Design Of Supercapacitors Research Articles

Enhancing quantum capacitance in BNyne/Graphene heterostructures through transition-metal dopants for high-performance supercapacitors

Using Density functional theory (DFT), we investigated the charge storage capacity, quantum capacitance (CQ), geometry and electronic structures of BNyne/graphene heterostructures (BNyneGHs), as well as the impact of transition-metal dopants on their CQ. Our results showed that doping was more effective than vacancy defects in improving the CQ of BNyneGHs. Ti-doped BNyneGHs exhibited the highest CQ value of 360.08 μF/cm2, making them ideal positive electrode materials for supercapacitors (SCs). The presence of doping agents was found to enhance the density of states (DOS) around the Fermi level, resulting in improved CQ. Our calculations identified potential cathode or anode materials for high-energy-density SCs, providing theoretical support for the design of high-capacitance SCs.

Bimetallic ions modified 2‐methylimidazolium functionalized polypyrrole/graphene oxide for the improved supercapacitor

AbstractThin films with two‐dimensional (2D) nanostructures possess good environmental stability, thinner thickness and large surface area, which are widely used as a promising modified electrode material in the field of energy storage, supercapacitors, electrochemical sensors and biosensors. Herein, unique bimetallic ions modified polypyrrole/graphene oxide (PPy/GO) nanosheets, including Co2+‐Zr4+/(2‐MeIm)x@PPy/GO and Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4), are prepared by using 2‐methylimidazolium (2‐MeIm) as the linkers between PPy/GO and metal ions. The obtained electrodes constructed by Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4) and Co2+‐Zr4+/(2‐MeIm)x@PPy/GO exhibit improved capacitor electrochemical properties due to the reversible redox reaction, the large specific surface area and the high theoretical specific capacitance value of the metal ions compared to the unmodified PPy/GO. Especially, the specific capacitance value of Co2+‐Run+/(2‐MeIm)x@PPy/GO (n = 0, 4) electrode reaches 321.78 F g−1 at a current density of 1 A g−1 and the capacitance retention rate is achieved to 100% in the long cycle charge/discharge test after 10 000 cycles (10 A g−1). It will provide a practical experience for the design and preparation of supercapacitors based on bimetallic ions modified PPy/GO.

Hierarchical Bi2O3 nanosheets and ZIF-8 derived porous nitrogen-doped carbon fibers as novel assembled nanocomposites for high-performance flexible supercapacitors

The unique design of the core–shell heterostructure is significant for obtaining electrode materials with excellent electrochemical properties. In this paper, porous carbon nanofibers (NPC@PPZ) embedded with N-doped porous carbon nanoparticles are used to construct flexible electrodes (NPC@PPZ@Bi2O3). Zeolite imidazole skeleton (ZIF)-8 and poly(methyl methacrylate) (PMMA) derived porous carbon fibers and Bi2O3 nanosheets, were utilized as the porous core and multilayer shell, respectively. The unique core and shell result in abundant pores and channels for fast ion transport and storage, high specific surface area, and additional electroactive sites. This perfect structural design enables the NPC@PPZ@Bi2O3 composite electrode to have excellent electrochemical performance. The results show that this electrode can obtain a high specific capacitance of 697 F g−1 at a current density of 1 A g−1 and a stable cycling performance at a high current density of 5 A g−1. The strategy developed in this study provides a new approach for the design and fabrication of flexible supercapacitors by electrostatic spinning combined with hierarchical porous structures.

Effects of Extreme Low Temperatures on Carbon-Based Supercapacitors

This comprehensive study delves into the effects of severe cold exposure, specifically liquid nitrogen temperatures, on the functionality of carbon-based supercapacitors. It identifies a slight reduction in capacitance, a direct consequence of the degradation of electrode materials. This degradation is linked to the glass transition in the styrene butadiene rubber binder, leading to decreased adhesion of the active materials in the electrodes. The study highlights the escalated charge transfer resistance post-exposure, pointing to a decrease in efficiency. Significantly, this research emphasizes the crucial role of binder materials in supercapacitor design for low-temperature environments, suggesting that both electrolytes and binders should be equally considered in the development of supercapacitors for harsh climates. The findings contribute valuable insights into enhancing supercapacitor resilience and performance in extreme conditions, paving the way for more robust energy storage solutions. Figure 1

New Engineering Science Insights into the Electrode Materials Pairing of Electrochemical Energy Storage Devices.

