Solid-state Supercapacitor Device Research Articles

Facile combustion synthesis of Granular-like La1-xSrxMnO3 Perovskites as electrode material for supercapacitor application

This study focuses on synthesizing a series of perovskite-type La1-xSrxMnO3 materials using a solution combustion method to investigate the impact of varying concentrations of La and Sr. The samples were prepared with different La and Sr concentrations (La1-xSrxMnO3, X = 0, 0.2, 0.4, 0.6, and 0.8) and labeled as LSMO-2 (La0.8Sr0.2MnO3), LSMO-3 (La0.6Sr0.4MnO3), LSMO-4 (La0.4Sr0.6MnO3), LSMO-5 (La0.2Sr0.8MnO3. The structural, morphological, and compositional characteristics of the synthesized electrodes were thoroughly analyzed. X-ray diffraction (XRD) confirmed the formation of a rhombohedral structure with an R-3c space group, while Fourier-transform infrared spectroscopy (FT-IR) verified the presence of all functional groups in the samples. Field emission scanning electron microscopy (FE-SEM) revealed a cluster of nanopowder morphology, and compositional analysis further validated the formation of the prepared samples. The electrodes were then screen-printed onto Ni-foam and evaluated for their electrochemical performance. Notably, the La1-xSrxMnO3 electrode demonstrated a high specific capacitance of 1271.5 F/g at a current density of 10 mA/cm2 and maintained 83.45 % cyclic stability after 10,000 cycles. Moreover, the power law was employed to investigate the charge storage mechanism of the LMSO-4 electrode. To assess the practical application potential of the La1-xSrxMnO3 electrode, a solid-state supercapacitor device was fabricated, and its performance was investigated. The device achieved a maximum specific capacitance of 206 F/g at 5 mA, with an energy density of 16 Wh/kg and a power density of 2400 W/kg, retaining 94 % of its performance after 5000 cycles. Overall, La1-xSrxMnO3 electrodes show great promise as materials for supercapacitor applications due to their impressive electrochemical properties.

Theoretical and experimental studies on 2D β-NiS battery-type electrodes for high-performance supercapacitor

Recently, quirky features and eccentric structures of transition metal sulfides have grasped great attention to remove roadblocks and unwrap fresh avenues for electrodes in energy storage devices. Herein, we developed a 2D beta phase nickel sulfide nanosheets (2D β-NiS NSs) electrode with remarkable enhancement in charge storage properties. When served as active electrodes for electrochemical tests, 2D NiS NSs exhibited ultra-high capacitance of 2693 Fg−1 at 1 mVs−1 and specific capacity of 219 mAhg−1 at 1 Ag−1. The symmetric battery type solid-state supercapacitor device comprising 2D β-NiS NSs electrodes exhibits specific capacity of 83.43 mAhg−1at 2 Ag−1 over broad potential range of 0.7V with good cycling performance, and energy and power density of 28.9 Whkg−1 (@ 2 Ag−1) and 21 kWkg−1 (@ 6 Ag−1) respectively. Complementary first-principles density functional theory (DFT) calculations accomplished to explore the electrolyte ion interactions with nickel sulfide nanostructures defining 2D NiS NSs as a potential candidate for real-time applications.

A flexible solid-state asymmetric supercapacitor device comprising cobalt hydroxide and biomass-derived porous carbon.

Development in the field of alternative and renewable energy sources is becoming necessary considering the current energy demands of the growing technologies. The main challenge associated with the produced energy is to store it for future use, such that it can be used when needed. Supercapacitors are among the electrochemical energy storage systems that provides higher power density, faster charging-discharging, high specific capacitance (C S), and long cycling life. Herein, the fabrication of a flexible solid-state asymmetric supercapacitor (ASC) device is reported, where Co(OH)2 hollow spheres and biomass-derived porous carbon (PC) are the cathode and anode, respectively. Co(OH)2 is a highly redox active material, whereas PC is an electric double-layer capacitive (EDLC) material. In this device, aqueous KOH solution (electrolyte) encapsulated in PVA gel (separator) was used to bind the electrodes. This Co(OH)2//PC ASC device exhibited a high C S of 260 F g-1 (at 2 A g-1). It retained ∼91% of the initial C S value (at 6 A g-1) till ∼5000 cycles. Electrochemical impedance spectroscopy (EIS) study confirmed low internal resistance (0.95 Ω) and charge transfer resistance (1.41 Ω) values of Co(OH)2//PC. These results indicate that the high electron transfer process in the electrode-electrolyte interface during the electrochemical reaction, which is responsible for the excellent performance of this ASC device. The high-performance Co(OH)2//PC ASC device exhibited an energy density of 76.7 W h kg-1 at a power density of 1416.9 W kg-1. To demonstrate its practical use, LED lights were illuminated using this Co(OH)2//PC ASC device.

