A lithium battery module recycling detection method, device and system

Abstract

This invention relates to the field of battery testing technology, specifically to a method, apparatus, and system for recycling and testing lithium battery modules. The invention obtains the voltage rebound coefficient at each time point after the current cutoff; based on the time characteristics of different times after the current cutoff and different preset response time constants, it obtains the unit step response function value at each response time constant at each time point after the current cutoff; based on the unit step response function values ​​at all response time constants and the voltage rebound coefficient at different times after the current cutoff, it obtains the optimal voltage drop component for different response time constants and obtains the abnormal residual energy value; combined with the electrode temperature distribution at different times, it obtains the contact impedance coupling coefficient and diffusion impedance coupling coefficient; and performs recycling and testing on the lithium battery module. This invention improves the accuracy of module recycling by accurately analyzing the abnormal residual energy value and using a thermoelectric characteristic coupling criterion based on the electrode temperature rise rate.

Description

Technical Field

[0001] This invention relates to the field of battery testing technology, specifically to a method, apparatus, and system for testing the recycling of lithium battery modules. Background Technology

[0002] Lithium battery modules face complex challenges in condition assessment during recycling testing. The impedance characteristics of the module are a key indicator for judging its health status and physical structural integrity.

[0003] In existing technologies, the DC internal resistance (DCR) test method only measures the total voltage drop for module recycling testing. However, considering that the impedance source of the voltage drop cannot be distinguished, modules with loose connections are mistakenly judged as scrap, or healthy modules in low-temperature environments are mistakenly judged as severely aged, resulting in the waste of high-value resources. While electrochemical impedance spectroscopy (EIS) technology can separate the impedance source in the frequency domain, the test time is long and the equipment is expensive, making it difficult to meet the needs of large-scale rapid testing, resulting in poor effectiveness of recycling testing. Summary of the Invention

[0004] To address the limitations of existing technologies that only measure total voltage drop and cannot distinguish the source of the problem, as well as the long testing time of electrochemical impedance spectroscopy (EIS) leading to poor effectiveness in recycling detection, this invention aims to provide a method, apparatus, and system for recycling and detecting lithium battery modules. The specific technical solution adopted is as follows: This invention proposes a method for recycling and testing lithium battery modules, the method comprising: The module terminal voltage and terminal temperature, as well as the current cutoff time, are obtained at each moment after a discharge pulse is applied to the lithium battery module. Based on the module terminal voltage at different times, the voltage rebound coefficient at each time after the current cutoff time is obtained; based on the time characteristics at different times after the current cutoff time and different preset response time constants, the unit step response function value at each response time constant at each time after the current cutoff time is obtained; based on the unit step response function values ​​at all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, the optimal voltage drop component at different response time constants is obtained, and the theoretical voltage rebound coefficient at different times after the current cutoff time is obtained. Based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time, the abnormal residual energy value is obtained; based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time, the contact impedance coupling coefficient and the diffusion impedance coupling coefficient are obtained. The lithium battery module is recycled based on the abnormal residual energy value, contact impedance coupling coefficient, and diffusion impedance coupling coefficient.

[0005] Furthermore, the method for obtaining the voltage rebound coefficient includes: The module terminal voltage at the moment immediately preceding the current cutoff time is taken as the load terminal voltage. The difference between the module terminal voltage and the load terminal voltage at each time after the current cutoff time is obtained, and is used as the voltage rebound coefficient at each time after the current cutoff time.

[0006] Furthermore, the method for obtaining the unit step response function value includes: The time difference is obtained as the difference between each moment after the current cutoff moment and the current cutoff moment. Calculate the ratio of the time difference to each preset response time constant, and obtain the unit step response function value of each response time constant at each moment after the current cutoff time based on the exponential decay law.

[0007] Furthermore, the method for obtaining the optimal component of the voltage drop includes: A one-dimensional column vector is constructed using the unit step response function values ​​at each response time constant at different times after the current cutoff time; the column vectors corresponding to all response time constants are merged to obtain the unit step response matrix. The voltage rebound coefficients at different times are used to form a rebound column vector; the preset voltage drop components with different response time constants are used to form a preset voltage drop column vector. Obtain the product vector between the unit step response matrix and the preset pressure drop column vector, obtain the square of the relative distance between the product vector and the rebound column vector, and take the minimum value function to form the objective function; use the non-negative least squares method to solve the objective function to obtain the preset optimal pressure drop column vector, including the optimal pressure drop components with different response time constants.

