Secondary batteries

Abstract

To provide a secondary battery capable of suppressing pressure rise inside the battery and suppressing intrusion of water vapor from the outside into the battery with a simple structure.SOLUTION: In a secondary battery 1 including a case 11 having an opening 11a, a lid member 12 that seals the opening 11a, and electrode terminals 13 and 14, the lid member 12 is provided with a through hole 20 and a resin portion 21 that closes the through hole 20, and at least a part of the resin portion 21 is an exhaust portion 22 formed of a resin having a solubility parameter (SP value) of 23 (Mpa)1 / 2 or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to secondary batteries. [Background technology]

[0002] In secondary batteries, repeated charging and discharging, as well as aging, increase the amount of electrolyte decomposition products (gases) generated inside the battery, leading to an increase in internal pressure. Therefore, in batteries where the mounting holes that penetrate the lid and the electrode terminals are sealed with a resin that has high gas barrier performance (low gas permeability), the high airtightness prevents the electrolyte decomposition gases generated inside the battery from being released to the outside, making it easy for the internal pressure to rise. To cope with this pressure rise inside the battery during normal use, measures are needed to improve the pressure resistance of the battery casing, such as increasing the opening pressure of the release valve, increasing the thickness and rigidity of the case, and increasing the penetration length of the sealing / sealing weld. As a result, material costs and welding difficulty increase, which may lead to a decrease in yield and an increase in the cost of the battery.

[0003] Here, gas permeability can be increased by thinning the resin that seals the through-holes in the lid and the electrode terminals. However, thinning the resin increases the amount of water vapor that enters the inside of the battery, and also worsens the insulation performance due to a decrease in the strength of the resin and a shortening of the insulation distance.

[0004] For example, in the secondary battery described in Patent Document 1, two types of gaskets are used in combination to seal the space between the lid (lid member) and the current collector terminal (electrode terminal) in order to discharge electrolyte decomposition gas generated inside the battery to the outside. In this secondary battery, two types of gaskets with different gas permeability coefficients are placed in close contact, with a first gasket with high gas permeability on the outside of the battery and a second gasket with low gas permeability on the inside of the battery. As a result, there are two gas permeability paths to and from the inside of the battery, passing through the first gasket and the second gasket, and the gas permeability of the second gasket is utilized to discharge electrolyte decomposition gas generated inside the battery to the outside. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-181544 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in the above-mentioned secondary battery, the second gasket, which has high gas permeability, allows water vapor to easily pass through from the outside into the battery, potentially accelerating battery degradation. Furthermore, using two types of gaskets increases the number of parts, increasing the complexity of assembly work and potentially worsening the yield.

[0007] Therefore, this disclosure is made to solve the above-mentioned problems and aims to provide a secondary battery that can suppress the rise in pressure inside the battery and suppress the intrusion of water vapor from the outside into the battery, with a simple structure. [Means for solving the problem]

[0008] One form of this disclosure made to solve the above problem is: A case with an opening, A lid member that seals the aforementioned opening, In a secondary battery having electrode terminals, The lid member is provided with a through hole and a resin portion that closes the through hole. At least a portion of the aforementioned resin part has a solubility parameter (SP value) of 23 (Mpa) 1 / 2 The exhaust section is characterized by being made of the following resin.

[0009] As a result, part or all of the resin portion that closes the through-hole of the lid member becomes an exhaust vent, allowing the exhaust vent to be positioned in the through-hole of the lid member. Furthermore, the solubility parameter (SP value) is 23 (MPa). 1 / 2The following resins tend to have high permeability of hydrogen and carbon dioxide, which are electrolyte decomposition gases generated inside batteries, and low permeability of water vapor. Currently, commercially available resins have a solubility parameter (SP value) of 10 (MPa). 1 / 2 Since the following do not exist, the resin forming the exhaust section has a solubility parameter (SP value) of 10-23 (MPa). 1 / 2 It becomes a resin.

[0010] Therefore, the exhaust section has a solubility parameter (SP value) of 23 (MPa). 1 / 2 By forming the structure from the resin described below, electrolyte volatiles such as ethylene carbonate are retained within the battery through the exhaust section located in the through-hole of the lid member, while only electrolyte decomposition gases such as carbon dioxide are discharged to the outside, and water vapor is prevented from entering the battery from the outside. Therefore, this exhaust section, with its extremely simple structure without the need to combine multiple parts, can suppress pressure rise within the battery, preventing malfunction of the battery's current cutoff mechanism and gas discharge valve. Furthermore, because pressure rise within the battery is suppressed, it becomes possible to thin the case and lid members, use non-rigid materials, and relax the penetration length in sealing and sealing welding, thereby reducing the weight and cost of the battery.

