JP2013161773A - Pole plate and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat wound electrode battery capable of ensuring the reliability of a welded portion between a power collection tab and a lead while preventing a breakage in a power collection part during welding and ensuring sufficient number of laminates of the power collection part enabling charging/discharging of a large current.SOLUTION: A sash-like pole plate received in a battery being wound therein includes: a sash-like electrode part with the surface formed with an electrode activation material layer; and plural power collection portions with the surface formed with no electrode activation material layer, which is formed to protrude from the edge in the width direction from the electrode. When an electrode is formed in a flat shape being wound, a cut is formed in the power collection part in a portion where the electrode group is folded.

Description

  The present invention relates to an electrode plate for a secondary battery and a secondary battery.

  In recent years, interest in environmental issues and clean energy has been increasing, and development of batteries and storage batteries mounted on electric vehicles and hybrid electric vehicles has been promoted. Such a battery is required to have a discharge performance at a large current.

  As a battery that exhibits such performance, a battery having a wound electrode body in which a strip-shaped electrode plate is wound (hereinafter referred to as a wound electrode battery) is known. In the battery, usually, a wound electrode body is enclosed with an electrolyte in a case, and power is taken out from the wound electrode body through leads connected to the positive electrode plate and the negative electrode plate.

  As such a wound-type electrode battery, in Patent Document 1, a strip-shaped electrode portion in which an uncoated portion where a mixture containing a power generation element such as an electrode active material is not applied is formed is spaced along the longitudinal direction. It is disclosed that a plurality of convex portions (current collecting portions) arranged side by side are formed, and when the electrode portion is wound, the plurality of convex portions are stacked to form a current collecting tab. Here, the positive electrode plate and the negative electrode plate are overlapped and wound so that the positive electrode current collector portion and the negative electrode current collector portion are alternately arranged along the longitudinal direction of the electrode portion. A lead for connecting to the outside is connected to the current collecting tab by welding. The electrode body in the wound electrode battery is formed in a flat shape, and in order to obtain a flat shape, the electrode portion and the current collecting tab are bent with a large curvature.

US Patent Application Publication No. 2009/0239133

  In the flat wound electrode battery having the above configuration, when a lead is welded to each current collecting tab, considerable force is applied due to the repulsive force of the bent portion of the current collecting tab and the volume of the current collecting tab itself. It is necessary to weld while applying pressure. If the pressurization is not sufficient, welding of the current collecting tab and the lead becomes uneven, and the reliability of the welded portion cannot be maintained.

  In the wound electrode battery, the area of the wound electrode portion is increased by increasing the length of the band-shaped electrode portion, and the current density flowing per unit area is reduced, thereby enabling charging and discharging of a large current. At this time, as the length of the electrode portion increases, the number of current collecting portions increases, so that the number of stacked current collecting portions when the current collecting tab is formed increases. When the number of stacked current collecting portions in the current collecting tab is increased in this way, the repulsive force of the bent portion of the current collecting tab and the volume of the current collecting tab itself further increase. Therefore, it is necessary to increase the pressure during lead welding. Arise.

  However, when a large pressing force is applied when the lead is welded to the current collecting tab as described above, there is a problem that the current collecting portion is easily broken.

  In view of the above, the present invention provides a flat wound-type electrode battery that has a sufficient number of stacked current collecting portions that enable charging and discharging of a large current, and is reliable in the welded portion between the current collecting tab and the lead. It is an object of the present invention to provide an electrode plate and a wound electrode battery that can secure the property and suppress the occurrence of breakage of the current collector during welding.

  The present invention is a strip-shaped electrode plate wound and accommodated in a battery, the strip-shaped electrode portion having an electrode active material layer formed on the surface, and no electrode active material layer formed on the surface, A plurality of current collectors formed so as to protrude from the end in the width direction of the electrode part, and when configuring an electrode body formed in a flat shape in a state of winding the electrode part, The electrode plate for a secondary battery, wherein a cut portion is formed in the current collecting portion at a portion where the electrode body is bent.

  The present invention also includes an electrode body that is formed into a flat shape by winding the belt-like positive electrode plate and the negative electrode plate, which are the above-described electrode plates, through a belt-like separator, and the electrode body and the electrolytic solution are housed therein. A positive electrode lead that is connected to a positive electrode current collecting tab formed by laminating the plurality of current collector portions of the positive electrode plate, and the plurality of current collector portions of the negative electrode plate. A negative electrode lead connected to a negative electrode current collecting tab formed by laminating and projecting to the outside of the case, the positive electrode current collecting tab facing each of both surfaces of the positive electrode lead, and both surfaces of the negative electrode lead It is also a secondary battery in which the negative electrode current collecting tab faces each other.

