Cyclic Galvanostatic Charge-discharge Research Articles

In-situ vacancy defects triggered via organic solvent-water fusion for improved OER, HER, and supercapacitor performance

Simplifying the design of high-performance electrodes via efficient catalyst design is critical for alkaline water electrolysis and supercapacitor applications. Towards that end, we have developed the environmentally benign synthesis of ultrathin nanosheets of NiFe-layered double hydroxides (LDH) with inbuilt oxygen vacancies (VO) in this report. These NiFe-layered double hydroxide (GNiFe-LDH-VO) materials require low overpotentials for the oxygen evolution reaction (OER, η50 = 200 and η100 = 220 mV) with a small Tafel slope of 52.21 mV dec−1. The ex-situ characterizations and theoretical calculations suggest that oxygen vacancies configure to a more active state, resulting in the low binding energy of oxo intermediates, and thus much lower overpotential. Besides, it could operate stably for 100 h at current densities of 100 mA cm−2 for OER. It is significant that oxygen vacancies in GNiFe-LDH-VO aid in lowering the main obstacle of multistep OER, which will provide recommendations for the development of high-efficiency catalysts through in situ activation. In addition, GNiFe-LDH-VO exhibits a high areal capacitance of 1.6024 F cm−2 at a current density of 1 mA cm−2, with a capacitance retention ratio of 96.1% after 5000 galvanostatic charge-discharge (GCD) cycles when they are used as supercapacitor electrodes.

Recyclable organic radical electrodes for metal-free batteries.

Organic batteries are one of the possible routes for transitioning to sustainable energy storage solutions. However, the recycling of organic batteries, which is a key step toward achieving circularity, is not easily achieved. This work shows the direct recycling of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl) (PTMA) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm) based composite electrodes. After charge-discharge cycling, the electrodes are deconstructed using a solubilizing-solvent and then reconstructed using a casting-solvent. The electrochemical properties of the original and recycled electrodes are compared using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycling, from which it is discovered using time-of-flight secondary ion mass spectrometry (ToF-SIMS) that recycling can be challenged by the formation of a solid-electrolyte interphase (SEI). In turn, an additive is proposed to modify the SEI layer and improve the properties after recycling. Last, an anionic rocking chair battery consisting of PTAm electrodes as both positive and negative electrodes is demonstrated, in which the electrodes are recycled to form new battery. This work gives demonstrates the recycling of composite electrodes for organic batteries and provides insights into the challenges and possible solutions for recycling the next-generation electrochemical energy storage devices.

In-situ growth of MCo2O4 nanospheres (M: Mn, Ni) over g-C3N4@PPy as high-performance and novel composites for sustainable supercapacitors

Introducing and using novel conductive organic–inorganic material systems for the supercapacitor industry is rapidly emerging. In this work, the well-defined MCo2O4 nanospheres (M: Mn, Ni) are successfully grown on the graphitic carbon nitride/polypyrrole (g-C3N4@PPy) nanoparticles by hydrothermal/polymerization process. XPS, FT-IR, XRD, BET, and SEM techniques were employed to investigate the physical and chemical properties as well as the surface characteristics of MCo2O4 nanospheres. The electrochemical behavior of the developed electrode was investigated by electrochemical techniques such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Moreover, owing to the advantageous proportion of aspect ratio and relatively low electrode and electrolyte resistance, the highest specific capacitance value for g-C3N4@PPy@MnCo2O4 and g-C3N4@PPy@NiCo2O4 supercapacitors was obtained as 350.00 and 258.26 F g−1, with a current density of 0.5 A g−1, respectively. Also, capacitance retention of supercapacitors after 5000 GCD cycles was achieved by 92.71 %, and 94.55 % respectively. These results demonstrate that the decorated nanospheres on g-C3N4@PPy exhibit excellent capacitive properties and stability, indicating their potential for use in the field of energy storage.

