non-aqueous electrolyte battery

Abstract

This non-aqueous electrolyte battery is provided with a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material and an expanded metal. The expanded metal includes frames that constitute a net. The frames of the expanded metal include four bars surrounding each opening of the net, and connectors connecting the bars to one another. At least one of the bars at each opening has a bent or curved shape.

Description

[Technical Field]

[0001] The present disclosure relates to non-aqueous electrolyte batteries. [Background technology]

[0002] Positive and negative electrodes of nonaqueous electrolyte batteries are sometimes constructed by filling a core with a mixture containing an active material, a conductive additive, and a binder. For example, Patent Document 1 discloses a method for producing a positive electrode plate by pressing a sheet of a molded positive electrode mixture onto a lath core made of a 0.1 mm thick stainless steel plate processed to a mesh with a center-to-center dimension SW of 1.5 mm in the short direction, a center-to-center dimension LW of 3.0 mm in the long direction, and a three-dimensional thickness of 0.2 mm.

[0003] Patent Document 2 discloses that in a lead-acid battery using an aqueous electrolyte, when a lead-tin alloy is expanded to obtain a positive electrode grid, the grid is formed into a mesh structure in which the maximum and minimum points of a plurality of continuous curves overlap each other to form intersections, thereby eliminating uneven distribution of distortion during the expansion process, preventing the occurrence of minute cracks inside the grid that could induce corrosion, and suppressing localized corrosion and the resulting deterioration of the lead-acid battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3015579 specification [Patent Document 2] Japanese Patent Application Publication No. 07-94190 Summary of the Invention

[0005] In non-aqueous electrolyte batteries, electrodes (e.g., positive electrodes) are typically produced by filling an expanded metal with a mixture containing an active material, a binder, etc., and then rolling it, as disclosed in Patent Document 1. Expanded metal is a metal plate that has been stretched with numerous cuts to form numerous openings in a mesh pattern (e.g., a diamond pattern).

[0006] Normally, the filling and rolling of the composite material is carried out in the same direction as the short grain direction (SW direction) of the expanded metal. When stresses such as tensile stress and compression are applied to the expanded metal during this process, the distance in the short grain direction of the expanded metal increases, and the distance in the long grain direction (LW direction) decreases, causing the entire bone to deform.

[0007] The elongation of expanded metal is basically due to the physical properties of the base material that makes up the expanded metal. If stress during filling and rolling exceeds the elongation of the base material, the SW may stretch excessively and break. As a result, the current collection ability of the electrode may decrease, and battery performance such as discharge capacity may decrease.

[0008] One aspect of the present disclosure relates to a nonaqueous electrolyte battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte, wherein the positive electrode includes a positive electrode active material and an expanded metal, the expanded metal includes a rib portion forming a mesh, the rib portion includes four or more crosspiece portions surrounding openings of the mesh and connecting portions connecting the crosspieces together, the number of crosspieces per opening is four or more, and at least one crosspiece per opening has a bent or curved shape.

[0009] According to the present disclosure, a nonaqueous electrolyte battery with high energy density and excellent discharge performance can be realized. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of a current collector made of expanded metal. [Figure 2] FIG. 2 is a schematic diagram showing the general configuration of an apparatus used to manufacture the expanded metal of FIG. [Figure 3A] 10A and 10B are schematic diagrams showing examples of curved or bent shapes of crosspieces. [Figure 3B] 10A and 10B are schematic diagrams showing examples of curved or bent shapes of crosspieces. [Figure 3C] 10A and 10B are schematic diagrams showing examples of curved or bent shapes of crosspieces. [Figure 3D] 10A and 10B are schematic diagrams showing examples of curved or bent shapes of crosspieces. [Figure 4] 1 is a partially cross-sectional front view of a nonaqueous electrolyte battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] A non-aqueous electrolyte battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material and an expanded metal.

[0012] Expanded metal is a metal sheet that has been stretched with numerous cuts to form numerous openings in a mesh pattern (e.g., a diamond pattern). The mesh of expanded metal refers to the netting. The center-to-center distance of expanded metal refers to the distance between the centers of the meshes.

[0013] The expanded metal includes ribs that form the mesh. The ribs include crosspieces that surround the openings of the mesh and connectors that connect the crosspieces. There are four or more crosspieces per opening, and at least one crosspiece per opening has a bent or curved shape.

[0014] In an expanded metal, the crosspieces are typically formed linearly extending from one connection to the other. However, in the nonaqueous electrolyte battery according to this embodiment, at least one of the crosspieces is not linear but has a bent or curved shape. This provides extensibility to the crosspieces. Therefore, in the battery manufacturing process, after the expanded metal is filled with a material mixture, the expanded metal is rolled to produce an electrode. This causes the bent or curved portions to stretch (or bend) in response to tensile or compressive stress applied to the expanded metal. This prevents the expanded metal from elongating beyond the inherent elongation of the material. This prevents deformation and breakage of the entire rib portion of the expanded metal. As a result, even when the material mixture is densely packed, the current collection performance of the electrode is not reduced, resulting in a nonaqueous electrolyte battery with high energy density and excellent discharge performance.

[0015] In Patent Document 2, the expanded metal is curved near the intersections of the grid to suppress uneven distribution of strain during the expanding process and prevent the occurrence of microcracks that cause localized corrosion, but does not take into consideration the elongation of the grid that occurs during rolling. Therefore, the invention described in Patent Document 2 is completely different from the present invention, which aims to suppress breakage due to excessive deformation of the expanded metal during rolling. The issue of suppressing corrosion of the grid, which is an issue addressed by the invention described in Patent Document 2, is specific to lead-acid batteries that use a lead-tin alloy for the grid, and does not exist in the nonaqueous electrolyte battery of the present invention.

