Battery lithium precipitation detection method, device and system and storage medium

Abstract

The invention discloses a battery lithium precipitation detection method, device and system and a storage medium, and the method comprises the steps: employing second impedance data in a discharging process under the same state of charge as a reference of first impedance data in a charging process under the same state of charge, and determining whether a to-be-detected battery precipitates lithium in the charging process or not, the influence of the change of the environment temperature and the state of charge of the battery on the detection result can be eliminated, and the accuracy of the detection result is improved. The first impedance data in the discharging process and the second impedance data in the charging process can be obtained when the battery works, so that all battery working conditions in practical application can be covered, and the method can be applied to batteries of different models and has universality; compared with the method for obtaining the data of the control group through experiments, the method has the advantages that the complicated and high-cost experiment process can be omitted, and the cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery testing, and in particular to a battery lithium deposition detection method, device, system and storage medium. Background Art

[0002] Currently, in order to determine whether a battery has lithium deposition during the charging process, some control group data is needed. These control group data are obtained through experiments. However, the data obtained from the experiments cannot cover all battery operating conditions in actual applications, nor can they be applied to other types of batteries, and are not universal. Summary of the invention

[0003] The embodiments of the present invention provide a battery lithium deposition detection method, device, system and storage medium, aiming to solve the technical problem that the battery lithium deposition detection method is not universal.

[0004] In a first aspect, an embodiment of the present application provides a battery lithium deposition detection method, the battery lithium deposition detection method comprising:

[0005] Acquire a plurality of first impedance data of the battery to be tested under a plurality of different charge states during the charging process, and acquire a plurality of second impedance data of the battery to be tested under the plurality of different charge states during the discharging process;

[0006] Whether lithium is deposited in the battery to be tested during charging is determined according to the plurality of first impedance data and the plurality of second impedance data.

[0007] In this embodiment, a plurality of first impedance data of the battery to be tested under a plurality of different charge states are obtained during the charging process, and a plurality of second impedance data of the battery to be tested under the plurality of different charge states are obtained during the discharging process, that is, the first impedance data during the discharging process and the second impedance data during the charging process are obtained for each of the plurality of different charge states. Since the changes in the battery impedance data caused by the ambient temperature and the charge state of the battery during the discharging process and the charging process are the same, and the battery will not produce lithium deposition during the discharging process, but the changes in the ambient temperature and the charge state of the battery still exist during the discharging process. Therefore, by using the second impedance data during the discharging process under the same charge state as the reference of the first impedance data during the charging process under the same charge state to determine whether the battery to be tested has lithium deposition during the charging process, the influence of the changes in the ambient temperature and the charge state of the battery on the detection results can be eliminated, thereby improving the accuracy of the detection results. And because the first impedance data during the discharge process and the second impedance data during the charging process can both be obtained when the battery is working, they can cover all battery operating conditions in actual applications and can also be applied to batteries of different models, thus having universality. Compared with obtaining the data of the control group through experiments, the method can also omit the complicated and costly experimental process and save costs.

[0008] In some embodiments, determining whether the battery to be tested undergoes lithium deposition during charging according to the plurality of first impedance data and the plurality of second impedance data includes:

[0009] Whether lithium is deposited in the battery to be tested during charging is determined according to a trend of a change in the first impedance data relative to the second impedance data.

[0010] In this embodiment, whether lithium is deposited during the charging process of the battery to be tested is determined specifically according to the trend of the change of the first impedance data relative to the second impedance data.

[0011] In some embodiments, before determining whether the battery to be tested undergoes lithium deposition during charging according to a trend of the first impedance data relative to the second impedance data, the method further includes:

[0012] For each of the plurality of different states of charge, calculating a difference between the first impedance data and the second impedance data in each state of charge;

[0013] A trend of a change of the first impedance data relative to the second impedance data is determined according to the plurality of differences under the plurality of different states of charge.

[0014] In this embodiment, the difference between the first impedance data and the second impedance data in each of a plurality of different charge states is calculated, and the trend of the first impedance data relative to the second impedance data is determined based on the obtained differences in the plurality of different charge states.

[0015] In some embodiments, before determining the trend of the first impedance data relative to the second impedance data according to the plurality of differences under the plurality of different states of charge, the method further includes:

[0016] Determine whether there are multiple consecutive states of charge where the difference is not 0;

[0017] When the difference values ​​under a plurality of consecutive charge states are not zero, a step of determining a change trend of the first impedance data relative to the second impedance data according to the plurality of difference values ​​under the plurality of different charge states is performed.

[0018] In the technical solution of the embodiment of the present application, when it is determined that the difference under multiple consecutive charge states is not 0, the trend of the change of the first impedance data relative to the second impedance data is determined based on the multiple difference values. That is, when all the difference values ​​under multiple charge states are 0, or when the difference values ​​under a few discontinuous charge states are not 0, there is no need to execute the step of "determining the trend of the change of the first impedance data relative to the second impedance data", which can simplify the process and improve detection efficiency.

[0019] In some embodiments, before determining whether the battery to be tested undergoes lithium deposition during charging according to a trend of the first impedance data relative to the second impedance data, the method further includes:

[0020] For each of the plurality of different states of charge, calculating a ratio of the first impedance data to the second impedance data in each state of charge;

[0021] A trend of a change in the first impedance data relative to the second impedance data is determined according to the multiple ratios under the multiple different states of charge.

[0022] In this embodiment, the ratio of the first impedance data to the second impedance data in each of a plurality of different charge states is calculated, and the trend of the change of the first impedance data relative to the second impedance data is determined based on the obtained ratios in the plurality of different charge states.

[0023] In some embodiments, before determining the trend of the first impedance data relative to the second impedance data according to the multiple ratios under the multiple different states of charge, the method further includes:

[0024] Determining whether there are multiple consecutive states of charge where the ratio is not 1;

[0025] When the ratio under a plurality of consecutive charge states is not 1, the step of determining a change trend of the first impedance data relative to the second impedance data based on the plurality of ratios under the plurality of different charge states is performed again.

[0026] In the technical solution of the embodiment of the present application, when it is determined that the ratio of multiple consecutive charge states is not 1, the trend of the change of the first impedance data relative to the second impedance data is determined based on the multiple ratios. That is, when multiple ratios are 1, or the ratio of a few discontinuous charge states is not 1, there is no need to execute the step of "determining the trend of the change of the first impedance data relative to the second impedance data", which can simplify the process and improve detection efficiency.

[0027] In some embodiments, determining whether the battery to be tested undergoes lithium deposition during charging according to the plurality of first impedance data and the plurality of second impedance data includes:

[0028] determining a trend of the first impedance data as the state of charge changes;

[0029] determining a trend of the second impedance data as the state of charge changes;

[0030] Whether lithium is deposited in the battery to be tested during charging is determined according to a trend of the first impedance data changing with the state of charge and a trend of the second impedance data changing with the state of charge.

[0031] In this embodiment, by determining the trend of the first impedance data changing with the state of charge and the trend of the second impedance data changing with the state of charge, and comparing the changing trends of the first impedance data and the second impedance data, it is determined whether the battery to be tested has lithium deposited during the charging process.

[0032] In some embodiments, the multiple different states of charge include multiple states of charge with values ​​between 50% and 100%. In this embodiment, since lithium deposition of the battery generally occurs at a stage where the state of charge is greater than 50% during the charging process, the accuracy of lithium deposition detection can be improved by ensuring that the collected state of charge is between 50% and 100%.

[0033] In some embodiments, a difference between a maximum value and a minimum value among the plurality of different states of charge is greater than 40%.

