Journal of the Korean Electrochemical Society (전기화학회지)

The Korean Electrochemical Society (한국전기화학회)
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Effect of Electrode Design on Electrochemical Performance of Highly Loaded LiCoO2 Positive Electrode in Lithium-ion Batteries

리튬이온 이차전지용 고로딩 LiCoO2 양극의 전극설계에 따른 전기화학적 성능연구

  • Kim, Haebeen (Graduate School of Knowledge-Based Technology and Energy, Korea Polytechnic University) ;
  • Ryu, Ji Heon (Graduate School of Knowledge-Based Technology and Energy, Korea Polytechnic University)
  • 김해빈 (한국산업기술대학교 지식기반기술.에너지대학원) ;
  • 류지헌 (한국산업기술대학교 지식기반기술.에너지대학원)
  • Received : 2020.03.23
  • Accepted : 2020.04.26
  • Published : 2020.05.31
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Abstract

Highly loaded LiCoO2 positive electrodes are prepared to construct high-energy density lithium-ion batteries, their electrochemical performances are evaluated. For the standard electrode, a loading of about 2.2 mAh/㎠ is used, and for a high-loading electrode, an electrode is manufactured with a loading level of about 4.4 mAh/㎠. The content of carbon black as electronic conducting additive, and the porosity of the electrode are configured differently to compare the effects of electron conduction and ionic conduction in the highly loaded LiCoO2 electrode. It is expected that the electrochemical performance is improved as the amount of the carbon black increases, but the specific capacity of the LiCoO2 electrode containing 7.5 weight% carbon black is rather reduced. When the conductive material is excessively provided, an increase of electrode thickness by the low content of the LiCoO2 active material in the same loading level of the electrode is predicted as a cause of polarization growth. When the electrode porosity increases, the path of ionic transport can be extended, but the electron conduction within the electrode is disadvantageous because the contact between the active material and the carbon black particles decreases. As the electrode porosity is lowered through the sufficient calendaring of the electrode, the electrochemical performance is improved because of the better contact between particles in the electrode and the reduced electrode thickness. In the electrode design for the high-loading, it is very important to construct the path of electron conduction as well as the ion transfer and to reduce the electrode thickness.

고에너지 밀도의 리튬이온 이차전지를 구성하기 위하여 고로딩 LiCoO2 양극을 구성하였으며, 이의 전극설계를 다르게 하며 전기화학적 특성을 비교하였다. 기준로딩을 적용한 전극의 경우 약 2.2 mAh/㎠의 로딩값을 가지도록 하고, 고로딩 전극의 경우 약 4.4 mAh/㎠의 로딩값을 가지도록 전극을 제조하였다. 이때 도전재인 카본블랙의 함량과 전극의 기공도를 다르게 구성하여 전극 내의 전자전도도와 이온전도도가 고로딩 전극의 성능에 주는 영향을 비교하였다. 도전재의 함량이 증가할수록 전기화학적 성능이 향상될 것으로 기대하였으나, 도전재의 함량이 7.5 질량%까지 증가하게 되면 오히려 성능의 저하가 발생하였다. 이는 도전재가 충분히 제공된 경우에는, 동일한 로딩의 전극구성에서 활물질인 LiCoO2 구성비의 감소로 인해 전극두께가 증가하기 때문에 이로 인한 분극증가가 원인으로 판단된다. 그리고 전극의 기공도를 증가시키게 되면 이온전달의 경로는 확장될 수 있으나, 입자들 간의 접촉이 저하되고 전극의 두께가 증가하기 때문에 전극 내 전자전달은 불리하게 된다. 따라서, 전극의 압착을 강하게 하여 기공도를 낮출수록 전자전달이 개선되어 전지의 성능이 향상되었다. 고로딩 전극의 제조에 있어서는 전자전달의 경로를 충분히 확보하면서 전극두께를 감소시키는 전극설계가 필요하다.

Keywords

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