Cycle aging test and performance evaluation method, equipment, system and storage medium for battery cells

Abstract

The present application discloses a method, device, system and storage medium for cycle aging test and performance evaluation of a battery cell, which are applied to the field of testing technology. The cycle aging test method of the battery cell comprises: performing a charging operation on the battery cell to be tested in this round of aging test; performing a discharging operation on the battery cell to be tested after charging is completed, so that the battery cell to be tested enters an over-discharge state, wherein the over-discharge state is a state reached after the battery cell to be tested reaches a full discharge state and continues to perform a discharging operation on the battery cell to be tested; data collection is performed on the battery cell to be tested that enters the over-discharge state to obtain the total discharge amount and expansion force of this round of aging test, and the next round of aging test is cycled until the cycle aging test is stopped, thereby alleviating the problem of low efficiency of aging test of the battery cell and improving the efficiency of accelerated cycle aging test of the battery cell.

Description

Technical Field

[0001] The present application relates to the field of testing technology, and in particular to a method, device, system and storage medium for cycle aging testing and performance evaluation of battery cells. Background Art

[0002] During the use of the battery cell, the SEI (Solid Electrolyte Interphase) film of the battery cell will thicken, and the positive and negative pole pieces will rebound, resulting in an irreversible increase in the battery cell expansion force. In order to prevent the battery cell expansion force from exceeding the design strength of the battery cell structural parts, the battery cell needs to be subjected to aging testing.

[0003] During the aging test, the battery cell cycle charge and discharge are generally controlled based on the design standards of the battery cell to verify whether the increase in the battery cell expansion force exceeds the design strength of the battery cell's structural parts. As a result, the conventional cycle charge and discharge test method has a longer test cycle, affecting the efficiency of the battery cell aging test. Summary of the invention

[0004] In view of the above problems, the present application provides a method, device, system and storage medium for cycle aging testing and performance evaluation of battery cells, aiming to alleviate the technical problem of low efficiency of aging testing of battery cells.

[0005] In a first aspect, the present application provides a method for a cyclic aging test of a battery cell, comprising: performing a charging operation on the battery cell to be tested in this round of aging test; performing a discharging operation on the battery cell to be tested that has completed charging, so that the battery cell to be tested enters an over-discharge state, wherein the over-discharge state is a state reached after the battery cell to be tested reaches a full discharge state and continues to perform a discharging operation on the battery cell to be tested; collecting data on the battery cell to be tested that has entered the over-discharge state to obtain the total discharge amount and expansion force of this round of aging test, and cycling into the next round of aging test until the cyclic aging test is stopped.

[0006] In the embodiment of the present application, the total discharge amount and expansion force of each round of aging test are collected by sequentially performing charging and discharging operations on the battery cell to be tested, and controlling the battery cell to be tested to enter an over-discharge state. Since over-discharge accelerates the destruction of the SEI film and the expansion of the battery cell to be tested, the capacity decay and aging of the battery cell to be tested are accelerated, so that the battery cell to be tested can reach the EOL (End-of-life, end of design life) state faster, thereby improving the efficiency of the accelerated cycle aging test of the battery cell.

[0007] In one embodiment, in the first discharge stage, a discharge operation is performed on the battery cell to be tested based on the first discharge rate. If the battery cell to be tested enters a target power-deficient state, the second discharge stage is entered; in the second discharge stage, a discharge operation is performed on the battery cell to be tested based on the second discharge rate. If the battery cell to be tested enters a fully discharged state, the third discharge stage is entered; in the third discharge stage, a discharge operation is performed on the battery cell to be tested based on the third discharge rate; wherein the first discharge rate, the second discharge rate, and the third discharge rate decrease in sequence.

[0008] In the embodiment of the present application, the discharge process of the battery cell to be tested is divided into multiple discharge stages, and discharge is performed based on the corresponding discharge rate in each discharge stage, so that the battery cell to be tested reaches different states. Since the discharge rate corresponding to each discharge stage decreases successively, the discharge speed of the battery cell to be tested decreases from fast to slow, which can not only improve the discharge speed of the battery cell to be tested, but also reduce the risk of lithium plating.

[0009] In one embodiment, the first discharge rate is 1C-2C, the second discharge rate is 0.05C-0.33C, and the third discharge rate is 0.02C-0.1C.

[0010] In the embodiment of the present application, by setting a different discharge rate for each discharge stage and providing an optional range of discharge rate, a suitable discharge rate can be selected for discharge in different discharge stages to balance the discharge efficiency of the battery cell to be tested in different discharge stages and reduce the risk of lithium plating.

[0011] In one embodiment, it is determined that the remaining power of the battery cell to be tested reaches a first preset power, and the battery cell to be tested is judged to have entered a target power-deficient state, and the first preset power is 4% SOC~15% SOC; and / or, it is determined that the remaining power of the battery cell to be tested reaches a second preset power, and the battery cell to be tested is judged to have entered a full discharge state, and the second preset power is 0% SOC~2% SOC.

[0012] In the embodiment of the present application, by setting the first preset power and the second preset power, during the discharge process, the remaining power of the battery cell to be tested is compared with the corresponding preset power in each discharge stage, so as to accurately determine the state of the battery cell to be tested, so as to accurately control the discharge of the battery cell to be tested.

[0013] In one embodiment, it is determined that the lithium insertion degree of the battery cell to be tested reaches a preset lithium insertion degree, and the discharge operation is stopped. The preset lithium insertion degree is -10% SOC to -5% SOC.

[0014] In the embodiment of the present application, a preset lithium insertion degree is set. During the discharge process, the state of the battery cell to be tested is determined by comparing the lithium insertion degree of the battery cell to be tested with the preset lithium insertion degree. Since the lithium insertion degree reflects the degree of lithium insertion in the graphite of the battery cell to be tested, the lithium insertion degree gradually decreases with the increase of discharge time. The discharge degree of the battery cell to be tested is controlled by the lithium insertion degree of the battery cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the battery cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the battery cell to be tested.

[0015] In one embodiment, it is determined that the energy of the battery cell to be tested reaches a preset energy, and the discharge operation is stopped, and the preset energy is -10%J~-5%J.

[0016] In the embodiment of the present application, a preset energy is set. During the discharge process, the state of the battery cell to be tested is determined by comparing the energy of the battery cell to be tested with the preset energy. Since the energy reflects the total amount of electric energy that can be released by the battery cell to be tested under certain conditions, the energy of the battery cell to be tested gradually decreases with the increase of discharge time. The discharge degree of the battery cell to be tested is controlled by the energy of the battery cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the battery cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the battery cell to be tested.

[0017] In one embodiment, the capacity decay rate of the battery cell to be tested is determined based on the total discharge amount; if the capacity decay rate does not reach the preset capacity decay rate, the next round of aging test is entered; if the capacity decay rate reaches the preset capacity decay rate, the cyclic aging test is stopped.

[0018] In the embodiment of the present application, by comparing the current capacity decay rate of the battery cell to be tested with the preset capacity decay rate, the aging degree of the battery cell to be tested can be quantitatively evaluated.

[0019] In one embodiment, the test temperature during each round of aging test is 45° C.-60° C.

[0020] In the embodiment of the present application, an aging test is performed in a high temperature test environment to accelerate the capacity decay and aging of the battery cell to be tested, so that the battery cell to be tested can reach the EOL state faster.

[0021] In one embodiment, during the charging process, at least two charging stages are provided, and the charging rates corresponding to the respective charging stages decrease in sequence.

[0022] In the embodiment of the present application, the charging process of the battery cell to be tested is divided into multiple charging stages, and discharge is performed based on the corresponding charging rate in each charging stage, so that the battery cell to be tested reaches different states. Since the charging rate corresponding to each charging stage decreases successively, the charging speed of the battery cell to be tested decreases from fast to slow, which can not only improve the charging speed of the battery cell to be tested, but also reduce the risk of lithium plating.

[0023] In a second aspect, the present application provides a method for evaluating the performance of a battery cell, comprising: obtaining the total discharge capacity of an aging test of the battery cell to be tested, and determining the capacity decay rate of the battery cell to be tested based on the total discharge capacity; obtaining a measured expansion force corresponding to the capacity decay rate; obtaining a true expansion force of the battery cell to be tested based on the standard expansion force and the measured expansion force; and determining a performance evaluation result of the battery cell to be tested based on the capacity decay rate and the true expansion force.

[0024] In the embodiment of the present application, the real expansion force of the battery cell to be tested is obtained based on the standard expansion force and the measured expansion force; the performance evaluation result of the battery cell to be tested is determined based on the capacity attenuation rate and the real expansion force of the battery cell to be tested. Since the expansion force obtained by the cycle acceleration test is corrected, the real expansion force of the battery cell to be tested is obtained, thereby improving the accuracy of the performance evaluation result of the battery cell to be tested.

[0025] In one embodiment, the standard expansion force includes a standard internal pressure, and the measured expansion force includes a measured external expansion force and a measured internal pressure. A correction value of the measured external expansion force is determined based on the measured internal pressure and the standard internal pressure. The actual expansion force of the battery cell to be tested is obtained based on the difference between the measured external expansion force and the correction value.

[0026] In the embodiment of the present application, the influence of the internal air pressure of the battery cell to be tested on the actually measured external expansion force of the battery cell to be tested is taken into consideration, and the internal air pressure of the battery cell to be tested is used to correct the actually measured external expansion force of the battery cell to be tested, so that the determined real expansion force is more accurate.

[0027] In one embodiment, the difference between the measured internal pressure and the standard internal pressure is determined; the size of the battery cell to be measured, the correction coefficient and the gravity constant are obtained; and the correction value of the measured external expansion force is obtained based on the difference, the size, the correction coefficient and the gravity constant.

[0028] The embodiment of the present application can calculate the correction value of the measured external expansion force based on the difference between the measured internal pressure and the standard internal pressure, the size of the battery cell to be measured, the correction coefficient and the gravity constant. Since the calculation process of the correction value takes into account the influence of the measured internal pressure and the standard internal pressure, the accuracy of the correction value can be improved, making the actual external expansion force obtained by subsequent correction more accurate.

[0029] In a third aspect, the present application provides a battery cell cycle aging test device, comprising:

[0030] The charging module is used to charge the battery cells to be tested in this round of aging test;

[0031] A discharge module is used to perform a discharge operation on the battery cell to be tested after charging is completed, so that the battery cell to be tested enters an over-discharge state, wherein the over-discharge state is a state reached after the battery cell to be tested continues to perform a discharge operation after reaching a full discharge state;

[0032] The data acquisition module is used to collect data from the battery cells to be tested that have entered an over-discharge state, obtain the total discharge capacity and expansion force of this round of aging test, and cycle into the next round of aging test until the cycle aging test is stopped.

[0033] In a fourth aspect, the present application provides a performance evaluation device for a battery cell, comprising:

[0034] An acquisition module is used to acquire the capacity attenuation rate of the battery cell to be tested, and to acquire the measured expansion force and the standard expansion force corresponding to the capacity attenuation rate;

[0035] A correction module, used to obtain the real expansion force of the battery cell to be tested according to the standard expansion force and the measured expansion force;

[0036] The evaluation module is used to determine the performance evaluation result of the battery cell to be tested based on the capacity decay rate and the real expansion force of the battery cell to be tested.

[0037] In a fifth aspect, the present application provides a battery cell cycle aging test device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the battery cell cycle aging test method as described above.

[0038] In a sixth aspect, the present application provides a battery cell performance evaluation device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the battery cell performance evaluation method as described above.

[0039] In the seventh aspect, the present application provides a battery cell testing and evaluation system, including: a battery cell cyclic aging test device; a battery cell performance evaluation device; and an expansion force monitoring module for monitoring the expansion force generated by the aging test of the battery cell to be tested; the battery cell cyclic aging test device and the expansion force monitoring module are respectively connected to the battery cell performance evaluation device.

