Lithium secondary battery
View Patent ↗The present invention provides a lithium secondary battery which has improved safety, mainly coming from use of an electrolyte solution which is not inflammable at room temperature (20° C.), while not deteriorating output characteristics at low temperatures and room temperature or output maintenance characteristics after storage at high temperature (50° C.). The lithium secondary battery of the present invention, encased in a container, is provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution containing a cyclic carbonate and a linear carbonate as solvents and a compound such as VC at composition ratios of 18.0 to 30.0%, 74.0 to 81.9% and 0.1 to 1.0%, respectively, based on the whole solvents, all percentages by volume.
1. A lithium secondary battery provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution, wherein
solvents of the electrolyte solution consist of ethylene carbonate (EC) in an amount of 18.0 to 30.0% by volume, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), wherein a DMC/EMC ratio by volume is 0.8 to 1.3 and vinylene carbonate (VC) in an amount of 0.1 to 1.0% by volume based on the whole solvents, wherein the electrolyte solution has an ion conductivity of 2 mS/cm or more at −30° C.
2. A lithium secondary battery provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution, wherein
the electrolyte solution comprises as solvents ethylene carbonate (EC) in an amount of 18.0 to 30.0% by volume, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a DMC/EMC ratio by volume is 0.8 to 1.3, and vinylene carbonate (VC) in an amount of 0.1 to 1.0% by volume based on the whole solvents, wherein the electrolyte solution has an ion conductivity of 2 mS/cm or more at −30° C.
3. The lithium secondary battery according to claim 2 , wherein the vinylene carbonate (VC) accounts for an amount of 0.1 to 0.6% by volume based on the whole solvents.
4. A lithium secondary battery provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution, wherein
the electrolyte solution comprises as solvents ethylene carbonate (EC) in an amount of 18.0 to 30.0% by volume, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a DMC/EMC ratio by volume is 0.8 to 1.3, and vinylene carbonate (VC):
the cathode comprises a cathode mixture and a cathode-side current collector,
the cathode mixture comprising a cathode-active material, an electroconductive agent and a binder is spread on the cathode-side current collector to form a cathode mixture layer thereon, the cathode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer,
the anode comprises an anode mixture and an anode-side current collector, and
the anode mixture comprising an anode-active material, an electroconductive agent and a binder is spread on the anode-side current collector to form an anode mixture layer thereon, the anode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer.
5. The lithium secondary battery according to claim 2 , wherein the DMC and EMC are incorporated in a DMC/EMC ratio of 0.8 to 1.0 by volume.
6. The lithium secondary battery according to claim 2 , wherein the electrolyte solution has a flash point of 20° C. or higher.
7. The lithium secondary battery according to claim 2 , wherein the dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are contained in the electrolyte solution in an amount of up to 81.9% by volume based on the whole solvents.
8. The lithium secondary battery according to claim 7 , wherein the vinylene carbonate (VC) accounts for an amount of 0.1 to 0.6% by volume based on the whole solvents.
9. The lithium secondary battery according to claim 2 , wherein:
the cathode comprises a cathode mixture and a cathode-side current collector,
the cathode mixture comprising a cathode-active material, an electroconductive agent and a binder is spread on the cathode-side current collector to form a cathode mixture layer thereon, the cathode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer,
the anode comprises an anode mixture and an anode-side current collector, and
the anode mixture comprising an anode-active material, an electroconductive agent and a binder is spread on the anode-side current collector to form an anode mixture layer thereon, the anode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer.
10. The lithium secondary battery according to claim 7 , wherein the DMC and EMC are incorporated in a DMC/EMC ratio of 0.8 to 1.0 by volume.
11. The lithium secondary battery according to claim 7 , wherein the electrolyte solution has a flash point of 20° C. or higher.
12. The lithium secondary battery according to claim 7 , wherein the dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are present in an amount of 60 to 81.9% by volume based on the whole solvents.
13. The lithium secondary battery according to claim 7 , wherein the dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are present in an amount of 66 to 81.9% by volume based on the whole solvents.
14. The lithium secondary battery according to claim 7 , wherein the dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are present in an amount of 70 to 81.9% by volume based on the whole solvents.
15. In an electric vehicle, the improvement comprising a power source comprising the lithium secondary battery according to claim 7 .
