Negative-electrode active material and preparation method thereof, secondary battery, and battery module, battery pack, and apparatus containing such secondary battery
This application discloses a negative-electrode active material and a preparation method thereof, a secondary battery, and a battery module, a battery pack, and an apparatus that include such secondary battery. The negative-electrode active material includes a core and a coating layer covering at least part of a surface of the core, where the core includes artificial graphite, the coating layer includes amorphous carbon, a volume-based particle size distribution of the negative-electrode active material satisfies D v 99≤24 μm, a volume-based median particle size D v 50 of the negative-electrode active material satisfies 8 μm≤D v 50≤15 μm, D v 99 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 99%, and D v 50 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 50%.
1. A negative-electrode active material, comprising granulated artificial graphite particles having an amorphous carbon coating layer covering at least part of surfaces of the granulated artificial graphite particles, wherein
D v 10, a particle size corresponding to a cumulative volume distribution percentage reaching 10%, of the negative-electrode active material is 6 μm-8 μm;
D v 50, a particle size corresponding to cumulative volume distribution percentage reaching 50%, of the negative-electrode active material is 11 μm-13 μm;
D v 90, a particle size corresponding to cumulative volume distribution percentage reaching 90%, of the negative-electrode active material is 14 μm-17 μm;
D v 99, a particle size corresponding to cumulative volume distribution percentage reaching 99%, of the negative-electrode active material is 18 μm-21 μm;
a particle size uniformity of the negative-electrode active material is 0.32-0.38; and
a particle size specific surface area of the negative-electrode active material is 0.4 m 2 /g-0.75 m 2 /g;
wherein the negative-electrode active material is prepared by a method that comprises:
preparing a core material, wherein the core material comprises the granulated artificial graphite particles;
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;
wherein after the heat treatment, 70%-95% of the particles of the negative-electrode active material are agglomerated.
2. The negative-electrode active material according to claim 1 , 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, D v 50 of the coke raw material is 7 μm-12 μm, and D v 99 of the coke raw material is 15 μm-21 μm;
after the shaping, D v 50 of the precursor is 8 μm-13 μm, D v 99 of the precursor is 16 μm-22 μm, and a particle size uniformity of the precursor U 1 satisfies 0.2≤U 1 ≤0.55;
D v 50 of the granulated product is 9 μm-15 μm, and D v 99 of the granulated product is 17 μm-24 μm.
3. The negative-electrode active material according to claim 2 ,
wherein the coke raw material contains an amount C 1 of volatile substances, and 1 wt %≤C 1 ≤12 wt % of the coke raw material; and
wherein a binder is added to the precursor during granulating the precursor, an amount of the binder added to the precursor in weight percentage of the precursor is C 2 , and C 1 , C 2 and U 1 satisfy:
21≤( C 1 +C 2 )/ U 1 ≤50.
4. The negative-electrode active material according to claim 2 , wherein the coke raw material comprises one or more of petroleum-based non-needle coke, petroleum-based needle coke, and petroleum green coke.
5. The negative-electrode active material according to claim 2 , wherein a binder is added to the precursor during granulating the precursor, and the preparation method satisfies the following condition:
20≤( C 1 +C 2 +C 3 )/ U 2 ≤56
wherein
C 1 is a weight percentage of volatile substances in the coke raw material,
C 2 is an amount of the binder added to the precursor in weight percentage of the precursor, and
C 3 is an amount of the organic carbon source mixed to the core material in weight percentage of the granulated artificial graphite.
6. The negative-electrode active material according to claim 1 , wherein the negative-electrode active material further satisfies one or more of the following conditions:
a graphitization degree of the negative-electrode active material is 91.0%-96.0%;
a gram capacity of the negative-electrode active material is 345 mAh/g-360mAb/g;
a tap density of the negative-electrode active material is 0.9 g/cm 3 -1.3 g/cm 3 ; and
a powder compacted density of the negative-electrode active material under a pressure of 2 kN is 1.55 g/cm 3 -1.67 g/cm 3 .
7. A secondary battery, comprising a negative-electrode plate, wherein the negative-electrode plate comprises the negative-electrode active material according to claim 1 .