JP3583589B2 - Sheet type battery - Google Patents

Description

【００５９】
表１から明らかなように、正極リード及び負極リードが突出している端部を除く封止部が同一方向に折り曲げられた構成の実施例１〜３の二次電池は、折り曲げ加工前に比べて体積効率を向上できることがわかる。特に、実施例１の二次電池の体積効率が著しく高いことがわかる。また、二つ折りにした熱融着シール用フィルムで素電池を被覆した実施例１〜２の二次電池は、２枚の熱融着シール用フィルムで素電池を被覆した実施例３の二次電池に比べて、高温環境下におけるサイクル寿命が長いことがわかる。
これに対し、リードが固定された端部も含めて封止部が折り返された比較例の二次電池は、リードが折り曲がるために内部短絡を生じることがわかる。
【００６０】
【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） ）を示す断面図。
【図２】図１の二次電池の要部を示す斜視図。
【図３】図１の二次電池における熱融着部を折り返す前の状態を示す上面図。
【図４】図１の二次電池を示す上面図。
【図５】本発明に係るシート形電池の一例であるポリマー電解質二次電池（ｂ） における融着部を折り返す前の状態を示す上面図。
【図６】本発明に係るシート形電池の一例であるポリマー電解質二次電池（ｂ） を示す上面図。
【図７】本発明に係るシート形電池の一例であるポリマー電解質二次電池（ｃ） における融着部を折り返す前の状態を示す上面図。
【図８】本発明に係るシート形電池の一例であるポリマー電解質二次電池（ｃ） を示す上面図。
【図９】比較例のポリマー電解質二次電池における融着部を折り返す前の状態を示す上面図。
【図１０】比較例のポリマー電解質二次電池を示す上面図。
【符号の説明】
１…素電池、
４…負極、
５…正極、
８…固体ポリマー電解質層、
９…正極端子、
１０…負極端子、
１３…熱融着シール用フィルム
１４…融着部。[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 heat sealing 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 sheet-like positive electrode,Sheet negative electrode,Positive electrode lead electrically connected to the positive electrode,Negative electrode lead electrically connected to the negative electrode, And non-aqueous electrolyteCell containingWhen,
The unit cellAnd a container made of laminated film
With
The laminate film has a polyethylene terephthalate (PET) layer / aluminum foil layer / polyethylene layer / ionomer resin layer laminated in this order,
In the container, the unit cell is covered with the laminate film such that the ionomer resin layer is the innermost layer, and the tips of the positive electrode lead and the negative electrode lead project outside, and the three sides of the three sides that are open are covered by the container. The innermost layer is sealed by heat sealing.
Both ends along the longitudinal direction of the three sides of the heat-sealed portion are folded back to one surface of the container and fixed with an adhesive tape,
The positive electrode lead and the negative electrode lead protrude from the remaining heat-sealed portion.A sheet-type battery is provided.
[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) to (c) shown in FIGS.
(1) Polymer electrolyte secondary battery (a)
FIG. 1 is a cross-sectional view showing an example of a sheet-type battery (sheet-type polymer electrolyte secondary battery) according to the present invention, FIG. 2 is a perspective view showing a main part of the secondary battery in FIG. 1, and FIG. FIG. 4 is a top view showing a state before the heat-sealed portion of the next battery is folded back, and FIG. 4 is a top view showing the secondary battery of FIG.
