Li_3V_2(PO_4)_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(英文)  

Electrochemical Behavior and Reasons for the Decrease in Capacity of the Li_3V_2(PO_4)_3/C Cathode Material in Different Voltage Ranges

作　　者：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] 

机构地区：[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

出　　处：《物理化学学报》2015年第2期277-284,共8页Acta Physico-Chimica Sinica

基　　金：supported by the China Postdoctoral Science Foundation (2014M562322);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Li_3V_2(PO_4)_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Li_3V_2(PO_4)_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=150m A·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,Li_3V_2(PO_4)_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Li_3V_2(PO_4)_3在3.0-4.8 V区间容量衰减的主要原因.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.

关 键 词：Li3V2(PO4)3/C 电化学行为 电压区间 容量衰减 

分 类 号：O614.111[理学—无机化学] TM912[理学—化学]