Understanding the nucleation and growth of the degenerated surface structure of the layered transition metal oxide cathodes for lithium-ion batteries by operando Raman spectroscopy

The well-defined layered structure for Li+ (de)intercalation of transition metal oxide cathodes plays a crucial role in delivering high capacity for lithium-ion batteries. Therefore, structural deformations of the layered structure are often considered as the evidence of deterioration in the battery performance and stability. In this study, the surface degradation mechanism of the layered LiNi1/3Co1/3Mn1/3O2 cathode is examined on charge-discharge using an operando Raman cell. We revealed the surface degradation process of the cathode with the A1g Raman spectral window (similar to 600 cm(-1)) in the voltage range of 2.8-4.35 V, and proposed the nucleation-merging mechanism. The spectral shifts and mappings have been compared between the early-stage and later-stage cycles (>= 15 cycles). It has been identified that the degradation process not only involves the structural changes (i.e., nucleation of the degenerated layers), but also the growth/merging between the degenerated layers during charge and discharge. This observation provides key information on how the reconstructed surface can expand during cycling.

Automated summary

In this study, the surface degradation mechanism of the layered LiNi1/3Co1/3Mn1/3O2 cathode was examined using an operando Raman cell. It was found that the degradation process involves nucleation of degenerated layers and growth/merging between the degenerated layers during charge and discharge, providing key information on how the reconstructed surface can expand during cycling.