Semi-solid lithium battery safety test method

Abstract

The invention particularly relates to a semi-solid lithium battery safety test method, which relates to the technical field of lithium battery safety test, and comprises the following steps: acquiring sufficient baseline capacitance data in a standard environment and a battery state matched with the test, calculating a capacitance average value and a standard deviation, and storing qualified baseline parameters after validity verification is completed. According to the invention, an integrated high-frequency test circuit of a main loop, a signal injection branch and a signal acquisition branch is adopted, and orthogonal demodulation and real-time equivalent capacitance calculation are matched, so that the measurement precision and in-situ characterization capability of a lithium battery safety test are remarkably improved; dC components are isolated through AC coupling, wiring is shielded, electromagnetic interference is suppressed, the problem that high-frequency signals are interfered by charging and discharging DC and environmental noise in a traditional test is solved, microstructure changes such as the internal polar distance of a battery cell, the dielectric state of electrolyte and interface contact can be captured in real time by means of optimal frequency band injection and high-speed acquisition demodulation, and the test accuracy is improved. The defect that only macroparameters such as voltage, temperature and external force can be monitored in a traditional test is overcome.

Description

Technical Field

[0001] This invention relates to the field of lithium battery safety testing technology, and in particular to a method for testing the safety of semi-solid lithium batteries. Background Technology

[0002] Semi-solid lithium batteries combine the advantages of interface-friendly liquid lithium batteries and high safety of solid lithium batteries, making them an important development direction for new energy power batteries. However, due to the presence of a partially liquid electrolyte and a solid-liquid composite interface, they still pose risks of internal short circuits and thermal runaway under mechanical abuse such as extrusion and puncture, necessitating precise and early warning-enabled safety testing methods.

[0003] Existing safety tests for semi-solid lithium batteries mostly follow the standards of traditional liquid batteries, relying on monitoring parameters such as terminal voltage, temperature, and pressure / displacement. These tests can only trigger alarms after a short circuit or thermal runaway occurs, and cannot achieve early determination of physical deformation, interface damage, and short circuit failure. At the same time, semi-solid electrolytes have rheological properties, and traditional DC parameters are difficult to reflect changes in their internal dielectric state and microstructure.

[0004] The high-frequency signal injection method can reflect minute changes in internal electrode spacing, electrolyte dielectric constant, and interface contact state through the battery's equivalent capacitance, thus adapting to the structural characteristics of semi-solid-state batteries.

[0005] However, existing technologies have the following drawbacks:

[0006] Without an integrated anti-interference circuit for the main circuit, signal injection, and signal acquisition, high-frequency signals are susceptible to the DC component of charging and discharging and electromagnetic interference.

[0007] The lack of dynamic baseline calibration and validity verification adapted to the rheological characteristics of semi-solid batteries makes it easy for background noise to cause misjudgments.

[0008] Without establishing a tiered threshold determination logic for capacitance change rate / second derivative, it is impossible to accurately distinguish between the three stages of early warning, alarm, and failure.

[0009] The signal processing has poor real-time performance, making it impossible to synchronously correlate mechanical parameters with dynamic changes in capacitance, resulting in insufficient integrity and traceability of test data.

[0010] Therefore, a safety testing method for semi-solid lithium batteries is proposed to address the aforementioned issues. Summary of the Invention

[0011] The purpose of this invention is to provide a safety testing method for semi-solid-state lithium batteries in order to solve the above-mentioned problems.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A safety testing method for semi-solid-state lithium batteries includes:

[0014] An integrated high-frequency injection test circuit, including a main circuit, a signal injection branch, and a signal acquisition branch, was constructed. After completing the component selection, connection, and parameter setting, debugging and calibration were performed.

[0015] The high-frequency AC voltage response signal is preprocessed to decompose it into in-phase and quadrature components, and the real-time equivalent capacitance value is calculated.

[0016] Collect sufficient baseline capacitance data under standard conditions and battery conditions matched to the test, calculate the average capacitance and standard deviation, and store qualified baseline parameters after completing the validity verification.

[0017] Prepare the equipment and parameters for the squeeze / needle puncture mechanical abuse test according to the standard and fix the battery. Simultaneously perform the test and dynamic monitoring of the equivalent capacitance. Based on the threshold of capacitance-related parameters, complete the three-stage state determination of early warning, alarm and failure.

[0018] The various data collected in the experiment are time-stamped, synchronized, filtered, completed, and classified for storage. Correlation analysis of capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification are carried out to output the test results.

[0019] Preferably, the construction of an integrated high-frequency injection test circuit including a main circuit, a signal injection branch, and a signal acquisition branch, followed by component selection, connection, and parameter setting, and then debugging and calibration, specifically includes:

[0020] The test circuit consists of three parts: the main circuit, the signal injection branch, and the signal acquisition branch. Each branch is independent and does not interfere with each other. They are connected to the semi-solid battery under test through a common interface. The specific connection relationship is as follows: the positive and negative terminals of the semi-solid battery under test are connected to the output terminal of the main circuit, the output terminal of the signal injection branch, and the input terminal of the signal acquisition branch, respectively.

[0021] The main circuit provides a normal charging and discharging environment for the semi-solid battery under test, or maintains the battery in an open circuit state to simulate the actual working scenario of the battery.

[0022] The signal injection branch injects a stable, single-frequency high-frequency sinusoidal current signal into the positive and negative electrodes of the semi-solid battery under test, which serves as the excitation signal for capacitance monitoring. Its frequency and amplitude are set according to preset requirements.

[0023] Preferably, the method further includes:

[0024] The signal acquisition branch acquires the high-frequency AC voltage response signal across the semi-solid-state battery under test. , and the injected high-frequency current signal correspond;

[0025] After the circuit is built, debugging and calibration are carried out, including no-load debugging, load calibration, and linkage debugging.

[0026] Preferably, the preprocessing of the acquired high-frequency AC voltage response signal to decompose it into in-phase and quadrature components and calculate the real-time equivalent capacitance value specifically includes:

[0027] A high-pass filtering algorithm is used to filter the acquired voltage signal, removing the DC component and retaining only the high-frequency AC component.

[0028] A moving average filtering algorithm is used to smooth the voltage signal after removing the DC component;

[0029] The preprocessed voltage signal With the injected high-frequency current signal Perform timeline synchronization and alignment;

[0030] Two reference signals are generated, one being the in-phase reference signal. and quadrature reference signals ,in , The frequency of the injected high-frequency signal;

[0031] The frequency and amplitude of the reference signal and the injected current signal They are identical, only their phases differ;

[0032] The preprocessed voltage signal ,in The voltage signal amplitude, The phase difference between the voltage signal and the injected current signal is compared with the in-phase reference signal. Orthogonal reference signal The mixing process yields two mixed signals: an in-phase mixed signal and a frequency-mixed signal. Quadrature mixing signal ;

[0033] The two mixing signals are subjected to low-pass filtering to remove high-frequency harmonic components and extract low-frequency DC components, which are the amplitudes of the in-phase and quadrature components.

[0034] Preferably, the method further includes real-time equivalent capacitance calculation:

[0035] According to Ohm's law, the reactance of a capacitor... equal to the quadrature component voltage With injected alternating current The ratio;

[0036] Capacitive With equivalent capacitance The relationship is (The negative sign indicates that the capacitive reactance and inductance are out of phase.) By transforming the formula, we obtain the following formula for calculating the real-time equivalent capacitance:

[0037] ;

[0038] in, The frequency of the injected high-frequency signal.

[0039] Preferably, the step of collecting sufficient baseline capacitance data under standard conditions and battery conditions matched to the test, calculating the average capacitance and standard deviation, and storing qualified baseline parameters after completing validity verification specifically includes:

[0040] Baseline acquisition environmental conditions control includes test environment temperature, humidity, absence of electromagnetic interference, and absence of vibration;

[0041] The battery status maintains the working state of the main circuit, ensuring that the electrochemical state of the battery is consistent with the experimental state;

[0042] The baseline acquisition duration meets the preset duration requirement, ensuring that enough capacitance data is collected to accurately reflect the fluctuation range of background noise.

