Method and apparatus for stress control in battery charge-discharge cycles

Abstract

The application provides a battery stress control method and device in a charge-discharge cycle, and belongs to the technical field of battery application.The battery stress control method in a charge-discharge cycle comprises the following steps: obtaining first data of stress of a battery varying with voltage by performing a calibration charge-discharge cycle test on the battery; based on the first data, setting an external stress configuration of the battery, so that the sum of the internal stress of the battery and the external stress is a fixed value; and based on the set external stress configuration, performing a multi-cycle charge-discharge cycle test on the battery; after the multi-cycle charge-discharge cycle test is completed, repeating the calibration charge-discharge cycle test and updating the external stress configuration. The battery stress control method in a charge-discharge cycle is performed by the battery stress control device in a charge-discharge cycle, which can stably provide external stress, and at the same time, can maintain the battery in a stable state, so as to prolong the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery application technology, and in particular to a method and device for controlling stress during battery charge and discharge cycles. Background Technology

[0002] With the development of the electric vehicle industry, the requirements for driving range are becoming increasingly stringent, and silicon-based anode materials are gradually gaining attention. Meanwhile, electric vehicle batteries, especially pouch lithium-ion batteries, are rapidly entering the public eye due to their high energy density and are expected to be widely adopted. However, the volume change of the silicon-based anode material in pouch lithium-ion batteries during charging and discharging leads to poorer contact between the positive and negative electrodes, and the binding effect of the aluminum-plastic film is relatively weak, so additional clamps are generally required.

[0003] Currently, common clamps are ordinary stainless steel plates fixed with bolts. However, as lithium ions continuously insert and extract into the electrode material, the significant volume change of the material, especially the volume effect of silicon-based materials, causes the battery volume to increase. Furthermore, this expansion continues to accumulate during battery cycling, and under the action of external clamps, the internal stress of the battery cannot be released, continuously increasing and rapidly degrading cycle performance. Therefore, a method for controlling stress during battery charge-discharge cycles is needed. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the related art. To this end, this application provides a method and apparatus for controlling stress during battery charge and discharge cycles, in order to solve the problem that clamps in the prior art cannot alleviate the internal stress of the battery. It realizes that the clamps can apply external force to the battery according to the internal stress of the battery, so that the sum of the external stress and the internal stress of the battery remains constant, thereby maintaining the battery in a stable state and extending the cycle life of the battery.

[0005] In a first aspect, the present invention provides a method for controlling stress during battery charge-discharge cycles, comprising: The battery is subjected to a calibrated charge-discharge cycle test to obtain first data on the stress variation of the battery with voltage. Based on the first data, the external stress configuration of the battery is set so that the sum of the internal stress and the external stress of the battery is a fixed value; and Based on the set external stress configuration, a multi-cycle charge-discharge test is performed on the battery; after the multi-cycle charge-discharge test is completed, the calibration charge-discharge test is repeated, and the external stress configuration is updated.

[0006] According to a method for controlling stress during battery charge-discharge cycles provided by the present invention, the calibration charge-discharge cycle test includes: A one-week charge-discharge cycle test was performed on the battery starting from 0% state of charge (SOC) at a current of 0.05 C.

[0007] According to a method for controlling stress during battery charge-discharge cycles provided by the present invention, the charge-discharge cycle test includes: Charge-discharge cycle tests were performed using constant current and constant voltage charging and constant current discharging.

[0008] According to a method for controlling stress during a battery charge-discharge cycle provided by the present invention, the setting of the external stress configuration applied to the battery includes: reducing the external stress when the internal stress increases, or increasing the external stress when the internal stress of the battery decreases.

[0009] According to the present invention, a method for controlling stress during battery charge-discharge cycles is provided, wherein the fixed value is between 0 MPa and 3 MPa.

[0010] According to the present invention, a method for controlling stress during battery charge-discharge cycles is provided, wherein the fixed value is 1 MPa or 2 MPa.

