Sheet-shaped battery

Abstract

Provided is a sheet-shaped battery capable of reducing a voltage drop caused by the electric resistance of electrode terminals of the sheet-shaped battery when electrically connected to an external device. A sheet-shaped battery 10 includes a positive electrode 20, a negative electrode 30, and an exterior body 40. The positive electrode 20 is composed of a material having an electric resistance larger than the electric resistance of the material constituting a negative electrode terminal 32. A positive electrode terminal 22 of the positive electrode 20 has a positive electrode connection portion 25, in a part exposed to the outside from the exterior body 40, to which the positive electrode terminal of the external device is connected. The negative electrode terminal 32 of the negative electrode 30 has a negative electrode connection portion 35, in a part exposed to the outside from the exterior body 40, to which the negative electrode terminal of the external device is connected. The positive electrode connection portion 25 has an area larger than the area of the negative electrode connection portion 35.

Description

Sheet-type battery

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

[0002] Sheet-shaped batteries having a sheet-like shape are known. For example, Patent Document 1 discloses a laminated battery having a rectangular exterior member and a positive electrode and a negative electrode housed in the exterior member. In the laminated battery of Patent Document 1, a portion of the positive electrode current collector has a lead portion extending to the outside of the exterior member. Also, in the laminated battery of Patent Document 1, a portion of the negative electrode current collector has a lead portion extending to the outside of the exterior member.

[0003] International Publication No. 2021 / 079695

[0004] In the laminate battery of Patent Document 1, the width of the positive electrode lead portion is the same as the width of the negative electrode lead portion. If the electrical resistance of the positive electrode lead portion and the negative electrode lead portion of the laminate battery of Patent Document 1 differs, the voltage drop due to the resistance of the electrode terminal will be greater at the terminal with the higher electrical resistance. In other words, when the laminate battery is electrically connected to an external device, a voltage drop will occur due to the electrical resistance of the battery electrode terminal.

[0005] In a sheet-type battery, when electrically connected to an external device, it is desired to reduce a voltage drop caused by the electrical resistance of the electrode terminals.

[0006] An object of the present invention is to provide a sheet-type battery that can reduce the voltage drop that occurs due to the electrical resistance at the electrode terminals of the sheet-type battery when electrically connected to an external device.

[0007] A sheet-type battery according to one embodiment of the present invention includes a positive electrode, a negative electrode, and an exterior housing that houses a portion of each of the positive electrode and the negative electrode. The positive electrode includes a plate-shaped positive electrode current collector housed within the exterior housing and a positive electrode terminal integrally formed from the same material as the positive electrode current collector and partially exposed to the outside from the exterior housing. The negative electrode includes a plate-shaped negative electrode current collector housed within the exterior housing and stacked in the thickness direction on the positive electrode current collector, and a negative electrode terminal integrally formed from the same material as the negative electrode current collector and partially exposed to the outside from the exterior housing. The positive electrode is made of a material having a higher electrical resistance than the material constituting the negative electrode. The positive electrode terminal has a positive electrode connection portion at the portion exposed to the outside from the exterior housing to which a positive electrode terminal of an external device is connected. The negative electrode terminal has a negative electrode connection portion at the portion exposed to the outside from the exterior housing to which a negative electrode terminal of the external device is connected. The positive electrode connecting portion has an area larger than an area of ​​the negative electrode connecting portion (first configuration).

[0008] In the above-described configuration, the area of ​​the positive electrode connection portion of the positive electrode terminal, which is made of a material having a higher electrical resistance than the electrical resistance of the material constituting the negative electrode terminal, is larger than the area of ​​the negative electrode connection portion of the negative electrode terminal.

[0009] Therefore, the electrical resistance of the positive electrode connection part can be reduced compared to when the area of ​​the positive electrode connection part and the area of ​​the negative electrode connection part are the same.

[0010] If the electrical resistance of the material constituting the positive terminal is greater than the electrical resistance of the material constituting the negative terminal, the voltage drop caused by the electrical resistance at the positive electrode connection part will be greater than that at the negative electrode connection part. Therefore, with the above-described configuration, when the battery is electrically connected to an external device, the voltage drop caused by the electrical resistance of the electrode terminals of the battery can be effectively reduced.

[0011] Furthermore, by forming the positive electrode current collector and the positive electrode terminal integrally from the same material, and by forming the negative electrode current collector and the negative electrode terminal integrally from the same material, the manufacturing process of the positive electrode and the negative electrode can be simplified.

[0012] In the sheet-type battery according to the first configuration, the positive electrode current collector and the positive electrode terminal are made of a porous material having electrical conductivity (second configuration).

[0013] The above-described configuration can reduce the current collection resistance of the electrode, thereby reducing the internal resistance of the electrode and improving the load characteristics.

[0014] In the sheet-type battery according to the second configuration, the positive electrode current collector and the positive electrode terminal are made of a carbon material (third configuration).

[0015] As described above, by adopting a carbon material as a porous material in the positive electrode, reactions such as corrosion of the positive electrode current collector and positive electrode terminal, which are subjected to a high potential, can be suppressed, thereby achieving favorable battery performance.

[0016] In the sheet-type battery according to the third configuration, the negative electrode current collector and the negative electrode terminal are made of a metal material (fourth configuration).

[0017] Carbon materials have higher electrical resistance than metal materials. Furthermore, depending on the type of metal material, the electrical resistivity may differ from that of carbon materials by several orders of magnitude. With the above-described configuration, even when materials with different electrical resistivities are used on the positive and negative electrode sides, the voltage drop due to the difference in electrical resistance between the positive electrode material and the negative electrode material can be reduced.

[0018] In the sheet-type battery according to the fourth configuration, the negative electrode current collector acts as a negative electrode active material (fifth configuration).

