Synergy of Nyquist and Bode electrochemical impedance spectroscopy studies to commercial type lithium ion batteries

A new analytical approach has been developed by the combination of Nyquist and Bode plots in a two-electrode system and was used to evaluate a solid electrolyte interface (SEI) formation and the charge transfer reaction on electrode's surface. Nyquist analysis cannot completely explain the capacitance behavior of the formation process of SEI and the charge transfer reaction on electrode's surfaces, which are constrained by the multiple effects of electrolyte combination, formation conditions, and electrode materials, respectively. In this study, the Nyquist analysis results indicate that the SEI formed from electrolyte additive, maleimide (MI), reduces the charge transfer resistance of the two-electrode/electrolyte interfaces by 5.3%. Furthermore, Bode analysis indicates that this SEI formed from MI effectively alleviates the surface heterogeneity of cathode and anode electrodes. In addition, a 10% ionic diffusivity improvement at the anode interface results in an enhancement of the battery energy density. The Bode plot can compensate for the limitations inherent in the Nyquist plot, which is commonly applied to commercial battery systems.