Lithium battery pole piece impedance evaluation method and evaluation system

Abstract

The invention relates to the technical field of battery measurement, and discloses a lithium battery pole piece impedance evaluation method and evaluation system. The lithium battery pole piece impedance evaluation method comprises the following steps: acquiring parameters of at least one standard lithium battery, wherein the parameters of the standard lithium battery comprise the internal resistance of the standard lithium battery and the relative area of a pole piece; calculating a reference value according to the parameters of the standard lithium battery; acquiring parameters of the abnormal lithium battery, wherein the parameters of the abnormal lithium battery comprise the internal resistance of the abnormal lithium battery and the relative area of a pole piece; calculating a to-be-compared value according to the parameters of the abnormal lithium battery; if the to-be-compared value is within the preset range of the reference value, determining that the pole piece impedance of the abnormal lithium battery is normal; and if the to-be-compared value is not within the preset range of the reference value, determining that the pole piece impedance of the abnormal lithium battery is abnormal. According to the method, whether the impedance of the pole piece of the battery is abnormal or not can be judged without disassembling the battery, so that the failure analysis of the battery can be accelerated, and the production efficiency of the battery and the effectiveness of quality control are greatly improved.

Description

Technical Field

[0001] The present application relates to the field of battery measurement technology, and in particular to an evaluation method and system for evaluating the impedance of a lithium battery electrode. Background Art

[0002] With the rapid development of my country's electric vehicle and electric bicycle market, in order to reduce the quality problems of lithium-ion batteries in actual applications, such as cycle life attenuation and safety hazards, higher standards have been put forward for the production process and product quality of lithium-ion batteries.

[0003] The direct current impedance (DCIR) and alternating current impedance (ACIR) of a battery are the result of the combined effects of the impedances of its many internal components, and it is very difficult to directly subdivide these impedances to the pole piece level. When an abnormality is detected in the battery impedance during failure analysis, it is difficult to quickly determine whether the problem is caused by structural or welding defects, or by problems in the pole piece manufacturing process. The traditional method of evaluating pole piece impedance often requires destructive disassembly of the battery, removal of the pole piece, and then a special impedance test on it. This method is not only time-consuming and labor-intensive, but also cannot be applied to online monitoring, which greatly limits production efficiency and the effectiveness of quality control. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a method and system for evaluating the impedance of a lithium battery electrode, which can effectively solve the problem of evaluating the impedance of the electrode by destructive disassembly of the battery in the prior art, which is not only time-consuming and labor-intensive, but also cannot be applied to online monitoring, greatly limiting the production efficiency and the effectiveness of quality control.

[0005] In a first aspect, an embodiment of the present application provides a method for evaluating the impedance of a lithium battery pole piece, comprising: obtaining parameters of at least one standard lithium battery, wherein the parameters of the standard lithium battery include an internal resistance of the standard lithium battery and a relative area of ​​a pole piece of the standard lithium battery;

[0006] Calculating a reference value according to the parameters of the standard lithium battery;

[0007] Obtaining the same parameters of the abnormal lithium battery;

[0008] Calculating a value to be compared according to the parameter of the abnormal lithium battery;

[0009] Determine whether the value to be compared is within a preset range of the reference value;

[0010] If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal;

[0011] If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

[0012] In some embodiments, the internal resistance of the standard lithium battery includes a DC internal resistance and an AC internal resistance, and the calculating of the reference value according to the parameters of the standard lithium battery includes:

[0013] The reference value is obtained by multiplying the difference between the DC internal resistance and the AC internal resistance of the standard lithium battery by the relative area of ​​the pole pieces of the standard lithium battery;

[0014] The calculating the value to be compared according to the parameter of the abnormal lithium battery comprises:

[0015] The value to be compared is obtained by multiplying the difference between the DC internal resistance and the AC internal resistance of the abnormal lithium battery by the relative area of ​​the pole pieces of the abnormal lithium battery.

[0016] In some embodiments, the preset range of the reference value includes: the range between plus and minus three times the standard deviation of the average value of each of the reference values.