[0043] Preferably, the method further includes:

[0044] After the baseline data is collected, the real-time equivalent capacitance value during the baseline period is calculated. Perform statistical analysis and calculate the average capacitance. and standard deviation ;

[0045] After the baseline parameters are calculated, the validity of the baseline is verified to ensure that the baseline can accurately reflect the initial stable state of the battery and avoid misjudgment in subsequent monitoring due to invalid baselines. Specific verification methods include fluctuation amplitude verification, trend verification, and repeatability verification.

[0046] Valid baseline parameters are stored in the computer and used as threshold settings.

[0047] Preferably, the equipment and parameters for the crush / needle puncture mechanical abuse test are prepared according to standards, and the battery is fixed. The test and equivalent capacitance dynamic monitoring are performed simultaneously. Based on capacitance-related parameter thresholds, a three-stage state determination of early warning, alarm, and failure is completed. Specifically, this includes:

[0048] Mechanical abuse tests shall be conducted using either extrusion or needle penetration tests. For extrusion tests, an electric extrusion testing machine shall be used, and for needle penetration tests, an electric needle penetration testing machine shall be used.

[0049] The extrusion test is terminated under two conditions; the test can be terminated if either condition is met:

[0050] The tested battery experienced a short circuit;

[0051] The extrusion displacement reaches a preset percentage of the initial battery thickness;

[0052] During the extrusion process, extrusion pressure and extrusion displacement data are collected in real time;

[0053] Warning Phase Determination Logic: The battery is determined to enter the warning phase if both of the following conditions are met simultaneously:

[0054] Condition 1: Real-time capacitance change rate , The deformation threshold is set based on baseline parameters;

[0055] Condition 2: The terminal voltage at both ends of the battery Remain unchanged;

[0056] Deformation threshold Setting method: ,in The baseline standard deviation, The capacitance calculation period;

[0057] Alarm Stage Determination Logic: The battery is determined to enter the alarm stage if any of the following conditions are met:

[0058] Condition 1: Second derivative of real-time capacitance , The interface damage threshold is set based on baseline parameters;

[0059] Condition 2: Equivalent capacitance value And the rate of change of capacitance Persistently greater than ;

[0060] Interface damage threshold Setting method: ;

[0061] Failure phase:

[0062] Determination logic: A battery is determined to have entered the failure stage if any of the following conditions are met:

[0063] Condition 1: Real-time equivalent capacitance value ;

[0064] Condition 2: Battery terminal voltage If the voltage drop exceeds a preset allowable threshold within a preset time period, and continues to drop until the difference between the voltage drop and 0V is less than a preset threshold, and the difference in capacitance value within a preset time period exceeds a preset threshold, it is determined to be a short circuit failure.

[0065] Preferably, the process of synchronizing, filtering, and classifying the various data collected in the experiment, performing correlation analysis between capacitance and mechanical parameters, extracting critical deformation points, and verifying repeatability, and finally outputting test results containing complete information, specifically includes:

[0066] After synchronizing and aligning the data, the aligned and filtered datasets are classified and stored according to baseline data, early warning stage data, alarm stage data, and failure stage data. At the same time, a data index table is generated to mark the time range and key data nodes of each stage.

[0067] Based on the synchronized dataset, the correlation between equivalent capacitance change and mechanical force and displacement is analyzed to verify the effectiveness. Specifically, this includes correlation analysis between capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification analysis.

[0068] After the data correlation analysis is completed, a formal test report is output, which includes basic experimental information, baseline parameters, a summary of data from the entire experimental process, and correlation analysis results.

[0069] Based on the test results, the mechanical safety level of the tested semi-solid-state battery was evaluated.

[0070] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0071] 1. This invention significantly improves the measurement accuracy and in-situ characterization capability of lithium battery safety testing by adopting an integrated high-frequency test circuit consisting of a main circuit, a signal injection branch, and a signal acquisition branch, combined with orthogonal demodulation and real-time equivalent capacitance calculation. By isolating DC components through AC coupling and suppressing electromagnetic interference through shielded wiring, it solves the problem of interference of DC during charging and discharging and environmental noise on high-frequency signals in traditional testing. Relying on optimal frequency band injection and high-speed acquisition and demodulation, it can capture microstructural changes such as electrode spacing, electrolyte dielectric state, and interface contact inside the cell in real time, making up for the shortcomings of traditional testing which can only monitor macroscopic parameters such as voltage, temperature, and external force.

[0072] 2. This invention achieves early warning and enhanced safety controllability in lithium battery safety testing through dynamic baseline calibration and a three-stage grading judgment logic. A qualified baseline is set for the rheological characteristics of the semi-solid electrolyte, and fluctuation, trend, and repeatability verification are completed, effectively avoiding misjudgments caused by background noise. Based on the capacitance change rate and second derivative, warning, alarm, and failure grading thresholds are constructed, enabling early identification of risks when physical deformation or interface damage occurs in the cell, far earlier than traditional voltage surge-based short-circuit alarms, allowing sufficient time for test safety intervention. Simultaneously, it achieves synchronous alignment and correlation analysis of multi-source data (capacity, voltage, mechanical force, displacement), accurately extracting critical deformation parameters. This improves the operational safety of abuse tests such as needle penetration and compression, and provides quantitative basis for cell structure optimization and safety design improvements. Attached Figure Description

[0073] Further details, features, and advantages of this application are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0074] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0075] Several embodiments of this application will now be described in more detail with reference to the accompanying drawings to enable those skilled in the art to implement this application. This application may be embodied in many different forms and for various purposes and should not be limited to the embodiments set forth herein. These embodiments are provided to make this application thorough and complete, and to fully convey the scope of this application to those skilled in the art. The embodiments described do not limit this application.

[0076] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the relevant field and / or the context of this specification, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0077] Example 1

[0078] Its specific implementation method is combined with the appendix Figure 1 Please provide a detailed explanation.

[0079] Appendix Figure 1 The flowchart of a semi-solid-state lithium battery safety test method provided in this embodiment of the invention shows the complete steps from setting up the main circuit and signal injection branch to synchronizing and aligning the various data collected in the test with timestamps.

[0080] In this embodiment, it includes:

[0081] An integrated high-frequency injection test circuit, including a main circuit, a signal injection branch, and a signal acquisition branch, was constructed. After completing the component selection, connection, and parameter setting, no-load, load, and linkage debugging and calibration were performed to ensure circuit signal stability and measurement accuracy.

[0082] Specifically, it includes:

[0083] This step forms the hardware foundation of the entire testing method. Its core is constructing an integrated test circuit comprising the main circuit (charge / discharge circuit), signal injection branch, and signal acquisition branch. It clarifies the component selection, connection methods, and parameter settings for each branch, ensuring that high-frequency AC signals can be stably injected into the battery and that the AC response signals at both ends of the battery can be accurately acquired. The specific operation is as follows:

[0084] Overall circuit architecture description:

[0085] The test circuit consists of three parts: a main circuit (used to maintain the battery in normal charging / discharging state or open circuit state), a signal injection branch (used to inject a high-frequency sinusoidal AC excitation signal into the battery), and a signal acquisition branch (used to acquire the AC voltage response signal at both ends of the battery). Each branch is independent and does not interfere with each other, and is connected to the semi-solid battery under test through a common interface. Specifically, the positive and negative terminals of the semi-solid battery under test are connected to the output terminal of the main circuit, the output terminal of the signal injection branch, and the input terminal of the signal acquisition branch, respectively, to ensure that the three signals can act on the battery synchronously without signal interference.

[0086] Construction of the main loop:

[0087] The core function of the main circuit is to provide a normal charging and discharging environment for the semi-solid-state battery under test, or to maintain the battery in an open-circuit state, simulating the actual working scenarios of the battery (such as charging state, discharging state, and resting state), to ensure that the test results are consistent with actual applications. The specific construction requirements are as follows:

[0088] Device selection: Select a conventional battery charge and discharge test cabinet (e.g., Xinwei BTS-5V10A charge and discharge test system). Its technical parameters are as follows: voltage range 0.5V, current range 0~10A, charge and discharge modes support constant current charging, constant current discharging, constant voltage charging, and open circuit resting, control accuracy ≤±0.1%FS, sampling frequency ≥1Hz, and can record the battery's DC voltage and DC current data in real time.

