Flexible Supercapacitor Electrodes Research Articles

Self-healable and Robust Film Based on Electroactive Polymer Brush as Electrode for Flexible Supercapacitor

Self-healable and Robust Film Based on Electroactive Polymer Brush as Electrode for Flexible Supercapacitor

Highly stable MXene/g-PPy@sulfonated cellulose composite electrodes for flexible supercapacitors

Traditional two-dimensional transition metal carbides/nitrides (MXene) have gained much academic concern due to their excellent physicochemical properties, but their susceptibility to self-stacking leads to poor cyclic stability. In this paper, an MXene-based electrode active material was successfully prepared. The generated modified PPy (g-PPy) increases the active site, increases the accessibility of ions, and can give full play to the pseudocapacitance. By the combination of modified PPy (g-PPy) nanoparticles with pseudocapacitive behavior polymerized in situ on sulfonated cellulose (SC) and MXene, not only the electrochemical performance was improved by exploiting the synergy between different electrode materials and different energy storage mechanisms, but also the MXene as a skeleton limited the volume expansion and contraction of PPy during charge/discharge cycles and the g-PPy and SC composites (g-PPy@SC) as a spacer supported the MXene layer, resulting in much higher cycle stability. Cycle stability of 98.4 % even after 10,000 cycle tests. In addition, a symmetric supercapacitor assembled from this electrode material maintains a stability of 84.4 % under 10,000 cycles at a low temperature of −40 °C. Therefore, this study provides a feasible method for the preparation of MXene-based electrodes with high cycling stability.

Regulating Functional Groups Enhances the Performance of Flexible Microporous MXene/Bacterial Cellulose Electrodes in Supercapacitors.

Ultrathin MXene-based films exhibit superior conductivity and high capacitance, showing promise as electrodes for flexible supercapacitors. This work describes a simple method to enhance the performance of MXene-based supercapacitors by expanding and stabilizing the interlayer space between MXene flakes while controlling the functional groups to improve the conductivity. Ti3C2Tx MXene flakes are treated with bacterial cellulose (BC) and NaOH to form a composite MXene/BC (A-M/BC) electrode with a microporous interlayer and high surface area (62.47 m2 g-1). Annealing the films at low temperature partially carbonizes BC, increasing the overall electrical conductivity of the films. Improvement in conductivity is also attributed to the reduction of -F, -Cl, and -OH functional groups, leaving -Na and -O functional groups on the surface. As a result, the A-M/BC electrode demonstrates a capacitance of 594 F g-1 at a current density of 1 A g-1 in 3 M H2SO4, which represents a ∼2× increase over similarly processed films without BC (309 F g-1) or pure MXene (298 F g-1). The corresponding device has an energy density of 9.63 Wh kg-1 at a power density of 250 W kg-1. BC is inexpensive and enhances the overall performance of MXene-based film electrodes in electronic devices. This method underscores the importance of functional group regulation in enhancing MXene-based materials for energy storage.

Flexible Supercapacitor Electrodes Based on Nitrogen-Doped Carbon Derived from Polyimide/Graphene

Flexible Supercapacitor Electrodes Based on Nitrogen-Doped Carbon Derived from Polyimide/Graphene

Scalable one-step synthesis of reduced graphene oxide: Towards flexible transparent conductive films and active supercapacitor electrodes

The reduced graphene oxide (rGO) thin films have attracted much attention in flexible electronic devices and supercapacitors (SCs). However, the chemical reduction mechanism of GO needs to be clarified, and the one-step process at low temperatures for preparing high-quality rGO thin films from GO dispersions is still blank in the research field. Here, we propose a one-step operation to spray GO dispersions onto substrate or current collector under a hydroiodic acid (HI) atmosphere while simultaneously achieving the preparation of rGO thin films. This pioneering metal-free, transfer-free, fast, low-temperature, environmentally friendly, and scalable spraying technology enables large-scale production of high-quality rGO. This method realizes the preparation of highly conductive and high transmittance rGO thin films on flexible polyimide and polyethylene terephthalate substrates, as well as the preparation of rGO thin films on current collectors as SCs electrodes. Density functional theory calculations show that oxygen-containing functional groups on the surface of GO exhibit a stronger adsorption energy for HI, and have a low energy barrier during reduction by HI. Ab initio molecular dynamics simulated the possible reduction reaction path between GO and HI at 90 °C, demonstrating that HI molecules can effectively reduce GO. Furthermore, the sheet resistance of the transparent conductive film created using the method developed in this study reaches approximately 1000 Ω/sq (80 % transparency), and the specific capacitance of the SCs electrode film created in this method is 433.2 F/g (5 mV/s, 1 M H2SO4). Our study not only validates the efficacy of the one-step synthesis method for rGO thin films but also provides theoretical insights into the underlying reaction mechanism. This work holds significant promise for advancing applications in various electronics by facilitating large-scale production of high-quality rGO thin films.

