Cell structure and solid-state battery

Abstract

This cell structure (1) includes: a cell laminate (10) provided with a conductive extension part (12); an exterior body (20) that is formed while maintaining airtightness of an internal space (S) and is also formed so as to be plastically deformable; and an internal cover (30) including a first internal cover split body (31) and a second internal cover split body (32), which are capable of being split in a lamination direction (D1). The first internal cover split body (31) is formed with a first excess length part (33a) that protrudes outward, and the second internal cover split body (32) is formed with a second excess length part (33b) that protrudes outward. The first excess length part (33a) is fixed in contact with the second excess length part (33b), or is fixed to the second excess length part (33b) with the conductive extension part (12) interposed therebetween.

Description

Cell structure and solid-state battery

[0001] The present invention relates to a cell structure and a solid-state battery.

[0002] Patent Document 1 discloses a solid-state battery including a battery cell, a flexible exterior, a first housing portion, and a second housing portion. The first housing portion and the second housing portion support the battery cell. The flexible exterior houses the first housing portion and the second housing portion on which the battery cell is supported.

[0003] Japanese Patent Application Laid-Open No. 2019-57436

[0004] In the device disclosed in Patent Document 1, when the battery cell expands, a load is applied to the first housing portion and the second housing portion. As a result, the exterior may undergo plastic deformation, and there is room for improvement in the structure of the solid-state battery.

[0005] The present invention has been made under the above circumstances, and an object thereof is to provide a cell structure and a solid-state battery capable of suppressing plastic deformation of the exterior as the cell laminate expands and contracts.

[0006] To achieve the above object, the cell structure according to the present invention has a first electrode, a second electrode, and an electrolyte disposed between these electrodes, and a battery cell capable of charging power is stacked in multiple layers. A cell laminate provided with a conductive extension portion drawn out from the battery cell to the outside, an internal space in which the cell laminate is housed is provided, and the internal space is formed while maintaining airtightness and is formed to be deformable. An exterior, an internal cover installed inside the exterior and covering the cell laminate, and having a first internal cover split body and a second internal cover split body that can be split at least in the stacking direction in which the cell laminate is stacked. A first extra length portion protruding outward is formed in the first internal cover split body, and a second extra length portion protruding outward is formed in the second internal cover split body. The first extra length portion is fixed in contact with the second extra length portion, or is fixed with the conductive extension portion sandwiched between the second extra length portion.

[0007] According to the present invention, the first excess portion is fixed in direct contact with the second excess portion, or fixed to the second excess portion with a conductive extension in between. Therefore, the first internal cover segment can be stably fixed to the second internal cover segment. As a result, stress generated due to the expansion and contraction of the cell laminate is blocked by the internal cover and its transmission to the outer casing can be suppressed. Consequently, plastic deformation of the outer casing due to the expansion and contraction of the cell laminate can be suppressed.

[0008] This is a plan view of a cell structure according to Embodiment 1 of the present invention. This is an exploded perspective view of a cell structure according to Embodiment 1. This is a cross-sectional view taken along line III-III in Figure 1. This is a cross-sectional view of a cell structure after expansion of a cell laminate. This is an exploded cross-sectional view of a cell structure according to Embodiment 1. This is a cross-sectional view taken along line VI-VI in Figure 1. This is a cross-sectional view taken along line VII-VII in Figure 1. This is a cross-sectional view for explaining the deformation of the outer casing and inner cover of a cell structure after expansion of a cell laminate. This is a cross-sectional view for explaining the method of forming the excess length forming portion of a cell structure according to Embodiment 1. This is a cross-sectional view of a cell structure according to a comparative example. This is a simplified cross-sectional view (1) for explaining the effects of a cell structure according to Embodiment 1. This is a simplified cross-sectional view (2) for explaining the effects of a cell structure according to Embodiment 1. This is a simplified cross-sectional view (3) for explaining the effects of a cell structure according to Embodiment 1. This is a simplified cross-sectional view (4) for explaining the effects of a cell structure according to Embodiment 1. This is a simplified cross-sectional view (5) for explaining the effects of a cell structure according to Embodiment 1. This is a cross-sectional view of a cell structure according to Embodiment 2. This is a cross-sectional view for explaining the operation of a cell structure according to Embodiment 2. This is a cross-sectional view of the cell structure according to Embodiment 3. This is a cross-sectional view of the cell structure according to Embodiment 4. This is a cross-sectional view of the cell structure according to Embodiment 5. This is a cross-sectional view of the cell structure according to Embodiment 6.

[0009] Embodiment 1. Hereinafter, a cell structure 1 according to Embodiment 1 and a solid-state battery equipped therewith will be described with reference to the figures. For ease of understanding, mutually orthogonal XYZ coordinates will be set and referred to as appropriate. As shown in Figure 3, the Z axis direction of the XYZ coordinates is the same direction as the stacking direction D1 in which the battery cells 11 of the cell structure 1 are stacked. Also, the XY plane is the same plane as the plane orthogonal to the stacking direction D1. In each figure, the same reference numerals indicate the same or corresponding parts.

