Lithium ion battery thermal runaway early warning method, equipment and medium

Abstract

The invention relates to a lithium ion battery thermal runaway early warning method and device and a medium, and the method comprises the steps: setting an AC excitation power supply parameter, and outputting a sine excitation current with a preset frequency and amplitude; injecting the polymer into a single battery through a four-probe method; synchronously acquiring an injection current signal and a response voltage signal; through fast Fourier transform analysis, the amplitude and the phase of a signal fundamental frequency component are extracted; and calculating the electrochemical impedance under the frequency. And in combination with an electrochemical impedance-thermal runaway precursor mapping database established by a pre-experiment, converting the impedance value into a corresponding thermal runaway risk level, and outputting corresponding early warning information. According to the method, lithium dendrite growth and internal micro short circuit signs can be captured in advance, and the early warning time efficiency is remarkably improved compared with traditional voltage / temperature monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery thermal runaway early warning, in particular to a lithium ion battery thermal runaway early warning method, device and medium. BACKGROUND

[0002] With the transformation of global energy structure to low carbonization, electrochemical energy storage technology has become a key means to support renewable energy grid connection. Among them, lithium ion batteries dominate the energy storage field due to their high energy density and long cycle life. However, the problem of thermal runaway seriously threatens system safety: the uncontrolled chain heat release reaction is triggered by mechanical abuse (such as damage to the separator), electrochemical abuse (such as lithium dendrite growth caused by overcharging), or thermal abuse (such as heat dissipation failure) in the battery, eventually leading to combustion or explosion. In recent years, fire accidents caused by thermal runaway in energy storage power stations have occurred frequently, not only causing significant economic losses, but also causing a crisis of public trust in new energy technology.

[0003] Currently, lithium ion battery thermal runaway early warning mainly relies on battery management system (BMS) to monitor external characteristic parameters such as voltage, current, temperature and internal pressure. The existing technology usually determines thermal runaway based on a combination of preset thresholds (such as voltage drop + temperature rise + abnormal pressure). However, this method has fundamental flaws: 1. Hysteresis: external parameters only show significant abnormalities in the middle and later stages of thermal runaway, and cannot capture early internal electrochemical state changes (such as lithium dendrite growth and micro-short circuit formation); 2. False / missed report risk: external interference (such as environmental temperature fluctuations) can easily interfere with the judgment, while internal side reactions (such as SEI film decomposition) may not be characterized; 3. Insufficient safety time window: thermal runaway has entered an irreversible stage when the warning is given, and personnel emergency disposal time is extremely short.

[0004] In essence, the core cause of thermal runaway is the heat production-heat dissipation imbalance caused by internal short circuit. Traditional methods are difficult to directly perceive the electrochemical reaction state inside the battery, especially the changes in low-frequency (0.1-10 Hz) diffusion impedance, which can indicate risk precursors such as lithium dendrite growth. Although electrochemical impedance spectroscopy (EIS) technology can theoretically reflect the internal state, existing solutions have the following limitations: Low measurement accuracy: the internal resistance of energy storage batteries is extremely small (about 0.2 mΩ), and the contact resistance interference causes significant errors in the traditional two-probe method; Poor real-time performance: wide frequency scanning takes too long, which cannot meet the online monitoring requirements; Weak working condition adaptability: noise interference in complex electromagnetic environments reduces the signal-to-noise ratio of the signal.

[0005] 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

[0006] 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 the abnormality of the internal electrochemical state of the battery.

[0007] 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: Setting the working parameters of the alternating excitation power supply, outputting a sinusoidal excitation current with a preset frequency and a preset amplitude; Injecting the sinusoidal excitation current into the target battery monomer by the four-probe method; Synchronously collecting 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; Performing fast Fourier transform analysis on the collected excitation current signal and response voltage signal to extract the amplitude and phase information of the fundamental frequency component; 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; 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; Outputting the early warning information corresponding to the thermal runaway risk level.

[0008] Further, the preset frequency is 20Hz, and the preset amplitude is 5A.

[0009] 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.

[0010] Further, the response voltage signal is collected by using a 24-bit delta-sigma analog-to-digital converter.

[0011] Further, the method for performing fast Fourier transform analysis on the collected excitation current signal and response voltage signal to extract the amplitude and phase information of the fundamental frequency component comprises: Intercepting multiple period data of the stable section of the excitation current signal and the response voltage signal; Applying a Hanning window to the intercepted data; 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; determining the frequency point index corresponding to the fundamental frequency; extracting the amplitude and phase of the fundamental frequency component from the complex frequency spectrum.

