Power grid decommissioned lead-acid storage battery capacity consistency screening method based on electrochemical impedance spectroscopy characteristic parameters

Abstract

The invention belongs to the technical field of echelon recycling of retired lead-acid storage batteries, and particularly relates to a lead-acid storage battery capacity consistency screening method based on electrochemical impedance spectroscopy characteristic parameters. The method comprises the following steps: by taking 104 power grid decommissioned GFM series valve-regulated sealed lead-acid storage batteries as objects, firstly, measuring an electrochemical impedance spectrum in a range of 0.01 Hz-1 kHz by utilizing a Coster CS2350H electrochemical workstation, acquiring data by injecting a tiny voltage signal, and calculating impedance through Fourier transform; and then the actual residual capacity is measured through a specific charging and discharging process by using charging and discharging testing equipment. According to a measured impedance spectrum curve, after effectiveness is detected through KK transformation, part of frequency band data is removed, LR (CR) (QR) is selected to establish an equivalent circuit model, impedance spectrum fitting is carried out to determine capacity consistency screening characteristic parameters, finally 24 single batteries with good capacity consistency are screened out from 104 batteries to be recombined and reused, the difference between the maximum capacity and the minimum capacity of the selected batteries is only 48Ah, and the maximum capacity and the minimum capacity of the selected batteries are only 48Ah. And an effective way is provided for improving the screening efficiency and resource reutilization of the retired lead-acid storage battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of cascade reuse of retired lead-acid batteries, and in particular relates to a method for screening the capacity consistency of lead-acid batteries based on characteristic parameters of electrochemical impedance spectroscopy. Background Art

[0002] Currently, lead-acid batteries are widely used in uninterruptible power supplies (UPS), renewable energy storage, and grid peak shifting due to their stable performance, long production cycles, mature technology, high operating voltage, wide operating temperature range, float charge, and shallow charge and discharge capabilities. Traditional lead-acid batteries have a short cycle life, with a theoretical cycle life of only about one-third that of lithium-ion batteries. Therefore, there is still considerable room for improving the cycle life of lead-acid batteries, especially those that utilize new materials, structures, and technologies, such as bipolar lead-acid and lead-carbon batteries. When battery capacity drops to 80%, it becomes unable to meet the power needs of electric vehicles and faces retirement. However, from a battery perspective, if retired batteries are simply scrapped, their service life will be severely shortened, energy efficiency will be reduced, and resources will be significantly wasted.

[0003] The technology of cascade reuse of retired lead-acid batteries has become a hot topic in current research. In existing studies, according to different consistency screening indicators, the screening methods are divided into four categories: single parameter screening method, multi-parameter screening method, dynamic voltage characteristic screening method and electrochemical impedance spectroscopy technology. The charge and discharge voltage curves of batteries contain rich parameter information. If the charge and discharge voltage curves of two batteries have a high degree of overlap, it indicates that the two batteries have good consistency. However, the battery operating conditions are complex, and the single-parameter screening method cannot fully evaluate the internal state of the battery. The consistency screening method that uses the battery's discharge capacity, terminal voltage, internal resistance and self-discharge rate as sorting variables takes into account both the static and dynamic parameters of the battery. It is simple to operate and has good screening effects. However, due to the large number of battery companies and battery types, it is difficult to determine a unified sorting threshold. At the same time, since different parameters are tested "sequentially", this method is extremely time-consuming and its practicality needs to be further improved. The dynamic voltage characteristic screening method is based on the internal characteristics of the secondary battery from the charging platform to the charging cut-off voltage. In essence, the batteries sorted out are more consistent than conventional sorting methods. However, this method relies on parameters such as the battery's discharge energy, energy efficiency, DC internal resistance and open-circuit voltage. These parameters will change during the use of the battery, resulting in a decrease in screening accuracy.

