battery storage

Abstract

The battery case and lid are welded together more securely. [Solution] The storage battery 1 has a battery case 5 and a lid 6. The storage battery 1 has an adhesive strength of 19 MPa or more after welding the battery case 5 and the lid 6, and the fracture strain of the welded portion between the battery case 5 and the lid 6 is 0.1 or more.

Description

Technical Field

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[0001] The present disclosure relates to a storage battery.

Background Art

[0002] There is known a storage battery having a battery case that houses a power storage member therein and a lid welded to the battery case so as to seal an upper opening of the battery case. For example, Patent Document 1 describes that in a large sealed battery, even if there is a variation in the height dimension of the battery case, the height position of the battery case or the hot plate is adjusted so that the melting allowance becomes constant, and the battery case and the lid are welded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when the welded portions of the battery case and the lid are melted using a hot plate having a Teflon (registered trademark) coating on its surface, the melting of the welded portions may be insufficient. When the battery case and the lid are welded in such a state, many non-bonded portions that are not properly welded to each other may occur between the welded surface of the battery case and the welded surface of the lid. When many non-bonded portions occur in the welded portion, the adhesion strength between the battery case and the lid is not sufficient, and it is also conceivable that the electrolyte in the battery case leaks to the outside due to cracks occurring in the welded portion.

[0005] Therefore, the present disclosure describes a storage battery capable of more appropriately welding a battery case and a lid.

Means for Solving the Problems

[0006] A battery according to one aspect of the present disclosure is [1] a battery having a battery case for housing an energy storage member and a lid welded to the battery case, wherein the adhesive strength between the battery case and the lid after welding is 19 MPa or more, and the fracture strain of the welded portion between the battery case and the lid is 0.1 or more.

[0007] In this battery, the adhesive strength between the battery case and the lid is 19 MPa or higher, and the fracture strain of the welded portion is 0.1 or higher. In this state, the occurrence of unadhesive portions is suppressed at the welded portion between the battery case and the lid, resulting in a sufficiently welded state. As a result, crack formation at the welded portion is suppressed in this battery. Thus, this battery allows for more appropriate welding of the battery case and the lid. The adhesive strength between the battery case and the lid may be 21 MPa or higher, 23 MPa or higher, or 25 MPa or higher.

[0008] The above-mentioned storage battery may also be [2] "the storage battery described in [1] above, wherein the battery case and the lid are made of polyolefin." In this case, the battery can be easily welded together by melting the battery case and lid, which are made of polyolefin.

[0009] The above-mentioned storage battery may also be [3] "the storage battery described in [1] or [2] above, wherein the height of the battery case is 400 mm or more." In this case, even if the height of the battery case is 400 mm or more, the battery case and the lid can be welded together more appropriately.

[0010] The above-mentioned battery may also be [4] "a battery described in any of [1] to [3] above, which is a valve-regulated type battery." In this case, even if the battery is a valve-regulated type battery, the battery case and the lid can be welded together more appropriately.

[0011] The above-mentioned storage battery may also be [5] "a storage battery described in any of [1] to [4] above, which is a lead-acid battery." In this case, even if the storage battery is a lead-acid battery using lead, the battery case and the lid can be welded together more appropriately. [Effects of the Invention]

[0012] According to one aspect of this disclosure, the battery case and the lid can be welded together more effectively. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is an exploded perspective view showing an example of a battery according to this embodiment. [Figure 2] Figure 2 is an end view showing the welded portion between the battery case and the lid. [Figure 3] Figure 3(a) is an end view showing the melting of the welded portion of the battery case and the welded portion of the lid by a hot plate. Figure 3(b) is an end view showing the state after the welded portion of the battery case and the welded portion of the lid have been melted by the hot plate. [Figure 4] Figure 4 is a schematic diagram illustrating the method for measuring adhesive strength and fracture strain. [Modes for carrying out the invention]

[0014] The following describes exemplary embodiments with reference to the drawings. In each drawing, the same or equivalent elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0015] <Battery storage> The battery 1 shown in Figure 1 is a battery used, for example, in automobiles, electric vehicles, power supply devices, etc. Battery 1 may be, for example, an alkaline battery or a valve-regulated lead-acid battery. In the valve-regulated lead-acid battery, there is no free electrolyte flowing inside the battery. Therefore, it has the advantage that the electrolyte will not spill even if the battery is placed on its side. In addition, even if an electrolysis reaction of water occurs in a valve-regulated lead-acid battery during charging, the generation of hydrogen gas can be suppressed. This has the effect of reducing the oxygen gas generated by the chemical reaction on the surface of the negative electrode plate back into water and returning it to the electrolyte.

