Retired battery screening method and retired battery screening equipment

Abstract

The embodiment of the present application provides a retired battery screening method and retired battery screening device. The method includes: obtaining a predetermined standard impedance for retired batteries; the standard impedance is obtained based on the impedance of retired batteries in different health states; obtaining the initial battery capacity of the battery to be tested, and determining the charging current of the battery to be tested based on the initial battery capacity; the initial battery capacity is the rated capacity of the battery to be tested before it is used; when the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested; wherein the fully charged state is a state where the charging current is charged to the charging cut-off voltage of the battery to be tested, and constant voltage charging is performed at the charging cut-off voltage until the current reaches the cut-off current; based on the test impedance and the standard impedance, the screening results of retired batteries are obtained. The method is used to achieve the effect of improving the accuracy of retired battery screening.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a retired battery screening method and retired battery screening equipment. Background Art

[0002] With the development of new energy, batteries, as an important part of new energy, have also developed rapidly. Inconsistencies in materials, processes, equipment, etc. during the production and manufacturing of batteries will further increase the differences in batteries in subsequent use.

[0003] After the power battery of a car is retired, it may still retain about 80% of its initial capacity, which means that there is a large room for utilization. The cascade utilization of retired batteries also has great economic value. In order to improve the utilization value of retired batteries, multiple retired batteries can be reassembled to obtain a new battery pack. However, the inconsistency between retired batteries will bring difficulties to battery reassembly. The inconsistency of batteries will lead to increased safety risks and reduced life of the reassembled battery pack.

[0004] The conventional technology can obtain the impedance of the battery by measuring the internal resistance at a specific frequency, and thus screen the batteries by the battery impedance. However, the applicant found during the implementation process that the conventional technology has at least the problem of low screening accuracy. Summary of the invention

[0005] Based on this, it is necessary to address the above technical issues. The embodiments of the present application provide a retired battery screening method and a retired battery screening device to achieve the effect of improving the accuracy of retired battery screening.

[0006] In a first aspect, an embodiment of the present application provides a method for screening retired batteries, the method comprising:

[0007] Obtaining a predetermined standard impedance for retired batteries; the standard impedance is obtained based on the impedance of retired batteries in different health states;

[0008] Obtaining the initial battery capacity of the battery to be tested, and determining the charging current of the battery to be tested according to the initial battery capacity; the initial battery capacity is the rated capacity of the battery to be tested before being used;

[0009] Determine the test impedance of the retired battery when the battery to be tested is charged to a fully charged state; wherein the fully charged state is a state where the battery to be tested is charged to a charging cut-off voltage of the battery to be tested by a charging current, and constant voltage charging is performed at the charging cut-off voltage until the current reaches a cut-off current;

[0010] Based on the test impedance and the standard impedance, a screening result of the battery to be tested is obtained.

[0011] In a possible implementation manner, obtaining a predetermined standard impedance for a retired battery includes:

[0012] Obtain the initial battery capacities corresponding to multiple retired batteries in different health states;

[0013] Based on the initial battery capacity of each retired battery, a charging current of each retired battery is obtained;

[0014] Determining the battery impedance of each retired battery when each retired battery is charged to a fully charged state by the charging current of each retired battery;

[0015] Based on the battery impedances of a plurality of retired batteries, a standard impedance is obtained.

[0016] In a possible implementation, obtaining a standard impedance based on battery impedances of a plurality of retired batteries includes:

[0017] Obtain an average impedance of multiple battery impedances, and obtain an impedance threshold according to the average impedance;

[0018] Eliminate retired batteries corresponding to battery impedances greater than an impedance threshold;

[0019] Based on the battery impedance corresponding to the retired batteries that are not eliminated, the standard impedance is obtained.

[0020] In a possible implementation manner, obtaining a predetermined standard impedance for a retired battery includes:

[0021] Obtain multiple cycle test results of each retired battery; the multiple cycle test results include coulomb efficiency test results and battery capacity test results;

[0022] Determine the internal health status of each retired battery according to the coulomb efficiency test results of each retired battery and the battery capacity test results of each retired battery;

[0023] Eliminate retired batteries whose internal health status does not meet the health status conditions;

[0024] The standard impedance is obtained according to the battery impedance corresponding to the retired batteries that are not eliminated.

[0025] In a possible implementation, determining the internal health status of each retired battery according to the coulomb efficiency test result of each retired battery and the battery capacity test result of each retired battery includes:

[0026] Determine the degree of difference between the coulombic efficiency of each cycle test and the preset coulombic efficiency in the coulombic efficiency test result of the current retired battery; wherein the current retired battery is any one of the multiple retired batteries;

[0027] Obtaining the battery capacity difference between the first tested battery capacity and the last tested battery capacity in the battery capacity test results of the currently retired battery;

[0028] According to the difference degrees of multiple coulomb efficiencies and battery capacities, the internal health status of the currently retired battery is obtained.

[0029] In a possible implementation manner, when the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested includes:

[0030] When the battery to be tested is charged to a fully charged state, obtaining an impedance test result of the battery to be tested in a constant current electrochemical impedance test;

[0031] According to the impedance test results, the electrochemical impedance spectrum of the battery to be tested is obtained;

[0032] Based on the electrochemical impedance spectroscopy, the test impedance of the battery to be tested is obtained.

[0033] In one possible implementation, the standard impedance is characterized by a standard impedance interval;

[0034] Based on the test impedance and standard impedance, the screening results of the battery to be tested are obtained, including:

[0035] If the test impedance is within the standard impedance range, the battery to be tested passes the screening;

[0036] If the test impedance is not within the standard impedance range, the battery to be tested fails the screening.

[0037] In a second aspect, an embodiment of the present application provides a retired battery screening device, including: a memory, a processor;

[0038] Memory stores computer-executable instructions;

[0039] The processor executes the computer-executable instructions stored in the memory, so that the processor performs the above-mentioned method.

[0040] In a third aspect, an embodiment of the present application provides a retired battery screening system, the system comprising:

[0041] A charging and discharging device, used to charge the battery to be tested to a fully charged state based on the charging current of the battery to be tested; the charging current is determined according to the initial battery capacity of the battery to be tested, and the initial battery capacity is the rated capacity of the battery to be tested before it is used;

[0042] Electrochemical impedance testing equipment, used to test the battery to be tested and obtain the test impedance of the battery to be tested;

[0043] Such as the retired battery screening equipment mentioned above.

[0044] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the first aspect above and / or various possible implementations of the first aspect.

