JP2005011731A - Flat-shaped nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat-shaped nonaqueous electrolyte secondary battery prevented from explosion and scatter of content even when excessively charged or discharged. <P>SOLUTION: On the flat-shaped nonaqueous electrolyte secondary battery, a negative electrode case and a positive electrode case made of metal have linear parts at least on their two sides, and the points of contact of respective linear parts are joined by a curved line. The negative electrode case and the positive electrode case are fitted to each other through an insulation gasket, and the end part of an opening of the positive electrode case has a sealing structure folded by a caulking process. An electrode group formed by winding the belt-shaped positive and negative electrodes through the separator, and the nonaqueous electrolyte are housed in the structure. Since grooves are formed at a center of the negative electrode case, and the grooves are extended to the side surface thereof, the explosion is prevented even when the inner pressure of the battery is increased, and a nonaqueous secondary battery excellent in safety is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２３】
上記表１に示すように、実施例の電池では電池の内容物の飛び出しが起こらないことはもちろんのこと、電池の破裂が起こらなかった。
【００２４】
【発明の効果】
以上説明したとおり、本発明によれば、電池の内圧が上昇する異常時においても、電池の破裂が起こらない安全性に優れた非水電解質二次電池が得られた。
【図面の簡単な説明】
【図１】本発明の実施例１の電池断面図。
【図２】図１のＡ−Ａ方向からみた平面図。
【図３】本発明の実施例２の平面図。
【図４】内圧上昇時の実施例１の電池の断面図。
【符号の説明】
１…正極ケース、２…正極、３…セパレータ、４…負極、５…負極ケース、６…絶縁ガスケット、７…絶縁塗料、８，９，１０，１１…溝。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat non-aqueous electrolyte secondary battery, and more particularly to a flat non-aqueous electrolyte secondary battery excellent in safety in which the battery does not rupture even when an abnormality such as overcharge or overdischarge occurs.
[0002]
[Prior art]
Downsizing of devices used is accelerating mainly on small information terminals such as mobile phones and PDAs, and secondary batteries as a main power source are also required to be downsized. On the other hand, a metal negative electrode case also serving as a negative electrode terminal as disclosed in Patent Document 1 or Patent Document 2 and a metal positive electrode case also serving as a positive electrode terminal are fitted via an insulating gasket, and further, a positive electrode case Alternatively, in a flat nonaqueous electrolyte secondary battery having a sealing structure in which the negative electrode case is crimped by caulking, and in which a power generation element including at least a positive electrode, a separator, and a negative electrode and a nonaqueous electrolyte are included, An electrode group having positive and negative electrode facing surfaces in which at least three or more positive electrodes and negative electrodes are opposed to each other through a separator when a cross section in a vertical direction parallel to the flat surface of the battery is viewed, and the electrode A flat nonaqueous electrolyte secondary battery in which the sum of the positive and negative electrode facing areas in the group is larger than the opening area of the insulating gasket has been proposed as a battery that satisfies the demand for miniaturization.
[0003]
[Patent Document 1]
JP 2001-68143 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-68160
However, since the battery having the sealing structure in which the positive electrode case or the negative electrode case is crimped by the crimping process through the insulating gasket as described above has improved sealing performance, when the battery is overcharged or overdischarged, Even if the internal pressure of the battery increases due to gas generation due to decomposition or the like, the gas does not leak and may eventually burst. For this reason, the current situation is that a circuit having a function of detecting the voltage or surface temperature of the battery in the event of an abnormality and interrupting the current at a certain level or more is provided, or a safety valve is provided to allow gas to escape.
[0005]
However, when a circuit is provided, the battery capacity is limited due to cost increase and circuit volume, and when a safety valve is provided, the electrolyte blown out from the safety valve may erode on a circuit board such as an electric device. There was a risk that the circuit itself would become unusable.
[0006]
[Problems to be solved by the invention]
The present invention has been made to cope with the above situation, and the problem is that the battery does not rupture even when abnormalities such as overcharge and overdischarge occur, and the flat shape does not cause the battery contents to jump out. The object is to provide a non-aqueous electrolyte secondary battery.
