JP2014002836A - Wound secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a wound secondary battery.SOLUTION: The wound secondary battery includes a shaft core, and an electrode group wound around the shaft core. The electrode group has a positive electrode and a negative electrode, and the shaft core has such a structure that a sheet material is wound cylindrically. The shaft core is provided with slits at the outermost peripheral end thereof, in the winding direction of the electrode group. The slit does not reach the innermost periphery of the shaft core in the winding direction of the electrode group. Following relation is satisfied; L≥πR, where R is the external diameter of the shaft core, and L is the length of the slit. The number of the slits is 2 or more and 20 or less, and the number of turns of the sheet material is 1 or more and 5 or less.

Description

  The present invention relates to a wound secondary battery.

  Lithium ion secondary batteries (hereinafter referred to as lithium ion batteries) that use the insertion and extraction of lithium ions for charge / discharge reactions provide higher energy density than conventional lead batteries and nickel cadmium batteries, and contribute to charge / discharge reactions Because of the fact that almost no lithium is deposited on the electrode as metallic lithium, the capacity is reproducible when charging and discharging are repeated, and stable charging and discharging characteristics can be obtained. The battery is highly expected as a battery that can be applied to various applications such as a power source for portable electronic devices, a power source for assisting disasters, and a power source for moving bodies such as automobiles and motorcycles.

  For example, in Patent Document 1, in a nonaqueous electrolyte secondary battery, a cylindrical center pin is inserted through a hollow portion of an electrode group. The center pin has a main body part 11 along a part of the inner wall surface of the hollow part, a slit part extending in the axial direction, and an R part 13 provided at an end in the circumferential direction, and a radius r of the R part 13 Is a structure satisfying r ≧ (d / 2) when the thickness of the center pin in the main body 11 is d, so that the center pin is placed in the electrode group even when the capacity becomes large. A technology for providing a non-aqueous electrolyte secondary battery that can suppress gas and improve the gas exhaust efficiency has been proposed. Further, Patent Document 2 includes a power generation element in which a belt-like positive and negative electrode is wound through a belt-like separator, and the power generation element has a core in which a sheet material is wound in a cylindrical shape at the center of the power generation element. There has been proposed a technique for providing a battery having a good assembly workability and a small variation in battery performance by using a battery in which the winding direction of the core is opposite to the winding direction of the core.

JP 2009-64689 A JP 2003-346879 A

  In Patent Document 1, since the slit of the center pin is formed in a direction perpendicular to the winding direction of the electrode group, the center pin follows the expansion / contraction of the electrode accompanying charging / discharging of the wound secondary battery. It is difficult to extend the life of the wound secondary battery. In Patent Document 2, since no slit is formed in the core of the sheet material wound in a cylindrical shape, it is difficult to follow the expansion / contraction of the electrode accompanying charging / discharging of the wound secondary battery by the center pin, It is difficult to extend the life of the wound secondary battery.

  Therefore, an object of the present invention is to extend the life of a wound secondary battery.

The features of the present invention are as follows, for example.
A wound secondary battery having a shaft core and an electrode group wound around the shaft core, wherein the electrode group has a positive electrode and a negative electrode, and the shaft core is formed by winding a sheet material in a cylindrical shape A wound type secondary battery having a structure, wherein a slit is provided at an outermost peripheral end of the shaft core in the winding direction of the electrode group.

  According to the present invention, it is possible to extend the life of a wound secondary battery. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 3 is a longitudinal sectional view of a cylindrical lithium ion secondary battery. The AA horizontal sectional view of FIG. FIG. The axial center deformation | transformation figure at the time of compressive stress application. The figure showing one Embodiment of an axial center. The horizontal sectional view of an axial center. The figure showing one Embodiment of an axial center.

  Hereinafter, the best mode for carrying out the present invention will be described by way of specific examples, but the present invention is not limited thereto. Further, the drawings in the embodiments are schematic diagrams and do not guarantee the accuracy of the positional relationship, dimensions, etc. in the drawings. Various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in this specification. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

  “Parallel” or “vertical” in the present invention is not necessarily strictly parallel or vertical, and may have a certain degree of inclination with respect to a reference direction. With respect to the reference direction, it is desirable that the angle is 0 degree when parallel and 90 degrees when perpendicular. In the specification, numerical ranges indicated using “to” indicate ranges including numerical values described before and after “to” as the minimum value and the maximum value, respectively.