[0016] As shown in Figure 1, the battery 1 comprises a plurality of positive electrode plates 2 (energy storage members), a plurality of negative electrode plates 3 (energy storage members), a plurality of separators 4, a box-shaped battery case 5 having an upper opening 5a, and a lid 6 that closes the upper opening 5a of the battery case 5. The lid 6 is provided with a control valve 7 for discharging excess gas to the outside of the battery case 5, a positive electrode terminal 8 for connecting the positive electrode plates 2 to the outside, and a negative electrode terminal 9 for connecting the negative electrode plates 3 to the outside.

[0017] Within the battery case 5, positive electrode plates 2 and negative electrode plates 3 are arranged alternately. In addition, a separator 4 is placed between the positive electrode plates 2 and the negative electrode plates 3. This stacked array of electrode plates, consisting of positive electrode plates 2, negative electrode plates 3, and separator 4, is housed within the battery case 5.

[0018] Multiple positive electrode plates 2 are electrically connected to each other by connecting the lugs 2a on each positive electrode plate 2 via straps 2b. Similarly, multiple negative electrode plates 3 are electrically connected to each other by connecting the lugs 3a on each negative electrode plate 3 via straps 3b. The straps 2b of the positive electrode plates 2 are provided with positive electrode posts 2c for connecting the positive electrode plates 2 to the positive electrode terminals 8. Similarly, the straps 3b of the negative electrode plates 3 are provided with negative electrode posts 3c for connecting the negative electrode plates 3 to the negative electrode terminals 9.

[0019] The electrolytic cell 5 has a substantially rectangular parallelepiped shape with an upper opening 5a. The electrolytic cell 5 can accommodate a plate group composed of a positive electrode plate 2, a negative electrode plate 3, and a separator 4. Further, an electrolytic solution such as dilute sulfuric acid is accommodated in the electrolytic cell 5. The material of the electrolytic cell 5 is not particularly limited as long as it has resistance to electrolytic solutions such as dilute sulfuric acid. For example, the electrolytic cell 5 is formed of polyolefin such as PP (polypropylene) or PE (polyethylene). The height of the electrolytic cell 5 is 400 mm or more. However, the material of the electrolytic cell 5 and the height of the electrolytic cell 5 are not limited thereto.

[0020] The lid 6 seals the upper opening 5a of the electrolytic cell 5. The lid 6 is formed of, for example, the same material as the electrolytic cell 5. The lid 6 is heat-welded to the electrolytic cell 5 so as to seal the upper opening 5a of the electrolytic cell 5. In the following, when indicating up and down, the side where the lid 6 is disposed with respect to the electrolytic cell 5 is defined as "up", and the opposite side is defined as "down".

[0021] <Details of the welded portion> As shown in FIG. 2, an electrolytic cell welding portion 50, which is a portion welded to the lid 6, is provided in the upper portion of the electrolytic cell 5. The electrolytic cell welding portion 50 has a substantially square frame shape in the present embodiment. The electrolytic cell welding portion 50 forms the upper opening 5a of the electrolytic cell 5. On the lower surface side (the surface on the electrolytic cell 5 side) of the lid 6, a lid welding portion 60, which is a portion welded to the electrolytic cell 5, is provided. The lid welding portion 60 has a shape corresponding to the electrolytic cell welding portion 5 of the electrolytic cell 5.

[0022] An electrolytic cell melting portion 51 is formed at the upper end portion of the electrolytic cell welding portion 50 by melting the upper end portion of the electrolytic cell welding portion 50. A lid melting portion 61 is formed at the lower end portion of the lid welding portion 60 by melting the lower end portion of the lid welding portion 60. The lid 6 is attached to the electrolytic cell 5 by welding the electrolytic cell melting portion 51 of the electrolytic cell welding portion 50 and the lid melting portion 61 of the lid welding portion 60 to each other.

