Lithium primary battery

Abstract

This lithium primary battery comprises a current-collecting wire that electrically connects an electrode body and a sealed body or a battery container. The electrode body is provided with a positive electrode, a negative electrode, and a separator. The negative electrode includes at least one species selected from the group consisting of metallic lithium and a lithium alloy. The current collecting wire is provided with a first lead that is connected to one of the positive electrode and the negative electrode, a second lead that is connected to the sealed body or the battery container, and an overdischarge suppression element that is interposed between the first lead and the second lead. The overdischarge suppression element has a first metal layer that is connected to the first lead and is thinner than the first lead, a second metal layer that is connected to the second lead and is thinner than the second lead, and an electrically conductive layer interposed between the first metal layer and the second metal layer, which are positioned facing each other. The electrically conductive layer contains a resin and an electrically conductive material dispersed in the resin. The electrically conductive material occludes lithium ions at a potential lower than that of the positive electrode.

Description

[Technical field]

[0001] The present invention relates to a lithium primary battery. [Background technology]

[0002] Lithium primary batteries are widely used as power sources for consumer and industrial purposes due to their high voltage and excellent long-term storage characteristics. Depending on the application, multiple lithium primary batteries may be connected in series or parallel.

[0003] When multiple batteries are connected and used, some of the batteries may become over-discharged, causing heat generation and swelling. For example, if there is an individual difference in the discharge capacity of each battery, a battery with a small discharge capacity may be discharged beyond the rated capacity. If the discharge proceeds beyond 100% of the rated capacity of the positive electrode (the limit value for lithium absorption), metallic lithium may precipitate in the form of dendrites on the surface of the positive electrode, penetrating the separator and causing an internal short circuit. Current concentration occurs at the short circuited part, causing the battery to heat up, and the battery may swell due to an increase in internal pressure caused by the decomposition reaction gas of the electrolyte. Therefore, in industrial applications, efforts are being made to control the discharge of each battery by placing a diode in advance for each battery. On the other hand, in consumer devices, similar measures are difficult because there is no individual battery control by the device, and it is therefore necessary to improve the resistance of the battery itself (the battery body).

[0004] Patent Document 1 teaches a battery that is characterized by the electrically insulated conductive polymer piece, whose resistance value increases rapidly with an increase in temperature, being inserted in series in the current path inside the battery case leading to a terminal portion for external connection.

[0005] Patent Document 2 teaches a sealed battery in which an electrode collector 8 is interrupted by a portion protruding from an electrode 3 and composed of an electrode side collector portion 8a and a terminal side collector portion 8b, and a conductive plastic member 9 is interposed between the electrode and terminal side collector portions 8a and 8b, the conductive plastic member 9 having a temperature-electrical resistance characteristic in which the electrical resistance exhibits an extremely low electrical resistance at room temperature but rapidly increases to a high resistance when the temperature inside the battery becomes high, and the electrode side collector portion 8a and the terminal side collector portion 8b are electrically connected by the conductive plastic member 9.

[0006] Patent Document 3 teaches a battery characterized in that at least one electrode of a power generating element housed in the battery is electrically connected to an external terminal of this electrode via a PTC element housed in the battery. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 61-74257 [Patent Document 2] Japanese Utility Model Application Publication No. 1-29973 [Patent Document 3] Japanese Utility Model Application Publication No. 63-202072 Summary of the Invention

[0008] However, the conductive polymer pieces, conductive plastic members, or PTC elements provided in the batteries of Patent Documents 1 to 3 do not fully consider at least the case where the battery is in an overdischarged state, and are activated only when the battery temperature becomes high (e.g., 80°C or higher). Therefore, heat generation in the battery cannot be sufficiently suppressed, and the battery may swell. In addition, if the battery temperature drops, a current may flow through the battery, so that the battery may continue to be in an overdischarged state, making it difficult to safely dispose of the battery.

[0009] One aspect of the present invention provides a battery comprising an electrode assembly, a non-aqueous electrolyte, a battery can containing the electrode assembly and the non-aqueous electrolyte, a sealing body that seals an opening of the battery can, and a current collecting wire that electrically connects the electrode assembly and the sealing body or the electrode assembly and the battery can, the electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the negative electrode containing metallic lithium or a lithium alloy, the current collecting wire being connected to a first lead connected to one of the positive electrode and the negative electrode, and the sealing body or the battery can. the over-discharge prevention element has a first metal layer connected to the first lead and thinner than the first lead, a second metal layer connected to the second lead and thinner than the second lead, and a conductive layer interposed between the first metal layer and the second metal layer arranged opposite each other, the conductive layer including a resin and a conductive material dispersed in the resin, and the conductive material absorbs lithium ions at a lower potential than the positive electrode.