[0034] In this embodiment, the span of multiple different charge states among multiple different charge states is ensured to be greater than 40%, so as to reduce the influence of sampling error on the lithium deposition detection result.

[0035] In some embodiments, the step of obtaining a plurality of first impedance data of the battery under test at a plurality of different charge states during the charging process includes:

[0036] During the charging process, a plurality of charge states of the battery to be tested during the charging process and a plurality of impedance data corresponding to the plurality of charge states are collected, wherein one charge state corresponds to one impedance data;

[0037] Determine a first relational expression satisfying the relationship between the multiple charge states and the multiple impedance data collected during the charging process;

[0038] A plurality of first impedance data under a plurality of different states of charge are determined according to the first relationship, and the plurality of different states of charge are preset.

[0039] The technical solution of the embodiment of the present application specifically provides how to obtain multiple first impedance data of the battery to be tested under multiple different charge states during the charging process.

[0040] In some embodiments, before determining a first relationship that satisfies the relationship between the multiple charge states and the multiple impedance data collected during the charging process, the method further includes:

[0041] Clearing abnormal charge states among the multiple charge states collected during the charging process and impedance data corresponding to the abnormal charge states;

[0042] Abnormal impedance data among a plurality of impedance data collected during the charging process and a charge state corresponding to the abnormal impedance data are cleared.

[0043] In this embodiment, the charge state and impedance data after the abnormal data is cleared are used to perform lithium deposition detection and judgment, which can eliminate the influence of the abnormal data on the lithium deposition detection result.

[0044] In a second aspect, an embodiment of the present invention further provides a battery lithium deposition detection device, the battery lithium deposition detection device comprising:

[0045] An acquisition module, used for acquiring a plurality of first impedance data of the battery to be tested under a plurality of different charge states during a charging process, and also used for acquiring a plurality of second impedance data of the battery to be tested under the plurality of different charge states during a discharging process;

[0046] The processing module is used to determine whether the battery to be tested has lithium deposition during charging according to the multiple first impedance data and the multiple second impedance data.

[0047] In a third aspect, an embodiment of the present invention further provides a battery lithium deposition detection system, on which the battery lithium deposition detection method as described above is executed.

[0048] In a fourth aspect, an embodiment of the present invention further provides a storage medium, on which a program is stored, and when the program is executed by a processor, the battery lithium deposition detection method as described above is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0050] Figure 1 This is a schematic diagram of the structure of a system according to an embodiment of the present application;

[0051] Figure 2 A schematic diagram of a flow chart of an embodiment of a method for detecting lithium deposition in a battery according to an embodiment of the present invention;

[0052] Figure 3 Another flow chart of an embodiment of a method for detecting lithium deposition in a battery is provided in accordance with an embodiment of the present invention;

[0053] Figure 4 Another flow chart of an embodiment of a method for detecting lithium deposition in a battery is provided in accordance with an embodiment of the present invention;

[0054] Figure 5 Schematic diagram showing that the difference shows an increasing trend as the state of charge changes in an embodiment of the present invention;

[0055] Figure 6 is a schematic diagram showing that the difference value remains unchanged as the state of charge changes in an embodiment of the present invention;

[0056] Figure 7 Another flow chart of an embodiment of a method for detecting lithium deposition in a battery is provided in accordance with an embodiment of the present invention;

[0057] Figure 8 It is a schematic diagram showing that the ratio shows a decreasing trend as the state of charge changes in an embodiment of the present invention;

[0058] Fig. 9 It is a schematic diagram showing that the ratio shows an upward trend as the state of charge changes in an embodiment of the present invention;

[0059] Fig.10 is a schematic diagram showing that the ratio remains unchanged as the state of charge changes in an embodiment of the present invention;

[0060] Fig.11 Another flow chart of an embodiment of a method for detecting lithium deposition in a battery is provided in accordance with an embodiment of the present invention;

[0061] Fig.12 It is a schematic diagram of the first impedance data and the second impedance data changing with the state of charge SOC when the battery does not undergo lithium deposition in an embodiment of the present invention;

[0062] Fig.13 It is a schematic diagram of the first impedance data and the second impedance data changing with the state of charge SOC in the case of lithium deposition in the battery in an embodiment of the present invention;

[0063] Fig.14 This is a schematic structural diagram of an embodiment of a device according to an embodiment of the present invention.

[0064] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0065] The following embodiments of the technical solution of the present invention are 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 invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[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 the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention 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 invention, 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 invention, 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 invention. The appearance of the phrase in various places 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 invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may 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] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0071] In the description of the embodiments of the present invention, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0072] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0073] As a widely used electrochemical energy storage device, the safety of lithium-ion batteries has always attracted much attention. A large number of studies on the failure mechanism of lithium-ion batteries have shown that lithium plating is an important cause of lithium-ion battery capacity decline and even fire and explosion.

[0074] Lithium deposition refers to the abnormal phenomenon that during the charging process of lithium-ion batteries, lithium ions are not embedded in the negative electrode material on the negative electrode side, but are deposited on the negative electrode surface in the form of metallic lithium. It is more likely to occur during low temperature, fast charging, overcharging, etc. The deposited metallic lithium often does not form a flat coating, but exists in the form of dendrites, which are called lithium dendrites. Lithium dendrites have very strong reduction activity and a large specific surface area, and their growth can bring many hazards. For example, excessively grown lithium dendrites may pierce the diaphragm, causing a short circuit between the positive and negative electrodes, and even cause the lithium-ion battery to catch fire and explode. Therefore, lithium deposition detection of lithium-ion batteries is very necessary.

[0075] When the battery precipitates lithium during the charging process, the AC impedance of the battery will show a downward trend due to the precipitation of lithium metal at the negative electrode of the battery. Therefore, the impedance of the battery during the charging process can be monitored online in real time to determine whether the battery is precipitating lithium during the charging process. However, during the charging process of the battery, the changes in the battery state of charge (SOC) and the ambient temperature will also lead to a decrease in the battery AC impedance. Therefore, when judging whether the battery has lithium precipitated during the charging process, some control group data are needed. For example, data on the change of the impedance of the battery during the charging process at different ambient temperatures can be obtained in advance in the laboratory. By controlling the ambient temperature of the battery to be constant during the detection, and comparing the data on the change of the impedance of the battery during the charging process with the data obtained from the experiment at the same ambient temperature, it can be determined whether the battery is precipitating lithium during the charging process. However, the data obtained from the experiment cannot cover all battery conditions in actual applications, and cannot be applied to other types of batteries, and are not universal. And experiments need to be conducted in advance, the process is complicated and costly.

[0076] In order to solve the above defects, the changes in the battery impedance data caused by the ambient temperature and the state of charge of the battery during the discharge process and the charging process of the battery in this application are the same, and the battery will not produce lithium precipitation during the discharge process, but the changes in the ambient temperature and the state of charge of the battery still exist during the discharge process. Therefore, the second impedance data during the discharge process under the same state of charge is used as the reference of the first impedance data during the charging process under the same state of charge to determine whether the battery to be tested has lithium precipitation during the charging process, which can eliminate the influence of the changes in the ambient temperature and the state of charge of the battery on the test results and improve the accuracy of the test results. And because the first impedance data during the discharge process and the second impedance data during the charging process can both be obtained when the battery is working, therefore, all battery operating conditions in practical applications can be covered, and can also be applied to batteries of different models, with universality; compared with obtaining the data of the control group through experiments, it can also save complex and costly experimental processes and save costs.

[0077] Based on the above considerations, in order to solve the technical problem that the battery lithium plating detection method is not universal, after in-depth research, a battery lithium plating detection method, device, system and storage medium are proposed, which are suitable for various battery working conditions and various models of batteries.