[0004] Electrochemical impedance spectroscopy (EIS) applies sinusoidal AC perturbation signals at different frequencies to a battery, measures the response signals at both ends, and performs a fast Fourier transform (FFT) on the excitation and response signals to calculate the battery's complex impedance spectrum. The real component represents the battery's resistance, and the imaginary component represents its capacitance and inductance. This technique provides rich electrode kinetic information by measuring the battery's impedance over a specific frequency range, and has great potential for applications in lithium battery SOx estimation, degradation pattern recognition, internal temperature estimation, and safety testing. A rapid screening and reassembly method for retired lead-acid batteries based on short-duration pulse discharge and EIS is a solution to the current problems of low screening efficiency, high energy consumption, and low grouping rate. Currently, the most commonly used method for analyzing the internal state information of batteries contained in EIS is based on equivalent circuit models. These methods use the pulse voltage difference, DC internal resistance, EIS curve shape characteristics, and equivalent circuit model parameters as screening indicators to develop mathematical models for the screening and reassembly of retired lead-acid batteries. However, the sheer number of retired batteries presents a pressing challenge in determining battery status in real time and enabling rapid screening and reassembly. Summary of the Invention

[0005] This invention aims to solve the problem of retired battery screening. By measuring the relevant data of retired lead-acid batteries in the power grid, an equivalent circuit model is established to find the relevant screening parameters, and battery cells with consistent capacity are screened for reorganization and reuse, thereby improving screening efficiency and resource utilization. The technical solution of this invention is as follows:

[0006] The method for screening the capacity consistency of retired lead-acid batteries in power grids based on characteristic parameters of electrochemical impedance spectroscopy includes the following steps:

[0007] S1: Use an electrochemical workstation to measure the electrochemical impedance spectroscopy of several retired lead-acid batteries;

[0008] S2: Use charge and discharge test equipment to measure the actual remaining capacity of each retired lead-acid battery;

[0009] S3: Establish an equivalent circuit, fit the electrochemical impedance spectrum of the lead-acid battery and analyze the corresponding relationship between the circuit component parameters and the lead-acid battery capacity. Based on this relationship, obtain the characteristic parameters and conditions for determining capacity consistency screening; the circuit component parameters include the ohmic internal resistance R ohm , SEI film resistance R SEI and transfer impedance R ct .

[0010] S4: Select battery cells with some characteristic parameters that meet the requirements from several retired lead-acid batteries as batteries with good capacity consistency, and reassemble them for reuse.

[0011] Preferably, in S1, the frequency range of impedance measurement is selected to be 0.01 Hz-1 kHz.

[0012] Preferably, in S1, measuring the electrochemical impedance spectrum of the retired lead-acid battery is specifically measured by an electrochemical workstation, injecting a small current signal into the battery, collecting the current excitation signal i[n] and the voltage response signal u[n], performing fast Fourier transform on each, and obtaining frequency domain signals I(jω) and U(jω):

[0013]

[0014] Where i[n] is the current excitation signal, u[n] is the voltage response signal, ω represents the angular frequency, n represents the number of discrete signal points, and j is the imaginary unit;

[0015] Calculate the impedance Z(jω) of the battery under test based on the frequency domain signals I(jω) and U(jω):

[0016] Z(jω)=U(jω) / I(jω)=Z’+Z”;

[0017] Wherein, I(jω) and U(jω) are the frequency domain signals calculated by the above formula, and Z' and Z" represent the real impedance and imaginary impedance of the battery to be tested, respectively.

[0018] Preferably, in S2, the actual remaining capacity of each retired lead-acid battery is measured, and the specific operation is as follows: the battery is left to stand for 1 hour, discharged at a constant current rate of 1C to a cut-off voltage of 1.8V, and after standing for 1 hour, it is charged at a constant current and constant voltage rate of 1.5C to a rated nominal voltage of 2V, and the discharge capacity is detected; the above operation is repeated three times, and the average value of the three discharge capacities is calculated as the accurate value of the current remaining capacity of the battery.

[0019] Preferably, in said S3, before establishing the equivalent circuit, the electrochemical impedance spectrum of the lead-acid battery is first subjected to a Kramers-Kronig (KK) transformation, and the electrochemical impedance data with a Kramers-Kronig transformation result residual exceeding ±1% are eliminated.