[0010] According to the lithium primary battery of the present invention, the safety of the battery during overdischarge is improved. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic vertical cross-sectional front view of a portion of a lithium primary battery according to an embodiment of the present invention; [Diagram 2] FIG. 2A is a plan view showing the configuration of a current collecting wire that electrically connects an electrode body and a sealing body according to one embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along line bb. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The lithium primary battery according to the present invention comprises an electrode body, a non-aqueous electrolyte, a battery can containing the electrode body and the non-aqueous electrolyte, a sealing body that seals the opening of the battery can, and a current collecting wire that electrically connects the electrode body and the sealing body or the electrode body and the battery can.

[0013] The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The negative electrode includes metallic lithium or a lithium alloy. The positive electrode includes, for example, manganese dioxide as a positive electrode active material.

[0014] Here, the current collecting wire (first current collecting wire) includes a first lead connected to one of the positive and negative electrodes, a second lead connected to the sealing body or the battery can, and an over-discharge prevention element interposed between the first and second leads. That is, the over-discharge prevention element is disposed midway along the first current collecting wire and connects the first and second leads in series. The first current collecting wire may be connected to either the positive or negative electrode.

[0015] When the first current collecting wire connects one of the positive electrode and the negative electrode to the sealing body, the lithium primary battery may further have another current collecting wire (second current collecting wire) that connects the other of the positive electrode and the negative electrode to the battery can. Similarly, when the first current collecting wire connects one of the positive electrode and the negative electrode to the battery can, the lithium primary battery may further have another current collecting wire (second current collecting wire) that connects the other of the positive electrode and the negative electrode to the sealing body.

[0016] The over-discharge prevention element has a first metal layer connected to the first lead and thinner than the first lead, a second metal layer connected to the second lead and thinner than the second lead, and a conductive layer interposed between the first metal layer and the second metal layer arranged opposite each other. In this case, one end of the first lead may be connected to the positive electrode or the negative electrode, and the other end may be connected to the first metal layer. Also, one end of the second lead may be connected to the sealing body or the battery can, and the other end may be connected to the second metal layer. The conductive layer is arranged to fill at least a part of the gap between the first metal layer and the second metal layer. The current flowing through the current collecting wire flows from the electrode to the first lead, the first metal layer, the conductive layer, the second metal layer, the second lead, the sealing body or the battery can (or vice versa).

[0017] The first and second leads are each flexible and made of, for example, metal foil, so that the current collector wire as a whole is flexible. The second current collector wire is also made of, for example, metal foil.

[0018] When the first collector wire (or the second collector wire) is connected to the positive electrode, the material of the metal foil constituting the first lead and the second lead may be, for example, stainless steel (SUS) (preferably SUS444 or SUS316), aluminum (Al), an Al alloy, titanium (Ti), a Ti alloy, etc.

[0019] When the first current collecting wire (or the second current collecting wire) is connected to the negative electrode, the material of the metal foil constituting the first lead and the second lead may be, for example, nickel (Ni), Ni alloy, copper (Cu), Cu alloy, iron (Fe), Fe alloy, SUS, etc. Also, 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.

[0020] The conductive layer includes a resin and a conductive material dispersed in the resin. The conductive material absorbs lithium ions at a potential lower than that of the positive electrode. That is, when the battery is discharged beyond the rated capacity and is in an overdischarged state, the conductive material absorbs lithium ions. As a result, the resistance of the conductive layer increases at the beginning of the overdischarge, and the current is suppressed. Therefore, the heat generation and expansion of the battery are effectively suppressed, and the safety of the battery is improved.

[0021] The principle will be explained below. If the discharge continues even after the positive electrode is sufficiently filled with lithium ions, the lithium ions not absorbed in the positive electrode are absorbed in the conductive material, and the conductive material expands. When the conductive material expands, the conductive layer expands or deforms, and the resistance of the conductive layer increases rapidly. The response speed at this time is very fast, and the heat generation and swelling of the battery can be effectively suppressed. In addition, the absorption of lithium ions by the conductive material proceeds regardless of the battery temperature, so that the heat generation and swelling of the battery can be avoided. In other words, it is not necessary to increase the battery temperature to expand the resin in the conductive layer in order to increase the resistance of the conductive layer. In addition, the increase in the resistance of the conductive layer is irreversible, and the battery is prevented from continuing to be in an overdischarge state thereafter. Therefore, the battery can be safely disposed of.

[0022] The current collecting wire is disposed, for example, in the space between the electrode body and the sealing body, or in the space between the electrode body and the bottom of the battery can. Therefore, the over-discharge prevention element (conductive layer) disposed in the middle of the current path of the current collecting wire (i.e., between the first lead and the second lead) is held in the space between the electrode body and the sealing body or the battery can by the tension of the current collecting wire, and the conductive layer is unlikely to be subjected to a pressing force in the thickness direction. In other words, the over-discharge prevention element is held mainly by the first lead and the second lead. Therefore, when the conductive material absorbs lithium ions, the thickness of the conductive layer changes significantly, and the resistance of the conductive layer is likely to increase sharply.

[0023] In addition, the resistance of the conductive layer increases when the conductive material expands even if the resin does not expand. This is thought to be because the expansion of the conductive material forms voids in the conductive layer, reducing the number of contact points between the conductive materials.

