Direct-current impedance testing method and device and medium

Abstract

The invention discloses a direct-current impedance testing method and device and a medium, and relates to the field of battery testing, and the method comprises the steps: testing impedance data of a target battery at different frequencies based on an electrochemical impedance spectroscopy testing method; based on the impedance data of the target battery under different frequencies, performing parameter fitting on the constructed equivalent circuit model to obtain impedance parameters of each component of the equivalent circuit model; determining a time domain differential equation set according to the impedance parameter of each component of the equivalent circuit model; according to the current values of the target battery at any two moments, through the time domain differential equation set, overpotential values caused by each component of the equivalent circuit model at the two moments are calculated; calculating a voltage value of the target battery at each moment according to an overpotential value caused by each component of the equivalent circuit model at each moment; calculating a DC impedance value of the target battery according to the voltage values and the current values of the target battery at the two moments; according to the invention, lossless and rapid testing of the DC impedance of the battery is realized.

Description

Technical Field

[0001] The present application relates to the technical field of battery testing, and in particular to a direct current impedance testing method, device and medium. Background Art

[0002] When evaluating battery performance, it is usually necessary to evaluate the DC impedance characteristics of the battery. DC impedance refers to the impedance characteristics of the battery under DC current excitation. By measuring the DC impedance of the battery, the electrochemical characteristics of the battery can be obtained.

[0003] In the prior art, the hybrid pulse power characteristic test (HPPC) method is often used to test the DC impedance and other properties of the battery. However, the HPPC test process is relatively complicated and requires applying pulses of different currents and constantly adjusting the battery's state of charge. Certain specific scenarios may even damage the battery's performance and affect the accuracy and reliability of subsequent experiments. Summary of the invention

[0004] The purpose of the present application is to provide a DC impedance testing method, device and medium to solve the problem that the HPPC testing method is used in the prior art to test the DC impedance of a battery, which results in a complicated testing process and is likely to damage battery performance.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a DC impedance testing method, comprising:

[0007] Based on the electrochemical impedance spectroscopy test method, the impedance data of the target battery at different frequencies is tested;

[0008] Based on the impedance data of the target battery at different frequencies, parameter fitting is performed on the constructed equivalent circuit model to obtain the impedance parameters of each component of the equivalent circuit model;

[0009] Determine a group of time-domain differential equations according to the impedance parameters of each component of the equivalent circuit model; wherein the group of time-domain differential equations includes a plurality of time-domain differential equations, each of which corresponds to a time-domain differential equation of the impedance parameter of any component of the equivalent circuit model, the resulting overpotential, and the current of the target battery, and the time-domain differential equation in which the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional-order differential equation, and the order of the fractional-order differential equation is the exponent of the CPE component;

[0010] According to the current value of the target battery at two arbitrary moments, the overpotential values ​​caused by each component of the equivalent circuit model at the two moments are calculated by using the time domain differential equation group;

[0011] Calculating the voltage value of the target battery at each said moment according to the overpotential value caused by each component of the equivalent circuit model at each said moment;

[0012] The DC impedance value of the target battery is calculated according to the voltage value and the current value of the target battery at the two moments.

[0013] Optionally, performing parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies includes:

[0014] According to the objective function, the first optimization algorithm is used to find the optimal value within the search range of the parameters of each component of the equivalent circuit model; wherein the objective function is an error function between experimental values ​​and calculated values, the experimental values ​​are the impedance data of the target battery at different frequencies, and the calculated values ​​are the impedance data of the equivalent circuit model at different frequencies.

[0015] Optionally, performing parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies also includes:

[0016] After optimizing within the search range of the parameters of each component of the equivalent circuit model by using the first optimization algorithm according to the objective function, the optimization result of the first optimization algorithm is optimized by using the second optimization algorithm.

[0017] Optionally, the first optimization algorithm comprises a genetic algorithm, a simulated annealing algorithm, a particle swarm algorithm, a variant of a genetic algorithm, a variant of a simulated annealing algorithm, or a variant of a particle swarm algorithm;

[0018] The second optimization algorithm includes the Levenberg-Marquardt method;

[0019] The error function includes mean square error, root mean square error, mean absolute error, relative error or mean relative error.

