Enhancing Electrochemical Performance of CoF2–Li Batteries via Honeycombed Nanocomposite Cathode

Metal fluoride–lithium batteries have been viewed as very promising candidates for next-generation rechargeable batteries with higher energy densities. However, the intrinsic insulating properties of metal fluoride cathode lead to the poor reaction kinetics and unsatisfactory electrochemical performance. Herein, a honeycombed CoF2@C nanocomposite with a high specific surface area up to 180.4 m2 g–1, in which the nanosized CoF2 particles with size of 5–25 nm are evenly embedded in the honeycombed carbon framework, is prepared by the low-temperature fluorination of honeycombed Co@C nanocomposite precursor. As expected, the as-produced CoF2@C nanocomposite can deliver a high-capacity utilization of 365 mAh g–1 and an average capacity retention of 81.9% over 300 cycles at a current density of 110 mA g–1, as well as a reasonable capacity of 205 mAh g–1 at 1100 mA g–1. Such excellent electrochemical performance is due to the unique configuration that achieves the nanoconfinement of conversion reaction in the metal fluoride cathode. To be specific, on the one hand, the honeycombed structure provides uniformly isolated nanospace to inhibit the volume expansion and product agglomeration in the conversion reaction. On the other hand, the excellent reaction kinetics is attributed to the three-dimensional electron and ion conduction pathway, that is, the electrons are conducted through the honeycombed carbon walls, while Li+ are transferred via the interconnected honeycomb channels, facilitating the high-capacity utilization.