[0024] The over-discharge prevention element is disposed near the electrode body so as to ensure contact with the non-aqueous electrolyte. The closer the conductive layer is disposed to the electrode, the more rapidly the absorption of lithium ions proceeds, and the faster the response speed of current suppression. When the length of the first current collecting wire is L, the distance from the connection point between the first lead and the electrode to the center of the over-discharge prevention element (i.e., the conductive layer) is preferably 2L / 3 or less, and more preferably L / 2 or less. From the viewpoint of faster response speed, it is preferable that the conductive layer is closer to the negative electrode, so the first current collecting wire may be connected to the negative electrode.

[0025] The initial resistance value of the over-discharge prevention element in DC is preferably as small as possible, for example, 70 mΩ or less, more preferably 40 mΩ or less, and even more preferably 10 mΩ or less. Therefore, the thickness of the conductive layer is preferably, for example, 100 μm or more and 400 μm or less, and more preferably, for example, 200 μm or more and 300 μm or less. If the thickness is within this range, it is easy to form a conductive layer that has excellent response speed of current inhibition and small initial resistance value.

[0026] The over-discharge prevention element is composed of a laminate of a first metal layer, a conductive layer, and a second metal layer. In the laminate, the first metal layer is made thinner than the first lead, and the second metal layer is made thinner than the second lead, so that the conductive layer changes in thickness faster, and the response speed of current suppression is faster. The thicknesses of the first metal layer and the second metal layer may be, for example, 0.15 to 0.65 times the thicknesses of the first lead and the second lead, respectively.

[0027] The change in the thickness of the conductive layer is considered to progress from the side of the conductive layer that is in contact with the non-aqueous electrolyte. If the first metal layer and the second metal layer are not used, for example, it is difficult to control the exposed state of the side of the conductive layer, and it is also difficult to control the rate at which lithium ions penetrate into the conductive layer, which may result in a slower response speed of current suppression or a failure of current suppression.

[0028] When the first lead and the second lead are flexible strip-shaped, the first current collecting wire is also flexible strip-shaped overall. Here, when the first lead and the second lead are both narrow strip-shaped, the connection area between the over-discharge prevention element or the conductive layer and each lead is likely to be small. On the other hand, from the viewpoint of minimizing the internal resistance during normal discharge, it is preferable that the connection area is as large as possible. When the first lead is connected to the first metal layer and the second lead is connected to the second metal layer, the connection area can be increased by making the dimensions of each metal layer larger than the width of each lead.

[0029] The width of the first lead and the second lead is not particularly limited, but in the case of a general-purpose lithium primary battery, it is, for example, 3.0 mm to 5.0 mm. Meanwhile, the first metal layer and the second metal layer may be, for example, a plate member having a width 1.1 to 2.0 times the width of each lead, and may be, for example, a disk shape having a diameter larger than the width of each lead.

[0030] The conductive layer may have an elliptical or polygonal shape, but is most preferably circular. In the case of a circular shape, lithium ions can be absorbed uniformly from the outer edge of the conductive layer, so that the conductive layer is likely to expand uniformly, and the response speed of the current suppression becomes faster. In the case of a polygonal shape, the absorption speed of lithium ions differs between the corners and the straight lines, and there may be a portion where the change in the thickness of the conductive layer is small.

[0031] When the conductive layer has a circular shape, the first metal layer and the second metal layer may have a circular shape corresponding to the shape of the conductive layer. In this case, the over-discharge prevention element as a whole has a disk shape. In this case, the diameter D1 of the first metal layer and the diameter D2 of the second metal layer may be the same, and the D1 / D2 ratio may be designed to satisfy 0.95≦D1 / D2≦1.05. In addition, a circular shape does not necessarily mean a mathematically strict circular shape, but may be one that can be regarded as substantially circular. For example, the circularity may be 0.95 or more, and preferably 0.99 or more.

[0032] The thickness of the first lead and the second lead is not particularly limited, but in the case of a general-purpose lithium primary battery, it is, for example, 70 μm to 150 μm. The thickness T1 of the first metal layer and the thickness T2 of the second metal layer may be the same, and may be designed so that the T1 / T2 ratio satisfies, for example, 0.95≦T1 / T2≦1.05. The thickness of each metal layer may be, for example, the average value of the thicknesses of the metal layers measured at any five points.

[0033] The connection between the first lead and the first metal layer and the connection between the second lead and the second metal layer may be performed by soldering, brazing, resistance welding, cold welding, friction welding, friction stir welding, ultrasonic welding, diffusion bonding, arc welding, electron beam welding, laser welding, etc. Bonding with a conductive adhesive is also possible.

[0034] The mechanical strength of the connection between the first lead and the first metal layer, and the connection between the second lead and the second metal layer is important. A specific method for measuring the mechanical strength is as follows. The over-discharge suppression element is fixed, and a tensile shear load is applied to either the first or second lead in parallel to the connection at a constant speed of 20 cm / min. The mechanical strength is determined as the breaking strength. It is preferable that the mechanical strength is 30 N or more. When connecting at multiple points, it is preferable that the total strength of the connection points is 30 N or more.

