JP2003229100A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact thin-type battery of high energy density. <P>SOLUTION: This battery is provided with a sheathing container 1, a positive electrode and a negative electrode arranged in the sheathing container, and an electrolyte arranged between them. The positive electrode or a negative electrode active substance layer 4 is formed on the inner surface of the sheathing container. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly to a thin battery structure having a high energy density.

[0002]

2. Description of the Related Art In recent years, mobile phones, PDAs, and notebook personal computers have a strong tendency to be made thinner, and a rectangular battery has been desired as a power source thereof. The prismatic battery can reduce the dead space in the device design as compared with the cylindrical battery, and thus contributes greatly to the reduction in thickness and size. Further, the demand for the thickness of the prismatic battery has been diversified, and the demand for an extremely thin specification is expected.

For example, in a conventional lithium battery, as shown in a sectional view of FIG. 8, an exploded explanatory view of FIG. 9, and an overall explanatory view of FIG. 10, an aluminum film 101 whose outer surface is covered with a reinforcing resin 102 is used. Adhesive 1 applied to
Two positive electrode plates 1 in which the outer peripheral portion is welded at 03 to form a bag-shaped outer container, and the positive electrode active material 104a is formed inside the outer container.
A negative electrode plate 106 provided with a negative electrode active material 106a is formed between 04 and a separator 105 formed of a bag-shaped polypropylene porous film.
It is formed by leading out the negative electrode terminal 108.

In such a lithium battery, as shown in FIG.
As is clear from the exploded explanatory view of No. 2, when the upper surface area is considered to be constant, the uncoated area can be approximated to an area approximately twice this area. This is based on the fact that the uncoated area reduced by reducing the number of laminated layers is a slight one.

[0005]

As the number of laminated layers is reduced, the total uncoated area is reduced, but the uncoated area is almost constant. That is, the proportion of the uncoated area in the battery increases as the number of stacked layers decreases, that is, as the battery becomes thinner, so that the thinner the battery becomes, the lower the energy density becomes.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small-sized and thin battery having a high energy density.

[0007]

A battery of the present invention comprises an outer container, a positive electrode and a negative electrode arranged in the outer container, and an electrolyte arranged between the outer container and the outer container. A positive electrode or negative electrode active material layer is formed on the inner surface, and the outer container constitutes one of the positive electrode and the negative electrode.

According to this structure, since the active material layer is directly formed on the inner surface of the outer container, the thickness is not wasted. Further, the inner surface of the outer container can be effectively utilized to the maximum extent, and the energy density can be improved. In particular, the effect becomes more remarkable in a battery having a small number of layers. Further, even if the material forming the outer container is formed thin, since it is reinforced by the active material layer, the mechanical strength of the outer container is also increased.

Further, it is preferable that the outer container constitutes a current collector. According to this configuration,
Since the current collector also serves as the outer container, the outer container can be effectively used, and the resistance of the electrode itself can be reduced.

Preferably, the outer container is made of a film having at least a thin metal plate and an adhesive layer, the adhesive layer is adhered to form a bag-like body, and the bag is exposed inside the bag-like body. It is characterized in that a positive electrode or negative electrode active material layer is formed on the surface of the thin metal plate. According to this structure, the outer container is formed of a flexible film including a thin metal plate and an adhesive layer, and the positive electrode active material layer is formed on the inner surface of the film, so that the conductive film is curved. The surface becomes the surface area of the positive electrode active material layer as it is, and it becomes possible to form a thin battery having a large effective electrode area.

The outer container uses an aluminum laminate material in which an insulating resin layer made of a nylon layer or a polyethylene terephthalate layer is formed on the outer surface of a metal thin plate made of aluminum, and an adhesive layer is provided on the inner surface. Is preferred. According to this structure, it is strong and the current collecting resistance can be reduced.

