咪唑六氟磷酸盐聚离子液体凝胶电解质的辐射合成及性能研究

Radiation Synthesis and Properties of Imidazolium Hexafluorophosphate Poly(ionic liquid) Gel Electrolytes

以1-乙烯基-3-烷基咪唑六氟磷酸盐C_nvimPF_6(n=6,12)为单体,(1,6-亚己基)-双(3-乙烯基咪唑)六氟磷酸盐为交联剂,六氟磷酸锂为添加剂,混合碳酸酯为溶剂,采用辐射引发聚合、交联合成了新型的聚离子液体凝胶电解质(简称PC_nvimPF_6-Li GPE),并研究了离子液体单体侧链长度、单体浓度、交联剂含量对PC_nvimPF_6-Li GPE性能的影响.结果表明所合成的PC_nvimPF_6-Li GPE具有良好的力学性能和高离子电导率,最大离子电导率可达7.18 mS/cm.

Poly（ionic liquid）s have been used as electrolytes in lithium-ion battery due to their good electrochemical properties and thermal stability. In this work, we firstly synthesized organic poly（ionic liquid） gel, PC_nvimPF_6, by γ-ray radiation inducing polymerization of 1-alkyl-3-vinylimidazolium hexafluorophosphate（[Cnvim]PF6）（n = 6, 12）, with 1,1′-（1,6-ethylidene）-bis（3-vinylimidazolium） hexafluorophosphate as crosslinking agent in a mixed carbonate ester solution. The gel fraction of the resultant gel increased along with the radiation absorbed dose, while the degree of equilibrium swelling（EDS） of the gel decreased, and the changes of the gel fraction and EDS were no longer obvious with the radiation absorbed dose above 20 kGy. FTIR results showed that the characteristic vibration absorption peaks of C=C for [Cnvim]PF6 from 1654 cm^（-1） to 1656 cm^（-1） disappeared after radiation, indicating the successful synthesis of PC_nvimPF_6 gel. TGA experiment indicated that PC_nvimPF_6 gel was of good thermal stability. Based on this PC_nvimPF_6 gel, a novel gel polymer electrolyte（GPE）, PC_nvimPF_6-Li GPE, was prepared by adding 1 mol/L Li PF6 into monomer solution using one-step radiation synthesis. Effects of the alkyl chain length of the monomer, the contents of the monomer and the crosslinking agent on the property of PC_nvimPF_6-Li GPE were investigated. The obtained PC_nvimPF_6-Li GPE exhibited good mechanical property and high ionic conductivity. The ionic conductivity of the GPE increased with the decrease of monomer concentration and alkyl chain length, and changed slightly with the content of crosslinking agent. As the monomer concentration increased, the compressive strength（σm） of the GPE increased, and the compressive strain（εm） decreased. The σmof the GPE ranged from 40 k Pa to 1685 k Pa, and its ionic conductivity from 1.5 mS/cm to 7.18 mS/cm. The highest ionic conductivity（7.18 mS/cm） was obtained for a sample prepared using 0.4 mol/L C6 vim PF6 monomer solution containing 8 mol% of crosslinker and 1 mol/L Li PF6. It is expected that the resultant PC_nvimPF_6-Li GPE is a promising candidate for lithium-ion battery electrolytes.