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 0.8 Co 0.1 Mn 0.1 O 2 (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.