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High‐performance supercapacitive electrode materials have received significant attention from researchers worldwide, thus aiming for comparable performance similar to the extensively used rechargeable batteries. For emerging energy storage technologies like flexible supercapacitors, transition metal chalcogenides (TMCs) have been in the spotlight due to their promising electrochemical features compared to other electrode materials. Among the synthesis techniques, electrodeposition‐mediated preparation of thin films of TMCs offered an affordable binder‐free approach for electrode fabrication that effectively improved the supercapacitor performance. Hence, this review mainly focussed on the electrodeposition‐based syntheses of single/ multinary chalcogenides and their composites for supercapacitors applications. Further, the effects of different deposition parameters were discussed for boosting the supercapacitor performance. Finally, this review outlined the existing challenges and future perspectives in this research domain, which will assist the upcoming exploration in the energy storage field. [ABSTRACT FROM AUTHOR]

In the recent times research towards solid state supercapacitors (SSS) have increased drastically due to the promising performance in futuristic technologies particularly in portable and flexible electronics like smart watches, smart fabrics, foldable smartphones and tablets. Also, when compared to supercapacitors using liquid electrolyte, solid electrolyte has several advantages like high energy density, safety, high cycle life, flexible form factor, and less environmental impact. The crucial factor determining the sustainability of a technology is the eco‐friendliness since the natural resources are being exploited in a wide scale. Numerous studies have focused on biodegradable materials for supercapacitor electrodes, electrolytes, and other inactive components. Making use of these biodegradable materials to design a SSS enables the technology to sustain for a very long time since biodegradable materials are not only environment friendly but also, they show relatively high performance. This review focuses on recent progress of different biodegradable electrodes, and electrolytes along with their properties, electrochemical performance and biodegradable capabilities for SSS have been analyzed and provides a concise summary enabling readers to understand the importance of biodegradable materials and to narrow down the research in a more rational way. [ABSTRACT FROM AUTHOR]

Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co3O4@Mo-Co3O4 nanosheets and Co3O4 nano-needles were calculated to be 814, and 615 C g−1 at a current density of 1 A g−1, respectively. The electrode of the composite Co3O4@Mo-Co3O4 nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co3O4@Mo-Co3O4//AC device achieved a maximum specific energy of 51.35 Wh Kg−1 and power density of 790 W kg−1. The Co3O4@Mo-Co3O4//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co3O4@Mo-Co3O4 nanocomposite is a very promising electrode material and a stabled supercapacitor. [ABSTRACT FROM AUTHOR]

In order to upgrade existing electronic technology, we need simultaneously to advance power supply devices to match emerging requirements. Owing to the rapidly growing wearable and portable electronics markets, the demand to develop flexible energy storage devices is among the top priorities for humankind. Flexible supercapacitors (FSCs) have attracted tremendous attention, owing to their unrivaled electrochemical performances, long cyclability and mechanical flexibility. Carbon nanotubes (CNTs), long recognized for their mechanical toughness, with an elastic strain limit of up to 20%, are regarded as potential candidates for FSC electrodes. Along with excellent mechanical properties, high electrical conductivity, and large surface area, their assemblage adaptability from one-dimensional fibers to two-dimensional films to three-dimensional sponges makes CNTs attractive. In this review, we have summarized various assemblies of CNT structures, and their involvement in various device configurations of FSCs. Furthermore, to present a clear scenario of recent developments, we discuss the electrochemical performance of fabricated flexible devices of different CNT structures and their composites, including additional properties such as compressibility and stretchability. Additionally, the drawbacks and benefits of the study and further potential scopes are distinctly emphasized for future researchers. [ABSTRACT FROM AUTHOR]

There is a growing interest in supercapacitors as energy storage systems due to their high specific power, fast charge/discharge rates, and long cycling stability. Researchers have focused recently on developing nanomaterials to enhance the capacitive performance of supercapacitors. The inclusion of electroactive components, such as transition metal oxides (TMOs), carbonbased materials, and conducting polymers (CPs), is believed to play an important role in improving the electrochemical behavior of the electrode materials. Nevertheless, supercapacitors containing TMOs, carbon-based materials, and CPs commonly suffer from inferior ion-transport kinetics and poor electronic conductivity, which can affect the rate capability and cycling stability of the electrodes. Therefore, the development of TMO/CP and TMO/carbon-based electrode materials has gained widespread attention because they synergistically combine the advantages of both materials, enabling revolutionary applications in the electrochemical field. In general, TMOs have given good performance as electrodes for supercapacitors by further increasing the performance of the electrode when two metal cations are introduced into a single crystal structure. This Review describes and highlights recent progress in the development of bimetallic oxides regarding their design approach, configurations, and electrochemical properties for supercapacitor applications, at the same time providing new opportunities for future energy storage technologies. [ABSTRACT FROM AUTHOR]

