Negative active material, lithium secondary battery including the same, and method of manufacturing the negative active material

A method of manufacturing a negative active material, the method comprising:

• mixing a first composition and a second composition to prepare a third composition, wherein,
• the first composition comprises a first polymer and a non-aqueous solvent, the first polymer comprising a first functional group and being at least one of polyamic acid, polyimide, or a copolymer thereof,
• the second composition comprises water and a second polymer comprising a second functional group, wherein the second polymer is water-soluble, and
• at least one of the first polymer and the second polymer further comprises a halogen group;
• contacting a surface of an active material core and the third composition to form a coated surface;
• and
• heat-treating the coated surface at a temperature of about 160° C. or greater to form a polymer layer comprising a third polymer on the surface of the active material core, wherein the third polymer is a cross-linked product of the first polymer and the second polymer, and the first polymer and the second polymer are cross-linked by an ester bond that is formed by a reaction of the first functional group and the second functional group.