The effect of ammonia concentration on the morphology and electrochemical properties of LiFePO4 synthesized by ammonia assisted hydrothermal route

• Published in: Electrochimica acta 2012-08, Vol.76, p.120-129
• Main Authors: Shu, Hongbo, Wang, Xianyou, Wu, Qiang, Liu, Li, Liang, Qianqian, Yang, Shunyi, Ju, Bowei, Yang, Xiukang, Zhang, Xiaoyan, Wang, Yingping, Wei, Qiliang, Hu, Benan, Liao, Yuqing, Jiang, Huimin
• Format: Article
• Language: English
• Subjects: Ammonia assisted hydrothermal synthesis; Ammonia concentration; Applied sciences; Chemistry; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Electrochemical properties; Electrochemistry; Exact sciences and technology; General and physical chemistry; LiFePO4/C composite; Lithium ion batteries
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2012.04.156

► The LiFePO4/C is synthesized by a ammonia assisted hydrothermal method at various ammonia concentrations. ► The concentrations of ammonia affect the morphology and performance of samples. ► The LiFePO4/C microspheres synthesized with 0.4molL−1 ammonia exhibit excellent electrochemical performance. ► The ammonia assisted hydrothermal method is a promising process for preparing high performance LiFePO4/C. The LiFePO4/C composites with different morphology are synthesized by an ammonia assisted hydrothermal method at various ammonia concentrations (from 0 to 1.6molL−1) using inexpensive Fe(NO3)3 and LiOH as raw materials. The influences of the ammonia concentration on the structure, morphology and electrochemical properties of the LiFePO4/C composite are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS). The results demonstrate that the ammonia concentrations markedly impact the morphology and electrochemical properties of the LiFePO4/C. With the change of ammonia concentrations, the LiFePO4/C synthesized with 0.4molL−1 ammonia shows the smallest average particle size, the most uniform microsphere particle distribution and relatively high tap density (1.27gcm−3). In addition, the sample appears a high discharge capacity of 153.9mAhg−1 at the first cycle as well as stable cycling performance (the capacity was not almost changed till 100 cycles) at a rate of 1C (170mAg−1). Moreover, it exhibits a good rate capability and still shows a high discharge capacity of over 125mAhg−1 even at a rate of 5C.