  According to the present invention, in the flat wound electrode battery, since the bent portion does not exist in the current collecting tab due to the formation of the cut portion, when the lead is welded to the current collecting tab, the current collecting tab is bent. No repulsive force due to the part is generated. Therefore, it is possible to weld the current collecting tab and the lead without causing breakage in the current collecting portion while ensuring uniformity in welding of the current collecting tab and the lead. As a result, it is not necessary to reduce the number of stacked current collecting portions in the current collecting tab, so that a large current can be charged and discharged in the battery.

  In addition, since the number of welds included on one side of the current collecting tab is halved by the formation of the cut portion, it is possible to obtain stable welding strength.

  Furthermore, wrinkles that can occur when the electrode active material layer is rolled can be suppressed by the cut portion.

Schematic which shows the inside of the case of the wound electrode battery which concerns on one Embodiment Schematic which expand | deploys and shows a part of electrode body of the wound electrode battery which concerns on one Embodiment. The top view which shows a part of positive electrode plate contained in the wound electrode battery which concerns on Example 1. FIG. The top view which shows a part of positive electrode plate contained in the wound electrode battery which concerns on Example 2. FIG. The top view which shows a part of positive electrode plate contained in the wound electrode battery which concerns on Example 3. FIG. The top view which shows a part of positive electrode plate contained in the wound electrode battery which concerns on Example 4. FIG. The top view which shows a part of positive electrode plate contained in the wound electrode battery which concerns on the comparative example 1

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to this.

  FIG. 1 is a schematic perspective view showing the inside of a case of a wound electrode battery. As shown in FIG. 1, the wound electrode battery includes a flat pouch-type case 10 and a flat-shaped wound electrode body 14 housed in the case 10 together with an electrolyte solution 12. The wound electrode body 14 has positive electrode current collecting tabs 16A and 16B and negative electrode current collecting tabs 18A and 18B that protrude to one side in the winding axis direction (that is, an end in the width direction of the electrode plate). Each of the positive electrode current collecting tabs 16A and 16B and the negative electrode current collecting tabs 18A and 18B is formed by laminating a plurality of current collecting portions which are uncoated portions.

  One side of the positive electrode lead 20 having the resin film 23 on a part of the surface is joined to the inside of the positive electrode current collecting tab 16A (that is, the winding shaft side) at a portion other than the resin film, and inside the positive electrode current collecting tab 16B The back surface of the positive electrode lead 20 is also joined at a portion other than the resin film. One side of the negative electrode lead 22 having the resin film 23 on a part of the surface is joined to the inner side of the negative electrode current collecting tab 18A, and the back surface of the negative electrode lead 22 is joined to the inner side of the negative electrode current collecting tab 18B. Similarly, it is joined at portions other than the resin film. Thus, current collecting tabs are bonded to both surfaces of each lead. That is, the lead is sandwiched between separate current collecting tabs from both sides and joined to each current collecting tab. In the conventional electrode, a bent portion is present in the current collecting tab. However, in the present invention, since each of the current collecting portions is separated by providing a cutting portion, there is no bent portion in the current collecting tab. The outer end face of the lead (that is, the end face on the side not facing the winding shaft) faces the cut portion and does not face the current collecting tab. In FIG. 1, the outer end face of the lead protrudes from the cut portion to the outside of the current collecting tab. By providing the cutting portion in this manner, the number of welds included on one side of the current collecting tab is halved compared to a conventional battery, so that stable welding strength can be obtained.

  Each resin film 23 is heat-sealed to the case 10. As a result, the positive electrode lead 20 and the negative electrode lead 22 penetrate the case 10 in an airtight manner and protrude to the outside, and are electrically insulated from the case 10. The electric power generated in the wound electrode body 14 is taken out through the positive electrode current collecting tabs 16A and 16B, the negative electrode current collecting tabs 18A and 18B, the positive electrode lead 20 and the negative electrode lead 22.

