JP2000268790A - Thin battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin battery thinning in profile reduced in weight and enhanced in reliability. SOLUTION: This thin battery has a unit cell 2 and a multi-layered armor film 1. The unit cell 2 is constructed of a sheet-like positive electrode 2c and a sheet-like negative electrode 2b laminated and disposed through a sheet-like separator 2a having ion conductivity to the main surface of the sheet-like positive electrode 2c. The multi-layered outer film 1 derives external terminals 3 and 4 corresponding to the positive and negative electrodes 2c' and 2b' of the unit cell 2 and liquid-tightly seals the sealed part of the unit cell 2 by heat fusion of a heat-fusible resin layer 1a. In this case, the sealed part of the external terminals 3a and 4 is welded and sealed through at least the heat-fusible resin layer 1a having a thickness of 5 μm on one side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art As power sources for portable telephones, television cameras, and the like, small, lightweight, thin, large-capacity, and high-voltage power sources are required, and a positive electrode layer, a polymer electrolyte layer, and a negative electrode layer are required. A thickness provided with a battery element portion (electrode element or power generation element) in which a unit cell (laminated body) or a stack of a plurality of such unit cells is integrated in a sheet shape (thin shape). Polymer lithium batteries of about 0.5 mm are also known (for example, US Pat. No. 5,296,318).
Specification).

FIG. 4 is a perspective view showing a conventional thin battery. In FIG. 4, 1 is an exterior film, 2 is a unit cell, and 3 is a positive external terminal (terminal for external connection), one end of which is connected to the positive electrode of the unit cell and the other end of which is led out of the exterior film 1 in a liquid-tight manner. Reference numeral 4 denotes a negative external terminal (terminal for external connection), one end of which is connected to the negative electrode of the unit cell and the other end of which is led out of the exterior film 1 in a liquid-tight manner.

Here, the unit cell 2 comprises a sheet-like separator carrying an electrolytic solution, a lithium-containing metal oxide laminated and arranged on one main surface of the sheet-like separator as an active material, and a positive electrode current collector. A sheet-shaped positive electrode having a sheet-shaped negative electrode having a negative electrode current collector and a lithium metal or a carbonaceous material that occludes / releases lithium as an active material laminated and arranged on the other main surface of the sheet-shaped separator 1 Have been.

The sheet-like separator is made of an electrolyte-retaining polymer such as hexafluoropropylene-
It is a polymer-electrolyte system such as a vinylidene fluoride copolymer. The sheet-shaped positive electrode is composed of an active material such as a metal oxide containing lithium, an electrolyte retaining polymer, and a positive electrode current collector. Further, the sheet-shaped negative electrode is composed of, for example, an active material that stores and releases lithium ions, an electrolyte-retaining polymer, and a negative electrode current collector.

More specifically, the sheet-shaped positive electrode is formed by welding and connecting one end of an aluminum foil piece to a protruding / extending portion of a positive electrode current collector (for example, a foil of a luminium, a punched metal, an expanded metal). A positive external terminal (terminal for external connection) 3 and a sheet-shaped negative electrode are provided with a piece of copper foil on a protruding / extending portion of a negative electrode current collector (for example, copper foil, punched metal, ex-band metal). , One end of which is welded and connected, and a negative external terminal (external connection terminal) 4 is provided.
These sheet-like electrodes and sheet-like separators are laminated to form a unit cell 2.

The exterior film 1 is composed of a unit cell 2
Is sealed in a liquid-tight or air-tight manner, but both the positive and negative external terminals 3 and 4 are collectively sealed and led out in a liquid-tight or air-tight manner while being led out of the sealed body formed by the exterior film 1. are doing.

The production of this kind of lightweight and flexible thin battery is generally performed as follows. First,
The unit cell 2 is produced by combining the sheet-shaped positive electrode, the sheet-shaped separator (polymer-electrolyte), and the sheet-shaped negative electrode in a stacked state. Thereafter, the corresponding external terminal pieces 3 and 4 are aligned and welded to the projecting / extending portions of the current collectors of both sheet electrodes of the unit cell 2.

Next, the exterior film 1 is laminated on both sides.
While arranging (bending one resin film and wrapping both main surfaces), each external terminal 3, 4 connected to each current collector
Of the exterior film 1 are hermetically bonded / integrated via heat bonding (thermal welding) or an adhesive layer, and sealed. I have.

