JP4166906B2 - Manufacturing method of sheet type battery - Google Patents

Description

【００４０】
【表２】

【００４１】
表１、表２の結果より、本発明の製造方法で作成したシート型電池は、何れも、比較例と比べて特性劣化は認められず、信頼性が低下していないことがわかる。
【００４２】
以上の結果より明らかなように、外装体に未シール部を作製し、初回の充放電後に、その部分に穴をあけガス抜きを行い、その後、再シールを行うという方法でガス抜きをすることで、電池の信頼性を低下させることなく、簡単な工程でガス抜きを行うことができる。また、外装体にガス抜き孔を設けるのは一時的であり、しかも、ガス抜き孔が小さいため、電解質の吸湿、電解質の組成変化などの不都合は生じない。
【００４３】
【発明の効果】
本発明のシート型電池の製造方法によれば、薄く軽量な外装体にリチウムイオン二次電池などの電池素体を封入する際に問題となる初期充電時に発生するガスを材料のムダを生じずに簡単にガス抜きできる。
【図面の簡単な説明】
【図１】本発明のシート型電池の製造方法において、電池素体を外装体に封入した状態を示す平面図である。
【図２】図１のＡ−Ａ線に沿った断面図である。
【図３】図１のＢ部の拡大図であり、（ａ）は未接合部を形成した状態、（ｂ）はガス抜き孔を穿設した状態、（ｃ）は未接合部を接合した状態を示す。
【図４】（ａ）、（ｂ）は未接合部の他の形状を示す平面図である。
【符号の説明】
１０ 電池素体
１１ リード線
１２ リード線
１３ 正極
１４ 負極
１５ 固体電解質
２０ 外装体
３１ 第１接合部
３２ 第２接合部
４０ 未接合部
４１ 屈曲した連通部
５０ ガス抜き孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a sheet-type battery in which the gas generated during the initial charge of a battery body such as a lithium ion secondary battery is easily degassed.
[0002]
[Prior art]
At present, various types of batteries are widely used from the field of electronics to large-size vehicles intended for automobile use or power storage. In such a battery, a liquid is usually used as the electrolytic solution. However, by replacing this with a solid, it is expected that liquid leakage can be prevented or a sheet structure can be formed. It attracts attention. In particular, if lithium-ion secondary batteries and the like that are currently being rapidly used in mobile phones, notebook personal computers, etc., can be made into sheets or stacked and miniaturized, it is predicted that application development will be further accelerated.
[0003]
When such a solid electrolyte is used, a ceramic material, a polymer material, or a composite material thereof has been proposed. Among them, a gel electrolyte obtained by plasticizing a polymer electrolyte with an electrolytic solution has both high liquid conductivity and high polymer plasticity, and is considered promising for electrolyte development.
[0004]
By the way, one of the advantages of a battery using such a solid electrolyte is that it enables a thin and large area, that is, a sheet-like form. This further accelerates the development of application uses. Furthermore, in order to bring out the advantages of such a sheet type battery, when a metal case is used like a conventional cylindrical or rectangular battery, the weight and thickness of the entire battery account for a large proportion of the metal case. The reason for the battery is offset. Therefore, in order to take advantage of the advantage, it is necessary to apply an exterior case that can be reduced in weight. Therefore, as an outer case of such a sheet-type battery, for example, a resin-made thin case or a flexible bag-like body such as aluminum, generally an aluminum laminate pack is used.
[0005]
[Problems to be solved by the invention]
However, since a thick metal can is conventionally used for a lithium ion secondary battery, the outer case is formed by gas generated inside the battery at the first charge performed in the final stage of manufacture after being enclosed in the outer case. Although the problem of swelling does not occur, there is a problem that when the resin-made thin case or a flexible bag-like body such as aluminum is used for the case, the outer case is swollen due to gas generation. Therefore, in the manufacturing process of a lithium ion secondary battery, it is necessary to remove the generated gas in order to ensure safety and thinness.
[0006]
As a degassing method that occurs at the time of the initial charging, a method in which the first charging is performed in a state where an opening portion is created in a part of the exterior case and then the opening portion is sealed can be considered.
[0007]
However, in the lithium ion secondary battery, there is a problem that a nonaqueous electrolytic solution is used and the electrolytic solution dislikes moisture. Therefore, when the outer package is not sealed, a constant current power source or a constant voltage power source must be installed in a dry environment with a dew point of −30 degrees or less, which causes a problem in terms of cost and efficiency. In addition, there is also a problem that a composition change of the electrolytic solution occurs due to evaporation of easily volatile components in the electrolytic solution.
