Lithium-ion battery mechanical performance evaluation methods, equipment, media and program products

Abstract

The present application provides a method, device, medium and program product for evaluating the mechanical properties of lithium-ion batteries, and relates to the technical field of battery performance testing. The method monitors whether there are battery pole pieces between the pressure plates through a pressure sensor to ensure the accuracy of the test. When there are battery pole pieces, the test process can be accurately controlled by applying pressure at a preset pressure rate and monitoring the pressure value and deformation displacement data in real time. Stopping the pressurization when the minimum deformation threshold or the maximum pressure threshold is reached can effectively protect the battery pole piece. Finally, the pole piece flexibility is determined based on the deformation displacement data and pressure changes, which provides accurate data support for evaluating the pole piece flexibility of lithium-ion batteries and helps improve the quality and safety of batteries.

Description

Technical Field

[0001] The present application relates to the technical field of battery performance testing, and in particular to a method, device, medium and program product for evaluating the mechanical properties of a lithium-ion battery. Background Art

[0002] As a new type of environmentally friendly next-generation battery, lithium-ion batteries have the advantages of high operating voltage, high energy density, and no memory effect. They have been widely used in wearable devices, electric vehicles and other fields. During the use of lithium-ion batteries, the mechanical properties of the battery, especially the flexibility, directly affect the cycle life and safety of the battery. Therefore, accurate evaluation of the flexibility of lithium-ion batteries is of great significance to improving battery quality.

[0003] The current test method for the flexibility of lithium battery pole pieces includes workers taking a flat pole piece, folding it in half and rolling it, and testing the force required to break the pole piece on a tensile testing machine. The value obtained by dividing the force to break the pole piece by the force on the pole piece is used to represent the flexibility of the pole piece.

[0004] However, the existing method of tensile testing destroys the sample, and folding and rolling will cause certain mechanical damage to the pole piece, which will affect the subsequent tensile test results and reduce the accuracy of the results. In addition, the test method relies too much on manual operation and the test efficiency is low. Summary of the invention

[0005] The present application provides a lithium-ion battery mechanical property evaluation method, device, medium and program product for accurately and efficiently evaluating the flexibility of a lithium-ion battery electrode.

[0006] In the first aspect, the present application provides a method for evaluating the mechanical properties of a lithium-ion battery, which is applied to a mechanical properties evaluation device, wherein the mechanical properties evaluation device includes a pressing plate, a fixing plate, a distance measuring device and a guide rail, wherein a pressure sensor is arranged in the pressing plate, and the pressing plate and the fixing plate are combined to clamp a curled battery pole piece, wherein the distance measuring device is used to measure the deformation displacement data of the battery pole piece in the horizontal direction during the pressurization process, and wherein the guide rail is used to move the pressing plate in a preset direction to apply pressure to the battery pole piece, wherein the method includes: after detecting that a user turns on a test function, monitoring the pressure sensor through the pressure sensor Whether the battery pole piece exists between the pressure plates; if so, the pressure plate is controlled to pressurize the battery pole piece at a preset pressurization rate, and during the pressurization process, the real-time pressure value of the pressure plate is determined by the pressure sensor, and the deformation displacement data of the battery pole piece is determined according to the distance measuring device; when the deformation displacement data reaches the minimum deformation threshold or when the pressure of the pressure plate on the battery pole piece exceeds the maximum pressure threshold, the pressure plate is controlled to stop the pressurization work; after determining the pressure change according to the real-time pressure value, the pole piece flexibility of the battery pole piece is determined according to the deformation displacement data and the pressure change.

[0007] By adopting the above technical solution, the method monitors whether there are battery pole pieces between the pressure plates through pressure sensors to ensure the accuracy of the test. When there are battery pole pieces, the pressure is applied at a preset pressure rate and the pressure value and deformation displacement data are monitored in real time, so that the test process can be accurately controlled. When the minimum deformation threshold or the maximum pressure threshold is reached, the pressure is stopped, which can effectively protect the battery pole piece. Finally, the pole piece flexibility is determined based on the deformation displacement data and pressure changes, which provides accurate data support for evaluating the mechanical properties of lithium-ion batteries and helps to improve the quality and safety of batteries.

[0008] In combination with some embodiments of the first aspect, in some embodiments, if any, after the step of controlling the pressing plate to pressurize the battery pole piece at a preset pressurization rate, the step also includes: controlling the pressing plate to generate a dynamic vibration load, the frequency of the dynamic vibration load varies with the pressurization rate of the pressing plate; determining the dynamic displacement response of the battery pole piece at different dynamic vibration load frequencies according to the ranging device; determining the resonant frequency of the battery pole piece according to the dynamic displacement response; determining the natural frequency of the battery pole piece according to the resonant frequency of the battery pole piece; comparing the natural frequency with a preset frequency range, and determining the first flexibility of the battery pole piece according to the comparison result.

[0009] By adopting the above technical solution, the dimension of flexibility evaluation is enriched through dynamic testing. The introduction of dynamic vibration load can more comprehensively reflect the dynamic performance of battery pole pieces in actual use, making flexibility evaluation more accurate and providing a more reliable basis for optimizing the design and manufacture of battery pole pieces.

