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The reasonable construction of Prussian blue analogue (PBA) derivative electrode materials with unique structural characteristics and multiple redox active sites has attracted extensive attention in the field of energy storage. Herein, the battery-type electrodes of silver-decorated cobaltosic oxide (Ag@Co3O4, denoted as Ag3@CO) and bismuth–iron oxide (Bi2O3@BiFeO3, denoted as BO@BFO) have been proposed by an in situ oxidation strategy of PBAs. It is surprising that the silver nanoparticles of Ag3@CO are uniformly distributed in the cobalt oxide phase, further improving its electrical conductivity and accelerating the electron transfer rate. The irregular rod nanostructure of BO@BFO enhances its reaction kinetics by augmenting the interfacial contact area. Furthermore, the integration of binary metals not only offers numerous redox reaction centers but also heightens synergistic effects of pseudocapacitive dominated multielectron phase conversion, resulting in enhanced capacity and rate capability. The optimized Ag3@CO cathode material exhibits a discharge-specific capacity of up to 1027 C g–1 at a current density of 1 A g–1, maintaining an impressive rate of 82.77% despite the high current density of 10 A g–1. In addition, the BO@BFO offers a capacity of 615 C g–1 and is utilized as an anode to establish an asymmetric solid-state supercapacitor (ASC). Notably, the assembled Ag3@CO//BO@BFO ASC device within a voltage window of 1.8 V has achieved an energy density of 55 Wh kg–1 at a power density of 1640 W kg–1; moreover, the fully charged device can light up a red LED and drive a small electric fan, demonstrating its potential in practical applications. This work underscores the immense potential of PBA derivative materials of Ag@Co3O4 and Bi2O3@BiFeO3 for driving high-performance ASC technology forward. [ABSTRACT FROM AUTHOR]

Supercapacitors have emerged today as a compelling choice in the realm of renewable and clean energy storage. They possess several outstanding features such as high-power density, quick charging/discharging, long-cycle life, safety, and environment friendliness. These features make them an attractive option for a wide range of applications, including renewable energy systems, transportation, consumer electronics, energy harvesting, medical, aerospace, and defense. However, supercapacitors suffer from some limitations, such as low-energy density compared to alternative energy storage technologies like lithium-ion batteries. Through meticulous selection and optimization of electrode materials, it is possible to tackle this challenge while simultaneously enhancing the energy storage capacity and preserving their other favorable characteristics. Thus, the choice of electrode materials plays a decisive role in determining the overall performance of supercapacitors. In this review paper, an elaborate description of the technologies, operational principles, and recent progress behind the two significant transition metal oxides, namely RuO2 and MnO2, along with their integration with PANi, a crucial conducting polymer, employed as electrode materials in supercapacitors, are presented. The performance of these nanocomposite electrode materials with a primary consideration on their binary forms has been analyzed and reviewed by the parameters like energy density, power density, specific capacitance, cyclic performance, and rate capability. Detailed discussion is made regarding the structure of the materials prepared using varied synthesis processes with special focus on the morphology and capacitance values, future prospects, and how do they align with the desired performance attributes. [ABSTRACT FROM AUTHOR]

