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Advances in Metal Chalcogenides and Metal Oxides Supercapacitors: A Comprehensive Review of Fundamental Mechanisms and Recent Progress
Abstract
The rising worldwide demand for energy storage devices has driven significant advancements in studies regarding supercapacitor (SC), particularly in the context of renewable green energy systems and electronics. SCs have come up as a critical technology, providing ultra-fast charging, long lifespan and high-power density when compared to conventional batteries. These attributes make SCs ideal for applications that needs surging energy delivery, such as electric vehicles and grid energy storage systems. Lately wide range of research has been focused on enhancing the energy density through the development of advanced evolved materials and device architectures. This review article discusses recent advancements in SC, particularly in electrode materials, such as transition metal oxides (e.g., RuO2, MnO2, V2O5) and metal chalcogenides (e.g., MoS2), which exhibit high surface area, great electrical conductivity, and mechanical stability. These materials, alongside carbon-based materials like graphene and conducting polymers, have demonstrated significant improvements in charge storage capacity and energy transfer efficiency. Hybrid materials containing metal oxides with carbon-based contents have shown great promise in enhancing both energy and power densities. The review also discusses recent trends in electrolytes, including ionic liquids, aqueous solutions, and solid-state electrolytes, which have played significant role in improving SC performance by widening the voltage window and enhancing stability. Despite these technological advancements, challenges such as cost-effective material production and scalability remain barriers to widespread commercialization. The customization of SCs into hybrid energy storage systems alongside batteries and fuel cells presents a promising avenue for future development. This review article pins down the importance of ongoing research to overcome these challenges while fully realizing the potential of SCs in the evolving energy landscape.
Fabrication of working electrode for electrochemical characterization using the successive ionic layer adsorption and reaction (SILAR) technique.
Transition metal oxides with various valence states have high specific capacitance and have attracted much attention. However, the poor cycle stability caused by material agglomeration seriously limits the play of its high activity. Herein, we create a stress dispersion structure (CuxO composite porous carbon net) by in situ lyophilization and one-step carbonization, effectively anchoring highly reactive copper oxides and highly conductive carbon networks combined with high nitrogen doping of 10.7%, to investigate their electrochemical performance in supercapacitors. Specifically, the specific capacitance of CuxO@NPC can be as high as 392 F/g (0.5 A/g) in the three-electrode system with 6 mol/L KOH as electrolyte. When applied to the two-electrode system, the cycle stability of the whole device can reach 97% after 10,000 cycles.
Present report explores microrod-shaped bimetallic cobalt iron phosphate grown through a cost-effective, single-run chemical route at 70 °C on stainless steel substrate. XRD, FTIR, TEM, and XPS analyses confirm the formation of the Co3Fe4(PO4)6 phase, wherein cobalt exhibits a +2 oxidation state, and iron adopts a +3 oxidation state. SEM analysis reveals the interlocking arrangement of micro-rods. Obtained surface architecture enhances structural integrity and establishes an efficient electrical channel for electron transfer which excels exceptional specific capacitance to 1643 F/g at a 5 mV/s scan rate (1208 F/g at 2.5 mA/cm²) with an impressive stability of 98% at 5000 CV cycles. These excellent outcomes spurred the fabrication of a symmetric supercapacitor, exhibiting 170 F/g specific capacitance at 5 mV/s with a 1.3 V potential window. In-depth analysis has been conducted to identify the origin of capacitive behavior, examining both surface and diffusion-controlled charge components. Through a practical demonstration, the constructed device effectively operated a 1 V DC fan, showcasing its promising practical applications.
One of the interesting energy technologies is a hybrid (asymmetric) device, has an exceptional power density, a
quick charging/discharging process, and outstanding cycle stability. Herein, tungsten oxide (W18O49) and its
nanocomposites with reduced graphene oxide (rGO) and cerium oxide (CeO2) were hydrothermally synthesized.
The phase stability and crystalline nature were confirmed by X-ray diffraction (XRD). Scanning electron mi�croscopy (SEM) was employed to analyze the morphological features of the synthesized materials, while
UV–visible and photoluminescence techniques were used to evaluate their optical characteristics. The rGO/
W18O49 nanocomposites exhibit an improved specific capacity of 723 C/g at 1 A/g which is better than W18O49
(519 C/g at 1 A/g) and CeO2/W18O49 (385 C/g at 1 A/g). XPS assessment confirms that the rGO increases
conductivity by lowering binding energies in W and O bondings. Due to the high specific capacity of rGO/
W18O49, the material is employed as an anode material for hybrid supercapacitors. The fabricated device depicts
an excellent energy density of 11.25 Wh/kg with 2250 W/kg power density at 3 mA/g current density. Moreover,
the fabricated device showed a remarkable rate capability of ~ 93.26 % with 88.29 % columbic efficiency.