[0007]
[Means for Solving the Problems]
In the above-described conventional flat nonaqueous electrolyte secondary battery, the electrode and the outer can are directly connected to the positive electrode case and the negative electrode case, respectively, without using lead terminals or the like, and the upper and lower portions of the electrode group are the electrode current collectors. Utilizing the advantage of collecting current in the battery, the battery has excellent safety without causing battery rupture when the internal pressure of the battery rises in the event of an abnormality, and without using an electrolyte solution or using a protection circuit Has been developing.
[0008]
As a result of extensive research, the present inventors have found that a metal negative electrode case that also serves as a negative electrode terminal and a metal positive electrode case that also serves as a positive electrode terminal each have two or more straight portions, and contact points of the respective straight portions. Is connected by a curve, and the negative electrode case and the positive electrode case are fitted via an insulating gasket, and the opening end of the positive electrode case is bent by caulking, and at least the inside thereof has a sealing structure. In a flat non-aqueous electrolyte secondary battery including a non-aqueous electrolyte, an electrode group that is a power generation element wound through a belt-like positive electrode, a negative electrode, and a separator, and a region in which a groove is provided in the center of the negative electrode case; A flat nonaqueous electrolyte secondary battery provided with a groove extending from the groove to the side surface of the negative electrode case is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, examples and comparative examples of the present invention will be described in detail.
(Example 1)
FIG. 1 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery to which the present invention is applied, and FIG. 2 is a plan view seen from the direction AA of FIG.
[0010]
As shown in the figure, a metal positive electrode case 1 also serving as a positive electrode terminal and a metal negative electrode case 5 also serving as a negative electrode terminal each have two or more straight portions, and the contact points of the respective straight portions are connected by a curve. The positive electrode case 1 and the negative electrode case 5 are fitted via an insulating gasket 6 and have a sealing structure in which the open end of the positive electrode case 1 is bent by caulking, and a belt-like positive electrode is formed inside An electrode group in which 2 and a negative electrode 4 are wound through a separator 3 and a nonaqueous electrolyte are included.
[0011]
Further, a rectangular groove 8 that is a symmetrical groove is provided in the center of the negative electrode case 5, and the grooves 9 are provided radially therefrom. By providing this groove 9, the deformation increases when the internal pressure in the battery rises, and in particular, the deformation in the vertical direction of the portion covered with the groove at the center of the negative electrode case 5 increases, and even if the internal pressure increases slightly. As shown in FIG. 4, the case is deformed, the contact between the electrode group and the battery case is completely cut off, and no subsequent current flows, thereby preventing an increase in internal pressure.
[0012]
The contact between the battery case and the electrode group may be made by contacting the electrode group and the part covered with the groove of the battery case, and the other part is subjected to an insulation treatment such as masking on the electrode group itself or the case itself. If so, the contact of the above part is hindered in the event of an abnormality.
[0013]
With respect to the groove, the main point is a square or circular shape at the center and a shape of a line extending radially therefrom, and the shape and depth of the groove are not particularly limited. The positive electrode active material, the negative electrode active material, the separator, and the electrolytic solution are not particularly limited.
[0014]
Moreover, in the said Example, when a square or circular shape and the groove | channel extended from it are provided in the surface of a case, or when it forms in the back side of a case, an external appearance is good and the effect is the same as that of a present Example.
[0015]
Next, a method for manufacturing the battery of Example 1 will be described.
First, 5 parts by mass of acetylene black and 5 parts by mass of graphite powder as a conductive material are added to 2100 parts by mass of LiCoO2, 5 parts by mass of polyvinylidene fluoride as a binder, diluted with N-methylpyrrolidone, mixed and mixed. A positive electrode mixture was obtained. Next, this positive electrode mixture was applied to one side of a 0.02 mm thick aluminum foil as a positive electrode current collector by a doctor blade method and dried to form a positive electrode active substance-containing layer on the aluminum foil surface. Thereafter, coating and drying were repeated until the coating film thickness of the positive electrode active material-containing layer became 0.15 mm on both sides, to produce a double-sided coated positive electrode. Next, the positive electrode 2 cut out to a length of 19 mm in width, 200 mm in length, and 0.15 mm in thickness by stripping the aluminum layer from the active substance-containing layer of 10 mm from one end of the electrode body. Was made.
