JPH07153490A - Battery - Google Patents

Abstract

PURPOSE:To provide a battery having excellent performance by using band-like electrodes formed with many active material layers into a square pattern on a current collector, and winding them into a wound body to form an electrode body so that the current collector portion formed with no active material layer is arranged at the bent portion had a small radius of curvature, CONSTITUTION:Band-like electrodes formed with many active material layers into a square pattern on a current collector are used, and they are wound into a bound body to form an electrode body so that the active material layers are arranged on a pair of parallel sides. They are wound into the wound body to form the electrode body so that a current collector portion 22 formed with no active material layer is arranged. The electrode body is arranged with electrode presser plates 5 in parallel on both sides of the active material layers, and it is stored in an angular iron battery can 4 applied with Ni plating. Negative electrode leads 6 guided from negative electrodes 2 are welded on the upper inner wall of a battery can 4. Positive leads 7 guided from positive electrodes 2 are welded to a positive electrode external terminal 9 fitted to a cover body 8 via a polypropylene packing 10 in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a prismatic battery, and more particularly to a method for assembling a laminated electrode body which is a power generating element.

[0002]

2. Description of the Related Art With the progress of miniaturization of electronic equipment, there is an increasing demand for small high-capacity batteries as a power source. In order to meet the demand, attempts have been made to put into practical use a prismatic battery, which is advantageous in terms of occupied volume efficiency, instead of the cylindrical battery which is common to most batteries up to now. In fact, as the nickel-cadmium secondary battery, a prismatic so-called gum-type secondary battery has been put into practical use. Furthermore, non-aqueous electrolyte batteries such as lithium batteries, which are expected to have high energy density as a battery system, have been actively developed, and high-performance non-aqueous electrolyte batteries have already been put into practical use as cylindrical batteries. In the future, the realization of a prismatic non-aqueous electrolyte battery is most desired. on the other hand,
There is no sign of global environmental destruction, and there is a strong demand for full-scale realization of wind power generation and solar power generation that will replace fossil fuels, as well as realization of electric vehicles. In order to realize these, it is indispensable to complete a high energy density secondary battery as a power storage or a power source for driving an electric vehicle. Therefore, the development of a prismatic non-aqueous electrolyte secondary battery is most desired not only from the small high-capacity battery demanded by electronic devices but also from the need for large high energy density batteries. As a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using a carbon electrode as a negative electrode, which utilizes the inflow / outflow of lithium ions from / to carbon, has already been put into practical use as a cylindrical battery and used in video cameras and the like. Started to be. This battery is called a lithium ion secondary battery, and typically uses LiCoO ₂ , LiMn ₂ O ₄ , or the like as a positive electrode material,
A carbonaceous material such as coke or graphite is used for the negative electrode. In this battery, the carbon helium ion in the electrode is doped during charging, and the lithium ion is dedoped from the carbon during discharging, and the carbon itself does not undergo a large change in the crystal structure during charging and discharging, which is extremely stable. It exhibits charge / discharge characteristics and shows little deterioration in characteristics due to charge / discharge, and specifically, it is possible to repeat charge / discharge 1000 times or more. However, the difficulty in making the non-aqueous electrolyte battery square is its mass productivity. The conventional method of assembling a prismatic battery is to stack a number of strip-shaped electrodes with positive and negative electrodes alternately sandwiching a separator to create a prismatic laminated electrode body, and place it in a prismatic battery case for assembly. . In particular, in the case of non-aqueous electrolyte batteries, unlike aqueous solution batteries such as existing nickel-cadmium batteries, the electrolyte resistance is high, so in order to obtain sufficient characteristics, stack a large number of thin electrodes and increase the electrode area. We need to increase it. Therefore, in the non-aqueous electrolyte type prismatic battery, the number of laminated layers is very large, which further makes it difficult to assemble a laminated body of electrodes. At present, this work is largely done manually, and mechanization for mass production is extremely difficult. In the case of a cylindrical battery, the battery element is manufactured by winding a strip-shaped electrode in a roll shape to form a wound body, which is housed in a cylindrical battery can. The creation of the wound body has made considerable progress in the manufacturing technology of conventional nickel-cadmium batteries and aluminum electrolytic capacitors, and of course it is also applied to the manufacture of cylindrical non-aqueous electrolyte batteries, which is a big problem in the battery assembly method in mass production. There is no.
An attempt was made to apply the technology of the cylindrical battery to make a battery element for a rectangular battery with a rectangular winding body. However, in the rectangular winding body, a point where a bent portion with an extremely small radius of curvature occurs However, this is a big difference from the cylindrical wound body, and in an attempt to make a square wound body up to now, the active material layer is bent with an extremely small radius of curvature, so that the active material is a collector. Peeled off from the
The powder of the active material thus generated penetrates the separator and causes an internal short circuit in the battery, resulting in a very low yield. Particularly in the case of a lithium-ion secondary battery, the positive electrode using LiCoO ₂ , LiMn ₂ O _4, etc. as the active material has a pressure-molded active material layer that is hard and brittle, and therefore has a very small polar radius in the positive electrode active material layer. When bent, the active material layer peels off from the current collector, which causes an internal short circuit.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to provide a method for assembling a prismatic laminated electrode body having high productivity for mass production of a prismatic battery, especially a prismatic nonaqueous electrolyte battery. is there.

