Flat nonaqueous battery

Abstract

A flat nonaqueous battery according to the present application comprises: a positive electrode including a molded body of a positive electrode mixture; a negative electrode; a separator; and a nonaqueous electrolyte. The negative electrode includes a lithium layer and a Li-Al alloy layer formed on the separator-side surface of the lithium layer. The separator is constructed by laminating two or more layers of polyolefin nonwoven fabric. A portion of the separator positioned between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100-200 μm. The basis weight of the separator is 50 g / m2 to 110 g / m2.

Description

flat non-aqueous battery

[0001] This invention relates to a flat-type non-aqueous battery that can prevent short circuits between the positive and negative electrodes and has excellent load characteristics at low temperatures.

[0002] Flat-type non-aqueous batteries, which combine a positive electrode made of a molded positive electrode mixture (pellet) and a negative electrode made of lithium metal, are used in a variety of applications due to their characteristics such as high capacity and high voltage. In particular, the demand for flat-type non-aqueous batteries as power sources for automotive equipment has been growing in recent years.

[0003] On the other hand, in flat-type non-aqueous batteries, a Li-Al alloy layer is sometimes formed on the separator-side surface of the Li metal of the negative electrode to improve load characteristics. By alloying the surface of the Li metal layer with Al, the crystal grains of the alloy layer on the surface of the negative electrode are refined, and fine irregularities are formed on the surface of the alloy layer (hereinafter simply referred to as "refinement of the negative electrode surface"), which increases the reaction area of ​​the negative electrode and improves load characteristics.

[0004] However, because the irregularities formed on the surface of the negative electrode alloy layer are fine, when a fibrous separator such as a nonwoven fabric is used, the irregularities formed on the surface of the negative electrode alloy layer tend to penetrate into the pores of the separator. Furthermore, the refined crystal grains of the alloy layer may also break down into fine powder and fall off, penetrating into the pores of the separator.

[0005] Furthermore, in the case of a positive electrode, which consists of a positive electrode mixture containing positive electrode active material such as manganese dioxide and conductive additives, strong vibrations may cause the positive electrode active material and conductive additives to detach from the positive electrode mixture and enter the pores of the fibrous separator.

[0006] Therefore, in flat-type non-aqueous batteries, which combine a positive electrode made of a molded positive electrode mixture and a negative electrode formed by forming a Li-Al alloy layer on the surface of a Li metal layer, especially in applications that are susceptible to vibration, such as vehicle tire puncture sensors, the positive electrode material, such as the positive electrode active material and conductive additive that have entered the separator, and the negative electrode material due to irregularities or pulverization formed on the surface of the negative electrode alloy layer, tend to come into contact within the separator, easily causing a short circuit.

[0007] To address these challenges, Patent Document 1 describes a material with an average fiber diameter of 2.5 to 3.5 μm and a basis weight of 40 to 100 g / m². 2 It has been proposed to use a separator made of nonwoven fabric.

[0008] Japanese Patent Publication No. 2005-340117

[0009] However, it has been found that the measures described in Patent Document 1 alone are insufficient when, for example, increasing the proportion of Al and further promoting pulverization by the Li-Al alloy layer formed on the surface of the Li metal layer in order to improve the load characteristics at low temperatures below -20°C.

[0010] This invention solves the aforementioned problems and provides a flat-type non-aqueous battery having a negative electrode having a Li metal layer and a Li-Al alloy layer formed on its surface, which prevents short circuits between the positive and negative electrodes and suppresses the deterioration of load characteristics at low temperatures.

[0011] The flat-type non-aqueous battery of the present invention comprises a positive electrode including a molded body of a positive electrode mixture, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the negative electrode comprises a lithium layer and a Li-Al alloy layer formed on the separator-side surface of the lithium layer, the separator is constructed by laminating two or more layers of polyolefin nonwoven fabric, the portion of the separator located between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100 to 200 μm, and the basis weight of the separator is 50 g / m². 2 110g / m or more 2 The following characteristics apply:

[0012] According to this invention, it is possible to provide a flat-type non-aqueous battery that can prevent short circuits between the positive and negative electrodes, even in applications that are susceptible to vibration, such as vehicle tire puncture sensors, and that suppresses the deterioration of load characteristics at low temperatures.

[0013] Figure 1 is a schematic cross-sectional view of a flat-type non-aqueous battery according to an embodiment. Figure 2 is an enlarged view of section A in Figure 1.

