Method, system, medium and equipment for detecting external insulation damage of square lithium ion battery

Abstract

The invention discloses a square lithium ion battery external insulation damage detection method, system, medium and equipment, and the method comprises the steps: carrying out the electrochemical impedance spectrum measurement of a square battery with an external insulation state to be detected, and obtaining an electrochemical impedance spectrum; building an equivalent circuit based on the electrochemical impedance spectrum to obtain each characterization electrical element parameter in the equivalent circuit; high-frequency insulation resistance and interface capacitance in the equivalent circuit are extracted, and the damage condition of the outer insulation film of the square lithium ion battery is detected through parameter differences.

Description

Technical Field

[0001] The present invention relates to the technical field of block lithium-ion battery detection, and in particular to a method, system, medium and equipment for detecting damage to the external insulation of a block lithium-ion battery. Background Art

[0002] With the rapid development of lithium-ion battery technology, its application areas and usage are rapidly expanding. Among numerous applications, block-shaped lithium-ion batteries are widely used in powering electric vehicles, energy storage systems in energy storage power stations, and a variety of other scenarios. Well-known domestic lithium-ion battery manufacturers, such as CATL, are seeing their battery production scale and capacity increase year by year. Currently, the most commonly used material for lithium-ion battery casings is aluminum, which maintains the same potential as the battery's positive electrode. Typically, a layer of PET insulating blue film is applied to the exterior of the aluminum casing to provide insulation. However, during the lithium-ion battery production process, various accidents, such as collisions, drops, and scratches, can damage the PET insulating blue film on the battery surface. Block-shaped lithium-ion batteries, in particular, are more susceptible to damage to the outer insulation layer due to their unique shape. Once the outer insulation layer is damaged, the lithium-ion battery may cause a series of safety issues during actual use, including but not limited to short circuits, leakage, and even fire or explosion in severe cases. Therefore, rigorous testing of the integrity of the outer insulation layer before lithium-ion batteries are officially shipped is crucial. Currently, battery manufacturers use relatively limited methods to inspect finished batteries before they ship, mostly relying on manual visual inspection. This method is not only inefficient but also susceptible to subjective operator judgment, which can affect the accuracy of test results. While conventional factory voltage withstand tests can help identify damage to the battery's external insulation layer to a certain extent, in order to further improve detection efficiency and accuracy, it is particularly important to research and develop a highly efficient detection method for external insulation damage in lithium-ion battery blocks. Such a method would have broad application prospects.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0004] The present invention provides a method, system, medium and equipment for detecting damage to the external insulation of a block lithium-ion battery. Electrochemical impedance spectroscopy is used to characterize the overall information of the lithium-ion battery. The method is not only simple and fast to measure, but also can perform non-destructive testing and accurately identify damage to the external insulation of the lithium-ion battery.

[0005] A method for detecting damage to the external insulation of a lithium-ion battery comprises:

[0006] Step S100: Perform electrochemical impedance spectroscopy measurement on the square battery with the external insulation state to be detected to obtain an electrochemical impedance spectrum;

[0007] Step S200: Build an equivalent circuit based on the electrochemical impedance spectrum to obtain the parameters of each electrical component in the equivalent circuit;

[0008] Step S300: Extract the high-frequency insulation resistance and interfacial capacitance in the equivalent circuit, and use the parameter differences to detect the damage condition of the external insulation film of the square lithium-ion battery.

[0009] In the described method for detecting external insulation damage of a square lithium-ion battery, the electrochemical impedance spectrum includes the real part of impedance, the negative imaginary part of impedance, the error of the real part of impedance, the error of the imaginary part of impedance, the impedance value, the phase angle value, and the frequency corresponding to each set of simulation data.

[0010] In the described method for detecting external insulation damage of a square lithium-ion battery, the electrical component parameters include a constant phase element CPE, and its impedance is

[0011]

[0012] where Z is the impedance value of the component; Y0 is the capacitance value per unit area; ω is the angular frequency of the signal; n is the capacitance dispersion effect coefficient, 0 < n < 1; j is the imaginary unit, j.

[0013] In the described method for detecting external insulation damage of a square lithium-ion battery, the test temperature of the electrochemical impedance spectrum of the square lithium-ion battery is room temperature 25°C.

