Method for manufacturing negative active material, and negative active material and lithium secondary battery using same
A method for preparing a negative electrode active material, a negative electrode active material prepared using the same, and a lithium secondary battery, and in particular, to a method for preparing a negative electrode active material including the steps of (a) preparing a coating composition including a precursor of metal-phosphorus-oxynitride; (b) forming a precursor layer on a negative electrode active material with the coating composition of (a) using a solution process; and (c) forming a metal-phosphorus-oxynitride protective layer on the negative electrode active material by heat treating the negative electrode active material having the precursor layer formed thereon. The method for preparing a negative electrode active material uses a solution process, which is advantageous in terms of simplifying the whole process and reducing costs, and high capacity, high stabilization and long lifetime are obtained as well by the formed protective layer having excellent properties.
1. A method for preparing a negative electrode active material comprising:
(a) preparing a coating composition comprising a precursor of metal-phosphorus-oxynitride;
(b) forming a precursor layer on a negative electrode active material with the coating composition of (a) using a solution process; and
(c) forming a metal-phosphorus-oxynitride protective layer on the negative electrode active material by heat treating the negative electrode active material having the precursor layer formed thereon.
2. The method for preparing a negative electrode active material of claim 1 , wherein the precursor of metal-phosphorus-oxynitride is prepared by a reaction of a compound comprising a phosphorus-nitrogen bond with a metal salt compound.
3. The method for preparing a negative electrode active material of claim 2 , wherein the compound comprising the phosphorus-nitrogen bond comprises at least one selected from the compounds represented by the following Chemical Formulae 1 to 3:
wherein each X 1 is the same or different from each other and each independently is OR 1 , F, Cl, Br or I, wherein R 1 is an alkyl group having 1 to 5 carbon atoms;
wherein R 2 and R 3 are the same or different from each other and each independently is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms;
wherein each X 2 is the same or different from each other and each independently is R 4 , OR 5 , NR 6 R 7 , F, Cl, Br or I, wherein R 4 to R 7 are the same or different from each other and each independently is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms, and
n is an integer of 100 to 100,000.
4. The method for preparing a negative electrode active material of claim 2 , wherein the metal salt compound comprises at least one metal selected from the group consisting of lithium, sodium, magnesium, calcium, zinc and aluminum.
5. The method for preparing a negative electrode active material of claim 1 , wherein the coating composition comprises a compound comprising a phosphorus-nitrogen bond, a metal salt compound and an organic solvent.
6. The method for preparing a negative electrode active material of claim 5 , wherein the coating composition comprises, based on a total weight of the composition, the compound comprising the phosphorus-nitrogen bond in an amount of from 0.002 to 27% by weight, the metal salt compound in an amount of from 0.0005 to 12% by weight, and the organic solvent in an amount of from 70 to 99.99% by weight.
7. The method for preparing a negative electrode active material of claim 5 , wherein the coating composition further comprises a chalcogen compound.
8. The method for preparing a negative electrode active material of claim 1 , wherein the negative electrode active material comprises at least one selected from the group consisting of lithium metal, lithium alloys, transition metal composite oxides, silicon-based materials, tin-based materials and carbon-based materials.
9. The method for preparing a negative electrode active material of claim 1 , wherein the negative electrode active material has a spherical, an elliptical, a spindle, a scaly, a plate, a fibrous, a rod, a core-shell or an atypical shape.
10. The method for preparing a negative electrode active material of claim 1 , wherein, in step (b), the solution process comprises at least one method selected from the group consisting of spray coating, spin coating, dip coating, inkjet printing, offset printing, reverse offset printing, gravure printing and roll printing.
11. The method for preparing a negative electrode active material of claim 1 , wherein, in step (c), the heat treatment is carried out in a temperature range of 150° C. or higher and lower than 500° C.
12. The method for preparing a negative electrode active material of claim 1 , further comprising, prior to step (c), removing an organic solvent included in the precursor layer formed from step (b).
13. The method for preparing a negative electrode active material of claim 1 , wherein the metal-phosphorus-oxynitride protective layer formed from step (c) comprises amorphous metal-phosphorus-oxynitride.