Synthesis of apricot kernel shell–based cellulose, hard carbon production for sustainable energy storage applications and investigation of electrochemical properties

The development of sustainable energy systems based on renewable resources increases the importance of environmentally friendly and cost-effective solutions in energy storage technologies. In this study, the production and performance of hard carbon materials that can be used as anode electrodes in sodium-ion batteries using biomass-based apricot kernel shells were investigated. Three different materials were selected as carbon precursors: apricot kernel shell (KCK), cellulose (S) isolated from this biomass and nanocellulose (NS). Three different processing approaches were applied on each material: i) basic carbonization process, ii) carbonization after chemical activation with sodium carbonate and iii) carbonization followed by Mn doping with hydrothermal treatment. The obtained carbon-based materials were characterized in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis and Raman spectroscopy. Na-ion battery tests of the obtained and structured carbon-based materials were performed on half-cell type CR2O32 batteries. Electrochemical characterizations were performed using cyclic voltammetry (CV), galvanostatic charge/discharge cycling, and rate capability (C-rate) tests at various current densities. At low current density (0.05 A/g), the highest initial discharge capacity was obtained in the alkali-treated nanocellulose-based electrode with 451.99 mAh/g. As a result of the C-rate tests, it was determined that the apricot kernel shell-based and alkali-activated sample showed the highest capacity at low current, while the Mn-doped versions were the samples that preserved their capacity best at high current. The findings show that both chemical activation and Mn doping processes have significant effects on electrochemical performance; especially, they increase the structural strength and cycling stability of alkali-treated carbons. These results indicate that apricot kernel shell and its derivative carbon materials can be evaluated as potential anode materials for sodium-ion batteries.