Lithium primary battery

Abstract

A lithium primary battery according to the present invention comprises an outer can, a wound-type electrode body, and a non-aqueous electrolytic solution. A positive electrode, a negative electrode, and a separator interposed therebetween are wound in the wound-type electrode body. The positive electrode contains manganese dioxide. The negative electrode contains at least one selected from a group consisting of metallic lithium including lithium alloys and metallic lithium, and has a first main surface and a second main surface on a side opposite from the first main surface. The first main surface and the entirety of the second main surface oppose the positive electrode. A total area S of the first main surface and second main surface satisfies 250 cm2 ≤ S ≤ 700 cm2, and a thickness Tp of the positive electrode satisfies 0.8 mm ≤ Tp ≤ 1.4 mm. An outer diameter D of the outer can satisfies 25 mm ≤ D ≤ 37 mm, and an interval C between the outer can and the wound-type electrode body satisfies 0.3 mm ≤ C ≤ 1.0 mm.

Description

[Technical field]

[0001] The present disclosure relates to lithium primary batteries. [Background technology]

[0002] In recent years, the use of ICT (Information and Communication Technology), including DX (Digital Transformation), has been accelerating. Smart meters are one example of ICT-based devices that have already become widespread. For devices used for such purposes, primary batteries are often used as independent power sources when power cannot be obtained from electric wires. Primary batteries used for such purposes are required to have performance such as long life, high capacity, and stable discharge at various currents, from large pulse discharge currents for ICT communications to small currents for normal operation. To ensure these performances, there is an increasing demand for larger primary batteries.

[0003] Patent Document 1 proposes using an electrode winding body in a cylindrical nonaqueous electrolyte battery, in which a positive electrode sheet obtained by a specific manufacturing method is used and a positive electrode, a negative electrode, and a separator are wound so that the number of windings, defined by the winding start end and the winding end end of the positive electrode, is 1.0 to 4.0 turns.

[0004] Patent Document 2 proposes that in a wound electrode body of a cylindrical nonaqueous electrolyte primary battery, a positive electrode having a thickness of 1.4 mm or more is used, and two sheets of resin microporous films having a thickness of 7 to 20 μm are placed between the positive electrode active material layer and the negative electrode active material layer.

[0005] Patent Document 3 discloses a battery using a positive electrode containing manganese dioxide and a negative electrode containing at least one selected from the group consisting of metallic lithium and lithium alloys and having a first main surface and a second main surface opposite to the first main surface, the entire first main surface and the second main surface facing the positive electrode, and the total area of ​​the first main surface and the second main surface being 100 cm 2 over 180cm 2The following wound electrode body is proposed for use in a lithium primary battery. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-032584 A [Patent Document 2] International Publication No. 2020 / 054662 [Patent Document 3] International Publication No. 2020 / 095500 Summary of the Invention

[0007] In order to ensure high capacity in a lithium primary battery using a wound electrode body, it is common to make the battery larger (for example, to increase the diameter) or to increase the thickness of the electrode of the wound electrode body. However, when the lithium primary battery is discharged in a state in which the outer diameter of the battery is large and the thickness of the wound electrode body is increased, the thickness of the positive electrode expands in the opposing parts, the thickness of the negative electrode decreases, and the thickness of the separator changes, making it difficult to keep the thickness balance of each part of the wound electrode body uniform. It is also difficult to keep the amount of electrolyte held by the positive electrode and the separator uniform. Therefore, unevenness in the discharge reaction is likely to occur. In particular, when the outer diameter of a lithium primary battery is increased to increase the size, the number of turns of the electrode body increases and the electrode area increases, so that unevenness in the discharge reaction becomes noticeable.

[0008] More specifically, the positive electrode expands during discharge and its thickness increases. Meanwhile, the lithium of the negative electrode becomes thinner due to a dissolution reaction. Therefore, the larger the thickness of the electrode or the number of windings, the greater the change in thickness during discharge, making it difficult to maintain a certain degree of uniformity in the thickness balance at each part where the positive electrode and the negative electrode face each other. Therefore, the discharge reaction of the wound electrode body does not proceed evenly inside, and differences occur depending on the part inside the electrode body. A separator is inserted between the positive electrode and the negative electrode to ensure insulation and to hold the electrolyte. The separator has some function of buffering the stress associated with the change in the thickness of the electrode. However, as the electrode itself becomes thicker, the change in the thickness of the electrode also increases, and the change exceeds the limit that the separator can buffer, making it difficult to fully relieve the stress associated with the change in the thickness of the electrode. In addition, when the thickness of the separator changes, the amount of electrolyte held by the separator also changes.

[0009] The effect of the change in thickness of the electrodes and separators in the electrode body is small at the beginning of discharge, but as discharge progresses, the effect becomes more pronounced. For example, if a large pulse discharge current for ICT communication is applied at a medium depth of discharge of 40 to 60%, the voltage drop becomes large and communication may become impossible. On the other hand, at the end of discharge, when the depth of discharge is even deeper at 80 to 90%, the voltage drop is small and communication becomes possible even if a large pulse discharge current for ICT communication is applied. There is a demand for a long-life, high-capacity lithium primary battery that can perform stable discharge at various currents, from the large pulse discharge current for ICT communication to the small current for normal operation, regardless of the depth of discharge of the battery.

