Flat web and battery module including same

Abstract

The flat web includes a plurality of hollow tubes. Each hollow tube has an octagonal cross section with eight walls. The eight walls include a first surface wall and a second surface wall, each having a length A, two side walls perpendicular to the surface walls, each having a length B, and four connecting walls. B / A is 0.2 or greater and 1 or less. Adjacent side walls of adjacent hollow tubes are joined to form a flat web having a first flat surface including the first surface wall and a second flat surface including the second surface wall. Each connecting wall independently connects one of the surface walls to one of the side walls. Each wall has a thickness T, and each hollow tube has a height H from the first surface wall to the second surface wall. T / H is 0.02 or greater and 0.25 or less.

Description

[Technical Field]

[0001] The present disclosure relates to flat webs that may be used for cushioning applications in battery modules. Summary of the Invention

[0002] In some embodiments, the present disclosure provides a flat web comprising a plurality of hollow tubes. Each hollow tube has an octagonal cross section comprising eight walls. The eight walls include a first surface wall and a second surface wall, each having a length A, two side walls perpendicular to the surface walls, each having a length B, and four connecting walls. Adjacent side walls of adjacent hollow tubes are joined to form a flat web having a first flat surface comprising the first surface wall and a second flat surface comprising the second surface wall. Each connecting wall independently connects one of the surface walls to one of the side walls, and is configured such that the interior angle between the one of the surface walls and the connecting wall is X. Each wall has a thickness T, and each hollow tube has a height H from the first surface wall to the second surface wall. In some embodiments, B / A is 0.2 to 1, T / H is 0.02 to 0.25, and X is 100 degrees to 140 degrees.

[0003] In some embodiments, the present disclosure provides a flat web comprising a plurality of hollow tubes. Each hollow tube has an octagonal cross section comprising eight walls. The eight walls include a first surface wall and a second surface wall, each having a length A; two side walls perpendicular to the surface walls, each having a length B; and four connecting walls, each connecting wall independently connecting one of the surface walls to one of the side walls. Adjacent side walls of adjacent hollow tubes are joined to form a flat web comprising a single layer of the hollow tubes, the flat web having a first flat surface comprising the first surface wall and an opposite second flat surface comprising the second surface wall. In some embodiments, the compressive stress of the single layer of hollow tubes at 20% compression is 300 kPa or more, and the compressive stress at 60% compression is no more than three times the compressive stress at 20% compression.

[0004] In some embodiments, the present disclosure provides a battery module including at least one battery cell and at least one flat web of the present disclosure disposed along a surface of the at least one battery cell.

[0005] These and other aspects will become apparent from the following detailed description, although this brief summary should not be construed as limiting the subject matter of the claimable invention. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view of a flat web according to some embodiments.

[0007] [Figure 2] FIG. 2 is a schematic plot illustrating the relationship between compressive stress on a monolayer of a hollow tube and the compressibility of the monolayer, according to some embodiments.

[0008] [Figure 3] FIG. 3 is a schematic side view of a battery module according to some embodiments.

[0009] [Figure 4] FIG. 4 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 5] FIG. 5 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 6] FIG. 6 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 7] FIG. 7 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 8]FIG. 8 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 9] FIG. 9 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials. [Figure 10] FIG. 10 is a plot of compressive stress versus compressive strain for various flat webs and compressible materials.

[0010] [Figure 11] FIG. 11 is a plot illustrating the relationship between compressive stress and compressive strain of a flat web based on different interior angles of the hollow octagonal tubes of the flat web in some embodiments.

[0011] [Figure 12] FIG. 12 is a plot illustrating the initial compressive strain and plateau range of the stress-strain plateau as a function of the interior angle of a flat-web hollow octagonal tube according to some embodiments.

[0012] [Figure 13] FIG. 13 is a plot illustrating the relationship between compressive stress and compressive strain for various flat webs based on different interior angles and ratios of wall thickness T to height H of hollow octagonal tubes in some embodiments.

[0013] [Figure 14] FIG. 14 is a plot illustrating the initial compressive strain and plateau range in the stress-strain plateau as a function of the ratio of wall thickness T to height H for some embodiments.

[0014] [Figure 15] FIG. 15 is a plot illustrating compressive stress versus compressive strain for various flat webs in accordance with some embodiments.