[0010]

However, in the case of the thin battery having the above structure, there are the following disadvantages. In other words, in making the thin battery of the above configuration thinner and lighter, an aluminum foil is internally layered as an exterior film to prevent the penetration and penetration of moisture, while the heat-sealing or bonding surface is formed by a heat-sealing resin layer ( A multilayer film formed of a resin layer containing maleic anhydride or the like as a modifying group in the molecule) is used.

The sealing with the exterior film is performed by making the heat-fusible resin layers face each other, and fusing and joining the heat-fusible resin layers by applying pressure and heat. by the way,
In the configuration of the polymer lithium battery, in the case where it is difficult to form a liquid-tight or air-tight fusion / joining due to the influence and action of the surface unevenness accompanying the thinning of the exterior film in addition to the thinning of the unit cell 2 itself. There is.

Particularly, in the region where the external terminals 3 and 4 are sealed and led out, the opposing surface of the opposing heat-fusible resin layer is three-dimensionally uneven due to the interposition of the external terminals 3 and 4. Voids are easily formed on the outer peripheral surfaces of 3, 4. Therefore,
In order to fuse and join the areas of the external terminals 3 and 4 in a liquid-tight or air-tight manner, the outer peripheral surfaces of the external terminals 3 and 4 are sufficiently filled and fused by the heat-fusing action of the heat-fusible resin layer. It is assumed that they are close. However, in reality, the external terminals 3 and 4
In some cases, the regions are not fused or bonded in a liquid-tight or air-tight manner, and there is a concern that the production yield of the polymer lithium battery may be reduced, or the quality or reliability of the polymer lithium battery may be impaired.

The present inventors have solved the above concerns,
The thickness of the heat-fusible resin layer was changed with respect to the thickness of the external terminals 3 and 4 (the surface of the heat-sealing surface has irregularities), and liquid-tight or air-tight fusion / bonding / sealing properties were examined. As a result, it has been found that the sum of the thicknesses of the opposing heat-fusible resin layers affects at least the region in which the external terminals 3 and 4 are led out and sealed.

That is, the lead-out / sealing regions of the external terminals 3 and 4 have a configuration in which the heat-fusible resin layer is interposed. It has been confirmed that when the thickness of one side of is set to 5 μm or more, the possibility that the external terminals 3 and 4 are not liquid-tightly or air-tightly fused / joined is completely eliminated. Further, the pressing force at the time of heat fusion in the regions of the external terminals 3 and 4 depends on the constitution of the multilayer exterior film, the material of the heat fusion resin layer and the like, but is generally 15 kgf / cm ^2. Over 35 kgf / cm
^{When it is} less than about ^{2, the} possibility that liquid-tight or air-tight fusion / joining is not performed is completely eliminated.

The present invention has been made based on the above findings, and it is an object of the present invention to provide a thin battery having a reduced thickness, a reduced weight, and improved reliability, and a method of manufacturing such a thin battery. I do.

[0016]

According to a first aspect of the present invention, there is provided a unit comprising a sheet-like positive electrode, and a sheet-like negative electrode laminated and arranged on a main surface of the sheet-like positive electrode via a sheet-like separator having ion conductivity. A thin type having a cell and a multi-layer exterior film for leading external terminals corresponding to the positive and negative electrodes of the unit cell and sealing the unit cell by heat-sealing a sealed portion with a heat-fusible resin layer. Batteries,
The thin battery is characterized in that the sealing portion of the external terminal is welded and sealed by inserting a heat-fusible resin layer of at least 5 μm thickness on one side.

A second aspect of the present invention is a process for assembling a unit cell comprising a sheet-like positive electrode and a sheet-like negative electrode laminated and arranged on a main surface of the sheet-like positive electrode via a sheet-like separator having ion conductivity. The unit cell is positioned on the surface of the multilayer exterior film provided with the heat-fusible resin layer, and the positive and negative external terminals are led out to be liquid-tight by heat-sealing the stacked multilayer exterior film edges. And a step of injecting a required non-aqueous electrolyte in a liquid-tight sealing process with the multilayer exterior resin film, wherein the multilayer exterior resin film is And a heat-fusible resin layer having a metal foil as an inner layer and facing at least in an external terminal region is set to be thicker than an external terminal thickness.

