Power capability analysis in lithium ion batteries using electrochemical impedance spectroscopy

In this study, time-dependent discharge resistance and its power capability determined by current pulse experiments (CPE) were investigated according to changes in the state-of-charge and storage temperature. Using pattern analysis of the obtained resistance, two components comprising total discharge resistance were separately obtained and compared with the best fitting results of electrochemical impedance spectroscopy (EIS). From this comparison, an initial abrupt resistance drop was found to be a major determining factor of power capability and associated with electrolyte/electric transport in the bulk/film phase. This drop was also found to be associated with a charge transfer reaction at the electrode interphase, indicative of a correlation between the initial resistance drop in CPE and semi-circle resistance in EIS. The following resistance relaxation was possibly due to a chemical diffusion process of lithium ion. After storage at high temperature, it was observed that an increase in discharge resistance was mostly attributable to larger film resistance.