There are factors that pose a challenge to having a high-performance lithium-air battery, as shown above. The main limiting factors of lithium-oxygen batteries will be discussed below. Overpotentials Overpotential problems occur with lithium-oxygen batteries because the charging and discharging potentials deviate from the standard potential. Overpotentials are the extra energy required to drive reactions at a specific current density. Thus, the battery capacity depends on the clogging of the reduction products in the porous cathode. A large potential difference is required to dissociate lithium peroxide during charging. Therefore, the use of catalyst plays an important role in reducing the overpotential problem observed in the lithium-oxygen battery problem. Catalysts Secondly, catalysts can reduce the problem of asymmetry between charging/discharging overpotentials in order to improve the round trip efficiency of lithium-oxygen battery. The catalyst can also help dissociate the reduction product into lithium metal and oxygen. It not only helps the discharge reaction, but also increases the battery capacity. 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 are the most important mechanism in the battery reaction kinetics. First, the porous cathode must have a good oxygen path for oxygen to pass through the electrolyte. At the same time, the diffusion of lithium ions from the anode side is important. Solubility also plays an important role in the kinetic reaction of the battery. Oxygen becomes less mobile as it dissolves in the electrolyte compared to oxygen in the gas phase. This affects the reaction kinetics and overall performance of the battery. Therefore, designing the battery structure that maximizes the diffusion and solubility of oxygen through the porous electrode to the cathode and also the diffusion of lithium ions from the anode side is essential to achieve efficient lithium-air batteries. The main point is to overcome the overpotential problem by selecting a suitable catalyst. It is stated that the logarithmic increase in overpotential during the discharge time with the passage of time with a constant current density is due to the gradual clogging of Li2O2, a chemical compound with high electronic resistivity, to the pores of the cathode which not only increases the overall resistance internal resistance but also reduces reaction kinetics. The pore clogging effect will also result in a relatively short discharge time compared to the theoretical discharge time. A suitable catalyst can alter the reaction mechanism and reduce the activation energy of the reaction, thus reducing the overpotential problem.
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