Battery, battery pack, and electric device

Abstract

This disclosure provides a battery, a battery pack, and an electrical device. The battery includes a casing and a top cover, with a weld seam formed at the welding joint area between the top cover and the casing. An insulating film is covered on the battery, comprising a main body and an extension. At the short side of the upper end face, the weld seam protrudes from the upper end face by a maximum dimension R mm along the height axis, and the extension seam has a maximum dimension L mm along a first axis, where 0.003 ≤ R / L ≤ 0.08. Compared with related technologies, this disclosure ensures that the ratio between the maximum spacing R of the weld seam along the height axis and the maximum dimension L of the extension seam at the short side of the upper end face satisfies 0.003 ≤ R / L ≤ 0.08. This ensures that the extension seam of the insulating film fits tightly against the top cover, preventing the risk of damage due to edge lifting; simultaneously, it ensures that the weld seam has sufficient structural strength and tear resistance, reducing the risk of battery seal failure.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to a battery, a battery pack, and an electrical device. Background Technology

[0002] In related technologies, the battery includes a casing and a top cover. The casing forms an inner cavity to accommodate the battery cells. The top cover and the casing are connected by welding to close the opening of the inner cavity, and a weld is formed in the welded joint area.

[0003] The battery surface is covered with an insulating film (blue film). The insulating film is used to achieve electrical insulation and mechanical protection, prevent the battery from short-circuiting with external components, and prevent the welds from being scratched and damaged by collisions. However, it is difficult for the insulating film to fit tightly against the top cover and weld surface, and the insulating film may peel up, affecting the protective effect of the insulating film. Summary of the Invention

[0004] The purpose of this disclosure is to provide a battery, battery pack, and electrical equipment to solve the technical problems in the related art. It can ensure the structural strength of the weld, avoid weld failure at the short side, and prevent the insulating film from curling.

[0005] In a first aspect, this disclosure provides a battery, including a housing and a top cover. The housing has an inner cavity for accommodating a battery cell. The housing has an upper end face with a long side extending along a first axial direction and a short side extending along a second axial direction. The first axial direction, the second axial direction, and the height axial direction are all perpendicular to each other. The inner cavity forms an opening at the upper end face. The top cover is welded to the housing to close the opening. The welded joint area between the top cover and the housing forms a weld seam. An insulating film is adhered and covered to the outer shell. The insulating film includes an integrally connected main body and an extension. The main body covers at least the side of the outer shell. The extension direction of the side is perpendicular to the top cover. The extension covers the top cover and extends from the edge of the top cover toward the center of the top cover. The extension covers the short side of the outer shell. The weld protrudes upward from the top cover along the height axis, and the maximum dimension of the weld protruding from the upper end face is R mm. At the short side of the upper end face, the extension covers the weld. Along the first axis, the maximum dimension of the extension on the top cover is L mm, where 0.003 ≤ R / L ≤ 0.08.

[0006] Secondly, this disclosure provides a battery pack including the aforementioned battery.

[0007] Thirdly, this disclosure provides an electrical device including the aforementioned battery pack.

[0008] Compared with related technologies, this disclosure limits the ratio of the maximum spacing R of the weld along the height axis to the maximum dimension L of the extension of the insulating film at the short side of the upper end face, ensuring that: 0.003 ≤ R / L ≤ 0.08. This ensures that the extension of the insulating film fits tightly against the top cover, preventing the risk of damage caused by warping; at the same time, it ensures that the weld has sufficient structural strength and tear resistance, reducing the risk of battery seal failure. Attached Figure Description

[0009] Figure 1 This is a perspective view of the battery provided in an embodiment of this disclosure.

[0010] Figure 2 This is a perspective view of the battery casing provided in an embodiment of this disclosure.

[0011] Figure 3 yes Figure 1 A top view of the provided battery.

[0012] Figure 4 yes Figure 3 A sectional view along the AA direction.

[0013] Figure 5 yes Figure 4 A magnified structural diagram of point B, which has one of its annotation forms.

[0014] Figure 6 yes Figure 4 A magnified structural diagram of point B with another labeling format.

[0015] Explanation of reference numerals in the attached figures: 1. Outer shell; 2. Top cover; 3. Inner cavity; 4. Opening; 5. Upper end face; 51. Long side; 52. Short side; 6. First gap; 7. Weld; 8. Pore; 9. Insulating film; 91. Main body; 92. Extension; D1, First Axis; D2, Second Axis; D3, Height Axis. Detailed Implementation

[0016] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0017] Existing battery packs often employ a stacking method where large battery faces face each other to suppress deformation of the long side of the battery top cover. However, this results in a lack of effective constraint on the short side of the top cover, making the weld seams prone to stress concentration and failure due to repeated tearing. Related technologies address this by increasing the weld wire dimensions, causing the weld wire to protrude beyond the top cover. This ensures the structural strength of the weld wire, preventing structural failure that could trigger severe thermal runaway within the battery, leading to the top cover flying off, increasing the thermal runaway opening area, and affecting the thermal safety of adjacent batteries.