[0017] In some embodiments, the standard lithium battery and the abnormal lithium battery are of the same chemical system.

[0018] In some embodiments, the internal resistance of the standard lithium battery includes a DC internal resistance and an AC internal resistance, and when the DC internal resistance and the AC internal resistance are obtained, the charge state of the standard lithium battery remains consistent;

[0019] The state of charge of the standard lithium battery is set to 30%-80% of the total battery volume of the standard lithium battery.

[0020] In some embodiments, obtaining the DC internal resistance of the standard lithium battery includes:

[0021] Adjusting the state of charge of the standard lithium battery to a preset state of charge;

[0022] Recording the current voltage and current of the standard lithium battery;

[0023] Discharging the standard lithium battery at a current of a preset test rate for a preset time;

[0024] Recording the discharge voltage of the standard lithium battery;

[0025] The DC internal resistance of the standard lithium battery is obtained according to the current voltage, the post-discharge voltage, the current current and the current of the preset test rate.

[0026] In some embodiments, the preset test ratio ranges from 1-10C, and the preset time ranges from 1-10S.

[0027] In some embodiments, an internal resistance meter is used to obtain the AC internal resistance of the standard lithium battery at a preset frequency.

[0028] In some embodiments, the acquisition of each of the parameters of the lithium battery pole piece impedance evaluation method is performed under a standard environment of 25°C±3°C.

[0029] In a second aspect, an embodiment of the present application provides a lithium battery pole piece impedance evaluation system, comprising: at least one standard lithium battery, an abnormal lithium battery and a control terminal;

[0030] The control terminal is used to obtain parameters of at least one standard lithium battery, wherein the parameters of the standard lithium battery include the internal resistance of the standard lithium battery and the relative area of ​​the pole pieces of the standard lithium battery;

[0031] And according to the parameters of the standard lithium battery, a reference value is calculated;

[0032] The control terminal is also used to obtain the same parameters of the abnormal lithium battery;

[0033] and calculating a value to be compared according to the parameter of the abnormal lithium battery;

[0034] and also used to determine whether the value to be compared is within a preset range of the reference value;

[0035] If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal;

[0036] If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

[0037] The embodiments of the present application have the following beneficial effects:

[0038] The evaluation method of the lithium battery pole piece impedance of the present application includes: obtaining the parameters of at least one standard lithium battery, the parameters of the standard lithium battery include the internal resistance of the standard lithium battery and the relative area of ​​the pole piece of the standard lithium battery; calculating the reference value according to the parameters of the standard lithium battery; obtaining the parameters of the abnormal lithium battery, the parameters of the abnormal lithium battery include the internal resistance of the abnormal lithium battery and the relative area of ​​the pole piece of the abnormal lithium battery; calculating the value to be compared according to the parameters of the abnormal lithium battery; judging whether the value to be compared is within the preset range of the reference value; if the value to be compared is within the preset range of the reference value, judging that the pole piece impedance of the abnormal lithium battery is normal; if the value to be compared is not within the preset range of the reference value, judging that the pole piece impedance of the abnormal lithium battery is abnormal. Using the evaluation method of the present application, it is possible to judge whether the pole piece impedance of the battery is abnormal without disassembling the battery, thereby accelerating the failure analysis of the battery, and can also check the consistency of the battery according to the pole piece impedance of the battery, and sort and group the battery, which greatly improves the production efficiency of the battery and the effectiveness of quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 A schematic diagram showing a flow chart of a method for evaluating the impedance of a lithium battery electrode sheet according to an embodiment of the present application is shown;

[0041] Figure 2 A schematic diagram of a process for obtaining the DC internal resistance of a standard lithium battery in an embodiment of the present application is shown;

[0042] Figure 3 A schematic diagram showing the comparison of the electrode sheet surface resistance of a normal batch of electrode sheets and an electrode sheet after pressure increase in an embodiment of the present application is shown;

[0043] Figure 4 A schematic diagram showing a comparison between a baseline value of a normal battery and a value to be compared of a battery after pressure increase in an embodiment of the present application is shown;

