JP2002289257A - Flat nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat nonaqueous electrolyte secondary battery attempting reduction of defects in manufacturing batteries due to loose electrodes and improved battery performance. SOLUTION: The flat nonaqueous electrolyte secondary battery comprises a sealed structure having a negative electrode metal case and a positive electrode metal case which are caulked through an insulating gasket. The structure contains a group of electrodes made by wounding a positive electrode, a negative electrode and a separator, and a nonaqueous electrolyte. A positive electrode component and a negative electrode component, having conductivity respectively to one or the other of the outer surfaces of the electrodes in the direction parallel to the flat surface of the flat battery, are exposed and connected either to the positive electrode case or a battery case. The leading end parts of the outer periphery of the positive electrode and the negative electrode in the group of electrodes formed by wounding sheet electrode units, a separator positioned at the inner surface thereof, and the other electrode positioned at the inner surface of the separator are respectively individually stopped winding at both of the two side R parts of the group of electrodes. This structure prevents the electrodes from loosening and shifting, improves the battery performance and can prevent a short circuit between the group of electrodes and the battery case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 for improving battery performance by preventing loosening of electrodes and preventing a short circuit between an electrode group and a battery case. Battery.

[0002]

2. Description of the Related Art The miniaturization of equipment used has been accelerating, especially for small information terminals such as cellular phones and PDAs, and there is a demand for miniaturization of secondary batteries as main power supplies. To meet this demand, a metal negative electrode case also serving as the negative electrode terminal and a metal positive electrode case also serving as the positive electrode terminal are fitted via an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking. Having a closed structure, at least a positive electrode therein, a separator,
In a flat nonaqueous electrolyte secondary battery including a nonaqueous electrolyte and a power generating element including a negative electrode, when a cross section in a direction perpendicular to a flat surface of the flat battery is viewed, at least three or more positive electrodes and a negative electrode A flat nonaqueous electrolyte secondary battery in which an electrode group having positive and negative electrode facing surfaces facing each other via a separator is housed, and the sum of the positive and negative electrode facing areas in the electrode group is larger than the opening area of the insulating gasket Have been proposed.

[0003] Such a flat non-aqueous electrolyte secondary battery is
From at least a positive electrode, a separator, and an electrode group including a negative electrode,
A positive electrode component having conductivity is exposed on one outer surface in a direction horizontal to the flat surface of the flat battery, the positive electrode component is directly connected to the positive electrode case, and the flat electrode of the electrode group is horizontal to the flat surface of the flat battery. The negative electrode component having conductivity is exposed from the other outer surface in the other direction, and is brought into direct contact with the negative electrode case to collect current between the electrode group and the battery case also serving as an external terminal. Therefore, a complicated manufacturing process, such as a cylindrical battery, in which a tab terminal taken out from the center of the electrode group is bent in a complicated manner and welded to a safety element, a sealing pin, a battery can, etc. to collect current, is used. There are advantages such as good workability because they do not have.

However, these flat non-aqueous electrolyte secondary batteries employ a method in which the electrode group is brought into direct contact with the battery case to collect current. When fitting and caulking the battery case, the loose electrode may bite between the battery case and the gasket, causing liquid leakage therefrom. In addition, unlike the cylindrical or square batteries, the above-described flat batteries have a very close position between the positive electrode case and the negative electrode case via a gasket. There is a problem that the R portion of the group and the tip of the electrode contact the side of the battery case of the other electrode, and the battery easily causes an internal short circuit.

In addition, even if the electrodes are not loosened or displaced enough to cause an internal short-circuit during battery assembly, the electrodes repeatedly expand and contract due to charge and discharge. As a result, the slackness of the electrodes increases and internal short-circuits occur. In some cases, the balance of lithium ion transfer between the positive electrode and the negative electrode may be lost due to a shift of the positive electrode and the negative electrode via the separator, which may cause deterioration of battery characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to cope with the above situation, and has as its object to reduce defects during battery fabrication due to loose electrodes and to improve the battery performance. A non-aqueous electrolyte secondary battery is provided.