[0018] Because the weld lines protrude from the top cover, the top of the top cover is uneven, forming an uneven surface. When the insulating film is applied to the outer surface of the battery casing, the insulating film preferentially adheres to the side of the battery casing and extends from the side of the casing towards the top cover. This requires edge fixing on the top surface of the top cover. However, due to the weld lines protruding from the top cover, the insulating film locally warps on the surface it adheres to, causing the insulating film to detach from the top cover and affecting the external insulation safety of the battery. In practical applications, if the weld protrudes too much from the battery surface, the insulating film cannot adhere tightly to the top cover and weld surface, resulting in edge warping and affecting the protective effect of the insulating film. If the weld protrudes too little, the weld size is reduced, which decreases the structural strength and tear resistance of the weld. The short sides of the battery, lacking effective restraint, are prone to weld failure due to repeated tearing.

[0019] Reference Figures 1 to 6 As shown, this disclosure provides a battery, including a housing 1 and a top cover 2 that covers the housing 1, the housing 1 and the top cover 2 together forming the battery casing.

[0020] The housing 1 is a component used to provide a receiving space to house the electrode assembly and other components and isolate them from the outside environment. The housing 1 generally includes a body with an opening at at least one end and an inner cavity 3. The opening of the housing 1 can be closed by a top cover 2 to seal and isolate the internal environment of the battery cell from the external environment. The materials of the housing include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, aluminum-plastic film, etc.

[0021] The top cover 2 is a component that closes the opening of the outer shell 1 to isolate the internal environment of the battery cell from the external environment; the material of the top cover 2 includes, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, aluminum-plastic film, etc.

[0022] In one feasible implementation, the battery casing 1 is a cuboid structure. To better illustrate the battery structure, this disclosure defines a three-dimensional rectangular coordinate system, defining the direction of the long side 51 of the top surface of the battery as the first axis D1, the direction of the short side 52 of the top surface of the battery as the second axis D2, and the height direction of the battery as the height axis D3. The first axis D1, the second axis D2, and the height axis D3 are perpendicular to each other.

[0023] An inner cavity 3 for accommodating battery cells and electrolyte is integrally formed within the outer casing 1. The outer casing 1 has an upper end face 5, which has a long side 51 extending along a first axial direction D1 and a short side 52 extending along a second axial direction D2. The normal direction of the upper end face 5 is the height axial direction D3. Among the multiple batteries constituting the battery pack, the multiple batteries are arranged in an array along the second axial direction D2, with the large surfaces of adjacent batteries in contact. An opening 4 is formed in the upper end face 5 of the inner cavity 3. The opening 4 is a through area of ​​the inner cavity 3 on the upper end face 5. The shape of the opening 4 matches the shape of the top cover 2. Components such as battery cells and electrolyte are assembled into the inner cavity 3 through the opening 4.

[0024] A battery cell is the basic unit of a battery, typically consisting of a positive electrode, a negative electrode, and a separator. Lithium-ion cells primarily function by the movement of lithium ions between the positive and negative electrodes. In cylindrical cells, the three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid cells, the thin-film structure is wound or stacked into an electrode assembly with a roughly cuboid shape.

[0025] Electrolytes are liquid electrolytes that transport active ions. They are liquid materials that conduct ions while isolating electrons; electrolytes are composed of chemical substances such as solvents, electrolyte salts, and additives; solvents can be carbonates, carboxylic acid esters, or ethers; electrolyte salts can be lithium salts, sodium salts, or zinc salts; additives can be vinylene carbonate, fluoroethylene carbonate, propylene sulfite, vinyl sulfite, etc.

[0026] At least a portion of the top cover 2 extends into the inner cavity 3 through the opening 4 to form a nested fit. In one feasible embodiment, the cross-section of the top cover 2 along the height axis D3 is a "T"-shaped structure or a flat plate structure, and there is a first gap 6 between the top cover 2 extending into the inner cavity 3 and the outer shell 1. The top cover 2 and the outer shell 1 are welded together to close the opening 4, connecting the top cover 2 and the outer shell 1 into an integral structure and closing the first gap 6 between the top cover 2 and the outer shell 1. The welding method can be top welding or side welding.

[0027] The weld seam 7 is formed at the welding interface between the top cover 2 and the outer shell 1. The high temperature during welding melts the metal materials of the top cover 2 and the outer shell 1, forming a molten pool. The molten pool fills the first gap 6 between the top cover 2 and the outer shell 1 and then solidifies to form the weld seam 7. The weld seam 7 can connect the top cover 2 and the outer shell 1 into a whole and disperse the stress generated by the battery under vibration or impact conditions.

