METHOD OF PREPARING NEGATIVE ELECTRODE ACTIVE MATERIAL

Disclosed is a method of preparing a negative electrode active material which includes (a) dispersing an active material core in a solution containing a surfactant to coat the surfactant on the active material core, (b) adding and dispersing a first precursor, which is bondable with the surfactant by electrostatic attraction, in the solution, (c) adding and dispersing a second precursor, which is bondable with the first precursor by electrostatic attraction, in the solution, (d) preparing a lithium compound precursor by a hydrothermal reaction of the first precursor and the second precursor in the solution, and (e) performing a heat treatment on the lithium compound precursor to thermally decompose the surfactant, and forming a protective layer containing a lithium compound on the active material core, wherein one of the first precursor and the second precursor is at least one selected from lithium hydroxide, lithium oxide, lithium nitrate or lithium sulfate.