Binder-free laser induced graphene-MnO2 composite electrodes for high areal energy density flexible supercapacitors

The synthesis of Laser-Induced Graphene (LIG) through the laser ablation process of carbon-containing materials is a rapid and scalable process which enables the production of graphene in a cost-effective manner. In recent years, metal oxide – graphene composite electrodes have gained a lot of importance due to their use in various Energy Storage Devices (ESDs). In our investigation, we manufacture composite electrodes of manganese dioxide (MnO2) and LIG through a hydrothermal process and use it as electrodes in Flexible Supercapacitors. This method deviates from traditional procedures as it eliminates the requirement for binders in creating composite electrodes, given that MnO2 can be directly deposited onto the LIG electrodes. The assembled all-Flexible Supercapacitor (FSC), featuring unique LIG-MnO2 composite electrodes, showcased a remarkable areal capacitance of 66.5 mF cm−2 at 5 mV s−1 scan rate. The device also exhibited a very high areal energy density (2.3 mWh cm−2) and power density (19.7 mW cm−2) at 0.2 mA cm−2 current density. Also, 82 % capacitance retention was observed at the end of 2000 cycles and the device also exhibited a good flexibility during bending tests, as evidenced by an 80 % capacitance retention after 100 bending cycles.

Construction of novel coaxial electrospun polyetherimide@polyaniline core-shell fibrous membranes as free-standing flexible electrodes for supercapacitors

Designing porous and flexible electrodes with excellent electrochemical properties is crucial to fabricate high-performance flexible supercapacitors. Conductive polymer-based electrospun fibers are expected to be an ideal material for constructing flexible electrodes due to the enormous specific surface area, unique pore structure and inherent flexibility. However, the exploration of such electrospun fibers with facile preparation methods and high areal capacitance remains challenging. Herein, a novel polyetherimide@polyaniline core-shell fibrous membranes (PEI@PANI CFMs) is fabricated via simply coaxial electrospinning and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) secondary doping. With the aid of polyetherimide, highly concentrated emeraldine base polyaniline (EB-PANI) can be perfectly wrapped on the surface of fibers without any spinning assistants, ensuring the well-developed pore structures, superior hydrophilicity, good electrical conductivity and outstanding mechanical flexibility. Benefiting from the synergistic effect of structure and constituents, such flexible PEI@PANI CFMs as electrode materials can provide more accessible electrochemical active sites and decrease the ion diffusion resistance. Therefore, the PEI@PANI CFMs present outstanding areal capacitance of 1159.9 mF cm−2 and remarkable energy density of 46.91 μW h cm−2 in the electrodes and symmetric supercapacitors, demonstrating great potential for applications in flexible energy storage field. This fabrication strategy provides a simple and practicable way to manufacture polyaniline-based fibrous membranes for high-performance flexible electrode materials.

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

Ti–Cr–N Nanopyramid/Nitrogen-Doped Carbon Quantum Dot/Stainless Steel Mesh as a Flexible Supercapacitor Electrode

PPy-PdO modified MXene for flexible binder-free electrodes for asymmetric supercapacitors: Insights from experimental and DFT investigations

Binder-free, flexible electrodes of V2C MXene, V2C-PPy, and V2C-PPy-PdO (a ternary composite of vanadium carbide, polypyrrole, and palladium oxide) were fabricated using a simplified, one-step electrodeposition method. A comprehensive assessment has subsequently been conducted on the microstructural and electrochemical attributes of these electrode materials when utilized in supercapacitors with a 1 M H2SO4 electrolyte. Notably, an impressive specific capacitance of 487F g−1 is achieved for V2C-PPy-PdO ternary composite at 1 A/g. This exceptional performance is due to the considerable active surface area and inherent structural stability of the host material. These factors significantly enhanced the electrochemical reaction kinetics and cyclic reversibility. Furthermore, the V2C-PPy-PdO composite demonstrated a notable specific capacitance of 250F g−1 when integrated into an asymmetric coin cell configuration alongside activated porous carbon under a current density of 1 A/g. Remarkably, it maintained an outstanding capacitance retention of 92 % across 10,000 charge–discharge cycles. Our experimental discoveries were additionally substantiated through the Density Functional Theory calculations, which unveiled that the inclusion of PdO within the V2C-PPy-PdO composite led to an augmentation of electronic states near the Fermi level. This increase in electronic states ultimately improved the quantum capacitance, rendering the V2C-PPy-PdO composite a highly promising candidate for supercapacitor applications.

