JP2008171632A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery in which a tensile force exerted on a positive electrode plate prevents cutting or cracks from occurring without limiting a positive electrode active material of a positive electrode plate in an electrode group and a binder to a compound having prescribed physical properties or the like, and moreover, regardless of the rigidity of the positive electrode plate. <P>SOLUTION: The nonaqueous electrolyte secondary battery 1 is composed by housing a flat wound shaped electrode group (electrode element) 2 in which a negative electrode plate 3 obtained by coating a negative electrode mixture on a copper current collector and a positive electrode plate 4 obtained by coating a positive electrode mixture on an A1 current collector are wound via a separator 5, and a nonaqueous electrolytic solution in a battery case 6. At a curved part on the innermost circumferential side of the electrode group 2, an insulating adhesive tape 43 is stuck onto the outer surface of the positive electrode plate 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte secondary battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound via a separator.

  In recent years, portable electronic devices such as mobile phones, notebook personal computers, and video cameras have been improved in performance, size, and weight. Non-aqueous electrolytes are used as high energy density secondary batteries used in these electronic devices. The use of lithium-ion batteries using is increasing.

A lithium ion battery includes, for example, a negative electrode plate in which a carbon material that absorbs and releases lithium ions is held by a current collector, and a lithium composite oxide that absorbs and releases lithium ions such as a lithium cobalt composite oxide (positive electrode active material). Is held between a negative electrode plate and a positive electrode plate while holding an electrolyte solution in which a lithium salt such as LiClO ₄ and LiPF ₆ is dissolved in an aprotic organic solvent. And a separator that prevents a short circuit between the two electrodes. The positive electrode plate and the negative electrode plate are formed into thin sheets or foils, which are sequentially stacked via separators, or wound into a spiral or oval shape to form an electrode group, and this electrode group is made of aluminum, etc. After being accommodated in the battery case, an electrolytic solution is injected and sealed to form a battery.

  For the binder of the positive electrode plate, polyvinylidene fluoride (PVDF) or the like is used. When the positive electrode plate is densified using PVDF or the like, the positive electrode mixture itself becomes hard, and when the positive electrode plate is wound in an oval shape in a side view to form an electrode group, the positive electrode plate is formed at the innermost curved portion Had a problem of being bent or nearly cracked in the positive electrode plate. The part divided by cutting cannot participate in charging / discharging, and there is a problem that the discharge capacity is reduced.

In Patent Document 1, as a positive electrode mixture, a positive electrode active material having a particle diameter of 5 to 10 μm and a binder having a molecular weight of 350,000 to 2,000,000 are used to improve the flexibility of the positive electrode plate, and generation of cuts or cracks. An invention of a non-aqueous electrolyte secondary battery that prevents this is disclosed.
Patent Document 2 discloses a non-aqueous solution that uses a fluorine-based polymer copolymer having a tensile fracture elongation of 400% or more as a binder, thereby improving the flexibility of the positive electrode plate and preventing the occurrence of cutting or cracking. An invention of an electrolyte secondary battery is disclosed.

Patent Document 3, by using the positive electrode active material a particle size no maximum value in the region of less than 5 [mu] m, BET specific surface area is less than 0.30 m ² / g or more 1.00 m ² / g, the positive electrode plate An invention of a non-aqueous electrolyte secondary battery that improves the flexibility of the battery and prevents the occurrence of cutting or cracking is disclosed.
Patent Document 4 discloses an invention of a non-aqueous electrolyte secondary battery that uses a fluorine-based copolymer as a binder to improve the flexibility of the positive electrode plate and prevent the occurrence of cutting or cracking. Yes.
In Patent Document 5, by sticking a tape to the inner surface of the positive electrode plate at the position of the beginning of winding, the radius of curvature of the bent portion at the time of winding of the electrode group is increased, thereby preventing the occurrence of cutting or cracking. The disclosed invention of a nonaqueous electrolyte secondary battery is disclosed.
JP 2006-139968 A JP 2005-174833 A JP 2005-196990 A JP 2002-222651 A JP 2003-157902 A

However, in the invention of the non-aqueous electrolyte secondary battery of Patent Document 1, the particle size of the active material is limited in order to increase the flexibility of the positive electrode plate, and in general, an active material with good discharge characteristics and a small particle size. There is a problem that the substance cannot be used.
Further, in the invention of the non-aqueous electrolyte secondary battery of Patent Document 2 and Patent Document 4, the fluorine-based polymer copolymer used as a binder is expensive compared to PVDF or the like that is not a copolymer, Further, there is a problem that the electrode plate is liable to swell due to the swelling of the electrolytic solution.
In the invention of the nonaqueous electrolyte secondary battery of Patent Document 3, there is a problem that the active material to be used is narrowly limited.
In the invention of the non-aqueous electrolyte secondary battery of Patent Document 5, in order to exert the effect of preventing cutting, a tape that is not sticky in half in the length direction is used as a tape to be affixed to the inner surface of the positive electrode plate. There is a problem that the manufacturing process of the tape or the positive electrode plate becomes complicated.

