Li3V2(PO4)3/C的P123辅助流变相法制备及电化学性能

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. 3.0-4.3 V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129.8 mAh·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、109.1 mAh·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.

P123-Assisted Rheological Phase Reaction Synthesis and Electrochemical Performance of Li3V2(PO4)3/C Cathode

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 V₂O₅, 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.