Method for testing internal resistance of three-electrode battery based on internal resistance proportion analysis

Abstract

The invention provides a three-electrode battery internal resistance testing method based on internal resistance proportion analysis, and the method comprises the steps: carrying out the electrochemical steady-state impedance spectroscopy (EIS) testing of a positive electrode, a negative electrode and a whole battery of a three-electrode battery, and calculating the ohmic internal resistance and the electrochemical polarization internal resistance corresponding to the positive electrode and the negative electrode of the three-electrode battery according to a Nyquist diagram obtained through the testing; obtaining the response time of each polarization internal resistance obtained by the EIS test, and carrying out a hybrid pulse power characteristic HPPC test on the three-electrode battery through direct current excitation; and calculating the concentration polarization internal resistance corresponding to the positive electrode and the negative electrode of the three-electrode battery according to the voltage difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance. According to the method, the EIS test and the HPPC test are sequentially carried out on the battery, the proportions of different types of internal resistances corresponding to the positive electrode and the negative electrode of the battery can be accurately calculated, and the accuracy and the pertinence of the battery internal resistance test are improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery internal resistance testing, and in particular to a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis. Background Art

[0002] At present, in energy products such as large energy storage equipment, batteries are the core components of energy products, and the size of the battery's internal resistance is a key factor affecting many electrochemical properties of the battery. For example, for energy storage lithium batteries, energy efficiency is one of its extremely important electrochemical properties, and the battery's internal resistance directly affects the battery's energy efficiency. Reducing the battery's internal resistance can improve the battery's energy efficiency, so it is necessary to accurately test the battery's internal resistance.

[0003] In the related art, when measuring the internal resistance of a battery, the DC method or AC method is generally used for measurement. However, in actual applications, the internal resistance of a battery may be divided into multiple categories. For example, for a lithium battery, its internal resistance is mainly divided into three polarization internal resistances: ohmic polarization internal resistance, electrochemical polarization internal resistance, and concentration polarization internal resistance. The internal resistance measurement method in the above-mentioned related art can only measure the overall internal resistance value, and cannot measure the resistance values ​​of different internal resistances after the battery internal resistance is split. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the first purpose of the present application is to propose a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis. This method can accurately calculate the ratio of different types of internal resistance corresponding to the positive and negative electrodes of the battery by performing EIS testing and HPPC testing on the battery in sequence, thereby improving the accuracy and pertinence of the battery internal resistance test and helping to reduce the battery internal resistance.

[0006] The second objective of the present application is to propose a three-electrode battery internal resistance testing system based on internal resistance ratio analysis.

[0007] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0008] To achieve the above-mentioned purpose, the first aspect of the present application is to propose a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, comprising the following steps:

[0009] Conducting electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively, and calculating the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist plot obtained from the test;

[0010] Obtaining the response time of each polarization internal resistance obtained by the EIS test, and performing a hybrid pulse power characteristics HPPC test on the three-electrode battery through direct current excitation;

[0011] According to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance, the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery is calculated.

[0012] Optionally, in one embodiment of the present application, the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated based on the Nyquist diagram obtained by the test, including: fitting the Nyquist diagram to obtain the circuit equivalent model corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery; according to the corresponding circuit equivalent model, respectively calculating the solid electrolyte interface impedance or charge transfer impedance corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery, the ohmic polarization internal resistance and the electrochemical polarization internal resistance.

[0013] Optionally, in one embodiment of the present application, the electrochemical steady-state impedance spectroscopy EIS test is performed on the positive electrode, the negative electrode and the full battery of the three-electrode battery respectively, including: when the EIS test is performed on the positive electrode, the positive electrode is connected to the counter electrode and the sensing electrode, the negative electrode is connected to the working electrode, and the third electrode is connected to the reference electrode; when the EIS test is performed on the negative electrode, the positive electrode is connected to the working electrode, the negative electrode is connected to the counter electrode and the sensing electrode, and the third electrode is connected to the reference electrode; when the EIS test is performed on the full battery, the positive electrode is connected to the counter electrode and the sensing electrode, and the negative electrode is connected to the working electrode and the reference electrode.

[0014] Optionally, in one embodiment of the present application, the hybrid pulse power characteristics HPPC test of the three-electrode battery by DC excitation includes: recording the voltage difference change between the target electrode to be tested and the third electrode under the action of the DC excitation by a multi-channel detector, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multi-channel detector is respectively connected to the target electrode and the third electrode, and the target electrode is the positive electrode or the negative electrode.

