Lithium primary battery

Abstract

A lithium primary battery, comprising a collector electrically connecting an electrode body to a sealing body or a battery can, the electrode body comprising a positive electrode, a negative electrode and a separator, the negative electrode comprising at least one selected from metallic lithium and a lithium alloy, the collector comprising 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 overdischarge suppression element between the first lead and the second lead, the overdischarge suppression element comprising 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 between the first metal layer and the second metal layer arranged opposite to each other, the conductive layer comprising a resin and a conductive material dispersed in the resin, the conductive material absorbing lithium ions at a lower potential than the positive electrode.

Description

Technical Field

[0001] The present invention relates to lithium primary batteries. Background Art

[0002] Lithium primary batteries are widely used as power sources for civil and industrial use because they have excellent long-term storage characteristics at high voltages. Depending on the application, multiple lithium primary batteries may be connected in series or in parallel for use.

[0003] When multiple batteries are connected and used, some of the batteries become over-discharged, generating heat and swelling. For example, when there are individual differences in the discharge capacity of each battery, the battery with a small discharge capacity can be discharged to a capacity above the rated capacity. If the discharge is performed in a manner exceeding 100% of the rated capacity of the positive electrode (the limit value that can absorb lithium), the metallic lithium precipitates in the form of dendrites on the surface of the positive electrode, which can penetrate the separator and cause an internal short circuit. Current concentration occurs in the short-circuit portion, the battery heats up, or the internal pressure rises due to the decomposition reaction gas of the electrolyte, causing swelling in the battery. Therefore, for industrial use, efforts have been made to configure a diode in each battery in advance to control the discharge of each battery. On the other hand, for civilian equipment, since there is no individual battery control according to the equipment, the same response is difficult, and the endurance of the battery itself (battery body) is sought to be improved.

[0004] Patent Document 1 teaches a battery characterized in that a conductive polymer sheet whose resistance value increases sharply due to a temperature rise is inserted in electrical series into a current path in a battery case that reaches a terminal for external connection.

[0005] Patent document 2 teaches a sealed battery, characterized in that the electrode collector 8 is interrupted at the portion protruding from the electrode 3 and is composed of an electrode side collector portion 8a and a terminal side collector portion 8b, between which a conductive plastic component 9 having a temperature-resistance characteristic of showing an extremely low resistance value at room temperature and rapidly becoming a high resistance value when the temperature inside the battery becomes high is inserted, and the above-mentioned electrode side collector portion 8a and the terminal side collector portion 8b are electrically connected via the conductive plastic component 9.

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

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 61-74257

[0010] Patent Document 2: Japanese Utility Model Publication No. 1-29973

[0011] Patent Document 3: Japanese Utility Model Application Laid-Open No. 63-202072 Summary of the invention

[0012] However, the conductive polymer sheets, conductive plastic parts or PTC elements of the batteries of Patent Documents 1 to 3 do not fully consider the situation that the battery becomes over-discharged, and the battery temperature is operated from a high temperature (e.g., 80° C. or above). Therefore, the heat generation of the battery cannot be fully suppressed, and the battery may swell. In addition, if the battery temperature drops, current may flow through the battery thereafter, so there is a possibility that the battery continues to be in an over-discharged state, making it difficult to safely discard the battery.

[0013] One aspect of the present invention relates to a lithium primary battery, comprising an electrode body, a non-aqueous electrolyte, a battery can containing the electrode body and the non-aqueous electrolyte, a sealing body for sealing an opening of the battery can, and a collector electrically connecting the electrode body to the sealing body or the electrode body to the battery can, wherein the electrode body comprises a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, the negative electrode comprises metallic lithium, or metallic lithium and a lithium alloy, the collector comprises a first lead connected to one of the positive electrode and the negative electrode, a first lead connected to the positive electrode, and a first lead connected to the negative electrode. A sealing body or a second lead of the battery can, and an overdischarge suppression element between the first lead and the second lead, the overdischarge suppression element having 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 between the first metal layer and the second metal layer arranged opposite to each other, the conductive layer comprising a resin and a conductive material dispersed in the resin, the conductive material absorbing lithium ions at a lower potential than the positive electrode.

[0014] According to the lithium primary battery of the present invention, the safety of the battery during overdischarge is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a front view schematically showing a portion of a lithium primary battery according to one embodiment of the present invention in longitudinal section.

