Symmetric Supercapacitor Device Research Articles

Ion‐exchange synthesis of microporous Co 3 S 4 for enhanced electrochemical energy storage

Replacing oxygen in an oxide-based material with sulfur can produce improved flexibility and more efficient electron transport in its structure leading to enhanced electrical performance. Herein, facile template-free growth of free-standing cobalt (II, III) oxide (Co3O4) on Ni foam via a mild hydrothermal technique followed by its transformation to cobalt (II, III) sulfide (Co3S4) via an ion-exchange is reported. The microstructural morphology, phase, and porosity of the prepared Co3O4 and Co3S4 are characterized by FESEM, XRD, Raman, XPS, TEM, and BET analyses. The electrochemical performance of the Co3S4 film with a microporous morphology is considerably superior to that of Co3O4, exhibiting a high specific capacitance of 1604 F g−1 (905 F g−1 for Co3O4), the excellent restorative ability of ~99% at 1 A g−1 (~96% for Co3O4), and good retention of 98% at 10 A g−1 (~70% for Co3O4). The Co3S4 electrode shows excellent capacitance endurance even after 10 000 charge/discharge cycles and a high energy density of 128.32 Wh kg−1 at 0.72 kW kg−1. A fabricated symmetric Co3S4 supercapacitor device also reveals superior charge/discharge, restorative, and retention performances compared to a Co3O4 one. The excellent supercapacitive performance of phase-transformed Co3S4 electrode is due its large electrochemically active surface area along with synergetic effect of small charge transfer resistance and high relative diffusion coefficient.

Layered nanoreactor assisted to produce B-doped and P-doped 3D carbon nanostructures for supercapacitor electrodes

In the use of the electric double layer capacitors (EDLCs) with carbon electrode materials, what remains an important technological challenge is that existing carbon electrodes suffer from low energy density and low volumetric capacitance, the today's need for making energy storage architectures. The incorporation of the n-type and/or p-type dopant elements in carbon structure may result in an enhancement in the capacitance. Accordingly, the idea to use the layered nanoreactors was applied to produce phosphorous-doped and boron-doped porous carbon nanostructures with high specific capacitance (CS) values when used in supercapacitor electrodes. So that, the best P-doped and B-doped carbon electrodes show the CS values of 322 and 275 F/g, respectively, at a current density of 1 A/g in the three-electrode system. A symmetric supercapacitor device made using the best doped carbon material (CG-P) showed a CS value of 163.2 F/g at a current density of 0.1 A/g. Herein, this work shows that the high values of CS for carbon materials are due to high accessible surface area, excellent pore size distribution, the presence and uniform dispersion of the dopant agents in carbon structures.

Unraveling the structure and electrochemical supercapacitive performance of novel tungsten bronze synthesized by facile template-free hydrothermal method

In this study, we report a facile hydrothermal method for preparing novel tungsten oxide bronze (HxWO3) and nanostructured tungsten oxide (WO3) using different structure-directing agents. The effects of phase and morphology of the hydrothermally fabricated nanostructured WO3 on the charging/discharging performance of electrochemical pseudocapacitors are thoroughly investigated. Most of the as-prepared samples exhibit WO3•0•33H2O orthorhombic structure, whereas post annealing at 350 °C promotes phase transformation to a phase-pure hexagonal structure (h-WO3). Scanning electron microscope (SEM) images show a variation of the prepared samples’ morphology between one-, two-, and three dimensions. The difference in structure between the developed bronze and the known WO3 phases is confirmed by Raman spectroscopic investigations. The optical bandgap estimated from diffuse reflectance is the highest for novel HxWO3 (2.84 eV) and h-WO3 (2.73– 2.80 eV), whereas it is lowest for the monoclinic phase (2.66 eV). X-ray photoelectron spectroscopy (XPS) analysis confirms the formation of higher amount of oxygen vacancies in h-WO3 than HxWO3. An exceptional capacitance of 1280 F/g at 1 A/g is obtained for h-WO3 when tested in 0.5-M H2SO4 aqueous electrolyte, which is superior to HxWO3. The symmetrical supercapacitor device of HxWO3 exhibits an energy density of 8 W h/kg with high stability and good capacitive retention. The number and size of the various crystallographic tunnels in the fabricated h-WO3 are found to be the primary driving forces for improving the capacitive performance and stability.

