Curvature engineering unlocks low-potential sodium storage in hard carbon

Hard carbon (HC) anodes exhibiting a distinct low-potential plateau (LPP) are crucial for enhancing the energy density of sodium-ion batteries.We demonstrate that closed-pore formation is governed by carbon-layer bending, underscoring the significance of enhanced curvature. We introduce a cellulose depolymerization–reconstruction strategy that increases carbon-layer curvature and yields closed pores, thereby enabling LPP-dominated Na + storage. The resulting curvature-engineered hard carbon (H-HC) delivers a reversible capacity of 326.66 mAh g -1 at 20 mA g -1 , of which 214.38 mAh g -1 (≈ 65.6%) is attributable to the LPP. By contrast, directly carbonized HC yields a total capacity of 218.96 mAh g -1 with an LPP contribution of 135.18 mAh g -1 at the same current density. This work establishes enhanced carbon-layer curvature as a pivotal design parameter for closed-pore formation and LPP performance, offering guidance for advanced carbon anode design in SIBs.