JP4565713B2 - Sheet-like lithium battery structure and method for producing sheet-like lithium battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet-like lithium battery structure and a method for producing a sheet-like lithium battery.
[0002]
[Prior art]
In recent years, portable electronic devices such as mobile phones and notebook computers have been downsized and enhanced in functionality, and there has been a growing demand for long-term use. Therefore, power sources used for such electronic devices are also required to have characteristics such as small size, light weight, thin shape, large capacity, and high voltage. An example of such a battery is a sheet-like lithium battery.
[0003]
The sheet-like lithium battery basically has a structure in which a separator and an electrolyte are interposed between positive and negative electrode sheets and sealed with a suitable exterior sheet. The separator and the electrolyte include a solid or gel electrolyte that has both functions as one and a separator in which the liquid electrolyte is impregnated. Since the sheet-like lithium battery has such a structure, it has features such that it can be thinned, stacked, light because there is no can, and free in shape.
[0004]
[Problems to be solved by the invention]
As described above, the sheet-like lithium battery has excellent characteristics, but it is necessary that the positive electrode sheet or the negative electrode sheet and the separator (or solid or gel electrolyte) are always in close contact with each other. In JP-A-10-97872, the first sheet is banded and cut into a goodwill shape, the second sheet is banded and wrapped with a separator, and the first and second sheets are stacked. A technique is disclosed in which a battery is produced by folding a first sheet through a second sheet at each cut of the first sheet so that the vertical relationship between the first and second sheets changes alternately. According to this technique, it is possible to surely prevent the sheet from shifting, but the effect of preventing the looseness of the adhesion cannot be expected so much.
[0005]
Further, in a battery using an electrolyte in which a separator is impregnated as an electrolyte, when the temperature becomes high during use, the electrolyte is vaporized and gas is generated. Japanese Patent Application Laid-Open No. 2000-58103 discloses a technique for releasing a gas generated at high temperatures by providing a strip-like active material application missing portion and / or a small hole in a positive electrode and / or a negative electrode. However, gas is not generated only in the finished battery, but also in the manufacturing process, for example, gas is generated by a small amount of water inside the battery during initial charging, or gas is generated in other processes. The technique disclosed in Japanese Patent Application Laid-Open No. 2000-58103 does not consider any gas generation in the manufacturing process and does not disclose an efficient structure for releasing generated gas in the manufacturing process.
[0006]
The present invention has been made in view of such circumstances, and the object of the present invention is to prevent the looseness of the adhesion between the electrode sheet and the separator and the mutual displacement by a simple method, and the manufacturing process. It is to provide a sheet-like lithium battery structure and a method for producing a sheet-like lithium battery that can efficiently release gas generated therein.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a sheet-like lithium battery in which an electrode sheet and a separator are bonded via an adhesive and a large number of small holes are opened in the outermost current collector to release the generated gas. The structure and the manufacturing method of the sheet-like lithium battery were used.
[0008]
Specifically, the invention according to claim 1 is a sheet form in which a positive electrode sheet coated with an active material on one side of a current collector is laminated on both sides of a negative electrode sheet coated with an active material on both sides of the current collector. A lithium battery structure,
The negative electrode sheet and the positive electrode sheet are opposed to each other with an active material coating surface, and a separator is provided between them.
The negative electrode sheet and the separator are bonded via an adhesive layer,
The positive electrode sheet and the separator are bonded via an adhesive layer,
The current collector of the positive electrode sheet has a sheet-like lithium battery structure in which a large number of small holes are opened.
[0009]
With such a configuration, the positive electrode sheet and the separator, and the negative electrode sheet and the separator are bonded, and thus do not peel off or shift. Further, the electrode sheet and the separator can be kept in close contact and prevented from shifting by a simple process of applying and bonding the adhesive.
[0010]
The current collector of the positive electrode sheet constitutes the outermost surface of the battery, and since a large number of small holes are opened in the battery, the vaporizing solvent is used in the step of drying the adhesive after the positive electrode sheet and the separator are bonded together. This gas can be efficiently discharged out of the battery, and gas generated during other manufacturing processes can also be effectively discharged out of the battery. Furthermore, since there are a large number of small holes when impregnating the electrolytic solution, the penetration of the electrolytic solution is performed rapidly.
[0011]
Next, the invention according to claim 2 is the invention according to claim 1,
The adhesive layer is porous so as to have ion permeability, and has a sheet-like lithium battery structure.