Bio-Inspired Quinone Macromolecules Grafted on O, N, S, P Codoped Carbon Paper for High Energy Density Electrochemical

Growing environmental concerns have spurred investments in intermittent renewable energies and electric vehicles. The parallel boom in portable consumer electronics has placed considerable stress on electrochemical energy storage, creating environmental and availability issues for key inorganic materials. The need to switch to bio-sourced, widely available, organic materials is confronted by the low conductivity and stability of most candidates and the difficulties of creating an efficient, metal-free current collector. In this work, we present an acidic thermal oxidative treatment utilizing carbon paper as an efficient electrode for biosourced organic molecules. Following deposition of bio-sourced materials sepia melanin and catechin (a tannin) with high specific capacitance and energy density showed very promising results for supercapacitors. Up to 228 F/g capacitance, with 100% retention after 5 000 cycles, 100% coulombic efficiency, 69.71, 81.25 W h/kg and 22.20 and 12.66 kW/kg energy and power densities for sepia melanin and catechin, respectively, were achieved for symmetric supercapacitor devices.

Superior cycle stability performance of a symmetric coin cell fabricated using KOH activated bio-char derived from agricultural waste – Cajanus cajan stems

Approximately 25 million tons of stems of Cajanus cajan are available as residue after harvesting the seeds. Currently, most of the stems are burnt or buried and do not have any major applications. The exploitation such unconventional agricultural waste to get novel bio-char and its chemical activation for efficient construction of symmetric supercapacitor device (SSD) is important from economic and conservational outlook. Herein, we demonstrate for the first-time utilization of stems of Cajanus cajan for the fabrication of SSD. Initially, the stems of Cajanus cajan were carbonized (CC) and activated using KOH at two different temperatures 700 & 800 °C (CC-1 & CC-2) in N2 atmosphere. All the carbon materials were characterized by powder X-ray diffraction (P-XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analytical techniques. CC-1 & CC-2 exhibited almost the same electrochemical performances were found to be higher than CC in the presence of 1 M KOH solution in a three-electrode system. A symmetric coin cell was fabricated using CC-2, exhibited specific capacitance (Cs), energy density (ED) & power density (PD) of 126 F/g, 30.6 Wh/kg & 1.1 kW/kg respectively. Further, the device exhibited 50,000 cycle stability at high current densities (25 & 50 A/g) with 100% coulombic efficiency. The device was able to power four red colored LEDs connected in series for up to 8 min without any change in luminescence hence showing high potential to be used for supercapacitor applications.

Rational design of active layer configuration with parallel graphene/polyaniline composite films for high-performance supercapacitor electrode

For the traditional supercapacitors based on the graphene@polyaniline (PANI) film prepared by electropolymerization, the interfacial contact between the graphene substrate and PANI shell plays a vital role in improving the PANI stability and the electrochemical capacitance of the active layer. In this work, we propose a novel strategy that the reduced graphene oxide (RGO) hydrogel film with given size could be divided into two for respective PANI electrodeposition and the two graphene@PANI films are assembled parallelly on carbon cloth to obtain the supercapacitor electrode. Owing to the additional lateral RGO/PANI interface, the resulting electrode delivers a high specific capacitance of 949 F g−1 at 1 A g−1 and 760 F g−1 even at the high current density of 20 A g−1. The corresponding binder-free symmetric supercapacitor device could attain a maximum energy density of 18.2 Wh kg−1 and a maximum power density of 4.75 kW kg−1, with a high capacitance retention of 93.1% after 10000 charge/discharge cycles. These superior properties of the electrodes based on the parallel RGO/PANI films testify the rational design of the active layer configuration for enhanced interfacial effect. This work would provide a novel pathway towards the preparation of high-performance supercapacitor electrodes.

