Multifunctional mechanical testing device and method for square lithium ion battery

Abstract

The application relates to a multifunctional mechanical testing device and method for a square lithium ion battery, which comprises a bottom plate, a first fixed plate, a second fixed plate, a movable plate, a servo electric cylinder, a spoke pressure sensor, a displacement sensor and a controller, the first fixed plate and the second fixed plate are fixed on the bottom plate in parallel, the movable plate is movably arranged between the first fixed plate and the second fixed plate, and a square lithium ion battery to be tested is clamped between the first fixed plate and the movable plate; the servo electric cylinder is drivingly connected with the movable plate; the spoke pressure sensor is installed on the movable plate and used for measuring the pre-tightening force borne by the square lithium ion battery; the displacement sensor is installed on the second fixed plate and used for measuring the displacement of the movable plate; the servo electric cylinder, the pressure sensor and the displacement sensor are electrically connected with the controller, so that various mechanical tests of the square lithium ion battery are realized. The application has high integration, low cost, flexible measurement mode and high precision.

Description

Technical Field

[0001] This invention relates to the field of battery performance testing technology, and in particular to a multifunctional mechanical testing device and method for square lithium-ion batteries. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage technologies, prismatic lithium-ion batteries have become a core component of CTP (Cell to Pack) battery pack designs due to their structural stability and high assembly efficiency. In CTP technology, prismatic lithium-ion batteries are directly bonded to the battery pack base plate via bottom adhesive coating, eliminating the need for traditional module structures. This design presents new challenges for testing prismatic lithium-ion batteries and their connection methods.

[0003] Currently, there are some publicly available technical solutions for the mechanical testing and related adhesive performance evaluation of prismatic lithium-ion batteries. For example, a universal testing machine with a pressure plate is used to conduct compression tests on prismatic lithium-ion batteries to calculate their elastic modulus; another example is the use of standard lap joint test pieces to evaluate the shear strength of the adhesive. However, existing technologies still have the following shortcomings: First, in the testing of the equivalent elastic coefficient of square lithium-ion batteries, existing equipment is mostly general-purpose universal testing machines, which are bulky and expensive. Ordinary testing machines cannot guarantee high parallelism of the pressure plates during movement, which easily leads to off-center loading, resulting in deviations between the measured force-displacement data and the equivalent elastic coefficient under actual working conditions.

[0004] Secondly, regarding the adhesive bonding performance testing of the bottom adhesive in CTP (Cell-to-Pack) batteries, the standard adhesive overlap test uses a metal-to-metal standard test piece, which differs significantly from actual operating conditions. In practical applications, square lithium-ion battery casings are typically wrapped with an insulating blue film, and the stress mode is a combination of peeling and shearing, rather than pure shearing. Furthermore, the boundary constraints of the adhesive layer are completely different from those of the standard test piece. Therefore, the results of the standard overlap test cannot accurately predict the bonding performance and failure strength of the bottom adhesive in a CTP battery pack under actual service conditions.

[0005] Third, in terms of expansion force testing, existing measuring devices are typically single-function, capable of only measuring expansion force. More importantly, existing devices usually place the prismatic lithium-ion batteries on their side during testing, meaning the large surface area of ​​the battery is horizontal. However, in actual CTP battery packs, prismatic lithium-ion batteries are placed vertically. This side-lying posture alters the distribution of the electrolyte inside the prismatic lithium-ion battery and the effect of gravity on the expansion behavior of the separator and electrodes, resulting in discrepancies between the measured expansion force data and the performance of the prismatic lithium-ion battery in its actual vertical orientation. Summary of the Invention

