JP7108358B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

In the present invention, a plate-shaped positive electrode terminal is connected to the positive electrode of the electrode plate group in which the positive electrode and the negative electrode are alternately laminated with a separator interposed therebetween, and a flat plate-shaped negative electrode terminal is connected to the negative electrode. is covered with a laminate film, the positive electrode terminal and the negative electrode terminal are led out from the ends of the covered laminate film, and the entire ends of the covered laminate film are overlapped and heat-sealed. It relates to electrolyte batteries.

A positive terminal and a negative terminal are connected to the positive electrode and the negative electrode of the electrode plate group in which the positive electrode and the negative electrode are alternately laminated with a separator interposed therebetween. A non-aqueous electrolyte battery is known in which the entire circumference of the edge of a laminate film is heat-sealed (Patent Document 1).

Such non-aqueous electrolyte batteries have problems due to heat during heat sealing. It has been proposed to improve the formed sealant layer to prevent this (Patent Document 2).

JP 2010-10042 A JP-A-2002-343311

In the present invention, the problem when heat sealing a laminated film is not only the short circuit between the metal foil and the terminal in the laminated film, but also the heat sealing may cause capacity deterioration and short circuit in the battery due to perforation and shrinkage of the separator. Find out and try to eliminate them.

The present inventors made the discovery as a result of earnestly studying whether or not this problem could be solved regardless of the material.

In the present invention, a plate-like positive electrode terminal is welded to the positive electrode of an electrode plate group in which a positive electrode and a negative electrode are alternately laminated with separators interposed therebetween, and a flat plate-like negative electrode terminal is welded to the negative electrode. is covered with a laminate film, the positive electrode terminal and the negative electrode terminal are led out from the ends of the covered laminate film, and the entire ends of the covered laminate film are overlapped and heat-sealed. In the electrolyte secondary battery, the heat seal width of the terminal lead-out part is 5 mm or more, the heat seal width of the terminal lead-out part is L1, and the length from the welded part of each positive electrode and negative electrode terminal to the heat sealed part The value of L1/L2 is set to 1.0 or less when the length is L2, and the length L2 is obtained from the shortest distance between the welded portion and the heat-sealed portion, each having a predetermined width, facing each other . It is something to do.

According to the present invention, by defining the relationship between the width of the heat seal and the length from the welded portion of each terminal to the heat seal portion, it is possible to prevent puncture and shrinkage of the separator during heat sealing. .

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing for demonstrating this invention embodiment.

An embodiment of the present invention will be described based on the drawings.

FIG. 1 is a cross-sectional view for explaining one embodiment of the present invention. In the drawings, 1 is a non-aqueous electrolyte secondary battery of one embodiment, specifically a lithium ion secondary battery.

2 is a positive electrode plate containing 90% by mass of lithium cobalt oxide ( LixCoO ₂ , where x is 0≤x≤1) powder, 3% by mass of acetylene black, 3% by mass of graphite and 4% by mass of polyvinylidene fluoride (PVdF). An N-methyl-2-pyrrolidone (NMP) solution is added to the powder composed of and mixed to prepare an active material slurry, which is applied to the current collector 21 made of a sheet-like aluminum foil having a thickness of 15 μm. A streak-like uncoated portion was formed at the end in the length direction, applied, vacuum dried at 100 ° C. for 2 hours, and then a streak-like uncoated portion was similarly formed at the end on the other side. Then, the slurry was applied to the substrate and vacuum-dried in the same manner. At this time, the uncoated portions on the front and back were positioned in the same direction. After that, the sheet coated with the active material on both sides was roll-pressed to obtain 8 rectangular positive electrode plates 2 (coating portion dimensions: 100 mm×100 mm) so that each sheet had an uncoated portion. The positive electrode plate 2 has a thickness of 100 μm and a packing density of 3.3 g/cm ³ .

3 is a negative electrode plate, and ion-exchanged water is added to powder composed of 97% by mass of artificial graphite powder having an average particle size of 20 μm, 2% by mass of styrene-butadiene rubber (SBR), and 1% by mass of carboxymethyl cellulose (CMC). An active material slurry is prepared by mixing, and this is applied to both sides of a current collector 31 made of a sheet-like copper foil having a thickness of 10 μm, forming streak-like unapplied portions at the ends in the longitudinal direction, Vacuum dried at 100° C. for 2 hours. The uncoated portions on the front and back were positioned in the same direction. The sheet coated with the active material on both sides in this way was roll-pressed to obtain 9 rectangular negative electrode plates 3 (104 mm×104 mm coated area) so that each sheet had an uncoated area. The packing density of the negative electrode is 1.4 g/ cm ³ .

The positive electrode plate 2 and the negative electrode plate 3 were alternately laminated with a polypropylene microporous separator 4 having a thickness of 30 μm and a size of 108 mm×108 mm interposed therebetween. A separator 4 was also arranged outside the negative electrode plate 3 located on the outermost side. (Separator/Negative Electrode/Separator/Positive Electrode/Separator/.../Negative Electrode/Separator) The uncoated portions of the positive electrode plate 2 and the negative electrode plate 3 were arranged in the opposite directions. . After lamination, the four corners were fixed with adhesive tape (not shown) to prevent interlayer separation.

