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CuFeS2 has many advantages, like high electrical conductivity, multiple redox centers, natural abundance and nontoxic. However, the low capacitance limits their application. In this work, we use carbon spheres (CS) prepared from starch to modify CuFeS2. The prepared CuFeS2/CS shows special structures with the CS as the core and CuFeS2 as the shell. These CuFeS2/CS nanocomposites show improved capacitive performance. CuFeS2/CS has a specific capacitance of 349.4 F g − 1 at 0.5 A g − 1 , four times that of pristine CuFeS2 (88.8 F g − 1) , which might be attributed to the increased electrolyte diffusion capacity. The cyclic stability is also slightly improved, from 86.4% of the pristine CuFeS2 to 90.5% of the CuFeS2/CS nanocomposites due to the rigid structure of both crystal CuFeS2 and firm CS. These CuFeS2/CS nanocomposites are expected to be used in high-performance supercapacitor applications. CuFeS2/CS nanocomposites have a special structure, with the CS as the core and CuFeS2 as the shell. They show improved capacitive performance, with the specific capacitance of 349.4 F g–1 for CuFeS2/CS at the current density of 0.5 A g–1, which is almost 4 times that of pristine CuFeS2 (88.8 F g–1). Cyclic stability is also slightly improved, from 86.4% of the pristine CuFeS2 to 90.5% of the CuFeS2/CS nanocomposites. [ABSTRACT FROM AUTHOR]

In this paper, a high‐gain bidirectional DC–DC converter is presented for electric vehicles where low terminal voltage source like a supercapacitor is used along with the battery. The supercapacitor provides or absorbs large amount power during acceleration and deacceleration and extends the life of main energy source, that is, battery. The supercapacitor terminal voltage varies considerably during charging and discharging activities; hence, a bidirectional DC–DC converter with a high‐voltage conversion ratio must be used to connect the lower supercapacitor voltage to the higher DC‐link voltage. Such application requires steep voltage conversion ratio along with continuous gain‐based bidirectional DC–DC converters. In this study, a typical CuK converter is employed to produce a voltage gain of 3X and X/3 with the ability to transmit power in both directions. The suggested bidirectional converter has a continuous current on both the low‐ and high‐voltage sides, which reduces the requirement for filter capacitance and increases the lifespan of the supercapacitor and DC‐link capacitor. Further, inherent inrush current safety is provided by the proposed converter as the inclusion of an inductor in the path of capacitor charging or discharging. Both in the charging and discharging phases, a detailed steady‐state analysis of the proposed circuit was performed. Moreover, a deep discharge analysis of the supercapacitor and its implication on the performance of the converter is also investigated. [ABSTRACT FROM AUTHOR]

Present work reports on the synthesis of NiO-incorporated nanotorous ZrO2 synthesized by facile co-precipitation method for supercapacitor application. The as-synthesized composite was characterised using FTIR and XRD confirming the successful synthesis of ZrO2-NiO composite (ZNC). FESEM analysis also revealed morphology transition from nanoclusters of tiny ZrO2 particles and stacked flakes of NiO to self-assembled nanotorus ZNC. Electrochemical analyses (like CV, GCD, EIS) also revealed improved electrochemical behaviour of ZrO2 whose specific capacitance increased from 87.77 F/g to 251 F/g in ZNC at 1 A/g. This could be attributed to the synergistic effect of nanotorous morphology in the presence of NiO. These observations were well complemented by a reduced band gap (~ 2.96 eV) and lower charge transfer and solution resistance. A mechanistic insight was also proposed for a deeper understanding of the development of torous structured material. This work provides a closer look into how NiO-driven torous morphology of ZrO2-NiO composite has improved the electrochemical performance of ZrO2. [ABSTRACT FROM AUTHOR]

Designing potential architectures by the modification of conventional electrode materials is an effective approach in the development of high performance supercapacitor electrodes. The present study investigated the effect of varying anodization voltages (50, 75, and 100 V) on the morphology and electrochemical properties of titanium nanotubes (TNT). Molybdenum was doped onto TNT using a simple hydrothermal procedure, followed by thermal treatment at 450 °C. The study effectively demonstrated control over the dimensions of the nanotube structure by adjusting the anodization voltage. Additionally, it was found that the tube diameters were increased due to etching during the hydrothermal treatment with the Mo precursor, which potentially enhanced the supercapacitive performance of Mo‐doped TNT. Further, structural analysis revealed that Mo doping improved both crystallinity and electrode stability. With an optimal anodization voltage of 100 V, TNT and Molybdenum‐doped TNT could exhibit capacitance value of 13.34 and 326.54 mF cm−2 respectively, at a current density of 1 mA cm−2. Furthermore, the electrode demonstrated good cyclic stability with 88% capacitance retention and 97% coulombic efficiency after 5000 cycles. An impressive energy density of 87.03 µWh cm−2 and a power density of 799.99 µW cm−2 could be achieved with this sample in an asymmetrical device. [ABSTRACT FROM AUTHOR]

With its distinctive multiple electrochemical reaction, iron vanadate (FeV3O9.2.6H2O) is considered as a promising electrode material for energy storage. However, it has a relatively low practical specific capacitance. Therefore, using the low temperature sol–gel synthesis process, transition metal doping was used to enhance the electrochemical performance of layered structured FeV3O9.2.6H2O (FVO). According to this study, FVO doped with transition metals with larger interlayer spacing exhibited superior electrochemical performance than undoped FVO. The Mn-doped FVO electrode showed the highest specific capacitance and retention of 143 Fg−1 and 87%, respectively, while the undoped FVO showed 78 Fg−1 and 54%. [ABSTRACT FROM AUTHOR]

The Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo2O4 nanosheet could self-assemble on the Co3O4 nanowire. The structure and morphology of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge–discharge, charge–discharge cycle, and electrochemical impedance and then compared with the Co3O4 nanowire. The results show that the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could reach a high value of 2034 F g−1 at a current density of 2.5 A g−1. After 5000 galvanostatic charge–discharge cycles, the specific capacitance of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) Ti3C2T x MXene-based materials have attracted widespread attraction in the field of energy storage owing to their high conductivity and accordion-like structure. However, challenges such as restacking and oxidative degradation of the Ti3C2T x MXene structure lead to poor stability, low conductivity, low specific capacitance and, consequently, a low specific energy, hindering their extensive adoption at an industrial scale. In this study, a ternary MXene/polyaniline (PANI)/ZnO (MPZ) composite has been synthesized via surface engineering of two-dimensional (2D) MXene using one-dimensional (1D) PANI nanowires and ZnO nanoparticles to enhance its specific energy and stability while sustaining its specific power. 1D PANI nanowires and ZnO nanoparticles act as spacers to prevent restacking, while also exposing the suppressed redox active sites of 2D MXene and preventing it from being oxidized by forming a porous conductive network all over the surface of the MXene. PANI and ZnO also provide additional electroactive redox sites by forming p–n heterojunctions, thus enhancing faradaic redox reactions and the specific capacitance of the MPZ composite. As a result, the overall electrochemical performance and stability of the ternary MPZ composite are enhanced due to the synergistic interactions among the individual components within the ternary MPZ composite. At a low current density of 0.1 A g−1, the ternary MPZ composite exhibited a maximum specific capacitance of 651.96 F g−1 and a highest specific energy of 32.59 Wh Kg−1 while maintaining a specific power of 60 W Kg−1 as compared to MXene and binary MP composite. Furthermore, it showcased exceptional cyclic stability over 10 000 cycles with 94.75% and 92.95% capacitive retention at 0.6 A g−1 current density and 40 mV s−1 scan rate, respectively. Thus, this current study highlights an effective strategy to enhance the specific energy of MXene-based supercapacitors through surface engineering and the construction of p–n heterojunctions within the composite. [ABSTRACT FROM AUTHOR]

