Journal of the Korean Electrochemical Society (전기화학회지)

The Korean Electrochemical Society (한국전기화학회)
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Improvement of Structure and Electrochemical Properties of LiNi0.5Mn1.5O4 for High Voltage Class Cathode Material by Cr Substitution

Cr 치환을 이용한 고전압용 양극 활물질 LiNi0.5Mn1.5O4의 구조와 전기화학적 성능의 개선

  • Eom, Won-Sob (Department of Materials Science & Engineering, College of Engineering, Korea University) ;
  • Kim, Yool-Koo (Department of Materials Science & Engineering, College of Engineering, Korea University) ;
  • Cho, Won-Il (Eco-Nano Research Center, Korea Institute of Science and Technology) ;
  • Jang, Ho (Department of Materials Science & Engineering, College of Engineering, Korea University)
  • 엄원섭 (고려대학교 공과대학 신소재공학과) ;
  • 김율구 (고려대학교 공과대학 신소재공학과) ;
  • 조원일 (한국과학기술연구원 나노환경센터) ;
  • 장호 (고려대학교 공과대학 신소재공학과)
  • Published : 2005.05.01
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Abstract

The cathode material, $LiNi_{0.5}Mn_{1.5}O_4$, for high voltage applications of Li-ion batteries exhibits impurity phases due to oxygen deficiency during the high temperature heat treatment. The impurity phase reduces the electrochemical properties of the electrode since the deficiency spinel structure disturbs the lithium ion intercalation and deintercalation. In this study, Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4(0{\leq}x{\leq}0.05)$ powders are synthesized by a sol-gel method in order to reduce the amount of the impurity phases in the $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4$. Thermal analysis of the cathode material shows that the $LiNi_{0.5}Mn_{1.5}O_4$ without Cr substitution looses $2\%$ of its weight due to oxygen deficiency but the amount of weight loss is diminished when Cr is substituted. XRD analysis also supports the reduction of the impurity phases in the cathode after chromium substitution, suggesting that the improvement of the electrochemical properties such as the capacity retention and electrochemical stability are attributed to the low content of impurity phases in the Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4.$

고전압 용 양극산화물 $LiNi_{0.5}Mn_{1.5}O_4$는 고온에서 합성 시, 입자 내에 산소결함에 의한 불순물상을 만들게 된다. 불순물상은 불완전한 스피넬 구조를 형성하며 리튬이온의 삽입$\cdot$탈리를 방해하여 전극의 성능을 감소시킨다. 본 연구에서는 고온 열처리 시 생성되는 이러한 불순물상의 거동을 파악하기 위해 크롬을 치환한 $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4(0{\leq}x{\leq}0.05)$를 졸$\cdot$겔법을 이용하여 합성하여 고온 열분석을 실시하였다. 열분석 결과 크롬이 치환되지 않은 양극활물질은 산소결함에 의한 $2\%$의 무게 감소를 보였으나, 크롬이 치환된 경우 무게 감소분이 줄어들어 불순물 생성이 억제됨을 알 수 있었다. XRD 분석에서도 크롬이 치환된 경우 불순물 상이 억제됨을 나타내었으며 불순물상의 감소로 인해 크롬을 첨가한 양극활물질 $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4$를 사용한 경우 충·방전 실험 시 가역 용량과 싸이클 안정성이 향상됨을 볼 수 있었다.

Keywords

References

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  1. Electrochemical Characteristics of LiNi0.5Mn1.5O4Spinel as 5 V Class Cathode Material for Lithium Secondary Batteries vol.8, pp.4, 2005, https://doi.org/10.5229/JKES.2005.8.4.172