Plane selective surface by-product formation and reconstruction mechanisms in Ni-rich cathodes for Li-ion batteries Debasis Nayak a,e , Farheen Sayed b,e , Adam Lovett a,e , Se Hun Joo a,e , Venkat Daramalla c,e , Amogh Mahadevegowda a,e , Caterina Ducati a,e , Ben F. Spencer d , Chris J. Pickard a,e , Clare P. Grey b,e , Siâ n E. Dutton c,e , Judith L. MacManus-Driscoll a,e a Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK, b Department of Chemistry, University of Cambridge, CB2 1EWCambridge, UK, c Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK, d Department of Materials, University of Manchester, M13 9PL, UK, e The Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, UK High Ni-rich layered cathodes, such as; LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) materials, offer very high capacity and excellent rate capability. However, the cyclic performance is poor compared to cathodes with lower Ni content. Due to high surface reactivity, first-cycle irreversibility is high in all these Ni- rich cathodes. Such surface reactions lead to different electrochemically inactive phases and reduce cyclic performance. Herein, we report a comprehensive analysis of plane selective cathode and electrolyte interface reactions and link the relationship between the formation of different cathode-electrolyte interphase (CEI) by- products with surface reconstruction mechanisms. Moreover, we established a guiding principle of coating strategy to enhance plane selective surface properties. Both bulk and thin-film Ni-rich NMC811 electrodes were used to investigate the surface properties. We fabricated epitaxial thin films of Ni-rich NMC811 cathodes of different orientations; (104), (018), and (003), and Al 2 O 3 was chosen as a model coating material to understand how it modulates surface properties. We find that the surface by-products depend highly on the surface charge and subsequent change with Al 2 O 3 coating. Likewise, the surface reconstruction depends on the NMC-811 growth direction and the coating layers exposed to the electrolyte. References 1. R. Hendriks, D.M. Cunha, D.P. Singh, M. Huijben, Enhanced Lithium Transport by Control of Crystal Orientation in Spinel LiMn2O 4 Thin Film Cathodes, ACS Appl. Energy Mater. 1 (2018) 7046–7051. https://doi.org/10.1021/acsaem.8b01477. 2. D.P. Singh, Y.A. Birkhölzer, D.M. Cunha, T. Dubbelink, S. Huang, T.A. Hendriks, C. Lievens, M. Huijben, Enhanced Cycling and Rate Capability by Epitaxially Matched Conductive Cubic TiO Coating on LiCoO 2 Cathode Films, ACS Appl. Energy Mater. 4 (2021) 5024–5033. https://doi.org/10.1021/acsaem.1c00603. 3. D. Kramer, G. Ceder, Tailoring the morphology of LiCoO 2 : A first principles study, Chem. Mater. 21 (2009) 3799–3809. https:// doi.org/10.1021/cm9008943. 4. C. Liang, R.C. Longo, F. Kong, C. Zhang, Y. Nie, Y. Zheng, K. Cho, Ab Initio Study on Surface Segregation and Anisotropy of Ni-Rich LiNi 1–2y Co y Mn y O 2 (NCM) ( y ≤ 0.1) Cathodes, ACS Appl. Mater. Interfaces. 10 (2018) 6673–6680. https://doi. org/10.1021/acsami.7b17424. 5. N.D. Phillip, R.E. Ruther, X. Sang, Y. Wang, R.R. Unocic, A.S. Westover, C. Daniel, G.M. Veith, Synthesis of Ni-Rich Thin-Film Cathode as Model System for Lithium Ion Batteries, ACS Appl. Energy Mater. 2 (2019) 1405–1412. https://doi. org/10.1021/acsaem.8b01982. 6. A.M. Wise, C. Ban, J.N. Weker, S. Misra, A.S. Cavanagh, Z. Wu, Z. Li, M.S. Whittingham, K. Xu, S.M. George, M.F. Toney, Effect of Al 2 O 3 Coating on Stabilizing LiNi 0.4 Mn 0.4 Co 0.2 O 2 Cathodes, Chem. Mater. 27 (2015) 6146–6154. https://doi. org/10.1021/acs.chemmater.5b02952.
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