A method for manufacturing an internal short-circuit fault battery

Abstract

This invention discloses a method for manufacturing an internal short-circuit fault battery. First, a short-circuit triggering device, an internal temperature measuring device, and a reference electrode device are fabricated. Next, the internal short-circuit battery is fabricated by punching holes in a prepared separator, then placing the perforated separator at a designated position during the stacking process, simultaneously adding the three fabricated devices. The reference electrode device, internal temperature measuring device, and internal short-circuit triggering device are then wrapped at their intersections with the aluminum-plastic film using tab adhesive and PP tubing. Finally, after the battery is volume-adjusted, the injection port is sealed to obtain the internal short-circuit battery. This invention achieves controllable internal short-circuit triggering time and measurable internal temperature and potential. Furthermore, single-layer and ten-layer test batteries demonstrate that the introduction of the short-circuit triggering device, internal temperature measuring device, and reference electrode device significantly affects some performance characteristics of the single-layer battery, while having almost no impact on the ten-layer battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, specifically relating to a method for manufacturing a battery with internal short-circuit faults. Background Technology

[0002] In recent years, with the rapid development of the electric vehicle industry, the safety performance of lithium-ion batteries has become a focus of industry attention. Internal short-circuit faults caused by manufacturing defects or misuse severely damage battery reliability and threaten the safe and stable operation of electric vehicles. Although there have been numerous studies simulating internal short-circuit faults, most focus on single-trigger internal short circuits leading to battery thermal runaway, failing to effectively simulate the early behavior of internal short circuits. Therefore, it is necessary to fabricate internal short-circuit fault batteries with controllable triggering and measurable internal temperature and electrode potential to study the initial development and evolution of internal short circuits.

[0003] In the prior art, patent application number CN201911141703 discloses a lithium-ion battery containing an internal short-circuit device. The manufacturing process is relatively complex, and the heating and fusing of the insulating paraffin layer poses certain risks. Furthermore, there is no internal measuring device, making it impossible to monitor the local temperature rise inside the battery and the battery electrode potential when an early internal short circuit occurs, which poses a safety hazard. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for manufacturing a battery with internal short circuit faults.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for manufacturing an internal short-circuit fault battery, comprising the following steps:

[0006] S1. Fabricate a short-circuit triggering device, an internal temperature measuring device, and a reference electrode device;

[0007] S2. To manufacture an internal short-circuit battery, perforate the pre-prepared separator during the stacking process, and then add the three devices manufactured in step S1.

[0008] S3. Using tab adhesive and PP tubing, the junction of the reference electrode device, internal temperature measuring device, and internal short-circuit trigger device with the edge of the aluminum-plastic film is covered. Then, the internal short-circuit battery with ruptured separator is pre-sealed. After vacuuming the pre-sealed battery, it is placed in a glove box, an appropriate amount of electrolyte is injected, and it is left to stand for a period of time. The battery after electrolyte injection is pre-charged, formed, and volume-adjusted. The battery pre-charge and formation process needs to maintain negative pressure to extract the gas generated inside the battery. Finally, after the battery is volume-adjusted, the electrolyte injection port is sealed to obtain the internal short-circuit battery.

[0009] Preferably, in step S2, a hole is punched in the center of the diaphragm.

[0010] Furthermore, the short-circuit triggering device described in step S1 includes a copper strip and a separator. The front end of the copper strip completely covers the separator hole. The short-circuit triggering device is placed at the negative electrode active material of the battery. The front end of the copper strip of the triggering device covers the separator hole, the tail end of the triggering device extends to the outside of the battery, and the part of the copper strip that is in contact with the material is covered and fixed with the separator.

[0011] Furthermore, the internal temperature measuring device mentioned in step S1 is a thermocouple measuring wire, there is a gap between the measuring point and the center of the diaphragm hole, the measuring point is covered with a high temperature resistant material, and the measuring wire extends to the outside of the battery.

[0012] Furthermore, the reference electrode device described in step S1 is manufactured by depositing lithium on the surface of enameled copper wire. After the battery is manufactured, lithium is plated onto the reference electrode device by the positive electrode and copper wire, and the negative electrode and copper wire.

[0013] Furthermore, the short-circuit triggering method refers to: extending the end of the short-circuit triggering device to the outside of the PP pipe and connecting it to the PP pipe with a PP pipe plug; when a short circuit is triggered, the device and the PP pipe plug move simultaneously; the PP pipe plug is always connected to the PP pipe.

[0014] Furthermore, the method for manufacturing the internally short-circuited battery with diaphragm perforation includes the following steps:

[0015] S21. The positive and negative electrode sheets coated with active materials on both sides, the separator, the positive and negative electrode tabs, the aluminum-plastic film, and the electrolyte are dried in a vacuum drying oven to dry the battery materials.