[0010] A lithium primary battery according to one aspect of the present disclosure includes an outer can, and a wound electrode assembly and a non-aqueous electrolyte housed in the outer can. In the wound electrode assembly, a sheet-shaped positive electrode, a sheet-shaped negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound. The positive electrode includes a positive electrode mixture containing manganese dioxide. The negative electrode includes at least one selected from the group consisting of metallic lithium containing a lithium alloy and metallic lithium, and has a first main surface and a second main surface opposite to the first main surface. The entire second main surface and the first main surface of the negative electrode face the positive electrode. The total area S of the first main surface and the second main surface is 250 cm 2 ≦S≦700cm 2 The thickness Tp of the positive electrode satisfies 0.8 mm≦Tp≦1.4 mm. The outer diameter D of the outer can satisfies 25 mm≦D≦37 mm. The distance C between the outer can and the wound electrode body satisfies 0.3 mm≦C≦1.0 mm.

[0011] This lithium primary battery has a high capacity and can discharge stably even when the discharge progresses. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a front view showing a schematic vertical cross section of a portion of a lithium primary battery according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a diagram showing evaluation results of a lithium primary battery according to an embodiment of the present disclosure. [Diagram 3] FIG. 1 is a diagram showing evaluation results of a lithium primary battery according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a diagram showing evaluation results of a lithium primary battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] 1 is a front view showing a schematic vertical cross section of a cylindrical lithium primary battery 10 according to an embodiment of the present disclosure. Regardless of the cylindrical shape, low-height coin- or button-shaped lithium primary batteries 10 are also included in the present invention.

[0014] The lithium primary battery 10 includes a cylindrical outer can 100 with a bottom, a wound electrode assembly 200 housed in the outer can 100, and a sealing body 300 that seals the opening of the outer can 100. The outer can 100 has a cylindrical side wall 101 having opening ends 101A and 101B opposite each other, and a bottom 102 that seals the opening 501B of the opening end 101B of the side wall 101. The sealing body 300 is fixed to the opening end 101A of the outer can 100 by welding. The sealing body 300 seals the opening 501A of the opening end 101A of the side wall 101 of the outer can 100. An opening is formed in the center of the sealing body 300, and an external terminal 330 is disposed in this opening. An insulating gasket 310 is disposed between the external terminal 330 and the sealing body 300.

[0015] The wound 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, about a central axis 200C. An internal lead wire 210 is connected to one of the positive electrode 201 and the negative electrode 202 (in the illustrated example, the negative electrode 202). The internal lead wire 210 is connected to an external terminal 330 by welding or the like. Another internal lead wire 220 is connected to the other of the positive electrode 201 and the negative electrode 202 (in the illustrated example, the positive electrode 201). The internal lead wire 220 is electrically connected to the inner surface of the exterior can 100 by welding or the like.

[0016] The negative electrode 202 has a first main surface 202A and a second main surface 202B opposite to the first main surface 202A. In the wound electrode body 200 in which the first main surface 202A faces the central axis 200C and the second main surface 202B faces outward from the wound electrode body 200, the entire second main surface 202B of the negative electrode 202 and the first main surface 202A face the positive electrode 201 via the separator 203. The wound electrode body 200 is stored inside the exterior can 100 together with the non-aqueous electrolyte 204. 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. The electrode body 200 and the side wall 101 of the exterior can 100 face each other via a gap 200D of interval C.

[0017] The positive electrode 201 contains a positive electrode mixture containing manganese dioxide. The negative electrode 202 contains at least one selected from the group consisting of metallic lithium and metallic lithium containing a lithium alloy, and has a first main surface 202A and a second main surface 202B opposite to the first main surface 202A. The entire first main surface 202A and the entire second main surface 202B face the positive electrode 201. In this case, the outermost electrode of the electrode body 200 becomes the positive electrode 201. The following conditions (a) to (d) are listed for the lithium primary battery 10. The total area S of the first main surface 202A and the second main surface 202B of the negative electrode 202 is 250 cm 2 ≦S≦700cm 2 (a) The thickness Tp of the positive electrode 201 satisfies 0.8 mm≦Tp≦1.4 mm (b). The outer diameter D of the exterior can 100 satisfies 25 mm≦D≦37 mm (c). The distance C between the exterior can 100 and the wound electrode body 200 satisfies 0.3 mm≦C≦1.0 mm (d).

[0018] Patent Documents 1 to 3 specifically describe a lithium primary battery with an outer diameter D of the outer can 100 of about 17 mm, which is a size A slightly larger than the size AA. In contrast, the lithium primary battery of the present disclosure relates to a battery with an outer diameter D of the outer can 100 of 25 mm≦D≦37 mm, which is a size C to C (sizes C to D). The lithium primary battery of the present disclosure is larger in size, with an outer diameter about 1.5 to 2 times that of Patent Documents 1 to 3, and an electrode area about 2 to 4 times. The present inventors have found that the problems that cannot be solved by batteries of conventional configurations can be solved by simultaneously combining the above four conditions (a) to (d).