[0020] Optionally, the equivalent circuit model includes an inductor component, a first resistor component, a parallel component and a Warburg component connected in sequence; wherein at least one parallel component is provided, and each parallel component includes a CPE component and a second resistor component connected in parallel;

[0021] The impedance parameters of each component of the equivalent circuit model include: the impedance of the inductor component, the first resistor component, the parallel component and the Warburg component, and the index of the parallel component and the Warburg component; wherein the impedance of the parallel component includes the impedance of its second resistor component and the impedance of the CPE component, and the index of the parallel component includes the index of its CPE component;

[0022] The impedance data of the equivalent circuit model at different frequencies are calculated according to the following formula:

[0023]

[0024] Wherein, Z(ω) is the complex impedance of the equivalent circuit model at the frequency ω, j is an imaginary unit, L is the impedance of the inductor component, R0 is the impedance of the first resistor component, R i is the impedance of the second resistance component of the i-th parallel component, Q i is the impedance of the CPE component of the i-th parallel component, p i is the index of the CPE component of the ith parallel component, p i The value range of is (0,1), m is the number of the parallel components, 1≤m≤3, W is the impedance of the Warburg component, n is the index of the Warburg component, and the value range of n is (0,1).

[0025] Optionally, determining the time domain differential equation group according to the impedance parameters of each component of the equivalent circuit model includes:

[0026] Substituting the impedance parameters of each component of the equivalent circuit model into the following equation, a time domain differential equation group including the fractional-order differential equation is obtained:

[0027]

[0028] Among them, V L is the overpotential caused by the inductor component, V0 is the overpotential caused by the first resistor component; V i is the overpotential caused by the i-th parallel component, if m=1, i={1}, if m=2, i={1,2}, if m=3, i={1,2,3}; V4 is the overpotential caused by the Warburg component;

[0029] The calculating, according to the current value of the target battery at two arbitrary moments, the overpotential value caused by each component of the equivalent circuit model at the two moments through the time domain differential equation group, comprises:

[0030] Substitute the current values ​​of the target battery at two arbitrary moments into the time domain differential equations, and calculate the V L , V0, V i and V4.

[0031] Optionally, the calculating the voltage value of the target battery at each said moment according to the overpotential value caused by each component of the equivalent circuit model at each said moment comprises:

[0032] V at each momentL , V0, V i Substitute V and V4 into the following formula to calculate the voltage value V of the target battery at each time:

[0033]

[0034] Wherein, OCV is the open circuit voltage of the target battery.

[0035] Optionally, the calculating the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the two moments includes:

[0036] Substitute the voltage and current values ​​of the target battery at the two moments into the following formula to calculate the DC resistance value DCR of the target battery:

[0037]

[0038] Among them, V s is the voltage value of the target battery at the first moment, V t is the voltage value of the target battery at the second moment, I s is the current value of the target battery at the first moment, I t is the current value of the target battery at the second moment.

[0039] In a second aspect, the present application provides a DC impedance testing device, comprising:

[0040] Impedance test module, used to test the impedance data of the target battery at different frequencies based on the electrochemical impedance spectroscopy test method;

[0041] A parameter fitting module, used to perform parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies, and obtain the impedance parameters of each component of the equivalent circuit model;

[0042] An equation determination module, configured to determine a group of time-domain differential equations according to the impedance parameters of each component of the equivalent circuit model; wherein the group of time-domain differential equations includes a plurality of time-domain differential equations, each of which corresponds to a time-domain differential equation of the impedance parameter of any component of the equivalent circuit model, the resulting overpotential, and the current of the target battery, and the time-domain differential equation in which the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional-order differential equation, and the order of the fractional-order differential equation is the exponent of the CPE component;

[0043] An overpotential calculation module, used to calculate the overpotential values ​​caused by each component of the equivalent circuit model at the two arbitrary moments according to the current value of the target battery at the two arbitrary moments through the time domain differential equation group;

[0044] A voltage calculation module, used to calculate the voltage value of the target battery at each said moment according to the overpotential value caused by each component of the equivalent circuit model at each said moment;

[0045] The impedance calculation module is used to calculate the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the two moments.

[0046] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the above-mentioned DC impedance testing methods.

