Battery cell and electric apparatus

Abstract

A battery cell and an electric apparatus. The battery cell comprises a battery cell casing, an electrode assembly, and a tab assembly, wherein the battery cell casing comprises a main body portion and a sealing portion; the electrode assembly is arranged in the main body portion; and the tab assembly comprises a tab and two pieces of insulating adhesive, the tab being connected to the electrode assembly and extending from the sealing portion, in the direction of thickness of the tab, the tab being arranged between the two pieces of insulating adhesive, and the insulating adhesive connecting the battery cell casing to the tab. At 25°C, the tensile force between the insulating adhesive and the battery cell casing and / or the tab ranges from 5 N / mm to 10 N / mm, thereby improving the packaging tensile force of the insulating adhesive under room temperature conditions and improving the packaging reliability of the battery cell under room temperature conditions; and at 120°C, the tensile force between the insulating adhesive and the battery cell casing and / or the tab ranges from 0.01 N / mm to 0.2 N / mm, thereby facilitating the rapid formation of a pressure relief channel after the battery cell expands, improving the heat dissipation efficiency and thus improving the safety performance of the battery cell.

Description

Battery cells and electrical equipment Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery cell and an electrical device. Background Technology

[0002] With the continuous updating and development of lithium-ion battery technology, the application fields of lithium-ion batteries are also expanding. As a result, the safety of battery cells is receiving increasing public attention. Lithium-ion battery safety accidents characterized by thermal runaway caused by external short circuits occur frequently, which poses a certain obstacle to the development of lithium-ion batteries. How to solve the problem of battery cell safety is a difficult problem that the lithium-ion battery industry cannot avoid. Summary of the Invention

[0003] In view of this, it is necessary to provide a battery cell and electrical equipment to improve safety.

[0004] This application provides a battery cell, including a cell housing, an electrode assembly, and a tab assembly. The cell housing includes a main body and a sealing portion. The electrode assembly is disposed within the main body. The tab assembly includes a tab and two insulating adhesives. The tab connects to the electrode assembly and extends from the sealing portion. Along the thickness direction of the tab, the tab is disposed between the two insulating adhesives, which connect the cell housing and the tab. At 25°C, the tensile force between the insulating adhesive and the cell housing and / or the tab ranges from 5 N / mm to 10 N / mm, improving the encapsulation tensile force of the insulating adhesive under room temperature conditions and enhancing the encapsulation reliability of the battery cell under room temperature conditions. When the tensile force exceeds 10 N / mm, the packaging bag is prone to rupture. At 120°C, the tensile force between the insulating adhesive and the cell housing and / or the tab ranges from 0.01 N / mm to 0.2 N / mm, which facilitates the rapid formation of a pressure relief channel after the battery cell expands, improving heat dissipation efficiency and thus enhancing the safety performance of the battery cell.

[0005] In one or more of the above optional embodiments, at 25°C, the tensile force between the insulating adhesive and the cell housing and / or tabs ranges from 6.5 N / mm to 10 N / mm. This further improves the encapsulation tensile force of the insulating adhesive under room temperature conditions, thereby enhancing the encapsulation reliability of the cell under room temperature conditions.

[0006] In one or more of the above optional embodiments, at 120°C, the tensile force between the insulating adhesive and the cell housing and / or tabs ranges from 0.01 N / mm to 0.1 N / mm. This further facilitates the rapid formation of pressure relief channels after the cell expands, improving heat dissipation efficiency and thus enhancing the safety performance of the cell.

[0007] In one or more of the above optional embodiments, at 95°C, the tensile force between the insulating adhesive and the cell housing and / or tabs ranges from 0.2 N / mm to 2 N / mm. Under operating conditions at 95°C, the cell's encapsulation reliability still meets requirements, reducing the occurrence of leakage.

[0008] In one or more of the above optional embodiments, at 95°C, the tensile force between the insulating adhesive and the cell housing and / or tabs ranges from 0.8 N / mm to 2 N / mm. Under operating conditions at 95°C, the cell's encapsulation reliability still meets requirements, further reducing the occurrence of leakage.

[0009] In one or more of the above optional embodiments, the insulating adhesive includes a surface layer, which is connected to the cell housing or tabs. The melt flow index of the surface layer at 230°C and a 2.16 kg load is 4 g / 10 min to 20 g / 10 min. If the melt flow index of the surface layer at 230°C and a 2.16 kg load is less than 4 g / 10 min, the fluidity of the surface layer after melting is too low, which is not conducive to expanding the overflow clumps formed after the surface layer melts, reducing the encapsulation pull force of the insulating adhesive under room temperature conditions, reducing the encapsulation reliability of the cell under room temperature conditions, and affecting the rapid formation of pressure relief channels after the cell expands, reducing heat dissipation efficiency and hindering the improvement of the cell's safety performance. If the melt flow index of the surface layer at 230°C and a 2.16 kg load is greater than 20 g / 10 min, the fluidity of the surface layer after melting is too high, which can easily lead to cell leakage and affect the cell's sealing performance. By limiting the melt flow index of the surface layer to 4g / 10min-20g / 10min at 230℃ and 2.16kg load, the fluidity of the surface layer after melting is improved, forming a tighter overflow clump at the sealing edge, increasing the encapsulation pull force of the insulating adhesive under normal temperature conditions, and improving the encapsulation reliability of the battery cell under normal temperature conditions. When the battery cell experiences thermal runaway and / or pressure relief, the high fluidity of the surface layer at high temperatures allows the encapsulation strength of the battery cell to decrease rapidly, enabling the high-temperature gas inside the battery cell to be rapidly depressurized and dissipated at the surface layer, improving heat dissipation efficiency and thus enhancing the safety performance of the battery cell.

[0010] In one or more of the above optional embodiments, the melt flow index of the surface layer at 230°C and 2.16 kg load is 7.1 g / 10 min to 12 g / 10 min, which makes it easier to meet the high temperature fluidity requirements, and the encapsulation thickness is easier to control, further improving the encapsulation reliability and safety performance of the battery cell under normal temperature conditions.

[0011] In one or more of the above optional embodiments, the surface layer has at least a first melting point and a second melting point. The range of the first melting point A is 50℃≤A≤120℃, and the range of the second melting point B is 120℃<B≤170℃. By setting multiple melting points, it can melt within the temperature range of the first melting point and the second melting point, effectively controlling the melting and pressure relief point of the insulating adhesive, further facilitating the rapid formation of pressure relief channels and improving the heat dissipation efficiency of the battery cell.

