Battery cell and battery pack
By setting through holes in the heat-shrink film, the problem of electrolyte not being able to wet quickly is solved, enabling rapid and sufficient electrolyte wetting and reducing the risk of short circuits, thereby improving the electrical performance and safety of the battery cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SVOLT ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2026-02-12
- Publication Date
- 2026-05-12
AI Technical Summary
The heat-shrink film covering of traditional new energy batteries is too airtight, which prevents the electrolyte from quickly and fully penetrating into the electrode assembly, resulting in abnormal cell performance.
Through holes are provided on the heat-shrink film, which are located on the large surfaces on both sides of the heat-shrink film. The heat-shrink film is then fitted around the outer periphery of the electrode assembly. When heated, the heat-shrink film tightly covers the electrode assembly, ensuring that the electrolyte can quickly and fully wet the interior of the electrode assembly, while reducing the risk of short circuit.
By setting through holes, the wetting effect of the electrolyte is improved, lithium plating in the cell is avoided, the performance of the cell is improved, the risk of short circuit is reduced, and the cell can work normally.
Smart Images
Figure CN121688150B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, specifically to a battery cell and battery pack. Background Technology
[0002] With the increasing maturity of new energy battery technology, new energy batteries are widely used as power batteries in electric vehicles and energy storage fields. Therefore, the requirements for the performance and safety of new energy batteries are becoming increasingly stringent. Traditional new energy batteries, such as blade lithium-ion cells, involve wrapping the electrode assembly with a heat-shrink film, then inserting the electrode assembly into the cell housing. A cover plate is then welded and sealed to the cell housing, thus encapsulating the electrode assembly inside the cell housing. The heat-shrink film serves to prevent short circuits between the electrode assembly and the cell housing, providing insulation and withstand voltage protection. The cell then uses the cover plate to lead out the positive and negative terminals for charging and discharging.
[0003] However, in related technologies, when heat-shrinkable film is wrapped around the electrode assembly, the heat-shrinkable film wraps the electrode assembly too tightly, causing the electrolyte to be unable to quickly and fully penetrate the interior of the electrode assembly, resulting in lithium plating in the cell and causing abnormal electrical performance of the cell. Summary of the Invention
[0004] In view of this, the present invention provides a battery cell and battery pack to solve the problem that the electrolyte cannot quickly and fully wet the inside of the electrode assembly, resulting in abnormal battery cell electrical performance.
[0005] In a first aspect, the present invention provides a battery cell, comprising:
[0006] A battery cell housing having a receiving cavity and an opening communicating with the receiving cavity;
[0007] An electrode assembly, which is installed within the receiving cavity through the opening;
[0008] A heat-shrinkable film is applied around the outer periphery of the electrode assembly and, after being heated, covers the electrode assembly.
[0009] The heat shrink film has through holes along the Z direction, and the through holes are located on the large surfaces on both sides of the heat shrink film.
[0010] Beneficial effects: The heat-shrink film, applied to the outer periphery of the electrode assembly, shrinks upon heating, tightly covering the assembly. This prevents scratches during insertion into the cell housing. The film also provides insulation and protection, preventing short circuits caused by contact between the electrode assembly and the cell housing. By creating through-holes in the heat-shrink film, electrolyte can flow into the electrode assembly during injection, increasing wetting effectiveness and allowing for rapid and thorough penetration. This prevents lithium plating and improves cell performance. Since electrode plates are prone to leakage on narrow sides, and active material can easily detach from these sides, increasing the risk of short circuits, placing through-holes on the larger surfaces of the heat-shrink film effectively reduces this risk, ensuring the cell's electrical performance and normal operation.
[0011] In one optional embodiment, along the X direction, both ends of the heat-shrinkable film are provided with folded edges, which are respectively attached to the end faces of the electrode assembly.
[0012] In one optional implementation, the width L1 of the folded edge satisfies 1mm≤L1≤50mm.
[0013] In one alternative implementation, along the Z direction, the spacing L2 between the folded edges satisfies 3mm ≤ L2 ≤ 20mm.
[0014] In one optional embodiment, the diameter d of the through hole satisfies 1mm≤d≤5mm.
