Cyclic Galvanostatic Charge-discharge Research Articles

A high‐performance hybrid supercapacitor electrode based on ZnO/nitrogen‐doped carbon nanohybrid

AbstractHybrid nanomaterials offer promising properties to serve as an electrode for hybrid supercapacitors. Herein, dye (rhodamine B, RhB) encapsulated zeolitic imidazolate frameworks (RhB@ZIF‐8) was synthesized at room temperature via triethylamine (TEA)‐assisted method. The material was used as a precursor for synthesizing zinc oxide embedded nitrogen‐doped carbon (ZnO@N‐doped C) via the carbonization at different temperatures (400°C, 600°C, and 800°C). The materials were characterized using X‐ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), high‐resolution transmission electron microscope (HR‐TEM), energy‐dispersive X‐ray mapping (EDX), nitrogen adsorption–desorption isotherm, and X‐ray photoelectron microscope (XPS). ZnO@N‐doped C nanocrystals (15–20 nm) were used as an electrode for a hybrid supercapacitor. ZnO@N‐doped C exhibited a high capacitance of 1200 F·g−1 at a current density of 1 A·g−1 without losing any capacitance (87.7% of initial capacitance) even after 1000 galvanostatic charge–discharge cycles (GCDCs). The presence of a guest molecule such as RhB improved the capacitance of the carbonized ZIF‐8 two‐fold compared with the carbonized materials using conventional ZIF‐8.

Charge storage behavior of sugar derived carbon/MnO2 composite electrode material for high-performance supercapacitors

Herein, we present an efficient and simple method to develop a 3D-Carbon /MnO2 (C/MnO2) composite active material for high-performance supercapacitors. MnO2 nanorods are synthesized by the hydrothermal process, and corresponding carbon composite is synthesized from table sugar precursors using the combustion process. MnO2 has rod-like morphologies and forms 3D electrode architectures with carbon, and contains about 5–10 nm of carbon coating. The charge storage behavior studied by galvanostatic charge-discharge cycling shows capacitance of 416 F g−1 at 1 A g−1 with capacitance retention of 90% after 5000 cycles. The superior electrochemical performance is attributed to the one–dimensional ion transport of Mn ion, the in-situ 3D electrode architecture, and carbon coating that enhances the conductivity and the surface area of MnO2. C/MnO2 composite exhibits an energy density of 60 Wh kg−1 with a power density of 201 W kg−1. The combined pseudocapacitive behavior of MnO2 and electric double-layer capacitors property of carbon exhibits significant electrochemical performance in the aqueous electrolyte. The synthesis approach uses environment benign active materials with the low cost of electrode fabrication provides an alternative route for the development of high-performance supercapacitors.

Three-dimensional bundle-like multiwalled carbon nanotubes composite for supercapacitor electrode application

Bundle-type mutil-walled carbon nanotubes (MWCNTs) composite electrode is the first investigation and publication for the supercapacitor application. According to the thermogravimetric analysis results, as-synthesized BCNTs are considered as the electrode materials for supercapacitors and electrochemical double-layer capacitor in this study. The Brunauer–Emmett–Teller specific surface area of as-prepared bundled carbon nanotubes (BCNTs) is 95.29 m2/g given to a type III isotherm and H3 hysteresis loops. Slow scanning rates promote and enhance to achieve high Cb because of the superior conductivity of CNT bundles and one side close-layered Ni/Mg/Mo alloy inside the BCNT-based electrode and facile electron diffusivity between electrolyte and electrode. The specific capacitance Cs (1,560 F/g) is nearly equal to the maximum specific capacitance, which the BCNT-based composite electrode can actually be able to charge or fill in. The maximum energy density value is 195 Wh/kg with corresponding power density values of 0.21 kW/kg. Furthermore, the active 3D BCNTs material fabricated electrode enhances to contact the electrolyte directly and decreases the ion diffusion limitation. Electrochemical impedance spectroscopy spectrum summarized as the low-frequency area controls by mass transfer limitation, and the high-frequency area dominates by charge transfer of kinetic control. After 2,000 consecutive cyclic voltammetry sacnings and galvanostatic charge-discharge cycles at a current density of 1.67 A/g performs, the specific capacitance retentions of 3D BCNTs electrodes achieved 128.2 and 77.3%, respectively. Three-dimensional BCNT composite electrodes exhibit good conductivity and low charge transfer resistance, which is beneficial to fast charge transfer between the BCNTs electrode materials and electrolytes.

