JP2006216354A - Nonaqueous electrolyte solution primary cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte solution primary cell excellent in long-term reliability capable of constant ratio discharge at a comparatively low load for a long period of time, with excellent heavy-load pulse discharge characteristics maintained. <P>SOLUTION: For the nonaqueous electrolyte solution primary cell equipped with a cathode made by laminating two cathode mixture layers containing active matters and conductive additives through a collector, the two cathode mixture layers contain the active matters with different potentials. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte primary battery.

  As the current non-aqueous electrolyte primary battery, for example, a high-capacity type battery (for example, Patent Document 1) corresponding to a use as a drive power source of a device that is used for a long time with a relatively light load. On the other hand, there is a type (for example, Patent Document 2) corresponding to an application in which a heavy load is instantaneously applied, such as for a device requiring pulse discharge. However, there are cases where both heavy load pulse discharge (for flash) and constant rate discharge (for driving other than flash) at a relatively light load for a long period of time are required, like a battery for a power supply of a camera.

JP 2000-315497 A JP 59-78460 A

  Examples of the method for improving the heavy load pulse discharge characteristics of the nonaqueous electrolyte primary battery include (1) increasing the area of the electrode and (2) improving the separator. However, in the conventional high-capacity non-aqueous electrolyte primary battery suitable for light load applications, the heavy load pulse discharge characteristics are improved by the above methods (1) and (2), and the above-described camera driving power source and the like. Even when trying to make a battery suitable for the above, there are the following problems.

  That is, in the method (1), for example, the electrode is formed as a wound electrode body. However, even when the electrode is formed as described above, the volume of the battery is limited. Therefore, there is a limit to securing a capacity suitable for long-term constant rate discharge with a light load while making the electrode suitable for heavy load pulse discharge characteristics. Also, in the method (2), it is often necessary to reduce the thickness as a result of improvement of the separator. For this reason, there is a problem that the risk of short-circuiting during production and long-term storage increases, and long-term reliability is impaired. Thus, with the conventional method, it is difficult to provide a battery that has a good heavy-load pulse discharge characteristic and can perform a constant rate discharge at a relatively light load over a long period of time.

  The present invention has been made in view of the above circumstances, and its purpose is to have excellent heavy-load pulse discharge characteristics, and capable of constant rate discharge at a relatively light load over a long period of time, and excellent long-term reliability. Another object is to provide a non-aqueous electrolyte primary battery.

  The non-aqueous electrolyte primary battery of the present invention that has achieved the above object has a positive electrode in which two positive electrode mixture layers containing an active material and a conductive additive are laminated via a current collector. In addition, the two positive electrode mixture layers are characterized in that the potentials of the active materials contained are different.

  According to the present invention, it is possible to provide a non-aqueous electrolyte primary battery excellent in both heavy load pulse discharge characteristics and long-term continuity of constant rate discharge at a relatively light load.

  Hereinafter, the configuration of the nonaqueous electrolyte primary battery of the present invention will be described in detail.

  The positive electrode according to the battery of the present invention includes an active material and a conductive auxiliary agent, and two positive electrode mixture layers formed by binding them with a binder are formed on both surfaces of a current collector. These two positive electrode mixture layers contain active materials having different potentials, and a layer containing a higher potential active material (that is, a positive electrode mixture layer containing a high potential active material) is included. It works more preferentially during constant rate discharge at relatively light loads. In addition, during heavy load pulse discharge, a layer containing a higher potential active material and a layer containing a lower potential active material (that is, a positive electrode mixture layer containing a lower potential active material) Works. These two positive electrode mixture layers are connected in parallel by a current collector interposed therebetween, and are configured such that each positive electrode mixture layer can suitably act according to a required discharge.

Examples of the positive electrode active material that can be used for the positive electrode according to the present invention include manganese dioxide (MnO ₂ ), lithium manganate, carbon fluoride, lithium titanate, iron disulfide, and copper oxide. Examples of the combination of the active material in the positive electrode mixture layer containing the low potential active material and the active material in the positive electrode mixture layer containing the high potential active material include, for example, lithium manganate / manganese dioxide, titanic acid Lithium / manganese dioxide, lithium titanate / lithium manganate, lithium titanate / iron disulfide, lithium titanate / copper oxide (the active material / high potential of the positive electrode mixture layer containing the low potential active material) Means an active material related to a positive electrode mixture layer containing an active material). These potential differences can be compared with the potential based on the metal Li. For example, lithium manganate (LiMn ₃ O ₆ ) is 3.5 V, manganese dioxide (MnO ₂ ) is 3.6 V, and the theoretical electric capacity of each is lithium manganate is 202 mAh / g, and manganese dioxide is 308 mAh / g.

