The present application provides a negative
electrode material and a preparation method thereof, a negative
electrode sheet and a
sodium ion battery, which relate to the field of
new energy technology. The negative
electrode material provided in the present application includes a core and a soft
carbon coating layer coated on the surface of the core, the core includes hard carbon and carbon dots distributed inside and on the surface of the hard carbon, and closed pores are distributed inside the hard carbon. The soft
carbon coating modifies the surface of the material, reduces the material specific surface area, and improves the first efficiency of the hard carbon material; the carbon dots are cross-linked with the
coal-based precursor to inhibit the graphitization of the precursor material during high-temperature
carbonization, increase the degree of disorder, help to form closed pores, and improve the
sodium storage performance of the hard carbon material. The negative
electrode material of the present application uses
coal as a precursor material, mixes
asphalt and carbon dots to form a composite precursor as an
anode, an
inert electrode as a
cathode, and a mixed acid solution as an
electrolyte. The composite precursor is electrolytically modified by an electrochemical method, and then separated, washed, and dried to obtain a modified composite precursor, which is finally obtained by
sintering.