A Test Method for Internal Resistance of Three-Electrode Batteries Based on Internal Resistance Ratio Analysis

Abstract

This application proposes a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis. The method includes: performing electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode, and the entire cell of the three-electrode battery; calculating the ohmic internal resistance and electrochemical polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery based on the obtained Nyquist plots; obtaining the response time of each polarization internal resistance obtained from the EIS test; and performing hybrid pulse power characteristic (HPPC) tests on the three-electrode battery using DC excitation; and calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery based on the voltage difference changes between the electrodes obtained from the HPPC test and the response time of each polarization internal resistance. This method, by sequentially performing EIS and HPPC tests on the battery, can accurately calculate the proportion of different types of internal resistance corresponding to the positive and negative electrodes, improving the accuracy and specificity of battery internal resistance testing.

Description

Technical Field

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

[0002] Currently, batteries are the core component of energy products such as large-scale energy storage devices, and the internal resistance of the battery is a key factor affecting many electrochemical performance characteristics of the cell. For example, for lithium batteries used in energy storage, energy efficiency is one of its most important electrochemical performance characteristics, and the internal resistance of the battery directly affects the battery's energy efficiency. Reducing the internal resistance of the battery can improve the battery's energy efficiency, therefore, it is necessary to accurately test the internal resistance of the battery.

[0003] In related technologies, battery internal resistance is generally measured using either DC or AC methods. However, in practical applications, battery internal resistance can be categorized into several types. For example, for lithium batteries, the internal resistance is mainly divided into three major polarization resistances: ohmic polarization resistance, electrochemical polarization resistance, and concentration polarization resistance. The internal resistance measurement methods mentioned above can only measure the overall internal resistance value and cannot measure the individual resistance values ​​after breaking down the battery's internal resistance. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art.

[0005] Therefore, the first objective of this application is to propose a test method for 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 and HPPC tests on the battery in sequence, thereby improving the accuracy and specificity of the battery internal resistance test and helping to reduce the battery internal resistance.

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

[0007] The third objective of this application is to provide a non-transitory computer-readable storage medium.

[0008] To achieve the above objectives, the first aspect of this 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] Electrochemical steady-state impedance spectroscopy (EIS) tests were performed on the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the tests, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery were calculated.

[0010] The response time of each polarization internal resistance obtained from the EIS test is obtained, and the hybrid pulse power characteristic HPPC test is performed on the three-electrode battery by DC excitation.

[0011] Based on the pressure difference changes between the electrodes of the three-electrode battery obtained from the HPPC test, and the response time of each polarization resistance, the concentration polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery is calculated.

[0012] Optionally, in one embodiment of this application, the step of calculating the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery based on the Nyquist plot obtained by testing includes: fitting the Nyquist plot to obtain the circuit equivalent models corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery; and calculating the solid electrolyte interface impedance or charge transfer impedance, the ohmic polarization resistance, and the electrochemical polarization resistance corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively, based on the corresponding circuit equivalent models.

[0013] Optionally, in one embodiment of this application, performing electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode, and full cell of a three-electrode battery respectively includes: when performing EIS testing on the positive electrode, connecting the positive electrode to the counter electrode and the sensing electrode, connecting the negative electrode to the working electrode, and connecting the third electrode to the reference electrode; when performing EIS testing on the negative electrode, connecting the positive electrode to the working electrode, connecting the negative electrode to the counter electrode and the sensing electrode, and connecting the third electrode to the reference electrode; when performing EIS testing on the full cell, connecting the positive electrode to the counter electrode and the sensing electrode, and connecting the negative electrode to the working electrode and the reference electrode.

[0014] Optionally, in one embodiment of this application, the method of performing a hybrid pulse power characteristic (HPPC) test on the three-electrode battery by DC excitation includes: recording the voltage difference change between the target electrode and the third electrode under the DC excitation using a multiplexer, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multiplexer is connected to the target electrode and the third electrode respectively, wherein the target electrode is the positive electrode or the negative electrode.