Nanostructure modulation of Co3O4 films by varying anion sources for pseudocapacitor applications

We controllable designed and synthesized four kinds of three-dimensional (3D) hierarchical nanostructured Co3O4 thin films directly deposited on the nickel foam surface by a facile chemical bath deposition method. The morphologies of the Co3O4 films were regulated by using different anions (SO42−, NO3−, Cl−, and CH3COO−) originated from the precursors. The effect of different anions on the surface morphologies and pseudocapacitance behaviors of Co3O4 films was investigated by multiple electrochemical methods, including cyclic voltammetry (CV), galvanostatic charge-discharge cycles (GCD) and electrochemical impedance spectroscopies (EIS). The results indicated that the anions in the precursor salts greatly affected the morphology and porosity of the Co3O4 thin film, and consequently exhibited the different electrochemical performances in 2.0 M KOH electrolyte. The Co3O4 thin film prepared from cobalt acetate shown excellent electrochemical performance among the four different Co3O4 thin films electrodes, such as a high specific capacitance (743.8 F·g−1) and nice cycling stability (95.8% retention after 1000 charge-discharges at a high current density of 5 A·g−1). Furthermore, this work also provides a facile large-scale fabrication method to prepare secondary nanostructure on pseudocapacitance materials, such as graphene, transition metal oxides, carbon fibers, for enhancing the electrochemical performance of supercapacitor at low operation temperature.

Sn/C composite anodes for bulk-type all-solid-state batteries

A simple method of realizing all-solid-state lithium batteries (ASS-LIBs), employing a Sn/C composite anode and glassy solid electrolyte LiI-Li3PS4 (LPSI), possessing desirable capacity and cycle life, is proposed. The composite anode, containing Sn/C, LPSI, and carbon fiber, is synthesized via a straightforward, one-step, manual grinding. Potentiodynamic cycling with galvanostatic acceleration (PCGA) analysis and cyclic voltammetry of Sn/C|LPSI|Li cells demonstrate that electrochemical processes of graphite are promoted by integrating it with Sn. The improvement appears as increased battery capacity in galvanostatic charge-discharge cycling. The Sn/C|LPSI|Li exhibits a capacity of 400 mAh g−1 in the 1st cycle at 0.033C, which is about 83% of the nominal capacity of the composite. Throughout the course of 30 cycles, the cell retains a capacity above 320 mAh g−1 and a coulombic efficiency above 98%. The retention of its high capacity suggests that the pulverization of Sn was physically suppressed by using solid-state materials, i.e. LPSI and graphite. It is demonstrated that the combination of LPSI electrolyte and Sn/C enables a simple and time-efficient preparation of ASS-LIBs with stable and safe performance.

Probing the effect of Mg doping on triclinic Na2Mn3O7 transition metal oxide as cathode material for sodium-ion batteries

