Cylindrical battery cell and electric equipment

Abstract

The invention provides a cylindrical battery cell and electric equipment. The cylindrical battery cell comprises an electrode assembly with a winding structure, and the electrode assembly is provided with a center hole. The center needle is arranged in the center hole, the center needle is of a tubular structure, the center needle comprises a first part and a second part in the axial direction of the center needle, the first part and the second part both comprise base materials, the first part further comprises heat conduction materials embedded in the base materials, and the heat conductivity of the first part is larger than that of the second part. Heat, close to the first part, of the electrode assembly can be conducted to the second part more quickly, so that heat distribution in the electrode assembly in the winding axis direction is more uniform, and the problems that internal heat of the electrode assembly is accumulated in the position close to the first part, and short circuit is caused by sinking in the electrode assembly can be solved; therefore, the risk of thermal runaway of the cylindrical battery cell can be reduced, and the safety of the cylindrical battery cell is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a cylindrical battery cell and an electrical device thereof. Background Technology

[0002] Currently, with the rapid development of new energy technologies, battery cells have been widely used in electronic devices, electric vehicles, electric two-wheelers, power tools, and other fields. As the application of battery cells becomes more widespread, higher requirements are being placed on their safety. Summary of the Invention

[0003] This application provides a cylindrical battery cell and an electrical device that can improve the safety of the cylindrical battery cell.

[0004] In a first aspect, this application provides a cylindrical battery cell, which includes an electrode assembly with a wound structure and a central hole. A central pin is disposed within the central hole and has a tubular structure. Along the axial direction of the central pin, the central pin includes a first part and a second part, both of which include a base material. The first part further includes a thermally conductive material embedded in the base material, and the thermal conductivity of the first part is greater than that of the second part.

[0005] In the above technical solution, by making both the first part and the second part include a matrix material, and the first part also includes a thermally conductive material embedded in the matrix material, the thermal conductivity of the first part is greater than that of the second part, so that the thermal conductivity of the first part is better, and the heat of the electrode assembly near the first part can be conducted to the second part more quickly. This makes the heat distribution inside the electrode assembly along the winding axis more uniform, which can reduce the problem of heat accumulation inside the electrode assembly near the first part and the problem of short circuit caused by indentation inside the electrode assembly. This can reduce the risk of thermal runaway of cylindrical cells and improve the safety of cylindrical cells.

[0006] In some embodiments of this application, the thermal conductivity of the first part is P1, the thermal conductivity of the second part is P2, and 3≤P1 / P2≤15.

[0007] In the above technical solution, when P1 / P2 is greater than or equal to 3, P1 is not too small, resulting in better thermal conductivity in the first part. This allows for faster heat transfer from the electrode assembly near the first part to the second part, leading to a more uniform heat distribution along the winding axis within the electrode assembly. This reduces the accumulation of internal heat near the first part and the risk of short circuits caused by indentation within the electrode assembly, thus mitigating the risk of thermal runaway in cylindrical cells and improving their safety. Since embedding thermally conductive material in the matrix material affects the support force of the center pin, when P1 / P2 is less than or equal to 15, the difference in thermal conductivity between the first and second parts is not too large. This reduces stress concentration at the interface caused by the large difference in expansion when heated, reducing the risk of center pin cracking. Simultaneously, since embedding thermally conductive material in the matrix material reduces the strength of the first part, when P1 / P2 is less than or equal to 15... When P2 is less than or equal to 15, the strength of the first part is not too small, which reduces the risk of misalignment of the electrode plates in the winding axis direction due to insufficient support force of the center pin on the electrode assembly, thus improving the safety of the cylindrical cell. Therefore, when 3≤P1 / P2≤15, it can reduce the risk of thermal runaway of the cylindrical cell, improve the safety of the cylindrical cell, reduce the risk of cracking of the center pin, and reduce the risk of misalignment of the electrode plates in the winding axis direction due to insufficient support force of the center pin on the electrode assembly, thus improving the safety of the cylindrical cell.

