JPH11162421A - Sheet type battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization factor of a battery by arranging a stacked electrode whose one side of the outermost layer is a positive electrode and other side is a negative electrode, and an outer jacket material housing the stacked electrode, and whose inner surface facing the positive electrode functions as a positive current collector and inner surface facing the negative electrode functions as a negative current collector. SOLUTION: A sheet type secondary battery has a positive electrode layer 2 and a negative electrode layer 4 on the both sides of a positive current collector 1 and a negative current collector 3 each made of porous metal plate, and a gelled electrolyte layer 5 between the positive electrode layer 2 and the negative electrode layer 4 to form a stacked electrode. A rectangular frame 12 made of heat fusible resin seals the periphery with a first film 9 of an outer jacket material covering the top surface of the stacked electrode by arranging a metal layer 8 of the same kind as the positive current collector 1, and a second film 11 of the outer jacket material covering the bottom surface of the stacked electrode by arranging a metal layer 10 of the same kind as the negative current collector 3. An outer positive terminal 13 and an outer negative terminal 14 are formed by cutting out the corners of the first and second films 9, 11 and exposing the metal layers 8, 10. To prevent short of the positive and negative terminals 13, 14 in assembling, the positive and negative terminals 13, 14 are formed so as not to face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sheet-type battery.

[0002]

2. Description of the Related Art In recent years, a sheet-type battery having a thickness of about 0.5 mm, such as a sheet-type lithium ion secondary battery, has attracted attention as a power source for cordless devices such as portable personal computers, which emphasize small size and light weight. , Its development is being actively promoted.

[0003] Important element technologies for the practical use of the sheet-type battery include selection of active materials for a positive electrode and a negative electrode, a technology for forming a battery, and a technology for sealing a thin power generation element with an exterior material. When the sealing property of the thin power generating element by the exterior material is reduced, not only does the electrolyte constituting the power generating element volatilize and leak to reduce the battery reaction, but also moisture easily enters from the outside to reduce the performance. Invite.

[0004] For this reason, the conventional sheet-type battery is characterized in that a thin power generating element having a positive electrode, a separator and a negative electrode in an exterior material having a heat-fusible resin film disposed on the inner surface is electrically connected to the positive and negative electrodes. The externally connected external terminals are housed so as to extend from an opening edge of the exterior material, and the heat-fusible resin films are heat-sealed to each other at the opening edge to thereby connect the power generating element to the exterior. It has a structure sealed inside the material. The exterior material is, for example, a laminated film in which a heat-fusible resin film, a barrier film such as an aluminum foil, and a rigid resin film such as a polyethylene terephthalate film are laminated at least in this order.
However, the sheet-type battery is not always sufficient in the utilization factor and the tightness of the thin power generating element by the exterior material.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet-type battery having an improved utilization factor.

[0006]

According to the present invention, there is provided a sheet-type battery in which one outermost layer is a positive electrode and the other outermost layer is a negative electrode, the stacked electrode is housed, and is opposed to the positive electrode. An inner surface that functions as a current collector of the positive electrode, and an exterior material that functions as a current collector of the negative electrode has an inner surface facing the negative electrode.

In the sheet type battery according to the present invention, a laminated electrode whose outermost layer is one of a positive electrode and a negative electrode, and the laminated electrode is housed, and an inner surface facing the outermost layer electrode has the above-mentioned structure. And an exterior material functioning as a current collector for the electrode.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of a sheet type battery (first sheet type lithium ion secondary battery) according to the present invention will be described in detail with reference to FIGS. FIG. 1 shows a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a sheet-type lithium ion secondary battery of FIG.
FIG. 2 is a perspective view showing a state where the secondary battery of FIG. 1 is disassembled.

