Composite cathode active material and secondary battery including the same
A composite cathode active material including: a core particle; a first coating layer; and a second coating layer; wherein the core particle includes a cathode active material, the first and second coating layers cover a surface of the core particle, the first coating layer includes a first lithium-containing compound, wherein the first lithium-containing compound includes zirconium, niobium, titanium, aluminum, or a combination thereof, the second coating layer includes a second lithium-containing compound, wherein the second lithium-containing compound includes germanium, niobium, gallium, or a combination thereof, and the first lithium-containing compound is different from the second lithium-containing compound.
1. A composite cathode active material comprising:
a core particle;
a first coating layer; and
a second coating layer,
wherein
the core particle comprises a lithium transition metal oxide having a layered halite structure,
the first and second coating layers cover a surface of the core particle,
the first coating layer comprises a first lithium-containing compound, wherein the first lithium-containing compound comprises aLi 2 O—ZrO 2 where 0.1≤a≤2, lithium titanium oxide, lithium aluminum oxide, lithium niobium oxide, or a combination thereof,
the second coating layer comprises a second lithium-containing compound, wherein the second lithium-containing compound comprises germanium, niobium, gallium, or a combination thereof,
the first lithium-containing compound is different from the second lithium-containing compound,
the first coating layer is disposed on the surface of the core particle, and the second coating layer is disposed on a surface of the first coating layer,
the first coating layer has a thickness of about 1 nanometer to about 50 nanometers,
a total thickness of the first coating layer and the second coating layer is greater than about 1 nanometer to about 500 nanometers,
the composite cathode active material comprises a plurality of core particles, and
the core particles of the plurality of core particles have a mean particle diameter of about 0.1 micrometers to about 10 micrometers.
2. The composite cathode active material of claim 1 , wherein the first coating layer is disposed directly on the surface of the core particle, and the second coating layer is disposed directly on a surface of the first coating layer.
3. The composite cathode active material of claim 1 , wherein the second lithium-containing compound comprises lithium germanium oxide, lithium niobium oxide, lithium gallium oxide, or a combination thereof.
4. A cathode comprising the composite cathode active material according to claim 1 .
5. A lithium secondary battery comprising:
the cathode according to claim 4 ;
an anode; and
a sulfide solid electrolyte between the cathode and the anode.
6. A composite cathode active material comprising:
a core particle;
a first coating layer; and
a second coating layer,
wherein
the core particle comprises a cathode active material,
the first and second coating layers cover a surface of the core particle,
the first coating layer comprises a first lithium-containing compound, wherein the first lithium-containing compound comprises zirconium, niobium, titanium, aluminum, or a combination thereof,
the second coating layer comprises a second lithium-containing compound, wherein the second lithium-containing compound comprises germanium, niobium, gallium, or a combination thereof,
the first lithium-containing compound is different from the second lithium-containing compound,
the first coating layer is disposed on the surface of the core particle, and the second coating layer is disposed on a surface of the first coating layer, and
the core particle comprises LiNi x Co y M z O 2 where M is aluminum or manganese, 0<x<1, 0<y<1, and x+y+z=1,
the first coating layer has a thickness of about 1 nanometer to about 50 nanometers,
a total thickness of the first coating layer and the second coating layer is greater than about 1 nanometer to about 500 nanometers,
the composite cathode active material comprises a plurality of core particles, and
the core particles of the plurality of core particles have a mean particle diameter of about 0.1 micrometer to about 10 micrometers.
7. The composite cathode active material of claim 6 , wherein 0.5<x<1.
8. A cathode comprising the composite cathode active material according to claim 6 .
9. A lithium secondary battery comprising:
the cathode according to claim 8 ;
an anode; and
a sulfide solid electrolyte between the cathode and the anode.
10. An all-solid-state lithium secondary battery comprising:
a cathode comprising a composite cathode active material comprising
a core particle;
a first coating layer; and
a second coating layer,
wherein
the core particle comprises a cathode active material,
the first and second coating layers cover a surface of the core particle,
the first coating layer comprises a first lithium-containing compound, wherein the first lithium-containing compound comprises zirconium, niobium, titanium, aluminum, or a combination thereof,
the second coating layer comprises a second lithium-containing compound, wherein the second lithium-containing compound comprises germanium, niobium, gallium, or a combination thereof,
the first lithium-containing compound is different from the second lithium-containing compound,
the first coating layer is disposed on the surface of the core particle, and the second coating layer is disposed on a surface of the first coating layer,
an anode; and
an electrolyte between the cathode and the anode,
wherein the electrolyte comprises a sulfide solid electrolyte,
the first coating layer has a thickness of about 1 nanometer to about 50 nanometers,
a total thickness of the first coating layer and the second coating layer is greater than about 1 nanometer to about 500 nanometers,
the composite cathode active material comprises a plurality of core particles, and
the core particles of the plurality of core particles have a mean particle diameter of about 0.1 micrometers to about 10 micrometers.
11. The all-solid-state lithium secondary battery of claim 10 , wherein the sulfide solid electrolyte comprises sulfur, lithium, and phosphorus, silicon, boron, aluminum, germanium, zinc, gallium, indium, a halogen, or a combination thereof.
12. The all-solid-state lithium secondary battery of claim 10 , wherein the sulfide solid electrolyte comprises lithium sulfide and silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof.
13. The all-solid-state lithium secondary battery of claim 10 , wherein the sulfide solid electrolyte comprises Li 2 S and P 2 S 5 .
14. The all-solid-state lithium secondary battery of claim 10 , wherein the sulfide solid electrolyte is in a form of a particle.