[0006] The purpose of this invention is to provide a multifunctional mechanical testing device and method for square lithium-ion batteries to solve the aforementioned technical problems. Therefore, the technical solution adopted by this invention is as follows: According to one aspect of the present invention, a multifunctional mechanical testing device for a square lithium-ion battery is provided, comprising: Base plate; A first fixed plate, a second fixed plate, and a movable plate are provided. The first fixed plate and the second fixed plate are fixed to the base plate in parallel with each other. The movable plate is movably disposed between the first fixed plate and the second fixed plate. The square lithium-ion battery to be tested is clamped between the first fixed plate and the movable plate. A servo electric cylinder, wherein the servo electric cylinder is drivenly connected to the movable plate; A spoke pressure sensor, mounted on the movable plate, is used to measure the preload force on the square lithium-ion battery; A displacement sensor is mounted on the second fixed plate and is used to measure the displacement of the movable plate; The controller, in which the servo cylinder, pressure sensor, and displacement sensor are electrically connected, enables various mechanical tests on the square lithium battery.

[0007] In one embodiment, the testing device further includes a guide shaft, the two ends of which are fixed to the first fixed plate and the second fixed plate, respectively. A linear bearing is mounted on the movable plate and is sleeved on the guide shaft.

[0008] In one embodiment, the number of guide shafts is four, arranged in a square.

[0009] In one embodiment, a simulated adhesive layer is pre-coated or pasted onto the base plate.

[0010] In one embodiment, the driving mechanism is...

[0011] In one embodiment, the spoke pressure sensor is fixed to the movable plate, and the telescopic rod of the servo cylinder is fixedly connected to the center hole of the spoke pressure sensor.

[0012] In one embodiment, the displacement sensor is mounted on the second fixing plate via a displacement sensor bracket. One end of the displacement sensor bracket is a threaded section, and the other end is an elastic conical chuck. The second fixing plate has a conical hole that mates with the elastic conical chuck. The rod of the displacement sensor passes through the inner hole of the elastic conical chuck and the threaded section. When a nut is tightened on the threaded section, the elastic conical chuck contracts inward under radial constraint, thus clamping and fixing the rod of the displacement sensor.

[0013] According to another aspect of the present invention, a multifunctional mechanical testing method for square lithium-ion batteries is also provided, comprising: A multifunctional mechanical testing device for square lithium-ion batteries as described above is provided; The equivalent elastic coefficient of a square lithium-ion battery was measured. The adhesive bonding performance and failure strength of the bottom coating of a square lithium-ion battery were tested. The expansion force of a square lithium-ion battery under constant displacement conditions was measured. The expansion characteristics of a square lithium-ion battery under constant pressure were measured.

[0014] In one embodiment, measuring the equivalent elastic coefficient of the square lithium-ion battery includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate. The controller drives the servo cylinder to move the movable plate toward the first fixed plate to compress the square lithium-ion battery. During this process, the controller simultaneously records the pressure value of the pressure sensor and the displacement value of the displacement sensor. After compression, a curve is plotted with displacement as the abscissa and pressure as the ordinate. A segment with good linearity is selected for fitting, and the resulting slope is the equivalent elastic coefficient of the square lithium-ion battery in the corresponding compression range.

[0015] In one embodiment, the testing of the bottom adhesive bonding performance and failure strength of the square lithium-ion battery includes: Structural adhesive is applied to the base plate according to the actual CTP process. Then, the bottom of the square lithium-ion battery is attached to the structural adhesive and cured according to the curing process requirements to bond the square lithium-ion battery and the base plate together. Place the square lithium-ion battery on the testing device; The servo electric cylinder is activated, driving the movable plate to apply a horizontal thrust to the square lithium-ion battery. The controller records the force and displacement data throughout the loading process. When the force-displacement curve drops sharply, it indicates that the adhesive layer has debonded and failed. By recording the peak force at this time and combining it with the actual bonding area of ​​the adhesive layer, the failure strength of the adhesive layer under actual working conditions can be calculated.