[Display omitted] Nickel-aluminium layered double hydroxides (NiAl-LDHs) have emerged as promising electrode materials for supercapacitors (SCs) due to their inherently high specific surface area and theoretical specific capacitance, which are primarily attributed to the rapid pseudocapacitive response at the surface. However, NiAl-LDHs typically form agglomerated nanosheets, leading to a significant reduction in specific surface area, which is crucial for enhancing the number of active sites and improving the capacitive properties of the materials. To overcome this limitation, 2D nanostructures were assembled into 3D architectures by synthesizing NiAl-LDHs with distinct morphologies in a one-step hydrothermal process using an alkaline agent (NH 4 F). This approach resulted in the formation of 3D NiAl-LDH/HN 4 F structures, which exhibit a larger contact area and a greater number of redox-active sites. Consequently, the 3D NiAl-LDH/HN 4 F electrodes demonstrated a significantly higher specific surface area, leading to remarkable improvements in specific capacitance (1219 ± 30F g−1) and energy density (61 ± 1 Wh kg−1) compared to their 2D counterparts. This structural enhancement increases both the surface area and active site density while providing a new framework for designing high-performance LDH-based electrodes. [ABSTRACT FROM AUTHOR]

Despite graphene being considered an ideal supercapacitor electrode material, its use in commercial devices is limited because few methods exist to produce high‐quality graphene at a large scale and low cost. A simple method is reported to synthesize 3D graphene by graphenization of coal tar pitch with a K2CO3 catalyst. This produces 3D graphenes with high specific surface areas up to 2113 m2 g−1 and exceptional crystallinity (Raman ID/IG as low as ≈0.15). The material has an outstanding specific capacitance of 182.6 F g−1 at a current density of 1.0 A g−1. This occurs at a mass loading of 30 mg cm−2 which is 3 times higher than commercial requirements, yielding an ultra‐high areal capacitance of 5.48 F cm−2. The K2CO3 is recycled and reused over 10 cycles with material quality and electrocapacitive performance of 3D graphene retained and verified after each cycle. The synthesis method and resulting electrocapacitive performance properties create new opportunities for using 3D graphene more broadly in practical supercapacitor devices. [ABSTRACT FROM AUTHOR]

Cobalt- and calcium-based metal–organic frameworks (Co-MOF and Ca-MOF) [Co (tpa) (Mi) and Ca (tpa)] (tpa = terephthalic acid and Mi = methyl imidazole) were synthesised through solvothermal method. Structural characterisation revealed that metal centres are equally occupied by Co2+ and Ca2+ ions. Supercapacitive behaviour of synthesised Co-MOF and Ca-MOF was evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements in 6 M KOH as electrolyte. The Co- and Ca-MOFs exhibited outstanding specific capacitance of 1726 and 185 Fg−1 at a discharge current density of 1 Ag−1, good rate capability, and 97.4% capacitance retention after 3000 cycles. To the best of our knowledge, Co-MOFs and Ca-MOFs are used in supercapacitor, and their encouraging properties indicate that Co-/Ca-MOF can be a promising candidate as an advanced electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

In this research, manganese cobaltite (MCO) nanoparticles with different morphologies were synthesized by a simple hydrothermal method with excellent electrochemical properties. To investigate the physical features of prepared samples, XRD analysis was used to study the crystalline structure. The SEM and TEM proved that the morphology of synthesized materials formed as flake and nanoplane structures. The electrode of samples was prepared using the hydrothermal method and the electrochemical properties of samples were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cyclic stability analysis. Results showed that the flake structures of nanoparticles revealed the highest capacitance of 1971.98 F ⋅ g − 1 at 0.5 Ag − 1 as well as longer stability compared to the others with the nanoplane structure. The high cyclic stability of 91.47% after 5000 cycles introduces this electrode as a durable and promising electrode for use in energy storage devices. [ABSTRACT FROM AUTHOR]

As the precursor of 2D i -MXene, i -MAX phase appeals lots of exertions on the improvement of its chemical diversity, among which alloying is an effective strategy. Herein, we report on the synthesis of the M-alloyed i -MAX phase (Mo 0.75 M 0.25) 4/3 Er 2/3 GaC (M = Ti, V, Nb, Ta, W). Structure analysis identifies all of them as Cmcm orthorhombic. The corresponding M-alloyed i -MXene, (Mo 0.75 M 0.25) 1.33 CT z (M = Ti, V, Nb, Ta, W), was synthesized by HF etching and shows potential as an electrode for supercapacitors due to its improved charge storage performance and cyclic stability. A volumetric capacitance of 431.7 F g−1 was delivered at the scan rate of 2 mV s−1 for (Mo 0 · 75 V 0.25) 1.33 CT z , and a 94.8% capacitance was retained after 10,000 charge/discharge cycles for (Mo 0 · 75 W 0.25) 1.33 CT z. Modelling was performed to better understand the mechanism improving the electrochemical capacitance and to clarify the i-MXene alloying process. The alloying strategy shows a novel and simple way to control i-MXene's surface termination, which will make it facilitate to use in applications like high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

