Secondary battery

Abstract

To uniformize a reaction part of a secondary battery.SOLUTION: In a rechargeable battery in which a positive electrode 110 having a positive electrode tab 113 (current-collecting tab), a negative electrode 120 having a negative electrode tab 123 (current-collecting tab), and separators 130 that hold electrolytes are stacked, the air-permeation resistance of nearby regions 130a and 130b near the positive electrode tab 113 and / or the negative electrode tab 123 in the separators 130 is set to be greater than the air-permeation resistance of a separation region 130c away from the positive electrode tab 113 and / or the negative electrode tab 123.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Conventionally, in a non-aqueous electrolyte secondary battery having a wound electrode assembly that has a positive electrode plate, a separator, and a negative electrode plate and that includes a flat portion and a curved portion, a secondary battery is known in which the air permeability (air permeability resistance) of the flat portion of the separator at the outermost periphery of the wound electrode assembly is 161% to 278% of the air permeability of the curved portion (see, for example, Patent Document 1). It is believed that having such an air permeability tends to reduce deterioration of the electrode plate in the flat portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-77116 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if the separator has a set air permeability as in Patent Document 1, it is expected that the uniformity of the reaction may be easily impaired, and partial deterioration may easily occur, especially when the cell is enlarged (high aspect ratio) or under high-rate conditions.

[0005] The present invention has been made in view of the above points, and has as its object to easily achieve uniformity in the reaction. [Means for solving the problem]

[0006] To achieve the above objectives, The present invention provides a positive electrode having a current collecting tab and a sheet of conductive material; a negative electrode having a current collecting tab and a sheet of conductive material; a separator for holding an electrolyte; and a secondary battery in which the separator and the separator are stacked, The separator has a higher air permeability resistance in a vicinity region near the current collecting tab than in a remote region that is farther from the current collecting tab than the vicinity region.

[0007] This makes it possible to make the reaction uniform between the region near the current collecting tab and the remote region that is farther away from the current collecting tab than the region near the current collecting tab, thereby suppressing partial deterioration. [Effects of the Invention]

[0008] In the present invention, the reaction can be easily made uniform. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view schematically illustrating the configuration of a secondary battery 100 according to the first embodiment. [Figure 2] FIG. 2 is a front view schematically showing the configuration of the separator 130. As shown in FIG. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the reaction distribution of the secondary battery 100. As shown in FIG. [Figure 4] FIG. 4 is a front view schematically showing the configuration of a separator 130 according to a modification of the first embodiment. [Figure 5] FIG. 5 is a perspective view showing the appearance of the secondary battery 100 according to the second embodiment. [Figure 6] FIG. 6 is a front view schematically showing the configuration of a separator 130 according to the second embodiment. [Figure 7] FIG. 7 is a front view schematically showing the configuration of a separator 130 according to another example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each of the following embodiments and modifications, components having the same functions as those in other embodiments will be designated by the same reference numerals and will not be described again.

[0011] (Overall composition) 1 is a schematic exploded perspective view showing the configuration of a secondary battery 100 (battery cell) according to embodiment 1. The secondary battery 100 may be, for example, a lithium-ion battery or a nickel-metal hydride battery.

[0012] The secondary battery 100 has a plurality of positive electrodes 110, a plurality of negative electrodes 120, a plurality of separators 130 respectively positioned between the positive electrodes 110 and the negative electrodes 120, and an electrolyte solution.

[0013] 1, the secondary battery 100 may be a stacked battery formed by stacking, for example, a plurality of rectangular sheet-shaped positive electrodes 110, a plurality of rectangular sheet-shaped negative electrodes 120, and a plurality of rectangular sheet-shaped separators 130. In this case, the size of the secondary battery 100 may be, for example, a rectangular shape with a length of 5 cm to 11 cm and a width of 10 cm to 200 cm.