[0078] The battery lithium deposition detection method, device, system and storage medium in the present application can be applied to the following scenarios, for example, performing lithium deposition detection on batteries before leaving the factory, performing online lithium deposition detection on batteries loaded on vehicles, etc.

[0079] Realizable, the battery lithium deposition detection method, device, system and storage medium in this application can also be applied to vehicle-mounted battery safety monitoring scenarios. For example, it can be applied to online safety monitoring of new energy vehicles. When lithium deposition of lithium batteries is serious, it will cause diaphragm puncture, which may trigger thermal runaway and lead to safety risks. Some thermal runaway usually occurs during the charging process. Therefore, the risk of thermal runaway can be reduced by real-time monitoring of whether the battery is depositing lithium during the charging process.

[0080] Realizable, the battery lithium plating detection method, device, system and storage medium in this application can also be applied to dynamic fast charging scenarios. For example, one of the pain points of new energy vehicles is that the charging time is relatively long and the user experience is not good. When the car is fast charging, one of the biggest risks is the generation of lithium plating. By monitoring the impedance data of the charging process, the various charging conditions when the battery does not plating lithium can be determined to determine the charging parameters that can achieve fast charging when the battery does not plating lithium, thereby achieving dynamic fast charging and speeding up the charging process.

[0081] In order to better understand the embodiments of the present application, the battery lithium deposition detection method, device, system and storage medium provided according to the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0082] The battery lithium deposition detection method provided in the embodiment of the present application may be executed by a battery lithium deposition detection system, and the battery lithium deposition detection system may be used to perform lithium deposition detection on a battery to be tested (such as a lithium-ion battery).

[0083] For the sake of convenience, here we use Figure 1 The battery lithium deposition detection system shown serves as a specific application environment of the battery lithium deposition detection method provided in this embodiment. The system is only a possible example, and does not limit the specific application environment of the battery lithium deposition detection method provided in the embodiment of the present application. The battery lithium deposition detection method provided in the embodiment of the present application can also be applied to other systems.

[0084] like Figure 1As shown, a battery lithium deposition detection system is provided with a data acquisition module, which is used to obtain multiple first impedance data of the battery to be tested under multiple different charge states during the charging process, and multiple second impedance data of the battery to be tested under the multiple different charge states during the discharge process from the battery management system. A processing module is also provided on the battery lithium deposition detection, and the processing module is used to determine whether the battery to be tested has lithium deposition during the charging process according to the multiple first impedance data and multiple second impedance data acquired by the data acquisition module. The second impedance data during the discharge process under the same charge state is used as the reference of the first impedance data during the charging process under the same charge state to determine whether the battery to be tested has lithium deposition during the charging process, which can eliminate the influence of the change of the ambient temperature and the charge state of the battery on the detection result and improve the accuracy of the detection result. And because the first impedance data during the discharge process and the second impedance data during the charging process can be obtained when the battery is working, all battery working conditions in practical applications can be covered, and it can also be applied to batteries of different models, which has universality; compared with obtaining the data of the control group through experiments, it can also save the complex and costly experimental process and save costs.

[0085] In some embodiments of the present invention, reference Figure 2 , an embodiment of the present invention provides a battery lithium deposition detection method, which may include:

[0086] Step S10: acquiring a plurality of first impedance data of the battery under test at a plurality of different charge states during the charging process, and acquiring a plurality of second impedance data of the battery under test at a plurality of different charge states during the discharging process.

[0087] Specifically, in order to facilitate obtaining the first impedance data of the battery to be tested under multiple different states of charge during the charging process. In one embodiment, during the charging process of the battery to be tested, each time the state of charge increases by a preset value, an alternating current of a preset period is applied to the battery to be tested, which may be a periodic signal such as a sine wave, a square wave, or a triangular wave. Among them, the value range of the preset value may be [1%, 5%]. The smaller the preset value, the higher the accuracy of the battery lithium deposition detection. However, the first impedance data of the battery to be tested corresponding to each of the different states of charge at the preset frequency and the subsequent calculation amount are obtained. In addition, the preset period is determined based on the preset frequency, and the preset frequency is less than or equal to 0.1HZ. For example, the preset value is 5%, and the preset frequency is 0.1HZ. Then, every time the state of charge increases by 5%, the charging device applies an alternating current of a preset period of 10s (1s / 0.1HZ=10s) to the battery to be tested. In this way, every time the state of charge increases by 5%, the first impedance data of the battery to be tested at a preset frequency and the current state of charge can be obtained. For example, the first impedance data of the state of charge SOC of 0%, 5%, 10%, 15%, ..., 95%, and 100% can be obtained respectively.

[0088] In another embodiment, during the charging process of the battery to be tested, an alternating current of a preset period can be applied to the battery to be tested at preset time intervals. At this time, the difference in the state of charge of the battery corresponding to two adjacent sampling times is not necessarily the same. Assuming that the preset time is 5 seconds, the first impedance data of the state of charge SOC of 0%, 2%, 5%, 10%, 14%, 20%, etc. can be obtained respectively.

[0089] It should be understood that the method for obtaining the second impedance data during the discharge process is the same as the method for obtaining the first impedance data during the charging process, and reference may be made to the above content, which will not be repeated here.

[0090] It is worth noting that the cycle of the AC power applied during the discharge process of the battery to be tested is the same as the cycle of the AC power applied during the charging process of the battery to be tested; and the waveform of the AC power applied during the discharge process of the battery to be tested is also the same as the waveform of the AC power applied during the charging process of the battery to be tested.

[0091] Step S20: determining whether lithium is deposited during the charging process of the battery to be tested according to the plurality of first impedance data and the plurality of second impedance data.

[0092] Specifically, each of the multiple different charge states corresponds to a first impedance data and a second impedance data. The second impedance data during the discharge process under the same charge state can be used as a reference for the first impedance data during the charging process under the same charge state to determine whether the battery to be tested has lithium deposition during the charging process.

[0093] In this embodiment, a plurality of first impedance data of the battery to be tested under a plurality of different charge states are obtained during the charging process, and a plurality of second impedance data of the battery to be tested under the plurality of different charge states are obtained during the discharging process, that is, the first impedance data during the discharging process and the second impedance data during the charging process are obtained for each of the plurality of different charge states. Since the changes in the battery impedance data caused by the ambient temperature and the charge state of the battery during the discharging process and the charging process are the same, and the battery will not produce lithium deposition during the discharging process, but the changes in the ambient temperature and the charge state of the battery still exist during the discharging process. Therefore, by using the second impedance data during the discharging process under the same charge state as the reference of the first impedance data during the charging process under the same charge state to determine whether the battery to be tested has lithium deposition during the charging process, the influence of the changes in the ambient temperature and the charge state of the battery on the detection results can be eliminated, thereby improving the accuracy of the detection results. And because the first impedance data during the discharge process and the second impedance data during the charging process can both be obtained when the battery is working, they can cover all battery operating conditions in actual applications and can also be applied to batteries of different models, thus having universality. Compared with obtaining the data of the control group through experiments, the method can also omit the complicated and costly experimental process and save costs.

[0094] In some embodiments, whether lithium is deposited during charging of the battery to be tested is determined based on the trend of the first impedance data relative to the second impedance data. Figure 3 , step S20 specifically includes:

[0095] Step S201: determining a trend of a change of the first impedance data relative to the second impedance data according to a plurality of first impedance data and a plurality of second impedance data.

