JPH10255847A - Secondary battery and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary batterry having a simple structure, a sufficient reaction area and no capacity decrease caused by a clearance generated between electrodes due to repetitive charging/discharging, by laminating and winding sheet-like positive and negative electrodes through sheet-like separators, and by arranging a packing material in a central space of an obtained flat rectangular parallelopiped electrode element. SOLUTION: A sheet-like positive electrode 4 mainly composed of lithium manganate or the like and a negative electrode 5 mainly composed of a carbonaceous material or the like capable of freely doping-dedoping a lithium ion, are laminated through separators 6 and 7. This laminated body is wound around a plate-like core to form an electrode element 3 of a flat rectangular parallelopiped as a whole. Afterwards, a filling material 10 is applied in a central space after the core is removed. This filling material 10 is preferably a plate shape having a thickness of 40 to 98% of a thickness of the central space and a width of 50 to 95% of a width dimension. This electrode element 3 is housed in a flat rectangular parallelopiped battery can 2, and a nonaqueous electrolyte is sealed in it, to obtain a secondary battery 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sheet-like positive and negative electrode wound in an elliptical spiral shape via a separator,
The secondary battery in which the positive and negative electrodes wound in an elliptical shape are housed inside a flat rectangular parallelepiped container and the container is filled with a non-aqueous electrolyte, and a method for manufacturing the secondary battery .

[0002]

2. Description of the Related Art In recent years, remarkable progress in electronic technology has realized a reduction in size and weight of electronic devices one after another. Along with this, batteries used for portable information terminals are also required to be smaller and lighter and have higher energy density. In addition, due to recent environmental problems, particularly the consideration of air pollution, electric vehicles (EVs) that do not emit carbon monoxide or nitrogen compounds have also attracted attention, and the weight and density of large secondary batteries have been reduced. It has been demanded.

Conventionally, aqueous secondary batteries such as lead batteries and nickel-cadmium batteries have been the mainstream as general-purpose secondary batteries. However, although these aqueous batteries are excellent in cycle characteristics, they are not sufficiently satisfactory in terms of battery weight and energy density.

On the other hand, in recent years, a non-aqueous electrolyte secondary battery using a material capable of doping / dedoping lithium ions, such as lithium, a lithium alloy or a carbon material, for a negative electrode and a lithium composite oxide for a positive electrode. Research and development. This non-aqueous electrolyte secondary battery has attracted attention because of its advantages such as high energy density, low self-discharge, and lightness.

As described above, in the field of electronic equipment, the size and weight of the electronic equipment have been reduced, and in order to cope with this, the battery is required to have a flat rectangular parallelepiped shape from the viewpoint of effective use of the base in the equipment. Is increasing. Also,
Similarly, in the case of an EV mounted, it may be formed in a flat rectangular parallelepiped from the viewpoint of effective use of space in the device. As a battery electrode having such a shape, a structure in which a plurality of strip-shaped positive and negative electrodes are alternately stacked via a separator is generally used.

[0006] However, it is said that it is difficult to optimize the overall thickness of the electrode having a laminated structure as described above. For example, when a relatively thick strip-shaped positive and negative electrode is used, the number of each of the strip-shaped positive and negative electrodes accommodated in the battery can is reduced, so that the structure of the electrode is simplified and the productivity is improved.
On the other hand, since the reaction area of the electrode becomes small, the heavy load characteristics of the battery become insufficient and the battery is not suitable for quick charging.

On the other hand, when the strip-shaped electrode is made thin, the reaction area becomes large, and the heavy load characteristics of the battery are improved. However, this requires a large number of electrodes, which complicates the structure and reduces productivity.

Therefore, as an electrode which can secure a reaction area without complicating the structure of the electrode, a long sheet-like positive / negative electrode is laminated via a separator, and this is wound in a number of turns. The use of electrode elements has been proposed. The wound electrode element has a structure in which a large number of positive and negative electrodes are stacked when viewed in a vertical cross section, and a large electrode reaction area can be obtained. On the other hand, since only one positive and negative electrode is required, the structure is extremely simple.

[0009]

In the structure in which the sheet-like positive and negative electrodes are wound as described above, a sufficient reaction area can be ensured while simplifying the structure of the electrodes. However, when this wound electrode body element is applied to a rectangular battery, the following problems occur.

