JP4736525B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a nonaqueous electrolyte secondary battery, for example, a polymer lithium secondary battery in which a wound electrode body is produced on a flat surface and sealed with an aluminum laminate exterior material.

  In recent years, portable electronic devices such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistants) have become widespread, and lithium ion batteries having advantages such as high voltage, high energy density, and light weight are widely used as power sources.

  Furthermore, as a countermeasure against liquid leakage that becomes a problem when using a liquid electrolyte, for example, an electrolyte that uses a gel polymer film in which a polymer is impregnated with a nonaqueous electrolyte, or an all-solid electrolyte A polymer lithium secondary battery using the above has been put into practical use.

  As described in Patent Document 1 below, the conventional polymer lithium secondary battery has a wound electrode body formed into a flat shape, and the wound electrode body is formed in a recess formed by stamping and forming an aluminum laminate exterior material. Is inserted, the raw part of the exterior material is folded back to the upper part of the concave part, and the outer peripheral part of the concave part is heat-sealed. The wound electrode body has a single-sided current collector exposed portion on the inner peripheral side and the outer peripheral side, and covers the positive electrode and the negative electrode lead disposed on the current collector exposed portion at the positive electrode and negative electrode end portions with an insulating material, An insulating material is provided on the electrodes facing the positive and negative electrode leads. By providing the insulating material, an electrical short circuit due to contact between the positive electrode and the negative electrode due to secular change or application of a pressing force from the outside is prevented.

  Here, a belt-like positive electrode and a belt-like negative electrode are laminated with an electrolyte and a separator interposed therebetween, wound in the longitudinal direction, and a positive electrode and a negative electrode lead are respectively led out from the positive electrode and the negative electrode. Called the body.

JP 2001-266946 A

  However, in the conventional polymer lithium secondary battery, depending on the electrode winding start and winding end positions, the battery thickness varies, and the battery capacity cannot be obtained efficiently, and the volume energy density is low. There was a problem of lowering.

  Therefore, an object of the present invention is to define the winding start position and winding end position of the electrode, thereby suppressing variation in battery thickness and obtaining battery capacity efficiently, so that the volume energy density is high. The object is to provide a water electrolyte secondary battery.

In order to solve the above-described problems, the present invention provides:
The positive electrode and the negative electrode are wound with a separator and an electrolyte interposed therebetween, and have a flat wound electrode body in which the positive electrode is positioned on the outermost periphery,
The cross-sectional shape in the thickness direction of the wound electrode body is divided into two in the thickness direction to define one side and the other side,
The cross-sectional shape is
A first arc portion, a second arc portion, a side connecting a folding start point which is one end of the first arc portion and a folding end point which is one end of the second arc portion, and the first arc portion The other end of the second arcuate part and the side connecting the return start point that is the other end of the second arc portion,
The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided so that at least one surface of the positive electrode current collector is exposed;
The negative electrode comprises a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is provided so that at least one surface of the negative electrode current collector is exposed;
A positive electrode lead and a negative electrode lead are provided in parallel on a flat region other than the first arc portion and the second arc portion of the wound electrode body, and on the outermost peripheral side of the wound electrode body,
The positive electrode lead and the negative electrode lead, and the positive electrode active material layer application end and the negative electrode active material layer application end on the winding start side are located on one side,
The winding active side positive electrode active material layer application end is located within the range sandwiched between the first arc portion side edge of the positive electrode lead and the second arc portion side edge of the negative electrode lead,
The non-aqueous electrolyte secondary battery has a positive electrode active material layer application end and a negative electrode active material layer application end on the winding end side located in the first arc portion.

This invention
The positive electrode and the negative electrode are wound with a separator and an electrolyte interposed therebetween, and have a flat wound electrode body in which the positive electrode is positioned on the outermost periphery,
The cross-sectional shape in the thickness direction of the wound electrode body is divided into two in the thickness direction to define one side and the other side,
The cross-sectional shape is
A first arc portion, a second arc portion, a side connecting a folding start point which is one end of the first arc portion and a folding end point which is one end of the second arc portion, and the first arc portion The other end of the second arcuate part and the side connecting the return start point that is the other end of the second arc portion,
The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided so that at least one surface of the positive electrode current collector is exposed;
The negative electrode comprises a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is provided so that at least one surface of the negative electrode current collector is exposed;
A positive electrode lead and a negative electrode lead are provided in parallel on a flat region other than the first arc portion and the second arc portion of the wound electrode body , and on the outermost peripheral side of the wound electrode body,
The positive electrode active material layer application end and the negative electrode active material layer application end on the winding start side are located on one side, the positive electrode lead and the negative electrode lead are located on the other side,
The positive electrode active material layer application end on the winding start side is located within a range sandwiched between the edge on the first arc portion side of the positive electrode lead and the folding start point of the second arc portion,
Winding a positive electrode active material layer non-aqueous electrolyte secondary battery that is located within the first arcuate portion in the coating end portion and the end-side anode active material layer coating end wound end side.

  According to the present invention, by defining the winding start position and winding end position of the electrode, it is possible to increase the volume energy density by suppressing variations in battery thickness and efficiently obtaining the battery capacity. .