In the first and second aspects of the present invention, the sheet-shaped positive electrode has a current collector made of, for example, aluminum foil, aluminum mesh, aluminum band metal, aluminum punch metal, or the like. Then, a part of the current collector is extended as a terminal portion, and the positive electrode active material is applied to the entire surface of the current collector except for the terminal portion. Note that an aluminum foil piece or the like is welded as an external terminal to the extending end of the current collector forming the terminal portion.

On the other hand, the sheet-shaped negative electrode has a current collector made of, for example, copper foil, copper band metal, copper punch metal, or the like. Then, a part of the current collector is extended as a terminal portion, and a negative electrode active material is applied to the entire surfaces of the current collector except for the terminal portion. Note that a copper foil piece or the like is welded as an external terminal to the extended end of the current collector forming the terminal portion.

In the first and second aspects of the present invention, the positive electrode active material on which the sheet-shaped positive electrode is adhered and supported is a lithium-containing metal oxide that absorbs and releases lithium ions, such as a lithium-manganese composite oxide and a lithium-containing cobalt oxide. , Lithium-containing nickel cobalt oxide, lithium-containing amorphous vanadium pentoxide, manganese dioxide, chalcogen compounds, and the like.

The negative electrode active material that the sheet-shaped negative electrode adheres and carries is one that absorbs and releases lithium ions, and examples thereof include fired products of bisphenol resin, polyacrylonitrile, and cellulose, and fired products of coke and pitch. These may take the form containing natural or artificial graphite, carbon black, acetylene black, Ketjen black, nickel powder, nickel powder and the like.

Further, the electrolyte which is impregnated and supported by the separator interposed between the above-mentioned sheet-like positive electrode and negative electrode to form an ion conductor is, for example, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, etc. Lithium perchlorate, lithium hexafluorophosphate, lithium borotetrafluoride, lithium arsenide hexafluoride, lithium trifluoromethanesulfonate, etc. in a nonaqueous solvent such as diethyl carbonate, methyl ethyl carbonate, etc. Dissolved to an extent. Here, examples of the electrolyte-holding polymer-electrolyte system that functions as a separator include polymers such as hexafluoropropylene-vinylidene fluoride copolymer.

According to the first and second aspects of the present invention, the exterior film for integrally sealing the unit cell (battery element portion) comprises:
Multilayer type with a heat-fusible resin layer as the surface to be bonded (sealing surface) and a metal foil for moisture prevention etc.
It is a film of about 20mm. For example, a heat-fusible resin layer made of a polypropylene resin with a thickness of about 60 to 100 μm modified with an acid such as maleic anhydride, a thin aluminum foil with a thickness of about 10 to 40 μm, and a polyethylene terephthalate resin with a thickness of about 5 to 15 μm Films obtained by sequentially laminating and integrating films can be used. It should be noted that the polyethylene terephthalate resin film contributes to the reinforcing property of the unit cell in the multilayer outer layer film itself.

Here, the thickness of the heat-fusible resin layer is important, and the thickness is such that the opposing surfaces are fused together, and the state of the bonding / sealing region surface, specifically, the flatness and the unevenness It is set in consideration of. That is, it is necessary to select and set a large sum of the thicknesses of the heat-fusible resin layers on the opposing surfaces as compared to the thicknesses of the positive and negative external terminals led out of the exterior film for enclosing the unit cell. . More specifically, if the thickness is set to 10 μm or more (preferably about 15 to 30 μm) before the heat welding, after the heat welding and sealing, the outer peripheral surfaces of the positive and negative connection terminals will be 5 μm or less.
It is fused (welded) and sealed with a heat-fusible resin layer of about 10 μm interposed.

The liquid-tight or air-tight sealing with the exterior film is performed by heating or irradiating the edges of the exterior film positioned on both sides of the unit cell.
This is easily performed by heat fusion.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. 1, 2 and 3. FIG.

Example 1 Preparation of Sheet-Shaped Positive Electrode A vinylidene fluoride-hexafluoropropylene copolymer (trade name: KYNAR2801, manufactured by Elphatochem Co.) was dissolved in acetone, and dibutyl phthalate and lithium-containing cobalt were added to this ascentone solution. Oxide (L
iCoO ₂ ) was added and mixed to prepare a positive electrode paste. Next, while leaving an uncoated portion at one end of a porous current collector made of aluminum lath metal prepared in advance, using a knife coater, applying the paste for the positive electrode,
Drying was performed with dry air.