Fabrication of solid-state symmetrical supercapacitor device based on constructed novel Gr-Cu-MoO2 disk electrodes based on Co-replacement reactions

The use of graphite-based substrates has attracted the attention of many researchers due to their high-performance capacitive behavior. Graphite Disk (GD) electrodes due to being more robust and capacity than graphite sheets can be used on an industrial scale. In this research, for the first time, by using the co-replacement method as a straightforward and without wasting energy method, MoO2 and Cu nanostructures with particular morphology were in-situ co-replaced on GD substrates based on commercial graphite and Zn-metal powder. The results of the scanning electron microscopy analysis clearly showed the MoO2–Cu nanosheet formed on the porous GD (PGC) electrode, which has caused a tremendous increase in the capacitance and cyclic stability due to the augment in the surface area and synergistic effect of MoO2–Cu nanostructure. Also, different characterization analysis results confirmed the co-replacement of MoO2 and Cu nanostructures onto the PGD electrode. Electrochemical investigation exhibited that this electrode has an extraordinary capacity of 28526 mF/cm2 at 2 mA/cm2 in 1M H2SO4. The investigation of the capacitive behavior of the MoO2–Cu/PGD supercapacitor device showed that the fabricated supercapacitor device has an astonished capacitance of 4916.98 mF/cm2 (145.27 F/g), power of 18017.34 mW/cm2, and energy density of 4154.84 mWh/cm2 at 1 mA/cm2.

Enhancing capacitive performance of MoS2 through Fe doping: Synthesis, characterization, and electrochemical evaluation for supercapacitor applications

The capacitive performance of bare MoS2 is limited due to its poor electronic conductivity. Therefore, we tried to dope different weight percentages (2 %, 4 %, 6 %, 8 %, and 10 %) of Iron (Fe) into the MoS2 to promote more active sites to improve its energy storage capacity. Given this, we have synthesized bare MoS2 and Fe-doped MoS2 using the hydrothermal method for electrochemical charge storage application. The effect of doping was well assessed using different physicochemical tests. The electrochemical properties of the bare MoS2 and Fe-doped MoS2 were evaluated using a three-electrode setup in a 3 M KOH aqueous electrolyte. As a result, the 8 % Fe-doped MoS2 electrode material demonstrates the maximum specific capacitance (CSP) of 545 F/g @ 1 A/g with 84.8 % capacitive retention over 2000 cycles at 5 A/g. Additionally, we fabricated an asymmetric solid-state supercapacitor device, which reveals a high CSP of 74.28 F/g at 4 A/g with an energy density of 72.79 Wh/kg and a power density of 10.07 kW/kg. The results asserted that the Fe-doped MoS2 is a potential electrode material for supercapacitor application.

“Unveiling marigold assembled micro flowers of tungsten oxide towards solid-state flexible pouch and coin cell supercapacitors”

Marigold analogues micro flowers of tungsten oxide (WO3) have been grown in thin film form through simple and cost-effective solution chemistry approach on stainless steel substrate. Aqueous precursor involving WO4-2 ions agglomerated as self-sacrificing template growing initially into the nano-petal, followed by self-assembly; leading to marigold analogues micro flower surface architecture. This enthralling morphology motivated us not only to fabricate supercapacitive electrode but also to design complete solid-state supercapacitor devices in dual configurations: flexible pouch cell and coin cell. Interestingly, both devices even in symmetric configuration yields remarkable potential window of 1.82 V when sandwiched by gel inclusive of Li+ ions dispersed in non-conducting polyvinyl alcohol matrix. Solid-state flexible pouch cell and coin cell delivered specific capacitances of 103.98 ± 3.59 and 30.09 ± 1.03 F/g respectively at a scan rate of 5 mV/s. Assembled electrode, coin-cell and flexible pouch-cells have been well assessed in-depth through specific capacitances using cyclic voltammetry and galvanostatic charge discharge, diffusive and capacitive contributions, mechanical bending tests, electrochemical active surface area, and electrochemical impedance analysis. Practical applicability has been demonstrated for designed flexible pouch cell to run small fan and light emitting diode panel whereas coin cell to run light emitting diode panel.

