Charge-discharge Time Research Articles

Robust electrochemical performance of polypyrrole (PPy) and polyindole (PIn) based hybrid electrode materials for supercapacitor application: A review

Abstract One of the basic intentions of science and technology is the evolution of novel and more efficient devices to make human life more easy and comfortable. A supercapacitor is one such device that can be utilized as a complementary and to some extent a replacement of electrochemical battery to store electrical energy. The performance of a supercapacitor very much depends on the electrode material used and hence a variety of materials are employed to form electrodes of supercapacitors in order to improve its performance. In this review, we have discussed the preparation and properties of polypyrrole (PPy) and polyindole (PIn) based electrode material for supercapacitor applications. PPy shows a high degree of flexibility which makes it markedly suitable and applicable for making flexible supercapacitors. PIn exhibit slow hydrolytic degradation and hence long charge-discharge time. Thus, PIn can be utilized to form supercapacitors having the ability to store energy for a longer period of time. Nonetheless, their properties can be enhanced by using binary and ternary composites of PPy and PIn with different carbon-based and metal-based materials. This review briefly discusses some of these composites and devices formed by them.

Cross-linked amphoteric membrane: Sulphonated poly(ether ether ketone) grafted with 2,4,6-tris(dimethylaminomethyl)phenol using functionalized side chain spacers for vanadium redox flow battery

Herein, we report a novel synthesis of sulphonated poly(ether ether ketone) (SPK) grafted with 2,4,6-tris(dimethylaminomethyl)phenol (TAP) for preparation of amphoteric ion-exchange membrane (AIEM). Cross-linking has been achieved by using di-bromo alkane with different number of carbon chains (C6 & C10), and different AIEMs are assessed for vanadium redox flow battery (VRFB). These AIEMs are architected to contain –SO3H groups maintained conductivity, while –NH3+ groups for reduction in vanadium permeability with improve charge-discharge time via acid-base interactions. Structural and surface morphology of AIEMs have been elucidated by different spectral techniques (FTIR, 1H NMR, SEM, and AFM). Cross-linking and acid-base interactions effectively reduced water uptake, swelling ratio, VO+2 permeability and improved ion-exchange capacity, conductivity, along with membrane stabilities. Due to good synergy between conductivity and VO+2 permeability, cross-linked AIEM with six number of carbon chains (CQSPK-6) exhibited higher Coulombic (CE: 98.4% vs 91.2%) and energy efficiency (81.4% vs~76%) than Nafion 117 membrane at 60 mA cm−2 in single cell VRFB. Further, CQSPK-6 AIEM maintained stable performance during in-situ cycle test (100 cycles) at 60 mA cm−2. Hence, AIEM based on cross-linked SPK grafted with high molality of functional groups via side chain spacer is a promising candidate for an efficient VRFB system.

Preparation and performance of polypropylene separator modified by SiO2/PVA layer for lithium batteries

AbstractAn aqueous silica (SiO2) dispersion was prepared by using silica as ceramic particles, polyvinyl alcohol (PVA) as a binder and deionized water as a dispersion medium. A SiO2 ceramic layer was applied to the surface of the polypropylene (PP) separator by dip coating. The separators before and after modification were characterized by XRD, SEM, DTA, lyophilic performance test, contact angle test and heat resistance test. The separators were assembled into lithium-ion batteries for electrochemical performance test. The results show that after the successful introduction of SiO2/PVA coating on the surface of PP separator, the lyophilic and heat resistance and electrochemical performance of PP separator have been improved significantly. The battery rate performance and cycle performance are significantly improved. Especially the capacity retention rate of the original separator was only 75.79% at 100 charge-discharge times, and that of the modified separator was as high as 87.18%.

Hollow-tubular porous carbon derived from cotton with high productivity for enhanced performance supercapacitor

Hollow-tubular porous carbon is synthesized from NaH2PO4 layer coating natural biomass cotton fiber through a facile carbonization and KOH–KNO3 activation process. It shows that the obtained porous carbon keeps the initial fiber structure of hollow-tubular, resulting in a high surface area of 1508 m2 g−1 and obvious mesoporous structure (9.18 nm). With coating of NaH2PO4 layer, high productivity (27.3%) of the obtained carbon can be achieved which is two times higher than the untreated cotton. The obtained porous carbon exhibits high specific capacitance (278 F g−1 at 1 A g−1) and excellent rate capability (208 F g−1 at 100 A g−1), showing the much higher rate performance than that of other biomass-derived carbon materials. Moreover, the carbon also displays a superior-short charge-discharge time (1.89 s at 100 A g−1) and super long cycle life (94.3% retention over 10 × 104 cycles at 100 A g−1). This excellent electrochemical performance mainly belongs to its special hollow-tubular morphology and activated porous structure. Hence, this method is a new strategy for the porous carbon production as high-power supercapacitor material with larger product yield and special structures which are inherited from natural biomass.

