Battery cell structure capable of preventing falling failure and preparation method of battery cell structure

Abstract

The invention discloses a cell structure capable of preventing falling failure and a preparation method thereof, and relates to the technical field of lithium batteries, the structure comprises a naked cell and an outer packaging material, the naked cell is provided with a hot melt adhesive, and the hot melt adhesive is used for enhancing the bonding force between the naked cell and the outer packaging material; the bare battery core is formed by winding a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, the positive plate is connected with the positive tab, and the negative plate is connected with the negative tab. The hot melt adhesive is arranged on the two end surfaces of the naked battery cell in the height direction, so that the bonding force between the naked battery cell and the outer packaging material is effectively enhanced; due to the improvement, relative displacement between the naked battery cell and the outer packaging material in the falling process is prevented, so that the damage to the battery cell structure is avoided; and the anti-falling performance of the battery cell is remarkably improved, so that the battery cell has more excellent performance in a roller falling test, and the performance reduction and failure risks caused by falling are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a battery cell structure capable of preventing drop failure and a preparation method thereof. BACKGROUND

[0002] In the actual application process of lithium ion batteries, various mechanical impacts are inevitable, among which drop is particularly common.

[0003] As a core means for evaluating the drop resistance of batteries, the drum drop test plays a vital role in the evaluation of battery safety performance. This test mainly simulates the situation that the battery may fall from a high place such as a transportation tool or a workbench during transportation, handling and maintenance.

[0004] However, the traditional battery cell structure does not perform well in the drum drop test.

[0005] Under high-frequency drop test, the traditional battery cell structure is prone to internal structure damage, which leads to significant decline in battery performance, and even complete failure. In-depth analysis of the causes shows that the connection and fixation of the components inside the battery cell are not stable enough. When subjected to drop impact, relative displacement between components is likely to occur, thereby damaging the normal structure of the battery cell.

[0006] On the one hand, during the drop process, the tab is continuously subjected to pulling force. If the connection between the tab and the current collector is not firm enough, this continuous pulling force may cause the bare battery cell to form a spiral deformation, thereby causing internal short circuit or high resistance problems, which seriously affect the performance and safety of the battery.

[0007] On the other hand, for soft package battery cells, if the adhesion between the aluminum plastic film packaging and the battery cell is not strong enough, the movement of the bare battery cell in the packaging bag during the drop will cause stress concentration, resulting in abnormal wrinkles of the aluminum plastic film, and even causing leakage problem, which seriously threatens the safety performance of the battery. SUMMARY

[0008] The purpose of the present application is to provide a battery cell structure capable of preventing drop failure and a preparation method thereof to solve the problems in the background art.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A battery cell structure capable of preventing drop failure, comprising a bare battery cell and an outer packaging material, wherein the bare battery cell is provided with hot melt adhesive, and the hot melt adhesive is used to enhance the adhesion between the bare battery cell and the outer packaging material. The bare battery cell is formed by winding a positive electrode sheet, a negative electrode sheet and a separator between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is connected with a positive tab, and the negative electrode sheet is connected with a negative tab.

[0010] Preferably, the positive and negative tabs are provided with winding glue therebetween.

[0011] Preferably, the positive tab is made of aluminum material, the negative tab is made of nickel material, and the positive and negative tabs are designed with thickening.

[0012] Preferably, the separator is a polyethylene separator or a polypropylene separator.

[0013] Preferably, the hot melt glue is arranged at both ends of the bare cell in the height direction.

[0014] Preferably, the outer packaging material is an aluminum plastic film.

[0015] A preparation method of a cell structure for preventing drop failure according to any one of the above claims, comprising the following steps: Step one: uniformly coating the electrode active material on the current collector, thereby forming a positive coating layer on the positive tab and a negative coating layer on the negative tab; Step two: cold pressing the coated positive and negative tabs; Step three: welding the positive and negative tabs at appropriate positions of the positive and negative tabs, respectively; Step four: winding the treated positive and negative tabs with the separator to form a bare cell; Step five: winding and fixing the bare cell by winding glue between the positive and negative tabs; Step six: arranging hot melt glue at both ends of the bare cell in the height direction; Step seven: packaging the bare cell provided with hot melt glue with an outer packaging material, and then performing the processes of baking, liquid injection, formation, and capacity test to make a cell.