Optimizing phosphorene nanosheets for high performance all-solid asymmetric supercapacitors: A theoretical and experimental insight

This study probably for the first-time introduced a phase and morphology-tuned scalable, cost-effective method for large-scale production of Black Phosphorous/Phosphorene (BP), and investigated their in-depth electrochemical properties. Utilizing a one-pot mild wet chemical-assisted hydrothermal route in ethylenediamine, high-quality BP nanosheets were synthesized from amorphous red phosphorus (RP) with nearly 100 % conversion efficiency, yielding 7.1352 g for one batch at 130–170 °C. The resulting phosphorene nanosheets exhibited a small crystalline size (2.708 nm), hierarchically porous morphology, a 1.64 eV direct optical bandgap aligned with theoretically calculated bandgap using LDA approximation, and various structural defects, along with large specific surface area (50 m2g−1) and reduced number of layers (4–5) compared to prior literatures, suggesting electrochemical superiority. CV and GCD measurements in the potential window of −0.7 V to 0.1 V revealed its highest pseudo-capacitance response (84.91 %), reaching a maximum specific capacitance value of 759.748 Fg−1 at current density 2 Ag−1, surpassing all previous records. Moreover, BP displayed excellent cyclic stability of 89.8 % after 10,000 cycles, making it an excellent electrode material for supercapacitors. A solid-state asymmetric supercapacitor device (HASD), using BP, successfully lighted up 6 red LEDs for 10 s, achieving maximum specific energy density at 73.43 Wkg−1 at a power density of 1500 Wkg−1.

Friendly Environmental Strategies to Recycle Zinc-Carbon Batteries for Excellent Gel Polymer Electrolyte (PVA-ZnSO4-H2SO4) and Carbon Materials for Symmetrical Solid-State Supercapacitors.

In this report, we introduce a novel idea to prepare a redox additive in a gel polymer electrolyte system of PVA-ZnSO4-H2SO4 based on zinc-carbon battery recycling. Here, zinc cans from spent zinc-carbon batteries are dissolved completely in 1 M H2SO4 to obtain a redox additive in an aqueous electrolyte of ZnSO4-H2SO4. Moreover, carbon nanoparticles and graphene nanosheets were synthesized from carbon rod and carbon powder from spent zinc-carbon batteries by only one step of washing and electrochemical exfoliation, respectively, which have good electrochemical capability. The three-electrode system using a ZnSO4-H2SO4 electrolyte with carbon nanoparticles and graphene nanosheets as working electrodes shows high electrochemical adaptability, which points out its promising application in supercapacitor devices. Thus, the symmetrical solid-state supercapacitor devices based on the sandwich structure of graphene nanosheets/PVA-ZnSO4-H2SO4/graphene nanosheets illustrated the highest energy density of 39.17 W h kg-1 at a power density of 1700 W kg-1. While symmetrical devices based on carbon nanoparticles/PVA-ZnSO4-H2SO4/carbon nanoparticles exhibited a maximum energy density of 35.65 W h kg-1 at a power density of 1700 W kg-1. Moreover, these devices illustrate strong durability after 5000 cycles, with approximately 90.2% and 73.1% remaining, respectively. These results provide a promising strategy for almost completely recycling zinc-carbon batteries, one of the most popular dry batteries.

In-depth analysis of VARTM-based solid-state supercapacitors utilizing CNT-dispersed cobalt-bismuth-samarium ternary hydroxide on woven carbon fiber for enhanced energy storage

