Secondary battery

Abstract

This secondary battery comprises: a battery element that has a solid electrolyte layer, a positive electrode layer, and a negative electrode layer; an exterior laminate material that accommodates the battery element; and a resin filler that is filled in the exterior laminate material. The battery element is configured so that metal lithium is deposited on the negative electrode layer during charging. The filler and the exterior laminate material are bonded at all contact portions. The filler is disposed so as to cover at least the side surfaces of the battery element. During charging, the exterior laminate material expands in the lamination direction by being pressed by the battery element that expands, and contracts in a direction perpendicular to the lamination direction. During charging, the filler is pressed against the metallic lithium deposited by the contracting exterior laminate material.

Description

secondary battery

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

[0002] Known secondary batteries have a structure in which a negative electrode current collector foil, a negative electrode layer, a solid electrolyte layer, a positive electrode layer, and a positive electrode current collector foil are stacked in this order. In this specification, the stacked structure consisting of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer is sometimes referred to as a battery element.

[0003] In such secondary batteries, a covering material is sometimes disposed to cover the side surfaces of the battery element for various reasons. The covering material is generally made of an insulating resin material.

[0004] In relation to the above, Patent Document 1 (JP2018-116812A) discloses a "method for manufacturing an all-solid-state lithium-ion battery, comprising: a first step of stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer to form a stacked battery having both end faces and side surfaces in the stacking direction; a second step of charging the stacked battery to a charge rate of 100% or more and 112% or less; a third step of covering at least the side surfaces of the charged stacked battery with an uncured thermosetting resin; and a fourth step of heating and curing the thermosetting resin." According to the description in Patent Document 1, this manufacturing method is capable of suppressing cracking of the cured resin due to expansion of the negative electrode during charging, even when discharge and charging are repeated.

[0005] The present inventors have been studying lithium deposition secondary batteries, which are batteries configured so that metallic lithium is deposited on the negative electrode during charging.

[0006] The inventors also expect the coating material covering the side surface of the battery element to have the function of applying a load uniformly to the battery element. In a secondary battery using a solid electrolyte layer, a large restraint load is applied to the battery element to obtain desired charge / discharge characteristics. It is desirable that the restraint load be applied uniformly. However, the positions of the outer edges of the multiple layers included in the battery element may be misaligned. In other words, unevenness may be formed on the side surface of the battery element. If unevenness is formed on the side surface, it becomes difficult to apply a load uniformly to the battery element. In contrast, if the side surface of the battery element is covered with a coating material, such unevenness can be absorbed. Therefore, the load can be applied uniformly.

[0007] However, in Li deposition-type secondary batteries, metallic lithium is deposited on the negative electrode during charging, as described above. Spaces may form between the deposited metallic lithium and the coating material. Such space may impair the coating material's required function of uniformly applying a load.

[0008] Therefore, an object of the present invention is to provide a technique capable of preventing the formation of a space between the deposited metallic lithium and the coating material in a Li deposition type secondary battery.

[0009] In one aspect, a secondary battery according to the present invention includes a battery element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer, the positive electrode layer and the negative electrode layer being arranged to sandwich the solid electrolyte layer in the stacking direction; an exterior laminate material that houses the battery element; and a resin filler material that is filled in the exterior laminate material so as to fill a space formed between the battery element and the interior of the exterior laminate material. The battery element is configured so that metallic lithium is deposited on the negative electrode layer during charging. The filler material and the exterior laminate material are bonded at all contact areas. The filler material is arranged so as to cover at least the side surfaces of the battery element. The exterior laminate material is configured so that, during charging, the expanding battery element pushes the filler material in the stacking direction and contracts in a direction perpendicular to the stacking direction. The filler material is configured so that, during charging, the contracting exterior laminate material presses against the deposited metallic lithium.

