The Impact of Dual‐Salt Electrolyte with Low Fluorine Content on the Performance of Layered Transition Metal Oxides for Sodium‐Ion Batteries

In this work, the characterization of novel electrolytes based on the combination of propylene carbonate (PC) solvent with sodium bis(fluorosulfonyl)imide (NaFSI) and sodium difluoro(oxalato)borate (NaDFOB), as well as their application in sodium-ion batteries (SIBs) is presented. The results show that dual-salt electrolytes have a wide electrochemical stability window, excellent transport properties, and mostly suppress anodic dissolution. When combined with P2-Na_2/3Al_1/9Fe_1/9Mn_2/3Ni_1/9O₂ (P2-AFMNO) cathode electrode for SIBs operating at 4.3 V vs Na⁺/Na, they enable high performance and stability. XPS investigation revealed that this performance is related to the formation of a thin and homogeneous cathode electrolyte interphase (CEI) at the electrode surface.