The comparative study of carbon cathodes with and without cobalt phthalocyanine (CoPc) in BCX cells (the Li/SOCl2 cell containing BrCl in the electrolyte) has been carried out by using electrochemical impedance spectroscopy (EIS), constant current discharge curves, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. It is shown that CoPc can improve both the capacity and the voltage of discharge for the BCX cell, and enhance the stability of the open-circuit voltage of the BCX cell. The addition of CoPc to carbon cathode of BCX cells can also decrease the impedance value of the porous carbon cathode, resulting in the considerable decrease of both film resistance and electron transfer resistance. The microstructure and composition of the discharge products on carbon cathodes have been studied using SEM/EDS and XPS analysis.