Search Results (30)

Tea waste contains various substances with phenolic hydroxyl groups, including lignin, tannins, tea polyphenols, etc., which are rarely utilized. In this study, tea waste was directly dispersed with graphene oxide to prepare tea waste/reduced graphene oxide (TW/rGO) hydrogel through a one-step hydrothermal method. The prepared hydrogel presented a continuous three-dimensional porous structure and exhibited good mechanical properties with a compressive strength of 53.4 ± 4.0 kPa. It also showed excellent electrochemical performance as an electrode material. Its specific capacitance reached 434.7 F g⁻¹ at a current density of 1 A g⁻¹, and its capacitance retention was 55.8% when the current density was increased to 100 A g⁻¹. In addition, an TW/rGO assembled all-solid-state supercapacitor demonstrated a superior specific capacitance of 372.8 F g⁻¹ and a competitive energy density of 12.9 Wh kg⁻¹ at 1 A g⁻¹. Full article

Solid-state electrolytes have received widespread attention for solving the problem of the leakage of liquid electrolytes and effectively improving the overall performance of supercapacitors. However, the electrochemical performance and environmental friendliness of solid-state electrolytes still need to be further improved. Here, a binary biomass-based solid electrolyte film (LSE) was successfully synthesized through the incorporation of lignin nanoparticles (LNPs) with sodium alginate (SA). The impact of the mass ratio of SA to LNPs on the microstructure, porosity, electrolyte absorption capacity, ionic conductivity, and electrochemical properties of the LSE was thoroughly investigated. The results indicated that as the proportion of SA increased from 5% to 15% of LNPs, the pore structure of the LSE became increasingly uniform and abundant. Consequently, enhancements were observed in porosity, liquid absorption capacity, ionic conductivity, and overall electrochemical performance. Notably, at an SA amount of 15% of LNPs, the ionic conductivity of the resultant LSE-15 was recorded at 14.10 mS cm⁻¹, with the porosity and liquid absorption capacity reaching 58.4% and 308%, respectively. LSE-15 was employed as a solid electrolyte, while LNP-based carbon aerogel (LCA) served as the two electrodes in the construction of a symmetric all-solid-state supercapacitor (SSC). The SSC device demonstrated exceptional electrochemical storage capacity, achieving a specific capacitance of 197 F g⁻¹ at 0.5 A g⁻¹, along with a maximum energy and power density of 27.33 W h kg⁻¹ and 4998 W kg⁻¹, respectively. Furthermore, the SSC device exhibited highly stable electrochemical performance under extreme conditions, including compression, bending, and both series and parallel connections. Therefore, the development and application of binary biomass-based solid electrolyte films in supercapacitors represent a promising strategy for harnessing high-value biomass resources in the field of energy storage. Full article

Nowadays, owing to the new technological and industrial requirements for equipment, such as flexibility or multifunctionally, the development of all-solid-state supercapacitors and Li-ion batteries has become a goal for researchers. For these purposes, the composite material approach has been widely proposed due to the promising features of woven carbon fiber as a substrate material for this type of material. Carbon fiber displays excellent mechanical properties, flexibility, and high electrical conductivity, allowing it to act as a substrate and a collector at the same time. However, carbon fiber’s energy-storage capability is limited. Several coatings have been proposed for this, with nanostructured transition metal oxides being one of the most popular due to their high theoretical capacity and surface area. In this overview, the main techniques used to achieve these coatings—such as solvothermal synthesis, MOF-derived obtention, and electrochemical deposition—are summarized, as well as the main strategies for alleviating the low electrical conductivity of transition metal oxides, which is the main drawback of these materials. Full article

Solid polymer electrolytes (SPE) and composite polymer electrolytes (CPE) serve as crucial components in all-solid-state energy storage devices. Structural batteries and supercapacitors present a promising alternative for electric vehicles, integrating structural functionality with energy storage capability. However, despite their potential, these applications are hampered by various challenges, particularly in the realm of developing new solid polymer electrolytes that require more investigation. In this study, novel solid polymer electrolytes and composite polymer electrolytes were synthesized using epoxy resin blends, ionic liquid, lithium salt, and alumina nanoparticles and subsequently characterized. Among the formulations tested, the optimal system, designated as L70P30ILE40Li1MAl2 and containing 40 wt.% of ionic liquid and 5.7 wt.% of lithium salt, exhibited exceptional mechanical properties. It displayed a remarkable storage modulus of 1.2 GPa and reached ionic conductivities of 0.085 mS/cm at 60 °C. Furthermore, a proof-of-concept supercapacitor was fabricated, demonstrating the practical application of the developed electrolyte system. Full article