[0011] According to the present invention, a method for controlling stress during battery charge-discharge cycles is provided, wherein the test cycle of the multi-cycle charge-discharge cycle test is 50 cycles, 100 cycles, 150 cycles or 200 cycles.

[0012] In a second aspect, the present invention also provides a stress control device during battery charge-discharge cycles, comprising: A clamping device includes a fixed clamping plate and a movable clamping plate, and the clamping device is used to clamp a battery; A pressure sensing device is disposed between the battery and the movable clamp, and is used to measure the internal stress of the battery; A drive device, electrically connected to the movable clamping plate, controls the movement of the movable clamping plate; and The controller executes the stress control method during the battery charge-discharge cycle described in the first aspect above to control the drive device.

[0013] According to the present invention, a method for controlling stress during battery charge-discharge cycles is provided, wherein the pressure sensing device is a stress sensing plate and the driving device is a motor.

[0014] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the steps of the method for controlling stress in the battery charge-discharge cycle described in the first aspect.

[0015] This invention provides a method and apparatus for controlling stress during battery charge-discharge cycles. The method involves performing a calibrated charge-discharge cycle test on the battery to obtain first data on the stress variation of the battery with voltage; based on the first data, setting an external stress configuration for the battery so that the sum of the internal stress and the external stress is a fixed value; and performing a multi-cycle charge-discharge cycle test on the battery based on the set external stress configuration; after the multi-cycle charge-discharge cycle test is completed, the calibrated charge-discharge cycle test is repeated, and the external stress configuration is updated. By implementing this method and apparatus for controlling stress during battery charge-discharge cycles, external stress can be stably provided while maintaining the battery in a stable state, thereby extending the battery's cycle life. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for controlling stress during a battery charge-discharge cycle provided by the present invention; Figure 2 This is a schematic diagram of the curve showing the change in battery thickness with voltage provided by the present invention; Figure 3 This is a schematic diagram of the structure of a stress control device for battery charging and discharging cycles provided by the present invention.

[0018] Figure 4 This is a schematic diagram of the physical structure of an electronic device provided by the present invention.

[0019] Figure label: 1. Fixed clamping plate; 2. Movable clamping plate; 3. Pressure sensing device; 4. Drive device; 5. Bolt; 6. Battery.

[0020] Best practice

[0021] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] Prior art 1 proposes a stress relief layer and a silicon anode lithium-ion battery with a stress relief layer, which can release battery expansion stress. However, this method introduces other inactive materials into the battery, reducing the battery's specific energy. Prior art 2 proposes a clamping plate that uses springs to provide space for the expansion of the cell during cycling, releasing internal battery stress. However, due to the presence of springs, this method is difficult to apply sufficient pressure to the battery.

[0025] The following is in conjunction with the appendix Figures 1 to 3 The present invention provides a detailed description of the method and apparatus for controlling stress during battery charge-discharge cycles.

[0026] Before detailing the invention, the concept of battery charge-discharge cycles will be explained. One battery charge-discharge cycle refers to the battery completing one full charge-discharge cycle. A complete charge-discharge cycle refers to the entire process of the battery discharging from a fully charged state (usually 100% capacity) to a fully discharged state (usually 0% capacity) and then recharging back to a fully charged state. During this process, the battery undergoes a complete cycle from charging to discharging and then back to charging. After completing one full charge-discharge cycle, the battery's capacity will be fully charged from its lowest value to its highest value.

[0027] Figure 1 This is a flowchart of a method for controlling stress during battery charge-discharge cycles provided by the present invention. Figure 1 As shown, the control method includes: Step 1: Perform a calibrated charge-discharge cycle test on the battery to obtain the first data on the stress change of the battery with voltage; Step 2: Based on the first data, configure the external stress on the battery so that the sum of the internal stress and the external stress of the battery is a fixed value; and Step 3: Perform a multi-cycle charge-discharge test on the battery based on the set external stress configuration; after the multi-cycle charge-discharge test is completed, repeat the calibration charge-discharge test and update the external stress configuration.