MOF-derived α-Fe2O3@Fe3O4 on carbon fiber fabric for lithium-ion anode applications

Owing to the current development in emerging fields as electric motoring, biomedical sensors or new generation of mobile phones, new functionalities are required for the new generation of Li-ion batteries as flexibility or structurality. Thus, Metal-Organic Framework (MOF)-derived α-Fe2O3@Fe3O4 coating on carbon fiber fabric has been developed in this study for Lithium-ion battery anode purposes. MOF-derived synthesis is a well-known strategy to obtain Transition Metal Oxides (TMOs) which better electrochemical performance than bare TMOs. On the other hand, synthesis on carbon fiber fabric allows to develop new electrodes for multifunctional energy storage devices in which the coating provides high specific capacity, while the carbon fiber substrate provides stiffness but high flexibility, mechanical strength, and electrical conductivity. This TMO coating was achieved by a novel MOF MIL-100 direct synthesis on carbon fiber and subsequent calcination, the effects of calcination on the composition, texture and morphology of the coating, as well as its electrochemical performance, were studied. As the best result, calcinated samples during 2 h showed the optimal synergic effects between the coating and carbon fiber, exhibiting a specific capacity of 328.6 mAh/g at 25 mA/g, an excellent rate capability and a capacity retention of 89.7 % after 100 galvanostatic charge-discharge cycles. Nevertheless, it is important to note that the novelty of this work is not only based on the electrochemical performance but also on the novel synthesis of MIL-100 directly over the carbon fibers. This novel synthesis opens the way to new variety of TMO coatings for electrodes of all-solid-state energy storage devices.

Sustainable graphene production for solution-processed microsupercapacitors and multipurpose flexible electronics

The growing demand for portable and wearable electronics, Internet of Things microdevices, and wireless sensor networks has led to the development of miniaturized energy storage devices, such as microsupercapacitors (mSCs). With excellent electrical conductivity and high surface area in a layered structure, graphene materials are ideal for mSCs, but current manufacturing methods still hinder their widespread integration. Here, we propose a sustainable approach for the rapid and eco-friendly production of few-layer graphene flakes based on the exfoliation of graphite in water by a combination of high-shear mixing and a high-pressure airless spray. An all-carbon composite paste with high electrical conductivity and tunable viscosity was designed to fabricate planar, interdigitated mSCs on polyethylene terephthalate (PET). The flexible, metal-free mSCs achieved a Coulombic efficiency close to 100%, with areal and volumetric capacitances of 6.16 mF cm-2 and 2.46Fcm-3, respectively. The maximum energy density exceeds 200 μWh cm-3 with 91.5% capacitance retention after 10000 galvanostatic chargedischarge cycles. The mSCs retain the same performance when subjected to a wide bending range and can be easily modularized to adjust the voltage and capacitance outputs. Finally, high-performance coatings for electromagnetic interference shielding and wearable strain sensors are also fabricated to demonstrate the multipurpose applicability of the graphene-based paste.

The construction of a flexible solid-state asymmetric supercapacitor device using nickel-copper oxide nanoplates and carbon nanosphere serving as positive and negative electrode, respectively with excellent electrochemical capabilities

Here, nickel-copper oxide nanoplates (NCN) and carbon nanosphere (CNS) as positive and negative electrodes are synthesised via a hydrothermal protocol without adding any surfactant and binders. The NCN and CNS electrodes in KOH electrolyte exhibit superior specific capacitance of ∼ 2362.5 F g−1 and ∼ 246.11 F g−1 at 1 A g−1 respectively. The NCN and CNS retained 98.54 % and 97.88 % of the initial capacitance after 3000 galvanostatic charge–discharge (GCD) cycles, respectively. Additionally, an asymmetric supercapacitor (ASC) device NCN//CNS is constructed using NCN and CNS as positive and negative electrodes, utilizing poly(vinyl alcohol) PVA − KOH gel electrolyte separator. The ASC device demonstrates a maximum energy density of 50.4 Wh kg−1 (181.44 KJ kg−1) with a power density ∼ 750 W kg−1 at 1 A g−1, maintaining 90.4 % cyclic stability after 10,000 GCD cycles. The electrochemical outputs of the device present significant potential for the advancement of high-performance ASC devices in electronic applications.

High-performance electrochromic WO3/POM–MXene energy storage device with color-based energy indication

