A solid-state battery cycling test method and test apparatus

Abstract

A solid-state battery cycle test method and test equipment, relates to the technical field of measuring electrical variables, for improving the accuracy of the evaluation of the electrochemical performance of solid-state battery materials. In the method, the test equipment determines the interface constraint modulus, a force-electricity coupling characteristic parameter, based on the electrochemical data and mechanical data of the solid-state battery during the cycle process, then constructs the modulus evolution curve of the interface constraint modulus with the number of charge and discharge cycles, and analyzes the time sequence relationship between the derivative of the modulus evolution curve and the capacity attenuation, so that the failure reason is attributed to the interface pressure contact failure in the physical layer before the macro performance failure of the solid-state battery, thereby improving the accuracy of the evaluation of the electrochemical performance of the solid-state battery material.

Description

Technical Field

[0001] This application relates to the field of electrical variable measurement technology, and in particular to a method and equipment for solid-state battery cycle testing. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage technologies, the demand for energy storage devices with high energy density and high safety is becoming increasingly urgent. Solid-state batteries are an important development direction for next-generation battery technology, using solid electrolytes to replace organic electrolytes, thereby improving battery safety and energy density.

[0003] In the laboratory research and development and basic performance testing phase of solid-state battery materials, related technologies typically employ modular simulated battery molds for assembly and testing. These molds often utilize threaded sleeve structures. Technicians apply axial preload to the internal electrode components by tightening bolts or nuts. The assembled battery mold is then connected to a battery charge-discharge tester, where voltage, current, and capacity data are collected by setting a charge-discharge program to evaluate the electrochemical performance of the battery materials.

[0004] However, during charge-discharge cycles, lithium ion insertion and extraction occur in the electrode material, causing periodic expansion and contraction of volume (breathing effect). The bolt-locked molds used in related technologies cannot reflect the thickness changes of the battery caused by the breathing effect during charge-discharge cycles. This makes it difficult for researchers to determine on the same time axis whether the inflection point of performance degradation is induced by abnormal fluctuations in interface pressure when faced with test results such as capacity decay, thus reducing the accuracy of the electrochemical performance evaluation of solid-state battery materials. Summary of the Invention

[0005] This application provides a method and equipment for cycling tests of solid-state batteries, which can improve the accuracy of evaluating the electrochemical performance of solid-state battery materials.

[0006] In a first aspect, a method for cycle testing of solid-state batteries is provided, characterized by its application in a testing device connected to a battery charge-discharge tester and a solid-state battery test mold. The method includes: acquiring voltage and current data of the solid-state battery transmitted by the battery charge-discharge tester, and mold cavity pressure data and electrode deformation thickness data transmitted by the solid-state battery test mold, based on a synchronous clock signal; determining multiple single charge-discharge cycles of the solid-state battery based on the current data, and locating the charging expansion range corresponding to the lithium-ion intercalation process in each single charge-discharge cycle; in each charging expansion range, using the difference between the maximum and minimum values ​​of the mold cavity pressure data as the pressure breathing amplitude, and using the difference between the maximum and minimum values ​​of the electrode deformation thickness data... The difference between the minimum and maximum values ​​is used as the thickness breathing amplitude; the ratio of the pressure breathing amplitude to the thickness breathing amplitude is determined as the interface constraint modulus, which characterizes the degree of physical contact between the solid-state battery interface; a modulus evolution curve is constructed with the number of charge-discharge cycles as the abscissa and the interface constraint modulus as the ordinate; when the decay rate of the discharge capacity of a single charge-discharge cycle relative to the discharge capacity of the first single charge-discharge cycle exceeds a preset failure threshold, the first derivative of the modulus decay curve before exceeding the preset failure threshold is calculated; if the first derivative of the modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds the preset failure threshold, it is determined that the performance degradation of the solid-state battery is induced by interface pressure contact failure.

[0007] By adopting the above technical solution, the testing equipment determines the interface constraint modulus, a characteristic parameter of force-electric coupling, based on the electrochemical and mechanical data of solid-state batteries during cycling. Then, it constructs the modulus evolution curve of the interface constraint modulus with the number of charge-discharge cycles. By analyzing the temporal relationship between the derivative of the modulus evolution curve and the capacity decay, the failure can be attributed to physical interface pressure contact failure before the solid-state battery experiences macroscopic performance failure, thereby improving the accuracy of the electrochemical performance evaluation of solid-state battery materials.

[0008] In conjunction with some embodiments of the first aspect, in some embodiments, the step of determining the ratio of pressure breathing amplitude to thickness breathing amplitude as the interface constraint modulus characterizing the degree of physical contact at the solid-state battery interface specifically includes: within the charging expansion range, extracting pressure data segments and thickness data segments whose state of charge is within a preset linear range from the mold cavity pressure data and electrode deformation thickness data; performing linear regression fitting with the thickness data segment as the independent variable and the pressure data segment as the dependent variable to obtain the slope of the fitted line; using the slope of the fitted line as the equivalent ratio of pressure breathing amplitude to thickness breathing amplitude; and determining the equivalent ratio as the interface constraint modulus for a single charge-discharge cycle.