[0015] In one optional embodiment, the distance L3 between the through hole and both sides of the electrode group along the X direction satisfies 3mm≤L3≤297mm; the distance L4 between the through hole and both sides of the electrode group along the Y direction satisfies 3mm≤L4≤297mm.
[0016] In one optional embodiment, the width w of the electrode group satisfies 50mm≤w≤300mm; the distance L5 between the through hole and the center line of the electrode group satisfies 4mm≤L5≤146mm and 0.4≤L5 / (w / 2)≤0.8.
[0017] In one alternative implementation, along the X direction, the distance L6 between two adjacent through holes satisfies 10mm≤L6≤250mm.
[0018] In one optional embodiment, the cross-sectional perimeter Z1 of the electrode assembly satisfies 150mm≤Z1≤450mm; after the heat-shrinkable film is fitted into the electrode assembly, the gap L7 between the heat-shrinkable film and the electrode assembly satisfies 0.5mm≤L7≤10mm; the heating shrinkage rate D of the heat-shrinkable film satisfies 3%≤D≤40%, and satisfies 4mm≤(Z1+4L7)×D-4L7≤40mm.
[0019] Secondly, the present invention also provides a battery pack, comprising:
[0020] Box;
[0021] Multiple battery cells as described above are housed within the housing.
[0022] Beneficial effects: The battery pack also includes a housing, which houses multiple battery cells. The housing prevents liquids or other foreign objects from affecting the charging or discharging of the cells. Moreover, placing multiple battery cells inside the battery pack's housing can increase the overall energy density of the battery pack and improve its performance. Attached Figure Description
[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0024] Figure 1 This is a schematic diagram of the structure of a battery cell electrode assembly combined with a heat-shrinkable film according to an embodiment of the present invention;
[0025] Figure 2 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention;
[0026] Figure 3 for Figure 2 The cross-sectional view of the battery cell along the AA direction is shown;
[0027] Figure 4 for Figure 3 The cross-sectional view of the battery cell along the BB direction is shown;
[0028] Figure 5 This is a schematic diagram of the structure of a battery cell before heat shrinking, according to an embodiment of the present invention.
[0029] Figure 6 This is a top view of a battery cell after heat shrinking of the heat shrink film according to an embodiment of the present invention;
[0030] Figure 7This is a left view of a battery cell after heat shrinking of the heat-shrink film according to an embodiment of the present invention.
[0031] Explanation of reference numerals in the attached figures:
[0032] 10. Battery cell; 100. Heat shrink film; 110. Through hole; 120. Folded edge; 200. Electrode assembly; 210. Electrode tab. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0034] The battery cells in this embodiment of the invention can be cylindrical, prismatic, pouch cells, or other shapes. Prismatic cells may include prismatic cells, blade cells, or other polyprismatic cells, such as hexagonal or octagonal prismatic cells; however, this embodiment of the invention is not limited to these.
[0035] Taking blade battery cells as an example, combined with Figures 1 to 7 The following describes embodiments of the present invention.
[0036] According to an embodiment of the present invention, in one aspect, in conjunction with [see also...] Figures 1 to 4 A battery cell 10 is provided, comprising: a battery cell housing having a receiving cavity and an opening communicating with the receiving cavity; an electrode assembly 200, which is installed in the receiving cavity through the opening; a heat-shrinkable film 100, which is sleeved on the outer periphery of the electrode assembly 200 and covers the electrode assembly 200 after being heated; and a through hole 110 is provided on the heat-shrinkable film 100, which is located on the large surfaces on both sides of the heat-shrinkable film 100 along the Z direction.
[0037] In this embodiment, the cell housing serves as the outer shell of the cell 10, having a receiving cavity and an opening. It accommodates and protects internal components such as the electrode assembly 200, while also providing mechanical support to prevent damage to the cell 10 from external forces. The receiving cavity of the cell housing is formed by two opposing large surfaces and two opposing narrow sides. Openings communicating with the receiving cavity are provided at both ends of the cell housing. The electrode assembly 200 can pass through any opening to be installed within the receiving cavity of the cell housing. The electrode assembly 200 is provided with tabs 210, which can conduct current from the electrode assembly 200. The tabs 210 include a positive tab and a negative tab. The cell 10 also includes a cover plate, which serves to fix and seal the internal components, including the electrode assembly 200, within the cell housing. This prevents external impurities and moisture from entering, and also avoids leakage of the internal electrolyte, providing a stable working environment for the inside of the cell 10. The cover plate is equipped with terminals for connecting to external circuits to enable the charging and discharging functions of the battery cell 10. In addition, the cover plate also contains safety components such as explosion-proof sheets, which automatically release pressure when the internal pressure of the battery is too high to prevent the battery cell 10 from exploding and ensure the safety of the battery cell 10.
