Supercapacitor Positive Electrode Research Articles

Performance study of bimetallic Mn-Zn porous flower-like nanosheets as supercapacitor positive electrode materials

As environmental and carbon emission issues become increasingly severe, electrochemical energy storage systems have gained attention. Compared to traditional supercapacitors, zinc-ion hybrid capacitors (ZIHCs) are not only environmentally friendly but also cost-effective. MnO2, with its low cost, eco-friendliness, high theoretical capacity, and stable crystal structure, is considered a promising positive electrode material. In this study, the morphology of MnO2 was optimized using electrodeposition. During cycling, zinc ions reversibly intercalate and extract from MnO2, forming a cactus-like nanoflower structure. This structure is loose and porous, providing ample reaction space for active materials. The assembled device exhibits excellent performance in both energy density (85.68 Wh kg−1) and stability (91.60 %).

Impact of trivalent Yttrium on the structural and optical properties of CaAl2O4: New frontier in supercapacitor positive electrode

In this work, trivalent Yttrium doped calcium aluminate (CaAl2O4:x% Y3+) were synthesized for the first time. Through Photoluminescence (PL) spectroscopy and Commission Internationale de l’Eclairage (CIE), CaAl2O4:0.1 % Y3+ has demonstrated to be a potential high emitting phosphor material amongst other high concentration Y3+ doped samples, emitting a vibrant blue – pink hue where others are emitting a transiting hue from blue to green within a white vertex region. FTIR and UV–Vis have confirmed the prepared material and the presence of Y dopant. The SEM showed insignificant morphological change and the presence of pores, which were quantified using BJH and DFT methods to be micro – and meso–pores. Moreover, CaAl2O4 is also being reported as a positive electrode in supercapacitors for the first time. The analysis shows that it has superior performance within 1 M KOH electrolyte, with a specific capacity of 47.71 mA h g−1 at 1 A g−1 and a maximum power of 39.68 kW kg−1. Trasatti's method showed a surface (138 Fg-1) and diffusion (695 Fg-1) contribution ratio of 17:83 (%) of the total stored energy. It has a capacity retention and columbic efficiency of 100 % at the end of 10 000 cycles, which was achieved via utilization of all micropores reaction sites. The EIS showed a small solution resistance of 0.75 Ω, indicating high ionic conductivity and a phase angle of – 50 °. Thus, these results show that CaAl2O4 is a potential candidate for photoluminescence and energy storage application.

High performance hybrid supercapacitors assembled with multi-cavity nickel cobalt sulfide hollow microspheres as cathode and porous typha-derived carbon as anode

Unique hollow structures hold bright promise in the field of energy storage applications, but it is still challenging to synthesize bimetallic sulfide composites with complex hollow structures. In the present work, a NixCo1−xS2/NiCo2S4 composite with multi cavity hollow sphere structure is prepared by a simple liquid-phase reaction and solvothermal sulfurization and used as a supercapacitor positive electrode material. Benefiting from the well-designed unique structure and synergy between the nickel and cobalt elements, the composite exhibits excellent electrochemistry with a specific capacity of 797 C g−1 at 1 A g−1 and possesses good rate capability (78.8 % retention at 20 A g−1). In addition, Typha-derived carbon is prepared by calcination using discarded biomass Typha. And, a hybrid supercapacitor device is assembled by using NixCo1−xS2/NiCo2S4 and Typha-derived carbon as cathode and anode. The device exhibits a high energy density of 82.7 Wh kg−1 at 513.5 W kg−1 and possesses superior long-term cycling capacity (84.6 % after 10,000 cycles), indicating the great application potential of the composites in the field of supercapacitors. More importantly, the unique structural design and facile operation methods provide new ideas and broad prospects for the synthesis of complex metal sulfide materials in the energy storage field later.