[0008] In some embodiments of this application, 4≤P1 / P2≤10.

[0009] In the above technical solution, when P1 / P2 is greater than or equal to 4, P1 is not too small, the heat conduction effect of the first part is better, and the heat of the electrode assembly near the first part can be conducted to the second part more quickly. This makes the heat distribution inside the electrode assembly along the winding axis more uniform, which can further reduce the problem of heat accumulation inside the electrode assembly near the first part and the problem of short circuit caused by indentation inside the electrode assembly. This can reduce the risk of thermal runaway of the cylindrical cell and further improve the safety of the cylindrical cell. Since the thermally conductive material embedded in the matrix material will affect the support force of the center pin, when P1 / When P2 is less than or equal to 10, the difference in thermal conductivity between the first and second parts is not too large, reducing the problem of interface stress concentration caused by the large difference in expansion when the first and second parts are heated, and further reducing the risk of center pin cracking. At the same time, since the thermally conductive material embedded in the matrix material reduces the strength of the first part, when P1 / P2 is less than or equal to 10, the strength of the first part is not too small, which can reduce the risk of the electrode assembly's electrode plates being misaligned in the winding axis direction due to insufficient support force from the center pin, and further improve the safety of the cylindrical cell. Therefore, when 4≤P1 / P2≤10, the risk of thermal runaway of the cylindrical cell can be further reduced, improving the safety of the cylindrical cell, and the risk of center pin cracking can also be further reduced. At the same time, the risk of the electrode assembly's electrode plates being misaligned in the winding axis direction due to insufficient support force from the center pin can also be reduced, further improving the safety of the cylindrical cell.

[0010] In some embodiments of this application, the thermal conductivity of the first part is P1, 0.7W / m·K≤P1≤4.5W / m·K.

[0011] In the above technical solution, when P1 is greater than or equal to 0.7 W / m·K, ensuring that P1 is not too small, the heat conduction effect of the first part is better, and the heat of the electrode assembly near the first part can be conducted to the second part more quickly. This makes the heat distribution inside the electrode assembly along the winding axis more uniform, reducing the accumulation of internal heat near the first part and the problem of short circuits caused by indentation inside the electrode assembly. This reduces the risk of thermal runaway in cylindrical cells and improves the safety of cylindrical cells. When P1 is less than or equal to 4.5 W / m·K... The value of K ensures that P1 is not too large, and the strength of the first part is not too small. This reduces the risk of misalignment of the electrode plates in the winding axis direction due to insufficient support force from the center to the electrode assembly, thus improving the safety of the cylindrical cell. Therefore, when 0.7W / m·K≤P1≤4.5W / m·K, it can both reduce the risk of thermal runaway of the cylindrical cell and improve its safety, and also reduce the risk of misalignment of the electrode plates in the winding axis direction due to insufficient support force from the center to the electrode assembly, thus improving the safety of the cylindrical cell.

[0012] In some embodiments of this application, the thermal conductivity of the second part is P2, 0.1 W / m·K ≤ P2 ≤ 0.3 W / m·K.

[0013] In the above technical solution, when P2 is greater than or equal to 0.1 W / m·K, ensuring that P2 is not too small, the second part can also play a role in conducting heat, reducing the accumulation of internal heat near the second part of the electrode assembly and the problem of short circuits caused by indentation inside the electrode assembly. This reduces the risk of thermal runaway in cylindrical cells and improves their safety. When P2 is less than or equal to 0.3 W / m·K, ensuring that P2 is not too small, the second part has greater strength, providing better support for the electrode assembly from the center, reducing the risk of indentation of the inner ring of the electrode assembly, and thus improving the safety and cycle life of cylindrical cells. Therefore, when 0.1 W / m·K ≤ P2 ≤ 0.3 W / m·K, it can both reduce the accumulation of internal heat near the second part of the electrode assembly and the problem of short circuits caused by indentation inside the electrode assembly, thereby reducing the risk of thermal runaway in cylindrical cells and improving their safety, and also reduce the risk of indentation of the inner ring of the electrode assembly, thus improving the safety and cycle life of cylindrical cells.

