JP3583909B2 - Sheet type battery - Google Patents

Description

表１，２から明らかなように、実施例１〜２の二次電池は、それぞれ、比較例１，２の二次電池に比べて単位体積当たりのエネルギー効率を向上できることがわかる。
【００７０】
【発明の効果】
以上詳述したように本発明によれば、高い気密性を維持しつつ、単位体積当たりのエネルギー効率を向上することができ、信頼性が高いシート形電池を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るシート形電池の一例（シート形ポリマー電解質二次電池（ａ） ）を示す上面図。
【図２】図１Ａ−Ａ線に沿う断面図。
【図３】図１の二次電池の組立方法を説明するための斜視図。
【図４】本発明に係るシート形電池の一例（シート形ポリマー電解質二次電池（ｂ） ）を示す上面図。
【図５】図４の二次電池の組立方法を説明するための斜視図。
【図６】比較例１のポリマー電解質二次電池を示す上面図。
【図７】比較例２のポリマー電解質二次電池を示す上面図。
【符号の説明】
１ａ…熱融着シール用フィルム、
２…正極リード、
３…負極リード、
４ａ、４ｂ…封止用フィルム。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet-type battery having a structure in which a power generation element is housed in a film.
[0002]
[Prior art]
In recent years, with the development of electronic devices, there has been a demand for the development of a non-aqueous electrolyte secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. As such a secondary battery, a negative electrode containing lithium or a lithium alloy as an active material, and a suspension containing an oxide, sulfide, or selenide of molybdenum, vanadium, titanium, or niobium as an active material were applied. 2. Description of the Related Art A lithium secondary battery including a positive electrode made of a current collector and a non-aqueous electrolyte is known.
[0003]
Recently, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, such as coke, graphite, carbon fiber, a resin fired body, and pyrolysis gas phase carbon, has been used as a negative electrode, and a lithium cobalt oxide or lithium manganese has been used as a positive electrode. Development and commercialization of lithium ion secondary batteries using oxides are being actively conducted.
[0004]
Initially, the form of these non-aqueous electrolyte secondary batteries was mainly coin-shaped or cylindrical, but with the diversification of applications, there is a demand for those that have a form with excellent volumetric efficiency such as square or oval. Is growing. In addition, for the purpose of further weight reduction and size reduction, it has been studied to change the container for housing the power generation element from a conventional metal outer can to a film material.
[0005]
As this film material, a metal foil such as an aluminum foil is disposed at the center so that gas such as water vapor and oxygen is not exchanged inside and outside the film, and the metal foil such as polyethylene terephthalate is used as an outermost layer from physical impact. A composite film (laminated film) in which a resin layer for protection and a heat-fusible resin layer such as an ionomer are provided as an innermost layer is generally used. To seal a battery using the composite film, first, a content to be a power generation element is disposed between two composite films so that the power generation element and the innermost layer are in contact with each other. This is performed by heat-pressing the sides and bonding the innermost layers at the periphery of the film. By sealing the power generation element with a film material in this way, the battery can be made thinner and lighter.
[0006]
In a battery having a structure sealed with a film material as described above, in order to make the airtightness of the battery comparable to that using a conventional metal outer can, it is necessary to increase the area of the fused portion to some extent. .
[0007]
However, when the fused portion is widened, the outer shape of the secondary battery is increased by the size of the fused portion. Therefore, there is a problem that the battery capacity is low for the size and the energy efficiency per unit volume is low. .
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a sheet-type battery with improved energy efficiency per unit volume while maintaining high airtightness.
[0009]
[Means for Solving the Problems]
According to the present invention, a unit cell including a sheet-like positive electrode, a sheet-like negative electrode, a positive electrode lead, and the anode lead,
A tubular film that covers the unit cell so that the tips of the positive electrode lead and the negative electrode lead project outside, and both openings are sealed by heat fusion.
A sheet-type battery comprising:
The tubular film is formed by stacking two heat-sealing sealing films provided with a heat-sealing layer such that the heat-sealing layers are opposed to each other. A sheet-type battery is provided which is sandwiched and covered with a sealing film as an adhesive layer from the outside and fixed by heat fusion .
