JP2003217668A - Wound electrode body and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with high energy density. <P>SOLUTION: In the nonaqueous electrolyte secondary battery, a wound electrode body 20 is stored in an outer case 10. In the wound electrode body 20, electrodes 1 and 2 with a mix layer mainly made of an active material formed on either surface of a band-shaped collector are layered via a band-shaped separator and wound round many turns spirally. The wound electrode body 20 is flat shaped, and the mix layer is not formed on a surface of one electrode which doesn't face the other electrode in an innermost wound layer 12. The mix layer is not formed on the surface facing the outer case 10 in an outermost wound layer 13 of the wound electrode body 20. Further, the shape of the opening of the outer case 10 is a rectangle whose short sides are rounded. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wound electrode body. The present invention also relates to a non-aqueous electrolyte secondary battery using this wound electrode body.

[0002]

2. Description of the Related Art Recently, a VTR with a built-in camera, a mobile phone,
With the emergence of new portable electronic devices such as laptop computers, which are becoming smaller and lighter, secondary batteries have come into the limelight as portable portable power sources, resulting in higher energy density. There is active research and development.

Under such circumstances, a lithium ion secondary battery using a non-aqueous electrolyte has been proposed as a secondary battery having a higher energy density than an aqueous electrolyte secondary battery such as a lead battery and a nickel cadmium battery. The battery has a high energy density, can exhibit a long life cycle, has little self-discharge, and is an excellent secondary battery with no memory effect.
Demand has been increasing in recent years.

The battery form of the lithium ion secondary battery includes a cylindrical battery in which an electrode element wound in a spiral shape is inserted in a cylindrical case, a folded electrode or a rectangular laminated electrode element, and a strip-shaped positive and negative electrode. There is a prismatic battery in which a spirally wound electrode body is wound into a prismatic case. The latter prismatic battery has higher space efficiency than the cylindrical battery, and the demand for it is increasing with the recent thinning of the device.

The prismatic outer case is made of iron, stainless steel, aluminum / aluminum alloy or the like and is processed by various molding methods to house the winding electrode body.

[0006]

However, the corners of the outer case are clearly formed. On the other hand, since the corners of the electrode body of the spirally wound electrode body are arcuate, the corners of the outer case are not formed. Voids cause the battery capacity not to be maximized, and uneven strength due to uneven thickness of the outer case,
Due to uneven case deformation due to internal pressure, or increase in manufacturing man-hours during molding, the molding speed has decreased and the manufacturing price has increased.

As the spirally wound electrode body, a strip-shaped sheet-shaped positive electrode and a strip-shaped sheet-shaped negative electrode are laminated via a separator made of a porous plastic sheet that insulates them, and this is used as a winding core. It is produced by winding the core and then pulling out the core. It has been proposed in Japanese Patent Laid-Open Nos. 8-1553519 and 8-171917 that a core having a circular cross section or an elliptical cross section is effective as a winding core used for such winding.

When the wound electrode body thus obtained is inserted into the rectangular outer case, the wound electrode body is crushed from the diametrical direction in accordance with the shape of the outer case to have an oval cross section. It is a wound electrode body.

However, as for the structure of this wound electrode body, since the wound outermost peripheral layer of the wound electrode body has a structure in which the active material mixture layer is also formed on the surface not facing the positive electrode, When the wound electrode body is inserted into the outer case, the active material layer falls off,
Since peeling occurs and productivity is significantly reduced, productivity is taken into consideration by further winding the separator around the outermost circumference of the wound electrode body facing the outer case.

As for the structure of the spirally wound electrode body, an active material mixture layer is also formed on the surface of the spirally wound outermost layer of the spirally wound electrode body not facing the positive electrode. As for the winding innermost layer, the active material mixture layer is also formed on the surface that does not face the negative electrode, and there is an active material mixture layer that does not participate in the electrode reaction. I was invited.

The present invention has been made in view of the above problems, and an object thereof is to provide a non-aqueous electrolyte secondary battery having a high energy density and a wound electrode body used in this battery.

[0012]

The wound electrode body of the present invention comprises:
Electrodes having a mixture layer mainly composed of an active material formed on both sides of a strip-shaped current collector are laminated with a strip-shaped separator interposed therebetween, and wound in a spirally wound electrode body, which is wound many times. The electrode body has a flat shape, and the winding innermost layer has no mixture layer formed on the surface where one electrode does not face the other electrode.

In the winding outermost layer of the above-mentioned winding electrode body, it is desirable that no mixture layer is formed on the surface where one electrode does not face the other electrode.

In the non-aqueous electrolyte secondary battery of the present invention, electrodes each having a mixture layer mainly composed of an active material formed on both sides of a strip-shaped current collector are laminated with a strip-shaped separator interposed therebetween, and then swirled many times. In a non-aqueous electrolyte secondary battery in which a wound electrode body wound in a spiral shape is housed in an outer case, the wound electrode body has a flat shape and one electrode of the winding innermost layer is the other electrode. The material mixture layer is not formed on the surface not opposed to.

It is preferable that the winding outermost layer of the above-mentioned winding electrode body is not formed with the mixture layer facing the outer case. Further, it is more preferable that the shape of the opening of the outer case be a shape in which the short side of the rectangle is rounded.

