Chinese baijiu spent grains-based high-performance porous hard carbon for sodium-ion battery anodes

Hard carbon is considered to be a viable choice for anode materials in sodium-ion batteries due to its low cost and high specific capacity for sodium storage. The wasted grains derived from Chinese baijiu possess significant potential as biomass-based precursors for the production of hard carbon compounds. However, their use as biomass material has been mostly ignored. Therefore, this research focuses on the use of discarded grains from baijiu as a raw material for the production of porous hard carbon materials, specifically for the anode of sodium-ion batteries. The proposed synthesis procedure involves the use of a ZnCl2 chemical treatment to generate hard carbon materials that possess a porous structure and exhibit graphitic features. In comparison to the direct carbonization synthesis process, the use of ZnCl2 treatment on porous hard carbon results in notable enhancements in electrochemical performance, including specific capacity and rate capability, while simultaneously preserving exceptional long-term cycle stability. Especially, the enhanced capacity mostly manifests in the low-voltage plateau region, and the high plateau capacity can maintained even at higher specific currents, which is suitable for high-rate application, exceeding the typical commercial hard carbon materials used in sodium-ion batteries.