[0014] In some embodiments of this application, along the axial direction of the center needle, the height of the center needle is H0, the height of the first part is H1, and 10%≤H1 / H0≤70%.

[0015] In the above technical solution, when H1 / H0 is greater than or equal to 10%, ensuring that H1 is not too small, the first part can conduct heat further, resulting in a more uniform heat distribution within the electrode assembly along the winding axis. This reduces the accumulation of internal heat near the first part and the problem of short circuits caused by indentation within the electrode assembly, thereby reducing the risk of thermal runaway in cylindrical cells and improving their safety. And / or, when H0 is not too small, the central support area for the electrode assembly is larger, resulting in a higher support effect and reducing the risk of thermal runaway in the cylindrical cell. The risk of indentation of the inner ring of the electrode assembly is reduced, which helps improve the safety and cycle life of the cylindrical cell. When H1 / H0 is less than or equal to 70%, H1 is not too large, and the overall strength of the center pin is not too small, which reduces the risk of indentation of the inner ring of the electrode assembly, thus improving the safety and cycle life of the cylindrical cell. And / or, H0 is not too large, which reduces the risk of the center pin detaching from the center hole, thus improving the safety of the cylindrical cell. Therefore, when 10%≤H1 / H0≤70%, the cylindrical cell has high safety and cycle life.

[0016] In some embodiments of this application, 20% ≤ H1 / H0 ≤ 50%.

[0017] In the above technical solution, when H1 / H0 is greater than or equal to 20%, ensuring that H1 is not too small, the first part can conduct heat further, making the heat distribution inside the electrode assembly along the winding axis more uniform. This further reduces the problem of heat accumulation near the first part inside the electrode assembly and the problem of short circuits caused by indentation inside the electrode assembly, thereby further reducing the risk of thermal runaway in cylindrical cells and further improving the safety of cylindrical cells; and / or, when H0 is not too small, the central support area for the electrode assembly is larger, the support effect is higher, and the heat distribution inside the electrode assembly is further reduced. The risk of indentation of the inner ring of the component is reduced, which helps to further improve the safety and cycle life of the cylindrical cell. When H1 / H0 is less than or equal to 50%, H1 is not too large, and the overall strength of the center pin is not too small, which can further reduce the risk of indentation of the inner ring of the electrode component, thus improving the safety and cycle life of the cylindrical cell. And / or, it ensures that H0 is not too large, which reduces the risk of the center pin detaching from the center hole, further improving the safety of the cylindrical cell. Therefore, when 20%≤H1 / H0≤50%, the cylindrical cell has high safety and cycle life.

[0018] In some embodiments of this application, along the axial direction of the center needle, the height of the center needle is H0, the height of the second part is H2, and 30%≤H2 / H0≤90%.

[0019] In the above technical solutions, when H2 / H0 is greater than or equal to 30%, H2 is not too small, and the overall strength of the center pin is not too small, which reduces the risk of indentation of the inner ring of the electrode assembly, thus improving the safety and cycle life of the cylindrical cell; and / or, when H0 is not too small, the center pin has a larger support area for the electrode assembly, resulting in a higher support effect, further reducing the risk of indentation of the inner ring of the electrode assembly, thus further improving the safety and cycle life of the cylindrical cell; when H2 / H0 is less than or equal to 90%, H2 is not too large, and the heat transfer of the center pin... The better conduction effect makes the heat distribution inside the electrode assembly more uniform along the winding axis, which can further reduce the problem of heat accumulation near the first part and short circuit caused by indentation inside the electrode assembly, thereby further reducing the risk of thermal runaway of the cylindrical cell and further improving the safety of the cylindrical cell; and / or, it prevents H0 from being too large, which can reduce the risk of the center pin detaching from the center hole and further improve the safety of the cylindrical cell; therefore, when 30%≤H2 / H0≤90%, the cylindrical cell has high safety and cycle life.

