Battery pressurization structure

Abstract

Provided is a storage battery pressurization structure in which the following are pressurized from the thickness direction: a structural body comprising a storage battery cell 3 including an electrode 31 which is packaged by an outer packaging material 33; or a structural body comprising a layered body in which a plurality of the storage battery cells 3 are layered. The storage battery pressurization structure comprises: a pair of end plates 1U, 1L disposed at both ends in the thickness direction of the structural body; and a fastening bolt 21 and a nut 22 that fasten the pair of end plates 1U, 1L to each other. An elastic body 5 is disposed at at least one position which is sandwiched between the end plate 1U, 1L and the structural body, and a rigid body 4 is disposed at a position sandwiched between the elastic body 5 and the structural body. A deformation suppression means (e.g., a recess 41), which is capable of suppressing deformation of the elastic body in a direction perpendicular to the thickness direction, is further included in one of the end plate 1U, 1L, the elastic body 5, and the rigid body 4.

Description

[Technical Field]

[0001] The present invention relates to a pressurizing structure for a storage battery. [Background technology]

[0002] JP2009-99383A discloses a pressure application structure for a stack of energy storage elements, which includes a pair of end plates arranged at both ends of the stack in the thickness direction, and a plate-like elastic body that holds the end plates from above and below and applies pressure to the stack in the stacking direction. Summary of the Invention

[0003] When pressurizing the electrode part of an all-solid-state battery using lithium metal, it is necessary to apply a higher pressure than conventional methods in order to bond the solid-state electrodes to each other at the interface, in addition to being able to follow the expansion and contraction in the thickness direction that accompanies charging and discharging. However, with the pressurizing structure of Patent Document 1, it is difficult to apply a uniform surface pressure to the electrode part, and there was a problem in that it was not possible to apply an appropriate pressure.

[0004] An object of the present invention is to provide a pressure applying structure for a storage battery that can apply uniform and appropriate surface pressure to an electrode portion.

[0005] According to one aspect of the present invention, there is provided a storage battery pressure structure for applying pressure from the thickness direction to a structure made of storage battery cells including electrode parts packaged with a laminated exterior material, or a structure made of a stack of a plurality of such storage battery cells. This pressure structure includes a pair of end plates arranged at both ends of the structure in the thickness direction, and fastening members for fastening the pair of end plates together. Also, a pressure member at a position sandwiched between the end plates and the structure is provided. 1 The elastic bodies are disposed at two or more locations, and the rigid body is disposed at a position sandwiched between the elastic bodies and the structure. Any of the end plates, the elastic bodies, and the rigid body further includes a deformation suppression means capable of suppressing deformation of the elastic bodies in a direction perpendicular to the thickness direction. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 is a perspective view of a pressurizing structure for a storage battery according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the pressurizing structure for the storage battery according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing an example of an electrode portion that constitutes the pressure applying structure of the storage battery according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a pressure applying structure for a storage battery according to a first comparative example. [Figure 5] FIG. 5 is a cross-sectional view of a pressurizing structure for a storage battery according to a second comparative example. [Figure 6] FIG. 6 is a cross-sectional view of a pressure applying structure for a storage battery according to a third comparative example. [Figure 7] FIG. 7 is a plan view showing an arrangement for measuring the surface pressure distribution of the electrode portion. [Figure 8A] FIG. 8A is a diagram showing the distribution of surface pressure applied to the electrode portion of the first embodiment. [Figure 8B] FIG. 8B is a diagram showing the distribution of surface pressure applied to the electrode portion of the first comparative example. [Figure 8C] FIG. 8C is a diagram showing the distribution of surface pressure applied to the electrode portion of the second comparative example. [Figure 8D] FIG. 8D is a diagram showing the distribution of surface pressure applied to the electrode portion of the third comparative example. [Figure 9A] FIG. 9A is a diagram showing the procedure for quantitatively evaluating the surface pressure distribution, in which the part of the pressure-sensitive paper pressed by the electrode part is divided into a plurality of areas. [Figure 9B] FIG. 9B is a diagram showing the procedure for quantitatively evaluating the surface pressure distribution, in which the surface pressure for each area is calculated, and the average value of the overall surface pressure is calculated from the surface pressure of each area. [Figure 10] FIG. 10 is a table showing quantitative evaluation of the surface pressure distribution in Comparative Example 1-3 and Example 1-3. [Figure 11] FIG. 11 is a table showing quantitative evaluation of the surface pressure distribution in Examples 3-7. [Figure 12] FIG. 12 is a cross-sectional view of a pressurizing structure for a storage battery according to the second embodiment. [Figure 13] FIG. 13 is a cross-sectional view of a pressurizing structure for a storage battery according to the third embodiment. [Figure 14] FIG. 14 is a table showing quantitative evaluation of the surface pressure distribution in Examples 8 to 10 and Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0007] [First embodiment] Fig. 1 is a perspective view of the pressure applying structure for a storage battery according to the first embodiment. Fig. 2 is a cross-sectional view of the pressure applying structure for a storage battery according to the first embodiment. Fig. 3 is a cross-sectional view showing an example of an electrode unit 31 constituting the pressure applying structure for a storage battery according to the first embodiment.

[0008] 1 and 2, in the storage battery pressurizing structure of the first embodiment, a storage battery cell 3 (structure) or a stack (structure) of multiple storage battery cells 3 is sandwiched between an upper end plate 1U and a lower end plate 1L in the drawings. Furthermore, an elastic body 5 and a rigid body 4 are sandwiched between the structure and the end plate 1U. The rigid body 4 contacts the storage battery cell 3, and the elastic body 5 contacts the end plate 1U.

[0009] Here, the storage battery cell 3 is, for example, an all-solid-state battery, and includes an electrode portion 31, an insulating layer 32 that is arranged on the outer periphery of the electrode portion 31 and protects the outer periphery of the electrode portion 31, and an exterior material 33 that packages the electrode portion 31 and the insulating layer 32.

