Battery pole piece uniformity test method, device, equipment, medium and program

Abstract

The application provides a battery electrode sheet uniformity test method, device, equipment, medium and program, and belongs to the technical field of batteries. The test method comprises the following steps: obtaining a plurality of electrochemical impedance spectra of a plurality of test positions of a to-be-tested electrode sheet based on a pre-constructed locally symmetrical battery; the locally symmetrical battery is pre-constructed according to the following steps: obtaining the to-be-tested electrode sheet; obtaining an auxiliary test electrode sheet, the auxiliary test electrode sheet and the to-be-tested electrode sheet have undergone at least one same processing procedure, and the area of the auxiliary test electrode sheet is smaller than that of the to-be-tested electrode sheet; and adding a separator between the to-be-tested electrode sheet and the auxiliary test electrode sheet to obtain the locally symmetrical battery; determining a plurality of characteristic resistances of the to-be-tested electrode sheet according to the plurality of electrochemical impedance spectra; and determining the uniformity of the to-be-tested electrode sheet based on the plurality of characteristic resistances of the to-be-tested electrode sheet. The method can efficiently evaluate the uniformity of the electrode sheet electrical performance, and can provide a theoretical basis for process optimization in the battery processing process and positioning of battery failure causes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery pole piece uniformity testing method, device, equipment, medium and program. BACKGROUND

[0002] Energy saving and emission reduction is the key to social sustainable development. Rechargeable batteries have the characteristics of storing or releasing energy as needed, and are widely used in various electric devices or energy storage systems, and are an important part of promoting energy transformation and sustainable development. For the new energy industry, battery technology is an important factor for its development.

[0003] The battery pole piece is an important part of the battery and has a crucial influence on the performance of the battery. If the uniformity of the battery pole piece is poor, it may lead to uneven current distribution inside the battery, abnormal battery internal resistance, and other problems, causing excessive polarization, electrode material aging and damage. However, in the manufacturing and failure analysis of batteries, the analysis of the uniformity of the pole piece can only provide macroscopic physical parameters, and lacks data support at the mesoscale (micron to millimeter level). SUMMARY

[0004] The present application aims to at least solve the technical problem of lacking mesoscale testing and analysis of pole piece uniformity in the background art. Therefore, one object of the present application is to provide a battery pole piece uniformity testing method, so as to efficiently evaluate the uniformity of the pole piece and improve the accuracy of the test results.

[0005] Embodiments of the first aspect of the present application provide a battery pole piece uniformity testing method, comprising: obtaining a plurality of electrochemical impedance spectra of a plurality of test positions of a to-be-tested pole piece based on a pre-constructed locally symmetric battery, wherein the locally symmetric battery is pre-constructed according to the following steps: obtaining the to-be-tested pole piece; obtaining an auxiliary test pole piece, the auxiliary test pole piece and the to-be-tested pole piece having undergone at least one same processing procedure, and the area of the auxiliary test pole piece being smaller than that of the to-be-tested pole piece; and adding a separator between the to-be-tested pole piece and the auxiliary test pole piece to obtain the locally symmetric battery; determining a plurality of characteristic resistances of the to-be-tested pole piece according to the plurality of electrochemical impedance spectra; and determining the uniformity of the to-be-tested pole piece based on the plurality of characteristic resistances of the to-be-tested pole piece.

[0006] In the technical solution of the embodiment of the application, the uniformity of the electrode performance of the to-be-tested electrode sheet can be efficiently evaluated on a mesoscopic level by testing different positions of the to-be-tested electrode sheet and determining the characteristic resistance of the to-be-tested electrode sheet according to the obtained electrochemical impedance spectrum, and a theoretical basis can be provided for process optimization in the battery processing process and positioning of the battery failure cause. The local symmetrical battery is constructed by using the auxiliary test electrode sheet and the to-be-tested electrode sheet, the multiple test positions on the to-be-tested electrode sheet can be tested, and the accurate electrochemical impedance spectrum test result of the to-be-tested electrode sheet can be obtained. The area of the auxiliary test electrode sheet is set to be smaller than the area of the to-be-tested electrode sheet, so that the auxiliary test electrode sheet can be moved at different positions of the to-be-tested electrode sheet according to different test positions, and sufficient detection of the electrochemical impedance spectrum can be realized.

[0007] In some embodiments, the auxiliary test electrode sheet is a circular electrode sheet with a diameter of not greater than 5 millimeters. By using a smaller auxiliary test electrode sheet, the detection resolution can be improved, and thus the detection accuracy can be improved.

[0008] In some embodiments, based on the pre-constructed local symmetrical battery, obtaining the multiple electrochemical impedance spectrums of the multiple test positions of the to-be-tested electrode sheet includes: immersing the local symmetrical battery in an electrolyte; moving the auxiliary test electrode sheet to any one of the multiple test positions; and obtaining the electrochemical impedance spectrum of the test position. By detecting the electrochemical impedance spectrums of different test positions, the characteristic resistance of different positions of the to-be-tested electrode sheet can be obtained, and thus accurate detection of the uniformity of the to-be-tested electrode sheet can be realized.

[0009] In some embodiments, immersing the local symmetrical battery in the electrolyte includes: immersing the local symmetrical battery in the electrolyte so that the electrolyte completely immerses the local symmetrical battery; and applying a predetermined pressure to the local symmetrical battery. By completely immersing the local symmetrical battery in the electrolyte and applying a pressure to the local symmetrical battery, the detection result of the electrochemical impedance spectrum can be more accurate and more consistent with the actual situation of the to-be-tested electrode sheet.

[0010] In some embodiments, the predetermined pressure is set to be greater than or equal to 0.1 megapascal and less than or equal to 2 megapascal. By reasonably designing the pressure applied to the local symmetrical battery, the accuracy of the test result can be improved.

[0011] In some embodiments, the determining the plurality of characteristic resistances of the to-be-tested electrode sheet according to the plurality of electrochemical impedance spectrums comprises: in response to the to-be-tested electrode sheet being a first type of to-be-tested electrode sheet, determining a plurality of first characteristic resistances of the to-be-tested electrode sheet, the first characteristic resistances being used to indicate the resistance generated in the charge transfer process; and in response to the to-be-tested electrode sheet being a second type of to-be-tested electrode sheet, determining a plurality of second characteristic resistances of the to-be-tested electrode sheet, the second characteristic resistances being used to indicate the resistance suffered by the electrolyte when transmitting in the electrode sheet pores. According to different types of electrode sheets, different characteristic resistances are determined, which can more accurately reflect the characteristics of the electrode sheet, and the uniformity detection result obtained therefrom is also more true.

