Non-destructive diagnosis method for lithium plating in lithium-ion batteries

Abstract

The present application relates to the technical field of battery, especially relates to a lithium ion battery lithium precipitation lossless diagnosis method, which comprises the following steps: S1, analyzing the characteristic parameters of the electrochemical curve of the battery; S2, if the electrochemical curve characteristic parameter is less than zero, then proceed to the next step, otherwise return to the previous step; S3, placing a pressure sensing film on a pressure loading device, placing the battery on the pressure sensing film, and using the pressure loading device to apply a set pre-pressure to the battery; S4, cyclically charging and discharging the battery within a set time; S5, determining the lithium precipitation area using a display device in communication with the pressure sensing film; S6, using a neutron Bragg edge imaging method to perform lossless scanning on the lithium precipitation area to obtain a Bragg edge diffraction spectrum. The present application can analyze the lithium precipitation area and the content of lithium precipitation of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a non-destructive diagnostic method for lithium plating in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in production and daily life. During charging, Li+ ions are extracted from the positive electrode and inserted into the negative electrode. However, under abnormal conditions, such as insufficient lithium insertion space in the negative electrode, excessive resistance to Li+ insertion into the negative electrode, or Li+ ions extracting too quickly from the positive electrode but not inserting into the negative electrode in equal amounts, the Li+ ions that cannot insert into the negative electrode can only gain electrons on the surface of the negative electrode, thus forming silvery-white metallic lithium, a phenomenon known as lithium plating. Lithium plating not only degrades battery performance and significantly shortens cycle life but also limits the battery's fast-charging capacity and may cause disasters such as combustion and explosion. However, current technologies can only determine whether lithium plating occurs, but cannot analyze the lithium plating area or the amount of lithium plating in the lithium-ion battery, thus hindering further analysis and optimization of lithium-ion batteries.

[0003] Therefore, a non-destructive diagnostic method for lithium plating in lithium-ion batteries is needed to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a non-destructive diagnostic method for lithium plating in lithium-ion batteries, which can analyze the lithium plating area and the content of lithium plating in lithium-ion batteries.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A non-destructive diagnostic method for lithium plating in lithium-ion batteries includes the following steps:

[0007] S1. Analyze the characteristic parameters of the battery's electrochemical curve;

[0008] S2. If the characteristic parameters of the electrochemical curve are less than zero, proceed to the next step; otherwise, return to the previous step.

[0009] S3. Place a pressure-sensing membrane on the pressure loading device, place the battery on the pressure-sensing membrane, and apply a set pre-pressure to the battery using the pressure loading device.

[0010] S4. The battery is cycled through charging and discharging within a set time period;

[0011] S5. Determine the lithium plating region using a display device that is communicatively connected to the pressure-sensing membrane;

[0012] S6. The lithium plating region is non-destructively scanned using the neutron Bragg edge imaging characterization method to obtain the Bragg edge diffraction spectrum.

[0013] Furthermore, in step S1, the electrochemical curve is the voltage fluctuation curve of the battery.

[0014] Furthermore, in step S3, the pre-pressure is set according to the type and volume of the battery.

[0015] Furthermore, in step S3, a first pressure pad is placed on the upper surface of the battery, and a second pressure pad is provided on the lower surface of the pressure-sensing membrane.

[0016] Furthermore, the area of ​​the lower end face of the first pressure pad is larger than the area of ​​the upper end face of the battery.

[0017] Furthermore, the area of ​​the upper end face of the second pressure pad is larger than the area of ​​the lower end face of the battery.

[0018] Furthermore, in step S3, a pressure display is provided on the pressure loading device, and the pressure display is used to display the value of the pre-pressure.

[0019] Furthermore, in step S5, the display device displays different shades of color according to the pressure condition of the pressure-sensing membrane.

[0020] Furthermore, in step S5, a line mark is made in the lithium plating area.

[0021] The beneficial effects of this invention are:

