Secondary battery

Abstract

A secondary battery according to the present invention comprises: a battery element that has a positive electrode layer, a negative electrode layer, and an electrolyte layer which includes a solid electrolyte; and an exterior body that houses the battery element. The exterior body has a sealing part that is sealed so that a space in which the battery element is housed is sealed. The sealing part includes: a first sealing layer that is formed of a first sealing resin; a second sealing layer that is formed of a second sealing resin and that is disposed on the outer side relative to the first sealing layer; and a first trap layer that is provided between the first sealing layer and the second sealing layer and that is configured to trap moisture. The first sealing layer is configured to have a smaller moisture permeation amount than the second sealing layer.

Description

secondary battery

[0001] The present invention relates to a secondary battery.

[0002] A known secondary battery has a structure in which a negative electrode current collector foil, a negative electrode layer, an electrolyte layer, a positive electrode layer, and a positive electrode current collector foil are stacked in this order, and the stack is housed in a film-like exterior body. In this specification, the stack including the negative electrode layer, the electrolyte layer, and the positive electrode layer is referred to as a battery element. One of the functions required of the exterior body is to prevent moisture from penetrating.

[0003] Japanese Patent Laid-Open Publication No. 2003-187762 discloses a nonaqueous electrolyte battery in which a battery element including a positive electrode, a negative electrode, and an electrolyte is housed in a laminated outer casing, the laminated outer casing having a sealing portion and a water-absorbing member sealed by the sealing portion. In the examples of Patent Literature 1, an electrolytic solution is used as the electrolyte. In this nonaqueous electrolyte battery, the water-absorbing member provided in the laminated outer casing can capture moisture that penetrates into the battery.

[0004] However, batteries using solid electrolytes (e.g., all-solid-state batteries) are known as secondary batteries. Secondary batteries containing solid electrolytes react very sensitively to moisture. Therefore, it is necessary to more reliably prevent moisture from entering.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a secondary battery using a solid electrolyte that can more reliably prevent moisture from entering.

[0006] According to one aspect of the present invention, there is provided a secondary battery including a battery element having an electrolyte layer containing a solid electrolyte, a positive electrode layer, and a negative electrode layer, and an exterior housing that houses the battery element. The exterior housing has a seal portion that is a sealed portion that hermetically seals the space that houses the battery element. The seal portion includes a first seal layer formed from a first seal resin, a second seal layer formed from a second seal resin and positioned outside the first seal layer, and a first trap layer disposed between the first seal layer and the second seal layer and configured to trap moisture. The first seal layer is configured to have a lower moisture permeation rate than the second seal layer.

[0007] FIG. 1 is a bird's-eye view of the secondary battery according to this embodiment, as seen from above. FIG. 2 is a cross-sectional view showing a sealing portion of the secondary battery 1 according to the first embodiment. FIG. 3 is a schematic cross-sectional view for explaining the secondary battery 1 according to Configuration Example 5. FIG. 4 is a schematic cross-sectional view for explaining the secondary battery 1 according to Configuration Example 7. FIG. 5 is a schematic cross-sectional view for explaining the secondary battery 1 according to Configuration Example 8. FIG. 6 is a schematic cross-sectional view for explaining the secondary battery 1 according to Configuration Example 9. FIG. 7 is a schematic cross-sectional view for explaining the secondary battery 1 according to the second embodiment. FIG. 8 is a schematic cross-sectional view for explaining the secondary battery 1 according to the third embodiment.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] First Embodiment Fig. 1 is a top view of a secondary battery 1 according to a first embodiment. As shown in Fig. 1, the secondary battery 1 has a battery element 2 and an exterior body 3. The battery element 2 is housed inside the exterior body 3. The secondary battery 1 according to this embodiment is provided as a so-called cell.

[0010] The battery element 2 has a structure in which a negative electrode layer, an electrolyte layer, and a positive electrode layer (not shown) are stacked. The electrolyte layer contains a solid electrolyte. The secondary battery according to this embodiment includes so-called all-solid-state batteries.