[0015] Optionally, in one embodiment of the present application, the obtaining of the response time of each polarization internal resistance obtained by the EIS test includes: obtaining a Bode diagram obtained by the EIS test, wherein the Bode diagram is composed of an impedance modulus and a frequency; obtaining the response time corresponding to each polarization internal resistance from the Bode diagram according to a conversion relationship between time and frequency; after the hybrid pulse power characteristics HPPC test is performed on the three-electrode battery by DC excitation, it also includes: determining the voltage difference change between the electrodes from the HPPC test data according to the response time corresponding to each polarization internal resistance.

[0016] Optionally, in one embodiment of the present application, before calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, it also includes: determining the instantaneous pressure difference change at the moment the excitation current is turned on and off, and calculating the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the target electrode based on the instantaneous pressure difference change and the current value of the DC excitation; the calculation of the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery includes: determining the pressure difference change of the target electrode caused by the concentration polarization internal resistance, and calculating the concentration polarization internal resistance corresponding to the target electrode in combination with the pressure difference change of the target electrode, the steady-state voltage before and after the battery test, and the current value of the DC excitation.

[0017] Optionally, in one embodiment of the present application, after calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, it also includes: optimizing the battery cell manufacturing process, battery material process and battery usage management based on the proportion of multiple polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

[0018] To achieve the above purpose, the second aspect of the present application further proposes a three-electrode battery internal resistance testing system based on internal resistance ratio analysis, comprising the following modules:

[0019] The first test module is used to perform electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively, and calculate the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist diagram obtained by the test;

[0020] The second test module is used to obtain the response time of each polarization internal resistance obtained by the EIS test, and to perform a hybrid pulse power characteristic HPPC test on the three-electrode battery through DC excitation;

[0021] The calculation module is used to calculate the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance.

[0022] In order to implement the above-mentioned embodiments, the third aspect embodiment of the present application also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the computer program is executed by the processor, the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis in the above-mentioned first aspect is implemented.

[0023] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects: by performing EIS test and HPPC test on the three-electrode battery in turn, the present application can accurately calculate the proportion of different types of internal resistances such as ohmic polarization internal resistance, electrochemical polarization internal resistance and concentration polarization internal resistance corresponding to the positive and negative electrodes of the battery, and conduct a more detailed analysis and disassembly of the three major polarization internal resistances corresponding to the positive and negative electrodes of the battery. Thus, based on the obtained data on the proportion of each part of the internal resistance, the present application can accurately and efficiently reduce the internal resistance part with a larger proportion, thereby effectively improving the relevant electrochemical properties of the battery cell, which is beneficial to improving the energy efficiency of the three-electrode battery. Moreover, based on the data on the proportion of each part of the internal resistance, reliable data support can be provided for battery optimization in many aspects such as battery manufacturing process, battery materials and battery use management, which is beneficial to further improve battery performance. Thus, the present application improves the accuracy and pertinence of battery internal resistance testing.

[0024] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A flow chart of a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis proposed in an embodiment of the present application;

[0027] Figure 2 (a) is a schematic diagram of an electrode connection method for performing EIS testing on a positive electrode proposed in an embodiment of the present application;

[0028] Figure 2 (b) is a schematic diagram of an electrode connection method for performing EIS testing on a negative electrode proposed in an embodiment of the present application;

[0029] Figure 2 (c) is a schematic diagram of an electrode connection method for performing EIS testing on a full battery proposed in an embodiment of the present application;

[0030] Figure 3 A Nyquist diagram including EIS test results of positive electrode, negative electrode and full battery proposed in an embodiment of the present application;

[0031] Figure 4 A schematic diagram of a circuit equivalent model proposed in an embodiment of the present application;

[0032] Figure 5 A schematic diagram of monitoring the potential between the negative electrode and the third electrode of a battery by a multi-channel detector proposed in an embodiment of the present application;

[0033] Figure 6 A schematic diagram of a potential change between a negative electrode and a third electrode of a battery proposed in an embodiment of the present application;

[0034] Figure 7 A Pareto chart of the internal resistance ratio of a size A battery proposed in an embodiment of the present application;

[0035] Figure 8 A Pareto chart of the internal resistance ratio of a size B battery proposed in an embodiment of the present application;

[0036] Fig. 9 A Pareto chart of the internal resistance ratio of a C-size battery proposed in an embodiment of the present application;

[0037] Fig.10 A pie chart showing the internal resistance ratio of a size A battery proposed in an embodiment of the present application;

