Primary battery

Abstract

A primary battery according to the present disclosure comprises: a bottomed cylindrical case for housing an electrolyte and an electrode group which has a first end surface and in which a positive electrode (21) and a negative electrode (22) composed of a consumable metal are wound with a separator (23) therebetween, the bottomed cylindrical case being electrically connected to the positive electrode (21); a sealing body that is electrically connected to the negative electrode (22) and seals an opening of the case; a negative electrode lead (60) that electrically connects the negative electrode (22) and the sealing body; and a first electrolyte shielding part (71) that has an interposed part (71a) interposed between the negative electrode (22) and the negative electrode lead (60) and covers a part of the negative electrode lead (60). The first electrolyte shielding part (71) extends across an end part (21a) on the side of a first end surface of the positive electrode (21) in the winding axis direction of the electrode group.

Description

primary battery

[0001] The present disclosure relates to primary batteries.

[0002] Conventionally, primary batteries having a negative electrode made of a consumable metal have been known (for example, Patent Document 1). Patent Document 1 discloses a "non-aqueous electrolyte battery including an electrode assembly in which a positive electrode plate and a negative electrode plate made of a consumable metal plate such as a lithium plate or a sodium plate are closely arranged with a separator interposed therebetween, and a positive electrode current collector tab and an insulating member protecting the tab are disposed on the positive electrode plate, and an exposed portion that is not shielded by the positive electrode current collector tab and the insulating member remains in a width direction region facing the negative electrode plate."

[0003] Publication No. 5-31810

[0004] When multiple primary batteries are connected and used, some of the primary batteries may enter an overdischarge state and generate heat. For example, when a lithium primary battery enters an overdischarge state, the negative electrode lead or case dissolves, depositing metal on the positive electrode surface in the form of dendrites, which may penetrate the separator and cause an internal short circuit. Current concentration occurs at the short circuited area, which can cause the battery to generate heat. Even the nonaqueous electrolyte battery of Patent Document 1 may generate heat during such overdischarge. In such a situation, one of the objectives of the present disclosure is to suppress heat generation during overdischarge.

[0005] One aspect of the present disclosure relates to a primary battery, the primary battery comprising: a wound electrode group including a positive electrode, a negative electrode made of a consumable metal, and a separator interposed between the positive electrode and the negative electrode, the wound electrode group having a first end face and an opposite second end face; an electrolyte; a cylindrical case containing the electrode group and the electrolyte and electrically connected to the positive electrode; a sealer sealing an opening of the case; a negative electrode lead having a first main surface connected to the negative electrode and an opposite second main surface, the negative electrode lead protruding from the first end face and electrically connecting the negative electrode to the sealer; and a first electrolyte shielding portion having an intervening portion interposed between the first main surface of the negative electrode lead and an end of the negative electrode facing the first end face, the first electrolyte shielding portion covering a portion of the first main surface and a portion of the second main surface, the first electrolyte shielding portion extending across an end of the positive electrode facing the first end face in a winding axis direction of the electrode group.

[0006] According to the present disclosure, heat generation during overdischarge can be suppressed.

[0007] Fig. 1 is a front view showing a schematic vertical cross section of a part of a primary battery of embodiment 1. Fig. 2 is a view showing an enlarged view of a main part of the primary battery of embodiment 1, where (a) is a front view and (b) is a side view showing only the negative electrode lead and each electrolyte shielding part. Fig. 3 is a view showing an enlarged view of a main part of a primary battery of embodiment 2, where (a) is a front view and (b) is a side view showing only the negative electrode lead and each electrolyte shielding part. Fig. 4 is a front view showing an enlarged view of a main part of a primary battery of embodiment 3.

[0008] An embodiment of a primary battery according to the present disclosure will be described below using examples. However, the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0009] The primary battery according to the present disclosure includes an electrode group, an electrolyte, a case, a sealing body, a negative electrode lead, and a first electrolyte shielding portion. Note that, although a lithium primary battery will be described below as an example of the primary battery, the primary battery according to the present disclosure may be any other type of primary battery.

[0010] The electrode assembly is a wound electrode assembly having a positive electrode, a negative electrode, and a separator, and having a first end surface and a second end surface opposite to the first end surface. The negative electrode is made of a consumable metal (in this example, metallic lithium or a lithium alloy). The separator is interposed between the positive electrode and the negative electrode. In the direction of the winding axis of the electrode assembly, the length of the positive electrode may be greater than the length of the negative electrode, and the length of the separator may be greater than the length of the positive electrode.

