Energy density improvement by controlling the properties of conductive agents in Ni-rich cathodes

A conductive agent, which is typically added to overcome the low electronic conductivity of Ni-rich-layered oxides, plays a significant role toward performance improvement of layered-oxide-based cathodes. Herein, the effects of the specific surface area, powder density, and aggregation characteristics of a conductive agent on Li1.03Ni0.88Co0.08Mn0.04O2 (Ni-rich NCM) cathode performance are studied. The aggregation of conductive agents is disadvantageous for the distribution/arrangement of active materials and leads to polarization on the electrode surface. The specific surface area, which is proportional to porosity, contributes to the acceleration of electrode kinetics. However, the application of high pressure that makes a conductive agent excessively dense can degrade kinetic performance in the electrode. The low powder density of a conductive agent results in a nonhomogeneous electrode morphology and inhibits the mobility of Li ions in the electrolyte because of the segregation of the active materials from conductive agents. Powder density has a dominant effect on electrochemical performance. Even if the same active material is used, cycle retention is improved by 15%. In conclusion, the larger the specific surface area, the lower the powder density. Moreover, the less well-aggregated the conductive agent, the higher the performance of the Ni-rich NCM cathodes.