[0014] (Flat-type non-aqueous battery) An embodiment of the flat-type non-aqueous battery of the present invention will be described. The flat-type non-aqueous battery of this embodiment comprises a positive electrode including a molded body of a positive electrode mixture, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode includes a lithium layer and a Li-Al alloy layer formed on the separator side surface of the lithium layer. The separator is constructed by laminating two or more layers of polyolefin nonwoven fabric. The portion of the separator located between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100 to 200 μm. The basis weight of the separator is 50 g / m². 2 110g / m or more 2 The following applies:

[0015] In the flat-type non-aqueous battery of this embodiment, the negative electrode includes a lithium layer and a Li-Al alloy layer formed on the separator-side surface of the lithium layer. When the lithium layer alloys with Al on the separator-side surface of the negative electrode to form the Li-Al alloy layer, the crystal grains on the surface of the lithium layer become finer, and fine irregularities are formed on the surface of the Li-Al alloy layer. As a result, the reaction area of ​​the negative electrode increases, and the load characteristics can be improved.

[0016] Furthermore, in the flat-type non-aqueous battery of this embodiment, the separator is constructed by laminating two or more layers of polyolefin nonwoven fabric, the portion of the separator located between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100 to 200 μm, and the basis weight of the separator is 50 g / m². 2 110g / m or more 2 As a result of the following settings, the pores in the separator are miniaturized, making it difficult for the negative electrode material from the negative electrode and the positive electrode material from the positive electrode, whose surfaces have been refined, to penetrate into the pores of the separator. Therefore, it is possible to prevent the negative electrode material and the positive electrode material from coming into contact within the separator and causing a short circuit.

[0017] Furthermore, by laminating two or more layers of polyolefin nonwoven fabric to form a separator, even if fine through-holes exist within the nonwoven fabric, the probability of the continuity of these through-holes being interrupted at the interface of the multiple layers of nonwoven fabric increases. This makes it more reliable to prevent positive electrode material detached from the positive electrode or finely powdered negative electrode material from penetrating the separator and coming into contact with each other, thus preventing short circuits. In this case, the separator may be constructed by laminating multiple nonwoven fabrics of the same material, or by laminating one nonwoven fabric of different materials at a time.

[0018] In particular, a positive electrode made of a molded body of a positive electrode mixture containing a positive electrode active material such as manganese dioxide and a conductive additive is prone to the positive electrode active material and conductive additive falling off the mixture and entering the pores of the fibrous separator when subjected to strong vibrations. However, even when using such a positive electrode, the compression separator according to this embodiment can effectively prevent short circuits between the positive and negative electrodes.

[0019] The flat-type non-aqueous battery of this embodiment will be described below with reference to the drawings. Figure 1 is a schematic cross-sectional view showing an example of the flat-type non-aqueous battery of this embodiment, and Figure 2 is an enlarged view of part A in Figure 1. In Figure 1, the flat-type non-aqueous battery 1 has a stacked electrode body 40 and a non-aqueous electrolyte (not shown) sealed inside S of an outer casing, which is composed of an outer casing 10, a sealing casing 20, and a gasket 30 interposed between them. The stacked electrode body 40 is composed of a substantially cylindrical positive electrode 41 made of a molded positive electrode mixture, a disc-shaped negative electrode 42 with a Li-Al alloy layer 42b formed on one side surface of a lithium layer 42a, and a separator 43. The portion of the separator 43 located between the positive electrode 41 and the negative electrode 42 is compressed by the positive electrode 41 and the negative electrode 42.

[0020] The sealed can 20 is fitted into the opening of the outer can 10 via a gasket 30, and the open end of the outer can 10 is tightened inward, causing the gasket 30 to come into contact with the sealed can 20, thereby sealing the opening of the outer can 10 and creating a sealed structure inside the outer body S.

[0021] The outer casing 10 comprises a circular bottom portion 11 and a cylindrical peripheral wall portion 12 formed continuously with the bottom portion 11 on its outer circumference. A mesh member 51 is joined to the inner bottom surface of the bottom portion 11. During battery assembly, the mesh member 51 is pressurized to bite into the positive electrode mixture of the positive electrode 41. The mesh member 51 strengthens the electrical contact between the outer casing 10 and the positive electrode 41.

