Electrode Materials For Energy Storage Research Articles

Preparation and properties of two-dimensional Ti2CT x MXene based on electroetching method

The continuous advancements in wearable electronics have drawn significant attention toward 2D MXenes materials for energy storage owing to their abundant availability, adaptability, and distinctive physicochemical properties. Two unresolved concerns currently revolve around environmental pollution by F-containing etching and finite kinetics caused because of re-stacking of nanosheets. In this study, Al was electrochemically etched from porous Ti2AlC electrodes without the use of fluorine, through a selective electrochemical etching process in dilute hydrochloric acid. Subsequently, Ti2CT x MXene was vertically grown on carbon fiber (CF) substrates. The resulting Ti2CT x @CF electrodes are lightweight, thin, and flexible, exhibiting a surface capacitance of 330 mF cm−2 at a constant current density of 1 mA cm−2 after 2000 cycles. They display a surface capacitance retention of 96.16% and a high energy density of 45.3 μWh cm−2 at a power density of 0.497 mW cm−2. These metrics underscore the Ti2CT x @CF electrode’s commendable multifunctionality, electrochemical performance, ion transport efficiency, and charge storage capacity. Moreover, a flexible energy storage electrode material with a high area capacity was developed by combining Ti2CT x MXene nanosheets, possessing a large specific surface area, with a flexible carbon fabric substrate.

Preparation of Nb5+ Doped Na3V2(PO4)3 Cathode Material for Sodium Ion Batteries.

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) due to the abundance and low cost of sodium resources. Cathode material plays a crucial role in the performance of sodium ion batteries determining the capacity, cycling stability, and rate capability. Na3V2(PO4)3 (NVP) is a promising cathode material due to its stable three-dimensional NASICON structure, but its discharge capacity is low and its decay is serious with the increase of cycle period. We focused on modifying NVP cathode material by coating carbon and doping Nb5+ ions for synergistic electrochemical properties of carbon-coated NVP@C as a cathode material. X-ray diffraction analysis was performed to confirm the phase purity and crystal structure of the Nb5+ doped NVP material, which exhibited characteristic diffraction peaks that matched well with the NASICON structure. Nb5+-doped NVP@C@Nbx materials were prepared using the sol-gel method and characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman and Brunauer -Emmett-Teller (BET) analysis. First-principles calculations were performed based on density functional theory. VASP and PAW methods were chosen for these calculations. GGA in the PBE framework served as the exchange-correlation functional. The results showed the NVP unit cell consisted of six NVP structural motifs, each containing octahedral VO6 and tetrahedral PO4 groups to form a polyanionomer [V2(PO4)3] along with the c-axis direction by PO4 groups, which had Na1(6b) and Na2(18e) sites. And PDOS revealed that after Nb doping, the d orbitals of the Nb atoms also contributed electrons that were concentrated near the Fermi surface. Additionally, the decrease in the effective mass after Nb doping indicated that the electrons could move more freely through the material, implying an enhancement of the electron mobility. The electrochemical properties of the Nb5+ doped NVP@C@Nb cathode material were evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge tests, electrochemical impedance spectroscopy (EIS), and X-ray photoelectric spectroscopy (XPS). The results showed that NVP@C@Nb0.15 achieved an initial discharge capacity as high as 114.27 mAhg-1, with a discharge capacity of 106.38 mAhg-1 maintained after 500 cycles at 0.5C, and the retention rate of the NVP@C@Nb0.15 composite reached an impressive 90.22%. NVP@C@Nb0.15 exhibited low resistance and high capacity, enabling it to create more vacancies and modulate crystal structure, ultimately enhancing the electrochemical properties of NVP. The outstanding performance can be attributed to the Nb5+-doped carbon layer, which not only improves electronic conductivity but also shortens the diffusion length of Na+ ions and electrons, as well as reduces volume changes in electrode materials. These preliminary results suggested that the as-obtained NVP@C@Nb0.15 composite was a promising novel cathode electrode material for efficient sodium energy storage.

