Battery steel strip testing method and battery steel strip testing device

Abstract

The invention provides a battery steel strip testing method and a battery steel strip testing device, and relates to the technical field of batteries. The battery steel strip testing method comprises the following steps: S1, estimating the expansive force of a battery module; s2, the two end plate profiling jigs are oppositely arranged at intervals, and the steel belt is annularly wound around the two end plate profiling jigs; and S3, the expansive force obtained in the step S1 is applied to the two end plate profiling jigs from the position between the two end plate profiling jigs, at least one test period is continuously applied, and the deformation amount of the steel belt is recorded. The structure and the force application mode are improved, so that the stress condition of the steel belt is close to the actual condition as much as possible, the accuracy of the test result is improved, and the situation that the steel belt selected according to the test result is fractured or bound to be invalid in the later period of battery circulation is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery steel strip testing method and a battery steel strip testing device. Background Art

[0002] A battery module generally includes multiple battery cells. After the multiple battery cells are stacked and pressed with a certain pre-pressure, they are locked by a steel belt. In addition to the battery itself having a certain pre-pressure, the temperature may rise after the electrochemical reaction during use and generate a certain expansion force. Therefore, the steel belt is required to have good anti-expansion performance. Therefore, the steel belt used in the battery is generally tested for tensile performance. In the related technology, there are generally two ways to test the tensile performance of the steel belt. One is to use a tensile testing machine to test the tensile strength of the steel belt raw material. The other is to make the steel belt into a ring shape for binding the battery and then wind it on the mold. The expansion force is applied to the steel belt through the mold. The force value is increased step by step during the test, and the deformation of the steel belt is recorded to obtain the ability of the steel belt to resist the expansion force.

[0003] The above test method cannot reflect the stress conditions of the steel belt in actual application. The test results deviate greatly from the actual stress of the steel belt. After verifying the design of the steel belt selection according to this test data, the steel belt often breaks or fails in binding in the later stage of battery cycle. Summary of the invention

[0004] Embodiments of the present invention provide a battery steel strip testing method and a battery steel strip testing device to improve the accuracy of the test results.

[0005] In a first aspect, an embodiment of the present invention provides a battery steel strip testing method, comprising:

[0006] S1, estimated expansion force of the battery module;

[0007] S2, arranging two end plate profiling jigs opposite to each other and at an interval, and winding the steel belt around the two end plate profiling jigs in an annular manner;

[0008] S3, applying the expansion force obtained in S1 to the two end plate profiling jigs from between the two end plate profiling jigs, continuously applying the expansion force for at least one test cycle, and recording the deformation of the steel strip.

[0009] In one embodiment of the present application, the test period is ≥ 30 days.

[0010] In one embodiment of the present application, the S1 includes:

[0011] S11, establishing a finite element model of a battery module, wherein the battery module includes a plurality of components, and the plurality of components include a crossbeam, an end plate, a conductive bar, an anchoring connector, and a steel belt;

[0012] S12, setting the material mechanical properties of the end plate, the conductive bar, the anchor connector and the steel strip, establishing contact relationships between the multiple components, defining boundary conditions, and applying a temperature load to the finite element model;

[0013] S13, and calculating the expansion force.

[0014] In one embodiment of the present application, the boundary conditions include: the bottom of the end plate is fixed to the cross beam through the anchor connector, and the bottom of the cross beam is fully constrained.

[0015] In one embodiment of the present application, the two end plates are fixed to the cross beam via four anchoring connectors, and each of the anchoring connectors applies a first torque.

[0016] In one embodiment of the present application, the formula for calculating the expansion force is: Among them, E is the elastic modulus, ν is Poisson's ratio, σ is stress, and ɑ ij is the expansion coefficient and ΔΤ is the temperature rise.

[0017] In one embodiment of the present application, in step S3, the expansion force minus the press-fitting pre-tightening force of the battery module is applied to the two end plate profiling jigs.

[0018] In one embodiment of the present application, the end plate profiling jig comprises a first surface, a second surface, a third surface, a fourth surface, a bottom surface and a top surface connected end to end in sequence, the first surface, the second surface and the fourth surface are used to contact the steel strip, and the third surface is used to withstand the expansion force;

[0019] One end of the first surface connected to the top surface is inclined toward a direction away from the third surface.

[0020] In one embodiment of the present application, the inclination angle of the first surface is 5-20°.

[0021] In one embodiment of the present application, a notch is provided on the first surface, the notch is adjacent to the top surface, and the notch is spaced apart from the second surface and the fourth surface.

[0022] In a second aspect, an embodiment of the present application further provides a battery steel strip testing device, which uses the battery steel strip testing method described in any one of the first aspects to test the steel strip.

