Li_3V_2(PO_4)_3/C的P123辅助流变相法制备及电化学性能  

P123-Assisted Rheological Phase Reaction Synthesis and Electrochemical Performance of Li_3V_2(PO_4 )_3 /C Cathode

作　　者：元志红[1] 马珺[1] 陈星[1] 刘开宇[1] 

机构地区：[1]中南大学化学化工学院,长沙410083

出　　处：《物理化学学报》2012年第12期2898-2904,共7页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(21071153; 20976198)资助项目~~

摘　　要：以V2O5、NH4H2PO4、LiOH、柠檬酸、三嵌段聚合物表面活性剂P123为原料,用流变相(RPR)法制备了Li3V2(PO4)3/C正极材料.用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等方法表征,结果表明:材料为单一纯相的单斜晶体结构,颗粒均匀并呈现珊瑚结构;恒流充放电,循环伏安(CV)及电化学交流阻抗(EIS)等电化学性能测试表明,采用P123辅助合成材料电化学性能明显优于未采用P123辅助合成材料.3.0-4.3V放电区间,0.1C充放电下P123辅助合成Li3V2(PO4)3/C材料首次放电比容量为129.8mAh·g-1,经过50次循环后容量只衰减0.9%;倍率性能及循环性能优异,1C、10C、25C的首次放电比容量分别为128.2、121.3、109.1mAh·g-1,50次循环后容量保持率分别为99.1%,96.9%,90.7%.这归因于三嵌段聚合物P123作为分散剂的同时也作为有机碳源在颗粒表面及间隙形成碳网络,有利于材料导电率的改善,降低了其电荷转移阻抗,减小了电极充放电过程的极化现象.A monoclinic Li3V2（PO4）3/C cathode has been synthesized for use in lithium ion battery applications via a P123-assisted rheological phase reaction （RPR） method. Li3V2（PO4）3/C composite materials were prepared from a mixture of V2O3, LiH2PO4, LiOH, citric acid, and triblock copolymer surfactant P123. The composite material was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The electrochemical performance was tested by Galvanostatic charge-discharge tests, cyclic voltammetry （CV）, and electrochemical impedance spectroscopy （EIS）. The P123-assisted Li3V2（PO4）3/C assumes a pure monoclinic crystal structure and exhibits a high initial discharge capacity of 128.9 mAh. g-1, which only decreases by 0.9% of its initial value after 50 cycles at 0.1C between 3.0 and 4.3 V. Moreover, the cathode displays good fast rate performance, displaying discharge capacities of 128.2, 121.3, and 109.1 mAh . g-1 and capacity retentions after 50 charge-discharge cycles of 99.1%, 96.9%, and 90.7% at rates of 1C, 10C, and 25C, respectively. The introduction of the triblock copolymer surfactant P123 to the RPR system is attributed to the excellent electrochemical performance. It acts as a surfactant as well as an organic carbon source, and forms a carbon network in the particle surface, which helps improve the material conductivity rate, and reduce the charge transfer resistance and electrode polarity effects during the charge-discharge process.

关 键 词：锂离子电池 正极材料 磷酸钒锂 流变相法 三嵌段聚合物表面活性剂P123 

分 类 号：TM912[电气工程—电力电子与电力传动]