JP3139174B2 - Manufacturing method of thin non-aqueous electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin non-aqueous electrolyte battery requiring high load characteristics, and more particularly to a method of forming an electrode plate group. In recent years, with the remarkable portability and intelligence of cordless information and communication devices such as mobile phones and camcorders, small and lightweight batteries with a high energy density have been required as power sources for their driving. Liquid batteries, especially lithium secondary batteries, are highly expected as the mainstay of next-generation batteries, and their potential market size is very large. As for the shape of the battery, there is a growing demand for a thin sealed battery from the viewpoint of making the device thinner and effectively using space.

[0002]

2. Description of the Related Art Nickel-cadmium storage batteries and lead storage batteries, and recently nickel-hydrogen storage batteries, have been developed and put into practical use as thin, sealed batteries. In these battery systems, a high-concentration aqueous solution of an alkali or acid is used as an electrolytic solution, and the electrode plate group is configured by alternately stacking strip-shaped electrode plates with a positive electrode and a negative electrode via a separator.

However, a battery using a non-aqueous electrolyte containing an organic electrolyte as a main component, such as a lithium battery, has a low conductivity of the electrolyte, and therefore has a thickness similar to that of the above battery system. When the electrode group is constituted by the above-described electrode plates, there is a problem that sufficient high load characteristics cannot be obtained, and in the case of a secondary battery, quick charging cannot be performed.

In order to solve these problems, it is conceivable to reduce the thickness of the electrode plates to increase the number thereof, to increase the effective reaction area, and to lower the current density. It is difficult, and the configuration of the electrode group is extremely difficult.

[0005] In order to solve the above-mentioned problems, the present inventors have constructed an electrode plate group by spirally winding a sheet-like positive electrode and a negative electrode with a separator interposed therebetween and using a flat plate. Or a pole with a circular cross-section that is basically circular or elliptical, wound around a core, removed from the core, and then compressed in the diameter direction to form an elliptical pole. A method of constructing a plate group is proposed.

[0006]

However, when a flat plate is used as a winding core and the electrode plate group is formed by spirally winding the electrode plate, the electrode plate and the separator are both tensioned in the plane direction in the plane portion of the group. However, since no force is applied in a direction perpendicular to the plane, the electrode plate and the separator do not adhere uniformly.
For this reason, the distance between the electrodes varies, and the reaction of the positive and negative electrodes becomes uneven. In the case of a secondary battery, a predetermined charge / discharge capacity cannot be obtained at the beginning of charge / discharge. In addition, in the case of a primary battery, there is a problem that the variation in discharge capacity becomes large.

A group of electrode plates having a cross section of an oblong shape after being spirally wound using a rod-shaped core whose cross section is basically circular or elliptical, and then compressed in the diameter direction. However, although the above-mentioned problem relating to uniform contact of the electrode plate and the separator can be solved, there is a problem that the positional relationship between the folded end portion and the lead is not constant during compression molding. This is not a problem for cylindrical batteries because their cross-sectional shape is circular and symmetric.
A battery having a rectangular or similar cross-sectional shape has directionality, and leads must be arranged at certain positions in the electrode group in order to securely connect the electrode plates to external terminals of the battery.

[0008]

In order to achieve this object, the present invention is to provide a spirally wound core comprising a sheet-like positive electrode and a negative electrode interposed between separators and three or more rods combined in parallel. After being wound in a shape and removed from the core, it is compressed in the short axis direction to form an elliptical cross-sectional shape, thereby forming an electrode plate group.

[0009]

According to the above-described method for forming the electrode group, a thin non-aqueous electrolyte battery having excellent high load characteristics and small capacity variation, or a thin non-aqueous electrolyte solution having excellent quick charge characteristics and stable charge / discharge capacity. A secondary battery can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 (Secondary Battery) FIG. 1 (a) is a cross sectional view of a thin lithium secondary battery of the present invention, and FIG. 1 (b) is a partially enlarged view thereof.

