Electrochemical impedance spectroscopy data processing method, device and equipment and storage medium

Abstract

The invention provides an electrochemical impedance spectroscopy data processing method and device, equipment and a storage medium. The method comprises the following steps: automatically determining a first electrochemical impedance spectroscopy measurement data set conforming to a high-frequency equivalent circuit model of an electrochemical system and a second electrochemical impedance spectroscopy measurement data set conforming to a low-frequency equivalent circuit model of the electrochemical system from electrochemical impedance spectroscopy measurement data; and performing fitting calculation according to the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function, and performing linear fitting according to the impedance real part and the impedance imaginary part in the second electrochemical impedance spectroscopy measurement data set to obtain the diffusion slope of the electrochemical system. Automatic measurement of each equivalent element of the electrochemical system is realized, the complexity of manual operation is reduced, and an operator does not need to have rich electrochemical knowledge and experience.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical alternating current impedance spectroscopy, and in particular to an electrochemical impedance spectroscopy data processing method, device, equipment and storage medium. Background Art

[0002] EIS (Electrochemical Impedance Spectroscopy) is an electrochemical characterization method that analyzes and studies the surface behavior of the system, such as the electrode kinetic process, by measuring the change in the impedance of the target system with a given sinusoidal wave frequency.

[0003] The AC impedance method belongs to transient electrochemical technology, which is used to analyze the reaction mechanism of the electrochemical system and calculate the relevant parameters of the system. This method controls the current (or potential of the system) of the electrochemical system to change sinusoidally over time under small amplitude conditions, and measures the change of the corresponding system potential (or current) over time, or directly measures the AC impedance (or admittance) of the system. In this way, the physical properties of the interface and the electrochemical reactions that occur, such as the mode of electrode reaction, diffusion coefficient, exchange current density, etc., can be understood. Therefore, it has a wide range of applications in actual scientific research. At present, AC impedance technology is widely used, such as studying the electrode reaction process, metal corrosion mechanism and corrosion resistance, corrosion inhibitor performance evaluation in the field of electrochemistry; studying the performance of biofilms in the field of biology; studying the performance of electronic components and conductive materials in the field of physics; studying the mechanical properties of materials in materials science and the performance evaluation after surface modification. However, electrochemical impedance spectroscopy is essentially a black-box dynamic system. The large amount of impedance data measured by it cannot intuitively reflect the content we need to study. We need to measure the AC impedance of the object to be measured at different frequencies and analyze the characteristics of the object to be measured through a certain frequency range. Therefore, how to combine the AC impedance method to process the impedance spectrum data and realize fast fitting of the electrochemical impedance spectrum data to obtain the estimation of each equivalent component of the electrochemical system has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an electrochemical impedance spectroscopy data processing method, device, equipment and storage medium to solve the above-mentioned technical problems.

[0005] In one aspect, a method for processing electrochemical impedance spectroscopy data is provided, comprising:

[0006] Acquire multiple sets of electrochemical impedance spectroscopy measurement data of the electrochemical system; each set of the electrochemical impedance spectroscopy measurement data includes the frequency of the disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency;

[0007] Determining a first electrochemical impedance spectroscopy measurement data set conforming to a high-frequency equivalent circuit model of the electrochemical system and a second electrochemical impedance spectroscopy measurement data set conforming to a low-frequency equivalent circuit model of the electrochemical system from the electrochemical impedance spectroscopy measurement data; the high-frequency equivalent circuit model includes Rct and CdI connected in parallel, and Rs connected in series with the Rct and the CdI, wherein the Rs represents an ohmic impedance of an electrolyte of the electrochemical system, the Rct represents a charge transfer impedance at an interface of an active material of the electrochemical system, and the CdI represents an equivalent capacitance of charges on an electrode of the electrochemical system;

[0008] Performing a fitting calculation based on the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function; the first model function is a function established according to the high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include the ohmic impedance Rs, the charge transfer impedance Rct and the equivalent capacitance CdI;

[0009] A linear fit is performed based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectroscopy measurement data set to obtain a diffusion slope of the electrochemical system.

[0010] In the above embodiment, a fitting calculation is performed based on the first electrochemical impedance spectrum measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function, and a linear fitting is performed based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set to obtain the diffusion slope of the electrochemical system, thereby realizing the automatic measurement of each equivalent element of the electrochemical system, reducing the complexity of manual operation, and not requiring the operator to have rich electrochemical knowledge and experience.

[0011] In one embodiment, determining a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system and a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system from the electrochemical impedance spectroscopy measurement data comprises:

[0012] Calculating the gradient value of each group of electrochemical impedance spectroscopy measurement data;

[0013] Determining a frequency dividing point between a high frequency range and a low frequency range of the disturbance signal applied to the electrochemical system according to the gradient value;

[0014] The electrochemical impedance spectroscopy measurement data with a frequency greater than or equal to the frequency dividing point is used as data in a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and the electrochemical impedance spectroscopy measurement data with a frequency less than the frequency dividing point is used as data in a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system.

[0015] In the above embodiment, the frequency dividing point of the high frequency range and the low frequency range is determined by the gradient value of each group of electrochemical impedance spectroscopy measurement data, so as to clarify the specific frequency range of the high frequency band and the low frequency band, thereby ensuring the accuracy of the high frequency partition and the low frequency partition.

[0016] In one embodiment, calculating the gradient value of each group of electrochemical impedance spectroscopy measurement data includes:

[0017] According to the formula Calculate the gradient value of each group of electrochemical impedance spectroscopy measurement data; wherein, del n represents the gradient value of the electrochemical impedance spectroscopy measurement data of the nth group, Zi n+1 He Zi n-1 Respectively represent the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n+1th group and the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n-1th group, Zr n+1 and Zr n-1 respectively represent the real impedance part of the electrochemical impedance spectroscopy measurement data of the n+1th group and the real impedance part of the electrochemical impedance spectroscopy measurement data of the n-1th group;

[0018] The step of determining the frequency demarcation point between the high frequency range and the low frequency range of the disturbance signal applied to the electrochemical system according to the gradient value comprises:

[0019] The frequency in the electrochemical impedance spectrum measurement data corresponding to the inflection point where the gradient value changes from a negative value to a positive value is used as a frequency dividing point between a high frequency range and a low frequency range of the disturbance signal applied to the electrochemical system.