[0019] The above-described configuration eliminates the need to form a layer containing a negative electrode active material, and the process of producing the negative electrode can be simplified.

[0020] In the sheet-type battery according to the first configuration, the width of the positive electrode connection portion of the positive electrode terminal is larger than the width of the negative electrode connection portion of the negative electrode terminal (sixth configuration).

[0021] According to the above-described configuration, the electrical resistance and contact resistance can be more preferably reduced.

[0022] In the sheet-type battery according to the first configuration, the positive electrode terminal extends in one direction relative to the positive electrode current collector, and the negative electrode terminal extends in the same direction relative to the negative electrode current collector (seventh configuration).

[0023] According to the above-described configuration, the positive electrode connection portion of the positive terminal and the negative electrode connection portion of the negative terminal can be aligned in position, thereby making it possible to make the connection portion with the external device compact.

[0024] In the sheet-type battery according to the sixth configuration, the exterior body has, at the end in one direction, a positive electrode cutout portion for exposing the positive electrode terminal and a negative electrode cutout portion for exposing the negative electrode terminal (eighth configuration).

[0025] According to the above-described configuration, the positive and negative electrode terminals are prevented from protruding beyond the end of the exterior body in one direction, thereby making it possible to make the size of the sheet-type battery compact when viewed in the thickness direction.

[0026] According to an exemplary embodiment of the present invention, the positive electrode includes a plate-shaped positive electrode current collector housed inside the exterior housing and a positive electrode terminal integrally formed with the positive electrode current collector from the same material, a portion of which is exposed to the outside from the exterior housing. The negative electrode includes a plate-shaped negative electrode current collector housed inside the exterior housing and stacked on the positive electrode current collector in the thickness direction, and a negative electrode terminal integrally formed with the same material as the negative electrode current collector, a portion of which is exposed to the outside from the exterior housing. The positive electrode is made of a material having a higher electrical resistance than the material constituting the negative electrode. The positive electrode terminal has a positive electrode connection portion at a portion exposed to the outside from the exterior housing, to which a positive electrode terminal of an external device is connected. The negative electrode terminal has a negative electrode connection portion at a portion exposed to the outside from the exterior housing, to which a negative electrode terminal of the external device is connected. The positive electrode connection portion has an area larger than that of the negative electrode connection portion. This effectively reduces the voltage drop that occurs due to the electrical resistance of the battery's electrode terminals when electrically connected to an external device.

[0027] FIG. 1 is a diagram showing a schematic configuration of a sheet-type battery according to this embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is an exploded perspective view showing a schematic configuration of a sheet-type battery according to this embodiment. FIG. 5 is a diagram showing a schematic configuration of a sheet-type battery according to a modified example. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. FIG. 7 is a diagram showing the shapes of positive electrodes according to examples and comparative examples. FIG. 8 is a diagram showing the shapes of negative electrodes according to examples and comparative examples. FIG. 9 is a graph showing test results of voltage drop characteristics.

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0029] In addition, in each figure used in this specification, the arrangement of each component is shown schematically to explain the interrelationship of each component in the embodiment of the present invention, and differs from the actual dimensional ratio, etc.

[0030] In the following, sheet-type batteries 10, 11 that are rectangular in the thickness direction are exemplified. The thickness direction of the sheet-type batteries 10, 11 is simply referred to as the "thickness direction." The direction in which one pair of sides of the rectangular sheet-type batteries 10, 11 extend is referred to as the "length direction," and the direction in which the remaining pair of sides extend is referred to as the "width direction." The length direction and width direction are perpendicular to each other. The thickness direction is perpendicular to both the length direction and the width direction.

[0031] (Embodiment) (Overall Configuration) Fig. 1 is a diagram showing a schematic configuration of a sheet-type battery 10 according to this embodiment. Fig. 1 shows the sheet-type battery 10 as viewed in the thickness direction. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is an exploded perspective view showing a schematic configuration of the sheet-type battery 10 according to this embodiment.

[0032] 1 to 4 , the sheet-type battery 10 is a battery that supplies power to an external device (not shown). The sheet-type battery 10 is, for example, a primary battery or a secondary battery. The sheet-type battery 10 is, for example, a manganese battery, an alkaline battery, or a lithium battery. The external device is not particularly limited, but may be, for example, a wearable sensor device that is worn on the body to measure physiological data such as body temperature, pulse rate, or sweat rate. The sheet-type battery 10 includes a positive electrode 20, a negative electrode 30, a separator 52, and an exterior body 40.

[0033] (Positive Electrode) The positive electrode 20 has a positive electrode current collector 21 and a positive electrode terminal 22. The positive electrode current collector 21 is plate-shaped. The positive electrode current collector 21 is housed inside an exterior body 40.

[0034] The positive electrode terminal 22 is integrally formed with the positive electrode current collector 21 using the same material. The positive electrode terminal 22 and the positive electrode current collector 21 may be made of a metal material or a non-metallic material such as a carbon material. The positive electrode current collector 21 of the positive electrode 20 may be made of, for example, a porous material having electrical conductivity. This configuration can reduce the current collection resistance of the positive electrode 20. This can improve the current collection function inside the positive electrode 20. This reduces the internal resistance of the positive electrode 20 and improves the load characteristics. The positive electrode terminal 22 extends in one direction, i.e., the lengthwise direction, relative to the positive electrode current collector 21.

[0035] A portion of the positive electrode terminal 22 is exposed to the outside from the exterior body 40. The positive electrode terminal 22 has a positive electrode connection part 25, which is connected to a positive electrode terminal of an external device, in the part exposed to the outside from the exterior body 40. In other words, the positive electrode connection part 25 is located at one end of the positive electrode terminal 22 in the longitudinal direction.

[0036] The positive electrode current collector 21 may be made of a porous member obtained by, for example, subjecting a metal substrate such as nickel or stainless steel to a reticulation process, foaming process, punching process, or expanding process.