  The present invention has been made in view of such circumstances, and an insulating adhesive tape is applied to at least the outer peripheral surface of the positive electrode plate, including at least the apex of the curved portion, in the curved portion on the inner peripheral side of the electrode group. By sticking, the positive electrode active material and the binder are not limited to compounds having predetermined physical properties and the like, and even when the positive electrode plate is hard, it is prevented that a tensile force is exerted to cause cutting or cracking. An object of the present invention is to provide a non-aqueous electrolyte secondary battery.

  Further, the present invention provides the smallest radius of curvature by applying an insulating adhesive tape to at least the outer surface of the positive electrode plate, including at least the apex of the curved portion, at the innermost circumferential curved portion of the electrode group. An object of the present invention is to provide a nonaqueous electrolyte secondary battery in which cutting or cracking at the time of bending of a portion is reliably prevented.

  The present invention is a curved portion on the inner peripheral side of the electrode group that is wound in an oval shape in a side view and is likely to be cut or cracked in the positive electrode plate when bent, and has an insulating property on at least the outer surface of the positive electrode plate. An object of the present invention is to provide a non-aqueous electrolyte secondary battery in which cutting or cracking of the positive electrode plate is effectively prevented by applying an adhesive tape.

  The nonaqueous electrolyte secondary battery according to the first invention is a nonaqueous electrolyte secondary battery comprising an electrode group formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, and is a curved portion on at least the inner peripheral side of the electrode group. An insulating adhesive tape is affixed to at least the outer surface of the positive electrode plate including at least the apex of the curved portion.

A tensile force acts on the outer peripheral side of the curved portion when the positive electrode plate is wound.
In the present invention, an insulating adhesive tape is affixed to at least the outer surface of the positive electrode plate, including at least the apex of the curved portion. Therefore, the positive electrode active material and the binder are limited to compounds having predetermined physical properties. Even if the positive electrode plate is hard, the positive electrode plate is prevented from being cut or cracked.
Further, in the present invention, for the tape base material of the adhesive tape, there is no need to limit the area to which the adhesive is applied, and because only the adhesive tape is attached to a predetermined position on the outer peripheral side of the positive electrode plate, Manufacture of an adhesive tape and an electrode group can be performed easily.

  The nonaqueous electrolyte secondary battery according to a second aspect of the present invention is the first aspect of the invention, wherein the non-aqueous electrolyte secondary battery has an insulating property at the innermost peripheral curved portion of the electrode group, at least on the outer surface of the positive electrode plate including the apex of the curved portion. The adhesive tape of this is stuck.

  The innermost peripheral curved portion has a small radius of curvature and is most likely to be cut or cracked when bent. In the present invention, since the adhesive tape is attached to the innermost peripheral curved portion, the positive electrode plate Cutting or cracking is reliably prevented.

  A nonaqueous electrolyte secondary battery according to a third aspect of the present invention is characterized in that, in the first or second aspect, the electrode group is wound so that the shape in a side view is an ellipse.

  In the electrode group wound in an oval shape in a side view, the radius of curvature on the inner peripheral side is small, and the positive electrode plate is likely to be cut or cracked when bent. In the present invention, since the insulating adhesive tape is affixed to at least the outer surface of the positive electrode plate of this electrode group including at least the apex of the curved portion, cutting or cracking of the positive electrode plate is effectively prevented. ing.

According to the first aspect of the invention, since the insulating adhesive tape is applied to at least the outer surface of the positive electrode plate, including at least the apex of the curved portion, at least at the inner circumferential side of the electrode group, The material and the binder are not limited to compounds having predetermined physical properties and the like, and it is possible to prevent the positive electrode plate from being cut or cracked due to the tensile force.
And it is not necessary to limit the area where the adhesive is applied to the tape base material of the adhesive tape, and since only the adhesive tape is applied to a predetermined position of the positive electrode plate, It can be done easily.
Therefore, according to the present invention, even if the electrode plate is densified and the positive electrode plate is hard, the positive electrode plate is not cut or cracked during the production of the electrode group, and the non-aqueous material realizing high energy density is realized. An electrolyte secondary battery can be manufactured easily and without problems.

