Lithium embedding uniformity detection device for negative plate of battery

Abstract

The utility model provides a lithium embedding uniformity detection device for a negative plate of a battery. The lithium embedding uniformity detection device comprises a voltage detection piece and a reference metal sheet isolated from the negative plate to be tested of the battery, the reference metal sheet is infiltrated with an electrolyte; the voltage detection piece is provided with a negative conductive end and a positive conductive end, the negative conductive end is electrically connected with the reference metal sheet, and the positive conductive end can move relative to the negative plate to be tested so as to abut against different positions of the negative plate to be tested; the voltage detection part is used for detecting potential differences between the to-be-tested negative plate and the reference metal plate at different positions, so that the lithium intercalation amount of the to-be-tested negative plate is determined according to the potential differences, and the lithium intercalation condition of the to-be-tested negative plate can be judged.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a device for detecting the uniformity of lithium intercalation in the negative electrode of a battery. Background Technology

[0002] Batteries, such as lithium-ion batteries, are widely used in various electronic products and new energy vehicles. A lithium-ion battery consists of a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. The positive and negative electrodes are immersed in an electrolyte, allowing lithium ions to be inserted into the negative electrode via the electrolyte, thus achieving directional conduction of lithium ions to complete the charging process of the battery.

[0003] When the lithium intercalation capability at a certain location on the negative electrode is poor, the negative electrode is at risk of lithium plating, resulting in lithium dendrites. The deposited metallic lithium reacts with the electrolyte, consuming active lithium and accelerating battery capacity decay. Furthermore, lithium dendrites can easily puncture the separator, causing a short circuit and leading to safety issues and battery failure. Therefore, determining the lithium intercalation status of the negative electrode is a crucial issue that urgently needs to be addressed. Utility Model Content

[0004] In view of this, the present invention aims to provide a device for detecting the uniformity of lithium intercalation in the negative electrode of a battery, thereby determining the lithium intercalation status of the negative electrode.

[0005] This utility model provides a device for detecting the uniformity of lithium intercalation in the negative electrode of a battery, including a voltage detection element and a reference metal sheet isolated from the negative electrode of the battery to be tested.

[0006] The reference metal sheet is impregnated with an electrolyte; the voltage detection device has a negative conductive end and a positive conductive end, the negative conductive end is electrically connected to the reference metal sheet, and the positive conductive end can move relative to the negative electrode sheet to be tested to abut against different positions on the negative electrode sheet to be tested.

[0007] The voltage detection device is used to detect the potential difference between the negative electrode sheet under test and the reference metal sheet at different positions, so as to determine the lithium intercalation amount of the negative electrode sheet under test based on the potential difference.

[0008] Optionally, a connector is provided between the reference metal sheet and the negative conductive terminal;

[0009] The reference metal sheet and the negative conductive terminal are connected by the connector.

[0010] Optionally, the connector is made of conductive adhesive.

[0011] Optionally, the voltage detection device includes a negative probe, one end of which is formed as the negative conductive terminal;

[0012] The connector is detachably connected to at least one of the reference metal sheet and the negative electrode probe.

[0013] Optionally, one end of the connector is connected to the reference metal sheet, and the other end of the connector abuts against the negative electrode probe;

[0014] The connector can extend and retract in a first direction, so that the negative conductive end can move toward the reference metal sheet to abut against the reference metal sheet, or move toward the reference metal sheet to separate from the reference metal sheet.

[0015] Optionally, the connector includes a spring;

[0016] The spring is sleeved on the outer periphery of the negative probe; the negative probe has an abutting protrusion extending radially along the negative probe; the other end of the spring abuts against the side of the abutting protrusion facing the reference metal sheet.

[0017] Optionally, the battery negative electrode lithium intercalation uniformity detection device further includes a separator, and the reference metal sheet is isolated from the negative electrode to be tested through the separator;

[0018] The voltage detection device includes a negative probe, one end of which is formed as the negative conductive terminal; the diaphragm is located at the negative conductive terminal, and the area of ​​the diaphragm is larger than the area of ​​the reference metal sheet, so that the diaphragm is drawn together from the side of the reference metal sheet away from the negative conductive terminal toward the outer periphery of the negative probe and connected to the negative probe.

[0019] Optionally, the diaphragm is secured to the outer periphery of the negative electrode probe by a binding member.

[0020] Optionally, the diaphragm includes an isolation portion and at least two connecting portions; the isolation portion is located on the side of the reference metal sheet opposite to the negative conductive end;

[0021] At least two of the connecting portions are connected circumferentially to the outer periphery of the isolation portion and are connected to the negative probe;

[0022] The end of the connecting portion that is connected to the isolation portion is 3mm-6mm away from the outer edge of the reference metal sheet.

[0023] Optionally, a support member is provided between the negative electrode probe and the diaphragm;

[0024] The support extends along the second direction, and the projection of the reference metal sheet on the support is located within the area enclosed by the outer contour of the support, so that the diaphragm abuts against the outer edge of the support when it is closed.