[0037] The positive electrode current collector 21 may also be made of a porous carbon material. Examples of the porous carbon member include a porous carbon sheet made of fibrous carbon, such as carbon paper, carbon cloth, or carbon felt. The porous carbon sheet may have a single-layer structure or a multi-layer structure. The multi-layer porous carbon sheet may have a structure in which carbon papers, carbon cloths, or carbon felts are stacked together. The multi-layer carbon sheet may also have a multi-layer structure in which two or more of carbon paper, carbon cloth, and carbon felt are stacked together. The fiber diameter of the fibrous carbon is preferably 2 to 30 μm. The thickness of the porous carbon sheet made of fibrous carbon is preferably 50 μm to 500 μm.

[0038] In the positive electrode 20, a high potential is applied to the material. Therefore, depending on the materials used for the positive electrode current collector 21 and the positive electrode terminal 22, the positive electrode current collector 21 and the positive electrode terminal 22 may react with the electrolyte, causing corrosion reactions and the like. As described above, by using a carbon material as a porous material for the positive electrode current collector 21, reactions such as corrosion of the positive electrode current collector 21 and the positive electrode terminal 22, which are applied with a high potential, can be suppressed, thereby achieving favorable battery performance. Furthermore, when the positive electrode current collector 21 of the positive electrode 20 is made of a metal material, the positive electrode 20 may be configured by supporting a catalyst on the surface or inside of the positive electrode current collector 21. The positive electrode terminal 22 of the positive electrode 20 may be made non-porous by compression processing or the like.

[0039] For example, a cathode active material is contained in the cathode of a primary battery or secondary battery such as a manganese battery, an alkaline battery, or a lithium battery. When the cathode 20 of the sheet-like battery 10 is configured to contain a cathode active material, the cathode 20 is configured by holding the cathode active material on the surface or inside of the cathode current collector 21. Examples of the cathode active material include silver oxide (silver (I) oxide, silver (II) oxide, etc.), manganese oxide such as manganese dioxide, nickel oxyhydroxide, composite oxides of silver and cobalt, nickel or bismuth, vanadium oxide, niobium oxide, titanium oxide, sulfides such as iron disulfide, graphite fluoride, and various lithium-containing composite oxides. Examples of various lithium-containing composite oxides include, for example, Li ｘ Mn ３ O ６ (0<x<2), Li ｘ MnO ２ Lithium-containing manganese oxides such as (0<x<1), Li ｘ Ti ５／３ O ４ (4 / 3≦x<7 / 3), LiMn ２ O ４ or a spinel-structured composite oxide in which some of the elements are replaced with other elements, Li １＋ｘ M １ O ２ (-0.1<x<0.1, M １ Lithium-containing composite oxides having a layered structure represented by the following: Co, Ni, Mn, Al, Mg, etc.; LiM ２ P.O. ４ (M ２ olivine type compounds represented by the formula (I): Co, Ni, Mn, Fe, etc.

[0040] (Negative Electrode) The negative electrode 30 includes a negative electrode current collector 31 and a negative electrode terminal 32 .

[0041] The negative electrode current collector 31 is housed inside the exterior body 40 in a state where it is stacked on the positive electrode current collector 21 in the thickness direction. The negative electrode current collector 31 is in the form of a plate.

[0042] The negative electrode terminal 32 is integrally formed with the negative electrode current collector 31 from the same material. The negative electrode terminal 32 extends in one direction of the lengthwise direction relative to the negative electrode current collector 31. The negative electrode terminal 32 is positioned alongside the positive electrode terminal 22 in the widthwise direction. A portion of the negative electrode terminal 32 is exposed to the outside from the exterior body 40. The negative electrode terminal 32 has a negative electrode connection portion 35, which is connected to the negative electrode terminal of the external device, in the portion exposed to the outside from the exterior body 40. In other words, the negative electrode connection portion 35 is positioned at one end of the negative electrode terminal 32 in the lengthwise direction.

[0043] The negative electrode current collector 31 can only perform the function of collecting current for the negative electrode 30. When the negative electrode current collector 31 only performs the function of collecting current for the negative electrode, the negative electrode 30 is configured by forming a layer containing a negative electrode active material on the negative electrode current collector 31. On the other hand, the negative electrode current collector 31 can also function as the negative electrode active material. When the negative electrode current collector 31 functions as the negative electrode active material, there is no need to separately form a layer containing a negative electrode active material, and the negative electrode 30 can also be configured with only the negative electrode current collector 31 and the negative electrode terminal 32. This can simplify the process of manufacturing the negative electrode 30.

[0044] When forming a layer containing a negative electrode active material, powder or foil of a metal (e.g., zinc, magnesium, aluminum, lithium, and alloys thereof) containing a component that functions as a negative electrode active material can be used as the negative electrode active material. When the electrolyte is an aqueous solution, a zinc alloy is preferably used, and examples of the alloy component include indium, bismuth, and aluminum. For example, the content of bismuth is preferably 0.005% by mass or more, more preferably 0.02% by mass or more, and preferably 0.7% by mass or less, and more preferably 0.5% by mass or less.

[0045] On the other hand, when the negative electrode current collector 31 is used as the negative electrode active material, the negative electrode current collector 31 may be made of a metal material such as a metal foil containing a component that functions as the negative electrode active material, and the negative electrode 30 (negative electrode current collector 31 and negative electrode terminal 32) may be made of, for example, a foil of zinc or a zinc alloy, a foil of magnesium or a magnesium alloy, or a foil of aluminum or an aluminum alloy. The alloy components that make up the zinc alloy may be the same as those described above.

