Negative electrode active material and secondary battery comprising same

1. A negative electrode active material which comprises artificial graphite having a large particle diameter and natural graphite having a small particle diameter,

wherein an average particle diameter ratio of the small particle and the large particle is 1:1.5-1:5;

each of the artificial graphite having a large particle diameter and the natural graphite having a small particle diameter is further provided with a coating layer containing amorphous carbon;

the coating layer is present in an amount of 1-10 parts by weight based on 100 parts by weight of a sum of the artificial graphite having a large particle diameter and the natural graphite having a small particle diameter; and

a content ratio of the artificial graphite having a large particle diameter and the natural graphite having a small particle diameter is 1:9-4:6.

2. The negative electrode active material according to claim 1 , wherein the artificial graphite has an average particle diameter of 18-30 μm.

3. The negative electrode active material according to claim 1 , wherein the natural graphite has an average particle diameter of 5-13 μm.

4. A negative electrode comprising a current collector, and a negative electrode active material layer formed on at least one surface of the current collector and comprising the negative electrode active material as defined in claim 1 .

5. The negative electrode according to claim 4 , wherein the negative electrode active material layer further comprises at least one of a binder, conductive material and a dispersant.

6. A secondary battery comprising a positive electrode, the negative electrode as defined in claim 4 , and a separator interposed between the positive electrode and the negative electrode.

7. A secondary battery according to claim 6 , which is a lithium secondary battery.