Thereafter, the outer shape of the coated portion of the positive electrode paste and the dimensions of the uncoated portion are cut into predetermined lengths and widths, and the uncoated portion serving as a terminal portion has an electrolyte non-impregnated positive electrode layer on both surfaces. To produce a sheet-like positive electrode having a protruding (extending) structure.

Preparation of sheet-shaped negative electrode After dissolving vinylidene fluoride-hexafluoropropylene copolymer (trade name: KYNAR2801, manufactured by Elphatochem Co.) in acetone, dibutyl phthalate and mesofused pitch-based carbon fiber were added to this ascentone solution. (Manufactured by Petka) was added and mixed to prepare a negative electrode paste. Next, the paste for the negative electrode was applied using a knife coater while leaving an uncoated portion at one end of a porous current collector made of copper lath metal prepared in advance, and dried with dry air. Was done.

Thereafter, the outer shape of the negative electrode paste-coated portion and the dimensions of the uncoated portion are cut into predetermined lengths and widths, and the negative electrode layer impregnated with the electrolyte is provided on both sides, while the uncoated portion serving as a terminal portion is formed. A sheet-shaped negative electrode in which a portion was protruded (extended) was produced.

Preparation of Solid Polymer Electrolyte Material A powder of vinylidene fluoride-hexafluoropropylene copolymer (trade name: KYNAR2801, manufactured by Elphatochem Co.) was dissolved in acetone, and dibutyl phthalate was added to this ascentone solution and mixed. Paste was prepared. Next, it was applied to a smooth glass plate surface prepared in advance and dried with dry air. After that, the solid polymer electrolyte material 1 not impregnated with the electrolyte was prepared by peeling off the glass plate and cutting it into a predetermined outer dimension.

Preparation of non-electrolytic solution LiPF ₆ (electrolyte) was added to a mixed solvent of ethylene carbonate and dimethyl carbonate (non-aqueous solvent) at a volume ratio of 1: 1.
Was dissolved at a rate of 1 mol / l to prepare a non-electrolytic solution.

On both main surface sides of the sheet-shaped negative electrode prepared above,
After the solid polymer electrolyte material and the sheet-shaped positive electrode were sequentially positioned and laminated, they were passed between rigid rollers heated to 130 ° C. and heated and pressed to produce a unit cell. Thereafter, the unit cell was immersed in methanol to elute and remove dibutyl phthalate in the sheet-shaped positive electrode, sheet-shaped negative electrode, and solid polymer electrolyte material to form a porous structure.

Next, the unit cells having the porous structure are stacked so that the current collector protrusions (extensions) forming the terminals of the same polarity are located at substantially the same position, and the thickness of the external terminals is formed. Are mechanically and electrically joined by welding or the like to an aluminum foil piece having a thickness of 0.1 mm and a copper foil piece having a thickness of 0.1 mm.

On the other hand, a thickness obtained by laminating and integrating an acid-modified polypropylene resin film having a thickness of about 70 μm, an aluminum foil having a thickness of about 20 μm, and a polyethylene terephthalate resin film having a thickness of about 10 μm prepared in advance. A unit cell (battery element portion) is positioned and arranged on the surface of the acid-modified polypropylene resin film of the 0.11 mm exterior film so that the tip of the external terminal extends, and is bent (folded) at the center in the long side direction. Was.

Next, the side from which the tip of the external terminal was extended was heat-sealed to a width of 5 mm and sealed. That is, 210 ° C
The edge of the external terminal at which the tip end extended was sandwiched by a seal bar whose temperature had been adjusted to ² mm, and pressure was applied at 20 kgf / cm ² for 7 seconds to perform heat fusion. Further, one side in the width direction of the exterior film in which the unit cell is installed is sandwiched by a seal bar also adjusted to 210 ° C., and pressurized at 13 kgf / cm ² for 5 seconds.
Thermal fusion was performed to a width of 5 mm.