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of a wound electrode body 10 according to an embodiment of the present invention. As shown in FIG. 1, the wound electrode body 10 includes a positive electrode in which a positive electrode active material layer 3 is provided on both surfaces of a positive electrode current collector 1, and a negative electrode active material layer 5 in both surfaces of a negative electrode current collector 4. The negative electrode is wound many times through the separator 9.

  The positive electrode active material layer 3 is provided so that one surface of the positive electrode current collector 1 is exposed. The negative electrode active material layer 5 is provided so that one surface of the negative electrode current collector 4 is exposed. The positive electrode is located on the outermost periphery of the wound electrode body 10. A negative electrode lead 7 is provided at the end of the negative electrode. A positive electrode lead 2 is provided at a predetermined position of the positive electrode. The positive electrode lead 2 and the negative electrode lead 7 are provided in parallel on the outermost peripheral side of the wound electrode body 10. By providing the positive electrode lead 2 and the negative electrode lead 7 in parallel with the outermost periphery, a space for bending the lead can be eliminated, and the volume energy density can be increased.

  The cross-sectional shape of the wound electrode body 10 includes a first arc portion 26a, a second arc portion 26d, sides, and sides. The first arc portion 26a is a range connected from the folding start point 26b of the winding end electrode to the folding end point 26c. The second arc portion 26d is a range connected from the folding start point 26e of the winding start side electrode to the folding end point 26f. One side is a range connected by a folding start point 26b of the first arc portion 26a and a folding end point 26f of the second arc portion 26d. The other side is a range connected by the folding end point 26c of the first arc portion 26a and the folding start point 26e of the second arc portion 26d.

  The wound electrode body 10 is divided into two in the thickness direction by the center line 25, and one side and the other side are defined. The positive electrode active material layer application end portion 21 and the negative electrode active material layer application end portion 22 on the winding start side, and the positive electrode lead 2 and the negative electrode lead 7 are located on one side. The positive electrode active material layer application end portion 21 on the winding start side is within a range sandwiched between the edge on the first arc portion 26 a side of the positive electrode lead 2 and the edge on the second arc portion 26 d side of the negative electrode lead 7. To position. The positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are located in the first arc portion 26a.

  Here, the positive electrode active material layer application end portion refers to a boundary portion between the portion where the positive electrode current collector 1 is exposed and the positive electrode active material layer 3. The negative electrode active material layer application end portion refers to a boundary portion between the portion where the negative electrode current collector 4 is exposed and the negative electrode active material layer 5.

  On the positive electrode, the insulating material 6 is provided at a position facing the end of the negative electrode. The insulating material 6 has a function of preventing an electrical short circuit. The positive electrode current collector 1 is extended from the winding end side positive electrode active material layer application end portion 23. The negative electrode lead 7 is joined to the end portion of the negative electrode by, for example, spot or ultrasonic welding. The positive electrode lead 2 is joined to the outermost periphery of the wound electrode body 10 in parallel with the negative electrode lead 7 by, for example, spot welding or ultrasonic welding.

  The positive electrode lead 2 and the negative electrode lead 7 may not be metal as long as they are electrochemically and chemically stable and can conduct electricity. Examples of the positive electrode lead 2 include aluminum (Al). Examples of the negative electrode lead 7 include copper (Cu) and nickel (Ni).

  When the positive electrode active material layer coating end portion 21 on the winding start side overlaps the negative electrode lead 7, the battery thickness on the positive electrode lead 2 increases as the thickness of the positive electrode overlapped with the positive electrode lead 2 increases. Variation occurs and the volume energy density is low.

  Therefore, as shown in FIG. 1, the positive electrode active material layer coating end portion 21 on the winding start side is the edge on the first arc portion 26 a side of the positive electrode lead 2 and the edge on the second arc portion 26 d side of the negative electrode lead 7. The positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are positioned in the first arc portion 26a. With this configuration, variation in battery thickness can be suppressed, battery capacity can be obtained efficiently, and volume energy density can be increased.

[Positive electrode]
The positive electrode includes a strip-shaped positive electrode current collector 1 and a positive electrode active material layer 3 formed on both surfaces of the positive electrode current collector 1. The positive electrode current collector 1 is a net-like material made of, for example, metal foil or metal. Examples of the metal include stainless steel, copper, nickel, and aluminum, and aluminum is particularly preferable. The positive electrode active material layer 3 is composed of, for example, a positive electrode active material, a conductive agent, and a binder (binder).

[Positive electrode active material]
As the positive electrode active material, a known positive electrode material such as a transition metal oxide that can be doped / undoped with lithium ions can be used. Moreover, a metal oxide, a metal sulfide, or a specific polymer can be used according to the kind of battery.

