Battery lithium plating detection and potential aging warning method and system

Abstract

A lithium ion battery lithium extraction detection method, potential aging early warning method, battery management system and battery system belong to the technical field of battery, the specific scheme includes the following steps: step one, in the relaxation process after the first charge of fresh battery ends, the first relaxation impedance A1 and the second relaxation impedance B1 after a fixed time interval are obtained, the difference between the second relaxation impedance B1 and the first relaxation impedance A1 is recorded as Z1; step two, in the relaxation process after the nth charge of the battery ends, the first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval are obtained, the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein, n>1; step three, if Z n is greater than Z1, it is determined that the battery occurs lithium extraction; if Z n is less than or equal to Z1, it is determined that the battery does not occur lithium extraction. The present application carries out nondestructive testing on the lithium extraction of lithium ion battery, and the detection method is simple and easy to operate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a lithium precipitation detection method, a potential aging early warning method, a battery management system and a battery system of a lithium ion battery. BACKGROUND

[0002] As a kind of green energy, lithium ion batteries have the advantages of high voltage, large energy density, no memory effect, etc., and have developed rapidly in recent years and have been widely used in many fields.

[0003] Lithium precipitation is an abnormal phenomenon that easily occurs in the charging process of a lithium ion battery, especially in the case of fast charging or low-temperature charging. When the electrode potential of graphite is lower than that of lithium, lithium ions gather on the surface of graphite and cannot be inserted in time, resulting in lithium precipitation. Lithium precipitation not only accelerates capacity decay and shortens the service life, but also the precipitated lithium may pierce the battery separator, causing a short circuit and thus causing safety problems. The above situations will accelerate the aging of lithium ion batteries, leading to reduced battery performance and even more serious consequences. Therefore, in order to ensure the normal use of the battery and reduce the risk, it is necessary to detect lithium precipitation in time and give early warning of potential aging.

[0004] In the related art, the disassembly method is gradually replaced by non-destructive testing. The disassembly method is a destructive detection method, which generally involves disassembling the battery after charging to observe and determine the lithium precipitation. This method cannot monitor the lithium precipitation of the battery in real time, and the operation is complex, which reduces the detection efficiency. Common non-destructive testing methods include thickness measurement method, differential capacity method, voltage relaxation method, etc. The lithium precipitation of the battery can be obtained without disassembling the battery. However, the change in battery thickness is not only caused by lithium precipitation, but also by gas production and electrode expansion, which will affect the battery thickness and cause measurement errors. The detection sensitivity of the differential capacity and voltage relaxation method is low, and only a large amount of lithium precipitation can be detected. In the testing process of lithium ion batteries, it is of great significance to develop a simple and accurate lithium precipitation detection and potential aging early warning method to determine the state of lithium ion batteries. SUMMARY

[0005] To solve the problems in the background art, the application provides a lithium ion battery lithium precipitation detection method, a potential aging early warning method, a battery management system and a battery system.

[0006] To achieve the above purpose, the application adopts the following technical solutions:

[0007] A lithium ion battery lithium precipitation detection method, comprising the following steps:

[0008] Step one, during the relaxation process after the first charging of the fresh battery, the first relaxation impedance A1 and the second relaxation impedance B1 after a fixed time interval are obtained, and the difference between the second relaxation impedance B1 and the first relaxation impedance A1 is recorded as Z1;

[0009] Step two, during the relaxation process after the n-th charging of the battery, the first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval are obtained, and the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein n>1;

[0010] Step three, if Z n is greater than Z1, it is determined that lithium precipitation occurs in the battery; if Z n is less than or equal to Z1, it is determined that lithium precipitation does not occur in the battery.

[0011] Further, the fixed time interval is 10-60 min.

[0012] Further, the temperature of the charging process, the relaxation process and the relaxation impedance obtaining process of the battery is the same, and is a constant temperature condition.

[0013] A potential aging early warning method of a lithium ion battery, comprising the following steps:

[0014] S1, during the relaxation process after the n-th charging of the battery, the first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval are obtained, and the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein n takes a value of 1 to a predetermined cycle number;

[0015] S2, a curve graph is drawn with the cycle number of the battery as the horizontal coordinate and Z n as the vertical coordinate, and if an extreme value appears in the curve graph, it is determined that the battery has a potential aging phenomenon.

[0016] Further, the extreme value is a critical value of potential aging of the battery.

