Dual-Functional Chemical Pre-Sodiation of Carbon-Coated Hard Carbon Anodes with Initial Coulombic Efficiency up to 99.5% for Sodium-Ion Batteries

• • The dual-functional pre-sodiation strategy elevates ICE from 54.2% (untreated HC) to 99.5% (pCH4-HC), directly addressing the primary bottleneck for commercial SIB anodes. • • pCH4-HC delivers a high reversible capacity of 321.7 mAh g−1, indicating effective compensation for initial sodium loss and enhanced active site utilization. • • Long-term cycling stability is demonstrated with 74.0% capacity retention after 1000 cycles at 300 mA g−1, underscoring the durability of the NaF-rich SEI. • • Full-cell integration with NFM cathode yields 81.9 mAh g−1 after 100 cycles, proving practical viability for large-scale energy storage applications.