Adiponitrile (C6H8N2): A New Bi‐Functional Additive for High‐Performance Li‐Metal Batteries

AbstractRechargeable batteries with a Li metal anode and Ni‐rich Li[NixCoyMn1−x−y]O2 cathode (Li/Ni‐rich NCM battery) have been emerging as promising energy storage devices because of their high‐energy density. However, Li/Ni‐rich NCM batteries have been plagued by the issue of the thermodynamic instability of the Li metal anode and aggressive surface chemistry of the Ni‐rich cathode against electrolyte solution. In this study, a bi‐functional additive, adiponitrile (C6H8N2), is proposed which can effectively stabilize both the Li metal anode and Ni‐rich NCM cathode interfaces. In the Li/Ni‐rich NCM battery, the addition of 1 wt% adiponitrile in 0.8 m LiTFSI + 0.2 M LiDFOB + 0.05 M LiPF6 dissolved in EMC/FEC = 3:1 electrolyte helps to produce a conductive and robust Li anode/electrolyte interface, while strong coordination between Ni4+ on the delithiated Ni‐rich cathode and nitrile group in adiponitrile reduces parasitic reactions between the electrolyte and Ni‐rich cathode surface. Therefore, upon using 1 wt% adiponitrile, the Li/full concentration gradient Li[Ni0.73Co0.10Mn0.15Al0.02]O2 battery achieves an unprecedented cycle retention of 75% over 830 cycles under high‐capacity loading of 1.8 mAh cm−2 and fast charge–discharge time of 2 h. This work marks an important step in the development of high‐performance Li/Ni‐rich NCM batteries with efficient electrolyte additives.

A 3D porous NCNT sponge anode modified with chitosan and Polyaniline for high-performance microbial fuel cell

A microbial fuel cell (MFC) is a potential bio-electrochemical technology that utilizes microorganisms to convert chemical energy into electrical energy. The low power output of MFCs remain the bottleneck for their practical applications. In this paper, a novel, biocompatible and bioelectrocatalytic composite chitosan-nitrogen doped carbon nanotubes-polyaniline (CS-NCNT-PANI) was prepared in situ on the 3D porous NCNT/sponge and applied to an MFC anode. The PANI was grafted on the CS-NCNT backbone to synthesize the ternary composite. This bioanode not only increased the active surface area and capacity but also facilitated bacterial adhesion and enrichment of microbes. Compared with the NCNT/sponge electrode, the charge transfer impedance of the ternary composite bioanode decreased from 14.07 Ω to 2.25 Ω, and the maximum power density increased from 1.4 W·m−3 to 4.2 W·m−3; meanwhile, during the chronoamperometric experiment with a charge-discharge time of 60–60 min, the cumulative charge of the composite bioanode was 18,865.8 C·m−2, which is much higher than that of the NCNT/S anode (3625.3 C·m−2). High-throughput sequencing technology revealed that the ternary composite bioanode had good biocompatibility and high diversity. Therefore, this synthesized ternary composite is a promising candidate as a capacitive and biocompatible anode material in MFC.

Fluorine-doped tin oxide/ hematite/ Ni(OH)2/ Prussian white photoelectrode for use in a visible-light-assisted pseudocapacitor

Herein, a fluorine-doped tin oxide/hematite/nickel hydroxide/Prussian white photoelectrode is fabricated for use in a visible-light-assisted pseudocapacitor. A visible-light-assisted pseudocapacitor is a two-electrode device that uses both electrical and solar energy sources to charge and store energy. The photoelectrode consists of a thin layer of Prussian white deposited on a nickel hydroxide modified hematite film. The hematite is used as a photoactive material, nickel hydroxide and Prussian white are employed as the pseudo-capacitive electroactive materials. Fluorine-doped tin oxide/hematite/nickel hydroxide/Prussian white has a much higher charge-discharge time and areal capacitance under illumination. A galvanostatic charge-discharge curve shows an areal capacitance of 2.16 mF cm−2 under illumination, that is 940-fold higher than that in the dark. This behavior is attributed to the presence of photogenerated charges that increase the conductivity and facilitate charge transfer reactions. The electrochemical impedance spectroscopy shows that the charge transfer resistance under illumination is 633 Ω which is more than three times lower than 2220 Ω under dark. Therefore, under dark pseudocapacitive charge storage reactions do not occur significantly, because of the high resistance of semiconductor. While under illumination, photogenerated charges reduce charge transfer resistance. Thus, the pseudocapacitive reaction is progressed and the charge is stored.