Preferably, the negative electrode is housed in the outer container so as to face the positive electrode active material layer of the outer container while being inserted in the bag-shaped separator. According to this structure, the positive electrode and the negative electrode are reliably opposed to each other with the separator interposed therebetween, and the reliability is high.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment) As shown in FIG. 1, a schematic cross-sectional view of the lithium secondary battery, FIG. 2 is an enlarged cross-sectional view showing a manufacturing process of a main part, and FIG. The positive electrode active material layer 4 is directly formed on the inner surface of the aluminum film 1 as an exterior body coated with. A negative electrode plate 6 in which the negative electrode active material 6a is applied to the negative electrode current collector 6b is disposed between the positive electrode active material layers 4 via a separator 5 made of a bag-shaped polypropylene porous film. It is formed by leading out the positive electrode terminal 7 and the negative electrode terminal 8. An electrolytic solution is injected between the positive electrode active material layer 4 and the negative electrode active material 6a.

Here, the negative electrode plate is obtained by kneading graphite powder as a negative electrode active material and fluororesin (PVDF) as a binder, and coating the mixture on a negative electrode current collector 6 made of copper foil. Was used. In addition, the outer container serving as the positive electrode has lithium cobalt oxide, graphite powder and carbon black as a conductive agent, and a binder as a binder on the inner surface of an aluminum film 1 formed by adhering a reinforcing resin 2 made of a nylon layer on the outer surface. What was kneaded with the fluororesin (PVDF) of was applied, dried, and then pressed.

1. Preparation of Positive Electrode First, as shown in FIG. 2A, a reinforcing resin 2 made of a nylon layer having a thickness of 25 μm was formed on one surface of an aluminum film 1 having a thickness of 40 μm via an adhesive layer 2S made of a polyurethane layer having a thickness of 3 μm. Form.

After that, lithium cobalt oxide represented by LiCoO ₂ , graphite powder, carbon black and fluororesin (PVDF) are mixed and kneaded at 90: 3: 2: 5 to prepare a mixture. Then, this was applied to the inner surface of the aluminum film 1 by a doctor blade method so as to have a weight of 383 g / m ^2, and an active material layer 4 was formed as shown in FIG. 2 (b).

After that, it was compressed to 134 μm by a pressing method as shown in FIG. 2 (c). Then, as shown in FIG. 2D, an unnecessary active material is scraped off using a cotton swab containing acetone to obtain a positive electrode having a laminated core structure having a positive electrode active material with a surface area of 21.25 cm ² .

Finally, as shown in FIG. 2 (e), an adhesive layer 3 made of a modified polypropylene sheet cut into the shape of the adhesive portion is adhered. Then, fold this back, 15
Heat in a vacuum of 0 ° C. to form a bag-shaped outer container. FIG. 4 is a cross-sectional view of the outer container after the heat fusion. FIG. 5 is a diagram showing a state before adhesion.

2. Preparation of Negative Electrode Graphite powder as negative electrode active material ((00
2) The interplanar spacing d002 is 3.356 angstroms, the crystallite thickness Lc is 80 nm or more, and the average particle diameter is 8 μm.
m) and fluororesin (PVDF) as a binder 9
The mixture was mixed at a mass ratio of 5: 5, and this was applied to a negative electrode current collector 6b made of copper foil having a thickness of 12 μm by a doctor blade method so as to be 168 g / m ^2, and compressed to 122 μm. It was cut out to form a negative electrode active material layer 6a having a surface area of 23.49 cm ^{2, and} a negative electrode plate 6 was obtained.

Then, the negative electrode terminal 8 is attached to form a negative electrode plate as shown in FIG. In addition, as the negative electrode active material, other than this, a carbon-based material capable of inserting / desorbing lithium ions, for example, graphite, carbon black, coke, glassy carbon, carbon fiber, or a fired body thereof is suitable. Further, oxides capable of inserting and removing lithium ions such as tin oxide and titanium oxide may be used.

3. Preparation of Electrolyte Solution 1 mol / liter lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a weight ratio of 3: 7. Polypropylene glycol diacrylate (molecular weight 300) was mixed with the electrolytic solution in a mass ratio of 15: 1. Further, 5000 ppm of t-hexyl peroxypivalate was added to this mixed solution as a polymerization initiator to prepare a liquid composition for gel electrolyte.