That is, an electrode element having a wound structure is usually
It is manufactured by using a core having a circular cross section, an elliptical cross section, or a flat plate, winding the above-described electrode laminate many times on the core, and extracting the core from the core after the winding. When the electrode element of the winding structure is used for a rectangular battery,
Further, it is necessary to compress and accommodate the wound body in the diametrical direction according to the shape of the container.

However, when a battery having a positive electrode composed mainly of lithium manganate as a main component and a negative electrode composed mainly of a carbon material capable of being doped / dedoped with lithium ions as a main component has a wound structure, the fault surface after charging is observed. It was found that a gap was partially left between the positive and negative electrodes. The gap is caused by the fact that the positive electrode contracts and the negative electrode expands upon charging, so that the stress deforms the central space of the wound structure of the electrode element, and a gap is generated between the positive and negative electrodes. This gap is generated after the first charge, and the gap once generated is not eliminated by the subsequent repetition of charge and discharge. As a result, the electrode reaction becomes non-uniform and the battery capacity is reduced.

This phenomenon becomes more conspicuous as the central space of the wound electrode element increases, that is, as the size of the wound electrode element increases. In the case of a small and thin rectangular parallelepiped battery used for portable information devices, etc., a winding method or a method of shaping a wound electrode may be able to cope with such a case, but it is not perfect. In particular, when the wound-structured electrode element is large, the above-described method also causes problems such as the occurrence of electrode breakage in the wound-structured electrode element.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a structure in which sheet-like positive and negative electrodes laminated via a separator are wound into a flat rectangular parallelepiped shape and housed in a container. In a secondary battery, a secondary battery in which a gap does not occur between the positive and negative electrodes even when charging and discharging are repeated,
It is an object of the present invention to provide a manufacturing method thereof.

[0014]

In the secondary battery of the present invention, sheet-like positive and negative electrodes are laminated via a sheet-like separator, and this is wound to form an overall flat rectangular parallelepiped electrode element. In a secondary battery formed and containing this electrode element in a flat rectangular parallelepiped container in which a non-aqueous electrolyte is sealed, a filler was provided in the central space of the electrode element.

Therefore, since the filler is disposed in the central space of the electrode element having a sheet-like positive / negative wound structure, even if the sheet-like positive / negative electrode expands / contracts due to repetition of charging and discharging, the positive / negative electrode does not change. The generation of a gap between the electrodes is prevented. Note that such a structure in which the filler is disposed in the central space of the wound electrode element is known as insertion of a pipe-shaped pin in a cylindrical battery.

However, this is because the heat dissipation of the electrode elements is mainly performed on a daily basis and is not formed so as to prevent the generation of a gap due to the contraction of the sheet-like electrode. Also, needless to say, cylindrical batteries have poor space efficiency and hinder miniaturization of equipment using the batteries. In that regard, a battery having a flat rectangular parallelepiped container has a good space efficiency and can contribute to miniaturization of a device using the battery. No attempt has been made to dispose the filler in the central space of the wound electrode element.

The filler used in the present invention may be any member that can prevent the occurrence of a gap due to the expansion and contraction of the sheet-like positive and negative electrodes as described above. For example, the filler may be a flat rectangular parallelepiped made of resin or aluminum. Allow plate materials. Further, the sheet-shaped electrode may be a member that can be wound and can be a positive and negative electrode, and a structure in which an electrode lead is attached to one end is allowed.

As the positive electrode, a positive electrode mixture slurry is uniformly applied to both sides of a band-shaped aluminum foil serving as a positive electrode current collector, and the slurry is dried and then entirely formed by compression to form a band. Tolerate. As the positive electrode mixture slurry, one in which a positive electrode mixture is dispersed in N-methyl 2-pyrrolidone is allowed. As the positive electrode mixture, 92 parts by weight of LiMn204 as a positive electrode active material and 5 parts of graphite as a conductive agent are used. A mixture of 3 parts by weight of polyvinylidene fluoride as a binder is allowed. LiMn204, which is a positive electrode active material, is produced by mixing lithium carbonate and manganese dioxide, and baking this in air at 780 ° C. for up to 12 hours.