[0089] Connection method: Connect the positive output terminal of the charge / discharge test cabinet to the positive tab of the semi-solid-state battery under test via a wire, and connect the negative output terminal of the charge / discharge test cabinet to the negative tab of the semi-solid-state battery under test via a wire; the wires should be high-temperature resistant, low-impedance copper core wires (wire diameter ≥ 1m). The connection parts are welded to ensure good contact and avoid excessive contact resistance from affecting the test accuracy (the contact resistance should be controlled to ≤1mΩ).

[0090] Operating parameter settings: Based on the specifications of the semi-solid-state battery under test (such as rated voltage and rated capacity), set the operating state of the main circuit. There are two modes, which can be selected according to the testing requirements:

[0091] Mode 1: Open circuit static mode (suitable for testing the mechanical safety of batteries in a static state). The charge and discharge test cabinet is set to an open circuit state, and no DC current is input or output to the battery. Only the initial voltage of the battery (i.e., open circuit voltage) is maintained. The static time is ≥30 minutes to ensure the stability of the internal electrochemical state of the battery and avoid interference from electrochemical reactions to capacitor monitoring.

[0092] Mode 2: Charge and discharge mode (suitable for testing the mechanical safety of the battery under operating conditions). The charge and discharge parameters are set as follows: constant current charging current is 0.5C (C is the battery's rated capacity). After charging to the battery's rated voltage, it switches to constant voltage charging with a cutoff current of 0.05C. The constant current discharging current is 0.5C, discharging to the battery's cutoff voltage (usually 0.8 times the rated voltage). Mechanical abuse tests are performed simultaneously during the charge and discharge process to ensure that the test scenario closely matches the actual operating conditions of the battery.

[0093] Construction of the signal injection branch:

[0094] The core function of the signal injection branch is to inject a stable, single-frequency high-frequency sinusoidal current signal into the positive and negative electrodes of the semi-solid-state battery under test, serving as the excitation signal for capacitance monitoring. Its frequency and amplitude must be strictly set to ensure accurate reflection of the battery's dielectric characteristics. Specific construction requirements are as follows:

[0095] Component selection: The signal injection branch consists of a signal generator, an AC coupling circuit, and a current-limiting resistor. The selection and parameter requirements for each component are as follows:

[0096] Signal Generator: A high-precision function signal generator (e.g., Keysight 33522B function signal generator) should be selected. The technical specifications are as follows: output signal type is sine wave, frequency range is 1Hz~1MHz, frequency accuracy is ≤±0.01%, and amplitude range is 0~10. Peak-to-peak value, amplitude accuracy ≤ ±0.1%, output impedance 50Ω, and frequency and amplitude can be adjusted and stabilized in real time via software.

[0097] AC coupling circuit: A capacitor coupling circuit (the core component is a ceramic capacitor) is selected. The parameters of the ceramic capacitor are: capacitance value 100nF~1μF, withstand voltage ≥10V, operating frequency range 1kHz~1MHz, and temperature coefficient ≤±10% / ℃. The function of the AC coupling circuit is to isolate the DC component output by the signal generator, allowing only high-frequency AC signals to pass through, avoiding interference from DC signals on the electrochemical state of the battery, and preventing the DC voltage of the battery from reverse-damaging the signal generator.

[0098] Current limiting resistor: A high-precision metal film resistor is selected with the following parameters: resistance value 100Ω~1kΩ, power ≥1W, accuracy ≤±1%, temperature coefficient ≤±50ppm / ℃. The function of the current limiting resistor is to limit the amplitude of the AC current injected into the battery, so as to avoid excessive AC current from damaging the internal structure of the battery (such as breaking down the electrolyte and burning the electrode), and at the same time stabilize the current output of the signal injection branch.

[0099] Connection method: The output terminal of the signal generator is connected to the input terminal of the AC coupling circuit; the output terminal of the AC coupling circuit is connected to one end of the current-limiting resistor; the other end of the current-limiting resistor is connected to the positive terminal of the semi-solid-state battery under test; the ground terminal of the signal generator is connected to the negative terminal of the semi-solid-state battery under test, forming a complete signal injection loop; shielded wires (diameter ≥ 0.5m) are used for connection. To avoid external electromagnetic interference affecting the stability of high-frequency signals, the shielding layer is grounded (grounding resistance ≤ 1Ω).

[0100] Signal parameter settings:

[0101] Frequency selection: The frequency of the injected high-frequency sinusoidal current signal is determined to be 1kHz~100kHz, with 5kHz~50kHz preferred (this range is the optimal response range of the dielectric characteristics of the semi-solid electrolyte, based on the following: at low frequencies (<1kHz), the electrochemical reactions inside the battery (such as lithium-ion diffusion) dominate, the capacitance characteristics are masked, and the equivalent capacitance cannot be accurately measured; at high frequencies (>100kHz), the lead inductance and contact inductance of the wires dominate, which will interfere with the measurement of the capacitance signal, leading to an increase in measurement error; in the 1kHz~100kHz range, the equivalent capacitance characteristics of the battery are most obvious, the dielectric response is most stable, and the measurement accuracy is highest).

[0102] Amplitude selection: Sets the peak value of the injected high-frequency sinusoidal current signal. The amplitude is set to 1mA~10mA (the specific amplitude is adjusted according to the battery capacity; for example, for a battery with a rated capacity of 1Ah, the amplitude is set to 15mA; for a battery with a rated capacity of 5Ah, the amplitude is set to 5~10mA) to ensure that the signal amplitude is large enough to be accurately acquired by the signal acquisition branch, while being small enough not to affect the electrochemical state of the battery (not to trigger the polarization reaction of the battery or damage the electrolyte).

[0103] Signal waveform: Sine waves are strictly selected, with waveform distortion ≤1%. Avoid introducing harmonic interference from non-sine wave signals such as square waves and triangular waves to ensure the singularity of the excitation signal and facilitate subsequent signal processing and parameter extraction.

[0104] Also includes:

[0105] Construction of the signal acquisition branch:

[0106] The core function of the signal acquisition branch is to accurately acquire the high-frequency AC voltage response signal across the semi-solid-state battery under test. This signal is related to the injected high-frequency current signal. Correspondingly, this is the core data for subsequent extraction of impedance components and calculation of equivalent capacitance. The specific construction requirements are as follows:

[0107] Component Selection: The signal acquisition branch consists of a high-precision differential probe, a data acquisition card, and a computer. The selection and parameter requirements for each component are as follows:

[0108] High-precision differential probe: A high-frequency differential voltage probe (e.g., Tektronix P5200A differential probe) is selected. The technical parameters are as follows: voltage measurement range 0-10Vpp, bandwidth 1Hz~1GHz, input impedance ≥1MΩ, common-mode rejection ratio (CMRR) ≥80dB@1kHz, sampling accuracy ≤±0.1%. It can accurately acquire the AC voltage signal at both ends of the battery and effectively suppress common-mode interference (such as external electromagnetic interference and DC voltage interference in the main circuit).

[0109] Data Acquisition Card: A high-speed data acquisition card should be selected, with the following technical parameters: sampling frequency ≥ 1MS / s (megasamples / second), resolution ≥ 16 bits, number of input channels ≥ 2, input voltage range ±10V, capable of synchronously acquiring voltage signals output by differential probes and converting analog signals into digital signals for transmission to a computer for processing; the sampling frequency of the data acquisition card must be much higher than the frequency of the injected high-frequency signal (at least 10 times the injection frequency, for example, when the injection frequency is 10kHz, the sampling frequency should be set to 100MS / s) to ensure that the acquired signal is complete and distortion-free.

[0110] Computer: Select an industrial computer with configurations that meet the data processing requirements, with a CPU ≥ Intel Core i7, memory ≥ 16GB, hard disk ≥ 512GB, and installed signal processing software (such as LabVIEW, MATLAB) to receive digital signals transmitted by the data acquisition card and perform subsequent operations such as quadrature demodulation, parameter extraction, capacitance calculation, and data storage.