[0035] The material of the first metal layer and the second metal layer may be, for example, Ni, Cu, SUS, etc. Also, materials that can be used as the material of a current collecting wire, such as a two-layer clad material or a three-layer clad material, may be used.

[0036] The conductive material may be any material that absorbs lithium ions at a lower potential than the positive electrode, and may include at least one selected from the group consisting of metals, metalloids, and carbon materials. As the metal, at least one selected from the group consisting of Al, Zn, Cd, In, Sn, Pb, Ti, and Bi may be used. These may form an alloy. As the metalloid, at least one selected from the group consisting of Ge, Si, Se, and Te may be used. These may form a compound. As the carbon material, at least one selected from the group consisting of graphite, non-graphitizable carbon, carbon black, and carbon fiber may be used. Among these, carbon materials are preferred because they are highly stable in the battery and inexpensive. Among the carbon materials, carbon black is preferred because it is easy to form a thin, highly conductive conductive layer.

[0037] The conductive material may be a particulate material. The average particle size (D50) of the primary particles of the particulate material is preferably 10 nm to 200 nm. If it is 10 nm or more, it is easy to increase the dispersibility of the particulate material in the conductive layer and to reduce the initial resistance. Also, if it is 200 nm or less, it is easy to control the thickness of the conductive layer to be thin and to reduce the initial resistance.

[0038] The average particle size of primary particles (hereinafter referred to as D50) is the 50% cumulative value (median diameter) in the volume-based particle size (particle size) distribution measured using the induction diffraction grating method after ultrasonically dispersing particulate material in a dispersion medium. Measurement devices include the Single Nanoparticle Size Measurement Device IG-1000 Plus (manufactured by Shimadzu Corporation).

[0039] Examples of resins that can be used to disperse the conductive material include rubber (natural rubber, synthetic rubber, etc.), polyolefins (polyethylene, polypropylene, etc.), copolymers of at least one type of olefin and at least one type of polar comonomer, polyarylene, polyester, polyamide, polycarbonate, fluororesin, acrylic polymers, silicone polymers, vinyl ester polymers, etc. These resins may be used alone or in combination of two or more.

[0040] Synthetic rubbers include polyisoprene rubber, styrene-butadiene (SB) rubber, styrene-isoprene (SI) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, styrene-butadiene-styrene block copolymer (SBS) rubber, styrene-ethylene-butylene-styrene block copolymer (SEBS) rubber, styrene-ethylene-propylene-styrene block copolymer (SEPS) rubber, styrene-ethylene-propylene block copolymer (SEP) rubber, reclaimed rubber, butyl rubber, polyisobutylene, and modified versions of these rubber-based polymers.

[0041] The content of the conductive material in the conductive layer (i.e., the content of the conductive material in the total of the resin and the conductive material) may be appropriately selected so as to ensure sufficient conductivity. The content of the conductive material in the conductive layer is preferably, for example, 5% by mass to 80% by mass. By making it 5% by mass or more, the initial resistance of the conductive layer is easily reduced. Furthermore, by making it 80% by mass or less, the process of forming the conductive layer becomes easier. In particular, when carbon black is used as the conductive material, the content of the conductive material in the conductive layer is preferably, for example, 10% by mass to 80% by mass.

[0042] FIG. 1 is a schematic partial vertical cross-sectional front view of a lithium primary battery according to one embodiment of the present invention.

[0043] The lithium primary battery 10 includes a cylindrical battery can 100 with a bottom, a wound electrode body 200 housed in the battery can 100, and a sealing plate 310 that closes the opening of the battery can 100. The periphery of the sealing plate 310 is fixed to the vicinity of the opening of the battery can 100 by welding. An opening is formed in the center of the sealing plate 310, and an external terminal 330 is disposed in this opening. An insulating gasket 320 is disposed between the external terminal 330 and the sealing plate 310. The sealing plate 310, the external terminal 330, and the gasket 320 constitute a sealing body 300.

[0044] The battery can 100 and the sealing plate 310 are each 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.

[0045] The electrode body 200 is constructed by spirally winding a sheet-shaped positive electrode 201 and a sheet-shaped negative electrode 202 with a sheet-shaped separator 203 interposed therebetween. One end of a first current collector wire 210 is connected to one of the positive electrode 201 and the negative electrode 202 (negative electrode 202 in the illustrated example). The other end of the first current collector wire 210 is connected to an external terminal 330 by welding or the like. That is, the first current collector wire 210 connects the negative electrode 202 to the external terminal 330, thereby electrically connecting the electrode body 200 and the sealing body 300. One end of a second current collector wire 220 is connected to the other of the positive electrode 201 and the negative electrode 202 (positive electrode 201 in the illustrated example). The other end of the second current collector wire 220 is connected to the inner surface of the battery can 100 by welding or the like.

