PNNL

Abstract

Electrochemical driven functioning of battery inevitably induces thermal and mechanical effects, which in turn couple with the electrochemical effect and collectively govern the performance of the battery. However, such a coupling effect, favorable or detrimental, has never been explicitly vindicated. Here, for the first time, we use in-situ transmission electron microscopy to demonstrate such a coupling effect. We discover that supplying a thermal perturbation to the delithiated LiNi0.6Mn0.2Co0.2O2 will trigger the explosive nucleation and propagation of intragranular cracks in the lattice, providing us a unique chance to directly visualize the cracking mechanism and dynamics. We reveal that thermal stress associated with electrochemically induced phase-inhomogeneity and internal-pressure due to oxygen evolution are the primary driving forces for the intragranular cracking, resembling a “popcorn” fracture mechanism. The present work unveils that, for battery performance, the intricate coupling of electrochemical, thermal and mechanical effects will surpass the superposition of individual effect.