[0028] The method for controlling stress during battery charge-discharge cycles provided in this invention obtains first data on the stress variation of the battery with voltage by performing a calibrated charge-discharge cycle test on the battery. Based on the first data, the external stress configuration of the battery is set so that the sum of the internal stress and the external stress of the battery is a fixed value. This ensures that when the internal pressure of the battery changes with the battery voltage, the external stress on the battery also changes, but the sum of the internal stress and the external stress remains at a fixed value. Therefore, the battery remains in a stable state, avoiding the problem of rapid decline in battery cycle performance caused by the inability to release internal stress.

[0029] In this application, the battery can be a lithium-ion battery, which can be selected from any one of ternary lithium batteries, lithium iron phosphate batteries, and nickel-metal hydride batteries. Therefore, there are few or no special restrictions on the types of batteries used for charge-discharge cycles.

[0030] Based on the above embodiments, the calibration charge-discharge cycle test includes: The battery was subjected to a one-week charge-discharge cycle test starting from 0% state of charge (SOC) and at a current of 0.05 C.

[0031] In embodiments of the present invention, 0% state of charge (SOC) means that the battery has been completely depleted, with no remaining charge. When SOC is 0%, it indicates that the battery has been fully discharged, and capacity testing under these conditions can more accurately assess the actual capacity of the battery. Setting SOC to 0% also prevents over-discharge of the battery, thereby extending its lifespan.

[0032] Based on the above embodiments, the charge-discharge cycle test includes: Charge-discharge cycle tests were performed using constant current and constant voltage charging and constant current discharging.

[0033] In embodiments of the present invention, charge-discharge cycle testing can be performed using constant current / constant voltage charging and constant current discharging. Constant current / constant voltage charging allows for rapid replenishment of the battery's energy using a larger constant current during the initial charging phase. Once the battery voltage reaches a set cutoff voltage, it automatically switches to constant voltage charging. In this phase, the charging current gradually decreases as the battery capacity increases until it reaches a set minimum current value, thus preventing overcharging and improving charging efficiency and safety. Constant current discharging maintains a constant battery current, ensuring battery discharge efficiency and lifespan, reducing capacity loss, and maintaining stable battery performance.

[0034] In an embodiment of the present invention, the configuration of the external stress on the battery includes: reducing the external stress when the internal stress increases, or increasing the external stress when the internal stress of the battery decreases.

[0035] Reference Figure 2 , Figure 2 This is a schematic diagram of the battery thickness versus voltage curve provided by the present invention. This curve was plotted using the results of a constant displacement in-situ stress test. The constant displacement in-situ stress test allows for real-time monitoring of internal stress changes during battery charge-discharge cycle applications. Batteries, especially lithium-ion batteries, experience lithium insertion / extraction and temperature increases during charge-discharge processes, leading to changes in battery thickness and the generation of thermal stress. These changes in thickness and stress can alter battery performance, adversely affecting battery life and reliability. Figure 2 In the diagram, the dashed line represents the battery thickness, the solid line represents the battery voltage during charge / discharge testing, and the short horizontal line represents the battery current during charge / discharge testing. According to... Figure 2 It is known that the thickness of a battery increases with increasing voltage and decreases with decreasing voltage. When the battery voltage is stable, the thickness remains constant. Therefore, the external stress on the battery can be adjusted according to the battery voltage to control the sum of internal and external stresses to remain at a fixed value, thereby maintaining the battery in a relatively stable state and extending its cycle life.

[0036] Based on the above embodiments, the fixed value is between 0 MPa and 3 MPa. During battery charge-discharge cycle testing, the sum of the external stress and internal stress received by the battery should not be too large. This is because the electrode materials expand and contract during charging and discharging, generating internal stress. If the externally applied force is too large, it will exacerbate this stress, potentially causing the electrode materials to detach or crack, thereby increasing the battery's internal resistance, reducing cycle performance and capacity, and ultimately leading to battery failure. To avoid reducing battery cycle performance, this application sets the fixed value between 0 MPa and 3 MPa, preferably 1 MPa or 2 MPa. By setting the external force on the battery between 0 MPa and 3 MPa, the detachment or cracking of the electrode materials due to excessive external force is avoided, thereby reducing the battery's internal resistance and improving its cycle performance.