[0010] A solid-state battery is a battery having a plurality of battery cells 11, each of which a solid electrolyte is placed between an anode (first electrode) and a cathode (second electrode). Solid-state batteries are used as automotive batteries, replacing conventional batteries such as lithium-ion secondary batteries that use organic electrolytes. The solid-state battery comprises a cell structure 1 as shown in Figures 1 and 2. The cell structure 1 is rectangular and plate-shaped, having a long side 1a on the +Y side, a long side 1b on the -Y side, a short side 1c on the +X side, and a short side 1d on the -X side when viewed from the +Z side. In this embodiment 1, the cell structure 1 comprises, for example, a cell stack 10, an outer casing 20, and an inner cover 30. In addition to the cell stack 10, the outer casing 20, and the inner cover 30, the cell structure 1 also comprises an excess length forming portion 33 that surrounds the entire circumference of the cell stack 10, as shown in Figures 3, 4, and 5.

[0011] The cell stack 10 has a plurality of battery cells 11 and conductive extensions 12. In Figures 3, 6, and 7, the dashed lines show the shapes of the outer casing 20 and inner cover 30 deformed by the expansion of the cell stack 10. In this embodiment 1, when the charged cell stack 10 expands, the outer casing 20 undergoes elastic deformation without deforming to the plastic deformation range, as shown by the dashed lines. The inner cover 30 maintains its shape. Then, as shown by the solid lines, when the cell stack 10 is discharged and contracts, the outer casing 20 elastically recovers and returns to its original shape.

[0012] The battery cell 11 is a unit cell that constitutes the cell stack 10 and is formed by stacking multiple layers. The battery cell 11 is also formed to be rechargeable. When the battery cell 11 is charged, it expands in the stacking direction D1. In this embodiment 1, when the cell stack 10 having the battery cell 11 is charged, its thickness changes from t0 before expansion to t1 after expansion. The maximum expansion length L2 of the cell stack 10 in the stacking direction D1 is given by t1 - t0 (L2 = t1 - t0). t0 is the thickness when the charge level is 0%, and t1 is the thickness when the charge level is 100%.

[0013] The conductive extensions 12 are drawn out from each of the battery cells 11. The foils (tabs) drawn out from each of the battery cells 11 are then aggregated and drawn out to the outside of the casing 20. The conductive extensions 12 are made of a conductive material. Specifically, the conductive extensions 12 are current collector foils made by overlapping foils. For example, aluminum foil is used for the positive electrode and copper foil is used for the negative electrode of the conductive extension 12. The conductive extensions 12 supply power for charging the battery cells 11 and output power from the battery to the outside. In this embodiment 1, one of the positive and negative electrodes of the conductive extension 12 is drawn out in the +X direction, and the other of the positive and negative electrodes is drawn out in the opposite -X direction. However, it is not limited to this. Both the positive and negative electrodes may be drawn out in either the -X direction or the +X direction. Furthermore, the conductive extension portion 12 may have the other of the positive and negative electrodes drawn out in the -X direction, and one of the positive and negative electrodes drawn out in the +X direction. In addition, the conductive extension portion 12 may have tab leads welded to the current collector foil.

[0014] The outer casing is a laminated material that maintains internal airtightness. The outer casing 20 is formed in a rectangular shape, having a long side on the +Y side, a long side on the -Y side, a short side on the +X side, and a short side on the -X side when viewed from the +Z side. The outer casing 20 is also provided with an internal space S for housing the cell laminate 10. The outer casing 20 is formed to be deformable in order to absorb the expansion of the cell laminate 10 so that cracks and other damage do not occur due to the expansion of the cell laminate 10. The outer casing 20 is formed from a material that is capable of elastic and plastic deformation, for example. Specifically, the materials that form the outer casing 20 are, for example, aluminum and resin. For example, the outer casing 20 is formed from an aluminum layer and resin layers provided on its outer and inner surfaces. The outer casing 20 is also formed while maintaining airtightness of the internal space S to the outside.

[0015] The internal space S is sealed with an inert gas or an inert liquid, or maintained under vacuum by vacuuming, to prevent the materials forming the cell laminate 10 from reacting with the surrounding air.

[0016] The outer casing 20 has at least a first outer casing segment 21 and a second outer casing segment 22 that can be divided in the stacking direction D1. In this embodiment 1, the outer casing 20 is illustrated as having two first outer casing segments 21 and a second outer casing segment 22. However, it is not limited to this. The outer casing 20 may have three or more segments. Also, the direction in which the first outer casing segment 21 and the second outer casing segment 22 are divided is not limited to the stacking direction D1. The direction in which the first outer casing segment 21 and the second outer casing segment 22 are divided may be a direction other than the stacking direction D1.

[0017] The first outer casing segment 21 has a first projection 25a formed on it. The first projection 25a is formed to protrude outward from the cell structure 1. The first projection 25a is formed to protrude outward from all sides of the outer casing 20: the long side on the +Y side, the long side on the -Y side, the short side on the +X side, and the short side on the -X side.