16. The electric vehicle according to claim 15 , wherein the electric vehicle is a hybrid electric vehicle.
17. A lithium secondary battery, comprising a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution, wherein the electrolyte solution comprises as solvents ethylene carbonate (EC) in an amount of 18.0 to 30.0% by volume, vinylene carbonate (VC) in an amount of 0.1 to 1.0% by volume, and the balance comprising dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a DMC/EMC ratio by volume of 0.8 to 1.3, wherein the electrolyte solution has an ion conductivity of 2 mS/cm or more at −30° C.
18. The lithium secondary battery according to claim 17 , wherein:
the cathode comprises a cathode mixture and a cathode-side current collector,
the cathode mixture comprising a cathode-active material, an electroconductive agent and a binder is spread on the cathode-side current collector to form a cathode mixture layer thereon, the cathode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer,
the anode comprises an anode mixture and an anode-side current collector, and
the anode mixture comprising an anode-active material, an electroconductive agent and a binder is spread on the anode-side current collector to form an anode mixture layer thereon, the anode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer.
19. The lithium secondary battery according to claim 17 , wherein the DMC and EMC are incorporated in a DMC/EMC ratio of 0.8 to 1.0 by volume.
20. The lithium secondary battery according to claim 17 , wherein the electrolyte solution has a flash point of 20° C. or higher.
21. In an electric vehicle, the improvement comprising a power source comprising the lithium secondary battery according to claim 17 .
22. The electric vehicle according to claim 21 , wherein the electric vehicle is a hybrid electric vehicle.
23. The lithium secondary battery according to claim 1 , wherein the vinylene carbonate (VC) accounts for an amount of 0.1 to 0.6% by volume based on the whole solvents.
24. The lithium secondary battery according to claim 4 , wherein the vinylene carbonate (VC) accounts for an amount of 0.1 to 0.6% by volume based on the whole solvents.
25. The lithium secondary battery according to claim 17 , wherein the vinylene carbonate (VC) accounts for an amount of 0.1 to 0.6% by volume based on the whole solvents.
26. A lithium secondary battery provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution, wherein
the electrolyte solution comprises as solvents ethylene carbonate (EC) in an amount of 18.0 to 30.0% by volume, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a DMC/EMC ratio by volume is 0.8 to 1.3, and vinylene carbonate (VC) in an amount of 0.1 to 0.6% by volume based on the whole solvents.
27. The lithium secondary battery according to claim 26 , wherein the cathode comprises a lithium composite oxide represented by the formula LiMn x M1 y M2 z O 2 (wherein, M1 is at least one selected from the group consisting of Co and Ni, M2 is at least one selected from the group consisting of Co, Ni, Al, B, Fe, Mg and Cr, x+y+z=1, 0.2≦x≦0.6, 0.2≦y≦0.4 and 0.05≦z≦0.4).
28. The lithium secondary battery according to claim 26 , wherein the anode comprises at least one of carbonaceous material, an oxide of an element belonging to the IV group and a nitride of an element belonging to the IV group.
29. The lithium secondary battery according to claim 26 , wherein:
the cathode comprises a cathode mixture and a cathode-side current collector,
the cathode mixture comprising a cathode-active material, an electroconductive agent and a binder is spread on the cathode-side current collector to form a cathode mixture layer thereon, the cathode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer,
the anode comprises an anode mixture and an anode-side current collector, and
the anode mixture comprising an anode-active material, an electroconductive agent and a binder is spread on the anode-side current collector to form an anode mixture layer thereon, the anode mixture layer having a porosity of 25 to 40% by volume, inclusive, based on the layer.
30. The lithium secondary battery according to claim 26 , wherein the DMC and EMC are incorporated in a DMC/EMC ratio of 0.8 to 1.0 by volume.
31. The lithium secondary battery according to claim 26 , wherein the anode comprises a carbonaceous material having a d 002 value of 0.39 nm or less.
32. The lithium secondary battery according to claim 30 , wherein:
the cathode is formed by spreading, on an aluminum foil, a cathode mixture comprising a lithium composite oxide, an electroconductive agent mainly composed of graphite-base carbonaceous material and a binder,
the cathode mixture layer has a porosity of 25 to 40% by volume, inclusive, based on the layer,
the anode is formed by spreading, on a copper foil, an anode mixture comprising amorphous carbon, an electroconductive agent and a binder, and
the anode mixture layer has a porosity of 25 to 40% by volume, inclusive, based on the layer.
33. The lithium secondary battery according to claim 32 , wherein the electrolyte solution has a flash point of 20° C. or higher and an ion conductivity of 2 mS/cm or more at −30° C.
34. The lithium secondary battery according to claim 26 , wherein the solvents of the electrolyte solution consist essentially of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and vinylene carbonate (VC).