Lithium battery
A lithium battery including: a positive electrode including an overlithiated lithium transition metal oxide having a layered structure; a negative electrode including a silicon-based negative active material; and an electrolyte between the positive electrode and the negative electrode, the electrolyte including an electrolytic solution including a fluorinated ether solvent in an amount of 3 vol % or more based on the total volume of the electrolytic solution.
1. A lithium battery comprising:
a positive electrode comprising an overlithiated transition metal oxide having a layered structure;
a negative electrode comprising a silicon-based negative active material; and
an electrolyte between the positive electrode and the negative electrode, the electrolyte comprising an electrolytic solution comprising a fluorinated ether solvent in an amount of 3 vol % or more based on the total volume of the electrolytic solution,
wherein the overlithiated transition metal oxide comprises a compound represented by Formula 1 below:
x Li 2 MO 3 -(1- x )LiM′O 2 , <Formula 1>
wherein 0<x<1, M is at least one metal selected from Period 4 transition metals and Period 5 transition metals having a mean oxidation number of +4, and M′ is at least one metal selected from Period 4 transition metals and Period 5 transition metals having a mean oxidation number of +3.
2. The lithium battery of claim 1 , wherein the fluorinated ether solvent comprises at least one compound represented by Formulae 4 to 6 below:
Rf1-O—Rf2 <Formula 4>
Rf1-O—R <Formula 5>
Rf1-O —(R′—O) n —Rf 2 <Formula 6>
wherein Rf1 and Rf2 are each independently a linear or branched C1 to C12 fluoroalkyl group having at least one hydrogen atom substituted with a fluoro group, R is a linear or branched C1 to C12 alkyl group, R′ is a linear or branched C1 to C5 alkylene group, and n is an integer of 1 to 5.
3. The lithium battery of claim 2 , wherein Rf1 or Rf2 are each independently a fluoroalkyl group selected from the group consisting of HCF 2 —, CF 3 —, HCF 2 CF 2 —, CH 3 CF 2 —, CF 3 CH 2 —, CF 3 CF 2 —, (CF 3 ) 2 CH—, HCF 2 CF 2 CH 2 —, CF 3 CH 2 CH 2 —, HCF 2 CF 2 CF 2 CH 2 —, HCF 2 CF 2 CF 2 CF 2 CH 2 —, CF 3 CF 2 CH 2 —, CF 3 CFHCF 2 CH 2 —, HCF 2 CF(CF 3 )CH 2 —, and CF 3 CF 2 CH 2 CH 2 — .
4. The lithium battery of claim 2 , wherein R is an alkyl group selected from the group consisting of —CH 3 , —C 2 H 5 , —C 3 H 7 , and —CH(CH 3 )CH 3 .
5. The lithium battery of claim 2 , wherein R′ is an alkylene group selected from the group consisting of —CH 2 —, —CH 2 CH 2 —, and —CH 2 CH 2 CH 2 —.
6. The lithium battery of claim 1 , wherein the fluorinated ether solvent is selected from the group consisting of HCF 2 CF 2 CH 2 OCF 2 CF 2 H, HCF 2 CF 2 CH 2 OCF 2 CH 3 , CF 3 CF 2 CH 2 OCF 2 CF 2 H, CF 3 CF 2 CH 2 OCF 2 H, HCF 2 CF 2 OCH 2 CF 3 , HCF 2 CF 2 CH 2 OCF 2 CFHCF 3 , CF 3 CF 2 CH 2 OCF 2 CFHCF 3 , HCF 2 CF 2 CH 2 OCH 2 CFHCF 3 , CF 3 CF 2 CH 2 OCH 2 CFHCF 3 , HCF 2 CF 2 CH 2 OCH 3 , and combinations thereof.
7. The lithium battery of claim 1 , wherein the electrolytic solution comprises the fluorinated ether solvent in an amount of about 3 to about 70 vol % based on the total volume of the electrolytic solution.
8. The lithium battery of claim 1 , wherein the electrolytic solution comprises the fluorinated ether solvent in an amount of about 10 vol % or more based on the total volume of the electrolytic solution.
9. The lithium battery of claim 1 , wherein the electrolyte further comprises an additive selected from the group consisting of tris(trimethylsilyl) phosphate (TMSPa), lithium difluorooxalatoborate (LiFOB), vinylcarbonate (VC), propanesultone (PS), succinitrile (SN), LiBF 4 , a silane compound, a silazane compound, and combinations thereof.
10. The lithium battery of claim 9 , wherein each of the silane compound and the silazane compound has a functional group capable of forming of a siloxane bond.
11. The lithium battery of claim 10 , wherein the functional group is selected from the group consisting of acryl, amino, epoxy, methoxy, and vinyl.
12. The lithium battery of claim 9 , wherein the electrolytic solution comprises the additive in an amount in a range of about 0.01 to about 10 wt % based on the total weight of the electrolytic solution.
13. The lithium battery of claim 1 , wherein the electrolytic solution further comprises a carbonate-based compound, an ester-based compound, an ether-based compound, a ketone-based compound, an alcohol-based compound, an aprotic solvent, or a combination thereof.
14. The lithium battery of claim 13 , wherein the carbonate-based compound comprises a chain carbonate compound and a fluoro carbonate compound.
15. The lithium battery of claim 14 , wherein the fluoro carbonate compound is present in an amount from about 1 to about 30 vol % based on the total volume of the electrolytic solution.
16. The lithium battery of claim 1 , wherein the overlithiated transition metal oxide comprises at least one compound represented by Formulae 2 to 5 below:
x Li 2 Mn 0 3 -(1- x )LiNi a Co b Mn c O 2 , <Formula 2>
wherein 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1;
x Li 2 MO 3 - y LiM'O 2 - z Li 1+d Mn 2-d O 4 , <Formula 3>
wherein x+y+z=1, 0<x<1, 0<y<1, 0<z<1, and 0<d<0.33, M is at least one metal selected from Period 4 transition metals and Period 5 transition metals having a mean oxidation number of + 4 , M′ is at least one metal selected from Period 4 transition metals and Period 5 transition metals having a mean oxidation number of +3, and M″ is at least one metal selected from Period 4 transition metals and Period 5 transition metals having a combined mean oxidation number of +3 or +4;
Li[Li x Me y]O 2+d , <Formula 4>
wherein x+y=1, 0<x<1, 0≦d≦0.1, and Me is at least one metal selected from the group consisting of Mn, V, Cr, Fe, Co, Ni, Zr, Re, Al, B, Ge, Ru, Sn, Ti, Nb, Mo, and Pt; and
Li[Li x Ni a Co b Mn c ]O 2+d, <Formula 5>
wherein x+a+b+c=1, 0<x<1, 0<a<1, 0<b<1, 0<c<1, and 0≦d≦0.1.
17. The lithium battery of claim 1 , wherein the silicon-based negative active material comprises a material selected from the group consisting of Si, SiO x (O<x<2), Si—Z alloy, and combinations thereof, wherein Z is alkali metal, alkali earth metal, a Group 11 element, a Group 12 element, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof, and is not Si.
18. The lithium battery of claim 1 , wherein the silicon-based negative active material has a nano-structure having a dimension of at least one region thereof being less than about 500 nm.
19. The lithium battery of claim 18 , wherein the nano-structure has a structure selected from the group consisting of nanoparticle, nanopowder, nanowire, nanorod, nanofiber, nanocrystal, nanodot, nanoribbon and combinations thereof.