Pairing the positive and negative electrodes with their individual dynamic characteristics at a realistic cell level is essential to the practical optimal design of electrochemical energy storage devices. However, the complex relationship between the performance data measured for individual electrodes and the two-electrode cells used in practice often makes an optimal pairing experimentally challenging. Taking advantage of the developed tunable graphene-based electrodes with controllable structure, experiments with machine learning are successfully united to generate a large pool of capacitance data for graphene-based electrode materials with varied slit pore sizes, thicknesses, and charging rates and numerically pair them into different combinations for two-electrode cells. The results show that the optimal pairing parameters of positive and negative electrodes vary considerably with the operation rate of the cells and are even influenced by the thickness of inactive components. The best-performing individual electrode does not necessarily result in optimal cell-level performance. The machine learning-assisted pairing approach presents much higher efficiency compared with the traditional trial-and-error approach for the optimal design of supercapacitors. The new engineering science insights observed in this work enable the adoption of artificial intelligence techniques to efficiently translate well-developed high-performance individual electrode materials into real energy storage devices.

New insights into the role of nitrogen doping in microporous carbon on the capacitive charge storage mechanism: From ab initio to machine learning accelerated molecular dynamics

Fundamental understandings of the relationship between ion-electrode interaction and structural feature in porous carbon electrodes at a molecular level provides guidelines for the design of high-performance electric double layer supercapacitors. It is certified by experiments that porous carbon structures doped with nitrogen show enhanced capacitive performance. However, in the theoretical simulations, the fundamental charge storage mechanism is still elusive. In particular, the recent experimental result shows that the generally ignored nitrolic nitrogen (N5) in porous carbon exhibits a positive effect on capacitance, while graphitic nitrogen (N3) does the opposite, which is against with the simulation results based the 2D-modeled porous graphene structure. Here, we perform ab initio molecular dynamics simulations on the N3 and N5-doped carbon/electrolyte interfaces, including both 2D planar and 3D microporous carbon electrodes. Our calculation indicates that N3 in the 3D pore hinders the electrolyte transport, while N5-doped micropore still serves as an electrolyte transport channel through the formation of H-bond. The charge storage mechanism is further elucidated by the analysis of the well equilibrated interfaces obtained from the machine learning force field accelerated molecular dynamics. Our work provides a new insight into the effect of nitrogen doping in 3D porous carbon, which is exactly opposite to the 2D planar graphene. Therefore, we emphasize that differences in the electrochemical conditions of 2D planar and 3D microporous carbon electrodes should be fully considered when analyzing the effects of surface chemistry on charge storage mechanisms.

Machine Learning-Based Prediction of Cyclic Voltammetry Behavior of Substitution of Zinc and Cobalt in BiFeO3/Bi25FeO40 for Supercapacitor Applications.

Artificial intelligence and machine learning have become indispensable tools across various disciplines in the present century. In that way, the role of artificial intelligence and machine learning in energy storage devices was investigated. As a preliminary study, the data derived from electrochemical studies were used for the prediction. The prediction of current from cyclic voltammetry (CV) studies was undertaken for bismuth ferrite (BFO), substitution of zinc in BFO (BFZO), and substitution of cobalt in BFO composite (BFCO). CV is a vital electrochemical technique used for studying the electrochemical behavior of any material. The electrochemical study provides insights into the energy storage behavior of the material through the specific capacitance. The machine learning models, such as Artificial Neural Network (ANN), Random Forest (RF), and XGBoost (XGB), are trained and implemented to predict current at different scan rates. These models are trained and validated using the data collected from a CHI 600E electrochemical workstation. Multiple trials of experiments were performed to build the most optimum model for the material. The predicted values provide promising results and align well with the experimental data. The XGBoost, ANN and RF models perform well for the CV data set with an average testing accuracy >97%. Also, a meta-model was created using stacking of the above three machine learning models which further improved the predictive performance, achieving a slightly higher average testing accuracy of over 97.73%. The outcomes from the models can promote the development of machine learning applications in the field of electrochemistry and provide insights into optimizing supercapacitor performance and design through data-driven approaches.

