High Discharge Current Density Research Articles

Ultrathin SnO nanosheets as anode materials for rechargeable lithium-ion batteries

SnO ultrathin nanosheets with a highly pure crystal phase were successfully prepared via a simple and effective hydrothermal process, using tin dichloride dihydrate (SnCl2·2H2O) as a stannous source in the presence of hexamethylenetetramine (HMT). SEM and TEM images showed that the obtained SnO products are uniform and ultrathin nanosheets. The electrochemical properties results indicated that the obtained SnO nanosheets exhibited excellent discharge capacity, the reversible capacity was 559mAhg−1 after 20 cycles, and the SnO nanosheets retain high capacity even at high discharge current densities. The enhanced performance was attributed to the unique structure of ultrathin SnO nanosheets and highly pure crystal phase.

Graphene/Au composite paper as flexible current collector to improve electrochemical performances of CFx cathode

We report the application of free-standing, lightweight, and flexible graphene/Au composite paper (GACP), as a current collector for CFx cathode. At a high discharge current density of 4000 mA g−1 (5C), the capacity of the CF1.0 loaded on GACP current collector is 653 mAh g−1, while CF1.0 loaded on Al foil failed at 800 mA g−1 (1C). Using GACP, both excellent rate capability and specific capacity can be achieved simultaneously, owing to its undulant surface structure and flexible contact with the CFx composite active layer. Our results provide a new strategy to design both high power and energy densities CFx cathode.

Preparation and characterization of flower-like microspheres of nano-NiO as electrode material for supercapacitor

NiO electrode material was prepared by a facile and environment-friendly hydrothermal method combined with subsequent calcination. The prepared samples were characterized by SEM, XRD and nitrogen adsorption. The electrochemical performances were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and cycle life. The condition of synthesis on the electrochemical performance of NiO was studied. The results show that the prepared NiO is a nanosize material with a special morphology of flower-like microspheres. It has a high specific capacitance of 762Fg−1 at 1Ag−1 and 598Fg−1 at high discharge current density of 10Ag−1. Furthermore, it exhibits an outstanding cycling performance and stability reflected by a high capacitive retention of 96% after the subsequent 1000 cycles at a high current density of 15Ag−1.

Large scale production of biomass-derived N-doped porous carbon spheres for oxygen reduction and supercapacitors

The urgent need for sustainable energy development depends on the progress of green technologies, which have steered hot research areas into environmentally benign approaches via inexpensive precursors and abundant resources obtained directly from nature for energy devices such as fuel cells and supercapacitors. By using fermented rice as starting materials, we herein demonstrate a facile, green and scalable approach to synthesize porous N-doped carbon spheres characterised by high specific surface areas (2105.9 m2 g−1) and high porosity (1.14 cm3 g−1), which exhibit not only excellent electrocatalytic activity toward the four-electron oxygen reduction reaction with long-term stability for fuel cells, but also have excellent resistance to crossover effects and CO poisoning superior to that of the commercial Pt/C catalyst. Furthermore, the naturally derived porous N-doped carbon spheres, used as the active electrode materials, present superior performance for capacitors with a capacitance of 219 F g−1 at a high discharge current density of 15 A g−1 and good cycling stability for over 4400 cycles. This work shows a good example for taking advantage of the abundant resources provided by nature, and opening the door for the creation of functional materials with promising applications in high-performance renewable devices related to energy conversion and storage.