[0047] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0048] The present application provides a DC impedance test method, device and medium, which tests the impedance data of a target battery at different frequencies based on an electrochemical impedance spectroscopy test method. The electrochemical impedance spectroscopy test method is a method for obtaining the impedance data of a battery at different frequencies by applying electrical signal disturbances of different frequencies. At the same time, the electrochemical impedance spectroscopy test method does not need to adjust the state of charge of the battery, does not need to perform complex experiments with multiple rates and multiple discharge times, and does not need to consider the changes in the battery state after charging and discharging. Compared with the HPPC test method, the test process is simpler, the disturbance amplitude of the electrical signal is smaller, and it is not easy to damage the battery, so it can be maintained. The original performance of the battery; the impedance behavior of the target battery is simulated by constructing an equivalent circuit model, and based on the impedance data of the target battery at different frequencies, the constructed equivalent circuit model is parameter-fitted to obtain the parameters of each component of the equivalent circuit model, so as to ensure that the equivalent circuit model can accurately simulate the impedance behavior of the target battery; through the parameters of each component of the equivalent circuit model, a time-domain differential equation group is determined, and each time-domain differential equation of the time-domain differential equation group corresponds to the impedance parameter of any component of the equivalent circuit model, the resulting overpotential and the time-domain differential equation of the current of the target battery, so as to associate the current of the target battery with the equivalent circuit model, The impedance behavior of the target battery is simulated by using an equivalent circuit model; in the time-domain differential equation group, the time-domain differential equation in which the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional-order differential equation, and the order of the fractional-order differential equation is the exponent of the CPE component. Compared with the integer-order differential equation, the calculation result of the fractional-order differential equation is more accurate, so that the equivalent circuit model can more accurately simulate the impedance behavior of the target battery; through the time-domain differential equation group including the fractional-order differential equation, according to the current value of the target battery at any two times, the overpotential value caused by each component of the equivalent circuit model at the two said times is calculated, and then according to the The overpotential value caused by each component of the effective circuit model at each moment is calculated, and the voltage value of the target battery at each moment is obtained, so as to obtain the voltage value of the target battery at any two selected moments, and realize the current value of the target battery at any two moments, and accurately calculate the voltage value of the target battery at any two selected moments based on the time domain differential equation group including fractional differential equations; by calculating the DC impedance value of the target battery according to the voltage value and current value of the target battery at the two selected moments, the DC impedance of the target battery is accurately tested, and compared with the HPPC test method, there is no need for complex data analysis, which further simplifies the DC impedance test process. In summary, the embodiment of the present application realizes the non-destructive and rapid testing of the DC impedance of the battery, and the testing process is simpler, which solves the problem that the HPPC test method is used in the prior art to test the DC impedance of the battery, resulting in a complex testing process and easy damage to the battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 A schematic diagram of a flow chart of a DC impedance testing method provided in one embodiment of the present application;

[0051] Figure 2 A schematic diagram of the structure of an equivalent circuit model provided in one embodiment of the present application;

[0052] Figure 3 A schematic diagram of functional modules of a DC impedance testing device provided in one embodiment of the present application;

[0053] Figure 4 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0055] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0056] In an exemplary embodiment, Figure 1 As shown, a DC impedance test method is provided, including the following steps 101 to 106. Among them:

[0057] Step 101 : testing impedance data of a target battery at different frequencies based on an electrochemical impedance spectroscopy (EIS) testing method.

[0058] In the embodiment of the present application, an electrochemical impedance spectroscopy test method is used to apply electrical signal disturbances of different frequencies to the target battery to obtain the response of the target battery at different frequencies, and then the impedance data of the target battery at different frequencies is obtained according to the following formula:

[0059]

[0060] Among them, Z ωrepresents the impedance data of the target battery at a frequency ω, I' and V' represent a sinusoidal electrical signal with a frequency ω applied to the target battery and the response of the target battery to the applied disturbance; for example, in a voltage control mode, a sinusoidal voltage signal V' with a frequency ω is applied to the target battery, and I' is the current response of the target battery under the disturbance of V'; for example, in a voltage control mode, a sinusoidal current signal I' with a frequency ω is applied to the target battery, and V' is the voltage response of the target battery under the disturbance of I'; FFT(V') represents fast Fourier transform of V' to obtain the frequency spectrum of the voltage signal V'; FFT(I') represents fast Fourier transform of I' to obtain the frequency spectrum of the current signal I'; It means that at the frequency ω, the frequency domain value of the voltage signal V' is divided by the frequency domain value of the corresponding current signal I', where the division is a complex number division, to obtain the complex impedance at the frequency.

[0061] Step 102: Based on the impedance data of the target battery at different frequencies, the constructed equivalent circuit model is parameter fitted to obtain the impedance parameters of each component of the equivalent circuit model.

[0062] In the embodiments of the present application, there is no specific limitation on the structure of the equivalent circuit model, and it can be selected according to actual needs. For example, a first-order equivalent circuit model, a second-order equivalent circuit model, or a third-order equivalent circuit model can be selected.

[0063] Step 103, determining a group of time-domain differential equations according to the impedance parameters of each component of the equivalent circuit model; wherein the group of time-domain differential equations includes multiple time-domain differential equations, each of which corresponds to a time-domain differential equation of the parameters of any component of the equivalent circuit model, the resulting overpotential, and the current of the target battery, and the time-domain differential equation in which the impedance parameters of the CPE component of the equivalent circuit model are located is a fractional-order differential equation, and the order of the fractional-order differential equation is the exponent of the CPE component.