[0010] FIG. 1 is a schematic cross-sectional view showing a secondary battery according to a first embodiment. FIG. 2 is a view showing a cross section perpendicular to the tab direction of the secondary battery. FIG. 3 is a schematic cross-sectional view showing a configuration of a secondary battery during charging and discharging. FIG. 4A is a schematic cross-sectional view showing a secondary battery according to a second embodiment. FIG. 4B is a schematic cross-sectional view showing a secondary battery according to a reference example related to the second embodiment. FIG. 5 is a schematic cross-sectional view showing a secondary battery according to a reference example related to the second embodiment. FIG. 6 is a view for explaining the effects of the third embodiment. FIG. 7 is a schematic cross-sectional view showing a reference example related to the fourth embodiment. FIG. 8 is a schematic cross-sectional view showing a secondary battery according to a fifth embodiment. FIG. 9A is a schematic cross-sectional view showing a secondary battery according to a sixth embodiment. FIG. 9B is a schematic cross-sectional view showing a reference example related to the sixth embodiment. FIG. 10A is a schematic cross-sectional view showing a secondary battery according to a seventh embodiment. FIG. 10B is a schematic cross-sectional view showing a reference example related to the seventh embodiment. FIG. 11A is a schematic cross-sectional view showing a secondary battery according to an eighth embodiment. FIG. 11B is a schematic cross-sectional view showing a reference example related to the eighth embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] (1) First Embodiment FIG. 1 is a schematic cross-sectional view showing a secondary battery 1 according to a first embodiment. Note that FIG. 1 shows the configuration in a discharged state. The secondary battery 1 according to this embodiment is a secondary battery using a solid electrolyte layer as the electrolyte layer. The secondary battery 1 according to this embodiment includes so-called all-solid-state batteries. Furthermore, the secondary battery 1 according to this embodiment is provided as a so-called cell.

[0013] As shown in FIG. 1, the secondary battery 1 includes a battery element 2, current collector foils 6 (positive electrode current collector foil 6-1 and negative electrode current collector foil 6-2), an exterior laminate material 7, and a filler material 8.

[0014] The battery element 2 is housed in an exterior laminate material 7. The battery element 2 is sandwiched between a positive electrode current collector foil 6-1 and a negative electrode current collector foil 6-2 in the stacking direction. In the example shown in FIG. 1, a plurality of battery elements 2, a plurality of positive electrode current collector foils 6-1, and a plurality of negative electrode current collector foils 6-2 are provided. Specifically, a plurality of battery elements 2 are stacked in the stacking direction, with each current collector foil (6-1 or 6-2) sandwiched between them. In other words, a plurality of positive electrode current collector foils 6-1 and a plurality of negative electrode current collector foils 6-2 are alternately arranged in the stacking direction, with the battery element 2 sandwiched between them.

[0015] The battery element 2 is pressurized so as to be compressed in the stacking direction. For example, although not shown, a pair of end plates are disposed on the outer sides in the stacking direction of the configuration shown in Fig. 1. A restraining load is applied to the battery element 2 along the stacking direction via the pair of end plates.

[0016] The battery element 2 is a part that realizes charge and discharge functions. The battery element 2 has a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5. The positive electrode layer 4 and the negative electrode layer 5 are arranged to sandwich the solid electrolyte layer 3 in the stacking direction. The battery element 2 is arranged between the positive electrode current collector foil 6-1 and the negative electrode current collector foil 6-2 so that the positive electrode layer 4 faces the positive electrode current collector foil 6-1 and the negative electrode layer 5 faces the negative electrode current collector foil 6-2. In the example shown in FIG. 1 , the outer peripheral edges of the solid electrolyte layer 3 and the negative electrode layer 5 are located outside the outer peripheral edge of the positive electrode layer 4 when viewed along the stacking direction.

[0017] The battery element 2 is configured so that metallic lithium is deposited as a negative electrode active material in the negative electrode layer 5 during charging. That is, the secondary battery 1 according to this embodiment is a Li deposition type secondary battery. Common secondary batteries are known in which the negative electrode layer is formed of carbon, silicon, or the like. In such secondary batteries, lithium is incorporated into the negative electrode layer during charging. In contrast, in Li deposition type secondary batteries, metallic lithium is "deposited" in the negative electrode layer to form a layer. Therefore, the thickness of the negative electrode layer increases during charging by the thickness of the deposited metallic lithium.

[0018] Specifically, the anode layer 5 includes an anode intermediate layer 5-1. The anode intermediate layer 5-1 is provided to control the location of deposition of metallic lithium. In a discharged state, the anode intermediate layer 5-1 is disposed between the solid electrolyte layer 3 and the anode current collector foil 6-2. That is, in a discharged state, the anode layer 5 is composed of the anode intermediate layer 5-1. During charging, lithium ions migrate from the cathode layer 4 to the anode layer 5 via the solid electrolyte layer 3. The migrated lithium ions precipitate as metallic lithium between the anode intermediate layer 5-1 and the anode current collector foil 6-2. The provision of the anode intermediate layer 5-1 prevents metallic lithium from being deposited in unintended locations. Furthermore, because metallic lithium is highly reactive, direct contact of metallic lithium with the solid electrolyte layer 3 could damage the solid electrolyte layer 3. The provision of the anode intermediate layer 5-1 prevents direct contact between metallic lithium and the solid electrolyte layer 3, thereby preventing damage to the solid electrolyte layer 3. During discharge, metallic lithium migrates as lithium ions from the negative electrode layer 5 to the positive electrode layer 4 and is absorbed in the positive electrode layer 4. As a result, metallic lithium is almost completely lost from the negative electrode layer 5, and the thickness of the negative electrode layer 5 decreases.

