Secondary battery

Abstract

To make the reaction site of a secondary battery uniform.SOLUTION: A secondary 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 a separator 130 that holds an electrolyte are stacked includes a current density control portion (hole 111a) that controls the current density of the current flowing between the positive electrode 110 and the negative electrode 120 in the vicinity of the positive electrode tab 113 and / or the negative electrode tab 123 so as to reduce the current density.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a secondary battery comprising a positive electrode, a carbon negative electrode capable of absorbing and releasing lithium ions, and a non-aqueous electrolyte, in which holes or grooves are provided in at least one of the positive electrode and the negative electrode.

[0003] According to Patent Document 1, even if the area of ​​the electrode is increased, it is possible to prevent a decrease in battery efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-283116 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if holes are provided in the positive and negative electrodes as in Patent Document 1, if the area of ​​the electrodes is increased, it is expected that the uniformity of the reaction sites will be easily lost, making partial deterioration more likely to occur.

[0006] The present invention has been made in view of the above points, and has as its object to easily achieve uniformity of reaction sites. [Means for solving the problem]

[0007] To achieve the above objectives, The present invention provides a positive electrode having a current collecting tab; a negative electrode having a current collecting tab; a separator that holds an electrolyte, The device is characterized by having a current density control unit that controls the current density of the current flowing between the positive electrode and the negative electrode in the vicinity of the current collecting tab so as to decrease the current density.

[0008] This reduces and uniforms the current density in the vicinity of the current collecting tab, dispersing the reaction sites and making the temperature rise uniform. [Effects of the Invention]

[0009] In the present invention, the reaction sites can be easily made uniform. [Brief explanation of the drawings]

[0010] [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 showing the configuration of the positive electrode foil 111. 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 showing the configuration of a positive electrode foil 111 according to a modified example 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 showing the configuration of a positive electrode foil 111 and a negative electrode foil 121 according to the second embodiment. [Figure 7] FIG. 7 is a front view showing the configuration of a positive electrode foil 111 and a negative electrode foil 121 according to another example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] The positive electrode foil 111 is a member for transferring electrons to the positive electrode composite 112. The positive electrode foil 111 is made of a conductive material. The positive electrode foil 111 may be made of, for example, copper, nickel, or zinc. The positive electrode foil 111 is in 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, for example, 5.9 cm to 7.2 cm in length and 130 cm to 350 cm in width.

[0018] The positive electrode composite 112 is a member for causing a charge / discharge reaction on the positive electrode side. The positive electrode composite 112 is provided on the positive electrode foil 111. For example, the positive electrode composite 112 may be provided on both sides of the positive electrode foil 111. The material of the positive electrode composite 112 may be LiFePO4 or a ternary material that is a mixture of Li, Mn, Co, and Ni.

[0019] The positive electrode tab 113 is provided to transfer electrons between the positive electrode foil 111 and the positive electrode composite 112, between 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. For example, in the case of a rectangular positive electrode foil 111, the positive electrode tab 113 may be provided on one side of the positive electrode foil 111.

[0020] 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 that of the positive electrode foil 111. The positive electrode tab 113 may be provided by extending from the outer periphery of the positive electrode foil 111. In other words, the positive electrode tab 113 may be provided continuously from the outer periphery of the positive electrode foil 111. The positive electrode tab 113 may be provided by attaching a member separate from 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.

[0021] The negative electrode 120 includes a negative electrode foil 121, a negative electrode composite 122, a negative electrode tab 123 (current collecting tab), and an electrolyte. The negative electrode 120 is in a sheet shape. 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 to have the same size as the positive electrode 110, for example.

[0022] 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.

[0023] 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-based compound such as graphite or a silicon-based compound.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The electrolyte is a material for transferring lithium ions required for causing charge-discharge reactions between the positive electrode 110 and the negative electrode 120. The electrolyte is a non-aqueous 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, for example, LiPF6 (lithium hexafluorophosphate) or LiFSI (lithium bis(fluorosulfonyl)imide).

[0028] The current density control section is provided in at least one of the positive electrode foil 111 and the negative electrode foil 121. The current density control section is a member for partially increasing the resistance of the positive electrode foil 111 or the negative electrode foil 121 and partially decreasing the current density. This allows the locations where charge / discharge reactions occur in the positive electrode 110 or the negative electrode 120 to be dispersed throughout the positive electrode 110 or the negative electrode 120. As a result, the temperature rise in the secondary battery 100 can be made uniform.

[0029] The current density control section may be provided, for example, by opening holes 111a in the positive electrode foil 111 or the negative electrode foil 121. In this case, the holes 111a may be provided by punching or by using a laser, for example.

[0030] The current density control section may be provided, for example, by providing an insulating region on the positive electrode foil 111 or the negative electrode foil 121. The insulating region may be formed, for example, by applying a non-conductive material. The non-conductive material may be, for example, polypropylene or polyethylene.