[0008] Furthermore, the method for obtaining the theoretical voltage rebound coefficient includes: The product between the unit step response matrix and the preset optimal pressure drop column vector is obtained as the theoretical rebound column vector. Obtain the theoretical voltage rebound coefficients at different times after the current cutoff time from the theoretical rebound column vector.

[0009] Furthermore, the method for obtaining the abnormal residual energy value includes: The root mean square value of the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at all times after the current cutoff time is obtained as the abnormal residual energy value.

[0010] Furthermore, the method for obtaining the contact impedance coupling coefficient includes: A temperature line is fitted to the electrode temperature at different times within the historical range of the current cutoff time. The slope of the temperature line is obtained. If the slope is greater than or equal to a preset slope threshold, the slope is used as the temperature rise rate coefficient; if the slope is less than the preset slope threshold, the temperature rise rate coefficient is set to 0. Based on the optimal voltage drop component and temperature rise rate coefficient of the minimum response time constant in the preset response time constant, the contact impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the contact impedance coupling coefficient.

[0011] Furthermore, the method for obtaining the diffusion impedance coupling coefficient includes: Based on the optimal voltage drop component and temperature rise rate coefficient of the maximum response time constant in the preset response time constant, the diffusion impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the diffusion impedance coupling coefficient.

[0012] This invention also proposes a lithium battery module recycling and testing device, including a data acquisition module, a voltage rebound analysis module, an impedance coupling assessment module, and a recycling detection module. The data acquisition module is used to acquire the module terminal voltage and terminal temperature at each moment after the lithium battery module is subjected to a discharge pulse, as well as the current cutoff time. The voltage rebound analysis module is used to obtain the voltage rebound coefficient at each time after the current cutoff time based on the module terminal voltage at different times; to obtain the unit step response function value at each response time constant at each time after the current cutoff time based on the time characteristics at different times after the current cutoff time and different preset response time constants; and to obtain the optimal voltage drop component at different response time constants based on the unit step response function values ​​at all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, and to obtain the theoretical voltage rebound coefficient at different times after the current cutoff time. The impedance coupling evaluation module is used to obtain the abnormal residual energy value based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time; and to obtain the contact impedance coupling coefficient and the diffusion impedance coupling coefficient based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time. The recycling detection module is used to perform recycling detection on lithium battery modules based on abnormal residual energy values, contact impedance coupling coefficients, and diffusion impedance coupling coefficients.

[0013] The present invention also proposes a lithium battery module recycling and detection system, wherein the system stores a program or instructions, and when the program or instructions are executed by a processor, the steps of a lithium battery module recycling and detection method as described above are implemented.

[0014] The present invention has the following beneficial effects: This invention obtains the voltage rebound coefficient at each moment after the current cutoff time based on the module terminal voltage at different times; it obtains the unit step response function value at each response time constant at each moment after the current cutoff time based on the time characteristics at different moments after the current cutoff time and different preset response time constants, reflecting the theoretical recovery degree of different response time constants at each moment; it obtains the optimal voltage drop component of different response time constants based on the unit step response function values ​​of all response time constants at different moments after the current cutoff time and the voltage rebound coefficient at different moments, obtaining the abnormal residual energy value, reflecting the level of nonlinear anomalies not covered by theory; it obtains the contact impedance coupling coefficient and diffusion impedance coupling coefficient based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different moments within the historical range of the current cutoff time, characterizing the degree of physical connection failure and the degree of cell aging; and it performs recycling detection on lithium battery modules. This invention improves the accuracy of module recycling by accurately analyzing abnormal residual energy values ​​and using thermoelectric characteristic coupling criteria based on electrode temperature rise rate. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating a lithium battery module recycling and testing method provided in one embodiment of the present invention; Figure 2 This is a structural block diagram of a lithium battery module recycling and testing device provided in one embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a lithium battery module recycling and testing method, apparatus, and system proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details the specific solution of the lithium battery module recycling and testing method, apparatus, and system provided by the present invention.