[0045] The retired battery screening method and retired battery screening device provided in the embodiments of the present application, the present application predetermines the standard impedance of retired batteries through the impedance of retired batteries in different health states, and the test impedance obtained by testing the battery to be tested in a fully charged state can be used to screen the battery to be tested according to the test impedance of the battery to be tested and the standard impedance of the retired battery. Compared with the traditional technology, the present application obtains the test impedance more accurately in a fully charged state, and further screens based on the standard impedance and the test impedance, which can effectively screen out retired batteries with poor battery capacity, and can also screen retired batteries with faster battery capacity decay, thereby improving the accuracy of retired battery screening. In addition, the present application can realize simple and fast standard impedance selection, and the standard impedance selection is relatively simple, thereby improving the efficiency of screening retired batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0047] Figure 1 A schematic diagram of the structure of a retired battery screening system provided in this application;

[0048] Figure 2 Schematic diagram of the process of retired battery screening method provided for this application Figure 1 ;

[0049] Figure 3 Schematic diagram of the process of retired battery screening method provided for this application Figure 2 ;

[0050] Figure 4 Schematic diagram of the EIS (electrochemical impedance spectroscopy) components provided for this application;

[0051] Figure 5 Electrochemical impedance spectra of retired batteries with different SOH provided for this application;

[0052] Figure 6 The test results of the cycle performance test of retired batteries provided in this application are shown in Figure 2. Figure 1 ;

[0053] Figure 7 The test results of the cycle performance test of retired batteries provided in this application are shown in Figure 2. Figure 2 ;

[0054] Figure 8 The test results of the cycle performance test of retired batteries provided in this application are shown in Figure 2. Figure 3 ;

[0055] Fig. 9 A schematic diagram of the electrochemical impedance spectrum of the battery to be tested provided in this application;

[0056] Fig.10 The cycle performance test diagram of the battery to be tested provided in this application;

[0057] Fig.11 Schematic diagram of the process of retired battery screening method provided for this application Figure 3 ;

[0058] Fig.12 Schematic diagram of the process of retired battery screening method provided for this application Figure 4 ;

[0059] Fig.13 Schematic diagram of the process of retired battery screening method provided for this application Figure 5 ,

[0060] Fig.14 A schematic diagram of the structure of the retired battery screening device provided for this application;

[0061] Fig.15 A schematic diagram of the structure of the retired battery screening equipment provided for this application.

[0062] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the present application clearer, exemplary embodiments will be described in detail here, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present application. On the contrary, they are merely examples of devices and implementation methods consistent with some aspects of the present application as detailed in the attached claims. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0064] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein, for example, can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a series of units, systems, products or devices are not necessarily limited to those units clearly listed, but may include units that are not clearly listed or inherent to these products or devices.

[0065] With the need to solve the problems of energy shortage and environmental pollution, the new energy industry has entered a period of rapid development. As an important part of new energy, batteries have also received widespread attention from all walks of life. In the field of electric vehicles, the power batteries of electric vehicles may still retain about 80% of their initial capacity after retirement, which has a large utilization space. The cascade utilization of retired batteries also has great economic value. In order to improve the utilization value of retired batteries, multiple retired batteries can be reorganized to obtain new battery packs. However, retired lithium-ion power batteries have different historical operating conditions, internal deterioration conditions, and deterioration modes. Therefore, retired batteries have inconsistent capacity, life, and attenuation modes. The inconsistency between retired batteries will bring difficulties to battery reorganization. The inconsistency of batteries will lead to increased safety risks and reduced life of the reorganized battery packs.

[0066] In order to maximize the utilization value of retired batteries, it is necessary to screen and eliminate batteries with poor performance. In the prior art, some lithium-ion battery internal resistance screening methods first perform EIS tests on a certain type of battery to obtain an EIS impedance spectrum. The frequency of the ohmic internal resistance and polarization internal resistance of this type of battery is obtained from the EIS impedance spectrum, and the battery resistance is tested with this frequency internal resistance tester. Then, a certain amount of data measured for the first time is processed to obtain the ohmic internal resistance and polarization internal resistance range of normal batteries, and finally screening is performed based on the ohmic internal resistance and polarization internal resistance range. However, this technology has at least the following disadvantages: ① This technology is more suitable for the screening of new batteries, but not for the cascade utilization of retired batteries. The health of retired batteries is different, and the corresponding characteristic frequencies of the battery's ohmic internal resistance and polarization internal resistance are also different. Therefore, it is impossible to effectively obtain the battery's ohmic internal resistance and polarization internal resistance by measuring the internal resistance test at two specific frequencies. That is, the accuracy of the prior art for the screening of retired batteries is not high.

[0067] In the prior art, there is also a method for selecting and grouping power lithium battery packs, which uses the AC impedance method to test the ohmic impedance, SEI membrane impedance, charge impedance, solid phase diffusion impedance and discharge capacity of the single battery, and then groups the single battery according to the standard that the difference in discharge capacity, ohmic impedance, SEI membrane impedance, charge exchange impedance and solid phase diffusion impedance between the single batteries are between 1% and 5%, respectively, to obtain a power lithium battery pack. However, this technology has at least the following disadvantages: ① For retired batteries, the internal deterioration is complicated, and the various impedance changes of the battery are relatively complex; ② There are multiple parameters for screening, and the screening standards are too complicated; For batteries with higher health, the screening efficiency is relatively low, and the screening accuracy is also low.

[0068] In combination with the above-mentioned prior art, it can be known that in the prior art, the retired battery screening method has at least technical problems of low screening accuracy and low screening efficiency.

[0069] The retired battery screening method provided in the present application achieves the screening of retired batteries by accurately obtaining the test impedance in a fully charged state, and further screening the test impedance based on a predetermined standard impedance. It can effectively screen out retired batteries with poor battery capacity, and can also screen out retired batteries with faster battery capacity decay, thereby solving the technical problem of low screening accuracy in retired battery screening.

[0070] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0071] like Figure 1 As shown, the embodiment of the present application provides a retired battery screening system 10, and the retired battery screening method provided by the embodiment of the present application can be applied to Figure 1 In the application environment shown, the retired battery screening system includes: a charging and discharging device 101, an electrochemical impedance testing device 102 and a retired battery screening device 103.

[0072] The charging and discharging device 101 is used to provide a charging current corresponding to the battery to be tested, and charge the battery to be tested to a fully charged state. Among them, the charging current corresponding to the test battery can be determined in advance based on the battery capacity of the battery to be tested when it is a new battery. The electrochemical impedance testing device 102 is used to test the battery to be tested and obtain the test impedance of the battery to be tested. The retired battery screening device 103 is used to execute the retired battery screening method provided in the embodiment of the present application. Among them, the retired battery screening device can be a terminal, and the terminal can be but is not limited to various personal computers, laptops, smart phones, tablet computers, Internet of Things devices and portable wearable devices.

