The effect of carbon black (acetylene black) as a cathode additive in lithium batteries was studied using electrochemical and X-ray photoelectron spectroscopy (XPS) measurements. The characteristic discharge curves for various weight percent (wt.%) of carbon black were obtained. The optimum wt.% of carbon black as a compromise between the desire to have active material present and the necessity to have a conduction path through the pores of the electrodes was obtained. It is shown that the behavior of carbon exhibits porosity rather than electronic conductivity. XPS results show that the C 1s peak at 283 eV corresponding to acetylene black, decreases during discharge and increases during charge. These results suggest that porosity of the electrode decreases during discharge and increases during charge.