As shown in FIG. 1, a first sheet type lithium ion secondary battery according to the present invention has a positive electrode having a structure in which a positive electrode layer 2 is supported on both surfaces of a current collector 1 made of a porous metal plate. A negative electrode having a structure in which a negative electrode layer 4 is supported on both surfaces of a current collector 3 formed of a porous metal plate, and a gel electrolyte layer 5 disposed between the positive electrode layer 2 and the negative electrode layer 4. And a laminated electrode having the same. A strip-shaped positive electrode terminal 6 made of the same metal plate as the positive electrode current collector 1 extends from the positive electrode current collector 1. A strip-shaped negative electrode terminal 7 made of the same metal plate as the negative electrode current collector 3 extends from the negative electrode current collector 3. As shown in FIG. 2, the positive electrode terminal 6 is folded on the upper surface of the laminated electrode. The negative electrode terminal 7 is folded back on the lower surface of the laminated electrode. A first film 9 (exterior material) in which a layer 8 made of the same kind of metal as the positive electrode current collector 1 is disposed on the inner surface covers the upper surface of the laminated electrode. The positive electrode terminal 6 is fixed to the metal layer 8 by, for example, welding. A second film 11 (exterior material) having an inner surface on which a layer 10 made of the same kind of metal as the negative electrode current collector 3 is disposed covers the lower surface of the laminated electrode. The negative electrode terminal 7 is fixed to the metal layer 10 by, for example, welding. A rectangular frame 12 made of a heat-sealing resin is arranged between the periphery of the first film 9 and the periphery of the second film 11. The first film 9 is heat-sealed by the rectangular frame 12.
The laminated electrode is sealed in the second film 11. The external positive terminal 13 is connected to the first film 9.
The first film 9 is formed by notching a corner of the main body of the first film 9 in a rectangular shape to expose the metal layer 8. The external negative electrode terminal 14 is formed by exposing the metal layer 10 by cutting a corner of the main body of the second film 11 into a rectangle in the second film 11. From the viewpoint of avoiding a short circuit when the sheet-type lithium-ion secondary battery is incorporated in a device or the like, the external positive terminal 13 and the external negative terminal 14 are arranged at positions not facing each other.

As the positive electrode, the negative electrode, and the electrolyte layer of the sheet-type lithium ion secondary battery, for example, those described below can be used. (Positive Electrode) This positive electrode is formed of a material in which a positive electrode layer containing a material that stores and releases lithium ions, a nonaqueous electrolyte, and a polymer that holds the electrolyte is supported on a current collector.

Examples of the 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, and lithium-containing cobalt oxide such as LiCoO ₂ ). , Lithium-containing nickel cobalt oxide, lithium-containing amorphous vanadium pentoxide, etc.),
Chalcogen compounds (for example, titanium disulfide, molybdenum disulfide, etc.) can be exemplified. Among them, lithium manganese composite oxide, lithium-containing cobalt oxide,
It is preferable to use lithium-containing nickel oxide.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent. As the non-aqueous solvent,
Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DE
C), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (TH
F) and 2-methyltetrahydrofuran. The non-aqueous solvents may be used alone or as a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF ₆ ), lithium borotetrafluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN
(CF ₃ SO ₃ ) ₂ ].

It is desirable that the amount of the electrolyte dissolved in the non-aqueous solvent be 0.2 mol / l to 2 mol / l. Examples of the polymer having a function of retaining the nonaqueous electrolyte include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and the like. Can be used. The copolymerization ratio of the HFP depends on the method of synthesizing the copolymer, but is usually at most about 20% by weight.

The positive electrode may contain 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.

As the positive electrode current collector, for example, aluminum expanded metal, aluminum mesh, aluminum punched metal, etc. can be used. (Negative Electrode) The negative electrode is formed from a material in which a negative electrode layer containing a material that stores and releases lithium ions, a nonaqueous electrolyte, and a polymer that holds the electrolyte is supported on a current collector.

