Preparation method of hard carbon negative electrode material for sodium ion battery

The invention discloses a preparation method of a hard carbon negative electrode material for a sodium-ion battery, which comprises the following steps: low-temperature carbonization, crushing, low-temperature reduction, hydrothermal pore forming, soft carbon dipping and coating, high-temperature carbonization and screening to obtain the hard carbon negative electrode material for the sodium-ion battery. Oxygen-containing functional groups in the material are removed through low-temperature reduction and hydrogen, closed pores are favorably formed, the hard carbon capacity is improved, in addition, organic acid zinc performs pore forming on the interior of the material through a pyrolytic reaction, a sodium storage space is favorably improved, the capacity is improved, the organic acid zinc can be removed after being heated, decomposed and washed, the risk of impurity introduction is avoided, and the method is suitable for industrial production. The surface of the hard carbon material is uniformly coated with