Origin of environmentally structural susceptibility of nickel-based layered oxide cathodes

Environmental susceptibility is an intrinsic property associated with the handling and storage process of nickel-based layered oxide materials in ambient air, which combines with electrochemical factors to determine the cathode performance. Nonetheless, the mechanism underlying such environmental effect has not been well elucidated yet. In this work, using atomic-resolution imaging and spectroscopy, we discover that chemical desodification of Ni-based sodium oxides upon air-exposure triggers extensive initiation and propagation of intragranular cracks along the a-b plane in the lattice, which is distinct from the dense interphase layer for chemically delithiated Ni-based lithium oxides. We rationalize that the diverse environmental susceptibility of Ni-based layered oxides is dictated by Li/Na chemical reaction-diffusion-induced structural evolution or failure, based on the ab initio calculation and numerical kinetic modeling. The established correlation between reaction-diffusion-induced stress fields and structural changes provides new visions for developing high energy and high stability Ni-based layered cathode materials.