[0020] In some embodiments of this application, the electrode assembly includes a main body, a positive electrode tab, and a negative electrode tab, which are respectively disposed at both ends of the main body along the winding axis of the electrode assembly. Along the winding axis, the first portion is closer to the positive electrode tab than the second portion.

[0021] In the above technical solution, since the positive electrode tab generates more heat than the negative electrode tab, by making the first part closer to the positive electrode tab than the second part along the winding axis, the heat generated at the positive electrode tab can be conducted to the second part more quickly through the first part. This makes the heat distribution inside the electrode assembly along the winding axis more uniform, which can reduce the accumulation of internal heat near the positive electrode tab and the problem of short circuit caused by indentation inside the electrode assembly. This can reduce the risk of thermal runaway of cylindrical cells and improve the safety of cylindrical cells.

[0022] In some embodiments of this application, the electrode assembly includes a negative electrode sheet, which includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector along its thickness direction. The negative active material layer includes a negative active material, which is a silicon-based material. Based on the total mass of the negative active material layer, the mass content percentage of silicon element in the silicon-based material is Csi. The cross-sectional area of ​​the central hole is S1, and the cross-sectional area of ​​the central pin is S2, where q×Csi≤S2 / S1≤0.98, and 0.1≤q≤1.0. The cross-section is perpendicular to the winding axis of the electrode assembly.

[0023] In the above technical solution, when S2 / S1 is greater than or equal to q×Csi, the volume ratio of the central pin inside the central hole is not too small, reducing the risk that the central pin's supporting role is too delayed (for example, the electrode assembly is sunken in a certain distance before the central pin can play a supporting role). This reduces the risk of the inner ring of the electrode assembly sinking, which is beneficial to improving the safety and cycle life of the cylindrical cell. When S2 / S1 is less than or equal to 0.98, the risk that the stress of the electrode assembly cannot be released due to excessive compression of the electrode assembly by the central pin is reduced, resulting in better wetting effect of the electrolyte between the electrode plates of the electrode assembly and better cycle performance of the cylindrical cell. Therefore, when q×Csi≤S2 / S1≤0.98, it can not only reduce the risk of the inner ring of the electrode assembly sinking, which is beneficial to improving the safety and cycle life of the cylindrical cell, but also make the wetting effect of the electrolyte between the electrode plates of the electrode assembly better, resulting in better cycle performance of the cylindrical cell.

[0024] In some embodiments of this application, 0.4 ≤ S2 / S1 ≤ 0.7.

[0025] In the above technical solution, when S2 / S1 is greater than or equal to 0.4, the volume ratio of the central pin inside the central hole is not too small, reducing the risk that the central pin's supporting role is too delayed (for example, the electrode assembly is recessed by a certain distance before the central pin can play a supporting role). This further reduces the risk of the inner ring of the electrode assembly being recessed, which is beneficial to further improving the safety and cycle life of the cylindrical cell. When S2 / S1 is less than or equal to 0.7, the risk that the stress of the electrode assembly cannot be released due to excessive compression of the electrode assembly by the central pin is reduced, which further improves the wetting effect of the electrolyte between the electrode plates of the electrode assembly and the cycle performance of the cylindrical cell. Therefore, when 0.4≤S2 / S1≤0.7, it can further reduce the risk of the inner ring of the electrode assembly being recessed, which is beneficial to further improving the safety and cycle life of the cylindrical cell, and can also further improve the wetting effect of the electrolyte between the electrode plates of the electrode assembly and the cycle performance of the cylindrical cell.

[0026] In some embodiments of this application, 1% ≤ Csi ≤ 40%.

