Electrode comprising lithium nickel oxide layer, method for preparing the same, and electrochromic device comprising the same

1. A method of preparing an electrode containing lithium nickel oxide, in which nickel has a single oxidation number, the method comprising the steps of:

a) preparing an electrode comprising a lithium nickel oxide (Li x Ni 1-y O, herein, 0.4<x<1, and 0<y<1) layer formed on a conductive substrate; and

b) applying an oxidation voltage to the electrode, and then applying a reduction voltage to the electrode, wherein the oxidation voltage and the reduction voltage are applied to the electrode by using a voltage applying means, which can contact with an entire outer circumference of the electrode, is disposed on the entire outer circumference of the electrode, and contacts with the electrode; or by using a voltage applying means which is disposed on the outer circumference of the electrode with a predetermined interval and contacts with the electrode, and

the lithium nickel oxide is represented by following Formula 1:

Li x Ni 1-y O wherein 0.4<x<1 and 0<y<1.  [Formula 1]

2. The method as claimed in claim 1 , wherein the oxidation voltage and the reduction voltage are applied to an entire outer circumference of the electrode.

3. The method as claimed in claim 1 , wherein the oxidation voltage and the reduction voltage are applied by horizontally disposing the electrode comprising the lithium nickel oxide layer and a reductive counter electrode above a ground surface in an electrochemical cell comprising an electrolyte.

4. The method as claimed in claim 1 , wherein in step b), the oxidation voltage and the reduction voltage are alternately applied in an electrochemical cell comprising an electrolyte having lithium ions (Li + ) and a reductive counter electrode.

5. The method as claimed in claim 1 , wherein a contact ratio of the voltage applying means and the electrode is 70˜100% in the outer circumference of the electrode.

6. The method as claimed in claim 1 , wherein the voltage applying means comprises a metal of no reactivity with an electrolyte or is coated with a metal of no reactivity with an electrolyte.

7. The method as claimed in claim 1 , wherein the voltage applying means comprises or is coated with one or more metal selected from the group including Pt, Ir, Pd, and Ta, or an alloy of the materials.

8. The method as claimed in claim 1 , wherein in step b), the applied oxidation voltage is within a range of 1˜3.2V, and the applied reduction voltage is within a range of −1˜−2.7V.

9. The method as claimed in claim 1 , wherein in step b), the oxidation and the reduction voltage are applied until the electrode is completely oxidized or reduced.

10. The method as claimed in claim 1 , wherein in step b), at application of the reduction voltage, the electrode is completely reduced so that light transmittance is 60% or more at a wavelength of 500 nm.

11. The method as claimed in claim 1 , wherein in step b), temperature is higher than 15° C. and lower than a boiling point or a decomposition point of an electrolyte.

12. The method as claimed in claim 1 , wherein in step b), the oxidation voltage and the reduction voltage are repeatedly applied 1˜10 times.

13. The method as claimed in claim 1 further comprises the step of heat-treating the electrode comprising the lithium nickel oxide layer, between the steps a) and b).

14. The method as claimed in claim 13 , wherein the step of heat-treating is performed at 100˜350° C. for 30 minutes ˜3 hours.

15. The method as claimed in claim 1 , wherein a thickness of the lithium nickel oxide layer formed on the conductive substrate is 150 nm˜10 μm.

16. An electrode comprising a lithium nickel oxide layer formed on a conductive substrate, and Ni having a single oxidation number in lithium nickel oxide, which is prepared by the method as claimed in claim 1 .

17. The electrode as claimed in claim 16 , wherein the oxidation number is +2 or +3.

18. An electrochromic device comprising

a) a first electrode;

b) a second electrode;

c) an electrochromic material; and

d) an electrolyte,

wherein, the first electrode or the second electrode is the electrode as claimed in claim 16 .

19. The method as claimed in claim 1 , wherein the voltage applying means comprises a metal of no reactivity with an electrolyte or is coated with a metal of no reactivity with an electrolyte.

20. The method as claimed in claim 1 , wherein the voltage applying means comprises or is coated with one or more metal selected from the group including Pt, Ir, Pd, and Ta, or an alloy of the materials.

21. The method as claimed in claim 1 , wherein the oxidation voltage and the reduction voltage are uniformly applied to the entire outer circumference of the electrode with a predetermined interval.