According to the wound electrode body and the non-aqueous electrolyte secondary battery of the present invention, the wound electrode body has a flat shape, and one electrode of the wound innermost peripheral layer does not face the other electrode. Since no mixture layer is formed on the surface, all the mixture layers of the innermost winding layer can be made to face the mixture layers of other electrodes.

Further, according to the winding electrode body and the non-aqueous electrolyte secondary battery of the present invention, the winding outermost layer of the winding electrode body is bonded to the surface where one electrode does not face the other electrode. Since no agent layer is formed, all the agent layers of the outermost circumferential layer can be made to face the agent layers of other electrodes.

Further, according to the non-aqueous electrolyte secondary battery of the present invention, since the shape of the opening of the outer case is such that the short side of the rectangle is rounded, the winding electrode body and the outer case are It is possible to prevent the formation of voids between them.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, the winding electrode body used in the non-aqueous electrolyte secondary battery will be described. First, the structure of the winding electrode body will be described. FIG. 1 is a view showing a cross section of a non-aqueous electrolyte secondary battery of the present invention, showing a structure of a wound electrode body and a shape of an outer case.

The spirally wound electrode body 20 is formed by laminating a strip-shaped positive electrode 2 and a strip-shaped negative electrode 1 via a strip-shaped separator (not shown) and spirally winding the strip-shaped positive electrode 2 multiple times. Further, the winding electrode body 20 has a flat type shape whose cross section is crushed from the vertical direction in the drawing.

Next, a method of manufacturing the winding electrode body 20 will be described. FIG. 2 shows an example of the positional relationship between the positive electrode 2, the negative electrode 1, and the separator 3 before winding the wound electrode body 20 of the present invention, and the positive electrode mixture layer non-existing region 16 and the negative electrode mixture layer non-existent. It is a figure which shows the example of the position of the area | region 17.

First, the positive electrode 2 will be described. Positive electrode 2
Is composed of a positive electrode current collector 15, a positive electrode mixture layer 18, and a positive electrode lead 4.

The positive electrode current collector 15 is made of a strip-shaped metal foil.
The positive electrode current collector 15 has a function as a conduction path for electrons that enter and leave the positive electrode mixture layer 18. In addition, the positive electrode current collector 15
Is made of aluminum. As can be seen from the beginning of winding A in FIG. 2, the tip (left end in the drawing) of the positive electrode current collector 15 is on the left side of the first turning point 21. Further, as can be seen from the end of winding B in FIG. 2, the terminal end (right end in the drawing) of the positive electrode current collector 15 is near the left side of the last turning point 21.

Here, the turnaround point 21 will be described. As described with reference to FIG. 1, the winding electrode body 20 has a flat shape, and the folded portion of this flat shape corresponds to the folding point 21. That is, in FIG. 1, the point where a straight line passing through the center of the upper and lower parallel sides of the flat shape and parallel to the upper and lower parallel sides intersects with the rolled positive electrode 2, negative electrode 1 or separator is the folded back. Corresponds to point 21. Furthermore, at the turning point 21 in FIG.
The positive electrode 2, the negative electrode 1, and the separator 3 are folded back.

Incidentally, in FIG. 2, this turning point 21
Are evenly spaced at the beginning of winding A and at the end of winding B, but in reality, as the positive electrode 2, the negative electrode 1, and the separator 3 are wound, the winding body becomes larger, so the length of one round is long. Is getting longer. Therefore, the intervals between the turn-around points 21 increase as they approach the end of winding, but they are shown as equal intervals in the drawing as a model.

The positive electrode mixture layer 18 is a thin film formed on both surfaces of the positive electrode current collector 15. Electrode reactions are proceeding in the positive electrode mixture layer 18.

The positive electrode mixture layer 18 includes a positive electrode active material, a conductive agent,
And a binder mixture. Here, the positive electrode active material is not particularly limited, but preferably contains a sufficient amount of Li, for example, the general formula LiMO ₂ (where M
Represents at least one of Co, Ni, Mn, Fe, Al, V, and Ti), and a complex metal oxide composed of lithium and a transition metal, an intercalation compound containing Li, or the like can be used.

The width of the positive electrode material mixture layer 18 will be examined. Among the positive electrode mixture layers, the upper positive electrode mixture layer 18 (formed on the upper surface of the positive electrode current collector 15 in the sectional view of FIG. 2) and the lower positive electrode mixture layer 18 (cross section of FIG. 2) In the figure, the width is the same as that of the positive electrode current collector 15) formed on the lower surface of the positive electrode current collector 15.

Next, the positive electrode mixture layer 18 will be examined in the lengthwise direction. The upper positive electrode mixture layer 18 starts near the right side of the third turning point 21 from the beginning and ends near the left side of the last turning point 21. The lower positive electrode mixture layer 18 starts near the right side of the first turning point 21 and ends near the left side of the last turning point 21.

Comparing the upper positive electrode mixture layer 18 and the lower positive electrode mixture layer 18 in the longitudinal direction, the tip of the upper positive electrode mixture layer 18 is more than that of the lower positive electrode mixture layer 18. It exists on the right side by a width twice as large as the turn-around point interval (the interval between two adjacent turn-around points). Then, a region where the positive electrode mixture layer is not formed, that is, a positive electrode mixture layer absent region 16 is formed on the upper surface of the positive electrode current collector 15. At the end of the volume,
The end of the upper layer positive electrode mixture layer 18 and the end of the lower layer positive electrode mixture layer 18 are at the same point.

