JP2003157888A - Plate-like secondary battery and method of manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of preventing a twist of an electrode group caused by the expansion-contraction of electrodes at charging-discharging time, and superior in the cycle service life. SOLUTION: This plate-like secondary battery covers the electrode group having a flat cross-sectional shape with an enclosing material by winding belt- like laminated bodies by successively laminating the positive electrode, an electrolyte layer, and the negative electrode, and is arranged so as to form a void part between the two belt-like laminated bodies mutually adjacent on the major axis of a right-angled directional cross section to the winding axis of the flat electrode group. This manufacturing method of the plate-like secondary battery is characterized by manufacturing the plate-like secondary battery by sealing the electrode group in the enclosing material by a process of forming the electrode group having the flat cross-sectional shape by pressing the belt-like laminated bodies after cylindrically winding the belt-like laminated bodies, interposing a separator between the positive electrode and the negative electrode, sandwiching a spacer between the adjacent belt-like laminated bodies, followed by a process of impregnating a nonaqueous electrolyte into this electrode group, and a process of extracting the spacer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat secondary battery having high volume energy density, which hardly causes twisting even after repeated charging and discharging, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the performance and miniaturization of electronic devices such as mobile phones and notebook personal computers have made remarkable progress, and they are one of the base technologies for reducing the size and weight of these electronic devices. Can improve the performance of the secondary battery used as a power source, but further higher performance is required, so higher performance is required.

In particular, non-aqueous lithium ion secondary batteries are
Due to its high battery voltage, high discharge capacity, and excellent recycling characteristics, it has been particularly actively researched in recent years so that it can be used in the above-mentioned applications.

Further, the development of a thin flat plate secondary battery using an aluminum can or a laminated film as an exterior material has attracted particular attention because of its high volume energy density.

However, in the secondary battery thus constructed as a thin flat plate secondary battery, stress is generated in the electrode group due to the expansion and contraction of the electrodes due to charging and discharging, and the secondary batteries are particularly thinly folded. Improperly twisting in the electrode group causes the battery shape to be deformed, resulting in unevenness, or being bent, making it difficult to take out the battery stored in the narrow battery storage box, or difficult to store. Had problems such as a decrease in energy capacity per volume and an adverse effect on cycle characteristics.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flat secondary battery capable of suppressing twisting of an electrode group due to expansion and contraction of electrodes.

[0007]

The present inventor has conducted extensive studies in view of the above problems, and as a result, in order to prevent twisting of the electrode group due to expansion and contraction of the electrode due to charge and discharge, The present invention has been completed based on the finding that twisting can be solved by absorbing deformation stress by providing a void in the winding axis direction.

That is, the flat secondary battery of the present invention is a flat secondary battery in which a strip-shaped laminated body in which a positive electrode, an electrolyte layer and a negative electrode are sequentially laminated is wound and an electrode group having a flat cross section is covered with an exterior material. In the secondary battery, the flat electrode group is arranged so that a void portion is formed between the two strip-shaped laminated bodies adjacent to each other on a long axis of a cross section in a direction perpendicular to a winding axis of the flat electrode group. To do.

According to another aspect of the present invention, there is provided a method for manufacturing a flat secondary battery, wherein a strip-shaped laminated body having a separator interposed between a positive electrode and a negative electrode is provided with a spacer between adjacent strip-shaped laminated bodies. After sandwiching and winding in a cylindrical shape, pressing to form an electrode group having a flat cross-sectional shape, a step of impregnating the electrode group with a non-aqueous electrolyte, a step of extracting a spacer, the electrode group Is sealed in an exterior material to manufacture a flat secondary battery.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION [I] Flat plate secondary battery (1) Outline of structure The flat plate secondary battery 1 of the present invention has the following members (i) to ( iv), and the void portion 8 is formed on the major axis L in a cross section perpendicular to the length direction of the winding shaft 7 of the electrode group 6.

Member (i): Sheet-shaped positive electrode 3 including a positive electrode current collector and a positive electrode active material layer carried on one side or both sides of the positive electrode current collector, and one side of the negative electrode current collector and the negative electrode current collector Alternatively, a sheet-shaped negative electrode 5 including a negative electrode active material layer that is supported on both surfaces and that includes a material that absorbs and releases electrolyte ions,
A strip-shaped laminated body 9 in which the sheet-shaped separator 5 disposed between the positive electrode 3 and the negative electrode 5 is laminated is folded and folded,
Electrode group 6 having a flat cross-sectional shape in which a void portion 8 is formed at least at one location on the long axis L in a cross section perpendicular to the length direction of the winding shaft 7 Member (ii): The electrode group 6 is impregnated Solvent Member (iii): Electrolyte Member (iv) Dissolved in the Solvent: Exterior Material 2 (2) in which the Electrode Group 6 is Stored Specific Description of Structure The flat plate secondary battery 1 of the present invention is shown in the drawings. In describing in detail, a thin lithium-ion battery, which is one of particularly suitable non-aqueous electrolyte batteries, will be specifically described below.

FIG. 1 is a schematic view showing a cross-sectional view of a thin lithium ion secondary battery. In this flat plate-shaped secondary battery 1, the strip-shaped laminated body including the positive electrode 3, the negative electrode 5, and the separator 4 may not necessarily be integrated, but under the following condition (a) or condition (b). It is preferably integrated under the conditions as described.

Condition (a): The positive electrode 3 and the separator 4 are integrated by a polymer having an adhesive property present in at least a part of the boundary between them, and the negative electrode 5 and the separator 4 are Are integrated by at least a part of the boundary of the adhesive polymer. In particular, the positive electrode 3 and the separator 4
Are integrated with the adhesive polymer interspersed in the interior and the boundary thereof, and the negative electrode 5 and the separator 4 are integrated with the adhesive polymer interspersed in the interior and the boundary. It is desirable that they are integrated.

Condition (b): The strip-shaped laminate comprising the positive electrode 3, the negative electrode 5 and the separator 4 is the positive electrode 3.
And the binder contained in the negative electrode 5 is integrated by thermosetting. This condition (a) or condition (b)
With such a configuration, it is possible to further reduce the swelling of the exterior material 2, which is preferable.

The performance also the flat secondary battery 1, the battery capacity (Ah) and 1
The product of the battery internal impedance (mΩ) at 10 kHz
It is desirable to be in the range of 110 mΩ · Ah, preferably 20 to 60 mΩ · Ah.

By setting the product of the capacity and the impedance within the above range, the large current charge / discharge cycle characteristics can be further improved. Here, the battery capacity is a nominal capacity or a discharge capacity when discharged at 0.2C.

