Electrochemical Performance For Supercapacitors Research Articles

The Conversion of Li2SnO3 Li-Ion Hybrid Supercapacitors from Pastes Containing LiCl-SnCl2 Liquid Precursors Using an Atmospheric-Pressure Plasma Jet

We fabricate lithium tin-based oxide Li2SnO3 on carbon cloth from a gel-state precursor containing LiCl and SnCl2·2H2O using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ treatment provides both a high-temperature environment for the conversion of precursor into Li2SnO3 and nitrogen plasma reactive species for electrode surface modification. Here, the best electrochemical performance for the Li2SnO3 Li-ion hybrid supercapacitors (Li–HSCs) is achieved with 480 s of APPJ processing. The areal capacity of the 480 s APPJ-processed Li2SnO3 Li–HSCs reached 46.113 mC/cm2. The results indicate that APPJ is an effective tool for the rapid conversion processing of Li2SnO3 electrodes for Li–HSCs.

Enhancing sp3 content in diamond-like carbon thin film electrodes by pulsed laser annealing for durable charge storage performance

In this work, diamond-like carbon (DLC) thin film electrodes were grown on Si substrate by pulsed laser deposition (PLD) technique, and the implication of pulsed laser annealing (PLA) treatment on their electrochemical supercapacitor performance was examined by three electrode systems in 1 M Na2SO4 electrolyte solutions. The SEM micrographs exhibit a sheet-like wrinkled surface of DLC film on Si which later transformed into tiny hierarchical heap-like structures with enhanced surface roughness. The Raman spectra confirm signature of the D and G peaks of pristine DLC film at ~1352 cm−1 (1356 cm−1 after PLA) and 1591 cm−1 (1589 cm−1 after PLA), and appearance of minor T2g (diamond) (1332 cm−1) peaks with an increment of the sp3 content after PLA treatment. The X-ray photoelectron spectroscopy (XPS) spectra were deconvoluted into three different contributions CC (sp2), CC (sp3), and CO, and their sp3 percentages were estimated ~48.9 %, and 64.7 % before and after annealing. The area under cyclic voltammetry (CV) curve and galvanostatic charging discharging (GCD) performance of PLA-treated DLC film were improved and the highest areal-specific capacitance was obtained to be ~48.25 mF/cm2 for scan rate of 5 mV/s and 36.01 mF/cm2 for current density of 2 mA/cm2, respectively. Excellent charging discharging cyclic stability of PLA treated electrode was observed over 5000 cycles, and Coulombic efficiency and capacitance retention were determined to be ~93.5 % and ~ 97.3 %, respectively. The electrochemical impedance spectroscopy (EIS) was performed to obtain the Nyquist plot (Z′vs.Z′′) of both electrodes before and after the stability test, and a small degradation in impedance was observed. The Nyquist plots were fitted with the well-known Randles equivalent circuit model Rs(Cdl(RctZw)) and substantial curtailment of Warburg resistance (Zw) in PLA-induced DLC electrode signifies the dominance of the diffusion-controlled region in the charging-discharging process. Minor changes in the Nyquist plot before and after the stability test manifest the enduring charge kinetics of both electrodes and PLA-treated DLC exhibits better cyclic stability. PLA techniques have a great impact on upgrading the areal-specific capacitance, capacitance retention with high Coulombic efficiency, and stability with negligible impedance loss of the DLC film electrodes.

Home-made chemical vapor deposition-based synthesis of binder-free nanostructured magnesium-molybdenum-sulfide electrode materials for supercapacitor application

