Physical and electrochemical properties of LiCOPO_4/C nanocomposites prepared by a combination of emulsion drip combustion and wet ball-milling followed by heat treatment

摘要

The combination of emulsion drip combustion at 600 ℃ and wet ball-milling followed by heat treatment at 500 ℃ in a N2 + 3% H_2 atmosphere was performed for the preparation of LiCoPO_4/C nanocomposites. The obtained material consisted of agglomerates of LiCoPO_4 primary particles with a geometric mean diameter of 70 nm, which were covered by a thick layer of amorphous carbon. A cell containing the LiCoPO_4/C nanocomposites exhibited a discharge capacity of 134 mAh g~(-1) at a charge-discharge rate of 0.1 C. However, the discharge profile of the LiCoPO_4/C nanocomposites had a long tail, which may be due to the limited lithium ion diffusion caused by the thick carbon layer that formed on the LiCoPO_4 primary particles. The LiCoPO_4/C nanocomposites prepared from a mixture of kerosene and heptane with equal volumes consisted of agglomerates of the primary particles with a geometric mean diameter of 97 nm, which were covered by a thin layer of amorphous carbon with a thickness on the order of 10 nm. Furthermore, they delivered a high energy density of 595 Wh kg~(-1) at a charge-discharge rate of 0.1 C and exhibited reasonable cyclability, retaining 87% of the initial energy density after 25 cycles.