NEGATIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, METHOD FOR PREPARING THE SAME AND LITHIUM SECONDARY BATTERY COMPRISING THEREOF

摘要

In the present invention, i) a first particle comprising crystalline flaky graphite fragment particles having an average thickness of 0.01 to 0.2 μm and an average particle diameter of 2 to 200 μm, the crystalline flaky graphite fragment particles and the average bonded to the surface thereof A second particle including silicon (Si) particles having a particle diameter of 5 to 500 nm, and a matrix including amorphous carbon or soft carbon, wherein the first particles and the second particles are in the matrix. A granulated particle core having a structure in which particles are randomly distributed and bonded, and ii) the first particles and the second particles are stacked together with the matrix in the concentric direction of the core on the surface of the granulated particle core. It provides a negative electrode active material for a lithium secondary battery comprising spheroidized granulated particles including the conjugated surface layer. The negative active material for a lithium secondary battery according to the present invention includes a second particle formed by bonding nano-sized silicon (Si) particles to crystalline flaky graphite fragment particles, thereby uniformly dispersing the silicon particles in the active material particles. Since electrical contact between the silicon particles and the crystalline flaky graphite fragment particles can be maintained, it can be usefully used as a negative electrode active material of a lithium secondary battery with a high charge/discharge capacity and a long cycle life compared to the prior art.