Combining the merits of battery and supercapacitor into a single device represents a major scientific and technological challenge. From a design perspective, electrode material plays a key role in the device and the fundamental difficulty lies in incorporating a high density of active sites into a stable material with excellent charge transfer kinetics. Here, the synthesis is reported of a nearly full‐oxygen‐functionalized 2D conductive transition metal carbide (Ti3C2Oy) with ultrahigh density of Ti─O/═O redox‐active sites by nucleophilic substitution and in situ oxidation under the presence of a proper electrophilic reagent (K+). The fabricated electrode delivered exceptionally high gravimetric and volumetric capacitance (1,082 F g−1 and 3,182 F cm−3 in a potential window of 0.85 V, approximating the theoretical capacity of many transition metal oxides), fast charging/discharging in tens of seconds across a wide range of temperature (−70 to 60 °C), and excellent structural and chemical stability. These promising results provide avenues for the development of high‐energy, high‐power storage devices as well as electromagnetic shielding, and electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Pseudocapacitors are an emerging class of energy storage materials that offer an attractive compromise between the energy density of batteries and power density of electric double‐layer capacitors. Decreasing particle size and increasing surface area of battery materials is a common approach for introducing pseudocapacitive behavior and increasing power density. However, in many cases, as the crystal size is reduced, lattice disorder of unknown extent is also introduced, making it difficult to characterize the relative contribution of size and disorder to fast‐charging performance. In this work, a series of nanostructured MoS2 materials are synthesized with different crystallite sizes and degrees of crystallinity to decouple the effects of size and disorder on charge/discharge kinetics. The extent and type of disorder in each material is quantified by total X‐ray scattering experiments and pair distribution function analyses. Electrochemical characterization, including galvanostatic rate capability, cyclic voltammetry, and various kinetic analyses, are used to demonstrate that both decreasing particle size and introducing lattice disorder are effective strategies for increasing charge storage kinetics, and that the effects are additive. Finally, operando X‐ray diffraction measurements show that both size and disorder can be used suppress first‐order Li+ intercalation‐induced phase transitions, a key feature for enabling pseudocapacitive charge storage. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional (3D) interconnected porous Ni/SiC skeleton (3D Ni/SiC) was synthesized by binder-free hydrogen bubble template-assisted electrodeposition in an electrolyte containing Ni2+ ions and SiC nanopowders. This 3D Ni/SiC skeleton served as a substrate for directly synthesizing nickel–cobalt layered double hydroxide (LDH) nanosheets via electrodeposition, allowing the formation of a nickel–cobalt LDH nanosheet-decorated 3D Ni/SiC skeleton (NiCo@3D Ni/SiC). The multiscale hierarchical structure of NiCo@3D Ni/SiC was attributed to the synergistic interaction between the pseudocapacitor (3D Ni skeleton and Ni–Co LDH) and electrochemical double-layer capacitor (SiC nanopowders). It provided a large specific surface area to expose numerous active Ni and Co sites for Faradaic redox reactions, resulting in an enhanced pseudocapacitance. The as-fabricated NiCo@3D Ni/SiC structure demonstrated excellent rate capability with a high areal capacitance of 1565 mF cm−2 at a current density of 1 mA cm−2. Additionally, symmetrical supercapacitor devices based on this structure successfully powered commercial light-emitting diodes, indicating the potential of as-fabricated NiCo@3D Ni/SiC in practical energy storage applications. [ABSTRACT FROM AUTHOR]

Due to the difficult access of the electrolyte into the nanoconfined space of nanoporous reduced graphene oxide (rGO) electrodes, achieving the optimal electrochemical performance of these devices becomes a challenge. In this work, the dynamics of interfacial‐governed phenomena are investigated during a voltage‐controlled electrochemical activation of nanoporous rGO electrodes that leads to an enhanced electrochemical performance in terms of areal capacitance and electrochemical impedance. In situ/operando characterization techniques are used to reveal the dynamics of the irreversible material changes introduced during the activation process, including ionic diffusion and water confinement within the nanopores, along with the reduction of oxygenated groups and the decrease of the rGO interlayer distance. Furthermore, operando techniques are used to uncover the origin of the complex polarization‐dependent dynamic response of rGO electrodes. The study reveals that the reversible protonation/deprotonation of remaining functional groups and the cation electro‐adsorption/desorption process in the graphene basal plane govern the pseudocapacitive performance of nanoporous rGO electrodes. This work brings new understanding of the complex interplay between surface chemistry, ion confinement, and desolvation processes occurring during electrochemical cycling in nanoporous rGO electrodes, offering new insights for designing high‐performing electrodes based on nanoporous rGO. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2)‐based electrode materials can exhibit a pseudocapacitive charge storage mechanism induced by nanosized dimension of the crystalline domains, which is why control over material structure via synthesis conditions is of significance. In this study, we investigate how the use of different sulfide precursors, specifically thiourea (TU), thioacetamide (TAA), and L‐cysteine (LC), during the hydrothermal synthesis of MoS2, affects its physicochemical, and consequently, electrochemical properties. The three materials obtained exhibit distinct morphologies, ranging from micron‐sized architectures (MoS2 TU), to nanosized flakes (MoS2 TAA and LC). While all three synthesized samples exhibit pseudocapacitive Li+ intercalation properties, the capacity retention of the latter two consisting of nanosized flakes is further improved at high cycling rates. The individual charge storage properties are analyzed by operando X‐ray diffraction, dilatometry, and 3D Bode analysis, revealing a correlation between the morphology, porosity, and the electrochemical intercalation behavior of the obtained electrode materials. The results demonstrate a facile strategy to control MoS2 structure and related functionality by choice of hydrothermal synthesis precursors. [ABSTRACT FROM AUTHOR]