[0111] Connection method: The two input terminals of the differential probe are connected to the positive and negative tabs of the semi-solid battery under test through probes respectively (the contact between the probe and the tabs must be tight, and the contact resistance ≤1mΩ). The output terminal of the differential probe is connected to the input channel of the data acquisition card. The data acquisition card is connected to the industrial computer through the PCIe interface to form a complete signal acquisition loop. Shielded wires are used for connection, and the shielding layer is grounded to avoid electromagnetic interference affecting the signal acquisition accuracy.

[0112] Data acquisition parameter settings:

[0113] Sampling frequency: Set the sampling frequency of the data acquisition card to 1MS / s~10MS / s. The specific frequency should be adjusted according to the frequency of the injected high-frequency signal to ensure that the sampling frequency is ≥10 times the injection frequency (for example, when the injection frequency is 5kHz, the sampling frequency is set to 50MS / s; when the injection frequency is 100kHz, the sampling frequency is set to 1MS / s).

[0114] Sampling duration: The sampling duration should be consistent with the duration of the mechanical abuse test, and a baseline acquisition duration of 30 minutes should be reserved in advance (for baseline setting). For example, if the mechanical abuse test duration is 60 minutes, the sampling duration should be set to 90 minutes to ensure that the complete sequence of baseline data and test process data can be collected.

[0115] Data storage: Set the data storage format to CSV (for easy subsequent data correlation analysis), and the storage frequency to be consistent with the capacitance calculation frequency (e.g., store a set of capacitance data, voltage data, and current data every 10ms). Set the storage path to the computer's local hard drive or an external mobile storage device to ensure that the data is not lost and is traceable.

[0116] Circuit debugging and calibration:

[0117] After the circuit is built, debugging and calibration are performed to ensure that each branch works properly, the signal is stable, and the measurement is accurate, including:

[0118] No-load debugging: Disconnect the semi-solid battery under test, start the signal generator, data acquisition card, and computer, inject a high-frequency sinusoidal current signal with a set frequency and amplitude, and observe the voltage signal acquired by the data acquisition card. Ensure that the signal waveform is sinusoidal, without distortion, and with a stable amplitude. If there is distortion or interference, adjust the grounding status of the shielding wire and the output parameters of the signal generator until the signal is stable.

[0119] Load calibration: Select a standard capacitor (with a known capacitance value that is close to the initial equivalent capacitance value of the battery under test, for example, if the initial equivalent capacitance is 100nF, select a 100nF standard capacitor) to replace the battery under test, connect it to the test circuit, inject a high-frequency signal, collect the voltage response signal, calculate the equivalent capacitance value, and compare it with the nominal value of the standard capacitor. If the measurement error is >±1%, adjust the calibration parameters of the differential probe and the sampling parameters of the data acquisition card until the measurement error is ≤±1% to ensure the measurement accuracy of the test circuit.

[0120] Linkage debugging: Connect the semi-solid battery under test to the circuit, start the main circuit, signal injection branch, and signal acquisition branch, keep the main circuit open and stationary, inject a high-frequency signal, collect voltage and current data for 30 minutes, observe the stability of the data, and ensure that the fluctuation of the capacitance measurement value is ≤±2% (i.e., the background noise is within a reasonable range). If the fluctuation is too large, check the wire connection and contact resistance, eliminate interference factors, until the data is stable.

[0121] The high-frequency AC voltage response signal is preprocessed, and the in-phase and quadrature components are decomposed by the quadrature demodulation algorithm. The real-time equivalent capacitance value is calculated according to the formula, ensuring the calculation accuracy and real-time performance, and the relevant calculation results are stored.

[0122] Specifically, it includes:

[0123] Signal preprocessing:

[0124] High-frequency AC voltage response signal acquired The signal may contain a small amount of DC component (from the battery open-circuit voltage or charge / discharge voltage in the main circuit) and high-frequency noise (from external electromagnetic interference). Preprocessing is required to remove interference and extract the valid signal. The specific preprocessing steps are as follows:

[0125] DC component removal: A high-pass filtering algorithm (with the filter cutoff frequency set to 100Hz) is used to filter the acquired voltage signal, removing the DC component from the signal and retaining only the high-frequency AC component (i.e., the component with the same frequency as the injected signal), thus avoiding interference from the DC component to the demodulation results. The high-pass filtering algorithm can be implemented using MATLAB or LabVIEW software. An FIR filter with a filter order of 1024 is selected to ensure that the filtered signal is distortion-free.

[0126] High-frequency noise removal: A moving average filtering algorithm is used to smooth the voltage signal after removing the DC component, reducing the impact of high-frequency noise. The specific parameters are set as follows: the moving window size is 100 sampling points (adjusted according to the sampling frequency, for example: if the sampling frequency is 1MS / s, the moving window size is 100 sampling points, and the corresponding smoothing time is 0.1ms). The signal is weighted and averaged through the moving window to make the signal waveform smoother, while retaining the key features of capacitance change (avoiding the masking of abrupt capacitance changes due to over-filtering).

[0127] Signal synchronization alignment: This involves aligning the pre-processed voltage signal... With the injected high-frequency current signal Time axis synchronization alignment is performed to ensure that the timestamps of the two signals are consistent (error ≤ 1μs), providing a prerequisite for subsequent quadrature demodulation. Synchronization alignment can be achieved through software, using the synchronization trigger signal output by the signal generator as the trigger signal for the data acquisition card, ensuring that the acquisition of voltage and current signals starts and stops synchronously.

[0128] Implementation of orthogonal demodulation algorithm:

[0129] The core of the quadrature demodulation algorithm is to convert the preprocessed high-frequency AC voltage signal into a signal. The signal is mixed and low-pass filtered with two reference signals of the same frequency and with a 90° phase difference (in-phase reference signal and quadrature reference signal) to decompose it into in-phase component (Realpart, corresponding to resistance component) and quadrature component (Quadraturepart, corresponding to reactance component). The specific implementation steps are as follows:

[0130] Reference signal generation: Two reference signals are generated using software (such as MATLAB), one of which is an in-phase reference signal. and quadrature reference signals ,in , The frequency of the injected high-frequency signal is consistent with the output frequency of the signal generator.

[0131] The frequency and amplitude of the reference signal and the injected current signal They are completely identical, only differing in phase (the in-phase reference signal and the injected current signal are in phase, while the quadrature reference signal and the injected current signal are 90° out of phase).

[0132] Frequency mixing: This process converts the pre-processed voltage signal into a frequency-mixing signal. ,in The voltage signal amplitude, The phase difference between the voltage signal and the injected current signal is compared with the in-phase reference signal. Orthogonal reference signal Mixing (i.e., multiplication) yields two mixed signals, as shown in the following formula:

[0133] In-phase mixer signal : ;

[0134] Quadrature mixing signal : ;

[0135] Low-pass filtering: Perform low-pass filtering on both mixing signals to remove high-frequency harmonic components (frequency 2). The low-frequency DC component is extracted, which is the amplitude of the in-phase component and the quadrature component, as detailed below:

[0136] Low-pass filter selection: Select Butterworth low-pass filter with a cutoff frequency of 100Hz (far lower than the injected signal frequency; for example, when the injection frequency is 1kHz, a cutoff frequency of 100Hz can effectively remove the 2kHz harmonic components). The filter order is 8th to ensure that the harmonic components are completely removed while retaining the DC components.

[0137] Component extraction: After low-pass filtering, the in-phase mixer signal The output DC component is This component is the in-phase component of the voltage signal, corresponding to the battery's equivalent internal resistance. Quadrature mixing signal The output DC component is This component is the quadrature component of the voltage signal, corresponding to the battery's equivalent reactance. .

[0138] Note: The orthogonal demodulation algorithm can be implemented by writing a program in LabVIEW software. The program flow is as follows: signal import, preprocessing, reference signal generation, mixing, low-pass filtering, component extraction, and data storage. This ensures the real-time performance of the algorithm, that is, demodulation and component extraction can be completed within 1μs for each set of signals acquired (e.g., every 10μs). This meets the requirements for subsequent real-time capacitance calculation.