[0012] In some embodiments, the determining the plurality of characteristic resistances of the to-be-tested electrode sheet according to the plurality of electrochemical impedance spectrums comprises: determining the plurality of characteristic resistances according to a pre-constructed equivalent circuit model and the plurality of electrochemical impedance spectrums. In the process of determining the characteristic resistances, the equivalent circuit model of the to-be-tested electrode sheet is constructed, which can obtain the characteristic resistances more in line with the characteristics of the electrode sheet, and improve the accuracy of the result.

[0013] In some embodiments, the test method further comprises: obtaining the voltage applied to the to-be-tested electrode sheet. By obtaining the voltage applied to the to-be-tested electrode sheet, in combination with the equivalent circuit model, the corresponding characteristic resistance can be obtained, so as to determine the uniformity detection result of the to-be-tested electrode sheet.

[0014] In some embodiments, the determining the uniformity of the to-be-tested electrode sheet based on the plurality of characteristic resistances of the to-be-tested electrode sheet comprises: determining at least one statistical parameter of the plurality of characteristic resistances; and determining the uniformity of the to-be-tested electrode sheet according to the at least one statistical parameter. By extracting the statistical parameters of the respective characteristic resistances, the quantitative evaluation of the electrical performance of the electrode sheet can be realized according to the changes of these parameters, so as to obtain the detection result of the uniformity of the electrode sheet, and realize the efficient evaluation of the uniformity of the electrode sheet.

[0015] In some embodiments, the at least one statistical parameter comprises at least one of a mean value, a standard deviation, and a coefficient of variation. By selecting appropriate statistical parameters, more accurate detection results can be obtained.

[0016] In some embodiments, the determining the uniformity of the to-be-tested electrode sheet according to the at least one statistical parameter comprises: in response to any one of the at least one statistical parameter exceeding a pre-set parameter threshold, determining that the uniformity of the to-be-tested electrode sheet does not meet the uniformity requirement. According to whether the statistical parameter exceeds the pre-set threshold, the electrode sheet with poor uniformity can be quickly identified, and the detection efficiency is improved.

[0017] In some embodiments, the plurality of test positions are arranged in sequence along a predetermined direction on the to-be-tested electrode sheet. By determining reasonable test positions, the characteristic resistances obtained can fully reflect the electrical performance changes of the to-be-tested electrode sheet, so as to obtain accurate electrode sheet uniformity detection results.

[0018] The embodiment of the second aspect of the present application provides a battery pole piece uniformity testing device, comprising: a first module, comprising obtaining a plurality of electrochemical impedance spectra of a plurality of test positions of a to-be-tested pole piece based on a pre-constructed locally symmetric battery, wherein the locally symmetric battery is pre-constructed according to the following steps: obtaining the to-be-tested pole piece; obtaining an auxiliary test pole piece, the auxiliary test pole piece and the to-be-tested pole piece undergo at least one same processing procedure, and the area of the auxiliary test pole piece is smaller than that of the to-be-tested pole piece; and adding a separator between the to-be-tested pole piece and the auxiliary test pole piece to obtain the locally symmetric battery; a second module, comprising determining a plurality of characteristic resistances of the to-be-tested pole piece according to the plurality of electrochemical impedance spectra; and a third module, comprising determining the uniformity of the to-be-tested pole piece based on the plurality of characteristic resistances of the to-be-tested pole piece.

[0019] The embodiment of the third aspect of the present application provides a computing device, comprising: at least one processor; and at least one memory communicatively connected with the at least one processor, the at least one memory storing instructions, which, when executed by the at least one processor alone or jointly, cause the computing device to perform the test method in the above-mentioned embodiments.

[0020] The embodiment of the fourth aspect of the present application provides a computer readable storage medium, which stores instructions, which, when executed by one or more processors of a computing device alone or jointly, cause the computing device to perform the test method in the above-mentioned embodiments.

[0021] The embodiment of the fifth aspect of the present application provides a computer program product, comprising instructions, which, when executed by one or more processors of a computing device alone or jointly, cause the computing device to perform the test method described above.

[0022] The above description is only a summary of the technical solutions of the present application, in order to enable the technical means of the present application to be more clearly understood, and to be implemented in accordance with the content of the description, and in order to enable the above and other purposes, features and advantages of the present application to be more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0023] In the drawings, identical or similar components or elements are denoted by identical reference numerals throughout the several views, unless otherwise specified. The drawings are not necessarily to scale. It is to be understood that these drawings only depict some embodiments in accordance with the disclosure and should not be considered to limit the scope of the disclosure.

[0024] Figure 1 Flowchart of the battery pole piece uniformity testing method of some embodiments of the present application;

[0025] Figure 2Flowchart for constructing a locally symmetric battery for some embodiments of the present application;

[0026] Figure 3 Schematic diagram of a locally symmetric battery for some embodiments of the present application;

[0027] Figure 4 Flowchart for obtaining an electrochemical impedance spectrum for some embodiments of the present application;

[0028] Figure 5 Flowchart for immersing a locally symmetric battery in an electrolyte for some embodiments of the present application;

[0029] Figure 6 Flowchart for determining a characteristic resistance for some embodiments of the present application;

[0030] Figure 7 Flowchart for determining the uniformity of a test electrode for some embodiments of the present application;

[0031] Figure 8 Schematic diagram of an electrochemical impedance spectrum of a first type of test electrode for some embodiments of the present application;

[0032] Figure 9 Schematic diagram of a first characteristic resistance for some embodiments of the present application;

[0033] Figure 10 Schematic diagram of an electrochemical impedance spectrum of a second type of test electrode for some embodiments of the present application;

[0034] Figure 11 Schematic diagram of a second characteristic resistance for some embodiments of the present application;

[0035] Figure 12 Schematic block diagram of a test device for the uniformity of a battery electrode for some embodiments of the present application;

[0036] Figure 13 Schematic block diagram of a computing device for some embodiments of the present application;

[0037] Figure 14 Flowchart of a test method for the uniformity of a battery electrode for some embodiments of the present application. DETAILED DESCRIPTION

[0038] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise required by context, singular terms shall include pluralities and vice versa. Unless otherwise required by context, the use herein of the singular is also to be construed as a reference to the plural and vice versa.

[0040] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited.

[0041] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification is not necessarily all referring to the same embodiment, or to a particular embodiment, or to a particular set of embodiments, and is not necessarily mutually exclusive of other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0043] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0044] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. The orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as limiting the embodiments of the present application. The device or element indicated must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0045] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0046] At present, from the development of market situation, the application of rechargeable battery is more and more widely. Rechargeable battery is not only applied to energy storage power supply system of hydropower, thermal power, wind power and solar power station, but also widely used in various electronic equipment, such as electric bicycle, electric motorcycle, electric vehicle and other electric vehicles, military equipment and aerospace and other fields. With the continuous expansion of the application field of rechargeable battery, the market demand is also increasing.