[0020] Preferably, before using electrochemical impedance spectroscopy data to screen the capacity consistency of lead-acid batteries, the reliability of the measured electrochemical impedance spectroscopy data must be ensured. The Kramers-Kronig transform establishes a connection between the real and imaginary parts of the electrochemical impedance data through an integral formula to verify whether the lead-acid battery system under test meets causality, linearity and stability, thereby determining whether the measured electrochemical impedance spectroscopy data is valid. Generally speaking, electrochemical impedance data with a Kramers-Kronig transform result residual exceeding ±1% is considered invalid.

[0021] Kramers-Kronig (KK) transformation is a mathematical formula used to verify the validity of electrochemical impedance spectroscopy data. Kramers-Kronig (KK) transformation is performed on the real and imaginary parts of electrochemical impedance.

[0022] Preferably, the equivalent circuit of the retired lead-acid battery is: LR(CR)(QR).

[0023] Preferably, the equivalent circuit model consists of an inductor element L, an ohmic resistor R ohm , capacitance element C, SEI film resistance R SEI , constant phase element Q and transfer impedance R ct composition.

[0024] Preferably, the relationship between the circuit element parameters and the battery capacity is: when the internal resistance is too large, the battery voltage changes rapidly, thereby shortening the battery's charge and discharge time, reducing the charge and discharge capacity, and reducing the service life. The characteristic parameters for capacity consistency screening obtained based on the relationship between the circuit element parameters and the battery capacity are: the sum R of the impedances in the high, medium, and low frequency ranges, and the relevant condition is: the sum R of the impedances is within 100 orders of magnitude.

[0025] Preferably, the sum of the impedances R in the three frequency ranges is expressed as follows:

[0026] R=R ohm +R SEI +R ct ;

[0027] Where R ohm Represents the ohmic resistance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R SEI represents the SEI film impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R ct represents the transfer impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery.

[0028] Preferably, the number of retired lead-acid batteries is 104, and the retired lead-acid batteries are GFM series valve-regulated sealed lead-acid batteries with a nominal voltage of 2V, a nominal capacity of 500Ah, a charging current of 50A, a float charge voltage of 2.23V, and an equalization charge voltage of 2.3V.

[0029] The beneficial effects of the present invention are:

[0030] 1. This invention implements capacity consistency screening for 104 retired lead-acid batteries from the power grid based on characteristic parameters of electrochemical impedance spectroscopy. Equivalent circuit elements are used to analyze the internal state information of the batteries contained in the electrochemical impedance spectroscopy curve.

[0031] 2. The present invention analyzes the equivalent circuit element parameters corresponding to the EIS of 104 retired lead-acid batteries to determine the characteristic parameters related to battery capacity and perform consistency screening.

[0032] 3. The characteristic parameters of the present invention are selected based on the working principle of the battery. Since the greater the internal resistance of the battery, the more heat it generates during the charge and discharge process, and the less available energy the battery has, low internal resistance is a criterion for judging the better performance of lead-acid batteries.

[0033] 4. Through equivalent circuit fitting, the present invention discovered that the impedance values of 104 retired lead-acid batteries varied significantly. Plotting this parameter against battery capacity reveals a wide range of remaining capacities among the 104 retired lead-acid batteries, with the difference between the maximum and minimum capacities being 145 Ah.

[0034] 5. The maximum and minimum capacities of the 24 lead-acid batteries screened for characteristic parameter consistency in the present invention differ by only 48 Ah. The capacity of each battery is close to the average level of the battery pack, facilitating capacity balancing during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of an embodiment of a method for screening consistency of retired lead-acid batteries in power grids based on characteristic parameters of electrochemical impedance spectroscopy.

[0036] Figure 2 This is the electrochemical impedance spectroscopy test results of 104 retired lead-acid batteries from the power grid.

[0037] Figure 3 These are the KK test results of electrochemical impedance spectroscopy of 104 retired lead-acid batteries from the power grid.

[0038] Figure 4 It is a typical electrochemical impedance spectroscopy.

[0039] Figure 5 FIG. 1 is an equivalent circuit diagram established according to the shape of the electrochemical impedance spectroscopy according to an embodiment.

