JP2007242519A - Square battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of preventing cut off of an electrode plate core in the boundary part between the outermost circumferential electrode plate core and adhesive tape even if the flat spiral electrode group is formed by applying high pressure by sticking a rolling stop tape in the outermost circumference of the flat spiral electrode group and optimizing the sticking position. <P>SOLUTION: In an electrode plate 11 arranged in the outermost circumference of the spiral electrode group 10, the inner circumferential side has a both surface coated part coated with an active material on both surfaces of a core 11a, the outer circumferential side continuing to the both surface coated part has one surface core exposed part 11c in which only the one surface of the core on the inner surface is coated with the active material and the core of the outer surface is exposed, the outermost circumferential side continuing to the one surface core exposed part 11c has a both surface core exposed part 11d where the both surfaces of the core are not coated with the active material, one end of a rolling stop tape is stuck to the both surface core exposed part 11d in a curvature part (a round part) of a flat spiral electrode group 10, and the other end of the rolling stop tape is stuck to the one surface core exposed part 11c in a curvature part (a round part) of the flat spiral electrode group 10. <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. A square battery comprising a flat spiral electrode group wound in a flat spiral shape so as to face the negative electrode plate with a separator interposed therebetween, and a winding stopper tape attached to the outermost periphery of the flat spiral electrode group About.

  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, for example, as shown in FIG. 7 (in addition, FIG. 7 is a cross-sectional view schematically showing a state in which a fracture portion is generated in the core body at the boundary portion with the winding tape by the applied pressure) There arises a problem that the electrode plate core 11a is cut at the boundary portion α between the outermost electrode plate core 11a (in FIG. 7, 11b indicates an active material layer) and the adhesive tape 14. This has increased the demand for higher capacity for this type of non-aqueous electrolyte secondary battery, and has increased the filling amount of the active material to meet this demand for higher capacity.

  For this reason, a thin metal foil (usually an aluminum foil as a positive electrode core and a copper foil as a negative electrode core) has come to be used with a thickness of 8 to 30 μm of the electrode plate core that holds the active material. is there. And in order to increase the filling amount of an active material as much as possible in the electrode plate core body which consists of such a thin metal foil, an active material will be filled with high density. 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 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, and as a battery This causes a problem that the function cannot be performed and charging / discharging cannot be performed.

  Therefore, the present invention has been made to solve the above problems, and affixing a winding tape on the outermost periphery of the flat spiral electrode group, and optimizing the adhering position with a high applied pressure. An object of the present invention is to provide a battery that does not cause the electrode plate core to be cut at the boundary between the outermost electrode plate core and the adhesive tape even if it is pressure-formed into a flat spiral electrode group. To do.

  The prismatic battery of the present invention includes 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 flat spiral electrode group wound in a flat spiral shape so that the negative electrode plate with the separator is opposed to each other via a separator, and a winding tape is attached to the outermost periphery of the flat spiral electrode group ing. And in order to achieve the said objective, in the electrode plate arrange | positioned at the outermost periphery of a spiral electrode group, the inner peripheral side is equipped with the double-sided application part by which the active material was apply | coated to both surfaces of the core, and it continues to this. The outer peripheral side is provided with a single-sided core exposed portion where the active material is applied only to one side of the inner surface of the core and the outer surface is exposed, and the outermost continuous side is continuous with both sides of the core not coated with the active material. While having a core exposed portion, one end of the winding tape is adhered to the double-sided core exposed portion by a curvature portion (R portion) of the flat spiral electrode group, and the other end of the winding tape Is attached to the single-sided core exposed portion at the curvature portion (R portion) of the flat spiral electrode group. Alternatively, one end of the winding tape is attached to the double-sided core exposed portion at the flat portion of the flat spiral electrode group, and the other end portion of the winding tape is a curved portion (R portion) of the flat spiral electrode group. ) Is attached to the single-side application part.

  Here, in the electrode group attached so that both the tip portions of the winding tape are positioned at the curvature portion (R portion) of the flat electrode group, the winding tape is fixed at both tip portions of the winding tape. There was no breakage in the core at the boundary with the tape. One end of the winding tape is attached to the single-sided core exposed part located at the curvature part (R part) of the flat electrode group, and the other end part is located at the flat part of the flat electrode group. Even in the electrode group adhered to the double-sided core exposed portion, no breakage occurred in the core at the boundary with the winding tape. This is because when both ends of the tape for winding are located at the curvature portion (R portion) of the flat electrode group, it is difficult for pressure to be directly applied to this portion. Conceivable. In addition, even if the other side of the winding tape is attached to the double-sided core exposed part located in the flat part of the flat electrode group, there is no active material layer under the double-sided core exposed part, so pressurization It is considered that sometimes the core body acts as a cushion and prevents the core body from being broken.