Multi-metal hydroxides possess unique physical and chemical properties, making them promising candidates for supercapacitor working electrodes. Enhancing their electrochemical performance can be achieved through a combination with carbon materials. In this study, we synthesized a composite material by hydrothermally dispersed 4, 6, and 10 wt% carbon nanotubes (CNT) into ternary cobalt-bismuth-samarium hydroxide (CoBiSm-TOH). These nanocomposites were employed as the material for the working electrode in a supercapacitor. The findings reveal that at 1.5 A/g, the specific capacitance of CNT3@CoBiSm-TOH, using a three-electrode system, was found to be 852.91 F/g, higher than that of CoBi-BOH, CoBiSm-TOH, CNT1@CoBiSm-TOH and CNT5@CoBiSm-TOH—measuring 699.69, 750.34, 789.54 and 817.79 F/g, respectively. Moreover, CNT3@CoBiSm-TOH electrodes exhibited a capacitance retention of around 88% over 10,000 cycles. To demonstrate practical applicability, CNT3@CoBiSm-TOH was grown on woven carbon fiber (WCF), and a solid-state supercapacitor device was developed using the VARTM (vacuum-assisted resin transfer molding). This device displayed a specific capacitance of 272.67 F/g at 2.25 A/g. Notably, it achieved a maximum energy density of 53.01 Wh/kg at a power density of 750 W/kg and sustained excellent cycle stability over 50,000 cycles, maintaining 70% of its initial capacitance. These results underscore the importance of interfacial nanoengineering and provide crucial insights for the development of future energy storage devices.

Eco-friendly preparation of nitrogen-doped porous carbon materials for enhanced solid-state supercapacitor device

In the last years, researchers all over the world have been looking for biomass-derived porous carbon materials, due to the possibilities for large-scale synthesis, easy to control the pore structure, and high specific surface area. Activated heteroatom doped porous carbon (AHPC) with a high porosity was made by treating inexpensive waste Ficus elastica leaves with a base. The electrochemical performance of the produced activated carbon has been evaluated in various electrolytes, including basic, neutral, and acidic electrolytes. At a current density of 1 A/g in the acidic electrolyte, the specific capacitance of the activated carbon AHPC electrode is higher, 456 F/g, compared to other electrolytes. The symmetric supercapacitor device is built using PVA-H2SO4 gel electrolyte, and its electrochemical performance is evaluated. In addition, the energy density of the built symmetric supercapacitor device is higher than the existing commercial supercapacitors, achieving 62 Wh/kg at a power density of 15.2 kW/kg. This is because the porous carbon has a hierarchical pore distribution and a heteroatom-enriched structure, which allows for rapid charge/mass diffusion channels, and a vast ion-accessible network.

The construction of a flexible solid-state asymmetric supercapacitor device using nickel-copper oxide nanoplates and carbon nanosphere serving as positive and negative electrode, respectively with excellent electrochemical capabilities

Here, nickel-copper oxide nanoplates (NCN) and carbon nanosphere (CNS) as positive and negative electrodes are synthesised via a hydrothermal protocol without adding any surfactant and binders. The NCN and CNS electrodes in KOH electrolyte exhibit superior specific capacitance of ∼ 2362.5 F g−1 and ∼ 246.11 F g−1 at 1 A g−1 respectively. The NCN and CNS retained 98.54 % and 97.88 % of the initial capacitance after 3000 galvanostatic charge–discharge (GCD) cycles, respectively. Additionally, an asymmetric supercapacitor (ASC) device NCN//CNS is constructed using NCN and CNS as positive and negative electrodes, utilizing poly(vinyl alcohol) PVA − KOH gel electrolyte separator. The ASC device demonstrates a maximum energy density of 50.4 Wh kg−1 (181.44 KJ kg−1) with a power density ∼ 750 W kg−1 at 1 A g−1, maintaining 90.4 % cyclic stability after 10,000 GCD cycles. The electrochemical outputs of the device present significant potential for the advancement of high-performance ASC devices in electronic applications.

In-situ growth of 3D amorphous Ni-Co-Mn phosphate on 2D Ti3C2Tx nanocomposite for commercial-level hybrid energy storage application

