Battery cell and electric device

Abstract

The application discloses an electric core and an electric device. The electric core comprises an electric core shell, an electrode assembly, a negative electrode tab, a positive electrode tab, a first insulating glue and a second insulating glue. The electric core shell comprises a main body part and a sealing part. The electrode assembly comprises a negative electrode sheet, a positive electrode sheet and a separation film arranged between the negative electrode sheet and the positive electrode sheet. The negative electrode tab is connected to the negative electrode sheet. The positive electrode tab is connected to the positive electrode sheet. The first insulating glue comprises a first connecting layer, the first connecting layer is connected to the electric core shell and the negative electrode tab, the first connecting layer has at least a first melting point and a second melting point, the range of the first melting point A is 50 DEG C <= A <= 120 DEG C, the range of the second melting point B is 120 DEG C < B <= 170 DEG C. The second insulating glue comprises a second connecting layer, the second connecting layer is connected to the electric core shell and the positive electrode tab, the melting point C of the second connecting layer is in the range of 110 DEG C <= C <= 145 DEG C, and the ratio of the cross-sectional area of the negative electrode tab to the cross-sectional area of the positive electrode tab is 0.5-0.95 along the direction perpendicular to the current path.

Description

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 battery cell housing, an electrode assembly, a negative electrode tab, a positive electrode tab, a first insulating adhesive, and a second insulating adhesive. The battery cell housing includes a main body and a sealing portion. The electrode assembly is disposed within the main body and includes a negative electrode plate, a positive electrode plate, and a separator film disposed between the negative and positive electrode plates, with a portion of the negative electrode plate extending beyond the positive electrode plate. The negative electrode tab connects to the negative electrode plate and extends beyond the sealing portion. The positive electrode tab connects to the positive electrode plate and extends beyond the sealing portion. The first insulating adhesive includes a first connecting layer, at least partially connected to the battery cell housing or the negative electrode tab. The first connecting 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℃. The second insulating adhesive includes a second connecting layer, at least partially connected to the battery cell housing or the positive electrode tab. The range of the melting point C of the second connecting layer is 110℃ ≤ C ≤ 145℃. Along the direction perpendicular to the current path, the ratio of the cross-sectional area of ​​the negative electrode tab to that of the positive electrode tab is 0.5-0.95. The first connecting layer, by setting multiple melting point ranges, can melt within the temperature range of the first and second melting points, effectively controlling the melting and pressure relief point of the first insulating adhesive. By reducing the cross-sectional area of ​​the negative electrode tab, its resistance is increased, thereby increasing the Joule heat of the negative electrode tab, which is beneficial for the melting of the first insulating adhesive, facilitating the rapid formation of a pressure relief channel, improving the heat dissipation efficiency of the battery cell, and allowing the negative electrode plate to extend beyond the positive electrode plate, reducing the risk of a short circuit caused by contact between the negative and positive electrode plates. The second connecting layer, by setting a higher melting point range, reduces the risk of a short circuit caused by the positive electrode tab contacting the negative electrode plate after melting the second insulating adhesive and the separator. On the other hand, after rapid pressure relief of the battery cell, the internal air pressure is insufficient, reducing the risk of a short circuit caused by excessive expansion and deformation of the battery cell, which could force the positive electrode tab to contact the negative electrode plate at the bending point.

[0005] In one or more of the above optional embodiments, the melt flow index of the first connecting layer at 230°C and a 2.16kg load is 4g / 10min-20g / 10min. If the melt flow index of the first connecting layer at 230°C and a 2.16kg load is less than 4g / 10min, the fluidity of the first connecting layer after melting is low, which is not conducive to expanding the overflow clumps formed after the first connecting layer melts, reducing the encapsulation pull force of the first insulating adhesive under room temperature conditions, reducing the encapsulation reliability of the battery cell under room temperature conditions, and affecting the rapid formation of pressure relief channels after the battery cell expands, reducing heat dissipation efficiency, and is not conducive to improving the safety performance of the battery cell. If the melt flow index of the first connecting layer at 230°C and a 2.16kg load is greater than 20g / 10min, the fluidity of the first connecting layer after melting is too high, which can easily lead to leakage of the battery cell and affect the sealing performance of the battery cell. By limiting the melt flow index of the first connecting layer to 4g / 10min-20g / 10min at 230℃ and 2.16kg load, the fluidity of the first connecting layer after melting is improved, forming a tighter overflow clump at the sealing edge. This increases the encapsulation pull force of the first insulating adhesive under room temperature conditions, thereby improving the encapsulation reliability of the battery cell under room temperature conditions. When the battery cell experiences thermal runaway and / or pressure relief, the high fluidity of the first connecting layer at high temperatures allows the encapsulation strength of the battery cell to decrease rapidly. This enables the high-temperature gas inside the battery cell to be rapidly depressurized and dissipated at the first connecting layer, improving heat dissipation efficiency and thus enhancing the safety performance of the battery cell.

[0006] In one or more of the above optional embodiments, the melt flow index of the first connecting layer at 230°C and 2.16kg load is 7g / 10min-12g / 10min, which makes it easier to meet the requirements of high temperature fluidity and mechanical strength, and the encapsulation thickness is easier to control, further improving the encapsulation reliability and safety performance of the battery cell under normal temperature conditions.

[0007] In one or more of the above optional embodiments, the melt flow index of the second connecting layer at 230°C and a load of 2.16 kg is 0.1 g / 10 min to 8 g / 10 min. The low melt flow index and high melting point of the second connecting layer reduce the fluidity of the melt, thereby reducing the risk of short circuit caused by the positive electrode tab melting the second insulating adhesive and the separator and coming into contact with the negative electrode sheet, thus providing good insulation.

[0008] The ratio of the cross-sectional area of ​​the negative electrode tab to that of the positive electrode tab in the width direction is 0.6-0.8. This further improves heat dissipation and reduces the risk of short circuits.

[0009] In one or more of the above optional embodiments, the difference between the second melting point B and the melting point C of the second connecting layer is less than 50°C. By matching the encapsulation temperature of the second insulating adhesive with the second melting point B, the same sealing temperature is sufficient to simultaneously melt the first and second insulating adhesives during the encapsulation process, and the melting effect is controllable. The overall sealing parallelism is good, meeting the encapsulation requirements and improving encapsulation reliability.