[0012] In one or more of the above optional embodiments, at 230°C and under a load of 2.16 kg, the melt index of the base layer is lower than that of the surface layer. The melt index of the base layer is 0.1 g / 10 min to 5 g / 10 min, which reduces the fluidity of the base layer melt, supports the surface layer, and helps to improve the sealing and insulation of the battery cell. The small melt index of the base layer helps to reduce the appearance of the exposed insulating adhesive due to heat curling and deformation. At the same time, Joule heat is easily generated during the conduction process of the electrode tab. The base layer has a high melting point and a small melt index, which plays an insulating role.

[0013] In one or more of the above optional embodiments, the surface layer must satisfy at least one of the following conditions: the number-average molecular weight Mn of the surface layer is 10,000 g / mol to 130,000 g / mol; if the number-average molecular weight of the surface layer is less than 10,000 g / mol, the melt viscosity of the surface layer is too low, which is not conducive to processing and molding, and easily leads to excessively high fluidity after the surface layer melts, reducing the packaging reliability of the battery cell under normal temperature conditions; if the number-average molecular weight of the surface layer is greater than 130,000 g / mol, the melt viscosity of the surface layer is too high, which is not conducive to processing and molding, and easily leads to increased brittleness of the surface layer, making it prone to cracking under external force. By limiting the number-average molecular weight Mn of the surface layer to 10,000 g / mol to 130,000 g / mol, the packaging reliability of the battery cell under normal temperature conditions and the mechanical strength of the insulating adhesive are improved. It is also beneficial to control the melting point and melt index of the surface layer, and effectively regulate the melting pressure relief point of the surface layer. The weight-average molecular weight (Mw) of the surface layer is 100,000 g / mol to 800,000 g / mol. If the weight-average molecular weight is less than 100,000 g / mol, the mechanical strength of the surface layer is low; if it is greater than 800,000 g / mol, the melt viscosity is too high, which is not conducive to flow. By limiting the weight-average molecular weight (Mw) of the surface layer to 100,000 g / mol to 800,000 g / mol, the encapsulation reliability of the battery cell under normal temperature conditions and the mechanical strength of the insulating adhesive are improved. This is beneficial for controlling the melting point and melt flow index of the surface layer, effectively regulating the melting pressure relief point of the surface layer. A Mw / Mn ratio of 3-10 improves the polydispersity index of the material, broadens the melting point range of the surface layer, and allows for adjustment of the melt flow index. This is beneficial for increasing the material's fluidity at high temperatures, allowing for rapid melting after reaching the melting point, and the collapse of the surface layer structure to form pressure relief channels, thus improving the heat dissipation efficiency of the battery cell.

[0014] In one or more of the above optional embodiments, the melting point of the base layer is higher than that of the surface layer. The melting point range of the base layer is 140℃-500℃. It supports the surface layer and reduces the risk of short circuits caused by the melting of the base layer, such as short circuits between the metal layers of the tabs and the battery cell housing or between electrodes of different polarities. This is beneficial to improving the insulation of the insulating adhesive.

[0015] In one or more of the above optional embodiments, the number average molecular weight of the base layer is at least 70,000 g / mol, which is beneficial to improving the insulation and mechanical strength of the insulating adhesive and reducing damage to the sealing part during the drop process.

[0016] In one or more of the above optional embodiments, the surface layer includes a first crystallinity and a second crystallinity, wherein the first crystallinity is 1%-30% and the second crystallinity is 0.01%-5%. Materials with a high first crystallinity have stronger intermolecular forces and a higher melting point. Materials with a low second crystallinity have weaker intermolecular forces; as the temperature rises, these low-crystallinity components preferentially melt, disrupting the ordered structure. Since these low-crystallinity components are uniformly distributed in the surface layer, their melting accelerates the collapse and melting of the overall surface layer structure. This facilitates controlling the melting of the surface layer within the temperature range of the first and second melting points, effectively regulating the melting pressure relief point of the insulating adhesive.

[0017] In one or more of the above optional embodiments, the crystallinity of the insulating adhesive is 2%-35%. If the crystallinity of the insulating adhesive is less than 2%, the fluidity after melting is too high, which can easily lead to leakage of the battery cell; if the crystallinity of the insulating adhesive is greater than 35%, the fluidity after melting is low, which affects the formation of rapid pressure relief channels, reduces heat dissipation efficiency, and is not conducive to improving the safety performance of the battery cell. By limiting the total crystallinity of the insulating adhesive to 2%-35%, it is beneficial to control the melting of the insulating adhesive within the temperature range of the first melting point and the second melting point, effectively regulate the melting pressure relief point of the insulating adhesive, facilitate the rapid formation of pressure relief channels in the battery cell, improve heat dissipation efficiency and safety performance, and achieve reliable sealing of the insulating adhesive.

[0018] In one or more of the above optional embodiments, the insulating adhesive includes a first degree of crystallinity, a second degree of crystallinity, and a third degree of crystallinity, wherein the first degree of crystallinity is 1%-30%, the second degree of crystallinity is 0.01%-5%, and the third degree of crystallinity is 0.01%-5%. This is beneficial for controlling the melting of the insulating adhesive within the temperature range of the first melting point and the second melting point, and for providing better insulation and mechanical strength, effectively controlling the melting pressure relief point of the insulating adhesive 32.

[0019] In one or more of the above optional embodiments, the tab includes a first section, a second section, and a third section. At least a portion of the first section is connected to the electrode assembly. The second section is bent to connect to the first section; the second section accounts for 5%-70% of the cell thickness, which helps reduce the risk of tab breakage during drop, and the use of insulating adhesive reduces the risk of short circuits caused by the second section contacting the metal layer of the cell casing or electrodes of different polarities. The third section is bent to connect to the second section, and a portion of the third section extends out of the sealing portion.

[0020] In one or more of the above optional embodiments, the sealing part includes two first adhesive layers, the sealing part includes a first region that does not overlap with the insulating adhesive, the two first adhesive layers located in the first region are bonded together, the thickness of the base layer is less than twice the sum of the thicknesses of the two first adhesive layers, or the sum of the thicknesses of the base layers on both sides of the tab is less than the sum of the thicknesses of the two first adhesive layers, thereby reducing the appearance of pore channels in the sealing part due to thickness differences and reducing the risk of leakage and short circuit.

[0021] In one or more of the above optional embodiments, the sum of the thickness of the insulating adhesive and the thickness of the first adhesive layer is less than the sum of the thicknesses of the two first adhesive layers, further reducing the presence of pore channels in the sealing part due to thickness differences, and reducing the risk of leakage and short circuit.