Owing to the nanometer size range, Quantum Dots (QDs) have exhibited unique physical and chemical properties which are favourable for different applications. Especially, due to their quantum confinement effect, excellent optoelectronic characteristics is been observed. This considerable progress has not only uplifted the singular usage of QDs, but also encouraged to prepare various hybrid materials to achieve superior efficiency by eliminating certain shortcomings. Such issues can be overcome by compositing QDs with polymers. Via employing polymer composite with QDs (PQDs) for supercapacitor applications, adequate conductivity, stability, excellent energy density, and better specific capacitance is been achieved which we have elaborately discussed in this review. Researchers have already explored various types of polymer nanocomposite with different QDs such as carbonaceous QDs, transition metal oxide/sulphide QDs etc. as electrode material for supercapacitor application. Synthesis, application outcome, benefits, and drawbacks of these are explained to portray a better understanding. From the existing studies it is clearly confirmed that with using PQDs electrical conductivity, electrochemical reactivity, and the charge accumulation on the surface have prominently been improved which effected the fabricated supercapacitor device performance. More comprehensive fundamentals and observations are explained in the current review which indicates their promising scopes in upcoming times. [ABSTRACT FROM AUTHOR]

Energy generation can be clean and sustainable if it is dependent on renewable resources and it can be prominently utilized if stored efficiently. Recently, biomass-derived carbon and polymers have been focused on developing less hazardous eco-friendly electrodes for energy storage devices. We have focused on boosting the supercapacitor's energy storage ability by engineering efficient electrodes in this context. The well-known conductive polymer, polyaniline (PANI), deposited on nickel foam (NF) is used as a positive electrode, while the activated carbon derived from jute sticks (JAC) deposited on NF is used as a negative electrode. The asymmetric supercapacitor (ASC) is fabricated for the electrochemical studies and found that the device has exhibited an energy density of 24 µWh/cm2 at a power density of 3571 µW/cm2. Furthermore, the ASC PANI/NF//KOH//JAC/NF has exhibited good stability with ~86% capacitance retention even after 1000 cycles. Thus, the enhanced electrochemical performances of ASC are congregated by depositing PANI on NF that boosts the electrode's conductivity. Such deposition patterns are assured by faster ions diffusion, higher surface area, and ample electroactive sites for better electrolyte interaction. Besides advancing technology, such work also encourages sustainability. [ABSTRACT FROM AUTHOR]

• Facile, solid-state, low temperature synthesized layered molybdenum boride found out to be of thin nanosheets. • MoB are found to be electrochemically active in acid and neutral electrolyte, where the nanosheets provide a higher surface area for the electrolyte ion interaction. • MoB was directly employed as a negative electrode, against the activated carbon as a positive electrode for the asymmetric supercapacitors. • The device was found to deliver a high energy density and power density with long-term stability in charge/discharge cyclings. • Interestingly, it was discovered that the outcomes of the electrochemical performance of asymmetric supercapacitors could be tuned by the electrolyte. [Display omitted] The survey of 2D materials has triggered the energy storage and conversion research. In molybdenum-based 2D layered materials are of great significance, due to their remarkable properties. In this work, simple solid-state synthesis and formation of molybdenum boride has been explored with various characteristic techniques. The advanced characterization techniques like XRD, TEM, XPS, BET, have been used to understand the crystallinity, morphology, and surface area of the layered MoB (LMB). The electrochemical performances of LMB electrode were verified with different aqueous electrolytes. The LMB electrode has been found to store higher charge in H 2 SO 4 than Na 2 SO 4 electrolyte. The LMB electrode delivered a specific capacitance of 445 F g−1 in H 2 SO 4 where 130 F g−1 in Na 2 SO 4 at a current density of 1 A g−1. Such behavior may be due to ionic size and mobility of ions in the electrolyte. The asymmetric supercapacitors have been fabricated with LMB and activated carbon (AC) electrode then the device performance was examined in both the electrolyte. On optimization, it was found the device works well in potential window 1.4 V in H 2 SO 4 while the potential window was extended to 1.8 V in Na 2 SO 4 electrolyte. The device was found to deliver an energy density of 14 W h kg−1 at a power density of 16.8 kW kg−1 for H 2 SO 4 with a better capacity retention of 98% for 2000 cycles. Thus, LMB electrode in supercapacitor application has been demonstrated for the first time, which can instigate more investigations for layered molybdenum-based electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]