Negative active material, lithium secondary battery comprising the negative active material and manufacturing method thereof

Abstract

Disclosed are an anode active material, a non-aqueous lithium secondary battery, and a preparation method thereof. The surface of a carbonaceous material is modified without using an electrolyte additive, and the reactivity and structural stability of the surface is improved, thereby obtaining long lifetime characteristics without deteriorating charge/discharge efficiency and rate characteristics when applied as an anode active material of a non-aqueous lithium secondary battery. The anode active material comprises a carbonaceous material, and a coating layer formed on the surface of the carbonaceous material through hetero atom substitution, wherein the hetero atom can be phosphorus (P) or sulfur (S). A side reaction with an electrolyte on the surface of the carbonaceous material is inhibited and the structural stability of the surface is enhanced by forming a coating layer on the surface of the carbonaceous material with a hetero atom such as phosphorus (P) or sulfur (S).

1 . An anode active material for use in a non-aqueous lithium secondary battery, comprising:
 a carbonaceous material; and   a coating layer of hetero elements formed on the surface of the carbonaceous material,   wherein the hetero elements include phosphorus (P).   
     
     
         2 . The anode active material of  claim 1 , wherein the hetero elements include sulfur (S). 
     
     
         3 . The anode active material of  claim 1 , wherein the carbonaceous material includes at least one of artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbeads, petroleum coke, plastic resins, carbon fiber and pyrocarbon. 
     
     
         4 . The anode active material of  claim 3 , wherein the carbonaceous material has L a(110) >10 nm and L c(002) >10 nm L,
 wherein L a(110) =0.89λ/[B 110 cos(θ 110 )] and L s(002) =0.89λ/[B 002 cos(θ 002 )],   wherein λ is the wavelength of Cu Kα(λ=0.15418 nm) and B is a full width at half-maximum (FWHM) value with respect to (110) or (002) peak according to Bragg diffraction angle.   
     
     
         5 . The anode active material of  claim 4 , wherein the carbonaceous material has 0.344 nm or less as d 002  with respect to (002) peak. 
     
     
         6 . The anode active material of  claim 3 , wherein the carbonaceous material has a specific surface area of less than 10 m 2 /g. 
     
     
         7 . The anode active material of  claim 3 , wherein the carbonaceous material has a degree of graphitization in the range of 0.4 to 1.0, and the degree of graphitization is calculated according to (degree of graphitization)=(3.44−d 002 )/(0.086). 
     
     
         8 . The anode active material of  claim 1 , wherein the content of the coating layer is less than 10 wt % with respect to the carbonaceous material. 
     
     
         9 . The anode active material of  claim 8 , wherein the coating layer is formed uniformly on the overall surface of the carbonaceous material or formed on part of the surface of the carbonaceous material. 
     
     
         10 . A lithium secondary battery including an anode formed of an anode active material that includes a carbonaceous material and a coating layer of hetero elements formed on the surface of the carbonaceous material, wherein the hetero elements include phosphorus (P) or sulfur (S). 
     
     
         11 . A method for fabricating an anode active material for use in a non-aqueous lithium secondary battery, the method comprising:
 preparing a carbonaceous material and a hetero element material; and   forming a coating layer of hetero elements on the surface of the carbonaceous material using the hetero element material,   wherein the hetero elements include phosphorus (P).   
     
     
         12 . The method of  claim 11 , wherein the hetero elements further include sulfur (S). 
     
     
         13 . The method of  claim 12 , wherein the hetero element material includes at least one of NH 4 PF 6 , (NH 4 ) 2 PO 4 , NH 4 PO 3 , (NH 4 ) 2 SO 3 , (NH 4 ) 2 SO 4 , NH 4 SO 4 , and (NH 4 ) 2 S 2 O 8 . 
     
     
         14 . The method of  claim 13 , wherein the forming of the coating layer comprises:
 dissolving the hetero element material in a solvent to form a solution;   uniformly mixing the carbonaceous material with the solution to form a mixture;   vacuum-drying the mixture; and   performing heat treatment on the dried material through thermal decomposition to form the coating layer based on the hetero elements on the surface of the carbonaceous material.