[0023] The battery case melting portion 51 has a shape that protrudes inward and outward from the upper end of the battery case welding portion 50. In other words, the width X1 (length in the inward and outward direction of the battery case 5) of the battery case melting portion 51 is greater than the width X (thickness) of the portion of the battery case welding portion 50 in which the battery case melting portion 51 is not formed. Similarly, the lid melting portion 61 has a shape that protrudes inward and outward from the lower end of the lid welding portion 60. In other words, the width Y1 (length in the inward and outward direction of the battery case 5) of the lid melting portion 61 is greater than the width Y (thickness) of the portion of the lid welding portion 60 in which the lid melting portion 61 is not formed.

[0024] In the storage battery 1, the welded portion 50 of the battery case 5 and the welded portion 60 of the lid 6 are welded to each other in such a way that the following conditions (1) and (2) are satisfied. Condition (1): The adhesive strength after welding between the welded portion 50 of the battery case 5 and the welded portion 60 of the lid 6 is 19 MPa or higher. Condition (2): The fracture strain at the welded portion between the welded portion 50 of the battery case 5 and the welded portion 60 of the lid 6 is 0.1 or greater.

[0025] <Welding method> An example of a welding method for the battery case 5 and the lid 6 will be described. As shown in Figure 3(a), a heating plate 10 is placed between the battery case welding portion 50 of the battery case 5 and the lid welding portion 60 of the lid 6. As shown in Figure 3(b), the heating plate 10 is sandwiched between the battery case welding portion 50 and the lid welding portion 60, and the heat from the heating plate 10 melts the upper end of the battery case welding portion 50 and the lower end of the lid welding portion 60, respectively. For example, the upper end of the battery case welding portion 50 and the lower end of the lid welding portion 60 are melted by about 1 mm to 2 mm in the vertical direction (sandwiching direction). The melting rate when melting the upper end of the battery case welding portion 50 and the lower end of the lid welding portion 60 can be, for example, about 1 mm / s to 3 mm / s. The heat (temperature) of the heating plate 10 can be set in the range of 1.1 to 2 times the melting point (Tm) of the materials of the battery case 5 and the lid 6.

[0026] As the upper end of the battery case welding portion 50 is melted by approximately 1 mm to 2 mm in the vertical direction, the molten portion flows out (protrudes) toward the inside and outside of the battery case 5, forming a battery case melted portion 51 at the upper end of the battery case welding portion 50. Similarly, as the lower end of the lid welding portion 60 is melted by approximately 1 mm to 2 mm in the vertical direction, the molten portion flows out (protrudes) toward the inside and outside of the battery case 5, forming a lid melted portion 61 at the lower end of the lid welding portion 60.

[0027] Then, in order to sufficiently melt the cell melting portion 51 of the cell welding portion 50 and the lid melting portion 61 of the lid welding portion 60, the state in which the hot plate 10 is sandwiched between the cell welding portion 50 and the lid welding portion 60 (the state shown in Figure 3(b)) is maintained for a predetermined time. In other words, the state in which the cell melting portion 51 and the lid melting portion 61 are melted by the hot plate 10 is maintained for a predetermined time. For example, a fluororesin layer may be formed on the surface of the hot plate 10 to prevent the materials of the cell 5 and lid 6 from adhering to the hot plate 10. In such cases, where a fluororesin layer is formed on the surface of the hot plate 10, it is preferable to maintain the state in which the hot plate 10 is sandwiched between the cell welding portion 50 and the lid welding portion 60 for, for example, 10 to 30 seconds. Examples of the fluororesin include Teflon.

[0028] After the molten cell portion 51 of the battery case welding portion 50 and the molten lid portion 61 of the lid welding portion 60 have sufficiently melted, the hot plate 10 is removed. Then, as shown in Figure 2, the molten battery case portion 51 and the molten lid portion 61 are brought into close contact with each other. As a result, the battery case welding surface 51a facing the lid welding portion 61 in the battery case welding portion 51 and the lid welding surface 61a facing the battery case welding portion 51 in the lid welding portion 61 are welded to each other.

