Investigation of the charge/discharge characteristics of aqueous zinc–ferric chloride batteries

In a Zn–FeCl₃ battery, zinc granules were used as the anode and ammonium chloride as the electrolyte in both the anode and cathode zones, with ferric chloride as the active cathode substance and carbon felt as an inert cathode. A PE-01 homogeneous membrane was used as the membrane between the anode and cathode zones, with 100 ml of solution in both the anode and cathode zones. The charge/discharge characteristic of the battery was investigated for various concentrations of ferric chloride and ammonium chloride. At present, there are still some difficulties in using this zinc–ferric chloride battery as a rechargeable battery because zinc cannot be electrodeposited very well. However, it can possibly be used as a fuel cell and the operating lifetime of the fuel cell is very long. The actual energy density of a Zn–FeCl₃ fuel cells is approximately equal to the actual energy density of a Pb–PbO₂ battery. When a mixed solution of 2 M ferric chloride and 2 M ammonium chloride was used in the cathode zone with 4–5 M ammonium chloride in the anode zone, a better discharge characteristic was obtained, with a discharge time of approximately 14–15 h at 5 Ω. The most remarkable advantages for Zn–FeCl₃ fuel cell are that both zinc and ferric chloride are very cheap and environmentally friendly, with flat discharge voltage characteristics.     

Surface treatment of zinc anodes to improve discharge capacity and suppress hydrogen gas evolution

The shape change and redistribution of zinc anode material over the electrode during repeated cycling have been identified as the main factors that can limit the life of alkaline zinc-air batteries. Li₂O–2B₂O₃ (lithium boron oxide, LBO) glass with high Li⁺ conductivity and stability can be coated on the surface of zinc powders. The structures of the surface-treated and pristine zinc powders were characterized by XRD, SEM, TEM, ESCA and BET analyses. XRD patterns of LBO-coated zinc powders revealed that the coating did not affect the crystal structure. TEM images of LBO-coated on the zinc particles were compact with an average passivation layer of about 250 nm. The LBO layer can prevent zinc from coming into direct contact with the KOH electrolyte and minimize the side reactions within the batteries. The 0.1 wt.% LBO-coated zinc anode material provided an initial discharge capacity of 1.70 Ah at 0.5 V, while the pristine zinc electrode delivered only 1.57 Ah. A surface-treated zinc electrode can increase discharge capacity, decrease hydrogen evolution reaction, and reduce self-discharge. The results indicated that surface treatment should be effective for improving the comprehensive properties of anode materials for zinc-air batteries.     

Synthetic silver oxide and mercury-free zinc electrodes for silver–zinc reserve batteries

Reserve activated silver oxide–zinc cells were constructed with synthetic silver oxide (Ag₂O) electrodes with Pb-treated zinc electrodes produced by a non-electrolytic process. The cells were tested before and after thermally accelerated aging. At discharge rates up to 80 mA cm⁻², the discharge was limited by the Ag₂O electrode, with a coulombic efficiency between 89–99%. At higher rates, the cells are apparently zinc-limited. Test cells were artificially aged at 90°C for 19 h and discharged at 21°C at 80 mA cm⁻². No capacity loss was measured, but a delayed activation rise time was noted (192 ms fresh vs. 567 ms aged). The delay is thought to be caused by zinc passivation due to the outgassing of cell materials.     

Zinc morphology in zinc-nickel flow assisted batteries and impact on performance

The zinc morphology on repeated charging and discharging in flow-assisted zinc-nickel oxide cells was studied. The results show that higher charge rates cause more dendritic growth of zinc deposition on charging and tend to cause deterioration of battery cells. However, when the electrolyte velocity is higher than 15 cm s⁻¹, the direction of dendrites was distorted toward the flow direction and the internal short circuit was suppressed. Good cycle life was obtained - 1500 cycles at 100% depth of discharge and C/2 charge and discharge rate. Also, the battery was scaled up to a 100 Wh prismatic cell, and more than 200 cycles were obtained.     

