JP3073809B2 - High capacity secondary 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 high-capacity, high-energy-density battery, and more particularly to a battery which makes it easier to insert an electrode body into an outer can, thereby making more effective use of the space inside the outer can.

[0002]

2. Description of the Related Art In general, a battery has a positive electrode and a negative electrode facing each other with a separator interposed therebetween. The output characteristics of the battery
It is proportional to the area of the surface where the positive and negative electrodes face each other, and this area needs to be large in order to extract a large current. Usually, in order to obtain a large area, a structure in which positive and negative electrodes are stacked in multiple layers via a separator or a structure in which the electrodes are wound into a roll is generally used. Has been inserted.

In order to increase the electric capacity of the battery and increase the energy density, it is necessary to fill as many electrodes as possible in the outer can. Therefore, the gap between the electrode body and the outer can is very small and the insertion becomes very difficult, which is a limitation in producing a battery with high energy density. JP-A-60-
As described in Japanese Patent No. 170171, there is a method of wrapping an adhesive tape around an electrode body, narrowing the shape, and inserting it into a can. However, it is not effective except for a cylindrical electrode body.

[0004] In particular, in the case of a non-aqueous battery, the conductivity of the electrolyte is low, so that a larger area is required. For example, a non-aqueous electrolyte battery using a lithium composite oxide as a positive electrode active material disclosed in JP-A-55-136131, or JP-A-62-90863 and JP-A-63-299056. Non-aqueous electrolyte battery disclosed in, that is, using a lithium composite oxide for the positive electrode active material, a non-aqueous electrolyte battery using a carbonaceous material for the negative electrode active material, the electrodes used are thin, soft electrodes Because it is relatively suitable for bending,
It is also possible to produce a flat electrode body, such as a crushed cylindrical electrode body.

[0005] Such a flat battery can be used more effectively in volume than a normal cylindrical battery, so that a high energy density can be expected. However, since this electrode body uses the electrode as described above, the interlayer easily spreads and the shape of the electrode body becomes unstable. For this reason, insertion is more difficult than with a cylindrical electrode body.

[0006]

When the electrode body is inserted, there is a possibility that the lower end face of the electrode body, especially the outermost separator or the electrode, may be damaged such as being turned or damaged. In particular, in the case of a laminated electrode body or an electrode body wound in a non-cylindrical shape, it is difficult to keep the shape of the electrode body because the layers are easily spread, and the dimensions of the bottom surface of the electrode body are larger than the dimensions of the can opening. Also tends to be large.

For this reason, when the electrode body is inserted into the outer can, a load is easily applied to the lower end face of the electrode body, and in order to perform stable insertion, the number of layers of the electrode body to be filled in the outer can must be reduced to some extent. However, it was a major bottleneck when trying to improve the battery capacity. In order to solve this problem, it is necessary to improve the structure of the electrode body, and it is necessary to suppress damage during insertion.

The present invention, certain positive electrode, a specific negative electrode and separator as basic components, in the battery comprising involving them, to eliminate damage during insertion into the outer can of the electrode body, to facilitate insertion In this way, an object is to obtain a battery with high capacity and high energy density.

[0009]

Means for Solving the Problems As a result of various studies to achieve the above object, the present inventors have found that lithium ion
Dedoped and doped lithium composite oxide as positive electrode
The positive electrode used for the active material and the lithium ion
In a battery having a negative electrode and a separator made of a carbonaceous material capable of de-doping and doping an electrode as a basic component, an electrode body obtained by laminating or rolling up a positive electrode, a negative electrode and a separator is applied to an outer can. the end surface of the insertion sides, by depositing an insulating plate, a high capacity,
Found that high energy density batteries can be obtained
Thus, the present invention has been completed .

Hereinafter, the present invention will be described specifically. In the present invention, a battery having a high capacity and a high energy density can be eliminated by inserting an insulating plate integrally with the bottom end surface of the electrode body, thereby preventing the electrode body from being damaged when the electrode body is inserted into the outer can. Can be obtained.

In the present invention, the material of the insulating plate is not particularly limited as long as it can provide electrical insulation between the electrode body and the outer can, and a resin such as polyethylene or polypropylene may be used. It is preferable to use a heat-resistant resin such as polyester, nylon, polyimide, or aromatic polyamide, which has relatively high heat resistance, or a glass cloth, considering that the insulating property can be maintained even when the temperature becomes high when the battery is abnormal.

Further, it is necessary that one side of the insulating plate is an adhesive surface, or that an adhesive is applied to one side of the insulating plate or the bottom surface of the electrode body. The thickness of the insulating plate must be 50 μm or more to ensure insulation, but if it is too thick, it is necessary to reduce the length of the electrode that can be stored in the outer can, and the effect of improving the battery capacity is halved. 500 μm or less, more preferably 2 μm or less.
The thickness is set to 00 μm or less.