[0020] Please see Figure 1 The diagram illustrates a flowchart of a lithium battery module recycling and testing method according to an embodiment of the present invention. The specific method includes: Step S1: Obtain the module terminal voltage and terminal temperature at each moment after the lithium battery module is subjected to a discharge pulse, as well as the current cutoff time.

[0021] In an embodiment of the present invention, in order to capture the transient response at the moment of load removal and obtain thermal characteristics with strong noise resistance, the charging and discharging cabinet is controlled to apply a constant current discharge pulse of standard intensity to the lithium battery module. The temperature sensor is in close contact with the metal surface of the terminal post or the bus connection. In order to excite sufficiently significant physical characteristics that are close to the accelerated operating conditions in actual battery use, the test results are more practically valuable. In an embodiment of the present invention, the standard current intensity is set to 1.5 times the rated capacity based on relevant historical experience. Since the remaining power of different retired modules varies, their open-circuit voltages exhibit significant DC level differences. To eliminate DC bias and random quantization noise from industrial temperature sensors, the module terminal voltage and electrode temperature are sampled at a lower sampling frequency to reduce the amount of data. In this embodiment of the invention, the sampling frequency is set to 10Hz, meaning that the module terminal voltage and electrode temperature are acquired every 100ms. In other embodiments of the invention, the sampling frequency can be set according to specific circumstances, and is not limited or elaborated here. It should be noted that the method for obtaining the current cutoff time includes: real-time monitoring of the loop current. When the current drops to 0 amperes, the system marks the corresponding moment as the current cutoff time. The current is sampled and analyzed at a relatively high sampling frequency to accurately capture the instant when the current returns to zero. In the embodiments of the present invention, the current sampling frequency is 1 kHz, that is, the current is monitored once every 1 ms. In other embodiments of the present invention, the sampling frequency can be set according to specific circumstances, which will not be limited or elaborated here.

[0022] Step S2: Based on the module terminal voltage at different times, obtain the voltage rebound coefficient at each time after the current cutoff time; based on the time characteristics at different times after the current cutoff time and different preset response time constants, obtain the unit step response function value at each response time constant at each time after the current cutoff time; based on the unit step response function values ​​at all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, obtain the optimal voltage drop component at different response time constants, and obtain the theoretical voltage rebound coefficient at different times after the current cutoff time.

[0023] The remaining power of different retired modules varies, and their open-circuit voltages have significant DC level differences. In order to extract pure response characteristics and eliminate the influence of absolute voltage levels, deviation analysis is performed based on the current cutoff time. Based on the module terminal voltage at different times, the voltage rebound coefficient at each time after the current cutoff time is obtained.

[0024] Preferably, in one embodiment of the present invention, the method for obtaining the voltage rebound coefficient includes: Using the module terminal voltage at the moment immediately preceding the current cutoff time as the load terminal voltage reflects the load voltage level including impedance voltage drop before the current is removed, providing reference information for subsequent quantification of voltage rebound. The difference between the module terminal voltage and the load terminal voltage at each time after the current cutoff time is obtained, and is used as the voltage rebound coefficient at each time after the current cutoff time.

[0025] The response speed to current cutoff varies within the battery module. Therefore, based on different preset response time constants, response characteristics that conform to the corresponding preset response time constants are separated. Based on the time characteristics at different times after the current cutoff time and different preset response time constants, the unit step response function value at each response time constant at each time after the current cutoff time is obtained.

[0026] Preferably, in one embodiment of the present invention, the method for obtaining the unit step response function value includes: The time difference is obtained as the difference between each moment after the current cutoff moment and the current cutoff moment. Calculate the ratio of the time difference to each preset response time constant, and obtain the unit step response function value of each response time constant at each moment after the current cutoff time based on the exponential decay law.

[0027] It should be noted that, in one embodiment of the present invention, the exponential function with the natural constant as its base is used. The formula for the unit step response function, exhibiting exponential decay, is as follows: ,in, This represents the time difference between the relative current cutoff times; Indicates the response time constant; This represents an exponential function with the natural constant as its base.