[0022] In one or more of the above optional embodiments, at least one of the following conditions must be met: the surface layer accounts for 30%-44% of the thickness of the insulating adhesive. If the thickness of the surface layer is too small (less than 30%), it will affect the connection strength of the surface layer. If the overflow clumps formed after the surface layer melts are too small, the encapsulation pull force of the insulating adhesive under room temperature conditions will be reduced, the encapsulation reliability of the battery cell under room temperature conditions will be reduced, and the pressure relief channel formed by the melting of the surface layer will be reduced, which is not conducive to pressure relief. If the thickness of the surface layer is too large (greater than 44%), the thickness difference will be large, which will affect the encapsulation reliability. By limiting the thickness of the surface layer to 30% to 44% of the thickness of the insulating adhesive, the thickness difference will be reduced, which will help improve the encapsulation reliability of the battery cell under room temperature conditions. The base layer accounts for 6%-20% of the thickness of the insulating adhesive. If the thickness of the base layer is too small (less than 6%), the tabs covered by the base layer will be easily exposed, leading to short circuits. If the thickness of the base layer is too large (greater than 20%), it will affect the encapsulation pull force of the insulating adhesive under room temperature conditions, and pore channels will easily appear, leading to leakage. By limiting the thickness of the base layer to 6% to 20% of the insulating adhesive thickness, it is beneficial to reduce the presence of pore channels in the battery cell, thereby reducing the risk of leakage and short circuits. The insulating adhesive includes a second adhesive layer that connects the base layer and the surface layer. The thickness of the second adhesive layer is 1% to 4% of the insulating adhesive thickness. If the second adhesive layer is less than 1% of the insulating adhesive thickness, the connection strength between the base layer and the surface layer is low. If the second adhesive layer is greater than 4% of the insulating adhesive thickness, the thickness of the insulating adhesive increases, increasing the thickness difference between the first, second, and third thicknesses, which can easily affect the encapsulation reliability of the battery cell under normal temperature conditions. By limiting the thickness of the second adhesive layer to 1% to 4% of the insulating adhesive thickness, the thickness difference between the first, second, and third thicknesses is reduced, improving the connection strength between the base layer and the surface layer, as well as the encapsulation reliability of the battery cell under normal temperature conditions.

[0023] Embodiments of this application provide an electrical device including the battery cell from any of the above embodiments. Attached Figure Description

[0024] Figure 1 shows a schematic diagram of the cross-sectional structure of the battery cell in some embodiments.

[0025] Figure 2 shows a partial schematic diagram of the battery cell in some embodiments.

[0026] Figure 3 shows a partial schematic diagram of the battery cell in some other embodiments.

[0027] Figure 4 shows a schematic diagram of the electrical equipment in some embodiments.

[0028] Key component symbols: Cell 100, Cell housing 10, Main body 11, Sealing part 12, First region 121, First adhesive layer 101, Metal layer 102, Outer layer 103, Electrode assembly 20, First electrode 21, Second electrode 22, Separator 23, Tab assembly 30, Tab 31, First section 311, Second section 312, Third section 313, Insulating adhesive 32, Base layer 322, Surface layer 321, Second adhesive layer 323, Electrical equipment 200

[0029] The following specific embodiments will further illustrate this application in conjunction with the above-described accompanying drawings. Detailed Implementation

[0030] The following specific embodiments are exemplary and not limiting, and are intended to provide a basic understanding of this application, and are not intended to identify key or decisive elements of this application or limit the scope of protection. As long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.

[0031] When a component is considered to be "located" on another component, it can be directly on the other component or may also be interspersed with other components. When a component is considered to be "connected" to another component, it can be directly connected to the other component or may also be interspersed with other components.

[0032] Unless otherwise defined, the term "multiple" in this document, when used to describe the number of components, specifically means that the component is two or more.

[0033] Some embodiments of this application will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0034] Please refer to Figure 1. One embodiment of this application provides a battery cell 100, including a battery cell housing 10 and an electrode assembly 20. The battery cell housing 10 includes a main body portion 11 and a sealing portion 12, with the main body portion 11 connected to the sealing portion 12, and the electrode assembly 20 disposed within the main body portion 11.

[0035] In some embodiments, the battery cell 100 includes a tab assembly 30, which includes a tab 31 and two insulating adhesives 32. The tab 31 is connected to the electrode assembly 20 and extends from the sealing portion 12 out of the battery cell housing 10. The tab 31 is disposed between the two insulating adhesives 32 along the thickness direction of the tab 31. The insulating adhesives 32 connect the battery cell housing 10 and the tab 31.

[0036] In some embodiments, at 25°C, the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 ranges from 5 N / mm to 10 N / mm, improving the encapsulation tensile force of the insulating adhesive 32 under normal temperature conditions and enhancing the encapsulation reliability of the cell 100 under normal temperature conditions. A tensile force exceeding 10 N / mm can easily cause the packaging bag to rupture. At 120°C, the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 ranges from 0.01 N / mm to 0.2 N / mm, which facilitates the rapid formation of a pressure relief channel after the cell 100 expands, improving heat dissipation efficiency and thus enhancing the safety performance of the cell 100.

[0037] Optionally, the tensile strength of the insulating adhesive 32 at 25°C can be any one or any combination of two of the following: 5 N / mm, 5.5 N / mm, 6 N / mm, 6.5 N / mm, 7 N / mm, 7.5 N / mm, 8 N / mm, 8.5 N / mm, 9 N / mm, 9.5 N / mm, and 10 N / mm.

[0038] Optionally, the tensile strength of the insulating adhesive 32 at 120°C can be any one or any combination of two of the following: 0.01 N / mm, 0.02 N / mm, 0.03 N / mm, 0.04 N / mm, 0.05 N / mm, 0.06 N / mm, 0.07 N / mm, 0.08 N / mm, 0.09 N / mm, 0.1 N / mm, 0.11 N / mm, 0.12 N / mm, 0.13 N / mm, 0.14 N / mm, 0.15 N / mm, 0.16 N / mm, 0.17 N / mm, 0.18 N / mm, 0.19 N / mm, and 0.2 N / mm.

[0039] In some embodiments, at 25°C, the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 ranges from 6.5 N / mm to 10 N / mm, further improving the encapsulation tensile force of the insulating adhesive 32 under normal temperature conditions and enhancing the encapsulation reliability of the cell 100 under normal temperature conditions.

[0040] In some embodiments, at 120°C, the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 ranges from 0.01 N / mm to 0.1 N / mm, which further facilitates the rapid formation of a pressure relief channel after the cell 100 expands, improves heat dissipation efficiency, and thereby enhances the safety performance of the cell 100.

[0041] In some embodiments, the tensile strength of the insulating adhesive 32 at 95°C ranges from 0.2N / mm to 2N / mm, and the encapsulation reliability of the battery cell 100 can still meet the requirements under operating conditions at 95°C, reducing the occurrence of leakage.