[0011]
The polymer electrolyte secondary battery (a) includes a unit cell 1 as shown in FIG. The unit cell 1 includes a negative electrode 4 having a structure in which a negative electrode layer 2 is supported on both surfaces of a net-like current collector 3 such as a copper expanded metal. Two positive electrodes 5 are arranged on both surfaces of the negative electrode 4. Each positive electrode 5 has a structure in which a positive electrode layer 6 containing an active material is supported on both surfaces of a net-like current collector 7 such as an aluminum expanded metal. The solid electrolyte layer 8 is interposed between the positive electrode 5 and the negative electrode 4. The current collector 7 of each of the positive electrodes 5 has a band-shaped positive terminal 9 in a portion located on the near side in FIG. The current collector 3 of the negative electrode 4 has a strip-shaped negative electrode terminal 10 at a position where the current collector 3 does not overlap with the positive electrode terminal 9 (for example, a portion located on the back side in FIG. 1). The two positive electrode terminals 9 are fixed to a belt-shaped positive electrode lead 11 by welding. On the other hand, the negative electrode terminal 10 is fixed to a strip-shaped negative electrode lead 12 (shown in FIGS. 3 and 4 described later) by welding.
[0012]
Such a unit cell is accommodated in a heat-sealing film 13 folded in two along the horizontal direction with the tips of the positive electrode lead 11 and the negative electrode lead 12 protruding from one end of the film. . The bent end (closed end) of the film faces the end from which the positive electrode lead 11 and the negative electrode lead 12 protrude. The three open sides of the film 13 are bonded by heat fusion as shown in FIGS. The heat-sealed portion is folded in the same direction (for example, the upper surface of the film 13) except for the ends where the tips of the two leads project, and is fixed with an adhesive 15 such as an adhesive tape.
[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, a rectangular heat-sealing film 13 is folded in two along the horizontal direction, and a unit cell having the above-described structure is used as a tip of the positive electrode lead 11 and the negative electrode lead 12. Is coated so as to project outside. At this time, the folded end of the film 13 is made to face the end where the lead protrudes. The three open ends of the film 13 are bonded by heat fusion. In the heat-sealed part 14 (the area shown by oblique lines in FIG. 3), the end along the longitudinal direction is folded back from the arrow, and is fixed to the upper surface of the film 13 with an adhesive tape. A sheet-type polymer electrolyte secondary battery (a) shown in FIG.
[0014]
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.
[0015]
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).
[0016]
Examples of the metal forming the metal layer of the heat sealing film include aluminum, nickel, and the like.
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.
[0017]
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).
[0018]
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.
(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.
[0019]
As the positive electrode active material, various oxides (for example, LiMn₂  O₄  Lithium manganese composite oxide such as manganese dioxide such as LiNiO₂  Lithium-containing nickel oxide such as LiCoO₂  For example, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, amorphous vanadium pentoxide containing lithium, 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.
[0020]
The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.
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.
[0021]
As the electrolyte, for example, lithium perchlorate (LiClO₄  ), Lithium hexafluorophosphate (LiPF)₆  ), Lithium borotetrafluoride (LiBF₄  ), Lithium arsenic hexafluoride (LiAsF)₆  ), Lithium trifluoromethanesulfonate (LiCF₃  SO₃  ), Lithium bistrifluoromethylsulfonylimide [LiN (CF₃  SO₃  )₂  ] And other lithium salts.
[0022]
The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / l to 2 mol / l.
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.
[0023]
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.
[0024]
The positive electrode terminal 9 and the lead 11 can be formed of, for example, aluminum. Further, as the positive electrode terminal 9, a mesh-like one such as a mesh or a plate-like one can be used.
[0025]
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.
[0026]
The positive electrode can be produced, for example, by a method described below.
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, a positive electrode not impregnated with the electrolyte is formed. 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 the nonaqueous electrolyte. The lamination of the positive electrode layer on the current collector may be performed by applying the paste to the current collector.
[0027]
Examples of the plasticizer include dibutyl phthalate (DBP), dimethyl phthalate (DMP), diethyl phthalate (DEP), propylene carbonate (PC), and tris-butoxyethyl phosphate.
[0028]
(Negative electrode)
This negative electrode is formed of a negative electrode active material, a nonaqueous electrolyte, and a negative electrode layer containing a polymer holding the electrolyte supported on a current collector.
[0029]
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, mesophase pitch, and 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.
[0030]
As the non-aqueous electrolyte and the polymer, the same ones as described for the positive electrode described above are used.
