Sodium Ion Diffusion Behavior in Multiple Open/Closed Pore Ratios of Novel β-Cyclodextrin-Derived Hard Carbon Anode Materials.

Abstract

Plateau-dominated hard carbon with a high rate of performance is challenging to obtain, and the in-depth mechanism of pore structure on the diffusion of sodium ions remains unclear. In this study, a facile liquid-phase molecular reconstruction strategy is proposed to regulate the orientation of the β-cyclodextrin molecules and prepare spherical hard carbon with continuous and ordered pore channels. Through detailed characterization, this approach is confirmed to optimize the accumulation of Na⁺ in the dispersion region, thus improving the plateau kinetics and enhancing the utilization of closed pores. The as-obtained β-cyclodextrin-derived spherical hard carbon has a much greater specific surface area (129 m² g^-1) than the pristine sample (2.91 m² g^-1) but a similar initial Coulombic efficiency. Additionally, the plateau region still exists when the current density is at 30 C (7.5 A g^-1), contributing to a high capacity of 179 mAh g^-1. This study provides a meaningful promotion to kinetics of hard carbon at the low-voltage region.