  As described above, by using materials having different potentials as the active materials contained in each positive electrode mixture layer formed through the current collector, for example, when discharge at a relatively light load is required. Contains a high-potential active material, and the positive electrode mixture layer having a higher potential acts preferentially to achieve efficient discharge. Even when discharge under heavy load is required, at the beginning of discharge, a positive electrode mixture layer having a higher potential (that is, a positive electrode mixture layer containing a high-potential active material) acts preferentially and discharges. However, with the discharge, the discharge capacity of the mixture layer can hardly be consumed and a significant potential drop occurs, and a positive electrode mixture layer having a lower potential (that is, containing a low potential active material). When the potential of the positive electrode mixture layer) is reached, the lower potential positive electrode mixture layer acts together with the higher potential positive electrode mixture layer. Therefore, even in heavy load discharge, a large amount of electricity can be discharged.

  An active material related to a positive electrode mixture layer containing a low potential active material is an active material that can be used as a positive electrode material of a secondary battery. For example, in a battery using Li ions, It is also preferable to have a site that can be occluded / released. When such an active material is used as the low-potential active material, for example, the capacity of the positive electrode mixture layer containing the low-potential active material is increased in the layer due to the discharge (heavy load pulse discharge) that acts preferentially. Even if the consumption of the lithium ion proceeds, the Li ions taken into the layer move to the positive electrode mixture layer side containing the high-potential active material that exists via the current collector, so that the low-potential layer has a low potential. The positive electrode mixture layer containing the active material is charged. Therefore, a heavy load pulse discharge can be performed more than the theoretical electric capacity of the positive electrode mixture layer containing the active material having a low potential.

  In the positive electrode mixture layer containing a low-potential active material, examples of the active material for ensuring the charging effect include various compounds used as the positive electrode active material in conventionally known non-aqueous secondary batteries. Can be used. Specific examples include lithium composite oxides such as lithium manganate and lithium titanate. And when using the said active material for the positive mix layer containing a low potential active material, the active material of the positive mix layer containing a low potential active material, and the positive electrode containing a high potential active material As a combination with the active material of the mixture layer, lithium manganate / manganese dioxide, lithium titanate / manganese dioxide, lithium titanate / lithium manganate (above, the positive electrode mixture layer containing a low potential active material) Active material / active material relating to positive electrode mixture layer containing high-potential active material).

  Examples of the conductive auxiliary in the positive electrode mixture layer include flaky graphite, acetylene black, ketjen black, carbon black, and the like, and these can be used alone or in combination of two or more. Each of the two positive electrode mixture layers may contain the same type of conductive assistant, or may contain different types of conductive assistants.

  Examples of the binder in the positive electrode mixture layer include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene, and a polymer of propylene hexafluoride.

  The active material content in each positive electrode mixture layer is, for example, 73% by mass or more, more preferably 80% by mass or more, and 91% by mass when the total component amount of each positive electrode mixture layer is 100% by mass. % Or less, more preferably 87% by mass or less. If the content of the active material in each positive electrode mixture layer is too small, the battery capacity may be reduced. If the content is too large, the amount of other components may be reduced, which may cause inconvenience.

  In addition, the content of the conductive additive in each positive electrode mixture layer is, for example, 2% by mass or more, more preferably 3% by mass or more, assuming that the total component amount of these layers is 100% by mass, and 25 It is preferable to set it as mass% or less, More preferably, it is 20 mass% or less. If the content of the conductive auxiliary agent in each positive electrode mixture layer is too small, the conductivity of the positive electrode mixture layer may be insufficient. May occur.

  Further, the positive electrode mixture layers may have the same conductive auxiliary agent content and may be different within a range not impairing the effects of the present invention, but the positive electrode mixture containing a low potential active material. It is preferable that the conductive auxiliary agent content rate in a layer is higher than the conductive auxiliary agent content rate in the positive mix layer containing an active material of high potential. From the viewpoint of enhancing the heavy load pulse discharge characteristics, it is preferable to improve the conductivity of the positive electrode mixture layer. On the other hand, in order to ensure the light load discharge characteristics, it is preferable to ensure the heavy load pulse discharge characteristics. However, it is preferable to decrease the amount of the conductive auxiliary agent and increase the amount of the active material from the viewpoint of securing the discharge capacity. Therefore, by making the conductive additive content in the positive electrode mixture layer containing the low potential active material higher than the conductive auxiliary agent content in the positive electrode mixture layer containing the high potential active material, In the positive electrode mixture layer containing the active material, the conductivity is increased and a good structure is obtained by heavy load pulse discharge, while in the positive electrode mixture layer containing the high potential active material, the electric capacity is increased and the light load is increased. In order to secure the continuity of discharge in the case, a better configuration can be obtained. In this case, the content of the conductive additive in the positive electrode mixture layer containing the low-potential active material is, for example, 7% by mass or more, more preferably 10% by mass, when the total component amount of the layer is 100% by mass. % Or more and 25% by mass or less, more preferably 20% by mass or less, and the content of the conductive assistant in the positive electrode mixture layer containing the high-potential active material is the total composition of the layer. When the amount of the component is 100% by mass, for example, it is desirably 2% by mass or more, more preferably 3% by mass or more and 7% by mass or less, more preferably 5% by mass or less. While satisfying the auxiliary agent content, the positive electrode mixture layer containing a low potential active material has a higher conductive auxiliary agent content than the positive electrode mixture layer containing a high potential active material. do it. In addition, the difference in the content of the conductive additive between the positive electrode mixture layer containing the low potential active material and the positive electrode mixture layer containing the high potential active material is, for example, the positive electrode mixture containing the high potential active material. The conductive auxiliary agent content (mass basis) in the positive electrode mixture layer containing the low potential active material is preferably about 2 to 10 times the conductive auxiliary agent content (mass basis) in the agent layer. .