[0012] Further, the amplitude of the electrochemical impedance is calculated according to 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 according to 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; and the electrochemical impedance in complex form is generated according to the amplitude of the electrochemical impedance and the phase angle of the electrochemical impedance.

[0013] Further, the calculation formula of the electrochemical impedance is as follows: 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 .

[0014] Further, the electrochemical impedance-thermal runaway precursor mapping relationship database is obtained through a pre-experiment, and the pre-experiment includes: applying a sinusoidal excitation current with a preset frequency and a preset amplitude to a plurality of battery monomers of the same specification during standard charge-discharge cycling; During the cycling process, the excitation current signal and the response voltage signal are collected by the four-probe method, and the electrochemical impedance change curve of the battery monomer is calculated; After the standard charge-discharge cycling, the battery monomer is subjected to one charge-discharge cycle and triggers thermal runaway, and the electrochemical impedance change curve during the process is recorded; Based on the calculation result of the electrochemical impedance change curve and the recording result of the electrochemical impedance change curve, a mapping relationship between the electrochemical impedance data and the thermal runaway precursor is established.

[0015] 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.

[0016] 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.

[0017] The beneficial effects of the present application are: 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 electrochemical impedance in 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 cycles of steady-state section are 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

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows.

[0019] Figure 1 is a flow chart of a lithium ion battery thermal runaway early warning method disclosed by the embodiments of the present application.

[0020] Figure 2 is a test principle diagram of the mapping relationship between the electrochemical impedance and the thermal runaway precursor disclosed by the embodiments of the present application.

[0021] Figure 3 is a lithium ion battery fixed frequency AC impedance measurement schematic disclosed by the embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to enable personnel 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 below in conjunction with 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 belong to the scope of protection of the present application.

[0023] According to the embodiment of the present application, it should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set 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.

[0024] 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 disclose a lithium ion battery thermal runaway early warning method based on fixed frequency AC impedance. In one embodiment, the method is: outputting a sine excitation current with a specific frequency through an AC excitation current source, after channel selection, injecting into the battery monomer to be tested, synchronously obtaining the response voltage of the specified battery monomer from the voltage signal acquisition unit, performing Fast Fourier Transform (FFT) analysis on the collected electric signal, filtering out the noise other than the test frequency, using mathematical software to perform peak searching processing, and calculating the electrochemical impedance of the measured battery 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.

[0025] The method of the present application will be described in detail below: As shown in Figure 1 , the present application provides a lithium ion battery thermal runaway early warning method, comprising the following steps: Step S100, setting the working parameters of the AC excitation power supply, outputting a sine excitation current with a preset frequency and a preset amplitude; This step is to generate a sine AC excitation signal for detecting the internal state of the battery, and its expression is: Among them, the amplitude and the frequency of the excitation current are key parameters selected after strict argumentation, is a time variable, Phase angle vs. time Linearly increases.

[0026] The selection of the AC excitation power supply operating parameters is based on the following: The excitation current amplitude selection is based on the following: The internal resistance of the energy storage lithium ion battery is usually small. Taking the currently popular 314 Ah energy storage lithium ion battery as an example, its internal resistance is about 0.2 mΩ. In order not to affect the normal operation of the battery, the excitation voltage generated by the sinusoidal current output by the AC excitation power supply on the battery should be as small as possible. However, too small a signal will reduce the measurement accuracy. Therefore, a comprehensive trade-off is made between ensuring high-precision acquisition (μV level resolution) and avoiding significant interference, and the excitation current amplitude is finally selected as = 5 A. At this time, the response voltage generated is about 1 mV.

[0027] The excitation current frequency selection is based on the following: Based on the Randles equivalent circuit model, the electrochemical impedance of the battery can be represented by ohmic impedance, charge transfer impedance, and diffusion impedance: wherein, Z is the electrochemical impedance of the battery, R is the ohmic impedance, Zc is the charge transfer impedance, Zd is the diffusion impedance, C is the double-layer capacitance, j is the imaginary unit, ω is the angular frequency, f is the actual frequency. Diffusion impedance The slope change at low frequencies 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 circuits exist in 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. Therefore, the preset frequency of the sampling excitation current is selected as 20 Hz.

