Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi_0.5Mn_1.5O₄ Cathode for Long-Life Lithium-Ion Batteries

High-voltage spinel LiNi_0.5Mn_1.5O₄ (LNMO) is a promising next-generation cathode material due to its structural stability, high operation voltage, and low cost. However, the cycle life of LNMO cells is compromised by detrimental electrode–electrolyte reactions, chemical crossover, and rapid anode degradation. Here, we demonstrate that the cycling stability of LNMO can be effectively enhanced by a high-energy laser treatment. Advanced characterizations unveil that the laser treatment induces partial decomposition of the polyvinylidene fluoride binder and formation of a surface LiF phase, which mitigates electrode–electrolyte side reactions and reduces the generation of dissolved transition-metal ions and acidic crossover species. As a result, the solid electrolyte interphase of the graphite counter electrode is thin and is composed of fewer electrolyte decomposition products. This work demonstrates the potential of laser treatment in tuning the surface chemistry of cathode materials for lithium-ion batteries.