It is most effective that the size of the insulating plate is not smaller than the size covering the end face of the outermost electrode at the bottom of the electrode body and not larger than the inside dimension of the opening of the outer can. The insulating plate may be larger than the bottom of the electrode body, and the surplus portion may be folded and attached to the side wall of the electrode body. 2 of thickness
It is necessary to select the thickness of the insulating plate so that the size obtained by adding the size becomes smaller than the size of the opening of the outer can.

The battery of the present invention is not particularly limited as long as it comprises a positive electrode, a negative electrode, and a separator as basic components. However, from the viewpoint of easily obtaining a high-capacity battery, a non-aqueous battery is used. Known elements applicable to the above-described battery, particularly to the non-aqueous secondary battery, can be appropriately used.

As the positive electrode active material, one capable of dedoping and doping lithium , for example, LiCoO 2
Lithium cobalt oxides such as _2, LiMnO _2, L
Li, such as lithium manganese oxide such as iMn ₂ O ₄
Lithium Ru advantageously used a composite oxide.

As the negative electrode active material, a carbonaceous material which can be doped and dedoped with lithium ions is used.
You . For example, graphite, pyrolytic carbon, pitch coke, needle coke, and a fired body of an organic polymer (a fired body of a phenol resin, acrylic fiber, or the like) can be used.

The metal foil as a current collector has a thickness of 50
１1 μm, and copper, nickel, aluminum, stainless steel and the like can be used. As shown in FIG. 1, an oval or square-shaped roll obtained by winding a metal foil having the above-mentioned active material and a binder bonded to one or both surfaces of the metal foil via a separator 5 is used as a battery. It is common to insert into the outer can 2, attach a lead tab, impregnate with a non-aqueous electrolyte solution, and seal.

The non-aqueous electrolyte used in the present invention includes, for example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiB
Lithium salts such as F ₄ can be used alone or in combination. Examples of the solvent for the electrolyte solution include one or two of propylene carbonate, ethylene carbonate, 1,2-dimethoxymethane, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, acetonitrile, vinyl formate, vinyl acetate, and the like. The above can be used.

As the separator, a single membrane of a polyolefin microporous membrane such as polyethylene or polypropylene, or one or two of these membranes can be used. Further, nonwoven fabrics such as polyolefin, polyester, polyamide, and cellulose can be used alone or in combination with the microporous membrane. The shape of the battery outer can, it is necessary to use a long circular or square shape. Further, the material of the outer can is not particularly limited, but copper, stainless steel and the like can be advantageously used.

[0020]

According to the present invention, the shape of the bottom of the electrode body can be made constant with respect to the size of the opening of the outer can, and insertion becomes easy. Particularly, in a non-aqueous battery, the effect is remarkable in the case of an electrode body having a structure in which positive and negative electrodes and a separator are wound in an oval or square shape .

In such an electrode body, the gap between the respective layers is likely to widen after the production, so that the thickness of the electrode body becomes larger than an ideal thickness when there is almost no gap between the electrode bodies.
Since the thickness of the electrode body may be larger than the inner size of the opening of the outer can, the electrode body is efficiently inserted inside the outer can,
It is difficult to fill.

On the other hand, in the present invention, the lithium complex acid
Oxide as the positive electrode active material and carbonaceous material as the negative electrode active material.
In such a battery, the insulating plate is attached to the bottom of the electrode body to stabilize the shape, so that even if the number of electrode layers is increased, the bottom surface of the electrode body may be damaged. Insertion can be performed without any trouble, and a battery with high capacity and high energy density can be obtained. Further, since it is not necessary to dispose the insulating plate on the bottom of the can in advance, the assembly / insertion process can be simplified, and it is effective to eliminate defects such as forgetting to insert the insulating plate and inconvenient arrangement.

[0023]

The present invention will be described in more detail with reference to the following Examples, which do not limit the scope of the present invention. The positive electrode is a suspension obtained by adding the same amount of a 5% solution of polyvinylidene fluoride in DMF to a compound obtained by adding a carbon-based conductive filler of 5% to the active material LiCoO ₂ , and forming a suspension on both sides of the aluminum foil or It was prepared by uniformly coating one side. The electrode thickness is 198 μm on both sides and 104 μm on one side. The negative electrode was made by pulverizing a carbonaceous material having a true specific gravity of 2.3 as an active material to an average particle diameter of about 10 μm, and adding the same amount of a 5% solution of polyvinylidene fluoride in DMF to form a suspension. Alternatively, it was prepared by uniformly applying to both surfaces or one surface of a copper foil.

The electrode thickness is 250 μm on both sides and 135 μm on one side. As the separator, a 35 μm polyethylene microporous membrane was used. Using an electrode body composed of the above positive and negative electrodes and a separator, L
A battery was prepared using a 0.6 mol / L iClO ₄ propylene carbonate solution.

