Secondary battery cell

Abstract

The utility model provides a kind of secondary battery monomer with the structure that can effectively inhibit the liquid volume reduction of electrolyte caused by evaporation.The secondary battery monomer includes cell shell, electrode body, electrolyte and resin plate.The electrode body is housed in the cell shell, the electrolyte is sealed in the cell shell, and the resin plate floats on the electrolyte in a manner of covering the surface of the electrolyte.

Description

Technical Field

[0001] This disclosure relates to a secondary battery cell. Background Technology

[0002] Patent Document 1 discloses a method for confirming the electrolyte level in a battery. The method is characterized by resin particles colored with dyes and / or pigments floating on the electrolyte surface of an automotive battery covered by a semi-transparent container.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-115558 However, the electrolyte encapsulated within the cell casing of a secondary battery cell typically forms an interface with an air layer, leading to a reduction in electrolyte volume due to evaporation. To address this issue, as in the battery described in Patent Document 1, a configuration in which resin particles float in the electrolyte allows the electrolyte to evaporate from the gaps between the resin particles. Furthermore, when the resin particles have a shape that facilitates rotation, such as spheres, the interfacial area between the electrolyte and the air layer increases, potentially promoting electrolyte evaporation. Utility Model Content

[0004] This disclosure was made in view of the above-mentioned problems, and its purpose is to provide a secondary battery cell with a structure that can effectively suppress the reduction of electrolyte volume due to evaporation.

[0005] The secondary battery cell disclosed herein comprises: a cell housing; an electrode body housed within the cell housing; an electrolyte sealed within the cell housing; and a resin plate floating on the electrolyte in a manner that covers the surface of the electrolyte.

[0006] Preferably, in the vertical direction, the density of the lower part of the resin board may be higher than the density of the upper part of the resin board.

[0007] Preferably, the electrode body can be a wound electrode body, and the cell housing can be a square cell housing. When viewed from above, the resin plate can float on the electrolyte filled between the wound electrode body and the square cell housing.

[0008] Preferably, the resin plate may be formed of a resin material with low reactivity with the electrolyte.

[0009] According to this disclosure, by covering the surface of the electrolyte with a resin plate, the interface between the electrolyte and the air layer can be reduced. Furthermore, by covering the surface of the electrolyte with a resin plate (i.e., a plate-shaped resin component), the tendency for the component (resin plate) floating on the electrolyte to rotate easily is suppressed. Thus, the reduction in electrolyte volume due to evaporation can be effectively suppressed. Attached Figure Description

[0010] Figure 1A This is a three-dimensional schematic diagram showing the structure of the secondary battery cell involved in this embodiment.

[0011] Figure 1B This is a diagram showing the internal structure of a single secondary battery cell as viewed from the Z-direction.

[0012] Figure 2 This is a schematic diagram used to illustrate the problems existing in a single battery cell containing electrolyte sealed inside the cell casing.

[0013] Figure 3 This is a diagram used to illustrate the resin plate structure involved in this embodiment.

[0014] Figure 4 It is used for explanation Figure 3 A schematic diagram showing the specific structure of the resin board.

[0015] Figure 5 It is a graph showing the relationship between interfacial pressure and electrolyte evaporation. Detailed Implementation

[0016] Embodiments of this disclosure are described with reference to the accompanying drawings.

[0017] Figure 1A and Figure 1B This is a schematic diagram showing the structure of the secondary battery cell (hereinafter referred to as battery cell) 10 involved in this embodiment. Figure 1A and Figure 1B In the diagram, the Z-direction represents the height of the battery cell 10. The X-direction is the direction of the short side of the cell casing 12, which is perpendicular to the Z-direction. The Y-direction is the direction of the long side of the cell casing 12, which is perpendicular to the Z-direction. More specifically, Figure 1A This is a 3D view of battery cell 10. Figure 1B This is a diagram showing the internal structure of the battery cell 10 as viewed from the Z direction.

[0018] The battery cell 10 can be installed in a vehicle, for example, as a battery module comprising multiple battery cells 10, to supply power to the vehicle. As an example, the battery cell 10 is a lithium-ion battery. The battery cell 10 includes a cell housing 12, a pair of external terminals (positive external terminal and negative external terminal) 14, one or more electrode bodies 16, and an electrolyte 18.

