There are factors that represent as a challenge to have high performance Li-Air Battery as shown above. The following will discuss the primary limiting factors of lithium-oxygen battery.
Overpotentials
Overpotential problem occur on lithium-oxygen batteries because the charging and discharging potentials deviate from standard potential. The overpotentials are the extra energy required to drive the reactions at a specific current density. Then, capacity of the battery is dependent on the clogging of reduction products in the porous cathode. In order to dissociate the lithium peroxide on charging, large potential difference is needed. Therefore, the use of catalyst plays an important role in reducing the overpotential problem observed in li-oxygen battery problem.
Catalysts
Second, catalysts can reduce the asymmetry problem between charge/discharge overpotentials in order to improve the round-trip efficiency of the lithium-oxygen battery. Catalyst can also help to dissociate the reduction product back to lithium metal and oxygen. Not only assisting the discharge reaction, but also increasing the capacity of the battery. Adding catalysts degrades the electrolyte solution which decreases the charge/discharge performance and also decreases the life of lithium – air batteries.
Diffusion and solubility
Diffusion and solubility is the most important mechanism in reaction kinetics of the battery. First, porous cathode must have good oxygen path for oxygen to pass through to electrolyte. At the same time, diffusion of the lithium ions from anodic side is important.
Solubility also plays important role in the kinetics reaction of the battery. Oxygen becomes less mobile while dissolve into the electrolyte compared to oxygen in gas phase. This effects the reaction kinetics and overall performance of the battery.
Therefore, designing the structure of battery that maximize the diffusion and solubility of oxygen through porous electrode at the cathode and also diffusion of lithium ions from anodic side is essential to achieve efficient lithium – air batteries.
The main point is to overcome overpotential problem by selecting a suitable catalyst. It is stated that the logarithmically increase of over potential during discharge time as time proceeds with a constant current density is due to the gradual clogging of Li2O2, a chemical compound with high electronic resistivity, at the pores of the cathode which not only increases the overall internal resistance but also reduces the reaction kinetics. The effect of the clogging of the pores will also result in relatively short discharging time as compared to theoretical time of discharge. A suitable catalyst can alter the reaction mechanism and reduce the reaction activation energy, which will then reduce the over potential problem.
The purpose of the experiment is to study the rate of reaction through varying of concentrations of a catalyst or temperatures with a constant pH, and through the data obtained the rate law, constants, and activation energies can be experimentally determined. The rate law determines how the speed of a reaction occurs thus allowing the study of the overall mechanism formation in reactions. In the general form of the rate law it is A + B C or r=k[A]x[B]y. The rate of reaction can be affected by the concentration such as A and B in the previous equation, order of reactions, and the rate constant with each species in an overall chemical reaction. As a result, the rate law must be determined experimentally. In general, in a multi-step reac...
These reasons are why Lithium-Ion Batteries are some of the most viable options when designing new gadgets. But, the structure of these batteries are why these batteries are being used for new gadgets. A Lithium-Ion Batt...
This is the most common battery that people use today like Energizer or Duracle batteries. The most common form of a primary cell is the Leclanche cell, invented by a French chemist Georges Leclanche in the 1860s. The electrolyte for this battery consisted of a mixture of ammonium chloride and zinc chloride made into a paste. The negative electrode is zinc, and is the outside shell of the cell, and the positive electrode is a carbon rod that runs through the center of the cell. This rod is surrounded by a mixture of carbon and manganese dioxide. This battery produces about 1.5 volts.
The solution for the resistance to oxidation of p-toluic acid was solved by the discovery of bromide-controlled air oxidation in 1955 that was led to the implementation of AMOCO process [28-31]. In AMOCO process, the oxidation of para-xylene was conducted using a combination of three ions as a homogeneous catalyst which is cobalt, manganese and bromide ions. Acetic acid and oxygen/air were used as solvent and oxidant, respectively [32]. The common bromide ion sources are hydrobromic acid (HBr) and sodium bromide (NaBr). The oxidation operated at 175-225°C and 15-30 bar of oxygen. The terephthalic acid formed mostly in the form of solid due to the low solubility of terephthalic acid in the acetic acid. AMOCO process successfully gives a promising reaction yield, since more than 98% of para-xylene reacted, while terephthalic acid selectivity yield was about 95% in the reaction time of 8-24 hours (Scheme 3).
Some batteries consists of harmful toxic acids and it may have threats of leakage because of its liquid state. This is called gr...