[0019] From the viewpoint of the discharge characteristics of the battery, the area of ​​the negative electrode 202 is more important than the area of ​​the positive electrode 201. First, an effective range is determined for the total area S of the main surfaces 202A and 202B of the negative electrode 202, and then a range of thickness Tn of the negative electrode 202 that can obtain an effect is determined from the area of ​​the negative electrode 202, which is half of the total area S of the negative electrode 202, and the specific gravity of the components of the negative electrode 202. The configuration of the wound electrode body 200 is optimized by setting the thickness Tp of the combined positive electrode 201 to 0.8 mm≦Tp≦1.4 mm. When the total area S of the negative electrode 202 is 250 cm 2 If the total area S of the negative electrode 202 is less than 700 cm, the negative electrode 202 can handle the small discharge current of normal operation until the end of discharge, but cannot handle the large pulse discharge current for ICT communication. 2 If the thickness Tp is larger than 0.8 mm, the current collection efficiency decreases, making it difficult to obtain a large current for ICT communication, and the amount of auxiliary materials such as the separator 203 increases, making it impossible to achieve high energy density. If the thickness Tp of the positive electrode 201 is thinner than 0.8 mm, the balance of compensation due to the expansion of the positive electrode 201 due to the decrease in the thickness of the negative electrode 202 during discharge is easily lost, and discharge stability at each discharge depth is easily impaired. If the thickness Tp of the positive electrode 201 is thicker than 1.4 mm, the expansion of the positive electrode 201 becomes too large, and conversely, the reaction of the negative electrode 202 during discharge is accelerated, making it impossible to obtain a predetermined amount of discharge capacity. In addition, the difference between the maximum outer diameter and the minimum outer diameter of the electrode body 200 itself becomes even larger, and the cross section becomes farther from a perfect circle, making it impossible to achieve high density.

[0020] In addition, the distance C between the wound electrode body 200 and the exterior can 100 having an outer diameter D of 25 mm≦D≦37 mm satisfies 0.3 mm≦C≦1.0 mm. In the initial discharge state, the distance C between the wound electrode body 200 and the exterior can 100 is very important. The wound electrode body 200 is usually not a perfect circle, and has a maximum outer diameter and a minimum outer diameter. Therefore, the distance C must be within the range of 0.3 mm≦C≦1.0 mm, taking into account the maximum diameter. The distance C is preferably 0.4 mm≦C≦0.9 mm. If there is a portion where the distance C is smaller than 0.3 mm, when the discharge progresses to a medium level, the distance C will almost disappear, or there will be many portions where the wound electrode body 200 is completely pressed against the inner surface of the exterior can 100. Therefore, the effect of the pressure of the exterior can 100 on the state of the electrode body 200 during discharge will be large, and uneven reaction will easily occur. If the gap C is greater than 1.0 mm, gaps will develop between many parts of the electrode body 200 and the inner surface of the outer can 100 until the end of the discharge, and the electrode body 200 will not be affected by the pressure from the outer can 100 at all, causing the discharge to become unstable at the end of the discharge.

[0021] In the lithium primary battery 10 of the present disclosure, the above-mentioned configuration provides the following effects. The entire second main surface 202B and the first main surface 202A of the negative electrode 202 face the positive electrode 201, so that the electrode located on the outermost side (in other words, the outermost electrode) of the electrodes of the wound electrode body 200 becomes the positive electrode 201. As the discharge proceeds, the wound electrode body 200 expands in the outer diameter direction, and the inner surface of the outer can 100 and the outer periphery of the wound electrode body 200 come into contact. Since the outermost periphery of the electrodes of the wound electrode body 200 is the positive electrode 201, the positive electrode 201 and the separator 203 can cover the lithium of the negative electrode 202. As a result, when the positive electrode 201 expands and the electrode body 200 comes into contact with the inner surface of the outer can 100, the expansion of the positive electrode 201 is directed inward rather than outward due to the reaction force of the outer can 100. Therefore, the reduction in thickness due to the discharge of the negative electrode 202 can be compensated for in a well-balanced manner, and the stress due to the expansion of the electrode body 200 can be easily alleviated, thereby obtaining stable characteristics until the end of the discharge regardless of the depth of discharge. On the other hand, when the area of ​​the negative electrode 202 is large and the outermost periphery of the electrode of the wound electrode body 200 is the negative electrode 202, the pressure due to the expansion of the positive electrode 201 as the discharge progresses is directed outward, so that the negative electrode 202 near the outermost end, which is the end point of the winding of the positive electrode 201, is easily cut off, and the specified amount of discharge capacity cannot be obtained, making it difficult to solve the problem.

[0022] The thickness Tp of the positive electrode 201, the interval C, and the total area S of the negative electrode 202 are values ​​for the lithium primary battery 10 in the early stage of discharge. In this specification, the lithium primary battery 10 in the early stage of discharge means a lithium primary battery 10 with a depth of discharge (hereinafter referred to as DOD) of 10% or less. In order to stabilize the characteristics of the lithium primary battery 10, a small amount of discharge processing is performed after the assembly of the battery 10 in order to drop the battery voltage from about 3.6 V to about 3.2 V. This small amount of discharge is called pre-discharge. An unused lithium primary battery 10 in this pre-discharged state (at the time of shipment from the factory) is in a state of DOD 0%. It may be considered that the lithium primary battery 10 does not affect the values ​​defined in this specification for the lithium primary battery 10 in the early stage of discharge, not only when it is unused, but also when the DOD is in the range of 10% or less. DOD100% refers to the discharge capacity (rated discharge capacity, design capacity) when the battery 10 is discharged at the rated discharge current (for example, a current between 1 mA and 5 mA) and the voltage of the battery 10 reaches 2 V. The rated current setting differs depending on the size or capacity of the battery 10, but below a certain value, there is no difference in the resulting discharge capacity. The discharge capacity of each DOD is calculated based on the discharge capacity of DOD100% based on the rated current at this time.

[0023] The sheet-like negative electrode 202 has two main surfaces that occupy most of the surface of the negative electrode 202, one of which is the first main surface 202A, and the other main surface opposite to the first main surface 202A (in other words, the other main surface) is the second main surface 202B. The sheet-like negative electrode 202 has an end surface 202C that connects the first main surface 202A and the second main surface 202B, in addition to the first main surface 202A and the second main surface 202B. The area of ​​each main surface refers to the projected area of ​​each main surface in the thickness direction of the sheet when the sheet is flattened. In addition, when there is a portion on each main surface where neither metallic lithium nor metallic lithium containing a lithium alloy is present, the area of ​​this portion is excluded from the calculation of the area of ​​each main surface. The total area S of the first main surface 202A and the second main surface 202B does not include the area of ​​the end surface 202C. The total area S of the main surfaces 202A and 202B is substantially the area of ​​the portion of the surface of the negative electrode 202 that faces the positive electrode 201.