[0016] S22. Stack the cells in the order of separator, negative electrode, separator, and positive electrode, always keeping the current collectors of the uncoated positive and negative electrodes opposite each other. Drill holes in the pre-prepared separator and place the drilled separator between the 5th layer of positive and negative electrode materials during the battery stacking process. Then, use an ultrasonic welding machine to weld the positive and negative electrode tabs respectively. Place the battery with the welded tabs in an aluminum-plastic film and leave an injection port on one side. Use a sealing machine to pre-seal each edge of the battery. After vacuuming the pre-sealed battery, put it in a glove box, inject an appropriate amount of electrolyte, and let it stand for at least 24 hours.

[0017] S23. After the electrolyte injection is completed, the battery is pre-charged, formed, and volume-adjusted. During the pre-charge and formation process, the battery is kept under negative pressure to extract the gas generated inside the battery. Finally, after the battery is volume-adjusted, the electrolyte injection port is sealed.

[0018] The beneficial effects of adopting the above technical solution are:

[0019] This invention provides a method for manufacturing an internal short-circuit fault battery with controllable triggering time and measurable internal temperature and electrode potential. By manufacturing an internal short-circuit triggering device, an internal temperature measuring device, and a reference electrode device, the method achieves the goal of controllable internal short-circuit triggering time and measurable internal temperature and potential. At the same time, through single-layer and ten-layer test batteries, it is demonstrated that the introduction of the short-circuit triggering device, internal temperature measuring device, and reference electrode device has a serious impact on some performance of single-layer batteries, but has almost no impact on ten-layer batteries. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a flowchart illustrating the steps of the method for manufacturing an internal short-circuit fault battery in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the device structure placed inside the battery in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the performance characteristic curves of single-layer and ten-layer experimental batteries in the embodiments of the present invention;

[0024] Figure 4 This is a graph showing the voltage, internal and external temperatures, and impedance spectra of the battery with internal short-circuit faults in an embodiment of the present invention. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] See attached document Figure 1 This invention, taking a ten-layer ternary lithium-ion soft-pack battery as an example, provides a method for manufacturing a battery with internal short-circuit faults, wherein the dimensions of a single-layer battery material are... A 6mm diameter hole is drilled at the center of the fifth diaphragm.

[0027] This invention includes the fabrication of internally short-circuited batteries. The fabrication process for both normal and internally short-circuited batteries mainly includes stacking, welding, pre-sealing, electrolyte injection, pre-charging, formation, capacity setting, and final sealing. Before battery fabrication, positive and negative electrode sheets coated with active material on both sides, a separator, positive and negative electrode tabs, an aluminum-plastic film, and electrolyte are prepared and dried in a vacuum drying oven. Then, the batteries are stacked sequentially in the order of separator, negative electrode sheet, separator, and positive electrode sheet, always maintaining the current collectors on opposite sides of the uncoated positive and negative electrode sheets. The experimental batteries fabricated are mainly single-layer and ten-layer batteries. For internally short-circuited batteries with perforated separators, a hole punch is used to drill holes in the pre-prepared separator, and the perforated separator is placed in the designated position during battery stacking. Then, the positive and negative electrode tabs are welded using an ultrasonic welding machine. The battery with welded tabs is placed inside the aluminum-plastic film, leaving an electrolyte injection port on one side, and the edges of the battery are pre-sealed using a sealing machine. After vacuuming the pre-sealed battery, it is placed in a glove box, injected with an appropriate amount of electrolyte, and left to stand for at least 24 hours to allow for full electrolyte saturation. Following electrolyte injection, the battery undergoes pre-charging, formation, and volume adjustment. During pre-charging and formation, a negative pressure is maintained to remove any gas generated inside the battery. Finally, after volume adjustment, the electrolyte injection port is sealed, completing the battery manufacturing process.

[0028] This invention includes the fabrication of an internal short-circuit triggering device, an internal temperature measuring device, and a reference electrode device. The device dimensions are determined based on the battery dimensions and aperture size fabricated according to this invention. The device dimensions should be adjusted according to actual conditions during application. To ensure that no internal short circuit occurs before the battery is completed and to control the timing of the internal short circuit, an internal short-circuit triggering device is fabricated and added during the stacking process when fabricating the internally short-circuited battery, isolating the positive and negative electrode materials at the separator opening. The short-circuit triggering device mainly consists of a copper strip and a separator, such as... Figure 2 As shown in (a), the copper strip completely covers the diaphragm opening at the front end and is placed at the negative electrode active material of the battery, with its end extending outside the battery. To prevent internal short circuits between the positive and negative electrode active materials through the copper strip, the contact area between the copper strip and the material is covered and fixed by the diaphragm. When a short circuit needs to be triggered, the short circuit triggering device, extending outside the battery, is used to pull the device away from the diaphragm opening, ensuring direct contact between the positive and negative electrode materials of the battery.