[0042] Optionally, the tensile strength of the insulating adhesive 32 at 95°C can be any one or any combination of two of the following: 0.2 N / mm, 0.3 N / mm, 0.4 N / mm, 0.5 N / mm, 0.6 N / mm, 0.7 N / mm, 0.8 N / mm, 0.9 N / mm, 1.0 N / mm, 1.1 N / mm, 1.2 N / mm, 1.3 N / mm, 1.4 N / mm, 1.5 N / mm, 1.6 N / mm, 1.7 N / mm, 1.8 N / mm, 1.9 N / mm, and 2.0 N / mm.

[0043] In some embodiments, the tensile strength of the insulating adhesive 32 at 95°C ranges from 0.8 N / mm to 2 N / mm, and the encapsulation reliability of the battery cell 100 can still meet the requirements under operating conditions at 95°C, further reducing the occurrence of leakage.

[0044] In some embodiments, the cell housing 10 may be a packaging bag encapsulated with an encapsulation film (such as an aluminum-plastic film), that is, the cell 100 is a soft-pack cell.

[0045] Referring to Figure 2, in some embodiments, the cell housing 10 includes a first adhesive layer 101, a metal layer 102, and an outer layer 103 stacked together. The metal layer 102 is disposed between the first adhesive layer 101 and the outer layer 103, and the outer layer 103 is located as the outermost layer of the cell housing 10. The outer layer 103 can be a nylon layer or a composite layer of polyester resin (PET) and nylon, providing protection against pollution, corrosion, and external damage. The metal layer 102 can include one of aluminum and steel, providing waterproofing, barrier properties, and shaping of the cell housing 10. The first adhesive layer 101 is a heat-sealing layer, which can include a polymer, including one of polypropylene and polyethylene. It is used to seal the cell housing 10 by hot pressing and to separate the metal layer 102 from the electrode assembly 20, reducing the risk of electrolyte leakage and corrosion of the metal layer 102 within the cell housing 10.

[0046] In some embodiments, the electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separator 23, wherein the separator 23 is disposed between the first electrode 21 and the second electrode 22. The separator 23 is used to prevent the first electrode 21 and the second electrode 22 from directly contacting each other, thereby reducing the risk of short circuit between the first electrode 21 and the second electrode 22.

[0047] In some embodiments, the electrode assembly 20 is a wound structure, that is, the first electrode 21, the separator 23 and the second electrode 22 are stacked in sequence and then wound to form the electrode assembly 20.

[0048] In other embodiments, the electrode assembly 20 may also be a stacked structure, that is, the first electrode 21, the separator 23 and the second electrode 22 are stacked in sequence to form an electrode assembly unit, and multiple electrode assembly units are stacked to form the electrode assembly 20.

[0049] In some embodiments, the first electrode 21 is a negative electrode or a positive electrode, and the second electrode 22 is an electrode with the opposite polarity to the first electrode 21. This application will describe an example where the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode.

[0050] In some embodiments, the tab 31 includes a first segment 311, a second segment 312, and a third segment 313. At least a portion of the first segment 311 is connected to the first electrode 21 or the second electrode 22. The second segment 312 is bent and connected to the first segment 311. The third segment 313 is bent and connected to the second segment 312, and a portion of the third segment 313 extends out of the sealing portion 12. A portion of the third segment 313 extends out of the insulating adhesive 32 for connection with other components to perform energy transfer.

[0051] In some embodiments, the first segment 311 is welded to the first electrode 21 or the second electrode 22. The welding method includes laser welding, ultrasonic welding, etc.

[0052] In some embodiments, the length of the second segment 312 along the thickness direction of the cell 100 is 5%-70% of the thickness of the cell 100. This helps to reduce the risk of breakage of the tab 31 during a drop, and the presence of insulating adhesive 32 reduces the risk of short circuits caused by contact between the second segment 312 and the metal layer 102 or electrodes of different polarities. Optionally, the length of the second segment 312 can be any one of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% of the thickness of the cell 100.

[0053] Referring to Figure 2, in some embodiments, the insulating adhesive 32 includes a surface layer 321, which is connected to the cell housing 10 and / or the tab 31.

[0054] In some embodiments, the insulating adhesive 32 includes a base layer 322, and a surface layer 321 is attached to at least one side of the base layer 322 along the thickness direction of the base layer 322.

[0055] Optionally, a surface layer 321 is connected to one side of the base layer 322 along the thickness direction of the base layer 322.

[0056] Optionally, a surface layer 321 is connected to both sides of the base layer 322 along the thickness direction of the base layer 322. This application uses the example of a base layer 322 having a surface layer 321 connected to both sides as an example.

[0057] It is understood that in some embodiments, the thickness of the surface layer 321 on both sides of the base layer 322 is equal. In other embodiments, there is a tolerance in the thickness of the surface layer 321 on both sides of the base layer 322.

[0058] In some embodiments, the surface layer 321 has at least a first melting point and a second melting point. The range of the first melting point A is 50°C ≤ A ≤ 120°C, and the range of the second melting point B is 120°C < B ≤ 170°C. By setting multiple melting point ranges, the surface layer 321 can melt within the temperature range of the first melting point and the second melting point, effectively controlling the melting pressure relief point of the insulating adhesive 32 and improving the heat dissipation efficiency of the battery cell 100.

[0059] Optionally, the first melting point can be any one or any combination of two of the following: 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 119°C, and 120°C.

[0060] Optionally, the second melting point can be any one or any combination of two of the following: 120.1°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, and 170°C.

[0061] In some embodiments, the melting point of the base layer 322 is higher than that of the surface layer 321. The melting point range of the base layer 322 is 140°C-500°C. It supports the surface layer 321, reduces the risk of short circuit caused by melting of the base layer 322, which would lead to contact between the tab 31 and the metal layer 102 of the cell housing 10 or the electrode sheets of different polarities. This is beneficial to improving the insulation of the insulating adhesive 32.

[0062] Optionally, the melting point of the base layer 322 can be any one or any combination of two of the following: 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, and 500℃.

[0063] In some embodiments, along the thickness direction of the cell housing 10, the sealing portion 12 includes two first adhesive layers 101. Along the thickness direction of the cell housing 10, the sealing portion 12 includes a first region 121 that does not overlap with the insulating adhesive 32. The two first adhesive layers 101 located in the first region 121 are bonded together. The thickness of the base layer 322 is less than twice the sum of the thicknesses of the two first adhesive layers 101 after hot pressing, or the sum of the thicknesses of the base layers 322 on both sides of the tab 31 is less than the sum of the thicknesses of the two first adhesive layers 101. Because the base layer 322 has a high melting point and is not easily melted during encapsulation, excessive thickness of the base layer 322 after encapsulation can lead to pore channels, causing leakage. External moisture can easily enter the cell housing 10, potentially causing a short circuit. By setting the thickness of the base layer 322 to be less than half the sum of the thicknesses of the two first adhesive layers 101 after hot pressing, pore channels in the sealing portion 12 are reduced, lowering the risk of leakage and short circuits.