[0024] The interval C is the difference between the inner diameter Dd of the side wall 101 of the outer can 100 in which the wound electrode body 200 is housed and the maximum diameter of the wound electrode body 200. The inner diameter Dd of the outer can 100 is an average value of the inner diameters Dd measured at a plurality of points (for example, three points every 60°) along the inner circumferential surface of the side wall 101 of the outer can 100 at the center of the height direction along the central axis 200C of the electrode body 200 in the lithium primary battery 10. The maximum diameter of the electrode body 200 is the maximum diameter at the center of the height direction of the electrode body 200. The maximum diameter of the electrode body 200 is measured on the outermost peripheral surface of the electrode body 200. When the outermost periphery of the electrode body 200 is the separator 203, the maximum diameter of the electrode body 200 is determined including the outermost separator 203.

[0025] The outer diameter D of the side wall 101 of the outer can 100 is the average value obtained by measuring the outer diameters at multiple points (e.g., three points every 60°) along the outer peripheral surface of the side wall 101 of the outer can 100 at the center of the height direction of the electrode body 200 in the lithium primary battery 10.

[0026] The configuration of the cylindrical lithium primary battery 10 relating to the above aspect will be described in more detail below.

[0027] (wound electrode body) (positive electrode) The positive electrode active material may be manganese dioxide alone or may be mixed with manganese oxide or graphite fluoride. As the manganese dioxide, it is preferable to use electrolytic manganese dioxide neutralized with ammonia, sodium, lithium, etc. It is preferable to use calcined electrolytic manganese dioxide. Specifically, it is preferable to calcinate electrolytic manganese dioxide in air or oxygen at 300 to 450°C for about 6 to 12 hours. The oxidation number of manganese contained in manganese dioxide is typically tetravalent, but is not limited to tetravalent, and some reduction is allowed. Examples of manganese dioxide that can be used include MnO, Mn3O4, Mn2O3, and MnO2, and manganese dioxide is generally used as the main component. Manganese dioxide may be in a mixed crystal state including a plurality of crystal states. In addition, when using uncalcined electrolytic manganese dioxide, it is preferable to use manganese dioxide with a small specific surface area by increasing the crystallinity under the conditions during electrolytic synthesis. It is also possible to add a small amount of chemical manganese dioxide or the like.

[0028] The positive electrode 201 typically includes a positive electrode current collector in addition to the positive electrode mixture. The positive electrode 201 may include a positive electrode mixture layer.

[0029] The thickness Tp of the positive electrode 201 satisfies 0.8 mm≦Tp≦1.4 mm. From the viewpoint of increasing the capacity and easily securing a higher discharge voltage even when discharging progresses, Tp may be 1.0 mm≦Tp≦1.3 mm or 1.1≦Tp≦1.3 mm.

[0030] The thickness Tp of the positive electrode 201 is an average value of thicknesses measured at multiple locations (e.g., 10 locations) of the positive electrode 201 included in the electrode assembly 200 in the lithium primary battery 10 at the beginning of discharge. The thickness Tp of the positive electrode 201 is measured on a cross-sectional photograph of the lithium primary battery 10 perpendicular to the axial direction of the electrode assembly 200. The cross-sectional photograph is obtained by X-ray transmission or X-ray CT (Computed Tomography), etc.

[0031] The positive electrode mixture contains, in addition to a positive electrode active material, optional components such as a binder and a conductive agent.

[0032] Examples of the binder include fluororesin, polyacrylonitrile, polyimide resin, acrylic resin, polyolefin resin, and rubber polymer. The positive electrode mixture may contain one type of binder, or may contain two or more types of binder.

[0033] The conductive agent is preferably a carbon material. Examples of the carbon material include carbon black, 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.

[0034] Positive electrode mixture density d p For example, 2.5 g / cm 3 ≦d p ≦3.5g / cm 3 In order to further stabilize the discharge voltage, the density d p is 2.6g / cm 3 ≦d p ≦3.3g / cm 3 It is preferable that the following is satisfied.

[0035] Positive electrode mixture density d p is obtained from the thickness Tp of the positive electrode 201 and the mass and volume of the positive electrode mixture excluding the current collector after the positive electrode 201 is removed from the lithium primary battery 10 in the early stage of discharge, washed with a solvent, and dried.

[0036] Examples of the material of the positive electrode current collector include metal materials such as stainless steel, Al, and Ti. The metal material may be a simple metal or an alloy. Examples of the positive electrode current collector include a sheet and a porous body. A metal foil or the like may be used as the positive electrode current collector. In addition, a metal mesh (or net), an expanded metal, a punched metal, or the like may be used as the porous positive electrode current collector.

[0037] The method for producing the positive electrode 201 is not particularly limited. For example, the positive electrode 201 may be prepared by applying a positive electrode mixture to a positive electrode current collector, or by filling 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 producing the positive electrode 201, the positive electrode mixture may be used in a paste or clay-like form using a liquid medium in addition to the components of the positive electrode mixture, as necessary. Examples of the liquid medium include water and organic liquid medium. The liquid medium is liquid at room temperature (20° C. to 35° C.), for example. At an appropriate stage in producing the positive electrode 201, drying may be performed as necessary, and the positive electrode 201 may be compressed in the thickness direction.