The rational design of Fe2O3@MnO2 derived from Fe[Fe(CN)6]∙4H2O as negative electrode for asymmetric supercapacitor

Metal–organic frameworks (MOF)-derived nanomaterial have shown great promise as a supercapacitor anode materials. In this work, we successfully synthesized a novel Fe2O3@MnO2 composite with core–shell by hydrothermal techniques. MnO2 nanorods decorated on the Fe2O3 nanoparticles which was direct pyrolysis of Fe-PBA can combine of advantages of Fe2O3 and evenly dispersed MnO2 to obtain an ultra-wide voltage window of −1.1 V - 0.4 V and an excellent specific capacitance of 449 F g−1. The further constructed NiCo-LDH/rGO//Fe2O3@MnO2 asymmetric supercapacitor achieves a high energy density of 33.4 Wh kg−1 at a high power density of 800 W kg−1 and a capacity retention of more than 75 % after 10,000 cycle tests. This study not only corroborates the considerable potential of Fe2O3@MnO2 as anode material for supercapacitors, but also offers a novel approach to the design of asymmetric supercapacitors, which will facilitate the advancement of supercapacitor technology towards higher energy density and longer lifetime.

Morphology controlled synthesis of MnCo2S4 nanoflower structures for different metal precursors used for energy storage applications

Supercapacitors have been considered efficient energy storage devices because of their promising electrochemical charge storage capabilities. Nevertheless, an efficient electrode material is needed to fulfill the demands of current supercapacitor technology. This study examines the influence of various metal precursors (acetate (A), nitrate (N), and chloride (C)) on the morphology-dependent supercapacitor performance of MnCo2S4 (MCS) fabricated on nickel foam using an in situ hydrothermal method to obtain an optimized electrode material. The flower-like porous morphology of MCS N provides a maximum number of electrochemically active sites to the electrode material, enhancing the attainable surface area of the electrolyte upon increasing the electrochemical performance. The electrode material MnCo2S4 derived from a nitrate precursor exhibits higher specific capacity compared to MCS A and MCS C, reaching 2367C g−1 at 1 A g−1 and demonstrating 90 % cycles stability over 5000 cyclings. Likewise, an asymmetric supercapacitor (ASC) is developed by coupling activated carbon (negative electrode) with MnCo2S4 (positive electrode), yielding notable performance, such as 217 F g−1 capacitance at 1 A g−1, along with high energy and power densities of 63.3 Wh/kg and 6000 W kg−1, correspondingly. These outcomes emphasize the morphology-dependent behavior of MnCo2S4 in advancing supercapacitor design.

High-Performance Supercapacitors Based on Graphene/Activated Carbon Hybrid Electrodes Prepared via Dry Processing

Graphene has a high specific surface area and high electrical conductivity, and its addition to activated carbon electrodes should theoretically significantly improve the energy storage performance of supercapacitors. Unfortunately, such an ideal outcome is seldom verified in practical commercial supercapacitor design and production. In this paper, the oxygen-containing functional groups in graphene/activated carbon hybrids, which are prone to induce side reactions, are removed in the material synthesis stage by a special process design, and electrodes with high densities and low internal resistances are prepared by a dry process. On this basis, a carbon-coated aluminum foil collector with a full tab structure is designed and assembled with graphene/activated carbon hybrid electrodes to form a commercial supercapacitor in cylindrical configuration. The experimental tests confirmed that such supercapacitors have high capacity density, power density, low internal resistance (about 0.06 mΩ), good high-current charging/discharging characteristics, and a long lifetime, with more than 80% capacity retention after 10 W cycles.

