Large Hysteresis during Lithium Insertion into and Extraction from High‐Capacity Disordered Carbons

Perylene‐based disordered carbon (PBDC) heat‐treated at 550 °C for anodes in Li‐ion cells showed large hysteresis and a high reversible capacity of 800 mAh/g. The hysteresis was analyzed by polarization and impedance measurements. The overpotential during lithium extraction increased markedly in the range of open‐circuit potential, 0.5–1 V vs . The impedance spectra of PBDC during lithium insertion were significantly different from those during extraction. The charge‐transfer resistance for lithiated PBDC during extraction above 0.5 V was much larger than that for the PBDC during insertion. The chemical diffusion coefficient of lithium, DLi, of PBDC during lithium insertion decreased almost linearly from with increasing lithium storage capacity. The values of DLi during lithium extraction above 0.5 V were much smaller than those during insertion. The large hysteresis was due to the large charge‐transfer resistance and the slow diffusion of lithium during lithium extraction from the fully lithiated PBDC. The large charge‐transfer resistance during lithium extraction has been interpreted as the rectification of lithiated PBDC, which is similar to that of n‐type semiconductors under anodic polarization.