  The flat spiral electrode group works more effectively when the present invention is applied to a spiral electrode group wound in a spiral shape by pressure molding. In this case, if the applied pressure is less than 20 MPa, the thickness of the flat electrode group cannot be reduced, so that the distance between the positive electrode plate and the negative electrode plate cannot be shortened, and side reactions that cause deterioration are suppressed. The capacity maintenance rate is reduced. On the other hand, when the applied pressure is a large applied pressure exceeding 40 MPa, a broken portion is generated in the core body at the boundary with the winding tape. From these, it can be said that the pressure applied by pressure molding is desirably 20 MPa or more and 40 MPa or less. Furthermore, since aluminum foil has elasticity, it is desirable that the core of the electrode plate disposed on the outermost periphery of the wound electrode group is aluminum foil.

  In the prismatic battery of the present invention, since the attachment position of the winding tape to be attached to the outermost periphery of the flat electrode group is defined, the spiral electrode group is formed into a flat shape by press molding at a high pressure. Even so, it is possible to provide a battery in which the electrode plate core is not cut at the boundary 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 the state by which the electrode group was pressure-molded typically, FIG. 3 (a) is the sectional drawing, FIG.3 (b) is a cross section which expands and shows the A section of Fig.3 (a). FIG. In FIG. 3B, various adhesive tape attaching positions are collectively displayed, and any one of them is attached to the spiral electrode group as shown in FIG. 3A. FIG. 4 shows a spiral electrode group produced by preparing a spiral electrode group using the positive electrode plate shown in FIG. 1 and the negative electrode plate shown in FIG. 2, and sticking an adhesive tape on the surface of the spiral electrode group. It is a perspective view which shows typically the state by which it was press-molded. FIG. 5 is a graph showing the relationship of the battery thickness in the charged state with respect to the charge / discharge cycle. FIG. 6 is a graph showing the relationship of battery capacity to charge / discharge cycles.

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. The coating amount of this positive electrode mixture slurry is 450 g / m ² (one-side coating amount is 225 g / m ² ) on both surfaces of a positive electrode core (for example, made of aluminum foil or aluminum alloy foil and having a thickness of 15 μm). In this way, 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 11b 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 length x1 of the outer coating portion of the positive electrode core 11a (the positive electrode mixture layer 11b that becomes the outer side of the spiral when the positive electrode plate 11 is wound into a spiral electrode group) is 360 mm (x1 = 360 mm). The positive electrode mixture slurry was applied so that the length x2 of the non-application portions (core body exposed portions 11c and 11d) was 110 mm (x2 = 110 mm) to form the positive electrode mixture layer 11b. Further, the length y1 of the inner coating portion of the positive electrode core body 11a (the positive electrode mixture layer 11b that becomes the inner side of the spiral when the positive electrode plate 11 is wound into a spiral electrode group) is 425 mm (y1 = 425 mm), The positive electrode mixture slurry was applied so that the length y2 of the non-application portion (core exposed portion 11d) was 45 mm (y2 = 45 mm) to form the positive electrode mixture layer 11b.

  Further, when bent, it becomes the positive electrode lead 11f, and the positive electrode lead 11f extends from the upper end portion of the spiral electrode group 10 so that a substantially U-shaped cut is formed in the exposed portion 11d of the rear end portion of the positive electrode core body 11a. 11e was added. Thereby, in the positive electrode plate 11 located in the outermost peripheral part when it is set as the spiral electrode group, the double-sided core exposed part 11d (length) in which the positive electrode mixture layer 11b does not exist on the inner side and outer side of the winding end part. : Y2) is arranged, the positive electrode mixture layer 11b is present inside the inner side, and the single-sided core exposed portion 11c (length: x2-y2) where the positive electrode mixture layer 11b is not present is arranged outside. Will be.

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 so that the solid 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 is coated on both sides of a negative electrode core (for example, made of copper foil and having a thickness of 10 μm) 12a so that the coating amount is 250 g / m ² (the coated amount on one side is 125 g / m ² ). The negative electrode mixture layer 12b was formed by applying by a doctor boud method.

In this case, the negative electrode mixture slurry is applied so that the non-application portion 12c of the negative electrode mixture slurry having a predetermined width is formed on both surfaces of the negative electrode core body 12a that is the winding start portion when the spiral electrode group is formed. Thus, the negative electrode mixture layer 12b was formed. Next, the negative electrode mixture layer 12b was dried and then rolled with a roller press so that the filling density of the mixture was 1.5 g / cm ³ . Then, after vacuum-drying for 2 hours and cut into strips having a predetermined size, the negative electrode lead 12d was welded to the non-coated portion 12c to produce the negative electrode plate 12.