[0016] Figure 2 1 and 1 , a plan view (a) and a bb line cross-sectional view (b) showing the structure of a collector that electrically connects an electrode body and a sealing body according to one embodiment of the present invention. DETAILED DESCRIPTION

[0017] The lithium primary battery according to the present invention comprises an electrode body, a nonaqueous electrolyte, a battery can containing the electrode body and the nonaqueous electrolyte, a sealing body for sealing an opening of the battery can, and a collector electrically connecting the electrode body and the sealing body or the electrode body and the battery can.

[0018] The electrode body includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode. The negative electrode includes metallic lithium or metallic lithium and a lithium alloy. The positive electrode includes, for example, manganese dioxide as a positive electrode active material.

[0019] Here, the collector (first collector) includes: 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 overdischarge suppression element interposed between the first lead and the second lead. That is, the overdischarge suppression element is arranged in the middle of the first collector and connects the first lead and the second lead in series. The first collector can be connected to either the positive electrode or the negative electrode.

[0020] It should be noted that, when the first collector connects one of the positive electrode and the negative electrode to the sealing body, the lithium primary battery may further include another collector (second collector) connecting the other of the positive electrode and the negative electrode to the battery can. Similarly, when the first collector connects one of the positive electrode and the negative electrode to the battery can, the lithium primary battery may further include another collector (second collector) connecting the other of the positive electrode and the negative electrode to the sealing body.

[0021] The overdischarge suppression element comprises: a first metal layer connected to a first lead and thinner than the first lead, a second metal layer connected to a second lead and thinner than the second lead, and a conductive layer between the first metal layer and the second metal layer arranged opposite to each other. In this case, one end of the first lead can be connected to the positive electrode or the negative electrode, and the other end can be connected to the first metal layer. In addition, one end of the second lead can be connected to a sealing body or a battery can, and the other end can be connected to the second metal layer. The conductive layer is configured so as to fill at least a portion of the gap between the first metal layer and the second metal layer. The current flowing through the collector flows from the electrode in the order of 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 in the reverse order).

[0022] The first lead and the second lead are each flexible, and are formed of, for example, a metal foil. Thus, the collector is flexible as a whole. The second collector is also formed of, for example, a metal foil.

[0023] When the first collector (or the second collector) is connected to the positive electrode, the material of the metal foil constituting the first lead and the second lead can be, for example, stainless steel (SUS) (preferably SUS444 or SUS316), aluminum (Al), Al alloy, titanium (Ti), Ti alloy, etc.

[0024] When the first collector (or the second collector) is connected to the negative electrode, the material of the metal foil constituting the first lead and the second lead can be, for example, nickel (Ni), Ni alloy, copper (Cu), Cu alloy, iron (Fe), Fe alloy, SUS, etc. In addition, two-layer coating materials such as Ni / Cu, Ni / Fe, Ni / SUS, Cu / SUS, and three-layer coating materials such as Ni / Fe / Ni, Ni / Cu / Ni, SUS / Cu / SUS, and Ni / SUS / Ni can also be used.

[0025] 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. That is, if the battery is discharged to a capacity above the rated capacity and becomes an over-discharged state, the conductive material absorbs lithium ions. As a result, at the initial stage of over-discharge, the resistance of the conductive layer increases and the current is suppressed. As a result, the heating and expansion of the battery are effectively suppressed, and the safety of the battery is improved.

[0026] The principle is explained below. If the positive electrode is fully filled with lithium ions and continues to discharge, the lithium ions that are not absorbed by the positive electrode are absorbed by the conductive material, and the conductive material expands. If the conductive material expands, the conductive layer expands or deforms, and the resistance of the conductive layer rises sharply. The response speed at this time is very fast, and the heating and expansion of the battery can be effectively suppressed. In addition, since the absorption of lithium ions by the conductive material is carried out independently of the battery temperature, the heating and expansion of the battery can be avoided. That is, there is no need to increase the battery temperature and 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 thereafter, the battery is prevented from continuing to be in an over-discharged state. In this way, the battery can be safely discarded.

[0027] The collector is arranged, 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. As a result, the overdischarge suppression element (conductive layer) arranged in the middle of the current path of the collector (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 collector, and the conductive layer is not easily subjected to pressure in the thickness direction. In other words, the overdischarge suppression element is mainly held by the first lead and the second lead. Therefore, the thickness of the conductive layer changes greatly when the conductive material absorbs lithium ions, and the resistance increase of the conductive layer tends to become steep.

[0028] It should be noted that even if the resin does not expand, the resistance of the conductive layer increases due to the expansion of the conductive material. This is considered to be because the expansion of the conductive material forms voids in the conductive layer and reduces the number of contact points between the conductive materials.