[0040] In the embodiments of the present application, an accelerated cycle aging test can be performed on the battery cell to be tested by means of a cycle aging test device for the battery cell, the expansion force of the battery cell to be tested during the accelerated cycle aging test can be collected by means of an expansion force monitoring module, the performance of the battery cell to be tested can be evaluated by means of a performance evaluation device for the battery cell, and the technical problem of low efficiency in aging testing of the battery cell can be alleviated by means of the battery cell testing and evaluation system, thereby improving the efficiency of accelerated cycle aging testing and performance evaluation of the battery cell to be tested.

[0041] In one embodiment, the expansion force monitoring module includes: an external expansion force monitoring module and an internal pressure monitoring module.

[0042] In the embodiment of the present application, the external expansion force and internal pressure during the accelerated test of the battery cell to be tested are monitored by an external expansion force monitoring module and an internal pressure monitoring module, thereby achieving effective collection of the external expansion force and the internal pressure.

[0043] In one embodiment, the battery cell cycle aging test equipment includes:

[0044] A cell charge and discharge control module is used to perform charging and / or discharging operations on the cell to be tested in this round of aging test;

[0045] The control module is used to determine the capacity decay rate of the battery cell to be tested based on the total discharge amount; if the capacity decay rate does not reach the preset capacity decay rate, control the battery cell charge and discharge control module to enter the charging operation and / or discharging operation of the next round of aging test; or, if the capacity decay rate reaches the preset capacity decay rate, control the battery cell charge and discharge control module to stop working.

[0046] In the embodiment of the present application, the cycle aging test equipment based on the battery cell can perform charging operation and / or discharging operation through the battery cell charging and discharging control module. During the discharge operation, the battery cell to be tested can also be discharged at an accelerated rate, thereby accelerating the cycle aging test and realizing the accelerated cycle aging test of the battery cell to be tested with a short test time. In addition, the control module performs cycle control on the battery cell to be tested to realize the accelerated cycle aging test of the battery cell to be tested.

[0047] In an eighth aspect, the present application provides a storage medium, which is a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above-mentioned battery cell cycle aging test method are implemented, or when the computer program is executed by a processor, the steps of the above-mentioned battery cell performance evaluation method are implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0049] Figure 1 It is a schematic flow chart of a cycle aging test method of a battery cell in one embodiment of the present application;

[0050] Figure 2 It is a schematic flow chart of a cycle aging test method of a battery cell in another embodiment of the present application;

[0051] Figure 3 This is a flow chart of a cycle aging test method for a battery cell in another embodiment of the present application;

[0052] Figure 4 Schematic diagram of a flow chart of a method for evaluating the performance of a battery cell in one embodiment of the present application;

[0053] Figure 5 It is a schematic flow chart of a method for evaluating the performance of a battery cell in another embodiment of the present application;

[0054] Figure 6 A schematic diagram of a curve showing the capacity attenuation rate and the measured internal pressure of a battery cell to be tested in some embodiments of the present application;

[0055] Figure 7 Another schematic diagram of a curve showing the capacity attenuation rate of a battery cell to be tested and the measured external expansion force in some embodiments of the present application;

[0056] Figure 8 Schematic diagram of a flow chart of a method for evaluating the performance of a battery cell in another embodiment of the present application;

[0057] Fig. 9 A schematic diagram of the module structure of a cycle aging test device for a battery cell in some embodiments of the present application;

[0058] Fig.10 A schematic diagram of the module structure of a performance evaluation device for a battery cell in some embodiments of the present application;

[0059] Fig.11 It is a structural schematic diagram of a cycle aging test device for a battery cell in some embodiments of the present application;

[0060] Fig.12 A schematic diagram of the structure of a performance evaluation device for a battery cell in some embodiments of the present application;

[0061] Fig.13 A schematic diagram of the architecture of a battery cell testing and evaluation system in some embodiments of the present application;

[0062] Fig.14 It is a schematic diagram of the structure of a battery cell testing and evaluation system in another embodiment of the present application;

[0063] Fig.15 A schematic top view of an expansion force monitoring module and a cell structure to be tested in some embodiments of the present application;

[0064] Fig.16 It is a structural schematic diagram of a cycle aging test device for a battery cell in another embodiment of the present application. DETAILED DESCRIPTION

[0065] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0067] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0068] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0069] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0070] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0072] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0073] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps a and b, it means that the method may include steps a and b performed sequentially, or steps b and a performed sequentially. For example, if it is mentioned that the method may also include step c, it means that step c can be added to the method in any order, for example, the method may include steps a, b and c, or steps a, c and b, or steps c, a and b, etc.

[0074] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, "include" and "comprising" may represent that other components not listed may also be included or only listed components may be included or only listed components may be included.

[0075] With the continuous advancement of lithium-ion battery technology, its application in electric vehicles, portable electronic devices, energy storage systems and other fields is becoming more and more extensive. However, as the core component of lithium-ion batteries, the long-term stability and safety of the battery cell have always been the key factors restricting the development of lithium-ion battery technology. During the repeated charging and discharging process of the battery cell, the solid electrolyte interface will thicken, and the positive and negative pole pieces will rebound due to stress changes. These phenomena together lead to irreversible expansion forces inside the battery cell. If the expansion force of the battery cell exceeds the design strength of its structural parts, it will seriously threaten the overall performance and safety of the battery system.

[0076] In order to evaluate the expansion behavior of the battery cell during long-term use and ensure that it always works within a safe range, the battery cell aging test came into being. The core of the battery cell aging test is to simulate the actual use conditions of the battery cell, and to observe and record the changes in its expansion force during long-term use by controlling the battery cell to perform cyclic charge and discharge. This test method can effectively verify the durability and safety of the battery cell, and provide an important basis for the research and development and production of the battery cell.

[0077] The development of battery cell aging test can be traced back to the early days of lithium-ion battery technology. Initially, battery cell aging test mainly relied on simple charge and discharge cycle experiments, with a long test cycle and the accuracy of the test results was easily affected by many factors. With the continuous development of lithium-ion battery technology, battery cell aging test methods have gradually been improved and perfected.

[0078] In the early stage of battery cell aging test technology, the test was mainly carried out by manually controlling the charging and discharging equipment and recording data. This method not only has low test efficiency, but also the accuracy of the test results is difficult to guarantee. With the introduction of automation technology, battery cell aging test has gradually realized automated control and data collection, greatly improving test efficiency and accuracy.

[0079] However, despite significant progress in battery cell aging testing technology, conventional cyclic charge and discharge testing methods still face the problem of too long a testing cycle.

[0080] In order to shorten the test cycle and improve the test efficiency, the present application designs a cyclic aging test method for battery cells, which specifically includes: performing a charging operation on the battery cells to be tested in this round of aging test; performing a discharging operation on the battery cells to be tested that have completed charging, so that the battery cells to be tested enter an over-discharge state, wherein the over-discharge state is a state reached after the battery cells to be tested reach a full discharge state and continue to perform a discharging operation on the battery cells to be tested; collecting data on the battery cells to be tested that enter the over-discharge state to obtain the total discharge amount and expansion force of this round of aging test, and cyclically entering the next round of aging test until the cyclic aging test is stopped.

[0081] This application collects the total discharge amount and expansion force of each round of aging test by sequentially performing charging and discharging operations on the battery cell to be tested, and controlling the battery cell to be tested to enter an over-discharge state. Since over-discharge accelerates the destruction of the SEI film and the expansion of the battery cell to be tested, and accelerates the capacity decay and aging of the battery cell to be tested, the battery cell to be tested can reach the EOL state faster, thereby improving the efficiency of the accelerated cycle aging test of the battery cell.

[0082] Accordingly, in some embodiments of the present application, Figure 1 As shown, the embodiment of the present application provides a cyclic aging test method for a battery cell, and the present application can perform multiple rounds of aging tests until the battery cell reaches the EOL state. The total test time of each round of aging test can be the same, or the total test time of each round of aging test can be adjusted according to actual test requirements.

[0083] In each cycle of aging testing, the following steps were performed:

[0084] Step S10, performing a charging operation on the battery cell to be tested in this round of aging test.

[0085] The cells to be tested are the cells waiting to be subjected to accelerated cycle aging tests.

[0086] The charging operation refers to the process in which the battery cell to be tested is in a charging state and electrical energy is stored in the battery cell to be tested.

[0087] Step S20, performing a discharge operation on the battery cell to be tested that has finished charging, so that the battery cell to be tested enters an over-discharge state, wherein the over-discharge state is a state reached after the battery cell to be tested continues to be discharged after reaching a full discharge state.

[0088] The discharge operation refers to the process in which the battery cell to be tested is in a discharge state and the electrical energy in the battery cell is released.

[0089] Before performing the discharge operation on the battery cell to be tested, it is necessary to detect the voltage of the battery cell to be tested to check whether the voltage of the battery cell to be tested reaches the rated charging voltage upper limit, or check whether the power of the battery cell to be tested reaches the rated power upper limit. If so, it means that charging is completed and the battery cell to be tested is discharged.

[0090] In the related art, generally when the battery power is lower than a certain SOC, charging is not resumed, and discharging continues below a specified value, which is called over-discharge. Generally, over-discharge occurs when the battery power reaches the full discharge state of 0% SOC and then stops discharging. That is, the battery power in the over-discharge state in the related art is greater than 0% SOC. For example, the state where the battery power is in the range of 0% SOC to 20% SOC can be defined as an over-discharge state.

[0091] The over-discharge state of the present application refers to the phenomenon that the voltage or power of the cell to be tested drops below the rated discharge lower limit of the cell to be tested during the discharge process but continues to discharge, that is, the cell to be tested continues to discharge after reaching the full discharge state. The remaining power of the cell to be tested in the over-discharge state may be less than 0% SOC. For example, the state when the remaining power of the cell to be tested reaches 0.1% SOC~-5% SOC, or 0.1% SOC~-10% SOC, or 0.1% SOC~-15% SOC can be called an over-discharge state, where SOC represents the remaining power. The cell to be tested can be considered to have reached an over-discharge state when the lithium insertion degree of the cell to be tested is a negative value; the cell to be tested can also be considered to have reached an over-discharge state when the energy of the cell to be tested is a negative value.

[0092] It should be noted that discharging to 0% SOC is the normal use range of the battery cell to be tested, and the SEI film of the graphite negative electrode and the SEI film of the positive electrode will not be damaged. However, the present application reaches a negative SOC state, in which the SEI film of the negative electrode and the SEI film of the positive electrode will be damaged to a certain extent, and the subsequent repair process will lead to additional active lithium consumption, which will show an accelerated aging effect.

[0093] Specifically, over-discharge accelerates the decomposition of the solid electrolyte interface. The SEI film is a thin layer of solid electrolyte interface film formed on the surface of the negative electrode during the first charge of the cell to be tested. It is crucial to the stability and cycle life of the cell to be tested because it prevents solvent molecules from being co-embedded into the negative electrode and causing the cell to be tested to short-circuit. The formation of the SEI film is an irreversible process, and its composition and structure will change with the use and aging of the cell to be tested. During over-discharge, the anode (negative electrode) will be over-de-lithiated, resulting in the decomposition of the SEI film, because the excessive de-intercalation of lithium ions will destroy the structural stability of the SEI film. In addition, over-discharge will cause a significant change in the internal potential of the cell to be tested, especially the increase in the negative electrode potential. This potential change may accelerate the decomposition reaction of the SEI film because the stability of the SEI film is closely related to the potential. In addition, the decomposition of the SEI film may produce gases such as CO or CO2, which will cause the internal pressure of the cell to be tested to increase, further accelerating the destruction of the SEI film and the expansion of the cell to be tested. If the cell to be tested is recharged after over-discharge, a new SEI layer will be formed on the surface of the anode. However, the electrochemical performance and stability of this regenerated SEI layer are usually not as good as those of the original SEI layer, which will accelerate the capacity decay and aging of the battery cell to be tested, causing the battery cell to reach the EOL state faster.

[0094] During the test process, over-discharging the battery cell to be tested is usually performed to evaluate the limit performance, safety performance and discharge characteristics of the battery cell to be tested. Through over-discharge testing, we can understand the performance of the battery cell to be tested under extreme conditions, including the discharge capacity, discharge time and chemical reactions inside the battery cell to be tested. This information is crucial for evaluating the limit performance of the battery cell to be tested. Secondly, over-discharge is also an important means to evaluate the safety performance of the battery cell to be tested. In the case of over-discharge, the battery cell to be tested may produce dangerous situations such as high temperature, expansion force and even explosion. Through testing, we can understand the safety performance of the battery cell to be tested during over-discharge, and take corresponding safety measures to ensure the safety of the battery cell to be tested during use.

