Mixed conductor, electrochemical device including the same, and preparation method of mixed conductor
A mixed ionic and electronic conductor represented by Formula 1: T x Va y A 1-x-y M z O 3-δ , wherein T includes at least one monovalent cation, A includes at least one of a monovalent cation, a divalent cation, and a trivalent cation, M includes at least one of a trivalent cation, a tetravalent cation, and a pentavalent cation, M is an element other than Ti and Zr, Va is a vacancy, δ is an oxygen vacancy, 0<x, y≤0.25, 0<z<1, and 0≤δ≤1.
1. A mixed ionic and electronic conductor represented by Formula 1:
T x Va y A 1-x-y M z O 3-δ Formula 1
wherein, in Formula 1,
T comprises at least one monovalent cation,
A comprises at least one of a monovalent cation, a divalent cation, and a trivalent cation,
M comprises at least one of a trivalent cation, a tetravalent cation, and a pentavalent cation, and is an element other than Ti and Zr,
Va is a vacancy,
δ is an oxygen vacancy,
0<x, y≤0.25, 0<z≤1, and 0≤δ≤1.
2. The mixed conductor of claim 1 , wherein, in Formula 1, T comprises at least one monovalent alkali metal cation.
3. The mixed conductor of claim 1 , wherein, in Formula 1, M comprises a first cation and a second cation, and wherein an oxidation state of the first cation is different than an oxidation state of the second cation.
4. The mixed conductor of claim 1 , wherein, in Formula 1, M comprises at least one pentavalent cation.
5. The mixed conductor of claim 1 , wherein, in Formula 1, T comprises at least one of Li, Na, and K.
6. The mixed conductor of claim 1 , wherein, in Formula 1, A comprises at least one of H, Na, K, Rb, Cs, Ca, Sr, Ba, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Er, and Eu.
7. The mixed conductor of claim 1 , wherein, in Formula 1, M comprises at least one of Ni, Pd, Pb, Fe, Ir, Co, Rh, Mn, Cr, Ru, Re, Sn, V, Ge, W, Sc, Nb, Ta, and Mo.
8. The mixed conductor of claim 1 , wherein 0<x<0.3.
9. The mixed conductor of claim 1 , wherein δ is 0.
10. The mixed conductor of claim 1 , wherein the mixed conductor represented by Formula 1 is represented by Formula 2:
T x Va y A 1-x-y M′ z M″ 1-z O 3-δ Formula 2
wherein in Formula 2,
T comprises at least one monovalent cation,
A comprises at least one of a monovalent cation, a divalent cation, and a trivalent cation,
M′ and M″ each independently comprise at least one of a trivalent cation, a tetravalent cation, and a pentavalent cation,
M′ and M″ are each independently an element other than Ti and Zr,
Va is a vacancy,
δ is an oxygen vacancy,
0<x, y≤0.25, 0<z<1, and 0≤δ≤1.
11. The mixed conductor of claim 10 , wherein M′ has an oxygen vacancy formation energy value of 2.9 electron volts, or less.
12. The mixed conductor of claim 10 , wherein M′ comprises at least one of a trivalent cation and a tetravalent cation, and
M″ comprises at least one pentavalent cation.
13. The mixed conductor of claim 1 , wherein an electronic conductivity of the mixed conductor is greater than an ionic conductivity of the mixed conductor.
14. The mixed conductor of claim 1 , wherein an electronic conductivity of the mixed conductor is 4×10 −9 S/cm or greater at 25° C.
15. The mixed conductor of claim 1 , wherein an ionic conductivity of the mixed conductor is 1×10 −6 S/cm or greater at 25° C.
16. The mixed conductor of claim 1 , wherein the mixed conductor has a phase with a perovskite type crystal structure.
17. The mixed conductor of claim 1 , wherein the mixed conductor has a single peak at a diffraction angle of 23°±2.5° two-theta, when analyzed by X-ray diffraction using Cu Kα radiation.
18. An electrochemical device comprising the mixed conductor of claim 1 .
19. The electrochemical device of claim 18 , wherein the electrochemical device is a battery, an accumulator, a supercapacitor, a fuel cell, a sensor, or an electrochromic device.