[0015] [Figure 16]FIG. 16 is a plot illustrating the relationship between compressive stress of a flat web normalized by Young's modulus E and T / H for some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] To improve the range and efficiency of electric vehicles, current industry trends include increasing battery pack-level energy density through cell format consolidation and higher-energy-density lithium battery cell chemistries. Maintaining battery cell pressure and pressure uniformity in pouch-type and prismatic cells during volumetric changes associated with charge / discharge cycling is desirable for battery life and avoidance of failure modes. To date, foam materials have been used in an attempt to provide the desired pressure profile.

[0017] In the long term, the general trend is to move towards all-solid-state battery cells, which offer even higher energy densities (e.g., 500 Wh / kg) and superior safety compared to conventional lithium-ion batteries. However, maintaining the integrity of the Li-solid electrolyte interface to maintain low contact resistance during cell cycling requires a uniformity of lamination pressure beyond what conventional foam materials can provide. This poses a major challenge to the successful implementation of long-life all-solid-state battery cells in electric transportation.

[0018] As a result, there is a need for buffer materials that can provide an extended compression-load deflection (CFD) plateau that applies a relatively uniform force (stress) to the battery cell over a wide range of compression levels (strains) over the expected 10-year battery life. For example, in solid-state battery cells, a CFD plateau stress of at least 0.3 MPa (e.g., 0.3 to 5 MPa) may be desired to maintain contact between the solid electrolyte and the electrodes. In some solid-state battery cells, a CFD plateau stress of at least 0.4 MPa, 0.5 MPa, 0.8 MPa, or 1 MPa may be desired. Furthermore, to improve reliability and provide a wider operating range, a CFD plateau range extending at least from 20% to 60% strain is desired. While the CFD plateau may exhibit some stress change with compression, it is desirable that the rate of change be significantly smaller than the stress-compression curve region before and after the CFD plateau.

[0019] In some embodiments, it has been found that a flat web with octagonal hollow tubes bonded along its sidewalls can provide the desired CFD plateau stress and plateau width or span. In contrast, structures with hexagons or other shapes bonded along their sides result in lower CFD plateau stresses or narrower plateaus (see, e.g., FIG. 10). Other shapes, such as "squircles" (e.g., WO 2021 / 250478 (Ausen et al.)), have been found to exhibit large variations in compressive stress in the compression region where a plateau is desired (see FIG. 9), and tend to experience stress decreases with each compression cycle (see FIG. 9). Generally, after the first cycle (when residual stresses in the web can result in high stresses in the CFD curve), it is desirable for the CFD curve to remain stable for subsequent cycles (e.g., the octagonal hollow tube web shown in FIG. 8).

[0020] FIG. 1 is a schematic cross-sectional view of a flat web 100 according to some embodiments. The flat web 100 includes a plurality of hollow tubes 101, each having an octagonal cross section with eight walls. The eight walls include a first surface wall 111 and a second surface wall 112 having a length A, two side walls 121 and 122 perpendicular to the surface walls and having a length B, and four connecting walls 131, 132, 133, and 134, each connecting wall independently connecting one of the surface walls to one of the side walls, and the interior angle between the one of the surface walls and the connecting wall is X. Adjacent side walls 122 of adjacent hollow tubes are joined to form the flat web 100, which has a first flat surface 141 including the first surface wall 111 and a second flat surface 142 including the second surface wall 112. The flat web 100 may extend along first and second directions (e.g., the x-direction and the y-direction) and have a height H in a thickness direction (z-direction) perpendicular to these directions. The first and second flat surfaces 141 and 142 may be parallel to a plane defined by the first and second directions (the xy-plane), respectively. In some embodiments, the flat web 100 may extend substantially uniformly along its length (y-direction), and each cross-section perpendicular to its length (parallel to the xz-plane) may have a substantially identical shape within normal manufacturing variations. For example, the flat web 100 may be formed by extrusion along the y-direction. In some embodiments, the hollow tubes 101 may include at least 3, 4, 5, 8, 10, or 15 tubes.

