Pore structure engineering of wood-derived hard carbon enables their high-capacity and cycle-stable sodium storage properties

The pore structural designability of wood-derived hard carbons (WDHCs) lays an optimal foundation for acquiring a cost-efficient and green anode material for sodium-ion batteries. Here, a WDHCs material was reported for high-capacity and cycling-stable sodium storage through a pore forming-opening strategy. Associated with the natural holey texture of wood, the WDHCs displays a hierarchical pore structure by a precise chemical treatment and a high-temperature carbonization, creating the straight channels and plentiful closed nanopores. This well-constructed channel structure is conducive to the penetration of electrolyte and the transport of sodium ions. The closed nanopores constructed by the curved graphene layers are gradually unfolded upon cycling, thus providing higher reversible capacity in the platform zone. The surface-controlled pseudocapacitive reaction favored ultrafast ion transport mainly contributes to sodium storage capacity. As a result, the developed optimal anodes harvest a high sodium storage capacity of 439 mAh g−1 at 0.1 A g−1, and excellent long-term cycling stability of 248 mA h g−1 at 0.1 A g−1 over 500 cycles as well as the capacity retention close to 100%. The galvanostatic intermittent titration technique combined with electrochemical impedance spectroscopy proved that the WDHCs anode has fast charge transport kinetics, thus exhibiting excellent rate performance.