JP2000012070A - Secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the moisture adhered to a battery component during the manufacturing process of a battery to improve the performance of the battery. SOLUTION: A negative electrode and a positive electrode are vacuum dried independently (process 41: first vacuum drying). The drying conditions at this time are 200 deg.C, 0.1 Torr and 3 hours. The negative electrode and positive electrode dried under this condition are layered through a separator, and the layered product is wound on a core (process 42) to form an electrode element. The electrode element is inserted into a battery can and assembled by performing electric connection and the like (process 43), and then vacuum dried again (process 44: second vacuum drying). The drying condition at this time is 70 deg.C, 1 Torr, and 3 hours. After drying under this condition, a nonaqueous electrolyte is injected, and the battery can is sealed to a battery lid through a gasket, whereby the manufacture is ended (process 45).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery drying step in the manufacture of a secondary battery and a secondary battery manufactured by this manufacturing method.

[0002]

2. Description of the Related Art In recent years, secondary batteries that are repeatedly charged and used have been actively used in various fields. Among these, for example, a lithium ion secondary battery has excellent energy density and cycle characteristics.

As the lithium ion secondary battery, a positive electrode active material and a negative electrode active material are laminated with a separator interposed therebetween, wound around a winding core to form an electrode element, and this electrode element is mounted on a battery can. Some are manufactured by inserting and sealing the battery can and the battery lid via a gasket, and injecting an electrolytic solution.

FIG. 5 is a view showing a method of manufacturing the above-described lithium ion secondary battery. First, a negative electrode and a positive electrode manufactured by a predetermined method are vacuum-dried (step 5).
1). The drying is performed at 200 ° C. and 0.1 Torr for 3 hours. The negative electrode and the positive electrode dried under these conditions are laminated via a separator, and the laminate is wound around a winding core (step 52) to form an electrode element. After the electrode element is inserted into the battery can to assemble it by electrical connection or the like (Step 53), the battery can and the battery lid are welded through a gasket and sealed by laser welding or the like (Step 54). Thereafter, a non-aqueous electrolyte is injected from the injection port, and the injection port is sealed to complete the production.

Conventionally, a lithium ion secondary battery has been manufactured through the above-described steps. However, moisture adsorbed on the separator and other battery components as well as the negative electrode and the positive electrode may deteriorate the performance of the battery. Was known. For this reason, after the negative electrode and the positive electrode are applied to the current collector,
After being sufficiently dried before winding and other battery components were carefully dried, these components were assembled in a low humidity environment to produce a battery.

[0006] However, the moisture adsorbed on the electrode surface and components is once removed by being put into a drier and dried, but after being taken out of the drier, depending on the environment where it is left. Water will be adsorbed again,
This adsorbed moisture reduced the initial battery capacity.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a manufacturing method for removing water adhering to battery components during a battery manufacturing process to improve the performance of a battery, and an initial method for manufacturing the battery. It is intended to provide a secondary battery having a large battery capacity.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a positive electrode active material and a negative electrode active material are laminated with a separator interposed therebetween. And forming the electrode element in a battery can, and sealing the battery can and the battery lid with a gasket. In the method for manufacturing a secondary battery, after inserting the electrode element in the battery can, A method of manufacturing a secondary battery having a drying step of drying the electrode element before sealing the lid, and a secondary battery manufactured by the manufacturing method.

Further, a positive electrode active material and a negative electrode active material are laminated with a separator interposed therebetween, and the laminate is wound around a winding core to form an electrode element, and the electrode element is inserted into a battery can. In a method for manufacturing a secondary battery in which a battery lid is sealed via a gasket, a first drying step of drying the positive electrode active material and the negative electrode active material before winding them up, and inserting the electrode element into a battery can Then, before sealing the battery can and the battery lid, a method of manufacturing a secondary battery having a second drying step of drying the electrode element, and a secondary battery manufactured by this manufacturing method are provided. Thus, the above problem is solved.