[0073] In an exemplary embodiment, Figure 2 Schematic diagram of the process of retired battery screening method provided for this application Figure 1 ,like Figure 2 As shown, this method is applied to Figure 1 Taking the retired battery screening device 103 in the embodiment as an example, the method includes S201 to S204, wherein:

[0074] S201, obtaining a predetermined standard impedance for retired batteries; the standard impedance is obtained based on the impedances of retired batteries in different health states.

[0075] The retired battery may be a power battery retired from an electric vehicle, and the retired battery may be a lithium iron phosphate battery. The standard impedance may be an impedance corresponding to retired batteries in various health states determined in advance by testing, and the standard impedance may refer to a standard impedance range corresponding to retired batteries in various health states.

[0076] Exemplarily, the retired battery screening device can predetermine a standard impedance for screening retired batteries based on the battery impedances of retired batteries in various health states. For example, electrochemical impedance tests can be performed on retired batteries in various health states to obtain the battery impedances of each retired battery, and retired batteries with better health states can be screened out based on the battery impedances of multiple retired batteries, and the standard impedance can be determined based on the battery impedances corresponding to the screened retired batteries. As an example, a standard impedance range can be obtained based on the battery impedances of multiple retired batteries, and retired batteries can be further screened based on the standard impedance range. Among them, the battery impedance can include ohmic impedance, charge transfer impedance, and diffusion impedance. In one possible implementation, the standard impedance can be a standard ohmic impedance.

[0077] S202, obtaining an initial battery capacity of the battery to be tested, and determining a charging current of the battery to be tested according to the initial battery capacity; the initial battery capacity is a rated capacity of the battery to be tested before being used.

[0078] The battery to be tested refers to the retired battery to be tested and screened. The initial battery capacity can be the rated capacity of the battery to be tested as a new battery. The charging current refers to the current used to charge the battery to be tested.

[0079] Exemplarily, the retired battery screening device can determine the battery rated capacity of the battery to be tested as a new battery as the initial battery capacity, and can determine the charging current for charging the battery to be tested based on the initial battery capacity. Further, the battery to be tested can be charged based on the charging current to obtain the battery to be tested in a fully charged state, so as to improve the accuracy of obtaining the test impedance of the battery to be tested.

[0080] Optionally, a current density not greater than 0.5C of the rated capacity of the battery to be tested as a new battery may be used as the charging current.

[0081] S203, determining the test impedance of the battery to be tested when the battery to be tested is charged to a fully charged state; wherein the fully charged state is a state in which the battery to be tested is charged to a charging cut-off voltage of the battery to be tested by a charging current and constant voltage charging is performed at the charging cut-off voltage until the current reaches the cut-off current.

[0082] The fully charged state may be the state of the battery when the SOC=1, where SOC refers to the state of charge. The test impedance refers to the impedance obtained by measuring the impedance of the battery under test in the fully charged state. For example, if the standard impedance is a standard ohmic impedance, the test impedance is the ohmic impedance obtained by the test. The charging cut-off voltage may be a preset voltage value, and the cut-off current may be a current that can meet the current requirement of the fully charged state.

[0083] Exemplarily, a charging and discharging device can be used to perform constant current charging of the battery to be tested to a preset voltage value at a current density not greater than 0.5C of the rated capacity of the battery to be tested as a new battery, and then perform constant voltage charging at the preset voltage value until the current is less than 0.02C to obtain the battery to be tested in a fully charged state. After charging is completed, the battery to be tested can be left for 2 hours. Furthermore, an electrochemical impedance test device can be used to perform a constant current electrochemical impedance test on the battery to be tested within a preset frequency range to obtain test impedance data of the battery to be tested. The retired battery screening device can directly obtain the test impedance data of the battery to be tested through the electrochemical impedance test device, and can analyze the test impedance data to obtain the required test impedance, so as to further screen the battery to be tested according to the test impedance.

[0084] Optionally, the preset voltage value may be 3.8V, and the preset frequency range may be a frequency range of 2000-0.05 Hz.

[0085] In practical applications, there are certain differences in the battery capacity and health status of retired batteries. Therefore, the embodiment provided in the present application can ensure that retired batteries of different capacities are at the same level in the fully charged state by performing impedance testing on the batteries to be tested in the fully charged state, thereby making the test result more reliable. The fully charged state can amplify the differences between retired batteries in different health states, better distinguish retired batteries in good health states from retired batteries in poor health states, thereby improving the accuracy of retired battery screening.

[0086] S204, obtaining a screening result of retired batteries based on the test impedance and the standard impedance.

[0087] Exemplarily, the retired battery screening device can screen the battery to be tested according to the test impedance and the standard impedance. For example, the standard impedance can be a standard ohm impedance range, and the obtained test impedance should be the tested ohm impedance. If the tested ohm impedance is within the ohm impedance range, the battery to be tested can be retained, and if the tested ohm impedance is not within the ohm impedance range, the battery to be tested can be discarded.

[0088] It can be understood that by using the standard impedance as the screening standard and the test impedance obtained by testing the battery to be tested, a relatively accurate retired battery can be screened, so that the screened retired batteries can be better utilized for battery combination, the retired batteries can be reused, and the utilization value of the retired batteries can be improved. The above-mentioned retired battery screening method can improve the accuracy of screening.

[0089] In this embodiment, the method includes obtaining a predetermined standard impedance for retired batteries; the standard impedance is obtained based on the impedance of retired batteries in different health states; obtaining the initial battery capacity of the battery to be tested, and determining the charging current of the battery to be tested based on the initial battery capacity; the initial battery capacity is the rated capacity of the battery to be tested before it is used; when the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested; and obtaining the screening result of the battery to be tested based on the test impedance and the standard impedance. In practical applications, the standard impedance of retired batteries is predetermined by the impedance of retired batteries in different health states, and the test impedance obtained by testing the battery to be tested in a fully charged state can be used to screen the battery to be tested based on the test impedance of the battery to be tested and the standard impedance of the retired battery. Compared with the traditional technology, the present embodiment obtains the test impedance more accurately in the fully charged state, and further screens based on the standard impedance and the test impedance, which can effectively screen out retired batteries with poor battery capacity, and can also screen retired batteries with faster battery capacity decay, thereby improving the screening accuracy of retired battery screening.

[0090] In an exemplary embodiment, Figure 3Schematic diagram of the process of retired battery screening method provided for this application Figure 2 ,like Figure 3 As shown, in this embodiment Figure 2 Based on the embodiment, step S201 is described in detail. In step S201, a predetermined standard impedance for a retired battery is obtained, including: S301 to S304, wherein:

[0091] S301, obtaining initial battery capacities corresponding to a plurality of retired batteries in different health states.

[0092] Among them, the health status refers to the comparison between the current state of the battery and the state of the new battery, usually called SOH (State of Health). The initial battery capacity refers to the rated capacity of the retired battery when it was in the new battery state.

