As an integral part of a lithium-ion battery, carbonaceous conductive agents have an important impact on the performance of the battery. Carbon sources (e.g., granular Super-P and KS-15, linear carbon nanotube, layered graphene) with different morphologies were added into the battery as conductive agents, and the effects of their morphologies on the electrochemical performance and processability of spherical lithium iron phosphate were investigated. The results show that the linear carbon nanotube and layered graphene enable conductive agents to efficiently connect to the cathode materials, which contribute to improving the stability of the electrode-slurry and reducing the internal resistance of cells. The batteries using nanotubes and graphene as conductive agents showed weaker battery internal resistance, excellent electrochemical performance and low-temperature dischargeability. The battery using carbon nanotube as the conductive agent had the best overall performance with an internal resistance of 30 mΩ. The battery using a carbon nanotube as the conductive agent exhibited better low-temperature performance, whose discharge capacity at -20 °C can reach 343 mAh, corresponding to 65.0% of that at 25 °C.
Keywords: battery internal resistance; carbon nanotube; conductive material morphology; graphene; spherical lithium iron phosphate.