Triclinic Na2Mn3O7 has been identified as a promising material for high-capacity sodium-ion batteries. However, the knowledge on the effect of doping of metal ions and structural transformations of Na2Mn3O7 during dis(charge) is limited. Integration of alkali metal-ions, specially Mg2+ can enhance the electrochemical properties in transition metal oxides. Herein, a series of Mg2+ doped triclinic Na2Mn3O7 cathode materials was explored for the first time. Electrochemical analysis revealed that Mg2+ improves specific capacities, and rate capabilities. Ex situ X-ray diffraction (XRD) and Galvanostatic charge discharge cycling (GCD) showed that the triclinic phase reversibly converts into two monoclinic phases at high Na+ insertion levels. Na+ extraction at high potentials is supported by another biphasic region which converts to a major triclinic phase at the end of the charge. GCD, cyclic voltammetry (CV) and ex situ X-ray absorption spectroscopy (XAS) documented that the capacity mainly evolved through a Mn4+/3+ redox couple and a reversible O2-/n− redox reaction. CV and Galvanostatic intermittent titration techniques (GITT) showed that Mg2+ reduces the Na+-vacancy ordering and improves the Na+ diffusion. The 2 mol.% Mg-doped material exhibited a high specific capacity of 143 mAh/g after 30 cycles and a rate capability of 93 mAh/g (at 500 mA/g). GCD analysis demonstrated that O2-/n− redox is remarkably stable up to at least 90 cycles. Full cells made using the 0.5 mol.% Mg-doped material displayed a promising discharge specific capacity of 80 mAh/g. The effects of cation doping into the complex crystal structures, phase transformations during Na+ de(intercalation) and the importance of O2-/n− redox for achieving high capacities were uncovered. The findings of this work will guide the design of novel cathode materials for sodium-ion batteries.

Combining ReaxFF Simulations and Experiments to Evaluate the Structure-Property Characteristics of Polymeric Binders in Si-Based Li-Ion Batteries.

High energy capacity silicon (Si) anodes in Li-ion batteries incorporate polymeric binders to improve cycle life, which is otherwise limited by large volume and stress fluctuations during charging/discharging cycles. Several properties of the polymeric binder play a role in achieving optimal battery performance, including interfacial adhesion strength, mechanical elasticity, and lithium-ion conduction rate. In this work, we utilize atomistic simulations with the ReaxFF force field and complementary experiments to investigate how these properties dictate the performance of Si/binder anodes. We study three C/N/H-based polymer binders with varying structures (pyrolyzed polyacrylonitrile (PPAN), polyacrylonitrile (PAN), and polyaniline (PANI)) to determine how the structure-property characteristics of the binder affect performance. The Si/binder adhesion analysis reveals some counter-intuitive results: although an individual PANI chain has a stronger affinity to Si compared to PPAN, the PANI bulk binds weaker to the Si surface. Interfacial structural analyses from simulations of the bulk phase show that PANI chains have poor stacking at the interface, while PPAN chains exhibit dense and highly ordered stacking behavior, leading to stronger adhesion. PPAN also has a lower Young's modulus compared to PANI and PAN owing to its ordered and less entangled bulk structure. This added elasticity better accommodates volume changes associated with cycling, making it a more suitable candidate for Si anodes. Finally, both simulations and experimental measurements of Li-ion diffusion rates show higher Li mobility through PPAN than PAN and PANI because the ordered stacking of PPAN chains creates channels that are favorable for Li diffusion to the Si surface. Galvanostatic charge-discharge cycling experiments show that PPAN is indeed a highly promising binder for Si anodes in Li-ion batteries, retaining a capacity of ∼1400 mAh g-1 for 150 cycles. This work demonstrates that the orientation and structure of the polymer at and near the interface are essential for optimizing binder performance as well as showcases the initial steps for binder evaluation, selection, and application for electrodes in Li-ion batteries.

In-situ sputtered 2D-MoS2 nanoworms reinforced with molybdenum nitride towards enhanced Na-ion based supercapacitive electrodes

We report the fabrication of binder-free, low-cost and efficient hybrid supercapacitive electrode based on the hexagonal phase of two-dimensional MoS2 nanoworms reinforced with molybdenum nitride nanoflakes deposited on stainless steel (SS) substrate using reactive magnetron sputtering technique. The hybrid nanostructured MoS2–Mo2N/SS thin film working electrode delivers a high gravimetric capacitance (351.62 F g−1 at 0.25 mA cm−2) investigated in 1 M Na2SO4 aqueous solution. The physisorption/intercalation of sodium (Na+) ions in electroactive sites of MoS2–Mo2N composite ensures remarkable electrochemical performance. The deposited porous nanostructure with good electrical conductivity and better adhesion with the current collector demonstrates a high-energy density of 82.53 Wh kg−1 in addition to a high-power density of 24.98 kW kg−1. Further, excellent capacitance retention of 93.62% after 4000 galvanostatic charge–discharge cycles elucidated it as a promising candidate for realizing high-performance supercapacitor applications.