[0025] The support member has a clearance hole for the negative electrode probe to pass through so that the negative electrode conductive end abuts against the reference metal sheet; and / or, the support member is a rubber gasket.

[0026] The lithium intercalation uniformity detection device for the negative electrode of the battery provided in this application includes a voltage detection element and a reference metal sheet isolated from the negative electrode to be tested. The reference metal sheet is immersed in electrolyte. The negative conductive end of the voltage detection element is electrically connected to the reference metal sheet, and the positive conductive end of the voltage detection element can move relative to the negative electrode to be tested to abut against different positions on the negative electrode to be tested. This forms an electrical circuit between the reference metal sheet and the negative electrode to be tested, and the voltage detection element is used to detect the potential difference between the negative electrode to be tested and the reference metal sheet at different positions, so as to determine the amount of lithium intercalation of the negative electrode to be tested based on the potential difference. This method facilitates the movement of the positive conductive terminal on the negative electrode under test, and by using the potential difference detected by the voltage detection device at the corresponding position and the potential of the reference metal sheet, the potential at different positions of the negative electrode under test can be obtained. Since the potential of the negative electrode corresponds to the amount of lithium intercalation, the amount of lithium intercalation at the corresponding position of the negative electrode under test can be obtained by measuring the potential at different positions. This allows for the determination of the lithium intercalation status at different positions of the negative electrode under test. By comparing the amount of lithium intercalation at different positions of the negative electrode under test, the uniformity of lithium intercalation can be determined. This can, to some extent, prevent lithium plating on the negative electrode under test due to poor uniformity of lithium intercalation, thereby reducing the consumption of active lithium and mitigating battery capacity decay to some extent. At the same time, this method can also, to some extent, prevent lithium dendrites from piercing the battery separator and causing a short circuit, thus ensuring battery safety and cycle life. Furthermore, this method can provide a certain reference for research on issues such as battery capacity and life decay.

[0027] Meanwhile, compared to the solution of fixing the positive conductive end and the negative electrode sheet to be tested together, this method can improve the detection efficiency while detecting the uniformity of lithium intercalation of the negative electrode sheet to be tested, and eliminates the need to set up multiple positive conductive ends, thus simplifying the detection device. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the lithium intercalation uniformity detection device for the negative electrode sheet of the battery according to an embodiment of the present invention;

[0029] Figure 2This is a schematic diagram of the structure of the negative electrode probe and the reference metal sheet connected by a spring according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the diaphragm in one embodiment of the present invention, where the connecting portion has a separating part;

[0031] Figure 4 This is a schematic diagram of the structure of a support member provided between the negative electrode probe and the diaphragm according to an embodiment of the present invention;

[0032] Figure 5 This is a diagram showing the relationship between the lithium potential of the negative electrode and the state of charge of the battery during the charging process of a normal battery according to an embodiment of this utility model.

[0033] Figure 6 This is a schematic diagram of the lithium intercalation uniformity detection device for the negative electrode sheet of the battery described in this embodiment of the present invention during the third fold test of the negative electrode sheet to be tested.

[0034] Among them, 1. Voltage detection component; 11. Negative probe; 111. Negative conductive end; 112. Abutment protrusion; 12. Positive probe; 121. Positive conductive end; 2. Reference metal sheet; 3. Negative electrode sheet to be tested; 31. Negative electrode tab; 4. Connector; 5. Diaphragm; 51. Isolation part; 52. Connection part; 521. Separation part; 6. Support component; 61. First support component; 62. Second support component; 7. Binding component. Detailed Implementation

[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0036] A lithium-ion battery includes a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. The positive and negative electrodes are immersed in an electrolyte, and lithium ions can be inserted into the negative electrode through the electrolyte to achieve directional conduction of lithium ions and complete the charging process of the battery.

[0037] When the lithium intercalation capability at a certain location on the negative electrode is poor, the negative electrode is at risk of lithium plating, resulting in lithium dendrites. The deposited metallic lithium reacts with the electrolyte, consuming active lithium and accelerating battery capacity decay. Furthermore, lithium dendrites can easily puncture the separator, causing a short circuit and leading to safety issues and battery failure. Therefore, determining the lithium intercalation status of the negative electrode is a crucial issue that urgently needs to be addressed.

[0038] Based on this, this utility model provides a battery negative electrode lithium intercalation uniformity detection device. By setting a voltage detection element and a reference metal sheet isolated from the negative electrode to be tested, electrolyte is immersed on the reference metal sheet, and the negative conductive end of the voltage detection element is electrically connected to the reference metal sheet, the positive conductive end of the voltage detection element can move relative to the negative electrode to be tested to abut against different positions of the negative electrode to be tested. The voltage detection element detects the potential difference between the negative electrode to be tested and the reference metal sheet at different positions to obtain the lithium intercalation amount of the negative electrode at different positions, thereby determining the lithium intercalation status of the negative electrode.