Experimental analysis of solar air collector with PCM-honeycomb combination under the natural convection

Phase change material (PCM) is at the head of materials commonly used in latent heat storage. However, usually the main problem is that the heat conductivity of PCMs is low. Therefore, a novel solar air collector (SAC) combined the PCM-Rubitherm RT54HC with aluminum honeycomb was manufactured and investigated the effect of using honeycomb core on the collector thermal performance regarding heat storage with PCM under natural convection conditions. In the experiments, the heat storage material was tested in two forms with 26 kg capacity, PCM with honeycomb core in the first collector (type I) and only PCM in the second collector (type II), and also the third collector (type III) with a flat absorber plate for comparison. The first collector reached the PCM melting point about 50 min ago. Also, when we consider the peak point, an apparent 10 °C advantage is achieved in sensible heat storage in favor of type I. It is observed that the honeycomb core used as a heat transfer enhancer is effective in shortening the charge-discharge times, also a noticeable difference in sensible heat storage during the noon. The production of useful energy in Type I lasted 469 min and 539 min longer than type III, respectively. The thermal efficiencies under daylight were calculated as 10.1%, 10.9% and 13.6%, respectively. As a result, it can be said that the use of honeycomb core as heat conductivity enhancer material is very functional, in particular during the discharge period.

A comparative investigation of the effect of honeycomb core on the latent heat storage with PCM in solar air heater

The aims of this study were to comparatively investigate the effect of using PCM and honeycomb as the internal fin structure in the PCM panel on the thermal performance of solar air heater. The tests performed at six air mass flow rates from 0.008 to 0.048 kg/s. The heat storage material was tested in two forms, PCM with honeycomb core in the first heater (Type I) and only PCM in the second heater (Type II). The third heater (Type III) with a flat absorber plate (without PCM) was used for comparison. The average day-time thermal efficiency of the Type I-II heaters with PCM increased from 8.4% to 9.0% for the mass flow rates of 0.032, 0.04, and 0.048 kg/s, while from 0.8% to 8.0% decreased for the mass flow rates of 0.008, 0.016 and 0.024 kg/s. The use of honeycomb as the internal fin structure significantly reduces the charge-discharge time, while slightly reducing the instantaneous-daily thermal efficiency, and provides a temperature increase of up to 8.8 °C at the PCM-temperature. The daily thermal efficiency comparison between heaters with PCM was in favor of the heater without honeycomb at values ranging from 0.1% to 4.4%. Taking into consideration the daily thermal efficiency, the Type I-II heaters with PCM are more efficient between from 2.6 to 22.3%, especially at high mass flow rates. It took approximately one hour to equal the outlet air temperature of the Type-III with the inlet air temperature. In PCM heaters, the inlet-outlet temperatures are approximately equal to 6 to 10 h.

Enhanced energy storage and fast discharge properties of BaTiO3 based ceramics modified by Bi(Mg1/2Zr1/2)O3

Lead-free (1-x)BaTiO3-xBi(Mg1/2Zr1/2)O3 ((1-x)BT-xBMZ) ceramics with perovskite structure were synthesized by solid-state reaction methods. (1-x)BT-xBMZ solid solution transforms from tetragonal (x≤0.04) to pseudocubic (x≥0.08) and exhibits a dispersive dielectric behavior with respect to frequency, showing typical relaxor characteristics with BMZ increasing. The optimal energy storage density of 1.25 J cm−3 and energy efficiency of >95% are obtained at x = 0.15, with maximum dielectric breakdown strength of 185 kV cm-1 at 200 μm thickness., The energy storage density and energy efficiency of 0.85BT-0.15BMZ ceramics maintain at about 0.8 J cm−3 and 89% at 150 kV cm-1 over temperature range of 25 °C∼150 °C, exhibiting good thermal stability. The pulse discharge capability of 0.85BT-0.15BMZ ceramics were measured under different electric fields, showing a short charge-discharge time of 1.3 μs. Therefore (1-x)BT-xBMZ solid solution with high energy density and efficiency, good temperature stability and fast discharge speed, is promising candidate for high power applications.