[0016] Preferably, the positive coating layer of the positive tab has misalignment at the head and tail, and the negative coating layer of the negative tab has misalignment at the head but no misalignment at the tail.

[0017] Preferably, in step three, the distance between the tab glue and the current collector is controlled to be between 0.5 mm and 2 mm when welding the positive and negative tabs.

[0018] Compared with the prior art, the present application has the following advantages: 1. By arranging hot melt glue at both ends of the bare cell in the height direction, the present application effectively enhances the adhesion between the bare cell and the outer packaging material, prevents relative displacement between the bare cell and the outer packaging material during drop, avoids damage to the cell structure, significantly improves the drop resistance of the cell, makes the cell perform better in the drum drop test, and reduces the performance decline and failure risk caused by drop.

[0019] 2、The positive and negative tabs in the application are designed with thickening, which significantly enhances the mechanical strength and conductivity of the tabs. This design makes the tab connection inside the battery more secure, effectively reducing the problem of tab loosening or falling off caused by vibration, collision, etc. during the drum drop process. Further, it avoids the spiral deformation of the bare cell caused by continuous stress and pulling during the drop, thereby preventing internal short circuit or high internal resistance, improving the performance and safety of the battery. At the same time, the thickened tab design also helps to improve the stability of current transmission.

[0020] 3、The application sets a winding glue between the positive and negative tabs, further reinforcing the internal structure of the cell. This design effectively prevents the loosening or displacement of tab, separator and other components during the drop or vibration process, thereby indirectly improving the drop resistance of the cell and reducing the possibility of cell deformation during the drum drop process, ensuring the safe and stable operation of the battery.

[0021] 4、The application cooperates the hot melt glue on the two end faces of the bare cell in the height direction, the thickened tabs and the winding glue between the two tabs to reinforce the internal structure of the cell in all directions. The hot melt glue enhances the adhesion between the bare cell and the outer packaging material, preventing structural damage caused by relative displacement during the drop. The winding glue further fixes the internal components of the cell, preventing the loosening or displacement of the tab, separator and other components. The optimized tab ensures the stability of its own connection, reducing the deformation of the cell caused by tab problems. The synergistic effect of the three significantly improves the drop resistance of the cell, making the cell perform excellently in the drum drop test, greatly reducing the performance decline and failure risk caused by drop, and providing a strong guarantee for the safe and stable operation of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The structure of the application is shown in the figure.

[0023] Figure 2 The bare cell schematic diagram of the embodiment of the application is shown in the figure.

[0024] Figure 3 The bare cell schematic diagram of the comparative example of the application is shown in the figure.

[0025] Legend: 1, positive tab; 11, positive tab; 2, negative tab; 21, negative tab; 3, winding glue; 4, hot melt glue. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the application more clear and explicit, the application is further described in detail below with reference to the drawings and examples.

[0027] In one embodiment, as Figure 1 and Figure 2As shown, a battery cell structure capable of preventing falling failure includes a bare battery cell and an outer packaging material, the bare battery cell is provided with hot melt adhesive 4, which is used to enhance the adhesion between the bare battery cell and the outer packaging material. The bare battery cell is formed by winding the positive sheet 1, the negative sheet 2 and the diaphragm between the positive sheet 1 and the negative sheet 2, the positive sheet 1 is connected with the positive tab 11, and the negative sheet 2 is connected with the negative tab 21.

