Asymmetric Supercapacitor Research Articles

Investigation of electrochemical performance of gadolinium trichloride in asymmetric supercapacitor applications

The commercial Gadolinium tri chloride (GdCl3) electrode material exhibits high specific capacitance of 207.52Fg−1 in three electrode system at 1A/g with potential window 1.0 V. The GdCl3//Activated carbon (AC) asymmetric supercapacitor device in two electrode system achieves 188.14Fg−1 specific capacitance at 1 A/g with high potential window 1.7V. It possess high energy density 75.51Wh/kg, power density 850W/kg. and electrochemical stability of 92% of its initial capacitance after 5000 cycles. These demonstrate GdCl3 as an useful material for electrochemical energy storage devices. Further, electron paramagnetic resonance study on GdCl3 reveals g-factor 1.98 and line width ΔH = 221.8mT.

Z-scheme heterostructures confining rGO/protonated C3N5 junction supported CoCu LDH positive electrode and Fe3O4 negative electrode for supercapacitors

CoCu LDH stabilized reduced graphene oxide-linked N-rich protonated C3N5 (CoxCuy@rGO/P-CN) as a power source Z-scheme nanocomposite was rationally tailored engineered an electrodeposition approach. The electrochemical performance was regulated by adjusting the electrodeposition potential and manipulating the Co/Cu molar ratio. Hence, affording compelling evidence for fine-tuning the performance of pseudo-active compounds. Benefiting from abundant heterointerfaces and synergistic effects between LDH nanoarrays and rGO/P-CN heterojunction, the hierarchical ‒1.2V Co3Cu1@rGO/P-CN Z-scheme positive electrode achieves a higher capacitance of 1184 F g–1 at 1 A g–1 and good rate capability performance. Theoretical simulation outcomes illustrate that the Co3Cu1@rGO/P-CN nanocomposite has higher electronic conductivity and superior electronic transition capability, originating from robust interactions between valence and conduction bands, interfacial charge transfer, and built-in electric field at the LDH/rGO/P-CN interface. We also explore the Fe3O4@rGO/P-CN Z-scheme as a negative electrode material via a simple annealing process with a capacitance of 402 F g–1 at 1 A g–1 and an enhanced cyclic performance. Consequently, the as-assembled ‒1.2V Co3Cu1@rGO/P-CN//Fe3O4@rGO/P-CN asymmetric supercapacitor (ASC) cell acquires a remarkable energy density of 63.4 Wh kg–1 at 750 W kg–1 and displays an exceptional cycling activity with 88% retention after 11,000 cycles.

Nanostructured bismuth phosphate-based asymmetric supercapacitor: electrochemical evaluation and oscillator application

Phosphate-based materials have received significant attention for various applications. In supercapacitors, metal phosphates exhibit high capacitance and superior rate performance. In this work, a wet chemical route was applied for the fabrication of aniline stabilized monoclinic bismuth phosphate (BPO) particles within the size range of 4–10 nm. The synthesized material was utilized as an active component for the application of a supercapacitor. The performances of the material were examined on a nickel foam for a three-electrode electrochemical cell. The material showed the maximum specific capacitance (CSP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${C}_{SP}$$\\end{document}) value of 255 F.g−1 at the current density (CD) of 2 A.g−1. Further, an asymmetric supercapacitor (ASC) device was fabricated with BPO and single wall carbon nanotube (SWCNT) as negative and positive electrodes, respectively, which delivered a specific capacity (Qs)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(Qs)$$\\end{document} value of 1462 mAh.g−1 under the CD of 0.4 A.g−1 with the energy density (ED) and power density (PD) values of 2.2 Wh.kg−1 and 0.68 kW.kg−1, respectively. The device exhibited capacity retention and coulombic efficiency (CE) values of 84 and 95% at 0.9 A.g−1 for 10,000 galvanostatic charge–discharge (GCD) cycles. The ASC device generated a low-frequency waveform and has the potential to function as an oscillator.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.

