Anion-Derived Passivation Interphases for Anti-corrosion Na Metal and Hard Carbon Hybrid Anode of Sodium Batteries

Sodium batteries hold great promises for energy storage due to material abundance yet fall short in energy density. Hybrid anodes integrating sodium metal and hard carbon (HC) boost energy density yet face poor aging stability. Herein, we report a NaFSI/1,2-dimethoxyethane (DME)-1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) electrolyte, which enhances both anode and cathode interfacial stability via anion-derived interphases, mitigating hybrid anode corrosion and preserving cathode structural integrity during high voltage cycling. Consequently, the full cell with a high loading cathode (1.68 mAh cm –2 ) and limited Na inventory (N/P = 1.91) achieves 87.98% capacity retention after 200 cycles at 0.33 C and 99.82% average Coulombic efficiency. Notably, under intermittent cycling (24 h rest every 3 cycles), it retains 81.19% capacity after 100 cycles, outperforming conventional electrolytes that fail at ∼75 cycles. This study proposes an anti-corrosion electrolyte to realize hybrid sodium batteries with superior cycling longevity, providing insights into high energy density metal/ion batteries.