Supercapacitor Electrode Research Articles

Neutral-state black electrochromic polymer with enhanced supercapacitor electrode performance

Neutral-state black electrochromic materials are attracting attention, especially in the applications of displays, car-rear views, sensors, and electronic papers. This study aimed to obtain a black electrochromic polymer via electrochemical techniques. For this aim, the monomer of a green-electrochromic polymer, 4-(3,3-dihexyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-7-(3,3-dihexyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-8-yl)-2-cyclohexyl-2H-benzo-[d]imidazole (PBP), was copolymerized with 3,4-ethylenedioxythiophene (EDOT) with 2:1 and 2:2 (PBP: EDOT) monomer feed ratios. The resulting copolymer films were investigated in terms of their electrochromic properties. Equal feeded copolymerization resulted in a neutral-state black electrochromic polymer (L:11.5, a:1.5, b:-2.55) with satisfying responses in the electrochromic device application (100 % electroactivity maintenance after 300 switches with 1.4 s response time). Furthermore, increasing the quantity of EDOT in the copolymer chain improved the capacitive characteristics, showing that the equal-fed copolymer is a good candidate for a supercapacitor electrode (4.07 mF/cm2). The supercapacitor device application showed that the equal feeded copolymer has superior specific capacitance retention of 97 % after 500 charge/discharge cycle, with 100 % coulombic efficiency in each cycle. Moreover, the supercapacitor is capable of lighting a 1.5 V LED for >30 s.

Molten Salt Activation Combined with In-situ Surface Graphitization towards Wood-Derived Self-Supporting Carbon Electrodes with High Volumetric Specific Capacity for Zinc-Ion Hybrid Supercapacitors

Despite significant advancements in enhancing the gravimetric and areal specific capacities of carbon electrodes for zinc-ion hybrid supercapacitors (ZHSCs), the attainment of a high volumetric specific capacity remains a pivotal challenge. This research suggests an innovative method to boost the volumetric specific capacity of carbon electrodes by constructing self-supporting carbon electrodes derived from wood. The process involves a synergistic application of molten salt activation and in-situ surface graphitization. Specifically, pine wood (Pinus sylvestris var. mongolica Litv.) undergoes initial carbonization, followed by treatment with a molten salt electrolyte, generating a carbon material distinguished by a penetrating channel structure, a rich micro-mesoporous network, and distinct characteristics such as self-support and surface graphitization. These qualities contribute to a significant increase in the volumetric specific capacity of the resultant carbon electrode, achieving up to 26.3 mAh cm–3 at 2mAcm–2, surpassing commercial activated carbon and analogous materials in ZHSC applications. Additionally, a coin-cell ZHSC utilizing this innovative carbon electrode demonstrates exceptional performance, reaching up to 5.6 mAh or 12.6F per individual ZHSC, equivalent to 12.5Fcm–3 by volume. This performance not only outperforms commercial coin-cell supercapacitors but also aligns closely with the performance metrics of certain commercial coin-cell aqueous batteries. This approach provides a viable solution for augmenting the volumetric specific capacity of carbon electrodes in ZHSCs.

Electrodeposition on laser induced graphene dual conductive substrate as a free-standing electrode for asymmetric supercapacitors

Herein, combing laser-induced graphene (LIG) obtained by laser scribing on polyethersulfone (PES) films with carbon cloth (CC) forming novel dual conductive networks can cause the well-designed electrode materials possessing strong electric conductivity in favor of electron transferring. The free-standing NiCo/L-CC@PES-IG or Fe/L-CC@PES-IG have been prepared through laser scribing and electrodeposition processes at mild conditions. Fe/L-CC@PES-IG exhibits a high areal specific capacitance of 1544 mF cm−2 at a current density of 1 mA cm−2, which matches well with NiCo/L-CC@PES-IG (1840 mF cm−2). It is worth mentioning that the capacitance retention of NiCo/L-CC@PES-IG can reach 80 % at 10 mA cm−2, ca. 16 times that of NiCo/L-CC-IG (only 5 %) just adding small amount PES, which indicate that the dual conductive network synergistic effect of the external conductive graphene and the internal CC. The asymmetric supercapacitor (ASC) device is constructed using NiCo/L-CC@PES-IG as a positive electrode and Fe/L-CC@PES-IG as a negative electrode, which delivers a high areal energy density of 381 μWh cm−2 at the areal power density of 825.8 μW cm−2. This work provides a unique insight into the design of hybrid supercapacitor assembled with matching positive and negative electrodes, which will achieve the desired superhigh performance.