[0038] Fig.11 A pie chart showing the internal resistance ratio of a size B battery proposed in an embodiment of the present application;

[0039] Fig.12 A pie chart showing the internal resistance ratio of a C-size battery proposed in an embodiment of the present application;

[0040] Fig.13 A schematic diagram of the structure of a three-electrode battery internal resistance testing system based on internal resistance ratio analysis proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0041] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0042] It should be noted that for the three major polarization internal resistances of the three-electrode battery targeted by this application, the ohmic internal resistance mainly includes the electron transfer internal resistance of the positive and negative electrode current collectors and the internal resistance of the connecting welds between the various structural parts; the electrochemical polarization internal resistance mainly includes the charge transfer of the positive and negative electrode materials and the internal resistance between the positive and negative electrode materials and the CEI / SEI membrane; the concentration polarization internal resistance mainly includes the ion diffusion internal resistance between the positive and negative electrode materials and the ion diffusion internal resistance between the electrolyte and the diaphragm.

[0043] In order to quickly and effectively reduce the internal resistance of the battery and improve the battery's energy efficiency, it is necessary to analyze and disassemble the internal resistance of the battery in more detail to confirm the proportion of various types of polarization internal resistance corresponding to the positive and negative electrodes of the battery. However, the internal resistance measurement method in the related art cannot reasonably separate the various internal resistances of the battery cell, which makes it unsuitable for subsequent reduction of the internal resistance of the battery cell, and will waste a lot of resources and costs.

[0044] To this end, the present application proposes a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, and performs electrochemical steady-state impedance spectroscopy (EIS) test and direct current excitation (HPPC) test on the three-electrode battery. The potential between the positive / negative poles and the third electrode of the battery is monitored by a multi-channel collector, and the three major polarization internal resistances of the battery are specifically disassembled corresponding to the positive and negative poles of the battery according to the different response times of the internal resistance of each part.

[0045] It should also be noted that the response time of the polarization internal resistance of each part of the battery is as follows: Ohmic polarization internal resistance (R s ) is the instantaneous response; electrochemical polarization internal resistance (R ct ) is a microsecond response; concentration polarization internal resistance (R diff ) is a response in seconds.

[0046] A method and system for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis proposed in an embodiment of the present application will be described below with reference to the accompanying drawings.

[0047] Figure 1 This is a flow chart of a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis proposed in an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps:

[0048] Step S101, performing electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively, and calculating the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist diagram obtained from the test.

[0049] Among them, the three-electrode battery involved in the present application includes a positive electrode, a negative electrode and a third electrode, and the third electrode is a reference electrode.

[0050] Specifically, first, electrochemical steady-state impedance spectroscopy (EIS) tests are performed on the positive electrode, negative electrode and full battery of the three-electrode battery in turn on the electrochemical workstation. By analyzing and calculating the Nyquist diagram obtained by the EIS test, the specific values ​​of the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive electrode and negative electrode of the three-electrode battery can be obtained respectively.

[0051] Among them, when performing the EIS test, it is necessary to first connect the electrodes of the three-electrode battery to the electrochemical workstation wire. In one embodiment of the present application, the positive electrode, the negative electrode and the full battery of the three-electrode battery are respectively subjected to electrochemical steady-state impedance spectrum EIS test, including: in the case of performing the EIS test on the positive electrode, the positive electrode is connected to the counter electrode and the sensing electrode, the negative electrode is connected to the working electrode, and the third electrode is connected to the reference electrode; in the case of performing the EIS test on the negative electrode, the positive electrode is connected to the working electrode, the negative electrode is connected to the counter electrode and the sensing electrode, and the third electrode is connected to the reference electrode; in the case of performing the EIS test on the full battery, the positive electrode is connected to the counter electrode and the sensing electrode, and the negative electrode is connected to the working electrode and the reference electrode.

[0052] Specifically, in this embodiment, the connection method of the battery cell when measuring the impedance of each part of the positive and negative electrodes is as follows: Figure 2 (a) to Figure 2 (c) as shown. Figure 2 (a) Figure 2 (b) and Figure 2 (c) The wiring methods for EIS testing of the positive electrode, negative electrode and full battery of the three-electrode battery respectively. Figure 2 (a) to Figure 2 Different colors are used to distinguish different electrodes in (c).

[0053] in, Figure 2 In (a), the positive electrode of the battery is connected to the counter electrode (CE) and the sense electrode (SE), and the negative electrode of the battery is connected to the working electrode (WE), which is the detection electrode and indicator electrode during the test. The third electrode of the battery is connected to the reference electrode (RE) of the electrochemical workstation.