[0046] The wound electrode body 200 is housed inside the battery can 100 together with a non-aqueous electrolyte (not shown). To prevent internal short circuits, an upper insulating plate 230A and a lower insulating plate 230B are disposed on the upper and lower parts of the electrode body 200, respectively.

[0047] 2A is a plan view showing the configuration of the first current collector wire, and FIG. 2B is a cross-sectional view of the first current collector wire along line bb. The first current collector wire 210 is composed of a first lead 211, a second lead 212, and an over-discharge prevention element 213 interposed between them. The over-discharge prevention element 213 is composed of a first metal layer 214 connected to the first lead 211, a second metal layer 215 connected to the second lead 212, and a conductive layer 216 that entirely fills the gap between the first metal layer 214 and the second metal layer 215 that are arranged opposite each other. The conductive layer 216 includes a resin and a conductive material dispersed in the resin. The conductive material absorbs lithium ions at a potential lower than that of the positive electrode 201.

[0048] In the cross-sectional view (b), the end of the first lead 211 and the end of the second lead 212 are arranged so as to overlap each other in the thickness direction of the over-discharge prevention element 213. By forming such an overlap, it is possible to further increase the response speed of the current suppression. It is considered that the absorption reaction of lithium ions is likely to proceed quickly in the part of the conductive layer arranged between the overlapping ends of both leads. The overlap width W of both ends and the diameter D of the over-discharge prevention element may satisfy, for example, 0.2≦W / D≦0.9.

[0049] In the illustrated example, a cylindrical lithium primary battery has been described, but the present embodiment is not limited to this case and can be applied to other types of lithium primary batteries. The opening of the battery can may be sealed by crimping it to the periphery of the sealing body. In this case, an insulating gasket is disposed between the opening of the battery can and the periphery of the sealing body.

[0050] Next, a method for producing an overdischarge prevention element will be illustrated. First, a conductive material capable of absorbing lithium ions and a resin are uniformly kneaded to prepare a resin composition. For example, a conductive material is added to a molten resin or a resin solution containing a solvent and mixed uniformly. As a kneading device, a mixer equipped with a stirring blade such as a Banbury mixer, a roll mill, a kneader, a disperser, a high-speed mixer, a tumbler mixer, a planetary mixer, or a Shinagawa mixer is preferable.

[0051] Next, the resin composition is molded into a sheet material having a predetermined thickness by an extrusion method, a calendar method, or the like. When a liquid dispersion medium is used, the sheet material is dried to remove the dispersion medium. Next, a pair of metal layers are bonded to both sides of the sheet material to obtain a laminate of the pair of metal layers and the sheet material interposed therebetween. If the resin is a thermoplastic resin, the bonding can be performed, for example, by heat welding. The laminate is punched into a predetermined shape (for example, a disk shape) to obtain an overdischarge suppression composition. The pair of metal layers function as a first metal layer and a second metal layer, respectively. The sheet material functions as a conductive layer.

[0052] The components of a lithium primary battery are further described below.

[0053] (Negative electrode) The negative electrode contains metallic lithium or metallic lithium and a lithium alloy. Examples of the lithium alloy include Li-Al, Li-Sn, Li-Ni-Si, and Li-Pb. Among the lithium alloys, Li-Al alloys are preferred from the viewpoint of potential and alloying composition with lithium. The content of metal elements other than lithium contained in the lithium alloy is preferably 0.05% by mass or more and 1.0% by mass or less with respect to the metal elements alloyed with lithium. The metallic lithium may contain less than 0.05% by mass of elements other than lithium.

[0054] As the sheet-shaped negative electrode, for example, a metallic lithium foil or a composite sheet containing metallic lithium and a lithium alloy is used. In the composite, the lithium alloy may be dispersed in the metallic lithium in the form of particles. The sheet-shaped negative electrode may be formed, for example, by extruding metallic lithium or metallic lithium and a lithium alloy. The lithium alloy may be formed by attaching an Al lattice or the like to the surface of the metallic lithium foil to alloy the surface layer of the metallic lithium foil.

[0055] (positive electrode) The positive electrode includes a positive electrode active material. As the positive electrode active material, any material used for the positive electrodes of primary and secondary batteries can be selected and used. For example, manganese dioxide, graphite fluoride, iron sulfide, lithium manganate, etc. can be used. The positive electrode includes, for example, a positive electrode current collector and a positive electrode mixture layer including the positive electrode active material.

[0056] The material of the positive electrode current collector may be stainless steel, or a metal material containing Al and / or Ti. As the stainless steel, highly corrosion-resistant materials such as SUS444 and SUS316 are preferable. The metal material containing Al and / or Ti may be an alloy. As the positive electrode current collector, for example, a sheet or a porous body is used. As the positive electrode current collector, a metal foil or the like may be used. As the porous positive electrode current collector, a metal mesh (or net), an expanded metal, a punched metal, or the like may be used.