[0014] In the described method for detecting external insulation damage of a square lithium-ion battery, the measurement frequency range of the electrochemical impedance spectrum is from 0.1 Hz to 10,000 Hz.

[0015] In the described method for detecting external insulation damage of a square lithium-ion battery, the SOC of the square lithium-ion battery is uniformly in the 100% fully charged state.

[0016] In the described method for detecting external insulation damage of a square lithium-ion battery, the high-frequency insulation resistance corresponds to the Rp1 parameter in the equivalent circuit, and the interfacial capacitance corresponds to the Y03 parameter. Among them, the Rp1 parameter decreases with the increase of the external insulation damage degree, and the Y03 parameter increases with the increase of the damage degree. The high-frequency insulation resistance is compared with the set lower limit threshold. If it is lower than the lower limit threshold and the interfacial capacitance is higher than the set upper limit, it is determined that the external insulation is damaged.

[0017] A system for implementing the described method includes:

[0018] A collection module that performs electrochemical impedance spectroscopy measurement on the square battery with the external insulation state to be detected to obtain an electrochemical impedance spectrum;

[0019] An extraction module is used to construct an equivalent circuit based on the electrochemical impedance spectroscopy to obtain parameters of each electrical component in the equivalent circuit;

[0020] The detection module extracts the high-frequency insulation resistance and interface capacitance in the equivalent circuit and uses the parameter difference to detect the damage of the outer insulating film of the block lithium-ion battery.

[0021] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0022] An electronic device, comprising:

[0023] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0024] When the processor executes the program, the method described is implemented.

[0025] Compared with the existing technology, the present invention has the following advantages: The present invention can efficiently, accurately and non-destructively detect damage to the outer insulation layer of a square lithium-ion battery, greatly improving the efficiency and accuracy of detection. Through the measurement and analysis of electrochemical impedance spectroscopy, the impedance changes caused by damage to the outer insulation layer can be accurately captured, thereby effectively identifying damaged batteries. In addition, the method uses a customized fixture to control the irrelevant impedance of the measurement circuit, further enhancing the accuracy and reliability of the detection. This invention not only provides lithium-ion battery manufacturers with an efficient factory inspection tool, but also provides a solid guarantee for the safe use of batteries, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are intended only to illustrate preferred embodiments and are not to be construed as limiting the present invention. It should be understood that the drawings described below are merely examples of the present invention, and that those skilled in the art will be able to derive other drawings from these drawings without inventive effort. Throughout the drawings, identical reference numerals are used to denote identical components.

[0027] In the attached figure:

[0028] Figure 1 1 is a flow chart of a method for detecting damage to the external insulation of a lithium-ion battery based on electrochemical impedance spectroscopy in one embodiment of the present invention;

[0029] Figure 2This is a typical electrochemical impedance spectrum of a square lithium-ion battery in an embodiment of the present invention in the low-frequency domain;

[0030] Figure 3 1 is a schematic diagram of a circuit structure of a conventional lithium-ion battery equivalent circuit fitting model used for comparison in one embodiment of the present invention;

[0031] Figure 4 1 is a schematic diagram showing the fitting effect of a conventional lithium-ion battery equivalent circuit fitting model used as a comparison in one embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the circuit structure of an improved high-frequency band model of an equivalent circuit fitting of a method for detecting external insulation damage of a block lithium-ion battery based on electrochemical impedance spectroscopy in one embodiment of the present invention;

[0033] Figure 6 Schematic diagram of the circuit structure fitting effect of the improved high-frequency band model of the equivalent circuit fitting of the method for detecting external insulation damage of a block lithium-ion battery based on electrochemical impedance spectroscopy in one embodiment of the present invention;

[0034] FIG7( a ) is a schematic diagram showing an overview of the full test frequency bands of the Nyquist plot of the impedance spectrum of a lithium-ion battery under different external insulation states (intact insulation, small side insulation damage, medium side insulation damage, large side insulation damage, and complete insulation stripping) provided by one embodiment of the present invention;

[0035] Figure 7(b) is a close-up diagram of the low-frequency band in Figure 7(a);

[0036] FIG8 (a) is a schematic diagram of the circuit structure of an equivalent circuit model after parameter annotation in one embodiment of the present invention;

[0037] FIG8( b ) is a graph showing the correlation between the parameters in FIG8( a ) and the external insulation state of the lithium-ion battery.