[0012]
With such a configuration, the adhesive layer has ionic conductivity, and the charge / discharge characteristics of the battery are maintained.
[0013]
Next, the invention according to claim 3 is a positive electrode sheet in which a separator is laminated on both sides of a negative electrode sheet coated with an active material on both sides of a current collector, and further an active material is coated on one side of the current collector. Is a method for producing a sheet-like lithium battery in which the current collector is laminated on the outer surface,
The current collector of the positive electrode sheet has a large number of small holes,
A step of bonding the negative electrode sheet and the separator through a solution type adhesive, a step of bonding the positive electrode sheet and the separator through a solution type adhesive, and gasifying a solvent of the adhesive to form a positive electrode And a drying step for dissipating from the small holes of the current collector of the sheet.
[0014]
With such a configuration, it is possible to easily manufacture a battery that can release the gas generated in the battery efficiently outside the battery without peeling or shifting between the electrode sheet and the separator.
[0015]
【The invention's effect】
Since this invention is the above-mentioned structure, there exists an effect described below.
[0016]
Since the positive electrode sheet and the separator, and the negative electrode sheet and the separator are bonded via the adhesive layer, the electrode sheet and the separator are not peeled off or shifted, and the defect rate in the manufacturing process is reduced, which is simple. Because it is a process, the cost can be reduced.
[0017]
Since a large number of small holes are opened in the current collector of the positive electrode sheet, which is the outermost surface of the battery structure, the solvent gas of the adhesive can be passed and dried in a short time, thereby increasing the production rate. In addition, gas generated in other batteries can be efficiently discharged out of the battery, which is safe and increases productivity.
[0018]
Since the adhesive layer bonding the electrode sheet and the separator is porous, a battery having ion conductivity and substantially the same charge / discharge characteristics as when there is no adhesive layer is obtained.
[0019]
A step of adhering a separator to both surfaces of the negative electrode sheet via an adhesive, a step of adhering the separator via an adhesive to a positive electrode sheet having a large number of small holes opened in the current collector, and gasifying the solvent of the adhesive Since the battery is manufactured by a drying process that diffuses from the small holes of the current collector of the positive electrode sheet, the electrode sheet and the separator are not displaced, and the battery can efficiently release the gas generated in the battery. Can be manufactured easily and the manufacturing cost can be reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 shows a cross-sectional view of a sheet battery 10 of the present embodiment. There is a negative electrode sheet 9 in the middle in the vertical direction of the figure, and separators 4 are laminated on both sides of the adhesive 3 via an adhesive 3. Further, a positive electrode sheet 8 is laminated on the outer surface side of the active material layer 5 through the adhesive 3 with the active material layer 5 as the inner surface side.
[0022]
Next, each component constituting the battery 10 will be described.
[0023]
The negative electrode sheet 9 is formed by coating the negative electrode active material 2 on both surfaces of the negative electrode current collector 1. As the negative electrode current collector 1, a conductive metal such as copper, nickel, silver, SUS, or the like, having a thickness of 5 to 100 μm, particularly 8 to 50 μm, or a perforated foil, having a thickness of 20 to 300 μm, particularly 25 to 100 μm. Expanded metal or mesh metal is preferred. The active material 2 of the negative electrode is a carbonaceous material, and various natural graphites and artificial graphites, for example, graphites such as fibrous graphite, scaly graphite, and spherical graphite can be preferably exemplified. A binder such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or ethylene-propylene-diene polymer is mixed with such graphite and applied to both surfaces of the negative electrode current collector 1. The layer thickness of the negative electrode active material 2 is preferably 20 to 500 μm, and more preferably 50 to 200 μm.
[0024]
The separator 4 may be any material as long as it prevents the short circuit between the positive electrode and the negative electrode and has ionic conductivity, but from the viewpoint of ease of handling, electrical characteristics, and stability to the electrolytic solution. A polymer film is preferred. Examples of the polymer constituting the polymer film used as the separator 4 include polystyrene, polybutadiene and copolymers thereof, polyethylene oxide derivatives, polypropylene oxide derivatives, polymers containing the derivatives, polyacrylonitrile, polyvinyl pyrrolidone, polyvinylidene carbonate, Examples thereof include polyvinylidene fluoride and a copolymer of vinylidene fluoride and hexafluoropropylene. Such a polymer is dissolved in an appropriate solvent, and the film is formed and dried to form a film. An additive such as a plasticizer may be added to the solution for film formation. In this way, a porous separator 4 is produced. The thickness of the separator 4 is preferably 5 to 100 μm, and more preferably 20 to 60 μm because the battery characteristics are good.
