Electrochemical impedance spectroscopy (EIS) allows detailed investigations of polarization processes and is widely used to study the kinetics of electrode reaction in lithium-ion batteries. The distribution of relaxation times (DRT) calculated from the EIS offers a model-free approach for a deeper understanding of various electrochemical processes. A joint estimation method is proposed to identify the differential capacity caused by diffusion processes and the DRT for all polarization processes simultaneously. The differential capacity from EIS and the incremental capacity from incremental capacity analysis (ICA) have an equivalence verified by mathematical derivation. Different types of lithium-ion batteries are tested by the EIS and the ICA methods to verify the equivalence. The differential capacity extends the application of the ICA method.
Keywords electrochemical impedance spectroscopy, distribution of relaxation times, differential capacity, joint estimation method