[0047] The battery pole piece is an important part of the battery, which has a crucial influence on the performance of the battery. If the uniformity of the battery pole piece is poor, it may lead to uneven current distribution inside the battery, abnormal battery internal resistance, and other problems, such as excessive polarization, electrode material aging and damage. However, in the manufacturing and failure analysis of the battery, the analysis of the uniformity of the pole piece usually only uses macroscopic tests, such as punching standard size samples (usually ≥1 square centimeter (cm²)) at different positions of the pole piece (such as the edge, center and transition zone of the pole piece) to obtain local information, testing the thickness, mass and electrical conductivity of these samples respectively, and quantifying the process fluctuation by statistical method. However, these traditional test methods have single test dimension, which can only provide macroscopic physical parameters, and the electrical conductivity analysis is based on a simplified model (such as the uniform porous medium assumption model), without considering the mesoscopic structure of the actual electrode (such as porosity and tortuosity), lacking data support at mesoscopic scale (micron to millimeter), and unable to accurately and efficiently evaluate the uniformity of the battery pole piece, resulting in large errors in the detection results of the uniformity of the pole piece, especially unable to provide theoretical basis for the process parameters in the pole piece processing process and the failure analysis of the pole piece.

[0048] In order to realize the efficient and accurate determination of the uniformity of the pole piece, a test method is designed, which uses a local symmetrical battery to obtain the electrochemical impedance spectrum of the pole piece to be tested, and then obtains the characteristic resistance at different positions of the pole piece to be tested, so as to efficiently evaluate the uniformity of the pole piece to be tested.

[0049] Using such a test method, the uniformity of the electrical performance of the pole piece can be efficiently evaluated at the mesoscopic level, which can provide theoretical basis for process optimization in the battery processing process and positioning of the failure reason of the battery.

[0050] The test method disclosed in the embodiments of the present application can be used in the test process of a battery used in an electric device or an energy storage device such as a vehicle, a ship or an aircraft, but is not limited thereto. The test method disclosed in the present application can be used, so that efficient and accurate determination of the uniformity of the electrode sheet is facilitated.

[0051] The embodiments of the present application provide a test method for the uniformity of a battery electrode sheet. Referring to Figure 1 , the test method for the uniformity of the battery electrode sheet comprises steps 110 to 130.

[0052] In step 110, a plurality of electrochemical impedance spectra of a plurality of test positions of a to-be-tested electrode sheet are obtained based on a pre-constructed locally symmetrical battery.

[0053] In step 120, a plurality of characteristic resistances of the to-be-tested electrode sheet are determined according to the plurality of electrochemical impedance spectra.

[0054] In step 130, the uniformity of the to-be-tested electrode sheet is determined based on the plurality of characteristic resistances of the to-be-tested electrode sheet.

[0055] In the preparation process of the electrode sheet, the dispersion of the conductive agent in the positive and negative electrode sheets of the battery will be affected by many complex process control parameters such as slurry formula, stirring condition, coating / drying condition, etc. If the uniformity of the electrode sheet is poor, for example, the conductive agent is not evenly dispersed, the thickness consistency of the electrode sheet is poor, etc., the performance of the battery will be greatly affected. The test method in the present application can be used to test the uniformity and consistency of the electrode sheet.

[0056] Electrochemical impedance spectroscopy (EIS) is an important analysis method in the field of electrochemical testing, which can provide information about charge transfer, ion migration and diffusion, and electrode / electrolyte interface dynamics, and is crucial for determining battery reaction mechanisms and improving battery performance. It measures the corresponding current or potential response by applying a small amplitude sinusoidal wave potential or current disturbance on an electrochemical system, and then draws an impedance spectrum.

[0057] In step 110, the electrochemical impedance spectra of different test positions of the to-be-tested electrode sheet are tested by using a pre-constructed locally symmetrical battery. The symmetrical battery, i.e. the positive and negative electrodes use the same or similar electrode materials, has a symmetrical electrochemical interface and reaction mechanism, and in one example, a symmetrical battery can be assembled using two electrode sheets of the same material and process. The locally symmetrical battery used in step 110 can be in the form of forming a symmetrical battery only at the test position. The construction method of the locally symmetrical battery will be described in detail below.

[0058] When testing the electrochemical impedance spectrum, the locally symmetric battery needs to be rested to a predetermined open circuit voltage (OCV) or a specified state of charge (SOC) to eliminate the influence of transient polarization, and then a small amplitude and different frequency perturbation signal is applied to it, the impedance at different frequencies is calculated, and the electrochemical impedance spectrum at the test position is obtained, which can be plotted in the form of Nyquist or Bode diagram, etc.

[0059] The electrochemical impedance spectrum can be used to analyze and obtain various electrochemical parameters, so as to be used for evaluating the reaction activity and transport characteristics of the electrode / electrolyte interface, etc. In step 120, according to the electrochemical impedance spectrum at different test positions, the characteristic resistance of different test positions can be further determined. According to different types of electrode sheets, different types of characteristic resistances can be determined. The characteristic resistance may, for example, include a pore resistance (also referred to as an ion resistance, denoted as Rion below), which can represent the resistance to the transmission of ions inside the battery, mainly affected by the positive and negative electrode materials, the separator and the electrolyte; and a charge transfer resistance (denoted as Rct below), which can be used to represent the resistance parameter of the charge transfer process in the electrochemical battery or at the electrode interface, etc.

[0060] As described above, since the uniformity of the electrode sheet will affect the electrical performance of the battery, the electrical performance parameters will also reflect the uniformity of the electrode sheet. According to the electrical performance parameters, the uniformity of the electrode sheet can be evaluated. In step 130, according to the characteristic resistance obtained at different test positions of the electrode sheet to be tested, the uniformity of the electrode sheet to be tested can be determined. The specific process of determining the uniformity of the electrode sheet will be described in detail below.

[0061] By testing different positions of the electrode sheet to be tested and determining the characteristic resistance of the electrode sheet to be tested according to the obtained electrochemical impedance spectrum, the uniformity of the electrical performance of the electrode sheet can be efficiently evaluated at the mesoscopic level, which can provide a theoretical basis for process optimization during battery processing and positioning of battery failure causes, etc.

[0062] According to some embodiments of the present application, the locally symmetric battery is pre-constructed according to a first process 200. Referring to Figure 2 , the first process 200 includes steps 210 to 230.

[0063] Step 210, obtaining an electrode sheet to be tested.