[0010] In one or more of the above optional embodiments, the first insulating adhesive satisfies at least one of the following conditions: the first insulating adhesive includes a first base layer, a first connecting layer connects the first base layer, the melting point of the first base layer is higher than the melting point of the first connecting layer, and the melting point range of the first base layer is 140℃-220℃; at 230℃, the melt index of the first base layer under a 2.16kg load is less than the melt index of the first connecting layer, and the melt index of the first base layer is 0.1g / 10min-5g / 10min, which reduces the fluidity of the first base layer melt, supports the connecting layer, and is beneficial to improving the sealing of the battery cell and the insulation of the first insulating adhesive. The small melt index of the first base layer helps to reduce the appearance of the exposed part of the first insulating adhesive due to heat curling and deformation. At the same time, Joule heat is easily generated during the conduction process of the negative electrode tab. The high melting point and small melt index of the first base layer play an insulating role.

[0011] In one or more of the above optional embodiments, the second insulating adhesive includes a second base layer, and a second connecting layer connects to the second base layer. The melting point of the second base layer is higher than that of the second connecting layer, and the melting point range of the second base layer is 200℃-500℃. Supporting the second connecting layer reduces the risk of short circuits caused by melting of the second base layer, which could lead to contact between the positive electrode tab and the metal layer of the cell casing or the negative electrode sheet. This improves the insulation performance of the second insulating adhesive.

[0012] In one or more of the above optional embodiments, the negative electrode 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 to reduce the risk of breakage of the negative electrode tab during drop. By setting the melting point of the first insulating adhesive, the risk of short circuit caused by contact between the second section and the metal layer of the cell casing or the positive electrode sheet under extreme operating conditions is reduced. The third section is bent to connect to the second section, and a portion of the third section extends out of the sealing portion.

[0013] 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 first insulating adhesive, the two first adhesive layers located in the first region are bonded together, twice the thickness of the first base layer is less than the sum of the thicknesses of the two first adhesive layers, or the sum of the thicknesses of the first base layers on both sides of the negative electrode tab is less than the sum of the thicknesses of the two first adhesive layers, thereby reducing the presence of pore channels in the sealing part and reducing the risk of leakage and short circuit.

[0014] In one or more of the above optional embodiments, at least one of the following conditions must be met: the second connecting layer accounts for 30%-44% of the thickness of the second insulating adhesive; if the thickness of the second connecting layer is too small (less than 30%), it will affect the connection strength of the second connecting layer; if the overflow clump formed after the second connecting layer melts is too small, it will reduce the encapsulation pull force of the second insulating adhesive under normal temperature conditions, reduce the encapsulation reliability of the battery cell under normal temperature conditions, and reduce the pressure relief channel formed by the melting of the second connecting layer, which is not conducive to pressure relief. If the thickness of the second connecting layer is too large (greater than 44%), it can easily lead to an excessive thickness difference between the first region and the sealing part containing the second insulating adhesive, affecting the packaging reliability. By limiting the thickness of the second connecting layer to 30% to 44% of the thickness of the second insulating adhesive, the thickness difference is reduced, which helps improve the packaging reliability of the cell under normal temperature conditions. The second base layer accounts for 6% to 20% of the thickness of the second insulating adhesive. If the thickness of the second base layer is too small (less than 6%), the tabs covered by the second base layer are easily exposed, leading to short circuits. If the thickness of the second base layer is too large (greater than 20%), it affects the packaging pull force of the second insulating adhesive under normal temperature conditions, easily creating pore channels and leading to leakage. By limiting the thickness of the second base layer to 6% to 20% of the thickness of the second insulating adhesive, it helps reduce the occurrence of pore channels in the cell, which helps reduce the risk of leakage and short circuits. The second insulating adhesive includes a second adhesive layer, which connects the second base layer and the second connecting layer. The thickness of the second adhesive layer is 1% to 4% of the thickness of the second insulating adhesive. If the thickness of the second adhesive layer is less than 1% of the thickness of the second insulating adhesive, the connection strength between the second base layer and the second connecting layer is low. If the thickness of the second adhesive layer is greater than 4% of the thickness of the second insulating adhesive, the thickness of the second insulating adhesive increases, increasing the thickness difference and potentially affecting 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 thickness of the second insulating adhesive, the thickness difference is reduced, improving the connection strength between the second base layer and the second connecting layer, as well as the encapsulation reliability of the battery cell under normal temperature conditions.

[0015] In one or more of the above optional embodiments, the first connecting layer satisfies at least one of the following conditions: the number-average molecular weight Mn of the first connecting layer is 10000 g / mol to 130000 g / mol. If the number-average molecular weight of the first connecting layer is less than 10000 g / mol, the melt viscosity of the first connecting layer is too low, which is not conducive to processing and molding, and easily leads to high fluidity after the first connecting layer melts, reducing the packaging reliability of the battery cell under normal temperature conditions. If the number-average molecular weight of the first connecting layer is greater than 130000 g / mol, the melt viscosity of the first connecting layer is too high, which is not conducive to processing and molding, and easily leads to increased brittleness of the first connecting layer, making it prone to breakage under external force. By limiting the number-average molecular weight Mn of the first connecting layer to 10000 g / mol to 130000 g / mol, the packaging reliability of the battery cell under normal temperature conditions and the mechanical strength of the first insulating adhesive are improved. It is also beneficial to control the melting point and melt index of the first connecting layer and effectively regulate the melting pressure relief point of the first connecting layer. The weight-average molecular weight (Mw) of the first connecting layer is 100,000 g / mol to 800,000 g / mol. If the weight-average molecular weight of the first connecting layer is less than 100,000 g / mol, the mechanical strength of the first connecting layer is low; if the weight-average molecular weight of the first connecting layer is greater than 800,000 g / mol, the melt viscosity of the first connecting layer is too high, which is not conducive to flow. By limiting the weight-average molecular weight (Mw) of the first connecting 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 first insulating adhesive are improved. This is beneficial for controlling the melting point and melt flow index of the first connecting layer, and effectively regulating the melting pressure relief point of the first connecting layer. A Mw / Mn ratio of 3-10 improves the polydispersity index of the material, broadens the melting point range of the first connecting layer, and allows for adjustment of the melt flow index, which is beneficial for increasing the material's fluidity at high temperatures, allowing for rapid melting after reaching the melting point. The collapse of the first connecting layer structure forms a pressure relief channel, improving the heat dissipation efficiency of the battery cell.

[0016] In one or more of the above optional embodiments, at 25°C, the tensile force between the first insulating adhesive and the cell housing and / or the negative electrode tab ranges from 5 N / mm to 10 N / mm. This further improves the encapsulation tensile force and encapsulation reliability of the cell under normal temperature conditions. A tensile force exceeding 10 N / mm can easily cause the packaging bag to rupture.