Methanol conversion from methane and water vapor by electric discharge (Effect of electric discharge process on methane conversion)

The possibility of methanol conversion from a methane and water-vapor gas mixture was investigated for a new and highly efficient energy conversion system. Reforming process of methanol to hydrogen can be used for low-temperature thermal energy utilization. Direct methanol production from a methane and water-vapor mixture by spark or glowlike discharges has been achieved experimentally. A high methanol mole fraction of 0.5% has been obtained by both discharges. The effects of applied high voltage time, total pressure, and ratio of gas mixture on the conversion efficiency have been clarified experimentally. The electric energy consumption for methanol production by the spark discharge method is 1/100 that by the glow discharge method. The methanol conversion process has also been analyzed theoretically by considering the dissociation of the initial mixture gas by electrons and 104 elementary reactions. The results suggest that a very short period energy input such as a spark discharge can effectively produce methanol compared with a steady-state discharge such as a glowlike discharge. © 1999 Scripta Technica, Heat Trans Asian Res, 28(5): 404–417, 1999     

Preliminary study on zinc–air battery using zinc regeneration electrolysis with propanol oxidation as a counter electrode reaction

A zinc–air battery using zinc regeneration electrolysis with propanol oxidation as a counter electrode reaction is reported in this paper. It possesses functions of both zincate reduction and electrochemical preparation, showing the potential for increasing the electronic energy utilization. Charge/discharge tests and scanning electron microscopy (SEM) micrographs reveal that when a nickel sheet plated with the high-H₂-overpotential metal, cadmium, was used as the negative substrate electrode, the dendritic formation and hydrogen evolution are suppressed effectively, and granular zinc deposits become larger but relatively dense with the increase of charge time. The performance of batteries is favorable even if the charge time is as long as 5 h at the current density of 20 mA cm⁻². Better discharge performance is achieved using a ‘cavity-opening’ configuration for the discharge cell rather than a ‘gas-introducing’ configuration. The highest energy efficiency is up to 59.2%. That is, the energy consumed by organic electro-synthesis can be recovered by 59.2%. Cyclic voltammograms show that the sintered nickel electrode exhibits a good electro-catalysis activity for the propanol oxidation. The increase of propanol concentration conduces to an enhancement in the organic electro-synthesis efficiency. The organic electro-synthesis current efficiency of 82% can be obtained.     

Ignition of aluminum powders by electro-static discharge

Metal powder heating and ignition by an electro-static discharge, ESD (or spark) was investigated. For different spark voltages, ESD discharge energies transferred to the powder samples and respective spark radii are evaluated experimentally. Al powder was chosen as a popular metal fuel additive for many energetic formulations, and as a metal, for which spark initiation typically results in ignition of individual particles rather than in an aerosol flame consuming bulk of the powder. Al powders with nominal particle sizes of 3-4.5 μm and 10-14 μm were used in experiments. The finer powder was found to be strongly agglomerated while almost no agglomeration was observed for the coarser powder. Emission streaks produced by an empty steel sample holder struck by the spark and by the spark-heated and ignited Al particles were detected and differentiated. Emission traces of burning particles were acquired by a photodiode to determine burn times for the particles ignited by sparks with different energies. From the burn times, particle diameters were estimated using correlations reported in the literature. Burn times for the ignited Al particles clearly correlated with the Joule heat energy for the coarser (nom. 10-14 μm) powder, while the correlation was tentative for the finer powder used in this work. The results are interpreted considering the particle size distributions and assuming that particles are Joule heated so that the heating is more efficient for finer particles, with greater surface to volume ratio. It is further suggested that strong agglomeration observed for the finer Al powder skewed the expected correlation between the Joule heating energy and the size of ignited particles. Current experiments suggest several additional practical conclusions. The mechanisms of powder ejection and ignition by the ESD are not directly related to each other. The commonly considered minimum ignition energy is not a useful powder characteristic and depends strongly on the optical diagnostics used. It is proposed that more useful and readily measured quantitative indicators of the powder ignition sensitivity are the burn time of the particles ignited by the spark and the distance the burning particles travel, which respectively quantify how long and how far reaching is the spark’s ignition stimulation. Both parameters should be quantified for a specific spark energy or energy range.     