[0016] The bent or curved shape of the crosspiece may be either a convex or concave shape. When focusing on the contour line of a mesh that includes a bent or curved shape, if the contour line has a convex (concave) shape due to the bent or curved shape, the bent or curved shape is considered to be a convex (concave) shape.

[0017] The bent shape is formed by at least two straight lines. The bent shape may be formed by three or more straight lines. The curved shape may be formed by multiple curves. The bent or curved shape may have a convex shape or a concave shape, such as a wavy curve or a zigzag shape.

[0018] (Expanded Metal) An example of a current collector made of expanded metal is shown in Figure 1. (A) of Figure 1 is a top view, and (B) of Figure 1 is a cross-sectional view taken from the X1-X2 direction. T, SW, LW, and W in (A) of Figure 1 are the wall thickness T of the expanded metal, the center-to-center distance SW in the short direction, the center-to-center distance LW in the long direction, and the feed width W, respectively. The expanded metal 100 shown in Figure 1 can be produced, for example, by processing a metal plate using the manufacturing apparatus shown in Figure 2.

[0019] The expanded metal 100 has four crosspieces 101a to 101d that surround the openings of the mesh and connecting portions 102 that connect the crosspieces. The crosspieces 101a to 101d are processed into a curved shape (arc-shaped in the example of FIG. 1). In this case, when the expanded metal 100 is viewed from a distance, the shape of the mesh resembles a diamond. However, strictly speaking, the shape of the mesh is not diamond-shaped, but is a curve surrounded by four arcs. The radius of curvature of the four arcs is not particularly limited, but can be, for example, 1 to 4 mm.

[0020] By providing the crosspiece with a bent or curved shape, stress applied to the expanded metal during the battery manufacturing process is alleviated by the bent or curved portions stretching and / or by the application of bending stress to the bent or curved portions, thereby suppressing excessive stretching and breakage of the core material and enabling the realization of a nonaqueous electrolyte battery with high energy density and excellent discharge performance.

[0021] Of the crosspieces 101a to 101d, crosspieces 101a and 101c generally extend along a first direction, although the direction of extension changes at the curved portions. Crosspieces 101b and 101d generally extend along a second direction that intersects with the first direction, although the direction of extension changes at the curved portions. The first and second directions are parallel to a line connecting the connecting portions 102. Crosspieces 101a and 101c have the same curved shape, and when crosspiece 101a is translated in the second direction, it overlaps with crosspiece 101c. Crosspieces 101b and 101d have the same curved shape, and when crosspiece 101b is translated in the first direction, it overlaps with crosspiece 101d.

[0022] The expanded metal manufacturing apparatus 200 shown in FIG. 2 includes a lower blade 201 and an upper blade 202 that extend in a first direction D1 parallel to the main surface of a metal sheet 204. The upper blade 202 is movable in the up-down direction (a direction perpendicular to the metal sheet 204). By moving the upper blade 202 downward from the state shown in FIG. 2, it can form incisions in the metal sheet 204 and expand the incisions to form a mesh. The upper blade 202 can also move back and forth within a predetermined width in the first direction D1. In conjunction with the up-down movement of the upper blade 202, the metal sheet 204 is intermittently fed in a second direction D2 that is parallel to the main surface of the metal sheet 204 and perpendicular to the first direction. In addition, the upper blade 202 moves in the first direction D1 in conjunction with the transport of the metal sheet 204 in the second direction D2. As a result, cuts are made in the metal plate 204 at regular intervals in a staggered pattern, and the cut portions are expanded by the upper blade 202 to form a diamond-shaped mesh.

[0023] The upper blade 202 has a curved shape, and the crosspiece is thereby machined into a shape having a corresponding curved shape.

[0024] The thickness T of the expanded metal corresponds to the thickness of the metal plate 204 before processing in Figure 2. The feed width W roughly corresponds to the spacing between the cuts. The center-to-center distance SW in the short direction corresponds to the length of the shorter diagonal line of the diamond-shaped mesh. The center-to-center distance LW in the long direction corresponds to the length of the longer diagonal line of the diamond-shaped mesh.

[0025] In the example of FIG. 1, the crosspiece has a curved shape (arc shape). The curved shape is not limited to an arc, and may be any curved shape. Depending on the curved portion, the outline of the mesh (opening) has a convex or concave portion. The curved shape may be formed by a plurality of curves with different curvatures. The curved shape may be, for example, a shape with convex and concave portions, such as a wavy shape or an S-shape.

[0026] The crosspiece may have a bent shape. The bent shape is formed by at least two straight lines. The bent shape may be formed by three or more straight lines. Like the curved shape, the bent shape may also have a convex shape and a concave shape, such as a zigzag shape.

[0027] FIG. 3 shows other examples of curved or bent shapes of the crosspiece. FIGS. 3A to 3D each show an example in which a bent portion is provided on crosspiece 101a in FIG. 1. As shown in FIG. 3A, the bent shape may be a convex shape with three straight lines, or as shown in FIG. 3B, it may be a concave shape with three straight lines. Alternatively, as shown in FIG. 3C, it may have a zigzag shape formed by multiple straight lines. As shown in FIG. 3D, a convex shape may be formed on the crosspiece by two straight lines.