[0038] (Negative electrode) The negative electrode 202 contains at least one metal material selected from the group consisting of metallic lithium and metallic lithium containing a lithium alloy. Examples of the lithium alloy include Li-Al, Li-Sn, Li-Ni-Si, and Li-Pb. The content of metal elements other than lithium contained in the lithium alloy is, for example, 0.05% by mass or more and 1.0% by mass or less with respect to the lithium alloy.

[0039] For example, a metal foil is used as the sheet-shaped negative electrode 202. The sheet-shaped negative electrode 202 can be formed by extrusion molding the above-mentioned metal materials.

[0040] Tape or the like may be attached to a portion of the sheet-shaped negative electrode 202 in order to prevent the negative electrode 202 from being consumed and isolated during discharge. The width of the tape is preferably 0.5 mm or more and 3 mm or less in order not to inhibit the battery reaction. The tape may be attached to either the first main surface 202A or the second main surface 202B of the sheet-shaped negative electrode 202, or to both of them.

[0041] In the present disclosure, the first main surface 202A and the second main surface 202B of the negative electrode 202 are entirely opposed to the positive electrode 201. As a result, the electrode located at the outermost periphery in the wound electrode body 200 becomes the positive electrode 201.

[0042] It is preferable that the capacity Cn of the negative electrode 202 and the capacity Cp of the positive electrode 201 satisfy Cp≦Cn. Even at the end of discharge, the thickness of the negative electrode 202 is maintained to some extent due to the presence of unreacted lithium, and therefore, as an effect of the negative electrode 202, reaction unevenness can be reduced. The ratio Cn of the capacity Cn of the negative electrode 202 to the capacity Cp of the positive electrode 201: Cn / Cp is preferably greater than 1, and may be, for example, 1.05 or more, or 1.10 or more. From the viewpoint of ensuring a high energy density, it is preferable that the Cn / Cp ratio is 1.2 or less.

[0043] The capacity Cn and capacity Cp can be calculated by the following procedure. The positive electrode 201 is removed from the lithium primary battery 10 in the early stage of discharge, and the mass of manganese dioxide contained in the positive electrode 201 is calculated. The negative electrode 202 is removed from the lithium primary battery 10 in the early stage of discharge, and the mass of metallic lithium contained in the negative electrode 202 is calculated. The capacity Cp is calculated from the mass of manganese dioxide and the theoretical capacity of manganese dioxide (308 mAh / g). The capacity Cn is calculated from the mass of metallic lithium contained in the negative electrode 202 and the theoretical capacity of lithium (3860 mAh / g).

[0044] The total area S of the first main surface 202A and the second main surface 202B of the sheet-like negative electrode 202 is 250 cm 2 ≦S≦700cm 2 From the viewpoint of obtaining high discharge voltage and high capacity, 265 cm 2 ≦S≦680cm 2 It is preferable that the thickness is 300 cm. 2 ≦S≦500cm 2 is more preferred.

[0045] (Separator) For the separator 203, a porous sheet having ion permeability and insulating properties is used. Examples of the porous sheet include a microporous film, a woven fabric, and a nonwoven fabric. The separator 203 may have a single-layer structure or a multilayer structure. Examples of the separator 203 having a multilayer structure include a separator 203 including a plurality of layers having different materials and / or structures. In the separator 203 having a multilayer structure of three or more layers, some of the layers (e.g., two layers) may have the same material and structure, or all of the layers may have different materials and / or structures.

[0046] The separator 203 may be made of, for example, a polymeric material. Examples of the polymeric material include olefin resin, polyamide resin, polyimide resin (polyimide, polyamideimide, etc.), cellulose, polyphenylene sulfite, polytetrafluoroethylene, etc. The separator 203 may contain additives as necessary. Examples of the additives include inorganic fillers, etc.

[0047] The thickness Ts of the separator 203 can be selected, for example, from the range of 10 μm or more and 200 μm or less. When the separator 203 is made of a microporous film, the thickness Ts of the separator 203 may be, for example, from the range of 10 μm or more and 80 μm or less. From the viewpoint of keeping the internal resistance low and easily securing a higher discharge voltage even when the discharge progresses, the thickness Ts of the separator 203 made of a microporous film is preferably 30 μm or more and 50 μm or less. When the separator 203 including a nonwoven fabric is used, the thickness Ts of the separator 203 can be selected from the range of 100 μm or more and 200 μm or less. The microporous film and the nonwoven fabric may be combined.

[0048] (others) The wound electrode body 200 is formed by spirally winding a negative electrode 202, a positive electrode 201, and a separator 203 interposed between these electrodes. At this time, the negative electrode 202 and the positive electrode 201 are arranged with the separator 203 interposed between them so that the entire second main surface 202B and the first main surface 202A of the negative electrode 202 face the positive electrode 201.

[0049] The maximum diameter of the wound electrode body 200 is determined for the electrode body 200 removed from the lithium primary battery 10 in the early stage of discharge. More specifically, the diameters are measured at multiple locations (e.g., six locations) along the outermost peripheral surface in a direction perpendicular to the winding axis, and the maximum of these is taken as the maximum diameter of the electrode body 200. The diameter of the electrode body 200 is measured using a vernier caliper or the like.

[0050] (Non-aqueous electrolyte) The non-aqueous electrolyte 204 used in the lithium primary battery 10 has lithium ion conductivity. Such a non-aqueous electrolyte 204 contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0051] Examples of the lithium salt include lithium borofluoride, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium perchlorate, etc. The nonaqueous electrolyte solution 204 may contain one type of lithium salt or a combination of two or more types.

