Battery lithium precipitation detection method and device

Abstract

The invention relates to the technical field of batteries, and particularly provides a battery lithium precipitation detection method and device, and the method comprises the following steps: obtaining a differential curve of strain data of a target battery as a first change curve; acquiring a differential curve of the strain data of the reference battery as a second change curve; and comparing maximum peak intensity values of the first change curve and the second change curve, and judging whether lithium precipitation occurs in the target battery or not. According to the battery lithium precipitation detection method provided by the invention, the battery cell does not need to be disassembled, the safety is improved, meanwhile, whether lithium precipitation exists in the battery or not can be quickly and accurately judged, and the problems that a nondestructive detection method in the prior art is relatively poor in evaluation precision and low in accuracy are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method and device for detecting lithium deposition in batteries. Background Art

[0002] The fast charging performance of lithium-ion batteries is an important indicator of current market demand. However, excessive charging rate will cause lithium deposition on the surface of the negative electrode. At the same time, low-temperature charging is also likely to cause lithium deposition problems. The deposited lithium dendrites will seriously affect the battery capacity and cycle life, and there are certain safety risks.

[0003] Existing methods for detecting lithium deposition in lithium-ion batteries include disassembly and non-destructive testing. The disassembly method involves destructive disassembly of lithium-ion batteries, and then visually observing whether metallic lithium is deposited on the surface of the negative electrode. This method requires the destruction of the battery and there are serious safety hazards during the disassembly of the battery. It is easy for safety accidents to occur due to improper operation or poor production environment, resulting in property losses and even endangering the personal safety of workers. Therefore, non-destructive testing methods have become the current research focus of lithium deposition detection methods. However, the existing non-destructive testing methods have poor evaluation accuracy, which seriously affects the accuracy of lithium deposition evaluation, and there has been no report on non-destructive testing methods that use strain changes in lithium-ion batteries to identify lithium deposition.

[0004] Based on this technical background, the present invention proposes a battery lithium deposition detection method and device. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a battery lithium deposition detection method. The method detects battery lithium deposition without disassembling the battery cell, thereby improving safety. At the same time, it can quickly and accurately determine whether lithium is deposited inside the battery, solving the problem of poor evaluation precision and low accuracy of non-destructive testing methods in the prior art.

[0006] In order to achieve the above object, the first aspect of the present invention provides a battery lithium deposition detection method, the method comprising the following steps:

[0007] Acquire a differential curve of strain data of a target battery as a first variation curve;

[0008] Acquire a differential curve of strain data of a reference battery as a second variation curve;

[0009] Compare the maximum values ​​of the peak intensities of the first change curve and the second change curve to determine whether lithium deposition occurs in the target battery.

[0010] The second aspect of the present invention provides a battery lithium deposition detection device used in the above method, comprising:

[0011] A strain sensor, disposed on the target battery pack, for detecting strain data of the target battery pack;

[0012] A charging module, used for charging the target battery pack;

[0013] A BMS acquisition processing module, used to collect strain data and voltage data of the target battery pack, calculate the first-order differential of the strain data with respect to the voltage data to obtain a first strain differential, and use a variation curve of the first strain differential with respect to the voltage data as a first variation curve; and used to compare the peak intensity maximum values ​​of the first variation curve and the second variation curve to determine whether a lithium deposition alarm signal is issued;

[0014] The second variation curve is a differential curve of strain data of a reference battery;

[0015] The target battery group includes at least one target battery. When the number of the at least one target battery is more than one, each target battery is connected in parallel, in series, or in a combination of series and parallel.

[0016] The technical effects of the present invention include:

[0017] (1) The battery lithium deposition detection method proposed in the present invention does not require the battery cell to be disassembled for lithium deposition detection, thereby improving safety. At the same time, it can quickly and accurately determine whether lithium deposition occurs inside the battery, thereby solving the problem of poor evaluation precision and low accuracy of non-destructive detection methods in the prior art.

[0018] (2) The battery lithium plating detection method proposed in the present invention is based on real-time collection of strain data and voltage data of the target battery and the reference battery to obtain a first variation curve and a second variation curve of the strain differential with voltage. By comparing the maximum peak intensity of the first variation curve with the peak intensity of the second variation curve, it is determined whether lithium plating occurs in the target battery, thereby improving the precision and accuracy of the non-destructive detection method.