Novel porous carbon electrode derived from hypercross-linked polymer of poly(divinylbenzene-co-vinyl benzyl chloride) for supercapacitor applications

In the present study, pores enriched high surface area of carbon electrode obtained from hypercross-linked polymer of poly(divinylbenzene-co-vinylbenzyl chloride) [P(DVB:VBC)] for supercapacitor application. First, hypercross-linking reaction was carried out in [P(DVB:VBC)] via. simple Friedel-Crafts alkylation method (HCP) followed by pyrolysis at 800 °C (HCP-800). The surface morphology of the synthesized HCP and HCP-800 materials was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) technique. HCP-800 showed a remarkable surface area of 1027 m2 g−1 with the abundance of micropores. In addition, the oxidation state of the porous carbon was assessed by x-ray photo electron spectroscopy (XPS). In a three-electrode and symmetric two-electrode configurations, electrodes exhibited a supreme specific capacitance of 272 and 145 F g−1 in aqueous electrolyte, respectively. Specific energy of 39.47 Wh kg−1 at specific power of 699.96 W kg−1 is yielded from the symmetric supercapacitor device (SSCD). Furthermore, SSCD retains more than 94% of its residual capacitance after 5000 GCD cycles at a current density of 5 A g−1 suggests a good cyclic stability.

Gelatinization assisted synthesis of multi-heteroatoms enriched 3D honeycomb-like porous carbon for high-voltage supercapacitor device

Developing high-performance supercapacitors with low-cost electrode materials that possess high power energy while maintaining high specific energy is highly desirable and remains a major challenge. Herein, we report an N, S, P-multi-heteroatom co-doped three-dimensional (3D) honeycomb-like porous carbon nanosheets from garden cress seeds via facile two-step synthesis strategy involving gelatinization accompanied by KOH activation. The large specific surface area (1302.3 m2 g−1) and hierarchical porous structure has advantages of a well-balanced 3D interconnected micro-/meso‑/ and macropores for shorter ion pathway and provide rapid electrolyte penetration. When the as-obtained doped porous carbon is used as a supercapacitor electrode, it delivered high specific capacitance of 409 F g−1 and 279 F g−1 in aqueous three and two-electrode configuration, respectively. In addition, the device shows high cyclic stability of 93% even after 10,000 cycles. More importantly, the assembled symmetric supercapacitor device using 1 M tetraethylammonium tetrafluoroborate (TEABF4) as organic electrolyte (2.8 V) delivered outstanding specific energy of 31 Wh kg−1 (6.2 Wh L−1) at a specific power of 1300 W kg−1 (260 W L−1) and retained 25 Wh kg−1 even at a high specific power of 3000 W kg−1. Notably, the high voltage fabricated supercapacitor was able to power up various light-emitting diodes of voltage range from 1.8 to 3.8 V demonstrating its potential towards powering electronic devices. The strategy to employ cost-effective renewable garden cress seeds as biomass precursors to achieve hierarchical porous multi-heteroatom doped 3D carbon is of great interest for high-performance energy storage applications.

MoS2 incorporated carbon allotropes (activated carbon, graphene, MWCNT) as electrodes in symmetric supercapacitors

Symmetric supercapacitor devices were fabricated from MoS2 incorporated carbon allotropes such as activated carbon (AC)/MoS2, graphene/MoS2 and MWCNT/MoS2. The device performance was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The electrochemical properties of the devices fabricated from carbon allotropes (activated carbon, graphene, MWCNT) were remarkably enhanced to above 50% by the incorporation MoS2 phases. Out of the three fabricated devices, electrochemical performance of AC/MoS2 as found to be superior. The specific capacitance and energy density of this device is 216 ​F/g and 6.2 ​Wh/Kg respectively with excellent higher rate capability and longer cyclic durability. The devices fabricated from graphene/MoS2 and MWCNT/MoS2 has exhibited a specific capacitance value of 202 ​F/g and 161 ​F/g with an energy density value of 5.68 ​Wh/Kg and 3.95 ​Wh/Kg respectively.