[0009] By adopting the above technical solution, the interface constraint modulus is determined by extracting the linear interval with the highest data quality within the charging expansion interval and using the slope obtained by linear regression fitting. This avoids the interference of nonlinear effects in the early and late stages of charging and integrates information from hundreds or thousands of data points within the interval, thus making the calculated interface constraint modulus value more accurate.

[0010] In conjunction with some embodiments of the first aspect, in some embodiments, the step of locating the charging expansion interval corresponding to the lithium-ion intercalation process in each single charge-discharge cycle specifically includes: identifying a continuous time series belonging to the constant current charging stage from the current data; calculating the current variance within the continuous time series; and if the current variance is less than a preset fluctuation threshold, then truncating the continuous time series as the charging expansion interval.

[0011] By adopting the above technical solution, the test equipment can more accurately identify the constant current charging stage by calculating the current variance and comparing it with a preset threshold, thereby reducing interference from the constant voltage charging stage and the resting stage.

[0012] In conjunction with some embodiments of the first aspect, in some embodiments, the step of calculating the first derivative of modulus decay of the modulus evolution curve before the time corresponding to the time exceeding the preset failure threshold specifically includes: removing data from the first preset number of single charge-discharge cycles to eliminate nonlinear fluctuations in the activation stage of the solid-state battery; defining the second preset number of consecutive single charge-discharge cycles after the activation stage as the initial stable stage; performing linear fitting on the interface constraint modulus within the initial stable stage, and determining the slope obtained from the fitting as the reference derivative; calculating the instantaneous rate of change of each discrete point in the modulus evolution curve relative to the preceding point before the time corresponding to the time exceeding the preset failure threshold, to obtain the first derivative of modulus decay.

[0013] By adopting the above technical solution, the testing equipment uses the differential method to calculate the instantaneous rate of change, which can more sensitively capture every change in the modulus decay rate, thereby constructing a more refined derivative change curve.

[0014] In conjunction with some embodiments of the first aspect, in some embodiments, the step of if the first derivative of modulus decay shows a negative abrupt change characteristic before the discharge capacity decay rate exceeds a preset failure threshold specifically includes: calculating the difference between the first derivative of modulus decay and the reference derivative; if the difference is negative for a third consecutive preset number of charge-discharge cycles and the absolute value of the difference is greater than a preset slope deviation threshold, then it is confirmed that a negative abrupt change characteristic has occurred.

[0015] By adopting the above technical solution, the testing equipment reduces the impact of isolated jump points caused by data noise by setting the number of consecutive cycles and the slope deviation threshold, and only identifies those continuous and significant negative mutation features, thereby improving the accuracy of the electrochemical performance evaluation of solid-state battery materials.

[0016] In conjunction with some embodiments of the first aspect, in some embodiments, if the first derivative of modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold, the step of determining that the performance degradation of the solid-state battery is induced by interface pressure contact failure specifically includes: monitoring the reference return pressure corresponding to each single charge-discharge cycle, where the reference return pressure is the mold cavity pressure value transmitted by the solid-state battery test mold at the end of a single charge-discharge cycle; when the first derivative of modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold and the rate of change of the reference return pressure is less than a preset tooling relaxation threshold, the performance degradation is determined to be induced by interface pressure contact failure inside the solid-state battery.

[0017] By adopting the above technical solution, the testing equipment eliminates the interference caused by the relaxation of the testing fixture itself by additionally monitoring the reference return pressure parameter, thereby improving the accuracy of the evaluation of the electrochemical performance of solid-state battery materials.

[0018] In conjunction with some embodiments of the first aspect, in some embodiments, after determining that the performance degradation is induced by interface pressure contact failure inside the solid-state battery when the first derivative of modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold and the rate of change of the reference return pressure is less than a preset tooling relaxation threshold, the method further includes: if the rate of change of the reference return pressure is greater than or equal to the preset tooling relaxation threshold, then determining that the current test data is invalid and prompting to tighten the solid-state battery test mold.

[0019] By adopting the above technical solution, when data anomalies are detected that may be caused by loose tooling, the testing equipment automatically determines that the data is invalid and actively prompts the operator to intervene.

[0020] In a second aspect, embodiments of this application provide a test device comprising: one or more processors and a memory; the memory is coupled to the one or more processors and is used to store computer program code, the computer program code including computer instructions, wherein the one or more processors invoke the computer instructions to cause the test device to perform the method described in the first aspect and any possible implementation thereof.

[0021] Thirdly, embodiments of this application provide a computer program product containing instructions that, when the computer program product is run on a test device, cause the test device to execute the method described in the first aspect and any possible implementation thereof.

[0022] Fourthly, embodiments of this application provide a computer-readable storage medium including instructions that, when executed on a test device, cause the test device to perform the method described in the first aspect and any possible implementation thereof.

[0023] Understandably, the testing equipment provided in the second aspect, the computer program product provided in the third aspect, and the computer storage medium provided in the fourth aspect are all used to execute the methods provided in the embodiments of this application. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects in the corresponding methods, and will not be repeated here.