[0028] It should be noted that, in the embodiments of the present invention, the preset response time constant includes the response time constant of the lithium battery module corresponding to the fast contact impedance, medium-speed charge transfer impedance and low-speed diffusion impedance, in seconds. The response time constant increases sequentially and can be pre-configured specifically for modules of the same model. The method of obtaining the response time constant is as follows: before the test begins, a standard electrochemical impedance spectroscopy test is performed on a lithium battery module of the same model, and the characteristic frequencies corresponding to the high-frequency arc apex, the medium-frequency arc apex and the low-frequency diffusion initiation point are extracted. The reciprocal of these frequencies is taken as the response time constant. Subsequently, the obtained response time constant is directly called to participate in the calculation, without the need for real-time testing, thus reducing the test time.

[0029] The unit step response function value simulates the theoretical response trajectory of a first-order inertial element under a unit step excitation for each response time constant. The voltage rebound coefficient at different times reflects the amount of voltage recovery relative to the current cutoff time, eliminating the influence of the absolute voltage level and making it easier to quantify the voltage change caused by impedance under different response time constants. Based on the unit step response function values ​​at all response time constants after the current cutoff time and the voltage rebound coefficient at different times, the optimal voltage drop components for different response time constants are obtained.

[0030] Preferably, in one embodiment of the present invention, the method for obtaining the optimal voltage drop component includes: A one-dimensional column vector is constructed using the unit step response function values ​​at each response time constant at different times after the current cutoff time; the column vectors corresponding to all response time constants are merged to obtain the unit step response matrix. The voltage rebound coefficients at different times are used to form a rebound column vector; the preset voltage drop components with different response time constants are used to form a preset voltage drop column vector. Obtain the product vector between the unit step response matrix and the preset pressure drop column vector, obtain the square of the relative distance between the product vector and the rebound column vector, and take the minimum value function to form the objective function; use the non-negative least squares method to solve the objective function to obtain the preset optimal pressure drop column vector, including the optimal pressure drop components with different response time constants.

[0031] It should be noted that, in the embodiments of the present invention, the relative distance is obtained by calculating the Euclidean distance between the product vector and the bounce column vector, or by calculating the difference vector between the product vector and the bounce column vector, and then calculating the L2 norm of the difference vector as the relative distance; the specific means are well known to those skilled in the art and will not be described in detail here.

[0032] It should be noted that in physical reality, the direction of voltage drop caused by impedance must be consistent with the direction of current, and there is no physical meaning of negative impedance. Therefore, the non-negative least squares method is used to solve the objective function so that the elements of the preset voltage drop column vector satisfy the constraint that all are greater than or equal to 0, the objective function reaches the minimum value, and the corresponding preset voltage drop column vector is taken as the preset optimal voltage drop column vector. The specific non-negative least squares method is a technical means well known to those skilled in the art, and will not be elaborated here.

[0033] The preset optimal voltage drop column vector reflects the impedance response of an ideal battery without any micro-short circuits or structural damage. In order to quantify the degree of microstructural distortion, the voltage rebound trajectory under the current impedance level is restored based on the preset optimal voltage drop column vector and the unit step response matrix. The theoretical voltage rebound coefficients at different times after the current cutoff time are obtained.

[0034] Preferably, in one embodiment of the present invention, the method for obtaining the theoretical coefficient of voltage rebound includes: The product between the unit step response matrix and the preset optimal pressure drop column vector is obtained as the theoretical rebound column vector. Obtain the theoretical voltage rebound coefficients at different times after the current cutoff time from the theoretical rebound column vector.

[0035] Step S3: Based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time, obtain the abnormal residual energy value; based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time, obtain the contact impedance coupling coefficient and the diffusion impedance coupling coefficient.

[0036] Microstructural damage such as micro-short circuits, broken active particles, or electrode layer peeling exists within the module. Its voltage recovery process exhibits abnormal linear drift, local oscillations, or voltage drops caused by leakage current, none of which can be explained under ideal characteristics, appearing as residuals of the ideal fit. The difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient reflects the loss of structural integrity in the model's internal electrochemical behavior; the greater the difference, the more residuals exist. Based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff, abnormal residual energy values ​​are obtained.