As a typical pseudocapacitor material, VO_x possesses mixed valence states, making it an ideal electrode material for symmetric screen-printed supercapacitors. However, its high internal resistance and low energy density are the main hurdles to its widespread application. In this study, a two-dimensional PANI@VO_x nanobelt with a core-shell architecture was constructed via a two-step route. This strategy involves the preparation of VO_x using a solvothermal method, and a subsequent in situ polymerization process of the PANI. By virtue of the synergistic effect between the VO_x core and the PANI shell, the optimal VO_x@PANI has an enhanced conductivity of 0.7 ± 0.04 S/Ω, which can deliver a high specific capacitance of 347.5 F/g at 0.5 A/g, a decent cycling life of ~72.0%, and an outstanding Coulomb efficiency of ~100% after 5000 cycles at 5 A/g. Moreover, a flexible all-solid-state symmetric supercapacitor (VO_x@PANI SSC) with an in-planar interdigitated structure was screen-printed and assembled on a nickel current collector; it yielded a remarkable areal energy density of 115.17 μWh/cm² at an areal power density of 0.39 mW/cm², and possessed outstanding flexibility and mechanical performance. Notably, a “Xiaomi” hygrothermograph (3.0 V) was powered easily by tandem SSCs with an operating voltage of 3.1 V. Therefore, this advanced pseudocapacitor material with core-shell architecture opens novel ideas for flexible symmetric supercapacitors in powering portable/wearable products. Full article

Converting biowaste into carbon-based supercapacitor materials provides a new solution for high-performance and environmentally friendly energy storage applications. Herein, the hierarchical PAC/NiCo₂S₄ composite structure was fabricated through the combination of activation and sulfuration treatments. The PAC/NiCo₂S₄ electrode garnered advantages from its hierarchical structure and hollow architecture, resulting in a notable specific capacitance (1217.2 F g⁻¹ at 1.25 A g⁻¹) and superior cycling stability. Moreover, a novel all-solid-state asymmetric supercapacitor (ASC) was successfully constructed, utilizing PAC/NiCo₂S₄ as the cathode and PAC as the anode. The resultant device exhibited exceptionally high energy (49.7 Wh kg⁻¹) and power density (4785.5 W kg⁻¹), indicating the potential of this biomass-derived, hierarchical PAC/NiCo₂S₄ composite structure for employment in high-performance supercapacitors. Full article

Flexible supercapacitors are demanded for energy storage of wearable electronics. In this paper, a simple strategy for preparing flexible carbon fibers (CFs) with good energy storage capacity using a mixed acid treatment process is reported. When the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1, the carbon fiber electrodes have the best electrochemical performance with a high capacitance of 27.83 F g⁻¹ at 15 mA g⁻¹ and extremely high capacitance retention of 79.9% after 500 cycles at 100 mA g⁻¹. Furthermore, their energy density can reach 3.86 Wh kg⁻¹ with a power density of 7.5 W kg⁻¹. Such an excellent electrochemical performance of carbon fiber electrodes is attributed to their surface rich oxygen-containing functional groups, rough surface, and a certain number of graphene quantum dots (GQDs). Importantly, the all-solid-state flexible supercapacitor performs excellent bending stability performance with a capacitance retention of almost 100% after 500 times of bending at 180°, showing good prospects and applications in the field of flexible energy storage devices. Full article

In this study, an ionogel electrolyte (PAIM-X) consisting of 1-vinyl-3-methylimidazole bis (trifluoromethyl sulfonyl) imide ([VMIM][TFSI]), Polyacrylamide (PAAm), and MXene were prepared. The conductivity of PAIM-X and integral area of the voltammetric curve of the supercapacitor (PAIMSC) were improved by adding MXene. The addition of [VMIM][TFSI] enhanced the conductivity and applicable temperature of the ionogel electrolyte. At 90 °C, the conductivity of PAIM-4 can reach 36.4 mS/cm. In addition, spherical polyaniline with good electrochemical properties was synthesized and coated on graphite paper as an active substance. An all-solid-state supercapacitor was composed of PAIM-4, polyaniline electrode with 1.2 V potential window, pseudo-capacitors and high quality capacitors. The solvent 1-ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl imide) ([EMIM][TFSI]) and methanesulfonic acid (MSA) were introduced into the ionogel to promote the redox reaction of polyaniline (PANI). The mass specific capacitance of PAIMSC was 204.6 F/g and its energy density could reach 40.92 Wh/kg, which shows great potential for practical application at high temperature. The device had good rate performance and cycle performance, and its capacitance retention rate was still 91.56% after 10,000 cycles. In addition, the supercapacitor can work within the temperature range of −20 °C to 90 °C. These excellent electrochemical properties indicate that PAAm/IL/Mxene-X has broad application space and prospect. Full article

