Garlic-braid–derived activated biochar as a high-performance sulfur host for lithium–sulfur batteries

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Abstract
Lithium-sulfur (Li-S) batteries are promising next-generation energy storage systems due to their high theoretical energy density. However, their practical implementation is hindered by the low conductivity of sulfur and the polysulfide shuttle effect. In this work, garlic-braid-derived biochar was investigated as a sustainable sulfur host for Li-S battery cathodes. Biochar obtained from garlic braid biomass was chemically activated using potassium hydroxide to generate a highly porous carbon matrix. Sulfur was subsequently infiltrated into the activated biochar, and the resulting composite was evaluated as a cathode material in Li-S batteries. The activated biochar exhibited a well-developed porous structure, enabling a sulfur infiltration degree of 48 wt.%. The optimized cathode delivered an initial discharge capacity of 1,015 mAh/g and stabilized at approximately 700 mAh/g after 80 cycles at 0.1 C. Furthermore, a specific capacity of 491 mAh/g was achieved at 1 C, demonstrating favorable rate capability. The cells also exhibited stable Coulombic efficiency and good capacity retention during prolonged cycling. The enhanced electrochemical performance is attributed to the hierarchical porous structure generated by chemical activation, which promotes sulfur confinement, facilitates ion transport, and improves sulfur utilization. These findings demonstrate that garlic-braid-derived activated biochar is a promising and sustainable sulfur host for Li-S batteries, highlighting the importance of both biomass selection and pore structure engineering in the development of high-performance biochar-based cathodes.

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