[0022] The sealed can 20 comprises a circular flat portion 21 and a cylindrical side wall portion 22 formed continuously with the flat portion 21 on its outer circumference. The side wall portion 22 also has a base end portion 22a located on the flat portion 21 side, a stepped portion 22c extending radially outward from the base end portion 22a, and an enlarged diameter portion 22b having a larger diameter than the base end portion 22a. In other words, the side wall portion 22 has a stepped portion 22c formed between the base end portion 22a and the enlarged diameter portion 22b, connecting the two.

[0023] The gasket 30 is positioned to be sandwiched between the open end of the side wall portion 22 of the sealed can 20 and the bottom surface portion 11 of the outer can 10. Specifically, the gasket 30 comprises a ring-shaped base portion 31, an outer cylindrical wall 32 protruding from the outer peripheral edge of the base portion 31, and an inner cylindrical wall 33 extending from the inner peripheral edge of the base portion 31 in the same direction as the outer cylindrical wall 32.

[0024] Next, the components of the flat-type non-aqueous battery of this embodiment will be described.

[0025] <Negative Electrode> As shown in Figures 1 and 2, the negative electrode 42 of this embodiment comprises a lithium layer 42a and a Li-Al alloy layer 42b formed on the separator-side surface of the lithium layer 42a, with the Li-Al alloy layer 42b in contact with the separator 43. This refines the crystal grains of the Li-Al alloy layer and creates fine irregularities on the surface of the Li-Al alloy layer, thereby increasing the reaction area of ​​the negative electrode and improving the load characteristics. In the lithium layer 42a, the lithium layer refers to a layer containing the element Li, and includes a metallic lithium layer and a lithium alloy layer (excluding the Li-Al alloy layer 42b).

[0026] In order to sufficiently progress the refinement of the negative electrode surface and improve the load characteristics of the negative electrode, it is preferable that the content of Al contained in the Li—Al alloy layer is 3% or more, more preferably 6% or more, in terms of mass ratio in the total amount of Li and Al in the entire negative electrode including the metallic lithium layer. On the other hand, if the refinement of the negative electrode surface progresses too much, the refined Li—Al alloy is likely to penetrate to a position close to the positive electrode in the separator, and short circuit is likely to occur. Therefore, the content of Al contained in the Li—Al alloy layer is preferably 12% or less, more preferably 10% or less, in terms of mass ratio in the total amount of Li and Al in the entire negative electrode including the metallic lithium layer. For example, the content of Al contained in the above Li—Al alloy layer can be 3 to 10%, 3 to 12%, 6 to 10%, or 6 to 12% in terms of mass ratio in the total amount of Li and Al in the entire negative electrode.

[0027] The lithium layer 42a can be formed by processing metallic lithium or a lithium alloy into a disk shape. The metallic lithium used for the lithium layer 42a may contain inevitable impurities. Further, examples of the alloy components contained in the lithium alloy include elements other than Al, such as Fe, Ni, Co, Mn, Cr, V, Ti, Zr, Nb, Mo, Sn, and Si. The content of the elements serving as the alloy components of the lithium alloy is usually 10% by mass or less.

[0028] The negative electrode 42 can be obtained, for example, by laminating an aluminum foil on a lithium plate having a certain shape and a certain thickness to form a member for forming a negative electrode, using the member for forming a negative electrode as it is for assembling the battery, and after assembly, electrochemically reacting the lithium plate and the aluminum foil to form a Li—Al alloy, and forming a Li—Al alloy layer 42b on the surface of the lithium layer 42a on the separator side.

[0029] In the negative electrode 42, the thickness of the lithium layer 42a is not particularly limited, but it may be 100 μm or more and 2 mm or less according to the battery capacity. Also, the thickness of the aluminum foil for forming the Li—Al alloy layer 42b is not particularly limited, but if the aluminum foil is too thick, the thickness of the formed Li—Al alloy layer 42b becomes too thick and the strength of the negative electrode 42 decreases. Therefore, usually, the thickness of the aluminum foil is preferably in the range of 6 μm or more and 20 μm or less, and the thickness of the Li—Al alloy layer 42b is preferably 0.5 to 7% of the thickness of the lithium layer 42a.

[0030] Examples of the aluminum foil used for the negative electrode forming member include a foil made of Al (and inevitable impurities), and a foil made of an Al alloy containing, as alloy components, Cu, Fe, Ni, Co, Mn, Cr, V, Ti, Zr, Nb, Mo, etc., with the balance being Al and inevitable impurities (the total content of the alloy components is, for example, 10% by mass or less).

[0031] The lithium layer 42a and the Li—Al alloy layer 42b of the negative electrode 42 shown in FIGS. 1 and 2 can be identified by observing the cross section of the negative electrode 42 with a scanning electron microscope (SEM).

