Negative electrode for lithium secondary battery, method for preparing negative electrode for lithium secondary battery, and lithium secondary battery comprising negative electrode

1 . A negative electrode for a lithium secondary battery, comprising:

a negative electrode current collector layer;

a first negative electrode active material layer on one surface or both surfaces of the negative electrode current collector layer; and

a second negative electrode active material layer on a surface opposite to a surface of the first negative electrode active material layer facing the negative electrode current collector layer,

wherein the first negative electrode active material layer comprises a first negative electrode active material layer composition comprising a first negative electrode active material, and the second negative electrode active material layer comprises a second negative electrode active material layer composition comprising a second negative electrode active material,

the first negative electrode active material comprises one or more selected from the group consisting of SiOx, wherein x=0, and SiOx, wherein 0<x<2, and comprises 95 parts by weight or more of the SiOx, wherein x=0 based on 100 parts by weight of the first negative electrode active material,

the second negative electrode active material comprises a one or more selected from the group consisting of a carbon-containing active material, a silicon-containing active material, a metal-containing active material configured to form an alloy with lithium and a lithium-containing nitride,

a weight loading amount (A) of the first negative electrode active material layer composition and a weight loading amount (B) of the second negative electrode active material layer composition satisfy the following Equation 1:

10≤( B /( A+B ))×100(%)≤50, and  [Equation 1]

the weight loading amount (A) and weight loading amount (B) are in terms of mg/cm 2 and wherein the weight loading amount (A) is in a range of 40 mg/25 cm 2 or more and 140 mg/25 cm 2 or less and the weight loading amount (B) is in a range of 10 mg/25 cm 2 or more and 60 mg/25 cm 2 or less.

2 . The negative electrode of claim 1 , wherein the silicon-containing active material of the second negative electrode active material is present in an amount of 1 part by weight or more and 100 parts by weight or less based on 100 parts by weight of the second negative electrode active material.

3 . The negative electrode of claim 1 , wherein the silicon-containing active material of the second negative electrode active material comprises one or more selected from the group consisting of SiOx, wherein 0<x<2, SiC, and a Si alloy.

4 . The negative electrode of claim 1 , wherein the silicon-containing active material of the second negative electrode active material comprises SiOx, wherein 0<x<2.

5 . The negative electrode of claim 1 , wherein the first negative electrode active material is present in an amount of 60 parts by weight or more based on 100 parts by weight of the first negative electrode active material layer composition.

6 . The negative electrode of claim 1 , wherein a thickness of the second negative electrode active material layer is 25% or more and 45% or less of a total thickness of the first negative electrode active material layer and the second negative electrode active material layer.

7 . The negative electrode of claim 1 , wherein the first negative electrode active material layer composition further comprises one or more selected from the group consisting of a first negative electrode conductive material and a first negative electrode binder, and the second negative electrode active material layer composition further comprises one or more selected from the group consisting of a second negative electrode conductive material and a second negative electrode binder.

8 . The negative electrode of claim 7 , wherein the first negative electrode conductive material and the second negative electrode conductive material comprise one or more selected from the group consisting of a dotted conductive material, a linear conductive material, and a planar conductive material.

9 . A method for preparing a negative electrode for a lithium secondary battery, the method comprising:

providing a negative electrode current collector layer;

forming a first negative electrode active material layer by applying a first negative electrode active material layer composition on one surface or both surfaces of the negative electrode current collector layer; and

forming a second negative electrode active material layer by applying a second negative electrode active material layer composition to a surface of the first negative electrode active material layer opposite to a surface of the first negative electrode active material layer facing the negative electrode current collector layer,

wherein the first negative electrode active material comprises one or more selected from the group consisting of SiOx, wherein x=0, and SiOx, wherein 0<x<2, and comprises 95 parts by weight or more of the SiOx, wherein x=0 based on 100 parts by weight of the first negative electrode active material,

the second negative electrode active material comprises one or more selected from the group consisting of a carbon-containing active material, a silicon-containing active material, a metal-containing active material configured to form an alloy with lithium and a lithium-containing nitride,

a weight loading amount (A) of the first negative electrode active material layer composition and a weight loading amount (B) of the second negative electrode active material layer composition satisfy the following Equation 1:

10≤( B /( A+B ))×100(%)≤50, and  [Equation 1]

the weight loading amount (A) and weight loading amount (B) are in terms of mg/cm 2 and wherein the weight loading amount (A) is in a range of 40 mg/25 cm 2 or more and 140 mg/25 cm 2 or less and the weight loading amount (B) is in a range of 10 mg/25 cm 2 or more and 60 mg/25 cm 2 or less.

10 . The method of claim 9 , further comprising:

subjecting a negative electrode in which the first negative electrode active material layer and the second negative electrode active material layer are present on the negative electrode current collector to pre-lithiation,

wherein the subjecting of the negative electrode to pre-lithiation comprises at least one of: a lithium electroplating process, a lithium metal transfer process, a lithium metal deposition process, or a stabilized lithium metal powder (SLMP) coating process.

11 . A lithium secondary battery comprising:

a positive electrode;

the negative electrode for a lithium secondary battery of claim 1 ;

a separator provided between the positive electrode and the negative electrode; and

an electrolyte.

12 . The negative electrode of claim 1 , wherein the first negative electrode active material layer is in contact with an entire surface of the negative electrode current collector layer, and

wherein the second negative electrode active material layer is in contact with an entire surface of the first negative electrode active material layer.

13 . The method of claim 9 , wherein the first negative electrode active material layer is in contact with an entire surface of the negative electrode current collector layer, and

wherein the second negative electrode active material layer is in contact with an entire surface of the first negative electrode active material layer.

14 . The method of claim 9 , wherein the second negative active material layer is formed on the first negative electrode active material layer by a wet on dry process,

wherein the wet on dry process comprises:

applying the first negative electrode active material layer composition, drying the applied first negative electrode active material layer composition partially or completely, and

applying the second negative electrode active material layer composition to the first negative electrode active material layer.

15 . The method of claim 9 , wherein the second negative active material layer is formed on the first negative electrode active material layer by a wet on wet process,

wherein the wet on wet process comprises:

applying the first negative electrode active material layer composition, and applying the second negative electrode active material layer composition to the first negative electrode active material layer composition without drying the applied first negative electrode active material layer composition.

16 . The negative electrode of claim 1 , wherein the first negative electrode active material comprises 100 parts by weight of the SiOx, wherein x=0, based on 100 parts by weight of the first negative electrode active material.