[0028] The center distance SW in the short direction of the expanded metal and the center distance LW in the long direction are 2 mm. 2 ≦LW·SW≦20mm 2 It is preferable to satisfy 6 mm 2 ≦LW·SW≦20mm 2 It is more preferable to satisfy the following. 2 This allows the positive electrode active material layer to be formed by compression bonding without gaps, reducing variations in the density of the positive electrode active material, thereby suppressing unevenness in the battery reaction (e.g., discharge reaction) within the electrode plate and improving the discharge performance of the battery.

[0029] For example, when making a positive electrode by pressing two sheets of positive electrode mixture together from both sides with an expanded metal sandwiched between them, the LW and SW must be 2 mm. 2 If the distance is less than 2 mm, it is difficult for the sheets to be pressed together, which can cause unevenness in the density of the positive electrode mixture layer. Specifically, the density of the positive electrode mixture becomes high on the surface of the positive electrode, making it difficult for the positive electrode mixture to absorb the electrolyte. As a result, although the battery reaction proceeds near the surface, it is difficult for the reaction to proceed to the inside of the positive electrode mixture layer, and the battery reaction may not be uniform. However, if the distance between LW and SW is 2 mm, 2 By setting the temperature to the above level, the reaction is likely to proceed uniformly, and high discharge characteristics can be maintained.

[0030] On the other hand, as LW·SW is increased, the distance from the positive electrode active material to the expanded metal at the center of the mesh increases, which can lead to a decrease in current collection. 2 It is preferable that:

[0031] SW and LW are 2mm 2 More than 20mm 2 Less than (more preferably, 6 mm 2 More than 20mm 2 ) can be selected as follows:

[0032] The thickness of the positive electrode is preferably 0.3 mm or more and 3 mm or less. More preferably, the thickness of the positive electrode is 0.8 mm or more and 3 mm or less. The thicker the positive electrode, the greater the pressure applied to the expanded metal during filling, thereby enhancing the effect of expanding the expanded metal of the present invention. Furthermore, when the thickness of the positive electrode is 3 mm or less, the distance from the expanded metal to the outermost surface of the electrode is not too great, and a decrease in current collection performance can be suppressed.

[0033] Furthermore, if the thickness T or feed width W of the expanded metal is small, the core material (frame) is likely to break when the positive electrode mixture is crimped. This also increases electrical resistance and reduces current collection. On the other hand, increasing the thickness T or feed width W can prevent the core material (frame) from breaking when the positive electrode mixture is crimped. However, increasing the thickness T or feed width W increases the rigidity of the expanded metal, which can make it difficult to wind the electrodes to form an electrode group.

[0034] The thickness T is preferably 0.1 mm or more, more preferably 0.15 mm or more, so that the expanded metal does not become too thin, so that the expanded metal does not break when the positive electrode mixture is pressed against it, and so that the electrical resistance can be maintained low. On the other hand, if the thickness T is too large, the rigidity increases, making it difficult to process the expanded metal and to wind the electrode plates to form an electrode group (wound body). To facilitate processing of the expanded metal and the production of the wound body, the thickness T is preferably 0.3 mm or less.

[0035] Similarly, the feed width W is preferably 0.13 mm or more, more preferably 0.15 mm or more, so that the expanded metal does not become too thin, so that the expanded metal does not break when the positive electrode mixture is crimped, and so that the electrical resistance can be maintained low. On the other hand, if the feed width W is too large, the rigidity increases, which may make it difficult to wind the electrode plate to form an electrode assembly (wound body). Furthermore, the height H of the expanded metal increases, which may make it difficult to uniformly fill the expanded metal with the positive electrode mixture. To facilitate the formation of the wound body and to suppress density differences in the positive electrode mixture within the electrode plate, the feed width W is preferably 0.3 mm or less.

[0036] Furthermore, the ratio T / W of the wall thickness T to the feed width W is preferably 0.3 to 2.4, more preferably 0.5 to 2, and even more preferably 0.7 to 1.5. If the ratio T / W is less than 0.3, the joints of the expanded metal become bulky, making it difficult to bring the positive electrode mixture into close contact with the joints, and density variations in the positive electrode mixture are likely to occur. Furthermore, the expanded metal is likely to be stretched in the longitudinal direction during compression, which may cause deformation of the lattice shape and reduce current collection efficiency. On the other hand, if the ratio T / W is greater than 2.4, the wire becomes thicker, making it difficult to fill the positive electrode mixture, and density variations in the positive electrode mixture are likely to occur. By setting the ratio T / W in the range of 0.3 to 2.4, it is easy to uniformly fill the expanded metal with the positive electrode mixture, and non-uniform battery reactions are suppressed.

[0037] The height H of the expanded metal may be 0.5 mm or less. By setting the height H to 0.5 mm or less, it is possible to prevent the expanded metal from being exposed when the positive electrode mixture is pressed against the expanded metal. The height H may be reduced by rolling or stretching the expanded metal after processing.

[0038] The height H of the expanded metal refers to the maximum distance from the outer surface of the expanded metal to the flat surface when the expanded metal is placed on the flat surface. Generally, the height H is the distance between two parallel planes that contact the joint of the expanded metal from the outside. In the example of Figure 1, the length H in Figure 1(B) corresponds to the height H of the expanded metal.

[0039] When the expanded metal after processing is subjected to a rolling process or the like, the height H can be determined by cutting the expanded metal or electrode plate and analyzing the contour shape of the expanded metal at the cut surface.