Heteroatom(S) (N, S, P) Co‐Doped Reduced Graphene Oxide‐Based Binder‐Free Novel Energy Storage Electrode Material for High Energy Density Supercapacitor

AbstractThis manuscript reports a one‐pot synthesis of ternary heteroatoms (N/S/P) co‐doped reduced graphene oxide as an electrode material by simultaneous reduction/doping of/into graphene oxide employing eco‐friendly natural molecule(s) (thiamine monophosphate (TM) and thiamine pyrophosphate (TP)) under mild heating (≤60 °C) and near‐neutral pH (≤8) conditions. It produces N, S, P co‐doped rGO‐TM and N, S, P co‐doped rGO‐TP nanohybrids displaying a well‐connected porous microstructure with significantly doped atomic(%) ‐N (10.0%), S (4.1%), P (0.1%) and N (6.7%), S (2.0%), and P (0.5%), respectively. The symmetric supercapacitor designed using N, S, P‐rGO‐TM‐10 in water‐in‐salt 17 m NaClO4 electrolyte exhibits stable cell voltage of 3.0 V, superb gravimetric energy density (areal energy density) of 47.9 Wh kg−1@522.8 W g−1 (0.2363 Wh cm−2@ 2.5 W cm−2); the excellent cyclic stability (88.8 %) and Coulombic efficiency (99.2%) even after 20 000 cycles. Their energy storage capability is corroborated by the illumination of 109 white LEDs upon lighting a single SSC for 50 s each, driving a motor to run a fan, and forming the tandem device by joining three such cells in series.

Regulating intramolecular hydrogen bonds of p-phenylenediimidazole-based small-molecule compounds towards the enhanced lithium storage capacity

The use of redox-active organic electrode materials in energy storage is restricted due to their inferior solvent resistance, abysmal conductivity, and the resultant low practical capacity. To address these issues, a class of bipolar p-phenylenediimidazole-based small-molecule compounds are designed and fabricated. The π-conjugated backbone of these small molecules allows for electron delocalization on a big conjugation plane, endowing them with good conductivity and reaction reversibility. Furthermore, when the para-positions of phenylene are occupied by hydroxyl groups, as-formed intramolecular hydrogen bonds (N–H…O) between phenolic hydroxyl groups and the –NH groups of imidazole rings further enhance the structural planarity, resulting in higher π-conjugation degree and better conductivity, and thus higher utilization of active sites and electrode capacity, proved by both experimental results and theoretical calculations. The optimized composite electrode DBNQ@rGO-45 shows a high specific capacity (∼308 mA h g−1 at 100 mA g−1) and a long cycling stability (112.9 mA h g−1 after 6000 cycles at 2000 mA g−1). The significantly better electrochemical properties for hydroxyl group-containing compounds than those without hydroxyl groups attributed to intramolecular hydrogen bond-induced conjugation enhancement will inspire the structure design of organic electrodes for better energy storage.

Organic Electrode Materials for Energy Storage and Conversion: Mechanism, Characteristics, and Applications.

ConspectusLithium ion batteries (LIBs) with inorganic intercalation compounds as electrode active materials have become an indispensable part of human life. However, the rapid increase in their annual production raises concerns about limited mineral reserves and related environmental issues. Therefore, organic electrode materials (OEMs) for rechargeable batteries have once again come into the focus of researchers because of their design flexibility, sustainability, and environmental compatibility. Compared with conventional inorganic cathode materials for Li ion batteries, OEMs possess some unique characteristics including flexible molecular structure, weak intermolecular interaction, being highly soluble in electrolytes, and moderate electrochemical potentials. These unique characteristics make OEMs suitable for applications in multivalent ion batteries, low-temperature batteries, redox flow batteries, and decoupled water electrolysis. Specifically, the flexible molecular structure and weak intermolecular interaction of OEMs make multivalent ions easily accessible to the redox sites of OEMs and facilitate the desolvation process on the redox site, thus improving the low-temperature performance, while the highly soluble nature enables OEMs as redox couples for aqueous redox flow batteries. Finally, the moderate electrochemical potential and reversible proton storage and release of OEMs make them suitable as redox mediators for water electrolysis. Over the past ten years, although various new OEMs have been developed for Li-organic batteries, Na-organic batteries, Zn-organic batteries, and other battery systems, batteries with OEMs still face many challenges, such as poor cycle stability, inferior energy density, and limited rate capability. Therefore, previous reviews of OEMs mainly focused on organic molecular design for organic batteries or strategies to improve the electrochemical performance of OEMs. A comprehensive review to explore the characteristics of OEMs and establish the correlation between these characteristics and their specific application in energy storage and conversion is still lacking.In this Account, we initially provide an overview of the sustainability and environmental friendliness of OEMs for energy storage and conversion. Subsequently, we summarize the charge storage mechanisms of the different types of OEMs. Thereafter, we explore the characteristics of OEMs in comparison with conventional inorganic intercalation compounds including their structural flexibility, high solubility in the electrolyte, and appropriate electrochemical potential in order to establish the correlations between their characteristics and potential applications. Unlike previous reviews that mainly introduce the electrochemical performance progress of different organic batteries, this Account specifically focuses on some exceptional applications of OEMs corresponding to the characteristics of organic electrode materials in energy storage and conversion, as previously published by our groups. These applications include monovalent ion batteries, multivalent ion batteries, low-temperature batteries, redox flow batteries with soluble OEMs, and decoupled water electrolysis employing organic electrodes as redox mediators. We hope that this Account will make an invaluable contribution to the development of organic electrode materials for next-generation batteries and help to unlock a world of potential energy storage applications.