[0017] In one or more of the above optional embodiments, at 95°C, the tensile force between the first insulating adhesive and the cell housing and / or the negative electrode tab 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.

[0018] In one or more of the above optional embodiments, at 120°C, the tensile force between the first insulating adhesive and the cell housing and / or the negative electrode tab ranges from 0.01 N / mm to 0.1 N / mm. This further facilitates the rapid formation of a pressure relief channel after the cell expands, improves heat dissipation efficiency, and thus enhances the safety performance of the cell.

[0019] Embodiments of this application provide an electrical device including the battery cell from any of the above embodiments. Attached Figure Description

[0020] Figure 1 A cross-sectional structural schematic diagram of the battery cell is shown in some embodiments.

[0021] Figure 2 A structural schematic diagram of a cross-section of a battery cell is shown in some embodiments.

[0022] Figure 3 Partial schematic diagrams of the cell housing, negative electrode tab, and first insulating adhesive are shown in some embodiments.

[0023] Figure 4 Partial schematic diagrams of the cell housing, positive electrode tab, and second insulating adhesive are shown in some embodiments.

[0024] Figure 5 Schematic diagrams of electrical equipment in some embodiments are shown.

[0025] Explanation of key component symbols:

[0026] 100 cells

[0027] Cell casing 10

[0028] Main body 11

[0029] Sealing part 12

[0030] Area 121

[0031] Second area 122

[0032] First adhesive layer 101

[0033] Metal layer 102

[0034] Outer layer 103

[0035] Electrode assembly 20

[0036] Negative electrode plate 21

[0037] Positive electrode plate 22

[0038] Separator 23

[0039] Negative electrode tab 30

[0040] Section 31

[0041] Section 32

[0042] Section 33

[0043] Positive electrode tab 40

[0044] Section 41

[0045] Section 5, 42

[0046] Section 6, No. 43

[0047] First insulating adhesive 50

[0048] First connection layer 51

[0049] First grassroots level 52

[0050] Second insulating adhesive 60

[0051] Second connection layer 61

[0052] Second grassroots level 62

[0053] Second adhesive layer 63

[0054] 200 electrical appliances

[0055] The following specific embodiments will further illustrate this application in conjunction with the above-described accompanying drawings. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Please seeFigure 1 and Figure 2 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.

[0061] In some embodiments, the electrode assembly 20 includes a negative electrode 21, a positive electrode 22, and a separator 23 disposed between the negative electrode 21 and the positive electrode 22. The separator 23 is used to prevent the negative electrode 21 and the positive electrode 22 from directly contacting each other, thereby reducing the risk of short circuit between the negative electrode 21 and the positive electrode 22. A portion of the negative electrode 21 extends beyond the positive electrode 22.

[0062] In some embodiments, the battery cell 100 includes a negative electrode tab 30 and a positive electrode tab 40. The negative electrode tab 30 is connected to the negative electrode plate 21 and extends out of the sealing portion 12. The positive electrode tab 40 is connected to the positive electrode plate 22 and extends out of the sealing portion 12.

[0063] In some embodiments, the battery cell 100 includes a first insulating adhesive 50 and a second insulating adhesive 60. The first insulating adhesive 50 includes a first connecting layer 51, at least a portion of which is connected to the battery cell housing 10 or the negative electrode tab 30. The first connecting layer 51 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. The second insulating adhesive 60 includes a second connecting layer 61, at least a portion of which is connected to the battery cell housing 10 and the positive electrode tab 40. The range of the melting point C of the second connecting layer 61 is 110°C ≤ C ≤ 145°C. The first connecting layer 51, by setting multiple melting point ranges, 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 first insulating adhesive 50. This facilitates the rapid formation of a pressure relief channel, improves the heat dissipation efficiency of the battery cell 100, and allows the negative electrode plate 21 to extend beyond the positive electrode plate 22, reducing the risk of a short circuit caused by contact between the negative electrode tab 30 and the positive electrode plate 22. The second connecting layer 61, by setting a higher melting point range, reduces the risk of a short circuit caused by the positive electrode tab 40 contacting the negative electrode plate 21 after melting the second insulating adhesive 60 and the separator 23.

[0064] 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.

[0065] 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.

[0066] Optionally, the melting point C of the second connecting layer 61 can be any one or any combination of 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, and 145°C.

[0067] In some embodiments, along the thickness direction of the negative electrode tab 30, the negative electrode tab 30 is disposed between two first insulating adhesives 50, and the positive electrode tab 40 is disposed between two second insulating adhesives 60.

[0068] In some embodiments, along the direction perpendicular to the current path (i.e., the direction in which the tabs extend), the ratio of the cross-sectional area of ​​the negative tab 30 to the cross-sectional area of ​​the positive tab 40 is 0.5-0.95. The resistance formula is R = p1 / S (p: resistivity, l: length in the current direction, S: cross-sectional area through which the current flows), and the Joule heating formula is Q = I... 2 Rt(Q: Joule heat, I: current, R: resistance, t: time) increases the resistance of the negative electrode tab 30 by reducing its cross-sectional area, thereby increasing its Joule heat. This facilitates the melting of the first insulating adhesive 50, rapidly forming a pressure relief channel and improving the heat dissipation efficiency of the battery cell 100. On the other hand, after rapid pressure relief, the internal pressure of the battery cell is insufficient, reducing the risk of excessive expansion and deformation of the battery cell, which could cause the positive electrode tab 40 to contact the negative electrode plate 21 at the bending position, leading to a short circuit. If the ratio of the cross-sectional areas is too small, the Joule heat generated by the negative electrode tab 30 may be excessive, causing the battery cell 100 to reach the thermal runaway critical temperature and fail; this could lead to a short circuit at the bending point of the negative electrode tab 30. If the ratio of the cross-sectional areas is too large, the temperature rise of the negative electrode tab 30 may not be sufficient to cause the first insulating adhesive 50 to melt and release pressure, increasing the risk of excessive expansion and deformation of the battery cell, which could cause the positive electrode tab 40 to contact the negative electrode plate 21 at the bending position, leading to a short circuit. By limiting the cross-sectional area of ​​the negative electrode tab 30 to that of the positive electrode tab 40 to be 0.5-0.95 along the direction perpendicular to the current path, it is beneficial to improve heat dissipation and reduce the risk of short circuit at the positive electrode bend.