As the negative electrode, a negative electrode mixture slurry is applied to both sides of a 10 μm thick strip-shaped copper foil serving as a negative electrode current collector, and then dried and compressed to form a strip. Accept what you did. As the negative electrode mixture slurry,
N-methyl 2-pyrrolidone as a solvent in which a negative electrode mixture is dispersed is acceptable. As the negative electrode mixture, a mesophase-based carbon material powder as a carrier for an electrode active material is used.
0 parts by weight, polyvinylidene fluoride (PVD)
A mixture of 10 parts by weight of F) is allowed.

The container may have any shape as long as it has a flat rectangular parallelepiped shape, accommodates electrode elements of a similar shape, and can enclose a non-aqueous electrolyte. For example, a stainless steel can is acceptable.
As the non-aqueous electrolyte, a solution prepared by dissolving LiPF6 at a ratio of 1 mol / 1 in a mixed solvent of 30 parts by weight of ethylene carbonate and 70 parts by weight of diethyl carbonate is allowed.

As another invention in the above-described secondary battery, the filling is formed in a flat plate shape as a whole. Therefore, when the electrode element is wound so as to be accommodated in a flat rectangular parallelepiped container, the central space of the wound structure is appropriately charged with the flat-shaped filler.

In another aspect of the secondary battery as described above, the thickness of the filler is 40 to 98% of the thickness of the center space of the wound electrode element. Therefore, since the thickness dimension of the filler is 40% or more of the center space of the electrode element,
Even if the positive and negative electrodes expand and contract due to charging, generation of a gap is well prevented, and the thickness dimension of the filler is 9% of the central space of the electrode element.
Since it is 8% or less, the filler is easily inserted into the central space of the electrode element in the assembly process.

In another aspect of the secondary battery as described above, the width of the filling is 50 to 95% of the width of the center space of the wound electrode element. Therefore, since the width dimension of the filler is 50% or more of the center space of the electrode element, even if the positive and negative electrodes expand and contract due to charging, the generation of a gap is favorably prevented. Since it is 95% or less, the filler is easily inserted into the central space of the electrode element in the assembly process.

In another aspect of the above-described secondary battery, a recess is formed on the surface of the filler. Therefore, when providing an electrode lead at one end of a sheet-like electrode,
This electrode lead can be arranged in the recess of the filling. As the positive electrode lead, a structure in which an aluminum flat plate is welded to one end of the positive sheet electrode is allowed. As the negative electrode lead, for example, a nickel flat plate is used as the negative electrode lead. A structure welded to one end of a sheet-like electrode is allowed.

In another aspect of the secondary battery as described above, the filler is composed of a plurality of parts. Therefore, when an electrode lead is provided at one end of a sheet-like electrode, the electrode lead can be arranged in a gap between a plurality of components of the filler. In addition,
As the plurality of parts of the filler for realizing such a structure, for example, two prisms arranged side by side so that electrode leads can be arranged in a gap are allowed.

In another aspect of the above-described secondary battery, the filling is made of a material that does not chemically react with the non-aqueous electrolyte. Therefore, although the filler disposed in the central space of the electrode element is necessarily immersed in the non-aqueous electrolyte, the non-aqueous electrolyte does not react with the filler.

In another aspect of the above-described secondary battery, the positive electrode in the form of a sheet is formed mainly of lithium manganate, and the negative electrode in the form of a sheet is doped with lithium ions. It is formed mainly of a carbon material that can be undoped.

In the secondary battery having such a structure, when lithium ions intercalate from the positive electrode to the negative electrode during the first charge, the positive electrode dedoped with lithium ions contracts, and the negative electrode doped with lithium ions has a lattice constant. Become larger and expand. The generated stress acts to deform the center space of the wound structure of the electrode element. When the center space is deformed, a gap is generated between the stacked positive and negative electrodes. This gap does not contribute to the doping / de-doping of lithium ions during the operation of the battery, and the lithium ions that do not contribute to the concentration of the current density at the periphery of the gap are deposited as metallic lithium. Become. This deposition of gold-gold lithium causes the ultimate reduction in battery capacity and causes a decrease in battery performance. However, if the filler is arranged so that the center space of the wound structure of the electrode element is not deformed, no gap occurs between the positive and negative electrodes even when charged.

In the method for manufacturing a secondary battery according to the present invention, sheet-like positive and negative electrodes are laminated via a sheet-like separator,
The positive and negative electrodes laminated together with this separator are wound around a flat core to form the entire electrode element into a flat rectangular parallelepiped shape, and the core is removed from the center space of the wound structure of this electrode element and filled. The electrode element into which the filler was inserted was accommodated in a flat rectangular parallelepiped container, and a nonaqueous electrolyte was sealed in the container.