[0027] In the above technical solution, when Csi is greater than or equal to 1%, Csi is not too small, resulting in a higher specific capacity of the negative electrode sheet, which is beneficial to improving the energy density of the cylindrical cell. When Csi is less than or equal to 40%, Csi is not too large, and the deformation of the negative electrode sheet during the cyclic charging and discharging of the cylindrical cell is not too large, which can slow down the pulverization and delamination process of the negative electrode sheet and slow down the capacity decay of the cylindrical cell. Therefore, when 1%≤Csi≤40%, the specific capacity of the negative electrode sheet is higher, which is beneficial to improving the energy density of the cylindrical cell, and the pulverization and delamination process of the negative electrode sheet is also slowed down, which slows down the capacity decay of the cylindrical cell.

[0028] In some embodiments of this application, 5% ≤ Csi ≤ 20%.

[0029] In the above technical solution, when Csi is greater than or equal to 5%, Csi is not too small, resulting in a higher specific capacity of the negative electrode sheet, which is beneficial to further improving the energy density of the cylindrical cell. When Csi is less than or equal to 20%, Csi is not too large, and the deformation of the negative electrode sheet during the cyclic charging and discharging of the cylindrical cell is not too large, which can further slow down the pulverization and delamination process of the negative electrode sheet, and further slow down the capacity decay of the cylindrical cell. Therefore, when 5%≤Csi≤20%, it can not only further increase the specific capacity of the negative electrode sheet, which is beneficial to further improving the energy density of the cylindrical cell, but also further slow down the pulverization and delamination process of the negative electrode sheet, and further slow down the capacity decay of the cylindrical cell.

[0030] In some embodiments of this application, the compressive strength of the center pin is F, where 200N≤F≤1800N.

[0031] In the above technical solution, when F is greater than or equal to 200N, it prevents F from being too small, reducing the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell. Since the center pin generally improves its pressure resistance by increasing its wall thickness, when F is less than or equal to 1800N, it prevents F from being too large, allowing the inner hole of the center pin to have a larger space to accommodate gas, reducing the risk of premature opening of the pressure relief valve and causing cylindrical cell failure during thermal runaway. Therefore, when 200N≤F≤1800N, it can both reduce the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell, and allow the inner hole of the center pin to have a larger space to accommodate gas, reducing the risk of premature opening of the pressure relief valve and causing cylindrical cell failure during thermal runaway.

[0032] In some embodiments of this application, 500N≤F≤1000N.

[0033] In the above technical solution, when F is greater than or equal to 500N, it prevents F from being too small, further reducing the risk of indentation of the inner ring of the electrode assembly, which is beneficial to further improving the safety and cycle life of the cylindrical cell. Since the center pin generally improves its pressure resistance by increasing its wall thickness, when F is less than or equal to 1000N, it prevents F from being too large, allowing the inner hole of the center pin to have a larger space to accommodate gas, further reducing the risk of premature opening of the pressure relief valve and causing cylindrical cell failure during thermal runaway. Therefore, when 500N≤F≤1000N, it can not only further reduce the risk of indentation of the inner ring of the electrode assembly, which is beneficial to further improving the safety and cycle life of the cylindrical cell, but also allow the inner hole of the center pin to have a larger space to accommodate gas, further reducing the risk of premature opening of the pressure relief valve and causing cylindrical cell failure during thermal runaway.

[0034] In some embodiments of this application, the thermally conductive material includes a plurality of first thermally conductive particles and a plurality of second thermally conductive particles. The plurality of first thermally conductive particles are arranged at intervals along the circumference of the central needle, and the plurality of second thermally conductive particles are arranged at intervals along the circumference of the central needle. The first thermally conductive particles and the second thermally conductive particles are arranged alternately at intervals along the axial direction of the central needle.

[0035] In the above technical solution, by arranging multiple first heat-conducting particles at intervals along the circumference of the center needle, multiple second heat-conducting particles at intervals along the circumference of the center needle, and alternatingly arranging the first and second heat-conducting particles along the axial direction of the center needle, the distribution of the first and second heat-conducting particles in the first part can be more uniform, the overall thermal conductivity of the first part is better, and the heat of the electrode assembly near the first part can be conducted to the second part more quickly. This makes the heat distribution inside the electrode assembly along the winding axis more uniform, which can further reduce the problem of heat accumulation inside the electrode assembly near the first part and the problem of short circuit caused by indentation inside the electrode assembly. This can further reduce the risk of thermal runaway of the cylindrical battery cell and further improve the safety of the cylindrical battery cell.