[0069] Optionally, the ratio of the cross-sectional area of ​​the negative electrode tab 30 in the width direction to the cross-sectional area of ​​the positive electrode tab 40 in the width direction can be any one or any combination of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95.

[0070] In some embodiments, the ratio of the cross-sectional area of ​​the negative electrode tab 30 to the cross-sectional area of ​​the positive electrode tab 40 along the direction perpendicular to the current path is 0.6-0.8. This further improves heat dissipation and reduces the risk of short circuits.

[0071] In some embodiments, the negative electrode tab 30 is made of copper plated with nickel, and the positive electrode tab 40 is made of aluminum.

[0072] In some embodiments, the difference between the second melting point B of the first connecting layer 51 and the melting point C of the second connecting layer 61 is less than 50°C. By matching the second melting point B with the encapsulation temperature of the second insulating adhesive 60, the same sealing temperature is sufficient to simultaneously melt the first insulating adhesive 50 and the second insulating adhesive 60 during the encapsulation process. The melting effect is controllable, the overall sealing parallelism is good, the encapsulation requirements are met, and the encapsulation reliability is improved.

[0073] Please see Figure 3 In some embodiments, the cell housing 10 can be a packaging bag obtained by encapsulating with a film (such as aluminum-plastic film), that is, the cell 100 is a soft-pack cell.

[0074] In some embodiments, the battery 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 battery 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 battery 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 battery 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 battery cell housing 10.

[0075] Please see Figure 1 and Figure 2 In some embodiments, the electrode assembly 20 is a wound structure, that is, the negative electrode 21, the separator 23 and the positive electrode 22 are stacked in sequence and then wound to form the electrode assembly 20.

[0076] In other embodiments, the electrode assembly 20 may also be a stacked structure, that is, the negative electrode 21, the separator 23 and the positive 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.

[0077] In some embodiments, the negative electrode tab 30 includes a first segment 31, a second segment 32, and a third segment 33. At least a portion of the first segment 31 is connected to the negative electrode plate 21. The second segment 32 is bent to connect to the first segment 31. The third segment 33 is bent to connect to the second segment 32, and a portion of the third segment 33 extends out of the sealing portion 12. A portion of the third segment 33 extends out of the first insulating adhesive 50 for connection with other components to perform energy transfer.

[0078] In some embodiments, the first section 31 is welded to the negative electrode sheet 21. The welding method includes laser welding, ultrasonic welding, etc.

[0079] In some embodiments, the length of the second segment 32 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 negative electrode tab 30 during a drop, and by setting the melting point of the first insulating adhesive 50, the risk of short circuit caused by contact between the second segment 32 and the metal layer 102 or the positive electrode sheet 22 under extreme operating conditions is reduced. Optionally, the length of the second segment 32 is any one of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and 70% of the thickness of the cell 100.

[0080] In some embodiments, the positive electrode tab 40 includes a fourth segment 41, a fifth segment 42, and a sixth segment 43, with at least a portion of the fourth segment 41 connected to the positive electrode plate 22. The fifth segment 42 is bent to connect to the fourth segment 41. The sixth segment 43 is bent to connect to the fifth segment 42, with a portion of the sixth segment 43 extending out of the sealing portion 12. A portion of the sixth segment 43 extends out of the second insulating adhesive 60 for connection with other components to perform energy transfer.

[0081] In some embodiments, the fourth section 41 is welded to the positive electrode sheet 22. The welding method includes laser welding, ultrasonic welding, etc.

[0082] In some embodiments, the length of the fifth segment 42 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 positive electrode tab 40 during a drop, and by setting the melting point of the second insulating adhesive 60, the risk of short circuit caused by contact between the positive electrode tab 40 and the metal layer 102 or the negative electrode sheet 21 under extreme operating conditions is reduced. Optionally, the length of the fifth segment 42 is any one of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and 70% of the thickness of the cell 100.

[0083] In some embodiments, the melt flow index of the first connecting layer 51 at 230°C and a load of 2.16 kg is 4 g / 10 min to 20 g / 10 min. If the melt flow index of the first connecting layer 51 at 230°C and a load of 2.16 kg is less than 4 g / 10 min, the fluidity of the first connecting layer 51 after melting is low, which is not conducive to expanding the overflow agglomerates formed after the first connecting layer 51 melts, reducing the packaging reliability of the cell 100 under normal 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 the cell 100. If the melt flow index of the first connecting layer 51 at 230°C and a load of 2.16 kg is greater than 20 g / 10 min, the fluidity of the first connecting layer 51 after melting is too high, which can easily lead to leakage of the cell 100 and affect the sealing performance of the cell 100. By limiting the melt flow index of the first connecting layer 51 to 4g / 10min-20g / 10min at 230℃ and 2.16kg load, the fluidity of the first connecting layer 51 after melting is improved, forming a tighter overflow clump at the sealing edge, increasing the encapsulation pull force of the first insulating adhesive 50 under normal temperature conditions, and improving the encapsulation reliability of the cell 100 under normal temperature conditions. When the cell 100 experiences thermal runaway and / or pressure relief, the high fluidity of the first connecting layer 51 at high temperatures allows the encapsulation strength of the cell 100 to decrease rapidly, enabling the high-temperature gas inside the cell 100 to quickly depressurize and dissipate heat at the first connecting layer 51, improving heat dissipation efficiency, and thus enhancing the safety performance of the cell 100.

[0084] Optionally, the melt flow index of the first connecting layer 51 at 230°C and a load of 2.16 kg 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.

[0085] In some embodiments, the melt flow index of the first connecting layer 51 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 the cell 100 under normal temperature conditions.

[0086] In some embodiments, the melt flow index of the first connecting layer 51 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 the cell 100 under normal temperature conditions.

[0087] In some embodiments, the melt flow index of the second connecting layer 61 at 230°C and a load of 2.16 kg is 0.1 g / 10 min to 8 g / 10 min. The low melt flow index and high melting point of the second connecting layer 61 reduce the fluidity of the melt and reduce the risk of short circuit caused by the positive electrode tab 40 melting the second insulating adhesive 60 and the separator 23 and coming into contact with the negative electrode sheet 21, thus providing good insulation.

[0088] Optionally, the melt flow index of the second connecting layer 61 at 230°C and 2.16 kg load can be any one or any combination of two of the following: 0.1 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, and 8 g / 10 min.