[0046] The thickness of the negative electrode 30 is preferably 10 to 500 μm. When a carbon material is used for the positive electrode current collector 21 and the positive electrode terminal 22 and a metal material is used for the negative electrode current collector 31 and the negative electrode terminal 32, the carbon material has a higher electrical resistance than the metal material. Furthermore, depending on the type of metal material, the electrical resistivity may differ from that of the carbon material by several orders of magnitude. In the above-described configuration, even when materials with different electrical resistivities are used on the positive electrode 20 side and the negative electrode 30 side, the voltage drop due to the difference in electrical resistance between the material of the positive electrode 20 and the material of the negative electrode 30 can be reduced.

[0047] (Separator) The separator 52 has ion conductivity and electrical insulation. The separator 52 electrically insulates the positive electrode 20 from the negative electrode 30. The separator 52 may be a known separator commonly used in various batteries. The separator 52 may be, for example, a porous resin membrane, a semipermeable membrane, or a nonwoven fabric. The separator 52 may be, for example, a porous polyolefin film such as polyethylene (PE), polypropylene (PP), or an ethylene-propylene copolymer. The separator 52 may also be an ion exchange membrane.

[0048] (Exterior Body) The exterior body 40 accommodates a portion of each of the positive electrode 20 and the negative electrode 30. The exterior body 40 has a first sheet 41 and a second sheet 42.

[0049] The first sheet 41 and the second sheet 42 of the exterior body 40 are each rectangular when viewed in the thickness direction. The first sheet 41 and the second sheet 42 of the exterior body 40 can be made of a resin film such as a nylon film or a polyester film. Examples of the nylon film include nylon 66 film. Examples of the polyester film include polyethylene terephthalate (PET) film. The thickness of the resin film is preferably 20-100 μm. The first sheet 41 and the second sheet 42 are fused at the four edges of the rectangular periphery. The thickness T1 of the sheet-type battery 10 may be, for example, 0.1-5.0 mm, more preferably 0.2-2.0 mm. It is even more preferable that the thickness T1 of the sheet-type battery 10 be 1.0 mm or less.

[0050] An accommodation space SP is formed inside the exterior body 40 by the fused first sheet 41 and second sheet 42. The accommodation space SP accommodates the entire positive electrode current collector 21 and part of the positive electrode terminal 22 of the positive electrode 20, the separator 52, and the entire negative electrode current collector 31 and part of the negative electrode terminal 32 of the negative electrode 30. The exterior body 40 may be formed by folding back a single sheet. That is, the first sheet 41 and the second sheet 42 may not be separate sheets, but may be connected at one edge. In the case where the first sheet 41 and the second sheet 42 are connected at one edge, the first sheet 41 and the second sheet 42 can be fused together at three edges of the rectangular periphery, excluding the folded edge, to seal the exterior body 40.

[0051] The sheet-type battery 10 described above has a laminated structure in which, as shown in particular in FIGS. 2 to 4 , a first sheet 41, a positive electrode 20, a separator 52, a negative electrode 30, and a second sheet 42 are positioned in this order from one side to the other in the thickness direction.

[0052] An electrolyte (not shown) is sealed inside the exterior casing 40. The electrolyte can be, for example, an aqueous solution containing an electrolyte salt. The aqueous solution used as the electrolyte preferably has a pH of 3 or higher, more preferably 5 or higher, and preferably less than 12, more preferably 10 or lower, and even more preferably less than 7. An alkaline electrolyte with a pH higher than the above range can also be used. In the case of a lithium battery, a nonaqueous electrolyte is used.

[0053] Examples of electrolyte salts dissolved in the aqueous solution used as an electrolyte include chlorides such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, lithium chloride, and zinc chloride; hydroxides of alkali metals and alkaline earth metals (lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.), acetates (sodium acetate, potassium acetate, magnesium acetate, etc.), nitrates (sodium nitrate, potassium nitrate, magnesium nitrate, etc.), sulfates (sodium sulfate, potassium sulfate, magnesium sulfate, etc.), phosphates (sodium phosphate, potassium phosphate, magnesium phosphate, etc.), borates (sodium borate, potassium borate, magnesium borate, etc.), citrates (sodium citrate, potassium citrate, magnesium citrate, etc.), glutamate (sodium glutamate, potassium glutamate, magnesium glutamate, etc.); hydrogen carbonates of alkali metals (sodium hydrogen carbonate, potassium hydrogen carbonate, etc.); percarbonates of alkali metals (sodium percarbonate, potassium percarbonate, etc.); halogen-containing compounds such as fluorides; and polycarboxylic acids. The aqueous solution may contain one or more of these electrolyte salts.

[0054] The electrolyte salt is preferably a salt of a strong acid selected from hydrochloric acid, sulfuric acid, and nitric acid with a weak base such as ammonia, aluminum hydroxide, or a hydroxide of a metal element such as magnesium hydroxide, and more preferably an ammonium salt or a salt of a specific metal element. － , S.O. ４２－ , HSO ４ － and NO ３ － and at least one ion selected from Al ion, Mg ion, Fe ion and ammonium ion, and ammonium sulfate, ammonium hydrogen sulfate [(NH ４ ) HSO ４ ], ammonium salts such as ammonium chloride or ammonium nitrate; aluminum salts such as aluminum sulfate, aluminum chloride or aluminum nitrate; magnesium salts such as magnesium sulfate, magnesium chloride, magnesium chloride hydroxide [MgCl(OH)] or magnesium nitrate; iron (II) sulfate, ammonium iron (II) sulfate [(NH ４ ) ２ Fe(SO ４ ) ２ ], iron salts such as iron(III) sulfate, iron(II) chloride, or iron(II) nitrate; etc. The aqueous solution usable as the electrolyte may contain a water-soluble high-boiling solvent having a boiling point of 150°C or higher as a solvent together with water. In addition to the above-mentioned components, various known additives may be added to the aqueous solution as needed, as long as they do not impair the effects of the present invention. For example, zinc oxide may be added to prevent corrosion (oxidation) of the metal material used in the negative electrode. The aqueous solution may be gelled. The electrolyte may be solid.

