柔性聚合物电解质的制备及其电化学性能

Synthesis and Electrochemical Performance of Flexible Polymer Electrolyte

以不同质量比的丙烯酸甲酯（MA）和丙烯腈（AN）为单体,聚乙烯醇（PVA）为分散剂,采用绿色环保的改性乳液聚合法制得聚合物乳液,将聚合物乳液流延涂布制得柔性聚合物膜,进一步采用电解液浸润法制得系列柔性聚合物电解质膜（S1、S2、S3和S4）。通过傅里叶红外光谱仪（FTIR）、扫描电镜（SEM）、力学性能测定、热分析、交流阻抗（EIS）和充放电测试对材料的物理化学性能进行了表征。结果表明：当m（MA）∶m（AN）=23∶2（S2）时,聚合物膜的抗拉强度为14.3 MPa,断裂伸长率为248%,25℃时的离子电导率为0.95m S/cm。分别以LiCoO_2为正极、金属锂为负极,天然石墨为正极、金属锂为负极制备CR2032扣式锂离子电池并测试其循环伏安性能和充放电性能,4次循环伏安测试发现峰电位均无明显变化,0.1 C倍率下,首次放电比容量分别为142和307 mA·h/g,50次循环后分别为135和323 m A·h/g,1.0 C倍率下,LiCoO_2的放电比容量为134.3 mA·h/g,说明所制备的材料具有较好的电化学性能。

A series of emulsions were synthesized by an eco-friendly emulsion polymerization with different mass ratio of methyl acrylate（MA） and acrylonitrile（AN） as monomers, polyvinyl alcohol（PVA） as a stabilizer. Then, flexible polymer membranes were prepared by flow coating method. Subsequently, the resulting membranes were immersed into lithium ion electrolyte. Finally, four flexible polymer electrolyte membranes（S1, S2, S3 and S4） were obtained. The physicochemical property of the prepared materials were characterized by Fourier transform infrared（FTIR）, scanning electron microscope（SEM）, mechanical strength measurements, thermal analysis, electrochemical impedance spectroscopy（EIS） andcharge-discharge test. The results showed that the prepared polymer membrane S2 possessed a mechanical strength of 14.3 MPa and elongation of 248% with ionic conductivity of 0.95 m S/cm at 25 ℃ when the mass ratio of MA to AN was 23∶2. The electrochemical performances of lithium ion batteries using membrane S2 as separator, lithium as anode and Li Co O2 or natural graphite as cathode were studied by cyclic voltammetry（CV）, and charge/discharge technique. There was no significant change in the peak potential after 4 cycles. The Li Co O2 as cathode active material had an initial discharge capacity of 142 m A·h/g, while the graphite as cathode active material possessed an initial discharge capacity of 307 m A·h/g, and their corresponding discharge capacity were 135 and 323 m A·h/g after 50 cycles at 0.1 C rate. The battery delivered a discharge capacity of 134.3 m A·h/g based on the Li Co O2 active material in the cathode at 1.0 C rate, indicating that the prepared material exhibited excellent electrochemical performances.