Electrochromic energy storage devices (EESDs) with quantitative color-based visualization of their energy state have applications in smart displays and wearable intelligent electronics, as well as energy-efficient buildings. In addition, because of their ability to display their energy storage state accurately and in real time, the overcharging of energy-storage devices can be prevented, thus improving safety. WO3 is a classical electrochromic material, but EESDs based on WO3 can suffer from low coloration efficiencies and energy densities, as well as short cycle lives. However, compositing is a promising way to improve these properties. Therefore, in this study, an electrochromic WO3 nanoblock (NB)/Preyssler-type K12.5Na1.5[NaP5W30O110]-15H2O polyoxometallate (P5W30)//Ti3C2TX MXene energy storage device was prepared by a simple hydrothermal method. The WO3NB/P5W30 film was first deposited on a conductive substrate as the cathode and subsequently modified with the MXene film as the anode. The device exhibited a high coloration efficiency (145.02 cm2/C), excellent energy density (9.8 × 10−3 mWh/cm2), long cycle life (62.5 % retention rate after 5000 galvanostatic charge–discharge cycles), and excellent chromaticity difference (ΔE*, 25.91). These properties are not only due to the unique 2D layered structure of MXene but also the greater compatibility between the cathode and the anode (as shown by the q-values). In addition, compared to a WO3NB film alone, the composite WO3NB/P5W30 film had higher areal capacitance (12-times higher) and ΔE* (11-times higher), which is attributed to the synergism between the crystalline WO3 and amorphous polyoxometallate composite. This study provides an effective method for developing high-performance EESDs with quantitative color-based charge-state visualization and long cycle lives.

Polythiophene/nitrogen-doped reduced graphene oxide nanocomposite as a hybrid supercapacitor electrode

In this study polythiophene/nitrogen-doped reduced graphene oxide (Pth/n-rGO) was synthesized by in situ chemical polymerization. The correct synthesis of Pth/n-rGO nanocomposite was checked and confirmed through different spectral, elemental and morphological analysis. The supercapacitor performance of the Pth/n-rGO was higher than those of pure Pth and n-rGO in a neutral medium containing 1 M sodium sulfate. The highest energy density, specific capacitance, and power density values of 13.1 Wh kg−1, 455 F g−1, and 279 W kg−1 were achieved for the Pth/n-rGO nanocomposite. The Pth/n-rGO electrode also revealed commendable cyclic stability which it maintained 94% of its original specific capacitance and 125% coulombic efficiency during 1500 galvanostatic charge-discharge cycles. The superior charge-storage property of Pth/n-rGO is ascribed to the double-layer/pseudocapacitance charge storage synergistic effect. By considering the results of performance and stability for the Pth/n-rGO nanocomposite in this study, it could be good candidate for development of new supercapacitors electrode material.

LiTaO3 mixing effects to suppress side reactions at the LiNi0.8Co0.1Mn0.1O2 cathode and Li5.3PS4.3Cl1.7 solid electrolyte of all-solid-state lithium batteries

Suppressing the side reactions at the solid electrolyte-electrode interface in all-solid-state battery (ASSB) is very important aspect of improving battery performance. Coating an electrochemically stable material on the surface of cathode has been used to suppress the side reactions occurring at interface between solid electrolyte and cathode. However, to achieve effective suppression, the thickness of the coating film must be thin and uniform. Moreover, an expensive ethoxide series typically must be used as a starting material. In this study, LiTaO3 coating material was simply mixed with the solid electrolyte to measure the effect of suppressing side reactions. To synthesize the solid electrolyte Li5.3PS4.3Cl1.7 and the mixing material LiTaO3, high-energy ball milling and wet milling methods were used, respectively. The structural characteristics of the prepared solid electrolytes were studied by powder X-ray diffraction. The LiTaO3 mixed solid electrolyte based ASSB showed a high discharge capacity of 177.3 mAh/g in the initial cycle, whereas the bare solid electrolyte (Li5.3PS4.3Cl1.7) based ASSB showed a discharge capacity of 159.1 mAh/g. To understand the side reactions, electrochemical impedance spectroscopy (EIS) analysis was performed after galvanostatic charge-discharge cycles. The EIS analysis confirmed that the side reaction between a solid electrolyte and a cathode was effectively suppressed in LiTaO3 mixed solid electrolyte based ASSBs.

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.

Zinc Cobalt Sulfide/Reduced Graphene Oxide Nanocomposite for High‐Performance Asymmetric Supercapacitor: A Microwave‐Assisted Synthesis

In this work, the microwave‐assisted synthesis of ZnxCo1–xS/reduced graphene oxide (rGO) nanocomposite and the evaluation of its electrochemical properties for supercapacitor (SC) application are dealt with. The synergistic effect between ZnxCo1–xS and rGO along with the conducting network provided by rGO facilitates the conducive movement of ions and enhances the electrochemical performance of the nanocomposite. The stoichiometric ratio of Zn:Co:rGO plays a crucial role in the SC behavior of the material. In three electrode systems, a material shows a high specific capacitance of 1094 F g−1 at current density 1 A g−1. The material stores charge both diffusively as well as capacitively. An asymmetric SC with acetylene black as the negative electrode and ZnxCo1–xS/rGO as the positive electrode has a stable potential window 0–1.6 V. For the fabrication of the electrodes, Ni foam is used as the current collector. The energy density and power density of the SC are found to be 32.71 and 431.95 W kg−1, respectively. The Coulombic efficiency of the SC is found to be 107% while its capacitance retention is 86% after 10 000 galvanostatic charge–discharge cycles. The energy and power density of the SC are comparatively higher than many recently reported literature. The material exhibits superior electrochemical stability and reversibility and can be a suitable electrode material for SCs.