It is of great scientific and economic value to recycle waste poly (ethylene terephthalate) (PET) into high-value PET-based metal organic frameworks (MOFs) and further convert it into porous carbon for green energy storage applications. In the present study, a facile and costeffective hydrothermal process was developed to direct recycle waste PET bottles into MIL-53(Al) with a 100% conversation, then the MOFderived porous carbon was assembled into electrodes for high-performance supercapacitors. The results indicated that the as-synthesized carbon exhibited high SSA of 1712 m2 g-1 and unique accordion-like structure with hierarchical porosity. Benefit to these advantageous characters, the assembled three-electrode supercapacitor displayed high specific capacitances of 391 F g-1 at the current density of 0.5 A g-1 and good rate capability of 73.6% capacitance retention at 20 A g-1 in 6 mol L-1 KOH electrolyte. Furthermore, the assembled zinc ion capacitor still revealed outstanding capacitance of 335 F g-1 at 0.1 A g-1, excellent cycling stability of 92.2% capacitance retention after 10 000 cycles and ultra-high energy density of 150.3 Wh kg-1 at power density of 90 W kg-1 in 3 mol L-1 ZnSO4 electrolyte. It is believed that the current work provides a facile and effective strategy to recycle PET waste into high-valuable MOF, and further expands the applications of MOF-derived carbons for high-performance energy storage devices, so it is conducive to both pollution alleviation and sustainable economic development. [ABSTRACT FROM AUTHOR]

Difunctional devices have great potential in the application of many areas, they can perform two functions simultaneously, and structural difunctional supercapacitor is one of them. The difunctional supercapacitor can carry out bearing capacity and storge electric energy, but it's difficult to keep the balance between bearing capacity and energy storage capacity. In this work, the montmorillonite based geopolymer has a compressive strength of 31.6 MPa after curing for 28 days, and a compressive strength of 30.5 MPa after repolymerization. We use the geopolymer as the framework, and inject 0.5 M Na 2 SO 4 into the geopolymer to prepared a structural electrolyte. Then, the structural electrolyte membrane, electrodeposited MnO 2 , and an activated carbon are assembled into a difunctional supercapacitor. The maximum specific capacity reaches 2216.7 mF cm−2 at 1 mA cm−2 under 15 MPa, achieving a good balance between compressive strength and energy storage capacity. [ABSTRACT FROM AUTHOR]

In the present work, a novel composite of nickel sulfide (NiS) and potato peel‐derived carbon spheres (NiS/PPCS) with higher specific capacitance and cyclic performance was synthesized as electrode material for supercapacitor applications. The composite was deposited on a graphite rod to be use as an electrode. The electrochemical performance studies using CV, GCD, and EIS revealed that the prepared electrode showed an improved current response and higher specific capacitance than the pristine NiS electrode. The maximum specific capacitance for the NiS/PPCS electrode was found to be 2185 F/g at 0.2 A/g current density. More precisely, it was observed that the NiS/PPCS composite exhibited an excellent retention capacity of 95.04% after 20 000 continuous charge‐discharge cycles, showing its exceptional cyclic performance. The impedance studies revealed that the reaction between the NiS/PPCS electrode and electrolyte was rapid and highly reversible. Based on the findings of the electrochemical performances, NiS/PPCS electrode appears to be a potential candidate for highly efficient and economical asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

This study explores the impact of nickel (Ni) doping bismuth ferrite (BiFeO3) thin film synthesis by spray pyrolysis method. The structural and morphological study shows that the thin films are slightly amorphous with granular morphology. Investigated the supercapacitive behavior of synthesized material by using cyclic voltammetry, galvanostatic charge‐discharge, and electrochemical impedance spectroscopy. The thin films synthesized are capable of storing a 253.31 F/g capacitance at a 10 mV/s scan rate and by introducing nickel into the synthesis process, we obtained 312.12 F/g capacitance at a 10 mV/s scan rate. The material shows good cyclic stability after 91000 cycles. It is also observed that no structural and morphological changes were made by doping Ni into BiFeO3 thin films. The significant improvement in capacitance was displayed by Ni doping into BiFeO3 obtained via spray pyrolysis methods indicating its potential for use in supercapacitor applications. [ABSTRACT FROM AUTHOR]

Nanourchin VO2 nanostructures have been effectively synthesized by hydrothermal method. The synthesized hierarchical nanostructure has been characterized by various characterization techniques and electrochemical behaviour has been studied. X-ray diffraction analysis revealed the monoclinic phase and morphological analysis (FESEM) of VO2 showed nanourchin-like structure with arrangement of various nanorods in radial fashion. Over these nanorods, formation of secondary growth of asterisk-shape structure was observed. The width and length of nanorods were ~ 50 and ~ 75 nm, respectively. For the electrochemical measurements, 2032 type coin cells were fabricated using VO2 as electrode material. The electrochemical study of VO2 exhibited the pseudocapacitive behaviour with specific capacitance of 44 F g−1 in organic electrolyte with symmetric capacitor of two electrode system. The maximum energy density and power density were 44 and 8635 Wh kg−1, respectively. Cycling performance exhibited symmetric charge–discharge curves, and also specific capacitance was maintained up to 82% of initial value. [ABSTRACT FROM AUTHOR]

Nanourchin VO2 nanostructures have been effectively synthesized by hydrothermal method. The synthesized hierarchical nanostructure has been characterized by various characterization techniques and electrochemical behaviour has been studied. X-ray diffraction analysis revealed the monoclinic phase and morphological analysis (FESEM) of VO2 showed nanourchin-like structure with arrangement of various nanorods in radial fashion. Over these nanorods, formation of secondary growth of asterisk-shape structure was observed. The width and length of nanorods were ~ 50 and ~ 75 nm, respectively. For the electrochemical measurements, 2032 type coin cells were fabricated using VO2 as electrode material. The electrochemical study of VO2 exhibited the pseudocapacitive behaviour with specific capacitance of 44 F g−1 in organic electrolyte with symmetric capacitor of two electrode system. The maximum energy density and power density were 44 and 8635 Wh kg−1, respectively. Cycling performance exhibited symmetric charge–discharge curves, and also specific capacitance was maintained up to 82% of initial value. [ABSTRACT FROM AUTHOR]

The concept of pseudocapacitance is explored as a rapid and universal method for the state of health (SOH) determination of batteries and supercapacitors. In contrast to this, the state of the art considers the degradation of a series of full charge/discharge cycles. Lithium-ion batteries, sodium-ion batteries and supercapacitors of different cell chemistries are studied by impedance spectroscopy during lifetime testing. Faradaic and capacitive charge storage are distinguished by the relationship between the stored electric charge and capacitance. Batteries with a flat voltage–charge curve are best suited for impedance spectroscopy. There is a slight loss in the linear correlation between the pseudocapacitance and Ah capacity in regions of overcharge and deep discharge. The correct calculation of quantities related to complex impedance and differential capacitance is outlined, which may also be useful as an introductory text and tutorial for newcomers to the field. Novel diagram types are proposed for the purpose of the instant performance and failure diagnosis of batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