Flexible electrodes composed of flower-like MoS2 and MXene for supercapacitor applications

Flexible supercapacitors with high charge storage ability are needed for emerging applications in wearable electronics. Here, we introduce a novel flexible supercapacitor electrode by incorporating flower-like MoS2 into MXene via a hydrothermal technique. We mostly focused on the structural design for electrode configuration to enhance the charge storage mechanism. Three different electrodes composed of MoS2, MXene, and MoS2@MXene were fabricated via a versatile drop-casting and drying method. There are unique advantages of incorporating MoS2 with MXene such as the fast electron transfer, hydrophilicity of the interface, and structural stability. The MoS2@MXene // MXene flexible asymmetric supercapacitor device offered a high energy density of 1.21 W h /kg and a power density of 54.45 W /kg. Moreover, the asymmetric device exhibits nearly identical electrochemical behavior following 100 bending cycles at different angles. The high electrochemical activity of MoS2 and MXene and good interaction are ascribed to the superior electrochemical performance of the composite material. Furthermore, this research could guide the development of flexible, high-performance, and low-cost electrodes which will be useful in wearable electronics.

Nitrogen-Doped Activated Hollow Carbon Nanofibers with Controlled Hierarchical Pore Structures for High-Performance, Binder-Free, Flexible Supercapacitor Electrodes.

Carbon nanofibers (CNFs) are a fascinating electrode material for energy storage devices due to their one-dimensionality, interconnected networks, and chemical stability. However, a relatively low specific surface area of CNFs hinders their use as supercapacitor electrodes. Here, nitrogen-doped hollow CNFs with hierarchical pore structures are prepared via electrospinning of core-shell polymer nanofibers and subsequent carbonization and activation under an ammonia atmosphere. Hierarchical pore structures with micro-, meso-, and macropores are controlled by an ammonia etching effect during the carbonization of polymer nanofibers. In addition, a hollow structure in CNFs is obtained by thermal decomposition of the core polymer during the carbonization/activation. The nitrogen-doped activated hollow CNFs (ahCNFs) exhibited an exceptionally high specific surface area of 3618 m2/g with increased mesopores. Thus, a symmetric supercapacitor using ahCNFs electrodes with a 6 M KOH aqueous electrolyte provides a high specific capacitance of 208 F/g at a current density of 1 A/g, a high energy density of 7.22 W h/kg at a power density of 502 W/kg, a good rate capability, and cyclic stability. Moreover, the freestanding ahCNFs are used for flexible supercapacitor electrodes without any binder. This work demonstrates the great potential of highly porous ahCNFs for high-performance energy storage devices.

Low-cost, high-efficiency flexible supercapacitor electrodes synthesized from betel nut husk nanocellulose and polyaniline binary nanocomposite

Low-cost, high-efficiency flexible supercapacitor electrodes synthesized from betel nut husk nanocellulose and polyaniline binary nanocomposite

Self-assembled high polypyrrole loading flexible paper-based electrodes for high-performance supercapacitors

Despite the intriguing features of freestanding flexible electronic devices, such as their binder-free nature and cost-effectiveness, the limited loading capacity of active material poses a challenge to achieving practical high-performance flexible electrodes. We propose a novel approach that integrates multiple self-assembly and in-situ polymerization techniques to fabricate a high-loading paper-based flexible electrode (MXene/Polypyrrole/Paper) with exceptional areal capacitance. The approach enables polypyrrole to form a porous conductive network structure on the surface of paper fiber through MXene grafting via hydrogen bonding and electrostatic interaction, resulting in an exceptionally high polypyrrole loading of 10.0 mg/cm2 and a conductivity of 2.03 S/cm. Moreover, MXene-modified polypyrrole paper exhibits a more homogeneous pore size distribution ranging from 5 to 50 μm and an increased specific surface area of 3.11 m2/g. Additionally, we have optimized in-situ polymerization cycles for paper-based supercapacitors, resulting in a remarkable areal capacitance of 2316 mF/cm2 (at 2 mA/cm2). The capacitance retention rate and conductivity rate maintain over 90 % after undergoing 100 bends.The maximum energy density and cycling stability are characterized to be 83.6 μWh/cm2 and up to 96 % retention after 10,000 cycles. These results significantly outperform those previously reported for paper-based counterparts. Overall, our work presents a facile and versatile strategy for assembling high-loading, paper-based flexible supercapacitors network architecture that can be employed in developing large-scale energy storage devices.