[0010] End plate 1U and end plate 1L are fastened to each other by fastening means (fastening bolts 21, nuts 22). The fastening means (fastening bolts 21, nuts 22) are arranged so as to be centrosymmetric with respect to electrode portion 31 in plan view (see FIG. 7). In FIGS. 1 and 2, four fastening means (fastening bolts 21, nuts 22) are arranged, but more than four fastening means may be arranged.

[0011] The fastening force of the fastening means (fastening bolts 21, nuts 22) causes end plates 1U and 1L to press against storage battery cells 3, elastic bodies 5, and rigid bodies 4 in the thickness direction, applying a predetermined surface pressure to storage battery cells 3.

[0012] Although not shown in the drawings, it is also possible to sandwich the elastic body 5 and the rigid body 4 between the end plate 1L and the structure. In this case, the rigid body 4 contacts the storage battery cell 3, and the elastic body 5 contacts the end plate 1L.

[0013] As shown in Figures 1 and 2, the rigid body 4 is arranged so that its outer shape in a plan view accommodates the storage battery cell 3 (particularly the electrode portion 31) inside, and the main surface of the rigid body 4 facing the storage battery cell 3 is in surface contact with the storage battery cell 3 (particularly the electrode portion 31).

[0014] On the other hand, a recess 41 (deformation suppression means) is formed on the main surface of the rigid body 4 on the side of the end plate 1U, and the elastic body 5 is fitted into the recess 41. The recess 41 has an opening and an inner wall that are shaped to follow the external shape (rectangle) of the elastic body 5 in a plan view and are slightly smaller than the external shape of the elastic body 5 in a plan view.

[0015] The rigid body 4 (the same applies to the end plate 1U and the end plate 1L) is made of a highly rigid material such as stainless steel (SUS304).

[0016] The elastic body 5 is made of a material that has a lower elastic modulus (Young's modulus) than the rigid body 4 and a higher elastic limit than the rigid body 4, and silicone rubber 70° is suitable. Other materials that can be used for the elastic body 5 include silicone rubber 90°, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), Kapton (registered trademark), epoxy resin, polypropylene (PP), polytetrafluoroethylene (PTFE), rubber (natural rubber, synthetic rubber), etc.

[0017] In this embodiment, adjacent layers (described later) of the electrode portion 31 are in solid contact with each other, so it is necessary to apply an appropriate surface pressure (for example, 4 MPa or more) from the thickness direction to suppress a decrease in electrical conductivity and lithium ion conductivity.

[0018] In this embodiment, the elastic body 5 has the role of equalizing the pressing force from the end plate 1U (end plate 1L). However, when the elastic body 5 receives the pressing force from the end plate 1U (end plate 1L), it deforms in the planar direction (direction perpendicular to the thickness direction), and the surface pressure applied to the storage battery cells 3 decreases by the amount of deformation.

[0019] Accordingly, the elastic body 5 is fitted into the recess 41. This suppresses deformation of the elastic body 5 in the planar direction (direction perpendicular to the thickness direction), thereby increasing the efficiency with which the pressing force applied to the elastic body 5 is transmitted to the rigid body 4 and the storage battery cell 3. In addition, it is preferable that the thickness of the elastic body 5 exposed from the rigid body 4 (recess 41) be thinner than the thickness of the elastic body 5 fitted into the recess 41. This effectively suppresses deformation of the elastic body 5 in the planar direction.

[0020] 1 and 2, in the storage battery cell 3, the insulating layer 32 may be lower in height than the electrode portion 31, forming a step between the electrode portion 31 and the insulating layer 32. Therefore, when the elastic body 5 is pressed directly against the storage battery cell 3, the elastic body 5 deforms to follow the shape of the step, and as a result, for example, the surface pressure applied to the electrode portion 31 is distributed in a manner that decreases toward the outer periphery of the electrode portion 31.

[0021] However, in this embodiment, the rigid body 4 is disposed between the elastic body 5 and the storage battery cell 3, and the rigid body 4 can suppress deformation in the thickness direction of the portion of the elastic body 5 that is outside the outer shape of the electrode portion 31 in a plan view. This can improve the uniformity of the surface pressure applied to the electrode portion 31.

[0022] In the first embodiment, the elastic body 5 may be divided into multiple parts in the planar direction, but it is preferable that they are arranged in centrosymmetrical fashion around the electrode portion 31 in plan view. In addition, multiple recesses 41 are also arranged based on the arrangement of the electrode portion 31.

[0023] The recess 41 may be formed in the end plate 1U instead of the rigid body 4. Alternatively, the recess 41 may be formed in both the rigid body 4 and the end plate 1U. In this case, the thickness of the elastic body 5 is set to be greater than the sum of the depth of the recess 41 formed in the rigid body 4 and the depth of the recess 41 formed in the end plate 1U.

[0024] 3, the electrode unit 31 is a laminate obtained by laminating a positive electrode current collector foil 311, a positive electrode layer 314, a solid electrolyte layer 313, a negative electrode layer 315, and a negative electrode current collector foil 312 in this order. The electrode unit 31 may also be formed by laminating multiple such laminates. The electrode unit 31 may also be formed by laminating multiple layers of structures in which the positive electrode current collector foil 311, the positive electrode layer 314, the solid electrolyte layer 313, the negative electrode layer 315, the negative electrode current collector foil 312, the negative electrode layer 315, the solid electrolyte layer 313, the positive electrode layer 314, and the positive electrode current collector foil 311 are laminated in this order.

[0025] The positive electrode current collector foil 311 is a thin plate made of a metal such as aluminum (Al). The negative electrode current collector foil 312 is a thin plate made of a metal such as stainless steel (SUS) or copper (Cu). External electrodes that are electrically connected to the outside of the exterior packaging material 33 are connected to the positive electrode current collector foil 311 and the negative electrode current collector foil 312, respectively.