[0029] The overdischarge suppression element is arranged near the electrode body so that it can ensure contact with the non-aqueous electrolyte. The closer the conductive layer is arranged to the electrode, the faster the lithium ion absorption is carried out, and the faster the response speed of the current suppression is. When the length of the first collector is set to L, the distance from the connection point between the first lead and the electrode to the center of the overdischarge suppression element (i.e., the conductive layer) is preferably less than 2L / 3, and more preferably less than L / 2. From the viewpoint of further accelerating the response speed, it is desired that the conductive layer is as close to the negative electrode as possible, so the first collector can be connected to the negative electrode.

[0030] It is desirable that the initial resistance value of the DC of the overdischarge suppression element is as small as possible, for example, preferably 70 mΩ or less, more preferably 40 mΩ or less, and further preferably 10 mΩ or less. Therefore, the thickness of the conductive layer is preferably 100 μm or more and 400 μm or less, for example, more preferably 200 μm or more and 300 μm or less. If it is within such a thickness range, it is easy to form a conductive layer with excellent response speed of current suppression and small initial resistance value.

[0031] The overdischarge suppression element is composed of a laminate of a first metal layer, a conductive layer, and a second metal layer. In the laminate, by making the first metal layer thinner than the first lead and the second metal layer thinner than the second lead, the thickness change of the conductive layer becomes faster, and the response speed of current suppression becomes faster. The thickness of the first metal layer and the second metal layer can be, for example, 0.15 to 0.65 times the thickness of the first lead and the second lead, respectively.

[0032] It should be noted that it is believed that the change in the thickness of the conductive layer is carried out from the side of the conductive layer in contact with the nonaqueous electrolyte. When the first metal layer and the second metal layer are not used, for example, there is the following situation: it is difficult to control the exposure state of the side of the conductive layer, the control of the intrusion speed of lithium ions into the conductive layer also becomes difficult, the response speed of current suppression decreases, or current suppression becomes ineffective.

[0033] In the case where the first lead and the second lead are in the form of flexible strips, the first collector is also in the form of a flexible strip as a whole. Here, in the case where both the first lead and the second lead are in the form of narrow strips, the connection area between the overdischarge suppression element or the conductive layer and each lead is likely to become smaller. On the other hand, from the viewpoint of minimizing the internal resistance during normal discharge, it is desirable that the above-mentioned connection area is as large as possible. In the case where the first lead is connected to the first metal layer and the second lead is connected to the second metal layer, the above-mentioned connection area can be increased by making the size of each metal layer larger than the width of each lead.

[0034] The width of the first lead and the second lead is not particularly limited, but in the case of a general lithium primary battery, it is, for example, 3.0 mm to 5.0 mm. On the other hand, 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, or may be, for example, a disc having a diameter larger than the width of each lead.

[0035] It should be noted that the shape of the conductive layer may also be an ellipse, a polygon, etc., but a circle is most preferred. In the case of a circle, lithium ions can be uniformly absorbed from the outer edge of the conductive layer, so that the conductive layer is easy to expand uniformly, and the response speed of current suppression is further accelerated. In the case of a polygon, the absorption speed of lithium ions is different for the corner and the straight line, and a portion where the thickness change of the conductive layer is reduced may be generated.

[0036] When the shape of the conductive layer is circular, the shapes of the first metal layer and the second metal layer can be set to circular corresponding to the shape of the conductive layer. In this case, the over-discharge suppression element becomes a disc as a whole. At this time, the diameter D1 of the first metal layer and the diameter D2 of the second metal layer can be set to be the same, or the design can be made so that the D1 / D2 ratio satisfies 0.95≤D1 / D2≤1.05. In addition, the so-called circular does not necessarily mean a mathematically precise circle, but can be regarded as a circle in essence. For example, the circularity can be greater than 0.95, preferably greater than 0.99.

[0037] In addition, the thickness of the first lead and the second lead is not particularly limited, but in the case of a general lithium primary battery, it is preferably 70 μm to 150 μm. The thickness T1 of the first metal layer and the thickness T2 of the second metal layer can be set to be the same, or the design can be such that the T1 / T2 ratio satisfies, for example, 0.95≤T1 / T2≤1.05. The thickness of each metal layer can be, for example, the average value when the thickness of the metal layer is measured at any five positions.

[0038] The connection between the first lead and the first metal layer and the connection between the second lead and the second metal layer can be performed by welding, brazing, resistance welding, room temperature pressure welding, friction pressure welding, friction stir welding, ultrasonic welding, diffusion welding, arc welding, electron beam welding, laser welding, etc. The connection can also be performed by using a conductive adhesive.