Specifically, as the positive electrode active material, for example, a metal sulfide or oxide containing no lithium such as TiS ₂ , MoS ₂ , V ₂ O ₅ can be used. Further, lithium complex oxidation mainly composed of Li _X MO ₂ (wherein M represents one or more transition metals, X varies depending on the charge / discharge state of the battery, and is generally 0.05 ≦ X ≦ 1.10.) A thing etc. can be used. As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable. Specific examples of the lithium composite oxide include LiCoO ₂ , LiNiO ₂ , Li _X Ni _Y Co _1-Y O ₂ (where X and Y vary depending on the charge / discharge state of the battery, and generally 0 <X ≦ 1. 2, 0.7 <Y <1.02, and a lithium manganese composite oxide having a spinel structure. The lithium composite oxide is a positive electrode active material that can generate a high voltage and is excellent in energy density. The positive electrode 1 can be used by mixing a plurality of these positive electrode active materials.

  As the binder, a known binder usually used for this type of battery can be used. Examples of the binder include fluorine resins such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTEF).

  Moreover, as the positive electrode active material layer 3, you may make it contain a electrically conductive agent as needed. The conductive agent is not particularly limited as long as an appropriate amount can be mixed with the active material to impart conductivity, and for example, carbon powder such as graphite and carbon black can be used.

  As a method of forming the positive electrode active material layer 3, for example, a powdered positive electrode active material is mixed with a solvent together with a binder (binder), and if necessary, a dispersion paint is formed by a ball mill, a sand mill, a biaxial kneader or the like. After that, a method of coating on the positive electrode current collector and drying is preferably used. The type of the solvent used is not particularly limited as long as it is inactive to the positive electrode current collector 1 and can dissolve the binder. For example, commonly used inorganic and organic solvents such as N-methyl-2-pyrrolidone Any of these can be used.

  The coating apparatus is not particularly limited, and examples thereof include slide coating, extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, micro gravure, rod coater, blade coater and the like. The drying method is not particularly limited, and examples thereof include standing drying, a blast dryer, a hot air dryer, an infrared heater, and a far infrared heater.

[Negative electrode]
The negative electrode includes a strip-shaped negative electrode current collector 4 and negative electrode active material layers 5 formed on both surfaces of the negative electrode current collector 4. The negative electrode current collector 4 is a network made of metal foil or metal, for example. Examples of the metal include stainless steel, copper, nickel, and aluminum. Copper is particularly preferable. The negative electrode active material layer 5 is composed of, for example, a negative electrode active material, a conductive agent, and a binder (binder).

  As the negative electrode active material, any material can be used as long as it is electrochemically doped and dedoped with lithium at a potential of lithium metal of 2.0 V or less.

  A carbon material is preferable as a negative electrode active material because it can occlude and release lithium, for example, and has very little change in crystal structure accompanying charge / discharge and can provide good cycle characteristics. Examples of such a carbon material include graphite, non-graphitizable carbon, and graphitizable carbon. Graphite is particularly preferable because it has a high electrochemical equivalent and can provide a high energy density.

The graphite preferably has, for example, a true density of 2.10 g / cm ³ or more and a (002) plane spacing of less than 0.340 nm, a true density of 2.18 g / cm ³ or more, and a (002) plane. It is more preferable if the surface spacing is not less than 0.335 nm and not more than 0.337 nm. As the non-graphitizable carbon, for example, the (002) plane spacing is 0.37 nm or more, the true density is less than 1.70 g / cm ³ , and differential thermal analysis (DTA) in air. In which no exothermic peak is exhibited at 700 ° C. or higher.

  Specifically, for example, non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compounds A carbonaceous material such as a fired body (a product obtained by firing and carbonizing a phenol resin, a furan resin or the like at an appropriate temperature), carbon fiber, activated carbon, or carbon black can be used.

  Further, a metal capable of forming an alloy with lithium, an alloy thereof, or an intermetallic compound can also be used. Oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, tin oxide, etc. that dope and undope lithium with a relatively low potential, and other nitrides can be used as well.

  As the binder, for example, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyethylene, or the like can be used.

  As the conductive agent, for example, carbon powder such as graphite and carbon black can be used.

  The manufacturing method of the above-mentioned negative electrode and positive electrode is not ask | required. A method of adding a known binder, conductive material, etc. to the material and adding a solvent, a method of adding a known binder, etc. to the material and applying it by heating, a material alone or a conductive material, Although the method of mixing with an adhesive agent and performing a process such as molding to form a molded body electrode is adopted, it is not limited thereto.

  For example, an electrode can be produced by mixing with a binder, an organic solvent, etc. to form a slurry, and applying and drying on a current collector. Alternatively, regardless of the presence or absence of the binder, it is also possible to produce a strong electrode by pressure molding while applying heat to the active material.

[Electrolytes]
As the electrolyte, a gel electrolyte obtained by impregnating an organic polymer with a nonaqueous solvent and an electrolyte salt, and a solid electrolyte containing an electrolyte salt can be suitably used.

[Gel electrolyte]
As the gel electrolyte matrix, various polymers can be used as long as they absorb the non-aqueous electrolyte and gel. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and crosslinked products, and poly (acrylonitrile) Etc. can be used. As the gel electrolyte, it is desirable to use a fluorine-based polymer particularly from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

[Solid electrolyte]
As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. As the polymer compound, an ether polymer such as poly (ethylene oxide) or a crosslinked product thereof, a poly (methacrylate) ester compound, an acrylate compound, or the like can be used alone or copolymerized or mixed in the molecule.