[0064] In some embodiments, the sum of the thickness of the insulating adhesive 32 and the thickness of the first adhesive layer 101 is less than the sum of the thicknesses of the two first adhesive layers 101, further reducing the presence of pore channels in the sealing portion 12 and lowering the risk of leakage and short circuit.

[0065] In some embodiments, the melt flow index of surface layer 321 at 230°C and 2.16 kg load is 4 g / 10 min to 20 g / 10 min. If the melt flow index of surface layer 321 at 230°C and 2.16 kg load is less than 4 g / 10 min, the surface layer 321 becomes too fluid after melting, which is not conducive to expanding the overflow clumps formed after the surface layer 321 melts, reducing the encapsulation pull force of insulating adhesive 32 under room temperature conditions, reducing the encapsulation reliability of cell 100 under room temperature conditions, and affecting the rapid formation of pressure relief channels after the cell 100 expands, reducing heat dissipation efficiency and hindering the improvement of the safety performance of cell 100. If the melt flow index of surface layer 321 at 230°C and 2.16 kg load is greater than 20 g / 10 min, the surface layer 321 becomes too fluid after melting, which can easily lead to leakage of cell 100 and affect the sealing performance of cell 100. By limiting the melt flow index of surface layer 321 to 4g / 10min-20g / 10min at 230℃ and 2.16kg load, the fluidity of surface layer 321 after melting is improved, forming a tighter overflow clump at the sealing edge, increasing the encapsulation pull force of insulating adhesive 32 under normal temperature conditions, and improving the encapsulation reliability of cell 100 under normal temperature conditions. When cell 100 experiences thermal runaway and / or pressure relief, the high fluidity of surface layer 321 at high temperature allows the encapsulation strength of cell 100 to decrease rapidly, enabling the high-temperature gas inside cell 100 to be rapidly depressurized and dissipated at surface layer 321, improving heat dissipation efficiency and thus enhancing the safety performance of cell 100.

[0066] Optionally, the melt flow index of surface layer 321 at 230°C and 2.16 kg load can be any one or any combination of two of the following: 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min, 14 g / 10 min, 15 g / 10 min, 16 g / 10 min, 17 g / 10 min, 18 g / 10 min, 19 g / 10 min, and 20 g / 10 min.

[0067] In some embodiments, the melt flow index of surface layer 321 at 230°C and 2.16 kg load is 6 g / 10 min to 14 g / 10 min, which easily meets the high-temperature fluidity requirements and the sealing thickness is easy to control, further improving the packaging reliability and safety performance of cell 100 under normal temperature conditions.

[0068] In some embodiments, the melt flow index of surface layer 321 at 230°C and 2.16 kg load is 7.1 g / 10 min to 12 g / 10 min, which makes it easier to meet the high-temperature fluidity requirements and the sealing thickness is easier to control, further improving the packaging reliability and safety performance of cell 100 under normal temperature conditions.

[0069] In some embodiments, the melt flow index of the base layer 322 at 230°C and under a load of 2.16 kg is 0.1 g / 10 min to 5 g / 10 min, which reduces the fluidity of the melt of the base layer 322, supports the surface layer 321, and helps to improve the sealing and insulation of the battery cell 100. The low melt flow index of the base layer 322 helps to reduce the appearance of the exposed part of the insulating adhesive 32 due to heat curling and deformation. At the same time, the insulating adhesive 32 is prone to Joule heating during the conduction process of the tab. The high melting point and low melt flow index of the base layer 322 provide good insulation.

[0070] Optionally, the melt flow index of base layer 322 at 230℃ and 2.16kg load can be any one or any combination of two of the following: 0.1g / 10min, 1g / 10min, 2g / 10min, 3g / 10min, 4g / 10min, and 5g / 10min.

[0071] In some embodiments, the number average molecular weight of the base layer 322 is at least 70,000 g / mol, which is beneficial to improving the insulation and mechanical strength of the insulating adhesive 32 and reducing damage to the sealing part during drop.

[0072] In some embodiments, the number-average molecular weight Mn of the surface layer 321 is 10,000 g / mol to 130,000 g / mol. If the number-average molecular weight of the surface layer 321 is less than 10,000 g / mol, the melt viscosity of the surface layer 321 is too low, which is not conducive to processing and molding, and easily leads to high fluidity of the surface layer 321 after melting, reducing the encapsulation reliability of the cell 100 under normal temperature conditions. If the number-average molecular weight of the surface layer 321 is greater than 130,000 g / mol, the melt viscosity of the surface layer 321 is too high, which is not conducive to processing and molding, and easily leads to increased brittleness of the surface layer 321, making it prone to breakage under external force. By limiting the number-average molecular weight Mn of the surface layer 321 to 10,000 g / mol to 130,000 g / mol, the encapsulation reliability of the cell 100 under normal temperature conditions and the mechanical strength of the insulating adhesive are improved. This is beneficial for controlling the melting point and melt index of the surface layer 321, and effectively regulating the melting pressure relief point of the surface layer 321.

[0073] Optionally, the number-average molecular weight Mn of the surface layer 321 is any one or any combination of 10000 g / mol, 20000 g / mol, 30000 g / mol, 40000 g / mol, 50000 g / mol, 60000 g / mol, 70000 g / mol, 80000 g / mol, 90000 g / mol, 100000 g / mol, 110000 g / mol, 120000 g / mol, and 130000 g / mol.

[0074] In some embodiments, the weight-average molecular weight Mw of surface layer 321 is 100,000 g / mol to 800,000 g / mol. If the weight-average molecular weight of surface layer 321 is less than 100,000 g / mol, the mechanical strength of surface layer 321 is low; if the weight-average molecular weight of surface layer 321 is greater than 800,000 g / mol, the melt viscosity of surface layer 321 is too high, which is not conducive to flow. By limiting the weight-average molecular weight Mw of surface layer 321 to 100,000 g / mol to 800,000 g / mol, the encapsulation reliability of cell 100 under normal temperature conditions and the mechanical strength of insulating adhesive are improved. This is beneficial for controlling the melting point and melt flow index of surface layer 321 and effectively regulating the melting pressure relief point of surface layer 321.

[0075] Optionally, the weight-average molecular weight Mw of the surface layer 321 is any one or any combination of 100,000 g / mol, 200,000 g / mol, 300,000 g / mol, 400,000 g / mol, 500,000 g / mol, 600,000 g / mol, 700,000 g / mol, and 800,000 g / mol.