Direct growth of multilayered graphene nanofibers by chemical vapour deposition and their binder-free electrodes for symmetric supercapacitor devices

This work reports the direct growth of graphene nanofibers (GNFs) on metallic foils, namely nickel (Ni) and stainless steel (SS) and their use of direct device assembling of symmetric supercapacitor electrodes applications. GNFs were directly grown on Ni and SS through a chemical vapour deposition (CVD) technique, employing acetylene as a carbon source with 700 °C at 30 min. GNFs were grown on metallic foils with and without coating of NiNO3 catalytic layers by drop-casting method. As prepared GNFs on Ni and SS metallic foils were direct studied employing scanning electron microscope (SEM). The morphological images explored bending and curved nature forest growth of GNFs in cross-section micro-structure well growth of catalytic supports. The high-resolution morphological transmission electron microscope (TEM) results were explored highly branched multi-layers of graphene walls (d-spacing 0.34–0.48 nm) with GNFs size ranges of 100–50 nm. The micro-Raman spectrum results showed the IG/ID – 1.29 and also observed 2D-band at 2679.82 cm−1 for graphene layers for Ni-NiNO3-GNFs. The direct growth GNFs (Ni-NiNO3-GNFs) electrode was further investigated for the electrochemical supercapacitor device performance. The cyclic voltammetry (CV) results showed an ideal capacitive window (0.01–1.5 V) with impedance spectroscopy of 27.57 Ω Rct values. The direct assembled binder-free symmetric device is a new approach for supercapacitor applications with charge-discharge that Ni-NiNO3-GNFs sample has 24.66 F/g capacitance at 0.5 F/g. GNFs are in good contact with Ni and facilitate low Rct examined in impedance study. These overall results indicated well growth Ni-catalytic supports of bulk growth of graphene-like fibrous forest growth nanostructures on metallic foils. The prepared electrochemical energy storage symmetric device explored a good charge-discharge cycle as suitable for future high direct electrode applications for supercapacitor devices employing CVD techniques.

Superior energy‐power performance of N‐doped carbon nano‐onions‐based asymmetric and symmetric supercapacitor devices

Highly graphitic nitrogen-doped carbon nano-onions (N-CNO) have attracted much attention in the field of energy storage device applications. Herein, we have synthesized N-CNO by a simple flame pyrolysis method for symmetric and asymmetric (ASC) supercapacitor devices. The nitrogen doping is performed in-situ during the pyrolysis of pyrrole. The synthesized N-CNO has a high surface area of 49 m2 g−1 with 4 at% nitrogen content. The structural properties have confirmed the formation of graphitic N-CNO with highly ordered concentric graphene layers with proper lattice spacing. The fabricated symmetric and asymmetric devices have shown high specific capacitance and excellent energy-power performance. Especially, the ASC device shows a specific capacitance value 205 F g−1 with a high energy density (60 Wh kg−1) and power density (5.5 kW kg−1), leading to an increase in the power density by 260% for a mere 60% decrease in the energy density. In addition, both the novel symmetric and asymmetric devices have shown excellent capacity retention of 96% to 98% over 5000 cycles. The demonstrated results show the superior electrochemical performance of the active material, which indicates that the N-rich-CNOs can be used as a novel anode material in energy storage devices with high energy density and high power performance.

