Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (2): 277-284.

• ELECTROCHEMISTRY AND NEW ENERGY •

Electrochemical Behavior and Reasons for the Decrease in Capacity of the Li3V2(PO4)3/C Cathode Material in Different Voltage Ranges

TANG Yan1,2, ZHONG Yan-Jun2, OU Qing-Zhu2, LIU Heng1, ZHONG Ben-He2, GUO Xiao-Dong2, WANG Xin-Long2

1. 1. College of Materials Science and Engineering, Sichuan University, Chengdu 610065, P. R. China;
2. College of Chemical Engineering, Sichuan University, Chengdu 610065, P. R. China
• Received:2014-10-27 Revised:2014-12-17 Published:2015-01-26
• Contact: LIU Heng, WANG Xin-Long E-mail:h_liu@scu.edu.cn;wangxl@scu.edu.cn
• Supported by:

The project was supported by the China Postdoctoral Science Foundation (2014M562322) and Research Fund for the Doctoral Program of Higher Education, Ministry of Education of China (20120181120103).

Abstract:

Li3V2(PO4)3/C cathode material was synthesized by the sol-gel method. The electrochemical properties of the sample in different voltage ranges (3.0-4.5 V and 3.0-4.8 V) were investigated by galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results show that the cycling performance and rate capability of Li3V2(PO4)3/C in voltage range of 3.0-4.8 V are worse than those in voltage range of 3.0-4.5 V. The initial specific discharge capacity in voltage range of 3.0-4.5 V at 0.1C rate (1C=150 mA·g-1) is 127.0 mAh·g-1, and 99.5% of the initial capacity was maintained after 50 cycles in contrast to 168.2 mAh·g-1 and 78.5% in voltage range of 3.0-4.8 V. The discharge capacities in voltage ranges of 3.0-4.5 V and 3.0-4.8 V are 99.0% and 80.7% of the initial 0.1C rate respectively when the charge/discharge rate recovered to 0.1C rate after the high rate test. Part of the third lithium ion may be extracted at less than 4.5 V after several cycles in voltage range of 3.0-4.8 V with a capacity increase of 7.4%. CV results indicate that the irreversible capacity fading between 3.0 and 4.8 V may be attributed to irreversible behavior of the first lithium ion. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the structure of Li3V2(PO4)3 changes slightly after operating between 3.0 and 4.8 V. Inductively coupled plasma (ICP) results indicate the presence of dissolved V in the cycled electrolytes. The structural distortion and the V dissolved in the electrolyte may be the main reasons for the decrease in capacity.

MSC2000:

• O646