[0016]
Next, 2.5 parts by mass of styrene butadiene rubber and carboxymethyl cellulose as binders are added to 100 parts by mass of graphitized mesophase pitch carbon fiber powder, diluted and mixed with ion-exchanged water, and a slurry-like negative electrode mixture Got. The obtained negative electrode mixture was repeatedly applied and dried in the same manner as in the case of the positive electrode so that the thickness of the active substance-containing layer was 0.15 mm on a 0.02 mm thick copper foil as a negative electrode current collector. Then, a double-sided coated negative electrode was produced. Next, the active substance-containing layer of the 23 mm portion is removed from the end of one side of the electrode body, and the copper layer is stripped to form a current-carrying portion. The negative electrode 4 is cut into a length of 20 mm in width, 220 mm in length and 0.15 mm in thickness. Was made.
[0017]
Next, the positive and negative electrode energization part surface is the outer winding end side, and the positive electrode 2 and the negative electrode 4 are spirally wound between the positive electrode 2 and the negative electrode 4 with a separator 3 made of a polyethylene microporous film having a thickness of 25 μm. On the other hand, pressure was applied in a certain direction so as to have a positive and negative electrode facing portion in the horizontal direction until there was no space in the center of the wound electrode.
[0018]
After the produced electrode group is dried at 85 ° C. for 12 hours, as shown in FIG. 2, a rectangular groove 8 is provided at the center of the case in which the insulating gasket 6 is integrated, and a radial groove 9 is provided therefrom. A solvent in which ethylene carbonate and methyl ethyl carbonate are mixed at a volume ratio of 1: 1 on the inner bottom surface of the negative electrode case 5 so that the uncoated side of the single-side coated negative electrode plate of the electrode group is in contact with the negative electrode case 5 A non-aqueous electrolyte in which LiPF6 was dissolved at a rate of 1 mol / l as a supporting salt was injected, and a positive electrode case 1 made of stainless steel having a straight portion height of 2.8 mm and a curved portion height of 2.7 mm was fitted. After reversing upside down, the positive electrode case is crimped, shrunk, and a rectangular non-aqueous electrolyte secondary battery having a thickness of 3.2 mm, a length of 30 mm, and a width of 30 mm is produced. It was.
[0019]
(Example 2)
As shown in FIG. 3, a circular groove 10 is provided at the center of the case, and the negative electrode case 5 provided with the grooves 11 radially from the groove 10 and the positive electrode case 1 provided with no grooves are used. A flat nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 and was referred to as Example 2.
[0020]
(Comparative Example 1)
A flat non-aqueous electrolyte secondary battery similar to that in Example 1 was prepared except that a positive electrode and a negative electrode case having no groove in the case were used.
[0021]
Using each of the batteries of Examples 1 and 2 and Comparative Example 1 manufactured as described above, 48 h was initially charged at a constant current and a constant voltage of 4.2 V and 10 mA, and 48 h at a current value of 12 V and 1.5 A. An overcharge test was conducted and the number of ruptured batteries was observed. The results are shown in Table 1.
[0022]
[Table 1]

[0023]
As shown in Table 1 above, in the battery of the example, the battery contents did not pop out, and the battery did not rupture.
[0024]
【The invention's effect】
As described above, according to the present invention, a non-aqueous electrolyte secondary battery excellent in safety that does not rupture the battery even in an abnormal time when the internal pressure of the battery increases can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a battery according to Example 1 of the present invention.
FIG. 2 is a plan view seen from the direction AA in FIG.
FIG. 3 is a plan view of Embodiment 2 of the present invention.
4 is a cross-sectional view of the battery of Example 1 when the internal pressure is increased. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Negative electrode case, 6 ... Insulating gasket, 7 ... Insulating paint, 8, 9, 10, 11 ... Groove.

Claims (2)

A metal negative electrode case that also serves as a negative electrode terminal and a metal positive electrode case that also serves as a positive electrode terminal each have two or more straight portions, and the contact of each straight portion is connected by a curve, and the negative electrode case and the positive electrode The case has a sealing structure in which the case is fitted through an insulating gasket, and the opening end of the positive electrode case is bent by caulking, and at least the belt-like positive electrode and negative electrode are wound through the separator. In the flat nonaqueous electrolyte secondary battery containing the non-aqueous electrolyte and the electrode group as the power generation element, a region provided with a groove in the center of the negative electrode case and the side surface of the negative electrode case extended from this groove A flat non-aqueous electrolyte secondary battery comprising a groove. The flat nonaqueous electrolyte secondary battery according to claim 1, wherein the groove provided in the central portion of the negative electrode case is circular or square.

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