[0095] For example, it is necessary to ensure that within the set period of the battery cell to be tested, the increase in the expansion force of the battery cell to be tested cannot exceed the design strength of the structural parts of the battery cell to be tested, so that the battery cell to be tested can be used safely within the set period, thereby improving the safety and reliability of the battery cell to be tested. For example, within the warranty period, that is, the capacity attenuation rate of the battery cell to be tested is about 60%, and the increase in the expansion force of the battery cell to be tested cannot exceed the design strength of the structural parts of the battery cell to be tested. For example, the design strength here can be set to 3000 kg-force, that is, the capacity attenuation rate of the battery cell to be tested is about 60%, and the increase in the expansion force of the battery cell to be tested cannot exceed 3000 kg-force, so that the battery cell to be tested can be used safely within the warranty period.

[0096] Step S30, collecting data on the battery cells to be tested that have entered an over-discharge state, obtaining the total discharge capacity and expansion force of this round of aging test, and cyclically entering the next round of aging test until the cyclic aging test is stopped.

[0097] Data is collected for the battery cell to be tested when it enters the over-discharge state to obtain observation data of this round of aging test.

[0098] The observation data can be data directly observed or collected when the battery cell to be tested enters an over-discharge state. The observation data can also be data directly observed or collected during a round of accelerated cycle aging test, including all observation data during the charging operation and the discharging operation. The purpose of collecting observation data for each round of aging test is to facilitate the subsequent determination of the capacity attenuation rate and the evaluation of the life of the battery cell to be tested.

[0099] The observed data here can be the total discharge volume and expansion force.

[0100] The total discharge capacity refers to the total discharge capacity of the battery cell to be tested from the second state of charge (i.e., fully charged state) to the full discharge state. For example, if it is a two-stage discharge, the total discharge capacity is the discharge capacity of the first discharge stage. If it is a three-stage discharge, the total discharge capacity is the sum of the discharge capacity of the first discharge stage and the discharge capacity of the second discharge stage. For the specific contents of the two-stage discharge and the three-stage discharge, please refer to the subsequent embodiments. The total discharge capacity can also be the total change of the battery cell to be tested from the upper limit value of the total voltage to the lower limit value of the total voltage. As the number of aging tests increases, the total discharge capacity collected in each round of tests gradually decreases.

[0101] Expansion force refers to the force exerted on the outer casing of the battery cell to be tested due to the generation of gas and volume change of the battery cell material caused by the internal chemical reaction of the battery cell to be tested during the battery charging and discharging process. Specifically, when the battery cell to be tested is undergoing accelerated cycle testing, due to the additional process of solid electrolyte interface decomposition and intensified side reactions, these processes will produce gases insoluble in the electrolyte, mainly carbon monoxide, carbon dioxide, etc., which will cause the air pressure inside the battery cell to be tested to increase, and then cause the external expansion force of the battery cell to be tested to increase. Therefore, the expansion force can be subdivided into external expansion force and internal pressure. The expansion force of the battery cell to be tested has a certain impact on the performance and service life of the battery cell to be tested. If the expansion force is too high, it will cause excessive pressure on the outer casing of the battery cell to be tested, causing deformation or even rupture of the outer casing of the battery cell to be tested, thereby affecting the performance and service life of the battery.

[0102] The expansion force of a round of accelerated cycle aging test can be represented in the form of a time series. For example, assuming that the total test time of this round of aging test is set to 1 hour, that is, 3600 seconds, then an expansion force can be collected every second, and a time series is formed based on the expansion force collected every second. The expansion force of this round of aging test includes the expansion force collected every second.

[0103] By monitoring the expansion force of the battery cell to be tested, the performance change of the battery cell to be tested in the accelerated cycle aging test can be evaluated based on the monitored expansion force. It can also be used to evaluate the life of the battery cell to be tested. The expansion force can be combined to determine whether the battery cell to be tested has reached the EOL state. On this basis, the safety of the battery module during the accelerated cycle aging test can be confirmed and improved.

[0104] By sequentially charging and discharging the battery cell to be tested, a round of aging test for the battery cell to be tested is achieved. After the current round of aging test is completed, the next round of aging test is entered until the cycle aging test is stopped.

[0105] In the embodiment of the present application, the total discharge amount and expansion force of each round of aging test are collected by sequentially performing charging and discharging operations on the battery cell to be tested, and controlling the battery cell to be tested to enter an over-discharge state. Since over-discharge accelerates the destruction of the SEI film and the expansion of the battery cell to be tested, the capacity decay and aging of the battery cell to be tested are accelerated, so that the battery cell to be tested can reach the EOL state faster, thereby improving the efficiency of the accelerated cycle aging test of the battery cell.

[0106] In some embodiments of the present application, due to the internal characteristics of the battery cell to be tested, the test requirements and safety performance considerations, during the discharge process of the battery cell to be tested, the corresponding discharge rate can be set according to actual needs. For example, the internal structure of the battery cell to be tested includes positive and negative electrode materials, electrolytes, diaphragms, etc., which will affect its discharge performance. Different battery cell designs may cause it to exhibit different characteristics at different discharge stages, so different discharge rates need to be set to adapt to these changes. Alternatively, the positive and negative electrode materials and electrolyte properties of the battery cell directly affect its discharge capacity. For example, the lithium iron phosphate positive electrode material has a stable structure but poor conductivity, which may exhibit different discharge characteristics at different discharge stages. Alternatively, different application scenarios have different requirements for the discharge performance of the battery cell. For example, electric vehicles require the battery cell to have a higher discharge rate to support rapid acceleration and climbing; while the energy storage system pays more attention to the cycle stability and safety of the battery cell. Therefore, in practical applications, it is necessary to set a suitable discharge rate according to the specific application scenario.

[0107] In addition, in order to improve the discharge effect of the battery cell to be tested and improve the discharge efficiency of the battery cell to be tested, multiple discharge stages can be set, and discharge is performed based on different discharge rates in each discharge stage. The number of discharge stages can be set according to actual conditions. For example, the entire discharge process can be divided into three discharge stages or two discharge stages, or more than three discharge stages, one discharge stage, etc. When there are more discharge stages, the discharge process of the battery cell to be tested can be finely controlled, but the discharge efficiency is reduced. Therefore, it is necessary to select the appropriate number of discharge stages according to actual conditions.

[0108] Take the three discharge stages as an example, refer to Figure 2 , the discharge operation of the battery cell to be tested after charging is completed includes:

[0109] Step S21, in the first discharge stage, a discharge operation is performed on the battery cell to be tested based on a first discharge rate, and if the battery cell to be tested enters a target power-deficient state, a second discharge stage is entered.

[0110] The first discharge stage may be the first stage of the discharge operation when the battery cell to be tested enters after the charging operation is completed. At this time, the battery cell to be tested starts to discharge from the upper limit of the rated charging voltage or the upper limit of the rated power.

[0111] The discharge rate refers to a measure of the speed of discharge, specifically the current intensity required for the battery cell to be tested to discharge its battery cell capacity within a specified time. The discharge rate is usually represented by the letter It, which is numerically equal to the ratio of the discharge current to the capacity of the battery cell to be tested. For example, if a battery cell to be tested with a capacity of 100Ah is discharged with a current of 20A, its discharge rate is 0.2C, and C represents the capacity multiple of the battery cell to be tested. The capacity of the battery cell to be tested here can be the rated capacity of the battery cell to be tested or the design capacity of the battery cell to be tested, or it can be the actual capacity of the battery cell to be tested. For example, after the charging operation of the battery cell to be tested is completed, the discharge capacity value of the battery cell to be tested is tested during the discharge operation of the battery cell to be tested, and the discharge capacity value is used as the actual capacity of the battery cell to be tested. In some embodiments, the discharge rate can be adjusted once each time the discharge capacity value is tested, and the discharge rate can be adjusted by adjusting the discharge current, thereby reducing the possibility of lithium plating and reducing the risk of lithium plating.

[0112] The specific range of the discharge rate is not limited. Through experimental tests, it is found that the lower the discharge rate, the more obvious the accelerated aging effect is, but the longer the accelerated aging time is. The higher the discharge rate, the worse the accelerated aging effect is, but the accelerated aging time is shorter.

[0113] The first discharge rate is the discharge rate used by the battery cell to be tested during the first discharge stage.

[0114] The target power-deficient state refers to the state where the battery cell to be tested is insufficient in power and the voltage is low.

[0115] The second discharge stage refers to the second stage of the discharge operation of the battery cell to be tested. The discharge stage corresponding to when the battery cell to be tested reaches the target power-deficient state can be called the second discharge stage, or the stage entered by the battery cell to be tested after the first discharge stage ends can be called the second discharge stage.

[0116] In the first discharge stage, a discharge operation is performed on the battery cell to be tested based on a first discharge rate to release the electric energy in the battery cell to be tested, so that the battery cell to be tested gradually moves toward a target power-deficient state.

[0117] Step S22, in the second discharge stage, performing a discharge operation on the battery cell to be tested based on the second discharge rate, and if the battery cell to be tested enters a full discharge state, entering a third discharge stage.

[0118] The second discharge rate is the discharge rate used by the battery cell to be tested in the second discharge stage. The second discharge rate can be determined according to the ratio of the current discharge current to the capacity of the battery cell to be tested.

[0119] The full discharge state refers to the state corresponding to when the power of the battery cell to be tested reaches a preset minimum power, or the state corresponding to when the battery cell to be tested is discharged to a preset voltage.

[0120] The third discharge stage refers to the third stage of the discharge operation of the battery cell to be tested. The discharge stage corresponding to the battery cell to be tested reaching the full discharge state can be called the third discharge stage, or the stage entered by the battery cell to be tested after the second discharge stage ends can be called the third discharge stage.

[0121] Step S23: in the third discharge stage, a discharge operation is performed on the battery cell to be tested based on a third discharge rate.

[0122] The third discharge rate is the discharge rate used by the battery cell to be tested in the third discharge stage. The third discharge rate can be determined according to the ratio of the current discharge current to the capacity of the battery cell to be tested. The first discharge rate, the second discharge rate, and the third discharge rate decrease in sequence.

[0123] After the battery cell to be tested reaches the full discharge state, the battery cell to be tested is accelerated to discharge, accelerate the destruction of the SEI film and the expansion of the battery cell to be tested, accelerate the capacity decay and aging of the battery cell to be tested, so that the battery cell to be tested can reach the EOL state faster, and improve the efficiency of the accelerated cycle aging test of the battery cell.

[0124] In the embodiment of the present application, the discharge process of the battery cell to be tested is divided into multiple discharge stages, and discharge is performed based on the corresponding discharge rate in each discharge stage, so that the battery cell to be tested reaches different states. Since the discharge rate corresponding to each discharge stage decreases successively, the discharge speed of the battery cell to be tested decreases from fast to slow, which can not only improve the discharge speed of the battery cell to be tested, but also reduce the risk of lithium plating.

[0125] In some embodiments of the present application, the first discharge rate is 1C to 2C, the second discharge rate is 0.05C to 0.33C, and the third discharge rate is 0.02C to 0.1C, wherein C represents the capacity multiple of the battery cell to be tested.

[0126] The first discharge rate can be set to 1C. When the battery cell to be tested is discharged at a discharge rate of 1C, the discharge effect of the first discharge stage is optimal. The first discharge rate can also be set to 2C. When the battery cell to be tested is discharged at a discharge rate of 2C, the discharge efficiency of the battery cell to be tested can be improved, but some of the battery cells to be tested may have lithium deposition. The first discharge rate can also be set to 1.5, or one of the discharge rates of 0.9C, 2.1C, 1.1C, 1.2C, 1.3C, 1.4C, 1.6C, 1.7C, 1.8C, and 1.9C can be selected according to actual conditions.