[0093] S302: Obtaining a charging current of each retired battery based on the initial battery capacity of each retired battery.

[0094] The charging current refers to the current used to charge the retired battery.

[0095] S303 , when each retired battery is charged to a fully charged state by the charging current of each retired battery, determine the battery impedance of each retired battery.

[0096] Among them, the fully charged state refers to the state when the battery's SOC = 1. The battery impedance refers to the impedance of the retired battery in its current health state. Figure 4 Schematic diagram of the components of EIS (electrochemical impedance spectroscopy) shown. The battery impedance can include the ohmic impedance R ohm , charge transfer impedance R ct , and diffusion resistance R w As an example, the battery impedance provided in the embodiment of the present application is ohmic impedance, and the ohmic impedance R ohm The value of is the impedance on the real part (Z'') when the imaginary part (-Z'') is zero. The ohmic impedance can be used to effectively distinguish the internal states of batteries with different health levels, and can effectively screen out retired batteries with poor cycle performance (capacity drop).

[0097] S304 , obtaining a standard impedance based on the battery impedances of the plurality of retired batteries.

[0098] Exemplarily, the retired battery screening device can determine the battery rated capacity of multiple retired batteries in different health states in a new battery state as the initial battery capacity. And for each retired battery, the retired battery screening device can determine the charging current of the retired battery based on the initial battery capacity of the retired battery in the new battery state. Furthermore, the charging and discharging equipment can be used to charge each retired battery with the charging current corresponding to each retired battery, and multiple retired batteries in a fully charged state can be obtained. When each retired battery is in a fully charged state, the electrochemical impedance testing device can perform an electrochemical impedance test on each retired battery to obtain electrochemical impedance data of each retired battery. The retired battery screening device can directly obtain the electrochemical impedance data through the electrochemical impedance testing device, and can analyze the electrochemical impedance data to obtain the battery impedance of each retired battery. The retired battery screening device can determine the standard impedance of the retired battery based on the battery impedances of multiple retired batteries.

[0099] It can be understood that, similarly, in the process of screening the batteries to be tested, the impedance test is performed using the batteries to be tested in a fully charged state. Therefore, in the process of establishing the standard impedance, the impedance test should also be performed using retired batteries in a fully charged state and in a variety of different health states. The embodiment provided in the present application can ensure that retired batteries of different capacities are at the same level in a fully charged state by performing impedance tests on multiple retired batteries in a fully charged state. The impedance test can also be performed on the batteries to be tested and the retired batteries used for the health standard impedance at the same level standard, thereby making the test results more reliable. The fully charged state can amplify the differences between retired batteries in different health states, and better distinguish retired batteries in good health states from retired batteries in poor health states, thereby improving the accuracy of retired battery screening.

[0100] In practical applications, the retired battery screening equipment can determine the rated capacity of a certain number (for example, not less than 20) of retired batteries with different SOHs when in the new battery state. For each retired battery, the charging and discharging equipment can charge the retired battery to 3.8V at a constant current density of no more than 0.5C of the rated capacity when in the new battery state at room temperature, and then charge it at a constant voltage at 3.8V until the current is ≤0.02C. After charging, the battery is left for 2 hours. Among them, C is the rated capacity when in the new battery state.

[0101] The electrochemical impedance test equipment can perform constant current electrochemical impedance tests on retired batteries of multiple different SOHs in the batch within a frequency range of 2000-0.05Hz to obtain electrochemical impedance data of retired batteries of multiple different SOHs. The retired battery screening equipment can plot the electrochemical impedance data of retired batteries of multiple different SOHs in a Nyquist plot and analyze the impedance spectrum to obtain the ohmic impedance of each retired battery. It can further eliminate significant outlier data with an ohmic impedance greater than 200% of the average impedance value to obtain the ohmic impedance range of multiple batteries with different SOHs, and use this as the standard impedance.

[0102] It should be noted that the above values ​​are not unique, and different charging currents, charging voltages, and frequency ranges for impedance testing may be determined based on different retired batteries.

[0103] In this embodiment, by obtaining the initial battery capacities corresponding to a plurality of retired batteries in different health states, respectively, the charging current of each retired battery can be determined. By determining the battery impedance of each retired battery in a fully charged state, it is beneficial to accurately obtain the standard impedance. In this way, a wider range of standard impedances can be obtained through a plurality of retired batteries in different health states, which is beneficial to improve the accuracy of the standard impedance. In addition, impedance testing is performed in a fully charged state, so that the battery impedance obtained by the test is more accurate, thereby improving the accuracy of retired battery screening. At the same time, the present application can realize simple and fast standard impedance selection through the above-mentioned steps of selecting standard impedance. The standard impedance selection is relatively simple, and the internal states of batteries with different health degrees can be effectively distinguished by using ohmic impedance, so that retired batteries with poor cycle performance (capacity diving) can be effectively screened out.

[0104] In one embodiment, in step S304, obtaining a standard impedance based on the battery impedances of a plurality of retired batteries may specifically include:

[0105] Obtain an average impedance of multiple battery impedances, and obtain an impedance threshold according to the average impedance;

[0106] Eliminate retired batteries corresponding to battery impedances greater than an impedance threshold;

[0107] Based on the battery impedance corresponding to the retired batteries that are not eliminated, the standard impedance is obtained.

[0108] The average impedance may be an average value of multiple battery impedances. The impedance threshold may refer to a threshold set to exclude retired batteries corresponding to outlier battery impedances, and the threshold may be obtained based on the average impedance.

[0109] Exemplarily, the retired battery screening device can determine the battery impedance of multiple retired batteries in different health states, and can determine the average impedance of the multiple battery impedances, and determine the impedance threshold for eliminating retired batteries based on the average impedance of the retired batteries. The retired battery screening device can eliminate retired batteries corresponding to battery impedances greater than the impedance threshold to retrieve retired batteries corresponding to outlier battery impedances. The retired battery screening device can determine the standard impedance based on the battery impedances corresponding to the retired batteries that are not eliminated. For example, the standard impedance range of retired batteries can be determined based on the battery impedances of multiple retired batteries that are not eliminated.

[0110] Optionally, 200% of the average impedance value can be used as the impedance threshold, and the retired battery screening equipment can eliminate significant outlier data whose battery impedance is greater than 200% of the average impedance value, that is, eliminate retired batteries corresponding to battery impedances greater than 200% of the average impedance value, so as to improve the accuracy of the standard impedance.

[0111] In practical applications, such as Figure 5 Electrochemical impedance spectra of retired batteries with different SOH shown in Fig. Figure 5 The electrochemical impedances of the two retired batteries numbered #5737-42.60% and #4988-53.56% shown are significantly deviated from the electrochemical impedances of other SOH batteries, indicating that the internal health status of these two retired batteries is significantly worse than that of other retired batteries, so these two retired batteries need to be eliminated.