[0024] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0025] 1. The testing equipment determines the interface constraint modulus, a characteristic parameter of force-electric coupling, based on the electrochemical and mechanical data of solid-state batteries during cycling. Then, it constructs the modulus evolution curve of the interface constraint modulus with the number of charge-discharge cycles. By analyzing the derivative of the modulus evolution curve and the time-series relationship of capacity decay, the failure cause can be attributed to physical interface pressure contact failure before the solid-state battery experiences macroscopic performance failure, thereby improving the accuracy of the electrochemical performance evaluation of solid-state battery materials.

[0026] 2. The testing equipment extracts the linear interval with the highest data quality within the charging expansion range and uses the slope obtained by linear regression fitting to determine the interface constraint modulus, thereby avoiding the interference of nonlinear effects in the early and late stages of charging. Furthermore, it integrates information from hundreds or thousands of data points within the interval, making the calculated interface constraint modulus value more accurate.

[0027] 3. By additionally monitoring the baseline return pressure parameter, the testing equipment eliminates interference caused by the loosening of the testing fixture itself, thereby improving the accuracy of the evaluation of the electrochemical performance of solid-state battery materials. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a solid-state battery cycle testing method in an embodiment of this application.

[0029] Figure 2 This is another schematic flowchart of a solid-state battery cycle testing method in an embodiment of this application.

[0030] Figure 3This is a schematic diagram of the physical device structure of a test equipment in an embodiment of this application. Detailed Implementation

[0031] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to and includes any or all possible combinations of one or more of the listed items.

[0032] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0033] This application provides a method and equipment for cycling tests of solid-state batteries, which can improve the accuracy of evaluating the electrochemical performance of solid-state battery materials.

[0034] Please see Figure 1 This is a flowchart illustrating a solid-state battery cycle testing method in an embodiment of this application.

[0035] S101. Based on the synchronous clock signal, acquire the voltage and current data of the solid-state battery transmitted by the battery charge and discharge tester, as well as the mold cavity pressure data and electrode deformation thickness data transmitted by the solid-state battery test mold.

[0036] The synchronous clock signal refers to a unified time reference provided by the testing equipment to ensure that data points obtained from different physical devices are aligned on the timestamp. The battery charge / discharge tester is an instrument capable of charging and discharging batteries according to a preset program in constant current, constant voltage, and other modes, and recording voltage and current values. In this invention, the solid-state battery test mold specifically refers to a testing device with in-situ mechanical monitoring capabilities. It not only houses and encapsulates the core components of the solid-state battery (such as positive and negative electrodes and solid electrolyte), but also integrates pressure sensors (such as spoke-type or piezoelectric sensors) and high-precision displacement sensors (such as linear variable differential transformers (LVDTs) or laser displacement gauges) into its structure, thereby enabling real-time output of mold cavity pressure data and electrode deformation thickness data. The mold cavity pressure data refers to the resistance pressure exerted on the mold's limiting wall (pressure head) when the tested solid-state battery expands within a confined space. It measures the axial load on the entire mold system and represents the stress change perpendicular to the electrode stacking plane caused by lithium-ion intercalation / deintercalation within the tested solid-state battery. Electrode deformation thickness data is used to represent the microscopic expansion and contraction of the overall battery thickness during charging and discharging. In this application, the electrode assembly refers to the electrochemical reaction unit placed inside the solid-state battery test mold cavity, including but not limited to a stacked structure composed of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. During the test, this stacked structure as a whole undergoes thickness expansion and contraction.

[0037] Specifically, the testing equipment first establishes communication connections with the battery charge / discharge tester and the solid-state battery test mold, and sets a unified data acquisition frequency. After the test begins, the testing equipment sends synchronized start commands to the two external instruments. Based on this synchronized clock signal, the testing equipment simultaneously records four physical quantities at each sampling point (e.g., once per second): the instantaneous voltage (V) and instantaneous current (I) provided by the charge / discharge tester, and the instantaneous mold cavity pressure (P) and instantaneous electrode deformation thickness (T) provided by the integrated sensors of the solid-state battery test mold. Through this synchronized acquisition method, multiple sets of interrelated time-series data {V(t), I(t), P(t), T(t)} can be obtained, ensuring a one-to-one correspondence between the electrochemical response and the mechanical response in the time dimension.

[0038] S102. Based on current data, determine multiple single charge-discharge cycles of the solid-state battery, and locate the charging expansion range of the corresponding lithium-ion intercalation process in each single charge-discharge cycle.

[0039] A single charge-discharge cycle refers to a battery undergoing one complete charge and one complete discharge cycle, serving as the fundamental unit for evaluating battery cycle performance. Lithium-ion intercalation typically occurs during the charging phase. For example, with common cathode materials, lithium ions are extracted from the anode, pass through the electrolyte, and intercalate into the lattice of the cathode material. This process is often accompanied by the expansion of the electrode material's volume. The charging expansion range refers to the period during a single charge cycle where lithium-ion intercalation dominates, and the battery thickness and internal pressure exhibit a regular increase. This range provides the optimal window for analyzing the battery's "breathing" effect.

