JPH11273739A - Nanaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of internal short circuit in the case where a wound electrode body is formed by fixing a positive electrode and a negative electrode to a winding core and winding, thus improving reliability. SOLUTION: An ionic insulator is arranged between a positive mixture layer and a negative mixture layer so as to correspond to the thin part of the positive mixture layer and/or the negative mixture of a positive electrode 1 and/or a negative electrode of a layered product fixed to a winding core and wound around it. In the case where the positive electrode 1 is formed so that the positive mixture layer 18 has a thin part on the outermost circumferential side end side and/or the innermost circumferential side end side except for the outermost circumferential side end side and/or the innermost circumferential side end of a positive electrode current collector, ionic insulators 19, 20 are arranged between the positive mixture layer 18 and the negative mixture layer so as to correspond to the thin part of the positive mixture layer 18 on the outermost circumferential side end side and/or the innermost circumferential side end side of the positive electrode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery in which the occurrence of a short circuit is suppressed by arranging an ion insulator at a predetermined position and reliability is improved.

[0002]

2. Description of the Related Art Conventionally, nickel-cadmium batteries and lead batteries have been used as secondary batteries for electronic equipment. However, in recent years, with the advancement of electronic technology, the performance, size, and portability of electronic devices have advanced, and the demand for higher energy density of secondary batteries for electronic devices has increased. In a cadmium battery, a lead battery, and the like, there has been a problem that the discharge voltage is low and the energy density cannot be sufficiently increased.

Therefore, a secondary battery having a high discharge voltage, a small self-discharge, and a long cycle life has recently been developed.
Instead of a nickel-cadmium battery or a lead battery, a non-electrode using a lithium composite oxide such as a lithium-cobalt composite oxide is used for the positive electrode, using a material capable of doping and undoping lithium ions such as a carbon material for the negative electrode. Water electrolyte secondary batteries have been actively researched and developed.

In such a non-aqueous electrolyte secondary battery, the electrode structure is generally a wound electrode structure in order to obtain good characteristics such as heavy load discharge and cycle life.

That is, a strip-shaped positive electrode having a positive electrode mixture layer formed by applying a positive electrode mixture to both surfaces of a positive electrode current collector;
Similarly, a strip-shaped negative electrode having a negative electrode mixture layer formed by applying a negative electrode mixture on both surfaces of a negative electrode current collector is wound through a separator to form a wound electrode body.
In this case, the negative electrode facing the positive electrode is generally larger in width and length than the positive electrode in order to prevent an internal short circuit due to deposition of lithium during charging.

In the non-aqueous electrolyte secondary battery, the wound electrode body is accommodated in a battery can.

In order to manufacture such a non-aqueous electrolyte secondary battery, the positive electrode and the negative electrode are laminated with a separator interposed therebetween.
After winding this into a wound electrode body, and storing this wound electrode body in a battery can, a rod-shaped member called a center pin is inserted into the center of the wound electrode body, and the wound electrode body is wound. The shape is maintained.

In the above non-aqueous electrolyte secondary battery, since the wound electrode body is housed in the battery can, the positive electrode is likely to be pressed on the outermost peripheral side, so that the positive electrode can be continuously charged or stored in a high-temperature atmosphere. , An internal short circuit easily occurs due to elution of the positive electrode active material. Therefore, as disclosed in JP-A-5-182691, an ion insulator is disposed between the outermost periphery of the positive electrode and the negative electrode facing the outermost side, so as to solve the above-mentioned disadvantages. The ionic insulator means a material that insulates ions, and includes a material having conductivity.

However, in the non-aqueous electrolyte secondary battery, an internal short circuit due to elution of the positive electrode active material during continuous charging or storage in a high-temperature atmosphere hardly occurs on the innermost peripheral side. This is because, in the nonaqueous electrolyte secondary battery, the center pin is inserted after the wound electrode body is housed in the battery can, and there is a gap between the center pin and the innermost peripheral side of the wound electrode body. This is because the wound electrode body can be loosened toward the center side and is not pressed.