[0038] Furthermore, the heat-shrinkable film 100 is sleeve-shaped and is fitted onto the outer periphery of the electrode assembly 200. The heat-shrinkable film 100 and the electrode assembly 200 are placed in a suitable temperature environment, such as an ambient temperature preferably 80℃-200℃, and the placement time preferably 10s-120s, so that the heat-shrinkable film 100 shrinks due to heat and tightly covers the electrode assembly 200. This can prevent the electrode assembly 200 from being scratched during the process of placing the electrode assembly 200 into the battery cell housing. The heat-shrinkable film 100 also plays a certain role in insulation and protection, preventing the electrode assembly 200 from contacting the battery cell housing and causing a short circuit.
[0039] Furthermore, through holes 110 are provided on the heat-shrink film 100. The number and position of the through holes 110 can be set according to actual usage requirements. When electrolyte is injected into the electrode assembly 200, the electrolyte can flow into the electrode assembly 200 through the through holes 110, thereby increasing the wetting effect of the electrolyte and allowing the electrolyte to quickly and fully wet the electrode assembly 200, thus preventing lithium plating in the cell 10 and improving the performance of the cell 10.
[0040] Since the electrode group 200 of the blade battery cell 10 generally adopts a stacked design, the alignment of the large surfaces is mainly relied upon during the stacking of the electrode group 200. The edges of the electrode on the narrow side are easily exposed due to stacking errors, stress, etc., and cannot be completely covered by the outermost separator, making it easy for the active material of the electrode to fall off from the narrow side. When the heat shrink film 100 is wrapped around the surface of the electrode group 200, if a hole is made on the narrow side of the heat shrink film 100, the electrode edges and the detached active material that might otherwise be exposed will be directly exposed to the external environment, thus causing a short circuit. Therefore, placing the through holes 110 on the large surfaces on both sides of the heat shrink film 100 can prevent the active material of the electrode from falling off from the narrow side, thereby effectively reducing the risk of short circuit inside the battery cell 10, ensuring the electrical performance of the battery cell 10, and enabling the battery cell 10 to work normally.
[0041] See also Figures 5 to 7 In one embodiment, along the X direction, both ends of the heat shrink film 100 are provided with folded edges 120, which are respectively attached to the end face of the electrode assembly 200.
[0042] In this embodiment, when the heat-shrinkable film 100 is fitted onto the outer periphery of the electrode assembly 200 and is not heated and covered on the surface of the electrode assembly 200, the length of the heat-shrinkable film 100 in the X direction is slightly longer than the length of the main body of the electrode assembly 200. When the heat-shrinkable film 100 is heated and shrinks, it covers the outer periphery of the electrode assembly 200. The portion of the heat-shrinkable film 100 that extends beyond the main body of the electrode assembly 200 forms a folded edge 120 and is attached to the top end face of the electrode assembly 200. This ensures that the folded edge 120 is tightly attached to the upper and lower surfaces of the electrode assembly 200 in the X direction, thereby fully wrapping the electrode assembly 200, reducing the gap between the heat-shrinkable film 100 and the electrode assembly 200, and improving the overall sealing performance. Furthermore, when the heat-shrink film 100 shrinks due to heat, if it only covers the sides of the electrode assembly 200, wrinkles and warping may occur at both ends of the heat-shrink film 100 in the X direction due to concentrated shrinkage stress, affecting the fixation effect on the electrode assembly 200. By setting the folded edge 120, the ends of the heat-shrink film 100 extend and fit against the end face of the electrode assembly 200, dispersing the shrinkage stress of the shrink film, making the two ends of the heat-shrink film 100 more firmly attached to the electrode assembly 200 in the X direction, reducing the deformation of the heat-shrink film 100 after shrinkage, and ensuring the stability of the overall structure.