Novel flake-like Ni1−xSnxO2 particles were successfully prepared by template-free hydrothermal synthesis. The prepared samples were investigated for their properties by different characterization techniques. Scanning micrographs showed that the obtained particles consisted of nanoflakes. The X-ray diffraction results of the Ni1−xSnxO2 revealed the formation of mixed-phase Ni/SnO2 having the typical tetragonal structure of SnO2, and the cubic structure of Ni in a nanocrystalline nature. The doping with Ni had a certain influence on the host's lattice structure of SnO2 at different doping concentrations. Confirmation of the functional groups and the elements in the nanomaterials was accomplished using FTIR and EDS analyses. The electrochemical performance analysis of the prepared nanomaterials were carried out with the help of the CV, GCD, and EIS techniques. The specific capacitance of the synthesized nanomaterials with different concentrations of Ni dopant in SnO2 was analyzed at different scanning rates. Interestingly, a 5% Ni-doped SnO2 nanocomposite exhibited a maximum specific capacitance of 841.85 F g−1 at 5 mV s−1 in a 6 M KOH electrolyte. Further, to boost the electrochemical performance, a redox additive electrolyte was utilized, which exhibited a maximum specific capacitance of 2130.33 at 5 mV s−1 and an excellent capacitance retention of 93.22% after 10,000 GCD cycles. These excellent electrochemical characteristics suggest that the Ni/SnO2 nanocomposite could be utilized as an electrode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

MgCo 2 O 4 is a promising electrode material in electrochemical energy storage devices. In this work, the supercritical CO 2 -assisted solvothermal (SCAS) method was applied to synthesize MgCo 2 O 4 nanomaterials for the first time. The crystallite size of the MgCo 2 O 4 prepared by SCAS was significantly smaller than the one prepared by the ethanol solvothermal method, reaching 9.0 nm at a CO 2 pressure of 16 MPa. The as-prepared MgCo 2 O 4 nanospheres exhibited a special spherical structure with abundant irregular pores and a high specific surface area of 69.9 m2/g. X-ray photoelectron spectroscopy demonstrated that the Co3+/Co2+ ratio of the MgCo 2 O 4 was increased by the SCAS method and the mechanism of synthesizing MgCo 2 O 4 nanospheres was explored. In addition, the MgCo 2 O 4 electrode material prepared by the SCAS method exhibited a high specific capacitance of 741 F/g at 0.1 A/g. The results confirm that the SCAS method can synthesize ultrafine MgCo 2 O 4 nanoparticles with special morphology and high specific surface area, which are expected to be applied in high-performance electrode materials. [ABSTRACT FROM AUTHOR]

Nanostructured material like FeSe 2 has been synthesized through a simple and cost-effective hydrothermal method. The effect of cationic, non-ionic, and anionic surfactants has been studied on the structural, morphological, and electrochemical properties of FeSe 2 electrode material. The FeSe 2 electrode material prepared with the assistance of CTAB surfactant displayed a superior specific capacitance value of 401 F g −1 at a scan rate of 10 mV s −1 and 337 F g −1 at a current density of 3.3 A g −1, respectively. The maximum energy density of the symmetric supercapacitor cell fabricated with the same material is evaluated to be 47 Wh kg−1 at a power density of 1667 W kg−1. The addition of the surfactant cetyltrimethylammonium bromide (CTAB) during the synthesis process is found to have a significant impact on the charge storage capability of the material, which is attributed to an increase in active surface area, porosity, reduced crystallite size, and reduced bulk resistance, etc. The real-time use of CTAB-based FeSe 2 symmetric cells has been verified via illuminating different voltage light-emitting diodes. Further, the electronic properties and the quantum capacitance of FeSe 2 material synthesized without the assistance of any surfactant have been analyzed theoretically using first-principles density functional theory calculations. Acquired results unveil the potential growth of FeSe 2 electrode material in energy storage applications. [ABSTRACT FROM AUTHOR]

State‐of‐the art Electrochemical Double‐Layer Capacitors (EDLCs) usually extend their operating electrochemical stability window (ESW) by means of organic electrolytes, or highly concentrated aqueous (water‐in‐salt) electrolytes hindering parasitic water splitting reactions. Unfortunately, organic solvents and high concentrations of ions penalize the dielectric constant of the electrolyte, hence the capacitive performance. We suggest here a new concept of cost‐effective and sustainable aqueous electrolytes based on concentrated amino acid water solutions with a dielectric permittivity much higher than pure water, unlocking the capacitive performance of aqueous EDLC references. Amino acids are natural zwitterionic molecules with a large separation between the positive and negative moiety, leading to huge dipoles with excellent dielectric properties. Some of them (e. g., lysine and proline), have a solubility ≥ ${\ge }$ 10 m at ambient temperature. With an experimental characterization we prove that aqueous EDLCs based on electrolytes obtained with L‐ lysine or L‐proline added to 2 M NaNO3 solution have +50 % of gravimetric capacitance enhancement at low specific currents (0.1 A/g) compared to a reference device based on 2 M NaNO3 electrolyte without amino acids. A theoretical model suggests that this performance may be further enhanced by increasing the ionic accessibility of commercially available active materials, with porosity optimized to the size of amino acid ions. [ABSTRACT FROM AUTHOR]

Electrode materials with high electrochemical activity and outstanding stability is of great significance to improve the performance of supercapacitors. A composite material comprised of core-shell FeCo 2 O 4 @FeCo 2 S 4 nanospheres and MXene nanosheets was synthesized through solvothermal combined with self-assembly. The FeCo 2 O 4 @FeCo 2 S 4 -MXene hybrids as electrode materials exhibit a high specific capacitance of 1090.6 F g−1 at 1 A g−1. All-solid-state supercapacitor using FeCo 2 O 4 @FeCo 2 S 4 -MXene as the positive electrode possesses a high energy density of 49.8 Wh kg−1 at 800 W kg−1and great cycle life with 87.85 % retention over 20,000 cycles at 1 A g−1. The synergistic effect of FeCo 2 O 4 @FeCo 2 S 4 and MXene is the main reason for the exceptional electrochemical performance. FeCo 2 O 4 @FeCo 2 S 4 anchored to MXene prevents the restacking of MXene, while MXene provides a conductive network for accelerating carrier transfer and a skeleton for preventing FeCo 2 O 4 @FeCo 2 S 4 from collapsing during long-term cycling. In view of the above excellent performance, this study provides a feasible idea for future research on high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights: A low-strength-centrifugation-assisted approach for rapid gelation of Ti3C2Tx MXene with a very low dispersion concentration into multifunctional 3D architectures is developed. On the basis of pH-induced surface termination changes, the MXene gels exhibit reconfigurable internal structures and tunable rheological, tribological, electrochemical, infrared-emissive and photothermal-conversion properties. By adopting a gel with optimized pH value, high lubrication, remarkable capacitance, long-term capacitance retention and high-precision screen- or extrusion-printing into high-resolution anticounterfeiting patterns can be achieved. Due to the mutual repulsion between their hydrophilic surface terminations and the high surface energy facilitating their random restacking, 2D MXene nanosheets usually cannot self-assemble into 3D macroscopic gels with various applications in the absence of proper linking agents. In this work, a rapid spontaneous gelation of Ti3C2Tx MXene with a very low dispersion concentration of 0.5 mg mL−1 into multifunctional architectures under moderate centrifugation is illustrated. The as-prepared MXene gels exhibit reconfigurable internal structures and tunable rheological, tribological, electrochemical, infrared-emissive and photothermal-conversion properties based on the pH-induced changes in the surface chemistry of Ti3C2Tx nanosheets. By adopting a gel with optimized pH value, high lubrication, exceptional specific capacitances (~ 635 and ~ 408 F g−1 at 5 and 100 mV s−1, respectively), long-term capacitance retention (~ 96.7% after 10,000 cycles) and high-precision screen- or extrusion-printing into different high-resolution anticounterfeiting patterns can be achieved, thus displaying extensive potential applications in the fields of semi-solid lubrication, controllable devices, supercapacitors, information encryption and infrared camouflaging. [ABSTRACT FROM AUTHOR]

