A lithium ion battery thermal runaway early warning method, device and medium

Abstract

The present application relates to a kind of lithium ion battery thermal runaway early warning method, equipment and medium, the method comprises: setting AC excitation power parameter, outputting the sine excitation current of preset frequency and amplitude;By four-probe method, it is injected into battery monomer;Synchronous acquisition injection current signal and response voltage signal;By fast fourier transform analysis, extract the amplitude and phase of signal fundamental frequency component;According to this, the electrochemical impedance under the frequency is calculated.Combined with the electrochemical impedance-thermal runaway precursor mapping database established by pre-experiment, the impedance value is converted into the corresponding thermal runaway risk level, and the corresponding early warning information is output.The method can capture lithium dendrite growth and internal micro short circuit signs in advance, compared with traditional voltage / temperature monitoring, significantly improve the early warning time limit.

Description

Technical Field

[0001] This invention relates to the field of battery thermal runaway early warning technology, specifically to a method, device, and medium for early warning of thermal runaway in lithium-ion batteries. Background Technology

[0002] As the global energy structure transitions towards a low-carbon model, electrochemical energy storage technology has become a key means of supporting the grid connection of renewable energy. Among them, lithium-ion batteries dominate the energy storage field due to their advantages such as high energy density and long cycle life. However, their thermal runaway problem seriously threatens system safety: uncontrollable chain exothermic reactions are triggered inside the battery due to mechanical abuse (such as separator damage), electrochemical abuse (such as lithium dendrite growth caused by overcharging), or thermal abuse (such as heat dissipation failure), ultimately leading to combustion or explosion. In recent years, fires caused by thermal runaway in energy storage power stations have occurred frequently, causing not only significant economic losses but also triggering a crisis of public trust in new energy technologies.

[0003] Currently, early warning systems for thermal runaway in lithium-ion batteries primarily rely on the Battery Management System (BMS) to monitor external characteristic parameters such as voltage, current, temperature, and internal pressure. Existing technologies typically determine thermal runaway based on preset threshold combinations (such as voltage spikes + temperature surges + abnormal pressure). However, this method has a fundamental flaw:

[0004] 1. Lag: External parameters only show significant anomalies in the middle and late stages of thermal runaway, making it impossible to capture early changes in the internal electrochemical state (such as lithium dendrite growth and micro-short circuit formation).

[0005] 2. Risk of false alarms / missed alarms: External interference (such as fluctuations in ambient temperature) can easily interfere with the judgment, while internal side reactions (such as SEI membrane decomposition) may not be characterized;

[0006] 3. Insufficient safety window: By the time the warning is issued, thermal runaway has already entered an irreversible stage, and the time for emergency response is extremely short.

[0007] Essentially, the core cause of thermal runaway is the imbalance between heat generation and dissipation triggered by an internal short circuit. Traditional methods struggle to directly perceive the electrochemical reaction state inside the battery, especially since changes in diffusion impedance at low frequencies (0.1–10 Hz) can indicate precursors to risks such as lithium dendrite growth. While electrochemical impedance spectroscopy (EIS) can theoretically reflect the internal state, existing methods have the following limitations:

[0008] Low measurement accuracy: The internal resistance of the energy storage battery is extremely small (about 0.2 mΩ), and the interference of contact resistance causes significant errors in the traditional two-probe method;

[0009] Poor real-time performance: Wideband scanning takes too long and cannot meet the needs of online monitoring;

[0010] Weak working condition adaptability: noise interference in complex electromagnetic environment reduces signal signal-to-noise ratio.

[0011] Therefore, it is urgent to develop a thermal runaway early warning method that can early and accurately perceive the internal state of the battery, break through the lagging bottleneck of traditional external parameter monitoring, and realize the safety strategy change from "passive response" to "active prevention". SUMMARY

[0012] The application provides a lithium ion battery thermal runaway early warning method, device and medium, which aims to solve the problem that the traditional lithium ion battery thermal runaway early warning method relies on external parameters, resulting in early warning lag and inability to early perceive abnormal internal electrochemical state of the battery.