[0028] An insulating film 9, preferably a blue film, is coated on the battery to improve the insulation performance of the battery's outer surface. It can be applied to the outer surface of the casing 1 by adhesive or coating. The insulating film 9 is made of a polymer film with insulating properties, used for electrical insulation and mechanical protection. The material of the insulating film 9 can be any one of polyester film (PET, Polyethylene Terephthalate), polyimide (PI), polypropylene (PP), or polyethylene (PE). The insulating film 9 completely covers the outside of the battery casing 1. In one feasible embodiment, the insulating film 9 includes a main body 91 and an extension 92, which are integrally formed. The main body 91 covers at least the side of the casing 1, extending along the height axis D3 perpendicular to the surface of the top cover 2, providing insulation and mechanical protection to the side of the casing 1. The extension 92 folds upward and inward from the top of the side of the casing 1, extending and covering the upper surface of the top cover 2, providing protection to a portion of the top cover 2. The extension 92 extends from the periphery of the top cover 2 toward the center of the top cover 2. The extension 92 is finished on the surface of the top cover 2, and the edge of the insulating film 9 is finally attached to the top surface of the top cover 2 to complete the sealing and covering.

[0029] The extension 92 extends from the edge of the top cover 2 toward the center of the top cover 2. The edge of the top cover 2 is also the welding connection between the top cover 2 and the outer shell 1. The extension 92 covers the weld 7 from the edge of the top cover 2, which can also play a certain role in restraining and strengthening the weld 7 and providing mechanical protection. However, the protrusion of the weld 7 will also affect the adhesion of the insulating film 9. If the weld 7 protrudes too much, the surface of the weld will bulge too much, causing the insulating film 9 to curl up and reducing the insulation and protection effect.

[0030] At the short side 52 of the upper end face 5, along the height axis D3, the weld 7 protrudes from the upper end face 5 by a maximum dimension of R mm, where R represents the degree of protrusion of the weld 7, limited to 0.05 ≤ R ≤ 0.2. The value can be 0.05, 0.07, 0.1, 0.13, 0.15, 0.17, or 0.2, specifically the values ​​listed above, or any value between 0.05 and 0.2.

[0031] If R is too small, the weld 7 will be insufficiently thick, reducing its effective load-bearing area. This will prevent the effective dispersion and transmission of tearing stress generated under vibration or impact conditions, leading to stress concentration at weld 7 on the short side 52 and making it prone to cracking. If R is too large, the weld 7 will be too thick, affecting the coating of the insulating film 9 on the battery surface. This will result in insufficient adhesion of the insulating film 9, making it prone to detachment. In addition, excessive welding time will lead to excessive continuous heat input, causing deformation of the outer shell 1 or top cover 2, and exacerbating the failure risk of weld 7 on the short side 52.

[0032] Along the first axial direction D1, the maximum dimension of the extension 92 is L mm, where L represents the coverage length of the extension 92 at the short side 52, and is limited to 2 ≤ L ≤ 40. The value can be 2, 5, 10, 15, 20, 25, 30, 35, or 40, specifically the values ​​listed above, or any value between 2 and 40. If L is too small, the coverage length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery will be insufficient, resulting in decreased adhesion strength and easy detachment of the insulating film 9. Furthermore, the coverage area of ​​the extension 92 cannot completely cover the weld 7 at the short side 52 and the edge area of ​​the top cover 2, leading to insufficient constraint of the extension 92 on the weld 7 at the short side 52 and inability to effectively disperse the tearing stress on the weld 7. If L is too large, the insulation film 9 will cover too long along the first axial direction D1 at the short side 52 of the battery. Since the top cover 2 will be equipped with poles and explosion-proof valves, the excessively long extension 92 may interfere with these components and also affect the heat dissipation of the top cover 2, causing the explosion-proof valve to open abnormally.

[0033] In the embodiments provided in this disclosure, the relationship is defined as follows: 0.003 ≤ R / L ≤ 0.08. The value can be 0.003, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08. The value can specifically be one of the values ​​listed above, or any value between 0.003 and 0.08.

[0034] If this ratio is too small, the height of the weld 7 protrusion will be too small, resulting in insufficient structural strength of the weld 7 at the short side 52. The weld 7 at the short side 52 is prone to damage and cracking after being subjected to tearing stress under vibration or impact conditions. Alternatively, if the covering length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery is too long, the excessively long extension 92 may interfere with the poles and explosion-proof valves installed on the top cover 2, and will also affect the heat dissipation of the top cover 2, causing abnormal opening of the explosion-proof valve.