[0011] In the secondary battery described above, The exhaust section preferably comprises multiple resins of different materials.

[0012] By constructing the exhaust section with multiple resins of different materials in this way, the types of gases discharged to the outside through the exhaust section can be restricted. Therefore, only the gases that are to be discharged from inside the battery to the outside can be selectively discharged. As a result, electrolyte decomposition gases that tend to be generated (or are generated in large quantities) inside the battery can be efficiently discharged to the outside, depending on the specifications of the battery, and thus the pressure rise inside the battery can be effectively suppressed. The multiple resins of different materials may be arranged continuously (so that they are in contact with each other and overlapping), or there may be resin parts between the resins of different materials.

[0013] In any of the above secondary batteries, a part of the resin part is formed with the exhaust part, the through hole is disposed in the vicinity of the electrode terminal, the resin part preferably integrates the lid member and the electrode terminal and insulates the lid member and the electrode terminal from each other.

[0014] By doing so, when attaching the electrode terminal to the lid member, the resin part and the exhaust part can be formed, so there is no need to separately provide a process for forming the exhaust part, and it is possible to prevent a decrease in production efficiency due to providing the exhaust part.

[0015] In any of the above secondary batteries, the resin part has a bottomed hole that opens toward the outside of the battery, the exhaust part is preferably formed in the bottomed hole.

[0016] By providing a bottomed hole that opens toward the outside of the battery in the resin part and disposing the exhaust part in the bottomed hole, the exhaust part is covered by the resin part, so the exhaust part is not exposed inside the battery. Therefore, when the resin forming the exhaust part may melt in the electrolytic solution, it is possible to surely prevent the exhaust part from melting in the electrolytic solution.

Advantages of the Invention

[0017] According to the present disclosure, it is possible to provide a secondary battery that can suppress an increase in pressure inside the battery and suppress the intrusion of water vapor from the outside into the battery with a simple structure.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view showing a secondary battery of an embodiment. [Figure 2] It is a perspective view showing a lid member in which electrode terminals (negative electrode terminal and positive electrode terminal) are integrated by resin. [Figure 3]This is a cross-sectional view at position AA shown in Figure 2. [Figure 4] This figure shows the solubility parameter (SP value) and permeability performance of the resin used in the resin and exhaust sections. [Figure 5] This figure shows a first modified example of the resin part, including the exhaust section. [Figure 6] This figure shows a second modified example of the resin part, including the exhaust section. [Figure 7] This figure shows another form of the second modified example. [Figure 8] This figure shows another form of the second modified example. [Figure 9] This figure shows another form of the second modified example. [Figure 10] This figure shows a third modified example of the resin part, including the exhaust section. [Figure 11] This figure shows another form of the third modified example. [Figure 12] This figure shows a fourth modified example of the resin part, including the exhaust section. [Modes for carrying out the invention]

[0019] An embodiment of the secondary battery according to this disclosure will be described with reference to the drawings. First, the overall configuration of the secondary battery of this embodiment will be described in detail with reference to Figures 1 to 3. As shown in Figure 1, the secondary battery 1 of this embodiment has a case 11 with an opening 11a and a lid member 12 formed in the shape of a rectangular plate that seals the opening 11a. The case 11 and the lid member 12 are made of metal (for example, aluminum) and welded together. Inside the case 11 sealed by the lid member 12, an electrode body is housed, and a non-aqueous electrolyte is poured in and housed therein. The secondary battery 1 is equipped with a current cutoff mechanism and a gas discharge valve that operate when the pressure inside the battery rises and exceeds a predetermined value.

[0020] As shown in Figures 2 and 3, the lid member 12 and the electrode terminals (i.e., the negative electrode terminal 13 and the positive electrode terminal 14) are integrated by a resin part 15. In other words, the negative electrode terminal 13 and the positive electrode terminal 14 are fixed to the lid member 12. The resin part 15 insulates the lid member 12 from the negative electrode terminal 13 and from the lid member 12 from the positive electrode terminal 14. The negative electrode terminal 13 and the positive electrode terminal 14 (more specifically, the internal terminal 17, which will be described later) are each connected to an electrode body (not shown) housed in the case 11.