[0139] It also includes real-time equivalent capacitance calculation:

[0140] Based on the extracted quadrature components (reactance components) and the frequency of the injected high-frequency signal, the real-time equivalent capacitance value is calculated using a formula. The core assumption is that, in the high-frequency range of 1kHz to 100kHz, the equivalent circuit of the semi-solid-state battery under test can be simplified to a resistor-capacitor series model. - In the series model, the reactance component is contributed only by the capacitance (the inductance effect is negligible). The specific calculation steps are as follows:

[0141] Capacitor reactance calculation: According to Ohm's law, the reactance of a capacitor... (Capacitive reactance) equals the quadrature component voltage. With injected alternating current The ratio is given by the following formula:

[0142] ;

[0143] in, The instantaneous value of the injected high-frequency sinusoidal current signal, its amplitude Known parameters (such as 1mA~10mA) set for the signal generator can be obtained instantaneously through the synchronous output port of the signal generator and transmitted to the computer synchronously with the voltage signal to ensure calculation accuracy.

[0144] Real-time capacitance calculation: capacitive reactance With equivalent capacitance The relationship is (The negative sign indicates that the capacitive reactance and inductance are out of phase.) By transforming the formula, we obtain the following formula for calculating the real-time equivalent capacitance:

[0145] ;

[0146] in, The frequency of the injected high-frequency signal (known, such as 5kHz~50kHz) is a fixed value. Substituting this value into the formula allows us to calculate the equivalent capacitance value at each sampling time. ;

[0147] Guarantee of computational accuracy:

[0148] Sampling frequency requirements: The sampling frequency of the data acquisition card must be much higher than the injection frequency (at least 10 times) to ensure that the number of sampling points in each sine wave cycle is ≥10, so as to accurately calculate the instantaneous value and avoid calculation errors caused by insufficient sampling.

[0149] Real-time requirements: The frequency of capacitance calculation must be ≥100Hz (i.e., output a capacitance value every 10ms) to ensure that the dynamic changes of capacitance can be captured in real time, especially the sudden change signal of capacitance during mechanical abuse. If the calculation frequency is too low, the critical moment of capacitance change may be missed, affecting the accuracy of early warning.

[0150] Error Correction: Due to the presence of a small amount of lead inductance in actual circuits, there may be slight errors in capacitive reactance calculations. These errors can be corrected using software. The correction formula is as follows: ,in The lead inductance value (which can be determined through no-load testing, with a typical value of 1~10nH) is corrected before being substituted into the capacitance calculation formula to ensure that the calculation error is ≤±1%.

[0151] Calculation result storage: Real-time equivalent capacitance value at each sampling time. With the corresponding timestamp and in-phase component Orthogonal components They are stored together in CSV format, which facilitates subsequent baseline setting, dynamic monitoring, and data correlation analysis.

[0152] Collect sufficient baseline capacitance data under standard environment and battery conditions matched to the test, calculate the average capacitance value and standard deviation, and store qualified baseline parameters after validating the fluctuation range, trend and repeatability.

[0153] Specifically, it includes:

[0154] Because semi-solid electrolytes possess rheological properties (minor thermal fluctuations at the solid-liquid interface and slight movement of electrolyte particles), their equivalent capacitance value... Slight background fluctuations may occur (this is normal). Therefore, before conducting mechanical abuse tests, a dynamic baseline specific to semi-solid-state batteries needs to be established as a reference standard for subsequent dynamic monitoring and threshold determination. The specific operation is as follows:

[0155] Baseline acquisition conditions:

[0156] Baseline acquisition must be performed before the start of the mechanical abuse test to ensure that the acquired baseline data reflects the initial stable state of the battery. Specific conditions are set as follows:

[0157] Baseline acquisition environmental conditions control includes: the test environment temperature is controlled at 25±2℃, the humidity is controlled at 50±5%RH, there is no electromagnetic interference (environmental electromagnetic interference intensity ≤1μV / m), and there is no vibration (vibration amplitude ≤0.1mm), to avoid environmental factors causing capacitance value fluctuations and ensure the stability of baseline data.

[0158] Battery status: Maintain the operating status of the main circuit (consistent with the main circuit status of the subsequent mechanical abuse test; that is, if the main circuit is in an open-circuit static state during the test, it will also be in an open-circuit static state during baseline acquisition; if the main circuit is in a charging / discharging state during the test, it will also be in the same charging / discharging state during baseline acquisition), to ensure that the electrochemical state of the battery is consistent with the test state, and to avoid changes in the electrochemical state affecting the baseline data.

[0159] Acquisition duration: The baseline acquisition duration meets the preset duration requirement (≥30 min) to ensure that enough capacitance data is collected to accurately reflect the fluctuation range of background noise; if the initial capacitance value of the battery fluctuates greatly, the acquisition duration can be extended to 60 min until the capacitance data tends to stabilize (fluctuation amplitude ≤±2%).

[0160] Acquisition frequency: consistent with the acquisition frequency and capacitance calculation frequency of subsequent experiments (i.e., acquiring a set of data and calculating a capacitance value every 10ms) to ensure that the time resolution of the baseline data and the experimental data is consistent, which is convenient for subsequent comparative analysis.

[0161] Also includes:

[0162] Baseline parameter calculation:

[0163] After baseline data acquisition, the real-time equivalent capacitance values ​​during the baseline period are analyzed using software (such as MATLAB or Excel). Statistical analysis was performed to calculate two core baseline parameters: average capacitance. and standard deviation The specific calculation method is as follows:

[0164] Average capacitance This refers to the arithmetic mean of all capacitance data collected during the baseline acquisition period. The calculation formula is: ;

[0165] in, This represents the total number of capacitance data points collected during the baseline acquisition period (e.g., acquisition duration 30 minutes, calculation frequency 100 Hz). =30×60×100=180000), For the first The equivalent capacitance value at each sampling time.

[0166] This reflects the baseline value of the equivalent capacitance in the initial state of the battery, and all subsequent capacitance changes are referenced to this value.

[0167] Standard deviation That is, all capacitance data during the baseline acquisition period relative to the average value. The degree of dispersion is calculated using the following formula: ;

[0168] Standard deviation This reflects the range of background noise fluctuations in the capacitance during the baseline period; a larger value indicates greater background noise. Typically, it is required... ≤0.02 (i.e., fluctuation range ≤ ±2%). If it exceeds this range, the test circuit needs to be re-inspected, interference factors eliminated, and baseline data re-acquired.

[0169] Baseline validity verification:

[0170] After the baseline parameters are calculated, the validity of the baseline needs to be verified to ensure that it accurately reflects the initial stable state of the battery and to avoid misjudgments in subsequent monitoring due to invalid baselines. Specific verification methods include:

[0171] Fluctuation amplitude verification: Calculate the maximum fluctuation amplitude of capacitance data during the baseline period (i.e., the difference between the maximum and minimum capacitance values, divided by the average value). If the fluctuation range meets the preset requirement (≤±2%), the baseline is valid; if the fluctuation range is >±2%, the baseline is invalid and needs to be re-collected.

[0172] Trend verification: Plotting the capacitance-time curve during the baseline period ( - (The curve is used to observe the trend of the curve. If the curve does not have a significant upward or downward trend (i.e., it tends to be stable), then the baseline is valid. If the curve has a significant upward or downward trend (such as the capacitance value continuously rising or falling), it indicates that the internal electrochemical state of the battery is unstable or there is interference. The battery state needs to be adjusted, the interference needs to be eliminated, and the baseline data needs to be collected again.

[0173] Repeatability verification: Baseline data were collected three times, and the repeatability of each collection was calculated. and If 3 times The deviation is ≤ ±1%, 3 times. The deviation is ≤ ±0.005 If the baseline is good repeatability, it can be used as a reference for subsequent monitoring; if the deviation exceeds the range, the stability of the test system needs to be checked and the data collected again.