Therefore, in a secondary battery formed by such a manufacturing method, an electrode element having a similar winding structure is arranged inside a flat rectangular parallelepiped container in which a non-aqueous electrolyte is sealed. Since the filler is disposed in the central space of the electrode element, a gap may be generated between the positive and negative electrodes even if the sheet-like positive and negative electrodes expand and contract due to repetition of charging and discharging. Is prevented.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing an assembling structure of the secondary battery according to the present embodiment, FIG. 2 is a characteristic diagram showing a relationship between a battery capacity and a thickness dimension of a filler when charging and discharging are repeated, FIG. 3 is a characteristic diagram showing the relationship between the battery capacity and the width of the filler when charging and discharging are repeated,
FIG. 4 is a perspective view showing various modifications of the filler.

First, the secondary battery 1 of the present embodiment is similar to the one shown in FIG.
As shown in FIG. 1, a battery can 2 as a container is formed in a flat rectangular parallelepiped shape, and an electrode element 3 having a similar shape is accommodated in the inside thereof. The electrode element 3 includes sheet-like positive and negative electrodes 4 and 5 and sheet-like separators 6 and 7, and the electrodes 4 and 5 are wound in a stacked state with the separators 6 and 7 interposed therebetween. . Electrode leads 8 and 9 are attached to one ends of the electrodes 4 and 5, and a flat filling 10 is disposed in a central space of the electrode element 3.

As described above, the secondary battery 1 of the present embodiment has a flat rectangular parallelepiped shape, and therefore has a good space efficiency, and can be used for miniaturization of equipment using the same. And transport is also easy. The electrode element 3 is also formed in a flat rectangular parallelepiped shape so as to be accommodated in the battery can 2 having such a shape, but a filler 10 having a similar shape is arranged in the center space of the wound structure. Therefore, even if the sheet-like positive and negative electrodes 4 and 5 expand and contract due to charging and discharging, the center space is not deformed and a gap is not generated. For this reason,
The secondary battery 1 according to the present embodiment can stably exhibit good performance without a decrease in capacity even when charge and discharge are repeated.

In FIG. 1, in order to facilitate the description of the structure, the electrode element 3 projects upward from the battery can 2,
Although the state where the filler 10 protrudes upward from the electrode element 3 is shown, actually, the filler 10 is disposed inside the central space of the electrode element 3, and the electrode element 3 is It is arranged inside the battery can 2. In the drawings, a method for manufacturing the secondary battery 1 having the above-described structure will be described in detail below. First, the negative electrode 5
Was manufactured as follows. A powder of a mesophase-based carbon material was used as a carrier for the negative electrode active material,
0 parts by weight, polyvinylidene fluoride (PVD)
F) was mixed with 10 parts by weight to prepare a negative electrode mixture. Then, this negative electrode mixture was dispersed in N-methyl 2-pyrrolidone as a solvent to obtain a negative electrode mixture slurry.

This negative electrode mixture slurry is applied to both sides of a 10 μm-thick strip-shaped copper foil serving as a negative-side electrode current collector and dried, and then compression-formed to form a strip-shaped negative electrode 5. Made. The band-shaped negative electrode 5 had the same mixture thickness of 80 μm on both sides, a width of 39 mm, and a length of 465.
mm. Then, a flat plate made of nickel having a thickness of 0.1 mm and a width of 3 mm was welded to one end of the negative electrode 5 manufactured as described above to form a negative electrode lead 9.

The positive electrode 4 was manufactured as follows. First, mix lithium carbonate and manganese dioxide,
LiMn by firing in air at 780 ° C for up to 12 hours
204 was obtained. This LiMn204 is used as a positive electrode active material,
This was mixed with 92 parts by weight, 5 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder to prepare a positive electrode mixture. Then, this positive electrode mixture was mixed with N-
The mixture was dispersed in methyl 2-pyrrolidone to form a positive electrode mixture slurry.

This positive electrode mixture slurry is uniformly applied to both sides of a 25 μm-thick strip-shaped aluminum foil serving as a positive electrode current collector and dried, and then compression-formed to form a strip-shaped positive electrode 4. Produced. The band-shaped positive electrode 4 had the same mixture thickness of 80 μm on both sides, a width of 37 mm, and a length of 395 mm. Then, an aluminum flat plate having a thickness of 0.1 mm and a width of 3 mm was welded to one end of the positive electrode 4 manufactured as described above to form a positive electrode lead 8.