“One-for-two” strategy: The construction of high performance positive and negative electrode materials via one Co-based metal organic framework precursor for boosted hybrid supercapacitor energy density

In this work, using a Co-based metal organic framework (Co-MOF) array as precursor, the high performance supercapacitor positive electrode (CNVS: Ni/V-doped Co3S2@Co/Ni-doped VS2 hetero-structure) and negative electrode (CNFS: Fe/V-doped Co3S2@Co/Fe-doped VS2 hetero-structure) are successfully constructed by a “one-for-two” synthesis strategy. Benefiting from their unique hollow triangular arrays, rich mesoporous structure constructed by M3S2/MS2 heterogeneous interface, abundant active centers originating from the defect of elements doping, the optimized CNVS and CNFS can improve the transfer ratio of electrons and electrolytes for fast kinetics, and provide more electroactive sites for deeply redox reaction. Therefore, an outstanding specific capacitance of 6556 mF cm−2 (910.56 μA h cm−2) is achieved by CNVS electrode under 0–0.5 V (vs. Hg/HgO) at 2 mA cm−2, and the CFVS electrode displays a high specific capacitance of 6195 mF cm−2 (1720 μA h cm−2) under −0.1 to −1.1 V range (vs. Hg/HgO) at 5 mA cm−2. Furthermore, a high-performance hybrid supercapacitor (HSC) is assembled with CNVS as the positive electrode, and CFVS as the negative electrode, which presents an ultrahigh energy density of 0.83 mWh cm−2 at a power density of 4.56 mW cm−2, and excellent cycle performance of maintaining 79.6% initial capacity after 5000 cycles.

Metal organic frameworks derived Ni-doped hierarchical NiXCo1-XS@C bundled-like nanostructures for enhanced supercapacitors

Metal-organic frameworks (MOFs) and their derivatives in the area of energy store have received extensive attention. Here, 3D hierarchical bundle-like micro/nanostructure Ni-Co-MOFs were designed via a co-precipitation and external metal-atom doping strategy. Based on the distinctive precursor, a carbon coated Ni-Co-S nanoparticles were prepared through a two-step thermal annealing. The Ni doping into CoS can both regulates electronic structure and stabilizes Co species as electrode material for supercapacitor. By optimizing the content of Ni-doping, the fabricated NiXCo1-XS/C-3 with 25% Ni-doping shows remarkable specific capacitance (709 C/g at 1 A/g), superior rate capability and excellent cycling stability. An asymmetric supercapacitor with an energy density of 45.3 Wh/kg was acquired successfully in two-electrode system. NiXCo1-XS possess a high OH− adsorption energy compared to single NiS and CoS was proved by density functional theory calculations. Strong OH− adsorption ability is conducive to capture electrolyte ions, which leads to rapid redox reaction kinetics. In addition, this work provides new ideas for how to design metal sulfide-based supercapacitor positive electrode materials.

In-situ formation of α-Co(OH)2 nanosheet arrays on magnesium cobaltate nanowires for hybrid supercapacitors with enhanced electrochemical performance

In this work, the MgCo2O4@α-Co(OH)2 core–shell structure (MgCo2O4@α-Co(OH)2/NF) on foam nickel was prepared using hydrothermal annealing and chemical bath deposition processes to form a supercapacitor positive electrode. MgCo2O4@α-Co(OH)2/NF-2 composite material, with a deposition time of 20 min in a chemical bath, showed a specific capacitance of 1634.8 F g−1 at 1 A g−1, a long cycle stability of 89.4% (in 10,000 cycles) and a rate performance of 78.29%, with excellent electrochemical impedance performance (Rs ≈ 0.507 Ω). The MgCo2O4@α-Co(OH)2/NF-2//AC asymmetric supercapacitors (ASCs) showed a specific capacitance of 185.46 F g−1 at 1 A g−1, with a good long-cycle stability of 91.7% preservation rate after 10,000 cycles. At a power density of 773.19 W kg−1, the energy density is high (65.94 Wh kg−1). We demonstrated that three prepared ASCs devices can produce a diode with a rated voltage of 3 V that continues to emit light for 10 min. This study shows that the MgCo2O4@α-Co(OH)2/NF-2 electrode can be used as a positive electrode for high-efficiency energy storage devices.

Ultrathin Mn Doped Ni‐MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor

In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn0.1 -Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn0.1 -Ni-MOF/NF shows an areal capacity of 6.48 C cm-2 (specific capacity C: 1178 C g-1 ) at 2 mA cm-2 in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn0.1 -Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg-1 at 143.8 Wkg-1 power density with a capacitance retention of 83.6 % after 5000 cycles.