  As shown in FIG. 1, a cylindrical lithium ion secondary battery 1 of this embodiment includes an electrode group 3 wound so that a positive electrode and a negative electrode face each other via a separator, and an electrolyte solution of a battery can 4. It is a wound battery housed inside. The electrode group 3 is provided with a shaft core 2 at the top and an electrical insulating plate 5 at the upper and lower ends, the positive conductive lead 7 is the battery lid 6, and the negative conductive lead 8 is the bottom of the battery can 4. Then, an electrolyte is injected when the dehumidification atmosphere or the inert atmosphere is controlled, and a gasket 9 serving as an electric insulation and a gas seal is applied between the battery can 4 and the battery lid 6 so as to be sealed.

  A separator is inserted between the positive electrode and the negative electrode, and the electrode group 3 wound around the shaft core 2 is produced. As the shaft core 2, any known one can be used as long as it can carry a positive electrode, a separator, and a negative electrode. In addition to the cylindrical shape shown in FIG. 1, the electrode group 3 can have various shapes such as a positive electrode and a negative electrode wound in an arbitrary shape such as a flat shape.

  The shape of the battery can 4 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape in accordance with the shape of the electrode group 3. The material of the battery can 4 is selected from materials that are corrosion resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery can 4 is electrically connected to the positive electrode or the negative electrode, the material is not deteriorated due to corrosion of the battery can 4 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. The material of the battery can 4 is selected.

  The electrode group 3 is housed in the battery can 4, the positive electrode conductive lead 7 is connected to the inner wall of the battery can 4, and the negative electrode conductive lead 8 is connected to the bottom surface of the battery lid 6. The electrolyte is injected into the battery can 4 before the battery is sealed. There are two methods for injecting the electrolytic solution: a method of adding directly to the electrode group in a state where the battery lid 6 is released, and a method of adding from an injection port installed in the battery lid 6.

  Thereafter, the battery lid 6 is brought into close contact with the battery can 4 and the whole battery is sealed. If there is an electrolyte inlet, seal it as well. As a method for sealing the battery, there are known techniques such as welding and caulking.

  The lithium ion secondary battery according to an embodiment of the present invention can be manufactured by, for example, disposing the following negative electrode and positive electrode facing each other via a separator and injecting an electrolyte.

<Positive electrode>
The positive electrode is composed of a positive electrode active material, a conductive agent, a binder, and a current collector. Illustrative examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ . In addition, LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , Li ₄ Mn ₅ O ₁₂ , LiMn _2−x MxO ₂ (however, at least selected from the group consisting of M = Co, Ni, Fe, Cr, Zn, Ti) 1 type, x = 0.01-0.2), Li ₂ Mn ₃ MO ₈ (however, M = at least one selected from the group consisting of Fe, Co, Ni, Cu, Zn), Li _1-x A _x Mn ₂ O ₄ (where A = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, at least one selected from the group consisting of x, 0.01 to 0.1), LiNi _{1 -x} M _x O ₂ (however, at least one selected from the group consisting of M = Co, Fe, and Ga, x = 0.01 to 0.2), LiFeO ₂ , Fe ₂ (SO ₄ ) ₃ , LiCo _{1 -x} M _x O ₂ (provided that at least one selected from the group consisting of M = Ni, Fe, Mn _{x = 0.01~0.2), LiNi 1-} x M x O 2 ( however, M = Mn, Fe, Co , Al, Ga, Ca, at least one selected from the group consisting of Mg, x = 0 0.01-0.2), Fe (MoO ₄ ) ₃ , FeF ₃ , LiFePO ₄ , LiMnPO _{4 and the} like.

  The particle size of the positive electrode active material is usually defined so as to be equal to or less than the thickness of the mixture layer formed from the positive electrode active material, the conductive agent, and the binder. When there are coarse particles having a size equal to or greater than the thickness of the mixture layer in the positive electrode active material powder, the coarse particles can be removed in advance by sieving classification or wind classification to produce particles having a thickness of the mixture layer thickness or less. preferable.

  In addition, since the positive electrode active material is generally oxide-based and has high electrical resistance, a conductive agent made of carbon powder for supplementing electrical conductivity is used. Since both the positive electrode active material and the conductive agent are usually powders, a binder can be mixed with the powders, and the powders can be bonded together and simultaneously bonded to the current collector.