  The binder content in each positive electrode mixture layer is, for example, 2% by mass or more, more preferably 3% by mass or more, and 8% by mass, when the total constituent amount of each positive electrode mixture layer is 100% by mass. Hereinafter, it is more preferable that the content be 5% by mass or less. If the binder content in each positive electrode mixture layer is too small, the binding of the active material or the conductive auxiliary agent may be insufficient, and if it is too large, the amount of other components will decrease, resulting in inconvenience. May occur.

  The positive electrode mixture layer having a high-potential active material is required to have a relatively light load for a long period of time. Therefore, it is preferable that the positive electrode mixture layer has a suitable electric capacity. Even in a positive electrode mixture layer containing an active material having a potential, an electric capacity corresponding to a certain number of times of discharge is possible even if a large amount of discharge is not required in one heavy-load pulse discharge. It is desirable to have it. Thus, in order to ensure a good balance between the capacity for heavy load pulse discharge and the capacity for long-term discharge at a light load, for example, with respect to the electric capacity of the positive electrode mixture layer containing a low-potential active material. It is recommended that the electric capacity of the positive electrode mixture layer containing the active material having a high potential is 1.0 times or more, more preferably 2 times or more, and 10 times or less, more preferably 8 times or less. Is done. The electric capacity referred to in the present invention means a theoretical capacity.

  The thickness of the positive electrode mixture layer containing the low-potential active material is, for example, 0.1 mm or more, more preferably 0.2 mm or more, and 1.0 mm or less, more preferably 0.7 mm or less. desirable. The thickness of the positive electrode mixture layer containing the active material having a high potential is, for example, 0.2 mm or more, more preferably 0.3 mm or more, and 2.0 mm or less, more preferably 1.5 mm or less. It is desirable. It is recommended that the thicknesses of these two positive electrode mixture layers be selected from the above preferred thicknesses while satisfying the above electric capacity ratio.

  Examples of the current collector used for the positive electrode include those made of stainless steel such as SUS316, SUS430, and SUS444. Examples of the current collector include plain weave metal mesh, expanded metal, lath net, punching metal, metal foam, A foil (plate) etc. can be illustrated. The thickness of the current collector is preferably, for example, 0.05 mm to 0.2 mm. It is also desirable to apply a paste-like conductive material such as carbon paste or silver paste to the surface of such a current collector.

  The positive electrode is made into a pre-sheet by, for example, rolling a positive electrode mixture (slurry) formed by adding a conductive additive or a binder to the positive electrode active material and adding water or the like as necessary, using a roll or the like, A product obtained by drying and pulverizing this product and rolling it again into a sheet shape (that is, a sheet serving as a positive electrode mixture layer) can be manufactured by pressing the current collector and pressing it.

  In the non-aqueous electrolyte primary battery of the present invention, from the viewpoint of improving the heavy load characteristics, the positive electrode mixture layer containing a low potential active material is more likely to act more preferentially during discharge. It is preferable to have. Specifically, it is preferable that at least a positive electrode mixture layer containing a low-potential active material is disposed so as to face the negative electrode among the two positive electrode mixture layers.

  The negative electrode according to the present invention includes, for example, a lithium foil that is a negative electrode active material and a metal foil that is a negative electrode current collector. Examples of the material of the lithium foil include not only lithium metal but also lithium alloys such as lithium-aluminum. In particular, the negative electrode active material is a laminate obtained by bonding a lithium metal foil and an aluminum thin foil, and the aluminum thin foil side is at least a positive electrode mixture layer side containing a low potential active material. It is preferable to arrange. The laminated body of lithium metal foil and aluminum foil produces a lithium-aluminum alloy at the interface by touching the nonaqueous electrolyte described later in the battery. Therefore, when a laminate of a lithium metal foil and an aluminum thin foil is used, a lithium-aluminum alloy is formed on the surface of the lithium metal foil in the battery. At this time, the lithium-aluminum alloy is pulverized, so that the lithium metal On the alloy-containing surface of the foil, the specific surface area increases. Therefore, it becomes possible to discharge more efficiently by making this alloy-containing surface a surface facing the positive electrode mixture layer containing the active material having a low potential. In addition, as thickness of lithium foil, it is preferable that it is 0.1 mm-1 mm, for example. Moreover, when using the laminated body of said lithium metal foil and aluminum thin foil, the thickness of lithium metal foil shall be 0.1 mm-1 mm, and the thickness of aluminum thin foil is 0.005 mm-0.05 mm. It is desirable to do.