[0031] (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.

[0032] 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 opposite 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.

[0033] 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.

[0034] As shown in FIG. 2 , holes 111a having a diameter of, for example, 0.1 to 0.3 mm are formed in a predetermined pattern in at least the positive electrode foil 111 of the positive electrode 110 in the region near the positive electrode tab 113 and the negative electrode tab 123, thereby forming a current density control section that reduces the current density of the current flowing between the positive electrode 110 and the negative electrode 120 in the region near the positive electrode tab 113 and the negative electrode tab 123.

[0035] Here, the vicinity of the positive electrode tab 113 or the negative electrode tab 123 (i.e., the current collecting tab) refers to 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).

[0036] That is, at least near the surface of the positive electrode 110, current is less likely to flow between the positive electrode 110 and the negative electrode 120 in the areas where the holes 111a are formed, thereby reducing the current density. Therefore, if the holes 111a described above are not formed, the current density tends to be higher near the positive electrode tab 113 and the negative electrode tab 123 than in the areas between them. By facilitating a reduction in current density depending on the size and / or arrangement pattern of the holes 111a, the current density can be more easily uniformed across the entire surface of the positive electrode 110 and the negative electrode 120. Therefore, as schematically shown in FIG. 3, for example, when the holes 111a are formed (FIG. 3(b)), the reaction sites concentrated around the positive electrode tab 113 and the negative electrode tab 123 are dispersed, resulting in a more uniform temperature rise, compared to when the holes 111a are not formed (FIG. 3(a)). This suppresses the progression of partial degradation of the secondary battery 100, and a longer lifespan can be expected.

[0037] The holes 111a may be formed in the negative electrode 120, not limited to the positive electrode 110, or in both. The holes 111a do not necessarily need to be formed only near the positive electrode tab 113 or the negative electrode tab 123. The density of the holes 111a may decrease with increasing distance from the positive electrode tab 113 or the negative electrode tab 123, thereby enabling more uniformity. For example, as shown in FIG. 4, holes similar to those shown in Patent Document 1 may be formed in regions other than near the positive electrode tab 113 or the negative electrode tab 123, as long as the current density is appropriately set. The diameter of the holes 111a is not particularly limited, and may be any size that can be processed and that can achieve uniformity in the current density.

[0038] The holes 111a may be formed by punching the positive electrode foil or the negative electrode foil before the electrodes are formed, or by irradiating the positive electrode foil or the negative electrode foil with a laser before the electrodes are formed.

[0039] (Embodiment 2) The secondary battery 100 is not limited to those using flat positive electrodes 110 and negative electrodes 120 as described above. For example, as shown in FIG. 5 , strip-shaped positive electrodes 110 and negative electrodes 120 may be wound into a cylindrical shape, with positive electrode tabs 113 and negative electrode tabs 123 extending from the same widthwise direction or from one side and the other side of the strip. In this case, as shown in FIGS. 6 and 7 , holes 111a may be formed in a predetermined pattern in areas near the positive electrode tab 113 and negative electrode tab 123, thereby reducing the current density of the current flowing between the positive electrode 110 and negative electrode 120 in areas near the positive electrode tab 113 and negative electrode tab 123 and easily homogenizing the current density across the entire surface of the positive electrode 110 and negative electrode 120. This disperses the reaction sites that were concentrated around the positive electrode tab 113 and negative electrode tab 123, resulting in a more homogenous temperature rise. This suppresses the progression of partial deterioration of the secondary battery 100, and is expected to extend its lifespan.

[0040] (Embodiment 3) In order to control the current density, it is not limited to forming holes 111a in the positive electrode 110 and / or the negative electrode 120 as described above, but an insulating region (non-conductive material) may be formed in the region near the positive electrode tab 113 or the negative electrode tab 123 on the surface of at least one of the positive electrode 110 and the negative electrode 120. This also makes it possible to easily achieve uniformity of the reaction site.

[0041] The insulating region may be formed, for example, by replacing a portion of the current collector foil with a non-conductive agent or by coating the current collector foil with a non-conductive agent. This reduces the current density in the regions near the positive and negative electrode tabs, making it easy to achieve uniform reaction sites. [Explanation of symbols]

[0042] 100 Secondary battery 110 positive electrode 111 Positive electrode foil 111a hole 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

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 secondary battery comprising a current density control section that controls the current density between the positive electrode and the negative electrode in the vicinity of the current collecting tab so as to decrease the current density.

2. 2. The secondary battery of claim 1, a secondary battery characterized in that the current density control section is configured by the size and / or arrangement pattern of holes formed in the conductive material of at least one of the positive electrode and the negative electrode in a region near the current collecting tab.

3. 2. The secondary battery of claim 1, The current density control section is configured by the size and / or arrangement pattern of an insulating region formed in a region near the current collecting tab on at least one of the positive electrode and the negative electrode.

4. 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.

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 the same direction.

6. 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.

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 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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