[0018] The second outer casing segment 22 has a second projection 25b formed on it. The second projection 25b is formed to protrude outward from the cell structure 1. The second projection 25b is formed to protrude outward from all sides of the outer casing 20: the long side on the +Y side, the long side on the -Y side, the short side on the +X side, and the short side on the -X side.

[0019] Furthermore, the exterior body 20 has an excess covering portion 23, a side wall 24 (side wall covering portion), a ceiling wall 26, and a bottom wall 27. The angle between the excess covering portion 23 and the side wall 24 is a right angle (90°) when viewed in the Y-axis direction. The angle between the side wall 24 and the ceiling wall 26 is a right angle (90°) when viewed in the Y-axis direction. The angle between the side wall 24 and the bottom wall 27 is a right angle (90°) when viewed in the Y-axis direction.

[0020] The excess coverage portion 23 covers the excess length forming portion 33 from its tip to its base. The excess coverage portion 23 is formed in contact with the excess length forming portion 33 without any gaps. However, it is not limited to this, and the excess coverage portion 23 may have a gap with respect to the excess length forming portion 33.

[0021] The side wall 24 covers from the base end of the excess length forming portion 33 to the end portion 34a of the side wall 34 of the inner cover 30. The side wall 24 is formed in contact with the side wall 34 without any gaps. However, it is not limited to this, and the side wall 24 may have a gap with respect to the side wall 34.

[0022] The ceiling wall 26 covers the ceiling wall portion of the internal cover 30 on the +Z side. The ceiling wall 26 is formed to be in contact with the ceiling wall portion of the internal cover 30 on the +Z side without any gaps. However, it is not limited to this, and the ceiling wall 26 may have a gap with respect to the ceiling wall portion of the internal cover 30 on the +Z side.

[0023] The bottom wall 27 covers the bottom wall portion of the inner cover 30 on the -Z side. The bottom wall 27 is formed to be in contact with the bottom wall portion of the inner cover 30 on the -Z side without any gaps. However, it is not limited to this, and the bottom wall 27 may have a gap with respect to the bottom wall portion of the inner cover 30 on the -Z side.

[0024] Furthermore, a sealing portion 25 is formed in the outer casing 20. The sealing portion 25 is located near the outside of the excess length forming portion 33. Therefore, displacement of the excess length forming portion 33 outward can be suppressed. The sealing portion 25 is formed by the first protrusion 25a being in contact with and fixed to the second protrusion 25b, or by the conductive extension portion 12 being sandwiched between the first protrusion 25a and the second protrusion 25b. Specifically, as shown in Figures 3 and 6, on the +X and -X sides of the cell structure 1, the first protrusion 25a is fixed to the second protrusion 25b by the conductive extension portion 12. As shown in Figure 7, on the +Y and -Y sides of the cell structure 1, the first protrusion 25a is in direct contact with and fixed to the second protrusion 25b.

[0025] The internal cover 30 is a component that suppresses deformation of the outer casing and absorbs the displacement of the battery together with the outer casing. As shown in Figure 2, the internal cover 30 is formed in a rectangular shape, having a long side on the +Y side, a long side on the -Y side, a short side on the +X side, and a short side on the -X side when viewed from the +Z side. As shown in Figures 3, 6, and 7, the internal cover 30 is a case installed inside the outer casing 20. This internal cover 30 covers the cell stack 10. The internal cover 30 is formed to be deformable in order to absorb the expansion of the cell stack 10 so that cracks and the like do not occur due to the expansion of the cell stack 10. In addition, the strength of the internal cover 30 is formed to be higher than the strength of the outer casing 20. Specifically, the internal cover 30 is formed from a material that is capable of elastic and plastic deformation, for example. The material that forms the internal cover 30 is, for example, an aluminum plate in which both sides of the aluminum are coated with resin. Furthermore, the internal cover 30 is installed in close contact with the inside of the outer casing 20 before the battery cell 11 expands. This internal cover 30 has a first internal cover segment 31 and a second internal cover segment 32 that can be divided in the stacking direction D1.

[0026] The first internal cover segment 31 has a first excess length portion 33a formed thereon. The first excess length portion 33a is formed to protrude outward from the first internal cover segment 31 to the outside of the cell structure 1. The first excess length portion 33a is formed to protrude outward from all sides of the internal cover 30: the long side on the +Y side, the long side on the -Y side, the short side on the +X side, and the short side on the -X side.

[0027] The second internal cover segment 32 has a second excess portion 33b formed thereon. The second excess portion 33b is formed to protrude from the second internal cover segment 32 to the outside of the cell structure 1. The second excess portion 33b is formed to protrude from all sides of the internal cover 30: the long side on the +Y side, the long side on the -Y side, the short side on the +X side, and the short side on the -X side.

[0028] The first excess length portion 33a described above forms the excess length portion 33 by being fixed in contact with the second excess length portion 33b, or by being fixed with respect to the second excess length portion 33b with respect to the conductive extension portion 12. Specifically, on the short sides of the cell structure 1 on the +X and -X sides, as shown in Figures 3 and 6, the first excess length portion 33a is fixed with respect to the second excess length portion 33b with respect to the conductive extension portion 12. As shown in Figure 7, on the long sides of the cell structure 1 on the +Y and -Y sides, the first excess length portion 33a is fixed in direct contact with the second excess length portion 33b.