Environmentally benign synthesis and characterization of Bi2O3‐Sb2O3 nanocomposite: Investigation of its potential as electrode material in energy storage and generation applications

A shift to alternate energy sources is needed at the present time to address rising environmental concerns. The current research work aims to use a chemical‐free and green route to synthesize nanocomposite for their application as an electrode in the generation as well as storage of energy. Subsequently, the green synthesis of Bi2O3‐Sb2O3 nanocomposite was carried out using the leaf extract of Amaranthus viridis. The synthesized nanocomposite revealed a well‐arranged pattern of spherical nanoparticles with a crystal size of 29.43 nm and a band gap value of 2.5 eV. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) potentials of Bi2O3‐Sb2O3 were studied through linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS), whereas the energy storage studies were performed using cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) techniques. The synthesized nanomaterial showed promising results for HER with an overpotential value of 205 mV as compared with OER, where an overpotential value of 450 mV was observed. However, excellent cyclic stability was witnessed for both reactions up to 1000 cycles. CV studies revealed an outstanding capacitance value of 348 F/g at a scan rate of 2 mV/s, whereas a specific capacitance of 269.5 F/g at a current density of 0.5 A/g was observed using GCD. The 15 h of electrode stability further endorsed the potential of synthesized material for energy‐based applications.

Synthesis of Ni3V2O8-rGO composite nanostructure for high-performance hybrid supercapacitors via hydrothermal method

To address global energy demand, major efforts have been made to develop cutting-edge electrode materials for electrochemical energy storage (EES) devices. The present article discusses the hydrothermal synthesis of bare nickel vanadate and a nickel vanadate/reduced graphene oxide (Ni3V2O8-rGO) composite for supercapacitor applications. The physicochemical properties of pure Ni3V2O8 (NVO) and the Ni3V2O8-rGO (NVO-rGO) composite were investigated using a variety of characterization tools. The electrochemical traits of the NVO-rGO composite outperform bare NVO due to the synergistic effect. At a current density of 1 mAcm−2, the NVO and NVO-rGO nanostructures exhibit excellent specific capacitances of 85 Fg−1 and 108 Fg−1, respectively. These nanostructures also have energy densities of about 3.82 and 5.02 WhKg−1, with power densities of 141.75 and 151.57 WKg−1 for NVO and NVO-rGO composite, respectively. Electrochemical impedance spectroscopy (EIS) studies revealed a charge resistance of 2.05 Ω. The transfer coefficient and standard rate constant indicate that the charge storage mechanism is based on a quasi-reversible redox process. The present investigation demonstrates that the NVO-rGO composite has exceptional electrochemical performance. The outstanding electrochemical performance of both NVO and NVO-rGO underlines their potential as novel and promising materials for supercapacitor applications, implying significant feasibility for large-scale utilization.