[0036] In some embodiments of this application, the matrix material includes polypropylene and / or polyvinyl chloride; and / or, the first thermally conductive particle includes at least one of aluminum oxide, silicon carbide, and silicon nitride; and / or, the second thermally conductive particle includes at least one of boron nitride, beryllium oxide, and diamond.

[0037] In the above technical solution, by including polypropylene and / or polyvinyl chloride as the matrix material, the strength of the matrix material can be increased, the support effect of the center on the electrode assembly can be better, the risk of inward sinking of the inner ring of the electrode assembly can be reduced, and the safety and cycle life of the cylindrical cell can be improved.

[0038] By making the first thermally conductive particle include at least one of aluminum oxide, silicon carbide, and silicon nitride; and / or, the second thermally conductive particle includes at least one of boron nitride, beryllium oxide, and diamond, the thermal conductivity of the first and / or second thermally conductive particles can be improved, enabling faster conduction of heat from the electrode assembly near the first part to the second part. This results in a more uniform heat distribution within the electrode assembly along the winding axis, reducing the accumulation of internal heat near the first part and the problem of short circuits caused by indentation within the electrode assembly. Consequently, the risk of thermal runaway in cylindrical cells can be reduced, and the safety of cylindrical cells can be improved.

[0039] In some embodiments of this application, the volume percentage of the first thermally conductive particles in the first part is 40%-70%.

[0040] In the above technical solution, when the volume ratio of the first heat-conducting particles in the first part is greater than or equal to 40%, ensuring that the volume ratio of the first heat-conducting particles in the first part is not too small, the heat conduction effect of the first part is better, and it can more quickly conduct the heat of the electrode assembly near the first part to the second part, making the heat distribution inside the electrode assembly along the winding axis more uniform. This can reduce the accumulation of internal heat of the electrode assembly near the first part and the problem of short circuits caused by indentation inside the electrode assembly, thereby reducing the risk of thermal runaway of the cylindrical battery cell and improving the safety of the cylindrical battery cell; when the first part... The volume percentage of the thermally conductive particles is less than or equal to 70%, ensuring that the volume percentage of the first thermally conductive particles in the first part is not too large, the support strength of the first part is not too small, and the overall support strength of the center pin is relatively large. This reduces the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell. Therefore, when the volume percentage of the first thermally conductive particles in the first part is 40%-70%, it can reduce the risk of thermal runaway of the cylindrical cell, improve the safety of the cylindrical cell, and reduce the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell.

[0041] In some embodiments of this application, the volume percentage of the second heat-conducting particles in the first part is 5%-30%.

[0042] In the above technical solution, when the volume percentage of the second heat-conducting particles in the first part is greater than or equal to 5%, ensuring that the volume percentage of the second heat-conducting particles in the first part is not too small, the heat conduction effect of the first part is better, enabling faster transfer of heat from the electrode assembly near the first part to the second part. This results in a more uniform heat distribution within the electrode assembly along the winding axis, reducing the accumulation of internal heat near the first part and the problem of short circuits caused by indentation within the electrode assembly. This reduces the risk of thermal runaway in cylindrical cells and improves their safety. When the volume percentage of the second heat-conducting particles in the first part is greater than or equal to 5%, the heat conduction effect of the first part is better, allowing for faster transfer of heat from the electrode assembly near the first part to the second part. This results in a more uniform heat distribution within the electrode assembly along the winding axis, reducing the accumulation of internal heat near the first part and the problem of short circuits caused by indentation within the electrode assembly. This reduces the risk of thermal runaway in cylindrical cells and improves their safety. The volume percentage of the thermally conductive particles is less than or equal to 30%, ensuring that the volume percentage of the second thermally conductive particles in the first part is not too large, the support strength of the first part is not too small, and the overall support strength of the center pin is relatively large. This reduces the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell. Therefore, when the volume percentage of the second thermally conductive particles in the first part is 5%-30%, it can reduce the risk of thermal runaway of the cylindrical cell, improve the safety of the cylindrical cell, and reduce the risk of indentation of the inner ring of the electrode assembly, which is beneficial to improving the safety and cycle life of the cylindrical cell.

