From Sweet Potato Byproducts to Energy Storage: Unveiling the Potential of Foaming Syrup as a High-Performance Hard Carbon Anode for Sodium-Ion Batteries.

Contrary to lithium-ion batteries, which are constrained by the scarcity and prohibitive costs of lithium, sodium-ion batteries (SIBs) have gained significant attention in the realm of renewable energy. This surge in interest is primarily due to the abundance and cost-effectiveness of sodium, coupled with the advantages of safety and environmental sustainability. Biomass-derived precursors, characterized by their economic feasibility, structural flexibility, ease of fabrication, environmental benignity, and renewability, are considered ideal for the production of hard carbon materials. In this study, we employed a straightforward high-temperature pyrolysis technique to convert foaming syrup, a byproduct of sweet potato baking, into hard carbon materials (HST). A multifaceted characterization strategy, including SEM, TEM, XRD, Raman, and BET analyses, was utilized in conjunction with electrochemical performance tests. This integrated approach enabled the identification of the optimal carbonization temperature for HST at 1300 °C. The HST1300 material, derived from this temperature, was found to possess an ideal interlayer spacing, a balanced proportion of closed pores, and a favorable microstructural morphology. At a current density of 50 mA g, HST1300 demonstrated a commendable reversible specific capacity of 243.13 mAh g, along with an excellent rate capability, retaining 96.9% of its original capacity after 100 cycles. This research introduces a novel hard carbon material for SIBs anode applications and paves the way for the utilization of sweet potato byproducts.