Examples of the material include a carbonaceous material that stores and releases lithium ions. As such a carbonaceous material, for example, an organic polymer compound (for example,
Phenolic resin, polyacrylonitrile, cellulose, etc.) by firing, coke,
Examples thereof include those obtained by firing mesophase pitch, and carbonaceous materials typified by artificial graphite, natural graphite, and the like. Among them, 500 ℃
It is preferable to use a carbonaceous material obtained by calcining the mesophase pitch at a temperature of up to 3000 ° C. under normal pressure or reduced pressure.

As the non-aqueous electrolyte and the polymer, the same ones as those described for the positive electrode are used. The negative electrode sheet 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.

As the negative electrode current collector, for example, copper expanded metal, copper mesh, copper punched metal and the like can be used. (Gel-like electrolyte layer) This electrolyte layer contains a non-aqueous electrolyte and a polymer holding the electrolyte.

As the non-aqueous electrolyte and the polymer, those similar to those described for the above-mentioned positive electrode are used. From the viewpoint of further improving the strength, the electrolyte layer may include an inorganic filler such as silicon oxide powder.

(Exterior material) The first film 9 has a metal layer 8 (for example, aluminum foil) disposed on the inner surface. In particular, it is preferable that the inner surface is formed of the above-mentioned metal layer, and the outer surface is formed of a multilayer film made of a resin layer having moisture proof property, gas permeable property and chemical resistance such as polyethylene terephthalate (PET) or nylon. Specifically, a multilayer film of / Al foil / thermosetting resin (for example, melamine resin) / PET laminated from the inner surface side to the outer surface;
1 foil / the thermosetting resin / a multilayer film of nylon; and the like.

The second film 11 has a metal layer 10 (eg, copper foil) disposed on the inner surface. Among them,
It is preferable that the inner surface is made of the above-mentioned metal layer and the outer surface is made of a multilayer film made of a resin layer having moisture proofing property, air resistance and chemical resistance such as polyethylene terephthalate (PET) or nylon. Specifically, a multilayer film of copper foil / thermosetting resin (for example, melamine resin) / PET; copper foil / the thermosetting resin / a multilayer film of nylon; Can be used.

Examples of the heat-sealing resin forming the rectangular frame 12 include ionomer, modified polyethylene, a mixture of ionomer and polyethylene, and a mixture of ionomer and modified polyethylene.

Hereinafter, another example (second sheet type lithium ion secondary battery) of the sheet type battery according to the present invention will be described. FIG. 3 is a sectional view showing a second sheet type lithium ion secondary battery, and FIG. 4 is a perspective view showing a state where the secondary battery of FIG. 3 is disassembled.

As shown in FIG. 3, the second sheet type lithium ion secondary battery according to the present invention has a positive electrode having a structure in which a positive electrode layer 22 is supported on both surfaces of a current collector 21 formed of a porous metal plate. And a negative electrode having a structure in which a negative electrode layer 24 is supported on both surfaces of a current collector 23 formed of a porous metal plate, and a gel electrolyte layer 25 disposed between the positive electrode layer 22 and the negative electrode layer 24. And a laminated electrode having the same. The strip-shaped positive electrode terminals 26 made of the same metal plate as the positive electrode current collector 21 extend from the positive electrode current collector 21, respectively. As shown in FIG. 4, the upper positive electrode terminal 26 is folded on the upper surface of the laminated electrode. On the other hand, the lower positive electrode terminal 26 is folded back on the lower surface of the laminated electrode. As shown in FIGS. 3 and 4, a strip-shaped negative electrode terminal 27 made of a metal plate similar to the negative electrode current collector 23 extends from the negative electrode current collector 23. The strip-shaped external negative terminal 28 is connected to the tip of the negative terminal 27. The external negative terminal 28 can be formed, for example, from a copper foil. Two films 2
In layers 9 and 30 (exterior materials), layers 31 and 32 made of the same type of metal as the positive electrode current collector 21 are arranged on the inner surface. The two films 29 and 30 cover the upper and lower surfaces of the laminated electrode, respectively. The metal layer 3
An upper positive electrode terminal 26 is fixed to 1 by, for example, welding. On the other hand, the lower positive electrode terminal 2
6 is fixed by, for example, welding. The rectangular frames 33 and 34 made of the heat-sealing resin are respectively arranged in spaces surrounded by the periphery of the film 29 and the periphery of the film 30. The peripheral edges of the two films 29 and 30 are bonded together by thermal fusion using the rectangular frames 33 and 34. The laminated electrode includes the two films 2
Sealed inside 9,30. The external negative terminal 28
The rectangular frames 33, 34 with their tips protruding outside.
Is heat-sealed. The external positive terminals 35 and 36 are
The films 29, 30 are formed by exposing the metal layers 31, 32 by cutting the corners of the films 29, 30 into rectangular shapes.

