Engineered microstructure design of petroleum asphalt-derived hard carbon via dual chemical modification: process optimization for advanced sodium-ion battery anodes

Petroleum asphalt, featuring abundant resources, good structural stability and low cost, presents great potential as a precursor for high-value added materials. However, the ordered carbon layer structure and few surface defects in direct carbonized asphalt leads to poor Na⁺ storage capacity and rate performance. Herein, we develop a novel dual chemical modification strategy combining HNO₃ oxidation and MgSO₄ template liquid phase oxidized-formwork asphalt hard carbon (LOAHC@MgSO₄) with excellent Na⁺ storage property. The C=O groups and MgSO₄ template effectively inhibit the growth of carbon layer, promote the transformation of asphalt hard carbon material into disordered low-graphitized structure and open-closed pores. The LOAHC@MgSO₄ capacity is 318.5 mAh g⁻¹ at 10 mA g⁻¹, and maintains 192 mAh g⁻¹ after 250 cycles at 100 mA g⁻¹ (85.4 % capacity retention), demonstrating excellent rate and cycle performance. Furthermore, the assembled full cell exhibits a capacity retention rate of 94.5 % and 75 % at 150 and 600 mA g⁻¹ after 100 and 400 cycles, respectively. The full cell constructed with NVP (Na₃V₂(PO₄)₃) cathode and LOAHC@MgSO₄ anode, delivers an energy density of 172.8 Wh kg⁻¹ at 2130 W kg⁻¹ based on total mass of both electrodes. This work converts petroleum asphalt into a potential low-cost and efficient anode material for sodium-ion batteries, achieving high value-added utilization of petroleum asphalt.