[0016] In one embodiment, measuring the expansion force of a square lithium-ion battery under constant displacement conditions includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate. The controller drives the servo electric cylinder to compress the square lithium-ion battery by the movable plate. When the pressure sensor reading reaches the preset simulated preload value, the controller instructs the servo electric cylinder to stop moving and enter the position locking mode. Connect the square lithium-ion battery to an external charging and discharging device to begin a charge and discharge cycle. Throughout the entire charge and discharge process, the controller continuously records the readings from the spoke pressure sensor.

[0017] In one embodiment, measuring the expansion characteristics of a square lithium-ion battery under constant pressure conditions includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate; the servo cylinder is driven by the controller to compress the square lithium-ion battery with the movable plate until the reading of the pressure sensor reaches the preset preload value. The controller switches to constant pressure control mode, that is, with the preload value as the target value, it reads the feedback from the pressure sensor in real time and dynamically adjusts the extension and retraction position of the servo electric cylinder. When the square lithium-ion battery expands in volume during charging and discharging, causing the pressure to increase, the controller immediately instructs the servo cylinder to contract to release the excess pressure, so that the pressure sensor reading is always maintained near the preset value, avoiding a sudden drop in pressure; conversely, when the square lithium-ion battery contracts, causing the pressure to decrease, the controller instructs the servo cylinder to extend to compensate for the pressure. The controller records the changes in the displacement sensor and the charging and discharging parameters to obtain the variation law of the expansion displacement of the square lithium-ion battery with the state of charge under constant pressure boundary conditions.

[0018] The present invention, by adopting the above technical solution, has the following advantages: 1. This invention features high integration and low equipment cost. A single device can complete multiple key testing tasks, including testing the equivalent elastic coefficient of square lithium-ion batteries, testing the actual bonding performance of CTP bottom adhesive under working conditions, monitoring constant displacement expansion force, and studying constant pressure expansion characteristics, significantly reducing equipment procurement costs and laboratory space occupancy.

[0019] 2. This invention more closely reflects actual working conditions. In the adhesive performance test, the square lithium-ion battery casing and base plate are directly used as the adhesive, and the CTP coating process is reproduced. The measured failure strength and stiffness truly reflect the mechanical behavior of the product-level adhesive interface. In the expansion force test, the square lithium-ion battery is kept in a vertical position, consistent with the actual battery pack, eliminating the differences in electrolyte distribution and electrode expansion behavior caused by the square lithium-ion battery lying on its side, making the test data more valuable for engineering reference.

[0020] 3. This invention offers high measurement accuracy. The combination of four-axis guides and linear bearings ensures smooth movement and high parallelism of the movable plate, while the spoke pressure sensor provides excellent resistance to off-center loads. The synchronous acquisition of force and displacement provides a reliable data foundation for accurate calculations.

[0021] 4. The present invention offers flexible control modes. Through the controller's software algorithm, it is possible to simulate both constant displacement and constant pressure boundary conditions, providing a tool for studying the electro-mechanical coupling behavior of square lithium-ion batteries under different mechanical constraints. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of a multifunctional mechanical testing device for a square lithium-ion battery according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the installation structure of a displacement sensor according to an embodiment of the present invention.

[0023] Figure label: 1-First fixed plate; 2-Modible plate; 3-Second fixed plate; 4-Servo electric cylinder; 5-Pressure sensor; 6-Square lithium-ion battery; 7-Fixed base; 8-Guide shaft; 9-Linear bearing; 10-Base plate; 11-Displacement sensor; 12-Displacement sensor mounting bracket. Detailed Implementation

[0024] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to provide a clearer understanding of the purpose, features, and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative of the essential spirit of the technical solution of the present invention.

[0025] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0026] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0027] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0028] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0029] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0030] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0032] like Figure 1 and 2 As shown, according to one aspect of the present invention, a multifunctional mechanical testing device for a square lithium-ion battery is provided. The device includes a base plate 10, a first fixed plate 1, a movable plate 2, a second fixed plate 3, a servo electric cylinder 4, a spoke pressure sensor 5, a displacement sensor 11, and a controller (not shown).