[0010] In combination with some embodiments of the first aspect, in some embodiments, after comparing the natural frequency with the preset frequency range and determining the first flexibility of the battery pole piece according to the comparison result, it also includes: controlling the pressure plate to reversely stretch the battery pole piece at a preset stretching rate, and detecting multiple rebound tension values ​​in real time through the pressure sensor; during the reverse stretching process, continuously detecting the rebound deformation displacement change of the battery pole piece through the ranging device, determining the thickness change of the battery pole piece through a preset sensor, and determining the thickness recovery rate according to the thickness change; determining the second flexibility according to the multiple rebound tension values ​​and the rebound deformation displacement change, and determining the third flexibility according to the thickness recovery rate; adjusting the flexibility of the pole piece in combination with the first flexibility, the second flexibility and the third flexibility.

[0011] By adopting the above technical solutions, the reverse tensile test can simulate the stress conditions of the battery in different usage scenarios and evaluate flexibility in multiple dimensions. The comprehensive consideration of multiple parameters makes the evaluation results more comprehensive and accurate, which helps to improve the reliability and durability of the battery.

[0012] In combination with some embodiments of the first aspect, in some embodiments, the mechanical property evaluation equipment also includes a temperature control device and a heat insulation device. The temperature control device is arranged inside the pressure plate for controlling the temperature of the battery electrode. The heat insulation device is arranged outside the mechanical property evaluation equipment for isolating the test component from the external environment to reduce the impact of external temperature fluctuations. After detecting that the user turns on the test function, before the step of monitoring whether the battery electrode exists between the pressure plates through the pressure sensor, it also includes: receiving a temperature control instruction sent from the display end, and controlling the temperature device to adjust the temperature of the battery electrode according to the temperature control instruction.

[0013] By adopting the above technical solution, the performance of battery pole pieces can be tested under different temperature conditions, simulating various temperature environments in actual use. Accurate temperature control helps to gain a deeper understanding of the changes in the mechanical properties of battery pole pieces at different temperatures.

[0014] In combination with some embodiments of the first aspect, in some embodiments, the mechanical property evaluation equipment also includes a driving device and a torque sensor. The driving device is arranged on one side of the pressure plate to drive the pressure plate to rotate, and the torque sensor is used to detect the torsional force applied to the battery pole piece in real time. An angle sensor is arranged on one side of the driving device to detect the rotation angle of the pressure plate. After determining the pressure change according to the real-time pressure value, after determining the pole piece flexibility of the battery pole piece according to the deformation displacement data and the pressure change, it also includes: after receiving a torsion command sent from the display end, controlling the driving device to twist the pressure plate at a preset torsion rate; during the torsion process, monitoring the torsion angle in real time through the angle sensor, and monitoring the torsion force in real time through the torque sensor; determining the torsional flexibility of the battery pole piece through the monitoring results.

[0015] By adopting the above technical solution, the process adds the evaluation of the torsion performance of the battery pole piece, and comprehensively considers the various forces that the battery may be subjected to in actual use. Through multi-parameter monitoring, the comprehensive mechanical properties of the battery pole piece can be evaluated more accurately.

[0016] In combination with some embodiments of the first aspect, in some embodiments, after determining the pressure change according to the real-time pressure value, after the step of determining the pole piece flexibility of the battery pole piece according to the deformation displacement data and the pressure change, it also includes: determining a corresponding change curve according to the deformation displacement data and the pressure change; and sending the change curve to the display end for display.

[0017] By adopting the above technical solution, the test results are more intuitive, which makes it easier for users to quickly understand the change trend of the mechanical properties of the battery pole piece. The display of the change curve helps users to conduct more in-depth analysis and comparison.

[0018] In combination with some embodiments of the first aspect, in some embodiments, before the step of determining the corresponding change curve based on the deformation displacement data and the pressure change, it also includes: receiving the battery electrode parameters sent by the display end, binding the battery electrode parameters with corresponding experimental data, and the experimental data at least includes the deformation displacement data and the pressure change.

[0019] By adopting the above technical solution, specific battery electrode parameters are matched with corresponding test results, which is convenient for subsequent query and analysis. Parameter binding helps to establish a more complete database.

[0020] In a second aspect, the present application provides a mechanical property evaluation device, which includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code includes computer instructions, and the one or more processors call the computer instructions to enable the mechanical property evaluation device to perform the method described in the first aspect and any possible implementation method of the first aspect.

[0021] In a third aspect, the present application provides a computer-readable storage medium comprising instructions, which, when executed on a mechanical property evaluation device, causes the mechanical property evaluation device to perform the method described in the first aspect and any possible implementation of the first aspect.

[0022] In a fourth aspect, the present application provides a computer program product, which, when executed on a mechanical property evaluation device, enables the mechanical property evaluation device to execute the method described in the first aspect and any possible implementation manner of the first aspect.

[0023] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0024] 1. Due to the use of technical means such as pressure sensor monitoring, pressurization at a preset pressurization rate, stopping pressurization according to the minimum deformation threshold or the maximum pressure threshold, and determining the flexibility of the electrode according to the deformation displacement data and pressure changes, the problem of inaccurate evaluation of the mechanical properties of lithium-ion batteries in the prior art is effectively solved, thereby achieving the technical effect of providing accurate data support for evaluating the mechanical properties of lithium-ion batteries and improving battery quality and safety.