[0013] To achieve the above-mentioned purpose, the first aspect of the application provides a lithium ion battery thermal runaway early warning method, comprising the following steps:

[0014] Set the working parameters of the alternating excitation power supply, and output a sinusoidal excitation current with a preset frequency and a preset amplitude;

[0015] The sinusoidal excitation current is injected into the target battery monomer by the four-probe method;

[0016] Synchronously collect the excitation current signal injected into the target battery monomer and the response voltage signal of the target battery monomer under the action of the sinusoidal excitation current;

[0017] The collected excitation current signal and response voltage signal are subjected to fast Fourier transform analysis to extract the amplitude and phase information of the fundamental frequency component;

[0018] According to the extracted amplitude and phase information of the fundamental frequency component, the electrochemical impedance of the target battery monomer at the preset frequency is calculated;

[0019] According to the electrochemical impedance-thermal runaway precursor mapping relationship database established by the pre-experiment, the calculated electrochemical impedance is converted into the corresponding thermal runaway risk level;

[0020] Output the early warning information corresponding to the thermal runaway risk level.

[0021] Further, the preset frequency is 20Hz, and the preset amplitude is 5A.

[0022] Further, the four-probe method is used to inject the sinusoidal excitation current into the target battery monomer by separating the current injection channel and the voltage measurement channel.

[0023] Further, the 24-bit delta-sigma analog-to-digital converter is used to collect the response voltage signal.

[0024] Further, the method for extracting the amplitude and phase information of the fundamental frequency component by performing fast Fourier transform analysis on the collected excitation current signal and response voltage signal comprises:

[0025] Intercepting multiple cycle data of the stable section of the excitation current signal and the response voltage signal;

[0026] Applying a Hanning window to the intercepted data;

[0027] Performing fast Fourier transform analysis on the excitation current signal and the response voltage signal after applying the Hanning window to obtain complex frequency spectrum;

[0028] Determining the frequency point index corresponding to the fundamental frequency;

[0029] Extracting the amplitude and phase of the fundamental frequency component from the complex frequency spectrum.

[0030] Further, the amplitude of the electrochemical impedance is calculated according to the amplitude of the response voltage fundamental frequency component and the amplitude of the excitation current fundamental frequency component; the phase angle of the electrochemical impedance is calculated according to the phase angle of the response voltage fundamental frequency component and the phase angle of the excitation current fundamental frequency component; and the complex form of the electrochemical impedance is generated according to the amplitude of the electrochemical impedance and the phase angle of the electrochemical impedance.

[0031] Further, the calculation formula of the electrochemical impedance is as follows:

[0032]

[0033] wherein, is the electrochemical impedance in complex form, is the response voltage signal of the target battery monomer, is the excitation current signal injected into the battery, is the amplitude of the voltage signal; is the amplitude of the current signal, is the preset frequency of the excitation current, is the phase angle difference between the voltage and the current, is the amplitude of the electrochemical impedance, is the real part of the impedance, representing energy dissipation, is the imaginary part of the impedance, representing energy storage, is the imaginary unit, used to distinguish the real part and the imaginary part of the impedance, is a natural constant, is a time variable, indicates that the phase angle increases linearly with time .

[0034] Further, the electrochemical impedance-thermal runaway precursor mapping relationship database is obtained through a pre-experiment, and the pre-experiment comprises:

[0035] a plurality of same-specification battery monomers are subjected to standard charge-discharge cycles, and a sinusoidal excitation current with a preset frequency and a preset amplitude is applied;

[0036] During the cycles, the excitation current signal and the response voltage signal are collected by the four-probe method, and the electrochemical impedance variation curve of the battery monomer is calculated;

[0037] After the standard charge-discharge cycles, the battery monomer is subjected to one charge-discharge cycle and triggers thermal runaway, and the electrochemical impedance variation curve in this process is recorded;

[0038] Based on the calculation result of the electrochemical impedance variation curve and the recording result of the electrochemical impedance variation curve, a mapping relationship between the electrochemical impedance data and the thermal runaway precursor is established.