[0019] As described above, the exterior laminate material 7 houses the battery element 2. The exterior laminate material 7 has flexibility. For example, a laminate film of an aluminum film and a resin film is used as the exterior laminate material.

[0020] The current collector foils 6 (positive electrode current collector foil 6-1 and negative electrode current collector foil 6-2) are provided to electrically connect the battery element 2 to an external device. Each current collector foil (6-1 and 6-2) extends laterally from the connection portion with the battery element 2. The positive electrode current collector foil 6-1 and the negative electrode current collector foil 6-2 extend in opposite directions from the battery element 2. Although detailed illustration is omitted, the current collector foils 6 are gathered on the side of the battery element 2 and connected to a tab. The tab extends from the inside to the outside of the exterior laminate material 7, thereby enabling electrical connection to an external device.

[0021] Note that Fig. 1 depicts a cross section along the direction connecting the positive electrode tab and the negative electrode tab (hereinafter referred to as the tab direction). Meanwhile, Fig. 2 is a cross-sectional view of the secondary battery 1, showing a cross section perpendicular to the tab direction. As shown in Fig. 2, in a direction different from the tab direction, the outer peripheral edge of each current collector foil 6 (6-1 and 6-2) is generally aligned with the outer peripheral edge of each electrode layer (positive electrode layer 4 and negative electrode layer 5).

[0022] The filler 8 is made of resin. The filler 8 is filled in the exterior laminate material 7. The filler 8 fills the space formed between the battery element 2 and the exterior laminate material 7. The filler 8 is arranged so as to cover at least the side surface of the battery element 2. The filler 8 has flexibility to the extent that it deforms in response to deformation of the exterior laminate material 7.

[0023] The filler 8 and the exterior laminate 7 are bonded at all contact points. In this specification, "bonding" refers to two objects being in contact with each other in such a way that an attractive force acts on them without the application of an external force. Specifically, it refers to a state in which the surfaces of the objects are bonded together by chemical or physical forces, or both. In other words, in this specification, "bonding" is a concept that is distinct from simple "contact." The filler and the exterior laminate may be bonded together via an adhesive. In this case, the two surfaces are bonded together by chemical or physical forces, or both, using the adhesive as a medium. On the other hand, if the filler itself is a component that has adhesive properties, an adhesive need not necessarily be used.

[0024] The filler 8 functions as the "covering material" described above. That is, one of the roles of the filler 8 is to apply a uniform restraint load to the battery element 2. By covering the side surface of the battery element 2 with the filler 8, irregularities on the side surface of the battery element 2 are absorbed, and a uniform load can be applied to the battery element 2.

[0025] The above is a schematic configuration of the secondary battery 1 according to this embodiment. The secondary battery 1 having the above configuration prevents the formation of spaces on the sides of metallic lithium that precipitates during charging. This point will be described below.

[0026] 3A and 3B are schematic cross-sectional views showing the configuration of the secondary battery 1 during charging and discharging, illustrating the configuration at the end of the battery element 2. FIG. 3A shows the configuration in a discharging state. FIG. 3B and FIG. 3C show the configuration in a charging state. FIG. 3B shows the configuration of a reference example. On the other hand, FIG. 3C shows the configuration according to this embodiment.

[0027] During charging, as described above, metallic lithium 5-2 is precipitated in the negative electrode layer 5 of the battery element 2. If no special measures are taken (for example, if the space within the exterior laminate material 7 is not completely filled with the filler material 8), metallic lithium 5-2 may separate from the filler material 8 and precipitate, as shown in FIG. 3( b). That is, a space A may be formed between the metallic lithium 5-2 and the filler material 8. If a space A is formed, the function of the filler material 8 to uniformly apply a restraining load is impaired.

[0028] In contrast, in this embodiment, the space within the exterior laminate material 7 is filled with the filler material 8, so that during charging, the exterior laminate material 7 is pushed by the battery element 2 so as to expand in the stacking direction, as shown by arrow A in Figures 1 and 2. As a result, in the direction perpendicular to the stacking direction, tension generates a contracting force on the exterior laminate material 7 (see arrow B in Figures 1 and 2). As a result, the filler material 8 is pressed against the side surface of the battery element 2 by the exterior laminate material 7, and no space is formed to the side of the deposited metallic lithium.