[0076] In some embodiments, the polydispersity index Mw / Mn is 3-10, which improves the polydispersity index of the material, broadens the melting point range (melting range) of the surface layer 321, and can adjust the melt index, which is beneficial to increase the fluidity of the material at high temperatures, allowing it to melt rapidly after reaching the melting point. The surface layer 321 structure collapses to form a pressure relief channel, thereby improving the heat dissipation efficiency of the battery cell 100.

[0077] Optionally, the ratio of Mw / Mn can be any one of 3, 4, 5, 6, 7, 8, 9, 10 or any combination of two of them.

[0078] In some embodiments, the material of the surface layer 321 includes at least one selected from polyolefin resins, acid-modified polyolefin resins, polyethylene, polypropylene, ethylene elastomers, and styrene elastomers.

[0079] In some embodiments, the surface layer 321 includes a first crystallinity and a second crystallinity, wherein the first crystallinity is 1%-30% and the second crystallinity is 0.01%-5%. Materials with high first crystallinity have stronger intermolecular forces and generally have a higher melting point. Materials with low second crystallinity have weaker intermolecular forces. As the temperature rises, these low-crystallinity components preferentially melt, and the ordered structure is destroyed. Since these low-crystallinity components are uniformly distributed in the surface layer 321, when they melt, they accelerate the collapse and melting of the overall surface layer 321 structure. This is beneficial for controlling the melting of the surface layer 321 within the temperature range of the first and second melting points, and effectively regulating the melting pressure relief point of the insulating adhesive 32.

[0080] Optionally, the first degree of crystallinity can be a range of any one or any two of the following: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0081] Optionally, the second degree of crystallinity can be 0.01%, 0.03%, 0.05%, 0.07%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, or 2. A range consisting of any one or any two of the following: 3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5.0%.

[0082] In some embodiments, the crystallinity of the insulating adhesive 32 is 2%-35%, which is beneficial for controlling the melting and pressure relief point of the insulating adhesive 32, reducing the premature failure of the insulating adhesive 32, and preventing premature pressure relief failure of the battery cell 100.

[0083] Optionally, the insulating adhesive 32 can be a range of any one or any combination of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%.

[0084] In some embodiments, the surface layer 321 includes a first crystallinity, a second crystallinity, and a third crystallinity, wherein the first crystallinity is 1%-30%, the second crystallinity is 0.01%-5%, and the third crystallinity is 0.01%-5%, which is beneficial for controlling the melting of the insulating adhesive 32 within the temperature range of the first melting point and the second melting point, effectively regulating the melting pressure relief point of the insulating adhesive 32, and effectively improving the insulation and mechanical strength of the insulating adhesive 32.

[0085] Optionally, the third degree of crystallinity can be 0.01%, 0.03%, 0.05%, 0.07%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, or 2. A range consisting of any one or any two of the following: 3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5.0%.

[0086] Referring to Figure 3, in some embodiments, the insulating adhesive 32 includes a second adhesive layer 323, which bonds the base layer 322 and the surface layer 321.

[0087] In some embodiments, the thickness of the base layer 322 is 6% to 20% of the thickness of the insulating adhesive 32. If the thickness of the base layer 322 is too small (less than 6%), the tabs 31 covered by the base layer 322 are easily exposed, leading to a short circuit. If the thickness of the base layer 322 is too large (greater than 20%), it affects the encapsulation pull force of the insulating adhesive 32 under normal temperature conditions, easily resulting in pore channels and leakage. By limiting the thickness of the base layer 322 to 6% to 20% of the thickness of the insulating adhesive 32, it is beneficial to reduce the occurrence of pore channels in the cell 100, thereby reducing the risk of leakage and short circuit.

[0088] Optionally, the thickness of the base layer 322 can be any one or any combination of 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% of the thickness of the insulating adhesive 32.

[0089] In some embodiments, the thickness of the surface layer 321 is 30% to 44% of the thickness of the insulating adhesive 32. If the thickness of the surface layer 321 is too small (less than 30%), it affects the connection strength of the surface layer 321. The small size of the excess adhesive clumps formed after the surface layer 321 melts leads to a decrease in the encapsulation pull force of the insulating adhesive 32 under room temperature conditions, reducing the encapsulation reliability of the cell 100 under room temperature conditions. Furthermore, the reduced pressure relief channel formed by the melting of the surface layer 321 is detrimental to pressure relief. If the thickness of the surface layer 321 is too large (greater than 44%), the large thickness difference affects the encapsulation reliability. During the encapsulation process, along the thickness direction of the cell housing 310, two second adhesive layers 323 are bonded together and have a first thickness. The portion of the surface layer 321 extending along both sides of the tab 31 width direction is bonded together and has a second thickness. The insulating adhesive 32 located on both sides of the tab 31 thickness direction and the tab 31 have a third thickness. By limiting the thickness of the surface layer 321 to 30% to 44% of the thickness of the insulating adhesive 32, the thickness difference between the first thickness, the second thickness and the third thickness is reduced, which is beneficial to improving the encapsulation reliability of the cell under normal temperature conditions and is also beneficial to pressure relief.

[0090] Optionally, the thickness of the surface layer 321 is within the range of any one or any two of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, and 44% of the thickness of the insulating adhesive 32.

[0091] In some embodiments, the thickness of the second adhesive layer 323 is 1% to 4% of the thickness of the insulating adhesive 32. If the second adhesive layer 323 is less than 1% of the thickness of the insulating adhesive 32, the connection strength between the base layer 322 and the surface layer 321 is low. If the second adhesive layer 323 is greater than 4% of the thickness of the insulating adhesive 32, the thickness of the insulating adhesive 32 increases, increasing the thickness difference between the first thickness, the second thickness, and the third thickness, which can easily affect the encapsulation reliability of the cell 100 under normal temperature conditions. By limiting the thickness of the second adhesive layer 323 to 1% to 4% of the thickness of the insulating adhesive 32, the thickness difference between the first thickness, the second thickness, and the third thickness is reduced, thereby improving the connection strength between the base layer 322 and the surface layer 321 and the encapsulation reliability of the cell 100 under normal temperature conditions.

[0092] Optionally, the thickness of the second adhesive layer 323 is within the range of any one or any two of 1%, 2%, 3%, 4% of the thickness of the insulating adhesive 32.

[0093] The present application will be further described below through specific embodiments.