[0007]

In order to solve the above-mentioned problems, the present invention provides a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal, which are fitted via an insulating gasket. Further, the positive electrode case or the negative electrode case has a sealing structure in which the positive electrode case, the negative electrode, and a separator are wound therein, and a non-aqueous electrolyte is included therein. The positive electrode component having conductivity is exposed on one outer surface in a direction horizontal to the flat surface of the flat battery, and the positive electrode component is directly or electrically connected to the positive electrode case. The negative electrode component having conductivity is exposed from the other outer surface in the direction parallel to the flat surface of the battery, and is directly or electrically connected to the negative electrode case to collect the current of the battery case serving as the electrode group and the external terminal. In the flat non-aqueous electrolyte secondary battery, the outermost ends of the positive electrode and the negative electrode of the electrode group in which the sheet-shaped electrode unit is wound, the separator located on the inner surface thereof, and the other located on the inner surface of the separator The electrode is formed by individually winding both side R portions of two places of the electrode group.

[0008] In the winding for preventing the electrode from being wound and loosened, the ends corresponding to the outermost peripheral portions of the sheet-like positive and negative electrodes, the separator located on the inner surface thereof, and the other electrode located on the inner surface of the separator. It is sufficient that the electrodes are stopped. However, in this type of battery, since the ends of the positive and negative electrodes and the electrode case directly collect current, it is necessary to individually wind the positive end and the negative end. Further, the winding method is not particularly limited, but it is convenient and convenient to use an insulating adhesive or an insulating tape.

If the position where the adhesive is applied to the electrode or the position where the insulating tape is applied is hung on the flat surface of the flat battery and is applied, a reduction in the contact area between the electrode and the electrode case and a poor connection due to a step may occur. It is preferable that the adhesive or the insulating tape be attached to the R portion of the electrode group that does not contact the positive and negative electrode cases.

Further, if the outer R portion is completely covered with the insulating tape, the contact between the R portion and the battery case can be avoided. Even if it shifts, short circuit can be prevented.

As the material of the adhesive, any material may be used as long as it is stable to an electrolytic solution or lithium ion. Rubber, acrylic, cellulose, olefin, fluorine, silicon, sulfide, vinyl, etc. Styrene-butadiene rubber, carboxymethylcellulose, polyvinylidene fluoride, and the like, which are used as a binder for a battery positive electrode active material, may be used.

The tape may be made of a vitreous material, polytetrafluoroethylene (PTFE), or tetrafluoroethylene-hexafluoropropylene copolymer (FE).
P), tetrafluoroethylene-ethylene copolymer (E
TFE), a fluororesin such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), polyvinylidene fluoride (PVDF), polyimide,
Liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT),
A resin selected from polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and an acetate resin is preferable because it is stable with respect to an electrolytic solution and lithium ions. It is preferable to use an adhesive coated on one side or both sides. This battery focuses on the structure of the electrode group of the battery, including the method of winding the electrodes,
The positive electrode active material, the negative electrode active material, and the electrolyte are not limited.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention and comparative examples will be described in detail. (Embodiment 1) FIG. 1 is a sectional view of a flat nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. Hereinafter, a method for manufacturing the battery of Example 1 will be described. First, to 100 parts by mass of LiCoO ₂ , 5 parts by mass of acetylene black and 5 parts by mass of graphite powder were added as conductive agents, 5 parts by mass of polyvinylidene fluoride was added as a binder, and the mixture was diluted and mixed with N-methylpyrrolidone. A positive electrode mixture was obtained. Next, this positive electrode mixture was applied to both surfaces 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 surface of the aluminum foil. Thereafter, coating and drying were repeated until the coating thickness of the positive electrode active substance-containing layer reached 0.15 mm on both sides, thereby producing a double-side coated positive electrode.
Next, a 10 mm portion of the active substance-containing layer was removed from the end of one surface of the electrode body, and the aluminum layer was exposed and used as a current-carrying part to produce a positive electrode plate 2 cut out to a length of 15 mm and a length of 120 mm.

