Battery cell and battery pack

Abstract

The invention relates to the technical field of batteries, and discloses a battery cell and a battery pack, and the battery cell comprises a pole group and a packaging film. According to the battery cell with the structure, a relational expression among the area of the edge sealing area, the large-surface area of the packaging film and the tensile strength C of the fusion area of the two PP layers is established through a formula # imgabs0 #, and when the large-surface area of the packaging film changes, the area of the edge sealing area also changes, so that the edge sealing force of the edge sealing area can be effectively ensured; the area of the edge sealing area in the unit large surface area of the packaging film can be ensured, so that the connection force of the edge sealing area after the pole group expands can be improved, the edge sealing area can be effectively prevented from being stripped and failed after being pulled, and the sealing performance of the battery cell can be effectively ensured. Meanwhile, the # imgabs 1 # can prevent insufficient connecting force of the edge sealing area caused by too small area of the edge sealing area, can also avoid excessive area design of the edge sealing area caused by too large area of the edge sealing area, and can avoid waste of materials and space.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell and a battery pack. Background Art

[0002] Soft-pack batteries consist of a pole group and a packaging film. The packaging film comprises a packaging body and a sealing edge region. The packaging body wraps around the pole group, and the packaging film is then hot-pressed to seal the pole group within the packaging film. After hot-pressing, the packaging film around the pole group forms the sealing edge region. As the soft-pack battery expands during charge and discharge cycles, the pole group expands and squeezes the packaging film outward, causing tension in the sealing edge region. Existing soft-pack battery sealing edge regions are poorly designed. Expansion of the pole group can easily cause the two layers of packaging film in the sealing edge region to peel off, leading to seal failure. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell and a battery pack to solve the problem in the prior art that the size design of the edge sealing area of ​​the battery cell is unreasonable and the edge sealing area is prone to sealing failure after the battery cell cyclic expansion.

[0004] In a first aspect, the present invention provides a battery cell, comprising:

[0005] Pole group;

[0006] The packaging film includes a packaging body and a sealing edge area, wherein the packaging body is coated on the outside of the electrode group, and the sealing edge area is located on the outer peripheral side of the electrode group; the inner edge of the sealing edge area extends along the length direction of the battery cell for a length a, the inner edge of the sealing edge area extends along the width direction of the battery cell for a width b, and the width of the sealing edge area is W; the packaging film includes a PP layer in the thickness direction, and the tensile strength of the fusion area of ​​the two PP layers is C, The units of a, b, and W are mm, and the unit of C is MPa.

[0007] Beneficial effect: The battery cell of this structure can be Establish the relationship between the area of ​​the edge sealing area and the large surface area of ​​the packaging film and the tensile strength C of the fusion area of ​​the two PP layers. When the large surface area of ​​the packaging film changes, the area of ​​the edge sealing area also changes accordingly, thereby effectively ensuring the edge sealing force of the edge sealing area and the area of ​​the edge sealing area per unit large surface area of ​​the packaging film. This can ensure the connection strength of the edge sealing area after the electrode group expands, effectively prevent the edge sealing area from peeling off and failing after being pulled, and effectively ensure the sealing performance of the battery cell. At the same time It can prevent the edge banding area from being too small, which will lead to insufficient connection force in the edge banding area, and it can also prevent the edge banding area from being too large, which will lead to excessive design of the edge banding area, and can avoid wasting materials and space.

[0008] In an optional embodiment, 1 mm ≤ W ≤ 50 mm.

[0009] Beneficial effects: This setting can prevent the width of the edge sealing area from being too small, ensure the connection force between the two layers of packaging film in the edge sealing area, and effectively ensure the sealing effect of the edge sealing area after the battery cell cyclic expansion; at the same time, under the premise of ensuring the sealing performance of the edge sealing area, it can also prevent the width of the edge sealing area from being too large, avoid wasting materials and space, ensure the volume energy density of the battery cell and control the manufacturing cost of the battery cell.

[0010] In an optional embodiment, 5mm≤W≤10mm.

[0011] In an optional embodiment, 80 mm ≤ a ≤ 1000 mm, and 30 mm ≤ b ≤ 300 mm.

[0012] In an optional embodiment, a accommodating groove is provided on the packaging body, and the pole group is arranged in the accommodating groove; the corners of the accommodating groove are provided with arc corners, and the distance between the side of the arc corner facing the edge sealing area and the inner edge of the edge sealing area is D, 2mm≤D≤20mm.