Compositing LaSrMnO3 perovskite and graphene oxide nanoribbons for highly stable asymmetric electrochemical supercapacitors

The anticipated large contribution of renewable energy resources to the sector of energy production strongly motivated the development of energy storage technologies, of which supercapacitors have drawn a lot of attention. In this work, Lanthanum-Strontium-Manganese-oxide (LSMO) perovskite nanoparticles, graphene oxide nanoribbons (GONRs), and LSMO-GONRs composite were synthesized and tested as electrode materials for supercapacitor applications. The LSMO was synthesized using the co-precipitation/calcination method, while the GONRs were synthesized using the oxidative unzipping of multi-walled carbon nanotubes. The physical/chemical structures were studied using XRD, FT-IR, SEM, TEM, SAED, and XPS. In 1 M KOH, the LSMO-GONRs electrode exhibited a specific capacitance of 490F/g compared to 342F/g and 294F/g for GONRs and LSMO electrodes, respectively, at 1 A/g, showcasing a performance that is not just superior but truly impressive, to the different types of perovskite/carbon-based material composites. The fabricated asymmetric SC device of LSMO-GONRs//GONRs exhibited a potential window of 1.7 V, a specific capacitance of 92.3F/g, an energy density of 38 Wh/kg, and a power density of 860 W/kg at 1 A/g. Moreover, the LSMO-GONRs//GONRs device showed excellent capacity retention and Coulombic efficiency after 10,000 cycles at 10 A/g, revealing the promising employment of LSMO-GONRs composite as a highly stable material for supercapacitor applications.

Facile synthesis of MCo2O4(M= Ni, Cu, and Zn) materials for high-performing electrochemical capacitors with robust cyclic stability using redox additive electrolyte

Developing efficient electrochemical capacitors relies heavily on the quality of electrode materials and electrolytes used. This report presents the successful solvothermal synthesis of three cobaltites, NiCo2O4, CuCo2O4, and ZnCo2O4, and their electrochemical performance in a 2M KOH solution. Among the three cobaltites, NiCo2O4 showed the best electrochemical performance with a specific capacity of 178 C/g with FTO (fluorine-doped tin oxide) as the current collector. In addition, the performance of NiCo2O4 was tested in different aqueous electrolytes, including KOH, NaOH, NaCl, and Na2SO4, and the specific capacity was found to vary in the order of 2 M KOH > 2 M NaOH > 2 M NaCl > 2 M Na2SO4. The performance of NiCo2O4 was also assessed in various concentrations of KOH electrolyte (2 M KOH, 3 M KOH, and 4 M KOH), and the best performance was observed in 3 M KOH with a specific capacity of 928.3 C/g with Ni foam as the current collector. Finally, using redox additive electrolytes, the performance of synthesized NiCo2O4 was evaluated in both 3-electrode and 2-electrode systems. No studies have been conducted on the electrochemical performance of NiCo2O4 with KFCN redox additive in a 3 M KOH electrolyte. In the three-electrode system, NiCo2O4 showed a high specific capacity of 1005.5 C/g at 1 A/g, with 167 % capacity retention after 1000 charge-discharge cycles at a high current density of 30 A/g. The NiCo2O4//Activated Carbon asymmetric hybrid supercapacitors in two-electrode systems exhibited a maximum specific capacity of 115.6 C/g and a specific energy density of 85 Wh/kg at a specific current density of 1 A/g. They also showed a capacitive retention of 120% after 5000 charge-discharge cycles. The maximum power density was 13225 W/kg at a current density of 5 A/g while maintaining an energy density of 22 Wh/kg.

Layer-by-layer WS2-Cr heterojunction as a positive working electrode material for high-performance supercapattery applications

