JPH10106629A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery with its superior durability or productivity that improves brittleness or high cost of a roll metal foil that is a current collector material of a conventional non-aqueous electrolyte secondary battery. SOLUTION: A non-aqueous electrolyte secondary battery 1 forms a vortex- shaped laminating electrode body by winding a positive electrode 3 and a negative electrode 4 where an electrode substance layer is formed on a surface of a flat current collector intervening a separator around a winding core 2. At least one of the flat current collectors forming the positive electrode 3 and the negative electrode 4 is formed using a metal foil electrolyzed and precipitated. A laminating electrode body thus formed is inserted into a battery can 6 and tightened by a nut 8 via a cap 7. An organic electrolyte or the like in which LiPF6 is dissolved in a mixture solvent at a rate of 1mol/l is injected into the battery can 6 of such a constitution. Thereby, the non-aqueous electrolyte secondary battery 1 of the present invention using the electrode with improved durability or productivity can be constructed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery having a large capacity of, for example, 20 Ah or more per cell. More specifically, at least one of a positive electrode and a negative electrode current collector is formed of a metal by electrolytic deposition. Accordingly, the present invention relates to a non-aqueous electrolyte secondary battery having improved durability.

[0002]

2. Description of the Related Art In recent years, interest in environmental problems has increased,
Suppressing the emission of substances that lead to environmental destruction such as global warming and acid rain, such as ₂ or NO _X request is growing. As long as conventional fossil fuels are used as fuel for transportation equipment such as automobiles, it is not possible to suppress the emission of environmentally destructive substances such as CO ₂ and NO _X. In addition, current power generation systems are mainly based on nuclear power generation, thermal power generation, and hydroelectric power generation.These power generation systems, excluding hydroelectric power generation, operate on the order of several days to several months, and the power consumption difference between day and night It is not possible to adjust the amount of power generation in accordance with the power consumption having periodicity such as a monthly cycle and an annual cycle. Therefore, these power generation systems must generate power at the peak time, and waste power in a time period when the power consumption is small.

[0003] Such a situation is not preferable from the viewpoint of both environment and resources, and it is required to realize a method of consuming necessary energy by a load leveling device or the like to generate necessary power. In response to these requirements, conventional nickel-cadmium batteries and lead-acid batteries have not been able to adequately meet the demands in terms of capacity and energy density.

Under these circumstances, a so-called lithium ion secondary battery using a lithium composite oxide such as a lithium cobalt composite oxide for the positive electrode and a lithium ion-doped and undoped substance such as a carbon material for the negative electrode is used. The battery characteristics have been improved, and the batteries have been used as power sources for electric vehicles (EVs) and load leveling devices. A lithium ion secondary battery belonging to a nonaqueous electrolyte secondary battery has excellent features such as high energy density, low self-discharge, excellent cycle characteristics, and light weight. By the way, a metal foil is generally used as a current collector of the lithium ion secondary battery. For example, as a metal foil made of copper used as a negative electrode current collector, generally, a rolled copper foil having a thickness of 10 to 30 μm obtained by mechanically rolling a copper plate is used.

[0005] However, although the rolled copper foil has a certain level of tensile strength, it is hardened by work hardening by rolling. Has characteristics. Also,
Many material defects such as surface defects are also observed. Fatigue fracture due to alternating stress such as vibration is affected by the surface roughness (surface defect) of the material and the factors of notch sensitivity. That is, the rougher the surface and the higher the notch sensitivity (generally a brittle material), the more likely it is to cause fatigue fracture. When the lithium ion secondary battery as described above is considered as an energy source for transportation equipment, durability against vibration and impact is required. For the reasons described above, there is a demand for the development of an electrode current collector having few surface defects and having tenacity.

