Negative active material for rechargeable lithium battery, and method of preparing the same
An negative active material for a rechargeable lithium battery includes a nano-composite including a Si phase, a SiO 2 phase, and a metal oxide phase of formulation M y O, where M is a metal with an oxidation number x, a free energy of oxygen-bond formation ranging from −900 kJ/mol to −2000 kJ/mol, x, and x·y=2. The negative active material for a rechargeable lithium battery according to the present invention can improve initial capacity, initial efficiency, and cycle-life characteristics by suppressing its initial irreversible reaction.
1. A negative active material for a rechargeable lithium battery comprising a nano-composite comprising a Si phase, a SiO 2 phase, and a metal oxide phase of the formula M y O, wherein M is a metal with an oxidation number of x and a free energy of oxygen-bond formation ranging from −900 kJ/mol to −2000 kJ/mol, and x ·y=2, wherein M is selected from the group consisting of Al, Ca, Mg, Ti, and Li.
2. The negative active material of claim 1 , wherein the Si phase comprises Si nanograins.
3. The negative active material of claim 1 , wherein the nano-composite comprises 40 to 80 mol% of the Si phase.
4. The negative active material of claim 1 , wherein the nano-composite comprises 5 to 45 mol% of the SiO 2 phase.
5. The negative active material of claim 1 , wherein the metal oxide phase is amorphous.
6. The negative active material of claim 1 , wherein the nano-composite comprises 3 to 50 mol% of the metal oxide phase.
7. The negative active material of claim 1 , wherein the nano-composite has a SiO 2 infrared absorption spectrum ranging from 970 cm −1 to 1150 cm −1 .
8. The negative active material of claim 1 , wherein the nano-composite has a Si 2 p peak ranging from 99 eV to 106 eV according to X-ray spectroscopic analysis.
9. The negative active material of claim 1 , wherein the nano-composite has an Al 2p peak ranging from 74 to 77 eV when M is Al; a Ca 2 p peak ranging from 345 to 349 eV when M is Ca; and a Ti 2 p peak ranging from 457 to 461 eV when M is Ti according to X-ray spectroscopic analysis.
10. The negative active material of claim 1 , wherein the nano-composite is surface-treated with a conductive material having electrical conductivity of 1×10 6 S/m or more.
11. The negative active material of claim 10 , wherein the conductive material is surface-treated on the nano-composite in an amount of 50 wt% or less based on the total weight of the negative active material.
12. The negative active material of claim 1 , wherein the negative active material has an average particle size ranging from 0.1 μm to 100 μm.
13. The negative active material of claim 1 , wherein the negative active material has a specific surface area ranging from 1 m 2 /g to 100 m 2 /g.
14. A negative electrode comprising:
a current collector; and
an active material layer including a negative active material and a binder disposed on the current collector,
wherein the negative active material comprises a nano-composite comprising a Si phase, a SiO 2 phase, and a metal oxide phase of the formula M y O, wherein M is a metal with an oxidation number of x and a free energy of oxygen bond formation ranging from −900 kJ/mol to −2000 kJ/mol, and x ·y=2, wherein M is selected from the group consisting of Al, Ca, Mg, Ti, and Li.
15. The negative electrode of claim 14 , wherein the Si phase comprises Si nanograins.
16. The negative electrode of claim 14 , wherein the nano-composite comprises 40 to 80 mol% of the Si phase.
17. The negative electrode of claim 14 , wherein the nano-composite comprises 5 to 45 mol% of the SiO 2 phase.
18. The negative electrode of claim 14 , wherein the metal oxide phase is amorphous.
19. The negative electrode of claim 14 , wherein the nano-composite comprises 3 to 50 mol% of the metal oxide phase.
20. The negative electrode of claim 14 , wherein the nano-composite has a SiO 2 infrared absorption spectrum ranging from 970 cm −1 to 1150 cm −1 .
21. The negative electrode of claim 14 , wherein the nano-composite has a Si 2 p peak ranging from 99 eV to 106 eV according to X-ray spectroscopic analysis.
22. The negative electrode of claim 14 , wherein the nano-composite has an Al 2 p peak ranging from 74 to 77 eV when M is Al; a Ca 2p peak ranging from 345 to 349 eV when M is Ca; and a Ti 2 p peak ranging from 457 to 461 eV when M is Ti according to X-ray spectroscopic analysis.
23. The negative electrode of claim 14 , wherein the nano-composite is surface-treated with a conductive material having electrical conductivity of 1×10 6 S/m or more.
24. The negative electrode of claim 23 , wherein the conductive material is present in an amount of 50 wt% or less based on the total weight of the negative active material.
25. The negative electrode of claim 14 , wherein the negative active material has an average particle size ranging from 0.1 μm to 100 μm.
26. The negative electrode of claim 14 , wherein the negative active material has a specific surface area ranging from 1 m 2 /g to 100 m 2 /g.
27. A rechargeable lithium battery comprising a negative electrode according to claim 14 .