[0029] Furthermore, as shown in Figures 3, 4, and 5, the internal cover 30 is formed in a rectangular parallelepiped shape having side walls 34 parallel to the stacking direction D1, a top wall 36, and a bottom wall 37. In this embodiment 1, an excess length forming portion 33 protrudes from the side wall 34 of the internal cover 30. The angle between the excess length forming portion 33 and the side wall 34 is a right angle (90°) when viewed in the Y-axis direction. The angle between the side wall 34 and the top wall 36 is a right angle (90°) when viewed in the Y-axis direction. The angle between the side wall 34 and the bottom wall 37 is a right angle (90°) when viewed in the Y-axis direction.

[0030] The excess length forming portion 33 is formed to protrude in an intersecting direction (including the X-axis and Y-axis directions) that intersects the stacking direction D1. As a result, the excess length forming portion 33 is formed in a flange-like shape that extends in the intersecting direction from the entire circumference of the cell structure 1. Furthermore, the excess length forming portion 33 is formed together with the excess length covering portion 23 by being pressed from at least one of the two sides of the stacking direction D1.

[0031] As shown in Figure 8, in the inner cover 30, the length of the side wall 34 in the stacking direction D1 before the expansion of the cell laminate 10 is denoted as a, and the amount of protrusion of the excess length forming portion 33 is denoted as b. Then, the length from the outer end of the side wall 24 in the stacking direction D1 of the outer body 20, which is maximally deformed (thickness t1) by the expansion of the cell laminate 10, to the base end of the sealing portion 25 (the position corresponding to the tip of the excess length forming portion 33 or excess length covering portion 23 before expansion) is denoted as c. Since the length a is determined by the number of cells in the cell laminate 10, the length c is adjusted by the amount of protrusion b. The inner cover 30 is formed so that the length a + b is greater than the length c ((a + b) > c). In the outer body 20, the sum of the length of the side wall 24 in the stacking direction D1 before the expansion of the cell laminate 10 and the amount of protrusion of the excess length covering portion 23 follows the same principle.

[0032] Furthermore, in this embodiment 1, an inclined surface SF is formed on the excess length covering portion 23 and side wall 24 of the outer casing 20 that have been deformed by the expansion of the cell laminate 10. For example, the inclined surface SF is inclined with respect to the direction in which the excess length forming portion 33 protrudes. In this embodiment 1, the length of the inclined surface SF is length c.

[0033] When forming the cell structure 1 in this manner, for example, as shown in Figure 9, it is formed by pressing a tool D from at least one of the two sides in the stacking direction D1. When the tool D is pressed, a part of the outer casing 20 and the inner cover 30 deforms. As a result, the excess length forming portion 33 is formed together with the excess length covering portion 23. However, it is not limited to this. The excess length forming portion 33 and the excess length covering portion 23 may be formed by methods other than the pressing method.

[0034] As described above, in this embodiment 1, as shown in Figures 3, 6, and 7, the first excess portion 33a is fixed in contact with the second excess portion 33b, or fixed with respect to the second excess portion 33b with the conductive extension portion 12 in between. This allows the first internal cover segment 31 to be stably fixed to the second internal cover segment 32.

[0035] For example, as shown in Figure 10, in the case of a cell structure 1A in which no excess length forming portion 33 (first excess length portion 33a and second excess length portion 33b) is formed on the internal cover 30, the fixing of the first internal cover portion 31 to the second internal cover portion 32 becomes unstable. In that case, for example, the stress F1 generated due to the expansion of the cell laminate 10 is not sufficiently blocked by the internal cover 30 and is more easily transmitted to the outer casing 20 as shown by arrows F2 and F3. As a result, the outer casing 20 becomes more susceptible to plastic deformation due to the expansion and contraction of the cell laminate 10.

[0036] However, according to this embodiment 1, as shown in Figures 3, 6, and 7, the first internal cover segment 31 can be stably fixed to the second internal cover segment 32. Therefore, the stress generated due to the expansion and contraction of the cell laminate 10 is blocked by the internal cover 30 and is suppressed from being transmitted to the outer casing 20. As a result, plastic deformation of the outer casing 20 due to the expansion and contraction of the cell laminate 10 can be suppressed.

[0037] Furthermore, the cell structure 1 includes an internal cover 30. This makes it easier to assemble the outer casing 20 to the cell stack 10 and the internal cover 30 while forming the outer casing 20 into any desired shape during assembly of the cell structure 1. It also makes it easier to assemble the outer casing 20 to the cell stack 10 and the internal cover 30 without interfering with the cell stack 10.

[0038] Furthermore, in this embodiment 1, as shown in Figures 3, 5, and 6, the excess length forming portion 33 is formed to surround the entire circumference of the cell laminate 10. This allows the first excess length portion 33a to be fixed to the second excess length portion 33b even more stably. The internal cover 30 is installed inside the outer casing 20 and covers the cell laminate 10, so it can further suppress plastic deformation of the outer casing 20 due to the expansion and contraction of the cell laminate 10.