Divulging the electrochemical hydrogen storage of ternary BNP-doped carbon derived from biomass scaled to a pouch cell supercapacitor

Activated carbon materials have been studied extensively as electrode materials for supercapacitors (SCs), but their poor capacitance and energy density have hampered their growth. We present a one-step synthesis of a ternary boron-nitrogen-phosphorous-doped carbon (BNPC) from biomass hemp fibre to determine its electrochemical hydrogen storage ability using SC applications. FESEM micrographs reveal mixed morphologies like square, diamond and cylindrical-shaped nanosheets, confirming the hetero-atom doping into the carbon skeleton. The optimized BNPC electrode delivers a half-cell specific capacitance and hydrogen-storage capacity of 520 Fg-1 (1 Ag-1) and 360 mAhg−1 (10 mVs−1), respectively. To demonstrate the practicability of the as-prepared BNPC electrode, a symmetric pouch-cell supercapacitor device was assembled which exhibits a full-cell specific capacitance of 262.56 Fg-1 at 1 Ag-1 and a specific energy of ~118 Wh kg−1 at a specific power of ~5759 Wkg-1 with an operating potential window of 1.8 V and 99.7% capacitance retention over 10,000 cycles. This excellent electrochemical performance can be ascribed to the synergetic properties of fast-electrolyte-ion diffusion due to the doping of heteroatoms into the carbon matrix, high conductivity and high specific surface area and effective microporosity of BNPC (1555.5 m2g-1). Also, the chemical stability of the BNPC materials, was investigated with density functional theory (DFT)-single point calculations, where the least molecular orbital energy gap was obtained by the BNPC, which confirms its structural stability. Thus, the prepared ternary BNP-doped carbon derived from biomass has provided a new direction to enhance the electrochemical energy storage potential.

Multi-Doped Interconnected Carbon Nanospheres for High-Performance Supercapacitor

Abstract Heteroatom doping is an effective modification to improve electrochemical performance of carbon materials as electrodes in storage devices and multi-doping works better because of the synergistic effect. In this report, N/O/S multi-doped carbon nanospheres (SLS/PANI-700) are prepared from crosslinking hydrogel beads of polyaniline and sodium lignosulfonate. The addition of sodium lignosulfonate improves the electrochemical performance of PANI-based carbon significantly by changing micromorphology, building interconnected network, and offering diverse doping. SLS/PANI-700 has an ultrahigh specific surface area of 2861 m2 g−1, well-developed hierarchically porous structure, interconnected conducting carbon network, and high N and O concentration. Take these advantages, it delivers a very high capacitance of 487.7 F g−1 at 1 A g−1, and a superior rate retention with a capacitance of 373.6 F g−1 at a high current density of 20 A g−1 as electrode material. The assembled symmetric supercapacitor device exhibits a very high energy density of 43.68 Wh kg−1 at 488.98 W kg−1 and keeps 21.18 Wh kg−1 under a high power density of 8664.54 W kg−1. Based on these properties, SLS/PANI-700 possesses great promising potential as electrode material for advanced supercapacitors.

An in-situ Blowing-etching strategy for preparation of Macro-meso-micro hierarchical porous carbon and its supercapacitive property

With the development of society, there exists a great need for symmetric supercapacitors that can be charged and discharged in long cycles, which puts forward higher requirements for symmetric supercapacitor materials. Porous carbon supercapacitors have attracted much attention because of their excellent performance, yet it is still difficult to build a structure with hierarchical pore carbon. Here, we report a new idea of constructing hierarchically porous carbon materials (HPC) by an in-situ blowing-assisted high-temperature etching method, and the pore structure can be tuned to a certain extent. It has a large number of meso-microporous structure with three-dimensional macro- interconnections, which is confirmed by electron microscope and nitrogen isothermal adsorption experiments. As an electrode material for supercapacitors, the optimized HPC exhibits an outstanding rate capability of 255.5F·g−1 at a current density of 3 A·g−1 and 201.6F·g−1 at a current density of 10 A·g−1 as well as an excellent cycle stability (capacity retention of 97.5% after 5000 cycles). The excellent performance originates from the favorable pore configuration that the macro-mesopores effectively accelerate ion transport and the micropores’ interface store a large amount of charge. This work offering a new synthesis strategy and a new pore configuration prototype for the preparation of high-performance symmetric supercapacitor devices.