[0014] 5, the secondary battery 100 may be a cylindrical battery formed by stacking and then winding a strip-shaped positive electrode 110, a strip-shaped negative electrode 120, and a strip-shaped separator 130. In this case, the size of the secondary battery 100 may be, for example, a cylindrical shape with a diameter of 1.8 cm to 4.6 cm and a height of 6.5 cm to 8.0 cm.

[0015] The positive electrode 110 includes a positive electrode foil 111, a positive electrode composite 112, a positive electrode tab 113 (current collecting tab), and an electrolyte. The positive electrode 110 is in a sheet shape. The positive electrode 110 may be, for example, rectangular. The positive electrode 110 may be, for example, strip-shaped. The positive electrode 110 may be formed to have the same size as the negative electrode 120, for example.

[0016] The positive electrode foil 111 is a member for transferring electrons to and from the positive electrode composite material 112. The positive electrode foil 111 is formed of a conductive material. The positive electrode foil 111 may be, for example, copper, nickel, or zinc. The positive electrode foil 111 has a sheet shape. The positive electrode foil 111 may be, for example, rectangular. In this case, the size of the positive electrode foil 111 may be, for example, 4.5 cm to 10.5 cm in length and 9.5 cm to 190 cm in width. The positive electrode foil 111 may be, for example, strip-shaped. In this case, the size of the positive electrode foil 111 may be 5.9 cm to 7.2 cm in length and 130 cm to 350 cm in width.

[0017] The positive electrode composite material 112 is a member for causing charge and discharge reactions on the positive electrode side. The positive electrode composite material 112 is provided on the positive electrode foil 111. The positive electrode composite material 112 may be provided, for example, on both sides of the positive electrode foil 111. The material of the positive electrode composite material 112 is, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li xCoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), LiNi x Co y M z O2 (x + y + z = 1, x ≥ 0.8, M consists of Mn and Al), and lithium nickel cobalt manganese composite oxide (Li x Ni1 - y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) may also be used.

[0018] The positive electrode tab 113 is provided to transfer the electrons that the positive electrode foil 111 transfers between the positive electrode foil 111 and the positive electrode mixture 112 to the inside and outside of the positive electrode 110. The positive electrode tab 113 is provided on the outer periphery of the positive electrode foil 111. In the case of a rectangular positive electrode foil 111, for example, the positive electrode tab 113 may be provided on one side of the positive electrode foil 111.

[0019] The positive electrode tab 113 may be formed of, for example, the same material as the positive electrode foil 111. The positive electrode tab 113 may be formed of, for example, a material different from the positive electrode foil 111. The positive electrode tab 113 may be provided, for example, by extending from the outer periphery of the positive electrode foil 111. In other words, the positive electrode tab 113 may be provided continuously, for example, from the outer periphery of the positive electrode foil 111. The positive electrode tab 113 may be provided, for example, by attaching another member to the positive electrode foil 111. The size of the positive electrode tab 113 may be, for example, 2.5 cm to 5.5 cm in length and 1.5 cm to 3.5 cm in width.

[0020] The negative electrode 120 has a negative electrode foil 121, a negative electrode mixture 122, a negative electrode tab 123 (current collector tab), and an electrolytic solution. The negative electrode 120 is in sheet form. The negative electrode 120 may be, for example, rectangular. The negative electrode 120 may be, for example, strip-shaped. The negative electrode 120 may be formed, for example, to the same size as the positive electrode 110.

[0021] The negative electrode foil 121 is a member for transferring electrons to the negative electrode composite 122. The negative electrode foil 121 is made of a conductive material. The negative electrode foil 121 may be made of, for example, aluminum, titanium, or stainless steel. The negative electrode foil 121 is in a sheet shape. The negative electrode foil 121 may be, for example, rectangular. In this case, the size of the negative electrode foil 121 may be, for example, 4.5 cm to 10.5 cm in length and 9.5 cm to 190 cm in width. The negative electrode foil 121 may be, for example, strip-shaped. In this case, the size of the negative electrode foil 121 may be, for example, 5.9 cm to 7.2 cm in length and 125 cm to 336 cm in width.