[0010]

Incidentally, in the above-mentioned non-aqueous electrolyte secondary battery, its production has been carried out according to the following procedure. First, a strip-shaped positive electrode having a positive electrode mixture layer formed by applying a positive electrode mixture to both surfaces of a positive electrode current collector, and a negative electrode mixture formed by applying a negative electrode mixture to both surfaces of a negative electrode current collector A laminate is prepared by laminating a strip-shaped negative electrode having a layer with a separator interposed therebetween. next,
This laminate is fixed to a core serving as a center pin, and the laminate is wound around the core to form a wound electrode body. Next, the wound electrode body is housed in a battery can.

That is, while the center pin was previously inserted after the wound electrode body was housed in the battery can, the laminated body was wound around the core functioning as the center pin to form the wound electrode body. After that, it is stored in a battery can.

[0012] The change of the manufacturing process in this way causes the following inconveniences. In such a non-aqueous electrolyte secondary battery, as described above, in order to prevent an internal short circuit due to deposition of lithium during charging, the negative electrode facing the positive electrode is larger in width and length than the positive electrode. The thickness of the negative electrode mixture layer is made larger than that of the positive electrode mixture layer. In the positive electrode, the outermost end and / or the innermost end of the positive electrode current collector is left, and the positive electrode current collector has a thickness on the outermost and / or innermost end. The positive electrode mixture layer is formed so as to have a thin portion.

For this reason, at the innermost peripheral end and / or the innermost peripheral end, the thickness difference between the positive electrode material mixture layer and the negative electrode material mixture layer is very large, and sufficient lithium Cannot be supplied, the positive electrode active material of the positive electrode is dissolved during continuous charging or storage in a high-temperature atmosphere, and an internal short circuit is likely to occur.

At the innermost peripheral end, the positive electrode and the negative electrode are in a state of being strongly pressed against the core, and the expansion of the negative electrode at the time of charging causes the negative electrode to expand, particularly at the innermost peripheral end of the positive electrode. The end of the positive electrode mixture layer is likely to be pressed, causing a local potential rise, which also tends to cause an internal short circuit.

Accordingly, the present invention has been proposed in view of the above situation, and a fixed electrode is formed by winding a laminate in which a negative electrode and a positive electrode are laminated via a separator around a core. Even if it does, an attempt is made to provide a non-aqueous electrolyte secondary battery which is less likely to cause an internal short circuit and has good reliability.

[0016]

In order to solve the above problems, a nonaqueous electrolyte secondary battery according to the present invention has a positive electrode mixture layer formed on at least one main surface of a positive electrode current collector. A band-shaped positive electrode, and a band-shaped negative electrode in which a negative electrode mixture layer is formed on at least one main surface side of the negative electrode current collector, a laminated body laminated via a separator is fixed to a core, A non-aqueous electrolyte secondary battery having a wound electrode body wound around the winding core, and the wound electrode body is housed in a battery can, wherein at least the positive electrode mixture layer And / or an ion insulator is disposed between the positive electrode mixture layer and the negative electrode mixture layer corresponding to a portion where the thickness of the negative electrode mixture layer is small.

The above-mentioned ionic insulator means a resin film or the like having no pores large enough to allow the passage of ions.

In the non-aqueous electrolyte secondary battery according to the present invention, the positive electrode may be such that the positive electrode mixture layer is formed on the outermost end and / or the innermost end of the positive electrode current collector. The negative electrode is formed so as to have a thin portion on the outermost end side and / or the innermost end side, and the negative electrode is provided on the outermost end side and / or The negative electrode mixture layer is formed so that the thickness of the negative electrode mixture layer does not change even in a portion opposed to the portion where the thickness of the positive electrode mixture layer is thin on the innermost peripheral end side, and the outermost peripheral side of the positive electrode An ionic insulator may be disposed between the positive electrode mixture layer and the negative electrode mixture layer corresponding to a portion where the thickness of the positive electrode mixture layer is small on the end side and / or the innermost end side. preferable.

Further, in the nonaqueous electrolyte secondary battery of the present invention, the negative electrode mixture layer of the negative electrode is made of a carbon material capable of doping and undoping lithium, and the positive electrode mixture layer of the positive electrode is made of lithium. It is preferable that the transition metal composite oxide be used.

The non-aqueous electrolyte secondary battery of the present invention is housed in a battery can, fixed to a core, and wound on the positive electrode mixture layer of a positive electrode and / or a negative electrode of a laminate. And / or an ion insulator is disposed between the positive electrode mixture layer and the negative electrode mixture layer corresponding to a portion where the thickness of the negative electrode mixture layer is small. For this reason, even if the active material elutes from these thin portions, the elution of the active material to the electrode on the opposite side is prevented by the ionic insulator, and an internal short circuit is prevented. Further, even if these thin portions are compressed, the potential is not locally increased because the ionic insulator is provided, and an internal short circuit is prevented.