Although Mg–Li dual metal-ion batteries are proposed as a superior system that unite safety of Mg-batteries and performance of Li-ion based systems, its practical implantation is limited due to the lack of reliable high-performance cathodes. Herein, we report a high-performance Mg–Li dual metal-ion battery system based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres (NS) cathode. This 2D cathode displayed exceptional pseudocapacitance (a maximum of 93%) specific capacity (303 mAh g −1 at 25 mA g−1), rate performance (210 mAh g −1 at 1 A g−1), consistent cycling (retain ∼100% capacity for 3000 cycles at 1 A g−1), Coulombic efficiency (nearly 100%) and fast-charging (∼12.1 min). These properties are remarkably dominant to the existing Mg-Li dual metal-ion battery cathodes. Spectroscopic and microscopic mechanistic studies confirmed negligible structural changes during charge-discharge cycles of the TiO2-B nanosheet assembled spheres electrodes. Exceptional electrochemical properties of the 2D electrode is ascribed to remarkable pseudocapacitive Mg–Li dual metal-ion diffusion via the numerous nanointerfaces of TiO2-B caused by its hierarchical microstrucrure. Large surface area, nanosheet morphology, mesoporous structure and ultrathin nature also acted as secondary factors facilitating improved electrode-electrolyte contact. Demonstrated approach of pseudocapacitive type Mg-Li dual metal-ion intercalation through hierarchical nanointerfaces may be further utilized for the designing of numerous top-notch electrode materials for futuristic Mg–Li dual metal-ion batteries. [ABSTRACT FROM AUTHOR]

This review explores rational design strategies for electrode materials offered by nanoscale approaches aimed at achieving high energy and power density in energy storage devices. The focus is on delving into the underlying concepts and crucial factors impacting the energy storage electrode performance to outline, from these concepts, suitable ways to improve the electrode performance, moving beyond a mere summary of structures or materials. Therefore, the importance of a comprehensive approach considering the impact of both the electrode structure and the material type on the electrochemical processes is remarked. These factors are examined through illustrative examples of some materials, which were categorized by structural and compositional attributes rather than material type. The approach followed in this review is intended to offer valuable insights to guide the formulation of effective electrode designs for advanced energy storage systems. [ABSTRACT FROM AUTHOR]

This review article focuses on the potential of cobalt oxide composites with conducting polymers, particularly polypyrrole (PPy) and polyaniline (PANI), as advanced electrode materials for supercapacitors, batteries, and supercapatteries. Cobalt oxide, known for its high theoretical capacitance, is limited by poor conductivity and structural degradation during cycling. However, the integration of PPy and PANI has been proven to enhance the electrochemical performance through improved conductivity, increased pseudocapacitive effects, and enhanced structural integrity. This synergistic combination facilitates efficient charge transport and ion diffusion, resulting in improved cycling stability and energy storage capacity. Despite significant progress in synthesis techniques and composite design, challenges such as maintaining structural stability during prolonged cycling and scalability for mass production remain. This review highlights the synthesis methods, latest advancements, and electrochemical performance in cobalt oxide/PPy and cobalt oxide/PANI composites, emphasizing their potential to contribute to the development of next-generation energy storage devices. Further exploration into their application, especially in battery systems, is necessary to fully harness their capabilities and meet the increasing demands of energy storage technologies. [ABSTRACT FROM AUTHOR]