[0022] The negative electrode composite 122 is a member for causing a charge / discharge reaction on the negative electrode side. The negative electrode composite 122 is provided on the negative electrode foil 121. The negative electrode composite 122 may be provided on both sides of the negative electrode foil 121, for example. The material of the negative electrode composite 122 may be a carbon material. The carbon material may be, for example, graphite or non-graphitizable carbon. The material of the negative electrode composite 122 may be, for example, a silicon-based material. The silicon-based material may be, for example, silicon oxide or elemental silicon. The material of the negative electrode composite 122 may be, for example, a mixture of a carbon material and a silicon-based material. The material of the negative electrode composite 122 may be, for example, a transition metal oxide. The transition metal oxide may be, for example, lithium titanate (Li4Ti5O 12 The material of the negative electrode composite 122 may be, for example, lithium metal.

[0023] The negative electrode tab 123 is provided to transfer electrons between the negative electrode foil 121 and the negative electrode composite 122, between the inside and outside of the negative electrode 120. The negative electrode tab 123 is provided on the outer periphery of the negative electrode foil 121. For example, in the case of a rectangular negative electrode foil 121, the negative electrode tab 123 may be provided on one side of the negative electrode foil 121.

[0024] The negative electrode tab 123 may be formed of, for example, the same material as the negative electrode foil 121. The negative electrode tab 123 may be formed of, for example, a material different from that of the negative electrode foil 121. The negative electrode tab 123 may be provided by extending from the outer periphery of the negative electrode foil 121. In other words, the negative electrode tab 123 may be provided continuously from the outer periphery of the negative electrode foil 121. The negative electrode tab 123 may be provided by attaching a member separate from the negative electrode foil 121. The size of the negative electrode tab 123 may be, for example, 2.5 cm to 5.5 cm in length and 1.5 cm to 3.5 cm in width.

[0025] The separator 130 is a member that holds an electrolyte between the positive electrode 110 and the negative electrode 120. The separator 130 is provided to reduce the possibility of short-circuiting between the positive electrode 110 and the negative electrode 120 while allowing the movement of lithium ions. The separator 130 may be in a sheet shape. The separator 130 may be formed using a porous material. The separator 130 may be formed using a non-conductive material. The separator 130 may be made of, for example, polypropylene, polyethylene, nonwoven fabric, or the like. The size of the separator 130 may be, for example, 4.7 cm to 10.7 cm in length and 9.7 cm to 195 cm in width.

[0026] In the separator 130, for example, the air permeability resistance of the vicinity regions 130a and 130b near the positive electrode tab 113 and the negative electrode tab 123 is set to be greater than the air permeability resistance of the remote region 130c away from the positive electrode tab 113 and the negative electrode tab 123. Also, for example, the air permeability resistance of the vicinity region 130a near the positive electrode tab 113 is set to be greater than the air permeability resistance of the vicinity region 130b near the negative electrode tab 123. This can suppress charge / discharge reactions in the vicinity regions 130a and 130b and facilitate charge / discharge reactions in the remote region 130c, and can distribute the locations where charge / discharge reactions occur in the positive electrode 110 or the negative electrode 120 throughout the positive electrode 110 or the negative electrode 120. As a result, the temperature rise and degree of deterioration of the secondary battery 100 can be made uniform.

[0027] In this specification, "air resistance" refers to the "air resistance" defined in "JIS P8117:2009 Paper and paperboard - Air permeability and air resistance test method (intermediate range) - Gurley method." This air resistance is defined as the time required for a specified volume of air to permeate per unit area and unit pressure difference. The unit of air resistance is expressed in seconds per 100 mL. The method for setting the air resistance as described above is not particularly limited, and it may be set by various methods depending on the manufacturing method of the separator 130.