[0039] 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 are important. The specific method for measuring the mechanical strength is shown below. The mechanical strength is defined as the breaking strength when a tensile shear load is applied to either the first or second lead at a constant speed of 20 cm / min in parallel with the connection while the over-discharge suppression element is fixed. The mechanical strength is preferably 30N or more. When connections are made at multiple locations, it is preferred that the sum of the strengths of the connection locations be 30N or more.

[0040] The material of the first metal layer and the second metal layer may be, for example, Ni, Cu, SUS, etc. In addition, materials that can be used as materials for collectors, such as two-layer cladding materials and three-layer cladding materials, may also be used.

[0041] The conductive material is a material that absorbs lithium ions at a lower potential than the positive electrode, and may include, for example, at least one selected from metals, metalloids, and carbon materials. As a metal, for example, at least one selected from Al, Zn, Cd, In, Sn, Pb, Ti, and Bi may be used. They may form alloys. As a metalloid, for example, at least one selected from Ge, Si, Se, and Te may be used. They may form compounds. As a carbon material, for example, at least one selected from graphite, difficult-to-graphitize carbon, carbon black, and carbon fiber may be used. Among them, carbon materials are preferred in terms of high stability and low cost within the battery. In addition, among carbon materials, carbon black is preferred in terms of easy formation of a thin and highly conductive conductive layer.

[0042] 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 improve the dispersibility of the particulate material in the conductive layer and to reduce the initial resistance. In addition, by setting it to 200 nm or less, it is easy to control the thickness of the conductive layer to be thinner and to reduce the initial resistance.

[0043] The so-called average particle size of primary particles (hereinafter referred to as D50) is the value of the 50% cumulative value (median particle size) in the volume-based particle size (particle size) distribution measured by the inductive diffraction grating method after ultrasonic dispersion treatment of the particulate material in the dispersion medium. As a measuring device, there is a single nanoparticle size measuring device IG-1000Plus (manufactured by Shimadzu Corporation) and the like.

[0044] As the resin for dispersing the conductive material, rubber (natural rubber, synthetic rubber, etc.), polyolefin (polyethylene, polypropylene, etc.), copolymers of at least one olefin and at least one polar comonomer, polyarylene, polyester, polyamide, polycarbonate, fluororesin, acrylic polymer, silicone polymer, vinyl ester polymer, etc. can be used. These resins can be used alone or in combination of two or more.

[0045] Examples of the synthetic rubber 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, recycled rubber, butyl rubber, polyisobutylene, and rubber polymers such as modified products thereof.

[0046] 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) can be appropriately selected in a manner that can ensure sufficient conductivity. The content of the conductive material in the conductive layer is preferably, for example, 5% to 80% by mass. By setting it to 5% or more by mass, it is easy to reduce the initial resistance of the conductive layer. In addition, by setting it to 80% or less by mass, the formation process of the conductive layer becomes easy. Among them, when carbon black is used as the conductive material, the content of the conductive material in the conductive layer is preferably, for example, 10% to 80% by mass.

[0047] Figure 1 This is a front view schematically showing a portion of a lithium primary battery according to one embodiment of the present invention in longitudinal section.

[0048] The lithium primary battery 10 includes: a battery can 100 having a bottom, a wound electrode body 200 housed in the battery can 100, and a sealing plate 310 that blocks 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 arranged at the opening. An insulating gasket 320 is arranged between the external terminal 330 and the sealing plate 310. The sealing plate 310, the external terminal 330, and the sealing gasket 320 constitute a sealing body 300.

[0049] The battery can 100 and the sealing plate 310 are respectively made of, for example, iron, iron alloy (SUS, etc.), aluminum, aluminum alloy (aluminum alloy containing trace amounts of other metals such as manganese and copper, etc.), and may be plated as necessary.

[0050] The electrode body 200 is formed by winding a sheet-like positive electrode 201 and a sheet-like negative electrode 202 into a spiral shape via a sheet-like separator 203. One end of the first collector 210 is connected to one of the positive electrode 201 and the negative electrode 202 (the negative electrode 202 in the example shown in the figure). The other end of the first collector 210 is connected to the external terminal 330 by welding or the like. That is, the first collector 210 connects the negative electrode 202 to the external terminal 330, thereby electrically connecting the electrode body 200 to the sealing body 300. The other end of the positive electrode 201 and the negative electrode 202 (the positive electrode 201 in the example shown in the figure) is connected to one end of the second collector 220. The other end of the second collector 220 is connected to the inner surface of the battery can 100 by welding or the like.

[0051] The wound electrode body 200 is accommodated together with a non-aqueous electrolyte (not shown) in the battery can 100. To prevent internal short circuit, 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.

