JP2007242518A - Square battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery preventing cut off of an electrode plate core in the boundary between the outermost circumferential electrode plate core and an adhesive tape even if a flat rolled electrode group is formed by applying high pressure by prescribing the relation between the thickness of the electrode plate core and that of the adhesive tape. <P>SOLUTION: In the spiral electrode group 10 formed by rolling a positive plate forming a positive mix layer containing a positive active material on a positive electrode core 11a made of metal foil and a negative plate forming a negative mix containing a negative active material on a negative electrode core made of metal foil through a separator, a both surface core exposure part 11c where the mix layer is not formed is formed in the outermost circumference of the spiral electrode group 10, the adhesive tape 20 is stuck on the rolling finished part of the both surface core exposure part 11c, and the thickness t of the electrode plate core 11a and the thickness T of the adhesive tape 20 are regulated so that the ratio (T/t) of the thickness T of the adhesive tape 20 to the thickness t of the electrode plate core 11a is 1.8 or less (T/t≤1.8). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a positive electrode plate in which a positive electrode mixture layer containing a positive electrode active material is formed on a positive electrode core made of a metal foil, and a negative electrode mixture layer containing a negative electrode active material on a negative electrode core made of a metal foil. The present invention relates to a prismatic battery including a spiral electrode group wound so that a negative electrode plate faces each other with a separator interposed therebetween.

  In recent years, non-aqueous electrolyte secondary batteries that are small and light and have a high capacity have come to be used as power sources for portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers. In devices where this type of non-aqueous electrolyte secondary battery is used, the space to store the battery is often a square (flat box), so the power generation element is housed in a rectangular outer can. Often used square batteries. Such a prismatic battery is generally manufactured as follows.

  That is, a positive electrode mixture containing a positive electrode active material is applied to a positive electrode core (usually aluminum foil) to produce a positive electrode plate, and the negative electrode core (usually copper foil) contains a negative electrode active material. A negative electrode mixture is applied to produce a negative electrode plate. Then, after making these positive electrode plates and negative electrode plates oppose each other via a separator, they are spirally wound to form a spiral electrode group. And after press-molding such a spiral electrode group to make a flat electrode group, this is accommodated in a flat rectangular outer can, and a nonaqueous electrolyte is injected to form a nonaqueous electrolyte secondary battery. It is said.

In this case, the outermost electrode plate (usually, only the electrode plate core is present in the outermost electrode plate) so that the spiral electrode group produced as described above is not unwound. An adhesive tape for winding is stuck to fix the outermost periphery of the spiral electrode group. However, if the adhesive tape for winding is used, the portion where the adhesive tape is adhered and the portion where the tab is formed overlap each other, and the thickness of the portion increases. For this reason, it has been proposed, for example, in Patent Document 1 that the adhesive tape does not exist on the projection surface portion in the surface direction of the tab portion.
JP 2001-307759 A

  However, as proposed in Patent Document 1 described above, even if the adhesive tape is not present on the projection surface portion in the surface direction of the tab portion, the spiral electrode group is formed by pressure forming the spiral electrode group. In doing so, the problem arises that the electrode plate core is cut at the boundary between the outermost electrode plate core and the adhesive tape. This is because the demand for higher capacity for this type of non-aqueous electrolyte secondary battery is increased, and in order to meet this demand for higher capacity, the active material filling amount is increased. This is because a thin metal foil (usually an aluminum foil as the positive electrode core and a copper foil as the negative electrode core) having a thickness of 8 to 30 μm has been used.

  And in order to make the electrode plate core body made of such a metal foil as much as possible, the electrode plate core body made of the metal foil is used with an electrode plate filled with the active material at a high density. An electrode group is formed. For this reason, when it is set as a flat spiral electrode group, it is because it pressure-molded with high pressurization force (for example, about 20 MPa).

  By the way, when the electrode plate core is cut at the boundary portion between the outermost electrode plate core and the adhesive tape, the current collecting from the current collecting lead portion formed at the tip of the cut portion is not made. There is a problem that charging and discharging cannot be performed and the battery function is not achieved.

  Therefore, the present invention has been made to solve the above-described problems, and by appropriately defining the relationship between the thickness of the electrode plate core and the thickness of the adhesive tape, a flat spiral shape with a high pressure force is provided. An object of the present invention is to provide a battery in which the electrode plate core is not cut at the boundary portion between the outermost electrode plate core and the adhesive tape even if the electrode group is pressure-molded. .