[0039] Furthermore, in this embodiment 1, a sealing portion 25 is formed on the outer casing 20. Therefore, in this embodiment 1, the displacement of the inner cover in a direction parallel to the XY plane is suppressed (prevention of slippage) as the cell laminate 10 expands and contracts, and the airtightness of the internal space S of the outer casing 20 can be improved while suppressing plastic deformation of the outer casing 20.

[0040] Furthermore, in this embodiment 1, as shown in Figure 11A, the length a + b obtained by adding the protrusion amount b of the excess length forming portion 33 to the length a of the side wall 34 in the stacking direction D1 of the internal cover 30 is greater than the length c ((a + b) > c). Therefore, as shown in Figures 11B and 11C, even if the cell stack 10 expands, the length c(n) (length c(n): length that is displaced due to expansion) does not extend beyond the predetermined length a + b. For example, as shown in Figures 11D and 11E, the length c(n) of the excess length forming portion 33 and the side wall 34 is not equal to the length a+b ((a'+b')=c(n), where length a' is the length of the extended side wall 34 and protrusion amount b' is the protrusion amount of the extended excess length forming portion 33), nor is the length c(n) greater than the length a+b ((a''+b'')<c(n), where length a'' is the length of the extended side wall 34 and protrusion amount b'' is the protrusion amount of the extended excess length forming portion 33). As a result, for example, stress is not applied from the inner cover 30 to the outer casing 20, and tensile force is not applied to the outer casing 20. This makes it possible to suppress plastic deformation of the outer casing 20 in conjunction with the expansion and contraction of the cell laminate 10.

[0041] Embodiment 2. In the above Embodiment 1, as shown in FIGS. 3, 4, 6, and 7, when the side wall 24 of the exterior body 20 is deformed as the cell laminate 10 expands, it moves away from the side wall 34 of the inner cover 30, and a gap G is formed. However, it is not limited to this. Hereinafter, the cell structure 2 according to Embodiment 2 that can suppress the generation of the gap G between the exterior body 20 and the inner cover 30 will be described with reference to FIGS. 12 and 13. In FIG. 13, the two-dot chain line indicates the shapes of the exterior body 20 and the inner cover 30 deformed by the expansion of the cell laminate 10. Also, in this Embodiment 2, when the charged cell laminate 10 expands in the cell structure 2 including the cell laminate 10, the exterior body 20 elastically deforms without deforming to the plastic deformation range as shown by the two-dot chain line. The exterior body 20 deforms following the deformation of the inner cover 30. Then, as shown by the solid line, when the cell laminate 10 is discharged and contracts, the exterior body 20 and the inner cover 30 elastically recover and return to their original shapes.

[0042] Similar to the cell structure 1, as shown in FIG. 12, the cell structure 2 includes a cell laminate 10, an exterior body 20, an inner cover 30, and an extra-length forming portion 33. The exterior body 20 has an extra-length covering portion 23.

[0043] In this cell structure 2, the extra-length forming portion 33 is formed by pressing the tool D from at least one of both sides in the lamination direction D1 together with the extra-length covering portion 23. The extra-length forming portion 33 is formed so as to be able to elastically recover more than the extra-length covering portion 23. For this reason, the extra-length forming portion 33 contacts and is installed on the inner surface of the extra-length covering portion 23 by elastically recovering more than the extra-length covering portion 23 due to the reaction force based on the pressing force at the time of forming the extra-length forming portion 33. <

[0044] Furthermore, as shown in FIG. 13, the extra-length forming portion 33 is formed such that the pressing length L1 in the lamination direction D1 at the time of its formation is greater than 1 / 2 of the maximum expansion length L2 in the lamination direction D1 that occurs when the cell laminate 10 expands (L1 > L2 × 1 / 2).

[0045] As described above, in this second embodiment, the excess length forming portion 33 recovers elastically more than the excess length covering portion 23 due to the reaction force based on the pressing force applied during the formation of the excess length forming portion 33. For this reason, the excess length forming portion 33 is installed in contact with the inner surface of the excess length covering portion 23. This makes it possible to suppress the formation of a gap G between the inner cover 30 and the outer casing 20, regardless of whether the cell laminate 10 has expanded or not. Consequently, the inner cover 30 can protect the outer casing 20 from the expansion of the cell laminate 10. As a result, it is possible to suppress plastic deformation of the outer casing 20 in conjunction with the expansion of the cell laminate 10.

[0046] Furthermore, in this second embodiment, even if the cell laminate 10 expands, the outer end of the excess length forming portion 33 of the inner cover 30 remains in contact with the conductive extension portion 12. Therefore, as shown in the enlarged view of Figure 4, it is possible to prevent the outer end of the excess length forming portion 33 from separating from the conductive extension portion 12 and forming a gap G2. In addition, the negative pressure P1 in the internal space S prevents a part of the outer casing 20 from entering the gap G2.