[0044] Figure 5 A schematic diagram comparing the reference value of a 20Ah capacity battery cell and the value to be compared of a 15Ah capacity battery cell according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0046] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0047] Hereinafter, the terms "including", "having" and their cognates that can be used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0048] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0049] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0050] Considering that the prior art evaluates the pole piece impedance by destructively disassembling the battery, it is not only time-consuming and laborious, but also cannot be applied to online monitoring, which greatly limits the production efficiency and the effectiveness of quality control. The present application provides a lithium battery pole piece impedance evaluation method and evaluation system. By using the evaluation method of the present application, it is possible to determine whether the pole piece impedance of the battery is abnormal without disassembling the battery, thereby accelerating the failure analysis of the battery, and can also check the consistency of the battery according to the pole piece impedance of the battery, and sort and group the battery, which greatly improves the production efficiency of the battery and the effectiveness of quality control.

[0051] The method for evaluating the impedance of the lithium battery electrode is described below in conjunction with some specific embodiments.

[0052] Figure 1 The flowchart of the method for evaluating the impedance of a lithium battery electrode sheet according to an embodiment of the present application is shown. Exemplarily, the method includes steps S101-S107:

[0053] Step S101: obtaining parameters of at least one standard lithium battery, where the parameters of the standard lithium battery include the internal resistance of the standard lithium battery and the relative area of ​​the electrodes of the standard lithium battery.

[0054] It is understandable that a standard lithium battery refers to a lithium battery whose various parameters are within the normal range. The internal resistance of a standard lithium battery includes the DC internal resistance of a standard lithium battery and the AC internal resistance of a standard lithium battery. The DC internal resistance includes all resistances inside the battery, and the AC internal resistance reflects the resistance of the chemical reaction inside the lithium battery to the flow of current.

[0055] When obtaining the DC internal resistance and AC internal resistance of a standard lithium battery, the charge state of the standard lithium battery should remain consistent. The charge state of the standard lithium battery can be set according to the actual application situation. Demonstrationwise, the charge state of the standard lithium battery is set between 30% and 80% of the total battery volume. The battery impedance of lithium batteries within this range is relatively stable, which can reduce measurement errors and avoid the influence of extreme charge states on measurements, greatly ensuring the accuracy and reliability of DC internal resistance measurements. Maintaining the charge state in the middle range can reduce the pressure on the lithium battery and help extend the service life of the lithium battery.

[0056] Exemplarily, a transient high current load may be applied and a voltage drop may be measured, and the DC internal resistance may be calculated based on the voltage drop and the high current.

[0057] For example, in one embodiment, Figure 2 As shown, obtaining the DC internal resistance of a standard lithium battery includes the following sub-steps:

[0058] Step S201: adjusting the state of charge of the standard lithium battery to a preset state of charge.

[0059] The state of charge of the standard lithium battery is set between 30% and 80% of the total battery volume to ensure measurement accuracy.

[0060] Step S202: Record the current voltage and current of the standard lithium battery.

[0061] The current voltage and current of the lithium battery are measured. Exemplarily, the current voltage is set to V1, and the current current is set to I1.

[0062] Step S203: discharging the standard lithium battery with a current of a preset test rate for a preset time.

[0063] Exemplarily, the current of the preset test rate is I2, and the current and duration applied to the lithium battery can be set according to the actual application situation. Exemplarily, the test rate can be used to represent the current applied to the lithium battery. The test rate refers to the size of the discharge current used relative to the rated capacity of the lithium battery during measurement, that is, the rated capacity rate of the lithium battery. Exemplarily, the test rate range of the DC internal resistance is 1-10C, and the duration range of the applied current is 1-10S.

[0064] Step S204: Record the discharge voltage of the standard lithium battery.

[0065] After applying the current for a preset time, the voltage of the lithium battery is measured, and exemplary, the voltage after discharge is set to V2.

[0066] Step S205: obtaining the DC internal resistance of the standard lithium battery according to the current voltage, the voltage after discharge, the current current and the current of the preset test rate.

