Surfactant-aided impregnation of MnF2 into CNT fabrics as cathode material with high electrochemical performance for lithium ion batteries

Highlights: • Surfactant-aided impregnation of MnSiF₆ into CNT fabrics followed by annealing at 400 °C forms CNT-MnF₂ composites. • Flexible CNT-MnF₂ cathodes retained a specific charge capacity of 388 mAh/g in half-cell after 100 cycles at 0.1 C. • MnF₂ loading affects largely the capacity of CNT-MnF₂ and MnF₂ loading between 70% and 80% gives highest specific capacity. MnF₂ infiltrated-CNT fabrics was prepared by surfactant-aided impregnation of MnSiF₆ precursors in acid-treated CNT fabric followed by annealing MnSiF₆-loaded CNT fabric. The structural and morphological characterizations by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) confirmed the formation of MnF₂ nanoparticles (average size: 20–30 nm) within CNT fabric structure. Galvanostatic charge-discharge tests of CNT-MnF₂ nanocomposite fabrics showed excellent electrochemical performance and good cycle stability between 0.4 and 4.0 V vs Li/Li⁺. A specific capacity of 388 mAh/g was measured at 0.1C for CNT-MnF₂ fabric with 70% MnF₂ loading after 100 cycles. Stable cyclability and good rate performance were obtained at high charge-discharge cycling rates. MnF₂ loading largely affect the performance of MnF₂ infiltrated-CNT fabrics cathodes when lower than 70% MnF₂ loaded-CNT fabrics were prepared. It can be concluded that nano-sized active materials infiltrated inside conductive carbon matrix in optimized content can lead to rapid kinetics and stable performance for flexible metal fluoride-based cathode materials.