Experimental study of ignition of magnesium powder by electrostatic discharge

Ignition of non-aerosolized powders by electrostatic discharge (ESD) is investigated. A spherical powder of Mg, for which thermal ignition kinetics was described in the literature, was used in experiments. The experimental setup was built based on a commercially available apparatus for ESD ignition sensitivity testing. Additional diagnostics enabled measurements of electrical current, voltage, and spark and ignited powder emission in real time. The spark duration was of the order of a few μs. The spark current and voltage were always observed to have significant AC components. The electrical impedance of the spark discharge was determined experimentally using the recorded current traces and assuming that the spark and powder could be represented as a series LRC circuit. The optical emission was filtered to separate the signals produced by the spark plasma and by the heated and igniting powder. The radiation signal produced by the igniting powder was always delayed after the spark. The delay time decreased from about 3.5 to 0.5 ms as the spark energy increased from 10 to 60 mJ; the delay remained nearly constant when the spark energy continued to increase to over 100 mJ. For experiments where the powder volume decreased or where binder was introduced delay times were reduced. For the powder with a small amount of binder, the ignition delay continued to decrease for spark energies exceeding 60 mJ. Interpretation of the obtained experimental data suggests that the ignition is primarily due to direct Joule heating of the powder by the spark current.     

Discharge path observation and the statistical characteristics of discharge paths for long–air gap discharge for in‐operation wind turbines

When a wind turbine is in normal operation, the blades are rotating, and this blade rotation may affect the process of lightning striking the wind turbine. To investigate this problem, long‐gap discharge tests are performed in this study. Moreover, a multiple physical parameter synchronous observation platform is designed for a scaled wind turbine. Long‐gap discharge tests of a static and rotary‐scaled wind turbine with blade tip‐electrode gap distances of 1 to 8 m are conducted, and the discharge paths under different gaps and wind turbine operating conditions are obtained. The characteristic parameters—arc shape upon discharge, lengths of the downward and upward leaders, blade angle at the moment of discharge, and angle of upward leader initiation—are statistically analyzed. The analysis of the aforementioned data indicates that rotation has opposite effects on the discharge characteristic parameters under short and long gap distances. According to the analysis, blade rotation reduces the space charge density of the corona discharge near the tip, which leads to an increase in the field strength near the blade tip and a decrease in the field strength away from the blade tip. Short and long gaps have different degrees of influence on discharge, which changes the difficulty of upward leader initiation at the blade tip and consequently alters the entire discharge process. The obtained results can provide a reference for the lightning protection of wind turbines.     

Improvement of high-rate capability of alkaline Zn–MnO2 battery

Electrolytic dendritic-zinc powders of high surface area are prepared from an alkaline solution by a galvanostatic electrodeposition method. The surface morphology and microstructure of these powders are examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cylindrical AA-size alkaline zinc–manganese dioxide (Zn–MnO₂) batteries made with powders in anode gels are assembled and tested. The electrochemical characteristics of the batteries are evaluated by means of the ac impedance method and the constant-current discharge experiments. It is found that the high-rate performance of cells with dendritic-zinc powders is much better than that of cells with conventional molten-zinc powders.     

Hydrogen discharge simulation and testing of a metal-hydride container

The performance of a metal-hydride hydrogen storage container of cylindrical shape was experimentally and numerically evaluated at different discharge flow rates, following the discharge pressure as a function of time (discharge curve). The heat transfer in the radial direction was simulated by a one-dimensional finite difference method, subjected to the same conditions of the experimental measurements. The time evolution of the main thermodynamic parameters inside the container, was calculated by fitting the experimental results with the simulation. In addition, the sensitivity of the simulation with respect to the variation of the main parameters was assessed.     

