Solid ion conductor compound, solid electrolyte including the same, electrochemical cell including the same, and preparation method thereof

1. A solid ion conductor compound represented by Formula 1:

Li a M x Ho y X z   Formula 1

wherein, in Formula 1,

X is F, Cl, Br, I, or a combination thereof,

M is a metal element and is a divalent metal, a trivalent metal, a tetravalent metal, or a combination thereof, and

1≤a≤4, 0≤x<1.5, 0.5≤y≤1.5, and 4≤z≤9,

wherein the compound has X-ray diffraction peaks at 30° 2θ to 33° 2θ, 33° 2θ to 36° 2θ, 40° 2θ to 44° 2θ, and 48° 2θ to 52° 2θ, when analyzed using CuKα radiation, and

wherein a full width at half maximum of at least one peak at 40° 2θ to 44° 2θ is 0.35° 2θ or greater.

2. The solid ion conductor compound of claim 1 , wherein the solid ion conductor compound has an X-ray diffraction spectrum comprising diffraction peaks at 30° 2θ+0.5° 2θ, 31.5° 2θ±0.5° 2θ, 35° 2θ±0.5° 2θ, 41° 2θ±0.5° 2θ, 48.7° 2θ±0.5° 2θ, and 60° 2θ±0.5° 2θ, when analyzed using CuKα radiation.

3. The solid ion conductor compound of claim 1 , wherein the solid ion conductor compound has an X-ray diffraction spectrum comprising diffraction peaks at 30° 2θ+0.5° 2θ, 31.5° 2θ±0.5° 2θ, 35° 2θ±0.5° 2θ, 42° 2θ±0.5° 2θ, 48.7° 2θ±0.5° 2θ, and 60° 2θ±0.5° 2θ, when analyzed using CuKα radiation.

4. The solid ion conductor compound of claim 1 , wherein the halogen is Cl.

5. The solid ion conductor compound of claim 1 , wherein the halogen element is Cl and Br.

6. The solid ion conductor compound of claim 1 , wherein

the solid ion conductor compound comprises a first crystalline phase, a second crystalline phase, and an amorphous phase, and

the first crystalline phase and the second crystalline phase are the same or are different from each other, and

the amorphous phase is between the first crystalline phase and the second crystalline phase.

7. The solid ion conductor compound of claim 6 , wherein the first crystalline phase, the second crystalline phase, or both the first crystalline phase and the second crystalline phase have a layered rock salt crystal structure.

8. The solid ion conductor compound of claim 6 , wherein the first crystalline phase and the second crystalline phase each independently have a structure belonging to a C2/m space group, a P3m1 space group, or a combination thereof.

9. The solid ion conductor compound of claim 1 , wherein the solid ion conductor compound has an ionic conductivity of about 10′ Siemens per centimeter or more at 25° C.

10. The solid ion conductor compound of claim 1 , wherein the solid ion conductor compound is represented by Formula 2:

Li a M x Ho y X1 z1 X2 z2   Formula 2

wherein, in Formula 2,

X1 is Cl,

X2 is F, Br, I, or a combination thereof,

M is a metal element and is a divalent metal, a trivalent metal, a tetravalent metal, or a combination thereof, and

1≤a≤4, 0≤x<1.5, 0.5≤y≤1.5, 4≤z1<9, and 0<z2≤5.

11. The solid ion conductor compound of claim 10 , wherein X2 is Br.

12. The solid ion conductor compound of claim 10 , wherein M is Mg, Ca, Ba, Sr, In, Ga, Al, Ln, Ti, Zr, Hf, W, or a combination thereof.