[0023] Beneficial effects of the embodiments of the present invention:

[0024] In an embodiment of the present invention, two end plate profiling jigs are arranged to cooperate with the supporting annular steel belt, so that the arrangement of the steel belt is as close to the actual structure as possible. At the same time, the expansion force is first estimated, and then the estimated expansion force is applied between the two end plate profiling jigs and lasts for at least one test cycle, so that the steel belt is continuously subjected to the estimated expansion force. Therefore, by making improvements in the structure and the force application method, the force condition of the steel belt is made as close to the actual situation as possible, thereby improving the accuracy of the test results.

[0025] The embodiment of the present application also sets the opposite first surfaces of the two end plate profiling fixtures as inclined surfaces, so that the stress condition of the steel belt is closer to the upper steel belt that is subjected to greater stress, thereby reducing the situation where the steel belt test results are too low, resulting in actual breakage or restraint failure of the steel belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 is a flow chart of a battery steel strip testing method provided by an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of a steel belt wound around two end plate profiling jigs provided by an embodiment of the present invention;

[0029] Figure 3 is a flow chart of estimating the expansion force of the battery module in step S1 provided in an embodiment of the present invention;

[0030] Figure 4 is a front view of an end plate profiling jig provided by an embodiment of the present invention;

[0031] Figure 5 is a right side view of the end plate profiling jig provided by an embodiment of the present invention;

[0032] Figure 6 It is a top view of the end plate profiling jig provided in an embodiment of the present invention.

[0033] Icon: 1000-end plate profiling jig, 2000-steel strip, 1-first surface, 11-notch, 2-second surface, 3-third surface, 4-fourth surface, 5-bottom surface, 6-top surface, 7-through hole. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the drawings; while "inside" and "outside" refer to the outline of the device.

[0035] In the related art, there are generally two ways to test the tensile performance of steel strips. One is to use a tensile testing machine to test the tensile strength of the steel strip raw material, and the other is to make the steel strip into a ring shape for binding batteries and then wind it on a mold, and apply expansion force to the steel strip through the mold. During the test, the force applied to the steel strip is gradually increased, and the deformation of the steel strip is recorded until the steel strip breaks and fails, so as to obtain the ability of the steel strip to resist the expansion force.

[0036] Then, according to the test data, the appropriate steel belt type is selected for the production of battery modules. However, in the later stage of battery cycle, the steel belt may still break or fail. The inventor found that this is caused by the deviation between the relevant test method and the stress condition of the steel belt in actual application.

[0037] In view of this, an embodiment of the present application provides a battery steel strip testing method to make the test results closer to actual application conditions, improve the accuracy of the test results, and reduce the probability of steel strip breakage or binding failure in actual use.

[0038] like Figure 1 As shown, the battery steel strip test method includes:

[0039] S1, estimated expansion force of the battery module;

[0040] S2, two end plate profiling jigs 1000 are arranged opposite to each other and spaced apart, and the steel belt 2000 is wound around the two end plate profiling jigs 1000 in an annular manner, such as Figure 2 As shown;

[0041] S3, applying the expansion force obtained in S1 to the two end plate profiling jigs 1000 from between the two end plate profiling jigs 1000, continuously applying the expansion force for at least one test cycle, and recording the deformation amount of the steel strip 2000.

[0042] By setting two end plate profiling jigs 1000 to cooperate with the supporting annular steel belt 2000, the setting of the steel belt 2000 is made as close to the actual structure as possible. At the same time, the expansion force is first estimated, and then the estimated expansion force is applied between the two end plate profiling jigs 1000 and continued for at least one test cycle, so that the steel belt 2000 is continuously affected by the estimated expansion force. Therefore, by making improvements in the structure and the force application method, the force condition of the steel belt 2000 is made as close to the actual situation as possible, thereby achieving the purpose of improving the accuracy of the test results.

[0043] In the related art, although gradually increasing the tensile force value of the steel strip 2000 can test the instantaneous deformation of the steel strip 2000 under a certain force value, the rate of change of the expansion force value during normal operation of the battery is much lower than the rate of change of the force value in the test. The test results may be different when the steel strip 2000 is subjected to different force values ​​and different force change rates. The embodiment of the present application estimates the expansion force in actual conditions and then subjects the steel strip 2000 to the expansion force for more than one test cycle, so that the force application method is as close as possible to the actual force condition of the steel strip 2000.

[0044] In some embodiments, the duration of a test cycle is greater than or equal to 30 days.

[0045] In some embodiments, Figure 3 As shown, step S1 includes:

[0046] S11, establishing a finite element model of a battery module, wherein the battery module includes a plurality of components, and the plurality of components include a crossbeam, an end plate, a conductive bar, an anchoring connector, and a steel belt 2000;

[0047] S12, setting the material mechanical properties of the end plate, the conductive bar, the anchor connector and the steel belt 2000, establishing the contact relationship between the multiple components, defining the boundary conditions, and applying the temperature load to the finite element model;

[0048] S3, calculate the expansion force.