Hierarchical MnO2@NiCo2O4@Ti3SiC2/carbon cloth core-shell structure with superior electrochemical performance for all solid-state supercapacitors

Core-shell hierarchical structured composites have demonstrated great advantages in numerous energy storage devices. In particular, structured composites with rationally structural components and controllable morphology are the most effective in enhancing electrochemical properties. In this work, MnO2@NiCo2O4@Ti3SiC2/CC (carbon cloth) core-shell hierarchical structured composites were designed and successfully synthesized via electrospinning followed by a two-step hydrothermal reaction. The Ti3SiC2/CC nanofibers and core-shell nanoarrays were able to improve the specific capacitance and cycling stability. In the three-electrode system, the specific capacitance of MnO2@NiCo2O4@Ti3SiC2/CC was observed as 1938.2 F/g at a current density of 1 A/g, while the rate capability retention was observed as 81.7% between 1 and 10 A/g. Furthermore, a superior cycling stability was observed following 5000 cycles with a specific capacitance retention rate of 55.4%. Employing MnO2@NiCo2O4@Ti3SiC2/CC as the all solid-state supercapacitor positive electrode exhibited a high energy density of 58.0 W h/kg at the power density of 800 W/kg. Results demonstrate the potential of the MnO2@NiCo2O4@Ti3SiC2/CC as an electrode material with phenomenal electrochemical properties for supercapacitors.

The co-electrodeposition of NiCo dihydroxide/carbon nanotubes nanocomposite on Ni3Se2-modified nickel foam for hybrid supercapacitor

In this work, one-step electrodeposition of multiwalled carbon nanotube/NiCo dihydroxide nanocomposite (MWCNT/NiCo-DH) was developed to fabricate supercapacitor positive electrode. However, the poor adhesion of the composite to the Ni foam (NiF) seriously hampered its practical applications. We discovered that by modifying the Ni foam with Ni3Se2, the adhesion of the MWCNT/NiCo-DH to the Ni foam was dramatically improved. By investigating the obtained MWCNT/NiCo-DH/Ni3Se2/NiF, it was found out that the introduction of Ni3Se2 not only makes the electrode materials firmly attach to the surface of the Ni foam but also significantly enhances its electrochemical behaviors. MWCNT/NiCo-DH/Ni3Se2/NiF presents a high areal capacity of 3.55 C cm−2 at a very high current density of 60 mA cm−2. It is especially worth noting that MWCNT/NiCo-DH/Ni3Se2/NiF retains almost 100% of its initial capacity even after 2000 consecutive galvanostatic charge–discharge cycles, suggesting excellent cycling stability. An asymmetric supercapacitor (ASC) is also assembled with MWCNT/NiCo-DH/Ni3Se2/NiF as the positive electrode and active carbon as the negative electrode. The ASC displays a prominent energy density of 35.52 Wh kg−1 at a high power density of 485.12 W kg−1. The excellent capacitive performance of MWCNT/NiCo-DH/Ni3Se2/NiF is partly because of the modification of NiF with Ni3Se2 and partly due to the incorporation of MWCNT, which improves the electric conductivity of the electrode material.

Highly Rate Capable Nanoflower-like NiSe and WO3@PPy Composite Electrode Materials toward High Energy Density Flexible All-Solid-State Asymmetric Supercapacitor

An advanced novel all-solid-state asymmetric supercapacitor (ASC) device of high energy and power densities is designed on the basis of the nanoflower-like NiSe as the positive electrode and WO3@PPy composite as the negative one. The porous NiSe was prepared by facile selenization of predesigned NiO nanoflowers, and the WO3@PPy composite was synthesized through in situ oxidative polymerization of pyrrole in the presence of dispersed WO3 nanosticks which, in turn, was produced by a simple sulfate-assisted hydrothermal method. When tested as a supercapacitor positive electrode in the three-electrode system, the NiSe exhibits an appreciably higher specific capacitance of 1274 F g–1 at 2 A g–1 than that of the NiO nanoflower (774 F g–1). Again, as the negative electrode, the WO3@PPy composite also shows excellent electrochemical properties with a higher specific capacitance (586 F g–1 at 2 A g–1) than those of either of its components (WO3: 402 F g–1 and PPy: 224 F g–1). Based on these properties of the respe...