Further, the positive electrode current collector 15 has a region in which the positive electrode material mixture layer is not formed on both the upper surface and the lower surface thereof, and at the beginning of winding, there is one turn point interval from the tip,
At the end of the winding, there is some width from the end.

The positive electrode mixture layer 18 of both the upper and lower layers starts slightly to the right of the turning point 21 at the beginning of winding and ends slightly to the left of the turning point 21 at the end of winding. The reason for this will be described later.

The positive electrode lead 4 has a strip shape and is made of aluminum. The positive electrode lead 4 is fixed near the tip of the positive electrode current collector 15. The positive electrode lead 4 electrically connects the positive electrode current collector 15 and the positive electrode terminal.

Next, the negative electrode 1 will be described. Negative electrode 1
As shown in FIG. 2, the negative electrode current collector 14 and the negative electrode mixture layer 1
9 and the negative electrode lead 11.

The negative electrode current collector 14 is made of a strip-shaped metal foil,
Its width is slightly wider than that of the positive electrode current collector 15. Negative electrode current collector 1
4 has a function of providing a conduction path for electrons to and from the negative electrode mixture layer 19. The negative electrode current collector 14 is made of copper foil.

As can be seen from the beginning of winding A in FIG. 2, the tip of the negative electrode current collector 14 (the left end in the drawing) is located slightly to the left of the first turning point 21. Further, as can be seen from the end of winding B in FIG. 2, the terminal end (the right end in the drawing) of the negative electrode current collector 14 exists on the right side of the last turning point 21.

The negative electrode mixture layer 19 is composed of thin films formed on both surfaces of the negative electrode current collector 14. Negative electrode mixture layer 19
The electrode reaction is proceeding inside.

The negative electrode mixture layer 19 is made of a mixture of a negative electrode active material and a binder. As the negative electrode active material, a material capable of doping lithium ions with a relatively low-potential oxide or other oxide such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, or titanium oxide, and capable of dedoping are used. Can be used.

Examples of the negative electrode material that can be doped or dedoped with lithium ions include metals and semiconductors that can form alloys and compounds with lithium, and alloys and compounds thereof. These metals, alloys or compounds are represented by the chemical formula DsEtLiu, for example. In this chemical formula, D represents at least one kind of metal element and semiconductor element capable of forming an alloy or compound with lithium, and E represents at least one kind of metal element and semiconductor element other than lithium and D. The values of s, t, and u are s> 0, t ≧ 0, and u ≧ 0, respectively.

Among them, 4B is a metal element or a semiconductor element capable of forming an alloy or a compound with lithium.
A metal element or semiconductor element of the group is preferable, silicon or tin is particularly preferable, and silicon is most preferable. These alloys or compounds are also preferable, specifically, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ S.
n, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoS
i ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ S
i, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaS
Examples thereof include i ₂ , VSi ₂ , WSi _{2 and} ZnSi ₂ .

In addition to lithium and lithium alloys, carbon materials capable of doping and dedoping lithium ions can be used. The carbon material used for the negative electrode includes phenol resin, acrylic resin, vinyl halide resin, polyimide resin, polyamideimide resin, polyamide resin, polyacetylene, conjugated resin such as poly (p-phenylene), cellulose and its dielectric, and any Organic polymer compounds, especially furfuryl alcohol or furfural homopolymers, furan resins composed of copolymers, etc., and carbonaceous materials obtained by carbonizing the above organic materials as a starting material by a method such as firing. Materials and carbon materials such as graphites are preferred.

The width of the negative electrode material mixture layer 19 will be examined. Upper Negative Electrode Mixture Layer 19 and Lower Negative Electrode Mixture Layer 19
Both have the same width as the negative electrode current collector 14.

Next, the negative electrode mixture layer 19 will be examined in the longitudinal direction. The tip of the upper negative electrode mixture layer 19 is present at the first turning point 21 and the end is at the last turning point 21.
Exists in. The tip of the lower negative electrode mixture layer 19 has the same folding point 21 as the tip of the upper negative electrode mixture layer 19.
Exists in. Further, the terminal end is located at the third turn-back point 21 from the end.

Comparing the upper negative electrode mixture layer 19 and the lower negative electrode mixture layer 19 in the longitudinal direction, at the beginning of winding, the upper negative electrode mixture layer 19 and the lower negative electrode mixture layer 19 are from the same point. It has begun. At the end of the winding, the end of the lower negative electrode mixture layer 19 is located on the left side of the end of the upper negative electrode mixture layer 19 by a width twice the interval between the turning points. And
A region where the negative electrode mixture layer is not formed, that is, a region 17 where the negative electrode mixture layer does not exist is formed on the lower surface of the negative electrode current collector 14.

Further, in the negative electrode current collector 14, a region where the negative electrode mixture layer is not formed on both the upper surface and the lower surface exists at a slight width from the front end at the winding start, and at the winding end interval 1 from the end end at the winding end. There is enough.

The tip of the negative electrode mixture layer 19 is located directly above the turning point 21 and the end of the negative electrode mixture layer 19 is also located just above the turning point 21. On the other hand, as described above, in the positive electrode mixture layer 18, both the upper layer and the lower layer have their ends slightly to the right of the turning point 21, and their ends to the left of the turning point 21.