[0039] The lithium intercalation uniformity detection device for the negative electrode sheet of the battery provided by this utility model will be described in detail below with reference to the accompanying drawings and through specific embodiments:

[0040] Reference Figures 1 to 6 As shown, this embodiment provides a battery negative electrode lithium intercalation uniformity detection device, including a voltage detection element 1 and a reference metal sheet 2 isolated from the negative electrode 3 to be tested in the battery.

[0041] The reference metal sheet 2 is impregnated with an electrolyte. The voltage detection element 1 has a negative conductive end 111 and a positive conductive end 121. The negative conductive end 111 is electrically connected to the reference metal sheet 2, and the positive conductive end 121 can move relative to the negative electrode sheet 3 to be tested, so as to abut at different positions on the negative electrode sheet 3 to be tested.

[0042] Specifically, the voltage detection device 1 is used to detect the potential difference between the negative electrode 3 under test and the reference metal sheet 2 at different positions, so as to determine the lithium insertion amount of the negative electrode 3 under test based on the potential difference.

[0043] For example, before testing, the negative electrode 3 to be tested needs to be collected. The collected negative electrode 3 still contains electrolyte. Therefore, the negative electrode 3 can be unfolded and immersed in electrolyte on the reference metal sheet 2, which serves as a conductor, so that the negative electrode 3 and the reference metal sheet 2 are in the same electrolyte. The negative conductive terminal 111 of the voltage detection device 1 is electrically connected to the reference metal sheet 2, and the positive conductive terminal 121 is in contact with the negative electrode 3 to form an electrical circuit between the reference metal sheet 2 and the negative electrode 3. The voltage detection device 1 can detect the potential difference between the position of the negative electrode 3 corresponding to the positive conductive terminal 121 and the reference metal sheet 2. Since the potential of the reference metal sheet 2 is known, the potential at the position where the negative electrode 3 is in contact with the positive conductive terminal 121 can be obtained.

[0044] Of course, in other embodiments, electrolyte may be added again to the collected negative electrode 3 before testing.

[0045] The reference metal sheet 2 can be, for example, a lithium sheet or a copper sheet. When the reference metal sheet 2 is a lithium sheet, the detected potential of the electrode 3 under test is the lithium potential.

[0046] For example, during battery charging, lithium ions are continuously inserted from the positive electrode to the negative electrode, which causes changes in the potential of the negative electrode and the amount of lithium inserted, and causes the battery's state of charge (SOC) to increase continuously.

[0047] For example, if the reference metal sheet 2 is selected as a lithium sheet, the lithium intercalation uniformity detection device for the negative electrode sheet provided in this embodiment can be used to detect the lithium potential of the negative electrode sheet of a normal battery (e.g., a normal full cell) under different SOC conditions. (Refer to...) Figure 5 The figure illustrates the relationship between the lithium potential on the negative electrode of a normal battery and the battery's state of charge (SOC). It shows a one-to-one correspondence between the two, and as the SOC increases, the amount of lithium intercalated on the negative electrode also increases. Therefore, the SOC of the battery reflects the amount of lithium intercalated on the negative electrode; that is, the potential of the negative electrode corresponds to the amount of lithium intercalated. When the difference in lithium intercalation at different locations is relatively small, the lithium intercalation uniformity of the tested negative electrode 3 can be considered good.

[0048] For example, lithium ions have a deposition potential. When the potential of the negative electrode plate drops to near or below the deposition potential of lithium ions, lithium ions will no longer be able to intercalate into the negative electrode plate and will be deposited on the surface of the negative electrode plate in the form of metallic lithium. For instance, when the battery is charged at high rates or at low temperatures, the potential at different locations of the negative electrode plate 3 under test, obtained by the lithium intercalation uniformity detection device provided in this embodiment, can be compared with the deposition potential of lithium ions to determine the lithium deposition status at different locations of the negative electrode plate 3 under test, thereby ensuring the accuracy of the lithium deposition status determination.

[0049] For example, when collecting the negative electrode 3 to be tested, it is necessary to prevent the negative electrode 3 from being oxidized. Therefore, the battery can be disassembled in a low-temperature and low-humidity space, and then the negative electrode 3 to be tested can be placed in a sealed container with a low-humidity and low-oxidation atmosphere. For example, the negative electrode 3 to be tested can be vacuum-sealed with an aluminum-plastic film; or the battery can be disassembled directly in a glove box. The entire testing process can also be carried out in an inert gas-protected environment, such as a glove box, to prevent the negative electrode 3 to be tested and the reference metal sheet 2 from being oxidized.

[0050] When disassembling the battery in the glove box, to prevent electrolyte loss from the negative electrode 3 under test, the negative electrode 3 can be unfolded several times before testing. After testing, the remaining negative electrode 3 can be unfolded and tested. Alternatively, while ensuring the entire testing process is error-free, the speed of operation can be increased to reduce electrolyte loss from the negative electrode 3.

