Acta Chimica Sinica ›› 2014, Vol. 72 ›› Issue (6): 653-657.

Communication

### 高性能LiFePO4/碳纳米笼锂离子电池正极材料

1. 介观化学教育部重点实验室南京大学 化学化工学院 南京 210093
• 投稿日期:2014-03-28 发布日期:2014-05-30
• 通讯作者: 吴强，王喜章 E-mail:wangxzh@nju.edu.cn;wqchem@nju.edu.cn
• 基金资助:

项目受国家自然科学基金（Nos.51232003，21173114，21173115，21203092）和“973”项目（No.2013CB932902）资助.

### Carbon Nanocages Supported LiFePO4 Nanoparticles as High-Performance Cathode for Lithium Ion Batteries

Feng Rui, Wang Liwei, Lyu Zhiyang, Wu Qiang, Yang Lijun, Wang Xizhang, Hu Zheng

1. Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
• Received:2014-03-28 Published:2014-05-30
• Supported by:

Project supported by the National Natural Science Foundation of China (Nos.51232003, 21173114, 21173115, 21203092) and the "973" Programs (No.2013CB932902).

Olivine-type LiFePO4, as an important cathode material of lithium-ion batteries, has been paying numerous attentions owing to the high theoretical capacity, good cycle stability, environmental friendliness, safety, etc.But, for bulk LiFePO4 materials, there are some shortcomings such as the low conductivity of ca. 10-9 S·cm-1 and low diffusion coefficient of lithium ions.Some methods have been developed to improve its performance, including supporting, packaging, doping, and/or nanocrystallization.Carbon materials have been widely used in lithium-ion batteries as the conductive agent and modifier owing to the good conductivity, excellent electrochemical/mechanical stability, special pore structures favoring the mass transfer, low cost, and environmental friendliness.Among these, the conductivity and pore structure have a significant impact on the electrochemical performance of the cathode materials such as LiFePO4.The carbon nanomaterials with three-dimensional hierarchical structure are paying more and more attentions because of the special pore structure.Herein, we reported the high performance of the cathode materials, LiFePO4 supported on carbon nanocages (CNCs).CNCs are prepared using benzene as precursors and magnesium oxide as template, which have high specific surface area up to 1274 m2·g-1, excellent electrical conductivity of 1.44 S·cm-1, multiscale pore structure, etc.The LiFePO4/CNCs nanocomposite was prepared following the procedure.CNCs were impregnated with the Li+, Fe2+ and PO43- -containing acid solutions, the final products were obtained by sintering at 700 ℃ under the gaseous mixture of Ar and 5 vol.% H2.The component, structure, and electrochemical performances were investigated by X-ray diffraction, transmission electron microscope, thermogravimetry, and electrochemical tests.The LiFePO4 nanoparticles with the size of 10～25 nm were homogeneously dispersed on CNCs.The bulk conductivity of LiFePO4/CNCs was 0.529 S·cm-1, far higher than 2.27×10-9 S·cm-1 of pure LiFePO4.The LiFePO4/CNCs composite delivered a large discharge capacity of 163 mAh·g-1 at a rate of 0.1 C, close to the theoretical capacity of LiFePO4.Even at the high rates of 15 C and 30 C, the discharge capacities still reach 96 and 75 mAh·g-1, respectively.After 200 cycles at the high rate of 15 C, the tested cell still remains a specific capacity of 92 mAh·g-1.These results indicated that the LiFePO4/CNCs composite as cathode material of lithium-ion batteries possessed excellent high-rate performance and cycling stability, superior to the LiFePO4/CNTs composite.It could be ascribed to high surface area, hierarchical porous structure, and excellent electrical conductivity of CNCs support as well as the nanoscale size and high crystallinity of LiFePO4 particles.