原位包覆法制备LiVOPO_4@C复合材料及其电化学性能  

Preparation of LiVOPO_4@C Composite by In-situ Coating Technique and Its Electrochemical Properties

作　　者：熊利芝[1] 彭良斌[2] 费讲驰[1] 何则强[1] 

机构地区：[1]吉首大学生物资源与环境科学学院,湖南吉首416000 [2]吉首大学化学化工学院,湖南吉首416000

出　　处：《精细化工》2012年第12期1149-1153,1157,共6页Fine Chemicals

基　　金：国家自然科学基金(51142001;51262008;51202087);湖南省科技计划项目(2011TT2038);湖南省自然科学基金重点项目(12JJ2005);湖南省科技厅工业支撑计划重点项目;湖南省教育厅重点项目(12A109);湖南省教育厅青年项目(11B099)~~

摘　　要：以LiVOPO4、硼酸三正丁酯为原料,采用原位包覆法制备了LiVOPO4@C复合材料。采用元素分析、比表面分析、X射线衍射分析、扫描电镜分析以及电化学测试等手段对复合材料的组成、微观结构、表面形貌和电化学性能进行了研究。结果表明,硼酸三正丁酯中少量硼元素的存在,起到了阻止LiVOPO4中V4+被生成的碳还原成V3+而形成Li3V2(PO4)3等物质的作用,保证了纯的LiVOPO4@C复合材料的形成。硼酸三正丁酯热分解后包覆在LiVOPO4颗粒表面,形成了一层多孔碳。多孔碳为锂离子在电极中的传输提供了更为便捷的通道,增加了电极颗粒之间的电接触,有效阻止了LiVOPO4颗粒的聚集,降低了电池极化,改善了LiVOPO4的电化学性能。壳层厚度为8 nm左右的LiVOPO4@C复合材料的电导率达到1.35×10-8S/m,0.2 C时首次放电容量达到146.0 mA.h/g,经50次循环后材料的容量保持率为98.8%,1.0 C倍率下的容量保持率达到96.25%。LiVOPO4 @ C composite was prepared by in-situ coating technique using LiVOPO4 and tributyl borate as raw materials. The microstructure, surface morphology and electrochemical properties were characterized by means of various electrochemical methods in combination with elemental CHNS analysis, N2 adsorption-desorption isotherm measurements, X-ray diffraction （ XRD）, scanning electron microscope（SEM） and transmission electron microscopy（TEM）. It is found that the porous carbon layer is coated on the surface of LiVOPO4 due to the pyrolysis of tributyl borate. The existence of boron inhibits vanadium in LiVOPO4 reduction from V4＋ to V3＋ to form Li3V2 （PO4 ）3 as impurity, ensuring the formation of pure LiVOPO4 @ C composite. The porous carbon offers commodious channels for lithium ion to transfer in the electrode materials, improves the electric contact between the electrode particles, prevents the LiVOPO4 particles from aggregation, decreases the polarization of cell and thus improves the electrochemical properties of LiVOPO4 effectively. The electric conductivity of the LiVOPO4@ C composite with a shell thickness of 8 nm is more than 1.35 x 10-s S/m. The first discharge capacity of the LiVOPO4 @ C composite at 0. 2 C is 146.0 mA . h/g and 98.8% of the discharge capacity is maintained ,while 96. 25% of the discharge capacity is maintained after cycling at1.0 C for 50 times.

关 键 词：LiVOPO4 碳 原位包覆 硼酸三正丁酯 功能材料 

分 类 号：O646[理学—物理化学]