The strip-like positive and negative electrodes 4 and 5 produced as described above are connected to the negative electrode 5 and the negative electrode 5 through separators 6 and 7 made of a microporous polypropylene film having a thickness of 25 μm and a width of 41 mm. One of the separators 6, the positive electrode 4, and the second separator 7 are stacked in this order, and one end of the stacked body is fixed to a flat plate-shaped core (not shown) having a rectangular cross-sectional shape. Wound. After winding the laminated body around the core in this way, the final ends of the separators 6 and 7 located at the outermost periphery were fixed to the wound body with an adhesive tape 11 having a width of 15 mm. And the electrode element 3 was manufactured by extracting a core from a winding body.

A rectangular flat plate-shaped filler 10 made of polypropylene was inserted into the center space of the wound structure of the electrode element 3 thus manufactured, that is, where the core was located. The electrode element 3 on which the filler 10 is arranged is
It was housed in a flat rectangular parallelepiped battery can 2 made of stainless steel, and insulating plates (not shown) were arranged on both upper and lower surfaces of the electrode element 3.

Next, the positive electrode lead 8 was welded to the battery can 7, the negative electrode lead 8 was welded to the battery lid, and the battery lid was fixed to the battery can 7 by laser welding. Then, a non-aqueous electrolyte prepared by dissolving LiPF6 at a rate of 1 mol / 1 in a mixed solvent of 30 parts by weight of ethylene carbonate and 70 parts by weight of diethyl carbonate was prepared. The battery can 7 was kept confidential by injecting it from a liquid injecting section (not shown) and sealing the electrolyte pouring section. With the above process, thickness 9mm, width 26m
m, a flat rectangular parallelepiped non-aqueous electrolyte type secondary battery 1 having a height of 45 mm was produced.

As described above, the thickness of the filler 10 is increased from 10% to 95% of the dimension of the central space of the wound electrode element 3.
%, And a total of 10 rechargeable batteries 1 each having a filler whose width was changed from 10% to 95% for each 10%, and a constant current under conditions of an upper limit voltage of 4.2 V and a charging current of 0.5 A. Charge 2.
After performing for 5 hours, the battery capacity was measured after repeating the charge / discharge cycle of discharging the battery under the condition of a final voltage of 3.0 V up to 100 times.

FIGS. 2 and 3 show the capacity distribution of the 100 cycles. As is apparent from these drawings, the filling 10
Those having a thickness and a width of 50% to 90% have very little capacity reduction. This is because there is no gap between the positive and negative electrodes 4 and 5 of the electrode element 3 even when charging and discharging are repeated, since the filler 10 is inserted into the central space of the electrode element 3. From this, the filling 1 having a size of 50% to 90% of the thickness and width of the electrode element 3 in the center space of the wound structure of the electrode element 3
It has been found that placing 0 is effective in preventing the capacity of the secondary battery 1 from decreasing.

That is, the secondary battery 1 of the present embodiment has a flat rectangular parallelepiped shape and good space efficiency as described above, and the electrode elements 3 inside the secondary battery 1 are also formed in a flat rectangular parallelepiped shape. However, since the filler 10 having a similar shape is arranged in the center space of the wound structure, even if charge and discharge are repeated, gaps between the sheet-like positive and negative electrodes 4 and 5 are generated and the capacity is reduced. And good performance can be stably exhibited.

Further, as a method of manufacturing the secondary battery 1 of the present embodiment, the wound electrode element 3 is formed by a method similar to the conventional method, and the core is removed from the center space of the electrode element 3. Since the filling 10 is inserted, the filling 10
Can be easily realized in the central space of the electrode element 3.

Further, in the secondary battery 1 of the present embodiment, as described above, the thickness of the filler 10 is 40 to 98% of the central space of the electrode element 3 and the width is 50 to 95%. As a result, it is possible to satisfactorily prevent the formation of a gap between the positive and negative electrodes 4 and 5, and to easily insert the filler 10 into the central space of the electrode element 3, thereby lowering the battery capacity. It is possible to easily manufacture a structure that does not have the above.