[0011] The exterior body 3 is in the form of a film. That is, the exterior body 3 includes a film 4. The film 4 is, for example, a metal laminate film (a laminate of a metal foil such as aluminum foil and a resin layer). The exterior body 3 also includes a seal portion 5. The seal portion 5 is a portion where the film 4 is sealed so that the space that houses the battery element 2 is hermetically sealed.

[0012] In this embodiment, as an example, a case will be described in which the film 4 is formed from a single sheet. This sheet is folded back to sandwich the battery element 2 in the stacking direction, and the edges are sealed so that the internal space is an airtight space. That is, the seal portion 5 is provided along the outer periphery of the battery element 2, excluding the portion where the exterior body 3 is folded back. A tab 9 is connected to the battery element 2. The tab 9 extends from the connection portion with the battery element 2 to the outside of the exterior body 3. The exterior body 3 is sealed with the tab 9 sandwiched between them. That is, in the portion of the seal portion 5 that overlaps with the tab 9, the film 4 is adhered to the tab 9. In other portions of the seal portion 5, the films 4 are adhered to each other.

[0013] In this embodiment, the configuration of the sealing portion 5 is improved. Fig. 2 is a schematic cross-sectional view of the secondary battery 1 cut along the dashed line X in Fig. 1, showing the configuration of the sealing portion 5. Fig. 2 shows the configuration of the portion where the films 4 are bonded together. The detailed configuration of the sealing portion 5 will be further described with reference to Fig. 2.

[0014] 2 , the seal portion 5 includes a first seal layer 6, a first trap layer 7, and a second seal layer 8. These are arranged in this order along the inward-outward direction A. That is, the first seal layer 6 and the second seal layer 8 are separated by the first trap layer 7. The inward-outward direction A is a direction parallel to the film 4, and refers to a direction connecting the outer end (the end exposed to the outside) and the inner end (the end on the side of the space accommodating the battery element 2) of the seal portion 5.

[0015] The first trapping layer 7 is configured to trap moisture. A specific configuration example of the first trapping layer 7 will be described later.

[0016] The first sealing layer 6 and the second sealing layer 8 are layers that seal the exterior body 3. That is, the first sealing layer 6 and the second sealing layer 8 bond the films 4 together in the thickness direction. Although not shown, in the portion overlapping with the tab 9, the film 4 is bonded to the tab 9 via the first sealing layer 6 and the second sealing layer 8.

[0017] The first seal layer 6 and the second seal layer 8 are each made of resin. The first seal layer 6 is formed from a first seal resin, and the second seal layer 8 is formed from a second seal resin. The first seal resin and the second seal resin may be the same resin or different resins. The first seal resin and the second seal resin are, for example, thermocompression-bondable resins. That is, the exterior body 3 is sealed by thermocompression bonding at the first seal layer 6 and the second seal layer 8. Examples of the first seal resin and the second seal resin include thermoplastic resins. Examples of thermoplastic resins that can be used include polyethylene, polypropylene, and fluororesins.

[0018] Here, the first sealing layer 6 is configured to have a smaller moisture permeation rate than the second sealing layer 8. Specific configuration examples of the first sealing layer 6 and the second sealing layer 8 will be described later.

[0019] The above-described configuration more reliably suppresses moisture penetration. In a secondary battery 1 using the exterior body 3, the main route for moisture penetration is the seal portion 5. However, according to this embodiment, the first trapping layer 7 is provided inside the second seal layer 8. Therefore, even if moisture penetrates the second seal layer 8 from the outside of the secondary battery 1 to the inside, the penetrated moisture is captured by the first trapping layer 7. In other words, the presence of the first trapping layer 7 makes it possible to prevent moisture penetration.