[0094] 1. The specific method for hot box testing is as follows:

[0095] Adjust the furnace temperature to 25℃, place the lithium-ion cell sample inside the furnace and let it stand for 5 minutes; charge it to 3.0V with 0.2C DC; let it stand for 10 minutes; then charge it to 4.5V with 0.7C constant current, and then charge it to 0.025C constant voltage; let it stand for 10 minutes; take a photo before testing, measure the internal resistance of the voltage, and attach the temperature sensing wire to the surface of the cell. Then place the sample into the heating furnace chamber and raise the temperature to the target temperature (e.g., 130℃) at a rate of 5±2℃ / min and hold it at that temperature for 60 minutes. Take a photo after testing and measure the internal resistance of the voltage. If the cell does not catch fire or explode, it indicates that it has passed the hot box test. The highest temperature that can be passed is defined as the hot box window of the cell.

[0096] 2. High-temperature internal stress testing method:

[0097] After being fully charged at 1C, the lithium-ion battery is placed in a specially designed fixture. The fixture's length and width are the same as the battery's dimensions, but its thickness is 2% greater. The battery is then stored for 8 hours in a test environment at 95±2℃. The fixture restricts the expansion of the cell in the thickness direction, causing internal pressure to impact the sealing area. If the lithium-ion battery does not catch fire, explode, smoke, or leak, it passes the test. This test characterizes the reliability of the packaging under the most stringent high-temperature testing conditions.

[0098] 3. Packaging pull force test method:

[0099] Take a battery cell housing with an 8mm wide sealing part and an electrode assembly. Adhere the sealing part to the electrode assembly. Clamp the battery cell housing at one end of the tensile testing machine and the electrode assembly at the other end. Adjust the tensile testing machine to the test temperature at 10℃ / min. After holding the temperature for 30 seconds, stretch the tensile testing machine at a 180-degree angle at a tensile speed of 175mm / min until it breaks. Record the maximum tensile force of the tensile testing machine.

[0100] 4. Melt flow index test method:

[0101] Peel the surface layer from the insulating adhesive to obtain base and surface layer samples, taking approximately 2-10 grams of sample, the exact weight depending on the melt flow index (MFR) of the material and the testing conditions. Using a melt flow indexer, pulverize the sample into small particles to ensure uniformity. Set the test temperature to 230°C and the load to 2.16 kg. Place the sample into the barrel of the melt flow indexer. Heat to 230°C until the sample melts. Apply a 2.16 kg load, allowing the molten material to pass through a standard die. Record the weight of material passing through the die within a specified time. Melt Flow Index (MFR) = Weight of material passing through the die (g) / Test time (min).

[0102] 5. Test method for withstand voltage:

[0103] Using a probe pressed against the tabs 31 of the positive and negative terminals, and another probe piercing the conductive aluminum layer of the cell housing 10, a voltage of 100V and a pressure of 0.35Mpa on the surface of the cell 100 are applied between the two probes. If the resistance value of the test is required to be >20MΩ, it is considered to pass.

[0104] 6. Number-average molecular weight test method:

[0105] Gel permeation chromatography (GPC), a high-performance liquid chromatography technique, is used to determine molecular weight distribution by separating polymer chains of different molecular weights. The surface layer is peeled off from the insulating adhesive to obtain surface and base layer samples. Tetrahydrofuran (THF) solvent is selected to dissolve the sample and prepare a solution of appropriate concentration (typically 0.1-1 mg / mL). The sample solution is filtered using a 0.45 μm filter membrane to remove insoluble matter and particles. The test temperature is set to 30 °C, and the flow rate to 1 mL / min. The injection volume is set to 100 μL. The response signal of each molecular weight component is recorded using a detector. The detection signal is converted to molecular weight using a calibration curve, and the number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) are calculated.

[0106] 7. Methods for testing the ratio of air bubbles to porosity:

[0107] Sulfuric acid and hydrofluoric acid were used to corrode and remove the metal layer 312 and outer layer 313 above the insulating adhesive 100, respectively, exposing the second adhesive layer 311. The proportion of the area of ​​bubbles and pores to the total area of ​​the insulating adhesive 100 was determined by CCD observation and measurement.

[0108] 8. Short test:

[0109] The battery was pre-charged to 100% SOC. The sample was placed in a test environment of 55±5℃. After the cell surface temperature reached the test temperature, it was left to stand for 30 minutes. The positive and negative terminals of the sample were shorted using a load resistor of 80±20mΩ.

[0110] The test ends when one of the following conditions is met: no fire or explosion occurs; otherwise, the test is passed.

[0111] 1) The test lasts for 24 hours;

[0112] 2) The surface temperature of the battery cell drops to 20% below its peak value;

[0113] 9. Test methods for crystallinity and melting point:

[0114] The surface layer was peeled off from the insulating adhesive to obtain surface layer and base layer samples. Approximately 1-3 mg of sample was placed in a crucible and tested using a thermal analyzer at a temperature range of 25-800℃, a scan rate of 0.1-50 K / min, and under inert gas N2 conditions.

[0115] Preparation method of insulating adhesive 32: Particles with different melting points are mixed and stirred in a high-speed mixer at 25°C for 60 minutes, melt extruded and granulated in a progressive temperature range of 170°C-250°C, dried at 80°C, conveyed to a screw extruder through a vacuum feeder, melted and plasticized in a progressive temperature range of 180°C-250°C at 10MPa, co-extruded and cast through a die at 230°C and 5MPa, cooled to room temperature for molding, wound into a master roll, and cured at room temperature for 24 hours.

[0116] Then, a solvent-based adhesive (second adhesive layer 323) is applied to one side of the base layer 322, dried in an oven at 80°C, and laminated with the surface layer 321 at 100°C and 1 MPa. A solvent-based adhesive (second adhesive layer 323) is applied to the other side of the base layer 322, dried in an oven at 80°C, and laminated with another surface layer 321 at 100°C and 1 MPa. The layers are then cured at 60°C for 5 days. An insulating adhesive 32 is formed through rough and fine cutting.

[0117] The withstand voltage test was conducted in groups of 1000 cells 300. Among the qualified cells 300 that passed the withstand voltage test, 100 cells 300 were grouped together for bubble and porosity tests, short tests, high temperature internal stress tests, and hot box tests.

[0118] Table 1

[0119] From Examples 1-13 in Table 1, it can be seen that when the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 is 5N / mm-10N / mm at 25℃, and when the tensile force between the insulating adhesive 32 and the cell housing 10 and / or the tab 31 is 0.01N / mm-0.2N / mm at 120℃, the cell 100 passes the hot box test at higher temperatures, and the pass rate of the high-temperature internal stress test is improved. This is beneficial to improving the packaging reliability of the cell under normal temperature conditions, and it is also beneficial to quickly form a pressure relief channel after the cell expands, thereby improving the heat dissipation efficiency and thus improving the safety performance of the cell.