[0029] Furthermore, since the short-circuit resistance generated by the contact between the positive and negative electrode active materials is located inside the battery, the ohmic heat generated by the short-circuit current passing through this resistance may cause localized overheating within the battery. Therefore, an internal temperature measurement device is fabricated and incorporated into the battery during the stacking process to monitor internal temperature changes and compare the internal and external temperature differences of the battery in the case of an internal short circuit. The internal battery temperature is primarily measured using thermocouple wires, such as... Figure 2As shown in (b), the temperature measuring point and the center of the diaphragm hole are kept at a certain distance. The temperature measuring point is covered with high-temperature tape, and the temperature measuring wire extends to the outside of the battery and is connected to the temperature data acquisition instrument.

[0030] In addition to the short-circuit triggering device and internal temperature measurement device, a reference electrode device is added during the fabrication of the internal short-circuit battery to directly monitor the voltage of the positive and negative electrodes in order to investigate the thermodynamic characteristics of the active materials of the positive and negative electrodes. The reference electrode device is fabricated by depositing lithium on the surface of copper wire, such as... Figure 2 As shown in (c), the reference electrode device is made of enameled copper wire. The surface enameling layer is removed at a distance from both ends of the reference electrode device. One end is covered with a separator to encapsulate the exposed copper wire, which is placed between the short-circuit trigger device and the negative electrode tab during the stacking process. The other end extends to the outside of the battery and is welded to the tab for easy connection to charging and discharging equipment. To ensure a uniform distribution of the formed lithium deposition layer, lithium plating is performed between the positive electrode and the copper wire, and between the negative electrode and the copper wire, respectively. The structural diagram of the ten-layer battery containing the three internal devices is shown below. Figure 2 As shown in (d). After adding the internal short-circuit trigger device, reference electrode device, and internal temperature measuring device, to ensure the battery's airtightness, the reference electrode device, internal temperature measuring device, and the intersection of the internal short-circuit trigger device and the edge of the aluminum-plastic film are covered using tab adhesive and PP tubes, respectively, followed by pre-sealing. Since the short-circuit trigger device needs to be removed, its end needs to extend outside the PP tube and be connected to the PP tube using a PP tube plug. When removing the short-circuit trigger device, it needs to be moved simultaneously with the PP tube plug, ensuring that the PP tube plug remains connected to the PP tube at all times.

[0031] This invention includes performance testing of single-layer and ten-layer test batteries containing short-circuit triggering devices, internal temperature measuring devices, and reference electrode devices, to explore the impact of the introduced devices on battery performance.

[0032] For single-layer and ten-layer test batteries, multiple sets of normal batteries and internally short-circuited batteries (including short-circuit triggering devices, reference electrode devices, and internal temperature measurement devices) were fabricated simultaneously. Performance tests were conducted on the normal batteries and internally short-circuited batteries under conditions without triggering the internal short circuit to verify the impact of the short-circuit triggering device, reference electrode device, and internal temperature measurement device on battery performance. Battery performance tests mainly included capacity testing, self-discharge testing, equilibrium potential testing, and EIS testing. The relative capacity and self-discharge of single-layer and ten-layer batteries under normal conditions and under conditions including the short-circuit triggering device, internal temperature measurement device, and reference electrode device are plotted as follows: Figure 3As shown in (a) and (b), the addition of the short-circuit triggering device, reference electrode device, and internal temperature measurement device has a significant impact on the capacity and self-discharge characteristics of single-layer cells, but almost no impact on ten-layer cells. The equilibrium potential and Nyquist curves at 90% SOC of the single-layer and ten-layer experimental cells are plotted, as shown in (a) and (b). Figure 3 As shown in (c) and (d), for a single-layer cell, the addition of the device causes a slight shift in the equilibrium potential curve towards a lower potential. However, for a ten-layer cell, the equilibrium potential curve remains unchanged. Figure 3 As shown in (e) and (f), the impedance of both the single-layer and ten-layer test cells shows a slight increase in the Nyquist curve.

[0033] Based on the changes in the usable capacity, self-discharge, equilibrium potential, and impedance characteristics of the test battery, it can be concluded that the short-circuit triggering device, the reference electrode device, and the internal temperature measurement device have a significant impact on the performance of the single-layer test battery, while for the ten-layer battery, there is almost no impact except for a slight increase in impedance.