[0040] Figure 6 This is a diagram showing the electrochemical impedance spectroscopy fitting results using an equivalent circuit in one embodiment.

[0041] Figure 7 This is the distribution diagram of characteristic parameters of electrochemical impedance spectroscopy of 104 retired lead-acid batteries from the power grid.

[0042] Figure 8 This embodiment shows the consistency screening results of 104 retired lead-acid batteries from the power grid based on the characteristic parameters of electrochemical impedance spectroscopy. DETAILED DESCRIPTION

[0043] The method for screening the capacity consistency of retired lead-acid batteries in power grids based on characteristic parameters of electrochemical impedance spectroscopy includes the following steps:

[0044] S1: Use an electrochemical workstation to measure the electrochemical impedance spectroscopy of several retired lead-acid batteries;

[0045] S2: Use charge and discharge test equipment to measure the actual remaining capacity of each retired lead-acid battery;

[0046] S3: Establish an equivalent circuit, fit the electrochemical impedance spectrum of the lead-acid battery and analyze the circuit element parameters (ohmic internal resistance R ohm , SEI film resistance R SEI and transfer impedance R ct ) and the lead-acid battery capacity, and obtaining characteristic parameters and conditions for determining capacity consistency screening based on the relationship;

[0047] S4: Select battery cells with some characteristic parameters that meet the requirements from several retired lead-acid batteries as batteries with good capacity consistency, and reassemble them for reuse.

[0048] In S1, the frequency range of impedance measurement is selected as 0.01Hz-1kHz.

[0049] In S1, the electrochemical impedance spectrum of retired lead-acid batteries is measured by an electrochemical workstation. A small current signal is injected into the battery, and the current excitation signal i[n] and the voltage response signal u[n] are collected. Fast Fourier transform is performed on each of them to obtain frequency domain signals I(jω) and U(jω):

[0050]

[0051]

[0052] Where i[n] is the current excitation signal, u[n] is the voltage response signal, ω represents the angular frequency, n represents the number of discrete signal points, and j is the imaginary unit;

[0053] Calculate the impedance Z(jω) of the battery under test based on the frequency domain signals I(jω) and U(jω):

[0054] Z(jω)=U(jω) / I(jω)=Z’+Z”;

[0055] Wherein, I(jω) and U(jω) are the frequency domain signals calculated by the above formula, and Z' and Z" represent the real impedance and imaginary impedance of the battery to be tested, respectively.

[0056] In S2, the actual remaining capacity of each retired lead-acid battery is measured. The specific operation is as follows: the battery is left to stand for 1 hour, discharged at a constant current rate of 1C to a cut-off voltage of 1.8V, and after standing for 1 hour, it is charged at a constant current and constant voltage rate of 1.5C to a rated nominal voltage of 2V, and the discharge capacity is detected; the above operation is repeated three times, and the average value of the three discharge capacities is calculated as the accurate value of the current remaining capacity of the battery.

[0057] In S3, before establishing the equivalent circuit, the electrochemical impedance spectrum of the lead-acid battery is first subjected to a Kramers-Kronig transformation, and electrochemical impedance data with a residual error of the Kramers-Kronig transformation result exceeding ±1% are eliminated.

[0058] The equivalent circuit of a retired lead-acid battery is: LR(CR)(QR).

[0059] The equivalent circuit model consists of the inductor L and the ohmic resistor R ohm , capacitance element C, SEI film resistance R SEI , constant phase element Q and transfer impedance R ct composition.

[0060] The relationship between circuit component parameters and battery capacity is: when the internal resistance is too large, the battery voltage changes rapidly, thereby shortening the battery's charge and discharge time, reducing the charge and discharge capacity, and shortening the service life. The characteristic parameters for capacity consistency screening obtained based on the relationship between circuit component parameters and battery capacity are: the sum of impedances R in the high, medium, and low frequency ranges. The relevant condition is: the sum of impedances R is within 100 orders of magnitude.

[0061] The sum of the impedances in the three frequency ranges, R, is expressed as follows:

[0062] R=R ohm +R SEI +R ct ;

[0063] Where R ohm Represents the ohmic resistance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R SEI represents the SEI film impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R ct represents the transfer impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery.