[0017] Further, the fixed time interval is 10-60 min.

[0018] Further, the temperature of the charging process, the relaxation process and the relaxation impedance obtaining process of the battery is the same, and is a constant temperature condition.

[0019] A battery management system, comprising

[0020] The acquisition module is configured to acquire a first relaxation impedance A1 in a relaxation process after a first charging of a fresh battery ends and a second relaxation impedance B1 after a fixed time interval, and acquire a corresponding first relaxation impedance A n and the second relaxation impedance B after a fixed time interval n ; wherein n>1

[0021] The first determination module is configured to determine a difference between the second relaxation impedance B1 and the first relaxation impedance A1, denoted as Z1; and a difference between the second relaxation impedance B n and the corresponding first relaxation impedance A n , denoted as Z n .

[0022] The second determination module is configured to determine whether lithium precipitation occurs in the battery: if Z n is greater than Z1, it is determined that lithium precipitation occurs in the battery; and if Z n is less than or equal to Z1, it is determined that lithium precipitation does not occur in the battery.

[0023] The third determination module is configured to determine whether the battery has potential aging: a curve is drawn with the number of battery cycles as the horizontal coordinate and Z n as the vertical coordinate, and if the curve has an extreme value, it is determined that the battery has potential aging.

[0024] A battery system comprising the battery management system.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. The present application performs non-destructive testing on the lithium precipitation of lithium ion batteries, and the detection method is simple and easy to implement.

[0027] 2. The present application can provide early warning for potential aging of lithium ion batteries, ensure normal use of the battery, and reduce risks.

[0028] 3. The detection method in the present application is suitable for different models and sizes of batteries, and has a wide range of applications.

[0029] The present application solves the technical problem of delayed lithium precipitation detection and reduced battery service life caused by the fact that related lithium precipitation detection methods are not suitable for online detection, are complex to operate, and have a single function. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a flowchart of the lithium precipitation detection method and potential aging warning method of the lithium ion battery provided in embodiment 1;

[0031] Figure 2 is a relaxation impedance spectrum when lithium precipitation occurs in the lithium ion battery in embodiment 1;

[0032] Figure 3 is the relaxation impedance spectrum of the lithium ion battery in Example 1 when lithium precipitation does not occur;

[0033] Figure 4 is the relaxation impedance spectrum of the aged lithium ion battery in Example 1 when lithium precipitation occurs;

[0034] Figure 5 is the functional block diagram of the battery management system provided in Example 2;

[0035] Figure 6 is the functional block diagram of the battery system provided in Example 3;

[0036] In the figure, 51, the acquisition module, 52, the first determination module, 53, the second determination module, 54, the third determination module, 60, the battery, 61, the battery management system. DETAILED DESCRIPTION

[0037] The technical solutions in the present application will be described clearly and completely in combination with the drawings and examples. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all the other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application. DETAILED DESCRIPTION

[0039] A lithium ion battery lithium precipitation detection method, comprising the following steps:

[0040] Step one, in the relaxation process after the first charge of the fresh battery without lithium precipitation, the first relaxation impedance A1 and the second relaxation impedance B1 after a fixed time interval are obtained, and the difference between the second relaxation impedance B1 and the first relaxation impedance A1 is recorded as Z1; Z1 is the target reference value, and the target reference value is used to represent the critical value of lithium precipitation of the battery;

[0041] Step two, in the relaxation process after the n th charge of the battery, the first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval are obtained, and the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein, n>1;

[0042] Step three, if Z n is greater than Z1, it is determined that the battery has lithium precipitation; if Z n is less than or equal to Z1, it is determined that the battery does not have lithium precipitation.

[0043] Further, the fixed time interval is 10-60 min.

[0044] Furthermore, the charging process, relaxation process, and relaxation impedance acquisition process of the battery are all conducted at the same temperature, under isothermal conditions.

[0045] Lithium-ion batteries can be simplified into a repetitive process of charging, resting, and discharging during use, with lithium metal deposition occurring during the charging process. This invention focuses on the relaxation process after battery charging is completed, and provides a method for detecting lithium deposition in lithium-ion batteries.

