Effect of surface structure on irreversible capacities of graphtic carbon electrodes

摘要

In order to understand the effect of surface structure on the irreversible capacity of graphitic carbons, the electrochemical lithium intercalation behavior of various commercial carbons was studied for 1M LiPF_6 n EC/PC/DEC electrolytes. Flaky graphites exhibited nearly a constant irreversible capacity per unit area for the EC/DEC electrolyte, while other carbons with more compact morphology showed significantly larger value. The increase in the irreversible capacity induced by PC exhibited similar structural dependence. The irreversible capacities were quantitatively analyzed in terms of a simplistic model, which explicitly took into account different reactivity of EC and PC toward the basal and edge planes. As the graphite structure exfoliated in the presence of excess amount of PC, the reversibility of electrochemical lithium intercalation deteriorated quite abruptly above a certain threshold PC content. The structural factors controlling the onset of graphite exfoliation were also discussed.