[0054] Figure 2 In (b), the positive electrode of the battery is connected to WE, and the negative electrode is connected to CE and SE. Figure 2 When the three electrodes of the battery are tested in (c), the positive electrode of the battery is connected to CE and SE, and the negative electrode of the battery is connected to WE and RE.

[0055] Furthermore, after performing EIS tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively according to the above connection method, the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated according to the test results.

[0056] In one embodiment of the present application, the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated based on the Nyquist diagram obtained by the test, including: first fitting the Nyquist diagram to obtain the circuit equivalent model corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery; then, according to the corresponding circuit equivalent model, respectively calculating the solid electrolyte interface impedance or charge transfer impedance, ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery.

[0057] Specifically, in this embodiment, the test frequency range of the EIS test is 10mHz to 10kHz, the amplitude is 5mV, and the obtained Nyquist fitting diagram is an image of one or two semicircles with an intersection with the real axis and connected by a 45° oblique line. Figure 3 As shown, since the present application performs EIS tests on the positive electrode, negative electrode and full battery respectively, the obtained Nyquist diagram contains fitting curves obtained from three tests.

[0058] Furthermore, Figure 3 The circuit equivalent model is obtained by fitting the Nyquist diagram shown in FIG. 1 . Since the Nyquist diagram of the present application includes fitting curves under three tests, Figure 4 As shown, the fitted circuit equivalent model includes the circuit equivalent models corresponding to the positive electrode, negative electrode and full battery of the battery.

[0059] The circuit equivalent model includes the polarization internal resistance to be solved and each constant phase element (CPE). By analyzing and solving each circuit equivalent model, the specific resistance values ​​of the ohmic polarization internal resistance Rs, charge transfer impedance (RCEI) or solid electrolyte interface impedance (RSEI) and electrochemical polarization internal resistance Rct corresponding to the positive and negative electrodes of the battery can be obtained.

[0060] It should be noted that in this embodiment, for the lithium iron phosphate battery, since there is no CEI film on the positive electrode of the battery, the resistance of the RCEI part is zero. And through the example test, it is known that since RSEI is small, it is included in Rct in this embodiment and is collectively referred to as Rct. In the EIS test, the specific value of the concentration polarization internal resistance Rdiff cannot be obtained, so the resistance value of this part is obtained in the subsequent HPPC test.

[0061] Step S102, obtaining the response time of each polarization internal resistance obtained by the EIS test, and performing a hybrid pulse power characteristic HPPC test on the three-electrode battery through direct current excitation.

[0062] Specifically, after the EIS test is completed, the battery cell is excited by a DC current of a suitable rate on an electrochemical workstation or a charge and discharge cabinet, and a Hybrid Pulse Power Characterization (HPPC) test is performed on the three-electrode battery through the DC excitation.

[0063] In one embodiment of the present application, a hybrid pulse power characteristics HPPC test is performed on a three-electrode battery by DC excitation, including: recording the voltage difference change between the target electrode to be tested and the third electrode under the action of DC excitation by a multi-channel detector, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multi-channel detector is respectively connected to the target electrode and the third electrode, and the target electrode is the positive electrode or the negative electrode.

[0064] Specifically, in this embodiment, the potential between the positive electrode and the reference electrode, or the potential between the negative electrode and the reference electrode is monitored by a multi-channel recorder. The present application tests the positive and negative electrodes of the battery as target electrodes, respectively, and the concentration polarization internal resistance corresponding to the positive and negative electrodes of the battery can be obtained.

[0065] The following is an exemplary description of the HPPC test on the negative electrode of the battery.

[0066] As an example, when performing HPPC testing on the negative electrode of a battery, the connection between the battery and the electrochemical workstation is as follows: Figure 5 As shown, the multi-channel detector is connected to the negative electrode and the third electrode of the battery respectively, the negative electrode of the battery is also connected to the CE and SE of the electrochemical workstation, and the positive electrode of the battery is connected to the WE and RE of the electrochemical workstation.

[0067] During the current excitation process of this embodiment, the voltage difference change of the battery cell can be calculated by the following formula:

[0068] ΔU=ΔU SOC +IR

[0069] Among them, ΔU SOC is the change in the state of charge of the battery cell, I is the current value of DC excitation, and R is the internal resistance of the battery cell.

