| 摘要 |
PURPOSE: A negative electrode active material for a lithium secondary battery and its preparation method are provided, to improve the capacity and the cycle lifetime property compared with the already known negative electrode active material. CONSTITUTION: The negative electrode active material comprises a natural graphite having the surface coating layer represented by MXOk; and a crystalline carbon except amorphous or natural graphite, wherein M is at least one element selected from the group consisting of an alkali metal, an alkaline earth metal, elements of group 13, elements of group 14, a transition metal and a rare earth metal; X is an atom capable of forming a double bond with oxygen; and k is 2-4. Preferably M is at least one selected from the group consisting of Al, Ni, Co, Zr, Mn, Cr, Fe, Mg, Sr, V and Zr; and X is selected from the group consisting of P, S and W. The natural graphite is prepared by reacting a compound containing X and a compound containing M in water to prepare a coating solution; coating a natural graphite with the coating solution; and sintering the coated graphite at a temperature of 400-700 deg.C for 4-7 hours.
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