[0020] In the above embodiment, for each set of electrochemical impedance spectroscopy measurement data, the gradient value of the corresponding electrochemical impedance spectroscopy measurement data is calculated according to the real part and imaginary part of the impedance of the electrochemical impedance spectroscopy measurement data adjacent to the set of electrochemical impedance spectroscopy measurement data, thereby improving the accuracy of the calculation result.

[0021] In one embodiment, performing fitting calculation based on the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function includes:

[0022] Substituting the frequency in the first electrochemical impedance spectroscopy measurement data set into a first model function for calculation, and returning an equivalent impedance of the electrochemical system;

[0023] Based on the first electrochemical impedance spectroscopy measurement data set, the first model function is fitted with the least square method of the frequency and the equivalent impedance to obtain the optimal parameter value of each first model parameter in the first model function.

[0024] In the above implementation, the optimal parameter value of the first model parameter in the first model function is calculated by least square fitting, and the calculation speed is fast.

[0025] In one embodiment, after performing fitting calculation according to the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function, the method includes:

[0026] Substituting the optimal parameter value of the first model parameter into the first model function to obtain a first target model function;

[0027] Substituting each of the frequencies in the first electrochemical impedance spectroscopy measurement data set into the first target model function to obtain a fitting equivalent impedance corresponding to each of the electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set;

[0028] According to the formula Calculate the first goodness of fit of the first target model function; wherein R1 2 represents the first goodness of fit, y 1i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the first electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set;

[0029] The degree of fit of the first target model function is evaluated according to the first goodness of fit.

[0030] In the above implementation, the evaluation of the fitting degree of the first target model function is achieved through the first goodness of fit.

[0031] In one embodiment, the low-frequency equivalent circuit model includes the ohmic impedance Rs, the charge transfer impedance Rct and the diffusion impedance Zw of the electrochemical system during the diffusion process connected in series; the method further includes:

[0032] Substituting each of the frequencies in the second electrochemical impedance spectroscopy measurement data set into a second target model function to obtain a fitted equivalent impedance corresponding to each of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set; the second target model function is a function obtained by substituting the optimal parameter value of the ohmic impedance Rs and the optimal parameter value of the charge transfer impedance Rct into the second model function, and the second model function is a function established according to the low-frequency equivalent circuit model;

[0033] According to the formula Calculate the second goodness of fit of the second target model function; wherein R2 2 represents the second goodness of fit, y 2i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the second electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set;

[0034] The degree of fit of the second target model function is evaluated according to the second goodness of fit.

[0035] In the above implementation, the evaluation of the fitting degree of the second target model function is achieved through the second goodness of fit.

[0036] In one embodiment, the method further comprises:

[0037] The actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the first electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the first electrochemical impedance spectrum measurement data set are plotted in a first target coordinate system, and the actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the second electrochemical impedance spectrum measurement data set are plotted in a second target coordinate system; the first target coordinate system and the second target coordinate system are coordinate systems established with the real part of the impedance as the horizontal axis and the imaginary part of the impedance as the vertical axis.

[0038] In the above embodiment, the original data and the fitting data are presented simultaneously, which clearly and reliably reflects the characteristic electrochemical process.

[0039] In another aspect, an electrochemical impedance spectroscopy data processing device is provided, comprising:

[0040] An acquisition module, used for acquiring multiple groups of electrochemical impedance spectrum measurement data of the electrochemical system; each group of the electrochemical impedance spectrum measurement data includes the frequency of the disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency;

[0041] a determination module, configured to determine, from the electrochemical impedance spectroscopy measurement data, a first electrochemical impedance spectroscopy measurement data set conforming to a high-frequency equivalent circuit model of the electrochemical system, and a second electrochemical impedance spectroscopy measurement data set conforming to a low-frequency equivalent circuit model of the electrochemical system; the high-frequency equivalent circuit model comprises Rct and CdI connected in parallel, and Rs connected in series with the Rct and the CdI, wherein the Rs represents an ohmic impedance of an electrolyte of the electrochemical system, the Rct represents a charge transfer impedance at an interface of an active material of the electrochemical system, and the CdI represents an equivalent capacitance of charges on an electrode of the electrochemical system;

[0042] A first fitting module is used to perform fitting calculation according to the first electrochemical impedance spectrum measurement data set and a first model function to obtain the optimal parameter value of each first model parameter in the first model function; the first model function is a function established according to the high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include the ohmic impedance Rs, the charge transfer impedance Rct and the equivalent capacitance CdI;

[0043] The second fitting module is used to perform linear fitting based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set to obtain the diffusion slope of the electrochemical system.

[0044] On the other hand, an electronic device is provided, including a processor and a memory, wherein a computer program is stored in the memory, and the processor executes the computer program to implement any one of the above methods.

[0045] On the other hand, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by at least one processor, any one of the above methods is implemented.

[0046] The electrochemical impedance spectrum data processing method, device, equipment and storage medium provided in the present application automatically determine a first electrochemical impedance spectrum measurement data set that conforms to the high-frequency equivalent circuit model of the electrochemical system and a second electrochemical impedance spectrum measurement data set that conforms to the low-frequency equivalent circuit model of the electrochemical system from the electrochemical impedance spectrum measurement data, perform fitting calculations based on the first electrochemical impedance spectrum measurement data set and the first model function to obtain the optimal parameter values ​​of each first model parameter in the first model function, perform linear fitting based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set to obtain the diffusion slope of the electrochemical system, thereby realizing automatic measurement of each equivalent element of the electrochemical system, reducing the complexity of manual operation, and not requiring the operator to have rich electrochemical knowledge and experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of the process of the electrochemical impedance spectroscopy data processing method provided in Example 1 of the present application;

[0048] Figure 2 A schematic diagram of an equivalent circuit model of an electrochemical system provided in Example 1 of the present application;

[0049] Figure 3 A schematic diagram of a high-frequency equivalent circuit model of an electrochemical system provided in Example 1 of the present application;

[0050] Figure 4 A schematic diagram of a low-frequency equivalent circuit model of an electrochemical system provided in Example 1 of the present application;

[0051] Figure 5 A first fitting curve diagram provided in Example 1 of the present application;

[0052] Figure 6 A second fitting curve diagram provided in Example 1 of the present application;

