Negative electrode and secondary battery including same
The present invention relates to a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based active material and a negative electrode binder, wherein the negative electrode binder includes an aqueous binder and a rubber-based binder in a weight ratio of 82:18 to 88:12, and the aqueous binder includes at least one selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, and polyacryl amide.
1. A negative electrode comprising:
a negative electrode current collector; and
a negative electrode active material layer disposed on the negative electrode current collector, wherein
the negative electrode active material layer includes a silicon-based active material and a negative electrode binder, and
the negative electrode binder includes an aqueous binder and a rubber-based binder in a weight ratio of 82:18 to 88:12,
the aqueous binder includes polyvinyl alcohol and polyacrylic acid in a weight ratio of 55:45 to 80:20,
wherein the rubber-based binder is styrene butadiene rubber.
2. The negative electrode of claim 1 , wherein the silicon-based active material contains Si.
3. The negative electrode of claim 1 , wherein a thickness of the negative electrode active material layer is 10 μm to 40 μm.
4. The negative electrode of claim 1 , wherein
the negative electrode binder has a bending height of 1 cm or less,
wherein the bending height is measured by the following method comprising:
preparing a solution for forming a binder film by adding 2 g of the negative electrode binder to distilled water such that a solid content is 15 wt %;
applying the solution for forming a binder film to an area of 10 cm×10 cm on a square Teflon substrate having a size of 10 cm×10 cm;
drying the applied solution for forming a binder film at 60° C. for 48 hours to prepare the binder film including a vertex spaced apart from the Teflon substrate; and
defining, as a bending height, a maximum vertical distance between the binder film spaced apart from the Teflon substrate and the Teflon substrate, when the vertex spaced apart from the Teflon substrate is pressed vertically downward to the Teflon substrate with a force of 3 kgf.
5. The negative electrode of claim 1 , wherein:
the negative electrode active material layer includes: the silicon-based active material in an amount of 60 wt % to 90 wt %; and
the negative electrode binder in an amount of 10 wt % to 30 wt %.
6. The negative electrode of claim 1 , wherein the negative electrode active material layer further comprises a negative electrode conductive material.
7. The negative electrode of claim 6 , wherein the negative electrode active material layer includes the negative electrode conductive material in an amount of 5 wt % to 20 wt %.
8. The negative electrode of claim 1 , wherein a porosity of the negative electrode is 37% to 45%.
9. A secondary battery comprising:
a negative electrode according to claim 1 ;
a positive electrode opposing the negative electrode;
a separator interposed between the positive electrode and the negative electrode; and
an electrolyte.