[0052] Figure 2 1 is a top view (a) and a bb line cross-sectional view (b) showing the structure of the first collector. The first collector 210 is composed of a first lead 211, a second lead 212, and an overdischarge suppression element 213 interposed therebetween. The overdischarge suppression 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 fills the gap between the first metal layer 214 and the second metal layer 215 disposed opposite to 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 lower potential than the positive electrode 201.

[0053] 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 suppression element 213. By forming such an overlap, the response speed of current suppression can be further accelerated. It is believed that the portion of the conductive layer arranged between the ends of the two overlapping leads is easy to quickly perform the lithium ion absorption reaction. The overlapping width W of the two ends and the diameter D of the over-discharge suppression element can satisfy, for example, 0.2≤W / D≤0.9.

[0054] In the illustrated example, a cylindrical lithium primary battery is described, but the present embodiment is not limited to this case, and the present embodiment can also be applied to lithium primary batteries of other types. In addition, the opening of the battery can can also be sealed by riveting to the peripheral portion of the sealing body. In this case, an insulating sealing gasket is arranged between the opening of the battery can and the peripheral portion of the sealing body.

[0055] Next, the method for making an over-discharge suppression element is exemplified. First, a conductive material capable of absorbing lithium ions is uniformly mixed with a resin to prepare a resin composition. For example, a conductive material is added to a molten resin or a resin solution containing a solvent and uniformly mixed. As a mixing device, a mixer with stirring blades such as a Banbury mixer, a roller mill, a kneader, a disperser, a high-speed mixer, a drum mixer, a planetary mixer, and a Shinagawa mixer is preferred.

[0056] Next, the resin composition is formed into a sheet having a specified thickness by extrusion, calendaring, or the like. When a liquid dispersion medium is used, the sheet is dried and the dispersion medium is removed. Next, a pair of metal layers are bonded to both sides of the sheet to obtain a laminate of a pair of metal layers and a sheet therebetween. Regarding bonding, if the resin is a thermoplastic resin, it can be performed, for example, by thermal welding. An overdischarge suppression composition can be obtained by punching the laminate into a specified shape (e.g., a disc shape). A pair of metal layers act as the first metal layer and the second metal layer, respectively. The sheet acts as a conductive layer.

[0057] Hereinafter, the constituent elements of the lithium primary battery will be further described.

[0058] (negative electrode)

[0059] The negative electrode comprises metallic lithium or metallic lithium and a lithium alloy. Examples of lithium alloys include Li-Al, Li-Sn, Li-Ni-Si, and Li-Pb. Among lithium alloys, Li-Al alloys are preferred from the viewpoint of potential and alloying composition with lithium. Regarding the content of metal elements other than lithium contained in the lithium alloy, it is preferably set to 0.05 mass % or more and 1.0 mass % or less relative to the metal elements alloyed with lithium. It should be noted that metallic lithium may contain less than 0.05 mass % of elements other than lithium.

[0060] As a sheet-like negative electrode, for example, a metal lithium foil or a sheet containing a composite of metal lithium and a lithium alloy can be used. In the composite, the lithium alloy can be dispersed in the metal lithium in a particle-like manner. The sheet-like negative electrode can be formed by, for example, extruding metal lithium, or metal lithium and a lithium alloy. Regarding the lithium alloy, an Al lattice can be attached to the surface of the metal lithium foil and the surface layer of the metal lithium foil can be alloyed to form it.

[0061] (positive electrode)

[0062] The positive electrode includes a positive electrode active material. As the positive electrode active material, a material used for the positive electrode of a primary battery and a secondary battery can be arbitrarily selected and used. For example, manganese dioxide, graphite fluoride, iron sulfide, lithium manganate, etc. can be used. The positive electrode, for example, includes a positive electrode collector and a positive electrode mixture layer including the positive electrode active material.

[0063] As the material of the positive electrode collector, stainless steel, metal materials containing Al and / or Ti, etc. can be used. As stainless steel, highly corrosion-resistant stainless steel such as SUS444 and SUS316 are preferred. The metal material containing Al and / or Ti can be an alloy. As the positive electrode collector, for example, a sheet or a porous body is used. As the positive electrode collector, a metal foil or the like can also be used. In addition, as a porous positive electrode collector, a metal grid (or net), an expanded alloy, a punched metal, etc. can be used.