[0040] When SW is set to 1 mm or more, the relationship 1.5≦LW / SW≦3 may be satisfied. In this case, the anisotropy of the electrical resistance in the expanded metal is reduced, and high battery performance is obtained.

[0041] For example, the thickness T of the expanded metal satisfies 0.1 mm≦T≦0.3 mm, and SW and LW are 2 mm or less. 2 ≦LW·SW≦20mm 2 and the feed width W of the expanded metal may satisfy 0.13 mm≦W≦0.3 mm. This allows the use of a wound electrode group to maintain high battery performance (e.g., discharge performance) and achieve high energy density even when the positive electrode is formed to have a thickness of 0.8 mm or greater.

[0042] Expanded metal can be produced by processing a metal plate as described above, for example, using the apparatus shown in Figure 2. Examples of metal plates include stainless steel, aluminum, nickel, and titanium. Among these, stainless steels such as SUS444, SUS430, SUS304, and SUS316 are preferred. The tensile strength of the metal plate is not particularly limited, but is, for example, 400 to 550 N / mm 2 The range may be:

[0043] The tensile strength of the metal plate is 550N / mm 2 If the stress is greater than 400 N / mm, the expanded metal is likely to break partially due to its elongation. Also, the density difference in the positive electrode mixture is likely to become large. 2 If the tensile strength is smaller than this, the expanded metal is easily stretched and is less likely to break, but it becomes difficult to control the density and thickness of the positive electrode mixture. 2 Within this range, the expanded metal is stretched appropriately, preventing breakage, and the density and thickness of the positive electrode mixture can be easily controlled.

[0044] The expanded metal after processing may be subjected to a heat treatment (annealing treatment), which can reduce the Young's modulus of the expanded metal and facilitate winding the electrode plate group to produce an electrode body.

[0045] The Vickers hardness of the metal plate is preferably 230 HV or less, more preferably 160 HV or less. When the Vickers hardness of the metal plate is 230 HV or less, the electrode plate can be wound to obtain an electrode assembly with high circularity, and non-uniformity of the charge / discharge reaction can be suppressed. Furthermore, by setting the Vickers hardness to 160 HV or less, uniformity of the charge / discharge reaction (particularly the discharge reaction) is improved, and high discharge characteristics can be maintained even at a deep discharge depth exceeding 90%.

[0046] The material of the metal plate may be stainless steel, since the Vickers hardness can be easily reduced. When stainless steel is used, austenitic stainless steel (SUS304, SUS316, etc.) is preferable to ferritic stainless steel (SUS430, SUS444, etc.). The Vickers hardness of expanded metal produced by processing austenitic stainless steel can easily be reduced to 160 HV or less by heat treatment (annealing).

[0047] In the example shown in Figure 1, the mesh shape of the expanded metal can be approximated as a diamond, but it can also be a polygonal shape with more than four crosspieces. For example, in the device shown in Figure 2, by increasing the width X of the peaks and valleys of the upper blade 202, it is possible to produce a hexagonal expanded metal with six crosspieces per opening. It is sufficient that at least one of the six crosspieces has a bent or curved shape.

[0048] The shape of the mesh of the expanded metal after the battery is completed may be one in which the bent or curved shape has been deformed by stretching the crosspieces. The crosspieces may also be stretched to form a substantially straight shape. The more the expanded metal crosspieces are stretched, the more they approximate a diamond shape, but they may also approximate a polygonal shape (e.g., a hexagon). The shape of the expanded metal can be obtained from images of the expanded metal frame and crosspieces taken by passing an X-ray through the battery using an X-ray device. The SW and LW values ​​can also be obtained by measuring the dimensions from the images.

[0049] (Positive electrode active material / positive electrode mixture layer) The positive electrode active material may be contained in the positive electrode mixture layer together with a conductive additive and / or a binder. The density of the positive electrode mixture layer is 2.4 g / cm 3 More than 3.2g / cm 3 The density of the positive electrode mixture layer is preferably 2.4 g / cm or less. 3 By setting the density of the positive electrode mixture layer to 3.2 g / cm or more, the bonding strength of the positive electrode mixture layer is strengthened, the expansion of the electrode plate due to charge / discharge is suppressed, and the capacity can be maintained high. On the other hand, the higher the density of the positive electrode mixture layer, the higher the pressure required to press the positive electrode mixture onto the expanded metal, making the expanded metal more susceptible to fracture. However, when the density of the positive electrode mixture layer is set to 3.2 g / cm or more, the positive electrode mixture layer can be pressed against the expanded metal, making the expanded metal more susceptible to fracture. 3 From the viewpoint of battery capacity, the density of the positive electrode mixture layer is set to 2.8 g / cm or less, thereby preventing the expanded metal from breaking during compression. 3 More than 3.2g / cm 3 The following is preferred, and in this case the effect of the present invention is more pronounced.

[0050] The average particle diameter of the positive electrode active material filled into the expanded metal may be 15 μm to 80 μm, or may be 30 μm to 60 μm. When the average particle diameter of the positive electrode active material is 15 μm or more, a large amount of conductive additive adheres to the positive electrode active material particles, improving electrical connection with the expanded metal via the conductive additive. This improves current collection and improves charge / discharge performance. For example, it can suppress voltage drops during pulse discharge. On the other hand, if the average particle diameter is too large, the particles become bulky, which tends to reduce the mixture density and cause the conductive additive to be unevenly distributed in the gaps between the particles. By keeping the average particle diameter within 80 μm, it is possible to suppress decreases in mixture density and current collection.