[0035] If this ratio is too large, the weld seam 7 will have an excessively high protrusion, which will affect the coverage of the insulating film 9 on the battery surface, resulting in insufficient adhesion of the insulating film 9 and making it easy for the insulating film 9 to fall off. At the same time, if the welding time is too long, too much welding heat will be continuously input, causing deformation of the outer shell 1 or the top cover 2, which will increase the risk of failure of the weld seam 7 on the short side 52. Alternatively, if the coverage length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery is insufficient, the bonding strength will decrease, and the insulating film 9 will be easy to fall off. In addition, the coverage range of the extension 92 cannot completely cover the weld seam 7 at the short side 52 and the edge area of ​​the top cover 2, resulting in insufficient constraint of the extension 92 on the weld seam 7 at the short side 52, and failing to effectively disperse the tearing stress on the weld seam 7.

[0036] In one feasible implementation, at the short side 52 of the upper end face 5, along the first axial direction D1, the extension 92 extends beyond the edge of the weld 7 along the first axial direction D1, with the extension dimension between 0.01mm and 0.3mm. The value can be 0.01mm, 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3mm; specifically, it can be any value between 0.01mm and 0.3mm. The edge of the extension 92 is the boundary position of the extension 92 along the first axial direction D1, and the edge of the weld 7 is the boundary position of the weld 7 along the first axial direction D1. By controlling this minimum spacing within a preset value range, the coverage and protection range of the extension 92 over the weld 7 is ensured, while preventing interference between the extension 92 and the terminal post or explosion-proof valve, and also facilitating battery heat dissipation.

[0037] In the embodiments provided in this disclosure, at the short side 52 of the upper end face 5, along the first axial direction D1, the maximum distance between the surface of the weld 7 furthest from the outer shell 1 and the outer shell 1 is T mm, limited to 0.01 ≤ T ≤ 0.15. The value can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, or 0.15, specifically the values ​​listed above, or any value between 0.01 and 0.15. If T is too small, the weld 7 thickness is insufficient, the effective bearing area of ​​the weld 7 is reduced, and it cannot effectively disperse and transmit the tearing stress generated under vibration or impact conditions, leading to stress concentration at the short side 52 of the weld 7, which is prone to cracking. If T is too large, it will affect the bonding effect of the extension 92, resulting in a smaller area covered by the extension 92 on the weld 7, weakening the constraint and protective effect of the insulating film 9. At the same time, if the welding time is too long, excessive welding heat will be continuously input, causing deformation of the outer shell 1 and increasing the risk of failure of the weld 7 at the short side 52.

[0038] In the embodiments provided in this disclosure, at least a portion of the top cover 2 extends into the inner cavity 3 through the opening 4. A first gap 6 exists between the outer wall surface of the top cover 2 extending into the inner cavity 3 and the inner wall surface of the inner cavity 3. The first gap 6 is annular or strip-shaped. During welding, the molten pool fills into this first gap 6 to connect the outer shell 1 and the top cover 2 into a whole. Under vibration or impact conditions, stress concentration is easily generated at the first gap 6 in the weld 7, leading to damage and cracking of the weld 7.

[0039] In the embodiments provided in this disclosure, the lowest point of the weld 7 on the height axis D3 is misaligned with the first gap 6, thereby avoiding the problem of laser light leakage during the welding process. If the lowest point of the weld 7 coincides with the first gap 6 during the laser welding process, the laser energy may pass through the first gap 6 and directly act on the internal battery cell, causing damage to the battery cell.

[0040] By misaligning the lowest point of weld 7 with the first gap 6 along the height axis D3, the laser energy can be mainly applied to the outer shell 1 or the top cover 2. This ensures that the molten pool fully fills the first gap 6 to form a reliable weld structure, while preventing the laser from penetrating the first gap 6 and welding to the battery cell, thus avoiding damage.

[0041] Along the first axial direction D1, the distance between the surface of weld 7 furthest from the top cover 2 along the height axial direction D3 and the first gap 6 is K, where K ≤ 3mm. The value can be 0mm, 0.05mm, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, or 3mm; it can be any value between 0mm and 3mm, specifically those listed above. The surface of weld 7 furthest from the top cover 2 along the height axial direction D3 is the highest point of weld 7 protruding from the surface of the top cover 2. At this point, weld 7 is thickest and can withstand greater tearing stress, thus mitigating the negative impact of the first gap 6 to some extent.

[0042] Preferably, the surface of weld 7 furthest from the outer shell 1 is located on the extension line of the first gap 6. The highest part of weld 7 protruding from the surface of top cover 2 is aligned with the first gap 6, and all the stress concentrated at the first gap 6 is transferred to the highest point of weld 7, thereby maximizing the advantage of the highest structural strength at the thickest part of weld 7 and effectively reducing the risk of weld 7 cracking due to stress concentration.

[0043] In one feasible implementation, because the gas is not discharged in time during the solidification of the molten pool, pores 8 are present in the weld 7. Along the height axis D3, the orthographic projection of the pores 8 at least partially falls within the first gap 6. Since the pores 8 are located in the first gap 6, a critical welding area, they disrupt the continuity of the weld 7, reducing the effective load-bearing area of ​​the weld 7 and causing a decrease in structural strength and tear resistance. Therefore, the value is limited to 0.003 ≤ R / L ≤ 0.05. The value can be 0.003, 0.01, 0.02, 0.03, 0.04, or 0.05, specifically the values ​​listed above, or any value between 0.003 and 0.05.