The product of battery capacity and impedance is 10 to 1
The plate-shaped secondary battery 1 having a range of 10 mΩ · Ah can be manufactured by, for example, the manufacturing method (I) described later or the manufacturing method (II) described later. However, in the manufacturing method (I), the amount of the adhesive polymer added, the distribution of the adhesive polymer, and the initial charging condition are set so that the product of the battery capacity and the impedance is within the range of 10 to 110 mΩ · Ah. It is necessary to.

In the manufacturing method (II), the product of the battery capacity and the impedance is 10 to 110 mΩ · Ah with respect to the temperature and the press pressure for molding the electrode group and the initial charging condition.
It is necessary to set it so that it is within the range.

(3) Constituent member (A) In the positive electrode positive electrode, a conductive agent and a binder are appropriately suspended in a positive electrode active material in a solvent, and the suspension is applied to a current collector such as an aluminum foil, It is manufactured by drying and pressing into strip electrodes.

The positive electrode active material the positive electrode active material, various oxides, may be mentioned sulfides. Specifically, for example, manganese dioxide (Mn
O ₂ ), lithium manganese composite oxide (for example, LiM
n ₂ O ₄ or LiMnO ₂ ), lithium nickel composite oxide (for example, LiNiO ₂ ), lithium cobalt composite oxide (for example, LiCoO ₂ ), lithium nickel cobalt composite oxide (for example, LiNi _1-x Co).
_x O _2), lithium manganese cobalt composite oxides (for example, LiMnO _4), vanadium oxide _{(e.g., V} 2 O
₅ ) etc. can be mentioned. Further, an organic material such as a conductive polymer material or a disulfide-based polymer material can also be used.

A more preferable positive electrode active material is a lithium manganese composite oxide (for example, LiM) having a high battery voltage.
n ₂ O ₄ ), lithium nickel composite oxide (for example, L
iNiO ₂ ), lithium cobalt composite oxide (for example,
LiMn ₂ O ₄ ), lithium nickel cobalt composite oxide (eg LiNi _0.8 Co _0.2 O ₂ ), lithium manganese cobalt composite oxide (eg LiMn _x C)
o _{1-x O 2),} and the like can be given.

Conductive Agent Examples of the conductive agent include acetylene black, carbon black and graphite.

Binder As the binder , for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, etc. can be mentioned.

Mixing Ratio The mixing ratio of the positive electrode active material, the conductive agent, and the binder is generally 50 to 95% by weight of the positive electrode active material, 0 to 45% by weight of the conductive agent, and 0.5 to 20% of the binder. It is used within the range of 80% by weight, but preferably within the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

(B) Electrolyte Layer The electrolyte layer prevents electron conduction between the positive electrode and the negative electrode and has lithium ion conductivity. Usually, the electrolyte and a non-aqueous solvent is used to hold the electrolytic solution in a separator made of a porous material, instead of the electrolytic solution, a polymer gel electrolyte containing an electrolytic solution in the polymer It can also be used. Further, when using the polymer gel electrolyte, a polymer solid electrolyte containing only the electrolyte in the polymer or a lithium ion conductive inorganic solid electrolyte, only these materials without using a separator It can also be a layer.

[0026] As the separator the separator, there may be mentioned a known separator, for example, a synthetic resin nonwoven fabric, a polyethylene porous film, the use of porous polypropylene film or the like.

Non-Aqueous Solvent Specifically, a cyclic carbonate such as ethylene carbonate (EC) or propylene carbonate (PC), or a mixture of a cyclic carbonate and a non-aqueous solvent having a viscosity lower than that of the cyclic carbonate (hereinafter referred to as a second solvent). It is preferable to use a non-aqueous solvent mainly composed of a solvent.

Examples of the second solvent include chain carbonates such as dimethyl carbonate, methylethyl carbonate and diethyl carbonate, cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and the like.
Examples thereof include chain ethers such as dimethoxyethane and diethoxyethane, γ-butyrolactone, acetonitrile, methyl propionate and ethyl propionate.

Electrolytes Examples of electrolytes include alkali salts,
A lithium salt is particularly preferable.

As the lithium salt, lithium hexafluorophosphate (LiPF ₆ ) and lithium borofluoride (LiB) are used.
F ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), lithium perchlorate (LiClO ₄ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ) and the like can be mentioned. In particular, it is preferable to use lithium hexafluorophosphate (LiPF ₆ ) and lithium borofluoride (LiBF ₄ ).

(Dissolved Amount) The dissolved amount of the electrolyte in the non-aqueous solvent is 0.5 to
It is preferably 2.0 mol / liter.

Polymer gel electrolyte As the polymer gel electrolyte, the solvent and the electrolyte are dissolved in a polymer material to form a gel, and the polymer material is polyacrylonitrile, polyacrylate, polyvinylidene fluoride ( Examples thereof include polymers of monomers such as PVdF) and polyethylene oxide (PEO), or copolymers with other monomers.

Polymer Solid Electrolyte The polymer solid electrolyte is obtained by dissolving the above electrolyte in a polymer material and solidifying it. As a polymer material,
Polyacrylonitrile, polyvinylidene fluoride (PVd
Examples thereof include polymers of monomers such as F) and polyethylene oxide (PEO), and copolymers with other monomers.

Inorganic Solid Electrolyte As the inorganic solid electrolyte, a ceramic material containing lithium can be mentioned. Above all, Li ₃ N and Li ₃
It can be given PO ₄ -Li ₂ S-SiS ₂ glass.

(C) As the negative electrode, a conductive material and a binder are appropriately suspended in a negative electrode active material in a solvent, and the suspension is applied to a collector such as a copper foil.
It is manufactured by drying and pressing into strip electrodes.

(A) Suspended Negative Electrode Active Material As the negative electrode active material, a carbonaceous material can be mentioned.
Examples of the carbonaceous material include graphite, coke, carbon fiber, graphite material or carbonaceous material such as spherical carbon, thermosetting resin, isotropic pitch, mesophase pitch, mesophase carbon fiber, mesophase spherules (particularly, A mesophase carbon fiber is preferable because it has high capacity and charge / discharge cycle characteristics.) A graphite material or a carbonaceous material obtained by heat treatment at a temperature of generally 500 to 3000 ° C., preferably 2000 to 3000 ° C. Can be mentioned.

[0037] The conductive agent the conductive agent, there may be mentioned a known conductive agent include acetylene black, carbon black, be used graphite or the like.

[0038] As the binder the binder, there may be mentioned known binders, for example, polytetrafluoroethylene (PTF
E), polyvinylidene fluoride (PVdF), ethylene
Propylene-diene copolymer (EPDM), styrene
It is preferable to use butadiene rubber (SBR), carboxymethyl cellulose (CMC), or the like.

