Electrolyte Design Enabling a High‐Safety and High‐Performance Si Anode with a Tailored Electrode–Electrolyte Interphase

Silicon (Si) anodes are advantageous for application in lithium‐ion batteries in terms of their high theoretical capacity (4200 mAh g −1 ), appropriate operating voltage (<0.4 V vs Li/Li + ), and earth‐abundancy. Nevertheless, a large volume change of Si particles emerges with cycling, triggering unceasing breakage/re‐formation of the solid‐electrolyte interphase (SEI) and thereby the fast capacity degradation in traditional carbonate‐based electrolytes. Herein, it is demonstrated that superior cyclability of Si anode is achievable using a nonflammable ether‐based electrolyte with fluoroethylene carbonate and lithium oxalyldifluoroborate dual additives. By forming a high‐modulus SEI rich in fluoride (F) and boron (B) species, a high initial Coulombic efficiency of 90.2% is attained in Si/Li cells, accompanied with a low capacity‐fading rate of only 0.0615% per cycle (discharge capacity of 2041.9 mAh g −1 after 200 cycles). Full cells pairing the unmodified Si anode with commercial LiFePO 4 (≈13.92 mg cm −2 ) and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (≈17.9 mg cm −2 ) cathodes further show extended service life to 150 and 60 cycles, respectively, demonstrating the superior cathode‐compatibility realized with a thin and F, B‐rich cathode electrolyte interface. This work offers an easily scalable approach in developing high‐performance Si‐based batteries through Si/electrolyte interphase regulation.