH electrolyte at 2 mA constant current galvanostatic charge/discharge (GCD) analysis even though same etching time and quantity of MAX materials used. Surprisingly, all the samples show an increased specific capacitance up to 2000th cycles and a maximum value of around 170 % is reached and this value is maintained until 5000 charge-discharge cycle at 10 mA by GCD analysis. These electrochemical differences are investigated in terms TiAl bond termination and formation of O-Ti-O bonds due to the removal by Al during etching process. It is found from XPS analysis that -OH surface termination has occurred with F desorption and the interaction of K+ ion has increased the interlayer space between the individual layers. Moreover, the material has been phase transformed from Ti3C2 to TiO2/Ti3C2 hybrid crystal structure during the cycling stability test. The high dipole moment in TiO2/Ti3C2 hybrid structure due to the decreased work function has increased the specific capacitance of MXene electrode material. To the best of the authors' knowledge, this has not been observed previously and reported.

Evaluation of the Synergistic Effect of Graphene Oxide Sheets and Co3O4 Wrapped with Vertically Aligned Arrays of Poly (Aniline-Co-Melamine) Nanofibers for Energy Storage Applications.

In the present study, Co3O4 and graphene oxide (GO) are used as reinforcement materials in a copolymer matrix of poly(aniline-co-melamine) to synthesize ternary composites. The nanocomposite was prepared by oxidative in-situ polymerization and used as an electrode material for energy storage. The SEM images revealed the vertically aligned arrays of copolymer nanofibers, which entirely wrapped the GO sheets and Co3O4 nanoparticles. The EDX and mapping analysis confirmed the elemental composition and uniform distribution in the composite. The XRD patterns unveiled composites’ phase purity and crystallinity through characteristic peaks appearing at their respective 2θ values in the XRD spectrum. The FTIR spectrums endorse the successful synthesis of composites, whereas TGA analysis revealed the higher thermal stability of composites. The cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy are employed to elucidate the electrochemical features of electrodes. The ternary composite PMCoG-2 displayed the highest specific capacity of 134.36 C/g with 6 phr of GO, whereas PMCoG-1 and PMCoG-3 exhibited the specific capacities of 100.63 and 118.4 C/g having 3 phr and 12 phr GO at a scan rate of 0.003 V/s, respectively. The best electrochemical performance of PMCoG-2 is credited to the synergistic effect of constituents of the composite material.

The Co3O4–Co3(PO4)2 nanocomposite supercapacitor system: Synthesis, electrochemistry, temperature effects, and computational studies

Supercapacitors with improved storage capacity and longer operational times are in high demand. Herein we report the charge storage nanocomposite cobalt(II, III) oxide/cobalt(II) phosphate, Co3O4–Co3(PO4)2, formed in the calcination temperature range 600–800 °C showing varying degrees of crystallinity. The isolated Co3O4–Co3(PO4)2 nanocomposite was characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X-ray diffraction and high-resolution Transmission Electron Microscopy (HRTEM) and Scanning Electron Microscopy (SEM). Cyclic voltammetry studies based on a three-electrode system showed that Co3O4–Co3(PO4)2 formed at 700 °C exhibited the highest specific capacitance behaviour of 538.3 Fg-1 at 0.5 mVs−1 in 3 M KOH electrolyte. Galvanostatic charging and discharging studies showed a specific capacitance of 526.9 Fg-1 at 1 Ag-1 current density. The unrestricted Becke-3-Lee-Yang-Parr (UB3LYP) functional in conjunction with the 6–311g(d,p) basis set was used for quantum calculations of the thermo-chemical properties of the Co3(PO4)2 moiety in the nanocomposite. The entropy and heat capacity showed optimum temperature values for the nanocomposites in the order 600 °C > 800 °C > 700 °C, the most suited electrode material for charge storage was found at 700 °C. The electronic measurement for the cobalt(II) phosphate moiety in the nanocomposites indicated that the system was very polar with a low bandgap and good electronic and ionic conductivity.