[0029] The above is an outline of the first embodiment.

[0030] In this embodiment, the secondary battery 1 includes a plurality of battery elements 2, a plurality of positive electrode current collector foils 6-1, and a plurality of negative electrode current collector foils 6-2. However, the secondary battery 1 does not necessarily include a plurality of battery elements 2. Each of the battery element 2, the positive electrode current collector foil 6-1, and the negative electrode current collector foil 6-2 may be a single element.

[0031] In addition, in this embodiment, the case where the anode intermediate layer 5-1 is provided in the anode layer 5 has been described. However, the anode intermediate layer 5-1 is not an essential component. Even if the anode intermediate layer 5-1 is not present, a layer of metallic lithium 5-2 present in a charged state functions as the anode layer 5. A battery configured so that metallic lithium is deposited in the anode layer 5 is included in the secondary battery 1 according to this embodiment, even if the anode intermediate layer 5-1 is not provided.

[0032] (2) Second Embodiment Next, a second embodiment will be described. Note that detailed description will be omitted for the points where the same configuration as the previously described embodiment can be adopted.

[0033] Fig. 4A is a cross-sectional view schematically illustrating a secondary battery 1 according to this embodiment. Fig. 4A shows the configuration of an end portion of a battery element 2. In this embodiment, the adhesive portion of the filler 8 is devised. In Fig. 4A, the adhesive portion between the components is shown as an "adhesive region 9."

[0034] In this embodiment, the filler 8 is bonded to the current collector foils 6 (6-1 and 6-2) in addition to the exterior laminate material 7. Specifically, as shown in FIG. 4A , the portion of each current collector foil 6 that is connected to the battery element 2 (positive electrode layer 4 or negative electrode layer 5) is defined as the battery element connection portion 10-1. Furthermore, the portion of each current collector foil 6 that extends laterally from the battery element connection portion 10-1 (the portion that extends toward the tab) is defined as the extension portion 10-2. The filler 8 is bonded to the extension portion 10-2 of each current collector foil 6 (6-1 and 6-2). In the example shown in FIG. 4A , the filler 8 is bonded to the extension portion 10-2 of the negative electrode current collector foil 6-2.

[0035] According to this embodiment, the formation of spaces on the sides of the deposited metallic lithium 5-2 is more reliably prevented. FIG. 4B is a schematic cross-sectional view showing a secondary battery 1 according to a reference example. In this reference example, the filler 8 is not bonded to the current collector foil 6. During charging, the thickness of the negative electrode layer 5 increases as the metallic lithium 5-2 deposits. This causes the position of the current collector foil 6 (extension 10-2) to change in the stacking direction. This may cause the filler 8 to separate from the extension 10-2 in the stacking direction. As a result, spaces may form on the sides of the metallic lithium 5-2. In contrast, as shown in FIG. 4A, if the filler 8 is bonded to the extension 10-2, the filler 8 will not separate from the extension 10-2 even if the metallic lithium 5-2 deposits. This prevents spaces from forming on the sides of the metallic lithium 5-2.

[0036] The adhesive strength between the filler 8 and the extension 10-2 is preferably smaller than the adhesive strength between the filler 8 and the exterior laminate 7. FIG. 5 is a schematic diagram showing a secondary battery 1 according to a reference example related to this embodiment. In this reference example, the adhesive strength between the filler 8 and the extension 10-2 is greater than the adhesive strength between the filler 8 and the exterior laminate 7. In this reference example, as the battery element 2 expands and contracts, the filler 8 is pulled by the current collecting foil 6, which may cause the filler 8 and the exterior laminate 7 to peel off, forming a space (space A in the figure). If such a space is formed, the filler 8 becomes less likely to be pressed against the side surface of the battery element 2. On the other hand, if the adhesive strength between the filler 8 and the extension 10-2 is smaller than the adhesive strength between the filler 8 and the exterior laminate 7, the filler 8 and the exterior laminate 7 will be less likely to peel off. This allows the filler 8 to easily follow the deformation of the exterior laminate material 7 , and the filler 8 is pressed more reliably against the side surface of the battery element 2 .

