Enhancing Lithium‐Ion Battery Performance With Ultra‐Thin LiF Coating: A Study on Surface Vapor Deposition for LiNi_0.9Co_0.05Mn_0.05O₂ Cathode Material Stabilization

ABSTRACT High‐nickel ternary cathode (HNCM) materials are regarded as the primary choice for lithium‐ion batteries (LIBs) due to their high energy density. However, their development is limited by lithium–nickel mixing, microcrack generation, and surface side reactions. Herein, a combined roll‐to‐roll and vacuum vapor deposition process is used to prepare LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM9055) cathode material with a dense, ultrathin, and robust lithium fluoride (LiF) protective layer. Compared with traditional methods, this approach allows precise control over the thickness and rate of the deposited LiF layer, producing a uniform and robust protective layer that enhances surface stability. This approach not only effectively reduces direct contact between the electrolyte and the electrode surface, mitigating corrosion and side reactions, but also strengthens the structural integrity of the cathode, thereby significantly improving cycling stability. The NCM9055 with a 10 nm LiF layer exhibits enhanced electrochemical performance, especially at cut‐off voltages of 4.3 and 4.5 V, and also excellent cycling performance at 1 C. Additionally, the introduction of the LiF layer improves the thermal stability of NCM9055, further enhancing the safety of high‐nickel batteries. This study not only demonstrates the combination of roll‐to‐roll processing and vacuum vapor deposition as a fast and effective modification technique but also highlights the advantages of vacuum vapor deposition in forming a homogeneous and robust LiF layer, which is essential for rapid production and for improving the safety and energy density of HNCM materials in advanced LIBs.