  The prismatic battery of the present invention has a positive electrode plate in which a positive electrode mixture layer containing a positive electrode active material is formed on a positive electrode core made of metal foil, and a negative electrode mixture layer containing a negative electrode active material in a negative electrode core made of metal foil. A spiral electrode group wound so that the formed negative electrode plate is opposed to each other through a separator is provided. And in order to achieve the said objective, the core body exposed part in which the mixture layer is not formed is formed in the outermost periphery of a spiral electrode group, and an adhesive tape is affixed on the winding end part of the said core body exposed part. And the thickness of the electrode core so that the ratio (T / t) of the thickness T of the adhesive tape to the thickness t of the electrode core has a relationship of 1.8 or less (T / t ≦ 1.8). t and the thickness T of the adhesive tape are regulated.

  Here, regardless of the material of the adhesive tape, in the electrode group in which the ratio (T / t) of the thickness T of the adhesive tape to the thickness t of the electrode plate core is 1.80 or less, even if the press pressure is large, the core There was no breakage of the electrode core at the boundary between the body exposed portion and the adhesive tape. On the other hand, when the ratio (T / t) of the thickness T of the adhesive tape to the thickness t of the electrode core is greater than 1.80, the electrode plate is formed at the boundary between the core exposed portion and the adhesive tape when the press pressure increases. A broken part of the core body is generated. From this, it can be said that it is desirable to regulate the ratio (T / t) of the thickness T of the adhesive tape to the thickness t of the electrode plate core to be 1.8 or less.

  In addition, when the adhesive tape is formed so that the shape of the end portion is a curved shape other than a straight line or a rectangular shape, it is possible to disperse the pressure applied to the electrode plate core during pressing. Thus, it is possible to greatly reduce the possibility of the electrode plate core breaking, which is desirable. In this case, it is more preferable that a circular hole or the like is formed at the center of the adhesive tape because the amount of electrolyte solution filled can be increased by the volume of the circular hole.

  As described above, in the rectangular battery according to the present invention, since the relationship between the thickness of the electrode plate core and the thickness of the adhesive tape is specified, the spiral electrode group is formed into a flat shape by press molding at a high pressure. However, it is possible to provide a battery in which the electrode plate core is not cut at the boundary portion between the electrode plate core and the adhesive tape.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 6. However, the present invention is not limited to this embodiment, and may be changed as appropriate without changing the object of the present invention. It is possible to implement. 1 is a diagram schematically showing a positive electrode plate when the present invention is applied to a lithium ion battery, FIG. 1 (a) is a plan view thereof, and FIG. 1 (b) is a diagram of FIG. 1 (a). It is sectional drawing which shows an AA cross section. FIG. 2 is a diagram schematically showing a negative electrode plate when the present invention is applied to a lithium ion battery, FIG. 2 (a) is a plan view thereof, and FIG. 2 (b) is a cross-sectional view of FIG. It is sectional drawing which shows A cross section.

  FIG. 3 shows a spiral spiral electrode group produced by using the positive electrode plate shown in FIG. 1 and the negative electrode plate shown in FIG. 2, and an adhesive tape is attached to the surface of the spiral electrode group. It is a figure which shows typically the state by which the electrode group was pressure-molded, FIG. 3 (a) is the perspective view, FIG.3 (b) is the top view, FIG.3 (c) is the outermost periphery. It is sectional drawing which expands and shows typically the boundary part of an electrode plate core body and an adhesive tape. FIG. 4 is a graph showing the relationship of battery thickness to charge / discharge cycles. FIG. 5 is a graph showing the relationship between the battery capacity and the charge / discharge cycle. FIG. 6 is a plan view schematically showing various planar shapes used for the adhesive tape of the present invention.

1. Positive electrode plate First, 94 parts by mass of lithium cobaltate (LiCoO ₂ ) having an average particle diameter of 5 μm as a positive electrode active material and 3 parts by mass of artificial graphite powder as a conductive agent were mixed to prepare a positive electrode mixture. This positive electrode mixture and a vinylidene fluoride polymer as a binder dissolved in N-methyl-2-pyrrolidone (NMP) are mixed and kneaded so that the solid content is 3 parts by mass, and then a positive electrode mixture slurry Was prepared. This positive electrode mixture slurry is applied to both surfaces of a positive electrode core body (for example, aluminum foil or aluminum alloy foil) 11a having a predetermined thickness so that the coating amount is 450 g / m ² (the coating amount on one side is 225 g / m ² ). The positive electrode mixture layer 11b was formed on both surfaces of the positive electrode current collector 11a.