[0174] Validate valid baseline parameters ( and This data needs to be stored in the computer and directly accessed in subsequent steps, serving as the core reference for threshold setting and status determination.

[0175] Prepare the equipment and parameters for the extrusion / needle puncture mechanical abuse test according to the standard and fix the battery. Simultaneously perform the test and dynamic monitoring of the equivalent capacitance. Based on the threshold of capacitance-related parameters, complete the three-stage state judgment of early warning, alarm and failure and perform the corresponding operation.

[0176] Specifically, it includes:

[0177] This step is the core execution phase of the test method. Its core is to simultaneously perform mechanical abuse tests (crushing or nailing) on ​​the semi-solid-state battery and dynamically monitor its equivalent capacitance, comparing the real-time capacitance values. Combined with baseline parameters, and the rate of change of capacitance Second derivative The threshold determination enables early warning, alarm, and failure detection of battery mechanical safety. The specific operation is as follows:

[0178] Preparation for mechanical abuse test:

[0179] Mechanical abuse testing should use either a crush test or a needle penetration test (the two tests can be performed separately or sequentially, depending on the testing requirements). The test equipment and parameter settings must conform to the mechanical safety testing standards for semi-solid-state batteries (such as GB / T31485-2015 "Safety Requirements and Test Methods for Power Batteries for Electric Vehicles"). Specific preparations are as follows:

[0180] Selection of testing equipment:

[0181] Extrusion testing equipment: An electric extrusion testing machine (e.g., Sansitaijie CMT5105 electronic universal testing machine) is selected. The technical parameters are as follows: maximum extrusion force ≥100kN, adjustable extrusion speed range 0.1~10mm / min, displacement accuracy ≤±0.01mm, which can record the extrusion force and displacement data in real time during the extrusion process and transmit the data synchronously to an industrial computer for time axis alignment with capacitance data.

[0182] Needle penetration testing equipment: An electric needle penetration testing machine (e.g., Xinwei XW-Needle Penetration-01 Needle Penetration Testing Machine) is selected. The technical parameters are as follows: needle diameter 13mm (using 2mm stainless steel needles), needle penetration speed adjustable range 0.110mm / s, needle penetration depth adjustable range 0~50mm, displacement accuracy ≤±0.01mm, and the needle penetration force and displacement data during the needle penetration process can be recorded in real time and transmitted synchronously to an industrial computer.

[0183] Test parameter settings (taking the compression test as an example, the needle penetration test parameters can be adjusted accordingly):

[0184] Squeezing speed: Set to 1 mm / min (to meet standard requirements and simulate the slow squeezing experienced by the battery in actual use; if you need to simulate severe squeezing, you can adjust it to 5~10 mm / min).

[0185] Termination conditions: Two termination conditions are set for the extrusion test; the test will terminate if either condition is met:

[0186] The tested battery is short-circuited (i.e., capacitance value) →∞ and equivalent resistance →0);

[0187] The extrusion displacement reaches a preset percentage (50%) of the initial battery thickness (e.g., if the initial battery thickness is 5mm, the extrusion displacement stops when it reaches 2.5mm).

[0188] Data Acquisition: During the extrusion process, extrusion pressure (unit: kN) and extrusion displacement (unit: mm) data are collected in real time at a frequency of 100Hz, consistent with the frequency of capacitance data acquisition, to ensure time axis alignment.

[0189] Battery Fixing: Fix the semi-solid battery under test onto the fixture of the mechanical abuse test equipment. When fixing, ensure that the battery is subjected to uniform force (for the compression test) or that the needle penetration position is accurate (for the needle penetration test, the needle penetration position is the center area of ​​the battery) to avoid battery displacement that may lead to deviation in test results. At the same time, ensure that the positive and negative terminals of the battery are firmly connected to the test circuit to avoid wires falling off or poor contact during the test, which may affect capacitance monitoring.

[0190] Simultaneously with initiating the mechanical abuse test, a dynamic monitoring program is activated to collect and calculate the equivalent capacitance value in real time. Combining baseline parameters and capacitance change rate Second derivative of capacitance The system performs three stages of status determination (early warning, alarm, and failure). The determination logic, threshold settings, and physical meaning of each stage are as follows, where the thresholds are... , A semi-solid-state-specific threshold is set based on baseline parameters to ensure the accuracy of the determination.

[0191] Early warning stage (physical deformation stage):

[0192] If only physical deformation occurs inside the battery, without interface damage or short circuit, it represents an early warning stage for mechanical safety. The specific criteria for judgment are as follows:

[0193] Judgment Logic: The battery is determined to enter the warning stage if both of the following conditions are met simultaneously:

[0194] Condition 1: Real-time capacitance change rate , The deformation threshold is set based on baseline parameters;

[0195] Condition 2: The terminal voltage at both ends of the battery If the voltage remains unchanged (i.e., the voltage deviation from the baseline period is ≤ ±1%, with no significant decrease), it indicates that the battery has not experienced a short circuit or electrical failure.

[0196] Deformation threshold Setting method: ,in The baseline standard deviation, The capacitance calculation period is 10ms, or 0.01s.

[0197] For example: , ,but ;set up The basis is: the maximum rate of change of capacitance during the baseline period is ,Will Setting this value to 5 times can effectively distinguish between background noise and capacitance changes caused by actual physical deformation, thus avoiding false alarms.

[0198] Physical meaning: During the warning stage, the battery is subjected to mechanical compression or puncture, and the distance between the positive and negative electrodes... Decreasing the pressure density of the semi-solid electrolyte increases the equivalent capacitance value. The voltage rises sharply, and the rate of change of capacitance exceeds the threshold, but the separator is not damaged, the positive and negative electrodes are not in contact, and no short circuit occurs, so the terminal voltage of the battery remains stable. This is a buffer period unique to semi-solid-state batteries and is also the core stage for this solution to achieve early warning. At this time, warning signals (such as audible and visual alarms) can be used to remind staff to take protective measures.

[0199] Monitoring Operation: After entering the early warning stage, record the capacitance value in real time. Capacitance change rate The system records the corresponding timestamp, extrusion force (or needle force), and displacement data. Simultaneously, it triggers an audible and visual warning signal via an industrial computer (e.g., an external audible and visual alarm with an alarm frequency of 1Hz, a volume ≥80dB, and a yellow light) to remind staff that the battery has undergone early physical deformation and that the test status needs close monitoring. During the warning phase, monitoring continues until the alarm phase judgment conditions are met or the test is terminated.

[0200] Alarm phase (interface destruction phase):

[0201] This indicates that interface damage has occurred inside the battery (separation of the semi-solid electrolyte from the electrode, or micro-damage to the separator), but a short circuit has not yet occurred. This is an emergency alarm stage for mechanical safety, requiring timely intervention. The specific judgment criteria are as follows:

[0202] Judgment Logic: The battery is determined to enter the alarm stage if any of the following conditions are met:

[0203] Condition 1: Second derivative of real-time capacitance , The interface damage threshold is set based on baseline parameters;

[0204] Condition 2: Equivalent capacitance value (That is, if the capacitance value increases by more than 50% compared to the baseline average, it indicates a significant decrease in the electrode distance or a significant change in the electrolyte dielectric constant, and irreversible damage has occurred at the interface), and the rate of change in capacitance... Persistently greater than ;

[0205] Interface damage threshold Setting method: ,in The baseline standard deviation, The capacitance calculation period is 10ms, or 0.01s.

[0206] For example: , ,but ;set up The basis for this is that when the interface is damaged, the rate of change of capacitance will change abruptly, and the second derivative will increase significantly, far exceeding the fluctuation range during the baseline period, which can effectively distinguish between physical deformation and interface damage.

[0207] Physical meaning: As the mechanical force on the battery continues to increase, the solid-liquid interface between the semi-solid electrolyte and the electrode separates, and the separator suffers micro-damage (but not complete breakdown), resulting in an increase in the equivalent capacitance value. If the rate of change continues to rise and changes abruptly, the battery has not yet short-circuited, but it is close to the critical state of failure. If it continues to be subjected to mechanical abuse, it is very easy for short circuits and thermal runaway to occur.