  Examples of the material for the negative electrode current collector include copper, nickel, iron, and stainless steel. Since the internal volume of the outer can decreases by the thickness of the negative electrode current collector, the thickness dimension of the negative electrode current collector is preferably as small as possible, specifically, for example, 0.1 mm or less. Recommended. That is, if the negative electrode current collector is too thick, the amount of the lithium foil that is the negative electrode active material must be reduced, and the battery capacity may be reduced. Moreover, since it will be easy to tear when a negative electrode collector is too thin, it is desirable that the thickness of a negative electrode collector be 0.005 mm or more. Moreover, it is preferable that the width | variety of a negative electrode collector is the same as that of a lithium foil, or it is wider than it, and it is preferable that the area is 100 to 130% of the area of a lithium foil. By making the area of the negative electrode current collector as described above, the width of the negative electrode current collector is the same as or wider than the width of the lithium foil, and the length becomes longer, so the lithium foil along the periphery of the negative electrode current collector It is possible to prevent the electrical connection from being cut off due to disconnection.

  An example (vertical side view) of the form of the nonaqueous electrolyte primary battery of the present invention is shown in FIG. In FIG. 1, a non-aqueous electrolyte primary battery 1 is formed by winding a bottomed cylindrical outer can 2 having an upper opening, and a positive electrode and a negative electrode loaded in the outer can 2 via a separator. It has a sealing structure for sealing the upper electrode 3, the non-aqueous electrolyte (hereinafter simply referred to as “electrolyte”), and the upper opening of the outer can 2. In other words, the non-aqueous electrolyte primary battery 1 of FIG. 1 has a positive electrode and a negative electrode wound via a separator in a space surrounded by an outer can 2 and a sealing structure that seals the upper opening of the outer can 2. It has a power generation element such as a wound wound electrode body 3 and an electrolytic solution. The outer can 2 is made of iron or stainless steel.

  The sealing structure is attached to the cover plate 8 fixed to the inner peripheral edge of the upper opening of the outer can 2 and the opening formed in the center of the cover plate 8 through an insulating packing 9 made of polypropylene or the like. Terminal body 10 and insulating plate 11 disposed below cover plate 8. The insulating plate 11 is formed in a round plate shape that opens upward with an annular side wall 13 standing on the periphery of the disk-shaped base portion 12, and a gas passage 14 is opened at the center of the base portion 12. Yes. The cover plate 8 is fixed to the inner peripheral edge of the upper opening of the outer can 2 by laser welding or a crimp seal through packing while being received by the upper end of the side wall 13. As a countermeasure when the battery internal pressure suddenly increases, a thin portion (vent) can be provided on the lid 8 or the can bottom 2a of the outer can 2. The positive electrode 4 and the lower surface of the terminal body 10 are connected by a positive electrode lead body 15. Further, the negative electrode lead body 16 attached to the negative electrode 5 is welded to the upper inner surface of the outer can 2.

  FIG. 2 shows a cross-sectional plan view of the non-aqueous electrolyte primary battery shown in FIG. As shown in FIG. 2, the wound electrode body 3 is formed by winding a positive electrode 4 and a negative electrode 5 with a separator 6 interposed therebetween, and is formed in a substantially cylindrical shape as a whole. In the non-aqueous electrolyte primary battery shown in FIG. 2, the positive electrode 4 includes a positive electrode mixture layer 20 containing a low potential active material and a positive electrode mixture layer 21 containing a high potential active material. 22 is laminated. The negative electrode 5 has a structure in which a lithium foil 25 and a current collector 26 are laminated. 27 is a lithium metal foil having a lithium-aluminum alloy on the surface of the positive electrode 4, and a lithium-aluminum alloy is formed by using a laminate of the lithium metal foil and the aluminum foil and contacting the electrolyte in the battery 1. It is a thing. Here, in FIG. 2, C is a winding center portion of the wound electrode body 3, S is a winding start end portion of the positive electrode 4 in the wound electrode body 3, and E is a winding end portion of the wound electrode body 3. (Details will be described later). 1 and 2 show the case where the battery of the present invention has a cylindrical shape, the battery of the present invention may have a cylindrical shape (for example, a rectangular tube shape) other than the cylindrical shape. Moreover, it can also be set as the laminated battery which uses the laminated film which vapor-deposited the metal as an exterior material. Further, the electrode body may be a laminated electrode body in which the positive electrode and the negative electrode are laminated one or more times via a separator, instead of the wound electrode body shown in FIGS. 1 and 2 schematically show each component, and for example, the relationship of the thickness of each component does not necessarily have to be as shown in these drawings (FIGS. 3 and 4 described later). The same applies to