[0037] Preferably, in one embodiment of the present invention, the method for obtaining the abnormal residual energy value includes: The root mean square value of the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at all times after the current cutoff time is obtained as the abnormal residual energy value.

[0038] The formula is expressed as: ;in, Indicates the abnormal residual energy value; Indicates the number of times after the current cutoff time. Voltage rebound coefficient at time; Indicates the number of times after the current cutoff time. The theoretical coefficient of voltage rebound at time t; This indicates the number of all moments after the current cutoff time.

[0039] It should be noted that the root mean square value reflects the effective amplitude or energy level of the signal, while the abnormal residual energy value reflects the energy magnitude of the nonlinear components in the measured signal that cannot be explained by the standard electrochemical kinetic model, which helps to identify the degree of microstructural anomalies within the module.

[0040] A single impedance voltage drop component cannot completely distinguish between environmental factors and fault factors. Considering that low temperatures can lead to a decrease in diffusion rate or metal contraction, resulting in an increase in the voltage drop component, this is highly similar to the behavior of battery aging. The contact fault point is located at the terminal or bus connection, which is equivalent to the heat source being directly located at the temperature measurement point. This results in a higher optimal voltage drop component for faster response and direct heat conduction, leading to a significant temperature rise in the terminal. Battery aging is usually tested in normal or high temperature environments. The heat generated by its high impedance can accumulate and be reflected in the temperature rise of the terminal. This is manifested as a higher optimal voltage drop component for slower response and a higher temperature rise. Therefore, by combining the analysis of the optimal voltage drop component and the terminal temperature distribution at different times within the historical range of the current cutoff time, the contact impedance coupling coefficient and the diffusion impedance coupling coefficient can be quantified. Based on the optimal voltage drop component with different response time constants and the terminal temperature distribution at different times within the historical range of the current cutoff time, the contact impedance coupling coefficient and the diffusion impedance coupling coefficient can be obtained.

[0041] Preferably, in one embodiment of the present invention, the method for obtaining the contact impedance coupling coefficient includes: A temperature line is fitted to the electrode temperature at different times within the historical range of the current cutoff time. The slope of the temperature line is obtained. If the slope is greater than or equal to a preset slope threshold, the slope is used as the temperature rise rate coefficient; if the slope is less than the preset slope threshold, the temperature rise rate coefficient is set to 0. It should be noted that, in one embodiment of the present invention, the historical range is the range of pulse durations traced back from the current cutoff time as a reference; in other embodiments of the present invention, the size of the historical range can be set according to specific circumstances, and will not be limited or elaborated here.

[0042] It should be noted that the slope reflects the trend of temperature change. In one embodiment of the present invention, the slope is calculated by performing a linear fitting using the least squares method and dividing the difference between the pole temperature at the maximum and minimum moments on the temperature line by the absolute value of the difference between the corresponding moments. In other embodiments of the present invention, the slope can be obtained by taking the derivative of the fitted line. The specific means are well known to those skilled in the art and will not be described in detail here.

[0043] It should be noted that, in order to analyze the temperature rise rate coefficient, the more positive the slope, the larger the number, and the more the temperature tends to rise. Considering the fluctuation of the test environment or the sensor noise, the slope may result in a negative value or a very small positive value, and the temperature change shows a downward trend, with no temperature rise, making the temperature rise rate coefficient 0. In the embodiments of the present invention, the preset slope threshold is set to 0.01 based on relevant historical experience. In other embodiments of the present invention, the preset slope threshold can be set according to specific circumstances, which will not be limited or elaborated here.

[0044] Based on the optimal voltage drop component and temperature rise rate coefficient of the minimum response time constant in the preset response time constant, the contact impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the contact impedance coupling coefficient.

[0045] It should be noted that the minimum response time constant represents the optimal voltage drop component when the response is fastest. The larger the optimal voltage drop component, the greater the temperature rise rate, and the more it exhibits the characteristics of high temperature and high heat in physical connection failures. The larger the contact impedance coupling coefficient, the more it indicates that there is loosening or oxidation of the metal contact components.

[0046] In one embodiment of the present invention, the product of the temperature rise rate coefficient and the optimal component of the voltage drop of the minimum response time constant is obtained as the contact impedance coupling coefficient.