Graphene electrodes were firstly printed on recycled single‐use‐packets. Later, the Ni50Mn35In15 (NMI) alloy or Ca2.9Nd0.1Co3.9Cu0.1O9, (CNCCO) misfit perovskite was deposited on the graphene electrodes to enhance their capacitive performance. Next, flexible supercapacitors (SCs) were assembled by using such electrodes. The SCs made with NMI and CNCCO powders were named as GNMI‐SC, and GCNCCO‐SC, respectively. Those ones produced capacitances/energy‐densities of 761.8 F g−1/152.6 Wh kg−1 and 207.7 F g−1/41.6 Wh kg−1, respectively. Subsequently, a mixture 1 : 1 of NMI and CNCCO powders was melted/coalesced at 1700 °C by using a plasma treatment in argon atmosphere and obtained in this way a NMI/CNCCO composite powder. The SC made with this last composite generated a capacitance/energy‐density of 1235.2 F g−1/247.3 Wh kg−1. Those last values are 62–500 % higher than these for the GNMI‐SC, and GCNCCO‐SC devices. Other benefits obtained after the introduction of the NMI/CNCCO powders into the SCs were: 1) the formation of additional Cu2+, Mn4+, Nd2+ and In3+ species, which enhanced the capacitance; 2) the capacitance retention was maintained above 93 % after 500 cycles of charge discharge; and 3) the lowest values of series and charge transfer resistances were obtained, which favored the ion diffusion/storage in the SC electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] 1D-molybdenum disulfide (MoS 2) nanoscrolls displayed enhanced electrochemical properties compared to 2D-MoS 2 nanosheet counterparts. Rolling of nanosheets is the main fabrication route to nanoscrolls. However, owing to the conflict between chemical stability and multiple bending, the morphology transition from nanosheets to nanoscrolls is quite challenging. Herein we describe a reversible morphology transition from nanosheets to nanoscrolls by utilizing non-covalent interactions between MoS 2 nanosheets and phenothiazine based organic dye. Interestingly, nanoscrolls can easily be opened back into nanosheets by destroying the non-covalent interactions with organic solvents. The prepared nanoscrolls exhibited enhanced electrochemical properties than nanosheets. Compared to nanosheets, nanoscrolls exhibited comparatively lower overpotential with a Tafel slope of 141 mV dec-1 and high specific capacitance of 1868 F g−1. Hydrogen evolution by the Volmer-Heyrovsky mechanism being superior for the nanoscrolls is envisaged by the relatively increased availability of H ads sites at MoS 2 edges induced by scrolling. Whereas the high specific capacitance value of nanoscrolls is ascribed to the enhanced electrical double-layer capacitance mediated charge storage, which arises due to the synergistic effect of both scrolled structure and the electron-rich phenothiazine-based dye. [ABSTRACT FROM AUTHOR]

One-dimensional NiMoO4 nanofibers were successfully prepared by electrospinning and high-temperature calcination. The supercapacitor performance tests were conducted on the prepared materials in a three-electrode system, and it was found that the calcination temperature during the preparation of the fibers seriously affects the final morphology and electrochemical performance of the obtained samples. The sample with a calcination temperature of 500 °C has better performance, its specific capacitance can reach 1947 F g−1, and the retention rate is 82.35% after 3000 cycles of constant current charging–discharging. The improvement of electrochemical performance is primarily on account of the unique one-dimensional nanostructure of the material, which can both enhance the charge transfer efficiency and effectively increase the speed of electrolyte ion diffusion. [ABSTRACT FROM AUTHOR]

It is an effective way to prepare multi‐dimensional and multicomponent electrode material to enhance the capacitance of supercapacitors. The multi‐dimensional micro CuCo2O4/nano NiCo2S4 structure was synthesized by wrapping NiCo2S4 nanosheets on urchin‐like CuCo2O4 microspheres on the surface of nickel foam by two‐step hydrothermal method, and then electrochemical deposition. Due to the synergistic effect of the one‐dimensional CuCo2O4 and the two‐dimensional NiCo2S4 composite and its especial three‐dimensional core‐shell structure, the composite electrode shows excellent supercapacitor performance. The CuCo2O4@NiCo2S4 with three electrodeposition cycles (CCO@NCS‐3) exhibits a high specific capacitance of 2283.3 F g−1 at 1 A g−1, good rate capability (79.9 % capacitance retention at 10 A g−1) and cycling stability of 84.0 % over 3000 cycles. All these results indicate that the concepts of multi‐dimensional and multi‐component integration provide a general approach for the development of high‐performance materials. [ABSTRACT FROM AUTHOR]

Supercapacitors have attracted considerable attention due to their advantages, including being lightweight and having rapid charge–discharge, a good rate capability, and high cyclic stability. Electrodes are one of the most important factors influencing the performance of supercapacitors. Herein, a three-dimensional network of rough and porous micropebbles of CeCu2Si2 has been prepared using a one-step procedure and tested for the first time as a supercapacitor electrode. The synthesized material was extensively characterized in a three-electrode configuration using different electrochemical techniques, such as cyclic voltammetry (CV), galvanostatic charge and discharge (GCD) tests, and electrochemical impedance spectroscopy (EIS). CeCu2Si2 shows rather high mass-capacitance values: 278 F/g at 1 A/g and 295 F/g at 10 mV/s. Moreover, the material exhibits remarkable long-term stability: 98% of the initial capacitance was retained after 20,000 cycles at 10 A/g and the Coulombic efficiency remains equal to 100% at the end of the cycles. [ABSTRACT FROM AUTHOR]