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.
[0031]
The terminal 10 and the lead 12 of the front negative electrode can be formed of, for example, copper. The negative electrode terminal 10 may be a mesh-like one such as a mesh or a plate-like one.
[0032]
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.
[0033]
The negative electrode can be manufactured, for example, by a method described below.
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.
[0034]
As the plasticizer, the same plasticizer as described above for the positive electrode can be used.
(Solid polymer electrolyte layer)
The electrolyte layer includes a non-aqueous electrolyte and a polymer that holds the electrolyte.
[0035]
As the non-aqueous electrolyte and the polymer, the same ones as described for the positive electrode described above are used.
To the electrolyte layer, an inorganic filler such as silicon oxide powder may be added from the viewpoint of further improving the strength.
[0036]
The electrolyte layer can be produced, for example, by a method described below.
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.
[0037]
As the plasticizer, the same plasticizer as described above for the positive electrode can be used.
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.
[0038]
(2) Polymer electrolyte secondary battery (b)
FIG. 5 is a top view showing the polymer electrolyte secondary battery in a state before the fused portion is folded, and FIG. 6 is a top view showing the polymer electrolyte secondary battery (b) according to the present invention.
[0039]
The polymer electrolyte secondary battery (b) is manufactured, for example, by the method described below. As shown in FIG. 5, a rectangular heat-sealing sealing film 13 is folded in two along the horizontal direction, and an electric field having the same structure as that of the above-described secondary battery (a) is placed in the film 13 as a positive electrode. The leads 11 and the negative electrode lead 12 are arranged so that the tips thereof project outside. At this time, the closed end of the film 13 is made orthogonal to the end where the lead protrudes. The three open ends of the film 13 are bonded by heat fusion. The end along the longitudinal direction of the obtained fused portion 14 (the region shown by oblique lines in FIG. 5) is folded back from the arrow 1. Next, the end opposite to the end where the lead protrudes is folded back in the same direction as the first bend from arrow 2, and the folded two ends are attached to the upper surface of the film 13 with an adhesive such as an adhesive tape. By fixing, a polymer electrolyte secondary battery (b) as shown in FIG. 6 is manufactured.
[0040]
Examples of the heat-sealing film include those similar to those described for the secondary battery (a).
As shown in FIG. 6, the secondary battery (b) has a portion 16 (a region shown by an oblique lattice in FIG. 6) where folded back portions are overlapped. For this reason, the volume of the secondary battery (b) is calculated using the thickness of the portion where the overlapping portion 16 exists (the maximum battery thickness) as the battery thickness. Therefore, such a structure is preferable when the battery size is such that the volume increased due to the increase in the thickness is sufficiently smaller than the volume decreased due to the folded portion being folded back.
[0041]
(3) Polymer electrolyte secondary battery (c)
FIG. 7 is a top view showing the polymer electrolyte secondary battery in a state before the fused portion is folded, and FIG. 8 is a top view showing the polymer electrolyte secondary battery (c) according to the present invention.
[0042]
This polymer electrolyte secondary battery (c) is manufactured, for example, by the method described below. As shown in FIG. 7, two heat-sealing films 13 are overlapped with each other so that the heat-sealing layers face each other, and between the films 13, the same as in the above-described secondary battery (a). The elementary ground of the configuration is arranged so that the tips of the positive electrode lead 11 and the negative electrode lead 12 project outside. All four ends of the film 13 are bonded by heat fusion. In the obtained fused portion 14 (the region shown by oblique lines in FIG. 7), both ends along the longitudinal direction are turned back from arrow 1. Next, the end opposite to the end from which the positive electrode lead 11 and the negative electrode lead 12 protrude is folded in the same direction as the first bending from the arrow 2, and the folded three ends are attached to the upper surface of the film 13 with an adhesive tape. A polymer electrolyte secondary battery (c) having the structure shown in FIG. 8 is manufactured by fixing with an adhesive as described above.