[0052] 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 204 may contain one type of non-aqueous solvent, or may contain two or more types in combination.

[0053] The concentration of the lithium salt in the nonaqueous electrolyte solution 204 is, for example, 0.1 mol / L or more and 3.5 mol / L or less.

[0054] The non-aqueous electrolyte 204 may contain additives as necessary. Examples of additives include vinylene carbonate, fluoroethylene carbonate, and vinyl ethyl carbonate. The non-aqueous electrolyte 204 may contain one type of additive or a combination of two or more types of additives.

[0055] (Outer can) The exterior can 100 is made of stainless steel, iron, aluminum, or an aluminum alloy. Each material is designed to have a strength sufficient to suppress deformation of the exterior can 100 even if the positive electrode 201 expands, reduce variations in the discharge reaction, and stabilize the discharge voltage even as the discharge progresses. The exterior can 100 may be annealed or plated as necessary. Furthermore, by using a stainless steel exterior can 100, high durability capable of withstanding long-term use is easily obtained.

[0056] The thickness Tc of the exterior can 100 is preferably 0.25 mm or more. From the viewpoints of discharge stability and energy density, it is preferable that 0.3 mm≦Tc≦0.45 mm.

[0057] The thickness Tc of the outer can 100 is an average value obtained by measuring the thickness at multiple points (e.g., six points every 60°) along the inner circumferential surface of the outer can 100 at the center in the height direction of the electrode assembly 200 of the lithium primary battery 10. The thickness Tc of the outer can 100 is measured on a photograph of a cross section of the lithium primary battery 10 perpendicular to the direction along the central axis 200C of the electrode assembly 200.

[0058] The inner diameter Dd of the side wall 101 of the outer can 100 is measured on a cross-sectional photograph perpendicular to the direction of the central axis 200C of the electrode assembly 200 of the lithium primary battery 10. The interval C is calculated from the inner diameter Dd (average value) of the outer can 100 calculated as described above and the maximum diameter of the electrode assembly 200.

[0059] According to the above aspect of the present disclosure, the polarity of the exterior can 100 may be either the positive electrode 201 or the negative electrode 202. In the present disclosure, the outermost circumference of the wound electrode body 200 can have two basic configurations. The first is a configuration in which the separator 203 completely covers the positive electrode 201, which is the outermost electrode, and in addition, tape is attached to a part of the outermost circumference so that the separator 203 can be maintained in a wound state on the separator 203. The second is a configuration in which the separator 203 does not completely cover the positive electrode 201, which is the outermost electrode, with some or no separator 203, and tape is attached to a part of the outermost electrode to maintain the wound state. Regardless of the polarity of the exterior can 100, a combination of the separator 203 that completely covers the positive electrode 201, which is the outermost electrode, and tape is more preferable from the viewpoint of reducing the risk of internal short circuit due to excessive physical vibration or dropping, detachment of the mixture from the electrode, deformation of the electrode, etc. Furthermore, since there is no guarantee that the separator 203 or tape will not fail due to an external impact or the like, from the viewpoint of reducing the risk of an internal short circuit, it is more preferable to match the polarity of the outer can 100 and the outermost electrode by making the outer can 100 the positive electrode 201 and the outermost electrode the positive electrode 201. When the polarity of the outer can 100 and the electrode is the same, physical pressure welding is possible, but it is more preferable to apply an insulating coating to the inner surface of the outer can 100, as this can further reduce the risk of an internal short circuit.

[0060] (sealing body) The lithium primary battery 10 usually includes a sealing body 300 that seals the opening 501A of the exterior can 100. The sealing body 300 is made of stainless steel, iron, aluminum, or an aluminum alloy. From the viewpoint of easily ensuring durability and strength, the sealing body 300 is preferably made of stainless steel. The sealing body 300 may be annealed or plated as necessary.

[0061] The outer can 100 and the sealing body 300 may be electrically connected to either the positive electrode 201 or the negative electrode 202 of the electrode assembly 200, respectively. The opening 501A of the outer can 100 may be sealed by crimping the opening end 101A of the outer can 100 to the periphery of the sealing body 300, or may be sealed by laser welding the sealing body 300 and the periphery of the opening 501A of the outer can 100. When sealing is performed by the former method, an insulating gasket 310 is disposed between the opening end 101A of the outer can 100 and the periphery of the sealing body 300. When sealing is performed by the latter method, the sealing body 300 and the external terminal 330 are configured as separate members, and an insulating gasket 310 is disposed between the external terminal 330 and the sealing body 300. In applications requiring a long expected life, it is preferable to laser-weld the open end 101A of the exterior can 100 and the sealing body 300. In this case, the effects of air intrusion into the battery 10 or volatilization of the nonaqueous electrolyte solution 204 can be reduced, which is advantageous in terms of ensuring a longer life. Note that the effects of air intrusion or volatilization of the nonaqueous electrolyte solution 204 are multiplied by the number of years of use, and therefore the longer the number of years of use, the greater the effects are thought to be.

[0062] (others) The lithium primary battery 10 according to the above aspect of the present disclosure has a high capacity and can stably discharge even when the discharge progresses. In addition, a high output can be obtained and a relatively high discharge voltage can be secured even when the discharge progresses. Therefore, a long life can be obtained and the discharge performance of a large current such as a pulse current can be secured for a long period of time. Therefore, the lithium primary battery 10 is suitable for mounting in a device controlled to discharge a pulse current for a long period of time. Such a device is not particularly limited, but examples thereof include ICT devices having a communication function (e.g., a meter having a communication function). Examples of the meter include various meters such as an electric meter, a gas meter, and a water meter.