[0029] Furthermore, if the pressure is high when the molten battery case melting section 51 and the molten lid melting section 61 are brought into close contact with each other, for example, the amount of molten battery case melting section 51 and lid melting section 61 flowing out toward the inside and outside of the battery case 5 may increase. For this reason, the pressure when the molten battery case melting section 51 and the molten lid melting section 61 are brought into close contact with each other should be, for example, 0.3 MPa or less.

[0030] As described above, the battery case welding portion 50 of the battery case 5 and the lid welding portion 60 of the lid 6 are welded to each other in such a way that conditions (1) and (2) are met. To satisfy conditions (1) and (2), for example, the melting rate when melting the battery case welding portion 50 and the lid welding portion 60 is adjusted. To satisfy conditions (1) and (2), for example, the length of time that the battery case melting portion 51 and the lid melting portion 61 are kept in a molten state is adjusted by the hot plate 10. To satisfy conditions (1) and (2), for example, the pressure when bringing the molten battery case melting portion 51 and the molten lid melting portion 61 into close contact with each other is adjusted. In addition to these, each part of the welding method is adjusted to satisfy conditions (1) and (2) so that the battery case welding portion 50 of the battery case 5 and the lid welding portion 60 of the lid 6 are welded to each other.

[0031] <Examples 1-4> An example of a valve-regulated lead-acid battery manufactured to satisfy the above-described conditions (1) and (2) will now be described. The adhesive strength after bonding the battery case and the lid according to condition (1), and the fracture strain of the welded portion between the battery case and the lid according to condition (2), were measured using the battery case test piece 5A and the lid test piece 6A shown in Figure 4. In the battery case welded portion 50A of the battery case test piece 5A, the width X of the portion where the molten battery case portion 51A was not formed was set to 3 mm. The depth (length) of the battery case welded portion 50A was set to 10 mm. Similarly, in the lid welded portion 60A of the lid test piece 6A, the width Y of the portion where the molten lid portion 61A was not formed was set to 3 mm. The depth (length) of the lid welded portion 60A was set to 10 mm. The molten battery case portion 51A formed at the upper end of the battery case welded portion 50A and the molten lid portion 61A formed at the lower end of the lid welded portion 60A were welded to each other.

[0032] The battery case test piece 5A was held with gripper G1, and the lid test piece 6A was held with gripper G2. The initial distance L0 between gripper G1 and gripper G2 was set to 25 mm. With the battery case test piece 5A held by gripper G1 and the lid test piece 6A held by gripper G2, the distance between gripper G1 and gripper G2 was widened, and the adhesive strength under condition (1) and the fracture strain under condition (2) were measured.

[0033] The adhesive strength between the battery case and the lid after bonding under condition (1) was measured using a Shimadzu Autograph AGS-X measuring device. The measurement conditions were a tensile speed of 50 mm / min. The fracture strain between the battery case and the lid under condition (2) was calculated using the following formula (A). Calculation formula: ε=ΔL / L0…(A) ε: Fracture strain ΔL: Elongation at break = (distance between gripper G1 and gripper G2 just before break) - (initial distance L0 between gripper G1 and gripper G2) L0: Initial distance L0 between gripper G1 and gripper G2

[0034] Furthermore, before performing measurements related to conditions (1) and (2), the welding rate between the battery case test piece 5A and the lid test piece 6A was measured. The welding rate was calculated using the following formula (B). Formula: Welding rate (%) = Welding width W / Cell width X …(B) The welding width W is the length over which the welding surface 51aA of the molten cell portion 51A and the welding surface 61aA of the molten lid portion 61A are welded together in the width X direction (thickness direction) of the welded cell portion 50A. The welding width W is the bonding length when the cross-section of the welded portion between the cell test piece 5A and the lid test piece 6A is observed using X-ray CT (X-ray Computed Tomography), and portions where unbonded areas (gaps) exist are considered not to be bonded. The battery case width X is the width X (3 mm) of the portion of the battery case welded portion 50A where the battery case molten portion 51A is not formed.

[0035] A welding rate exceeding 100% occurs when the welding width W becomes larger than the battery case width X due to the flow of the melting parts 51A and 61A of the battery case. A welding rate less than 100% occurs when the welding width W is smaller than the battery case width X.

