Revealing Relationships between Surface Facets and Performance of LiNiO2 Cathodes

Abstract

Ni-rich layered oxides with a general formula of LiNi1-xMxO2 (M = Mn, Co, Al etc.) are currently considered the most promising cathode materials for lithium-ion batteries (LIBs). In order to further increase energy density, higher Ni content is desirable. Previous studies, however, showed that surface-related degradation reactions become more severe with increasing Ni content, especially at high operating voltages.2 Recent theory work has suggested that surface facets play an important role in the reactivities between LiNiO2 (LNO) and the electrolyte.3 Experimental understanding of the overall relationships between Ni-rich oxide surface and reactivities, on the other hand, is largely missing.In this study, we synthesized single-crystal LiNiO2 with different shapes and surface orientations, including Cubic with predominately (104)-family surfaces, Octahedron with predominately (012)-family and Truncated-polyhedron with mixed (001)-, (104)- and (012)-family surfaces. Note that synthesis of Ni-rich layered oxides with dominating (104) surfaces was not reported previously. We found that the Cubic-LNO sample consistently outperformed all other samples in terms of cycling stability and thermal stability, confirming (104) surface is preferrable for LNO cathodes with better cycle life and thermal safety. Our study not only identifies the optimal particle surface but also provides design insights for future development of Ni-rich layered oxide cathodes. References Bianchini, M.; Roca-Ayats, M.; Hartmann, P.; Brezesinski, T.; Janek, J., There and Back Again -The Journey of LiNiO2 as a Cathode Active Material. Angewandte Chemie International Edition 2019, 58 (31), 10434-10458.Liang, L.; Zhang, W.; Zhao, F.; Denis, D. K.; Zaman, F. u.; Hou, L.; Yuan, C., Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies. Advanced Materials Interfaces 2019, 7 (3), 1901749.Cho, E.; Seo, S.-W.; Min, K., Theoretical Prediction of Surface Stability and Morphology of LiNiO2 Cathode for Li Ion Batteries. ACS Applied Materials & Interfaces 2017, 9 (38), 33257-33266.