New Ion Substitution Method to Enhance Electrochemical Reversibility of Co-Rich Layered Materials for Li-Ion Batteries |
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Authors: | Pilgun Oh Jeongsik Yun Jae Hong Choi Gyutae Nam Seohyeon Park Tom James Embleton Moonsu Yoon Se Hun Joo Su Hwan Kim Haeseong Jang Hyungsub Kim Min Gyu Kim Sang Kyu Kwak Jaephil Cho |
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Institution: | 1. Department of Smart Green Technology Engineering, Pukyong National University, Busan, 48547 Republic of Korea;2. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0245 USA;3. Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919 Republic of Korea;4. Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon, 34057 Republic of Korea;5. Beamline Research Division, Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, 790-784 South Korea |
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Abstract: | The recent development of high-energy LiCoO2 (LCO) and progress in the material recycling technology have brought Co-based materials under the limelight, although their capacity still suffers from structural instability at highly delithiated states. Thus, in this study, a secondary doping ion substitution method is proposed to improve the electrochemical reversibility of LCO materials for Li-ion batteries. To overcome the instability of LCO at highly delithiated states, Na ions are utilized as functional dopants to exert the pillar effect at the Li sites. In addition, Fe-ion substitution (secondary dopant) is performed to provide thermodynamically stable surroundings for the Na-ion doping. Density functional theory calculations reveal that the formation energy for the Na-doped LCO is significantly reduced in the presence of Fe ions. Na and Fe doping improve the capacity retention as well as the average voltage decay at a cutoff voltage of 4.5 V. Furthermore, structural analysis indicates that the improved cycling stability results from the suppressed irreversible phase transition in the Na- and Fe-doped LCO. This paper highlights the fabrication of high-energy Co-rich materials for high voltage operations, via a novel ion substitution method, indicating a new avenue for the manufacturing of layered cathode materials with a long cycle life. |
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Keywords: | Fe doping layered cathode materials lithium-ion batteries Na doping secondary doping |
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