[0044] By appropriately increasing the protrusion height of weld 7, sufficient strength is ensured in weld 7, thereby improving its structural strength and tear resistance, and reducing the risk of weld 7 cracking. The coverage length of insulating film 9 along the first axial direction D1 at the short side 52 of the battery can remain unchanged to maintain the constraint effect on weld 7.

[0045] In another feasible implementation, the orthographic projection of the pore 8 is offset from the first gap 6, avoiding the main stress area of ​​the weld and minimizing damage to the structural strength of the weld 7. Therefore, the value is limited to 0.009 ≤ R / L ≤ 0.08. The value can be 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08. Specifically, the value can be one of the aforementioned values ​​or any value between 0.009 and 0.08.

[0046] This reduces the build-up height of weld 7, thereby reducing the amount of welding heat input and preventing thermal deformation of the outer casing 1 or top cover 2 due to excessive heat input. Simultaneously, it appropriately extends the coverage length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery, preventing edge warping.

[0047] In the embodiments provided in this disclosure, an insulating block is fixed on the top cover 2. The insulating block is a non-metallic component with insulating properties and can be fixed to the top cover 2 by various fixing methods such as adhesive or snap-fit. The insulating block can play a role in electrical isolation. The insulating block presses against the extension 92, thereby making the extension 92 fit tightly against the weld 7 and the surface of the top cover 2, effectively preventing the insulating film 9 from curling up.

[0048] After adding the insulating block and realizing the structure of the pressure extension 92, since there is no need to consider the warping problem of the insulating film 9, the value is limited to 0.003≤R / L≤0.06. The value can be 0.003, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06, specifically the values ​​listed above, or any value between 0.003 and 0.06. This increases the protrusion height of the weld 7, improving its structural strength and tear resistance. It effectively disperses and transmits tearing stress generated under vibration or impact conditions, reducing the risk of weld 7 damage and cracking.

[0049] In the embodiments provided in this disclosure, the thickness of the extension 92 is between 20 μm and 350 μm. The value can be 20 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm or 350 μm, and the value can be specifically the values ​​listed above, or any value between 20 μm and 350 μm.

[0050] If the extension 92 is too thin, its own strength and tear resistance will be insufficient, making it prone to damage and losing its insulating and mechanical protection functions. It will also fail to effectively constrain the weld 7. If the extension 92 is too thick, its flexibility will decrease, reducing its fit and making it difficult to adhere tightly to the weld 7, potentially leading to warping. Furthermore, an excessively thick extension 92 will also affect the heat dissipation of the top cover 2, causing abnormal opening of the explosion-proof valve.

[0051] In one feasible implementation, the insulating film 9 adopts a double-layer composite structure, having a substrate and an adhesive layer stacked on top of each other. The substrate is located on the outer side and is used for insulation and protection; the adhesive layer is located on the inner side and is used for adhesion and fixation. The adhesive layer is disposed between the outer shell and the substrate, and is bonded to the outer surface of the outer shell 1, fixing the entire insulating film 9 to the battery outer shell 1 for covering and positioning, preventing the insulating film 9 from shifting or falling off, and ensuring the reliability of the insulation covering during battery use.

[0052] The thickness of the adhesive layer is between 10um and 200um, and the value can be 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, or 200um. The value can be one of the values ​​listed above, or any value between 10um and 200um. Controlling the adhesive layer thickness within the preset range ensures sufficient bonding strength, allowing the insulating film 9 to adhere tightly to the weld seam 7 area of ​​the outer shell 1 and the top cover 2, preventing edge lifting that could affect the protective effect of the insulating film 9. On the other hand, it avoids excessive adhesive thickness, which could lead to adhesive overflow or uneven thickness.

[0053] The thickness of the substrate is between 10um and 150um, and the specific values ​​can be 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, or 150um. These values ​​can be specifically those listed above, or any value between 10um and 200um. Controlling the substrate thickness within the preset range ensures that the substrate provides sufficient insulation strength and abrasion resistance, while avoiding excessive thickness that could lead to encapsulation difficulties and poor adhesion.

[0054] Provided the overall dimensions of the insulating film 9 meet the requirements, the thickness of the adhesive layer is greater than the thickness of the substrate. A thicker adhesive layer provides stronger adhesion, resulting in greater bonding reliability for the insulating film 9. This ensures the insulating film 9 is firmly bonded to the surfaces of the outer shell 1 and the top cover 2, preventing the insulating film 9 from warping and shifting, thus guaranteeing the stability of the coating.