[0026] The solid electrolyte layer 313 contains a solid electrolyte as a main component and is a layer interposed between the positive electrode layer 314 and the negative electrode layer 315. Examples of the solid electrolyte material include sulfide solid electrolytes and oxide solid electrolytes, with sulfide solid electrolytes being preferred. Examples of sulfide solid electrolytes include lithium phosphorus sulfide compounds (e.g., argyrodite (Li6PS5Cl)), LGPS-based (e.g., Li 10 GeP2S 12 ) materials are preferred.

[0027] The positive electrode layer 314 preferably contains a sulfur-containing positive electrode active material. The type of sulfur-containing positive electrode active material is not particularly limited, but examples include elemental sulfur (S) as well as particles or thin films of organic sulfur compounds or inorganic sulfur compounds, as long as it is a material that can release lithium ions during charging and absorb lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur.

[0028] The negative electrode layer 315 is made of a negative electrode active material containing at least lithium metal or a lithium alloy. Alternatively, any material can be used for the negative electrode layer 315 as long as it can absorb lithium ions during charging and release lithium ions during discharging.

[0029] When the electrode part 31 is charged, the negative electrode layer 315 absorbs lithium ions conducted from the positive electrode layer 314 side as lithium metal, thereby increasing the thickness thereof. Conversely, when the electrode part 31 is discharged, the negative electrode layer 315 releases lithium metal as lithium ions toward the positive electrode layer 314 side, thereby decreasing the thickness thereof.

[0030] 1 and 2, the insulating layer 32 is arranged in a frame shape surrounding the outer periphery of the electrode portion 31. The insulating layer 32 can be made of ultraviolet-curable resins such as Aronix (registered trademark) and Aronoxetane (registered trademark). The insulating layer 32 can also be made of thermosetting resins, such as polyethylene terephthalate (PET) and epoxy resin. Other suitable materials for the insulating layer 32 include Kapton (registered trademark), polypropylene (PP), polytetrafluoroethylene (PTFE), and rubber (natural rubber, synthetic rubber).

[0031] [Surface pressure distribution] FIG. 4 is a cross-sectional view of the pressurizing structure of a storage battery of a first comparative example. FIG. 5 is a cross-sectional view of the pressurizing structure of a storage battery of a second comparative example. FIG. 6 is a cross-sectional view of the pressurizing structure of a storage battery of a third comparative example. FIG. 7 is a diagram showing an arrangement for measuring the surface pressure distribution of the electrode unit 31. FIG. 8A is a diagram showing the surface pressure distribution applied to the electrode unit 31 of the first embodiment. FIG. 8B is a diagram showing the surface pressure distribution applied to the electrode unit 31 of the first comparative example. FIG. 8C is a diagram showing the surface pressure distribution applied to the electrode unit 31 of the second comparative example. FIG. 8D is a diagram showing the surface pressure distribution applied to the electrode unit 31 of the third comparative example.

[0032] The inventors of the present application have investigated the surface pressure distribution of the electrode portion 31 in the storage battery pressurization structure of the first embodiment, comparing it with Comparative Examples 1 to 3. The surface pressure distribution was confirmed by the following procedure.

[0033] Pressure-sensitive paper 7 (Fujifilm Corporation's Prescale for low pressure (LW)) is placed on top of end plate 1L (jig), and then the storage battery cell 3, rigid body 4 (rigid body 4 is not present in Figures 5 and 6), elastic body 5 (elastic body 5 is not present in Figure 6), and end plate 1U (jig) are stacked in this order on top of the pressure-sensitive paper 7 at the center of end plate 1L (jig) (see Figures 4 and 7).

[0034] Then, the end plate 1U and the end plate 1L are fastened together using fastening means (fastening bolts 21, nuts 22) to compress the storage battery cells 3, rigid bodies 4, and elastic bodies 5. When fastening the fastening means (fastening bolts 21, nuts 22), a torque wrench is used, and the fastening means are tightened by a predetermined amount of rotation (for example, 45 degrees) in the order of (1) to (6) as shown in FIG. 7 until a predetermined torque and set pressure, which will be described later, are achieved.

[0035] Thereafter, the fastening means (fastening bolt 21, nut 22) is loosened and released, and the pressure-sensitive paper 7 is taken out to check the surface pressure.

[0036] In the pressurized structure of the storage battery of the first embodiment shown in FIG. 2 (pressure-sensitive paper 7 is not shown), the electrode portion 31 of the storage battery cell 3 has a rectangular shape of 20 mm x 20 mm in plan view, and the rigid body 4 (e.g., SUS304) has a thickness of 3 mm and a rectangular shape of 25 mm x 25 mm. The elastic body 5 (e.g., silicone rubber 70°) has a thickness of 2 mm and a rectangular shape of 20 mm x 20 mm in plan view. The recess 41 has a depth of approximately 1.5 mm and a rectangular shape of 20 mm x 20 mm in plan view. Therefore, before pressing, the elastic body 5 is exposed from the recess 41 (rigid body 4) by approximately 0.5 mm.

[0037] Here, the SUS304 used as the rigid body 4 was PARNN-25-25-3-CSC manufactured by Misumi (dimensions: 3×25×25, surface polishing Ra: 0.4 to 1.4 μm, flatness for a length of 100 mm: 0.05 mm, parallelism: 0.012 mm, full circumference chamfering).

[0038] The silicone rubber 70° used as the elastic body 5 was SR-70T (dimensions: 3×25×25, tolerance: <±0.25 mm, thickness deviation: <0.35 mm) manufactured by Tigers Polymer Co., Ltd.

[0039] The pressurizing structure of the storage battery of the first comparative example shown in Fig. 4 differs from that of the first embodiment in that it does not have a recess 41, and has a configuration in which an elastic body 5 is sandwiched between a rigid body 4 and an end plate 1U. The elastic body 5 (before pressurization) has a thickness of 3 mm and a rectangular shape of 25 mm x 25 mm in plan view, but when pressurized by fastening means (fastening bolts 21, nuts 22), it expands in the planar direction as shown by the dashed line.