Capacitive properties of novel Sb-doped Co3O4 electrode material synthesized by hydrothermal method

We are reporting here a novel antimony doped cobalt oxide based electrode material for supercapacitor application to overcome the current scenario of energy crises by offering excellent capacitive abilities. A facile hydrothermal route was employed to produce this antimony doped cobalt oxide material by varying content value of antimony in the range of 2–6 at. %. The X-ray diffraction results have successfully explored the cubic crystal structure along with phase composition of these as obtained Sb doped Co3O4 materials. The development of sub-micron sized structures-based material was explored by obtaining scanning electron microscopic images. The energy dispersive X-ray spectroscopy results have shown the highly pure nature of as obtained material. Cyclic voltammogram results have exhibited that among the SbCo-0, SbCo-2, SbCo-4 and SbCo-6 materials, SbCo-4 has exhibited higher specific capacitance value i.e 894.15 F/g than remaining, which was obtained by scanning the material at the scan rate of 5 mV/s. More significantly, Galvanostatic charge-discharge profiles obtained at different scan rates ranging from 1 to 10 A/g, for SbCo-4 material has shown even good capacitance retention i.e 75.70% at higher sweep rate, equal to 10 A/g. On the basis of electrochemical impedance spectroscopic analysis, it is concluded that this material has also shown excellent conductive properties. Furthermore, after performing 3000 galvanostatic charge-discharge cycles, it is concluded that this material can possessed an excellent cycling stability equal to 82.02%. All these excellent capacitive properties shown by this material have suggested that it can be proved as a potential applicant in the field of energy storage devices.

Graphene based sulfonated polyvinyl alcohol hydrogel nanocomposite for flexible supercapacitors

Graphene based sulfonated polyvinyl alcohol (PVA) hydrogel was synthesized and its performance as nanocomposite gel polymer electrolyte was investigated for application in quasi solid-state flexible supercapacitors. Hydrothermally reduced graphene (HRG) was synthesized through hydrothermal reduction of graphene oxide (GO). Sulfonated PVA hydrogel (SPVA) was synthesized with predetermined quantities of HRG to obtain nanocomposite gel polymer electrolytes coded as SPVA-HRG-x (x = content (wt.%) of HRG). The amorphous nature of SPVA-HRG-x was determined using X-ray diffraction (XRD) technique. The electrochemical performance of SPVA-HRG-x was evaluated using techniques like cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical spectroscopy (EIS) studies of a lab scale supercapacitor cell, fabricated using hydrothermally reduced carbon cloth (CCHy) current collectors coated with HRG (HRG-CCHy). In SPVA-HRG-0.5 electrolyte, HRG-CCHy exhibited specific capacitance of 200 F g-1 at 1 A g-1 and specific energy of 6.1 Wh kg-1 at specific power of 1 kW kg-1 and retained 93 % of its initial capacitance even after 5000 GCD cycles. The incorporation of SPVA with 0.5 wt.% of HRG-CCHy can be attributed to the increase in amorphous nature of SPVA-HRG-0.5, which in-turn lowers its impedance. This contributed to the remarkable supercapacitive behaviour of HRG-CCHy, demonstrating its potential as gel polymer electrolyte (GPE) for application in quasi solid-state flexible supercapacitors.