High performance tellurium-reduced graphene oxide pseudocapacitor electrodes

We report on facile preparation of Tellurium (Te)-reduced graphene oxide (rGO) electrodes for evaluation of electrochemical parameters. Initially, Te (0.5–11w/w %) was, in-situ, incorporated while reduction of graphene oxide. In material analysis, 1% Te optimised C/O ratio by rearrangement of C(O)O, separating oxygen from graphene plane, and self-oxidation. TeO bridging acted as an ideal strain buffer that modified nature of conjugation, folding, and exfoliated rGO sheets advantageous for pseudo-capacitive action. Electrochemical analysis, showed substantial increase in specific capacitance, Csp(@5 mV/s), for 1% Te-rGO, to 460 F/g from base rGO (270 F/g) with increase in charge-discharge time (CD@0.5A/g) 15 (rGO) to 100 s (Te-rGO). For two electrodes, CV (285 F/g @ 5 mV/s) and CD (260 F/g @0.25A/g) data was in well agreement with greatest CD ∼ 250 s for (1%). The CD time was retarded by a factor of six in both electrode studies, at 1%. The estimated energy, ED(Wh/kg), and power density, PD (W/kg), indicated that, both electrodes were at the interface of battery and electrode double layer capacitor (EDLC) region on Ragone plane. However, 1%Te-rGO at low PD(250) and high ED (8) have battery-like behaviour, whereas, at high PD (1002) and low ED(5) showed pseudo-capacitive action. Investigations on Nyquist, ac complex capacitance (Bode), and phase plots quantified contribution of impedances offered by surface, interface (electrolyte/active electrode/collector), charge transfer, and ions. Te-rGO showed excellent cycle stability 100% even after 2500 cycles @ 1A/g. By and large, 1% Te showed superior pseudo capacitive performance compared over high Te % and base rGO.

Preparation and microbial fuel cell application of sponge-structured hierarchical polyaniline-texture bioanode with an integration of electricity generation and energy storage

The choice of anode materials and structure has an important influence on the performance of microbial fuel cells (MFCs). In this paper, a flexible and compressible bioanode with the features of integration of electricity generation and energy storage in MFCs was reported. With sponge skeleton as the substrate, this bioanode has been coated with carbon nanotubes and graphene, and then aniline has been polymerized on it. Compared with a carbon nanotube-sponge electrode, the charge transfer impedance of the polyaniline composite bioanode decreases from 26.6 to 4.67 ohm, and the maximum power density increases from 259.7 to 571.5 mW m−2; meanwhile, with the charge–discharge time of 60–60 min, the stored charge increases by 4.7 times, and the steady current density increases by 6.2 times. These results can be ascribed to a synergistic effect of some factors including the great specific surface area and distinct macroporous architecture of the sponge substrate, the effect of two carbon nanomaterials on decreasing the bioanode resistance, the energy storage characteristic of polyaniline, and the good biocompatibility of coating materials. The MFC with the PANI/rGO/CNTs/S capacitive bioanode has a very good ability to synchronously produce electricity and store energy and can release the stored charge in short bursts, which is expected to meet the demand of electric equipment. Schematic illustrations of the fabrication process of PANI/rGO/CNTs/S electrode.

Ordered charge-discharge and optimal scheduling of energy storage battery

This paper presents a method to coordinate the discharge depth and charge-discharge times. The method is based on the operation strategy of the partial batteries used alternatively. Under certain premise, the concept of ordered charge-discharge is put forward, and the rules of ordered charge-discharge are explained in this paper. According to the relationship between the number of cycle times and the discharge depth, the number of the corresponding power distribution cell is obtained under maximum lifetime. By considering the balance of battery charge-discharge and state of charge, a power allocation strategy based on ordered charge-discharge is proposed, and the operation cost of the battery energy storage system is used as the evaluation index of the optimal scheduling. It is proved that the battery energy storage system under the ordered charge-discharge is more economical than the power sharing system, which shows the advantage of the battery charge-discharge.

One-step potentiostatic electrodeposition of polypyrrole/graphene oxide/multi-walled carbon nanotubes ternary nanocomposite for supercapacitor

A ternary nanocomposite consisting of polypyrrole (PPy), graphene oxide (GO) and multi-walled carbon nanotube (MWCNT) for supercapacitor was prepared via facile one step potentiostatic technique. Field emission scanning electron microscopy (FESEM) images displayed a randomly entangled nanostructure of MWCNT with rough wrinkle surface of GO incorporating with PPy granular structure represent the morphology of PPy/GO/MWCNT nanocomposite. The ternary nanocomposite was further justified its chemical composition by using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. PPy/GO/MWCNT exhibited a high specific capacitance of 358.69 F g−1 at a scan rate of 100 mV s−1 in 1 M Na2SO4, which is comparatively higher than both binary nanocomposites, PPy/MWCNT (207.52 F g−1) and PPy/GO (139.03 F g−1). The PPy/GO/MWCNT nanocomposite also possessed much longer charge-discharge time and excellent cycling stability (88.69%) with the specific energy of 40.45 Wh/kg and specific power of 441.24 W/kg. Therefore, PPy/GO/MWCNT nanocomposite is a potential electrode material for high-performance supercapacitor.

