Compound, method for preparation of the same, and lithium secondary battery comprising the same
View Patent ↗Disclosed are a novel compound, a method for preparing the same, and a lithium secondary battery comprising the same. More specifically, disclosed are a compound in which five MO 6 octahedrons are bonded to one another around one MO 6 octahedron such that the MO 6 octahedrons share a vertex, to form hollows and Li cations substituted instead of Na cations using an ion substitution method are present in the hollows, and a crystal structure thereof is not varied even upon intercalation and deintercalation of Li cations, a method for preparing the same, and a lithium secondary battery comprising the same as a cathode active material.
1. A cathode active material for a lithium secondary battery comprising at least one compound selected from compounds represented by the following Formula 1:
Li x Na 1−x Ru 2−y Me y O 4 (1)
wherein
0<x≦1;
0<y≦2;
Me is a metal or transition metal cation having an oxidation number of +2 to +4, and
wherein the compound has a crystal structure in which five RuO 6 octahedrons are bonded to one another around one RuO 6 octahedron such that the RuO 6 octahedrons share a vertex, to form hollows and Na cations and Li cations coexist in the hollows.
2. The cathode active material according to claim 1 , wherein x is 1.
3. The cathode active material according to claim 1 , wherein Me is at least one selected from the group consisting of Al, Mg, Ti, Fe, Co, Ni and Mn.
4. The cathode active material according to claim 1 , wherein the oxygen ion of Formula 1 is substituted by an anion (A) having an oxidation number of −1 or −2.
5. The cathode active material according to claim 4 , wherein the compound is represented by the following formula 2:
Li x Na 1−x Ru 2−y Me y O 4−z A z (2)
wherein
0<x≦1;
0<y≦2;
0≦z≦0.1;
Me is a metal or transition metal cation having an oxidation number of +2 to +4; and
A is an anion having an oxidation number of −1 or −2.
6. The cathode active material according to claim 5 , wherein A is at least one selected from the group consisting of halogen, S and N.
7. A cathode for a lithium secondary battery in which the cathode active material according to claim 1 is applied to a current collector.
8. A lithium secondary battery comprising the cathode according to claim 7 .
9. A battery module comprising the lithium secondary battery according to claim 8 as a unit cell.
10. A battery pack comprising the battery module according to claim 9 .
11. A device using the battery pack according to claim 10 as a power source.
12. The device according to claim 11 , wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a power storage device.
13. A method for preparing the compound represented by the following Formula 1 by mixing a Li compound with Na-Ru-based oxide and reacting the compound at a temperature of 300 to 700° C. for 10 to 14 hours by an ion substitution method:
Li x Na 1−x Ru 2−y Me y O 4 (1)
wherein
0<x≦1;
0<y≦2;
Me is a metal or transition metal cation having an oxidation number of +2 to +4, and
wherein the compound has a crystal structure in which five RuO 6 octahedrons are bonded to one another around one RuO 6 octahedron such that the RuO 6 octahedrons share a vertex, to form hollows and Na cations and Li cations coexist in the hollows.
14. The method according to claim 13 , wherein the Na—Ru-based oxide is NaRu 2 O 4 .
15. The method according to claim 14 , wherein NaRu 2 O 4 is synthesized by mixing Na 2 CO 3 with RuO 2 , and baking the mixture under an Ar atmosphere at a temperature of 800 to 1100° C. for 10 to 14 hours.
16. The method according to claim 13 , wherein the Li compound is LiX (in which X is an element having an oxidation number of −1).
17. The method according to claim 16 , wherein LiX is selected from the group consisting of LiI, LiCl and LiNO 3 .
18. The method according to claim 13 , wherein x is 1.
19. The method according to claim 13 , wherein Me is at least one selected from the group consisting of Al, Mg, Ti, Fe, Co, Ni and Mn.
20. The method according to claim 13 , wherein the oxygen ion of Formula 1 is substituted by an anion (A) having an oxidation number of −1 or −2.
21. The method according to claim 13 , wherein the compound is represented by the following formula 2:
Li x Na 1−x Ru 2−y Me y O 4−z A z (2)
wherein
0<x≦1;
0<y≦2;
0≦z≦0.1;
Me is a metal or transition metal cation having an oxidation number of +2 to +4; and
A is an anion having an oxidation number of −1 or −2.
22. The method according to claim 21 , wherein A is at least one selected from the group consisting of halogen, S and N.