CuWO4: A promising multifunctional electrode material for energy storage as in redox active solid-state asymmetric supercapacitor and an electrocatalyst for energy conversion in methanol electro-oxidation

• CuWO 4 has been prepared by quick co-precipitation route within 20 min. • ASC device shows specific capacity of 103 mAh g −1 at 1 A g −1 . • ASC device shows retention of 119.4% of initial capacity after 5000 cycles. • ASC device exhibits energy density of 103 Wh kg −1 at power density of 0.95 kW kg −1 . • For methanol oxidation, the CuWO 4 electrode exhibits 38 mA cm −2 at 0.5 V. This article reports the formation the multifunctional CuWO 4 nanoparticles towards the application of gel electrolyte-based supercapacitor and methanol electro-oxidation. The CuWO 4 nanoparticles were synthesized by a quick chemical co-precipitation route within 20 min. The hydrated precursor was treated at 600 °C for 2 h to convert in to final CuWO 4 products. Structural features of the prepared CuWO 4 were investigated by means of X-ray diffraction, electron microscopies, Fourier transform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy. The CuWO 4 electrode exhibits the specific capacity of 415 mAh g −1 at a current density of 2 A g −1 in three electrode configurations in 1 M Na 2 SO 4 and 3 mM KI mixed electrolyte. The electrode shows retention of 86.1% of its initial specific capacity after 10,000 galvanostatic charge–discharge cycles at 30 A g −1 . An asymmetric solid-state device was assembled by sandwiching the PVA-Na 2 SO 4 and 3 mM KI gel electrolyte in between the CuWO 4 nanoparticle and activated carbon electrodes. The device shows the specific capacity of 103 mAh g −1 at a current density of 1 A g −1 and device shows the retention of 93.4% after 5000 galvanostatic charge–discharge cycles at 7 A g −1 . The hybrid device exhibits energy density of 103 Wh kg −1 at power density of 0.95 kW kg −1 . In electro-catalysis of methanol, the CuWO 4 electrode exhibits the high current density of 38 mA cm −2 at 0.5 V and onset potential achieved as 0.38 V in mixed solution of 1 M KOH and 0.5 M methanol.

Self-Doped Activated Carbons from Car Exhaust as High-Performance Supercapacitor Electrode Materials for Sustainable Energy Storage System

Hydrocarbon based waste materials are emerging as an attractive source of generating activated carbons (ACs), having excellent potential for enormous in-field applications. In this study, it has been demonstrated that the carbon materials collected from the diesel engine exhaust could be a new source for preparing self-doped highly porous AC for high-performance supercapacitor applications. As the diesel engine exhaust carbon (DEEC) itself contains a large number of heteroatoms (O, N, S, and P), simple acid treatment (HCl) of DEEC resulted in a self-doped AC (SDAC_HCl) having contained a high level of heteroatoms as the dopant in it and consequently provided with a large specific surface area of 89 m2g−1. The pyrolytic treatment of DEEC with KOH further resulted in self-doped AC (SDAC_KOH) with an enhanced specific surface area of 549 m2g−1 due to the increase in porosity of AC. The supercapacitor performance of the AC materials is evaluated in a symmetric two-electrode cell. The ACs (SDAC_HCl and SDAC_KOH) have shown very high specific capacitance (C sp) with aqueous (sodium sulfate, Na2SO4), organic (tetraethylammonium tetrafluoroborate/acetonitrile, TEABF4/AN) and ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIM][Cl]) electrolytes. The highest C sp of 403 Fg−1 at the current density of 1 Ag−1 is obtained in SDAC_KOH with [BMIM][Cl] electrolyte. The C sp is 193 F g−1 at the high current density of 10 Ag−1, demonstrating the good compatibility of the electrolyte with the electrode material. The SDAC_KOH with [BMIM][Cl] is able to supply a high energy density of 35.8 Whkg−1 at a power density of 400 Wkg−1 which is very reasonably high compared to other reported AC materials. The SDAC_KOH has shown excellent stability in continuous galvanostatic charge-discharge cycles. The SDAC_KOH has retained 98% of its initial capacitance after 10000 cycles at a high current density of 5 Ag−1. The facile and effective strategies employed in this study in developing high-performance supercapacitor electrode materials from waste may help design and develop sustainable energy storage systems.