Any electrolyte salt used in the electrolyte can be used as long as it is used in this type of battery. Illustrative examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, LiBr and the like.

[Separator]
As the separator 9, for example, a polyolefin microporous film such as polyethylene or polypropylene can be suitably used.

[Insulating material]
The protective tape as the insulating material 6 can be an insulating material that is thin and thin and has sufficient strength. For example, a protective tape made of PET (polyethylene terephthalate) is preferably used.

  The wound electrode body 10 is manufactured in a flat shape, for example, and the winding is performed so that the positive electrode lead 2 and the negative electrode lead 7 are exposed from the outer material 34 in a recess formed by stamping and forming an outer material 34 made of, for example, aluminum laminate. The electrode body 10 is inserted, the unprocessed portion of the exterior material 34 is folded back to the upper part of the concave portion, and the outer peripheral portion of the concave portion is heat-sealed to seal the wound electrode body 10, and the polymer according to one embodiment of the present invention A lithium secondary battery is produced.

  FIG. 2 is a schematic diagram showing the configuration of a polymer lithium secondary battery according to an embodiment of the present invention. As shown in detail in FIG. 3, this battery has a wound electrode body 10 housed in a recess formed in a laminate film as an exterior material 34, and the periphery of the battery element 10 is, for example, heat-sealed. It is sealed by. From the wound electrode body 10, the positive electrode lead 2 connected to the positive electrode and the negative electrode lead 7 connected to the negative electrode are led out, and the positive electrode lead 2 and the negative electrode lead 7 are improved in adhesion to the exterior material 34. Therefore, sealants 33a and 33b, which are resin pieces, are covered.

  In one embodiment of the present invention, the polymer lithium secondary battery has a positive electrode lead 2 and a negative electrode lead 7 provided in parallel on the outermost peripheral side, and a positive electrode active material layer coating end portion 21 on the winding start side and a negative electrode active material The layer application end 22 and the positive electrode lead 2 and the negative electrode lead 7 are configured to be positioned on one side.

  In the polymer lithium secondary battery having such a configuration, the positive electrode active material layer application end portion 21 on the winding start side has the edge on the first arc portion 26 a side of the positive electrode lead 2 and the second arc portion of the negative electrode lead 7. The positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are located within the first arc portion 26a. Constitute.

  With this configuration, it is possible to stably provide a polymer lithium secondary battery with high energy density by suppressing variation in thickness and efficiently obtaining battery capacity.

  FIG. 4 is a cross-sectional view of a wound electrode body according to another embodiment of the present invention. As shown in FIG. 4, the wound electrode body 10 has a positive electrode active material layer application end portion 21 and a negative electrode active material layer application end portion 22 on one side, which are on the winding start side. Lead 7 is located on the other side. The positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are located in the first arc portion 26a. The positive electrode active material layer application end portion 21 on the winding start side is within a range sandwiched between the edge on the first arc portion 26a side of the positive electrode lead 2 and the folding start point 26e of the electrode of the second arc portion 26d. To position. In addition, since it is the same as that of the polymer lithium secondary battery which concerns on one Embodiment of this invention mentioned above except the said structure, description is abbreviate | omitted.

  In another embodiment of the present invention, the polymer lithium secondary battery is provided with the positive electrode lead 2 and the negative electrode lead 7 in parallel on the outermost peripheral side, and the positive electrode active material layer coating end 21 and the negative electrode active side on the winding start side. The material layer application end 22 is positioned on one side, and the positive electrode lead 2 and the negative electrode lead 7 are positioned on the other side.

  In the polymer lithium secondary battery having such a configuration, the positive electrode active material layer coating end portion 23 and the negative electrode active material layer coating end portion 24 on the winding end side are located in the first arc portion 26a, and the winding start side The positive electrode active material layer application end portion 21 of the positive electrode lead 2 is configured to be located within the range sandwiched between the edge on the first arc portion 26a side of the positive electrode lead 2 and the folding start point 26e of the second arc portion 26d. .

  With this configuration, it is possible to stably provide a polymer lithium secondary battery with high energy density by suppressing variation in thickness and efficiently obtaining battery capacity.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited only to these examples.

<Example 1>
The wound electrode body 10 shown in FIG. 1 was produced by the method described below. First, the positive electrode and negative electrode shown in FIG. 5 were produced. In the positive electrode shown in FIG. 5A, positive electrode active material layers 3 having different lengths are formed on both surfaces of the positive electrode current collector 1 so that one surface of the positive electrode current collector 1 is exposed. A positive electrode lead 2 is provided at a predetermined position. Specifically, as the positive electrode active material, first, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio). , calcined 5 hours at 900 ° C. in air to obtain lithium cobalt complex oxide as a positive electrode active material (LiCoO _2). Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture, A positive electrode mixture slurry was prepared by dispersing in some N-methyl-2-pyrrolidone. Subsequently, the positive electrode mixture slurry was uniformly applied to the positive electrode current collector 1 made of an aluminum foil having a thickness of 12 μm, dried, and then compression molded to form the positive electrode active material layer 3. The positive electrode active material layer 3 was applied such that the lengths of the positive electrode active material layers 3 on both sides were different so that one side of the positive electrode current collector had an exposed portion (hereinafter referred to as a single side exposed portion). A positive electrode lead 2 having a width of 4 mm and a thickness of 70 μm was joined to one end of the positive electrode current collector 1 on the one-side exposed portion side by spot welding. Here, in Example 1, the thickness of the positive electrode is 122 μm, the first positive electrode application length X is 381 mm, the second positive electrode application length Y is 309 mm, and the length between the first positive electrode application end and the positive electrode lead 2. The thickness Z was 25 mm.