As the mixed solvent, ethylene carbonate (EC), diethyl carbonate (DE
In addition to the mixture of C), an aprotic solvent having no ability to supply hydrogen ions is used. For example, dimethyl carbonate (DMC), ethylmethyl carbonate (E
It is possible to use a mixture of MC). Further, as the electrolyte, other than LiPF ₆ described above, LiPF _{6 -X}
(C ₂ F ₅ ) _X , LiBF ₄ , LiClO ₄ , LiN (SO ₂
An imide salt represented by C ₂ F ₅ ) ₂ can be used.

4. Preparation of Lithium Battery Next, as shown in FIG. 7, a porous film made of polypropylene is prepared as the separator 5. Then, the positive electrode active material layer 4 was formed on the inner surface produced as described above, and was housed in the bag-shaped separator 5 as shown in FIG. By mounting the negative electrode plate 6, injecting the above-mentioned electrolytic solution (liquid composition), and heating, the electrolytic solution is gelated, and the lithium ion secondary battery as shown in FIG. 1 is formed. According to this structure, the positive electrode and the negative electrode reliably face each other with the separator interposed therebetween, so that the reliability is high.

5. Preparation of Battery of Comparative Example A positive electrode plate was formed by the following method as shown in FIGS. 8 to 10, and a polypropylene layer of a laminate material having a nylon layer on the outer surface of an aluminum thin plate and a polypropylene layer on the inner surface Was adhered to form a bag. However, the entire bag-shaped inside is covered with the polypropylene layer, and the thin aluminum plate is not exposed. Other than that, it was formed in exactly the same manner as the lithium battery of the above-mentioned embodiment. Here, in the positive electrode plate, lithium cobalt oxide, graphite powder and carbon black as a conductive agent, and fluororesin (PVDF) as a binder were provided on the inner surface of the aluminum film 1 in the same manner as in the above-mentioned embodiment 90: 3. : 2:
The mixture kneaded at a mass ratio of 5 was applied to a current collector made of aluminum foil having a thickness of 15 μm by a doctor blade method so as to have a weight of 383 g / m ^2, and compressed to 134 μm.
Then, this was cut out to form a positive electrode having an active material layer with a surface area of 21.25 cm ² , and this was subjected to vacuum heat treatment at 150 ° C. Then, the same negative electrode plate, separator and electrolytic solution as those in the above-mentioned embodiment were used to prepare a battery in the same manner.

6. Evaluation test In this way, a cell with a nominal capacity of 100 mAh was designed,
The capacity, thickness and energy density were compared. The results are shown in Table 1 below.

[Table 1] From these results, it can be seen that the energy density of the battery of the present invention is improved by 3% or more, though the thickness is reduced by 4.4% or more.

In the above-mentioned embodiment, the positive electrode active material layer is formed on the outer container to form the positive electrode, but the negative electrode active material layer may be formed to the negative electrode.

Further, the positive electrode and the negative electrode are not limited to those having a single layer, but can be applied to those which form an electrode body having a laminated structure and those which form a spiral electrode body.

Further, in the above-described embodiment, the case where the outer container is made of a flexible material has been described, but as another embodiment, a punching metal in which the active material layer is formed by sintering, and a foamed state. A metal impregnated with an active material is used as the electrode plate for one electrode, and it is molded into a container, and the electrode plate for the other electrode is mounted inside, and the electrolytic solution is injected into this container. Then, the electrode terminals may be formed while being led out and sealed. In this case, a resin sleeve may be formed on the outer surface of the container, or a sol-gel method may be used to apply a ceramic coating such as a silica layer.