[0053] Figure 7 A third fitting curve diagram provided in Example 1 of the present application;

[0054] Figure 8 The Rs and Rct bar graphs of the electrochemical system provided in Example 1 of the present application;

[0055] Fig. 9 A schematic diagram of the structure of an electrochemical impedance spectroscopy data processing device provided in Example 2 of the present application;

[0056] Fig.10 This is a schematic diagram of the structure of an electronic device provided in Example 3 of the present application. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] Embodiment 1:

[0059] At present, the electrochemical impedance spectroscopy measurement data can be processed by AC impedance fitting software. The most commonly used processing software is ZView developed by Derek Johnson. The use of this software requires users to import the data to be processed and process the image according to their needs by setting parameters. When fitting the data, first select the appropriate data segment to obtain the initial value, and then establish an equivalent circuit according to the system for simulation and fitting. In this method, the electrochemical system is considered to be an equivalent circuit, which consists of basic components connected in series or in parallel, such as resistors (R), capacitors (C) and constant phase elements (CPE). After obtaining the best estimate of each component, the absolute error and relative error of each component are analyzed and the data is finally exported. The advantage of Zview in fitting electrochemical impedance spectra is that it is flexible in operation and can select a model suitable for the system according to one's own needs. However, manually establishing an equivalent circuit model requires rich electrochemical knowledge and experience, and the fitting results of different operating objects are quite different; and the overall process is relatively cumbersome, and the impedance results cannot be obtained quickly.

[0060] In view of this, the present application embodiment provides an electrochemical impedance spectroscopy data processing method to quickly fit the electrochemical impedance spectrum to obtain the estimated value of each component, see Figure 1 As shown, including:

[0061] S11: Acquire multiple sets of electrochemical impedance spectroscopy measurement data of the electrochemical system; each set of electrochemical impedance spectroscopy measurement data includes the frequency of the disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency.

[0062] S12: Determine, from the electrochemical impedance spectroscopy measurement data, a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system.

[0063] S13: Perform fitting calculation according to the first electrochemical impedance spectrum measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function. The first model function is a function established according to a high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include ohmic impedance Rs, charge transfer impedance Rct and equivalent capacitance CdI.

[0064] Specifically, define freq as the independent variable of the first model function, Rct, Cdl, and Rs as the first model parameters respectively, and return the expression Rct / (1+(1j*2*Π*freq)*Cdl*Rct)+Rs, calculate the optimal value array popt and parameter covariance pcov of the fit, and obtain the optimal solution that satisfies the model.

[0065] S14: performing linear fitting based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectroscopy measurement data set to obtain the diffusion slope of the electrochemical system.

[0066] The following is a detailed introduction to the contents of the above steps.

[0067] AC impedance is a vector that measures the resistance to AC current in a circuit. It has both magnitude and direction and can be represented by the capital letter "Z". Since it is a vector, it is divided into the real impedance Z' and the imaginary reactance Z", which can be expressed as: Z=Z'+Z".

[0068] In step S11 of the embodiment of the present application, a disturbance signal in a high-frequency range and a disturbance signal in a low-frequency range can be applied to the electrochemical system, wherein the disturbance signal can be an AC sinusoidal potential wave with a small amplitude and different frequencies. The real part and the imaginary part of the impedance of the electrochemical system are measured at each frequency, thereby obtaining multiple sets of electrochemical impedance spectroscopy measurement data.

[0069] In the embodiments of the present application, the high-frequency equivalent circuit model of the electrochemical system refers to the equivalent circuit model of the electrochemical system under a high-frequency disturbance signal, and the low-frequency equivalent circuit model refers to the equivalent circuit model of the electrochemical system under a low-frequency disturbance signal.

[0070] The electrochemical system in the embodiment of the present application can be a lithium-ion battery, such as a lithium-ion button battery. Of course, it can also be a mold battery, a soft-pack battery, a symmetrical battery, etc.

[0071] The equivalent circuit model of the electrochemical system is as follows: Figure 2 In the high frequency band, the time period of change is too short to allow material transfer to occur, that is, the effect of Warburg impedance (Zw) disappears. Therefore, the high frequency equivalent circuit model can be found in Figure 3 As shown, that is, the high-frequency equivalent circuit model includes Rct and CdI in parallel, and Rs in series with Rct and CdI, where Rs represents the ohmic impedance of the electrolyte of the electrochemical system, Rct represents the charge transfer impedance at the interface of the active material of the electrochemical system, and CdI represents the equivalent capacitance of the charge on the electrode of the electrochemical system. In the low-frequency band, Cdl can be regarded as an open circuit. Therefore, the low-frequency equivalent circuit model can be referred to Figure 4 As shown, that is, the low-frequency equivalent circuit model includes the ohmic impedance Rs, the charge transfer impedance Rct and the diffusion impedance Zw of the electrochemical system in the diffusion process connected in series.

[0072] The above step S12 may include the following sub-steps:

[0073] Sub-step 1: Calculate the gradient value of each group of electrochemical impedance spectroscopy measurement data.

[0074] Sub-step 2: Determine the frequency dividing point between the high frequency range and the low frequency range of the disturbance signal applied to the electrochemical system according to the gradient value.

[0075] Sub-step three: taking the electrochemical impedance spectroscopy measurement data having a frequency greater than or equal to the frequency dividing point as data in a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and taking the electrochemical impedance spectroscopy measurement data having a frequency less than the frequency dividing point as data in a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system.

[0076] In the above sub-step 1 of S12, the formula Calculate the gradient value of each group of electrochemical impedance spectroscopy measurement data; where del n represents the gradient value of the electrochemical impedance spectroscopy measurement data of the nth group, Zi n+1 He Zi n-1 Respectively represent the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n+1th group and the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n-1th group, Zr n+1 and Zr n-1 They respectively represent the real part of the impedance of the n+1th group of electrochemical impedance spectroscopy measurement data and the real part of the impedance of the n-1th group of electrochemical impedance spectroscopy measurement data.

[0077] Correspondingly, in the above sub-step 2 of S12, the frequency in the electrochemical impedance spectrum measurement data corresponding to the inflection point where the gradient value changes from negative to positive can be used as the frequency dividing point between the high frequency range and the low frequency range of the disturbance signal applied to the electrochemical system.