In-situ synthesis of coral reef-like synergistic zinc cobalt oxide and zinc manganese oxide composite as a battery-type electrode material for supercapacitors

Recently, in-situ preparation of metal oxide composite structures has gained much importance in fabricating electrode materials for energy storage and conversion devices because of its advantageous properties of beneficial interfacial contact, high conductivity, good synergism, short ion diffusion distance, better electrochemical performance, etc. Binary transition metal oxides (BTMOs) are given great attention for their significant electrochemical performances over primary MOs because of the two metal ions with different valent states for the redox reactions. In this study, we synthesize zinc cobalt oxide (ZnCo2O4) and zinc manganese oxide (ZnMn2O4) composite via a solvothermal synthetic method. The existence of both phases is identified using an X-ray diffraction analysis (XRD). The unique coral reef-like structures of the composite electrode are analysed via field emission scanning electron microscopy, and the nanostructure was identified using transmission electron microscopy. The X-ray photoelectron spectroscopy confirms the surface oxidation states of the composite and supports the XRD analysis. The synergetic composite electrode provides a large surface area of 50.86 m2 g−1 with many pores. The composite electrode has a specific capacity of 250 C g−1 at 1 A g−1. The ZCO/ZMO composite demonstrated impressive stability, retaining a specific capacity of 180 C g−1 at 6 A g−1 over 5000 cycles.

Morphologically tailored NiMn2O4nanocubic material for high energy-power density asymmetric supercapacitor and non-enzymatic H2O2 sensing

Developing an advanced material for energy storage and sensors is considered a key solution to meet future energy demands and economic challenges. The inverse spinel-structured NiMn2O4 emerges as a promising electrode material for next-gen energy storage due to its notable power capability, high energy density, and excellent cyclic stability. Nanostructuring enhances features not achievable in bulk materials, with a mixed morphology of nano-cubic and nanoflakes optimizing surface-to-volume ratio for effective use in energy storage devices. The addition of PVP as a surfactant, transforms the diffusion-controlled behavior to a capacitive mechanism, enhancing energy density and cyclic stability. Electrodes exhibit a specific capacitance of 816 F g−1 at 1 A g−1 and stable cyclic behavior over 5000 cycles in 1 M KOH. The constructed ASC device shows 96% cyclic stability over 10,000 cycles, maintaining an energy density of 8.8 Wh kg−1 at 6400 W kg−1 and reaching a maximum of 36.55 Wh kg−1 at 400 W kg−1. Electronic structural characteristics explained through density functional theory (DFT) contribute insights. Furthermore, the non-enzymatic NiMn4/GCE H2O2 sensor demonstrates high sensitivity, a low detection limit, and remarkable selectivity against various biological interferences across a broad concentration range.

Metal oxide-based nanocomposites as advanced electrode materials for enhancing electrochemical performance of Supercapacitors: A comprehensive review

In recent years, the escalating use of nonrenewable fossil fuels has emerged as a significant threat to global sustainability, prompting the need for renewable, cost-effective, and eco-friendly energy storage solutions. Supercapacitors (SCs) are notable for their high power density (PD), cycle stability, and swift charge/discharge rates, although they fall short in energy density (ED) compared to traditional batteries. The performance of SCs is greatly influenced by the electrode materials used, highlighting the importance of material innovation in tackling the challenges posed by increasing fossil fuel consumption. Transition metal oxides (TMOs), known for their redox activity in energy storage, have been thoroughly investigated for their exceptional specific capacitance, which ranges from 100 to 2000F g−1, surpassing that of electrical double-layer capacitors (EDLCs). TMOs such as ruthenium oxide (RuO2), manganese oxide (MnO2), nickel oxide (NiO), cobalt oxide (Co3O4), tin oxide (SnO2), zinc oxide (ZnO), tungsten oxide (WO3), and vanadium pentoxide (V2O5) are widely researched for their high theoretical capacitance, affordability, and longevity. This review emphasizes the groundbreaking potential of metal oxide nanocomposites (NCs) formed by combining them with graphene, carbon nanotubes (CNTs), and polymers, leading to synergistic enhancements in electrical conductivity, surface area, and charge storage capacity. This thorough review not only presents an in-depth analysis of current research but also sheds light on potential future developments, contributing to the ongoing progress in the field of advanced electrode materials for energy storage.