As the positive electrode, the negative electrode and the electrolyte layer of the sheet-type lithium ion secondary battery, the same ones as described in the first secondary battery can be used. The two films 29, 30 have metal layers 31, 3 on their inner surfaces.
2 (for example, aluminum foil). In particular, it is preferable that the inner surface is formed of the above-mentioned metal layer, and the outer surface is formed of a multilayer film made of a resin layer having moisture proof property, gas permeable property and chemical resistance such as polyethylene terephthalate (PET) or nylon. Specifically, a multilayer film similar to that described in the first film of the first secondary battery can be used.

As the heat-sealing resin forming the rectangular frames 33 and 34, the same ones as described in the first secondary battery can be used. As described in detail above, according to the sheet-type battery of the present invention, one outermost layer of the laminated electrode is a positive electrode, and the other outermost layer is a negative electrode, and the outer packaging material faces the positive electrode of the outermost layer. An inner surface functions as a current collector of the positive electrode, and an inner surface facing the negative electrode of the outermost layer functions as a current collector of the negative electrode. According to such a sheet-type battery, the current collection efficiency of the positive electrode and the negative electrode located at the outermost layers of the laminated electrode can be improved, so that the utilization factor can be improved and the discharge capacity can be increased.

Further, by forming the external positive and negative terminals on the surface of the exterior material, it is not necessary to extend the external positive and negative terminals from the sealing portion of the exterior material. It can be greatly improved.

As the exterior material, a first film having the same type of metal layer as the current collector of the positive electrode disposed on the inner surface, and a first film having the same type of metal layer as the current collector of the negative electrode disposed on the inner surface. 2
And electrically connecting the metal layer of the first film to the current collector of the outermost positive electrode, and bonding the metal layer of the second film to the outermost layer. By electrically connecting the current collector of the negative electrode, the inner surface of the exterior material can be used as a current collector of the positive and negative electrodes located in the outermost layer of the laminated electrode. as a result,
A sheet-type battery with improved utilization and discharge capacity can be realized.

The metal layer exposed by notching the surface of the first film of the exterior material is used as an external positive electrode terminal, and the metal layer exposed by notching the surface of the second film. Is used as an external negative electrode terminal, so that external positive and negative electrode terminals can be formed on the surface of the exterior material. As a result, it is possible to realize a sheet-type battery in which the sealing property of the laminated electrode by the exterior material is improved.

Further, according to another sheet-type battery according to the present invention, the outermost layer of the laminated electrode is one of the positive electrode and the negative electrode, and the outer package is formed of the outermost layer and the electrode located in the outermost layer. Opposing inner surfaces function as current collectors for the electrodes. According to such a sheet-type battery, the current collection efficiency of the positive electrode or the negative electrode located at the outermost layer of the laminated electrode can be improved, so that the utilization factor can be improved and the discharge capacity can be increased.

By forming the external electrode terminals on the surface of the exterior material, the external terminals of the electrodes located in the outermost layer do not have to be configured to extend from the sealing portion of the exterior material. Can improve the sealing property of the laminated electrode.

As the exterior material, a film having the same type of metal layer as the current collector of the electrode on the inner surface is used, and the metal layer of the film and the current collector of the outermost electrode are electrically connected. By connecting, the inner surface of the exterior material can be used as a current collector for an electrode located on the outermost layer of the laminated electrode. As a result, a sheet-type battery with improved utilization and discharge capacity can be realized.