Binder-free graphitic films with high conductivity for supercapacitor devices

The preparation of high-conductivity graphite-based thin films from electrochemically exfoliated graphite is demonstrated as a novel and viable method to produce current collector- and binder-free electrodes. The graphite exfoliation combines the anode oxidation with the bipolar effect upon the particles in solution that permits to obtain a stable suspension containing the exfoliated material. Carbon films fabricated by aluminum etching exhibit electrical conductivity of 31,250 S m−1, while the films produced without such chemical treatment show 13,600 S m−1. The films are then applied in a symmetrical solid-state supercapacitor device using PVA-H2SO4 electrolyte, displaying energy and power density of 10.84 μWh cm−2 and 0.086 mW cm−2, respectively. By volumetric means, the device constructed with 15 μm thickness activated carbon films exhibits energy and power densities varying from 2.15 Wh L−1 and 1346 W L−1 to 4.33 Wh L−1 and 34 W L−1 as the current density decreases. Moreover, the device has an excellent cycling stability, preserving >85% of its initial capacitance after one hundred thousand cycles. The methodology for carbon film preparation can be scale-up and such performance and stability of the devices make them promising candidates in the field of electrochemical energy storage.

High-performance solid-state supercapacitor based on sustainable synthesis of meso-macro porous carbon derived from hemp fibres via CO2 activation

Most porous carbons have been prepared using KOH, ZnCl2 as activating agents via chemical activation process, where toxic chemicals, elevated temperature and multi-stage preparation are involved. Herein, we report synthesis of porous carbon from hemp fibre (HFPC) via single step, low temperature carbonization followed by CO2 physical activation for high-performance solid state supercapacitor application in a PVA-KOH hydrogel as gel electrolyte. Detailed characterization and optimization studies based on varying the duration (hours) of activation yields HFPC-30 material that comprises of interconnected carbon network of meso and macro pores with a high specific surface area of 1060 m2g−1. This enables rapid ion transfer and efficient electrode- electrolyte interaction and HFPC-30 exhibit an excellent half-cell specific capacitance of ~600 Fg−1 at 1 Ag−1. The assembled symmetric supercapacitor device with HFPC-30 delivers a full-cell specific capacitance of ~457 Fg−1 in PVA-KOH hydrogel as gel electrolyte. A maximum specific energy of 25.3 Whkg−1 at ~4320 Wkg−1 specific power is obtained, which is very high compared to other reported carbon materials. Further, the assembled supercapacitor device works until 2V delivering a capacitance retention of ~85% after 10,000 cycles. Thus, biomass derived porous carbon material in a hydrogel electrolyte presents a novel strategy for developing highly promising sustainable electrodes for high energy, solid state supercapacitor applications.

Highly efficient solid-state synthesis of Co3O4 on multiwalled carbon nanotubes for supercapacitors

Synthesizing hybrid nanostructures through green protocols continues to attract great attention since it offers atom economy, simple processing, and environmental friendliness; and avoids using harsh chemical reagents. Herein we report the assembly of cobalt oxide on nitrogen-doped multiwalled carbon nanotubes (Co3O4-NMWCNT) composite synthesized by a green protocol with mechanochemical grinding for supercapacitor applications. The structural and morphological properties of the composites were confirmed by the aid of X-ray diffraction (XRD) studies, Raman spectroscopy, and scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM). The synthesized composite material exhibited tube-like morphology with the distribution of Co3O4 nanoparticles. Fabricated Co3O4-NMWCNT symmetric supercapacitor device was further investigated for its electrochemical properties, thereby leading a high specific capacitance 202 F/g at 1 A/g of current density, with 25 Wh/kg of energy density at 0.9 kW/kg of power density. Therefore, Co3O4-NMWCNT composite electrodes offer excellent capacitive performance for the energy storage system.