  The wound electrode body 14 is formed by laminating and winding a belt-like positive electrode plate 30 and a belt-like negative electrode plate 32 and a separator 33 interposed between the two electrode plates as shown in FIG. Is formed. The positive current collecting tabs 16A and 16B are formed by stacking a plurality of positive current collecting portions 26A and 26B, which are a plurality of convex regions protruding from the electrode portions of the positive electrode plate 30, and the negative current collecting tabs 18A and 18B are The negative electrode current collectors 28A and 28B of the negative electrode plate 32 are stacked to form a plurality of layers. Here, an electrode part is the main body of each strip | belt-shaped electrode plate in which the electrode active material layer was formed in the surface. The positive electrode current collectors 26A and 26B of the positive electrode plate 30 are separated by a cutting part 27, and this cutting part is located in a portion that becomes a bent part when the positive electrode plate 30 is wound into a flat shape. Similarly, the negative electrode current collectors 28A and 28B of the negative electrode plate 32 are separated by a cutting portion 29, and this cutting portion is located in a portion that becomes a bent portion when the negative electrode plate 32 is wound into a flat shape. .

  The cutting part is a vertically long notch that starts from the current collector end in the electrode plate width direction (the upper side of the current collector in FIG. 2) and extends substantially parallel to the electrode plate width direction. This cutting part is formed so as to divide one current collecting part in the conventional electrode plate. As a result, in the present invention, between the two current collecting parts (between 26A and 26B or 28A and 28B). The cutting part is located between the two.

  The length of the cut part in the electrode plate width direction (the length in the vertical direction in FIG. 2) is the length from the current collector end part in the electrode plate width direction to the boundary line between the current collector part and the electrode part. It is preferable that Although the cutting portion can achieve the effect of the present invention even if it enters the electrode portion to some extent, it is preferable that the cutting portion has a small amount of entry so as not to reduce the area of the electrode active material layer. Further, the cutting portion does not need to reach the boundary line between the current collecting portion and the electrode portion. As shown in FIG. 1, the cutting portion is formed at a size that allows the outer end surface of the lead to protrude from the cutting portion to the outside of the current collecting tab, thereby achieving the effect of the present invention. be able to.

  The width of the cut portion in the length direction of the electrode plate (the length in the horizontal direction in FIG. 2) is not particularly limited as long as the effect of the present invention can be achieved. However, the width is preferably equal to or greater than the thickness of the lead so that the outer end face of the lead can protrude from the cut portion to the outside of the current collecting tab as shown in FIG. 1 when welding the current collecting tab and the lead. Moreover, it is preferable that it is below the thickness of the flat electrode body finally formed.

  In FIG. 2, the cutting portions are provided so that the current collecting portions arranged on both sides of the cutting portion have an equal width (the length in the horizontal direction in FIG. 2), but the present invention is not limited to this. The widths of the current collectors on both sides may be different.

  The cutting part has a vertically long shape extending substantially parallel to the electrode plate width direction. Specifically, as shown in FIG. 3, it may be a vertically long rectangle in the electrode plate width direction. Moreover, as shown in FIG. 4, the shape provided with the circular punch hole in the lower end of the said rectangle may be sufficient. This shape is effective in preventing the electrode plate from breaking or cracking from the corner of the cut portion. As shown in FIG. 5, the above-described shapes may be used alternately. Further, as shown in FIG. 6, the cut portion may be a trapezoid that is vertically long in the plate width direction, the short side of the trapezoid is located on the electrode active material layer side, and the long side is in the plate width direction. Located at the end of the current collector. This shape is advantageous in terms of productivity because it is easy to form a cut portion.

  By setting the area of the cut portion large, wrinkles that may occur when the electrode active material layer is rolled can be suppressed. Since the thickness is different between the electrode active material layer that is the coated part and the current collector part that is the uncoated part, rolling will cause wrinkles near the boundary line between the electrode active material layer and the current collector part. Is likely to occur. The cutting portion has an effect of suppressing the occurrence of such wrinkles.

  The positive electrode plate 30 is formed of a conductive metal foil, for example, a strip-shaped aluminum sheet having a width of 150 mm and a length of 4 m, and the positive electrode active material layer 40 is formed on both surfaces of the positive electrode plate. The positive electrode active material layer 40 is formed in a strip shape over the entire length of the positive electrode plate. A plurality of convex portions are formed at one end portion (upper side in FIG. 2) of the positive electrode plate in the width direction, and no electrode active material is coated on the surface thereof. This is the positive electrode current collector 26A and the positive electrode current collector 26B. A cutting portion 27 is located between the positive electrode current collector 26A and the positive electrode current collector 26B. The positive electrode current collector 26A and the positive electrode current collector 26B are a set of current collectors, and such a set of current collectors collects current from the negative electrode plate when the positive electrode plate is stacked with the negative electrode plate and wound. A plurality of electrode plates are formed at intervals so that only the current collectors of the positive electrode plate are stacked without contacting each other. One set of positive electrode current collectors and another set of positive electrode current collectors adjacent thereto are formed at intervals so as to overlap each other when the electrode body is formed by winding.