[0057] The positive electrode mixture constituting the positive electrode mixture layer may contain, in addition to the positive electrode active material, a binder and / or a conductive agent as an optional component. Examples of the binder include fluororesin, polyacrylonitrile, polyimide resin, acrylic resin, polyolefin resin, and rubber-like polymer. Examples of the fluororesin include polytetrafluoroethylene and polyvinylidene fluoride. The positive electrode mixture may contain one type of binder, or two or more types.

[0058] 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.

[0059] The method for producing 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 a positive electrode current collector, or may be filled into a porous positive electrode current collector. 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 using a dispersion medium (for example, water and / or an organic medium) in addition to the components of the positive electrode mixture, as necessary. At an appropriate stage in preparing the positive electrode, drying may be performed as necessary, and the positive electrode may be compressed (rolled, etc.) in the thickness direction.

[0060] From the viewpoint of energy efficiency, it is preferable that the negative electrode capacity Cn is larger than the positive electrode capacity Cp. The ratio of the negative electrode capacity Cn to the positive electrode capacity Cp: Cn / Cp may be larger than 1, for example, 1.05 or more, or may be 1.10 or more. From the viewpoint of ensuring high energy density, it is preferable that the Cn / Cp ratio is 1.15 or less.

[0061] (Separator) The separator is a porous sheet having ion permeability and insulation 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 multi-layer structure. Examples of the separator having a multi-layer structure include a separator including a plurality of layers having different materials and / or structures.

[0062] The material of the separator is not particularly limited, but may be a polymer material. Examples of the polymer material include olefin resins (polyethylene, polypropylene, copolymers of ethylene and propylene, etc.), polyamide resins, polyimide resins (polyimide, polyamideimide, etc.), cellulose, polyphenylene sulfite (PPS), polytetrafluoroethylene (PTFE), etc. The separator may contain additives as necessary. Examples of the additives include inorganic fillers, etc.

[0063] The thickness of the separator can be selected, for example, from the range of 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.

[0064] (Non-aqueous electrolyte) The non-aqueous electrolyte used has 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.

[0065] The lithium salt may be any one used in the non-aqueous electrolyte of a lithium primary battery, 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 may contain two or more types of lithium salts.

[0066] Examples of non-aqueous solvents include, but are not limited to, esters (e.g., carbonate esters, γ-butyrolactone and other carboxylate esters), and ethers (1,2-dimethoxyethane and other). Examples of carbonate esters include cyclic carbonates (propylene carbonate, ethylene carbonate, and other), and chain carbonates (diethyl carbonate, ethyl methyl carbonate, and other). The non-aqueous electrolyte may contain one or more non-aqueous solvents.

[0067] 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.

[0068] The non-aqueous electrolyte may contain additives as necessary. Examples of additives include vinylene carbonate, fluoroethylene carbonate, vinyl ethyl carbonate, etc. The additives may be used alone or in combination of two or more.

[0069] [Example] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0070] Example 1 (1) Preparation of the positive electrode For the positive electrode, 100 parts by mass of electrolytic manganese dioxide that had been baked at 400°C for 7 hours was mixed with 5 parts by mass of acetylene black as a conductive agent, 5 parts by mass of polytetrafluoroethylene as a binder, and an appropriate amount of pure water to prepare a wet positive electrode mixture.

[0071] Next, the wet positive electrode mixture was filled into a positive electrode current collector made of stainless steel (SUS316) expand metal to prepare a positive electrode precursor, which was then dried, rolled by a roll press, and cut to a predetermined size to obtain a sheet-like positive electrode.

[0072] Next, a part of the filled positive electrode mixture was removed by ultrasonic waves, and a second current collecting wire (thickness 150 μm, width 5.0 mm) made of SUS316 was resistance welded to the exposed part of the positive electrode current collector.

[0073] (2) Preparation of the negative electrode The sheet-like metallic lithium was cut to a predetermined size to obtain a sheet-like negative electrode. A first nickel lead (thickness 70 μm, width 5.0 mm) was connected to a predetermined location of the negative electrode by pressure welding. The ratio of the negative electrode capacity Cn to the positive electrode capacity Cp: Cn / Cp was set to 1.1.

[0074] (3) Fabrication of over-discharge prevention element Carbon black (Ketjen Black ECP300J) with an average particle size (D50) of primary particles of 40 nm was used as a conductive material that absorbs lithium ions at a potential lower than that of the positive electrode, and polyolefin was used as a resin. Carbon black and polyolefin were mixed in a mass ratio of 45:55, dry-kneaded at 190°C using a roll mill, and then formed into a sheet material with a thickness of 230 μm by a calendaring method. Next, a pair of nickel foils with a thickness of 40 μm were pressed as metal layers on both sides of the sheet material by hot pressing (thermal welding) to obtain a laminate. Then, the laminate was punched into a disk shape with a diameter of 7.0 mm to obtain an over-discharge prevention element. The resistance in the thickness direction of the over-discharge prevention element was 50 mΩ. The resistance was measured by a direct current four-terminal method using a resistance meter RM3544 (manufactured by Hioki Electric Co., Ltd.).