Further, the rolled copper foil is limited in thickness and width, and it is difficult to obtain a wide rolled copper foil. That is, due to the hardening process by rolling, a thinner object is more likely to have a defect, and it is difficult to produce a homogeneous rolled copper foil. As described above, there is a possibility that the cost of the rolled copper foil is higher than that of the copper foil obtained by electrolytic deposition. In order to spread electric vehicles and load leveling devices using lithium ion secondary batteries, there is an urgent need to develop current collector materials having high durability and high productivity.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the brittleness and high cost of a rolled metal foil which is a current collector material of a conventional non-aqueous electrolyte secondary battery. And to provide a non-aqueous electrolyte secondary battery using a current collector material having excellent durability and productivity.

[0008]

The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode having a positive electrode active material coated on one or both surfaces of a positive electrode current collector, and a negative electrode active material on one or both surfaces of a negative electrode current collector. In a nonaqueous electrolyte secondary battery in which a negative electrode coated with a substance is laminated via a separator to form a laminated electrode body, at least one current collector of a positive electrode or a negative electrode current collector was produced by electrolytic deposition. The problem has been solved by using a metal foil.

Preferably, the non-aqueous electrolyte secondary battery comprises:
A large-capacity secondary battery having a battery capacity of 20 Ah or more per cell is desirable.

In the non-aqueous electrolyte secondary battery of the present invention, at least one of the positive electrode and the negative electrode current collector is formed using a metal foil produced by electrolytic deposition, so that the battery can withstand vibration and impact. Performance can be improved. Further, since the metal foil formed by electrolytic deposition has high productivity, a low-cost electrode can be supplied. Furthermore, since a uniform foil can be easily obtained even if the thickness of the metal foil by electrolytic deposition is reduced, the number of turns can be increased by using a thin electrode. Thereby, the reaction area of the electrode can be increased, and the battery output can be increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

First, the configuration of the non-aqueous electrolyte secondary battery of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing the inside of a cell of a nonaqueous electrolyte secondary battery of the present invention.

FIG. 1 shows a non-aqueous electrolyte secondary battery 1 of the present invention.
Is formed by winding a positive electrode 3 and a negative electrode 4 each having an electrode forming material layer formed on the surface of a flat current collector on a winding core 2 through a separator 5 of a microporous polypropylene film having a thickness of 25 μm, for example, to form a spiral stack. An electrode body is formed. A positive electrode current collecting lead 3a is extended to the positive electrode 3, and a negative electrode current collecting lead 4a is extended to the negative electrode 4, so that a positive electrode column 3b and a negative electrode column 4a are respectively provided.
b.

The laminated electrode body thus formed is inserted into a battery can 6 and fastened with a nut 8 via a cap 7. Battery can 6 having such a configuration
Then, an organic electrolyte obtained by dissolving LiPF ₆ in a mixed solvent at a ratio of 1 mol / l is injected into the nonaqueous electrolyte secondary battery 1 of the present invention.

The non-aqueous electrolyte secondary battery 1 of the present invention
As a feature of the present invention, at least one of the planar current collectors forming the positive electrode 3 and the negative electrode 4 is formed using electrolytically deposited electrolytic metal foil. Further, the non-aqueous electrolyte secondary battery 1 of the present invention has a large capacity of 20 Ah or more per cell for the purpose of application to an electric vehicle, a load leveling device, and the like. Since transportation equipment such as electric vehicles can be used under severe conditions, the nonaqueous electrolyte secondary battery 1 of the present invention has durability enough to maintain performance against external forces such as vibration and impact. Has been requested.

Next, examples of the nonaqueous electrolyte secondary battery and comparative examples will be described with reference to FIG. 1 and Table 1 in order to confirm the effects of the electrode of the present invention. It goes without saying that the present invention is not limited to this embodiment.

