Rapid Charge-discharge Research Articles

Heteroatom-doped core/shell carbonaceous framework materials: synthesis, characterization and electrochemical properties

Multiple heteroatom-doped core/shell carbonaceous framework materials showed a rapid charge–discharge capacity and excellent cycling stability, demonstrating great potential for anode materials for lithium ion batteries.

Density functional study of metal lithium atom adsorption on antimonene

<sec> Since the discovery of graphene, researchers have been being increasingly attracted by the emerging of a bunch of two-dimensional (2D) materials, such as BN, MoS<sub>2</sub> and black phosphorene. These materials possess outstanding physical and chemical properties, which could find great potential applications in nanoelectronics, energy conversion or storage, photocatalysts, etc. Recently, a theoretically predicted pucker layered material consisting of Sb atoms, antimonene, has been prepared, and is attracting the attention in the field of lithium ion batteries. </sec><sec>In this paper, based on first-principle density functional theory, the adsorption characteristics of Li atoms on antimony are studied, including the most stable adsorption configuration, the adsorption density and the diffusion path of Li atom on antimonene. The results show that the most stable adsorption configuration of Li atom is in the valley site, i.e. the center of the three Sb atoms in the top layer and one Sb in the bottom layer. The adsorption energy is 1.69 eV and the adsorption distance is 2.81 Å. The band structure shows that antimony is an indirect band gap semiconductor with a band gap of 1.08 eV. After the absorption of Li atom, the Fermi level enters into the conduction band, which shows an electronic property similar to metal. The analysis of density of states shows that the p-electronic state of Sb atom and the p and s electronic state of Li atom possess distinct resonance peaks, showing hybrid bonding characteristics. With the increase of the number of Li atoms adsorbed, the lattice structure and electronic structure of antimonene change greatly. The nudged elastic band calculation shows that the diffusion barrier of Li atom on antimony surface is 0.07 eV, and a smaller barrier height is beneficial to the rapid charge-discharge process. To sum up, antimony has a good potential as an anode material for lithium ion batteries.</sec>

Interfacial Coupling Effect in Organic/Inorganic Nanocomposites with High Energy Density.

Organic/inorganic nanocomposites (OINs) can be potentially used as high-performance capacitors due to their rapid charge-discharge capability along with respectable power density. The coupling effect of the filler/matrix interface plays a prominent role in the dielectric and electric properties of OINs. Along with a review of contemporary theoretical models, recent advances in interfacial optimization to improve energy density through careful interface control and design are also presented. Possible mechanisms that may improve energy density and potential applications for high-energy-density capacitors are also highlighted.

Ultra-high-voltage capacitor based on aluminum electrolytic–electrochemical hybrid electrodes

Low working voltage hinders the wide application of a single electrochemical capacitor, while the rapidly developing industry of electronic components urgently needs a kind of device combining the advantages of high voltage and energy capacity. This work successfully prepared a flexible packaging aluminum electrolytic–electrochemical hybrid capacitor with high working voltage and capacitance, using aluminum electrolytic capacitor anode foil as anode and activated carbon composite electrodes as cathode. The results show that the working voltage reaches 105 V. The single capacitance reaches 580 μF at a current of 100 mA cm−2, which is double than that of the traditional aluminum electrolytic capacitors at the same size. The hybrid capacitor exhibits superior energy storage density and rapid charge–discharge capacity. The gravimetric energy density and volume energy density for the hybrid capacitor is 0.49 J g−1 and 0.62 J cm−3, respectively. It also exhibits excellent cycling performance without obvious capacitance capacity fading. The increase in the energy density of the hybrid capacitor is mainly due to the use of aluminum electrolytic capacitor materials for the anode and the use of electrochemical capacitor material for the cathode, which increases the operating voltage and the specific capacitance.

Lithium sulfonate-grafted poly(vinylidenefluoride-hexafluoro propylene) ionomer as binder for lithium-ion batteries.

Lithium sulfonate-grafted poly(vinylidenefluoride-hexafluoro propylene) P(VDF-HFP) ionomers are synthesized through covalent attachment of taurine and used as binder for the LiFePO4 cathode of lithium-ion batteries(LIBs). The incorporation of the ionomer binders will add ionic conducting channels inside the electrodes, and prevent electrolyte depletion during rapid charge–discharge processes. It leads to an improved performance of LIBs using the ionomer binders including cycling stability and rate capability compared to that of LIBs using non-ionic binders (PVDF and PVDF-HFP). Therefore, the lithium sulfonate-grafted P(VDF-HFP) ionomers offer a new route to develop high-power LIBs.