[0051] For example, voltage detection device 1 can be a voltmeter, or it can also be a multimeter, oscilloscope, etc.

[0052] The battery negative electrode lithium intercalation uniformity detection device provided in this embodiment, by setting a voltage detection element 1 and a reference metal sheet 2 isolated from the negative electrode 3 to be tested, and by immersing the reference metal sheet 2 in electrolyte, the negative conductive end 111 of the voltage detection element 1 is electrically connected to the reference metal sheet 2, so that the positive conductive end 121 of the voltage detection element 1 can move relative to the negative electrode 3 to abut against different positions of the negative electrode 3 to form an electrical circuit between the reference metal sheet 2 and the negative electrode 3 to be tested, and the voltage detection element 1 is used to detect the potential difference between the negative electrode 3 to be tested and the reference metal sheet 2 at different positions, so as to determine the lithium intercalation amount of the negative electrode 3 to be tested based on the potential difference. This facilitates the movement of the positive conductive terminal 121 on the negative electrode 3 under test, and by using the potential difference at the corresponding position detected by the voltage detection device 1 and the potential of the reference metal sheet 2, the potential at different positions of the negative electrode 3 under test can be obtained. Since the potential of the negative electrode corresponds to the amount of lithium intercalation in the negative electrode, the amount of lithium intercalation at the corresponding position of the negative electrode 3 under test can be obtained by using the potential at different positions of the negative electrode 3 under test. This allows for the determination of the lithium intercalation status at different positions of the negative electrode 3 under test, and by comparing the amount of lithium intercalation at different positions of the negative electrode 3 under test, the uniformity of lithium intercalation in the negative electrode 3 under test can be determined. This can, to a certain extent, avoid the occurrence of lithium plating in the negative electrode 3 under test due to poor uniformity of lithium intercalation, thereby helping to reduce the consumption of active lithium and, to a certain extent, avoid the occurrence of battery capacity decay. At the same time, this can also, to a certain extent, prevent lithium dendrites from piercing the battery separator and causing a short circuit in the battery, thus ensuring the safety and cycle life of the battery. Moreover, this can also provide a certain reference for the research on battery capacity decay and other issues.

[0053] Meanwhile, compared with the solution of fixing the positive conductive end and the negative electrode sheet to be tested together, this method can improve the detection efficiency while detecting the lithium intercalation uniformity of the negative electrode sheet 3 to be tested, and eliminates the need to set multiple positive conductive ends 121, thus simplifying the detection device.

[0054] In some embodiments, refer to Figure 2 As shown, a connector 4 is provided between the reference metal sheet 2 and the negative conductive terminal 111. The reference metal sheet 2 and the negative conductive terminal 111 are connected by the connector 4.

[0055] This allows the reference metal sheet 2 and the negative conductive terminal 111 to be pre-connected and integrated, treating them as a single unit. This facilitates flexible and free movement of the reference metal sheet 2 and the negative conductive terminal 111 during the detection process, making detection convenient and improving detection efficiency.

[0056] For example, after the reference metal sheet 2 and the negative conductive terminal 111 are connected, the whole assembly can be stored in an inert environment.

[0057] For example, the positive conductive end 121 can be connected to the intermediate conductive sheet via the connector 4, and the intermediate conductive sheet can be made to abut against the negative electrode 3 to be tested, so as to realize the electrical connection between the positive conductive end 121 and the negative electrode 3 to be tested. This can increase the relative contact area between the positive conductive end 121 and the negative electrode 3 to be tested to a certain extent, so as to avoid the situation where the tip of the positive probe 12 pierces the negative electrode 3 to be tested, and ensure the accuracy of the test results.

[0058] In some embodiments, the connector 4 is a conductive adhesive, which can improve the reliability of the connection between the reference metal sheet 2 and the negative conductive terminal 111 while ensuring the electrical connection between them. This helps to ensure the stability of the entire detection device and thus ensures the smooth progress of the entire detection process.

[0059] In some embodiments, refer to Figure 2 As shown, the voltage detection device 1 includes a negative probe 11, one end of which is formed as a negative conductive terminal 111. The connector 4 is detachably connected to at least one of the reference metal sheet 2 and the negative probe 11.

[0060] With this configuration, if either the reference metal sheet 2 or the negative probe 11 is damaged, only the damaged component needs to be replaced. This can, to some extent, prevent the entire reference metal sheet 2 and negative probe 11 from being scrapped. In particular, it can reduce the wear and tear on the more expensive voltage detection component 1, which is beneficial for saving detection costs.