Coconut Shell-Derived Activated Carbon for High-Performance Solid-State Supercapacitors

Coconut shells, low-cost and renewable agro-wastes, were used as a starting material in the synthesis of hierarchical activated carbons via hydrothermal, KOH-activation, and carbonization techniques. The ratio of KOH to hydrochar was varied in a systemic manner to study how it influences the texture and electrochemical behavior of the capacitor. Coconut shell-based carbon coated on nickel foams presented a surface area of 1567 m2 g−1, with micropores as well as mesopores widely distributed. The sample showed superior electrochemical performance, attaining 449 F g−1 at 1 A g−1 in 6 M LiNO3 aqueous solution. The solid-state symmetric supercapacitor device delivered a specific capacitance of 88 F g−1 at 1 A g−1 and a high energy density of 48.9 Whkg−1 at a power density of 1 kW kg−1. At a wide voltage window of 2.0 V, the sample was highly stable during the cycle test, showing a 92% capacitance retention at 2 A g−1 after cycling for 5000 times. The superior performance is due to the sample possessing great BET surface area, a good distribution of pores, and the usage of a suitable electrolyte. This facilitates an electrical double layer that can be deployed for applications to store energy.

Hierarchical ITO nanofibers coated Mn3O4 nanoplates core-shell nanocomposites for high performance all-solid-state symmetric supercapacitor device

We have made a first attempt to build a novel Tin doped indium oxide@Manganese oxide (ITO@Mn3O4) nanocomposite electrode to overcome the detriments of Mn3O4 such as low conductivity and small potential window. Herein, we have synthesized the ITO@Mn3O4 nanocomposite by growing Mn3O4 nanoplates over ITO nanofibers synthesized by electrospinning technique. Benefitted from, the high conductivity and negative operating potential window of ITO exceptionally increased in the electrochemical performance of ITO@Mn3O4 was observed. The specific capacitance of optimized ITO@Mn3O4 nanocomposite reached up to 823 F/g at 1 mA/cm2 in a wide potential window of 2 V using Na2SO4 electrolyte. To determine the practical feasibility an ITO@Mn3O4//ITO@Mn3O4 all-solid-state symmetric device was developed, which operated very well in a 2.2 V voltage window. It was found to deliver a maximum energy density of 88 Wh/kg and a power density of 550 W/kg. This novel composite inferred the significance of using simple design to build a high-performance device.

Exploring the Functional Properties of Sodium Phytate Doped Polyaniline Nanofibers Modified FTO Electrodes for High-Performance Binder Free Symmetric Supercapacitors

The performance of high-rate supercapacitors requires fine morphological and electrical properties of the electrode. Polyaniline (PANI), as one of the most promising materials for energy storage, shows different behaviour on different substrates. The present study reports on the surface modification of fluorine doped tin oxide (FTO) with the sodium phytate doped PANI without any binder and its utilization as a novel current collector in symmetric supercapacitor devices. The electrochemical behaviour of the sodium phytate doped PANI thin film with and without a binder on fluorine doped tin oxide (FTO) as current collector was investigated by cyclic voltammetry (CV). The electrode without a binder showed higher electrocatalytic efficiency. A symmetrical cell configuration was therefore constructed with the binder-free electrodes. The device showed excellent electrochemical performance with high specific capacities of 550 Fg−1 at 1 Ag−1 and 355 Fg−1 at 40 Ag−1 calculated from galvanostatic discharge curves. The low charge transfer and solution resistances (RCT and RS) of 7.86 Ωcm² and 3.58 × 10−1 Ωcm², respectively, and superior rate capability of 66.9% over a wide current density range of 1 Ag−1 to 40 Ag−1 and excellent cycling stability with 90% of the original capacity over 1000 charge/discharge cycles at 40 Ag−1, indicated it to be an efficient energy storage device. Moreover, the gravimetric energy and power density of the supercapacitor was remarkably high, providing 73.8 Whkg−1 at 500 Wkg−1, respectively. The gravimetric energy density remained stable as the power density increased. It even reached up to 49.4 Whkg−1 at a power density of up to 20 Wkg−1.