Further, in the non-aqueous electrolyte secondary battery of the present invention, the positive electrode is such that the positive electrode mixture layer is left at the outermost end and / or the innermost end of the positive electrode current collector. The thinnest portion is formed on the outermost end side and / or the innermost end side, and the negative electrode is formed on the outermost end side and / or the outermost end side. The negative electrode mixture layer is formed so that the thickness of the negative electrode mixture layer does not change even in a portion opposed to the thin portion of the positive electrode mixture layer on the inner peripheral side end portion, and the outermost peripheral end of the positive electrode is formed. If an ionic insulator is arranged between the positive electrode mixture layer and the negative electrode mixture layer corresponding to the portion where the thickness of the positive electrode mixture layer is thinner on the outer side and / or the innermost end side, The outermost end and / or the innermost end where the thickness of the mixture layer and the negative electrode mixture layer are significantly different and the positive electrode is likely to be pressed. Internal short circuit is prevented in.

Further, in the non-aqueous electrolyte secondary battery of the present invention, the negative electrode mixture layer of the negative electrode is doped with lithium,
When formed from a undoped carbon material and the positive electrode mixture layer of the positive electrode is formed of a transition metal composite oxide containing lithium, the positive electrode is less likely to be pressed even if the negative electrode mixture layer expands during charging. , Internal short circuit hardly occurs.

[0023]

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

The non-aqueous electrolyte secondary battery to which the present invention is applied is as follows:
It is suitable as a power source for portable electronic devices such as a camera-integrated video tape recorder, a mobile phone, and a laptop computer. Further, the nonaqueous electrolyte secondary battery to which the present invention is applied is also suitable as a hybrid electric vehicle, a power supply for starting an engine, and the like. When used as a hybrid electric vehicle, a power source for starting an engine, or the like, both discharging and charging are often performed with a large amount of power for a short time of about several seconds, and the output density is more important than the capacity.

FIG. 1 shows a non-aqueous electrolyte secondary battery to which the present invention is applied.

That is, as shown in FIG. 1, a positive electrode 1 having both surfaces of a positive electrode current collector coated with a positive electrode mixture layer, and a negative electrode 2 having both surfaces of a negative electrode current collector coated with a negative electrode mixture layer were formed. Is laminated through a separator (not shown), and one end of the laminate in the longitudinal direction is fixed to the core 3, and in this state, the wound electrode body 4 is wound around the peripheral surface of the core 3. It is housed in the battery can 5.

As shown in FIG. 2, a positive electrode lead 6 is formed on the positive electrode 1 at a predetermined interval, and as shown in FIG. 1, the positive electrode lead 6 is led out for each layer in the laminating direction, for example. It will be. The positive leads 6 are bundled by a holding jig and connected together to a pole 7 made of, for example, pure aluminum by a method such as laser welding.

The same applies to the negative electrode 2 described above.
The negative electrode leads 8 are formed at predetermined intervals, and the negative electrode leads 8 are led out, for example, for each layer in the stacking direction as shown in FIG. The negative leads 8 are bundled by a holding jig and connected to the pole 9 made of, for example, pure copper by laser welding or the like.

Further, as shown in FIG. 1, a positive electrode cover 10 is attached to the end of the battery can 5 on the side where the positive electrode 6 is bundled by caulking through a gasket 11 and a ceramic abutment 12. , And are welded to the battery can 5 by a technique such as laser welding.

On the other hand, at the end where the negative electrode 8 is bundled, a negative electrode cover 14 is provided with a gasket 15 and a ceramic abutment 1.
It is attached by caulking via 6, further tightened by a nut 17, and welded to the battery can 5 by a technique such as laser welding.

In other words, the tips of the nuts 13 and 17 are configured to function as the positive and negative electrodes of the battery. Needless to say, the battery can 5 is filled with an electrolytic solution.

In the non-aqueous electrolyte secondary battery of this embodiment, as shown in FIG. 2, the positive electrode 1 has both ends of the positive electrode current collector and thin portions on both ends. Thus, the positive electrode mixture layer 18 is formed.