[0015] Optionally, in one embodiment of this application, obtaining the response time of each polarization resistance obtained by the EIS test includes: obtaining the Bode plot obtained by the EIS test, wherein the Bode plot consists of impedance magnitude and frequency; obtaining the response time corresponding to each polarization resistance from the Bode plot according to the time-frequency conversion relationship; after performing the hybrid pulse power characteristic HPPC test on the three-electrode battery by DC excitation, the method further includes: determining the voltage difference change between each electrode from the HPPC test data according to the response time corresponding to each polarization resistance.

[0016] Optionally, in one embodiment of this application, before calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: determining the instantaneous voltage 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 voltage 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 voltage 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 by combining the voltage 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 this application, after calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: optimizing the cell manufacturing process, battery material process, and battery usage management based on the proportion of various polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

[0018] To achieve the above objectives, a second aspect of this application also proposes a testing system for the internal resistance of a three-electrode battery 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 cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the test, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated.

[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 by DC excitation.

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

[0022] To implement the above embodiments, a third aspect of this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis as described in the first aspect.

[0023] The technical solution provided by the embodiments of this application brings at least the following beneficial effects: By sequentially performing EIS and HPPC tests on the three-electrode battery, this application can accurately calculate the proportions of different types of internal resistance, 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, thus providing a more detailed analysis and breakdown of the three major polarization internal resistances corresponding to the positive and negative electrodes. Therefore, based on the obtained data on the proportions of each part of the internal resistance, this application can accurately and efficiently reduce the larger proportion of internal resistance, thereby effectively improving the relevant electrochemical performance of the cell and contributing to improving the energy efficiency of the three-electrode battery. Furthermore, the data on the proportions of each part of the internal resistance can provide reliable data support for battery optimization in many aspects such as battery manufacturing processes, battery materials, and battery usage management, which is conducive to further improving battery performance. Therefore, this application improves the accuracy and specificity of battery internal resistance testing.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

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

[0026] Figure 1 This is a flowchart illustrating a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, as proposed in an embodiment of this application.

[0027] Figure 2 (a) is a schematic diagram of an electrode connection method for EIS testing of the positive electrode according to an embodiment of this application;

[0028] Figure 2 (b) is a schematic diagram of an electrode connection method for EIS testing of the negative electrode according to an embodiment of this application;

[0029] Figure 2 (c) is a schematic diagram of an electrode connection method for EIS testing of a full cell according to an embodiment of this application;

[0030] Figure 3 A schematic diagram of Nyquist containing EIS test results of the positive electrode, negative electrode, and full cell, as proposed in an embodiment of this application;

[0031] Figure 4 This is a schematic diagram of a circuit equivalent model proposed in an embodiment of this application;

[0032] Figure 5 This is a schematic diagram illustrating a method for monitoring the potential between the negative electrode and the third electrode of a battery using a multi-channel detector, as proposed in an embodiment of this application.

[0033] Figure 6 This is a schematic diagram illustrating the potential change between the negative electrode and the third electrode of a battery according to an embodiment of this application.

[0034] Figure 7 This application provides a Pareto chart of the internal resistance ratio of battery A as proposed in an embodiment.

[0035] Figure 8 A Pareto chart of the internal resistance ratio of a No. B battery is proposed in an embodiment of this application;

[0036] Figure 9 This application provides a Pareto chart of the internal resistance ratio of a C-type battery, as proposed in an embodiment.

[0037] Figure 10 A pie chart showing the percentage of internal resistance of a No. A battery according to an embodiment of this application;

[0038] Figure 11 A pie chart showing the percentage of internal resistance of a No. B battery as proposed in an embodiment of this application;

[0039] Figure 12 A pie chart showing the percentage of internal resistance of a C-type battery as proposed in an embodiment of this application;

[0040] Figure 13 This is a schematic diagram of the structure of a test system for the internal resistance of a three-electrode battery based on internal resistance ratio analysis, as proposed in an embodiment of this application. Detailed Implementation

[0041] The following describes embodiments of the present invention in detail, 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 are not to 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 in this application, the ohmic internal resistance macroscopically mainly includes the electron transfer internal resistance of the positive and negative electrode current collectors and the internal resistance of the connection solder joints between various structural components; 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 film; 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 separator.