[0028] In this embodiment, the hot melt adhesive 4 is used to enhance the adhesion between the bare battery cell and the outer packaging material, so as to prevent the relative displacement between the bare battery cell and the outer packaging material during the falling process, causing the damage of the battery cell structure, and the hot melt adhesive 4 can effectively absorb and disperse stress to prevent the relative displacement between the bare battery cell and the outer packaging material when the battery is impacted during the drum falling process.

[0029] In an optional embodiment, the positive tab 11 and the negative tab 21 are provided with the winding adhesive 3.

[0030] It should be noted that the winding adhesive 3 is provided between the positive tab 11 and the negative tab 21, which can enhance the stability of the internal structure of the battery cell, prevent the loosening or displacement of the sheet, diaphragm and other components during the falling or vibration process, and indirectly improve the anti-falling performance of the battery cell to prevent the deformation of the battery cell during the drum falling process.

[0031] Compared with being arranged on the right side of the positive tab 11, the winding adhesive 3 arranged between the positive tab 11 and the negative tab 21 can more reasonably utilize the internal space of the battery cell and can enhance the mechanical strength of the region, so that the overall structure of the battery cell is more stable.

[0032] The size of the winding adhesive 3 is 0.16mm*11mm, and the thickness of 0.16mm can provide sufficient adhesion and fixing effect without occupying too much internal space; the length of 11mm can effectively cover the key region between the positive and negative tabs, and ensure the fixing effect of the sheet, diaphragm and other components. During the falling or vibration process, the winding adhesive 3 can tightly fix the sheet, diaphragm and other components to prevent them from loosening or displacing, thereby indirectly improving the anti-falling performance of the battery cell.

[0033] In an optional embodiment, the positive tab 11 is made of aluminum material, the negative tab 21 is made of nickel material, and the positive tab 11 and the negative tab 21 adopt a thickening design.

[0034] It should be noted that the positive tab 11 is made of aluminum material, the negative tab 21 is made of nickel material, and both of them adopt a thickening design to enhance the mechanical strength and conductivity of the tab, and increase the thickness of the tab, so that the connection of the tab in the battery is more firm, and the problems of loosening and falling of the tab caused by vibration, collision and the like during the drum falling process are reduced.

[0035] The size of the positive tab 11 and the negative tab 21 is 0.08mm*6mm. The thickness of 0.08mm can ensure sufficient mechanical strength and electrical conductivity, and will not increase the internal space occupation and cost of the battery due to excessive thickness. The length of 6mm can meet the reliable connection with the current collector and other components, and ensure the stability of current transmission. The appropriate size design enables the tab to not only play a good conductive role in the battery, but also adapt to the internal structure layout of the battery, and work cooperatively with other components to further improve the overall performance of the battery.

[0036] In an optional embodiment, the separator is a polyethylene separator or a polypropylene separator.

[0037] It should be noted that the separator is made of polyethylene or polypropylene material. These two materials not only have good mechanical properties and can withstand the impact of the battery during the falling process, but also have excellent chemical stability, which can effectively isolate the positive and negative electrodes, prevent short circuit, and ensure the safe operation of the battery.

[0038] In an optional embodiment, the hot melt adhesive 4 is arranged at the two end faces in the height direction of the bare battery cell.

[0039] It should be noted that the hot melt adhesive 4 is arranged at the two end faces in the height direction of the bare battery cell, which not only increases the bonding area, but also ensures the firm bonding between the bare battery cell and the outer packaging material, effectively preventing the damage of the battery structure caused by relative displacement during the falling process. The width of the hot melt adhesive 4 is 20mm, which can ensure sufficient bonding strength, and will not increase the cost or have adverse effects on other performance of the battery due to excessive width.

[0040] In an optional embodiment, the outer packaging material is an aluminum plastic film.

[0041] It should be noted that the outer packaging material is an aluminum plastic film. This material is not only light and easy to carry, but also has good sealing performance and impact resistance, which can effectively protect the battery from the influence of external environment such as moisture and oxygen, thereby prolonging the service life of the battery.