As a result, when the positive electrode 2 and the negative electrode 1 are wound, the positive electrode mixture layer 18 is formed on the opposing positive electrode 2 and negative electrode 1.
The negative electrode mixture layer 19 is longer than the negative electrode mixture layer 19 in the length direction, and the negative electrode mixture layer 19 always includes the leading end and the terminal end of the positive electrode mixture layer 18. Further, in the positive electrode 2 and the negative electrode 1 facing each other, the negative electrode mixture layer 19 is wider than the positive electrode mixture layer 18 in the width direction.

This is to prevent the Li ions eluted from the positive electrode 2 from being deposited on the negative electrode current collector 14 in the electrode reaction and becoming inactive in the subsequent electrode reaction.

The negative electrode lead 11 has a strip shape,
It is made of nickel. The negative electrode lead 11 is fixed near the end of the negative electrode current collector 14. The negative electrode lead 11 electrically connects the negative electrode current collector 14 and the outer case.

The separator 3 is made of a strip-shaped thin film. The separator 3 can be formed of, for example, a microporous film of polyethylene, polypropylene, or polytetrafluoroethylene.

There are two separators 3, one of which is disposed above the positive electrode 2 and the other of which is disposed between the positive electrode 2 and the negative electrode 1. These two separators 3 are
The width is wider than the width of the positive electrode mixture layer 18 and the width of the negative electrode mixture layer 19. Further, when viewed in the length direction, the tip of the separator 3 is present on the left side of the first turning point 21, and the end thereof is on the slightly right side of the last turning point 21.
Thus, the separator 3 has a tip and a terminal outside the tip and the terminal of both the positive electrode material mixture layer 18 and the negative electrode material mixture layer 19. This is to reliably prevent the positive electrode mixture layer 18 and the negative electrode mixture layer 19 from directly contacting each other when the positive electrode 2 and the negative electrode 1 are wound.

Next, a wound electrode body is manufactured from the positive electrode 2, the negative electrode 1, and the separator 3 described above. First, the separator 3, the positive electrode 2, the separator 3, and the negative electrode 1 are laminated,
The separator 3 is fixed to the winding core and is wound many times. The direction of rolling is as follows. That is, at the beginning of winding in FIG. 2A, the tip of the separator 3 is fixed to the winding core, and then
Turn the winding core clockwise and rotate it.

When the winding is completed, the winding end is fixed with an adhesive tape. After that, the winding core is removed, and the winding electrode body is crushed into a flat shape. Next, as shown in FIG. 1, the flat wound electrode body 20 is attached to the outer case 1
Store at 0. Note that, in FIG. 1, the illustration of the positive electrode current collector in the positive electrode 2, the negative electrode current collector in the negative electrode 1, the separator, and the negative electrode lead is omitted.

The following can be seen from FIG. That is,
The winding innermost layer 12 of the positive electrode 2 (the innermost layer of the winding electrode body 20, which is a layer of the positive electrode 2 and includes the positive electrode material mixture layer-existing region 16 for approximately one round) is a positive electrode that does not face the negative electrode. The positive electrode material mixture layer is not formed on the portion of the current collector.

The winding outermost layer 13 of the negative electrode 1 (the outermost layer of the winding electrode body 20, which is a layer of the negative electrode 1 and includes the negative electrode material mixture layer nonexisting region 17 for about one round) is the positive electrode. The negative electrode mixture layer is not formed on the portion of the negative electrode current collector that does not face the above. In other words, the outermost circumferential layer 13 is the outer case 10.
The negative electrode material mixture layer is not formed facing the inside of the.

Next, another example of the wound electrode body will be described. FIG. 3 is a diagram showing another example of the positional relationship between the positive electrode, the negative electrode, and the separator before winding the winding electrode body, and another example of the position of the positive electrode / negative electrode mixture layer absent region. .

First, the winding start of FIG. 3A will be described.
The winding start in FIG. 3A differs from the winding start in FIG. 2A described above in the following points. That is, at the beginning of winding in FIG. 2A, the upper positive electrode mixture layer 18 starts near the right side of the third turn point 21 from the beginning, and the lower positive electrode mixture layer 18 starts near the right side of the first turn point 21. It has begun. The upper negative electrode mixture layer 19 starts from the first turning point 21, and the lower negative electrode mixture layer 19 starts from the first turning point 21 like the upper negative electrode mixture layer 19.

On the other hand, at the beginning of winding of FIG. 3A, the upper positive electrode mixture layer 18 has the third turning point 21 from the beginning.
Starting from the vicinity of the right side of, and the positive electrode mixture layer 18 of the lower layer also starts from the vicinity of the right side of the third turning point 21 from the beginning. In addition, the upper negative electrode mixture layer 19 starts from the third turning point 21 from the beginning, and the lower negative electrode mixture layer 19 is
It starts from the first turning point 21.

Next, the winding end of FIG. 3B will be described. The winding end in FIG. 3B differs from the above-described winding end in FIG. 2B in the following points. That is, at the end of the winding of FIG. 2B, the upper positive electrode mixture layer 18 ends near the left side of the last turning point 21, and the lower positive electrode mixture layer 18 ends near the left side of the last turning point 21. ing. Also,
The upper negative electrode mixture layer 19 ends at the last turnaround point 21, and the lower negative electrode mixture layer 19 ends at the third turnaround point 21.