[0112] In this embodiment, an impedance threshold can be obtained by obtaining the average impedance of multiple battery impedances; and further, retired batteries corresponding to battery impedances greater than the impedance threshold can be eliminated, and based on the battery impedances corresponding to retired batteries that are not eliminated, a standard impedance can be obtained, thereby improving the accuracy of the standard impedance, and further improving the accuracy of screening retired batteries.

[0113] In an exemplary embodiment, obtaining a predetermined standard impedance for a retired battery includes:

[0114] Obtain multiple cycle test results of each retired battery; the multiple cycle test results include coulomb efficiency test results and battery capacity test results;

[0115] Determine the internal health status of each retired battery according to the coulomb efficiency test results of each retired battery and the battery capacity test results of each retired battery;

[0116] Eliminate retired batteries whose internal health status does not meet the health status conditions;

[0117] The standard impedance is obtained according to the battery impedance corresponding to the retired batteries that are not eliminated.

[0118] Among them, the multiple cycle test results refer to the analysis results of multiple performance tests on retired batteries. The coulomb efficiency test results refer to the comparison results of multiple rounds of coulomb efficiency tests on retired batteries. The battery capacity test results refer to the comparison results of multiple rounds of battery capacity tests on retired batteries. The internal health status refers to the current health status of the retired battery, which can be characterized by the above test results. The health status condition refers to the conditions set for the health status, so as to eliminate retired batteries with poor health status and improve the accuracy of the standard impedance.

[0119] Exemplarily, the charging and discharging equipment can perform multiple cycle tests on each retired battery, and the retired battery screening equipment can directly obtain the coulomb efficiency test results and battery capacity test results of each retired battery through the charging and discharging equipment. For each retired battery, the retired battery screening equipment can obtain the internal health status of the retired battery based on the coulomb efficiency test results of the retired battery and the battery capacity test results of the retired battery. Furthermore, the retired battery screening equipment can eliminate retired batteries with poor internal health status. For example, the retired battery screening equipment can eliminate retired batteries with obvious coulomb efficiency attenuation and obvious battery capacity attenuation. The retired battery screening equipment can determine the standard impedance based on the battery impedance corresponding to the retired batteries that have not been eliminated. For example, the standard impedance range of retired batteries can be determined based on the battery impedance of multiple retired batteries that have not been eliminated.

[0120] In practical applications, the coulomb efficiency test results can characterize the coulomb efficiency decay rate of retired batteries during the test. The battery capacity test results can characterize the battery capacity decay rate of retired batteries during the test.

[0121] In this embodiment, the internal health status of each retired battery is determined through the coulomb efficiency test results of each retired battery and the battery capacity test results of each retired battery, so that the goal of eliminating retired batteries whose internal health status does not meet the health status conditions can be achieved, and the standard impedance is obtained based on the battery impedance corresponding to the retired batteries that are not eliminated, thereby improving the accuracy of the standard impedance, and further improving the accuracy of screening retired batteries using the standard impedance.

[0122] In one embodiment, the internal health status of each retired battery is determined according to the coulomb efficiency test result of each retired battery and the battery capacity test result of each retired battery, including:

[0123] Determine the degree of difference in coulombic efficiency between the coulombic efficiency of each cycle test and the preset coulombic efficiency in the coulombic efficiency test results of the current retired battery; wherein the current retired battery is any one of the multiple retired batteries.

[0124] Obtain the battery capacity difference between the first tested battery capacity and the last tested battery capacity in the battery capacity test results of the currently retired battery.

[0125] According to the difference degrees of multiple coulomb efficiencies and battery capacities, the internal health status of the currently retired battery is obtained.

[0126] Among them, coulombic efficiency refers to the percentage of the number of charges released during the battery discharge process to the number of charges input during the charging process under given conditions, or the ratio between the discharge capacity and the charging capacity. The degree of difference in coulombic efficiency can be the difference in coulombic efficiency. The degree of difference in battery capacity can be the difference in battery capacity. The preset coulombic efficiency refers to the preset value that the coulombic efficiency obtained in each test needs to be compared. The preset coulombic efficiency can generally be 100%. The battery health state can be evaluated by the degree to which the coulombic efficiency is close to 100%. As an example, if the coulombic efficiency of each cycle test is similar and close to 100%, it indicates that the battery health state is good.

[0127] Exemplarily, for each retired battery, the retired battery screening device can determine the coulombic efficiency of the retired battery during each cycle test, and can determine the degree of difference in coulombic efficiency between the coulombic efficiency of each cycle test and a preset coulombic efficiency to obtain multiple coulombic efficiency difference degrees.

[0128] The retired battery screening device can also determine the degree of difference in battery capacity between the battery capacity when the retired battery is first tested and the battery capacity when the retired battery is last tested. If the multiple coulomb efficiency difference degrees indicate that the coulomb efficiency of the retired battery is significantly different from the preset coulomb efficiency, and the battery capacity difference degree indicates that the battery capacity of the retired battery is significantly different between the first and last tests, it can be indicated that the retired battery is in a poor health state.

[0129] Optionally, the cycle performance of retired batteries with different SOH can be tested at a current density of 8A (ampere). Figure 6 As shown in the figure, the retired battery No. 5737-42.60% was tested for cycle performance at a current density of 8A. The coulombic efficiency of the retired battery gradually decreased with the cycle. In the fifth cycle, the coulombic efficiency was only 93.68%, and the discharge capacity of the fifth cycle was only 85.91% of that of the first cycle. This shows that a large number of side reactions occurred inside the retired battery during the cycle, causing the battery capacity to decay rapidly. Similarly, Figure 7As shown in the figure, when the retired battery No. 4988-53.56% was tested for cycle performance at a current density of 8A, the coulombic efficiency began to remain at around 98% from the second cycle. Although the coulombic efficiency of the retired battery No. 5737-42.60% was higher, its discharge capacity at the fifth cycle was only 94.49% of that of the first cycle, indicating that the capacity of the retired battery also had a relatively obvious attenuation during the cycle performance test. As a comparative example, the cycle performance of the retired battery No. 1805-52.76% is shown in the figure below. Figure 8 As shown in the figure, the coulombic efficiency was maintained above 99% throughout the five-cycle process, and the discharge capacity did not decay after five cycles, which shows that the internal health of the battery is good and the electrochemical performance is relatively stable. Figures 6 to 8 In the figure, the non-bold values ​​on the right vertical axis correspond to the Coulomb efficiency, and the bold values ​​correspond to the capacity ratio.