[0038] The present invention will be further explained below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0039] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0040] It should be noted that in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. The specification and claims do not distinguish components by the difference in nouns, but by the difference in the functions of the components. For example, the terms "comprising" or "including" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including but not limited to". The subsequent description in the specification is the preferred embodiment for implementing the present invention, but the description is for the purpose of the general principles of the specification and is not used to limit the scope of the present invention. The protection scope of the present invention shall be determined by the scope defined by the appended claims.

[0041] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific examples in conjunction with the drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

[0042] As Figure 1 shown in FIGS. 8(a) to 8(b), the method for detecting the outer insulation breakage of a square lithium-ion battery includes the following steps:

[0043] Step S100: Perform electrochemical impedance spectroscopy measurement on the square battery to be detected for the outer insulation state to obtain an electrochemical impedance spectrum;

[0044] Step S200: Build an equivalent circuit based on the electrochemical impedance spectrum to obtain the parameters of each electrical component in the equivalent circuit;

[0045] Step S300: Extract the high-frequency insulation resistance and interface capacitance in the equivalent circuit, and use the parameter differences to detect the breakage of the outer insulation film of the square lithium-ion battery.

[0046] In the preferred embodiment of the method for detecting the outer insulation breakage of a square lithium-ion battery, the electrochemical impedance spectrum includes the real part of the impedance, the negative imaginary part of the impedance, the error of the real part of the impedance, the error of the imaginary part of the impedance, the impedance value, the phase angle value, and the frequency corresponding to each set of simulation data. <000013​​​​​​​​​In a preferred embodiment of the method for detecting damage to the external insulation of a block lithium-ion battery, the electrochemical impedance spectroscopy test temperature of the block lithium-ion battery is room temperature, 25°C.

[0051] In a preferred embodiment of the method for detecting damage to the external insulation of a block lithium-ion battery, the electrochemical impedance spectroscopy measurement frequency range is 0.1 Hz to 10,000 Hz.

[0052] In a preferred embodiment of the method for detecting damage to the external insulation of a block lithium-ion battery, the SOC of the block lithium-ion batteries is uniformly 100% fully charged.

[0053] In a preferred embodiment of the method for detecting external insulation damage of a block lithium-ion battery, the high-frequency insulation resistance corresponds to the Rp1 parameter in the equivalent circuit, and the interface capacitance corresponds to the Y03 parameter, wherein the Rp1 parameter decreases as the degree of external insulation damage increases, and the Y03 parameter increases as the degree of damage increases. The high-frequency insulation resistance is compared with a set lower limit threshold. If it is lower than the lower limit threshold and the interface capacitance is higher than the set upper limit, it is determined that the external insulation is damaged.

[0054] A system for implementing the method includes:

[0055] An acquisition module is used to measure the electrochemical impedance spectrum of the square battery whose external insulation state is to be detected to obtain the electrochemical impedance spectrum;

[0056] An extraction module is used to construct an equivalent circuit based on the electrochemical impedance spectroscopy to obtain parameters of each electrical component in the equivalent circuit;

[0057] The detection module extracts the high-frequency insulation resistance and interface capacitance in the equivalent circuit and uses the parameter difference to detect the damage of the outer insulating film of the block lithium-ion battery.

[0058] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0059] An electronic device, comprising:

[0060] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0061] When the processor executes the program, the method described is implemented.

[0062] In one embodiment, a method for detecting external insulation damage of a lithium-ion battery based on electrochemical impedance spectroscopy includes:

[0063] Step S100: performing electrochemical impedance spectroscopy measurement on the square battery whose external insulation status is to be tested;

[0064] Step S200: Based on the electrochemical impedance spectrum measured in Step S100, construct an equivalent circuit to obtain the parameters of each electrical component in the equivalent circuit.

[0065] Step S300: Extract the high-frequency insulation resistance (Rins) and interface capacitance (Cinterface), which are the core components describing the state of the insulating blue film outside the aluminum shell, in the equivalent circuit model, and use the parameter differences to detect the damage of the external insulating film of the prismatic lithium-ion battery.