According to the present invention, a sheet-shaped positive electrode, a sheet-shaped negative electrode, a positive electrode lead, and a unit cell including a negative electrode lead,
A tubular film that covers the unit cell so that the tips of the positive electrode lead and the negative electrode lead project outside, and both openings are sealed by heat fusion.
A sheet-type battery comprising:
The tubular film is formed by folding the heat-sealing sealing film provided with the heat-sealing layer into two so that the heat-sealing layer is located inside, and opening the opening of the heat-sealing film. A sheet-type battery is provided in which the inner surface is sandwiched and covered with a sealing film as a heat-fusible layer from the outside and fixed by heat-sealing.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the sheet type battery according to the present invention will be described with reference to sheet type polymer electrolyte secondary batteries (a) and (b) shown in FIGS.
[0011]
(1) Polymer electrolyte secondary battery (a)
1 is a top view showing an example of a sheet-type battery according to the present invention (sheet-type polymer electrolyte secondary battery (a)). FIG. 2 is a cross-sectional view of the secondary battery of FIG. FIG. 2 is a perspective view for explaining a method of assembling the secondary battery of FIG. 1.
[0012]
As shown in FIG. 1, a unit cell is formed between two rectangular heat-sealing films 1a and (1b) in a state where the tips of a strip-shaped positive electrode lead 2 and a strip-shaped negative electrode lead 3 project outside. Are located. The sealing film 4a formed by vertically folding the strip-shaped heat-sealing film into two is sandwiched between the right ends along the longitudinal direction of the films 1a and 1b. Is bonded by heat fusion. The sealing film 4b formed by vertically folding the strip-shaped heat-sealing film into two is sandwiched between the film 1a and the left end along the longitudinal direction of the film 1b. Is bonded by heat fusion. The remaining openings formed between the film 1a and the film 1b, that is, both ends (regions indicated by dotted patterns in FIG. 1) orthogonal to the longitudinal direction of the film 1a and the film 1b are heat-sealed. Is sealed by. As shown in FIG. 2, the unit cell 5 includes a negative electrode 8 having a structure in which a negative electrode layer 6 is supported on both surfaces of a net-like current collector 7 such as a copper expanded metal. Two positive electrodes 9 are arranged on both surfaces of the negative electrode 8. Each positive electrode 9 has a structure in which a positive electrode layer 10 containing an active material is supported on both surfaces of a net-like current collector 11 such as an expanded metal made of aluminum. The solid electrolyte layer 12 is interposed between the positive electrode 9 and the negative electrode 8. The current collector 11 of each of the positive electrodes 9 has a band-shaped positive terminal 13 in a portion located on the near side in FIG. In addition, the current collector 7 of the negative electrode 8 has a strip-shaped negative electrode terminal 14 at a position where the current collector 7 does not overlap with the positive electrode terminal 13 (for example, a portion located on the back side in FIG. 2). The two positive electrode terminals 13 are arranged so as to be bundled together in a bag formed by folding the positive electrode lead 2 into three, and are fixed in the bag by welding. On the other hand, the tip of the negative electrode terminal 14 is disposed in a bag formed by folding the negative electrode lead 3 into three parts, and is fixed in the bag by welding.
[0013]
Such a sheet-type polymer electrolyte secondary battery (a) is manufactured, for example, by the method described below. First, as shown in FIG. 3, two rectangular heat-sealing films 1a and 1b are prepared. Further, each of the two strip-shaped heat sealing films is folded in two in the longitudinal direction to prepare heat sealing sealing films 4a and 4b. The right ends along the longitudinal direction of the film 1a and the film 1b are sandwiched by the sealing film 4a, and these are bonded by heat fusion. Further, the left ends of the films 1a and 1b along the longitudinal direction are sandwiched by the sealing film 4b, and these are bonded by heat fusion. The unit cell 5 having the above-described structure is arranged in the cylindrical film thus obtained such that the tips of the positive electrode lead 2 and the negative electrode lead 3 project outside. Then, the sheet-shaped polymer electrolyte secondary battery (a) having the structure shown in FIGS.
[0014]
In FIGS. 1 and 2 described above, two heat-sealing films are used, but one heat-sealing film can be folded into two. In this case, of the open ends of the folded film, two opposing ends are sealed with the sealing film as described above.