[0078] In the embodiment of the present application, the frequency dividing point of the high frequency range and the low frequency range is determined by the gradient value of each group of electrochemical impedance spectroscopy measurement data, so as to clarify the specific frequency range of the high frequency band and the low frequency band.

[0079] It should be noted that in the embodiment of the present application, the above steps can be implemented by a pre-written Python script. Of course, the above steps can also be implemented by scripts written in other languages.

[0080] Exemplarily, the frequency, the real part of the impedance, and the column number of the imaginary part of the impedance can be determined from the obtained electrochemical impedance spectrum measurement data and extracted and saved in the corresponding array for subsequent calls. In this example, the gradient values ​​of each group of electrochemical impedance spectrum measurement data can be traversed, and the complete data can be divided into two sets of data that conform to the high-frequency equivalent circuit model and the low-frequency equivalent circuit model. For example, the for in range method can be used to traverse the original test data, that is, the multiple groups of electrochemical impedance spectrum measurement data obtained in step S11, and then the gradient is calculated, and the selected function is used to filter the data to complete the grouping, and then the append function can be used to add the two sets of data to the new array for storage, so as to facilitate subsequent calls for fitting calculations.

[0081] Step S13 in the embodiment of the present application may specifically include the following sub-steps:

[0082] Sub-step 1: Substituting the frequency in the first electrochemical impedance spectroscopy measurement data set into the first model function for calculation, and returning the equivalent impedance of the electrochemical system.

[0083] Sub-step 2: Based on the first electrochemical impedance spectroscopy measurement data set, perform least squares fitting of the frequency and equivalent impedance on the first model function to obtain the optimal parameter value of each first model parameter in the first model function.

[0084] In an embodiment of the present application, the optimize.curve_fit function can be used to perform nonlinear least squares fitting on the original test data, find the optimal value array of fitting parameters popt and parameter covariance pcov, obtain the optimal curve, and assign the optimal value array, that is, the optimal parameter values ​​of Rct, Cdl and Rs to Rct, Cdl and Rs in the first model function respectively to obtain the first target model function.

[0085] It should be noted that, in the embodiment of the present application, the original frequency data in the first electrochemical impedance spectroscopy measurement data set can also be substituted into the obtained curve to obtain new fitted data points fit_Zr_rc and fit_Zi_rc, and the coefficient of determination is used to evaluate the fit between the new data points and the original data, that is, the first goodness of fit of the first target model function. Specifically, after step S13, the following steps can also be included:

[0086] Substituting the optimal parameter value of the first model parameter into the first model function to obtain a first target model function;

[0087] Substituting each frequency in the first electrochemical impedance spectroscopy measurement data set into the first target model function to obtain a fitting equivalent impedance corresponding to each electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set;

[0088] According to the formula Calculate the first goodness of fit of the first target model function; where R1 2 represents the first goodness of fit, y 1i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the first electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set;

[0089] The degree of fit of the first target model function is evaluated according to the first goodness of fit.

[0090] In this application example, the coefficient of determination R1 2 Measures the goodness of fit of the first objective model function, R1 2 The closer the value is to 1, the better the regression curve fits the observed value.

[0091] In step S14 of the embodiment of the present application, a linear fit can be performed based on the real part and the imaginary part of the impedance in the second electrochemical impedance spectroscopy measurement data set to obtain the slope of the fitting line, which is used as the diffusion slope of the electrochemical system.

[0092] After step S14 in the embodiment of the present application, the following steps may also be included:

[0093] Substitute each of the frequencies in the second electrochemical impedance spectroscopy measurement data set into the second target model function to obtain the fitted equivalent impedance corresponding to each of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set; the second target model function is a function obtained by substituting the optimal parameter value of the ohmic impedance Rs and the optimal parameter value of the charge transfer impedance Rct into the second model function, and the second model function is a function established according to the low-frequency equivalent circuit model. Specifically, define Zr_rw and Zi_rw as independent variables, slope a and intercept b as fitting parameters, and satisfy -b / a=R0, R0=Rs+Rct;

[0094] According to the formula Calculate the second goodness of fit of the second target model function; wherein R2 2 represents the second goodness of fit, y 2i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the second electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set;

[0095] The degree of fit of the second target model function is evaluated according to the second goodness of fit.

[0096] It can be understood that the independent variable of the second model function is the frequency of the disturbance signal applied to the electrochemical system, and the dependent variable of the second model function is the equivalent impedance of the electrochemical system. Therefore, the degree of fit of the linear fit in step S14 can also be evaluated through the second goodness of fit.

[0097] In this application example, the coefficient of determination R2 2 Measures the goodness of fit of a linear fit, R2 2 The closer the value is to 1, the better the linear equation fits the observed value.

[0098] It should be noted that in the embodiment of the present application, the actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the first electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the first electrochemical impedance spectrum measurement data set can also be plotted in the first target coordinate system, and the actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the second electrochemical impedance spectrum measurement data set can be plotted in the second target coordinate system; the first target coordinate system and the second target coordinate system are coordinate systems established with the real part of the impedance as the horizontal axis and the imaginary part of the impedance as the vertical axis.

[0099] Exemplarily, the drawing can be done in a partitioned manner, and the fitting image of the first target model function and the fitting image of the second target model function are respectively drawn on a 10*4 canvas. For example, the matplotlib module is used to draw the real part of the impedance as the horizontal axis and the imaginary part of the impedance as the vertical axis, and the original data is drawn into a scatter plot. The fitted data is drawn as a curve graph in the same coordinate system, and the fitting results and goodness of fit values ​​are added to the legend.

[0100] The following experimental examples are provided to verify the effectiveness of the electrochemical impedance spectroscopy data processing method provided in the embodiments of the present application.

[0101] Example 1:

[0102] Battery preparation:

[0103] The assembly of lithium-ion button cells is carried out in a glove box filled with argon gas, and the H2O and O2 contents in the glove box are both less than 0.1ppm. The specific battery composition is lithium metal anode, nickel cobalt manganese oxide (NCM), ternary cathode sheet, PP separator, 1M LiFSI electrolyte, and stainless steel button cell shell.

[0104] When assembling the battery, the lithium sheet used has a diameter of 16 mm and a thickness of 0.2 mm, the NCM ternary positive electrode sheet has a diameter of 12 mm, and the positive electrode material loading is 6 mg / cm 2 The diameter of the diaphragm is 18mm, the thickness is 8μm, the amount of LiFSI electrolyte is 5μL, and the specification of the button battery shell is 2032.

