Ionothermal synthesis and characterization of Li2MnSiO4/C composites as cathode materials for lithium-ion batteries

Li2MnSiO4 powders have been synthesized under mild conditions via an ionothermal synthesis method in ionic liquids of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), respectively, and then Li2MnSiO4/C cathode materials were prepared by solid-state reaction using sucrose as carbon source at high temperature. The structures and morphologies were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Li2MnSiO4 powders prepared in two ionic liquids present different morphologies and particle sizes and the length of alkyl chains on the imidazole ring plays important role in forming the size and morphology of material. The Li2MnSiO4 can crystallize in an orthorhombic structure with a space group of Pmn21 and form uniform material with the size of primary particle ranging from 50 to 80 nm, and Li2MnSiO4/C composites prepared via precursors produced in [BMIM]BF4 achieved the excellent electrochemical performance with an initial discharge capacity of 218.2 mAh g−1, and retained an effective discharge of 175.7 mAh g−1 after 50 cycles. Results reveal that the ionothermal synthesis could be a promising new route in preparing Li2MnSiO4 cathode material for lithium-ion batteries in decreasing particle size, reducing reaction conditions, and improving electrochemical performance.