[0028] It should be noted that this formula describes the equivalent circuit model of the lithium ion battery (Randles model) for explaining the physical composition of the impedance, and is not directly used for measurement and calculation. This model is only used to select the excitation frequency (f = 20 Hz) and to help understand why measuring the 20 Hz impedance can warn of thermal runaway.

[0029] In summary, by setting the amplitude (5 A) and frequency (20 Hz) of the excitation current, a core detection signal is generated that can effectively detect changes in the diffusion impedance of the battery (especially the low-frequency characteristics sensitive to lithium dendrites), while ensuring measurement accuracy and not interfering with the normal operation of the battery . ​

[0030] Step S200, injecting the sinusoidal excitation current into the target battery cell by four-probe method; It should be noted that the four-probe method is a classic electrical measurement method for accurately measuring the resistivity or conductivity of a material, which is suitable for low-resistance samples (such as the internal resistance test of lithium-ion battery electrode materials or 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.

[0031] Due to the extremely small internal resistance of large-capacity energy storage lithium batteries (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 miniature four-probe sensor is integrated into the battery management system to realize real-time online monitoring of the internal resistance of the battery.

[0032] 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; In order to realize the accurate measurement of the μV-level tiny voltage signal, a 24-bit Δ-Σ ADC is used in combination with a low-noise preamplifier to ensure extremely high voltage resolution. Most importantly, the excitation current injection and voltage acquisition channels are completely synchronized through a high-speed switching circuit and strict timing control, effectively eliminating the timing deviation caused by signal transmission delay, thereby ensuring the accuracy of the impedance measurement results.

[0033] Step S400, performing fast Fourier transform analysis on the collected excitation current signal and response voltage signal to extract the amplitude and phase information of the fundamental frequency component; This step extracts the fundamental frequency characteristics of the excitation current and response voltage through an anti-interference signal processing procedure, and the specific procedure is as follows: Step S401, intercepting 5 consecutive period data (sampling point number ) of the signal stable section, respectively subtracting the DC component (for example, in the formula, Vdc represents the DC mean value of the voltage signal) from the original voltage signal and the current signal to obtain pure AC components and , avoiding steady-state deviation interference, and the specific formula is as follows: ​ in, is the voltage signal after removing DC, is the current signal after DC removal, is the original voltage sampling value, is the original current sampling value, is the number of sampling points corresponding to the total number of intercepted signal cycles (5 cycles are taken in this method), Indicates in The instantaneous value of the battery response voltage measured at discrete sampling moments, Indicates in The instantaneous value of the excitation current injected into the battery at a discrete sampling moment, It is the index of the sum operation, that is, the temporary variable for traversing the sampling points.

[0034] Step S402: Apply a Hanning window to the DC-depleted signal to generate windowed voltage and current. This improves fundamental frequency resolution by suppressing frequency domain energy diffusion. The Hanning window is a bell-shaped window function with a smooth transition to zero at both ends. Its mathematical expression is: in, is the window function value, is the sampling point index; The purpose of applying a Hanning window is to reduce spectral leakage caused by signal truncation and improve the accuracy of spectrum analysis. Specifically, in the time domain, the signal is gradually attenuated at both ends to avoid the sudden changes caused by truncation. In the frequency domain, the main lobe of the spectrum is more concentrated and the side lobes decay more quickly, thereby more accurately extracting the amplitude and phase of the fundamental frequency component (20Hz).

[0035] The calculation process is as follows: First, according to the total points and the current index Calculate the window function value ; Secondly, remove the DC voltage signal Multiply by the window function value to get the windowed voltage signal ; Remove the DC current signal Multiply by the window function value to get the windowed current signal , the specific formula is as follows: in, is the windowed voltage signal, is the windowed current signal.

[0036] Step S403: Perform a fast Fourier transform (FFT) on the windowed signal to obtain a complex spectrum of voltage and a complex spectrum of current. The calculation formula is as follows: in, is the complex voltage spectrum, is the current complex spectrum, is the frequency index, is the Fourier kernel function, Is an imaginary unit.

[0037] Step S404: Calculate the frequency index corresponding to the fundamental frequency according to the sampling rate: in, is the frequency index, round means rounding to the nearest integer. is the sampling rate.