[0025] 2. Due to the adoption of technical means such as reverse stretching of the battery pole piece, detection of the rebound tension value, rebound deformation displacement change and thickness recovery rate through multiple sensors, and comprehensive determination and adjustment of the pole piece flexibility, the problem of the single dimension of battery pole piece flexibility evaluation in the prior art is effectively solved, thereby achieving the technical effect of multi-dimensional evaluation of battery pole piece flexibility and improving battery reliability and durability.

[0026] 3. Due to the use of technical means such as temperature control devices to adjust the temperature of battery electrodes, heat insulation devices to reduce the impact of external temperature fluctuations, and receiving temperature control instructions, the problem that the existing technology cannot accurately evaluate the performance of battery electrodes under different temperature conditions is effectively solved, thereby realizing the testing of battery electrode performance under different temperature environments, providing targeted data for battery optimization design and application, and improving the technical effect of battery adaptability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a structural schematic diagram of a method for evaluating mechanical properties of a lithium-ion battery in an embodiment of the present application;

[0028] Figure 2 It is a flow chart of a method for evaluating the mechanical properties of a lithium-ion battery in an embodiment of the present application;

[0029] Figure 3 is another schematic flow chart of the method for evaluating the mechanical properties of a lithium-ion battery in an embodiment of the present application;

[0030] Figure 4 It is a schematic diagram of the structure of a physical device of the mechanical property evaluation equipment in the embodiment of the present application. DETAILED DESCRIPTION

[0031] The terms used in the following embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to be used as limitations to the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of", "said", "above", "the" and "this" are intended to also include plural expressions, unless there is a clear indication to the contrary in the context. It should also be understood that the term "and / or" used in the present application refers to and includes any or all possible combinations of one or more listed items.

[0032] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features, and in the description of the embodiments of the present application, unless otherwise specified, "plurality" means two or more.

[0033] For ease of understanding, the structure of this application is described below. Figure 1 , Figure 1 It is a structural schematic diagram of the method for evaluating the mechanical properties of a lithium-ion battery in an embodiment of the present application.

[0034] The mechanical property evaluation equipment includes a pressing plate and a fixed plate, wherein the fixed plate is the stationary party. The pressing plate and the fixed plate are arranged opposite to each other, and the two work together to clamp the curled battery pole piece. The pressing plate and the fixed plate are arranged opposite to each other, and the two work together to clamp the curled battery pole piece, and measure the pressure applied by the pressing plate to the battery pole piece in real time. During the test, as the pressing plate moves along the guide rail and presses the pole piece, the pressure sensor in the pressing plate can accurately obtain tiny pressure change data. When the pressing plate applies pressure to the battery pole piece, the battery pole piece will deform in the horizontal direction. The distance measuring device can be a high-precision ruler that can accurately measure the displacement of this deformation. The guide rail plays the role of guiding the movement of the pressing plate in the equipment. It stipulates the moving direction of the pressing plate, ensuring that the pressing plate can accurately apply pressure to the battery pole piece along the preset direction.

[0035] The following describes the process of the method provided by this implementation in combination with the above structure. Figure 2 , is a flow chart of a method for evaluating the mechanical properties of a lithium-ion battery in an embodiment of the present application.

[0036] S201, after detecting that the user turns on the test function, monitoring whether the battery electrode exists between the pressure plates through the pressure sensor;

[0037] The user curls the battery electrode to be tested in advance, and then clicks a button similar to the start test to start the test. When the mechanical performance evaluation device starts and detects that the user has turned on the test function, the pressure sensor in the pressure plate is first initialized, which includes self-checking the circuit of the pressure sensor to ensure that the various electronic components of the sensor are working properly and can accurately measure the pressure signal. After the pressure sensor is initialized, the mechanical performance evaluation device adjusts the position of the pressure plate through a driving device (such as a motor, etc.) to keep a suitable distance between it and the fixed plate so that the battery electrode can be easily placed. This distance is usually adjusted according to the thickness and curling degree of the battery electrode. The user then places the curled battery electrode between the pressure plate and the fixed plate in a preset direction. When the position of the pressure plate is adjusted, the pressure sensor begins to monitor the pressure between the pressure plate and the fixed plate in real time. At this time, since there is no battery electrode placed, the pressure sensor should detect a small reference pressure, which may be caused by the weight of the pressure plate itself and some small pressure factors inside the device. By monitoring and recording this reference pressure, it is possible to accurately determine whether there is a battery electrode after the subsequent placement of the battery electrode and whether the measured pressure change is caused by the battery electrode.

[0038] In order to more accurately detect whether the battery pole piece is placed between the pressure plate and the fixed plate, in addition to the pressure sensor monitoring the pressure change, some tiny capacitive sensors can be set on the surface of the pressure plate and the fixed plate. When the battery pole piece is placed, the capacitance value of the capacitive sensor will change because the dielectric constant of the pole piece is different from that of the air. By monitoring the change in the capacitance value, it can be further confirmed whether the battery pole piece has been placed correctly.

[0039] In some embodiments, the flexibility of the battery pole piece may change significantly at different temperatures. In a low temperature environment, the material may become more brittle and less flexible; in a high temperature environment, the material may become softer and its mechanical properties may also be different. Therefore, in order to accurately evaluate the mechanical properties of the battery pole piece in different actual use environments, it is necessary to be able to simulate and control temperature conditions. The mechanical properties evaluation equipment has a communication interface, which is connected to the display terminal and can receive temperature control instructions sent by the user through the display terminal. The temperature control device is arranged inside the pressing plate, which may include a heating element and a cooling element. The temperature control device is also equipped with a temperature sensor for real-time monitoring of the temperature of the pressing plate.