[0011] The positive electrode may be formed in a long sheet shape (or a strip shape). The positive electrode may contain a positive electrode active material. The positive electrode active material may be any material used for the positive electrodes of primary batteries and secondary batteries. For example, manganese dioxide, graphite fluoride, iron sulfide, lithium manganate, etc. may be used. The positive electrode may have, for example, a positive electrode current collector and a positive electrode mixture layer containing the positive electrode active material.

[0012] The material for the positive electrode current collector may be stainless steel, a metal material containing Al and / or Ti, or the like. Highly corrosion-resistant stainless steel such as SUS444 or SUS316 is preferred. The metal material containing Al and / or Ti may be an alloy. For example, a sheet or a porous body may be used as the positive electrode current collector. Metal foil or the like may also be used as the positive electrode current collector. Furthermore, a metal mesh (or net), expanded metal, punched metal, or the like may also be used as the porous positive electrode current collector.

[0013] The positive electrode mixture constituting the positive electrode mixture layer may contain, in addition to the positive electrode active material, optional components such as a binder and / or a conductive agent. Examples of binders include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubber-like polymers. Examples of fluororesins include polytetrafluoroethylene and polyvinylidene fluoride. The positive electrode mixture may contain one type of binder, or two or more types.

[0014] The conductive agent is preferably a carbon material. Examples of the carbon material include carbon black (acetylene black, ketjen black, etc.), carbon nanotubes, and graphite. The positive electrode mixture may contain one or more conductive agents. The conductive agent may be present between the positive electrode current collector and the positive electrode mixture layer.

[0015] The method for manufacturing the positive electrode is not particularly limited. The positive electrode can be obtained, for example, by attaching a positive electrode mixture to a positive electrode current collector. For example, the positive electrode mixture may be applied to the positive electrode current collector or may be filled into a porous positive electrode current collector. Alternatively, the positive electrode mixture may be formed into a sheet and laminated so as to be in physical contact with the positive electrode current collector. When preparing the positive electrode, the positive electrode mixture may be used in a paste or clay-like form by adding the components of the positive electrode mixture to a dispersion medium (e.g., water and / or an organic medium) as needed. At an appropriate stage in preparing the positive electrode, drying may be performed, and the positive electrode may be compressed (e.g., rolled) in the thickness direction, as needed.

[0016] The negative electrode may be formed in a long sheet shape (or a strip shape). The negative electrode may contain metallic lithium, a lithium alloy, or metallic lithium and a lithium alloy. Examples of lithium alloys include those containing at least one of Ca, Mg, Al, Si, Zn, Sn, and Pb. The content of metal elements other than lithium contained in the lithium alloy is preferably 0.01% by mass or more and 1.0% by mass or less relative to the metal elements that are alloyed with lithium. Note that metallic lithium may contain less than 0.01% by mass of elements other than lithium.

[0017] Examples of the sheet-shaped negative electrode include a metallic lithium foil or a composite sheet containing metallic lithium and a lithium alloy. In the composite, the lithium alloy may be dispersed in the metallic lithium in the form of particles. The sheet-shaped negative electrode can be formed, for example, by extrusion molding metallic lithium, a lithium alloy, or a combination of metallic lithium and a lithium alloy. The lithium alloy may be formed by attaching an Al grid or the like to the surface of the metallic lithium foil to alloy the surface of the metallic lithium foil.

[0018] The separator is a porous sheet having ion permeability and insulating properties. Examples of the porous sheet include a microporous film, a woven fabric, and a nonwoven fabric. The separator may have a single-layer structure or a multilayer structure. Examples of a multilayer separator include a separator including multiple layers made of different materials and / or structures.

[0019] The separator may be made of any suitable material, including, but not limited to, polymeric materials. Examples of polymeric materials include olefin resins (such as polyethylene, polypropylene, and copolymers of ethylene and propylene), polyamide resins, polyimide resins (such as polyimide and polyamideimide), cellulose, polyphenylene sulfite (PPS), and polytetrafluoroethylene (PTFE). The separator may contain additives, if necessary. Examples of additives include inorganic fillers.