[0037] (3) Third Embodiment Next, a third embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0038] In this embodiment, the filler 8 is configured so as not to adhere to the deposited metallic lithium 5-2. As described above, the filler 8 is pressed against the metallic lithium 5-2, so the filler 8 and the metallic lithium 5-2 are in "contact." However, in this embodiment, the two are not "adhered" to each other. Specifically, the filler 8 is made of a material that does not cause any mutually attractive interaction between the filler 8 and the deposited metallic lithium 5-2.

[0039] The effects of this embodiment will be described with reference to FIG. 6 . FIG. 6( a) is a diagram illustrating a reference example related to this embodiment, showing the configuration in a charged state. Note that in FIG. 6( a), the adhesive portions between the components are indicated as "adhesion regions 9." In the reference example shown in FIG. 6( a), the filler 8 is formed of a material that adheres to the deposited metallic lithium 5-2. In a charged state, the filler 8 adheres to the side of the metallic lithium 5-2. During discharge, the metallic lithium 5-2 in the negative electrode layer 5 decreases. The filler 8 is attracted by the decreasing metallic lithium 5-2. As a result, as shown in FIG. 6( b), the filler 8 may enter between the negative electrode layer 5 (negative electrode intermediate layer 5-1) and the negative electrode current collector foil 6-2. In the region where the filler 8 enters, charge / discharge reactions do not occur, resulting in poor battery performance.

[0040] In contrast, in this embodiment, the filler 8 is made of a material that does not adhere to the deposited metallic lithium 5-2, so the filler 8 is not pulled by the metallic lithium 5-2 during discharge. Therefore, as shown in Figure 6(c), the filler 8 does not get between the negative electrode layer 5 (negative electrode intermediate layer 5-1) and the negative electrode current collector foil 6-2 even after discharge. This prevents deterioration of the charge / discharge characteristics.

[0041] (4) Fourth Embodiment Next, a fourth embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0042] In this embodiment, the position of the filler 8 is devised. The configuration of the secondary battery 1 according to this embodiment is reflected in FIGS. 1 and 2, so please refer to these figures. As shown in FIGS. 1 and 2, the filler 8 is not disposed on either side of the battery element 2 in the stacking direction. In other words, on either side of the battery element 2 in the stacking direction, the filler 8 is not present between the battery element 2 and the exterior laminate material 7. In the example shown in FIGS. 1 and 2, the current collector foil 6 (negative electrode current collector foil 6-2) located at the outermost position in the stacking direction is in direct contact with the exterior laminate material 7. In other words, the filler 8 is disposed only on the side of the battery element 2.

[0043] According to this embodiment, the formation of a space between the battery element 2 and the filler 8 is more reliably prevented. This point will be explained with reference to a reference example. Fig. 7 is a schematic cross-sectional view showing a reference example related to this embodiment. In this reference example, the filler 8 is also present on both sides of the battery element 2 in the stacking direction (see area "X" in the figure).

[0044] 7 , when the battery element 2 expands in the stacking direction, force is less likely to be applied from the battery element 2 to the exterior laminate material 7. That is, the force is more likely to be dissipated laterally between the battery element 2 and the exterior laminate material 7 in the stacking direction (region X) (see arrow C in FIG. 7 ). Therefore, a contracting force (arrow B in FIG. 7 ) is less likely to be generated on the side surface of the exterior laminate material 7, and the filler material 8 is less likely to be pressed against the side surface of the battery element 2.

[0045] In contrast, according to this embodiment, the filler 8 is not provided on either side of the battery element 2 in the stacking direction, so the force is less likely to be released to the sides. Therefore, expansion of the battery element 2 tends to apply a force to the exterior laminate material 7 along the stacking direction, and a contraction force tends to be generated in the direction perpendicular to the stacking direction. As a result, the filler 8 tends to be pressed against the side surfaces of the battery element 2, more reliably preventing the formation of spaces on the sides of the battery element 2.

[0046] (5) Fifth Embodiment Next, a fifth embodiment will be described. Detailed description will be omitted for the fact that the same configuration as the above-described embodiments can be adopted.

[0047] Fig. 8 is a schematic cross-sectional view showing a secondary battery 1 according to a fifth embodiment. Fig. 8 shows the configuration in a charged state. In this embodiment, the side surfaces of the exterior laminate material 7 are curved in the charged state. Specifically, the side surfaces of the exterior laminate material 7 are curved surfaces that bulge outward.

[0048] According to this embodiment, because the side surfaces are curved, the contraction force generated in the exterior laminate material 7 during charging is directed inward in the stacking direction (see the arrows in FIG. 8 ). As a result, the contraction force is less likely to escape outward in the stacking direction, and the filler material 8 is more likely to be pressed against the side surfaces of the battery element 2. As a result, the generation of spaces on the sides of the battery element 2 is more reliably prevented.