[0096] Specifically, in the present embodiment, in the process of determining the trend of the change of the first impedance data relative to the second impedance data, the changes of the first impedance data and the second impedance data under the same state of charge are compared. For example, when the state of charge changes from 50% to 60%, the second impedance data increases. At this time, if the first impedance data decreases when the state of charge changes from 50% to 60%, it can be determined that in the process of the state of charge changing from 50% to 60%, the trend of the change of the first impedance data relative to the second impedance data is: the first impedance data decreases as the second impedance data increases.

[0097] It should be noted that in the embodiment of the present application, as much first impedance data and second impedance data under charge states as possible are obtained, and an overall trend is determined for the changes in the first impedance data under charge states relative to the second impedance data, so as to avoid the influence of abnormalities of individual data on the detection results.

[0098] Step S202: determining whether lithium is deposited in the battery to be tested during charging according to a trend of a change in the first impedance data relative to the second impedance data.

[0099] After many experiments, it was found that when the battery does not precipitate lithium, the impedance of the battery will show a downward trend with the increase of the state of charge SOC in the first half of the battery charging (i.e., the stage when the state of charge SOC is less than 50%), and in the second half of the battery charging (i.e., the stage when the state of charge SOC is greater than 50%), the impedance of the battery will show an upward trend with the increase of the state of charge SOC. In the first half of the battery discharge (i.e., the stage when the state of charge SOC is greater than 50%), the impedance of the battery will show an upward trend with the increase of the state of charge SOC, and in the second half of the battery discharge (i.e., the stage when the state of charge SOC is less than 50%), the impedance of the battery will show a downward trend with the increase of the state of charge SOC. In other words, the trend of the impedance data of the battery charging segment changing with the state of charge when the battery does not precipitate lithium is the same as the trend of the impedance data of the battery discharge segment changing with the state of charge. When the impedance data of the battery charging segment and the impedance data of the battery discharging segment are displayed in the same coordinate system with the state of charge SOC on the horizontal axis and the impedance data on the vertical axis, the curve of the battery charging segment and the curve of the battery discharging segment should theoretically overlap.

[0100] When lithium is deposited in the battery, due to the attachment of lithium dendrites to the negative electrode of the battery, the trend of the battery impedance rising with the increase of the state of charge SOC may slow down, or even cause the battery impedance to show a downward trend with the increase of the state of charge SOC. Since the battery does not deposit lithium during the discharge process, the impedance of the battery in the first half of the discharge process (i.e., the stage where the state of charge SOC is greater than 50%) will still show an upward trend with the increase of the state of charge SOC. Therefore, the impedance data of the battery during the discharge process can be used as a reference to determine whether the battery is depositing lithium based on the trend of the first impedance data of the charging stage changing with the second impedance data of the discharge stage.

[0101] In the second half of battery charging (i.e., the stage where the state of charge SOC is greater than 50%), when the first impedance data in the battery charging segment increases with the increase of the second impedance data in the battery discharging segment, and the rate of increase of the second impedance data is significantly greater than the rate of increase of the first impedance data, it can be determined that the battery has a high probability of lithium deposition. For this situation, it is uniformly considered in this embodiment that lithium deposition occurs in the battery; when the first impedance data decreases with the increase of the second impedance data, it can be determined that the battery has lithium deposition.

[0102] It should be noted that the “trend of change” mentioned in this embodiment not only includes the direction of change, such as whether the first impedance data increases or decreases as the second impedance data increases; it also includes the speed of change, such as the speed at which the first impedance data increases as the second impedance data increases.

[0103] In some embodiments, by calculating the difference between the first impedance data and the second impedance data at each of a plurality of different states of charge, the trend of the first impedance data relative to the second impedance data is determined according to the obtained differences at the plurality of different states of charge. Figure 4 , step S201 specifically includes:

[0104] Step S2011: for each state of charge of a plurality of different states of charge, calculating a difference between the first impedance data and the second impedance data in each state of charge.

[0105] Specifically, when calculating the difference, the first impedance data and the second impedance data can be calculated by taking their modulus. For example, the first impedance data can be expressed as Z=R+j(XL-XC), where R is resistance, XL is inductive reactance, and XC is capacitive reactance. Then the modulus of the first impedance data is Alternatively, when calculating the difference, the first impedance data and the second impedance data may also be calculated by taking their real parts or imaginary parts.

[0106] Taking the impedance data as an example for calculation, the difference may be the modulus of the first impedance data minus the modulus of the second impedance data, or the modulus of the second impedance data minus the modulus of the first impedance data.

[0107] Step S2012: determining a change trend of the first impedance data relative to the second impedance data according to a plurality of difference values ​​under a plurality of different charge states.

[0108] In this embodiment, the trend of the first impedance data relative to the second impedance data can be determined based on the change trend of the multiple differences under multiple different states of charge. For example, the multiple differences under multiple different states of charge are displayed in a coordinate system with the state of charge SOC on the horizontal axis and the absolute value of the difference on the vertical axis, and a curve graph is drawn in the coordinate system. According to the change trend of the curve graph, the trend of the difference changing with the state of charge is determined. Figure 5 As shown, if the curve shows an upward trend, it means that the absolute value of the difference increases with the increase of the state of charge, and it also means that the gap between the first impedance data and the second impedance data is getting bigger and bigger. At this time, the trend of the change of the first impedance data relative to the second impedance data is determined as follows: as the state of charge increases, the increase of the first impedance data in the charging section is less than the increase of the second impedance data, or the increase of the first impedance data in the charging section is decreasing relative to the increase of the second impedance data in the discharging section. At this time, it can be determined that the battery to be tested is lithium deposited during the charging process. Figure 6 As shown, if the curve graph is a straight line perpendicular to the vertical axis (the intersection with the vertical axis is 0), it means that the first impedance data is the same as the second impedance data. At this time, it can be determined that the battery to be tested has no lithium deposition during the charging process.

[0109] In some embodiments, before determining the trend of change of the first impedance data relative to the second impedance data based on multiple differences under multiple different charge states, it also includes: determining whether there are multiple consecutive difference values ​​under charge states that are not 0; if the difference values ​​under multiple consecutive charge states are not 0, then executing the step of determining the trend of change of the first impedance data relative to the second impedance data based on multiple differences under multiple different charge states.

[0110] Specifically, since the battery does not undergo lithium deposition, the impedance data of the battery charging section and the impedance data of the battery discharging section under the same charge state are the same, such as Figure 6 As shown, the difference between the first impedance data and the second impedance data under the same state of charge is theoretically 0. At this time, the curve formed by the difference as the state of charge changes is a straight line perpendicular to the vertical axis (the intersection with the vertical axis is 0), which can determine that the battery to be tested has no lithium deposition during the charging process.

[0111] Taking into account the existence of sampling errors, if all the differences under multiple different charge states are 0, or the differences under a few discontinuous charge states are not 0, it indicates that the battery under test does not precipitate lithium during the charging process. In this case, there is no need to perform the step of "determining the trend of the change of the first impedance data relative to the second impedance data", which can simplify the process and improve the detection efficiency.

[0112] When the difference under multiple consecutive charge states is not 0, since it is impossible to determine whether it is caused by sampling error or battery lithium deposition, the trend of change of the first impedance data relative to the second impedance data can be further determined based on multiple differences under multiple different charge states to determine whether the battery has lithium deposition, thereby improving the accuracy of lithium deposition detection.

[0113] In some embodiments, by calculating the ratio of the first impedance data to the second impedance data at each of a plurality of different states of charge, the trend of the first impedance data relative to the second impedance data is determined according to the obtained ratios at the plurality of different states of charge. Figure 7 , step S201 specifically includes:

[0114] Step S2011 : For each state of charge of a plurality of different states of charge, calculate a ratio of the first impedance data to the second impedance data in each state of charge.