  The negative electrode plate 32 is formed of a conductive metal foil, for example, a strip-shaped copper sheet having a width of 150 mm and a length of 4 m, and the negative electrode active material layers 42 are formed on both surfaces of the negative electrode plate. The negative electrode active material layer 42 is formed in a strip shape over the entire length of the negative electrode plate. A plurality of convex portions are formed at one end portion (upper side in FIG. 2) of the negative electrode plate in the width direction, and no electrode active material is coated on the surface thereof. This is the negative electrode current collector 28A and the negative electrode current collector 28B. A cutting portion 29 is located between the negative electrode current collector 28A and the negative electrode current collector 28B. The negative electrode current collector 28A and the negative electrode current collector 28B are a set of current collectors. When such a set of current collectors is stacked with the negative electrode plate stacked on the positive electrode plate, the current collector of the positive electrode plate is collected. A plurality of electrodes are formed at intervals such that only the current collector of the negative electrode plate is laminated without contacting the electrode. One set of negative electrode current collectors and another set of negative electrode current collectors adjacent thereto are formed at intervals so as to overlap each other when the electrode body is formed by winding.

  The separator 33 is a band-shaped member having a width of 155 mm and a length of 4.4 m, and is disposed between the positive electrode plate 30 and the negative electrode plate 32 in a state of being in contact with the electrode active material layers of the positive electrode plate 30 and the negative electrode plate 32. Has been.

  The positive electrode plate 30 and the negative electrode plate 32 are overlapped so that the current collecting portion formed of the uncoated portion protrudes in the same direction from the upper side of the separator, and the flat wound electrode body 14 is formed. At that time, in the positive electrode plate 30, a plurality of positive electrode current collectors 26 </ b> A are stacked to form a positive electrode current collector tab 16 </ b> A integral with the electrode body 14, and a plurality of positive electrode current collectors 26 </ b> B are stacked to be integral with the electrode body 14. The positive electrode current collecting tab 16B is formed. Further, in the negative electrode plate 32, a plurality of negative electrode current collectors 28A are stacked to form a negative electrode current collector tab 18A that is integral with the electrode body 14, and a plurality of negative electrode current collectors 28B are stacked to be integral with the electrode body 14. A negative electrode current collecting tab 18B is formed.

  The electrode body 14 has a flat shape in which the outer peripheral shape extends in a direction perpendicular to the winding axis. Moreover, the electrode body 14 has a flat hollow portion partitioned on the innermost peripheral surface of the electrode plate. The electrode body 14 may be an electrode body formed by winding the positive electrode plate 30 and the negative electrode plate 32 in a flat shape via the separator 33, or the positive electrode plate and the negative electrode plate are wound via the separator. It may be an electrode body that is later deformed into a flat shape.

  As shown in FIG. 1, the electrode body 14 is housed in a pouch-type case 10, and a positive electrode lead 20 having a resin film 23 is joined to the positive electrode current collecting tabs 16 </ b> A and 16 </ b> B, and the negative electrode current collecting tabs 18 </ b> A, A negative electrode lead 22 having a resin film 23 is joined to 18B. Joining is performed by welding, for example. Each resin film 23 is heat-sealed to the case 10. As a result, the positive electrode lead 20 and the negative electrode lead 22 penetrate the case 10 in an airtight manner and protrude to the outside, and are electrically insulated from the case 10. The case 10 may be formed of aluminum, iron, stainless steel, or the like, and may be a tank-like container that can seal the inside and is stable with respect to an electrolytic solution and a potential.

  Next, each component of the wound electrode battery of this embodiment will be described.

<< Pouch type case >>
Case 10 is a pouch-type case and is made of an aluminum laminate sheet. The aluminum laminate sheet has a resin layer laminated on the surface of an aluminum foil. Examples of the resin material constituting the resin layer include polyethylene, polypropylene, polyethylene terephthalate, and nylon. These resin layers may be only one layer or may be a laminate of two or more layers. As a specific configuration, there may be mentioned a configuration in which polyethylene terephthalate, nylon, polypropylene, and aluminum are stacked.

<< Cathode >>
The positive electrode plate 30 includes a positive electrode current collector and a positive electrode active material layer provided on one or both surfaces of the positive electrode current collector. The positive electrode active material layer is composed of, for example, a positive electrode active material, a binder, and a conductive additive.