[0021] The negative terminal 13 and the positive terminal 14 have almost the same shape and are equipped with an external terminal 16 and an internal terminal 17 connected to an electrode body (not shown), respectively. The external terminal 16 and the internal terminal 17 are positioned on the outside of the battery and on the inside of the battery, with the cover member 12 in between. The external terminal 16 and the internal terminal 17 are connected and welded to each other via mounting holes 12a formed in the cover member 12. A busbar (not shown) connected to an external power source (not shown) is also connected to the external terminal 16.

[0022] In this embodiment of the secondary battery 1, as shown in Figure 3, a through-hole 20 is formed in the lid member 12. The through-hole 20 is located near the positive terminal 14. In this embodiment, the through-hole 20 is located near the positive terminal 14, but the location of the through-hole 20 is not particularly limited. That is, the through-hole 20 can be located, for example, near the negative terminal 13, or near the center of the lid member 12 (between the negative terminal 13 and the positive terminal 14).

[0023] This through-hole 20 is closed by a resin part 21. As shown in Figures 2 and 3, the resin part 21 is provided with an exhaust section 22. In other words, the exhaust section 22 is provided in a part of the resin part 21 that closes the through-hole 20. When viewed from above (viewed from the top side of the lid member 12), the exhaust section 22 is positioned to overlap with the through-hole 20. As shown in Figure 3, the exhaust section 22 is formed to penetrate the resin part 21, and a part of the exhaust section 22 (the bottom side) is exposed to the through-hole 20 (inside the battery).

[0024] Such an exhaust part 22 is formed of a resin having a solubility parameter (SP value) of 23 (Mpa) 1 / 2 or less. The solubility parameter (SP value) is a value calculated by Fedors' estimation method. The resin having a solubility parameter (SP value) of 23 (Mpa) 1 / 2 or less has a tendency to allow a relatively large amount of permeation of hydrogen and carbon dioxide, which are electrolyte decomposition gases generated inside the battery, and has a tendency to allow less permeation of water vapor.

[0025] Therefore, by forming the exhaust part 22 of a resin having a solubility parameter (SP value) of 23 (Mpa) 1 / 2 or less, volatile components of the electrolyte such as ethylene carbonate remain in the battery without permeating through the exhaust part 22, and only electrolyte decomposition gases such as carbon dioxide are discharged from the exhaust part 22 to the outside. On the other hand, the intrusion of water vapor from the outside into the battery through the exhaust part 22 is suppressed.

[0026] Note that the solubility parameter (SP value) of the resin forming the exhaust part 22 is preferably 20 (Mpa) 1 / 2 or less. This is because the permeation of electrolyte decomposition gases in the battery becomes larger and the permeation of water vapor becomes smaller.

[0027] In this embodiment, the resin part 21 is integrated with an outer resin part 15a formed on the upper surface side (outside the battery) of the lid member 12 in the resin part 15. That is, the resin part 21 and the resin part 15a are made of the same resin material and are integrally formed during resin molding when the positive electrode terminal 14 is attached to the lid member 12. Therefore, there is no need to separately provide a process for forming the resin part 21 including the exhaust part 22, and it is possible to prevent a decrease in the production efficiency of the secondary battery 1 due to the provision of the exhaust part 22.

[0028] In this embodiment, for example, PPS (polyphenylene sulfide) can be used as the resin part 21 (resin part 15). When PPS is used for the resin part 21, for example, PP (polypropylene), HDPE (high-density polyethylene), or PPE (polyphenylene ether) can be used as the exhaust part 22, as shown in Figure 4. By using these resins as the exhaust part 22, as is clear from Figure 4, the permeability of hydrogen (H2), hydrocarbons (CH4), and carbon dioxide (CO2), which make up the majority of the electrolyte decomposition gas in the exhaust part 22, becomes higher than that of the resin part 21. Therefore, the electrolyte decomposition gas generated inside the battery can be efficiently discharged to the outside through the exhaust part 22. On the other hand, the water vapor permeability in the exhaust part 22 is the same as or lower than that of the resin part 21, so that the intrusion of water vapor from the outside into the inside of the battery can be suppressed.

[0029] Thus, in the secondary battery 1, the exhaust section 22 has a very simple structure without combining multiple parts, which helps to suppress pressure rise inside the battery. Therefore, malfunctions of the current cutoff mechanism and gas discharge valve in the secondary battery 1 can be prevented. In addition, because the pressure rise inside the battery is suppressed, it becomes possible to make the case 11 and lid member 12 thinner and use non-rigid materials, and to relax the penetration length in sealing and sealing welding. As a result, the secondary battery 1 can be made lighter and less expensive.