[0067] Specifically, the DC internal resistance DCIR of the lithium battery = (V1-V2)×1000 / (I2-I1). Substitute the current voltage V1, the voltage after discharge V2, the current current I1 and the current I2 of the preset test rate into the above formula to obtain the DC internal resistance of the standard lithium battery.

[0068] The AC internal resistance of a standard lithium battery can be obtained by using an internal resistance meter for measuring the internal resistance of a lithium battery. The test frequency of the internal resistance meter can be set according to actual application conditions. For example, the test frequency is 1000 Hz.

[0069] Generally, the positive electrode area of ​​a standard lithium battery is smaller than the negative electrode area. The positive electrode area is the effective area, so the relative electrode area can be expressed by the positive electrode area. When calculating the relative electrode area of ​​a standard lithium battery, only the positive electrode area needs to be calculated.

[0070] Specifically, the total area of ​​the positive electrode sheet is obtained by multiplying the area of ​​a single positive electrode sheet by the number of positive electrode sheet layers.

[0071] It is understandable that only the parameters of a single standard lithium battery can be obtained, a single reference value can be obtained using the parameters of the single standard lithium battery, and the single reference value can be used to determine whether the pole piece impedance of the abnormal lithium battery is normal. Alternatively, the parameters of multiple standard lithium batteries can be obtained, multiple reference values ​​can be obtained using the parameters of the multiple standard lithium batteries, and the multiple reference values ​​can be used to comprehensively determine whether the pole piece impedance of the abnormal lithium battery is normal.

[0072] Step S102: Calculate a reference value according to the parameters of a standard lithium battery.

[0073] In electrochemistry, the product of resistance and capacitance is defined as the time constant. The time constant characterizes the corresponding speed in the electrochemical system and can describe the speed of processes such as charge transfer and diffusion in the electrochemical system. The DC internal resistance includes all the resistance inside the lithium battery, and the AC internal resistance reflects the resistance of the chemical reaction inside the lithium battery to the flow of current. By subtracting the DC internal resistance and the AC internal resistance of the lithium battery, the factors that affect the battery impedance other than the electrode sheet can be eliminated, that is, the obtained resistance impedance is only related to the electrode sheet.

[0074] The calculation formula of capacitance is: C = εS / 4πkd, where ε is a constant, S is the area of ​​the capacitor plates, d is the distance between the capacitor plates, and k is the electrostatic force constant. It is understandable that the standard lithium battery and the abnormal lithium battery have the same chemical system and the same pole piece configuration. Specifically, the lithium battery is made of the same material, the same ratio, the same coating process, etc., where the same coating process includes the same surface density, the same thickness, etc., that is, the standard lithium battery and the abnormal lithium battery have the same design except that the battery capacity may be different.

[0075] From the capacitance calculation formula, we know that when the standard lithium battery and the abnormal lithium battery are of the same chemical system, the relative area of ​​the capacitor plates is the only variable of capacitance.

[0076] This application multiplies the difference between the DC internal resistance and the AC internal resistance of a standard lithium battery by the relative area of ​​the pole piece of the standard lithium battery according to the time constant to obtain a reference value. And multiply the difference between the DC internal resistance and the AC internal resistance of an abnormal lithium battery by the relative area of ​​the pole piece of the abnormal lithium battery to obtain a value to be compared. By comparing the reference value with the value to be compared, it is possible to determine whether the pole piece impedance of the abnormal lithium battery is abnormal, thereby eliminating the need to disassemble the lithium battery, greatly improving the production efficiency of the battery and the effectiveness of quality control.

[0077] Specifically, in one implementation, the reference value is obtained by the following formula:

[0078] M=(DCIR-ACIR)×S

[0079] Among them, M represents the reference value; DCIR represents the DC internal resistance of the standard lithium battery; ACIR represents the AC internal resistance of the standard lithium battery; S represents the total area of ​​the positive electrode of the standard lithium battery.

[0080] Step S103: acquiring the same parameters of the abnormal lithium battery, where the parameters of the abnormal lithium battery include the internal resistance of the abnormal lithium battery and the relative area of ​​the electrode of the abnormal lithium battery.

