Additive-free solvothermal synthesis and Li-ion intercalation properties of dumbbell-shaped LiFePO4/C mesocrystals

Hierarchical dumbbell-shaped lithium iron phosphate (LiFePO4) mesocrystals were successfully fabricated via a simple one-step, rapid, additive-free solvothermal route. A mixture of dimethylformamide/ethylene glycol (DMF/EG) has been utilized as the co-solvent and found to play an important role in the formation of the hierarchical mesostructure. The obtained dumbbell-shaped mesocrystals consist of self-assembly LiFePO4 nanorods each with 2-3 μm in length and 30-50 nm in diameter. Further temperature treatment was applied to increase the crystallinity of the LiFePO4 mesocrystals. A high lithium ion intercalation capacity of 140 mA h g−1 was exhibited by the LiFePO4 mesocrystal when tested under a discharge rate of 17 mA g−1, which should be attributed to the fast intercalation reaction and easy mass and charge transfer offered by the large specific surface and short diffusion distance of dumbbell-shaped mesoporous composed of nano-sized LiFePO4 rods. The nanorods can be carbon coated in-situ by adding sucrose during the solvothermal process and the LiFePO4/C mesocrystals showed an improved electrochemical property at higher rates and good cyclic performance.