  In the negative electrode shown in FIG. 5B, negative electrode active material layers 5 having different lengths are formed on both surfaces of the negative electrode current collector 4 so that one surface of the negative electrode current collector 4 is exposed. The part is provided with a negative electrode lead 7. Specifically, a graphite powder having an average particle size of 25 μm was prepared as a negative electrode active material, and 90 parts by mass of the graphite powder and 10 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. . Next, the negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is uniformly applied to both surfaces of the negative electrode current collector 4 made of a copper foil having a thickness of 8 μm and dried. The negative electrode active material layer 5 was produced by compression molding with a roll press. The negative electrode active material layer 5 was applied so that the lengths of the negative electrode active material layers 5 on both sides were different so that one side of the negative electrode current collector 4 had an exposed portion. A negative electrode lead 7 having a width of 4 mm and a thickness of 70 μm was joined to one end of the negative electrode current collector 4 on one side exposed portion side by spot welding. Here, in Example 1, the thickness of the negative electrode is 108 μm, the first negative electrode coating length X is 385 mm, the second negative electrode coating length Y is 323 mm, and the length between the first negative electrode coating end and the negative electrode lead 7. The thickness Z was 3 mm.

Subsequently, a copolymer obtained by block copolymerization of polyvinylidene fluoride (PVDF) and hexafluoropropylene (HFP) at a mass ratio of PVDF: HFP = 93: 7, propylene carbonate (PC) and ethylene carbonate (EC) In a mixed solvent (PC: EC = 50: 50), an electrolyte solution in which 1.0 mol / L LiPF ₆ was dissolved as an electrolyte salt was mixed and dissolved to obtain a sol electrolyte. Next, the sol-like electrolyte was applied to the surface of the negative electrode active material layer 5, and a gel electrolyte layer 8 obtained by cooling and curing the electrolyte was further laminated.

  In this way, the positive electrode, the negative electrode, and the gel electrolyte layer 8 are produced, and these are stacked with a separator 9 made of polyethylene, and wound using a winding jig (not shown), whereby the wound electrode body 10 is obtained. Was made. A PET protective tape as the insulating material 6 was attached to the current collector exposed portion where the positive electrode lead 2 and the negative electrode lead 7 face each other. Here, in Example 1, as shown in FIG. 1, the positive electrode active material layer coating end portion 21 on the winding start side, the positive electrode lead 2 and the negative electrode lead 7 are positioned on one side, and winding starts. The positive electrode active material layer application end 21 on the side is located within a range sandwiched between the edge on the first arc portion 26a side of the positive electrode lead 2 and the edge on the second arc portion 26d side of the negative electrode lead 7, The positive electrode active material layer coating end portion 23 and the negative electrode active material layer coating end portion 24 on the winding end side were selected so as to be located in the first arc portion 26a.

  Next, a concave portion is formed by stamping and forming an aluminum laminate outer packaging material 34 in which a nylon film, an aluminum foil, and a polyethylene film are sequentially laminated, and the wound electrode body 10 is inserted into the concave portion. 34 raw parts were folded back to the upper part of the concave part, and the outer peripheral part of the concave part was thermally welded and sealed to produce a polymer lithium secondary battery having a width of 35 mm and a height of 62 mm.

