Independent Study Report
Reducing Number of Infiltration Cycles for La0.8Sr0.2FeO3-YSZ Cathodes
Xiaoyan Li
Abstract
In order to decrease the number of cycles of infiltration and maintain a comparable cathode performance, the viability of using a conductive composite scaffold of La0.8Sr0.2FeO3 and yttria-stablized zirconia (YSZ) with one infiltration cycle was investigated. The infiltration material is nitrate salt solution of La, Sr, Co and Fe to form La0.6Sr0.4Co0.2Fe0.8O3 perovskite phase. Cathodes fabricated from scaffolds using different ratios of LSF-YSZ were tested by impedance spectroscopy with the results showing that the ohmic resistance decreases as the amount of LSF increases. In addition, scaffolds calcined at 1350oC exhibited
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1,2 In this case, YSZ is included in the cathode to provide ionic conductivity, as well as enhancing the connection between the electrode and the YSZ electrolyte. YSZ in the electrode also helps match the thermal expansion of the electrode to the electrolyte.1-4 The functions of LSM in the composite cathode include providing electronic conductivity and catalytic activity, but with negligible contributions to ionic conductivity.4,5
The conventional method for fabricating the electrode is to deposit and sinter a mixture of the electrode composites onto a dense YSZ electrolyte.4 The sintering temperature must be a compromise, high enough to ensure the good connection between YSZ in the electrode and the electrolyte, but low enough to prevent solid state reactions between the electrode composites.2,5 Indeed, most conducting perovkites are unable to be prepared due to the formation of insulating phases at high temperatures required for YSZ sintering.4 Therefore, the infiltration method was initially developed to separate the high calcination temperature required to densify the YSZ electrolyte from the lower calcinations temperature needed for the other electrode components.1,4,5 Furthermore, the infiltration method provides a nonrandom structure where the electronically conductive components are deposited into the previously formed porous YSZ scaffold.1-4 Infiltration also forms superior
The doping iron increases the capacity of batteries, but this diminishes with extensive cycling. The detrimental effect of iron can be avoided by annealing. Ruthenium is another transition metal which can be used as a dopant which enhances the stability of the crystal structure. It also increases conductivity and improve performance of the battery. Chromium is another transition metal that can be used as a dopant. It reduces the ordering of lithium ions in LiMn2O4 spinel and this stabilizes the spinel structure. It also increases capacity retention during cycling. Zinc is used as a dopant in cathode materials as it has a stabilizing effect on the crystal structure. Addition of Zinc oxide also prevents reaction between the electrode and electrolyte. Titanium along with cobalt also acts as a stabilizer and also reduces dissolution of electrodes. Zirconium reduces reactivity levels between the electrode and the electrolyte and performs the same function as titanium by stabilizing the crystal structure. Aluminium is one of the most commonly used dopants in cathode materials. It performs the function of increasing capacity of the electrodes. The addition of aluminium improves electrode kinetics, structural modifications and microstructural effects. Some of the other dopants include Magnesium and Lathanum which increases the lattice parameter and improves the stability of the crystal structure and also
All the data was fitted satisfactorily using the equivalent circuit shown in Fig. 7. Where, Rs, CPE1 and R1 represent solution resistance, a constant- phase element corresponding to the double layer capacitance and the charge transfer resistance, respectively. CPE2 and R2 were added to account for the electrical elements of the outer layer. The following formula expressed the electrode impedance, Z, as follow:
so that the conductometric data were treated by Fuoss–Shedlovsky method [11] by using a computer program, to evaluate the ion-pair association constants of the studied salts and to re-evaluate the limiting molar conductance (Λ0), where they proposed the following equation:
If they are thicker or shorter this will change the rate of electrolysis over time. The larger the electrode, the more copper can be deposited on it and faster.
There are 3 types of metals for electricity conducting: metallic conductor, semiconductor, and superconductor. Metallic conductors allow the free flow of ions and electrons through a sample; and its conductivity decreases as the temperature increases.