Design of symmetric supercapacitor based on Co3O4/Carboxymethyl cellulose nanoflakes with excellent cyclic stability

An advanced electrode material having fine micro/nano-architecture that provide unique qualities like ultra-high charge storage capabilities, high specific area and efficient pathway for ion insertion will always have superior position in the energy sphere. The prime motive of the present work is to fabricate carboxymethyl cellulose (CMC) encapsulated cobalt oxide nanoflakes as pioneered electrodes for supercapacitors. Utilizing a Faradaic candidate (cobalt oxide), which traps charges abundantly that leads to attracting capacitance (381 F g−1 at a specific current of 1 A g−1) with least charge transfer resistance (0.87 Ω). Make use of CMC as host that supports the composite via providing admirable cyclic life (100 % capacitance retention even after 5000 continuous charge/discharge cycles). Un-interrupted charge delivery that probably attributed to the formation of flaky architecture of cobalt oxide which was encapsulated by carbon matrix. As the end, a symmetric supercapacitor was designed using Co3O4/C nanoflakes as both positive and negative electrode. The fabricated two cell could capable of maintaining its stability of 95.87 % from its initial value after 5000 cycles of charge and discharge at a practical current density of 20 A g−1. The outcomes of the present study (three and two cell configuration as well) will open new gateways in energy regime for next generation supercapacitors.

Organic Solvent Boosts Charge Storage and Charging Dynamics of Conductive MOF Supercapacitors.

Conductive metal-organic frameworks (c-MOFs) and ionic liquids (ILs) have emerged as auspicious combinations for high-performance supercapacitors. However, the nanoconfinement from c-MOFs and high viscosity of ILs slow down the charging process. This hindrance can, however, be resolved by adding solvent. Here, constant-potential molecular simulations are performed to scrutinize the solvent impact on charge storage and charging dynamics of MOF-IL-based supercapacitors. Conditions for >100% enhancement in capacity and ≈6 times increase in charging speed are found. These improvements are confirmed by synthesizing near-ideal c-MOFs and developing multiscale models linking molecular simulations to electrochemical measurements. Fundamentally, the findings elucidate that the solvent acts as an "ionophobic agent" to induce a substantial enhancement in charge storage, and as an "ion traffic police" to eliminate convoluted counterion and co-ion motion paths and create two distinct ion transport highways to accelerate charging dynamics. This work paves the way for the optimal design of MOF supercapacitors.

Unveiling a Novel Decomposition Pathway in Propylene Carbonate-Based Supercapacitors: Insights from a Jelly Roll Configuration Study.

This research elucidates novel insights into the electrochemical properties and degradation phenomena of propylene carbonate (PC)-based supercapacitors at a large-scale 18650 cylindrical jelly-roll cell level. Central to our findings is the identification of 2-ethyl-4-methyl-1,3-dioxolane (EMD) as a hitherto undocumented decomposition by-product, highlighting the nuanced complexity of PC electrolyte stability. We further demonstrate that elevated operational voltages precipitate accelerated electrolyte degradation, underscoring the criticality of defining the operational voltage window for maximizing device longevity. Employing advanced analytical techniques, including gas chromatography-mass spectrometry (GC-MS), this study meticulously analyzes electrolyte decomposition mechanisms. The outcomes offer pivotal insights into the operational constraints and chemical resilience of PC-based supercapacitors, contributing significantly to the optimization of supercapacitor design and application. By delineating a specific decomposition pathway, this investigation enriches the understanding of electrochemical dynamics in supercapacitor systems, providing a foundation for future research and technological advancement in energy storage devices.

Synthesis and Electrochemical Characterization of Nitrate-Doped Polypyrrole/Ag Nanowire Nanorods as Supercapacitors.

Polypyrrole (PPy)-capped silver nanowire (Ag NW) nanomaterials (core-shell rod-shaped Ag NW@PPy) were synthesized using a one-port suspension polymerization technique. The thickness of the PPy layer on the 50 nm thickness/15 μm length Ag NW was effectively controlled to 10, 40, 50, and 60 nm. Thin films cast from one-dimensional conductive Ag NW@PPy formed a three-dimensional (3D) conductive porous network structure and provided excellent electrochemical performance. The 3D Ag NW@PPy network can significantly reduce the internal resistance of the electrode and maintain structural stability. As a result, a high specific capacitance of 625 F/g at a scan rate of 1 mV/s was obtained from the 3D porous Ag NW@PPy composite film. The cycling performance over a long period exceeding 10,000 cycles was also evaluated. We expect that our core-shell-structured Ag NW@PPy composites and their 3D porous structure network films can be applied as electrochemical materials for the design and manufacturing of supercapacitors and other energy storage devices.