This study investigates the impact on the electrochemical performance of pristine sputtered WS2 through the strategic integration of a highly conductive chromium interfacial layer. This study involves the fabrication of two different samples via magnetron sputtering: type I, WS2-sputtered and type II, WS2/Cr (sputtering of Cr as an interfacial layer between sputtered-WS2 and NF). Afterward, structural, topographic and elemental composition of as-synthesized samples were inspected via XRD, SEM, Raman, and EDX. Following this, the energy storage performance were evaluated by employing CV, GCD, and EIS in three and two electrode assembly sequentially. In three electrode testing WS2 and WS2/Cr exhibited the specific capacity (Qs) of 661.79C g−1 and 1600C g−1 at 3 mV/s along with the capacity retention of 61.37 % (WS2) and 83.04 % (WS2/Cr), respectively. Similarly, through GCD WS2 shows the Qs of 637.34C g−1 at 0.8 A/g conversely, WS2/Cr exhibited the Qs of 1220C g−1 at 1.3 A/g. Besides, the WS2/Cr demonstrated long-term longevity (capacity retention of 83.13 %) after 5000 GCD cycles. Based on exclusive electrochemical performance of type II of two samples, an asymmetric battery-type hybrid supercapacitor (WS2/Cr//AC) was fabricated by incorporating WS2/Cr and activated carbon (AC) as working and counter electrodes. WS2/Cr//AC revealed the Qs of 352C g−1 (785F g-1) at 0.7 A/g. Besides, it deliberately delivered 81 Wh kg−1 and 1750 W kg−1 energy and power. The device exhibits excellent cyclic stability by maintaining its capacity after 5000 GCD cycles and illustrated 87.30 % capacity retention. Following that, semi-empirical approach was applied to quantify the capacitive and diffusive currents’ contribution in overall device’s performance. The results highlight that WS2/Cr hold colossal potential to fill the proficiency gap between presently keep-going devices and stern demands of future energy storage applications.

MnO2-decorated flexible carbon nanofibers with controllable hierarchical porous nanostructures for high energy density supercapacitors

Constructing hierarchical porous structures and reducing material size enhance the electrochemical efficiency of porous carbon-based electrodes. In this study, ultrafine hierarchical porous carbon-based nanofibers were synthesized via electrospinning a blend of polyacrylonitrile, polymethyl methacrylate (PMMA), and zinc acetate dihydrate (ZAH), followed by pre-oxidation, carbonization, and acid washing. Adjusting the ZAH content allowed precise control of fiber diameters (300-600nm) and promoted significant hierarchical porous structures, achieving an optimal mesopore to micropore ratio (1.65) and a high specific surface area (SSA) of 599 m²/g. MnO2 nanosheets were in-situ modified on the carbon nanofibers, forming a hybrid electrode (MnO2@HPCNFs) with excellent flexibility, high SSA value, and rich pore structure. This electrode demonstrated a specific capacitance value equal to 1035 F/g at 0.5 A/g and maintained 80.7% capacitance at 10 A/g. The assembled asymmetric supercapacitor achieved an energy density of 54.81 Wh/kg. This study presents new possibilities for binder-free, self-supporting electrodes in electrochemical energy storage devices.

A hierarchical Cu2SnO4@NiCo-LDH nanofilament structure as a new-potent electrode for energy storage

Our research continues to explore innovative, efficient electrode materials and new production processes for electrochemical devices. Supercapacitors remain at the forefront of energy storage solutions, thanks to their exceptional power density, cycling durability, and mechanical robustness. For the first time, we have developed a hierarchical Cu2SnO4@NiCo-LDH nanocomposite using a straightforward hydrothermal technique coupled with an annealing process on a nickel foam substrate. This study introduces the novel Cu2SnO4@NiCo-LDH (CSO@NC-LDH) material, distinguished by its unique nanofilament structure and impressive electrochemical properties, including a high specific capacitance of 2791.5 F g−1 at 1 A g−1. Additionally, we created an asymmetric supercapacitor using CSO@NC-LDH for the positive electrode and activated carbon (AC) for the negative electrode. This system showcases an outstanding energy density of 108.67 Wh kg−1 and a notable power density of 1.05 kW kg−1 at an operating voltage of 1.6 V. These exciting results highlight the promising potential of CSO@NC-LDH nanofilaments as advanced electrodes for next-generation energy storage devices.

MOF-on-MOF Derived Co2P/Ni2P Heterostructures for High-Performance Supercapacitors.