[0047] Preferably, in one embodiment of the present invention, the method for obtaining the diffusion impedance coupling coefficient includes: Based on the optimal voltage drop component and temperature rise rate coefficient of the maximum response time constant in the preset response time constant, the diffusion impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the diffusion impedance coupling coefficient.

[0048] It should be noted that the optimal component of the pressure drop in the maximum response time constant reflects the pressure drop change when the response is slowest. The greater the pressure drop change, the more impedance diffusion occurs within the time, the larger the temperature rise rate coefficient, and the larger the diffusion impedance coupling coefficient. The solid phase diffusion impedance and heat generation rate inside the module increase significantly in sync, indicating that it has entered the accelerated decay period and is more likely to enter the decay period.

[0049] In one embodiment of the present invention, the product of the temperature rise rate coefficient and the optimal component of the pressure drop of the maximum response time constant is obtained as the diffusion impedance coupling coefficient.

[0050] It should be noted that the contact impedance coupling coefficient and diffusion impedance coupling coefficient are obtained by multiplying the temperature rise rate coefficient and the optimal component of the pressure drop to obtain a composite dimension data. However, since the coupling coefficient does not represent a specific physical quantity of resistance or temperature, its value is only used for relative comparison and classification. Therefore, the data dimension will not be considered in the following analysis, and only the value will be analyzed.

[0051] It should be noted that, considering that the voltage drop component of the intermediate response time constant is usually positively correlated with the voltage drop component of the minimum response time constant during aging or at low temperatures, and that the voltage drop component of the minimum response time constant is more sensitive to battery capacity degradation, no separate threshold is set for the purpose of simplifying the production line's judgment logic.

[0052] Step S4: Based on the abnormal residual energy value, contact impedance coupling coefficient, and diffusion impedance coupling coefficient, the lithium battery module is recycled and tested.

[0053] Abnormal residual energy values ​​reflect the degree of residual defects with atypical structures. The larger the abnormal residual energy value, the more it deviates from the ideal voltage rebound. Contact impedance coupling coefficient reflects the high impedance and high thermal characteristics unique to connection faults. The larger the contact impedance coupling coefficient, the greater the characteristics and the more likely the fault features exist. Diffusion impedance coupling coefficient reflects the degree of impedance diffusion. The larger the diffusion impedance coupling coefficient, the more it is affected by the simultaneous and significant increase in solid-phase diffusion impedance and heat generation rate inside the module. Combining abnormal residual energy values, contact impedance coupling coefficients, and diffusion impedance coupling coefficients helps to comprehensively analyze the recycling status of lithium battery modules.

[0054] It should be noted that, in another embodiment of the present invention, the lithium battery module is recycled based on the obtained abnormal residual energy value, contact impedance coupling coefficient, and diffusion impedance coupling coefficient, including: comparing the abnormal residual energy value with a preset safety baseline threshold; if the abnormal residual energy value is greater than the preset safety baseline threshold, the battery module is marked as a high-risk product; if the abnormal residual energy value is less than or equal to the preset safety baseline threshold, the battery module is marked as a structurally qualified product; wherein, based on relevant historical experience, the safety baseline threshold is set to be within the range of 1.2 to 1.5 times the upper limit of the normal distribution of abnormal residual energy value of new batteries of the same model under standard test conditions, and is selected according to actual working conditions; The modules of structurally qualified products are analyzed, and the contact impedance coupling coefficient is compared with the preset connection failure threshold. If the contact impedance coupling coefficient is greater than the preset connection failure threshold, the module is marked as needing refurbishment; if the contact impedance coupling coefficient is less than or equal to the preset connection failure threshold, the module is marked as a qualified product. The preset connection failure threshold is set to 1.2 to 1.5 times the upper limit of the normal distribution of the contact impedance coupling coefficient of the reference module under standard torque locking condition, and is selected according to the actual working conditions. Analyzing the qualified modules, the diffusion impedance coupling coefficient is compared with the preset aging grading threshold. If the diffusion impedance coupling coefficient is less than or equal to the preset aging grading threshold, the module is marked as a healthy module; if the diffusion impedance coupling coefficient is greater than the preset aging grading threshold, the module is marked as an aged module. The preset aging grading threshold, based on relevant historical experience, is set as the measured value of the diffusion impedance coupling coefficient of the same model module at the nominal end of its lifespan, i.e., when the battery's state of health (SOH) is 80%.

