Kinetic Stability of Bulk LiNiO₂ and Surface Degradation by Oxygen Evolution in LiNiO₂-Based Cathode Materials

Capacity degradation by phase changes and oxygen evolution has been the largest obstacle for the ultimate commercialization of high-capacity LiNiO₂-based cathode materials. The ultimate thermodynamic and kinetic reasons of these limitations are not yet systematically studied, and the fundamental mechanisms are still poorly understood. In this work, both phenomena are studied by density functional theory simulations and validation experiments. It is found that during delithiation of LiNiO₂, decreased oxygen reduction induces a strong thermodynamic driving force for oxygen evolution in bulk. However, oxygen evolution is kinetically prohibited in the bulk phase due to a large oxygen migration kinetic barrier (2.4 eV). In contrast, surface regions provide a larger space for oxygen migration leading to facile oxygen evolution. These theoretical results are validated by experimental studies, and the kinetic stability of bulk LiNiO₂ is clearly confirmed. Based on these findings, a rational design strategy for protective surface coating is proposed.

Due to copyright restrictions and/or publisher's policy full text access from Treasures at UT Dallas is limited to current UTD affiliates (use the provided Link to Article).
Lithium ion batteries, Nickel, Nickel oxide, Molecular dynamics, Lithium
International Energy Joint R&D Program (No. 20168510011350) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Ministry of Knowledge Economy, Korean government. This work was also supported by the L&F Co.'s World Class 300 Project of the Korea Institute of Advancement of Technology (KIAT) funded by the Ministry of Trade, Industry and Energy (No. S2483103).
©2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim