Mixed conductor, method of preparing the mixed conductor, and cathode, lithium-air battery and electrochemical device each including the mixed conductor

Abstract

A mixed conductor, a method of preparing the same, and a cathode, a lithium-air battery, and an electrochemical device each including the mixed conductor. The mixed conductor is represented by Formula 1 and having electronic conductivity and ionic conductivity:LixMO2-δ  Formula 1wherein, in Formula 1, M is a Group 4 element, a Group 5 element, a Group 6 element, a Group 7 element, a Group 8 element, a Group 10 element, a Group 11 element, a Group 12 element, or a combination thereof, and 0<x<1 and 0≤δ≤1 are satisfied.

What is claimed is: 
     
         1 . A mixed conductor represented by Formula 1 and having electronic conductivity and ionic conductivity:
   Li x MO 2-δ   Formula 1
   wherein, in Formula 1, M is a Group 4 element, a Group 5 element, a Group 6 element, a Group 7 element, a Group 8 element, a Group 10 element, a Group 11 element, a Group 12 element, or a combination thereof, and 0<x<1 and 0<δ=1 are satisfied.   
     
     
         2 . The mixed conductor of  claim 1 , wherein M is cobalt, nickel, iron, manganese, vanadium, titanium, chromium, copper, zinc, or a combination thereof. 
     
     
         3 . The mixed conductor of  claim 1 , wherein, in Formula 1, x is from about 0.3 to about 0.5. 
     
     
         4 . The mixed conductor of  claim 1 , wherein the mixed conductor comprises a phase having a layered crystal structure. 
     
     
         5 . The mixed conductor of  claim 4 , wherein the mixed conductor comprises a layer of M-centered oxygen octahedra. 
     
     
         6 . The mixed conductor of  claim 1 , wherein the mixed conductor is a compound represented by Formula 2:
   Li x M 1   a M 2   b M 3   1-a-b O 2-δ   Formula 2
   wherein, in Formula 2, M 1  is Ni, Co, Mn, or a combination thereof,   M 2  and M 3  are each independently a Group 4 element, a Group 5 element, a Group 8 element, a Group 11 element, a Group 12 element, or a combination thereof, and 0<x<1, 0<a≤1, 0≤b<1, and 0<δ≤1 are satisfied.   
     
     
         7 . The mixed conductor of  claim 6 , wherein M 2  and M 3  are each independently iron, vanadium, titanium, chromium, copper, zinc, or a combination thereof. 
     
     
         8 . The mixed conductor of  claim 6 , wherein, in Formula 2, a is 1, b is 0, and M 1  has a mixed valence state and comprises metals having a plurality of a different oxidation numbers. 
     
     
         9 . The mixed conductor of  claim 1 , wherein the mixed conductor is Li x CO a O 2-δ , Li x CO a Ni 1-a O 2-δ , Li x CO a Ni b Mn 1-a-b O 2-δ , Li x Ni a O 2-δ , Li x Mn a O 2-δ , Li x Cr a O 2-δ , Li x CO a Mn b O 2-δ , Li x Ni a Mn b O 2-δ , Li x Cr a Mn b O 2-δ , or a combination thereof, and
 wherein, in each of the foregoing mixed conductors, each x is independently 0<x<1, each a is independently 0<a≤1, each b is independently 0≤b<1 and each δ is independently 0<δ≤1.   
     
     
         10 . The mixed conductor of  claim 1 , wherein the mixed conductor is Li 0.5 CoO 2-δ , Li 0.5 Co 0.5 Ni 0.5 O 2-δ , Li 0.5 NiO 2-δ , Li 0.5 MnO 2-δ , Li 0.5 CrO 2-δ , Li 0.5 Co 0.5 Mn 0.5 O 2-δ , Li 0.5 Ni 0.5 Mn 0.5 O 2-δ , Li 0.5 Cr 0.5 Mn 0.5 O 2-δ , Li 0.4 CoO 2-δ , Li 0.4 Co 0.5 Ni 0.5 O 2-δ , Li 0.4 NiO 2-δ , Li 0.4 MnO 2-δ , Li 0.4 CrO 2-δ , Li 0.4 Co 0.5 Mn 0.5 O 2-δ , Li 0.4 Ni 0.5 Mn 0.5 O 2-δ , Li 0.4 Cr 0.5 Mn 0.5 O 2-δ , Li 0.3 CoO 2-δ , Li 0.3 Co 0.5 Ni 0.5 O 2-δ , Li 0.3 NiO 2-δ , Li 0.3 MnO 2-δ , Li 0.3 CrO 2-δ , Li 0.3 Co 0.5 Mn 0.5 O 2 O 2-δ , Li 0.3 Ni 0.5 Mn 0.5 O 2-δ , Li 0.3  Cr 0.5 Mn 0.5 O 2-δ , Li 0.5 Co 0.4 Ni 0.6 O 2-δ , Li 0.5 Co 0.4 Mn 0.6 O 2-δ , Li 0.5 Ni 0.4 Mn 0.6 O 2-δ , Li 0.5 Cr 0.4 Mn 0.6 O 2-δ , Li 0.5 Co 0.3 Ni 0.7 O 2-δ , Li 0.3 Co 0.3 Mn 0.7 O 2-δ , Li 0.5 Ni 0.3 Mn 0.7 O 2-δ , Li 0.5 Cr 0.3 Mn 0.7 O 2-δ , Li 0.5 Co 0.2 Ni 0.8 O 2-δ , Li 0.5 Ni 0.8 Mn 0.2 O 2-δ , Li 0.5 Co 0.1 Ni 0.9 O 2-δ , Li 0.5 Ni 0.9 Mn 0.1 O 2-δ , Li 0.5 Co 0.6 Ni 0.4 O 2-δ , Li 0.5 Co 0.6 Mn 0.4 O 2-δ , Li 0.5 Ni 0.6 Mn 0.4 O 2-δ , Li 0.5 Cr 0.6 Mn 0.4 O 2-δ , or a combination thereof, and 0<δ≤1 is satisfied. 
     
     
         11 . The mixed conductor of  claim 1 , wherein an electronic conductivity of the mixed conductor is greater than an ionic conductivity thereof. 
     
     
         12 . The mixed conductor of  claim 1 , wherein the mixed conductor has an electronic conductivity greater than 4.0×10 −9  Siemens per centimeter at 25° C. 
     
     
         13 . The mixed conductor of  claim 1 , wherein the mixed conductor has an ionic conductivity of 1.0×10 −9  Siemens per centimeter or greater at 25° C. 
     
     
         14 . The mixed conductor of  claim 1 , wherein an X-ray diffraction spectrum of the mixed conductor includes a first peak at a diffraction angle of about 65° 2θ and a second peak at 67° 2θ, when analyzed using Cu Kα radiation. 
     
     
         15 . The mixed conductor of  claim 14 , wherein a maximum of the first peak is located in a range of about 65° 2θ to 66° 2θ, and
 a maximum of the second peak is located in a range of about 66° 2θ to about 67° 2θ. 
 
     
     
         16 . The mixed conductor of  claim 14 , wherein a height of the second peak is in a range of about 30% to about 50% of a height of the first peak. 
     
     
         17 . A method of preparing the mixed conductor of  claim 1 , the method comprising:
 mixing a lithium compound, an M-containing compound, and a solvent to obtain a mixture;   first thermally treating the mixture to obtain a first thermal treatment product;   pulverizing the first thermal treatment product to obtain a pulverized product; and   second thermally treating the pulverized product to prepare the mixed conductor of  claim 1 , wherein M in Formula 1 is a Group 4 element, a Group 5 element, a Group 6 element, a Group 7 element, a Group 8 element, a Group 10 element, a Group 11 element, a Group 12 element, or a combination thereof.   
     
     
         18 . The method of  claim 17 , wherein the second thermally treating comprises thermally treating at a temperature which is greater than a temperature of the first thermally treating. 
     
     
         19 . The method of  claim 17 , wherein the first thermally treating comprises treating at a temperature of about 400° C. to about 900° C. 
     
     
         20 . The method of  claim 17 , wherein the second thermally treating comprises treating at a temperature of about 400° C. to about 1,000° C. 
     
     
         21 . The method of  claim 17 , wherein the lithium compound is lithium oxide, lithium carbonate, lithium chloride, lithium sulfide, lithium nitrate, lithium phosphate, lithium hydroxide, or a combination thereof. 
     
     
         22 . The method of  claim 17 , wherein the M-containing compound is an M-containing oxide, an M-containing carbonate, an M-containing chloride, an M-containing phosphate, an M-containing hydroxide, an M-containing nitrate, an M-containing hydroxide, or a combination thereof. 
     
     
         23 . An electrochemical device comprising the mixed conductor of  claim 1 . 
     
     
         24 . The electrochemical device of  claim 23 , wherein the electrochemical device is a battery, an accumulator, a supercapacitor, a fuel cell, a sensor, or an electrochromic device.