Crystallographic Habit Tuning of Li₂MnSiO₄ Nanoplates for High-Capacity Lithium Battery Cathodes

Li₂MnSiO₄ has attracted significant attention as a cathode material for lithium ion batteries because of its high theoretical capacity (330 mA h g^-1 with two Li⁺ ions per formula unit), low cost, and environmentally friendly nature. However, its intrinsically poor Li diffusion, low electronic conductivity, and structural instability preclude its use in practical applications. Herein, elongated hexagonal prism-shaped Li₂MnSiO₄ nanoplates with preferentially exposed {001} and {210} facets have been successfully synthesized via a solvothermal method. Density functional theory calculations and experimental characterization reveal that the formation mechanism involves the decomposition of solid precursors to nanosheets, self-assembly into nanoplates, and Ostwald ripening. Hydroxyl-containing solvents such as ethylene glycol and diethylene glycol play a crucial role as capping agents in tuning the preferential growth. Li₂MnSiO₄@C nanoplates demonstrate a near theoretical discharge capacity of 326.7 mA h g^-1 at 0.05 C (1 C = 160 mA h g^-1), superior rate capability, and good cycling stability. The enhanced electrochemical performance is ascribed to the electrochemically active {001} and {210} exposed facets, which provide short and fast Li⁺ diffusion pathways along the [001] and [100] axes, a conformal carbon nanocoating, and a nanoscaled platelike structure, which offers a large electrode/electrolyte contact interface for Li⁺ extraction/insertion processes.