Carbon Nanotubes as Effective Interlayer for High Performance Li-I2 Batteries: Long Cycle Life and Superior Rate Performance

Highly soluble active materials, such as iodine, are of great potential to develop the research of rapid charge-discharge performance for Li-ion batteries. In this work, a new facile method is applied to construct the iodine/carbon electrode system, which is composed of a thin cathode film, prepared by directly mixing pure commercial iodine and superconducting carbon black, and a carbon nanotubes (CNTs) interlayer. The CNTs interlayer is inserted between pure iodine cathode and separator in the lithium-iodine battery. Electrochemical data reveals that the iodine cathode demonstrates a high capacity of 100 mAh g−1 and ∼100% columbic efficiency after 5000 cycles at a rate of 100C, which shows a great cycle stability and superior high-rate capability, based on the contributions from both the confinement effect of iodine species in CNTs interlayer and the quick liquid-phase diffusion of Li ions in Li-I2 battery.

Mesoporous silica wrapped with graphene oxide-conducting PANI nanowires as a novel hybrid electrode for supercapacitor

A high charge-carrier transport is an important aim in the synthesis of nanostructures for an effective supercapacitor. This article describes a methodology to prepare mesoporous silica nanoparticles (MSNs) wrapped with graphene oxide (GO) together with conducting polyaniline (PANI) wires. The morphology and chemical structure of the prepared samples have been tested by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD), whereas the stability and electrostatic interaction of the structures have been verified by thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The supercapacitive behaviour of these nanocomposites has been analysed by cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS). Compared with pristine MSNs and PANI, the 20%-GO@MSNs/PANI nanocomposite had the highest specific capacitance, reaching 412 F g−1. The nanocomposite structure maximizes the synergy between mesoporous metal oxide, conducting PANI, and GO, yielding a significantly enhanced specific capacitance, rapid charge–discharge rates, and good cycling stability of the resulting device. The wrapping with GO prevents the structural breakdown and acts as a highly conductive pathway by bridging the individual particles, whereas the MSNs nanoparticles greatly enlarge the specific surface area to facilitate ion transport and charge transfer throughout the cycling performance of supercapacitor. The approach adopted in this article can be applied for preparing similar novel functional materials in future for electrochemical applications.

Novel layered polyaniline-poly(hydroquinone)/graphene film as supercapacitor electrode with enhanced rate performance and cycling stability

It is a challenge to fabricate polyaniline (PANI) materials with high rate performance and excellent stability. Herein a new special supercapacitor electrode material of polyaniline-poly(hydroquinone)/graphene (PANI-PHQ/RGO) film with layered structure was prepared by chemical oxidative polymerization of aniline and hydroquinone (H2Q) in the presence of RGO hydrogel film. The synergistic effect and loose layered structure of the composite film facilitate fast diffusion and transportation of electrolyte ions through unimpeded channels during rapid charge-discharge process, resulting in high rate capability and stable cycling performance. As a result, the PANI-PHQ/RGO-61 film electrode exhibited 356 F g−1 at a current density of 0.5 A g−1 and high capacitance retention of 83% from 0.5 to 30 A g−1. Moreover, it presented an excellent cycling stability with 94% of capacitance retention in comparison with 60% of pure PANI electrode and an outstanding Coulombic efficiency of 99% after 1000 cycles of galvanostatic charge-discharge. These superior electrocapacitive properties make it one of promising candidates for electrochemical energy storage.

A Blended SPS-ESPS Control DAB-IBDC Converter for a Standalone Solar Power System

In sustainable energy applications, standalone solar power systems are mostly preferred for self-powered energy zones. In all standalone renewable power systems, batteries are still preferred as the common energy storage device. On the other hand, batteries are not applicable for high peak power demand applications because of their low power density. A supercapacitor is a preferable high-power density energy storage device for high peak power applications. A 2 kW, 50 kHz digital control dual active bridge isolated bi-directional dc-dc converter (DAB-IBDC) was developed for interfacing the supercapacitor bank in standalone solar power system. This paper proposes a blended SPS-ESPS digital control algorithm for a DAB-IBDC converter instead of using a traditional single-phase shift (SPS) control algorithm, which is commonly used for large input to output voltage varying applications. This proposed blended SPS-ESPS control algorithm achieved high power conversion efficiency during a large input to output voltage variation, over a traditional phase shift control algorithm by reducing the back-power flow and current stress in a circuit. This system also achieved maximum power point for solar modules and enhanced rapid charging-discharging for a supercapacitor bank. Both SPS and the blended SPS-ESPS control algorithms were verified experimentally using 2 kW DAB-IBDC topology implemented with standalone power system that combination of 2000 W input solar module and 158 Wh supercapacitor bank.