Polyxylylviologen Chloride as an Organic Electrode Material for Efficient Reversible Chloride-Ion Storage

Organic molecules such as viologens with a nitrogen redox center show promise as efficient anion storage materials in rechargeable batteries. However, the high solubility of viologens in liquid electrolytes limits their wide electrochemical application. Herein, an insoluble polymerized polyxylylviologen chloride (PXVCl2) is first developed as a chloride ion storage electrode in chloride ion batteries. The as-prepared PXVCl2 electrode exhibits a competitive discharge capacity of 140 mA h g–1 (86% of the theoretical discharge capacity) compared to that of the previously reported organic conducting polymer electrodes. The incorporation of graphene in the PXVCl2 material achieves significant improvements in reaction reversibility and rate capability of the PXVCl2 electrode. Importantly, the nitrogen redox reactions based on chloride ion transfer of the PXVCl2 electrode are demonstrated.

Hydrogen bond enforced polyaniline grown on activated carbon fibers substrate for wearable bracelet supercapacitor

The polyaniline grown on activated carbon fibers (PANI-ACF) was synthesized through an electrochemical deposition process to act as the energy storage electrode material for wearable bracelet supercapacitor application. The ACF was synthesized by activating carbon fibers through hydrothermal process in HNO3 solution and then thermal process in argon atmosphere, which kept the microporous surface structure and oxygen-containing functional groups. The ACF substrate could contributes to improving electrical conductivity and activation of PANI-ACF. The density functional theory calculation result shows that PANI-ACF has larger Fermi energy than PANI. The XPS spectrum measurements and Mulliken charge distribution analysis indicate the formation of interfacial hydrogen bond interaction between hydroxyl group of ACF and amino group of PANI in PANI-ACF. The HOMO-LUMO energy gap decreases from 2.62 eV of PANI to 0.23 eV of PANI-ACF, indicating the bonding interaction is beneficial to improve conductivity of PANI. The PANI-ACF achieves superior capacitance of 296.3 F g−1 at 1.0 A g−1 and maintains reasonable capacitance retention of 63.8 % when the current density increases from 1.0 to 10 A g−1. Electroactive PANI-ACF electrode was applied for wearable bracelet-supercapacitor, which exhibits the energy density of 30.42 Wh kg−1 at power density of 900 W kg−1. So, hydrogen bond enforced PANI-ACF electrode with high capacitance and flexibility properties presents the promising wearable energy storage application.

Rational design of freestanding necklace-like ZnSe with double N-doped carbon layer protection for efficient sodium storage

ZnSe, as a promising electrode material for sodium storage, has a high theoretical capacity, low cost, and excellent physicochemical properties. The poor reaction kinetics and huge volume variation of ZnSe hinder its practical applications. Therefore, in this study, ZnSe electrode materials embedded in carbon nanofibers (ZnSe@NC@NCNFs) were synthesized through electrospinning and selenization using a Zn-based metal-organic framework (Zn-MOF) precursor. During the calcination process, the MOF-derived porous N-doped carbon layer wraps the ZnSe nanoparticles, and the one-dimensional (1D) carbon nanofiber forms a second N-doped carbon protective layer. The interwoven nanofibers can be severed as a freestanding electrode for sodium storage without conductive and binder agents. In situ X-ray diffraction (XRD) demonstrates the formation of irreversible NaZn13 during the initial discharge process, which can act as sodiophilic sites and buffering matrices for subsequent Na+ insertion/extraction. The ZnSe@NC@NCNFs exhibit significant electrochemical performance for sodium storage with high reversible capacity and desired rate performance.