(B) Strip Electrode Current Collector The negative electrode layer contains a metal such as aluminum, magnesium, tin, or silicon, or a metal oxide, in addition to the above-mentioned one containing the carbon substance which absorbs and releases lithium ions. A metal compound selected from a metal sulfide or a metal nitride,
It may include a current collector such as a lithium alloy.

Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.

Examples of the metal sulfide include tin sulfide and titanium sulfide.

Examples of the metal nitrides include lithium cobalt nitride, lithium iron nitride and lithium manganese nitride.

Examples of the lithium alloy include lithium aluminum alloy, lithium tin alloy, lithium lead alloy, lithium silicon alloy and the like.

Coating, Drying, and Pressing The above-mentioned suspension was coated on the current collector in a thickness of 10 to 5000 μm, dried at a temperature of 50 to 200 ° C., and then 0.1 to
A band-shaped electrode can be obtained by pressing at a pressure of 10 t / cm ² .

(D) Adhesive Polymer It is desirable that the adhesive polymer is one that can maintain high adhesiveness while holding the non-aqueous electrolyte. It is even more preferable that such a polymer has high lithium ion conductivity.

Specifically, polyacrylonitrile, polyacrylate, polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), polyethylene oxide (P
EO) and the like. Among these, polyvinylidene fluoride is particularly preferable.

Polyvinylidene fluoride can hold a non-aqueous electrolytic solution, and when it contains a non-aqueous electrolytic solution, it partially gelates, so that the ionic conductivity can be improved. The adhesive polymer preferably has a porous structure having fine pores in the voids of the positive electrode, the negative electrode, and the separator. The adhesive polymer having a porous structure can hold the non-aqueous electrolytic solution.

(E) Exterior Material As the exterior material that covers the electrode group and the electrolyte, a first exterior material containing a resin layer or a second exterior material is used.

Since the first outer packaging material and the second outer packaging material are lightweight, the energy density per battery weight can be increased, but since they have flexibility, the electrode group or the non-aqueous electrolyte solution is used. It is easily deformed by the gas generated from it.

First Exterior Material The resin layer contained in the first exterior material can be formed of, for example, polyethylene, polypropylene or the like. Specifically, the first exterior material is a sheet in which a metal layer and protective layers arranged on both sides of the metal layer are integrated.

The metal layer plays a role of blocking moisture. Examples of the metal layer include aluminum, stainless steel, iron, copper, nickel and the like. Among these, it is preferable to use aluminum, which is lightweight and has a high moisture blocking function.

The metal layer may be formed of one kind of metal, but may be formed of an integrated body of two or more kinds of metal tubes. Out of the two protective layers disposed on both sides of the metal layer, the outer protective layer in contact with the outside serves to prevent damage to the metal layer. The outer protective layer is formed of one type of resin layer or two or more types of resin layers.

On the other hand, the protective layer on the inner side plays a role of preventing the metal layer from being corroded by the non-aqueous electrolyte. The inner protective layer is formed of one type of resin layer or two or more types of resin layers. Further, a heat-fusible resin can be provided on the surface of the protective layer on the inner side.

Second Exterior Material For the second exterior material, for example, a metal can or a film having a function of blocking moisture can be used.

The metal can can be formed of, for example, ferrous stainless steel or aluminum.

On the other hand, examples of the film having a function of blocking moisture include a laminate film including a metal layer and a flexible synthetic resin layer formed on at least a part of the metal layer. You can

Examples of the metal layer include aluminum, stainless steel, iron, copper and nickel.
Among these, it is preferable to use aluminum, which is lightweight and has a high moisture blocking function.

Examples of synthetic resins include polyethylene and polypropylene.

[II] Manufacturing Method of Flat Secondary Battery (1) Preparation of Cylindrical Multilayer Electrode Group (A) Preparation of Cylindrical Multilayer Electrode The flat plate secondary of the present invention as shown in FIGS. 1 and 2. Battery 1
In order to manufacture the above, as shown in FIG. 3, a strip-shaped laminated body 9 in which a sheet-shaped separator is interposed between a sheet-shaped positive electrode and a sheet-shaped negative electrode is formed, and a central portion of the strip-shaped laminated body 9 is formed. Is wound into a hollow cylindrical shape, and the cylindrical multilayer body 10
The electrode group 6 is formed.

(B) Inserting the spacer At that time, first, at the stage of winding a number of layers of the strip-shaped laminated body 9 into a cylindrical shape, as shown in FIG. Thus, the cylindrical central portion 13a of the outer layer portion and the cylindrical central portion 13b of the inner layer portion are
An electrode group 6 having a substantially cylindrical cross section, which is composed of a cylindrical multilayer body 10 having a plurality of central portions that do not coincide with, is produced.

Next, the electrode group 6 having a substantially cylindrical cross section, which is composed of the cylindrical multilayer body 10 in which the cylindrical central portion of the outer layer portion and the cylindrical central portion of the inner layer portion do not match each other. The spacer 12 sandwiched inside is removed.

Width of rod-shaped spacers 12 sandwiched when the cylindrical multilayer body 10 is formed (radial direction of cylinder)
Is preferably 0.5 to 10% in diameter with respect to the diameter of the electrode group 6 of the cylindrical multilayer body 10.

(2) Manufacture of flat electrode group Next, as shown in FIG. 4, the side surfaces of the substantially cylindrical electrode group 6 are pressed by the presses 15a and 15b, and as shown in FIG. The cross-sectional shape of the electrode group 6 is deformed into a flat electrode group 6 having semicircles at both ends and a flat plate at the center.

(3) Impregnation of Electrolyte Solution Then, the flat electrode group 6 is impregnated with an electrolyte solution in which a polymer having adhesiveness is dissolved in a solvent.

(4) Storage Further, as shown in FIG. 1, the flat electrode group 6 and the electrolyte solution are stored in the exterior material 2 and sealed.
The flat secondary battery 1 can be manufactured.

(5) Charging This plate-shaped secondary battery 1 is charged at 30 to 80 ° C., preferably 3
A secondary battery can be obtained by charging at 0.05 to 0.5 C, preferably 0.1 to 0.3 C under a temperature condition of 0 to 60 ° C.

[III] Manufacture of Suitable Flat Secondary Battery In the method of manufacturing the flat secondary battery 1 of the present invention, the product of battery capacity and impedance is 10 to 11 as described above.
In order to obtain the range of 0 mΩ · Ah, it is preferable to manufacture by the manufacturing method (I) or the manufacturing method (II) described below.

