MXene enabled binder-free FeOF cathode with high volumetric and gravimetric capacities for flexible lithium ion batteries

The vital challenge of iron oxyfluoride (FeOF) as conversion-type cathode material is the low electronic conductivity and huge volume expansion. Design of binder-free film electrode architecture consisted of nanosized active materials and highly conductive matrix not only can resolve these issues, but also can satisfy the escalating needs of flexible and wearable electronics. Nevertheless, synthesis of nanostructured FeOF is still complicated and time-consuming to date. Here, we report the facile preparation of FeOF nanorods using FeF₃•3H₂O as precursor through a mixed alcohols-assisted solvothermal method based on a homogeneous reaction mechanism for the first time, which can greatly shorten the reaction time as well as lower the energy consumption. After that, a flexible Ti₃C₂T_x MXene and FeOF composite (denoted as FeOF/MXene) film with high strength and high conductivity is prepared by a rational combination of electrostatic self-assembly and vacuum-assisted filtration processes. As resulted binder-free FeOF/MXene cathode presents a high capacity of 365.5 mAh g ^{− 1} at 100 mA g ^{− 1} and stable high-rate capacity of 202.6 mAh g ^{− 1} at 2000 mA g ^{− 1} after 400 cycles, which are very prominent among these reported FeOF-based electrodes. The reliable synthesis method and film electrode fabrication procedure are both time-efficient, scalable and cost-effective, which can pave a pathway for the practical application of FeOF and high-performance flexible lithium-ion batteries.