  As a separator that can be used in the present invention, a separator used in a conventionally known nonaqueous electrolyte primary battery, for example, a nonwoven fabric made of polyolefin such as polyethylene (PE) or polypropylene (PP), or a microporous film can be used. . For example, as a microporous film made of PE, “Hypore (trade name)” manufactured by Asahi Kasei Co., Ltd., “Cetilla (trade name)” manufactured by Tonen Chemical Co., Ltd., and the like can be used.

Examples of the electrolyte solution according to the non-aqueous electrolyte primary battery of the present invention include those prepared by dissolving LiBF ₆ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO _3, etc., as an electrolyte in a non-aqueous solvent such as an organic solvent. . Examples of the solvent include a mixture of a cyclic ester such as ethylene carbonate and propylene carbonate with a chain ether such as dimethoxyethane and a chain ester such as dimethyl carbonate. The concentration of the electrolyte in the electrolytic solution is preferably 0.3 to 1.5 mol / l.

  The spirally wound electrode body 3 can be produced, for example, according to a procedure as shown in FIGS. In FIG. 3 (excluding the enlarged view) and FIG. 4, the lithium metal foil-aluminum foil laminate 28 is simplified and shown as a single layer structure, but actually, as shown in the enlarged view of FIG. In addition, it is a laminate of lithium metal foil 28a and aluminum foil 28b, and is loaded into the battery and brought into contact with the electrolyte solution, thereby forming a lithium-aluminum alloy on the separator 6 side surface (opposite surface to the positive electrode 4). Lithium metal foil (27 in FIG. 2). First, as shown in FIG. 3, the heat-meltable tape 31 and then the separator 6 are placed on the upper surface of the central portion in the length direction of the negative electrode current collector 26.

  Next, the tape 31 is heated from this state, and the separator 6 is melted and fixed to the negative electrode current collector 26 through the tape 31 in an integral manner. The tape 31 can be a single-sided or double-sided adhesive tape. Next, the lithium metal foil 25 and the laminated body 28 are pressure-bonded and fixed at front and rear positions in the length direction of the negative electrode current collector 26 sandwiching the fixing portion of the separator 6. In other words, on one side of the negative electrode current collector 26, a portion where the lithium metal foil 25 as the negative electrode active material and the negative electrode current collector 26 without the laminated body 28 are exposed is provided, and the separator 6 is fixed to the exposed portion 30. To do. In this way, it is possible to obtain a laminate 32 in which the negative electrode current collector 26, the lithium metal foil 25, the lithium metal foil-aluminum foil laminate 28, and the separator 6 are bonded together in an integrated manner.

  Next, as shown in FIG. 4A, the laminate 32 is inserted between the transverse grooves 35 of the winding core 33. Here, alignment is performed so that the previous exposed portion 30, that is, the portion where the separator 6 is fixed by the tape 31 is located between the transverse grooves 35 of the winding core 33. The winding core 33 is rotated about a half circumference in one direction (clockwise in FIG. 4), and the laminate 32 is wound around the outer peripheral surface of the winding core 33 as shown in FIG. Next, the positive electrode 4 composed of the positive electrode mixture layers 20 and 21 and the current collector 22 is placed on the separator 6 so that the winding start end S side (see FIG. 2) is the winding core 33 side. Then, the laminate 32 is wound around the winding core 33. After winding the laminated body 32 and the positive electrode 4 with a winding core, the winding core 31 is extracted from the winding center C (see FIG. 2), and finally the winding termination E ( 2) is fixed with a fixing tape. In this way, as shown in FIG. 2, a wound electrode body 3 in which the exposed portion 30 is the winding center C and the positive electrode 4 and the negative electrode 5 are wound through the separator 6 can be obtained.

  The negative electrode current collector was previously wound around the winding core for about one turn, and then the lithium metal foil and the lithium metal foil-aluminum foil laminate constituting the negative electrode and the separator were overlapped to wrap around the positive electrode. A group may be inserted and wound to form a wound electrode body. In this case, the lithium metal foil and the lithium metal foil-aluminum foil laminate are not bonded to the negative electrode current collector at all.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. In addition, "%" used in a present Example is a mass reference | standard (mass%) unless there is particular notice.