[0039] To achieve the above-mentioned purpose, the second aspect of the present application provides an electronic device, comprising a memory and a processor, the memory is used to store the program supporting the processor to execute the lithium ion battery thermal runaway early warning method, and the processor is configured to execute the program stored in the memory.

[0040] To achieve the above-mentioned purpose, the third aspect of the present application provides a computer readable storage medium, and the computer readable storage medium stores a computer program, and the computer program is executed by the processor to execute the steps of the lithium ion battery thermal runaway early warning method.

[0041] The present application has the following beneficial effects:

[0042] Compared with the prior art, the lithium ion battery thermal runaway early warning method, device and medium provided by the present application realize the active capture of the thermal runaway precursor (such as lithium dendrite growth and micro-short circuit formation) by directly monitoring the early abnormal change of the internal electrochemical impedance of the lithium ion battery, thereby solving the early warning lag problem caused by the dependence of the traditional method on external parameters: first, a preset frequency sinusoidal excitation current is injected into the target battery monomer by the four-probe method, the current is injected by the outer probe, and the response voltage is synchronously collected by the inner probe, thereby completely avoiding the interference of the contact resistance on the measurement of the milliohm-level internal resistance of the battery; second, the excitation current and the response voltage signal are subjected to anti-interference signal processing (5-cycle steady-state section is intercepted, Hanning window is used to suppress frequency spectrum leakage, and FFT is used to extract the fundamental frequency component), and the diffusion impedance of the battery at the characteristic frequency is accurately calculated, which is extremely sensitive to the negative electrode lithium deposition and the micro-defects of the separator; finally, based on the impedance-risk mapping database constructed by the pre-experiment, the real-time impedance value is converted into a quantitative thermal runaway risk level, and the early warning is triggered in the initial stage when the internal side reaction accumulates heat but has not yet caused significant temperature / voltage abnormalities, thereby fundamentally breaking through the physical lag bottleneck of external parameter monitoring and realizing the safety strategy upgrade from "passive response" to "active prevention". BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced.

[0044] Figure 1 is a flow chart of a lithium ion battery thermal runaway early warning method disclosed in an embodiment of the present application.

[0045] Figure 2 is a test principle diagram of an electrochemical impedance and thermal runaway precursor mapping relationship disclosed in an embodiment of the present application.

[0046] Figure 3 is a constant frequency AC impedance measurement principle diagram of a lithium ion battery disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0048] According to the embodiments of the present application, it should be noted that the steps shown in the flow chart of the drawings can be executed in a computer system such as a group of computer executable instructions, and although the logical order is shown in the following manufacturing method, in some cases, the steps shown or described can be executed in an order different from here.

[0049] The purpose of the present application is to overcome the above-mentioned limitations of the existing lithium ion battery thermal runaway early warning method, and to disclose a lithium ion battery thermal runaway early warning method based on constant frequency AC impedance. In one embodiment, the method is: a specific frequency sinusoidal excitation current is output by an AC excitation current source, after channel selection, it is injected into the battery monomer to be tested, the response voltage of the specified battery monomer is obtained from the voltage signal acquisition unit at the same time, the collected electrical signal is analyzed by Fast Fourier Transform (FFT), the noise other than the test frequency is filtered out, the peak searching processing is performed by using mathematical software, and the electrochemical impedance of the measured battery is calculated according to the voltage and current waveform information. Based on the electrochemical impedance, the internal state of the battery is judged in real time, and the accurate early warning of the battery thermal runaway stage is realized.

[0050] The method of the present application will be described in detail as follows:

[0051] As Figure 1As shown, the present invention provides a method for early warning of thermal runaway in lithium-ion batteries, comprising the following steps:

[0052] Step S100: Set the operating parameters of the AC excitation power supply and output a sinusoidal excitation current with a preset frequency and preset amplitude;

[0053] This step involves generating a sinusoidal AC excitation signal for probing the internal state of the battery, the expression of which is:

[0054]

[0055] Among them, the amplitude of the excitation current and frequency These are key parameters selected through rigorous evaluation. For time variables, Indicates the phase angle as a function of time It increases linearly.