[0020] On the other hand, if only the first trapping layer 7 is provided, moisture may be released further inward from the first trapping layer 7 when the first trapping layer 7 becomes saturated or when a change in the external environment occurs. However, according to this embodiment, the first sealing layer 6, which is configured to have a lower moisture permeability than the second sealing layer 8, is disposed inside the first trapping layer 7. Therefore, even if moisture is released from the first trapping layer 7, the moisture is mainly released outward and is less likely to be released inward. This makes it possible to more reliably suppress moisture penetration.

[0021] The present embodiment has been briefly described above.

[0022] In the present embodiment, the case where the film 4 included in the exterior body 3 is a single sheet has been described. However, this configuration is merely an example, and the exterior body 3 may be any as long as it has the seal portion 5. For example, the exterior body 3 may include, as the film 4, two sheets arranged to sandwich the battery element 2 in the stacking direction, and the seal portion 5 may be the portion where the edges of the two sheets are sealed.

[0023] Next, details of each component included in the secondary battery 1 according to this embodiment will be described.

[0024] (Trapping Layer) First, the first trapping layer 7 will be described. The first trapping layer 7 may be configured to be able to trap moisture. For example, the first trapping layer 7 may simply be a space. Alternatively, the first trapping layer 7 may be a layer containing a substance that has the function of trapping moisture. Specific configurations of the trapping layer will be described below with reference to configuration examples.

[0025] (Configuration Example 1) In a preferred example, the first trapping layer 7 is configured to release the trapped moisture according to moisture equilibrium. For example, the first trapping layer 7 includes an adsorbent member 10 capable of reversibly adsorbing and releasing moisture (see FIG. 2). Examples of such adsorbent members 10 include zeolite, activated carbon, and silica gel.

[0026] With this configuration, moisture that penetrates from the outside of the secondary battery 1 through the second sealing layer 8 can be trapped more reliably in the first trapping layer 7 .

[0027] Additionally, first trapping layer 7 releases the moisture trapped by adsorbent member 10 due to moisture equilibrium. At this time, because the moisture permeability of first sealing layer 6 is smaller than that of second sealing layer 8, first trapping layer 7 can preferentially release moisture to the outside of secondary battery 1 via second sealing layer 8. For example, by placing secondary battery 1 in a dry environment, the moisture trapped in first trapping layer 7 can be released to the outside. This allows the moisture trapping ability of first trapping layer 7 to be restored.

[0028] (Configuration Example 2) In another preferred example, the first trapping layer 7 is configured to release trapped moisture when heated. For example, a material that releases trapped moisture when heated is used as the adsorbent member 10 described in Configuration Example 1. With this configuration, heating the seal portion 5 causes the first trapping layer 7 to release the moisture trapped by the adsorbent member 10. At this time, because the moisture permeation rate of the first seal layer 6 is smaller than that of the second seal layer 8, the first trapping layer 7 can preferentially release moisture to the outside of the secondary battery 1. This also allows the moisture trapping ability of the first trapping layer 7 to be regenerated.

[0029] (Configuration Example 3) In another preferred example, first trapping layer 7 contains inert gas 11 (see FIG. 2 ). For example, first trapping layer 7 is filled with inert gas 11 that does not contain moisture, instead of or in addition to adsorption member 10 in the above-described configuration example.

[0030] With this configuration, moisture that penetrates from the outside to the inside of the secondary battery 1 can be more reliably trapped in the first trapping layer 7 .

[0031] There is no particular limitation on the inert gas 11. For example, argon gas, nitrogen gas, or the like can be used as the inert gas 11.

[0032] (Configuration Example 4) In another preferred example, first trapping layer 7 includes sacrificial material 12 (see FIG. 2 ). Sacrificial material 12 is a substance that irreversibly adsorbs moisture. Sacrificial material 12 may be included in first trapping layer 7 in place of adsorption member 10 or inert gas 11 in the above-described configuration examples, or together with adsorption member 10 or inert gas 11.

[0033] By using the sacrificial material 12 , moisture that penetrates from the outside to the inside of the secondary battery 1 can be more reliably trapped in the first trapping layer 7 .