Next, styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC) are used as binders in 100 parts by mass of the graphitized mesophase pitch carbon fiber powder.
Was added in an amount of 2.5 parts by mass, and diluted with ion-exchanged water.
The mixture was mixed to obtain a slurry-like negative electrode mixture. The obtained negative electrode mixture was repeatedly applied and dried on a 0.02 mm-thick copper foil as a negative electrode current collector in the same manner as the positive electrode so that the thickness of the active substance-containing layer was 0.15 mm. Then, a double-sided coated negative electrode was produced. Next, the negative electrode plate 4 was cut out to a length of 15 mm and a length of 120 mm by removing the active substance-containing layer of 10 mm from one end of the electrode body and exposing the copper layer to serve as a current-carrying part.

Next, the positive / negative electrode conducting part surface is set to the outer peripheral winding end side, and a separator 3 made of a microporous polyethylene film having a thickness of 25 μm is interposed between the positive electrode plate 2 and the negative electrode plate 4 and spirally wound. Then, pressure was applied in a fixed direction so that the space at the center of the wound electrode was exhausted so as to have the positive and negative electrode facing portions in the horizontal direction with respect to the flat surface of the flat battery.

Thereafter, the outermost end of the positive electrode, the separator 3 located on the inner surface thereof, and the negative electrode portion located on the inner surface of the separator 3 are bonded together with an insulating tape 7 of polyester adhesive tape so that the outermost end is hidden. did. Similarly, the outermost end of the negative electrode was adhered to the outermost end by an insulating tape 7 made of a polyester adhesive tape.

FIG. 2 is a sectional view of a side surface R portion of the electrode group according to the first embodiment of the present invention. The prepared electrode group was heated at 85 ° C for 1
After drying for 2 hours, the negative electrode current-carrying part of the electrode group was placed in contact with the inner bottom surface of the negative electrode metal case 5 to which the insulating gasket 6 was integrated, and ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 1. A nonaqueous electrolyte obtained by dissolving LiPF ₆ as a supporting salt in a solvent at a rate of 1 mol / l is injected, and a stainless steel positive electrode case 1 is fitted so as to be in contact with the positive electrode conducting part of the electrode group. A positive non-aqueous electrolyte secondary battery of Example 1 having a thickness of 3 mm and a diameter of 24.5 mm was produced by caulking the positive electrode case 1 and sealing the positive electrode case 1.

(Embodiment 2) FIG. 3 is a sectional view of a side R portion of an electrode group according to Embodiment 2 of the present invention. The outermost end of the negative electrode 4, the separator 3 located on the inner surface thereof, and the positive electrode 2 located on the inner surface of the separator 3 were adhered with a polyester adhesive tape 7 so that the side R portion was entirely covered with the adhesive tape. Similarly, the outermost end portion of the positive electrode 2 was bonded with the polyester pressure-sensitive adhesive tape 7 so that the side R portion was entirely covered. Other steps were the same as in Example 1 to produce a flat nonaqueous electrolyte secondary battery of Example 2.

(Embodiment 3) FIG. 4 is a sectional view of a side R portion of an electrode group according to Embodiment 3 of the present invention. The end of the separator 3 is positioned on the side surface R, a double-sided tape 8 made of polyester is adhered from above the separator 3, and the separator 3 is fixed to the opposing positive electrode plate 2. 4 was bonded to the outermost end. Similarly, with respect to the outermost end of the positive electrode, the end of the separator 3 is located at the side R, and a double-sided tape 8 made of polyester is applied from above the separator 3 and the separator 3 is fixed to the opposing negative electrode plate 4. The operation of bonding the positive electrode 2 from above the double-sided tape 8 was performed. The other steps were the same as in Example 1 to produce a flat nonaqueous electrolyte secondary battery of Example 3.

(Embodiment 4) FIG. 5 is a sectional view of a side R portion of an electrode group in Embodiment 4 of the present invention. The end of the separator 3 is positioned on the side surface R, and a double-sided tape 8 made of polyester is attached to the inner surface of the separator 3, and the separator 3 is fixed to the facing positive electrode plate 2. 8 was adhered, and the outermost end of the negative electrode plate 4 was adhered from above. Similarly, with respect to the outermost end of the positive electrode, the end of the separator 3 is positioned on the side surface R, and a double-sided tape 8 made of polyester is attached to the inner surface of the separator 3, and the separator 3 is fixed to the opposing negative electrode plate 4. , Paste the double-sided tape 8 on the upper part of the separator 3,
An operation of bonding the positive electrode plate 2 was performed from above. The other steps were the same as in Example 1 to produce a flat nonaqueous electrolyte secondary battery of Example 4.

