In this study, ferric phosphate precursors were prepared by controlling precipitation time, and the resulting LiFe PO4 active materials were thoroughly investigated. Microscale LiFePO4 cathode materials, designed for high energy density at the cell level, were successfully synthesized through a 10 h co-precipitation. As the reaction time increased, smaller primary particles were aggregated more tightly, and the secondary particles exhibited a more spherical shape. Meanwhile, ammonia did not work effectively as a complexing agent. The carbon coated LiFePO4 (LiFePO4/C) synthesized from the 10 h ferric phosphate precursor exhibited larger primary and secondary particle sizes, a lower specific surface area, and higher crystallinity due to the sintering of the primary particles. Enhanced battery performance was achieved with the LiFePO4/C that was synthesized from the precursor with the smaller size, which exhibited the discharge capacity of 132.25 mAh ‧ g-1 at 0.1 C, 70 % capacity retention at 5 C compared with 0.1 C, and 99.9 % capacity retention after the 50th cycle. The better battery performance is attributed to the lower charge transfer resistance and higher ionic conductivity, resulting from smaller primary particle sizes and a shorter Li+ diffusion path.

Abstract
1. Introduction
2. Experimental Procedure
    2.1. Reagents
    2.2. Sample preparation
    2.3. Characterization
3. Results and Discussion
    3.1. Synthesis of intermediates and time dependenceon the coprecipitation method
    3.2. LiFePO4/C synthesis and characterization
    3.3. Electrochemical performance of different LiFePO4
4. Conclusion
Acknowledgement
References
Author Information

• Jeongwoo Lim(Department of Material Science, Chungnam National University, Daejeon 34134, Republic of Korea)
• Seokwon Seo(Department of Material Science, Chungnam National University, Daejeon 34134, Republic of Korea)
• Chunjoong Kim(Department of Material Science, Chungnam National University, Daejeon 34134, Republic of Korea) Corresponding author