[0047] Furthermore, in this second embodiment, the pressing length L1 is formed to be greater than half of the maximum expansion length L2 in the stacking direction D1 that occurs when the cell laminate 10 expands (L1 > L2 × 1 / 2). Since the pressing length of one side (33a, 33b) of the excess length forming portion 33 is longer than the expansion length of the other side (pressing > tension), the effect of suppressing the formation of a gap G between the inner cover 30 and the outer casing 20 can be further enhanced, regardless of whether the cell laminate 10 has expanded or not. Consequently, the inner cover 30 can protect the outer casing 20 from the expansion of the cell laminate 10. As a result, plastic deformation of the outer casing 20 due to the expansion of the cell laminate 10 can be suppressed.

[0048] Embodiment 3. In the above Embodiment 1, as shown in FIGS. 3, 6, and 7, the angle formed by the excess length forming portion 33 of the inner cover 30 and the side wall 34 is a right angle (90°) when viewed in the Y-axis direction. However, it is not limited to this. In the inner cover 30, the connection portion 34b between the excess length forming portion 33 and the side wall 34 does not have to be formed at a right angle. Hereinafter, the cell structure 3 according to Embodiment 3 in which the connection portion 34b between the excess length forming portion 33 and the side wall 34 is not formed at a right angle will be described with reference to FIG. 14. In FIG. 14, the two-dot chain line indicates the shapes of the exterior body 20 and the inner cover 30 deformed by the expansion of the cell laminate 10. Also, in this Embodiment 3, when the charged cell laminate 10 expands, the exterior body 20 of the cell structure 3 having the cell laminate 10 elastically deforms without being deformed to the plastic deformation range as indicated by the two-dot chain line. The exterior body 20 deforms following the deformation of the inner cover 30. Then, as indicated by the solid line, when the cell laminate 10 is discharged and contracts, the exterior body 20 and the inner cover 30 elastically recover and return to their original shapes.

[0049] Similar to the cell structure 1, as shown in FIG. 14, the cell structure 3 includes a cell laminate 10, an exterior body 20, an inner cover 30, and an excess length forming portion 33. The exterior body 20 has an excess length covering portion 23.

[0050] In this cell structure 3, a curved portion 38 is formed at the connection point between the excess length forming portion 33 of the inner cover 30 and the side wall 34, with a constant radius of curvature R. The strain on the surface of the curved portion 38 is formed to be below the plastic strain or below the yield point. Similarly, a curved portion (not indicated) is formed at the connection point between the excess length covering portion 23 of the outer casing 20 and the side wall 24, with a constant radius of curvature R. The strain on the surface of this curved portion (not indicated) is formed to be below the plastic strain or below the yield point. Because the curved portion 38 is formed in the inner cover 30, even if the cell laminate 10 expands, the connection point between the excess length forming portion 33 and the side wall 34 deforms in the elastic deformation range and does not deform beyond the yield point. As a result, deformation does not occur at the connection point between the excess length forming portion 33 and the side wall 34, and consequently, the inner cover 30 as a whole becomes less susceptible to deformation. Consequently, the internal cover 30 protects the outer casing 20 from the expansion of the cell laminate 10, thereby suppressing plastic deformation of the outer casing 20 that occurs as the cell laminate 10 expands.

[0051] Although the embodiments described above have been explained, the present invention is not limited to the embodiments described above.

[0052] Embodiment 4. For example, in this embodiment, as shown in Figures 3, 5, and 6, the first protrusion 25a of the sealing portion 25 is fixed to the second protrusion 25b with the conductive extension 12 in between. Also, as shown in Figure 7, the first protrusion 25a is fixed in contact with the second protrusion 25b. However, it is not limited to this. As shown in the cell structure 4 in Figure 15, the sealing portion 25 may be provided with a sealing layer 25c. In Figure 15, the dashed line shows the shape of the outer casing 20 and the inner cover 30 deformed by the expansion of the cell laminate 10. Also, in this embodiment 4, when the charged cell laminate 10 expands, the cell structure 4 equipped with the cell laminate 10 undergoes elastic deformation without deforming to the plastic deformation range, as shown by the dashed line. The outer casing 20 follows the deformation of the inner cover 30. Then, as shown by the solid line, when the cell laminate 10 is discharged and shrinks, the outer casing 20 and the inner cover 30 elastically recover and return to their original shape.

[0053] For example, the sealing layer 25c is made of a non-conductive material. Specifically, the sealing layer 25c is made of resin. The sealing layer 25c seals the space between the first protrusion 25a and the conductive extension 12, and also seals the space between the second protrusion 25b and the conductive extension 12. Furthermore, the sealing layer 25c seals the space between the first protrusion 25a and the second protrusion 25b. The first protrusion 25a is fixed to the second protrusion 25b with the conductive extension 12 and the sealing layer 25c sandwiched between them. Alternatively, the first protrusion 25a is fixed to the second protrusion 25b with the sealing layer 25c sandwiched between them. The excess length forming portion 33 of the internal cover 30 is provided so that its tip on the protruding direction side is in contact with the sealing layer 25c.