[0008]
In JP-A-10-308240, a storage space for storing a battery element body and a spare space communicating with the storage space are provided in an exterior case, and after initial charging, the storage space is stored in the spare space. A gas venting method is shown in which gas is stored, and then the communication portion between the spare space and the storage space is shut off, and the spare space is further excised. This degassing method is advantageous in terms of process, but requires unnecessary parts in the outer case, and those parts must be cut and the cut parts must be discarded. There is a problem that the burden is heavy.
[0009]
An object of the present invention is to easily degas the gas generated during initial charge / discharge, which is a problem when a battery body such as a lithium ion secondary battery is enclosed in a thin and lightweight exterior body without causing waste of material. It is providing the manufacturing method of a sheet type battery.
[0010]
[Means for Solving the Problems]
The above object is achieved by the present inventions (1) to (4) below.
(1) In a method for manufacturing a sheet-type battery in which a battery body is wrapped with an exterior film, the opening of the exterior film is joined, and the battery body is enclosed in the exterior body, one of the joint portions of the exterior body Forming a non-joined portion that communicates with the interior of the exterior body and is isolated from the exterior of the exterior body, and enclosing the battery body in the exterior body, and a gas in the unjoined portion A degassing step of opening a vent hole to allow communication between the inside and the outside of the outer package, and re-encapsulation of the battery element body in the outer package again by joining the non-joined portion and closing the vent hole It possesses a step, the non-bonded portion, the manufacturing method of the sheet-type battery having a communication portion that is bent.
(2) The manufacturing method of the sheet type battery according to (1), wherein the battery body uses a solid electrolyte.
(3) The manufacturing method of the sheet type battery according to (1) or (2), wherein the unjoined portion is formed using a horn or a mold having a concave portion in the shape of the unjoined portion .
(4) The method for producing a sheet-type battery according to any one of (1) to (3), wherein the exterior film is a heat-welding resin.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a method for producing a sheet type battery of the present invention will be described with reference to FIGS.
[0012]
As described above, the sheet type battery manufacturing method of the present invention is a sheet type battery in which a battery body is wrapped with an exterior film, the opening of the exterior film is joined, and the battery body is enclosed in the exterior body. In this manufacturing method, the battery element body is formed in the exterior body by forming an unjoined portion that communicates with the inside of the exterior body and is isolated from the outside of the exterior body at a part of the joint portion of the exterior body. A sealing step of sealing in, a degassing step of opening a degassing hole in the unjoined portion to allow communication between the inside and the exterior of the exterior body, and joining the unjoined portion to close the degassing hole again. A re-encapsulation step of encapsulating the battery body in the exterior body.
[0013]
First, in the first battery element sealing step, for example, a rectangular laminate film (heat-weldable resin) for exterior is folded and overlapped in the middle, and two opposite end portions of the three side openings are formed. Make a bag-like body by heat welding or ultrasonic welding, etc. so that the lead wire goes out of the battery body such as a sheet-like lithium ion secondary battery with the lead wire attached in it And the remaining one side is joined to enclose the battery body in the exterior body. Alternatively, the battery body may be placed in a laminated film that is folded and overlapped, and the three sides may be sealed simultaneously.
[0014]
FIG. 1 is a plan view showing a state in which the battery body is sealed in the exterior body as described above. In this sheet type battery, a sheet-like battery body 10 is enclosed in an exterior body 20 made of a film. On the three sides of the exterior body 20, first joint portions 31 are formed by joining the end portions of the folded film. Further, lead wires 11 and 12 respectively connected to the positive electrode and the negative electrode of the battery body 10 protrude from the exterior body 20.
[0015]
FIG. 2 shows an example of a cross-sectional structure along the line AA of the sheet-type battery shown in FIG. 1, and the battery is placed in the outer package 20 in which the ends of the two films 21 and 22 are joined. The element body 10 is accommodated. The battery body 10 has a structure in which, for example, a positive electrode 13 and a negative electrode 14 are superposed via a solid electrolyte 15 that also functions as a separator. In practice, a structure in which the positive electrode 13, the solid electrolyte 15, and the negative electrode 14 are laminated is generally used.
[0016]
In the present invention, as shown in FIG. 1, an unjoined portion 40 that communicates with the inside of the exterior body 20 and is isolated from the outside of the exterior body 20 is formed in a part of the first joint portion 31 of the exterior body. To do. An enlarged view of the unjoined portion 40 is shown in FIG.
