Pseudo Graphitic Mesoporous Hard Carbon via Rapid Pyrolysis for Advanced Sodium-Ion Battery Anodes

Biomass-derived hard carbons (HCs) are promising anode materials for sustainable and cost-effective sodium-ion batteries (SIBs). However, they usually suffer with low initial coulombic efficiency (ICE) and poor cycling stability due to structural defects and non-uniform pore distribution. In addition, the traditional pyrolysis methods are often energy-intensive and time-consuming, contributing significantly to a carbon footprint. Here, we have developed rapid and efficient microwave-pyrolysis processes to produce pseudo graphitic hard carbon (GHC) using pine wood waste (construction waste). The direct localized microwave-heating results in pseudo graphitized crystalline HC with enlarged interlayer spacing (0.345 nm) and closed mesoporous structure, helping to facilitate the reversible storage of sodium ions. As an anode material, the GHC exhibited a remarkable reversible capacity of 401 mAh/g, along with an impressive ICE of 72%, which is notably higher than that of other biomass-derived HCs produced via conventional pyrolysis methods. Furthermore, full-cell was assembled using GHC as anode and Na 3 V 2 (PO 4 ) 3 (NVP) as cathode for SIB and activated carbon (AC) for sodium-ion capacitors (SIC). Both systems exhibited excellent specific energy and power, along with good cycling stability. Moreover, Density functional theory (DFT) calculations further elucidate the electronic structure of GHC and confirm the favourable Na adsorption and intercalation behaviour associated with the optimized interlayer spacing. This work highlights the potential of microwave-assisted pyrolysis as a scalable and sustainable approach for converting biomass into high-performance HC anodes, paving the way for next-generation sodium-ion energy storage technologies.