Further, in the non-aqueous electrolyte secondary battery of this embodiment, in particular, a flat rectangular shape is formed so as to cover the positive electrode current collector portions at both ends of the positive electrode 1 and the thin portion of the positive electrode mixture layer 18. Ion insulators 19 and 20 are provided.

In the negative electrode 8, although the negative electrode mixture layer is formed leaving both ends of the negative electrode current collector, the negative electrode mixture layer is formed in a wider area in the longitudinal direction and the direction orthogonal to the positive electrode mixture layer 18. Have been.

That is, when one end of the positive electrode 1 and one end of the negative electrode 2 are joined together and the above-mentioned one end of the laminated body is fixed via a separator and wound around a core, the positive electrode 1 has an outermost end side and The thickness of the positive electrode mixture layer is thinner at the innermost end, and the negative electrode 8 is opposed to the thinner positive electrode mixture layer at the outermost end and the innermost end. The thickness of the negative electrode mixture layer does not change even in the portion where the negative electrode mixture layer is formed.

The positive electrode material mixture layer 18 and the negative electrode material mixture 18 correspond to the thinner portions of the positive electrode material mixture layer 18 on the outermost peripheral end and innermost peripheral end of the positive electrode 1. The ion insulators 19 and 20 are arranged between the layers.

Examples of the ion insulators 19 and 20 include resin films having no pores large enough to allow the passage of ions, and do not hinder conductivity. Further, the ion insulators 19 and 20 need to be insoluble in the electrolytic solution. More specifically, a film made of a resin such as polypropylene, polyethylene, polyimide, or polytetrafluoroethylene, or a film in which an adhesive layer is provided on these films may be used.

In this embodiment, the ion insulators 19 and 20 are used.
Was disposed on the positive electrode 1, but this ion insulator 1 was
9 and 20 may be provided between the positive electrode mixture layer and the negative electrode mixture layer, and may be provided on the separator, the negative electrode, or the like.

In this embodiment, the positive electrode 1 and the negative electrode 2 are configured as described above, but any of the materials commonly used for the mixture layer and the current collector constituting the positive electrode 1 and the negative electrode 2 are used. It is possible.

First, the positive electrode mixture layer comprises a positive electrode material capable of doping and undoping lithium ions, a conductive agent and a binder.

The cathode material preferably contains sufficient Li, for example, LiMO ₂ (where M is C
o, at least one of Ni, Mn, Fe, Al, V and Ti
Is a seed. ), A composite metal oxide comprising lithium and a transition metal, an intercalation compound containing Li, and the like are preferable.

As a conductive agent for imparting conductivity to the positive electrode and a binder for holding the positive electrode material on the positive electrode current collector, those commonly used can be used. For example, a fluorine-based resin such as polyvinylidene fluoride is used as the binder.

For example, graphite and carbon black are preferably used as the conductive agent, and fluorine resins such as polyvinylidene fluoride are preferably used as the binder.

The negative electrode mixture layer contains a negative electrode material capable of doping and undoping lithium ions and a binder.

As the negative electrode material, for example, a carbon material or the like is used. Examples of the carbon material include pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, and fired organic polymer compound (phenol resin, furan resin, etc.). Etc.), carbon fiber, activated carbon and the like.
As the negative electrode material, besides the carbon material, a crystalline or amorphous metal oxide capable of doping / dedoping lithium ions is also used.

As the binder for holding the negative electrode material on the negative electrode current collector, a commonly used binder can be used. For example, a fluorine-based resin such as polyvinylidene fluoride is used as the binder.

In this battery, a conventionally used non-aqueous electrolyte obtained by dissolving an electrolyte in a non-aqueous solvent such as an organic solvent is used.

The organic solvent is not particularly limited, but may be propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-dimexethane, diethyl carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane. , 4-
Examples thereof include methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, and the like, and these are used alone or as a mixed solvent of two or more kinds.

The electrolyte is not particularly limited, but may be LiClO ₄ , LiAsF ₆ , LiPF ₆ ,
BF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr,
LiSO ₃ CH ₃ and LiSO ₃ CF ₃ are exemplified.