[0055] In one feasible implementation, the extension 92 covers the long side 51 and the short side 52 of the top cover 2. The extension 92 covering the long side 51 is the first extension, and the extension 92 covering the short side 52 is the second extension. The size of the first extension is smaller than the size of the second extension.

[0056] The short side 52 of the top cover 2 lacks effective restraint, and the weld 7 is prone to stress concentration and failure due to repeated tearing. Furthermore, the weld 7 at the short side 52 protrudes from the surface of the top cover 2, which is an area where the insulating film 9 is prone to curling. Therefore, a larger second extension is provided to expand the coverage area of ​​the insulating film 9 at the short side 52, more fully cover the weld 7 corresponding to the short side 52, enhance the bonding and fixing effect, and further prevent the insulating film 9 from curling.

[0057] The long side 51 of the top cover 2 is effectively constrained by the large-area stacking of the battery pack. The tearing force on the weld 7 is much lower than that on the short side 52. The requirements for the coverage and bonding strength of the insulating film 9 are relatively low. Therefore, a smaller first extension is set up, which can not only meet the insulation protection requirements of the long side, but also avoid the extension being too large and interfering with components such as the pole and the explosion-proof valve. At the same time, it will also affect the heat dissipation of the top cover 2 and cause the explosion-proof valve to open abnormally.

[0058] Furthermore, the difference between the dimensions of the first extension and the second extension is less than or equal to 1.5 mm. This is to avoid an excessively large difference that would result in an overly long second extension, which would not only waste the insulating film 9 material but also cause interference with components such as the pole and explosion-proof valve, and would also affect the heat dissipation of the top cover 2, causing abnormal opening of the explosion-proof valve. On the other hand, it would result in the first extension being too small, making it difficult to fully cover the long side 51 and the corresponding weld 7, thus failing to meet the insulation protection requirements of the long side 51.

[0059] In one feasible embodiment, the extension 92 has an overlapping area located at the first gap 6, and the overlapping area includes at least two layers of insulating film 9. By bending and bonding the corresponding area of ​​the extension 92, the insulating film 9 is made into a state of two-layer superposition, and then the overlapping area is pasted and fixed to the surface of the top cover 2 to ensure that the insulating film 9 is tightly bonded, further improving the stability of the covering and preventing the extension 92 from curling up.

[0060] In the embodiments provided in this disclosure, the battery is defined as a flat block structure. The area where the short side 52 is located has higher requirements for the load-bearing capacity of the weld 7. The ratio of the length of the short side 52 to the length of the long side 51 is defined as being between 0.0167 and 0.8, and the value can be 0.0167, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8. The value can be specifically the values ​​listed above, or any value between 0.0167 and 0.8. Controlling the difference between the short side 52 and the long side 51 of the battery within a certain range can reduce the stress concentration in the welding area of ​​the short side 52 to a certain extent.

[0061] Based on this structure, at the short side 52 of the upper end face 5, the relationship is defined as follows: 0.01 ≤ R / L ≤ 0.08. The value can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08, specifically the values ​​listed above, or any value between 0.01 and 0.08. Since the welding area of ​​the short side 52 of the flat battery is more susceptible to vibration or impact, the weld 7 is more prone to cracking. Therefore, by increasing the lower limit of the relationship and appropriately increasing the protrusion height of the weld 7, sufficient strength is ensured, thereby improving the structural strength and tear resistance of the weld 7 and reducing the risk of cracking. The coverage length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery can remain unchanged to maintain the constraint effect on the weld 7.

[0062] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0063] Size measurement methods Use measuring instruments such as micrometers or calipers to measure parameters such as length, width, depth, diameter, radius, distance, and thickness. The area is then calculated using these parameters.

[0064] Battery manufacturing (1) Preparation of the positive electrode: The positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92-98):(4-1):(4-1).

[0065] (2) Preparation of negative electrode: The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90-96): (4-2): (2-1): (4-1).

[0066] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0067] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0068] (5) Battery fabrication: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare battery cell, which is then placed in a prismatic battery casing. The battery is dried, injected with electrolyte, sealed with a sealing device, and then subjected to settling, formation, and volume adjustment to obtain the battery.

[0069] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0070] The adhesive includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0071] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0072] The positive electrode current collector foil can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0073] The negative electrode current collector foil can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0074] In this test, the main active material of the positive electrode was selected from lithium iron phosphate, accounting for 98% of the mass of the positive active material, 0.5% of the conductive agent, and 1.5% of the binder; the active material of the negative electrode was selected from artificial graphite, accounting for 96.5% of the mass of the negative active material, 0.5% of the conductive agent, 0.5% of the thickener, and 2.5% of the binder.

[0075] The testing method is as follows: Test Method 1: Battery leakage rate under vibration conditions According to the above battery preparation method, for each embodiment and comparative example, 500 batteries will be prepared, 50 batteries will be grouped together, and they will be arranged along the width direction of the batteries to form a battery column. The battery columns will be arranged along the length direction of the batteries to form a battery pack. The values ​​of R and L for each embodiment and comparative example are shown in Table 2 below. Other test conditions are kept consistent.