[0056] The selection criteria for the operating parameters of the AC excitation power supply are as follows:

[0057] Selection of excitation current amplitude: The internal resistance of lithium-ion batteries for energy storage is typically low. Taking a mainstream 314Ah lithium-ion battery for energy storage as an example, its internal resistance is approximately 0.2mΩ. To avoid affecting the normal operation of the battery, the excitation voltage generated on the battery by the sinusoidal current output from the AC excitation power supply should be as small as possible. However, an excessively small signal will reduce measurement accuracy. Therefore, a comprehensive trade-off was made between ensuring high-precision acquisition (μV-level resolution) and avoiding significant interference, ultimately determining the appropriate excitation current amplitude. = 5A. The resulting response voltage is approximately 1mV.

[0058] Selection of excitation current frequency: Based on the Randle equivalent circuit model, the electrochemical impedance of the battery can be expressed by ohmic impedance, charge transfer impedance, and diffusion impedance.

[0059]

[0060] in, The electrochemical impedance of the battery, For ohmic impedance, For charge transfer impedance, For diffusion impedance, It is a double-layer capacitor. The imaginary unit, Angular frequency, This is the actual frequency. Diffusion impedance. The slope change in the low frequency band can indicate lithium dendrite growth. Therefore, the electrochemical impedance measured by the low frequency excitation current can provide technical support for analyzing whether micro-short circuit occurs inside the battery and whether there is a risk of thermal runaway. On the other hand, in order to ensure the timeliness of the early warning, the sampling period should not be too long, so the preset frequency of the sampling excitation current is comprehensively considered 20 Hz.

[0061] It should be noted that the formula describes the equivalent circuit model (Randles model) of the lithium ion battery, which is used to explain the physical composition of the impedance, not directly used for measurement and calculation. This model is only used to select the excitation frequency (20 Hz) to help understand why measuring the 20 Hz impedance can warn of thermal runaway. 20 Hz.

[0062] In summary, by setting the amplitude (5A) and frequency (20Hz) of the excitation current, a core detection signal is generated which can effectively detect the change of the diffusion impedance inside the battery (especially the low frequency characteristics sensitive to lithium dendrites), and can ensure the measurement accuracy and does not interfere with the normal operation of the battery .

[0063] Step S200, injecting the sinusoidal excitation current into the target battery cell by four-probe method;

[0064] It should be noted that the four-probe method is a classic electrical measurement method for accurately measuring the resistivity or conductivity of materials, which is suitable for low resistance samples (such as lithium ion battery electrode materials or internal resistance testing of finished batteries). The core idea is to separate the current injection and voltage measurement channels to eliminate the interference of probe contact resistance and wire resistance, thereby obtaining high-precision impedance data.

[0065] In view of the fact that the internal resistance of large-capacity energy storage lithium batteries is extremely small (usually less than 1 mΩ), the traditional two-probe method is easily disturbed by contact resistance and wire resistance, resulting in serious distortion of the results. The four-probe method completely avoids these interference factors by physically separating the current injection channel (outer probe) and the voltage measurement channel (inner probe), thereby significantly improving the accuracy of the milliohm-level internal resistance measurement. At the same time, in order to adapt to the environment of the energy storage system and realize the online monitoring of the internal resistance of the battery, the four-probe device is simplified, and a micro four-probe sensor is used, which is integrated into the battery management system to realize real-time online monitoring of the internal resistance of the battery.

[0066] Step S300, synchronously collecting the excitation current signal injected into the target battery cell and the response voltage signal of the target battery cell under the action of the sinusoidal excitation current;

[0067] To achieve precise measurement of micro-voltage signals at the μV level, a 24-bit Δ-Σ type ADC paired with a low-noise preamplifier is used to ensure extremely high voltage resolution. Most importantly, the excitation current injection and voltage acquisition channels are fully synchronized through a high-speed switching circuit and strict timing control, effectively eliminating timing deviations caused by signal transmission delays and thus guaranteeing the accuracy of impedance measurement results.