Characterization of a zinc-cerium flow battery

The performance of a divided, parallel-plate zinc-cerium redox flow battery using methanesulfonic acid electrolytes was studied. Eight two and three-dimensional electrodes were tested under both constant current density and constant cell voltage discharge. Carbon felt and the three-dimensional platinised titanium mesh electrodes exhibited superior performance over the 2-dimensional electrodes. The charge and discharge characteristics of the redox flow battery were studied under different operating conditions and Zn/Ce reactant, as well as methansulfonic acid concentration. The cell performance improved at higher operating temperatures and faster electrolyte flow velocities. The number of possible cycles increased at reduced states of charge. During 15 min charge/discharge per cycle experiment, 57 cycles were obtained and the zinc reaction was found to be the limiting process during long term operation.     

Analysis of the spatial uniformity of the combustion of a gaseous mixture initiated by a nanosecond discharge

The spatial uniformity of combustion in a gas mixture initiated by a high-voltage nanosecond volume discharge has been investigated at gas pressures of 0.3-2.4 atm and temperatures of 1100-2250 K. The experiments were carried out behind a reflected shock wave propagating in a mixture of methane and air diluted with argon. The autoignition time and the time of discharge-induced ignition were determined. It was found that, at relatively low pressures (∼0.5 atm), the discharge significantly decreased the ignition temperature (by 600 K). At higher pressures (1.5-2 atm), the ignition temperature fell by only 100 K. The emission from the discharge and combustion were registered with a nanosecond ICCD camera under various experimental conditions. Comprehensive measurements of the deposited energy and the waveforms of the discharge voltage and current with a nanosecond time resolution made it possible to determine the efficiency of this type of discharge for igniting combustible mixtures.     

锌精炼过程煤气消耗量组合预测模型及其应用

基于已有的锌精炼过程煤气消耗,结合现代新的预测理论技术,提出一种指数回归-灰色理论相结合的组合预测模型来预测锌精炼过程的煤气消耗量。实际预测结果表明,这一模型对于锌精炼过程的煤气消耗量的预测具有较高的精度,这为锌精炼过程的煤气消耗量预测提供了新的方法。     

Experimental studies of the performance of adsorbed natural gas storage system during discharge

In this work, comparative experiments were carried out to study the thermal effect of the adsorption heat on the discharge performance of an adsorbed natural gas (ANG) storage system. A storage vessel with u-shaped heat exchanging pipe round the central region was designed according to the temperature field determined by the finite element analysis of the adsorbent bed within 1 L cylinder. Discharge performances of the ANG on the activated carbon within the storage vessel were tested on a volumetrically built experimental unit. Results show that the central region of the adsorbent bed suffers from the severest temperature fluctuation in a short period of the initial discharge state; introduction of the hot water whose temperature is similar to that of the cooling water of a vehicular engine can significantly moderate the temperature fluctuation of the adsorbent bed, shorten the discharge process for about 60 % in comparing with that without the application of the supplemental heat. Conclusions are drawn that the heat from the cooling water of a vehicular engine should be a consideration to improve the discharge performance of the ANG storage system.     

Plasma treatment of zinc oxide-nanoparticles:polyaniline blend as an active layer for the hybrid bulk heterojunction solar cell applications

In this experimental work, plasma treatment of the active layer in the bulk heterojunction solar cells was studied. The active layers consisting of zinc oxide nanoparticles:polyaniline were spin-coated on indium tin oxide covered glasses then kept in the cold plasma medium for different treatment times. The J-V characteristics were considered under air mass 1.5G standard illumination, and variations of the open-circuit voltages and short circuit currents were studied under different treatment times. The results show that there is an optimum treatment time to improve the properties of the layers. In order to understand the origin of this effect, the Hall coefficient, along with ultraviolet-visible spectra were measured, and for studying the topological impact of plasma on the surface of the layers, atomic force microscopy and Fourier-transform infrared spectroscopy were considered. The measurements confirmed the time dependency of the open-circuit voltages and short circuit currents of the cells on the plasma treatment times. Atomic force microscopy of the layers shows the significant topological effects of the plasma treatments on the surface of the active layers for different treatment times.     