[0040] If the temperature is not controlled during the test, the fluctuation of the external environment temperature will cause the temperature of the battery pole piece to be inconsistent during each test. This will cause a large deviation in the test results and cannot accurately reflect the true performance of the battery pole piece. By setting a temperature control device and a heat insulation device, the temperature of the battery pole piece can be stabilized at a set value, ensuring that each test is carried out under the same temperature conditions, thereby improving the accuracy and repeatability of the test results. Therefore, the present application can also set the heat insulation device outside the mechanical performance evaluation device, which is usually made of heat insulation materials. These heat insulation materials have low thermal conductivity and can effectively prevent external heat from entering the inside of the device, and can also prevent the heat inside the device from being dissipated to the external environment, thereby reducing the impact of external temperature fluctuations on the test. When the control system receives the temperature control instruction, it will compare the temperature setting value in the instruction with the current temperature value fed back by the temperature sensor. If the current temperature is lower than the set value, the control system will start the heating element, and control the heating power by adjusting the current size of the heating element, so that the temperature of the press plate gradually increases. If the current temperature is higher than the set value, the control system will start the cooling element, and also control the cooling power by adjusting the current size of the cooling element, so that the temperature of the press plate gradually decreases. By setting up a temperature control function in the test equipment, the temperature conditions in these actual use environments can be simulated, and the mechanical properties of the battery electrodes at different temperatures can be more comprehensively evaluated.

[0041] S202, if it exists, control the pressing plate to pressurize the battery electrode piece at a preset pressing rate, determine the real-time pressure value of the pressing plate through the pressure sensor during the pressing process, and determine the deformation displacement data of the battery electrode piece according to the distance measuring device;

[0042] When the pressure sensor detects the presence of the battery pole piece, the control system of the mechanical performance evaluation equipment drives the pressing plate to move along the guide rail toward the fixed plate according to the preset pressure rate instruction, and applies pressure to the battery pole piece. The preset pressure rate is set according to the material properties and test requirements of the lithium-ion battery pole piece. In order to achieve accurate pressure rate control, the equipment can use a high-precision motor drive system and an advanced speed control algorithm. The motor drive system can provide stable power to ensure that the movement speed of the pressing plate is uniform. The speed control algorithm continuously adjusts the motor speed according to the real-time monitored pressing plate position and time information, so that the movement speed of the pressing plate is always kept within the preset pressure rate range. In the process of the pressing plate pressing the battery pole piece, the equipment measures the pressure applied by the pressing plate to the battery pole piece in real time through the pressure sensor. At the same time, as the pressing plate applies pressure to the battery pole piece, the battery pole piece will deform in the horizontal direction, and the distance measuring device determines the deformation displacement data through precise scale and measurement methods. When the pressing plate applies pressure to the pole piece, the relative position between the pole piece surface and the scale changes, and the deformation displacement value is obtained by reading the scale change on the distance measuring device.

[0043] S203, when the deformation displacement data reaches the minimum deformation threshold or when the pressure of the pressing plate on the battery electrode exceeds the maximum pressure threshold, control the pressing plate to stop the pressurization work;

[0044] Before the test begins, the minimum deformation threshold and the maximum pressure threshold are set according to the characteristics of the lithium-ion battery pole piece and the test requirements. The minimum deformation threshold is determined by considering the allowable deformation of the battery pole piece in actual application and the flexibility of the material, while the maximum pressure threshold is determined by comprehensively considering the strength and pressure resistance of the pole piece material. During the process of the pressure plate applying pressure to the battery pole piece, the control system of the equipment monitors the deformation displacement data and pressure value in real time. The control system quickly obtains these data through a high-speed data acquisition system. When the deformation displacement data reaches the minimum deformation threshold or the pressure value exceeds the maximum pressure threshold, the control system immediately issues a stop command to drive the pressure plate to stop pressurizing.

[0045] In some embodiments, before the test, the user can input the relevant parameters of the battery pole piece of this test through the display end, such as material, thickness, manufacturing batch, etc. These parameters are bound to the experimental data of this test in digital or text form, including deformation displacement and pressure change data. During the pressure loading process, the ranging sensor continuously collects the deformation displacement data of the battery pole piece, and the pressure sensor collects the pressure data in real time. After the test, the system automatically takes out the data of the two sensors and performs synchronous pairing to obtain the values ​​of deformation displacement and pressure at multiple time points, plots these discrete data points into the coordinate system, and determines a deformation displacement-pressure change curve by curve fitting. The curve is sent to the display end in the form of an image file for display to the user, and the parameters of the battery pole piece are bound to form a complete test analysis image. The user can intuitively analyze the mechanical properties of the battery pole piece through the curve on the display end, and can also compare and comprehensively judge the test curves of multiple batteries. All test and analysis images are automatically saved in the database for subsequent reference or big data processing.

[0046] S204, after determining the pressure change according to the real-time pressure value, determine the pole piece flexibility of the battery pole piece according to the deformation displacement data and the pressure change.