Molybdenum disulfides (MoS2) is considered as promising electrode materials (E-M) for high electrochemical performance (ECP) of lithium-ion batteries and supercapacitors due to their layered nanostructures. Herein, MoS2, MgS and hetrostructure MgS/MoS2 E-Ms comprising of nano-particles/sheets/needles like structures are synthesized on Nickel foam (Ni–F) by a simple home-made chemical vapor deposition (CVD) technique. The XRD analysis confirmed the formation of MoS2, MgS and MgS/MoS2 polycrystalline E-Ms growing along different directions. The FESEM analysis is confirmed that the addition of MgS layer over the surface of MoS2 change the surafce morphology from nano-particles to nano-needles. The change in structural and microstructural features is indicated the appearance of defects, micro-strain and dislocations density which are fruitful for excellent ECP. The cyclic voltammetry analysis is indicated the pseudocapacitive nature of the synthesized E-Ms. The maximum specific capacitance values for MoS2/Ni–F, MgS/Ni–F and MgS/MoS2/Ni–F E-Ms are 1273, 1688 and 3934 F/g at 1 A/g respectively. Moreover, the addition of MgS layer over MoS2/Ni–F is revealed the excellent cyclic stability of 98.76 % at current density of 10 A/g after 4000 cycles, energy density values are ranged from 79 to 136 W h/kg with homologous power density of 250–2500 W/kg and very small charge transfer resistance. The simulations of Power's Law and Dunn's model is confirmed that the excellent ECP is due to both capacitive and diffusive controlled contributions of heterostructured MgS/MoS2/Ni–F E-Ms. Additionally, MgS/MoS2/Ni–F E-Ms have both battery and pseudocapacitive nature due to unique nano-needles like morphology. The excellent electrochemical properties of MgS/MoS2/Ni–F E-Ms substantiate their potential applications in portable energy storage devices.

Metal oxide-based nanocomposites as advanced electrode materials for enhancing electrochemical performance of Supercapacitors: A comprehensive review

In recent years, the escalating use of nonrenewable fossil fuels has emerged as a significant threat to global sustainability, prompting the need for renewable, cost-effective, and eco-friendly energy storage solutions. Supercapacitors (SCs) are notable for their high power density (PD), cycle stability, and swift charge/discharge rates, although they fall short in energy density (ED) compared to traditional batteries. The performance of SCs is greatly influenced by the electrode materials used, highlighting the importance of material innovation in tackling the challenges posed by increasing fossil fuel consumption. Transition metal oxides (TMOs), known for their redox activity in energy storage, have been thoroughly investigated for their exceptional specific capacitance, which ranges from 100 to 2000F g−1, surpassing that of electrical double-layer capacitors (EDLCs). TMOs such as ruthenium oxide (RuO2), manganese oxide (MnO2), nickel oxide (NiO), cobalt oxide (Co3O4), tin oxide (SnO2), zinc oxide (ZnO), tungsten oxide (WO3), and vanadium pentoxide (V2O5) are widely researched for their high theoretical capacitance, affordability, and longevity. This review emphasizes the groundbreaking potential of metal oxide nanocomposites (NCs) formed by combining them with graphene, carbon nanotubes (CNTs), and polymers, leading to synergistic enhancements in electrical conductivity, surface area, and charge storage capacity. This thorough review not only presents an in-depth analysis of current research but also sheds light on potential future developments, contributing to the ongoing progress in the field of advanced electrode materials for energy storage.

Palladium enhanced electrochemical supercapacitive performance of Chromium oxide thin films synthesized by sputtering process

Recently, the use of transition metal oxide electrodes for supercapacitor applications has increased due to the possibility of variable mixed valence states. The present study has established the use of Pd-Cr2O3 composite thin films as a working electrode for high-performance supercapacitors. The reactive dc magnetron co-sputtering method has been used for the fabrication of thin film of Cr2O3 and Pd-Cr2O3 on SS-304 substrate. X-ray diffraction and X-ray photoemission spectroscopy techniques were used to examine the surface chemistry and phase purity of chromium oxide and Pd-Cr2O3 composite thin films. The incorporation of Pd in Cr2O3 delivers a drastic change in the surface morphology. Due to the modified morphology and electronic properties, a noticeable improvement in the electrochemical properties of Pd-Cr2O3 electrode is observed. The obtained value of specific capacitance for this electrode is 401 Fg−1 at 0.1 mAcm−2 scan rate and within the potential window range 0 to +1.2 V. This value of specific capacitance is almost twice in comparison to the Cr2O3 based electrode. The Pd-Cr2O3 composite thin film shows a good cycle retention capability of 8000 cycles with 87.5% retention. The obtained value of energy density and power density for Pd-Cr2O3 electrode was 80.2 Whkg−1 and 3.23 kWkg−1, respectively at 0.1 mAcm−2. Consequently, this composite material electrode can be seen as a promising advancement for electrodes in supercapacitor devices.

