Tailoring Crystal Structure and Morphology of LiFePO4/C Cathode Materials Synthesized by Heterogeneous Growth on Nanostructured LiFePO4 Seed Crystals

초록

Porous and coarse (5-10 mu m) LiFePO4/C composites with excellent electrochemical performance were synthesized by a growth technology using nanostructured (100-200 nm) LiFePO4 as seed crystals for the 2nd crystallization process. The porous and coarse LiFePO4/C presented a high initial discharge capacity (similar to 155 mA h g(-1) at 0.1 C), superior rate-capability (similar to 100 mA h g(-1) at 5 C, similar to 65 % of the discharge capacity at 0.1 C), and excellent cycling performance (similar to 131 mA h g(-1), similar to 98 % of its initial discharge capacity after 100 cycles at 1 C). The improvement in the rate-capability of the LiFePO4/C was attributed to the high reaction area resulted from the pore tunnels formed inside LiFePO4 particles and short Li-ion diffusion length. The improved cycling performance of the LiFePO4/C resulted from the enhanced structural stability against Li-deficient LiFePO4 phase formation after cycling by the expansion of the ID Li-ion diffusion channel in the LiFePO4 crystal structure.