Original data used to support the article "Starch as an efficient precursor for hard carbon anodes enables high-performance sodium-ion storage"

The microscopic morphology and structure were observed by scanning electron microscope (SEM, JSM-IT500LV, JEOL). The crystal structure was analyzed using an X-ray diffractometer (DX-2700BH) with a Cu target Kα-ray source (wavelength λ = 0.15406 nm) and scanning rate of 8 °/min. Raman spectra were recorded by using a Thermo Raman spectrometer (HE Evolution, HORIBA) with a laser wavelength of 532 nm and a spectral range of 200-2500 cm-1. The functional groups present in the samples were identified and analyzed using a Fourier transform infrared spectrometer (FT-IR, Nicolet iS20, Thermo Fisher Scientific Ltd.). A thermogravimetric analyzer (TG209F3) was used to study the pyrolysis behavior of the samples under a nitrogen atmosphere within the temperature range of 25-900 °C at a heating rate of 10 °C/min. The specific surface area and pore size distribution of the samples were determined by nitrogen adsorption measurements using a specific surface area and pore size analyzer (V-Sorb 4800TP, Ultrametrics).

A glass fiber diaphragm (GF/D, Whatman) was used as the separator, and the electrolyte consisted of 1M NaPF6 dissolved in a ternary solvent mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:2:2. Galvanostatic charge and discharge (GCD) testing was carried out on a battery test system (Newell, China) at 25 °C with potential range of 0.005 V - 2.5 V versus Na+/Na. Cyclic voltammetry (CV) tests were performed on a potentiostat (CHI660E, Chenhua, Shanghai, China) with a sweep rate of 0.1 mV/s.