[0046] The lithium plating detection method in this invention is a non-destructive testing method. By obtaining the first relaxation impedance of the lithium-ion battery after the nth charge cycle and the second relaxation impedance after a fixed time interval, it is determined whether lithium plating occurs in the lithium-ion battery during the charging process. Specific Implementation Method Two

[0048] A method for early warning of potential aging of lithium-ion batteries includes the following steps:

[0049] S1. During the relaxation process after the nth charging cycle of the battery, obtain the first relaxation impedance A. n and the second relaxation impedance B after a fixed time interval n The second relaxation impedance B n and the first relaxation impedance A n The difference is denoted as Z. n Where n ranges from 1 to the predetermined number of iterations;

[0050] S2, with the number of battery cycles as the x-axis, Z n Plot a curve on the ordinate. If the curve shows extreme values, it indicates that the battery has potential aging issues. n Z is used to characterize the extent of the lithium plating reaction. n The larger the value, the greater the degree of lithium plating reaction; as lithium plating continues, it causes battery aging, damage to materials and cells, and when Z... n After reaching its maximum value, Z... n It will decrease again, reaching an extreme value, Z. n Extreme values ​​are used to characterize the critical values ​​at which a battery may undergo potential aging. When Z... n The occurrence of extreme values ​​indicates that the battery has potential aging phenomena.

[0051] Furthermore, the fixed time interval is 10-60 minutes.

[0052] Furthermore, the charging process, relaxation process, and relaxation impedance acquisition process of the battery are all conducted at the same temperature, under isothermal conditions.

[0053] During the use of the lithium ion battery, with the progress of the cycle process, the materials and the battery cell will gradually age, causing the blocking of the intercalation channel, so that the lithium cannot be intercalated. Therefore, when Z n reaches the maximum value, due to the aging of the battery, Z n will decrease again, and an extreme value will appear, when Z n reaches the extreme value, it is determined that the battery has a potential aging phenomenon. Therefore, in the early stage of the battery cycle, the lithium precipitation can be diagnosed by the difference between the first relaxation impedance in the relaxation stage and the second relaxation impedance after a fixed time interval, and with the aging of the battery, in the later stage of the cycle, the potential aging of the battery can be warned in advance by analyzing Z n in the relaxation stage.

[0054] The lithium precipitation detection method and the potential aging warning method in the first embodiment and the second embodiment of the present application have a wide range of applications and can be applied to batteries of different models and different sizes. Embodiment three

[0056] A battery management system, comprising

[0057] an acquisition module, configured to acquire a first relaxation impedance A1 and a second relaxation impedance B1 after a fixed time interval in a relaxation process after the first cycle of charging of a fresh battery in which no lithium precipitation occurs, and to acquire a corresponding first relaxation impedance A n and a second relaxation impedance B n after a fixed time interval in a relaxation process after the n th cycle of charging; wherein n>1.

[0058] a first determination module, configured to determine the difference between the second relaxation impedance B1 and the first relaxation impedance A1, denoted as Z1; Z1 is the target reference value, and the target reference value is used to represent the critical value of lithium precipitation of the battery; the difference between the second relaxation impedance B n and the corresponding first relaxation impedance A n is denoted as Z n .

[0059] a second determination module, configured to determine whether the battery has lithium precipitation: if Z n is greater than Z1, it is determined that the battery has lithium precipitation; if Z n is less than or equal to Z1, it is determined that the battery does not have lithium precipitation.

[0060] a third determination module, configured to determine whether the battery has a potential aging: after a predetermined number of cycles, taking the cycle number of the battery as the abscissa and Z n as the ordinate to draw a curve, if the curve has an extreme value, it is determined that the battery has a potential aging phenomenon. Embodiment four

[0062] A battery system comprising a battery and the battery management system of embodiment three.

[0063] Embodiment 1

[0064] A lithium ion battery lithium precipitation detection method and potential aging early warning method, as shown in the figure, comprising the following steps: Figure 1

[0065] S01. In the relaxation process after the first charging of the fresh battery without lithium precipitation, the first relaxation impedance A1 and the second relaxation impedance B1 after a fixed time interval are obtained, and the difference between the second relaxation impedance B1 and the first relaxation impedance A1 is recorded as Z1; Z1 is the target reference value, which is used to represent the critical value of lithium precipitation of the battery;

[0066] S02. In the relaxation process after the n-th charging of the battery, the first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval are obtained, and the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein n>1;

[0067] S03. If Z n is greater than Z1, it is determined that the battery has lithium precipitation; if Z n is less than or equal to Z1, it is determined that the battery does not have lithium precipitation;

[0068] S04. Draw a curve with the number of battery cycles as the horizontal coordinate and Z n as the vertical coordinate, if the curve has an extreme value, it is determined that the battery has a potential aging phenomenon.