[0025]

Example 1 When a positive electrode 3 and a negative electrode 4 each coated with an active material on both sides were wound into a roll via a separator 5 and crushed into an oval shape by applying a load of 100 kg / cm ² with a press machine. As shown in FIG. 1, an oval insulating plate 6 made of Nomex paper having an adhesive surface was attached to the bottom of the oval electrode body 1. The dimensions of the insulating plate were 5.1 mm in width, 23.0 mm in the longitudinal direction of the ellipse, and 90 μm in thickness.

Table 1 shows the number of positive electrode layers and the thickness of the bottom surface of the electrode body, which were larger than 5.2 mm, as a result of measurement of the number of positive electrodes of the oval electrode body thus prepared. This elliptical electrode body has an inner size of 5.2 × 23.2 m.
m, and pushed into the bottom of the can until it reached the bottom of the can. After being removed from the can, the bottom surface of the electrode body was inspected for appearance. At this time, Table 1 shows the number of the outermost separators and the outermost electrodes that were damaged such as scratches and flipping. Table 2 shows the results of inspection of the capacity of the battery prepared by the method of the present embodiment.

[0027]

Embodiment 2 As an insulating plate, a width of 5.1 mm and a length of 2
The same operation as in Example 1 was performed except that a Kapton sheet having an adhesive surface with a thickness of 3.0 mm and a thickness of 100 μm was used. Table 1 shows the number of layers of the positive electrode, the thickness inspection result, and the appearance inspection result of the electrode body thus prepared. Table 2 shows the battery capacity inspection results.

[0028]

Example 3 Two positive electrodes coated with an active material on one side were used, and the uncoated surfaces were combined into one electrode. Similarly, one negative electrode coated with the active material on one side was used as one electrode. The positive electrode and the negative electrode were wound around via a separator.

At this time, at the outermost periphery of the electrode body, the outer electrode of the negative electrodes is shorter by one turn, and a metal surface on which the active material is not applied appears. The same operation as in Example 1 was performed except that an elliptical electrode body was used using such an electrode body. Table 1 shows the number of layers of the positive electrode of this electrode body, the result of the thickness inspection of the bottom portion after pressing, and the result of the appearance inspection. Table 2 shows the battery capacity inspection results.
Shown in

[0030]

[Comparative Example 1] A Nomex sheet having a width of 5.1 mm, an oblong direction of 23.0 mm and a thickness of 90 µm and having no adhesive surface was used as an elliptical insulating plate, and was previously placed in the bottom of an outer can. The same operation as in Example 1 was performed, except for placing it.

[0031]

Comparative Example 2 Using the same insulating plate as in Comparative Example 1, a positive electrode
The same operation as in Example 1 was performed, except that the negative electrode was an electrode body reduced by one layer each.

[0032]

Comparative Example 3 Except for using the same insulating plate as in Comparative Example 1,
The same operation as in Example 3 was performed.

[0033]

Comparative Example 4 The same operation as in Example 3 was performed except that the same insulating plate as in Comparative Example 1 was used, and the electrode body was reduced by two layers each of the single-sided coated positive electrode and the single-sided coated negative electrode. Table 1 shows the number of layers of the positive electrode of the electrode body prepared as in the above comparative example, the thickness measurement result of the bottom portion after pressing (the insulating plate is not attached), and the appearance inspection result. Also,
Table 2 shows the results of the battery capacity inspection.

[0034]

[Table 1] (Inspection results of electrode body)

Number of Positive Electrode Layers: The number of layers in Example 3, Comparative Example 3, and Comparative Example 4 is such that one-side coated electrode is one layer. Thickness inspection: Thickness greater than 5.2 mm was rejected. Appearance inspection: An electrode body that was found to be damaged was rejected. Number of inspections: 100 each.

[0036]

[Table 2] (Battery volume test results) Charge: 0.35 A, 4.2 V constant current / constant voltage, Discharge: 0.35 A constant current, 2.7 V cutoff.

[0037]

By adopting the battery structure according to the present invention, in a non-aqueous battery, the work of inserting a flat electrode body using a thin electrode into the outer can can be facilitated. Since the degree of filling of the electrodes can be increased, a battery having a high capacity and a high energy density can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a half cut section when an electrode body in an example of the present invention and a comparative example is inserted into an outer can.

[Description of Signs] 1 Electrode body 2 Outer can 3 Positive electrode 4 Negative electrode 5 Separator 6 Insulating plate

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 2/02 H01M 10/40

Claims (1)

(57) [Claims] 1. Dedoping and doping of lithium ions
Lithium composite oxide that can be used as a positive electrode active material and metal
Positive electrode with foil as current collector , lithium indium as negative electrode active material
Using a carbonaceous material that can be undoped and doped
In an elliptical or prismatic battery having a negative electrode and a separator as basic components using a metal foil as a current collector , an outer can of an electrode body obtained by laminating or rolling up a positive electrode, a negative electrode and a separator. A battery characterized in that an insulating plate is attached to the end face on the side where the battery is inserted.