Unraveling the structure–performance relationship in hard carbon for sodium-ion battery by coupling key structural parameters

Abstract

The electrochemical performance of hard carbon anode for sodium-ion batteries is primarily determined by the microstructure of the materials, and the challenge lies in establishing a structure–performance relationship at the molecular level. Thus far, an understanding of the intricate relationship between the structure and performance of hard carbon remains piecemeal, with research efforts scattered across various aspects. Hence, numerous controversies have arisen in this field. Herein, we provide new insights into the structure–performance relationship in hard carbon by coupling key structural parameters based on integrating theoretical computations and experimental data. Density functional theory calculations showed that the interlayer spacing determined the diffusion behavior of sodium ions in hard carbon, while appropriate defects and curvatures secured a high-quality intercalation capacity. Inspired by these theoretical results, we successfully developed a high-performance hard carbon with optimal microstructures through in situ molecular reconfiguration of biomass via a thermodynamically driven approach, which was demonstrated as an effective strategy to rationally regulate the microstructure of hard carbon by comprehensive physical characterizations from macroscopic to atomic level. More importantly, cylindrical batteries (18 650 and 33 140 types) fabricated from industrial-scale hard carbon exhibited fabulous sodium storage behaviors with excellent wide-range temperature performance (−40 to 100 °C), demonstrating great potential for achieving practical sodium-ion batteries with high energy density and durability in the future.