Solvent-free all-solid-state supercapacitors have recently received attention. Despite their highly specific capacitance, they suffer issues related to the solid–solid interface that degrade their performance during prolonged cycling. Here, we propose a novel strategy for improving the electrode–electrolyte interface by introducing a small amount of polymer into the activated carbon-based electrode. An electrode composition of 80AC:8SA:7AB:5[PEO_0.95 (LiClO₄)_0.05]—where AC, SA, and AB stand for activated carbon, sodium alginate binder, and acetylene black, respectively—is optimized. A composite membrane—viz., PEO-LiClO₄ reinforced with 38 wt% NASICON structured nano crystallites of Li_1.3Al_0.3Ti_1.7(PO₄)₃—is used as a solid electrolyte. Incorporating a small amount of salt-in-polymer (95PEO-5 LiClO₄) in the electrode matrix leads to a smooth interface formation, thereby improving the performance parameters of the all-solid-state supercapacitors (ASSCs). A typical supercapacitor with a polymer-incorporated electrode exhibits a specific capacitance of ~102 Fg⁻¹ at a discharge current of 1.5 Ag⁻¹ and an operating voltage of 2 V near room temperature. These ASSCs also exhibit relatively better galvanostatic charge–discharge cycling, coulombic efficiency, specific energy, and power in comparison to those based on conventional activated carbon. Full article

In this study, a flexible all-solid-state asymmetric supercapacitor (FASC) device has been successfully fabricated via full recycling of heated tobacco waste (HTW). Tobacco leaves and cellulose acetate tubes have been successfully carbonized (HTW-C) and mixed with metal oxides (MnO₂ and Fe₃O₄) to obtain highly active materials for supercapacitors. Moreover, poly(lactic acid) (PLA) filters have been successfully dissolved in an organic solvent and mixed with the as-prepared active materials using a simple paste mixing method. In addition, flexible MnO₂- and Fe₃O₄-mixed HTW-C/PLA electrodes (C-MnO₂/PLA and C-Fe₃O₄/PLA) have been successfully fabricated using the drop-casting method. The as-synthesized flexible C-MnO₂/PLA and C-Fe₃O₄/PLA electrodes have exhibited excellent electrical conductivity of 378 and 660 μS cm⁻¹, and high specific capacitance of 34.8 and 47.9 mF cm⁻² at 1 mA cm⁻², respectively. A practical FASC device (C-MnO₂/PLA//C-Fe₃O₄/PLA) has been assembled by employing the C-MnO₂/PLA as the positive electrode and C-Fe₃O₄/PLA as the negative electrode. The as-prepared FASC device showed a remarkable capacitance of 5.80 mF cm⁻² at 1 mA cm⁻². Additionally, the FASC device manifests stable electrochemical performance under harsh bending conditions, verifying the superb flexibility and sustainability of the device. To the best of our knowledge, this is the first study to report complete recycling of heated tobacco waste to prepare the practical FASC devices. With excellent electrochemical performance, the experiments described in this study successfully demonstrate the possibility of recycling new types of biomass in the future. Full article

Recent developments in embedded electronics require the development of micro sources of energy. In this paper, the fabrication of an on-chip interdigitated all-solid-state supercapacitor, using porous gold electrodes and a PVA/KOH quasisolid electrolyte, is demonstrated. The fabrication of the interdigitated porous gold electrode is performed using an original bottom-up approach. A templating method is used for porosity, using a wet chemistry process followed by microfabrication techniques. This paper reports the first example of an all-gold electrode micro-supercapacitor. The supercapacitor exhibits a specific capacitance equal to 0.28 mF·cm⁻² and a specific energy of 0.14 mJ·cm⁻². The capacitance value remains stable up to more than 8000 cycles. Full article