<Example 2>
The thickness of the positive electrode was 109 μm, and the thickness of the negative electrode was 96 μm. The first positive electrode coating length X was 424 mm, the second positive electrode coating length Y was 354 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 25 mm. The first negative electrode coating length X was 429 mm, the second negative electrode coating length Y was 396 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 3 mm. As shown in FIG. 4, the positive electrode active material layer application end 21 and the negative electrode active material layer application end 24 on the winding start side are located on one side, and the positive electrode lead 2 and the negative electrode lead 7 are located on the other side. In addition, the positive electrode active material layer coating end portion 21 on the winding start side is within a range sandwiched between the edge on the first arc portion 26a side of the positive electrode lead 2 and the folding start point 26e of the second arc portion 26d. I chose to be in position. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative Example 1>
The first positive electrode coating length X was 385 mm, the second positive electrode coating length Y was 313 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 25 mm. The first negative electrode coating length X was 389 mm, the second negative electrode coating length Y was 327 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 3 mm. As shown in FIG. 6, the positive electrode active material layer application end portion 21 on the winding start side is selected so as to be located within a range sandwiched between two edges of the negative electrode lead 7. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative example 2>
The first positive electrode coating length X was 386 mm, the second positive electrode coating length Y was 314 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 3 mm. The first negative electrode coating length X was 390 mm, the second negative electrode coating length Y was 328 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 3 mm. As shown in FIG. 7, the negative electrode active material layer application end portion 24 is not located in the first arc portion 26a, but is located on the same side as the positive electrode lead 2 and the negative electrode lead 7, and the first arc portion 26a. The folding end point 26c and the folding start point 26e of the second arc portion 26d are selected so as to be located within a range. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative Example 3>
The first positive electrode coating length X was 372 mm, the second positive electrode coating length Y was 300 mm, and the length Z from the first positive electrode coating end to the positive electrode lead was 34 mm. The first negative electrode coating length X was 376 mm, the second negative electrode coating length Y was 314 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 12 mm. As shown in FIG. 8, the positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are not located in the first arc portion 26 a, and the positive electrode active material on the winding end side The layer application end portion 23 is located on the other side different from the positive electrode lead 2 and the negative electrode lead 7, and is sandwiched between the folding start point 26b of the first arc portion 26a and the folding end point 26f of the second arc portion 26d. Chosen to be within the range. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative example 4>
The first positive electrode coating length X was 418 mm, the second positive electrode coating length Y was 348 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 25 mm. The first negative electrode coating length X was 426 mm, the second negative electrode coating length Y was 393 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 3 mm. As shown in FIG. 9, the positive electrode active material layer coating end 21 on the winding start side is located on one side, the positive electrode lead 2 and the negative electrode lead 7 are located on the other side, and the positive electrode active material on the winding start side is located. The material layer application end portion 21 was selected so as to be located within a range sandwiched between the edge of the positive electrode lead 2 on the first arc portion 26 a side and the edge of the negative electrode lead 7 on the second arc portion 26 d side. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative Example 5>
The first positive electrode coating length X was 430 mm, the second positive electrode coating length Y was 360 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 3 mm. The first negative electrode coating length X was 434 mm, the second negative electrode coating length Y was 402 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 3 mm. As shown in FIG. 10, the positive electrode active material layer coating end portion 21 on the winding start side is positioned on one side, the positive electrode lead 2 and the negative electrode lead 7 are positioned on the other side, and the positive electrode active material on the winding start side is positioned. The material layer application end portion 21 is located within the range sandwiched between the two edges of the negative electrode lead 7, and the positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are ended. It is not located in the first arc portion 26a on the side, but is located on the same side as the positive electrode lead 2 and the negative electrode lead 7, and the folding end point 26c of the first arc portion 26a and the second arc portion 26d It selected so that it might be located in the range pinched | interposed with the folding | turning start point 26e. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

<Comparative Example 6>
The first positive electrode coating length X was 415 mm, the second positive electrode coating length Y was 345 mm, and the length Z between the first positive electrode coating end and the positive electrode lead was 34 mm. The first negative electrode coating length X was 420 mm, the second negative electrode coating length Y was 387 mm, and the length Z between the first negative electrode coating end and the negative electrode lead was 12 mm. As shown in FIG. 11, the positive electrode active material layer application end 21 and the negative electrode active material layer application end 22 on the winding start side are located on one side, and the positive electrode lead 2 and the negative electrode lead 7 are located on the other side. However, the positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are not positioned within the first arc portion 26a on the winding end side, and the positive electrode active material on the winding end side The layer application end portion 23 is located on the other side different from the positive electrode lead 2 and the negative electrode lead 7, and is sandwiched between the folding start point 26b of the first arc portion 26a and the folding end point 26f of the second arc portion 26d. Chosen to be within the range. Except this, it carried out similarly to Example 1, and produced the polymer lithium secondary battery.

  The produced polymer lithium secondary battery was measured for battery capacity at 23 ° C. atmosphere and 0.2 C constant current discharge. Furthermore, the battery thickness and volume energy density on the positive electrode lead and the negative electrode lead were measured.

  Table 1 below summarizes these measurement results according to Example 1 and Comparative Examples 1 to 3. In Example 1 and Comparative Examples 1 to 3, the positive electrode active material layer application end 21 and the negative electrode active material layer application end 22 on the winding start side, and the positive electrode lead 2 and the negative electrode lead 7 are on one side. It is what is located.

  Comparative Example 1 is different from Example 1 in that the positive electrode active material layer coating end portion 21 on the winding start side is located within a range sandwiched between two edges of the negative electrode lead 7. Therefore, as shown in Table 1, the thickness of the battery on the positive electrode lead 2 is 3.68 mm, the thickness of the battery on the negative electrode lead 7 is 3.78 mm, and the thickness of the battery on the negative electrode lead 7 is It was thicker than the lead 2 and the battery thickness varied. As a result, the volume energy density was low as compared with Example 1.

  In Comparative Example 2, the positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are not located in the first arc portion 26a, and the negative electrode active material layer application end portion 24 is the positive electrode. It is located in the range sandwiched between the lead 2 and the negative electrode lead 7, and differs from the first embodiment in that the negative electrode overlaps the positive electrode lead 2 excessively. Therefore, as shown in Table 1, the thickness of the battery on the positive electrode lead 2 is 3.78 mm, the thickness of the battery on the negative electrode lead 7 is 3.68 mm, and the thickness of the battery on the positive electrode lead 2 is the negative electrode lead. 7 was larger than the thickness of the battery above 7, and the thickness of the battery varied. As a result, the volume energy density was low as compared with Example 1.

