LiFePO4와 Li4P2O7의 7 Li MAS NMR 특성 연구
7Li MAS NMR studies of Li4P2O7 and LiFePO4 materials
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초록
7Li Magic Angle Spinning(MAS) NMR Spectroscopy를 활용하여 Li4P2O7와 LiFePO4 물질에서7Li 핵의 NMR 특성 및 화합물 분자내의 국부적 구조 연구를 수행하였다. Li4P2O7와 LiFePO4 물질 연구는 리튬이온전지에서 고체-전해질 경계상(SEI, solid-electrolyte interphase) 물질 연구를 위한 것이다. Li4P2O7와 LiFePO4 분말은 고상합성법으로 제조하였다. 7Li MAS NMR 실험은 27oC에서 97oC의 영역에서 변온 실험을 수행하였으며 이는 주변 온도 변화 환경에서 Li4P2O7 물질 내의Li 핵의 구조 변화를 관찰하기 위한 것이다. 7Li MAS NMR 측정 결과 시료 온도가 27oC에서 97oC의 온도 분포 영역에서는 Li4P2O7 물질 내부의 Li 핵은 구조적으로 변화하지 않는 것이 확인되었다. 금번 실험을 통하여 LiFePO4 분말에 5.0 wt%이내로 포함되어있는 Li4P2O7 물질의7Li MAS NMR 신호를 측정할 수 있는 측정 조건을 알았다.
Abstract
7Li Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in Li4P2O7 and LiFePO4 materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of LiFePO4 as cathode material. Li4P2O7 and LiFePO4 were prepared by a solid-state reaction. The 7Li MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in Li4P2O7 system. The 7Li MAS NMR spectra of in Li4P2O7 indicate that the lithium local environments in Li4P2O7 were not changed in the temperature range between 27oC and 97oC. Through this work, we confirmed that the small amount of Li4P2O7 less than 5.0 wt% in LiFePO4 could be clearly measured by the 7Li MAS NMR spectroscopy at high spinning rate over than 11 kHz.
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