[0040] The pressurizing structure of the storage battery of the second comparative example shown in Fig. 5 differs from that of the first embodiment in that it does not have a rigid body 4 (recess 41), and has a configuration in which an elastic body 5 is sandwiched between the storage battery cell 3 and the end plate 1U. The elastic body 5 (before pressurization) has a thickness of 3 mm and a rectangular shape of 25 mm x 25 mm in plan view, but when pressurized by fastening means (fastening bolts 21, nuts 22), it expands in the planar direction as shown by the dashed lines, and the part outside the electrode portion 31 in plan view is deformed so as to bend toward the storage battery cell 3.

[0041] The pressure application structure of the storage battery of the third comparative example shown in FIG. 6 differs from that of the first embodiment in that the rigid body 4 (recess 41) and the elastic body 5 are absent.

[0042] 8A, in the case of the pressure-sensitive structure of the storage battery of the first embodiment, the pressure-sensitive paper 7 is colored so that the outer shape of the electrode portion 31 is transferred onto it, and the degree of coloring is also uniform (the surface pressure on the electrode portion 31 is also uniform). This is because, as described above, the elastic body 5 equalizes the pressing force from the end plate 1U in the surface direction, and fitting the elastic body 5 into the recess 41 prevents the elastic body 5 from expanding in the surface direction, thereby reducing the diffusion of the pressing force applied to the elastic body 5 in the surface direction, and therefore, a surface pressure corresponding to the pressing force from the end plate 1U can be applied to the entire electrode portion 31.

[0043] As shown in Fig. 8B, in the case of the pressure-sensitive structure of the storage battery of the first comparative example, the pressure-sensitive paper 7 is colored so that the outer shape of the electrode portion 31 is transferred, and the coloring degree is approximately uniform (the surface pressure on the electrode portion 31 is also approximately uniform), but the coloring degree is lighter than the coloring shown in Fig. 8A. This is because, as shown in Fig. 4, when the elastic body 5 receives a pressing force in the thickness direction, it expands in the surface direction as shown by the dashed line, and the pressing force applied to the rigid body 4 and the storage battery cell 3 decreases accordingly.

[0044] 8C , in the case of the pressure-sensitive structure of the second comparative example, the pressure-sensitive paper 7 is colored in a manner that makes the outline of the electrode portion 31 unclear, and has a color distribution in which the color becomes lighter from the portion facing the center of the electrode portion 31 toward the outside. This is because, as shown in FIG. 5 , when the elastic body 5 is subjected to a pressing force, it expands in the planar direction as indicated by the dashed line, and the portion located outside the electrode portion 31 in plan view deforms so as to bend toward the storage battery cell 3. Since this portion does not receive compressive stress, the pressing force received at the portion of the elastic body 5 that overlaps the electrode portion 31 in plan view is diffused more toward the outer periphery of the electrode portion 31 as it approaches the outer periphery of the electrode portion 31.

[0045] 8D, in the case of the pressure-sensitive structure of the third comparative example, the pressure-sensitive paper 7 is colored so that the outer shape of the electrode portion 31 is transferred to it, but the color distribution is such that a specific peripheral portion is extremely darkly colored and other peripheral portions opposite the specific peripheral portion are hardly colored. This is because the main surface of the end plate 1U facing the electrode portion 31 and the main surface of the electrode portion 31 are not completely parallel to each other, and the end plate 1U presses against the electrode portion 31 with the main surface of the end plate 1U tilted relative to the main surface of the electrode portion 31.

[0046] [Quantitative evaluation of surface pressure distribution] Fig. 9A is a diagram showing the procedure for quantitatively evaluating the surface pressure distribution, in which the part of the pressure-sensitive paper 7 pressed by the electrode part 31 is divided into multiple areas. Fig. 9B is a diagram showing the procedure for quantitatively evaluating the surface pressure distribution, in which the surface pressure for each area is calculated and the average value of the overall surface pressure is calculated from the surface pressure of each area. Fig. 10 is a table showing the quantitative evaluation of the surface pressure distribution for Comparative Example 1-3 and Example 1-3.

[0047] The surface pressure distribution of the electrode part 31 is quantitatively evaluated based on the color distribution formed on the pressure-sensitive paper 7. As an evaluation procedure, as shown in Fig. 9A, the part of the pressure-sensitive paper 7 to which the surface pressure of the electrode part 31 is transferred is divided into multiple parts (16 parts in Figs. 9A and 9B).

[0048] Then, for example, using a map showing the relationship between the coloring degree (brightness) of the pressure-sensitive paper 7 and the surface pressure, the average value of the coloring degree (brightness) of the pressure-sensitive paper 7 in each area is calculated, and the surface pressure corresponding to this average value is extracted from the map, as shown in Fig. 9B. Furthermore, the quality of the surface pressure distribution is determined taking into consideration the relationship between the average value of the surface pressure of the entire electrode part 31 obtained from multiple surface pressures and the set pressure (pressing force) of the fastening means (bolts, nuts 22), as well as variations in the multiple surface pressures.

[0049] Examples 1-3 shown in Figure 10 all have the configuration of Figure 2 (first embodiment), and use silicone rubber 70° (elastic modulus: 3.3 MPa) as the elastic body 5. Therefore, the dimensional maintenance rate in the planar direction of Examples 1-3 is 100% (no change). Furthermore, SUS304 (thickness: 3 mm, maximum deflection: 0.01 mm) is used as the rigid body 4 of Examples 1-3, and does not deform at least due to the set pressure (5 MPa) of the fastening means (fastening bolt 21, nut 22).