[0115] Specifically, when calculating the ratio, the modulus of the first impedance data and the second impedance data under the same charge state may be used for calculation; or the real part or imaginary part of the first impedance data and the second impedance data under the same charge state may be used for calculation. The ratio mentioned in the embodiment of the present invention may be the ratio of the first impedance data divided by the second impedance data under the same charge state, or may be the ratio of the second impedance data divided by the first impedance data under the same charge state.

[0116] Step S2012': Determine a change trend of the first impedance data relative to the second impedance data according to a plurality of ratios under a plurality of different charge states.

[0117] Specifically, the trend of the first impedance data relative to the second impedance data can be determined based on the change trends of multiple ratios under multiple different states of charge. For example, multiple ratios under multiple different states of charge are displayed in a coordinate system with the state of charge SOC on the horizontal axis and the absolute value of the difference on the vertical axis, and a curve graph is drawn in the coordinate system, and the trend of the ratio changing with the state of charge is determined based on the change trend of the curve graph.

[0118] In the case where the above ratio is the ratio of the first impedance data divided by the second impedance data at the same state of charge, Figure 8 As shown, if the curve shows a downward trend, it indicates that the ratio decreases with the increase of the state of charge. At this time, it can be determined that the trend of the first impedance data relative to the second impedance data is: as the state of charge increases, the increase of the first impedance data in the charging section is less than the increase of the second impedance data, or the increase of the first impedance data in the charging section is decreasing relative to the increase of the second impedance data in the discharging section. At this time, it can be determined that the battery to be tested is lithium deposited during the charging process.

[0119] In the case where the above ratio is the ratio of the second impedance data divided by the first impedance data at the same state of charge, Fig. 9 As shown, if the curve shows an upward trend, it indicates that the ratio increases with the increase of the state of charge. At this time, it can be determined that the trend of the first impedance data relative to the second impedance data is: as the state of charge increases, the increase of the first impedance data in the charging section is less than the increase of the second impedance data, or the increase of the first impedance data in the charging section relative to the second impedance data in the discharging section is decreasing. At this time, it can be determined that the battery to be tested is lithium deposited during the charging process.

[0120] In some embodiments, before determining the trend of change of the first impedance data relative to the second impedance data based on multiple ratios under multiple different charge states, it also includes: determining whether there are multiple consecutive ratios that are not 1; if the multiple consecutive ratios are not 1, then executing the step of determining the trend of change of the first impedance data relative to the second impedance data based on multiple ratios under multiple different charge states.

[0121] Specifically, since the battery does not undergo lithium deposition, the impedance data of the battery charging section and the impedance data of the battery discharging section under the same charge state are the same, such as Fig.10As shown, the ratio of the first impedance data to the second impedance data under the same state of charge is theoretically 1. At this time, the curve formed by the ratio changing with the state of charge is a straight line perpendicular to the vertical axis (the intersection with the vertical axis is 1), which can determine that the battery to be tested has no lithium deposition during the charging process.

[0122] Taking into account the existence of sampling errors, if all ratios under multiple different charge states are 1, or the ratios under a few discontinuous charge states are not 1, it indicates that the battery under test does not precipitate lithium during the charging process. In this case, there is no need to perform the step of "determining the trend of the change of the first impedance data relative to the second impedance data", which can simplify the process and improve the detection efficiency.

[0123] When the ratio under multiple consecutive charge states is not 1, since it is impossible to determine whether it is caused by sampling error or battery lithium deposition, the trend of change of the first impedance data relative to the second impedance data can be further determined based on multiple ratios under multiple different charge states to determine whether the battery has lithium deposition, thereby improving the accuracy of lithium deposition detection.

[0124] In some embodiments, by determining the trend of the first impedance data changing with the state of charge and the trend of the second impedance data changing with the state of charge, and by comparing the trend of the first impedance data and the second impedance data, it is determined whether the battery to be tested has lithium deposited during the charging process. Fig.11 , step S20 specifically includes:

[0125] Step S201 : determining a trend of the first impedance data changing with the state of charge, and determining a trend of the second impedance data changing with the state of charge.

[0126] Specifically, the trend of impedance data changing with the state of charge can be determined by drawing graphs such as curves, line graphs or bar graphs, or by directly calculating the change in the ratio of the difference between adjacent impedance data and the difference between adjacent states of charge.

[0127] In one example, a plurality of first impedance data under a plurality of different charge states are displayed in a coordinate system with the horizontal axis being the charge state and the vertical axis being the impedance modulus, and the plurality of first impedance data form a first curve in the coordinate system. A plurality of second impedance data under a plurality of different charge states are displayed in the above coordinate system, and the plurality of second impedance data form a second curve in the coordinate system. In this way, the similarities and differences in the change trends of the first curve and the second curve can be intuitively and accurately judged in the same coordinate system.

[0128] It should be understood that, in this embodiment, the vertical axis of the coordinate system is represented by the module of impedance. In practical applications, the vertical axis of the coordinate system can also be represented by the real part or imaginary part of impedance, which is not limited here.

[0129] Step S202': Determine whether the battery to be tested has lithium deposition during the charging process according to the trend of the first impedance data changing with the state of charge and the trend of the second impedance data changing with the state of charge.

[0130] Specifically, if Fig.12 As shown in the figure, when the battery does not precipitate lithium, the impedance of the battery will show a downward trend as the state of charge SOC increases in the first half of the battery charging (i.e., the stage when the state of charge SOC is less than 50%), and the impedance of the battery will show an upward trend as the state of charge SOC increases in the second half of the battery charging (i.e., the stage when the state of charge SOC is greater than 50%). That is to say, during the battery charging process, the first impedance data of the battery forms a U-shaped curve as the state of charge increases, as shown in FIG. Fig.12 During the battery discharge process, the second impedance data of the battery also forms a U-shaped curve as the state of charge increases, as shown in Fig.12 As shown by the solid line in the middle, the U-shaped curve formed during the battery charging process is roughly the same as the U-shaped curve formed during the battery discharging process.

[0131] When lithium is deposited in the battery, the curve formed during the battery discharge process is still a U-shaped curve, such as Fig.13 In the charging process, in the second half of the battery charging (i.e., the stage where the state of charge SOC is greater than 50%), the rising speed of the battery impedance in the charging stage is significantly slower than that in the discharging stage, as shown in Figure 2. Fig.13 As shown by the dotted line, the impedance of the battery in the charging stage shows a downward trend as the state of charge SOC increases, as shown in Fig.13 Shown by the dashed line.

[0132] Therefore, based on the trend of the second impedance data changing with the state of charge, if the direction of the trend of the first impedance data changing with the state of charge is different from the direction of the trend of the second impedance data changing with the state of charge, or the speed of the trend of the first impedance data changing with the state of charge is different from the speed of the trend of the second impedance data changing with the state of charge, it can be determined that the battery to be tested is lithium deposited during the charging process. Only when the direction of the trend of the two changes and the speed of the trend of the change are the same, it can be determined that the battery to be tested does not deposit lithium during the charging process.

[0133] It is feasible to compare a first curve formed by the first impedance data and the state of charge with a second curve formed by the second impedance data and the state of charge. If the first curve and the second curve change in the same direction and at the same slope, it is determined that the battery to be tested has not deposited lithium during the charging process; if the first curve and the second curve change in different directions or at different slopes, it is determined that the battery to be tested has deposited lithium during the charging process.

[0134] In some embodiments, the plurality of different states of charge include a plurality of states of charge with values ​​between 50% and 100%.