[0105] Electrochemical impedance spectroscopy:

[0106] The button cell prepared above was charged to 100% SOC, and an AC impedance spectrum test was performed with a frequency range of 0.01 to 1000000 Hz.

[0107] Fast data processing of AC impedance spectroscopy based on Python:

[0108] Step 1: Introduce Python open source numerical calculation, numerical analysis, and graphics drawing modules;

[0109] Step 2: Import the electrochemical impedance spectroscopy data of lithium-ion batteries, determine the column number of the frequency, real part of impedance, and imaginary part of impedance, and extract and save them into the corresponding array for subsequent program calls;

[0110] Step 3: Traverse the real part gradient of the impedance and divide the complete data into two sets of data that conform to the high-frequency equivalent circuit model and the low-frequency equivalent circuit model. Use the append function to add the two sets of data to a new array for storage;

[0111] Step 4: Establish a first model function according to the high-frequency equivalent circuit model, with frequency as the independent variable, charge transfer impedance Rct, double-layer capacitance Cdl, and ohmic impedance Rs as the first model parameters, and the analytical equation returns the equivalent impedance;

[0112] Step 5: Use the optimize.curve_fit function to perform nonlinear least squares fitting on the original data, find the optimal value array of fitting parameters popt and parameter covariance pcov, and obtain the optimal curve;

[0113] Step 6: Assign the optimal value array to Rct, Cdl and Rs respectively; substitute the original frequency data into the obtained curve to obtain the fitted new data points fit_Zr_rc and fit_Zi_rc, and use the coefficient of determination to evaluate the fit between the new data points and the original data, that is, to obtain the first goodness of fit mentioned above;

[0114] Step 7: Establish a second target model function according to the low-frequency equivalent circuit model, import the array that conforms to the low-frequency equivalent circuit model, and calculate the optimal parameter diffusion slope value using a linear fitting method;

[0115] Step 8: Use the coefficient of determination to evaluate the fit between the fitted data points and the original data, which is the second goodness of fit mentioned above;

[0116] Step 9: Draw the image in a partitioned manner. Draw the fitting image of the first target model function and the fitting image of the second target model function on a 10*4 canvas respectively. Use the real part of impedance as the horizontal axis and the imaginary part of impedance as the vertical axis. Draw the original data into a scatter plot. Draw the fitted data as a curve graph in the same coordinate system, and add the fitting results and goodness of fit values ​​in the legend.

[0117] Figure 5 This is the electrochemical AC impedance spectrum segmented fitting curve obtained in step 9 of Example 1. The left figure is the fitting result of the first target model function in the high-frequency range, showing ohmic impedance Rs: 3.41Ohms, double-layer capacitance Cdl: 4.22e-05F, charge transfer impedance Rct: 33.94Ohms, and the goodness of fit of the first target model function is 98.55%; the right figure is the fitting result of the second target model function in the low-frequency range, the diffusion process straight line slope slope: 10.96, and the goodness of fit of the second target model function is 99.05%.

[0118] Example 2:

[0119] Battery preparation:

[0120] The assembly of lithium-ion button cells is carried out in a glove box filled with argon gas, and the H2O and O2 contents in the glove box are both less than 0.1ppm. The specific battery composition is lithium metal anode, nickel cobalt manganese oxide (NCM), ternary cathode sheet, PP separator, 1M LiFSI electrolyte, and stainless steel button cell shell.

[0121] When assembling the battery, the lithium sheet used has a diameter of 16 mm and a thickness of 0.2 mm, the NCM ternary positive electrode sheet has a diameter of 12 mm, and the positive electrode material loading is 6 mg / cm 2 The diameter of the diaphragm is 18mm, the thickness is 8μm, the amount of LiFSI electrolyte is 5μL, and the specification of the button battery shell is 2032.

[0122] Electrochemical impedance spectroscopy:

[0123] The prepared button battery was charged to 100% SOC, and allowed to stand at room temperature for 45 days. The button battery after standing was subjected to an AC impedance spectrum test with a frequency range of 0.01 to 1000000 Hz.

[0124] Fast data processing of AC impedance spectroscopy based on Python:

[0125] Step 1: Introduce Python open source numerical calculation, numerical analysis, and graphics drawing modules;

[0126] Step 2: Import the electrochemical impedance spectroscopy data of lithium-ion batteries, determine the column number of the frequency, real part of impedance, and imaginary part of impedance, and extract and save them into the corresponding array for subsequent program calls;

[0127] Step 3: Traverse the real part gradient of the impedance and divide the complete data into two sets of data that conform to the high-frequency equivalent circuit model and the low-frequency equivalent circuit model. Use the append function to add the two sets of data to a new array for storage;

[0128] Step 4: Establish a first model function according to the high-frequency equivalent circuit model, with frequency as the independent variable, charge transfer impedance Rct, double-layer capacitance Cdl, and ohmic impedance Rs as the first model parameters, and the analytical equation returns the equivalent impedance;

[0129] Step 5: Use the optimize.curve_fit function to perform nonlinear least squares fitting on the original data, find the optimal value array of fitting parameters popt and parameter covariance pcov, and obtain the optimal curve;

[0130] Step 6: Assign the optimal value array to Rct, Cdl and Rs respectively; substitute the original frequency data into the obtained curve to obtain the fitted new data points fit_Zr_rc and fit_Zi_rc, and use the coefficient of determination to evaluate the fit between the new data points and the original data, that is, to obtain the first goodness of fit mentioned above;

[0131] Step 7: Establish a second target model function according to the low-frequency equivalent circuit model, import the array that conforms to the low-frequency equivalent circuit model, and calculate the optimal parameter diffusion slope value using a linear fitting method;

[0132] Step 8: Use the coefficient of determination to evaluate the fit between the fitted data points and the original data, which is the second goodness of fit mentioned above;

[0133] Step 9: Draw the image in a partitioned manner. Draw the fitting image of the first target model function and the fitting image of the second target model function on a 10*4 canvas respectively. Use the real part of impedance as the horizontal axis and the imaginary part of impedance as the vertical axis. Draw the original data into a scatter plot. Draw the fitted data as a curve graph in the same coordinate system, and add the fitting results and goodness of fit values ​​in the legend.