[0032] <Positive electrode> As the positive electrode 41 of the present embodiment, for example, a molded body obtained by pressure molding a positive electrode mixture containing a positive electrode active material, a conductive assistant, a binder, etc. into a pellet shape is used.

[0033] As the positive electrode active material, manganese oxide or a lithium manganese composite oxide is preferable. As the manganese oxide, manganese dioxide is particularly preferable. Examples of the lithium manganese composite oxide include oxides having a spinel structure such as LiMn2O4, oxides having a layered structure such as Li2MnO3 or LiMnO2, oxides in which Li is inserted into manganese dioxide, and low-crystalline oxides represented by compositions such as LiMn3O6 that can be synthesized at a relatively low temperature. Further, graphite fluoride may be used as the positive electrode active material.

[0034] The above-mentioned conductive additives can include, for example, carbon materials such as carbon black (acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc.), carbon fibers, conductive fibers such as metal fibers, fluorinated carbon, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives.

[0035] Examples of the above-mentioned binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), and polyvinylpyrrolidone (PVP).

[0036] The composition of the positive electrode mixture is preferably such that the positive electrode active material is 80 to 96% by mass, the conductive additive is 2 to 10% by mass, and the binder is 2 to 10% by mass. Furthermore, in order to increase the capacity of the battery, the thickness of the molded body made of the positive electrode mixture is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more, of the height of the internal space formed between the bottom surface 11 of the outer casing 10 and the flat surface 21 of the sealing casing 20. In addition, the larger the above value, the easier it is to compress the separator during sealing, and the easier it is to adjust the thickness of the separator after compression to a suitable range. On the other hand, in order to make the capacity ratio of the negative electrode to the positive electrode within an appropriate range, the thickness of the molded body made of the positive electrode mixture is preferably 80% or less, more preferably 75% or less, and particularly preferably 70% or less, of the height of the internal space.

[0037] <Separator> As the separator 43 of the present embodiment, for example, it is composed of a non-woven fabric made of polyolefin such as polyethylene, polypropylene, or polymethylpentene. The portion of the separator 43 located between the positive electrode 41 and the negative electrode 42 is compressed by the positive electrode 41 and the negative electrode 42. Also, in FIG. 2, the thickness X of the portion of the separator 43 located between the positive electrode 41 and the negative electrode 42 is set to 100 to 200 μm, and it is set to a thickness of 50% or less with respect to the original thickness of the separator 43, that is, the thickness Y before being compressed by the positive electrode 41 and the negative electrode 42. Further, the portion of the separator 43 that is not located between the positive electrode 41 and the negative electrode 42 extends outward from the laminated electrode body 40, and the thickness of this portion can be regarded as the thickness Y before the compression. Furthermore, the basis weight of the separator 43 is 50 g / m 2 or more and 110 g / m 2 or less is set.

[0038] The thickness X of the portion of the separator 43 located between the positive electrode 41 and the negative electrode 42 is set to 100 μm or more, preferably 120 μm or more, in order to prevent the distance between the positive electrode and the negative electrode from becoming too close and being prone to short circuit. Also, in order to compress the separator to a thickness below a certain level, press the fibers against each other to eliminate large pores, and make it difficult to cause a short circuit, the thickness of the separator after reducing the thickness is set to 200 μm or less, preferably 180 μm or less. For example, the thickness X of the portion of the separator 43 located between the positive electrode 41 and the negative electrode 42 can be 100 to 180 μm, 100 to 200 μm, 120 to 180 μm, or 120 to 200 μm.

[0039] The thickness of the separator 43 can be measured by a digital thickness gauge equipped with a measuring pin having a flat surface with a diameter of 6.5 mm.

[0040] The basis weight of the separator 43 is 50 g / m 2 or more in order to keep the amount of fibers of the separator at a certain level or more and prevent short circuit, preferably 60 g / m 2 or more, and more preferably 70 g / m 2The above is preferable. On the other hand, if the amount of fiber in the separator becomes too large, it may become difficult to compress the separator, or the load characteristics of the battery may deteriorate. Therefore, the basis weight of the separator should be 110 g / m². 2 The following applies: 90 g / m 2 The following is preferable. For example, the basis weight of the separator 43 is 50 to 90 g / m². 2 60-90 g / m 2 70-90 g / m 2 , 50-110g / m 2 , 60-110g / m 2 , 70-110g / m 2 It can be done this way.

