Fluorinated Mn3O4 nanospheres for lithium-ion batteries: Low-cost synthesis with enhanced capacity, cyclability and charge-transport

Abstract

A facile synthesis of fluorinated Mn3O4 nano-spheres (F-Mn3O4) from low-cost electrolytic manganese dioxide (EMD) at different temperatures and times has been reported. While the as-prepared materials are micron-sized (>200 nm) and the fluorinated Mn3O4 are nano-sized particles (<50 nm). Detailed characterization (using XRD, XPS, FESEM and EDX, electrochemistry including EIS) clearly prove the unique effects of the fluorination on the physico-electrochemical properties of the F-Mn3O4 nanomaterials, notably the dramatic transition from microstructure to nanostructure. The electrochemical performance of F-Mn3O4 is strongly enhanced by the fluorination with high specific capacity (931 mAh g-1 at 100 mA g-1), excellent capacity retention (87% after 100 cycles) and excellent rate capability (460 and 216 mAh g-1 at 1000 and 2000 mA g-1, respectively) compared to the pristine Mn3O4 materials with 556 mAh g-1 with the capacity retention of 73%. The performance of the F-Mn3O4, which is better or comparable with corresponding materials in the literature, gives exciting promise for potential development of high-performance low-cost manganese oxide-based anode materials for lithium-ion batteries. It is common knowledge in the battery research community that spherical particles are most preferred for industrial application due to improved packing density. Importantly, EIS data provide critical insight into the charge-transfer properties of the anode materials as a result of the fluorination process. The enhanced performance of the F-Mn3O4 is attributed to its nano-spherical morphology that favours good fluidity of particles and excellent tap density of the redox-active components.