[0028] Here, the air resistance may be varied discretely (stepwise) from the vicinity region 130a to the vicinity region 130b, or may be varied continuously.

[0029] The electrolyte is a material for transferring lithium ions necessary for charge-discharge reactions to occur between the positive electrode 110 and the negative electrode 120. The electrolyte is a nonaqueous electrolyte. The electrolyte may be, for example, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), or a mixture of the above organic solvents. The electrolyte may contain, for example, a lithium salt. The lithium salt may be lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenic (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), lithium bis(trifluorosulfonyl)imide (LiTFSI), or lithium bis(fluorosulfonyl)imide (LiFSI), or a mixture thereof.

[0030] (Embodiment 1) In Fig. 1, 110 is a sheet-shaped positive electrode, 120 is a sheet-shaped negative electrode, and a plurality of positive electrodes 110 and a plurality of negative electrodes 120 are alternately stacked one by one with separators 130 for holding an electrolyte interposed therebetween. The positive electrode 110 is a rectangular sheet-shaped positive electrode foil 111 (conductive material) with a positive electrode composite 112 formed on both sides. The negative electrode 120 is a rectangular sheet-shaped negative electrode foil 121 (conductive material) with a negative electrode composite 122 formed on both sides.

[0031] The positive electrode tab 113 (current collecting tab) of the positive electrode 110 extends laterally from one side of the positive electrode foil 111, and the negative electrode tab 123 (current collecting tab) of the negative electrode 120 extends laterally from the other side of the negative electrode foil 121 that faces the side of the positive electrode foil 111. That is, the positive electrode tab 113 and the negative electrode tab 123 extend in opposite directions. In other words, they are arranged to face each other on both sides of the portion where the positive electrode 110 and the negative electrode 120 are stacked with the separator 130 interposed therebetween.

[0032] The stacked positive electrode 110, negative electrode 120, and separator 130 are, for example, secured with tape to prevent the stack from collapsing, and are further covered on both sides with laminate films, and the edges of the laminate films on both sides are sealed with seals to prevent leakage of the electrolyte inside; however, since this is not the main focus of the present invention, a description thereof will be omitted for convenience.

[0033] 2, the separator 130 has air permeability resistances set to be greater in neighborhood regions 130a and 130b near the positive electrode tab 113 and the negative electrode tab 123 than in a separation region 130c between the positive electrode tab 113 and the negative electrode tab 123. The air permeability resistance of neighborhood region 130a near the positive electrode tab 113 is set to be greater than that of neighborhood region 130b near the negative electrode tab 123.

[0034] Here, the vicinity of the positive electrode tab 113 or the negative electrode tab 123 (i.e., the current collecting tab) refers to, for example, an area that is separated from the positive electrode tab 113 or the negative electrode tab 123 by a distance that is 20% of the distance between the positive electrode tab 113 and the negative electrode tab 123 (hereinafter referred to as the inter-tab distance).

[0035] The air permeability resistance is an index of fluid permeability. The higher the air permeability resistance, the more difficult it is for lithium ions to diffuse, thereby suppressing charge-discharge reactions. Therefore, as shown in FIG. 3, for example, compared to when the air permeability resistance is uniform across the entire surface of the separator 130 (FIG. 3(a)), the air permeability resistance of the neighboring regions 130a and 130b is set higher than that of the remote region 130c (FIG. 3(b)). This suppresses charge-discharge reactions in the neighboring regions 130a and 130b and facilitates charge-discharge reactions in the remote region 130c. This disperses the reaction sites that were concentrated around the positive electrode tab 113 and the negative electrode tab 123, resulting in a more uniform temperature rise. This suppresses the progression of partial degradation of the secondary battery 100, potentially extending its lifespan.

[0036] It should be noted that the regions are not limited to being divided into stages like the nearby regions 130a and 130b and the separated region 130c, but the air permeation resistance may be made smaller as the distance from the positive electrode tab 113 or the negative electrode tab 123 increases, thereby enabling more uniformity.