[0020] The thickness of the separator can be selected from the range of, for example, 10 μm to 200 μm. When the separator is made of a microporous film, the thickness of the separator is, for example, 10 μm to 80 μm, and preferably 20 μm to 70 μm.

[0021] The case is formed in a bottomed tubular shape (e.g., a bottomed cylindrical shape or a bottomed rectangular tubular shape) and contains the electrode group and the electrolyte. The case is electrically connected to the positive electrode of the electrode group. Therefore, the case functions as the positive electrode external terminal of the primary battery. The case may be made of, for example, iron, an iron alloy (such as SUS), aluminum, an aluminum alloy (such as an aluminum alloy containing trace amounts of other metals such as manganese or copper), or the like, and may be plated as necessary. The electrolyte may be a nonaqueous electrolyte.

[0022] The non-aqueous electrolyte may be one having lithium ion conductivity. Such a non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt as an electrolyte dissolved in the non-aqueous solvent. The non-aqueous electrolyte is prepared by dissolving the lithium salt in the non-aqueous solvent.

[0023] The lithium salt may be any of those used in non-aqueous electrolytes for lithium primary batteries, and may be used without any particular limitation. Examples of the lithium salt include lithium fluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium perchlorate. The non-aqueous electrolyte may contain one type of lithium salt, or two or more types of lithium salts.

[0024] Examples of non-aqueous solvents include, but are not limited to, esters (e.g., carbonate esters, carboxylate esters such as γ-butyrolactone, etc.) and ethers (1,2-dimethoxyethane, etc.). Examples of carbonate esters include cyclic carbonates (propylene carbonate, ethylene carbonate, etc.) and chain carbonates (diethyl carbonate, ethyl methyl carbonate, etc.). The non-aqueous electrolyte may contain one or more non-aqueous solvents.

[0025] The concentration of the lithium salt in the nonaqueous electrolyte is, for example, 0.1 mol / L or more and 3.5 mol / L or less.

[0026] The non-aqueous electrolyte may contain additives as needed. Examples of additives include vinylene carbonate, fluoroethylene carbonate, vinyl ethyl carbonate, phthalic anhydride, succinic anhydride, etc. The additives may be used alone or in combination of two or more.

[0027] The sealing body seals the opening of the case. The sealing body may have a conductive sealing plate welded to the edge of the opening of the case, a conductive external terminal disposed in an opening formed in the center of the sealing plate, and an insulating gasket interposed between them. In this case, the negative electrode lead may be connected to the external terminal. Alternatively, the sealing body may have at least one conductive member, and the edge of the opening of the case may be crimped to the peripheral edge of the sealing body via an insulating gasket. In this case, the negative electrode lead may be connected to at least one conductive member.

[0028] The negative electrode lead has a first main surface connected to the negative electrode and a second main surface opposite thereto. The negative electrode lead protrudes from the first end surface of the electrode assembly and electrically connects the negative electrode and the sealing body. Therefore, the sealing body functions as a negative electrode external terminal of the primary battery. The negative electrode lead may be formed in a strip shape (or a tape shape). The negative electrode lead may be made of a metal foil. Examples of materials that can be used for the metal foil include nickel (Ni), Ni alloys, copper (Cu), Cu alloys, iron (Fe), Fe alloys, and SUS. Alternatively, a two-layer clad material such as Ni / Cu, Ni / Fe, Ni / SUS, or Cu / SUS, or a three-layer clad material such as Ni / Fe / Ni, Ni / Cu / Ni, SUS / Cu / SUS, or Ni / SUS / Ni may be used.

[0029] The first electrolyte solution shielding portion has an intervening portion interposed between the first main surface of the negative electrode lead and the end portion of the negative electrode on the first end face side. The first electrolyte solution shielding portion covers a portion of the first main surface and a portion of the second main surface of the negative electrode lead. The first electrolyte solution shielding portion may also cover a portion of the side surface of the negative electrode lead connecting the first main surface and the second main surface. The first electrolyte solution shielding portion is desirably composed of an insulating and highly heat-resistant material, preferably including polyimide, polyamide, polyamideimide, etc. Among these, polyimide, wholly aromatic polyamide (aramid), etc. are preferred, and polyimide is particularly preferred. When the first electrolyte solution shielding portion includes polyimide, the first electrolyte solution shielding portion may include a material other than polyimide (e.g., polyolefin, polytetrafluoroethylene) or may be composed of a polymer alloy of polyimide and a resin other than polyimide. The first electrolyte solution shielding portion may be composed of, for example, an electrolyte solution shielding tape or electrolyte solution shielding coating containing these materials. The thickness of the first electrolyte solution shielding portion may be, for example, 7 μm or more and 700 μm or less.