[0036] Table 1 shows the adhesive strength, fracture strain, and welding rate of Examples 1 to 4, which were manufactured to satisfy the above conditions (1) and (2). Table 2 shows the adhesive strength, fracture strain, and welding rate of Comparative Examples 1 to 4, which did not satisfy the above conditions (1) and (2). [Table 1] [Table 2]

[0037] As can be seen from Tables 1 and 2, there is a tendency for adhesive strength to increase as the welding rate increases. When the welding rate is less than 100%, the welding width W is less than the battery case width X, indicating that the battery case and lid are not sufficiently welded together. Here, as shown in Table 3, the adhesive strength values ​​for Examples 1-4 and Comparative Examples 1-4 were plotted on a graph with welding rate on the horizontal axis and adhesive strength on the vertical axis. An approximate straight line K was created for the adhesive strength values ​​plotted on the graph. From the approximate straight line K, it was found that the adhesive strength at which the welding rate reaches 100% is approximately 19 MPa. In the graph in Table 3, circles represent the adhesive strengths of Examples 1-4, and triangles represent the adhesive strengths of Comparative Examples 1-4. [Table 3]

[0038] Furthermore, as can be seen from Tables 1 and 2, the higher the welding rate, the greater the fracture strain tends to be. Also, when the fracture strain is 0.1 or higher, the welding rate is 100% or higher. In other words, when the above-mentioned conditions (1) "adhesive strength: 19 MPa or higher" and (2) "fracture strain: 0.1 or higher" are met, the welding rate will be 100% or higher, and it can be said that the battery case and the lid are properly welded together.

[0039] Thus, in the battery 1, the adhesive strength between the battery case 5 and the lid 6 is 19 MPa or higher (condition (1)), and the fracture strain of the welded portion is 0.1 or higher (condition (2)). In this state, the welding rate of the welded portion between the battery case 5 and the lid 6 is 100% or higher, and the occurrence of unbonded portions in the welded portion between the battery case 5 and the lid 6 is suppressed, resulting in a sufficiently welded state. As a result, the occurrence of cracks in the welded portion is suppressed in this battery 1. In this way, the battery 1 can be welded more appropriately between the battery case 5 and the lid 6.

[0040] In one embodiment, the battery case 5 and lid 6 may be made of polyolefin. In this case, the battery 1 can easily weld the battery case 5 and lid 6, which are made of polyolefin, together by melting them.

[0041] In one embodiment, the height of the battery case 5 may be 400 mm or more. In this case, even if the battery case 5 is large and has a height of 400 mm or more, the battery case 5 and the lid 6 can be welded together more appropriately.

[0042] In one embodiment, the storage battery 1 may be a valve-regulated lead-acid battery. In this case, even if the storage battery 1 is a valve-regulated battery, the battery case 5 and the lid 6 can be welded together more appropriately. Also in this case, even if the storage battery 1 is a lead-acid battery using lead, the battery case 5 and the lid 6 can be welded together more appropriately.

[0043] Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above. For example, Examples 1 to 4 described above are just examples, and the present disclosure is not limited to these embodiments. Furthermore, the storage battery 1 may be a valve-regulated type storage battery using electrodes other than lead, or it may be a storage battery other than a valve-regulated type (for example, a lead-acid battery). [Explanation of symbols]

[0044] 1...Battery (valve-regulated lead-acid battery), 2...Positive electrode plate (energy storage component), 3...Negative electrode plate (energy storage component), 5...Battery case, 6...Lid.

Claims

1. A storage battery comprising a battery case for housing an energy storage member, and a lid welded to the battery case so as to seal the upper opening of the battery case, The adhesive strength between the battery case and the lid after welding is 19 MPa or more. A storage battery in which the fracture strain of the welded portion between the battery case and the lid is 0.1 or greater.

2. The battery according to claim 1, wherein the battery case and the lid are made of polyolefin.

3. The storage battery according to claim 1 or 2, wherein the height of the battery case is 400 mm or more.

4. The battery according to claim 1, which is a valve-regulated battery.

5. The battery according to claim 1, which is a lead-acid battery.

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