[0040] Specifically, after acquiring continuous current time-series data, the testing equipment first analyzes the data to identify the cycle period. Typically, the charging current is positive, the discharging current is negative, and the current is zero during the resting phase. By detecting the positive-to-negative switching points of the current value and the zero-value interval, the testing equipment can divide the entire data stream into multiple consecutive, numbered single charge-discharge cycles. After locating each single charge-discharge cycle, the testing equipment focuses its analysis on the charging phase. Because the current is relatively stable during the constant-current charging phase and is the main stage of lithium-ion intercalation, this phase is most suitable as the interval for characterizing expansion behavior. To more accurately locate this interval, the testing equipment further identifies a continuous time series with minimal current fluctuations during the charging phase, designating it as the charging expansion interval of that cycle for subsequent mechanical parameter calculations.

[0041] In some embodiments, the location of the charging expansion interval can be achieved in several ways: Optionally, it can be determined based on the current variance. Specifically, within the identified constant current charging data segment, the current data is scanned using a sliding window method. Then, the variance of the current data within each window is calculated. Next, the longest continuous time period with a variance value less than a preset fluctuation threshold is determined as the constant current charging stage, i.e., the charging expansion interval. Optionally, it can also be located based on the status record of the test program. Specifically, when the test equipment issues charging and discharging commands, it records the start and end timestamps of each test step (such as constant current charging, constant voltage charging, and resting). Then, during the data analysis phase, the start and end times of the constant current charging step of each cycle are directly read from the status log. Then, the corresponding time period is extracted from the synchronous data using the start and end times as the charging expansion interval.

[0042] S103. In each charging expansion range, the difference between the maximum and minimum values ​​of the mold cavity pressure data is taken as the pressure breathing amplitude, and the difference between the maximum and minimum values ​​of the electrode group deformation thickness data is taken as the thickness breathing amplitude.

[0043] Among them, pressure breathing amplitude refers to the maximum change in internal stress caused by the volume change due to lithium-ion intercalation in a solid-state battery within a single charging expansion range, reflecting the magnitude of the force generated when the solid-state battery breathes in a confined space. Thickness breathing amplitude refers to the maximum actual physical thickness expansion of the solid-state battery electrode assembly in the direction perpendicular to the electrode plane within the same range, reflecting the magnitude of deformation during solid-state battery breathing.

[0044] Specifically, for each identified charging expansion range, the testing equipment extracts the corresponding time-period mold cavity pressure data sequence and electrode deformation thickness data sequence from the synchronously stored data. Then, the testing equipment performs extreme value extraction on these two data sequences. For the pressure data sequence, the equipment finds its maximum pressure value P_max and minimum pressure value P_min, and then calculates the difference between them, i.e., the pressure breathing amplitude ΔP = P_max - P_min. Similarly, for the thickness data sequence, the testing equipment finds its maximum thickness value T_max and minimum thickness value T_min, and calculates the thickness breathing amplitude ΔT = T_max - T_min. These two amplitudes together describe the mechanical response behavior of the solid-state battery during a single charge.

[0045] S104. The ratio of pressure breathing amplitude to thickness breathing amplitude is determined as the interface constraint modulus, which characterizes the degree of physical contact between the solid-state battery interface.

[0046] The interface constraint modulus, defined in this invention, is a performance characterization parameter. Its physical meaning is similar to Young's modulus or the stiffness coefficient of a spring in materials mechanics, used to quantify the effective stiffness of the internal interfaces of a solid-state battery. A high interface constraint modulus means that even a small expansion in thickness can generate significant internal pressure, indicating tight, gapless contact between the battery's internal layers (electrodes and electrolytes, etc.). Conversely, a low interface constraint modulus means that even with significant expansion, the increase in internal pressure is very limited, potentially indicating interface delamination, poor contact, or internal voids.

[0047] Specifically, after calculating the pressure breathing amplitude ΔP and thickness breathing amplitude ΔT for a single charge-discharge cycle in S103, the test equipment performs a division operation: interface constraint modulus M = ΔP / ΔT. This calculated modulus value M is then associated with the current charge-discharge cycle number n, forming a data pair (n, M_n). This transforms two independent mechanical measurements into a single, physically meaningful composite index, which more intuitively reflects the physical contact state of the solid-solid interface inside the solid-state battery.

[0048] In some embodiments, the interface constraint modulus can be determined in several ways: Optionally, the testing equipment can first acquire the pressure breathing amplitude ΔP and the thickness breathing amplitude ΔT. Then, it is determined whether the thickness breathing amplitude ΔT is greater than a preset minimum effective expansion threshold (e.g., 0.1 micrometers) to avoid calculation errors caused by an excessively small or zero denominator. Next, if ΔT is greater than the threshold, the ratio M = ΔP / ΔT is directly calculated; if it is not greater, the modulus of the current cycle is marked as invalid. Optionally, normalization processing can also be used. Specifically, the pressure breathing amplitude and the thickness breathing amplitude are acquired. Then, the pressure breathing amplitude is divided by the initial preload pressure of the battery to obtain the normalized pressure change, and the thickness breathing amplitude is divided by the initial thickness of the battery to obtain the normalized thickness change (i.e., strain). Next, the ratio of the normalized pressure change to the normalized thickness change is determined as the interface constraint modulus. This can eliminate the influence of different initial assembly conditions.