[0075] (3) Preparation of the electrode body A cylindrical wound electrode body was constructed by spirally winding a positive electrode and a negative electrode with a separator between them, with the positive electrode being disposed on the outermost periphery. The separator used was a three-layered microporous film (40 μm thick) consisting of a polyethylene microporous layer (middle layer: 20 μm thick) and two polypropylene microporous layers (outer layers: 10 μm thick) sandwiching the middle layer.

[0076] (4) Preparation of non-aqueous electrolyte A non-aqueous electrolyte solution was prepared by dissolving lithium trifluoromethanesulfonate as a lithium salt at a concentration of 0.75 mol / L in a non-aqueous solvent prepared by mixing propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) in a volume ratio of 1:1:2.

[0077] (5) Assembly of lithium primary batteries The electrode body, with a ring-shaped lower insulating plate placed on the bottom, was inserted into a bottomed cylindrical battery can made of stainless steel (SUS316). A second current collecting wire was resistance welded to the inner bottom surface of the battery can, which also served as the positive electrode terminal.

[0078] Next, the free end of the first nickel lead pressed onto the negative electrode was resistance welded to one of the nickel foils of the over-discharge prevention element, and then one end of a separately prepared second nickel lead (thickness 70 μm, width 5.0 mm) was resistance welded to the other nickel foil of the over-discharge prevention element to form a first current collecting wire. The first and second leads have the same length, and when the length of the first current collecting wire is L, the distance from the connection point between the first lead and the negative electrode to the center of the over-discharge prevention element (conductive layer) is L / 2.

[0079] After placing an upper insulating plate on the top of the electrode body, the free end side of the second lead of the first current collector wire was resistance-welded to an external terminal (made of stainless steel (SUS316)) fixed to the sealing plate. Next, a nonaqueous electrolyte was poured into the battery can and allowed to permeate the electrode group. After that, a sealing plate was inserted near the opening of the battery can, and the open end of the battery can and the peripheral portion of the sealing plate were laser-welded. In this way, 400 sealed cylindrical lithium primary batteries (diameter 17 mm, height 33.5 mm) having the structure shown in Figure 1 were produced. Then, each battery was pre-discharged so that the battery voltage was 3.2 V.

[0080] Example 2 A battery was produced in the same manner as in Example 1, except that aluminum powder (D50=40 nm) was used as the conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0081] Example 3 A battery was produced in the same manner as in Example 1, except that tin powder (D50=40 nm) was used as the conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0082] Example 4 A battery was produced in the same manner as in Example 1, except that zinc powder (D50=40 nm) was used as the conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0083] Example 5 A battery was produced in the same manner as in Example 1, except that bismuth powder (D50=40 nm) was used as the conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0084] Comparative Example 1 Instead of the first current collecting wire, the following 1a current collecting wire was produced. The 1a current collecting wire was composed of a nickel lead b having the same length as the entire length of the first current collecting wire, and an over-discharge prevention element connected to one end of the lead b. The other end of the nickel lead b was connected to a predetermined location of the negative electrode by pressure welding. Meanwhile, one end of the nickel foil constituting the over-discharge prevention element was resistance welded to an external terminal fixed to the sealing plate.

[0085] Comparative Example 2 A battery was produced in the same manner as in Example 1, except that copper powder (D50=40 nm) was used as the conductive material.

[0086] (6) Evaluation The following safety evaluation was carried out using the prepared lithium primary batteries.

[0087] 100 of each type of battery were discharged to 100% of the rated capacity. Next, 100 12V battery groups were formed by connecting three unused batteries and one discharged battery in series, and discharged by connecting a 1Ω resistor at an ambient temperature of 20°C. Table 1 shows the maximum temperature reached at the center of the discharged battery and the swelling of the battery (height change rate R). The change rate of the battery outer diameter before and after the test was 0.1% or less, which is very small compared to the height change rate, and the change in outer diameter can be ignored. In Table 1, the batteries of Examples 1 to 5 are referred to as batteries A1 to A5, and the batteries of Comparative Examples 1 and 2 are referred to as batteries B1 to B2.

[0088] [Table 1]

[0089] In the batteries A1 to A5 of the embodiment, the maximum temperature reached was less than 40° C. and the height change rate was less than 1% in all the battery groups. This is because the resistance value of the conductive layer in the discharged batteries increased instantly and the overdischarge was completely stopped.

[0090] On the other hand, in the battery B1 of Comparative Example 1, the maximum temperature reached was 80°C or higher, and the battery swelled significantly. This is thought to be because the distance between the over-discharge prevention element and the electrode body was large, which made it impossible to ensure sufficient contact with the electrolyte, and because the over-discharge prevention element was directly connected to the external terminal, which suppressed the expansion and deformation of the conductive layer.