[0127] The second discharge rate can be set to 0.05C. When the battery cell to be tested is discharged at a discharge rate of 0.05C, the discharge effect of the second discharge stage is optimal. The second discharge rate can also be set to 0.33C. When the battery cell to be tested is discharged at a discharge rate of 0.33C, the discharge efficiency of the battery cell to be tested in the second discharge stage can be improved, but some of the battery cells to be tested may have lithium deposition. The second discharge rate can also be set to one of 0.04C, 0.34C, 0.1C, 0.2C, 0.3C, and 0.32C.

[0128] The third discharge rate can be set to 0.02C. When the battery cell to be tested is discharged at a discharge rate of 0.02C, the risk of lithium plating in the third discharge stage is reduced. The third discharge rate can also be set to 0.1C. When the battery cell to be tested is discharged at a discharge rate of 0.1C, the discharge efficiency of the battery cell to be tested in the third discharge stage can be improved, but some of the battery cells to be tested may have lithium plating. The third discharge rate can also be set to one of 0.04C, 0.34C, 0.1C, 0.2C, 0.3C, 0.32C, 0.04C~0.05C, and 0.05C. When the third discharge rate is 0.05C, the discharge effect in the third discharge stage is optimal.

[0129] In a feasible implementation, in the first discharge stage, a discharge operation is performed on the battery cell to be tested based on a 1C discharge rate. If the battery cell to be tested enters a target power-deficient state, the second discharge stage is entered; in the second discharge stage, a discharge operation is performed on the battery cell to be tested based on a 0.05C discharge rate. If the battery cell to be tested enters a fully discharged state, the third discharge stage is entered; in the third discharge stage, a discharge operation is performed on the battery cell to be tested based on a 0.04C~0.05C discharge rate, so that the discharge effect is optimized.

[0130] In the embodiment of the present application, by setting a different discharge rate for each discharge stage and providing an optional range of discharge rate, a suitable discharge rate can be selected for discharge in different discharge stages to balance the discharge efficiency of the battery cell to be tested in different discharge stages and reduce the risk of lithium plating.

[0131] In some embodiments of the present application, the cycle aging test method of the battery cell further includes:

[0132] It is determined that the remaining power of the battery cell to be tested reaches a first preset power, and the battery cell to be tested enters a target power-deficient state, wherein the first preset power is 4% SOC~15% SOC.

[0133] The remaining power of the battery to be tested refers to the amount of charge that the battery to be tested can still provide in its current state. It is an important indicator for evaluating the remaining storage capacity of the battery to be tested. The remaining power of the battery to be tested is usually expressed as a percentage such as SOC (State of Charge). This percentage is the ratio of the current remaining power of the battery to be tested to the power in its fully charged state.

[0134] The first preset power level and the second preset power level are power level thresholds, which can be set according to actual conditions. The first preset power level can also be set to any power level in the range of 4% SOC to 15% SOC.

[0135] It is determined that the remaining power of the battery cell to be tested reaches a second preset power, and the battery cell to be tested is determined to be in a full discharge state, wherein the second preset power is 0% SOC~2% SOC.

[0136] The second preset power level can also be set to any power value in the range of 0%SOC~2%SOC. For example, when the remaining power of the battery cell to be tested reaches 5%SOC, the battery cell to be tested is judged to have entered the target power-deficient state, and when the remaining power of the battery cell to be tested reaches 0%SOC, the battery cell to be tested is judged to have entered the full discharge state.

[0137] In the embodiment of the present application, by setting the first preset power and the second preset power, during the discharge process, the remaining power of the battery cell to be tested is compared with the corresponding preset power in each discharge stage, so as to accurately determine the state of the battery cell to be tested, so as to accurately control the discharge of the battery cell to be tested.

[0138] In some embodiments of the present application, the cycle aging test method of the battery cell further includes:

[0139] Determine that the lithium insertion degree of the battery cell to be tested reaches the preset lithium insertion degree, and stop the discharge operation. The preset lithium insertion degree is -10%SOC~-5%SOC.

[0140] The lithium insertion degree refers to the degree of lithium insertion in the graphite of the battery cell to be tested. It is a degree value. For example, one part of graphite can embed 6 parts of lithium, so when one part of lithium is embedded, the lithium insertion degree is expressed as 1 / 6.

[0141] The lithium insertion degree can be calculated based on the discharge current and discharge time, that is, the lithium insertion degree is equal to the cumulative product of the discharge current and the discharge time. As the discharge time increases or the number of discharges increases, the lithium insertion degree gradually decreases. The discharge degree of the battery cell to be tested is controlled by the lithium insertion degree of the battery cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the battery cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the battery cell to be tested.

[0142] The preset lithium insertion degree is a preset threshold value. The preset lithium insertion degrees of different types of battery cells to be tested are different, which can be determined according to experiments. The preset lithium insertion degree is -10%SOC~-5%SOC, wherein the preset lithium insertion degree can be -10%SOC, -5%SOC, -7%SOC, -8%SOC, -6%SOC. The preset lithium insertion degree can also be -11%SOC, or -4%SOC, and the corresponding preset lithium insertion degree can be selected according to the type of battery cell to be tested. It should be noted that too high a preset lithium insertion degree will cause the copper current collector to dissolve, and too low a preset lithium insertion degree will result in an unclear acceleration effect. When the lithium insertion degree of the battery cell to be tested reaches -8%SOC, the discharge effect of the battery cell to be tested is optimal.

[0143] When the lithium insertion degree of the battery cell to be tested reaches -10%SOC~-5%SOC, the battery cell to be tested will no longer be discharged. At this time, the discharge operation of the battery cell to be tested will stop, and this round of aging test will end.

[0144] In the embodiment of the present application, a preset lithium insertion degree is set. During the discharge process, the state of the battery cell to be tested is determined by comparing the lithium insertion degree of the battery cell to be tested with the preset lithium insertion degree. Since the lithium insertion degree reflects the degree of lithium insertion in the graphite of the battery cell to be tested, the lithium insertion degree gradually decreases with the increase of discharge time. The discharge degree of the battery cell to be tested is controlled by the lithium insertion degree of the battery cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the battery cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the battery cell to be tested.

[0145] In some embodiments of the present application, in addition to using the lithium insertion degree to determine whether the battery cell to be tested has entered an over-discharge state, the energy of the battery cell to be tested can also be used to determine the over-discharge state. The battery cell cycle aging test method also includes:

[0146] Make sure that the energy of the battery cell to be tested reaches the preset energy and stop the discharge operation. The preset energy is -10%J~-5%J.

[0147] Energy refers to the total energy stored inside the battery to be tested that can be converted into electrical energy or heat energy through chemical reactions, that is, the total amount of electrical energy that the battery to be tested can release under certain conditions. Energy can be expressed in joules. This energy comes from the chemical reaction between the positive and negative electrode materials inside the battery to be tested. When the battery to be tested is discharged, these chemical reactions will release energy, form current through the external circuit, and thus provide electrical energy.

[0148] Energy can be calculated based on discharge current, discharge voltage and discharge time, that is, energy is equal to the cumulative product of discharge current, discharge voltage and discharge time. As the discharge time or discharge frequency increases, the energy of the cell to be tested gradually decreases. The discharge degree of the cell to be tested is controlled by the energy of the cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the cell to be tested.

[0149] The preset energy is a preset threshold value. The preset energy of different types of cells to be tested is different, which can be determined based on experiments. The preset energy is -10%J~-5%J, where the preset energy can be -10%J, -5%J, -7%J, -8%J, or -6%J. The preset energy can also be -11%J, or -4%J, and the corresponding preset energy can be selected according to the type of cell to be tested. It should be noted that too high a preset energy will cause the copper current collector to dissolve, and too low a preset energy will result in an unclear acceleration effect. When the energy of the cell to be tested reaches -8%J, the discharge effect of the cell to be tested is optimal.

[0150] When the embedded energy of the cell to be tested reaches -10%J~-5%J, the cell to be tested will no longer be discharged. At this time, the discharge operation of the cell to be tested stops, and this round of aging test ends.

[0151] In the embodiment of the present application, a preset energy is set. During the discharge process, the state of the battery cell to be tested is determined by comparing the energy of the battery cell to be tested with the preset energy. Since the energy reflects the total amount of electric energy that can be released by the battery cell to be tested under certain conditions, the energy of the battery cell to be tested gradually decreases with the increase of discharge time. The discharge degree of the battery cell to be tested is controlled by the energy of the battery cell to be tested. An increase in the discharge degree will accelerate the decomposition of the solid electrolyte interface of the battery cell to be tested. When charging again, the repair of the solid electrolyte interface layer will occur and consume active lithium, thereby accelerating the attenuation of the life of the battery cell to be tested.

[0152] In some embodiments of the present application, taking two discharge stages as an example, performing a discharge operation on the battery cell to be tested includes: in the first discharge stage, performing a discharge operation on the battery cell to be tested based on the first discharge rate, and if the battery cell to be tested enters the target power-deficient state, entering the second discharge stage. In the second discharge stage, performing a discharge operation on the battery cell to be tested based on the third discharge rate, collecting data on the battery cell to be tested when it enters the over-discharge state, obtaining the total discharge amount and expansion force of this round of aging test, and cyclically entering the next round of aging test until the cycle aging test is stopped. The first discharge rate is 1C~2C, and the third discharge rate is 0.02C~0.1C.

[0153] When two discharge stages are used, the lithium insertion degree of the battery cell to be tested reaches the preset lithium insertion degree, and the discharge operation is stopped. The preset lithium insertion degree is -15%SOC~-10%SOC. Alternatively, the energy of the battery cell to be tested reaches the preset energy, and the discharge operation is stopped. The preset energy is -15%J~-10%J.

[0154] In the embodiment of the present application, after entering the target power-deficient state, the discharge operation is directly performed at the third discharge rate. Compared with the discharge in the above three discharge stages, although the charge and discharge control process is simplified, the discharge speed is reduced, so that the aging test efficiency is reduced.

[0155] In some embodiments of the present application, the discharge operation is performed on the battery cell to be tested by a constant current discharge mode. The constant current discharge mode refers to a discharge mode in which the current remains unchanged and the voltage gradually decreases during the discharge process. During the discharge operation by the constant current discharge mode, the current remains unchanged and the voltage gradually decreases. The discharge operation is performed on the battery cell to be tested by a constant current charging mode, so that the discharge of the battery cell to be tested can be achieved through a stable current.

[0156] In some embodiments of the present application, the battery cell to be tested is discharged by a constant voltage discharge mode. The constant voltage mode refers to a charging mode in which the voltage remains unchanged during the discharge process. During the discharge operation by the constant voltage discharge mode, the current is first small and then large. The battery cell to be tested is discharged by the constant voltage discharge mode, so that the discharge of the battery cell to be tested can be achieved through a stable voltage.

[0157] In some embodiments of the present application, the capacity decay rate of the battery cell to be tested can be calculated after each round of aging test, so as to evaluate the health status of the battery cell to be tested based on the capacity decay rate. A decrease in the capacity decay rate will directly lead to a decrease in the health status value, and then by monitoring the health status value of the battery cell to be tested, the remaining life and performance changes of the battery cell to be tested can be predicted.

[0158] Specifically, refer to Figure 3 , the cycle aging test method of the battery cell also includes:

[0159] Step S110, determining the capacity decay rate of the battery cell to be tested based on the total discharge capacity;

[0160] Capacity attenuation rate refers to the phenomenon that the performance of the battery cell under test gradually decreases during use. This is mainly manifested in the reduction of the capacity of the battery cell under test, the increase of internal resistance, and the reduction of charge and discharge power. These changes directly affect the health status and remaining life of the battery cell under test.

[0161] In a feasible implementation, the total discharge amount of the battery cell to be tested in the first round of accelerated cycle aging test can be obtained, and the total discharge amount of the battery cell to be tested in this round of aging test can be obtained; the capacity decay rate of the battery cell to be tested is determined according to the ratio of the total discharge amount of the battery cell to be tested in this round of aging test to the total discharge amount of the battery cell to be tested in the first round of accelerated cycle aging test. For example, the capacity decay rate of the battery cell to be tested is calculated using the following formula:

[0162] Fading=Qn / Q1*100%.