Constructing hierarchical lanthanum-doped nickel hydroxidenitrate nanoflowers with dilated lattice spacing for improving asymmetric supercapacitors

The novel lanthanum-doped nickel hydroxidenitrate (LaNiHN) nanoflowers are prepared by a facile one-step solvothermal growth method. The doping of La ions into the lattice of the NiHN nanoflowers can effectively increase the electrical conductivity, lattice volume and c-axis spacing of NiHN nanosheets and lead to rapid transfer of electrolyte ions and electrons between the nanosheet channels, resulting in a high specific capacity of 154 mAh g−1 (at 1 A g−1) and high rate performance for supercapacitor positive electrode. Moreover, the Fe2O3 supported on graphene nanosheets (Fe2O3/GNS) with high specific capacity and excellent stability is selected as negative electrode to match the LaNiHN nanoflowers positive electrode for assembly of a novel LaNiHN//Fe2O3/GNS asymmetric supercapacitor (ASC). By virtue of their excellent electrochemical properties and complementary working voltage, the as-assembled ASC possesses a wide operating voltage of 1.65 V, high energy density of 51 Wh kg−1 at a power density of 825 W kg−1, as well as the acceptable cycling stability of 87% capacity retention after 5000 cycles.

MOF-derived α-NiS nanorods on graphene as an electrode for high-energy-density supercapacitors

α-NiS/rGO nanohybrids synthesized from water-refluxed Ni-MOF-74/rGO were applied as a high-performance hybrid supercapacitor positive electrode for the first time.

Rational Construction of Hollow Core-Branch CoSe2 Nanoarrays for High-Performance Asymmetric Supercapacitor and Efficient Oxygen Evolution.

Metal selenides have great potential for electrochemical energy storage, but are relatively scarce investigated. Herein, a novel hollow core-branch CoSe2 nanoarray on carbon cloth is designed by a facile selenization reaction of predesigned CoO nanocones. And the electrochemical reaction mechanism of CoSe2 in supercapacitor is studied in detail for the first time. Compared with CoO, the hollow core-branch CoSe2 has both larger specific surface area and higher electrical conductivity. When tested as a supercapacitor positive electrode, the CoSe2 delivers a high specific capacitance of 759.5 F g-1 at 1 mA cm-2 , which is much larger than that of CoO nanocones (319.5 F g-1 ). In addition, the CoSe2 electrode exhibits excellent cycling stability in that a capacitance retention of 94.5% can be maintained after 5000 charge-discharge cycles at 5 mA cm-2 . An asymmetric supercapacitor using the CoSe2 as cathode and an N-doped carbon nanowall as anode is further assembled, which show a high energy density of 32.2 Wh kg-1 at a power density of 1914.7 W kg-1 , and maintains 24.9 Wh kg-1 when power density increased to 7354.8 W kg-1 . Moreover, the CoSe2 electrode also exhibits better oxygen evolution reaction activity than that of CoO.

Bifuntional petaloid nickel manganese layered double hydroxides decorated on a freestanding carbon foam for flexible asymmetric supercapacitor and oxygen evolution

In this work, we develop a bifunctional composite comprised of hierarchical flower-like NiMn-layered double hydroxides (LDH) nanoarrays grown on melamine sponge-derived carbon (SC). This composite material is used as a flexible asymmetric supercapacitor positive electrode and oxygen evaluation reaction (OER) electrocatalyst. Integrated carbon foams with controllable three-dimensional pores are easily obtained and served as conductive backbones for the growth of the flower-like NiMn-LDH nanoarrays. The as-prepared flexible electrode, combining a highly open scaffold-like structure with well-designed electron transfer channels, shows significantly enhanced cyclic stability (99.6% of the initial activity maintained after 5000 cycles) and high energy density (41.0 Wh·Kg−1) in aqueous electrolyte. The as-prepared SC@NiMn-LDH@G//NPC asymmetric supercapacitor can lighten a LED indicator for more than 10minutes. Additionally, this composite presents extremely low overpotentials (220mV at 10 mA·cm−2) and low Tafel slopes (30 mV·dec−1) in alkaline medium. This OER performance is one of the best reported so far among the state of art electrocatalysts.