3. Anti-winding adhesive tape Adhesive tape with a rubber adhesive applied as an adhesive to a base material made of polypropylene (PP) has a predetermined size (in this example, a thickness of 30 μm (in this case, the thickness is adhesive) (Including the thickness of the material), the width was 7 mm, and the height (length) was 45 mm).

  In addition to the polypropylene (PP) described above, the base material of the anti-winding adhesive tape 14 is polyphenylene sulfide (PPS), polyethylene, polyethylene terephthalate, polytetrafluoroethylene, unsaturated carboxylic acid ester polymer, cyano group-containing polymer. 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. 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, after preparing a separator 13 made of a polyethylene microporous film, the separator 13 is sandwiched between the positive electrode plate 11 and the negative electrode plate 12 manufactured as described above, and the spiral wound A spiral electrode group was produced by turning. In this case, the positive electrode plate 11 is laminated and wound so as to be disposed on the outermost periphery of the spiral electrode group, and the inside of the winding end end portion of the positive electrode plate 11 located on the outermost periphery portion of the spiral electrode group and A double-sided core exposed portion 11d (length: y2) in which the positive electrode mixture layer 11b does not exist is arranged on the outside, the positive electrode mixture layer 11b exists on the inner side of the inner side, and the positive electrode mixture layer 11b on the outer side. It was wound so that the single-sided core exposed portion 11c (length: x2-y2) in which there was not present was disposed.

  Thereafter, the above-described winding adhesive tape 14 is prepared, and the double-sided core exposed portion 11d of the positive electrode plate 11 disposed on the outermost periphery of the spiral electrode group obtained (both inside and outside in the winding direction). The portion where the positive electrode mixture layer 11b does not exist) and the single-sided core exposed portion 11c on the inner circumference side (the portion where only the outer side in the winding direction does not include the positive electrode mixture layer 11b) are passed. Adhesive tapes 14 were attached to prevent the spiral electrode group from unwinding. 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 the cross-sectional shape is long as shown in FIGS. Circular (flat) electrode groups 10 (a, b, c, d, e, f, g) were produced. At this time, the front end portion X of the positive electrode core body 11a of the positive electrode plate 11 disposed on the outermost periphery of the flat electrode group 10 is positioned at the curvature portion (R portion) (within the dotted line in FIG. 3B). Press molded.

In addition, the area of the pressing surface of the flat electrode group 10 after pressing was about 14.4 cm ² (3.2 cm × 4.5 cm). Here, 20 MPa so that one front end Y of the winding adhesive tape 14 is located at the single-sided core exposed portion 11c of the R portion and the other front end Z is located at the double-sided core exposed portion 11d of the R portion. The flat electrode group 10 formed by press molding with the applied pressure was defined as an electrode group a. Similarly, one end Y of the winding adhesive tape 14 is located at the single-sided core exposed part 11c of the R part, and the other end Z is located at the flat double-sided core exposed part 11d at the end of the R part. The electrode group b was press-molded with a pressure of 20 MPa. Also, one tip Y of the winding adhesive tape 14 is positioned at the R-side single-sided core exposed portion 11c, and the other tip Z is positioned at the flat double-sided core-exposed portion 11d at the tip of the R portion. Thus, what was press-molded with a pressure of 40 MPa was defined as an electrode group c.

  Further, one tip Y of the winding adhesive tape 14 is located at the R-side single-sided core exposed portion 11c, and the other tip Z is located at the flat double-sided core-exposed portion 11d at the tip of the R portion. Thus, what was press-molded with a pressure of 67 MPa was defined as an electrode group d. Further, one end Y of the winding adhesive tape 14 is positioned at the flat single-sided core exposed portion 11c at the tip of the R portion, and the other end Z is positioned at the double-sided core exposed portion 11d of the R portion. The electrode group e was press-molded with a pressure of 20 MPa. Further, one end Y of the winding adhesive tape 14 is positioned at the flat single-sided core exposed portion 11c at the tip of the R portion, and the other double-sided core exposed portion at the other end Z is flat at the tip of the R portion. The electrode group f was press-molded with a pressure of 20 MPa so as to be positioned at 11d. Further, one end Y of the winding adhesive tape 14 is positioned at the flat single-sided core exposed portion 11c at the tip of the R portion, and the other double-sided core exposed portion at the other end Z is flat at the tip of the R portion. The electrode group g was formed by press molding at a pressure of 14 MPa so as to be positioned at 11d.

