改性PVDF-HFP基凝胶电解质的合成及锂金属电池性能研究

开发高质量的固态电解质,对制造新一代安全稳定的固态锂金属电池具有重要意义。以聚偏氟乙烯–六氟丙烯(polyvinylidene fluoride-hexafluoropropylene, PVDF-HFP)为聚合物基体,引入MOF-808作为活性填料,采用溶液浇筑法制备了新型凝胶聚合物电解质。优化后的凝胶聚合物电解质在室温下的离子电导率高达3.21 mS/cm,电化学稳定窗口可达5.0 V、具有较高的Li^＋迁移数(0.63)、与锂金属具有良好的界面相容性。组装的磷酸铁锂全电池在0.5 C倍率下循环250次,容量保持率为86.7%。高性能凝胶聚合物电解质对提升锂金属电池的循环稳定性与安全性具有重要的应用价值。     

Anion-immobilized solid composite electrolytes based on metal-organic frameworks and superacid ZrO2 fillers for high-performance all solid-state lithium metal batteries

Anion-immobilized solid composite electrolytes (SCEs) are important to restrain the propagation of lithium dendrites for all solid-state lithium metal batteries (ASSLMBs). Herein, a novel SCEs based on metal-organic frameworks (MOFs, UiO-66-NH2) and superacid ZrO2 (S-ZrO2) fillers are proposed, and the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), thermo-gravimetric analyzer (TGA) and some other electrochemical measurements. The –NH2 groups of UiO-66-NH2 combines with F atoms of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) chains by hydrogen bonds, leading to a high electrochemical stability window of 5 V. Owing to the incorporation of UiO-66-NH2 and S-ZrO2 in PVDF-HFP polymer, the open met-al sites of MOFs and acid surfaces of S-ZrO2 can immobilize anions by strong Lewis acid-base interaction, which enhances the effect of im-mobilization anions, achieving a high Li-ion transference number (t+) of 0.72, and acquiring a high ionic conductivity of 1.05×10–4 S·cm–1 at 60°C. The symmetrical Li/Li cells with the anion-immobilized SCEs may steadily operate for over 600 h at 0.05 mA·cm–2 without the short-circuit occurring. Besides, the solid composite Li/LiFePO4 (LFP) cell with the anion-immobilized SCEs shows a superior discharge specific ca-pacity of 158 mAh·g–1 at 0.2 C. The results illustrate that the anion-immobilized SCEs are one of the most promising choices to optimize the performances of ASSLMBs.     

基于超支化聚醚的固体聚合物电解质性能研究

合成一种新型超支化聚醚类固体聚合物电解质. 通过交流阻抗技术测试分析了电解质的离子导电性能,结果表明:温度、锂盐添加量均对离子电导率有较大影响,当锂盐质量分数为30%时,电导率最高(80 ℃时5.45×10-4 S/cm;室温1.2×10-5 S/cm).     

碱处理改性PVDF-HFP聚合物电解质膜

通过碱液处理对聚偏氟乙烯-六氟丙烯(PVDF-HFP)聚合物电解质进行改性,并利用IR、XRD、SEM等表征了改性后聚合物电解质的组成和结构。SEM照片显示改性后的聚合物电解质膜呈海绵多孔状,有利于锂离子的传导。线形伏安扫描测得该聚合物电解质在6 V以内具有很好的电化学稳定性;交流阻抗方法测得20℃时改性后聚合物电解质的离子电导率为1.272×1-0 3S/cm。此改性方法简单,成本较低,且对环境无害。