[0043] In one embodiment, the width L1 of the folded edge 120 satisfies 1mm≤L1≤50mm.
[0044] In this embodiment, the width L1 of the folded edge 120 can be any value among 1mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, and 50mm, or a value between any two values. If the width L1 of the folded edge 120 is too small, such as less than 1mm, the heat-shrinkable film 100 may come off from the end face of the electrode group 200 after the battery cell 10 is subjected to force during use, exposing the edge of the end face of the electrode group 200. This would cause the edge of the end face of the electrode group 200 to short-circuit with the battery cell housing, thereby reducing the insulation effect of the heat-shrinkable film 100. If the width L1 of the folded edge 120 is too large, such as greater than 50mm, it will be difficult for the folded edge 120 of the heat-shrink film 100 to cover the tab 210. The heat-shrink film 100 around the tab 210 will wrinkle due to material accumulation, which may scratch the tab 210 and cause a short circuit inside the cell 10. By reasonably setting the width of the folded edge 120, it is ensured that the heat-shrink film 100 can cover the surface of the electrode group 200 more completely, thereby improving the insulation effect of the electrode group 200 and avoiding scratches on the tab 210, thus ensuring the electrical performance of the cell 10 and enabling the cell 10 to work normally.
[0045] In one embodiment, along the Z direction, the spacing L2 between the folded edges 120 satisfies 3mm≤L2≤20mm.
[0046] In this embodiment, the end face of the electrode assembly 200 needs to be reserved for the flow path of the electrolyte. When the folded edge 120 is attached to the end face of the electrode assembly 200, a certain distance needs to be reserved between the two folded edges 120 on the end face of the electrode assembly 200 to facilitate the flow of electrolyte into the electrode assembly 200. If the distance L2 between the two folded edges 120 on the end face of the electrode assembly 200 is too small, such as less than 3mm, it will result in the electrolyte injection channel on the end face of the electrode assembly 200 being too narrow, affecting the electrolyte wetting of the electrode assembly 200 and causing insufficient capacity of the cell 10. For example, because the electrolyte has a certain viscosity, when the distance L2 is too small, it will increase the flow resistance of the electrolyte, causing the electrode assembly 200 to be unable to be wetted by the electrolyte quickly, resulting in lithium plating in the cell 10, thereby causing abnormal electrical performance of the cell 10.
[0047] If the distance L2 between the two folded edges 120 on the end face of the electrode assembly 200 is too large, such as greater than 20mm, the width of the folded edges 120 will be reduced, which may lead to the heat shrink film 100 detaching from the end face of the electrode assembly 200, causing the edge of the electrode assembly 200 to short-circuit with the cell housing. Furthermore, an excessively wide distance L2 may result in excessive electrolyte injection, leaving some electrolyte unabsorbed by the electrode assembly 200 and remaining at the bottom of the cell housing, thus reducing the amount of electrolyte actually participating in the reaction and wasting resources. By reasonably setting the distance between the folded edges 120, the electrolyte can quickly and fully wet the electrode assembly 200, ensuring the electrical performance of the cell 10 and enabling it to function normally. Specifically, along the Z-direction, the distance L2 between the folded edges 120 can be any value from 3mm, 5mm, 8mm, 10mm, 12mm, 15mm, 18mm, and 20mm, or a value between any two of these values.
[0048] In one embodiment, the diameter d of the through hole 110 satisfies 1mm≤d≤5mm.
[0049] In this embodiment, the aperture d of the through hole 110 can be any value among 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, and 5mm, or a value between any two values. For example, when the electrolyte is a low-viscosity electrolyte, a smaller aperture through hole 110 can be selected, such as 1mm, 1.5mm, 2mm, 2.5mm, or 3mm. This through hole 110 can meet the flow requirements of the electrolyte while reducing the loss of insulation area. When the electrolyte is a high-viscosity electrolyte, a larger aperture through hole 110 can be selected, such as 3.5mm, 4mm, 4.5mm, or 5mm, to improve the wetting speed of the electrolyte. The size of the through hole 110 can also be adjusted according to the area of the electrode group 200. When the area of the electrode group 200 is small, a smaller through hole 110 diameter can be selected, such as 1mm, 1.5mm, 2mm, 2.5mm, 3mm, etc., to avoid the insulation area ratio being too large. When the area of the electrode group 200 is large, a larger through hole 110 diameter can be selected, such as 3.5mm, 4mm, 4.5mm, 5mm, etc., to accelerate the penetration of electrolyte into the depth of the electrode group 200.
