Dual-Topology-Driven Oxygenated Lattice Memory and Carbon-to-Oxygen Substitution Enable Graphite-like Subcrystalline Carbon for Na-Ion Batteries

The development of high-energy-density Na-ion batteries (NIBs) remains critically constrained by current hard carbon anodes, which suffer from low initial Coulombic efficiency (ICE) and limited plateau capacity. These limitations stem from their turbostratic structures, pervasive defects, and abundant oxygen-containing functional groups. This underscores the urgent need for graphite-mimetic carbons featuring enlarged (002) interlayer spacing, a design principle inspired by graphite's evolutionary replacement of hard and soft carbons in Li-ion batteries (LIBs). Here, we report a dual-topology-directed synthesis of graphite-like subcrystalline carbon (GLSC) via the synergistic effect of graphite crucible induction and coconut shell's 3D ordered skeletons. This synthesis process is driven by three critical steps: preserving the 3D ordered skeleton during low-temperature induction, manifesting the oxygenated lattice memory effect during the 3D ordered skeleton-to-2D lamellar structure transformation at medium-temperature, and realizing carbon-to-oxygen substitution with lattice repair at high-temperature. The resulting GLSC features a subcrystalline structure composed of nearly parallel carbon sheets, exhibiting a large (002) interlayer spacing of 3.65-3.97 Å. This characteristic distinguishes GLSC from graphite and hard carbon, enabling reversible Na⁺ intercalation/deintercalation. In 10 half-cell tests, GLSC electrodes achieved high ICE values (93.2-95.0%) and charge capacities (326.3-335.6 mAh g^-1) at 20 mA g^-1. Notably, the performance superiority of GLSC over hard carbon became more pronounced with increasing current density (e.g., 86.3% vs 40.6% ICE, 122.9 vs 56.5 mAh g^-1 charge capacity at 300 mA g^-1). Furthermore, GLSC exhibited extended low-potential plateau characteristics (similar to graphite in LIBs) in half-cell tests, enabling superior full-cell performance.