Elevating Supercapacitor Performance of Co3O4-g-C3N4 Nanocomposites Fabricated via the Hydrothermal Method.

The hydrothermal method has been utilized to synthesize graphitic carbon nitride (g-C3N4) polymers and cobalt oxide composites effectively. The weight percentage of g-C3N4 nanoparticles influenced the electrochemical performance of the Co3O4-g-C3N4 composite. In an aqueous electrolyte, the Co3O4-g-C3N4 composite electrode, produced with 150 mg of g-C3N4 nanoparticles, revealed remarkable electrochemical performance. With an increase in the weight percentage of g-C3N4 nanoparticles, the capacitive contribution of the Co3O4-g-C3N4 composite electrode increased. The Co3O4-g-C3N4-150 mg composite electrode shows a specific capacitance of 198 F/g. The optimized electrode, activated carbon, and polyvinyl alcohol gel with potassium hydroxide were used to develop an asymmetric supercapacitor. At a current density of 5 mA/cm2, the asymmetric supercapacitor demonstrated exceptional energy storage capacity with remarkable energy density and power density. The device retained great capacity over 6k galvanostatic charge-discharge (GCD) cycles, with no rise in series resistance following cyclic stability. The columbic efficiency of the asymmetric supercapacitor was likewise high.

Pseudocapacitive Kinetics in Synergistically Coupled MoS2-Mo2N Nanowires with Enhanced Interfaces toward All-Solid-State Flexible Supercapacitors.

Pseudocapacitive kinetics in rationally engineered nanostructures can deliver higher energy and power densities simultaneously. The present report reveals a high-performance all-solid-state flexible symmetric supercapacitor (FSSC) based on MoS2-Mo2N nanowires deposited directly on stainless steel mesh (MoS2-Mo2N/SSM) employing DC reactive magnetron co-sputtering technology. The abundance of synergistically coupled interfaces and junctions between MoS2 nanosheets and Mo2N nanostructures across the nanocomposite results in greater porosity, increased ionic conductivity, and superior electrical conductivity. Consequently, the FSSC device utilizing poly(vinyl alcohol)-sodium sulfate (PVA-Na2SO4) hydrogel electrolyte renders an outstanding cell capacitance of 252.09 F·g-1 (44.12 mF·cm-2) at 0.25 mA·cm-2 and high rate performance within a wide 1.3 V window. Dunn's and b-value analysis reveals significant energy storage by surface-controlled capacitive and pseudocapacitive mechanisms. Remarkably, the symmetric device boosts tremendous energy density ∼10.36 μWh·cm-2 (59.17 Wh·kg-1), superb power density ∼6.5 mW·cm-2 (37.14 kW·kg-1), ultrastable long cyclability (∼93.7% after 10,000 galvanostatic charge-discharge cycles), and impressive mechanical flexibility at 60°, 90°, and 120° bending angles.

Superior compatibility of silicon nanowire anodes in ionic liquid electrolytes

Silicon nanowire anodes were investigated in lithium-metal cells using different electrolyte formulations based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and N -trimethyl-N -butyl-ammonium bis(fluoro sulfonyl)imide ionic liquids. The lithium insertion process in the silicon anode was analyzed by cyclic voltammetry measurements, performed at different scan rates and for prolonged cycles, combined with impedance spectroscopy analysis. A galvanostatic charge-discharge cycling test was performed to analyze the electrochemical performances using different types of ionic liquids. A study of the Solid Electrolyte Interphase layer on the silicon nanowire electrode surface was carried out through X-ray photoelectron spectroscopy. In general, the silicon anodes in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide-based electrolytes show very good reversibility, reproducibility, and efficiency in the lithiation process, even at high scan rates, and exhibit a reversible capacity exceeding 1,000 mA h g-1 after 2,000 charge-discharge cycles, corresponding to 46% of the initial value.