Development of reduced graphene oxide from biowaste as an electrode material for vanadium redox flow battery

Vanadium redox flow battery (VRB) is a renowned electrochemical energy storage device for large scale applications owing to its promising storage capability, long life and safety. However, the lower efficiency of VRB system combined with the non-renewable graphite-based electrodes have limited the widespread of VRB commercial market. This study investigates the feasibility of converting renewable biomass waste, namely spent coffee beans, into reduced graphene oxide (rGO) as an alternate electrode material for VRB system. As prepared rGO has been thoroughly characterised and employed to design a modified electrode for VRB. The electrochemical performance of rGO based modified electrodes has been comprehensively examined using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge cycling. The results demonstrate that the energy, voltage and coulombic efficiencies of rGO based electrodes are over 90%, which are comparable to that of commercially used pristine graphite electrode. Moreover, a stable cyclic performance is observed for rGO based electrodes over a total of 65 cycles owing to their high electrocatalytic activity and improved charge transfer. The stable performance and comparable efficiency present promising potential of biomass derived rGO as a low-cost replacement to the commercial graphite as an electrode material for VRB applications.

Comparative investigation of different types of nickel foam samples for application in supercapacitors and other electrochemical devices

Nickel foam is widely used as a current lead/current collector and the basis of nickel hydroxide electrodes for various electrochemical devices – batteries, hybrid supercapacitors, devices for electrocatalytic oxidation of organic substances. The characteristics of commercial samples of nickel foam produced by Novomet-Perm (Russian Federation) obtained by electroless and then electrochemical nickel plating and Linyi Gelon LIB Co Ltd (China) obtained by electroless nickel plating were studied. The nature of passivity was determined by forming model samples of electrochemical and electroless nickel on a steel base. For the passive sample, activation was carried out by applying a layer of electrochemical nickel from an impact nickel plating solution. Activated, non-activated samples of nickel foam, as well as model samples, were studied by the methods of cyclic voltammetry and galvanostatic charge-discharge cycling in the supercapacitor mode. Comparative analysis of Chinese-made and Russian-made nickel foam samples showed significant passivity of the former – in cyclic voltammetry, the activity was 4.8 times lower, with galvanostatic charge-discharge cycling – 2.59 times lower. It was suggested that high passivity was determined by the fact that the sample consisted of Ni-P or Ni-B alloy. This assumption was proved by the method of natural simulation. The electrochemical activity of electroless nickel was 1.25 times lower than that of electrochemical nickel (according to cyclic voltammetry data) and 1.58 times lower (according to galvanostatic cycling data). For the first time, Chinese-made nickel foam (electroless nickel) was activated by applying a layer of electrochemical nickel from an impact nickel electrolyte. The high activation efficiency was shown as follows – on the cyclic curve, the specific current of the anodic peak increased 8.71 times, and with galvanostatic cycling, the increase in specific capacity was from 1.73 times (at i=120 mA/cm2) to 4.84 times (at i=20 mA/cm2)

Nanostructured high-performance electrolyte membranes based on polymer network post-assembly for high-temperature supercapacitors

The development of high-temperature supercapacitors highly relies on the explore of stable polymer electrolyte membranes (PEMs) with high ionic conductivities at high-temperature conditions. However, it is a challenge to achieve both high stability and high conductivity in a PEM at elevated temperatures. Herein, we report the fabrication of high-performance proton conductive PEMs suitable for high-temperature supercapacitors (HT-SCs), which is based on a post-assembly strategy to control the rearrangement of polymer networks in the PEMs. This strategy can create cross-linked PEMs with bicontinuous nanostructures, as well as highly stable and highly conductive features. Specifically, a series of bicontinuous PEMs are prepared by the controllable cross-linking of poly(ether-ether-ketone) and poly(4-vinylpyridine), followed by the inducement of phosphoric acid. These PEMs exhibit both a high proton conductivity of 70 mS cm−1 and a high modulus of 39.3 MPa at 150 ℃, which can serve as high-performance electrolytes. The HT-SCs based on these PEMs display a specific capacitance of 138.0 F g−1 and a high capacitance retention of 80.0% after 2500 galvanostatic charge–discharge cycles at 150 ℃, exhibiting excellent high-temperature capacitance and cycle stability. This post-assembly concept can provide a new route to design high-performance PEMs for HT-SC and other energy device applications.

