Lithium secondary battery
In one aspect, a lithium secondary battery that includes a positive electrode including a high-voltage positive active material; and a separator is provided. The high voltage positive active material can have a discharge plateau voltage of greater than or equal to about 4.6V with respect to a Li counter electrode, and the separator can include a porous substrate having a porosity of about 40% to about 60%.
1. A lithium secondary battery comprising
a positive electrode including a high-voltage positive active material; and
a separator, wherein the separator comprises a substrate of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer thereof,
wherein the high-voltage positive active material has a discharge plateau voltage of about 4.6V to about 5.3V with respect to a Li counter electrode and the high-voltage positive active material is selected from at least one olivine-based lithium metal phosphate and a compound represented by Chemical Formula 1:
Li 1+x Ni y Mn 2-y-z M z O 4+w Chemical Formula 1
wherein,
0≦x<0.2, 0.4≦y≦0.6, 0≦z≦0.2, 0≦w≦0.1, and
M is selected from the group consisting of Al, Ti, Mg, Zn, and combinations thereof, and
the separator comprises a porous substrate having porosity of about 40% to about 60%; and a coating layer on at least one side of the porous substrate, wherein the coating layer comprises a polymer and a metal filler.
2. The lithium secondary battery of claim 1 , wherein the metal filler comprises a component selected from the group consisting of metal oxide, metal hydroxide, metal phosphate, metal nitrate, metal carbonate, metal sulfate, metal alkoxide, metal oxide having a perovskite structure, ceramics, and combinations thereof.
3. The lithium secondary battery of claim 2 , wherein the metal filler is MgCO 3 , BaCO 3 , Li 2 CO 3 , Al(OH) 3 .H 2 O, Al 2 (SO 4 ) 3 , MgSO 4 , Al(OC 2 H 5 ) 3 , YPO 4 , (ZrO) 2 P 2 O 7 , ZrP 2 O 7 , Al(NO 3 ) 3 , a mixture of Al 2 (SO 4 ) 3 and Al(OC 2 H 5 ) 3 , LiAlO 2 , LiAl 5 O 8 , Li 5 AlO 4 , MgO, MgAl 2 O 4 , BaTiO 3 , CoAl 2 O 4 , Li 2 SiO 4 , Li 2 B 4 O 7 , Li 2 MoO 3 , Al(OH) 3 , AlPO 4 , Mg(OH) 2 , a mixture of Al 2 O 3 and AlPO 4 , Li 2 ZrO 3 , a mixture of Al 2 O 3 and Al(OH) 3 , AM 1 O 3 (A=Ca, Ba, Sr, Pb, and the like, M 1 =Ti, Zr, Sn, Hf, and the like) or Al 2 O 3 .
4. The lithium secondary battery of claim 3 , wherein the metal filler is Al 2 O 3 .
5. The lithium secondary battery of claim 4 , wherein the porous substrate comprises polyethylene.
6. The lithium secondary battery of claim 1 , wherein the polymer comprises a component selected from the group consisting of polyvinylidenefluoride (PVdF), poly(vinylidene-hexafluoropropylene) co-polymer (P(VdF-HFP)), polyethyleneoxide (PEO), polyacrylonitrile (PAN), polyimide (PI), polyamic acid (PAA), polyamideimide (PAI), and aramid.
7. The lithium secondary battery of claim 6 , wherein the polymer is poly(vinylidene-hexafluoropropylene) co-polymer (P(VdF-HFP)).
8. The lithium secondary battery of claim 1 , wherein the coating layer comprises about 5 wt % to about 80 wt % of a metal filler based on 100 wt % of the coating layer.
9. The lithium secondary battery of claim 1 , wherein the coating layer has a thickness of about 0.05 μm to about 5 μm.
10. The lithium secondary battery of claim 1 , wherein the separator has an entire thickness of about 5 μm to about 30 μm.
11. The lithium secondary battery of claim 1 , wherein the lithium secondary battery further comprises a negative electrode including a negative active material selected from natural graphite, artificial graphite, soft carbon, hard carbon, a mesophase pitch carbonized product, fired coke, silicon oxide, or silicon oxide coated with conductive carbon, and combinations thereof.
12. The lithium secondary battery of claim 1 , wherein the separator comprises a substrate of at least one kind of polyolefin-based monolayer or multilayer;
the lithium secondary battery further comprises a non-aqueous electrolyte; and
the non-aqueous electrolyte comprises a supporting electrolytic salt.
13. The lithium secondary battery of claim 12 , wherein the supporting electrolytic salt in the non-aqueous electrolyte has a concentration of about 0.5 M to about 2 M.
14. The lithium secondary battery of claim 12 , wherein the supporting electrolytic salt is LiPF 6 .
15. The lithium secondary battery of claim 12 , wherein the non-aqueous electrolyte is a mixture of ethyl carbonate, ethylmethyl carbonate and dimethyl carbonate.
16. The lithium secondary battery of claim 1 , wherein the high-voltage positive active material is LiNi 0.5 Mn 1.5 O 4 .