Synthesis and Characterization of Modified Centrifuged-Electrospun Carbon Nanofibers for High-Performance Supercapacitor Electrodes

Background: Incorporating novel multifunctional effective materials into supercapacitors electrode is an ongoing requirement for hybrid supercapacitors with enhanced electrochemical performance. Methods: Herein, modified plasma-grafted multiwalled carbon nanotubes (CMS) with improved dispersion are embedded within centrifugal-spun carbon nanofibers as a hierarchical template (CNFs-CMS) to facilitate the growth of subsequent active materials. CNFs-CMS is then electroless plated with acicular nickel (Ni) balls, followed by one-step hydrothermal co-deposition to grow Ni(OH)2-MnO2 hybrid nanosheets. Significant findingsA binder-free, 3D interconnected nanostructures of CNFs-CMS@Ni@Ni(OH)2-MnO2 electrode material is employed for an all-in-one hybrid supercapacitor that exhibits excellent electric double layer (EDLC), battery-like and pseudocapacitance (PC) properties, along with a high surface area (665 m2 g−1) and conductivity (2.96 S cm−1). The as-fabricated electrode demonstrates specific capacitance (Cs) of 1063.33 F g−1 at a high current density of 20 A g−1 in 3M KOH electrolyte, maintaining capacitance retention of 92.5 % after 10,000 galvanostatic charge-discharge cycles. An asymmetric supercapacitor pairing CNFs-CMS@Ni@Ni(OH)2-MnO2 with CNFs-CMS is established, attributes comparably high energy density (52.54 Wh kg−1) and power density (59 kW kg−1) across a potential window of 1.2 V.

One-step synthesis and fabrication of ZrMo2O8 nanostructures as advanced electrode material for energy storage applications

Nanostructures of metal molybdates show great potential as high-performance electrode materials for the forthcoming development of energy storage devices. In present work, ZrMo2O8 nanostructure was constructed using a simple chemical procedure and followed by examination with the aid of several spectral and analytical tools. The supercapacitive properties of ZrMo2O8 electrode material were investigated using Cyclic voltammetry (CV), Galvanostatic charge–discharge (GCD) and Electrochemical Impedance Spectroscopy measurements (EIS). The as-prepared ZrMo2O8 nanostructures as supercapacitor (SC) electrode material exhibited pseudocapacitive performance with notable value of 288C g−1 at 1 A/g, significant cycling stability and 92.5% capacity retention with the coulombic efficiency of 87.4% even after 5000 GCD cycles at 1 A/g. The morphological investigations indicated that the higher Specific capacity (Cs) was primarily caused by the significant increase in active sites as well as active surface area. The Bode phase angle plot of ZrMo2O8 exhibited a low frequency intercept, with emphasis at approximately −52° phase angle, indicating a superior redox signature. The results infered that ZrMo2O8 nanostructures are promising candidates for high performance energy storage applications.

Mechanically Robust and Highly Conductive Poly(ionic liquid)/Polyacrylamide Double-Network Hydrogel Electrolytes for Flexible Symmetric Supercapacitors with a Wide Operating Voltage Range.

Flexible electronic devices, such as supercapacitors (SCs), place high demands on the mechanical properties, ionic conductivity, and electrochemical stability of electrolytes. Hydrogels, which combine flexibility and the advantages of both solid and liquid electrolytes, will meet the demand. Here, we report the synthesis of novel poly(ionic liquid)/polyacrylamide double-network (DN) (PIL/PAM DN) hydrogel electrolytes containing different metal salts via a two-step γ-radiation method. The resultant Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte possesses excellent mechanical properties (tensile strength of 3.64 MPa, elongation at break of 446%) and high ionic conductivity (24.1 mS·cm-1). The corresponding flexible SC based on the Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte (SC-Li2SO4) presents improved ion diffusion, ideal electrochemical double-layer capacitor behavior, good rate capability, and excellent cyclic stability. Moreover, symmetric SC-Li2SO4 achieves a wide operating voltage range of up to 1.5 V, with a maximum energy density of 26.0 W h·kg-1 and a capacitance retention of 94.1% after 10,000 galvanostatic charge-discharge cycles, owing to the deactivation of free water molecules by the synergistic effect of PIL, PAM, and SO42-. Above all, the capacitance of SC-Li2SO4 is well-maintained after overcharge, overdischarge, short circuit, extreme temperature, compression, and bending tests, indicating its high security and flexibility. This work reveals the enormous application potential of PIL-based conductive hydrogel electrolytes for flexible electronic devices.