Next, after this positive electrode mixture layer 12 is dried, it is rolled with a roller press so that the packing density of the mixture is 3.7 g / cm ³ , and then cut into strips to a predetermined size. Thus, the positive electrode plate 11 was produced. In this case, the positive electrode mixture layer 11b does not exist on both surfaces of the positive electrode core 11a from the rear end of the positive electrode core 11a (the portion that becomes the winding end of the spiral electrode group) to L1 (L1 = 30 mm). The core body exposed portion 11c was used, and from that point to L2 (L2 = 60 mm), the single-sided core body exposed portion 11d in which the positive electrode mixture layer 11b was present only on one surface of the positive electrode core body 11a was formed.

Further, when bent, the positive electrode lead 11f is formed, and the positive electrode lead 11f extends from the upper end of the spiral electrode group 10 so that the double-sided core exposed portion 11c at the rear end of the positive electrode core 11a is substantially U-shaped. A cut 11e in a shape was made. When winding the positive electrode plate 11, the side where the positive electrode mixture layer 11 b exists only on one side of the positive electrode core body 11 a (the single-sided core body exposed portion 11 d side) faces the outside of the spiral electrode group 10. By winding, the outermost peripheral part of the spiral electrode group 10 can be used as the positive electrode core 11a, and the positive electrode core 11a and the inner surface of the battery outer can can be brought into contact with each other.
Here, the positive electrode plate 11 manufactured using the positive electrode core body 11a having a thickness (t) of 20 μm (t = 20 μm) is defined as a positive electrode plate x1, and the positive electrode core body 11a having a thickness (t) of 15 μm (t = 15 μm). The positive electrode plate 11 produced using the positive electrode plate x2 and the positive electrode plate 11 produced using the positive electrode core 11a having a thickness (t) of 13 μm (t = 13 μm) was designated as the positive electrode plate x3.

2. A negative electrode plate on the other hand, massive artificial graphite as an anode active material (in Lc values 1000Å or more, with d ₀₀₂ value is 3.358A, an average particle diameter of 20 [mu] m) powder and styrene solids 48% - butadiene rubber A dispersion of (SBR) was dispersed in water, and carboxymethyl cellulose (CMC) as a thickener was added to prepare a negative electrode mixture slurry. In this case, the negative electrode mixture slurry was prepared such that the solid content mass composition ratio after drying was 97: 1.5: 1.5 of the negative electrode active material: SBR: CMC. The obtained negative electrode mixture slurry was applied to both surfaces of a negative electrode core (for example, copper foil) 12a having a thickness of 10 μm by a doctor boud method so that the coating amount was 250 g / m ² (the coated amount on one side was 125 g / m ² ). It apply | coated and the negative mix layer 12b was formed.

Next, after drying the negative electrode mixture layer 12b, the negative electrode mixture layer 12b is rolled with a roller press so that the packing density of the mixture is 1.5 g / cm ³ , and then cut into strips to have predetermined dimensions. did. Subsequently, after vacuum-drying for 2 hours, it cut | disconnected in the strip shape of a predetermined dimension, the negative electrode lead 12d was welded to the edge part, and the negative electrode plate 12 was produced. In this case, both surfaces of the negative electrode core body 12a on which both surfaces of the negative electrode mixture layer 12b do not exist from the winding start end portion (the portion serving as the winding start portion of the spiral electrode group) to L3 (L3 = 30 mm) of the negative electrode core body 12a. The core exposed portion 12c was used.

3. Anti-winding adhesive tape Adhesive tape in which a rubber-based adhesive material 22 as an adhesive material is applied to a base material 21 made of polypropylene (PP) has a predetermined size (in this example, the width is 7 mm, the height ( The length was adjusted to 45 mm) to obtain an anti-winding adhesive tape 20 (y). In this case, the thickness (T) (the thickness in this case means the total thickness of the base material 21 and the adhesive material 22. The same applies hereinafter) of 40 μm (T = 40 μm). Is the tape y1, the tape having the thickness (T) of 30 μm (T = 30 μm) is the tape y2, the tape having the thickness (T) of 27 μm (T = 27 μm) is the tape y3, and the thickness (T) is 25 μm (T = 25 μm) was designated as tape y4, and one having a thickness (T) of 20 μm (T = 20 μm) was designated as tape y5.

