Electrochromic devices and method for forming such devices

1. An electrochromic device comprising a plurality of layers, including at least one planarizing layer, which primarily comprises an inorganic oxide and has an upper surface roughness which is less than or equal to half of the upper surface roughness of an underlying layer in contact with a lower surface of the at least one planarizing layer, wherein at least valleys of the underlying layer are filled by the lower surface of the at least one planarizing layer.

2. The electrochromic device of claim 1 , comprising:

at least one substrate;

a lower transparent conductor layer;

a first electrochromic layer;

an ion conductor layer;

a second electrochromic layer; and

an upper transparent conductor layer,

wherein: (a) the first electrochromic layer is a primary electrochromic layer and the second electrochromic layer is a secondary electrochromic layer, or (b) the first electrochromic layer is the secondary electrochromic layer and the second electrochromic layer is the primary electrochromic layer.

3. The electrochromic device of claim 2 , wherein:

the secondary electrochromic layer comprises a composition represented by the formula Li a NiM1 x M2 y O z , where M1 and M2 are different elements and are selected from the group consisting of B, Mn, Ti, Co, Zr, Al, P, Si, Ru, Ta, Nb, Mo, W, Ir, V, Cr, N, and combinations thereof, where a is from 1 to 5; x is from 0 to 1; y is from 0 to 1; and z is from 1.5 to 6, provided that x+y>0.

4. The electrochromic device of claim 3 , wherein a is 1.5 to 4.5.

5. The electrochromic device of claim 3 , wherein x is 0.5 to 0.8.

6. The electrochromic device of claim 3 , wherein y is 0.05 to 0.1.

7. The electrochromic device of claim 3 , wherein z is 2 to 5.

8. The electrochromic device of claim 3 , wherein the secondary electrochromic layer comprises a hygroscopic material.

9. The electrochromic device of claim 3 , wherein the secondary electrochromic layer comprises a large-grain thin film mixture, wherein a refractive index of a component material of the secondary electrochromic layer is similar to a refractive index in a bleached state, but different from a refractive index in a colored state, of remaining component materials of the secondary electrochromic layer.

10. The electrochromic device of claim 3 , wherein a Li ion storage capacity of the secondary electrochromic layer is at least 100 mC/cm 2 /um.

11. The electrochromic device of claim 3 , wherein a coloration efficiency of the secondary electrochromic layer is lower than 30 cm 2 /C.

12. The electrochromic device of claim 3 , wherein the secondary electrochromic layer has a transmittance of at least 50% of light in a bleached state, and no more than 20% of light in a colored state, where the light has a wavelength within a range from 400 nm to 950 nm.

13. The electrochromic device of claim 3 , wherein the secondary electrochromic layer is formed from a precursor solution comprising a nickel precursor selected from the group consisting of nickel nitrate, nickel acetate, nickel chloride, nickel acetylacetonate and nickel carbonate hydroxide, and a lithium precursor selected from the group consisting of lithium nitrate, lithium carbonate, lithium acetate, lithium hydroxide, and lithium trifluoromethanesulfonate.

14. The electrochromic device of claim 3 , wherein there is only one substrate and the layers constitute a monolithic stack.

15. The electrochromic device of claim 3 , wherein there are two substrates and the electrochromic device is in a form of a laminate.