[0025]
Although not shown in the figure, when the battery is completed, the separator 4 is impregnated with a non-aqueous electrolyte. As such an electrolytic solution, an electrolytic solution in which salts are dissolved in an organic solvent can be used. Examples of such salts include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , Li (CF ₃ SO ₂ ) ₂ N, etc., and one or a mixture of two or more of these is used. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, dimethyl sulfoxide, sulfolane, γ-butyrolactone, 1,2-dimethoxymethane, N, N-dimethylformamide, tetrahydrofuran, 1,3-dioxolane, 2-methyltetrahydrofuran, Examples thereof include diethyl ether, and one or a mixture of two or more of these can be used.
[0026]
Further, a known solid electrolyte layer that substantially separates the positive electrode sheet 8 and the negative electrode sheet 9 may be used as the separator 4.
[0027]
The adhesive 3 may be any material as long as it is a material that exhibits adhesion to both the active materials 2 and 5 and the separator 4, but is preferably a solution-type adhesive that becomes porous after application and drying. In particular, an adhesive mainly composed of the same polymer as that constituting the separator 4 is preferable. For example, by using a solution-type adhesive in which polyvinylidene fluoride is dissolved in methylacetamide, the adhesive layer 3 has ion permeability after drying, and Li ions move so that it has ion conductivity. become. The thickness of the adhesive 3 is preferably 5 to 100 μm after drying, and more preferably 20 to 40 μm, since the balance between adhesiveness and ionic conductivity is good. Further, the same adhesive may be used for the negative electrode side and the positive electrode side, or different adhesive agents may be used.
[0028]
The positive electrode sheet 8 is prepared by coating the active material 5 of the positive electrode on one surface of the current collector 6 of the positive electrode, and the active material 5 coating surface is disposed so as to face the negative electrode sheet 9. Examples of the material constituting the positive electrode current collector 6 include conductive metals such as aluminum, aluminum alloys, and titanium. The positive electrode active material 5 has a potential difference of at least 1 V from the negative electrode, for example, V ₂ O ₅ , MnO ₂ , LiMn ₂ O ₄ , LiCoO ₂ , LiNi _0.5 Co _0.5 O ₂ , LiNiO ₂ , Li—Co. -P-based composite oxides (such as LiCo _0.5 P _0.5 O ₂ , LiCo _0.4 P _0.6 O ₂ , LiCo _0.6 P _0.4 O ₂ , LiCo _0.3 Ni _0.3 P _0.4 O ₂ , LiCo _0.2 Ni _0.2 P _0.6 O ₂ ), TiS ₂ , MoS ₂ , MoO _{3 and the} like. Among these, a Li—Co based composite oxide that can particularly increase the electromotive force and charge / discharge voltage of the battery is particularly preferable. The active material is coated with a binder such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, ethylene-propylene-diene polymer. The layer thickness of the positive electrode active material 5 is preferably 20 to 500 μm, and more preferably 50 to 200 μm.
[0029]
A large number of small holes 7 are opened in the positive electrode current collector 6. The main function of the small holes 7 is that when the positive electrode sheet 8 and the separator 4 are bonded to each other through the adhesive 3 and dried, the solvent gas of the adhesive 3 passes through the small holes 7 and goes outside the system. Is to be released. When there is no small hole 7, the solvent gas of the adhesive 3 is released only from the end face of the sheet battery 10, so that drying takes a long time and productivity is lowered. The small hole 7 may have any shape. The size of the small hole 7 is preferably 0.1 to 1.5 mm in diameter when the shape is converted to a circle. If it is smaller than 0.1 mm, it becomes difficult for gas to pass through, and if it is larger than 1.5 mm, the battery capacity will be reduced too much. From the point of workability, it is more preferably 0.5 to 1.5 mm. The density of the small holes 7 is preferably 1 to 500 / cm ² . If it is less than 1 piece / cm ² , it takes too much time to dry the adhesive, and if it is more than 500 pieces / cm ² , processing and handling become difficult. 1 to 200 / cm ² is more preferable.