  Further, an adhesive tape in which a rubber adhesive as an adhesive 22 is applied to a base material 21 made of polyphenylene sulfide (PPS) has a predetermined size (in this example, the width is 7 mm and the height (length)). To 45 mm) to obtain an anti-winding adhesive tape 20 (z). In this case, a tape having a thickness (T) of 40 μm (T = 40 μm) is defined as tape z1, a tape having a thickness (T) of 30 μm (T = 30 μm) is defined as tape z2, and a thickness (T) of 27 μm (T = 27 μm). The tape was z3, the one with a thickness (T) of 25 μm (T = 25 μm) was tape z4, and the one with a thickness (T) of 20 μm (T = 20 μm) was tape z5.

  In addition to the above-described polypropylene (PP) and polyphenylene sulfide (PPS), the base material 21 of the anti-winding adhesive tape 20 includes polyethylene, polyethylene terephthalate, polytetrafluoroethylene, unsaturated carboxylic acid ester polymer, and cyano group. Polymers, polymers obtained by addition polymerization of chlorine-containing polymers such as polyvinyl chloride and polyvinylidene chloride, polymers by polyaddition such as polyurethane, polyurea and polycarbonate, polymers by polycondensation such as polyester, polyamide and polyimide are used. It may be.

  The pressure-sensitive adhesive is not particularly limited as long as it is not substantially dissolved or decomposed by the electrolytic solution. For example, the main polymer is a rubber-based pressure-sensitive adhesive such as polyisobutylene, silicon rubber, nitrile rubber, or neoprene, or an acrylic resin. Thermoplastic resins such as thermoplastic resins such as vinyl resins, fluorine resins and polyamides, amino resins, phenolic resins, polyester resins, epoxy resins and isocyanate resins may be used. Good.

4). Flat spiral electrode group Next, a separator (not shown) made of a polyethylene microporous film was prepared, and then between the positive electrode plate 11 (x1, x2, x3) and the negative electrode plate 12 manufactured as described above. A separator was sandwiched between and wound in a spiral shape to produce a spiral electrode group. In this case, the positive electrode core 11a was laminated and wound so that the portion where the positive electrode core 11a was exposed was disposed on the outermost periphery of the spiral electrode group. Thereafter, the end of the exposed portion 11d of the outermost positive electrode core 11a of the obtained spiral electrode group and the exposed portion of the positive electrode core 11a on the inner peripheral side are passed over. 20 (y1, y2, y3, y4, y5 and z1, z2, z3, z4, z5) were stuck to prevent the spiral electrode group 10 from being unwound.

Next, press forming is performed by controlling the pressure of the press so that a predetermined pressure is applied from both sides of the spiral electrode group produced as described above, and as shown in FIG. A flat electrode group 10 was produced. The area of the pressed surface of the flat electrode group 10 after pressing was about 14.4 cm ² (3.2 cm × 4.5 cm). Further, the press surface of the flat electrode group 10 includes a boundary portion between the winding adhesive tape and the electrode plate core. Here, an anti-winding pressure-sensitive adhesive tape y2 having a thickness (T) of 30 μm and a base material made of PP is applied to a spiral electrode group formed using a positive electrode plate x1 having a thickness (t) of the positive electrode core 11a of 20 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group a1.

  Similarly, an anti-winding adhesive tape y3 having a thickness (T) of 27 μm and a base material made of PP is applied to a spiral electrode group formed using a positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press forming with a press pressure of 20 MPa was defined as an electrode group a2. In addition, an anti-winding adhesive tape y4 having a thickness (T) of 25 μm is attached to the spiral electrode group formed using the positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group a3. In addition, an anti-winding adhesive tape y5 having a thickness (T) of 20 μm and a base material made of PP is attached to a spiral electrode group formed using a positive electrode plate x3 having a thickness (t) of the positive electrode core 11a of 13 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group a4.

  Further, the winding adhesive electrode y1 having a thickness (T) of 40 μm is attached to the spiral electrode group formed using the positive electrode plate x1 having a thickness (t) of the positive electrode core 11a of 20 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group a5. In addition, an anti-winding adhesive tape y2 having a thickness (T) of 30 μm is attached to the spiral electrode group formed using the positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group a6. In addition, an anti-winding adhesive tape y2 having a thickness (T) of 30 μm is attached to the spiral electrode group formed using the positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 14 MPa was defined as an electrode group a7.