[0063] [Example] The present disclosure will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples. Figures 2 to 4 are tables showing the specifications of the lithium primary battery 10 in examples and comparative examples.

[0064] Examples 1 to 16 and Comparative Examples 1 to 8 (1) Preparation of the positive electrode As the positive electrode 201, 92 parts by mass of electrolytic manganese dioxide that had been baked at 400° C. for 7 hours was mixed with 3 parts by mass of Ketjen 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.

[0065] Next, the wet positive electrode mixture was filled into a positive electrode current collector made of expanded metal made of stainless steel (SUS316) to prepare a positive electrode precursor. The positive electrode precursor was then dried, rolled by a roll press, and cut to a predetermined size to obtain a sheet-like positive electrode 201 having a thickness Tp shown in the table. At this time, the filling amount of the positive electrode mixture was adjusted so that the design capacity was the value shown in the table. The dimensions of the positive electrode 201 were adjusted so that the outermost electrode of the electrode body 200 was the positive electrode 201 when a negative electrode 202 having a total area S of the first main surface 202A and the second main surface 202B of the value shown in the table was used. However, in Comparative Example 1, the dimensions of the positive electrode 201 were adjusted so that the outermost electrode was the negative electrode 202.

[0066] (2) Preparation of the negative electrode Sheet-like Li and Li-Al alloy (Al content relative to the lithium contained in the negative electrode 202: 0.3% by mass) were cut to a predetermined dimension so that the total area S of the first main surface 202A and the second main surface 202B of the negative electrode 202 would be the value shown in the table, to obtain a sheet-like negative electrode 202. The dimensions (width, height, and / or thickness) of the sheet were adjusted so that the amount of Li contained in the negative electrode 202 was the same in each of the examples and comparative examples.

[0067] The ratio of the capacity Cn of the negative electrode 202 to the capacity Cp of the positive electrode 201: Cn / Cp was set to about 1.1.

[0068] (3) Preparation of the roll The positive electrode mixture was peeled off from a part of the positive electrode 201 to expose the positive electrode current collector, and a stainless steel positive electrode tab lead was resistance-welded to the exposed part. A nickel negative electrode tab lead was connected to a predetermined part of the negative electrode 202 by pressure welding. The positive electrode 201 and the negative electrode 202 were spirally wound around the central axis 200C with the separator 203 interposed therebetween to produce a wound body. In order to maintain the state of the wound body, the electrode body 200 was fixed with insulating tape to form a cylindrical wound electrode body 200. At this time, the positive electrode 201 and the negative electrode 202 were laminated so that the total area S of the first main surface 202A and the second main surface 202B of the negative electrode 202 was the value shown in the table, and the separator 203 was arranged so that the outermost electrode was completely covered. In the examples other than Comparative Example 1, the outermost electrode of the electrode assembly 200 was the positive electrode 201, and in Comparative Example 1, the outermost electrode of the electrode assembly 200 was the negative electrode 202.

[0069] For separator 203, a three-layer microporous film (thickness 40 μm) was used, which was composed of a polyethylene microporous layer (middle layer thickness 20 μm) and two polypropylene microporous layers (outer layers thickness 10 μm) sandwiching this middle layer.

[0070] (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 0.5 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.

[0071] (5) Assembly of lithium primary batteries The electrode body 200 was inserted into a bottomed cylindrical stainless steel (SUS316) outer can 100 having an outer diameter D and a thickness Tc shown in the table, with a ring-shaped lower insulating plate disposed at the bottom of the electrode body 200. The positive electrode tab lead was resistance-welded to the inner bottom surface of the outer can 100, and an upper insulating plate was disposed on the upper part of the electrode body 200, and then the negative electrode tab lead was resistance-welded to an external terminal 330 fixed to the sealing body 300. Next, a nonaqueous electrolyte was poured into the outer can 100 and allowed to permeate the electrode body 200. Thereafter, the sealing body 300 was inserted near the opening 501A of the outer can 100, and the opening end 101A of the outer can 100 and the fitting part of the sealing body 300 were laser-welded. In this way, five sealed cylindrical lithium primary batteries 10 having the structure shown in FIG. 1 were produced for each example. The interval C between the outer can 100 and the wound electrode body 200 in the assembled battery 10 is shown in the table. The interval C was adjusted by adjusting the thickness and length of each electrode. Then, each battery 10 was pre-discharged so that the voltage of the battery 10 was 3.2V.

[0072] (6) Evaluation Using the fabricated lithium primary battery 10, the discharge voltage at different depths of discharge (DOD) was evaluated according to the following procedure.

[0073] The pre-discharged lithium primary battery 10 was set to DOD 0%, and the minimum voltage was measured when it was discharged at 500 mA for 5 seconds at -40°C. The average value of the minimum voltages of the five lithium primary batteries 10 was calculated. This average value was used as the discharge voltage at DOD 0%.

[0074] The lithium primary battery 10, for which the discharge voltage at DOD 0% was determined, was discharged to DOD 50%, DOD 75%, and DOD 85% at 30 mA at 23° C. In each state, the battery was discharged at 500 mA for 5 seconds at −40° C., and the minimum voltage was measured and the average value was calculated.

[0075] The evaluation results of the examples and comparative examples are shown in Figures 2 to 4. Examples 1 to 16 are samples A1 to A16, and comparative examples 1 to 8 are samples B1 to B8.