[0022] This invention provides a non-destructive diagnostic method for lithium-ion battery lithium plating. It analyzes the characteristic parameters of the battery's chemical curve to determine the presence of lithium plating. If plating is present, the battery is placed on a pressure-sensing membrane of a pressure loading device. A predetermined pre-pressure is applied to the battery, and the battery is cycled through charge and discharge for a set time. Because the lithium plating sites expand relative to the non-plating sites, the force applied to the pressure-sensing membrane varies at different locations during charge and discharge. The lithium plating region is identified by a display device communicatively connected to the pressure-sensing membrane. Then, a non-destructive scan of the lithium plating region is performed using neutron Bragg edge imaging to obtain the Bragg edge diffraction spectrum. Since neutrons are sensitive to lithium and the light element C, the characteristic phase structures in the battery material (such as LiC6, LiC) are also considered. 12 Each phase has its corresponding neutron diffraction peak characteristics. By integrating and displaying the neutron Bragg edge diffraction spectra of these phases corresponding to a certain type of structure, a visualization of the distribution of different phases in the battery is formed, which enables quantitative analysis of lithium deposition. By using multiple methods in combination, it is possible to determine whether lithium deposition exists on the negative electrode surface, providing effective experimental evidence for the electrochemical performance analysis of lithium-ion batteries, thus providing a foundation for subsequent battery optimization. Attached Figure Description

[0023] Figure 1 This is a flowchart of a non-destructive diagnostic method for lithium plating in lithium-ion batteries according to the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings, not all of them.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] During charging, Li+ ions are extracted from the positive electrode and inserted into the negative electrode. However, when abnormal conditions occur, such as insufficient space for lithium insertion in the negative electrode, excessive resistance to Li+ insertion into the negative electrode, or Li+ ions being extracted from the positive electrode too quickly but unable to be inserted into the negative electrode in equal amounts, the Li+ ions that cannot be inserted into the negative electrode can only gain electrons on the surface of the negative electrode, thus forming silvery-white metallic lithium, resulting in lithium plating.

[0028] In order to perform localized and quantitative analysis of batteries exhibiting lithium plating, such as... Figure 1 As shown, this invention provides a non-destructive diagnostic method for lithium-ion battery lithium plating. The non-destructive diagnostic method for lithium-ion battery lithium plating includes the following steps:

[0029] S1. Analyze the characteristic parameters of the battery's electrochemical curve;

[0030] S2. If the characteristic parameters of the electrochemical curve are less than zero, proceed to the next step; otherwise, return to the previous step.

[0031] S3. Place a pressure-sensing membrane on the pressure loading device, place the battery on the pressure-sensing membrane, and apply a set pre-pressure to the battery using the pressure loading device.

[0032] S4. Cycle the battery to charge and discharge within the set time.

[0033] S5. Use a display device that is in communication with the pressure-sensing membrane to determine the lithium plating area;

[0034] S6. The lithium plating region was non-destructively scanned using the neutron Bragg edge imaging characterization method to obtain the Bragg edge diffraction spectrum.

[0035] Based on the characteristic parameters of the electrochemical curve, it is determined whether lithium plating has occurred in the battery. The lithium plating region is obtained based on the measurement of the battery's non-uniform pressure distribution. Neutron Bragg edge imaging is used to test the battery and obtain the distribution of the actual lithium insertion / extraction states in the lithium plating region under different charging states of the internal electrode materials. This allows for quantitative analysis of the active reversible lithium content in different regions and determination of the spatial distribution of irreversible lithium loss within the battery. Combining this with measurements of the pressure distribution generated in the lithium plating region in space increases the accuracy of the spatially resolved quantitative analysis of lithium plating.

[0036] Further, in step S1, the electrochemical curve is the battery's voltage fluctuation curve. Specifically, by charging and discharging the battery within a set time period using a testing station, the relationship between the second derivative of the voltage and the voltage is obtained, which is the voltage fluctuation curve. Based on the fact that the voltage fluctuation curve shows a value less than zero in the initial stage of discharge, it can be determined that lithium plating has occurred in the lithium battery.

[0037] Furthermore, in step S3, the pre-pressure is set according to the type and volume of the battery. Using different pre-pressures for different batteries enables accurate testing of different batteries.

[0038] Furthermore, in step S3, a first pressure pad is placed on the upper surface of the battery, and a second pressure pad is placed on the lower surface of the pressure-sensing membrane. By setting the first and second pressure pads, the pressure loading device can be prevented from directly applying force to the battery, thus protecting the battery.

[0039] Furthermore, the area of ​​the lower end face of the first pressure pad is larger than the area of ​​the upper end face of the battery. The area of ​​the upper end face of the second pressure pad is larger than the area of ​​the lower end face of the battery. With the above configuration, when pressure is applied to the battery using the pressure loading device, the first and second pressure pads ensure that the pressure is evenly distributed on the battery. This guarantees the accuracy of the pressure sensing membrane test.

[0040] Furthermore, in step S3, a pressure display is installed on the pressure loading device to show the pre-pressure value. By installing the pressure display, the pre-pressure applied to the battery can be displayed, facilitating real-time observation by testing personnel and preventing damage to the battery due to excessive pre-pressure.