(Invited) Linking Microporous Structure and Surface Properties with Energy Storage Device Performance of Well-Aligned Electrospun Carbon Fiber Electrodes

In an effort to more extensively utilize abundant US coal reserves, a zero-waste approach to depolymerize raw Powder River Basin (PRB) coal was invented using environmentally friendly ionic liquids. Coal-derived carbon nanofibers (CCNFs) mats were electrospun using extracted coal char as feedstock. It was revealed that the surface of resulting CCNFs mats was enriched with oxygen, while detailed porous structure characterization via Brunauer-Emmett-Teller (BET) and Dubinin-Radushkevish (D-R) methods showed significantly enhanced porosity in the microporous regime (micro- (pores < 2 nm). Consequently, it was observed that electrical conductivity also increased significantly, compared to carbon fibers without PRB coal. To investigate how fiber alignment affects physiochemical properties of CCNF, well-aligned CCNFs was fabricated by optimizing process parameters in electrospinning process. Both conductivity and microporous pore volume further increased in the well-aligned fibers, with respect to fibers randomly aligned. Based on electrochemical impedance spectroscopy (EIS), the well-aligned CCNFs also demonstrated excellent electrochemical properties, resulting from a cumulative result of the shortened ion transfer path, facilitated wettability from high surface oxygen concentration. Specifically, well-aligned CCNFs reached the specific capacitance of 1590 mF cm-2 at a current density of 4 mA cm-2 in 6M KOH solution. Moreover, a symmetrical carbon/carbon prototype supercapacitor cell, consisting of well-aligned CCNFs mats as electrodes, generated the energy density of 15 µWh cm-2 at a power density of 0.3 mW cm-2, corresponding to a current density of 1 mA cm-2, a gravimetric energy density of 30 Wh kg-1 at a power density of 0.6 kW kg-1 and volumetric energy density of 18.2 mWh cm-3 at a scan rate of 50 mV s-1. Finally, 93.0% specific capacitance remained after 10,000 cycles of galvanostatic charge-discharge, demonstrating that the CCNFs mats possess desired durability. Preliminary results showing CCNF performance as electrodes in sodium ion coin batteries will be briefly discussed.

Porous organic/inorganic polymers based on double-decker silsesquioxane for high-performance energy storage

Two porous organic/inorganic microporous polymers (TPE-DDSQ POIP and Car-DDSQ POIP) were prepared through the Sonogashira-Hagihara coupling reaction of DDSQBr with 1,1,2,2-tetrakis(4-ethynylphenyl)ethene (TPE-T), and 3,3´,6,6´-tetraethynyl-9,9´-bicarbazole (Car-T); respectively. The chemical structure and properties of these two materials including thermal stability, porosity, crystallinity, and morphology were characterized in detail by using various instruments. Based on TGA analyses, Car-DDSQ POIP exhibited high thermal degradation temperature up to 439 °C and char yield up to 77.4 wt.% because inorganic DDSQ unit could enhance the thermal stability as expected. The electrochemical results revealed that TPE-DDSQ POIP and Car-DDSQ POIP showed specific capacitance of 22 and 23 F g−1 at 1 A g−1; respectively in a three-electrode with KOH solution (6 M) as electrolyte and capacitance retention at about 93% after 2000 galvanostatic charge–discharge cycles.