  In Comparative Example 3, the electrode length is shorter than that in Example 1, and the positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are positioned in the first arc portion 26a. First, the positive electrode active material layer coating end 23 is located on the other side different from the positive electrode lead 2 and the negative electrode lead 7, and the folding start point 26 b of the first arc portion 26 a and the folding end point of the second arc portion 26 d. The second embodiment is different from the first embodiment in that it is located within a range sandwiched by 26f. Therefore, the thickness of the battery is the same as in Example 1, but the electrode length is short, so the positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are the first. Therefore, the battery capacity could not be obtained efficiently. As a result, as shown in Table 1, compared with Example 1, the battery capacity was small and the volume energy density was low.

  From the above results, the following was found. As in Example 1, the positive electrode lead 2 and the negative electrode lead 7 are provided in parallel on the outermost peripheral side, and the positive electrode active material layer application end portion 21 on the winding start side is the same as the positive electrode lead 2 and the negative electrode lead 7. In the polymer lithium secondary battery located on the side, the positive electrode active material layer coating end portion 21 on the winding start side has the edge on the first arc portion 26 a side of the positive electrode lead 2 and the second arc portion of the negative electrode lead 2. A configuration in which the positive electrode active material layer coating end portion 23 and the negative electrode active material layer coating end portion 24 on the winding end side are positioned in the first arc portion 26a, which is located in a range sandwiched between the edges on the 26d side. And With this configuration, battery variation can be suppressed, battery capacity can be obtained efficiently, and volume energy density can be increased.

  Table 2 below summarizes the measurement results according to Example 2 and Comparative Examples 4 to 6. In Example 2, Comparative Examples 4 to 6, the positive electrode active material layer application end 21 and the negative electrode active material layer application end 22 on the winding start side are on one side, and the positive electrode lead 2 and the negative electrode lead 7 are on the other side. It is located on the side.

  In Comparative Example 4, the positive electrode active material layer coating end portion 21 on the winding start side is composed of an edge on the first arc portion 26 a side of the positive electrode lead 2 and an edge on the second arc portion 26 d side of the negative electrode lead 7. The second embodiment is different from the second embodiment in that it is located within the sandwiched range. Therefore, as shown in Table 2, the thickness of the battery on the positive electrode lead 2 is 3.55 mm, the thickness of the battery on the negative electrode lead 7 is 3.66 mm, and the thickness on the positive electrode lead 2 is positive. As a result, the battery thickness varied. As a result, as shown in Table 2, the volume energy density was lower than that in Example 2.

  In Comparative Example 5, the positive electrode active material layer coating end portion 23 and the negative electrode active material layer coating end portion 24 on the winding end side are not positioned within the first arc portion 26 a, and the first arc portion 26 a of the positive electrode lead 2 is used. The second embodiment is different from the second embodiment in that it is located within a range sandwiched between the edge on the side and the edge on the second arc portion 26d side of the negative electrode lead 7. Therefore, as shown in Table 2, the battery thickness on the positive electrode lead 2 is 3.76 mm, the battery thickness on the negative electrode lead 7 is 3.65 mm, and the battery thickness on the positive electrode lead 2 is The thickness of the battery was thicker than that on the lead 7, resulting in variations in battery thickness. As a result, compared with Example 2, the measured battery capacity was large, but the volume energy density was low.

  In Comparative Example 6, the electrode length is shorter than that in Example 1, and the positive electrode active material layer application end 23 and the negative electrode active material layer application end 24 on the winding end side are positioned in the first arc portion 26a. The positive electrode active material layer coating end 23 is located on the other side different from the positive electrode lead 2 and the negative electrode lead 7, and the folding end point 26 b of the first arc portion 26 a and the folding end point of the second arc portion 26 d The second embodiment is different from the second embodiment in that it is located within a range sandwiched by 26f. Therefore, although the thickness was the same as that of Example 2, the electrode length was shorter than that of Example 1, and the battery capacity could not be obtained efficiently. As a result, as shown in Table 2, compared with Example 2, the battery capacity was small and the volume energy density was low.

  From the above results, the following was found. As in Example 2, the positive electrode lead 2 and the negative electrode lead 7 are provided in parallel on the outermost peripheral side, the positive electrode active material layer application end portion 21 and the negative electrode active material layer application end portion 22 on the winding start side, and the positive electrode In a polymer lithium secondary battery in which the lead 2 and the negative electrode lead 7 are located on different sides, the positive electrode active material layer application end portion 21 on the winding start side has an edge on the first arc portion 26 a side of the positive electrode lead 2. The positive electrode active material layer application end portion 23 and the negative electrode active material layer application end portion 24 on the winding end side are located within a range sandwiched by the folding start point 26e of the second arc portion 26d. The configuration is such that it is located within the portion 26a. With this configuration, variation in battery thickness can be suppressed, battery capacity can be obtained efficiently, and volume energy density can be increased.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, the shape of the battery to which the present invention can be applied is not limited to a flat shape, and can be applied to a square shape and a cylindrical shape.

