JPH11238500A - Roll type cylindrical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heavy current discharge characteristic by setting the total width of root parts of lead pieces in an electrode side edge to a specified % or more of the total length of the electrode side edge part, and providing a round part extending from the electrode side edge to the lead piece side edge in the root part of the lead piece. SOLUTION: A lead piece 1 is formed by providing an active material non- applied part on the side edge of an electrode and slitting this part, at prescribed intervals in the direction orthogonal to the rolling direction. The total width of the root parts of the lead pieces 1 in the electrode side edge is set to 70% or more of the total length of the electrode side edge part. In the root part of the lead piece 1, a round part 3 is provided extending from the electrode side edge to the lead piece 1 side edge or between the root parts of the adjacent lead pieces 1 having the same polarity. The round part 3 functions to prevent the collection of a stress to a specified position. According to this, the cut of the connecting part of the lead piece 1 with the electrode side edge and the root parts of the adjacent lead pieces having the same polarity can be suppressed, and the current collecting property of the electrode can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wound cylindrical battery.

[0002]

2. Description of the Related Art Conventionally, in the field of rechargeable secondary batteries, lead-acid batteries, nickel-cadmium batteries, nickel-
Aqueous solution batteries such as hydrogen batteries were the mainstream. However, in recent years, with the rapid spread of mobile phones and notebook personal computers, smaller and higher-capacity batteries have been required. In response to such demands, non-aqueous electrolyte-based lithium ion batteries using a lithium transition metal composite oxide such as lithium cobalt oxide for the positive electrode and a carbon material for the negative electrode have been developed. A lithium ion battery using a carbon material for the negative electrode has a lower energy density per unit volume than a secondary battery using metallic lithium for the negative electrode, but is safer and has a higher energy density than conventional aqueous batteries. It has the advantage of being, and is spreading rapidly.

In a non-aqueous electrolyte-based lithium ion battery having an ion conductivity that is inferior to that of an aqueous solution, the thickness of the electrode plate is reduced as much as possible to increase the area of the electrode plate, and the distance between the electrode plates is reduced to reduce the battery. The internal resistance is reduced to maintain high output characteristics without impairing the energy density per unit volume. In order to reduce the thickness of the electrode plate as much as possible, a technique in which a current collector is made of metal foil and an active material mixture is uniformly distributed on both surfaces thereof is generally applied. When the electrode area is increased, it becomes difficult to secure current collection from the current collector to the battery external terminal.
For example, when the current path is formed by one lead piece as disclosed in Japanese Patent Application Laid-Open No. Hei 6-310142, the current collecting property from the electrode plate position farthest from the lead piece is increased from the electrode plate position near the lead piece. Is inferior to the current collecting ability of Such a drawback is not so much a problem with a small battery having a rated capacity of up to 1000 mAh used as a power source for a notebook personal computer or a mobile phone, but has a problem with a large-capacity large battery used as a power source for an electric vehicle. . Therefore,
For example, in Japanese Unexamined Patent Publication No. 9-92335, an uncoated portion of an active material mixture (exposed portion of a metal foil current collector) is provided at a long side edge of a strip-shaped positive / negative electrode plate, and the uncoated portion is cut. By notching, a plurality of strip-shaped lead pieces having a width of 10 mm
It has been proposed that the current collecting property is formed uniformly at intervals of mm so that the current collecting property is uniformly improved over the entire electrode plate. At this time, the sum of the widths of the lead attachment roots at the electrode plate side edge is 67% of the total length of the electrode plate side edge.

[0004]

However, the above-mentioned Japanese Patent Application Laid-Open No.
If the technique of Japanese Patent No. 92335 is applied, the bonding ratio of a plurality of strip-shaped leads provided at equal intervals to the entire length of the electrode is relatively small, and desired characteristics cannot be obtained by high-current charging and discharging for electric vehicles and the like. . The problem to be solved by the present invention is to improve the large current discharge characteristics of a battery.