[0034] The sacrificial material 12 may be any material that can irreversibly absorb moisture. Examples of the material that can be used for the sacrificial material 12 include sulfides and metal powders that are used for the solid electrolyte of the secondary battery 1.

[0035] (First sealing layer and second sealing layer) Next, the configurations of the first sealing layer 6 and the second sealing layer 8 will be described. The first sealing layer 6 and the second sealing layer 8 may be configured so that the first sealing layer 6 has a lower moisture permeation rate, and their specific configurations are not particularly limited. In this specification, the phrase "the moisture permeation rate of the first sealing layer 6 is lower than that of the second sealing layer 8" means that, when placed in the same environment, the first sealing layer 6 is less susceptible to moisture permeation than the second sealing layer 8. The configurations of the first sealing layer 6 and the second sealing layer 8 will be described below with reference to configuration examples.

[0036] (Configuration Example 5) Fig. 3 is a schematic cross-sectional view showing a seal portion 5 according to Configuration Example 5. In a preferred example, as shown in Fig. 3, the first seal layer 6 is configured to be longer than the second seal layer 8 in the inward / outward direction A of the secondary battery 1. That is, the width of the first seal layer 6 is greater than the width of the second seal layer 8. For example, the width of the first seal layer 6 is at least twice the width of the second seal layer 8.

[0037] The moisture permeation rate of each sealing layer decreases as the length of the sealing layer in the moisture permeation direction (in the present invention, the inward / outward direction A) increases. Therefore, by providing the above-described configuration, the moisture permeation rate of the first sealing layer 6 can be made smaller than that of the second sealing layer 8. This makes it possible to more reliably suppress moisture penetration.

[0038] (Configuration Example 6) In another preferred example, the first seal resin forming the first seal layer 6 has a moisture permeability coefficient smaller than that of the second seal resin forming the second seal layer 8. By using such a resin, the moisture permeability of the first seal layer 6 can be made smaller than that of the second seal layer 8. This makes it possible to more reliably suppress moisture penetration.

[0039] As long as the moisture permeability coefficient of the first seal resin is smaller than that of the second seal resin, different resins may be used for both resins, or the same resin with different moisture permeability coefficients may be used.

[0040] (Configuration Example 7) Figure 4 is a schematic cross-sectional view showing a seal portion 5 according to Configuration Example 7. In the secondary battery 1 of this configuration example, the cross-sectional area of ​​the first seal layer 6 is smaller than the cross-sectional area of ​​the second seal layer 8. The cross-sectional area here refers to the cross-sectional area in a cross section including the inward / outward direction A and the up-down direction B (meaning the thickness direction of the film). In other words, when the direction in which the seal portion 5 extends in a planar view is defined as the "extension direction," the cross-sectional area refers to the cross-sectional area in a cross section perpendicular to the extension direction.

[0041] Specifically, in this configuration example, as shown in Fig. 4, the thickness of the first sealing layer 6 is thinner than the thickness of the second sealing layer 8. For example, the thickness of the first sealing layer 6 is equal to or less than half the thickness of the second sealing layer 8. As a result, the cross-sectional area of ​​the first sealing layer 6 in a cross section perpendicular to the inward / outward direction A of the secondary battery 1 is smaller than the cross-sectional area of ​​the second sealing layer 8.

[0042] The smaller the cross-sectional area of ​​each seal layer, the smaller the moisture permeation rate. Therefore, by adjusting the cross-sectional area of ​​each seal layer, the moisture permeation rate of the first seal layer 6 can be made smaller than that of the second seal layer 8. This makes it possible to more reliably suppress moisture penetration. The cross-sectional area and thickness of both seal layers can be adjusted by, for example, changing the load pressure of the laminator when crimping and molding the seal portion 5.

[0043] (Configuration Example 8) Fig. 5 is a schematic cross-sectional view showing Configuration Example 8. The secondary battery 1 of this configuration example can be said to be a modified example of Configuration Example 7. That is, in this configuration example as well, the cross-sectional area of ​​the first sealing layer 6 is smaller than the cross-sectional area of ​​the second sealing layer 8. However, in this configuration example, the shapes of the first sealing layer 6 and the second sealing layer 8 are further devised.