N-doped Bi2S3 nanoflower as an efficient supercapacitor electrode based on the highly concentrated salt electrolyte

As a low-cost and environmentally friendly new energy storage device, supercapacitors suffer from a low energy density, significantly restricting their potential applications. Hence, exploring supercapacitors with elevated energy density and wide potential windows has become a key research focus. Metal sulfides are receiving notable interest for their benefits, such as superb electrical conductivity, efficient charge storage, and cost-effectiveness. This study utilized ultrasonic methods to rapidly prepare Bi2S3 nanoflowers, followed by the synthesis of N-doped Bi2S3 through urea pyrolysis. And its supercapacitor behavior of N-doped Bi2S3 in 10 M NaNO3 electrolyte was studied. The assembled N–Bi2S3//N–Bi2S3 symmetric capacitor exhibited a high energy density of 112 Wh kg−1 when power density is 7828 W kg−1. The study provides a new scientific avenue for exploring the design of supercapacitors with high capacity and wide potential windows.

Effect of MXene Nanosheet Sticking on Supercapacitor Device Performance

Supercapacitors have garnered significant interest in recent years due to their high power density, rapid charge/discharge rates, and long cycle life. MXenes, a family of two-dimensional (2D) transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. However, one major challenge associated with incorporating MXenes in supercapacitor structures is the occurrence of sticking, wherein individual MXene flakes agglomerate, leading to reduced electrode performance. This review paper discusses various causes of sticking and approaches to preventing it, offering insights into the design and development of high-performance MXene-based supercapacitors. The morphology and size of MXene flakes, flake surface chemistry, thickness, surface area/volume ratio, electrode processing techniques (including solvent selection, additives incorporation, and deposition technology), and environmental factors were shown to be the basic factors resulting in sticking of MXene sheets. Among the strategies to mitigate this challenge, surface functionalization and passivation, integration with polymer matrices or carbon nanomaterials, and electrode processing optimization were considered. Possible paths for optimization and future directions of study, such as novel MXene compositions, understanding of interfaces and electrode–electrolyte interactions, development of advanced electrode architectures, and integration of energy storage systems, were assumed.

A Mott-Schottky analysis of mesoporous silicon in aqueous electrolyte solution by electrochemical impedance spectroscopy

Nanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. In recent years, it has been shown that filling the pores with aqueous electrolytes, in addition opens a particularly wide field for modifying and achieving active control of these functionalities, e.g., for electrochemo-mechanical actuation and tunable photonics, or for the design of on-chip supercapacitors. However, a mechanistic understanding of these new features has been hampered by the lack of a detailed characterization of the electrochemical behavior of mesoporous silicon in aqueous electrolytes. Here, the capacitive, potential-controlled charging of the electrical double layer in a mesoporous silicon electrode (pore diameter 7nm) imbibed with perchloric acid solution is studied by electrochemical impedance spectroscopy. Thorough measurements with detailed explanations of the observed phenomena lead to a comprehensive understanding of the capacitive properties of porous silicon. An analysis based on the Mott-Schottky equation enables the determination of essential parameters such as the flatband potential, the carrier concentration and the width of the space charge region. A comparison with bulk silicon shows that the flatband potential in particular is significantly altered by the introduction of nanopores, as it shifts from 1.4±0.1V to 1.9±0.2V.