[0089] Please see Figure 3 In some embodiments, the first insulating adhesive 50 includes a first base layer 52, and a first connecting layer 51 is connected to at least one side of the first base layer 52 along the thickness direction of the first base layer 52.

[0090] Optionally, a first connecting layer 51 is connected to one side of the first base layer 52 along the thickness direction of the first base layer 52.

[0091] Optionally, along the thickness direction of the first base layer 52, a first connecting layer 51 is connected to both sides of the first base layer 52. This application will describe the example where a first connecting layer 51 is connected to both sides of the first base layer 52.

[0092] It is understood that in some embodiments, the thickness of the first connecting layer 51 on both sides of the first base layer 52 is equal. In other embodiments, the thickness of the first connecting layer 51 on both sides of the first base layer 52 has a tolerance.

[0093] In some embodiments, the melting point of the first base layer 52 is higher than that of the first connecting layer 51. The melting point range of the first base layer 52 is 140°C-220°C. It supports the first connecting layer 51, reduces the risk of short circuit caused by melting of the first base layer 52, which would result in contact between the negative electrode tab 30 and the metal layer 102 of the cell housing 10 or the positive electrode tab 40. This is beneficial to improving the insulation of the cell 100.

[0094] Optionally, the melting point of the first base layer 52 can be any one or any combination of 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, and 220℃.

[0095] In some embodiments, the melt flow index of the first base layer 52 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 first base layer 52 and supports the first connecting layer 51. This is beneficial to improving the sealing and insulation properties of the battery cell 100. The low melt flow index of the first base layer 52 helps to reduce the appearance of the exposed part of the first insulating adhesive 50 due to heat curling and deformation. At the same time, the first insulating adhesive 50 is prone to Joule heating during the electrode tab conduction process. The first base layer 52 has a high melting point and a low melt flow index, which plays a good insulating role.

[0096] Optionally, the melt flow index of the first base layer 52 at 230°C and 2.16 kg load can be any one or any combination of two of the following: 0.1 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, and 5 g / 10 min.

[0097] 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 first insulating adhesive 50. The two first adhesive layers 101 located in the first region 121 are bonded together. The thickness of the first base layer 52 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 first base layers 52 on both sides of the negative electrode tab 30 is less than the sum of the thicknesses of the two first adhesive layers 101. Because the first base layer 52 has a high melting point and is not easily melted during encapsulation, excessive thickness of the first base layer 52 after encapsulation can lead to pore channels, causing leakage. External moisture can easily enter the cell housing 10, potentially causing a short circuit. By ensuring that half the thickness of the first base layer 52 is less than 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.

[0098] In some embodiments, the sum of the thickness of the first insulating adhesive 50 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 appearance of pore channels in the sealing portion 12 and lowering the risk of leakage and short circuit.

[0099] In some embodiments, the number average molecular weight of the first base layer 52 is at least 70,000 g / mol, which is beneficial to improving the insulation and mechanical strength of the cell 100 and reducing damage to the seal during drop.

[0100] In some embodiments, the number-average molecular weight Mn of the first connecting layer 51 is 10,000 g / mol to 130,000 g / mol. If the number-average molecular weight of the first connecting layer 51 is less than 10,000 g / mol, the melt viscosity of the first connecting layer 51 is too low, which is not conducive to processing and molding, and easily leads to high fluidity of the first connecting layer 51 after melting, reducing the encapsulation reliability of the battery cell 100 under normal temperature conditions. If the number-average molecular weight of the first connecting layer 51 is greater than 130,000 g / mol, the melt viscosity of the first connecting layer 51 is too high, which is not conducive to processing and molding, and easily leads to increased brittleness of the first connecting layer 51, making it prone to breakage under external force. By limiting the number-average molecular weight Mn of the first connecting layer 51 to 10,000 g / mol to 130,000 g / mol, the encapsulation reliability of the battery 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 first connecting layer 51, and effectively regulating the melting pressure relief point of the first connecting layer 51.

[0101] Optionally, the number-average molecular weight Mn of the first connecting layer 51 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.

[0102] In some embodiments, the weight-average molecular weight Mw of the first connecting layer 51 is 100,000 g / mol to 800,000 g / mol. If the weight-average molecular weight of the first connecting layer 51 is less than 100,000 g / mol, the mechanical strength of the first connecting layer 51 is low; if the weight-average molecular weight of the first connecting layer 51 is greater than 800,000 g / mol, the melt viscosity of the first connecting layer 51 is too high, which is not conducive to flow. By limiting the weight-average molecular weight Mw of the first connecting layer 51 to 100,000 g / mol to 800,000 g / mol, the encapsulation reliability of the battery 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 flow index of the first connecting layer 51 and effectively regulating the melting pressure relief point of the first connecting layer 51.

[0103] Optionally, the weight-average molecular weight Mw of the first connecting layer 51 is any one or any combination of two of the following: 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.

[0104] 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 first connecting layer 51, and at the same time reduces the melt index, which is beneficial to increase the fluidity of the material at high temperatures, allowing it to melt quickly after reaching the melting point. The structure of the first connecting layer 51 collapses to form a pressure relief channel, thereby improving the heat dissipation efficiency of the battery cell 100.

[0105] 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.

[0106] In some embodiments, the material of the first connecting layer 51 includes at least one selected from polyolefin resin, acid-modified polyolefin resin, polyethylene, polypropylene, ethylene elastomer, and styrene elastomer.

[0107] In some embodiments, the material of the second connecting layer 61 includes at least one selected from polyolefin resins, acid-modified polyolefin resins, polyethylene, polypropylene, ethylene elastomers, and styrene elastomers.

[0108] In some embodiments, the second insulating adhesive 60 includes a second base layer 62, and a second connecting layer 61 is connected to at least one side of the second base layer 62 along the thickness direction of the second base layer 62.

[0109] Optionally, a second connecting layer 61 is connected to one side of the second base layer 62 along the thickness direction of the second base layer 62.

[0110] Optionally, along the thickness direction of the second base layer 62, a second connecting layer 61 is connected to both sides of the second base layer 62. This application will describe the application using the example of a second base layer 62 having a second connecting layer 61 connected to both sides.

[0111] It is understood that in some embodiments, the thickness of the second connecting layer 61 on both sides of the second base layer 62 is equal. In other embodiments, the thickness of the second connecting layer 61 on both sides of the second base layer 62 has a tolerance.

