Non‐Fluorinated Electrolytes Enable Long‐Cycling Micron‐Sized Silicon Anodes

Microsized silicon (µm‐Si) anodes offer lower cost and higher tap density than their nanosized counterparts, however, their practical application remains challenging. A LiF‐rich solid electrolyte interphase (SEI) is widely considered essential for µm‐Si stable operation. However, potential environmental hazards of fluorides challenge the conventional use of lithium salts and additives for constructing LiF‐rich SEIs. Here, we present a non‐fluorinated electrolyte combining inorganic lithium salts (LiI/LiBr) with reduction‐resistant monoether solvents (tetrahydrofuran and hexyl methyl ether) forms a LiF‐free SEI that effectively addresses the rapid capacity fading of µm‐Si anodes. Unlike conventional mosaic‐structured SEI composed of oligomers and inorganic components (LiF and Li 2 O), our electrolyte forms high‐molecular‐weight polymers with binder‐like functionality at the silicon surface, preserving µm‐Si particle integrity and maintaining electrical connectivity even after pulverization. As a result, the µm‐Si electrode (D 50 = 4.65 µm) with an areal capacity of 3.15 mAh cm −2 achieves a Coulombic efficiency exceeding 99.95% and retains 92.12% of its initial capacity after 300 cycles at 0.3°C and 25°C. Furthermore, Li 3.75 Si||SPAN full cells achieve a capacity retention of over 79.43% after 150 cycles. This work provides an unconventional SEI design strategy for µm‐Si anodes.