Lithium secondary battery of improved rate capability with cathode containing nickel manganese complex oxide for high-voltage applications
View Patent ↗Disclosed is a lithium secondary battery with improved rate characteristics. More particularly, disclosed is a lithium secondary battery including a cathode, an anode, a separator disposed between the cathode and the anode, and an electrolyte, wherein the electrolyte includes a mixed solvent of a cyclic carbonate-based material and a propionate-based material, the cathode includes a lithium manganese composite oxide represented by Formula 1 below as a cathode active material, and the anode includes a lithium metal oxide represented by Formula 2 below as an anode active material: Li x M y Mn 2-y O 4-z A z (1) wherein 0.9≤x≤1.2, 0<y<2, and 0≤z<0.2; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi; and A is at least one monovalent or divalent anion. Li a M′ b O 4-c A c (2) wherein M′ is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al, and Zr; 0.1≤a≤4 and 0.2≤b≤4 wherein a and b are determined according to oxidation number of M′; 0≤c<0.2 wherein c is determined according to oxidation number of A; and A is at least one monovalent or divalent anion.
1. A lithium secondary battery comprising a cathode, an anode, a separator disposed between the cathode and the anode, and an electrolyte,
wherein the electrolyte comprises a mixed solvent of a cyclic carbonate-based material and a propionate-based material, the cathode comprises a lithium manganese composite oxide represented by Formula 1 below as a cathode active material, and the anode comprises a lithium metal oxide represented by Formula 2 below as an anode active material:
Li x M y Mn 2-y O 4-z A z (1)
wherein 0.9≤x≤1.2, 0<y<2, and 0≤z<0.2; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi; and A is at least one monovalent or divalent anion,
Li a M′ b O 4-c A c (2)
wherein M′ is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al, and Zr; 0.1≤a≤4 and 0.2≤b≤4 wherein a and b are determined according to oxidation number of M′; 0≤c<0.2 wherein c is determined according to oxidation number of A; and A is at least one monovalent or divalent anion,
wherein an amount of the cyclic carbonate-based material is in a range of 1 wt % to 30 wt % based on a total weight of the electrolyte,
wherein a mixing weight ratio of the cyclic carbonate-based material to the propionate-based material is in a range of 5 to 10:90 to 95,
wherein the lithium manganese composite oxide of Formula 1 is a lithium nickel manganese complex oxide (LNMO) represented by Formula 4 below:
Li x Ni y Mn 2-y O 4 (4)
wherein 0.9≤x≤1.2 and 0.4≤y≤0.5, and
wherein the lithium metal oxide of Formula 2 is a lithium titanium oxide (LTO) represented by Formula 5 below:
Li a Ti b O 4 (5)
wherein 0.5≤a≤3 and 1≤b≤2.5.
2. The lithium secondary battery according to claim 1 , wherein the propionate-based material is represented by Formula 3 below:
R 1 —COO—R 2 (3)
wherein R 1 is a substituted or unsubstituted ethyl group, and R 2 is a substituted or unsubstituted C 1 -C 4 linear or branched alkyl group.
3. The lithium secondary battery according to claim 1 , wherein the propionate-based material is one selected from methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), butyl propionate (BP), or combinations thereof.
4. The lithium secondary battery according to claim 1 , wherein the mixing weight ratio of the cyclic carbonate-based material to the propionate-based material is 10:90.
5. The lithium secondary battery according to claim 1 , wherein the lithium nickel manganese composite oxide of Formula 4 is LiNi 0.5 Mn 1.5 O 4 or LiNi 0.4 Mn 1.6 O 4 .
6. The lithium secondary battery according to claim 1 , wherein the lithium titanium oxide of Formula 5 is Li 1.33 Ti 1.67 O 4 or LiTi 2 O 4 .
7. A battery module comprising the lithium secondary battery according to claim 1 as a unit cell.
8. A battery pack comprising the battery module according to claim 7 .
9. A device comprising the battery pack according to claim 8 .
10. The device according to claim 9 , wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for storing power.