[0030]
The drilling of the positive electrode current collector 6 may be performed before or after the positive electrode active material 5 is applied. Further, any hole drilling method may be used as long as it has a hole such as punching, laser processing, or a process of pushing a needle. In FIG. 1, since the example which processed the hole after coating the positive electrode active material 5 was shown, the positive electrode active material 5 also has a small hole. However, as shown in FIG. 4, the positive electrode active material 5 may be applied after drilling the positive electrode current collector 6. In such a case, the small holes 7 are formed only in the positive electrode current collector 6. I'm open. Since the positive electrode active material 5 has good air permeability, a gas can be released regardless of whether a small hole is opened in the positive electrode active material 5.
[0031]
FIG. 3 shows an example of a step of drilling the positive electrode current collector 6. A positive electrode current collector 6 such as an aluminum foil is supplied from the unwinding roll 20 to the process. The positive electrode current collector 6 passes over the punching roll 21 in which a large number of needles 22 are planted, so that a large number of small holes are formed in the positive electrode current collector 6. Then, the active material is applied by the reverse roll coater 23. An active material coating solution 29 is supplied to the coating roll 26 from a pan 28 and measured by a doctor roll 27 to a predetermined thickness. Then, the coating liquid is transferred and applied to the positive electrode current collector 6 wound around the backup roll 25 and dried by the drying furnace 24. Such a drilling method is simple and preferable because it is only necessary to add the drilling roll 21 to the active material coating process. The positive electrode sheet produced from this step is shown in FIG. The peripheral portion of the small hole 7 of the positive electrode current collector 6 protrudes into the active material 5 because the small hole is made by the needle.
[0032]
The small holes 7 are useful not only for releasing gas out of the system when the adhesive 3 is dried, but also for releasing gas generated in the battery or impregnating with an electrolyte.
[0033]
Examples of the gas generated in the battery include an example of a gas generated at the time of initial charging in the manufacturing process, and an example of a gas generated at a high temperature described above after becoming a product. The former example is a phenomenon that occurs in a process in which a battery that is almost finished is first fully charged and left for several weeks. Gas is generated due to a very small amount of moisture in the battery. After the gas is removed, the battery is completely sealed to obtain a product. The small holes 7 serve to efficiently discharge the gas generated at this time and the gas generated after becoming the latter product, thereby enhancing safety.
[0034]
Further, the impregnation with the electrolytic solution is performed after the sheet battery 10 is assembled. Therefore, if there is no small hole 7, it is impregnated only from the end face of the separator 4, so that the impregnation time is required for a long time. In this embodiment, since there are the small holes 7, the electrolytic solution is also infiltrated from the small holes 7, so that the impregnation is completed in a short time and the productivity is increased.
[0035]
A production schematic diagram of the sheet-like battery 10 is shown in FIG. The process proceeds from left to right in the figure. The negative electrode active material 2 is applied to both surfaces of the negative electrode current collector 1 to obtain a negative electrode sheet 9 shown on the left side of FIG. The coating method may be roll coating, die coating, or the like.
[0036]
Next, the adhesive 3 is applied to both surfaces of the negative electrode sheet 9 and the separator 4 is bonded. What was obtained in this way is what is shown in the center of FIG. The adhesive 3 may be applied to the separator 4. However, since the surface roughness of the negative electrode active material 2 is larger than that of the separator 4, the adhesive 3 is preferably applied to the negative electrode sheet 9. Since the separator 4 is porous, the solvent of the adhesive 3 is quickly dried through the separator 4.
[0037]
The positive electrode sheet 8 is prepared separately in the process as shown in FIG. 3 (upper and lower in the center of FIG. 2), and the adhesive 3 is applied to the active material 5 application surface of the positive electrode sheet 8 and the outer surface side of the separator 4. Paste to. At this time, it is preferable to apply the adhesive 3 to the positive electrode sheet 8 for the same reason as that of the negative electrode sheet 9. At the time of this drying, the small holes 7 allow the solvent gas of the adhesive 3 to pass through and shorten the drying time. What was obtained in this way is the sheet-like battery 10 on the right side of FIG.