[0081] It is understandable that when obtaining the internal resistance of the abnormal lithium battery, the charge state of the abnormal lithium battery and the charge state of the standard lithium battery should be consistent.

[0082] The internal resistance of an abnormal lithium battery includes the DC internal resistance of an abnormal lithium battery and the AC internal resistance of an abnormal lithium battery. When obtaining the DC internal resistance and AC internal resistance of an abnormal lithium battery, the state of charge of the abnormal lithium battery should remain consistent. The state of charge of the abnormal lithium battery can be set according to the actual application. Demonstration, the state of charge of the abnormal lithium battery is set between 30% and 80% of the total battery volume. The method for obtaining the DC internal resistance of an abnormal lithium battery is the same as the method for obtaining the DC internal resistance of a standard lithium battery, and the method for obtaining the AC internal resistance of an abnormal lithium battery is the same as the method for obtaining the AC internal resistance of a standard lithium battery.

[0083] It is understandable that the total battery quantity of the abnormal lithium battery may be the same as the total battery quantity of the standard lithium battery, or the total battery quantity of the abnormal lithium battery may be different from the total battery quantity of the standard lithium battery.

[0084] Step S104: Calculate the value to be compared according to the parameters of the abnormal lithium battery.

[0085] Specifically, the difference between the DC internal resistance and the AC internal resistance of the abnormal lithium battery is multiplied by the relative area of ​​the electrode of the abnormal lithium battery to obtain the value to be compared.

[0086] Step S105: Determine whether the value to be compared is within a preset range of the reference value.

[0087] The preset range of the reference value can be set according to the actual application situation. Exemplarily, multiple reference values ​​are obtained according to the parameters of multiple standard lithium batteries, and the preset range is within the range of plus or minus three times the standard deviation of the average value of each reference value.

[0088] In one embodiment, the standard deviation is obtained by the following formula:

[0089]

[0090] Among them, S M represents standard deviation; M i represents the i-th reference value, where i is a positive integer; represents the average value of each benchmark value; n represents the number of benchmark values.

[0091] Step S106: If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal.

[0092] The default range is If the comparison value is within this range, the electrode impedance of the abnormal lithium battery is determined to be normal. It can be used to select and match the capacity and voltage of lithium batteries of the same chemical system according to the comparison value, and can also be used to test battery consistency.

[0093] Step S107: If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

[0094] If the comparison value is not If it is within the range, it is determined that the electrode impedance of the abnormal lithium battery is abnormal, which is helpful for failure analysis of the lithium battery.

[0095] In a data set that follows a normal distribution, approximately 99.7% of the data points will fall within the range of the mean plus or minus three standard deviations. By setting the preset range to plus or minus three times the standard deviation of the mean of each benchmark value, if the comparison value of an abnormal lithium battery exceeds this range, it can be judged that the comparison value is an abnormal value, and this comparison value is only related to the area and impedance of the electrode sheet. If there is no abnormality in the area of ​​the electrode sheet, it can be judged that the electrode sheet impedance of the abnormal lithium battery is abnormal, thereby ensuring the accuracy and reliability of the evaluation.

[0096] It is understandable that all steps of the lithium battery pole piece impedance evaluation method of the present application are carried out under a standard environment of 25°C ± 3°C. The accuracy of the measurement of the parameters of the lithium battery is further guaranteed. The lithium battery of the present application can be any type of lithium battery, the lithium battery can be an iron-lithium system battery, the lithium battery can also be a lithium manganese oxide system battery, the lithium battery can also be a ternary system battery, the lithium battery can also be a multi-material combination system battery, etc.

[0097] In this embodiment, the internal resistance and electrode relative area of ​​a standard lithium battery are used to calculate a reference value, providing a standard for abnormal batteries in the same system. This allows the determination of whether the battery electrode is normal without causing damage to the battery, thereby enabling rapid identification of the correlation between battery failure and electrode impedance after use, thereby accelerating battery failure analysis. Furthermore, for mass-produced batteries with low module capacity, the value to be compared can be compared with the reference value, thereby assisting in the screening of cells for mass-produced battery packs and improving the consistency of assembled batteries.