Single step auto-igniting combustion technique grown CeO2 and Ni-doped CeO2 nanostructures for multifunctional applications

In the present study, pristine and Ce1-xNixO2(x = 0.1) nanoparticles are grown by low cost modified combustion process. The surface morphology and phase pureness of the pristine and Ce1-xNixO2(x = 0.1) nanostructures is achieved by Scanning Electron Microscopy (SEM) and powder X-Ray Diffraction (XRD) techniques. The closed and open mode Z-scan studies reveal that these synthesized nanostructures possess excellent reverse saturation absorption behaviour, which can be utilized for optical limiting applications in defence and healthcare systems. By analyzing the photocatalytic properties against Eosin Yellow dye, the degradation efficiency of synthesized samples is found to be 91% and 93% respectively. Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopic (EIS) are the techniques which help to study the electrochemical properties of the synthesized materials for electrode materials of supercapacitor. From GCD, the specific capacitance of pristine and Ce1-xNixO2(x = 0.1) is 305 and 446 F g-1 respectively. Even after 2000 GCD cycles, the cyclic stability and coulombic efficiency of Ce1-xNixO2(x = 0.1) remains at 96.1% and 97.5%, while for pure CeO2 it is 88.3% and 91% respectively.

Highly Flexible and Tailorable Cobalt-Doped Cross-Linked Polyacrylamide-Based Electrolytes for Use in High-Performance Supercapacitors.

A novel hydrogel polymer electrolyte was prepared by incorporation of 1,4-butanediol diglycidyl ether (BG) to cross-linked polyacrylamide (PAM). The electrolyte (PAMBG) was modified with cobalt (II) sulfate with various doping ratios (PAMBGCoX) to increase the capacitance by increasing faradaic reactions. The supercapacitor device assembly was performed by using active carbon (AC) electrodes and hydrogel polymer electrolytes. The specific capacitance of the PAMBGCo5 device indicated 130 F g-1 , which is at least a seven-fold improvement due to the insertion of Co as a redox component. The electrolyte device, PAMBGCo5, displays superior performance having an energy density of 38 Wh kg-1 at a power density of 500 W kg-1 . Additionally, with the same hydrogel, the device performed 10,000 galvanostatic charge-discharge cycles via retaining 91% of the initial capacitance. A cost-effective electrolyte, PAMBGCo5, was tested in a carbon-based supercapacitor under bent and twisted conditions at various angles, confirming the robustness of the device.

Superior performance of electrodeposited CoMnS as novel electrode material for supercapattery devices

A series of cobalt manganese sulfide (CoMnS) grown directly on Ni foam substrate via co-electrodeposition technique to study an appropriate choice of deposition cycle numbers of cyclic voltammetry at a fixed scan rate. The binder free electrodes have been fabricated from a quick synthesis methodology by evaluating the binary metal sulfides for achieving an extremely high energy storage. By carefully selecting the synthesis methodology and ingredients, CoMnS displayed an excellent electrical conductivity and low internal resistance, which makes them a promising contender for energy storage applications. S2 electrode having 12 number of deposition cycles portrayed high electrochemical performance enactment by means of 2297 F/g specific capacitance from cyclic voltammetry (CV) at 3 mV/s, while 2291 F/g from galvanostatic charge discharge (GCD) at 10 A/g. The S2 electrode have smaller ESR value calculated from EIS analysis that elucidated high conductance. Furthermore, the hybrid supercapacitor device was formed by sandwiching activated carbon (negative electrode) with S2 electrode (positive electrode) detached thru 1 M KOH electrolyte drenched permeable membrane. The electrochemical characterizations of device resulted an outstanding specific energy of 106 Wh/kg at 5 A/g, specific power of 24,000 W/kg at 30 A/g and reveals an excellent capacitance retentivity of 94% at room temperature after 2500 GCD cycles. This study suggested that 12 cycle numbers for deposition are optimized as an appropriate mass loaded for superior electrochemical energy storage applications.