[0021] In some embodiments, it has been found that when X exceeds 140 degrees, the compressive stress at the CFD plateau may be lower than desired, and when X is less than 100 degrees, the CFD plateau may be shorter than desired (e.g., by the region of rapid stress increase in the CFD curve shifting to lower strain) (see Figures 11 and 15). In some embodiments, X may be 100, 105, 108, or 110 degrees or greater. In some embodiments, X may be 140, 135, 130, or 125 degrees or less. For example, in some embodiments, X may be 100 degrees or greater and 140 degrees or less, or 105 degrees or greater and 130 degrees or less, or 108 degrees or greater and 125 degrees or less.

[0022] Generally, a sufficiently large B / A ratio (e.g., B / A ≥ 0.2) is desirable to achieve the desired mechanical stability. For example, because octagonal shapes are joined together only by their sidewalls, the sidewalls must be long enough to provide sufficient bonding area to provide the desired mechanical stability. It has been found that a B / A ratio greater than 1 can alter the buckling mechanism and shorten the CFD plateau. In some embodiments, B / A may be 0.2, 0.3, or 0.4 or greater. In some embodiments, B / A may be 1, 0.9, or 0.8 or less. For example, in some embodiments, B / A may be 0.2 to 1, or 0.4 to 0.8 or less. In some embodiments, A may be 1, 2, 3, or 4 mm or greater. In some embodiments, A may be 15, 12, or 10 mm or less. For example, A may be in the range of 1 to 15 mm, or 2 to 12 mm. In some embodiments, B may be 0.4, 0.7, 1, 1.2, or 1.5 mm or greater. In some embodiments, B may be equal to or less than 6, 5, 4, or 3 mm. For example, B may be in the range of 0.4 to 6 mm, 0.7 to 5 mm, or 1 to 4 mm.

[0023] Each of the four connecting walls 131, 132, 133, and 134 may have a length C. In some embodiments, C / A may be 0.8 to 1.2, or 0.9 to 1.1, or 0.95 to 1.05. In some embodiments, C / A may be 1 or about 1. In some embodiments, a C / A of 1 or about 1 has been found to contribute to achieving desired CFD plateau stresses and plateau widths.

[0024] Each wall has a thickness T, and each hollow tube has a height H from the first surface wall 111 to the second surface wall 112. Dimensions are measured from the exterior unless otherwise specified. In some embodiments, it has been found that a T / H of 0.02 or greater results in a desired CFD plateau stress, and a T / H of 0.25 or less results in a desired CFD plateau width. T / H may be, for example, 0.02, 0.04, 0.06, 0.08, or 0.1 or greater, or 0.25, 0.2, 0.18, or 0.16 or less. For example, T / H may be 0.04 or greater but 0.25 or less, 0.08 or greater but 0.2 or less, or 0.1 or greater but 0.1 or greater but 0.18 or less. Increasing T / H within the above ranges may increase the stress along the CFD plateau, while decreasing T / H may widen the CFD plateau width (see Figures 13-14). In some embodiments, H / A may be 1.2, 1.5, 1.7, or 2 or greater, and 3.5, 3.25, 3, or 2.75 or less. For example, H / A may be 1.5 or greater and 3.25 or less, 1.7 or greater and 3 or less, or 2 or greater and 2.75 or less. In some embodiments, H may be 1, 2, 3, 4, 5, 6, or 7 mm or greater, and 25, 20, or 15 mm or less. For example, H may be in the range of 2 to 25 mm, 3 to 20 mm, or 4 to 15 mm. In some embodiments, B may be T or greater and H / 2 or less. For example, B / T may be 1.2 or 1.5 or greater, and B / H may be 0.4, 0.3, or 0.2 or less.

[0025] FIG. 2 is a schematic plot illustrating the relationship between compressive stress and compressibility for a single layer of a hollow tube, according to some embodiments. The plot includes a first portion 251 extending from a compressibility C1 (e.g., 20% or less compression) to a compressibility C2 (e.g., 60% or more compression). The first portion 251 may be located between a second portion 252 and a third portion 253. In some embodiments, the rate of change of compressive stress in the first portion 251 is less than the rates of change in the second and third portions 252, 253. The first portion 251 may be referred to as a "plateau portion" or a "CFD plateau." The compressive stress S1 at the compressibility C1 may be, for example, 100, 200, 300, 400, 500, 800, or 1000 kPa or greater. The compressive stress S2 at the compressibility C2 may be 0.8 times or more and 3, 2.5, 2, or 1.8 times or less than S1. In some embodiments, S2 may be 1.2 times or more than S1. Furthermore, S2 may be 7, 5, 3, or 2 MPa or less.