[0051] The average particle size of the positive electrode active material is measured and calculated in the state of particles or in the state of an electrode.

[0052] Regarding the particle state, the positive electrode active material is extracted from the positive electrode active material alone or from the mixture, and the median diameter (D50) of the particle size at which the cumulative frequency is 50% in the volume-based particle size distribution measured by quantitative laser diffraction / scattering is determined as the average particle size. Alternatively, the median value may be determined by measuring the particle size distribution of multiple active material particles (e.g., 100 or more) using an optical microscope using the equivalent circle diameter, major axis diameter, minor axis diameter, biaxial average diameter, and circumscribed rectangle equivalent diameter.

[0053] The electrode condition may be calculated by removing the positive electrode from the battery, cutting it to prepare a cross section of the positive electrode mixture layer, and observing it with a scanning electron microscope. The magnification is set so that 10 or more active material particles are included in each field of view, and the grain boundaries of the positive electrode active material are determined by image analysis of the cross-sectional photograph. The median value is determined by particle size distribution measurement using the diameter of a circle (equivalent circle) equal to the area of ​​the particles in the cross section, and is used as the average particle size. It is preferable to measure a total of 100 or more particles in multiple fields of view.

[0054] The present disclosure can be applied to any nonaqueous electrolyte battery that uses expanded metal as a current collector, regardless of whether it is a primary battery or a secondary battery, and regardless of the configuration of the positive and negative electrodes. In particular, when applied to a lithium primary battery that includes at least one of metallic lithium and a lithium alloy in the negative electrode, a battery with high capacity and excellent discharge characteristics can be realized. The nonaqueous electrolyte battery may have a cylindrical structure including a wound electrode group formed by spirally winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator interposed therebetween, or a flat-plate or coin-shaped battery having a single-layer or stacked electrode configuration in which a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator are stacked.

[0055] The battery of the present disclosure is not particularly limited as long as it is a nonaqueous electrolyte battery. The nonaqueous electrolyte battery according to this embodiment will be described in more detail below using a cylindrical lithium primary battery as an example.

[0056] [Lithium primary battery] (positive electrode) The positive electrode may include a positive electrode mixture layer and a positive electrode current collector that supports the positive electrode mixture layer. The positive electrode current collector includes an expanded metal. The positive electrode mixture layer can be obtained, for example, by pressing a wet positive electrode mixture prepared by adding an appropriate amount of water to a positive electrode active material and an additive in the thickness direction so as to fill the mesh of the expanded metal, and then drying the wet positive electrode mixture.

[0057] The positive electrode active material contained in the positive electrode may be manganese dioxide. A positive electrode containing manganese dioxide exhibits a relatively high voltage and has excellent pulse discharge characteristics. The manganese dioxide may be in a mixed crystal state containing a plurality of crystalline states. The positive electrode may contain a manganese oxide other than manganese dioxide. Examples of manganese oxide other than manganese dioxide include MnO, Mn3O4, Mn2O3, and Mn2O7. It is preferable that the main component of the manganese oxide contained in the positive electrode is manganese dioxide.

[0058] A portion of the manganese dioxide contained in the positive electrode may be doped with lithium. If the amount of lithium doped is small, high capacity can be ensured. Manganese dioxide and manganese dioxide doped with a small amount of lithium are x MnO2 (0≦x≦0.05). The average composition of the manganese oxides contained in the positive electrode is Li x MnO2 (0≦x≦0.05). The Li ratio x should be 0.05 or less in the initial discharge state of the lithium primary battery. The Li ratio x generally increases as the discharge of the lithium primary battery progresses. Theoretically, the oxidation number of manganese contained in manganese dioxide is tetravalent. However, if other manganese oxides are contained in the positive electrode or if manganese dioxide is doped with lithium, the oxidation number of manganese may become smaller than tetravalent. Therefore, Li x In MnO2, the average oxidation state of manganese is allowed to be slightly lower than tetravalent.

[0059] The positive electrode may contain other positive electrode active materials used in lithium primary batteries. Examples of other positive electrode active materials include graphite fluoride. The percentage of Li in the total positive electrode active material isx The proportion of MnO2 may be 90 mass % or more.

[0060] As the manganese dioxide, electrolytic manganese dioxide is preferably used. If necessary, electrolytic manganese dioxide may be subjected to at least one of neutralization, washing, and calcination. Electrolytic manganese dioxide is generally obtained by electrolysis of an aqueous manganese sulfate solution.

[0061] By adjusting the conditions during electrolysis, the crystallinity of manganese dioxide can be increased and the specific surface area of ​​electrolytic manganese dioxide can be reduced. x The BET specific surface area of ​​MnO2 is 10m 2 / g or more 50m 2 / g or less. x When the BET specific surface area of ​​MnO2 is within this range, in a lithium primary battery, the voltage drop during pulse discharge can be suppressed, self-discharge can be more effectively suppressed, and gas generation can be suppressed. In addition, a positive electrode mixture layer can be easily formed.

[0062] Li x The BET specific surface area of ​​MnO2 may be measured by a known method, for example, by the BET method using a specific surface area measuring device (for example, manufactured by Mountec Co., Ltd.) For example, LixMnO2 separated from the positive electrode removed from a battery may be used as a measurement sample.

