Mingliang Yu, Hongchang Hao, Jing Wang, Qiu Zhang, Zachary W Ragan, Marcos Lucero, Samuel P Murphy, Guangxia Feng, Mu-Huai Lu, Andrew Yang, Ankit Kumar Yadav, Zhenxing Feng, Kyriakos C Stylianou, Xiaolin Li, Chunsheng Wang, Tongchao Liu, Xueli Zheng, Xiulei Ji
Increasing the energy density of Li-ion batteries requires cathodes that can store more than one electron per transition-metal center. Iron-based conversion cathodes such as FeF3 are attractive due to their high theoretical capacity and low cost; however, their practical performance is limited by large voltage hysteresis, sluggish kinetics, and capacity loss during cycling. Here, we report a ball-milled FeF3/FePO4 composite cathode that combines the high capacity of FeF3 with the superior reversibility of FePO4. Compared to pure FeF3, the composite retains high capacity while exhibiting improved rate capability, lower polarization, and markedly enhanced cycling stability. After prelithiation, the composite delivers a reversible discharge capacity of 572 mAh g-1, corresponding to a specific energy of 1175 Wh kg-1. These results show that integration of FeF3 and FePO4 offers an effective route to cathodes that combine high capacity with high reversibility.