Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO4 is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO4O has two redox reactions (V5+/V4+/V3+) but low electrochemical activity. In this study, LiVPO4O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO4O1-xFx, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

1. Introduction
2. Experimental
    2.1 LiVPO4O1-xFx 합성
    2.2 LiVPO4O1-xFx 분석
    2.3 전기화학 셀 평가
3. Results and Discussion
    3.1 합성된 LiVPO4O1-xFx 분석
    3.2 LiVPO4O1-xFx 전기화학 물성 평가
4. Conclusion
Acknowledgement

• 김민경(광운대학교 전자재료공학과) | Minkyung Kim (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea) Corresponding author
• 이동휘(광운대학교 전자재료공학과) | Dong-hee Lee (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea)
• 여찬규(광운대학교 전자재료공학과) | Changyu Yeo (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea)
• 최수연(광운대학교 전자재료공학과) | Sooyeon Choi (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea)
• 최치원(광운대학교 전자재료공학과) | Chiwon Choi (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea)
• 윤현민(광운대학교 전자재료공학과) | Hyunmin Yoon (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Republic of Korea)