The decline in fossil fuels on the earth has become a primary global concern which has urged mankind to explore other viable alternatives. The exorbitant use of fuels by an ever-increasing global population demands a huge production of energy from renewable sources. Renewable energy sources like the sun, wind, and tides have been established as promising substitutes for fossil fuels. However, the availability of these renewable energy sources is dependent on weather and climatic conditions. Thus, this goal can only be achieved if the rate of energy production from renewable sources is enhanced under favorable weather conditions and can be stored using high energy storing devices for future utilization. The energy from renewable sources is principally stored in hydropower plants, superconducting magnetic energy storage systems, and batteries. [ABSTRACT FROM AUTHOR]

In this work, rutile-phase Ti0.95Nb0.95O4/C (TNO/C) composites with different carbon contents were obtained through solvothermal method and subsequent calcination. The effect of carbon component on the microstructure and electrochemical performances of TNO/C composites were investigated. The results indicate more oxygen vacancies, and higher contents of Nb4+ and Ti3+ can be obtained under higher carbon content, leading to enhanced conductivity. Besides serving as conductive agent, carbon component in TNO/C composites also acts as an active component for Li+ storage, and pseudocapacitance provided by carbon component increases with the increasing of its relative content. Therefore, TNO/C-27.0 composites with the highest carbon content in the as-prepared composites deliver the highest reversible capacities at different current densities and excellent cycling capability of 488 mAh·g−1 at 0.3 A·g−1 after 300 cycles and 331 mAh·g−1 at 1.0 A·g−1 after 500 cycles. [ABSTRACT FROM AUTHOR]

In thin LiNi1/3Mn1/3Co1/3O2 (NMC111) electrodes, pseudocapacitive behavior is notably enhanced due to their increased surface-to-volume ratio, which intensifies the role of the electrode–electrolyte interface. This behavior is driven by fast, reversible redox reactions and ion intercalation occurring near the surface, where the shorter diffusion path allows for more efficient ionic transport. The reduced thickness of the electrodes shortens the Li-ion diffusion distance, improving the diffusion coefficient by a factor of 40 compared to thicker electrodes, where ion transport is hindered by longer diffusion paths. The increased surface area and shorter diffusion paths promote faster electrochemical kinetics, allowing for quicker ion intercalation and deintercalation processes. The thin-film configuration enhances pseudocapacitive charge storage, which is essential for applications requiring rapid charge and discharge cycles. As a result, the combination of improved Li-ion diffusion and enhanced surface activity contributes to superior electrochemical performance, offering higher power densities, faster energy delivery, and better rate capability. This improvement in performance makes thin NMC111 electrodes particularly advantageous for applications such as high-power energy storage systems, where fast kinetics and high power densities are critical. These findings highlight the importance of interface engineering and material morphology in optimizing the performance of Li-ion batteries and similar electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

Interface storage is an exciting mechanism for electrode materials to obtain high‐energy and high‐power densities simultaneously. However, constructing suitable and abundant interfaces in composites to achieve interface‐dominated storage is greatly challenging. Here, it is demonstrated for the first time that interface‐dominated Zn2+ storage can be realized in the hydrogen‐bonding (H‐bonding) interface between vanadium oxide (VOx) and graphene oxide (GO). This interface featuring reversibility, universality, self‐healing nature, and high per‐volume concentration can store more Zn2+ faster than the bulk by decoupling transport and storage of Zn2+ and electrons through reversible break/reconstruction of the interfacial N···H─O bonds. Density functional theory calculations reveal that an appropriate number of N···H─O bonds is crucial for maintaining high reversibility of interface storage. Additionally, the presence of carbon vacancies in the GO plane near the interfacial bonds facilitates an expansion of the interface storage limitation. Finally, it is demonstrated that intercalation pseudocapacitance is the nature of interface storage, which circumvents the solid‐state diffusion limitation in the bulk and achieves a high level of pseudocapacitive storage in the interface (464 and 126 mAh g−1 at 0.1 and 10.0 A g−1, respectively). This work establishes an excellent paradigm for implementing interface‐dominated Zn2+ storage in H‐bonding interfaces and demonstrates exceptional universality and broad application prospects. [ABSTRACT FROM AUTHOR]