A combination of CoO and Co nanoparticles supported on electrospun carbon nanofibers as highly stable air electrodes

Bifunctional materials able to catalyze both the oxygen reduction (ORR) and the oxygen evolution (OER) reactions in alkaline media are still a challenge for the progress of energy conversion and storage devices such as metal-air batteries or unitized regenerative fuel cells. In this work, carbon nanofibers synthesized by electrospinning are modified with a combination of cobalt oxide and metallic cobalt (CoO-Co/CNF) and studied as a bifunctional air electrode for metal-air batteries. The performance of CoO-Co/CNF for both reactions is compared with state-of-the-art catalysts such as Pt/C and IrO2. The combination of cobalt oxide and metallic cobalt, finely distributed on the surface of graphitic carbon nanofibers, leads to a bifunctional catalyst with a half-wave potential for the ORR slightly better than Pt/C and a reversibility (ΔEOER-ORR) of 809 mV. The stability of CoO-Co/CNF is assessed by means of different stress tests: polarizations at high electrochemical potentials (2 V vs. RHE), rapid charge-discharge cycles at ±80 mA cm−2 and long durability tests by charging for 12 h at 60 mA cm−2 and discharging for 8 h at −80 mA cm−2. CoO-Co/CNF shows a remarkable stability, maintaining, at least, an 82% of its performance for the ORR after the stress tests, even when cycled for more than 100 h.

One-dimensional Co3O4 nanonet with enhanced rate performance for lithium ion batteries: Carbonyl-β-cyclodextrin inducing and kinetic analysis

Kinetics-limited solid-state diffusion rate results in low rate capacity, retarding the practical applications of Co3O4 anode materials. Construction of nanonet can introduce sufficient interior transport pathways for rapid charging-discharging. Here, we fabricate one-dimensional Co3O4 nanonet (1D-NN) through a facile hydrothermal method with subsequent heat treatment. The construction of nanonet is achieved by employing carbonyl-β-cyclodextrin (C-β-CD) as a crosslinking agent. With the absence of C-β-CD, 1D Co3O4 is also fabricated, while the constructing blocks are independent nanoparticles (1D-NP). Evaluated as anodes for lithium ion batteries, 1D-NN exhibits better rate capacity than 1D-NP. Furthermore, to extract the key reason of outstanding rate capacity, the kinetic properties with different time constants are studied by EIS, GITT and CV simultaneously. The charge transfer resistance and the apparent chemical diffusion coefficient of 1D-NN are more superior to that of 1D-NP. The results of this work show that the C-β-CD induced 1D nanonet structure is conducive to Li+ transport for enhanced rate performance.

Preparation of Polyaniline Graphene Carbon Nanotubes Three-dimensional Composites with High Rate Performance

Composites of polyaniline (PANI), graphene (RGO) and carbon nanotubes (CNTs) were prepared by in situ polymerization. The morphologies of the composites were examined by scanning electron microscopy and transmission electron microscopy, which showed that PANI were coated onto the surface of RGO and CNTs homogeneously and PANI/CNTs were embedded between and/or bridged PANI/RGO sheets. The composites with three-dimensional porous structure possessed higher specific surface area and pore volume compared to those of PANI and PANI/RGO. Such three-dimensional composites exhibited good capacitive performance during the rapid charge-discharge process. The capacitance values of PANI/RGO/CNTs were717 F g-1 and 450 F g-1 at the current densities of 1mV s-1and 200 mV s-1, respectively. The capacitance retention was 62.7% which was higher than that of PANI/RGO and PANI. The cycling performance indicated the long life stability of PANI/RGO/CNTs.

Green synthesis of NiO nanostructured materials using Hydrangea paniculata flower extracts and their efficient application as supercapacitor electrodes

In this report, for the first time, we have applied green synthesis NiO nanoparticles (NiO-NPs) as an electrode material for supercapacitor (SC). Hydrangea paniculata flower extracts were used for the green synthesis of NiO-NPs. The green synthesized NiO-NPs is found to be 33nm with surface area of 78.472m2g−1 along with pore volume and pore size of 0.149cm3g−1 and 4.061nm. The green synthesized NiO-NPs based electrode exhibit high specific capacitance of 752, 709, 644, 603 and 581Fg−1 at current densities of 2.5, 5, 10, 20, and 40Ag−1, respectively, are revealing excellent capacitance retention even at a high current density. More notably, the NiO-NPs electrodes also show outstanding cycling stability up to 5000cycles at 10Ag−1 without discernable capacitance fading. This superior electrochemical performance of NiO-NPs is mainly attributed to the nano-dimention of the particles, which shorten the diffusion path lengths for both ions and electrons, ease migration during the rapid charge-discharge process and consequently improve the effective electrochemical utilization of electroactive material.