[0070] It should be noted that during the DC current excitation process, the polarization internal resistance corresponding to the positive and negative electrodes of the battery can be calculated based on the change in the voltage difference between the electrodes and the time response characteristics of each polarization internal resistance. Therefore, after calculating all types of polarization internal resistances corresponding to the positive and negative electrodes of the battery, the purpose of polarization internal resistance disassembly can be achieved, that is, to determine the proportion of various polarization internal resistances corresponding to the positive and negative electrodes of the battery. Among them, the specific response time of each internal resistance required in this HPPC test can be obtained from the EIS test in the previous step.

[0071] In one embodiment of the present application, the response time of each polarization internal resistance obtained by the EIS test is obtained, including: obtaining a Bode diagram obtained by the EIS test, wherein the Bode diagram is composed of an impedance modulus and a frequency; obtaining the response time corresponding to each polarization internal resistance from the Bode diagram according to a conversion relationship between time and frequency; after performing a hybrid pulse power characteristic HPPC test on a three-electrode battery through DC excitation, it also includes: determining the voltage difference change between each electrode from the HPPC test data according to the response time corresponding to each polarization internal resistance.

[0072] Specifically, in the present embodiment, in the above EIS test, in addition to the Nyquist diagram, a Bode diagram consisting of impedance modulus and frequency can also be obtained. Then, through the conversion relationship between time and frequency, the specific response time of each part of the internal resistance can be obtained, and the time can be brought into the HPPC test data, and then the voltage difference change between the corresponding electrodes (in this example, the negative electrode and the third electrode) can be determined, so as to subsequently calculate the corresponding polarization internal resistance.

[0073] Step S103, calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance.

[0074] Specifically, according to the potential change between the target electrode and the third electrode during the DC charging process of the three-electrode battery, the polarization internal resistance corresponding to the target electrode can be calculated, including the concentration polarization internal resistance.

[0075] In one embodiment of the present application, before calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, it also includes: determining the instantaneous pressure difference change at the moment the excitation current is turned on and off, and calculating the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the target electrode based on the instantaneous pressure difference change and the current value of the DC excitation; calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, including: determining the pressure difference change of the target electrode caused by the concentration polarization internal resistance, combining the pressure difference change of the target electrode, the steady-state voltage before and after the battery test, and the current value of the DC excitation, to calculate the concentration polarization internal resistance corresponding to the target electrode.

[0076] Specifically, continue to refer to the example of performing HPPC test with the negative electrode as the target electrode in step S102. According to the obtained voltage difference change between the negative electrode and the third electrode, it can be generated Figure 6 Schematic diagram of the potential change between the negative electrode and the third electrode shown. Figure 6 The time value on the time coordinate axis can be used to calculate the response time mentioned above.

[0077] Among them, ΔU1 and ΔU2 are the pressure difference changes caused by the instantaneous connection and instantaneous disappearance of the current during the test, and this change is caused by the ohmic polarization internal resistance. However, in actual applications, since the minimum recording time interval of the multi-channel recorder is in the millisecond level, it is impossible to distinguish the ohmic polarization internal resistance of the instantaneous response and the electrochemical polarization internal resistance of the microsecond response. Therefore, in the test scheme of this embodiment, ΔU1 / I and ΔU2 / I are recorded as the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance, that is, (R S +R ct )’s specific resistance value.

[0078] Furthermore, Figure 6 The pressure difference change caused by the negative electrode potential dropping from U1 to U2 is caused by the concentration polarization internal resistance and charging. Therefore, the concentration polarization internal resistance Rdiff can be calculated by the following formula:

[0079] [(U1-U2)-(U0-U4)] / I

[0080] Among them, U0 is the steady-state voltage of the battery before testing, U4 is the steady-state voltage after the test is completed and left to stand for passivation, and I is the current value of DC excitation.

[0081] Therefore, this application can conduct a more detailed analysis and decomposition of the three major polarization internal resistances (RS, Rct and Rdiff) corresponding to the positive and negative electrodes of the battery by combining EIS and HPPC tests on the three-electrode battery. By proportionally calculating the specific resistance values ​​of each polarization internal resistance, the proportion of each part of the internal resistance corresponding to the positive and negative electrodes can be confirmed.

