In situ preparation of LiFePO4/C with unique copolymer carbon resource for superior performance lithium-ion batteries

Olivine-type LiFePO4, taking advantage of structure stability and environmental friendliness, points out a new direction towards development of Li-ion batteries applying in the plug-in hybrid vehicles. However, the inferior electronic conductivity (∼10−9 S cm−1 at 298 K) and lower lithium ion diffusion coefficient (∼1015 cm2 S−1 at 298 K) still hinder the farther application in power battery. To overcome the defects, LiFePO4/C composite with special copolymer carbon resource (polyacrylonitrile block polymethyl methacrylate) is synthesized successfully by in situ carbothermal reduction method. From BET, SEM and TEM, the sample obtained is coated by thin and homogeneous porous carbon layers, which may be induced by the copolymer carbon resource. The porous layers give opportunity to faster diffusion of Li-ion and closely contact between active substance and electrolyte, providing the high active sites. Unquestionably, the modified LiFePO4/C demonstrates such outstanding properties as high initial discharge capacity (165.3 mA h g−1 at 0.2C), superior rate capability (78.9 mA h g−1 at 30C), and excellent cycling performance with 98% cycle retention after 100 cycles at 0.2C. The well-designed LiFePO4/C cathode material becomes an increasingly eye-catching candidate applicable to the fields of rechargeable lithium ion batteries.