Positive electrode and lithium secondary battery including the same

1. A positive electrode which comprises a lithium transition metal composite oxide and a binder polymer, wherein the binder polymer has a functional group capable of adsorbing the transition metal ions of the lithium transition metal composite oxide,

wherein the binder polymer is formed by polymerization of single molecules containing the functional group and a binder backbone, and

wherein the binder backbone comprises at least one selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoroproyplee (PVDF-co-HFP), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylonitrile and polymethyl methacrylate,

wherein the functional group is chitosan and/or includes chitosan.

2. The positive electrode according to claim 1 , wherein the functional group capable of adsorbing the transition metal ions comprises at least one selected from the group consisting of a hydroxyl group, aldehyde group, carboxyl group, nitro group, carbonyl group, ether group, ester group, amine group, formyl group, phenol group, pyridine group and a phosphine group.

3. The positive electrode according to claim 1 , wherein the lithium transition metal composite oxide is at least one selected from the group consisting of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium nickel manganese oxide and lithium nickel manganese cobalt oxide.

4. The positive electrode according to claim 1 , wherein the single molecules comprising the functional group capable of adsorbing the transition metal ions is present in an amount of 0.01-2 parts by weight based on 100 parts by weight of the binder backbone.

5. The positive electrode according to claim 1 , which further comprises a positive electrode current collector coated with the lithium transition metal composite oxide and the binder polymer.

6. The positive electrode according to claim 5 , wherein the positive electrode current collector comprises at least one selected from the group consisting of stainless steel, aluminum, nickel, titanium and baked carbon.

7. A lithium secondary battery comprising a negative electrode, the positive electrode as defined in claim 1 , a separator interposed between the negative electrode and the positive electrode, and a non-aqueous electrolyte.