[0047] First, determine the pressure change according to the real-time pressure value. The control system of the equipment performs data analysis on the real-time pressure value collected and calculates the pressure change rate over time. If the pressure change rate is large and shows an upward trend, it means that the pressure on the pole piece during the pressurization process increases rapidly, which may mean that the pole piece material is harder and has a stronger resistance to pressure; if the pressure change rate is small and relatively stable, it may mean that the pole piece material is softer and the pressure increases relatively slowly during the pressurization process. Determine the pole piece flexibility of the battery pole piece based on the deformation displacement data and pressure changes. A common method is to calculate the ratio of deformation displacement to pressure, that is, flexibility. For example, at a certain point in time, the deformation displacement is 3mm and the pressure is 100N, then the flexibility is 3mm / 100N=0.03mm / N. By calculating the flexibility at different time points and analyzing its changing trend, the flexibility of the battery pole piece can be evaluated.

[0048] By adopting technical means such as pressure sensor monitoring, pressurization at a preset pressurization rate, stopping pressurization according to the minimum deformation threshold or the maximum pressure threshold, and determining the flexibility of the pole piece according to the deformation displacement data and pressure change, the problem of low efficiency in the mechanical property evaluation of lithium-ion batteries in the prior art is effectively solved, thereby achieving efficient evaluation of the mechanical properties of lithium-ion batteries.

[0049] After combining the above embodiments, the method provided by this embodiment is further described in more detail below. Figure 3, is another flow chart of the method for evaluating the mechanical properties of a lithium-ion battery in an embodiment of the present application.

[0050] S301, controlling the pressing plate to generate a dynamic vibration load, wherein the frequency of the dynamic vibration load varies with the pressing rate of the pressing plate;

[0051] In the actual use of lithium-ion batteries, the battery pole pieces are subject to various complex mechanical environments. For example, during the driving of electric vehicles, the battery will be subjected to dynamic loads due to the vibration of the vehicle; in wearable devices, the battery will also experience different degrees of vibration as the human body moves. Therefore, in order to more accurately evaluate the mechanical properties of the battery pole pieces, it is necessary to simulate these actual mechanical environments during the test process. The frequency of the dynamic vibration load varies with the pressure rate of the pressure plate based on the consideration of the characteristics of the battery pole piece at different stress stages. When the pressure plate presses the battery pole piece, the internal structure and stress distribution of the pole piece will change, and its response characteristics to vibration will also change accordingly. By correlating the frequency of the dynamic vibration load with the pressure rate, the dynamic mechanical environment to which the battery pole piece is subjected during the actual pressure process can be better simulated.

[0052] Before the test begins, a mapping algorithm between pressurization rate and frequency is determined based on the material properties and test requirements of the lithium-ion battery pole piece. This algorithm is based on a large amount of experimental data and theoretical analysis. For example, for a specific lithium-ion battery pole piece material, when the pressurization rate is within a certain range, a linear relationship may be used to determine the frequency, that is, frequency = k × pressurization rate + b (k and b are constants determined experimentally). Then after step S202, the preset pressurization rate is substituted into the predetermined mapping relationship algorithm to calculate the corresponding dynamic vibration load frequency value. In order to generate a dynamic vibration load, the pressure plate in the mechanical property evaluation equipment realizes the vibration function through a special drive device. This drive device can be a high-precision electromagnetic vibrator. The electromagnetic vibrator has an electromagnetic coil and a vibrating iron core inside.

[0053] After the control system calculates the frequency value of the dynamic vibration load, it adjusts the current size and direction in the electromagnetic coil to make the iron core vibrate periodically under the action of the electromagnetic force. This vibration is transmitted to the battery pole piece through the pressure plate, thereby generating a dynamic vibration load to simulate the complex mechanical environment received during actual use.

[0054] S302, determining the dynamic displacement response of the battery pole piece under different dynamic vibration load frequencies according to the distance measuring device;

[0055] The distance measuring device can be used to measure the real-time dynamic displacement response of the battery pole piece under different dynamic vibration load frequencies, that is, the deformation displacement data.

[0056] S303, determining the resonance frequency of the battery pole piece according to the dynamic displacement response;

[0057] The dynamic displacement response data is discretized, that is, the continuous displacement curve is divided into multiple data points according to a certain time interval or frequency interval. Then, the fast Fourier transform (FFT) algorithm is used to perform spectrum analysis on these discrete data points. The FFT algorithm can convert the time domain signal into a frequency domain signal, thereby clearly showing the energy distribution of the signal at different frequencies. In the frequency domain, the resonant frequency is expressed as the frequency corresponding to the energy peak. By finding the energy peak in the spectrum of the dynamic displacement response data, the resonant frequency of the battery pole piece can be determined.

[0058] S304, determining the natural frequency of the battery pole piece according to the resonance frequency of the battery pole piece;

[0059] According to the theoretical model in solid mechanics, the natural frequency of a system can be calculated from the resonant frequency of the system. Among them, the battery pole piece can be regarded as a simply supported beam model. Substituting the material parameters of the battery pole piece (such as density, elastic modulus, thickness, etc.) into the calculation formula of the natural frequency of the simply supported beam, and substituting the resonant frequency value obtained in step 2 into the formula, the natural frequency of the battery pole piece can be calculated.