[0076] As shown in FIG. 2, when the interval C is less than 0.3 mm or exceeds 1.0 mm, a drop in the discharge voltage is observed at DOD 50% (samples B2 and B3). In samples B2 and B3, the discharge voltage is slightly higher at DOD 75% than at DOD 50%, but it further drops at DOD 85%. A similar tendency is observed when the thickness Tp of the positive electrode 201 is less than 0.8 mm or exceeds 1.4 mm (samples B4 to B6). In other words, in these examples, the discharge voltage is not stable, and the discharge voltage drops significantly as the discharge progresses. This result is considered to be due to the fact that the distribution of the electrolyte 204 in samples B2, B3, B5, and B6 becomes more uneven, causing unevenness in the discharge reaction. In addition, in these comparative examples, it is considered that the discharge voltage drops at DOD 50% because it is difficult to balance the expansion of the positive electrode 201 and the contraction of the negative electrode 202. Sample B6 is an example in which the total area S of first main surface 202A and second main surface 202B is small, and it is believed that the discharge voltage was relatively low from the beginning because the reaction area was small.

[0077] In contrast to the results of the above comparative examples, when the gap C satisfies 0.3 mm≦C≦1.0 mm and the thickness Tp of the positive electrode 201 satisfies 0.8 mm≦Tp≦1.4 mm, no drop in discharge voltage is observed at DOD 50%, and a relatively high discharge voltage can be maintained even at DOD 85% (samples A1 to A7).

[0078] When the entire first main surface 202A and the second main surface 202B do not face the positive electrode 201 (when the outermost electrode of the electrode body 200 is the negative electrode 202), the discharge voltage dropped significantly as the discharge proceeded (sample B1). This is thought to be because the positive electrode 201 is not at the outermost periphery, and therefore no buffering effect is obtained during discharge, causing an uneven reaction, causing partial fracture of the lithium metal of the negative electrode 202, and increasing the resistance of the battery 10. When the outer diameter D of the exterior can 100 exceeds 37 mm or the total area S is less than 700 cm 2Even when the outer diameter D of the outer can 100 was less than 25 mm or the total area S was less than 250 cm, the discharge voltage dropped significantly as the discharge progressed (B7). This is thought to be because the electrode length became excessively long, and the number of broken parts of the negative electrode 202 increased as the discharge progressed. 2 When the temperature was less than 100° C., the discharge voltage dropped significantly as the discharge proceeded (sample B8). This is believed to be because it was difficult to secure a sufficient electrode area for the discharge reaction to occur.

[0079] As shown in Figures 3 and 4, even when the outer diameter D of the outer can 100 was 25 mm or 37 mm, as in the cases of samples A1 to A7, no drop in discharge voltage was observed at DOD 50%, and a relatively high discharge voltage was stably obtained even as the discharge progressed. [Industrial Applicability]

[0080] The lithium primary battery according to the above aspect of the present disclosure has a high capacity, is capable of stable discharge, and is suitable for use in ICT devices controlled to discharge a pulse current. Examples of such devices include various devices (electronic devices, electrical devices, etc.) equipped with a communication function, such as a meter (smart meter, etc.) equipped with a communication function. However, the uses of the lithium primary battery are not limited to these. [Explanation of symbols]

[0081] 10 Lithium primary batteries 100 outer can 200 Winding electrode body 201 Positive electrode 202 Negative electrode 203 Separator 204 Nonaqueous electrolyte 210 Internal lead wire 230A Upper insulation plate 230B Lower insulation plate 300 Sealing body 310 Gasket 330 External terminal

Claims

1. An outer can; A wound electrode body accommodated in the outer can; A nonaqueous electrolyte solution contained in the outer can; Equipped with The wound electrode body is A sheet-like positive electrode; a sheet-like negative electrode having a first main surface and a second main surface opposite to each other; a separator interposed between the positive electrode and the negative electrode; the positive electrode, the negative electrode, and the separator are laminated and wound around a central axis, the first main surface of the negative electrode faces the central axis of the wound electrode body, and the second main surface of the negative electrode faces outward from the wound electrode body, The positive electrode includes a positive electrode mixture including manganese dioxide, The negative electrode includes at least one selected from the group consisting of a lithium alloy and metallic lithium, the entire second principal surface and the first principal surface of the negative electrode face the positive electrode, The total area S of the first main surface and the second main surface of the negative electrode is 250 cm ２ ≦S≦700cm ２ Satisfying the above, The thickness Tp of the positive electrode satisfies 0.8 mm≦Tp≦1.4 mm, The outer diameter D of the outer can satisfies 25 mm≦D≦37 mm, A lithium primary battery, wherein a distance C between the outer can and the wound electrode body satisfies 0.3 mm≦C≦1.0 mm.

2. 2. The lithium primary battery according to claim 1, wherein the thickness Tc of the outer can satisfies 0.3 mm≦Tc≦0.45 mm.

3. 3. The lithium primary battery according to claim 1, wherein a capacity Cp of the positive electrode and a capacity Cn of the negative electrode satisfy Cp≦Cn.

4. The density d of the positive electrode mixture ｐ is 2.6 g / cm ３ ≦d ｐ ≦3.3 g / cm ３ The lithium primary battery according to claim 1 or 2, which satisfies the above.

5. 3. The lithium primary battery according to claim 1, wherein the separator is a microporous film having a thickness of 30 μm or more and 50 μm or less.

6. The container further includes a sealing body that seals an opening of the container.

3. The lithium primary battery according to claim 1, wherein the sealing body is laser welded to the outer casing.

7. 3. The lithium primary battery according to claim 1, wherein the outer can is made of stainless steel.

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