The external electrode terminals can be formed on the surface of the exterior material by using the metal layer exposed by cutting out the surface of the film of the exterior material as external electrode terminals. As a result, it is possible to realize a sheet-type battery in which the sealing property of the laminated electrode by the exterior material is improved.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Example 1) <Preparation of positive electrode> First, a lithium manganese composite oxide represented by a composition formula of LiMn ₂ O ₄ as an active material, carbon black, and vinylidene fluoride-hexafluoropropylene (VdF-HFP) were used. A mixed solution of the copolymer powder and dibutyl phthalate (DBP) as a plasticizer was mixed in acetone to prepare a paste. The mixing ratio of each material (LiMn ₂ O ₄ : VdF-HFP)
(Copolymer: carbon black: DBP) was 56% by weight: 17% by weight: 5% by weight: 22% by weight. The obtained paste is applied to a polyethylene terephthalate film (P
(ET film), and formed into a sheet to produce a positive electrode sheet not impregnated with a non-aqueous electrolyte.

An expanded metal made of aluminum was prepared as a positive electrode current collector having a strip-shaped terminal portion. The positive electrode sheet was hot-pressed on both surfaces of the current collector with a hot roll to produce a positive electrode not impregnated with a non-aqueous electrolyte.

<Preparation of Negative Electrode> Mesophase pitch carbon fiber as an active material, vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer powder,
A plasticizer {dibutyl phthalate (DBP)} was mixed in acetone to prepare a paste. The compounding ratio of the materials (carbon fiber: VdF-HFP copolymer: DBP)
58% by weight: 17% by weight: 25% by weight. The obtained paste is applied to a polyethylene terephthalate film (PE
T film) to form a sheet, thereby producing a negative electrode sheet not impregnated with an electrolytic solution.

A copper expanded metal was prepared as a negative electrode current collector having a strip-shaped terminal portion. The negative electrode sheet was heat-pressed on both surfaces of the current collector with a hot roll to produce a negative electrode impregnated with no electrolyte.

<Preparation of Gel Electrolyte Layer>
2.2 parts by weight of VdF-HFP copolymer powder
3.3 parts by weight and plasticizer dibutyl phthalate (DB
P) # 44.5 parts by weight 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.

<Preparation of Nonaqueous Electrolyte> A nonaqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 2: 1 was mixed with LiPF ₆ as an electrolyte at a concentration of 1 mol / mol. 1 to prepare a non-aqueous electrolyte.

<Assembly of Battery> The electrolyte layer was interposed between the positive electrode layer of the positive electrode and the negative electrode layer of the negative electrode, laminated, and heated and pressed by a heated rigid roll to produce a laminate. Such a laminate was immersed in methanol, and the DBP in the laminate was extracted with methanol and removed. After drying this, the outer dimensions except for the terminal part are 4 cm x
A 5 cm laminated electrode was produced. The positive electrode terminal portion was folded on the upper surface of the laminated electrode, and the negative electrode terminal portion was folded on the lower surface of the laminated electrode.

Next, a multilayer film in which a PET layer having a thickness of 75 μm, a thermosetting resin layer containing a melamine resin having a thickness of 5 μm, and a copper foil layer having a thickness of 20 μm were laminated in this order as a negative electrode packaging material was prepared. Prepared. An external negative electrode terminal was formed by notching a PET layer and a thermosetting resin layer at corners of the multilayer film and exposing the copper foil. The negative electrode exterior material was arranged so that the copper foil layer and the lower surface (negative electrode layer) of the multilayer electrode were in contact with the laminated electrode, and the negative electrode terminal was welded to the copper foil layer. Next, a rectangular frame having a thickness of 0.5 mm and made of ionomer-modified polypropylene was placed on the periphery of the negative electrode packaging material. A multilayer film was prepared in which a PET layer having a thickness of 75 μm, a thermosetting resin layer containing a melamine resin having a thickness of 5 μm, and an aluminum foil layer having a thickness of 20 μm were laminated in this order as a cathode exterior material. An external positive electrode terminal was formed by notching the PET layer and the thermosetting resin layer at the corners of the multilayer film in a rectangular shape and exposing the aluminum foil. The positive electrode exterior material was disposed so that the aluminum foil layer and the upper surface (positive electrode layer) of the multilayer electrode were in contact with the laminated electrode, and the positive electrode terminal was welded to the aluminum foil layer.
Note that, when the positive electrode packaging material was placed on the laminated electrode, the external negative electrode terminal of the negative electrode packaging material and the external positive electrode terminal of the positive electrode packaging material did not face each other.