[0034] This invention includes proof that three devices can achieve controllable triggering time and measurable internal temperature and electrode potential in a battery with an internal short-circuit fault. For example... Figure 4 As shown in (a), the voltage curves of the battery with an internal short circuit fault during a long period of rest before and after the internal short circuit is triggered are shown. By comparing the voltage curves, it can be seen that the battery exhibits more severe self-discharge after the internal short circuit is triggered. Therefore, the short-circuit triggering device can effectively trigger the battery to experience an internal short circuit fault. The internal and external temperature curves of the battery during the constant current charging test are shown in (a). Figure 4 As shown in (b), the internal temperature and external temperature exhibit the same variation pattern, with the internal temperature being higher than the external temperature. This indicates that the internal temperature measuring device can monitor the internal temperature. When using a reference electrode device to monitor the electrode potential, the effectiveness of the reference electrode device must first be proven. The effectiveness of the reference electrode device is verified by the fact that the total impedance between the positive and negative electrodes of the battery is essentially the same with and without the reference electrode device. The positive electrode impedance, negative electrode impedance, and total impedance between the positive and negative electrodes obtained through the reference electrode device are shown below. Figure 4 As shown in (c), the reference electrode device can simultaneously acquire the electrochemical impedance spectra of the positive and negative electrodes of the battery, and therefore the reference electrode device can also realize the measurement of electrode potential.

[0035] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a battery with internal short-circuit faults, characterized in that, Includes the following steps: S1. Fabricate a short-circuit triggering device, an internal temperature measuring device, and a reference electrode device; S2. To manufacture an internal short-circuit battery, perforate the pre-prepared separator during the stacking process, and then add the three devices manufactured in step S1. S3. Use tab adhesive and PP tube to cover the intersection of the reference electrode device, internal temperature measuring device and internal short circuit triggering device with the edge of the aluminum-plastic film. Then pre-seal the internal short circuit battery with ruptured separator. After vacuuming the pre-sealed battery, put it into the glove box, inject an appropriate amount of electrolyte, and let it stand for a period of time. After the electrolyte injection is completed, the battery is pre-charged, formed, and volume-adjusted. The battery pre-charge and formation process requires maintaining a negative pressure to extract the gas generated inside the battery. Finally, after the battery is volume-adjusted, the electrolyte injection port is sealed to obtain an internally short-circuited battery. The short-circuit triggering device described in step S1 includes a copper strip and a separator. The front end of the copper strip completely covers the separator hole. The short-circuit triggering device is placed on the negative electrode active material of the battery. The front end of the copper strip of the triggering device covers the separator hole, the tail end of the triggering device extends to the outside of the battery, and the part of the copper strip that is in contact with the material is covered and fixed with the separator.

2. The method for manufacturing an internal short-circuit fault battery according to claim 1, characterized in that, In step S2, a hole is punched in the center of the diaphragm.

3. The method for manufacturing an internal short-circuit fault battery according to claim 1, characterized in that, The internal temperature measuring device mentioned in step S1 is a thermocouple measuring wire. There is a gap between the measuring point and the center of the diaphragm hole. The measuring point is covered with a high-temperature resistant material, and the measuring wire extends to the outside of the battery.

4. The method for manufacturing an internal short-circuit fault battery according to claim 1, characterized in that, The reference electrode device described in step S1 is manufactured by depositing lithium on the surface of enameled copper wire. After the battery is manufactured, lithium is plated onto the reference electrode device by the positive electrode and copper wire, and the negative electrode and copper wire.

5. The method for manufacturing an internal short-circuit fault battery according to claim 1, characterized in that, The short-circuit triggering method refers to extending the end of the short-circuit triggering device to the outside of the PP pipe and connecting it to the PP pipe with a PP pipe plug. When a short circuit is triggered, the device and the PP pipe plug move simultaneously, while keeping the PP pipe plug connected to the PP pipe at all times.

6. The method for manufacturing an internal short-circuit fault battery according to claim 1, characterized in that, The method for manufacturing the internally short-circuited battery with diaphragm perforation includes the following steps: S21. The positive and negative electrode sheets coated with active materials on both sides, the separator, the positive and negative electrode tabs, the aluminum-plastic film, and the electrolyte are dried in a vacuum drying oven to dry the battery materials. S22. Stack the cells in the order of separator, negative electrode, separator, and positive electrode, always keeping the current collectors of the uncoated positive and negative electrodes opposite each other. Drill holes in the pre-prepared separator and place the drilled separator between the 5th layer of positive and negative electrode materials during the battery stacking process. Then, use an ultrasonic welding machine to weld the positive and negative electrode tabs respectively. Place the battery with the welded tabs in an aluminum-plastic film and leave an injection port on one side. Use a sealing machine to pre-seal each edge of the battery. After vacuuming the pre-sealed battery, put it in a glove box, inject an appropriate amount of electrolyte, and let it stand for at least 24 hours. S23. After the electrolyte injection is completed, the battery is pre-charged, formed, and volume-adjusted. During the pre-charge and formation process, the battery is kept under negative pressure to extract the gas generated inside the battery. Finally, after the battery is volume-adjusted, the electrolyte injection port is sealed.

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