[0049] The embodiments of the present application focus on the main force-bearing components such as the crossbeam, end plates, conductive bars, anchor connectors and steel belt 2000, and simplify other non-critical components. In step S11, in the finite element model of the battery module, the number of end plates is two, the crossbeam is arranged at the bottom of the two end plates, and they are connected as a whole through anchor connectors to press multiple battery cells inside, the conductive bar is arranged on the top of the multiple battery cells and connects the positive and negative poles of each battery cell, and the steel belt 2000 is wrapped around the two end plates and connected end to end to form a ring.

[0050] In step S12, setting boundary conditions includes: the bottom of the end plate is fixed to the beam through an anchor connector, and the bottom of the beam is fully constrained.

[0051] Optionally, the two end plates are fixed to the cross beam by four anchoring connectors, and each anchoring connector applies a first torque. In other words, the two end plates are respectively placed at both ends of the cross beam, and each end plate is fixed to the cross beam by two anchoring connectors. The anchoring connectors can be bolts, screws, etc.

[0052] In some embodiments, the first torque is configured to be 2.0-5.0 N·m. For example, the first torque is 2.2 N·m, 2.5 N·m, 2.8 N·m, 3.0 N·m, 3.3 N·m, 3.5 N·m, 3.7 N·m, 4.0 N·m, 4.2 N·m, 4.5 N·m, 4.8 N·m or 5.0 N·m, etc.

[0053] It should be noted that the temperature load in step S12 is the constraint force caused by the deformation of each component and mutual constraint under temperature change.

[0054] In step S13, the formula for calculating the expansion force is: Among them, E is the elastic modulus, ν is Poisson's ratio, σ is stress, ɑij is the expansion coefficient, ΔΤ is the temperature rise, and the temperature rise is the temperature change value that produces the temperature load.

[0055] In some embodiments, in step S3, the expansion force is subtracted from the pre-tightening force of the battery module before being applied to the two end plate profiling jigs 1000, thereby further improving the accuracy of the test results. The better the performance of the steel strip 2000, the higher the cost. By setting it in this way, it is avoided to select the steel strip 2000 with excessive performance, and the cost of the steel strip 2000 is reduced on the basis of ensuring the performance of the steel strip 2000.

[0056] In some embodiments, the applied temperature load is set to a temperature load when the battery state of charge (SOC) is 20-80%, so that the stress condition of the steel strip 2000 is closer to the actual use condition of the battery.

[0057] In some embodiments, multiple temperature loads are selected within the range of 20-80% SOC, the expansion force values ​​are calculated respectively, and then the maximum value is continuously applied to the two end plate profiling fixtures 1000 for more than one test cycle.

[0058] Figure 4 , Figure 5 and Figure 6 An end plate profiling jig 1000 provided in an embodiment of the present application is shown, and the end plate profiling jig 1000 includes a first surface 1, a second surface 2, a third surface 3, a fourth surface 4, a bottom surface 5 and a top surface 6 which are sequentially connected end to end.

[0059] The first surface 1, the second surface 2 and the fourth surface 4 are used to contact the steel strip 2000, and the third surface 3 is used to withstand the expansion force.

[0060] Among them, one end of the first surface 1 connected to the top surface 6 is inclined in a direction away from the third surface 3. That is, when the two end plate profiling jigs 1000 are arranged opposite to each other, the third surfaces 3 of the two are opposite to each other, the first surfaces 1 of the two are opposite to each other, and the two first surfaces 1 are inclined surfaces with the upper ends inclined outwards.

[0061] The inventors found that in practice, battery modules are generally bundled by two upper and lower side-by-side steel strips 2000 (hereinafter referred to as upper steel strip and lower steel strip for ease of description). Since the bottom of the end plate is fixed by a crossbeam, under the restraining effect of the crossbeam, when the battery expands, the force on the lower steel strip is smaller and the force on the upper steel strip is larger. In the existing test results, the actual force deviation of the upper and lower steel strips is large, especially the test results of the upper steel strip will be lower than the actual situation, and the upper steel strip will break or fail to bind more often in the later stage of the cycle. The embodiment of the present application sets the opposite first surfaces 1 of the two end plate profiling fixtures 1000 as inclined surfaces, so that the force of the steel strip 2000 is closer to the upper steel strip with greater force, thereby reducing the situation where the steel strip 2000 breaks or fails to bind in practice due to the low test results.

[0062] In some embodiments, Figure 4 As shown, the inclination angle of the first surface 1 is 5-20°.