Metal-organic frameworks (MOFs) have been widely used as versatile precursors to fabricate functional nanomaterials with well-defined structures for various applications. Herein, the presynthesized Ni-MOF nanosheets were grown on a Ni foam (NF) substrate, which then guided the nucleation and further growth of Prussian blue analogues (PBA) nanocubes to form MOF-on-MOF of the PBA/Ni-MOF film. This film was subsequently converted into a Co2P/Ni2P heterostructure. The NF-supported Co2P/Ni2P composites exhibited excellent supercapacitor performance, delivering a high specific capacity of 5124.2 mF cm-2 at 1 mA cm-2 and a remarkable capacity retention of 80.69% after 3000 cycles at 10 mA cm-2. An asymmetric supercapacitor assembled using Co2P/Ni2P/NF as the cathode and activated carbon as the anode yielded a maximum energy density of 0.34 mWh cm-2 at a power density of 1.50 mW cm-2. The enhanced supercapacitor performance is attributed to the synergistic effects of the Ni2P and Co2P components with multiple valence states as well as the unique hierarchical structure, which provides efficient pathways for electron and ion transport while mitigating volume expansion during energy storage. This synthetic strategy demonstrates an effective approach to fabricate phosphide-based hybrid materials for high-performance supercapacitor applications.

Hierarchical Nb@NbN core-shell-like nanocolumns for asymmetric supercapacitors

Transition metal nitrides (TMNs) are promising electrode materials for supercapacitors because of their high electrical conductivity and chemical stability. The rational design and facile synthesis of TMNs electrode materials with a unique nanostructure are the key to develop high-performance supercapacitors. Herein, we propose a two-step, binder-free, and eco-friendly approach utilizing magnetron sputtering at an oblique angle deposition configuration to fabricate hierarchical Nb@NbN core–shell-like nanocolumns for supercapacitors. This distinctive heterostructure not only creates lattice defects, increases active surface area, facilitates ion diffusion and charge transfer, but also optimizes the electronic structure and enhances the conductivity. As a result, the hierarchical Nb@NbN core–shell-like nanocolumn electrodes exhibit a high areal capacitance of 53.3 mF cm−2 at 1 mA cm−2 and an excellent capacitance retention of 93.5 % after 20,000 cycles, outperforming pristine NbN and the majority of previously reported TMNs electrodes. Moreover, the assembled Nb@NbN nanocolumns//VN thin films asymmetric supercapacitor device can deliver a maximum energy density of 49.8 mWh cm−3 and power density of 82 W cm−3. This work presents a facile and environmentally friendly strategy for the synthesis of TMNs core–shell-like nanocolumns, and further demonstrates their promising potential for use in supercapacitors.

A hierarchical surface-coated 3D-Nanoflower network of MoS2 with abundant reaction sites for high-performance asymmetric supercapacitor

A hierarchical surface-coated 3D-Nanoflower network of MoS2 with abundant reaction sites for high-performance asymmetric supercapacitor

Supercapacitor devices based on multiphase MgTiO3 perovskites doped with Mn2+ ions

Recently, perovskites have become a hotspot for researchers attempting to exploit metal and oxygen vacancies in structures of the form MTiO3, facilitating the convenient electron/hole migration, thus displaying interesting properties. Magnesium Titanate (MgTiO3) is a prominent part of the perovskite class, exhibiting remarkable electrical, thermal, and chemical properties. Undoped and Mn-doped MgTiO3 samples were obtained using a solid-state reaction starting from previously synthesized MgO and TiO2 powders, which were separately doped with different Mn ion concentrations. The resulting multiphase materials with a major MgTiO3 phase were thoroughly morpho-structurally analyzed employing XRD, STEM, Raman, PL, XPS, and EPR spectroscopy. The electrochemical results indicate that they show superior performance when used as electrode materials for supercapacitor application due to the high defect concentration as shown in EPR and PL spectroscopy and the ferroelectric behavior observed in XPS and XRD. When used in symmetric and asymmetric supercapacitor devices, they show promising results, with specific capacity values reaching up to 109 F/g for the symmetric and 609 F/g for the asymmetric devices, while energy and power density values reached 84.7 Wh/kg and 90.8 kW/kg respectively, proving a great potential in the energy storage field.

