Reducing Safety Hazards by Optimizing the Morphology of the LiNi0.5Co0.25Mn0.25O2 Cathode Material under Abuse Conditions

Owing to their excellent electrochemical performance, nickel- cobalt-manganese ternary oxide (NCM) cathode materials have been commercially produced at a large scale. However, NCM cathode materials pose significant safety hazards when used in practical applications, particularly under high-rate overcharging conditions. This is mainly reflected in the structural changes and severe gas evolution under abuse conditions, leading to a marked decline in the electrochemical performance of NCM cathodes. To solve this problem, herein, we proposed a morphology optimization strategy. Specifically, we introduced single-crystalline LiNi0.5Co0.25Mn0.25O2 (Ni50) with a larger primary particle size and agglomeration-free morphology. This strategy prevented the decline in electrochemical performance of Ni50 under high-rate overcharge conditions. The gas evolution and structural changes were analyzed in detail by online electrochemical mass spectrometry (OEMS) and in situ X-ray diffraction (XRD) analyses. Combined with other spectroscopy and microscopy results, the large primary particle size can lengthen the Li+ extraction pathways, which could prevent the excessive removal of Li+ from the bulk at high voltage and minimize the extent of structural change. Besides, decreasing the specific surface area of the cathode material inhibited the side reactions at the interphase. Moreover, this agglomeration-free morphology can prevent the microcracks' generation and propagation. This study provides a feasible method for reducing the safety hazards of NCM cathode materials.

Automated summary

This study proposes a morphology optimization strategy to address the safety hazards of NCM cathode materials under high-rate overcharging conditions. By introducing LiNi0.5Co0.25Mn0.25O2 (Ni50) with larger primary particle size and agglomeration-free morphology, the decline in electrochemical performance of Ni50 is prevented. The gas evolution and structural changes are analyzed, and it is found that the larger primary particle size lengthens Li+ extraction pathways and minimizes structural change, while decreasing the specific surface area inhibits side reactions.