In this paper, NiCo2S4 nanoelectrode materials were prepared by a two-step hydrothermal method. Physical and morphological characterization and electrochemical testing revealed that the prepared NiCo2S4 has a sea urchin-like layered three-dimensional network structure, which can fully increase the contact area with the electrolyte, increase the active sites and improve the electrochemical performance. The specific capacitance of the prepared NiCo2S4 nanomaterials reached 717.32 F/g. The cyclic voltammetry test curve as well as galvanostatic charge-discharge (GCD) test curve have perfect symmetry, good material reversibility. Electrochemical impedance spectroscopy (EIS) indicates materials with low impedance. The specific capacitance remained 76.8% after 3000 cycles and the electrochemical stability was good. NiCo2S4 electrode material has excellent electrochemical properties and has a promising application in supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

The ZnS–ZnO/graphitic carbon nitride (g-C3N4) nanocomposite was synthesized using the hydrothermal method, incorporating 0.05 g of g-C3N4 during the composite formation. The crystalline nature of the materials was confirmed through X-ray diffraction analysis. Scanning electron microscope and transmission electron microscope analyses revealed the morphological properties of the materials. The nanocomposite exhibited 2D g-C3N4 nanosheets with a thickness of 7.8 nm. Additionally, the nanocomposite consisted of spherical particles with an average particle size of 15 nm, which were distributed over the 2D g-C3N4 sheets. ZnS–ZnO/g-C3N4 nanocomposite consists of spherical particles with an average particle size of 15 nm that covers the 2D g-C3N4 sheets. ZnS–ZnO/g-C3N4 nanocomposites without/with polypyrrole are used as a paste for the two-symmetric electrodes hybrid supercapacitor. The charge (0.5 to 1.3 A/g), cyclic voltammetry (0.0 to 1.0 potential window), impedance, and stability for the prepared supercapacitor are studied using electrochemical measurements. ZnS–ZnO/g-C3N4 supercapacitors have a specific capacitance of 15.1 and 152.2 F/g without/with the physical addition of polypyrrole, respectively. Also, they have energy density values of 1.17 and 11.87 W h/kg, respectively. Through the Randles cell, The Rs in the supercapacitor without/with polypyrrole are 6.9 and 6.65 Ω, respectively. While the values of the semicircle diameter (Rct) are 0.37 and 0.25 Ω, respectively. Also, the capacitance retention values are 88.6 and 90.2% without/with polypyrrole addition until 500 runs of charge/discharge. These values confirm the behavior of the polypyrrole material in the enhancement of the supercapacitor efficiency, storage capacity, and stability. [ABSTRACT FROM AUTHOR]

As a typical pseudocapacitor material, VOx 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@VOx nanobelt with a core-shell architecture was constructed via a two-step route. This strategy involves the preparation of VOx using a solvothermal method, and a subsequent in situ polymerization process of the PANI. By virtue of the synergistic effect between the VOx core and the PANI shell, the optimal VOx@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 (VOx@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. [ABSTRACT FROM AUTHOR]

In this research study, the triplumbic tetroxide (Pb3O4)/tricobalt tetroxide (Co3O4) nanocomposites (NCs) were synthesized by using the modified process of inverse microemulsion for electrochemical applications. The cyclic voltammetry results indicated that the NCs exhibited excellent results in terms of the capacitance (with the highest specific capacitance and energy density values of 892.01 F g−1 and 60.70 W h g−1 respectively) for electrochemical applications. Moreover, after 4000 cycles, more than 89% capacitance was sustained for Pb3O4/Co3O4 composite representing their excellent stability. The enhanced supercapacitive properties of these NCs were ascribed to the development of the nanomaterials having a high surface area to volume ratio, enhanced conductivities, and good specific capacitance values acquired by modulating the Co3O4 content in the NCs. [ABSTRACT FROM AUTHOR]

The NiMn2O4/graphene oxide (GO) nanocomposite material was in situ grown on the surface of a nickel foam 3D skeleton by combining the solvent method with the microwave-assisted hydrothermal method and annealing; then, its performance was investigated as a superior supercapacitor electrode material. When nickel foam was soaked in GO aqueous or treated in nickel ion and manganese ion solution by the microwave-assisted hydrothermal method and annealing, gauze GO film or flower-spherical NiMn2O4 was formed on the nickel foam surface. If the two processes were combined in a different order, the final products on the nickel surface had a remarkably different morphology and phase structure. When GO film was first formed, the final products on the nickel surface were the composite of NiO and Mn3O4, while NiMn2O4/GO nanocomposite material can be obtained if NiMn2O4 was first formed (immersed in 2.5 mg/L GO solution). In a 6M KOH solution, the specific capacitance of the latter reached 700 F/g at 1 A/g which was superior to that of the former (only 35 F/g). However, the latter's specific capacitance was still inferior to that of in-situ grown NiMn2O4 on nickel foam (802 F/g). Though the gauze-formed GO film, almost covering the preformed flower-spherical NiMn2O4, can also contribute a certain specific capacitance, it also restricted the electrolyte diffusion and contact with NiMn2O4, accounting for the performance decrease of the NiMn2O4/GO nanocomposite. A convenient method was raised to fabricate the nanocomposite of carbon and double metal oxides. [ABSTRACT FROM AUTHOR]

In this study, the performance of two boron-containing compounds, C14H14BNO2·HCl (BCC1) and C38H38B2Cl2N4O4 (BCC2), as electrodes in supercapacitor applications was investigated in the presence of Na2SO4 and KOH electrolyte solutions. The specific capacitance values of the compounds were compared, and the results showed that trivalent boron (BCC1) exhibited higher specific capacitance values than tetravalent boron (BCC2) in both electrolyte solutions. In the presence of Na2SO4 electrolyte solution, the specific capacitance values of the trivalent (BCC1) and tetravalent (BCC2) boron compounds at a current density of 0.75 A/g were 135.21 and 94.87 F/g, respectively, while in the presence of KOH electrolyte, the specific capacitance values of the trivalent (BCC1) and tetravalent (BCC2) boron compounds at a current density of 0.75 A/g capacitance values were determined as 106.62 and 88.25 F/g, respectively. The cycling stability of the electrodes was also studied, and it was found that the capacitance of BCC1 electrode increased gradually over the cycles, while the capacitance of BCC2 electrode decreased. The study suggests that trivalent boron can be a promising material for supercapacitor applications. However, further research is required to optimize the cycling stability of the electrodes and understand the underlying mechanism. [ABSTRACT FROM AUTHOR]