Heteroatom Modification of Heterostructured CuS/Mn3O4 with Rich Defects for Solid-State Supercapacitors

Heterostructure construction and heteroatom modification are considered as effective approaches to modulate the electronic structure and boost the energy storage activity of electrode materials. Herein, oxygen-modified CuS/Mn3O4 (O-CuS/Mn3O4) heterogeneous nanoflakes with abundant defects are fabricated by solid-state grinding followed by NaBH4 treatment (NBHT) at room temperature using MnCu Prussian blue analogue (MnCu-PBA) as the precursor. During the NBHT, a portion of the sulfur atoms in CuS is removed, and the remaining sites in the lattice are occupied by oxygen in the water, resulting in an oxygen modification. Experimental results and theoretical calculations confirm that heterojunction, defect, and oxygen modification not only greatly facilitate the adsorption of OH– on the surface of the electrode material but also endow improved electrical conductivity, wettability, specific surface area, and active sites. Benefiting from these advantages, O-CuS/Mn3O4 exhibits an excellent specific capacitance of 1307 F g–1 at 1 A g–1. Moreover, the solid-state asymmetric supercapacitor with O-CuS/Mn3O4 and MnO2 (O-CuS/Mn3O4//MnO2) shows an outstanding energy density of 34.4 Wh kg–1 at 800.1 W·kg–1 and cyclic stability with 85.7% capacitance retention after 5000 cycles at 6 A g–1. Our work highlights the integration of heterojunction and oxygen modification to fabricate and optimize the energy storage electrode materials.

N-doped graphene modulated N-rich carbon nitride realizing a promising all-solid-state flexible supercapacitor

The fabrication of flexible supercapacitors comprising highly conducting energy storage electrode material catering high capacity, energy density and longer stability without cell deformation is a challenging task. Herein, we develop unique g-C3N4.7/N-doped graphene nanocomposite electrode material which shows robust charge storage characteristics via reducing the interfacial resistivity. A flexible all-solid-state symmetric device is assembled by employing g-C3N4.7/N-doped graphene composite and redox active ([EMIM][BF4]/PVDF/KOH/p-phenylenediamine) electrolyte cum separator. It delivers a high areal capacitance of 141 mF cm−2, power density of 0.70 mW cm−2 and an energy density of 0.047 mWh cm−2 at 1.11 mA cm−2 current density with 98.9% capacity retention at 2.2 V potential till 18,000 cycles and nearly 95% Coulombic efficiency till 20,000 cycles. Bending angle-based performance studies indicate the stability of capacity at any bending angles (0, 35, 60, 90, 150, 180°). The key to the significant functioning of the cell is ascribed to the advantageous synergism involved in g-C3N4.7/N-doped graphene nanocomposite, high surface area and mesoporous structure endowing high electrode-electrolyte interface interaction sites along with enhancement in the electronic conductivity as evidenced.

Electrochemical deposition of uniform and porous Co–Ni layered double hydroxide nanosheets on nickel foam for supercapacitor electrode with improved electrochemical efficiency

In this study, Co–Ni layered double hydroxide (LDH) nanosheets are synthesized on nickel foam (NF) using a simple, facile, and cost effective electrochemical deposition method. We present a comparative study of Co–Ni LDH nanosheets on NF for use in supercapacitor electrodes. The method is based on electrochemical deposition using cyclic voltammetry (CV) with different cycles (4, 6, 8, and 10 cycles). Compared to other cycles, the Co–Ni LDH nanosheets on NF as electrode materials obtained higher specific capacitance at eight cycles. In 1 M potassium hydroxide (KOH), a significant specific capacitance of 3130.8 F/g was obtained at a scan rate of 5 mV/s, with good cyclic stability of 72.4% capacitance retention after 3000 cycles. The uniform and porous structure of Co–Ni LDH nanosheets on NF and the fast ion transfer between the electrolyte–electrode interface and reduced resistance contribute to this superior electrochemical efficiency, confirmed by CV and electrochemical impedance (EIS) studies. Co–Ni LDH nanosheets on NF are promising candidates for low-cost high-efficiency energy storage electrode materials for supercapacitor applications because of their superior performance and ease of preparation.