[0135] Since battery lithium plating generally occurs in the second half of battery charging, that is, the stage when the battery state of charge (SOC) is greater than 50%, the "multiple different states of charge" mentioned in the embodiment of the present invention are in the range of 50% to 100% to improve the accuracy of lithium plating detection.

[0136] In some embodiments, the difference between the maximum and minimum values ​​of the multiple different states of charge is greater than 40%. By ensuring that the span of the multiple different states of charge is greater than 40%, the influence of sampling error on the lithium deposition detection result is reduced.

[0137] In the present application, a plurality of first impedance data of the battery to be tested in a plurality of different charge states during the charging process and a plurality of second impedance data during the discharging process are obtained, specifically including the following methods:

[0138] Method 1: When the state of charge data collected during the charging process is mostly the same as the state of charge data collected during the discharging process, the impedance data under the state of charge collected during the charging process can be directly used as the first impedance data, and the impedance data under the state of charge collected during the discharging process can be used as the second impedance data.

[0139] In one example, during the charging process of the battery to be tested, each time the state of charge increases by a preset value, an alternating current of a preset period is applied to the battery to be tested to obtain first impedance data; during the discharging process, each time the state of charge decreases by a preset value, an alternating current of a preset period is applied to the battery to be tested to obtain second impedance data. In this way, the first impedance data and the second impedance data under multiple different states of charge can be obtained.

[0140] In another example, during the charging process of the battery to be tested, an alternating current of a preset period is applied to the battery to be tested at each preset time interval to obtain current impedance data and current state of charge; during the discharging process of the battery to be tested, an alternating current of a preset period is applied to the battery to be tested at each preset time interval to obtain current impedance data and current state of charge. Since the state of charge data collected during the discharge process is not completely the same as the state of charge data collected during the charging process, the impedance data of the charging process when the state of charge data collected during the discharge process is the same as that collected during the charging process can be selected as the first impedance data, and the impedance data of the discharge process when the state of charge data collected during the discharge process is the same as that collected during the charging process can be selected as the second impedance data.

[0141] For example: During the charging process of the battery to be tested, the collected state of charge SOC is: 0%, 5%, 8%, 10%, 14%, 20%, 28%, 35%, 40%, 50%, 55%, 65%, 70%, 77%, 85%, 90%, 95%, 100%. During the discharging process of the battery to be tested, the collected state of charge SOC is 100%, 95%, 90%, 85%, 76%, 70%, 64%, 55%, 50%, 45%, 35%, 29%, 22%, 15%, 10%, 7%, 5%, 0%. Then, the charge states that are the same in the charging process and the discharging process include 0%, 5%, 10%, 35%, 40%, 50%, 55%, 70%, 85%, 90%, 95%, and 100%. The impedance data during the charging process under these same charge states can be selected as the first impedance data, and the impedance data during the discharging process under these same charge states can be selected as the second impedance data.

[0142] Method 2: When the state of charge data collected during the charging process is mostly different from the state of charge data collected during the discharging process, the impedance data under the state of charge collected during the charging process can be directly used as the first impedance data, or the impedance data under the state of charge collected during the discharging process can be used as the second impedance data.

[0143] If the state of charge data collected during the charging process is mostly different from the state of charge data collected during the discharging process, for example, the state of charge SOC collected during the charging process is: 0%, 5%, 8%, 10%, 14%, 20%, 28%, 35%, 40%, 50%, 55%, 65%, 70%, 77%, 85%, 90%, 95%, 100%; the state of charge SOC collected during the discharging process is: 100%, 94%, 90%, 85%, 76%, 69%, 64%, 56%, 49%, 45%, 35%, 29%, 22%, 15%, 10%, 7%, 4%, 0%. It can be seen that the state of charge SOC that is the same in the charging process and the discharging process is: 100%, 90%, 10% and 0%. If the lithium plating condition of the battery under test is directly judged based on the impedance data corresponding to the four states of charge (SOC), the conclusion obtained will not be accurate.

[0144] In view of this, the impedance data under the state of charge collected during the charging process is used as the first impedance data. Afterwards, a functional relationship that satisfies the relationship between the state of charge SOC collected during the discharge process and the corresponding impedance data is calculated, and the state of charge SOC collected during the charging process is sequentially substituted into the above functional relationship to obtain the second impedance data during the discharge process. Similarly, the impedance data under the charge collected during the discharge process is used as the second impedance data. Afterwards, a functional relationship that satisfies the relationship between the state of charge SOC collected during the charging process and the corresponding impedance data is calculated, and the state of charge SOC collected during the discharge process is sequentially substituted into the above functional relationship to obtain the first impedance data during the charging process.

[0145] Method three, obtaining a first relationship for the impedance data under the charge state collected during the charging process, and obtaining a second relationship for the impedance data under the charge state collected during the discharging process, substituting a preset plurality of different charge state SOCs into the first relationship to obtain a plurality of first impedance data, and substituting a preset plurality of different charge state SOCs into the second relationship to obtain a plurality of second impedance data.

[0146] In this embodiment, a plurality of first impedance data of a battery to be tested under a plurality of different charge states are obtained during the charging process, including: during the charging process, collecting a plurality of charge states of the battery to be tested during the charging process, and a plurality of impedance data corresponding to the plurality of charge states, one charge state corresponds to one impedance data; determining a first relationship that satisfies the relationship between the plurality of charge states and the plurality of impedance data during the charging process; determining a plurality of first impedance data under a plurality of different charge states according to the first relationship, the plurality of different charge states being preset.

[0147] Specifically, the preset multiple different states of charge SOC are, for example: 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%. The multiple different states of charge SOC in this embodiment are only for illustration and are not limited thereto.

[0148] During the charging process, multiple states of charge of the battery to be tested and multiple impedance data corresponding to the multiple states of charge can be collected, and a first relationship that satisfies the relationship between the multiple states of charge and the multiple impedance data during the charging process can be determined. Multiple first impedance data can be obtained by sequentially substituting the above-mentioned multiple different states of charge SOC into the above-mentioned first relationship.

[0149] Similarly, multiple states of charge of the battery to be tested during the discharge process and multiple impedance data corresponding to the multiple states of charge are collected, and a second relationship that satisfies the relationship between the multiple states of charge and the multiple impedance data during the discharge process is determined. Multiple second impedance data can be obtained by sequentially substituting the above-mentioned multiple different states of charge SOC into the above-mentioned second relationship.

[0150] Realistically, the first relational expression and the second relational expression may be obtained by fitting.

[0151] Realistically, in practical applications, the state of charge of the battery to be tested can be calculated by collecting the voltage signal and current signal of the battery to be tested.

[0152] In some embodiments, before determining a first relationship that satisfies the relationship between multiple charge states and multiple impedance data during the charging process, it also includes: clearing abnormal charge states among the multiple charge states collected during the charging process, and impedance data corresponding to the abnormal charge states, and clearing abnormal impedance data among the multiple impedance data collected during the charging process, and charge states corresponding to the abnormal impedance data.

[0153] Specifically, in this embodiment, before using the collected charge state and impedance data to determine whether the battery has lithium deposition, it is necessary to clear the abnormal charge state in the charge state collected during the charging process, and clear the impedance data corresponding to the abnormal charge state; it is also necessary to clear the abnormal impedance data in the impedance data collected during the charging process, and clear the charge state corresponding to the abnormal impedance data.

[0154] Similarly, before using the collected state of charge and impedance data to determine whether the battery has lithium deposition, it is also necessary to clear the abnormal state of charge in the state of charge collected during the discharge process, and clear the impedance data corresponding to the abnormal state of charge; and clear the abnormal impedance data in the impedance data collected during the discharge process, and clear the state of charge corresponding to the abnormal impedance data.

