Unraveling the Composition Effects in Chemo-Mechanical Behavior for Single-Crystal Ni Rich Cathodes

Nickel-rich lithium layered oxides (LiNi x Mn y Co z O2 (NMC), x + y + z = 1, x ≥ 0.6) with high accessible capacity, have received tremendous attention as the most promising cathode candidate for next-generation lithium-ion batteries1. To obtain cathode materials with superior electrochemical performance, substantial efforts have focused on optimizing materials’ chemical compositions. However, regardless of chemical compositions, most commercial NMC materials are typically agglomerates composed of primary nanograins (polycrystalline (PC) NMC) which suffer from severe anisotropic expanding or shrinking and thus rapid mechanical failure in the form of intergranular cracking2. To enhance the structural stability, single crystal (SC) NMC with pore-free and high-strength micron-scale particles have received considerable attention3. Owing to the changes in mechanical properties and degradation mechanisms, uncertainties persist regarding the applicability of established compositional design principles and structural degradation indicators in PC Ni rich cathodes to the newly developed SC counterparts4-5. Here we elucidate the intricate correlation between chemical composition and structural properties in SC Ni-rich cathodes using Co-free and Mn-free cathodes as the models. In this case, Mn and Co exhibit significantly different roles for SC cathodes in electrochemical behaviors compared to their PC analogues. By leveraging multi-scale and high dimensional characterization techniques, we reveal the composition effects in lattice strain generation, phase evolution and microcrack formation. This study deepens understanding of the relationship between chemical composition and chemo-mechanical behaviors for SC Ni rich cathodes, contributing to relevant development of rational design strategies and refined characterization methodology. References M. Li, J. Lu, Z. Chen, K. Amine. Adv. Mater. 2018, 30, e1800561. T. Liu, L. Yu, J. Lu, T. Zhou, X. Huang, Z. Cai, A. Dai, J. Gim, Y. Ren, X. Xiao, M. V. Holt, Y. S. Chu, I. Arslan, J. Wen, K. Amine. Nat. Commun. 2021, 12, 6024. J. Langdon, A. Manthiram. Energy Storage Mater. 2021, 37, 143-160. T. Liu, L. Yu, J. Liu, J. Lu, X. Bi, A. Dai, M. Li, M. Li, Z. Hu, L. Ma, D. Luo, J. Zheng, T. Wu, Y. Ren, J. Wen, F. Pan, K. Amine. Nat. Energy 2021, 3, 277-286. A. Aishova, G-T. Park, C. S. Yoon, Y-K Sun. Adv. Energy Mater. 2020, 10, 1903179.