Next, the three ends of the positive and negative electrode packaging materials were sealed by heating and pressing. 0.4 g of a non-aqueous electrolyte solution having the above composition was injected from the remaining end, and the laminated electrode was impregnated. Subsequently, by heating and pressurizing the end portion that has not been heat-sealed, the sheet-shaped lithium-ion battery having the above-described structure shown in FIGS. 1 and 2 and having an outer dimension of 5 cm × 6 cm and an electric capacity of 50 mAh is provided. A secondary battery was manufactured. (Comparative Example 1) An electrolyte layer similar to that of Example 1 was interposed between a positive electrode similar to that of Example 1 and a negative electrode similar to that of Example 1, laminated, and then heated and pressed by a heated rigid roll. A laminate was made. Such a laminate was immersed in methanol, and the DBP in the laminate was extracted with methanol and removed. This was dried. A strip-shaped aluminum foil was welded to the terminal part of the positive electrode as an external positive terminal. In addition, a strip-shaped copper foil was welded to the terminal portion of the negative electrode as an external negative electrode terminal, to produce a laminated electrode having an outer dimension of 4 cm × 5 cm excluding the terminal portion.

Next, as an exterior material, a 50 μm thick P
A multilayer film was prepared in which an ET layer, a thermosetting resin layer containing a melamine resin having a thickness of 5 μm, an aluminum foil having a thickness of 20 μm, and an ionomer resin layer having a thickness of 25 μm were laminated in this order. . The film was folded in two so that the ionomer resin layer was located inside, and the laminated electrode was covered so that the positive electrode lead and the negative electrode lead extended from the film. Two sides of the opening of the film were sealed by heat fusion. Next, 0.4 g of a non-aqueous electrolyte having the same composition as in Example 1 was injected from one end not subjected to the heat fusion, and the laminated electrode was impregnated. Subsequently, the non-heat-fused end portion is heat-fused to form a sheet-shaped lithium ion having a structure shown in FIG. 5 having an outer dimension of 5 cm × 6 cm excluding external terminal portions and an electric capacity of 50 mAh. A secondary battery was manufactured.

That is, as shown in FIG. 5, the secondary battery has a positive electrode having a structure in which a positive electrode layer 42 is supported on both surfaces of a current collector 41 and a negative electrode layer 44 on both surfaces of a current collector 43. And a negative electrode having the structure described above. Gel electrolyte layer 4
5 is arranged between the positive electrode layer 42 and the negative electrode layer 44. The positive electrode current collector 41 has a strip-shaped terminal portion 46 made of the same material as the current collector. The negative electrode current collector 43 has a strip-shaped terminal portion 47 made of the same material as the current collector at a position not facing the terminal portion 46.
The positive electrode lead 48 is connected to the strip-shaped terminal portion 46. The negative electrode lead 49 is connected to the negative electrode terminal 47. The positive electrode, the negative electrode, and the gel electrolyte layer (power generation element) are covered with a folded film 50. The opening of the film 50 is sealed by heat fusion.

The obtained secondary batteries of Example 1 and Comparative Example 1 were stored in a thermostat at 60 ° C. for one month, weighed, and the amount of decrease from the weight before storage at high temperature was determined. The results are shown in Table 1 below.