[0082] Based on the above embodiment, after calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, it also includes: optimizing the battery cell manufacturing process, battery material process and battery use management based on the proportion of multiple polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

[0083] Specifically, since this application combines the two test methods of EIS and HPPC to test the internal resistance of the three-electrode battery, it can accurately calculate the internal resistance ratio of each part of the positive and negative electrodes of the battery cell, and accurately and efficiently reduce the internal resistance part with a large proportion, thereby effectively improving certain electrochemical properties of the battery cell and enhancing the product advantages of the battery cell. In addition, the internal resistance ratio data of each part of the positive and negative electrodes of the battery cell can also be used to optimize the battery in many aspects.

[0084] As the first example, based on the calculated proportion of internal resistance of each part of the positive and negative electrodes of the battery cell, a single-factor experimental group is designed to understand the correlation between the battery cell manufacturing process and each internal resistance, such as the surface density of the positive and negative electrodes, the compaction density and the proportion of auxiliary materials, so as to improve and optimize the battery cell design and manufacturing ideas.

[0085] As a second example, based on the calculated proportion of internal resistance of each part of the positive and negative electrodes of the battery cell, through multi-group comparison, we can understand the correlation between the battery cell and the material end, and then associate it with the technical indicators of the material, such as the particle size of the positive and negative electrode materials, the proportion of primary / secondary particles, carbon coating and doping amount, etc., and feedback to the material end to achieve targeted improvement and optimization of the internal resistance of the battery cell.

[0086] As a third example, the calculated internal resistance ratios of the positive and negative poles of the battery cell can help optimize the use and management of the battery. The battery can be used and charged according to actual needs to avoid safety accidents and battery damage and extend the battery life.

[0087] In summary, the test method of the internal resistance of a three-electrode battery based on the analysis of the internal resistance ratio in the embodiment of the present application, by sequentially performing EIS tests and HPPC tests on the three-electrode battery, can accurately calculate the ratio of different types of internal resistances such as the ohmic polarization internal resistance, electrochemical polarization internal resistance, and concentration polarization internal resistance corresponding to the positive and negative electrodes of the battery, and the three major polarization internal resistances corresponding to the positive and negative electrodes of the battery are analyzed and disassembled in more detail. Thus, based on the obtained data on the proportion of each part in the internal resistance, the method can accurately and efficiently reduce the internal resistance part that accounts for a large proportion, thereby effectively improving the relevant electrochemical properties of the battery cell, which is beneficial to improving the energy efficiency of the three-electrode battery. Moreover, based on the data on the proportion of each part in the internal resistance, reliable data support can be provided for battery optimization in many aspects such as battery manufacturing process, battery materials, and battery use management, which is beneficial to further improve battery performance. Thus, the method improves the accuracy and pertinence of the battery internal resistance test.

[0088] Based on the above embodiments, in order to more fully illustrate the specific implementation process and experimental results of the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis of the present application, the process of testing multiple three-electrode batteries in a specific embodiment is exemplified below.

[0089] In this embodiment, a 3.4Ah-lithium iron phosphate-graphite system soft-pack three-electrode battery is selected, and three batteries A, B and C are selected for testing. Figure 2 The EIS test of the three-electrode battery was carried out on the electrochemical workstation. Figure 3 and Figure 4 The test results are fitted in a way to analyze the topological structure of the battery circuit, including the distribution of resistance, capacitance, and inductance and the way they are connected to each other, and an accurate circuit equivalent model is established to obtain accurate test data.

[0090] Among them, the EIS test fitting data of the three-electrode battery, and the disassembly of the ohmic polarization internal resistance and electrochemical polarization internal resistance of the positive and negative electrodes of the battery are shown in the following Table 1.

[0091] Table 1 Three-electrode battery EIS test results

[0092]

[0093] Furthermore, after the EIS test of the three-electrode battery was completed, the battery was subjected to an HPPC test, with an excitation current of 1C and an excitation duration of 120s. Figure 5 The wiring method shown can obtain the voltage changes between the positive and negative electrodes of the battery and between the negative electrode and the reference electrode. Then, according to the voltage difference change between the electrodes, the concentration polarization internal resistance between the positive and negative electrodes, the positive electrode-reference and the negative electrode-reference electrodes of the battery, as well as the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance are calculated. The test data obtained are shown in Table 2 below.

[0094] Table 2 Three-electrode battery DC excitation test results

[0095]

[0096] By comparing the ohmic polarization internal resistance, electrochemical polarization internal resistance and sum of the positive and negative electrodes of the three-electrode battery obtained by the EIS test and the HPPC test shown in Table 1 and Table 2, it can be obtained that the test results of the two test methods are consistent, thereby verifying the reliability of the test method of the present application.

