摘要
采用溶胶-凝胶法合成Li_3V_2(PO_4)_3/C正极材料,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电循环测试、电化学阻抗谱(EIS)、循环伏安(CV)等手段研究极片面密度和压实密度对Li_3V_2(PO_4)_3/C电化学性能的影响。结果表明:Li_3V_2(PO_4)_3/C的倍率性能随着面密度的增加而变差,且面密度越大极化现象越严重,20C时放电比容量差距高达22.8(mA·h)/g。EIS分析结果表明:随着面密度的增加,电荷转移阻抗增大,锂离子表观扩散系数降低。当极片压实密度过高或过低时,Li_3V_2(PO_4)_3/C的倍率性能均较差,压力为20 MPa时放电比容量最高,20C时放电比容量为94.0(mA·h)/g,而0和35 MPa时放电比容量仅70(mA·h)/g左右。EIS和CV测试结果表明:极片压实密度较小和较大的情况均不利于电荷和锂离子的转移。
Li3V2（PO4）3/C anode material was prepared by sol-gel method.The effects of surface density and press density of the cathode electrode on electrochemical performance of Li3V2（PO4）3/C were characterized by X-ray diffractometry（XRD）,scanning electron microscopy（SEM）,galvanostatic charge-discharge test,electrochemical impedance spectroscopy（EIS） and cyclic voltammetry（CV）.The results show that the rate capability of Li3V2（PO4）3/C electrode becomes worse with the increase of surface density,delivering a discharge specific capacity gap of as high as 22.8（mA·h）/g at 20 C,and is accompanied by a more severe polarization.The EIS results show that the charge transfer resistance increases and apparent lithium ion diffusion coefficient decreases with the increase of surface density.Besides,the rate capability of Li3V2（PO4）3/C is poor when the press density is either too low or too high.It is evidenced that Li3V2（PO4）3/C electrode pressed at the pressure of 20 MPa can provide the highest discharge capacity of 94.0（mA·h）/g at20 C,but only about 70（mA·h）/g at 0 and 35 MPa.The results of EIS and CV show that it is not conductive to the transformation of charge and lithium ion under too high or too low press density.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2015年第12期3404-3413,共10页
The Chinese Journal of Nonferrous Metals
基金
中国博士后科学基金资助项目(2014M562322)
高等学校博士学科点专项科研基金资助项目(20120181120103)