[0033] The first fixing plate 1 and the second fixing plate 3 are arranged opposite to and parallel to each other. The first fixing plate 1 and the second fixing plate 3 are fixed to the base plate 10 by bolts for easy assembly and disassembly. The base plate 10 is used to place the square lithium-ion battery 6 to be tested or a simulated bonding base plate. The distance between the first fixing plate 1 and the second fixing plate 3 can be set as needed. The first fixing plate 1 and the second fixing plate 2 can usually be made of aluminum, stainless steel or their alloys. The first fixing plate 1 and the second fixing plate 2 are the same size. In one embodiment, the dimensions of the first fixing plate 1 and the second fixing plate 2 are 30cm (length) × 30cm (width) × 1cm (thickness).

[0034] The movable plate 2 is located between the first fixed plate 1 and the second fixed plate 3. Four guide shafts 8 are fixed at both ends to the first fixed plate 1 and the second fixed plate 3 respectively, forming a parallel frame with high stability. Linear bearings 9 are installed at the four corners of the movable plate 2, and each linear bearing 9 is sleeved on the corresponding guide shaft 8, allowing the movable plate 2 to move linearly along the axial direction of the guide shaft 8. It should be understood that only two guide shafts 8 can be used. The guide shafts 8 can be made of stainless steel and have a polished surface to reduce friction.

[0035] The cylinder body of the servo cylinder 4 is fixed to the side of the second fixed plate 3 facing away from the movable plate 2. The telescopic rod of the servo cylinder 4 passes through the central circular hole in the second fixed plate 3 and extends towards the movable plate 2. The central hole of the spoke pressure sensor 5 has an internal thread, and the head of the telescopic rod of the servo cylinder 4 has an external thread; the two are directly fixedly connected by the threads. The other side of the spoke pressure sensor 5 is fixed to the center position of the movable plate 2 by screws. Therefore, the servo cylinder 4 can drive the spoke pressure sensor 5 and the movable plate to move back and forth together. The spoke pressure sensor 5 is used to measure the preload force on the square lithium-ion battery. The spoke pressure sensor 5 is commercially available.

[0036] The mounting base 7 is used to support the tail of the servo electric cylinder 4. Adjusting the height of the mounting base 7 ensures that the cylinder axis is parallel to the guide shaft 8. The mounting base 7 and the base plate 10 are fixed on the same support platform (not shown).

[0037] The displacement sensor 11 is fixed to the second fixing plate 3 by a displacement sensor mounting bracket 12. One end of the displacement sensor mounting bracket 12 is a threaded section, and the other end is an elastic conical chuck. The second fixing plate 3 has a conical hole that mates with the elastic conical chuck. The rod of the displacement sensor 11 passes through the inner hole of the elastic conical chuck and the threaded section. When the nut is tightened on the threaded section, the elastic conical chuck retracts inward under radial constraint, clamping and fixing the rod of the displacement sensor 11. The probe of the displacement sensor 11 rests against the side of the movable plate 2.

[0038] The entire device is controlled by a single controller, which receives signals from the spoke pressure sensor 5 and the displacement sensor 11, and outputs commands to control the movement of the servo cylinder 4. This controller can be a microcontroller, PLC, or similar device.

[0039] According to another aspect of the present invention, a multifunctional mechanical testing method for a square lithium-ion battery based on the above-described testing apparatus is also provided. The method includes: The equivalent elastic coefficient of a square lithium-ion battery is measured using the following steps: The square lithium-ion battery 6 to be tested is placed vertically between the first fixed plate 1 and the movable plate 2, with the left side of the square lithium-ion battery 6 in close contact with the right side of the first fixed plate 1. The controller drives the servo cylinder 4 to move the movable plate 2 towards the first fixed plate 1, compressing the square lithium-ion battery 6. During this process, the controller simultaneously records the pressure value of the spoke pressure sensor 5 and the displacement value of the displacement sensor 11. After compression, a curve is plotted with displacement as the abscissa and pressure as the ordinate. A segment with good linearity is selected for fitting, and the resulting slope is the equivalent elastic coefficient of the square lithium-ion battery within the corresponding compression range.