Chemically Deposited NiCo2O4 Thin Films for High-Performance Supercapacitors

Changes in climatic conditions resulting from the consumption of fossil fuels and their limited availability have affected the global ecology and economy. The shift towards a more sustainable energy economy has illustrated the need for the development of low cost and environmentally friendly energy storage systems. Supercapacitors, also known as ultracapacitors or electrochemical capacitors, warrant broad important applications in electric vehicles and mobile power sources due to the unique combination of their properties, such as rapid charge–discharge behavior and higher specific power density than batteries and fuel cells while possessing higher energy densities than conventional double layer capacitors. NiCo2O4-based materials have been intensively investigated for pseudocapacitors due to their high theoretical specific capacitance, good chemical and thermal stability, natural abundance, environmental benignity and low cost. In the present work, Nickel cobalt oxide (NiCo2O4) thin films have been systematically prepared using spray pyrolysis method for its application in supercapacitors. Briefly, we prepared two different aqueous solutions of 0.1 M nickel chloride and cobalt chloride by dissolving in de-ionized water (DIW), respectively. In the spray pyrolysis process, aqueous solutions of nickel and cobalt precursor mixed with volume ratio 1:2 were sprayed over the FTO substrates maintained at various temperatures in the form of mist using air-blast spray pyrolysis unit. The sprayed mist undergoes thermal decomposition to form the NiCo2O4 thin films. The electrochemical performance of the NiCo2O4 thin film was measured in a 2M KOH electrolyte with potential window 0 to 0.5 V. Galvanostatic charge– discharge (GCD) studies were also carried out. The field-emission scanning electron microscopy (FE-SEM) image shown in Fig. 1, reveal that compact and uniform thin films of cubic nickel cobaltite with particle size 10-20 nm has been obtained by the oxidation of Ni and Co precursors. Moreover, it is observed that nanostructured NiCo2O4 thin film deposited at 350 0C exhibit the best charge storage property with high specific capacitance of 752 F g−1 and excellent cycle stability over 1000 cycles. The high specific capacitance, remarkable rate capability and excellent cycling stability of the composites mean that they show promise for application in supercapacitors. Figure 1

The Importance of Electrolyte Composition to the Charge-Discharge Performance of Lithium-Ion Batteries Using Ionic Liquids

Ionic liquids such as 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) are still attractive candidates for use as electrolytes in electrochemical energy storage devices, because of their relatively low flammability and reactivity, and because of their electrochemical stability, wide liquidus temperature range, and acceptable ionic conductivity. We have reported a promising ionic liquid based on bis(fluorosulfonyl)imide (FSI-) for lithium-ion batteries since 2006. [1] This liquid with a lithium salt offers incredible charge-discharge performances; despite the relatively high viscosity of the electrolyte, it affords not only reversible and stable cycling but also rapid charge-discharge performance for both negative and positive electrodes. [2] In particular, we are interested in the mechanism of the high rate capability and high stability of the negative electrode of a LIB in FSI-based ionic liquids. By applying several electrochemical techniques, we also revealed the specific electrode–electrolyte interface formed in the presence of both Li+ and FSI- in the ionic liquid electrolyte [3]. On the negatively polarized carbon electrode, minimal Li+ can exist dominantly at the primary layer because of the moderately strong interaction between Li+ and FSI-, leading to the exclusion of EMIm+ away from the electrode. As a result, the presence of FSI-apparently improves the cathodic stability of the electrolyte. Herein, we report the results from charge-discharge tests, focusing on the effect of the electrolyte composition; we investigated how the high concentrated ionic liquid electrolyte including the lithium salts promotes the more stable and rapid charging-discharging of lithium-ion cell. To clarify the effect of concentration of LiFSI on the dependencies of the discharge capacity retention of a graphite electrode in EMImFSI and EMImTFSI (EMIm+ = 1-ethyl-3-methylimidazolium) on the charge-discharge C-rate, which were evaluated by determining the 5-cycle durability for each C-rate operation after primary charge-discharge cycling at the 0.1/0.1 C-rate, are summarized in Figure 1. Here, the discharge capacity retention was calculated as Cx /C 2, where Cx and C 2 are the specific discharge capacities for each cycle (x) and for the second cycle (1.0 C-rate), respectively. The remarkable aspect in this figure is that the high concentration (1.46 mol dm-3) of LiFSI improves the output characteristics in comparison with 0.43 mol dm-3 LiFSI/EMImFSI despite the electrolyte possessing a lower ionic conductivity, while 1.46 mol dm-3 LiTFSI/EMImFSI decreases the rate capability of the graphite compared with 0.43 mol dm-3LiTFSI/EMImFSI.