  According to the second invention, since the insulating adhesive tape is applied to at least the outer surface of the positive electrode plate, including at least the apex of the curved portion, in the innermost circumferential curved portion of the electrode group, the radius of curvature is Cutting or cracking during bending of the smallest part is reliably prevented.

  According to the third aspect of the present invention, the electrode plate is wound in an oval shape when viewed from the side, and is curved on the inner peripheral side of the electrode group that is likely to be cut or cracked when bent. Therefore, the positive electrode plate is effectively prevented from being cut or cracked.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
The non-aqueous electrolyte secondary battery (hereinafter referred to as a battery) of the present invention comprises, as its configuration, an electrode group formed by winding a positive electrode plate, a negative electrode plate and a separator, and a non-aqueous electrolyte contained in a battery case. .
The shape of the battery is not particularly limited, and the present invention can be applied to non-aqueous electrolyte secondary batteries having various shapes such as a square, cylindrical, and long cylindrical battery.
Below, a negative electrode plate, a positive electrode plate, a separator, and a nonaqueous electrolyte are explained in full detail.

(1) Negative electrode plate Examples of the negative electrode active material contained in the negative electrode of the battery of the present invention include, for example, alloys of Al, Si, Pb, Sn, Zn, Cd, etc. and Li, LiFe ₂ O ₃ , WO ₂ , MnO, etc. Transition metal oxides such as ₂ , carbon materials such as graphite and carbon, lithium nitride such as Li ₃ (Li ₃ N), metal lithium foil, or a mixture thereof can be used.
In the case of using a granular carbon material, for example, a negative electrode plate can be produced by forming a mixture comprising a negative electrode active material and a binder on a metal current collector such as copper. As this carbon material, it is preferable to use natural graphite or artificial graphite (mesophase graphite such as MCMB or MCF), and more preferably mesophase graphite (MCMB or MCF). Furthermore, you may use what coat | covered a part or all of the surface of natural graphite with the low crystalline carbon whose crystallinity is lower than natural graphite.

(2) Positive electrode plate Examples of the positive electrode active material used in the battery of the present invention include compounds that can occlude and release lithium, such as LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ . You may mix and use these.

In the case of using a granular positive electrode active material, the positive electrode plate can be produced, for example, by forming a mixture comprising positive electrode active material particles, a conductive additive and a binder on a metal current collector such as aluminum. I can do it.
In this case, the mixture is dissolved in a solvent to obtain a positive electrode paste, which is applied to both sides of the metal current collector and then dried. And it presses and cut | disconnects to a predetermined magnitude | size and obtains a positive electrode plate.
In the present invention, preferably, the obtained positive electrode plate is wound to produce an electrode group to be described later. Apply adhesive tape. The adhesive tape only needs to be affixed to at least the apex of the bending portion, but is preferably affixed over the entire bending portion.
And an adhesive tape may be affixed on the 1 or 2 or more position used as the curved part after the 2nd round as needed. In general, since the positive electrode plate is likely to be cut and cracked on the inner peripheral side where the radius of curvature of the curved portion is small, it is desirable that the adhesive tape be applied to at least the curved portion on the inner peripheral side of the positive electrode plate.
In addition, you may decide to affix an adhesive tape also to the position of the inner surface corresponding to the position where the adhesive tape of the said outer surface of the positive electrode plate is affixed.

The pressure-sensitive adhesive tape is required not to be peeled off when the electrode group is wound, and preferably has a pressure-sensitive adhesive strength of 0.1N / 10 mm or more in 10.4 of JIS Z0237 (measurement of peel strength at 180 degrees), More preferably, it is 1 N / 10 mm or more.
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive tape is not particularly limited as long as it does not adversely affect the battery. Specifically, acrylic such as butylacrylic acid, methacrylic acid, 2-ethylhexyl-acrylic acid copolymer, etc. Examples include acid compounds, rubber compounds such as SBR, silicone compounds, epoxy compounds, hydroquinone derivatives, phenol compounds, aromatic amine compounds, rosin resins, alkylphenol resins, and styrene resins.