[0015]
As the heat-sealing film, for example, a laminated film including an outermost layer having an insulating property, an innermost layer having a heat-sealing property, and a metal layer disposed between the outermost layer and the innermost layer Can be mentioned. Since such a film includes a metal layer inside, the airtightness of the secondary battery can be improved, which is preferable.
[0016]
The innermost layer of the heat sealing film can be formed from a layer containing a heat sealing resin such as ionomer, polyethylene (PE), polypropylene (PP), and ethylene vinyl acetate resin (EVA).
[0017]
Examples of the metal forming the metal layer of the heat sealing film include aluminum, nickel, and the like.
[0018]
The outermost layer of the heat sealing film can be formed from a layer containing an insulating resin such as polyethylene terephthalate (PET), polycarbonate, and nylon.
[0019]
Examples of the laminated film include (a) PET (outermost layer) / Al foil / PET / PP or PE (innermost layer), (b) PET (outermost layer) / Al foil / nylon / PE (innermost layer), (C) PET (outermost layer) / PE / Ni foil / ionomer (innermost layer), (d) Nylon (outermost layer) / PE, PET / PE / EVA, PET / ionomer (innermost layer), (e) PET ( (Outermost layer) / Nylon / PE, PET / PP, PET / Nylon / PP, PET / vinylidene chloride resin / PE, Al deposited PET / PE, PET / Al foil / PET / ionomer (innermost layer), (f) Polycarbonate ( (Outermost layer) / PE / EVA (innermost layer), and (g) PET (outermost layer) / Al foil / PE / ionomer (innermost layer).
[0020]
As the positive electrode, the negative electrode, and the electrolyte layer of the polymer electrolyte secondary battery, for example, those described below can be used.
[0021]
(Positive electrode)
The positive electrode is formed of a positive electrode layer containing a positive electrode active material, a non-aqueous electrolyte, and a polymer holding the electrolyte supported on a current collector.
[0022]
Examples of the positive electrode active material include various oxides (eg, lithium manganese composite oxide such as LiMn ₂ O ₄ , manganese dioxide, lithium-containing nickel oxide such as LiNiO ₂ , lithium-containing cobalt oxide such as LiCoO ₂ , Examples thereof include lithium-containing nickel cobalt oxide, lithium-containing amorphous vanadium pentoxide, and the like, and chalcogen compounds (for example, titanium disulfide, molybdenum disulfide, and the like). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.
[0023]
The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.
[0024]
Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and γ-butyrolactone (γ- BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvents may be used alone or as a mixture of two or more.
[0025]
Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borotetrafluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), and trifluoromethane sulfone. Lithium salts such as lithium acid (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₃ ) ₂ ] can be given.
[0026]
The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / l to 2 mol / l.
[0027]
Examples of the polymer holding the non-aqueous electrolyte include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, and a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP). Can be. The copolymerization ratio of the HFP depends on the method of synthesizing the copolymer, but is usually at most about 20% by weight.
[0028]
In FIGS. 1 and 2 described above, an aluminum expanded metal is used as the current collector of the positive electrode. However, for the current collector, for example, aluminum foil, aluminum mesh, aluminum punched metal, or the like may be used. good.
[0029]
The positive electrode terminal 13 and the lead 2 can be formed of, for example, aluminum. Further, as the positive electrode terminal 13, a mesh-like one such as a mesh or a plate-like one can be used.
[0030]
The positive electrode may include a conductive material from the viewpoint of improving conductivity. Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.
[0031]
The positive electrode can be produced, for example, by a method described below.
[0032]
After mixing the polymer holding the non-aqueous electrolyte, the plasticizer, the active material and the conductive material with an organic solvent in which the polymer is soluble to prepare a paste, and forming a film, the positive electrode is not impregnated with the electrolyte. Get the layers. The positive electrode can be obtained by stacking this on the current collector, removing the plasticizer in the positive electrode layer by, for example, solvent extraction, and then impregnating with the nonaqueous electrolyte. Further, the positive electrode layer may be laminated on the current collector by applying the paste to the current collector.
[0033]
Examples of the plasticizer include dibutyl phthalate (DBP), dimethyl phthalate (DMP), diethyl phthalate (DEP), propylene carbonate (PC), and tris-butoxyethyl phosphate.