  As the positive electrode current collector, an aluminum foil having a thickness of 10 to 100 μm, an aluminum perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like is used. In addition to aluminum, materials such as stainless steel and titanium are also applicable. In the present invention, any current collector can be used without being limited by the material, shape, manufacturing method and the like.

  A positive electrode slurry in which a positive electrode active material, a conductive agent, a binder, and an organic solvent are mixed is attached to a current collector by a doctor blade method, a dipping method, or a spray method, and then the organic solvent is dried and applied by a roll press. A positive electrode can be produced by pressure forming. In addition, a plurality of mixture layers can be laminated on the current collector by performing a plurality of times from application to drying.

<Negative electrode>
The negative electrode includes a negative electrode active material, a binder, and a current collector. When high rate charge / discharge is required, a conductive agent may be added. Examples of the negative electrode active material that can be used in the present invention include graphite and non-graphitic carbon, metals such as aluminum, silicon, and tin, and alloys thereof, lithium-containing transition metal nitride Li _(3-x) M _x N, silicon The lower oxide Li _x SiO _y (0 ≦ x, 0 <y <2) and the tin lower oxide Li _x SnO _y are selected from materials that form an alloy with lithium or materials that form an intermetallic compound. be able to.

  The material of the negative electrode active material is not particularly limited and can be used other than the above materials. However, when a part of the material such as a material having a large expansion and contraction is selected, if the range used by the negative electrode is too large, Resistance rise may be large. In this case, it is preferable to confirm whether or not the negative electrode potential is below a certain level as a condition for changing the battery voltage.

  However, it is preferable to contain graphite, and the graphite has a graphite interlayer distance (d002) of 0.335 nm or more and 0.338 nm or less. By including such graphite in the negative electrode, the potential curve of graphite has a stage structure, so that the cycle characteristics of the lithium ion secondary battery can be further improved. The graphite used for the negative electrode is natural graphite, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, needle coke, and petroleum coke that can absorb and release lithium ions chemically. , And polyacrylonitrile-based carbon fiber or the like. The graphite interlayer distance (d002) can be measured using XRD (X-Ray Diffraction Method) or the like.

  The non-graphite carbon used for the negative electrode is a carbon material excluding the above-mentioned graphite, and can absorb or release lithium ions. This includes a carbon material having a graphite layer spacing of 0.34 nm or more, which changes to graphite by high-temperature heat treatment at 2000 ° C. or more, a 5-membered or 6-membered cyclic hydrocarbon, and a cyclic oxygen-containing material. Amorphous carbon materials synthesized by pyrolysis of organic compounds are included.

Thus, a material that forms an alloy with lithium or a material that forms an intermetallic compound may be added to the negative electrode having a voltage change rate different from that of the positive electrode as the third negative electrode active material. Examples of the third negative electrode active material include metals such as aluminum, silicon, and tin and alloys thereof, lithium-containing transition metal nitrides Li _(3-x) M _x N, and lower oxides of silicon Li _x SiO _y ( 0 ≦ x, 0 <y <2), and the lower oxide Li _x SnO _{y of} tin. There is no restriction | limiting in particular in the material of a 3rd negative electrode active material, It can utilize also other than said material.

  Since the negative electrode active material generally used is a powder, a binder is mixed with the negative electrode active material so that the powders are bonded together and simultaneously bonded to the current collector. In the negative electrode included in the battery according to this embodiment, it is desirable that the particle size of the negative electrode active material be equal to or less than the thickness of the mixture layer formed from the negative electrode active material and the binder. When there are coarse particles having a size equal to or greater than the thickness of the mixture layer in the negative electrode active material powder, the coarse particles may be removed in advance by sieving classification or wind classification, and particles having a thickness of the mixture layer thickness or less may be used. preferable.

  For the current collector of the negative electrode, a copper foil having a thickness of 10 to 100 μm, a copper perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, or the like is used. In addition to copper, materials such as stainless steel, titanium, or nickel are also applicable. In the present invention, any current collector can be used without being limited by the material, shape, manufacturing method and the like.

  A negative electrode slurry in which a negative electrode active material, a binder, and an organic solvent are mixed is attached to a current collector by a doctor blade method, a dipping method, a spray method, or the like, and then the organic solvent is dried and pressure-molded by a roll press. Thereby, a negative electrode can be produced. Moreover, it is also possible to form a multilayer mixture layer on a current collector by carrying out a plurality of times from application to drying.