In this research, constructed NiCo 2− x Mn x O 4 @Ni-MOF-1 hybrid arrays exhibited a C s / C of 3543.5 F g ⁻¹ /2480.4 C g ⁻¹ . Additionally, they delivered superior OER activity with an overpotential of 296 mV and a Tafel slope of 131 mV dec ⁻¹ at 10 mA cm ⁻² .
In this study, a novel method is investigated for enhancing the electrochemical performance of MOFs, particularly Ni-MOFs, which have encountered challenges in energy storage applications owing to their limited electrical conductivity and stability.
This study focuses on the growth of Cu2O/CuO nanowires by one-step thermal oxidation using a flexible copper mesh at oxidation temperatures in the range of 300 to 600 °C in a controlled atmosphere of mixed-flow Ar and O2 gases. Thermal oxidation is one of the simplest used methods to obtain nanowires on a metal surface, offering advantages such as low production costs and the ability to produce metal oxides on a large scale without the use of hazardous chemical compounds. The growth of metal oxides on a conductive substrate, forming metal/oxide structures, has proven to be an effective method for enhancing charge-transfer efficiency. The as-synthesized Cu/Cu2O/CuO (Nw) electrodes were structurally and morphologically characterized using techniques such as XRD and SEM/EDX analysis to investigate the structure modification and morphologies of the materials. The supercapacitor properties of the as-developed Cu/Cu2O/CuO (Nw) electrodes were then examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS). The CV curves show that the Cu/Cu2O/CuO (Nw) structure acts as a positive electrode, and, at a scan rate of 5 mV s ⁻¹, the highest capacitance values reached 26.158 mF cm⁻² for the electrode oxidized at a temperature of 300 °C. The assessment of the flexibility of the electrodes was performed at various bending angles, including 0°, 45°, 90°, 135°, and 180°. The GCD analysis revealed a maximum specific capacitance of 21.198 mF cm⁻² at a low power density of 0.5 mA cm⁻² for the oxidation temperature of 300 °C. The cycle life assessment of the all of the as-obtained Cu/Cu2O/CuO (Nw) electrodes over 500 cycles was performed by GCD analysis, which confirmed their electrochemical stability.
Ternary metal sulfides (TMSs) have garnered significant attention as alternative electrode materials for rechargeable metal‐ion battery anodes and electrodes for electrochemical supercapacitors (SCs). With the escalating costs of lithium, research has shifted toward alternative sources like sodium‐ion batteries (NIBs) and potassium‐ion batteries (KIBs), offering cost‐effectiveness and greater natural abundance globally. However, pursuing suitable electrode materials beyond lithium‐ion batteries (LIBs), such as NIBs, KIBs, and SCs with enhanced energy and power density, remains a formidable challenge. In this context, TMSs demonstrate remarkable reversibility as NIB, KIB, and SC electrode materials, showcasing multi‐electron redox reactions, improved electronic conductivity, and higher theoretical capacities. Numerous research articles have highlighted the promising future of TMSs as electrodes for electrochemical energy conversion and storage (EECS). Nonetheless, practical applications are hindered by limitations, including structural stability during long‐standing cyclability, electronic conductivity, and scalability. This review systematically demonstrates how varying synthesis routes can tailor nanostructures and their influence on electrochemical activity. Additionally, an in‐depth literature survey is provided on the electrochemical performances of TMSs in NIBs, KIBs, and SCs and summarize recent advancements with the best available literature. Moreover, promising prospects and challenges are highlighted, expressing optimism that TMSs will emerge as pivotal electrodes for EECS.