An electrochemical route to holey graphene nanosheets for charge storage applications

Holey graphene nanosheets are potentially useful in several relevant technological applications, including electrochemical energy storage and molecular separation. Access to this material is mostly accomplished by resorting to standard graphene oxides obtained by common routes (e.g., the Hummers method). However, such a type of highly oxidized graphenes may not be the best option as a precursor to holey graphene on account of their chemical/structural heterogeneity and harsh synthesis conditions. Here, we report the use of highly oxidized graphene nanosheets derived by an electrochemical exfoliation/oxidation strategy as an alternative precursor to holey graphene. Compared to a standard graphene oxide with the same extent of oxidation, the electrochemically derived precursor exhibited larger aromatic domains, which provided a structural basis for its higher electrical conductivity, as well as smaller and denser oxidized regions, associated to a higher chemical homogeneity and lability of its oxygen-containing functional groups. Through selective chemical etching of the oxidized domains, the latter feature was exploited to afford holey graphene nanosheets having smaller and more uniform holes. When used as an electrode material for electrochemical charge storage, the electrochemically derived holey graphene outperformed its standard graphene oxide-based counterpart in terms of capacity and energy density. Overall, boasting distinct structural and chemical characteristics, highly oxidized graphene obtained by electrochemical means can be regarded as a prospective advantageous precursor to many graphene-based materials whose preparation has traditionally relied on the processing of graphene oxides.

Facile synthesis of Veitchia merilli coir-based porous carbon using combined chemical and physical activation routes as electrode material for energy storage

This study aimed to prepare Veitchia merilli coir (VMC) through pre-carbonisation process, followed by chemical activation using potassium hydroxide as an activating agent. The experiment was conducted under different pyrolytic physical activation temperatures of 650, 700, and 750 °C with the code VMS-650, VMS-700, and VMS-750 for each sample. Physical activation methods develop or modify the pore structure, specific surface area, and microstructure of activated carbon. Furthermore, the prepared VMCs were characterised using X-ray diffraction, Fourier transform infrared, scanning electron microscope, energy dispersive X-ray, and cyclic voltammetry with a symmetrical two-electrode system in 1 M H2SO4 solution. The microstructure analysis showed that the VMC carbon electrode has an amorphous structure with two broad peaks at 2θ angles around 26° and 44° corresponding to the (002) and (100) planes, with the L c VMS-700 having a value of 16.007 nm. The VMC electrode has a C≡C carbon bond as a functional group, which extends in bands from 2311.79 to 2373.51 cm−1. Meanwhile, the VMS-700 electrode shows a combined surface morphology of nanofibers as well as mesopores, and the energy dispersive X-ray results showed carbon content of 92.83%. The electrochemical properties of supercapacitor cells indicated this electrode had the highest specific capacitance value of 264.2 F g−1. From the obtained results, the respective physical and electrochemical properties of the carbon electrodes and supercapacitor cells showed that the activated VMC-700 at 700 °C is the optimum temperature to produce the best performance compared to 650 and 750 °C.

3DG/Se4.7S3.3 composites with different morphologies as new all-solid-state lithium storage electrode materials

Selenium-sulfur(SexSy) composites can be used as energy storage materials for lithium batteries benefit from their integration of the high capacity of sulfur and the high conductivity of selenium. Herein, we prepared amorphous three dimensional reduced graphene oxide/selenium sulfide(a-3DG/Se4.7S3.3) composites and crystalline 3DG/Se4.7S3.3(c-3DG/Se4.7S3.3) composites by in situ synthesis and hydrothermal methods, respectively, in order to research the effect of different morphologies of 3DG/Se4.7S3.3 composites on the electrochemical properties of all-solid-state lithium batteries. Our study found that the a-3DG/Se4.7S3.3 cathodes displayed greater capacity and outstanding rate performance, with an initial discharge capacity of 926 mAh g−1 and utilization rate of 103% at 1/2C. And a first discharge capacity of up to 706 mAh g−1 at 7 C. Although the first discharge capacity of c-3DG/Se4.7S3.3 was 523 mAh g−1, its cycling stability was significantly improved compared with that of a-3DG/Se4.7S3.3 cathodes, and the Coulombic efficiency remained above 97% after 60 cycles at ½ C. In this work, we investigate the performance of solid-state batteries by preparing new SexSy composites with different morphologies and rational design of electrodes in terms of structure and morphology, which provides ideas for the preparation of electrodes in the future.