[0064] The number of retired lead-acid batteries is 104, and the retired lead-acid batteries are GFM series valve-regulated sealed lead-acid batteries with a nominal voltage of 2V, a nominal capacity of 500Ah, a charging current of 50A, a float charge voltage of 2.23V, and an equalizing charge voltage of 2.3V.

[0065] Example

[0066] The present invention proposes a method for screening the capacity consistency of retired lead-acid batteries in power grids based on characteristic parameters of electrochemical impedance spectroscopy. Figure 1 As shown, the specific steps include:

[0067] Step 1: Use an electrochemical workstation to measure the electrochemical impedance spectra of 104 retired lead-acid batteries.

[0068] In this embodiment, the test object is a "Shuangdeng" GFM series valve-regulated sealed lead-acid battery, which has a nominal voltage of 2V, a nominal capacity of 500Ah, a charging current of 50A, a float charge voltage of 2.23V, and an equalization charge voltage of 2.3V.

[0069] In this example, an electrochemical impedance spectroscopy experiment was performed using an electrochemical workstation, and the impedance test frequency range was selected to be 0.01 Hz-1 kHz. The electrochemical impedance spectroscopy of retired lead-acid batteries was measured using an electrochemical workstation. A small current signal was injected into the battery, and the current excitation signal i[n] and the voltage response signal u[n] were collected. Fast Fourier transforms were performed on each of these signals to obtain frequency domain signals I(jω) and U(jω):

[0070]

[0071] Where i[n] is the current excitation signal, u[n] is the voltage response signal, ω represents the angular frequency, n represents the number of discrete signal points, and j is the imaginary unit;

[0072] Calculate the impedance Z(jω) of the battery under test based on the frequency domain signals I(jω) and U(jω):

[0073] Z(jω)=U(jω) / I(jω)=Z’+Z”;

[0074] Wherein, I(jω) and U(jω) are the frequency domain signals calculated by the above formula, and Z' and Z" represent the real impedance and imaginary impedance of the battery to be tested, respectively.

[0075] Step 2: Use a charge and discharge tester to measure the remaining capacity of 104 retired lead-acid batteries from the grid.

[0076] In this embodiment, the specific steps of the capacity test experiment are as follows: the battery is left to stand for 1 hour, and the battery is discharged at a constant current rate of 1C to a cut-off voltage of 1.8V in a charge and discharge tester. After standing for 1 hour, the battery is charged at a constant current and constant voltage rate of 1.5C to a rated nominal voltage of 2V in the charge and discharge tester, and the discharge capacity is calibrated as the current true capacity of the lead-acid battery. All the above steps constitute one capacity test, which is repeated three times. The accurate value of the current remaining capacity of the battery is obtained by calculating the average of the three capacity values.

[0077] In this embodiment, the capacity consistency screening of 104 retired lead-acid batteries based on characteristic parameters requires four steps:

[0078] Step 301: Using KK transformation to verify the validity of electrochemical impedance spectroscopy measurement results of 104 retired lead-acid batteries from the power grid;

[0079] Step 302: Establishing a suitable equivalent circuit model based on the KK test results and the shape of the electrochemical impedance spectroscopy curve;

[0080] Step 303: Use an equivalent circuit to fit the electrochemical impedance spectra of 104 retired lead-acid batteries, explore the corresponding relationship between circuit component parameters and the capacity of retired lead-acid batteries, and determine characteristic parameters for capacity consistency screening.

[0081] In this embodiment, the KK test result in step 301 is as follows: Figure 3 As shown, the residual of the impedance measurement result in the low-frequency part is relatively large, exceeding ±1%. The measurement results show that the impedance data in the frequency range of 0.01Hz-0.08Hz is invalid.