Electrochemical Fabrication of Coaxial Wavy‐Channel NiIIIO(OH)/Ni Nanocomposites for High‐Performance Supercapacitor Electrode Materials

AbstractThe supercapacitor electrode material reported herein is a type of NiIIIO(OH)/Ni coaxial nanocomposite with NiIIIO(OH) wrapping around a Ni scaffold, featuring vertically oriented nanochannels with periodically‐corrugated channel walls. A Ni scaffold was constructed through the electrodeposition of a Ni–Cu alloy film by using a square‐wave voltage followed by a dealloying treatment to selectively remove Cu. By further coating the fabricated Ni framework with NiIIIO(OH) through anodic electrodeposition, we obtained wavy‐channel NiIIIO(OH)/Ni coaxial nanostructures, which readily served as a supercapacitor electrode. The as‐fabricated supercapacitor electrode exhibited superior performance with a remarkable specific capacitance (SC) of 2372 F g−1 (after the contribution from the bare Ni scaffold was subtracted), measured at the charge and discharge rate of 1 A g−1. This is 48 % higher than the straight‐channel counterpart and is almost a three‐fold increase compared to the compact NiIIIO(OH) thin film. Moreover, superior cycling stability was achieved at high charge and discharge current densities, for example, only 10 % of the SC was lost over the first 200 cycles with no further change in the subsequent 800 cycles at 50 A g−1.

Mesoporous ITO/NiO with a core/shell structure for supercapacitors

In this study, a novel mesoporous NiO/ITO NW with a shell/core structure has been successfully synthesized by combining chemical vapor deposition (CVD) on titanium substrate and electrodeposition of HI–e (hexagonal lyotropic) nickel hydroxide through a lyotropic liquid crystalline (LLC) template, followed by calcination in air at 270°C. The electrode material is characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Both cyclic voltammetry (CV) and chronopotentiometry demonstrate enhanced electrochemical properties of NiO/ITO NWs composite electrode and improved supercapacitive behaviors as compared to bulk mesoporous nickel oxide film. Maximum specific capacitance of 1025Fg−1 at a discharge current density of 1Ag−1 in the potential ranges from 0V to 0.5V is determined by galvanostatic charge–discharge measurement in 1M KOH solution. The newly synthesized heterostructure also possesses high capacitance retention ratio at high discharge current densities and long-term electrochemical stability in an alkaline solution. Therefore, this study provides a promising electrode engineering technique for various applications.

Effect of temperature on the discharge and hydrogen evolution of lithium in alkaline aqueous solution

The effects of temperature on the discharge and hydrogen evolution of lithium anode in 4M (molL−1) LiOH solutions were investigated via hydrogen collection, polarization and SEM (scanning electron microscope). It was found that the hydrogen evolution rate is low below 30°C with low discharge current density and the discharge current density is high over 30 with high hydrogen evolution rate. The lithium anode shows the better electrochemical performance with high discharge current density, low hydrogen evolution, and less porous film at 30°C at 0.94ms−1 in 4M LiOH solutions.

Ethanol-based synthesis of hierarchically porous carbon using nanocrystalline beta zeolite template for high-rate electrical double layer capacitor

A porous carbon with a mesopore–micropore hierarchy has been synthesized using ethanol as a carbon source within a beta zeolite template, which possesses mesopores and micropores in a hierarchical manner. Various compounds have been evaluated as the carbon source in the carbon synthesis. The result indicates that ethanol vapor is suitable for the hierarchical carbon synthesis, as compared with propylene or acetylene gas. The advantage of ethanol is attributed to the formation of water from the ethanol decomposition during carbonization process. The water seems to assist in delaying the deposition of carbons at the exterior (or the mesopore walls). The resultant carbon after removal of the template is composed of regular micropores of 1-nm diameter and irregular mesopores of 10–30nm arranged in a hierarchical manner. The hierarchical carbon exhibits a very high electrical double-layer capacitance both at low and high discharge current densities in galvanostatic measurements, as compared to solely microporous or solely mesoporous carbons. The high performance is attributed to facile transport of electrolytes in the hierarchically porous structure.

Improved electrochemical properties of Li[Li0.2Ni0.17Mn0.56Co0.07]O2 cathode material via micro-structural rearrangement

To improve the rate capability of lithium-rich layered cathode material Li[Li0.2Ni0.17Mn0.56Co0.07]O2 a facile method aimed at micro-structural rearrangement was proposed. Through the combination of excess lithium and chemical activation post-treatment, the resulting material showed well ordered bulk and surface structures. The capacity retention for the modified material improved significantly (compared with untreated sample) at high discharge current densities. Moreover, the unique electrochemical behavior of the modified material reveals the existence of the chemically activated Li2MnO3 component within the composite.

