Fluorinated Carbons as Rechargeable Li-Ion Battery Cathodes in the Voltage Window of 0.5–4.8 V
Pengyu Chen, Cheng Jiang, Jie Jiang, Jian Zou, Qiwen Ran, Xin Wang, Xiaobin Niu, Liping Wang
Abstract
Fluorinated carbon (CFx) cathodes have the highest theoretical energy density among lithium primary batteries. However, it is still a huge challenge to be reversible. Here, CFx is proposed as a high-performance cathode material for rechargeable lithium-ion batteries in the extended voltage window of 0.5–4.8 V. Specifically, the fluorinated graphite CF0.88 exhibits an initial specific discharge capacity of 1382 mAh g–1 (2362 Wh kg–1) and a specific discharge capacity of 782 mAh g–1 at the 2nd cycle and maintains a specific discharge capacity of 543 mAh g–1 (508 Wh kg–1) after the 20th cycle. This rechargeable behavior is associated with the conversion of CFx to LiF + C (>1.5 V) and then to Li1+xFC (0.5–1.5 V) during the initial discharge process; Li1+xFC is reversible to LiF + C in the following charge–discharge process (0.5–4.8 V). By extending the voltage window, CFx cathodes can show new electrochemical behaviors. Our research has provided new Li-free cathode materials for rechargeable batteries and insights for improving the performance of a Li/CFx secondary battery.