[0026] The relationship between compressive stress and compressibility may be measured, for example, according to ASTM D3574-17 test standard or the modified ASTM D3574-17 test method described in the Examples. Performing multiple compression cycles and using data from the third compression cycle can eliminate or minimize the Mullins effect. For example, the compressive stress shown in FIG. 2 may be data from the third compression cycle. In some embodiments, the compressive stress in the second or subsequent compression cycles remains substantially unchanged.

[0027] In some embodiments, adjacent side walls of adjacent hollow tubes are joined to form a flat web 100 of a single layer of hollow tubes having a first flat surface 141 including a first surface wall 111 and an opposite second flat surface 142 including a second surface wall 112. In some embodiments, the single layer has a compressive stress (S1) at 20% compression (C1) of 300 kPa or more, and a compressive stress (S2) at 60% compression (C2) of 3, 2.5, 2, or 1.8 times or less than S1. In some embodiments, S2 may be greater than or equal to S1. Additionally, S1 may be greater than or equal to 400 kPa, 500 kPa, 800 kPa, or 1 MPa. In some embodiments, a plot showing the relationship between the compressive stress of a hollow tube monolayer and its compressibility includes a first portion 251 extending at least from 20% compression to 60% compression, in which the minimum compressive stress (C1) in the first portion 251 is 500 kPa or greater and the maximum compressive stress (C2) is 2 or 1.8 times the minimum compressive stress or less.

[0028] The flat web 100 may be produced, for example, by a profile extrusion process as generally described in International Publication No. WO2021 / 250478 (Ausen et al.), or by 3D printing as described in U.S. Pat. No. 5,121,329 (Crump), International Publication No. WO2020 / 044236 (Schadel et al.), WO2021 / 033138 (Sahni et al.), and WO2022 / 106998 (Schneiderman et al.).

[0029] In some embodiments, walls 111, 112, 121, 122, and 131-134 may comprise a polymer. The polymer may be a thermoset or thermoplastic polymer. In some embodiments, the polymer may be an extrudable thermoplastic resin. Suitable polymers include, for example, polyethylene (PP), polypropylene (PE), PP-PE copolymers, polyurethane, and urethane acrylate. In some embodiments, the walls may be non-porous (e.g., a non-porous polymer).

[0030] For example, representative polymers useful for profile extrusion and their modulus values ​​are shown in Table 1. The modulus at a given elongation is the tensile stress at that elongation divided by the elongation. Table 1: Properties of extrudable polymers [Table 1]

[0031] In some embodiments, the polymer may have a Young's modulus E of 0.3, 1, 2, 3, 4, 5, 8, or 10 MPa or greater. In some embodiments, the Young's modulus E may be 3500 MPa, 2000 MPa, 1000 MPa, 700 MPa, or 500 MPa or less. For example, in some embodiments, the polymer may have a Young's modulus E of 3 MPa or greater and 700 MPa or less. Generally, a higher Young's modulus allows for the use of thinner walls (smaller T) to achieve a desired stress. A Young's modulus E in the range of 3 to 700 MPa and a T / H in the range of 0.02 to 0.25 allows for useful CFD plateau stresses and plateau widths to be achieved, and allows for the use of a wide range of extrudable polymers. As further described in the Examples, the compressive stress along the CFD plateau as a function of T / H for the cases where X is an included angle of 110 degrees and 120 degrees was determined by computer simulation. The results are shown in Figure 17. The stress determined by the model is proportional to Young's modulus E and varies approximately with T / H according to a power law. In some embodiments, when n is 2.5 or greater and 2.6 or less, E(T / H) n For example, when the interior angle X is 120 degrees and T / H is 0.02, if the Young's modulus E is 700 MPa, then E(T / H) 2.5 is about 40 kPa, and the CFD plateau stress is about 120 kPa, which is useful for some applications. On the other hand, if the Young's modulus E is 100 MPa, then E(T / H) 2.5is about 6 kPa, and the CFD plateau stress is about 17 kPa, which is insufficient for some applications. As another example, if the interior angle X is 110 degrees and T / H is 0.1, and Young's modulus E is 50 MPa, then E(T / H) 2.6 is approximately 126 kPa, and the CFD plateau stress is approximately 690 kPa. As another example, if the interior angle X is 120 degrees, T / H is 0.25, and Young's modulus E is 3 MPa, then E(T / H) 2.5 The CFD plateau stress is approximately 94 kPa and the Young's modulus E may be measured, for example, according to ASTM D638-14.