[0034]
(Negative electrode)
The negative electrode is formed from a negative electrode active material, a nonaqueous electrolyte, and a negative electrode layer containing a polymer holding the electrolyte supported on a current collector.
[0035]
Examples of the negative electrode active material include carbonaceous materials that occlude and release lithium ions. Such carbonaceous materials include, for example, those obtained by firing organic polymer compounds (eg, phenolic resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and those made by artificial graphite. And carbonaceous materials represented by natural graphite and the like. Among them, it is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 500 ° C to 3000 ° C under normal pressure or reduced pressure.
[0036]
As the non-aqueous electrolyte and the polymer, the same ones as described for the positive electrode described above are used.
[0037]
In FIGS. 1 and 2 described above, a copper expanded metal is used as the current collector of the negative electrode. However, for example, a copper foil, a copper mesh, a copper punched metal, or the like may be used.
[0038]
The terminal 14 and the lead 3 of the front negative electrode can be formed of, for example, copper. The negative electrode terminal 14 may be a mesh-like one such as a mesh or a plate-like one.
[0039]
The negative electrode is allowed to contain conductive materials such as artificial graphite, natural graphite, carbon black, acetylene black, Ketjen black, nickel powder, and polyphenylene derivatives, and fillers such as olefin polymers and carbon fibers.
[0040]
The negative electrode can be manufactured, for example, by a method described below.
[0041]
After mixing the polymer holding the non-aqueous electrolyte, the plasticizer, and the active material with an organic solvent in which the polymer is soluble to prepare a paste, a negative electrode layer not impregnated with the electrolyte is obtained by forming a film. This is laminated on the current collector, the plasticizer in the negative electrode layer is removed by, for example, solvent extraction, and then the nonaqueous electrolyte is impregnated to obtain the negative electrode. The lamination of the negative electrode layer on the current collector may be performed by applying the paste to the current collector.
[0042]
As the plasticizer, the same plasticizer as described above for the positive electrode can be used.
[0043]
(Solid polymer electrolyte layer)
The electrolyte layer includes a non-aqueous electrolyte and a polymer that holds the electrolyte.
[0044]
As the non-aqueous electrolyte and the polymer, the same ones as described for the positive electrode described above are used.
[0045]
To the electrolyte layer, an inorganic filler such as silicon oxide powder may be added from the viewpoint of further improving the strength.
[0046]
The electrolyte layer can be produced, for example, by a method described below.
[0047]
After adding a plasticizer to the polymer holding the non-aqueous electrolyte, dissolving them in an organic solvent to prepare a paste, forming a film, removing the plasticizer in the obtained film by, for example, solvent extraction, It can be obtained by impregnating the non-aqueous electrolyte.
[0048]
As the plasticizer, the same plasticizer as described above for the positive electrode can be used.
[0049]
The extraction of the plasticizer and the impregnation of the non-aqueous electrolyte may be performed individually for the positive electrode, the negative electrode, and the solid electrolyte layer, or may be performed in a state where at least two of the positive electrode, the negative electrode, and the solid electrolyte layer are stacked. You can also.
[0050]
(2) Polymer electrolyte secondary battery (b)
FIG. 4 is a top view showing a polymer electrolyte secondary battery (b) as an example of a sheet-type battery according to the present invention, and FIG. 5 is a perspective view for explaining an assembling process of the secondary battery of FIG.
[0051]
As shown in FIG. 4, a unit cell having the same configuration as that described in the above-described secondary battery (a) is provided in the heat-sealing sealing film 15 folded in half. It is arranged with its tip protruding outside. The bent end of the film 15 is located at the left end along the longitudinal direction of the film 15. The sealing film 16 formed by folding a strip-shaped heat-sealing film vertically into two is bonded to the right end along the longitudinal direction of the film 15 by heat-sealing so as to sandwich this end. Have been. Both end portions (regions indicated by dotted patterns in FIG. 4) orthogonal to the longitudinal direction of the film 15 are sealed by heat fusion.