[0017]
The unjoined portion 40 shown in FIG. 3A is substantially L-shaped, includes a bent communication portion 41, and has a structure in which the innermost portion does not face the exterior body 20. The bending structure of the unbonded portion 40 is such that when the battery element body 10 comes into contact with the battery element body 10 when the battery element body 10 is inserted into the bag-shaped exterior body 20, the electrolyte solution adheres. This is to prevent adhesion and prevent the bonding strength of the unbonded portion 40 from being lowered. Moreover, it is for providing a distance as much as possible between the vent hole formed in the next step and the inside of the exterior body to ensure sealing.
[0018]
As a method for forming such an unbonded portion 40, for example, a horn having a shape of an unbonded portion so as not to hit the film on the surface that comes into contact with an exterior film of a type that performs ultrasonic welding or heat welding. Or a mold may be used.
[0019]
After the battery body 10 is sealed in the outer package 20 in which the unbonded portion 40 is formed, it is necessary to perform a charge / discharge operation at least once as a final stage of manufacturing or initial setting work in a lithium ion secondary battery. During this initial charging, gas is generated inside the battery, and the outer package 20 made of a film expands.
[0020]
Therefore, next, a degassing step is performed. In the present invention, as shown in FIG. 3B, for example, a needle is passed through the exterior body 20 of the unjoined portion 40, and the gas vent hole 50 that communicates the exterior and interior of the exterior body 20 is formed. The vent hole 50 is preferably as small as possible, and is preferably provided only on one of the two films constituting the unbonded portion 40. Of course, it may be formed so as to penetrate both films. Good. The formation position of the vent hole 50 is preferably the rear part of the unjoined part 40. This degassing step is preferably performed in a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.
[0021]
The size of the vent hole is usually about 0.3 to 1.5 mm in diameter, particularly about 0.5 to 1 mm.
[0022]
Next, in the re-encapsulation step, as shown in FIG. 3C, the unjoined portion 40 of the outer package 20 provided with the gas vent holes 50 is joined by an ultrasonic welding method or a heat welding method, 40 is formed in the 2nd junction part 32, the gas vent hole 50 is plugged up, and the battery body 10 is enclosed in the exterior body 20 again. In this case, the 2nd junction part 32 may join all the unjoined parts 40 provided in the substantially L shape, or may join the place beyond the unjoined part 40.
[0023]
3A, the distance a from the edge of the exterior body 20 is 1 mm or more, preferably 2 mm or more, and most preferably 3 mm or more to ensure sealing. It is desirable. Further, the width b of the air passage in which the vent hole of the unjoined portion is provided is 1 mm to 10 mm, particularly about 2 to 5 mm because the vent hole is usually in the above range, and the distance a can be secured. If present, it is preferable that the first joint portion 31 is located on the outer side. Furthermore, it is desirable to secure a distance c of 3 mm or more with respect to the inner edge of the first joint portion 31.
[0024]
According to such a degassing method, the gas generated during the initial charging can be surely extracted from the exterior body 20 by a simple method. Moreover, since the unjoined part 40 formed in the 1st junction part 31 of the exterior body 20 is finally joined, the intensity | strength of the exterior body 20, especially a junction part is not reduced. In addition, since no useless part is generated, it is advantageous in terms of cost and environment.
[0025]
In the above description, the unjoined portion has a substantially L shape, but the shape and position of the unjoined portion are not limited. About a shape, as shown to Fig.4 (a), you may provide the unjoined part 40a over the 1st junction part 31a full length of the one side of the exterior body 20. As shown in FIG. Moreover, as shown in FIG.4 (b), you may provide the rectangular unjoined part 40b in a part of 1st junction part 31b. The unjoined part 40 can be formed at any location of the first joined part 31.
[0026]
As a material of the outer package 20 that can be used in the method for manufacturing a sheet type battery of the present invention, chemical change does not occur due to contact with the battery body 10, and leakage of electrolyte and gas permeation can be prevented. Moreover, it is difficult to break and a film having good adhesiveness can be used. Specifically, a laminate of a reinforcing layer made of a synthetic resin, a gas barrier layer made of an inorganic foil made of an inorganic material such as metal (Al, etc.), glass, ceramics, and an adhesive resin layer is generally used. However, the present invention is not limited to such a laminate type, and can be used without particular limitation as long as it has characteristics as a functional film. Specifically, examples of the reinforcing layer and the adhesive resin layer include (modified) polypropylene, (modified) polyethylene, and ionomer.
[0027]
In the present invention, since it is easy to reduce the thickness and there is no risk of liquid leakage, it is preferable to use a polymer substance that gels by impregnation with an electrolyte as a separator. It is preferable to use a high molecular weight material. The gelled polymer substance works as a solid electrolyte by holding the electrolyte solution inside. Hereinafter, the battery body will be described by taking such a polymer battery as an example.