Disordered carbon is the state of the art anode material for Na‐ion batteries due to their increased interlayer spacing and good electronic conductivity. However, its practical application is hindered by average specific capacity, poor rate performance, low coulombic efficiency and limited cycling stability. Herein, we report the superior pseudocapacitance enhanced Na‐ion storage of in situ surface functionalized carbon nanosheets. Anodes composed of ultrathin (~15 nm) carbon nanosheets demonstrated excellent reversible specific capacity (375 mAh/g at 25 mA/g), rate performance (150 mAh/g at 2 A/g), long‐term cycling performance (1000 cycles at 1 A/g) and coulombic efficiency (~100 %). Considerably higher pseudocapacitance (up to ~78 %) is also identified in this case compared to amorphous carbon particles. Spectroscopic and electrochemical studies proved Na‐ion intercalation in to the disordered carbon and pseudocapacitive storage driven by oxygen‐containing surface functional groups. Outstanding electrochemical performance is credited to the synergy between diffusion limited intercalation and pseudocapacitive surface Na‐ion storage. The demonstrated synthetic method of in situ functionalized carbon nanosheets is inexpensive and scalable. The strategy of functional group and morphology induced pseudocapacitive Na‐ion storage offer new prospects to design high‐performance Na‐ion battery electrodes. [ABSTRACT FROM AUTHOR]

Redox-active porous organic polymers (POPs) demonstrate significant potential in supercapacitors. However, their intrinsic low electrical conductivity and stacking tendencies often lead to low utilization rates of redox-active sites within their structural units. Herein, polyimide POPs (donated as PMTA) are synthesized in situ on multi-walled carbon nanotubes (MWCNTs) from tetramino-benzoquinone (TABQ) and 1,4,5,8-naphthalene tetracarboxylic dianhydride (PMDA) monomers. The strong π–π stacking interactions drive the PMTA POPs and the MWCNTs together to form a PMTA/MWCNT composite. With the assistance of MWCNTs, the stacking issue and low conductivity of PMTA POPs are well addressed, leading to the obvious activation and enhanced utilization of the redox-active groups in the PMTA POPs. PMTA/MWCNT then achieves a high capacitance of 375.2 F g−1 at 1 A g−1 as compared to the pristine PMTA POPs (5.7 F g−1) and excellent cycling stability of 89.7% after 8000 cycles at 5 A g−1. Cyclic voltammetry (CV) and in situ Fourier-Transform Infrared (FT-IR) results reveal that the electrode reactions involve the reversible structural evolution of carbonyl groups, which are activated to provide rich pseudocapacitance. Asymmetric supercapacitors (ASCs) assembled with PMTA/MWCNTs and activated carbon (AC) offer a high energy density of 15.4 Wh kg−1 at 980.4 W kg−1 and maintain a capacitance retention of 125% after 10,000 cycles at 5 A g−1, indicating their good potential for practical applications. [ABSTRACT FROM AUTHOR]

