Anode active material and lithium secondary battery including the same
An anode active material according to an embodiment of the present invention includes a first graphite particle and a second graphite particle having a different particle diameter from that of the first graphite particle. A ratio of a pellet density relative to a. tap density of the anode active material is from 1.3 to 1.45. A particle deformation of the anode is suppressed to achieve a lithium secondary battery having improved long-term and high-energy properties.
1. An anode active material, comprising:
a first artificial graphite particle; and
a second artificial graphite particle having a different particle diameter from that of the first graphite particle and a hardness higher than that of the first graphite particle, wherein a pellet density and a tap density of the anode active material satisfy a relation of Equation 1:
1.3≤D P /D T ≤1.45 [Equation 1]
wherein, in Equation 1, D P is the pellet density (g/cm 3 ) of the anode active material, and D T is the tap density (g/cm 3 ) of the anode active material,
wherein, the pellet density is calculated using a height difference measured after putting 1 g of the anode active material into a cylindrical pelletizer with a diameter of 13 mm and pressurizing the pelletizer with 3 metric ton for 10 seconds,
wherein the tap density is measured from a volume and a weight of a sample obtained after filling the sample of 10 g of the anode active material in 25 ml measuring cylinder, and then tapping with a stroke length of 10 mm 3,000 times.
2. The anode active material of claim 1 , wherein an amount of the second graphite particle is in a range from 20 wt % to 40 wt % based on a total weight of the anode active material.
3. The anode active material of claim 1 , wherein the first graphite particle and the second graphite particle satisfy Equation 2:
0.3≤D 2 /D 1 ≤0.56 [Equation 2]
wherein, in Equation 2, D 1 is an average particle diameter (D 50 , μm) of the first graphite particle, and D 2 is an average particle diameter (D 50 , μm) of the second graphite particle.
4. The anode active material of claim 1 , wherein the average particle diameter (D 50 ) of the first graphite particle is from 16 μm to 19 μm.
5. The anode active material according to claim 1 , wherein an average particle diameter (D 50 ) of the second graphite particle is from 7 μm to 9 μm.
6. The anode active material of claim 1 , wherein the first graphite particle includes an assembly type artificial graphite.
7. An anode mixture for a lithium secondary battery comprising the anode active material of claim 1 and having a density of 1.8 g/cm 3 or more.
8. The anode mixture for a lithium secondary battery of claim 7 , further comprising a solvent, a conductive agent and a binder.
9. An anode for a lithium secondary battery, comprising:
an anode current collector; and
an anode active material layer formed on the anode current collector, the anode active material layer comprising the anode active material of claim 1 .
10. A lithium secondary battery, comprising:
a cathode; and
an anode facing the cathode and comprising the anode active material of claim 1 .