  The positive electrode current collector is a sheet-like member having conductivity, and is typically composed of a metal foil. As a material constituting the positive electrode current collector, metals such as aluminum and aluminum alloys can be suitably used. Since the positive electrode current collector is formed by extending the positive electrode current collector, it is made of the same material as the positive electrode current collector.

Examples of the positive electrode active material include manganese dioxide (MnO ₂ ), lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂ ), and lithium cobalt composite oxide. objects (e.g. Li _x CoO _2), lithium nickel cobalt composite oxide (e.g., _{LiNi 1-y Co y O 2} ), lithium manganese cobalt composite oxides (e.g., _{Li x Mn y Co 1-y} O 2), spinel type lithium Manganese nickel composite oxide (Li _x Mn _{2 -y} Ni _y O ₄ ), oxides such as lithium phosphorus oxide having an olivine structure (Li _x FePO ₄ ), and some of the metal elements constituting the above oxides Substances substituted with other metal elements can be used. In the above chemical formula, “x” and “y” may each be a value in the range of 0-1.

  Preferred positive electrode active materials include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, spinel type lithium manganese nickel composite oxide, lithium manganese cobalt composite oxide, lithium phosphoric acid Iron. These have a charge / discharge potential of, for example, 3.0 V or more and 5.0 V or less with respect to the potential of metallic lithium.

  As the binder, resin materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), carboxymethylcellulose (CMC), fluororubber, and styrene butadiene rubber (SBR) can be used.

  As the conductive assistant, carbon materials such as acetylene black (AB), carbon black, and graphite can be used.

<< Negative electrode plate >>
The negative electrode plate 32 includes a negative electrode current collector and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector. A negative electrode active material layer is comprised from a negative electrode active material, a binder, and a conductive support agent, for example.

  The negative electrode current collector is also a conductive sheet-like member, and is typically composed of a metal foil. As a material constituting the negative electrode current collector, metals such as nickel, nickel alloy, copper, copper alloy, aluminum, and aluminum alloy can be suitably used. Since the negative electrode current collector is formed by extending the negative electrode current collector, it is made of the same material as the negative electrode current collector.

Examples of the negative electrode active material include lithium metal, lithium alloy, lithium titanium composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), a carbon material that can occlude and release lithium ions, and a material that can form an alloy with lithium (so-called alloy-based active material). Substance). A typical carbon material is graphite. Examples of the alloy-based active material include tin, tin alloy, silicon, and silicon alloy. From the viewpoint of charge / discharge efficiency and cycle life, a carbon material or a lithium titanium composite oxide can be preferably used.

  As the binder and the conductive assistant, substances usable for those in the positive electrode plate can be similarly used.

  When the negative electrode active material layer includes a negative electrode active material having a noble potential of 1.0 V or more with respect to the potential of metallic lithium, the material constituting the negative electrode current collector is preferably aluminum or an aluminum alloy.

<< Separator >>
As the separator, a porous film, a nonwoven fabric or the like can be used. As a porous film, the porous film formed from polyethylene or a polypropylene, or the porous film which laminated | stacked these can be illustrated. As a nonwoven fabric, the nonwoven fabric formed from the cellulose or polyvinyl alcohol (PVA) can be illustrated.

<< Non-aqueous electrolyte >>
The electrode body 14 composed of the positive electrode plate 30, the negative electrode plate 32 and the separator 33 is impregnated with an electrolytic solution. Examples of the electrolytic solution include a liquid non-aqueous electrolyte containing an electrolyte and an organic solvent.

Examples of the electrolyte include lithium salts such as lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), and lithium tetrafluoroborate (LiBF ₄ ). From the viewpoint of chemical stability and high dielectric constant, it is preferable to use lithium hexafluorophosphate (LiPF ₆ ) as the main electrolyte. The “main electrolyte” means an electrolyte that is contained most in a molar ratio. The electrolyte can be dissolved in an organic solvent at a concentration of, for example, 0.5 to 2.0 mol / L to form an electrolytic solution.

  As the organic solvent, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC) can be used. Also, chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC), cyclic ethers such as tetrahydrofuran (THF) and 2 methyltetrahydrofuran (2MeTHF), chains such as dimethoxyethane (DME) An ether, acetonitrile (AN), sulfolane (SL) and the like can also be used. These organic solvents can be used alone or in the form of a mixture of two or more.