[0043] To quickly and effectively reduce battery internal resistance and improve energy efficiency, a more detailed analysis and breakdown of the battery's internal resistance is needed to determine the proportion of various types of polarization resistance corresponding to the positive and negative electrodes. However, existing internal resistance measurement methods cannot reasonably break down the various internal resistances of the battery cell, making them unsuitable for subsequent reduction of cell internal resistance and resulting in a waste of resources and costs.

[0044] Therefore, this application proposes a test method for the internal resistance of a three-electrode battery based on the internal resistance ratio analysis. The three-electrode battery is subjected to electrochemical steady-state impedance spectroscopy (EIS) test and DC excitation (HPPC) test. A multi-channel acquisition device is used to monitor the potential between the positive / negative electrode and the third electrode of the battery. Based on the different response times of the internal resistance of each part, the three polarization internal resistances of the battery are specifically disassembled to correspond to the positive and negative electrodes of the battery.

[0045] It should also be noted that the response times of the polarization resistance of different parts of the battery are as follows: Ohmic polarization resistance (R s The instantaneous response; the electrochemical polarization internal resistance (R) ct The response time is in the microsecond range; the concentration polarization internal resistance (R) is on the order of microseconds. diff The response time is in seconds.

[0046] The following description, with reference to the accompanying drawings, illustrates a method and system for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, as proposed in an embodiment of this application.

[0047] Figure 1 This is a flowchart illustrating a method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis, as proposed in an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0048] Step S101: Perform electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the tests, calculate the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery.

[0049] The three-electrode battery involved in this application includes a positive electrode, a negative electrode, and a third electrode, wherein the third electrode is a reference electrode.

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

[0051] In performing EIS testing, the electrodes of the three-electrode battery must first be connected to the electrochemical workstation wires. In one embodiment of this application, electrochemical steady-state impedance spectroscopy (EIS) testing is performed on the positive electrode, negative electrode, and the entire cell of the three-electrode battery, respectively. This includes: when performing EIS testing on the positive electrode, connecting the positive electrode to the counter electrode and the sensing electrode, connecting the negative electrode to the working electrode, and connecting the third electrode to the reference electrode; when performing EIS testing on the negative electrode, connecting the positive electrode to the working electrode, connecting the negative electrode to the counter electrode and the sensing electrode, and connecting the third electrode to the reference electrode; and when performing EIS testing on the entire cell, connecting the positive electrode to the counter electrode and the sensing electrode, and connecting the negative electrode to the working electrode and the reference electrode.

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

[0053] in, Figure 2 (a) The positive electrode of the battery is connected to the counter electrode (CE) and the sense electrode (SE). The counter electrode serves as the reverse electrode and auxiliary electrode during the test. The negative electrode of the battery is connected to the working electrode (WE), which serves as 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 (b) The positive terminal of the battery is connected to WE, and the negative terminal is connected to CE and SE. Figure 2 (c) When testing the three electrodes of the battery, 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 cell of the three-electrode battery according to the above connection method, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated based on the test results.

[0056] In one embodiment of this application, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated based on the Nyquist plot obtained by testing. This includes: first, fitting the Nyquist plot to obtain the circuit equivalent models corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery; and then, based on the corresponding circuit equivalent models, calculating the solid electrolyte interface impedance or charge transfer impedance, ohmic polarization resistance, and electrochemical polarization resistance corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively.

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

[0058] Furthermore, Figure 3 The Nyquist plot shown is used to fit the circuit equivalent model. Since the Nyquist plot of this application includes fitting curves under three tests, therefore, as... Figure 4 As shown, the fitted circuit equivalent model includes the circuit equivalent models corresponding to the positive electrode, negative electrode, and full cell of the battery.