The charge and discharge current of the secondary batteries of Example 1 and Comparative Example 1 was 20 mA, and the charge voltage was 4.2.
V and a discharge voltage of 2.7 V were subjected to 100 charge / discharge cycles, the weight was measured, and the amount of decrease from the weight before the charge / discharge cycle was determined. The results are shown in Table 1 below.

With respect to the secondary batteries of Example 1 and Comparative Example 1, the discharge capacity after 100 charge / discharge cycles of a charge / discharge current of 20 mA, a charge voltage of 4.2 V, and a discharge voltage of 2.7 V was measured. The measured capacity was calculated by calculating the ratio of the capacity to the design capacity by 100%, and the utilization rate was obtained. The results are shown in Table 1 below.

[0049]

[Table 1]

As is apparent from Table 1, the secondary battery of Example 1 has a smaller weight loss due to high-temperature storage and charge / discharge cycles than the secondary battery of Comparative Example 1, and the sealing of the laminated electrode by the exterior material. It can be seen that the properties can be improved. In addition, it can be seen that the utilization rate of the secondary battery of Example 1 can be improved as compared with the secondary battery of Comparative Example 1. (Example 2) Two positive electrodes similar to those in Example 1 and
And one gel electrolyte layer similar to that of Example 1 was prepared. The positive electrode and the negative electrode were alternately laminated with a gel electrolyte layer interposed therebetween, and these were heat-pressed with a heated rigid roll to produce 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 an external negative electrode terminal made of a strip-shaped copper foil was welded to the terminal portion of the negative electrode to produce a laminated electrode having a size excluding the terminal portion of 4 cm × 5 cm.

The upper positive electrode terminal of the obtained laminated electrode was folded back to the upper surface, and the lower positive electrode terminal was folded back to the lower surface. Next, two multilayer films in which a 75 μm-thick PET layer, a 5 μm-thick thermosetting resin layer containing a melamine resin, and a 20 μm-thick aluminum foil layer were laminated in this order as a positive electrode exterior material were used. Prepared. An external positive electrode terminal was formed by notching the PET layer and the thermosetting resin layer at the corners of each of the multilayer films in a rectangular shape and exposing the aluminum foil. One of the positive electrode exterior materials was arranged such that the aluminum foil layer and the lower surface of the multilayer electrode were in contact with the multilayer electrode, and the upper positive electrode terminal was fixed to the aluminum layer by welding. An upper rectangular frame and a lower rectangular frame made of ionomer-modified polypropylene having a thickness of 0.8 mm are placed on the periphery of the positive electrode packaging material, and the external negative electrode terminal of the laminated electrode is extended from between these rectangular frames. Was. The other of the positive electrode exterior materials was arranged so that the aluminum foil layer and the upper surface of the multilayer electrode were in contact with the multilayer electrode, and the lower positive electrode terminal was fixed to the aluminum layer by welding.

Next, the three ends of these positive electrode packaging materials were sealed by heating and pressing. 0.7 g of a non-aqueous electrolyte having the above composition was injected from the remaining end, and the laminated electrode was impregnated. Subsequently, by heating and pressurizing the end portion that has not been heat-sealed, the end portion having the above-described structure shown in FIGS.
cm, and a sheet-type lithium ion secondary battery having an electric capacity of 100 mAh was manufactured. Comparative Example 2 Two positive electrodes similar to those in Example 1 and
And one gel electrolyte layer similar to that of Example 1 was prepared. The positive electrode and the negative electrode were alternately laminated with a gel electrolyte layer interposed therebetween, and these were heat-pressed with a heated rigid roll to produce a laminate. Such a laminate was immersed in methanol, and the DBP in the laminate was extracted with methanol and removed. This was dried. The two terminal portions of the positive electrode were welded to a strip-shaped aluminum foil as an external positive terminal. Further, a strip-shaped copper foil as an external negative electrode terminal was welded to the terminal portion of the negative electrode, thereby producing a laminated electrode having an outer dimension of 4 cm × 5 cm excluding the terminal.