[0049] S105. Using the number of charge-discharge cycles as the abscissa and the interface constraint modulus as the ordinate, construct a modulus evolution curve that varies with the number of charge-discharge cycles.

[0050] The modulus evolution curve is a two-dimensional graph that shows how the interface constraint modulus changes as the battery ages (i.e., the number of cycles increases). The horizontal axis represents the number of charge-discharge cycles the battery has undergone, which is a measure of the battery's lifespan. The vertical axis represents the interface constraint modulus value corresponding to each cycle.

[0051] Specifically, the testing equipment maintains a data storage structure, such as a list or array. Each time the modulus calculation in S104 is completed, the equipment appends the resulting (cycle number n, modulus value M_n) data pair to this storage structure. As the cyclic testing progresses, this data list grows continuously, forming a time series. The testing equipment can plot this series of data points in a two-dimensional coordinate system, connecting the points with line segments to form a continuously changing modulus evolution curve. The overall trend, slope changes, and abrupt change points of this curve contain information about the degradation of solid-state battery interface stability.

[0052] In some embodiments, the modulus evolution curve can be constructed in several ways: Optionally, it can be dynamically plotted using a real-time graphical user interface (GUI). Specifically, a chart control is created on the test software interface. Then, after the modulus calculation is completed in each loop, new data points (loop number, modulus) are immediately added to the data source of the chart control. Next, the chart control is refreshed, allowing the user to observe the growth process of the modulus evolution curve in real time. Optionally, the modulus value calculated in each round, along with the loop number, can be sequentially written to a data file (such as a CSV or TXT file) throughout the entire loop test. After the test, a data analysis script or software (such as Python's Matplotlib library or Excel) is launched. The script then reads the data file and generates a complete modulus evolution curve in one go for subsequent analysis and reporting.

[0053] S106. When the decay rate of the discharge capacity of a single charge-discharge cycle relative to the discharge capacity of the first single charge-discharge cycle exceeds the preset failure threshold, calculate the first derivative of the modulus decay of the modulus evolution curve before the time corresponding to the time exceeding the preset failure threshold.

[0054] The discharge capacity decay rate refers to the percentage decrease in discharge capacity of the current cycle compared to the discharge capacity of the first single charge-discharge cycle. The preset failure threshold is a predefined standard, such as a decay rate of 20% (i.e., a capacity retention rate of 80%). Once this threshold is reached, the battery life is generally considered to have ended. The first derivative of modulus decay represents the slope of the modulus evolution curve, i.e., the rate of change of the interface constraint modulus with the number of cycles, reflecting the speed of interface performance degradation.

[0055] Specifically, after each charge-discharge cycle, the test equipment calculates not only the interface constraint modulus but also the discharge capacity of the current cycle and compares it with the discharge capacity of the first single charge-discharge cycle to obtain the real-time capacity decay rate. The test equipment continuously monitors whether this decay rate exceeds a preset failure threshold (e.g., 20%). Once the decay rate is detected to exceed the threshold for the first time in the Nth cycle, the test equipment focuses its analysis on all interface constraint modulus data prior to the Nth cycle. Then, it calculates the local slope of the modulus evolution curve within the interval from the 1st to the (N-1)th cycle, i.e., the first derivative. This derivative sequence reflects how the degradation rate of the internal physical contact state evolves before the battery's electrochemical performance fails.

[0056] In some embodiments, the first derivative of modulus decay can be calculated in several ways: Optionally, the data from the first few cycles (e.g., the first 5-10 cycles) can be discarded to eliminate the unstable effects of solid-state battery formation and activation stages. Then, a second predetermined number of consecutive charge-discharge cycles (e.g., the 11th-30th cycles) following the activation stage are defined as the initial stable stage. The interface-constrained modulus within the initial stable stage is linearly fitted, and the slope obtained from the fitting is determined as the baseline derivative (i.e., the initial stable decay rate). Next, for each cycle point n until failure, its instantaneous rate of change is calculated by difference to form a sequence of first derivatives. Optionally, a sliding window of fixed width (e.g., 10 cycles wide) can also be defined. Then, the window is slid backwards cycle by cycle from the starting point of the modulus evolution curve. Next, at each position of the window, a linear regression is performed on the 10 modulus data points within the window, and the slope obtained from the fitting is used as the first derivative value at the center point of the window. This method can obtain a smoother first derivative curve with stronger noise resistance.

[0057] S107. If the first derivative of modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds the preset failure threshold, then the performance degradation of the solid-state battery is determined to be induced by interfacial pressure contact failure.