Synthesis and characterization of SnO2-La2O3 for electrochemical supercapacitor performance in redox additive electrolyte

Synthesis and characterization of SnO2-La2O3 for electrochemical supercapacitor performance in redox additive electrolyte

RGO‐Modified CoWO4 Nanoparticles as New High‐Performance Electrode Materials with Enhanced Electrochemical Performances for Supercapacitors

A facile one‐pot hydrothermal method is provided for synthesis of the reduced graphene oxide‐cobalt tungstate (rGO@CoWO4) nanocomposites with the enhanced electrochemical performances for supercapacitors (SCs). The resulting nanocomposites are comprised of CoWO4 nanospheres that are well anchored on graphene sheets by in situ reducing. The BET‐specific surface area of CoWO4, rGO@CoWO4 nanocomposites are 101 and 167 m2 g−1, respectively. The electrochemical evaluations are carried out in a 1 M KOH solution as the electrolyte. The hybrid electrode shows excellent specific capacitance of 1145 F g−1 at a current density of 1 A g−1 with superior rate capability and satisfactory cycling stability (97.2% capacitance preserved after 10 000 cycles). The good electrochemical performance can be attributed to the increased electrical conductivity and the creation of new active sites due to the synergetic effect of rGO and CoWO4 nanospheres. Moreover, the cyclic stability tests demonstrat capacitance retention of about 97.2% after 10 000 cycles, suggesting the potential application of rGO@CoWO4 nanocomposites in energy storage devices. The asymmetric SCs assembled with rGO@CoWO4 and activated carbon exhibit high energy density (39.1 Wh kg−1) and power density (631.2 W kg−1 at 1 A g−1), with remarkable cycle life (96.7% over 10 000 cycles) while still maintaining 24.5 Wh kg−1 at an even higher power density of 5098 W kg−1. The above results indicate that the hybrid rGO@CoWO4 electrodes synthesized by this approach would be a promising candidate for practical application of high‐performance SCs.

Enhanced dye-sensitized solar cell performance and electrochemical capacitive behavior of bi-functional ZnO/NiO/Co3O4 ternary nanocomposite prepared by chemical co-precipitation method

Increasing prerequisites for sustainable energy storage and conversion technologies have necessitated the exploration of advanced materials with improved properties. Here, we present the synthesis and characterization of ZnO nanoparticles (NPs), ZnO/NiO, ZnO/Co3O4 and ZnO/NiO/Co3O4 NCs as promising bi-functional materials for dye-sensitized solar cell (DSSC) and electrochemical energy storage applications. A facile chemical co-precipitation approach was followed to synthesize pure ZnO NPs, ZnO/NiO, ZnO/Co3O4 and ZnO/NiO/Co3O4 NCs. The structural and morphological analyses revealed the successful integration of ZnO, NiO, and Co3O4 NPs and also the formation of well-defined core-shell and homogenous nanocomposite structures. The XRD and HRTEM analyses confirmed the crystalline nature and nanoscale morphology of synthesized materials, respectively. The photovoltaic performance of DSSC fabricated using ternary ZnO/NiO/Co3O4 NC photoanode showed optimum dye-loading and best solar to electrical energy conversion efficiency with Jsc of 11.29 mA cm−2 and ƞ of 4.66%, which was considerably higher than the DSSC fabricated using pure ZnO NPs photoanode (ƞ = 2.01%). The increment in photocurrent density (Jsc) could be ascribed to the perfect band alignment of NiO and Co3O4 NPs in the ternary NC. Further, the ZnO/NiO/Co3O4 NC photoanode integrated DSSC disclosed 97% retainment in energy conversion efficiency even after 10 days of operation. The electrochemical performance of supercapacitor fabricated using ternary ZnO/NiO/Co3O4 NC showed high specific capacitance of 534.7 Fg−1 at 1 Ag−1 with favourable rate ability (∼52% at 16 Ag−1), good cyclic stability (91.07%) and low internal resistance. Moreover, the ZnO/NiO/Co3O4 NC at a current density of 2 Ag−1 exhibited a significantly high capacitance value of 463.1 Fg−1, which was 1.93, 1.58 and 1.22 times greater than ZnO NPs, ZnO/Co3O4 NC and ZnO/NiO NC, respectively.

