A negative electrode with single-walled carbon nanotubes and a secondary battery containing the same

Abstract

The problem that this invention aims to solve is to provide a secondary battery in which the active material ensures sufficient conductivity, reduces resistance, and improves lifespan characteristics as the cycle progresses. [Solution] According to this embodiment, a negative electrode for a secondary battery is provided, wherein a negative electrode mixture is formed on at least one surface of a negative electrode current collector, the negative electrode mixture comprises a negative electrode active material and a conductive material, the negative electrode active material comprises a silicon-based active material, and the conductive material is composed of single-walled carbon nanotubes (SWCNTs), a method for manufacturing the same, and a secondary battery including the same.

Claims

1. A negative electrode for a secondary battery, wherein a negative electrode mixture is formed on at least one surface of the negative electrode current collector, The negative electrode mixture comprises a negative electrode active material and a conductive material. The aforementioned negative electrode active material includes a silicon-based active material. The conductive material is composed of single-walled carbon nanotubes (SWCNTs), forming the negative electrode.

2. The anode according to claim 1, wherein the single-walled carbon nanotubes are included in a first form that connects the surfaces of two or more anode active material particles and in a second form that covers the surface of each anode active material particle.

3. The negative electrode according to claim 2, wherein the content of the conductive material formed in the first embodiment is 40% to 70% by weight of the total content of the conductive material.

4. The negative electrode according to claim 1, wherein the diameter of the single-walled carbon nanotube is 1 nm to 2 nm.

5. The negative electrode according to claim 1, wherein the length of the single-walled carbon nanotube is 2 μm to 5 μm.

6. The negative electrode according to claim 1, wherein the aspect ratio of the single-walled carbon nanotube is 1000 to 5000.

7. The negative electrode according to claim 1, wherein the single-walled carbon nanotubes have a secondary shape in which they are bundled together.

8. The negative electrode according to claim 1, wherein the negative electrode mixture further comprises a binder and a dispersant.

9. A method for manufacturing a negative electrode for a secondary battery according to any one of claims 1 to 8, A method for manufacturing a negative electrode, wherein when producing a negative electrode active material slurry containing a conductive material composed of single-walled carbon nanotubes (SWCNTs), the conductive material composed of single-walled carbon nanotubes is introduced in segments.

10. The method for manufacturing a negative electrode according to claim 9, wherein the negative electrode active material slurry further contains a binder, and 30% to 60% by weight of the conductive material composed of single-walled carbon nanotubes is first mixed with the negative electrode active material, and the remaining 40% to 70% by weight of the conductive material composed of single-walled carbon nanotubes is added together with the binder and then mixed.

11. The method for manufacturing the negative electrode is as follows: (a) A step of preparing a predispersion by mixing a conductive material composed of single-walled carbon nanotubes (SWCNTs) with a dispersant and a solvent; (b) A step of adding a negative electrode active material to a portion of the pre-dispersion to produce an active material solution; (c) The step of adding the remaining pre-dispersion to the active material solution and adding a binder to produce an active material slurry; and (d) A step of manufacturing a negative electrode by applying the active material slurry to at least one surface of the negative electrode current collector, drying it, and rolling it; A method for manufacturing a negative electrode according to claim 9, including the method described in claim 9.

12. The method for producing a negative electrode according to claim 11, wherein in step (b), a negative electrode active material is added to 30% to 60% by weight of the predispersion based on the total weight of the predispersion, and in step (c), the remaining 40% to 70% by weight of the predispersion is added based on the total weight of the predispersion.

13. The negative electrode according to any one of claims 1 to 8; A positive electrode having a positive electrode mixture containing a positive electrode active material formed on at least one surface of the positive electrode current collector; A secondary battery in which an electrode assembly including a separator membrane interposed between the negative electrode and the positive electrode is built into a secondary battery case together with an electrolyte, The aforementioned secondary battery is a secondary battery in which the increase rate of the DCIR value over 100 cycles from the initial DCIR value is 47% or less.

14. The secondary battery according to claim 13, wherein the secondary battery has a retention rate of 91% or more of its discharge capacity after 100 discharge cycles relative to its initial discharge capacity.

15. The secondary battery according to claim 13, wherein the positive electrode active material comprises a lithium transition metal oxide represented by the following chemical formula 1: Li １＋ｘ Ni ａ Co ｂ Mn ｃ M １－（ａ＋ｂ＋ｃ） O ２－ｙ A ｙ (1) In the above formula, M is at least one selected from the group consisting of Cu, Ti, Mg, Al, Pt, and Zr. A is an oxygen-substituted halogen, 0 ≤ x ≤ 0.5, 0.8 ≤ a ≤ 1, 0 ≤ b ≤ 0.2, 0 ≤ c ≤ 0.2, 0.9 ≤ a + b + c ≤ 1, and 0 ≤ y ≤ 0.001.

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