Mild and cost-effective synthesis of iron fluoride–graphene nanocomposites for high-rate Li-ion battery cathodes

Abstract

Exploring high performance cathode materials is essential to realize the adoption of Li-ion batteries for application in electric vehicles and hybrid electric vehicles. FeF₃, as a typical iron-based fluoride, has been attracting considerable interest due to both the high electromotive force value of 2.7 V and the high theoretical capacity of 237 mA h g⁻¹ (1e⁻ transfer). In this study, we report a facile low-temperature solution phase approach for synthesis of uniform iron fluoride nanocrystals on reduced graphene sheets stably suspended in ethanol solution. The resulting hybrid of iron fluoride nanocrystals and graphene sheets showed high specific capacity and high rate performance for iron fluoride type cathode materials. High stable specific capacity of about 210 mA h g⁻¹ at a current density of 0.2 C was achieved, which is much higher than that of LiFePO₄ cathode material. Notably, these iron fluoride/nanocomposite cathode materials demonstrated superior rate capability, with discharge capacities of 176, 145 and 113 mA h g⁻¹ at 1, 2 and 5 C, respectively.