[0064] Step 220, obtaining an auxiliary test electrode sheet. The auxiliary test electrode sheet and the electrode sheet to be tested have undergone at least one same processing procedure.

[0065] Step 230: A separator is added between the electrode to be tested and the auxiliary test electrode to obtain a locally symmetrical cell.

[0066] In the preparation of electrode sheets, the process typically involves coating (uniformly applying positive and negative electrode slurries to a substrate) and rolling (rolling the coated electrode sheet to a certain thickness). After these processes, the electrode sheet is cut to obtain the desired electrode sheet for testing. The electrode sheet for testing obtained in step 210 and the auxiliary test electrode sheet obtained in step 220 both undergo at least one identical processing step. For example, they can be cut from the same processed electrode sheet to obtain the electrode sheet for testing and the auxiliary test electrode sheet, respectively. Because they undergo the same processing steps, the electrode sheet for testing and the auxiliary test electrode sheet have essentially the same material properties and electrical performance characteristics.

[0067] In step 230, a separator is added between the electrode to be tested and the auxiliary test electrode. The separator is a thin film used to isolate the positive and negative electrodes. Since the auxiliary test electrode and the electrode to be tested have basically the same material and electrical properties, a symmetrical battery can be formed by the auxiliary test electrode, the separator, and the electrode to be tested.

[0068] Figure 3 An example of a locally symmetric cell is illustrated below. Figure 3 As shown, the upper part is the auxiliary test electrode 302, and the lower part is the electrode under test 301. A diaphragm 303 is provided between the auxiliary test electrode 302 and the electrode under test 301. The area below the electrode under test can be, for example, a current collector, i.e., a structure or component that collects current.

[0069] By constructing a locally symmetrical cell using an auxiliary test electrode and the electrode under test, multiple test locations on the electrode under test can be tested, resulting in accurate electrochemical impedance spectroscopy test results.

[0070] According to some embodiments of this application, the area of ​​the auxiliary test electrode 302 is smaller than that of the electrode to be tested 301.

[0071] like Figure 3 As shown, the area of ​​the auxiliary test electrode 302 is smaller than that of the electrode under test 301. At the placement position of the auxiliary test electrode 302, the auxiliary test electrode 302, the separator 303, and the electrode under test 301 constitute a symmetrical cell, that is, a locally symmetrical cell.

[0072] Since the area of ​​the auxiliary test electrode 302 is smaller than that of the electrode 301 under test, the auxiliary test electrode 302 can be moved to different positions of the electrode 301 under test, that is, it can form a locally symmetrical cell with the electrode 301 under test at different test positions.

[0073] It should be understood that, although in Figure 3The area of the diaphragm 303 is shown to be approximately equal to the area of the auxiliary test electrode 302, but in other embodiments, the area of the diaphragm can be designed according to test requirements, for example, can be designed to be greater than the area of the auxiliary test electrode, equal to the area of the electrode to be tested, etc., which is not limited in the present application.

[0074] By setting the area of the auxiliary test electrode to be smaller than the area of the electrode to be tested, the auxiliary test electrode can be moved at different positions of the electrode to be tested according to different test positions, achieving sufficient detection of the electrochemical impedance spectrum.

[0075] According to some embodiments of the present application, the auxiliary test electrode is a circular electrode with a diameter of not greater than 5 millimeters (mm).

[0076] Due to the small size of the auxiliary test electrode, it has higher spatial resolution compared to traditional stacked symmetrical batteries (usually with a size of tens of millimeters). Even if the test position is at the edge of the electrode to be tested, the auxiliary test electrode can form a local symmetrical battery with the electrode to be tested at these edge positions, obtaining the electrochemical impedance spectrum corresponding to these edge positions.

[0077] In addition, due to the small size, the signal obtained in the test will not be averaged by a large area, and accurate test signals can also be obtained for some small area failure positions, such as lithium precipitation risk positions, etc., achieving accurate identification of failure signals.

[0078] Using a small-sized auxiliary test electrode, the electrochemical characteristics of a local micro-region (such as an electrode edge region) can be analyzed, improving the detection resolution and thus improving the detection accuracy.

[0079] According to some embodiments of the present application, with reference to Figure 4 , step 110 includes steps 410 to 430.

[0080] Step 410, immersing the local symmetrical battery in an electrolyte.

[0081] Step 420, moving the auxiliary test electrode to any one of the plurality of test positions.

[0082] Step 430, obtaining the electrochemical impedance spectrum of the test position.

[0083] In step 410, the local symmetrical battery is immersed in an electrolyte, so that the movement of electric charges can be achieved, and the detection of the electrochemical impedance spectrum can be performed.

[0084] In step 420, the auxiliary test electrode is moved to different test positions of the electrode under test, so that a partial symmetric cell is formed at each test position with the electrode under test. In step 430, electrochemical impedance spectroscopy is tested at different test positions.

[0085] As shown in Figure 3 , the auxiliary test electrode is moved to test position 1, test position 2, test position 3, and test position 4, to form a partial symmetric cell with the electrode under test at each test position, and to test the electrochemical impedance spectroscopy at each test position. After testing at one test position is completed, the auxiliary test electrode is moved to the next test position for testing. In one example, the testing time at each test position is less than 3 minutes.

[0086] In some embodiments, a three-axis precision displacement device can be used to move the auxiliary test electrode, so that sub-millimeter positioning of the auxiliary test electrode on the electrode under test is achieved. The three-axis precision displacement device integrates a three-axis displacement platform and a micro probe. The auxiliary test electrode can be driven by the micro probe, and can be moved to different positions of the electrode under test for electrochemical impedance spectroscopy testing, without the need to repeatedly assemble a symmetric cell, effectively improving the testing efficiency. In addition, since the same set of test equipment is used, the consistency of the test results is high, and the test error introduced during the test process can be reduced.

[0087] By detecting the electrochemical impedance spectroscopy at different test positions, the characteristic resistance of the electrode under test at different positions can be obtained, so that accurate detection of the uniformity of the electrode under test is achieved.

[0088] According to some embodiments of the present application, with reference to Figure 5 , step 410 includes steps 510 to 520.

[0089] In step 510, the partial symmetric cell is immersed in the electrolyte, so that the electrolyte completely immerses the partial symmetric cell.

[0090] In step 520, a predetermined pressure is applied to the partial symmetric cell.

[0091] In step 510, the partial symmetric cell is completely immersed in the electrolyte, for example, each surface of the partial symmetric cell can be located below the liquid level of the electrolyte, or the upper surface of the partial symmetric cell can be immersed in the electrolyte to a fixed depth below the liquid level, etc.