[0019] The cell housing 12 is, for example, a square cell housing with a cuboid shape. That is, the battery cell 10 is a square cell in one example. The cell housing 12 is formed of a metallic material such as aluminum. In one example, two electrode bodies 16 are housed in the cell housing 12.

[0020] A pair of external terminals 14 are electrically connected to each electrode body 16 via electrode leads and collector terminals (not shown).

[0021] Each electrode body 16 is formed in the shape of a plate. For example... Figure 1A and Figure 1B As shown, two electrode bodies 16 are arranged side-by-side, for example, with their thickness direction in the X direction. Each electrode body 16 includes a positive electrode and a negative electrode, forming a structure for holding the electrolyte 18 between the positive and negative electrodes. The electrode body 16 can be, for example, a wound electrode body or a stacked electrode body. Furthermore, the electrolyte 18 is sealed within the cell housing 12.

[0022] Figure 2 This is a schematic diagram used to illustrate the problems existing in a single battery cell containing electrolyte encapsulated within its casing. For example... Figure 2 As shown, the electrolyte, such as electrolyte 18, sealed within the cell casing has an interface with an air layer, which presents a problem of electrolyte volume reduction due to evaporation. This volume reduction due to evaporation causes changes in the internal impedance of the secondary battery cell. More specifically, the low-density (low-pressure) interface between the electrolyte and the air layer is one of the factors that accelerates electrolyte evaporation. Therefore, it is desirable for the secondary battery cell to have a structure that can effectively suppress electrolyte volume reduction due to evaporation.

[0023] Figure 3 This is a schematic diagram illustrating the structure of the resin plate 20 according to this embodiment. In view of the above-mentioned issues, the battery cell 10 of this embodiment is provided with a resin plate 20. For example... Figure 3 As shown, the resin plate 20 floats on the electrolyte 18 in such a way that it covers the surface of the electrolyte 18 inside the cell housing 12. In other words, the resin plate 20 is located between the electrolyte 18 and the air layer inside the cell housing 12. As a resin component with a plate shape, the resin plate 20 is formed to extend longer in the horizontal direction (e.g., the X and Y directions) relative to the Z direction (vertical direction).

[0024] When the wound electrode body 16 is housed within the square cell housing 12 of the square battery cell 10, as Figure 1B As shown, gaps exist between the wound electrode body 16 and the square cell housing 12, as indicated by positions P1 to P6. For example, when viewed from above, the resin plate 20 floats on the electrolyte 18 filling the space between the wound electrode body 16 and the square cell housing 12 (i.e., at positions P1 to P6). In other words, in this embodiment, the resin plate 20 is disposed at multiple locations within the cell housing 12.

[0025] Figure 4 It is used for explanation Figure 3The diagram shows the specific structure of the resin board 20. More specifically, the resin board 20 of this embodiment can be formed as follows. That is, as shown... Figure 4 As shown, in the vertical direction, the density of the lower part of the resin board 20 is higher than that of the upper part of the resin board 20.

[0026] exist Figure 4 In one example shown, the resin board 20 includes a low-density resin portion 22 and a high-density resin portion 24 with a higher density than the low-density resin portion 22. The high-density resin portion 24 forms the lower part of the resin board 20 in the vertical direction, and the low-density resin portion 22 is located above the high-density resin portion 24 in the vertical direction. Furthermore, the high-density resin portion 24 extends in the vertical direction and forms a structure surrounding the low-density resin portion 22 in the horizontal direction. Further, in Figure 4 In one example shown, the upper part of the low-density resin portion 22 in the vertical direction is also covered by the high-density resin portion 24.

[0027] Or, as Figure 4 In an alternative to the example shown, the resin board 20 may also be formed with a two-layer structure, namely, in the vertical direction, a plate-shaped low-density resin portion 22 is provided on the upper side, and a plate-shaped high-density resin portion 24 is provided on the lower side.

