Negative-electrode active material and preparation method thereof, secondary battery, and battery module, battery pack, and apparatus containing such secondary battery

A preparation method for a negative-electrode active material, comprising:

• preparing a core material, wherein the core material comprises granulated artificial graphite;
• mixing the core material with an organic carbon source;
• and
• heat treating the mixed core material at 700-1800° C., to form the negative-electrode active material having an amorphous carbon coating layer covering at least part of surfaces of the core material, wherein a graphitization degree of the negative-electrode active material is 91.0%-96.0%;
• wherein the granulated artificial graphite is prepared by a process that comprises:
• pulverizing a coke raw material;
• shaping the pulverized coke raw material to obtain a precursor;
• granulating the precursor to obtain a granulated product, wherein the granulated product comprises primary particles and secondary particles, and the secondary particles are obtained by agglomerating independently dispersed primary particles;
• and
• graphitizing the granulated product at a temperature of 2800° C. to 3200° C., to obtain the granulated artificial graphite,
• wherein, after pulverization, a volume-based median particle size Dv50 of the coke raw material is 7 μm-12 μm, and a volume-based particle size distribution Dv99 of the coke raw material is 15 μm-21 μm;
• wherein, after the shaping, a volume-based median particle size Dv50 of the precursor is 8 μm-13 μm, a volume-based particle size distribution Dv99 of the precursor is 16 μm-22 μm, and a particle size uniformity of the precursor U1 satisfies 0.2≤U1≤0.55;
• wherein a volume-based median particle size Dv50 of the granulated product is 9 μm-15 μm, and a volume-based particle size distribution Dv99 of the granulated product is 17 μm-24 μm;
• wherein a volume-based median particle size Dv50 of the granulated artificial graphite is 6 μm-14 μm, a volume-based particle size distribution Dv99 of the granulated artificial graphite is 17 μm-26 μm, and a particle size uniformity of the granulated artificial graphite U2 satisfies 0.22≤U2≤0.48;
• and
• wherein a particle size specific surface area of the negative-electrode active material is 0.4 m2/g-0.75 m2/g.