In the manufacturing method of the present invention, the electrode element is sufficiently dried, and a secondary battery having a large initial battery capacity is manufactured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS.
This will be described with reference to FIG. Here, FIG. 1 is a view showing an electrode element used in the present invention, and FIG. 2 is a sectional view of a battery using the electrode element shown in FIG. FIG. 3 is a diagram showing a first manufacturing process of the secondary battery of the present invention, and FIG. 4 is a diagram showing a second manufacturing process.

First, an electrode element of a non-aqueous electrolyte secondary battery will be described with reference to FIG. The negative electrode 1 is manufactured as follows. The carbonaceous material fired in an inert gas stream is pulverized to obtain carbon particles having an average particle diameter of 20 μm, and 90 parts by weight of the carbon particles and 10 parts by weight of vinylidene fluoride resin as a binder are mixed with N. Dispersed in methylpyrrolidone to form a slurry. This slurry is applied to both sides of a copper foil having a thickness of 10 μm to produce an electrode plate having a thickness of 180 μm. The negative electrode 1 is obtained by cutting a part of the electrode base plate while leaving an uncoated portion serving as the negative electrode lead 2.

The positive electrode 3 is manufactured as follows. 91 parts by weight of LiCoO ₂ powder having an average particle size of 15 μm,
6 parts by weight of graphite as a conductive material and 3 parts by weight of vinylidene fluoride resin as a binder are dispersed in N-methylpyrrolidone to form a slurry, and the slurry is applied to both sides of an aluminum foil to form a slurry. An electrode plate of 150 μm is prepared. A part of this electrode plate is cut to leave a non-coated part to be the positive electrode lead 4 to obtain a positive electrode 3.

The negative electrode 1 produced as described above
The positive electrode 3 and the positive electrode 3 are sequentially laminated with the separator 5 interposed therebetween, and are wound many times in the direction indicated by the arrow R around a cylindrical core 6 made of, for example, PP (polypropylene), PE (polyethylene), or the like. The uncoated portions of the negative electrode 1 and the positive electrode 3 are cut into strips in advance, and after winding, the negative electrode lead 2 is assembled on one side of the winding core 6 and the positive electrode lead 4 is assembled on the other side. To form an electrode element.

FIG. 2 is a cross-sectional view of a non-aqueous electrolyte secondary battery using the electrode element 7 formed as described above. The current collecting lead 8a is drawn out of the negative electrode lead 2 of the electrode element 7 and is summarized. Then, it is laser-welded by being sandwiched between the holding metal 9a and the current collector 10a. On the other hand, the current collecting lead 8b is pulled out from the positive electrode lead 4 of the electrode element 7 and put together, and is laser-welded by being sandwiched between the holding metal 9b and the current collecting portion 10b. Thereafter, the battery is housed in a battery can 11 made of stainless steel, and the current collector 10a and the bottom 11a of the battery can 11 are electrically connected to each other to form a negative electrode.
As a result, the battery lid 13 is electrically connected to form a positive electrode.

Thereafter, the battery can 11 and the battery lid 13 are sealed with a gasket 14 inside the battery can 11, and for example, 1 mol of LiBF ₄ is contained as an electrolytic solution in a mixed solvent of propylene carbonate and diethyl carbonate. A non-aqueous electrolyte secondary battery is formed by injecting the solution dissolved at a rate of 1 / liter from an inlet (not shown).

Next, a method of manufacturing the above-described nonaqueous electrolyte secondary battery, which is a feature of the present invention, will be described.

FIG. 3 shows a first manufacturing method, in which a negative electrode and a positive electrode are laminated via a separator, and the laminate is wound around a core (step 31) to form an electrode element. After assembling such an electrode element by inserting it into a battery can and establishing electrical connection (step 32), it is vacuum dried (step 33). Drying conditions at this time are 70 ° C. and 1 Torr for 3 hours. After drying under these conditions, inject a non-aqueous electrolyte,
The battery can and the battery lid are sealed via a gasket, and the production is completed (step 34).

According to the above-described first manufacturing method, since the battery can and the battery lid are dried immediately before sealing them with a gasket, it is possible to limit the amount of water present inside the battery to a small amount. A secondary battery having a large battery capacity can be manufactured.