[0082] In this embodiment, step 302 uses an equivalent circuit model to analyze the electrochemical impedance spectroscopy measurement results. A typical electrochemical impedance spectroscopy consists of three parts, including a high-frequency part, a medium-frequency part, and a low-frequency part. Figure 4 As shown, the corresponding equivalent circuit model uses inductance L to describe the high-frequency response, and the intersection of the electrochemical impedance spectrum and the real axis is the ohmic resistance R ohm The mid-frequency part is determined by the SEI film impedance R SEI and charge transfer resistance R ct The low frequency part uses Warburg element R w To describe.

[0083] In this embodiment, step 302 deletes the impedance data in the frequency range of 0.01Hz-0.08Hz according to the KK test result, and establishes the corresponding equivalent circuit model: LR(CR)(QR), as shown in FIG. Figure 5 As shown, the equivalent circuit model consists of an inductor element L, an ohmic resistor R ohm , capacitance element C, SEI film resistance R SEI , constant phase element Q and transfer impedance R ct composition.

[0084] In this embodiment, step 303 uses an equivalent circuit model to fit the electrochemical impedance spectrum, and the fitting effect is as follows: Figure 6As shown, the fitting error is 3.14E-4. The parameters of the above circuit components are obtained by fitting calculation. Based on the operating characteristics of lead-acid batteries, when the internal resistance is too large, the battery voltage changes quickly, shortening the battery charging and discharging time, reducing the charging and discharging capacity, and shortening the service life. Therefore, the sum of the impedances R in the three frequency intervals is selected as the characteristic parameter for consistency screening. The R value is calculated by the ohmic resistance R ohm , SEI film resistance R SEI and transfer impedance R ct The calculation formula is as follows:

[0085] R=R ohm +R SEI +R ct ;

[0086] Where R ohm Represents the ohmic resistance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R SEI represents the SEI film impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R ct represents the transfer impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery.

[0087] In this embodiment, step 303 analyzes the characteristic parameter R of the EIS of 104 retired lead-acid batteries from the power grid and finds that the R values of these batteries have a large difference in magnitude, such as Figure 7 As shown in the figure, the greater the internal resistance of the battery, the more heat it generates during the charge and discharge process, posing a greater safety hazard. At the same time, the available capacity of the battery will be greatly reduced. Therefore, the internal resistance R is used as a characteristic parameter for the capacity consistency screening of retired lead-acid batteries.

[0088] In this embodiment, step 303 plots the relationship between the characteristic parameter R and the battery capacity, such as Figure 8 As shown, the capacity of the 104 batteries varies greatly, with the difference between the maximum and minimum battery capacities being 145 Ah.

[0089] Step 4: 24 battery cells with qualified characteristic parameters are selected from 104 retired lead-acid batteries as batteries with good capacity consistency, and are reassembled for reuse.

[0090] In this embodiment, step 4 plots the relationship between the characteristic parameter R and the battery capacity, such as Figure 8 As shown, the capacities of the 104 batteries vary significantly, with the difference between the maximum and minimum capacities being 145 Ah. In this example, batteries with characteristic parameter R values within 100 orders of magnitude were selected. After characteristic parameter consistency screening, the maximum and minimum capacities of the 24 selected lead-acid batteries differed by only 48 Ah. The capacity of each battery is close to the average level of the battery pack, facilitating capacity balancing during operation.

[0091] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for screening the capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy, characterized in that: The following steps are involved: S1: Use an electrochemical workstation to measure the electrochemical impedance spectroscopy of several retired lead-acid batteries; S2: Use charge and discharge test equipment to measure the actual remaining capacity of each retired lead-acid battery; S3: Establish an equivalent circuit, fit the electrochemical impedance spectrum of the lead-acid battery, and analyze the corresponding relationship between the circuit component parameters and the lead-acid battery capacity. Based on this relationship, obtain the characteristic parameters and conditions for determining the capacity consistency screening; S4: Select battery cells with some characteristic parameters that meet the requirements from several retired lead-acid batteries as batteries with good capacity consistency, and reassemble them for reuse.

2. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: In the above-mentioned S1, the frequency range of impedance measurement is selected to be 0.01 Hz-1 kHz.