[0032] The polymer may be characterized by its hardness. In some embodiments, the polymer may have a hardness of 75, 80, or 85 Shore A or greater. The hardness may be, for example, up to 100 or 95 Shore A, or up to 70, 60, or 50 Shore D. Hardness may be measured, for example, according to ASTM D2240-15(2021).

[0033] The flat web may be characterized by its compression set. Compression set measures the amount of permanent deformation remaining after application and removal of force and is expressed as Ct = [(ti - tf) / ti] x 100%, where Ct is the compression set, ti is the initial thickness of the specimen, and tf is the final thickness after application and removal of force. Generally, a lower compression set is desirable. In some embodiments, the flat web may have a compression set of 20%, 15%, 10%, 5%, 4%, or 3% or less after 22 hours at 23°C. In some embodiments, the compression set may be 20%, 15%, 10%, or 5% or less after 22 hours at 70°C. Compression set may be measured, for example, according to ASTM D3574-17 Test D, or a modified ASTM D3574-17 Test D (using an oven temperature of 70°C) as described in the Examples.

[0034] The flat web may be used as a cushioning material within the battery module. FIG. 3 is a schematic side view of a battery module according to some embodiments. The battery module 20 includes at least one battery cell 22 and at least one flat web 100 disposed along the surface of the battery cell 22. For example, the first or second flat surface 141 or 142 of the flat web 100 may be disposed on the main surface of the battery cell 22. The at least one flat web 100 may include multiple flat webs 100. In some embodiments, the at least one battery cell 22 may include multiple battery cells arranged in a row, with one flat web 100 disposed between each pair of adjacent battery cells. The battery module 20 may also optionally include flat webs 100 between the battery cells disposed at both ends or one end of the row and the housing of the battery module 20. Additional flat webs 100 may be disposed along the upper and / or lower surfaces of the battery cells 22. In some embodiments, the battery cells 22 may be placed on a cooling plate 26 disposed on a tray 28. Related battery modules are described, for example, in International Publication No. WO2022 / 024085 (Wu et al.).

[0035] example material Table 2: Summary of materials used in the preparation of the examples [Table 2]

[0036] Test Method Used Compression Test Method The mechanical properties of the specimens were measured by compression using an Instron mechanical testing system (Model No. 5969). Custom-made steel compression plates with a diameter of 40 mm were used. Compression tests were performed according to a modified ASTM D3574-17 test standard. The compression rate was 5 mm / min, and the specimens were compressed to 70% compressive strain. After each cycle, the thickness was adjusted to account for permanent wear caused by compression. Compression tests were performed using a 50 kN load cell. Specimens were cut into 2.5 mm square pieces, and five compression cycles were performed for each test. Data from the third compression cycle was used to eliminate or minimize the Mullins effect. Compression set test method The compression set of the specimens was measured according to modified ASTM D3574-17 Test D. Specimens with a given width, height, and thickness were placed in a compression apparatus and compressed to 50% of their original thickness. Within 15 minutes, the deformed specimens were placed in a 70°C mechanical convection air oven for 22 hours. After 22 hours, the compression apparatus was removed from the oven, and the specimens were immediately removed from the apparatus. The specimens were then allowed to recover at room temperature for 30-40 minutes before their thickness was measured. The compression set was calculated according to the following formula: Ct = [(ti - tf) / ti] × 100%, where Ct is the compression set (%), ti is the initial thickness of the specimen, and tf is the final thickness.