[0043] In some embodiments of this application, the electrode assembly includes a negative electrode sheet, which includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector along its thickness direction. The negative active material layer includes a silicon-based material, and the coefficient of thermal expansion of the negative electrode sheet is k, where 0.1 ≤ k ≤ 1.0.

[0044] In the above technical solution, since the expansion coefficient of the negative electrode sheet is positively correlated with the mass content percentage of silicon (Csi) in the negative electrode active material, when k is greater than or equal to 0.1, k is not too small, resulting in a higher specific capacity of the negative electrode sheet, which is beneficial to improving the energy density of the cylindrical cell. When k is less than or equal to 1, k is not too large, and the deformation of the negative electrode sheet during the cyclic charging and discharging of the cylindrical cell is not too large, which can slow down the pulverization and delamination process of the negative electrode sheet and slow down the capacity decay of the cylindrical cell. Therefore, when 0.1≤k≤1.0, it can not only result in a higher specific capacity of the negative electrode sheet, which is beneficial to improving the energy density of the cylindrical cell, but also slow down the pulverization and delamination process of the negative electrode sheet and slow down the capacity decay of the cylindrical cell.

[0045] Secondly, this application provides an electrical device including a cylindrical battery cell as described above, the cylindrical battery cell being used to provide electrical energy. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings.

[0047] Figure 1 Cross-sectional views of cylindrical battery cells provided in some embodiments of this application; Figure 2 A schematic diagram of the structure of a cylindrical battery cell from one perspective, provided in some embodiments of this application; Figure 3 A cross-sectional view of the center pin of a cylindrical battery cell provided in some embodiments of this application; Figure 4 A schematic diagram of the structure of the center pin of a cylindrical battery cell provided in some embodiments of this application; Figure 5 for Figure 4 A cross-sectional view of the center pin of the cylindrical battery cell along the AA direction; Figure 6 for Figure 4 A cross-sectional view of the center pin of a cylindrical battery cell along the BB direction; Figure 7 for Figure 1A partially enlarged structural diagram of point C in a cylindrical battery cell; Figure 8 A schematic diagram of the negative electrode sheet of a cylindrical battery cell provided in some embodiments of this application; Figure 9 Scanning images of the electrode assembly of a cylindrical battery cell after 600 charge-discharge cycles, as provided in some embodiments of this application.

[0048] Icons: 10-Cylindrical cell; 100-Electrode assembly; 100a-Main body; 101-Center hole; 110-Positive electrode; 120-Negative electrode; 121-Negative current collector; 122-Negative active material layer; 130-Separator; 140-Positive electrode tab; 150-Negative electrode tab; 200-Shell; 210-Electrode post; 300-Center pin; 301-Base material; 302-Thermal conductive material; 3021-First thermally conductive particle; 3022-Second thermally conductive particle; 310-First part; 320-Second part; 410-First current collector; 420-Second current collector; X-Axis of the center pin; Y-Thickness direction of the negative current collector; Z-Wrapping axis of the electrode assembly. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0050] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having" and any variations thereof in the specification, claims and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0051] The terms "first," "second," etc., in the specification, claims, or the accompanying drawings of this application are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0052] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0053] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0054] With the development of the new energy industry, batteries are gradually moving towards higher safety and longer cycle life. During the manufacturing of cylindrical cells, the electrode assembly is wound into shape using a winding needle, and then the needle is pulled out, creating a central hole in the electrode assembly. During the charge-discharge cycle of the cylindrical cell, the electrode assembly expands, compressing the outer casing. Conversely, the electrode assembly receives a reaction force from the casing, causing the inner ring of the electrode assembly to form and potentially sink in, affecting the safety and cycle life of the cylindrical cell. By setting a central pin in the central hole, the central pin can support the electrode assembly, reducing the possibility of sinking. To reduce the risk of short circuits through the central pin, the central pin is generally made of insulating material, resulting in low thermal conductivity. Since a significant amount of heat is generated inside the cylindrical cell, if excessive heat is generated in a certain area and cannot be conducted through the central pin, it can cause localized overheating inside the cylindrical cell, posing a risk of thermal runaway and affecting its safety.