[0049] (6) Sixth Embodiment Next, a sixth embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0050] In this embodiment, the structure of the adhesive portion between the filler 8 and the battery element 2 is devised. Fig. 9A is a schematic cross-sectional view showing a secondary battery 1 according to a sixth embodiment. In Fig. 9A, the adhesive portion between the components is shown as an "adhesive region 9". As shown in Fig. 9A, the filler 8 is adhered to the positive electrode layer 4. More specifically, the filler 8 is adhered to the side surface of the positive electrode layer 4.

[0051] According to this embodiment, the filler 8 and the positive electrode layer 4 are bonded together, preventing the formation of spaces on the sides of the positive electrode layer 4. FIG. 9B is a schematic cross-sectional view showing a reference example related to this embodiment. If the filler 8 and the positive electrode layer 4 were not bonded together, there is a possibility that the filler 8 would separate from the side of the positive electrode layer 4, as shown in FIG. 9B. In contrast, according to this embodiment, the filler 8 and the positive electrode layer 4 are bonded together, preventing the filler 8 from separating from the positive electrode layer 4. This more reliably prevents the formation of spaces on the side of the battery element 2.

[0052] (7) Seventh Embodiment Next, a seventh embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0053] 10A is a schematic cross-sectional view showing a secondary battery 1 according to the seventh embodiment. In FIG. 10A, the bonded portions of the components are shown as bonded regions 9.

[0054] In this embodiment, it is assumed that the negative electrode layer 5 has a negative electrode intermediate layer 5-1. The filler 8 is bonded to the negative electrode intermediate layer 5-1. This prevents the formation of spaces on the sides of the negative electrode intermediate layer 5-1. FIG. 10B is a schematic cross-sectional view showing a reference example related to this embodiment, illustrating a configuration in which the filler 8 and the negative electrode intermediate layer 5-1 are not bonded. As shown in FIG. 10B, if the filler 8 and the negative electrode intermediate layer 5-1 are not bonded, the filler 8 may separate from the negative electrode intermediate layer 5-1. As a result, spaces (see A in the figure) may be formed on the sides of the negative electrode intermediate layer 5-1. On the other hand, according to this embodiment, the filler 8 is bonded to the negative electrode intermediate layer 5-1, so the filler 8 does not separate from the negative electrode intermediate layer 5-1. This prevents the formation of spaces on the sides of the negative electrode intermediate layer 5-1.

[0055] (8) Eighth Embodiment Next, an eighth embodiment will be described. Detailed description will be omitted for the points where the same configuration as the above-described embodiments can be adopted.

[0056] 11A is a schematic cross-sectional view showing a secondary battery 1 according to an eighth embodiment. In FIG. 11A, the bonded portions of the components are shown as bonded regions 9.

[0057] In this embodiment, as shown in FIG. 11A , the filler 8 is bonded to the solid electrolyte layer 3. This prevents spaces from being formed on the sides of the solid electrolyte layer 3. FIG. 11B is a schematic cross-sectional view showing a reference example related to this embodiment, illustrating a configuration in which the filler 8 and the solid electrolyte layer 3 are not bonded. As shown in FIG. 11B , if the filler 8 and the solid electrolyte layer 3 are not bonded, the filler 8 may separate from the solid electrolyte layer 3, and spaces (see A in the figure) may be formed on the sides of the solid electrolyte layer 3. In contrast, according to this embodiment, the filler 8 and the solid electrolyte layer 3 are bonded, preventing spaces from being formed on the sides of the solid electrolyte layer 3.

[0058] (9) Others The above has described the secondary batteries according to the first to eighth embodiments. Next, more specific configurations of the components included in the secondary battery 1 according to the above-described embodiments will be described.

[0059] (Filler) As described above, the filler 8 is made of resin. The filler 8 only needs to have flexibility to the extent that it can deform in response to deformation of the exterior laminate material 7. For example, the filler 8 has an elastic modulus (Young's modulus) of 20 MPa or less. Preferably, the elastic modulus of the filler 8 is 10 MPa or less.

[0060] Examples of materials that can be used to form the filler 8 include rubber and elastomer resin, polyethylene resin, polypropylene resin, epoxy resin, ethylene copolymer, and propylene copolymer.