[0066] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, the collected electrochemical impedance spectrum data includes the real part of impedance, the negative imaginary part of impedance, the error of the real part of impedance, the error of the imaginary part of impedance, the impedance value, the phase angle value, and the frequency corresponding to each set of simulation data. In addition, the equivalent circuit data includes the parameters of all electrical components after constructing the equivalent circuit.

[0067] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, the electrical components include a constant phase element CPE. The impedance expression of CPE is as follows:

[0068]

[0069] where Z is the impedance value of the component; Y0 is the capacitance value per unit area; ω is the angular frequency of the signal; n is the capacitance dispersion effect coefficient, 0 < n < 1; j is the imaginary unit, j.

[0070] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, the test temperature of the electrochemical impedance spectrum of the prismatic lithium-ion battery is room temperature 25°C.

[0071] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, the SOC of the prismatic lithium-ion battery is uniformly 100% (fully charged state) to avoid the influence of SOC on the impedance spectrum data.

[0072] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, threshold judgment and recognition are mainly carried out for the high-frequency insulation resistance (Rins) and interface capacitance (Cinterface) in combination with an algorithm.

[0073] In the method for detecting external insulation damage of a prismatic lithium-ion battery based on electrochemical impedance spectroscopy, due to the existence of stray impedance between the measurement loop and the ground and between each other, the present invention develops a customized fixture for measuring lithium-ion batteries to control the irrelevant impedance of the measurement loop to remain unchanged, highlighting the impedance change caused by the external insulation damage of the prismatic lithium-ion battery.

[0074] The present disclosure uses electrochemical impedance spectroscopy to characterize the overall information of lithium-ion batteries. Not only is the measurement simple and fast, it can also perform non-destructive testing and accurately identify external insulation damage of lithium-ion batteries.

[0075] In one embodiment, under actual testing conditions, parameters such as temperature, the battery's state of charge (SOC), and state of health (SOH) will affect the battery's internal structure and charge transfer efficiency, thereby affecting the results of the electrochemical impedance spectroscopy test. In the actual application scenario of external insulation testing of square lithium-ion batteries, the test object is a brand-new lithium battery with a constant state of health (SOH) of 100%. At the same time, it can be stipulated that the battery to be tested must be fully charged (SOC of 100%) before the external insulation testing process. Therefore, in the initial experiments, it is only necessary to control the measurement temperature to room temperature of 25°C and the SOC of the battery to be tested to 100% to ensure the authenticity of the experimentally measured electrochemical impedance spectroscopy data. This embodiment conducted electrochemical impedance spectroscopy tests on square lithium-ion batteries at 25°C, 100% SOC, and 100% SOH. The test results are shown in Table 1.

[0076] Table 1 Electrochemical impedance spectroscopy test data of parallel lithium batteries

[0077]

[0078] The table above shows the electrochemical impedance spectroscopy test results of a lithium-ion battery in the 0.1Hz-10000Hz frequency domain. The accuracy of the test results can be determined based on the errors in the real and imaginary impedance parts.

[0079] In another embodiment, a Nyquist graph can be drawn for a square lithium-ion battery based on the electrochemical impedance spectroscopy data, and then an equivalent circuit can be constructed. The horizontal axis of the Nyquist graph is the real part of the battery impedance, and the vertical axis is the negative imaginary part of the battery impedance. A typical image of a lithium-ion battery in the low-frequency domain is as follows: Figure 2 shown.

[0080] In this embodiment, when constructing an equivalent circuit model, the Randles equivalent circuit principle is generally followed. When analyzing the electrochemical impedance spectrum of a lithium-ion battery, circuit elements such as inductance, resistance, and capacitance are used to equivalently depict various parts of the electrochemical impedance spectrum curve, which reflect the internal characteristics of the battery. By combining these equivalent elements, a comprehensive equivalent circuit is formed, which enables a clearer and quantitative observation of the kinetic behavior of the battery. When constructing an equivalent circuit model for an electrochemical impedance spectrum, the lumped parameter elements commonly used include inductance, resistance, and capacitance; while the distributed parameter elements mainly include the constant phase angle element CPE and Warburg impedance.