Nickel-mixed chromium sulfide nanoparticle synthesis, characterization, and supercapacitor applications

Researchers are always encouraged to develop new electrode materials to design efficient, safe, and eco-friendly energy storage systems. Doping or mixing is an effective way to improve the electrochemical performance of supercapacitors. In this study, Ni-mixed Cr2S3 (Ni-Cr2S3) nanoparticles were synthesized through a hydrothermal technique with varying molar ratios of Ni and Cr. As prepared different Ni-Cr2S3 nanoparticles were characterized using XRD, XPS, FESEM, TEM, and EDX techniques. The results displayed that the structure and activity of the Ni-Cr2S3 were significantly influenced by the dopant quantity of Ni in Cr2S3. Among a series of Ni-Cr2S3 with various Ni:Cr ratios, the Ni-Cr2S3 (2:1) electrode exhibited a higher specific capacitance of 187.53 F g−1 at 0.5 A g−1 and good operational stability with 93.31 % retention over 5000 charge-discharge cycles. Moreover, the assembled sandwich-type symmetric supercapacitor (Ni-Cr2S3 (2:1)//Ni-Cr2S3 (2:1)) delivered the highest capacitance of 48.0 F g−1 at a current density of 1 A g−1 with excellent cycling performance of 91.26 % and Coulombic efficiency of 99.74 % after 5000 cycles at 5 A g−1. The Ni-Cr2S3 (2:1)//Ni-Cr2S3 (2:1) device possessed the energy/power density of 6.66 Wh kg−1/499.5 W kg−1, when increasing the current density it retained the energy/power density of 1.66 Wh kg−1/2988 W kg−1.

Enhanced Electrochemical Performance in Supercapacitors through Cu-Cy Based Metal-Organic Framework Electrodes.

In the quest for advanced energy storage, the fusion of organic and metallic constituents has led to the development of a novel metal-organic polymer, synthesized from Cyamelurate and copper (Cu-Cy), for supercapacitor electrodes. This study presents the synthesis of Cu-Cy as a thin film on stainless steel grids and directly on nickel foam, followed by extensive characterization to confirm phase purity and investigate structural details. SCXRD and PXRD analyses affirmed the material's synthesis and crystalline purity, while FTIR provided chemical bond insights. TGA assessed thermal stability, revealing robustness suitable for electrochemical applications. Electrochemical testing via cyclic voltammetry showed that nickel foam-supported Cu-Cy electrodes, without binders, achieved a remarkable specific capacity of 1210.89 F/g at 5mV/s. In contrast, the stainless-steel grid electrodes, with binders and conductive agents, reached 363.73 F/g. Additionally, Cu-Cy demonstrated excellent cyclization resistance, maintaining 90% capacity after 11,000 cycles. These results highlight Cu-Cy potential as a superior electrode material for supercapacitors, especially in binder-free configurations, paving the way for its use in cutting-edge energy storage solutions.

Synthesis and characterization of magnesium ferrite-activated carbon composites derived from orange peels for enhanced supercapacitor performance