[0064] For example, if the equivalent circuit model adopts a second-order equivalent circuit model, such as Figure 2As shown, it includes five components, namely, an inductor component L, a first resistor component R0, a first parallel component, a second parallel component and a Warburg component (a model component used to describe the diffusion control process in a battery) W, which are connected in sequence. The Warburg component belongs to a CPE component. The first parallel component includes a CPE component (constant phase element) Q1 and a second resistor component R1 in parallel, and the second parallel component includes a CPE component Q2 and a second resistor component R2 in parallel. The time domain differential equation group obtained in step 103 includes five time domain differential equations. The five time domain differential equations correspond to the impedance parameters of the five components of the equivalent circuit model, the time domain differential equations of the overpotential caused and the current of the target battery, and the time domain differential equations where the impedance parameters of the first parallel component, the second parallel component and the Warburg component are located are fractional differential equations. The orders of the three fractional differential equations correspond to the index of the CPE component Q1, the index of the CPE component Q2 and the index of the Warburg component.

[0065] Step 104 , according to the current value of the target battery at two arbitrary moments, the overpotential values ​​caused by each component of the equivalent circuit model at the two moments are calculated by using a group of time-domain differential equations.

[0066] In the embodiment of the present application, since each time-domain differential equation of the time-domain differential equation group corresponds to a time-domain differential equation of the parameters of any component of the equivalent circuit model, the overpotential caused and the current of the target battery, the current value of the target battery at a certain moment is substituted into the time-domain differential equation group to solve the overpotential caused by each component of the equivalent circuit model.

[0067] Step 105 , calculating the voltage value of the target battery at each moment according to the overpotential value caused by each component of the equivalent circuit model at each of the above two moments.

[0068] Step 106, calculating the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the above two moments.

[0069] Implement the above steps 101 to 106, and test the impedance data of the target battery at different frequencies based on the electrochemical impedance spectroscopy test method. The electrochemical impedance spectroscopy test method is a method for obtaining the impedance data of the battery at different frequencies by applying electrical signal disturbances of different frequencies. At the same time, the electrochemical impedance spectroscopy test method does not need to adjust the charge state of the battery, does not need to perform complex experiments with multiple rates and multiple discharge times, and does not need to consider the changes in the battery state after charging and discharging. Compared with the HPPC test method, the test process is simpler, the disturbance amplitude of the electrical signal is small, and it is not easy to damage the battery, so the original performance of the battery can be maintained; the impedance behavior of the target battery is simulated by constructing an equivalent circuit model, and based on the impedance data of the target battery at different frequencies, the constructed equivalent circuit model is parameterized to obtain the parameters of each component of the equivalent circuit model, so as to ensure that the equivalent circuit model can accurately Simulate the impedance behavior of the target battery; through the parameters of each component of the equivalent circuit model, determine the time domain differential equation group, and through the time domain differential equation group, according to the current value of the target battery at any two moments, calculate the overpotential value caused by each component of the equivalent circuit model at the two described moments, and then calculate the voltage value of the target battery at each moment according to the overpotential value caused by each component of the equivalent circuit model at each moment, and obtain the voltage value of the target battery at any two selected moments, and realize the current value of the target battery at any two moments, and calculate the voltage value of the target battery at any two selected moments based on the time domain differential equation group, and then calculate the DC impedance value of the target battery according to the voltage value and current value of the target battery at the two selected moments, and realize the test of the DC impedance of the target battery. Compared with the HPPC test method, there is no need to perform complex data analysis, and the DC impedance test process is further simplified. In summary, the embodiment of the present application realizes the non-destructive and rapid test of the DC impedance of the battery, and the test process is simpler, which solves the problem that the HPPC test method is used in the prior art to test the DC impedance of the battery, resulting in a complex test process and easy damage to the battery performance.

[0070] Optionally, in other embodiments of the present application, in order to improve the accuracy of the equivalent circuit model in simulating the impedance behavior of the target battery, in the above step 102, based on the impedance data of the target battery at different frequencies, the constructed equivalent circuit model is parameter fitted, including:

[0071] Step 201, according to the objective function, the first optimization algorithm is used to search for the best value within the search range of the parameters of each component of the equivalent circuit model; wherein the objective function is an error function between the experimental value and the calculated value, the experimental value is the impedance data of the target battery at different frequencies, and the calculated value is the impedance data of the equivalent circuit model at different frequencies.