[0069] In the lithium precipitation diagnosis and potential aging early warning method of the battery, in the relaxation process after charging is completed, the first relaxation impedance corresponding to the battery and the second relaxation impedance after a fixed time interval are obtained, and the relaxation impedance difference Z n of the battery is determined according to the first relaxation impedance and the second relaxation impedance; the two relaxation impedance difference Z1 of the fresh battery without lithium precipitation is used as the target reference value, which is used to represent the critical value of lithium precipitation of the battery; in the case where Z n is greater than the target reference value Z1, it is determined that the battery has lithium precipitation, otherwise, it is determined that the battery does not have lithium precipitation; after the battery is cycled for a predetermined number of times, the difference Z n between the two relaxation impedances after charging is completed in each cycle is used to represent the degree of lithium precipitation reaction, the greater Z n , the greater the degree of lithium precipitation reaction; as the lithium precipitation of the battery continues, it will cause the aging of the battery and the damage of the materials and the battery cell, when Z n reaches the maximum value, due to the aging of the battery, Z​n It will decrease again, reaching an extreme value, Z. n Extreme values ​​are used to characterize the critical values ​​at which a battery may undergo potential aging. When Z... n The occurrence of extreme values ​​indicates potential aging in the battery. This method achieves the goal of determining lithium plating and potential aging in batteries through online detection of impedance change rate, thereby greatly simplifying the detection process and indirectly improving battery life and safety.

[0070] Figure 2 The relaxation impedance spectrum of the lithium-ion battery in Example 1 when lithium plating occurs is shown. Figure 2 It can be seen that after lithium plating occurs in the battery, during the resting relaxation stage, there is a significant difference between the first relaxation impedance measured at 1 minute and the second relaxation impedance measured after a fixed time interval of 15 minutes. This phenomenon indicates that the lithium deposited during charging undergoes re-intercalation during the resting relaxation stage, causing the relaxation impedance to increase with the lithium re-intercalation process. Therefore, the difference Z obtained from the first relaxation impedance and the second relaxation impedance... n This indicates that lithium plating has occurred in the secondary battery.

[0071] Figure 3 This is the relaxation impedance spectrum of the lithium-ion battery in this embodiment when lithium plating has not occurred. Figure 3 It can be seen that when lithium plating has not occurred in the battery, during the resting relaxation phase, there is a small difference Z between the first relaxation impedance measured at 1 minute and the second relaxation impedance after a fixed time interval of 15 minutes. n Therefore, when the difference Z obtained through the first relaxation impedance and the second relaxation impedance... n If the value is less than the target reference value Z1, it can be determined that the battery has not undergone lithium plating.

[0072] Figure 4 This is the relaxation impedance spectrum of the aged lithium-ion battery exhibiting lithium plating in this embodiment, derived from... Figure 4 It is known that as lithium plating continues, it will cause battery aging, damage to materials and cells, and when Z... n After reaching its maximum value, Z... n It will decrease again until it approaches 0. Therefore, before the battery ages, Z... n Extreme values ​​will appear, which can be utilized using Z. n Extreme values ​​provide early warning of potential battery aging.

[0073] Example 2

[0074] Based on the lithium plating detection and potential aging warning method for lithium-ion batteries provided in Example 1 above, this example further provides a system for implementing each step of Example 1. Figure 5 This is a functional block diagram of the battery management system provided in Embodiment 2, as follows: Figure 5 As shown, the battery management system includes:

[0075] The acquisition module 51 is configured to acquire the first relaxation impedance A1 in the relaxation process after the first cycle of fresh battery charging ends and the second relaxation impedance B1 after a fixed time interval, and acquire the corresponding first relaxation impedance A n and the second relaxation impedance B n after a fixed time interval in the relaxation process after the n th cycle of charging ends, where n > 1.

[0076] The first determination module 52 is configured to determine the difference between the second relaxation impedance B1 and the first relaxation impedance A1, denoted as Z1; Z1 is the target reference value, which is used to represent the critical value of the battery lithium precipitation; the second relaxation impedance B n and the corresponding first relaxation impedance A n , denoted as Z n .

[0077] The second determination module 53 is configured to determine whether the battery has lithium precipitation: if Z n is greater than Z1, it is determined that the battery has lithium precipitation; if Z n is less than or equal to Z1, it is determined that the battery does not have lithium precipitation.

