Battery

Abstract

To provide a battery having excellent durability against a cooling cycle.SOLUTION: A battery according to an embodiment of the present disclosure includes: a case member (4 and 5); a terminal member 9 connected to a power generation element; and a resin member 11 that insulates and seals between the case member 5 and the terminal member 9, and a through hole 14 through which the terminal member 9 passes is formed in the case member 5. The resin member 11 includes: an inner part that contacts an inner surface of the case member 5; a hole inner part that fills a space between a wall surface of the through hole 14 and the terminal member 9; and an outer part that contacts an outer surface of the case member 5 and has a smaller volume than the inner part. The battery satisfies one of the following conditions of a first condition in which a thermal expansion coefficient of the case member 5 is larger than the thermal expansion coefficient of the inner part and a tensile strength of the inner part is lower than the tensile strength of the outer part and a second condition in which the thermal expansion coefficient of the case member 5 is smaller than the thermal expansion coefficient of the inner part and the tensile strength of the outer portion is lower than the tensile strength of the inner part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The disclosed technology relates to batteries. [Background technology]

[0002] In the battery described in Patent Document 1, a current collecting terminal is disposed so as to penetrate a case member. The current collecting terminal is connected to an electrode body. A terminal mounting hole through which the current collecting terminal passes is formed in the case member. An insulating material is embedded between the terminal mounting hole and the current collecting terminal. The insulating material is molded integrally with the case member and the current collecting terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-86813 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned conventional technology has the problem of poor durability against thermal cycles, because materials with different thermal expansion coefficients, such as metal (case members and current collector terminals) and resin (insulating material), are in close contact with each other.

[0005] An object of the present disclosure is to provide a battery that has excellent durability against thermal cycles. [Means for solving the problem]

[0006] A battery in one embodiment of the disclosed technology has a case member incorporating a power generating element, terminal members connected to the power generating element and penetrating the case member, and a resin member that insulates and seals between the case member and the terminal member, wherein the case member has a through hole formed therein for passing the terminal member, and the resin member includes an inner portion that contacts the inner surface of the case member, a hole interior that fills the space between the wall surface of the through hole and the terminal member, and an outer portion that contacts the outer surface of the case member and has a smaller volume than the inner portion, and satisfies either a first condition that the thermal expansion coefficient of the case member is greater than that of the inner portion and the tensile strength of the inner portion is lower than that of the outer portion, or a second condition that the thermal expansion coefficient of the case member is smaller than that of the inner portion and the tensile strength of the outer portion is lower than that of the inner portion.

[0007] In the battery of the above embodiment, the portions of the case member where the terminal member and resin member are provided tend to bend due to temperature. Under the first condition, they tend to bend inwardly convexly in cold weather and outwardly convexly when the temperature rises. Under the second condition, they tend to bend outwardly convexly in cold weather and inwardly convexly when the temperature rises. However, the portions of the resin member that stretch in cold weather (the inner portion under the first condition and the outer portion under the second condition) have low tensile strength, so they are less likely to crack even in cold weather.

[0008] In the battery of the above embodiment, it is desirable that the resin member contains a filler, and that if the first condition is met, the filler content of the inner portion is lower than that of the outer portion, and if the second condition is met, the filler content of the inner portion is higher than that of the outer portion. Alternatively, it is desirable that the resin member contains an elastomer, and if the first condition is met, the elastomer content of the inner portion is higher than that of the outer portion, and if the second condition is met, the elastomer content of the inner portion is lower than that of the outer portion. By doing so, the tensile strength relationship between the inner portion and the outer portion can be satisfied. It is also desirable that the base resin of the inner portion and the base resin of the outer portion are the same type.

[0009] In the battery of any of the above embodiments, it is desirable that a roughened surface region, in which metal and resin interpenetrate, be provided on at least a portion of the surface of the case member covered with the resin member and at least a portion of the surface of the terminal member covered with the resin member. The anchor structure provided by the roughened surface region contributes to improving adhesion between the case member and the resin member and between the terminal member and the resin member. Furthermore, since this embodiment satisfies the first or second condition, cracks are less likely to occur. [Effects of the Invention]

[0010] According to the disclosed technique, a battery having excellent durability against thermal cycles is provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a battery according to an embodiment. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 6 is a cross-sectional view showing only the resin member in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 shows a battery 1 according to an embodiment of the disclosed technology. The battery 1 has a power generating element 3 built into a case member 2. The case member 2 is composed of a box body 4 and a lid body 5. The box body 4 is a box-shaped member that houses the power generating element 3 and is open at the top. The lid body 5 is a plate-shaped member that closes the opening of the box body 4. Both the box body 4 and the lid body 5 are part of the case member 2. The power generating element 3 is an electrode assembly in which positive and negative electrode plates are integrated together with an electrolyte.