Waste wood tar based porous carbon electrodes for supercapacitors with excellent performances through condensation cross-linking modification

Wood tar is an unavoidable by-product during a slow-pyrolysis process of biomass, which is usually discarded as a waste and results in environment pollution. Recently, wood tar has been used as a starting material for carbon electrodes because of its thermoplasticity and high carbon content. However, wood tar is mainly composed of various light phenolic molecules, which usually leads to a low carbonization yield after carbonization and an inferior electrochemical performance after activation. In this work, in order to improve the carbonization rate and electrochemical performance of these materials, wood tar was first condensed and crosslinked with formaldehyde and urea via a condensation reaction to produce condensed macromolecular resins, which were then carbonized at 550°C and activated with KOH at 800°C to prepare high-performance nitrogen-doped carbon electrodes for supercapacitors. The samples possess high carbonization yield, large specific surface area (3515.1 m2g-1) and moderate nitrogen content (1.11%). The high-performance carbon electrodes fabricated by this method achieves a high capacitance of 437.8Fg-1 (6M KOH electrolyte) at 1A/g-1. The assembled supercapacitor has an energy density of 13.41Whkg-1 at a power density of 124.93Wkg-1. And the capacitance retention was essentially 100% after 10000 cycles at 5Ag-1. The study presents an innovative strategy for the production of porous carbon for supercapacitors using wood tar and improves carbonization yield via condensation cross-linking modification.

Ternary metal oxide carbon composite as high-performance electrode material for supercapacitor applications

Recently, ternary metal oxides carbon composites recognized as metal organic frameworks (MOFs) have gained striking attention for supercapacitor electrode material due to high surface area, porosity, chemical stability, tunable properties, redox activity, and eco-friendly material. ZIF-67 is a novel MOF possessing these characteristics. Therefore, the present work reports the development of ternary iron-nickel–cobalt ZIF-67 composites (FeNiCo ZIF-67) using co-precipitation method with the variation in molar concentration of iron oxide, nickel oxide, and cobalt oxide. Physico-chemical characterizations of developed materials were investigated through X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) to confirm the successful formation of composites and structure, morphology. Then, the electrodes were fabricated for all three synthesized composites and electrochemical analyses such as cyclic voltammetry (CV), galvanic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed. The results revealed the porous polyhedral structure of FeNiCo ZIF-67 with different compositions consisting of interconnected nanoparticles played an important role in increasing the charge storage capacity of the material. Among the composites, FeNiCo ZIF-67 (1:2:1) electrode material achieved the highest specific capacitance of 532.7 F/g at a current density of 1 A/g. FeNiCo ZIF-67 (1:2:1) exhibited maximum electrochemical active surface area 89.12. Electrochemical impedance spectroscopy (EIS) demonstrated the minimal resistance of 7.8 Ω by FeNiCo ZIF-67 (1:2:1) composite electrode compared to the other two electrode materials. Cyclic stability study revealed the capacitance retention of 91 % after 10,000 continuous charge discharge cycles at a current density of 10 A/g. Electrode material demonstrated an outstanding electrochemical performance, and this work could provide a simple strategy to fabricate FeNiCo ZIF-67 nanostructured electrode materials for supercapacitors.

Hydrangea-like NiMn Layered Double Hydroxide Grown on Biomass-Derived Porous Carbon as a High-Performance Supercapacitor Electrode

Hydrangea-like NiMn Layered Double Hydroxide Grown on Biomass-Derived Porous Carbon as a High-Performance Supercapacitor Electrode

Electrospun Mesoporous Ni0.5Zn0.5Fe2O4 - CNT - Hollow Carbon Ternary Composite Nanofibers as High Performance Electrodes for Advanced Symmetric Supercapacitors.