[0038]
FIG. 5 shows a view of the sheet-like battery manufactured in this way as viewed from above. In an actual sheet-like battery, the negative electrode sheet 9 has a continuous long shape as described above, and the positive electrode sheet 8 is cut into sheets and bonded to the negative electrode sheet 9. The positive electrode sheet 8 is bonded to the back side of the negative electrode sheet 9 at the same position as the front side. At this time, the positive electrode sheet 8 is smaller than the negative electrode sheet 9 in both the longitudinal direction and the width direction so that the negative electrode sheet 9 is positioned outside the end face of the positive electrode sheet 8. If the negative electrode sheet 9 is positioned inside the end face of the positive electrode sheet 8, the positive electrode active material is excessively present at the end of the negative electrode sheet 9 with respect to the negative electrode active material. A large amount of lithium ions come and cannot be accepted by the negative electrode, and dendrites are generated. Therefore, the negative electrode sheet 9 is positioned outside the end face of the positive electrode sheet 8 in order to make the negative electrode active material more excessive than the positive electrode active material so as to avoid the generation of dendrites.
[0039]
In order to make a product from this state, for example, only a portion of the negative electrode sheet 9 between the adjacent positive electrode sheets 8 at the left end of FIG. 5 (in the arrow of the cutting part A) is cut, and a predetermined number of positive electrode sheets 8 are separated. Then, only the portion of the negative electrode sheet 9 between the adjacent positive electrode sheets 8 is cut again. The number of the positive electrode sheets 8 varies depending on the capacity of the battery required as a product. Then, folding is performed at the fold portions A and B so that the adjacent positive electrode sheets 8 overlap each other. The folding direction is preferably different between the crease part A and the crease part B. For example, if the crease part A is a mountain fold, the crease part B is preferably a valley fold. After that, the positive electrode terminal and the negative electrode terminal are attached, wrapped with an exterior film, impregnated with an electrolytic solution, and an initial full charge, degassing, and sealing are completed.
[0040]
The above manufacturing process is only an example, and the present invention is not limited to this manufacturing process. The order of the steps may be changed, for example, the electrolytic solution impregnation may be performed before the wrapping with the exterior film, or another step may be added, for example, the inspection step may be put in the middle. .
[0041]
A sectional view of a battery product in which two adjacent positive electrode sheets 8 are stacked is shown in FIG. For example, this is manufactured by cutting at two cut portions B in FIG. 5 and folding the cut portion A between them. It is sealed with the exterior film 32, and the positive terminal 30 and the negative terminal 31 are exposed to the outside.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a battery of the present embodiment. FIG. 2 is a schematic diagram of manufacturing the battery of the present embodiment. FIG. 3 is a schematic diagram of an example of a method for manufacturing a positive electrode sheet. Cross-sectional view of positive electrode sheet [Fig. 5] Schematic diagram of long battery sheet [Fig. 6] Cross-sectional view of sheet-like battery product [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Negative electrode collector 2 Negative electrode active material 3 Adhesive 4 Separator 5 Positive electrode active material 6 Positive electrode current collector 7 Small hole 8 Positive electrode sheet 9 Negative electrode sheet 10 Sheet-like battery 20 Unwinding roll 21 Drilling roll 22 Needle 23 Reverse roll coater 24 Drying furnace 25 Backup roll 26 Coating roll 27 Doctor roll 28 Pan 29 Coating liquid 30 Positive electrode terminal 31 Negative electrode terminal 32 Exterior film A Folding part or cutting part B Folding part or cutting part

Claims (3)

A sheet-like lithium battery structure in which a positive electrode sheet coated with an active material on one side of a current collector is laminated on both sides of a negative electrode sheet coated with an active material on both sides of the current collector,
The negative electrode sheet and the positive electrode sheet are opposed to each other with an active material coating surface, and a separator is provided between them.
The negative electrode sheet and the separator are bonded via an adhesive layer,
The positive electrode sheet and the separator are bonded via an adhesive layer,
A sheet-like lithium battery structure in which a large number of small holes are opened in the current collector of the positive electrode sheet. In claim 1,
The sheet-like lithium battery structure, wherein the adhesive layer is porous so as to have ion permeability. A separator is laminated on both sides of the negative electrode sheet coated with an active material on both sides of the current collector, and a positive electrode sheet coated with an active material on one side of the current collector is placed on the current collector so that the current collector becomes the outer surface A method for producing a laminated sheet-like lithium battery,
The current collector of the positive electrode sheet has a large number of small holes,
A step of bonding the negative electrode sheet and the separator through a solution type adhesive, a step of bonding the positive electrode sheet and the separator through a solution type adhesive, and gasifying a solvent of the adhesive to form a positive electrode A method for producing a sheet-like lithium battery, comprising: a drying step of diffusing from a small hole of a current collector of the sheet.

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