[0013] Positive and negative terminal portions 6, 7 are provided near both ends of the lid body 5 in the longitudinal direction. Terminal surfaces 8 are exposed at both terminal portions 6, 7. The terminal surfaces 8 are part of the surfaces of terminal members 9, 10, which will be described later. The terminal members 9, 10 are insulated from the lid body 5 by a resin member 11. The resin member 11 also serves to seal the gap between the terminal member 9 and the lid body 5 and the gap between the terminal member 10 and the lid body 5.

[0014] The terminal member 9 will now be described. The terminal member 9 in a standalone state is shown in Figs. 2 to 4. Fig. 2 is a front view of the terminal member 9 as seen from the line of sight of arrow A in Fig. 3. Fig. 3 is a side view of the terminal member 9 as seen from the line of sight of arrow B in Fig. 2. In Fig. 3, in addition to the terminal member 9, a part of the power-generating element 3 is shown by a dashed line. Fig. 4 is a perspective view of the terminal member 9 as seen from the direction of arrow C in Figs. 2 and 3. The terminal member 9 is a conductive member that is connected to the power-generating element 3 inside the case member 2. The terminal member 9 is a member that is provided to penetrate the lid 5.

[0015] The terminal member 9 has an outer surface 24, a connecting portion 12, and an intermediate portion 13. The outer surface 24 is a portion for connection to an external conductor. The terminal surface 8 shown in FIG. 1 is the outward surface of the outer surface 24. The connecting portion 12 is a portion for connection to one of the electrode plates of the power generating element 3. The intermediate portion 13 is a portion that connects the outer surface 24 and the connecting portion 12.

[0016] The terminal member 10 is a conductive member having a shape obtained by flipping the terminal member 9 from side to side. The terminal member 9 and the terminal member 10 are generally made of different metals. For example, of the terminal members 9 and 10, aluminum is used for the positive electrode, and copper is used for the negative electrode.

[0017] The terminal portion 6 will now be described. FIG. 5 is a cross-sectional view of the terminal portion 6 in the lid body 5. FIG. 5 shows a vertical cross section parallel to the longitudinal direction of the lid body 5 indicated by arrows D and D in FIG. 1. The vertical cross section in FIG. 5 is taken at a position near the center of the lid body 5 in the width direction. As shown in FIG. 5, a through hole 14 is formed in the lid body 5. The through hole 14 is shaped to allow the terminal member 9 to pass through.

[0018] The lid body 5 and the terminal members 9 are not in contact with each other. The aforementioned resin member 11 is provided between the lid body 5 and the terminal members 9. The presence of the resin member 11 prevents contact between the lid body 5 and the terminal members 9. The resin member 11 also fills the through holes 14. The resin member 11 separates the internal space of the case member 2 from the external space. The resin member 11 is molded with the terminal members 9 positioned relative to the lid body 5. The resin member 11 integrates the lid body 5 and the terminal members 9. In this embodiment, the terminal surface 8 and the outer surface 15 of the resin member 11 are substantially flush with each other.

[0019] As shown in FIG. 6, the resin member 11 includes an inner portion 16, an inner hole portion 17, and an outer portion 18. The inner portion 16 is the portion of the resin member 11 that is located below the lid body 5 in FIG. 5. The inner hole portion 17 is similarly the portion within the thickness range of the lid body 5 in FIG. 5. The outer portion 18 is similarly the portion that is located above the lid body 5. In other words, the inner portion 16 is a portion that contacts the inner surface 19 of the lid body 5. The inner hole portion 17 is a portion that fills the space between the wall surface of the through hole 14 and the terminal member 9. The outer portion 18 is a portion that contacts the outer surface 20 of the lid body 5. For ease of explanation, FIG. 6 shows only the resin member 11. In reality, the resin member 11 having the shape shown in FIG. 6 does not exist as a separate component.

[0020] Comparing the volumes of the inner portion 16 and the outer portion 18, the volume of the outer portion 18 is smaller. This is because the height of the outer portion 18 and the terminal surface 8 protruding from the outer surface 20 cannot be made too large due to the need to connect the battery 1 to an external circuit. This means that the inner portion 16, which has a larger volume, becomes a more dominant factor than the outer portion 18 in determining the expansion and contraction of the resin member 11 relative to the lid 5 when there is a temperature change.