Supercapacitors have emerged as highly efficient energy storage devices, relying on electrochemical processes. The performance of these devices can be influenced by several factors, with key considerations including the selection of electrode materials and the type of electrolyte utilized. Transition metal oxide electrodes are commonly used in supercapacitors, as they greatly influence the electrochemical performance of these devices. Nonetheless, ferrites' low energy density poses a limitation. Hence, it is crucial to create electrode materials featuring unique and distinct structures, while also exploring the ideal electrolyte types, to enhance the electrochemical performance of supercapacitors incorporating magnesium ferrites (MF). In this study, we effectively prepared magnesium ferrites (MgFe2O4) supported on activated carbon (AC) derived from orange peels (OP) using a simple hydrothermal method. The resulting blends underwent comprehensive characterization employing various methods, including FTIR, XRD, TEM, SEM, EDX, and mapping analysis. Moreover, the electrochemical performance of MgFe2O4@AC composites was evaluated using GCD and CV techniques. Remarkably, the MF45-AC electrode material showed exceptional electrochemical behavior, demonstrating a specific capacitance of 870 F·g−1 within current density of 1.0 A g−1 and potential windows spanning from 0 to 0.5 V. Additionally, the prepared electrodes displayed exceptional cycling stability, with AC, MF, and MF45-AC retaining 89.6%, 94.2%, and 95.1% of their initial specific capacitance, respectively, even after 5000 cycles. These findings underscore the potential of MF-AC composites as superior electrode materials for supercapacitors. The development of such composites, combined with tailored electrolyte concentrations, holds significant promise for advancing the electrochemical performance and energy density of supercapacitor devices.

Microwave-assisted hydrothermal synthesis of NiO/Co3O4 nanosheets decorated on three-dimensional porous graphene for supercapacitors

Electrode material is the key part of capacitor, which seriously affects the electrochemical performance of supercapacitor. NiO/Co3O4 nanosheets decorated on three-dimensional porous graphene (NiO/Co3O4/3DGN) have been prepared though a microwave-assisted hydrothermal method. It is found that NiO can affect the crystallinity and morphology of Co3O4 in the composites. The composites possess excellent electrochemical performance with the special capacity of 1303.9 F g−1 (at 1 A g−1). The assembled NiO/Co3O4/3DGN//AC asymmetric supercapacitor device achieved an energy density of 18.8 Wh kg−1 at a power density of 750.4 W kg−1 and maintained 92.7% of the initial capacitance after 10,000 cycles. The excellent capacitance and rate capability of the composites can be attributed to its unique structural features. The large surface area and the rich porosity provide more activate sites and facilitate the fast diffusion of electrolyte during the charge/discharge process. The direct contact between NiO/Co3O4 nanosheets and 3DGN ensures effective charge transport.

Revealing the mechanism of Faradaic PN junction design strategy in enhancing electrochemical performance of supercapacitor

Heterostructure materials, owing to their unique interfaces, robust structures, and synergistic effects, are increasingly garnering attention for their potential to enhance the energy/power output and lifespan of energy storage devices. Nonetheless, the intricate relationship between the band theory of heterostructures and their design strategies still demands further exploration. In this study, a binder-free NiCo2O4@NiCoAl-layered double hydroxide (LDH) PN junction cathode was constructed through a straightforward hydrothermal reaction. Extensive characterization and first-principles calculations have substantiated that the redistribution of charge within the space charge region considerably boosts the Faradaic activity and augments the conductivity of the LDH component, demonstrating an impressive specific capacitance of 1434.0 C g−1. Furthermore, the analysis focusing on the width of the space charge region has shed light on the charge transfer mechanism during charging and discharging, thereby validating the efficacy of the PN junction material design strategy. This research underscores the pivotal role of semiconductor theory in heterostructures and illuminates the potential of Faradaic PN junction composite materials in battery-type energy storage applications.

Urea-treatment of CoOx carbon nanofibers to improve the electrochemical performance of supercapacitor using aqueous electrolytes

Supercapacitors (SCs) play a crucial role in flexible electronics, necessitating innovative approaches to enhance surface faradaic reactions and minimize faradaic diffusion while using aqueous electrolytes. Thus, the urea treatment of cobalt oxide (CoOx)-decorated carbon nanofibers (CNFs) is proposed in this study to decrease the contribution of faradaic diffusion-limited current. Flexible CoOx/CNF electrodes were obtained by annealing ZIF-67-grafted polyacrylonitrile (PAN) fibers via a wet chemical method. The urea treatment of CoOx/CNFs increased the content of sp2-hybridized carbon and pyridinic nitrogen, as confirmed by X-ray photoelectron spectroscopy, effectively enhancing conductivity and pseudocapacitive charge storage capability via nitrogen doping. Notably, urea-treated CoOx/CNF electrode samples exhibited a capacitance of 750 mF cm−2 at a scan rate of 10 mV s−1, while retaining more than 81 % capacitance at a higher scan rate of 100 mV s-1. The cyclic voltammetry curves during variable bending angle testing (0°, 45°, and 90°) exhibited negligible changes, indicating the excellent flexibility of the SCs. The CoOx/CNFs and urea-treated CoOx/CNFs exhibited 80 % and 91 % capacitance retentions, respectively, after 10,000 galvanostatic charge and discharge cycles. Furthermore, the attained energy densities of 76 and 61 µWh cm−2 at the respective power densities of 2 and 20 mW cm−2 indicated the excellent electrochemical performance of the optimal urea-treated CoOx/CNF electrode.