  In addition, a PPS base material 21 and an anti-winding adhesive tape z2 having a thickness (T) of 30 μm are attached to a spiral electrode group formed using a positive electrode plate x1 having a thickness (t) of the positive electrode core 11a of 20 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b1. Further, a PPS base material 21 and an anti-winding adhesive tape z3 having a thickness (T) of 27 μm are attached to a spiral electrode group formed using a positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b2.

  Further, a PPS base material 21 and an anti-winding adhesive tape z4 having a thickness (T) of 25 μm are attached to a spiral electrode group formed using a positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b3. In addition, a PPS base material 21 and an anti-winding adhesive tape z5 having a thickness (T) of 20 μm are attached to a spiral electrode group formed using a positive electrode plate x3 having a thickness (t) of the positive electrode core 11a of 13 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b4.

  Further, a PPS substrate 21 is attached to the spiral electrode group formed by using the positive electrode plate x1 having a thickness (t) of the positive electrode core 11a of 20 μm, and the anti-winding adhesive tape z1 having a thickness (T) of 40 μm is attached. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b5. Further, a PPS base material 21 and an anti-winding adhesive tape z2 having a thickness (T) of 30 μm are attached to a spiral electrode group formed using a positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 20 MPa was defined as an electrode group b6. Further, a PPS base material 21 and an anti-winding adhesive tape z2 having a thickness (T) of 30 μm are attached to a spiral electrode group formed using a positive electrode plate x2 having a thickness (t) of the positive electrode core 11a of 15 μm. The flat electrode group 10 formed by press molding at a press pressure of 14 MPa was defined as an electrode group b7.

Here, when producing the flat electrode groups a1 to a7 and b1 to b7 as described above, as shown in FIG. 3B, the exposed portion of the positive electrode core 11a and the adhesive tape 20 (y1 for winding) , Y2, y3, y4, y5 and z1, z2, z3, z4, z5), it is confirmed by visual observation whether or not the fracture portion X of the positive electrode core 11a has occurred, as shown in Table 1 below. Results were obtained.

  As is clear from the results in Table 1 above, the tape for the thickness t (μm) of the positive electrode core is used regardless of whether the material of the winding adhesive tape 20 is polypropylene (PP) or polyphenylene sulfide (PPS). In the electrode groups a1 to a4 and b1 to b4 having a thickness T (μm) ratio (T / t) of 1.80 or less, the positive electrode core 11a (positive electrode plate) is formed even if the press pressure is 20 MPa. x1 to x3) of the double-sided exposed portion 11c and the winding adhesive tape 20 (y2 to y5, z2 to z5) are caused to have a fracture portion X (see FIG. 3B) of the positive electrode core 11a. There wasn't.

On the other hand, in the electrode groups a7 and b7 formed at a press pressure of 2t, the ratio (T / t) of the tape thickness T (μm) to the thickness t (μm) of the positive electrode core is 2.00. The fracture portion X of the positive electrode core 11a did not occur at the boundary between the double-sided exposed portion 11c of the body 11a (positive electrode plate x2) and the adhesive tape 20 (y2, z2) for winding, but the press pressure was 20 MPa. In the case of the molded electrode groups a5 to a6 and b5 to b6, the fracture portion X (of the positive electrode core body 11a is formed at the boundary between the double-sided exposed portion 11c and the adhesive tape 20 for winding (y1, y2 and z1, z2). As shown in FIG. 3 (b).
Therefore, it is desirable that the ratio (T / t) of the tape thickness T (μm) of the anti-winding adhesive tape 20 to the thickness t (μm) of the positive electrode core body is desirably regulated to 1.80 or less. be able to.

5). Preparation of Nonaqueous Electrolyte Secondary Battery Next, a rectangular outer can made of aluminum having a height of 50 mm, a width of 34 mm, and a thickness of 5.2 mm was prepared. The material of the rectangular outer can is not limited to this, and for example, a material made of iron or an iron alloy may be used. Next, the electrode group a2 produced as described above (a pressure-bonded adhesive tape made of a positive electrode core 11a having a thickness of 15 μm and a PP base material having a thickness of 27 μm and press-molded at a press pressure of 20 MPa. ), A7 (which is pressure-molded at a pressure of 14 MPa using a pressure-sensitive adhesive tape made of a PP core having a thickness of 15 μm and a PP base material having a thickness of 30 μm). Inserted from each. Thereafter, the positive electrode current collecting lead 11f extending from the positive electrode plate 11 of each electrode group a2, a7 is welded to the outer can (also serving as the positive electrode terminal), and the negative electrode current collecting lead 12d extending from the negative electrode plate 12 is connected to the negative electrode. Welded to terminals.