[0052]
Such a sheet-type polymer electrolyte secondary battery (b) is manufactured, for example, by the method described below. First, as shown in FIG. 5, the rectangular heat-sealing film 15 is folded in two. Further, the strip-shaped heat sealing film is folded in two in the longitudinal direction to prepare a heat sealing sealing film 16. Of the two ends along the longitudinal direction of the film 15, the opening side (in FIG. 5, the right end along the longitudinal direction of the film 15) is sandwiched by the sealing film 16, and these are heat-sealed. Glue. The unit cell 5 having the above-described structure is arranged in the cylindrical film thus obtained such that the tips of the positive electrode lead 2 and the negative electrode lead 3 project outside. Next, the sheet-shaped polymer electrolyte secondary battery (b) having the above-described structure shown in FIG. 4 is manufactured by sealing both ends of the tubular film orthogonal to the longitudinal direction by heat sealing.
[0053]
Examples of the heat-sealing film include those similar to those described for the secondary battery (a).
[0054]
As described in detail above, a sheet-type battery according to the present invention includes a unit cell including a sheet-shaped positive electrode, a sheet-shaped negative electrode, a positive electrode lead, and a negative electrode lead. When covering the unit cell in a sheet-type battery having a structure obtained by coating the front ends of the positive electrode lead and the negative electrode lead with a film so as to protrude to the outside, and bonding the film by heat fusion, At least one end of the opening (except for the end where the positive electrode lead and the negative electrode lead protrude) formed in the film is sealed by attaching another film material, and the remaining opening is exposed to heat. It is characterized by being sealed by fusion. In such a battery, at least one end of a film end portion to be sealed (excluding an end portion where a positive electrode lead and a negative electrode lead protrude) is not heat-sealed, but is attached by another film material. Since it is sealed, the outermost dimension (battery size) can be reduced. As a result, the battery can maintain high airtightness and improve energy efficiency per unit volume.
[0055]
【Example】
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
[0056]
(Example 1)
<Preparation of positive electrode>
First, a copolymer powder of 56% by weight of a lithium manganese composite oxide represented by a composition formula of LiMn ₂ O ₄ as an active material, 5% by weight of carbon black, and vinylidene fluoride-hexafluoropropylene (VdF-HFP) 17% by weight and 22% by weight of dibutyl phthalate (DBP) as a plasticizer were mixed in NN-dimethylformamide to prepare a paste. The obtained paste was applied on a polyethylene terephthalate film (PET film) to form a sheet, and a positive electrode sheet not impregnated with a non-aqueous electrolyte was prepared. A positive electrode not impregnated with a non-aqueous electrolyte was prepared by heat-pressing the obtained positive electrode sheet on both sides of a current collector made of aluminum expanded metal and having a positive electrode terminal portion using a hot roll.
[0057]
<Preparation of negative electrode>
58% by weight of mesophase pitch carbon fiber as active material, 17% by weight of vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer powder, and 25% by weight of plasticizer {dibutyl phthalate (DBP)} A paste was prepared by mixing in -N-dimethylformamide. The obtained paste was applied on a polyethylene terephthalate film (PET film) and formed into a sheet, thereby producing a negative electrode sheet not impregnated with an electrolyte. A negative electrode not impregnated with an electrolytic solution was prepared by heat-pressing the obtained negative electrode sheet on both surfaces of a current collector made of copper expanded metal and having a negative electrode terminal portion using a hot roll.
[0058]
<Preparation of solid polymer electrolytic layer>
33.3% by weight of silicon oxide powder, 22.2% by weight of vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer powder, and 44.5% by weight of plasticizer {dibutyl phthalate (DBP)} Was mixed in acetone to form a paste. The obtained paste was applied on a polyethylene terephthalate film (PET film), formed into a sheet, and an electrolyte layer not impregnated with the electrolyte was prepared.
[0059]
<Preparation of non-aqueous electrolyte>
LiPF ₆ as an electrolyte is dissolved in a non-aqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 2: 1 so that the concentration becomes 1 mol / l, and the non-aqueous electrolysis is performed. A liquid was prepared.
[0060]
<Production of unit cell>
A rigid roll prepared by preparing two positive electrodes, one negative electrode, and two electrolyte layers, alternately laminating the positive electrode and the negative electrode with the electrolyte layer interposed therebetween, and heating them to 145 ° C. To form a laminate. Such a laminate was immersed in methanol, and the DBP in the laminate was extracted with methanol and removed. This was dried and immersed in a non-aqueous electrolyte having the above composition to impregnate the laminate with the electrolyte to produce a unit cell having a stack thickness of 2.0 mm and an outer diameter of 40 × 60 mm. .