[0041] The thickness of the portion of the separator 43 located between the positive and negative electrodes after compression is preferably 20% or more of the thickness before compression, more preferably 25% or more, and preferably 60% or less, and more preferably 45% or less. For example, the thickness after compression can be 20-45%, 20-60%, 25-45%, or 25-60% of the thickness before compression. This is because if the change in thickness due to compression is too large, it can lead to problems such as variations in the thickness after compression and variations in sealing performance. Also, if the change in thickness due to compression is too small, the pressing force received by the separator from the positive and negative electrodes will be small, and the separator may shift position due to vibration or the like. Furthermore, as the discharge progresses, the thickness of the negative electrode decreases and the distance between the positive and negative electrodes increases, which may create a gap between the separator and the positive or negative electrode, preventing the discharge reaction from progressing. However, by compressing the separator between the positive and negative electrodes to a certain extent, the thickness of the compressed separator will recover in accordance with the decrease in the thickness of the negative electrode, thereby preventing the aforementioned problem from occurring.

[0042] <Non-aqueous electrolyte> For the non-aqueous electrolyte, a solution is used in which a lithium salt is dissolved in an organic solvent.

[0043] Examples of organic solvents used in non-aqueous electrolytes include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; linear carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; linear esters such as methyl propionate; cyclic esters such as compounds having a lactone ring; linear ethers such as 1,2-dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile, and methoxypropionitrile; and sulfite esters such as ethylene glycol sulfite. Two or more of these can also be used in mixtures. To obtain a battery with better properties, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of cyclic carbonate and linear ether.

[0044] Examples of lithium salts used in non-aqueous electrolytes include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, LiCF3CO2, Li2C2F4(SO3)2, LiN(CF3SO2)2, LiC(CF3SO2)3, and LiC n F 2n+1 Examples include SO3 (2 ≤ n ≤ 7) and LiN(RfOSO2)2 [where Rf is a fluoroalkyl group].

[0045] The concentration of lithium salt in the non-aqueous electrolyte is preferably 0.3 mol / L or more and 1.2 mol / L or less.

[0046] <Outer Body> For the outer can 10 and sealing can 20 that constitute the outer body, for example, carbon steel or stainless steel can be used. In addition, the mesh member 51 joined to the inner bottom surface of the bottom portion 11 of the outer can 10 can be formed from metals such as nickel, aluminum, or stainless steel, and can be joined to the inner bottom surface of the bottom portion 11 of the outer can 10 by spot welding or the like. Furthermore, for the material of the gasket 30, polypropylene, polyphenylene sulfide, perfluoroalkoxyethylene, etc. can be used.

[0047] The flat non-aqueous battery 1 of this embodiment is coin-shaped, but it is not limited to a coin shape and may be thin and rectangular.

[0048] (Method for manufacturing a flat non-aqueous battery) Next, the method for manufacturing the flat non-aqueous battery of the present invention will be described. The flat non-aqueous battery of the present invention described above can be obtained, for example, by the steps of: manufacturing a negative electrode laminate for manufacturing a negative electrode by laminating an aluminum layer on the surface of a lithium layer; compressing a separator, which is made by laminating two or more layers of polyolefin nonwoven fabric, between a positive electrode and the aluminum layer of the negative electrode laminate; and manufacturing a negative electrode by reacting the aluminum layer of the negative electrode laminate with the Li of the lithium layer to form a Li-Al alloy layer on the surface of the lithium layer.

[0049] The negative electrode in the flat-type non-aqueous battery of the present invention can be obtained by electrochemically reacting the lithium layer and aluminum layer of the negative electrode laminate after the battery is assembled to form a Li-Al alloy, and then forming a Li-Al alloy layer on the separator side surface of the lithium layer. As a result, the crystal grains of the Li-Al alloy layer on the separator side surface of the negative electrode are refined, and fine irregularities are formed on the surface of the Li-Al alloy layer, increasing the reaction area of ​​the negative electrode and enabling the manufacture of a flat-type non-aqueous battery with excellent load characteristics.

[0050] Furthermore, in the manufacturing method of the flat-type non-aqueous battery, the portion of the separator located between the positive electrode and the negative electrode is compressed by the positive electrode and the negative electrode. As a result, the pores of the separator are miniaturized, and even if the miniaturized Li-Al alloy falls off from the negative electrode or a portion of the positive electrode mixture falls off from the positive electrode, it becomes difficult for them to enter the pores of the separator. In addition, since two or more layers of polyolefin nonwoven fabric are bonded together, even if the negative electrode material or positive electrode material enters the pores of the separator, it is stopped at the bonding surface, preventing the negative electrode material and the positive electrode material from coming into contact within the separator and causing a short circuit.