After this, after placing an insulating spacer in the opening of the rectangular outer can, a sealing plate is placed on the opening of the rectangular outer can, and then laser light is irradiated to these joints to A sealing plate was joined to the plate. Next, after injecting a non-aqueous electrolyte from an injection port provided on the sealing plate, the injection port is sealed and sealed, and the non-aqueous electrolyte secondary battery A2 (electrode group) having a design capacity of 1000 mAh is sealed. a2) and A7 (using electrode group a7) were prepared. A negative electrode terminal is disposed at the center of the sealing plate via an insulating gasket, and a thin-film gas discharge valve integrally formed with the sealing plate is disposed on the sealing plate. As the non-aqueous electrolyte, a solute composed of lithium hexafluorophosphate (LiPF ₆ ) is mixed with a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 3: 7. A non-aqueous solution in which 1 mol / liter was dissolved was used.

In this case, as the solute dissolved in the solvent, in addition to LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCF ₃ (CF ₂ ) ₃ SO ₃ or the like may be used. As the mixed solvent, in addition to the above-mentioned mixed solvent of EC and EMC, an aprotic solvent having no ability to supply hydrogen ions, for example, propylene carbonate (PC), vinylene carbonate (VC), butylene carbonate (BC ), Γ-butyrolactone (GBL), etc., and these and dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), 1,2-diethoxyethane (DEE), 1,2-dimethoxyethane (DME), ethoxy A mixed solvent with a low boiling point solvent such as methoxyethane (EME) may be used.

6). Charge / Discharge Cycle Test Each of these batteries A2 and A7 was charged at a constant current at room temperature (about 25 ° C.) with a charging current of 1000 mA (1 It) until the battery voltage reached 4.2V, and a constant voltage of 4.2V. The battery was charged at a constant voltage until the current value reached 10 mA. Thereafter, a charge / discharge cycle of discharging at a discharge current of 1000 mA (1 It) until the battery voltage reached 2.75 V was repeated 500 times. At this time, when the battery thickness (mm) was measured and the battery capacity (mAh) was measured after 1 cycle, 100 cycles, 300 cycles, and 500 cycles, the results were obtained as shown in Table 2 below.

Further, when the battery thickness expansion (mm) and capacity retention rate (%) after 100 cycles, 300 cycles, and 500 cycles with respect to the first cycle are obtained based on the measurement of the battery thickness, as shown in Table 2 below. Results were obtained. In addition, when the change of the battery thickness after 1 cycle, 100 cycles, 300 cycles, and 500 cycles was shown on the graph, the result as shown in FIG. 4 was obtained. Moreover, when the change of the battery capacity after 1 cycle, 100 cycles, 300 cycles, and 500 cycles was shown in the graph, the results as shown in FIG. 5 were obtained.

  As is clear from the results of Table 2 and FIG. 4, when the battery A2 and the battery A7 are compared, the battery A2 has a battery thickness of 0.13 mm at the beginning of the charge / discharge cycle (one cycle) than the battery A7. As a result, the battery thickness swell is small in each cycle, and the battery thickness swell is reduced by 0.22 mm in the results after 500 cycles. It can be seen that the result is 6% higher than that.

  Here, the battery A2 is initially thinner than the battery A7 because the battery A2 has a molding pressure of 20 MPa when the flat electrode group a2 is formed, and the flat electrode group a7 of the battery A7 has a pressure of 14 MPa. This is because the thickness of the flat electrode group a2 can be reduced because the pressure is larger than the molding pressure. When the molding pressure for forming the flat electrode group a2 is increased, the cycle characteristics after 500 cycles are less swollen than the initial thickness difference, and the capacity retention rate is improved. This is because, by reducing the thickness of the flat electrode group a2, the distance between the positive electrode plate 11 and the negative electrode plate 12 is shortened and the reaction becomes uniform. It is thought that it was suppressed.

