Lithium batteries using poly(ethylene oxide)-based non-aqueous electrolytes
Lithium-air cells using poly(ethyleneoxide) (PEO) siloxane-based or poly(ethyleneoxide) phosphate-based electrolytes may be prepared and exhibit improved charge carrying capacity. Such PEO silioxanes and phosphates generally have the formulas Ia, Ib, Ic, Id, IIa, IIb, IIc, where:
1. A lithium-air cell comprising:
a negative electrode;
an air positive electrode; and
a non-aqueous electrolyte comprising:
a lithium salt; and
a poly(ethyleneoxide) solvent that is a compound of Formula Ia, Ib, Ic, Id, or a mixture of any two or more thereof:
R 1 , R 2 , and R 3 are independently H, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms, or a group of Formula IIIa, IIIb, IIIc, or IIId;
R 4 , R 5 , and R 6 are independently H, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, or a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms; and
PEO 1 , PEO 2 , PEO 3 , PEO 4 , PEO 5 , PEO 6 , and PEO 7 are independently a poly(ethyleneoxide) group.
2. The lithium-air cell of claim 1 , wherein the poly(ethyleneoxide) solvent is a compound of Formula Ib, Ic, Id, or a mixture of any two or more thereof.
3. The lithium-air cell of claim 1 , wherein the electrolyte is not a gelled electrolyte.
4. The lithium-air cell of claim 1 , wherein PEO 1 , PEO 2 , PEO 3 , and PEO 4 are independently represented by Formula Va or Vb;
wherein;
R 7 is H, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms, or a group of Formula VI,
R 8 is H, a substituted or unsubstituted alkyl group having from 1 to 12 carbon atoms, or a substituted or unsubstituted alkenyl group having from 2 to 12 carbon atoms;
m represents an integer from 1 to 8,
n represents an integer from 0 to 20, and
q represents an integer from 0 to 8.
5. The lithium-air cell of claim 1 , further comprising a siloxanyl carbonate co-solvent.
6. The lithium-air cell of claim 5 , wherein the co-solvent is 1-[1-trimethylsiloxanyl-ethyl]ethylene carbonate.
7. The lithium-air cell of claim 1 , wherein the poly(ethyleneoxide) solvent is a poly(ethyleneoxide) siloxane selected from 2-[2-[2-[2-methoxy]ethoxy]ethoxy]ethoxy trimethyl silane, 2-[2-[2-methoxy]ethoxy]-ethoxy trimethyl silane, or a mixture thereof.
8. The lithium-air cell of claim 1 , wherein the poly(ethyleneoxide) solvent is present from about 5 wt % to about 95 wt %, wherein the wt % is calculated on the total weight of the poly(ethyleneoxide) solvent, the salt, and the electrode stabilizing additive.
9. The lithium-air cell of claim 1 , wherein the lithium salt is electrochemically and chemically stable in the presence of oxygen.
10. The lithium-air cell of claim 1 , wherein:
the lithium salt is selected from the group consisting of LiCF 3 CO 2 , LiC 2 F 5 CO 2 , LiClO 4 , LiBF 4 , LiAsF 6 , LiPF 6 , LiPF 2 (C 2 O 4 ) 2 , LiPF 4 C 2 O 4 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiN(SO 2 C 2 F 5 ) 2 ), lithium alkyl fluorophosphates, Li(C 2 O 4 ) 2 , LiBF 2 C 2 O 4 , Li 2 B 12 X 12-p H p , Li 2 B 10 X 10-y H y , and mixtures of any two or more thereof;
X is selected from the group consisting of OH, F, Cl, and Br;
p=0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12; and
y=0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.
11. The lithium-air cell of claim 1 , wherein the concentration of the lithium salt is from about 0.01 M to about 2.0 M.
12. The lithium-air cell of claim 1 further comprising an electrode stabilizing additive that can be oxidized or polymerized on the surface of a positive electrode, or can be reduced or polymerized on the surface of a negative electrode.
13. The lithium-air cell of claim 12 , wherein the concentration of the electrode stabilizing additive is from about 0.001 wt % to about 10 wt %.
14. The lithium-air cell of claim 1 , further comprising a crosslinking agent, a monofunctional monomeric compound, and a radical reaction initiator.
15. The lithium-air cell of claim 1 , wherein the negative electrode is lithium.
16. The lithium-air cell of claim 1 , wherein the air-positive electrode further comprises an additive to assist the reduction of oxygen.
17. The lithium-air cell of claim 16 , wherein the additive is selected from cobalt phthalocyanine, MnOOH, MnO x , CoO x , Pt, Pt 1-x Ru x , La 1-x Ca x CoO 3 , Co 3 O 4 , NiCO 2 O 4 , Pb 2 Ru 2 Pb 1-x O 1-y , Na x Pt 3 O 4 , or a mixture of any two or more thereof, and 0≦x≦1 and 0≦y≦1.