Low-Temperature Separating Lithium-Ion Battery Interfacial Polarization Based on Distribution of Relaxation Times (DRT) of Impedance

Noninvasive techniques for evaluating lithium-ion batteries treated as an important component of transportation electrification are of great importance. A method for separating and interpreting battery interfacial processes is proposed, which is based on the temperature dependence of battery impedance as found with the distribution of relaxation times (DRT) analysis. The battery interfacial processes are influenced stronger as the temperature decreases, and the DRT is useful to identify the processes coming from distinct boundaries. By using the abovementioned advantages, the processes at the interfaces of full cells are assigned to the corresponding cathode and anode. Four interfacial processes, i.e., particle/particle and electrode/current-collector contact process, passive film process, charge transfer in the anode, and charge transfer in the cathode, are effectively separated depending on their different responses to temperatures. The changes in temperature of the four interfacial processes for cycled commercial batteries are investigated. SEM and XRD techniques are employed to examine the aged electrodes. Activation energies against cycle numbers for each process are identified to verify the method reliability. This method has the benefit of easy identification and could separate the interfacial polarization of each electrode, providing new insights for the diagnosis for lithium-ion battery applications.