[0044] 5 , the first seal layer 6 and the second seal layer 8 each have an uneven structure in the up-down direction B. The uneven density of the first seal layer 6 in the cross-sectional view is configured to be greater than the uneven density of the second seal layer 8 in the cross-sectional view. For example, the uneven density of the first seal layer 6 is at least twice the uneven density of the second seal layer 8.

[0045] By providing the uneven structure as described above, the moisture permeation path in the sealing layer in the inward / outward direction A is extended relative to the linear length of the sealing layer. The longer the moisture permeation path, the smaller the moisture permeation amount of the sealing layer. Therefore, the greater the density of the unevenness, the smaller the moisture permeation amount of the sealing layer.

[0046] In this configuration example, the first seal layer 6 has a higher density of irregularities than the second seal layer 8, and therefore the first seal layer 6 has a lower moisture permeation rate than the second seal layer 8. This makes it possible to more reliably suppress moisture penetration.

[0047] The uneven structure of both sealing layers is provided, for example, by using a laminator capable of embossing when the seal portion 5 is pressure-molded. In this configuration example, only the first sealing layer 6 may have an uneven structure. That is, as long as the moisture permeation rate of the first sealing layer 6 can be made smaller than that of the second sealing layer 8, the second sealing layer 8 does not need to have an uneven structure.

[0048] 6 is a schematic cross-sectional view showing Configuration Example 9. In this configuration example, the compositions of the first seal resin forming the first seal layer 6 and the second seal resin forming the second seal layer 8 are devised.

[0049] In this configuration example, gas-impermeable filler 13 is dispersed in the first seal resin and the second seal resin. Furthermore, the density of the gas-impermeable filler 13 in the first seal resin is greater than the density of the gas-impermeable filler 13 in the second seal resin. For example, the density of the gas-impermeable filler 13 in the first seal resin is at least twice the density of the gas-impermeable filler 13 in the second seal resin.

[0050] By including a gas-impermeable filler in the sealing resin that constitutes the sealing layer, the amount of moisture permeating through the sealing layer can be reduced. Here, the higher the density of the gas-impermeable filler 13 inside the sealing layer, the more difficult it is for moisture to permeate through the inside of the sealing layer. Therefore, by increasing the density of the gas-impermeable filler in the first sealing resin, the amount of moisture permeating through the first sealing layer 6 can be made smaller than that of the second sealing layer 8. This makes it possible to more reliably suppress moisture penetration.

[0051] There are no particular limitations on the gas-impermeable filler 13. For example, inorganic fillers such as glass fibers and metal oxides can be used as the gas-impermeable filler 13.

[0052] In this configuration example, only the first seal resin may contain the gas-impermeable filler 13. In other words, as long as the moisture permeation rate of the first seal layer 6 can be made smaller than that of the second seal layer 8, the second seal resin does not need to contain the gas-impermeable filler 13.

[0053] This embodiment has been described above with reference to configuration examples 1 to 9. These configuration examples can be combined as long as they are not inconsistent. This makes it possible to more reliably suppress the intrusion of moisture.

[0054] Second Embodiment Next, a second embodiment will be described. Fig. 7 is a schematic cross-sectional view of the secondary battery 1 cut along dashed line X in Fig. 1, illustrating the second embodiment. The second embodiment described below falls within the scope of the present invention, just like the first embodiment and its configuration examples. Furthermore, detailed description of the fact that the same configuration as the previously described embodiments can be adopted will be omitted.

[0055] In this embodiment, a sacrificial layer 14 is further provided in the sealing portion 5. The sacrificial layer 14 is disposed on the inner side of the first trapping layer 7. The sacrificial layer 14 irreversibly adsorbs moisture. For example, the sacrificial layer 14 includes the sacrificial material 12 described above.