[0042] A preparation method of a battery cell structure for preventing falling failure according to any one of the above claims positive plate 1 to hot melt adhesive 4, comprising the following steps: Step one: uniformly coat the electrode active material on the current collector, so as to form a positive electrode coating on the positive plate 1 and a negative electrode coating on the negative plate 2; Step two: cold pressing the coated positive plate 1 and negative plate 2; Step three: welding the positive tab 11 and the negative tab 21 at appropriate positions of the positive plate 1 and the negative plate 2, respectively; Step four: winding the treated positive plate 1 and negative plate 2 with the separator to form a bare battery cell; Step five: wrapping the bare battery cell by winding the adhesive 3 between the positive tab 11 and the negative tab 21 to fix the bare battery cell; Step six: setting the hot melt adhesive 4 on both ends of the bare battery cell in the height direction; Step seven: packaging the bare battery cell with the hot melt adhesive 4 with the outer packaging material, and then performing the processes of baking, liquid injection, formation, and capacity test to make the battery cell.

[0043] It should be noted that the coated positive plate 1 and negative plate 2 are cold-pressed in step two to further improve the density and uniformity of the coating and enhance the mechanical strength of the plate, providing a stable plate basis for subsequent winding and packaging processes.

[0044] In step three, the positive tab 11 and the negative tab 21 are respectively welded at appropriate positions of the positive plate 1 and the negative plate 2 to ensure the welding quality and stability of the tabs.

[0045] In step five, the bare battery cell is fixed by winding the adhesive 3 between the positive tab 11 and the negative tab 21 to ensure that it can effectively enhance the stability of the internal structure of the battery cell.

[0046] In an optional embodiment, the positive coating head and tail of the positive plate 1 are misaligned; the negative coating head of the negative plate 2 is misaligned, and the tail is not misaligned.

[0047] It should be noted that the positive coating head and tail of the positive plate 1 are misaligned, the negative coating head of the negative plate 2 is misaligned, and the tail is not misaligned. The layout of the coating helps to reduce the risk of internal short circuit caused by coating misalignment in the drum drop test, improving the safety of the battery cell.

[0048] In an optional embodiment, when welding the positive tab 11 and the negative tab 21 in step three, the distance between the tab adhesive and the current collector is controlled to be between 0.5mm and 2mm.

[0049] It should be noted that if the distance is too small, less than 0.5mm, the local heat may be too concentrated during welding, causing the tab adhesive to melt excessively or even burn, affecting the welding strength, and also causing the conductivity between the tab and the current collector to decrease, increasing the internal resistance of the battery cell and reducing the performance of the battery cell. At the same time, a small distance also makes the welding operation difficult, increasing the risk of welding errors. Conversely, if the distance is too large, more than 2mm, the heat is difficult to effectively transfer to the contact position of the tab adhesive and the current collector during welding, resulting in weak welding and the possibility of virtual welding. During the subsequent use of the battery cell, under the action of external forces such as vibration or drop, the tab is prone to separation from the current collector, causing the battery cell to be disconnected and causing safety problems.

[0050] In order to make the technical solutions and advantages of the present application clearer, the present application and its beneficial effects will be further described in detail below with specific embodiments and the accompanying drawings of the specification, but the embodiments of the present application are not limited thereto.

[0051] Embodiment The size of the battery cell is 7.6mm*56mm*69.7mm, and the capacity specification is 5150mAh.

[0052] Preparation steps of the battery cell required by the embodiment: 1. The electrode active material is uniformly coated on the current collector, and the coating method is gap coating; 2. The coated positive plate 1 and negative plate 2 are cold-pressed; 3. In the gap reserved in the empty current collector, a suitable position is selected, a thickened tab is used, the size of the tab is 0.10mm*6mm, the tab is welded in the blank area of the current collector, and the distance between the tab adhesive and the current collector is controlled at the same time; 4. After the welded positive plate 1 and negative plate 2 are completed, the composite diaphragm is wound to complete the bare battery cell; 5. The bare battery cell is fixed by winding the adhesive 3 between the positive tab 11 and the negative tab 21; 6. The hot melt adhesive 4 is arranged on both ends of the bare battery cell in the height direction, and the width of the hot melt adhesive 4 is 20mm; 7. The bare battery cell provided with the hot melt adhesive 4 is packaged with an aluminum plastic film, and then a series of processes such as baking, liquid injection, formation, and capacity are carried out to prepare the required battery cell.

