Interfacial electrochemical analysis on LiCoO2/carbon nanotubes layers as cathode active composite in aqueous electrolytes

Electrochemical impedance spectroscopy (EIS) was applied to quantify and characterize different compositions of layered LiCoO2 electrodes fabricated with different carbon nanotubes (CNTs) additions and fixed binder content. Different LiCoO2/CNT ratios in aqueous solutions resulted in charge transfer and capacitance behavior at the interface. The CNT particles influenced the interfacial mechanisms; low scan rates revealed non reversible reactions, and different electrode compositions influenced the functionality of the particles according to the LiCoO2/CNTs ratios and surface characteristics. Cyclic voltammetry (CV) helped to determine the active state and identify the important potential peaks when LiCoO2 is mixed with CNT. A deterministic model based upon the impedance signal was performed; lithium intercalation inside the composite cathode is normalized and included in the faradaic current. Conservation of charge is considered for the cathodic process by a balance of the charge-discharge natural process on the electrode introducing kinetic parameters that describe the interfacial behavior. The model was validated with experimental data demonstrating the influence of the CNT in the capacitive mechanisms.