While MXene is widely used as an electrode material for supercapacitor, the intrinsic limitation of stacking caused by the interlayer van der Waals forces has yet to be overcome. In this work, a strategy is proposed to fabricate a composite scaffold electrode (MCN) by intercalating MXene with highly nitrogen‐doped carbon nanosheets (CN). The 2D structured CN, thermally converted and pickling from Zn‐hexamine (Zn‐HMT), serves as a spacer that effectively prevents the stacking of MXene and contributes to a hierarchically scaffolded structure, which is conducive to ion movement; meanwhile, the high nitrogen‐doping of CN tunes the electronic structure of MCN to facilitate charge transfer and providing additional pseudocapacitance. As a result, the MCN50 composite electrode achieves a high specific capacitance of 418.4 F g⁻¹ at 1 A g⁻¹. The assembled symmetric supercapacitor delivers a corresponding power density of 1658.9 W kg⁻¹ and an energy density of 30.8 Wh kg⁻¹. The all‐solid‐state zinc ion supercapacitor demonstrates a superior energy density of 68.4 Wh kg⁻¹ and a power density of 403.5 W kg⁻¹ and shows a high capacitance retention of 93% after 8000 charge‐discharge cycles. This study sheds a new light on the design and development of novel MXene‐based composite electrodes for high performance all‐solid‐state zinc ion supercapacitor.
For the sustainable growth of future generations, energy storage technologies like supercapacitors and batteries are becoming more and more common. However, reliable and high‐performance materials’ design and development is the key for the widespread adoption of batteries and supercapacitors. Quantum dots with fascinating and unusual properties are expected to revolutionize future technologies. However, while the recent discovery of quantum dots honored with a Nobel prize in Chemistry, their benefits for the tenacious problem of energy are not realized yet. In this context, herein, chemical‐composition tuning enabled exceptional performance of NiCo2O4(NCO)/graphene quantum dots (GQDs) is reported, which outperform the existing similar materials, in supercapacitors. A comprehensive study is performed on the synthesis, characterization, and electrochemical performance evaluation of highly functional NCO/GQDs in supercapacitors delivering enhanced energy efficiency. The high‐performance, functional NCO/GQDs electrode materials are synthesized by the incorporation of GQDs into NCO. The effect of variable amount of GQDs on the energy performance characteristics of NCO/GQDs in supercapacitors is studied systematically. In‐depth structural and chemical bonding analyses using X‐ray diffraction (XRD) and Raman spectroscopic studies indicate that all the NCO/GQDs composites crystallize in the spinel cubic phase of NiCo2O4 while graphene integration evident in all the NCO/GQDs. The scanning electron microscopy imaging analysis reveals homogeneously distributed spherical particles with a size distribution of 5–9 nm validating the formation of QDs. The high‐resolution transmission electron microscopy analyses reveal that the NCOQDs are anchored on graphene sheets, which provide a high surface area of 42.27 m²g⁻¹ and high mesoporosity for the composition of NCO/GQDs‐10%. In addition to establishing reliable electrical connection to graphene sheets, the NCOQDs provide reliable 3D‐conductive channels for rapid transport throughout the electrode as well as synergistic effects. Chemical‐composition tuning, and optimization yields NCO/GQDs‐10% to deliver the best specific capacitance of 3940 Fg⁻¹ at 0.5 Ag⁻¹, where the electrodes retain ≈98% capacitance after 5000 cycles. The NCO/GQD‐10%//AC asymmetric supercapacitor device demonstrates outstanding energy density and power density values of 118.04 Wh kg⁻¹ and 798.76 W kg⁻¹, respectively. The NCO/GQDs‐10%//NCO/GQDs‐10% symmetric supercapacitor device delivers excellent energy and power density of 24.30 Wh kg⁻¹ and 500 W kg⁻¹, respectively. These results demonstrate and conclude that NCO/GQDs are exceptional and prospective candidates for developing next‐generation high‐performance and sustainable energy storage devices.
Nickel‐cobalt (NiCo) phosphides (NCPs) possess high electrochemical activity, which makes them promising candidates for electrode materials in aqueous energy storage devices, such as supercapacitors and zinc (Zn) batteries. However, the actual specific capacitance and rate capability of NCPs require further improvement, which can be achieved through reasonable heterostructural design and loading conditions of active materials on substrates. Herein, novel hierarchical Bi‐NCP heterogeneous structures with built‐in electric fields consisting of bismuth (Bi) interlayers (electrodeposited on carbon cloth (CC)) are designed and fabricated to ensure the formation of uniform high‐load layered active materials for efficient charge and ion transport. The resulting CC/Bi‐NCP electrodes show a uniform, continuous, and high mass loading (>3.5 mg) with a superior capacitance reaching 1200 F g⁻¹ at 1 A g⁻¹ and 4129 mF cm⁻² at 1 mA cm⁻² combined with high‐rate capability and durable cyclic stability. Moreover, assembled hybrid supercapacitors (HSCs), supercapatteries, and alkaline Zn‐ion (AZBs) batteries constructed using these electrodes deliver high energy densities of 64.4, 81.8, and 319.1 Wh kg⁻¹, respectively. Overall, the constructed NCPs with excellent aqueous energy storage performance have the potential for the development of novel transition metal‐based heterostructure electrodes for advanced energy devices.
