Primary Limiting Factors of a Lithium-Oxygen Battery

Satisfactory Essays
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.
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.
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.
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