[0051] For example, the separator used in the manufacturing method of the flattened non-aqueous battery of the present invention before compression can be a nonwoven fabric of polyolefin resin with a thickness of 250 μm or more, preferably 300 μm or more, and 600 μm or less, preferably 550 μm or less.

[0052] The present application will be described in detail below based on the following examples. However, the following examples are not intended to limit the present application.

[0053] (Example 1) <Preparation of Separator> Two layers of polymethylpentene nonwoven fabric were laminated together to form a separator with a thickness of 480 μm and a basis weight of 75 g / m². 2 A separator was prepared.

[0054] <Fabrication of the positive electrode> A positive electrode mixture was prepared by mixing manganese dioxide, the positive electrode active material, carbon black, the conductive additive, and PTFE, the binder, in a mass ratio of 90:5:5. This mixture was then pressure-molded to produce a disc-shaped positive electrode with a diameter of 16 mm and a thickness of 1.8 mm, composed of molded positive electrode mixtures.

[0055] <Fabrication of negative electrode forming component> A metallic lithium piece was placed on the inner bottom surface of a circular stainless steel sealed can and shaped to form a circle in plan view, creating a lithium layer with a diameter of 16 mm and a thickness of 0.85 mm. Furthermore, an aluminum foil with a thickness of 12 μm was laminated on top of it to create a laminate of lithium and aluminum layers (negative electrode forming component) for forming the negative electrode.

[0056] <Preparation of Non-Aqueous Electrolyte> Propylene carbonate, 1,2-dimethoxyethane, and LiClO4 were mixed in a mass ratio of 55:40:5 to prepare a non-aqueous electrolyte containing LiClO4 at a concentration of 0.5 mol / L.

[0057] <Battery Assembly> A gasket was attached to a sealed can in which a laminate of a lithium layer and an aluminum layer was formed on the inner bottom surface, and the separator and the positive electrode were placed in order on the aluminum layer of the laminate.

[0058] Next, the non-aqueous electrolyte was dropped into the sealed can, and a stainless steel outer can, on which a circularly punched nickel mesh was spot-welded to the inner bottom surface, was placed over it. While pressing the outer can so that the separator was compressed, the open end of the outer can was tightened inward, and the gasket was brought into contact with the sealed can to seal the opening of the outer can, thereby assembling the flat-type non-aqueous battery. In the battery, the thickness of the molded body made of the positive electrode mixture was 64% of the height of the internal space formed between the bottom surface of the outer can and the flat surface of the sealed can.

[0059] After battery assembly, the aluminum layer of the laminate of lithium and aluminum layers reacted with lithium to form an alloy, resulting in a lithium negative electrode with a Li-Al alloy layer formed on the surface of the lithium layer.

[0060] Furthermore, the thickness of the separator located between the positive and negative electrodes was compressed to 150 μm during battery assembly. Consequently, its thickness became 31% of the original separator thickness before battery assembly.

[0061] (Example 2) A nonwoven fabric made of polymethylpentene was formed by laminating two layers together. Thickness: 320 μm, basis weight: 55 g / m² 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that a separator was used.

[0062] The thickness of the separator located between the positive and negative electrodes was compressed to 120 μm during battery assembly. Therefore, its thickness was 38% of the original separator thickness before battery assembly.

[0063] (Comparative Example 1) A nonwoven fabric made of polymethylpentene, formed by laminating two layers together, with a thickness of 500 μm and a basis weight of 120 g / m². 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that the separator was used in the assembly of the battery.

[0064] The thickness of the separator located between the positive and negative electrodes was compressed to 200 μm during battery assembly. Therefore, its thickness became 40% of the original separator thickness before battery assembly.

[0065] (Comparative Example 2) A nonwoven fabric made of polymethylpentene, formed by laminating two layers together, with a thickness of 280 μm and a basis weight of 45 g / m². 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that the separator was used in the assembly of the battery.

[0066] The thickness of the separator located between the positive and negative electrodes was compressed to 100 μm during battery assembly. Therefore, its thickness became 36% of the original separator thickness before battery assembly.