Next, an aluminum plate having a thickness of 0.25 mm, a width of 7 mm, and a length of 50 mm, which serves as the positive electrode terminal 22, was welded collectively by superposing the uncoated portions of the eight positive electrode plates 2 by ultrasonic welding . Similarly, a nickel-plated copper plate having a thickness of 0.25 mm, a width of 7 mm, and a length of 50 mm, which serves as the negative electrode terminal 32, was overlapped with the uncoated portions of the nine negative electrode plates 3 and welded together by ultrasonic welding . Prior to ultrasonic welding, the positive electrode terminal 22 and the negative electrode terminal 32 are formed by applying an electron beam crosslinked polypropylene having a thickness of 50 μm and an acid-modified polypropylene having a melting point of 130° C. to 140° C. in advance in the portion to be sealed by the exterior body. Both surfaces of the laminated sealant 5 were heat-sealed with the acid-modified polypropylene facing the terminal side. The size of the sealant 5 was such that it protruded on both sides by 2 mm in the width direction of the terminal, and the length direction was made 1 mm larger than the length of the heat seal.

A laminate film was used as the exterior body 6 that covers the laminated electrode plate group. This laminate film is a laminate film comprising a laminate of nylon with a thickness of 25 μm, soft aluminum with a thickness of 40 μm, and acid-modified polypropylene with a thickness of 40 μm and a melting point of 160°C. One is a container 61 which is cut into a predetermined size and deep-drawn into a cup-like shape having a size capable of containing the electrode plate group. The size of the deep drawing was approximately equal to the length and width of the electrode plate group including the portion not coated with the active material, and the depth was approximately equal to the thickness of the electrode plate group. After molding, a flange portion 62 was formed around the deep recess, and the width of the flange portion 62 was trimmed to a predetermined length. The electrode plate group (electrode laminate) was housed in the laminated film container 61 formed in this way. The positive and negative terminals 22 and 32 were installed at two locations on the flange portion 62 of the trimmed laminate film so as to face each other. The sealant 5 fused in advance to the terminal was made to extend over the flange portion 61 and protrude to the outside.

Next, a laminate film cut into a predetermined size was used as a lid 63 and placed on the container 61 containing the electrode laminate. The lid 63 had the same size as the top surface of the opening of the container 6 containing the electrode laminate, and was placed on top of the lid 63 .

In this way, after the cover 63 is superimposed on the flange portion 61, the sealant is applied by applying heat while applying pressure from above and below to the portion separated by a certain length L2 from the welded portion between the non-coated portion of each electrode plate and each terminal. A predetermined width (heat-sealed width) L1 including 5 was heat-sealed (heat-sealed) to fabricate a lithium-ion secondary battery including an exterior body 6 composed of a container 61 and a lid 63 .

At this time, a heater with a width of 10 mm is used to set the heat seal width L1 of the thermal fusion bonding to 10 mm, and the distance L2 between the uncoated portion of each electrode plate, the welded portion of each terminal, and the heat-sealed (thermally bonded) portion is varied. Table 1 shows the results of examining the presence or absence of defects such as separator holes and shrinkage when the value of the ratio of L1 and L2 (L1/L2) is changed. The distance L2 between the welded portion and the heat-sealed portion was obtained from the shortest distance between the welded portion and the heat-sealed portion, each having a predetermined width, facing each other.

Next, the value of the ratio of L1 and L2 (L1/L2) was set to 1 , and the presence or absence of defects such as separator holes and shrinkage when the heat seal width L1 was changed was investigated. Met. The width of the heater used for heat-sealing was the same as the heat-sealing width.

As is clear from these tables, the heat seal width L1 must be 5 mm or more, and the ratio (L1/L2) of the distance L2 between the uncoated portion of each electrode plate, the welded portion of each terminal, and the heat-sealed portion is It turned out that it is necessary to be 1.0 or less. When this condition is satisfied, problems such as puncture and shrinkage of the separator during the heat-sealing of the outer packaging can be resolved, and deterioration of the battery capacity and short-circuiting within the battery caused by this can be prevented. Furthermore, in the case of the heat-sealing width of 5 mm, even when the value of L1/L2 was changed, the same results as in the case of the heat-sealing width of 10 mm shown in Table 1 were obtained. It is known that the width of the heat seal is preferably 5 mm or more for other reasons such as prevention of electrolyte leakage and strength. Moreover, in the above embodiment, the case where the positive electrode terminal and the negative electrode terminal are provided at opposite positions was shown, but they may be provided in the same direction.

1 Lithium Ion Secondary Battery 2 Positive Electrode Plate 3 Negative Electrode Plate 4 Separator 5 Sealant 6 Exterior Body

Claims (1)

A plate-shaped positive electrode terminal is welded to the positive electrode of the electrode plate group in which the positive electrode and the negative electrode are alternately laminated with a separator interposed therebetween, and a flat plate-shaped negative electrode terminal is welded to the negative electrode. A non-aqueous electrolyte secondary battery constructed by covering and extending the positive electrode terminal and the negative electrode terminal from the ends of the covered laminate film to the outside, and by overlapping and heat-sealing the entire circumference of the ends of the covered laminate film. , the heat seal width L1 of the portion leading out the terminal is 5 mm or more, and the length from the welded portion between the uncoated portions of the positive and negative electrodes and each terminal to the heat sealed portion is L2, and the ratio of L1/L2 A non-aqueous electrolyte battery, wherein the value is 1.0 or less, and the length L2 is obtained from the shortest distance between the welded portion and the heat-sealed portion, each having a predetermined width, facing each other.

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