[0019] (3) The battery lithium plating detection method proposed in the present invention ensures that lithium plating does not occur when the reference battery is charged with a low rate current by setting the reference battery to be charged with a low rate current. At the same time, by setting the target battery and the reference battery to be of the same type, size and composition, the stability, reliability and comparability of the reference standard are ensured.

[0020] (4) The battery lithium deposition detection method proposed in the present invention realizes refined management of high-rate current charging and / or low-temperature charging by monitoring whether the target battery is undergoing lithium deposition and adjusting the charging strategy in a timely manner.

[0021] (5) The battery lithium deposition detection device proposed in the present invention monitors the charging status of the target battery in real time through the BMS acquisition and processing module, and adjusts the charging strategy in real time according to the battery charging status, making the battery lithium deposition detection more intelligent, safe and efficient.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0024] Figure 1 The present invention is a schematic flow chart of the battery lithium deposition detection method proposed by the present invention.

[0025] Figure 2 A schematic diagram comparing the strain data versus voltage data curves of a target battery and a reference battery collected in real time in the battery lithium deposition detection method proposed in Example 1 of the present invention;

[0026] Figure 3 A schematic diagram comparing the first change curve and the second change curve in the battery lithium deposition detection method proposed in Example 1 of the present invention;

[0027] Figure 4 A schematic diagram comparing the curves of strain data versus voltage data of a target battery and a reference battery collected in real time in the battery lithium deposition detection method proposed in Example 2 of the present invention;

[0028] Figure 5 A schematic diagram comparing the first change curve and the second change curve in the battery lithium deposition detection method proposed in Example 2 of the present invention;

[0029] Figure 6 A schematic diagram showing a comparison of curves of strain data versus voltage data of a target battery and a reference battery collected in real time in a battery lithium deposition detection method according to Embodiment 3 of the present invention;

[0030] Figure 7 A schematic diagram comparing the first change curve and the second change curve in the battery lithium deposition detection method proposed in Example 3 of the present invention;

[0031] Figure 8 A schematic diagram showing a comparison of curves of strain data versus voltage data of a target battery and a reference battery collected in real time in a battery lithium deposition detection method according to Embodiment 4 of the present invention;

[0032] Fig. 9 A schematic diagram comparing the first change curve and the second change curve in the battery lithium deposition detection method proposed in Example 4 of the present invention;

[0033] Fig.10This is a schematic diagram of the process of detecting battery lithium deposition by the battery lithium deposition detection device proposed in Example 5 of the present invention.

[0034] Description of reference numerals:

[0035] uε-strain data, duε / dV-the first order differential of strain data to voltage data, Voltage-voltage data. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0037] In the present invention, unless otherwise specified, directional words such as "upper" and "lower" generally refer to the upper and lower parts of a device in normal use. Figure 1 In the drawing direction, "inside" and "outside" refer to the outline of the device. In addition, the terms "first, second, third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first, second, third" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0038] The present invention provides a method for detecting lithium deposition in a battery. Figure 1 As shown, the method comprises the following steps:

[0039] Acquire a differential curve of strain data of a target battery as a first variation curve;

[0040] Acquire a differential curve of strain data of a reference battery as a second variation curve;

[0041] Compare the maximum values ​​of the peak intensities of the first change curve and the second change curve to determine whether lithium deposition occurs in the target battery.

[0042] In the present invention, the battery cell does not need to be disassembled to detect lithium deposition, which improves safety. At the same time, it can quickly and accurately determine whether lithium deposition occurs inside the battery, solving the problem of poor assessment precision and low accuracy of non-destructive testing methods in the prior art.

[0043] According to the present invention, obtaining a differential curve of strain data of a target battery includes: charging the target battery, collecting strain data and voltage data of the target battery in real time, calculating a first-order differential of the strain data with respect to the voltage data to obtain a first strain differential, and using a variation curve of the first strain differential with respect to the voltage data as a first variation curve;

[0044] Acquiring a differential curve of the strain data of the reference battery includes: acquiring a first-order differential of the strain data of the reference battery to the voltage data as a second strain differential, and taking a curve of the second strain differential changing with the voltage data as a second changing curve.