[0068] Step S400: Perform fast Fourier transform analysis on the acquired excitation current signal and response voltage signal to extract the amplitude and phase information of the fundamental frequency component;

[0069] This step extracts the fundamental frequency characteristics of the excitation current and response voltage through an anti-interference signal processing procedure. The specific procedure is as follows:

[0070] Step S401: Extract five consecutive cycles of data from the stable segment of the signal (number of sampling points is...). ), respectively from the original voltage signal and current signal Subtract its DC component (e.g., in the formula) (representing the DC mean of the voltage signal), thus obtaining the pure AC component. and To avoid steady-state deviation interference, the specific formula is as follows:

[0071]

[0072]

[0073] in, The voltage signal after DC removal. This is the current signal after DC removal. This is the original voltage sample value. This is the original current sampling value. This represents the number of sampling points corresponding to the total number of signal periods captured (this method uses 5 periods). Indicates the first The instantaneous value of the battery response voltage measured at each discrete sampling time. Indicates the first The instantaneous value of the excitation current injected into the battery at each discrete sampling time. This is the index for the summation operation, i.e., a temporary variable used to iterate through the sampling points.

[0074] Step S402: Apply a Hanning window to the DC-free signal to generate a windowed voltage and current. This improves the fundamental frequency resolution by suppressing frequency domain energy diffusion. The Hanning window is a window function with a bell-shaped shape, smoothly transitioning to zero at both ends. Its mathematical expression is:

[0075]

[0076] wherein, is a window function value, is a sampling point index;

[0077] The purpose of applying the Hanning window is to reduce the spectral leakage caused by signal truncation and improve the accuracy of spectral analysis. Specifically: in the time domain, the signal is gradually attenuated at both ends to avoid sudden changes caused by truncation; in the frequency domain, the main lobe of the spectrum is more concentrated, and the side lobe decays faster, so that the amplitude and phase of the fundamental frequency component (20 Hz) can be more accurately extracted.

[0078] The formula calculation process is as follows: first, according to the total number of points and the current index , the window function value is calculated; second, the voltage signal after removing direct current is multiplied by the window function value to obtain the windowed voltage signal ; the current signal after removing direct current is multiplied by the window function value to obtain the windowed current signal , and the specific formula is as follows:

[0079]

[0080]

[0081] wherein, is a windowed voltage signal, is a windowed current signal.

[0082] Step S403, performing fast Fourier transform (FFT) on the windowed signal to obtain voltage complex spectrum and current complex spectrum, and the calculation formula is as follows:

[0083]

[0084]

[0085] wherein, is a voltage complex spectrum, is a current complex spectrum, is a frequency point index, is a Fourier kernel function, is an imaginary unit.

[0086] Step S404, according to the sampling rate, the frequency point index corresponding to the fundamental frequency is calculated:

[0087]

[0088] wherein, is a frequency point index, and round represents rounding to the nearest integer, The sampling rate.

[0089] Step S405: Extract the fundamental frequency amplitude (voltage amplitude and current amplitude) and phase angle (voltage phase and current phase) from the frequency index:

[0090]

[0091]

[0092]

[0093]

[0094] in, Voltage amplitude, The current amplitude, For voltage signals at the fundamental frequency point Complex spectral values ​​at that location, For the current signal at the fundamental frequency Complex spectral values ​​at that location, The phase angle of the voltage signal. The phase angle of the current signal. This represents the real part of the complex voltage spectrum value. is the real part of the complex spectrum value of the current. This represents the imaginary part of the complex frequency spectrum of the voltage. This represents the imaginary part of the complex spectrum value of the current. It is the arctangent function in the four quadrants.