[0037] Sample flat webs were fabricated by 3D printing using the materials listed in Table 3 to create hollow octagonal tubes with the geometries listed in the table. The octagonal geometry was roughly the geometry shown in Figure 1, with a C / A of approximately 1 (e.g., within ±20%) and a B / A of approximately 0.5. The printing methods used were fused deposition modeling (FDM, also known as fused filament fabrication, FFF) for TPU92A and TPU95A, and stereolithography (SLA) for UA80A. The FDM method used is generally described in International Publication No. WO 2020 / 044236 (Schadel et al.) (see, e.g., page 12, line 20 to page 13, line 27). The SLA method used is generally described in International Publication No. WO 2022 / 106998 (Schneiderman et al.) (see, e.g., page 27, line 30 et seq.). Table 3: Materials and shapes used in Examples 1 to 20 [Table 3]

[0038] The compressive stress versus modulus of compression of the flat web was measured according to the method described in "Compression Test Method." The results at 20% and 60% compression are shown in Table 4. Table 4: Results of Examples 1 to 20 [Table 4]

[0039] Figures 4 and 5 are plots of compressive stress versus compressibility for Examples 17 and 5, respectively. For comparison, these figures also show results for PU foam and soft and firm silicone foam samples. The soft and firm silicone foams were generally made by methods described in International Publication No. WO 2021 / 176372 (Kempf et al.). Figure 6 is a plot of compressive stress versus compressibility for Examples 9 and 5. Figure 7 is a plot of compressive stress versus compressibility for Examples 5 and 6, respectively.

[0040] Compression set was measured for various samples as described in the "Compression Set Test Method." The results are shown in Table 5. Table 5: Compression Set Data [Table 5]

[0041] Octagonal continuous webs were produced using a 90 / 10 PP-PE 7810 / 8880 blend by the profile extrusion method generally described in International Publication No. WO 2021 / 250478 (Ausen et al.), except that the extrusion die was configured to extrude an octagonal shape. The extruded samples had a wall thickness of 0.24 mm and a height of 2.44 mm, resulting in a T / H ratio of 0.098. The interior angle X of the octagon was 150 degrees. The octagon had a C / A of approximately 1 and a B / A of approximately 0.5. As described elsewhere herein, decreasing the interior angle X can increase the compressive stress along the plateau of the CFD curve (see, e.g., Figure 11). For comparison, squircle webs were also produced by the profile extrusion method generally described in International Publication No. WO 2021 / 250478 (Ausen et al.). A nonlinear compression curve was observed for a similar specimen with a height of 1.88 mm. The squircle specimen was fabricated using PE 5230G. While the choice of material may affect the absolute value of the CFD curve, it appears to have little effect on the shape of the curve. The results are shown in Figures 8 and 9 for the octagonal and squircle webs, respectively. Each figure shows the curves for five compression cycles. In Figure 8, the curves for cycles 2 through 5 nearly overlap. In Figure 9, however, the compression portion of the curve for the squircle web decreases with each cycle.

[0042] Computer simulations were performed to determine the relationship between compressive stress and compressibility for various flat webs. The models included octagons and hexagons joined at their sides. The materials were modeled as linear elastic bodies with a Young's modulus of 1 GPa and a Poisson's ratio of 0.45. These values ​​are in the range appropriate for thermoplastic polyurethanes, for example. The octagons were modeled as T = 0.3 mm, H = 2.0 mm, X = 110°, A = C = 1 mm, and B = 0.5 mm. The hexagons were modeled as shapes with the same wall thickness and overall height as the octagons, with A and B = 1 mm and sides with 120° internal angles. The flat web under compression consisted of many repeating patterns and was modeled as a three-pattern unit structure sandwiched between two flat rigid plates. These flat rigid plates represented the battery surface adjacent to the flat web. Because the web thickness was sufficiently small compared to the other dimensions, the three pattern units were modeled using shell finite elements to represent the midsurface of the web. In this model, the dimensions T, H, X, A, B, and C were measured along the mid-plane (centerline) of the octagonal wall, rather than from the outer surface as shown schematically in Figure 1. The pattern depth was five times the side length (A). Simulations were performed using the LS-DYNA software, a general-purpose explicit dynamic finite element solver available from ANSYS, Inc. (Canonsburg, PA, USA). The results are shown in Figure 10. The resulting compressive stress is proportional to Young's modulus E in the model. Therefore, in Figure 10 and other model-based stress diagrams, the stress is normalized by Young's modulus E.