[0097] Based on the data obtained from the above tests, the proportion of the positive electrode-reference, negative electrode-reference, and ohmic polarization internal resistance (Rs), electrochemical polarization internal resistance (Rct), and concentration polarization internal resistance (Rdiff) between the positive and negative electrodes can be obtained, providing a theoretical basis for the subsequent electrochemical performance analysis of the battery cells. Among them, the final internal resistance disassembly data of each battery, that is, the proportion of each polarization internal resistance corresponding to the positive and negative electrodes, is shown in the following Table 3.

[0098] Table 3 Disassembly and proportion data of internal resistance of three batteries A / B / C

[0099]

[0100]

[0101] Based on the data shown in Table 3, we can get a schematic diagram of the internal resistance ratio of the three batteries A / B / C. Among them, the Pareto diagram of the internal resistance ratio of each battery is as follows: Figures 7 to 9 As shown, the pie chart of the internal resistance ratio of each battery is as follows Figures 10 to 12 shown.

[0102] Therefore, the internal resistance testing method of this embodiment which combines the EIS and HPPC tests can calculate the specific data of the internal resistance of each part of the battery and thus understand the proportion of the internal resistance of each part of the battery.

[0103] In order to implement the above embodiment, the present application also proposes a three-electrode battery internal resistance testing system based on internal resistance ratio analysis. Fig.13 This is a schematic diagram of the structure of a three-electrode battery internal resistance test system based on internal resistance ratio analysis proposed in an embodiment of the present application, such as Fig.13 As shown, the system includes:

[0104] The first test module 100 is used to perform an electrochemical steady-state impedance spectrum (EIS) test on the positive electrode, the negative electrode and the full battery of the three-electrode battery respectively, and calculate the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist diagram obtained by the test;

[0105] The second test module 200 is used to obtain the response time of each polarization internal resistance obtained by the EIS test, and to perform a hybrid pulse power characteristic HPPC test on the three-electrode battery through direct current excitation.

[0106] The calculation module 300 is used to calculate the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance.

[0107] Optionally, in one embodiment of the present application, the first test module 100 is specifically used to: fit the Nyquist diagram to obtain the circuit equivalent model corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery; according to the corresponding circuit equivalent model, respectively calculate the solid electrolyte interface impedance or charge transfer impedance, ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive electrode, negative electrode and full battery of the three-electrode battery.

[0108] Optionally, in one embodiment of the present application, the second test module 200 is specifically used to: record the voltage difference change between the target electrode to be tested and the third electrode under DC excitation through a multi-channel detector, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multi-channel detector is respectively connected to the target electrode and the third electrode, and the target electrode is a positive electrode or a negative electrode.

[0109] Optionally, in one embodiment of the present application, the second test module 200 is specifically used to: obtain a Bode plot obtained from an EIS test, wherein the Bode plot is composed of an impedance modulus and a frequency; obtain a response time corresponding to each polarization internal resistance from the Bode plot based on a conversion relationship between time and frequency; and determine a voltage difference change between each electrode from HPPC test data based on the response time corresponding to each polarization internal resistance.

[0110] Optionally, in one embodiment of the present application, the calculation module 300 is specifically used to: determine the instantaneous pressure difference change when the excitation current is turned on and off, and calculate the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the target electrode based on the instantaneous pressure difference change and the current value of the DC excitation; determine the pressure difference change of the target electrode caused by the concentration polarization internal resistance, and calculate the concentration polarization internal resistance corresponding to the target electrode in combination with the pressure difference change of the target electrode, the steady-state voltage before and after the battery test, and the current value of the DC excitation.

[0111] Optionally, in one embodiment of the present application, an optimization module is also included, which is used to optimize the battery cell manufacturing process, battery material process and battery usage management based on the proportion of multiple polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

[0112] It should be noted that the above explanation of the embodiment of the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis is also applicable to the system of this embodiment and will not be repeated here.

[0113] In summary, the three-electrode battery internal resistance test system based on internal resistance ratio analysis of the embodiment of the present application can accurately calculate the ratio of different types of internal resistances such as ohmic polarization internal resistance, electrochemical polarization internal resistance and concentration polarization internal resistance corresponding to the positive and negative electrodes of the battery by performing EIS test and HPPC test on the three-electrode battery in turn, and conduct a more detailed analysis and disassembly of the three major polarization internal resistances corresponding to the positive and negative electrodes of the battery, which is conducive to further improving battery performance. As a result, the system improves the accuracy and pertinence of battery internal resistance testing.