[0004]

Means for Solving the Problems According to the means of the present invention for solving the above problems, first, a metal foil or a metal mesh is used as a current collector, and a strip shape in which an active material layer is formed in a square pattern on the current collector. Prepare an electrode, sandwich the separator between the strip electrode and the counter electrode, and arrange the active material layer on a pair of sides, and arrange the portion of the current collector that does not form the active material layer to the portion where bending occurs. Then, the laminated electrode body is prepared as a wound body having at least one pair of parallel sides.

[0005]

The method for producing a battery element according to the present invention uses a strip electrode having a plurality of active material layers formed in a square pattern (21) on a current collector as shown in FIG. ), The electrode material is formed as a wound body by winding up so that the active material layer (21) is arranged on a pair of parallel sides, and a cylindrical wound body in the case of a conventional cylindrical battery. Can be created with a machine of the same principle as that of creating. The point at which the wound body having at least one pair of parallel sides is bent with an extremely small radius of curvature is a big difference from the cylindrical wound body. In an attempt, the active material layer in the bent portion having an extremely small radius of curvature is peeled off from the current collector, the powder of the active material thus generated penetrates the separator, and the battery is internally short-circuited. The yield was extremely poor.
However, in the present invention, a strip electrode for a conventional circular winding body,
That is, unlike the strip-shaped electrode in which the active material layer is continuously formed, at least the electrode in which the active material layer is easily peeled off by bending is formed with a large number of active material layers in a square pattern on the current collector. Prepared as a strip-shaped electrode, and the active material layer is arranged on a pair of parallel sides, and rolled up so that the current collector part not forming the active material layer is arranged on the part where bending with a small radius of curvature occurs. Since the wound body is produced by the above method, no internal short circuit due to peeling of the active material occurs.

[0006]

The present invention will be described in more detail with reference to the following examples.

