Abstract:

Incorporating inorganic fillers into polyethylene oxide (PEO)-based solid polymer electrolytes is a low-cost and effective method to improve their mechanical and electrochemical properties. The solid electrolyte composite of zeolite imidazole skeleton material (ZIF-8) and PEO was prepared using flow-casting method to effectively improve the electrochemical performance of the PEO solid electrolyte. Physical characterizations of scanning electron microscopy, X-ray diffraction, and electrochemical measurement methods, such as electrochemical impedance spectroscopy, linear sweep voltammetry, and charge-discharge cycle, proved that the PEO-based composite solid electrolyte CPE20 with 20%ZIF-8 nanoparticles had the lowest resistance, a broader electrochemical stability window, and an activation energy of 8.4×10^-3 eV. At 20 ℃, the conductivity of CPE20 reached 4.9×10^-5 S/cm, which is one order of magnitude higher than that of pure PEO. When the temperature was increased to 70 ℃, the conductivity reached 1.08×10^-3 S/cm. The number of lithium-ion transference of CPE20 increased to 0.46, while that of pure PEO solid electrolyte is 0.36. Thus, the CPE20 preparation of LiFePO₄||Li battery has good capacity and cycle performance at room temperature, with a capacity rate of more than 96%. Therefore, adding an appropriate amount of ZIF-8 inert filler can effectively reduce the crystallinity and increase the amorphous zone of the polymer. It can also promote the dissolution of lithium salts and improve the mobility of lithium ions, which make the composite solid electrolyte has more excellent electrochemical performance. Thus, the findings show that the PEO-based solid polymer electrolytes with ZIF-8 have potential application in solid-state lithium batteries.

Key words: chemical energy storage, electrolytes, polyvinyl oxide, zeolite imidazole skeleton material