Example 1
[Production of positive electrode]
First, in the following procedure, a positive electrode mixture (in mass ratio, solid content: moisture = 100: 30) for forming a positive electrode mixture layer containing a low potential active material is prepared, and the positive electrode mixture is prepared. A positive electrode mixture sheet for preparing an agent layer was prepared. Carbon black: 10% and lithium manganate (LiMn ₃ O ₆ ): 85% are mixed by dry using a planetary mixer for 5 minutes, and then water is adjusted to 20% (mass ratio) of solid content. Added and mixed for 5 minutes. PVDF dispersion ("D-1" manufactured by Daikin Industries, Ltd.) is prepared in an amount corresponding to 5% of the solid content of the positive electrode mixture, diluted with the remaining water, and added to the above mixture Then, a positive electrode mixture for forming a positive electrode mixture layer containing a low potential active material was obtained by mixing for 5 minutes.

  Using the above positive electrode mixture, two rolls having a diameter of 250 mm, adjusting the roll temperature to 125 ± 5 ° C., press pressure: 7 ton / cm, roll interval: 0.4 mm, rotation speed: 10 rpm The sheet was rolled and rolled. The positive electrode mixture (preliminary sheet) that passed through the roll was dried at 105 ± 5 ° C. until the residual moisture was 2% or less. Next, the dried preliminary sheet was pulverized by a pulverizer. At this time, the preliminary sheet was pulverized until it became twice or more the original apparent volume. Most of the particle size after pulverization was 1 mm or less, and PVDF added as a binder was also cut into fibers having a length of 1 mm or less. The pulverized material was formed into a sheet again by a roll. The positive electrode contains a low potential active material by adjusting the roll interval to 0.6 ± 0.05 mm, forming a sheet under the conditions of roll temperature: 125 ± 10 ° C., press pressure: 7 tons / cm, and rotation speed: 10 rpm. A positive electrode mixture sheet serving as a mixture layer was obtained. The obtained positive electrode mixture sheet has a thickness of 0.5 mm and an electric capacity (theoretical value) of about 350 mAh. The positive electrode mixture sheet was cut to obtain a sheet (20 in FIG. 2) having a width of 37 mm and a length of 51 mm.

  Next, a positive electrode mixture (in mass ratio, solid content: moisture = 100: 30) for forming a positive electrode mixture layer containing a high-potential active material is prepared by the following procedure. A positive electrode mixture sheet for preparing a mixture layer was prepared. Carbon black: 3% and manganese dioxide (manufactured by Tosoh Corporation): 92% were mixed using a planetary mixer in a dry process for 5 minutes, and then water was added to a solid content of 20% (mass ratio). And mixed for 5 minutes. PVDF dispersion ("D-1" manufactured by Daikin Industries, Ltd.) is prepared in an amount corresponding to 5% of the solid content of the positive electrode mixture, diluted with the remaining water, and added to the above mixture And mixing for 5 minutes to obtain a positive electrode mixture for forming a positive electrode mixture layer containing a high-potential active material.

  Using the above positive electrode mixture, two rolls having a diameter of 250 mm, adjusting the roll temperature to 125 ± 5 ° C., press pressure: 7 ton / cm, roll interval: 0.4 mm, rotation speed: 10 rpm The sheet was rolled and rolled. The positive electrode mixture (preliminary sheet) that passed through the roll was dried at 105 ± 5 ° C. until the residual moisture was 2% or less. Next, the dried preliminary sheet was pulverized by a pulverizer. At this time, the preliminary sheet was pulverized until it became twice or more the original apparent volume. Most of the particle size after pulverization was 1 mm or less, and PVDF added as a binder was also cut into fibers having a length of 1 mm or less. The pulverized material was formed into a sheet again by a roll. The positive electrode containing a high potential active material by adjusting the roll interval to 0.6 ± 0.05 mm, forming a sheet under the conditions of roll temperature: 125 ± 10 ° C., press pressure: 7 ton / cm, rotation speed: 10 rpm A positive electrode mixture sheet serving as a mixture layer was obtained. The obtained positive electrode mixture sheet has a thickness of 1.5 mm and an electric capacity (theoretical value) of about 2150 mAh. The positive electrode mixture sheet was cut to obtain a sheet (21 in FIG. 2) having a width of 37 mm and a length of 62 mm.

As the positive electrode current collector, an expanded metal made of stainless steel (SUS316) was used. This expanded metal was cut into a width of 34 mm and a length of 56 mm, and a stainless steel ribbon having a thickness of 0.1 mm and a width of 3 mm was attached to the central portion in the length direction by resistance welding as a positive electrode lead body. . Further, a carbon paste (manufactured by Nippon Graphite Co., Ltd.) was applied to the expanded metal so as not to crush the mesh, and then dried at a temperature of 105 ± 5 ° C. to obtain a positive electrode current collector. The coating amount of the carbon paste was set to 5 mg / cm ² after drying.