In addition, the present invention can be applied to a prismatic battery, a cylindrical battery, or a coin battery composed of an aluminum can or the like. FIG. 8 shows an example of a prismatic lithium battery composed of an aluminum can. This prismatic lithium battery is obtained by punching out an aluminum flat plate, coating the positive electrode active material 14 inside with the flange part cut off, and insulating the part where the negative electrode current collector 16b may come into contact. For the lid, the positive electrode active material 14 is applied to an aluminum flat plate, and ribs for connecting the negative electrode current collector 16b are punched in to insulate the surroundings. The positive electrode is obtained by applying the positive electrode active material 14 on both surfaces of the aluminum core 14S and leaving the uncoated part as a current collecting part. The negative electrode 16 is obtained by applying the negative electrode active material 16a on both surfaces of a negative electrode current collector 16b made of a copper core, and leaving the uncoated part as a current collecting part in a bag of the separator 15. In manufacturing, a laminated structure is formed and the negative electrode current collecting portion is fixed to the rib. Then, after the liquid injection, the laminated structure is housed in the can, the lid is temporarily fixed so that the positive electrode current collecting portion is sandwiched between the can and the lid, and the edge portion of the lid is laser-sealed. At this time, the positive electrode current collecting portion is also welded at the same time to ensure conduction with the exterior.

Further, the outer container is not limited to the aluminum foil, and a foamed metal impregnated with an active material or the like can be applied.

In the above embodiment, an example in which the present invention is applied to a polymer battery (polymer solid electrolyte battery) has been described, but the present invention can also be applied to a lithium ion battery or another battery. .

The term "polymer" as used herein means a polyether solid polymer, a polycarbonate solid polymer, a polyacrylonitrile solid polymer, and a copolymer or crosslinked polymer composed of two or more of these, or a polyfluoride. It is a solid electrolyte formed by combining a polymer selected from a fluorine-based solid polymer such as vinylidene chloride (PVdF), a lithium salt and an electrolytic solution into a gel.

[0033]

As described above, according to the present invention, since the active material layer is formed on the inner surface of the outer container and integrated with the electrode plate, the thickness can be reduced and the energy density can be improved. Therefore, it is possible to form a high-performance battery.

[Brief description of drawings]

FIG. 1 is a diagram showing a lithium battery according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of the positive electrode of the lithium battery according to the embodiment of the present invention.

FIG. 3 is an exploded view of the lithium battery according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view of an outer container (positive electrode) of a lithium battery according to an embodiment of the present invention.

FIG. 5 is an inner view of the outer container (positive electrode) of the lithium battery according to the embodiment of the present invention.

FIG. 6 is a diagram showing a negative electrode plate of a lithium battery according to an embodiment of the present invention.

FIG. 7 is a diagram showing a separator of a lithium battery according to an embodiment of the present invention.

FIG. 8 is a diagram showing a lithium battery according to another embodiment of the present invention.

FIG. 9 is a diagram showing a conventional lithium battery.

FIG. 10 is a manufacturing process diagram of a positive electrode of a conventional lithium battery.

FIG. 11 is an exploded view of a conventional lithium battery.

[Explanation of symbols]

1 aluminum sheet 2 Reinforcing resin 3 Adhesive resin 4 Positive electrode active material layer 5 separator 6 Negative plate 6a Negative electrode active material layer 6b Negative electrode current collector 7 Positive terminal 8 Negative electrode terminal

Continued front page    F-term (reference) 5H011 AA03 BB04 CC02 CC10 DD14                       DD21                 5H017 AA03 AS02 AS06 CC01 DD06                       EE01 EE07                 5H029 AJ03 AK03 AL07 AM03 AM05                       AM07 BJ04 DJ02 DJ07 EJ01                       EJ12

Claims (3)

[Claims] 1. An outer container, a positive electrode and a negative electrode arranged in the outer container, and an electrolyte arranged between the outer container and the positive electrode or the negative electrode active material layer on the inner surface of the outer container. A battery formed, wherein the outer container constitutes one of a positive electrode and a negative electrode. 2. The battery according to claim 1, wherein the outer container constitutes a current collector. 3. The outer container is made of a film having at least a metal thin plate and an adhesive layer, the adhesive layer is adhered to form a bag-shaped body, and the bag is exposed inside the bag-shaped body. The battery according to claim 1, wherein the positive electrode or the negative electrode active material layer is formed on the surface of the thin metal plate.