Cathode active material for lithium secondary battery and lithium secondary battery including the same
A cathode active material for a lithium secondary battery according to an embodiment of the present invention includes a plurality of a lithium-transition metal composite oxide particle having a shape of a secondary particle in which a plurality of primary particles are aggregated. The lithium-transition metal composite oxide particle includes a lithium-molybdenum-containing portion having a hexagonal close-packed structure formed between the primary particles.
1 . A cathode active material for a lithium secondary battery comprising a plurality of a lithium-transition metal composite oxide particle having a shape of a secondary particle in which primary particles are aggregated,
wherein the lithium-transition metal composite oxide particle comprises a lithium-molybdenum-containing portion having a hexagonal close-packed structure is formed between the primary particles having a hexagonal close-packed structure within an inner region of the secondary particle.
2 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-transition metal composite oxide particle does not include primary particles having a face centered cubic structure.
3 . The cathode active material for a lithium secondary battery according to claim 1 , wherein a content of molybdenum in the lithium-transition metal composite oxide particle measured through an inductively coupled plasma (ICP) analysis is in a range from 1,000 ppm to 14,000 ppm based on a total weight of the lithium-transition metal composite oxide particle.
4 . The cathode active material for a lithium secondary battery according to claim 3 , wherein the content of molybdenum in the lithium-transition metal composite oxide particle measured through the ICP analysis is in a range from 1,200 ppm to 7,000 ppm based on the total weight of the lithium-transition metal composite oxide particle.
5 . The cathode active material for a lithium secondary battery according to claim 1 , wherein a carbon content remaining on an outer surface of the lithium-transition metal composite oxide particle and between the primary particles measured by a CS (carbon-sulfur) analyzer is 1,200 ppm or less.
6 . The cathode active material for a lithium secondary battery according to claim 1 , wherein the lithium-molybdenum-containing portion is further present on an outer surface of the lithium-transition metal composite oxide particle.
7 . A lithium secondary battery, comprising:
a cathode comprising a cathode active material layer, the cathode active material layer comprising the cathode active material for a lithium secondary battery of claim 1 ; and
an anode facing the cathode.
8 . A method of preparing a cathode active material, comprising:
preparing preliminary lithium-transition metal composite oxide particles each having a shape of a secondary particle in which a plurality of primary particles are aggregated;
mixing the preliminary lithium-transition metal composite oxide particles with a molybdenum compound aqueous solution; and
heat-treating the mixed preliminary lithium-transition metal composite oxide particles and the molybdenum compound aqueous solution to form lithium-transition metal composite oxide particles comprising a lithium-molybdenum containing portion formed between the primary particles within an inner region of the secondary particle, the lithium-molybdenum containing portion and the primary particles having a hexagonal close-packed structure.
9 . The method of claim 8 , wherein the molybdenum compound aqueous solution comprises an ammonium molybdenum-based compound represented by Chemical Formula 2:
(NH 4 ) a Mo b A c [Chemical Formula 2]
wherein, in Chemical Formula 2, A represents O or S, 2≤a≤10, 1≤b≤10, and 4≤c≤30.
10 . The method of claim 9 , wherein the ammonium molybdenum-based compound includes at least one of ammonium orthomolybdate ((NH 4 ) 2 MoO 4 ), ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ) and ammonium tetrathiomolybdate ((NH 4 ) 2 MoS 4 ).
11 . The method of claim 9 , wherein an input amount of the ammonium molybdenum-based compound is in a range from 0.4 wt % to 2.5 wt % based on a total weight of the preliminary lithium-transition metal composite oxide particles.
12 . The method of claim 8 , wherein an amount of a solvent in the molybdenum compound aqueous solution is in a range from 2 wt % to 20 wt % based on a total weight of the preliminary lithium-transition metal composite oxide particles.
13 . The method of claim 8 , wherein the heat-treating is performed at a temperature ranging from 200° C. to 400° C.
14 . The method of claim 8 , wherein the preliminary lithium-transition metal composite oxide particles are mixed with the molybdenum compound aqueous solution without a water-washing treatment.