MXene, a new intercalation pseudocapacitive electrode material, possesses a high theoretical capacitance for supercapacitor application. However, limited accessible interlayer space and active sites are major challenges to achieve this high capacitance in practical application. In order to stimulate the electrochemical activity of MXene to a greater extent, herein, a method of hydrothermal treatment in NaOH solution with reducing reagent-citric acid is first proposed. After this treatment, the gravimetric capacitance of MXene exhibits a significant enhancement, about 250% of the original value, reaching 543 F g−1 at 2 mV s−1. This improved electrochemical performance is attributed to the tailoring of an interlayer structure and surface chemistry state. An expanded and homogenized interlayer space is created, which provides enough space for electrolyte ions storage. The –F terminations are replaced with O-containing groups, which enhances the hydrophilicity, facilitating the electrolyte's accessibility to MXene's surface, and makes MXene show stronger adsorption for electrolyte ion-H+, providing sufficient electrochemical active sites. The change in terminations further leads to the increase in Ti valence, which becomes more prone to reduction. This work establishes full knowledge of the rational MXene design for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

The present investigation details the hydrothermal production of RGO-NiO nanocomposite and examines the electrochemical performance of the composite electrode functioning on an adaptable carbon cloth substrate. The RGO-NiO nanostructures display incredible super-capacitive functionality when used in a two-electrode system with a 2 M KOH-PVA electrolyte. This is due to the unique characteristics of RGO, which functions as a flexible and expandable platform for creating NiO nanocrystals with a nanoscopic spherical morphology. Large surface areas in these nanostructures facilitate ion diffusion, which ultimately raises specific capacitance. The nanocomposite electrode as-prepared displays a robust two-electrode structure, a constant potential window between (0V and 0.45V), and specific capacitances of up to 749F/g from CV at a rate of scan of 5mV/s and 366F/g from GCD at 1A/g. 5000 cycles of cyclic stability were examined, and the capacitance retention was 91.23% after successive cycles. [ABSTRACT FROM AUTHOR]

Herein, an effective method of preparing CNT@NiM-OH nanocomposites by reacting dopamine-modified carbon nanotubes (CNT@PDA) with M(NO3)2 (M = Zn,Co) and 2-methylimidazole is reported. The research results show that CNTs are intertwined to form a network structure surrounded by NiM-OH in CNT@NiM-OH, which provides a more electrolyte contact area and reaction active sites. Electrochemical research indicates that CNT@NiM-OH exhibits excellent electrochemical properties for supercapacitors. The specific capacitances of CNT@NiCoZn-OH, CNT@NiZn-OH and CNT@NiCo-OH were 2039.63, 1930.03 and 1664.73 F/g, respectively, at 1 A/g. In addition, the specific capacitance retention rates of the three electrode materials after 1000 cycles were 97.7%, 99.0% and 85.4%, respectively. [ABSTRACT FROM AUTHOR]

Heteroatom doping is considered an effective method to substantially improve the electrochemical performance of Ti3C2Tx MXene for supercapacitors. Herein, a facile and controllable strategy, which combines heat treatment with phosphorous (P) doping by using sodium phosphinate (NaH2PO2) as a phosphorus source, is used to modify Ti3C2Tx. The intercalated ions from NaH2PO2 act as "pillars" to expand the interlayer space of MXene, which is conducive to electrolyte ion diffusion. On the other hand, P doping tailors the surface electronic state of MXene, optimizing electronic conductivity and reducing the free energy of H+ diffusion on the MXene surface. Meanwhile, P sites with lower electronegativity owning good electron donor characteristics are easy to share electrons with H+, which is beneficial to charge storage. Moreover, the adopted heat treatment replaces –F terminations with O-containing groups, which enhances the hydrophilicity and provides sufficient active sites. The change in surface functional groups increases the content of high valence-stated Ti with a high electrochemical activity that can accommodate more electrons during discharge. Synergistic modification of interlayer structure and chemical state improves the possibility of Ti3C2Tx for accommodating more H+ ions. Consequently, the modified electrode delivers a specific capacitance of 510 F g−1 at 2 mV s−1, and a capacitance retention of 90.2% at 20 A g−1 after 10,000 cycles. The work provides a coordinated strategy for the rational design of high-capacitance Ti3C2Tx MXene electrodes. [ABSTRACT FROM AUTHOR]

Supercapacitor material is an alternative in energy storage. Supercapacitors are charge storage devices that have a high energy density, fast charge/discharge rates, long service life, wide operating temperature range, and are environmentally friendly. Graphene is a nanomaterial that can be used as a supercapacitor because it has high conductivity and a large surface area, but graphene can experience agglomeration so it can affect its capacitance properties. The microwave-assisted method can be used in the synthesis of graphene. Several microwave-based techniques are becoming more popular for producing graphene and altering it. Due to its quick, precise, uniform, and volumetric heating, microwave heating is a promising method for the thermochemical treatment and reduction of graphene oxide to graphene. This research aimed to examine the effect of microwave irradiation time on the capacitive properties of graphene synthesis as a supercapacitor. Graphene oxide (GO) can be reduced into graphene quickly and easily using microwave pulses lasting 15 to 30 minutes to produce high-quality graphene fabrication. The characterization test was performed using UV-Vis, FTIR, SEM-EDX and cyclic voltammetry (CV). As a result, the optimum time is 25 minutes, and it showed an absorption peak at the 282 nm wavelength dan the CV analysis showed that the graphene has double capacitor properties with a specific capacitance of 140.7 F/g in 20 mV/s. Besides, the result of SEM indicated that graphene could be formed successfully. Its potential applications are also illustrated by emphasizing its usage as electrode material. Finally, its main challenges and prospects are considerably pointed out. [ABSTRACT FROM AUTHOR]

In this study, we utilized a successive ionic layer adsorption and reaction (SILAR) route to attach bismuth selenide (Bi 2 Se 3) nanoparticles on one dimensional (1D) cadmium sulfide nanowires (CdS NWs) at ambient temperature (27 °C) to design CdS@Bi 2 Se 3 core-shell nanostructure towards active electrode for supercapacitor application. To verify and explore the retrieved surface configuration, structural, elemental, compositional, and surface morphological investigations were performed. The designed CdS@Bi 2 Se 3 core-shell nanostructure not only offers the tremendous number of active areas, but also a continuous and quick one directional electron transport channels, demonstrating noticeable electrochemical performance with specific capacitance of 198 F g−1 (aerial capacitance 59.5 mF/cm2) with 80% cyclic retention @ 2000 cycles. Superior electrochemical activity was enhanced through the mutualistic involvement of Na+ ion insertion/extraction via non-stoichiometric bismuth selenide, which was well supported through electrochemical impedance (EIS) studies. [ABSTRACT FROM AUTHOR]