[0045] According to the present invention, obtaining the first-order differential of the strain data of the reference battery to the voltage data as the second strain differential includes:

[0046] The reference battery is charged with a low-rate current, the strain data and voltage data of the reference battery are collected in real time, and the first-order differential of the strain data with respect to the voltage data is calculated to obtain a second strain differential. Alternatively, when the reference battery is charged with a low-rate current, the model of the reference battery is simulated to obtain the first-order differential of the strain data with respect to the voltage data as the second strain differential.

[0047] In the present invention, based on the real-time collection of strain data and voltage data of the target battery and the reference battery, a first change curve and a second change curve of strain differential with voltage are obtained. By comparing the maximum values ​​of the peak intensities of the first change curve and the second change curve, it is determined whether lithium plating occurs in the target battery, thereby improving the precision and accuracy of the nondestructive testing method.

[0048] In the present invention, by setting the reference battery to be charged at a low rate current, it is ensured that lithium plating does not occur when the reference battery is charged at a low rate current. At the same time, by setting the target battery and the reference battery to be the same in type, size and composition, the stability, reliability and comparability of the reference standard are ensured.

[0049] Preferably, charging is constant current charging;

[0050] The low rate current is 0.05C~0.3C,

[0051] The temperature for low rate current charging is 25℃~45℃.

[0052] According to the present invention, the target battery and the reference battery are of the same type, size and composition;

[0053] The location points of the target battery and reference battery strain data collected in real time are the same;

[0054] The location point is any point on the battery surface, battery side, or battery bottom, preferably a point on the battery surface close to the positive electrode ear or the negative electrode ear.

[0055] In the present invention, the positive electrode active material of the target battery can be one or more of LiFePO4, LiMnxFe1-xPO4, LiMn2O4, LiCoO2, LiNixCoyMnzO2 (0<x, y, z<1, x+y+z=1); the negative electrode active material can be one or more of graphite, silicon carbon, mesophase carbon microspheres, hard carbon, and soft carbon.

[0056] In the present invention, by monitoring whether the target battery undergoes lithium deposition and timely adjusting the charging strategy, refined management of high-rate current charging and / or low-temperature charging is achieved.

[0057] Preferably, when the maximum peak intensity of the first variation curve is greater than the maximum peak intensity of the second variation curve, lithium deposition occurs inside the target battery;

[0058] When the reference battery is charged at a low rate current, lithium plating does not occur.

[0059] Preferably, when the maximum value of the peak intensity of the first variation curve is greater than twice the maximum value of the peak intensity of the second variation curve, lithium deposition occurs inside the target battery.

[0060] The present invention also provides a battery lithium deposition detection device used in the above method, comprising:

[0061] A strain sensor is disposed on the target battery pack and is used to detect strain data of the target battery pack;

[0062] A charging module, used for charging the target battery pack;

[0063] The BMS acquisition processing module is used to collect the strain data and voltage data of the target battery pack, calculate the first-order differential of the strain data to the voltage data to obtain the first strain differential, and use the change curve of the first strain differential with the voltage data as the first change curve; and is used to compare the peak intensity maximum values ​​of the first change curve and the second change curve to determine whether to issue a lithium deposition alarm signal;

[0064] The second variation curve is a differential curve of the strain data of the reference battery;

[0065] The target battery group includes at least one target battery. When the number of the at least one target battery is more than one, each target battery is connected in parallel, in series, or in a combination of series and parallel.

[0066] Preferably, when the maximum peak intensity of the first variation curve is greater than the maximum peak intensity of the second variation curve, a lithium deposition alarm signal is issued.

[0067] Preferably, when the maximum value of the peak intensity of the first variation curve is greater than twice the maximum value of the peak intensity of the second variation curve, a lithium deposition alarm signal is issued;

[0068] The BMS acquisition and processing module is selected from any one of a computer, a single chip microcomputer, a DSP, and a FPGA.

[0069] In the present invention, the charging status of the target battery is monitored in real time through the BMS acquisition and processing module, and the charging strategy is adjusted in real time according to the battery charging status, so that the battery lithium plating detection is more intelligent, safe and efficient.

[0070] The present invention will be described in more detail below through specific embodiments.