[0040] The adhesion performance and failure strength of the bottom adhesive coating of a square lithium-ion battery under actual working conditions were measured. The specific steps are as follows: First, prepare a base plate 10. Apply structural adhesive to the base plate 10 according to the actual CTP process. Then, attach the bottom of the square lithium-ion battery 6 to the adhesive layer and cure it according to the curing process requirements to bond the square lithium-ion battery and the base plate together. Place the assembly in the testing device. When placing the square lithium-ion battery 6, its left side should not directly contact the first fixed plate 1 to ensure that there is no interference from other external forces during the movement. Start the servo cylinder 4 to drive the movable plate 2 to apply a horizontal thrust to the square lithium-ion battery. At this time, the horizontal thrust on the square lithium-ion battery 6 is completely balanced by the adhesive force of the bottom adhesive layer. The controller records the force and displacement data throughout the loading process. The force value represents the tangential force borne by the adhesive layer, and the displacement value represents the relative shear displacement between the square lithium-ion battery and the base plate. When the force-displacement curve drops sharply, it indicates that the adhesive layer has debonded and failed. Record the peak force at this time. Combined with the actual bonding area of ​​the adhesive layer, the failure strength of the adhesive layer under actual working conditions can be calculated.

[0041] The expansion force of a square lithium-ion battery under constant displacement conditions is measured using the following steps: The square lithium-ion battery 6 to be tested is placed vertically between the first fixed plate 1 and the movable plate 2, with the left side of the square lithium-ion battery 6 in close contact with the right side of the first fixed plate 1. The servo cylinder 4 is driven to compress the square lithium-ion battery 6 using the movable plate 2. When the reading of the spoke pressure sensor 5 reaches the preset simulated preload value, the controller instructs the servo cylinder to stop moving and enter a position locking mode. At this time, the square lithium-ion battery 6 is compressed to a constant thickness. Subsequently, the square lithium-ion battery 6 is connected to an external charging and discharging device to begin a charging and discharging cycle. Throughout the charging and discharging process, the controller continuously records the readings of the spoke pressure sensor 5. Since the square lithium-ion battery 6 expands in volume during charging, under the constant displacement boundary condition where the movable plate 2 is locked, this expansion translates into an increase in pressure on the movable plate 2. Therefore, the change in the force sensor reading reflects the change in the expansion force of the square lithium-ion battery 6 with its state of charge.

[0042] The expansion characteristics of a square lithium-ion battery under constant pressure are measured. The specific steps are as follows: the square lithium-ion battery 6 to be tested is placed vertically between the first fixed plate 1 and the movable plate 2, and the left side of the square lithium-ion battery 6 is pressed against the right side of the first fixed plate 1; the servo cylinder 4 is driven by the controller to compress the square lithium-ion battery 6 by the movable plate 2 until the reading of the spoke pressure sensor 5 reaches the preset preload value. Subsequently, the controller switches to constant pressure control mode, that is, using the preload value as the target value, reading the feedback from the force sensor in real time and dynamically adjusting the extension and retraction position of the servo cylinder 4; when the square lithium-ion battery 6 expands in volume during charging and discharging, causing the pressure to increase, the controller immediately instructs the servo cylinder 4 to slightly contract to release the excess pressure, so that the reading of the force sensor is always maintained near the preset value, avoiding a sudden drop in pressure; conversely, when the square lithium-ion battery 6 contracts, causing the pressure to decrease, the controller instructs the servo cylinder to slightly extend to compensate for the pressure; during this process, the controller simultaneously records the changes in the displacement sensor and the charging and discharging parameters, thereby obtaining the variation law of the expansion displacement of the square lithium-ion battery 6 under constant pressure boundary conditions with the state of charge.