[0060] S305, comparing the natural frequency with a preset frequency range, and determining a first flexibility of the battery electrode according to the comparison result;

[0061] According to the battery pole pieces of different materials and structures, pre-test to determine the standard range of their natural frequencies and establish a corresponding frequency range database. Compare the natural frequency value of the battery pole piece obtained by the test with the standard frequency range in the database. If the natural frequency of the test sample falls within the standard range, it means that the dynamic mechanical strength of the battery pole piece meets the design requirements and confirms that its first flexibility is qualified. If the natural frequency of the test sample is higher or lower than the standard range, it means that the dynamic mechanical strength of the battery pole piece does not meet the standard and the first flexibility is unqualified. According to the degree of deviation between the natural frequency and the standard range, the excellent grade of the first flexibility of the battery pole piece can be evaluated.

[0062] S306, controlling the pressing plate to reversely stretch the battery electrode sheet at a preset stretching rate, and detecting multiple rebound tension values ​​in real time through the pressure sensor;

[0063] After step S203, the pressing plate can also be controlled to reverse stretch the battery electrode. The preset stretching rate can be set in advance according to the material properties and test requirements of the lithium-ion battery electrode. The equipment realizes precise control of the stretching rate of the pressing plate through a high-precision motor drive system. The motor drive system provides stable power to ensure that the pressing plate moves in a preset direction. During the reverse stretching of the battery electrode by the pressing plate, the pressure sensor in the pressing plate detects multiple rebound tension values ​​in real time.

[0064] S307, during the reverse stretching process, continuously detecting the rebound deformation displacement change of the battery electrode sheet through the distance measuring device, determining the thickness change of the battery electrode sheet through a preset sensor, and determining the thickness recovery rate according to the thickness change;

[0065] The distance measuring device continuously detects the rebound deformation displacement change of the battery pole piece during the reverse stretching process. An ultrasonic thickness sensor can also be used. Its working principle is to calculate the thickness change of the pole piece according to the propagation time and speed of the ultrasonic wave in the pole piece by transmitting and receiving ultrasonic signals. Before use, the ultrasonic thickness sensor needs to be calibrated. During the calibration process, a standard sample of known thickness is used for measurement, and the sensor parameters are adjusted so that the measurement result is consistent with the actual thickness of the standard sample.

[0066] According to the formula, thickness recovery rate = (battery pole piece thickness after decompression - battery pole piece thickness during pressurization) / battery pole piece thickness before decompression, the battery pole piece thickness before decompression here refers to the thickness of the pole piece when it is not subjected to reverse stretching (i.e., original state), the battery pole piece thickness during pressurization refers to the thickness of the pole piece when it reaches the maximum stretching degree during the reverse stretching process, and the battery pole piece thickness after decompression refers to the thickness of the pole piece after recovering after a period of time after reverse stretching. Flexibility includes not only the deformation ability of the pole piece when subjected to force, but also the ability to return to its original state after the force disappears. The thickness recovery rate directly measures the degree to which the pole piece recovers to its original thickness after reverse stretching, and is a quantitative reflection of the elastic recovery ability of the pole piece.

[0067] S308, determining a second flexibility according to the multiple rebound tension values ​​and the rebound deformation displacement change, and determining a third flexibility according to the thickness recovery rate;

[0068] The mechanical property evaluation equipment first determines the second flexibility based on multiple rebound tensile force values ​​and rebound deformation displacement changes. By calculating the flexibility at different time points and analyzing its change trend, the second flexibility of the battery pole piece can be evaluated. During the entire reverse stretching process, the equipment continuously records the rebound tensile force value and rebound deformation displacement change data, and uses enough data points to accurately depict the change curve of flexibility. At the same time, the thickness recovery rate can be directly used as an indicator of the third flexibility, and the thickness recovery rate can also be graded to determine the third flexibility. For example, pole pieces with a thickness recovery rate greater than 80% are rated as high flexibility grades, pole pieces with a thickness recovery rate between 60%-80% are rated as medium flexibility grades, and pole pieces with a thickness recovery rate less than 60% are rated as low flexibility grades.

[0069] S309, adjusting the flexibility of the pole piece in combination with the first flexibility, the second flexibility and the third flexibility.

[0070] The mechanical performance evaluation equipment first needs to determine a comprehensive flexibility index in order to adjust the flexibility of the pole piece. The weighted average method can be used to calculate the comprehensive flexibility. For example, according to the importance of the first flexibility, the second flexibility and the third flexibility to the flexibility of the battery pole piece, different weights are assigned to them respectively. These weights can be determined based on the actual application requirements of the battery pole piece and a large amount of experimental data.

[0071] In some embodiments, when the mechanical property evaluation device determines that the comprehensive flexibility does not meet the requirements, the process parameters that need to be adjusted and the adjustment range are determined according to the pre-set rules, wherein the pre-set rules are determined based on a large amount of experimental data and actual production experience. During the research and development stage, a large number of tests will be conducted on battery poles prepared with different materials and processes to collect various data, including pole flexibility data under different process parameters. For example, if the comprehensive flexibility index is too low, and the analysis results show that it is caused by excessive compaction pressure, the mechanical property evaluation device may instruct the actuator to reduce the compaction pressure. The actuator is responsible for specific process parameter adjustment operations. The actuator can be a motor or other device that can change the process parameters. For example, if the compaction pressure is to be adjusted, the actuator will adjust the speed of the motor to achieve a change in the pressure of the pressing plate, so that the flexibility of the battery pole can be measured more accurately.

