Anode active material with a core-shell structure, lithium secondary battery comprising same, and method for preparing anode active material with a core-shell structure
View Patent ↗An anode active material and a method for preparing the same, wherein the anode active material has a core-shell structure having formula (MOx-Liy)-C (here, M is a metal (or metalloid), x is greater than 0 and less than 1.5, and y is greater than 0 and less than 4) and including a core part containing an alloy of a metal (or metalloid) oxide-Li (MOx-Liy) and a shell part containing a carbon material coated on a surface of the core part, wherein the shell part contains lithium in an amount less than 5 atm % in the surface and the inner portion thereof. The anode active material can provide high capacity, excellent cycle characteristics, excellent volume expansion control capability, and high initial efficiency.
1. A method for preparing an anode active material having a core-shell structure, the method comprising:
(S1) coating a carbon material on the surface of a core part containing an oxide of metal or metalloid to form a composite;
(S2) mixing the composite formed in the step of (S1) with a lithium metal powder, followed by thermal treatment to carry out alloying of lithium and the metal or metalloid to form a thermally treated material; and
(S3) bringing the thermally treated material formed by the step of (S2) into acid-treatment to improve an initial efficiency of the anode active material and to suppress gas generation in a water-based slurry,
wherein the anode active material has a core-shell structure of formula (MO x —Li y )—C,
wherein M is a metal or metalloid, x is greater than 0 and less than 1.5, and y is greater than 0 and less than 4,
wherein the acid used in the acid-treatment has a concentration of 0.5 M to 3 M,
wherein the acid-treatment is carried out for 0.5 to 5 hours, and
wherein the anode active material having the core-shell structure has pH 8.75 to 10 in a water-based system.
2. The method of claim 1 , wherein the acid-treatment is carried out using at least one acid selected from a group consisting of hydrochloric acid (HCl), perchloric acid, nitric acid, and sulfuric acid.
3. The method of claim 1 , wherein the metal for metalloid is selected from a group consisting of Si, Sn, Al, Sb, Bi, As, Ge, Pb, Zn, Cd, In, Ti, Ga, and an alloy thereof.
4. The method of claim 1 , wherein the metal Or metalloid is any one selected from a group consisting of SiO, SnO, SnO2 and a mixture thereof.
5. The method of claim 1 , wherein the core part has a diameter of 0.05 μm to 30 μm.
6. The method of claim 1 , wherein the carbon material is crystalline carbon, amorphous carbon, or a mixture thereof.
7. The method of claim 1 , wherein the carbon material of the shell part is present in an amount of 0.05 wt % to 30 wt % based on the weight of the anode active material.
8. The method of claim 1 , wherein in the alloying of lithium and the metal or metalloid, the composite formed in the step of (S1) and the lithium metal powder is used in a weight ratio of 70:30 to 98:2.