[0055] The exterior body 40 has a positive electrode cutout 421 for exposing a portion of the positive electrode terminal 22 and a negative electrode cutout 422 for exposing a portion of the negative electrode terminal 32 at one end in the longitudinal direction of the sheet-type battery 10. In the above-described configuration, the positive electrode connection portion 25 is exposed to the outside from the positive electrode cutout 421. The negative electrode connection portion 35 is exposed to the outside from the negative electrode cutout 422. The other thickness-wise surfaces of the positive electrode connection portion 25 and the negative electrode connection portion 35 are welded to the first sheet 41.

[0056] The positive electrode cutout 421 and the negative electrode cutout 422 are located at one end of the second sheet 42 in the longitudinal direction, side by side in the width direction. The positive electrode cutout 421 and the negative electrode cutout 422 have a rectangular shape formed by cutting out one end of the second sheet 42 in the longitudinal direction on the other side of the longitudinal direction. One thickness-wise surface of the positive electrode terminal 22 has a peripheral portion on three sides that is aligned with the positive electrode cutout 421 when viewed in the thickness direction, and is welded to the second sheet 42. In other words, one thickness-wise surface of the positive electrode terminal 22 has a portion located on the other side of the longitudinal direction, one width-wise portion, and the other width-wise portion welded to the second sheet 42 with respect to the positive electrode connection portion 25. One thickness-wise surface of the negative electrode terminal 32 has a peripheral portion on three sides that is aligned with the negative electrode cutout 422 when viewed in the thickness direction, and is welded to the second sheet 42. In other words, of one thickness-wise surface of the negative electrode terminal 32, the portion located on the other side in the lengthwise direction relative to the negative electrode connection portion 35, the portion located on one side in the widthwise direction, and the portion located on the other side are welded to the second sheet 42.

[0057] The above-described configuration prevents the positive electrode terminal 22 and the negative electrode terminal 32 from protruding outward from one end of the exterior body 40 in the longitudinal direction. This allows the size of the sheet-type battery 10 to be compact when viewed in the thickness direction. Furthermore, the sealing performance near the positive electrode terminal 22 and the negative electrode terminal 32 can be improved.

[0058] (Details of Positive Electrode and Negative Electrode) As described above, the positive electrode 20 is made of a material having a higher electrical resistance than the material constituting the negative electrode 30. The materials for the positive electrode 20 and the negative electrode 30 can be a combination that satisfies the above-mentioned relationship in terms of electrical resistance and is used in known batteries. In the sheet-type battery 10, the positive electrode connection portion 25 of the positive electrode terminal 22 has an area larger than the area of ​​the negative electrode connection portion 35 of the negative electrode terminal 32.

[0059] More specifically, the width of the positive electrode terminal 22 is larger than the width of the negative electrode terminal 32. Furthermore, the width W21 of the positive electrode connection portion 25 of the positive electrode terminal 22 is larger than the width W31 of the negative electrode connection portion 35 of the negative electrode terminal 32. The length L21 of the positive electrode connection portion 25 of the positive electrode terminal 22 is the same as the length L31 of the negative electrode connection portion 35 of the negative electrode terminal 32.

[0060] Furthermore, by making the length L21 of the positive electrode connection portion 25 of the positive electrode terminal 22 longer than the length L31 of the negative electrode connection portion 35 of the negative electrode terminal 32, the difference between the electrical resistance of the positive electrode connection portion 25 and the contact resistance of the negative electrode connection portion 35 can be reduced.

[0061] On the other hand, if the length L21 of the positive electrode connection part 25 is to be increased, it is necessary to ensure that the positive electrode terminal 22 has a certain length or more, and the exterior body 40 must be increased accordingly. Therefore, in order to make the size of the sheet-type battery 10 compact, it is preferable that the length L21 of the positive electrode connection part 25 and the length L31 of the negative electrode connection part 35 are as similar as possible, and for example, it is preferable that the ratio of the length L21 of the positive electrode connection part 25 to the length L31 of the negative electrode connection part 35, L21 / L31, be 0.9 to 1.1.

[0062] Furthermore, by making the thickness of the positive electrode terminal 22 thicker than the thickness of the negative electrode terminal 32, the difference between the electrical resistance of the positive electrode terminal 22 and the electrical resistance of the negative electrode terminal 32 can be reduced. On the other hand, if the thickness of the positive electrode terminal 22 is made too thick, the sealing performance in the vicinity of the positive electrode terminal 22 decreases. For this reason, the ratio t1 / t2 of the thickness t2 of the negative electrode terminal 32 to the thickness t1 of the positive electrode terminal 22 is preferably 10 or less, more preferably 5 or less, and particularly preferably 2 or less.

[0063] According to the above-described configuration, for example, when the thickness t1 of the positive electrode connecting portion 25 and the thickness t1 of the negative electrode connecting portion 35 are specified to predetermined thicknesses in design, the electrical resistance in the positive electrode 20 can be more preferably reduced.

[0064] Furthermore, according to the above-described configuration, for example, when the length L21 of the positive electrode connection portion 25 and the length L31 of the negative electrode connection portion 35 are specified to predetermined lengths in design, the electrical resistance and contact resistance in the positive electrode 20 can be more preferably reduced.

[0065] In the above-described configuration, the area of ​​the positive electrode connection portion 25 of the positive electrode terminal 22, which is made of a material having a higher electrical resistance than the electrical resistance of the material constituting the negative electrode terminal 32, is larger than the area of ​​the negative electrode connection portion 35 of the negative electrode terminal 32. In addition, the thickness of the positive electrode terminal 22 is greater than the thickness of the negative electrode terminal 32.