[0072] In the embodiments of the present application, due to the use of technical means such as reverse stretching of the battery pole piece, detection of the rebound tension value, rebound deformation displacement change and thickness recovery rate through multiple sensors, and comprehensive determination and adjustment of the pole piece flexibility, the problem of the single dimension of battery pole piece flexibility evaluation in the prior art is effectively solved, thereby realizing multi-dimensional evaluation of battery pole piece flexibility.

[0073] In some embodiments, lithium-ion batteries may be subjected to various forces during actual use, including torsional forces. For some application scenarios that require frequent bending or twisting, such as flexible electronic devices and wearable devices, the battery pole piece needs to have good torsional flexibility. In order to further comprehensively test the flexibility of the battery pole piece, the mechanical performance evaluation device may also include a drive device and a torque sensor. The drive device is arranged on one side of the pressing plate, usually a motor and a matching transmission mechanism. After receiving the torsion command sent by the user through the display terminal, the control system controls the speed of the motor according to the preset torsion rate command. The motor transmits power to the pressing plate through a transmission mechanism (such as gears, belts, etc.), so that the pressing plate rotates at a preset torsion rate. The angle sensor is arranged on one side of the drive device to detect the rotation angle of the pressing plate. It can be a sensor based on optical principles (such as photoelectric encoders) or electromagnetic principles (such as rotary transformers). Taking the photoelectric encoder as an example, it determines the rotation angle of the pressing plate by detecting the blocking or penetration of light. When the pressing plate rotates, the grating disk inside the photoelectric encoder also rotates, and the light is received by the photoelectric detector through the gap of the grating disk. The rotation angle of the pressing plate can be accurately calculated according to the change of light. The torque sensor is used to detect the torsional force applied to the battery pole piece in real time. It can be based on the principle of strain gauge. When the torsional force acts on the sensor, the strain gauge inside the sensor will deform, causing its resistance value to change. By measuring the change in resistance value and based on the pre-calibrated relationship, the magnitude of the torsional force can be calculated. During the torsion process, the device continuously obtains the torsional angle data monitored by the angle sensor and the torsional force data monitored by the torque sensor. The torsional flexibility can be determined by calculating the ratio of the torsional angle to the torsional force.

[0074] The following describes the mechanical performance evaluation device in the embodiment of the present invention from the perspective of hardware processing. Figure 4 , which is a schematic diagram of a physical device structure of a mechanical property evaluation device in an embodiment of the present application.

[0075] It should be noted that Figure 4 The structure of the mechanical property evaluation device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present invention.

[0076] like Figure 4As shown, the mechanical property evaluation device includes a central processing unit (CPU) 401, which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM) 402 or the program loaded from the storage part 408 to the random access memory (RAM) 403, such as executing the method described in the above embodiment. In the RAM 403, various programs and data required for system operation are also stored. The CPU 401, the ROM 402, and the RAM 403 are connected to each other through the bus 404. The input / output (I / O) interface 405 is also connected to the bus 404.

[0077] The following components are connected to the I / O interface 405: an input section 406 including an audio input device, a button switch, etc.; an output section 407 including a liquid crystal display (LCD) and an audio output device, an indicator light, etc.; a storage section 408 including a hard disk, etc.; and a communication section 409 including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication section 409 performs communication processing via a network such as the Internet. A drive 410 is also connected to the I / O interface 405 as needed. A removable medium 411, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 410 as needed so that a computer program read therefrom is installed into the storage section 408 as needed.

[0078] In particular, according to an embodiment of the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a computer program for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through the communication part 409, and / or installed from a removable medium 411. When the computer program is executed by the central processing unit (CPU) 401, various functions defined in the present invention are performed.

[0079] It should be noted that specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in combination with an instruction execution system, apparatus, or device.

[0080] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present invention. Each box in the flowchart or block diagram may represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings.

[0081] Specifically, the mechanical property evaluation device of this embodiment includes a processor and a memory. The memory stores a computer program. When the computer program is executed by the processor, the lithium-ion battery mechanical property evaluation method provided in the above embodiment is implemented.

[0082] As another aspect, the present invention further provides a computer-readable storage medium, which may be included in the mechanical performance evaluation device described in the above embodiment; or may exist independently without being assembled into the mechanical performance evaluation device. The above storage medium carries one or more computer programs, and when the above one or more computer programs are executed by a processor of the mechanical performance evaluation device, the mechanical performance evaluation device implements the lithium-ion battery mechanical performance evaluation method provided in the above embodiment.

[0083] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0084] As used in the above embodiments, the term "when..." may be interpreted to mean "if..." or "after..." or "in response to determining..." or "in response to detecting...", depending on the context. Similarly, the phrases "upon determining..." or "if (the stated condition or event) is detected" may be interpreted to mean "if determining..." or "in response to determining..." or "upon detecting (the stated condition or event)" or "in response to detecting (the stated condition or event)", depending on the context.

[0085] Those skilled in the art can understand that to implement all or part of the processes in the above-mentioned embodiments, the processes can be completed by computer programs to instruct related hardware, and the programs can be stored in computer-readable storage media. When the programs are executed, they can include the processes of the above-mentioned method embodiments. The aforementioned storage media include: ROM or random access memory RAM, magnetic disk or optical disk and other media that can store program codes.