A battery-type cathode with RuO2 modified Ni11(HPO3)8(OH)6 for asymmetric supercapacitors

Phosphates are a kind of promising electrode materials because they can provide numerous cavities and several reaction sites to be favored for storing anions and cations. However, the widespread application of phosphates are limited by their intrinsically low electronic conductivity. RuO2/hydrated RuO2 exhibits high conductivity and excellent electrochemical properties. Reducing its dosage and increasing its specific surface area are the research concerns. Combining less RuO2 to Nickel phosphate (NiP) is expected to improve the electrochemical performance. RuO2-modified NiP (NiP-RuO2) electrode material is synthesized by a one-step hydrothermal reaction and its structural morphology and capacitive properties are investigated. The results indicate that NiP-RuO2 electrode consists of hydrated RuO2 and Ni11(HPO3)8(OH)6, and exhibits excellent battery-type electrochemical supercapacitor performance with a specific capacity of 878.06 C/g at 1 A/g. According to density functional theory (DFT) analysis, Ru-doped Ni11(HPO3)8(OH)6 has a narrower forbidden band width and higher conductivity than Ni11(HPO3)8(OH)6. Furthermore, the asymmetric supercapacitor (ASC) assembled by NiP-RuO2/NF and activated carbon (AC) electrode achieves a high energy density (43.58 Wh/kg) at a power density of 923.47 W/kg. When two ASC devices are connected in series, ten light-emitting diodes (LEDs) can be illuminated for ten minutes.

Self-healable PVA-Borax-K2SO4 hydrogel electrolyte for flexible symmetric supercapacitors

The self-healing hydrogel materials are formed from the reaction between polyvinyl alcohol (PVA) and sodium tetraborate (Borax). The O-B-C vibration peak from the FT-IR spectrum is used to confirm the formation of the self-healing hydrogel structure. With 0.5 M concentration K2SO4, the resistivity of PVA-Borax-K2SO4 material is evaluated by Bode cure and obtained at 4.13 Ω.cm. With the improvement in hybrid structure, the flexible supercapacitor (FSS) devices were fabricated from two carbon fiber fabrics as symmetric electrodes with a self-healing hydrogel material (PVA-Borax-K2SO4) as electrolyte and separator. The electrochemical performances of flexible symmetric supercapacitor (FSS) devices are measured by cyclic voltammetric, charge/discharge, and impedance tests. The specific capacitance of FSS obtained 1.725 mF/cm2 at 0.05 mA/cm2 discharge current. Moreover, the stability of the FSS device attained confirmation by the comparison of the specific capacitance at 2 and 50 cycles.

Molecularly-regulating oxygen-containing functional groups of ramie activated carbon for high-performance supercapacitors

Effectively managing oxygen-containing functional groups (OCFGs) within activated carbon and methodically elucidating their intricate types and proportions are essential for considerably improving the electrochemical performance of carbon-based supercapacitors. Herein, we designed a ZnCl2-based molecular regulation strategy to introduce OCFGs into ramie-activated carbon (RAC), managing different OCFGs and revealing their structure–activity relationship with electrochemical performance. Thus, this regulated RAC, with a 3.5-fold enhancement in advantageous OCFGs (a-OCFGs: CO and COO), exhibits a supreme specific capacitance of 286.4F g−1 at 1 A/g and an excellent capacitance retention rate of 89.7 % at 20 A/g in an aqueous electrolyte, considerably surpassing that of nonregulated RAC (212.0F g−1 and 81.9 %). This confirms that a-OCFGs provide ample ion-storage accommodation and suppress solvent electronic oxidation, thereby enhancing electrochemical performance. Furthermore, its electrochemical performance is competitive with that of the commercial YP-50F (129.2F g−1 at 1 A/g). Therefore, this work not only highlights the contributions of specific OCFGs to high electrochemical performance but also designs a promising commercial electrode material to meet the demands of OCFGs-adequate carbon-based energy storage devices.