The separator is not particularly limited, and examples thereof include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. In particular, a synthetic resin microporous membrane is preferably used,
Among them, a polyolefin-based microporous film is suitably used in terms of thickness, film strength, film resistance and the like. Specifically, a microporous membrane made of polyethylene and polypropylene or a microporous membrane obtained by combining these is used.

The shape of the current collector of the electrode is not particularly limited, but a foil shape or a mesh shape such as a mesh or expanded metal is used. As a material used for the positive electrode current collector, for example, aluminum, stainless steel, nickel, or the like is preferably used. Materials used for the negative electrode current collector include, for example, copper, stainless steel,
It is preferable to use nickel or the like.

The material for forming the battery can 5 is as follows.
Examples include iron, nickel, stainless steel, and aluminum. If electrochemical corrosion occurs in the non-aqueous electrolyte during operation of the battery using these, plating may be performed.

The non-aqueous electrolyte secondary battery of the present example
However, the positive electrode mixture layer leaves the outermost end side and the innermost end side of the positive electrode current collector, and the thinner part on the outermost end side and the innermost end side The negative electrode 2 is also formed in a portion opposite to the portion where the thickness of the positive electrode mixture layer is thinner at the outermost end portion and the innermost end portion. The positive electrode mixture layer 18 is formed so that the thickness of the positive electrode mixture layer does not change, and corresponds to the portion where the thickness of the positive electrode mixture layer 18 on the outermost peripheral end side and the innermost peripheral end side of the positive electrode 1 is thin. Then, ion insulators 19 and 20 are arranged between the positive electrode mixture layer 18 and the negative electrode mixture layer.

From the above, the positive electrode active material has a large difference in thickness between the positive electrode material mixture layer 18 and the negative electrode material mixture layer, and the positive electrode active material is located at the outermost and innermost end portions where the positive electrode 1 is easily pressed. Even if eluted, the movement of the eluted active material to the negative electrode 2 is prevented by the ionic insulators 19 and 20, and even if these thin portions are compressed, the ionic insulators 19 and 20 are disposed, so that the localized portions are localized. A potential rise does not occur, an internal short circuit is prevented, and the reliability is improved.

Further, in the non-aqueous electrolyte secondary battery of the present embodiment, the negative electrode mixture layer of the negative electrode 2 is doped with lithium.
When the positive electrode mixture layer of the positive electrode 1 is formed of a transition metal composite oxide containing lithium when the negative electrode mixture layer is formed of a undoped carbon material and the positive electrode mixture layer of the positive electrode 1 is expanded during charging, the positive electrode 1 does not compress. Hardly suffers from internal short circuits.

Furthermore, if the ion insulators 19 and 20 are arranged so as to cover the positive electrode current collector portions on both ends of the positive electrode 1 and the thin portion of the positive electrode material mixture layer 18 as in this example, For example, the positive electrode current collector made of, for example, aluminum is completely covered, and it is possible to prevent an internal short circuit due to burrs or the like of the positive electrode current collector, thereby further improving reliability.

[0057]

EXAMPLE Next, in order to confirm the effects of the present invention, a battery was actually manufactured and its characteristics were examined.

Production of Battery First, a negative electrode was produced.

First, as a negative electrode mixture, a carbon material having an average particle size of 20 (μm) obtained by firing in an inert gas stream as a negative electrode material and then pulverized is combined with 90 (parts by weight). 10 (parts by weight) of vinylidene fluoride resin as an adhesive and N
-Prepared as a slurry dispersed in methylpyrrolidone.

Then, this was applied to predetermined places on both sides of a negative electrode current collector, which is a copper foil having a thickness of 10 (μm), to form a negative electrode mixture layer, and the total thickness was 180 (μm). A negative electrode plate was used. Then, the negative electrode plate is cut, a part of the negative electrode plate where the negative electrode mixture layer is not formed is left to form a negative electrode lead, and the longitudinal direction is 6940.
(Mm), a negative electrode having an uncoated portion with a width of 35 (mm) above and below in a direction orthogonal to this and having a negative electrode mixture layer of 348 (mm) width was obtained. In the negative electrode, width 1
A strip-shaped negative electrode lead having a length of 0 (mm) and a length of 30 (mm) was formed at a pitch of 15 (mm).

Next, a positive electrode was manufactured.

First, as the positive electrode mixture, 91 (parts by weight) of LiCoO ₂ powder having an average particle size of 15 (μm) as a positive electrode material and 3 (parts by weight) of vinylidene fluoride resin as a binder were used. It was prepared as a slurry dispersed in N-methylpyrrolidone.