[0043] Compared with the prior art, the present invention has the following advantages: 1. High integration and low cost: A single device can complete multiple key testing tasks, such as testing the equivalent elastic coefficient of square lithium-ion batteries, testing the actual working condition bonding performance of CTP bottom adhesive, monitoring constant displacement expansion force, and studying constant pressure expansion characteristics, which significantly reduces equipment procurement costs and laboratory space occupancy.

[0044] 2. Closer to Real-World Conditions: In the adhesive performance test, the square lithium-ion battery casing and base plate were directly used as the bonding materials, and the CTP coating process was replicated. The measured failure strength and stiffness accurately reflect the mechanical behavior of the product-level adhesive interface. In the expansion force test, the square lithium-ion battery was placed vertically, consistent with the actual battery pack, eliminating the differences in electrolyte distribution and electrode expansion behavior caused by the square lithium-ion battery lying on its side, making the test data more valuable for engineering reference.

[0045] 3. High measurement accuracy: The combination of four-axis guide and linear bearing ensures the smoothness and high parallelism of the moving plate movement. The wheel spoke pressure sensor has good anti-eccentric load capability, and the synchronous acquisition of force and displacement provides a reliable data basis for accurate calculation.

[0046] 4. Flexible control modes: Through the controller's software algorithm, it is possible to simulate both constant displacement boundary conditions and constant pressure boundary conditions, providing a tool for studying the electro-mechanical coupling behavior of square lithium-ion batteries under different mechanical constraints.

[0047] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A multifunctional mechanical testing device for square lithium-ion batteries, characterized in that, include: Base plate; A first fixed plate, a second fixed plate, and a movable plate are provided. The first fixed plate and the second fixed plate are fixed to the base plate in parallel with each other. The movable plate is movably disposed between the first fixed plate and the second fixed plate. The square lithium-ion battery to be tested is clamped between the first fixed plate and the movable plate. A servo electric cylinder, wherein the servo electric cylinder is drivenly connected to the movable plate; A spoke pressure sensor, mounted on the movable plate, is used to measure the preload force on the square lithium-ion battery; A displacement sensor is mounted on the second fixed plate and is used to measure the displacement of the movable plate; The controller, in which the servo cylinder, pressure sensor, and displacement sensor are electrically connected, enables various mechanical tests on the square lithium battery.

2. The multifunctional mechanical testing device for square lithium-ion batteries according to claim 1, characterized in that, It also includes a guide shaft, the two ends of which are fixed to the first fixed plate and the second fixed plate respectively. A linear bearing is installed on the movable plate and the linear bearing is sleeved on the guide shaft.

3. The multifunctional mechanical testing device for square lithium-ion batteries according to claim 2, characterized in that, The guide shafts consist of four shafts arranged in a square pattern.

4. The multifunctional mechanical testing device for square lithium-ion batteries according to claim 1, characterized in that, The base plate is pre-coated or pasted with a simulated adhesive layer.

5. The multifunctional mechanical testing device for square lithium-ion batteries according to claim 1, characterized in that, The spoke pressure sensor is fixed to the movable plate, and the telescopic rod of the servo electric cylinder is fixedly connected to the center hole of the spoke pressure sensor.

6. The multifunctional mechanical testing device for square lithium-ion batteries according to claim 1, characterized in that, The displacement sensor is mounted on the second fixed plate via a displacement sensor bracket. One end of the displacement sensor bracket is a threaded section, and the other end is an elastic conical chuck. The second fixed plate has a conical hole that mates with the elastic conical chuck. The rod of the displacement sensor passes through the inner hole of the elastic conical chuck and the threaded section. When the nut is tightened on the threaded section, the elastic conical chuck retracts inward under radial constraint, clamping and fixing the rod of the displacement sensor.

