The electronic conductivities of all the positive electrode active materials for lithium ion batteries (LIB) are very low. One of the most effective methods to decrease the polarization extent of positive electrode, to increase the specific chargedischarge capacities of active materials and to increase the chargedischarge current densities is to select one kind of electronic conductive reagent with high electronic conductivity and mix it with binder to build up a good electronic conductive network. The results of measurements have shown that the electronic conductivity of polyaniline (PAn) (σPAn=18.39 S/cm) is greater than that of acetylene black (AB) (σAB=7.77 S/cm). The galvanostatic experiment (current density I=15 mA/g) of the above PAn was done, and no other conductive reagent was used. In the third cycle, the specific discharge capacity D3 was 60.8 mAh/g and the charge and discharge efficiency η3 was 94.56%. The experiment results have shown that PAn in the positive electrodes has both the function of electronic conductive reagents and that of active materials. Galvanostatic experiments were conducted with the LiFePO4/C as the positive electrode active materials and PAn as the electronic conductive reagent to take the place of AB. When the current density was 15 mA/g, 30 mA/g, 45 mA/g, 60 mA/g, 75 mA/g, 90 mA/g and 120 mA/g, respectively, all the specific charge and discharge capacities increased. After charging and discharging with large current density (120 mA/g), the positive electrode charged and discharged with the original small current density (15 mA/g). The specific charge and discharge capacities were almost unchanged. It was shown that the storing lithium ions structure of LiFePO4/C did not change.