[0050] On the other hand, in Example 1-3, the tightening torque of the fastening means and the set pressure (pressure) applied to the electrode portion 31 side are changed.

[0051] In Example 1, the torque was set to 0.32 Nm, and the set pressure (pressing force) was set to 1.5 MPa. As a result, in Example 1, the average surface pressure was 1.42 MPa, the surface pressure difference was 0.5 MPa, the surface pressure maintenance rate was 95%, and the surface pressure difference / average surface pressure was 35%.

[0052] In Example 2, the torque was set to 0.64 Nm, and the set pressure (pressing force) was set to 3 MPa. As a result, in Example 2, the average surface pressure was 2.9 MPa, the surface pressure difference was 0.98 MPa, the surface pressure maintenance rate was 97%, and the surface pressure difference / average surface pressure was 34%.

[0053] In Example 3, the torque was set to 1.06 Nm, and the set pressure (pressing force) was set to 5 MPa. As a result, in Example 3, the average surface pressure was 4.81 MPa, the surface pressure difference was 1.75 MPa, the surface pressure maintenance rate was 96%, and the surface pressure difference / average surface pressure was 36%.

[0054] Here, the surface pressure difference is the difference between the maximum and minimum surface pressures among the surface pressures in the multiple areas shown in Fig. 9. The surface pressure maintenance rate is the average surface pressure / set pressure (the precision of the set pressure applied to the electrode part 31), and it can be said that the closer it is to 100%, the more uniform the surface pressure distribution. Furthermore, the lower the value of the surface pressure difference / average surface pressure, the less variation there is in the surface pressure distribution, and the better it can be said to be.

[0055] In Examples 1-3, the average surface pressure and the difference in surface pressure are proportional to the torque and the set pressure, but the surface pressure maintenance rate and the difference in surface pressure / average surface pressure are almost constant.

[0056] In the first embodiment (FIG. 2), the surface pressure distribution is nearly uniform as shown in FIG. 8A. However, even if the tightening state of the fastening means changes as shown in FIG. 10, the surface pressure distribution in the electrode portion 31 does not change significantly except for the average value (absolute value) of the surface pressure, and can be said to be stable. Furthermore, although the thickness of the storage battery cell 3 (electrode portion 31) changes with charging and discharging, it is believed that such thickness changes do not result in a significant change in the surface pressure distribution. Therefore, the first embodiment (FIG. 2) can stably form a good surface pressure distribution and reduce variations in the capacity and output of the storage battery cell 3.

[0057] On the other hand, Comparative Example 1 has the configuration shown in Fig. 6, i.e., a configuration in which the end plate 1U directly presses the storage battery cell 3. In this case, the torque was set to 0.32 Nm, and the set pressure (pressing force) was set to 3 MPa. As a result, in Comparative Example 1, the average surface pressure was 3.9 MPa, the surface pressure difference was 2.95 MPa, the surface pressure maintenance rate was 130%, and the surface pressure difference / average surface pressure ratio was 76%.

[0058] In Comparative Example 1, the average surface pressure is higher than the set pressure, and the surface pressure maintenance rate is also high, exceeding 100%. This is because, as shown in FIG. 8D , Comparative Example 1 has a surface pressure distribution in which extremely strong surface pressure is applied to a specific peripheral portion, while almost no surface pressure is applied to other peripheral portions opposite the specific peripheral portion. Furthermore, in Comparative Example 1, the tendency of the surface pressure distribution does not change even when the torque and set pressure are changed. Therefore, in Comparative Example 1, it is difficult to apply uniform surface pressure to the entire electrode portion 31, and sufficient capacity and output of the storage battery cell 3 cannot be obtained.

[0059] Comparative Examples 2 and 3 have the configuration shown in FIG. 4, i.e., a configuration without deformation suppression means (recesses 41) for suppressing deformation in the planar direction of the elastic body 5. In Comparative Examples 2 and 3, 70° silicone rubber was used as the elastic body 5. In Comparative Example 2, the torque was set to 0.64 Nm and the set pressure was set to 3 MPa. In Comparative Example 3, the torque was set to 1.06 and the set pressure was set to 5 MPa.

[0060] In Comparative Examples 2 and 3, the dimensional maintenance rate in the plane direction of the elastic body 5 was 119%. This indicates that when the elastic body 5 was subjected to a pressing force, it was crushed in the thickness direction, and the length of one side was extended by 19%. Therefore, in Comparative Examples 2 and 3, the displacement in the plane direction of the elastic body 5 increased toward the outer periphery of the elastic body 5, and the pressing force applied to the rigid body 4 decreased accordingly.

[0061] Therefore, in Comparative Examples 2 and 3, due to the rigidity of the rigid body 4, the surface pressure distribution between the rigid body 4 and the storage battery cell 3 is relatively uniform as shown in Figure 8B, but the surface pressure distribution between the elastic body 5 and the rigid body 4 is the surface pressure distribution shown in Figure 8C.

[0062] In Comparative Example 2, the average surface pressure was 2.2 MPa, the surface pressure difference was 1.4 MPa, the surface pressure maintenance rate was 73%, and the surface pressure difference / average surface pressure was 64%. In Comparative Example 3, the average surface pressure was 3 MPa, the surface pressure difference was 2.5 MPa, the surface pressure maintenance rate was 60%, and the surface pressure difference / average surface pressure was 83%.

[0063] In Comparative Examples 2 and 3, the surface pressure maintenance ratios were significantly lower than 100%. This is because, as shown in FIG. 8C , the component of the pressing force received from the end plate 1U that escapes outward in the surface direction increases toward the outer periphery of the elastic body 5. In Comparative Examples 2 and 3, increasing the torque and set pressure reduced the surface pressure maintenance ratio and increased the surface pressure difference / average surface pressure. This is because increasing the torque and set pressure more significantly manifests the tendency of the surface pressure distribution between the elastic body 5 and the rigid body 4 shown in FIG. 8C . Therefore, although Comparative Examples 2 and 3 can apply a uniform surface pressure to the electrode unit 31, the capacity and output of the storage battery cell 3 may fluctuate due to changes in the torque and set pressure. Furthermore, the capacity and output may also fluctuate due to changes in the thickness direction of the storage battery cell 3 (electrode unit 31) during charging and discharging, resulting in unstable operation of the storage battery cell 3.