Improved electro-grafting of nitropyrene onto onion-like carbon via in situ electrochemical reduction and polymerization: tailoring redox energy density of the supercapacitor positive electrode

Physical grafting of 1-nitropyrene (Pyr-NO2) onto carbon onion via in situ reduction of the NO2 group and pyrene polymerization for supercapacitor positive electrode.

(Science for Solving Society’s Problems Challenge Grant Winner) Self-Powered Supercapacitive Microbial Fuel Cell

A self-powered supercapacitive microbial fuel cell (MFC) is here reported. Microbial fuel cell (MFC) is an interesting bio-electrochemical technology that is used for wastewater treatment with simultaneous organic removal and electricity generation. Due to the much lower current/power production compared to hydrogen and methanol fuel cells, a smart design is desired to increase performance up to the levels required for real applications. The most used method to store/deliver energy from an MFC at high rate is coupling it with an external supercapacitor with capacitances in the order of Farads1. The main disadvantage of this approach is that high capacitance supercapacitors require long time to be recharged at the low MFC current regimes. This makes the MFC-Supercapacitor system working with long recharge stand-by time and low switch-on/off frequency. Here, a microbial fuel cell has been integrated with internal supercapacitor (SC)2. The MFC anode was the SC negative electrode. Its potential (≈-0.5 V vs Ag/AgCl) was related to the presence of bacteria that consumed the oxygen present into the solution and colonize the carbon brush electrode. The MFC cathode, an air-breathing cathode working at ≈+0.1 V vs Ag/AgCl, was the SC positive electrode. Single chamber MFC filled with 50% volume of 0.1M phosphate buffer saline (PBS) solution and 50% activated sludge was used during the experiments. Galvanostatic discharges were performed with current pulses up to 4 mA. An MFC with activated carbon (AC)-based cathode featured a maximum power of 2.98 Wm-2 (5.36 Wm-3) which was mainly affected by the cathode ohmic losses. In order to further enhance the output, two strategies were adopted. The first one was simply enhance the overall cell voltage by utilizing cathode catalysts with higher potential like non-platinum based catalyst (iron-aminoantipyrine (Fe-AAPyr))3 or enzymatic-based catalyst (bilirubin oxidase (BOx)4). The second option was to utilize an additional high capacitive electrode of low resistance, short-circuited with the cathode, coupled with the negative electrode (MFC-AdE). The AdE used was a carbon brush coated with AC. The first option brought to the increase of the voltage from 0.6V with AC to 0.68V with Fe-AAPyr and to 0.78V with BOx cathode. Figure 1 showed the discharge of the MFC using Fe-AAPyr cathode with and without the AdE. Consequently, maximum power (Pmax) achieved 6.53 Wm-2 (11.76 Wm-3) and 4 Wm-2 (7.2 Wm-3) using BOx and Fe-AAPyr, respectively. The use of AdE significantly reduced the cell ohmic drop and led to a much important improvement (Figure 1). Pulses discharges up to 45 mA were performed. The cell resistance decreased by one order of magnitude allowing higher current pulses and power generated. In fact, Pmax was 84.4 Wm-2 (152 Wm-3) with BOx cathode, 62.2 Wm-2 (112 Wm-3) with Fe-AAPyr and 26.7 Wm-2 (49 Wm-3) with AC cathode. The addition of the AdE is a smart and easy way to overcome the ohmic losses of the system. This current/power output is in the same range of MFCs coupled with external supercapacitors. The main advantage of the system here reported is the much shorter recharging time (in the order of seconds/minutes) of interest for applications that have to be powered with more frequent pulses, like sensors. Also, utilization of the MFC electrodes as the supercapacitor electrodes makes the system simpler and more compact. Acknowledments CS was funded by the Electrochemical Society and Bill & Melinda Gates Foundation under initiative: “Applying Electrochemistry to Complex Global Challenges”. FS acknowledges financial support by Università di Bologna (Researcher Mobility Program).