Anomalous metal segregation in lithium-rich material provides design rules for stable cathode in lithium-ion battery

Lin, Ruoqian AU - Hu, Enyuan AU - Liu, Mingjie AU - Wang, Yi AU - Cheng, Hao AU - Wu, Jinpeng AU - Zheng, Jin-Cheng AU - Wu, Qin AU - Bak, Seongmin AU - Tong, Xiao AU - Zhang, Rui AU - Yang, Wanli AU - Persson, Kristin A. AU - Yu, Xiqian AU - Yang, Xiao-Qing AU - Xin, Huolin L. PY - Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA | Ruoqian Lin, Mingjie Liu, Qin Wu, Xiao Tong & Huolin L. Xin - Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973, USA | Enyuan Hu, Seongmin Bak & Xiao-Qing Yang - Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China | Yi Wang & Xiqian Yu - Department of Physics and the Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Xiamen University, 361005, Xiamen, China | Hao Cheng & Jin-Cheng Zheng - Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA | Jinpeng Wu & Wanli Yang - Xiamen University Malaysia, 439000, Sepang, Selangor, Malaysia | Jin-Cheng Zheng - Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA | Rui Zhang - Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA | Kristin A. Persson - Department of Materials Science, University of California Berkeley, Berkeley, CA, 94720, USA | Kristin A. Persson

Despite the importance of studying the instability of delithiated cathode materials, it remains difficult to underpin the degradation mechanism of lithium-rich cathode materials due to the complication of combined chemical and structural evolutions. Herein, we use state-of-the-art electron microscopy tools, in conjunction with synchrotron X-ray techniques and first-principle calculations to study a 4d-element-containing compound, Li2Ru0.5Mn0.5O3. We find surprisingly, after cycling, ruthenium segregates out as metallic nanoclusters on the reconstructed surface. Our calculations show that the unexpected ruthenium metal segregation is due to its thermodynamic insolubility in the oxygen deprived surface. This insolubility can disrupt the reconstructed surface, which explains the formation of a porous structure in this material. This work reveals the importance of studying the thermodynamic stability of the reconstructed film on the cathode materials and offers a theoretical guidance for choosing manganese substituting elements in lithium-rich as well as stoichiometric layer-layer compounds for stabilizing the cathode surface.

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