Organic electrolytic solution and lithium battery using the same
An organic electrolytic solution includes a lithium salt and an organic solvent containing a phosphonate compound, and a lithium battery utilizes the organic electrolytic solution. When using the organic electrolyte containing the phosphonate compound to manufacture a lithium secondary battery, the lithium secondary battery has improved stability to reduction-induced decomposition, reduced first cycle irreversible capacity, and improved charging/discharging efficiency and lifespan. In addition, the lithium secondary battery does not swell beyond a predetermined thickness range after formation and standard charging at room temperature and has improved reliability. Even when the lithium secondary battery swells seriously at a high temperature, its capacity is high enough for practical applications. The capacity of the lithium secondary battery may substantially be recovered after being left at a high temperature.
1. An organic electrolytic solution comprising a lithium salt, an organic solvent, and a phosphonate compound of formula (1) below:
wherein R 1 and R 2 are independently selected from among a substituted or unsubstituted C 1 –C 20 alkyl group, a substituted or unsubstituted C 1 –C 20 alkoxy group, a substituted or unsubstituted C 2 –C 20 alkenyl group, a substituted or unsubstituted C 6 –C 30 aryl group, a substituted or unsubstituted C 7 –C 30 aralkyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted C 2 –C 30 heteroaryl group, a substituted or unsubstituted C 3 –C 30 heteroaralkyl group, a substituted or unsubstituted C 2 –C 30 heteroaryloxy group, a substituted or unsubstituted C 5 –C 20 cycloalkyl group, and a substituted or unsubstituted C 2 –C 20 heterocycloalkyl group; and R 3 and R 4 are independently selected from among a hydrogen atom and a substituted or unsubstituted C 1 –C 20 alkyl group.
2. The organic electrolytic solution of claim 1 , wherein an amount of the phosphonate compound of said formula (1) is in a range of 0.1–50% by weight with respect to 50–99.9% by weight of the organic solvent.
3. The organic electrolytic solution of claim 1 , wherein the phosphonate compound of said formula (1) is at least one of diethyl vinyl phosphonate and dimethyl vinyl phosphonate.
4. The organic electrolytic solution of claim 1 , wherein the organic solvent comprises a high dielectric constant solvent and a low boiling point solvent.
5. The organic electrolytic solution of claim 4 , wherein the high dielectric constant solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone, and an amount of the high dielectric constant solvent is in a range of 10–90% by volume based on a total volume of the organic solvent.
6. The organic electrolytic solution of claim 4 , wherein the low boiling point solvent is at least one selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, dimethoxyethane, C 1 –C 13 fatty acid ester derivatives, and an amount of the low boiling point solvent is in a range of 10–90% by volume based on a total volume of the organic solvent.
7. The organic electrolytic solution of claim 1 , wherein a concentration of the lithium salt is in a range of 0.5–2.0 M.
8. A lithium battery comprising:
a cathode;
an anode;
a separator interposed between the cathode and the anode; and
an organic electrolytic solution comprising a lithium salt, an organic solvent and a phosphonate compound of formula (1) below:
wherein R 1 and R 2 are independently selected from among a substituted or unsubstituted C 1 –C 20 alkyl group, a substituted or unsubstituted C 1 –C 20 alkoxy group, a substituted or unsubstituted C 2 –C 20 alkenyl group, a substituted or unsubstituted C 6 –C 30 aryl group, a substituted or unsubstituted C 7 –C 30 aralkyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted C 2 –C 30 heteroaryl group, a substituted or unsubstituted C 3 –C 30 heteroaralkyl group, a substituted or unsubstituted C 2 –C 30 heteroaryloxy group, a substituted or unsubstituted C 5 –C 20 cycloalkyl group, and a substituted or unsubstituted C 2 –C 20 heterocycloalkyl group; and R 3 and R 4 are independently selected from among a hydrogen atom and a substituted or unsubstituted C 1 –C 20 alkyl group.
9. The lithium battery of claim 8 , wherein the cathode contains at least one selected from the group consisting of lithium composite oxide, single substance sulfur, kasolite comprising Li 2 S n where n≧1, organo-sulfur, and (C 2 S x ) y where x ranges from 2.5 to 20 and y≧2.
10. The lithium battery of claim 8 , wherein the anode is selected from the group consisting of a lithium metal electrode, a lithium-metal alloy electrode, a lithium-inert sulfur composite electrode, a carbonaceous electrode, and a graphite electrode.
11. The lithium battery of claim 8 , wherein an amount of the phosphonate compound of said formula (1) is in a range of 0.1–50% by weight with respect to 50–99.9% by weight of the organic solvent.
12. The lithium battery of claim 8 , wherein the phosphonate compound of said formula (1) is at least one of diethyl vinyl phosphonate and dimethyl vinyl phosphonate.
13. The lithium battery of claim 8 , wherein the organic solvent comprises a high dielectric constant solvent and a low boiling point solvent.
14. The lithium battery of claim 8 , wherein the high dielectric constant solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone, and an amount of the high dielectric constant solvent is in a range of 10–90% by volume based on a total volume of the organic solvent.
15. The lithium battery of claim 8 , wherein the low boiling point solvent is at least one selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, dimethoxyethane, C 1 –C 13 fatty acid ester derivatives, and an amount of the low boiling point solvent is in a range of 10–90% by volume based on a total volume of the organic solvent.
16. The lithium battery of claim 8 , wherein a concentration of the lithium salt is in a range of 0.5–2.0 M.
17. The lithium battery of claim 9 , wherein the lithium composite oxide is selected from the group consisting of LiCoO 2 , LiMn x O 2x , LiNi 1-x Mn x O 2 , where x=1 or 2, and Ni 1-x-y Co x Mn y O 2 .
18. The lithium battery of claim 8 , wherein the separator comprises a glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or any combination thereof.
19. The lithium battery of claim 8 , wherein the separator is formed by:
mixing a polymer resin, a filling agent and a solvent to form a separator composition; and
one of:
coating the separator composition on an electrode to form the separator; and
casting the separator composition on a support, drying to form a separator film and laminating the electrode with the separator film,
wherein the polymer resin is a vinylidenefluoride-hexafluoropropylene copolymer containing 8–25% by weight of hexafluoropropylene.
20. The lithium battery of claim 8 , wherein the lithium battery comprises an electrode assembly that comprises the cathode, the anode, and the separator rolled/folded together and sealed into a battery case, wherein the organic electrolytic solution is injected into the battery case.