On the other hand, at the end of winding in FIG. 3B, the upper positive electrode mixture layer 18 ends near the left side of the last turn-around point 21, and the lower positive electrode mixture layer 18 ends at the last turn-around point. It ends near the third left from 21. Further, the upper negative electrode mixture layer 19 ends at the third turning point 21 from the last, and the lower negative electrode mixture layer 19 also ends at the third turning point 21 from the last.

The combinations of the winding start and winding end shown in FIGS. 2 and 3 can be arbitrarily adopted. That is, the combination of the winding start of FIG. 2 and the winding end of FIG.
A combination of the winding start of FIG. 3 and the winding end of FIG. 2, and
There are three combinations of the winding start of FIG. 3 and the winding end of FIG.

2 and 3, the example in which the separator 3, the positive electrode 2, the separator 3, and the negative electrode 1 are laminated in this order has been described, but the present invention is not limited to this. In addition, the negative electrode 1, the separator 3, the positive electrode 2, and the separator 3 may be laminated in this order. FIG. 4 is a diagram showing another example of the positional relationship between the positive electrode, the negative electrode, and the separator and another example of the position of the positive electrode / negative electrode mixture layer non-existing region before the winding electrode body is wound. .

First, the winding start of FIG. 4A will be described.
First, in the above example at the beginning of winding of FIG. 4A, the upper negative electrode mixture layer 1
9 starts from the third turning point 21 from the beginning, and the lower negative electrode mixture layer 19 starts from the first turning point 21. The upper positive electrode mixture layer 18 starts from the vicinity of the right side of the first turnaround point 21 and starts from the lower positive electrode mixture layer 1
8 also starts near the right side of the first turning point 21.

In the lower example of the beginning of winding of FIG. 4A, the upper negative electrode mixture layer 19 starts from the third turn point 21 from the beginning, and the lower negative electrode mixture layer 19 also turns into the third turn point 21 from the first. It starts from. In addition, the positive electrode mixture layer 1 of the upper layer
8 starts from the vicinity of the right side of the third turning point 21 from the beginning, and the lower positive electrode mixture layer 18 has the first turning point 2
It starts near the right side of 1.

Next, the winding end of FIG. 4B will be described. First, in the above example at the end of winding of FIG. 4B, the upper negative electrode mixture layer 19 ends at the final turnaround point 21, and the lower negative electrode mixture layer 19 ends at the third turnaround point 2.
It ends with 1. The upper positive electrode mixture layer 18 ends near the left side of the third turning point 21 from the end, and the lower positive electrode mixture layer 18 ends near the left side of the third turning point 21 from the last. There is.

In the lower example at the end of winding in FIG. 4B, the upper negative electrode material mixture layer 19 ends at the final turning point 21,
The lower negative electrode material mixture layer 19 also ends at the final turning point 21. Further, the upper positive electrode mixture layer 18 ends near the left side of the last turning point 21, and the lower positive electrode mixture layer 18 ends near the left side of the third turning point 21 from the last.

The combination of winding start and winding end shown in FIG. 4 can be arbitrarily adopted. That is, it is possible to adopt four combinations of the upper and lower examples of the winding end with respect to the upper and lower examples.

2 and 3, an example in which the separator 3, the positive electrode 2, the separator 3 and the negative electrode 1 are laminated in this order has been described. However, the positional relationship of the positive electrode, the negative electrode, and the separator before winding the winding electrode body is not limited to these. In addition, a positive electrode 2, a separator 3, a negative electrode 1, and a separator 3 stacked in this order may be employed. In this case, separator 3
Therefore, it is necessary that the positive electrode and the negative electrode are insulated.

Further, in FIG. 4, an example in which the negative electrode 1, the separator 3, the positive electrode 2, and the separator 3 are laminated in this order has been described. However, before winding the winding electrode body,
The positional relationship between the positive electrode, the negative electrode, and the separator is not limited to these. Besides, it is possible to employ a laminate in which the separator 3, the negative electrode 1, the separator 3, and the positive electrode 2 are laminated in this order. In this case, the separator 3 needs to insulate the positive electrode and the negative electrode, and the separator 3 needs to insulate the positive electrode and the outer case 10.

In the above example, the case where the length of the positive electrode material mixture layer non-existing region 16 or the negative electrode material mixture layer non-existing region 17 is about two folding point intervals is described. It is not limited to cases. In addition, it is needless to say that the present invention can be applied even when the length of the positive electrode mixture layer absent region 16 or the negative electrode mixture layer absent region 17 is shorter than about two folding point intervals.

Specifically, the present invention is applied to the positive electrode mixture layer non-existing region 16 or the negative electrode mixture layer non-existing region 17 as long as the length thereof is approximately two when converted into the turn-around point interval. can do. The reason is that if the length is within this range, each mixture layer that does not participate in the electrode reaction is eliminated and it is efficient.

Next, a non-aqueous electrolyte secondary battery using the above-mentioned wound electrode body will be described. FIG. 5 is a cross-sectional view of the non-aqueous electrolyte secondary battery of the present invention. As can be seen from FIG. 5, the non-aqueous electrolyte secondary battery includes an outer case 10, a wound electrode body 20, an insulating material 9, a positive electrode terminal 6, a gasket 5, a battery lid 7, and the like.