  Next, in a state where the positive electrode current collector is interposed between the positive electrode mixture sheet containing the low-potential active material and the positive electrode mixture sheet containing the high-potential active material, Fixed and united the three. Specifically, the positive electrode mixture sheet containing a low-potential active material and the positive electrode mixture sheet containing a high-potential active material are aligned at one end in the length direction, and the end of the positive electrode current collector is Set the two positive electrode mixture sheets so that they do not protrude from one end of the two positive electrode mixture sheets. In this state, press the 5 mm portion of the two positive electrode mixture sheets from one end of the two positive electrode mixture sheets by pressing. By doing so, the three parties were integrated. Thereafter, the two positive electrode mixture sheets and the positive electrode current collector were integrated, and dried with hot air at 250 ± 10 ° C. for 6 hours to obtain a positive electrode.

[Production of negative electrode]
The negative electrode has a width: 39 mm, length: 170 mm, thickness: 0.01 mm on a copper foil (negative electrode current collector), width: 37 mm, length: 87 mm, and thickness: 0.30 mm lithium metal foil. A laminate obtained by bonding aluminum foil of 0.006 mm and a lithium metal foil having a width of 37 mm, a length of 50 mm, and a thickness of 0.3 mm were arranged. At this time, the lithium metal foil and the aluminum foil were laminated such that the lithium metal foil side was the copper foil side. First, a nickel negative electrode lead body having a width of 3 mm, a length of 20 mm, and a thickness of 0.1 mm was pressure-bonded to a lithium metal foil. Thereafter, as shown in FIG. 3, the two laminates were placed on the copper foil in a separated state to produce a negative electrode.

[Production of wound electrode body]
As a separator, using a microporous polyethylene film ["Hypore" (trade name) manufactured by Asahi Kasei Co., Ltd.] having a width: 44 mm, a length: 170 mm, and a thickness: 20 μm, as shown in FIG. A separator was attached via an adhesive tape. This was sandwiched between two winding cores having a diameter of 3.5 mm and wound once (FIGS. 4A and 4B). Next, the negative electrode was wound once with the separator, and then the side on which the positive electrode was fixed was placed on the winding core side and wound. After winding, the copper foil covered the outermost periphery. Thus, a wound electrode body as shown in FIG. 2 was obtained.

[Battery assembly]
The assembly process of the nonaqueous electrolyte primary battery will be described with reference to FIG. An insulating plate made of polypropylene having a thickness of 0.2 mm is inserted into the inner bottom portion 2a of the bottomed cylindrical outer can 2 made of nickel-plated iron can, and the wound electrode body 3 is placed thereon, and the positive electrode lead body 15 Was inserted in a posture facing upward. The negative electrode lead body 16 of the wound electrode body 3 was resistance welded to the inner surface of the outer can 2, and the positive electrode lead body 15 was resistance welded to the lower surface of the terminal plate 10 after inserting the insulating plate 11. At this point, the insulation resistance was measured and it was confirmed that there was no short circuit.

As the electrolyte, a non-aqueous solution prepared by dissolving LiClO ₄ at a concentration of 0.5 mol / l in a mixed solvent of propylene carbonate and dimethoxyethane (volume ratio of 1: 2) was prepared, and this was used as an outer can. 3.5 ml was injected into 2. The injection was divided into three times, and the whole amount was injected while reducing the pressure in the final step. After the electrolyte solution is injected, the cover plate 8 is fitted into the upper opening of the outer can 2, and the inner peripheral portion of the opening end of the outer can 2 and the outer peripheral portion of the cover plate 8 are welded by laser welding. 2 openings were sealed.

[Post-treatment (preliminary discharge, aging)]
The sealed battery was preliminarily discharged with a resistance of 1Ω for 30 seconds, stored at 70 ° C. for 6 hours, and then subjected to a secondary preliminary discharge with a constant resistance of 1Ω for 1 minute. The battery after the preliminary discharge was aged at room temperature for 7 days, the open circuit voltage was measured to confirm that a stable voltage was obtained, and a nonaqueous electrolyte primary battery having an outer diameter of 17 mm and a total height of 45 mm was obtained. Obtained. The electric capacity (theoretical value) of the positive electrode in this battery was 2500 mAh.

Comparative Example 1
A positive electrode mixture sheet having a thickness of 1.0 mm was prepared in the same manner as the positive electrode mixture sheet forming method for forming a positive electrode mixture layer containing a high potential active material in Example 1. From this positive electrode mixture sheet, an inner periphery positive electrode mixture sheet (corresponding to 20 in FIG. 2) having a length of 51 mm and a width of 37 mm, and an outer periphery positive electrode mixture having a length of 62 mm and a width of 37 mm A sheet (corresponding to 21 in FIG. 2) was obtained. These positive electrode mixture sheets were used in the same manner as in Example 1 except that they were used instead of the positive electrode mixture sheet containing a low potential active material and the positive electrode mixture sheet containing a high potential active material. An electrolyte primary battery was produced. The electric capacity (theoretical value) of the positive electrode in this battery was 2600 mAh.