[0163] Among them, Q1 represents the total discharge capacity of the battery cell to be tested in the first round of accelerated cycle aging test, Qn represents the total discharge capacity of the battery cell to be tested in this round of aging test, and Fading represents the capacity decay rate of the battery cell to be tested. In other embodiments, Q1 can also be a preset total discharge capacity, for example, it can be set to the rated capacity of the battery cell to be tested.

[0164] Step S120: If the capacity decay rate does not reach the preset capacity decay rate, the next round of aging test is entered.

[0165] The preset capacity decay rate is a preset value, which can be set according to the design standards of different cells to be tested, or according to the warranty period of different types of cells to be tested. For example, the preset capacity decay rate can be set to 60% to 65%. In other embodiments, the preset capacity decay rate can also be set to other values.

[0166] If the capacity decay rate does not reach the preset capacity decay rate, it means that the performance of the battery cell to be tested has declined to a certain extent, but has not reached the set capacity decay rate. At this time, the battery cell to be tested can continue to be subjected to aging test to confirm its remaining life and performance.

[0167] Step S130: If the capacity decay rate reaches a preset capacity decay rate, the cycle aging test is stopped.

[0168] If the capacity decay rate reaches the preset capacity decay rate, it means that the performance of the battery cell to be tested has declined to the set capacity decay rate. At this time, the aging test can be stopped, and subsequent analysis can be performed based on the expansion force collected in this round. For example, the performance of the battery cell to be tested can be evaluated based on the expansion force to evaluate whether the increase in the expansion force exceeds the design strength of the structural parts of the battery cell to be tested when the preset capacity decay rate is reached.

[0169] In the embodiment of the present application, by comparing the current capacity decay rate of the battery cell to be tested with the preset capacity decay rate, the aging degree of the battery cell to be tested can be quantitatively evaluated.

[0170] In some embodiments of the present application, in addition to calculating the capacity decay rate of the battery cell to be tested after each round of aging test, so as to evaluate the health status of the battery cell to be tested based on the capacity decay rate, a preset round of accelerated cycle aging test can also be set. When the number of aging tests reaches the preset round, the capacity decay rate of the battery cell to be tested is obtained, and the capacity decay rate of the battery cell to be tested is calculated, so as to evaluate the health status of the battery cell to be tested based on the capacity decay rate. The specific value of the preset round is not limited, for example, it can be 0 times (i.e. before the test), the 50th time, the 100th time, etc., but it is not limited to this, and can be determined in combination with actual test requirements.

[0171] In an embodiment of the present application, when the number of aging tests reaches a preset number of rounds, the capacity decay rate of the battery cell to be tested is obtained, and the capacity decay rate of the battery cell to be tested is calculated to evaluate the health status of the battery cell to be tested based on the capacity decay rate. This method can avoid frequent calculation of the capacity decay rate and reduce computing overhead.

[0172] In some embodiments of the present application, high temperature increases the diffusion rate of lithium ions inside the battery cell, making the migration of lithium ions between the positive and negative electrodes faster, thereby accelerating the main reaction. At the same time, high temperature will also increase the conductivity of the electrolyte inside the battery cell, reduce the internal resistance of the battery cell, and further promote the transmission of current and the migration of lithium ions. In addition, high temperature will accelerate the decomposition reaction of the electrolyte, produce gas and soluble substances, which will further affect the performance and safety of the battery cell. High temperature will also accelerate the loss of active substances, such as the shedding of positive electrode materials, the pulverization of negative electrode materials, etc., which will lead to the decay of the battery cell capacity. The solid electrolyte interface membrane is a protective film formed by the battery cell during the first charging process, which can prevent the direct contact between the electrolyte and the negative electrode material, thereby protecting the battery cell from damage. However, high temperature will destroy the stability of the solid electrolyte interface membrane, causing it to gradually decompose, resulting in a short circuit inside the battery cell and a rapid decay of the capacity. That is, high temperature will accelerate the occurrence of side reactions and main reactions, resulting in accelerated decay of the life of the battery cell to be tested. Therefore, in order to accelerate the capacity attenuation and aging of the battery cell to be tested so that the battery cell to be tested can reach the EOL state faster, the test temperature in each round of aging test is set to 45°C~60°C.

[0173] The battery cell to be tested can be placed in a high temperature box, and the temperature in the high temperature box is set to a preset test temperature to achieve aging testing of the battery cell to be tested in a high temperature environment.

[0174] For example, the battery cell to be tested may be subjected to an accelerated cycle aging test at 45°C; or, the battery cell to be tested may be subjected to an accelerated cycle aging test at 60°C. The battery cell to be tested may also be subjected to an accelerated cycle aging test at any temperature between 45°C and 60°C.

[0175] In the embodiment of the present application, an aging test is performed in a high temperature test environment to accelerate the capacity decay and aging of the battery cell to be tested, so that the battery cell to be tested can reach the EOL state faster.

[0176] In some embodiments of the present application, due to the internal characteristics of the battery cell to be tested, test requirements, and safety performance considerations, during the charging process of the battery cell to be tested, the corresponding charging rate can be set according to actual needs. For example, the internal structure of the battery cell to be tested includes positive and negative electrode materials, electrolytes, diaphragms, etc., which will affect its charging performance. Different battery cell designs may cause it to exhibit different characteristics at different charging stages, so different charging rates need to be set to adapt to these changes. In addition, in order to improve the charging effect of the battery cell to be tested and improve the charging efficiency of the battery cell to be tested, multiple charging stages can be set, and charging is performed based on different charging rates in each charging stage. The number of charging stages can be set according to actual conditions. During the charging process, at least two charging stages are set, and the charging rates corresponding to each charging stage are reduced in sequence.

[0177] For example, the entire charging process can be divided into three charging stages or two charging stages, or more than three charging stages, one charging stage, etc. When there are more charging stages, the charging process of the battery cell to be tested can be finely controlled, but the charging efficiency is reduced. Therefore, it is necessary to select a suitable number of charging stages according to actual conditions.

[0178] Taking two charging stages as an example, in the first charging stage, the battery cell to be tested in this round of aging test is charged based on the first charging rate. If the battery cell to be tested enters the first state of charge, the second charging stage is entered; in the second charging stage, the battery cell to be tested in this round of aging test is charged based on the second charging rate. If the battery cell to be tested enters the second state of charge, it indicates that charging is completed. The first charging rate is 1C~2C, and the second charging rate is 0.05C~0.33C.

[0179] The charging rate refers to a measure of charging speed, specifically the current intensity required when the battery cell to be tested is charged to its maximum battery cell capacity within a specified time. The charging rate is usually represented by the letter It, which is numerically equal to the ratio of the charging current to the capacity of the battery cell to be tested. For example, if a battery cell to be tested with a capacity of 100Ah is charged with a current of 20A, its charging rate is 0.2C, and C represents the capacity multiple of the battery cell to be tested. The capacity of the battery cell to be tested here can be the rated capacity of the battery cell to be tested or the design capacity of the battery cell to be tested, or it can be the actual capacity of the battery cell to be tested. For example, during the charging operation of the battery cell to be tested, the charging capacity value of the battery cell to be tested is tested, and the charging capacity value is used as the actual capacity of the battery cell to be tested. In some embodiments, the charging rate can be adjusted once each time the charging capacity value is tested, and the charging current can be adjusted to achieve the adjustment of the charging rate, thereby reducing the possibility of lithium plating and reducing the risk of lithium plating. The specific range of the charging rate is not limited. Through experiments and tests, it was found that the lower the charging rate, the more obvious the accelerated aging effect, but the longer the accelerated aging time, the higher the charging rate, the worse the accelerated aging effect, but the shorter the accelerated aging time.

[0180] The first charging rate refers to the charging rate used by the battery cell to be tested in the first charging stage.

[0181] The first charging rate can be set to 1C. When the battery cell to be tested is charged at a charging rate of 1C, the charging effect of the first charging stage is optimal. The first charging rate can also be set to 2C. When the battery cell to be tested is charged at a charging rate of 2C, the charging efficiency of the battery cell to be tested can be improved, but some of the battery cells to be tested may have lithium deposition. The first charging rate can also be set to 1.5, or the charging rate can be selected to be 0.9C, 2.1C, 1.1C, 1.2C, 1.3C, 1.4C, 1.6C, 1.7C, 1.8C, 1.9C according to actual conditions.

[0182] The second charging rate can be set to 0.05C. When the battery cell to be tested is charged at a charging rate of 0.05C, the charging effect of the second charging stage is optimal. The second charging rate can also be set to 0.33C. When the battery cell to be tested is charged at a charging rate of 0.33C, the charging efficiency of the battery cell to be tested in the second discharge stage can be improved, but some of the battery cells to be tested may have lithium deposition. The second charging rate can also be set to 0.04C, 0.34C, 0.1C, 0.2C, 0.3C, 0.32C.

[0183] The first state of charge can be set to 95% SOC, and the second state of charge is a fully charged state, which can be set to 100% SOC. It can be understood that in other embodiments, the first state of charge and the second state of charge can be set to other values.

[0184] In the embodiment of the present application, the charging process of the battery cell to be tested is divided into multiple charging stages, and discharge is performed based on the corresponding charging rate in each charging stage, so that the battery cell to be tested reaches different states. Since the charging rate corresponding to each charging stage decreases successively, the charging speed of the battery cell to be tested decreases from fast to slow, which can not only improve the charging speed of the battery cell to be tested, but also reduce the risk of lithium plating.

[0185] In some embodiments of the present application, the battery cell to be tested is charged by a constant current charging mode. The constant current charging mode refers to a charging mode in which the current remains constant and the voltage gradually increases during the charging process. During the charging operation by the constant current charging mode, the current remains constant and the voltage gradually increases. The battery cell to be tested is charged by the constant current charging mode, so that the battery cell to be tested can be charged with a stable current.

[0186] In some embodiments of the present application, the battery cell to be tested is charged in a constant voltage mode. The constant voltage charging mode refers to a charging mode in which the voltage remains unchanged during the charging process. During the charging operation in the constant voltage charging mode, the voltage remains unchanged and the current gradually decreases. During the discharge operation in the constant voltage charging mode, the current is first small and then large. The battery cell to be tested is charged in the constant voltage charging mode, so that the battery cell to be tested can be charged with a stable voltage.

[0187] In some embodiments of the present application, before performing a charging operation on the battery cell to be tested in this round of aging test, the battery cell to be tested may be placed in a high temperature box and left to stand for a first period of time.

[0188] The specific duration of the first duration is not limited, and the first duration can be set to 5 to 20 minutes. It is understandable that the first duration can also be set to other durations.

[0189] Before charging the battery cell of this round of aging test, the battery cell is left to stand for a first period of time, so that the battery cell gradually tends to a stable state after the previous round of aging test. After the battery cell tends to a stable state, the battery cell is charged for the next round of aging test, which can help improve the stability and reliability of the accelerated cycle aging test. In addition, during the high-temperature standing process, the chemical reaction inside the battery cell will tend to balance, making the various performance indicators of the battery cell more stable.

[0190] In some embodiments of the present application, after charging is completed, the battery cell to be tested is left to stand for a second period of time, and then a discharge operation is performed on the battery cell to be tested.

[0191] The specific duration of the second duration is not limited, and the second duration can be set to 10 minutes. It is understandable that the second duration can also be set to other durations.

[0192] After the charging operation of the battery cell to be tested is completed, the battery cell to be tested is allowed to stand for a second period of time so that the battery cell to be tested can gradually tend to a stable state after the charging operation. After the battery cell to be tested tends to a stable state, the battery cell to be tested is discharged to accelerate the test, which can help improve the stability and reliability of the accelerated cycle aging test.

[0193] In some embodiments of the present application, if the battery cell to be tested enters a fully discharged state, the battery cell to be tested enters a third discharge stage after being left to stand for a third period of time.

[0194] The specific duration of the third duration is not limited, and the second duration can be set to 5 minutes. It is understandable that the third duration can also be set to other durations.