Flow rate measurement via isothermal discharge method for hydrogen

The thesis of this study is to investigate that the measurement accuracy of the isothermal discharge method for hydrogen gas with an isothermal tank which is designed for measuring the flow rate characteristics of pneumatic components. Compressed hydrogen in an isothermal tank, which is combined three types of orifice, is discharged from 700 kPa (abs) to atmospheric pressure. The average temperature in the tank during discharge is measured experimentally. In consequence, when the maximum discharge rate is 37 kPa/s during discharge hydrogen, the measurement error is less than 3% in whole discharge time. The temperature response phenomenon in hydrogen is discussed qualitatively in the view point of the internal energy change. The internal energy change immediately after the discharge started was negative because the release enthalpy was larger than the quantity of heat obtained from the stuffing material. After a certain period of time elapsed, the enthalpy change became equal to the heat exchange between the internal hydrogen and the stuffing material.     

Study on the electrochemical properties of zinc/polyindole secondary battery

This study is intended to develop an aqueous zinc/polyindole secondary battery system. Polyindole, which is synthesized by chemical oxidation using ammonium peroxydisulfate as oxidants, is used as cathode active materials. Zn foil and ZnCl₂ are used as anode active materials and the electrolytic solution, respectively. FTIR and NMR test are carried out to confirm the polymerization of indole and the chemical structure of polyindole. The performance of zinc/polyindole secondary battery system is evaluated in term of cyclic voltammogram, discharge capacity and durability test. The battery achieves 2.0 V during the charging process and shows about 80-60 Ah kg⁻¹ discharge capacity at discharge current density of 200-1000 A m⁻², respectively. The battery is successively charged and discharged at constant current densities, the discharge capacity density and energy density decreases only by 2.0% and 3.5% at 200th cycle, respectively. This result shows that the zinc/polyindole battery has the good characteristics of charge/discharge performance. With the development of the battery system, this sort of battery would be promising in future applications.     

Modeling and hybrid simulation of slow discharge process of adsorbed methane tanks

The slow discharge process of a methane tank filled with porous carbonaceous adsorptive material is modelled and solved by the Integral Transform Method, yielding a hybrid numerical-analytical solution of the related energy equation. A transient one-dimensional nonlinear formulation is adopted, which includes the compressed and adsorbed gas thermal capacitances, the reservoir wall thermal capacitance effect and the gas compressibility influence. The overall mass balance is employed to determine the pressure field evolution, here assumed as spatially uniform. A thorough covalidation analysis is performed, with both numerical and experimental data available in the literature, and the relative importance of some terms in the energy equation formulation is inspected. Finally, different possibilities for the reduction of the adverse effect of the heat of adsorption on storage capacity are proposed and investigated.     

Study on the long-term discharge and redox stability of symmetric flat-tube solid oxide fuel cells

In this work, we investigated the stabilities of a newly developed symmetric flat-tube solid oxide fuel cells with double-sided cathodes (DSC cells) for long-term discharge and redox cycling operations. The DSC cell was discharged at 750°Cusing pure H₂ fuel for ca. 2030 h and the degradation rate was ca. 10% per one thousand hours. In addition, H₂ and air were alternatively supplied to the anode of DSC cells for tens of cycles in order to investigate the redox-stability. The duration time of oxidation process was found to be dominant for the stability of the cell. The microstructure of the DSC cells before and after these tests were investigated in order to clarify the degradation mechanisms. A great number of Ni particles with a diameter of ca. 2 μm was exsolved in the large pores of anode support layer after the redox cycling test with long duration time of oxidation. Such phenomenon induced by redox cycling has not been reported in the literatures. Based on the experimental data, the mechanisms were discussed.