[0134] Figure 6This is the electrochemical AC impedance spectrum segmented fitting curve obtained in step 9 of Example 2. The left figure is the RC model fitting result in the high-frequency range, showing ohmic impedance Rs: 5.01Ohms, double-layer capacitance Cdl: 4.29e-05F, charge transfer impedance Rct: 60.27Ohms, and the goodness of fit of the first target model function is 98.74%; the right figure is the fitting result of the second target model function in the low-frequency range, the diffusion process straight line slope slope: 8.64, and the goodness of fit of the second target model function is 99.31%.

[0135] Example 3:

[0136] Battery preparation:

[0137] The assembly of lithium-ion button cells is carried out in a glove box filled with argon gas, and the H2O and O2 contents in the glove box are both less than 0.1ppm. The specific battery composition is lithium metal anode, nickel cobalt manganese oxide (NCM), ternary cathode sheet, PP separator, 1M LiFSI electrolyte, and stainless steel button cell shell.

[0138] Among them, when assembling the battery, the lithium sheet used has a diameter of 16mm and a thickness of 0.2mm, the NCM ternary positive electrode sheet has a diameter of 12mm, the positive electrode material loading is 6mg / cm2, the diaphragm has a diameter of 18mm and a thickness of 8μm, the LiFSI electrolyte dosage is 5μL, and the button battery shell specification is 2032.

[0139] Electrochemical impedance spectroscopy:

[0140] The prepared button battery was charged to 50% SOC, and allowed to stand at room temperature for 45 days. The button battery after standing was subjected to an AC impedance spectrum test with a frequency range of 0.01 to 1000000 Hz.

[0141] Fast data processing of AC impedance spectroscopy based on Python:

[0142] Step 1: Introduce Python open source numerical calculation, numerical analysis, and graphics drawing modules;

[0143] Step 2: Import the electrochemical impedance spectroscopy data of lithium-ion batteries, determine the column number of the frequency, real part of impedance, and imaginary part of impedance, and extract and save them into the corresponding array for subsequent program calls;

[0144] Step 3: Traverse the real part gradient of the impedance and divide the complete data into two sets of data that conform to the high-frequency equivalent circuit model and the low-frequency equivalent circuit model. Use the append function to add the two sets of data to a new array for storage;

[0145] Step 4: Establish a first model function according to the high-frequency equivalent circuit model, with frequency as the independent variable, charge transfer impedance Rct, double-layer capacitance Cdl, and ohmic impedance Rs as the first model parameters, and the analytical equation returns the equivalent impedance;

[0146] Step 5: Use the optimize.curve_fit function to perform nonlinear least squares fitting on the original data, find the optimal value array of fitting parameters popt and parameter covariance pcov, and obtain the optimal curve;

[0147] Step 6: Assign the optimal value array to Rct, Cdl and Rs respectively; substitute the original frequency data into the obtained curve to obtain the fitted new data points fit_Zr_rc and fit_Zi_rc, and use the coefficient of determination to evaluate the fit between the new data points and the original data, that is, to obtain the first goodness of fit mentioned above;

[0148] Step 7: Establish a second target model function according to the low-frequency equivalent circuit model, import the array that conforms to the low-frequency equivalent circuit model, and calculate the optimal parameter diffusion slope value using a linear fitting method;

[0149] Step 8: Use the coefficient of determination to evaluate the fit between the fitted data points and the original data, which is the second goodness of fit mentioned above;

[0150] Step 9: Draw the image in a partitioned manner. Draw the fitting image of the first target model function and the fitting image of the second target model function on a 10*4 canvas respectively. Use the real part of impedance as the horizontal axis and the imaginary part of impedance as the vertical axis. Draw the original data into a scatter plot. Draw the fitted data as a curve graph in the same coordinate system, and add the fitting results and goodness of fit values ​​in the legend.

[0151] Figure 7 This is the electrochemical AC impedance spectrum segmented fitting curve obtained in step 9 of Example 3. The left figure is the fitting result of the first target model function in the high-frequency range, showing ohmic impedance Rs: 4.18ohms, double-layer capacitance Cdl: 4.18e-05F, charge transfer impedance Rct: 47.70Ohms, and the goodness of fit of the first target model function is 99.16%; the right figure is the fitting result of the second target model function in the low-frequency range, the diffusion process straight line slope slope: 9.67, and the goodness of fit of the second target model function is 99.26%.

[0152] Figure 8The Rs and Rct bar graphs obtained in Examples 1, 2, and 3 are shown. It can be seen that the Rs and Rct of the 100% SOC lithium-ion battery have changed before and after standing, and the increase in Rct is more significant, resulting in a significant increase in the total impedance, indicating that the charge transfer impedance is the dominant factor in the calendar aging process, which corresponds to the degradation of the positive electrode material and affects the interface transmission process; after the same 45-day calendar aging, the 50% SOC lithium-ion battery is also dominated by the increase in Rct compared to the 100% SOC battery, but the impedance increase is smaller, indicating that the higher state of charge and the high reaction activity of the positive electrode material will lead to a greater degree of transition metal dissolution CEI formation during storage, increase the resistance to the reaction and deintercalation of the active material, and aggravate the calendar aging of the battery.

[0153] Through the above examples, it can be seen that the electrochemical impedance spectroscopy data processing method provided in the embodiment of the present application is reliable and can quickly and conveniently obtain the resistance value of each component. The results can reversely guide battery design optimization, standardize lithium-ion battery storage methods, and slow down aging and attenuation behavior.