[0061]
<Assembly of battery>
In a state where a total of two positive electrode terminals of the unit cell are bundled into one, a positive electrode lead (made of a belt-shaped aluminum foil having a thickness of 0.5 mm) is placed in a bag formed by folding the triode into three. These were fixed by ultrasonic welding. Further, the negative electrode terminal was placed in a bag formed by folding a negative electrode lead (formed of a 0.5 mm thick strip-shaped copper foil) into three, and these were fixed by ultrasonic welding.
[0062]
On the other hand, as a heat-sealing film, a rectangular composite film having a thickness of 0.1 mm, in which a polyethylene terephthalate layer, an aluminum foil layer, a polyethylene layer and an ionomer resin layer are laminated in this order (dimensions: 50 × 90 mm) Were prepared. The two films were stacked so that the ionomer resin layer (heat-fusible resin layer) was located inside. In addition, two strip-shaped composite films (dimensions 23 × 90 mm) having a thickness of 0.1 mm were prepared, and each film was vertically folded into two to produce a sealing film. Both end portions along the longitudinal direction of the two composite film bodies were sandwiched by the respective sealing films, and these were bonded by heat fusion to produce a cylindrical film. The unit cells were arranged in the tubular film such that the tips of the positive electrode lead and the negative electrode lead protruded outside. Subsequently, the two open sides of the tubular film are formed with a fusion width of 10 mm so as to have a margin for the unit cell size and the heat-sealed portion so that the influence of the heat-sealing does not appear on the unit cell. By heat fusion, the polymer electrolyte secondary having the structure shown in FIGS. 1 and 2 having a thickness of 2.4 mm, an outer diameter of 50 × 90 mm excluding the lead portion, and an electric capacity of 150 mAh. 100 batteries were manufactured.
[0063]
(Example 2)
A unit cell was produced in the same manner as in Example 1 described above. A rectangular composite film (thickness: 0.1 mm, dimensions: 103 × 90 mm) made of the same material as in Example 1 was prepared and folded in two along the horizontal direction. In addition, a strip-shaped composite film (dimensions 23 × 90 mm) having a thickness of 0.1 mm was prepared, and the film was folded vertically into two parts to produce a sealing film. Of the open ends of the folded film, the end facing the folded end is sandwiched between the sealing films, and these are bonded by heat fusion to produce a tubular film. did. The unit cells were arranged in the tubular film such that the tips of the positive electrode lead and the negative electrode lead protruded outside. Subsequently, the two open sides of the tubular film are formed with a fusion width of 10 mm so as to have a margin for the unit cell size and the heat-sealed portion so that the influence of the heat-sealing does not appear on the unit cell. By heat fusion, a polymer electrolyte secondary battery having the structure shown in FIG. 4 described above, a thickness of 2.4 mm, an outer diameter of 50 × 90 mm excluding the lead portion, and an electric capacity of 150 mAh is obtained. 100 were produced.
[0064]
(Comparative Example 1)
A unit cell was produced in the same manner as in Example 1 described above. Two rectangular composite films (thickness 0.1 mm, dimensions 70 × 90 mm) of the same material as in Example 1 were prepared, and these two films were placed on each other with an ionomer resin layer (heat-fusible resin layer). ) Were stacked so as to face each other. The unit cell was disposed between the two films so that the tips of the positive electrode lead and the negative electrode lead protruded outside. Subsequently, all the four sides of the film are heat-fused with a fusion width of 10 mm so as to have a margin for the cell dimensions and the heat-fused portion so that the influence of the heat fusion does not appear on the cell. Thus, 100 polymer electrolyte secondary batteries having a structure as shown in FIG. 6, a thickness of 2.2 mm, an outer diameter of 70 × 90 mm excluding the lead portion, and an electric capacity of 150 mAh were manufactured.
[0065]
That is, as shown in FIG. 6, each secondary battery is formed by laminating two heat-sealing films 21 by heat-sealing such that the heat-sealing layer is located inside. Inside, the unit cell has a structure in which the positive electrode lead 2 and the negative electrode lead 3 are housed with the tips of the cells protruding outside. The hatched area in the film 21 indicates a heat-sealed portion.