[0013] Beneficial Effects: This arrangement maintains sufficient spacing between the inner edge of the edge seal and the R-corner edge, preventing high-temperature damage to the R-corner during heat sealing. This ensures the strength of the packaging film in the R-corner area after prolonged use and expansion of the battery cell through charge and discharge cycles, preventing cracking and effectively ensuring the film's seal. Furthermore, the requirement of 2mm ≤ D ≤ 20mm prevents excessive spacing between the inner edge of the edge seal and the R-corner, thus avoiding waste of material and space.

[0014] In an optional embodiment, 5 mm ≤ D ≤ 10 mm.

[0015] In an optional embodiment, the total penetration depth of the fusion region of the two PP layers of the two packaging films is h1, the thickness of the single PP layer is h2, and 0.3≤h1 / 2h2≤0.8.

[0016] Beneficial effects: This can prevent the total melting depth of the two PP layers from being too small, ensure the bonding strength between the two PP layers, and thus ensure the sealing of the edge sealing area; at the same time, it can also avoid the total melting depth of the two PP layers from being too large, which may cause the PP layer to be over-melted, and ensure the bonding strength between the PP layer and the non-PP layer of the packaging film, and ensure the sealing of the edge sealing area after the battery cell expands during long-term use.

[0017] In an optional embodiment, 0.024 mm ≤ h1 ≤ 0.24 mm, and 0.04 mm ≤ h2 ≤ 0.15 mm.

[0018] In an optional embodiment, the distance between the side surface of the pole group and the inner edge of the edge sealing area is d, and 1mm≤d≤50mm.

[0019] Beneficial effects: This arrangement can prevent the distance between the side of the electrode group and the inner edge of the edge sealing area from being too small, and can prevent the heat from scalding the diaphragm of the electrode group during heat sealing of the packaging film, thereby causing a short circuit in the battery cell, thereby ensuring the safety performance of the battery cell; at the same time, it can also prevent the distance between the side of the electrode group and the inner edge of the edge sealing area from being too large, thereby affecting the volume energy density of the battery cell, and avoiding waste of materials and space.

[0020] In a second aspect, the present invention further provides a battery pack comprising any one of the above-mentioned battery cells. The battery pack comprises the battery cell and has the same technical effects as the battery cell, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present invention;

[0023] Figure 2 for Figure 1 AA sectional view;

[0024] Figure 3 for Figure 2 A partial enlarged schematic diagram of the middle A.

[0025] Description of reference numerals:

[0026] 1. Electrode group; 2. Encapsulation film; 21. Encapsulation body; 211. Accommodation groove; 22. Edge sealing area; 23. PP layer; 24. Non-PP layer; DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0028] The battery cell includes an electrode group and a packaging film. The inner layer of the packaging film is a PP layer, and the outer layer is a non-PP layer. During the packaging process of the packaging film, the sealing head is first heated, and then the sealing head uses force to hot-press the two layers of packaging film. When the PP layer of the inner layer of the packaging film reaches the specified temperature, the PP layer melts and the PP layers of the two layers of packaging film are bonded together, thereby achieving heat sealing of the packaging film.

[0029] After the battery cell expands during charge and discharge cycles, the electrode group also expands. This expansion pushes the packaging film outward, causing tension on the packaging film at the edge seal area. In related art, the size of the battery cell edge seal area is not properly designed, resulting in insufficient connection strength between the two layers of packaging film in the edge seal area. This expansion of the electrode group can easily lead to the two layers of packaging film in the edge seal area peeling off, resulting in sealing failure in the edge seal area.

[0030] The following combination Figures 1 to 3 , describing embodiments of the present invention.

[0031] According to an embodiment of the present invention, on the one hand, a battery cell is provided, comprising an electrode group 1 and a packaging film 2 .

[0032] The packaging film 2 includes a packaging body 21 and a sealing edge 22. The packaging body 21 is wrapped around the electrode group 1, and the sealing edge 22 is located on the outer periphery of the electrode group 1. The inner edge of the sealing edge 22 extends along the length direction of the battery cell for a length a, and the inner edge of the sealing edge 22 extends along the width direction of the battery cell for a width b. The width of the sealing edge 22 is W. The packaging film 2 includes a PP layer 23 in the thickness direction. The tensile strength of the fusion area of ​​the two PP layers 23 is C. The units of a, b, and W are mm, and the unit of C is MPa.

[0033] The tensile strength C of the fused region of the two PP layers 23 is an inherent parameter of the material of the packaging film 2 and is determined by the material of the packaging film 2 . The tensile strength C of the fused region of the two PP layers 23 of different packaging films 2 is different.