[0072] In the embodiment of the present application, the result of optimizing within the preset range of the parameters of each component of the equivalent circuit model by the first optimization algorithm is the parameters of each component of the equivalent circuit model. The impedance data of the target battery at different frequencies is the impedance data of the target battery at different frequencies obtained by the test in step 101. The impedance calculation formula of the equivalent circuit model can be obtained according to the structure of the equivalent circuit model. The form of the error function and the first optimization algorithm are not specifically limited, and can be set according to actual needs. The first optimization algorithm is not specifically limited, and can be selected according to actual needs. For example, the first optimization algorithm uses a genetic algorithm. When the genetic algorithm is used for optimization, not only the search interval of the parameters of each component of the equivalent circuit model is preset, but also the population size and number of iterations of the genetic algorithm are set. Through continuous selection, crossover, and mutation, and in each iteration process, the fitness value is calculated according to the objective function. When the number of iterations reaches the set value or the change in the fitness value is less than the first set value, the optimization is terminated to obtain the optimization result. In the optimization process, the smaller the value of the objective function, the better the fitting effect, and the more accurate the impedance parameter value obtained.

[0073] Optionally, in other embodiments of the present application, the above-mentioned error function includes but is not limited to mean square error, root mean square error, mean absolute error, relative error or mean relative error.

[0074] Optionally, in other embodiments of the present application, the first optimization algorithm mentioned above includes but is not limited to a genetic algorithm, a simulated annealing algorithm, a particle swarm algorithm, a variant of a genetic algorithm, a variant of a simulated annealing algorithm, or a variant of a particle swarm algorithm.

[0075] In the embodiments of the present application, there is no specific limitation on the variants of the genetic algorithm, the simulated annealing algorithm, and the particle swarm algorithm, and they can be selected according to actual needs.

[0076] Optionally, in other embodiments of the present application, in order to avoid the problem that the first optimization algorithm is prone to fall into a local optimum, parameter fitting is performed on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies, further comprising:

[0077] Step 202: Optimize the optimization result of the first optimization algorithm by using the second optimization algorithm.

[0078] In the embodiment of the present application, the parameter value obtained by the first optimization algorithm is used as the initial value of the second optimization algorithm, and the second optimization algorithm is used for iterative calculation. When the objective function value obtained by the two previous calculations is less than the second set value, the iterative calculation of the second optimization algorithm is exited to obtain the final impedance parameters of each component of the equivalent circuit model. In the embodiment of the present application, the second optimization algorithm is not specifically limited and can be selected according to actual needs, preferably using the LM (Levenberg-Marquardt) method.

[0079] Optionally, in other embodiments of the present application, the above-mentioned equivalent circuit model includes an inductor component, a first resistor component, a parallel component and a Warburg component connected in sequence; wherein, at least one parallel component is provided, and each parallel component includes a CPE component and a second resistor component in parallel.

[0080] Correspondingly, the impedance parameters of each component of the equivalent circuit model include: the impedance of the inductor component, the first resistor component, the parallel component and the Warburg component, and the index of the parallel component and the Warburg component; wherein the impedance of the parallel component includes the impedance of its second resistor component and the impedance of the CPE component, and the index of the parallel component includes the index of its CPE component.

[0081] Optionally, in other embodiments of the present application, the impedance data of the equivalent circuit model at different frequencies is calculated according to the following formula:

[0082]

[0083] Where Z(ω) is the complex impedance of the equivalent circuit model at frequency ω, j is the imaginary unit, L is the impedance of the inductor component, R0 is the impedance of the first resistor component, R i is the impedance of the second resistance component of the i-th parallel component, Q i is the impedance of the CPE component of the i-th parallel component, p i is the index of the CPE component of the ith parallel component, p i The value range of is (0,1), m is the number of parallel components in the equivalent circuit model, 1≤m≤3, W is the impedance of the Warburg component, n is the index of the Warburg component, and the value range of n is (0,1).

[0084] In the embodiment of the present application, if a first-order equivalent circuit model is adopted, m=1; if a second-order equivalent circuit model is adopted, m=2; if a third-order equivalent circuit model is adopted, m=3.

[0085] Optionally, in other embodiments of the present application, the above step 103 includes:

[0086] Substituting the impedance parameters of each component of the equivalent circuit model into the following equation, we obtain a set of time domain differential equations including fractional-order differential equations:

[0087]

[0088] Among them, V L is the overpotential caused by the inductor component, V0 is the overpotential caused by the first resistor component; V i is the overpotential caused by the ith parallel component; if m=1, i={1}; if m=2, i={1,2}; if m=3, i={1,2,3}; V4 is the overpotential caused by the Warburg component. i The value range of and n is (0,1), so and is a fractional order differential equation.