[0092] In step 520, a certain pressure is applied to the partial symmetric cell, and the electrochemical impedance spectroscopy is tested under the pressure.

[0093] The partial symmetrical battery is fully immersed in the electrolyte and pressure is applied to the partial symmetrical battery, so that the detection result of the electrochemical impedance spectrum is more accurate and more consistent with the real situation of the electrode sheet to be detected.

[0094] According to some embodiments of the present application, the predetermined pressure is set to be greater than or equal to 0.1 MPa (MPa) and less than or equal to 2 MPa.

[0095] The pressure applied to the partial symmetrical battery can be adjusted according to the test requirements, for example, it can be set according to different types of electrode sheets, electrolyte types, etc. The predetermined pressure can be adjusted in the pressure range of 0.1 MPa to 2 MPa.

[0096] By reasonably designing the pressure applied to the partial symmetrical battery, the accuracy of the test result can be improved.

[0097] According to some embodiments of the present application, with reference to Figure 6 , step 120 includes steps 610 to 620.

[0098] Step 610, in response to the electrode sheet to be detected being a first type of electrode sheet to be detected, a plurality of first characteristic resistances of the electrode sheet to be detected are determined. The first characteristic resistance is used to indicate the resistance generated in the charge transfer process.

[0099] Step 620, in response to the electrode sheet to be detected being a second type of electrode sheet to be detected, a plurality of second characteristic resistances of the electrode sheet to be detected are determined. The second characteristic resistance is used to indicate the resistance encountered by the electrolyte when transmitting in the electrode sheet pores.

[0100] For different types of electrode sheets to be detected, the electrode sheet uniformity may affect different electrical properties, for example, the characteristic resistance that can reflect the electrode sheet uniformity is usually different, and there is a certain type of characteristic resistance that can better reflect the electrode sheet uniformity. Therefore, according to the type of the electrode sheet to be detected, the corresponding characteristic resistance can be determined, so that the uniformity of the electrode sheet to be detected can be more accurately reflected.

[0101] The first type of electrode sheet to be detected can refer to a charged electrode sheet, for example, in the preparation process of the battery, after the formation process, the SOC of the battery is adjusted (for example, the SOC of the battery is adjusted to 50%), and after the adjustment is completed, the electrode sheet is taken out from the battery for testing. At this time, the electrode sheet to be detected has electricity, which can also be called a charged electrode sheet. For this type of electrode sheet to be detected, the charge transfer resistance Rct can more accurately reflect the electrode sheet uniformity. At this time, the first characteristic resistance can be determined as the charge transfer resistance Rct.

[0102] The second type of electrode under test can be an electrode obtained after processes such as coating and low-temperature rolling (also known as cold pressing), and can also be called a cold-pressed electrode. For this type of electrode under test, the pore resistance Rion can usually more accurately reflect the uniformity of the electrode. In this case, the second characteristic resistance can be determined as the pore resistance Rion.

[0103] By determining different characteristic resistances based on different types of electrodes, the characteristics of the electrodes can be reflected more accurately, and the uniformity test results obtained accordingly will be more realistic.

[0104] According to some embodiments of this application, step 120 includes: determining a plurality of characteristic resistances based on a pre-constructed equivalent circuit model and a plurality of electrochemical impedance spectra.

[0105] When performing electrochemical impedance spectroscopy tests on an electrochemical system, the electrochemical system can be regarded as an equivalent circuit composed of basic components such as resistors (R), capacitors (C), and inductors (L) connected in series or parallel.

[0106] Since electrochemical impedance spectroscopy reflects the relationship between impedance and frequency, and impedance is a complex number including real and imaginary parts, corresponding to resistance and capacitance characteristics respectively, the characteristic resistance can be determined based on the electrochemical impedance spectroscopy and the equivalent circuit.

[0107] The equivalent circuit can be pre-constructed according to different electrode types, battery types, etc. For example, it can include different circuit forms such as a circuit in series with resistor R and capacitor C, or a circuit in parallel with resistor R and capacitor C.

[0108] Figure 8 The diagram illustrates the electrochemical impedance spectroscopy at different test locations for the first type of electrode (with electrode plate). For example... Figure 8 As shown, electrochemical impedance spectroscopy was measured at 10 test locations (test location 1 to test location 10) on the electrode under test. The first characteristic resistance (Rct) at each test location is shown below. Figure 9 As shown.

[0109] Figure 10 The diagram illustrates the electrochemical impedance spectroscopy at different test locations for the second type of electrode (cold-pressed electrode). For example... Figure 10 As shown, electrochemical impedance spectroscopy was measured at 10 test locations (test location 1 to test location 10) on the electrode under test. The second characteristic resistance (Rion) at each test location is shown below. Figure 11 As shown.

[0110] In the process of determining the characteristic resistance, constructing an equivalent circuit model of the electrode under test can yield a characteristic resistance that better matches the characteristics of the electrode, thereby improving the accuracy of the results.

[0111] According to some embodiments of the present application, the test method 100 further comprises: obtaining the voltage applied to the electrode sheet to be tested.

[0112] As described above, when testing the electrochemical impedance spectrum, a predetermined voltage is applied, and an AC perturbation signal is applied. The voltage applied to the electrode sheet to be tested can also be understood as the open circuit voltage OCV of the locally symmetrical battery. For different test positions, the OCV at each test position can be determined respectively, for use in the process of determining the uniformity of the electrode sheet.

[0113] By obtaining the voltage applied to the electrode sheet to be tested, in combination with the equivalent circuit model, the corresponding characteristic resistance can be obtained, so as to determine the uniformity detection result of the electrode sheet to be tested.

[0114] According to some embodiments of the present application, with reference to Figure 7 , step 130 comprises steps 710 to 720.

[0115] Step 710: determining at least one statistical parameter of the plurality of characteristic resistances.

[0116] Step 720: determining the uniformity of the electrode sheet to be tested according to the at least one statistical parameter.

[0117] Since the characteristic resistances at different positions can reflect the electrical performance of these positions, that is, if the consistency of the characteristic resistances at different positions is good, the electrical performance of these positions is also consistent, that is, the uniformity of the electrode sheet is good. The statistical parameter of the characteristic resistance can reflect the consistency of the characteristic resistances, and therefore, the consistency of the characteristic resistances at different test positions can be determined according to the statistical parameters of the characteristic resistances corresponding to the different test positions, and the uniformity of the electrode sheet to be tested can be determined.

[0118] By extracting the statistical parameters of each characteristic resistance, quantitative evaluation of the electrical performance of the electrode sheet can be realized according to the changes of these parameters, so as to obtain the detection result of the uniformity of the electrode sheet, and realize efficient evaluation of the uniformity of the electrode sheet.