To overcome the limited electronic conductivity and capacity of single and binary transition metal phosphates (TMPs), highly electrochemical active materials and rational structural design of ternary TMPs composite are urgently required. In this study, we successfully synthesized an amorphous 3D Ni-Co-Mn phosphate@2D Ti3C2Tx (MXene) nanocomposite (NCMP series) through the electrodeposition method. The amorphous Ni-Co-Mn phosphate effectively restricts the self-accumulation of MXene nanosheets, resulting in the development of a porous nanostructure. This structure exposes more active sites, expands the ion transport path, and enhances the conductivity of the Ni-Co-Mn phosphate@Ti3C2Tx material. Owing to the synergistic effect offered by Ni-Co-Mn phosphate and MXene nanocomposite, the anchored Ni-Co-Mn phosphate@Ti3C2Tx (NCMP-5) electrode delivers an elevated capacity of 342 mAh/g (1230 C/g) at 5.0 A/g, surpassing the pristine Ni-Co-Mn phosphate (NCMP-4, 260 mAh/g) and MXene (33.3 mAh/g). Moreover, a hybrid solid-state supercapacitor (HSSC) device is assembled with NCMP-5 as a cathode and reduced graphene oxide (rGO) as an anode within a polymer gel (PVA-KOH) electrolyte. Notably, the fabricated HSSC device displays a supreme specific capacity of 27.5 mAh/g (99 C/g) and a high (volumetric) energy density of 22 Wh/kg (3.6 Wh/cm3) at a power density of 0.80 kW/kg (0.13 kW/cm3) for 1.0 A/g. Moreover, the HSSC device retains 95.4 % of its initial capacity even after 10,000 cycles. Importantly, the operational potential window of two serially connected HSSC devices approaches +3.2 V, enabling different colored commercial light-emitting diodes (LEDs) to be efficiently illuminated. Eventually, the remarkable supercapacitive characteristics of the 3D@2D amorphous Ni-Co-Mn phosphate@MXene nanocomposite make it an attractive choice for advanced electroactive materials in upcoming hybrid energy storage technologies.

Metal oxide-mixed polymer-based hybrid electrochromic supercapacitor: improved efficiency and dual band switching

The inclusion of charge storage properties in electrochromic devices (ECDs) has gained much interest and has evolved into a promising emerging energy-related field due to multifunctional smart device applications. Here, an organic–inorganic solid-state asymmetric electrochromic supercapacitor device (ESCD) containing nano-CoTiO3-mixed poly-3-hexylthiophene and WO3 as two electrodes has been designed to study electrochromic and supercapacitor properties. The electrochemical properties of CoTiO3 show a pseudocapacitive-type charge storage capability, which has been utilized to enhance the electrochromic performance of the ESCD with additional charge storage ability. The device shows charge storage properties with fast charging and slow discharging, giving very high coulombic efficiency with a specific capacitance of 6.4 mF cm−2 at 0.2 mA cm−2 current density. The device shows excellent electrochromic supercapacitive properties with a color contrast of ∼50% and a short switching time of ∼1 s at a 515 nm wavelength with excellent cyclic stability. The device exhibits the capability to cut near infrared wavelength (700 nm and 850 nm) and has a potential application as a heat filtering device. Thus, the addition of pseudocapacitive-type materials in ECDs enhances the capacitive performance along with electrochromic properties, which makes ECDs more suitable for real life applications.

NiMnCo-LDH in-situ derived from ZIF-67@ZnO as self-supporting electrode for asymmetric supercapacitor device

Metal-organic frameworks have attracted much attention due to their abundant redox sites and tunable characteristics, which are advantageous for energy storage applications. However, the low electrical conductivity, poor physical strength and undesirable capacity seriously hinder their applications. Therefore, designing effective and convenient strategies to build composites with unique structures will be of practical significance. Herein, we successfully generate NMC-LDH/ZnO@CC nanocomposites by growing ortho-hexagonal nickel–cobalt layered double hydroxide (NMC-LDH) nanosheets in-situ on ZIF-67 precursor covering vertical arrays of ZnO nanorods. As a result of the unqiue ortho-hexagonal structure, highly ordered arrangement of active substances and multi-dimensional spaces of the prepared NMC-LDH/ZnO@CC binder-free electrode, its capacitance is as high as 9258 mF cm−2 at a current density of 2 mA cm−2 and the capacitance retention is maintained at 87.5 % after 5000 cycles. Furthermore, in order to explore the practical value of the prepared binder-free electrode, the NMC-LDH/ZnO@CC//AC solid-state asymmetric supercapacitor device is assembled. The energy density of the assembled supercapacitor is 24.6 W h kg−1 at a power density of 170 W kg−1 and 1020 W kg−1 at an energy density of 11.8 W h kg−1. In addition, a versatile instrument for monitoring air humidity, time and ambient temperature in portable environments can be powered by a single ultracapacitor unit for more than 30 min. Overall, this study provides a unique strategy for synthesizing ZIF derivatives with novel morphologies for electrochemical energy storage applications.