[0061] (Negative Electrode Intermediate Layer) As described above, the negative electrode intermediate layer 5-1 only needs to have the function of controlling the deposition location of metallic lithium and protecting the solid electrolyte layer from the deposited metallic lithium. For example, the negative electrode intermediate layer is realized by a layer containing metal particles such as silver and carbon particles. These may be dispersed in a binder resin. The thickness of the negative electrode intermediate layer is preferably thinner than the thickness of the metallic lithium 5-2 deposited in a charged state. The thickness of the negative electrode intermediate layer is, for example, 1 to 50 μm.

[0062] (Solid Electrolyte Layer) The solid electrolyte layer is solid and may be made of any material as long as it functions as an electrolyte layer in a secondary battery. The solid electrolyte layer may include, for example, a resin binder and a solid electrolyte dispersed in the resin binder. The solid electrolyte preferably includes a sulfide solid electrolyte. The thickness of the solid electrolyte layer is, for example, 5 to 100 μm.

[0063] (Positive Electrode Layer) The positive electrode layer may be formed of a material that can release lithium ions during charging and absorb lithium ions during discharging. The positive electrode layer may be formed of a material containing, for example, a resin binder and a positive electrode active material dispersed in the resin binder. For example, a lithium metal composite oxide may be used as the positive electrode active material. For example, the lithium metal composite oxide may be LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , and Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ , and LiNi ０．５ Mn １．５ O ４ spinel-type compounds such as LiFePO ４ , and LiMnPO ４ Olivine type compounds such as Li ２ FeSiO ４ , and Li ２ MnSiO ４ In addition, Si-containing compounds such as Li ４ Ti ５ O １２ The thickness of the positive electrode layer is, for example, 10 to 500 μm, and preferably 50 to 200 μm.

[0064] (Negative electrode current collector foil and positive electrode current collector foil) The negative electrode current collector foil and positive electrode current collector foil are not particularly limited. For example, the negative electrode current collector foil may be a thin film of copper, a copper alloy, nickel, a nickel alloy, or the like. The positive electrode current collector foil may be, for example, an aluminum foil.

[0065] [Addendum] The main aspects and effects of the present invention are summarized below as appendices.

[0066] (Supplementary Note 1) A secondary battery comprising: a battery element 2 having a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5, the positive electrode layer 4 and the negative electrode layer 5 being arranged so as to sandwich the solid electrolyte layer 3 in the stacking direction; an exterior laminate material 7 that houses the battery element 2; and a resin filler 8 that is filled in the exterior laminate material 7 so as to fill a space formed between the battery element 2 and the interior of the exterior laminate material 7, the battery element 2 being configured so that metallic lithium precipitates on the negative electrode layer 5 during charging, the filler 8 and the exterior laminate material 7 being bonded to each other at all contact portions, the filler 8 being disposed so as to cover at least the side surfaces of the battery element 2, the exterior laminate material 7 being configured so as to expand in the stacking direction due to being pressed by the expanding battery element 2 during charging and to contract in a direction perpendicular to the stacking direction, and the filler 8 being configured so as to be pressed against the precipitated metallic lithium 5-2 by the contracting exterior laminate material 7 during charging.

[0067] According to the above-described configuration, the filler 8 is pressed against the deposited metallic lithium 5-2 during charging, thereby preventing the formation of spaces on the sides of the metallic lithium 5-2.

[0068] (Appendix 2) The secondary battery according to Appendix 1, further comprising a current collecting foil 6 connected to the battery element 2, the current collecting foil 6 comprising a battery element connection portion 10-1 connected to the battery element 2 and an extension portion 10-2 extending laterally from the battery element connection portion 10-1, and the filler 8 further adhered to the extension portion 10-2.

[0069] According to the above-described configuration, even if metallic lithium 5-2 is precipitated, the filler 8 and the extension portion 10-2 are not separated, so that the formation of spaces on the sides of the metallic lithium 5-2 is prevented.

[0070] (Supplementary Note 3) The secondary battery according to Supplementary Note 2, wherein the adhesive strength between the filler 8 and the extending portion 10-2 is smaller than the adhesive strength between the filler 8 and the exterior laminate material 7.

[0071] According to the above-described configuration, the filler 8 is prevented from being pulled by the extension portion 10-2 and peeling off from the exterior laminate material 7.

[0072] (Supplementary Note 4) The secondary battery according to any one of Supplementary Notes 1 to 3, wherein the filler 8 is configured so as not to adhere to the deposited metallic lithium 5-2.

[0073] According to the above-described configuration, the filler 8 is less likely to be pulled by the decreasing amount of metallic lithium 5-2 during discharge, which prevents the filler 8 from entering between the negative electrode layer 5 and the negative electrode current collector foil 6-2.