[0095] Step S500: Calculate the electrochemical impedance of the target battery cell at the preset frequency based on the extracted fundamental frequency component amplitude and phase information;

[0096] The formula for calculating electrochemical impedance is as follows:

[0097]

[0098] in, Electrochemical impedance in complex form The response voltage signal of the target battery cell. This is the excitation current signal injected into the battery. The amplitude of the voltage signal; The amplitude of the current signal. The preset frequency of the excitation current, The phase angle difference between voltage and current. The amplitude of the electrochemical impedance. The real part of the impedance represents energy dissipation. This represents the imaginary part of the impedance, indicating energy storage. is the imaginary unit, used to distinguish the real and imaginary parts of impedance, is the natural constant, is the time variable, denotes the phase angle as a function of time increases linearly.

[0099] The specific derivation process is as follows:

[0100] Step S501, define the complex form of voltage and current;

[0101] In a sinusoidal alternating current circuit, the voltage and the current can be represented in complex exponential form:

[0102] Current expression (current as phase reference, initial phase 0):

[0103]

[0104] Voltage expression (including phase difference ):

[0105]

[0106] Step S502, substitute the impedance definition formula;

[0107] Impedance is defined as the complex ratio of voltage to current:

[0108]

[0109] Step S503, simplify the exponential term;

[0110] Through the rules of exponential operation and the properties of division :

[0111]

[0112] Step S504, introduce the impedance amplitude;

[0113] Let the impedance amplitude (complex form of Ohm's law), we get:

[0114]

[0115] This is the polar form of impedance (amplitude + phase);

[0116] Step S505, convert to rectangular coordinate form (complex form);

[0117] Apply Euler's formula :

[0118]

[0119] Finally, the complex form is obtained:

[0120]

[0121] wherein, is the impedance amplitude, is the impedance phase difference, and the amplitude (voltage amplitude and current amplitude ) and phase information (voltage phase and current phase ) of the fundamental component extracted by step S400 are used to calculate the electrochemical impedance of the target battery monomer at a preset frequency (f is 20 Hz).

[0122] Step S600: According to the electrochemical impedance-thermal runaway precursor mapping relationship database established by the pre-experiment, the calculated electrochemical impedance is converted into the corresponding thermal runaway risk level.

[0123] The mapping relationship between the electrochemical impedance data of the battery and the thermal runaway precursor needs to be obtained through pre-experiments. First, an electrochemical impedance data-thermal runaway precursor mapping relationship test circuit as shown in Figure 2 is needed to be built, and the circuit structure is as follows:

[0124] The positive and negative electrodes of the measured battery are directly connected to the charge-discharge machine through wires for performing standard charge-discharge cycles to simulate actual operating conditions; at the same time, an alternating excitation current source is connected in parallel across the battery, outputting a sinusoidal excitation current with a frequency of 20 Hz and an amplitude of 5 A; a four-probe method is used, in which the current injection channel (outer probe) is used to apply the excitation signal, and the voltage measurement channel (inner probe) is independently connected to the electrodes of the battery to collect the response voltage signal with high precision, thereby avoiding the interference of contact resistance and wire resistance and ensuring the impedance measurement accuracy. The entire circuit processes the voltage signal through a low-noise preamplifier and a 24-bit delta-sigma ADC, and is integrated with a data processing module for real-time analysis of electrochemical impedance changes. A voltmeter (V) is connected in parallel across the measured battery to accurately measure the battery terminal voltage, and an ammeter (A) is connected in series in the main loop to measure the total loop current. The charge-discharge machine and the measured battery form a continuous current path to ensure that the excitation signal passes through the battery body.

[0125] The specific method of the pre-experiment is as follows:

[0126] Step S601: According to the electrochemical impedance data-thermal runaway precursor mapping relationship test circuit, the electrochemical impedance data of the battery monomer is measured under the condition of the same temperature and the same state of charge (SOC) as the target battery monomer. Figure 2The test circuit for mapping the electrochemical impedance data and the thermal runaway precursor is built, the battery to be measured is connected with the charge-discharge machine, the standard charge-discharge cycle is performed at room temperature according to the standard charge-discharge requirement, and at the same time, the alternating excitation current source is connected to the two ends of the battery, and the amplitude of the sinusoidal excitation current is 5 A and the frequency is 20 Hz.