[0066] Therefore, the electrical resistance of the positive electrode connecting portion 25 can be reduced compared to when the areas of the positive electrode connecting portion 25 and the negative electrode connecting portion 35 are the same. Also, the electrical resistance of the positive electrode terminal 22 can be reduced compared to when the thickness of the positive electrode terminal 22 and the thickness of the negative electrode terminal 32 are the same.

[0067] If the electrical resistance of the material that constitutes the positive electrode terminal 22 is greater than the electrical resistance of the material that constitutes the negative electrode terminal 32 , the effect of the voltage drop caused by the electrical resistance at the positive electrode terminal 22 will be greater than that at the negative electrode terminal 32 .

[0068] Therefore, with the above-described configuration, when electrically connected to an external device, it is possible to effectively reduce the voltage drop caused by the electrical resistance of the electrode terminals of the sheet-type battery 10 .

[0069] Furthermore, since the positive electrode current collector 21 and the positive electrode terminal 22 are integrally formed from the same material, and the negative electrode current collector 31 and the negative electrode terminal 32 are integrally formed from the same material, the manufacturing process of the positive electrode 20 and the negative electrode 30 can be simplified.

[0070] In addition, in the sheet-type battery 10, both the positive terminal 22 and the negative terminal 32 extend in one direction, i.e., the lengthwise direction. With the above-described configuration, the positive electrode connection portion 25 of the positive terminal 22 and the negative electrode connection portion 35 of the negative terminal 32 can be aligned at one end of the sheet-type battery 10 in the lengthwise direction. This allows the connection portion with an external device to be made compact.

[0071] (Modification) Figure 5 is a cross-sectional view showing a schematic configuration of a sheet-type battery 11 according to a modification. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. The sheet-type battery 11 according to the modification differs from the sheet-type battery 10 according to the above embodiment in that it is an air battery. In the following, the same components as those in the above embodiment are designated by the same reference numerals and will not be described again.

[0072] 5 and 6, the sheet-like battery 11 has a laminated structure in which a first sheet 41, a negative electrode 301, a separator 52, a positive electrode 201, a water-repellent film 55, and a second sheet 43 are positioned in this order from one side to the other side in the thickness direction.

[0073] The positive electrode 201 has a positive electrode current collector 21 and a positive electrode terminal 22. The positive electrode current collector 21 of the positive electrode 201, which serves as an air electrode using oxygen in the air as the positive electrode active material, can be made of, for example, a conductive porous material. The positive electrode current collector 21 may also be made of a porous carbon material. In this case, the positive electrode current collector 21 may function as a catalyst. For example, the positive electrode current collector 21 can have a structure equivalent to that of the porous carbon member described for the positive electrode 20 of the above embodiment.

[0074] A catalyst may be supported on the surface or inside of the positive electrode current collector 21 of the positive electrode 201. The positive electrode terminal 22 of the positive electrode 201 may be made non-porous by compression processing or the like.

[0075] The negative electrode 301 has a negative electrode current collector 31 and a negative electrode terminal 32. The negative electrode 301 can be made of a metal material such as a metal foil containing a component that functions as a negative electrode active material. The negative electrode 301 can be made of, for example, a foil of zinc or a zinc alloy, a foil of magnesium or a magnesium alloy, or a foil of aluminum or an aluminum alloy. The thickness of the negative electrode 301 is preferably 10 to 500 μm.

[0076] As in the above-described configuration, even when a carbon material is used for the positive electrode current collector 21 and the positive electrode terminal 22 of the positive electrode 201 and a metal material is used for the negative electrode current collector 31 and the negative electrode terminal 32 of the negative electrode 301, the voltage drop due to the difference in electrical resistance between the material of the positive electrode 201 and the material of the negative electrode 301 can be reduced.

[0077] The exterior body 40 has a first sheet 41 and a second sheet 43. The second sheet 43 has air holes 431 that penetrate the second sheet 43 in the thickness direction at a position that overlaps the positive electrode current collector 21 when viewed in the thickness direction.

[0078] The water-repellent film 55 is a film that is water-repellent but allows air to pass through. The water-repellent film 55 can be formed, for example, from a resin film such as a fluororesin or polyolefin-based resin. Examples of the fluororesin include polytetrafluoroethylene (PTFE). Examples of the polyolefin-based resin include polypropylene and polyethylene. The thickness of the water-repellent film is preferably 50-250 μm. The water-repellent film 55 is heat-welded to the other surface of the second sheet 43 in the thickness direction using a hot-melt resin or the like. The sheet-like battery 11 has the water-repellent film 55, which prevents electrolyte from leaking from the exterior body 40 through the air holes 431 while allowing air to enter the positive electrode 20 through the air holes 431.

[0079] A manganese battery was fabricated and tested to confirm the effects of the sheet-type battery 10 according to the embodiment. The evaluation method and results for confirming the effects are described below. However, the following examples do not limit the present invention.

[0080] Examples 1 and 2 <Positive Electrode> 80.8 parts by mass of electrolytic manganese dioxide (average particle size: 2.1 μm), 9.2 parts by mass of acetylene black (conductive additive), 6.0 parts by mass of ammonium polyacrylate (binder), and 4.0 parts by mass of zinc oxide were added and dispersed in a mixed solvent of water and ethanol at a mass ratio of 90:10 so that the total proportion (solid content concentration) of all components excluding the solvent was 60 mass%, thereby preparing a slurry of a positive electrode mixture.

[0081] The slurry was applied in stripes to porous carbon paper (thickness: 150 μm, porosity: 75%, air permeability (Gurley): 70 sec / 100 ml) and dried, thereby retaining the positive electrode mixture in the pores and on the surface of one side of the carbon paper. Subsequently, the slurry was applied in stripes to the other side of the carbon paper and dried, thereby producing a positive electrode sheet having a portion that retained the positive electrode mixture and a portion that did not retain the positive electrode mixture inside the carbon paper and on both the one and other sides.