[0053] The bare battery cell of the embodiment is as shown in Figure 2 .

[0054] Comparative Example The size of the battery cell is 7.6mm*56mm*69.7mm, and the capacity specification is 5150mAh.

[0055] Preparation steps of the battery cell required by the comparative example: 1. The electrode active material is uniformly coated on the current collector, and the coating method is gap coating; 2. The coated positive plate 1 and negative plate 2 are cold-pressed; 3. In the gap reserved in the empty current collector, a suitable position is selected, a conventional tab is used, the size of the tab is 0.08mm*6mm, the tab is welded in the blank area of the current collector, and the distance between the tab adhesive and the current collector is controlled at the same time; 4. After the welded positive plate 1 and negative plate 2 are completed, the composite diaphragm is wound to complete the bare battery cell; 5. The bare battery cell is fixed by winding the adhesive 3 on the right side of the positive tab 11. 6. Hot melt glue 4 is arranged on the end face of the bare cell, and the width of the hot melt glue 4 is 25 mm; 7. The bare cell provided with the hot melt glue 4 is packaged with an aluminum plastic film, and then a series of processes such as baking, liquid injection, formation, and capacity are performed to prepare the required cell.

[0056] The comparative bare cell is as shown in Figure 3

[0057] The cells prepared in the above comparative examples and examples are subjected to a drum drop test and a charge-discharge rate test: The prepared cells of the comparative examples and examples are subjected to a drum drop test, and the drum test conditions are as follows: drop frequency: 10 times / minute, drop height: 500 mm, and drop times: 500 times.

[0058] The test results of the drum are shown in Table 1. As can be seen from the table, after 500 times of drum drop, the cells of the comparative examples and examples are all normal, but after 500 times of drop, the cells continue to drop for 300 times. By observing the test results of the cells, the cells of the examples do not appear to be broken, but the cells of the comparative examples have a voltage of zero and an internal resistance out of range, indicating that the traditional glue sticking structure and the conventional tab cell have internal tab tearing and cell structure deformation and damage. Therefore, it can be seen that the thickened tab and the new structure of the electric cell are more stable in the drum drop test.

[0059] Table 1

[0060] According to the test results and Table 1, it is concluded that in the drum drop test, the cells prepared in the examples have higher drop resistance due to the use of thickened tabs, reinforced internal structure of the cell, and hot melt glue to enhance the bonding force between the bare cell and the outer packaging material.

[0061] Specifically, the internal structure of the cell of the example remains more complete during the drop process, the tab and the current collector are stably connected, and there is no problem of loose or falling off of the tab due to vibration and collision, effectively reducing the risk of failure of the cell due to drop.

[0062] In contrast, the comparative cell performs poorly in the drum drop test. Due to the use of conventional tab design, the internal structure of the cell is not fully reinforced, and the hot melt glue layout is not reasonable, etc., the internal structure of the comparative cell is more likely to be damaged during the drop process, such as tab loosening, diaphragm displacement, etc., resulting in a decrease in the performance of the cell or even failure.

[0063] ​Compared with the conventional tab, the thickened tab can better fix the internal components in the drum drop test, prevent the displacement of the tab, diaphragm and other components due to impact, and avoid the problems of aluminum plastic film wrinkling or liquid leakage.

