The effect of pressure on the electroanalytical response of graphite anodes and LiCoO₂ cathodes for Li-ion batteries

The effect of the application of pressure during the preparation of composite flaky synthetic graphite anodes and LiCoO₂ cathodes on their electrochemical behavior in Li insertion and de-insertion processes was studied using voltammetry, chronopotentiometry, electrochemical impedance spectroscopy (EIS), and ex situ AFM imaging. Unpressurized graphite electrodes reach a higher capacity and have faster kinetics than the same electrodes compressed or rolled at 5 × 10³ kg cm^-3. In contrast, the performance of rolled or compressed LiCoO₂ electrodes in terms of capacity and kinetics was better than the performance of the unpressed electrodes. AFM imaging of pristine and cycled electrodes demonstrated a pronounced effect of pressure on the morphology of graphite electrodes, whereas the impact of pressure on the morphology of LiCoO₂ electrodes was found to be much less pronounced. It was concluded that compressing graphite electrodes has an adverse effect on the contact between the active mass and ions in solution, while compressing LiCoO₂ electrodes does not adversely affect the contact between solution species and the active mass, but rather, improves inter-particle electrical contact.