[0089] In the embodiment of the present application, the time domain differential equation corresponding to the impedance parameters of the CPE component and the Warburg component is a fractional differential equation, and its order corresponds to the exponent of the CPE component and the Warburg component. The calculation result of the fractional differential equation is more accurate. By combining the fractional differential equation with the equivalent circuit model, the impedance behavior of the target battery can be simulated by the equivalent circuit model to improve the accuracy of testing its DC impedance. In addition, the fractional differential equation can establish a direct connection with the complex impedance Z (ω) of the equivalent circuit model through the impedance parameters of the equivalent circuit model, so that the static electrochemical impedance spectrum can be converted into a dynamic impedance characteristic. This characteristic enables the EIS test method to effectively replace the HPPC test and become a simpler method for obtaining the DC impedance of the battery. Combining the EIS test method with the fractional differential equation can not only achieve an effective replacement for the HPPC test method, but also more conveniently obtain the DC impedance of the battery, providing new ideas and methods for evaluating and optimizing battery performance.

[0090] Accordingly, the above step 104 includes:

[0091] Substitute the current value of the target battery at two arbitrary moments into the above formula to calculate the V L , V0, V i and V4.

[0092] Optionally, in other embodiments of the present application, the above step 105 includes:

[0093] The V at each of the above two moments is L , V0, V i Substitute V4 into the following formula to calculate the voltage value V of the target battery at each moment:

[0094]

[0095] Wherein, OCV is the open circuit voltage of the target battery.

[0096] Optionally, in other embodiments of the present application, the above step 106 includes:

[0097] Substitute the voltage and current values ​​of the target battery at the above two moments into the following formula to calculate the DC resistance value DCR of the target battery:

[0098]

[0099] Among them, V s is the voltage value of the target battery at the first moment, V t is the voltage value of the target battery at the second moment, I s is the current value of the target battery at the first moment, I t is the current value of the target battery at the second moment.

[0100] Based on the same inventive concept, the embodiment of the present application also provides a DC impedance test device for implementing the DC impedance test method involved above. The implementation solution provided by the device to solve the problem is similar to the implementation solution recorded in the above method, so the specific limitations in one or more DC impedance test device embodiments provided below can refer to the limitations of the DC impedance test method above, and will not be repeated here.

[0101] In an exemplary embodiment, Figure 3 As shown, a DC impedance testing device 30 is provided, comprising:

[0102] The impedance testing module 301 is used to test the impedance data of the target battery at different frequencies based on the electrochemical impedance spectroscopy testing method;

[0103] A parameter fitting module 302 is used to perform parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies to obtain the impedance parameters of each component of the equivalent circuit model;

[0104] The equation determination module 303 is used to determine a time-domain differential equation group according to the impedance parameters of each component of the equivalent circuit model; wherein the time-domain differential equation group includes multiple time-domain differential equations, each of which corresponds to the impedance parameter of any component of the equivalent circuit model, the time-domain differential equation of the overpotential caused and the current of the target battery, and the time-domain differential equation where the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional differential equation, and the order of the fractional differential equation is the exponent of the CPE component;

[0105] The overpotential calculation module 304 is used to calculate the overpotential values ​​caused by each component of the equivalent circuit model at two arbitrary moments according to the current value of the target battery at the two arbitrary moments through a group of time-domain differential equations;

[0106] The voltage calculation module 305 is used to calculate the voltage value of the target battery at each of the above two moments according to the overpotential value caused by each component of the equivalent circuit model at each of the above two moments;

[0107] The impedance calculation module 306 is used to calculate the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the above two moments.

[0108] Optionally, in other embodiments of the present application, the parameter fitting module 302 is further used for:

[0109] According to the objective function, the first optimization algorithm is used to find the best value within the search range of the parameters of each component of the equivalent circuit model; wherein the objective function is the error function between the experimental value and the calculated value, the experimental value is the impedance data of the target battery at different frequencies, and the calculated value is the impedance data of the equivalent circuit model at different frequencies.

[0110] In the embodiments of the present application, the relevant introduction of the first optimization algorithm is detailed in the description of the above method embodiments, which will not be repeated here.

[0111] Optionally, in other embodiments of the present application, the parameter fitting module 302 is further used for:

[0112] The optimization result of the first optimization algorithm is optimized by the second optimization algorithm.

[0113] In the embodiments of the present application, the relevant introduction of the second optimization algorithm is detailed in the description of the above method embodiments, which will not be repeated here.

[0114] Optionally, in other embodiments of the present application, the above-mentioned equivalent circuit model includes an inductor component, a first resistor component, a parallel component and a Warburg component connected in sequence; wherein, at least one parallel component is provided, and each parallel component includes a CPE component and a second resistor component in parallel.

[0115] Correspondingly, the impedance parameters of each component of the equivalent circuit model include: the impedance of the inductor component, the first resistor component, the parallel component and the Warburg component, and the index of the parallel component and the Warburg component; wherein the impedance of the parallel component includes the impedance of its second resistor component and the impedance of the CPE component, and the index of the parallel component includes the index of its CPE component.

