Anode for lithium secondary battery and method for manufacturing same
Disclosed herein relates to a negative electrode for lithium secondary battery and a method for manufacturing the same. The negative electrode has a structure in which a first negative electrode active layer and a second negative electrode active layer are sequentially stacked on a negative electrode current collector. By controlling alignment (O.I) of the carbon-based active material to be lower in the second negative electrode active layer than in the first negative electrode active layer, and by preparing a low percentage of pores in the second negative electrode active layer, it is possible to have a flow path for the electrolyte to move inside the negative electrode active layer even after the rolling process of the negative electrode active layer. The negative electrode also has a high wetting ability to the electrolyte and high energy density.
1 . A negative electrode for lithium secondary battery comprising:
a negative electrode current collector; a first negative electrode active layer provided on at least one surface of the negative electrode current collector, the first negative electrode active layer containing carbon-based active material; and a second negative electrode active layer provided on the first negative electrode active layer, the second negative electrode active layer containing carbon-based active material,
wherein
the second negative electrode active layer has an alignment, O.I 2nd , of the carbon-based active material represented by Equation 1 of 0.4 to 0.9, wherein
an alignment, O.I 1st , of the carbon-based active material contained in the first negative electrode active layer has a ratio of 105% to 150% with respect to the alignment, O.I 2nd , of the carbon-based active material contained in the second negative electrode active layer, and
porosity of the second negative electrode active layer is from 15% to 25%:
O
.
I
=
I
004
/
I
1
1
0
[
Equation
1
]
wherein,
I 004 represents an area of a peak representing the [0,0,4] crystal face in an X-ray diffraction (XRD) measurement of the first or the second negative electrode active layer,
I 110 represents an area of a peak representing the [1,1,0] crystal face in an X-ray diffraction (XRD) measurement of the first or the second negative electrode active layer,
the carbon-based active material in the first negative electrode active layer and the carbon-based active material in the second negative electrode active layer have an average particle diameter D50 of 1 μm to 3 μm, and
wherein the negative electrode is configured to satisfy the wetting ability to polycarbonate as represented by the following Equation 2:
1
≤
WT
/
O
.
I
2
n
d
≤
1
6
[
Equation
2
]
wherein,
WT represents a time in a unit of second it takes for 1 drop of polycarbonate containing 2-5 μl to impregnate an area of 1 cm 2 of the negative electrode.
2 . The negative electrode for lithium secondary battery of claim 1 , wherein
a total thickness of the first and second negative electrode active layers is from 50 μm to 300 μm.
3 . The negative electrode for lithium secondary battery of claim 1 , wherein
the second negative electrode active layer has a BET specific surface area of from 0.20 to 0.62 m 2 /g.
4 . The negative electrode for lithium secondary battery of claim 1 , wherein
the carbon-based active material includes at least one of natural graphite or synthetic graphite.