[0130] In practical applications, such as Figure 5 The electrochemical impedance of the retired battery #1805-52.76% shown does not deviate from the electrochemical impedance of the batteries with other SOH, such as Figure 8 The internal health status of the retired battery numbered #1805-52.76% is good. The above two methods prove each other that if the electrochemical impedance of the retired battery meets the impedance threshold, the retired battery is in good health; if the retired battery is in good health, the electrochemical impedance of the retired battery meets the impedance threshold. Based on the above cycle performance data analysis combined with the ohmic impedance data obtained by the impedance spectrum, the ohmic impedance standard range of this model battery is 0.5-1.5mΩ.

[0131] In this embodiment, by determining the degree of difference in coulombic efficiency between the first test and the last test in the coulombic efficiency test results of the current retired battery, and obtaining the degree of difference in battery capacity between the first test and the last test in the battery capacity test results of the current retired battery, the internal health status of the current retired battery can be obtained, so that the health status of the retired battery can be better determined, which is conducive to screening the battery impedance of retired batteries with better health status as the standard impedance, thereby improving the accuracy of screening retired batteries using the standard impedance.

[0132] In an exemplary embodiment, when the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested includes:

[0133] When the battery to be tested is charged to a fully charged state, obtaining an impedance test result of the battery to be tested in a constant current electrochemical impedance test;

[0134] According to the impedance test results, the electrochemical impedance spectrum of the battery to be tested is obtained;

[0135] Based on the electrochemical impedance spectroscopy, the test impedance of the battery to be tested is obtained.

[0136] The impedance test result may be electrochemical impedance data of a constant current electrochemical impedance test. Electrochemical impedance spectroscopy refers to data used to analyze the battery impedance of retired batteries.

[0137] Exemplarily, the retired battery screening device can obtain the electrochemical impedance data of the battery to be tested in the constant current electrochemical impedance test through the electrochemical impedance testing device, and the electrochemical impedance data can be plotted as a Nyquist plot. The retired battery screening device can analyze the electrochemical impedance spectrum of the battery to be tested to obtain the test impedance of the battery to be tested. As an example, the test impedance here can be ohmic impedance.

[0138] In this embodiment, the electrochemical impedance spectrum of the battery to be tested is obtained by the impedance test result in the fully charged state, and the electrochemical impedance spectrum of the battery to be tested can be further obtained, and the test impedance of the battery to be tested can be obtained based on the electrochemical impedance spectrum, so that the test impedance of the battery to be tested can be effectively and accurately obtained, thereby improving the accuracy of the test resistance, and further improving the accuracy of screening retired batteries using the test resistance. At the same time, the process of extracting the test impedance is simple, which improves the efficiency of screening retired batteries.

[0139] In an exemplary embodiment, the standard impedance is characterized by a standard impedance interval;

[0140] Based on the test impedance and standard impedance, the screening results of the battery to be tested are obtained, including:

[0141] If the test impedance is within the standard impedance range, the battery to be tested passes the screening;

[0142] If the test impedance is not within the standard impedance range, the battery to be tested fails the screening.

[0143] Among them, the standard impedance interval refers to the standard impedance range.

[0144] For example, if the test impedance is within the standard impedance range, it means that the battery to be tested has passed the screening and can be retained for battery reorganization of retired batteries. If the test impedance is not within the standard impedance range, it means that the battery to be tested has failed the screening and needs to be discarded.

[0145] In practical applications, such as Fig. 9 The electrochemical impedance spectrum of the battery under test can be obtained from Fig. 9From the electrochemical impedance spectra of the six tested batteries, it can be seen that the ohmic impedance of the tested battery numbered #0154-49.76% is significantly greater than 1.5 mΩ. Figure 5 and Figure 8 The ohmic impedance standard range of the retired battery is 0.5-1.5 mΩ, and the battery to be tested should be rejected.

[0146] like Fig.10 The cycle performance test diagram of the battery to be tested, numbered #0154-49.76%, is shown in FIG. Fig.10 It can be seen that the coulombic efficiency of the tested battery during the five cycles is around 99%, but it is lower than that of the battery with the same Figure 8 The coulombic efficiency of the #1805-52.76% battery is low, and its discharge capacity after five cycles is only 98.67% of the initial capacity, indicating that the capacity of the tested battery also decays relatively significantly during the cycle process. Therefore, this also illustrates the correctness of the retired battery screening method provided in this application. Fig.10 In the figure, the non-bold values ​​on the right vertical axis correspond to the Coulomb efficiency, and the bold values ​​correspond to the capacity ratio.

[0147] In an exemplary embodiment, Fig.11 Schematic diagram of the process of retired battery screening method provided for this application Figure 3 ,like Fig.11 As shown, in this embodiment Figure 2 Based on the embodiment, the retired battery screening method is described in detail, and the method is applied to Figure 1 Taking the retired battery screening device in the example as an example, the method includes S1101 to S1112, wherein:

[0148] S1101, obtaining initial battery capacities corresponding to a plurality of retired batteries in different health states.

[0149] S1102: Obtaining a charging current of each retired battery based on the initial battery capacity of each retired battery.

[0150] S1103, when each retired battery is charged to a fully charged state by the charging current of each retired battery, determining the battery impedance of each retired battery.

[0151] S1104, obtaining an average impedance of multiple battery impedances, and obtaining an impedance threshold according to the average impedance.

[0152] S1105, removing retired batteries corresponding to battery impedances greater than an impedance threshold.

[0153] S1106, obtaining a standard impedance based on the battery impedance corresponding to the retired batteries that are not eliminated.

[0154] S1107, obtaining the initial battery capacity of the battery to be tested, and determining the charging current of the battery to be tested according to the initial battery capacity.

[0155] S1108, when the battery to be tested is charged to a fully charged state by the charging current, obtaining an impedance test result of the battery to be tested in a constant current electrochemical impedance test.

[0156] S1109, obtaining an electrochemical impedance spectrum of the battery to be tested according to the impedance test result.

[0157] S1110, obtaining a test impedance of the battery to be tested based on the electrochemical impedance spectroscopy.

[0158] S1111, if the test impedance is within the standard impedance range, the battery to be tested passes the screening; the standard impedance is characterized by the standard impedance range.

[0159] S1113, if the test impedance is not within the standard impedance range, the battery to be tested fails the screening.

[0160] Each step in this embodiment can be implemented by the above-mentioned embodiments or a combination of multiple embodiments, which will not be described in detail here.