[0034] The edge sealing area 22 has a certain width, which includes an inner edge and an outer edge set at a certain distance from the inner edge. The distance between the inner edge and the outer edge is the width of the edge sealing area 22. 2a+2b is the circumference of the inner edge of the edge sealing area 22, (2a+2b)*W is the area of ​​the edge sealing area 22, and a*b is the area of ​​the packaging film 2 inside the inner edge of the edge sealing area 22. This area is the area of ​​the large surface of the packaging film 2. After the battery cell charge and discharge cycle electrode group 1 expands, the edge sealing area 22 is pulled and the large surface of the packaging film 2 is compressed. The larger the large surface area of ​​the packaging film 2, the greater the pressure on the large surface. At this time, in order to ensure the sealing of the two PP layers 23 of the edge sealing area 22, the battery cell requires a greater packaging force for the edge sealing area 22; the smaller the large surface area of ​​the packaging film 2, the smaller the pressure on the large surface, and the smaller the packaging force required for the edge sealing area 22. The battery cell of this structure is calculated by the formula Establish a relationship between the area of ​​the edge sealing area 22 and the large surface area of ​​the packaging film 2 and the tensile strength C of the fusion area of ​​the two PP layers 23. When the large surface area of ​​the packaging film 2 changes, the area of ​​the edge sealing area 22 also changes accordingly, thereby effectively ensuring the edge sealing force of the edge sealing area 22 and the area of ​​the edge sealing area 22 per unit large surface area of ​​the packaging film 2. This can ensure the connection strength of the edge sealing area 22 after the electrode group 1 expands, effectively prevent the edge sealing area 22 from peeling off and failing after being pulled, and effectively ensure the sealing performance of the battery cell. At the same time This can prevent the edge sealing area 22 from being too small, which may result in insufficient connection force in the edge sealing area 22 , and can also prevent the edge sealing area 22 from being too large, which may result in excessive area design in the edge sealing area 22 , thereby avoiding waste of materials and space.

[0035] Different packaging film 2 materials are selected. Different packaging films 2 have different tensile strengths C. Different packaging films 2 are used to design cells with different a, b, and W. Charge and discharge cycle tests are carried out on the cells. The test results are shown in Table 1.

[0036] Table 1

[0037]

[0038] It can be seen from Examples 1 to 5 in Table 1 that when a, b, and W satisfy the formula When the area of ​​the edge sealing area 22 is designed reasonably, the battery cell does not fail after the charge and discharge cycle test; it can be seen from Comparative Examples 1 to 3 that when When the edge sealing area 22 is too small, the connection force of the edge sealing area 22 is insufficient. After the battery cell charge and discharge cycle expansion test, the edge sealing area 22 leaks and the sealing of the edge sealing area 22 fails.

[0039] The tensile strength C of the fused region of the two PP layers 23 is determined by the material of the PP layer 23 of the packaging film 2 , and is generally 40 MPa≤C≤80 MPa.

[0040] The width W of the edge sealing area 22 affects the connection force of the edge sealing area 22, thereby affecting the sealing performance of the edge sealing area 22 after the battery cell expands during cycling. Figure 3 As shown, 1mm≤W≤50mm. This setting can prevent the width of the edge sealing area 22 from being too small, ensure the connection force between the two layers of packaging films 2 in the edge sealing area 22, and effectively ensure the sealing effect of the edge sealing area 22 after the battery cell cyclic expansion; at the same time, under the premise of ensuring that the sealing performance of the edge sealing area 22 is met, the width of the edge sealing area 22 can also be prevented from being too large, which can avoid wasting materials and space, and can ensure the volume energy density of the battery cell and control the manufacturing cost of the battery cell.

[0041] In some embodiments, the width W of the edge sealing area 22 satisfies 5mm≤W≤10mm. This setting can further optimize the width W of the edge sealing area 22, ensure the connection force between the two layers of packaging films 2 in the edge sealing area 22, and effectively ensure the sealing effect of the edge sealing area 22 after the battery cell cyclic expansion; at the same time, it can also prevent the width of the edge sealing area 22 from being too large, thereby avoiding waste of materials and space.

[0042] like Figure 1 As shown, the battery cell has a long side and a wide side. In some embodiments, the width of the edge sealing area 22 in the long side and the wide side of the battery cell is the same.

[0043] In some embodiments, as Figure 1 As shown, 80 mm ≤ a ≤ 1000 mm, 30 mm ≤ b ≤ 300 mm, and the length and width of the inner edge of the edge sealing area 22 can be flexibly adjusted according to the length and width of the electrode group 1 .