The outer case 10 is a container having the same sectional shape from the opening to the bottom. The shape of the opening of the outer case 10 is a flat shape, that is, a shape in which a short side of a rectangle is rounded. Specifically, as shown in FIG. 1, the upper and lower sides of the drawing are parallel to each other, and the left and right sides thereof are semi-circular. The parallel part and the semi-circular part are continuous.

The shape of the opening of the outer case 10 is not limited to the above shape. In addition, the upper and lower parts in the drawing are parallel to each other, and various shapes can be adopted in the left and right parts continuous to the parallel part. For example, on the left and right, half an ellipse, a quadratic curve,
Curves such as cubic curve, cycloid curve, open triangle,
An open polygon such as a quadrangle and a pentagon can be adopted. That is, it is possible to employ a flat type sealing body that summarizes these forms.

Further, the parallel portions are not limited to parallel ones, but may have a gentle curve, for example, the entire cross-sectional shape may be elliptical or the like. In short, any shape can be adopted as long as it is along the outer shape of the winding electrode body 20.

Any material can be used for the outer case 10, and iron, nickel, stainless steel, aluminum or the like can be used. In addition, when corrosion occurs due to a non-aqueous electrolyte, it can be used by plating or the like.

The outer case 10 having the above flat shape.
Can be manufactured by any method. For example, it can be manufactured by ironing a Ni-plated steel plate with a mold and forming by deep drawing.

In this molding process, in the case of a rectangular outer case, the strength is non-uniform due to thickness unevenness, or the number of manufacturing processes at the time of molding is increased, resulting in a decrease in molding speed and an increase in manufacturing cost.

On the other hand, in the case of an outer case having elliptical or rectangular corners formed in an arc shape, uneven thickness is less likely to occur and molding can be performed easily, which reduces the number of manufacturing steps and the molding speed. It is possible to increase the cost and reduce the manufacturing cost.

A winding electrode body 20 is housed in the outer case 10. As the winding electrode body 20, the various winding electrode bodies described above can be adopted. The wound electrode body 20 is impregnated with a nonaqueous electrolytic solution. As this non-aqueous electrolytic solution, a solution in which an electrolyte is dissolved in a non-aqueous solvent can be used.

For example, as the non-aqueous solvent, propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane, γ-butyrolactone, valero. Lactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be used alone or in combination of two or more.

As an electrolyte soluble in such a non-aqueous solvent
As long as it is used in this type of battery,
One or more kinds can be mixed and used. For example LiPF₆Is good
Suitable but other LiClO_Four, LiAsF₆, Li
BF_Four, LiB (C₆H_Five) _Four, CH₃SO₃Li, C
F₃SO₃LI, LiN (CF₃SO₂)₂, LiC
(CF₃SO₂)₃, LiCl, LiBr, etc. can also be used
Is.

As shown in FIG. 5, the insulating material 9 is arranged above and below the winding electrodes 20 and 20 to insulate the positive electrode from the outer case 10, the negative electrode from the positive electrode lead 4, and the negative electrode from the positive electrode terminal 6. The insulation is secured with.

The positive electrode terminal 6 is attached to the battery lid 7 via the gasket 5. Here, the gasket 5 is made of, for example, a polyolefin resin having electrolytic solution resistance, a fluororesin such as polypropylene, or a resin molded product made of a copolymer of perfluoroalkyl vinyl ether and tetrafluoroethylene.

The positive electrode lead 4 fixed to the positive electrode current collector of the wound electrode body 20 is welded to the positive electrode terminal 6 to secure the electrical connection between the positive electrode and the positive electrode terminal 6. Further, the negative electrode lead 11 fixed to the negative electrode current collector of the wound electrode body 20 is welded to the inside of the outer case 10 to secure the electrical connection between the negative electrode and the outer case 10.

From the above, according to the present embodiment,
The winding outermost layer of the spirally wound electrode body is configured such that the mixture layer is not formed on the surface facing the outer case and not facing the other electrode, and the spirally innermost circumference layer of the spirally wound electrode body is formed. It is possible to provide a non-aqueous electrolyte secondary battery having a high energy density by adopting a configuration in which the electrode layer arranged at is not formed with the mixture layer on the surface not facing the other electrode.

Further, in a non-aqueous electrolyte secondary battery in which an electrode having a mixture layer formed on both sides of a current collector is wound a large number of times with a separator interposed therebetween, the opening has an elliptical or rectangular corner. An outer case having a shape formed in an arc shape is used, or the above-mentioned elliptic powder, a curve such as a quadratic curve, a cubic curve, a cycloid curve, an open triangle, a quadrangle, and a pentagon are opened. Space efficiency can be improved by using an outer case formed in a polygonal shape or the like. That is, the four corner spaces of the outer case can be reduced.

In the above embodiment, the example of the lithium ion secondary battery has been described, but the present invention is not limited to this battery. The present invention can employ a flat sealed battery including this lithium ion secondary battery.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0090]

EXAMPLES Next, examples of the present invention will be specifically described. However, it goes without saying that the present invention is not limited to these examples. First, a method for manufacturing a battery sample used in this example will be described. Example FIG. 1 shows the structure of the non-aqueous electrolyte secondary battery produced in this example. Such a flat-shaped battery was manufactured as follows. First, the positive electrode 2 was manufactured as follows. 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate are mixed and baked in air at 900 ° C. for 5 hours to obtain LiC.
oO ₂ was obtained. As a positive electrode active material, 91 parts by mass of this LiCoO ₂ , 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride (PVDF) as a binder were mixed to obtain a positive electrode mixture. This positive electrode mixture was dispersed in N-methylpyrrolidone to form a slurry (paste form).