[0005]

Means for Solving the Problems To achieve the above object, a wound cylindrical battery according to the present invention comprises an electrode plate group in which a strip-shaped positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween. A plurality of lead pieces 1 are led out from one side edge of the plate and / or the negative electrode plate in a direction perpendicular to the winding direction for each electrode plate, and the lead pieces 1 are electrically connected to the battery external terminals. The total width of the roots of the lead pieces 1 at the plate side edge is 70% or more of the total length of the electrode plate side edge. In the above configuration, it is most preferable that the sum of the widths of the lead fixing roots at the electrode plate side edge is 100% of the total length of the electrode plate side edge. This configuration can be obtained by forming a lead piece 1 by a method in which an active material non-applied portion is provided on the side edge of the electrode plate, and cuts 2 are formed in the portion at predetermined intervals in a direction perpendicular to the winding direction. Things. In this configuration, since there is no space between adjacent lead pieces 1 of the same polarity, the current collecting property of the electrode plate is the best. In the above configuration, it is preferable that the R portion 3 is provided at the root portion of the lead piece 1 from the side edge of the electrode plate to the side edge portion of the lead piece 1 or between adjacent root portions of the same polarity. The reason for this is that it is effective in suppressing the cut at the connection between the lead piece 1 and the side edge of the electrode plate and at the adjacent root of the same polarity.
Here, for convenience, it is expressed as an R portion, which indicates a curve at the base of the lead piece 1 that functions so that stress is not concentrated on a specific place when the lead piece 1 is handled.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail by taking a cylindrical lithium ion battery as an example with reference to the drawings. (Preparation of positive electrode plate) Lithium manganate (L
iMn ₂ O ₄ ) To 100 parts by weight of powder, 10 parts by weight of flaky graphite (average particle size: 20 μm) as a conductive agent and 10 parts by weight of polyvinylidene fluoride as a binder were added, and N was added as a dispersion solvent. The slurry obtained by adding and kneading methylpyrrolidone was applied to both sides of an aluminum foil having a thickness of 20 μm.
At this time, an uncoated portion having a width of 30 mm was left on one side edge in the electrode plate length direction. After drying, pressing and cutting, the width is 130m.
m, a length of 2000 mm, and a positive electrode plate having a thickness of 200 μm of the active material applied portion. 25 m on the uncoated part as shown in FIG.
Cuts 2 are made at m intervals. In this example, an R portion (φ2) is further provided between adjacent root portions of the lead pieces 1 of the same polarity.

(Preparation of negative electrode plate) Graphite powder 100
10 parts by weight of polyvinylidene fluoride as a binder was added to parts by weight, N-methylpyrrolidone as a dispersion solvent was added thereto, and a kneaded slurry was applied to both sides of a rolled copper foil having a thickness of 10 μm. At this time, a width of 30
mm was left uncoated. Thereafter, drying, pressing, and cutting were performed to obtain a negative electrode plate having a width of 135 mm, a length of 2200 mm, and a thickness of the active material application portion of 130 μm. As shown in FIG. 1, cuts 2 are made in the uncoated portion at intervals of 25 mm. In this example, the R portion 3 (φ
2) is provided.

(Production of Battery) The positive electrode plate and the negative electrode plate produced above are wound together with a polyethylene separator having a thickness of 40 μm. Lead piece 1 of positive electrode plate and lead piece 1 of negative electrode plate
Are wound so as to be located at both ends of the winding group. Thereafter, the winding group is inserted into a cylindrical battery container. FIG.
As shown in (1), all the lead pieces 1 led out from the positive electrode plate are sandwiched between the peripheral surface of the upper lid 4 also serving as a positive electrode external terminal and the metal fitting, and the upper lid 4, the lead piece 1, and the metal fitting are then laser-welded. To obtain the respective continuity. The operation of connecting the negative electrode external terminal and the lead piece 1 derived from the negative electrode plate was also performed in the same manner as the connection operation of the positive external terminal and the lead piece 1 derived from the positive electrode plate shown in FIG.