Phosphorus-doped carbon nitride for enhanced supercapacitor performance and energy storage applications

Exploiting the advantages of graphitic carbon nitride doped with phosphorus (xP-CN) electrodes were designed for high-performance hybrid asymmetric supercapacitor via facile hydrothermal and thermal decomposition techniques. The structural, surface chemistry, functional and morphological characterizations evidence depict successful phosphorus incorporation in Carbon Nitride (CN). X-ray photoelectron spectroscopy analysis shows that phosphorus (P) atoms have replaced corner carbon atoms in the CN structure. These findings clearly demonstrate that the presence of phosphorus doping improves the electrochemical activity of the electrodes. The designed three-electrode system has a specific capacitance of 189.36 F/g with a current density of 1 A/g. Phosphorus doping has been discovered to play a significant role in improving both specific capacitance and cycling stability. The capacitance retention of the two-electrode solid-state device has 97.2 % after 5000 cycles. These electrochemical evaluations reveal that the xP-CN electrode exhibits superior electrochemical performances than pristine CN. This doping strategy for CN presents a novel and efficient approach for crafting high-performance supercapacitors.

A porous three-dimensional Cu-MOF: Preparation and application in supercapacitors, low temperature hydrogen storage and gas separation

Due to its unique porosity, metal–organic frameworks (MOFs) have great application prospects in the fields of gas adsorption and separation. However, the synthesis of multi-functional MOFs is still a great challenge. Herein, a multi-functional Cu-MOF of {[Cu2(TPTA)(H2O)2]·2DMF·NMP·4H2O}n with a porosity of 62.0 % was designed and synthesized. The H2 adsorption amount of Cu-MOF is about 289.2 cm3 g−1 at 77 K and 1 bar. Meanwhile, the selectivity adsorption of Cu-MOF towards CO2 over CH4 (V:V = 0.5:0.5), CO2/N2 (V:V = 0.5:0.5) and CO2/H2 (V:V = 0.5:0.5) is 95.1, 139.2 and 147.5, respectively, which is 1.5 times higher than the previously reported Cu-MOFs. The Cu-MOF@NF//AC asymmetric supercapacitor demonstrates high specific capacitance (53.4 F g−1) and stability (90.3 % after 2000 cycles). Furthermore, this work presents a novel approach to design multifunctional materials with low temperature hydrogen storage, gas separation and energy storage properties.

Non-cytotoxic, biocompatible pyrochlore Cerium Zirconium Oxide nanoparticles for asymmetric supercapacitor applications

A novel biocompatible and non-cytotoxic Ce2Zr2O7 (CZO) nano-sized particles were developed by a straightforward hydrothermal method. Cubic structure with Fd-3m space group (227) of prepared nanoparticles has been confirmed from X-ray diffraction (XRD) patterns. Nano-sphere like particle morphology was conspicuously noticed from the FE-SEM and TEM investigations thoroughly. Particle size, inter-planar distance, SAED pattern and elemental presence were affirmatively evaluated. The elemental presence in the sample and their ionic states were systematically investigated through X-ray photoelectron spectroscopy analysis. We have investigated the cytotoxicity of the Ce2Zr2O7 nanoparticles on C2C12 (mouse myoblast cell line) cells and observed to be non-cytotoxicity on C2C12 cells which supports the eco-friendly and biocompatible nanoparticles. We have investigated the electrochemical performance of Ce2Zr2O7 nanoparticles using various electrolytes such as Na2SO4, Li2SO4 and KOH. We have obtained the predominant electrochemical performance of 250 F g−1 at 0.05 A g−1 along with appreciable cycling durability from KOH electrolyte interestingly. In addition, we fabricated asymmetric supercapacitor device and evaluated its energy and power densities systematically. We have evaluated maximum energy and power densities are in the order of 13 Wh kg−1 and 3692 W kg−1, respectively. Therefore, eco-friendly and biocompatible Ce2Zr2O7 nanoparticles could be suggested as a contender for the electrode substance for supercapacitor applications. This investigation has also been an usher hope of further technological advancement in the field of nano-biomedical along with energy storage research fields.