12. The crocodile clips are attached to the copper electrodes of the experimental apparatus and the power supply is turned on. Simultaneously, the stopclock is started. The thermometer is checked every 30s. 13. After 300s the stopclock is stopped and the power supply is turned off. The negative cathode is carefully removed and is dried using a hair dryer. 14. When dry the negative cathode is placed on the electronic milligram balance and its final mass is recorded. 15. The positive anode and negative anode of the experimental apparatus are disposed and the electrolyte is poured out to ensure that the anode slime (impurities) does not contaminate the solution. 16. The electrodes of the experimental apparatus are replaced with new copper strips. 17. Steps 7 to 16 are repeated. However, this time, the rheostat is adjusted using the calibration apparatus until the multimeter shows approximate readings of 0.40 A, 0.60 A, 0.80 A and 1.00 A respectively. 18. Time permitting, the entire experiment is repeated. Safety Copper sulphate may cause irritation and burns if it comes into contact with the eyes. As standard lab procedure, safety goggles and lab coats must be worn at all times. Control of Variables Volume of Electrolyte Used
A lot of information from different sources was gathered with the purpose of comparing different Li-ion batteries mechanisms, cathode and anode materials, structure and fabrication procedures, and their respective advantages and disadvantages.
In 20 years, our vision is that perovskites will replace the majority of silicon-based solar panels. Perovskite solar cells are composed of perovskite-structured compounds, which are any material with the same crystal structure as calcium titanium oxide (CaTiO3) such as methylammonium lead halides (CH3NH3PbX3, where X represents iodine, bromine, or chlorine). This is because the original “true” perovskite mineral when it was first found (by Gustav Rose in 1839 in the Ural Mountains of Russia) is CaTiO3, so any material with the same crystal structure as the mineral can also be classified as perovskite. It has the generic form ABX3; A is an organic cation, B is an inorganic cation, and X3 is a small halogen anion.
It has been found that the use of complexing agents in the trivalent chromium electrolyte solution work to generate stable complexes with Cr3+ through ligand exchange which are then easily reducible to metallic chromium. Not only does this now allow chromium deposition to take place, but it also improves the current efficiency of the electrodeposit. The process of co-depositing chromium as an alloy with other metals has shown to enhance the physical and chemical properties of the metal as opposed to individual electrodepositions; an ability that is unattainable for hexavalent chromium, giving an immediate advantage. In addition, the outcome of
The cathode impetus layer is accepted to comprise of a blend of impetus platinum, ionomer layer electrolyte also, void space. The little impetus particles, either all alone or bolstered on moderately extensive carbon dark particles, are secured by a thin, consistent layer of ionomer. The spatial organize z is characterized with the goal that the positive heading indicates from the cathode terminal the layer with its birthplace situated at the interface between the cathode
Fig. 3. Cyclic voltammograms (A) and Nyquist plots (B) recorded at bare GCE (a), β-Ni(OH)2/GCE (b) and β-Ni(OH)2@CDs/GCE (c) in a 0.1 M KCl solution containing 5 mM Fe(CN)63-/4-. Inset of Fig. 3B: Equivalent circuit applied to fit impedance measurements, where: Rs is the resistance of electrolyte solution; Rct is the charge transfer resistance, W is warburg impedance and CPE is constant phase element.
In order to decrease the number of cycles of infiltration and maintain a comparable cathode performance, the viability of using a conductive LSF-YSZ composite scaffold with one infiltration cycle of LSCF was investigated. XRD patterns of LSF-YSZ powder presented that at 1400oC and 1300oC calcination, an obvious shift in LSF peak occurred, indicating Zr doping into LSF and forming a less conductive phase. Different ratios of LSF-YSZ scaffolds were tested by impedance spectroscopy with the results showing that the ohmic resistance decreases as the amount of LSF increases, and 1350oC scaffold has a much lower ohmic resistance than the 1400oC one. A pure YSZ cell infiltrated with 35 wt% LSCF was used as reference and by comparing it with a cell composed of 70:30 LSF-YSZ scaffold calcined at 1350oC with one cycle of LSCF infiltration, a comparable cell performance both in ohmic and non-ohmic parts was achieved.
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We have now discussed the two extremes in electronic materials; a conductor, and an insulator we will now move to a material that lies in between these two, a semiconductor. The
As a feasible alternative to continuous operation, recently, a high temperature liquid metal-air energy storage cell (LMAESC) in conjunction with a solid oxide electrolyte has been investigated applying post-transition metals such as In [7], Sn [7–17], Sb [18–25], Pb [7], and Bi [12] as a sacrificial electrode, so-called liquid metal anode (LMA). Since these liquid metals has relatively low melting point, it can improve the anode polarization by incorporating liquid wetting materials to spread on the