Preparation of NiMoO4 porous nanosheets by freezing method as adhesive-free electrodes for high-performance flexible supercapacitors

Preparation of NiMoO4 porous nanosheets by freezing method as adhesive-free electrodes for high-performance flexible supercapacitors

Rational nanoarchitectonics of polypyrrole/graphene/polyimide composite fibrous membranes with enhanced electrochemical performance as self-supporting flexible electrodes for supercapacitors

Constructing self-supporting electrodes with the combination of excellent flexibility and superior electrochemical properties is essential to the development of high-performance supercapacitors for flexible electronics and wearable devices. Herein, a highly flexible polypyrrole/reduced graphene oxide/modified-polyimide composite fibrous membranes (PPy/RGO/M-PI CFMs) are prepared via electrostatic self-assembly of reduced graphene oxide (RGO) and in-situ deposition of polypyrrole onto SnCl2-modified polyimide electrospun fibrous membranes (M-PI FMs). M-PI FMs ensure rich pore structure and remarkable flexible properties, the electronic conductivity of the sample is greatly promoted by RGO, and polypyrrole (PPy) provide the capability of high redox pseudo capacitive charge storage for the electrode. Benefiting from the compact assembly of RGO and the uniform deposition of polypyrrole on the fiber surface of the M-PI FMs, the synthesized PPy/RGO/M-PI CFMs have a remarkable area capacitance of 1437.1 mF cm−2, a long cycle life of 84.9 % retention over 5000 cycles, and outstanding mechanical stability. And the assembled symmetric supercapacitor with PPy/RGO/M-PI CFMs deliver an exceptional area capacitance of 363.1 mF cm−2, superior energy density of 32.3 μWh cm−2 and 77.6 % capacitance retention after 5000 cycles. Therefore, this flexible and free-standing PPy/RGO/M-PI CFMs can be regarded as a promising candidate for flexible supercapacitor electrodes.

Fabrication of Polypyrrole/Reduced Graphene Oxide/Silk as a High-Performance Electrode for Fiber-Shaped Flexible Supercapacitor

Fabrication of Polypyrrole/Reduced Graphene Oxide/Silk as a High-Performance Electrode for Fiber-Shaped Flexible Supercapacitor

Binder-Free Flexible Chickpea Pod Derived Activated Carbon-Carbon Nanofiber Composite for Supercapacitor Application

In the present study, a novel carbon-carbon composite electrode was prepared by embedding activated carbon derived from chickpea pods and evaluated its potential as an electrode for supercapacitors. A simple, single-step electrospinning technique was used for the synthesis of activated carbon-carbon nanofiber composite. The synthesized activated carbon-carbon nanofiber composite electrode is flexible and binder-free with high specific surface area, micro and mesopores, interconnected fiber-to-flake morphology and possess high graphitization. Additionally, rapid electrolyte diffusion has resulted in a low charge transfer resistance due to interconnected morphology. In 6 M KOH electrolyte, composite binder-free electrode shows a specific capacitance of 147 F g−1 at 0.5 A g−1 compared to activated carbon (AC) electrodes that showed a specific capacitance of 120 F g−1 at 0.5 A g−1. It exhibits an energy density of 13 Wh k g−1 at 0.366 W k g−1 power density. It also showed impressive cyclic stability by retaining 93.5% of initial capacitance till 1200 cycles at 1 A g−1. Overall, the study presents an easy-to-use, low-cost, eco-friendly, and flexible electrode for supercapacitors that is free of binder.

In situ synergistic reduced graphene oxide-boron carbon nitride nanosheet heterostructures for high-performance fabric-based supercapacitors.

We develop a new type of heterostructure nanocomposite made of reduced graphene oxide-boron carbon nitride nanosheets (rGO-BCN) by B-C covalent bonds. The rGO-BCN nanocomposite delivers a large specific surface and excellent electrochemical properties, and is then constructed into flexible fabric-based high-performance supercapacitor electrodes based on the microfluidic electrospinning technology.