<< Lead >>
The leads 20 and 22 are members extending from the space or sealing surface inside the battery to the outside of the case, and are terminals that are electrically connected to the current collecting tab and draw current from the inside of the battery to the outside. The connection between the lead and the current collecting tab is performed by superimposing the lead on one surface of the current collecting tab and connecting them together by welding or the like. A resin film 23 is disposed at a portion where the lead is sandwiched between the sealing surfaces of the case as an insulating seal portion for an electrode that covers the outer surface of the lead. As a material constituting the lead, metals such as aluminum, aluminum alloy, nickel, nickel alloy, copper, copper alloy, and stainless steel can be used. As a material constituting the resin film, resins such as polypropylene and polyethylene can be used. It is preferable to perform a surface treatment such as etching on the bonding portion between the resin film and the metal.

<< Production method >>
Next, a method for manufacturing the flat wound electrode battery of the present invention will be described.

  In the wound electrode battery of the present invention, first, after manufacturing the positive electrode plate 30 and the negative electrode plate 32, the wound electrode body 14 is formed by winding the positive electrode plate 30 and the negative electrode plate 32 through a separator, After the positive electrode lead 20 and the negative electrode lead 22 are welded to the positive electrode current collecting tabs 16A and 16B and the negative electrode current collecting tabs 18A and 18B of the electrode body 14, they can be manufactured by sealing together with the electrolyte 12 in the case 10. .

  Regarding the production of the electrode plate, first, the positive electrode plate 30 is produced by forming the positive electrode active material layers 40 on both surfaces of the belt-like aluminum sheet. In order to form the positive electrode active material layer 40, a paste-like mixture containing the positive electrode active material is applied to the surface of the band-shaped aluminum sheet and dried. At this time, application is performed while providing an uncoated portion in consideration of the width of the current collecting portion in the electrode plate width direction, and then the density of the electrode active material layer is improved by rolling. The rolling conditions can be appropriately set in consideration of the density of the desired electrode active material layer.

  Next, a plurality of convex current collecting portions are formed on an uncoated portion formed continuously at the longitudinal end portion of the positive electrode plate. Here, no cutting part is provided, and the set of current collecting parts described above is continuously formed without being separated into two at this point. A plurality of sets of current collectors are formed so that the vicinity of the center in the longitudinal direction of the substrate is positioned at the flat bent portion when the flat wound electrode body 14 is formed. Next, a cutting portion is provided by cutting out a partial region of the current collecting portion to be located in the bent portion into a predetermined shape. However, the cutting part can be formed at the same time as the current collecting part by using a punching die.

  On the other hand, the negative electrode plate 32 having the negative electrode active material layers 42 on both sides of the strip-shaped copper sheet is also manufactured by the same method as that for the positive electrode plate. After that, the positive electrode plate 30 is wound around a reel using a winding device to form a roll, and similarly, the negative electrode plate 32 is wound around another reel to form a roll. The separator 33 is also a roll.

  Next, the positive electrode plate 30, the negative electrode plate 32, and the separator 33 are pulled out, stacked, and wound around a winding core. At that time, by rotating the winding core, the positive electrode plate 30 and the negative electrode plate 32 are overlapped so that the current collecting portions 26A, 26B, 28A, 28B protrude in the same direction from the end portions in the width direction of the separator 33. And wound on the winding core. After the electrode body 14 is formed by winding a predetermined length, the positive electrode plate 30, the negative electrode plate 32, and the separator 33 are cut. Subsequently, the electrode body is extracted from the winding core, and the wound electrode body is pressed into a flat shape. Thereby, the flat wound electrode body 14 is obtained.

  Then, the positive electrode lead 20 is joined to the plurality of positive electrode current collectors 26A and the plurality of positive electrode current collectors 26B protruding to one side of the electrode body 14, and the plurality of negative electrode current collectors 28A and The negative electrode lead 22 is joined to the plurality of negative electrode current collectors 28B. At this time, the lower end of the lead is disposed so as not to contact the electrode active material layer and the separator, the positive electrode lead 20 is sandwiched between the positive electrode current collector 26A and the positive electrode current collector 26B, and the negative electrode current collector 28A. The negative electrode lead 22 is sandwiched between the negative electrode current collector 28B and welding is performed. As a method for joining the lead and the current collector, electric welding such as spot welding and seam welding, or welding methods such as ultrasonic welding can be used. By this welding, the positive lead 20 is joined to the positive current collecting tab 16 and the positive current collecting tab 16B, and the negative lead 22 is joined to the negative current collecting tab 18A and the negative current collecting tab 18B.