[0030] The first electrolyte shielding portion extends across the end of the positive electrode on the first end face side in the winding axis direction of the electrode group. In other words, the end of the positive electrode is located between one end and the other end of the first electrolyte shielding portion in the winding axis direction. That is, the negative electrode lead is covered by the first electrolyte shielding portion in a region facing the end of the positive electrode. As described above, the first electrolyte shielding portion has an intervening portion interposed between the first main surface of the negative electrode lead and the end of the negative electrode on the first end face side. In the nonaqueous electrolyte battery of Patent Document 1, the electrolyte shielding member 9 shown in each drawing of the same document does not have such an intervening portion. Therefore, in this battery, during overdischarge, nonaqueous electrolyte may penetrate into the gap between the electrolyte shielding member 9 and the negative electrode plate 4 and the negative electrode current collecting tab 8 (the approximately triangular gap in the region facing the end of the positive electrode in Figure 2 of the same document), potentially generating heat according to the mechanism described above. In contrast, the first electrolyte solution shielding portion of the present disclosure, which has an interposed portion and extends across the end of the positive electrode, prevents contact of the electrolyte with the negative electrode lead in the region where the first electrolyte solution shielding portion is located (or the region where the negative electrode lead faces the end of the positive electrode) during overdischarge, thereby suppressing heat generation according to the above-mentioned mechanism. The distance in the direction of the winding axis between one end of the first electrolyte solution shielding portion (e.g., the end on the first end face side) and the end of the positive electrode on the first end face side may be, for example, 1 mm or more and 30 mm or less. The distance in the direction of the winding axis between the other end of the first electrolyte solution shielding portion (e.g., the end on the second end face side or the end of the interposed portion) and the end of the positive electrode on the first end face side may be, for example, 1 mm or more and 30 mm or less. Setting the distances between both ends of the first electrolyte solution shielding portion and the end of the positive electrode on the first end face side in this manner further enhances the heat generation suppression effect during overdischarge.

[0031] The first electrolyte solution shielding portion may extend across the end of the separator on the first end face side in the winding axis direction of the electrode group. In other words, the end of the separator on the first end face side (and the end of the positive electrode on the first end face side) may be located between one end and the other end of the first electrolyte solution shielding portion in the winding axis direction. Because the end of the separator on the first end face side is located outward from the end of the positive electrode on the first end face side in the winding axis direction, this configuration allows a wider range of the negative electrode lead to be covered by the first electrolyte solution shielding portion. This further suppresses electrolyte penetration, and ultimately further suppresses heat generation during overdischarge.

[0032] The primary battery may further include a second electrolyte solution shielding part provided on the second main surface side of the negative electrode lead and covering a part of the first electrolyte solution shielding part and a part of the negative electrode lead. The second electrolyte solution shielding part may cover the connection part between the negative electrode lead and the negative electrode when viewed from the normal direction of the second main surface. The constituent material of the second electrolyte solution shielding part may be selected from the constituent materials exemplified for the first electrolyte solution shielding part and may be the same as or different from the constituent material of the first electrolyte solution shielding part. The part of the first electrolyte solution shielding part may be a part of the first electrolyte solution shielding part that covers the second main surface of the negative electrode lead, and part or all of the part covering the second main surface may be covered by the second electrolyte solution shielding part. The part of the negative electrode lead may include a part of the negative electrode lead that protrudes toward the electrode group beyond the first electrolyte solution shielding part (hereinafter also referred to as a protruding part), and part or all of the protruding part may be covered by the second electrolyte solution shielding part. The electrical connection between the negative electrode lead and the negative electrode may be formed, for example, by crimping, ultrasonic welding, or the like. Because such a connection cannot be covered by the first electrolyte shield, unless some countermeasure is taken, the portion of the negative electrode lead corresponding to the connection (or the aforementioned protruding portion) may be eluted during overdischarge. In contrast, in this configuration, the connection is covered by the second electrolyte shield when viewed from the normal direction of the second main surface, thereby preventing a portion of the negative electrode lead from eluting during overdischarge. The thickness of the second electrolyte shield may be, for example, 7 μm or more and 700 μm or less.