Nanoparticulate Mn0.3Ce0.7O2: a novel electrocatalyst with improved power performance for metal/air batteries

In this work, a novel electrocatalyst, Mn0.3Ce0.7O2, with relatively high power performance has been, for the first time, proposed for metal/air batteries. The as-prepared samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) and nitrogen sorption experiments. Meanwhile, electrocatalytic activity towards the reduction of oxygen of Mn0.3Ce0.7O2 is compared with those of the pure MnO2 and CeO2. It is observed that the Mn0.3Ce0.7O2 solid solution is well formed after the calcination. Electrochemical results show that Mn0.3Ce0.7O2 exhibits much higher electrocatalytic activity in the oxygen reduction reaction (ORR) than pure MnO2 under high discharge current density, which is probably attributed to the effective activation of molecular oxygen over the Mn0.3Ce0.7O2 solid solution and higher surface area.

Electrochemical properties of electrospun polyindole nanofibers as a polymer electrode for lithium ion secondary battery

Polyindole nanofiber is prepared using electrospinning technique for the first time and evaluated as cathode active material for application in lithium ion battery. Surface morphology of the cathode is studied using scanning electron microscope. It shows porous structure constructed by nanofibers with diameter ranged from 347 nm to 180 nm. Electrochemical evaluation of the Li/polyindole nanofiber battery shows good cycling properties as well as fast charge and discharge properties. The battery achieves about 3.0 V electromotive force with discharge capacity of 83 mAh g−1 which is about 99% of theoretical value. There is slow capacity fading during cycling and the discharge capacity drops to 72% of theoretical capacity after 500 cycles at discharge current density of 40 mA g−1. At higher discharge current density like 200 mA g−1 and 400 mA g−1, the cell still can deliver stable discharge capacity of 79 mAh g−1 and 70 mAh g−1. Temperature performances test of the Li/polyindole nanofiber battery shows that the discharge capacity of the Li/polyindole nanofiber battery increases with temperature increasing. In summary, the test results have proved that polyindole nanofiber is a good candidate as cathode material for lithium ion battery.

Electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes as hierarchical electrodes for supercapacitors

This letter reports the fabrication and electrochemical properties of electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes (CNTs) as hierarchical electrodes for supercapacitors. The specific capacitance of the fabricated electrodes was measured up to 185 F/g at the low discharge current density of 625 mA/g; a decrease of 38% was detected at the high discharge current density of 2.5 A/g. The morphology and microstructure of the electrodes were examined by electron microscopy, and the unique connectivity of the hybrid nanomaterials was responsible for the high specific capacitance and low intrinsic contact electric resistance of the hierarchical electrodes.

Fabrication of a mesoporous Co(OH)2/ITO nanowire composite electrode and its application in supercapacitors

A novel mesoporous α-Co(OH)2/ITO NWs heterostructure has been successfully synthesized via a new method of combining chemical vapor deposition (CVD) on a titanium substrate and electrodeposition through a hexagonal lyotropic liquid crystalline (LLC) phase for electrochemical energy storage application. Electrochemical measurements demonstrate the improved ionic conductivity of an electrode and enhanced supercapacitive behavior, as compared to a mesoporous cobalt hydroxide film on a titanium current collector without indium tin oxide (ITO) NWs as “electron highways”. Galvanostatic charge–discharge measurements in 1 M KOH solution prove that the electrode of the as-prepared heterostructure possesses excellent electrochemical capacitance, in the potential range from −0.1 V to 0.5 V with a maximum specific capacitance of 1128 F g−1 at a discharge current density of 1 A g−1. The unique mesoporous α-Co(OH)2/ITO NWs heterostructure provides a high capacitance retention ratio at high discharge current densities and long-term electrochemical stability in an alkaline solution.