Spinel ferrites have attracted considerable interest in energy storage systems due to their unique magnetic, electrical and catalytic properties. However, they suffer from poor electronic conductivity and low specific capacity. We have addressed this limitation by synthesizing composite hollow carbon nanofibers (HCNF) embedded with nanostructured Nickel Zinc Ferrite (NZF) and Multiwalled carbon nanotubes (CNT), through coaxial electrospinning. These ternary composite nanofibers NZF-CNT-HCNF have a high specific capacity of 833 C g-1 at a current density of 1 A g-1 and have a capacity retention of 90 % after 3000 cycles. Their performance is much better than pure NZF fibers (180 C g-1) or hollow carbon nanofibers (96 C g-1), suggesting synergy between various constituents of the composite. A symmetric supercapacitor fabricated from NZF-CNT-HCNF composite nanofibers (30 % NZF) has a high specific capacity of 302 C g-1 (302 A g-1) at a current density of 1 A g-1 and has a capacity retention of 95 % after 5000 cycles. At the same current density, the device has a high energy density of 39 Whkg-1 and power density of 1000 Wkg-1 at a current density of 1 A g-1. This performance can be attributed to the high specific surface area (776 m2 g-1), mesoporosity (pore size ~4 nm), interconnectedness of the nanofibers and high electrical conductivity of CNTs. These fibers can be used as light-weight high performance electrode materials in advanced energy storage devices.

Preparation by Wet-spinning and Properties Polyaniline-Polyethersulfone Fibers for Flexible Supercapacitor Electrodes

Preparation by Wet-spinning and Properties Polyaniline-Polyethersulfone Fibers for Flexible Supercapacitor Electrodes

Highly conducting Laser-Induced Graphene-Ag nanoparticle composite as an effective supercapacitor electrode with anti-fungal properties.

This study presents a simple and an environmentally friendly approach to make Laser-Induced Graphene (LIG) based supercapacitor electrodes anchored with abundant Silver Nanoparticles (AgNPs). LIG, was synthesized using a CO2 laser writing technique on polyimide substrate. The LIG-Ag composite was prepared using two techniques, drop-coating, and screen-printing. Ag nanoparticles prepared using the plant extract of Swietenia Macrophylla was utilized to drop-coat AgNP on LIG substrate. Screen-printing was done by using a commercial Ag-ink and a suitable mesh. The supercapacitor made from screen-printed electrodes and supercapacitor made form drop-coated electrodes showed a high specific capacitance of 118 mF/cm2, 38 mF/cm2, and a high energy density of 2.42 mWh/cm2, 0.05 mWh/cm2 respectively. The screen-printed composite of LIG and AgNP was further studied for its anti-fungal properties and proved to be effective against Candida sp.

Enhancing activated carbon supercapacitor electrodes using sputtered Cu-doped BiFeO3 thin films.

This work describes the fabrication of a composite supercapacitor electrode made of Cu-doped BiFeO (Cu-BFO) films on an activated carbon (AC) electrode using radio-frequency (RF) magnetron sputtering. To prevent exfoliation of Cu-BFO and AC upon immersion in an electrolyte, the nickel foam sandwiching electrode technique was introduced. The Cu-BFO films significantly enhanced electrochemical properties, increasing specific capacitance by up to 151% compared to that of an AC electrode. This was attributed to Faradaic reactions and specific surface area in the Cu-BFO/AC electrode. The highest specific capacitance achieved was 169 F at 0.5 A , and cycling stability retention was 93.12% after 500 cycles. However, the remaining percentage of the specific capacitance decreased differently with increasing thickness, which is also discussed. Furthermore, an asymmetric supercapacitor using Cu-BFO/AC and AC electrodes demonstrated a high energy density of 4.71 Wh , power density of 2.66 kW , and over 90% retention after 1000 cycles, highlighting its durability. The uniform RF magnetron sputtering deposition is vital for mass production. Combined with impressive retention in asymmetric supercapacitors, this scalability suggests a promising pathway for large-scale manufacturing. Consequently, this work could pave the way for the large-scale production of supercapacitors.