Furthermore, in the secondary battery 1 of the present embodiment, since the filler 10 is formed in a flat rectangular parallelepiped shape, the electrode element 3 is formed in a flat rectangular parallelepiped shape corresponding to the battery can 2.
Center space can be accurately filled. Further, the secondary battery 1 of the present embodiment has a
0 is added, but since the filler 10 is made of a material that does not chemically react with the non-aqueous electrolyte, the filler 1
0 does not react with the non-aqueous electrolyte to lower the performance of the battery.

The present invention is not limited to the above-described embodiment, but allows various modifications without departing from the gist of the present invention. For example, in the above-described embodiment, the core is removed from the center space of the electrode element 3 manufactured in the same manner as in the related art, and the filler 10 is inserted. However, the electrodes 4 and 5 and the separators 6 and 7 are added to the filler 10 from the beginning. Can be wound to form the electrode element 3.

In this case, it is difficult to use the conventional production equipment, but it is not necessary to remove the core and insert the filler 10. Further, since the thickness and width of the filler 10 can be set to 100% of the central space of the electrode element 3, it is possible to reliably prevent a gap from being generated between the sheet-like electrodes 6 and 7. it can.

In the above-described embodiment, the filling material 10 is exemplified as a simple flat plate. However, since it is only necessary to maintain the outer shape capable of preventing the deformation of the central space of the electrode element 3, for example, FIG. As shown in FIG. 5, it is also possible to form a filler 22 having a lightening hole 21 having a diameter of about 2 mm continuously formed of aluminum or the like so as to reduce the overall weight and increase the volume of the non-aqueous electrolyte. .

Further, in the above-described embodiment, the sheet-like electrodes 5 and 6 having the electrode leads 8 and 9 mounted on one end, respectively, are wound around the plate-like filler 10, but in this case, the electrode leads 8 and 9 are wound. Due to the thickness of 9, the outer shape of the electrode element 3 may be hindered. If this is a problem, see FIG.
As shown in FIG. 4B, a filler 24 is formed in a shape in which a concave portion 23 is formed on the surface, and the electrode lead 8 is positioned in the concave portion 23. As shown in FIG. Are formed side by side at predetermined intervals to form a filler 26,
It is preferable that the electrode lead 8 be located in the gap.

[0051]

Since the present invention is configured as described above, it has the following effects.

In the secondary battery according to the first aspect of the present invention, sheet-like positive and negative electrodes are laminated via a sheet-like separator, and this is wound to form an overall flat rectangular parallelepiped electrode element. In a secondary battery in which this electrode element is accommodated in a flat rectangular parallelepiped container in which a nonaqueous electrolyte is sealed, by providing a filler in the central space of the electrode element, the container is flat. Since it is a rectangular parallelepiped, space efficiency is good, and even if the sheet-like positive and negative electrodes of a wound structure housed in a container of such a shape expand and contract due to repetition of charging and discharging, deformation of its central space Is prevented by the filler, so that it is possible to prevent a decrease in battery capacity due to a gap between the electrodes.

According to a second aspect of the present invention, there is provided the secondary battery according to the first aspect, wherein the filling is formed in a flat plate shape as a whole, so that the filling is accommodated in a flat rectangular parallelepiped container. When an electrode element having a wound structure is formed, the center space thereof can be accurately filled with the filling material, and a gap between the positive and negative electrodes due to deformation of the center space can be favorably prevented.

According to a third aspect of the invention, there is provided the secondary battery according to the second aspect, wherein the thickness of the filler is 40 to 98% of the thickness of the center space of the wound electrode element. Since the thickness of the filler is 40% or more of the center space of the electrode element, it is possible to prevent the occurrence of a gap between the positive and negative electrodes, and the thickness of the filler is 98% of the center space of the electrode element. % Or less, the filler can be easily inserted into the central space of the electrode element, and a structure capable of favorably preventing a decrease in battery capacity can be realized with good productivity.

The invention described in claim 4 is the second or third invention.
Wherein the width of the filler is 50% to 95% of the width of the center space of the wound electrode element.
Since the width dimension of the filler is 50% or more of the center space of the electrode element, it is possible to prevent a gap from being generated between the positive and negative electrodes, and to reduce the width dimension of the electrode element. Since it is 95% or less of the central space, the filler can be easily inserted into the central space of the electrode element, and a structure capable of favorably preventing a decrease in battery capacity can be realized with good productivity.