[0059] The obtained circuit equivalent model includes the polarization 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 resistance Rs, charge transfer impedance (RCEI) or solid electrolyte interface impedance (RSEI), and electrochemical polarization 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 lithium iron phosphate batteries, since there is no CEI film at the positive electrode, the resistance of the RCEI portion is zero. Furthermore, through example testing, it was found that because the RSEI is relatively small, it is included in Rct in this embodiment, and collectively referred to as Rct. The specific value of the concentration polarization resistance Rdiff cannot be obtained in EIS testing; therefore, this resistance value will be obtained in subsequent HPPC testing.

[0061] Step S102: Obtain the response time of each polarization internal resistance obtained from the EIS test, and perform a hybrid pulse power characteristic HPPC test on the three-electrode battery through DC excitation.

[0062] Specifically, after completing the EIS test, the battery cell is then subjected to a DC current excitation of an appropriate rate on an electrochemical workstation or charge / discharge cabinet. This DC excitation is used to perform Hybrid Pulse Power Characterization (HPPC) testing on the three-electrode battery.

[0063] In one embodiment of this application, a hybrid pulse power characteristic (HPPC) test is performed on a three-electrode battery by DC excitation, including: recording the voltage difference change between the target electrode and the third electrode under DC excitation using a multiplexer, wherein the voltage difference change is calculated based on the current value of the DC excitation, and the multiplexer is connected to the target electrode and the third electrode respectively, and the target electrode is either a positive electrode or a 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. This application uses the positive and negative electrodes of the battery as target electrodes for testing, and the concentration polarization internal resistance corresponding to the positive and negative electrodes of the battery can be obtained.

[0065] The following example illustrates the HPPC test performed on the negative electrode of a battery.

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

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

[0068] ΔU=ΔU SOC +IR

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

[0070] It should be noted that during DC current excitation, the polarization resistances corresponding to the positive and negative electrodes can be calculated based on the changes in voltage difference between the electrodes and the time response characteristics of each polarization resistance. Therefore, after calculating all types of polarization resistances corresponding to the positive and negative electrodes, the purpose of polarization resistance decomposition can be achieved, i.e., determining the proportion of each type of polarization resistance corresponding to the positive and negative electrodes. The specific response time of each resistance required in this HPPC test can be obtained from the EIS test in the previous step.

[0071] In one embodiment of this application, obtaining the response time of each polarization internal resistance obtained from EIS testing includes: obtaining a Bode plot obtained from EIS testing, wherein the Bode plot consists of impedance magnitude and frequency; obtaining the response time corresponding to each polarization internal resistance from the Bode plot according to the time-frequency conversion relationship; after performing hybrid pulse power characteristic HPPC testing on the three-electrode battery by DC excitation, the method further 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 this embodiment, in the EIS test described above, in addition to the Nyquist plot, a Bode plot composed of impedance magnitude and frequency can also be obtained. By converting time to frequency, the specific response time of each part of the internal resistance can be obtained. Substituting this time into the HPPC test data, the voltage difference change between the corresponding electrodes (in this example, the negative electrode and the third electrode) can be determined, so that the corresponding polarization internal resistance can be calculated subsequently.

[0073] Step S103: Based on the pressure difference changes between each electrode of the three-electrode battery obtained from the HPPC test, and the response time of each polarization resistance, calculate the concentration polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery.

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

[0075] In one embodiment of this application, before calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: determining the instantaneous voltage 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 voltage 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 includes: determining the voltage 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 by combining the voltage difference change of the target electrode, the steady-state voltage of the battery before and after the test, and the current value of the DC excitation.

[0076] Specifically, continue referring to the example of HPPC testing with the negative electrode as the target electrode in step S102. Based on the obtained pressure difference change between the negative electrode and the third electrode, a... Figure 6 The diagram shows the potential change between the negative electrode and the third electrode. Figure 6 The time values ​​on the time axis can be used to calculate the response time as described above.

