A long pursuit in developing high-energy batteries is the prognosis and improvement of thermal stability. Here, we report new understandings of the thermo-chemical transformation mechanism of delithiated Ni-rich cathodes at different length scales. Our in situ measurements resolve the dynamic thermo-chemical interactions inside delithiated particles, illustrating the correlation between thermal performance and spatial distribution of various thermo-chemical interactions. Statistical analyses of thermally active and sluggish regions in cathode particles show that these minority regions govern thermal stability. We propose effective strategies to manipulate thermo-chemical interaction dynamics and to minimize the propagation of thermally active regions in these battery materials.
