超临界法制备PVDF-HFP-PEO共混聚合物电解质及其性能研究

Preparation of PVDF-HFP-PEO blending polymer electrolyte by supercritical method and study on its properties

针对单一聚合物电解质在室温条件下离子电导率低、电解质与电极界面稳定性差的问题,采用超临界CO_(2)相分离法制备掺杂适当比例聚氧化乙烯(PEO)的聚偏氟乙烯-六氟丙烯(PVDF-HFP)基电解质,并通过共混改性得到多孔PVDF-HFP-PEO聚合物薄膜。结果表明,该聚合物薄膜具有较高孔隙率与吸液率,热分解温度超过380℃,热稳定性较好;吸附电解液后,该电解质离子电导率为5.13 mS/cm。组装成Li//PVDF-HFP-PEO电解质//LiFePO4扣式电池后,1 C倍率循环下正极首圈放电容量达到128.5 mAh/g,循环70圈后,正极放电容量剩余122.8 mAh/g。

Single-polymer based electrolyte has the problems such as low ionic conductivity and poor stability of interface between electrolyte and electrode at room temperature.Polyvinylidene fluoride-hexafluoropropylene(PVDF-HFP) based electrolyte doped with an appropriate proportion of polyethylene oxide(PEO) is prepared through supercritical CO_(2)phase separation method, and blended and modified into porous PVDF-HFP-PEO polymer film.It is verified that this polymer film has high porosity and liquid absorption, and its thermal decomposition temperature exceeds 380℃ and it also exhibits a good thermal stability.After adsorbing the electrolyte solution, the ionic conductivity of the electrolyte is 5.13 mS·cm-1.Li//PVDF-HFP-PEO electrolyte//LiFePO4button battery is assembled, and the first cycle discharge capacity of the positive electrode under 1 C rate reaches 128.5 m·Ah·g-1.The discharge capacity of the positive electrode remains 122.8 m·Ah·g-1after 70 cycles.