In situ dual growth of graphitic structures in biomass carbon to yield a potassium-ion battery anode with high initial coulombic efficiency

Abstract

Biomass carbon material has good potential as an anode for potassium-ion batteries (KIBs). However, it suffers from a low initial coulombic efficiency (ICE), which hinders its mass adoption. The formation of large-sized graphitic structures in biomass carbon can improve ICE. However, the commonly reported methods are still inadequate for realising this due to the random distribution of small-sized amorphous carbon domains and the existence of defective structures. Herein, a facile method is reported to prepare biomass carbon with long-distance and large-sized graphitic structures by co-annealing the precursor (tea-waste) powder and recyclable template pellet (petroleum coke pre-loaded with Fe₂O₃ particles) at 1300 °C for catalytic graphitization. This process can allow the embedding of the external graphitic crystals into the defects of the biomass carbon. The hybrid framework is useful for reducing the irreversible K-ion trapping by increasing the amount of reversible insertion sites, providing more reversible K-ion transportation channels, shortening the diffusion distance in the carbon interlayers, and enhancing reversible K-ion adsorption at the defects/edges. The as-prepared biomass carbon delivered a high ICE of 85.6% and a high reversible capacity of 367 mA h g⁻¹. Also, based on the result, the as-prepared biomass carbon could exhibit good compatibility as an electrode for a sodium-ion battery with an ICE of 92.3% and a reversible capacity of 408 mA h g⁻¹. Therefore, utilizing a soft carbon pellet loaded with a catalyst as a recyclable template can be highly beneficial in enhancing the ICE for KIBs and other alkali-ion batteries.