[0028] Furthermore, the resin plate 20 is preferably made as large as possible to maintain its plate shape while having a density and center of gravity structure that adequately ensures the distance D between the upper surface of the resin plate 20 and the surface of the electrolyte 18. This, compared to the case where the resin plate 20 is formed as a thin film, more effectively suppresses the formation of an interface between the electrolyte and the air layer on the upper surface of the resin plate 20.

[0029] The resin plate 20 is formed, for example, of a resin material with low reactivity with the electrolyte 18. This resin material can be, for example, polyethylene or polypropylene. More specifically, the low-density resin portion 22 and the high-density resin portion 24 can be formed from the same resin material with different densities, or from resin materials with different densities and types.

[0030] As described above, the secondary battery cell 10 of this embodiment includes a resin plate 20 that floats on the electrolyte 18 in a manner that covers the surface of the electrolyte 18. By covering the surface of the electrolyte 18 with the resin plate 20, the interface between the electrolyte 18 and the air layer can be reduced. Figure 5 This is a graph showing the relationship between interfacial pressure and electrolyte evaporation. For example... Figure 5As shown, the higher the interfacial pressure, the less electrolyte evaporates from that interface. Since the resin plate 20 has a higher density than the air layer, the interfacial pressure with the electrolyte 18 can be made higher than that with the air layer through the resin plate 20. This reduces the evaporation rate of the electrolyte 18. Furthermore, by covering the surface of the electrolyte 18 with the resin plate 20 (i.e., the plate-shaped resin component), the component (resin plate 20) floating on the electrolyte 18 to cover the aforementioned interface can be prevented from easily rotating. This also avoids or suppresses the increase in the interfacial area between the electrolyte 18 and the air layer caused by the rotation of the resin plate 20 with the electrolyte 18 attached to it.

[0031] In summary, the secondary battery cell 10 equipped with the resin plate 20 described in this embodiment can effectively suppress the reduction of electrolyte 18 volume due to evaporation. Furthermore, since the resin plate 20 has a floating structure, even if the electrolyte 18 level changes over time, the effect of reducing electrolyte 18 evaporation can be well maintained.

[0032] Furthermore, in this embodiment, the resin plate 20 is formed such that, in the vertical direction, the density of its lower portion is higher than that of its upper portion. Therefore, the high-density portion of the resin plate 20 (e.g., the high-density resin portion 24) will form an interface with the electrolyte 18. Thus, compared to the case where the low-density portion forms an interface with the electrolyte 18, the escape of the electrolyte 18 after evaporation can be more effectively suppressed. In addition, since the lower portion of the resin plate 20 has a high-density structure, the center of gravity of the resin plate 20 can be lowered, thereby more effectively suppressing the rotation of the resin plate 20 floating on the electrolyte 18.

[0033] Furthermore, in this embodiment, the resin plate 20 is configured such that, when viewed from above, it floats between the wound electrode body 16 and the square cell housing 12 (e.g., Figure 1B The electrolyte 18 is applied to the middle portions (P1 to P6). As a result, in the secondary battery cell 10 with a square cell having a wound electrode body 16, the reduction of electrolyte 18 due to evaporation can be effectively suppressed, and the additional effect of suppressing the horizontal vibration and movement of the wound electrode body 16 inside the square cell housing 12 by the resin plate 20 can also be obtained.

Claims

1. A secondary battery cell, characterized in that, have: Battery cell casing; The electrode body is housed within the battery cell housing; Electrolyte, sealed inside the cell housing; and A resin plate floats on the electrolyte in such a way that it covers the surface of the electrolyte. The resin board includes a low-density resin portion and a high-density resin portion with a higher density than the low-density resin portion, the high-density resin portion forming the lower part of the resin board in the vertical direction. The low-density resin portion is located above the high-density resin portion in the vertical direction. The high-density resin portion extends vertically and forms a structure surrounding the low-density resin portion in the horizontal direction.

2. The secondary battery cell according to claim 1, characterized in that, The electrode body is a wound electrode body, and the cell housing is a square cell housing. When viewed from above, the resin plate floats on the electrolyte filling the space between the wound electrode body and the square cell housing.

3. The secondary battery cell according to claim 1, characterized in that, The resin plate is formed of a resin material with low reactivity with the electrolyte.

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