[0038] Step S405: extract the fundamental frequency amplitude (voltage amplitude and current amplitude) and phase angle (voltage phase and current phase) from the frequency point index: in, is the voltage amplitude, is the current amplitude, is the voltage signal at the fundamental frequency The complex spectrum value at is the current signal at the fundamental frequency point The complex spectrum value at is the phase angle of the voltage signal, is the phase angle of the current signal, is the real part of the voltage complex spectrum value, is the real part of the current complex spectrum value, is the imaginary part of the voltage complex spectrum value, is the imaginary part of the current complex spectrum value, is the four-quadrant inverse tangent function.

[0039] Step S500, calculating the electrochemical impedance of the target battery cell at the preset frequency based on the extracted fundamental frequency component amplitude and phase information; The calculation formula of electrochemical impedance is as follows: in, is the electrochemical impedance in complex form, is the response voltage signal of the target battery cell, the amplitude of the voltage signal; 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, representing energy dissipation, the imaginary part of the impedance, representing energy storage, the imaginary unit, used to distinguish the real and imaginary parts of the impedance, the natural constant, the time variable, the phase angle increases linearly with time .

[0040] The specific derivation process is as follows: Step S501, define the complex form of voltage and current; In a sinusoidal alternating current circuit, the voltage and the current can be expressed in complex exponential form: Current expression (current as phase reference, initial phase 0): Voltage expression (including phase difference ): Step S502, substitute the impedance definition formula; Impedance is defined as the complex ratio of voltage to current: Step S503, simplify the exponential term; Through the rules of exponential operation and the properties of division : Step S504, introduce the impedance amplitude; Let the impedance amplitude (complex form of Ohm's law), we get: This is the polar form of impedance (amplitude + phase); Step S505, convert to rectangular coordinate form (complex form); Apply Euler's formula : Finally, we get the complex form: wherein, is the impedance amplitude, is the impedance phase difference, and further the amplitude (voltage amplitude and current amplitude ) and phase information (voltage phase and current phase ) of the fundamental component extracted by step S400 are calculated to obtain the electrochemical impedance of the target battery cell at a preset frequency (f = 20 Hz).

[0041] 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; The mapping relationship between the electrochemical impedance data of the battery and the thermal runaway precursor needs to be obtained through pre-experiment. First, an electrochemical impedance data and thermal runaway precursor mapping relationship test circuit as shown in Figure 2 is needed to be built. The circuit structure is as follows: 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 accuracy of impedance measurement. 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.

[0042] The specific method of the pre-experiment is as follows: Step S601, according to the standard Figure 2 , the electrochemical impedance data and thermal runaway precursor mapping relationship test circuit is built, the measured battery is connected with the charge-discharge machine, and the standard charge-discharge cycle is carried out under room temperature conditions according to the standard charge-discharge requirements, and at the same time the alternating excitation current source is connected across the battery, outputting a sinusoidal excitation current with an amplitude of 5 A and a frequency of 20 Hz.

[0043] ​Step S602, under a standard charge-discharge cycle, the excitation current and the response voltage are collected by four-probe method to obtain the impedance change curve of the battery in the standard charge-discharge cycle. The standard charge-discharge cycle is repeated for 3 times.

[0044] Step S603, after obtaining the impedance change curve of the battery in the standard charge-discharge cycle, a quasi charge-discharge cycle is performed again, and the impedance change curve of the battery is recorded by triggering the thermal runaway of the battery by heating during the cycle.

[0045] 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.

[0046] Step S700, output the early warning information corresponding to the thermal runaway risk level.

[0047] Figure 3 The lithium ion battery fixed frequency alternating current impedance measurement principle diagram, according to the principle diagram shown, 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 send the processed battery state parameters 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 early warning information is output. Through the cooperation of signal excitation, collection, management and analysis, the precise measurement of the impedance characteristics of the battery is realized.

[0048] The present application realizes the early warning of lithium ion battery thermal runaway by introducing fixed frequency alternating current impedance technology, and provides bottom perception technology support for energy storage system safety. By monitoring the low-frequency electrochemical impedance change in real time, this method can capture the signs of lithium dendrite growth and internal micro-short circuit in advance, and the warning time of traditional voltage / temperature monitoring is significantly improved. The core advantage is to directly perceive the electrochemical impedance of the battery, based on the electrochemical impedance-thermal runaway risk mapping relationship obtained by pre-experiment, a strong causal relationship between electrochemical impedance and thermal runaway risk is established. In addition, the present application adopts four-probe method and micro sensor design, combined with high-precision signal processing technology, the anti-interference ability of signal collection is improved, and the method can still run reliably under complex working conditions.