Next, this was applied to predetermined positions on both surfaces of a positive electrode current collector, which is an aluminum foil having a thickness of 20 (μm), to form a positive electrode mixture layer, and the total thickness was 150 (μm). Of the positive electrode plate. The positive electrode mixture layer was formed so as to have thin portions at both ends in the longitudinal direction of the positive electrode current collector. Next, the positive electrode plate is cut, and a part of the positive electrode plate where the positive electrode mixture layer is not formed is left to form a positive electrode lead, and the longitudinal direction is 6940.
(Mm), a positive electrode in which a positive electrode mixture layer having a width of 342 (mm) and an uncoated portion having a width of 35 (mm) above and below in a direction perpendicular to the above was formed. In the above positive electrode, width 1
Strip-shaped positive leads having a length of 0 (mm) and a length of 30 (mm) were formed at a pitch of 15 (mm).

Then, at both ends of the positive electrode in the longitudinal direction,
A polyimide film was disposed as an ionic insulator covering the thin portion of the positive electrode current collector and the positive electrode mixture layer.

The thickness of the separator is 38 (μm).
Thus, a polyethylene film having micropores of such a size as not to transmit ions having a size of 353 × 7600 (mm) was prepared.

Next, a laminate was formed by laminating the above separator, negative electrode, separator and positive electrode in this order.

Further, an outer diameter of 17 (mm) and an inner diameter of 14 (m
m), a winding core having a length of 354 (mm) was prepared, and one end of the above-mentioned laminated body was fixed thereto and wound around the winding core to form a wound electrode body.

Then, in order to manufacture a non-aqueous electrolyte secondary battery having a structure similar to that of the non-aqueous electrolyte secondary battery shown in FIG. 1, the wound electrode body was housed in a battery can. Then, the positive electrode lead and the negative electrode lead were bundled by a holding jig, and were collectively connected to a pole made of pure aluminum or the like and a pole made of pure copper or the like and connected by a method such as laser welding.

Next, for example, a negative electrode cover is attached to the end where the negative electrode is bundled by caulking through a gasket and a ceramic butt, and the positive electrode cover is attached to the end where the positive electrode is bundled. Mounted by swaging through gaskets and ceramic butts.

Subsequently, an electrolytic solution was filled in the battery can through a liquid inlet of the negative electrode cover or the positive electrode cover. Although the electrolytic solution is not particularly limited, here, a solution prepared by dissolving 1 (mol / liter) of LiBF ₄ as an electrolyte in a mixed solvent of propylene carbonate and dimethyl carbonate is used.

Next, the positive electrode cover and the negative electrode cover were tightened with nuts, respectively, and were welded to the battery can by a technique such as laser welding to complete a non-aqueous electrolyte secondary battery. Note that this non-aqueous electrolyte secondary battery is referred to as Sample 1.

Further, a non-aqueous electrolyte secondary battery similar to that of Sample 1 was manufactured except that the ion insulator of Sample 1 was changed to polytetrafluoroethylene, and this was designated as Sample 2.

Further, a polyethylene film as an ionic insulator large enough to cover the positive electrode current collector and the positive electrode mixture layer is provided at positions corresponding to both longitudinal ends of the positive electrode on the surface of the separator facing the positive electrode. Thus, a nonaqueous electrolyte secondary battery having no positive electrode provided with an ionic insulator was prepared, and this was designated as Sample 3.

Further, a polypropylene film as an ionic insulator large enough to cover the positive electrode current collector and the positive electrode material mixture layer is provided at positions corresponding to both longitudinal ends of the positive electrode on the surface of the negative electrode facing the positive electrode. Then, a non-aqueous electrolyte secondary battery having no positive electrode provided with an ionic insulator was prepared, and this was designated as Sample 4.

Then, for comparison, a nonaqueous electrolyte secondary battery similar to that of Sample 1 was manufactured without disposing an ion insulator, and this was designated as Sample 5.

Subsequently, the incidence of an internal short circuit immediately after the trial production of each sample and the incidence of an internal short circuit after a storage test at a high temperature were examined.

