A Trailblazing Quenching Strategy for Simultaneous LiF Formation at Surface and Intergranular Interfaces for Enhanced Stability of High-Ni NCM Cathodes

Water-washing effectively removes surface residual lithium from high-Ni LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) cathodes; however, it inevitably degrades the electrochemical performance. To address this issue, integrated strategies targeting the conversion of surface residual lithium into artificial coating layers on high-Ni NCM cathodes have been proposed; however, these require further processing, thus hindering their industrial application. This study proposes a trailblazing strategy for directly converting residual lithium into a LiF layer simultaneously formed on both the surface of secondary particles and the interfaces between the primary particles of high-Ni NCM, without requiring further processing. This is achieved by modifying the conventional sintering process, with the main change being the replacement of the final air-cooling step with quenching, performed using a fluorinated ketone as a quenching medium. Furthermore, through controlled experiments conducted at various quenching temperatures, the distinct roles of surface and interfacial LiF in influencing the structural stability of high-Ni NCM cathodes are elucidated. Surface LiF primarily prevents electrolyte-induced side reactions, while interfacial LiF plays a crucial role in mitigating microcrack formation. Therefore, the full cell assembled using high-Ni NCM with surface and interfacial LiF layers and a graphite anode demonstrate a stable cycling performance over 300 cycles, highlighting the practical potential of this process.