[0155] In this embodiment, the charge state and impedance data after the abnormal data is cleared are used to perform lithium deposition detection and judgment, which can eliminate the influence of the abnormal data on the lithium deposition detection result.

[0156] In one example, the quartile method can be used to remove abnormal data in the collected state of charge and impedance data. Specifically, the first and fourth quartiles of the state of charge data distribution are calculated, and the state of charge outside the quartile range is an abnormal value; the first and fourth quartiles of the impedance data distribution are calculated, and the impedance data outside the quartile range is an abnormal value.

[0157] In another example, the 3σ criterion method can be used to remove abnormal data in the collected state of charge and impedance data. Specifically, the average value and standard deviation of all collected states of charge are calculated, and the state of charge outside the range of three times the standard deviation of the average value is generally determined as an abnormal value; the average value and standard deviation of all collected impedance data are calculated, and the impedance data outside the range of three times the standard deviation of the average value is generally determined as an abnormal value.

[0158] In some embodiments, the battery to be tested adopts a constant voltage charging method during the charging process and a constant voltage discharging method during the discharging process. Alternatively, the battery to be tested adopts a constant current charging method during the charging process and a constant current discharging method during the discharging process; or, the battery to be tested adopts a constant current and constant voltage charging method during the charging process and a constant current and constant voltage discharging method during the discharging process.

[0159] Specifically, in order to ensure that the battery is in the same state of charge during the charging process and the discharging process, and the ambient temperature of the battery is roughly the same, it is necessary to ensure that the battery adopts the same charging and discharging method during the charging and discharging process. For example, if the battery to be tested adopts a constant voltage charging method during the charging process, then a constant voltage discharge method must be adopted during the discharging process. For another example, if the battery to be tested adopts a constant current charging method during the charging process, then a constant current discharge method must be adopted during the discharging process. For another example, if the battery to be tested adopts a constant current and constant voltage charging method during the charging process, then a constant current and constant voltage discharge method must be adopted during the discharging process.

[0160] In practical applications, the charging and discharging method can be selected according to actual needs, and this is not limited in this embodiment.

[0161] In one embodiment of the present application, a method for lithium plating detection is as follows.

[0162] First, the impedance data of the battery to be tested during the discharge process is selected through the signal of the battery management system (BMS), and the impedance data of a complete discharge segment is selected, wherein the interval span of the state of charge SOC corresponding to the impedance data should be as long as possible, the interval span of SOC needs to be at least greater than about 40%, and the interval span of SOC needs to include data after the state of charge SOC is 50%.

[0163] Secondly, the electrical signals (including voltage signals and current signals) and impedance data during the charging process are collected, and the state of charge corresponding to the impedance data is calculated according to the electrical signals during the charging process. The state of charge and impedance data collected during the charging process are combined into an array, and the data in the array are subjected to outlier elimination processing, and the elimination method adopts but is not limited to the 4-quantile method. Realistically, the outlier value after elimination can be replaced by the previous value.

[0164] Afterwards, the selected state of charge and impedance data during the discharge process are also formed into an array, and the data in the array are also processed to eliminate abnormal values.

[0165] Then, the processed array in the charging process and the array in the discharging process are divided into N equal parts according to the SOC interval to form a new array.

[0166] For example, suppose the state of charge SOC collected during the charging process is 0%, 5%, 8%, 10%, 14%, 20%, 28%, 35%, 40%, 50%, 55%, 65%, 70%, 77%, 85%, 90%, 95%, 100%. The state of charge SOC collected during the discharge process is 100%, 94%, 90%, 85%, 76%, 69%, 64%, 56%, 49%, 45%, 35%, 29%, 22%, 15%, 10%, 7%, 4%, 0%. It can be seen that the state of charge SOC collected during the charging process is the same as the state of charge SOC collected during the discharge process: 100%, 90%, 10% and 0%. If the lithium plating condition of the battery to be tested is directly judged based on these four state of charge SOC data, the conclusion obtained is not accurate. Therefore, it is necessary to divide the collected state of charge SOC during the charging process into equal parts, and to divide the state of charge SOC during the discharging process into equal parts, and the divided state of charge SOC is, for example: 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%. The first impedance data during the charging process and the first impedance data during the discharging process are recalculated according to the divided state of charge SOC, so that two new arrays can be obtained.

[0167] Finally, subtract the data in the two new arrays. Specifically, for the same state of charge, a subtracted array can be obtained by subtracting the second impedance data corresponding to the discharge process from the first impedance data corresponding to the charging process. The absolute value of the difference in the subtracted array is displayed in a coordinate system with the horizontal axis being the state of charge SOC and the vertical axis being the absolute value of the difference. If the curve formed in the coordinate system shows an upward trend, it is determined that the battery to be tested deposits lithium during the charging process; if the curve formed in the coordinate system is close to a straight line perpendicular to the vertical axis (the vertical coordinate of the straight line is close to 0), it is determined that the battery to be tested does not deposit lithium during the charging process.

[0168] To achieve the above purpose, the present invention further provides a battery lithium deposition detection device. Fig.12 An embodiment structure diagram of a device provided in an embodiment of the present application is shown, and the battery lithium deposition detection device includes:

[0169] An acquisition module 10 is used to acquire a plurality of first impedance data of the battery under test at a plurality of different charge states during a charging process, and to acquire a plurality of second impedance data of the battery under test at the plurality of different charge states during a discharging process;

[0170] The processing module 20 is used to determine whether lithium is deposited in the battery to be tested during charging according to the plurality of first impedance data and the plurality of second impedance data.

[0171] In this embodiment, a plurality of first impedance data of the battery to be tested under a plurality of different charge states are obtained during the charging process, and a plurality of second impedance data of the battery to be tested under the plurality of different charge states are obtained during the discharging process, that is, the first impedance data during the discharging process and the second impedance data during the charging process are obtained for each of the plurality of different charge states. Since the changes in the battery impedance data caused by the ambient temperature and the charge state of the battery during the discharging process and the charging process are the same, and the battery will not produce lithium deposition during the discharging process, but the changes in the ambient temperature and the charge state of the battery still exist during the discharging process. Therefore, by using the second impedance data during the discharging process under the same charge state as the reference of the first impedance data during the charging process under the same charge state to determine whether the battery to be tested has lithium deposition during the charging process, the influence of the changes in the ambient temperature and the charge state of the battery on the detection results can be eliminated, thereby improving the accuracy of the detection results. And because the first impedance data during the discharge process and the second impedance data during the charging process can both be obtained when the battery is working, they can cover all battery operating conditions in actual applications and can also be applied to batteries of different models, thus having universality. Compared with obtaining the data of the control group through experiments, the method can also omit the complicated and costly experimental process and save costs.

[0172] In one embodiment, the processing module 20 is further used to determine whether the battery to be tested has lithium deposited during the charging process according to a trend of a change in the first impedance data relative to the second impedance data.

[0173] In one embodiment, the processing module 20 is further used to calculate the difference between the first impedance data and the second impedance data at each charge state for each of the multiple different charge states before determining whether lithium is deposited in the battery to be tested during the charging process based on the trend of the change of the first impedance data relative to the second impedance data; and determine the trend of the change of the first impedance data relative to the second impedance data based on the multiple differences under the multiple different charge states.

[0174] In one embodiment, the processing module 20 is further used to determine whether there are multiple consecutive charge states where the difference is not 0 before determining the trend of the change of the first impedance data relative to the second impedance data based on the multiple difference values ​​under the multiple different charge states; and if the difference under multiple consecutive charge states is not 0, perform the step of determining the trend of the change of the first impedance data relative to the second impedance data based on the multiple difference values ​​under the multiple different charge states.