[0208] Monitoring Operation: After entering the alarm stage, in addition to continuously recording all the data required for the early warning stage, the data storage frequency is increased to a set of data every 5ms. At the same time, an emergency alarm signal is triggered (the audible and visual alarm switches to red, the alarm frequency is increased to 2Hz, and the volume is ≥90dB). A signal is also sent to the mechanical abuse test equipment through the industrial computer to suspend the test process (if it is necessary to continue monitoring the short circuit process, the squeezing / needling speed can be reduced to 0.05mm / min). Based on the alarm signal, the staff can determine whether it is necessary to terminate the test or take other protective measures to avoid danger.

[0209] Failure phase (short circuit phase):

[0210] If an internal short circuit occurs in the battery, it constitutes a mechanical safety failure, and the test must be terminated immediately to ensure test safety. The specific judgment requirements are as follows:

[0211] Determination logic: The battery is determined to have entered the failure stage (short circuit failure) if any of the following conditions are met:

[0212] Condition 1: Real-time equivalent capacitance value (That is, as the calculated value of capacitance approaches infinity, the corresponding capacitive reactance) ), and equivalent internal resistance (In-phase component );

[0213] Condition 2: Battery terminal voltage If the voltage drop exceeds the preset allowable threshold within a preset time period, or if the voltage drop is ≥50% within 10ms (e.g., for a battery with a rated voltage of 3.7V, the voltage drops rapidly to below 1.85V), and the voltage continues to drop until the difference between the voltage drop and 0V is less than the preset threshold, and the difference in capacitance value within the preset time period is greater than the preset threshold, it is determined to be a short circuit failure.

[0214] Physical meaning: The mechanical force has caused the separator to break down completely, and the positive and negative electrodes are in direct contact, resulting in an internal short circuit. After the short circuit occurs, a large amount of heat is generated inside the battery, which can easily lead to thermal runaway, fire, explosion and other dangers. At this time, the battery has completely lost its safety and the test must be terminated immediately to avoid a safety accident.

[0215] Monitoring Operation: Upon entering the failure stage, a safety alarm signal is immediately triggered (the audible and visual alarm sounds continuously, and the red light remains on). Simultaneously, the industrial computer sends an emergency stop signal to the mechanical abuse testing equipment to terminate the squeezing / needling operation. Signal injection, signal acquisition, and capacitance calculation are stopped synchronously, and all test data (including data from the early warning and alarm stages before the short circuit, as well as capacitance, voltage, current, force, and displacement data at the moment of the short circuit) are saved. Personnel must shut off the power to the test circuit, safely handle the test equipment and battery, and record the test results, noting the failure time and characteristics.

[0216] Additional notes: If the battery has reached the test termination condition (such as the compression displacement reaching 50% of the initial battery thickness) but has not entered the failure stage during the mechanical abuse test, the test will be terminated. It will be determined that the battery has not experienced short-circuit failure under the test conditions. All test data will be recorded, and the correlation between capacitance changes and mechanical forces during the warning and alarm stages will be analyzed in detail.

[0217] The various data collected in the experiment are time-stamped, synchronized, filtered, completed, and classified for storage. Correlation analysis of capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification are carried out. Finally, test results with complete information are output.

[0218] Specifically, it includes:

[0219] This step is the final stage of the testing method. Its core is to synchronize, align, and correlate the data collected throughout the experiment, outputting the test results to provide data support for the mechanical safety assessment of semi-solid-state batteries. The specific operations are as follows:

[0220] Data synchronization and alignment:

[0221] Because multiple types of data (capacitance data, voltage data, current data, extrusion / needle force data, and displacement data) were collected simultaneously during the experiment, and the collection frequency of each type of data was consistent (100Hz), but there may be slight time deviations (≤1μs), synchronization alignment processing is required. The specific operation is as follows:

[0222] Timestamp alignment: Using the trigger time of the data acquisition card in the signal acquisition branch as the reference time, the force and displacement data transmitted by the mechanical abuse test equipment, as well as the DC voltage and current data transmitted by the main circuit charge and discharge test cabinet, are aligned according to the timestamp to ensure that all types of data at the same moment correspond one-to-one, and the time deviation is controlled within ≤1μs; the alignment operation can be implemented through MATLAB software, using a timestamp matching algorithm to correct small time deviations.

[0223] Data filtering and completion: The aligned dataset is filtered to remove invalid data (such as interfering data before the experiment and redundant data after the experiment). If there is a small amount of missing data (missing rate ≤ 0.1%), linear interpolation is used to complete the dataset to ensure its integrity. If the missing rate is > 0.1%, the data for this experiment is deemed invalid and the experiment needs to be repeated.

[0224] Data classification and storage: The aligned and filtered datasets are classified and stored as baseline data, early warning stage data, alarm stage data, and failure stage data (if failure occurs). The storage format is still CSV. At the same time, a data index table is generated to mark the time range and key data nodes of each stage (such as early warning time, alarm time, and failure time) to facilitate subsequent query and analysis.

[0225] Data correlation analysis:

[0226] Based on the synchronized dataset, the correlation between the change in equivalent capacitance and mechanical force and displacement is analyzed to verify the effectiveness of the test method. The specific analysis operation is as follows:

[0227] Correlation analysis between capacitance and mechanical parameters: Plot capacitance values ​​with time as the horizontal axis. -Time, rate of change of capacitance Four curves—time, extrusion force / needle force-time, and displacement-time—are overlaid and displayed on the same coordinate system. The changing trends of each curve and their corresponding time nodes are analyzed. The key verifications are: whether the warning time is earlier than the short-circuit failure time (if failure occurs), the correlation between the sudden change in capacitance and the sudden change in mechanical force, and the positive correlation between the change in capacitance and the change in displacement, forming a correlation analysis report.

[0228] Critical Deformation Point Extraction: Based on the correlation analysis curve, the critical deformation point is extracted, which is the mechanical force and displacement value corresponding to the moment when the capacitance begins to change abruptly (entering the warning stage). This value is the critical parameter for early physical deformation of the semi-solid battery and can be used as a reference for battery mechanical safety design. For example, in the extrusion test of a certain semi-solid battery, the extrusion force corresponding to the warning moment is 20kN and the extrusion displacement is 0.5mm. This parameter is the critical deformation parameter of the battery under extrusion and can be used to optimize the battery structure design (such as adjusting the electrolyte thickness and separator strength) and improve mechanical safety.

[0229] Repeatability verification analysis: For 3-5 semi-solid batteries of the same specification and batch, repeat the above mechanical abuse test and testing procedure, extract the critical deformation point, warning time, alarm time, and failure time (if any) of each battery, calculate the average value and standard deviation of each parameter, and verify the repeatability of this test method; if the standard deviation of each parameter is ≤ ±5%, it indicates that this method has good repeatability, the test results are reliable, and it can be used for mechanical safety testing of batch semi-solid batteries.

[0230] Test results output:

[0231] After the data correlation analysis is completed, a formal test report will be generated. The report should include the following core contents:

[0232] Basic test information: Specifications of the semi-solid battery under test (rated voltage, rated capacity, electrode size, electrolyte type), test type (extrusion / needle penetration), test parameters (extrusion speed / needle penetration speed, termination conditions), test environment conditions (temperature, humidity);

[0233] Baseline parameter: Average capacitance Standard deviation and threshold , The set value;

[0234] Summary of data throughout the experiment: time range of each stage (baseline, early warning, alarm, failure), key data (capacitance value, capacitance change rate, voltage, force, displacement), and judgment results of each stage;

[0235] Correlation analysis results: correlation curves between capacitance change and mechanical force and displacement, critical deformation point parameters, and experimental conclusions (such as "the semi-solid battery enters the warning stage when the extrusion speed is 1 mm / min and the extrusion force reaches 20 kN, enters the alarm stage at 35 kN, and experiences short-circuit failure at 50 kN, with a critical deformation displacement of 0.5 mm").

[0236] Safety assessment: Based on the test results, assess the mechanical safety level of the tested semi-solid battery and propose optimization suggestions (such as adjusting the separator thickness, optimizing the electrolyte density, and improving the critical deformation capability).