[0077] ΔU1 and ΔU2 are the voltage difference changes caused by the instantaneous connection and disappearance of the current during the test, which are caused by the ohmic polarization resistance. However, in practical applications, since the minimum recording time interval of a multi-channel recorder is on the order of milliseconds, it is impossible to distinguish between the ohmic polarization resistance of the instantaneous response and the electrochemical polarization 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 resistance and the electrochemical polarization resistance, which allows the calculation of (R). S +R ct The specific resistance value.

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

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

[0080] Where U0 is the steady-state voltage of the battery before testing, U4 is the steady-state voltage after testing and resting and desensitizing, and I is the DC excitation current value.

[0081] Therefore, this application uses a combination of EIS and HPPC testing on the three-electrode battery to perform a more detailed analysis and breakdown of the three polarization internal resistances (RS, Rct, and Rdiff) corresponding to the positive and negative electrodes. By calculating the proportion of each polarization internal resistance value, the proportion of each part of the internal resistance corresponding to the positive and negative electrodes can be confirmed.

[0082] Based on the above embodiments, after calculating the concentration polarization internal resistance corresponding to the positive and negative electrodes of the three-electrode battery, the method further includes: optimizing the cell manufacturing process, battery material process, and battery usage management based on the proportion of various polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

[0083] Specifically, this application combines EIS and HPPC testing methods to perform internal resistance testing on three-electrode batteries. This allows for accurate calculation of the internal resistance ratio of each part of the positive and negative electrodes, enabling precise and efficient reduction of the larger internal resistance components. This effectively improves certain electrochemical properties of the battery cell, enhancing its product advantages. Furthermore, the internal resistance ratio data of each part of the positive and negative electrodes can be used to optimize the battery in various aspects.

[0084] As a first example, based on the calculated internal resistance ratios of the positive and negative electrodes of the battery cell, single-factor experimental groups are designed to understand the correlation between the battery cell manufacturing process and various internal resistances, such as the surface density of the positive and negative electrodes, compaction density, and the proportion of auxiliary materials. This can improve and optimize the battery cell design and manufacturing approach.

[0085] As a second example, based on the calculated internal resistance ratios of the positive and negative electrodes of the battery cell, the correlation between the battery cell and the material end is understood through multi-group comparisons. This is then linked to the technical indicators of the material, such as the particle size of the positive and negative electrode materials, the ratio of primary / secondary particles, carbon coating and doping amount, etc., and feedback is given to the material end to achieve targeted improvement and optimization of the battery cell's internal resistance.

[0086] As a third example, calculating the internal resistance ratio of each part of the positive and negative electrodes of the battery cell helps to optimize the use and management of the battery, allowing for the use and charging management of the battery according to actual needs, thereby avoiding safety accidents and battery damage, and extending battery life.

[0087] In summary, the three-electrode battery internal resistance testing method based on internal resistance ratio analysis in this application, by sequentially performing EIS and HPPC tests on the three-electrode battery, can accurately calculate the ratio of different types of internal resistance, 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. This provides a more detailed analysis and breakdown of the three major polarization internal resistances corresponding to the positive and negative electrodes. Therefore, based on the obtained ratio data of each component of the internal resistance, this method can accurately and efficiently reduce the larger proportion of internal resistance, thereby effectively improving the relevant electrochemical performance of the cell and contributing to improved energy efficiency of the three-electrode battery. Furthermore, the ratio data of each component of the internal resistance can provide reliable data support for battery optimization in many aspects, such as battery manufacturing processes, battery materials, and battery usage management, which is conducive to further improving battery performance. Thus, this method improves the accuracy and specificity of battery internal resistance testing.

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

[0089] In this embodiment, a 3.4Ah-lithium iron phosphate-graphite system soft-pack three-electrode battery was selected, and three batteries, A, B, and C, were used for testing. First, referring to... Figure 2 The wiring method was used to perform EIS testing on the three-electrode cell on an electrochemical workstation. Based on... Figure 3 and Figure 4 The test results are fitted using this method, and the topology of the battery circuit is analyzed, including the distribution of resistors, capacitors, and inductors and their interconnections. An accurate circuit equivalent model is then established to obtain accurate test data.