Thereafter, the above-mentioned sealed body was dried under reduced pressure for 12 hours, and then mounted in a glove box set at a dew point of −50 ° C., and an opening in the width direction of the outer film (another side).
A predetermined amount of electrolyte solution is injected through. After the injection of the electrolyte, the other side of the opening was sandwiched by a seal bar whose temperature was adjusted to 210 ° C., pressurized at 13 kgf / cm ² for 5 seconds, and thermally fused to a width of 5 mm. To produce a thin battery.

Next, after performing the constant current / constant voltage charging and the constant current / constant voltage discharging on the manufactured thin batteries, the outside of the sealing region is cut off to manufacture 100 thin batteries. did.

FIG. 1 is a cross-sectional view showing the structure of the main part of the thin battery manufactured as described above, wherein 1 is an outer layer film, 2 is a unit cell, and 3 (4) is an external terminal. Here, the outer layer film 1 has an acid-modified polypropylene resin film 1a, an aluminum foil 1b,
And a polyethylene terephthalate resin film 1c laminated and integrated, and the acid-modified polypropylene resin film 1a acts as a bonding surface.

The unit cell 2 supports a solid polymer electrolyte material (separator) 2b and a positive electrode active material on both main surfaces of a sheet-shaped negative electrode 2a containing a current collector 2a 'supporting the negative electrode active material. Sheet-shaped positive electrode with built-in current collector 2c '
2c, which is formed by heating and pressing after positioning and laminating these.

FIG. 3 is a sectional view showing the lead-out and sealing portions of the positive electrode external terminal 3 and the negative electrode external terminal 4 of the thin battery manufactured as described above. Here, the fusion bonding portion of the multilayer outer layer film 1 composed of the acid-modified polypropylene resin film 1a, the aluminum foil 1b, and the polyethylene terephthalate resin film 1c is formed by the fusion of the acid-modified polypropylene resin film 1a (one side thickness: 20 μm). ) To form a dense joint.

Example 2 In the case of Example 1, instead of applying a pressure of 20 kgf / cm ² , the sides of the external terminals 3 and 4 from which the tips were extended were thermally fused and sealed with a width of 5 mm. Under the same conditions except that the pressure was set to 30 kgf / cm ² , 100 thin batteries were manufactured. In addition,
In the lead-out areas of the external terminals 3 and 4, dense bonding was formed by fusing the acid-modified polypropylene resin film 1a (about 10 μm in thickness on one side).

Example 3 In the case of Example 1, instead of applying a pressure of 20 kgf / cm ² , the sides of the external terminals 3 and 4 where the tips were extended were thermally fused and sealed with a width of 5 mm. Under the same conditions except that the pressure was set to 33 kgf / cm ² , 100 thin batteries were manufactured. In addition,
In the lead-out areas of the external terminals 3 and 4, a dense bond was formed by fusing the acid-modified polypropylene resin film 1a (about 5 μm on one side).

Comparative Example 1 In the case of Example 1, the same conditions were used except that the thickness of the acid-modified polypropylene resin film 1a of the outer layer film was set to 2/5 of the thickness (0.1 mm) of the external terminals 3 and 4. Manufactured 100 thin batteries. In the lead-out regions of the external terminals 3 and 4, the joint was formed by fusing the acid-modified polypropylene resin film 1a (about 5 μm in thickness).

COMPARATIVE EXAMPLE 2 In the case of Example 1, instead of applying a pressure of 20 kgf / cm ² , the sides of the external terminals 3 and 4 where the tips were extended were thermally fused and sealed with a width of 5 mm. 100 thin batteries were manufactured under the same conditions, except that the pressure was 35 kgf / cm ² . In addition,
In the lead-out areas of the external terminals 3 and 4, the joint was formed by fusing the acid-modified polypropylene resin film 1a (one side thickness is about 3 μm).

100 thin batteries according to each of the above examples and 100 thin batteries according to each comparative example were charged to an open circuit voltage of 4.2 V in an atmosphere of 20 ° C., and 50 of them were dried at 60 ° C. The battery was stored for one month in an atmosphere, and the weight change of the battery was measured, and the results of liquid leakage from the fused / sealed portion were visually and odorically confirmed. Table 1 shows the results.

[0047]

[Table 1] As can be seen from Table 1, in the case of the thin batteries according to the examples, no weight loss and no liquid leakage were observed, and excellent airtightness was maintained even in a high temperature environment. On the other hand, in the case of the thin battery of Comparative Example 1, a reduction in the weight of the battery is observed, and a liquid leak in the external terminal sealing region is also observed.