[0033] The primary battery may further include a third electrolyte solution shielding part provided on the first main surface side of the negative electrode lead and covering a part of the first electrolyte solution shielding part and a part of the negative electrode. The third electrolyte solution shielding part may cover the connection part between the negative electrode lead and the negative electrode when viewed from the normal direction of the first main surface. The constituent material of the third electrolyte solution shielding part may be selected from the constituent materials exemplified for the first electrolyte solution shielding part and may be the same as or different from the constituent material of the first electrolyte solution shielding part. The part of the first electrolyte solution shielding part may be a part of the first electrolyte solution shielding part that covers the first main surface of the negative electrode lead, and part or all of the part that covers the first main surface may be covered by the third electrolyte solution shielding part. The part of the negative electrode may be a part of the negative electrode facing the protruding part, and part or all of the facing part may be covered by the third electrolyte solution shielding part. As described above, the part of the negative electrode lead corresponding to the connection part may be eluted during overdischarge. In contrast, in the present configuration, the connection portion is covered by the third electrolyte solution shielding portion when viewed from the normal direction of the first main surface, thereby suppressing the elution of a portion of the negative electrode lead during overdischarge. This suppression effect is particularly significant when the primary battery includes both the second electrolyte solution shielding portion and the third electrolyte solution shielding portion. The thickness of the third electrolyte solution shielding portion may be, for example, 7 μm or more and 700 μm or less.

[0034] The first electrolyte shielding portion may be formed by an electrolyte shielding tape wound around the negative electrode lead. In this case, the first main surface, the second main surface, and the side surfaces of the negative electrode lead can be covered with a single electrolyte shielding tape. In addition, the number of components required to form the first electrolyte shielding portion can be reduced to one, and it is sufficient to position a single electrolyte shielding tape relative to the negative electrode lead, making it easy to form the first electrolyte shielding portion. Note that, although this effect may be weakened, two or more electrolyte shielding tapes may be wound around the negative electrode lead. Furthermore, the first electrolyte shielding portion may be formed by a plurality of electrolyte shielding tapes attached to the negative electrode lead from the first main surface side and the second main surface side.

[0035] As described above, according to the present disclosure, by covering a predetermined portion of the negative electrode lead with a first electrolyte solution shielding portion having an interposed portion, heat generation in the primary battery during overdischarge can be suppressed.

[0036] An example of a primary battery according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example primary battery described below. The components of the example primary battery described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Of the components of the example primary battery described below, components that are not essential for the primary battery according to the present disclosure may be omitted. Note that the drawings shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0037] Embodiment 1 A description will be given of embodiment 1 of the present disclosure. As shown in Figures 1 and 2, a primary battery 10 of this embodiment includes an electrode group 20, a case 30, a sealing body 40, a negative electrode lead 60, a first electrolyte solution shielding part 71, and a second electrolyte solution shielding part 72. To prevent internal short circuits, an upper insulating plate 81 and a lower insulating plate 82 are disposed on the upper and lower parts of the electrode group 20, respectively.

[0038] The electrode group 20 is a wound electrode group having a positive electrode 21, a negative electrode 22, and a separator 23 interposed therebetween, and has a first end face (upper end face in FIG. 1 ) and an opposite second end face (lower end face in FIG. 1 ). The electrode group 20 is configured by spirally winding a long sheet-shaped positive electrode 21 and a long sheet-shaped negative electrode 22 with a long sheet-shaped separator 23 interposed therebetween. The positive electrode 21 contains a positive electrode active material (manganese dioxide in this example). The negative electrode 22 is configured with a consumable metal (metallic lithium in this example). The separator 23 is configured with a microporous film made of polyolefin. In the winding axis direction of the electrode group 20 (the vertical direction in FIG. 1 ), the length dimension of the positive electrode 21 is greater than the length dimension of the negative electrode 22, and the length dimension of the separator 23 is greater than the length dimension of the positive electrode 21.