In FIG. 1, reference numeral 1 denotes a positive electrode plate, which is formed by mixing lithium carbonate (LiCO ₃ ) and tricobalt tetroxide (Co ₃ O ₄ ), and sintering at 900 ° C. in air to form lithium cobalt oxide (LiCoO ₂ ). Active material. After mixing 3% by weight of acetylene black as a conductive agent, 7% by weight of an aqueous dispersion of polytetrafluoroethylene resin was kneaded as a binder into a paste, and the mixture was formed into a paste made of aluminum foil. It is applied on both sides of the material, dried and rolled. A part of the mixture is peeled off, and the positive electrode lead plate 4 is spot-welded. The dimensions of this positive electrode plate are 34 mm in width, 95 mm in length, and 0.17 mm in thickness.

The negative electrode plate 2 is composed mainly of spheroidal graphite having a mesophase pitch heat-treated at 2800 ° C. in an argon atmosphere and kneaded with 5% by weight of an aqueous dispersion of polytetrafluoroethylene resin as a binder. The paste mixture is applied to both sides of a core material made of copper foil, dried and rolled. A negative electrode lead plate 5 is spot-welded to the end. The dimensions of this negative electrode plate are 36 mm wide,
The length is 132 mm and the thickness is 0.205 mm.

Preliminary studies were conducted on various carbon materials having different physical properties and structures, which are the main materials of the negative electrode. As a result, the lattice spacing (d ₀₀₂ ) determined by the powder X-ray diffraction method was 0.34.
It was found that a carbon material of 2 nm or less has a high capacity and is excellent in reversibility. Incidentally, the spherical graphite obtained by heat-treating the mesophase pitch at 2800 ° C. in an argon atmosphere has a lattice spacing (d ₀₀₂ ) by powder X-ray diffraction.
0.342 nm or less.

As the separator 3, a porous film made of polypropylene was cut more widely than the positive electrode plate and the negative electrode plate.

The positive and negative electrodes and the separator are stacked as shown in FIG. 2, and a core A7 composed of a large-diameter rod and a core B8 composed of two small-diameter rods are arranged in parallel on both sides thereof. Core B8
After the separator tip is fixed and wound in a spiral with the combined core, the end of the separator is fixed with an adhesive tape made of polypropylene to form an electrode group. Was extracted. Then, the electrode plate group was further compressed in the diameter direction to form an oval cross-sectional shape. The battery of Example 1 was constructed using this electrode plate group.

Next, although not shown, after the lower insulating plate is inserted into the inner bottom of the battery case 6, the preceding electrode plate group is housed,
Further, an upper insulating ring was inserted. After the grooves were formed in the upper part of the battery case 6, the positive and negative electrode leads were spot-welded to mutually insulated terminals provided on the sealing plate, and a non-aqueous electrolyte was injected. Non-aqueous electrolytes are ethylene carbonate (EC) and diethylene carbonate (DEC)
Was mixed at a volume ratio of 1: 1 and 1 mol / l of lithium hexafluorophosphate (LiPF ₆ ) was used.
Then, the battery was sealed to form a battery. The dimensions of this battery are 6 mm in thickness, 17 mm in width, and 48 mm in height.

The capacity of the thin sealed lithium secondary battery constructed as described above in the initial charge and discharge was evaluated. As Comparative Example 1, the same parts as in Example 1 were used.
A battery using an electrode group having a flat plate as a core, as shown in FIG. 3A as Comparative Example 2, in which a step portion was provided on the circumference of a rod having a basically circular cross-sectional shape. Using a core 9, a pin 10 is arranged on this step, the tip of the separator is fixed with the pin 10, the coil is wound in a spiral, the end of the separator is fixed with an adhesive tape made of polypropylene, and then the pin 10 is removed. As shown in FIG. 3B as a comparative example 3, a battery in which an electrode group was formed by extracting an electrode group from the core 9 and further compressing the electrode group in the diameter direction to form an oval cross-sectional shape.
A core 1 in which an elliptical rod whose cross-sectional shape is basically divided into two
After fixing the separator in the groove portion 1 and winding it spirally, fixing the separator end with an adhesive tape made of polypropylene, extracting the electrode plate group from the core 11 and further compressing it in the diametric direction to lengthen the cross-sectional shape Batteries using the electrode group formed by molding into a circular shape were each constructed and evaluated.

