Hard Carbon with Sieving Closed-pore Structure as Anode Material for Sodium-ion Battery

Hard carbon with sieving closed-pore structure and its preparation method are disclosed. Biomass mixture such as cotton, farm biowaste, or a mixture with 70-90% cellulose, 9-20% hemicellulose, and 1-10% lignin, etc., is applied as the raw material. This mixture is subjected to calcination at temperatures ranging from 300 to 600° C., resulting in a pre-carbonized precursor. The precursor is then washed with an alkaline solution. Finally, the precursor undergoes a second calcination at a temperature between 900 to 1400° C. to yield the hard carbon product with sieving closed-pore structure.