  Next, the electrode body 14 to which the positive electrode lead 20 and the negative electrode lead 22 are joined is placed in the case 10, heat sealed except for a part for injection, and then electrolyzed in the case 10 from the part that is not heat sealed. Liquid 12 is injected. And after repeating pressure reduction and atmospheric pressure release, the flat-shaped wound electrode battery is manufactured by heat-sealing the part which was not heat-sealed.

  In the above, the manufacturing method in the case of forming a cutting part in advance on the electrode plate before winding has been described. However, it is also possible to form the cut portion in the current collecting portion located in the bent portion after forming the electrode body including the electrode plate not provided with the cut portion. However, it is difficult in the process to form the cut portion for the wound electrode body, and there is a possibility that the separator and the electrode plate may be damaged during the formation. Therefore, it is preferable to form a cutting portion in advance on the electrode plate before winding.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

(Comparative Example 1)
In the positive electrode plate manufacturing method described above, 100 parts by weight of LiNi _5/6 Co _1/6 O ₂ is used as the positive electrode active material, 2 parts by weight of acetylene black is used as the conductive additive, and 2 parts of polyvinylidene fluoride is used as the binder. An appropriate amount of N-methyl-2-pyrrolidone was added so that the solid content concentration was about 50%, and the mixture was stirred and kneaded with a double-arm kneader to prepare a positive electrode mixture paste.

Next, this positive electrode mixture paste was applied to the surface of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, while an uncoated part having a width of 13 mm was left at the widthwise end of the current collector, and the coating weight on one side thereof Was applied with a comma coater so as to be 5 mg / cm ^2, and was applied to a reel while drying at 110 ° C.

  The thickness was adjusted by rolling so that the thickness of the obtained positive electrode plate was 46 μm. Next, a convex current collector was formed on the uncoated part. At this time, it was formed such that the position of the start point of the convex current collector portion was in accordance with Equation 1 and the end point was in accordance with Equation 2. The positive electrode plate A shown in FIG. 7 was produced by the above. Here, no cutting part is provided.

In the negative electrode plate manufacturing method described above, 100 parts by weight of Li ₄ Ti ₅ O ₁₂ is used as the negative electrode active material, 9 parts by weight of acetylene black is used as the conductive additive, and 6 parts by weight of polyvinylidene fluoride is used as the binder. An appropriate amount of N-methyl-2-pyrrolidone was added so that the partial concentration was about 50%, and the mixture was stirred and kneaded with a double-arm kneader to prepare a negative electrode mixture paste.

Next, this negative electrode mixture paste was applied to the surface of a negative electrode current collector made of an aluminum foil having a thickness of 15 μm, while an uncoated portion having a width of 11 mm was left at the widthwise end of the current collector, and the coating weight on one side thereof Was applied with a comma coater so as to be 6.4 mg / cm ^2, and was applied to a reel while drying at 110 ° C.

  The thickness was adjusted by rolling so that the thickness of the obtained negative electrode plate was 72 μm. Next, a convex current collector was formed on the uncoated part. At this time, it was formed so that the position of the start point of the convex current collector was in accordance with Equation 3 and the end point was in accordance with Equation 4. The negative electrode plate a was produced by the above. Here, no cutting part is provided.

Formula 1 T _sn = 125 × n−88 n: Number of laps Formula 2 T _en = 124 × n + 21
Formula 3 t _sn = 123 × n−63
Formula 4 t _en = 124 × n + 24
The obtained positive electrode plate A and negative electrode plate a were wound together with a separator made of polyethylene having a thickness of 20 μm to produce a wound electrode body A. A lead made of an aluminum plate having a thickness of 0.15 mm and a width of 30 mm provided with a resin film for lamination welding on the positive electrode current collectors 26A and 26B and the negative electrode current collectors 28A and 28B thus formed is ultrasonically applied. Connected by welding. The number of stacked current collecting portions in the formed positive electrode current collecting tab was 32, and the number of stacked current collecting portions in the negative electrode current collecting tab was 33. At this time, welding was successful by increasing the pressurizing conditions in the ultrasonic welding machine, but some breakage occurred in the current collecting portion at the uppermost portion of the current collecting tab (that is, the side not in contact with the lead).

Example 1
After forming the convex current collectors on the positive electrode plate and the negative electrode plate, a vertically elongated strip as shown in FIG. 3 is provided at the center of each convex current collector (that is, the portion corresponding to the bent part after winding). A positive electrode plate and a negative electrode plate were produced in the same manner as in Comparative Example 1 except that a rectangular cutout (width in the longitudinal direction of the electrode plate: about 1 mm) was provided. Using the obtained positive electrode plate and negative electrode plate, a wound electrode body was produced in the same manner as in Comparative Example 1. The lead was connected by ultrasonic welding so that the lead was sandwiched between the cutout portions of the wound electrode body. At this time, welding was successful under a pressure condition lower than that of Comparative Example 1, and the current collector did not break.