Flexible self-supporting CoFe-LDH/MXene film as a chloride ions storage electrode in capacitive deionization

Excessive chloride ions (Cl-) are undesirable in water. However, most of the research on the application of capacitive deionization in desalination has focused on cation storage electrode materials, whereas less on the equally important Cl- storage electrode materials. Herein, the CoFe-Layered Double Hydroxide (CoFe-LDH) prepared by chemical co-precipitation was composited with MXene through simple vacuum filtration to form a self-supporting CoFe-LDH/Ti3C2Tx film electrode, and used as the anode material to store Cl- in the hybrid capacitive deionization system. The CoFe-LDH/Ti3C2Tx composite film has a hierarchical micro-mesoporous architecture, larger electrochemical capacity, and desalination capacity, reaching 149.25 ± 6.17 mg g−1 at a current density of 50 mA g−1 and desalination rate of 3.86 mg g−1 min−1 at 100 mA g−1. This work provides potential inspiration for the Cl- storage electrode for capacitive deionization technology.

Hollow FeS2 nanospheres encapsulated in N/S co-doped carbon nanofibers as electrode material for electrochemical energy storage

Pyrite iron sulfide (FeS2) is a fascinating electrode material for energy reserve devices because of its high theoretical capacity, non-polluting nature and abundant resources. However, the practical application has been extremely inhibited owing to its poor rate capacity and short cyclability caused by volume change during charge/discharge processes. In this article, a novel nanocomposite that is hollow FeS2 nanospheres encapsulated in N/S co-doped carbon nanofibers (FeS2CNFs) was synthesized through electrostatic spinning. The FeS2CNFs nanocomposite demonstrates a terrific specific capacity of 511 F g−1 at 1 A g−1 for all-solid-state supercapacitors. The FeS2CNFs as electrode material for sodium-ion batteries (SIB) displays a specific capacity of 827.7 mAh g−1 and possesses a capacity of 490.6 mAh g−1 at 0.05 A g−1 after 200 cycles. The results indicate that this encapsulated structure can guarantee the integrity of electrode materials. And the abundant defects in carbon nanofibers caused by N/S co-doping may increase electrochemical reaction sites to facilitate charge transfer. The N/S co-doped FeS2CNFs nanocomposite exhibits a great potential for applying in SIB and supercapacitors.

Ultrafast flashlight sintered mesoporous NiO nanosheets for stable asymmetric supercapacitors

Ultrafast flashlight sintering (FLS) has become an important green manufacturing technology for the structural reformation of various nanomaterials. Nickel oxide (NiO) has been extensively studied as a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacitance, low cost, and appropriate chemical compatibility. This study reports the fabrication of mesoporous ultrathin NiO nanosheets on carbon cloth (CC) as green electrodes for flexible supercapacitors (SCs) through an exceptional ultrafast millisecond FLS process at room temperature. The optimized FLS-NiO@i12J electrode exhibited a remarkable specific capacity of 202.3 mA h g−1 (1215 F g−1) at a current density of 2 A g−1. Strikingly, the as-fabricated FLS-NiO electrodes outperformed the time and energy-consuming conventional thermally annealed (CTA) NiO electrodes. Furthermore, the flexible FLS-NiO@i12J//rGO asymmetric SCs deliver a remarkable energy density of 47.18 Wh kg−1 at a power density of 758.37 W Kg−1 and extraordinary cycling stability performance after 15,000 cycles. In addition, the FLS-NiO@i12J electrodes offer unique mesoporous structures, high surface areas, and numerous open-pore channels of ultrathin NiO nanosheets that facilitate fast transport of ions and rapid redox reactions. Thus, the present approach is promising for designing advanced electrode materials for flexible energy storage applications.

