中央研究院 原子與分子科學研究所

The specific capacity of commercially available cathode carbon coated LiFePO₄ is typically 120-160 mAh g^-1, lower than the theoretical value 170 mAh g^-1. We discover that the carbon coated LiFePO₄ surface-modified with 2 wt% of the electrochemically exfoliated graphene layers is able to reach 208 mAh g^-1 in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes. The highly conductive grapheneflakes wrapping around carbon coated LiFePO₄ also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to ~100% Coulombic efficiency.  Such a scalable approach can be applied to other cathode systems, boosting up the capacity for various Li batteries.