In situ lithiated FeF3/C nanocomposite as high energy conversion-reaction cathode for lithium-ion batteries

Transition metal fluorides (such as FeF3 and FeF2) based on conversion chemistry have been considered as a promising alternative to the intercalation cathode materials due to the high capacity and high energy density. However, the critical challenges for these materials come from the absence of Li source in them, and low power density and poor cycling stability. Herein, pre-lithiated FeF3 with extremely small size of Fe and LiF nanoparticles (both similar to 6 nm) homogeneously embedded in the carbon matrix were synthesized using a facile and scalable in situ strategy. Benefited from the ultra-small Fe and LiF nanoparticles, uniform distribution, and intimate contact between the active species and the carbon matrix, the particle-to-particle interfacial resistance and diffusion length for Li and F are dramatically reduced. As a result, a high specific capacity of over 400 mA h g(-1) with a discharge energy density of similar to 700 W h kg(-1) and favorable cycling performance are achieved, making such composite a promising high-capacity cathode for LIBs. Furthermore, the built-in Li source in this composite renders it a drop-in replacement for cathode materials used in the current LIB configurations, thus paving the way for the practical applications in the text generation of high energy density LIBs. (C) 2016 Elsevier B.V. All rights reserved.