@article{32499,
  author = {Judith Alvarado and Chenxi Wei and Dennis Nordlund and Thomas Kroll and Dimosthenis Sokaras and Yangchao Tian and Yijin Liu and Marca M Doeff},
  title = {Thermal stress-induced charge and structure heterogeneity in emerging cathode materials},
  abstract = {<p><span>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 LiNi</span><span>0.8</span><span>Mn</span><span>0.1</span><span>Co</span><span>0.1</span><span>O</span><span>2</span><span>&nbsp;(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’s thermal robustness for battery performance and safety.</span></p>},
  year = {2019},
  journal = {Materials Today},
  month = {12/2019},
  issn = {13697021},
  doi = {10.1016/j.mattod.2019.11.009},
  language = {eng},
}