<Separator>
A separator is inserted between the positive electrode and the negative electrode produced by the above method to prevent a short circuit between the positive electrode and the negative electrode. The separator can be a polyolefin polymer sheet made of polyethylene, polypropylene, or the like, or a two-layer structure in which a polyolefin polymer and a fluorine polymer sheet typified by tetrafluoropolyethylene are welded. is there. A mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator so that the separator does not shrink when the battery temperature increases. Since these separators need to allow lithium ions to permeate during charge / discharge of the battery, they can generally be used for lithium ion batteries if the pore diameter is 0.01 to 10 μm and the porosity is 20 to 90%.

<Electrolyte>
As a representative example of the electrolyte that can be used in an embodiment of the present invention, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte, a solvent obtained by mixing dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate with ethylene carbonate, Alternatively, there is a solution in which lithium borofluoride (LiBF ₄ ) is dissolved. The present invention is not limited to the type of solvent and electrolyte, and the mixing ratio of solvents, and other electrolytes can be used.

  Examples of non-aqueous solvents that can be used for the electrolyte include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 2 -Methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2- There are non-aqueous solvents such as oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, or chloropropylene carbonate. Other solvents may be used as long as they do not decompose on the positive electrode or the negative electrode incorporated in the battery of the present invention.

In addition, examples of the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi There are different types of lithium salts. A nonaqueous electrolytic solution obtained by dissolving these salts in the above-mentioned solvent can be used as a battery electrolytic solution. An electrolyte other than this may be used as long as it does not decompose on the positive electrode and the negative electrode of the battery according to this embodiment.

  When a solid polymer electrolyte (polymer electrolyte) is used, an ion conductive polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used for the electrolyte. When these solid polymer electrolytes are used, there is an advantage that the separator 11 can be omitted.

Furthermore, an ionic liquid can be used. For example, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), mixed complex of lithium salt LiN (SO ₂ CF ₃ ) ₂ (LiTFSI), triglyme and tetraglyme, cyclic quaternary ammonium cation (N-methyl) -N-propylpyrrolidinium is exemplified)) and an imide anion (bis (fluorosulfonyl) imide is exemplified), a combination that does not decompose at the positive electrode and the negative electrode is selected, and the battery according to this embodiment is selected. Can be used.

<Axis core>
2 is a horizontal sectional view taken along line AA in FIG. In the center of an electrode group 3 composed of a positive electrode, a separator, and a negative electrode, an axial core 2 in which a sheet material is wound in a cylindrical shape is provided.

  A developed view of the shaft core 2 is shown in FIG. A slit 100 is provided from one end (a in FIG. 3) of the sheet material in a direction perpendicular to the axial direction of the shaft core 2, and the slit 100 is formed up to b in FIG. (C in FIG. 3) is not reached. In other words, the shaft core 2 is provided with a slit 100 in the direction parallel to the winding direction of the electrode group 3 and at the outermost periphery of the shaft core 2, and the slit 100 reaches the innermost periphery of the shaft core 2. do not do. When the slit 100 is formed obliquely with a certain inclination with respect to the direction parallel to the winding direction of the electrode group 3, the axial core 2 is wound around the electrode group 3 when compressive stress is applied to the axial core 2. There is a possibility of extending in a direction perpendicular to the direction (long axis direction of the shaft core 2). Therefore, it is desirable that the angle between the direction in which the slit is formed and the direction parallel to the winding direction of the electrode group 3 is about 0 degree to 10 degrees. However, even when the shaft core 2 extends in a direction perpendicular to the winding direction of the electrode group 3, coil springs corresponding to expansion and contraction of the shaft core 2 in the major axis direction are provided above and below the shaft core 2. The elongation in the direction perpendicular to the winding direction of the electrode group 3 of the shaft core 2 can be reduced.

  By rolling the sheet material into a cylindrical shape, it functions as a spring by the repulsive force of the sheet material. When compressive stress is generated from the electrode group 3 to the shaft core 2, one end of the sheet material wound in a cylindrical shape as shown in FIG. When the compressive stress is weakened, the stress is applied in the direction from the winding axis to the battery can 4 by the repulsive force of the spring, and returns to its original state. Thus, it can be expected that the loosening of the electrode group 3 is suppressed by the shaft core 2 following the expansion and contraction of the electrode. The repulsive force of the spring obtained by winding the sheet material into a cylindrical shape can be adjusted by the material of the sheet material, the plate thickness, the number of slits, and the number of windings.

