Green upcycling of retired asphalt into “vortex-crosslinked” carbon anodes for high-performance sodium-ion batteries

Abstract

The environmental burden of waste asphalt and the performance limitations of sodium-ion battery anodes pose dual challenges in energy and sustainability. To address the low capacity and poor initial coulombic efficiency of directly carbonized asphalt-derived carbons, this study introduces a MgO-templated dual-stage carbonization strategy that transforms retired asphalt into “vortex-crosslinked” carbon architectures (PWAC-800) with exceptional sodium storage capabilities. During initial carbonization, synergistic interactions between asphalt and MgO create a 3D cavity network, while secondary carbonization drives controlled contraction and multidirectional stacking of carbon microcrystallites, forming a unique vortex-interconnected topology. This architecture features expanded interlayer spacing (3.59 Å vs. 3.54 Å), optimized specific surface area (43.1 m² g⁻¹ vs. 27.8 m² g⁻¹), and highly disordered microcrystalline arrangements, collectively enhancing Na⁺ diffusion kinetics and active site density. The optimized PWAC-800 delivers a high reversible capacity of 299 mAh g⁻¹ at 0.1 C with an ICE of 82%, and retains 93% capacity (182 mAh g⁻¹) after 600 cycles at 4 C, outperforming most reported asphalt-derived carbons. In situ electrochemical analysis and full-cell testing further validate its practicality. This work not only establishes a “waste-to-wealth” paradigm for repurposing retired asphalt but also pioneers a structural engineering approach for high-capacity, durable SIB anodes, bridging environmental remediation with advanced energy storage innovation.