7. A multifunctional mechanical testing method for square lithium-ion batteries, characterized in that, include: A multifunctional mechanical testing device for square lithium-ion batteries as described in any one of claims 1-6 is provided; The equivalent elastic coefficient of a square lithium-ion battery was measured. The adhesive bonding performance and failure strength of the bottom coating of a square lithium-ion battery were tested. The expansion force of a square lithium-ion battery under constant displacement conditions was measured. The expansion characteristics of a square lithium-ion battery under constant pressure were measured.

8. The multifunctional mechanical testing method for square lithium-ion batteries according to claim 7, characterized in that, The measurement of the equivalent elastic coefficient of the square lithium-ion battery includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate. The controller drives the servo cylinder to move the movable plate towards the first fixed plate to compress the square lithium-ion battery. During this process, the controller simultaneously records the pressure value of the pressure sensor and the displacement value of the displacement sensor. After compression, a curve is plotted with displacement as the abscissa and pressure as the ordinate. A segment with good linearity is selected for fitting, and the resulting slope is the equivalent elastic coefficient of the square lithium-ion battery in the corresponding compression range.

9. The multifunctional mechanical testing method for square lithium-ion batteries according to claim 7, characterized in that, The tests on the bottom adhesive bonding performance and failure strength of the square lithium-ion battery include: Structural adhesive is applied to the base plate according to the actual CTP process. Then, the bottom of the square lithium-ion battery is attached to the structural adhesive and cured according to the curing process requirements to bond the square lithium-ion battery and the base plate together. Place the square lithium-ion battery on the testing device; The servo electric cylinder is activated, driving the movable plate to apply a horizontal thrust to the square lithium-ion battery. The controller records the force and displacement data throughout the loading process. When the force-displacement curve drops sharply, it indicates that the adhesive layer has debonded and failed. By recording the peak force at this time and combining it with the actual bonding area of ​​the adhesive layer, the failure strength of the adhesive layer under actual working conditions can be calculated.

10. The multifunctional mechanical testing method for square lithium-ion batteries according to claim 7, characterized in that, The measurement of the expansion force of a square lithium-ion battery under constant displacement conditions includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate. The controller drives the servo electric cylinder to compress the square lithium-ion battery by the movable plate. When the pressure sensor reading reaches the preset simulated preload value, the controller instructs the servo electric cylinder to stop moving and enter the position locking mode. Connect the square lithium-ion battery to an external charging and discharging device to begin a charge and discharge cycle. Throughout the entire charge and discharge process, the controller continuously records the readings from the spoke pressure sensor.

11. The multifunctional mechanical testing method for square lithium-ion batteries according to claim 7, characterized in that, The measurement of the expansion characteristics of a square lithium-ion battery under constant pressure conditions includes: The square lithium-ion battery to be tested is placed vertically between the first fixed plate and the movable plate, with the left side of the square lithium-ion battery in close contact with the right side of the first fixed plate; the servo cylinder is driven by the controller to compress the square lithium-ion battery with the movable plate until the reading of the pressure sensor reaches the preset preload value. The controller switches to constant pressure control mode, that is, with the preload value as the target value, it reads the feedback from the pressure sensor in real time and dynamically adjusts the extension and retraction position of the servo electric cylinder. When the square lithium-ion battery expands in volume during charging and discharging, causing the pressure to increase, the controller immediately instructs the servo cylinder to contract to release the excess pressure, so that the pressure sensor reading is always maintained near the preset value, avoiding a sudden drop in pressure; conversely, when the square lithium-ion battery contracts, causing the pressure to decrease, the controller instructs the servo cylinder to extend to compensate for the pressure. The controller records the changes in the displacement sensor and the charging and discharging parameters to obtain the variation law of the expansion displacement of the square lithium-ion battery with the state of charge under constant pressure boundary conditions.

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