Facile Electrochemical Activity of Monoclinic LiMnSiO as Potential Cathode for Li-Ion Batteries.

Synthesis of pure single-phase LiMnSiO is challenging because of its rich polymorphism. Here, we demonstrate our success in preparing crystalline pure, battery-grade monoclinic phase LiMnSiO (LMS) employing the temperature-programmed reaction technique. Systematic analysis of the electrochemical behavior of LiMnSiO reveals its excellent battery activity in the monoclinic phase, with an initial discharge capacity of ∼250 mAh g associated with the reversible intercalation of more than one Li. The extraction of Li ions from LiMnSiO corresponding to the oxidation of Mn to Mn then to Mn appears as single oxidation/reduction peaks at 4.3/3.9 V in the first charge/discharge sweep of cyclic voltammogram within the potential window of 3.0-4.4 V. However, an extension of cathodic sweep to 2.5 V results in the appearance of an additional redox peak at 2.7/3.1 V vs Li/Li due to the reversible phase transition of monoclinic phase into battery-active orthorhombic phase induced by Jahn-Teller-active Mn as evident from ex situ X-ray diffractograms. Indeed, the reversible intercalation of Li into the newly formed phase accounts for the high specific capacity of LMS within the potential window of 2.5-4.4 V. The capacity loss in the repeated cycles of monoclinic LiMnSiO is explained by the formation of MnO owing to the dissolution of Mn.