[0037] 4, even when the positive electrode tab 113 and the negative electrode tab 123 are provided side by side on the same peripheral edge of the secondary battery 100, the air permeability resistance of the vicinity regions 130a and 130b near the positive electrode tab 113 and the negative electrode tab 123 may be set to be greater than the air permeability resistance of the separation region 130c, and the air permeability resistance of the vicinity region 130a near the positive electrode tab 113 may be set to be greater than the air permeability resistance of the vicinity region 130b near the negative electrode tab 123. The air permeability resistances of the vicinity regions 130a and 130b do not necessarily have to be different, and may be set to be equal.

[0038] (Embodiment 2) The secondary battery 100 is not limited to those using flat positive and negative electrodes 110 and 120 as described above. For example, as shown in FIG. 5 , a strip-shaped positive electrode 110, a negative electrode 120, and a separator 130 may be wound into a cylindrical shape, with a positive electrode tab 113 and a negative electrode tab 123 extending from the same widthwise direction or from one side and the other side of the strip. In this case, too, as shown in FIGS. 6 and 7 , by setting the ISO air permeability of the vicinity regions 130a and 130b near the positive and negative electrode tabs 113 and 123 to be smaller than the ISO air permeability of the separation region 130c, the regions where charge and discharge reactions occur in the positive and negative electrodes 110 and 120 can be dispersed throughout the positive and negative electrodes 110 and 120. As a result, the temperature rise and deterioration of the secondary battery 100 can be uniform. [Explanation of symbols]

[0039] 100 Secondary battery 110 positive electrode 111 Positive electrode foil 112 Positive electrode mixture 113 Positive electrode tab 120 negative electrode 121 Negative electrode foil 122 Negative electrode mixture 123 Negative electrode tab 130 Separator 130a Nearby area 130b Nearby area 130c isolated area

Claims

1. a positive electrode having a current collecting tab and a sheet of conductive material; a negative electrode having a current collecting tab and a sheet of conductive material; a separator for holding an electrolyte; and a secondary battery in which the separator and the separator are stacked, a separator having a vicinity region adjacent to the current collecting tab, the vicinity region having a higher air permeability resistance than a remote region that is farther from the current collecting tab than the vicinity region;

2. 2. The secondary battery of claim 1, a separator having a higher air permeability resistance in a region adjacent to the current collecting tab of the positive electrode than a region adjacent to the current collecting tab of the negative electrode;

3. The secondary battery according to any one of claims 1 and 2, A secondary battery characterized in that the air resistance of the separator varies discretely between regions of high air resistance and regions of low air resistance.

4. The secondary battery according to any one of claims 1 and 2, A secondary battery characterized in that the air resistance of the separator changes continuously between a region of high air resistance and a region of low air resistance.

5. 2. The secondary battery of claim 1, The positive electrode and the negative electrode are each formed in a rectangular plate shape, A secondary battery, characterized in that the current collecting tab of the positive electrode and the current collecting tab of the negative electrode extend in opposite directions.

6. 2. The secondary battery of claim 1, The positive electrode and the negative electrode are each formed in a rectangular plate shape, A secondary battery, characterized in that the current collecting tab of the positive electrode and the current collecting tab of the negative electrode extend in the same direction.

7. 2. The secondary battery of claim 1, The positive electrode and the negative electrode are formed by stacking and winding a strip of the positive electrode and the negative electrode, The secondary battery is characterized in that the current collecting tabs of the positive electrode and the negative electrode each extend to one side in the width direction of the band.

8. 2. The secondary battery of claim 1, The positive electrode and the negative electrode are formed by stacking and winding a strip of the positive electrode and the negative electrode, The current collecting tab of the positive electrode is provided to extend to one side in the width direction of the strip, The secondary battery is characterized in that the current collecting tab of the positive electrode extends to the other side in the width direction of the band.

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