[0037] The following describes the stress control device for battery charge-discharge cycles provided by the present invention. The stress control device for battery charge-discharge cycles described below can be referred to in correspondence with the stress control method for battery charge-discharge cycles described above.

[0038] Reference Figure 3 , Figure 3 This is a schematic diagram of the structure of a stress control device for battery charging and discharging cycles provided by the present invention. Figure 3 As shown, the stress control device during battery charge-discharge cycles includes a clamping device, a pressure sensing device 3, a driving device 4, and a controller. The clamping device includes a fixed clamping plate 1 and a movable clamping plate 2, and is used to clamp the battery 6. The pressure sensing device 3 is disposed between the battery 6 and the movable clamping plate 2, and is used to measure the internal stress of the battery 6. The driving device 4 is electrically connected to the movable clamping plate 2 to control its movement. The fixed clamping plate 1 and the movable clamping plate 2 can be fixed by bolts 5. In other embodiments, the fixed clamping plate 1 and the movable clamping plate 2 can also be connected by screws or other secure and easily disassembled methods; this application does not limit the connection method of the fixed clamping plate 1 and the movable clamping plate 2. The driving device 4 is electrically connected to the movable clamping plate 2 to control its movement.

[0039] The controller (not shown in the accompanying drawings) executes the stress control method described above during the battery charge-discharge cycle to control the drive device 4. Specifically, before testing, the sum of the battery's internal stress and the applied external stress can be set to a value between 0 MPa and 3 MPa, for example, 1 MPa. When the controller reads the sum of the battery's internal stress measured by the pressure sensing device 3, the controller can determine the magnitude of the external stress applied to the battery by the movable clamp based on the sum of the internal and external stresses and the value of the internal stress. Finally, the controller controls the drive device 4 to apply external stress to the battery by the movable clamp 3.

[0040] Based on the above embodiments, the pressure sensing device can be a stress sensing plate, or other devices capable of measuring the internal stress of the battery. The driving device can be a motor, or other devices capable of driving the movable clamp 3 to move. This invention does not impose any particular limitations on the pressure sensing device and the driving device.

[0041] Figure 4 A schematic diagram of the physical structure of an electronic device provided by the present invention, such as... Figure 4 As shown, the electronic device may include: a processor 410, a communication interface 420, a memory 430, and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other via the communication bus 440. The processor 410 can call logical instructions in the memory 430 to execute the stress control method in the battery charge-discharge cycle described above, the method including: The battery is subjected to a calibrated charge-discharge cycle test to obtain first data on the stress variation of the battery with voltage. Based on the first data, the external stress configuration of the battery is set so that the sum of the internal stress and the external stress of the battery is a fixed value; and Based on the set external stress configuration, a multi-cycle charge-discharge test is performed on the battery; after the multi-cycle charge-discharge test is completed, the calibration charge-discharge test is repeated, and the external stress configuration is updated.

[0042] Furthermore, the logical instructions in the aforementioned memory 430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0043] The method for controlling stress during battery charge-discharge cycles of the present invention will be further described below through examples and comparative examples.

[0044] Example 1: Step 1: Perform a full charge-discharge test (one week) on a 1.2Ah ternary / silicon-based soft-pack lithium-ion battery starting from 0% SOC at a 0.05C current, calibrating the first data point on the change of internal stress with voltage. Step 2: Based on the obtained first data point, set the external stress on the battery, controlling the sum of internal and external stresses to 1MPa. Step 3: Perform a charge-discharge cycle test using a 1C constant current / constant voltage charging method and a 1C constant current discharging method. Repeat Step 1 every 200 charge-discharge cycles, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1MPa.

[0045] Example 2: Step 1: Starting from 0% SOC, a ternary / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1 MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Step 1 is repeated every 100 charge-discharge cycles, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1 MPa.

[0046] Example 3: Step 1: Starting from 0% SOC, a ternary / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1 MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1 MPa.