[0021] In the battery 1, special relationships are satisfied with respect to the magnitude relationship of the thermal expansion coefficients between the lid body 5 and the inner portion 16, and the magnitude relationship of the tensile strength between the inner portion 16 and the outer portion 18. There are two types of special relationships, a first condition and a second condition, and either one of the conditions must be satisfied.

[0022] The first and second conditions are as follows: First condition: The thermal expansion coefficient of the lid body 5 is greater than the thermal expansion coefficient of the inner portion 16, and the tensile strength of the inner portion 16 is lower than the tensile strength of the outer portion . Second condition: the thermal expansion coefficient of the lid body 5 is smaller than that of the inner portion 16 , and the tensile strength of the outer portion 18 is lower than that of the inner portion 16 .

[0023] The first condition will be explained. Under the first condition, based on the magnitude relationship of the thermal expansion coefficients described above, the expansion and contraction of the lid body 5 is more significant than the expansion and contraction of the inner portion 16 in response to temperature changes. For this reason, the lid body 5 shown in FIG. 5 tends to curve downward convexly in cold weather and upward convexly when the temperature rises.

[0024] Focusing on cold weather, the inner portion 16 is also curved downward convexly. This is because the upper surface of the inner portion 16 is dragged by the contraction of the lid body 5 and contracts more strongly than normal. Meanwhile, tensile stress is applied to the lower surface of the inner portion 16, which is the stretching side. This tensile stress is a factor that causes the inner portion 16 to crack and peel from the terminal member 9 and the lid body 5. However, under the first condition, the inner portion 16 is highly flexible, so cracking and peeling do not actually occur even in cold weather.

[0025] Conversely, when the temperature rises, the outer portion 18 becomes elongated and tensile stress is applied to its upper surface. However, when the temperature rises, the resin softens to a certain extent due to the high temperature. Therefore, the outer portion 18 also has a certain degree of flexibility, so cracks and the like do not occur in the outer portion 18 when the temperature rises.

[0026] The second condition will now be described. Under the second condition, based on the magnitude relationship between the thermal expansion coefficients, the expansion and contraction of the inner portion 16 in response to temperature changes is more pronounced than that of the lid body 5. Therefore, contrary to the first condition, the lid body 5 tends to curve upward convexly in cold weather and downward convexly when the temperature rises.

[0027] Focusing on cold weather, the outer portion 18 also curves upward convexly. This is because the lower surface of the outer portion 18 is dragged by the contraction of the lid body 5 and contracts more strongly than normal. Meanwhile, tensile stress is applied to the upper surface of the outer portion 18. This tensile stress is a factor that causes cracking and peeling of the outer portion 18. However, under the second condition, the outer portion 18 is highly flexible, so cracking and peeling do not actually occur even in cold weather.

[0028] Conversely, when the temperature rises, tensile stress is applied to the lower surface of the inner portion 16. However, when the temperature rises, the resin of the inner portion 16 also softens to some extent due to the high temperature, so cracks and the like do not occur in the inner portion 16 when the temperature rises.

[0029] As described above, the battery 1 of this embodiment satisfies either the first or second condition, thereby suppressing cracking and peeling in the resin member 11 both in cold weather and at elevated temperatures, and therefore the battery 1 has excellent durability against thermal cycles.

[0030] As described above, in the resin member 11 of this embodiment, the inner portion 16 and the outer portion 18 have different properties. The inner portion 16 and the outer portion 18 have different tensile strengths at least. The inner portion 16 and the outer portion 18 may also have different thermal expansion coefficients. There are three methods for imparting such different properties to the inner portion 16 and the outer portion 18: A method of using a composite resin containing filler as the resin member 11 and varying the filler blending ratio. A method of using a composite resin containing elastomer as the resin member 11 and varying the blending ratio of the elastomer. -Method of using different types of base resin

[0031] The method using a filler will be described. A filler is a minute solid. For example, glass fiber, glass powder, etc. can be used as a filler. Assuming that the base resin is the same, the higher the filler content, the higher the tensile strength of the composite resin. Therefore, under the first condition, the outer portion 18 has a higher filler content than the inner portion 16, and under the second condition, the inner portion 16 has a higher filler content than the outer portion 18.