[0119] According to some embodiments of the present application, the at least one statistical parameter comprises at least one of the mean, the standard deviation and the coefficient of variation.

[0120] In step 710, at least one of the average value, the standard deviation and the coefficient of variation of the plurality of characteristic resistances can be determined. The average value represents the mean value of the plurality of characteristic resistances. The standard deviation is used to describe the degree of dispersion of the individual characteristic resistances, also referred to as standard deviation or experimental standard deviation, and is defined as the square root of the average distance of the data from the mean value. The coefficient of variation (COV) is also referred to as the dispersion coefficient and is a normalized measure of the degree of dispersion of a probability distribution, and is defined as the ratio of the standard deviation to the average value, i.e. COV = standard deviation / average value.

[0121] In Figure 9 the example shown, for the first characteristic resistances at the 10 test positions, the average value (indicated as Ave in Figure 9 ), the standard deviation (indicated as Std in Figure 9 ) and the coefficient of variation (indicated as COV in Figure 9 ) can be determined, respectively. As shown in Figure 9 , for this test electrode, the average value of the first characteristic resistances is 16.86, the standard deviation is 1.03 and the coefficient of variation is 6.09%.

[0122] In Figure 11 the example shown, for the second characteristic resistances at the 10 test positions, the average value (indicated as Ave in Figure 11 ), the standard deviation (indicated as Std in Figure 11 ) and the coefficient of variation (indicated as COV in Figure 11 ) can be determined, respectively. As shown in Figure 11 , for this test electrode, the average value of the second characteristic resistances is 22.64, the standard deviation is 0.84 and the coefficient of variation is 3.70%.

[0123] By selecting appropriate statistical parameters, more accurate detection results can be obtained.

[0124] According to some embodiments of the present application, step 720 comprises determining that the uniformity of the test electrode does not meet the uniformity requirement in response to any one of the at least one statistical parameter exceeding a pre-set parameter threshold.

[0125] When a certain statistical parameter of the characteristic resistances exceeds the pre-set threshold, it indicates that the consistency of the characteristic resistances at different test positions is poor, and the electrode uniformity is poor. Different parameter thresholds can be set for different types of electrodes and batteries, which are not limited by the present application. In one example, whether the coefficient of variation exceeds the threshold can be used to determine whether the uniformity of the test electrode meets the requirement, for example, for a certain cold-pressed electrode, when the COV of the pore resistance Rion is greater than 15%, the electrode can be determined to have poor uniformity and not to meet the uniformity requirement.

[0126] In some embodiments, the processing quality and / or failure risk of different positions of the test electrode tab can be evaluated according to the characteristic resistances at different positions. The statistical parameters of these characteristic resistances provide a theoretical basis for process optimization, and can accurately locate the failure sensitive position and determine the failure cause. In some embodiments, a cross-scale correlation model of electrode tab manufacturing process-electrode tab micro-zone impedance characteristics-electrode tab performance degradation mechanism can be established according to the characteristic resistances at different positions and the process parameters in the electrode tab processing process.

[0127] Quantitative determination of the electrode tab uniformity according to the characteristic resistance can be used to improve the processing technology of the electrode tab, for example, to drive the parameter optimization of the coating process, the consistency control of the compaction density, the optimization of key processes such as the improvement of the solid electrolyte interface (SEI) film quality. In addition, due to the differences in the interface state such as the electrolyte infiltration uniformity, the stress field distribution heterogeneity and the SEI film formation integrity, it will lead to the difference in the electrode tab impedance spatial distribution, and then cause the difference in the electrochemical polarization distribution, and finally may cause the local lithium deposition risk, that is, the abnormal phenomenon of metal lithium deposition or formation of dendrites on the surface of the electrode tab. Therefore, by obtaining the electrochemical impedance spectrum of different test positions on the test electrode tab, and analyzing the characteristic resistances of different test positions, the failure sensitive area of the electrode tab can be accurately located and the possible failure cause can be analyzed.

[0128] According to whether the statistical parameter exceeds the predetermined threshold value, the electrode tab with poor uniformity can be quickly identified, and the detection efficiency is improved.

[0129] According to some embodiments of the present application, the plurality of test positions are arranged in sequence along a predetermined direction on the test electrode tab.

[0130] In the test process of the electrochemical impedance spectrum, the test positions can be arranged in sequence along one direction of the test electrode tab, and the electrochemical impedance spectrum of each test position is obtained by moving the auxiliary test electrode tab. In one example, the plurality of test positions can be arranged in sequence along the current collector side (i.e., located on one side of the current collector or the tab) to the slitting side (i.e., when slitting the large-area electrode tab into a certain width of electrode tab strip, the side where the slitting is performed) of the test electrode tab, as shown in Figure 8 and Figure 10 The test position 1 to the test position 10 are arranged in sequence along the current collector side to the slitting side of the test electrode tab.

[0131] By determining reasonable test positions, the characteristic resistances obtained can fully reflect the change of the electrical performance of the test electrode tab, so as to obtain accurate electrode tab uniformity detection results.

[0132] Based on the same technical concept, the application provides a device for testing uniformity of a battery pole piece. The embodiments of the device for testing uniformity of the battery pole piece can refer to the embodiments of the method for testing uniformity of the battery pole piece, and the repeated parts will not be described herein again. It is referred to Figure 12 The device 1200 for testing uniformity of the battery pole piece includes a first module 1210, a second module 1220, and a third module 1230.

[0133] The first module 1210 is configured to include a locally symmetrical battery constructed in advance, and obtain a plurality of electrochemical impedance spectrums of a plurality of test positions of a to-be-tested pole piece.

[0134] The second module 1220 is configured to determine a plurality of characteristic resistances of the to-be-tested pole piece according to the plurality of electrochemical impedance spectrums.

[0135] The third module 1230 is configured to determine the uniformity of the to-be-tested pole piece based on the plurality of characteristic resistances of the to-be-tested pole piece.

[0136] The first module 1210, the second module 1220, and the third module 1230 in the device 1200 for testing uniformity of the battery pole piece can correspond to steps 110 to 130 in the method 100 for testing uniformity of the battery pole piece, and for the sake of brevity, will not be described herein again. It should be understood that, corresponding to the embodiments of the method 100 for testing uniformity of the battery pole piece, the embodiments of the device 1200 for testing uniformity of the battery pole piece can also include more modules.

[0137] It should be noted that the functions of various modules discussed herein can be divided into multiple modules, and / or at least some functions of multiple modules can be combined into a single module. The specific module discussed herein performing an action includes the specific module itself performing the action, or alternatively, the specific module calling or otherwise accessing another component or module that performs the action (or performs the action in conjunction with the specific module). Therefore, the specific module performing an action can include the specific module itself performing the action and / or another module performing the action that the specific module calls or otherwise accesses.

