%0 Journal Article
%A Chenxi Wei
%A Yan Zhang
%A Sang-Jun Lee
%A Linqin Mu
%A Jin Liu
%A Chenxu Wang
%A Yang Yang
%A Marca M Doeff
%A Piero Pianetta
%A Dennis Nordlund
%A Xi-Wen Du
%A Yangchao Tian
%A Kejie Zhao
%A Jun-Sik Lee
%A Feng Lin
%A Yijin Liu
%B Journal of Materials Chemistry A
%D 2018
%G eng
%N 45
%P 23055 - 23061
%R 10.1039/C8TA08973F
%T Thermally driven mesoscale chemomechanical interplay in Li <sub>0.5</sub> Ni <sub>0.6</sub>Mn <sub>0.2</sub>Co <sub>0.2</sub>O <sub>2</sub>  cathode materials
%V 6
%8 10/2018
%! J. Mater. Chem. A
%X <p><span>While Li ion batteries are intended to be operated within a mild temperature window, their structural and chemical complexity could lead to unanticipated local electrochemical events that could cause extreme temperature spikes, which, in turn, could trigger more undesired and sophisticated reactions in the system. Visualizing and understanding the response of battery electrode materials to thermal abuse conditions could potentially offer a knowledge basis for the prevention and mitigation of the safety hazards. Here we show a comprehensive investigation of thermally driven chemomechanical interplay in a Li</span><small><span>0.5</span></small><span>Ni</span><small><span>0.6</span></small><span>Mn</span><small><span>0.2</span></small><span>Co</span><small><span>0.2</span></small><span>O</span><small><span>2</span></small><span>&nbsp;(charged NMC622) cathode material. We report that, at the early stage of the thermal abuse, oxygen release and internal Li migration occur concurrently, and are accompanied by mechanical disintegration at the mesoscale. At the later stage, Li protrusions are observed on the secondary particle surface due to the limited lithium solubility in non-layered lattices. The extraction of both oxygen and lithium from the host material at elevated temperature could influence the chemistry and safety at the cell level&nbsp;</span><em>via</em><span>&nbsp;rearrangement of the electron and ion diffusion pathways, reduction of the coulombic efficiency, and/or causing an internal short circuit that could provoke a thermal runaway.</span></p>