Secondary battery cell

Abstract

The present invention provides a secondary battery cell having a configuration that can effectively suppress the decrease in the amount of electrolyte due to evaporation. [Solution] The secondary battery cell comprises a cell case, an electrode body, an electrolyte, and a resin plate. The electrode body is housed in the cell case. The electrolyte is sealed in the cell case. The resin plate floats in the electrolyte so as to cover its surface.

Description

Technical Field

[0001] The present disclosure relates to a secondary battery cell.

Background Art

[0002] Patent Document 1 discloses a method for checking the level of a battery electrolyte. This checking method is characterized by floating resin particles colored with a dye and / or a pigment on the electrolyte level of a battery covered with a translucent container.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the electrolyte enclosed in the cell case of a secondary battery cell usually has an interface with an air layer, and there is a problem that the liquid volume of the electrolyte decreases due to evaporation. With respect to this problem, in the configuration of floating resin particles in the electrolyte as in the battery described in Patent Document 1, the electrolyte evaporates through the gaps between the resin particles. Further, if the resin particles have a shape that is easy to rotate, such as a sphere, the interface between the electrolyte and the air layer increases, and there is a possibility that the evaporation of the electrolyte is promoted.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a secondary battery cell having a configuration capable of effectively suppressing a decrease in the liquid volume of the electrolyte due to evaporation.

Means for Solving the Problems

[0006] The secondary battery cell according to this disclosure comprises a cell case, an electrode body, an electrolyte, and a resin plate. The electrode body is housed in the cell case. The electrolyte is sealed in the cell case. The resin plate floats in the electrolyte so as to cover its surface. [Effects of the Invention]

[0007] 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 member), it is possible to suppress the rotation of the member (resin plate) floating in the electrolyte to cover the interface. As a result, it becomes possible to effectively suppress the decrease in the volume of the electrolyte due to evaporation. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the schematic configuration of a secondary battery cell according to an embodiment. [Figure 2] This diagram is used to explain the challenges of a battery cell in which an electrolyte solution is sealed in a cell case. [Figure 3] This is a diagram illustrating the structure of the resin plate according to the embodiment. [Figure 4] This figure illustrates the specific structure of the resin plate shown in Figure 3. [Figure 5] This graph shows the relationship between interface pressure and the rate of electrolyte evaporation. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described with reference to the attached drawings.

[0010] 1. Configuration of a secondary battery cell Figure 1 is a diagram showing the schematic configuration of a secondary battery cell (hereinafter simply referred to as a battery cell) 10 according to this embodiment. In Figure 1, the Z direction is the height direction of the battery cell 10. The X direction is the direction of the shorter side of the cell case 12 perpendicular to the Z direction. The Y direction is the direction of the longer side of the cell case 12 perpendicular to the Z direction. More specifically, Figure 1(A) is a perspective view of the battery cell 10, and Figure 1(B) is a view of the internal structure of the battery cell 10 from the Z direction.

[0011] The battery cell 10 is installed in a vehicle, for example, as a battery module containing multiple battery cells 10, and supplies power to the vehicle. The battery cell 10 is, as an example, a lithium-ion battery. The battery cell 10 includes a cell case 12, a pair of external terminals (positive electrode external terminal and negative electrode external terminal) 14, one or more electrode bodies 16, and an electrolyte 18.

[0012] The cell case 12 is, for example, a rectangular cell case having a rectangular parallelepiped shape. That is, the battery cell 10 is, for example, a rectangular cell. The cell case 12 is formed of a metal material such as aluminum. For example, the cell case 12 houses two electrode bodies 16.

[0013] A pair of external terminals 14 are electrically connected to each electrode body 16 via electrode tabs and current collector terminals, which are not shown in the figure.