[0071] Example 1

[0072] like Figure 1 , Figure 2 , Figure 3 As shown, a battery is selected as the target battery. The target battery is charged from 0% SOC to 100% SOC at a constant current of 0.5C at 25°C. The strain value uε1 and voltage value V1 of the target battery at 0% SOC to 100% SOC are collected, and the first-order differential of strain duε1 / dV1 of the target battery is calculated. The variation curve of the first-order differential of strain duε1 / dV1 of the target battery with the battery voltage V1 is plotted as the first variation curve.

[0073] A lithium-ion battery of the same model as the target battery is selected as a reference battery. The reference battery is charged at a low rate current of 0.3C at 45°C. The strain value uε' and voltage V' value of the reference battery at 0% SOC to 100% SOC are collected, and the first-order differential of strain duε' / dV' of the reference battery is calculated. The variation curve of the first-order differential of strain duε' / dV' of the reference battery with the battery voltage V is plotted as the second variation curve.

[0074] The maximum peak intensity of the duε1 / dV1-V1 curve of the target battery is smaller than the maximum peak intensity of the duε' / dV'-V' curve of the reference battery, so the target battery does not deposit lithium under this operating condition.

[0075] Example 2

[0076] like Figure 1 , Figure 4 , Figure 5 As shown, a battery is selected as the target battery. The target battery is charged from 0% SOC to 100% SOC at a constant current of 1C at 25°C. The strain value uε2 and voltage V2 value of the target battery at 0% SOC to 100% SOC are collected, and the first-order differential of strain duε2 / dV2 of the target battery is calculated. The variation curve of the first-order differential of strain duε / dV2 of the target battery with the battery voltage V2 is plotted as the first variation curve.

[0077] The test of the reference battery is the same as that of Example 1.

[0078] The maximum peak intensity of the duε2 / dV2-V2 curve of the target battery is smaller than the maximum peak intensity of the duε' / dV'-V' curve of the reference battery, so the target battery does not deposit lithium under this operating condition.

[0079] Example 3

[0080] like Figure 1 , Figure 6 , Figure 7 As shown, a battery is selected as the target battery. The target battery is charged from 0% SOC to 100% SOC at a constant current of 1C at 10°C. The strain value uε3 and voltage V3 value of the target battery at 0% SOC to 100% SOC are collected, and the first-order differential of strain duε3 / dV3 of the target battery is calculated. The variation curve of the first-order differential of strain duε3 / dV3 of the target battery with the battery voltage V3 is plotted as the first variation curve.

[0081] The test of the reference battery is the same as that of Example 1.

[0082] The maximum peak intensity of the duε3 / dV3-V3 curve of the target battery is greater than the maximum peak intensity of the duε' / dV'-V' curve of the reference battery, so the target battery undergoes lithium deposition under this operating condition.

[0083] Example 4

[0084] like Figure 1 , Figure 8 , Fig. 9 As shown, a battery is selected as the target battery. The target battery is charged from 0% SOC to 100% SOC at a constant current of 1.5C at 10°C. The strain value uε4 and voltage V4 value of the target battery at 0% SOC to 100% SOC are collected, and the first-order differential of strain duε4 / dV4 of the target battery is calculated. The variation curve of the first-order differential of strain duε4 / dV4 of the target battery with the battery voltage V4 is plotted and used as the first variation curve.

[0085] The test of the reference battery is the same as that of Example 1.

[0086] The maximum peak intensity of the duε4 / dV4-V4 curve of the target battery is greater than the maximum peak intensity of the duε' / dV'-V' curve of the reference battery, so the target battery undergoes lithium deposition under this operating condition.

[0087] Example 5

[0088] like Fig.10 As shown, in this embodiment, a strain sensor is adhered to the surface of the target battery, and the acquisition line of the strain sensor is connected to the acquisition module of the BMS. The maximum peak intensity of the duε' / dV'-V' curve of the reference battery in Example 1 is used as the BMS alarm signal threshold. When the battery system detects that the duε / dV of the target battery is greater than 2 times the maximum value of duε' / dV', the BMS alarms and reduces the charging current in time.

