반응성 무기물을 포함하는 분리막으로 제조된 리튬폴리머전지의 전기화학적 특성

Abstract

소형 에너지 저장장치에서 많이 사용되고 있는 리튬이차전지는 전기 자동차 등의 발달로 중대형화 수요가 증가함에 따라 고용량과 안정성에 대한 관심이 높아지고 있다. 본 연구에서는 누액과 화재의 위험이 없는 겔 폴리머 전지를 사용하여 안전성과 수명특성을 향상시킨 전지를 제조하고자 하였다. 제 1장에서는 음극에 주로 사용되는 리튬메탈 전극은 높은 용량과 작동 전압을 갖는 장점이 있지만 리튬 덴드라이트를 형성하여 사이클 성능을 열화시키고 단락을 가져올 수 있다는 단점이 있어 리튬파우더전극을 사용하여 전류밀도를 낮춰 덴드라이트 성장을 억제하고자 하였다. 여기에 겔 폴리머 전해질과 반응성 무기물을 포함하는 복합 분리막을 함께 사용하여 계면 안정성을 향상시킨 장수명의 이차 전지를 제조하였다. 높은 용량을 갖는 LiV3O8 양극을 이용하여 충•방전 테스트를 진행해본 결과 300 회 사이클에서 안정된 용량 특성을 보이는 전지를 제조할 수 있었으며 리튬 덴드라이트를 효과적으로 억제할 뿐만 아니라 300 회 충•방전 과정 이후에도 파우더 모양을 유지하고 있음을 확인하였다. 또한 LiTFSI 염을 사용했음에도 겔 폴리머 전해질과 복합 분리막이 알루미늄 집전체 부식현상을 줄여 사이클 수명을 향상시켰다. 제 2장에서는 반응성 무기물로 구성된 복합 분리막으로 리튬이온폴리머전지를 제조하여 전기화학적 특성 변화를 고찰하였다. 표면에 이중 결합기를 갖는 구형의 반응성 무기물은 인시츄 라디칼 가교 반응이 가능하여 가교제와 가교 반응을 할 수 있으므로 복합 분리막 위에 효과적인 유-무기 하이브리드 복합층을 형성하여 전지 조립 과정이나 반복되는 충•방전과정 동안에도 분리막 위에서 견고하게 유지될 수 있다. Graphite/LiNi1/3Co1/3Mn1/3O2 전지를 제조하여 상온 및 고온에서 충•방전 테스트를 진행한 결과, 반응성 무기물을 이용함으로써 전지의 열적 안정성 향상 및 안정한 계면이 형성되고, X-ray photoelectron spectroscopy (XPS) 분석을 통해 HF scavenger 의 역할을 확인하였다. 이로 인해 복합 분리막과 겔 폴리머 전해질을 사용한 전지는 상온 및 고온에서의 수명특성이 향상됨을 보여주었다.|Rechargeable Li-ion batteries are important components of the mobile, portable, computing equipment. The demand for high energy battery system for electric vehicles and energy storage system has increased. So, the issue of safety and high capacity electrode is an interesting field. In this study, gel polymer electrolyte used to improve safety and cycle life of lithium-ion batteries. Lithium metal as an anode is the most electropositive as well as the lightest metal, thus facilitating the storage systems with high energy density. However, the use of lithium metal electrode has been limited by the occurrence of dendrite growth during repeated charge and discharge cycles, since it gives rise to safety problems and gradual degradation of cycling efficiency. In chapter 1, to suppress of dendritic formation, we use lithium powder electrode system that has higher surface area than lithium metal. Gel polymer electrolyte and composite separator containing reactive inorganic particles was used together to improve interfacial stability and attenuate aluminum current collector corrosion. The lithium polymer cells composed of a lithium powder anode, a cross-linked gel polymer electrolyte and a LiV3O8 cathode, were assembled and their cycling performance was evaluated. In chapter 2, the composite separator composed of reactive inorganic particles was investigated for improving lithium-ion polymer batteries performances. The reactive inorganic particles containing reactive vinyl groups that permit the in-situ radical cross-linking reaction are synthesized with uniform spherical shape. Not only inorganic particles can react with gel polymer precursors, also form effective organic-inorganic hybrid composite polymer layers on the composite separator. Therefore, the inorganic particles are well attached on the separator during cycling process. Compared to a polyethylene separator, the composite separator help stabilize the electrode/electrolyte interface during repeated cycling at both room temperature and high temperature. Stable composite layer and HF scavenger ability of reactive inorganic particles attributed to the improvement of cyclic performance of lithium-ion polymer batteries (graphite/LiNi1/3Co1/3Mn1/3O2) assembled with composite separator.; Rechargeable Li-ion batteries are important components of the mobile, portable, computing equipment. The demand for high energy battery system for electric vehicles and energy storage system has increased. So, the issue of safety and high capacity electrode is an interesting field. In this study, gel polymer electrolyte used to improve safety and cycle life of lithium-ion batteries. Lithium metal as an anode is the most electropositive as well as the lightest metal, thus facilitating the storage systems with high energy density. However, the use of lithium metal electrode has been limited by the occurrence of dendrite growth during repeated charge and discharge cycles, since it gives rise to safety problems and gradual degradation of cycling efficiency. In chapter 1, to suppress of dendritic formation, we use lithium powder electrode system that has higher surface area than lithium metal. Gel polymer electrolyte and composite separator containing reactive inorganic particles was used together to improve interfacial stability and attenuate aluminum current collector corrosion. The lithium polymer cells composed of a lithium powder anode, a cross-linked gel polymer electrolyte and a LiV3O8 cathode, were assembled and their cycling performance was evaluated. In chapter 2, the composite separator composed of reactive inorganic particles was investigated for improving lithium-ion polymer batteries performances. The reactive inorganic particles containing reactive vinyl groups that permit the in-situ radical cross-linking reaction are synthesized with uniform spherical shape. Not only inorganic particles can react with gel polymer precursors, also form effective organic-inorganic hybrid composite polymer layers on the composite separator. Therefore, the inorganic particles are well attached on the separator during cycling process. Compared to a polyethylene separator, the composite separator help stabilize the electrode/electrolyte interface during repeated cycling at both room temperature and high temperature. Stable composite layer and HF scavenger ability of reactive inorganic particles attributed to the improvement of cyclic performance of lithium-ion polymer batteries (graphite/LiNi1/3Co1/3Mn1/3O2) assembled with composite separator.