Biowaste-derived carbon as an electrode material for sodium batteries and capacitors

Abstract

The conversion of inexpensive, plentiful, and renewable biomass into porous carbon materials for use in sodium-ion batteries and supercapacitor electrodes has garnered attention in recent years. This study presents a novel approach where blackberry seeds were carbonized and chemically activated with potassium hydroxide (KOH) to form activated carbons (ACs). The synthesized blackberry seed-derived activated carbon (BBSDAC's) morphology, defectiveness, crystal structure, and textural characteristics were characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), and low-temperature nitrogen physisorption. The characterization confirmed that the biocarbon has a good surface area with micropores and defectiveness. The electrochemical performance of the sodium-ion energy storage of the biocarbon was investigated in a half-cell, yielding a discharge capacity of 322 mAh g⁻¹ at a rate of 100 mA g⁻¹ with good rate capability, as well as outstanding cycling stability, retaining 99% of its capacity after 200 cycles. Even after 10 months of rest, the cell showed no capacity decay. Additionally, activated carbon was investigated in an aqueous solution as an electrode material for sodium-ion capacitors. The BBSDAC 700 exhibits remarkable characteristics with a high specific capacitance of 218 F g⁻¹ at a current density of 1 A g⁻¹ and excellent cycling stability with around 99.0% coulombic efficiency after 10 000 cycles. The capacitor demonstrated an energy density of around 20 Wh kg⁻¹. The findings show that the BBSDAC 700 electrode advances the electrode materials used in energy storage applications.