Nitrogen-doped carbon nanofibers derived from phenolic-resin-based analogues for high-performance lithium-ion batteries

The preparation of one-dimensional (1-D) carbon nanofibers (CNFs) for lithium-ion battery (LIB) anode materials plays a crucial role in electrochemical energy storage, but it still remains a great challenge due to the limited synthesis methods. Herein, we use a facile strategy to prepare the nitrogen-doped porous CNFs with high aspect ratio by direct pyrolysis of their phenolic-resin-based precursors in ammonium atmosphere. The polymer precursors are synthesized via a hydrothermal approach and have very high carbon yield over 50% in mass. Benefited from the unique 1-D porous structure, high nitrogen content and good conductivity, the ammonium-treated N-doped porous CNFs demonstrate an outstanding electrochemical lithium storage performance. The as-prepared N-doped porous CNFs demonstrates a high irreversible capacity of 325.2 mA h g−1 at 1000 mA g−1 together with an excellent long cycling performance (485.1 mA h g−1 at 500 mA g−1) after 500 cycles. This work offers a facile preparation strategy of the N-doped porous CNFs for high-efficiency energy storage electrode materials.

Prolific intercalation of VO2 (D)/polypyrrole/g-C3N4 as an energy storing electrode with remarkable capacitance

VO2 (D)/polypyrrole/g-C3N4 composites are synthesized through in situ chemical oxidation polymerization, and used as an electrode material for excellent energy storage.

Freestanding carbon nanofibers encapsulating MOF-derived NiSe with in-situ porous carbon protective layer for sodium storage

NiSe is considered to be an effective sodium storage electrode material due to its eminent theoretical capacity and ultra-long-term cycle life. Nonetheless, the large volume fluctuation and slow reaction kinetics cause NiSe to exhibit poor rate performance and cycle stability. Furthermore, the conventional electrode preparation technique necessitates the use of conductive and binder chemicals, resulting in poor electrochemical performance. To address these issues, freestanding NiSe-based electrodes (NiSe@C@NCNFs) are successfully fabricated via electrospinning Ni-MOF precursors and subsequent selenization reactions that NiSe nanoparticles are in-situ protected by MOF-derived porous carbon, thus ensuring the long-term cycling stability for sodium storage. Furthermore, the unique electrode structure design can improve the anode-electrolyte interface contact, shortening the sodium ionic transport path and quickening reaction kinetics. According to corresponding kinetics analysis, the sodiation/desodiation process of NiSe@C@NCNFs is a dominant surface pseudo-capacitance process, guaranteeing their prominent rate capability.

Highly ordered nanoscale phosphomolybdate-grafted polyaniline/metal hybrid layered structures prepared via secondary sputtering phenomenon as high-performance pseudocapacitor electrodes

The development of energy storage electrode materials is important for enhancing the electrochemical performance of supercapacitors. Despite extensive research on improving electrochemical performance with polymer-based materials, electrode materials with micro/nanostructures are needed for fast and efficient ion and electron transfer. In this work, highly ordered phosphomolybdate (PMoO)-grafted polyaniline (PMoO-PAI) deposited onto Au hole-cylinder nanopillar arrays is developed for high-performance pseudocapacitors. The three-dimensional nanostructured arrays are easily fabricated by secondary sputtering lithography, which has recently gained attention and features a high resolution of 10 nm, a high aspect ratio greater than 20, excellent uniformity/accuracy/precision, and compatibility with large area substrates. These 10 nm scale Au nanostructures with a high aspect ratio of ∼30 on Au substrates facilitate efficient ion and electron transfer. The resultant PMoO-PAI electrode exhibits outstanding electrochemical performance, including a high specific capacitance of 114 mF cm−2, a high-rate capability of 88%, and excellent long-term stability.