[0054] In the cell structure 4, even if the cell laminate 10 expands and the excess length forming portion 33 of the internal cover 30 deforms, the tip of the excess length forming portion 33 on the protruding direction side contacts the sealing layer 25c, suppressing deformation in the X direction (protruding direction). Consequently, the internal cover 30 protects the outer casing 20 from the expansion of the cell laminate 10, thereby suppressing plastic deformation of the outer casing 20 that occurs with the expansion of the cell laminate 10.

[0055] Embodiment 5. In Embodiment 4 described above, the tip of the excess length forming portion 33 protrudes toward the sealing layer 25c. However, it is not limited to this. As shown in the cell structure 5 in Figure 16, the tip of the excess length forming portion 33 may have a bent portion 39 that is bent toward the opposite side of the protruding direction. In this case, the bent portion 39 is provided in contact with the sealing layer 25c. The amount of strain on the surface of the bent portion 39 is formed to be less than or equal to the plastic strain or below the yield point. In Figure 16, the dashed line shows the shape of the outer casing 20 and the inner cover 30 deformed by the expansion of the cell laminate 10. In Embodiment 5, when the charged cell laminate 10 expands, the cell structure 5 equipped with the cell laminate 10 undergoes elastic deformation without deforming to the plastic deformation region, as shown by the dashed line. The outer casing 20 deforms in accordance with the deformation of the inner cover 30. Then, as shown by the solid line, when the cell laminate 10 is discharged and shrinks, the outer casing 20 and the inner cover 30 elastically recover and return to their original shape.

[0056] In the cell structure 5, when the cell laminate 10 expands and the excess length forming portion 33 of the internal cover 30 deforms, the bent portion 39 formed at the tip of the excess length forming portion 33 on the protruding side comes into contact with the sealing layer 25c. Since the pressure on the sealing layer 25c is distributed, damage to the sealing layer 25c can be suppressed.

[0057] Embodiment 6. Alternatively, as shown in Figure 17, the cell structure 6 may have bulging portions 29 and 39-2 formed on the outer casing 20 and the inner cover 30, which bulge outwards in the stacking direction D1. The bulging portion 29 bulges away from the end of the cell stack 10 in the stacking direction D1. The bulging portion 39-2 of the inner cover 30 and the bulging portion 29 of the outer casing 20 are formed to bulge inwards from the upper part of the side surface of the cell stack 10 in an oblique outward direction.

[0058] In the cell structure 6, even if the cell laminate 10 expands and the excess length forming portion 33 of the internal cover 30 deforms, the end of the cell laminate 10 in the stacking direction D1 contacts the inner surface of the internal cover 30, thereby preventing damage to the cell laminate 10.

[0059] Other embodiments. In the above embodiment, the cell stack 10 is exemplified as having a plurality of battery cells 11, as shown in Figure 3. However, it is not limited to this. The cell stack 10 may have only one battery cell 11.

[0060] Furthermore, in the above embodiment, the side wall 34 of the internal cover 30 is provided upright, as shown in Figure 3. However, it is not limited to this. The side wall 34 of the internal cover 30 may also be provided at an angle.

[0061] Furthermore, in the above embodiment, the battery comprising the cell structure 1 is a solid-state battery. However, the solid-state battery may use an organic solid electrolyte or a liquid electrolyte in part. Alternatively, it may use an inorganic solid electrolyte.

[0062] Furthermore, in the above embodiment, the material forming the exterior body 20 is, for example, aluminum. However, it is not limited to this. The material forming the exterior body 20 may be something other than aluminum.

[0063] Furthermore, in the above embodiment, the internal cover 30 is exemplified as having two first internal cover segments 31 and a second internal cover segment 32. However, it is not limited to this. The internal cover 30 may have three or more segments. Also, the direction in which the first internal cover segment 31 and the second internal cover segment 32 are separated is not limited to the stacking direction D1. The direction in which the first internal cover segment 31 and the second internal cover segment 32 are separated may be a direction other than the stacking direction D1.

[0064] Furthermore, in the above embodiment, the material forming the internal cover 30 is, for example, an aluminum plate with both sides coated with resin. However, it is not limited to this. The material forming the internal cover 30 may be something other than an aluminum plate with both sides coated with resin. The material of the internal cover 30 may be, for example, stainless steel, which is a material that is resistant to deformation.

[0065] The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of disclosure are considered to be within the scope of the invention.

[0066] 1, 1A, 2, 3, 4, 5, 6: Cell structure, 1a, 1b: Long side, 1c, 1d: Short side, 10: Cell stack, 11: Battery cell, 12: Conductive extension, 20: Outer casing, 21: First outer casing segment, 22: Second outer casing segment, 23: Excess length covering, 24: Side wall (side wall covering), 25: Sealing part, 25a: First protrusion, 25b: Second protrusion, 25c: Sealing layer, 26: Top wall, 27: Bottom wall, 29, 39-2: Bulging part, 30: Inner cover, 31: First inner cover segment, 32: Second inner cover segment, 33: Excess length forming part, 33a: First excess length part, 33b: Second excess length part, 34: Side wall, 34a: End, 34b: Connection part, 36: Top wall, 37: Bottom wall, 38: curved section, 39: bent section, S: internal space, D: tool, D1: lamination direction, G, G2: gap, F1: stress, F2, F3: arrow, P1: negative pressure, R: radius of curvature, SF: inclined surface, a, a', a'': length of the side wall in the lamination direction, b, b', b'': amount of protrusion of the excess length forming section, a+b, a'+b', a''+b'': added length, c, c(n): length from the outer end of the side wall to the base end of the sealing section in the lamination direction of the outer body which is maximally deformed by the expansion of the cell laminate, t0: thickness before expansion, t1: thickness after expansion, L1: pressing length in the lamination direction when forming the excess length forming section, L2: maximum expansion length in the lamination direction of the cell laminate.