[0030] Furthermore, the amount of gas permeating through the exhaust section 22 can be adjusted by changing the thickness and material of the exhaust section 22. Therefore, the material and thickness of the exhaust section 22 should be determined through experiments or other means to achieve the optimal permeation amount according to the specifications of the battery.

[0031] In addition to the resins mentioned above, the resin used in the exhaust section 22 may also be, for example, polyvinylidene chloride, polyamide 11,12, polychlorotrifluoroethylene, polytetrafluoroethylene, etc. These resins are hydrophobic because they do not contain ester or hydroxyl group (functional group) structures that retain moisture, or if they do, the proportion of these functional groups relative to the molecular weight is small, and their solubility parameter (SP value) is 23 (MPa). 1 / 2 The following applies:

[0032] Furthermore, it is preferable to use a resin with a relatively high degree of crystallinity for the exhaust section 22. This is because the higher the degree of crystallinity of the resin, the less permeable water vapor becomes, thus effectively suppressing the intrusion of water vapor from the outside into the battery through the exhaust section 22.

[0033] Furthermore, the resin used in the resin part 21 (resin part 15) must not dissolve in the electrolyte, but it is not limited to the above-mentioned PPS; for example, polyolefins such as PP or halogenated polymers such as fluororesins can be used.

[0034] Here, a modified example of the resin part 21 including the exhaust section 22 will be described with reference to Figures 5 to 12. Figures 5 to 12 are schematic cross-sectional views showing the vicinity of the exhaust section.

[0035] First, in the first modified example, as shown in Figure 5, a closed hole 21a opening to the outside of the battery is provided in the resin part 21 where the exhaust part 22 is located. Then, a solubility parameter (SP value) of 23 (Mpa) is provided in this closed hole 21a. 1 / 2The exhaust section 22 is formed by filling it with the following resin. This prevents the exhaust section 22 from being exposed to the through hole 20 (inside the battery). Therefore, it is possible to reliably prevent the exhaust section 22 from dissolving in the electrolyte, and thus a resin that may dissolve in the electrolyte can be used for the exhaust section 22. It is preferable that the thickness of the bottom of the bottomed hole 21a provided in the resin section 21 be as thin as possible while maintaining the required strength. This is because the resin section 21 does not obstruct the permeability of the exhaust section 22 as much as possible.

[0036] Next, in the second modified example, as shown in Figure 6, the resin part 21 is integrated not only with the resin part 15a of the resin part 15, but also with the inner resin part 15b formed on the lower surface side of the lid member 12. As a result, the thickness of the resin part 21 is increased, so the exhaust part 22 provided in the resin part 15 can be composed of multiple exhaust parts 22a, 22b. The exhaust parts 22a and 22b are made of resins of different materials. Therefore, the type of gas discharged to the outside via the exhaust parts 22 (22a, 22b) can be narrowed, so only the type of gas that you want to discharge from inside the battery to the outside can be selectively discharged. Accordingly, depending on the specifications of the battery, electrolyte decomposition gas that is likely to be generated (generated in large quantities) inside the battery can be efficiently discharged to the outside, so the pressure rise inside the battery can be effectively suppressed.

[0037] Even when the resin part 21 is integrally formed with the resin part 15a formed on the upper surface side of the lid member 12 of the resin part 15, as in the above embodiment, it is possible to increase the thickness of the resin part 21 to provide multiple exhaust parts 22a, 22b. However, in this case, the height of the exhaust part 22 will be higher than the height of the electrode terminals, which may get in the way when attaching the busbar. Also, since the exhaust part 22 will have a protruding shape, there is a risk that the exhaust part 22 may be damaged. For this reason, when the exhaust part 22 is composed of multiple exhaust parts 22a, 22b, it is preferable to integrate the resin part 21 not only with the outer resin part 15a of the resin part 15 but also with the inner resin part 15b, as in the second modified example.

[0038] Furthermore, if there is a risk of the exhaust section 22b melting into the electrolyte, as shown in Figure 7, a bottomed hole 21a opening to the outside of the battery can be provided in the part of the resin section 21 where the exhaust sections 22a and 22b are located, as illustrated in the first modified example, and the exhaust sections 22a and 22b can be placed on top of the bottomed hole 21a.

