Negative electrode and secondary battery comprising the same

1. A negative electrode comprising:

a current collector and a negative electrode active material layer disposed on the current collector, wherein

the negative electrode active material layer includes:

a negative electrode active material;

carbon black; and

a binder, wherein

the negative electrode active material includes silicon particles,

the binder includes a copolymer containing a poly(vinylalcohol) unit and an ionized and substituted acrylate unit, the binder being included in the negative electrode active material layer in an amount of 18 wt % to 22 wt %,

an average particle diameter (D 50 ) of the silicon particles is 5 μm to 7 μm,

wherein, in the binder, a molar fraction of the ionized and substituted acrylate among units except for the poly(vinylalcohol) unit is 98 mol % to 100 mol %, and

wherein a specific surface area of the carbon black is 50 m 2 /g to 65 m 2 /g.

2. The negative electrode of claim 1 , wherein the poly(vinylalcohol) unit comprises a unit of Formula 1 below:

and the ionized and substituted acrylate unit comprises a unit of Formula 2 below:

wherein in Formula 2, R is each independently at least one metal selected from the group consisting of Na, Li, and K.

3. The negative electrode of claim 1 , wherein the copolymer comprises the poly(vinylalcohol) unit and the ionized and substituted acrylate unit at a weight ratio of 6:4 to 8:2.

4. The negative electrode of claim 1 , wherein the ionized and substituted acrylate is at least one selected from the group consisting of sodium acrylate and lithium acrylate.

5. The negative electrode of claim 1 , wherein a weight average molecular weight of the copolymer is 100,000 to 500,000.

6. The negative electrode of claim 1 , wherein, when the carbon black is heat treated at 600° C. to 700° C. for 90-180 minutes, the weight loss rate of the carbon black is 0.05% to 0.25%.

7. The negative electrode of claim 1 , wherein the carbon black is included in the negative electrode active material layer in an amount of 7 wt % to 13 wt %.

8. The negative electrode of claim 1 , wherein

the negative electrode active material further comprises graphite,

the silicon particles have a D 10 of 0.2 μm or greater and a D 90 of 20 μm or less,

the difference between the D 10 and the D 90 is 15 μm or less, and

the negative electrode further comprises an additive.

9. A secondary battery comprising:

the negative electrode of claim 1 ;

a positive electrode;

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

an electrolyte.

10. The negative electrode of claim 1 , wherein the copolymer comprises 2 mol % or less of an acrylate that is not ionized and substituted.

11. The negative electrode of claim 1 , wherein the copolymer does not contain an acrylate that is not ionized and substituted.

12. The negative electrode of claim 1 , wherein an average particle diameter (D 50 ) of the silicon particles is 6 μm to 7 μm.

13. The negative electrode of claim 1 , wherein an average particle diameter (D 50 ) of the silicon particles is 5 μm to 6 μm.

14. The negative electrode of claim 1 , wherein the carbon black is included in the negative electrode active material layer in an amount of 8 wt % to 12 wt.

15. The negative electrode of claim 1 , wherein the carbon black is included in the negative electrode active material layer in an amount of 9 wt % to 11 wt %.

16. The negative electrode of claim 1 , wherein a weight ratio of the silicon particles and the binder is 1:0.228 to 1:0.343.

17. The negative electrode of claim 1 , wherein a weight ratio of the silicon particles and the binder is 1:0.242 to 1:0.329.