[0044] like Figure 2 and Figure 3 As shown, the package body 21 is provided with a receiving groove 211, and the electrode group 1 is disposed within the receiving groove 211. The corners of the notch of the receiving groove 211 are provided with rounded corners. The distance D between the edge of the rounded corner facing the edge seal area 22 and the inner edge of the edge seal area is 2mm≤D≤20mm, where the distance D between the edge of the rounded corner facing the edge seal area 22 and the inner edge of the edge seal area is the minimum distance between any point of the edge of the rounded corner facing the edge seal area 22 and the inner edge of the edge seal area 22. The rounded corner is the rounded angle set at the edge of the receiving groove 211, which ensures a smooth transition at the edge of the receiving groove 211. The accommodating groove 211 is formed by stamping. After stamping, the R-corner position is deformed by force, resulting in stress at the R-corner position. If the distance D between the edge of the R-corner facing the edge seal area 22 and the inner edge of the edge seal area is too small, the high temperature transferred to the R-corner area during the heat sealing process of the edge seal area 22 will cause excessive stress in the R-corner area, resulting in poor structural strength of the R-corner area. After the battery cell expands during long-term use and charge-discharge cycles, the R-corner area is prone to cracking, causing the sealing of the packaging film 2 to fail. 2mm≤D≤20mm. This setting ensures sufficient distance between the inner edge of the edge seal area 22 and the R-corner position, preventing high temperature damage to the R-corner area during the heat sealing process. It also ensures the strength of the packaging film 2 in the R-corner area and prevents cracking of the packaging film 2 in the R-corner area after long-term use and charge-discharge cycle expansion of the battery cell, effectively ensuring the sealing of the packaging film 2. 2mm≤D≤20mm also prevents excessive distance between the inner edge of the edge seal area 22 and the R-corner area, thus avoiding waste of material and space.

[0045] In some optional embodiments, 5mm≤D≤10mm. This setting can further optimize the distance between the inner edge of the edge-sealing area 22 and the rounded corner. During the heat-sealing process, it can prevent high temperature damage to the rounded corner area. After the battery cell expands after long-term use and charge-discharge cycles, it can ensure the strength of the packaging film 2 in the rounded corner area, prevent the packaging film 2 in the rounded corner area from cracking, and effectively ensure the sealing of the packaging film 2. It can also avoid the waste of material and space caused by an excessive distance between the inner edge of the edge-sealing area 22 and the rounded corner.

[0046] The total penetration depth of the fusion area of ​​the two PP layers 23 affects the connection force between the two PP layers 23, as well as the bonding force between the PP layer 23 and the non-PP layer 24. If the total penetration depth is too small, the connection force between the two PP layers 23 will be insufficient, which will affect the sealing of the edge sealing area 22; if the total penetration depth is too large, the PP layer 23 will be over-melted, and the bonding force between the PP layer 23 and the non-PP layer 24 of the packaging film 2 will be destroyed. After the battery cell is used for a long time and expands cyclically, the PP layer 23 and the non-PP layer 24 in the edge sealing area 22 will crack and peel off, resulting in failure of the sealing of the edge sealing area 22. In order to avoid these problems, such as Figure 3 As shown, in some embodiments, the total melting depth of the two PP layers 23 in the fusion area of ​​the two-layer packaging film 2 is h1, the thickness of the single PP layer 23 is h2, and 0.3≤h1 / 2h2≤0.8. 2h2 is the total thickness of the two PP layers 23, h1 / 2h2 is the ratio of the total melting depth of the two PP layers 23 to the total thickness of the two PP layers 23, and the ratio of the two thicknesses satisfies 0.3≤h1 / 2h2≤0.8. This can prevent the total melting depth of the two PP layers 23 from being too small, ensure the bonding strength between the two PP layers 23, and thus ensure the sealing of the edge sealing area 22; at the same time, it can also avoid the total melting depth of the two PP layers 23 being too large, resulting in over-melting of the PP layer 23, ensure the bonding strength between the PP layer 23 and the non-PP layer 24 of the packaging film 2, and ensure the sealing of the edge sealing area 22 after the battery cell is expanded during long-term use.

[0047] In some optional embodiments, such as Figure 3 As shown, 0.024mm≤h1≤0.24mm, 0.04mm≤h2≤0.15mm, which can prevent the total melting depth of the two PP layers 23 from being too small, ensure the bonding strength between the two PP layers 23, and thus ensure the sealing of the edge sealing area 22; at the same time, it can also avoid the total melting depth of the two PP layers 23 being too large, which may cause the PP layer 23 to be over-melted, and ensure the bonding strength between the PP layer 23 and the non-PP layer 24 of the packaging film 2, and ensure the sealing of the edge sealing area 22 after the battery cell is used for a long time and expands cyclically.

[0048] Battery cells with different h1 and h2 were designed, and charge-discharge cycle tests were carried out on the battery cells. The test results are shown in Table 2.