[0039] Furthermore, in the second modified example, as shown in Figure 8, the exhaust section 22 may be configured to penetrate the resin section 21 as in the above embodiment, or, as shown in Figure 9, a bottomed hole 21a may be provided in the resin section 21 as in the first modified example, and the exhaust section 22, which is made of a single resin, may be placed in the bottomed hole 21a.

[0040] Next, in the third modification, as shown in Figure 10, the entire resin part 21 becomes the exhaust part 22. In other words, the exhaust part 22 closes the through hole 20. Therefore, in the third modification, the exhaust part 22 is exposed inside the battery, so the exhaust part 22 needs to be made of a resin that does not dissolve in the electrolyte. This third modification is applicable, for example, when it is difficult to provide the resin part 21. In addition, in the third modification, as shown in Figure 11, the exhaust part 22 can also be made of multiple exhaust parts 22a, 22b, similar to the second modification.

[0041] Finally, in the fourth modification, as shown in Figure 12, the resin part 21 is not formed integrally with the resin part 15 but is formed separately. This fourth modification is applicable, for example, when the through hole 20 is formed at a position away from the negative terminal 13 or positive terminal 14 (for example, near the center of the lid member 12), and it is difficult to integrally mold the resin part 21 with the resin part 15. Note that the fourth modification is not limited to the same embodiment as illustrated in Figure 12, and can also be applied in combination with, for example, the embodiment of the first modification or the embodiment of the third modification.

[0042] As described above, according to the secondary battery 1 of this embodiment, at least a part of the resin portion 21(15) that closes the through hole 20 of the lid member 12 is used as an exhaust portion 22, and the exhaust portion 22 is positioned in the through hole 20 of the lid member 12. The exhaust portion 22 has a solubility parameter (SP value) of 23 (Mpa) 1 / 2 Because it is formed from the following resin, electrolyte volatiles are retained inside the battery through the exhaust section 22, while only electrolyte decomposition gases are discharged to the outside, and water vapor is prevented from entering the battery from the outside. Therefore, in the secondary battery 1, the pressure rise inside the battery can be suppressed by the exhaust section 22 with such a simple structure, and malfunctions of the current cutoff mechanism and gas discharge valve provided in the secondary battery 1 can be prevented. In addition, because the pressure rise inside the battery is suppressed in the secondary battery 1, it is possible to make the case 11 and lid member 12 thinner or use non-rigid materials, and to relax the penetration length in sealing and sealing welding, thereby achieving weight reduction and cost reduction.

[0043] It should be noted that the above embodiments are merely illustrative examples and do not limit this disclosure in any way. Various improvements and modifications are possible without departing from the gist of the disclosure. [Explanation of symbols]

[0044] 1 Secondary battery 11 cases 11a opening 12 Lid member 13 Negative terminal 14 Positive terminal 15 Resin part 20 through holes 21 Resin part 21a Bottomed hole 22 Exhaust section

Claims

1. A case with an opening, A lid member that seals the aforementioned opening, External terminals, In a secondary battery having internal terminals, The cover member is provided with a mounting hole for connecting the external terminal and the internal terminal, a through hole, and a resin portion that closes the through hole and insulates the external terminal and the internal terminal from the cover member. At least a portion of the resin part has a solubility parameter (SP value) of 23 (MPa). １／２ The exhaust section is made of the following resin: The secondary battery is characterized in that the exhaust section is positioned so as to overlap with the through-hole when viewed from the upper surface of the lid member.

2. In the secondary battery described in claim 1, The exhaust section comprises multiple resins of different materials. A secondary battery characterized by the following features.

3. In the secondary battery described in claim 1 or claim 2, The exhaust section is formed in a part of the resin part. The through-hole is located near the external terminal and the internal terminal. The aforementioned resin part integrates the lid member, the external terminal, and the internal terminal. A secondary battery characterized by the following features.

4. A case with an opening, A lid member that seals the aforementioned opening, In a secondary battery having electrode terminals, The lid member is provided with a through hole and a resin portion that closes the through hole. At least a portion of the resin part has a solubility parameter (SP value) of 23 (MPa). １／２ The exhaust section is made of the following resin: The exhaust section is formed in a part of the resin part. The through hole is located near the electrode terminal. The resin part integrates the lid member and the electrode terminal and provides insulation between the lid member and the electrode terminal. The aforementioned resin part has a bottomed hole that opens toward the outside of the battery, The exhaust section is formed in the aforementioned bottomed hole. The secondary battery is characterized in that the exhaust section is positioned so as to overlap with the through-hole when viewed from the upper surface of the lid member.

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