[0082] Furthermore, the positive electrode sheet was punched into a shape having a positive electrode current collector with dimensions of height L221 × width W221 = 15 mm × 15 mm, which holds the positive electrode mixture, and positive electrode terminals with two widths and lengths L222 = 10 mm, which do not hold the positive electrode mixture, to obtain two types of positive electrodes with a theoretical capacity of approximately 50 mAh. The two widths are as follows: the positive electrode terminal of Example 1 has a width W2221 = 6 mm, and the positive electrode terminal of Example 2 has a width W2222 = 8 mm. Note that in Figure 7, the shape of the positive electrode terminal with a width W2221 = 6 mm of Example 1 is shown by a dashed line. In Figure 7, the shape of the positive electrode terminal with a width W2222 = 8 mm of Example 2 is shown by a solid line.

[0083] <Negative electrode> An electrolytic zinc foil (thickness: 0.1 mm) made of a zinc alloy containing 0.05% by mass of Bi as an additive element was punched into a shape having a negative electrode current collector with dimensions of height L231 × width W231 = 15 mm × 15 mm and a negative electrode terminal with dimensions of height L232 × width W232 = 5 mm × 10 mm, to produce the negative electrode shown in FIG. 8.

[0084] <Electrolyte> An aqueous solution (pH=4.7) in which lithium chloride (concentration: 30% by mass) was dissolved was used as the electrolyte.

[0085] <Separator> The separator is a PP nonwoven film (thickness: 200 μm, basis weight: 48 g / m ２ ) was used.

[0086] <Exterior Body> Two aluminum laminate films (thickness: 65 μm) each having a size of 25 mm × 30 mm and each having a PET film on the outer surface of an aluminum foil and a PP film as a heat-sealable resin layer on the inner surface were prepared. The two aluminum laminate films were used as base materials constituting the exterior body.

[0087] <Assembly of Battery> The positive electrode, the separator, and the negative electrode were stacked in this order on one aluminum laminate film, and then the other aluminum laminate film was placed on top of that. Next, the three peripheral sides of the two aluminum laminate films were heat-sealed to each other to form a bag-like shape, and 0.1 ml of the electrolyte solution was poured through the opening, and the opening was then heat-sealed to produce two types of sheet-like batteries (manganese batteries) with different widths of positive electrode terminal.

[0088] The widths of the welded portions between the first sheet 41 and the second sheet 42 at both widthwise ends of the positive electrode connection portion 25 and the negative electrode connection portion 35 are adjusted so that the ratios of the widths W2221 and W2222 of the positive electrode terminal to the width W232 of the negative electrode terminal are approximately the same as the ratios of the area of ​​the positive electrode connection portion 25 to the area of ​​the negative electrode connection portion 35 (see also Figure 1).

[0089] (Comparative Examples 1 and 2) <Positive Electrode> The positive electrode sheet described in Examples 1 and 2 was punched into a shape having a positive electrode current collector with dimensions of height L221 × width W221 = 15 mm × 15 mm and positive electrode terminals of two widths and length L222 = 10 mm to obtain positive electrodes. The two widths are as follows: The positive electrode terminal of Comparative Example 1 has a width W2223 = 2 mm, and the positive electrode terminal of Comparative Example 2 has a width W2224 = 4 mm. In Figure 7, the dashed lines show the shape of the positive electrode terminal of Comparative Example 1 with a width W2223 = 2 mm and the shape of the positive electrode terminal of Comparative Example 2 with a width W2224 = 4 mm.

[0090] <Assembly of Battery> Two types of sheet-type batteries having different widths of the negative electrode terminal were fabricated in the same manner as in Examples 1 and 2, except that the above-described positive electrode was used.

[0091] (Evaluation Test) For the sheet-type batteries of Comparative Examples 1 and 2 and Examples 1 and 2, pulse discharge (pulse current value: 50 mA, pulse width: 10 msec, pulse interval: 3 sec) was repeated 10 times at a temperature of 20°C. The closed circuit voltage (CCV) of the battery was measured at the 10th discharge, and the difference (voltage drop) between the open circuit voltage (OCV) of the battery before the start of pulse discharge and the CCV was calculated. To evaluate the results, the ratio of the width of the positive electrode terminal to the width of the negative electrode terminal (= width of positive electrode terminal / width of negative electrode terminal) was calculated. In other words, the ratio of the width of the positive electrode terminal to the width of the negative electrode terminal is the ratio of the area of ​​the positive electrode connection portion at the positive electrode terminal to the area of ​​the negative electrode connection portion at the negative electrode terminal. Furthermore, when the ratio of the area of ​​the positive electrode connection portion at the positive electrode terminal to the area of ​​the negative electrode connection portion at the negative electrode terminal is greater than 1.0, the positive electrode connection portion has a larger area than the area of ​​the negative electrode connection portion. Figure 9 shows a plot of voltage drop versus terminal width ratio.

[0092] The voltage drop of the battery when discharged at a relatively large current is small, for example, when the terminal width ratio is 1.2 or greater. It can be concluded that favorable voltage drop characteristics are obtained when the terminal width ratio is 1.2 or greater. On the other hand, the voltage drop suddenly increases when the terminal width ratio is 0.8 or less. This is presumably because, when the terminal width ratio is less than 1.2, the effect of the significantly larger resistivity of the positive terminal compared to the negative terminal becomes more pronounced. From these results, it is considered that favorable voltage drop characteristics are obtained at least when the terminal width ratio is greater than 1.0. That is, it can be said that the favorable voltage drop characteristics are obtained when the ratio of the area of ​​the positive electrode connection portion at the positive terminal to the area of ​​the negative electrode connection portion at the negative terminal is greater than 1.0. Furthermore, it is even more preferable that the terminal width ratio or the ratio of the area of ​​the positive electrode connection portion at the positive terminal to the area of ​​the negative electrode connection portion at the negative terminal is 1.5 or greater. It is preferable to make the width of the positive electrode larger than the width of the negative electrode so as to reduce the voltage drop within the range of width or length that can be realized in terms of design of the sheet-type battery.

