β-Diketone 작용기를 갖는 PEO 계 리튬 이차전지용 고분자 전해질 합성 및 특성

Abstract

Poly (ethylene oxide) is the most widely studied for polymer electrolytes in the lithium secondary battery. However, PEO itself shows low Li+ ion conductivity and can not be used alone as an electrolyte. In this study, PEOs were modified with acetylacetone which was thought to be able to interact very well with Li+ ion via tautomerization. The acetylacetone was reacted with hydroxyl group at the end of PEO chain. PEO used have hydroxyl group either at one end (ACAC-PEG) or at both of the end of the chain (DiACAC-PEG) and are either low molecular weight liquid or high molecular weight solid. The ionic conductivity of liquid ACAC-PEG increased more than twice and that of liquid DiACAC-PEG increased more than three times compared to those of unreacted PEGs. ACAC-PEG (mw:2000) formed a gel when propylene carbonate (PC) was added more than 5μl. When 10μl of PC was added, the ion conductivity of the ACAC-PEG/PC gel increased about 3.5 times. The smaller the molecular weight of electrolyte, the higher the ion conductivity due to the greater mobility of the chain in the liquid and the gel electrolyte. Also both of the liquid electrolyte and the gel electrolyte either DiACAC or ACAC-PEG had higher ionic conductivity than unreacted PEG, which were improved due to the β-diketone functional group having high dipole-ion interaction with lithium ion.