Synergistic effects of CoS-decorated Ni-MOF with hierarchical structures for high-performance supercapacitor electrode materials

To further improve the electrochemical performance of supercapacitor, the construction of composite based electrode material was proved to be an effective strategy. Herein, CoS-decorated Ni-MOF composites with hierarchical structures and obvious synergistic effects were synthesized by one-step hydrothermal and subsequent electrodeposition route. Benefitting from the increased surface roughness with more exposed active sites, the hierarchical structure with high space utilization rate for rapid ion transport as well as the improved conductivity and entire robustness, the optimal composites exhibited an excellent specific capacitance (2167.5 F g−1 at 1 A g−1), outstanding rate performance (up to 70.1% even at 5 A g−1) and the good cycle stability (80.12% capacity retention after 3500 cycles). The corresponding assembled asymmetric supercapacitors could reach an energy density 92.18 Wh kg−1 when the power density of was 1626.71 W kg−1, which overwhelmed most other reported works. What is more, the capacity retention could maintain 73.34% even after 7000 cycles, indicating the excellent cycle stability. Overall, to our knowledge, this is the first report on a synergistic effect of a combination of Ni-MOF and CoS. The constructed composites exhibited great potential as promising candidates for high-performance energy storage devices.

N,S‐Co‐Doped Activated Carbon Prepared by a Thiourea‐Assisted “Cutting” Method and their Application as High‐Performance Supercapacitors

AbstractBiomass has been considered a potential source for preparing carbon materials due to its environmentally friendly and renewable characteristics. In this work, N, S co‐doping activated carbon materials were easily prepared by using rice straw as the carbon source. In addition to being heteroatom source, thiourea can fragment the carbon particles into smaller pieces and create plenty of micropores during the carbonization process. Both theoretical and experimental analyses demonstrate that the incorporation of S and N species into carbon can improve the electrochemical performance of supercapacitors. The as‐made N, S co‐doping activated carbon materials, when used as electrodes, exhibit a high specific capacitance of 256 F g−1 at a current density of 1 A g−1 and maintain a good rate capacitance of 65 % even at a high current density of 50 A g−1. This work may offer valuable guidance for the application of rice straw derived carbon in supercapacitors.

Wet spinning of MXene (V2CTX) based fiber fabric with high electrochemical performance for flexible supercapacitor

Flexible supercapacitor is highly important to future wearable textile electronics and metaverse technologies, yet they are still limited by their unfulfilled specific capacitance and energy density. Here, a MXene (V2CTX) based fiber fabric (MFF) was developed via a synergistic flow driven assembly strategy for high-performance supercapacitors. Adapted through reliable approaches of indirect etching, organic cation intercalation, and wet spinning, the MFF presents rich active sites, ordered paths, a moderate specific surface area (41.1 m2 g−1), good flexibility and reproducibility. Admirably, the resulting fibrillar meshwork structure was found to be highly conducive to increasing energy density and reducing the electrochemical polarization. In this regard, a relatively good capacitance of 731 F g−1 is achieved at a current density of 0.5 A g−1 in H2SO4 electrolyte. Furthermore, the assembled asymmetric solid-state supercapacitor (FSC) exhibits high specific capacitance of 401.2 F g−1 at 0.5 A g−1, long cycle stability (5000 cycles) and high mechanical flexibility (5000 bending cycles). Benefiting from this outstanding electrochemical performance, the FSCs using EMIBF4/PVDF-HFP as electrolyte can be implied as reliable power source to flexible displaying and health monitoring. This work provides a novel MXene (V2CTX) based fiber fabric for constructing flexible electrode, promising to open an avenue toward wearable devices.