[0091] The maximum temperature reached in battery B2 of Comparative Example 2 was 80° C. or higher, and the battery swelled significantly. This is believed to be because the conductive material Cu was unable to absorb lithium, and the conductive layer was unable to expand. [Industrial Applicability]

[0092] The lithium primary battery according to the present invention is excellent in safety against over-discharge and is therefore suitable for incorporation into devices in which multiple batteries are connected and used, such as AEDs (automated external defibrillators), lights, and other devices. [Explanation of symbols]

[0093] 10 Lithium primary batteries 100 Battery Cans 200 Electrode body 201 Positive electrode 202 Negative electrode 203 Separator 210 First current collector wire 211 1st Lead 212 2nd Lead 213 Over-discharge prevention element 214 1st metal layer 215 2nd metal layer 216 Conductive Layer 220 Second collector wire 230A Upper insulation plate 230B Lower insulation plate 300 Sealing body 310 Sealing plate 320 Gasket 330 External terminal

Claims

1. an electrode assembly, a non-aqueous electrolyte, a battery can containing the electrode assembly and the non-aqueous electrolyte, a sealing body that seals an opening of the battery can, and a current collecting wire that electrically connects the electrode assembly and the sealing body; an insulating plate provided between the electrode body and the sealing body; The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The negative electrode comprises metallic lithium or a metallic lithium and a lithium alloy, the current collecting wire comprises a first lead connected to one of the positive electrode and the negative electrode, a second lead connected to the sealing body, and an over-discharge prevention element interposed between the first lead and the second lead; the over-discharge prevention element has a first metal layer connected to the first lead and thinner than the first lead, a second metal layer connected to the second lead and thinner than the second lead, and a conductive layer interposed between the first metal layer and the second metal layer arranged opposite each other, the conductive layer includes a resin and a conductive material dispersed in the resin, the over-discharge prevention element is disposed between the insulating plate and the sealing body, When the length of the current collecting wire is L, the distance from the connection point between the first lead and the positive electrode or the negative electrode to the center of the over-discharge prevention element is 2L / 3 or less, The conductive material absorbs lithium ions at a lower potential than the positive electrode.

2. an electrode assembly, a non-aqueous electrolyte, a battery can containing the electrode assembly and the non-aqueous electrolyte, a sealing body that seals an opening of the battery can, and a current collecting wire that electrically connects the electrode assembly and the sealing body or the electrode assembly and the battery can; The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The negative electrode comprises metallic lithium or a metallic lithium and a lithium alloy, the current collecting wire comprises a first lead connected to one of the positive electrode and the negative electrode, a second lead connected to the sealing body or the battery can, and an over-discharge prevention element interposed between the first lead and the second lead; the over-discharge prevention element has a first metal layer connected to the first lead and thinner than the first lead, a second metal layer connected to the second lead and thinner than the second lead, and a conductive layer interposed between the first metal layer and the second metal layer arranged opposite each other, the conductive layer includes a resin and a conductive material dispersed in the resin, The conductive material absorbs lithium ions at a lower potential than the positive electrode, The conductive layer is held so as not to be subjected to a pressing force in a thickness direction.

3. 3. The lithium primary battery according to claim 1, wherein the first lead is connected to the negative electrode.

4. 4. The lithium primary battery according to claim 1, wherein the conductive layer has a circular shape.

5. The lithium primary battery according to any one of claims 1 to 4, wherein the positive electrode contains manganese dioxide as a positive electrode active material.

6. The lithium primary battery according to any one of claims 1 to 5, wherein the conductive material comprises at least one selected from the group consisting of metals, semi-metals, and carbon materials.

7. 7. The lithium primary battery according to claim 6, wherein the metal comprises at least one selected from the group consisting of Al, Zn, Cd, In, Sn, Pb, Ti and Bi.

8. 7. The lithium primary battery according to claim 6, wherein the metalloid comprises at least one selected from the group consisting of Ge, Si, Se, and Te.

9. 7. The lithium primary battery according to claim 6, wherein the carbon material comprises at least one selected from the group consisting of graphite, non-graphitizable carbon, carbon black, and carbon fiber.

10. an electrode assembly, a non-aqueous electrolyte, a battery can containing the electrode assembly and the non-aqueous electrolyte, a sealing body that seals an opening of the battery can, and a current collecting wire that electrically connects the electrode assembly and the sealing body or the electrode assembly and the battery can; The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The negative electrode comprises metallic lithium or a metallic lithium and a lithium alloy, the current collecting wire comprises a first lead connected to one of the positive electrode and the negative electrode, a second lead connected to the sealing body or the battery can, and an over-discharge prevention element interposed between the first lead and the second lead; the over-discharge prevention element has a first metal layer connected to the first lead and thinner than the first lead, a second metal layer connected to the second lead and thinner than the second lead, and a conductive layer interposed between the first metal layer and the second metal layer arranged opposite each other, the conductive layer includes a resin and a conductive material dispersed in the resin, The conductive material absorbs lithium ions at a lower potential than the positive electrode, The conductive layer has a circular shape.

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