Tuning properties of binary functionalization of Sc2C MXenes for supercapacitor electrodes

Surface functionalization of two-dimensional (2D) materials like Sc2C MXenes offers a promising avenue for tailoring their properties for various applications. At the same time, significant research has focused on pure terminations involving oxygen (-O), fluorine (-F), or hydroxyl (-OH) groups. Binary surface functionalization still needs to be explored. Our work addresses this gap by investigating binary functionalized Sc2C monolayers, specifically Sc2CFN and Sc2COS. Using first-principles calculations, we explore the structural, electronic, and quantum capacitance (CQ) properties of pristine Sc2C and functionalized Sc2CFN and Sc2COS. The CQ measurements reveal distinctive electronic behaviour, with Sc2CFN and Sc2COS exhibiting indirect bandgaps of 0.90 and 1.48 eV, respectively. Introducing functional groups induces a metal-to-semiconductor transition, enhancing charge storage at the cathode and increasing the CQ to 371.64 and 341.23 μF/cm2 for Sc2CFN and Sc2COS, respectively. As far as energy applications are concerned, we also calculate the Shockley-Queisser (SQ) efficiency, which is a widely accepted quantity to get an estimate of the photovoltaic efficiency of 28.77 % for Sc2CFN and 32.97 % for Sc2COS materials. Additionally, we analyze the current-voltage (IV) characteristics, uncovering negative differential conductance (NDC) effects in Sc2COS, indicative of its potential for fast molecular switching applications. Our study provides valuable insights into the properties of binary functionalized Sc2C MXenes, paving the way for their utilization in energy storage and nanoelectronic devices.

In-Situ Preparation of Iron(II)-phthalocyanine@multi-Walled-CNTs Nanocomposite for Quasi-Solid-State Flexible Symmetric Supercapacitors with Long Cycling Life.

The construction of supercapacitor electrode materials with exceptional performance is crucial to the commercialisation of flexible supercapacitors. Here, a novel in-situ precipitation technique was applied for constructing iron(II)-phthalocyanine (FePc) based nanocomposite as the electrode material in quasi-solid-state flexible supercapacitors. The highly redox-active FePc nanostructures were grown in the multi-walled-CNTs (MWCNTs) networks, which shows convenient electron/electrolyte ion transport pathways along with outstanding structural stability, leading to high energy storage and long cycling life. The electrode of FePc@MWCNTs delivered a higher specific capacity than that of individual MWCNTs and FePc. The quasi-solid-state symmetric flexible device that was constructed using FePc@MWCNTs electrode demonstrated impressive performance with a maximum energy density of 29.7 Wh kg-1 and a maximum power density of 4000 W kg-1. Moreover, the device demonstrated superior durability and flexibility, as evidenced by its exceptional cyclic stability (111.3 %) even after 30000 cycles at 8 A g-1. These results reveal that the FePc@MWCNTs nanocomposite prepared by this simple in-situ precipitation method is promising as electrode material for next-generation flexible wearable power sources.

Role of synthetic process parameters of nano-sized cobalt/nickel oxide in controlling their structural characteristics and electrochemical energy performance as supercapacitor electrodes

The synthesis of nano-sized bimetallic Cobalt/Nickel oxides (Ni1.5Co1.5O4) with a 1:1 Co/Ni atomic ratio has been achieved using a surfactant-free co-precipitation/hydrothermal process. The growth mechanism of Cobalt/Nickel oxides Ni1.5Co1.5O4 is elucidated by tuning the synthesis process parameters, including co-precipitation pH and hydrothermal time. The formation of Cobalt/Nickel oxides Ni1.5Co1.5O4 oxide began with the nucleation of cobalt nickel hydroxide nanoplates through the co-precipitation process, followed by dissolution-recrystallization, stacked hexagonal nano-flakes, and a flower-like microstructure. The electrochemical performances of the oxides were evaluated, with the largest surface area observed at pH 9 being the main factor for the best super-capacitive performance. As hydrothermal time increased, the structural directing growth forward, resulted in the formation of a nano-flower structure with a larger surface area. The as-prepared cobalt nickel oxide exhibited a maximum specific capacitance value of 525.5 F g-1 at a current density of 1 A g-1 and energy and power densities of 88.2 WhKg-1 and 606 WKg-1, respectively.

