AUTHOR=Zeng Taotao , Fan Changling , Wen Zheng , Li Qiyuan , Zhou Zeyan , Han Shaochang , Liu Jinshui 

TITLE=Effect of Environmental Temperature on the Content of Impurity Li3V2(PO4)3/C in LiVPO4F/C Cathode for Lithium-ion Batteries

JOURNAL=Frontiers in Chemistry

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2018.00283

DOI=10.3389/fchem.2018.00283

ISSN=2296-2646

ABSTRACT=<p>Previous studies have shown that the impurity Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> in LiVPO<sub>4</sub>F will adversely affect its electrochemical performance. In this work, we show that the crystalline composition of LiVPO<sub>4</sub>F/C is mainly influenced by the environmental temperature. The content of Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> formed in LiVPO<sub>4</sub>F/C is 0, 11.84 and 18.75% at environmental temperatures of 10, 20, and 30°C, respectively. For the sample LVPF-30C, the SEM pattern shows a kind of alveolate microstructure and the result of selected area electron diffraction shows two sets of patterns. The LiVPO<sub>4</sub>F/C cathode without impurity phase Li<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> was prepared at 10°C. The selected area electron diffraction result proves that the lattice pattern of LiVPO<sub>4</sub>F is a regular parallelogram. Electrochemical tests show that only one flat plateau around 4.2 V appears in the charge/discharge curve, and the reversible capacity is 140.4 mAh·g<sup>−1</sup> at 0.1 C, and 116.3 mAh·g<sup>−1</sup> at 5 C. From these analyses, it is reasonable to speculate that synthesizing LiVPO<sub>4</sub>F/C at a low environmental temperature is a practical strategy to obtain pure crystalline phase and good electrochemical performance.</p>