[0112] In some embodiments, the melting point of the second base layer 62 is higher than that of the second connecting layer 61. The melting point range of the second base layer 62 is 200°C-500°C. It supports the second connecting layer 61 and reduces the risk of short circuit caused by the melting of the second base layer 62, which would result in contact between the positive electrode tab 40 and the metal layer 102 of the cell housing 10 or the negative electrode sheet 21. This is beneficial to improving the insulation of the second insulating adhesive 60.

[0113] Optionally, the melting point of the second base layer 62 can be any one or any combination of two of the following: 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℃.

[0114] In some embodiments, along the thickness direction of the cell housing 10, the sealing portion 12 includes a second region 122 that does not overlap with the first insulating adhesive 50. Two first adhesive layers 101 located in the second region 122 are bonded together. The thickness of the second base layer 62 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 second base layers 62 on both sides of the positive electrode tab 40 is less than the sum of the thicknesses of the two first adhesive layers 101. Because the second base layer 62 has a high melting point, it is not easy to melt during the encapsulation process. If the thickness of the second base layer 62 is too large, it will not melt after encapsulation and will easily form pore channels, leading to leakage. External moisture can easily enter the inside of the cell housing 10, which can easily cause a short circuit. By making the thickness of the second base layer 62 less than half the sum of the thicknesses of the two first adhesive layers 101 after hot pressing, the formation of pore channels in the sealing portion 12 is reduced, thus reducing the risk of leakage and short circuit.

[0115] In some embodiments, the sum of the thickness of the second insulating adhesive 60 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.

[0116] Please see Figure 4 In some embodiments, the second insulating adhesive 60 includes a second adhesive layer 63, which bonds the second base layer 62 and the second connecting layer 61.

[0117] In some embodiments, the thickness of the second base layer 62 is 6% to 20% of the thickness of the second insulating adhesive 60. If the thickness of the second base layer 62 is too small (less than 6%), the positive electrode tab 40 covered by the second base layer 62 is easily exposed, leading to a short circuit. If the thickness of the second base layer 62 is too large (greater than 20%), it affects the encapsulation pull force of the second insulating adhesive 60 under normal temperature conditions, easily resulting in pore channels and leakage. By limiting the thickness of the second base layer 62 to 6% to 20% of the thickness of the second insulating adhesive 60, it is beneficial to reduce the occurrence of pore channels in the cell 100, thereby reducing the risk of leakage and short circuit.

[0118] Optionally, the thickness of the second base layer 62 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 second insulating adhesive 60.

[0119] In some embodiments, the thickness of the second connecting layer 61 is 30% to 44% of the thickness of the second insulating adhesive 60. If the thickness of the second connecting layer 61 is too small (less than 30%), it affects the connection strength of the second connecting layer 61. The excess adhesive clumps formed after the second connecting layer 61 melts are too small, resulting in a decrease in the encapsulation pull force of the second insulating adhesive 60 under room temperature conditions, a decrease in the encapsulation reliability of the cell 100 under room temperature conditions, and a reduction in the pressure relief channel formed by the melting of the second connecting layer 61, which is not conducive to pressure relief. If the thickness of the second connecting layer 61 is too large (greater than 44%), it is easy to cause an excessive thickness difference between the first region 121 and the sealing portion 12 containing the second insulating adhesive 60, affecting the encapsulation reliability. During the encapsulation process, along the thickness direction of the cell housing 310, two first adhesive layers 101 are bonded together and have a first thickness. The portion of the second connecting layer 61 extending along both sides of the width direction of the positive electrode tab 40 is bonded together and has a second thickness. The second insulating adhesive 60 located on both sides of the thickness direction of the positive electrode tab 40 and the positive electrode tab 40 have a third thickness. By limiting the thickness of the second connecting layer 61 to 30% to 44% of the thickness of the second insulating adhesive 60, 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 100 under normal temperature conditions and is also beneficial to pressure relief.

[0120] Optionally, the thickness of the second connecting layer 61 is within the range of any one or any two of the following: 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, and 44% of the thickness of the second insulating adhesive 60.

[0121] In some embodiments, the thickness of the second adhesive layer 63 is 1% to 4% of the thickness of the second insulating adhesive 60. If the second adhesive layer 63 is less than 1% of the thickness of the second insulating adhesive 60, the connection strength between the second base layer 62 and the second connecting layer 61 is low. If the second adhesive layer 63 is greater than 4% of the thickness of the second insulating adhesive 60, the thickness of the second insulating adhesive 60 increases, increasing the thickness difference between the first, second, and third thicknesses, which can easily affect the encapsulation reliability of the battery cell 100 under normal temperature conditions. By limiting the thickness of the second adhesive layer 63 to 1% to 4% of the thickness of the second insulating adhesive 60, the thickness difference between the first, second, and third thicknesses is reduced, thereby improving the connection strength between the second base layer 62 and the second connecting layer 61 and the encapsulation reliability of the battery cell 100 under normal temperature conditions.

[0122] Optionally, the thickness of the second adhesive layer 63 is within the range of any one or any two of 1%, 2%, 3%, 4% of the thickness of the first insulating adhesive 50.

[0123] In some embodiments, at 25°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 is in the range of 5N / mm-10N / mm, which improves the encapsulation tensile force of the first insulating adhesive 50 under normal temperature conditions and improves the encapsulation reliability of the cell 100 under normal temperature conditions.

[0124] Optionally, the tensile strength of the first insulating adhesive 50 at 25°C can be any one or any combination of two of the following: 5N / mm, 5.5N / mm, 6N / mm, 6.5N / mm, 7N / mm, 7.5N / mm, 8N / mm, 8.5N / mm, 9N / mm, 9.5N / mm, and 10N / mm.

[0125] In some embodiments, at 25°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 ranges from 6.5 N / mm to 10 N / mm, further improving the encapsulation tensile force of the first insulating adhesive 50 under normal temperature conditions and enhancing the encapsulation reliability of the cell 100 under normal temperature conditions.

[0126] In some embodiments, at 95°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 ranges from 0.2 N / mm to 2 N / mm. Under the operating conditions of 95°C, the cell 100 can still meet the requirements for encapsulation reliability, reducing the occurrence of leakage.

[0127] Optionally, the tensile strength of the first insulating adhesive 50 at 95°C can be 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, or 1.0 N / mm.

[0128] 1.1N / mm, 1.2N / mm, 1.3N / mm, 1.4N / mm, 1.5N / mm, 1.6N / mm, 1.7N / mm,

[0129] The range of any one or any two of 1.8 N / mm, 1.9 N / mm, and 2.0 N / mm.