Carbon bi-metallic molybdenum tungsten oxide composite as a potential electrode for high-performance asymmetric supercapacitor

Molybdenum tungsten oxide (MTO) bi-metallic structure was synthesized using Pechini method. Asymmetric supercapacitor (SC) was constructed using MTO/ active carbon (AC) and H2SO4 electrolyte. Different AC: MTO weight ratios proved a high impact on composite electrochemical performance. Galvanostatic charge-discharge tests demonstrated a capacitance of 336.75 F/g, with 37.11 % capacitance shrinking upon increasing the applied current to 5 A/g (50-fold) from 0.1 A/g. Such high-rate capabilities were attributed to lattice spacing induced by inserting tungsten (W) into the MO lattice. The optimized ratio of MTO/AC possesses a high specific energy and power of ∼120 Wh/kg and 256 kW/kg at 0.1 and 80 A/g, respectively. Moreover, the composite is showing ∼100 % retention values after 20k cycling at a high current of 80 A/g. Unlike many reports of using first-class transition metal oxides for energy storage devices, bi-heavy metal composite functionalization in SC applications is scarce. This potential composite between porous carbon and bi-heavy metal oxide suggested talented electrode materials for energy storage systems.

Fabrication of high-performance asymmetric supercapacitor using hybrid niobium (V) oxide anchored La2O3 nanocomposite for high energy density performance

Fabrication of high-performance asymmetric supercapacitor using hybrid niobium (V) oxide anchored La2O3 nanocomposite for high energy density performance

Fabrication of asymmetric supercapacitors by laser processing of activated carbon-based electrodes produced from rice husk waste

The development of supercapacitors (SCs) by using carbon electrodes obtained from biomass waste simultaneously promotes the optimized use of the renewable energy by its high-powered storage, and the reduction of contamination in nature. Such industrial sector would be an excellent opportunity also for the developing nations, promoting their economic growth by the conversion of biowaste into added value goods. However, such carbon may not reach the desired performance for SCs. In this work, we used laser processing technology for enhancing the capacitance of SC electrodes composed of activated carbon obtained from rice husk produced in Nigerian farmlands. The activated carbon powder was synthesized by conventional carbonization-chemical activation processes and treated with microwaves. Afterwards, the CO2 laser processing of thin film electrodes composed of a mixture of the carbon powder with carbon black (conductive additive), and precursors as urea (for doping of the activated carbon with nitrogen), or manganese nitrate (for the crystallization of pseudocapacitive Mn3O4 nanoparticles on the carbon surface) was carried out for obtaining enhanced positrodes and negatrodes. The resulting hybrid electrodes exhibited a 3-fold increase of the capacitance (up to 134 F/g @ 10 mV/s) as compared to the raw carbon in the [0, 0.8] V potential window. Asymmetric SC devices integrated by carbon (-)//carbon-Mn3O4 (+) laser-treated electrodes, operating at 1.2 V voltage, revealed up to 300 × higher energy and power densities than symmetric SCs composed of raw carbon electrodes.

Synthesis of Ni(OH)2‐g‐C3N4/C Composite by Biological Template for Asymmetric Supercapacitor

Nickel hydroxide (Ni(OH)2) is recognized as a promising material for electrodes in supercapacitors owing to its exceptional theoretical specific capacitance. However, Ni(OH)2 has several drawbacks, including a short cycle life, susceptibility to volume expansion, and poor electrical conductivity. In this work, Ni(OH)2 nanosheets anchored on layered g‐C3N4/C (Ni(OH)2–g–C3N4/C) are designed by biological template induction and a hydrothermal method. Ni(OH)2–g–C3N4/C has unique petal‐like structures, which can provide a vertical charge transport channel to increase reaction potential of the material during the charge–discharge process. The introduction of biomass carbon can solve the problem of the bulk phase accumulation of g‐C3N4 and can also improve the overall conductivity of the composite. Compared to Ni(OH)2 (522 F g−1), g‐C3N4/C (76.2 F g−1), and g‐C3N4 (16 F g−1), the Ni(OH)2–g–C3N4/C‐0.75 (NGC‐0.75) composite exhibits the highest specific capacitance of 1034 F g−1 at 1 A g−1. Furthermore, after 5000 cycles at 5 A g−1, the capacitance of the material is maintained at 85.97%. Meanwhile, the asymmetric supercapacitor based on the NGC‐0.75 shows a high energy density of 18.29 Wh kg−1 at the power density of 400.02 W kg−1 with excellent cyclic stability of 127.45% over 10 000 cycles.