[0056] According to this configuration, in addition to the same effects as those of the first embodiment and its configuration example, the following effects can be obtained.

[0057] Even if the moisture trapped in the first trapping layer 7 moves further inward, the sacrificial layer 14 irreversibly adsorbs the moisture. The moisture adsorbed in the sacrificial layer 14 is not released. Therefore, the penetration of moisture can be more reliably suppressed.

[0058] 7, the sacrificial layer 14 is disposed so as to be located at the innermost part of the sealing part 5 in the inward / outward direction A of the secondary battery 1. However, the sacrificial layer 14 only needs to be disposed more inward than the first trapping layer 7 in the inward / outward direction A, and does not necessarily have to be located at the innermost part of the sealing part 5.

[0059] Third Embodiment Next, a third embodiment will be described. Fig. 8 is a schematic cross-sectional view of the secondary battery 1 cut along the dashed line X in Fig. 1, illustrating the third embodiment. The third embodiment described below falls within the scope of the present invention, as do the first embodiment and its configuration example and the second embodiment. Furthermore, detailed description of the fact that the same configuration as the previously described embodiments can be adopted will be omitted.

[0060] In this embodiment, the seal portion 5 is further provided with a second trap layer 15 and a third seal layer 16. The second trap layer 15 is disposed on the outside of the second seal layer 8. The second trap layer 15 is configured to trap moisture, similar to the first trap layer 7. The third seal layer 16 is formed from a third seal resin and disposed on the outside of the second trap layer 15. Similar to the first seal layer 6 and the second seal layer 8, the third seal layer 16 bonds the films 4 together (and the film 4 and the tab where the tab is provided). Here, the second seal layer 8 is configured to have a smaller moisture permeation rate than the third seal layer 16.

[0061] That is, in this embodiment, the configurations applied to the first seal layer 6 and the second seal layer 8 in the first embodiment and each of its configuration examples can also be applied to the second seal layer 8 and the third seal layer 16. As a result, the second seal layer 8 has a smaller moisture permeation rate than the third seal layer 16.

[0062] According to this configuration, in addition to the same effects as those of the first embodiment and its configuration example, the following effects can be obtained.

[0063] The more inwardly positioned the seal layers are in the seal unit 5, the smaller the amount of moisture that permeates through them. That is, the further moisture penetrates into the seal unit 5 in the inward / outward direction A from the outside of the secondary battery 1, the more difficult it is for moisture to permeate through the seal layers. This makes it possible to more reliably suppress moisture penetration.

[0064] In addition, the second trap layer 15 in this embodiment, like the first trap layer 7, may be simply space, or may contain substances that capture moisture, such as an adsorption member 10, an inert gas 11, and a sacrificial material 12.

[0065] Although the present embodiment has been described with reference to a configuration including three seal layers and two trap layers, the number of seal layers and trap layers is not particularly limited. That is, the seal unit 5 may further include N trap layers and N seal layers (N is a natural number) arranged alternately outside the third seal layer 16, within a feasible range. In this case, the moisture permeation rate of each seal layer is configured to be smaller as it approaches the center.

[0066] Although the embodiments of the present invention have been described above, the configurations described in the above embodiments merely show some of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0067] [Addendum] The main aspects and effects of the present invention are summarized below as appendices.

[0068] (Note 1) A secondary battery comprising: a battery element 2 having an electrolyte layer containing a solid electrolyte, a positive electrode layer, and a negative electrode layer; and an exterior body 3 that houses the battery element 2, wherein the exterior body 3 has a seal portion 5 that is a sealed portion that hermetically seals a space that houses the battery element 2, and the seal portion 5 comprises: a first seal layer 6 formed of a first seal resin; a second seal layer 8 formed of a second seal resin and positioned outside the first seal layer 6; and a first trap layer 7 provided between the first seal layer 6 and the second seal layer 8 and configured to trap moisture, wherein the first seal layer 6 is configured to have a smaller amount of moisture permeation than the second seal layer 8.