The adhesive tape is required not to stretch greatly when the electrode group is wound, and the tensile strength at 8 (tensile strength and elongation) of JIS Z0237 is preferably 1 N / 10 mm or more, and 10 N / 10 mm. More preferably, it is the above.
The elongation at 8 of JIS Z0237 is preferably 100% or less, and more preferably 50% or less.
The material of the tape base material is not particularly limited as long as it does not adversely affect the battery, and specific examples include synthetic resins such as polyphenylene sulfide (PPS), polypropylene, polyimide, polyester, and polystyrene.

(3) Separator As a separator used in the battery of the present invention, a porous polymer film such as a porous polyolefin film or a porous polyvinyl chloride film, or a lithium ion or ion conductive polymer electrolyte film is used alone or in combination. Can be used.

(4) Electrode group The electrode group is sandwiched between the positive electrode plate and the negative electrode plate, and is sandwiched between two winding cores so that the side on which the adhesive tape of the positive electrode plate is attached is the outer peripheral side. Obtained by rotating the wick.

(5) Nonaqueous electrolyte Examples of the nonaqueous electrolyte solvent used in the battery of the present invention include ethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, and 1,2-dimethoxy. Ethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate , Non-aqueous solvents such as dipropyl carbonate, methylpropyl carbonate and the like, and these can be used alone or in combination. In addition, it may contain an appropriate amount of an additive such as a polymerization agent such as biphenyl or cyclohexylbenzene.

The nonaqueous electrolyte is used by dissolving the supporting salt in these nonaqueous solvents. As supporting salts, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ CO ₂ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiCF ₃ CF ₂ CF ₂ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ , LiN (COCF ₂ CF ₃ ) ₂ , LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiFOB (lithium difluorooxalate borate), and LiBOB ( A salt such as lithium bisoxalate borate) or a mixture thereof can be used.

  The present invention will be described below with reference to preferred examples. However, the present invention is not limited to the examples, and can be appropriately modified and implemented without departing from the scope of the present invention. .

[Example 1]
FIG. 1 is a cross-sectional view showing a nonaqueous electrolyte secondary battery (battery) 1 according to the present invention.
The battery 1 is a flat winding in which a negative electrode plate 3 obtained by applying a negative electrode mixture to a copper current collector and a positive electrode plate 4 obtained by applying a positive electrode mixture to an Al current collector are wound through a separator 5. A rectangular battery having a height of 37 mm, a width of 35 mm, and a thickness of approximately 5.5 mm, in which a battery case 6 is housed in a battery case 6. A battery lid 7 having a safety valve 8 and a negative electrode terminal 9 is attached to the battery case 6 by laser welding. The negative electrode terminal 9 is connected to the negative electrode plate 3 via the negative electrode lead 10, and the positive electrode plate 4 is in contact with and electrically connected to the inner surface of the side wall of the battery case 6. An adhesive tape 43 described later is affixed to the entire curved portion 4 a centering on the vertex 4 b on the innermost peripheral side of the positive electrode plate 4.

FIG. 2 is a plan view showing the positive electrode plate 4, and FIG. 3 is a cross-sectional view showing the positive electrode plate 4.
The positive electrode plate 4 was produced as follows.
LiCoO ₂ particles having an average particle diameter of 3 μm as a positive electrode active material, acetylene black (AB) as a conductive additive, and PVDF as a binder are LiCoO ₂ / AB / PVDF = 94/3/3 (parts by mass) A positive electrode paste was prepared by mixing the mixture into a positive electrode mixture and dispersing it in N-methyl-2-pyrrolidone (NMP).
Using a doctor blade, uniformly apply this positive electrode paste on both surfaces of a current collector 41 made of 15 μm thick Al foil so that the mass of the positive electrode mixture excluding NMP is 0.020 g / cm ² per side. Then, drying was performed at 150 ° C. for 1 hour. Then, the electrode plate is pressed so as to have a thickness of 130 μm at room temperature, cut so that the electrode plate has a width of 30 mm, and the mixture layers 42 and 42 are formed on both surfaces of the current collector 41. A plate 4 was obtained.

  Thereafter, the adhesive tape 43 having a width of 10 mm and a length of 30 mm is placed at a position 25 mm from the winding start side (inner peripheral side) end of the outer surface when the positive electrode plate 4 is wound. Affixed with the center line in the longitudinal direction aligned. The base material 43a of the adhesive tape 43 is made of PPS, and its thickness is 25 μm. The adhesive layer 43b is formed by applying a butylacrylic acid adhesive to the base material 43a.

