Low-Defect Carbon Host Enabling Robust Zero-Excess Sodium Metal Batteries Without Presodiation

Zero-excess Na metal batteries offer transformative potential for future energy-dense, low-cost energy storage, yet face aggravated cycling/rate deterioration due to irrecoverable Na⁺ depletion. While state-of-the-art sodiophilic carbon hosts enable highly reversible plating/stripping with impressive stability, they rely heavily on artificial presodiation to offset irreversible Na⁺ consumption by sodiophilic defective sites, a fundamental barrier to practical zero-excess configurations. Here, we propose a low-defect carbon host (LDCH) that eliminates the need for presodiation while maintaining exceptional sodiophilicity even at high charging rates. Mechanistic studies show that LDCH operates primarily through a low-potential plateau storage mechanism, which enhances Na affinity, reduces the nucleation barrier, and suppresses irreversible Na⁺ loss by 4.67 times compared to defective counterparts. Crucially, LDCH circumvents the sodiophobic transition observed in defect-rich carbon counterparts under fast-charging operation, attributed to hidden sodiophilic seed sites near 0 V with rapid kinetics. The resulting zero-excess Na metal battery achieves an unprecedented 84.6% initial Coulombic efficiency without pre-cycling (vs. 66.1% for defective hosts), delivers an energy density of 281.1 Wh kg⁻¹, 75% capacity retention after 110 cycles and 5 C fast charging, representing a breaking combination of energy/durability/rate. This low-defect engineering strategy redefines carbon host design principle, resolving the long-standing presodiation dilemma in zero-excess sodium metal batteries.