[0175] In one embodiment, the processing module 20 is further used to calculate the ratio of the first impedance data to the second impedance data at each state of charge for each of the multiple different states of charge before determining whether lithium is deposited in the battery to be tested during the charging process based on the trend of the change of the first impedance data relative to the second impedance data; and determine the trend of the change of the first impedance data relative to the second impedance data based on the multiple ratios under the multiple different states of charge.

[0176] In one embodiment, the processing module 20 is further used to determine whether there are multiple consecutive charge states where the ratio is not 1 before determining the trend of the change of the first impedance data relative to the second impedance data based on the multiple ratios under the multiple different charge states; and if the ratio under multiple consecutive charge states is not 1, perform the step of determining the trend of the change of the first impedance data relative to the second impedance data based on the multiple ratios under the multiple different charge states.

[0177] In one embodiment, the processing module 20 is further used to determine the trend of the first impedance data changing with the state of charge; determine the trend of the second impedance data changing with the state of charge; and determine whether the battery to be tested has lithium deposition during the charging process based on the trend of the first impedance data changing with the state of charge and the trend of the second impedance data changing with the state of charge.

[0178] In one embodiment, the plurality of different states of charge include a plurality of states of charge with values ​​between 50% and 100%.

[0179] In one embodiment, a difference between a maximum value and a minimum value among the plurality of different states of charge is greater than 40%.

[0180] In one embodiment, the acquisition module 10 is also used to collect multiple charge states of the battery to be tested during the charging process, and multiple impedance data corresponding to the multiple charge states, one charge state corresponds to one impedance data; determine a first relationship that satisfies the relationship between the multiple charge states and the multiple impedance data collected during the charging process; determine multiple first impedance data under multiple different charge states according to the first relationship, and the multiple different charge states are preset.

[0181] In one embodiment, the processing module 20 is further used to clear abnormal charge states among the multiple charge states collected during the charging process and the impedance data corresponding to the abnormal charge states before the acquisition module 10 determines that a first relationship between the multiple charge states and the multiple impedance data collected during the charging process is satisfied, and to clear abnormal impedance data among the multiple impedance data collected during the charging process and the charge states corresponding to the abnormal impedance data.

[0182] To achieve the above objectives, an embodiment of the present invention further provides a battery lithium deposition detection system, which executes the above battery lithium deposition detection method.

[0183] To achieve the above-mentioned purpose, an embodiment of the present invention further proposes a storage medium, on which a program is stored, and when the program is executed by a processor, the battery lithium deposition detection method as described above is implemented.

[0184] Since the storage medium adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0185] 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 battery lithium deposition detection method, characterized in that: The battery lithium deposition detection method comprises: Acquire a plurality of first impedance data of the battery to be tested under a plurality of different charge states during the charging process; Acquire a plurality of second impedance data of the battery to be tested under the plurality of different charge states during the discharge process; Whether lithium is deposited in the battery to be tested during charging is determined according to the plurality of first impedance data and the plurality of second impedance data.

2. The battery lithium deposition detection method according to claim 1, characterized in that: The step of determining whether lithium is deposited in the battery to be tested during charging according to the plurality of first impedance data and the plurality of second impedance data comprises: Whether lithium is deposited in the battery to be tested during charging is determined according to a trend of a change in the first impedance data relative to the second impedance data.

3. The battery lithium deposition detection method according to claim 2, characterized in that: Before determining whether the battery to be tested has lithium deposition during charging according to the trend of the first impedance data relative to the second impedance data, the method further includes: For each of the plurality of different states of charge, calculating a difference between the first impedance data and the second impedance data in each state of charge; A trend of a change of the first impedance data relative to the second impedance data is determined according to the plurality of differences under the plurality of different states of charge.

4. The battery lithium deposition detection method according to claim 3, characterized in that: Before determining the change trend of the first impedance data relative to the second impedance data according to the plurality of differences under the plurality of different states of charge, the method further includes: Determine whether there are multiple consecutive states of charge where the difference is not 0; When the difference values ​​under a plurality of consecutive charge states are not zero, a step of determining a change trend of the first impedance data relative to the second impedance data according to the plurality of difference values ​​under the plurality of different charge states is performed.

5. The battery lithium deposition detection method according to claim 2, characterized in that: Before determining whether the battery to be tested has lithium deposition during charging according to the trend of the first impedance data relative to the second impedance data, the method further includes: For each of the plurality of different states of charge, calculating a ratio of the first impedance data to the second impedance data in each state of charge; A trend of a change in the first impedance data relative to the second impedance data is determined according to the multiple ratios under the multiple different states of charge.

6. The battery lithium deposition detection method according to claim 5, characterized in that: Before determining the trend of the change of the first impedance data relative to the second impedance data according to the multiple ratios under the multiple different states of charge, the method further includes: Determining whether there are multiple consecutive states of charge where the ratio is not 1; When the ratio under a plurality of consecutive charge states is not 1, the step of determining a change trend of the first impedance data relative to the second impedance data based on the plurality of ratios under the plurality of different charge states is performed again.

7. The battery lithium deposition detection method according to claim 1, characterized in that: The step of determining whether lithium is deposited in the battery to be tested during charging according to the plurality of first impedance data and the plurality of second impedance data comprises: determining a trend of the first impedance data as the state of charge changes; determining a trend of the second impedance data as the state of charge changes; Whether lithium is deposited in the battery to be tested during charging is determined according to a trend of the first impedance data changing with the state of charge and a trend of the second impedance data changing with the state of charge.

8. The battery lithium deposition detection method according to any one of claims 1 to 7, characterized in that: The multiple different states of charge include multiple states of charge with values ​​between 50% and 100%.

9. The battery lithium deposition detection method according to any one of claims 1 to 8, characterized in that: A difference between a maximum value and a minimum value among the plurality of different states of charge is greater than 40%.

10. The battery lithium deposition detection method according to any one of claims 1 to 9, characterized in that: The step of obtaining a plurality of first impedance data of the battery to be tested under a plurality of different charge states during the charging process includes: During the charging process, a plurality of charge states of the battery to be tested during the charging process and a plurality of impedance data corresponding to the plurality of charge states are collected, wherein one charge state corresponds to one impedance data; Determine a first relational expression satisfying the relationship between the multiple charge states and the multiple impedance data collected during the charging process; A plurality of first impedance data under a plurality of different states of charge are determined according to the first relationship, and the plurality of different states of charge are preset.

11. The battery lithium deposition detection method according to claim 10, characterized in that: Before determining a first relationship that satisfies the relationship between the multiple charge states and the multiple impedance data collected during the charging process, the method further includes: Clearing abnormal charge states among the multiple charge states collected during the charging process and impedance data corresponding to the abnormal charge states; Abnormal impedance data among a plurality of impedance data collected during the charging process and a charge state corresponding to the abnormal impedance data are cleared.

12. A battery lithium deposition detection device, characterized in that: The battery lithium deposition detection device comprises: An acquisition module, used for acquiring a plurality of first impedance data of the battery to be tested under a plurality of different charge states during a charging process, and also used for acquiring a plurality of second impedance data of the battery to be tested under the plurality of different charge states during a discharging process; The processing module is used to determine whether the battery to be tested has lithium deposition during charging according to the multiple first impedance data and the multiple second impedance data.

13. A battery lithium deposition detection system, characterized in that: The battery lithium deposition detection method as described in any one of claims 1 to 11 is executed on the system.

14. A storage medium, characterized in that: The storage medium stores a program, and when the program is executed by the processor, the battery lithium deposition detection method as described in any one of claims 1 to 11 is implemented.

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