物理化学学报 >> 2015, Vol. 31 >> Issue (2): 277-284.doi: 10.3866/PKU.WHXB201412172

电化学和新能源 上一篇    下一篇

Li3V2(PO4)3/C正极材料在不同电压区间的电化学行为及容量衰减原因

唐艳1,2, 钟艳君2, 欧庆祝2, 刘恒1, 钟本和2, 郭孝东2, 王辛龙2   

  1. 1. 四川大学材料科学与工程学院, 成都 610065;
    2. 四川大学化学工程学院, 成都 610065
  • 收稿日期:2014-10-27 修回日期:2014-12-17 发布日期:2015-01-26
  • 通讯作者: 刘恒, 王辛龙 E-mail:h_liu@scu.edu.cn;wangxl@scu.edu.cn
  • 基金资助:

    中国博士后科学基金(2014M562322)和高等学校博士学科点专项科研基金(20120181120103)资助项目

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).

摘要:

采用溶胶-凝胶法制备锂离子电池正极材料Li3V2(PO4)3/C. 通过恒电流充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等方法, 研究了Li3V2(PO4)3/C 在不同电压区间的电化学行为(3.0-4.5 V和3.0-4.8 V). 结果表明, 3.0-4.8 V电压区间的循环性能和倍率性能均不及3.0-4.5 V电压区间的. 3.0-4.5 V区间0.1C (1C=150mA·g-1)倍率首次放电比容量为127.0 mAh·g-1, 循环50次后容量保持率为99.5%, 而3.0-4.8 V区间的分别为168.2 mAh·g-1和78.5%. 经过高倍率测试后再回到0.1C倍率充放电, 3.0-4.5 V和3.0-4.8 V的放电比容量分别为初始0.1C倍率的99.0%和80.7%. 经过3.0-4.8 V电压区间测试后, 少部分第三个锂离子能够在低于4.5V的电压脱出, 使3.0-4.5 V电压区间的放电比容量提升了7.4%. CV结果表明3.0-4.8 V区间的容量损失主要表现为第一个锂离子的不可逆损失. 极片的X射线衍射(XRD)和X射线光电子能谱(XPS)分析测试结果表明经过3.0-4.8 V测试后, Li3V2(PO4)3的结构发生了轻微的改变. 电感耦合等离子体(ICP)测试结果表明循环后的电解液中含有少量的V. 结构变形和V溶解可能是Li3V2(PO4)3在3.0-4.8 V区间容量衰减的主要原因.

关键词: Li3V2(PO4)3/C, 电化学行为, 电压区间, 容量衰减

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.

Key words: Li3V2(PO4)3/C, Electrochemical behavior, Voltage range, Capacity fading

MSC2000: 

  • O646