Deriving Stable SEI Layer and Preventing Aluminum Current Collector Corrosion via Preferential Decomposition of Concentrated Lithium Salt for Lithium‐Ion Batteries

ABSTRACT Among promising lithium salts for electrolyte in lithium‐ion batteries (LIBs), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) forms a more stable inorganic‐rich SEI layer. However, its implementation is limited by severe aluminum current collector corrosion. Since lithium hexafluorophosphate (LiPF 6 ) contributes a stable passivation layer for aluminum, a simply‐mixed LiPF 6 ‐LiTFSI dual‐salt electrolyte offers reduced corrosion. However, its corrosion inhibition capability is not complete. Herein, we propose a SEI‐stabilizing and corrosion‐preventing layer (SCL) that realizes spatial separation of salts, which confines concentrated LiTFSI within a polyethylene glycol dimethacrylate (PEGDMA) network at the anode‐LiPF 6 electrolyte interface. The locally high concentration of LiTFSI in SCL induces a kinetic preference that overrides the thermodynamic preference of LiPF 6 , which enables targeted decomposition of LiTFSI to form a robust SEI layer, while using only a small amount of LiTFSI. Furthermore, SCL demonstrates excellent corrosion‐inhibiting behavior compared to a simply‐mixed LiPF 6 ‐LiTFSI dual‐salt electrolyte. Consequently, SCL enables stable cycling of high‐loading (21.4 mg cm −2 ) practical NCM811/graphite full cells with 93.57% capacity retention after 100 cycles at a high current density of 2.2 mA cm −2 . This strategy enables selective electrochemical reactions through spatial confinement to enhance LIB performance, while suppressing side reactions and reducing costs, providing a scalable approach for next‐generation electrolyte design.