(1) Manufacturing Method (I) In the above manufacturing method (I), the belt-shaped laminate 10 obtained by interposing the porous sheet as the separator 4 between the positive electrode 3 and the negative electrode 5 is formed into a cylindrical multilayer. At the time of winding, after the spacer 12 is sandwiched and wound, the spacer 12 is extracted, and then pressed to produce a first electrode group 6 having a flat cross section, and the electrode group 6 has adhesiveness. A second step of impregnating a solution in which a polymer is dissolved in a solvent, a third step of drying the solution, a fourth step of impregnating a nonaqueous electrolytic solution into an electrode group, and the electrode group 6 in an exterior material. The fifth step of assembling the thin non-aqueous electrolyte secondary battery by sealing, and the secondary battery at a temperature of 30 to 80 ° C. for 0.05 to 0.5.
The method comprises a sixth step of charging with C. However,
The manufacturing method of the flat secondary battery 1 of the present invention is not limited to the above-mentioned form as long as it is within the scope of the present invention. The production method (I) will be described more specifically.

<Manufacturing Method (I)> (First Step) A strip-shaped laminated body 10 is produced by interposing a porous sheet as a separator 4 between the positive electrode 3 and the negative electrode 5.
Then, the central portion of the strip-shaped laminated body 9 is wound into a hollow cylindrical shape to form the electrode group 6 including the cylindrical multilayer body 10.

As shown in FIG. 3, the electrode group 6 is spirally wound between the positive electrode 3 and the negative electrode 5 via the separator 4 which does not hold the polymer and has an adhesive property.

When manufactured by such a method, in a second step to be described later, a solution of a polymer having adhesiveness is permeated into the positive electrode 3, the negative electrode 5 and the separator 4, while the boundary between the positive electrode 3 and the separator 4 and the negative electrode and the separator 4 are made. It is possible to prevent the aqueous solution from penetrating the entire boundary of No. 4.

As a result, it becomes possible to intersperse the adhesive polymer on the positive electrode 3, the negative electrode 5 and the separator 4, and at the same time, at the boundary between the positive electrode 3 and the separator 4 and the boundary between the negative electrode 5 and the separator 4, the adhesive property is improved. Polymers having a can be scattered.

The spirally wound electrode group 6 wound between the positive electrode 3 and the negative electrode 5 with the polymer-non-holding separator 4 having adhesiveness is the electrode group with the winding center axis 11 as the center of rotation. 6, the positive electrode 3, the negative electrode 5, and the separator 4 are wound in a spiral shape by feeding the positive electrode 3, the negative electrode 5, and the separator 4 in accordance with the rotation. After the total number of attempts to open the voids 8 between the electrodes is wound around the winding center shaft 11, the spacer 12 is inserted outside the spirally wound electrode group 6.

After that, when the winding center shaft 11 is rotated about the rotation center, as shown in FIG.
A wound electrode group 6 is obtained in a state where is inserted in the layer. At this time, the spacer 12 is preferably inserted when the electrode group 6 is wound up in one layer or two layers. This is because when the position of the void portion 8 in the electrode group 6 is located inside the electrode group 6, the total length of the finally wound electrode can be made longer, and the battery capacity can be increased. Is. Further, the position of the void portion in the electrode group 6 is
It can also be mentioned that the inner side of the electrode group 6 can more effectively relieve the stress in the electrode group 6, and the twist of the electrode group 6 can be reduced.

The shape of the winding center shaft 11 and the spacer 12 may be a cylindrical shape, a prismatic shape, or any other shape which is symmetrical with the axis. Further, the positive electrode 3, the negative electrode 5, and the separator 4 do not necessarily have to be fed in a combined state from one direction as shown by the winding center axis 11. Depending on the structure of the winding device, the positive electrode 3, the negative electrode 5, and the separator 4 may be separately fed from multiple directions, and may be wound around the winding center shaft 11 and simultaneously combined.

The positive electrode 3 is produced, for example, by suspending a conductive agent and a binder in a suitable solvent in a positive electrode active material, applying the suspension to a current collector, and drying it to form a thin plate. It Examples of the positive electrode active material, the conductive agent, the binder, and the current collector may be the same as those described in the section of the positive electrode (A) described above.

For the negative electrode 5, for example, a carbonaceous material that absorbs and releases lithium ions and a binder are kneaded in the presence of a solvent, and the obtained suspension is applied to a current collector and dried. ,
It is produced by pressing once at a desired pressure or by multi-step pressing 2 to 5 times.

As the carbonaceous material, the binder and the current collector, the same ones as described in the section of the (C) negative electrode can be mentioned. As the porous sheet used for the separator 4, the same one as described in the section of the above-mentioned (B) Electrolyte layer can be used.

As shown in FIG. 4, the electrode group 6 formed of the cylindrical multilayer body 10 by inserting the spacer 12 into the strip-shaped laminated body 9 is pressed by using a press or the like as shown in FIG. The electrode group 6 having a flat cross section is formed.

At least one void 8 is formed on the major axis of the cross section perpendicular to the winding axis of the flat electrode group 6, and the length d of the cross section of the void 8 is flat. 2.5 to the outermost length L of the cross section of the electrode group 6
It is preferably formed so as to be in the range of 10%, particularly 2.5 to 5.0%. If it is smaller than this numerical range, it may not be able to be relaxed when the expansion and contraction of the electrode group 6 is large. If it is larger than this numerical range, the density of the electrode group 6 may be lowered and the battery capacity may be lowered.

The location where the void 8 is formed is preferably present in the first or second layer of the flat electrode group 6, or in the layer near the center of the electrode group 6 composed of multiple layers. .
With such a structure, the expansion and contraction of the electrode group 6 due to charging and discharging can be alleviated by the voids in the electrode group, and the shape of the battery can be maintained.

(Second step) The electrode group 6 is housed in a bag-shaped exterior material so that the laminated surface can be seen from the opening. A solution obtained by dissolving a polymer having adhesiveness in a solvent is injected into the electrode group 6 in the exterior material through the opening to impregnate the electrode group 6 with the solution.

As the exterior material 2, the same materials as those described in the section of the above-mentioned (E) Exterior material can be mentioned. Examples of the adhesive polymer include the same as those described in the section of the above-mentioned adhesive polymer (D). Particularly, PVdF is preferable.

It is desirable to use an organic solvent having a boiling point of 200 ° C. or less as the solvent. The organic solvent includes
For example, dimethylformamide (boiling point 153 ° C.) can be mentioned.

If the boiling point of the organic solvent exceeds 200 ° C., the drying time may be long when the temperature for vacuum drying described below is 100 ° C. or less.