[0039] The case 30 is formed in a cylindrical shape with a bottom, and contains the electrode group 20 and a non-aqueous electrolyte (not shown). The case 30 is made of an iron alloy (SUS in this example). The case 30 is electrically connected to the positive electrode 21 of the electrode group 20 via a positive electrode lead 50. Therefore, the case 30 functions as a positive electrode external terminal of the primary battery 10. One end of the positive electrode lead 50 may be connected to the positive electrode 21 by welding or the like. The other end of the positive electrode lead 50 may be connected to the inner bottom surface of the case 30 by welding or the like. The non-aqueous electrolyte is an example of an electrolyte.

[0040] The sealing body 40 seals the opening of the case 30. The sealing body 40 has a conductive sealing plate 41 in contact with the edge of the opening of the case 30, a conductive external terminal 42 disposed in an opening formed in the center of the sealing plate 41, and an insulating gasket 43 interposed between the two. As will be described later, the external terminal 42 is electrically connected to the negative electrode 22 of the electrode group 20 via a negative electrode lead 60. Therefore, the external terminal 42 functions as a negative electrode external terminal of the primary battery 10.

[0041] The negative electrode lead 60 has a first main surface 61 connected to the negative electrode 22, a second main surface 62 opposite to the first main surface 61, and a side surface 63 connecting the two. The negative electrode lead 60 is made of a strip-shaped metal foil. The negative electrode lead 60 protrudes from the first end surface of the electrode group 20 and electrically connects the negative electrode 22 of the electrode group 20 to the external terminal 42 of the sealing body 40. One end of the negative electrode lead 60 may be connected to the negative electrode 22 by welding or the like. The other end of the negative electrode lead 60 may be connected to the external terminal 42 of the sealing body 40 by welding or the like. In FIG. 2 , the connection J between the negative electrode lead 60 and the negative electrode 22 is indicated by a thick cross (×).

[0042] The first electrolyte solution shielding portion 71 covers a portion of the first main surface 61, a portion of the second main surface 62, and a portion of the side surface 63 of the negative electrode lead 60. The portion of the first main surface 61, a portion of the second main surface 62, and a portion of the side surface 63 at least partially (e.g., 80% or more) overlap with one another in the winding axis direction of the electrode group 20. The first electrolyte solution shielding portion 71 has an interposed portion 71a interposed between the first main surface 61 of the negative electrode lead 60 and the end portion 22a on the first end face side of the negative electrode 22. The first electrolyte solution shielding portion 71 is composed of an electrolyte solution shielding tape wound around the negative electrode lead 60. The electrolyte solution shielding tape contains polyimide. The electrolyte solution shielding tape is wound around the negative electrode lead 60 in a direction perpendicular to the winding axis direction of the electrode group 20.

[0043] The first electrolyte solution shielding portion 71 extends, in the direction of the winding axis of the electrode group 20, straddling the end 21 a (upper end in FIG. 2 ) on the first end face side of the positive electrode 21. The first electrolyte solution shielding portion 71 also extends, in the direction of the winding axis of the electrode group 20, straddling the end 23 a (upper end in FIG. 2 ) on the first end face side of the separator 23.

[0044] The second electrolyte solution shielding portion 72 is provided on the second main surface 62 side of the negative electrode lead 60 (the left side in FIG. 2( a) ), and covers a part of the first electrolyte solution shielding portion 71 and a part of the negative electrode lead 60. As shown in FIG. 2( b) , the second electrolyte solution shielding portion 72 covers the connection portion J between the negative electrode lead 60 and the negative electrode 22 when viewed from the normal direction of the second main surface 62. When viewed from the normal direction of the second main surface 62, the second electrolyte solution shielding portion 72 covers a portion of the negative electrode lead 60 that protrudes further toward the electrode group 20 side (the lower side in FIG. 2 ) than the first electrolyte solution shielding portion 71. When viewed from the normal direction of the second main surface 62, the second electrolyte solution shielding portion 72 covers the first electrolyte solution shielding portion 71. The second electrolyte solution shielding portion 72 is composed of an electrolyte solution shielding tape attached across the negative electrode lead 60 and the first electrolyte solution shielding portion 71. The electrolyte shielding tape includes a polyimide.