Supercapacitors incorporating hollow cobalt sulfide hexagonal nanosheets

We have prepared hollow cobalt sulfide (CoS) hexagonal nanosheets (HNSs) from Co(NO 3) 2 and thioacetamide in the presence of poly(vinylpyrrolidone) (PVP) at 100 °C under alkaline condition. The as-prepared hollow CoS HNSs have an average edge length ca. 110 ± 27 nm and an outer shell of 16 ± 4 nm in thickness from 500 counts. The CoS HNSs are deposited onto transparent fluorine-doped tin oxide (FTO) substrates through a drop-dry process to prepare two types of supercapacitors (SCs); high rate and large per-area capacitance. The electrolyte used in this study is KOH (aq). The CoS HNSs (8 μg cm −2) electrodes exhibit excellent capacity properties, including high energy density (13.2 h kg −1), power density (17.5 kW kg −1), energy deliverable efficiency (81.3–85.3%), and stable cycle life (over 10,000 cycles) at a high discharge current density of 64.6 A g −1. With their fast charging and discharging rates (<3 s), the CoS HNSs show characteristics of high-rate SCs. The CoS HNS SCs having high mass loading (9.7 mg cm −2) provide high per-area capacitance of 1.35 F cm −2 and per-mass capacitance of 138 F g −1, respectively, showing characteristics of SCs with large per-area capacitance. Our results have demonstrated the potential of the CoS HNS electrodes hold great practical potential in many fields such as automobile and computer industries.

Supercapacitors based on self-assembled graphene organogel

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

Effect of Y(OH) 3 microparticles on the electrochemical performance of alkaline zinc electrodes

This work focused on the zinc powder coated with Y(OH) 3 microparticles by means of ultrasonic immersion for performance improvement of zinc electrodes in alkaline battery systems. Scanning electron microscopy and other characterization techniques were applied to examine the influence of the ultrasonic power on the sonochemical growth of Y(OH) 3 microparticles in direct contact with zinc powder. Electrochemical properties of zinc electrodes containing Y(OH) 3 microparticles were discussed through the measurements of potentiodynamic polarization and cyclic voltammetry. Simultaneously, the test cells making use of such modified zinc powder were assembled to further evaluate the availability of Y(OH) 3 microparticles in improving the cycle properties of zinc electrodes. It was found that good alkaline environment generated by ultrasonic irradiation of high power led to the formation of Y(OH) 3 microparticles on the surface of modified zinc powder due to high-energy jets of immersion solution. In particular, the Y(OH) 3 microparticles formed with the ultrasonic power of 440 W made the greatest contributions to hinder the corrosion of zinc electrode and the dissolution of zinc oxidation products in alkaline electrolyte as compared with other power parameters. Besides, the detections of assembled cells at a high discharge current density of 250 mA/cm 2 revealed that the Y(OH) 3 microparticles obtained with ultrasonic power of 440 W provided the alkaline zinc electrode with low capacity loss and persistent cycle behavior. The great improvement over the corrosion behavior and cycle properties of zinc electrode is possibly ascribed to the uniform distribution of Y(OH) 3 microparticles on the surface of modified zinc powder.

Preparation and electrochemical properties of lamellar MnO 2 for supercapacitors

Lamellar birnessite-type MnO 2 materials were prepared by changing the pH of the initial reaction system via hydrothermal synthesis. The interlayer spacing of MnO 2 with a layered structure increased gradually when the initial pH value varied from 12.43 to 2.81, while the MnO 2, composed of α-MnO 2 and γ-MnO 2, had a rod-like structure at pH 0.63. Electrochemical studies indicated that the specific capacitance of birnessite-type MnO 2 was much higher than that of rod-like MnO 2 at high discharge current densities due to the lamellar structure with fast intercalation/deintercalation of protons and high utilization of MnO 2. The initial specific capacitance of MnO 2 prepared at pH 2.81 was 242.1 F g −1 at 2 mA cm −2 in 2 mol L −1 (NH 4) 2SO 4 aqueous electrolyte. The capacitance increased by about 8.1% of initial capacitance after 200 cycles at a current density of 100 mA cm −2.