The lower limit of the boiling point of the organic solvent is 50 ° C.
Is preferred. When the boiling point of the organic solvent is less than 50 ° C., the organic solvent may evaporate during the injection of the solution into the electrode group. The upper limit of the boiling point is 1
The boiling point is more preferably 80 ° C., and the lower limit of the boiling point is more preferably 100 ° C.

The concentration of the adhesive polymer in the solution is preferably in the range of 0.05 to 2.5% by weight. This is due to the following reasons. If the concentration is less than 0.05% by weight, it may be difficult to bond the positive and negative electrodes 3, 5 and the separator 4 with sufficient strength.

On the other hand, if the concentration exceeds 2.5% by weight, it may be difficult to obtain sufficient porosity to hold the non-aqueous electrolyte, and the interface impedance of the electrode may be significantly increased. When the interfacial impedance increases, the capacity and the large current discharge characteristics decrease significantly. A more preferable range of the concentration is 0.1 to 1.5% by weight.

The injection amount of the solution may be in the range of 0.1 to 2 ml per 100 mAh of battery capacity when the concentration of the adhesive polymer in the solution is 0.05 to 2.5% by weight. preferable. This is due to the following reasons. If the injection amount is less than 0.1 ml, it may be difficult to sufficiently improve the adhesion between the positive electrode 3, the negative electrode 5, and the separator 4. On the other hand, the injection volume is 2 ml
If it exceeds the range, the lithium ion conductivity of the secondary battery may decrease and the internal resistance may increase, and it may be difficult to improve the discharge capacity, the large current discharge characteristic and the charge / discharge cycle characteristic. A more preferable range of the injection amount is 0.15 to 1 ml per 100 mAh of battery capacity.

(Third Step) The solvent in the solution is evaporated by subjecting the electrode group 6 to vacuum drying, so that the adhesive polymer is present in the voids of the positive electrode 3, the negative electrode 5 and the separator 4. . By this step, the positive electrode 3 and the separator 4 are adhered to each other by a polymer having an adhesive property which is scattered inside and on the boundary between them, and the negative electrode 5 and the separator 4 are scattered on inside and the boundary between them. It is adhered by a polymer having an adhesive property. Further, by this vacuum drying, the water contained in the electrode group 6 can be removed at the same time.

The electrode group 6 is allowed to contain a small amount of solvent. The vacuum drying is preferably performed at 100 ° C. or lower. This is due to the following reasons. If the vacuum drying temperature exceeds 100 ° C., the separator 4 may be significantly shrunk. When the heat shrinkage increases, the separator 4 warps, which makes it difficult to firmly bond the positive electrode 3, the negative electrode 5, and the separator 4 together. Further, the heat shrinkage described above is likely to occur remarkably when the porous film containing polyethylene or polypropylene is used as the separator 4. Although the heat shrinkage of the separator 4 can be suppressed as the vacuum drying temperature becomes lower, if the vacuum drying temperature is lower than 40 ° C., it may be difficult to sufficiently evaporate the solvent. Therefore, the vacuum drying temperature is more preferably 40 to 100 ° C.

(Fourth Step) A nonaqueous electrolytic solution is injected and impregnated into the electrode group 6 in the exterior material 2.

As the non-aqueous electrolyte, the above-mentioned (B) is used.
The same thing as what was demonstrated in the column of an electrolyte layer can be used.

(Fifth Step) After that, the thin non-aqueous electrolyte secondary battery is assembled by sealing the opening of the package 2. In the above-described manufacturing method, the electrode group 6 is injected into the exterior material 2 by injecting the solution in which the adhesive polymer is dissolved.
However, the injection may be performed without storing in the exterior material 2. In this case, first, the electrode group 6 is manufactured with the separator 4 interposed between the positive electrode 3 and the negative electrode 5. After the electrode group 6 is impregnated with the solution, the electrode group 6 is vacuum dried to evaporate the solvent of the solution, so that the positive electrode 3, the negative electrode 5, and the separator 4 have high adhesiveness. Make the molecule exist. A thin non-aqueous electrolyte secondary battery can be manufactured by housing such an electrode group 6 in the exterior material 2 and then injecting a non-aqueous electrolyte and sealing and the like. An adhesive may be applied to the outer periphery of the electrode group 6 before being housed in the exterior material 2. Thereby, the electrode group 6 can be bonded to the exterior material 2. In this case, a metal can can be used as the exterior material 2 instead of the film.

(Sixth Step) The secondary battery assembled as described above is initially charged under a temperature condition of 30 ° C. to 80 ° C. at a charging rate of 0.05 C or more and 0.5 C or less. Charging under this condition may be performed for only one cycle or may be performed for two cycles or more. Further, it may be stored under a temperature condition of 30 ° C. to 80 ° C. for about 1 to 20 hours before initial charging.

Here, the 1C charge rate is the nominal capacity (A
It is a current value required to charge h) in 1 hour.
The reason for defining the temperature of the initial charge in the above range is as follows. If the initial charging temperature is lower than 30 ° C., it becomes difficult to uniformly impregnate the positive electrode 3, the negative electrode 5 and the separator 4 with the non-aqueous electrolytic solution because the viscosity of the non-aqueous electrolytic solution remains high, and the internal impedance is lowered. And the utilization rate of the active material decreases. On the other hand, the initial charging temperature is 80
If the temperature exceeds ° C, the binder contained in the positive electrode 3 and the negative electrode 5 deteriorates.

The charge rate of the first charge is 0.05 to 0.5C.
By setting the range to, the positive electrode 3 and the negative electrode 5 by charging
Since the expansion can be moderately delayed, the nonaqueous electrolytic solution can be uniformly permeated into the positive electrode 3 and the negative electrode 5.
By including such steps, the electrodes 3, 5
Since the non-aqueous electrolyte can be uniformly impregnated in the voids of the separator 4 and the separator 4, the internal impedance of the non-aqueous electrolyte secondary battery at 1 kHz can be reduced, and the product of the battery capacity and the internal impedance of 1 kHz is 10 mΩ. -Ah or more and 110 mΩ-Ah or less can be set. As a result, the utilization rate of the active material can be increased, so that the substantial capacity of the battery can be increased. In addition, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.

Next, a non-aqueous electrolyte secondary battery provided with the electrode group 6 satisfying the above-mentioned condition (b) will be described.
In this secondary battery, the positive electrode 3, the negative electrode 5, and the separator 4 are integrated by thermosetting the binder contained in the positive electrode 3 and the negative electrode 5.

The separator 4 is the second one described above.
The same thing as what was demonstrated in the column of (B) electrolyte layer in the non-aqueous electrolyte secondary battery of is used. Further, as the exterior material 2 for accommodating the electrode group 6, the above-mentioned second
In the non-aqueous electrolyte secondary battery, the same one as described in the section of (6) Exterior material is used.