13. The solid ion conductor compound of claim 1 , wherein the solid ion conductor compound is Li 3-2x Mg x HoCl 6 wherein 0<x<1.5, Li 3-2x Ca x HoCl 6 wherein 0<x<1.5, Li 3-2x Ba x HoCl 6 wherein 0<x<1.5, Li 3-2x Sr x HoCl 6 wherein 0<x<1.5, Li 3-3x In x HoCl 6 wherein 0<x<1, Li 3-3x Ga x HoCl 6 wherein 0<x<1, Li 3-3x Al x HoCl 6 wherein 0<x<1, Li 3-3x Ln x HoCl 6 wherein 0<x<1, Li 3-4x Ti x HoCl 6 wherein 0<x<0.75, Li 3-4x Zr x HoCl 6 wherein 0<x<0.75, Li 3-4x Hf x HoCl 6 wherein 0<x<0.75, Li 3-4x W x HoCl 6 wherein 0<x<0.75, Li 3-2x Mg x HoCl 5 Br wherein 0<x<1.5, Li 3-2x Ca x HoCl 5 Br wherein 0<x<1.5, Li 3-2x Ba x HoCl 5 Br wherein 0<x<1.5, Li 3-2x Sr x HoCl 5 Br wherein 0<x<1.5, Li 3-3x In x HoCl 5 Br wherein 0<x<1, Li 3-3x Ga x HoCl 5 Br wherein 0<x<1, Li 3-3x Al x HoCl 5 Br wherein 0<x<1, Li 3-3x Ln x HoCl 5 Br wherein 0<x<1, Li 3-4x Ti x HoCl 5 Br wherein 0<x<0.75, Li 3_4x Zr x HoCl 5 Br wherein 0<x<0.75, Li 3-4x Hf x HoCl 5 Br wherein 0<x<0.75, Li 3_4x W x HoCl 5 Br wherein 0<x<0.75, Li 3 HoCl 6 , Li 3 HoCl 5 Br, Li 2.25 HoCl 5.25 , Li 3.25 HoCl 6.25 , or a combination thereof.

14. A solid electrolyte comprising the solid ion conductor compound of claim 1 .

15. An electrochemical cell comprising:

a cathode layer comprising a cathode active material layer;

an anode layer comprising an anode active material layer; and

an electrolyte layer between the cathode layer and the anode layer,

wherein the cathode active material layer, the electrolyte layer, or a combination of both the cathode active material layer and the electrolyte layer comprise the solid ion conductor compound of claim 1 .

16. The electrochemical cell of claim 15 , wherein the electrochemical cell is an all-solid secondary battery.

17. A method of preparing a solid ion conductor compound, the method comprising:

providing a mixture comprising a lithium precursor and a holmium precursor; and

reacting the mixture in a solid phase to obtain the solid ion conductor compound represented by Formula 1:

Li a M x Ho y X z   Formula 1

wherein, in Formula 1,

X is F, Cl, Br, I, or a combination thereof,

M is a metal element and is a divalent metal, a trivalent metal, a tetravalent metal, or a combination thereof, and

1≤a≤4, 0≤x<1.5, 0.5≤y≤1.5, and 4≤z≤9,

wherein the compound has X-ray diffraction peaks at 30° 2θ to 33° 2θ, 33° 2θ to 36° 2θ, 40° 2θ to 44° 2θ, and 48° 2θ to 52° 2θ, when analyzed using CuKα radiation, and

wherein a full width at half maximum of at least one peak at 40° 2θ to 44° 2θ is 0.35° 2θ or greater.

18. The method of claim 17 , wherein the reacting of the mixture in the solid phase comprises:

ball-mill-mixing the mixture in an inert atmosphere.

19. The method of claim 18 , wherein the ball-mill-mixing comprises a cycle alternating between a first time interval and a second time interval, wherein the first time interval comprises the ball-mill mixing and the second time interval comprises a rest period.

20. The method of claim 19 , wherein the cycle is repeated for a time period of about 22 hours to about 26 hours.

21. The method of claim 18 , wherein the reacting of the mixture further comprises drying the mixture.

22. The method of claim 17 , wherein the solid ion conductor compound is prepared at a temperature of about 20° C. to about 25° C., and the method does not comprise a calcination step.