[0138] It should also be understood that various technologies can be described herein in the general context of software hardware elements or program modules. The above with respect to Figure 12The various modules described can be implemented in hardware or in hardware combined with software and / or firmware. For example, the modules can be implemented as computer program code / instructions configured to be executed in one or more processors and stored in a computer-readable storage medium. Alternatively, the modules can be implemented as hardware logic / circuitry. The hardware logic / circuitry can include an integrated circuit chip (including one or more components of a processor (e.g., a Central Processing Unit (CPU), a microcontroller, a microprocessor, a Digital Signal Processor (DSP), etc.), a memory, one or more communication interfaces, and / or other circuitry) and can optionally execute received program code and / or include embedded firmware to perform functionality.

[0139] An embodiment of the present application provides a computing device 1300, as shown in Figure 13 Figure 13 An example configuration of a computing device 1300 that can be used to implement the battery electrode sheet uniformity testing method 100 described herein is shown. For example, the battery electrode sheet uniformity testing apparatus 1200 described above can be implemented, in whole or at least in part, by the computing device 1300 or a similar device or system.

[0140] The computing device 1300 can include at least one processor 1305, memory 1307, communication interface(s) 1302, display device 1301, other input / output (I / O) devices 1303, and one or more mass storage devices 1306, which are able to communicate with one another by way of a bus 1304 or other appropriate connection. The memory 1307 has instructions stored thereon that, when executed by the processor 1305, cause the processor 1305 to perform the battery electrode sheet uniformity testing method as in the above-described embodiments.

[0141] The computing device 1300 can be various different types of devices. Examples of the computing device 1300 include, but are not limited to: a desktop computer, a server computer, a notebook or netbook computer, a mobile device (e.g., a tablet computer, a cellular or other wireless phone (e.g., a smart phone), a notepad computer, a mobile station), a wearable device (e.g., glasses, a watch), an entertainment device (e.g., an entertainment appliance, a set-top box, a game console), a television or other display device, an automobile computer, and so forth.

[0142] ​The processor 1305 can be a single processing unit or a plurality of processing units, all of which can include single or multiple computing units or multiple cores. The processor 1305 can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and / or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor 1305 can be configured to fetch and execute computer-readable instructions stored in the memory 1307, the mass storage device 1306, or any other computer-readable medium.

[0143] The memory 1307 and the mass storage device 1306 are examples of computer-readable storage media for storage of information such as computer-readable instructions, data structures, program code, computer programs, etc. For example, the memory 1307 can generally include both volatile memory and nonvolatile memory (e.g., RAM, ROM, etc.). Moreover, the mass storage device 1306 can generally include hard disk drives, solid state drives, removable media, including external and removable drives, memory cards, flash memory, floppy disks, optical disks (e.g., CD or DVD), storage arrays, network attached storage, storage area networks, etc. The memory 1307 and the mass storage device 1306 can both be collectively referred to herein as the memory or computer-readable storage media, and can be non-transitory media capable of storing computer-readable, processor-executable program instructions as computer program code that can be executed by the processor 1305 as a particular machine configured to implement the operations and functions described in the examples herein.

[0144] A number of program modules can be stored on the mass storage device 1306. These programs include an operating system 1308, one or more application programs 1309, other programs 1310, and program data 1311, and they can be loaded into the memory 1307 for execution. Examples of such application programs or program modules can include, for example, computer program logic (e.g., computer program code or instructions) for implementing the battery electrode uniformity testing device 1200 (including the first module 1210, the second module 1220, and the third module 1230), the battery electrode uniformity testing method 100 (including any suitable steps of the battery electrode uniformity testing method 100), and / or additional embodiments described herein, for example, to implement the following components / functions.

[0145] Although the Figure 13The operating system 1308, the application programs 1309, the other programs 1310, and the program data 1311, or portions thereof, can also be implemented using any form of computer-readable media that is accessible by the computing device 1300, including but not limited to volatile and non-volatile, removable and non-removable media, magnetic and optical, including storage arrays and networks distributed over a variety of computer system configurations.

[0146] One or more communication interfaces 1302 are used to exchange data with other devices, such as over a network, direct connection, or the like. Such communication interfaces can be one or more of: any type of network interface (e.g., network interface cards (NICs)), wired or wireless (such as IEEE 802.11 wireless LAN (WLAN)) wireless interfaces, Worldwide Interoperability Microwave Access (Wi-MAX) interfaces, Ethernet interfaces, Universal Serial Bus (USB) interfaces, cellular network interfaces, Bluetooth™ interfaces, near-field communication (NFC) interfaces, and the like. The communication interfaces 1302 can facilitate communications within a variety of networks and protocol types, including wired networks (e.g., LAN, cable, etc.) and wireless networks (e.g., WLAN, cellular, satellite, etc.), the Internet, and the like. The communication interfaces 1302 can also provide communication with external storage devices (not shown), such as storage arrays, network attached storage, storage area networks, and the like.

[0147] In some examples, a display device 1301, such as a monitor, can be included for displaying information and images to a user. Other I / O devices 1303 can be devices that receive various inputs from a user and provide various outputs to the user, and can include touch input devices, gesture input devices, cameras, keyboards, remote controls, mice, printers, audio input / output devices, and the like.

[0148] The technology described herein can be supported by the various configurations of the computing device 1300 and is not limited to the specific examples described herein. For example, the functionality can also be implemented all or in part through use of a distributed system, such as over a "cloud." Clouds include and / or comprise platforms that abstract the underlying functionality of the hardware (e.g., servers) and software resources of the resource. Resources can include applications and / or data, that can be utilized while being executed on servers that are remote from the computing device 1300. Resources can also include services provided over the Internet and / or through a subscriber network, such as a cellular or Wi-Fi network. The platform can abstract resources and functionality to connect the computing device 1300 with other

[0149] The embodiments of the present application further provide a computer readable storage medium having instructions stored thereon, which, when executed by one or more processors of a computing device, alone or in combination, cause the computing device to perform the method in any of the above embodiments.

[0150] Computer readable storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computer device.

[0151] The embodiments of the present application further provide a computer program product comprising instructions, which, when executed by one or more processors of a computing device, alone or in combination, cause the computing device to perform the method in any of the above embodiments.

[0152] A specific embodiment of the present application is described below. It should be understood that the specific embodiment is described for illustrative purposes only and should not be construed as a limitation of the present application.

