Negative electrode for secondary battery and secondary battery including the negative electrode

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

a current collector;

an interlayer directly on the current collector and consisting of a cation-substituted polycarboxylic acid; and

a negative electrode active material layer directly on the interlayer, wherein the negative electrode active material layer comprises a negative electrode active material and a binder,

wherein a polycarboxylic acid of the cation-substituted polycarboxylic acid is polyacrylic acid, polymethacrylic acid, polymaleic acid, poly(acrylate-co-maleic acid), poly(methylvinylether-alt-maleic acid), poly(butadiene-co-maleic acid), or a combination thereof, wherein a cation of the cation-substituted polycarboxylic acid is at least one selected from a lithium ion (Li + ), a sodium ion (Na + ), a potassium ion (K + ), and an ammonium ion (NH 4 + ),

and the negative electrode active material is at least one selected from silicon, a silicon oxide, a silicon alloy, a mixture of a silicon-comprising material and graphite, and a composite of the silicon-comprising material and the graphite, wherein the binder has a same composition as the interlayer.

2. The negative electrode of claim 1 , wherein a weight average molecular weight of the cation-substituted polycarboxylic acid is from about 1,000 to about 1,000,000 Daltons.

3. The negative electrode of claim 1 , wherein a glass transition temperature of the cation-substituted polycarboxylic acid is about 50° C. or greater.

4. The negative electrode of claim 1 , wherein a melting point of the cation-substituted polycarboxylic acid is about 100° C. or higher.

5. The negative electrode of claim 1 , wherein a thickness of the interlayer is from about 100 nanometers to about 10 micrometers.

6. The negative electrode of claim 1 , wherein a thickness of the interlayer is from about 100 nanometers to about 2 micrometers.

7. The negative electrode of claim 1 , wherein the cation-substituted polycarboxylic acid is a lithium polyacrylate, a lithium polymethacrylate, a poly(acrylate-co-maleic acid) lithium salt, a poly(methylvinylether-alt-maleic acid) lithium salt, a poly(butadiene-co-maleic acid) lithium salt, or a combination thereof.

8. The negative electrode of claim 1 , wherein the binder consists of the cation-substituted polycarboxylic acid.

9. The negative electrode of claim 1 , wherein the interlayer does not include a conducting agent.

10. The negative electrode of claim 1 , wherein the binder consists of the cation-substituted polycarboxylic acid, and an amount of the cation-substituted polycarboxylic acid contained in the interlayer is greater than an amount of the cation-substituted polycarboxylic acid contained in the negative electrode active material layer.

11. The negative electrode of claim 1 , wherein a cation of the cation-substituted polycarboxylic acid comprises at least 50 mole percent of the cation with respect to a molar equivalent of an acid group of the polycarboxylic acid.

12. The negative electrode of claim 1 , wherein the cation-substituted polycarboxylic acid is lithium polyacrylate, and the negative electrode active material comprises at least one selected from silicon, a silicon oxide, a silicon alloy, a mixture of a silicon-comprising material and graphite, and a composite of the silicon-comprising material and the graphite.

13. The negative electrode of claim 1 , wherein an amount of the binder is about 1 part to about 20 parts by weight, based on 100 parts by weight of the negative electrode active material layer.

14. A secondary battery comprising the negative electrode of claim 1 .

15. The secondary battery of claim 14 , wherein the secondary battery is a lithium secondary battery.

16. A flexible battery comprising the negative electrode of claim 1 .