Cycling Stability of a 2D Pristine MOF Supercapacitors

AbstractTwo‐dimensional (2D) metal–organic frameworks (MOFs) have been a worldwide research interest due to their potential application in supercapacitors. Herein, a cobalt‐based layered MOF ([Co2(μ‐SO4)(Hppza)2(H2O)3]n, namely, SEU‐1; H2ppza=3‐(pyridin‐4‐yl)‐1H‐pyrazole‐5‐carboxylic acid) has been synthesized via a one‐step solvothermal method. Single X‐ray diffraction analysis shows that the SEU‐1 exhibits a (3,3,4)‐connected 2D structure with a Schläfli symbol of (62 ⋅ 8)(63)(64 ⋅ 8 ⋅ 10). Variable‐temperature magnetic susceptibility data display that antiferromagnetic interactions between two CoII ions exist in SEU‐1. The supercapacitive performance has been evaluated in the three‐electrode system. Its maximum specific capacitance is 145.5 F g−1 at 1 A g−1, along with the specific capacitance retention of 92.7 % at the current density of 5 A g−1 after 6000 cycles in 3 M KOH solution. These results demonstrate that SEU‐1 is a good candidate for electrode material for electrochemical energy storage.

Recent progress on construction and applications of metal‐organic frameworks‐based materials for lithium‐ion batteries and supercapacitors

AbstractMetal‐organic frameworks (MOFs), a special sort of three‐dimensional crystalline porous lattices composed of organic multi‐site connectors and metal nodes, are characterized by unique porosity and high specific surface area, which have attracted a wide range of interest as electrode materials for the electrochemical energy storage devices in recent years. In this contribution, we outline the current research progress on the construction of pristine MOFs, MOF composites, and MOF derivatives and their applications as electrode materials in supercapacitors (SCs) and lithium‐ion batteries (LIBs). Specifically, we discuss the shortcomings of MOFs‐based electrode materials for SCs and LIBs. The innovative work on performance improvements by combining MOFs with other conductive materials and derivating MOFs into metal sulfides, metal oxides, metal phosphides, and porous carbon is also presented in detail. Finally, our perspectives on the challenges in the future for a grasp of the potential mechanisms are tentatively provided. This review will inspire more developments and applications of MOFs‐based electrode materials for electrochemical energy storage.

Anion substitution-induced CuCoSe hollow nanotubes as multifunctional electrode materials for supercapacitors and overall water splitting

Developing highly efficient non-noble-metal electrode materials for energy storage and conversion is crucial for advancing sustainable and renewable energy. In this study, a facile and effective anion substitution-induced approach was designed to synthesize uniform CuCoSe hollow nanotubes. Impressively, the obtained CuCoSe hollow nanotubes reach an exceptional mass-specific capacitance of 2,853.1F·g−1 at 10 A·g−1, with intriguing rate capability and desirable capacitance retention after 5,000 cycles. The assembled CuCoSe//CuCoSe symmetrical supercapacitor device exhibits a high energy density of 218.9 Wh·kg−1 at a power density of 4,000 kW·kg−1. Furthermore, the CuCoSe hollow nanotubes show exceptional performances in both oxygen and hydrogen evolution reactions, necessitating low overpotentials of 94.4 and 33.4 mV at 10 mA·cm−2. When used as a bifunctional electrocatalyst, the assembled CuCoSe||CuCoSe electrolytic cell affords a low cell voltage of 1.40 V to drive 10 mA·cm−2, significantly superior to other commercial electrolyzers and most reported bifunctional electrocatalysts. Experimental and density functional theory calculations suggest that selenides substituted CuCo-layered double hydroxides can greatly enhance the electrochemical performances. This work will be beneficial for the design of the next generation of energy storage and conversion technologies.