Further, the remaining 50 pieces were stored in a dry atmosphere at 90 ° C. for 4 hours (assuming the car was left on the dashboard in summer), and the weight change of the battery was measured. Table 2 shows the results of safety test evaluations in which liquid leakage from the stop was confirmed visually or by odor.

[0049]

[Table 2] Generally, when stored for 4 hours in a dry atmosphere at 90 ° C., the vapor pressure of the electrolytic solution increases and the internal pressure inside the battery increases due to the generation of decomposition gas of the electrolytic solution due to the reaction of the sheet-shaped positive electrode or the sheet-shaped negative electrode. Then, the fusion / separation of the joint portion occurs. However, in the case of the thin battery according to each embodiment,
No reduction in weight of the battery and no leakage were observed, and excellent fusion / bonding properties were maintained even in a high-temperature environment, and there was no danger of fusion / bonding peeling off.
On the other hand, in the case of the thin battery of Comparative Example 1, a decrease in the weight of the battery was observed, and liquid leakage in the external terminal sealing region was also observed. In the case of the thin battery of Comparative Example 2, the weight of the battery decreased. And a tendency that peeling or the like easily occurs in the external terminal sealing region.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the configuration of the unit cell, the sheet-shaped positive electrode, the solid polymer electrolyte material (separator sheet), and the sheet-shaped negative electrode may be set to have a combination of other materials, shapes and dimensions, or a plurality of units. A configuration in which cells are stacked may be employed.
Further, the multilayer type exterior film may be a multilayer type other than those exemplified.

[0051]

According to the first aspect of the present invention, there is provided a thin battery in which unit cells and external terminals are hermetically sealed and whose hermetic sealing is formed by durable fusion / bonding. That is, it is possible to provide a thin and lightweight battery having high durability or reliability maintaining good liquid tightness or air tightness even when used under high temperature.

According to the second aspect of the present invention, it is possible to provide a thin and lightweight battery which is mass-produced, has high yield, and has high durability and high reliability.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing a configuration of a main part of a thin battery according to an embodiment.

FIG. 2 is a cross-sectional view showing a configuration example of a main part of a multilayer exterior film used for the configuration of the thin battery according to the embodiment.

FIG. 3 is an enlarged sectional view showing a configuration of a sealing portion of an external terminal of the thin battery according to the embodiment.

FIG. 4 is a top view showing a configuration of a main part of a thin battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer outer layer film 1a ... Heat-fusible resin layer 1b, 1d ... Reinforcing film 1c ... Moisture-proof metal foil 2 ... Unit cell 2a ... Sheet negative electrode 2a ', 2b', 2c ' … Current collector 2b… Separator 2c… Sheet positive electrode 3, 4… External terminal (terminal for external connection)

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) CJ05 CJ13 DJ02 DJ03 DJ04 DJ05 EJ12 EJ14 HJ04

Claims (2)

[Claims] 1. A unit cell comprising a sheet-like positive electrode, a sheet-like negative electrode laminated and arranged on a main surface of the sheet-like positive electrode via a sheet-like separator having ion conductivity, and positive and negative electrodes of the unit cell A multilayer battery that derives an external terminal corresponding to and seals the unit cell by heat-sealing the sealed portion with a heat-fusible resin layer, comprising: A thin battery wherein the sealing portion is fused and sealed with a heat-fusible resin layer having a thickness of at least 5 μm interposed on one side. 2. A step of assembling a unit cell composed of a sheet-like positive electrode and a sheet-like negative electrode laminated and arranged on a main surface of the sheet-like positive electrode via a sheet-like separator having ion conductivity; A step of positioning on the surface of the multilayer exterior film having a fusible resin layer, leading out positive and negative external terminals, and sealing the edges of the laminated multilayer exterior film in a liquid-tight manner by heat-sealing the edges thereof. In the liquid-tight sealing process by the multilayer exterior resin film,
Injecting a required non-aqueous electrolyte solution, comprising: a heat-sealing property in which the multilayered exterior resin film has a metal foil as an inner layer and faces at least in an external terminal region. A method for manufacturing a thin battery, wherein the resin layer is set thicker than the thickness of the external terminals.