[0050] If the aperture d of the through hole 110 is too small, such as less than 1 mm, it will hinder the electrolyte from entering the electrode assembly 200 through the through hole 110. Furthermore, after the heat-shrink film 100 shrinks, the material at the through hole 110 is easily compressed and wrinkled, thus affecting the installation of the electrode assembly 200 into the cell housing. If the aperture d of the through hole 110 is too large, such as greater than 5 mm, after the heat-shrink film 100 shrinks, it is easy for the through hole 110 to become uneven, and the heat-shrink film 100 is prone to warping, thus affecting the installation of the electrode assembly 200 into the cell housing. By properly setting the aperture of the through hole 110, it can be ensured that the electrolyte can wet the electrode assembly 200 without affecting its installation into the cell housing.
[0051] In one embodiment, the distance L3 between the through hole 110 and the electrode group 200 on both sides along the X direction satisfies 3mm≤L3≤297mm; the distance L4 between the through hole 110 and the electrode group 200 on both sides along the Y direction satisfies 3mm≤L4≤297mm.
[0052] In this embodiment, the distance between the through hole 110 and the boundary of the electrode group 200 is L3, the distance between the through hole 110 and the electrode group 200 on both sides along the X direction, and L4, the distance between the through hole 110 and the electrode group 200 on both sides along the Y direction. The distance L3 between the through hole 110 and the electrode group 200 on both sides along the X direction can be any value from 3mm, 10mm, 30mm, 50mm, 100mm, 150mm, 200mm, 250mm, and 297mm, or a value between any two values; the distance L4 between the through hole 110 and the electrode group 200 on both sides along the Y direction can be any value from 3mm, 10mm, 30mm, 50mm, 100mm, 150mm, 200mm, 250mm, and 297mm, or a value between any two values. The values of L3 and L4 can be the same or different, and can be set according to actual usage requirements.
[0053] When the width or length of the electrode group 200 is large, the upper limit of the distance L3 and / or L4 between the through hole 110 and the boundary of the electrode group 200 is relatively large. If L3 and / or L4 are too small, such as less than 3 mm, the through hole 110 is too close to the boundary of the electrode group 200, and the edge of the through hole 110 may overlap with the vulnerable area of the boundary of the electrode group 200, resulting in a decrease in the insulation and physical protection capability of the heat shrink film 100 in this area, increasing the risk of short circuit between the electrode sheet and the cell housing. Moreover, the electrolyte requirement at the edge of the electrode group 200 is relatively small. If the through hole 110 is too close to the boundary of the electrode group 200, it will cause excessive accumulation of electrolyte in the edge area of the electrode group 200, while the electrolyte wetting in the middle area of the electrode group 200 will be insufficient, resulting in uneven capacity performance of the cell 10. By reasonably setting the distance between the through hole 110 and the boundary of the electrode group 200, the electrolyte can be evenly wetted throughout the electrode group 200 to ensure the capacity of the cell 10, thereby ensuring the electrical performance of the cell 10.
[0054] In one embodiment, the width w of the electrode group 200 satisfies 50mm≤w≤300mm; the distance L5 between the through hole 110 and the center line of the electrode group 200 satisfies 4mm≤L5≤146mm and 0.4≤L5 / (w / 2)≤0.8.
[0055] In this embodiment, the width w of the electrode assembly 200 can be any value among 50mm, 100mm, 150mm, 200mm, 250mm, and 300mm, or any value between two of these. If the width w of the electrode assembly 200 is too small, such as less than 50mm, the effective reaction area of the electrode assembly 200 will be insufficient, making it difficult for the energy density of the electrode assembly 200 to meet the usage requirements. If the width w of the assembly is too large, such as greater than 300mm, it will increase the difficulty of molding the cell casing, and it will be difficult to ensure the flatness of the heat shrink film 100 during the assembly and packaging of the electrode assembly 200. Furthermore, the penetration distance of the electrolyte in the width direction of the electrode assembly 200 will be too long, making it difficult to achieve uniform wetting even with the assistance of the through hole 110.