[0028]
As polymer materials that can be used as solid electrolytes,
1) A polymer of an acrylate containing ethylene oxide which is a photopolymerizable monomer and a polyfunctional acrylate,
2) polyacrylonitrile,
3) Polyalkylene oxides such as polyethylene oxide and polypropylene oxide,
4) Polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene chloride (CTFE) copolymer [P (VDF-CTFE)], vinylidene fluoride-hexafluoro Fluoropolymers such as propylene fluororubber, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene fluororubber [P (VDF-TFE-HFP)], vinylidene fluoride-tetrafluoroethylene-perfluoroalkyl vinyl ether fluororubber, etc. Can be mentioned. As the vinylidene fluoride polymer, in particular, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene (HFP), a copolymer of vinylidene fluoride and trifluoroethylene chloride [P (VDF-CTFE )] Is preferred. The VDF-CTFE copolymer is, for example, from Central Glass Co., Ltd. under the trade name “Cefral Soft (G150, G180)” (VDF-CTFE as the main chain and VDF as the side chain) from Nippon Solvay Co., Ltd. It is sold under the trade name “Solef 31508”. VDF-HFP copolymer is available from Elf Atchem as trade names “KynarFlex2750 (VDF: HFP = 85: 15 wt%)”, “KynarFlex2801 (VDF: HFP = 90: 10 wt%)”, etc. Are sold under the trade names “Solef 11008”, “Solef 11010”, “Solef 21508”, “Solef 21510”, etc. In the vinylidene fluoride polymer, the proportion of vinylidene fluoride is preferably 50% by weight or more, particularly preferably 70% by weight or more.
[0029]
As the solvent for dissolving the polymer substance, for example, acetone, tetrahydrofuran, methyl acetate, or the like can be used.
[0030]
As the electrode active material, for example, a carbon material, lithium metal, a lithium alloy or an oxide material is used for the negative electrode, and lithium ions can be intercalated / deintercalated, for example, oxide or carbon for the positive electrode. May be used. The carbon material used as the electrode active material may be appropriately selected from, for example, mesocarbon microbeads (MCMB), natural or artificial graphite, resin-fired carbon material, carbon black, carbon fiber, and the like. These are used as powders. The oxide capable of intercalating and deintercalating lithium ions is preferably a composite oxide containing lithium, and examples thereof include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiV ₂ O ₄ . The average particle size of the oxide powder is preferably about 1 to 40 μm.
[0031]
Examples of the conductive aid used for the electrode include graphite, carbon black, carbon fiber, nickel, aluminum, copper, silver and the like, and graphite and carbon black are particularly preferable.
[0032]
The method for molding the polymer substance is not particularly limited. For example, in the case of producing a film-shaped molded body, a polymer solution may be applied on a substrate. This substrate can be anything as long as it is smooth. For example, a polyester film, glass, a polytetrafluoroethylene film, etc. are mentioned. The means for applying the polymer solution to the substrate is not particularly limited, and may be appropriately determined according to the material and shape of the substrate. Generally, metal mask printing, electrostatic coating, dip coating, spraying, etc. A coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, or the like may be used. Thereafter, the solvent is removed by evaporation. The removal of the solvent can be performed at room temperature, but may be performed by heating. Furthermore, if necessary, pressing is performed by a flat plate press, a calendar roll, or the like. In manufacturing the electrode, a compact containing the active material is thermocompression bonded to the current collector. In addition, you may obtain a film-form molded object by apply | coating the polymer solution containing an active material directly to a collector. In that case, after applying to the current collector, pressing may be performed.
[0033]
For the current collector, metal foil, metal mesh, or punched metal is used. As a constituent material of the current collector, for example, aluminum is used for the positive electrode, and for example, copper and nickel are used for the negative electrode.
[0034]
【Example】
<Example>
A positive electrode slurry made of a fluorine-based polymer such as LiCoO ₂ , carbon black, graphite, PVDF, and N-methyl-2-pyrrolidone (NMP) was applied on an aluminum foil to prepare a positive electrode. Two types of positive electrodes were produced in terms of the battery configuration: a single-sided coating shape on a 60 μm foil and a double-sided coating shape on a 20 μm foil. A negative electrode slurry consisting of mesocarbon microbeads (MCMB), carbon black, PVDF and other fluorine-based polymers, and NMP was coated on both sides of a 10 μm-thick copper foil to prepare a negative electrode. The separator was prepared by forming a sheet of slurry obtained by mixing PVDF homopolymer and PVDF copolymer in a mixed solvent of acetone and toluene by the doctor blade method.