3. The method for screening capacity consistency of retired lead-acid batteries based on electrochemical impedance spectroscopy characteristic parameters according to claim 1 is characterized in that: In S1, the electrochemical impedance spectrum of retired lead-acid batteries is measured by an electrochemical workstation. A small current signal is injected into the battery, and the current excitation signal i[n] and the voltage response signal u[n] are collected. Fast Fourier transform is performed on each of them to obtain frequency domain signals I(jω) and U(jω): Where i[n] is the current excitation signal, u[n] is the voltage response signal, ω represents the angular frequency, n represents the number of discrete signal points, and j is the imaginary unit; Calculate the impedance Z(jω) of the battery under test based on the frequency domain signals I(jω) and U(jω): Z(jω)=U(jω) / I(jω)=Z’+Z”; Wherein, I(jω) and U(jω) are the frequency domain signals calculated by the above formula, and Z' and Z" represent the real impedance and imaginary impedance of the battery to be tested, respectively.

4. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: In S2, the actual remaining capacity of each retired lead-acid battery is measured. The specific operation is as follows: the battery is left to stand for 1 hour, discharged at a constant current rate of 1C to a cut-off voltage of 1.8V, and after standing for 1 hour, it is charged at a constant current and constant voltage rate of 1.5C to a rated nominal voltage of 2V, and the discharge capacity is detected; the above operation is repeated three times, and the average value of the three discharge capacities is calculated as the accurate value of the current remaining capacity of the battery.

5. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: In the above S3, before establishing the equivalent circuit, the electrochemical impedance spectrum of the lead-acid battery is first subjected to Kramers-Kronig transformation, and the electrochemical impedance data with a residual error of the Kramers-Kronig transformation result exceeding ±1% are eliminated.

6. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 5, characterized in that: Before using electrochemical impedance spectroscopy data to screen the capacity consistency of lead-acid batteries, the reliability of the measured electrochemical impedance spectroscopy data must be ensured. The Kramers-Kronig transform establishes the relationship between the real and imaginary parts of the electrochemical impedance data through an integral formula to verify whether the lead-acid battery system under test meets causality, linearity and stability, thereby determining whether the measured electrochemical impedance spectroscopy data is valid. Generally speaking, electrochemical impedance data with a Kramers-Kronig transform result residual exceeding ±1% is considered invalid.

7. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 6, characterized in that: Causality means that there is a causal relationship between the excitation signal injected into the lead-acid battery system and the response signal at both ends of the lead-acid battery system, that is, the response signal is only a response to the excitation signal; linearity means that the response signal is a linear function of the excitation signal; stability means that the lead-acid battery system under test is stable.

8. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: The equivalent circuit of the retired lead-acid battery is: LR(CR)(QR).

9. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1 or 8, characterized in that: The equivalent circuit model is composed of an inductor element L, an ohmic resistor R ohm , capacitance element C, SEI film resistance R SEI , constant phase element Q and transfer impedance R ct composition.

10. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: The relationship between circuit component parameters and battery capacity is: when the internal resistance is too large, the battery voltage changes rapidly, thereby shortening the battery's charge and discharge time, reducing the charge and discharge capacity, and shortening the service life. The characteristic parameters for capacity consistency screening obtained based on the relationship between circuit component parameters and battery capacity are: the sum of impedances R in the high, medium, and low frequency ranges. The relevant condition is: the sum of impedances R is within 100 orders of magnitude.

11. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 10, characterized in that: The sum of the impedances in the three frequency ranges, R, is expressed as follows: R=R ohm +R SEI +R ct ; Where R ohm Represents the ohmic resistance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R SEI represents the SEI film impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery, R ct represents the transfer impedance parameter obtained by fitting the electrochemical impedance spectrum of the lead-acid battery.

12. The method for screening capacity consistency of retired lead-acid batteries from power grids based on characteristic parameters of electrochemical impedance spectroscopy according to claim 1, characterized in that: The number of retired lead-acid batteries is 104, and the retired lead-acid batteries are GFM series valve-regulated sealed lead-acid batteries with a nominal voltage of 2V, a nominal capacity of 500Ah, a charging current of 50A, a float charge voltage of 2.23V, and an equalization charge voltage of 2.3V.

Images