Thereafter, a battery container (not shown) is sealed with the upper lid 4 and a metal fitting, a predetermined amount of electrolyte is injected into the battery container from a liquid inlet (not shown) in the upper lid 4, and the liquid inlet is sealed. Thus, a cylindrical lithium ion battery was manufactured. As the electrolytic solution, a solution obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) at 1 mol / liter in a mixed solution of ethylene carbonate and dimethyl carbonate was used. The rated capacity of this battery is 10 Ah.

In this embodiment, the present invention is applied to the lead pieces of the polar plates of both polarities. For example, a cylindrical battery container also serves as the negative electrode external terminal, the outermost periphery of the winding group is the negative electrode surface, For a battery having a structure in which the inner wall and the negative electrode surface are electrically connected by pressure contact, the present invention is applied only to the lead piece of the electrode plate having one polarity. In this example, a lithium ion battery is illustrated, but the battery system is not limited. However, the application of the present invention is particularly effective for a lithium ion battery because it is necessary to increase the electrode area as described above, and it is highly necessary to provide a plurality of lead pieces on one electrode plate to improve the current collecting property. It is.

In this embodiment, lithium manganate is used for the positive electrode, graphite is used for the negative electrode, and lithium hexafluorophosphate dissolved at 1 mol / l in a mixed solution of ethylene carbonate and dimethyl carbonate is used for the electrolyte. The method for producing the battery of the present invention is not particularly limited, and any of binders, positive and negative electrode active materials, and non-aqueous electrolytes which are commonly used can be used. However, when lithium manganate, which is lower in cost than lithium cobaltate, is used as the positive electrode active material, the present invention is particularly considered to be effective (including partially substituted materials with other elements).
This is because lithium manganate generally has lower electron conductivity than lithium cobalt oxide, lithium nickelate, or the like, and is expected to improve the conductivity of an electrode plate containing the same. In this example, the rated capacity is 1000
Although a large non-aqueous electrolyte battery having a rated capacity of 10 Ah exceeding mAh is described, the configuration of the present invention can be applied to a small non-aqueous electrolyte battery having a rated capacity of 1000 mAh or less. The effect of improving power efficiency is obtained.

The binders that can be used in other than this example include Teflon, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene /
Examples include butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes, polymers such as acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, and chloroprene, and mixtures thereof. The positive electrode active material that can be used in other than this example is a material into which lithium can be inserted and desorbed, and a material into which a sufficient amount of lithium has been inserted in advance is preferable. For example, a lithium transition metal composite oxide, such as a lithium-cobalt composite oxide, a lithium-nickel composite oxide, a lithium-manganese composite oxide, or a lithium-vanadium composite oxide. Further, a material in which a part of these lithium transition metal composite oxides is substituted with another element may be used. There is no particular limitation on the negative electrode active material that can be used other than in this example. For example, lithium metals, lithium alloys, various graphite materials, carbonaceous materials such as coke, and conductive polymers such as polyacetylene are suitable.

As the electrolytic solution, an electrolytic solution obtained by dissolving a general lithium salt as an electrolyte in an organic solvent is used. However, the lithium salt or organic solvent used is not particularly limited. For example, as the electrolyte, LiClO ₄ ,
LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C
_{6 H 5) 4, CH 3} SO 3 Li, CF 3 SO 3 Li and the like or a mixture thereof is used. As the organic solvent, propylene carbonate, ethylene carbonate, 1,2-
Dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethylether, sulfolane, methylsulfolane, acetonitrile, propionitonyl and the like, or two or more thereof Is used.