The negative electrode plate 3 was produced as follows.
Graphite (graphite) as the negative electrode active material and PVDF as the binder were mixed at a mass ratio of 90:10 to form a negative electrode mixture, and an appropriate amount of NMP was added and dispersed therein to obtain a negative electrode paste.
After this negative electrode paste is uniformly applied to both sides of a 10 μm thick copper foil current collector using a doctor blade so that the mass of the negative electrode mixture excluding NMP is 0.0095 g / cm ² per side. And drying at 150 ° C. for 1 hour. And the electrode plate was pressed so that thickness might be set to 145 micrometers at room temperature, and it cut | disconnected so that the width | variety of an electrode plate might be set to 31 mm, and the negative electrode plate 3 was obtained.

  As the separator 5, a polyethylene microporous film having a thickness of about 16 μm was used.

  In the electrode group 2, the separator 5 is sandwiched between the positive electrode plate 4 and the negative electrode plate 3, which is the surface on which the adhesive tape 43 of the positive electrode plate 4 is pasted with two winding cores having a width of 35 mm and a thickness of 1 mm. Was prepared by rotating the winding core between the outer surface and the outer surface. Thereby, as described above, the adhesive tape 43 is attached to the entire curved portion 4a on the innermost peripheral side of the positive electrode plate 4 of the electrode group 2.

As the non-aqueous electrolyte, a solution obtained by dissolving 1.1 mol / L of LiPF ₆ in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 was used.

[Comparative Example 1]
A battery was fabricated in the same manner as in Example 1 except that the adhesive tape 43 was affixed to the inner surface when the positive electrode plate 4 was wound.

[Comparative Example 2]
A battery was fabricated in the same manner as in Example 1 without attaching the adhesive tape 43 to the positive electrode plate 4.

  10 cells of each of the batteries of Example 1 and Comparative Examples 1 and 2 were produced. For each battery, the electrode group 2 was developed, and the presence or absence of cracks and cuts in the positive electrode plate 4 was visually confirmed, and the number of defects was recorded. The results are shown in Table 1 below.

  From Table 1, in the case of Example 1, neither the positive electrode plate 4 was cracked nor cut, but in the case of Comparative Example 1, all of the positive electrode plates 4 were cut. It can be seen that cracks occurred in the positive electrode plates 4, the two positive electrode plates 4 were cut, and a total of six were defective.

In the case of Comparative Example 2 in which the adhesive tape 43 was not applied, a total of six positive electrode plates 4 were defective, whereas in the case of Example 1 in which the adhesive tape 43 was applied to the outer surface, the positive electrode plate 4 had Since no cutting or cracking occurred at all, it was confirmed that the adhesive tape 43 was stuck to the outer surface of the positive electrode plate 4 to prevent cracking.
On the other hand, in the case of Comparative Example 1 in which the adhesive tape 43 was applied to the inner surface of the positive electrode plate 4, the positive electrode plate 4 was all cut, resulting in inferior results to Comparative Example 2 in which the adhesive tape 43 was not applied. .
From the above results, it can be seen that the adhesive tape 43 needs to be affixed to at least the outer surface of the positive electrode plate 4 in order to achieve the effect of preventing cracks of the positive electrode plate 4.

The cause of the superiority or inferiority of the crack prevention effect due to the surface on which the adhesive tape 43 is applied to the positive electrode plate 4 is considered as follows.
When the electrode group 2 is wound, the positive electrode plate 4 is bent at an acute angle, and at the bent portion, a tensile force is applied to the outer surface of the positive electrode plate 4 and a compressive force is applied to the inner surface.

  As described above, a compression force is applied to the mixture layer 42 on the inner peripheral side of the positive electrode plate 4, but when the positive electrode mixture is filled at a high density, the mixture layer 42 is difficult to compress. The compressive force applied to the mixture layer 42 on the circumferential side is the force that pushes the mixture to the outside of the positive electrode plate 4 (current collector 41 side) and the inside of the positive electrode plate 4 (center side of the electrode group 2). It is considered that the force is divided into two forces acting to exfoliate the mixture and peel the mixture.