[0064] The positive electrode mixture constituting the positive electrode mixture layer may also include a binder and / or a conductive agent as an arbitrary component in addition to the positive electrode active material. As the binder, for example, fluororesin, polyacrylonitrile, polyimide resin, acrylic resin, polyolefin resin, rubber-like polymer, etc. may be cited. As the fluororesin, polytetrafluoroethylene, polyvinylidene fluoride, etc. may be cited. The positive electrode mixture may include one binder, or may include two or more binders.

[0065] As the conductive agent, a carbon material is preferred. Examples of the carbon material include carbon black (acetylene black, Ketjen black, etc.), carbon nanotubes, and graphite. The positive electrode mixture may include one or more conductive agents. The conductive agent may also be present between the positive electrode current collector and the positive electrode mixture layer.

[0066] There is no particular limitation on the method for manufacturing the positive electrode. The positive electrode can be obtained, for example, by attaching the positive electrode mixture to the positive electrode collector. For example, the positive electrode mixture can be applied to the positive electrode collector, or the positive electrode mixture can be filled in a porous positive electrode collector. In addition, the positive electrode mixture can be formed into a sheet and stacked so that it is in physical contact with the positive electrode collector. When making the positive electrode, the positive electrode mixture can be used in a paste or clay form in addition to the constituent components of the positive electrode mixture using a dispersion medium (for example, water and / or an organic medium). At an appropriate stage in the production of the positive electrode, drying can be performed as required, and compression (calendering, etc.) in the thickness direction of the positive electrode can also be performed.

[0067] From the viewpoint of energy efficiency, the capacity Cn of the negative electrode is preferably larger than the capacity Cp of the positive electrode. The ratio of the capacity Cn of the negative electrode to the capacity Cp of the positive electrode: Cn / Cp may be greater than 1, for example, 1.05 or more, or 1.10 or more. From the viewpoint of ensuring high energy density, the Cn / Cp ratio is preferably 1.15 or less.

[0068] (Spacer)

[0069] The spacer uses a porous sheet having ion permeability and insulation. Examples of the porous sheet include microporous membranes, woven fabrics, and nonwoven fabrics. The spacer may be a single-layer structure or a multi-layer structure. Examples of the multi-layer structure spacer include a spacer including multiple layers of different materials and / or structures.

[0070] The material of the spacer is not particularly limited and can be a polymer material. As the polymer material, olefin resins (polyethylene, polypropylene, and copolymers of ethylene and propylene, etc.), polyamide resins, polyimide resins (polyimide, polyamide-imide, etc.), cellulose, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), etc. can be cited. As needed, the spacer can contain additives. As additives, inorganic fillers, etc. can be cited.

[0071] The thickness of the separator can be selected from the range of, for example, 10 μm to 200 μm. When the separator is formed of a microporous film, the thickness of the separator is, for example, 10 μm to 80 μm, preferably 20 μm to 70 μm.

[0072] (Non-aqueous electrolyte)

[0073] As the non-aqueous electrolyte, a non-aqueous electrolyte having lithium ion conductivity is used. 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.

[0074] As the lithium salt, any lithium salt that can be used in a non-aqueous electrolyte of a lithium primary battery can be used without particular limitation. Examples of the lithium salt include lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium perchlorate. The non-aqueous electrolyte may contain one lithium salt or two or more lithium salts.

[0075] As the non-aqueous solvent, for example, esters (such as carbonates, carboxylates such as γ-butyrolactone, etc.), ethers (1,2-dimethoxyethane, etc.) can be cited, but are not limited to these. As carbonates, cyclic carbonates (propylene carbonate, ethylene carbonate, etc.), chain carbonates (diethyl carbonate, methyl ethyl carbonate, etc.) can be cited. The non-aqueous electrolyte can contain one or more non-aqueous solvents.

[0076] The concentration of the lithium salt in the non-aqueous electrolyte is, for example, 0.1 mol / L or more and 3.5 mol / L or less.

[0077] The non-aqueous electrolyte may contain additives as required. Examples of the additives include vinylene carbonate, fluoroethylene carbonate, vinyl ethyl carbonate, etc. The additives may be used alone or in combination of two or more.

[0078] [Example]

[0079] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0080] 《Example 1》

[0081] (1) Preparation of positive electrode

[0082] As a positive electrode, 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 were added to 100 parts by mass of electrolytic manganese dioxide calcined at 400° C. for 7 hours and kneaded to prepare a wet positive electrode mixture.

[0083] Next, the wet positive electrode mixture is filled into a positive electrode current collector formed of an expanded alloy made of stainless steel (SUS316) to prepare a positive electrode precursor. Thereafter, the positive electrode precursor is dried, rolled by a roll press, and cut into a predetermined size to obtain a sheet-shaped positive electrode.