[0032] If the base resin is the same, and the higher the filler content, the smaller the thermal expansion coefficient of the composite resin. If the base resin of resin member 11 is, for example, PPS resin, and lid 5 is made of, for example, aluminum, the thermal expansion coefficient of the base resin is nearly twice that of lid 5.

[0033] Under the first condition, the filler content of the inner portion 16 is increased to such an extent that the thermal expansion coefficient of the composite resin of the inner portion 16 is lower than that of aluminum. Under the first condition, the filler content of the outer portion 18 is even higher. Under the second condition, the filler content of the inner portion 16 is reduced to such an extent that the thermal expansion coefficient of the composite resin of the inner portion 16 is not lower than that of aluminum. Under the second condition, the filler content of the outer portion 18 is even lower. In the case of a method using a filler, the first or second condition is satisfied by adjusting the filler content as described above.

[0034] We will now explain the method using elastomers. Elastomers are polymeric materials with a low modulus of elasticity and viscoelasticity. Assuming the base resin is the same, the lower the elastomer content, the higher the tensile strength of the composite resin. Therefore, under the first condition, the elastomer content of the inner portion 16 is higher than that of the outer portion 18, and under the second condition, the elastomer content of the outer portion 18 is higher than that of the inner portion 16.

[0035] Assuming the base resin is the same, the lower the elastomer content, the smaller the thermal expansion coefficient of the composite resin. Under the first condition, the elastomer content of the inner portion 16 is reduced to a level where the thermal expansion coefficient of the composite resin of the inner portion 16 is lower than that of aluminum. Under the first condition, the elastomer content of the outer portion 18 is even lower. Under the second condition, the elastomer content of the inner portion 16 is increased to a level where the thermal expansion coefficient of the composite resin of the inner portion 16 is not lower than that of aluminum. Under the second condition, the elastomer content of the outer portion 18 is even higher. When using an elastomer, adjusting the elastomer content as described above satisfies the first or second condition.

[0036] The following describes a method using different types of base resins. For example, even PPS resins come in a variety of types depending on factors such as molecular weight and the degree of crosslinking. The resin type for the inner portion 16 and the resin type for the outer portion 18 can be selected so that the first or second condition is satisfied.

[0037] Although the above description of the resin member 11 did not refer to the hole interior 17, the properties of the hole interior 17 may be the same as either the inner portion 16 or the outer portion 18. Alternatively, the boundary between the portion with the same properties as the inner portion 16 and the portion with the same properties as the outer portion 18 may be located in the middle of the hole interior 17.

[0038] Resin member 11, which has portions of two resin types with different properties, is molded using two types of raw resin. With terminal member 9 positioned and held relative to through-hole 14 in lid 5, raw resin for inner portion 16 is supplied from below to form inner portion 16. Alternatively, inner portion 16 and hole interior 17 are formed. Then, raw resin for outer portion 18 is supplied from above to form outer portion 18. Alternatively, outer portion 18 and hole interior 17 are formed. When a composite resin is used, the filler or elastomer is blended into the base resin first.

[0039] If the base resins of the inner portion 16 and the outer portion 18 are the same or have a high affinity, a mixed layer may form at the contact point between the two resin types depending on the molding conditions. In this case, there is an advantage that peeling between the two resin types is unlikely to occur during subsequent thermal cycling.

[0040] Next, the anchor structure of the terminal portion 6 will be described. In the terminal portion 6 of the battery 1 of this embodiment, an anchor structure is provided on the joint surface between the metal part (the cover body 5 and the terminal member 9) and the resin member 11. The anchor structure is provided within the area of the surface of the metal part that is covered by the resin member 11. The anchor structure is a roughened surface area where the metal and the resin interpenetrate. In Figure 5, the portion of the anchor structure that appears in the cross-sectional view is indicated by a thick line 21.

[0041] In the anchor structure, the metal part and the resin part 11 are interlocked. This provides good adhesion between the metal part and the resin part 11, making them less likely to separate. However, this also makes the resin part 11 more likely to crack when the lid 5 bends, such as during cold weather or warm weather. Cracks are more likely to occur on the side of the inner part 16 or outer part 18 of the resin part 11 that is subjected to tensile stress. When the anchor structure is provided, the tensile stress is not alleviated by separation between the metal part and the resin part 11, making cracks more likely to occur. However, in the resin part 11 of this embodiment, the properties of the inner part 16 and outer part 18 are appropriately set, as in the first or second condition described above. Therefore, cracks are less likely to occur even when the anchor structure is provided.