Here, when producing the flat electrode groups a to g as described above, for example, as shown in FIG. 7, the boundary portions (Y end, Z end) between the positive electrode core body 11 a and the winding adhesive tape 14. The results shown in Table 1 below were obtained when it was visually confirmed whether or not the fracture portion α of the positive electrode core 11a occurred.

  As is apparent from the results in Table 1 above, the electrode group adhered so that the leading end portions Y and Z of the winding adhesive tape 14 are positioned on the R portions 11 c and 11 d of the flat electrode group 10. In a, the fracture portion α (see FIG. 7) did not occur in the positive electrode core 11a at the boundary with the positive electrode core 11a at both the Y end and the Z end of the winding adhesive tape 14. Further, the leading end Y of the winding adhesive tape 14 is positioned on the R portion 11c of the flat electrode group 10 (the positive electrode mixture layer 11b is present inside the spiral), and the other leading end Z is flat. In the electrode groups b and c attached so as to be positioned on the flat 11d of the electrode group 10 (both the inside and outside of the spiral have no positive electrode mixture layer 11b), the boundary with the positive electrode core 11a The broken portion α (see FIG. 7) did not occur in the positive electrode core 11a.

  However, in the electrode group d that is press-molded with a pressing force for forming the flat electrode group 10 of 67 MPa, the leading end Y of the anti-adhesive tape 14 is the R portion 11c of the flat electrode group 10 ( The inner side of the spiral is located on the positive electrode mixture layer 11b), and the other tip Z is flat 11d of the flat electrode group 10 (the positive electrode mixture layer 11b does not exist on both the inner side and the outer side of the spiral). ) Even if it was attached so as to be positioned above, a fracture portion α (see FIG. 7) was produced at the boundary between the tip Z of the adhesive tape 14 and the positive electrode core 11a.

  On the other hand, the front end Y of the winding adhesive tape 14 is positioned on the flat 11c at the tip of the R portion of the flat electrode group 10 (the positive electrode mixture layer 11b exists inside the spiral), and the other end In the electrode groups e and f attached so that the portion Z is located on the flat 11d of the flat electrode group 10 (the positive electrode mixture layer 11b does not exist on both the inside and outside of the spiral), the adhesive tape 14 As a result, a rupture portion α (see FIG. 7) is generated at the boundary portion between the front end portion Y and the positive electrode core 11a. However, in the electrode group g that is press-molded with a pressure applied to the flat electrode group 10 of 14 MPa, the tip Y of the anti-adhesive tape 14 is the tip of the R portion of the flat electrode group 10. Even if the other tip Z is located on the flat 11c and is attached so that the other tip Z is located on the flat 11d of the flat electrode group 10, the tip Y of the adhesive tape 14 and the positive electrode core 11a The fracture portion α (see FIG. 7) did not occur at the boundary portion.

  For these reasons, one end portion (Y end) of the winding tape is adhered to the single-sided core exposed portion 11c of the curvature portion (R portion) of the flat spiral electrode group, and the other end portion (Z end). Also, it can be said that it is desirable that the flat spiral electrode group is adhered to the double-sided core exposed portion 11d at the curvature portion (R portion). Alternatively, one end (Y end) of the winding tape is attached to the single-sided core exposed portion 11c of the curved portion (R portion) of the flat spiral electrode group, and the other end (Z end) is a flat spiral. It can be said that it is desirable to stick to the flat double-sided core exposed part 11d at the tip of the curvature part (R part) of the electrode group.

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 a produced as described above (a pressure-bonding adhesive tape was used and pressed at a pressing pressure of 20 MPa), g (a winding pressure-sensitive adhesive tape was used and the pressing pressure was 14 MPa) The molded ones) were respectively inserted from the openings of the rectangular outer cans. Thereafter, the positive electrode current collecting lead 11f extending from the positive electrode plate 11 of each electrode group a, g 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 A (electrode group) having a design capacity of 1000 mAh is sealed. a) and G (using electrode group g) were prepared. In addition, the negative electrode terminal is arrange | positioned through the insulating gasket in the center part of the sealing board, and the gas exhaust valve is arrange | positioned in this negative electrode terminal. As the non-aqueous electrolyte, 1 mol / liter of a solute composed of lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a solvent in which ethylene carbonate (EC) and ethyl carbonate (EMC) are mixed at an equal volume ratio. A non-aqueous solution 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). Charging / discharging cycle test Each of these batteries A and G 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 4.2 V, and a constant voltage of 4.2 V 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 600 times. At this time, when the battery thickness (mm) was measured and the battery capacity (mAr) 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. 5 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 result as shown in FIG. 6 was obtained.