The positive electrode 3 has a structure in which a positive electrode active material layer containing an active material, a binder and a conductive agent is carried on one side or both sides of a current collector. As the active material, the binder, the conductive agent, and the current collector, the same ones as described in the section of the (A) positive electrode in the above-mentioned second non-aqueous electrolyte secondary battery are used.

The thickness of the positive electrode active material layer is set in the range of 10 to 100 μm for the same reason as described above. When the positive electrode active material layer is supported on both surfaces of the positive electrode current collector, the total thickness of the positive electrode active material layer is in the range of 20 to 200 μm. The lower limit value of the positive electrode active material layer is preferably 30 μm, and more preferably 50 μm. On the other hand, the upper limit of the positive electrode active material layer is preferably 85 μm, and more preferably 60 μm. The thickness of the positive electrode active material layer is preferably in the range of 10 to 60 μm for the same reason as described above for the second non-aqueous electrolyte secondary battery. A more preferable range is 30 to
It is 50 μm.

The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The porosity of the positive electrode active material layer is preferably in the range of 25 to 40% for the same reason as described above. A more preferable range of the porosity is 30 to 35%.

The negative electrode 5 has a structure in which a negative electrode active material layer containing a carbonaceous material that absorbs and releases lithium ions and a binder is carried on one side or both sides of a current collector. As the carbonaceous material, the binder, and the current collector, the same ones as described in the section of (2) Negative electrode in the second non-aqueous electrolyte secondary battery described above are used.

The thickness of the negative electrode active material layer is preferably in the range of 10 to 100 μm for the same reason as described above. When the negative electrode active material layer is supported on both surfaces of the negative electrode current collector, the total thickness of the negative electrode active material layer is 20 to
It is desirable to set it in the range of 200 μm. The lower limit value of the negative electrode active material layer is preferably 30 μm, more preferably 50 μm. On the other hand, the upper limit of the negative electrode active material layer is preferably 85 μm, more preferably 60 μm. The thickness of the negative electrode active material layer is the same as that of the second
For the same reason as described for the non-aqueous electrolyte secondary battery in (1), the range of 10 to 60 μm is preferable.
A more preferable range is 30 to 50 μm.

The porosity of the negative electrode active material layer is preferably in the range of 35 to 50% for the same reason as described above. The more preferable range of the porosity is 35 to 45%.
Is.

The blending ratio of the carbonaceous material and the binder is 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.
It is preferably in the range of. In particular, it is preferable that one side of the carbonaceous material is in the range of 10 to 70 g / cm 2 in the state where the negative electrode is manufactured.

The density of the negative electrode active material layer is 1.20.
It is preferably in the range of 1.50 g / cm ³ .

(2) Manufacturing Method (II) In the above manufacturing method (II), the belt-shaped laminate 10 obtained by interposing the porous sheet as the separator 4 between the positive electrode 3 and the negative electrode 5 is formed into a cylindrical multilayer. At the time of winding, after the spacer 12 is wound, the spacer 12 is extracted, and then pressed to produce a first electrode group 6 having a flat cross-sectional shape, and the electrode group 6 at 40 to 120 ° C. A second step of molding while heating to a third step, a third step of impregnating the electrode group 6 with a non-aqueous electrolytic solution, and a non-aqueous electrolytic solution secondary battery are assembled by sealing the electrode group 6 in an exterior material 2. In the fourth step, and in the secondary battery, under the temperature condition of 30 ℃ ~ 80 ℃, 0.05
Fifth to perform initial charging at a charging rate of C or more and 0.5C or less
And a method. However, the manufacturing method of the flat secondary battery 1 of the present invention is not limited to the above-mentioned embodiment as long as it is within the scope of the present invention. The production method (II) will be described more specifically.

<Manufacturing Method (II)> (First Step) A strip-shaped laminated body 10 is produced by interposing a porous sheet as the separator 4 between the positive electrode 3 and the negative electrode 5.
Then, the central portion of the strip-shaped laminated body 9 is wound into a hollow cylindrical shape, and as shown in FIG.
The electrode group 6 is formed.

The spirally wound electrode group 6 wound between the positive electrode 3 and the negative electrode 5 with the separator 4 interposed therebetween has a winding center axis 11
Is rotated in the direction of rotation of the electrode group 6 with respect to the center of rotation, and the winding center axis 1 of the positive electrode 3, the negative electrode 5 and the separator 4 is rotated.
It is wound in a spiral shape by feeding 1 in accordance with the rotation. After the total number of attempts to open the voids 8 between the electrodes is wound around the winding center shaft 11, the spacer 12 is inserted outside the spirally wound electrode group 6.

After that, when the winding center shaft 11 is rotated about the rotation center, as shown in FIG.
A wound electrode group 6 is obtained in a state where is inserted in the layer. At this time, the spacer 12 is preferably inserted when the electrode group 6 is wound up in one layer or two layers. This is because when the position of the void portion 8 in the electrode group 6 is located inside the electrode group 6, the total length of the finally wound electrode can be made longer, and the battery capacity can be increased. Is. Further, when the position of the void 8 in the electrode group 6 is inside the electrode group 6, the stress in the electrode group 6 can be more effectively relieved, and the twist of the electrode group 6 can be reduced. Can also be mentioned.

The winding center shaft 11 and the spacer 12 may have a cylindrical shape, a prismatic shape, or any other symmetrical shape. Further, the positive electrode 3, the negative electrode 5, and the separator 4 do not necessarily have to be fed in a combined state from one direction as shown by the winding center axis 11. Depending on the structure of the winding device, the positive electrode 3, the negative electrode 5, and the separator 4 may be separately fed from multiple directions, and may be wound around the winding center shaft 11 and simultaneously combined.

The positive electrode 3 is produced, for example, by suspending a conductive agent and a binder in a suitable solvent in a positive electrode active material, applying the suspension to a current collector, and drying it to form a thin plate. It Examples of the positive electrode active material, the conductive agent, the binder, and the current collector may be the same as those described in the section of the positive electrode (A) described above.

For the negative electrode 5, for example, a carbonaceous material that absorbs and releases lithium ions and a binder are kneaded in the presence of a solvent, and the obtained suspension is applied to a current collector and dried. ,
It is produced by pressing once at a desired pressure or by multi-step pressing 2 to 5 times.

Examples of the carbonaceous material, the binder and the current collector are the same as those described in the section of the (C) negative electrode.

As the porous sheet of the separator 4, the same one as described in the section (B) Electrolyte layer can be used. An electrode group 6 including a cylindrical multilayer body 10 by inserting a spacer 12 into the strip laminated body 9
As shown in FIG. 4, it is pressed using a press or the like to form an electrode group 6 having a flat cross section as shown in FIG.