[0049] According to another aspect of the embodiments of the present application, an electronic device is also provided, which comprises a processor and a memory, the processor being configured to implement the steps of the method when executing the computer program stored in the memory.

[0050] In the above-described embodiments of the present application, the description of each embodiment focuses on different aspects, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0051] In several embodiments provided in the present application, it should be understood that the disclosed technical contents can be implemented by other manners. Among them, the apparatus embodiment described above is only schematic, for example, the division of the units can be a logical function division, and in actual implementation, there can be another division manner, 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 units or modules shown or discussed can be indirect coupling or communication connection through some interfaces, units or modules, which can be electrical or other forms.

[0052] 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 integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0053] When the integrated unit is realized in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or 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, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. The foregoing 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.

[0054] The above description is only the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be regarded as the protection scope of the present application.

Claims

1. A lithium-ion battery thermal runaway early warning method, characterized in that: The steps include: Setting the operating parameters of the AC excitation power supply to output a sinusoidal excitation current with a preset frequency and amplitude; Injecting the sinusoidal excitation current into the target battery cell through a four-probe method; Synchronously collecting an excitation current signal injected into the target battery cell and a response voltage signal of the target battery cell under the action of the sinusoidal excitation current; Performing fast Fourier transform analysis on the collected excitation current signal and the response voltage signal to extract the amplitude and phase information of the fundamental frequency component; Calculating the electrochemical impedance of the target battery cell at the preset frequency based on the extracted fundamental frequency component amplitude and phase information; According to the electrochemical impedance-thermal runaway precursor mapping relationship database established in the preliminary experiment, the calculated electrochemical impedance is converted into the corresponding thermal runaway risk level; Outputting warning information corresponding to the thermal runaway risk level.

2. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: The preset frequency is 20 Hz, and the preset amplitude is 5A.

3. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: The sinusoidal excitation current is injected into the target battery cell using a four-probe method that separates a current injection channel and a voltage measurement channel.

4. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: A 24-bit delta-sigma analog-to-digital converter is used to acquire the response voltage signal.

5. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: The method of performing fast Fourier transform analysis on the collected excitation current signal and the response voltage signal to extract the amplitude and phase information of the fundamental frequency component includes: intercepting a plurality of periodic data of the stable segments of the excitation current signal and the response voltage signal; Apply a Hanning window to the truncated data; Performing fast Fourier transform analysis on the excitation current signal and the response voltage signal after applying the Hanning window to obtain a complex spectrum; Determine the frequency index corresponding to the fundamental frequency; Extract the magnitude and phase of the fundamental frequency component from the complex spectrum.

6. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: Calculating the amplitude of the electrochemical impedance according to 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 according to 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, and the electrochemical impedance in complex form is generated according to the amplitude of the electrochemical impedance and the phase angle of the electrochemical impedance.

7. The lithium-ion battery thermal runaway early warning method according to claim 6, characterized in that: The calculation formula of the electrochemical impedance is as follows: in, is the electrochemical impedance in complex form, is the response voltage signal of the target battery cell, 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 voltage and current, is the amplitude of electrochemical impedance, is the real part of the impedance, representing energy dissipation, is the imaginary part of the impedance, representing energy storage, is an imaginary unit used to distinguish the real and imaginary parts of impedance. is a natural constant, is the time variable, Represents the phase angle over time Linear increase.

8. The lithium-ion battery thermal runaway early warning method according to claim 1, wherein: The electrochemical impedance-thermal runaway precursor mapping relationship database is obtained through a preliminary experiment, and the preliminary experiment includes: Perform standard charge and discharge cycles on multiple battery cells of the same specifications while applying a sinusoidal excitation current with a preset frequency and amplitude; During the cycle, the excitation current signal and response voltage signal are collected by the four-probe method, and the electrochemical impedance change curve of the battery cell is calculated; After the standard charge and discharge cycle, the battery cell is subjected to a charge and discharge cycle and thermal runaway is triggered, and the electrochemical impedance change curve during this process is recorded; Based on the calculation results and recording results of the electrochemical impedance change curve, a mapping relationship between electrochemical impedance data and thermal runaway precursors is established.

9. An electronic device comprising a memory and a processor, characterized in that: The memory is used to store a program that supports the processor to execute the lithium-ion battery thermal runaway warning method according to any one of claims 1 to 8, and the processor is configured to execute the program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the lithium-ion battery thermal runaway early warning method according to any one of claims 1 to 8 are executed.

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