[0063] Li x The median particle diameter of MnO2 may be 15 μm or more and 80 μm or less. When the median particle diameter (median diameter D50) is in this range, the positive electrode active material Li x MnO2 connects to the current collector (expanded metal) via numerous conductive additives, improving current collection. It also prevents a decrease in mix density, which would otherwise lead to uneven distribution of conductive additives in the gaps between particles, resulting in a decrease in current collection. This improves discharge performance and suppresses voltage drops during pulse discharge.

[0064] Li xThe median particle size of MnO2 is the median of the particle size distribution determined by, for example, quantitative laser diffraction and scattering (qLD) method. x MnO2 can be used as a measurement sample. For the measurement, for example, an SALD-7500nano manufactured by Shimadzu Corporation is used.

[0065] The positive electrode mixture may contain a binder in addition to the positive electrode active material. The positive electrode mixture may also contain a conductive agent.

[0066] Examples of the binder include fluororesin, rubber particles, and acrylic resin.

[0067] Examples of the conductive agent include conductive carbon materials, such as natural graphite, artificial graphite, carbon black, and carbon fiber.

[0068] (Negative electrode) The negative electrode may contain metallic lithium or a lithium alloy, or may contain both metallic lithium and a lithium alloy. For example, a composite containing metallic lithium and a lithium alloy may be used for the negative electrode.

[0069] Examples of lithium alloys include Li-Al alloys, Li-Sn alloys, Li-Ni-Si alloys, Li-Pb alloys, etc. The content of metal elements other than lithium contained in the lithium alloy is preferably 0.05 to 15 mass % from the viewpoints of ensuring discharge capacity and stabilizing internal resistance.

[0070] The metallic lithium, lithium alloy, or composite thereof is formed into any shape and thickness depending on the shape, dimensions, performance specifications, etc. of the lithium primary battery.

[0071] A sheet of metallic lithium, a lithium alloy, or a composite thereof may be used for the negative electrode. The sheet can be obtained, for example, by extrusion. More specifically, in cylindrical batteries, a foil of metallic lithium or a lithium alloy having a shape with a longitudinal direction and a transverse direction is used.

[0072] In the case of a cylindrical battery, a long tape comprising a resin substrate and an adhesive layer may be attached along the longitudinal direction to at least one main surface of the negative electrode. The main surface refers to the surface facing the positive electrode. The width of this tape is preferably 0.5 mm or more and 3 mm or less. This tape serves to prevent the negative electrode from being torn off and causing current collection problems when the lithium component of the negative electrode is consumed by a reaction at the end of discharge.

[0073] Examples of materials that can be used for the resin substrate include fluororesin, polyimide, polyphenylene sulfide, polyethersulfone, polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, etc. Among these, polyolefins are preferred, and polypropylene is more preferred.

[0074] The adhesive layer contains, for example, at least one component selected from the group consisting of a rubber component, a silicone component, and an acrylic resin component. Specifically, the rubber component may be synthetic rubber or natural rubber. Examples of synthetic rubber include butyl rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, neoprene, polyisobutylene, acrylonitrile-butadiene rubber, styrene-isoprene block copolymer, styrene-butadiene block copolymer, and styrene-ethylene-butadiene block copolymer. Examples of silicone components include organic compounds having a polysiloxane structure and silicone-based polymers. Examples of silicone-based polymers include peroxide-curable silicones and addition reaction silicones. The acrylic resin component can be a polymer containing an acrylic monomer such as acrylic acid, methacrylic acid, an acrylic acid ester, or a methacrylic acid ester, and examples thereof include homopolymers or copolymers of acrylic monomers such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate, octyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. The adhesive layer may contain a crosslinker, a plasticizer, and a tackifier.

[0075] (electrolyte) The electrolyte (nonaqueous electrolyte) may be, for example, a nonaqueous electrolytic solution in which lithium salt or lithium ions are dissolved in a nonaqueous solvent.

[0076] (non-aqueous solvent) Examples of non-aqueous solvents include organic solvents that are commonly used in non-aqueous electrolytes for lithium primary batteries. Examples of non-aqueous solvents include ethers, esters, and carbonate esters. Examples of non-aqueous solvents that can be used include dimethyl ether, γ-butyl lactone, propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane. The non-aqueous electrolyte may contain one non-aqueous solvent or two or more non-aqueous solvents.

[0077] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the nonaqueous solvent preferably contains a cyclic carbonate ester with a high boiling point and a chain ether that has low viscosity even at low temperatures. The cyclic carbonate ester preferably contains at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC), with PC being particularly preferred. The chain ether preferably has a viscosity of 1 mPa·s or less at 25°C, and particularly preferably contains dimethoxyethane (DME). The viscosity of the nonaqueous solvent is measured using a Rheosens m-VROC microsample viscometer at 25°C and a shear rate of 10,000 (1 / s).

[0078] (lithium salts) The non-aqueous electrolyte may contain a lithium salt other than the cyclic imide component. Examples of the lithium salt include lithium salts used as solutes in lithium primary batteries. Examples of such lithium salts include LiCF3SO3, LiN(CF3SO2)2, LiClO4, LiBF4, LiPF6, and LiR a SO3(R a is a fluorinated alkyl group with 1 to 4 carbon atoms), LiFSO3, LiN(SO2R b )(SO2R c )(R b and R c are each independently a fluorinated alkyl group having 1 to 4 carbon atoms), LiN(FSO2)2, LiPO2F 2、 Examples of lithium salts include LiB(C2O4)2 and LiBF2(C2O4). The non-aqueous electrolyte may contain one or more of these lithium salts.