[0061] In some embodiments, refer to Figure 2As shown, one end of the connector 4 is connected to the reference metal sheet 2, and the other end of the connector 4 abuts against the negative electrode probe 11. The connector 4 can extend and retract along a first direction, so that the negative electrode conductive end 111 can move toward the reference metal sheet 2 to abut against the reference metal sheet 2, or move away from the reference metal sheet 2 to separate from the reference metal sheet 2. The first direction can be... Figure 2 The up and down directions are shown.

[0062] This allows the connector 4 and the reference metal sheet 2 to be integrated into a single unit. By making the connector 4 abut against the negative probe 11, the connector 4 and the reference metal sheet 2 can be detachably connected to the negative probe 11. When the reference metal sheet 2 needs to be replaced, only the connector 4 and the reference metal sheet 2 as a whole need to be replaced, which helps to reduce the wear and tear on the more expensive voltage detection component 1 and lower the detection cost.

[0063] At the same time, by enabling connector 4 to move along when under force... Figure 2 The device can extend and retract in the vertical direction to allow the negative conductive end 111 and the reference metal sheet 2 to come into contact to achieve electrical connection, or to disconnect the negative conductive end 111 and the reference metal sheet 2 to break the connection, making detection convenient.

[0064] Exemplary, in some embodiments, reference is made to Figure 1 As shown, the voltage detection device 1 may also include a positive probe 12, one end of which is formed as a positive conductive terminal 121.

[0065] In some embodiments, refer to Figure 2 As shown, the connector 4 includes a spring, so that the negative conductive end 111 and the reference metal plate 2 can be contacted or separated by the extension and contraction of the spring. The connector 4 has a simple structure, and it can also play a certain role in buffering the reference metal plate 2 and the negative probe 11, thereby providing good protection for the reference metal plate 2 and the negative probe 11.

[0066] Of course, in other implementations, connector 4 can also be a cylinder, telescopic rod, etc.

[0067] In some embodiments, refer to Figure 2 As shown, a spring is sleeved on the outer periphery of the negative probe 11. The negative probe 11 has an abutment protrusion 112 extending radially along the negative probe 11. The other end of the spring abuts against the side of the abutment protrusion 112 facing the reference metal sheet 2.

[0068] This not only ensures the contact between the spring and the negative probe 11, but also guides the extension and retraction of the spring through the negative probe 11, improving the stability of the spring's extension and retraction, thereby improving detection efficiency.

[0069] In some embodiments, refer to Figures 1 to 6 As shown, the battery negative electrode lithium intercalation uniformity detection device also includes a separator 5, and the reference metal sheet 2 and the negative electrode sheet 3 to be tested are isolated by the separator 5.

[0070] In this way, the diaphragm 5 isolates the reference metal sheet 2 and the negative electrode sheet 3 under test, thereby ensuring the isolation effect between the reference metal sheet 2 and the negative electrode sheet 3 under test, which is conducive to ensuring the smooth progress of the testing process.

[0071] For example, during testing, the negative electrode 3 to be tested can be unfolded first, then an electrolyte can be dropped onto the upper surface of the negative electrode 3 to be tested, then a diaphragm 5 can be placed on the surface of the dropped electrolyte, then a reference metal sheet 2 can be placed on the upper surface of the diaphragm 5, and finally the negative electrode conductive end 111 can be pressed down to abut against the reference metal sheet 2, and the positive electrode conductive end 121 can be abutted against different positions of the negative electrode 3 to be tested, and then the test can be performed.

[0072] The area of ​​the reference metal sheet 2 can be set according to the test requirements. For example, a lithium sheet commonly used in button batteries with a diameter between 4.8mm and 12mm can be selected as the reference metal sheet 2. This can avoid waste caused by the reference metal sheet 2 being too large. At the same time, during the test, uneven force on the reference metal sheet 2 may lead to insufficient contact between the reference metal sheet 2 and the negative electrode sheet 3 under test with the electrolyte, which may affect the detection accuracy. Moreover, this can also avoid the situation where the detection is inconvenient when the reference metal sheet 2 is too small.

[0073] In some embodiments, refer to Figures 1 to 4 As shown, the diaphragm 5 is located at the negative electrode conductive end 111. The area of ​​the diaphragm 5 is larger than the area of ​​the reference metal sheet 2, so that the diaphragm 5 is folded together from the side of the reference metal sheet 2 away from the negative electrode conductive end 111 toward the outer periphery of the negative electrode probe 11 and connected to the negative electrode probe 11.

[0074] This allows for the integration of the diaphragm 5 with the negative electrode probe 11 and the reference metal sheet 2, thus achieving the integration of the diaphragm 5, negative electrode probe 11 and reference metal sheet 2. During detection, the diaphragm 5, negative electrode probe 11 and reference metal sheet 2 can be moved simultaneously, thereby further improving detection efficiency.

[0075] In some embodiments, refer to Figure 2 As shown, the diaphragm 5 is tied to the outer periphery of the negative electrode probe 11 by the binding member 7, which makes the connection between the diaphragm 5 and the negative electrode probe 11 simple and convenient.

