METHOD OF PREPARING CARBON NANOTUBE-OLIVINE TYPE LITHIUM MANGANESE PHOSPHATE COMPOSITES AND LITHIUM SECONDARY BATTERY USING THE SAME
Provided are a method of preparing carbon nanotube-olivine type lithium manganese phosphate composites and a lithium secondary battery using the same. The method includes acid-treating a carbon nanotube to purify the carbon nanotube by adding an acid solution to the carbon nanotube, forming a precursor mixture of the carbon nanotube and a metal precursor of olivine type lithium manganese phosphate, and heat-treating the precursor mixture. The carbon nanotube-olivine type lithium manganese phosphate composites can provide high energy density per unit volume and can improve output characteristics.
1 . A method of preparing carbon nanotube-olivine type lithium manganese phosphate composites, the method comprising:
acid-treating a carbon nanotube to purify the carbon nanotube by adding an acid solution to the carbon nanotube;
forming a precursor mixture of the carbon nanotube and a metal precursor of olivine type lithium manganese phosphate; and
heat-treating the precursor mixture.
2 . The method of claim 1 , wherein the lithium manganese phosphate is represented by the Formula 1:
LiMn (1-x) M x PO 4 [Formula 1]
wherein M is at least one element selected from the group consisting of Ni, Fe, Zr, Co, Mg, Mo, Al, Ag, Y and Nb, and 0≦x<1.
3 . The method of claim 1 , wherein the acid-treating of the carbon nanotube comprises agitating the carbon nanotube with the acid solution at a temperature of 60 to 80° C. for 8 to 12 hours.
4 . The method of claim 1 , wherein the acid solution includes at least one of sulfuric acid, nitric acid and chloric acid and is an acidic solution having a mole concentration of 1 to 6 M.
5 . The method of claim 1 , wherein the preparing the precursor mixture comprises mixing carbon nanotube in an amount of 1 to 10 wt % based on the weight of the metal precursor.
6 . The method of claim 1 , wherein the heat-treating is performed at a temperature in a range of 550 to 900° C. for 6 to 12 hours.
7 . The method of claim 1 , wherein the carbon nanotube has an average diameter of 1 nm or greater and an average length of 10 μm or greater.
8 . A positive electrode composition comprising the carbon nanotube-olivine type lithium manganese phosphate composites of claim 1 .
9 . The composition of claim 8 , further comprising at least one of carbon black and carbon nanotube.
10 . The composition of claim 9 , wherein the carbon nanotube is acid-treated in an acid solution having a mole concentration of 1 to 6 M.
11 . A lithium secondary battery manufactured using the positive electrode composition of claim 8 .
12 . A lithium secondary battery manufactured using the positive electrode composition of claim 9 .
13 . A lithium secondary battery manufactured using the positive electrode composition of claim 10 .