  As is apparent from the results of Table 2 and FIG. 4, when the battery A and the battery G are compared, the battery A has a battery thickness of 0.15 mm at the beginning of the charge / discharge cycle (one cycle) than the battery G. As a result, the battery thickness swell is small in each cycle, and the battery thickness swell is reduced by 0.27 mm in the result after 500 cycles. It can be seen that the result is higher by 7%.

  Here, the initial thickness of the battery A is thinner than that of the battery G. The battery A has a molding pressure of 20 MPa when forming the flat electrode group a, and 14 MPa of the flat electrode group g of the battery G. This is because the thickness of the flat electrode group a can be reduced because the pressure is larger than the molding pressure. When the molding pressure for forming the flat electrode group a 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 a, 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.

  In the above-described embodiment, the example in which the present invention is applied to the non-aqueous electrolyte secondary battery has been described. However, the prismatic battery of the present invention is not limited to the non-aqueous electrolyte secondary battery, and is arranged on the outermost periphery. If it is a square battery in which a flat spiral electrode group with a winding tape attached is housed in a rectangular metal outer can, it can be used for alkaline storage batteries such as nickel-hydrogen storage and nickel-cadmium storage batteries, and other storage batteries. It is clear that it can be applied. 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. FIG. 3A is a cross-sectional view thereof, and FIG. 3B is an enlarged cross-sectional view of a portion A of FIG. 3A. 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. It is a perspective view which shows typically the state performed. It is a graph which shows the relationship of the battery thickness in the charging condition with respect to a charging / discharging cycle. It is a graph which shows the relationship of the battery capacity with respect to a charging / discharging cycle. It is sectional drawing which shows typically the state which produced the fracture | rupture part in the core of the boundary part with the tape for winding with the applied pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Flat electrode group, 11 ... Positive electrode plate, 11a ... Positive electrode core body, 11b ... Positive electrode mixture layer, 11c ... Single-sided core body exposed part, 11d ... Double-sided core body exposed part, 11e ... Notch part, 11f ... Positive electrode collection Electric leads, 12 ... Negative electrode plate, 12b ... Negative electrode mixture layer, 12d ... Negative electrode current collecting lead, 14 ... Anti-winding adhesive tape

Claims (5)

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; Is a prismatic battery comprising a flat spiral electrode group wound in a flat spiral shape so as to face each other with a separator interposed therebetween, and a winding tape attached to the outermost periphery of the flat spiral electrode group. ,
In the electrode plate disposed on the outermost periphery of the spiral electrode group, the inner peripheral side includes a double-sided coating portion in which an active material is applied to both surfaces of the core body, and the outer peripheral side continuous thereto is one side of the inner surface of the core body. The outer surface is provided with a single-sided core exposed portion where the active material is applied only on the outer surface and the core is exposed, and the outermost peripheral side continuous therewith has a double-sided core exposed portion where the active material is not applied on both sides of the core. With
One end portion of the winding tape is attached to the double-sided core exposed portion at a curvature portion (R portion) of a flat spiral electrode group, and the other end portion of the winding tape is a flat spiral electrode group. A prismatic battery characterized in that it is adhered to the single-sided core exposed portion at a curvature portion (R portion). 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; Is a prismatic battery comprising a flat spiral electrode group wound in a flat spiral shape so as to face each other with a separator interposed therebetween, and a winding tape attached to the outermost periphery of the flat spiral electrode group. ,
In the electrode plate disposed on the outermost periphery of the spiral electrode group, the inner peripheral side includes a double-sided coating portion in which an active material is applied to both surfaces of the core body, and the outer peripheral side continuous thereto is one side of the inner surface of the core body. The outer surface is provided with a single-sided core exposed portion where the active material is applied only on the outer surface and the core is exposed, and the outermost peripheral side continuous therewith has a double-sided core exposed portion where the active material is not applied on both sides of the core. With
One end portion of the winding tape is a flat portion of a flat spiral electrode group and is attached to the double-sided core exposed portion, and the other end portion of the winding tape is a curvature portion (R of the flat spiral electrode group). Part) is attached to the single-side application part.   The said flat spiral electrode group is a spirally wound electrode group formed by pressure molding after the winding tape is adhered to the spiral electrode group wound in a spiral shape. 2. The square battery according to 2.   The square battery according to claim 3, wherein the pressure applied by the pressure molding is 20 MPa or more and 40 MPa or less. The prismatic battery according to any one of claims 1 to 4, wherein the core of the electrode plate disposed on the outermost periphery of the spiral electrode group is an aluminum foil.

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