[0043]
Examples of the heat-sealing film include those similar to those described for the secondary battery (a).
As described in detail above, the sheet-type battery according to the present invention includes a sheet-shaped positive electrode, a sheet-shaped negative electrode, a positive electrode lead electrically connected to the positive electrode, and a negative electrode electrically connected to the negative electrode. And a unit cell including a lead. The unit cell is covered with a heat sealing film so that the tips of the positive electrode lead and the negative electrode lead project outside, and the open end of the film is heated. A sheet-type battery having a structure obtained by sealing by fusion, wherein the heat-fused portion of the film, except for the end where the positive electrode lead and the negative electrode lead project, one of the films. It is characterized by being folded back on one side or both sides. In such a battery, since the fused portion of the film is folded on one side or both sides of the film except for the end portion where the positive electrode lead and the negative electrode lead are fused, the outermost dimension ( Battery size) can be reduced. As a result, the battery can maintain high airtightness and improve energy efficiency per unit volume. In particular, as in the above-described secondary battery (a), a rectangular heat-sealing film for sealing is folded laterally, and the unit cell is used to project the lead end to the outside and the folded end of the film to project the lead. Coating is performed so as to face the end, the open end of the film is heat-sealed, and the fused portion is folded back except for the lead protruding end, thereby further improving the energy efficiency per unit volume. can do.
[0044]
Further, for example, by covering the unit cell with the heat-sealing sealing film which is folded in two as in the above-mentioned secondary batteries (a) and (b), it is possible to reduce the number of ends required for heat-sealing. Therefore, the airtightness can be improved. As a result, for example, in a polymer electrolyte secondary battery, the cycle life, particularly the cycle life in a high temperature environment, can be improved.
[0045]
【Example】
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
(Example 1)
<Preparation of positive electrode>
First, as an active material, the composition formula is LiMn.₂  O₄  56% by weight of a lithium manganese composite oxide represented by the following formula, 5% by weight of carbon black, 17% by weight of a vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer powder, and dibutyl phthalate (PBT) as a plasticizer. DBP) was 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.
[0046]
<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.
[0047]
<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.
[0048]
<Preparation of non-aqueous electrolyte>
LiPF as an electrolyte in a non-aqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 2: 1₆  Was dissolved at a concentration of 1 mol / l to prepare a non-aqueous electrolyte.
[0049]
<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 1.0 mm and an outer diameter of 25 × 50 mm. .
[0050]
<Assembly of battery>
A total of two positive electrode terminals and a positive electrode lead (consisting of a belt-like aluminum foil having a thickness of 0.5 mm) of the unit cell were fixed by ultrasonic welding. Further, the negative electrode terminal and the negative electrode lead (formed of a 0.5 mm thick strip-shaped copper foil) were fixed by ultrasonic welding.
[0051]
On the other hand, 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 were laminated in this order, was prepared as a heat seal film. Next, the film is folded in two along the horizontal direction, and the film is used to fold the cell so that the tips of the positive electrode lead and the negative electrode lead project outside, and the surface of the cell and the ionomer resin of the film. The coating was performed so that the layers (heat-fusible resin layers) faced each other. At this time, the closed end of the film was opposed to the lead projecting end. Subsequently, the three open sides of the film were heated and fused at a fusion width of 10 mm so as to have a margin for the unit cell dimensions and the heat-fused portion so that the influence of the heat fusion did not appear on the unit cell. By mounting, 100 polymer electrolyte secondary batteries having the structure shown in FIG. 3 described above, a thickness of 1.2 mm, an outer diameter of 50 × 65 mm excluding the lead portion, and an electric capacity of 50 mAh were obtained. Manufactured.
[0052]
Next, as shown in FIG. 3 described above, the two sealed portions except for the lead fixing portion of each of the secondary batteries are folded in the same direction, and are fixed with an adhesive tape having a thickness of 0.1 mm. A sheet-type polymer electrolyte secondary battery having the structures shown in 1, 3, 4 and having a maximum thickness of 1.5 mm and an outer diameter of 30 × 65 mm excluding the lead portion was obtained.
