Negative electrode active material and method of preparing the same
View Patent ↗Provided are a negative electrode active material and a method of preparing the same, and particularly, the present invention relates to a negative electrode active material including a core including natural graphite, and a shell surrounding the core and including a roughened amorphous carbon layer. Since the negative electrode active material according to the present invention has a roughened surface, adhesion may be improved by using a less amount of a binder due to an anchoring effect in which curved surfaces of active material particles in contact with each other are anchored. Thus, an increase in resistance due to the use of an excessive amount of the binder may be prevented while achieving high loading in a negative electrode. Also, since a specific surface area is increased due to the roughened surface, access of lithium ions becomes easy, and thus, high output of a battery may be obtained.
1. A negative electrode active material comprising:
a core including natural graphite; and
a shell including a roughened amorphous carbon layer which is formed on a surface of the core,
wherein the roughened amorphous carbon layer comprises a first rough surface having a surface roughness (Ra) of 1 μm to 5 μm and a second rough surface having a surface roughness of 0.01 μm to 1 μm on the first rough surface.
2. The negative electrode active material of claim 1 , wherein the natural graphite is spherical.
3. The negative electrode active material of claim 1 , wherein the amorphous carbon layer is included in an amount of 2 wt % to 5 wt % based on the total weight of the negative electrode active material.
4. The negative electrode active material of claim 1 , wherein the amorphous carbon layer is prepared from at least one soft carbon raw material selected from the group consisting of a coal-derived pitch, a petroleum-derived pitch, polyvinyl chloride, a mesophase pitch, a tar, and low molecular weight heavy oil; at least one hard carbon raw material selected from the group consisting of a polyvinyl alcohol resin, a furfuryl alcohol resin, triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, an ethylene-propylene-diene monomer, poly acrylic acid, sodium polyacrylate, polyacrylonitrile, glucose, gelatin, saccharides, a phenolic resin, a naphthalene resin, a polyamide resin, a furan resin, a polyimide resin, a cellulose resin, a styrene resin, an epoxy resin, and a vinyl chloride resin; or a combination thereof.
5. A method of preparing the negative electrode active material of claim 1 , the method comprising steps of:
forming an amorphous carbon layer on a surface of natural graphite (step 1); and
roughening a surface of the amorphous carbon layer of step 1 by mechanical processing (step 2).
6. The method of claim 5 , wherein the mechanical processing of step 2 is performed by spheronization equipment.
7. The method of claim 6 , wherein the spheronization equipment is equipped with a needle-shaped roughening cutter.
8. The method of claim 5 , wherein the natural graphite of step 1 is spherical.
9. The method of claim 5 , wherein the amorphous carbon layer roughened in step 2 is included in an amount of 2 wt % to 5 wt % based on the total weight of the negative electrode active material.
10. The method of claim 5 , wherein the amorphous carbon layer roughened in step 2 has a surface roughness (Ra) of 0.01 μm to 5 μm.
11. The method of claim 5 , wherein the amorphous carbon layer roughened in step 2 comprises a first rough surface having a surface roughness (Ra) of 1 μm to 5 μm and a second rough surface having a surface roughness of 0.01 μm to 1 μm on the first rough surface.
12. The method of claim 5 , wherein the amorphous carbon layer roughened in step 2 has a specific surface area which is increased by 1.5 times to 2.0 times in comparison to a specific surface area of the amorphous carbon layer before roughened.
13. The method of claim 5 , wherein the amorphous carbon layer is prepared from at least one soft carbon raw material selected from the group consisting of a coal-derived pitch, a petroleum-derived pitch, polyvinyl chloride, a mesophase pitch, a tar, and low molecular weight heavy oil; at least one hard carbon raw material selected from the group consisting of a polyvinyl alcohol resin, a furfuryl alcohol resin, triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, an ethylene-propylene-diene monomer, poly acrylic acid, sodium polyacrylate, polyacrylonitrile, glucose, gelatin, saccharides, a phenolic resin, a naphthalene resin, a polyamide resin, a furan resin, a polyimide resin, a cellulose resin, a styrene resin, an epoxy resin, and a vinyl chloride resin; or a combination thereof.
14. A negative electrode comprising:
an electrode collector; and
a negative electrode material mixture layer including the negative electrode active material of claim 1 which is formed on the electrode collector.
15. A secondary battery comprising:
the negative electrode of claim 14 ;
a positive electrode coated with a positive electrode material mixture including a positive electrode active material;
a separator disposed between the negative electrode and the positive electrode; and
an electrolyte solution.
16. A battery module comprising the secondary battery of claim 15 as a unit cell.
17. A battery pack comprising the battery module of claim 16 and used as a power source of a medium and large sized device.
18. The battery pack of claim 17 , wherein the medium and large sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.