As a result, in Samples 1 to 4, the incidence of internal short-circuit immediately after trial production was 0/100, and the incidence of internal short-circuit after storage test at high temperature was 0/5. On the other hand, in Sample 5, the incidence of internal short-circuit immediately after trial production was 2/100, and the incidence of internal short-circuit after storage test at high temperature was 5/5.

That is, as in the non-aqueous electrolyte secondary battery of the present invention, the positive electrode mixture layer corresponding to the thin portion of the positive electrode mixture layer and / or the negative electrode mixture layer of the positive electrode and / or the negative electrode corresponds to If an ionic insulator is arranged between the agent layer and the negative electrode mixture layer, even if the active material elutes from the thin portion, the movement of the eluted active material to the opposite electrode is performed by the ionic insulator. And an internal short circuit is prevented. Further, even if these thin portions are compressed, the potential is not locally increased because the ionic insulator is provided, and an internal short circuit is prevented. From these, it was confirmed that the reliability was improved.

Further, according to the present invention, it was confirmed that the reliability under high temperature was improved.

[0080]

As described above, in the nonaqueous electrolyte secondary battery according to the present invention, the positive electrode of the laminated body housed in the battery can, fixed to the core, and wound therearound as well as/
Alternatively, an ionic insulator is disposed between the positive electrode mixture layer and the negative electrode mixture layer corresponding to a portion where the thickness of the positive electrode mixture layer and / or the negative electrode mixture layer of the negative electrode is small. Therefore, an internal short circuit is prevented, and high reliability is secured.

Further, in the nonaqueous electrolyte secondary battery of the present invention, the positive electrode is such that the positive electrode mixture layer is left on the outermost end and / or the innermost end of the positive electrode current collector. The thinnest portion is formed on the outermost end side and / or the innermost end side, and the negative electrode is formed on the outermost end side and / or the outermost end side. The negative electrode mixture layer is formed so that the thickness of the negative electrode mixture layer does not change even in a portion opposed to the thin portion of the positive electrode mixture layer on the inner peripheral side end portion, and the outermost peripheral end of the positive electrode is formed. If an ionic insulator is arranged between the positive electrode mixture layer and the negative electrode mixture layer corresponding to the portion where the thickness of the positive electrode mixture layer is thinner on the outer side and / or the innermost end side, The outermost end and / or the innermost end where the thickness of the mixture layer and the negative electrode mixture layer are significantly different and the positive electrode is likely to be pressed. Internal short circuit is prevented, high reliability is ensured in.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 2 is a plan view showing a configuration of a positive electrode of the nonaqueous electrolyte secondary battery.

[Explanation of symbols]

1 positive electrode, 2 negative electrode, 3 winding core, 4 winding electrode body, 5
Battery can, 6 positive lead, 8 negative lead

Claims (3)

[Claims] 1. A strip-shaped positive electrode having a positive electrode mixture layer formed on at least one main surface of a positive electrode current collector, and a negative electrode mixture layer formed on at least one main surface of a negative electrode current collector. A laminate obtained by laminating a strip-shaped negative electrode with a separator interposed therebetween is fixed to a core, and has a wound electrode body wound around the core. A nonaqueous electrolyte secondary battery housed in a battery can, wherein the positive electrode mixture layer and / or the negative electrode correspond to at least a portion where the thickness of the positive electrode mixture layer and / or the negative electrode mixture layer is small. A non-aqueous electrolyte secondary battery, wherein an ionic insulator is disposed between mixture layers. 2. The positive electrode, wherein the positive electrode mixture layer leaves the outermost end and / or the innermost end of the positive electrode current collector, and the outermost end and / or the innermost end of the positive electrode current collector. The negative electrode has a thickness of the positive electrode mixture layer at the outermost end and / or the innermost end. The negative electrode mixture layer is formed so that the thickness of the negative electrode mixture layer does not change even in a portion opposed to the thin portion, and the outermost end and / or the innermost end of the positive electrode The non-aqueous electrolyte secondary according to claim 1, wherein an ionic insulator is disposed between the positive electrode mixture layer and the negative electrode mixture layer corresponding to a portion where the thickness of the positive electrode mixture layer is small. battery. 3. The negative electrode mixture layer of the negative electrode comprises a lithium-doped and undoped carbon material, and the positive electrode mixture layer of the positive electrode comprises a transition metal composite oxide containing lithium. Item 2. The non-aqueous electrolyte secondary battery according to Item 1.