[0098] In order to further verify the effectiveness of the method of the present application, two groups of examples are used for illustration below.

[0099] Example 1:

[0100] Obtain a batch of pole pieces produced with normal process parameters and pole pieces produced with a rolling pressure increased by 20% compared with a batch of normal process parameters. The other production processes of the two batches of pole pieces except the rolling pressure remain the same. Randomly select three pole piece samples from the normal batch and the batch with increased pressure, and measure the pole piece surface resistance of each sample, such as Figure 3 As shown, the electrode sheet surface resistance of the sample after the rolling pressure is increased is higher than the electrode sheet surface resistance of the sample of the normal batch. The electrode sheet impedance includes the electrode sheet surface resistance, that is, the electrode sheet impedance after the rolling pressure is increased is higher than the electrode sheet impedance of the normal batch.

[0101] The two batches of electrode sheets are assembled into two batches of battery cells according to the normal process. It can be understood that the battery cells include at least one positive electrode sheet and one negative electrode sheet, and the two batches of battery cells are assembled into two batches of batteries according to the normal process. When the charge state of the two batches of batteries is 50% of the total battery volume, the DC internal resistance and AC internal resistance of the two batches of batteries are tested. The test frequency of the AC internal resistance is 1000 Hz, the test rate of the DC internal resistance is 1C, and the duration is 3S.

[0102] Obtain the relative areas of the pole pieces of the two batches of batteries, and calculate the reference value M of each normal battery and the comparison value N of each battery after the pressure is increased according to the relative areas of the pole pieces, DC internal resistance and AC internal resistance of the two batches of batteries, such as Figure 4 As shown, each comparison value is higher than the average value of each reference value by three times the standard deviation, that is, the battery electrode impedance is abnormal after the roller pressure is increased. The evaluation method of the present application can accurately determine whether the battery impedance is abnormal.

[0103] Example 2:

[0104] A batch of 20Ah capacity battery cells produced with normal process parameters and a batch of 15Ah capacity battery cells produced with normal process parameters were obtained. Except for the positive and negative electrode areas, the other parameters of the two batches of battery cells were the same.

[0105] The two batches of battery cells were assembled into two batches of batteries according to the normal process. When the charge state of the two batches of batteries was 60% of the total battery volume, the DC internal resistance and AC internal resistance of the two batches of batteries were tested. The test frequency of the AC internal resistance was 1000 Hz, the test rate of the DC internal resistance was 2C, and the duration was 1S.

[0106] Obtain the relative areas of the pole pieces of the two batches of batteries, and calculate the reference value M1 of the 20Ah capacity battery and the comparison value N1 of the 15Ah capacity battery according to the relative areas of the pole pieces, DC internal resistance and AC internal resistance of the two batches of batteries, as shown in Figure 5 As shown, each comparison value is within plus or minus three standard deviations of the average value of the reference value, that is, the electrode impedance of the 15Ah capacity battery is normal. Through the evaluation method of the present application, it can be determined whether there is any abnormality in the electrode impedance of batteries with different capacities in the same system.

[0107] The present application also provides a lithium battery pole piece impedance evaluation system, comprising at least one standard lithium battery, an abnormal lithium battery and a control terminal;

[0108] The control terminal is used to obtain parameters of at least one standard lithium battery, where the parameters of the standard lithium battery include the internal resistance of the standard lithium battery and the relative area of ​​the pole pieces of the standard lithium battery;

[0109] And calculate the benchmark value based on the parameters of the standard lithium battery;

[0110] The control terminal is also used to obtain the same parameters of abnormal lithium batteries;

[0111] And according to the parameters of the abnormal lithium battery, the value to be compared is calculated;

[0112] and also used to determine whether the value to be compared is within a preset range of the reference value;

[0113] If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal;

[0114] If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

[0115] It can be understood that the control terminal of this embodiment can execute each step of the evaluation method of the above embodiment, and the optional items in the above embodiment are also applicable to this embodiment, so they will not be described repeatedly.