[0127] In step S602, the impedance change curve of the battery in the standard charge-discharge cycle is obtained by collecting the excitation current and the response voltage through the four-probe method in the standard charge-discharge cycle. The standard charge-discharge cycle is repeated for three times.

[0128] In step S603, after the impedance change curve of the battery in the standard charge-discharge cycle is obtained, a quasi charge-discharge cycle is performed again, the thermal runaway of the battery is triggered by heating in the cycle process, and the impedance change curve of the battery is recorded.

[0129] In step S604, 100 batteries of the same specification are selected, and steps S602-S603 are repeated, and the mapping relationship between the electrochemical impedance data and the thermal runaway precursor is summarized.

[0130] In step S700, the warning information corresponding to the thermal runaway risk level is output.

[0131] Figure 3 The lithium ion battery fixed-frequency alternating current impedance measurement principle diagram is shown in the figure. According to the principle diagram shown in the figure, the lithium ion battery fixed-frequency alternating current impedance measurement system works through the following closed loop process: the alternating current excitation power supply generates a current signal of a specific frequency (constrained by fixed frequency design) , the signal is selected by the channel switching module and injected into the series lithium ion battery pack; the voltage and current collection module synchronously acquires the battery terminal voltage and current signal, and transmits it to the battery management system (BMS); the BMS and the energy management system (EMS) perform bidirectional data interaction, and at the same time, the processed battery state parameters are sent to the data processing and analysis module; the electrochemical impedance of the target battery monomer at the preset frequency is calculated through the data processing and analysis module, the thermal runaway risk level of the system is judged according to the electrochemical impedance, and the corresponding warning information is output. Through the cooperation of signal excitation, collection, management and analysis, the system realizes the accurate measurement of the impedance characteristics of the battery.

[0132] The application realizes early warning of thermal runaway of lithium ion batteries by introducing a fixed frequency alternating current impedance technology, and provides bottom perception technology support for safety of energy storage systems. By monitoring the change of low-frequency electrochemical impedance in real time, the method can capture the signs of lithium dendrite growth and internal micro-short circuit in advance, and the warning time of the method is significantly improved compared with traditional voltage / temperature monitoring. The core advantage is that the electrochemical impedance of the battery is directly perceived, and based on the electrochemical impedance-thermal runaway risk mapping relationship obtained through pre-experiment, a strong causal relationship between the electrochemical impedance and the thermal runaway risk is established. In addition, the application adopts a four-probe method and a micro-sensor design, and combines high-precision signal processing technology to improve the anti-interference ability of signal acquisition, and ensure that the method can still operate reliably under complex working conditions.

[0133] According to another aspect of the embodiments of the present application, an electronic device is also provided, which includes a processor and a memory, and the processor is configured to implement the steps of the method when executing the computer program stored in the memory.

[0134] In the above-mentioned embodiments of the present application, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0135] In several embodiments provided in the present application, it should be understood that the disclosed technical contents can be implemented by other ways. Among them, the above-described device embodiments are only schematic, for example, the division of the units can be a logical function division, and actual implementation can have another division way, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed units can be indirect coupling or communication connection through some interfaces, units or modules, which can be electrical or other forms.

[0136] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The above integrated unit can be realized in the form of hardware or in the form of software functional unit.

[0137] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application, essentially or in other words, the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, including a number of instructions to make a computer device (which can be a personal computer, a server or a network device, etc.) execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various media that can store program codes.

