一种新型物理交联型凝胶聚合物电解质的制备与表征

以甲氧基聚乙二醇甲基丙烯酸酯(MPEGM)和十六烷基聚乙二醇甲基丙烯酸酯(HPEGM)为单体, 三乙二醇二甲醚(TEGDME)为增塑剂, 与锂盐(高氯酸锂, LiClO₄)和光引发剂(安息香二甲醚, DMPA)复合制成光敏体系, 经紫外(UV)固化得到物理交联型凝胶聚合物电解质(GPE)薄膜. 用红外(IR)光谱、差热分析(DSC)、拉伸测试和交流阻抗(AC) 等方法对聚合物基体和电解质的性能进行了研究.结果表明: 当共聚物P(MPEGM-co-HPEGM)中HPEGM含量为50%(w)时, 十六烷基链段(C₁₆)在聚氧化乙烯(PEO)链段静电斥力的作用下发生聚集, 自组装形成了物理交联, 提高了共聚物的空间稳定性; 温度和电解质中各组分的含量对电导率均有较大的影响, 综合性能较好的电解质在30℃时电导率可达0.87×10^-3 S·cm^-1; 采用循环伏安法测得该电解质的电化学窗口为0~4.5 V (vs. Li/Li⁺), 可以满足锂离子电池的应用要求; 组装成的LiFePO₄/GPE/Li电池, 在30℃下以0.1 C和0.2 C倍率进行充放电测试, 首次放电容量分别为154.7和148.0 mAh·g^-1.

Synthesis and Characterization of a Novel Physically Cross-Linked Gel Polymer Electrolyte

A physically cross-linked gel polymer electrolyte (GPE) was obtained by photo-induced radical polymerization of a mixture of methoxy-poly(ethylene glycol) methacrylate (MPEGM), hexadecal-poly (ethylene glycol) methacrylate (HPEGM), triethylene glycol dimethyl ether (TEGDME), lithium salt (lithium perchlorate, LiClO₄) and photo-initiator (2, 2-Dimethoxy-2-phenylacetophenone, DMPA). The resulting polymers and gel polymer electrolytes were characterized by infrared spectroscopy (IR), differential scanning calorimetry (DSC), tensile test, and alternating current (AC) impedance measurements. The results showed that the physically cross-linked polymer matrix was formed by C₁₆ aggregation with the effect of electrostatic repulsion of PEO chains when the HPEGM content was high. The ionic conductivity of the obtained GPE is affected by its composition and the temperature. The GPE prepared with the optimum composition exhibited excellent mechanical properties and a relatively high ionic conductivity (up to 0.87×10^?3 S·cm^-1 at 30℃). In addition, the GPE was found to present a wide electrochemical window (from 0 V to 4.5 V vs. Li/Li⁺). In addition, a coin cell based on the gel electrolyte, with LiFePO₄/C as the cathode and metallic lithium as the anode, showed a discharge capacity as high as 154.7 mAh·g^-1 and 148.0 mAh·g^-1 at 30℃ under of 0.1 C and 0.2 C, respectively.