[0090] The results obtained by fitting the EIS test data of the three-electrode battery and disassembling the ohmic polarization resistance and electrochemical polarization resistance of the positive and negative electrodes are shown in Table 1 below.

[0091] Table 1. EIS Test Results of Three-Electrode Cells

[0092]

[0093] Furthermore, after the EIS test of the three-electrode battery was completed, the battery underwent HPPC testing, with an excitation current of 1C and an excitation duration of 120s. Based on the above... Figure 5 The wiring diagram shown allows us to obtain the voltage changes between the positive and negative electrodes of the battery, as well as between the negative electrode and the reference electrode. Based on the voltage difference changes between the electrodes, we can then calculate the concentration polarization resistance between the positive and negative electrodes, between the positive and reference electrodes, and between the negative and reference electrodes, as well as the sum of the ohmic and electrochemical polarization resistances. The resulting test data are shown in Table 2 below.

[0094] Table 2. Results of DC Excitation Test for Three-Electrode Cells

[0095]

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

[0097] Based on the data obtained from the above tests, the proportions of the positive electrode-reference, negative electrode-reference, and positive and negative electrode internal resistances (Rs, Rct, and Rdiff) can be obtained, providing a theoretical basis for subsequent electrochemical performance analysis of the battery cell. The final internal resistance breakdown data for each battery, i.e., the proportions of each polarization internal resistance corresponding to the positive and negative electrodes, are shown in Table 3 below.

[0098] Table 3. Internal resistance analysis and percentage data for batteries A, B, and C.

[0099]

[0100]

[0101] Based on the data shown in Table 3, a schematic diagram of the internal resistance percentages of the three batteries A, B, and C can be obtained. The Pareto plot of the internal resistance percentages of each battery is shown below. Figures 7 to 9 As shown in the pie chart, the percentage of internal resistance of each battery is as follows: Figures 10 to 12 As shown.

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

[0103] To achieve the above embodiments, this application also proposes a testing system for the internal resistance of a three-electrode battery based on internal resistance ratio analysis. Figure 13 This is a schematic diagram of the structure of a three-electrode battery internal resistance testing system based on internal resistance ratio analysis, as proposed in an embodiment of this application. Figure 13 As shown, the system includes:

[0104] The first test module 100 is used to perform electrochemical steady-state impedance spectroscopy (EIS) tests on the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the test, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated.

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

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

[0107] Optionally, in one embodiment of this application, the first test module 100 is specifically used to: fit the Nyquist diagram to obtain the circuit equivalent models corresponding to the positive electrode, negative electrode and full cell of the three-electrode battery; and 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 cell of the three-electrode battery, respectively, based on the corresponding circuit equivalent models.

[0108] Optionally, in one embodiment of this application, the second test module 200 is specifically used to: record the voltage difference change between the target electrode and the third electrode under DC excitation using 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 connected to the target electrode and the third electrode respectively, and the target electrode is a positive electrode or a negative electrode.

[0109] Optionally, in one embodiment of this application, the second test module 200 is specifically used to: acquire the Bode plot obtained from the EIS test, wherein the Bode plot consists of impedance magnitude and frequency; acquire the response time corresponding to each polarization internal resistance from the Bode plot according to the time-frequency conversion relationship; and determine the voltage difference change between each electrode from the HPPC test data according to the response time corresponding to each polarization internal resistance.

[0110] Optionally, in one embodiment of this application, the calculation module 300 is specifically used to: determine the instantaneous voltage difference change at the moment 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 voltage difference change and the current value of the DC excitation; determine the voltage 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 by combining the voltage 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 this application, an optimization module is also included, which is used to optimize the cell manufacturing process, battery material process and battery usage management based on the proportion of various polarization internal resistances corresponding to the positive and negative electrodes of the three-electrode battery.