[0069] According to the above-described configuration, the intrusion of moisture into the interior of the secondary battery 1 can be more reliably prevented.

[0070] (Supplementary Note 2) The secondary battery according to Supplementary Note 1, wherein the first trapping layer 7 is configured to release the trapped moisture through moisture equilibrium.

[0071] Since the first sealing layer 6 has a lower moisture permeability than the second sealing layer 8, the above configuration allows the moisture trapped in the first trapping layer 7 to be preferentially released to the outside of the secondary battery 1. This also allows the moisture trapping ability of the first trapping layer 7 to be regenerated.

[0072] (Supplementary Note 3) The secondary battery according to Supplementary Note 1 or 2, wherein the first trapping layer 7 is configured to release the trapped moisture when heated.

[0073] Because first sealing layer 6 has a lower moisture permeability than second sealing layer 8, the above configuration allows heating seal portion 5 to preferentially release moisture trapped in first trapping layer 7 to the outside of secondary battery 1. In addition, heating can restore the moisture trapping ability of first trapping layer 7.

[0074] (Supplementary Note 4) The secondary battery according to any one of Supplementary Notes 1 to 3, wherein the first trapping layer 7 contains an inert gas 11.

[0075] According to the above configuration, moisture that penetrates from the outside to the inside of the secondary battery 1 can be more reliably trapped in the first trapping layer 7 .

[0076] (Supplementary Note 5) The secondary battery according to any one of Supplementary Notes 1 to 4, wherein the first sealing layer 6 is longer than the second sealing layer 8 in the inner-outer direction A.

[0077] The moisture permeation rate of each seal layer decreases as the length of each seal layer in the inner / outer direction A increases, and therefore, with the above configuration, the first seal layer 6 has a smaller moisture permeation rate than the second seal layer 8. This makes it possible to more reliably prevent moisture from penetrating into the secondary battery 1.

[0078] (Supplementary Note 6) The secondary battery according to any one of Supplementary Notes 1 to 5, wherein the moisture permeability coefficient of the first sealing resin is smaller than the moisture permeability coefficient of the second sealing resin.

[0079] According to the above configuration, the first sealing layer 6 has a smaller moisture permeability than the second sealing layer 8. This makes it possible to more reliably prevent moisture from penetrating into the interior of the secondary battery 1.

[0080] (Supplementary Note 7) The secondary battery according to any one of Supplementary Notes 1 to 6, wherein the cross-sectional area of ​​the first sealing layer 6 is smaller than the cross-sectional area of ​​the second sealing layer 8.

[0081] The smaller the cross-sectional area of ​​each seal layer, the smaller the moisture permeation rate of each seal layer. Therefore, with the above configuration, the first seal layer 6 has a smaller moisture permeation rate than the second seal layer 8. This makes it possible to more reliably prevent moisture from penetrating into the secondary battery 1.

[0082] (Appendix 8) The secondary battery according to Appendix 7, wherein the first sealing layer 6 has an uneven structure in a cross-sectional view, and the density of the unevenness in the cross-sectional view of the first sealing layer 6 is greater than the density of the unevenness in the cross-sectional view of the second sealing layer 8.

[0083] According to the above configuration, the moisture permeation path in the first sealing layer 6 in the direction A of the secondary battery 1 is longer than the moisture permeation path in the second sealing layer 8 in the direction A of the secondary battery 1. Therefore, the first sealing layer 6 has a smaller moisture permeation rate than the second sealing layer 8. This makes it possible to more reliably prevent moisture from penetrating into the secondary battery 1.

[0084] (Appendix 9) The secondary battery according to any one of Appendices 1 to 8, wherein gas-impermeable filler 13 is dispersed in the first seal resin, and the density of gas-impermeable filler 13 in the first seal resin is greater than the density of gas-impermeable filler 13 in the second seal resin.