Lithium‐ion insertion/deinsertion in anode at slow rates limits the power performance of energy storage devices. Here, a new pseudocapacitive electrode with high reversible capacity during cycling has been proposed for a lithium‐ion capacitor. The lithium‐fluoride garnet, namely Na3Fe2Li3F12, is obtained via precipitation from an aqueous solution at room temperature using abundant materials and exhibits a high discharge capacity of 746 mAh g−1. After the first charging cycle, the energy is stored via fast pseudocapacitive faradaic reactions which are facilitated by the nanocrystalline transport pathways with no structural modification to the electrode. The high stability window of F‐garnet allows extracting cell voltages of 2.2–3.2 V in a lithium‐ion capacitor where it is coupled with a porous carbon‐based positive electrode, with a high energy efficiency of 93 % maintained for 10000 charge/discharge cycles. This study opens a new research direction concerning pseudocapacitive anode materials for enhancing power performance and even replacing the traditional battery‐like anode materials. [ABSTRACT FROM AUTHOR]

With rapidly growing commercial markets of portable electronics, supercapacitors (SCs) have become one of the most promising energy storage devices due to their unique characteristics. However, the low energy densities severely restrict their practical application. Furthermore, the liquid-electrolyte has leak issues under deformation, resulting in device failure or performance degradation. Herein, a novel material which has a porous carbon (PC) nanostructure skeleton connected by tannic acid (TA) with Co metal compounds which can provide pseudocapacitance is designed. PC is derived by activation C60 which is sp2 carbon that ensures the efficient transmission of electrons and Co metal compounds increase the active site of the Faraday redox reaction and improve the specific capacitance. TA makes porous carbon skeleton and Co metal compounds more closely linked, effectively improving ion transport efficiency and optimizing cycle performance. The composite showed a reversible specific capacity of 1475 mF cm−2 at a charge/discharge current density of 2 mA cm−2 and a specific capacity of 1174 mF cm−2 at 30 mA cm−2 when measured by a three-electrode system conducted in 2.0 M KOH electrolyte. In addition, the assembled solid-state symmetric SCs with the electrode materials have excellent cycling stability that cycled for 5000 cycles at 5 mA cm−2 and the capacitance retention rate reached 95.76%. The device can also provide continuous and stable energy that lights up the red light-emitting diode (LED) with excellent bendability. This strategy provides a novel device design method and can be effectively applied to future flexible electronic products. [ABSTRACT FROM AUTHOR]

In this work, Mn2P2O7 nanoparticles were synthesized via hydrothermal route without any templates or surfactants followed by heat treatment at 700 ∘ C. The as-prepared samples were characterized and described using thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), Scanning electron microscopy (SEM) analysis. The resultant product was evaluated for electrochemical properties in organic electrolyte between −1.4 and 1.6 V using cyclic voltammetry in ambient condition. It revealed the specific capacitance of 565 F/g at scan rate of 5 mV/s. The outstanding pseudocapacitive performance was absorbed due to the faradaic oxidation and reduction reactions related to the intercalation/de-intercalation of the tetrabutylammonium cation (TBA +) electrolyte and inorganic pyrophosphate lattice. It was believed that the cost effective Mn2P2O7 nanoparticles may be promising electrode materials for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Abstract Supercapacitors have emerged as a prominent area of research in energy storage technology, primarily because of their high power density and notable stability compared to batteries. However, their practical implementation is hindered by their low energy densities and insufficient long‐term stability. In this study, bulk porous Nb4N5 and Ta3N5 single crystals with excellent pseudocapacitance and electrical conductivity are successfully prepared by solid‐phase transformation method. These monolithic porous single crystals (PSC) exhibit a long‐range ordered crystalline architecture and substantial specific surface area, which facilitate rapid charge transport and ion diffusion within the electrolyte‐permeated crystal lattice. Notably, the areal capacitance of the porous Nb4N5 single crystals is 12.9 F cm−2 at a current density of 6 mA cm−2 and 35.08 F cm−2 at a scan rate of 1 mV s−1. Furthermore, the energy density reached 1.79 mWh cm−2 at a power density of 20 mW cm−2, demonstrating their high energy storage capability. Moreover, these porous Nb4N5 single crystals exhibited robust capacitance retention and exceptional cycling stability, making them promising candidates for use as electrodes in energy storage applications. These results underscore the significant potential of porous metal nitride single crystals in advancing the field of capacitive energy storage.