(Embodiment 5) FIG. 6 is a sectional view of a side surface R portion of an electrode group according to Embodiment 5 of the present invention. The end of the separator 3 is positioned on the side surface R, and a double-sided tape 8 made of polyester is applied to the inner surface of the separator 3 to fix the separator 3 to the opposing negative electrode plate 4. , And a single-sided tape 7 was applied from above and fixed to the positive electrode. Similarly, with respect to the outermost end of the negative electrode, the end of the separator 3 is located at the side R portion,
A polyester double-sided tape 8 is attached to the inner surface of the separator 3 and the separator 3 is fixed to the opposed positive electrode plate 2,
Further, the outermost end of the negative electrode plate 4 was superimposed on the upper part of the separator 3, and a single-sided tape 7 was attached and fixed from the uppermost end of the negative electrode. Other steps were the same as in Example 1 to produce a flat nonaqueous electrolyte secondary battery of Example 5.

Example 6 A flat nonaqueous electrolyte secondary battery of Example 6 was produced in the same manner as in Example 4 except that SBR was applied and affixed in place of the polyester double-sided tape.

Example 7 A flat nonaqueous electrolyte secondary battery of Example 7 was produced in the same manner as in Example 5 except that SBR was applied and affixed instead of the double-sided tape of polyester.

(Comparative Example 1)
The negative electrode plate 4 is wound and pressed in a fixed direction so as to have a positive / negative electrode facing portion in the horizontal direction with respect to the flat surface of the flat battery until there is no space at the center of the wound electrode. A flat nonaqueous electrolyte secondary battery of Comparative Example 1 was manufactured in the same manner as in Example 1 except that a battery was manufactured using the group.

(Reference Example 1) The flattened tape of Reference Example 1 was applied in the same manner as in Example 1 except that the winding tape was attached so as to hang from the flat surface of the positive electrode of the electrode group to the flat surface of the negative electrode via the side surface R. A non-aqueous electrolyte secondary battery was manufactured.

In the 1,000 batteries of Examples 1 to 7, Comparative Example 1 and Reference Example 1 produced as described above, 4.2
V, 3 mA constant current and constant voltage for 48 hours
After standing at room temperature for a day, the open circuit voltage was measured. Table 1 shows the number of batteries having an open circuit voltage of 4.0 V or less. Then, the batteries whose open circuit voltage after 3 days was 4.0 V or more
00 pieces were sorted, left for 100 days in an atmosphere of 45 ° C. and 93%, and the leakage was confirmed with a magnifying glass.

Further, 200 other batteries were selected and discharged at a constant current of 30 mA in an atmosphere of 20 ° C., and the discharge capacity until the closed circuit voltage became 3.0 V was measured. Thereafter, the battery was charged for 3 hours at a constant current and a constant voltage of 4.2 V and 30 mA, and this was set as one cycle, and the cycle was repeated 100 times.
Table 1 shows the number of batteries in which the maintenance ratio of the discharge capacity at the 100th cycle with respect to the initial discharge capacity was 50% or less.

Further, 200 other batteries were selected and the temperature was set at 20 ° C.
Under an atmosphere with a constant current of 180 mA, and the discharge capacity was measured until the closed circuit voltage reached 3.0 V. Table 1 shows utilization rates of the discharge capacity at 180 mA with respect to the discharge capacity at 30 mA described above.

[0029]

[Table 1]

As is clear from Table 1, the battery of this embodiment includes the outermost ends of the positive electrode and the negative electrode of the electrode group, the separator located on the inner surface thereof, and the other electrode located on the inner surface of the separator. Since the two side surfaces R of the electrode group are individually wound with an insulating tape or an adhesive,
OV deterioration after initial charge, liquid leakage after storage, and cycle deterioration are very small as compared with the unwrapped battery of the comparative example. In particular, Example 2 in which the entire side R portion of the electrode group is covered is even better. Further, when the winding tape described as Reference Example 1 was attached so as to hang from the flat surface of the positive electrode of the electrode group to the flat surface of the negative electrode via the side surface R portion, the internal resistance of the battery was increased, and the heavy load characteristics were poor. Dropped.