7). Examination of the outer shape of the adhesive tape for winding As described above, a result was obtained that the molding pressure when forming the flat electrode group should be as large as possible. Then, the external shape of the adhesive tape for winding prevention which can make the shaping | molding pressure at the time of forming a flat electrode group still larger was examined below.
Here, in the anti-winding adhesive tape 30 shown in FIG. 6A, the vicinity of both side surfaces of a rectangular tape having a thickness (T) of 30 μm is punched into a semicircular shape, and the outermost periphery of the flat electrode group The peripheral shape parallel to the boundary with the exposed portion of the positive electrode core 11a is formed to be a discontinuous arc side 31. Further, in the anti-winding adhesive tape 40 shown in FIG. 6B, the vicinity of both side surfaces of a rectangular tape having a thickness (T) of 30 μm is punched into a triangle, and the positive electrode on the outermost periphery of the flat electrode group Both peripheral shapes parallel to the boundary with the exposed portion of the core body 11a are formed to be discontinuous triangular sides 41.

  Further, in the anti-winding adhesive tape 50 shown in FIG. 6 (c), the vicinity of both side surfaces of a rectangular tape having a thickness (T) of 30 μm is punched into a square, and the positive electrode on the outermost periphery of the flat electrode group Both peripheral shapes parallel to the boundary with the exposed portion of the core body 11a are formed to be discontinuous square sides 41. Furthermore, in the anti-winding adhesive tape 60 shown in FIG. 6 (d), the vicinity of both sides of a rectangular tape having a thickness (T) of 30 μm is punched in a semicircular shape, and the outermost periphery of the flat electrode group Both peripheral shapes parallel to the boundary with the exposed portion of the positive electrode core 11a are formed so as to be discontinuous arc sides 61, and circular holes 62 are arranged in a row at the central portion of these peripheral portions. It is formed to become.

  Next, the above-mentioned pressure-sensitive adhesive tapes 20, 30, 40, 50, 60 for the outermost peripheral part of the spiral electrode group formed using the positive electrode plate x1 having the positive electrode core 11a having the thickness (t) of 20 μm described above. The flat electrode groups c1, c2, c3, c4, and c5 formed by pressure forming at a pressure of 27 MPa were prepared. In this case, one using the winding adhesive tape 20 is referred to as an electrode group c1, one using the winding adhesive tape 30 is referred to as an electrode group c2, and one using the winding adhesive tape 40 is referred to as an electrode group c3. The one using the winding adhesive tape 50 was designated as an electrode group c4, and the one using the winding adhesive tape 60 was designated as an electrode group c5.

And when producing flat electrode group c1, c2, c3, c4, c5, as shown in FIG.3 (b), the exposed part of the positive electrode core 11a and the adhesive tapes 20, 30, 40, 50 for winding are shown. , 60, it was confirmed by visual inspection whether or not the fracture portion X of the positive electrode core 11a occurred. The results shown in Table 3 below were obtained.

As is clear from the results of Table 3 above, in the flat electrode group c1, a rupture portion X of the positive electrode core body 11a is generated at the boundary with the winding adhesive tape 20 by pressing a press pressure of 27 MPa. On the other hand, in the flat electrode groups c2 to c5, the positive electrode core body 11a is broken at the boundary with the winding adhesive tape 30, 40, 50, 60 even if it is formed with a press pressure of 27 MPa. It can be seen that part X does not occur. This is presumably because the pressure at the time of pressing can be dispersed by applying a change such as a curve or a zigzag shape to the periphery (edge portions) of the adhesive tape for winding without making it linear. As a result, the possibility of breakage can be greatly reduced.
In addition, when the circular holes 62 are formed in one row at the center of both sides like the winding adhesive tape 60, the filling amount of the electrolyte is increased by the volume of the circular holes 62 row. It is desirable because it becomes possible.

  In the above-described embodiment, an example in which the present invention is applied to a non-aqueous electrolyte secondary battery has been described. However, the prismatic battery of the present invention is not limited to a non-aqueous electrolyte secondary battery, and is connected to one end. If the electrode group in which the positive electrode core exposed part is formed in the part and the negative electrode core exposed part is formed in the other end is a prismatic battery housed in a rectangular parallelepiped metal outer can, nickel-hydrogen storage It is apparent that the present invention can also be applied to an alkaline storage battery such as a nickel-cadmium storage battery, other storage batteries, and a primary battery such as a lithium battery. The prismatic battery of the present invention is not strictly limited to a rectangular parallelepiped shape in the shape of the outer can in which the electrode group is accommodated, and a battery in which the electrode group is accommodated in an outer can whose cross-sectional shape is oval. Is included.