[0195] After the battery cell to be tested enters the full discharge state, by leaving the battery cell to be tested stationary for a third period of time, the battery cell to be tested can gradually tend to a stable state after being fully discharged. After the battery cell to be tested tends to the stable state, the battery cell to be tested is over-discharged to accelerate the test, which can help improve the stability and reliability of the accelerated cycle aging test.

[0196] When performing an accelerated cycle aging test on the battery cell to be tested, multiple rounds of accelerated cycle testing may be performed. In a specific example, a round of accelerated cycle aging testing may be performed as follows:

[0197] (1) Let it sit for a certain period of time, for example 5 minutes.

[0198] (2) Charge the battery cell to be tested at a 1C charge rate until the battery cell to be tested is quickly charged to a high state of charge, such as 95% SOC.

[0199] (3) Charge the battery cell to be tested at a charging rate of 0.33C until the battery cell to be tested reaches a fully charged state, for example, 100% SOC.

[0200] (4) Let it stand for a certain period of time, such as 10 minutes.

[0201] (5) Discharge the battery cell to be tested at a 1C discharge rate until the battery cell to be tested is quickly discharged to a low state of charge, such as 5% SOC.

[0202] (6) The battery cell to be tested is discharged at a discharge rate of 0.33C until the battery cell to be tested reaches a full discharge state, for example, 0% SOC.

[0203] (7) Let it stand for a certain period of time, for example 5 minutes.

[0204] (8) Accelerate the discharge of the battery cell to be tested at a discharge rate of 0.05 until it is discharged to -8% SOC energy or -8% SOC lithium insertion degree.

[0205] (9) Calculate the capacity decay rate of the battery cell to be tested in this round and end this round of cycle acceleration test.

[0206] Repeat each round of the accelerated cycle aging test process until a preset number of cycles is reached or the EOL state of the battery cell to be tested is reached.

[0207] It should be understood that during the above-mentioned accelerated cycle aging test, when the battery cell to be tested is discharged for accelerated aging, the temperature of accelerated aging can be set to further enhance the accelerated effect of cycle aging. In some embodiments, the preset test temperature of the accelerated cycle aging test can be set to 45 ~ 60°C (degrees Celsius), denoted as T, so that the acceleration effect of high temperature can be achieved. Since the battery cell to be tested will also generate heat during the charging and discharging process, the temperature will also rise to a certain extent, so a cooling device can be configured at the same time. When the preset test temperature is greater than the T preset value (such as 5°C), the cooling device is turned on to cool down the battery cell to be tested and reduce the safety impact of excessive temperature. When the preset test temperature is lower than the T preset value (such as 5°C), the cooling device is turned off to maintain the battery cell to be tested in a high temperature environment to achieve the acceleration effect of high temperature.

[0208] In some embodiments of the present application, Figure 4 As shown, the embodiment of the present application provides a method for evaluating the performance of a battery cell, which can be used to evaluate the performance of the battery cell after each round of accelerated cycle aging test, or after a preset number of cycles. Specifically, the method for evaluating the performance of the battery cell includes:

[0209] Step S210, obtaining the total discharge capacity of the battery cell to be tested during the aging test, and determining the capacity decay rate of the battery cell to be tested based on the total discharge capacity.

[0210] Obtaining the total discharge capacity of the battery cell to be tested during the aging test means obtaining the total discharge capacity of the battery cell to be tested during this round of accelerated cycle aging test. It can also be the total discharge capacity of each round of aging test.

[0211] The capacity attenuation rate may be a data value calculated after this round of aging test.

[0212] The specific implementation method of determining the capacity decay rate of the battery cell to be tested based on the total discharge amount can refer to the above embodiment and will not be described in detail here.

[0213] Step S220, obtaining the measured expansion force corresponding to the capacity decay rate.

[0214] The measured expansion force refers to the expansion force of the battery cell to be tested, which is collected in real time during the accelerated cycle aging test of the battery cell to be tested. The measured expansion force can be a data value collected during this round of accelerated cycle aging test; or it can be the maximum measured expansion force obtained from all the measured expansion forces collected during the current round of accelerated cycle aging test, where the expansion force is collected once at every preset time interval. Among them, the preset time interval can be set according to the actual situation, for example, the measured expansion force is collected once every 1 second, or once every 5 minutes. The maximum measured expansion force is preferably used for subsequent life evaluation.

[0215] The standard expansion force refers to the standard expansion force of the battery cell to be tested, which is collected in real time during the normal cycle aging test of the battery cell to be tested. The standard expansion force can be a data value collected during this round of normal cycle aging test; or it can be the maximum standard expansion force obtained from all the expansion forces collected during the expansion force collected once at every preset time interval during this round of normal cycle aging test. The preset time interval can be set according to the actual situation, for example, the standard expansion force can be collected once every 1 second, or once every 5 minutes. The maximum standard expansion force is preferably used for subsequent life evaluation.

[0216] It should be noted that the difference between the normal cycle aging test and the accelerated cycle aging test is that the normal cycle aging test only performs normal cycle charge and discharge, and does not perform accelerated discharge on the battery cell to be tested.

[0217] The standard expansion force can be collected in advance and stored in the database, that is, the corresponding relationship between different capacity decay rates and corresponding standard expansion forces is established in advance. After obtaining the capacity decay rate calculated by this round of accelerated cycle aging test and the measured expansion force collected, the corresponding standard expansion force can be obtained from the database based on the calculated capacity decay rate to compare the obtained standard expansion force with the measured expansion force.

[0218] Step S230, obtaining the real expansion force of the battery cell to be tested according to the standard expansion force and the measured expansion force.

[0219] Compared with the battery cells under normal cycle aging test, the battery cells under accelerated cycle test will produce gases that are insoluble in the electrolyte, mainly carbon monoxide, carbon dioxide, etc., which will cause the air pressure inside the battery cells under test to increase, making the detected expansion force inaccurate, and further affecting the accuracy of the performance evaluation results of the battery cells under test. Therefore, in order to improve the accuracy of the performance evaluation results of the battery cells under test, it is necessary to correct the expansion force obtained by the accelerated cycle test to obtain the true expansion force of the battery cells under test.

[0220] The true expansion force of the battery cell to be tested refers to the expansion force obtained after correction.

[0221] In a feasible implementation manner, the measured expansion force may be corrected based on the standard expansion force to obtain the real expansion force of the battery cell to be tested.

[0222] In another feasible implementation, when the standard expansion force is the maximum standard expansion force and the measured expansion force is the maximum measured expansion force, the maximum standard expansion force may be used to correct the maximum measured expansion force to obtain the true expansion force of the battery cell to be tested.

[0223] Step S240, determining the performance evaluation result of the battery cell to be tested based on the capacity decay rate and the actual expansion force.

[0224] The performance evaluation results include: under the capacity attenuation rate, the actual expansion force of the tested battery cell is greater than or equal to the preset expansion force corresponding to the design strength of the tested battery cell structure, or under the capacity attenuation rate, the actual expansion force of the tested battery cell is less than the preset expansion force corresponding to the design strength of the tested battery cell structure. The preset expansion force can be set according to the type of different tested battery cells.

[0225] In a feasible implementation manner, the performance evaluation result of the battery cell to be tested can be determined based on the capacity decay rate and the actual expansion force in this round of aging test.

[0226] In another feasible implementation, the capacity attenuation rate and true expansion force corresponding to each round of aging test can also be obtained, and the performance evaluation results of the battery cells to be tested can be jointly determined based on the capacity attenuation rate and true expansion force corresponding to each round of aging test to improve the accuracy of the performance evaluation results of the battery cells.

[0227] In the embodiment of the present application, the real expansion force of the battery cell to be tested is obtained based on the standard expansion force and the measured expansion force; the performance evaluation result of the battery cell to be tested is determined based on the capacity attenuation rate and the real expansion force of the battery cell to be tested. Since the expansion force obtained by the cycle acceleration test is corrected, the real expansion force of the battery cell to be tested is obtained, thereby improving the accuracy of the performance evaluation result of the battery cell to be tested.

[0228] In some embodiments of the present application, compared with the normal cycle aging test of the battery cell to be tested, the accelerated cycle aging test of the battery cell to be tested will produce gases that are insoluble in the electrolyte, mainly carbon monoxide, carbon dioxide, etc., which will cause the air pressure inside the battery cell to be tested to increase, and then cause the external expansion force of the accelerated battery cell to increase. Therefore, it is also necessary to monitor the internal air pressure of the battery cell to be tested to establish an expansion force correction model for the battery cell to be tested. Specifically, the standard expansion force includes the standard internal pressure, and the measured expansion force includes the measured external expansion force and the measured internal pressure. Figure 5 According to the standard expansion force and the measured expansion force, the real expansion force of the battery cell to be tested includes:

[0229] Step S231, determining a correction value of the measured external expansion force based on the measured internal pressure and the standard internal pressure.

[0230] The measured internal pressure refers to the measured internal air pressure of the battery cell to be tested during the accelerated cycle aging test. The measured internal pressure can be a data value collected during this round of accelerated cycle aging test; or it can be the maximum measured internal pressure obtained from all the internal pressures collected during the current round of accelerated cycle aging test, where the internal pressure is collected once at preset time intervals. The preset time interval can be set according to actual conditions, for example, collecting the internal pressure once every 1 second, or collecting the internal pressure once every 5 minutes. The maximum measured internal pressure is preferably used for subsequent life evaluation.

[0231] The standard internal pressure refers to the measured internal air pressure of the battery cell to be tested during the normal cycle aging test, and the standard internal pressure is about 0.1MPa. The standard internal pressure can be a data value collected during this round of normal cycle aging test; or it can be the maximum standard internal pressure obtained from all the expansion forces collected during the internal pressure collected at every preset time interval during this round of normal cycle aging test. Among them, the preset time interval can be set according to the actual situation, for example, the standard internal pressure is collected once every 1 second, or once every 5 minutes. The maximum standard internal pressure is preferably used for subsequent life evaluation.

[0232] The measured external expansion force refers to the measured external expansion force of the battery cell to be tested during the accelerated cycle aging test. The measured external expansion force can be a data value collected during this round of accelerated cycle aging test; or it can be the maximum measured external expansion force obtained from all the external expansion forces collected during the current round of accelerated cycle aging test, where the external expansion force is collected once at every preset time interval. Among them, the preset time interval can be set according to the actual situation, for example, the measured external expansion force is collected once every 1 second, or the measured external expansion force is collected once every 5 minutes. The maximum measured external expansion force is preferably used for subsequent life evaluation.

[0233] The correction value may be the difference between the actually measured internal pressure and the standard internal pressure, or may be a preset coefficient associated with the difference, and the correction value is used to correct the actually measured internal pressure.

[0234] In a possible implementation manner, the correction value of the maximum measured external expansion force is determined according to the difference between the maximum measured internal pressure and the maximum standard internal pressure.

[0235] Step S232, obtaining the real expansion force of the battery cell to be tested according to the difference between the measured external expansion force and the correction value.

[0236] In a feasible implementation manner, the actual expansion force of the battery cell to be tested is obtained by subtracting the measured external expansion force from the correction value.

[0237] In other embodiments, the standard external expansion force may be directly used to correct the measured external expansion force to obtain the real expansion force of the battery cell to be tested.

[0238] The capacity decay rate of the cell under test and the measured internal pressure collected in each round of accelerated cycle test can be fitted to obtain Figure 6 The curve shown. Figure 6 The horizontal axis SOH represents the capacity attenuation rate, the vertical axis represents the measured internal pressure, the red curve is the fitting curve of the capacity attenuation rate of the battery cell to be tested and the measured internal pressure during the accelerated cycle aging test, and the black curve is the fitting curve of the capacity attenuation rate of the battery cell to be tested and the standard internal pressure during the normal cycle aging test.

[0239] The capacity decay rate of the cell under test and the measured external expansion force collected in each round of accelerated cycle test can be fitted to obtain Figure 7 The curve shown. Figure 7 The horizontal axis SOH in the figure represents the capacity decay rate, and the vertical axis represents the measured external expansion force. The red curve is the fitting curve of the capacity decay rate of the battery cell under test and the measured external expansion force during the accelerated cycle aging test, and the black curve is the fitting curve of the capacity decay rate of the battery cell under test and the standard external expansion force during the normal cycle aging test. The correction model of this application is used to correct the correction, and the corrected curve is as follows: Figure 7 The blue curve in .

