Positive electrode active material with improved output and lithium secondary battery comprising the same
View Patent ↗A mixed positive electrode active material comprising a lithium manganese oxide represented by following [Chemical Formula 1] and a second positive electrode active material represented by following [Chemical Formula 2], and a lithium secondary battery comprising the same are disclosed. a Li 2 MnO 3 .(1− a )Li x MO 2 [Chemical Formula 1] In [Chemical Formula 1], 0<a<1, 0.9≦x≦1.2, and M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe. Li 4-x Mn 5-2x-y CO 3x M y O 12 [Chemical Formula 2] In [Chemical Formula 2], 0<x<1.5, 0≦y<0.5, and M is at least one of transition metal elements. By comprising Mn-rich and Co-doped Li 4 Mn 5 O 12 , a rapid output decrease at a low SOC section may be relaxed to enlarge an available SOC section. Improved output may be obtained throughout an entire SOC section when compared with a case using pure Li 4 Mn 5 O 12 .
1. A lithium secondary battery comprising a positive electrode, wherein the positive electrode comprises a mixed positive electrode active material comprising a lithium manganese oxide represented by following [Chemical Formula 1] and a second positive electrode active material represented by following [Chemical Formula 2]:
a Li 2 MnO 3 . (1- a )Li x MO 2 Chemical Formula 1]
in [Chemical Formula 1], 0<a<1, 0.9<x<1.2, and M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe,
Li 4-x ,Mn 5-2x-y Co 3x M y O 12 Chemical Formula 2]
in [Chemical Formula 2], 0<x<1.5, 0<y<0.5, and M is at least one of transition metal elements,
wherein all outputs in a state of charge section of 10% to 40% are at least about 67% when compared with an output in a state of charge section of 50%.
2. The lithium secondary battery of claim 1 , wherein the mixed positive electrode active material comprises the lithium manganese oxide represented by following [Chemical Formula 1] and the second positive electrode active material represented by following [Chemical Formula 2]:
a Li 2 MnO 3 —(1- a )LiMO 2 [Chemical Formula 1]
in [Chemical Formula 1], 0<a<1, and M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe,
Li 4-x Mn 5-2x Co 3x O 12 [Chemical Formula 2]
in [Chemical Formula 2], 0.1<x<0.5,
wherein particle sizes of the lithium manganese oxide and the second positive electrode active material are uniform.
3. The lithium secondary battery of claim 1 , wherein an amount of the second positive electrode active material is 10 to 30 parts by weight based on 100 parts by weight of a total amount of the mixed positive electrode active material.
4. The lithium secondary battery of claim 1 , wherein the mixed positive electrode active material further comprises a conductive material and a binder besides the lithium manganese oxide and the second positive electrode active material.
5. The lithium secondary battery of claim 4 , wherein the conductive material is graphite or conductive carbon.
6. The lithium secondary battery of claim 4 , wherein an amount of the conductive material is 0.5 to 15 parts by weight based on 100 parts by weight of a total amount of the mixed positive electrode active material.
7. The lithium secondary battery of claim 5 , wherein the conductive carbon comprises a carbon black selected from the group consisting of acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; a material having a crystalline structure of graphene or graphite; and mixture thereof.
8. The lithium secondary battery of claim 1 , wherein the mixed positive electrode material further comprises at least one lithium-containing metal oxide selected from the group consisting of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium cobalt-nickel oxides, lithium cobalt-manganese oxides, lithium manganese-nickel oxides, lithium cobalt-nickel-manganese oxides, and substituted or doped oxides thereof by other element(s).
9. The lithium secondary battery of claim 8 , wherein the other element is at least one selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W and Bi.
10. The lithium secondary battery of claim 8 , wherein the lithium-containing metal oxide is comprised by 50 parts by weight or less based on 100 parts by weight of the mixed positive electrode active material.
11. The lithium secondary battery of claim 1 , wherein the outputs in a state of charge section of 10% to 40% are from about 67% to about 90% when compared with an output in a state of charge section of 50%.
12. The lithium secondary battery of claim 1 , wherein the lithium secondary battery is used in a plug-in hybrid electric vehicle (PHEV).
13. The lithium secondary battery of claim 1 , wherein the lithium secondary battery is used in an electric vehicle (EV).
14. The lithium secondary battery of claim 1 , wherein the lithium secondary battery maintains a discharge capacity of about 160 mAh/g.