[0130] In some embodiments, at 95°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 ranges from 0.8 N / mm to 2 N / mm. Under the operating conditions of 95°C, the encapsulation reliability of the cell 100 can still meet the requirements, further reducing the occurrence of leakage.

[0131] In some embodiments, at 120°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 is in the range of 0.01 N / mm to 0.2 N / mm, which is beneficial for the cell 100 to quickly form a pressure relief channel after expansion, improve heat dissipation efficiency, and thus improve the safety performance of the cell 100.

[0132] Optionally, the tensile strength of the first insulating adhesive 50 at 120°C can be 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, etc.

[0133] The range of any one or any two of 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.

[0134] In some embodiments, at 120°C, the tensile force between the first insulating adhesive 50 and the cell housing 10 and / or the negative electrode tab 30 is in the range of 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.

[0135] In some embodiments, at 25°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 is in the range of 5N / mm-10N / mm, which improves the encapsulation tensile force of the second insulating adhesive 60 under normal temperature conditions and improves the encapsulation reliability of the cell 100 under normal temperature conditions.

[0136] Optionally, the tensile strength of the second insulating adhesive 60 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.

[0137] In some embodiments, at 25°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 ranges from 6.5 N / mm to 10 N / mm, further improving the encapsulation tensile force of the second insulating adhesive 60 under normal temperature conditions and enhancing the encapsulation reliability of the cell 100 under normal temperature conditions.

[0138] In some embodiments, at 95°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 is in the range of 0.2N / mm-2N / mm. Under the operating conditions of 95°C, the encapsulation reliability of the cell 100 can still meet the requirements, reducing the occurrence of leakage.

[0139] Optionally, the tensile strength of the second insulating adhesive 60 at 95°C can be 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, or 1.0 N / mm.

[0140] 1.1N / mm, 1.2N / mm, 1.3N / mm, 1.4N / mm, 1.5N / mm, 1.6N / mm, 1.7N / mm,

[0141] The range of any one or any two of 1.8 N / mm, 1.9 N / mm, and 2.0 N / mm.

[0142] In some embodiments, at 95°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 ranges from 0.8 N / mm to 2 N / mm. Under the operating conditions of 95°C, the encapsulation reliability of the cell 100 can still meet the requirements, further reducing the occurrence of leakage.

[0143] In some embodiments, at 120°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 is in the range of 0.01 N / mm to 0.2 N / mm, which is beneficial for the rapid formation of a pressure relief channel after the cell 100 expands, thereby improving heat dissipation efficiency and thus enhancing the safety performance of the cell 100.

[0144] Optionally, the tensile strength of the second insulating adhesive 60 at 120°C can be 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, etc.

[0145] The range of any one or any two of 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.

[0146] In some embodiments, at 120°C, the tensile force between the second insulating adhesive 60 and the cell housing 10 and / or the positive electrode tab 40 is in the range of 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.

[0147] The present application will be further described below through specific embodiments.

[0148] 1. The specific method for hot box testing is as follows:

[0149] 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.

[0150] 2. High-temperature internal stress testing method:

[0151] 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.

[0152] 3. Melt flow index test method:

[0153] Take approximately 2-10 grams of sample; the exact weight depends on the melt flow index (MFR) of the material and the testing conditions. Using a melt flow indexer, pulverize the polymer material into small particles to ensure sample homogeneity. 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 the load, allowing the molten material to pass through a standard die. Record the weight of the material passing through the die within a specified time. Melt Flow Index (MFR) = Weight of material passing through the die (g) / Test time (min).

[0154] 4.60mohm Short test method:

[0155] 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.

[0156] The test ends when one of the following conditions is met: no fire or explosion occurs; otherwise, the test is passed.

[0157] 1) The test lasts for 24 hours;

[0158] 2) The surface temperature of the battery cell drops to 20% below its peak value;

[0159] 5. Method for testing melting point:

[0160] Taking the first insulating adhesive 50 as an example, the first connecting layer 51 is peeled off to obtain samples of the first connecting layer 51 and the first base layer 52. Approximately 1-3 mg of the sample is 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.

[0161] 6. Packaging pull force test method:

[0162] 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 two ends of the tensile testing machine at 180 degrees and a tensile speed of 175mm / min until it breaks. Record the maximum tensile force of the tensile testing machine.

[0163] 7. Parallelism Test Method

[0164] Starting from one end of the sealing part 12 of the battery cell 100 in the sealing direction, clamp the surface of the main body part 11 in the thickness direction and peel off the sealing interface at a speed of 2cm / min until the sealing length direction is completely peeled off. Observe the interface after peeling. If at least one side of the corresponding position of the two sides of the interface after peeling is milky, it is considered OK. If both sides are transparent, it is NG.

[0165] Preparation method of the first insulating adhesive 50: At least two particles with different melting points of the first connecting layer 51 are mixed and stirred in a high-speed mixer at 25°C for 60 minutes, and then melt-extruded and granulated in a temperature range of 170°C-250°C. The particles are dried at 80°C. The particles of the first base layer 52 are treated in the same way as above. Then, the secondary particles of the first connecting layer 51 and the secondary particles of the first base layer 52 are respectively transported to two different screw extruders through two vacuum feeders, and melt-plasticized in a temperature range of 180°C-250°C at 10MPa. Then, they are co-extruded and cast through three dies at 230°C and 5MPa, cooled to room temperature for molding, rolled into a master roll, and cured at room temperature for 24 hours.

[0166] Preparation method of the second insulating adhesive 60: The particles of the second base layer 62 are mixed and stirred in a high-temperature mixer at 25°C for 60 minutes, and then melt-extruded and granulated in a progressive temperature range of 200°C-600°C. The particles are dried at 80°C and conveyed to the screw extruder through a vacuum feeder. They are then melt-plasticized in a progressive temperature range of 200°C-600°C at 10MPa. Finally, they are co-extruded and cast through a die at 200°C-600°C (the melt-plasticization temperature is selected according to the actual base material) and 5MPa. The mixture is cooled to room temperature and then rolled into a master roll. It is then cured at room temperature for 24 hours.

[0167] Then, the particles of the second connecting layer 61 are blended and stirred in a high-speed mixer at 25°C for 60 minutes, and then melt-extruded and granulated in a progressive temperature range of 170°C-250°C. The particles are dried at 80°C. They are then conveyed to a screw extruder via a vacuum feeder and melt-plasticized in a progressive temperature range of 180°C-250°C at 10MPa. A solvent adhesive (second adhesive layer 63) is coated on one side of the second base layer 62, and dried in an oven at 80°C. The solvent adhesive is then laminated with the second connecting layer 61 at 100°C and 1MPa. A solvent adhesive (second adhesive layer 63) is coated on the other side of the second base layer 62, and dried in an oven at 80°C. The solvent adhesive is then laminated with another second connecting layer 61 at 100°C and 1MPa, and cured at 60°C for 5 days. The second insulating adhesive 60 is formed by rough cutting and fine cutting.