[0014]

EXAMPLE A lithium ion battery (Example 1) manufactured by the method described in the above embodiment of the present invention was compared with each battery (Examples 2 to 4 and Comparative Examples 1 to 3) manufactured by the following method. did. (Preparation of Batteries of Examples 2 to 4) Table 1 shows the total ratio (abbreviated as A) of the width of the base of the lead piece 1 at the positive / negative electrode plate side edges to the total length of the positive / negative electrode side edges. The batteries of Examples 2 to 4 were manufactured under the same conditions as in Example 1 except for the above changes. In other words, when producing the lead pieces of the electrode plates used in the batteries of Examples 2 to 4, notches 2 were made as in Example 1 but a notch was made and a certain distance was set between adjacent lead pieces 1. The distance. At the base of the lead piece 1, an R portion (φ2) was provided from the electrode plate side edge to the lead side edge.

(Preparation of batteries of Comparative Examples 1 to 3) The batteries of Examples 2 to 4 were prepared under the same conditions as those of Examples 2 to 4 except that the value of A was changed as shown in Table 1.

The above batteries were compared with respect to internal resistance and discharge rate characteristics by a direct current method. The internal resistance measurement by the direct current method was performed as follows. Constant current,
After 100% charging at a 2-hour rate (1 / 2C), the battery voltage difference at the time of discharging for 10 seconds at a 1-hour rate (1C) and a 20-minute rate (3C), and Ohm's law (R = V / I ) Was used to determine the internal resistance. In the discharge rate characteristic test, the battery was charged at a constant current of 8 hours and discharged at a final voltage of 3.2 V at 8 hours (1/8 C), 1 hour (1 C), and 10 minutes (6 C). The discharge capacity was measured. Table 1 shows the results of the internal resistance and discharge rate characteristic tests in the direct current method. The discharge rate characteristic is a ratio of 6C discharge capacity to 1 / 8C discharge ((C6
/ (C1 / 8)) × 100).

[0017]

The batteries of Examples 1 to 4 of the present invention in which A is 70% or more by making cuts or cuts in the uncoated portion of the current collector are the batteries of Comparative Examples 1 to 3 in which A is less than 70%. It can be seen that the internal resistance is reduced as compared with that of Example 1, and the high current discharge characteristics at a high rate are excellent.

[0019]

According to the present invention, the high-current discharge characteristics of the battery can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an electrode plate according to the present invention.

FIG. 2 is a longitudinal sectional view of a main part of the wound cylindrical battery of the present invention.

[Explanation of symbols]

 1. Lead piece 2. Notch 3. R part 4. Top lid

Claims (7)

[Claims] An electrode group comprising a strip-shaped positive electrode plate and a negative electrode plate wound with a separator interposed therebetween, and a lead extending from a side edge of the positive electrode plate and / or the negative electrode plate in a direction perpendicular to the winding direction. In a wound cylindrical battery in which a plurality of pieces are led out for each electrode plate, and the lead pieces are electrically connected to battery external terminals, the total width of the roots of the lead pieces at the side edges of the electrode plate Is 70% or more of the entire length of the side edge of the electrode plate. 2. The wound cylindrical battery according to claim 1, wherein the sum of the widths of the roots of the lead at the edge of the electrode plate is 100% of the total length of the edge of the electrode plate. 3. The lead-removing root portion has an R portion from the side edge of the electrode plate to the side edge of one side of the lead.
The wound cylindrical battery according to the above. 4. The method according to claim 1, further comprising the step of:
The wound cylindrical battery according to claim 2, which has an R portion. 5. The battery according to claim 1, wherein the battery is a lithium ion battery.
A wound cylindrical battery according to any one of claims 1 to 4. 6. The total length of the lower end of the positive electrode lead directly connected to the positive electrode side edge is at least 70% of the total length of the positive electrode side edge, and the positive electrode active material is manganese. The wound cylindrical battery according to claim 5, wherein the battery is mainly composed of lithium oxide. 7. The wound cylindrical battery according to claim 1, wherein the rated capacity of the battery is more than 1000 mAh.