[0076] Meanwhile, when the connector 4 is detachably connected to at least one of the reference metal sheet 2 and the negative electrode probe 11, and the reference metal sheet 2 needs to be replaced, it is only necessary to untie the diaphragm 5 with the binding 7, making the connection and replacement of the reference metal sheet 2 and the like convenient.

[0077] Of course, in other embodiments, the diaphragm 5 and the negative electrode probe 11 can also be connected by Velcro or removable adhesive tape.

[0078] In some embodiments, refer to Figure 3 As shown, the diaphragm 5 includes an isolation portion 51 and at least two connecting portions 52. The isolation portion 51 is located on the side of the reference metal sheet 2 opposite to the negative conductive terminal 111. The at least two connecting portions 52 are connected to the outer periphery of the isolation portion 51 along the circumferential direction and are connected to the negative probe 11.

[0079] In other words, the two adjacent connecting parts 52 are independent of each other along the circumference of the isolation part 51, so that each connecting part 52 can individually bypass the reference metal sheet 2 and retract towards the negative electrode probe 11. Thus, compared to the diaphragm, it is a complete membrane sheet. The diaphragm retracts directly towards the negative electrode probe after corresponding with the reference metal sheet. This can, to a certain extent, avoid the occurrence of wrinkles at the joint between the connecting part 52 and the isolation part 51 when the connecting part 52 retracts and connects with the negative electrode probe 11. This can, to a certain extent, prevent the wrinkles at the joint from extending to the isolation part 51 and affecting the wetting of the electrolyte on the reference metal sheet 2 and the negative electrode sheet 3 under test. This ensures the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2, which is beneficial to ensuring the detection accuracy.

[0080] For example, refer to Figure 3 As shown, for example, scissors can be used to cut the portion of the diaphragm 5 located outside the reference metal sheet 2 at least twice, forming a separation portion 521 at the cut position. The portion of the diaphragm 5 located outside the reference metal sheet 2 can be divided into at least two connecting portions 52 by the separation portion 521.

[0081] In some embodiments, refer to Figure 3 As shown, the end of the connecting portion 52 that is connected to the isolation portion 51 is 3mm-6mm away from the outer edge of the reference metal sheet 2.

[0082] For example, the distance between the end of the connecting portion 52 connected to the isolation portion 51 and the outer edge of the reference metal sheet 2 can be specifically referred to Figure 3 The d in the figure means that d is between 3mm and 6mm. For example, d can be 3mm, 3.5mm, 3.8mm, 4.5mm, 5mm, 5.3mm, 6mm, etc.

[0083] Compared to the above-mentioned solution with too small a distance, this can, to a certain extent, avoid the situation where the reference metal sheet 2 comes into contact with the negative electrode sheet 3 under test during the testing process, thus preventing a short circuit and ensuring the isolation effect of the diaphragm 5 on the reference metal sheet 2 and the negative electrode sheet 3 under test. Moreover, compared to the above-mentioned solution with too large a distance, it can further ensure the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2.

[0084] In some embodiments, refer to Figure 1 and Figure 4 As shown, a support member 6 is disposed between the negative electrode probe 11 and the diaphragm 5. The support member 6 extends along a second direction, and the projection of the reference metal sheet 2 onto the support member 6 is located within the area enclosed by the outer contour of the support member 6, so that the diaphragm 5 abuts against the outer edge of the support member 6 when it is retracted. Specifically, the second direction is... Figure 4 The left and right directions in the middle.

[0085] With this configuration, when the diaphragm 5 retracts toward the negative electrode probe 11, the support member 6 can expand the diaphragm 5 to a certain extent, so as to ensure the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2.

[0086] In some embodiments, the support member 6 has a clearance hole for the negative electrode probe 11 to pass through so that the negative electrode conductive end 111 abuts against the reference metal sheet 2.

[0087] This ensures the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2, while also allowing the negative electrode probe 11 to extend through the clearance hole to contact the reference metal sheet 2, thus achieving electrical connection between the negative electrode conductive end 111 and the reference metal sheet 2, making it convenient to use.

[0088] In some embodiments, the support 6 is a rubber pad. This ensures the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2, while also making the support 6 lightweight. This helps to prevent the reference metal sheet 2 from being subjected to pressure away from the negative electrode probe 11 due to the weight of the support 6 during the testing process, which could cause the reference metal sheet 2 to easily detach from the negative electrode probe 11 (e.g., the adhesive joint between the negative electrode conductive end 111 and the reference metal sheet 2 to loosen and separate). This ensures the smooth progress of the testing process. Of course, the support 6 can also be a foam pad, etc.

[0089] For example, refer to Figure 4 As shown, for example, the support member 6 includes a first support member 61 placed on the reference metal sheet 2, and the area of ​​the first support member 61 is larger than the area of ​​the reference metal sheet 2. The tip of the negative electrode tester 11 is used to pierce the first support member 61 to form the above-mentioned clearance hole on the first support member 61, so that the negative electrode conductive end 111 and the reference metal sheet 2 can contact each other. Then the diaphragm 5 is gathered on the barrel of the negative electrode tester 11.