[0116] Accordingly, the above parameter fitting module 302 is also used for:

[0117] The impedance data of the equivalent circuit model at different frequencies is calculated according to the following formula:

[0118]

[0119] Where Z(ω) is the complex impedance of the equivalent circuit model at frequency ω, j is the imaginary unit, L is the impedance of the inductor component, R0 is the impedance of the first resistor component, R i is the impedance of the second resistance component of the i-th parallel component, Q i is the impedance of the CPE component of the i-th parallel component, p i is the index of the CPE component of the ith parallel component, p i The value range of is (0,1), m is the number of parallel components in the equivalent circuit model, 1≤m≤3, W is the impedance of the Warburg component, n is the index of the Warburg component, and the value range of n is (0,1).

[0120] In the embodiment of the present application, if a first-order equivalent circuit model is adopted, m=1; if a second-order equivalent circuit model is adopted, m=2; if a third-order equivalent circuit model is adopted, m=3.

[0121] Optionally, in other embodiments of the present application, the equation determination module 303 is further used for:

[0122] Substituting the impedance parameters of each component of the equivalent circuit model into the following equation, we obtain a set of time domain differential equations including fractional-order differential equations:

[0123]

[0124] Among them, V L is the overpotential caused by the inductor component, V0 is the overpotential caused by the first resistor component; V i is the overpotential caused by the i-th parallel component; if m=1, i={1}; if m=2, i={1,2}; if m=3, i={1,2,3}; V4 is the overpotential caused by the Warburg component.

[0125] Optionally, in other embodiments of the present application, the overpotential calculation module 304 is further used for:

[0126] Substitute the current value of the target battery at two arbitrary moments into the above formula to calculate the V L , V0, V i and V i .

[0127] Optionally, in other embodiments of the present application, the voltage calculation module 305 is further used for:

[0128] The V at each of the above two moments is L , V0, V i Substitute V4 into the following formula to calculate the voltage value V of the target battery at each moment:

[0129]

[0130] Wherein, OCV is the open circuit voltage of the target battery.

[0131] Optionally, in other embodiments of the present application, the impedance calculation module 306 is further used for:

[0132] Substitute the voltage and current values ​​of the target battery at the above two moments into the following formula to calculate the DC resistance value DCR of the target battery:

[0133]

[0134] Among them, V s is the voltage value of the target battery at the first moment, V t is the voltage value of the target battery at the second moment, I s is the current value of the target battery at the first moment, I t is the current value of the target battery at the second moment.

[0135] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 4 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store DC impedance test data. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a DC impedance test method is implemented.

[0136] Those skilled in the art will understand that Figure 4The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0137] In an exemplary embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0138] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0139] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0140] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0141] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0142] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0143] The technical features of the above embodiments may be arbitrarily combined. 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.

[0144] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A DC impedance testing method, characterized in that: The DC impedance testing method comprises: Based on the electrochemical impedance spectroscopy test method, the impedance data of the target battery at different frequencies is tested; Based on the impedance data of the target battery at different frequencies, the constructed equivalent circuit model is parameter-fitted to obtain the impedance parameters of each component of the equivalent circuit model; Determine a group of time-domain differential equations according to the impedance parameters of each component of the equivalent circuit model; wherein the group of time-domain differential equations includes multiple time-domain differential equations, and the time-domain differential equations correspond to the impedance parameters of any component of the equivalent circuit model, the resulting overpotential, and the current of the target battery, and the time-domain differential equation where the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional-order differential equation, and the order of the fractional-order differential equation is the exponent of the CPE component; According to the current value of the target battery at two arbitrary moments, the overpotential values ​​caused by each component of the equivalent circuit model at the two moments are calculated by using the time domain differential equation group; Calculating the voltage value of the target battery at each said moment according to the overpotential value caused by each component of the equivalent circuit model at each said moment; The DC impedance value of the target battery is calculated according to the voltage value and the current value of the target battery at the two moments.

2. The DC impedance testing method according to claim 1, characterized in that: The method of performing parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies includes: According to the objective function, the first optimization algorithm is used to find the optimal value within the search range of the parameters of each component of the equivalent circuit model; wherein the objective function is an error function between experimental values ​​and calculated values, the experimental values ​​are the impedance data of the target battery at different frequencies, and the calculated values ​​are the impedance data of the equivalent circuit model at different frequencies.

3. The DC impedance testing method according to claim 2, characterized in that: The method of performing parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies also includes: After optimizing within the search range of the parameters of each component of the equivalent circuit model by using the first optimization algorithm according to the objective function, the optimization result of the first optimization algorithm is optimized by using the second optimization algorithm.