At least one void portion 8 is formed on the long axis of the cross section in the direction perpendicular to the winding axis of the flat electrode group 6, and the length d of the cross section of the void portion 8 is flat. 2.5 to the outermost length L of the cross section of the electrode group 6
It is preferably formed so as to be in the range of 10%, particularly 2.5 to 5.0%.

The location where the void 8 is formed is preferably present in the first or second layer of the flat electrode group 6, or in a layer near the center of the electrode group 6 composed of multiple layers. .
With such a structure, the expansion / contraction of the electrode group 6 due to charge / discharge can be alleviated by the void portion 8 in the electrode group 6, and the shape of the battery can be maintained.

(Second Step) The electrode group 6 is set to 40-120.
Mold while heating to ℃. The molding can be performed by, for example, press molding or fitting into a molding die.

[0120] describing the reason for heating of the electrode group 6 when performing the molding of the pressurized heat the electrode group 6 below. The electrode group 6 does not contain an adhesive polymer. Therefore, when the electrode group 6 is molded at room temperature, springback occurs after molding, that is, a gap is formed between the positive electrode 3 and the separator 4 and between the negative electrode 5 and the separator 4. As a result, the contact area between the positive electrode 3 and the separator 4 and the contact area between the negative electrode 5 and the separator 4 decrease, so that the internal impedance increases.

By molding the electrode group 6 at a temperature of 40 ° C. or higher, the binder contained in the positive electrode 3 and the negative electrode 5 can be thermoset, so that the hardness of the electrode group 6 can be increased. As a result, the spring back after molding can be suppressed, so that the contact area between the positive electrode 3 and the separator 4 and the contact area between the negative electrode 5 and the separator 4 can be improved, and the contact area can be repeated by charging and discharging cycles. Can also be maintained.

On the other hand, if the temperature of the electrode group 6 exceeds 120 ° C., the separator 4 may be significantly shrunk.
A more preferable temperature is 60 to 100 ° C. Molding while heating to the specific temperature described above, for example, under normal pressure,
Alternatively, it can be performed under reduced pressure or under vacuum. It is desirable to carry out under reduced pressure or under vacuum because the efficiency of removing water from the electrode group 6 is improved.

Press Molding When the above molding is performed by press molding, the pressing pressure is
It is preferably in the range of 0.01 to 20 kg / cm ² . This is due to the following reasons. If the pressing pressure is lower than 0.01 kg / cm ^2, it may be difficult to suppress springback after molding.
On the other hand, when the pressing pressure is higher than 20 kg / cm ² , the porosity 8 in the electrode group 6 may decrease, and thus the nonaqueous electrolytic solution holding amount of the electrode group 6 may be insufficient.

(Third Step) The electrode group 6 is housed in the bag-shaped film exterior material 2. Then, the nonaqueous electrolytic solution is injected and impregnated into the electrode group 6 in the exterior material 2.

(Fourth Step) The above-mentioned non-aqueous electrolyte secondary battery is assembled by sealing the opening of the exterior member 2 with the electrode group 6 impregnated with the non-aqueous electrolyte solution. At this time, a metal can can be used instead of the film as the exterior material 2 (fifth step). The secondary battery assembled as described above has a temperature of 30 ° C.
Initial charging is performed at a charging rate of 0.05 C or more and 0.5 C or less under a temperature condition of -80 ° C. Charging under this condition is 1
Only the cycle may be performed, or two or more cycles may be performed. In addition, before the first charge, under the temperature condition of 30 ℃ ~ 80 ℃ 1
It may be stored for about 20 hours to 20 hours.

The temperature of the initial charge and the charge rate of the initial charge are defined in the above range for the same reason as described above. By including such a step, it is possible to uniformly impregnate the voids of the electrodes 3 and 5 and the separator 4 with the non-aqueous electrolytic solution, and thus to reduce the internal impedance of 1 kHz of the non-aqueous electrolytic solution secondary battery. The product of the battery capacity and the internal impedance of 1 kHz can be set in the range of 10 mΩ · Ah or more and 110 mΩ · Ah or less. As a result, the utilization rate of the active material can be increased, so that the substantial capacity of the battery can be increased. In addition, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.

In the second non-aqueous electrolyte secondary battery according to the present invention, a can made of aluminum or the like is used as the exterior material 2, and the electrode group 6 composed of the positive electrode 3, the negative electrode 5 and the separator 4 is wound. It may be a structure inserted in a can. In that case, the adhesive portion or the polymer having adhesiveness may not be provided.

According to such a secondary battery, since the amount of gas generated can be reduced, it is possible to prevent the exterior material 2 made of a sheet including a resin layer and having a thickness of 0.5 mm or less from swelling. . As a result, the lightweight exterior material 2 can be used, and practical large current discharge characteristics and charge / discharge cycle characteristics can be maintained. Therefore, the large current discharge characteristics are excellent, the life is long, and the weight energy is high. A high density non-aqueous electrolyte secondary battery can be realized.

[0129]

EXAMPLES Examples of the present invention will be described below with reference to FIG. 1, but the present invention is not limited to the examples as long as the gist of the invention is not exceeded. [I] Evaluation method (1) Electrode spacing The electrode spacing was measured by photographing the cross section of the electrode group by X-ray CT.

(2) Battery twist The battery twist is determined by using X-ray CT (TOSMICRON manufactured by Toshiba FA System Engineering Co., Ltd.) for the thickness of the electrode group before the initial charge and the thickness of the electrode group after the charge.
The twist was measured.

(3) Volume Energy Density The volume energy density was measured by estimating the battery volume from the battery thickness and determining the ratio with the 0.2 C discharge capacity.

[II] Examples and Comparative Examples Example 1 <Preparation of Non-Aqueous Electrolyte> In a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (MEC) and diethyl carbonate (DEC) (mixing volume ratio 1: 1:
1) LiP dissolved in a concentration of 1.0 mol / liter
F ₆ and L dissolved in a concentration of 1.0 mol / liter
A non-aqueous electrolyte solution of iN (C ₂ F ₅ SO ₂ ) _{2 was} prepared.

<Production of Positive Electrode> 91% by weight of lithium cobalt oxide (LiCoO ₂ ) powder as a positive electrode active material was 2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF), and N. -Methylpyrrolidone (NMP) solution is added and mixed to a thickness of 15μ
A positive electrode having an electrode density of 3.0 g / cm ³ was prepared by applying the aluminum foil current collector of m.