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

[0113] In summary, the three-electrode battery internal resistance testing system based on internal resistance ratio analysis in this application embodiment, by sequentially performing EIS and HPPC tests on the three-electrode battery, can accurately calculate the ratio of different types of internal resistance, 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. This provides a more detailed analysis and breakdown of the three major polarization internal resistances corresponding to the positive and negative electrodes, which is beneficial for further improving battery performance. Therefore, this system improves the accuracy and specificity of battery internal resistance testing.

[0114] To implement the above embodiments, this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method for testing the internal resistance of a three-electrode battery based on internal resistance ratio analysis as described in any one of the first aspects of the embodiments above.

[0115] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0116] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0117] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0118] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0119] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0120] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0121] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can 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 is understood that the above embodiments are exemplary and should not be construed as limiting the present application. Persons skilled in the art may make changes, modifications, substitutions, and variations to 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, Includes the following steps: Electrochemical steady-state impedance spectroscopy (EIS) tests were performed on the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the tests, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery were calculated. The response time of each polarization internal resistance obtained from the EIS test is obtained, and the hybrid pulse power characteristic HPPC test is performed on the three-electrode battery by DC excitation. Based on the pressure difference changes between the electrodes of the three-electrode battery obtained from the HPPC test, and the response time of each polarization resistance, the concentration polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery is calculated.

2. The test method according to claim 1, characterized in that, The calculation of the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery based on the Nyquist plot obtained from the test includes: The Nyquist plot is fitted to obtain the equivalent circuit models corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery; Based on the corresponding circuit equivalent model, calculate the solid electrolyte interface impedance or charge transfer impedance, the ohmic polarization internal resistance, and the electrochemical polarization internal resistance of the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively.

3. The test method according to claim 1, characterized in that, The electrochemical steady-state impedance spectroscopy (EIS) tests were performed on the positive electrode, negative electrode, and full cell of the three-electrode battery, respectively, including: When performing EIS testing 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 performing EIS testing 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 performing an EIS test on the full cell, 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 test method according to claim 3, characterized in that, The method of performing hybrid pulse power characteristic (HPPC) testing on the three-electrode battery via DC excitation includes: The voltage difference change between the target electrode and the third electrode under 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 connected to the target electrode and the third electrode respectively, and the target electrode is the positive electrode or the negative electrode.

5. The test method according to claim 1, characterized in that, The response time for obtaining each polarization resistance obtained from the EIS test includes: Obtain the Bode plot obtained from the EIS test, wherein the Bode plot consists of impedance magnitude and frequency; Based on the time-frequency conversion relationship, the response time corresponding to each polarization resistance is obtained from the Bode plot; After performing the hybrid pulse power characteristic HPPC test on the three-electrode battery using DC excitation, the method further includes: The pressure difference change between the electrodes is determined from the HPPC test data based on the response time corresponding to each polarization resistance.

6. The test 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 voltage difference change at the moment 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 voltage 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: Determine the voltage 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 by combining the voltage difference change of the target electrode, the steady-state voltage before and after the battery test, and the DC excitation current value.

7. The test 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 cell manufacturing process, battery material process, and battery usage management are optimized.

8. A testing system for the internal resistance of a three-electrode battery 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 cell of the three-electrode battery, respectively. Based on the Nyquist plot obtained from the test, the ohmic polarization resistance and electrochemical polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery are calculated. 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 by DC excitation. The calculation module is used to calculate the concentration polarization resistance corresponding to the positive and negative electrodes of the three-electrode battery based on the pressure difference change between each electrode of the three-electrode battery obtained by the HPPC test and the response time of each polarization resistance.

9. The testing system according to claim 8, characterized in that, The first test module is specifically used for: The Nyquist plot is fitted to obtain the equivalent circuit models corresponding to the positive electrode, negative electrode, and full cell of the three-electrode battery; Based on the corresponding circuit equivalent model, calculate the solid electrolyte interface impedance or charge transfer impedance, the ohmic polarization internal resistance, and the electrochemical polarization internal resistance of the positive electrode, negative electrode, and full cell of the three-electrode battery, 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 the processor, it implements the test method for the internal resistance of a three-electrode battery based on the internal resistance ratio analysis as described in any one of claims 1-7.

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