[0161] The retired battery screening method provided in the embodiment of the present application can predetermine the standard impedance of retired batteries through the impedances of retired batteries in different health states, and the test impedance obtained by testing the battery to be tested in a fully charged state can be used to screen the battery to be tested based on the test impedance of the battery to be tested and the standard impedance of the retired batteries. Compared with traditional technologies, the present application can obtain the test impedance more accurately in a fully charged state, and further perform screening based on the standard impedance and the test impedance, which can effectively screen out retired batteries with poor battery capacity, and can also screen retired batteries with faster battery capacity decay, thereby improving the screening accuracy of retired battery screening.

[0162] In an exemplary embodiment, Fig.12 Schematic diagram of the process of retired battery screening method provided for this application Figure 4 ,like Fig.12 As shown, in this embodiment Figure 2 Based on the embodiment, the steps of obtaining the standard ohmic impedance range are described in detail. The method includes S1201 to S1204, wherein:

[0163] S1201, select multiple (no less than 20) retired batteries with different SOH, charge them to 3.8V at room temperature with a current density not greater than 0.5C of the rated capacity of the new battery, and then charge them at a constant voltage at 3.8V until the current is ≤0.02C. After charging, place the battery for 2 hours.

[0164] S1202, select a frequency range of 2000-0.05HZ and perform a constant current electrochemical impedance test on the retired batteries of different SOHs in this batch.

[0165] S1203, plotting the electrochemical impedance data of retired batteries with different SOHs into a Nyquist plot.

[0166] S1204, analyzing the impedance spectrum to obtain the ohmic impedance of the battery, eliminating significant outlier data whose ohmic impedance is greater than 200% of the average impedance value, and obtaining the ohmic impedance range of multiple different SOH batteries, which is used as the standard impedance range.

[0167] Fig.13 Schematic diagram of the process of retired battery screening method provided for this application Figure 5 ,like Fig.13 As shown, in this embodiment Figure 2 Based on the embodiment, a method for screening retired batteries is described in detail. The method includes S1301 to S1304, wherein:

[0168] S1301, at room temperature, the battery to be tested is charged to 3.8V at a current density of 0.5C not greater than the rated capacity of the new battery, and then charged at a constant voltage of 3.8V until the current is ≤0.02C. After charging, it is left for two hours.

[0169] S1302, performing a constant current electrochemical impedance test on the battery to be tested within a frequency range of 2000-0.05HZ.

[0170] S1303, analyzing the impedance spectrum to obtain the ohmic impedance of the battery to be tested.

[0171] S1304: If the ohmic impedance of the battery to be tested exceeds the standard impedance range, the battery to be tested is rejected; if the ohmic impedance of the battery to be tested is within the standard impedance range, the battery to be tested is retained.

[0172] The various steps in this embodiment may correspond to the above-mentioned embodiments or a combination of multiple embodiments, so the specific implementation of this embodiment will not be described in detail here.

[0173] In this embodiment, a simple and fast standard impedance selection can be achieved. The standard impedance selection is relatively simple. The internal state of batteries with different health levels can be effectively distinguished by using ohmic impedance, and retired batteries with poor cycle performance (capacity drop) can be effectively screened out. In addition, this application can use the EIS of batteries with different SOHs at full charge (100% SOC) to screen out retired batteries with better internal states, remove the drop batteries, ensure that the internal conditions of the batteries in the reorganized module are relatively consistent, improve the utilization rate of the batteries in the module, extend the module life, and reduce the occurrence of safety accidents.

[0174] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned 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 explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can 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.

[0175] Fig.14 The schematic diagram of the structure of the retired battery screening device provided in this application is as follows: Fig.14 As shown, the retired battery screening device 140 provided in this embodiment includes:

[0176] The standard impedance acquisition module 1401 is used to acquire a predetermined standard impedance for retired batteries; the standard impedance is obtained based on the impedance of retired batteries in different health states.

[0177] The initial capacity acquisition and charge-discharge module 1402 is used to acquire the initial battery capacity of the battery to be tested and determine the charging current of the battery to be tested according to the initial battery capacity; the initial battery capacity is the rated capacity of the battery to be tested before being used.

[0178] The test impedance determination module 1403 is used to determine the test impedance of the battery to be tested when the battery to be tested is charged to a fully charged state; wherein the fully charged state is a state in which the battery to be tested is charged to a charging cut-off voltage of the battery to be tested by a charging current and constant voltage charging is performed at the charging cut-off voltage until the current reaches a cut-off current.

[0179] The screening result determination module 1404 is used to obtain the screening result of the retired batteries based on the test impedance and the standard impedance.

[0180] In an exemplary embodiment, the standard impedance acquisition module 1401 is used to obtain the initial battery capacities corresponding to a plurality of retired batteries in different health states; obtain the charging current of each retired battery based on the initial battery capacity of each retired battery; determine the battery impedance of each retired battery when each retired battery is charged to a fully charged state using the charging current of each retired battery; and obtain the standard impedance based on the battery impedances of a plurality of retired batteries.

[0181] In an exemplary embodiment, the standard impedance acquisition module 1401 is used to obtain the average impedance of multiple battery impedances, obtain an impedance threshold based on the average impedance; eliminate retired batteries corresponding to battery impedances greater than the impedance threshold; and obtain standard impedance based on the battery impedances corresponding to retired batteries that are not eliminated.

[0182] In an exemplary embodiment, the standard impedance acquisition module 1401 is used to obtain multiple cycle test results of each retired battery; the multiple cycle test results include coulomb efficiency test results and battery capacity test results; determine the internal health status of each retired battery based on the coulomb efficiency test results of each retired battery and the battery capacity test results of each retired battery; eliminate retired batteries whose internal health status does not meet the health status conditions; and obtain the standard impedance based on the battery impedance corresponding to the retired batteries that are not eliminated.

[0183] In an exemplary embodiment, the standard impedance acquisition module 1401 is used to determine the degree of difference in coulombic efficiency between the coulombic efficiency of each cycle test and the preset coulombic efficiency in the coulombic efficiency test results of the current retired battery; wherein the current retired battery is any one of a plurality of retired batteries; obtain the degree of difference in battery capacity between the battery capacity of the first test and the battery capacity of the last test in the battery capacity test results of the current retired battery; and obtain the internal health status of the current retired battery based on a plurality of coulombic efficiency difference degrees and battery capacity difference degrees.

[0184] In an exemplary embodiment, the test impedance determination module 1403 is used to obtain an impedance test result of the battery to be tested in a constant current electrochemical impedance test when the battery to be tested is charged to a fully charged state; obtain an electrochemical impedance spectrum of the battery to be tested based on the impedance test result; and obtain a test impedance of the battery to be tested based on the electrochemical impedance spectrum.

[0185] In an exemplary embodiment, the standard impedance is characterized by a standard impedance interval; the screening result determination module 1404 is used to determine that if the test impedance is within the standard impedance interval, the battery to be tested passes the screening; if the test impedance is not within the standard impedance interval, the battery to be tested fails the screening.