<Production of Negative Electrode> 3000 as a carbonaceous material
Mesophase pitch carbon fiber heat-treated at ℃ (fiber diameter 8 μm, average fiber length 20 μm, average surface spacing (d00
2) 93% by weight of powder of 0.3360 nm and 7% by weight of polyvinylidene fluoride (PVdF) as a binder were mixed, and 10 holes per 10 cm ² were provided with 0.5 mm diameter holes. Porous copper foil with a thickness of 15μ
m) was applied to a current collector, dried, and pressed to produce a negative electrode having an electrode density of 1.4 g / cm ³ and a negative electrode layer supported on the current collector.

<Production of Electrode Group> A strip-shaped positive electrode lead is welded to the positive electrode current collector, a strip-shaped negative electrode lead is welded to the negative electrode current collector, and then the positive electrode is made of a polyethylene porous film. The separator, the negative electrode, and the separator are laminated in this order, and the first layer has a width of 21.6 mm on the major axis and the second layer has a width of 24.7 m on the major axis.
It wound with m. At this time, the maximum distance between the opposing electrodes on the long axis was about 2.1 mm. Further, the third and subsequent layers were wound in close contact with each other without leaving a gap from the second layer, and finally a flat electrode group composed of 10 layers was produced. Here, the ratio of the maximum distance on the major axis between the opposing electrodes is about 5.0% with respect to the outermost battery width of 35.0 mm.

Next, a 100 μm-thick laminated film in which both sides of the aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was housed therein so that the above-mentioned laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent, in an amount of 0.3% by weight. The obtained solution was injected into the electrode group in the laminate film such that the amount per battery capacity of 100 mAh was 0.2 ml, the solution was permeated into the electrode group, and the entire surface of the electrode group was infiltrated. Attached.

Next, the electrode group in the laminate film is vacuum-dried at 80 for 12 hours to evaporate the organic solvent to retain the adhesive polymer in the voids of the positive electrode, the negative electrode and the separator. A porous adhesive portion was formed on the surface of the electrode group. The total amount of polyvinylidene fluoride (PVdF) was 0.6 mg per 100 mAh of battery capacity.

The non-aqueous electrolyte solution was injected into the electrode group in the laminate film so that the amount of the non-aqueous electrolyte solution was 4.7 g per 1 Ah of battery capacity, and a thin non-aqueous electrolyte secondary battery was assembled.

This non-aqueous electrolyte secondary battery was left in a high temperature environment of 40 ° C. for 5 hours as a first charging step, and then under the environment, constant current / constant voltage charging at 0.2 C to 4.2 V. After 10 hours, the twist and volume energy density of the battery were measured. The results are shown in Table 1.

Examples 2 to 5 A thin type non-woven fabric was prepared in the same manner as in Example 1 except that the maximum distance on the major axis between the opposing electrodes of the first layer and the second layer was changed as shown in Table 1. A water electrolyte secondary battery was produced and the same evaluation was performed. The results are shown in Table 1.

Comparative Examples 1 and 2 A thin, non-thin film was prepared in the same manner as in Example 1 except that the maximum distance on the major axis between the opposing electrodes of the first layer and the second layer was changed as shown in Table 1. A water electrolyte secondary battery was produced and the same evaluation was performed. The results are shown in Table 1.

[0142]

[Table 1] From the results shown in Table 1 above, it is possible to form voids on the long axis of the cross section perpendicular to the winding axis of the flat electrode group, particularly within the range of 2.5 to 10%. It can be understood that the flat secondary battery has a high volume energy density and is less likely to be twisted even after repeated charging and discharging.

[0143]

As described above in detail, the flat secondary battery of the present invention can suppress twisting of the electrode group.

[Brief description of drawings]

FIG. 1 is a perspective view of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a cross-sectional view of the non-aqueous electrolyte secondary battery of FIG. 1 taken along the line AA.

FIG. 3 is a perspective view showing a state in which a spacer is sandwiched when a strip-shaped laminated body in which a separator is interposed between a positive electrode and a negative electrode is rolled into a cylindrical multilayer.

[Fig. 4] Fig. 4 is a view showing an initial stage of pressing at the time of forming an electrode group having a flat cross-sectional shape by removing the spacer from a cylindrical multi-layered electrode group wound with a spacer in between and pressing it with a press. It is sectional drawing of the electrode group at the time.

[Explanation of symbols]

1 Flat secondary battery 2 Exterior materials 3 positive electrode 3a positive electrode tab 4 separator 5 Negative electrode 5a Negative electrode tab 6 electrode group 7 winding shaft 8 void 9 Band-shaped laminate 10 Cylindrical multilayer 10a outer layer portion 10b inner layer portion 11 winding center axis 12 spacers 13a Cylindrical center of outer layer 13b Cylindrical center of inner layer 14 Direction of rotation of electrode group 15a, 15b Press d Length of void L Flat electrode group length Long axis of M section

Continued front page    (72) Inventor Yuichi Sato             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center F term (reference) 5H028 AA01 AA05 BB04 BB07 BB19                       CC02 CC10 CC12 HH06                 5H029 AJ03 AJ05 AJ14 AK02 AK03                       AK05 AK16 AL06 AL07 AM03                       AM04 AM05 AM07 AM12 AM16                       BJ04 CJ03 CJ07 HJ04

Claims (5)

[Claims] 1. A flat secondary battery in which a strip-shaped laminated body in which a positive electrode, an electrolyte layer and a negative electrode are sequentially laminated is wound, and an electrode group having a flat cross section is covered with an exterior material. A flat plate-shaped secondary battery, wherein the flat secondary battery is arranged so that a void portion is formed between the two strip-shaped laminated bodies that are adjacent to each other on a long axis of a cross section perpendicular to the winding axis. 2. The flat plate according to claim 1, wherein a width d of the void is within a range of 2.5 to 10% with respect to a length L of a cross section of the flat electrode group. Rechargeable battery. 3. The flat secondary battery according to claim 1, wherein the electrolyte layer contains a non-aqueous solvent and a lithium salt. 4. A strip-shaped laminated body in which a separator is interposed between a positive electrode and a negative electrode is wound into a cylindrical shape with a spacer sandwiched between adjacent strip-shaped laminated bodies, and then pressed to have a flat cross-sectional shape. A process of forming an electrode group, a process of impregnating the electrode group with a non-aqueous electrolyte, a process of extracting a spacer, and a process of sealing the electrode group in an exterior material to manufacture a flat secondary battery. And a method for manufacturing a flat secondary battery. 5. The flat plate-shaped secondary according to claim 4, wherein the width of the spacer is within a range of 2.5 to 10% with respect to the diameter of the cylindrical electrode group wound in multiple layers. Battery manufacturing method.