Synchronously reconfiguring closed pore and interlayer spacing of wood-derived hard carbon via hot-pressing for advanced sodium-ion batteries

Abstract

Biomass-derived hard-carbon materials have attracted considerable interest due to their abundant availability and high sodium storage capacities. However, optimizing the sodium storage performance of these materials requires precise control of the components and microstructure of the biomass. Herein, we report a simple and effective hot-press densification strategy to optimize the closed-pore structure and microcrystalline properties of carbonized wood fiber (CWF), significantly improving the platform capacity and initial coulombic efficiency (ICE) of sodium-ion batteries (SIBs). These results demonstrate that an appropriate hot-pressing treatment promotes the recrystallization of amorphous cellulose in WF, facilitates the decomposition of hemicellulose, and contributes to the formation of more closed pores, larger interlayer spacing, and smaller specific surface area during high-temperature carbonization. Molecular dynamics simulations are employed to elucidate the mechanism by which an increase in defect structures during hot pressing leads to an expansion of the interlayer spacing and an increase in sp² carbon content during pyrolysis. Under the conditions of an initial moisture content of 50% of WF and a pressing pressure of 6 MPa, the densified carbonized wood fibers (DCWF-6) exhibit a high specific capacity of 427.1 mA h g⁻¹ at a current density of 0.1 A g⁻¹, with an ICE of 86%. In addition, they show excellent rate performance, maintaining a specific capacity of 197.7 mA h g⁻¹ at a current density of 4.0 A g⁻¹. This simple, low-cost hot-press densification strategy is highly effective and holds great promise for improving the energy density of SIBs with potential applicability to other biomass precursors.