FIG. 4 shows changes in the discharge capacity in the first 15 cycles of Example 1 and Comparative Examples 1 to 3. The charge / discharge current was 40 mA, the charge end voltage was 4.1 V, and the discharge end voltage was 2.5 V. As is clear from FIG. 4, the discharge capacities of Example 1 and Comparative Examples 2 and 3 are stabilized in 3 and 4 cycles, whereas Comparative Example 1 initially charges / discharges only about 70%, and finally reaches 13 cycles. Stabilize. The reason for this is
This is probably due to the difference in the degree of uniform adhesion of the electrode plates. That is, as shown in FIG. 1 (b), in Example 1 and Comparative Examples 2 and 3, after the electrode plate group is formed by winding into a rhombus shape, a circle or an ellipse, and further compressed in the diameter direction, The stress remains in the electrode plate group, and the group plane portion is microscopically curved due to the stress, so that the electrode plates are easily brought into close contact with each other. On the other hand, in Comparative Example 1, as shown in FIG. 5, the electrode plate and the separator are tensioned in the plane direction in the plane portion of the group, but no force is applied in the direction perpendicular to the surface. Does not adhere evenly. As a result, the distance between the electrodes varies, and the reaction between the positive and negative electrodes becomes non-uniform. Therefore, the reaction becomes uniform as charging and discharging are performed and the electrode plate repeatedly expands and contracts, but it takes 10 cycles or more until the capacity is stabilized.

FIG. 6 shows the distribution of the distances of the positive and negative electrode leads from the turn of the electrode plate group. It can be seen that in Example 1 and Comparative Example 1, the distribution is small and the positions of the leads are constant. On the other hand, in Comparative Example 3, the variation is slightly large, and in Comparative Example 2, the variation in the lead position is considerably large. Although not shown, when spot-welding the tips of the leads to mutually insulated terminals provided on the sealing plate for connection with the external terminals of the battery, in Comparative Examples 2 and 3, the positional relationship between the two was determined. Means not constant.

Example 2 (Primary Battery) The basic structure is the same as that of FIG. A positive electrode plate was produced in the same manner as in Example 1 except that manganese dioxide was used as the positive electrode active material. Its dimensions are 36mm wide and 132m long.
m, the thickness is 0.225 mm.

The negative electrode was produced by pressing a negative electrode lead plate similar to that of Example 1 on metallic lithium. The dimensions of the negative electrode plate are 34 mm in width, 95 mm in length, and 0.15 mm in thickness.

As the separator, a porous film made of polypropylene was cut more widely than the positive electrode plate and the negative electrode plate.

Using these positive and negative electrodes and separator, an electrode plate group was formed in the same manner as in Example 1, and 50 batteries were formed. As the electrolyte, propylene carbonate (P
C) and dimethoxyethane (DME) in a volume ratio of 1:
1 and mixed with lithium perchlorate (LiClO ₄ )
Was dissolved at 1 mol / l. The dimensions of these batteries are 6 mm in thickness, 17 mm in width, and 48 mm in height.

A battery using an electrode plate group formed by winding a flat plate as a core using the same parts as in Example 2 and Comparative Examples 2 and 3 as Comparative Examples 5 and 6, respectively.
In the same manner as in the above, a battery constituting an electrode plate group was prepared and evaluated.

FIG. 7 shows 20 of Comparative Example 2 and Comparative Examples 4 to 6.
4 shows the distribution of the discharge capacity of a 20 mA constant-current discharge at ℃. The discharge end voltage is 2V. As is clear from FIG. 7, Example 2 and Comparative Examples 5 and 6 have a relatively small capacity variation based on the variation of the active material filling amount, whereas Comparative Example 2 has a relatively large capacity biased toward the small capacity side. Has a distribution.