Next, as shown in FIG. 2, the positive electrode current collector 1
A strip-shaped aluminum foil having a thickness of 20 μm was used as 5, and the positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 15, dried, and then compression molded to obtain a strip positive electrode.

In this strip-shaped positive electrode, an electrode having a structure in which the positive electrode mixture is not applied is provided on one surface of the positive electrode current collector which does not face the negative electrode mixture layer in the portion arranged in the innermost peripheral layer of the wound electrode body. It was made.

Next, the negative electrode 1 was produced as follows. 90 parts by mass of graphite carbon material powder and 10 parts by mass of polyvinylidene fluoride (PVDF) as a binder were mixed to prepare a negative electrode mixture. This negative electrode mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste form).

Then, as shown in FIG. 2, a strip-shaped copper foil having a thickness of 15 μm was used as the negative electrode current collector, and the negative electrode mixture slurry was uniformly applied to both surfaces of the negative electrode current collector and dried. After that, compression molding was performed to obtain a strip-shaped negative electrode.

In this strip-shaped negative electrode, an electrode having a structure in which the negative electrode mixture was not applied to one surface of the current collector which did not face the positive electrode mixture layer in the portion arranged in the outermost peripheral layer of the wound electrode body was prepared. .

Negative electrode 1 and positive electrode 2 produced as described above
Were laminated via a separator 3 made of a microporous polypropylene film. That is, the separator 3, the positive electrode 2, the separator 3, and the negative electrode 1 were laminated in this order, and the separator was fixed to a winding core having a substantially rhombic cross section and wound. In addition,
The diamond-shaped winding core has a length ratio of two diagonals of 1: 3,
An arc-shaped curved finish was used at each corner of the winding core.

After winding the electrode laminate around the winding core in this way, the final end of the copper foil, which is the negative electrode current collector located at the outermost periphery, was fixed with the element adhesive tape 8 having a width of 40 mm. And
The winding core was taken out from the wound body and crushed in the diametrical direction to be compressed into an elliptical cross section, thereby producing a wound electrode body.

The wound electrode body thus prepared is housed in a nickel-plated iron outer case 10 having parallel parts and arc-shaped corners as shown in FIG.
The insulating material 9 was arranged on both upper and lower surfaces of the wound electrode body.

Then, as shown in FIG. 5, the nickel negative electrode lead 11 is led out from the negative electrode current collector to form the outer case 1.
0, the aluminum positive electrode lead 4 is led out from the positive electrode current collector, and the battery lid 7 is inserted through the gasket 5 in advance.
Was welded to the positive electrode terminal 6 attached to the. Then, the outer case 10 and the battery lid 7 were fixed by laser welding. The battery lid 7 is provided with a cleaving valve in advance.

Next, an electrolyte injection port (not shown)
More than 1 mol of LiPF _{6 in} a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of dimethyl carbonate.
An electrolytic solution prepared by dissolving it at a ratio of 1 was injected, and then the electrolytic solution injection port was welded to maintain the airtightness in the battery. In this way, height 50 mm, width 34 mm,
Fifty flat type lithium ion secondary batteries having a thickness of 6 mm were produced.

[Comparative Example] A comparative example will be described with reference to FIG. In the comparative example, as compared with the example, in the portion where the strip-shaped negative electrode is arranged in the outermost peripheral layer of the spirally wound electrode body, the negative electrode mixture is also applied to one surface of the current collector that does not face the positive electrode mixture layer. ,
Further, the strip-shaped positive electrode uses an electrode in which the positive electrode mixture is applied to one surface of the current collector that does not face the negative electrode mixture layer in the portion arranged in the innermost peripheral layer of the wound electrode body.

The winding electrode body 20 was housed in an outer case 10 having a rectangular opening as shown in FIG. As described above, the outer case 10 used was a rectangular case whose corners were clearly formed. Fifty lithium ion secondary batteries were produced in the same manner as in the example except for the above.

Next, the evaluation of the battery samples of Examples and Comparative Examples produced above will be described. First, a method for evaluating battery samples of Examples and Comparative Examples will be described. Here, with respect to each of the manufactured batteries of the example and the comparative example, the battery capacity after charging at a constant voltage of 4.2 V and a constant current of 400 mA for 5 hours was measured.

The battery capacity was measured as follows.
That is, 2.7 mA at a constant current of 400 mA after the above charging.
The capacity when discharged to 5 V was measured.

Next, the evaluation results of the battery samples of Examples and Comparative Examples will be described. In the example, the electrode having the active material layer formed on both sides of the current collector is wound many times through the separator, in the non-aqueous electrolyte secondary battery, the opening has an elliptical or rectangular corner portion. Space efficiency is improved by using an outer case having an arcuate shape, and the outermost outermost layer of the winding electrode body faces the outer case and does not face the other positive electrode. In the configuration in which the negative electrode mixture layer is not formed, and the innermost circumferential winding layer of the wound electrode body has a configuration in which the positive electrode mixture layer is not formed on the surface that does not face the negative electrode, As shown in Table 1, improvement in capacity was confirmed.

