What are the components of the internal resistance of lithium batteries

In a broad sense, the composition of the internal resistance of a lithium battery is the same as the ohmic resistance (IR). Both activation polarization and concentration polarization can be understood as components of battery internal resistance, or activation resistance and concentration resistance. The size of activation polarization and concentration polarization requires the establishment of a chaotic mathematical model for accounting. The internal impedance is composed of the following parts: ☆Ionic resistance ①The electrolyte inside the barrier affects the element's electrolyte conductivity, the area, thickness, porosity, and bending coefficient of the barrier (Gurley) ②The electrolyte inside the positive electrode affects the element's electrolyte conductivity, Positive electrode thickness, thickness, porosity, bending coefficient ③The electrolyte inside the negative electrode affects the electrolyte conductivity, positive electrode thickness, thickness, porosity, bending coefficient ☆Electronic resistance ①The active material of the two electrodes affects the electrode conductivity and thickness 、Area ②The current collector (copper foil and aluminum foil) affects the element thickness, width, length, number and orientation of the tabs. ③Leads (tabs, poles, internal conductive connection elements) affect the dimensions and conductivity of the elements ☆ active material The electrochemical impedance of the positive electrode material and the anode material of aluminum foil and the electrochemical impedance of the copper foil battery with the current collector. Make an equivalent circuit diagram of the electrode, which is mainly composed of ohmic impedance Rb, electric double layer capacitance Cd, electrochemical response impedance Rct and dispersion resistance Rw . Generally speaking, during the intercalation and extraction cycles of lithium ions, the Rb value generally does not change much, while the changes in Cd and Rct are more distinct. The battery impedance is mainly reflected in the electrochemical reaction impedance, and the ohmic impedance is relatively small. It can be seen from the figure below. As the temperature decreases, the battery impedance gradually rises, and after falling to 0°C, the impedance speed increases, and the cathode impedance shows a similar trend. From a numerical point of view, the battery impedance primarily comes from the contribution of the cathode impedance. It is true that during the entire cycle of the battery, the impedance of the cathode occupies the most important part of the impedance of the entire battery, which is only slightly smaller than the impedance of the entire battery. As the charge and discharge cycle progresses, the cathode impedance increases, and the impedance of the battery also increases. Therefore, it is necessary to pay special attention to the cathode resistance test during the electrode manufacturing process. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it.