[0153] Figure 14 An embodiment 1400 of a test method for battery electrode sheet uniformity is illustrated. A to-be-tested electrode sheet is obtained, and a circular electrode sheet with a diameter not greater than 5 mm is cut as an auxiliary test electrode sheet. A separator is added between the auxiliary test electrode sheet and the to-be-tested electrode sheet to form a partial symmetrical battery. The partial symmetrical battery is completely immersed in an electrolyte, and a pressure of 0.1 MPa to 2 MPa is applied thereto. The auxiliary test electrode sheet is moved according to different test positions of the to-be-tested electrode sheet, and the electrochemical impedance spectrum of each test position is detected. After the electrochemical impedance spectrum corresponding to different test positions is obtained, the characteristic resistance corresponding to the to-be-tested electrode sheet is determined according to different electrode sheet types. If the to-be-tested electrode sheet is a charged electrode sheet, the characteristic resistance can be determined as the charge transfer resistance Rct; if the to-be-tested electrode sheet is a cold-pressed electrode sheet, the characteristic resistance can be determined as the pore resistance Rion.

[0154] After the characteristic resistances corresponding to different test positions are obtained, statistical parameters of the characteristic resistances can be determined, for example, at least one of the average value, the standard deviation and the coefficient of variation of the characteristic resistances is determined. When a certain statistical parameter exceeds a predetermined threshold value, it is considered that the electrode sheet uniformity is poor and does not meet the uniformity requirement. For example, if the COV of the pore resistance Rion of a certain cold-pressed electrode sheet is greater than 15%, the electrode sheet is determined to be poor in uniformity and does not meet the uniformity requirement.

[0155] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for testing the uniformity of battery electrode sheets, characterized in that, include: Based on a pre-constructed locally symmetric cell, multiple electrochemical impedance spectra are obtained at multiple test locations on the electrode under test, wherein the locally symmetric cell is pre-constructed according to the following steps: Obtain the electrode to be tested; Obtain an auxiliary test electrode, wherein the auxiliary test electrode and the electrode under test undergo at least one of the same processing steps, and the area of ​​the auxiliary test electrode is smaller than that of the electrode under test; and A separator is added between the electrode under test and the auxiliary test electrode to obtain the locally symmetric cell, wherein obtaining multiple electrochemical impedance spectra at multiple test locations of the electrode under test based on the pre-constructed locally symmetric cell includes: Immersing the locally symmetrical battery in an electrolyte includes: The locally symmetric cell is immersed in the electrolyte so that the electrolyte completely submerges the locally symmetric cell; and A predetermined pressure is applied to the locally symmetrical cell; Move the auxiliary test electrode to any one of the plurality of test positions; and Obtain the electrochemical impedance spectroscopy at this test location; Based on the multiple electrochemical impedance spectra, multiple characteristic resistances of the electrode under test are determined; and The uniformity of the electrode under test is determined based on multiple characteristic resistances of the electrode under test.

2. The test method according to claim 1, characterized in that, The auxiliary test electrode is a circular electrode with a diameter of no more than 5 mm.

3. The test method according to claim 1, characterized in that, The predetermined pressure is set to be greater than or equal to 0.1 MPa and less than or equal to 2 MPa.

4. The test method according to claim 1, characterized in that, The step of determining the multiple characteristic resistances of the electrode under test based on the multiple electrochemical impedance spectra includes: In response to the electrode under test being a first type of electrode under test, a plurality of first characteristic resistances of the electrode under test are determined, the first characteristic resistances being used to indicate the resistance generated during charge transfer; and In response to the fact that the electrode under test is a second type of electrode under test, a plurality of second characteristic resistances of the electrode under test are determined, the second characteristic resistances being used to indicate the resistance encountered by the electrolyte during transport in the pores of the electrode.

5. The test method according to claim 1, characterized in that, The step of determining the multiple characteristic resistances of the electrode under test based on the multiple electrochemical impedance spectra includes: The multiple characteristic resistances are determined based on the pre-constructed equivalent circuit model and the multiple electrochemical impedance spectra.

6. The test method according to claim 1, characterized in that, The testing method also includes: Obtain the voltage applied to the electrode under test.

7. The test method according to claim 1, characterized in that, Determining the uniformity of the electrode under test based on multiple characteristic resistances includes: Determine at least one statistical parameter of the plurality of characteristic resistors; and The uniformity of the electrode under test is determined based on at least one statistical parameter.

8. The test method according to claim 7, characterized in that, The at least one statistical parameter includes at least one of the mean, standard deviation, and coefficient of variation.

9. The test method according to claim 7 or 8, characterized in that, Determining the uniformity of the electrode under test based on the at least one statistical parameter includes: In response to any one of the at least one statistical parameter exceeding a preset parameter threshold, it is determined that the uniformity of the electrode under test does not meet the uniformity requirement.

10. The test method according to claim 1, characterized in that, The plurality of test positions are arranged sequentially along a predetermined direction on the electrode to be tested.

11. A testing device for the uniformity of battery electrode sheets, characterized in that, include: A first module is used to obtain multiple electrochemical impedance spectra at multiple test locations of an electrode under test based on a pre-constructed locally symmetric cell. The locally symmetric cell is pre-constructed according to the following steps: obtaining the electrode under test; obtaining an auxiliary test electrode, which undergoes at least one identical processing step as the electrode under test, and the area of ​​the auxiliary test electrode is smaller than that of the electrode under test; and adding a separator between the electrode under test and the auxiliary test electrode to obtain the locally symmetric cell. The process of obtaining multiple electrochemical impedance spectra at multiple test locations of the electrode under test based on the pre-constructed locally symmetric cell includes: immersing the locally symmetric cell in an electrolyte, including: immersing the locally symmetric cell in the electrolyte such that the electrolyte completely submerges the locally symmetric cell; applying a predetermined pressure to the locally symmetric cell; moving the auxiliary test electrode to any one of the multiple test locations; and obtaining the electrochemical impedance spectrum at that test location. The second module is used to determine multiple characteristic resistances of the electrode under test based on the multiple electrochemical impedance spectra; and The third module is used to determine the uniformity of the electrode under test based on multiple characteristic resistances of the electrode under test.

12. A computing device, characterized in that, include: At least one processor; as well as At least one memory communicatively connected to the at least one processor, the at least one memory storing instructions that, when executed individually or jointly by the at least one processor, cause the computing device to perform the test method of any one of claims 1 to 10.

13. A computer-readable storage medium, characterized in that, The device stores instructions that, when executed individually or jointly by one or more processors of the computing device, cause the computing device to perform the test method of any one of claims 1 to 10.

14. A computer program product, characterized in that, The instruction includes instructions that, when executed individually or jointly by one or more processors of a computing device, cause the computing device to perform the test method of any one of claims 1 to 10.

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