One-Step Synthesis of NiCo-LDH@Ni(OH)2 Heterostructure Foams on Biomass-Derived Porous Carbon for High-Performance Supercapacitors.

Layered double hydroxides (LDHs) have attracted much attention as pseudocapacitor supercapacitor electrodes because of their high theoretical specific capacity. However, LDHs have drawbacks such as poor electrical conductivity, and their specific capacities are lower than the theoretical values. In this work, NNCLDH@OPC electrodes are constructed via in situ synthesis of heterostructure foams (NNCLDH) consisting of NiCo-LDH and Ni(OH)2 on pomelo peel-derived porous carbon (OPC) through a one-step solvothermal method using ZIF-67 as a template. Owing to the synergistic effect of the 3D nanofoam structure and the multicomponent heterostructure as well as the conductive porous carbon support, the NNCLDH/OPC exhibited ultrahigh electrochemical performance as well as excellent cycling stability: a specific capacity of 3290 F g-1 at 1 A g-1 and a capacitance retention of 77.8% after 4000 cycles at a current density of 10 A g-1. In addition, the assembled NNCLDH@OPC//OPC asymmetric supercapacitor (ASC) has a maximum energy density of 51Wh kg-1 with a power density of 812W kg-1 and a maximum power density of 16kW kg-1 at a current density of 20 A g-1. These results demonstrate the significant application potential of NNCLDH/OPC composites in supercapacitor electrodes.

Novel asymmetrical oxime ligand-based coordination compounds in conducting copolymer as a useful electrodes for electrochemical supercapacitors

Novel asymmetrical oxime ligand-based coordination compounds in conducting copolymer as a useful electrodes for electrochemical supercapacitors

Enhanced Electrochemical Performance of Highly Porous CeO2-Doped Zr Nanoparticles for Supercapacitor Applications.

The aim of this work was to develop an ultrasonic-assisted synthesis method for the fabrication of CeO2-doped Zr nanoparticles that would improve the performance of supercapacitor electrodes. This method, which eliminates the need for high-temperature calcination, involves embedding CeO2 into Zr nanoparticles through 1 hr (CeO2-Zr-1) and 2 hrs (CeO2-Zr-2) of ultrasonic irradiation, resulting in the formation of nanostructures with significant improvements in their electrochemical properties. Through physicochemical analysis, we observed that the CeO2-doped Zr nanoparticles, particularly those treated for 2 hrs (CeO2-Zr-2), exhibit superior crystalline phase purity, optimal chemical surface composition, minimal agglomeration with particle sizes below 50 nm, and an impressive average surface area of 178 m2/g. Compared to the 1 hr irradiation samples (CeO2-Zr-1) and undoped CeO2 nanoparticles, the (CeO2-Zr-2) electrodes demonstrated a remarkable capacitance of 198 Fg-1 at a current density of 1 A/g while maintaining ~94.9% of their capacity after 3750 cycles. This indicates not only good reversibility but also exceptional stability. In (CeO2-Zr-2) samples, the nanospherical structure achieved through ultrasonic synthesis is responsible for the enhanced capacitive behavior and stability, along with the synergistic effects caused by Zr doping, which improves the CeO2 nanoparticle conductivity to a significant extent. Surface areas of the electrodes are larger due to the combination of these two materials, which contribute to their superior performance.