The distribution of the distance of the positive and negative electrode leads from the return of the electrode plate group was the same as in FIG. That is, in Example 2 and Comparative Example 4, the distribution is small and the positions of the leads are constant. On the other hand, in Comparative Example 6, the variation is slightly large, and in Comparative Example 5, the variation in the lead position is considerably large.

As described above, a sheet-shaped positive electrode and a negative electrode are interposed with a separator interposed therebetween, and are wound spirally by a core in which three or more rods are combined in parallel. By adopting a structure that forms an electrode group by compressing in the axial direction and shaping the cross-sectional shape into an elliptical shape, it is suitable for thin non-aqueous electrolyte batteries with excellent high load characteristics, small capacity variations, and rapid charging characteristics. An excellent, non-aqueous electrolyte secondary battery with stable charge / discharge capacity can be obtained, and its lead position is fixed, and it is insulated from each other provided on the sealing plate for connection with the external terminal of the battery. Spot welding can be easily performed on the terminals.

In the embodiment, the core is formed by combining three rods in parallel. However, it was confirmed that the same effect can be obtained by combining four or more rods for the above purpose. .

Further, in the embodiment, the lithium secondary battery using the lithium ion intercalation / deintercalation has been described. However, the lithium secondary battery using sodium, calcium or the like other alkali metal or alkaline earth metal ions may be used. Aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery using an alkali metal such as lithium, sodium, or calcium, or alkaline earth metal as a negative electrode, non-aqueous electrolyte secondary battery using an alkali metal such as sodium, calcium, or an alkaline earth metal as a negative electrode Water electrolyte primary batteries are also effective.

[0031]

As described above, according to the present invention, a sheet-like positive electrode, a negative electrode and a separator are spirally wound by a core in which three or more rods are combined in parallel, and this is removed from the core. After compressing in the short axis direction, forming the electrode plate group into an elliptical cross-sectional shape, it is excellent in high load characteristics and has a thin non-aqueous electrolyte battery with little capacity variation, or fast charging characteristics. It is possible to obtain a thin non-aqueous electrolyte secondary battery excellent in charge and discharge capacity. In addition, the position where the lead is taken out from the electrode plate group is fixed, so that spot welding can be easily performed on mutually insulated terminals provided on the sealing plate for connection with the external terminal of the battery.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing the configuration of a thin nonaqueous electrolyte battery according to the present invention. FIG.

FIG. 2 is a schematic view showing a method for forming an electrode group according to the present invention.

FIGS. 3A and 3B are schematic diagrams illustrating a method of forming an electrode group of a comparative example. (A) Comparative example using a core having a circular cross section. (B) Comparative example using a core having an elliptical cross section.

FIG. 4 is a diagram showing a change in discharge capacity in initial charging and discharging in Example 1 and Comparative Examples 1 to 3.

FIG. 5 is an enlarged view of a group of Comparative Example 1.

FIG. 6 is a diagram showing a distribution of lead positions in Example 1 and Comparative Examples 1 to 3.

FIG. 7 is a diagram showing distribution of discharge capacity in Example 2 and Comparative Examples 4 to 6.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Positive electrode lead 5 Negative electrode lead 6 Battery case 7 Large diameter core rod A 8 Small diameter core rod B 9 Core with a circular cross section 10 Pin 11 Elliptical cross section Core

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-74496 (JP, A) JP-A-57-163965 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 4/02-4/04 H01M 10/04

Claims (1)

(57) [Claims] 1. A spiral electrode plate comprising a sheet-like positive electrode and a negative electrode, with a separator interposed therebetween, spirally wound by a core in which three or more rods are combined in parallel, and removed from the core. A method for manufacturing a thin non-aqueous electrolyte battery in which a group of electrode plates formed by compressing a group in the short axis direction and shaping the cross section into an elliptical shape is housed in a battery case.