[0089] The battery lithium deposition detection method proposed in the embodiment of the present invention does not need to disassemble the battery cell to detect battery lithium deposition, thereby improving safety. At the same time, it can quickly and accurately determine whether lithium deposition occurs inside the battery, thereby solving the problem of poor evaluation precision and low accuracy of non-destructive testing methods in the prior art. At the same time, the method is based on real-time acquisition of strain data and voltage data of the target battery and the reference battery to obtain a first change curve and a second change curve of strain differential with voltage change. By comparing the maximum values ​​of the peak intensities of the first change curve and the second change curve, it is determined whether lithium deposition occurs in the target battery, thereby improving the precision and accuracy of the non-destructive testing method.

[0090] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A battery lithium deposition detection method, characterized in that: The method comprises the following steps: Acquire a differential curve of strain data of a target battery as a first variation curve; Acquire a differential curve of strain data of a reference battery as a second variation curve; Compare the maximum values ​​of the peak intensities of the first change curve and the second change curve to determine whether lithium deposition occurs in the target battery.

2. The method according to claim 1, characterized in that: The step of obtaining a differential curve of the strain data of the target battery includes: charging the target battery, collecting the strain data and voltage data of the target battery in real time, calculating the first-order differential of the strain data with respect to the voltage data to obtain a first strain differential, and using a curve of the first strain differential changing with respect to the voltage data as a first change curve; The obtaining of the differential curve of the strain data of the reference battery includes: obtaining the first-order differential of the strain data of the reference battery with respect to the voltage data as the second strain differential, and taking the variation curve of the second strain differential with respect to the voltage data as the second variation curve.

3. The method according to claim 2, characterized in that The step of obtaining the first-order differential of the strain data of the reference battery to the voltage data as the second strain differential comprises: The reference battery is charged with a low-rate current, strain data and voltage data of the reference battery are collected in real time, and the first-order differential of the strain data with respect to the voltage data is calculated to obtain a second strain differential. Alternatively, when the reference battery is charged with a low-rate current, the first-order differential of the strain data with respect to the voltage data of the reference battery is obtained by simulating a model of the reference battery as the second strain differential.

4. The method according to claim 3, characterized in that The charging is constant current charging; The low rate current is 0.05C to 0.3C; The temperature of the low-rate current charging is 25° C. to 45° C.

5. The method according to claim 3, characterized in that: The target battery and the reference battery are of the same type, size and composition; The position points of the target battery and the reference battery strain data collected in real time are the same; The position point is any point on the battery surface, the battery side, or the battery bottom, and is preferably a point on the battery surface close to the positive electrode ear or the negative electrode ear.

6. The method according to claim 3, characterized in that When the maximum peak intensity of the first variation curve is greater than the maximum peak intensity of the second variation curve, lithium deposition occurs inside the target battery; The reference battery will not undergo lithium plating when charged with a low rate current.

7. The method according to claim 6, characterized in that When the maximum value of the peak intensity of the first variation curve is greater than twice the maximum value of the peak intensity of the second variation curve, lithium deposition occurs inside the target battery.

8. A battery lithium deposition detection device, characterized in that: include: A strain sensor, disposed on the target battery pack, for detecting strain data of the target battery pack; A charging module, used for charging the target battery pack; A BMS acquisition processing module, used to collect strain data and voltage data of the target battery pack, calculate the first-order differential of the strain data with respect to the voltage data to obtain a first strain differential, and use a variation curve of the first strain differential with respect to the voltage data as a first variation curve; and used to compare the peak intensity maximum values ​​of the first variation curve and the second variation curve to determine whether a lithium deposition alarm signal is issued; The second variation curve is a differential curve of strain data of a reference battery; The target battery group includes at least one target battery. When the number of the at least one target battery is more than one, each target battery is connected in parallel, in series, or in a combination of series and parallel.

9. The device according to claim 8, characterized in that When the maximum peak intensity of the first variation curve is greater than the maximum peak intensity of the second variation curve, a lithium deposition alarm signal is issued.

10. The device according to claim 9, characterized in that When the maximum value of the peak intensity of the first variation curve is greater than twice the maximum value of the peak intensity of the second variation curve, a lithium deposition alarm signal is issued; The BMS acquisition and processing module is selected from any one of a computer, a single chip microcomputer, a DSP, and a FPGA.

Images