Graphene, the most fascinating 2D form of carbon with closely packed carbon atoms arranged in a layer, needs more attention in various fields. For its unique electrical, mechanical, and chemical properties with a large surface area, graphene has been in the limelight since its first report. Graphene has extraordinary properties, making it the most promising electrode component for applications in supercapacitors. However, the persistent re-stacking of carbon layers in graphene, caused by firm interlayer van der Waals attractions, significantly impairs the performance of supercapacitors. As a result, many strategies have been used to get around the aforementioned problems. The utilization of graphene-based nanomaterials has been implemented to surmount the aforementioned constraints and considerably enhance the performance of supercapacitors. This review highlights recent progress in graphene-based nanomaterials with metal oxide, sulfides, phosphides, nitrides, carbides, and conducting polymers, focusing on their synthetic approach, configurations, and electrochemical properties for supercapacitors. It discusses new possibilities that could increase the performance of next-generation supercapacitors.
Hybrid capacitors are emerging because of their ability to store large amounts of energy, cycle through charges quickly, and maintain stability even in harsh environments or at extreme temperatures. Hybrid capacitors with monovalent cations such as Li + , Na + , and K + have been extensively studied. However, the flammable nature of organic electrolytes and the reactive alkali metallic electrodes have raised safety concerns. This has prompted the development of novel aqueous multivalent cation storage systems, which can provide several benefits, including high capacity and energy density, rapid charge transfer, and low cost. With these advantages and the energy storage properties, multivalent cations such as Zn 2+ , Mg 2+ , Ca 2+ , and Al 3+ have been applied to multivalent-ion hybrid capacitors (MIHCs), and the latest developments and design ideas for these have been recently reviewed. However, an overview from the perspective of materials with unique advantages and experimental designs remains limited. Carbon-based nanomaterials are leading candidates for next-generation energy storage devices due to their outstanding properties in MIHCs. The use of carbon-based nanomaterials is attractive because these materials are inexpensive, scalable, safe, and non-toxic. They are also bioactive at the anode interface, allowing them to promote electrochemical reactions with redox species that would otherwise not take place. This paper reviews recent advances in MIHCs and related carbon-based materials and discusses the utilization of carbon materials in MIHCs and ideas for material design, electrochemical behavior, energy storage mechanisms, electrode design, and future research prospects. Based on the integration of related challenges and development, we aim to provide insights and commercialization reference for laboratory research. For the first time, combined with global intellectual property analysis, this paper summarizes the current main research institutions and enterprises of various hybrid capacitors, and provides important technical competition information and development trends for researchers and practitioners in the field of energy storage. Simultaneously, we provide a perspective for the development of MIHCs, a description of the existing research, and guidelines for the design, production, commercialization, and advancement of unique high-performance electrochemical energy storage devices. Broader context This paper reviews recent advances in MIHCs and related carbon-based materials, discusses the utilization of carbon materials in MIHCs and ideas for material design, electrochemical behavior, energy storage mechanisms, electrode design, and future research prospects. Based on the integration of related challenges and development, we aim to provide insights and commercialization reference for laboratory research. In addition to summarizing the research progress in energy storage technology, materials science, etc., the global commercialization of the energy storage field is also discussed. For the first time, combined with global intellectual property analysis, this paper summarizes the current main research institutions and enterprises of various hybrid capacitors, and provides important technical competition information and development trends for researchers and practitioners in the field of energy storage. Simultaneously, we provide a perspective for the development of MIHCs, a description of the existing research, and guidelines for the design, production, commercialization, and advancement of unique high-performance electrochemical energy storage devices.