The invention according to claim 5 provides the invention according to claims 2 to 5
The secondary battery according to any one of the above, wherein the concave portion is formed on the surface of the filler, so that even when the electrode lead is attached to one end of the sheet-like electrode, the electrode lead is provided in the concave portion of the filler. In this case, the electrode element can be formed in a flat rectangular parallelepiped shape as a whole.

The invention according to claim 6 provides the invention according to claims 2 to 4
The secondary battery according to any one of the above, wherein the filler is composed of a plurality of parts, so that even when an electrode lead is attached to one end of a sheet-like electrode, the electrode lead is disposed in a recess of the filler. In this case, the electrode element can be formed in a flat rectangular parallelepiped shape as a whole.

The invention according to claim 7 is the invention according to claims 1 to 6
The secondary battery according to any one of the above, wherein the filler is made of a material that does not chemically react with the non-aqueous electrolyte, thereby preventing the filler from reacting with the non-aqueous electrolyte and deteriorating the performance of the battery. Is done.

The invention according to claim 8 is the invention according to claims 1 to 7
The secondary battery according to any one of the above, wherein the sheet-like positive electrode is formed mainly of lithium manganate, and the sheet-like negative electrode is doped with lithium ions.
Since the undoped carbon material is formed as a main component, the sheet-like positive and negative electrodes expand and contract by charging and discharging, but since the filler is located in the central space of the wound structure, the electrode is There is no reduction in capacity due to generation of a gap between them.

According to a ninth aspect of the present invention, in the method for manufacturing a secondary battery, sheet-like positive and negative electrodes are laminated via a sheet-like separator, and the positive and negative electrodes laminated together with the separator are formed into a flat core. The electrode element is formed into a flat rectangular parallelepiped shape as a whole, the core is removed from the center space of the wound structure of the electrode element, a filler is inserted, and the electrode element into which the filler is inserted is removed. By filling the non-aqueous electrolyte inside the flat rectangular parallelepiped container and filling the non-aqueous electrolyte inside the container, the filler is disposed in the center space of the flat rectangular parallelepiped wound electrode element. Can be easily realized.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a secondary battery according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a change in battery capacity when the thickness of a filler with respect to a center space of an electrode element is changed.

FIG. 3 is a characteristic diagram showing a change in battery capacity when the width of the filling material with respect to the center space of the electrode element is changed.

FIG. 4 shows various modifications of the packing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Battery can which is a container 3 Electrode element 4,5 Electrode 6,7 Separator 8,9 Electrode lead 10 Filler 11 Adhesive tape 21 Lightening hole 22 Filler 23 Depression 24 Filler 25 Parts 26 Filler

Claims (9)

[Claims] 1. A sheet-like positive / negative electrode is laminated via a sheet-like separator, and this is wound to form an overall flat rectangular parallelepiped electrode element. A secondary battery housed in an enclosed flat rectangular parallelepiped container, characterized in that a filler is provided in a central space of the electrode element. 2. The secondary battery according to claim 1, wherein the filler is formed in a flat plate shape as a whole. 3. The secondary battery according to claim 2, wherein the thickness of the filling is 40 to 98% of the thickness of the center space of the wound electrode element. 4. The secondary battery according to claim 2, wherein the width of the filler is 50 to 95% of the width of the center space of the wound electrode element. 5. The secondary battery according to claim 2, wherein a recess is formed on a surface of the filling. 6. The secondary battery according to claim 2, wherein the filler comprises a plurality of parts. 7. The secondary battery according to claim 1, wherein the filler is made of a material that does not chemically react with the non-aqueous electrolyte. 8. A sheet-shaped positive electrode is formed mainly of lithium manganate, and a sheet-shaped negative electrode is formed mainly of a carbon material capable of freely doping / dedoping lithium ions. The secondary battery according to any one of claims 1 to 7, wherein 9. A sheet-like positive / negative electrode is laminated via a sheet-like separator, and the positive / negative electrode laminated together with the separator is wound around a plate-shaped core, so that the electrode element is entirely flat rectangular parallelepiped. The core is removed from the center space of the wound structure of the electrode element, a filler is inserted, and the electrode element into which the filler is inserted is accommodated in a flat rectangular parallelepiped container. A method for manufacturing a secondary battery, wherein a non-aqueous electrolyte is sealed in a container.