[0047] Comparative Example 1: A ternary / silicon-based soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 1C constant current constant voltage charging and 1C constant current discharging manner.

[0048] Example 4: Step 1: Starting from 0% SOC, a ternary / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1 MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1 MPa.

[0049] Example 5: Step 1: Starting from 0% SOC, a ternary / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to 1 MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1 MPa.

[0050] Example 6: Step 1: Starting from 0% SOC, a ternary / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 2MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery, still controlling the sum of internal and external stresses to be 1MPa.

[0051] Comparative Example 2: A ternary / silicon-based soft-pack lithium-ion battery with a rated capacity of 7Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 1C constant current constant voltage charging and 1C constant current discharging manner.

[0052] Example 7: Step 1, a ternary / silicon-based soft-pack lithium-ion battery with a rated capacity of 1.2Ah is subjected to a complete charge-discharge test at 0.05C for one week, starting from 0% SOC, to calibrate the first data on the change of internal stress with voltage. Step 2, based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to 1MPa. Step 3, a charge-discharge cycle test is performed using 2C constant current constant voltage charging and 2C constant current discharging. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery, still controlling the sum of internal and external stresses to 1MPa.

[0053] Comparative Example 3: A ternary / silicon-based soft-pack lithium-ion battery with a rated capacity of 7Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing using a 2C constant current constant voltage charging method and a 2C constant current discharging method.

[0054] Example 8: Step 1: Starting from 0% SOC, a ternary / graphite soft-pack lithium-ion battery is subjected to a complete one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1MPa.

[0055] Comparative Example 4: A ternary / graphite soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 1C constant current constant voltage charging and 1C constant current discharging manner.

[0056] Example 9: Step 1: Starting from 0% SOC, a 1.2Ah lithium iron phosphate / graphite soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1MPa.

[0057] Comparative Example 5: A lithium iron phosphate / graphite soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle test in a 1C constant current constant voltage charging and 1C constant current discharging mode.

[0058] Example 10: Step 1, a 1.2Ah lithium-rich / graphite soft-pack lithium-ion battery with a rated capacity is subjected to a full one-week charge-discharge test starting from 0% SOC at a current of 0.05C, and the first data for the change of internal stress with voltage is calibrated. Step 2, based on the obtained first data, the external stress on the battery is set, and the sum of the internal and external stresses of the battery is controlled to be 1MPa. Step 3, a charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, and the external stress on the battery is adjusted, still controlling the sum of the internal and external stresses of the battery to be 1MPa.

[0059] Comparative Example 6: A lithium-rich / graphite soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 1C constant current constant voltage charging and 1C constant current discharging manner.

[0060] Example 11: Step 1, a 1.2Ah lithium iron phosphate / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test starting from 0% SOC at a current of 0.05C, and the first data for the change of internal stress with voltage is calibrated. Step 2, based on the obtained first data, the external stress on the battery is set, and the sum of the internal and external stresses is controlled to be 1MPa. Step 3, a charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, and the external stress on the battery is adjusted, still controlling the sum of the internal and external stresses to be 1MPa.

[0061] Comparative Example 7: A lithium iron phosphate / silicon-based soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 2C constant current constant voltage charging and 2C constant current discharging manner.

[0062] Example 12: Step 1: Starting from 0% SOC, a 1.2Ah lithium-rich / silicon-based soft-pack lithium-ion battery is subjected to a full one-week charge-discharge test at a current of 0.05C to calibrate the first data on the change of internal stress with voltage. Step 2: Based on the obtained first data, the external stress on the battery is set, controlling the sum of internal and external stresses to be 1MPa. Step 3: A charge-discharge cycle test is performed using a 1C constant current constant voltage charging and 1C constant current discharging method. Every 50 charge-discharge cycles, Step 1 is repeated, adjusting the external stress on the battery to maintain the sum of internal and external stresses at 1MPa.