Surfactant-assisted preparation of all-gel-state flexible supercapacitor with remarkable electrochemical performance based on polyaniline-polyacrylamide/sodium alginate hydrogels

The electrochemical performance of polyaniline-based all-gel-state supercapacitor (AGSSC) is significantly depended on the dispersity and mass loaded of polyaniline (PANI). In this manuscript, inspired by the properties of surfactant, sodium dodecylbenzene sulfonate (SDBS) was introduced to prepare various PANI-polyacrylamide/sodium alginate/SDBS (PANIy-PSSx) AGSSCs. With presence of SDBS, the electrochemical performance of PANIy-PSSx AGSSCs was greatly improved, displaying a trend of initial rise and then decrease with increasing concentration of SDBS from 0 to 0.75 wt%. As the content of SDBS was 0.5 wt%, the resulting PANI1.0-PSS0.5 AGSSC displayed the optimum electrochemical properties with area capacitance and energy density of 913.79 mF/cm2 and 81.23 μWh/cm2, respectively. The capacitance rate of PANI1.0-PSS0.5 AGSSC was still more than 93 % after 2000 cycles of sequential CV scans at the scan rate of 200 mV/s. These data were greatly higher than many reported PANI-based AGSSCs. Moreover, the resultant PANI1.0-PSS0.5 AGSSC could maintain high electrochemical performance even after various operations, such as compression, puncture, fluctuating temperature, bending situations and various voltage windows and series-parallel connections. The resultant PANI1.0-PSS0.5 AGSSC had the wide potentials to satisfy the real application requirements. This study offered a facile strategy for design and preparation of flexible supercapacitor with excellent electrochemical performance.

Quantum capacitance, structural, optical and electronic properties of Zr2CT2 (T = F, P, Cl, Se, Br, O, S, OH) MXenes: A DFT study

Surface functionalization with termination functional groups plays a crucial role in the design of supercapacitors and electrode materials, whereas the understanding of the relevant mechanisms is still rather limited. Here, the quantum capacitance, work function and the related electronic and optical properties of eight functionalized MXenes Zr2CT2 monolayers (with functional group T = O, F, S, Cl, Br, OH, P and Se) are comprehensively investigated, by employing the first-principle calculations. All systems except Zr2CP2 are found to exhibit good stability. Modification with oxygen functional groups makes Zr2C change from metal to semiconductors. Surface functionalization modifies the work function of the MXenes by altering the Fermi level and the associated electron transfers. Particularly, the extremely low work function of Zr2C(OH)2 may enhance its power efficiency in optoelectronic fields. Introduction of functional groups may tune the density of electronic states near the Fermi level and effectively modulate the quantum capacitance and type of electrode materials. Zr2C suitable for symmetric supercapacitors and the modified systems applicable for potential anode or cathode materials are illustrated. The types of these electrode materials would not change in a wide voltage range. Further analyses on the optical properties and Bader charge are conducted for these materials.

Exploring the potential of reduced graphene oxide/polyaniline (rGO@PANI) nanocomposites for high-performance supercapacitor application

This study introduces a facile synthesis method for synthesizing reduced graphene oxide (rGO) nanosheets with surface decoration of polyaniline (PANI). The resultant rGO@PANI nanocomposite (NC) exhibit substantial potential as advanced electrode materials for high-performance supercapacitors. The strategic integration of PANI onto the rGO surface serves dual purposes, effectively mitigating agglomeration of rGO films and augmenting their utility in supercapacitor applications. The PANI coating manifests a highly porous and nanosized morphology, fostering increased surface area and optimized mass transport by reducing diffusion kinetics. The nanosized structure of PANI contributes to the maximization of active sites, thereby bolstering the efficacy of the nanocomposites for diverse applications. The inherent conductive nature of the rGO surface significantly expedites electron transport, thereby amplifying the overall electrochemical performance of the nanocomposites. To systematically evaluate the influence of PANI concentration on the electrode performance, varying concentrations of PANI were incorporated. Notably, an elevated PANI concentration was found to enhance the response owing to the unique morphology of PANI. Remarkably, the 5 % rGO@PANI NC emerged as the most promising candidate, demonstrating exceptional response characteristics with a specific capacitance of 314.2 F/g at a current density of 1 A/g. Furthermore, this catalyst exhibits outstanding long-term stability, retaining approximately 92 % of its capacitance even after enduring 4000 cycles. This research underscores the significance of the synergistic integration of rGO and PANI in the design of high-performance supercapacitors. The elucidation of the underlying mechanisms governing the improved electrochemical properties contributes to the fundamental understanding of nanocomposite behavior, thereby paving the way for the rational design of next-generation energy storage materials.