[0081] The conventional lithium-ion battery equivalent circuit fitting model is fitted from the low and medium frequency regions. The circuit structure is as follows: Figure 3 As shown in the figure, for the Nyquist diagram under external insulation damage conditions, the conventional model has a poor fitting effect in the high frequency region, see Figure 4 In this embodiment, the equivalent circuit fitting model of conventional lithium-ion batteries is optimized. The specific circuit form is shown in Figure 5 , the fitting effect is shown in Figure 6 . The optimized equivalent circuit model has a better fitting effect in the high-frequency region and can more accurately reflect the impedance changes caused by external insulation damage of square lithium-ion batteries. In addition, the model also takes into account the complex characteristics inside the battery, such as charge transfer resistance, double-layer capacitance, and diffusion impedance, thereby improving the accuracy and reliability of the model. In practical applications, by comparing the Nyquist plots and equivalent circuit models of normal batteries and batteries with damaged external insulation, the difference between the two can be intuitively observed. The shape of the Nyquist plot of a normal battery is regular, and the parameter values ​​in the equivalent circuit model are stable; while the shape of the Nyquist plot of a battery with damaged external insulation will show obvious changes, and some parameter values ​​in the equivalent circuit model will also fluctuate significantly. These differences provide a strong basis for accurately identifying the damage of the external insulation of lithium-ion batteries.

[0082] In another embodiment, a method for detecting damage to the external insulation of a lithium-ion battery block based on electrochemical impedance spectroscopy is described in principle.

[0083] In this example, lithium-ion battery cells were classified based on their external insulation conditions, including intact insulation, minor side damage, medium side damage, major side damage, and complete insulation stripping. The test temperature was maintained at 25°C, and the battery's SOC and SOH were 100%.

[0084] The electrochemical impedance spectroscopy test results are shown in Figures 7(a) and 7(b). Figure 7(a) provides an overview of the Nyquist plot for the impedance spectrum across the entire test frequency range, while Figure 7(b) provides a close-up of the mid- and low-frequency bands. Figures 7(a) and 7(b) show significant differences in the electrochemical impedance spectra under the influence of the single variable of different external insulation states for the cubic lithium-ion batteries, primarily in the slope of the high-frequency band and the semicircular radius of the mid-frequency band. By testing and analyzing the electrochemical impedance spectra of cubic lithium-ion batteries under different external insulation states, a corresponding relationship between the battery's external insulation state and the electrochemical impedance spectroscopy characteristics can be established. This relationship provides a theoretical basis for a method for detecting external insulation damage in cubic lithium-ion batteries based on electrochemical impedance spectroscopy. In practical applications, effective detection of external insulation damage in cubic lithium-ion batteries can be achieved by measuring the battery's electrochemical impedance spectrum and determining its characteristic parameters based on the battery's external insulation state.

[0085] To further clarify the characteristic parameters corresponding to the external insulation state of a lithium-ion battery in the lithium-ion battery equivalent circuit, in this embodiment, a parameter correlation analysis was performed using Origin software. The results are shown in Figures 8(a) and 8(b). Figure 8(a) labels each parameter on the equivalent circuit model, while Figure 8(b) shows the correlation between each parameter in the equivalent circuit model and the external insulation state of the lithium-ion battery. The darker the color or the closer the square number is to 1, the more sensitive the parameter is to changes in the external insulation state of the lithium-ion battery. As can be seen in Figure 8(b), the characteristic parameters Rp1 and L1 are inversely correlated with the external insulation state: the greater the insulation damage, the smaller the Rp1 and L1 values; while Y03 is positively correlated with the external insulation state: the greater the insulation damage, the larger the Y03 value.

[0086] According to theoretical derivation, R ins (High-frequency insulation resistance) indicates the ability of the lithium-ion battery's insulating blue film to block current. When the blue film is intact, the aluminum shell and the external environment (such as metal brackets or humid air) are in a high-resistance insulation state; if the blue film is damaged, the aluminum shell forms a conductive path with the outside world through the damaged point, resulting in R ins Significantly decreased. interface Interfacial capacitance reflects the polarization behavior at the interface between the blue film and the aluminum shell. When the blue film is damaged or peeled off, electrolyte or moisture penetrates the interface, increasing the effective contact area and the capacitance.