[0076] The battery was mounted on a vibration table according to GB / T2423.43. The testing procedure was carried out according to GB / T2423.56. Random and fixed-frequency vibration loads were applied in each direction, and the loading sequence should preferably be random z-axis, fixed-frequency z-axis, random y-axis, fixed-frequency y-axis, random x-axis, fixed-frequency x-axis (the direction of the line connecting the front and rear of the battery is the x-axis direction, and the other horizontal direction perpendicular to the x-axis direction is the y-axis direction). The vibration frequency, power spectral density (PSD), vibration time, etc. are shown in Table 1 below.

[0077] Table 1: After the vibration ends, observe the junction between the short side of the battery top cover 2 and the battery casing 1 to see if any leakage occurs. The leakage rate is calculated as (number of batteries that leaked / 100). 100%.

[0078] If the battery leakage rate is less than or equal to 1%, the test result is considered good; if the battery leakage rate is greater than 1% but less than 3%, the test result is considered qualified; if the battery leakage rate is greater than 3%, it is considered unqualified.

[0079] Test Method 2: Insulating Film Lifting Test Following the battery preparation method described above, 500 batteries were prepared for each embodiment and comparative example. First, the battery cell was placed inside the casing 1, and the top cover 2 was welded to the casing 1 using laser welding technology. During the welding process, the welding power was maintained at 2000W, and the welding speed was set to 50mm / s. After welding, an insulating film 9 was pasted onto the outside of the battery casing 1. The insulating film 9 covered the bottom and sides of the battery, and partially extended to the top cover 2, covering its four edges. Ten days after pasting, the lifting rate of the insulating film 9 was observed. If the lifting rate was less than 1%, it was considered good; if the lifting rate was greater than 1% but less than 3%, it was considered acceptable; and if the lifting rate was greater than 3%, it was considered unacceptable.

[0080] Table 2: According to the test results in Table 2 above, combined with Examples 1-14, when the formula value of R / L satisfies 0.003≤R / L≤0.08, the protrusion height of weld 7 is compatible with the coverage length of insulating film 9. After testing, under vibration conditions, the welding structure of the short side 52 of the battery is stable and there is no cracking that would lead to battery leakage. After disassembling the battery, the insulating film 9 is tightly attached to the top cover 2 without any warping. In Example 14, when the L value is 42mm, the insulating film 9 will affect the setting of functional structural components such as the upper pole or injection hole of the top cover 2.

[0081] In Comparative Example 1, the formula value of R / L is less than 0.003, which leads to insufficient structural strength of the weld 7 at the short side 52. Under vibration or impact conditions, the weld 7 at the short side 52 is prone to damage and cracking after being subjected to tearing stress. In Comparative Example 2, the formula value of R / L is greater than 0.08, resulting in insufficient coverage length of the insulating film 9 along the first axial direction D1 at the short side 52 of the battery, reduced adhesion strength, and the insulating film 9 is prone to detachment.

[0082] Secondly, this disclosure provides a battery pack including at least two batteries as described above, the at least two batteries being arranged along a second axis D2. Because the batteries are stacked along the large surface direction of the batteries on the second axis D2, adjacent batteries are close to each other, creating constraints. This results in weaker constraints on the short side 52 of the upper surface 5 of the battery casing 1. Under vibration or impact conditions, the weld 7 at the short side 52 is more prone to stress concentration, increasing the risk of cracking at the weld 7 at the short side 52.

[0083] Furthermore, multiple batteries arranged along the second axis D2 form a battery pack. The ratio of the battery pack's dimension along the second axis D2 to its dimension along the first axis D1 is greater than or equal to 5, and the value can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a larger value. The value can be one of the aforementioned listed values ​​or any value greater than 5. The batteries within the battery pack are mainly close to each other and form constraints along the second axis D2. However, the short side 52 of the upper end face 5 of the battery is in a state of weak constraint. Under vibration or impact conditions, the weld 7 at the short side 52 is prone to stress concentration, posing a significant risk of cracking.

[0084] Thirdly, this disclosure provides an electrical device that may include the aforementioned battery pack.

[0085] Battery packs can serve as operating power for electrical equipment or as driving power for electrical equipment, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. By way of example only, electrical equipment can be, but is not limited to, vehicles, ships, aircraft, household appliances, and industrial equipment. For example, vehicles can be passenger cars, trucks, construction vehicles, etc.

[0086] In addition, electrical equipment can also be used for the storage, conversion, and release of recyclable electrical energy.

[0087] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of this disclosure. The above description is only a preferred embodiment of this disclosure, but this disclosure does not limit the scope of implementation to what is shown in the figures. Any changes made in accordance with the concept of this disclosure, or modifications to equivalent embodiments with equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of this disclosure.