  The expansion / contraction direction of the active material is not always perpendicular to the current collector, but is often randomly oriented. Therefore, the expansion / contraction direction of the electrode is not only perpendicular to the current collector but also in the horizontal direction. Also occurs. Although the stress can be dispersed in the vertical direction at the portions located at the upper and lower ends in the direction of the axial center of the electrode formed by coating, the stress from the upper and lower ends tends to concentrate in the central portion of the electrode. Therefore, if a cylindrical shaft core that does not contain a cylinder or a slit, or an axial core that has a slit in the axial direction of the axial core, when a distribution of compressive stress in the axial direction and the vertical direction of the axial core occurs, In the electrode center portion where the compressive stress is strong, the collapse of the electrode mixture layer is more remarkable. When a shaft core (sheet material without slits) obtained by rolling a sheet material into a cylindrical shape is used, the shaft core contracts corresponding to the portion where the compressive stress is strongest. There is a risk of creating a space between the two.

  On the other hand, the amount of contraction of the shaft core can be adjusted according to the compressive stress distribution of the electrode group by providing the shaft core with slits in the direction perpendicular to the axial direction of the shaft core. At this time, when the slit provided in the sheet material reaches the other end, that is, when the shaft core obtained by dividing the sheet material is used, each shaft core can act independently, so that the stress of the electrode group It is expected that each shaft core contracts according to the distribution. However, when an independent shaft core is used, by repeating the cycle, the electrode group moves along the compressive stress gradient of the electrode group, creating a large space at the joint of the shaft core, and the electrode group may buckle. . On the other hand, the splitting of the shaft core 2 can be prevented by preventing the slit 100 inserted into one end of the sheet material from reaching the other end as shown in FIG.

  As a manufacturing method of the shaft core 2, one end where the slit 100 is not inserted is set inside and wound into a cylindrical shape. The repulsive force of the spring may be increased by overlapping the sheet material and rolling it in a cylindrical shape. The tip of the slit 100 is preferably chamfered so that the shaft core 2 does not break through the separator and the electrode when deformed.

  When the separator is wound around the shaft core 2 after the shaft core 2 is manufactured, it is desirable that the shaft core 2 and the separator are not welded or bonded with an adhesive or the like. Thereby, when the shaft core 2 moves with expansion and contraction of the electrode, the separator can be prevented from following the movement of the shaft core 2 and wrinkling the separator.

  As shown in FIG. 5, a reinforcing plate 110 may be provided at one end (in FIG. 5, the innermost peripheral end of the shaft core 2) where the slit 100 is not inserted. By providing the reinforcing plate 110, the rigidity of the portion where the slit 100 does not reach is increased, and refraction of the shaft core 2 when a strong external stress in the direction perpendicular to the axial direction of the shaft core 2 is applied is suppressed. Examples of the reinforcing plate 110 include metals and resins, but are not limited thereto.

  In addition to using the reinforcing plate 110 as a method of increasing the rigidity of the portion where the slit 100 does not reach, one end not including the slit 100 is connected to a cylinder or circular note having an outer diameter smaller than the inner diameter of the shaft core 2. There is a method of winding the part where the slit 100 does not reach with a higher curvature than the part where the slit 100 is inserted. When the winding is performed by increasing the curvature of the portion where the slit 100 is not inserted, the rigidity can be increased as the number of times of winding is increased.

  One end of the divided sheet material may be connected by the above-described reinforcing plate, cylinder, circle note, etc., in addition to another sheet material. In this case, the shaft core 2 has a structure in which strip-shaped sheet materials are arranged in the direction of the shaft core 2 as shown in FIG. When the number of the slits 100 is increased, the interval between the slits 100 is narrowed and is twisted and deformed by the stress when the slits 100 are inserted. Therefore, by arranging strip-shaped sheet materials and welding them to the auxiliary electrode plate 110, the above deformation is suppressed and the processing of the shaft core 2 is facilitated.

  The material of the sheet material is not limited, and an elastic material such as a natural polymer sheet such as cellulose, a resin sheet, a carbon sheet, a glass fiber sheet, a metal sheet, or the like can be used. Since the separator used for insulating the positive electrode and the negative electrode is poor in elastic force, it is desirable to use a material having high elastic force as the sheet material. As a sheet material, a gap for allowing lithium ions to pass therethrough may be formed, or a dense structure may be formed.

  The thickness of the sheet material is not limited, but is preferably a thickness that does not bend due to yield stress during winding, or a thickness that does not impair the repulsive force as a spring.