[0114] In order to implement the above-mentioned embodiments, the present application also proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, it implements a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis as described in any one of the above-mentioned first aspect embodiments.

[0115] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0116] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0117] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0118] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0119] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0120] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0121] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0122] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, characterized in that: The following steps are involved: Conducting electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively, and calculating the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist plot obtained from the test; Obtaining the response time of each polarization internal resistance obtained by the EIS test, and performing a hybrid pulse power characteristics HPPC test on the three-electrode battery through direct current excitation; According to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance, the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery is calculated.

2. The testing method according to claim 1, characterized in that: The method of calculating the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist diagram obtained by the test includes: Fitting the Nyquist diagram to obtain a circuit equivalent model corresponding to the positive electrode, the negative electrode and the full battery of the three-electrode battery; According to the corresponding circuit equivalent model, the solid electrolyte interface impedance or charge transfer impedance, the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the positive electrode, the negative electrode and the full battery of the three-electrode battery are calculated respectively.

3. The testing method according to claim 1, characterized in that: The electrochemical steady-state impedance spectrum EIS test is performed on the positive electrode, the negative electrode and the full battery of the three-electrode battery respectively, including: In the case of performing an EIS test on the positive electrode, the positive electrode is connected to a counter electrode and a sensing electrode, the negative electrode is connected to a working electrode, and the third electrode is connected to a reference electrode; When the negative electrode is subjected to an EIS test, the positive electrode is connected to the working electrode, the negative electrode is connected to the counter electrode and the sensing electrode, and the third electrode is connected to the reference electrode; When the full battery is subjected to an EIS test, the positive electrode is connected to the counter electrode and the sensing electrode, and the negative electrode is connected to the working electrode and the reference electrode.

4. The testing method according to claim 3, characterized in that: The hybrid pulse power characteristics HPPC test of the three-electrode battery by direct current excitation comprises: The voltage difference change between the target electrode to be tested and the third electrode under the action of the DC excitation is recorded by a multi-channel detector, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multi-channel detector is respectively connected to the target electrode and the third electrode, and the target electrode is the positive electrode or the negative electrode.

5. The testing method according to claim 1, characterized in that: The obtaining the response time of each polarization internal resistance obtained by the EIS test includes: Obtaining a Bode plot obtained by the EIS test, wherein the Bode plot consists of an impedance modulus and a frequency; According to the conversion relationship between time and frequency, obtaining the response time corresponding to each polarization internal resistance from the Bode diagram; After the hybrid pulse power characteristics HPPC test is performed on the three-electrode battery by direct current excitation, the method further comprises: According to the response time corresponding to each polarization internal resistance, the voltage difference change between the electrodes is determined from the HPPC test data.

6. The testing method according to claim 4, characterized in that: Before calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: Determine the instantaneous pressure difference change when the excitation current is turned on and off, and calculate the sum of the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the target electrode according to the instantaneous pressure difference change and the current value of the DC excitation; The calculating of the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery includes: The pressure difference change of the target electrode caused by the concentration polarization internal resistance is determined, and the concentration polarization internal resistance corresponding to the target electrode is calculated by combining the pressure difference change of the target electrode, the steady-state voltage before and after the battery test, and the current value of the DC excitation.

7. The testing method according to claim 1, characterized in that: After calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: Based on the proportions of various polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery, the battery cell manufacturing process, battery material process and battery usage management are optimized.

8. A three-electrode battery internal resistance test system based on internal resistance ratio analysis, characterized in that: Includes the following modules: The first test module is used to perform electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode and full battery of the three-electrode battery respectively, and calculate the ohmic polarization internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the Nyquist diagram obtained by the test; The second test module is used to obtain the response time of each polarization internal resistance obtained by the EIS test, and to perform a hybrid pulse power characteristic HPPC test on the three-electrode battery through DC excitation; The calculation module is used to calculate the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery according to the pressure difference change between the electrodes of the three-electrode battery obtained by the HPPC test and the response time of each polarization internal resistance.

9. The test system according to claim 8, characterized in that: The first test module is specifically used for: Fitting the Nyquist diagram to obtain a circuit equivalent model corresponding to the positive electrode, the negative electrode and the full battery of the three-electrode battery; According to the corresponding circuit equivalent model, the solid electrolyte interface impedance or charge transfer impedance, the ohmic polarization internal resistance and the electrochemical polarization internal resistance corresponding to the positive electrode, the negative electrode and the full battery of the three-electrode battery are calculated respectively.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis as described in any one of claims 1 to 7 is implemented.

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