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Biomass materials with representative morphologies and compositions were employed to study the activation effect of KHCO3. As the activation time increased from 1 to 3 h, the products derived from puffed rice and pleurotus eryngii achieved a hierarchical porous structure, while the products derived from cotton still presented a microporous structure. In the electrochemical test of a three-electrode system, the specific capacitance of these products was 352, 319, and 216 F g−1, respectively. In the two-electrode system, the PR-2-based symmetric supercapacitor presented with a specific capacitance of 280.7 F g−1 at 0.5 A g−1, and the energy density of 14.03 Wh kg−1 at 150.04 W kg−1 and an energy density retention of 73.7% was at an even higher power density of 8380.4 W kg−1. After 10,000 cycles of charging and discharging at 5 A g−1, the specific capacitance retention of the supercapacitor reached 108.8%. Based on the experimental analysis, a likely mechanism for the formation of pores was proposed. The results indicate that biomass materials with soft layered or a network structure are the best candidates to obtain a hierarchical porous structure by KHCO3 activation. [ABSTRACT FROM AUTHOR]

Due to their rich and adjustable porous network structure, paper-based functional materials have become a research hotspot in the field of energy storage. However, reasonably designing and making full use of the rich pore structure of paper-based materials to improve the electrochemical performance of paper-based energy storage devices still faces many challenges. Herein, we propose a structure engineering technique to develop a conductive integrated gradient porous paper-based (CIGPP) supercapacitor, and the kinetics process for the influence of gradient holes on the electrochemical performance of the CIGPP is investigated through experimental tests and COMSOL simulations. All results indicate that the gradient holes endow the CIGPP with an enhanced electrochemical performance. Specifically, the CIGPP shows a significant improvement in the specific capacitance, displays rich frequency response characteristics for electrolyte ions, and exhibits a good rate performance. Also, the CIGPP supercapacitor exhibits a low self-discharge and maintains a stable electrochemical performance in different electrolyte environments because of gradient holes. More importantly, when the CIGPP is used as a substrate to fabricate a CIGPP-PANI hybrid, it still maintains good electrochemical properties. In addition, the CIGPP supercapacitor also shows excellent stability and sensitivity for monitoring human motion and deaf-mute voicing, showing potential application prospects. This study provides a reference and feasible way for the design of structure-engineered integrated paper-based energy storage devices with outstanding comprehensive electrochemical performance. [ABSTRACT FROM AUTHOR]

This investigation is motivated by the need in the development of manganese oxide cathodes for supercapacitors with high capacitance at high charge–discharge rates and enhanced capacitance retention in a wide range of charge–discharge rates. It also addresses the challenge of eliminating the time-consuming activation procedure, which limits the applications of Mn3O4 cathodes. The new approach is based on the use of environmentally friendly and biocompatible pH modifiers–dispersants, such as polyethylenimine (PEI) and meglumine (MG) for hydrothermal synthesis. In this approach, the use of inorganic alkalis is avoided. We demonstrate the benefits of this approach for the fabrication of manganese oxide nanoparticles, such as Mn-PEI and Mn-MG. Electrodes with a high active mass of 40 mg cm−2 are fabricated and electrochemically tested in 0.5 M Na2SO4 electrolyte. The method of electrode material fabrication offers benefits for the accelerated electrode activation procedure, which is practically eliminated for Mn-MG electrodes. The Mn-MG electrodes showed a remarkably high capacitance of 3.68 F cm−2 (93.19 F g−1) at a sweep rate of 100 mV s−1 and a high capacitance retention of 90.6% in the CV sweep range of 1–100 mV s−1. [ABSTRACT FROM AUTHOR]

The electrochemical performance of flexible carbon-nanotube (CN) based supercapacitors (SCs) is reported in this research. A mixture of Boron nitride (BN), graphene (G) and lithium titanate (Li 2 TiO 3 , LiTi) was added on the SC electrodes to enhance their capacitance/energy-density. SC devices were fabricated with the names of CN-SC, CN/BNG-SC and CN/BNG + LiTi-SC and generated a capacitance/energy density of 329.7 F g−1/7.3 Wh kg−1, 890.2 F g−1/35.2 Wh kg−1 and 1662.6 F g−1/124.2 Wh kg−1, respectively. From those last values, we realize that adding BN, G and LiTi (CN/BNG + LiTi-SC), enhanced the capacitance and the energy density by ~ 4 and ≈ 16 times, respectively. Interestingly, the output voltage of the SCs also increased from 0.1 to 0.4 V after adding these three compounds to their electrodes. The SC electrodes were analyzed by UV–vis absorbance, Raman and XPS and found the presence of defects (oxygen vacancies) and Ti3+/Ti4+ species, which worked as redox centers for the charge storage. Moreover, the best CN/BNG + LiTi-SC device was subjected to 500 bending/charging-discharging cycles and maintained a capacitance of 86–97% despite the mechanical deformations. Finally, we demonstrated that the incorporation of the BN and LiTi materials on the SC electrodes produced a widening of the operating voltage window from 1.2 to 2.2 V, which is of particular interest to increase the lifetime of portable energy sources. [ABSTRACT FROM AUTHOR]

2D decorated nanostructures are fast emerging as efficient electrode materials for electrochemical devices. Au decorated SnO2, synthesized using co-precipitation and hydrothermal methods, can become a useful electrode material for supercapacitors. Au incorporation helps to mitigate the conductivity issues of SnO2 nanostructures. The superior 2D-flake like morphology leads to appreciable performance enhancement, with specific capacitance of 234 F g−1 at 1 A g−1 current density, which is much larger than that observed in pristine SnO2. The high cycling stability of Au-decorated SnO2 clearly shows its usefulness for high-performance supercapacitors. A theoretical model is also reported to explain the electrochemical results. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) with hierarchical porous structures have been attracting intense interest currently due to their promising applications in catalysis, energy storage, drug delivery, and photocatalysis. Current fabrication methods usually employ template-assisted synthesis or thermal annealing at high temperatures. However, large-scale production of hierarchical porous metal–organic framework (MOF) particles with a simple procedure and mild condition is still a challenge, which hampers their application. To address this issue, we proposed a gelation-based production method and achieved hierarchical porous zeolitic imidazolate framework-67 (called HP-ZIF67-G thereafter) particles conveniently. This method is based on a metal–organic gelation process through a mechanically stimulated wet chemical reaction of metal ions and ligands. The interior of the gel system is composed of small nano and submicron ZIF-67 particles as well as the employed solvent. The relatively large pore size of the graded pore channels spontaneously formed during the growth process is conducive to the increased transfer rate of substances within the particles. It is proposed that the Brownian motion amplitude of the solute is greatly reduced in the gel state, which leads to porous defects inside the nanoparticles. Furthermore, HP-ZIF67-G nanoparticles interwoven with polyaniline (PANI) exhibited an exceptional electrochemical charge storage performance with an areal capacitance of 2500 mF cm−2, surpassing those of many MOF materials. This stimulates new studies on MOF-based gel systems to obtain hierarchical porous metal–organic frameworks which should benefit further applications in a wide spectrum of fields ranging from fundamental research to industrial applications. [ABSTRACT FROM AUTHOR]