[0014] Each electrode body 16 is formed in a plate shape. As shown in Figure 1, two electrode bodies 16 are arranged side by side, for example, with the X direction as their thickness direction. The electrode body 16 includes a positive electrode and a negative electrode, and is formed to hold an electrolyte 18 between the positive electrode and the negative electrode. The electrode body 16 is, for example, a wound electrode body, but it may also be a laminated electrode body. The cell case 12 is sealed with the electrolyte 18.

[0015] Figure 2 is a diagram used to explain the problems of battery cells in which electrolyte is sealed in a cell case. Electrolytes sealed in a cell case, such as electrolyte 18, have an interface with an air layer, as shown in Figure 2, and face the problem of a decrease in the amount of electrolyte due to evaporation. This decrease in liquid volume due to evaporation leads to a decrease in the internal resistance of the secondary battery cell. More specifically, low-density (pressure) interfaces, such as the interface between the electrolyte and the air layer, contribute to accelerating the evaporation of the electrolyte. Therefore, it is desirable for secondary battery cells to have a configuration that can effectively suppress the decrease in the amount of electrolyte due to evaporation.

[0016] Figure 3 is a diagram illustrating the configuration of the resin plate 20 according to this embodiment. In view of the above problems, the battery cell 10 according to this embodiment includes a resin plate 20. As shown in Figure 3, the resin plate 20 floats in the electrolyte 18 so as to cover the surface of the electrolyte 18 inside the cell case 12. In other words, the resin plate 20 is interposed between the electrolyte 18 and the air layer inside the cell case 12. The resin plate 20, which is a plate-shaped resin member, is formed to be longer in the horizontal direction (for example, in the X direction and Y direction) than in the Z direction (vertical direction).

[0017] In the example where a wound electrode body 16 is housed in a rectangular cell case 12 of a rectangular battery cell 10, there is a gap between the wound electrode body 16 and the rectangular cell case 12, as shown by P1 to P6 in Figure 2. The resin plate 20 floats in the electrolyte 18 that fills the space between the wound electrode body 16 and the rectangular cell case 12 (each of the locations P1 to P6) when the rectangular cell case 12 is viewed from above (see Figure 2). In other words, in this example, the resin plate 20 is provided at multiple locations within the cell case 12.

[0018] Figure 4 is a diagram illustrating the specific structure of the resin plate 20 shown in Figure 3. More specifically, the resin plate 20 according to this embodiment may be formed as follows. That is, as shown in Figure 4, in the vertical direction, the lower part of the resin plate 20 is denser than the upper part of the resin plate 20.

[0019] In an example shown in FIG. 4, the resin plate 20 includes a low-density resin portion 22 and a high-density resin portion 24 having a higher density than the low-density resin portion 22. The high-density resin portion 24 constitutes the lower part of the resin plate 20 in the vertical direction. The low-density resin portion 22 is located above the high-density resin portion 24 in the vertical direction. And the high-density resin portion 24 is formed to extend along the vertical direction and surround the periphery of the low-density resin portion 22 in the horizontal direction. Additionally, in an example shown in FIG. 4, the upper part of the low-density resin portion 22 in the vertical direction is also covered by the high-density resin portion 24.

[0020] Alternatively, instead of the example shown in FIG. 4, the resin plate 20 may be formed to have two layers, for example, a plate-shaped low-density resin portion 22 located on the upper side in the vertical direction and a plate-shaped high-density resin portion 24 located on the lower side in the same direction.

[0021] Additionally, while having a plate shape, the resin plate 20 is desirably as large as possible so as to have a density and a center-of-gravity structure that can sufficiently ensure the distance D between the upper surface of the resin plate 20 and the surface of the electrolytic solution 18. Thereby, compared with an example where the resin plate 20 is formed in a thin-film shape, it is possible to effectively suppress the formation of an interface between the electrolytic solution and the air layer on the upper surface of the resin plate 20.

[0022] The resin plate 20 is formed using, for example, a resin material having low reactivity with the electrolytic solution 18. The resin material is, for example, polyethylene or polypropylene. More specifically, the low-density resin portion 22 and the high-density resin portion 24 may be formed of, for example, the same type of resin material having different densities, or may be formed of resin materials having different densities and types.