[0067] (Comparative Example 3) A nonwoven fabric made of polymethylpentene, formed by laminating two layers together, with a thickness of 550 μm and a basis weight of 75 g / m². 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that the separator was used in the assembly of the battery.

[0068] The thickness of the separator located between the positive and negative electrodes was compressed to 240 μm during battery assembly. Therefore, it became 44% of the original separator thickness before battery assembly.

[0069] (Comparative Example 4) A nonwoven fabric made of polymethylpentene, formed by laminating two layers together, with a thickness of 320 μm and a basis weight of 75 g / m². 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that the separator was used in the assembly of the battery.

[0070] The thickness of the separator located between the positive and negative electrodes was compressed to 80 μm during battery assembly. Therefore, its thickness was 25% of the original separator thickness before battery assembly.

[0071] (Comparative Example 5) A single layer of polypropylene nonwoven fabric with a thickness of 480 μm and a basis weight of 75 g / m². 2 A flat-type non-aqueous battery was assembled in the same manner as in Example 1, except that the separator was used in the assembly of the battery.

[0072] The thickness of the separator located between the positive and negative electrodes was compressed to 150 μm during battery assembly. Therefore, its thickness was 31% of the original separator thickness before battery assembly.

[0073] The reliability and load characteristics of the batteries prepared in Examples 1-2 and Comparative Examples 1-5 were evaluated.

[0074] <Reliability Evaluation> Ten batteries each from the examples and comparative examples were subjected to vibration tests under the following conditions. A sinusoidal vibration was applied sequentially to the battery in three directions: length, width, and height. The sinusoidal sweep was performed as a logarithmic sweep, moving back and forth in the range of 7 Hz to 200 Hz for 15 minutes while changing the frequency, and this sweep was repeated 12 times in each of the three directions. Between 7 Hz and 18 Hz, the sweep was performed so that the peak acceleration was maintained at 1 G. From 18 Hz onward, the sweep was performed up to the frequency (approximately 50 Hz) where the peak acceleration reached 8 G while maintaining the total amplitude at 0.8 mm, and further up to 200 Hz, the sweep was performed so that the peak acceleration was maintained at 1 G.

[0075] The open-circuit voltage (OCV) of each battery subjected to the aforementioned test was measured, and batteries with a voltage of 3.1V or less were identified as short-circuited batteries. The reliability of the batteries was evaluated based on the number of such batteries.

[0076] <Evaluation of Load Characteristics> For the batteries of Example 1, Example 2, Comparative Example 1, and Comparative Example 4, which did not exhibit short circuits in the reliability evaluation, and the battery of Comparative Example 2, a separate battery was prepared from the one used in the above test. After discharging an amount equivalent to 120 mAh of electricity at room temperature, it was kept in a constant temperature bath at -40°C. After the battery temperature had decreased, discharge was performed at a current of 10 mA, and the discharge voltage (CCV) of the battery 10 ms after the start of discharge was measured to evaluate the load characteristics at low temperatures.

[0077] The evaluation results are shown in Table 1, along with the separator configuration of each battery.

[0078]

[0079] In the batteries of Examples 1-2 and Comparative Examples 1-5, in which a Li-Al alloy layer was formed on the surface of the lithium layer of the negative electrode, the batteries of Examples 1-2 used a separator made by laminating two or more layers of polyolefin nonwoven fabric, and the part of the separator located between the positive electrode and the negative electrode was compressed to a thickness of 100-200 μm, with a basis weight of 50-110 g / m². 2This design suppresses short-circuits, resulting in a battery with superior load characteristics.

[0080] On the other hand, the battery in Comparative Example 1 suffered a decrease in load characteristics because the separator's basis weight was too large, the battery in Comparative Example 2 suffered a short circuit because the separator's basis weight was too small, the battery in Comparative Example 3 suffered a short circuit because the separator between the positive and negative electrodes was too thick and the separator was not compressed sufficiently, the battery in Comparative Example 4 suffered a decrease in load characteristics because the separator between the positive and negative electrodes was too thin and the separator was compressed too much, and the battery in Comparative Example 5 suffered a short circuit because it used a separator composed of only one layer of polyolefin nonwoven fabric.