4. The DC impedance testing method according to claim 3, characterized in that: The first optimization algorithm comprises a genetic algorithm, a simulated annealing algorithm, a particle swarm algorithm, a variant of a genetic algorithm, a variant of a simulated annealing algorithm or a variant of a particle swarm algorithm; The second optimization algorithm includes the Levenberg-Marquardt method; The error function includes mean square error, root mean square error, mean absolute error, relative error or mean relative error.

5. The DC impedance testing method according to claim 2, characterized in that: The equivalent circuit model includes an inductor component, a first resistor component, a parallel component and a Warburg component connected in sequence; wherein at least one parallel component is provided, and each parallel component includes a CPE component and a second resistor component connected in parallel; The impedance parameters of each component of the equivalent circuit model include: the impedance of the inductor component, the first resistor component, the parallel component and the Warburg component, and the index of the parallel component and the Warburg component; wherein the impedance of the parallel component includes the impedance of its second resistor component and the impedance of the CPE component, and the index of the parallel component includes the index of its CPE component; The impedance data of the equivalent circuit model at different frequencies are calculated according to the following formula: Wherein, Z(ω) is the complex impedance of the equivalent circuit model at the frequency ω, j is an imaginary unit, L is the impedance of the inductor component, R0 is the impedance of the first resistor component, R i is the impedance of the second resistance component of the i-th parallel component, Q i is the impedance of the CPE component of the i-th parallel component, p i is the index of the CPE component of the ith parallel component, p i The value range of is (0,1), m is the number of the parallel components, 1≤m≤3, W is the impedance of the Warburg component, n is the index of the Warburg component, and the value range of n is (0,1).

6. The DC impedance testing method according to claim 5, characterized in that: Determining the time domain differential equation group according to the impedance parameters of each component of the equivalent circuit model includes: Substituting the impedance parameters of each component of the equivalent circuit model into the following equation, a time domain differential equation group including the fractional-order differential equation is obtained: Among them, V L is the overpotential caused by the inductor component, V0 is the overpotential caused by the first resistor component; V i is the overpotential caused by the i-th parallel component, if m=1, i={1}, if m=2, i={1,2}, if m=3, i={1,2,3}; V4 is the overpotential caused by the Warburg component; The calculating, according to the current value of the target battery at two arbitrary moments, the overpotential value caused by each component of the equivalent circuit model at the two moments by the time domain differential equation group, comprises: Substitute the current values ​​of the target battery at two arbitrary moments into the time domain differential equations, and calculate the V L , V0, V i and V4.

7. The DC impedance testing method according to claim 6, characterized in that: The calculating the voltage value of the target battery at each moment according to the overpotential value caused by each component of the equivalent circuit model at each moment comprises: V at each moment L , V0, V i Substitute V and V4 into the following formula to calculate the voltage value V of the target battery at each time: Wherein, OCV is the open circuit voltage of the target battery.

8. The DC impedance testing method according to claim 1, characterized in that: The step of calculating the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the two moments includes: Substitute the voltage and current values ​​of the target battery at the two moments into the following formula to calculate the DC resistance value DCR of the target battery: Among them, V s is the voltage value of the target battery at the first moment, V t is the voltage value of the target battery at the second moment, I s is the current value of the target battery at the first moment, I t is the current value of the target battery at the second moment.

9. A DC impedance test device, characterized in that: The DC impedance testing device comprises: Impedance test module, used to test the impedance data of the target battery at different frequencies based on the electrochemical impedance spectroscopy test method; A parameter fitting module, used to perform parameter fitting on the constructed equivalent circuit model based on the impedance data of the target battery at different frequencies, and obtain the impedance parameters of each component of the equivalent circuit model; An equation determination module, used to determine a time-domain differential equation group according to the impedance parameters of each component of the equivalent circuit model; wherein the time-domain differential equation group includes multiple time-domain differential equations, each of which corresponds to a time-domain differential equation of the impedance parameter of any component of the equivalent circuit model, the resulting overpotential and the current of the target battery, and the time-domain differential equation where the impedance parameter of the CPE component of the equivalent circuit model is located is a fractional differential equation, and the order of the fractional differential equation is the exponent of the CPE component; An overpotential calculation module, used to calculate the overpotential values ​​caused by each component of the equivalent circuit model at the two arbitrary moments according to the current value of the target battery at the two arbitrary moments through the time domain differential equation group; A voltage calculation module, used to calculate the voltage value of the target battery at each said moment according to the overpotential value caused by each component of the equivalent circuit model at each said moment; The impedance calculation module is used to calculate the DC impedance value of the target battery according to the voltage value and the current value of the target battery at the two moments.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the DC impedance testing method described in any one of claims 1 to 8 are implemented.

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