[0056] The distance L5 between the through hole 110 and the center line of the electrode group 200 can be any value among 4mm, 10mm, 30mm, 50mm, 70mm, 90mm, 110mm, 130mm, and 146mm, or any value between any two. If the distance L5 between the through hole 110 and the center line of the electrode group 200 is too small, such as less than 4mm, then the through hole 110 is too close to the center line of the electrode group 200. During the use of the battery pack, the cells 10 continuously expand cyclically, and the central areas of two adjacent cells 10 will expand and compress. The electrical spacing is too small, making the heat shrink film 100 easily punctured, resulting in insulation failure at the through hole 110.
[0057] Furthermore, the width w of the electrode assembly 200 and the distance L5 between the through hole 110 and the center line of the electrode assembly 200 need to satisfy 0.4 ≤ L5 / (w / 2) ≤ 0.8, so that the through hole 110 is located at a position 60%-80% offset from the center line towards the edge of the electrode assembly 200. When the electrode assembly 200 needs to be wetted with electrolyte, the electrolyte can flow into the electrode assembly 200 from the through hole 110 and flow in two directions: the center of the electrode assembly 200 and the edge of the electrode assembly 200, thereby achieving uniform wetting of the electrolyte across the width of the electrode assembly 200. If L5 / (w / 2) > 0.8, the through hole 110 is too close to the edge of the electrode assembly 200, causing the electrolyte to seep through the through hole 110 and preferentially flow towards the edge, resulting in insufficient wetting of the central area of the electrode assembly 200. By reasonably setting the distance between the through hole 110 and the center line of the electrode group 200, the through hole 110 is reasonably positioned on the large surface of the heat shrink film 100, so that the electrolyte can uniformly and quickly wet the electrode group 200 to ensure the electrical performance of the battery cell 10.
[0058] In one embodiment, along the X direction, the distance L6 between two adjacent through holes 110 satisfies 10mm≤L6≤250mm.
[0059] In this embodiment, along the X direction, the distance L6 between two adjacent through holes 110 can be any value from 10mm, 20mm, 30mm, 50mm, 70mm, 100mm, 150mm, 200mm, and 250mm, or a value between any two of these values. If L6 is too small, such as less than 10mm, the distance between the two through holes 110 along the X direction will be too short, which may cause the electrolyte to concentrate too much in a local area of the electrode assembly 200, thus failing to uniformly wet the entire electrode assembly 200. If L6 is too large, such as greater than 250mm, some areas inside the electrode assembly 200 may be far from the through holes 110, making it difficult for the electrolyte to reach them, resulting in insufficient rapid wetting of the electrode assembly 200 and affecting the performance of the cell 10. By reasonably setting the distance between two adjacent through holes 110 along the X direction, the electrolyte can have a relatively reasonable flow space and penetration path within the electrode assembly 200, ensuring that all parts of the electrode assembly 200 are fully wetted, thereby guaranteeing the capacity and performance of the cell 10.
[0060] In one embodiment, the cross-sectional perimeter Z1 of the electrode assembly 200 satisfies 150mm≤Z1≤450mm; after the heat shrink film 100 is fitted into the electrode assembly 200, the gap L7 between the heat shrink film 100 and the electrode assembly 200 satisfies 0.5mm≤L7≤10mm; the heating shrinkage rate D of the heat shrink film 100 satisfies 3%≤D≤40%, and satisfies 4mm≤(Z1+4L7)×D-4L7≤40mm.
[0061] In this embodiment, the cross-section of the electrode group 200 is perpendicular to the Z-direction. The perimeter Z1 of the electrode group 200 can be any value among 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, and 450mm, or a value between any two values. If the perimeter Z1 of the electrode group 200 is too small, such as less than 150mm, the size of the electrode group 200 will be too small, resulting in insufficient effective reaction area and difficulty in meeting the capacity requirements of the cell 10. If the perimeter Z1 of the electrode group 200 is too large, such as greater than 450mm, the cross-section of the electrode group 200 will be too large, making it difficult to ensure uniform shrinkage during the heat shrink film 100 wrapping, increasing the difficulty of cell casing encapsulation, and reducing the uniformity of wall thickness during cell casing stretching. By reasonably setting the perimeter of the electrode group 200, the cell 10 can meet most capacity requirements and facilitate cell 10 encapsulation.