[0084] Next, a portion of the filled positive electrode mixture was removed by ultrasonic wave, and a second collector line (thickness 150 μm, width 5.0 mm) made of SUS316 was resistance-welded to the portion where the positive electrode current collector was exposed.

[0085] (2) Preparation of negative electrode

[0086] The sheet of metal lithium was cut into a predetermined size to obtain a sheet of negative electrode. A nickel first lead (thickness 70 μm, width 5.0 mm) was connected to a predetermined position of the negative electrode by crimping. The ratio of the negative electrode capacity Cn to the positive electrode capacity Cp: Cn / Cp was set to 1.1.

[0087] (3) Fabrication of overdischarge suppression element

[0088] As a conductive material for absorbing lithium ions at a lower potential than the positive electrode, carbon black (Ketjen Black ECP300J) with an average particle size (D50) of 40 nm in primary particles was used, and polyolefin was used as a resin. Carbon black and polyolefin were mixed in a mass ratio of 45:55, and after dry kneading at 190°C using a roller mill, they were formed into a sheet with a thickness of 230 μm by a calendering method. Next, a pair of nickel foils with a thickness of 40 μm were pressed as metal layers on both sides of the sheet by hot pressing (thermal welding) to obtain a laminate. Thereafter, the laminate was punched into a disc shape with a diameter of 7.0 mm to obtain an over-discharge suppression element. The resistance of the over-discharge suppression element in the thickness direction was 50 mΩ. For resistance measurement, a resistance meter RM3544 (manufactured by Hioki Electric Co., Ltd.) was used and measured by a DC four-terminal method.

[0089] (4) Preparation of electrode body

[0090] The positive electrode and the negative electrode were wound in a spiral shape with a separator between them to form a cylindrical wound electrode body so that the positive electrode was arranged at the outermost periphery. The separator used a three-layer microporous film (thickness 40 μm) consisting of a polyethylene microporous layer (middle layer: thickness 20 μm) and two polypropylene microporous layers (outer layer: thickness 10 μm) sandwiching the middle layer.

[0091] (5) Preparation of non-aqueous electrolyte

[0092] A nonaqueous electrolyte was prepared by dissolving lithium trifluoromethanesulfonate as a lithium salt at a concentration of 0.75 mol / L in a nonaqueous solvent obtained by mixing propylene carbonate (PC), ethylene carbonate (EC) and 1,2-dimethoxyethane (DME) at a volume ratio of 1:1:2.

[0093] (6) Assembly of lithium primary batteries

[0094] The electrode body was inserted into a bottomed cylindrical stainless steel (SUS316) battery can with a ring-shaped lower insulating plate disposed at its bottom. The second collector was resistance-welded to the inner bottom surface of the battery can also serving as the positive electrode terminal.

[0095] Next, the free end side of the nickel first lead wire crimped to the negative electrode was resistance-welded to one nickel foil of the overdischarge suppression element, and one end of the nickel second lead wire (thickness 70 μm, width 5.0 mm) prepared separately in advance was resistance-welded to the other nickel foil of the overdischarge suppression element, thereby forming the first collector wire. The length of the first lead wire and the second lead wire is the same, and when the length of the first collector wire is L, the distance from the connection point of the first lead wire and the negative electrode to the center of the overdischarge suppression element (conductive layer) is L / 2.

[0096] After placing the upper insulating plate on the upper part of the electrode body, the free end side of the second lead of the first collector was resistance welded to the external terminal (made of stainless steel (SUS316)) fixed to the sealing plate. Next, the non-aqueous electrolyte was injected into the battery can and allowed to penetrate into the electrode group. Thereafter, the sealing plate was inserted near the opening of the battery can, and the opening end of the battery can and the peripheral part of the sealing plate were laser welded. In this way, 400 batteries with Figure 1 A sealed cylindrical lithium primary battery (diameter 17 mm, height 33.5 mm) of the structure shown was then pre-discharged to a battery voltage of 3.2V.

[0097] 《Example 2》

[0098] A battery was produced in the same manner as in Example 1 except that aluminum powder (D50=40 nm) was used as a conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0099] 《Example 3》

[0100] A battery was produced in the same manner as in Example 1 except that tin powder (D50=40 nm) was used as a conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0101] 《Example 4》

[0102] A battery was produced in the same manner as in Example 1 except that zinc powder (D50=40 nm) was used as a conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0103] 《Example 5》

[0104] A battery was prepared in the same manner as in Example 1 except that bismuth powder (D50=40 nm) was used as a conductive material that absorbs lithium ions at a lower potential than the positive electrode.