One fell swoop strategized bipolar energy device for triboelectric energy harvesting and electrochemical energy storage

Bipolar energy devices are an essential feature due to the enlargement of intelligent and portable electronics in the present decade. In this work, we demonstrated a bipolar energy device using binder-free MnO2 deposited on carbon cloth (CC) by a one-step electrochemical deposition process (EDP), which was employed for solid-state supercapacitor device (SSCD) and another side of CC with Kapton (KP) as TENG device. The efficiency of the bare CC electrode was boosted by growing uniform porous MnO2 nanoballs on the surface of CC, the standalone CC electrode was aided as a positive tribo-layer, and the Kapton film as the negative tribo-layer in the TENG device. The constructed CC-KP TENG device generated a maximum peak power of 15.11 μW, whereas the MnO2 SSCD delivered energy/power density of 37.41 Wh kg−1/10000 W kg−1, respectively. Overall, the results conclude that these types of bipolar energy devices were splendid and could be used in miniatured low-power electronic devices.

Stoichiometrically Optimized Electrochromic Complex [V2O2+ξ(OH)3-ξ] Based Electrode: Prototype Supercapacitor with Multicolor Indicator.

The systematic structure modification of metal oxides is becoming more attractive, and effective strategies for structural tunning are highly desirable for improving their practical color-modulating energy storage performances. Here, the ability of a stoichiometrically tuned oxide-hydroxide complex of porous vanadium oxide, namely [V2O2+ξ(OH)3-ξ]ξ = 0:3 for multifunctional electrochromic supercapacitor application is demonstrated. Theoretically, the pre-optimized oxide complex is synthesized using a simple wet chemical etching technique in its optimized stoichiometry [V2O2+ξ(OH)3-ξ] with ξ=0, providing more electroactive surface sites. The multifunctional electrode shows a high charge storage property of 610Fg-1 at 1Ag-1, as well as good electrochromic properties with high color contrast of 70% and 50% at 428 and 640nm wavelengths, faster switching, and high coloration efficiency. When assembled in a solid-state symmetric electrochromic supercapacitor device, it exhibits an ultrahigh power density of 1066mWcm-2, high energy density of 246mWhcm-2, and high specific capacitance of 290mFcm-2 at 0.2mAcm-2. A prepared prototype device displays red when fully charged, green when half charged, and blue when fully discharged. A clear evidence of optimizing the multifunctional performance of electrochromic supercapacitor by stoichiometrical tuning is presented along with demonstrating a device prototype of a 25cm2 large device for real-life applications.

Polybenzidine-MnO2 nanocomposite on anodized graphite sheet as a novel system for high-performance supercapacitors

In this work, we report for the first time the in-situ synthesis of polybenzidine‑manganese oxide (PB-MnO2) nanocomposite on anodized graphite sheet (AGS). The PB-MnO2/AGS electrode is easily fabricated through the electrochemical anodization of the graphite sheet followed by the polymerization of the benzidine monomer using KMnO4 as an oxidant and MnO2 source. The results of various instrumental analysis confirm that the PB-MnO2 nanocomposite is successfully formed on the AGS without any binder. Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques strongly prove the pseudocapacitive nature of the electrode. The PB-MnO2/AGS electrode shows a high capacitance of 950 mF cm−2 at 0.5 mA cm−2 in 1.0 M H2SO4 solution with a maximum power and energy density of 64.65 mWh cm−2 and 1.75 W cm−2. Solid-state symmetrical supercapacitor device fabricated with PB-MnO2/AGS electrode shows that this device has an excellent specific capacity of about 190.27 mF cm−2 at 0.5 mA cm−2 and maximum power and energy density of 12.375 W cm−2 and 85.625 mWh cm−2. The cyclic life of 87.22 % after 5000 GCD cycles without any ohmic drop indicates that the PB-MnO2/AGS electrode can be a promising candidate for the fabrication of high-performance supercapacitor devices in the future.