[0062] The gap L7 between the heat-shrink film 100 and the electrode assembly 200 is the distance between the inner surface of the heat-shrink film 100 and the outer surface of the electrode assembly 200 after the heat-shrink film 100 is fitted onto the electrode assembly 200. The gap L7 can be any value from 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, and 10mm, or a value between any two of these. By appropriately setting the gap between the heat-shrink film 100 and the electrode assembly 200, shrinkage space is reserved for the heat-shrink film 100. If the gap L7 is too small, such as less than 0.5mm, it will be difficult to fit the heat-shrink film 100 onto the electrode assembly 200, and the heat-shrink film 100 may easily get stuck. Moreover, if the heat-shrink film 100 is too tightly attached to the electrode assembly 200 before heat shrinking, there will be insufficient buffer space during shrinkage, which may cause deformation of the electrode assembly 200 due to local stress concentration. If the gap L7 is too large, such as greater than 10mm, the heat-shrink film 100 will not be able to evenly wrap the electrode assembly 200 during heat shrinkage, and wrinkles may easily occur.
[0063] Furthermore, the shrinkage rate D of the heat-shrink film 100 is between 3% and 40%. The cross-sectional perimeter Z1 of the electrode assembly 200, the gap L7 between the heat-shrink film 100 and the electrode assembly 200, and the shrinkage rate D of the heat-shrink film 100 need to satisfy 4mm ≤ (Z1 + 4L7) × D - 4L7 ≤ 40mm. The shrinkage rate D of the heat-shrink film 100 is the shrinkage ratio of the perimeter of the heat-shrink film 100 after heating. By reasonably setting the relationship between Z1, L7, and D, it is ensured that the heat-shrink film 100 can tightly adhere to the electrode assembly 200 after shrinkage, avoiding loosening of the electrode assembly 200; it can also prevent the heat-shrink film 100 from shrinking excessively, avoiding excessive extrusion force exerted by the heat-shrink film 100 on the electrode assembly 200. The shrinkage rate D of the heat shrink film 100 can be any value or a value between any two of the following: 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%. (Z1+4L7)×D-4L7 can be any value or a value between any two of the following: 4mm, 8mm, 12mm, 16mm, 20mm, 24mm, 28mm, 32mm, 36mm, 40mm.
[0064] The following examples and comparative examples verify the influence of the parameters of the heat shrink film 100 and the electrode assembly 200 on its performance. The examples and comparative examples are shown in Table 1. The heat shrink film 100 and the electrode assembly 200 are designed with different parameters, and the relevant tests are carried out on the battery cell 10 and the corresponding test results are recorded.
[0065] Table 1
[0066]
[0067] As shown in Table 1, when L1 is below the lower limit, during charge-discharge cycle testing of cell 10, the heat-shrink film 100 expands during the cycle expansion, and the folded edge 120 shrinks, causing a short circuit. When L1 is above the upper limit, during production, near the tab, the heat-shrink film 100 shrinks and wrinkles, scratching the tab. When L5 / (w / 2) is below the lower limit, during charge-discharge cycle testing of cell 10, a short circuit occurs during the cycle expansion of cell 10, and disassembly reveals that the opening area is punctured. When (Z1+4L7)×D-4L7 is below the lower limit, during the manufacturing process of cell 10, the heat shrink film 100 does not tightly wrap the electrode assembly 200 after shrinking, making it difficult for the electrode assembly 200 to be installed in the casing, and causing wrinkles and scratches on the heat shrink film 100; when (Z1+4L7)×D-4L7 is above the upper limit, the heat shrink film 100 wraps too tightly after shrinking, causing the edges of the electrode assembly 200 to be damaged, resulting in electrode breakage and short circuit.
[0068] According to an embodiment of the present invention, in a second aspect, a battery pack is also provided, comprising: a housing; and a plurality of battery cells 10, wherein the plurality of battery cells 10 are housed within the housing. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells 10; furthermore, by arranging the plurality of battery cells 10 within the housing of the battery pack, the overall energy density of the battery pack can be increased, thereby improving the performance of the battery pack.
