The buckwheat-derived hard carbon as an anode material for sodium-ion energy storage system

Biomass-derived hard carbon (HC) has attracted much attention as a promising electrode material for sodium-ion batteries (SIBs) due to its unique properties such as high porosity, large surface area and adjustable pore size distribution. This work presents the results of electrochemical studies of HC derived from buckwheat seeds. The HCs were preoxidized at 300 °C and synthesized using a pyrolysis method in the range 600–1400 °C. It was found that the electrochemical characteristics of the HC anodes are strongly dependent on the morphology and structure. Furthermore, the positive effect of preoxidation on the porosity of HC was confirmed. Although all buckwheat-derived HC-based anodes showed stable cyclability over 100 cycles with CE of approximately 97–98 %, the preoxidized HCs pyrolyzed at 1400 °C achieved the highest reversible capacity of 330.23 mAh g−1 with excellent stability. Additional study using "single particle" measurement of HC1400 and HCox1400 showed that the preoxidation may significantly contribute to the improvement of the mass transfer.