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Polarization phenomenon in lithium batteries
Source：Corrtest
Time：2021-12-24
View：0
Polarization is an important issue in chemical power sources, and opinions vary on the understanding of polarization in lithium batteries. Synthesizing documents and materials, we make the explanation as follows:
Voltage plateau reduction during discharge of lithium batteries is mainly resulted from the ohmic resistance and polarization resistance, and the polarization resistance is caused by the polarization phenomenon inside the lithium battery. The polarization inside the lithium battery is mainly divided into activation polarization and concentration polarization.
Electrochemical polarization is mainly caused by the electrode activation energy when lithium battery chemical reactions occur. It is reflected in the calculation of the BV equation. From aspect of physical explanation, the discharge rate on the surface of the electrode active particles is slower than the electron migration rate. As a result, the actual potential on the surface of the cathode particles deviates from the equilibrium potential, causing activation polarization. This polarization phenomenon is mainly determined by the activation energy of the electrode's electrochemical reaction.
Concentration polarization phenomenon, as the name implies, is caused by concentration difference. During the charging and discharging process, the Li+ migration rate inside the electrode particles is very small compared with the electrolyte, it is generally considered that the internal diffusion of the electrode is the control step of the Li+ diffusion rate. The Li+ migration rate inside the electrode particles is much lower than the electrochemical reaction rate on the surface of electrode particles, which causes concentration polarization. It will further aggravate the deviation of the electrode potential from the equilibrium potential. That’s why there is phenomenon that the voltage of the lithium battery has a rapid drop (not a sudden drop) at the beginning of the discharge and a fast rise (not a sudden rise) after the discharge ends. This is precisely caused by the slowness of Li+ migration inside the electrode.
The sudden drop at the beginning of the discharge and the sudden rise at the end of the discharge emphasized here are caused by the ohmic voltage drop and activation polarization. In response time, ohmic polarization
Voltage plateau reduction during discharge of lithium batteries is mainly resulted from the ohmic resistance and polarization resistance, and the polarization resistance is caused by the polarization phenomenon inside the lithium battery. The polarization inside the lithium battery is mainly divided into activation polarization and concentration polarization.
Electrochemical polarization is mainly caused by the electrode activation energy when lithium battery chemical reactions occur. It is reflected in the calculation of the BV equation. From aspect of physical explanation, the discharge rate on the surface of the electrode active particles is slower than the electron migration rate. As a result, the actual potential on the surface of the cathode particles deviates from the equilibrium potential, causing activation polarization. This polarization phenomenon is mainly determined by the activation energy of the electrode's electrochemical reaction.
Concentration polarization phenomenon, as the name implies, is caused by concentration difference. During the charging and discharging process, the Li+ migration rate inside the electrode particles is very small compared with the electrolyte, it is generally considered that the internal diffusion of the electrode is the control step of the Li+ diffusion rate. The Li+ migration rate inside the electrode particles is much lower than the electrochemical reaction rate on the surface of electrode particles, which causes concentration polarization. It will further aggravate the deviation of the electrode potential from the equilibrium potential. That’s why there is phenomenon that the voltage of the lithium battery has a rapid drop (not a sudden drop) at the beginning of the discharge and a fast rise (not a sudden rise) after the discharge ends. This is precisely caused by the slowness of Li+ migration inside the electrode.
The sudden drop at the beginning of the discharge and the sudden rise at the end of the discharge emphasized here are caused by the ohmic voltage drop and activation polarization. In response time, ohmic polarization
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