[0087] Combining theoretical derivation with experimental correlation analysis, it can be concluded that the Rp1 parameter in the equivalent circuit model is strongly correlated with Rins (high-frequency insulation resistance), and the Y03 parameter is strongly correlated with C interface (Interface capacitance) is strongly correlated. Therefore, by monitoring changes in the Rp1 and Y03 parameters, changes in the external insulation state of the block lithium-ion battery can be indirectly assessed. In actual operation, when a significant decrease in the Rp1 value is detected while a significant increase in the Y03 value is observed, it may indicate damage to the battery's external insulation layer, laying the foundation for subsequent data-driven methods to detect the external insulation state of block lithium-ion batteries.

[0088] A method system for detecting inconsistency of parallel lithium battery modules based on impedance analysis includes:

[0089] Obtain the module, measure and obtain the electrochemical impedance spectrum of the lithium-ion battery module to be tested;

[0090] An extraction module, connected to the acquisition unit, extracts the simulation data of the lithium-ion battery to be tested and the equivalent circuit model data based on the electrochemical impedance spectroscopy;

[0091] The detection module is connected to the advance unit. The detection unit will use the two important parameters Rp1 and Y03 of the equivalent circuit to determine the damage of the external insulation of the block lithium-ion battery, so as to realize the damage detection of the external insulation blue film of the block lithium-ion battery to be tested.

[0092] In a preferred embodiment of the system, the extraction unit includes an equivalent construction unit for constructing an equivalent circuit. In a preferred embodiment of the system, a custom measurement fixture for securing the lithium-ion battery is also included. The fixture is designed to shield against external stray impedance, ensuring that the measurement circuit reflects only the impedance changes of the battery itself caused by external insulation damage.

[0093] In one embodiment, a method for detecting external insulation damage of a lithium-ion battery based on electrochemical impedance spectroscopy includes the following steps:

[0094] S100: Under the conditions of controlling the battery state of charge to be fully charged and the ambient temperature to be room temperature (25°C), electrochemical impedance spectroscopy (EIS) was performed on a square lithium-ion battery with an aluminum shell covered with a PET insulating blue film to obtain the real and imaginary impedance information, as well as the phase angle and frequency.

[0095] In this step, we selected the lithium-ion battery samples to be tested, setting their SOC (State of Charge) to 100%, indicating a fully charged state, and their SOH (State of Health) to 100%. The test temperature was controlled at 25°C to ensure consistent experimental conditions. Electrochemical impedance spectroscopy (EIS) measurements were performed on the lithium-ion battery using an electrochemical workstation, with a measurement frequency range of 0.1 Hz to 10,000 Hz.

[0096] The data collected includes:

[0097] Real part of impedance Z′;

[0098] Negative imaginary part of impedance -Z′′;

[0099] Impedance real part error;

[0100] Impedance imaginary part error;

[0101] Impedance value |Z|;

[0102] Phase angle value;

[0103] The frequency corresponding to each set of data.

[0104] In addition, a customized fixture was used for measurement during the test to shield the influence of external stray impedance, so that the impedance change in the measurement loop only reflects the effect caused by the damage of the outer insulation layer of the square lithium-ion battery.

[0105] S200: Based on the measured electrochemical impedance spectroscopy data, an equivalent circuit model is established, wherein the equivalent circuit model at least includes a high-frequency insulation resistance (R ins ) and interface capacitance (C interface );

[0106] Based on the electrochemical impedance spectroscopy data obtained by S100, a Nyquist plot is drawn, with the horizontal axis representing the real impedance part, Z′, and the vertical axis representing the negative imaginary impedance part, -Z′′. An equivalent circuit model is constructed through fitting to explain and quantify the electrochemical behavior within the battery.

[0107] The equivalent circuit model of conventional lithium-ion batteries is fitted from the low and medium frequency regions, such as Figure 3 However, its fitting effect in the high frequency region is poor, as shown in Figure 4 To this end, this embodiment optimizes the conventional model and proposes an improved equivalent circuit model suitable for high frequency bands, as shown in Figure 5 As shown, the fitting effect is better, as Figure 6 shown.

[0108] The equivalent circuit model contains multiple electrical components, including:

[0109] High frequency insulation resistance R ins Characterize the ability of the PET insulating blue film on the outside of the battery aluminum shell to hinder current;

[0110] Interface capacitance C interface Reflects the interfacial polarization behavior between the blue film and the aluminum shell;

[0111] The constant phase element CPE is used to replace the ideal capacitor to describe the interface diffusion effect. Its expression is as follows:

[0112] in:

[0113] Z: component impedance value;

[0114] Y0: capacitance per unit area;

[0115] ω: angular frequency;

[0116] n: diffusion coefficient, 0 <n<10<n<1;

[0117] j: imaginary unit.