Claims

1. A method for evaluating the mechanical properties of a lithium-ion battery, applied to a mechanical properties evaluation device, characterized in that: The mechanical property evaluation device comprises a pressing plate, a fixing plate, a distance measuring device and a guide rail, wherein a pressure sensor is arranged in the pressing plate, the pressing plate and the fixing plate are combined to clamp the curled battery pole piece, the distance measuring device is used to measure the deformation displacement data of the battery pole piece in the horizontal direction during the pressurization process, and the guide rail is used to move the pressing plate in a preset direction to apply pressure to the battery pole piece, and the method comprises: After detecting that the user turns on the test function, monitoring whether the battery electrode sheet exists between the pressure plates through the pressure sensor; If it exists, the pressing plate is controlled to pressurize the battery electrode piece at a preset pressing rate, and during the pressing process, the real-time pressure value of the pressing plate is determined by the pressure sensor, and the deformation displacement data of the battery electrode piece is determined according to the distance measuring device; When the deformation displacement data reaches the minimum deformation threshold or when the pressure of the pressing plate on the battery electrode exceeds the maximum pressure threshold, the pressing plate is controlled to stop the pressurization work; After determining the pressure change according to the real-time pressure value, determining the pole piece flexibility of the battery pole piece according to the deformation displacement data and the pressure change; If present, after the step of controlling the pressing plate to pressurize the battery electrode sheet at a preset pressing rate, the method further includes: Controlling the pressing plate to generate a dynamic vibration load, wherein the frequency of the dynamic vibration load varies with the pressing rate of the pressing plate; Determining the dynamic displacement response of the battery pole piece at different dynamic vibration load frequencies according to the distance measuring device; Determining the resonant frequency of the battery pole piece according to the dynamic displacement response; Determining the natural frequency of the battery pole piece according to the resonant frequency of the battery pole piece; Comparing the natural frequency with a preset frequency range, and determining a first flexibility of the battery electrode according to the comparison result; After the step of comparing the natural frequency with the preset frequency range and determining the first flexibility of the battery pole piece according to the comparison result, the method further includes: Controlling the pressing plate to reversely stretch the battery electrode sheet at a preset stretching rate, and detecting multiple rebound tension values ​​in real time through the pressure sensor; During the reverse stretching process, the distance measuring device continuously detects the change in the rebound deformation displacement of the battery pole piece, determines the thickness change of the battery pole piece through a preset sensor, and determines the thickness recovery rate according to the thickness change; Determine a second flexibility according to the plurality of rebound tension values ​​and the rebound deformation displacement change, and determine a third flexibility according to the thickness recovery rate; adjusting the flexibility of the pole piece in combination with the first flexibility, the second flexibility and the third flexibility to determine a comprehensive flexibility; When it is determined that the comprehensive flexibility does not meet the set requirements, the process parameters that need to be adjusted and the range of adjustment are determined according to pre-set rules; adjusting the operating parameters of the actuator according to the process parameters or the adjustment amplitude; The mechanical property evaluation device further includes a temperature control device and a heat insulation device, wherein the temperature control device is arranged inside the pressing plate and is used to control the temperature of the battery pole piece, and the heat insulation device is arranged outside the mechanical property evaluation device and is used to isolate the test component from the external environment to reduce the influence of external temperature fluctuations. After detecting that the user turns on the test function, before the step of monitoring whether the battery pole piece exists between the pressing plates through the pressure sensor, it also includes: Receiving a temperature control instruction sent from the display terminal, and controlling the temperature control device to adjust the temperature of the battery electrode according to the temperature control instruction; The mechanical property evaluation device further includes a driving device and a torque sensor, wherein the driving device is arranged at one side of the pressing plate and is used to drive the pressing plate to rotate, and the torque sensor is used to detect the torsional force applied to the battery pole piece in real time, and an angle sensor is arranged at one side of the driving device and is used to detect the rotation angle of the pressing plate. After determining the pressure change according to the real-time pressure value, after determining the pole piece flexibility of the battery pole piece according to the deformation displacement data and the pressure change, the device further includes: After receiving the twisting instruction sent by the display end, controlling the driving device to twist the pressing plate at a preset twisting rate; During the torsion process, the torsion angle is monitored in real time by the angle sensor, and the torsion force is monitored in real time by the torque sensor; The torsional flexibility of the battery pole piece is determined through the monitoring results.

2. The method according to claim 1, characterized in that After determining the pressure change according to the real-time pressure value, and determining the flexibility of the battery pole piece according to the deformation displacement data and the pressure change, the method further includes: Determine a corresponding change curve according to the deformation displacement data and the pressure change; The change curve is sent to a display terminal for display.

3. The method according to claim 2, characterized in that Before the step of determining the corresponding change curve according to the deformation displacement data and the pressure change, the method further includes: The battery pole piece parameters sent from the display end are received, and the battery pole piece parameters are bound to corresponding experimental data, wherein the experimental data at least includes the deformation displacement data and the pressure change condition.

4. A mechanical performance evaluation device, characterized in that: The mechanical property evaluation device includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code includes computer instructions, and the one or more processors call the computer instructions to enable the mechanical property evaluation device to perform the method described in any one of claims 1-3.

5. A computer-readable storage medium comprising instructions, characterized in that: When the instructions are executed on a mechanical property evaluation device, the mechanical property evaluation device is caused to perform the method according to any one of claims 1 to 3.

6. A computer program product, characterized in that When the computer program product is run on a mechanical property evaluation device, the mechanical property evaluation device is enabled to perform the method according to any one of claims 1 to 3.

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