Abstract: Iron-substituted cobalt-free lithium-rich manganese-based materials, with advantages of high specific capacity, high safety, and low cost, have been considered as the potential cathodes for lithium ion batteries. However, challenges, such as poor cycle stability and fast voltage fade during cycling under high potential, hinder these materials from commercialization. Here, we developed a method to directly coat LiF on the particle surface of Li_1.2Ni_0.15Fe_0.1Mn_0.55O₂. A uniform and flat film was successfully formed with a thickness about 3 nm, which can effectively protect the cathode material from irreversible phase transition during the deintercalation of Li⁺. After surface coating with 0.5wt% LiF, the cycling stability of Li_1.2Ni_0.15Fe_0.1Mn_0.55O₂ cycled at high potential was significantly improved and the voltage fade was largely suppressed.