[0118] S300: Extract the high-frequency insulation resistance (R ins ) and interface capacitance (C interface ), combined with the preset threshold or change trend, it is determined whether the outer insulating blue film of the block lithium-ion battery is damaged.

[0119] According to the theoretical deduction and experimental correlation analysis, R ins and C interface There are two parameters that are highly sensitive to the external insulation status:

[0120] When the blue film is intact, the aluminum shell is in a high-resistance insulation state with the external environment. ins Higher value;

[0121] If the blue film is damaged, the aluminum shell forms a conductive path with the outside world through the damaged point, resulting in R ins Significant decrease;

[0122] At the same time, as the electrolyte or moisture penetrates into the interface between the blue film and the aluminum shell, the effective contact area increases, and C interface The value increases.

[0123] Furthermore, by classifying and testing block lithium-ion batteries under different external insulation conditions (such as intact insulation, small side insulation damage, medium side insulation damage, large side insulation damage, and complete insulation stripping), and using Origin software to perform parameter correlation analysis, the results are shown in Figures 8(a) and 8(b):

[0124] R p1 Parameters and R ins Strong correlation;

[0125] Y 03 Parameters and C interface Strong correlation;

[0126] R p1 It decreases as the degree of external insulation damage increases;

[0127] Y 03 It increases with the degree of damage.

[0128] Therefore, in the actual detection process, when R p1 The value decreases significantly and Y 03 When the value increases significantly, it can be determined that the outer insulation layer of the battery is damaged, thereby achieving accurate identification of the outer insulation status of the battery.

[0129] Example 2: Comparative Experiment of Electrochemical Impedance Spectroscopy under Different External Insulation States

[0130] In order to verify the effectiveness of the above detection method, this embodiment selected five square lithium-ion battery samples with different external insulation states for testing, namely:

[0131] Insulation is intact;

[0132] Insulation damage on small side;

[0133] Insulation damage in the side;

[0134] Damaged large side;

[0135] Insulation stripped completely.

[0136] All batteries meet the following requirements:

[0137] The test temperature is 25℃;

[0138] SOC is 100%;

[0139] SOH is 100%.

[0140] The electrochemical impedance spectroscopy test results are shown in Figure 7(a) and Figure 7(b):

[0141] Figure 7 (a) shows an overview of the Nyquist plot for the full test frequency band (0.1 Hz to 10,000 Hz);

[0142] Figure 7 (b) is a close-up of the mid- and low-frequency bands.

[0143] As can be seen from the figure, the electrochemical impedance spectroscopy shows obvious differences under different external insulation states:

[0144] In the high frequency band, the slope changes significantly;

[0145] The radius of the semicircular arc in the mid-frequency band decreases as the degree of damage increases.

[0146] These differences indicate that electrochemical impedance spectroscopy can accurately reflect changes in the external insulation state, providing a theoretical basis for subsequent automated detection based on impedance characteristic parameters.

[0147] This example uses electrochemical impedance spectroscopy (EIS) technology to construct an equivalent circuit model suitable for detecting external insulation damage in lithium-ion batteries, and extracts two key parameters: high-frequency insulation resistance (R ins ) and interface capacitance (C interface By analyzing the variations in these two parameters under different external insulation conditions, the system achieves nondestructive, rapid, and quantitative detection of damage to the battery's external insulation layer. Non-contact measurement avoids damage to the battery; rapid detection makes it suitable for large-scale production lines; quantifiable parameter changes facilitate automatic algorithm identification and judgment; and customized fixture design effectively eliminates external interference, improving detection accuracy.