[0085] The higher the density of the gas-impermeable filler 13 inside the sealing layer, the more difficult it is for moisture to permeate through the sealing layer. Therefore, with the above configuration, the first sealing layer 6 has a lower moisture permeation rate than the second sealing layer 8. This makes it possible to more reliably prevent moisture from penetrating into the secondary battery 1.

[0086] (Appendix 10) The secondary battery according to any one of Appendices 1 to 9, wherein the sealing portion 5 further has a sacrificial layer 14 arranged on the inner side of the first trapping layer 7, and the sacrificial layer 14 is configured to irreversibly adsorb moisture.

[0087] According to the above configuration, even if the moisture trapped by the first trapping layer 7 permeates the first sealing layer 6, the sacrificial layer 14 irreversibly adsorbs the moisture, thereby more reliably preventing the moisture from penetrating into the secondary battery 1.

[0088] (Appendix 11) The secondary battery according to any one of Appendices 1 to 10, wherein the sealing portion 5 further includes a second trapping layer 15 disposed outside the second sealing layer 8, and a third sealing layer 16 formed of a third sealing resin and disposed outside the second trapping layer 15, and the second sealing layer 8 is configured to have a smaller amount of moisture permeation than the third sealing layer 16.

[0089] According to the above configuration, the amount of moisture permeation decreases as the sealing layers provided in the sealing unit 5 are positioned further inside in the direction A of the secondary battery 1. In other words, the further moisture permeates the sealing layer from the outside of the secondary battery 1, the more difficult it is for moisture to permeate the sealing layer as the moisture penetrates further into the sealing unit 5 in the direction A. This makes it possible to more reliably prevent moisture from permeating the interior of the secondary battery 1.

Claims

1. A secondary battery comprising: a battery element having an electrolyte layer containing a solid electrolyte, a positive electrode layer, and a negative electrode layer; and an exterior housing that houses the battery element, wherein the exterior housing has a seal portion that is a sealed portion that hermetically seals the space that houses the battery element, and the seal portion comprises: a first seal layer formed from a first seal resin; a second seal layer formed from a second seal resin and positioned outside the first seal layer; and a first trap layer that is provided between the first seal layer and the second seal layer and configured to trap moisture, wherein the first seal layer is configured to have a smaller moisture permeation rate than the second seal layer.

2. A secondary battery according to claim 1, wherein the first trapping layer is configured to release trapped moisture through moisture equilibrium.

3. The secondary battery according to claim 1, wherein the first trapping layer is configured to release trapped moisture when heated.

4. The secondary battery according to claim 1 or 2, wherein the first trapping layer contains an inert gas.

5. A secondary battery according to claim 1 or 2, wherein the first sealing layer is longer than the second sealing layer in the inner-outer direction.

6. A secondary battery according to claim 1 or 2, wherein the moisture permeability coefficient of the first sealing resin is smaller than the moisture permeability coefficient of the second sealing resin.

7. A secondary battery according to claim 1 or 2, wherein the cross-sectional area of ​​the first sealing layer is smaller than the cross-sectional area of ​​the second sealing layer.

8. A secondary battery according to claim 7, wherein the first sealing layer has an uneven structure in a cross-sectional view, and the density of the unevenness in the cross-sectional view of the first sealing layer is greater than the density of the unevenness in the cross-sectional view of the second sealing layer.

9. A secondary battery according to claim 1 or 2, wherein a gas-impermeable filler is dispersed in the first sealing resin, and the density of the gas-impermeable filler in the first sealing resin is greater than the density of the gas-impermeable filler in the second sealing resin.

10. A secondary battery according to claim 1 or 2, wherein the sealing portion further has a sacrificial layer disposed inside the first trapping layer, and the sacrificial layer is configured to irreversibly adsorb moisture.

11. A secondary battery as claimed in claim 1 or 2, wherein the sealing portion further comprises: a second trap layer disposed on the outside of the second sealing layer; and a third sealing layer formed from a third sealing resin and disposed on the outside of the second trap layer, and wherein the second sealing layer is configured to have a smaller amount of moisture permeation than the third sealing layer.

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