[0064] In Comparative Examples 2 and 3, when adhesive is applied between the elastic body 5 and the rigid body 4 and the elastic body 5 is joined to the rigid body 4, it is possible to suppress to some extent the outward expansion of the elastic body 5 in the planar direction. However, this suppression is only possible in the portion of the elastic body 5 that is close to the rigid body 4 in the thickness direction, and the effect of suppressing expansion in the planar direction decreases the further away from the rigid body 4 in the thickness direction.

[0065] On the other hand, in Example 1-3 (FIG. 2), when the elastic body 5 is pressed by the end plate 1U, it is compressed in a manner that it sinks toward the recess 41. Therefore, expansion in the planar direction of the portion of the elastic body 5 exposed from the recess 41 is suppressed by the amount of sinking. Furthermore, the portion of the elastic body 5 that sinks and is fitted into the recess 41 does not expand in the planar direction.

[0066] Fig. 11 is a table showing the quantitative evaluation of the surface pressure distribution of Example 3-7. Example 3-7 is a quantitative evaluation of the surface pressure distribution when the material of the elastic body 5 is changed in the configuration of the first embodiment shown in Fig. 2.

[0067] As mentioned above, Example 3 uses 70° silicone rubber (modulus of elasticity (modulus of elasticity at which the compressive strain is 5 to 10% when the compressive pressure is 5 MPa, the same applies below): 3.3 MPa) as the elastic body 5. In addition, with regard to the elastic body 5, Example 4 uses natural rubber (modulus of elasticity: 2.9 MPa), Example 5 uses 90° silicone rubber (modulus of elasticity: 12 MPa), Example 6 uses polypropylene (PP, modulus of elasticity (flexural strength): 37 MPa), and Example 7 uses polyethylene terephthalate-glass 30% (PET-GF30, containing 30% glass, modulus of elasticity (compressive strength): 173 MPa).

[0068] The dimensions of the elastic body 5 used in Example 4-7 are the same as those in Example 3 (3 mm × 25 mm × 25 mm). The torque and set pressure used in Example 4-7 are also the same as those in Example 3 (torque: 1.06, set pressure: 5 MPa).

[0069] With the above settings, in Example 4, the average surface pressure was 4.7 MPa, the surface pressure difference was 1.8 MPa, the surface pressure maintenance rate was 94%, and the surface pressure difference / surface pressure average was 38%. In Example 5, the average surface pressure was 4.85 MPa, the surface pressure difference was 2.2 MPa, the surface pressure maintenance rate was 97%, and the surface pressure difference / surface pressure average was 45%. In Example 6, the average surface pressure was 4.91 MPa, the surface pressure difference was 2.3 MPa, the surface pressure maintenance rate was 98%, and the surface pressure difference / surface pressure average was 47%. In Example 7, the average surface pressure was 4.93 MPa, the surface pressure difference was 2.4 MPa, the surface pressure maintenance rate was 99%, and the surface pressure difference / surface pressure average was 49%.

[0070] As shown in Example 3-7, the higher the modulus of elasticity of the elastic body 5, the higher the average surface pressure, the difference in surface pressure, the maintenance rate of surface pressure, and the difference in surface pressure / average surface pressure increase, but the rate of increase is small. Furthermore, even Example 4, which has the lowest modulus of elasticity among Examples 4-7, achieves a surface pressure maintenance rate of 94%. Furthermore, in Example 7, which has the highest modulus of elasticity among Examples 3-7, the difference in surface pressure / average surface pressure is 49%, Surface pressure maintenance rate is 99%.

[0071] Therefore, in the configuration of the first embodiment (FIG. 2), as long as the elastic modulus of the elastic body 5 is kept lower than the elastic modulus of the rigid body 4 (for example, SUS304), a good surface pressure distribution can be achieved in the electrode portion 31.

[0072] Furthermore, for example, if the elastic body 5 has an elastic modulus such that the compressive strain at a set pressure (5 MPa) is 5 to 10%, it will not be completely embedded in the recess 41 when compressed, and the surface pressure distribution at the electrode part 31 can be made uniform.

[0073] From the above, any material having an elastic modulus in the range of, for example, 0.5 MPa to 200 MPa can be used for the elastic body 5. Furthermore, considering Example 7, a material that causes the difference between the surface pressure applied to the center and the surface pressure applied to the peripheral edge of the electrode portion 31 to be 2.4 MPa or less (a rough estimate of 3.0 MPa or less) is suitable for the elastic body 5.

[0074] [Effects of the first embodiment] According to the first embodiment, the storage battery pressurizing structure applies pressure in a thickness direction to a structure made up of storage battery cells 3 each including an electrode portion 31 packaged in a laminated exterior material (exterior material 33), or to a structure made up of a stack of a plurality of the storage battery cells 3. The pressurizing structure includes a pair of end plates (end plate 1U, end plate 1L) arranged at both ends of the structure (e.g., storage battery cell 3) in the thickness direction, and fastening members (fastening bolts 21, nuts 22) that fasten the pair of end plates (end plate 1U, end plate 1L) together. An elastic body 5 is arranged in at least one position sandwiched between the end plate (end plate 1U, end plate 1L) and the structure (e.g., storage battery cell 3). A rigid body 4 is arranged at a position sandwiched between the elastic body 5 and the structure (e.g., storage battery cell 3). Any of the end plate (end plate 1U, end plate 1L), the elastic body 5, or the rigid body 4 further includes a deformation suppression means capable of suppressing deformation of the elastic body 5 in a direction perpendicular to the thickness direction.

