Designing Spherical Sucrose-Derived Hard Carbon Materials with Abundant Closed Pores via Amino-Aldehyde Condensation

Hydrothermal carbonization of sucrose is a conventional method for preparing hard carbon (HC) microsphere precursors; the construction of closed pores plays a crucial role in enhancing the platform capacity of sugar-based HC materials. This work proposes a strategy of a cohydrothermal method with sucrose and organic amine molecules to regulate the content of closed pores. Amine molecules undergo an amine-aldehyde condensation reaction with furfural intermediates during the hydrothermal process of sucrose, participating in the formation of carbon precursors. During the carbonization process, the presence of amine molecules accelerates the pyrolysis of the precursor and alters the microstructure of the HC microsphere precursor. This ultimately leads to the construction of closed pore structures during subsequent carbonization, thereby significantly enhancing the platform capacity. Research finds that different amine molecules affect the sodium ion storage behavior of the HC anode materials. Specifically, aniline-involved sucrose-derived HC (HCBS) and benzylamine-involved sucrose-derived HC (HCBIS) deliver large closed-pore volume of 0.072 m3 g–1 and 0.095 m3 g–1, respectively, much higher than sucrose-derived HC (HCS) of 0.024 m3 g–1. HCBS exhibits a remarkable reversible capacity of 382 mA h g–1 at a current density of 0.020 A g–1. Ex situ Raman tests demonstrate that the plateau capacity of HCBS (277 mA h g–1) results from both sodium ion intercalation and closed pore filling; conversely, the plateau capacity of HCBIS is primarily attributed to closed-pore filling. This work proposes a novel design concept to create abundant closed pores HC from sucrose, contributing to the rational design of the pore structure of sugar-based HC.