[0081] With respect to embodiments of the present application including the above-described Examples 1 and 2, the following additional embodiments are further disclosed. (Additional Embodiment 1) A flat-type non-aqueous battery comprising a positive electrode including a molded body of a positive electrode mixture, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the negative electrode includes a lithium layer and a Li-Al alloy layer formed on the separator-side surface of the lithium layer, the separator is constructed by laminating two or more layers of polyolefin nonwoven fabric, the portion of the separator located between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100 to 200 μm, and the basis weight of the separator is 50 g / m² 2 110g / m or more 2A flat-type non-aqueous battery characterized by the following: (Appendix form 2) The portion of the separator located between the positive electrode and the negative electrode has a thickness of 20 to 60% of the thickness before compression, as described in Appendix form 1. (Appendix form 3) The flat-type non-aqueous battery according to Appendix form 1 or 2, wherein the polyolefin nonwoven fabric is composed of polymethylpentene. (Appendix form 4) The flat-type non-aqueous battery according to any one of Appendix forms 1 to 3, wherein the Al content in the Li-Al alloy layer of the negative electrode is 3 to 12% by mass ratio of the total amount of Li and Al in the entire negative electrode. (Appendix form 5) A flat non-aqueous battery according to any one of the appendix forms 1 to 4, wherein the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte are sealed inside an outer casing composed of an outer casing, a sealing casing, and a gasket interposed between them, the outer casing having a circular bottom portion and a cylindrical peripheral wall portion formed continuously with the bottom portion on its outer circumference, the sealing casing having a circular flat portion and a cylindrical side wall portion formed continuously with the flat portion on its outer circumference, and the thickness of the molded positive electrode mixture is 40% or more of the height of the internal space formed between the bottom portion of the outer casing and the flat portion of the sealing casing. (Appendix form 6) A flat non-aqueous battery according to appendix form 5, wherein the thickness of the molded positive electrode mixture is 80% or less of the height of the internal space formed between the bottom portion of the outer casing and the flat portion of the sealing casing.

[0082] This application can also be implemented in forms other than those described above. The embodiments disclosed herein are examples and are not limiting. The scope of this application shall be interpreted in accordance with the claims attached, which take precedence over the description in the above specification, and all modifications within the scope equivalent to the claims shall be included in the claims.

[0083] Because the flat-type non-aqueous battery of this invention has high reliability and load characteristics, it can be suitably applied to applications where it is necessary to maintain good capacity over a long period of time, such as power supply applications for in-vehicle equipment and power supply applications for outdoor equipment, by taking advantage of these characteristics.

[0084] 1 Flat-type non-aqueous battery 10 Outer casing 11 Bottom section 12 Peripheral wall section 20 Sealing section 21 Flat section 22 Side wall section 30 Gasket 31 Base section 32 Outer cylinder wall 33 Inner cylinder wall 40 Laminated electrode 41 Positive electrode 42 Negative electrode 43 Separator 51 Mesh member

Claims

1. A flat-type non-aqueous battery comprising a positive electrode including a molded body of a positive electrode mixture, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the negative electrode includes a lithium layer and a Li-Al alloy layer formed on the separator-side surface of the lithium layer, the separator is constructed by laminating two or more layers of polyolefin nonwoven fabric, the portion of the separator located between the positive electrode and the negative electrode is compressed between the positive electrode and the negative electrode to a thickness of 100 to 200 μm, and the basis weight of the separator is 50 g / m². 2 110g / m or more 2 A flat, non-aqueous battery characterized by the following:

2. The flat non-aqueous battery according to claim 1, wherein the portion of the separator located between the positive electrode and the negative electrode has a thickness of 20 to 60% of the thickness before compression.

3. The flat-type non-aqueous battery according to claim 1 or 2, wherein the polyolefin nonwoven fabric is composed of polymethylpentene.

4. The flat-type non-aqueous battery according to claim 1 or 2, wherein the Al content in the Li-Al alloy layer of the negative electrode is 3 to 12% by mass ratio of the total amount of Li and Al in the entire negative electrode.

5. The flat non-aqueous battery according to claim 1 or 2, wherein the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte are sealed inside an outer casing comprising an outer casing, a sealing casing, and a gasket interposed between them, the outer casing comprising a circular bottom portion and a cylindrical peripheral wall portion formed continuously with the bottom portion on its outer circumference, the sealing casing comprising a circular flat portion and a cylindrical side wall portion formed continuously with the flat portion on its outer circumference, and the thickness of the molded positive electrode mixture is 40% or more of the height of the internal space formed between the bottom portion of the outer casing and the flat portion of the sealing casing.

6. The flat-type non-aqueous battery according to claim 5, wherein the thickness of the molded body of the positive electrode mixture is 80% or less of the height of the internal space formed between the bottom surface of the outer can and the flat surface of the sealing can.

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