Cathode materials for lithium battery having higher performance
View Patent ↗Provided is a cathode material for a lithium secondary battery, comprising a heat-treated mixture of an oxide powder (a) represented by Formula I and an oxide powder (b) represented by Formula II, wherein a mixing ratio of the oxide powder (a):oxide powder (b) is in a range of 30:70 to 90:10, the oxide powder (a) is monolithic particles having a D50 of more than 10 μm, and the oxide powder (b) is agglomerated particles having a D50 of less than 10 μm, and heat treatment is carried out at a temperature of 400° C. or higher. LiCoO 2 (I) Li z MO 2 (II) wherein 0.95<z<1.1; M=Ni 1-x-y Mn x Co y , 0 <y<0.5, and a ratio of Mn to Ni (x/(1−x−y)) is in a range of 0.4 to 1.1.
1. A cathode material for a lithium secondary battery, comprising:
a heat-treated mixture of an oxide powder (a) represented by Formula I and an oxide powder (b) represented by Formula II;
wherein:
(1) a mixing ratio of the oxide powder (a):oxide powder (b) is in the range of 30:70 to 40:60 by weight;
(2) the oxide powder (a) is monolithic particles having a D50 of more than 10 μm; and
(3) the oxide powder (b) is agglomerated particles having a D50 of less than 10 μm;
LiCoO 2 (I)
Li z MO 2 (II)
wherein 0.95<z<1.1; M=Ni 1-x-y Mn x Co y , 0<y<0.5, and a ratio of Mn to Ni (x/(1−x−y)) is in the range of 0.4 to 1.1,
wherein lithium chemical potentials of the oxide powders (a) and (b) are equilibrated in the heat-treated mixture, and
wherein the equilibrated lithium chemical potential is higher than a lithium chemical potential for coexistence of oxide powder (a) with cobalt oxide, and lower than a lithium chemical potential for coexistence of oxide powder (a) and lithium carbonate (Li 2 CO 3 ).
2. The cathode material according to claim 1 , wherein the oxide powder (a) has a D50 of more than 15 μm and the oxide powder (b) has a D50 of less than 8 μm.
3. The cathode material according to claim 2 , wherein the oxide powder (a) has a D50 of 20 to 30 μm and the oxide powder (b) has a D50 of 4 to 7 μm.
4. The cathode material according to claim 1 , wherein the oxide powder (b) is composed of an agglomerate of fine particles.
5. The cathode material according to claim 4 , wherein more than 90% of the powder (b) is composed of the agglomerate of fine particles having a particle size of 1 to 4 μm.
6. A lithium secondary battery comprising the cathode material of claim 1 .
7. The cathode material according to claim 1 , wherein the mixture of the oxide powder (a) and the oxide powder (b) is heat treated at a temperature of 400° C. or higher.
8. The cathode material according to claim 1 , where the heat-treated mixture consists of oxide powder (a) and oxide powder (b).