Microwave assisted activation of silkworm excrement for fast adsorption of methylene blue and high performance supercapacitor

The activated carbon (AC) with an exceptionally high surface area was made of silkworm excrement (SE) by microwave-assisted KOH activation (MAKA). It was investigated for the potential applications in methylene blue (MB) adsorption and a supercapacitor electrode. The effect of activation time on the AC properties and performance was studied. The physical and chemical properties of the as-prepared samples were analyzed by FE-SEM, TEM, N2 adsorption, and Raman spectroscopy. Remarkably, the AC with the largest specific surface area (SAs) of 2530.3 m2g−1 was produced by partial carbonization of SE at 400 °C (SE400-5) and then activated for only 5 min. The large SAs is attributed to the abundance of micro-pores, leading to the enhanced MB absorption performance, as equilibrium was reached within 10 min at 25 ppm of MB concentration. The maximum MB adsorption capacity for SE400-5 was 902.56 mg g−1. The adsorption isotherms revealed that the Langmuir model best fits the empirical data (R2 ≥ 0.9813), indicating monolayer adsorption. The kinetic model fitted well to the Pseudo-second-order (PSO) (R2 ≥ 0.9691). CV, GCD, and EIS measurements also evaluated the electrochemical properties of all samples. The electrodes were made without the addition of conductive material. The SE400-5 also had the lowest total resistance and highest total effective capacitance, which resulted in its highest specific capacitance (Cs) of 322 F g−1 at 0.5 A g−1. The capacitive retention of SE400-5 remained as high as 98% even after 10,000 cycles at 10 A g−1. These results demonstrate that SE is a viable source of AC for MB adsorption and a supercapacitor electrode.Graphical abstract

A Minireview of Multimetallic Iron‐Based Oxides for Supercapacitive Negative Electrode Materials

The serious mismatch between the positive and negative electrodes of supercapacitors (SCs) makes it imperative to develop high‐performance negative electrode materials. Among them, multimetallic iron‐based oxides (MIBOs) are intensively investigated attributed to their high theoretical specific capacitance, wide operating potential window, copious electrochemical active sites, variable metal oxidation states, and abundant redox centers. This paper briefly introduces some essential information on SCs and the most common synthesis methods of MIBOs. Also, the research progress of several important MIBOs and their composites is discussed. Finally, the existing problems and challenges of MIBOs are summarized and future outlooks are likewise proposed.

High‐Performance Supercapacitor Electrodes Based on Porosity‐Controllable Carbon Paper by Centrifugal Spinning

Carbon paper is widely utilized in supercapacitors primarily for its notable attributes, including high specific surface area, commendable electrical conductivity, and excellent chemical stability. Then investigate the effect of carbon paper with different porosities as supercapacitor substrates on the electrochemical performance of electrodes. Meanwhile, tungsten oxide is grown on the surface of carbon paper using the hydrothermal method to test the electrochemical performance of the composite electrode. The prepared carbon paper and oxygen‐deficient tungsten oxide (WOx) composite electrode (CP@WOx) exhibit an area‐specific capacitance of 915.8 mF/cm² at a current density of 5 mA/cm². In addition, the electrode exhibits good cycling stability. After 20,000 cycles, the capacitance remains 104.1% of the original capacity at 50 mA/cm² current density. Solid‐state symmetric supercapacitors assembled using CP@WOx electrode exhibit excellent performance in terms of surface energy density of 6.25 µWh/cm2(at a power density of 0.6 mW/cm2) and maintain 100.4% of their original capacity after 7000 charge/discharge cycles. Relying on the higher productivity advantage of centrifugal spinning technology over electrostatic spinning technology and other preparation processes, this study develops a new way of thinking for the large‐scale production of composite electrode materials, which has more considerable potential for large‐scale development.

SiC-induced modification of MnCo2O4 nanoneedles fabricated on Ni foam for binder-free electrodes in high-performance asymmetrical supercapacitors

Supercapacitors with large energy densities are required for commercial applications. Herein, the urchin-like and hexagonal MnCo2O4/SiC composite is prepared in situ on Ni foam. The urchin-like MnCo2O4/SiC consists of nanoneedle clusters with a length of about 10 μm and a diameter of 20 nm. The MnCo2O4/SiC||AC asymmetrical supercapacitor (ASCs) shows an energy density of 90.3 Wh/kg (1.73F cm−2) at a power density of 1.25 kW/kg together with 92.1 % retention of the specific capacitance after 10,000 cycles. The results reveal excellent properties and large commercial potential.