(Example 2)
After forming the convex current collector on the positive electrode plate and the negative electrode plate, a vertically elongated rectangular notch (pole) is formed at the center of each convex current collector (that is, the portion corresponding to the bent portion after winding). The width in the longitudinal direction of the plate is about 1 mm), and a punch hole with a diameter of 3 mm is formed at the tip portion thereof, and a notch portion having a shape as shown in FIG. Thus, a positive electrode plate and a negative electrode plate were produced. Using the obtained positive electrode plate and negative electrode plate, a wound electrode body was produced in the same manner as in Comparative Example 1. The lead was connected by ultrasonic welding so that the lead was sandwiched between the cutout portions of the wound electrode body. At this time, welding was successful under the same conditions as in Example 1, and the current collector did not break.

(Example 3)
As shown in FIG. 5, after forming the convex current collecting portions on the positive electrode plate and the negative electrode plate, the center of each convex current collecting portion (that is, the portion corresponding to the bent portion after winding) is shown in Example 1. A positive electrode plate and a negative electrode plate were produced in the same manner as in Example 1 except that the same notch portions and the same notch portions as in Example 2 were alternately provided. Using the obtained positive electrode plate and negative electrode plate, a wound electrode body was produced in the same manner as in Comparative Example 1. The lead was connected by ultrasonic welding so that the lead was sandwiched between the cutout portions of the wound electrode body. At this time, welding was successful under the same conditions as in Example 1, and the current collector did not break.

Example 4
After forming the convex current collecting portions on the positive electrode plate and the negative electrode plate, an electrode active material layer as shown in FIG. 6 is provided at the center of each convex current collecting portion (that is, the portion corresponding to the bent portion after winding). A positive electrode plate and a negative electrode plate were produced in the same manner as in Example 1 except that a trapezoidal notch portion having a short side on the side was provided. Using the obtained positive electrode plate and negative electrode plate, a wound electrode body was produced in the same manner as in Comparative Example 1. The lead was connected by ultrasonic welding so that the lead was sandwiched between the cutout portions of the wound electrode body. At this time, welding was successful under the same conditions as in Example 1, and the current collector did not break.

  The present invention can be advantageously applied to a secondary battery for the energy field, for example, a secondary battery for in-vehicle use or general home use.

DESCRIPTION OF SYMBOLS 10 Case 12 Electrolyte 14 Winding type electrode body 16A, 16B Positive electrode current collection tab 18A, 18B Negative electrode current collection tab 20 Positive electrode lead 22 Negative electrode lead 23 Resin film 26A, 26B Positive electrode current collection part 27, 29 Cutting part 28A, 28B Negative electrode Current collector 30 Positive electrode plate 32 Negative electrode plate 33 Separator

Claims (4)

A strip-shaped electrode plate wound and housed in a battery,
A strip-shaped electrode part having an electrode active material layer formed on the surface;
An electrode active material layer is not formed on the surface, and has a plurality of current collectors formed so as to protrude from the end in the width direction of the electrode part,
When the electrode body is formed in a flat shape in a state where the electrode portion is wound, a cutting portion is formed in the current collecting portion in a portion where the electrode group is bent. Polar plate.   The shape of the cut portion is a vertically long rectangle in the width direction of the electrode plate, or a shape having a circular punch hole at the lower end of the rectangle, and these are formed alone or in combination. The electrode plate for a secondary battery according to claim 1.   The electrode plate for a secondary battery according to claim 1, wherein a shape of the cut portion is a trapezoid having a short side on the electrode active material layer side. An electrode body formed into a flat shape by winding the belt-like positive electrode plate and the negative electrode plate, which are the electrode plates according to any one of claims 1 to 3, via a belt-like separator,
A case in which the electrode body and the electrolytic solution are housed, and
A positive electrode lead connected to a positive electrode current collecting tab formed by laminating the plurality of current collecting portions of the positive electrode plate, and protruding to the outside of the case;
A negative electrode lead connected to a negative electrode current collecting tab formed by laminating the plurality of current collecting portions of the negative electrode plate, and protruding outside the case, and
The secondary battery, wherein the positive electrode current collecting tab faces each of both surfaces of the positive electrode lead, and the negative electrode current collecting tab faces each of both surfaces of the negative electrode lead.

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