EXAMPLE LiCoO ₂ was used as a positive electrode active material, and graphite as a conductive agent and polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture, which was dispersed in N-methyl-2-pyrrolidone. A slurry was formed. This is applied to an Al foil to form a positive electrode 3
Was prepared. As the negative electrode active material, carbon capable of doping and undoping Li ions was used. This carbon is mixed with polyvinylidene fluoride as a binder and mixed with N-solvent.
It was dispersed in methylpyrrolidone to form a slurry. This slurry was applied to an electrolytic copper foil to produce a negative electrode 4. These positive electrode 3 and negative electrode 4 were configured as shown in FIG. 1 to produce a large-capacity nonaqueous electrolyte secondary battery 1 of the present invention.

Comparative Example A slurry for the positive electrode 3 and the negative electrode 4 was prepared in the same manner as in the above example. The positive electrode 3 was applied to an Al foil in the same manner as in the example, and the negative electrode 4 was applied to a rolled copper foil in a conventional manner. Each electrode was produced. Using these positive electrode 3 and negative electrode 4, a comparative large-capacity non-aqueous electrolyte secondary battery having a configuration as shown in FIG. 1 was produced.

Table 1 shows the results of a vibration test performed on each of the large capacity nonaqueous electrolyte secondary batteries of Examples and Comparative Examples. Vibration conditions are vibration acceleration 3.0G, vibration time 25
The time and the number of samples were each one sample.

[0020]

[Table 1]

The results of the above vibration test proved that the use of electrolytic copper foil for the current collector improved the durability against vibration.

Although the preferred embodiment of the present invention has been described in detail above, the present invention can be implemented in various embodiments other than this embodiment. For example, the electrolytic metal foil which has been electrolytically deposited may be applied to the positive electrode, and may be applied to a square or flat battery in addition to the cylindrical nonaqueous electrolyte secondary battery described as the embodiment. It goes without saying that the same effect can be obtained even if the present invention is applied not only to the non-aqueous electrolyte secondary battery but also to a lithium ion secondary battery belonging to the secondary battery.

[0023]

According to the non-aqueous electrolyte secondary battery of the present invention,
Since at least one of the planar current collectors forming the positive electrode and the negative electrode is formed of electrolytically deposited metal foil, the durability of the battery against vibration and impact can be improved. Further, the metal foil formed by electrolytic deposition has higher productivity than the metal foil formed by conventional rolling, and has the effect of supplying electrodes at low cost. Furthermore, since a uniform foil is easily obtained even if the thickness of the metal foil by electrolytic deposition is reduced, the number of turns can be increased by using a thin electrode. As a result, the reaction area of the electrode can be increased to increase the battery output, which is beneficial.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the inside of a cell of a nonaqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

1 ... non-aqueous electrolyte secondary battery of the present invention, 2 ... core, 3 ...
... Positive electrode, 3a ... Positive electrode current collecting lead, 3b ... Positive electrode column, 4
... Negative electrode, 4a... Negative electrode current collecting lead, 4b.
5 ... separator, 6 ... battery can, 7 ... cap, 8
……nut

Claims (5)

[Claims] 1. A laminated electrode comprising: a positive electrode having a positive electrode active material coated on one or both surfaces of a positive electrode current collector; and a negative electrode having a negative electrode active material coated on one or both surfaces of a negative electrode current collector with a separator interposed therebetween. In a non-aqueous electrolyte secondary battery that forms a body, at least one of the positive electrode current collector and the negative electrode current collector is formed using a metal foil produced by electrolytic deposition. Non-aqueous electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is a large-capacity secondary battery having a battery capacity of 20 Ah or more per cell. 3. The electrode constituent material of the positive electrode is formed of a metal oxide containing at least lithium, and the electrode constituent material of the negative electrode is formed of a material capable of doping and undoping lithium. The non-aqueous electrolyte secondary battery according to claim 1. 4. The non-aqueous electrolyte according to claim 1, wherein the positive electrode, the separator, and the negative electrode are spirally laminated to form a cylindrical shape. Rechargeable battery. 5. The non-aqueous electrolyte solution according to claim 1, wherein the positive electrode, the separator, and the negative electrode are stacked in an N-stage shape to form a square shape. Next battery.