Lewis Acid‐Enabled Functional SEI/CEI Design for Durable Lithium Metal Batteries

The development of practical lithium metal batteries requires facile strategies that simultaneously stabilize anode and cathode interfaces while eliminating their native surface oxides. However, the reported research could rarely achieve this dual functionality. Herein, we have developed a dual‐side‐modification strategy using tributylphosphonium tetrafluoroborate (TBPFB) as a Lewis acid to synchronously eliminate the heterogeneous native oxide layers and reconstruct multifunctional inorganic interfaces on both the cathode and anode. The constructed artificial interface on the lithium anode contains LiF, LiBO 2 , Li 3 P, and Li 3 PO 4 , boosting the anode stability by reducing the Li + desolvation barrier and enabling uniform Li + transport. Meanwhile, the LiF‐rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode interface suppresses side reactions and particle cracking, protecting the cathode from transition metal dissolution. Based on the benefits brought by the multifunctional interfaces, the Li||Li symmetric cells achieve a cycling lifespan of over 1700 h, while the Li||NCM811 full cells retain 77% capacity after 500 cycles. Additionally, a 2 Ah pouch cell with an energy density of 423.1 Wh kg −1 maintains over 90% capacity after 100 cycles. This work provides a simple but highly efficient surface modification strategy that stabilizes the most critical interfaces in lithium metal batteries.