Next, a multilayer film similar to that of Comparative Example 1 was prepared as an exterior material. The film was folded in two so that the ionomer resin layer was located inside, and the laminated electrode was covered so that the positive electrode lead and the negative electrode lead extended from the film. Two sides of the opening of the film were sealed by heat fusion. Next, 0.7 g of a non-aqueous electrolytic solution having the same composition as in Example 1 was injected from one end not thermally fused, and the laminated electrode was impregnated. Subsequently, the non-heat-fused end portion was heat-fused to produce a sheet-type lithium-ion secondary battery having an outer dimension of 5 cm × 6 cm excluding the external terminal portion and an electric capacity of 100 mAh.

The obtained secondary batteries of Example 2 and Comparative Example 2 were stored in a thermostat at 60 ° C. for one month, weighed, and the amount of reduction from the weight before high-temperature storage was determined. The results are shown in Table 2 below.

The secondary batteries of Example 2 and Comparative Example 2 had a charge / discharge current of 20 mA and a charge voltage of 4.2.
V and a discharge voltage of 2.7 V were subjected to 100 charge / discharge cycles, the weight was measured, and the amount of decrease from the weight before the charge / discharge cycle was determined. The results are shown in Table 2 below.

With respect to the secondary batteries of Example 2 and Comparative Example 2, the discharge capacity when 100 charge / discharge cycles of a charge / discharge current of 20 mA, a charge voltage of 4.2 V, and a discharge voltage of 2.7 V were performed. The ratio was measured and the ratio of the capacity to the design capacity was calculated as a percentage, and the utilization was determined. The results are shown in Table 2 below.

[0057]

[Table 2]

As is clear from Table 2, the secondary battery of Example 2 has a smaller weight loss due to high-temperature storage and charge / discharge cycles than the secondary battery of Comparative Example 2, and the sealing of the laminated electrode by the exterior material. It can be seen that the properties can be improved. Further, it can be seen that the utilization rate of the secondary battery of Example 2 can be improved as compared with the secondary battery of Comparative Example 2.

[0059]

As described in detail above, according to the present invention, it is possible to provide a sheet-type lithium ion secondary battery having an improved utilization factor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a sheet-type battery (sheet-type lithium-ion secondary battery) according to the present invention.

FIG. 2 is a perspective view showing a state in which the secondary battery of FIG. 1 is disassembled.

FIG. 3 is a cross-sectional view showing another example of a sheet-type battery according to the present invention (a sheet-type lithium-ion secondary battery).

FIG. 4 is an exemplary perspective view showing a state where the secondary battery of FIG. 3 is disassembled;

FIG. 5 is a cross-sectional view illustrating a sheet-type lithium-ion secondary battery of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Positive electrode collector, 2 ... Positive electrode layer, 3 ... Negative electrode current collector, 4 ... Negative electrode layer, 5 ... Gel electrolyte layer, 6 ... Positive electrode terminal part, 7 ... Negative electrode terminal part, 8 ... Metal layer, 9 ... 1st film (positive casing material), 10: metal layer, 11: second film (negative casing material), 12: rectangular frame made of heat-fusible resin, 13: external positive terminal.

Claims (4)

[Claims] 1. A laminated electrode in which one outermost layer is a positive electrode and the other outermost layer is a negative electrode;
A sheet-type battery comprising: an inner surface facing the positive electrode serving as a current collector for the positive electrode; and an outer material facing the negative electrode serving as a current collector for the negative electrode. 2. The sheet-type battery according to claim 1, wherein the exterior material has an external positive terminal and an external negative terminal on a surface. 3. A laminated electrode in which an outermost layer is one of a positive electrode and a negative electrode, and the laminated electrode is housed, and an inner surface facing the outermost layer electrode functions as a current collector of the electrode. A sheet-type battery comprising: 4. The sheet-type battery according to claim 3, wherein the exterior material has external electrode terminals on a surface.