Synthesis and Characterization of Spherical Li₂Fe_0.5V_0.5SiO₄/C Composite for High-Performance Cathode Material of Lithium-Ion Secondary Batteries

Spherical Li 2 Fe 0.5 V 0.5 SiO 4 /C composite has been successfully synthesized by a spray drying technique followed by two-step solid-state reaction. The coated carbon layers are obtained by chemical vapor deposition (CVD) using ethanol as carbon source. Our results demonstrated that vanadium ions have been doped into the lattice of orthosilicate structure. The Li 2 Fe 0.5 V 0.5 SiO 4 /C composite exhibited good rate capability and high initial discharge capacity of 226.2 mAh·g −1 at 0.1 C, which corresponds to 1.34 mole of Li + per formula unit. These excellent electrochemical properties could be ascribed to the substitution of vanadium in orthosilicate structure because partial vanadium ions can be oxidized up to V 5+ during charging process, which greatly increases the capacity as well as the rate and cycle performance. These results indicate that the spherical Li 2 Fe 0.5 V 0.5 SiO 4 /C composite will be a very promising cathode material for lithium-ion secondary batteries.