[0105] Comparative Example 1

[0106] The following 1a collector was produced to replace the 1 collector. The 1a collector consists of a nickel lead wire b having the same length as the total length of the 1 collector and an overdischarge suppression element connected to one end of the lead wire b. The other end of the nickel lead wire b is connected to a predetermined position of the negative electrode by crimping. On the other hand, a nickel foil resistor constituting the overdischarge suppression element is welded to an external terminal fixed to the sealing plate.

[0107] 《Comparative Example 2》

[0108] 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.

[0109] (7) Evaluation

[0110] The following safety evaluation was performed using the produced lithium primary batteries.

[0111] 100 batteries were discharged to 100% of the rated capacity. Next, 3 unused batteries and 1 discharged battery were connected in series to form a battery pack of 100 12V batteries, and discharged by connecting a 1Ω resistor at an ambient temperature of 20°C. Table 1 shows the maximum temperature reached in the center of the discharged battery, and the expansion of the battery (height change rate R). It should be noted that the rate of change in the outer diameter of the battery before and after the test is less than 0.1%, which is very small compared to the height change rate, and the change in the 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 to 2 are referred to as Batteries B1 to B2.

[0112] [Table 1]

[0113]

[0114] For batteries A1 to A5 of the embodiment, the highest temperature reached in all battery groups was less than 40°C and the height change rate was less than 1%. This is because the resistance value of the conductive layer in the discharged battery increases instantaneously and the overdischarge stops completely.

[0115] On the other hand, for the battery B1 of comparative example 1, the maximum reached temperature was 80°C or higher, and the battery expanded greatly. This is considered to be because the distance between the overdischarge suppression element and the electrode body was large, and the contact with the electrolyte could not be sufficiently ensured, and the overdischarge suppression element was directly connected to the external terminal, resulting in the expansion and deformation of the conductive layer being suppressed.

[0116] The maximum temperature reached in battery B2 of Comparative Example 2 was also 80° C. or higher, and the battery expanded greatly. This is probably because Cu, the conductive material, could not absorb lithium, and the conductive layer could not expand.

[0117] Industrial Applicability

[0118] The lithium primary battery according to the present invention is excellent in safety against overdischarge and is therefore suitable for being mounted on a device in which a plurality of batteries are connected and used. Examples of such devices include various devices such as AEDs (automated external defibrillators) and lamps.

[0119] Description of Reference Numerals

[0120] 10 Lithium primary battery

[0121] 100 Battery Cans

[0122] 200 Electrode body

[0123] 201 Positive electrode

[0124] 202 Negative electrode

[0125] 203 Spacer

[0126] 210 Episode 1 Wire

[0127] 211 1st lead

[0128] 212 2nd lead

[0129] 213 Overdischarge suppression element

[0130] 214 1st metal layer

[0131] 215 2nd Metal Layer

[0132] 216 Conductive layer

[0133] 220 Episode 2 Wire

[0134] 230A Upper insulation plate

[0135] 230B Lower insulation board

[0136] 300 Sealing body

[0137] 310 Sealing plate

[0138] 320 Gasket

[0139] 330 external terminal

Claims

1. A lithium primary battery comprising an electrode body, a non-aqueous electrolyte, a battery can containing the electrode body and the non-aqueous electrolyte, a sealing body for sealing an opening of the battery can, a collector for electrically connecting the electrode body and the sealing body, and an insulating plate provided between the electrode body and the sealing body, The electrode body 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 metallic lithium and a lithium alloy, The collector includes a first lead connected to one of the positive electrode and the negative electrode, a second lead connected to the sealing body, and an overdischarge suppression element interposed between the first lead and the second lead. The overdischarge suppression element includes 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 disposed opposite to 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 overdischarge suppression element is disposed between the insulating plate and the sealing body. When the length of the collecting line 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 overdischarge suppression element is equal to or less than 2L / 3.

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

3. The lithium primary battery according to claim 1, in, The conductive layer is circular in shape.

4. The lithium primary battery according to claim 1, in, The positive electrode includes manganese dioxide as a positive electrode active material.

5. The lithium primary battery according to claim 1, in, The conductive material includes at least one selected from metals, metalloids, and carbon materials.

6. The lithium primary battery according to claim 5, in, The metal includes at least one selected from the group consisting of Al, Zn, Cd, In, Sn, Pb, Ti, and Bi.

7. The lithium primary battery according to claim 5, in, The metalloid includes at least one selected from the group consisting of Ge, Si, Se, and Te.

8. The lithium primary battery according to claim 5, in, The carbon material includes at least one selected from graphite, non-graphitizable carbon, carbon black, and carbon fiber.

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