While occasionally being able to charge and discharge more quickly than batteries, carbon‐based electrochemical supercapacitors (SCs) are nevertheless limited by their simplicity of processing, adjustable porosity, and lack of electrocatalytic active sites for a range of redox reactions. Even SCs based on the most stable form of carbon (sp³ carbon/diamond) have a poor energy density and inadequate capacitance retention during long charge/discharge cycles, limiting their practical applications. To construct a SC with improved cycling stability/energy density Mn‐ion implanted (high‐dose; 10¹⁵–10¹⁷ ions cm⁻²) boron doped diamond (Mn‐BDD) films have been prepared. Mn ion implantation and post‐annealing process results in an in situ graphitization (sp² phase) and growth of MnO2 phase with roundish granular grains on the BDD film, which is favorable for ion transport. The dual advantage of both sp² (graphitic phase) and sp³ (diamond phase) carbons with an additional pseudocapacitor (MnO2) component provides a unique and critical function in achieving high‐energy SC performance. The capacitance of Mn‐BDD electrode in a redox active aqueous electrolyte (0.05 M Fe(CN)63‐/4− + 1 M Na2SO4) is as high as 51 mF cm⁻² at 10 mV s⁻¹ with exceptional cyclic stability (≈100% capacitance even after 10 000 charge/discharge cycles) placing it among the best‐performing SCs. Furthermore, the ultrahigh capacitance retention (≈80% retention after 88 000 charge/discharge cycles) in a gel electrolyte containing a two‐electrode configuration shows a promising prospect for high‐rate electrochemical capacitive energy storage applications.
MXenes, a two-dimensional transition metal carbide, nitride, and carbonitride family, have received a lot of interest in recent years due to their unique properties and diverse applications. This review presents a comprehensive analysis of the applications and electrochemical characteristics of MXenes, providing a nuanced viewpoint on their potential impact in various fields. MXenes have a large surface area, high electrical conductivity , and variable surface chemistry, making them appealing candidates for energy storage, catalysis, sensing, and electronic device applications. The electrochemical characteristics of MXenes are fully investigated, including charge storage capacity and ion diffusion kinetics, highlighting their usefulness for supercapacitors, lithium-ion batteries, and other energy storage devices. Furthermore, this study digs into the interactions of MXenes with various electrolytes, offering insight into the obstacles and potential related to their practical application. The review also discusses the strategies employed to modify MXene properties and enhance their performance in surface chemistries across various energy storage devices and bio/sensor and clarify the correlations between their electrochemical properties and the required functions. Ultimately, this work provides a comprehensive outlook on the current state of MXene research, emphasizing the potentially transformative role of these materials in advancing technology across various domains.
Electrodes and electrolytes have a significant impact on the performance of supercapacitors. Electrodes are responsible for various energy storage mechanisms in supercapacitors, while electrolytes are crucial for defining energy density, power density, cyclic stability, and efficiency of devices. Various electrolytes, from aqueous to ionic liquid, have been studied and implemented as potential electrolytes for supercapacitors. The ionic size, conductivity, mobility, diffusion coefficient, and viscosity of electrolytes affect the device’s capacitance. Electrode type and its interaction with electrolytes are other factors to consider when choosing an electrolyte for a supercapacitor. In this review, an attempt has been made to provide a comprehensive and straightforward overview of the numerous electrolytes widely used for supercapacitor study and how these electrolytes interact with the electrodes to improve the performance of the supercapacitors.
The flexible energy storage device of high demand in wearable and portable electronics. Flexible supercapacitors have benefits over flexible batteries, and their development relies on the use of flexible components. Gel polymer electrolytes have the merits of liquid and solid electrolytes and are used in flexible devices. In this study, a gel derived from chia seed was used as a flexible electrolyte material, and its rheological, thermal, and electrochemical properties were investigated. High thermal stability and shear thinning behavior were observed via the electrolyte state of the chia mucilage gel. Compared to the conventional salt electrolyte, the chia mucilage gel electrolyte-based supercapacitor exhibited a more rectangular cyclic voltammetry (CV) curve, longer discharging time in galvanostatic charge–discharge (GCD) analysis, and low charge transfer resistance in electrochemical impedance spectroscopy (EIS). The maximum specific capacitance of 7.77 F g⁻¹ and power density of 287.7 W kg⁻¹ were measured, and stable capacitance retention of 94% was achieved after 10,000 cycles of charge/discharge with harsh input conditions. The biodegradability was also confirmed by the degraded mucilage film in soil after 30 days. The plant-driven chia mucilage gel electrolyte can facilitate the realization of flexible supercapacitors for the energy storage devices of the future.