Although the embodiment of the present invention has been described using a flat non-aqueous solvent secondary battery using a non-aqueous solvent as a non-aqueous electrolyte, a polymer secondary battery using a polymer electrolyte as a non-aqueous electrolyte has been described. Of course, the present invention can also be applied to a solid electrolyte secondary battery using a solid electrolyte, and a polymer thin film or a solid electrolyte membrane can be used instead of the resin separator.
Although the shape of the battery has been described based on the coin-shaped non-aqueous electrolyte sealed by crimping of the positive electrode case, it is also possible to replace the positive and negative electrodes and seal by crimping of the negative electrode case. Further, the shape of the battery does not need to be a perfect circle, and the present invention can be applied to a flat nonaqueous electrolyte secondary battery having a special shape such as an oval shape.

[0032]

As described above, according to the present invention, in the flat nonaqueous electrolyte secondary battery, the outermost end portions of the positive electrode plate and the negative electrode plate of the electrode group in which the sheet-like electrode unit is wound are formed. ,
The separator located on the inner surface and the other electrode positioned on the inner surface of the separator are individually wound around the two side surfaces R of the electrode group to prevent loosening and misalignment of the electrodes. It is possible to provide a flat non-aqueous electrolyte secondary battery that is capable of improving the performance and preventing a short circuit between the electrode group and the battery case, is far superior to the conventional battery, and has an extremely large industrial value. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a side R portion of the electrode group of FIG. 1;

FIG. 3 is a sectional view of a side R portion of an electrode group according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a side surface R portion of an electrode group according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a side R portion of an electrode group according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a side R portion of an electrode group according to a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Positive electrode plate, 3 ... Separator, 4 ... Negative electrode plate, 5 ... Negative electrode case, 6 ... Insulating gasket, 7 ... Insulating tape (single-sided adhesive applied), 8 ... Insulating tape (double-sided adhesive applied) .

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuo Udagawa 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H029 AJ14 AK03 AL07 AM03 AM07 BJ03 BJ14 CJ01 CJ07 DJ02

Claims (4)

[Claims] A metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted via an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking. A positive electrode, a negative electrode, an electrode group formed by winding a separator, and a non-aqueous electrolyte are enclosed therein, and further, one of the outer surfaces in a direction horizontal to the flat surface of the flat battery of the electrode group. The positive electrode component having conductivity is exposed, the positive electrode component is directly or electrically connected to the positive electrode case, and the conductive material is supplied from the other outer surface in the direction parallel to the flat surface of the flat battery of the electrode group. In a flat non-aqueous electrolyte secondary battery having a structure in which a negative electrode constituent material having a property is exposed and directly or electrically contacted with a negative electrode case to collect current of a battery case serving also as an electrode group and an external terminal, a sheet-shaped The outermost ends of the positive electrode and the negative electrode of the electrode group in which the electrode unit is wound, the separator positioned on the inner surface thereof, and the other electrode positioned on the inner surface of the separator,
A flat non-aqueous electrolyte secondary battery in which both side R portions of the two electrode groups are individually wound. 2. The outermost end of the positive electrode sheet or the negative electrode sheet constituting the electrode group extends to the side surface R of the electrode group, and the separator located on the inner surface of the outermost end is also the outermost end. Extends to the side surface R of the electrode group, and the outermost end portion of the electrode sheet, the separator, and the other electrode located on the inner surface of the separator are respectively bonded at the side surface R by an adhesive. The flat nonaqueous electrolyte secondary battery according to the above. 3. The outermost end of the positive electrode sheet or the negative electrode sheet constituting the electrode group extends to the side surface R of the electrode group, and the separator located on the inner surface of the outermost outermost end also has the outermost end. 2. The group according to claim 1, wherein the outermost end portion of the electrode sheet, the separator, and the other electrode positioned on the inner surface of the separator are bonded to each other by an insulating tape at the side surface R portion. Flat non-aqueous electrolyte secondary battery. 4. The flat nonaqueous electrolyte secondary battery according to claim 1, wherein the side surface R of the electrode group is completely covered with an insulating tape.