[0154] The electrochemical impedance spectroscopy data processing method provided in the embodiment of the present application imports the electrochemical impedance spectroscopy file, that is, inputs the file name, and the python script performs fitting calculations, uses the least squares method to quickly obtain the Rs, Rct, and Cdl values, and presents the original data and the fitted data of the graph at the same time. The entire calculation process only takes 3 to 5 seconds, which greatly reduces the complexity of manual operation and does not require the user to have rich electrochemical knowledge and experience; the model has a high goodness of fit, fits the original data, and can clearly and reliably reflect the characteristic electrochemical process. For example, by using the fresh lithium-ion button battery described later and the lithium-ion button battery that has undergone 45 days of calendar aging to perform the above test, the changing trends of various impedances before and after calendar aging can be distinguished: such as the ohmic impedance Rs of the electrolyte, the charge transfer impedance Rct of the electrochemical reaction at the interface of the active material, and the equivalent capacitance Cdl of the charge accumulated on the electrode, which is positively correlated with the lithium ion diffusion rate, and the slope of the straight line slope corresponding to the occurrence of the electrochemical process can be clearly identified; if the increase in Rs reflects the increase in body resistance caused by the consumption of lithium ions in the electrolyte, and the increase in Rct reflects the increase in charge transfer impedance generated at the CEI interface due to the degradation of the cathode transition metal, the impact of lithium-ion battery calendar aging on lithium-ion button batteries can be known. ; For example, by using the aforementioned different states of charge SOC, i.e., 50% SOC lithium-ion button batteries and 100% SOC lithium-ion button batteries, it is possible to distinguish the changing trends of various impedances of lithium-ion button batteries with different SOCs during calendar aging: such as through the ohmic impedance Rs of the electrolyte, the charge transfer impedance Rct through interface mass transfer, and the equivalent capacitance Cdl of the charges accumulated on the electrode and the slope slope of the straight line positively correlated with the lithium ion diffusion rate, to semi-quantify the extent of the electrochemical process occurring under different SOCs; such as by comparing the degree of change of Rs, Rct, etc. of lithium-ion button batteries with different SOCs after 45 days of aging, the dominant factors affecting the calendar aging of lithium-ion batteries are known.

[0155] It should be understood that, although the various steps in the above-mentioned flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the above-mentioned flow chart may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

[0156] Embodiment 2:

[0157] Based on the same inventive concept, see Fig. 9As shown, the embodiment of the present application also provides an electrochemical impedance spectroscopy data processing device, characterized in that it includes:

[0158] An acquisition module 901 is used to acquire multiple sets of electrochemical impedance spectrum measurement data of an electrochemical system; each set of the electrochemical impedance spectrum measurement data includes the frequency of a disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency;

[0159] A determination module 902 is used to determine a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system from the electrochemical impedance spectroscopy measurement data; the high-frequency equivalent circuit model includes Rct and CdI connected in parallel, and Rs connected in series with the Rct and the CdI, wherein the Rs represents an ohmic impedance of an electrolyte of the electrochemical system, the Rct represents a charge transfer impedance at an interface of an active material of the electrochemical system, and the CdI represents an equivalent capacitance of charges on an electrode of the electrochemical system;

[0160] A first fitting module 903 is used to perform fitting calculation according to the first electrochemical impedance spectrum measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function; the first model function is a function established according to the high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include the ohmic impedance Rs, the charge transfer impedance Rct and the equivalent capacitance CdI;

[0161] The second fitting module 904 is used to perform linear fitting based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set to obtain the diffusion slope of the electrochemical system.

[0162] It should be noted that, for the sake of brevity, the contents described in the above embodiments will not be repeated in this embodiment.

[0163] Embodiment three:

[0164] See also Fig.10 As shown, an embodiment of the present application provides an electronic device, including a processor 1001 and a memory 1002, wherein the memory 1002 stores a computer program, and the processor 1001 executes the computer program to implement the steps of the method introduced above, which will not be repeated here.

[0165] The processor 1001 may be an integrated circuit chip with signal processing capabilities. The processor 1001 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. It may implement or execute various methods, steps and logic block diagrams disclosed in the embodiments of the present application. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0166] The memory 1002 may include, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable read-only memory (EPROM), electrically erasable read-only memory (EEPROM), etc.

[0167] This embodiment also provides a computer-readable storage medium, such as a floppy disk, a CD, a hard disk, a flash memory, a USB flash disk, an SD card, an MMC card, etc., in which one or more programs for implementing the above steps are stored. These one or more programs can be executed by one or more processors to implement the steps of the method in the above embodiment 1, which will not be repeated here.

[0168] It should be noted that the diagram provided in the present embodiment only illustrates the basic concept of the present invention in a schematic manner, so the diagram only shows the components related to the present invention rather than drawing according to the number, shape and size of the components during actual implementation. The type, quantity and ratio of each component during actual implementation can be a random change, and the component layout type may also be more complicated. The structure, ratio, size, etc. illustrated in the drawings of the present specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions that the present invention can implement, so they have no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effect that the present invention can produce and the purpose that can be achieved. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of narration, and are not used to limit the scope of the present invention. The change or adjustment of its relative relationship should also be regarded as the scope of the present invention without substantially changing the technical content.

[0169] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for processing electrochemical impedance spectroscopy data, characterized in that: include: Acquire multiple sets of electrochemical impedance spectroscopy measurement data of the electrochemical system; each set of the electrochemical impedance spectroscopy measurement data includes the frequency of the disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency; Determining a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system from the electrochemical impedance spectroscopy measurement data; the high-frequency equivalent circuit model includes Rct and Cd I connected in parallel, and Rs connected in series with the Rct and the Cd I, wherein the Rs represents an ohmic impedance of an electrolyte of the electrochemical system, the Rct represents a charge transfer impedance at an interface of an active material of the electrochemical system, and the Cd I represents an equivalent capacitance of charges on an electrode of the electrochemical system; Performing fitting calculation according to the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function; the first model function is a function established according to the high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include the ohmic impedance Rs, the charge transfer impedance Rct and the equivalent capacitance Cd I; A linear fit is performed based on the real part of the impedance and the imaginary part of the impedance in the second electrochemical impedance spectroscopy measurement data set to obtain a diffusion slope of the electrochemical system.

2. The electrochemical impedance spectroscopy data processing method according to claim 1, characterized in that: The method of determining, from the electrochemical impedance spectroscopy measurement data, a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system and a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system comprises: Calculating the gradient value of each group of electrochemical impedance spectroscopy measurement data; Determining a frequency dividing point between a high frequency range and a low frequency range of the disturbance signal applied to the electrochemical system according to the gradient value; The electrochemical impedance spectroscopy measurement data with a frequency greater than or equal to the frequency dividing point is used as data in a first electrochemical impedance spectroscopy measurement data set that conforms to a high-frequency equivalent circuit model of the electrochemical system, and the electrochemical impedance spectroscopy measurement data with a frequency less than the frequency dividing point is used as data in a second electrochemical impedance spectroscopy measurement data set that conforms to a low-frequency equivalent circuit model of the electrochemical system.