[0058] Among them, the negative abrupt change characteristic refers to a significant and drastic change in the first derivative of modulus decay (i.e., the slope of the modulus curve) in a short period of time, moving in a negative direction. For example, the slope suddenly jumps from a small negative value (e.g., -0.1) to a much larger negative value (e.g., -2.0), indicating a sudden acceleration in the deterioration rate of interface integrity. Interface pressure contact failure refers to the loss of good physical contact between the electrode / electrolyte interface inside the solid-state battery due to stress accumulation, material pulverization, or dendrite growth during cycling, resulting in a sharp increase in interface resistance and thus rapid capacity decay.

[0059] Specifically, the testing equipment compares the first derivative sequence calculated in S106 with a normal decay behavior. This normal behavior can be defined by the benchmark derivative in the initial stable phase. The testing equipment checks point by point whether there are points or intervals where the first derivative value is much smaller (i.e., the absolute value is much larger) than the benchmark derivative before capacity failure occurs. If the testing equipment finds that the modulus decay first derivative exhibits this negative abrupt change characteristic before the capacity decay rate exceeds the preset failure threshold, a causal chain is established: the interface integrity first deteriorates rapidly (modulus slope abrupt change), and then manifests as the collapse of electrochemical performance (capacity decay). Based on this leading characteristic in the time sequence, the testing equipment ultimately determines that the decline in battery performance is caused by internal interfacial pressure contact failure, rather than the slow chemical aging of the material itself. In addition, to eliminate misjudgments caused by loose test fixtures, the testing equipment also detects the reference return pressure for each single charge-discharge cycle. The reference return pressure is the pressure value transmitted within the mold cavity of the solid-state battery test mold at the end of a single charge-discharge cycle. Only if the rate of change of the reference return pressure is less than a preset fixture relaxation threshold is a negative change attributed to interface pressure contact failure within the solid-state battery. If the rate of change of the reference return pressure is greater than or equal to the preset fixture relaxation threshold, the testing equipment determines the current test data to be invalid and prompts the user to tighten the solid-state battery test mold.

[0060] In some embodiments, negative abrupt change characteristics can be determined in several ways: Optionally, the difference between the modulus decay first derivative sequence and the baseline derivative can be calculated. Then, it is checked whether this difference is negative for multiple consecutive cycles (e.g., three consecutive cycles) and whether the absolute value is greater than a preset slope deviation threshold (e.g., five times the absolute value of the baseline derivative). If the above conditions are met, a negative abrupt change characteristic is confirmed. Optionally, a statistical process control-based method can also be used. Specifically, the first derivative data of the initial stable phase is used as a control group, and its mean and standard deviation are calculated. Then, a control chart is established, where the center line is the mean, and the upper and lower control limits are the mean plus or minus three standard deviations. Next, subsequent first derivative points are monitored. Once a point is found to fall outside the lower control limit, it can be determined as a statistically significant out-of-control point, i.e., a negative abrupt change characteristic.

[0061] In the above embodiments, the testing equipment determines the interface constraint modulus, a characteristic parameter of force-electric coupling, based on the electrochemical and mechanical data of the solid-state battery during cycling. Then, it constructs the modulus evolution curve of the interface constraint modulus with the number of charge-discharge cycles. By analyzing the temporal relationship between the derivative of the modulus evolution curve and the capacity decay, the failure cause can be attributed to physical interface pressure contact failure before the solid-state battery experiences macroscopic performance failure, thereby improving the accuracy of the electrochemical performance evaluation of solid-state battery materials.

[0062] However, sensor signals may contain noise, or the battery may exhibit nonlinear mechanical behavior at both ends of the charging process (low SOC and high SOC regions) due to phase transitions or increased polarization. Using the maximum and minimum values ​​across the entire charging expansion range to calculate the amplitude may cause unnecessary fluctuations in the calculated interface constraint modulus value between cycles, thus affecting the smoothness of the modulus evolution curve and the accuracy of derivative calculations.

[0063] Please see Figure 2 This is another flowchart illustrating a solid-state battery cycle testing method in an embodiment of this application.

[0064] S201. Based on the synchronous clock signal, acquire the voltage and current data of the solid-state battery transmitted by the battery charge and discharge tester, as well as the mold cavity pressure data and electrode deformation thickness data transmitted by the solid-state battery test mold.

[0065] S202. Based on current data, determine multiple single charge-discharge cycles of the solid-state battery and locate the charging expansion range of the corresponding lithium-ion intercalation process in each single charge-discharge cycle.

[0066] S203. In each charging expansion range, the difference between the maximum and minimum values ​​of the mold cavity pressure data is taken as the pressure breathing amplitude, and the difference between the maximum and minimum values ​​of the electrode group deformation thickness data is taken as the thickness breathing amplitude.

[0067] Step S201 is similar to step S101, step S202 is similar to step S102, and step S203 is similar to step S103, so they will not be described again here.

[0068] S204. Within the charging expansion range, extract pressure data segments and thickness data segments whose charging state is within a preset linear range from the mold cavity pressure data and electrode group deformation thickness data.

[0069] The State of Charge (SOC) represents the percentage of remaining battery capacity. The preset linear range refers to a specific SOC range within which the battery's thickness expansion and pressure increase during charging are approximately linearly related to the SOC (or charging time), such as an SOC range from 20% to 80%. This range is chosen to exclude interference from nonlinear phase transitions or polarization effects that may exist at the beginning and end of charging. The pressure data segment and thickness data segment are subsets extracted from the mold cavity pressure data and electrode deformation thickness data during the charging expansion range, respectively, based on the aforementioned preset linear range.