Electrochemical Investigation of Lithium Perchlorate-Doped Polypyrrole Growing on Titanium Substrate

Lithium perchlorate-doped polypyrrole growing on titanium substrate (LiClO4-PPy/Ti) has been fabricated to act as electroactive electrode material for feasible electrochemical energy storage. A theoretical and experimental investigation is adopted to disclose the conductivity, electroactivity properties and interfacial interaction-dependent capacitance of LiClO4-PPy/Ti electrode. The experimental measurement results disclose that LiClO4-PPy/Ti reveals lower ohmic resistance (0.2226 Ω cm−2) and charge transfer resistance (2116 Ω cm−2) to exhibit higher electrochemical conductivity, a more reactive surface, and feasible ion diffusion to present higher double-layer capacitance (0.1930 mF cm−2) rather than LiClO4/Ti (0.3660 Ω cm−2, 65,250 Ω cm−2, 0.0334 mF cm−2). LiClO4-PPy/Ti reveals higher Faradaic capacitance caused by the reversible doping and dedoping process of perchlorate ion on PPy than the electrical double-layer capacitance of LiClO4/Ti caused by the reversible adsorption and desorption process of the LiClO4 electrolyte on Ti. Theoretical simulation calculation results prove that a more intensive electrostatic interaction of pyrrole N···Ti (2.450 Å) in LiClO4-PPy/Ti rather than perchlorate O···Ti (3.537 Å) in LiClO4/Ti. LiClO4-PPy/Ti exhibits higher density of states (57.321 electrons/eV) at Fermi energy and lower HOMO-LUMO molecule orbital energy gap (0.032 eV) than LiClO4/Ti (9.652 electrons/eV, 0.340 eV) to present the enhanced electronic conductivity. LiClO4-PPy/Ti also exhibits a more declined interface energy (−1.461 × 104) than LiClO4/Ti (−5.202 × 103 eV) to present the intensified interfacial interaction. LiClO4-PPy/Ti accordingly exhibits much higher specific capacitances of 0.123~0.0122 mF cm−2 at current densities of 0.01~0.10 mA cm−2 rather than LiClO4/Ti (0.010~0.0095 mF cm−2, presenting superior electroactivity and electrochemical capacitance properties. LiClO4-PPy/Ti could well act as the electroactive supercapacitor electrode for feasible energy storage.

Surface exsolved NiFeOx nanocatalyst for enhanced alkaline oxygen evolution catalysis

A synergistically improved alkaline oxygen evolution catalyst of the NiFeOx nanoalloy oxide structure is introduced using an in-situ exsolution method. The separately doped Ni and Fe ions are exsolved on the surface of the perovskite as homogeneously distributed NiFeOx oxide alloy catalysts via following reduction and oxidation processes. The incorporation of additional Fe into the surface embedded NiFeOx catalyst improved the inherent oxygen evolution reaction (OER) property with fast reaction kinetics. Density functional theory (DFT) result indicates the lowest OER overpotential of NiFeOx catalyst is originated from the reduced energy barrier of surface *O formation from *OH group. The NiFeOx exsolved catalyst shows the smallest overpotential of 0.49 V (j = 10 mA∙cm−2) and Tafel slope (93 mV∙dec-1), compared with that of single NiO (0.54 V, 132 mV∙dec-1) and Fe3O4 catalyst. This study provides an effective method for developing nanosized OER catalysts for various energy conversion and storage electrode materials.

Dibutyl benzotriazolium tetrafluoroborate doped PANI as an electrode material for energy storage

This work is on the reporting of the synthesis of 1,3-dibutyl-1,2,3-benzotriazolium tetrafluoroborate-doped polyaniline through interfacial polymerization and its material characterizations through FT-IR, XRD, EDS, FESEM, XPS, BET, and TGA and electrochemical property evaluation through CV, EIS, and GCD. The electrode was tested in an ionic liquid electrolyte solution with a 3-electrode setup, which gave an effective potential window from −1.5 to 1.0 V. PANI-DIBUTBTBF4 electrodes were tested on benzotriazolium tetrafluoroborate gel polymer electrolyte using poly(vinylidenefluoride-co-hexafluoropropylene) as host polymer for supercapacitor application through evaluating the electrochemical properties of the fabricated prototype with CV, EIS, and GCD. The SC prototype showed an efficient electrochemical window of 3.5 V. And at 0–3.5 V, it shows a high specific capacitance of 1417.88 F g−1 at a scan rate of 2 mV s−1, and from the galvanostatic charge discharge cycle at a current density of 0.32 A g−1, an energy density of 7.11 mW h g−1 and a power density of 555.06 mW g−1 were observed. The prototype retains a capacitance of 89 % even after 3000 cycles. A single swagelok cell charged at 2 V for 20 min was able to light a red (1.6 V, 20 mA) LED brightly for 5 min, which demonstrated its practical applicability.