[0186] The retired battery screening device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and this embodiment will not be described in detail here.

[0187] Fig.15 This is a schematic diagram of the structure of the retired battery screening equipment provided in this application. Fig.15 As shown, the electronic device 150 provided in this embodiment includes: at least one processor 1501 and a memory 1502. Optionally, the device 150 also includes a communication component 1503. The processor 1501, the memory 1502 and the communication component 1503 are connected via a bus 1504.

[0188] In a specific implementation process, at least one processor 1501 executes the computer-executable instructions stored in the memory 1502, so that at least one processor 1501 executes the above method.

[0189] The specific implementation process of the processor 1501 can be found in the above method embodiment, and its implementation principle and technical effect are similar, so this embodiment will not be repeated here.

[0190] In the above embodiments, it should be understood that the processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the invention can be directly implemented as a hardware processor, or can be implemented by a combination of hardware and software modules in the processor.

[0191] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (NVM), such as at least one disk storage.

[0192] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0193] Figure 1 The embodiment of the present application provides a retired battery screening system. The embodiment of the present application provides a retired battery screening system, which includes:

[0194] A charging and discharging device, used to charge the battery to be tested to a fully charged state based on the charging current of the battery to be tested; the charging current is determined according to the initial battery capacity of the battery to be tested, and the initial battery capacity is the rated capacity of the battery to be tested before it is used;

[0195] Electrochemical impedance testing equipment, used to test the battery to be tested and obtain the test impedance of the battery to be tested;

[0196] Such as the retired battery screening equipment mentioned above.

[0197] The retired battery screening system provided in the present application predetermines the standard impedance of retired batteries through retired battery screening equipment, and determines the charging current of the battery to be tested, so that the charging and discharging equipment can charge the battery to be tested to a fully charged state based on the charging current of the battery to be tested; the electrochemical impedance testing equipment can test the battery to be tested and obtain the test impedance of the battery to be tested; the retired battery screening equipment performs screening based on the standard impedance and the test impedance, and can effectively screen out retired batteries with poor battery capacity, and can also screen out retired batteries with faster battery capacity decay, thereby improving the screening accuracy of retired battery screening.

[0198] The present application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0199] The present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When a processor executes the computer-executable instructions, the above method is implemented.

[0200] The above-mentioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0201] An exemplary readable storage medium is coupled to a processor so that the processor can read information from the readable storage medium and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (Application Specific Integrated Circuits, referred to as: ASIC). Of course, the processor and the readable storage medium can also exist in the device as discrete components.

[0202] The division of units is only a logical function division, and there may be other divisions in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0203] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0204] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0205] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0206] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0207] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for screening retired batteries, characterized in that: The method comprises: Obtaining a predetermined standard impedance for a retired battery; the standard impedance is obtained based on the impedances of retired batteries in different health states; Acquire the initial battery capacity of the battery to be tested, and determine the charging current of the battery to be tested according to the initial battery capacity; the initial battery capacity is the rated capacity of the battery to be tested before being used; When the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested; wherein the fully charged state is charging to a charging cut-off voltage of the battery to be tested by the charging current, and performing constant voltage charging at the charging cut-off voltage until the current reaches a cut-off current state; Based on the test impedance and the standard impedance, obtaining a screening result of retired batteries; The step of obtaining a predetermined standard impedance for a retired battery includes: Obtaining multiple cycle test results of each of the retired batteries; the multiple cycle test results include coulomb efficiency test results and battery capacity test results; Determine the degree of difference between the coulombic efficiency of each cycle test and the preset coulombic efficiency in the coulombic efficiency test result of the current retired battery; wherein the current retired battery is any one of the multiple retired batteries; the coulombic efficiency refers to the percentage of the number of charges discharged during the discharge process of the battery to the number of charges input during the charging process or the ratio between the discharge capacity and the charging capacity of the battery under given conditions; Obtaining, in the battery capacity test result of the currently retired battery, a degree of difference in battery capacity between a first tested battery capacity and a last tested battery capacity; Obtaining the internal health status of the currently retired battery according to the multiple coulomb efficiency difference degrees and the battery capacity difference degrees; Eliminate retired batteries whose internal health status does not meet the health status conditions; The standard impedance is obtained according to the battery impedance corresponding to the retired batteries that are not eliminated.

2. The method according to claim 1, characterized in that: The obtaining of a predetermined standard impedance for a retired battery further includes: Obtain the initial battery capacities corresponding to multiple retired batteries in different health states; Based on the initial battery capacity of each of the retired batteries, obtaining a charging current of each of the retired batteries; When each of the retired batteries is charged to a fully charged state by the charging current of each of the retired batteries, determining the battery impedance of each of the retired batteries; The standard impedance is obtained based on the battery impedances of a plurality of the retired batteries.

3. The method according to claim 2, characterized in that The step of obtaining the standard impedance based on the battery impedances of the plurality of retired batteries comprises: Obtaining an average impedance of a plurality of battery impedances, and obtaining an impedance threshold according to the average impedance; Eliminate retired batteries corresponding to battery impedances greater than the impedance threshold; The standard impedance is obtained based on the battery impedance corresponding to the retired batteries that are not eliminated.

4. The method according to claim 1, characterized in that: When the battery to be tested is charged to a fully charged state, determining the test impedance of the battery to be tested includes: When the battery to be tested is charged to a fully charged state, obtaining an impedance test result of the battery to be tested in a constant current electrochemical impedance test; Obtaining an electrochemical impedance spectrum of the battery to be tested according to the impedance test result; Based on the electrochemical impedance spectrum, a test impedance of the battery to be tested is obtained.

5. The method according to claim 3, characterized in that: The standard impedance is characterized by a standard impedance interval; the standard impedance interval is an ohmic impedance range of batteries in multiple different health states obtained based on the battery impedance corresponding to the retired batteries that are not eliminated; The step of obtaining a screening result of the battery to be tested based on the test impedance and the standard impedance includes: If the test impedance is within the standard impedance range, the battery to be tested passes the screening; If the test impedance is not within the standard impedance range, the battery to be tested fails the screening.

6. A retired battery screening device, characterized in that: include: Memory, processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method according to any one of claims 1 to 5.

7. A retired battery screening system, characterized in that: The system comprises: A charging and discharging device, used to charge the battery to be tested to a fully charged state based on the charging current of the battery to be tested; the charging current is determined according to the initial battery capacity of the battery to be tested, and the initial battery capacity is the rated capacity of the battery to be tested before it is used; An electrochemical impedance testing device, used to test the battery to be tested and obtain the test impedance of the battery to be tested; The retired battery screening device as claimed in claim 6.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 5 when executed by a processor.

9. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the computer program is used to implement the method according to any one of claims 1 to 5.

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