[0075] According to this embodiment, the elastic body 5 uniformly distributes the pressing force of the fastening means (fastening bolts 21, nuts 22) via the end plates (end plate 1U, end plate 1L), and the deformation suppression means (e.g., recesses 41) suppresses the expansion of the elastic body 5 in the planar direction, thereby suppressing the diffusion of the pressing force in the elastic body 5 in the planar direction.In addition, the rigid body 4 suppresses the deformation of the elastic body 5 in the thickness direction, making it possible to apply pressure uniformly and appropriately to the storage battery cells 3 (especially the electrode portions 31).

[0076] In this embodiment, the deformation suppression means is recesses 41 formed in the rigid body 4 and / or the end plates (end plate 1U, end plate 1L) and into which the outer peripheries of the elastic bodies 5 are fitted. This allows the deformation suppression means to be realized with a simple configuration. In particular, the portions of the elastic bodies 5 fitted into the recesses 41 do not expand in the planar direction due to the pressing force from the end plates (end plate 1U, end plate 1L), and the pressing force can be reliably transmitted as surface pressure to the storage battery cells 3.

[0077] [Second and third embodiments] Fig. 12 is a cross-sectional view of a pressurizing structure for a storage battery according to a second embodiment. Fig. 13 is a cross-sectional view of a pressurizing structure for a storage battery according to a third embodiment.

[0078] 12, in the pressure application structure of the storage battery of the second embodiment, the deformation suppression means is arranged to cover the outer periphery of the elastic body 5 in a plan view, and the outer periphery 51 is made of a material with a higher elastic modulus than the elastic body 5. By covering the outer periphery of the elastic body 5 in this way, expansion of the elastic body 5 in the planar direction is suppressed, and accordingly, a decrease in the surface pressure applied to the storage battery cells 3 (electrode portions 31) can be suppressed.

[0079] When, for example, silicone rubber 70° (elastic modulus 3.3 GPa) is used as the elastic body 5, the outer peripheral portion 51 is preferably made of polymethyl methacrylate resin (PMMA, elastic modulus (flexural strength): 125 MPa), polytetrafluoroethylene resin (PTFE, elastic modulus (compressive strength): 11.8 MPa), or the like. The outer peripheral portion 51 may be made of acrylonitrile butadiene styrene (ABS, modulus of elasticity (flexural strength): 64 MPa), polycarbonate (PC, modulus of elasticity (flexural strength): 85 GPa), polyoxymethylene (POM, modulus of elasticity (flexural strength): 88 MPa), polyphenylene sulfide (PPS, modulus of elasticity (flexural strength): 142 MPa), polyethylene terephthalate (PET, modulus of elasticity (compressive strength): 76-103 MPa), polyethylene terephthalate-glass 30% (PET-GF30, containing 30% glass, modulus of elasticity (compressive strength): 173), polyether ether ketone (PEEK, modulus of elasticity (flexural strength): 142 MPa), poly a Suitable materials include polyamide 6 (PA6, modulus of elasticity (flexural strength): 96 MPa), polybutylene terephthalate (PBT, modulus of elasticity (flexural strength): 93 MPa), polyethylene (PE, modulus of elasticity (flexural strength): 20 MPa), polyethersulfone (PES, modulus of elasticity (flexural strength): 129 MPa), polyphenylene ether (PPE, modulus of elasticity (flexural strength): 94 MPa), and metaxylenediamine 6 / glass fiber 50% (MXD-6-GF50, modulus of elasticity (flexural strength): 189 MPa).

[0080] 13, in the pressurizing structure of the storage battery of the third embodiment, the deformation suppression means is a fibrous material (reinforcing cloth 52) arranged in a mesh pattern inside the elastic body 5. The reinforcing cloth 52 is a material formed by weaving fibers such as nylon, fluorocarbon, and polyethylene, and has high tensile strength. The elastic body 5 containing the reinforcing cloth 52 (composite elastic body) is formed by impregnating the reinforcing cloth 52 with a material such as natural rubber and then vulcanizing it.

[0081] The elastic body 5 containing the reinforcing fabric 52 is formed by impregnating the reinforcing fabric 52 with a thermosetting resin material and then thermally curing the material or by exposing the material to ultraviolet light. hardAlternatively, the reinforcing fabric 52 may be impregnated with a curable resin material and then cured by irradiating it with ultraviolet light.

[0082] Even if a pressing force is applied from the thickness direction to the elastic body 5 containing this reinforcing cloth 52, the reinforcing cloth 52 suppresses expansion of the elastic body 5 in the planar direction, thereby suppressing a decrease in the surface pressure applied to the storage battery cell 3 (electrode portion 31).

[0083] FIG. 14 shows an example 8 - 10 10 is a table showing quantitative evaluation of the surface pressure distribution in Comparative Example 1 and Comparative Example 4. Quantitative evaluation of the surface pressure distribution was also carried out for the second and third embodiments.

[0084] Examples 8 and 9 have the configuration of the second embodiment shown in Fig. 12, and use 70° silicone rubber as the elastic body 5. For the outer periphery 51, example 8 uses polymethyl methacrylate resin (PMMA, elastic modulus (flexural strength): 125 MPa), and example 9 uses polytetrafluoroethylene resin (PTFE, elastic modulus (compressive strength): 11.8 MPa).

[0085] Other than that, the dimensions of the elastic body 5 (including the outer peripheral portion 51) are the same as those of the elastic body 5 of Comparative Example 1 (3 mm×25 mm×25 mm), and the torque and set pressure are the same as those of Examples 3-7.

[0086] In Examples 8 and 9, unlike the first embodiment, the elastic body 5 is not fitted into the recess 41. However, the outer periphery of the elastic body 5 is covered with an outer peripheral portion 51 having a higher elastic modulus than the elastic body 5, and the outer peripheral portion 51 restricts the expansion of the elastic body 5 in the planar direction. Therefore, in Examples 8 and 9 (second embodiment), the dimensional retention rate of the elastic body 5 in the planar direction is 100%.