The design of supercapacitor materials with both high mass loading and high areal capacity is a major strategy to overcome relatively low energy density of supercapacitors. Herein, NiCo‐layered double hydroxide (NiCo‐LDH)/NiCoOOH composite films with both ultrahigh mass loading and high areal capacity are prepared by a two‐step cyclic voltammetry method. The films consist of NiCo‐LDH/NiCoOOH microspheres assembled with ultrafine nanosheets with highly ordered pore distribution from macropores to micropores and abundant defect active sites, which are conducive to the transport of electrolyte ions, increasing the reaction kinetics, and greatly improving the utilization of active material. The optimal film with hierarchical microstructure featuring an ultrahigh mass loading of 80 mg cm ⁻² not only exhibits a state‐of‐the‐art high areal capacity of 14.7 mAh cm ⁻² , but also shows a record‐high energy density of 10.7 mWh cm ⁻² , as well as presents remarkable mechanical stabilityand superior capacity retention of 99% after 20000 galvanostatic charge‐discharge cycles. Moreover, by combining the experimental analysis and theoretical calculations, the mechanism of preferential conversion of the NiCo‐LDH in the subtle defect region to NiCoOOH by electrochemistry and the synergistic effect in electrochemical energy storage of the NiCo‐LDH and NiCoOOH phases is proposed.
Exploring anode materials with an excellent electrochemical performance is of great significance for supercapacitor applications. In this work, a N-doped-carbon-nanofiber (NCNF)-supported Fe3C/Fe2O3 nanoparticle (NCFCO) composite was synthesized via the facile carbonizing and subsequent annealing of electrospinning nanofibers containing an Fe source. In the hybrid structure, the porous carbon nanofibers used as a substrate could provide fast electron and ion transport for the Faradic reactions of Fe3C/Fe2O3 during charge–discharge cycling. The as-obtained NCFCO yields a high specific capacitance of 590.1 F g⁻¹ at 2 A g⁻¹, superior to that of NCNF-supported Fe3C nanoparticles (NCFC, 261.7 F g⁻¹), and NCNFs/Fe2O3 (NCFO, 398.3 F g⁻¹). The asymmetric supercapacitor, which was assembled using the NCFCO anode and activated carbon cathode, delivered a large energy density of 14.2 Wh kg⁻¹ at 800 W kg⁻¹. Additionally, it demonstrated an impressive capacitance retention of 96.7%, even after 10,000 cycles. The superior electrochemical performance can be ascribed to the synergistic contributions of NCNF and Fe3C/Fe2O3.
Metal–organic frameworks (MOFs)-derived metallic oxide compounds exhibit a tunable structure and intriguing activity and have received intensive investigation in recent years. Herein, this work reports metal–organic frameworks (MOFs)-derived cobalt oxide/carbon nanotubes (MWCNTx@Co3O4) composites by calcining the MWCNTx@ZIF-67 precursor in one step. The morphology and structure of the composite were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization. The compositions and valence states of the compounds were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Benefiting from the structurally stable MOFs-derived porous cobalt oxide frameworks and the homogeneous conductive carbon nanotubes, the synthesized MWCNTx@Co3O4 composites display a maximum specific capacitance of 206.89 F·g⁻¹ at 1.0 A·g⁻¹. In addition, the specific capacitance of the MWCNT3@Co3O4//activated carbon (AC) asymmetric capacitor reaches 50 F·g⁻¹, and has an excellent electrochemical performance. These results suggest that the MWCNTx@Co3O4 composites can be a potential candidate for electrochemical energy storage devices.