High-Energy-Density Polymer Nanocomposites Composed of Newly Structured One-Dimensional BaTiO3@Al2O3 Nanofibers

Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm-3 at 420 MV m-1 and the fast charge-discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.

Synthesis and Charge Storage Properties of Hierarchical Niobium Pentoxide/Carbon/Niobium Carbide (MXene) Hybrid Materials

Orthorhombic niobium pentoxide (T-Nb2O5) offers high capacitance and fast charging–discharging rate capabilities when used as an electrode material for Li-ion capacitors. A homogeneous distribution of T-Nb2O5 nanoparticles in a highly conductive matrix represents a promising approach to maximize its energy and power densities. Here we report a one-step CO2 oxidation of two-dimensional (2D) Nb2CTx, a member of the MXenes family of 2D transition metal carbides, which leads to a hierarchical hybrid material with T-Nb2O5 nanoparticles uniformly supported on the surface of Nb2CTx sheets with disordered carbon. The oxidation temperature, duration, and CO2 flow rate determine the T-Nb2O5 crystallite size as well as the structure, composition, and the charge storage properties of the hybrid material. Fifty micrometer thick electrodes of the hybrid material exhibit high capacitance (330 C g–1 and 660 mF cm–2 at a charge–discharge time of 4 min) and good cycling performance in a nonaqueous lithium electrolyte. The ...

Research of Li-Ion Battery’s Upper Equalizer Circuit

Due to small size, large power density, high individual voltage, low self-discharging, and low internal resistance, li-ion battery substitutes other types of battery used as power supply. In practice, because of difference of every cell, after a period of charge-discharge time, the upper limit voltage of every unit becomes various, seriously affects the system’s performance. The idea of upper equalizer is released, then, a further research is made on the equalizer circuit of li-ion battery. The experiment result proves the correctness of design on li-ion battery equalizer circuits.

Research of Li-Ion Battery’s Equalizer Circuit Based on TL431

Li-ion battery, as a new type of energy storage equipment, has small size, large power density, high individual voltage, low rate of self-discharging and small self-resistance etc. It substitutes the traditional power battery in AGV.In practical process, due to the difference of battery cells, after a period of charge-discharge time, the upper and lower voltage limits of every unit of batteries become various, seriously affecting the system performance. The idea of upper and lower equalizer is released for this case. Then, a further research is made on the equalizer circuit of li-ion battery. The experiment result proves the correctness of design on several types of lithium battery equalizer circuit.

Flexible binder-free metal fibril mat-supported silicon anode for high-performance lithium-ion batteries.

We report the fabrication of a flexible and binder-free metal fibril mat-supported Si anode (Si@SFM) by a simple process. The fabricated Si@SFM anode showed a high discharge capacity, ∼3000 mAh g(-1) at a current rate of 300 mA g(-1), and exhibited stable capacity retention, 90% at a 1 C rate (2000 mA g(-1)) after 200 cycles. The rate capability of the electrode was still high even when both the charge and the discharge current rates were markedly increased at the same time (1234 mAh g(-1) for charge-discharge time of ∼12 min). Moreover, owing to its mechanical flexibility, the Si@SFM can be adopted as a key component of flexible lithium-ion batteries (LIBs). After cell packaging, the rechargeable flexible battery under bending stress showed only a little capacity fading (86% of initial capacity) at 1000 mA g(-1) over 150 cycles. These results suggest that the Si@SFM electrode is readily suitable for use in rechargeable flexible LIBs.

New Li-ion Battery Evaluation Research Based on Thermal Property and Heat Generation Behavior of Battery

We do a new Li-ion battery evaluation research on the effects of cell resistance and polarization on the energy loss in batteries based on thermal property and heat generation behavior of battery. Series of 18650 cells with different capacities and electrode materials are evaluated by measuring input and output energy which change with charge-discharge time and current. Based on the results of these tests, we build a model of energy loss in cells' charge-discharge process, which include Joule heat and polarization heat impact factors. It was reported that Joule heat was caused by cell resistance, which included DC-resistance and reaction resistance, and reaction resistance could not be easily obtained through routine test method. Using this new method, we can get the total resistance R and the polarization parameter η. The relationship between R, η, and temperature is also investigated in order to build a general model for series of different Li-ion batteries, and the research can be used in the performance evaluation, state of charge prediction and the measuring of consistency of the batteries.