Gel polymer electrolytes with a satisfied ionic conductivity have attracted interest in flexible energy storage technologies, such as supercapacitors and rechargeable batteries. However, the poor mechanical strength inhibits its widespread application. One of the most significant ways to avoid the drawbacks of the gel polymer electrolytes without compromising their ion transportation capabilities is to create a self−healing structure with the cross−linking segment. Herein, a new kind of macromolecule chemical cross−linked network ionic gel polymer electrolyte (MCIGPE) with superior electrochemical characteristics, a high flexibility, and an excellent self−healing ability were designed, based on chitosan and dibenzaldehyde−terminated poly (ethylene glycol) (PEGDA) via dynamic imine bonds. The ionic conductivity of the MCIGPE−65 can achieve 2.75 × 10⁻² S cm⁻¹. A symmetric all−solid−state supercapacitor employing carbon cloth as current collectors, activated a carbon film as electrodes, and MCIGPE−65 as a gel polymer electrolyte exhibits a high specific capacitance of 51.1 F g⁻¹ at 1 A g⁻¹, and the energy density of 7.1 Wh kg⁻¹ at a power density of 500.2 W kg⁻¹. This research proves the enormous potential of incorporating, environmentally and economically, chitosan into gel polymer electrolytes for supercapacitors. Full article

In this study, an asymmetric supercapacitor (ASSC) device is assembled by the deposition and annealing of silver-doped mixed metal oxides on reduced graphene oxide (rGO)/Ni foam and activated carbon (AC) on Ni foam as positive and negative electrodes, respectively. The best performing Ag:MnCoNiO active material is synthesized on rGO/Ni foam using chronopotentiometry combined with heat treatment. The XRD study clearly confirms the crystalline nature of the electrode with MnCo₂O₄ and MnNi₂O₄ phases. FT-IR and XPS studies revealed the formation of Ag:MnCoNiO/rGO on Ni foam. SEM images show a thin-film layer of fabricated material on the surface of rGO/Ni foam. The supercapacitor properties were tested in two- and three-electrode configurations, with cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) experiments in a 6 M KOH aqueous electrolyte. In the three-electrode configuration, reversible faradic reactions can be observed in a potential range of 0.0 and +0.6 V vs. Hg/HgSO₄. In the two-electrode device configuration, the system exhibits a maximum energy density of 45.5 Wh kg⁻¹ and provides a maximum power density of 4.5 kW kg⁻¹. The results showed that the doping of Ag in a MnCoNiO electrode shows promising properties, achieved by a very simple fabrication process. The results showcase the synergistic effects achieved by mixed multiple-component metal oxides, leading to improved supercapacitive properties. Full article

A flexible all-solid-state supercapacitor with fast charging speed and high power density is a promising high-performance energy storage and sensor device in photovoltaic systems. Two-dimensional black phosphorus (BP) is a prospective electrode nanomaterial, but it struggles to fully exert its properties limited by its self-stacking. Herein, by embedding carbon nanoparticles into the interlayer of BP microplates, the designed BP/carbon nanoframe (BP/C NF) forms a certain nano-gap on the substrate for promoting the orderly transport of charges. The corresponding supercapacitor BP/C SC has a capacity of 372 F g⁻¹, which is higher than that constructed from BP microplates (32.6 F g⁻¹). Moreover, the BP/C SC exhibits good stability with a ca. 90% of capacitance retentions after 10,000 repeated bending and long-term cycles. Thus, the proposed strategy of using BP/carbon nanoframes is feasible to develop exceptional flexible energy devices, and it can guide the design of relevant two-dimensional nanocomposites. Full article

Personal, portable, and wearable electronics have become items of extensive use in daily life. Their fabrication requires flexible electronic components with high storage capability or with continuous power supplies (such as solar cells). In addition, formerly rigid tools such as electrochromic windows find new utilizations if they are fabricated with flexible characteristics. Flexibility and performances are determined by the material composition and fabrication procedures. In this regard, low-cost, easy-to-handle materials and processes are an asset in the overall production processes and items fruition. In the present mini-review, the most recent approaches are described in the production of flexible electronic devices based on NiO as low-cost material enhancing the overall performances. In particular, flexible NiO-based all-solid-state supercapacitors, electrodes electrochromic devices, temperature devices, and ReRAM are discussed, thus showing the potential of NiO as material for future developments in opto-electronic devices. Full article