[0043] Simulations were performed on a side-jointed octagon with T / H = 0.075, 0.1, and 0.15, X = 110, 120, 135, and 150 degrees, B / A = 0.5 and 0.75, and C / A = 1. The results are shown in Figures 11 through 16. Figure 11 is a plot of compressive stress versus compressive strain for various interior angles X, where T / H = 0.15 and B / A = 0.5. Figure 12 is a plot of the initial compressive strain and plateau range of the stress-strain plateau as a function of interior angle X. Figure 13 is a plot of compressive stress versus compressive strain for various interior angles X and T / H values. Figure 14 is a plot of the initial compressive strain and plateau range of the stress-strain plateau as a function of T / H. In Figures 13 and 14, B / A was set to 0.5. The results in Figure 13 are shown for heights H of 2 mm (gray curve) and 4 mm (black curve). Figure 15 shows a plot of compressive stress versus compressive strain for various interior angles X and B / A at T / H=0.15. Figure 16 shows the compressive stress σ on the CFD plateau for X=110° and 120°. p The ratio of Young's modulus E to T / H is plotted against T / H, showing how the compressive stress in the model varies in proportion to Young's modulus E and T / H.

[0044] Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A flat web comprising a plurality of hollow tubes, each hollow tube having an octagonal cross section comprising eight walls, said eight walls comprising: a first surface wall and a second surface wall, each having a length A; two side walls perpendicular to the surface wall, each having a length B; four connecting walls, each connecting wall independently connecting one of the surface walls and one of the side walls, and configured such that an interior angle between the one of the surface walls and the connecting wall is X; Equipped with each said wall having a thickness T, and each said hollow tube having a height H from said first surface wall to said second surface wall; adjacent side walls of adjacent hollow tubes are joined to form a planar web having a first planar surface including said first surface wall and a second planar surface including said second surface wall; B / A is 0.2 or more and 1 or less, T / H is 0.02 or more and 0.25 or less, A flat web wherein X is equal to or greater than 100 degrees and equal to or less than 140 degrees.

2. 2. The flat web of claim 1, wherein T / H is 0.08 or more and 0.2 or less, X is 105 degrees or more and 130 degrees or less, and B / A is 0.4 or more and 0.8 or less.

3. 3. The flat web according to claim 1, wherein each of the four connecting walls has a length C, and C / A is 0.8 to 1.

2.

4. A flat web according to any one of claims 1 to 3, wherein the walls are non-porous.

5. A flat web according to any one of claims 1 to 4, wherein the walls comprise a polymer.

6. 6. The flat web of claim 5, wherein the flat web has a compression set of 20% or less after being held at 23[deg.] C. for 22 hours.

7. 7. A flat web according to claim 5 or 6, wherein the polymer has a Young's modulus E of 3 MPa to 700 MPa.

8. When n is 2.5 or more and 2.6 or less, E(T / H) ｎ 8. The flat web of claim 7, wherein the modulus of elasticity is 30 kPa or greater.

9. at least one battery cell; At least one flat web according to any one of claims 1 to 8 arranged along a surface of the at least one battery cell; A battery module comprising:

10. A flat web comprising a plurality of hollow tubes, each hollow tube having an octagonal cross section comprising eight walls, said eight walls comprising: a first surface wall and a second surface wall, each having a length A; two side walls perpendicular to the surface wall, each having a length B; four connecting walls, each connecting wall independently connecting one of the surface walls and one of the side walls; Equipped with adjacent side walls of adjacent hollow tubes are joined to form a flat web consisting of a single layer of said hollow tubes having a first planar surface including said first surface wall and an opposite second planar surface including said second surface wall; A flat web in which a single layer of the hollow tube has a compressive stress of 300 kPa or more when compressed by 20% and a compressive stress of 60% or less that is three times the compressive stress when compressed by 20%.

11. 11. The flat web according to claim 10, wherein the interior angle X between each surface wall and each connecting wall connected thereto is 100 degrees or more and 140 degrees or less.

12. 12. A flat web according to claim 10 or 11, wherein each wall has a thickness T and each hollow tube has a height H from the first surface wall to the second surface wall, with T / H being greater than or equal to 0.02 and less than or equal to 0.

25.

13. 13. The flat web according to claim 10, wherein B / A is 0.2 or more and 1 or less.

14. 14. The flat web of claim 10, wherein a plot of compressive stress for a single layer of the hollow tube versus compressibility of the single layer includes a first portion extending at least from 20% compression to 60% compression, wherein the minimum compressive stress in the first portion is 500 kPa or greater and the maximum compressive stress is less than or equal to two times the minimum compressive stress.

15. at least one battery cell; At least one flat web according to any one of claims 10 to 14, arranged along a surface of the at least one battery cell; A battery module comprising:

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