Accordingly, when the adhesive tape 43 is applied to the inner surface of the positive electrode plate 4 as in Comparative Example 1, the applied adhesive tape 43 prevents the mixture from peeling off from the positive electrode plate 4, so that all of the compression force is the mixture. It is considered that the force is pushed out to the outside of the positive electrode plate 4 and the positive electrode plate 4 is likely to be cut and cracked. In the case of the comparative example 2, since the adhesive tape 43 is not affixed to the inner surface of the positive electrode plate 4, the force to peel the mixture is not suppressed, and the mixture swells to the inner peripheral side. It is considered that the force of pushing the mixture to the outside of the positive electrode plate 4 is small, and the incidence of cutting and cracking is lower than that of Comparative Example 1.
In the case of Example 1, the adhesive tape 43 is not affixed to the inner surface of the positive electrode plate 4, and the mixture slightly bulges to the inner peripheral side. Then, cracking and cutting of the positive electrode plate 4 due to the pulling force acting on the outer surface of the positive electrode plate 4 are suppressed by applying the adhesive tape 43.

As described above, by sticking the adhesive tape 43 to the outer surface of the positive electrode plate 4, it is possible to prevent the positive electrode plate 4 from being cut and cracked when the electrode group 2 is wound.
Therefore, in the present invention, since a positive electrode plate, which is conventionally filled with a high density and has been hard to be cut or cracked, can be used as a constituent member of the battery, a battery having a high energy density can be easily obtained. Can be produced without problems.
As described above, when the adhesive tape 43 is affixed to the outer surface of the positive electrode plate 4, the adhesive tape 43 can be affixed to the inner surface in correspondence with the position where the adhesive tape 43 is affixed.

Moreover, in the said Example, although demonstrated about the case where the adhesive tape 43 was affixed on the innermost peripheral side of the positive electrode plate 4, it is not limited to this, The part which a cutting | disconnection or crack occurs in the positive electrode plate 4 is provided. When it covers a plurality of portions, the adhesive tape 43 can be attached to the portions.
FIG. 4 is a side view showing a case where adhesive tapes 43, 43, 43 are attached to three positions of the positive electrode plate 4 of the electrode group 2.
In the electrode group 2, adhesive tapes 43, 43, and 43 are attached to the outermost surface of the positive electrode plate 4 at three locations: the innermost curved portion 4 a, the next curved portion 4 c, and the next curved portion 4 d. . Thereby, cutting | disconnection and generation | occurrence | production of a crack of the curved parts 4c and 4d of the positive electrode plate 4 are also prevented.
Further, the present invention does not prevent the adhesive tape 43 from being attached to the other part of the positive electrode plate 4.

  Moreover, in the said Example, although the case where the electrode group 2 was wound so that the shape of a side view was an ellipse was demonstrated, it is not limited to this, The side surface of the electrode group 2 is demonstrated. The visual shape may be elliptical. When the shape of the electrode group 2 in a side view is an ellipse, the radius of curvature on the inner peripheral side is small, and the positive electrode plate 4 is likely to be cut or cracked when bent. In addition, the adhesive tape 43 is affixed to effectively prevent the positive electrode plate 4 from being cut or cracked.

The electrode group 2 having an oval shape in a side view is not limited to the one that is wound in an oval shape from the beginning, and is wound into a cylindrical shape and then pressed into a flat shape. It may be obtained. In this case, the adhesive tape 43 is affixed to the curved portion of the positive electrode plate 4, thereby preventing the positive electrode plate 4 from being cut or cracked when a force is applied.
Furthermore, the members constituting the battery are not limited to those described in the embodiments.

It is sectional drawing which shows the nonaqueous electrolyte secondary battery (battery) which concerns on this invention. It is a top view which shows a positive electrode plate. It is sectional drawing which shows a positive electrode plate. It is a side view which shows the electrode group at the time of sticking an adhesive tape to three places of a positive electrode plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Electrode group 3 Negative electrode 4 Positive electrode plate 4a, 4c, 4d Curved part 4b Vertex 41 Current collector 42 Mixture layer 43 Adhesive tape 43a Base material 43b Adhesive layer 5 Separator 6 Battery case 7 Case lid 8 Safety valve 9 Negative terminal 10 Negative lead

Claims (3)

In a non-aqueous electrolyte secondary battery comprising an electrode group formed by winding a positive electrode plate and a negative electrode plate through a separator,
An insulating adhesive tape is affixed to at least the outer surface of the positive electrode plate and including at least the apex of the curved portion at least on the inner circumferential side of the electrode group. Next battery.   The insulating adhesive tape is affixed to the innermost peripheral curved portion of the electrode group on at least the outer surface of the positive electrode plate and including at least the apex of the curved portion. Non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode group is wound so that a shape in a side view is an ellipse.

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