Thermal stress-induced charge and structure heterogeneity in emerging cathode materials

Thermal stress-induced charge and structure heterogeneity in emerging cathode materials

TitleThermal stress-induced charge and structure heterogeneity in emerging cathode materials
Publication TypeJournal Article
Year of Publication2019
AuthorsJudith Alvarado, Chenxi Wei, Dennis Nordlund, Thomas Kroll, Dimosthenis Sokaras, Yangchao Tian, Yijin Liu, Marca M Doeff
JournalMaterials Today
Date Published12/2019
ISSN13697021
Abstract

Nickel-rich layered oxide cathode materials are attractive near-term candidates for boosting the energy density of next generation lithium-ion batteries. The practical implementation of these materials is, however, hindered by unsatisfactory capacity retention, poor thermal stability, and oxygen release as a consequence of structural decomposition, which may have serious safety consequences. The undesired side reactions are often exothermic, causing complicated electro-chemo-mechanical interplay at elevated temperatures. In this work, we explore the effects of thermal exposure on chemically delithiated LiNi0.8Mn0.1Co0.1O2 (NMC-811) at a practical state-of-charge (50% Li content) and an over-charged state (25% Li content). A systematic study using a suite of advanced synchrotron radiation characterization tools reveals the dynamics of thermal behavior of the charged NMC-811, which involves sophisticated structural and chemical evolution; e.g. lattice phase transformation, transition metal (TM) cation migration and valence change, and lithium redistribution. These intertwined processes exhibit a complex 3D spatial heterogeneity and, collectively, form a valence state gradient throughout the particles. Our study sheds light on the response of NMC-811 to elevated temperature and highlights the importance of the cathode‚Äôs thermal robustness for battery performance and safety.

DOI10.1016/j.mattod.2019.11.009
Short TitleMaterials Today
Refereed DesignationRefereed