[0063] Comparative Example 8: A lithium-rich / silicon-based soft-pack lithium-ion battery with a rated capacity of 1.2Ah was clamped in a common stainless steel fixture and subjected to charge-discharge cycle testing in a 2C constant current constant voltage charging and 2C constant current discharging manner.

[0064] Comparative Example 9: A ternary / silicon-based soft-pack lithium-ion battery with a rated capacity of 1.2Ah was subjected to charge-discharge cycle test according to the force adjustment cycle. At the end of the previous force adjustment cycle, the force application device unloaded the load on the clamp and applied the load on the clamp again at the beginning of the next force adjustment cycle, so that the clamping force on the soft-pack lithium-ion battery reached the preset pressure. During the force adjustment cycle, the position of the force application end of the force application device on the clamp remained unchanged.

[0065] The test results of the above embodiments and comparative examples are shown in Table 1.

[0066] Table 1

[0067] As shown in Table 1, the battery thickness retention rates after 100 and 500 charge-discharge cycles reveal that after 100 cycles, the test results obtained in the embodiments of the present invention are quite similar to those obtained in the comparative examples. However, after 500 cycles, the test results differ significantly from those obtained in the comparative examples. For instance, the 500-cycle retention rate of Comparative Example 1 is approximately 20% lower than that of Example 3. In other words, as the number of charge-discharge cycles increases, the stress control method provided by the present invention makes it easier to stabilize the battery, thereby further extending its cycle life.

[0068] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0069] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling stress during battery charge-discharge cycles, characterized in that, The method includes: A calibration charge-discharge cycle test is performed on the battery to obtain first data on the stress change of the battery with voltage; wherein, the calibration charge-discharge cycle test includes performing a charge-discharge cycle test on the battery once from 0% state of charge (SOC) with a current of 0.05C; in the calibration charge-discharge cycle test, the internal stress change of the battery is monitored in real time by a pressure sensing device disposed between the battery and the clamp for holding the battery; Based on the first data, the external stress configuration of the battery is set so that the sum of the internal stress and the external stress of the battery is a fixed value; and Based on the set external stress configuration, a multi-cycle charge-discharge test is performed on the battery. During the multi-cycle charge-discharge test, the internal stress of the battery is monitored in real time by the pressure sensing device. The controller reads the internal stress of the battery measured by the pressure sensing device, and based on the constraint that the sum of the internal stress and the external stress is a fixed value, and the value of the internal stress, the magnitude of the external stress is determined, and the drive device is controlled to dynamically adjust the external stress to maintain the sum of the internal stress and the external stress at the fixed value. After the multi-cycle charge-discharge test is completed, the calibration charge-discharge test is repeated, and the external stress configuration is updated.

2. The method according to claim 1, characterized in that, The charge-discharge cycle test includes: Charge-discharge cycle tests were performed using constant current and constant voltage charging and constant current discharging.

3. The method according to claim 1 or 2, characterized in that, The configuration of the external stress on the battery includes: reducing the external stress when the internal stress increases, or increasing the external stress when the internal stress of the battery decreases.

4. The method according to claim 1 or 2, characterized in that, The fixed value is between 0 MPa and 3 MPa.

5. The method according to claim 4, characterized in that, The fixed value is 1 MPa or 2 MPa.

6. The method according to claim 1 or 2, characterized in that, The test cycle for the multi-cycle charge-discharge cycle test is 50 weeks, 100 weeks, 150 weeks, or 200 weeks.

7. A device for controlling stress during battery charge-discharge cycles, comprising: A clamping device, including a fixed clamping plate and a movable clamping plate, is used to clamp a battery; A pressure sensing device is disposed between the battery and the movable clamp, and is used to measure the internal stress of the battery; as well as A drive device is electrically connected to the movable clamping plate to control the movement of the movable clamping plate; as well as The controller executes the stress control method in the battery charge-discharge cycle as described in any one of claims 1 to 6 to control the drive device.

8. The control device according to claim 7, characterized in that, The pressure sensing device is a stress sensing plate; the driving device is a motor.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method for controlling stress in a battery charge-discharge cycle as described in any one of claims 1 to 6.

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