Confined Iron Fluoride@CMK‐3 Nanocomposite as an Ultrahigh Rate Capability Cathode for Li‐Ion Batteries

A facile and advanced architecture design of FeF 3 ·0.33H 2 O impregnated CMK‐3 nanocomposite (FeF 3 ·0.33H 2 O@CMK‐3) is presented. In the FeF 3 ·0.33H 2 O@CMK‐3 nanocomposite, mesoporous carbon CMK‐3 can provide enough passageways for electron and Li + transport to the confined nanosized FeF 3 ·0.33H 2 O. The intimate conductive contact between the FeF 3 ·0.33H 2 O nanoparticles and the carbon framework not only provides an expressway of electron transfer for Li + insertion/extraction but also suppresses the growth and agglomeration of FeF 3 ·0.33H 2 O during the crystallization process. As expected, the nanostructured materials exhibit impressive rate capability and excellent cyclicity. Remarkably, even under an ultrahigh charge/discharge rate of 50 C (the charge or discharge process takes a mere 72 s), the confined FeF 3 ·0.33H 2 O@CMK‐3 still shows a high specific capacity of 78 mAh g −1 . By combining confined nanosized active material, high electron conductivity, and open framework, the FeF 3 ·0.33H 2 O@CMK‐3 nanocomposite demonstrates excellent high‐rate capability and good cycling properties.