[0087] With the above settings, the average surface pressure was 4.3 MPa, the surface pressure difference was 1.81 MPa, the surface pressure maintenance rate was 86%, and the surface pressure difference / average surface pressure was 42% in Example 8. In Example 9, the average surface pressure was 4.2 MPa, the surface pressure difference was 1.92 MPa, the surface pressure maintenance rate was 84%, and the surface pressure difference / average surface pressure was 46%.

[0088] The material of outer peripheral portion 51 used in Example 8 (PMMA (elastic modulus: 125 MPa)) and the material of outer peripheral portion 51 used in Example 9 (PTFE (elastic modulus: 11.8 MPa)) have significantly different elastic moduli. However, no significant differences were observed in the surface pressure maintenance rate and surface pressure difference / average surface pressure between Example 8 and Example 9, and the surface pressure maintenance rates exceeded 80% in both cases.

[0089] Therefore, in the configuration of the second embodiment, if the elastic modulus of the outer peripheral portion 51 is sufficiently greater than the elastic modulus of the elastic body 5, no large difference occurs in the surface pressure maintenance rate and the surface pressure difference / surface pressure average, and a high surface pressure maintenance rate can be maintained. Therefore, even in the pressure application structure of the storage battery of the second embodiment, a uniform and appropriate surface pressure distribution can be stably achieved for the electrode portion 31, and variations in the capacity and output of the storage battery cell 3 can be reduced.

[0090] Example 10 had the configuration of the third embodiment shown in FIG. 13, and a natural rubber sheet containing a reinforcing fabric 52 was used as the elastic body 5 containing the reinforcing fabric 52 .

[0091] Comparative Example 4 uses a natural rubber sheet without reinforcing fabric 52, and has a configuration substantially similar to that of Comparative Example 1 (FIG. 4).

[0092] Additionally, the dimensions of the elastic body 5 (natural rubber sheet) are the same as those of the elastic body 5 of Comparative Example 1 (3 mm×25 mm×25 mm), and the torque and set pressure are the same as those of Examples 3-7.

[0093] In Example 10, unlike the first embodiment, the elastic body 5 is not fitted into the recess 41. However, a reinforcing cloth 52 is arranged inside the elastic body 5, and the reinforcing cloth 52 restricts the expansion of the elastic body 5 in the planar direction. Therefore, in Example 10 (first embodiment), the dimensional maintenance rate of the elastic body 5 in the planar direction is 110%. On the other hand, in Comparative Example 4, since there is no reinforcing cloth 52, the elastic body 5 expands in the planar direction due to the pressing force from the end plate 1U, and the dimensional maintenance rate in the planar direction is 120%.

[0094] With the above settings, the average surface pressure was 4 MPa, the surface pressure difference was 1.9 MPa, the surface pressure maintenance rate was 80%, and the surface pressure difference / average surface pressure was 48% in Example 10. In Comparative Example 4, the average surface pressure was 3.2 MPa, the surface pressure difference was 2.6 MPa, the surface pressure maintenance rate was 64%, and the surface pressure difference / average surface pressure was 81%.

[0095] In Example 10, the surface pressure maintenance rate was 80%, which was lower than Examples 1-9. However, the surface pressure difference was 1.9 MPa, which was better than Examples 5-7 ( FIG. 11 ) and Example 9. As described above, in Example 10, the surface-direction dimension maintenance rate of the elastic body 5 was 110%, but the reinforcing fabric 52 hardly expanded in the surface direction due to the pressing force from the end plate 1U, thereby suppressing the surface-direction expansion of the elastic body 5. Therefore, the surface pressure difference and surface pressure maintenance rate do not change significantly due to changes in torque and set pressure, or changes in thickness accompanying charging and discharging of the storage battery cell 3. Therefore, Example 10, i.e., the third embodiment ( FIG. 13 ), can stably form a uniform and appropriate surface pressure distribution and reduce variations in the capacity and output of the storage battery cell 3.

[0096] On the other hand, in Comparative Example 4, there is no means for suppressing expansion of the elastic body 5 in the planar direction, and the surface pressure difference and surface pressure maintenance rate can change significantly due to changes in torque and set pressure, and changes in thickness accompanying charging and discharging of the storage battery cell 3. Therefore, in Comparative Example 4, it is difficult to form a good surface pressure distribution, and it is also difficult to reduce variations in capacity and output of the storage battery cell 3.

[0097] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

[0098] This application claims priority based on Patent Application No. 2021-172698 filed with the Japan Patent Office on October 21, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A storage battery pressurization structure that applies pressure from a thickness direction to a structure made of storage battery cells including electrode portions packaged with a laminate exterior material, or a structure made of a stack of a plurality of the storage battery cells, a pair of end plates arranged at both ends of the structure in the thickness direction; a fastening member that fastens the pair of end plates to each other, an elastic body is disposed at one or more positions between the end plate and the structure; a rigid body is disposed at a position sandwiched between the elastic body and the structure; A pressure application structure for a storage battery, further including a deformation suppression means in any one of the end plate, the elastic body, and the rigid body, capable of suppressing deformation of the elastic body in a direction perpendicular to the thickness direction.

2. The deformation suppression means is The storage battery pressurizing structure according to claim 1 , wherein the rigid body and / or the end plate are formed with recesses into which the outer periphery of the elastic body is fitted.

3. The deformation suppression means is 2. The storage battery pressurizing structure according to claim 1, wherein the outer periphery is arranged to cover the outer periphery of the elastic body and is made of a material having a higher elastic modulus than the elastic body.

4. The deformation suppression means is 2. The storage battery pressurizing structure according to claim 1, wherein the elastic body is made of a fibrous material arranged in a mesh pattern inside the elastic body.

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