[0079] (others) The concentration of lithium ions contained in the electrolyte (total concentration of lithium salts) is, for example, 0.2 to 2.0 mol / L, and may be 0.3 to 1.5 mol / L.

[0080] The electrolyte may contain additives as needed. Examples of such additives include propane sultone and vinylene carbonate. The total concentration of such additives contained in the non-aqueous electrolyte is, for example, 0.003 to 5 mol / L.

[0081] (separator) Lithium primary batteries typically include a separator interposed between a positive electrode and a negative electrode. The separator may be a porous sheet made of an insulating material that is resistant to the internal environment of a lithium primary battery. Specific examples of the separator include a synthetic resin nonwoven fabric, a synthetic resin microporous membrane, and a laminate thereof.

[0082] Examples of synthetic resins used for nonwoven fabrics include polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Examples of synthetic resins used for microporous membranes include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers. The microporous membrane may contain inorganic particles as needed.

[0083] The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0084] 4 shows a partially cross-sectional front view of a cylindrical lithium primary battery according to one embodiment of the present disclosure. In the lithium primary battery 10, an electrode group, in which a positive electrode 1 and a negative electrode 2 are wound with a separator 3 interposed therebetween, is housed in a battery case 9 together with a non-aqueous electrolyte (not shown). A sealing plate 8 is attached to the opening of the battery case 9. A positive electrode lead 4 connected to a current collector 1a of the positive electrode 1 is connected to the sealing plate 8. A negative electrode lead 5 connected to the negative electrode 2 is connected to the case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are arranged on the top and bottom of the electrode group, respectively, to prevent internal short circuits.

[0085] [Example] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0086] 《Batteries A1~A3》 (1) Preparation of the positive electrode 100 parts by mass of electrolytic manganese dioxide and 5 parts by mass of Ketjen black, a conductive agent, were mixed, and then 5 parts by mass of polytetrafluoroethylene, a binder, and an appropriate amount of pure water were added and kneaded to prepare a wet positive electrode mixture.

[0087] An expanded metal was prepared as a positive electrode current collector. The expanded metal was made of stainless steel (SUS316), and after being processed into an expanded metal, it was subjected to heat treatment (annealing) at 1000°C for 10 minutes in a reducing atmosphere.

[0088] The expanded metal used had a center-to-center distance SW of 2 mm in the short direction and a center-to-center distance LW of 4 mm in the long direction, with four connecting parts forming a roughly diamond-shaped mesh opening. However, the sides of the diamond (the crosspieces) were not straight, but formed into arc-shaped curves, similar to the shape shown in Figure 1(A). The maximum distance from the curve represented by the center line of the arc-shaped crosspieces to the line connecting the connecting parts (dimension Y in Figure 1(A)) was 0.2 mm.

[0089] Two pairs of rolls were prepared. For each pair, a positive electrode mixture was placed between the pair of rolls to obtain a positive electrode mixture sheet. The two obtained positive electrode mixture sheets were pressed together on both sides using an expandable metal and dried to obtain a positive electrode precursor. The positive electrode precursor was then rolled using another pair of rolls to obtain a positive electrode with a predetermined positive electrode mixture density. The thickness of the rolled positive electrode was 0.8 mm.

[0090] Thereafter, the positive electrode was cut into a strip having a width of 42 mm with the shorter side of the expanded metal as the longitudinal direction. Subsequently, a portion of the filled positive electrode mixture was peeled off, and a tab lead made of SUS316 was resistance-welded to the exposed portion of the positive electrode current collector.

[0091] (2) Preparation of the negative electrode The negative electrode was obtained by cutting the metallic lithium foil into a strip of a predetermined size (width 40 mm). A nickel tab lead was connected to the negative electrode at a predetermined position by pressure welding.

[0092] (3) Preparation of electrode groups The positive and negative electrodes were stacked with a separator between them and wound around a 4 mm diameter core, with the axis parallel to the longitudinal direction of the expanded metal. A 25 μm thick polyethylene microporous membrane was used as the separator.

[0093] (4) Preparation of non-aqueous electrolyte PC and DME were mixed at a volume ratio of 4:6. LiCF3SO3 was dissolved in the resulting mixture to a concentration of 0.5 mol / L to prepare a non-aqueous electrolyte.

[0094] (5) Assembly of lithium primary batteries A cylindrical battery case with a bottom made of nickel-plated steel sheet of a predetermined size was prepared. The electrode group was inserted into the battery case with a ring-shaped lower insulating plate attached to the bottom. The positive electrode tab lead was then connected to the inner surface of the sealing plate, and the negative electrode tab lead was connected to the inner bottom surface of the battery case.

[0095] Next, a nonaqueous electrolyte was poured into the battery case, and an upper insulating plate was placed on the electrode group. The opening of the battery case was then sealed with a sealing plate. Each battery was then pre-discharged to a battery voltage of 3.2 V. In this way, a test lithium primary battery (diameter 17 mm, height 50 mm) with a design capacity of 3 Ah was completed, as shown in Figure 3.

[0096] The average particle size (median value D50) of the MnO2 contained in the positive electrode was 25 μm.

[0097] In the preparation of the positive electrode, the thickness of the positive electrode precursor and the pressure during rolling were changed to prepare batteries A1 to A3 with different positive electrode mixture densities. In battery A1, the positive electrode mixture density was 2.6 g / cm 3 In battery A2, the positive electrode mixture density was 2.8 g / cm 3In battery A3, the positive electrode mixture density was 3.0 g / cm 3 It was decided.

[0098] In this way, test lithium primary batteries A1 to A3 were produced and evaluated by the following methods.