Next, a second manufacturing method shown in FIG. 4 will be described. First, the negative electrode and the positive electrode are individually vacuum dried (step 41: first vacuum drying). The drying is performed at 200 ° C. and 0.1 Torr for 3 hours. The negative electrode and the positive electrode dried under these conditions are laminated via a separator, and the laminate is wound around a winding core (step 42).
An electrode element is formed. After assembling the electrode element by inserting it into a battery can and establishing electrical connection (step 43), the electrode element is vacuum dried again (step 44: second vacuum drying). Drying conditions at this time are 70 ° C. and 1 Torr for 3 hours. After drying under these conditions, a non-aqueous electrolyte is injected, and the battery can and the battery lid are sealed via a gasket to complete the production (step 45).

According to the second manufacturing method described above, the negative electrode and the positive electrode are individually dried before winding, and further, immediately before the battery can and the battery lid are closed with a gasket. In addition, the amount of water present inside the battery can be limited to an extremely low amount, and a secondary battery having a large initial battery capacity can be manufactured.

Next, as a comparative example, the initial battery capacity of the secondary battery manufactured by the conventional manufacturing method shown in FIG. 5 and the secondary battery manufactured by the second manufacturing method according to the present invention shown in FIG. The initial battery capacity of the battery was measured by the following method, and the results are shown in Table 1.

Battery Capacity Measurement Method The battery thus prepared was initially charged under the conditions of a charging voltage of 4.2 V, a charging current of 17 A, and a charging time of 9.5 hours.
Aging is performed for 20 days in an environment of ° C. After aging, discharge is performed at a discharge current of 30 A and a final voltage of 2.5 V.
After discharging, the battery was charged again at a charging voltage of 4.2 V, a charging current of 45 A, and a charging time of 4, and then discharged under the above-described conditions to measure the discharge capacity, which was taken as the battery capacity.

[0024]

[Table 1]

As is clear from the measurement results shown in Table 1, it can be seen that the secondary battery manufactured by the manufacturing method of the present invention has a large initial electric capacity.

It should be noted that the present invention is not limited to the above-described secondary battery, but may be applied to a battery having another structure to which the technical idea of the present invention can be applied.

[0027]

As is apparent from the above description, according to the present invention, it is possible to effectively remove moisture adhering to battery components during the battery manufacturing process, and to provide a secondary battery having a large initial capacity. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing an electrode element of a secondary battery.

FIG. 2 is a sectional view of a battery using the electrode element shown in FIG.

FIG. 3 is a view showing a first manufacturing process of the secondary battery of the present invention.

FIG. 4 is a view showing a second manufacturing process of the secondary battery of the present invention.

FIG. 5 is a view showing a manufacturing process of a conventional secondary battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Negative electrode, 2 ... Negative electrode lead, 3 ... Positive electrode, 4 ... Positive electrode lead, 5 ... Separator, 6 ... Core, 7 ... Electrode element, 8a, 8b ... Current collecting lead, 9a, 9b ... Hold down fitting, 10a , 10b: current collector, 11: battery can, 12: lead, 13: battery lid, 14: gasket

Claims (4)

[Claims] 1. A positive electrode active material and a negative electrode active material are laminated via a separator, and the laminate is wound around a winding core to form an electrode element, and the electrode element is inserted into a battery can. In a method for manufacturing a secondary battery in which a battery lid is sealed via a gasket, a drying step of drying the electrode element after inserting the electrode element into a battery can and before sealing the battery can and the battery lid. A method for manufacturing a secondary battery, comprising: 2. A positive electrode active material and a negative electrode active material are laminated via a separator, and the laminate is wound around a winding core to form an electrode element, and the electrode element is inserted into a battery can. In a method for manufacturing a secondary battery in which a battery lid is sealed via a gasket, a first drying step of drying the positive electrode active material and the negative electrode active material before winding them up, and inserting the electrode element into a battery can And a second drying step of drying the electrode element before sealing the battery can and the battery lid. 3. A secondary battery manufactured by the manufacturing method according to claim 1. 4. A secondary battery manufactured by the manufacturing method according to claim 2.