Electrochemical characterization and structural analysis of (In2O3)/(Fe2O3) nanocomposites for high-performance supercapacitors

This study presents a comprehensive investigation of the electrochemical characteristics and structural properties of novel nanocomposites with varying compositions of (In2O3)x/(Fe2O3)1-x, where x ranges from 1 to 0. These nanocomposites were synthesized using a versatile and cost-effective co-precipitation method. The crystallographic structure and morphology of the synthesized samples were thoroughly analyzed using Powder X-ray diffraction (PXRD) and Tunneling Electron Microscopy (TEM). Advanced analytical techniques were employed including Positron Annihilation Lifetime Spectroscopy (PALS) and Coincidence Doppler Broadening Spectroscopy (CDBS) to uncover critical insights into the structural and molecular properties of these nanocomposites. PALS analysis revealed valuable insights into the pore characteristics of the nanocomposites, while CDBS identified crucial molecular interactions within the materials. Electrochemical characterization of the nanocomposites is carried out using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical-impedance-spectroscopy (EIS) measurements. The (In2O3)0.3/(Fe2O3)0.7 nanocomposite exhibits a remarkable specific capacitance of 945 F g-1 at 1 A g-1 and exceptional rate performance, retaining 93.6% of its specific capacitance at a six-fold higher current density. Moreover, this nanocomposite electrode demonstrates outstanding cyclic stability, maintaining 92.1% of its specific capacitance even after 3000 GCD cycles at 8 A g-1. These findings suggest that the novel composition and integrated electrochemical properties of the (In2O3)0.3/(Fe2O3)0.7 nanocomposite hold great promise for enhancing the performance of next-generation electrochemical capacitors. This research contributes valuable insights into the design and development of advanced energy storage materials with applications in various high-performance energy storage devices.

Polybenzidine-MnO2 nanocomposite on anodized graphite sheet as a novel system for high-performance supercapacitors

In this work, we report for the first time the in-situ synthesis of polybenzidine‑manganese oxide (PB-MnO2) nanocomposite on anodized graphite sheet (AGS). The PB-MnO2/AGS electrode is easily fabricated through the electrochemical anodization of the graphite sheet followed by the polymerization of the benzidine monomer using KMnO4 as an oxidant and MnO2 source. The results of various instrumental analysis confirm that the PB-MnO2 nanocomposite is successfully formed on the AGS without any binder. Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques strongly prove the pseudocapacitive nature of the electrode. The PB-MnO2/AGS electrode shows a high capacitance of 950 mF cm−2 at 0.5 mA cm−2 in 1.0 M H2SO4 solution with a maximum power and energy density of 64.65 mWh cm−2 and 1.75 W cm−2. Solid-state symmetrical supercapacitor device fabricated with PB-MnO2/AGS electrode shows that this device has an excellent specific capacity of about 190.27 mF cm−2 at 0.5 mA cm−2 and maximum power and energy density of 12.375 W cm−2 and 85.625 mWh cm−2. The cyclic life of 87.22 % after 5000 GCD cycles without any ohmic drop indicates that the PB-MnO2/AGS electrode can be a promising candidate for the fabrication of high-performance supercapacitor devices in the future.

High energy density biomass-derived activated carbon materials for sustainable energy storage

Biomass-derived activated carbons are promising materials for sustainable energy storage systems such as aqueous supercapacitors and Zn-ion capacitors due to their abundance, low cost, tunable porosity, and heteroatom-rich structures. Herein, we report biomass derived carbon materials fabrication via a two-step activation method. The activated carbons possess well-tuned pore structures and high heteroatom content, resulting in remarkable surface area, ultrahigh micropore volume, and good wettability. The symmetrical supercapacitors and aqueous Zn-ion capacitors were assembled using the produced activated carbons. The 2PA-6-800 supercapacitor delivers an ultrahigh rate capability (up to 10,000 mV s−1) and promising cycle life, retaining 66.3 % of its initial performance after 33,000 galvanostatic charge–discharge cycles. The assembled 2PA-6-800-based ZIC delivers a superior specific capacitance of 785.0 F g−1, a maximum energy density of 352.5 Wh kg−1, and a remarkable power density of 60.3 kW kg−1. The outstanding performance is attributed to the two-step activation method, high heteroatom content, and the structural integrity of the biomass derived AC to the ZIC device architecture. This work contributes to the design and development of high-performance, safe, and sustainable energy storage systems.