[0093] While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and can be practiced by appropriately modifying the above-described embodiments within the scope of the spirit thereof.

[0094] Although not specifically described in the above embodiments, an external device equipped with a sheet-shaped battery is also included in the scope of the present invention.

[0095] In the above embodiment, the sheet-type battery 10 has one positive electrode 20 and one negative electrode 30. However, the sheet-type battery may have a configuration including at least a plurality of positive electrodes and a plurality of negative electrodes. For example, the sheet-type battery may have a configuration in which negative electrode terminals are disposed on both sides of a positive electrode terminal of a positive electrode in the width direction, and the positive electrode and the negative electrode are stacked with a separator interposed therebetween.

[0096] In the above embodiment, the sheet-type battery 10 has a rectangular shape when viewed in the thickness direction. However, the sheet-type battery may have a shape other than a rectangular shape when viewed in the thickness direction. For example, the sheet-type battery may have a polygonal shape, a closed curve shape, a circle shape, or an ellipse shape when viewed in the thickness direction.

[0097] In the above embodiment, the sheet-type battery 10 has one positive electrode 20 and one negative electrode 30. However, the sheet-type battery may have two positive electrodes positioned side by side on one side and the other side in the width direction of the negative electrode.

[0098] In the above embodiment, the positive electrode terminal 22 extends in one of the longitudinal directions relative to the positive electrode current collector 21. The negative electrode terminal 32 extends in one of the longitudinal directions relative to the negative electrode current collector 31. However, the positive electrode terminal or the negative electrode terminal may extend in a direction different from the longitudinal direction. For example, the positive electrode terminal may extend in one direction, while the negative electrode terminal may extend in the other direction opposite to the one direction. The positive electrode terminal may extend in a direction intersecting the extension direction of the negative electrode terminal.

[0099] In the above embodiment, the length L21 of the positive electrode connection portion 25 of the positive electrode terminal 22 is the same as the length L31 of the negative electrode connection portion 35 of the negative electrode terminal 32. However, the length of the positive electrode connection portion may be different from the length of the negative electrode connection portion. Alternatively, the length of the positive electrode connection portion may be different from the length of the negative electrode connection portion, and the width of the positive electrode connection portion may be the same as the width of the negative electrode connection portion.

[0100] In the above embodiment, the second sheet 42 of the exterior body 40 has a positive electrode cutout portion 421 and a negative electrode cutout portion 422. However, the second sheet does not have to have a positive electrode cutout portion and a negative electrode cutout portion. In addition, the positive electrode terminal and the negative electrode terminal may protrude outward from one end of the exterior body in the longitudinal direction.

[0101] The present invention can be used in a sheet-type battery having a positive electrode, a negative electrode, and an exterior body.

[0102] 10, 11: Sheet-shaped battery 20, 201: Positive electrode 21: Positive electrode current collector 22: Positive electrode terminal 25: Positive electrode connection part 30, 202: Negative electrode 31: Negative electrode current collector 32: Negative electrode terminal 35: Negative electrode connection part 40: Exterior body 41: First sheet 42, 43: Second sheet 421: Positive electrode cutout part 422: Negative electrode cutout part 431: Air hole 52: Separator 55: Water-repellent film SP: Storage space

Claims

1. A sheet-type battery having a positive electrode, a negative electrode, and an exterior housing that houses a portion of each of the positive electrode and the negative electrode, wherein the positive electrode comprises: a plate-shaped positive electrode current collector housed within the exterior housing; and a positive electrode terminal that is formed integrally with the positive electrode current collector from the same material as the exterior housing, a portion of which is exposed to the outside from the exterior; the negative electrode comprises: a plate-shaped negative electrode current collector housed within the exterior housing and overlapped in the thickness direction on the positive electrode current collector; and a negative electrode terminal that is formed integrally with the negative electrode current collector from the same material as the negative electrode current collector, a portion of which is exposed to the outside from the exterior housing; the positive electrode is made of a material that has a higher electrical resistance than the electrical resistance of a material constituting the negative electrode; the positive electrode terminal has a positive electrode connection part at a part that is exposed to the outside from the exterior housing, to which a positive electrode terminal of an external device is connected; and the negative electrode terminal has a negative electrode connection part at a part that is exposed to the outside from the exterior housing, The positive electrode connection portion has an area larger than an area of ​​the negative electrode connection portion.

2. A sheet-type battery according to claim 1, wherein the positive electrode current collector and the positive electrode terminal are made of a porous material having electrical conductivity.

3. A sheet-type battery according to claim 2, wherein the positive electrode current collector and the positive electrode terminal are made of a carbon material.

4. A sheet-type battery according to claim 3, wherein the negative electrode current collector and the negative electrode terminal are made of a metal material.

5. A sheet-type battery according to claim 4, wherein the negative electrode current collector acts as a negative electrode active material.

6. A sheet-type battery according to claim 1, wherein the width of the positive electrode connection portion of the positive electrode terminal is greater than the width of the negative electrode connection portion of the negative electrode terminal.

7. A sheet-type battery according to claim 1, wherein the positive electrode terminal extends in one direction relative to the positive electrode current collector, and the negative electrode terminal extends in the same direction relative to the negative electrode current collector.

8. A sheet-type battery according to claim 7, wherein the outer casing has, at the end in one direction, a positive electrode cutout portion for exposing the positive electrode terminal, and a negative electrode cutout portion for exposing the negative electrode terminal.

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