[0069] The battery pack mentioned in the embodiments of the present invention may include one or more battery cells 10 as a single physical module to provide higher voltage and capacity. When there are multiple battery cells 10, the multiple battery cells 10 are connected in series, parallel, or mixed through a busbar. Multiple battery cells 10 can be directly assembled into a battery pack, or they can be first assembled into battery modules, and then the battery modules are assembled into a battery pack.
[0070] In some implementations, the battery cell 10 can be a secondary battery cell, which refers to a battery cell that can be reactivated by charging after discharge and continue to be used. The battery cell can be a lithium-ion battery cell, sodium-ion battery cell, sodium-lithium-ion battery cell, lithium-sulfur battery cell, magnesium-ion battery cell, nickel-metal hydride battery cell, nickel-cadmium battery cell, lead-acid battery cell, etc., and the embodiments of the present invention are not limited to this.
[0071] In some implementations, the battery cell 10 in the embodiments of the present invention can be a metal battery cell. Specifically, the metal battery cell may include a lithium metal secondary battery cell, a sodium metal battery cell, or a magnesium metal battery cell, etc. The embodiments of the present invention do not limit this.
[0072] The electrode assembly 200 of the battery cell 10 includes a positive electrode, a negative electrode, and an insulating component. During the charging and discharging process of the battery cell 10, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The insulating component is disposed between the positive and negative electrodes to prevent short circuits between them while allowing active ions to pass through.
[0073] In some implementations, the positive electrode can be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.
[0074] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.
[0075] In some implementations, the negative electrode can be a negative electrode sheet, which may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.
[0076] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.
[0077] In some implementations, the separator is a separator membrane. This invention does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.
[0078] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.
[0079] In some implementations, the separator is a solid electrolyte. The solid electrolyte is placed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.
[0080] In some implementations, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This invention does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.
[0081] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.
[0082] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. A battery cell, characterized in that, include: A battery cell housing having a receiving cavity and an opening communicating with the receiving cavity; An electrode assembly, which is installed within the receiving cavity through the opening; A heat-shrinkable film is applied around the outer periphery of the electrode assembly and, after being heated, covers the electrode assembly. The heat shrink film has through holes along the Z direction, and the through holes are located on the large surfaces on both sides of the heat shrink film. The diameter d of the through hole satisfies 1mm≤d≤4mm; The width w of the electrode group satisfies 50mm≤w≤300mm; the distance L5 between the through hole and the center line of the electrode group satisfies 4mm≤L5≤146mm and 0.4≤L5 / (w / 2)≤0.
8. The cross-sectional perimeter Z1 of the electrode assembly satisfies 150mm≤Z1≤450mm; after the heat-shrinkable film is fitted into the electrode assembly, the gap L7 between the heat-shrinkable film and the electrode assembly satisfies 0.5mm≤L7≤10mm; the heating shrinkage rate D of the heat-shrinkable film satisfies 3%≤D≤40% and 4mm≤(Z1+4L7)×D-4L7≤40mm.
2. The battery cell according to claim 1, characterized in that, Along the X direction, both ends of the heat-shrinkable film are provided with folded edges, which are attached to the end face of the electrode assembly.
3. The battery cell according to claim 2, characterized in that, The width L1 of the folded edge satisfies 1mm≤L1≤50mm.
4. The battery cell according to claim 2, characterized in that, Along the Z direction, the spacing L2 between the folded edges satisfies 3mm≤L2≤20mm.
5. The battery cell according to claim 1, characterized in that, The distance L3 between the through hole and both sides of the electrode group along the X direction satisfies 3mm≤L3≤297mm; the distance L4 between the through hole and both sides of the electrode group along the Y direction satisfies 3mm≤L4≤297mm.
6. The battery cell according to claim 1, characterized in that, Along the X direction, the distance L6 between two adjacent through holes satisfies 10mm≤L6≤250mm.
7. A battery pack, characterized in that, include: Box; A plurality of battery cells as described in any one of claims 1-6, wherein the plurality of battery cells are housed in the housing.