[0099] (6) Evaluation The lithium primary battery immediately after assembly was discharged with a pulse current of 500 mA for 1 second, and the battery voltage V1 after pulse discharge was measured. Note that the discharge was performed in an environment of 25°C.

[0100] 《Batteries B1~B3》 In the preparation of the positive electrode, an expanded metal having a roughly diamond-shaped mesh opening with four connecting parts was used, and the sides of the diamond were formed into roughly straight lines. The center-to-center distance SW in the short direction of the expanded metal was 2 mm, and the center-to-center distance LW in the long direction was 4 mm. Except for this, test lithium primary batteries B1 to B3 were prepared in the same manner as batteries A1 to A3 and evaluated in the same manner. For battery B1, the positive electrode mixture density was 2.6 g / cm 3 In battery B2, the positive electrode mixture density was 2.8 g / cm 3 In battery B3, the positive electrode mixture density was 3.0 g / cm 3 It was decided.

[0101] Table 1 shows the evaluation results of the voltage V1 after pulse discharge for lithium primary batteries A1 to A3 and B1 to B3. Batteries A1 to A3 are examples, and batteries B1 to B3 are comparative examples. Table 1 also shows the positive electrode mixture density for each battery. For batteries A1 to 3 and B1 to B3, the longitudinal lengths of the positive and negative electrodes after cutting were adjusted according to the positive electrode mixture density so as to achieve a constant design capacity. In addition, the thickness of the negative electrode was adjusted so as to achieve a capacity sufficient for the positive electrode's design capacity.

[0102] As can be seen from Table 1, batteries A1 to A3, which used expanded metal with curved crosspieces, were able to maintain a higher voltage V1 after pulse discharge than batteries B1 to B3, which used conventional expanded metal with straight crosspieces. Furthermore, no fracture of the expanded metal was observed during the preparation of the positive electrode.

[0103] The positive electrode mixture density is 2.6 g / cm 3 In the case of Battery B1, the voltage V1 after pulse discharge was 2.80 V, which was lower than that of Battery A1. 3 When the positive electrode mixture density was 3.0 g / cm, the voltage V1 after pulse discharge in Battery B2 was 2.50 V, which was significantly lower than that of Battery A2. When the positive electrode used in Battery B2 was examined, it was found that the force applied to the expanded metal during rolling of the positive electrode precursor was large, causing partial fracture of the expanded metal. 3 In battery B3, the expanded metal had more broken portions than battery B2, and a wound electrode group could not be produced, so the battery did not function.

[0104] In contrast, the batteries A1 to A3 were able to maintain a high post-pulse discharge voltage V1 of 2.85 V regardless of the positive electrode mixture density.

[0105] [Table 1] [Industrial Applicability]

[0106] The nonaqueous electrolyte battery of the present disclosure has a high energy density and excellent discharge characteristics, and therefore can be suitably used, for example, as a main power source or memory backup power source for various meters. [Explanation of symbols]

[0107] 1 positive electrode 1a Positive electrode current collector 2 negative electrode 3 Separator 4 Positive lead 5 Negative lead 6 Upper insulating plate 7 Lower insulating plate 8 Sealing plate 9 Battery case 10. Lithium primary batteries 100 Expanded Metal 101a~101d Cross section 102 Connection 200 Expanded metal manufacturing equipment 201 Lower blade 202 Upper blade 204 Metal plate

Claims

1. A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, the positive electrode includes a positive electrode active material and an expanded metal; The expanded metal includes a rib portion that forms a mesh, The rib portion includes a rib portion surrounding an opening of the mesh and a connecting portion connecting the rib portions to each other, The number of the crosspieces per opening is four or more, At least one of the crosspieces per opening has a bent shape, The nonaqueous electrolyte battery, wherein the bent shape is formed by two or more straight lines.

2. A non-aqueous electrolyte battery comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte, the positive electrode includes a positive electrode active material and an expanded metal; The expanded metal includes a rib portion that forms a mesh, The rib portion includes a rib portion surrounding an opening of the mesh and a connecting portion connecting the rib portions to each other, The number of the crosspieces per opening is four or more, At least one of the crosspieces per opening has an arc shape with a curvature radius of 1 to 4 mm.

3. The center distance SW in the short direction and the center distance LW in the long direction of the expanded metal are 2 mm ２ ≦LW・SW≦20mm ２ The nonaqueous electrolyte battery according to claim 1 or 2, which satisfies the above.

4. The nonaqueous electrolyte battery according to claim 3, wherein the center-to-center distance SW and the center-to-center distance LW satisfy 6 mm 2 ≦LW·SW≦20 mm 2 .

5. The thickness T of the expanded metal satisfies 0.1 mm≦T≦0.3 mm, 5. The nonaqueous electrolyte battery according to claim 1, wherein a feed width W of the expanded metal satisfies 0.13 mm≦W≦0.3 mm.

6. 6. The nonaqueous electrolyte battery according to claim 1, wherein the positive electrode has a thickness of 0.3 mm or more and 3 mm or less.

7. 7. The nonaqueous electrolyte battery according to claim 1, wherein SW is 1 mm or more and 1.5≦LW / SW≦3 is satisfied.

8. 8. The nonaqueous electrolyte battery according to claim 1, wherein the positive electrode active material contains manganese dioxide.

9. The positive electrode mixture density is 2.4 g / cm ３ 3.2g / cm or more ３ 9. The nonaqueous electrolyte battery according to claim 8, wherein:

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