Due to physical reasons, Tesla vehicles cannot be recharged comparably quickly to a petroleum fuel-powered car
The current moves the molecules towards the cathode or anode. The speed of the moving molecules depends on the size, shape, and charge. The properties of the gel will definitely affect the movement. Small molecules are expected to move easily and faster through the pores. Materials and Methods: Experiment: 1st step to make the gel: pour distilled water and agarose in a beaker.
There are many techniques of battery modelling are present. Few of them are mentioned here with their merits and demerits are given below:
Electrolytes are liquids that conduct electricity. Most need to be dissolved into water or another solvent. Battery¡¦s have an electrolyte in them, either as a liquid or as a paste. Liquid electrolytes are used in electrolysis, electroplating, and other chemical processes. When electrolytes dissolve they release positive and negative ions. The released ions carry electric charges between electrodes, in the solution. Cations (a positively charged ion that migrates to the cathode, a negative electrode) carry positive electric charges toward the cathode. Anions carry negative electric charges toward the anode, positive electrode. Strong electrolytes release many ions and conduct electricity well. Weak electrolytes, like acetic acid, don¡¦t release many ions and conduct poorly. Non electrolytes, like sugar, release no ions and form non conducting solutions. A couple electrolytes conduct electricity as solids. These solid electrolytes have ions that can move and carry charges without solvents. There are two ways to be able to have ions that are able to conduct electricity, the dissociation of Ionic Compounds, and the Ionization of Polar Covalent Molecular Substances. The Dissociation of Ionic Compounds is where particles are ionically (electrically) bonded together. They already made out of cations and anions, but in their solid state the ions are locked into position in their crystal structure, and can¡¦t move around. When the ionic compound is dissolved into water the water molecules, which are polar,(having a positive and a negative end) will be attracted to the positive ions. This attraction of different charges will create tension in the crystal and it will overcome the attice (the arrangement of molecules in a crystalline solid) energy keeping the crystal in place.
Investigating the Effects of Temperature on the Rate of Reaction between Magnesium and Hydrochloric Acid Introduction Chemical kinetics is the study and examination of chemical reactions regarding re-arrangement of atoms, reaction rates, effect of various variables, and more. Chemical reaction rates, are the rates of change in amounts or concentrations of either products or reactants. Concentration of solutions, surface area, catalysts, temperature and the nature of reactants are all factors that can influence the rate of reaction. Increasing the concentration of a solution allows the rate of reaction to increase because highly concentrated solutions have more molecules and as a result the molecules collide faster. Surface area also affects reaction rate because when the surface area of a reactant is increased, more particles are exposed to the other reactant.
For the electrode layers made of a carbon black−supported catalyst that has a tendency for agglomeration, previous studies have shown a significant decrease in the activation overvoltage by forming the three-phase boundary (i.e., ionomer, catalyst, and gas) in the primary pores, or the interspaces between carbon black particles in an agglomerate, and the secondary pores, or the interspaces between the agglomerates, which can expedite the redox reactions forward in electrodes, increase the catalyst utilization, and the fuel cell performance [4-6]. It has been demonstrated that the ionomer molecules that can be in the primary pores of carbon black particles (< 40 nm in diameter) should have a low molecular weight [7] or can be formed by polymerization of monomers present in the primary pores [8]. In contrast, the ionomer molecules with molecular weights of the order of several hundred thousand grams per mole (e.g., Nafion) cannot penetrate the primary pores and only remain in the secondary por...
Gather and process information to identify applications of cathodic protection, and use available evidence to identify the reasons for their use and the chemistry involved
At the cathode the hydrogen ions gain an electron. They are discharged and are converted into hydrogen gas: 2H (+) + 2e (-) → H2 At the anode, the hydroxide, not the sulphate ions are discharged. Water and oxygen gas are formed: 4OH (-) → 2 H2O + O2 + 4e (-) The hydrogen gas can be collected and measured. The greater the volume of hydrogen gas formed over a set period of time, the faster electrolysis is occurring.
Time - The longer time can let more copper ions from the anode to the cathode if the current are the same. There are still more factors which can affect the mass deposited during electroplating. 3). Distance between two electrodes - If the distance between the two electrodes is greater, the copper ions require to travel more from the anode to the cathode.
In modern society, there are several analytical methods to analysis the chemical compounds such as HPLC, GC, MS. However, for the redox reaction specifically, it is widely used through the electroanalytical methods which is cyclic voltammetry. It can be used in electrode absorption phenomenon, and electrochemical reaction products. It is commonly used in organic compounds and the biology materials mechanisms for the oxidation-reduction reaction research.