It is sectional drawing of the wound type electrode body which concerns on one Embodiment of this invention. It is the schematic diagram which showed the structure of the polymer lithium secondary battery which concerns on one Embodiment of this invention. It is the schematic diagram which showed the structure of the polymer lithium secondary battery which concerns on one Embodiment of this invention in detail. It is sectional drawing of the wound type electrode body which concerns on other embodiment of this invention. It is sectional drawing of the positive electrode and negative electrode which concern on one Embodiment of this invention. It is sectional drawing of the wound type electrode body which concerns on a comparative example. It is sectional drawing of the wound type electrode body which concerns on a comparative example. It is sectional drawing of the wound type electrode body which concerns on a comparative example. It is sectional drawing of the wound type electrode body which concerns on a comparative example. It is sectional drawing of the wound type electrode body which concerns on a comparative example. It is sectional drawing of the wound type electrode body which concerns on a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Positive electrode collector 2 ... Positive electrode lead 3 ... Positive electrode active material layer 4 ... Negative electrode collector 5 ... Negative electrode active material layer 6 ... Insulating material 7 ... Negative electrode lead DESCRIPTION OF SYMBOLS 8 ... Gel electrolyte layer 9 ... Separator 10 ... Winding electrode body 21,23 ... Positive electrode active material layer application end part 22, 24 ... Negative electrode active material layer application end part 25 ... Center line 26a ... first arc portion 26b, 26e ... folding start point 26c, 26f ... folding end point 26d ... second arc portion 34 ... exterior material

Claims (6)

The positive electrode and the negative electrode are wound with a separator and an electrolyte interposed therebetween, and have a flat wound electrode body in which the positive electrode is positioned on the outermost periphery,
The cross-sectional shape in the thickness direction of the wound electrode body is divided into two in the thickness direction to define one side and the other side,
The cross-sectional shape is
A first arc part, a second arc part, a side connecting a folding start point which is one end of the first arc part and a folding end point which is one end of the second arc part, and the first arc part It consists of a side that connects a folding end point that is the other end of the arc portion and a folding start point that is the other end of the second arc portion,
The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided so that at least one surface of the positive electrode current collector is exposed;
The negative electrode is composed of a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is provided so that at least one surface of the negative electrode current collector is exposed,
A positive electrode lead and a negative electrode lead are provided in parallel on a flat region other than the first arc portion and the second arc portion of the wound electrode body, and on the outermost peripheral side of the wound electrode body,
The positive electrode lead and the negative electrode lead, and the positive electrode active material layer application end and the negative electrode active material layer application end on the winding start side are located on the one side,
The positive electrode active material layer coating end on the winding start side is within a range sandwiched between the edge on the first arc portion side of the positive electrode lead and the edge on the second arc portion side of the negative electrode lead. Position to,
The nonaqueous electrolyte secondary battery in which the positive electrode active material layer application end and the negative electrode active material layer application end on the winding end side are located in a first arc portion. In claim 1,
A nonaqueous electrolyte secondary battery in which exposed portions of the positive electrode current collector and the negative electrode current collector are covered with an insulating material. In claim 1,
The wound electrode body is covered with an exterior material,
A non-aqueous electrolyte secondary battery in which the positive electrode lead and the negative electrode lead are exposed from the exterior material. The positive electrode and the negative electrode are wound with a separator and an electrolyte interposed therebetween, and have a flat wound electrode body in which the positive electrode is positioned on the outermost periphery,
The cross-sectional shape in the thickness direction of the wound electrode body is divided into two in the thickness direction to define one side and the other side,
The cross-sectional shape is
A first arc part, a second arc part, a side connecting a folding start point which is one end of the first arc part and a folding end point which is one end of the second arc part, and the first arc part It consists of a side that connects a folding end point that is the other end of the arc portion and a folding start point that is the other end of the second arc portion,
The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided so that at least one surface of the positive electrode current collector is exposed;
The negative electrode is composed of a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is provided so that at least one surface of the negative electrode current collector is exposed,
A positive electrode lead and a negative electrode lead are provided in parallel on a flat region other than the first arc portion and the second arc portion of the wound electrode body, and on the outermost peripheral side of the wound electrode body,
The positive electrode active material layer application end and the negative electrode active material layer application end on the winding start side are located on the one side, the positive electrode lead and the negative electrode lead are located on the other side,
The positive electrode active material layer application end on the winding start side is located within a range sandwiched between the edge on the first arc portion side of the positive electrode lead and the folding start point of the second arc portion,
A non-aqueous electrolyte secondary battery in which a winding end side positive electrode active material layer application end and a negative electrode active material layer application end are located within a first arc portion on the winding end side. In claim 4,
A nonaqueous electrolyte secondary battery in which exposed portions of the positive electrode current collector and the negative electrode current collector are covered with an insulating material. In claim 4,
The wound electrode body is covered with an exterior material,
A non-aqueous electrolyte secondary battery in which the positive electrode lead and the negative electrode lead are exposed from the exterior material.

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