[0120] As can be seen from Examples 1-6 to 1-8 in Table 1, when the surface layer 321 is at 230°C, the melt index under a load of 2.16 kg is 7.1 g / 10 min to 12 g / 10 min, which is beneficial for the cell 100 to pass the hot box test at a higher temperature, and the pass rate of the high temperature internal stress test and the pass rate of the withstand voltage test are higher.

[0121] Referring to Figure 4, this application also provides an electrical device 200 employing the aforementioned battery cell 100. In one embodiment, the electrical device 200 of this application may be, but is not limited to, electronic devices, drones, backup power supplies, electric vehicles, electric motorcycles, electric-assisted bicycles, power tools, large household batteries, etc.

[0122] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the spirit and essence of this application fall within the scope of this application's disclosure.

Claims

1. A battery cell, characterized in that, include: The battery cell casing includes a main body and a sealing part; Electrode assemblies are disposed within the main body portion; The electrode assembly includes an electrode tab and two insulating adhesives. The electrode tab is connected to the electrode assembly and extends from the sealing portion. Along the thickness direction of the electrode tab, the electrode tab is disposed between the two insulating adhesives. The insulating adhesives connect the cell housing and the electrode tab. At 25°C, the tensile force between the insulating adhesive and the battery cell housing and / or the electrode tab ranges from 5 N / mm to 10 N / mm; at 120°C, the tensile force between the insulating adhesive and the battery cell housing and / or the electrode tab ranges from 0.01 N / mm to 0.2 N / mm. The tensile force test method between the insulating adhesive and the battery cell housing and / or the electrode tab is as follows: Take a battery cell housing with a sealing part with a width of 8 mm and the electrode tab assembly, and bond the sealing part to the electrode tab assembly. Clamp the battery cell housing at one end of the tensile testing machine and the electrode tab at the other end of the tensile testing machine. Adjust the tensile testing machine to the test temperature at 10°C / min. After holding the temperature for 30 seconds, stretch the tensile testing machine at a 180-degree angle at a tensile speed of 175 mm / min until it breaks. Record the maximum tensile force of the tensile testing machine.

2. The battery cell as described in claim 1, characterized in that, At 25°C, the tensile force between the insulating adhesive and the cell housing and / or the tabs ranges from 6.5 N / mm to 10 N / mm.

3. The battery cell as described in claim 1, characterized in that, At 120°C, the tensile force between the insulating adhesive and the cell housing and / or the tab is in the range of 0.01 N / mm to 0.1 N / mm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, Take the sealing part with a width of 8mm, clamp the battery cell housing at one end of the tensile testing machine, and clamp the electrode tab at the other end of the tensile testing machine. The tensile testing machine heats up to 95℃ at 10℃ / min and holds for 30s. The tensile force between the insulating adhesive and the battery cell housing and / or the electrode tab is 0.2N / mm-2N / mm.

5. The battery cell as described in claim 4, characterized in that, At 95°C, the tensile force between the insulating adhesive and the cell housing and / or the tabs ranges from 0.8 N / mm to 2 N / mm.

6. The battery cell as described in claim 1, characterized in that, The insulating adhesive includes a surface layer, which is connected to the cell housing or the electrode tab; The surface layer has a melt flow index of 4 g / 10 min to 20 g / 10 min at 230°C and a load of 2.16 kg.

7. The battery cell as described in claim 6, characterized in that, The surface layer has a melt flow index of 7.1 g / 10 min to 12 g / 10 min at 230°C and a load of 2.16 kg.

8. The battery cell as described in claim 1, characterized in that, The insulating adhesive includes a surface layer, the surface layer having at least a first melting point and a second melting point, the first melting point A being in the range of 50℃≤A≤120℃, and the second melting point B being in the range of 120℃<B≤170℃.

9. The battery cell as described in claim 1, characterized in that, The insulating adhesive includes a surface layer, and the surface layer satisfies at least one of the following conditions: 1) The number-average molecular weight Mn of the surface layer is 10000 g / mol - 130000 g / mol; 2) The weight-average molecular weight Mw of the surface layer is 100,000 g / mol - 800,000 g / mol; 3) Mw / Mn: 3-10.

10. The battery cell as described in claim 1, characterized in that, The insulating adhesive includes a surface layer, which has a first degree of crystallinity and a second degree of crystallinity, wherein the first degree of crystallinity is 1%-30% and the second degree of crystallinity is 0.01%-5%.

11. The battery cell as described in claim 10, characterized in that, The crystallinity of the insulating adhesive is 2%-35%.

12. The battery cell according to any one of claims 1 to 9, characterized in that, The insulating adhesive has a first degree of crystallinity, a second degree of crystallinity, and a third degree of crystallinity, wherein the first degree of crystallinity is 1%-30%, the second degree of crystallinity is 0.01%-5%, and the third degree of crystallinity is 0.01%-5%.

13. The battery cell according to any one of claims 6 to 11, characterized in that, The insulating adhesive includes a base layer, and the surface layer is connected to the base layer along the thickness direction of the base layer; The melt flow index of the base layer at 230℃ and 2.16kg load is less than that of the surface layer. The melt flow index of the base layer is 0.1g / 10min-5g / 10min.

14. The battery cell as described in claim 13, characterized in that, The melting point of the base layer is higher than that of the surface layer, and the melting point range of the base layer is 140℃-500℃.

15. The battery cell as described in claim 13 or 14, characterized in that, The number-average molecular weight of the base layer is at least 70,000 g / mol.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The electrode includes a first section, a second section, and a third section; At least a portion of the first segment is connected to the electrode assembly; The second section is bent and connected to the first section; the second section accounts for 5%-70% of the thickness of the battery cell; The third section is bent and connected to the second section, and a portion of the third section extends out of the sealing part.

17. The battery cell as described in claim 16, characterized in that, The sealing part includes two first adhesive layers, and the sealing part includes a first region that does not overlap with the insulating adhesive. The two first adhesive layers located in the first region are bonded together. The thickness of the base layer is less than twice the sum of the thicknesses of the two first adhesive layers, or the sum of the thicknesses of the base layers on both sides of the tab is less than the sum of the thicknesses of the two first adhesive layers.

18. The battery cell according to any one of claims 13 to 15, characterized in that, At least one of the following conditions must be met: 1) The surface layer accounts for 30%-44% of the thickness of the insulating adhesive; 2) The base layer accounts for 6%-20% of the thickness of the insulating adhesive; 3) The insulating adhesive includes a second adhesive layer that connects the base layer and the surface layer, and the thickness of the second adhesive layer is 1% to 4% of the thickness of the insulating adhesive.

19. An electrical appliance, characterized in that, Includes the battery cell as described in any one of claims 1 to 18.

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