(Example 2)
A unit cell was prepared and leads were attached in the same manner as in Example 1 described above. A rectangular composite film of the same thickness and material as in Example 1 was prepared and folded in two along the horizontal direction. With this film, the unit cell is placed such that the tips of the positive electrode lead and the negative electrode lead project outside, and the ionomer resin layer (heat-fusible resin layer) of the film faces the surface of the unit cell. Coated. At this time, the closed end of the film was perpendicular to the lead projecting end. Subsequently, the three open sides of the film were heated and fused at a fusion width of 10 mm so as to have a margin for the unit cell dimensions and the heat-fused portion so that the influence of the heat fusion was not exerted on the unit cell. By mounting, 100 polymer electrolyte secondary batteries having the structure shown in FIG. 5 described above, a thickness of 1.2 mm, an outer diameter of 40 × 75 mm excluding the lead portion, and an electric capacity of 50 mAh were obtained. Manufactured.
[0053]
Next, as shown in FIG. 5 described above, the two sealing portions except for the lead fixing portion of each of the secondary batteries are folded in the same direction, and are fixed with an adhesive tape having a thickness of 0.1 mm, thereby obtaining the above-described diagram. 6, a sheet-type polymer electrolyte secondary battery having a maximum thickness of 1.8 mm (thickness of a portion 16 where two sealing portions overlap) and an outer diameter of 30 × 65 mm excluding a lead portion. did.
(Example 3)
A unit cell was prepared and leads were attached in the same manner as in Example 1 described above. Two rectangular composite films having the same thickness and material as in Example 1 were prepared. The two films were arranged such that their ionomer resin layers (heat-fusible resin layers) faced each other. Between these, the unit cells were arranged such that the tips of the positive electrode lead and the negative electrode lead protruded outside. Subsequently, all the four sides of the film were heated and fused with a fusion width of 1.0 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. As a result, 100 polymer electrolyte secondary batteries having the structure shown in FIG. 7 described above, a thickness of 1.2 mm, an outer diameter of 50 × 75 mm excluding the lead portion, and an electric capacity of 50 mAh are manufactured. did.
[0054]
Next, as shown in FIG. 7 described above, the three sealing portions except for the lead fixing portion of each of the secondary batteries are folded in the same direction and fixed with an adhesive tape having a thickness of 0.1 mm. 8, having a maximum thickness of 1.8 mm (the thickness of the portion 16 where the two sealing portions overlap) and an outer diameter of 30 × 65 mm excluding the lead portion. Battery.
(Comparative example)
A unit cell was prepared and leads were attached in the same manner as in Example 1 described above. The unit cell was sealed in a rectangular composite film of the same thickness and material as in Example 1 in the same manner as in Example 1, and had the structure shown in FIG. 9 and had a thickness of 1.2 mm, excluding the lead portion. 100 polymer electrolyte secondary batteries having an outer diameter of 50 × 65 mm and an electric capacity of 50 mAh were manufactured.
[0055]
Next, as shown in FIG. 9, both ends along the longitudinal direction of the sealing portion 14 (the area shown by oblique lines in FIG. 9) of each of the secondary batteries are folded back from the arrow 1, and the portion where the lead is fixed is shown. Is folded in the same direction as the first time from arrow 2 and is fixed with an adhesive tape having a thickness of 0.1 mm, thereby having a structure shown in FIG. 10 and a portion 16 where two sealing portions 14 overlap (FIG. 10). The thickness (maximum thickness) of the region indicated by the oblique lattice (the maximum thickness) was 1.9 mm including the thickness of the lead, and the sheet-type polymer electrolyte secondary battery had an outer diameter of 30 × 55 mm excluding the lead.