[0063] In some embodiments, in combination Figure 5 and Figure 6 As shown, the first surface 1 is provided with a notch 11, the notch 11 is adjacent to the top surface 6, and the notch 11 is spaced apart from the second surface 2 and the fourth surface 4. The main stress-bearing parts of the steel strip 2000 are the connection positions of the first surface 1 and the second surface 2, and the connection positions of the first surface 1 and the fourth surface 4, that is, the two end corners of the first surface 1. By providing the notch 11 in the middle of the first surface 1 near the top edge, it plays a role in saving materials and reducing the cost of the end plate profiling jig 1000.

[0064] In some embodiments, the connection positions between the first surface 1 and the second surface 2 and the connection positions between the first surface 1 and the fourth surface 4 are rounded corners to prevent the steel strip 2000 from being damaged due to excessive stress concentration at the corners, thereby reducing the test accuracy.

[0065] In some embodiments, the end plate profiling jig 1000 is made of a metal material with a certain hardness and toughness, such as stainless steel, copper or iron. Figure 2 , Figure 4 , Figure 5 and Figure 6As shown, the length of the end plate profiling jig 1000 in the first direction X is equal to the length of the actual middle end plate, the thickness of the end plate profiling jig 1000 in the second direction Y is equal to the thickness of the actual middle end plate, and the height of the end plate profiling jig 1000 in the third direction Z is greater than the width of the steel strip 2000.

[0066] In a second aspect, an embodiment of the present application further provides a battery steel strip testing device, which uses the battery steel strip testing method provided in any embodiment of the first aspect to test the steel strip 2000.

[0067] Exemplarily, the testing device includes a testing machine and two end plate profiling fixtures 1000 disposed opposite and spaced apart, such as Figure 6 As shown, each end plate profiling jig 1000 is provided with two through holes 7 penetrating the bottom surface 5 and the top surface 6, and a bolt or other anchor is arranged in each through hole 7 to connect the two end plate profiling jigs 1000 to the test bench of the testing machine, and the execution end of the testing machine is arranged between the two end plate profiling jigs 1000, and the steel belt 2000 is annularly wound around the two end plate profiling jigs 1000, and then the estimated battery module expansion force is applied to the two end plate profiling jigs 1000 through the execution end of the testing machine, and the force is continuously applied for at least one test cycle (such as 30 days), and the deformation of the steel belt 2000 is recorded.

[0068] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A battery steel strip testing method, characterized in that: include: S1, estimated expansion force of the battery module; S2, arranging two end plate profiling jigs opposite to each other and at an interval, and winding the steel belt around the two end plate profiling jigs in an annular manner; S3, applying the expansion force obtained in S1 to the two end plate profiling jigs from between the two end plate profiling jigs, continuously applying the expansion force for at least one test cycle, and recording the deformation of the steel strip.

2. The battery steel strip testing method according to claim 1, characterized in that: The test period is ≥ 30 days.

3. The battery steel strip testing method according to claim 1 or 2, characterized in that: The S1 includes: S11, establishing a finite element model of a battery module, wherein the battery module includes a plurality of components, and the plurality of components include a crossbeam, an end plate, a conductive bar, an anchoring connector, and a steel belt; S12, setting the material mechanical properties of the end plate, the conductive bar, the anchor connector and the steel strip, establishing contact relationships between the multiple components, defining boundary conditions, and applying a temperature load to the finite element model; S13, calculating the expansion force.

4. The battery steel strip testing method according to claim 3, characterized in that: The boundary conditions include: the bottom of the end plate is fixed to the cross beam through the anchor connector, and the bottom of the cross beam is fully constrained.

5. The battery steel strip testing method according to claim 4, characterized in that: The two end plates are fixed to the cross beam via four anchoring connectors, and each of the anchoring connectors applies a first torque.

6. The battery steel strip testing method according to claim 4, characterized in that: The formula for calculating the expansion force is: Among them, E is the elastic modulus, ν is Poisson's ratio, σ is stress, ɑij is the expansion coefficient, and ΔΤ is the temperature rise.

7. The battery steel strip testing method according to claim 6, characterized in that: In step S3, the expansion force minus the press-fit pre-tightening force of the battery module is applied to the two end plate profiling jigs.

8. The battery steel strip testing method according to claim 1, characterized in that: The end plate profiling jig comprises a first surface, a second surface, a third surface, a fourth surface, a bottom surface and a top surface connected end to end in sequence, the first surface, the second surface and the fourth surface are used to contact the steel strip, and the third surface is used to bear the expansion force; One end of the first surface connected to the top surface is inclined toward a direction away from the third surface.

9. The battery steel strip testing method according to claim 8, characterized in that: The inclination angle of the first surface is 5-20°.

10. The battery steel strip testing method according to claim 8, characterized in that: The first surface is provided with a notch, the notch is adjacent to the top surface, and the notch is spaced apart from the second surface and the fourth surface.

11. A battery steel strip testing device, characterized in that: The steel strip is tested using the battery steel strip testing method described in any one of claims 1 to 10.

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