[0078] The third determination module 54 is configured to determine whether the battery has potential aging: after a predetermined number of cycles, the battery cycle number is taken as the horizontal coordinate and Z n is taken as the vertical coordinate to draw a curve, if the curve has an extreme value, it is determined that the battery has potential aging phenomenon.

[0079] Since each unit in the embodiment can perform the method shown in the embodiment, the parts not described in detail in the embodiment can refer to the related description of the method. Figure 1 Figure 1

[0080] Embodiment 3

[0081] The embodiment further provides a battery system for implementing each step in the embodiment 1. Figure 6 The embodiment provides a functional block diagram of the battery system. As shown in the embodiment, the battery system includes a battery 60 and the battery management system 61 described above. The parts not described in detail in the embodiment can refer to the related description of the battery management system 61. Figure 6 Figure 1 Figure 5

[0082] ​​​​​Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature or implementation described herein. The specification can include implicit combinations of explicitly mentioned features and / or implicit combinations of implicitly mentioned features. Such combinations are also expressly included within the scope of the specification and an embodiment.

Claims

1. A method for detecting lithium precipitation of a lithium ion battery, characterized by: Comprising the following steps: Step one, in the relaxation process after the first charge of fresh battery, get the first relaxation impedance A1 and the second relaxation impedance B1 after fixed time interval, the difference between the second relaxation impedance B1 and the first relaxation impedance A1 is Z1; Step two, during the relaxation process after the end of the n-th cycle of charging, the first relaxation impedance A is obtained n and the second relaxation impedance B after a fixed time interval n , the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; Wherein, n>1; Step three, if Z n greater than Z1, it is determined that lithium precipitation occurs in the battery; if Z n less than or equal to Z1, it is determined that lithium precipitation does not occur in the battery.

2. The lithium precipitation detection method of the lithium ion battery according to claim 1, characterized in that: The fixed time interval is 10-60 min. 3.The lithium ion battery lithium precipitation detection method according to claim 1, characterized in that: The temperature of the charging process, relaxation process and relaxation impedance acquisition process of the battery is the same, which is constant temperature condition.

4. A method for potential aging warning of a lithium-ion battery, characterized in that: Comprising the following steps: S1, obtaining a first relaxation impedance A during a relaxation process after the end of the n th cycle of charging of the battery n and a second relaxation impedance B after a fixed time interval n , the difference between the second relaxation impedance B n and the first relaxation impedance A n is recorded as Z n ; wherein n takes a value from 1 to a predetermined number of cycles; S2, plot the curve with the battery cycle number as the horizontal coordinate and Z n as the vertical coordinate. If the curve has an extreme value, it is determined that the battery has a potential aging phenomenon.

5. A method of early warning of potential aging of a lithium-ion battery according to claim 4, characterized in that: The extreme value is the critical value of potential aging of the battery.

6. A method of early warning of potential aging of a lithium-ion battery as claimed in claim 4, wherein: The fixed time interval is 10-60 min.

7. A method of early warning of potential aging of a lithium-ion battery as claimed in claim 4, wherein: The temperature of the charging process, relaxation process and relaxation impedance acquisition process of the battery is the same, which is constant temperature condition.

8. A battery management system, characterized by: Comprising The acquisition module is configured to acquire a first relaxation impedance A1 in a relaxation process after a first charging of a fresh battery ends and a second relaxation impedance B1 after a fixed time interval, and acquire a corresponding first relaxation impedance A n and a second relaxation impedance B after a fixed time interval in a relaxation process after the n-th charging ends n ; wherein n>1. a first determination module configured to determine a difference between the second relaxation impedance B1 and the first relaxation impedance A1, denoted as Z1; and a second determination module configured to determine a difference between the second relaxation impedance B n and the corresponding first relaxation impedance A n , denoted as Z n . The second determining module is configured to determine whether lithium precipitation occurs in the battery: if Z n is greater than Z1, it is determined that lithium precipitation occurs in the battery; if Z n is less than or equal to Z1, it is determined that lithium precipitation does not occur in the battery. A third determining module is configured to determine whether the battery has potential aging, i.e., to plot a curve with the number of battery cycles as the horizontal coordinate and Z n as the vertical coordinate, and if the curve has an extreme value, it is determined that the battery has potential aging.

9. A battery system characterized by: The battery management system of claim 8.

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