[0023] 2. Effects As described above, the secondary battery cell 10 according to this embodiment is equipped with a resin plate 20 that floats on the electrolyte 18 so as to cover the surface of the electrolyte 18. By covering the surface of the electrolyte 18 with the resin plate 20 in this way, the interface between the electrolyte 18 and the air layer can be reduced. Figure 5 is a graph showing the relationship between the pressure at the interface and the amount of electrolyte evaporation. As shown in Figure 5, the higher the pressure at the interface, the less electrolyte evaporates from that interface. Since the resin plate 20 is denser than the air layer, the resin plate 20 can increase the pressure at the interface with the electrolyte 18 compared to the air layer. This reduces the amount of electrolyte 18 evaporation. In addition, by covering the surface of the electrolyte 18 with the resin plate 20 (i.e., a plate-shaped resin member), it is possible to suppress the rotation of the member (resin plate 20) floating on the electrolyte 18 to cover the interface. This prevents or suppresses the increase in the interface between the electrolyte 18 and the air layer caused by the rotation of the resin plate 20 to which the electrolyte 18 adheres.

[0024] From the above, the secondary battery cell 10 equipped with the resin plate 20 according to this embodiment makes it possible to effectively suppress the decrease in the liquid volume of the electrolyte 18 due to evaporation. In addition, because the resin plate 20 has a floating structure, even if the liquid level of the electrolyte 18 changes over time, the effect of reducing the amount of evaporation of the electrolyte 18 can be well maintained.

[0025] Furthermore, in this embodiment, the resin plate 20 is formed such that the lower part of the resin plate 20 is denser than the upper part in the vertical direction. As a result, the denser portion of the resin plate 20 (e.g., the dense resin portion 24) forms an interface with the electrolyte 18. Therefore, compared to the case where the less dense portion forms the interface with the electrolyte 18, the permeation of the electrolyte 18 after evaporation can be suppressed more effectively. In addition, because the lower part of the resin plate 20 is denser, the center of gravity of the resin plate 20 can be lowered, so the rotation of the resin plate 20 floating in the electrolyte 18 can be suppressed more effectively.

[0026] Furthermore, the resin plate 20 according to this embodiment is positioned to float in the electrolyte 18 that fills the space between the wound electrode body 16 and the rectangular cell case 12 (e.g., parts P1 to P6 in Figure 2) when the rectangular cell case 12 is viewed from above. This effectively suppresses the decrease in the amount of electrolyte 18 due to evaporation in the secondary battery cell 10, which is a rectangular cell having a wound electrode body 16, and also provides the secondary effect of suppressing the horizontal vibration and movement of the wound electrode body 16 within the rectangular cell case 12 by the resin plate 20. [Explanation of Symbols]

[0027] 10 Secondary battery cell, 12 Cell case (prismatic cell case), 14 External terminals, 16 Electrode body (wound electrode body), 18 Electrolyte, 20 Resin plate, 22 Low-density resin part, 24 High-density resin part

Claims

1. Cell case and, The electrode body housed in the cell case, The electrolyte sealed in the aforementioned cell case, A resin plate floating in the electrolyte so as to cover the surface of the electrolyte, Equipped with Secondary battery cell.

2. A secondary battery cell according to claim 1, In the vertical direction, the lower part of the resin plate is denser than the upper part of the resin plate. Secondary battery cell.

3. A secondary battery cell according to claim 1 or 2, The electrode body is a wound-type electrode body, The aforementioned cell case is a rectangular cell case, The resin plate is floating in the electrolyte that fills the space between the wound electrode body and the rectangular cell case when the rectangular cell case is viewed from above. Secondary battery cell.

4. A secondary battery cell according to claim 1 or 2, The resin plate is formed from a resin material that has low reactivity with the electrolyte. Secondary battery cell.

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