[0240] In the embodiment of the present application, the influence of the internal air pressure of the battery cell to be tested on the actually measured external expansion force of the battery cell to be tested is taken into consideration, and the internal air pressure of the battery cell to be tested is used to correct the actually measured external expansion force of the battery cell to be tested, so that the determined real expansion force is more accurate.

[0241] In some embodiments of the present application, reference Figure 8 , based on the measured internal pressure and the standard internal pressure, the correction value of the measured external expansion force is determined including:

[0242] Step S2311, determine the difference between the measured internal pressure and the standard internal pressure.

[0243] In a feasible implementation manner, the measured internal pressure is the maximum measured internal pressure of the current round of accelerated cycle aging test, and the standard internal pressure is the maximum standard internal pressure of the current round of normal cycle aging test. Determining the difference between the measured internal pressure and the standard internal pressure includes: determining the difference between the maximum measured internal pressure of the current round of accelerated cycle aging test and the maximum standard internal pressure of the current round of normal cycle aging test.

[0244] Step S2312, obtaining the size, correction coefficient and gravity constant of the battery cell to be tested.

[0245] The battery cells to be tested have different sizes due to their different types. The size of the battery cells to be tested can be calculated based on the product of the length and height of the battery cells to be tested.

[0246] The correction factor is an experimentally determined and preset value, which is determined by the design of the battery cell to be tested.

[0247] The gravitational constant is also known as the universal gravitational constant, which is the coefficient in the formula in the law of universal gravitation that represents the relationship between gravity and the mass and distance of two objects.

[0248] Step S2313, obtaining a correction value of the measured external expansion force according to the difference, size, correction coefficient and gravity constant.

[0249] In a feasible implementation manner, a correction value of the measured external expansion force may be obtained according to the product of the difference, the size, the correction coefficient and the gravity constant.

[0250] The embodiment of the present application can calculate the correction value of the measured external expansion force based on the difference between the measured internal pressure and the standard internal pressure, the size of the battery cell to be measured, the correction coefficient and the gravity constant. Since the calculation process of the correction value takes into account the influence of the measured internal pressure and the standard internal pressure, the accuracy of the correction value can be improved, making the actual external expansion force obtained by subsequent correction more accurate.

[0251] For example, the correction model of the measured external expansion force involved in this application can be expressed as:

[0252] .

[0253] in, is the actual external expansion force of the cell under test during the cycle acceleration test (in kgf). It is the measured external expansion force of the battery cell under test during the cycle acceleration test (in kgf). It is the measured internal pressure of the battery cell under test during the cycle acceleration test (in MPa). is the standard internal pressure of the battery cell to be tested during normal cycle testing (in MPa), b is the length of the battery cell to be tested (in m), c is the height of the battery cell to be tested (in m), b*c is the size of the battery cell to be tested (in m*m), g is the gravity constant, and k is the correction factor.

[0254] In the embodiment of the present application, the correction model of the measured external expansion force is provided, and the measured external expansion force is corrected by the correction model, so that the accurate real external expansion force is obtained more accurately.

[0255] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0256] In some embodiments of the present application, corresponding to the cycle aging test method of the battery cell provided in the above embodiment, Fig. 9 This is a structural block diagram of a battery cell cycle aging test device provided in an embodiment of the present application. For the sake of ease of explanation, only the parts related to the embodiment of the present application are shown.

[0257] Reference Fig. 9 , provides a battery cell cycle aging test device, the battery cell cycle aging test device includes:

[0258] The charging module 10 is used to perform charging operation on the battery cells to be tested in this round of aging test.

[0259] The discharge module 20 is used to perform a discharge operation on the battery cell to be tested after charging is completed, so that the battery cell to be tested enters an over-discharge state, wherein the over-discharge state is a state reached after the battery cell to be tested reaches a full discharge state and continues to perform a discharge operation on the battery cell to be tested.

[0260] The data acquisition module 30 is used to collect data on the battery cell to be tested that has entered an over-discharge state, obtain the total discharge capacity and expansion force of this round of aging test, and cycle into the next round of aging test until the cycle aging test is stopped.

[0261] In some embodiments, the discharge module 20 is used to perform a discharge operation on the battery cell to be tested based on a first discharge rate in a first discharge stage, and enter a second discharge stage if the battery cell to be tested enters a target power-deficient state; in the second discharge stage, perform a discharge operation on the battery cell to be tested based on a second discharge rate, and enter a third discharge stage if the battery cell to be tested enters a fully discharged state; in the third discharge stage, perform a discharge operation on the battery cell to be tested based on a third discharge rate; wherein the first discharge rate, the second discharge rate, and the third discharge rate decrease in sequence.

[0262] In some embodiments, the first discharge rate is 1C-2C, the second discharge rate is 0.05C-0.33C, and the third discharge rate is 0.02C-0.1C.

[0263] In some embodiments, it is determined that the remaining power of the battery cell to be tested reaches a first preset power level, and the battery cell to be tested is judged to have entered a target power-deficient state, and the first preset power level is 4% SOC~15% SOC; and or, it is determined that the remaining power of the battery cell to be tested reaches a second preset power level, and the battery cell to be tested is judged to have entered a full discharge state, and the second preset power level is 0% SOC~2% SOC.

[0264] In some embodiments, it is determined that the lithium insertion degree of the battery cell to be tested reaches a preset lithium insertion degree, and the discharge operation is stopped. The preset lithium insertion degree is -10% SOC to -5% SOC.

[0265] In some embodiments, it is determined that the energy of the battery cell to be tested reaches a preset energy, and the discharge operation is stopped, and the preset energy is -10%J~-5%J.

[0266] In some embodiments, the observed data is the total discharge capacity and expansion force of the battery cell to be tested.

[0267] In some embodiments, the capacity decay rate of the battery cell to be tested can also be determined based on the total discharge amount; if the capacity decay rate does not reach the preset capacity decay rate, the next round of aging test is entered; if the capacity decay rate reaches the preset capacity decay rate, the cyclic aging test is stopped.

[0268] In some embodiments, the test temperature during each round of aging test is 45° C. to 60° C.

[0269] In some embodiments, during the charging process, at least two charging stages are provided, and the charging rates corresponding to the respective charging stages decrease in sequence.

[0270] The battery cell cycle aging test equipment provided by the present application adopts the battery cell cycle aging test method in the above embodiment, which can alleviate the problem of low efficiency of battery cell aging test. Compared with the prior art, the beneficial effects of the battery cell cycle aging test equipment provided by the present application are the same as the beneficial effects of the battery cell cycle aging test method provided by the above embodiment, and other technical features in the battery cell cycle aging test equipment are the same as the features disclosed in the above embodiment method, which will not be repeated here.

[0271] In some embodiments of the present application, corresponding to the performance evaluation method of the battery cell provided in the above embodiments, Fig.10 is a structural block diagram of a performance evaluation device for a battery cell provided in an embodiment of the present application. For the sake of convenience, only the parts related to the embodiment of the present application are shown. Fig.10 , provides a performance evaluation device for a battery cell, the performance evaluation of the battery cell includes:

[0272] The capacity decay rate determination module 40 is used to obtain the total discharge amount of the battery cell to be tested during the aging test, and determine the capacity decay rate of the battery cell to be tested based on the total discharge amount;

[0273] An acquisition module 50 is used to acquire a measured expansion force corresponding to a capacity decay rate;

[0274] A correction module 60, used to obtain the real expansion force of the battery cell to be tested according to the standard expansion force and the measured expansion force;

[0275] The evaluation module 70 is used to determine the performance evaluation result of the battery cell to be tested based on the capacity decay rate and the actual expansion force.

[0276] In some embodiments, the standard expansion force includes a standard internal pressure, the measured expansion force includes a measured external expansion force and a measured internal pressure, and the correction module 60 is used to determine a correction value of the measured external expansion force based on the measured internal pressure and the standard internal pressure; and obtain the actual expansion force of the battery cell to be tested according to the difference between the measured external expansion force and the correction value.

[0277] In some embodiments, the evaluation module 70 is used to determine the difference between the measured internal pressure and the standard internal pressure; obtain the size, correction coefficient and gravity constant of the battery cell to be tested; and obtain the correction value of the measured external expansion force based on the difference, size, correction coefficient and gravity constant.

[0278] The performance evaluation device for the battery cell provided in the present application adopts the performance evaluation method for the battery cell in the above-mentioned embodiment, which can alleviate the problem of inaccurate performance evaluation results of the battery cell to be tested. Compared with the prior art, the beneficial effects of the performance evaluation device for the battery cell provided in the present application are the same as the beneficial effects of the performance evaluation method for the battery cell provided in the above-mentioned embodiment, and other technical features in the performance evaluation device for the battery cell are the same as the features disclosed in the above-mentioned embodiment method, which will not be repeated here.

[0279] In some embodiments of the present application, a battery cell cycle aging test device is provided. The battery cell cycle aging test device may be a server, and its internal structure diagram may be as shown in FIG. Fig.11 The battery cell cycle aging test device includes a processor, a memory and a network interface connected via a system bus.

[0280] Among them, the processor of the battery cell cycle aging test device is used to provide computing and control capabilities. The memory of the battery cell cycle aging test device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the battery cell cycle aging test device is used to store data related to the accelerated cycle aging test of the battery cell, such as the above-mentioned discharge rate, charging rate, etc. The network interface of the battery cell cycle aging test device is used to communicate with an external terminal through a network connection. The computer program is executed by the processor to implement a battery cell cycle aging test method.

[0281] Those skilled in the art will understand that Fig.11 The structure shown in the figure is only a block diagram of a part of the structure related to the scheme of the present application, and does not constitute a limitation on the cycle aging test equipment of the battery cell to which the scheme of the present application is applied. The specific cycle aging test equipment of the battery cell may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0282] In one embodiment, a battery cell cycle aging test device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of the battery cell cycle aging test method in any of the above embodiments are implemented.

[0283] In some embodiments of the present application, a performance evaluation device for a battery cell is provided. The performance evaluation device for the battery cell may be a server, and its internal structure diagram may be as shown in FIG. Fig.12 The performance evaluation device of the battery cell includes a processor, a memory and a network interface connected through a system bus.

[0284] Among them, the processor of the performance evaluation device of the battery cell is used to provide computing and control capabilities. The memory of the performance evaluation device of the battery cell includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the performance evaluation device of the battery cell is used to store data related to the performance evaluation of the battery cell, such as the above-mentioned discharge rate, charging rate, etc. The network interface of the performance evaluation device of the battery cell is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a performance evaluation method of a battery cell is implemented.

[0285] Those skilled in the art will understand that Fig.12The structure shown in the figure is only a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the performance evaluation device of the battery cell to which the scheme of the present application is applied. The specific performance evaluation device of the battery cell may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0286] In one embodiment, a battery cell performance evaluation device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of the battery cell performance evaluation method in any of the above embodiments are implemented.

[0287] In some embodiments of the present application, Fig.13 As shown, the battery cell testing and evaluation system includes: a battery cell cycle aging test device 80; a battery cell performance evaluation device 90; and an expansion force monitoring module 100 for monitoring the expansion force generated by the aging test of the battery cell to be tested; the battery cell cycle aging test device 80 and the expansion force monitoring module 100 are respectively connected to the battery cell performance evaluation device 90.

[0288] In the embodiment of the present application, the battery cell cycle aging test equipment 80 can be used to perform an accelerated cycle aging test on the battery cell to be tested, the expansion force of the battery cell to be tested during the accelerated cycle aging test can be collected by the expansion force monitoring module 100, and the performance of the battery cell to be tested can be evaluated by the battery cell performance evaluation equipment 90. Through the battery cell testing and evaluation system, the technical problem of low efficiency of battery cell aging testing can be alleviated, and the efficiency of accelerated cycle aging testing and performance evaluation of the battery cell to be tested can be improved.