[0106]

[Table 1]

As can be seen from Table 1, the capacity of the comparative example is 325 Wh / l, while the capacity of the example is 35.
It is increased by 3 Wh / l and 28 Wh / l. The specific increase is as follows.

By forming the positive electrode mixture layer-free region and the negative electrode mixture layer-free region, the capacity is increased by 4.3%. That is, the capacity of the comparative example was 325 Wh / l, whereas it was 339 Wh / l.

By rounding the left and right sides of the outer case, the capacity is increased by 4.1%. That is,
The above-mentioned capacity 339Wh / l is increased to 353Wh / l.

From the above, according to the present embodiment, the layer of the spirally wound electrode body on the side not facing the reaction portion in the outermost layer of winding or the innermost layer of winding is a mixture layer. By using an electrode that is not formed, a component that does not contribute to the electrode reaction can be eliminated, and high capacity and high energy density can be realized.

In the case of a rectangular outer case, the void can be eliminated by forming the opening into an elliptical shape or a rectangular corner into an arc shape. Furthermore, the close contact of the wound electrode body with the outer case can be enhanced. In addition, since a space for accommodating the battery of the electronic device can be provided, it becomes easy to design the housing including the control circuit by utilizing the space. Also, a heat radiation space for charging and discharging a large current can be secured. From this, a non-aqueous electrolyte secondary battery having high reliability and high energy density can be provided.

By providing the positive electrode mixture layer absent region and the negative electrode mixture layer absent region, a spatial margin is created, and the spatial margin further increases the positive electrode mixture layer and the negative electrode mixture layer. Can be made. In this case, the length of the positive electrode and the negative electrode can be increased as in the example, but in addition to this, the thickness of the positive electrode material mixture layer and the negative electrode material mixture layer may be increased. Of course, both may be increased.

[0113]

The present invention has the following effects. The wound electrode body has a flat shape and the innermost wound layer does not have a mixture layer formed on the surface where one electrode does not face the other electrode, or the wound electrode body is wound. In the outermost peripheral layer, the mixture layer is not formed on the surface where one electrode does not face the other electrode, or the shape of the opening of the outer case is rounded on the short side of the rectangle. Since it has a shape, a battery with high energy density can be provided.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a non-aqueous electrolyte secondary battery of the present invention, showing a configuration of a wound electrode body and a shape of an outer case.

FIG. 2 shows an example of the positional relationship between the positive electrode, the negative electrode, and the separator before winding the wound electrode body of the present invention,
It is a figure which shows the example of the position of the negative electrode mixture layer nonexistence area | region.

FIG. 3 shows another example of the positional relationship between the positive electrode, the negative electrode, and the separator, and another example of the position of the positive electrode / negative electrode mixture layer non-existing region before winding the wound electrode body of the present invention. It is a figure.

FIG. 4 shows another example of the positional relationship between the positive electrode, the negative electrode, and the separator, and another example of the position of the positive electrode / negative electrode mixture layer non-existing region before winding the wound electrode body of the present invention. It is a figure.

FIG. 5 is a cross-sectional view of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 6 is a view showing a cross section of a conventional non-aqueous electrolyte secondary battery, showing a configuration of a wound electrode body and a shape of an outer case.

FIG. 7 is a diagram showing an example of a positional relationship between a positive electrode, a negative electrode, and a separator before winding a conventional wound electrode body.

[Explanation of symbols]

1 ... Negative electrode, 2 ... Positive electrode, 3 ... Separator, 4 ... Positive electrode lead, 5 ... Gasket, 6 ... Positive electrode terminal, 7 ...
Battery cover, 8 ... Element adhesive tape, 9 ... Insulation material, 10 ...
Outer case, 11 ... Negative electrode lead, 12 ... Winding innermost layer, 13 ... Rolling outermost layer, 14 ... Negative electrode current collector, 1
5: Positive electrode current collector, 16: Positive electrode mixture layer non-existing region, 1
7: negative electrode mixture layer non-existing region, 18: positive electrode mixture layer, 1
9: negative electrode mixture layer, 20: winding electrode body, 21: folding point

Claims (5)

[Claims] 1. A winding electrode in which electrodes each having a mixture layer mainly composed of an active material formed on both sides of a strip-shaped current collector are laminated with a strip-shaped separator interposed therebetween and spirally wound many times. In the body, the winding electrode body has a flat shape, and the winding innermost peripheral layer is characterized by not forming a mixture layer on the surface where one electrode does not face the other electrode. Electrode body. 2. The winding outermost layer of the winding electrode body, wherein the mixture layer is not formed on the surface where one electrode does not face the other electrode. Time electrode body. 3. A winding electrode in which electrodes each having a mixture layer mainly containing an active material formed on both sides of a strip-shaped current collector are laminated with a strip-shaped separator interposed therebetween and spirally wound many times. In a non-aqueous electrolyte secondary battery in which the body is housed in an outer case, the spirally wound electrode body has a flat shape, and the innermost spiral wound layer has one electrode on a surface not facing the other electrode. A non-aqueous electrolyte secondary battery having no agent layer formed thereon. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein the winding outermost layer of the winding electrode body has no mixture layer facing the outer case. 5. The nonaqueous electrolyte secondary battery according to claim 4, wherein the shape of the opening of the outer case is a shape in which a short side of a rectangle is rounded.