ChemInform Abstract: Graphene‐Based Materials for Lithium‐Ion Hybrid Supercapacitors

AbstractReview: 73 refs.

Graphene-Based Materials for Lithium-Ion Hybrid Supercapacitors.

Lithium-ion hybrid supercapacitors (LIHSs), also called Li-ion capacitors, have attracted much attention due to the combination of the rapid charge-discharge and long cycle life of supercapacitors and the high energy-storage capacity of lithium-ion batteries. Thus, LIHSs are expected to become the ultimate power source for hybrid and all-electric vehicles in the near future. As an electrode material, graphene has many advantages, including high surface area and porous structure, high electric conductivity, and high chemical and thermal stability, etc. Compared with other electrode materials, such as activated carbon, graphite, and metal oxides, graphene-based materials with 3D open frameworks show higher effective specific surface area, better control of channels, and higher conductivity, which make them better candidates for LIHS applications. Here, the latest advances in electrode materials for LIHSs are briefly summarized, with an emphasis on graphene-based electrode materials (including 3D graphene networks) for LIHS applications. An outlook is also presented to highlight some future directions.

Design of an electrolyte composition for stable and rapid charging–discharging of a graphite negative electrode in a bis(fluorosulfonyl)imide-based ionic liquid

We evaluate the effects of lithium salt on the charge–discharge performance of a graphite negative electrode in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid-based electrolytes. Although the graphite negative electrode exhibits good cyclability and rate capability in both 0.43 mol dm−3 LiFSI/EMImFSI and LiTFSI/EMImFSI (TFSI− = bis(trifluoromethylsulfonyl)imide) at room temperature, only the LiFSI/EMImFSI system enables the graphite electrode to be operated with sufficient discharge capacity at the low temperature of 0 °C, even though there is no noticeable difference in ionic conductivity, compared with LiTFSI/EMImFSI. Furthermore, a clear difference in the low-temperature behaviors of the two cells composed of EMImFSI with a high-concentration of lithium salts is observed. Additionally, charge–discharge operation of the graphite electrode at C-rate of over 5.0 can be achieved using of the high-concentration LiFSI/EMImFSI electrolyte. Considering the low-temperature characteristics in both high-concentration electrolytes, the stable and rapid charge–discharge operation in the high-concentration LiFSI/EMImFSI is presumably attributed to a suitable electrode/electrolyte interface with low resistivity. These results suggest that optimization of the electrolyte composition can realize safe and high-performance lithium-ion batteries that utilize ionic liquid-based electrolytes.

High-performance lithium-ion battery and symmetric supercapacitors based on FeCo₂O₄ nanoflakes electrodes.

A successive preparation of FeCo2O4 nanoflakes arrays on nickel foam substrates is achieved by a simple hydrothermal synthesis method. After 170 cycles, a high capacity of 905 mAh g(-1) at 200 mA g(-1) current density and very good rate capabilities are obtained for lithium-ion battery because of the 2D porous structures of the nanoflakes arrays. The distinctive structural features provide the battery with excellent electrochemical performance. The symmetric supercapacitor on nonaqueous electrolyte demonstrates high specific capacitance of 433 F g(-1) at 0.1 A g(-1) and 16.7 F g(-1) at high scan rate of 5 V s(-1) and excellent cyclic performance of 2500 cycles of charge-discharge cycling at 2 A g(-1) current density, revealing excellent long-term cyclability of the electrode even under rapid charge-discharge conditions.

Building flexible Li4Ti5O12/CNT lithium-ion battery anodes with superior rate performance and ultralong cycling stability

Nanostructured Li4Ti5O12/CNT composite particles were synthesized using an aerosol spray drying process followed by thermal annealing. After assembling into CNT networks, lightweight, flexible and binder-free Li4Ti5O12/CNT anodes were fabricated for lithium-ion batteries. Electrodes fabricated from these nanocomposites showed effective electron and ion transport and, more importantly, more robust structure compared to traditional binder-bonded electrodes. The electrodes delivered a high reversible capacity and superior rate performance up to an extremely high rate of 100C. Moreover, ultralong cycling stability was attained through 8000 rapid charge-discharge cycles with 89% capacity retention. These results demonstrate the feasibility of ultrafast batteries.