@article{32567,
  author = {Srinivasan Ramakrishnan and Byungchun Park and Jue Wu and Wanli Yang and Bryan D McCloskey},
  title = {Extended Interfacial Stability through Simple Acid Rinsing in a Li-Rich Oxide Cathode Material},
  abstract = {<p><span>Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (&gt;250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO</span><span>2</span><span>&nbsp;and O</span><span>2</span><span>&nbsp;evolution, ∼90% and ∼100% respectively, during the first charge up to 4.8 V vs Li</span><span>+/0</span><span>. CO</span><span>2</span><span>&nbsp;suppression is related to Li</span><span>2</span><span>CO</span><span>3</span><span>&nbsp;removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cycling and rate performance in comparison to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation (“O-redox”) during Li</span><span>+</span><span>&nbsp;removal by a novel&nbsp;</span><em>ex situ</em><span>&nbsp;acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the activation plateau region at around 4.5 V. X-ray photoelectron spectra and Mn L-edge X-ray absorption spectra of the cathode powders reveal a Li</span><span>+</span><span>&nbsp;deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, O K-edge resonant inelastic X-ray scattering shows that the lattice O-redox behavior is largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cycling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.</span></p>},
  year = {2020},
  journal = {Journal of the American Chemical Society},
  volume = {142},
  pages = {8522 - 8531},
  month = {04/2020},
  issn = {0002-7863},
  doi = {10.1021/jacs.0c02859},
  language = {eng},
}