Engineered nano-architecture for enhanced energy storage capabilities of MoS2/CNT-heterostructures: A potential supercapacitor electrode

Hydrothermal synthesis was utilized to achieve the direct growth of molybdenum disulphide (MoS2) nanoflakes on carbon nanotubes (CNT). Through this method, MoS2/CNT heterostructures with engineered microstructure have been obtained by suitably optimizing the synthesis conditions. Raman, X-ray photoelectron spectroscopy, and electron microscopy have been utilized to characterize the heterostructure. The present study investigated the influence of varying amounts of CNT and MoS2 within the heterostructure on its electrochemical properties. The optimization of the heterostructure morphology has resulted in enhanced electrochemical performance, with a high specific capacitance of ∼436 F/g at 1 A/g, along with good rate capability. The charge storage mechanism was explained by using Dunn's power law. Further, the MoS2/CNT heterostructure was employed to fabricate a solid-state symmetric supercapacitor. The device exhibited a specific capacitance of ∼164 F/g at 1 A/g, along with good cyclic stability, retaining 96 % of its capacitance after 1000 cycles. Additionally, the device demonstrated high energy and power density values of ∼27 Wh/Kg and 603 W/Kg, respectively. The present study indicates that the MoS2/CNT heterostructure holds great promise as an electrode material for high-performance solid-state supercapacitor devices.

Facile chemical synthesis of BaO:MgO nanorods for designing distinctive solid-state asymmetric supercapacitor device with activated carbon

The successive ionic layer adsorption and reaction (SILAR) technique was adapted to produce the interconnected complex network of BaO:MgO nanorods on a flexible stainless-steel (SS) substrate surface. The phase and surface morphology of the BaO:MgO electrode were examined from the X-ray diffraction and scanning electron microscopy measurements, respectively, which endowed electrochemical specific capacitance (SC) of 528.77 F/g at a 2 mV/s scan rate with great rate capability and cycling performance of 94.33 % over 5000 cyclic voltammetry cycles. Fabricated BaO:MgO//AC asymmetric solid-state supercapacitor device, using polyvinyl alcohol and potassium hydroxide gel as an electrolyte, demonstrated distinctive energy storage performance, i.e., a specific capacitance (SC) of 259.07 F/g with an energy density of 57.27 Wh/kg and a power density of 2.34 kW/kg at a current density of 4 mA/cm2. The results demonstrated the facile method for synthesizing a spherical nanorod network of BaO:MgO and made them promising electrode materials for energy storage applications. The use of a solid-state supercapacitor device to illuminate an LED demonstrated the commercial feasibility of both the materials utilized and the design type.

Bio-based conductive polyurethane composites derived from renewable castor oil with enhanced self-healing ability for flexible supercapacitors

To alleviate the pressure on the petrochemical industry and address environmental concerns, the utilization of polyurethane (PU) derived from castor oil (CO) (as an ester polyol replacement of petrochemical-based materials) has garnered significant attention in recent decades. Extending the service life of materials requires imparting self-healing properties to vegetable oil-based polymers, an aspect that has received limited attention in current studies. However, low self-healing efficiency still poses a significant challenge, and non-conductivity also remains an obstacle in current research, crucial for their application in electronic devices. In this work, we present the first series of electrically self-healing biopolymer composites constructed by incorporating carbon nanotube (CNT) networks into crosslinked castor oil-based polyurethane (BPU) through a simple curing process. These materials address the challenges mentioned above and exhibit improved mechanical, electrical, and self-healing capabilities compared to other bio-based self-healing materials. The resulting BPU/CNT composite demonstrated exceptional repeated self-healing capacity, restoring both mechanical properties and electrical performance even after experiencing severe mechanical damage. Notably, this composite served as a conductive substrate in flexible solid-state supercapacitor (FSSC) devices. Consequently, the FSSC derived from the composite conductive substrate achieved an impressive 92.4 % self-healing efficiency even after undergoing 7 cutting/healing cycles. The device remained virtually unchanged even after being bent at a 180° angle with a bending radius of 1.6 mm, indicating excellent repeatability and durability. The exceptional self-healing ability, with ∼98 % electrical recovery at 100 °C for 70 s and 93 % at 80 °C after 6 min, of these composites was attributed to the synergistic interactions of the dynamic exchange reactions of disulfide bonds and dense hydrogen bonds within the BPU matrix, which provide a reversible dynamic polymer network. The healing efficiency of these dynamic bonds was evaluated by adjusting the composition ratio of the long linear chain of pTHF in hybrid polyols of the crosslinked polymer network. Overall, this work highlights a series of green, simple, and highly efficient self-healing polymer composites derived from renewable castor oil, and it establishes an essential framework for future sustainable polymer composite design.