[0045] Second Embodiment A second embodiment of the present disclosure will be described. The primary battery 10 of this embodiment differs from the first embodiment in that it includes a third electrolyte solution shielding portion 73. The following mainly describes the differences from the first embodiment.

[0046] As shown in Fig. 3 , the primary battery 10 of this embodiment includes a third electrolyte solution shielding portion 73. The third electrolyte solution shielding portion 73 is provided on the first main surface 61 side of the negative electrode lead 60 (the right side in Fig. 3( a) ) and covers the bottom portion of the first electrolyte solution shielding portion 71 and a portion of the negative electrode 22. As shown in Fig. 3( b) , when viewed from the normal direction of the first main surface 61, the third electrolyte solution shielding portion 73 covers the connection portion J between the negative electrode lead 60 and the negative electrode 22. When viewed from the normal direction of the first main surface 61, the third electrolyte solution shielding portion 73 covers a portion of the negative electrode lead 60 that protrudes closer to the electrode group 20 than the first electrolyte solution shielding portion 71. When viewed from the normal direction of the first main surface 61, the third electrolyte solution shielding portion 73 covers the first electrolyte solution shielding portion 71. The third electrolyte shielding portion 73 is composed of an electrolyte shielding tape that is attached across the negative electrode lead 60, the first electrolyte shielding portion 71, and the negative electrode 22. The electrolyte shielding tape contains polyimide.

[0047] Third Embodiment A third embodiment of the present disclosure will be described. As shown in Fig. 4, the primary battery 10 of this embodiment does not include a second electrolyte solution shielding portion 72. The other configurations are the same as those of the first embodiment.

[0048] <<Notes>> The above description of the embodiment discloses the following techniques.

[0049] a first electrolyte shielding portion having an intervening portion interposed between the first main surface of the negative electrode lead and an end of the negative electrode on the first end surface side, the first electrolyte shielding portion covering a portion of the first main surface and a portion of the second main surface, wherein the first electrolyte shielding portion extends across the end of the positive electrode on the first end surface side in a direction of a winding axis of the electrode group.

[0050] (Technology 2) The primary battery according to Technology 1, wherein the first electrolyte solution shielding portion extends across an end of the separator on the first end face side in the winding axis direction.

[0051] (Technology 3) The primary battery according to Technology 1 or 2, further comprising a second electrolyte solution shielding part provided on the second main surface side of the negative electrode lead and covering a part of the first electrolyte solution shielding part and a part of the negative electrode lead, wherein the second electrolyte solution shielding part covers a connection part between the negative electrode lead and the negative electrode when viewed from a normal direction of the second main surface.

[0052] (Technology 4) The primary battery according to Technology 3, further comprising a third electrolyte solution shielding part provided on the first main surface side of the negative electrode lead and covering a part of the first electrolyte solution shielding part and a part of the negative electrode, wherein the third electrolyte solution shielding part covers the connection part between the negative electrode lead and the negative electrode when viewed from a normal direction of the first main surface.

[0053] (Technology 5) The primary battery according to any one of Technologies 1 to 4, wherein the first electrolyte shielding portion is formed of an electrolyte shielding tape wound around the negative electrode lead.

[0054] The behavior of the batteries of Examples 1 to 3 and Comparative Examples 1 and 2 shown below during overdischarge was evaluated. Specifically, each battery was discharged to 95% of its rated capacity, followed by a constant current sweep of 50 mA. After the voltage rose to 4 V, the sweep was switched to a constant voltage sweep. These constant current sweeps and constant voltage sweeps (i.e., battery overdischarge) were performed at an ambient temperature of 25°C. Except for Example 2, in which no overdischarge occurred, overdischarge continued until 3200 mAh of electricity was discharged. The maximum temperature reached by the case during overdischarge, as well as the presence or absence of dissolution of the case or negative electrode lead, were then evaluated.

[0055] Example 1 A battery of the type shown in the above-described embodiment 1, i.e., a primary battery having a first and second electrolyte shielding portion and a positive polarity case, was evaluated. The maximum temperature reached by the case during overdischarge was 25°C, and heat generation was not substantially observed. Furthermore, the case did not melt during overdischarge, and the protruding portion of the negative electrode lead that was not covered by the first electrolyte shielding portion melted slightly.