[0237] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0238] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

[0239] It should be noted that, in this document, the use of relational terms such as "first" and "second" is merely for distinguishing one entity or operation from another, and does not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0240] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0241] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0242] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0243] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0244] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0245] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0246] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A safety testing method for semi-solid-state lithium batteries, characterized in that, include: An integrated high-frequency injection test circuit, including a main circuit, a signal injection branch, and a signal acquisition branch, was constructed. After completing the component selection, connection, and parameter setting, debugging and calibration were performed. The high-frequency AC voltage response signal is preprocessed to decompose it into in-phase and quadrature components, and the real-time equivalent capacitance value is calculated. Collect sufficient baseline capacitance data under standard conditions and battery conditions matched to the test, calculate the average capacitance and standard deviation, and store qualified baseline parameters after completing the validity verification. Prepare the equipment and parameters for the squeeze / needle puncture mechanical abuse test according to the standard and fix the battery. Simultaneously perform the test and dynamic monitoring of the equivalent capacitance. Based on the threshold of capacitance-related parameters, complete the three-stage state determination of early warning, alarm and failure. The various data collected in the experiment are time-stamped, synchronized, filtered, completed, and classified for storage. Correlation analysis of capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification are carried out to output the test results.

2. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, An integrated high-frequency injection test circuit, including a main circuit, a signal injection branch, and a signal acquisition branch, was constructed. After completing component selection, connection, and parameter setting, debugging and calibration were performed, specifically including: The test circuit consists of three parts: the main circuit, the signal injection branch, and the signal acquisition branch. Each branch is independent and does not interfere with each other. They are connected to the semi-solid battery under test through a common interface. The specific connection relationship is as follows: the positive and negative terminals of the semi-solid battery under test are connected to the output terminal of the main circuit, the output terminal of the signal injection branch, and the input terminal of the signal acquisition branch, respectively. The main circuit provides a normal charging and discharging environment for the semi-solid battery under test, or maintains the battery in an open circuit state to simulate the actual working scenario of the battery. The signal injection branch injects a stable, single-frequency high-frequency sinusoidal current signal into the positive and negative electrodes of the semi-solid battery under test, which serves as the excitation signal for capacitance monitoring. Its frequency and amplitude are set according to preset requirements.

3. The method for testing the safety of a semi-solid-state lithium battery according to claim 2, characterized in that, Also includes: The signal acquisition branch acquires the high-frequency AC voltage response signal across the semi-solid-state battery under test. , and the injected high-frequency current signal correspond; After the circuit is built, debugging and calibration are carried out, including no-load debugging, load calibration, and linkage debugging.

4. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, The acquired high-frequency AC voltage response signal is preprocessed to decompose it into in-phase and quadrature components, and the real-time equivalent capacitance value is calculated. Specifically, this includes: A high-pass filtering algorithm is used to filter the acquired voltage signal, removing the DC component and retaining only the high-frequency AC component. A moving average filtering algorithm is used to smooth the voltage signal after removing the DC component; The preprocessed voltage signal With the injected high-frequency current signal Perform timeline synchronization and alignment; Two reference signals are generated, one being the in-phase reference signal. and quadrature reference signals ,in , The frequency of the injected high-frequency signal; The frequency and amplitude of the reference signal and the injected current signal They are identical, only their phases differ; The preprocessed voltage signal ,in The voltage signal amplitude, The phase difference between the voltage signal and the injected current signal is compared with the in-phase reference signal. Orthogonal reference signal The mixing process yields two mixed signals: an in-phase mixed signal and a frequency-mixed signal. Quadrature mixing signal ; The two mixing signals are subjected to low-pass filtering to remove high-frequency harmonic components and extract low-frequency DC components, which are the amplitudes of the in-phase and quadrature components.

5. The method for testing the safety of a semi-solid-state lithium battery according to claim 4, characterized in that, It also includes real-time equivalent capacitance calculation: According to Ohm's law, the reactance of a capacitor... equal to the quadrature component voltage With injected alternating current The ratio; Capacitive With equivalent capacitance The relationship is (The negative sign indicates that the capacitive reactance and inductance are out of phase.) By transforming the formula, we obtain the following formula for calculating the real-time equivalent capacitance: ； in, The frequency of the injected high-frequency signal.

6. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, Acquire sufficient baseline capacitance data under standard conditions and battery conditions matched to the test, calculate the average capacitance and standard deviation, and store the qualified baseline parameters after validity verification. Specifically, these include: Baseline acquisition environmental conditions control includes test environment temperature, humidity, absence of electromagnetic interference, and absence of vibration; The battery status maintains the working state of the main circuit, ensuring that the electrochemical state of the battery is consistent with the experimental state; The baseline acquisition duration meets the preset duration requirement, ensuring that enough capacitance data is collected to accurately reflect the fluctuation range of background noise.

7. The method for testing the safety of a semi-solid-state lithium battery according to claim 6, characterized in that, Also includes: After the baseline data is collected, the real-time equivalent capacitance value during the baseline period is calculated. Perform statistical analysis and calculate the average capacitance. and standard deviation ; After the baseline parameters are calculated, the validity of the baseline is verified to ensure that the baseline can accurately reflect the initial stable state of the battery and avoid misjudgment in subsequent monitoring due to invalid baselines. Specific verification methods include fluctuation amplitude verification, trend verification, and repeatability verification. Valid baseline parameters are stored in the computer and used as threshold settings.

8. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, Prepare the equipment and parameters for the crush / needle puncture mechanical abuse test according to the standard and fix the battery. Simultaneously perform the test and dynamic monitoring of the equivalent capacitance. Based on the capacitance-related parameter thresholds, complete the three-stage state determination of early warning, alarm, and failure, specifically including: Mechanical abuse tests can be performed using either extrusion or needle penetration tests. The extrusion test has two termination conditions, and the test can be terminated if either condition is met, including the test battery experiencing a short circuit or the extrusion displacement reaching a preset percentage of the battery's initial thickness. During the extrusion process, extrusion pressure and extrusion displacement data are collected in real time; Early warning stage determination logic: Simultaneously satisfying: Condition 1: Real-time capacitance change rate , The deformation threshold is set based on baseline parameters; Condition 2: The terminal voltage at both ends of the battery Remain unchanged; Deformation threshold Setting method: ,in The baseline standard deviation, The period for capacitor calculation.

9. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, Also includes: Alarm stage determination logic: Meets any of the following conditions: Condition 1: Second derivative of real-time capacitance , The interface damage threshold is set based on baseline parameters; Condition 2: Equivalent capacitance value And the rate of change of capacitance Persistently greater than ; Interface damage threshold Setting method: ; Failure stage determination logic: satisfying any of the following conditions: Condition 1: Real-time equivalent capacitance value ; Condition 2: Battery terminal voltage If the voltage drop exceeds a preset allowable threshold within a preset time period, and continues to drop until the difference between the voltage drop and 0V is less than a preset threshold, and the difference in capacitance value within a preset time period exceeds a preset threshold, it is determined to be a short circuit failure.

10. The method for testing the safety of a semi-solid-state lithium battery according to claim 1, characterized in that, The various data collected in the experiment are timestamped, aligned, filtered, completed, and categorized for storage. Correlation analysis of capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification are then performed. Finally, test results containing complete information are output, including: After synchronizing and aligning the data, the aligned and filtered datasets are classified and stored according to baseline data, early warning stage data, alarm stage data, and failure stage data. At the same time, a data index table is generated to mark the time range and key data nodes of each stage. Based on the synchronized dataset, the correlation between equivalent capacitance change and mechanical force and displacement is analyzed to verify the effectiveness. Specifically, this includes correlation analysis between capacitance and mechanical parameters, extraction of critical deformation points, and repeatability verification analysis. After the data correlation analysis is completed, a formal test report is output, which includes basic experimental information, baseline parameters, a summary of data from the entire experimental process, and correlation analysis results. Based on the test results, the mechanical safety level of the tested semi-solid-state battery was evaluated.

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