Doped Micron Silicon and Mxene Based Composite Anodes for High-Performance Li-Ion Batteries

With the world's energy needs constantly increasing, renewable energy sources must be technologically advanced and integrated with energy storage devices to ensure their uninterrupted operation. In recent decades, researchers have devoted substantial efforts to improve the energy density of lithium-ion batteries (LIBs) [1]. While graphite remains the commercial anode in LIBs, it’s very low theoretical capacity (372 mAh g-1) restricts its use in high-energy applications. Silicon (Si), owing to its high theoretical capacity of 4200 mAh g-1, natural abundance, and appropriate Li uptake potential (0.4 V vs Li/Li+), is a promising anode material [2]. However, its massive volume expansion restricts its practical use.In this study, micron-sized Si particles are combined with graphite. Micron Si is less expensive, and the synthesis process is simpler. The well-ground mixture (Si-G) is mixed with a polymer solution to generate pyrolytic carbon (upon carbonising). This aids in the buffering of mechanical stresses caused by Si volume expansion. Furthermore, direct exposure of Si to the electrolyte is avoided, stabilising the solid electrolyte interphase (SEI). The addition of a dopant improves the intrinsic conductivity of the material, resulting in increased capacity by providing electron and Li-ion transport channels. To further enhance the composite's performance, synthesized Mxene is added to promote the charge transport between micron Si. Using various techniques such as SEM-EDAX, XRD, Raman, and XPS spectroscopy, the composite's morphology and structure is studied which reveals uniformly distributed Si, C, and Mxene sheets that retain the sheet architecture.As an anode, the composite exhibits outstanding electrochemical performance which was evident by its impressive lithium storage specific capacity of 2003 mAh g-1 (based on weight of Si) even after long term cycling (at 1C rate). Additionally, the composite demonstrates superior rate performance with a specific capacity of 2439 mAh g-1 at 10 C rate, highlighting its potential for high-power applications. Moreover, the electrode displayed a low charge transfer impedance and fast electron transport, which improved the electrochemical performance. The reason for this improved performance is the unique structure consisting of Mxene and doping, which significantly increased the Li ion diffusion and the active sites. Also, low-cost micron Si is used which has a high tap density. Thus, this work provides an approach to develop high-capacity LIBs based on silicon. Keywords: Lithium-ion battery, micron silicon anode, Mxene, doping. References Liu, L. Kang, J. Hu, E. Jung, J. Zhang, S.C. Jun, Y. Yamauchi, Unlocking the Potential of Oxygen-Deficient Copper-Doped Co 3 O 4 Nanocrystals Confined in Carbon as an Advanced Electrode for Flexible Solid-State Supercapacitors, ACS Energy Lett. 6 (2021) 3011–3019. https://doi.org/10.1021/acsenergylett.1c01373.Zhou, Y. Liu, C. Du, Y. Ren, T. Mu, P. Zuo, G. Yin, Y. Ma, X. Cheng, Y. Gao, Polyaniline-encapsulated silicon on three-dimensional carbon nanotubes foam with enhanced electrochemical performance for lithium-ion batteries, Journal of Power Sources. 381 (2018) 156–163. https://doi.org/10.1016/j.jpowsour.2018.02.009.

Facile synthesis of layered reduced graphene oxide/polyaniline (rGO/PANI) composite electrode for flexible asymmetric solid-state supercapacitor

For supercapacitors, composite electrodes with a combination of reduced graphene oxide and polyaniline (rGO/PANI) have gained a lot of attention due to their synergistic effects. In this study, rGO-PANI composite thin films were deposited on a stainless steel substrate with various mass loadings by successive ionic layer adsorption and reaction (SILAR) method. The specific surface area rises from 13 m2 g−1 to 30 m2 g−1 with the introduction of rGO. Due to the composition modification and specific surface area enhancement, the specific capacitance (capacity) of 1348 F g−1 (1255C g−1) was obtained at 0.89 mg cm−2 mass deposition. Additionally, rGO/PANI/PVA-H2SO4/AC flexible asymmetric solid-state supercapacitor (ASSS) showed specific energy of 20 Wh kg−1 at specific power of 1198 W kg−1. The device maintained almost 96 % of Cs at bending angle of 160° and 75 % over 5000 cycles. This work illustrates a simple way to improve the capacity and stability of PANI via rGO composition for supercapacitor applications.