Dominant Lithium‐Ion Conduction and Desolvation Regulation Enabled by Lithiated Monodisperse Nanospheres Composite Separator for High‐Nickel Lithium Batteries

Commercial polyolefin (PE) separators are incompatible with high‐energy lithium metal batteries (LMBs) with high‐nickel cathodes, owing to their poor electrolyte wettability, low desolvation efficiency, and severe polarization. Herein, a sulfonated‐lithiated melamine‐formaldehyde (MFSO) nanospheres functionalized PE separator (MFSO@PE) is developed. The MFSO@PE separator has excellent wettability for the electrolyte; the triazine rings, amine groups, and sulfonic acid groups () in the MFSO act as effective Li + ‐affinitive sites. A synergistic regulation mechanism was revealed: the outer facilitates Li + desolvation, while the inner N‐rich framework provides weak coordination to lower desolvation energy. Furthermore, the effectively repels anions, alleviating concentration polarization and increasing the Li + transference number. Consequently, the composite separator enables Li||Li symmetric cells to operate stably for 2000 h. In Li||NCM811 cells, the MFSO@PE separator achieved 800 stable cycles at 3 C with a low‐capacity decay rate of 0.031% per cycle, while high‐loading graphite||NCM811 cells maintain 80% capacity (137.2 mAh g −1 ) after 1000 cycles at 1 C. Moreover, the MFSO@PE separator effectively captures Ni, Co, and Mn ions and prevents them from migrating to the anode. This work presents a dominant Li + conduction and desolvation regulation nanosphere‐based coating strategy for high‐rate, long‐life high‐nickel batteries.