[0035]
The above-mentioned electrode and separator are cut into a predetermined shape, and a battery is formed by laminating an adhesive dotted at the center of the sheet, such as a positive electrode, a separator, a negative electrode, a separator, a positive electrode,. Was made. An ethylene-methacrylic acid copolymer was used as the adhesive. After the lead is taken out by welding the aluminum wire to the positive electrode tab and the nickel wire to the negative electrode tab, the lead is taken out of the laminate temporarily bonded with this adhesive, and then immersed in 1M-LiPF ₆ / EC + DMC (1: 2) and gelled. Excess electrolyte was removed.
[0036]
On the other hand, a bag-shaped aluminum laminate pack having an unjoined portion shown in FIG. 1 was prepared. The produced battery was put in a bag-like aluminum laminate pack, and the opening was adhered and sealed. Then, in order to integrate the structures in the laminate pack, hot pressing was performed at 70 to 90 ° C. After the first charge / discharge, a vent hole was made in the unjoined part, the gas was vented, and then the unjoined part was resealed.
[0037]
Table 1 shows the cycle retention ratio of the battery thus prepared at 500 cycles, and Table 2 shows the storage characteristics at 60 ° C. for 1 week.
[0038]
<Comparative example>
A normal aluminum laminate pack was used for the battery outer package produced in the same manner as in the example, the battery was enclosed as it was, initial charging was performed, and a sheet type battery was produced without degassing. Table 1 shows the capacity retention of 500 cycles of the produced battery, and Table 2 shows the storage characteristics at 60 ° C. for 1 week. In addition, the capacity | capacitance fall after the preservation | save with respect to before storage is shown as total loss, and the capacity | capacitance fall after performing charging / discharging once after a preservation | save is shown as permanentros.
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
From the results of Tables 1 and 2, it can be seen that the sheet-type batteries produced by the production method of the present invention are not deteriorated in the characteristics as compared with the comparative examples, and the reliability is not lowered.
[0042]
As is clear from the above results, an unsealed part is produced in the exterior body, and after the first charge / discharge, a hole is made in the part, and the part is degassed, and then degassed by resealing. Thus, degassing can be performed by a simple process without reducing the reliability of the battery. In addition, provision of a gas vent hole in the exterior body is temporary, and since the gas vent hole is small, inconveniences such as moisture absorption of the electrolyte and change in the composition of the electrolyte do not occur.
[0043]
【The invention's effect】
According to the method for manufacturing a sheet-type battery of the present invention, gas generated during initial charging, which is a problem when a battery body such as a lithium ion secondary battery is sealed in a thin and lightweight exterior body, is not wasted. Easy to vent.
[Brief description of the drawings]
FIG. 1 is a plan view showing a state in which a battery body is enclosed in an exterior body in a method for producing a sheet type battery of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
3 is an enlarged view of a portion B in FIG. 1, in which (a) shows a state where an unjoined portion is formed, (b) shows a state where a vent hole is formed, and (c) shows a state where an unjoined portion is joined. Indicates the state.
4A and 4B are plan views showing other shapes of unjoined portions. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Battery body 11 Lead wire 12 Lead wire 13 Positive electrode 14 Negative electrode 15 Solid electrolyte 20 Exterior body 31 1st junction part 32 2nd junction part 40 Unjoined part 41 Bent communication part 50 Gas vent hole

Claims (4)

In a method for manufacturing a sheet-type battery in which a battery body is wrapped with an exterior film, the opening of the exterior film is joined, and the battery body is enclosed in the exterior body.
A sealing step of enclosing the battery body in the exterior body by forming an unjoined portion that communicates with the interior of the exterior body and is isolated from the outside of the exterior body in a part of the joint portion of the exterior body When,
A degassing step of opening a degassing hole in the unjoined portion and communicating the interior and exterior of the exterior body;
Possess a resealing step of sealing the battery element again closes the gas release openings by joining the unbonded portion to the outer package,
The manufacturing method of the sheet-type battery in which the unjoined part has a bent communication part .   The method for manufacturing a sheet type battery according to claim 1, wherein the battery body uses a solid electrolyte. The manufacturing method of the sheet-type battery according to claim 1 or 2, wherein the unbonded portion is formed using a horn or a mold having a concave portion in the shape of the unbonded portion .   The sheet-type battery manufacturing method according to claim 1, wherein the exterior film is a heat-welding resin.

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