Electrochemical discharge performance of Mg-Li based alloys in NaCl solution

Mg–Li–Al–Sn and Mg–Li–Al–Sn–Ce alloys were prepared using a vacuum induction melting method. Their electrochemical oxidation behavior in NaCl solution was investigated by means of potentiodynamic and chronoamperometric measurements. The surface morphology after discharge was examined using scanning electron microscopy. Utilization efficiency was estimated with a mass-loss method. The results indicated that Mg–Li–Al–Sn has a higher discharge current density but lower utilization efficiency than Mg–Li–Al–Sn–Ce. The typical utilization efficiency after continuous discharging at constant potential of −1.0 for 2 h is 65% and 70% for Mg–Li–Al–Sn and Mg–Li–Al–Sn–Ce, respectively. The utilization efficiency decreased with the increase of anodic potential. Both alloys have similar self-discharge rate in NaCl solution at open-circuit potential.

High-scattered growth of Y(OH) 3 microparticles on zinc powder using an ultrasonic immersion method for superior alkaline battery system

Novel electrode materials have been developed using the modification technique of ultrasonic immersion by metallurgical bonding of Y(OH) 3 microparticles with zinc powder. Studies on characterization measurements confirm that the application of ultrasound during the immersion promotes the quick growth of Y(OH) 3 microparticles with high-scattered nature and good adhesion on zinc powder. According to cyclic detections of laboratory batteries at a high discharge current density of 250 mA cm −2, the Y(OH) 3 microparticles have a beneficial impact on increasing cycle life and lowering capacity loss of batteries. As compared with simple immersion process, it is interesting to note that the much greater discharge capacity is achieved with no prominent fading for the cell using the zinc powder modified with ultrasonic immersion, due to the presence of larger content and better adhesion of Y(OH) 3 microparticles. Moreover, the Y(OH) 3 microparticles favor effectively the reservation of 322.6 mAh g −1 capacity (more than 66% of the initial capacity at the 1st cycle) after 50 cycles.

Sonochemical Fabrication and Electrochemical Performance of Electrode Materials Containing Rare Earth Yttrium

In order to improve the electrochemical performance of zinc electrodes in alkaline batteries, several sonochemically modified zinc powders were successfully prepared in different concentrations of Y(NO3)3 solutions by means of ultrasonic immersion. Moreover, the formation of Y(OH)3/Y2O3 on modified zinc powder, the corrosion inhibition and cyclic performance of corresponding zinc electrodes were investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical and other techniques. The results showed that Y(OH)3/Y2O3 particles were uniformly distributed on sonochemically modified zinc powder with 0.036 mol·L-1 Y(NO3)3 solution. Simultaneously, the yttrium compounds grew preferentially on the defect sites of zinc powder surface, and prevented the dissolution and diffusion of zincate anions into alkaline electrolyte during the electrochemical process. All these results contributed to the facts that the inhibition efficiency of zinc electrode achieved 79.6%, and differential value between anodic and cathodic peak potentials decreased by 285 mV at the 20th cyclic voltammogram. Simulated silver-zinc batteries were assembled using bare zinc powder and the zinc powder modified with 0.036 mol·L-1 Y(NO3)3 solution. According to the detections of the batteries at a high discharge current density of 250 mA·cm-2, capacity loss of zinc electrode containing the modified zinc powder reached only 62.7 mAh·g-1 from the 1st to 30th cycles, and discharge capacity of 322.6 mAh·g-1 was still reserved after 50 cycles. Therefore, a conclusion was drawn that discharge capacity and cycle life of zinc electrodes were obviously enhanced owing to the application of sonochemically modified zinc powder.