[0090] For example, refer to Figure 4 As shown, the support member 6 can also include a second support member 62, located between the first support member 61 and the reference metal sheet 2, so that the tip of the negative electrode probe 11 simultaneously pierces the second support member 62. The area of ​​the second support member 62 can be equal to the area of ​​the first support member 61 to ensure reliable support for the reference metal sheet 2, thereby further ensuring the flatness of the contact surface between the diaphragm 5 and the reference metal sheet 2.

[0091] The first support member 61 and the second support member 62 can both be rubber pads, foam pads, etc.

[0092] Taking a 71Ah square aluminum-cased battery (e.g., a wound-cell battery) based on an NCM613 / graphite system as an example, three of these batteries were tested for capacity. The test procedure was as follows: the battery was charged to 4.3V at 25℃ and a constant current of 71A, then charged at a constant voltage until the current was less than or equal to 3.55A; after resting for 30 minutes, it was discharged to 2.8V at a constant current of 71A; and then rested for another 30 minutes. The battery capacity test results were: the discharged capacities of the three batteries were 60.3Ah, 61.0Ah, and 65.7Ah, respectively, while the theoretical calculation result was 71Ah. The actual results were worse than the theoretical design result, indicating that the battery may have a failure problem. Therefore, failure analysis of this battery is required.

[0093] Reference Figure 5 It can be seen that when the battery SOC is greater than 20%, the lithium potential of the negative electrode does not change significantly with different SOC states. Therefore, the difference in lithium intercalation of the negative electrode cannot be accurately analyzed based on the difference in lithium potential. When the battery SOC is less than 10%, even if the change in battery SOC is small, the change in lithium potential of the negative electrode will be large. In other words, even if the change in lithium potential of the negative electrode is large, the difference in battery SOC will be relatively small, meaning the difference in lithium intercalation of the negative electrode will be relatively small. If this range of battery SOC is selected, the error in using the lithium potential of the negative electrode to reflect the amount of lithium intercalation of the negative electrode will be large. Considering all factors, a full-cell SOC range of 10% to 20% is appropriate. At this range, the lithium potential of the negative electrode can accurately reflect the lithium intercalation status of the negative electrode while reducing judgment errors.

[0094] Next, the uniformity of lithium intercalation in the negative electrode sheet is tested using the negative electrode sheet lithium intercalation testing device provided in this embodiment. During the test, a reference lithium sheet is selected as the reference metal sheet 2. One of the batteries of the above-mentioned model is taken, for example, its SOC is adjusted to 15%, and then the negative electrode sheet is disassembled in the glove box. This negative electrode sheet is used as the negative electrode sheet to be tested 3. The negative electrode sheet has a negative electrode tab 31. Different positions of the negative electrode sheet (for example, reference...) are used to test the negative electrode sheet. Figure 6As shown, the lithium potential was measured three times at different folds of the battery, corresponding to the negative electrode tab side A, the positive electrode tab side B, the middle of the large surface of the electrode C, and the slit side D).

[0095]

[0096] Reference Figure 6 As shown, first unfold the 6-fold negative electrode sheet on the outer side of one of the cores ( Figure 6 The dashed lines within the negative electrode sheet indicate the creases of two connected negative electrode sheets. A reference lithium sheet is placed on the surface of the third negative electrode sheet. The lithium potential at different locations on the negative electrode sheet is then measured, and the test results are shown above.

[0097] Then, the core was unrolled to the middle, and the reference lithium sheet was repositioned. The lithium potential at different locations on the two folds of the negative electrode was measured, and the test results are as follows:

[0098]

[0099] Then, the core was fully unrolled, and reference lithium sheets were repositioned on the surfaces of the negative electrode at the second-to-last and fourth-to-last folds, respectively. The lithium potential at different positions on the negative electrode at the second-to-last and fourth-to-last folds was measured, and the test results are as follows:

[0100]

[0101] Comparing the above test results, it was found that: 1) the lithium potential varies to varying degrees at different folds of the negative electrode, indicating that the lithium intercalation of the negative electrode is very uneven; 2) different regions within the same fold of the negative electrode also exhibit differences in lithium potential; 3) the same regions with different folds also exhibit differences in lithium potential; 4) the lithium potential of the negative electrode also varies at different folds from the outside to the inside of the core. This indicates that the lithium intercalation of this battery varies significantly and without a pattern, thus eliminating the possibility of determining the cause of battery failure based solely on lithium intercalation.