[0289] In some embodiments of the present application, Fig.14 As shown, the expansion force monitoring module includes: an external expansion force monitoring module 101 and an internal pressure monitoring module 102 .

[0290] The internal pressure monitoring module 102 may be a barometer, through which the internal pressure of the battery cell to be tested can be monitored. The external expansion force monitoring module 101 may be a pressure sensor, through which the external expansion force of the battery cell to be tested can be monitored.

[0291] As a specific example, the top view of the expansion force monitoring module 100 and the battery cell to be tested 110 is as shown in FIG. Fig.15 As shown. Fig.15As shown, the expansion force monitoring module 100 includes an external expansion force monitoring module 101 and an internal pressure monitoring module 102, and also includes a clamping assembly, the clamping assembly includes a first clamping portion 103, a second clamping portion 104 and a third clamping portion 105, the external expansion force monitoring module 101 is arranged between the first clamping portion 103 and the second clamping portion 104, and the battery cell to be tested is arranged between the second clamping portion 104 and the third clamping portion 105. By setting the clamping assembly and setting the external expansion force monitoring module 101 between the first clamping portion 103 and the second clamping portion 104, it can be more conducive to the fixation of the external expansion force monitoring module, reduce the shaking of the external expansion force monitoring module, and also help to improve the accuracy of the internal pressure measured by the external expansion force monitoring module. Among them, the internal pressure monitoring module 102 is connected to the corrosion-resistant Teflon tube, the Teflon tube is connected to the tip of the gas-producing nail, and the bottom of the gas-producing nail is welded and sealed with the injection port of the battery cell to be tested.

[0292] In the embodiment of the present application, the external expansion force and internal pressure during the accelerated test of the battery cell to be tested are monitored by an external expansion force monitoring module and an internal pressure monitoring module, thereby achieving effective collection of the external expansion force and the internal pressure.

[0293] In some embodiments of the present application, Fig.16 As shown, the battery cell cycle aging test equipment 80 includes:

[0294] The battery cell charging and discharging control module 81 is used to perform charging operation and / or discharging operation on the battery cell to be tested in this round of aging test.

[0295] The control module 82 is used to determine the capacity decay rate of the battery cell to be tested based on the total discharge amount; if the capacity decay rate does not reach the preset capacity decay rate, the battery cell charge and discharge control module 81 is controlled to enter the charging operation and / or discharging operation of the next round of aging test; or, if the capacity decay rate reaches the preset capacity decay rate, the battery cell charge and discharge control module 81 is controlled to stop working to stop the cyclic aging test.

[0296] Among them, the battery cell charge and discharge control module 81 can not only realize large current charge and discharge operations, such as providing large current charge and discharge operations of 50A~300A, but also realize small current charge and discharge operations, such as realizing small current discharge operations of 0.5A~10A.

[0297] After the battery cell charge and discharge control module 81 completes the current round of cycle aging of the battery cell to be tested, the total discharge amount can be sent to the control module 82, and the capacity decay rate of the battery cell to be tested can be calculated by the control module 82. If the capacity decay rate does not reach the preset capacity decay rate, a first control signal is sent to the battery cell charge and discharge control module 81, and the battery cell charge and discharge control module 81 starts to perform the charging operation and / or discharging operation of the next round of aging test after receiving the first control signal. If the capacity decay rate reaches the preset capacity decay rate, a second control signal is sent to the battery cell charge and discharge control module 81, and the battery cell charge and discharge control module 81 controls the battery cell charge and discharge control module 81 to stop working after receiving the second control signal, thereby completing multiple rounds of accelerated cycle aging tests on the battery cell to be tested.

[0298] In the embodiment of the present application, the cycle aging test equipment based on the battery cell can perform charging operation and / or discharging operation through the battery cell charging and discharging control module. During the discharge operation, the battery cell to be tested can also be discharged at an accelerated rate, thereby accelerating the cycle aging test and realizing the accelerated cycle aging test of the battery cell to be tested with a short test time. In addition, the control module performs cycle control on the battery cell to be tested to realize the accelerated cycle aging test of the battery cell to be tested.

[0299] In some embodiments of the present application, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the battery cell cycle aging test method in any of the above embodiments are implemented. Alternatively, when the computer program is executed by a processor, the steps of the battery cell cycle aging test method in any of the above embodiments are implemented.

[0300] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A cycle aging test method for a battery cell, characterized in that: The cycle aging test method of the battery cell includes: Perform charging operation on the battery cells to be tested in this round of aging test; In the first discharge stage, a discharge operation is performed on the battery cell to be tested based on a first discharge rate, and if the battery cell to be tested enters a target power-deficient state, a second discharge stage is entered; In the second discharge stage, a discharge operation is performed on the battery cell to be tested based on a second discharge rate, and if the battery cell to be tested enters a full discharge state, a third discharge stage is entered; In the third discharge stage, a discharge operation is performed on the battery cell to be tested based on a third discharge rate, so that the battery cell to be tested enters an over-discharge state, wherein the first discharge rate, the second discharge rate, and the third discharge rate are successively reduced, and the over-discharge state is a state reached after the battery cell to be tested reaches a full discharge state and the discharge operation is continued to be performed on the battery cell to be tested, and the over-discharge state is a state corresponding to when the lithium insertion degree of the battery cell to be tested is a negative value or the energy of the battery cell to be tested is a negative value; Data is collected for the battery cell to be tested that has entered the over-discharge state to obtain the total discharge capacity and expansion force of this round of aging test, and the next round of aging test is cycled until the cyclic aging test is stopped, wherein the total discharge capacity and expansion force collected in each round of aging test are used to evaluate the performance of the battery cell to be tested.

2. The battery cell cycle aging test method according to claim 1, characterized in that: The first discharge rate is 1C-2C, the second discharge rate is 0.05C-0.33C, and the third discharge rate is 0.02C-0.1C.

3. The battery cell cycle aging test method according to claim 1, characterized in that: The battery cell cycle aging test method further includes: Determining that the remaining power of the battery cell to be tested reaches a first preset power, and determining that the battery cell to be tested enters the target power-deficient state, wherein the first preset power is 4% SOC~15% SOC; and / or, Determine that the remaining power of the battery cell to be tested reaches a second preset power, and determine that the battery cell to be tested enters the full discharge state, wherein the second preset power is 0% SOC~2% SOC.

4. The battery cell cycle aging test method according to claim 1, characterized in that: The battery cell cycle aging test method further includes: It is determined that the lithium insertion degree of the battery cell to be tested reaches a preset lithium insertion degree, and the discharge operation is stopped, wherein the preset lithium insertion degree is -10% SOC to -5% SOC.

5. The battery cell cycle aging test method according to claim 1, characterized in that: The battery cell cycle aging test method further includes: Determine that the energy of the battery cell to be tested reaches a preset energy, and stop the discharge operation, wherein the preset energy is -10%J~-5%J.

6. The battery cell cycle aging test method according to any one of claims 1 to 5, characterized in that: The battery cell cycle aging test method further includes: Based on the total discharge amount, determining the capacity decay rate of the battery cell to be tested; If the capacity attenuation rate does not reach the preset capacity attenuation rate, the next round of aging test is entered; If the capacity decay rate reaches the preset capacity decay rate, the cycle aging test is stopped.

7. The battery cell cycle aging test method according to claim 6, characterized in that: The test temperature for each round of aging test is 45℃~60℃.

8. The battery cell cycle aging test method according to claim 1, characterized in that: The cycle aging test of the battery cell includes: During the charging process, at least two charging stages are provided, and the charging rates corresponding to the charging stages decrease in sequence.

9. A method for evaluating the performance of a battery cell, characterized in that: The performance evaluation method of the battery cell comprises: Obtaining a total discharge amount of an aging test of the battery cell to be tested, and determining a capacity decay rate of the battery cell to be tested based on the total discharge amount; Obtaining a measured expansion force corresponding to the capacity decay rate, wherein the measured expansion force includes a maximum measured external expansion force and a maximum measured internal pressure, and the standard expansion force includes a maximum standard internal pressure; determining a correction value of the maximum measured external expansion force based on a difference between the maximum measured internal pressure and the maximum standard internal pressure; Obtaining a true expansion force of the battery cell to be tested according to a difference between the maximum measured external expansion force and the correction value; Based on the capacity decay rate and the true expansion force, a performance evaluation result of the battery cell to be tested is determined.

10. The performance evaluation method of a battery cell according to claim 9, characterized in that: The determining, based on the maximum measured internal pressure and the maximum standard internal pressure, a correction value of the maximum measured external expansion force comprises: determining a difference between the maximum measured internal pressure and the maximum standard internal pressure; Obtaining the size, correction factor and gravity constant of the battery cell to be tested; A correction value of the maximum measured external expansion force is obtained according to the difference, the size, the correction coefficient and the gravity constant.

11. A battery cell cycle aging test device, characterized in that: The battery cell cycle aging test equipment includes: The charging module is used to charge the battery cells to be tested in this round of aging test; A discharge module, used for, in a first discharge stage, performing a discharge operation on the battery cell to be tested based on a first discharge rate, and if the battery cell to be tested enters a target power-deficient state, entering a second discharge stage; in a second discharge stage, performing a discharge operation on the battery cell to be tested based on a second discharge rate, and if the battery cell to be tested enters a fully discharged state, entering a third discharge stage; in a third discharge stage, performing a discharge operation on the battery cell to be tested based on a third discharge rate, so that the battery cell to be tested enters an over-discharge state, wherein the first discharge rate, the second discharge rate, and the third discharge rate decrease in sequence, and the over-discharge state is a state reached after the battery cell to be tested reaches a fully discharged state and the discharge operation continues to be performed on the battery cell to be tested, and the over-discharge state is a state corresponding to when the lithium insertion degree of the battery cell to be tested is a negative value or the energy of the battery cell to be tested is a negative value; The data acquisition module is used to collect data on the battery cell to be tested that has entered the over-discharge state, obtain the total discharge capacity and expansion force of this round of aging test, and cycle into the next round of aging test until the cyclic aging test is stopped, wherein the total discharge capacity and expansion force collected in each round of aging test are used to evaluate the performance of the battery cell to be tested.

12. A performance evaluation device for a battery cell, characterized in that: The performance evaluation equipment of the battery cell comprises: A capacity decay rate determination module is used to obtain the total discharge amount of the battery cell to be tested during the aging test, and determine the capacity decay rate of the battery cell to be tested based on the total discharge amount; an acquisition module, configured to acquire a measured expansion force corresponding to the capacity decay rate, wherein the measured expansion force includes a maximum measured external expansion force and a maximum measured internal pressure, and the standard expansion force includes a maximum standard internal pressure; a correction module, configured to determine a correction value of the maximum measured external expansion force based on a difference between the maximum measured internal pressure and the maximum standard internal pressure; and obtain a true expansion force of the battery cell to be tested according to the difference between the maximum measured external expansion force and the correction value; An evaluation module is used to determine a performance evaluation result of the battery cell to be tested based on the capacity decay rate and the true expansion force.

13. A battery cell cycle aging test device, characterized in that: The battery cell cycle aging test equipment comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the battery cell cycle aging test method as described in any one of claims 1 to 8.

14. A performance evaluation device for a battery cell, characterized in that: The battery cell performance evaluation device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the battery cell performance evaluation method as claimed in claim 9 or 10.

15. A battery cell testing and evaluation system, characterized in that: The battery cell testing and evaluation system includes: The battery cell cycle aging test device as claimed in claim 13; The performance evaluation device of a battery cell as claimed in claim 14; and Expansion force monitoring module, used to monitor the expansion force generated by the aging test of the battery cell to be tested; The battery cell cycle aging test device and the expansion force monitoring module are respectively connected to the battery cell performance evaluation device.

16. The battery cell testing and evaluation system according to claim 15, characterized in that: The expansion force monitoring module includes: an external expansion force monitoring module and an internal pressure monitoring module.

17. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the battery cell cycle aging test method as described in any one of claims 1 to 8 are implemented, or when the computer program is executed by a processor, the steps of the battery cell performance evaluation method as described in claim 9 or 10 are implemented.

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