[0064] Compared with being arranged on the right side of the positive tab 11, the positive and negative tabs 11 and 21 arranged around the glue 3 are basically unchanged in position after the drum drop test, and no obvious displacement phenomenon occurs. While the conventional battery with the glue arranged on the right side of the positive tab, the internal tab is dislocated, the diaphragm is damaged, and other problems occur under the same test conditions, which leads to a significant decline in battery performance. This fully proves the significant advantage of arranging the glue 3 between the positive and negative tabs in fixing the internal components.

[0065] Compared with arranging the hot melt glue 4 on the end face of the bare battery cell, Arranging the hot melt glue 4 on the two end faces in the height direction can form a "sandwich" fixing structure to tightly combine the bare battery cell with the shell or module shell. This design can evenly disperse mechanical stress and reduce the risk of cell displacement caused by vibration or impact. For example, during the driving of an electric vehicle, the battery pack needs to withstand continuous vibration, and full-face fixation can reduce the probability of cell loosening and avoid tab breakage or internal short circuit.

[0066] Arranging the hot melt glue 4 only on the end face may cause the middle region of the battery cell to lack support and be prone to bending deformation when dropped or mechanically impacted. While the two end faces are fixed, a continuous support can be formed to enhance the overall bending stiffness and improve the mechanical reliability of the battery pack.

[0067] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A cell structure to prevent drop failure, characterized in that, Includes bare battery cells and outer packaging materials, wherein hot melt adhesive (4) is provided on the bare battery cells, and the hot melt adhesive (4) is used to enhance the adhesion between the bare battery cells and the outer packaging materials; The bare cell is formed by winding a positive electrode (1), a negative electrode (2) and a spacer film disposed between the positive electrode (1) and the negative electrode (2). The positive electrode (1) is connected to the positive electrode tab (11), and the negative electrode (2) is connected to the negative electrode tab (21).

2. The cell structure for preventing drop failure according to claim 1, characterized in that, A rubber wrapping (3) is provided between the positive electrode tab (11) and the negative electrode tab (21).

3. The cell structure for preventing drop failure according to claim 2, characterized in that, The positive electrode tab (11) is made of aluminum, the negative electrode tab (21) is made of nickel, and the positive electrode tab (11) and the negative electrode tab (21) are designed with thickening.

4. The cell structure for preventing drop failure according to claim 2, characterized in that, The diaphragm is a polyethylene diaphragm or a polypropylene diaphragm.

5. The cell structure for preventing drop failure according to claim 1, characterized in that, The hot melt adhesive (4) is applied to both ends of the bare battery cell in the height direction.

6. The cell structure for preventing drop failure according to claim 1, characterized in that, The outer packaging material is aluminum-plastic film.

7. A method for preparing a cell structure to prevent drop failure according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: The electrode active material is uniformly coated on the current collector, thereby forming a positive electrode coating on the positive electrode sheet (1) and a negative electrode coating on the negative electrode sheet (2); Step 2: Cold press the coated positive electrode (1) and negative electrode (2); Step 3: Weld the positive electrode tab (11) and the negative electrode tab (21) to the appropriate positions on the positive electrode plate (1) and the negative electrode plate (2), respectively. Step 4: The processed positive electrode (1) and negative electrode (2) are wound together with the separator to form a bare cell; Step 5: Secure the bare battery cell by wrapping it with adhesive (3) between the positive tab (11) and the negative tab (21); Step 6: Apply hot melt adhesive (4) to both ends of the bare cell in the height direction; Step 7: The bare battery cell with hot melt adhesive (4) is sealed with the outer packaging material, and then baked, injected with liquid, formed and capacity tested to make the battery cell.

8. The method for preparing a cell structure to prevent drop failure according to claim 7, characterized in that, The positive electrode coating of the positive electrode sheet (1) is misaligned at both the head and tail; the negative electrode coating of the negative electrode sheet (2) is misaligned at the head but not at the tail.

9. The method for preparing a cell structure to prevent drop failure according to claim 7, characterized in that, When welding the positive electrode tab (11) and negative electrode tab (21) in step three, the distance between the electrode tab adhesive and the current collector should be controlled between 0.5 mm and 2 mm.

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