[0116] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow diagram, and the combination of boxes in the structure diagram and / or the flow diagram, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0117] In addition, the functional modules or units in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0118] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application.

[0119] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for evaluating the impedance of a lithium battery electrode, characterized in that: include: Acquire parameters of at least one standard lithium battery, wherein the parameters of the standard lithium battery include an internal resistance of the standard lithium battery and a relative area of ​​pole pieces of the standard lithium battery; Calculating a reference value according to the parameters of the standard lithium battery; Obtaining the same parameters of the abnormal lithium battery; Calculating a value to be compared according to the parameter of the abnormal lithium battery; Determine whether the value to be compared is within a preset range of the reference value; If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal; If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

2. The method for evaluating the impedance of a lithium battery electrode according to claim 1, characterized in that: The internal resistance of the standard lithium battery includes a DC internal resistance and an AC internal resistance. The calculation of the reference value according to the parameters of the standard lithium battery includes: The reference value is obtained by multiplying the difference between the DC internal resistance and the AC internal resistance of the standard lithium battery by the relative area of ​​the pole pieces of the standard lithium battery; The calculating the value to be compared according to the parameter of the abnormal lithium battery comprises: The value to be compared is obtained by multiplying the difference between the DC internal resistance and the AC internal resistance of the abnormal lithium battery by the relative area of ​​the pole pieces of the abnormal lithium battery.

3. The method for evaluating the impedance of a lithium battery electrode according to claim 1, characterized in that: The preset range of the reference value includes: the range between the average value of each reference value plus or minus three times the standard deviation.

4. The method for evaluating the impedance of a lithium battery electrode according to claim 1, characterized in that: The standard lithium battery and the abnormal lithium battery are of the same chemical system.

5. The method for evaluating the impedance of a lithium battery electrode according to claim 1, characterized in that: The internal resistance of the standard lithium battery includes a direct current internal resistance and an alternating current internal resistance. When the direct current internal resistance and the alternating current internal resistance are obtained, the state of charge of the standard lithium battery remains consistent. The state of charge of the standard lithium battery is set to 30%-80% of the total battery volume of the standard lithium battery.

6. The method for evaluating the impedance of a lithium battery pole piece according to claim 5, characterized in that: The obtaining of the DC internal resistance includes: Adjusting the state of charge of the standard lithium battery to a preset state of charge; Recording the current voltage and current of the standard lithium battery; Discharging the standard lithium battery at a current of a preset test rate for a preset time; Recording the discharge voltage of the standard lithium battery; The DC internal resistance of the standard lithium battery is obtained according to the current voltage, the post-discharge voltage, the current current and the current of the preset test rate.

7. The method for evaluating the impedance of a lithium battery electrode according to claim 6, characterized in that: The preset test ratio ranges from 1 to 10C, and the preset time ranges from 1 to 10S.

8. The method for evaluating the impedance of a lithium battery electrode according to claim 5, characterized in that: The AC internal resistance of the standard lithium battery is obtained by using an internal resistance meter at a preset frequency.

9. The method for evaluating the impedance of a lithium battery electrode according to claim 1, characterized in that: The acquisition of each parameter of the lithium battery pole piece impedance evaluation method is carried out under a standard environment of 25°C±3°C.

10. A lithium battery pole piece impedance evaluation system, characterized in that: include: At least one standard lithium battery, abnormal lithium battery and control terminal; The control terminal is used to obtain parameters of at least one standard lithium battery, wherein the parameters of the standard lithium battery include the internal resistance of the standard lithium battery and the relative area of ​​the pole pieces of the standard lithium battery; And according to the parameters of the standard lithium battery, a reference value is calculated; The control terminal is also used to obtain the same parameters of the abnormal lithium battery; and calculating a value to be compared according to the parameter of the abnormal lithium battery; and also used to determine whether the value to be compared is within a preset range of the reference value; If the value to be compared is within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is normal; If the value to be compared is not within the preset range of the reference value, it is determined that the electrode impedance of the abnormal lithium battery is abnormal.

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