Carbon and Nitrogen‐Co‐Doped Se/NiSe2/CoSe2 Nanocomposite as Superior Performance Electrode Material in Hybrid Supercapacitors

AbstractMetal selenides are essential electrode materials for promising electrochemical energy storage with comparable or improved electrochemical performance than metal oxides. Herein, Se/NiSe2/CoSe2 (S/NS/CS) is fabricated using a solvothermal approach with the assistance of polyethyleneimine, followed by annealing at different temperatures (300, 400, 500, and 600 °C) for one hour under an argon atmosphere. After annealing, all electrodes’ physical and electrochemical properties were examined, which determined that the best electrode is NiCo2O4/NiO (NCO/NO) formed at 500 °C. Additional hydrothermal method uses NCO/NO with SeO2 as a selenium source to prepare S/NS/CS nanocomposite, with a specific surface architecture that enables easy ion movement and robust conductivity, giving it exceptional electrochemical energy storage properties. It exhibited a remarkable capacitance of 468 F g−1 at a current density of 0.5 A g−1. For practical applications, the hybrid S/NS/CS//AC device was designed using S/NS/CS as a positive electrode and commercial activated carbon (AC) as a negative electrode. The asymmetric device demonstrated an excellent capacitance of 142 F g−1 (189 C g−1) and a superb specific energy of 44 Wh kg−1 at a specific power of 840 W kg−1 at a current density of 1 A g−1, providing 80 % capacity retention and 100 % coulombic efficiency after 5000 cycles.

Supercapacitor Performance of MXene-Coated Carbon Nanofiber Electrodes

MXenes consisting of thin layers of transition metal carbides or nitrides are good candidates for electrode materials due to their excellent electrical conductivity and fast ion transfer. Electrospun carbon nanofibers are highly porous and electrically conductive, making them attractive for electrode materials. In this study, free-standing electrodes were prepared by the dip-coating of carbon nanofibers (CNFs) in the MXene (Ti3C2) colloidal solution, which was synthesized via the wet-etching of MAX (Ti3AlC2) phase, and their chemical structures were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. In addition, scanning and transmission electron microscopy were used to investigate the morphological and crystallographic features of MXene-coated CNFs. Surface area and pore volumes were investigated by nitrogen adsorption/desorption measurements. Supercapacitor performance was studied by assembling a 3-electrode system with 1M aqueous sodium sulfate solution as an electrolyte. MXene-coated CNFs exhibited a maximum specific capacitance of 514 F/g at 0.5 A/g, with energy and power densities of 71.4 Wh/kg at 0.5 A/g and 2.3 kW/kg at 5 A/g, respectively, which are relevantly higher compared to the pristine CNFs due to the pseudocapacitive behavior of MXenes. They also showed comparable cyclic stability during 5000 cycles with the CNFs. This result indicates that MXene-coated carbon nanofibers can be effective electrode materials for electrochemical energy storage.

Manganese ferrite/reduced graphene oxide composites as energy storage electrode materials for supercapacitors

Manganese ferrite/reduced graphene oxide composites as energy storage electrode materials for supercapacitors

Membrane based In-situ reduction of graphene oxide for electrochemical supercapacitor application

Reduced graphene oxide (rGO) is a widely studied electrode material for energy storage, however, its strong re-stacking tendency during chemical reduction always leads to a degraded specific surface area and thus limits its performance. Therefore, it is necessary to control the morphology of rGO during the reduction process. Here, we develop a novel in-situ membrane-based method for the reduction of graphene oxide (GO) using a green and efficient vitamin C (VC) aqueous solution as reductant. The obtained electrode material (vitamin C reduced GO via membrane-based method, VG-M) exhibits a specific capacitance of 174 F/g at 1 A/g and 75.9% of retention at 40 A/g, which is about 9 times better than the highly self-stacked material from conventional methods (vitamin C reduced GO via stirring method, VG-S). This designed method successfully achieves the maintenance of rGO sheet morphology through laminar confinement in GO membrane and presents a simple approach towards two-dimensional (2D) material morphology control.