[0148] The present invention performs measurements under the conditions of controlling the battery state of charge to be fully charged and the ambient temperature to be room temperature (25°C). Ensure that all test samples are under the same charge and temperature conditions, thereby eliminating the influence of these variables on the electrochemical impedance spectroscopy results and improving the accuracy and comparability of the data. Use a customized fixture to shield the influence of external stray impedance. Reduce the interference of external factors in the measurement process of the block lithium-ion battery, so that the measured data can more truly reflect the characteristics of the battery itself, especially the state of its outer insulation layer. Based on the measured data, a high-frequency insulation resistance (R ins ) and interface capacitance (C interface ) and optimized for high frequency bands. By building an accurate equivalent circuit model to simulate the electrochemical behavior inside the battery, especially the response characteristics in the high frequency band, it is possible to more accurately identify the changes caused by the damage of the external insulating blue film. Extract the high frequency insulation resistance (R ins ) and interface capacitance (C interface ), combined with the preset threshold or change trend, determine whether the battery's external insulating blue film is damaged.

[0149] By analyzing key parameters, the status of the battery's external insulation layer can be quantitatively evaluated, enabling rapid and non-destructive detection of battery external insulation damage, while also improving the objectivity and reliability of the test results.

[0150] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and are not restrictive. A person skilled in the art, guided by this specification and without departing from the scope of protection of the claims of the present invention, may also devise various forms, all of which fall within the scope of protection of the present invention.

Claims

1. A method for detecting damage to the external insulation of a lithium-ion battery, characterized in that: It includes the following steps: Step S100: Perform electrochemical impedance spectroscopy measurement on the square battery with the external insulation state to be detected to obtain the electrochemical impedance spectrum; Step S200: Build an equivalent circuit based on the electrochemical impedance spectrum to obtain the parameters of each electrical component in the equivalent circuit; Step S300: Extract the high-frequency insulation resistance and interface capacitance in the equivalent circuit, and use the parameter differences to detect the damage condition of the external insulation film of the square lithium-ion battery.

2. A method for detecting external insulation damage of a lithium-ion battery according to claim 1, characterized in that: Preferably, the electrochemical impedance spectrum includes the real part of impedance, the negative imaginary part of impedance, the error of the real part of impedance, the error of the imaginary part of impedance, the impedance value, the phase angle value, and the frequency corresponding to each group of simulation data.

3. The method for detecting external insulation damage of a lithium-ion battery according to claim 1, wherein: The parameters of the electrical component include the constant phase element CPE, and its impedance is ； where Z is the impedance value of the component; Y0 is the capacitance value per unit area; ω is the angular frequency of the signal; n is the capacitance dispersion effect coefficient, 0 < n < 1; j is the imaginary unit, j.

4. The method for detecting external insulation damage of a lithium-ion battery according to claim 1, wherein: The test temperature of the electrochemical impedance spectrum of the square lithium-ion battery is room temperature 25°C.

5. The method for detecting external insulation damage of a lithium-ion battery according to claim 1, wherein: The measurement frequency range of the electrochemical impedance spectrum is 0.1 Hz to 10,000 Hz.

6. The method for detecting external insulation damage of a lithium-ion battery according to claim 1, wherein: The SOC of the square lithium-ion battery is uniformly in the 100% fully charged state.

7. The method for detecting external insulation damage of a lithium-ion battery according to claim 1, wherein: The high-frequency insulation resistance corresponds to the Rp1 parameter in the equivalent circuit, and the interface capacitance corresponds to the Y03 parameter. Among them, the Rp1 parameter decreases with the increase of the external insulation damage degree, and the Y03 parameter increases with the increase of the damage degree. The high-frequency insulation resistance is compared with the set lower limit threshold. If it is lower than the lower limit threshold and the interface capacitance is higher than the set upper limit, it is determined that the external insulation is damaged.

8. A system for implementing the method according to any one of claims 1 to 7, characterized in that: It includes: A collection module that performs electrochemical impedance spectroscopy measurement on the square battery with the external insulation state to be detected to obtain the electrochemical impedance spectrum; An extraction module that builds an equivalent circuit based on the electrochemical impedance spectrum to obtain the parameters of each electrical component in the equivalent circuit; A detection module that extracts the high-frequency insulation resistance and interface capacitance in the equivalent circuit, and uses the parameter differences to detect the damage condition of the external insulation film of the square lithium-ion battery.

9. A computer storage medium, characterized in that The storage medium includes computer instructions, which when running on a computer, cause the computer to execute the method according to any one of claims 1-7.

10. An electronic device, characterized in that: The electronic device includes: A memory, a processor, and a computer program stored on the memory and executable on the processor. Among them, When the processor executes the program, it implements the method according to any one of claims 1-7.

Images