Comparative Example 2
A positive electrode mixture sheet having a thickness of 1.0 mm was prepared in the same manner as the positive electrode mixture sheet preparation method for forming a positive electrode mixture layer containing a low-potential active material in Example 1. From this positive electrode mixture sheet, an inner periphery positive electrode mixture sheet (corresponding to 20 in FIG. 2) having a length of 51 mm and a width of 37 mm, and an outer periphery positive electrode mixture having a length of 62 mm and a width of 37 mm A sheet (corresponding to 21 in FIG. 2) was obtained. These positive electrode mixture sheets were used in the same manner as in Example 1 except that they were used instead of the positive electrode mixture sheet containing a low potential active material and the positive electrode mixture sheet containing a high potential active material. An electrolyte primary battery was produced. The electric capacity (theoretical value) of the positive electrode in this battery was 1700 mAh.

  The following pulse discharge tests and constant rate discharge tests were performed on the batteries of the examples and comparative examples. The results are shown in Table 1.

<Pulse discharge test>
For each of the above batteries, the base discharge current is 20 μA at 20 ° C., the pulse discharge is performed by discharging the 1 A pulse current for 3 seconds at intervals of 5 minutes, and the voltage when the 1 A pulse current flows is 2.0 V or less. The number of pulse discharges required to decrease to a maximum was measured. In addition, the number of samples of each battery was set to five, and the average value was made into the pulse discharge capacity of each Example and a comparative example.

  As can be seen from Table 1, the nonaqueous electrolyte primary battery of Example 1 had a higher number of pulse discharges and superior heavy load pulse discharge characteristics than the battery of Comparative Example 1 having a large positive electrode theoretical capacity in the battery. Moreover, the number of pulse discharges was larger and the heavy load pulse discharge characteristics were superior to those of the battery of Comparative Example 2 using the positive electrode having excellent heavy load characteristics.

  In addition, about 100 batteries of Example 1, when the open circuit voltage after storing for 30 days at 20 degreeC was measured, what is less than 3.24V does not generate | occur | produce and it is confirmed that it is a battery satisfying long-term reliability. did it.

  Furthermore, about each battery of an Example and a comparative example, at 20 degreeC, 5 mA constant current discharge is performed, and a utilization rate is divided by dividing the discharge capacity until a voltage falls to 2.0 V or less by the positive electrode theoretical capacity. As a result, all the batteries were 95% or more, and no difference was observed between the batteries with respect to the constant rate discharge characteristics.

  Thus, the nonaqueous electrolyte primary battery of Example 1 not only has excellent heavy load pulse discharge characteristics, but also has a constant rate discharge characteristic at a relatively light load. It is as good as the comparative example battery) and also has excellent long-term reliability.

It is a vertical side view which shows an example of the nonaqueous electrolyte primary battery of this invention. It is a cross-sectional top view which shows an example of the nonaqueous electrolyte primary battery of this invention. It is a figure for demonstrating the preparation methods of the winding electrode body which concerns on the nonaqueous electrolyte primary battery of this invention. It is a figure for demonstrating the preparation methods of the winding electrode body which concerns on the nonaqueous electrolyte primary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte primary battery 2 Exterior can 3 Winding electrode body 4 Positive electrode 5 Negative electrode 6 Separator 20 Positive electrode mixture layer containing a low potential active material 21 Positive electrode mixture layer containing a high potential active material 22 Positive electrode collection Electric current 25 Lithium metal foil 26 Negative electrode current collector 27 Lithium-aluminum alloy-containing lithium metal foil 28 Lithium metal foil-aluminum foil laminate 28a Lithium metal foil 28b Aluminum foil 31 Tape 33 Winding core

Claims (4)

A nonaqueous electrolyte primary battery having a positive electrode in which two positive electrode mixture layers containing an active material and a conductive additive are laminated via a current collector,
The non-aqueous electrolyte primary battery, wherein the two positive electrode mixture layers have different potentials of active materials contained therein.   2. The non-aqueous electrolyte primary battery according to claim 1, wherein at least a positive electrode mixture layer containing an active material having a low potential is disposed so as to face the negative electrode.   The non-aqueous electrolyte primary battery according to claim 2, wherein the negative electrode has a lithium metal foil containing a lithium-aluminum alloy on a surface facing at least a positive electrode mixture layer containing a low potential active material. The electric capacity of a positive electrode mixture layer containing a high potential active material is 1.0 to 10 times that of a positive electrode mixture layer containing a low potential active material. The nonaqueous electrolyte primary battery according to any one of the above.

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