Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries |
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Authors: | Zhong Sheng-kui Yin Zhou-lan Wang Zhi-xing and Chen Qi-yuan |
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Affiliation: | 1. School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China; 2. Department of Materials and Chemistry, Guilin University of Technology, Guilin 541004, China; 3. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China |
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Abstract: | A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction (CTR) process. Firstly,
V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization
of the vanadium as V3+ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with LiF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurement. XRD
studies show that LiVPO4F synthesized has triclinic structure(space group p
), isostructural with the naturally occurring mineral tavorite, LiFePO4·OH. SEM image exhibits that the particle size is about 2 μm together with homogenous distribution. Electrochemical test shows
that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V (vs Li/Li+), and the capacity retains 89 mA·h/g after 30 cycles.
Foundation item: Project(50302016) supported by the National Natural Science Foundation of China |
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Keywords: | lithium ion batteries cathode material LiVPO4F carbon-thermal reduction method |
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