[0138] The above is only the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for early warning of thermal runaway in lithium-ion batteries, characterized in that, Includes the following steps: Set the operating parameters of the AC excitation power supply and output a sinusoidal excitation current with a preset frequency and preset amplitude. The sinusoidal excitation current is injected into the target battery cell using a four-probe method; The excitation current signal injected into the target battery cell and the response voltage signal of the target battery cell under the action of the sinusoidal excitation current are acquired simultaneously. Fast Fourier transform analysis is performed on the acquired excitation current signal and response voltage signal to extract the amplitude and phase information of the fundamental frequency component; Based on the extracted fundamental frequency component amplitude and phase information, the electrochemical impedance of the target battery cell at the preset frequency is calculated. Based on the electrochemical impedance-thermal runaway precursor mapping database established by the preliminary experiment, the calculated electrochemical impedance is converted into the corresponding thermal runaway risk level. Output early warning information corresponding to the thermal runaway risk level; The preset frequency is 20Hz, and the preset amplitude is 5A; The electrochemical impedance-thermal runaway precursor mapping database was obtained through preliminary experiments, which included: Perform standard charge-discharge cycles on multiple battery cells of the same specification, while simultaneously applying a sinusoidal excitation current with a preset frequency and preset amplitude. During the cycling process, the excitation current signal and response voltage signal were acquired using the four-probe method, and the electrochemical impedance change curve of the battery cell was calculated. After a standard charge-discharge cycle, a single battery cell is subjected to a charge-discharge cycle and thermal runaway is triggered. The electrochemical impedance spectroscopy curves during this process are recorded. Based on the calculation results and the recorded results of the electrochemical impedance change curves, a mapping relationship between electrochemical impedance data and precursors of thermal runaway is established.

2. The lithium-ion battery thermal runaway early warning method as described in claim 1, characterized in that, The sinusoidal excitation current is injected into the target battery cell using a four-probe method that separates the current injection channel and the voltage measurement channel.

3. The lithium-ion battery thermal runaway early warning method as described in claim 1, characterized in that, The response voltage signal was acquired using a 24-bit Δ-Σ analog-to-digital converter.

4. The lithium-ion battery thermal runaway early warning method as described in claim 1, characterized in that, The method for extracting the amplitude and phase information of the fundamental frequency component by performing fast Fourier transform analysis on the acquired excitation current signal and response voltage signal includes: Extract multiple cycles of data from the stable segment of the excitation current signal and the response voltage signal; Apply a Hanning window to the captured data; The excitation current signal and the response voltage signal after applying the Hanning window are analyzed by Fast Fourier Transform to obtain complex spectra; Determine the frequency index corresponding to the fundamental frequency; Extract the amplitude and phase of the fundamental frequency component from the complex spectrum.

5. The lithium-ion battery thermal runaway early warning method as described in claim 1, characterized in that, The amplitude of the electrochemical impedance is calculated based on the amplitude of the fundamental frequency component of the response voltage and the amplitude of the fundamental frequency component of the excitation current. The phase angle of the electrochemical impedance is calculated based on the phase angle of the fundamental frequency component of the response voltage and the phase angle of the fundamental frequency component of the excitation current. Based on the amplitude of the electrochemical impedance and the phase angle of the electrochemical impedance, a complex form of the electrochemical impedance is generated.

6. The lithium-ion battery thermal runaway early warning method as described in claim 5, characterized in that, The formula for calculating the electrochemical impedance is as follows: in, Electrochemical impedance in complex form The response voltage signal of the target battery cell. This is the excitation current signal injected into the battery. The amplitude of the voltage signal; The amplitude of the current signal. The preset frequency of the excitation current, The phase angle difference between voltage and current. The amplitude of the electrochemical impedance. The real part of the impedance represents energy dissipation. This represents the imaginary part of the impedance, indicating energy storage. The imaginary unit is used to distinguish between the real and imaginary parts of impedance. It is a natural constant. For time variables, Indicates the phase angle as a function of time It increases linearly.

7. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing the lithium-ion battery thermal runaway early warning method according to any one of claims 1-6, and the processor is configured to execute the program stored in the memory.

8. A computer-readable storage medium storing a computer program thereon, characterized in that, When the computer program is run by the processor, it executes the steps of the lithium-ion battery thermal runaway early warning method according to any one of claims 1-6.

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