Claims

1. A cell structure comprising: a cell stack comprising multiple layers of battery cells, each having a first electrode, a second electrode, and an electrolyte disposed between the electrodes, and capable of charging power, and having conductive extensions extending outward from the battery cells; an outer casing having an internal space in which the cell stack is housed, formed while maintaining the airtightness of the internal space, and formed to be deformable; an inner cover installed inside the outer casing and covering the cell stack, having at least a first inner cover division and a second inner cover division that are divisible in the stacking direction in which the cell stack is stacked; and an excess length forming portion provided on the inner cover and protruding outward, wherein the excess length forming portion has a first excess length portion protruding outward from the first inner cover division and a second excess length portion protruding outward from the second inner cover division, and the first excess length portion is in contact with and fixed to the second excess length portion, or is fixed to the second excess length portion with the conductive extension in between.

2. The cell structure according to claim 1, wherein the excess length forming portion is formed to surround the entire circumference of the cell stack and protrudes in a direction intersecting the stacking direction.

3. The cell structure according to claim 1, wherein the outer casing comprises a first outer casing segment and a second outer casing segment that are separable in the stacking direction, the first outer casing segment has a first projection that protrudes outward, and the second outer casing segment has a second projection that protrudes outward, and the outer casing has a sealing portion formed by the first projection being in contact with and fixed to the second projection, or by the conductive extension being fixed to the second projection, and the sealing portion is provided at a position closer to the outside of the excess length forming portion.

4. The cell structure according to claim 3, wherein the internal cover is formed in a shape having a side wall parallel to the stacking direction, the excess length forming portion is formed protruding from the side wall, the outer casing has an excess length covering portion that covers from the tip to the base end of the excess length forming portion, and a side wall covering portion that covers from the base end to the end of the side wall in the stacking direction, and the length a + b obtained by adding the amount of protrusion b of the excess length forming portion to the length a of the side wall of the internal cover in the stacking direction is greater than the length c from the outer end of the side wall covering portion in the stacking direction of the outer casing, which has been deformed by the expansion of the cell stack, to the base end of the sealing portion ((a + b) > c).

5. The cell structure according to claim 1, wherein the internal cover is formed in a shape having side walls parallel to the stacking direction, the excess length forming portion is formed protruding from the side walls, the outer casing has an excess length covering portion that covers from the tip to the base end of the excess length forming portion, and a side wall covering portion that covers from the base end to the end of the side wall in the stacking direction, the excess length covering portion and the excess length forming portion are formed by pressing from at least one of both sides in the stacking direction, and the excess length forming portion is installed in contact with the inner surface of the excess length covering portion by elastically recovering more than the excess length covering portion due to the reaction force based on the pressing force when the excess length forming portion is formed.

6. The cell structure according to claim 5, wherein the pressing length L1 in the stacking direction during the formation of the excess length forming portion is greater than half of the maximum expansion length L2 in the stacking direction that occurs when the cell stack expands.

7. The cell structure according to claim 1, wherein the internal cover is formed in a shape having side walls parallel to the stacking direction, the excess length forming portion is formed protruding from the side walls, a curved portion is formed at the connection between the excess length forming portion and the side walls, and the amount of strain on the surface of the curved portion is formed to be less than or equal to the plastic strain or the yield point.

8. The cell structure according to claim 1, wherein the outer casing comprises a first outer casing segment and a second outer casing segment that are separable in the stacking direction, the first outer casing segment has a first projection that protrudes outward, and the second outer casing segment has a second projection that protrudes outward, the outer casing has a sealing segment formed by the first projection being fixed to the second projection with a sealing layer in between, or by the second projection being fixed with the conductive extension and the sealing layer in between, the sealing segment is provided at a position closer to the outside of the excess length forming segment, and the tip of the excess length forming segment on the projection direction side is in contact with the sealing layer.

9. The cell structure according to claim 8, wherein the tip of the excess length forming portion on the protruding direction side has a bent portion that is bent to the opposite side of the protruding direction, the bent portion is in contact with the sealing layer, and the amount of strain on the surface of the bent portion is formed to be less than or equal to the plastic strain or the yield point.

10. The cell structure according to claim 1, wherein the internal cover and the outer casing have bulging portions that bulge outward in the stacking direction, and the bulging portions bulge away from the ends of the cell stack in the stacking direction.

11. A solid-state battery comprising the cell structure described in any one of claims 1 to 10.

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