Atomic scale evolution of the surface chemistry in Li[Ni,Mn,Co]O2 cathode for Li-ion batteries stored in air

TL;DR

This study uses atom probe tomography to analyze the atomic-scale surface chemistry changes in LiNi0.8Mn0.1Co0.1O2 cathodes exposed to air, revealing the formation of Li2CO3 and providing insights into cathode degradation.

Contribution

It introduces atom probe tomography for atomic-scale analysis of cathode surface chemistry evolution in air exposure, which was not previously possible with conventional techniques.

Findings

Li2CO3 forms on the surface after air exposure

Atomic-scale analysis reveals rapid surface chemistry changes

Insights aid in improving cathode synthesis and stability

Abstract

Layered LiMO2 (M = Ni, Co, Mn, and Al mixture) cathode materials used for Li-ion batteries are reputed to be highly reactive through their surface, where the chemistry changes rapidly when exposed to ambient air. However, conventional electron/spectroscopy-based techniques or thermogravimetric analysis fails to capture the underlying atom-scale chemistry of vulnerable Li species. To study the evolution of the surface composition at the atomic scale, here we use atom probe tomography and probed the surface species formed during exposure of a LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material to air. The compositional analysis evidences the formation of Li2CO3. Site specific examination from a cracked region of an NMC811 particle also suggests the predominant presence of Li2CO3. These insights will help to design improved protocols for cathode synthesis and cell assembly, as well as critical knowledge for cathode degradation