[0102] Subsequently, researchers analyzed and investigated the reasons for the large differences in lithium intercalation and found that it was due to uneven mixing of the slurry in the positive electrode. After the slurry of the unevenly mixed positive electrode was coated to form the positive electrode, the amount of ternary active material (the electrode includes the current collector and the active material layer disposed on at least one side of the current collector; when the ternary active material is the material of the corresponding active material layer when the electrode is a positive electrode) varied at different locations of the positive electrode. Therefore, the amount of lithium ions that could be extracted from different areas of the positive electrode would vary, resulting in differences in the amount of lithium ions intercalated into the negative electrode.

[0103] In this document, 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 a fixed connection or an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, the terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0104] In this document, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0105] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications or equivalent substitutions made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A device for detecting the uniformity of lithium intercalation in the negative electrode of a battery, characterized in that, Includes a voltage detection element (1) and a reference metal sheet (2) isolated from the negative electrode sheet (3) to be tested of the battery; The reference metal sheet (2) is impregnated with an electrolyte; the voltage detection device (1) has a negative conductive end (111) and a positive conductive end (121), the negative conductive end (111) is electrically connected to the reference metal sheet (2), and the positive conductive end (121) can move relative to the negative electrode sheet (3) to abut against different positions of the negative electrode sheet (3) to be tested; The voltage detection device (1) is used to detect the potential difference between the negative electrode sheet (3) under test and the reference metal sheet (2) at different positions, so as to determine the lithium insertion amount of the negative electrode sheet (3) under test based on the potential difference.

2. The battery negative electrode lithium intercalation uniformity detection device according to claim 1, characterized in that, A connector (4) is provided between the reference metal sheet (2) and the negative conductive end (111); The reference metal sheet (2) and the negative conductive terminal (111) are connected by the connector (4).

3. The battery negative electrode lithium intercalation uniformity detection device according to claim 2, characterized in that, The connector (4) is a conductive adhesive.

4. The battery negative electrode lithium intercalation uniformity detection device according to claim 2, characterized in that, The voltage detection device (1) includes a negative probe (11), one end of which is formed as the negative conductive terminal (111); The connector (4) is detachably connected to at least one of the reference metal sheet (2) and the negative electrode probe (11).

5. The battery negative electrode lithium intercalation uniformity detection device according to claim 4, characterized in that, One end of the connector (4) is connected to the reference metal sheet (2), and the other end of the connector (4) abuts against the negative electrode probe (11); The connector (4) can extend and retract in a first direction so that the negative conductive end (111) can move toward the reference metal sheet (2) to abut against the reference metal sheet (2), or move away from the reference metal sheet (2) to separate from the reference metal sheet (2).

6. The battery negative electrode lithium intercalation uniformity detection device according to claim 5, characterized in that, The connector (4) includes a spring; The spring is sleeved on the outer periphery of the negative probe (11); the negative probe (11) has an abutment protrusion (112) extending radially along the negative probe (11); the other end of the spring abuts against one side of the abutment protrusion (112) facing the reference metal sheet (2).

7. The battery negative electrode lithium intercalation uniformity detection device according to any one of claims 2 to 6, characterized in that, The battery negative electrode lithium intercalation uniformity detection device also includes a separator (5), and the reference metal sheet (2) and the negative electrode sheet (3) to be tested are separated by the separator (5); The voltage detection device (1) includes a negative probe (11), one end of which is formed as the negative conductive end (111); the diaphragm (5) is located at the negative conductive end (111), and the area of ​​the diaphragm (5) is larger than the area of ​​the reference metal sheet (2), so that the diaphragm (5) is drawn together from the side of the reference metal sheet (2) away from the negative conductive end (111) and close to the outer periphery of the negative probe (11) and connected to the negative probe (11).

8. The battery negative electrode lithium intercalation uniformity detection device according to claim 7, characterized in that, The diaphragm (5) is tied to the outer periphery of the negative electrode probe (11) by a binding member (7).

9. The battery negative electrode lithium intercalation uniformity detection device according to claim 7, characterized in that, The diaphragm (5) includes an isolation portion (51) and at least two connecting portions (52); the isolation portion (51) is located on the side of the reference metal sheet (2) away from the negative electrode conductive end (111); At least two of the connecting portions (52) are connected circumferentially to the outer periphery of the isolation portion (51) and connected to the negative probe (11); The end of the connecting portion (52) that is connected to the isolation portion (51) is 3mm-6mm away from the outer edge of the reference metal sheet (2).

10. The battery negative electrode lithium intercalation uniformity detection device according to claim 7, characterized in that, A support member (6) is provided between the negative electrode probe (11) and the diaphragm (5); The support member (6) extends along the second direction, and the projection of the reference metal sheet (2) on the support member (6) is located in the area enclosed by the outer contour of the support member (6), so that the diaphragm (5) abuts against the outer edge of the support member (6) when it is closed. The support member (6) has a clearance hole for the negative electrode probe (11) to pass through so that the negative electrode conductive end (111) abuts against the reference metal sheet (2); and / or, the support member (6) is a rubber pad.

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