[0049] Table 2

[0050]

[0051] It can be seen from Examples 1 to 3 in Table 2 that when h1 and h2 satisfy 0.3≤h1 / 2h2≤0.8, the battery cell is well sealed and does not fail after cyclic expansion; it can be seen from Comparative Example 1 in Table 2 that when h1 / 2h2<0.3, the total melting depth of the two PP layers 23 is too small, the bonding force between the two PP layers 23 is insufficient, and the sealing of the edge sealing area 22 fails after cyclic expansion of the battery cell; it can be seen from Comparative Example 2 in Table 2 that when h1 / 2h2>0.8, the total melting depth of the two PP layers 23 is too large, resulting in over-melting of the PP layer 23, insufficient bonding force between the PP layer 23 and the non-PP layer 24 of the packaging film 2, leakage after cyclic expansion of the battery cell, and sealing of the edge sealing area 22 fail.

[0052] like Figure 3 As shown, in some embodiments, the distance between the side of the electrode group 1 and the inner edge of the edge sealing area 22 is d, 1mm≤d≤50mm. This setting can prevent the distance between the side of the electrode group 1 and the inner edge of the edge sealing area 22 from being too small, and can prevent the heat from scalding the diaphragm of the electrode group 1 during the heat sealing of the packaging film 2, thereby causing a short circuit in the battery cell, thereby ensuring the safety performance of the battery cell; at the same time, it can also prevent the distance between the side of the electrode group 1 and the inner edge of the edge sealing area 22 from being too large, thereby affecting the volume energy density of the battery cell, and avoiding waste of materials and space.

[0053] According to an embodiment of the present invention, on the other hand, a battery pack is provided, comprising the battery cell of the above embodiment.

[0054] The battery pack of this structure has the battery cells in it through the formula Establish a relationship between the area of ​​the edge sealing area 22 and the large surface area of ​​the packaging film 2 and the tensile strength C of the fusion area of ​​the two PP layers 23. When the large surface area of ​​the packaging film 2 changes, the area of ​​the edge sealing area 22 also changes accordingly, thereby effectively ensuring the edge sealing force of the edge sealing area 22 and the area of ​​the edge sealing area 22 per unit large surface area. This can ensure the connection strength of the edge sealing area 22 after the electrode group 1 expands, effectively prevent the edge sealing area 22 from peeling off and failing after being pulled, and effectively ensure the sealing performance of the battery cell. At the same time This can prevent the edge sealing area 22 from being too small, which may result in insufficient connection force in the edge sealing area 22 , and can also prevent the edge sealing area 22 from being too large, which may result in excessive area design in the edge sealing area 22 , thereby avoiding waste of materials and space.

[0055] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: Pole group; The packaging film includes a packaging body and a sealing edge area, wherein the packaging body is coated on the outside of the electrode group, and the sealing edge area is located on the outer peripheral side of the electrode group; the inner edge of the sealing edge area extends along the length direction of the battery cell for a length a, the inner edge of the sealing edge area extends along the width direction of the battery cell for a width b, and the width of the sealing edge area is W; the packaging film includes a PP layer in the thickness direction, and the tensile strength of the fusion area of ​​the two PP layers is C, The units of a, b, and W are mm, and the unit of C is MPa.

2. The battery cell according to claim 1, characterized in that 1mm≤W≤50mm.

3. The battery cell according to claim 2, characterized in that 5mm≤W≤10mm.

4. The battery cell according to any one of claims 1 to 3, characterized in that: 80mm≤a≤1000mm, 30mm≤b≤300mm.

5. The battery cell according to any one of claims 1 to 3, characterized in that: The packaging body is provided with a receiving groove, and the electrode group is arranged in the receiving groove; the corners of the receiving groove are provided with arc corners, and the distance between the side of the arc corner facing the edge sealing area and the inner edge of the edge sealing area is D, 2mm≤D≤20mm.

6. The battery cell according to claim 5, characterized in that 5mm≤D≤10mm.

7. The battery cell according to any one of claims 1 to 3, characterized in that: The total penetration depth of the fusion region of the two PP layers of the two packaging films is h1, the thickness of the single PP layer is h2, and 0.3≤h1 / 2h2≤0.

8.

8. The battery cell according to claim 7, characterized in that: 0.024mm≤h1≤0.24mm, 0.04mm≤h2≤0.15mm.

9. The battery cell according to any one of claims 1 to 3, characterized in that: The distance between the side surface of the pole group and the inner edge of the edge sealing area is d, 1mm≤d≤50mm.

10. A battery pack, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 9.

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