[0041] Furthermore, in step S5, the display device displays different shades of color based on the pressure applied to the pressure-sensing membrane. Specifically, the inspector can directly read the pressure distribution within the battery space from the display device, and the pressure magnitude is determined by the depth of the color displayed on the pressure-sensing membrane, facilitating the inspector's rapid identification of lithium plating areas.

[0042] Furthermore, in step S5, lines are drawn to mark the lithium-plated region. These lines facilitate rapid location determination during subsequent non-destructive scanning of the lithium-plated region using the neutron Bragg edge imaging characterization method, thus improving detection efficiency.

[0043] Furthermore, the distribution of reversible and irreversible lithium content in the battery was confirmed using neutron Bragg edge imaging. Analysis of Bragg edge diffraction spectra revealed the specific phase structure of the electrode material in different regions of the battery, and the intensity of the diffraction peaks corresponded to the content of that phase. By comparing the content of the two phases in the charged and discharged states, the content of lithium reversibly inserted and extracted into the lithium battery electrode material in that region could be determined, along with the content of irreversible dead lithium at that location. This enabled the measurement of the distribution of reversible and irreversible lithium content throughout the entire lithium battery.

[0044] Specifically, for the negative electrode side of a battery, such as a graphite negative electrode, if there is a high content of lithium-ion intercalation in its structure, the neutron Bragg edge diffraction peak of that phase will be stronger. Therefore, it can be determined that there is less lithium plating in that region, and the corresponding region will experience relatively less pressure from battery expansion. Conversely, if there is more lithium plating in a certain region of the battery, there will be fewer lithium ions reversibly entering the negative electrode structure. The diffraction peak of the phase (LiC6) corresponding to the lithium intercalation state (discharge state) of the negative electrode will be weaker. Therefore, more lithium ions will accumulate in that region through lithium plating, forming greater local pressure. For the local area of ​​a battery with irreversible lithium plating, this region contains multiple crystal structures in the charging state. Taking the graphite negative electrode as an example, it contains LiC6, LiC... 12 and LiC 24 By comparing the peak intensities of diffraction peaks of different phases in this region, the proportions of different phases can be compared, thus revealing the actual lithium intercalation content and inferring the irreversible lithium content in the region, thereby achieving quantitative analysis of lithium deposition.

[0045] The above method can also be used for the detection and analysis of metal ion precipitation in secondary rechargeable batteries such as sodium-ion batteries, lithium-sulfur batteries, and lithium-air batteries, which will not be elaborated on here.

[0046] Compared to current research methods on lithium plating in lithium batteries, this method offers more accurate and comprehensive measurements of lithium plating. By analyzing the spatial distribution of lithium plating in lithium batteries, we can determine the underlying causes of this behavior, providing a framework for understanding the triggering mechanisms behind lithium plating and laying the foundation for subsequent battery optimization.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A non-destructive diagnostic method for lithium plating in lithium-ion batteries, characterized in that, Includes the following steps: S1. Analyze the characteristic parameters of the battery's electrochemical curve; S2. If the characteristic parameters of the electrochemical curve are less than zero, proceed to the next step; otherwise, return to the previous step. S3. Place a pressure-sensing membrane on the pressure loading device, place the battery on the pressure-sensing membrane, and apply a set pre-pressure to the battery using the pressure loading device. S4. The battery is cycled through charging and discharging within a set time period; S5. Determine the lithium plating area using a display device that is communicatively connected to the pressure-sensing membrane; S6. The lithium plating region is non-destructively scanned using the neutron Bragg edge imaging characterization method to obtain the Bragg edge diffraction spectrum. In step S5, the display device displays different shades of color according to the pressure condition of the pressure-sensing membrane.

2. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 1, characterized in that, In step S1, the electrochemical curve is the voltage fluctuation curve of the battery.

3. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 1, characterized in that, In step S3, the pre-pressure is set according to the type and volume of the battery.

4. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 1, characterized in that, In step S3, a first pressure pad is placed on the upper surface of the battery, and a second pressure pad is placed on the lower surface of the pressure sensing membrane.

5. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 4, characterized in that, The area of ​​the lower end face of the first pressure pad is greater than the area of ​​the upper end face of the battery.

6. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 4, characterized in that, The area of ​​the upper end face of the second pressure pad is greater than the area of ​​the lower end face of the battery.

7. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 1, characterized in that, In step S3, a pressure display is installed on the pressure loading device, and the pressure display is used to display the value of the pre-pressure.

8. The non-destructive diagnostic method for lithium plating in lithium-ion batteries according to claim 1, characterized in that, In step S5, the lithium plating area is marked with lines.

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