[0042] The portions of the cover 5 and the terminal member 9 that will become the anchor structures are subjected to a surface roughening treatment in advance. The roughened areas have fine irregularities of about several tens to several hundreds of nanometers in size. When the resin member 11 is molded, the raw resin flows into the recesses of the irregularities to form the anchor structures.

[0043] 2 and 3 show a roughened area 22, which is the area of the terminal member 9 where the roughening treatment is performed. The roughened area 22 of the terminal member 9 extends from the level of the lower surface 23 of the outer-facing portion 24 to approximately the middle of the connection portion 12. The lower surface 23 is also roughened. The terminal surface 8 is not roughened. The lower limit of the roughened area 22 does not need to be set too strictly. There is no particular problem if the roughened area 22 extends below the area that will come into contact with the resin member 11.

[0044] The above has been described regarding the resin member 11 of the terminal portion 6, but the same applies to the resin member 11 of the terminal portion 7. An anchor structure can also be provided in the terminal portion 7. The roughened surface range of the terminal member 10 for this purpose is not particularly different from that shown in FIGS.

[0045] As described above in detail, according to this embodiment, the resin member 11 between the lid 5 and the terminal members 9 and 10 that penetrate it satisfies the first or second condition described above. This prevents cracking of the resin member 11. In particular, cracking is less likely to occur in areas that tend to expand in cold weather, which is where cracking is likely to occur. This results in a battery 1 that has excellent durability against cold-heat cycles.

[0046] The present embodiment and examples are merely illustrative and do not limit the presently disclosed technology in any way. Therefore, the presently disclosed technology can naturally be improved and modified in various ways without departing from the spirit and scope of the present disclosure. For example, the type of battery 1 is not important. It can be a lithium-ion battery, a nickel-metal hydride battery, an all-solid-state battery, or any other type. The presently disclosed technology can be applied to both the positive and negative terminals 6 and 7 of the battery 1, or to only one of them.

[0047] The raw resin constituting the resin member 11 may be a composite resin in which both a filler and an elastomer are blended into a base resin. The type of resin used for the base resin of the resin member 11 may be a resin other than PPS resin. The material of the lid body 5 may be a metal other than aluminum. The range of the anchor structure portions of the terminal members 9, 10 and the lid body 5 may be only a portion of the range that comes into contact with the resin of the resin member 11, rather than the entire range. [Explanation of symbols]

[0048] 1 battery 2 Case parts 3 Power generation elements 4 box body 5 Lid 8 Terminal surface 9 Terminal material 10 Terminal member 11 Resin parts 12 Connection 13 Middle section 14 Through holes 16 Inner part 17 Inside the hole 18 Outer part 21 Thick line 22 Roughening range 24 External Relations

Claims

1. a case member incorporating a power generating element; a terminal member connected to the power generating element and provided to penetrate the case member; and a resin member that insulates and seals the case member and the terminal member, The case member has a through hole formed therein through which the terminal member passes, The resin member includes: an inner portion in contact with the inner surface of the case member; an interior of the through hole that fills a gap between a wall surface of the through hole and the terminal member; an outer portion in contact with an outer surface of the case member and having a smaller volume than the inner portion; A battery that satisfies either a first condition that the thermal expansion coefficient of the case member is greater than the thermal expansion coefficient of the inner portion and the tensile strength of the inner portion is lower than the tensile strength of the outer portion, or a second condition that the thermal expansion coefficient of the case member is smaller than the thermal expansion coefficient of the inner portion and the tensile strength of the outer portion is lower than the tensile strength of the inner portion.

2. 2. The battery according to claim 1, wherein the resin member contains a filler, When the first condition is satisfied, the filler content of the inner portion is lower than the filler content of the outer portion, When the second condition is satisfied, the filler content of the inner portion is higher than the filler content of the outer portion.

3. 2. The battery according to claim 1, wherein the resin member contains an elastomer, When the first condition is satisfied, the elastomer content of the inner portion is higher than the elastomer content of the outer portion, When the second condition is satisfied, the elastomer content of the inner portion is lower than the elastomer content of the outer portion.

4. The battery according to claim 2 or claim 3, A battery in which the base resin of the inner portion and the base resin of the outer portion are of the same type.

5. 4. The battery according to claim 1, wherein: A battery in which a roughened surface area in which metal and resin interpenetrate is provided on at least a portion of the surface of the case member that is covered with the resin member and at least a portion of the surface of the terminal member that is covered with the resin member.

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