[0074] (Appendix 5) The secondary battery according to any one of Appendices 1 to 4, wherein no filler 8 is disposed between the battery element 2 and the exterior laminate material 7 on both sides of the battery element 2 in the stacking direction.

[0075] With the above-described configuration, the force applied from the battery element 2 to the exterior laminate material 7 in the stacking direction during charging is less likely to be released to the side. This makes it easier for a contraction force to be generated in the exterior laminate material 7 in a direction perpendicular to the stacking direction, making it easier for the filler material 8 to be pressed against the deposited metallic lithium 5-2. As a result, it is possible to more reliably prevent the formation of spaces to the sides of the deposited metallic lithium 5-2.

[0076] (Supplementary Note 6) The secondary battery according to any one of Supplementary Notes 1 to 5, wherein in a charged state, the side surface of the exterior laminate material 7 is a curved surface that bulges outward.

[0077] With the above-described configuration, the contraction force generated in the exterior laminate material 7 during charging tends to be directed inward in the stacking direction, so that the filler material 8 is more reliably pressed against the side surface of the battery element 2, more reliably preventing the formation of voids.

[0078] (Supplementary Note 7) The secondary battery according to any one of Supplementary Notes 1 to 6, wherein the filler 8 is further bonded to the positive electrode layer 4.

[0079] According to the above-described configuration, the formation of a space between the filler 8 and the positive electrode layer 4 is prevented.

[0080] (Appendix 8) The secondary battery according to any one of Appendices 1 to 7, further comprising: a negative electrode current collector foil (6-2) disposed on the negative electrode layer (5); the negative electrode layer (5) has a negative electrode intermediate layer (5-1); the battery element (2) is configured such that metallic lithium (5-2) is deposited between the negative electrode intermediate layer (5-1) and the negative electrode current collector foil (6-2); and the filler (8) is further bonded to the negative electrode intermediate layer (5-1).

[0081] According to the above-described configuration, the formation of a space between the filler 8 and the negative electrode intermediate layer 5-1 is prevented.

[0082] (Supplementary Note 9) The secondary battery according to any one of Supplementary Notes 1 to 8, wherein the filler 8 is further adhered to the solid electrolyte layer 3.

[0083] According to the above-described configuration, the formation of a space between the filler 8 and the solid electrolyte layer 3 is prevented.

Claims

1. A secondary battery comprising: a battery element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer, the positive electrode layer and the negative electrode layer being arranged to sandwich the solid electrolyte layer in the stacking direction; an exterior laminate material that houses the battery element; and a resin filler material that is filled in the exterior laminate material so as to fill a space formed between the battery element and the interior of the exterior laminate material, wherein the battery element is configured so that metallic lithium is deposited on the negative electrode layer during charging, the filler material and the exterior laminate material are bonded at all contact points, the filler material is arranged so as to cover at least the side surfaces of the battery element, the exterior laminate material is configured so that during charging, the exterior laminate material expands in the stacking direction due to being pressed by the expanding battery element and contracts in a direction perpendicular to the stacking direction, and the filler material is configured so as to be pressed against the deposited metallic lithium by the contracting exterior laminate material during charging.

2. A secondary battery according to claim 1, further comprising a current collecting foil connected to the battery element, the current collecting foil comprising a battery element connecting portion connected to the battery element and an extension portion extending laterally from the battery element connecting portion, and the filler material further being adhered to the extension portion.

3. A secondary battery according to claim 2, wherein the adhesive strength between the filler and the extension is smaller than the adhesive strength between the filler and the exterior laminate material.

4. A secondary battery according to claim 1 or 2, wherein the filler is configured so as not to adhere to the deposited metallic lithium.

5. A secondary battery according to claim 1 or 2, wherein the filler is not disposed between the battery element and the exterior laminate material on both sides of the battery element in the stacking direction.

6. A secondary battery according to claim 1 or 2, wherein, in a charged state, the side surfaces of the exterior laminate material are curved surfaces that bulge outward.

7. A secondary battery according to claim 1 or 2, wherein the filler is further adhered to the positive electrode layer.

8. A secondary battery according to claim 1, comprising a negative electrode current collector foil disposed on the negative electrode layer, the negative electrode layer having a negative electrode intermediate layer, the battery element being configured so that the metallic lithium is deposited between the negative electrode intermediate layer and the negative electrode current collector foil, and the filler material being further adhered to the negative electrode intermediate layer.

9. A secondary battery according to claim 1 or 2, wherein the filler is further adhered to the solid electrolyte layer.

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