[0056] Example 2 A battery of the type shown in the above-described embodiment 2, i.e., a primary battery having first to third electrolyte shielding portions and a positive polarity case, was evaluated. The maximum temperature reached by the case during overdischarge was 25°C, and heat generation was not substantially observed. Furthermore, neither the case nor the negative electrode lead melted during overdischarge. In particular, the primary battery of this example did not experience overdischarge during a constant voltage sweep.

[0057] Example 3 A battery of the type shown in the above-described embodiment 3, i.e., a primary battery having a first electrolyte solution shielding portion and a case with a positive polarity, was evaluated. The maximum temperature reached by the case during overdischarge was 25°C, and heat generation was not substantially observed. Furthermore, the case did not melt during overdischarge, and only the protruding portion of the negative electrode lead that was not covered by the first electrolyte solution shielding portion melted.

[0058] Comparative Example 1: A battery of the type disclosed in Patent Document 1, i.e., a primary battery having no first electrolyte shielding portion and a positive polarity case, was evaluated. The maximum temperature of the case during overdischarge was higher than 25°C, and heat generation was observed. Furthermore, the case did not melt during overdischarge, but most of the negative electrode lead melted.

[0059] Comparative Example 2: A secondary battery was evaluated that had components corresponding to the first to third electrolyte shielding portions and a case with negative polarity (i.e., the case was electrically connected to the negative electrode of the electrode group via the negative electrode lead). The maximum temperature of the case during overdischarge was higher than 25°C, and heat generation was observed. Furthermore, during overdischarge, part of the case melted, and most of the negative electrode lead also melted.

[0060] As described above, the primary batteries of each Example did not generate heat during overdischarge and the degree of dissolution of the negative electrode lead was small compared to the primary batteries or secondary batteries of each Comparative Example. Therefore, it can be said that the superiority of each Example was demonstrated.

[0061] The present disclosure can be used in primary batteries.

[0062] 10: Primary battery 20: Electrode group 21: Positive electrode 21a: End 22: Negative electrode 22a: End 23: Separator 23a: End 30: Case 40: Sealing body 41: Sealing plate 42: External terminal 43: Gasket 50: Positive electrode lead 60: Negative electrode lead 61: First main surface 62: Second main surface 63: Side surface 71: First electrolyte solution shielding portion 71a: Interposition portion 72: Second electrolyte solution shielding portion 73: Third electrolyte solution shielding portion 81: Upper insulating plate 82: Lower insulating plate J: Connection portion

Claims

1. A wound electrode group having a positive electrode, a negative electrode composed of a consumable metal, and a separator interposed between the positive electrode and the negative electrode, the electrode group having a first end face and a second end face on the opposite side thereof; an electrolytic solution; a bottomed cylindrical case that houses the electrode group and the electrolytic solution and is electrically connected to the positive electrode; a sealing body that seals the opening of the case; a negative electrode lead having a first main face connected to the negative electrode and a second main face on the opposite side thereof, the negative electrode lead protruding from the first end face to electrically connect the negative electrode and the sealing body; and a first electrolytic solution shielding portion having an intervening portion interposed between the first main face of the negative electrode lead and an end portion on the first end face side of the negative electrode, the first electrolytic solution shielding portion covering a part of the first main face and a part of the second main face. The first electrolytic solution shielding portion extends across the end portion on the first end face side of the positive electrode in the winding axis direction of the electrode group. A primary battery.

2. The primary battery according to claim 1, wherein the first electrolytic solution shielding portion extends across the end portion on the first end face side of the separator in the winding axis direction.

3. Further comprising a second electrolytic solution shielding portion provided on the second main face side of the negative electrode lead and covering a part of the first electrolytic solution shielding portion and a part of the negative electrode lead. The second electrolytic solution shielding portion covers the connection portion between the negative electrode lead and the negative electrode when viewed from the normal direction of the second main face. The primary battery according to claim 1 or 2.

4. Further comprising a third electrolytic solution shielding portion provided on the first main face side of the negative electrode lead and covering a part of the first electrolytic solution shielding portion and a part of the negative electrode. The third electrolytic solution shielding portion covers the connection portion between the negative electrode lead and the negative electrode when viewed from the normal direction of the first main face. The primary battery according to claim 3.

5. The primary battery according to claim 1 or 2, wherein the first electrolytic solution shielding portion is composed of an electrolytic solution shielding tape wound around the negative electrode lead.

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