The sluggish ionic transport in thick electrodes and freezing electrolytes has limited electrochemical energy storage devices in lots of harsh environments for practical applications. Here, a 3D‐printed proton pseudocapacitor based on high‐mass loading 3D‐printed WO3 anodes, Prussian blue analogue cathodes, and anti‐freezing electrolytes is developed, which can achieve state‐of‐the‐art electrochemical performance at low temperature. Benefiting from the cross‐scale 3D electrode structure using a 3D printing direct ink writing technique, the 3D‐printed cathode realizes an ultrahigh areal capacitance of 7.39 F cm−2 at a high areal mass loading of 23.51 mg cm−2. Moreover, the 3D‐printed pseudocapacitor delivers an areal capacitance of 3.44 F cm–2 and excellent areal energy density (1.08 mWh cm–2). Owing to the fast ion kinetics in 3D electrodes and the high ionic conductivity of hybrid electrolyte, the 3D‐printed supercapacitor delivers 61.04% of the room‐temperature capacitance even at −60°C. This work provides an effective strategy for the practical applications of energy storage devices with complex physical structure at extreme temperatures. This article is protected by copyright. All rights reserved
Bifunctional devices combining display and energy storage capabilities are crucial for next-generation optoelectronic technology. This study investigates the application of nickel oxide (NiO) thin films for bifunctional electrochromic energy storage systems. The amorphous Ni(OH)2 thin films were electrodeposited with a focus on their time-dependent properties. The Scharifker-Hills model revealed a mixed nucleation process during the electrodeposition. The deposited thin films were examined for their physicochemical properties using X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron Spectroscopy (XPS), and morphological studies. Rietveld refinement of the XRD pattern confirmed a cubic NiO polycrystalline phase, while XPS identified Ni3+ as the dominant oxidation state. Significant morphological changes were observed with the varying deposition time. The NiO electrode deposited for 120 minutes exhibited optimal characteristics, including the highest areal capacitance of 161.77 mF/cm2, along with excellent cyclic stability of 96.5% even after 2000 CV cycles. The electrochromic study demonstrated optical modulation ranging within 55-82% at 532 nm, with a maximum coloration efficiency of 86.90 cm2/C. This research demonstrates the viability of NiO thin films as bifunctional electrochromic energy storage systems and the advancement of optoelectronic devices that integrate display and energy storage functionalities.
Exploring non-toxic, multiple oxidation state iron phosphate (Co 3 Fe 4 (PO 4 ) 6 ) anchored MWCNTs with blossomed micro platelets surface architecture as a supercapacitive electrode and design of a large-scale (10 × 4 cm ² ) symmetric device powering a DC fan.
Energy storage materials have been receiving attention during the past two decades. Supercapacitors, in specific, have emerged as promising energy storage devices, especially for flexible electronics. The development of supercapacitor materials is crucial to advance their performance and multifunctionality. Supercapacitors have been shown to possess higher energy densities than conventional capacitors and higher power densities than batteries. Advancements in electrochemical supercapacitor cells are heavily sought after. This review showed that the progress made in supercapacitors’ materials led to the development of novel electrode materials, heat-resistant separators, flexible supercapacitors, and highly conductive electrolytic solutions. Therefore, supercapacitors' electrochemical performance, power density, charge storage density, specific capacitance, and charge/discharge rates were eventually enhanced. Moreover, research is being conducted to operate supercapacitors in soft electronics by improving their solid-state flexibility. This paper also provided a comprehensive overview of the recent developments in high-temperature capacitive energy storage, the various applications of supercapacitor cells in the industry, supercapacitors design, as well as the challenges involved. This work concluded that the biggest challenge of producing supercapacitors is manufacturing them at a low cost to make them economically viable energy storage options.
MXenes, a new category of 2D nanomaterials, have garnered interdisciplinary attention since groundbreaking work on Ti3C2Tx in 2011. The distinctive properties of MXene, including its high electrical conductivity, excellent anisotropic carrier mobility, and rich surface functionalities with tunable electronic structure, make it suitable for sensing applications. This review provides an overview of the recent advancements in the use of MXenes in chemiresistive gas sensors. The discussion begins with exploring the diverse range of MXene structures and compositions, along with contemporary developments in their synthesis methodologies. Following this, it elucidates the gas sensing parameters, principles, and techniques for fabricating sensing films using MXene-based materials. Subsequently, this review explores multiple strategies to comprehensively understand and systematically advance MXene through surface and heterointerface engineering. It highlights several surface engineering strategies for MXene, encompassing the tailoring of surface terminations, introduction of active sites, surface functionalization, intercalation of MXene with metal ions or organic molecules, surface oxidation, and heteroatom doping. Furthermore, it delves into heterointerface engineering strategies involving composites of noble metals, metal oxides (MOs), graphene, transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), and polymers to enhance the gas-sensing capabilities of MXene. The engineering of MXene-based materials facilitates synergistic effects and complementary advantages, introduces catalytic sites, constructs heterojunctions, promotes charge transfer, improves carrier transport, and/or introduces protective/sieving/enrichment layers. These collective improvements effectively enhance the gas sensors' sensitivity, selectivity, and stability. Finally, this review underscores ongoing challenges and prospects for the future advancement of MXene-based gas sensors.