[0070] Specifically, the testing equipment first estimates the State of Charge (SOC) at any point within the charging expansion range based on the total duration of the expansion interval and the constant current value. Then, it calculates the corresponding time window based on a preset linear SOC range (e.g., 20% to 80%). Finally, using this time window, it extracts the corresponding pressure data segment and thickness data segment from the mold cavity pressure data and electrode deformation thickness data sequence within the charging expansion range. These two data segments represent the mechanical response of the solid-state battery in the most stable and representative expansion stage.

[0071] S205. Using the thickness data segment as the independent variable and the pressure data segment as the dependent variable, perform linear regression fitting to obtain the slope of the fitted line.

[0072] Specifically, the testing equipment pairs the data points from the thickness and pressure data segments extracted from S204 according to their timestamps, forming a series of (thickness, pressure) coordinate points. Then, linear regression algorithms such as least squares are applied to fit these coordinate points, calculating an optimally fitted line P=m*T+b. This finds a slope m and an intercept b that minimizes the sum of the squared distances from all data points to this line. Ultimately, m is the core result of this step; this slope m quantifies the linear correlation between pressure and thickness during the most stable expansion phase of the battery.

[0073] S206. The slope of the fitted straight line is used as the equivalent ratio of the pressure breathing amplitude to the thickness breathing amplitude.

[0074] The equivalent ratio is a concept introduced in this step, which aims to illustrate that the slope obtained through linear fitting is physically equivalent to the ratio of pressure amplitude to thickness amplitude calculated using the (maximum-minimum) method. However, compared to the latter, it is a more robust and accurate ratio in a statistical sense, calculated based on a large number of data points within the interval.

[0075] Specifically, this step is a conceptual bridge. In the previous step S205, the testing equipment obtained the slope *m* of the fitted straight line. Since the slope is defined as the change in the dependent variable divided by the change in the independent variable, this slope *m* naturally represents the ratio of pressure to thickness change. This step logically recognizes this slope *m* as the equivalent ratio of the pressure breathing amplitude to the thickness breathing amplitude, thus allowing it to replace the ratio calculated using the two-point extremum method in S104. The advantage of this is that the ratio is no longer limited to two potentially noisy extrema points, but rather incorporates information from hundreds or thousands of data points within the linear interval, thereby enhancing the robustness and repeatability of the calculation results.

[0076] S207. The equivalent ratio is determined as the interface constraint modulus for a single charge-discharge cycle.

[0077] S208. Using the number of charge-discharge cycles as the abscissa and the interface constraint modulus as the ordinate, construct a modulus evolution curve that varies with the number of charge-discharge cycles.

[0078] S209. When the decay rate of the discharge capacity of a single charge-discharge cycle relative to the discharge capacity of the first single charge-discharge cycle exceeds a preset failure threshold, calculate the first derivative of the modulus decay of the modulus evolution curve before the time corresponding to the time exceeding the preset failure threshold.

[0079] S210. If the first derivative of modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds the preset failure threshold, then the performance degradation of the solid-state battery is determined to be induced by interfacial pressure contact failure.

[0080] Step S208 is similar to step S105, step S209 is similar to step S106, and step S210 is similar to step S107, so they will not be described again here.

[0081] In the above embodiments, the testing equipment further filters out the linear interval with the best data quality within the charging expansion interval, and uses linear regression fitting to calculate the ratio of pressure to thickness change, thereby determining the interface constraint modulus. This avoids interference from data noise and nonlinear behavior, resulting in a smoother modulus evolution curve and a clearer trend.

[0082] The above describes a solid-state battery cycle testing method in the embodiments of this application. The exemplary testing device 300 provided in the embodiments of this application is described below.

[0083] Figure 3 This is an exemplary hardware structure diagram of the test device 300 provided in an embodiment of this application. In some embodiments, the test device 300 is a computer device. The computer device includes a processor, a memory, and a network interface connected via a system bus. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the computer device is used to store data. The network interface of the computer device is used to communicate with other external terminals or servers via a network connection. In some embodiments, the network interface can be a wired network interface; in some embodiments, the network interface can also be a wireless network interface. When the computer program is executed by the processor, it implements a solid-state battery cycle testing method according to an embodiment of this application.

[0084] Those skilled in the art will understand that Figure 3The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0085] In some embodiments of this application, a computer-readable storage medium is also provided, including instructions that, when executed on the test device 300, cause the test device 300 to perform a solid-state battery cycle test method according to an embodiment of this application.

