• • The U-HC sample achieves an ICE of 89.84% and a discharge capacity of 354.18 mAh g⁻¹ at 35 mA g⁻¹, surpassing baseline PF-derived hard carbons (ICE ≤82%) and marking a >7% absolute improvement—critical for reducing first-cycle capacity loss in commercial SIB cells.
• • Pore-forming modification elevates ICE beyond 86% for all modified samples, directly addressing the irreversible sodium trapping that plagues conventional hard carbon anodes and enabling higher usable energy density.
• • The highest solid-content phenolic resin (U-HC) yields the best electrochemical performance, establishing a clear correlation between precursor solid content and ICE, which provides a scalable selection criterion for industrial precursor procurement.
• • The protocol combines pore-forming agents, cross-linking curing, and ball-milling, demonstrating a reproducible route to tune pore architecture; this is essential for manufacturing consistency, as ICE variations of even 2–3% can significantly impact cell balancing and cost.