EXAMPLE A specific battery of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG. 1 is a schematic vertical cross-sectional view showing the structure of a battery according to the present invention, FIG. 2 is a plan view of a strip-shaped electrode, and FIG. 3 shows a winding start (a) and a winding end (b) of an electrode winding body. FIG. First, an electrode winding body embodying the present invention is prepared as follows. When mesocarbon microbeads are used as the negative electrode active material, peeling due to bending is unlikely to occur, so the negative electrode body is prepared by a conventional method. That is, like the conventional strip-shaped electrode for a circularly wound body, it is formed as a strip-shaped electrode in which an active material layer is continuously formed. Mesocarbon microbeads heat-treated at 2800 ° C. in a nitrogen stream (BET specific surface area = 0.8 m ²
/ G, d002 = 3.37Å) 90 parts by weight and 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder are wet-mixed with a solvent N-methyl-2-pyrrolidone to form a paste. Next, 0.01 m using this paste as a current collector
An active material layer is applied as a continuous layer on both sides of the copper foil of m, dried and pressure-molded to prepare a strip-shaped negative electrode body (1). The density of the active material layer after molding is preferably about 1.28 to 1.35 g / cc. The positive electrode body is prepared as follows. Commercially available manganese dioxide (MnO ₂ ) and lithium carbonate (Li ₂
A mixture having a CO ₃ ) molar ratio of 1: 0.25 is calcined in air at 800 ° C. for 8 hours, ground, and then calcined again in air at 800 ° C. for another 8 hours. This re-baking step is repeated several times to adjust LiMn ₂ O ₄ . Next, LiMn ₂ O ₄
89 parts by weight, 3 parts by weight of acetylene black as a conductive agent, 4 parts by weight of graphite, and 5 parts by weight of polyvinylidene fluoride as a binder are wet mixed with N-methyl-2-pyrrolidone to prepare a paste. On both sides of 0.02mm aluminum foil using the strike as a current collector,
As shown in (4), a strip-shaped positive electrode body (2) is prepared by applying a square pattern (21) while leaving a part of the uncoated portion (22), drying and pressing. The density of the active material layer after pressure molding is preferably about 2.8 to 3.2 g / cc. The pattern coating of the active material layer here can be performed by a coating technique such as an existing printing technique. The pattern of the active material layer is W × Ln
The specific dimensions in this embodiment in the square pattern are
W is 40.5 mm for the negative electrode and Wc = for the positive electrode.
Implement at 38.5 mm. Ln starts from L ₁ = 34 mm and is increased to L ₁₆ = 36 mm in the _16th pattern as n increases. In addition, the width Hn of the active material uncoated portion between the patterns of the active material layer is H ₁ =
2. The number is increased from 5 mm to H ₁₅ = 9.5 mm as n increases. Next, the strip negative electrode body (1) and the positive electrode body (2) have a polypropylene porous film (3) as a separator, and FIG. As shown in the schematic diagram of the beginning of winding of the electrode body, two core plates (3
3) sandwiching the separator (3), the negative electrode body (1) between the core plate (33) and the separator (3b), and the positive electrode body (2) between the core plate (33) and the separator (3a). Each is sandwiched and wound in the direction of the arrow to form a wound body. When the winding of the electrodes is completed, the wound body is removed from the core plate (33). By pressing the wound body from the side surface, the gap after the core plate is pulled out comes into close contact, and its cross section is shown in FIG.
It becomes as shown in (b). Active material layer of positive electrode body (21)
Are arranged on a pair of parallel sides, and a current collector part (2
A laminated electrode body for a prismatic battery is completed as a wound body in which 2) is arranged. In this example, LiMn ₂ was used as the positive electrode active material.
Since O ₄ is used, the positive electrode active material layer is hard and brittle,
Although it is easily peeled off from the current collector upon bending, in the wound body of the present embodiment, the portion (22) where the active material layer is not formed is arranged at the portion where bending with a small radius of curvature occurs. Therefore, there is no need to worry about peeling of the active material layer. Further, as shown in FIG. 1, the electrode body has electrode holding plates (stainless steel plate having a thickness of 0.2 mm) on both sides in parallel with the active material layer.
(5) is placed and housed in a nickel-plated iron square battery can (4). The negative electrode lead (6) taken out from the negative electrode (1) is welded to the inner wall of the upper part of the battery can. The positive electrode lead (7) taken out from the positive electrode (2) has a polypropylene packing (10) sandwiched in advance to cover the lid ( 8)
Weld to the positive electrode external terminal (9) attached to. The lid (8) is installed in the opening of the battery can (4), and the battery can and the lid are laser-welded to seal the battery can. At the end of the welding operation, the electrolytic solution is injected into the battery can through the small hole (11) made in the bottom of the battery can (4). In the combination of the positive electrode material and the negative electrode material used in this example, an electrolytic solution in which 1.5 mol / liter of LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) is optimal. is there. The specific injection of the electrolytic solution is performed as follows. The battery can is soaked in the above-mentioned electrolytic solution with the small hole (11) at the bottom of the battery down, and the battery can is soaked up to about half, and the pressure is reduced in the vacuum chamber. At this time, the gas in the battery can is sucked and discharged from the small hole (11) at the bottom of the battery can, and then the vacuum chamber is returned to normal pressure, so that the electrolytic solution enters the battery can. After injection of electrolyte, iron metal pole (12)
To the small hole (11) at the bottom of the battery can and pass an electric current, heat is generated by the contact resistance of both metals and welded to close the small hole. With the battery structure shown in FIG. 1, the external dimensions are 50 mm x 40 m.
A square non-aqueous electrolyte secondary battery (A) of m × 7.8 mm is completed. In this embodiment, since the wound body is formed by winding so that the current collector portion where the active material layer is not formed is arranged at the portion where the electrode winding body is bent, the internal short circuit due to the peeling of the active material is prevented. It didn't happen.

[0008]

According to the present invention, a band-shaped electrode in which a large number of active material layers are formed in a rectangular pattern on a current collector is used, and an active material layer is not formed in a bent portion having a small radius of curvature. A battery for a prismatic battery with a machine of the same principle as that for winding a cylindrical body in the case of a conventional cylindrical battery to wind up so that the body part is arranged and to create an electrode body as a wound body. It makes it possible to create a device. Unlike the conventional strip electrode in which the active material layer is continuously formed, the strip electrode in the present invention does not cause internal short circuit due to peeling of the active material. As a result, it becomes possible to provide a prismatic battery with high energy density that can be used in a wide range of applications by mass production, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a battery structure of an example.

FIG. 2 is a plan view of an electrode showing an active material layer pattern of a strip electrode.

FIG. 3 is a schematic cross-sectional view showing the beginning and end of winding of the electrode body in the example.

[Explanation of symbols]

1 is a negative electrode, 2 is a positive electrode, 3 is a separator, 4 is a battery can, 5
Is an electrode pressing plate, 6 is a negative electrode lead, 7 is a positive electrode lead, 8
Is a lid, 9 is a positive electrode external terminal, 10 is packing, 11 is a small hole, 12 is a metal pole, 21 is an active material layer, 22 is a portion where an active material layer is not formed, and 33 is a core plate of a winder.

Claims (1)

[Claims] 1. In a battery in which an electrode body composed of a positive electrode and a negative electrode laminated with a separator sandwiched therebetween is housed in a rectangular container, at least one of the negative electrode and the positive electrode is a metal foil or a metal mesh. Is a band-shaped electrode in which a plurality of active material layers are formed in a rectangular pattern on the current collector, and the band-shaped electrode is sandwiched between a counter electrode and a pair of parallel sides. The active material layer is disposed on the electrode, and the portion of the current collector on which the active material layer is not formed is disposed on the portion where bending occurs, so that the electrode body is formed as a wound body having at least one pair of parallel sides. A prismatic battery characterized by being