Lithium transition metal silicates Li₂MSiO₄ (M = Fe, Mn, Co, etc.) have been under intense research due to their high theoretical capacity of 330 mAh/g_. However, most of the present work have been focused on the electrochemistry of the high temperature monoclinic phase (m-LFS), which shows clear phase transition to a thermodynamically stable low-temperature orthorhombic phase (o-LFS) during cycling. In this context we thought of interest to investigate the cycling behavior of the low-temperature o-LFS that we synthesized via hydrothermal processing. However, as synthesized o-LFS crystals have large ~1.5 µm size, which is undesirable for li-ion intercalation. Therefore, for particle size reduction, we used high energy planetary ball milling and obtained nanoparticles of ~50 nm. Interestingly, XRD results showed improved crystallinity during ball milling. Moreover, electrochemical performance of such mechanically activated nanoparticles showed improved capacity with increasing milling time. This intriguing (unusual) behavior could have significant implications to the development of high capacity LIB materials.

Keywords: Li₂FeSiO₄; Orthorhombic; Low temperature; Electrochemical performance; Li-ion battery