[0056]
For each of the obtained secondary batteries of Examples 1 to 3 and Comparative Example, the volume efficiency (Wh / l; calculated from the outer diameter excluding the lead portion) and bending when the average operating voltage was 3.8 V were obtained. The number of subsequent internal short circuits was determined, and the results are shown in Table 1 below. The volume efficiency was determined before and after the sealing portion was bent. The volume efficiency in Table 1 is an average value of 100 secondary batteries.
[0057]
Further, for each of the secondary batteries of Examples 1 to 3 and Comparative Example, a cycle evaluation was performed at a charge / discharge rate of 1.0 C, 4.5 V cut charge, 3.0 V cut discharge, and a cycle temperature of 60 ° C. Was measured until the value was less than 50%, and the results are shown in Table 1 below. Note that the cycle life in Table 1 is an average value of 100 secondary batteries.
[0058]
[Table 1]

[0059]
As is clear from Table 1, the secondary batteries of Examples 1 to 3 in which the sealing portions except for the ends where the positive electrode lead and the negative electrode lead protrude are bent in the same direction, as compared with before the bending process. It can be seen that the volume efficiency can be improved. In particular, it can be seen that the volume efficiency of the secondary battery of Example 1 is extremely high. In addition, the secondary batteries of Examples 1 and 2 in which the unit cells were covered with the heat-sealing film folded in half were the secondary batteries of Example 3 in which the unit cells were covered with the two heat-sealing films. It can be seen that the cycle life in a high temperature environment is longer than that of the battery.
On the other hand, it can be understood that the secondary battery of the comparative example in which the sealing portion is folded back including the end portion to which the lead is fixed causes an internal short circuit because the lead is bent.
[0060]
【The invention's effect】
As described in detail above, 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-type battery.
[Brief description of the drawings]
FIG. 1 is a cross-sectional 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 perspective view showing a main part of the secondary battery of FIG.
FIG. 3 is a top view showing a state before the heat-sealed portion in the secondary battery of FIG. 1 is folded back.
FIG. 4 is a top view showing the secondary battery of FIG. 1;
FIG. 5 is a top view showing a state before a fused portion is folded back in a polymer electrolyte secondary battery (b) which is an example of a sheet-type battery according to the present invention.
FIG. 6 is a top view showing a polymer electrolyte secondary battery (b) as an example of a sheet-type battery according to the present invention.
FIG. 7 is a top view showing a state before a fused portion is folded back in a polymer electrolyte secondary battery (c) which is an example of a sheet-type battery according to the present invention.
FIG. 8 is a top view showing a polymer electrolyte secondary battery (c) as an example of a sheet-type battery according to the present invention.
FIG. 9 is a top view showing a state before folding back a fused portion in a polymer electrolyte secondary battery of a comparative example.
FIG. 10 is a top view showing a polymer electrolyte secondary battery of a comparative example.
[Explanation of symbols]
1. Unit cells,
4 ... negative electrode,
5 ... positive electrode,
8. Solid polymer electrolyte layer,
9 ... Positive terminal,
10 ... negative electrode terminal,
13 ... Heat sealing film
14 ... fusion part

Claims (1)

Sheet-like positive electrode, a sheet-shaped negative electrode, said positive electrode and electrically connected to the positive electrode lead, the unit cell comprising said negative electrode and electrically connected to the negative electrode lead, and a nonaqueous electrolyte,
A container made of a laminated film in which the unit cells are stored;
With
The laminate film has a polyethylene terephthalate (PET) layer / aluminum foil layer / polyethylene layer / ionomer resin layer laminated in this order,
In the container, the unit cell is covered with the laminate film such that the ionomer resin layer is the innermost layer, and the tips of the positive electrode lead and the negative electrode lead project outside, and the three sides of the three sides that are open are covered by the container. The innermost layer is sealed by heat sealing.
Both ends along the longitudinal direction of the three sides of the heat-sealed portion are folded back to one surface of the container and fixed with an adhesive tape,
The sheet-type battery wherein the positive electrode lead and the negative electrode lead protrude from the remaining heat-sealed portion .

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