3. The electrochemical impedance spectroscopy data processing method according to claim 2, characterized in that: Calculating the gradient value of each group of electrochemical impedance spectroscopy measurement data, including: According to the formula Calculate the gradient value of each group of electrochemical impedance spectroscopy measurement data; wherein, del n represents the gradient value of the electrochemical impedance spectroscopy measurement data of the nth group, Zi n+1 He Zi n-1 Respectively represent the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n+1th group and the imaginary impedance part of the electrochemical impedance spectroscopy measurement data of the n-1th group, Zr n+1 and Zr n-1 respectively represent the real impedance part of the electrochemical impedance spectroscopy measurement data of the n+1th group and the real impedance part of the electrochemical impedance spectroscopy measurement data of the n-1th group; The step of determining the frequency demarcation point between the high frequency range and the low frequency range of the disturbance signal applied to the electrochemical system according to the gradient value comprises: The frequency in the electrochemical impedance spectrum measurement data corresponding to the inflection point where the gradient value changes from a negative value to a positive value is used as a frequency dividing point between a high frequency range and a low frequency range of the disturbance signal applied to the electrochemical system.

4. The electrochemical impedance spectroscopy data processing method according to claim 1, characterized in that: The performing fitting calculation according to the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function includes: Substituting the frequency in the first electrochemical impedance spectroscopy measurement data set into a first model function for calculation, and returning an equivalent impedance of the electrochemical system; Based on the first electrochemical impedance spectroscopy measurement data set, the first model function is fitted with the least square method of the frequency and the equivalent impedance to obtain the optimal parameter value of each first model parameter in the first model function.

5. The electrochemical impedance spectroscopy data processing method according to claim 1, characterized in that: After performing fitting calculation according to the first electrochemical impedance spectroscopy measurement data set and the first model function to obtain the optimal parameter value of each first model parameter in the first model function, the method includes: Substituting the optimal parameter value of the first model parameter into the first model function to obtain a first target model function; Substituting each of the frequencies in the first electrochemical impedance spectroscopy measurement data set into the first target model function to obtain a fitting equivalent impedance corresponding to each of the electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set; According to the formula Calculate the first goodness of fit of the first target model function; wherein R1 2 represents the first goodness of fit, y 1i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the first electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of electrochemical impedance spectroscopy measurement data in the first electrochemical impedance spectroscopy measurement data set; The degree of fit of the first target model function is evaluated according to the first goodness of fit.

6. The electrochemical impedance spectroscopy data processing method according to claim 5, characterized in that: The low-frequency equivalent circuit model includes the ohmic impedance Rs, the charge transfer impedance Rct and the diffusion impedance Zw of the electrochemical system in the diffusion process connected in series; the method further includes: Substituting each of the frequencies in the second electrochemical impedance spectroscopy measurement data set into a second target model function to obtain a fitted equivalent impedance corresponding to each of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set; the second target model function is a function obtained by substituting the optimal parameter value of the ohmic impedance Rs and the optimal parameter value of the charge transfer impedance Rct into the second model function, and the second model function is a function established according to the low-frequency equivalent circuit model; According to the formula Calculate the second goodness of fit of the second target model function; wherein R2 2 represents the second goodness of fit, y 2i represents an actual equivalent impedance consisting of the real impedance part and the imaginary impedance part of the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set, represents the average value of each of the actual equivalent impedances corresponding to the second electrochemical impedance spectroscopy measurement data set, represents the fitted equivalent impedance corresponding to the i-th group of the electrochemical impedance spectroscopy measurement data in the second electrochemical impedance spectroscopy measurement data set; The degree of fit of the second target model function is evaluated according to the second goodness of fit.

7. The electrochemical impedance spectroscopy data processing method according to claim 6, characterized in that: The method further comprises: The actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the first electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the first electrochemical impedance spectrum measurement data set are plotted in a first target coordinate system, and the actual equivalent impedance composed of each real part of the impedance and the corresponding imaginary part of the impedance in the second electrochemical impedance spectrum measurement data set, and each fitted equivalent impedance in the second electrochemical impedance spectrum measurement data set are plotted in a second target coordinate system; the first target coordinate system and the second target coordinate system are coordinate systems established with the real part of the impedance as the horizontal axis and the imaginary part of the impedance as the vertical axis.

8. An electrochemical impedance spectroscopy data processing device, characterized in that: include: An acquisition module, used for acquiring multiple groups of electrochemical impedance spectrum measurement data of the electrochemical system; each group of the electrochemical impedance spectrum measurement data includes the frequency of the disturbance signal applied to the electrochemical system, and the real impedance part and the imaginary impedance part of the electrochemical system measured at the frequency; a determination module, configured to determine, from the electrochemical impedance spectroscopy measurement data, a first electrochemical impedance spectroscopy measurement data set conforming to a high-frequency equivalent circuit model of the electrochemical system, and a second electrochemical impedance spectroscopy measurement data set conforming to a low-frequency equivalent circuit model of the electrochemical system; the high-frequency equivalent circuit model comprises Rct and Cd I connected in parallel, and Rs connected in series with the Rct and the Cd I, wherein the Rs represents an ohmic impedance of an electrolyte of the electrochemical system, the Rct represents a charge transfer impedance at an interface of an active material of the electrochemical system, and the Cd I represents an equivalent capacitance of charges on an electrode of the electrochemical system; a first fitting module, configured to perform fitting calculation according to the first electrochemical impedance spectrum measurement data set and a first model function to obtain an optimal parameter value of each first model parameter in the first model function; the first model function is a function established according to the high-frequency equivalent circuit model, and the independent variable of the first model function is the frequency of the disturbance signal applied to the electrochemical system, the dependent variable of the first model function is the equivalent impedance of the electrochemical system, and the first model parameters include the ohmic impedance Rs, the charge transfer impedance Rct and the equivalent capacitance Cd I; The second fitting module is used to perform linear fitting based on the real part of impedance and the imaginary part of impedance in the second electrochemical impedance spectrum measurement data set to obtain the diffusion slope of the electrochemical system.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein a computer program is stored in the memory, and the processor executes the computer program to implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by at least one processor, the method according to any one of claims 1 to 7 is implemented.

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