[0055] Based on this, the abnormal residual energy value, contact impedance coupling coefficient and diffusion impedance coupling coefficient are obtained to make disposal decisions for module recycling detection, avoid the characteristics of fault masking decay and environmental interference misjudgment, and help improve recycling efficiency.

[0056] In summary, this invention obtains the voltage rebound coefficient at each moment after the current cutoff time based on the module terminal voltage at different times; it obtains the unit step response function value at each response time constant at each moment after the current cutoff time based on the time characteristics at different moments after the current cutoff time and different preset response time constants; it obtains the optimal voltage drop component at different response time constants and the abnormal residual energy value based on the unit step response function value at different moments after the current cutoff time and the voltage rebound coefficient at different times; it obtains the contact impedance coupling coefficient and diffusion impedance coupling coefficient based on the optimal voltage drop component at different response time constants and the electrode temperature distribution at different moments within the historical range of the current cutoff time; and it performs recycling detection on the lithium battery module. This invention improves the accuracy of module recycling by accurately analyzing the abnormal residual energy value and using the thermoelectric characteristic coupling criterion based on the electrode temperature rise rate.

[0057] Based on the same concept as the lithium battery module recycling and testing method provided in this application embodiment, this embodiment proposes a lithium battery module recycling and testing device, such as... Figure 2 As shown, it includes a data acquisition module 201, a voltage rebound analysis module 202, an impedance coupling assessment module 203, and a recovery detection module 204. The data acquisition module 201 is used to acquire the module terminal voltage and terminal temperature at each moment after the lithium battery module is subjected to a discharge pulse, as well as the current cutoff time. The voltage rebound analysis module 202 is used to obtain the voltage rebound coefficient at each time after the current cutoff time based on the module terminal voltage at different times; to obtain the unit step response function value at each time after the current cutoff time at each response time constant based on the time characteristics at different times after the current cutoff time and different preset response time constants; and to obtain the optimal voltage drop component at different response time constants based on the unit step response function values ​​at all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, and to obtain the theoretical voltage rebound coefficient at different times after the current cutoff time. Impedance coupling evaluation module 203 is used to obtain the abnormal residual energy value based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time; and to obtain the contact impedance coupling coefficient and diffusion impedance coupling coefficient based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time. The recycling detection module 204 is used to perform recycling detection on the lithium battery module based on the abnormal residual energy value, contact impedance coupling coefficient and diffusion impedance coupling coefficient.

[0058] It should be understood that the lithium battery module recycling detection device provided in this embodiment is used to execute the above-described lithium battery module recycling detection method, and therefore has the same beneficial effects as the method adopted, run or implemented by the application stored therein.

[0059] The present invention also provides a lithium battery module recycling and detection system, wherein the system stores a program or instructions, and when the program or instructions are executed by a processor, the steps of the lithium battery module recycling and detection method described above are implemented.

[0060] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0061] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for recycling and testing lithium battery modules, characterized in that, The method includes: The module terminal voltage and terminal temperature, as well as the current cutoff time, are obtained at each moment after a discharge pulse is applied to the lithium battery module. Based on the module terminal voltage at different times, the voltage rebound coefficient at each time after the current cutoff time is obtained; based on the time characteristics at different times after the current cutoff time and different preset response time constants, the unit step response function value at each response time constant at each time after the current cutoff time is obtained; based on the unit step response function values ​​at all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, the optimal voltage drop component at different response time constants is obtained, and the theoretical voltage rebound coefficient at different times after the current cutoff time is obtained. Based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time, the abnormal residual energy value is obtained; based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time, the contact impedance coupling coefficient and the diffusion impedance coupling coefficient are obtained. The lithium battery module is recycled based on the abnormal residual energy value, contact impedance coupling coefficient, and diffusion impedance coupling coefficient.

2. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the voltage rebound coefficient includes: The module terminal voltage at the moment immediately preceding the current cutoff time is taken as the load terminal voltage. The difference between the module terminal voltage and the load terminal voltage at each time after the current cutoff time is obtained, and is used as the voltage rebound coefficient at each time after the current cutoff time.

3. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the unit step response function value includes: The time difference is obtained as the difference between each moment after the current cutoff moment and the current cutoff moment. Calculate the ratio of the time difference to each preset response time constant, and obtain the unit step response function value of each response time constant at each moment after the current cutoff time based on the exponential decay law.

4. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the optimal component of the pressure drop includes: A one-dimensional column vector is constructed using the unit step response function values ​​at each response time constant at different times after the current cutoff time; the column vectors corresponding to all response time constants are merged to obtain the unit step response matrix. The voltage rebound coefficients at different times are used to form a rebound column vector; the preset voltage drop components with different response time constants are used to form a preset voltage drop column vector. Obtain the product vector between the unit step response matrix and the preset pressure drop column vector, obtain the square of the relative distance between the product vector and the rebound column vector, and take the minimum value function to form the objective function; use the non-negative least squares method to solve the objective function to obtain the preset optimal pressure drop column vector, including the optimal pressure drop components with different response time constants.

5. The lithium battery module recycling and testing method according to claim 4, characterized in that, The method for obtaining the theoretical coefficient of voltage rebound includes: The product between the unit step response matrix and the preset optimal pressure drop column vector is obtained as the theoretical rebound column vector. Obtain the theoretical voltage rebound coefficients at different times after the current cutoff time from the theoretical rebound column vector.

6. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the abnormal residual energy value includes: The root mean square value of the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at all times after the current cutoff time is obtained as the abnormal residual energy value.

7. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the contact impedance coupling coefficient includes: A temperature line is fitted to the electrode temperature at different times within the historical range of the current cutoff time. The slope of the temperature line is obtained. If the slope is greater than or equal to a preset slope threshold, the slope is used as the temperature rise rate coefficient; if the slope is less than the preset slope threshold, the temperature rise rate coefficient is set to 0. Based on the optimal voltage drop component and temperature rise rate coefficient of the minimum response time constant in the preset response time constant, the contact impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the contact impedance coupling coefficient.

8. The lithium battery module recycling and testing method according to claim 1, characterized in that, The method for obtaining the diffusion impedance coupling coefficient includes: Based on the optimal voltage drop component and temperature rise rate coefficient of the maximum response time constant in the preset response time constant, the diffusion impedance coupling coefficient is obtained. Both the optimal voltage drop component and the temperature rise rate coefficient are positively correlated with the diffusion impedance coupling coefficient.

9. A lithium battery module recycling and testing device, characterized in that, Includes a data acquisition module, a voltage rebound analysis module, an impedance coupling assessment module, and a recycling detection module. The data acquisition module is used to acquire the module terminal voltage and terminal temperature at each moment after the lithium battery module is subjected to a discharge pulse, as well as the current cutoff time. The voltage rebound analysis module is used to obtain the voltage rebound coefficient at each time after the current cutoff time based on the module terminal voltage at different times; and to obtain the unit step response function value at each time after the current cutoff time at each response time constant based on the time characteristics at different times after the current cutoff time and different preset response time constants. Based on the unit step response function values ​​of all response time constants at different times after the current cutoff time and the voltage rebound coefficient at different times, the optimal voltage drop components of different response time constants are obtained, and the theoretical voltage rebound coefficients at different times after the current cutoff time are obtained. The impedance coupling evaluation module is used to obtain the abnormal residual energy value based on the difference between the voltage rebound coefficient and the theoretical voltage rebound coefficient at different times after the current cutoff time; and to obtain the contact impedance coupling coefficient and the diffusion impedance coupling coefficient based on the optimal voltage drop component of different response time constants and the electrode temperature distribution at different times within the historical range of the current cutoff time. The recycling detection module is used to perform recycling detection on lithium battery modules based on abnormal residual energy values, contact impedance coupling coefficients, and diffusion impedance coupling coefficients.

10. A lithium battery module recycling and detection system, characterized in that, The system stores programs or instructions, which, when executed by a processor, implement the steps of the lithium battery module recycling and detection method as described in any one of claims 1 to 8.

Images