Unraveling 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 materials, and the challenge lies in establishing structure-performance relationship at molecular level. So far, the understanding of intricate relationship between structure and performance in hard carbon remains piecemeal, with research efforts scattered across various aspects, thereby numerous controversies have arisen in this field. Here, we provide new insights into structure-performance relationship in hard carbon by coupling key structural parameters based on integrating theoretical computations and experimental data. Density functional theory calculations show that interlayer spacing determines diffusion behavior of sodium ions in hard carbon, while appropriate defect and curvature secure high-quality intercalation capacity. Inspired by these theoretical results, we successfully produce high-performance hard carbon with optimal microstructures through in-situ molecular reconfiguration of biomass via thermodynamically-driven approach, which is 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 (18650 and 33140 types) fabricated from industrial-scale hard carbon exhibit fabulous sodium storage behaviors with excellent wide-range temperature performance (-40-100 oC), demonstrating great potential for achieving practical sodium-ion batteries with high energy density and durability in the future.