A growing family of two-dimensional materials have become exotic candidates for the development of electrodes for the applications of energy storage and conversion due to their excellent unique properties. The ongoing technological advancement emphasizes creating cost-effective, sustainable two-dimensional materials. These materials, with high density and unstable bonds, undergo restructuring for reduced surface energy. MXenes and graphene are two important two-dimensional layered materials that have grabbed the attention for the development of many applications. Due to unique properties such as electron confinement in a plane, increase in surface-to-volume ratio and removal of van-der waals interaction, two-dimensional materials play an important role in comparison with bulk materials. MXenes and graphene have exceptional conducting properties due to their nano-sheet-like structures. MXenes are mainly obtained after the exfoliation of different transition metals whereas graphene is a tightly bound hexagonal structure of carbon atoms. These materials have limitless extraordinary applications in the field of transistors, sensors, battery electrodes, supercapacitors, and photo-detectors. The objective of this work is to provide a comprehensive review of different synthesis approaches, structures, properties, ion intercalation and applications of MXenes and graphene towards energy storage and conversion. This review provides a broad and comparative analysis of MXenes and graphene and it will be extensively helpful to understand the basic properties and their usage as energy storage and conversion materials. The outcome of this review will function as a repository, enabling the expansion of research and development within the realm of energy storage and conversion applications.
The redox additive in an aqueous gel electrolyte is reported as one of the efficient methods to improve the electrochemical supercapacitor performance. Here, we report the role of redox additive, potassium ferricyanide((K3[Fe(CN)6]), referred to as KFCN) for improving the electrochemical performance of binder-free, CuCo2O4 (CCO) nanowire arrays (NWs) based solid state symmetric supercapacitors (SSCs). The crystal structure and morphology of prepared CCO films are confirmed by X-ray diffraction (XRD) and field emission-transmission electron microscopy (FE-TEM). The elemental composition of CCO films is estimated as Cu0.5Co2.77O3.82 via energy-dispersive X-ray spectroscopy (EDS) analysis. Surprisingly, the areal capacitance (or energy density at 5 mAcm−2) is significantly improved from 0.58 F cm−2 (or 0.016 mWh cm−2) to 10.5 F cm−2 (or 0.296 mWh cm−2), respectively, after the addition of KFCN to aqueous KOH electrolyte, as compared to bare KOH. Furthermore, CCO exhibits decent cyclic stability with 90 % capacitance retention up to 5000 CV cycles at the scan rate of 100 mV s−1. Moreover, 2-terminal CCO NWs-based SSCs, employed with PVA-KOH-KFCN gel electrolyte, demonstrate a wider potential window of −0.9 to 0.9 V (1.8 V) with a 7-fold increase of energy density from 9.1 to 65 Wh kg−1, as compared with that of PVA-KOH gel electrolyte. As practical validation, the operation of Red-LED for 3 min is demonstrated with PVA-KOH-KFCN gel-based SSC, manifesting that adding redox substance in aqueous electrolytes is one of the promising strategies for portable and wearable energy storage systems
Because of their apparent and intrinsic advantages—including their high-power density and high-rate capability, which result from their high surface areas, appropriate pore distributions, tailored morphologies, heterostructures, and diverse types of composites—pseudocapacitive materials have been identified as versatile electrode materials for supercapacitors (SCs) in energy-storage systems (ESSs). In this review, we first summarize the origin, historical development, and basic principles of pseudocapacitive materials in order to understand their fundamental electrochemical properties. Next, we present synthesis strategies that promote the electrochemical performance of pseudocapacitive materials for SCs by utilizing rational design and fabrication techniques. Then, we highlight the latest advances, focusing on the composition/morphology and structure/electrochemical performance relationships of advanced electrode materials with high-energy densities. Specifically, we discuss the following categories: (i) traditional electrode materials (transition-metal oxides/hydroxides and their composites) and (ii) emerging electrode materials, including niobium pentoxide (Nb2O5), layered double hydroxides (LDHs), MXenes, and metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). Finally, we provide some of our own insights into the major challenges of and prospective directions for developing pseudocapacitive materials for SCs. We hope this Review will help to provide some guidance in the new era of electrode materials for SCs.