Rate effect on lithium-ion graphite electrode performance

The electrochemical performance of lithium-ion graphite electrodes with particle diameter in the range of 6–44 µm was evaluated at different discharge (intercalation)/charge (deintercalation) rates (C to C/60). The electrode capacity depends on both the average particle size and rate. With a simple rate programme, the electrode performance is dependent on the cycling rate. The capacity of small graphite particles (6 µm) at C/2 rate was 80% of that achieved at C/24 rate (∼372 mAh g−1). The capacity of large graphite particles (44 µm) obtained at fast rates (C/2) was only 25% of that obtained under near-equilibrium conditions (C/24). The electrode capacity, however, is nearly independent of the charge rate when the electrode is fully intercalated using a modified rate programme containing a constant-voltage hold at 0.005 V (vs Li+/Li) for several hours. The electrochemical behaviour is related to the physicochemical properties of the graphite particles.