Claims

1. A battery, characterized in that, The device includes an outer casing and a top cover. The outer casing has an internal cavity for accommodating the battery cell. The outer casing has an upper end face with a long side extending along a first axial direction and a short side extending along a second axial direction. The first axial direction, the second axial direction, and the height axial direction are all perpendicular to each other. The internal cavity forms an opening at the upper end face. The top cover is welded to the outer casing to close the opening. The welded joint area between the top cover and the outer casing forms a weld seam. An insulating film is adhered and covered to the outer shell. The insulating film includes an integrally connected main body and an extension. The main body covers at least the side of the outer shell. The extension direction of the side is perpendicular to the top cover. The extension covers the top cover and extends from the edge of the top cover toward the center of the top cover. The extension covers the short side of the outer shell. The weld protrudes upward from the top cover along the height axis, and the maximum dimension of the weld protruding from the upper end face is R mm. At the short side of the upper end face, the extension covers the weld. Along the first axis, the maximum dimension of the extension on the top cover is L mm, where 0.003 ≤ R / L ≤ 0.

08.

2. The battery according to claim 1, characterized in that, At the short side of the upper end face, along the first axial direction, the extension extends beyond the edge of the weld in the first axial direction, with the extension dimension being between 0.01mm and 0.3mm.

3. The battery according to claim 1, characterized in that, At the short side of the upper end face, along the first axis, the maximum distance between the weld seam and the surface farthest from the outer shell is T mm, where 0.01 ≤ T ≤ 0.

15.

4. The battery according to claim 1, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the top cover extending into the inner cavity and the outer shell sidewall, wherein the lowest point of the weld in the height axial direction is offset from the first gap.

5. The battery according to claim 1, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the top cover extending into the inner cavity and the sidewall of the outer shell. Along a first axial direction, the distance between the surface of the weld furthest from the top cover and the first gap along the height axial direction is K, where K≤3mm.

6. The battery according to claim 1, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the outer wall surface of the top cover extending into the inner cavity and the inner wall surface of the inner cavity, wherein the surface of the weld furthest from the top cover along the height axis lies on the extension line of the first gap.

7. The battery according to claim 1, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the outer wall surface of the top cover extending into the inner cavity and the inner wall surface of the inner cavity. The weld has pores, and the orthographic projection of the pores along the height axis falls at least partially within the extension, wherein 0.003≤R / L≤0.

05.

8. The battery according to claim 1, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the outer wall surface of the top cover extending into the inner cavity and the inner wall surface of the inner cavity. The weld has pores, and the orthographic projection of the pores is offset from the first gap along the height axis, wherein 0.009≤R / L≤0.

08.

9. The battery according to claim 1, characterized in that, An insulating block is fixed on the top cover and presses against the extension, wherein 0.003≤R / L≤0.

06.

10. The battery according to claim 1, characterized in that, The thickness of the extension is between 20um and 350um.

11. The battery according to any one of claims 1-10, characterized in that, The insulating film has a substrate and an adhesive layer stacked in phase. The adhesive layer is disposed between the outer shell and the substrate and is bonded to the outer surface of the outer shell. The thickness of the adhesive layer is between 10um and 200um, and the thickness of the substrate is between 10um and 150um.

12. The battery according to claim 11, characterized in that, The thickness of the adhesive layer is greater than the thickness of the substrate.

13. The battery according to any one of claims 1-10, characterized in that, The extension covers the long and short sides of the top cover. The extension covering the long side is the first extension, and the extension covering the short side is the second extension. The size of the first extension is smaller than the size of the second extension.

14. The battery according to claim 13, characterized in that, The difference between the size of the first extension and the size of the second extension is less than or equal to 1.5 mm.

15. The battery according to any one of claims 1-10, characterized in that, At least a portion of the top cover extends into the inner cavity through the opening, and a first gap exists between the outer wall surface of the top cover extending into the inner cavity and the inner wall surface of the inner cavity. The extension forms an overlapping area located at the first gap, and the overlapping area includes at least two layers of the insulating film.

16. The battery according to claim 1, characterized in that, The ratio of the length of the short side to the length of the long side is between 0.0167 and 0.8, where 0.01 ≤ R / L ≤ 0.

08.

17. The battery according to claim 1, characterized in that, 0.05≤R≤0.2, and / or, 2≤L≤40.

18. A battery pack, characterized in that, It includes at least two batteries as described in any one of claims 1-18, wherein the at least two batteries are arranged upward along the second axis.

19. The battery pack according to claim 18, characterized in that, A plurality of the batteries arranged along the second axis constitute a battery pack, wherein the ratio of the dimension of the battery pack along the second axis to the dimension of the battery pack along the first axis is greater than or equal to 5.

20. An electrical appliance, characterized in that, Includes the battery pack as described in any one of claims 18-19.

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