In the above-described embodiment, the example in which lithium cobaltate is used as the positive electrode active material has been described. In addition to lithium cobaltate, lithium-containing transition metal composite oxides such as lithium nickelate and lithium manganate, or dioxide dioxide Metal oxides such as manganese (MnO ₂ ), vanadium pentoxide, niobium pentoxide, and metal chalcogenides such as titanium disulfide and molybdenum disulfide can also be used.

  In the embodiment described above, an example in which natural graphite is used as the negative electrode active material has been described. However, in addition to natural graphite, a carbon-based material capable of occluding and releasing lithium ions, such as carbon black, coke, and glass. Known carbon, carbon fiber, or a fired body thereof, artificial graphite, amorphous oxide, or the like may be used. Similarly, a silicon-based material that can occlude and release lithium ions, or a mixture of silicon and a carbon-based material may be used. Of course, the present invention can be applied even when lithium or an alloy mainly composed of lithium is used for the negative electrode.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the positive electrode plate at the time of applying this invention to a lithium ion battery, Fig.1 (a) is the top view, FIG.1 (b) shows the AA cross section of Fig.1 (a). It is sectional drawing shown. FIG. 2 is a diagram schematically illustrating a negative electrode plate when the present invention is applied to a lithium ion battery, FIG. 2A is a plan view thereof, and FIG. 2B is a cross-sectional view taken along line AA in FIG. It is sectional drawing shown. A spiral electrode group is prepared using the positive electrode plate shown in FIG. 1 and the negative electrode plate shown in FIG. 2, and an adhesive tape is attached to the surface of the spiral electrode group, and then pressure molding is performed on the flat spiral electrode group. 3 (a) is a perspective view thereof, FIG. 3 (b) is a plan view thereof, and FIG. 3 (c) is an outermost electrode plate core. It is sectional drawing which expands and shows typically the boundary part with an adhesive tape. It is a graph which shows the relationship of the battery thickness with respect to charging / discharging cycle. It is a graph which shows the relationship of the battery capacity with respect to a charging / discharging cycle. It is a top view which shows typically the various planar shape used for the adhesive tape of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Flat electrode group, 11 ... Positive electrode plate, 11a ... Positive electrode core, 11b ... Positive electrode mixture layer, 11c ... Double-sided core exposed part of positive electrode core, 11d ... Single-sided core exposed part of positive electrode core, 11e ... notch part, 11f ... positive electrode current collecting lead, 12 ... negative electrode plate, 12b ... negative electrode mixture layer, 12c ... double-sided core exposed part of negative electrode core body, 12d ... negative electrode current collecting lead, 20 ... adhesive tape for winding DESCRIPTION OF SYMBOLS 21 ... Base material, 22 ... Adhesive, 30 ... Adhesive tape for winding, 31 ... Arc side, 40 ... Adhesive tape for winding, 41 ... Triangular side, 50 ... Adhesive tape for winding, 51 ... Square side, 60 ... Adhesive tape for winding, 61 ... Arc side, 62 ... Round hole

Claims (4)

A positive electrode plate in which a positive electrode mixture layer containing a positive electrode active material is formed on a positive electrode core made of metal foil, and a negative electrode plate in which a negative electrode mixture layer containing a negative electrode active material is formed on a negative electrode core made of metal foil. A prismatic battery comprising spiral electrode groups wound so as to face each other via a separator,
While the outermost periphery of the spiral electrode group is formed with a core exposed portion where a mixture layer is not formed, and an adhesive tape is attached to the winding end portion of the core exposed portion,
The thickness (T) of the core so that the ratio (T / t) of the thickness (T) of the adhesive tape to the thickness t of the core has a relationship of 1.8 or less (T / t ≦ 1.8). And a thickness t of the adhesive tape are regulated.   The prismatic battery according to claim 1, wherein the adhesive tape is formed so that an end portion has a curved shape other than a straight line or a rectangular shape.   The prismatic battery according to claim 1 or 2, wherein the core is an aluminum foil and a positive electrode core. The rectangular battery according to any one of claims 1 to 3, wherein the spiral electrode group is pressure-molded so as to be flat after the adhesive tape is attached.

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