[0086] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0087] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as meaning "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as meaning "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0088] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0089] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM or random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for cycling tests of solid-state batteries, characterized in that, The method is applied to testing equipment, which is connected to a battery charge / discharge tester and a solid-state battery test mold, and includes: The voltage and current data of the solid-state battery transmitted by the battery charge and discharge tester, as well as the mold cavity pressure data and electrode deformation thickness data transmitted by the solid-state battery test mold, are obtained based on the synchronous clock signal. Based on the current data, multiple single charge-discharge cycles of the solid-state battery are determined, and the charging expansion range of the corresponding lithium-ion intercalation process in each single charge-discharge cycle is located. In each of the charging expansion intervals, the difference between the maximum and minimum values ​​of the mold cavity pressure data is taken as the pressure breathing amplitude, and the difference between the maximum and minimum values ​​of the electrode group deformation thickness data is taken as the thickness breathing amplitude. The ratio of the pressure breathing amplitude to the thickness breathing amplitude is determined as the interface constraint modulus, which characterizes the degree of physical contact between the solid-state battery interface. With the number of charge-discharge cycles as the x-axis and the interface constraint modulus as the y-axis, a modulus evolution curve is constructed as a function of the number of charge-discharge cycles. When the decay rate of the discharge capacity of the single charge-discharge cycle relative to the discharge capacity of the first single charge-discharge cycle exceeds a preset failure threshold, the first derivative of the modulus decay of the modulus evolution curve before the time corresponding to the time exceeding the preset failure threshold is calculated. If the first derivative of the modulus decay exhibits a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold, then the performance degradation of the solid-state battery is determined to be induced by interfacial pressure contact failure.

2. The method according to claim 1, characterized in that, The step of determining the ratio of the pressure breathing amplitude to the thickness breathing amplitude as the interface constraint modulus characterizing the degree of physical contact tightness at the solid-state battery interface is replaced by the following steps: Within the charging expansion range, pressure data segments and thickness data segments with the state of charge in a preset linear range are extracted from the mold cavity pressure data and the electrode group deformation thickness data. Using the thickness data segment as the independent variable and the pressure data segment as the dependent variable, a linear regression is performed to obtain the slope of the fitted line. The slope of the fitted straight line is used as the equivalent ratio of the pressure breathing amplitude to the thickness breathing amplitude. The equivalent ratio is determined as the interface constraint modulus of the single charge-discharge cycle.

3. The method according to claim 1, characterized in that, The step of locating the charging expansion range corresponding to the lithium-ion intercalation process in each single charge-discharge cycle specifically includes: Identify the continuous time series belonging to the constant current charging stage from the current data; Calculate the current variance within the continuous time series; If the current variance is less than a preset fluctuation threshold, then the continuous time series is truncated as the charging expansion interval.

4. The method according to claim 1, characterized in that, The step of calculating the first derivative of the modulus decay of the modulus evolution curve before exceeding the preset failure threshold specifically includes: The data from the first preset number of single charge-discharge cycles are removed to eliminate nonlinear fluctuations during the activation phase of the solid-state battery. The second predetermined number of consecutive single charge-discharge cycles following the activation phase are defined as the initial stable phase; The interface constraint modulus during the initial stable phase is linearly fitted, and the slope obtained from the fitting is determined as the benchmark derivative. The instantaneous rate of change of each discrete point in the modulus evolution curve relative to the preceding point is calculated before the time corresponding to the time exceeding the preset failure threshold, and the first derivative of the modulus decay is obtained.

5. The method according to claim 4, characterized in that, The step of stating that if the first derivative of the modulus decay exhibits a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold specifically includes: Calculate the difference between the first derivative of the modulus decay and the reference derivative; If the difference is negative for a third consecutive set number of charge-discharge cycles and the absolute value of the difference is greater than a preset slope deviation threshold, then the negative abrupt change characteristic is confirmed to have occurred.

6. The method according to claim 1, characterized in that, The step of determining that the performance degradation of the solid-state battery is induced by interfacial pressure contact failure if the first derivative of the modulus decay shows a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold specifically includes: Monitor the reference return pressure corresponding to each single charge-discharge cycle. The reference return pressure is the pressure value of the mold cavity transmitted by the solid-state battery test mold at the end of the single charge-discharge cycle. When the first derivative of the modulus decay exhibits a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold, and the rate of change of the reference repositioning pressure is less than a preset tooling relaxation threshold, it is determined that the performance degradation is induced by interface pressure contact failure inside the solid-state battery.

7. The method according to claim 6, characterized in that, After determining that the performance degradation is induced by interface pressure contact failure inside the solid-state battery when the first derivative of the modulus decay exhibits a negative abrupt change before the discharge capacity decay rate exceeds a preset failure threshold and the rate of change of the reference repositioning pressure is less than a preset tooling relaxation threshold, the method further includes: If the rate of change of the reference return pressure is greater than or equal to the preset tooling relaxation threshold, the current test data is determined to be invalid, and a prompt is made to tighten the solid-state battery test mold.

8. A testing device, characterized in that, The test 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 including computer instructions, and the one or more processors call the computer instructions to cause the test device to perform the method as described in any one of claims 1-7.

9. A computer program product containing instructions, characterized in that, When the computer program product is run on a test device, the test device performs the method as described in any one of claims 1-7.

10. A computer-readable storage medium comprising instructions, characterized in that, When the instructions are executed on the test equipment, the test equipment performs the method as described in any one of claims 1-7.

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