[0168] High-temperature internal stress test, 60mohm short test and hot box test were conducted on groups of 100 cells.

[0169] Table 1

[0170]

[0171]

[0172] As shown in Table 1, along the direction perpendicular to the current path, the ratio of the cross-sectional area of ​​the negative electrode tab 30 to that of the positive electrode tab 40 is 0.5-0.95. This results in a high pass rate in the 60mohm short test, which is beneficial for improving heat dissipation and reducing the risk of short circuits. When the ratio of the cross-sectional area of ​​the negative electrode tab 30 to that of the positive electrode tab 40 is 0.6-0.8, the pass rate in the 60mohm short test is further improved, which further enhances heat dissipation and reduces the risk of short circuits.

[0173] As shown in Table 1, when the range of the first melting point A is 50℃≤A≤120℃, the range of the second melting point B is 120℃<B≤170℃, and the range of the melting point C of the second connecting layer 61 is 110℃≤C≤145℃, the difference between the second melting point B and the melting point C is less than 50℃. This is beneficial for the cell 100 to pass the hot box test at higher temperatures, and the pass rate of the high temperature internal stress test and the 60mohm Short test is higher. This is conducive to the rapid formation of pressure relief channels, improving the heat dissipation efficiency of the cell 100, reducing the risk of short circuit of the cell 100, and the overall sealing parallelism is good, meeting the packaging requirements.

[0174] Please see Figure 5 This application also provides an electrical device 200 using 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.

[0175] 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; An electrode assembly is disposed within the main body portion. The electrode assembly includes a negative electrode plate, a positive electrode plate, and a separator disposed between the negative electrode plate and the positive electrode plate. A portion of the negative electrode plate extends out of the positive electrode plate. The negative electrode tab connects to the negative electrode plate and extends out of the sealing part; A positive electrode tab connects to the positive electrode plate and extends beyond the sealing portion; The first insulating adhesive includes a first connecting layer, at least partially connected to the battery cell housing or the negative electrode tab. The first connecting 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℃. The second insulating adhesive includes a second connecting layer, at least partially connected to the cell housing or the positive electrode tab, wherein the melting point C of the second connecting layer is in the range of 110℃≤C≤145℃; Along the direction perpendicular to the current path, the ratio of the cross-sectional area of ​​the negative electrode tab to the cross-sectional area of ​​the positive electrode tab is 0.5-0.

95.

2. The battery cell as described in claim 1, characterized in that, The melt flow index of the first connecting layer at 230°C and 2.16 kg load is 4 g / 10 min to 20 g / 10 min.

3. The battery cell as described in claim 2, characterized in that, The melt flow index of the first connecting layer at 230°C and a load of 2.16 kg is 7 g / 10 min to 12 g / 10 min.

4. The battery cell as described in claim 1, characterized in that, The melt flow index of the second connecting layer at 230°C and 2.16 kg load is 0.1 g / 10 min to 8 g / 10 min.

5. The battery cell as described in claim 1, characterized in that, The ratio of the cross-sectional area of ​​the negative electrode tab in the width direction to the cross-sectional area of ​​the positive electrode tab in the width direction is 0.6-0.

8.

6. The battery cell as described in claim 1, characterized in that, The difference between the second melting point B and the melting point C of the second connecting layer is less than 50°C.

7. The battery cell as described in claim 1, characterized in that, The first insulating adhesive must satisfy at least one of the following conditions: a) The first insulating adhesive includes a first base layer, the first connecting layer is connected to the first base layer, the melting point of the first base layer is higher than the melting point of the first connecting layer, and the melting point range of the first base layer is 140℃-220℃. b) At 230°C, the melt index of the first base layer under a load of 2.16 kg is less than that of the first connecting layer. The melt index of the first base layer is 0.1 g / 10 min - 5 g / 10 min.

8. The battery cell as described in claim 1, characterized in that, The second insulating adhesive includes a second base layer, and a second connecting layer connects the second base layer. The melting point of the second base layer is higher than that of the second connecting layer, and the melting point range of the second base layer is 200℃-500℃.

9. The battery cell as described in claim 7, characterized in that, The negative electrode tab 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.

10. The battery cell as described in claim 9, characterized in that, The battery cell housing includes two first adhesive layers, the sealing portion includes a first region that does not overlap with the first insulating adhesive, the two first adhesive layers located in the first region are bonded together, twice the thickness of the first base layer is less than the sum of the thicknesses of the two first adhesive layers, or the sum of the thicknesses of the first base layers on both sides of the negative electrode tab is less than the sum of the thicknesses of the two first adhesive layers.

11. The battery cell as described in claim 8, characterized in that, At least one of the following conditions must be met: 1) The second connecting layer accounts for 30%-44% of the thickness of the second insulating adhesive; 2) The second base layer accounts for 6%-20% of the thickness of the second insulating adhesive; 3) The second insulating adhesive includes a second adhesive layer, which connects the second base layer and the second connecting layer, and the thickness of the second adhesive layer is 1% to 4% of the thickness of the second insulating adhesive.

12. The battery cell as described in claim 1, characterized in that, The first connection layer must satisfy at least one of the following conditions: 1) The number-average molecular weight Mn of the first connecting layer is 10000 g / mol - 130000 g / mol; 2) The weight-average molecular weight Mw of the first connecting layer is 100,000 g / mol - 800,000 g / mol; 3) Mw / Mn: 3-10.

13. The battery cell as described in claim 1, characterized in that, At least one of the following conditions must be met: a) At 25°C, the tensile force between the first insulating adhesive and the battery cell housing and / or the negative electrode tab is in the range of 5 N / mm to 10 N / mm. At 95°C, the tensile force between the first insulating adhesive and the battery cell housing and / or the negative electrode tab ranges from 0.2 N / mm to 2 N / mm. At 120°C, the tensile force between the first insulating adhesive and the cell housing and / or the negative electrode tab ranges from 0.01 N / mm to 0.2 N / mm.

14. An electrical appliance, characterized in that, Includes the battery cell as described in any one of claims 1 to 13.

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