[0066]
(Comparative Example 2)
A unit cell was produced in the same manner as in Example 1 described above. A rectangular composite film (having a thickness of 0.1 mm and a size of 123 × 90 mm) made of the same material as in Example 1 was prepared and folded in two along the lateral direction so that the heat-fusible resin layer was positioned inside. I made it. The unit cells were arranged in this film such that the tips of the positive electrode lead and the negative electrode lead protruded outside. Subsequently, the three sides of the opening of the film were heated and fused at a fusion width of 10 mm so as to have a margin for the dimensions of the cell and the heat-fused portion so that the influence of the heat fusion did not appear on the cell. By mounting, 100 polymer electrolyte secondary batteries having a structure as shown in FIG. 7, a thickness of 2.2 mm, an outer diameter of 60 × 90 mm excluding the lead portion, and an electric capacity of 150 mAh are manufactured. did.
[0067]
That is, as shown in FIG. 7, each of the secondary batteries is bonded by heat-sealing a heat-sealing sealing film 22 which is folded in two in the lateral direction so that the heat-fusible resin layer is located inside. Has a structure in which a unit cell is housed in a bag formed by the method described above, with the tips of the positive electrode lead 2 and the negative electrode lead 3 protruding outside. The hatched area in the film 22 indicates a heat-sealed portion.
[0068]
For each of the obtained secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2, the volume efficiency when the average operating voltage was 3.8 V (Wh / l; calculated from the outer diameter except for the lead portion). And the results are shown in Tables 1 and 2 below. The volume efficiencies in Tables 1 and 2 are the average values of 100 secondary batteries.
[0069]

As is clear from Tables 1 and 2, it can be seen that the secondary batteries of Examples 1 and 2 can improve the energy efficiency per unit volume as compared with the secondary batteries of Comparative Examples 1 and 2, respectively.
[0070]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to improve the energy efficiency per unit volume while maintaining high airtightness, and to provide a highly reliable sheet battery.
[Brief description of the drawings]
FIG. 1 is a top view showing an example of a sheet-type battery according to the present invention (a sheet-type polymer electrolyte secondary battery (a)).
FIG. 2 is a sectional view taken along the line AA of FIG. 1;
FIG. 3 is a perspective view for explaining a method of assembling the secondary battery of FIG. 1;
FIG. 4 is a top view showing an example of a sheet-type battery according to the present invention (a sheet-type polymer electrolyte secondary battery (b)).
FIG. 5 is a perspective view for explaining a method of assembling the secondary battery of FIG. 4;
FIG. 6 is a top view showing a polymer electrolyte secondary battery of Comparative Example 1.
FIG. 7 is a top view showing a polymer electrolyte secondary battery of Comparative Example 2.
[Explanation of symbols]
1a: Film for heat sealing,
2. Positive electrode lead,
3: Negative electrode lead,
4a, 4b: sealing film.

Claims (2)

A unit cell including a sheet-like positive electrode, a sheet-like negative electrode, a positive electrode lead, and the anode lead,
A tubular film that covers the unit cell so that the tips of the positive electrode lead and the negative electrode lead project outside, and both openings are sealed by heat fusion.
A sheet-type battery comprising:
The tubular film is formed by stacking two heat-sealing films provided with a heat-sealing layer such that the heat-sealing layers are opposed to each other. A sheet-type battery, which is sandwiched and covered with a sealing film as an adhesive layer from the outside and fixed by heat fusion . A sheet-shaped positive electrode, a sheet-shaped negative electrode, a unit cell including a positive electrode lead, and a negative electrode lead,
  A tubular film that covers the unit cell so that the tips of the positive electrode lead and the negative electrode lead project outside, and both openings are sealed by heat fusion.
A sheet-type battery comprising:
  The tubular film is formed by folding the heat-sealing film provided with the heat-sealing layer into two such that the heat-sealing layer is located inside, and opening the heat-sealing film. A sheet-type battery having an inner surface sandwiched and covered with a sealing film as a heat-fusible layer from the outside and fixed by heat-sealing.

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