  The number of slits 100 is not limited, but if the number of slits is small, the repulsive force of the spring composed of one slit 100 becomes strong, while the number of springs that can cope with the pressure distribution is small. As the number of slits 100 increases, the repulsive force of each spring tends to become weaker, while the pressure distribution in the battery axis direction can be more easily handled. Therefore, the number of slits 100 is preferably 2 or more and 20 or less, more preferably 5 or more and 10 or less.

  The number of sheeting is not particularly limited, but is preferably 1 or more and 5 or less. If it is less than 1 mm, both ends of the sheet material will not overlap. If it is 5 turns or more, the strength of the shaft core 2 and the repulsive force of the spring increase, but the overlapping area of the sheet material is large, so the resistance due to friction increases, and the shaft core is difficult to contract when a compressive stress is applied.

  When the outer diameter of the shaft core 2 is R and the length of the slit 100 is L, it is desirable to satisfy the relationship of L ≧ πR. When the length L of the slit 100 is equal to or less than πR, a portion where the slit 100 is not in contact with the electrode group 3. Since the site | part which does not enter the slit 100 is a continuous body, the quantity which deform | transforms according to compressive-stress distribution is small. Therefore, by setting the length L of the slit 100 to be equal to or greater than πR, it is possible to prevent the occurrence of a portion that changes according to the pressure distribution and a portion that does not change. The end that does not reach the slit 100 does not need to be completely overlapped with the sheet material, and the curvature may be increased toward the center, and the end that does not reach the slit 100 may be floated in the center of the cylinder.

  The use of the wound secondary battery according to the present invention is not particularly limited. For example, it can be used as a power source for portable information communication devices such as a personal computer, a word processor, a cordless telephone cordless handset, an electronic book player, a cellular phone, a car phone, a handy terminal, a transceiver, and a portable wireless device. Also, as a power source for various portable devices such as portable copiers, electronic notebooks, calculators, LCD TVs, radios, tape recorders, headphone stereos, portable CD players, video movies, electric shavers, electronic translators, voice input devices, memory cards, etc. Can be used. In addition, it can be used as household electric appliances such as refrigerators, air conditioners, TVs, stereos, water heaters, oven microwaves, dishwashers, dryers, washing machines, lighting fixtures, toys and the like. Moreover, it can be used as a battery for electric tools and nursing equipment (electric wheelchairs, electric beds, electric bathing facilities, etc.) regardless of whether they are for home use or business use. Furthermore, as industrial applications, as power sources for medical equipment, construction machinery, power storage systems, elevators, unmanned mobile vehicles, and mobiles such as electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, golf carts, turret vehicles, etc. The present invention can be applied as a power source. Furthermore, it is also possible to charge the battery module of the present invention with electric power generated from a solar cell or a fuel cell and use it as a power storage system that can be used outside the ground, such as a space station, spacecraft, or space base.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Shaft core 3 Electrode group 4 Battery can 5 Electrical insulation board
6 Battery cover 7 Conductive lead for positive electrode 8 Conductive lead for negative electrode 9 Gasket 100 Slit 110 Reinforcing plate

Claims (6)

The shaft core,
An electrode group wound around the shaft core, and a wound type secondary battery comprising:
The electrode group has a positive electrode and a negative electrode,
The shaft core has a structure in which a sheet material is wound in a cylindrical shape,
A wound secondary battery in which the slit is provided in the outermost peripheral end portion of the shaft core in the winding direction of the electrode group. In claim 1,
The slit is a wound secondary battery that does not reach the innermost circumference of the shaft core in the winding direction of the electrode group. In claim 2,
A wound secondary battery in which a reinforcing material is provided at the innermost peripheral end of the shaft core. In any one of Claims 1 thru | or 3,
When the outer diameter of the shaft core is R and the length of the slit is L,
A wound secondary battery that satisfies the relationship L ≧ πR. In claim 1,
The shaft core is a structure in which a plurality of strip-shaped sheet materials are arranged in a direction perpendicular to the winding direction of the electrode group and wound in a cylindrical shape,
A wound secondary battery in which a reinforcing material is provided at the innermost peripheral end of the shaft core. In any one of Claims 1 thru | or 5,
The number of the slits is 2 or more and 20 or less,
The wound type secondary battery in which the number of rolls of the sheet material is 1 roll or more and 5 rolls or less.