[0055] To improve the safety of cylindrical battery cells, this application provides a cylindrical battery cell including an electrode assembly with a wound structure and a central hole. A central pin is disposed within the central hole and has a tubular structure. Along the axial direction of the central pin, the central pin includes a first part and a second part, both of which include a base material. The first part also includes a thermally conductive material embedded in the base material, and the thermal conductivity of the first part is greater than that of the second part.

[0056] In this cylindrical cell structure, by making both the first and second parts include a matrix material, and the first part also includes a thermally conductive material embedded in the matrix material, the thermal conductivity of the first part is greater than that of the second part, resulting in better thermal conductivity of the first part. This allows the heat from the electrode assembly near the first part to be conducted to the second part more quickly, making the heat distribution inside the electrode assembly along the winding axis more uniform. This reduces the accumulation of internal heat near the first part and the problem of short circuits caused by indentation inside the electrode assembly, thereby reducing the risk of thermal runaway in the cylindrical cell and improving its safety.

[0057] The cylindrical battery cell provided in this application embodiment can be a secondary battery, such as a lithium-ion battery, sodium-ion battery, or magnesium-ion battery, etc., and this application embodiment is not limited in this respect. The electrochemical device can be cylindrical, flat, cuboid, hexagonal, or other shapes, etc., and this application embodiment is not limited in this respect either.

[0058] This application provides an electrical device that uses cylindrical battery cells as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0059] See Figure 1 and Figure 2 , Figure 1 Cross-sectional views of cylindrical battery cells provided in some embodiments of this application; Figure 2 This is a schematic diagram of the structure of a cylindrical battery cell provided in some embodiments of this application from one perspective.

[0060] This application provides a cylindrical battery cell 10, which includes an electrode assembly 100 with a wound structure. The electrode assembly 100 includes a positive electrode 110, a negative electrode 120, and a separator 130. The separator 130 is disposed between the positive electrode 110 and the negative electrode 120 to insulate and separate the positive electrode 110 and the negative electrode 120, thereby reducing the risk of short circuit in the cylindrical battery cell 10. The cylindrical battery cell 10 has advantages such as high energy density, good stability, long service life, and high charging rate.

[0061] The cylindrical cell 10 also includes a housing 200 and an electrolyte (not shown in the figure), with the electrode assembly 100 and electrolyte housed within the housing 200. The cylindrical cell 10 primarily operates by the movement of metal ions between the positive electrode 110 and the negative electrode 120. The positive electrode 110 includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, and the portion of the positive current collector without the positive active material layer serves as a positive electrode tab 140, through which electrical energy can be input or output from the positive electrode 110. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary materials (such as lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.), or lithium manganese oxide, etc. The negative electrode 120 includes a negative current collector 121 and a negative active material layer 122. The negative active material layer 122 is coated on the surface of the negative current collector 121. The portion of the negative current collector 121 without the negative active material layer 122 serves as a negative electrode tab 150, through which electrical energy can be input or output from the negative electrode 120. The material of the negative current collector 121 can be copper, and the negative active material can be carbon or silicon, etc. The separator 130 can be made of polypropylene (PP) or polyethylene (PE), etc. The electrolyte can include organic solvents, lithium salts, etc.

[0062] In some embodiments, the cylindrical cell 10 further includes a center pin 300, and the electrode assembly 100 has a center hole 101, with the center pin 300 disposed within the center hole 101.

[0063] By setting the center pin 300, when the electrode assembly 100 expands, the center pin 300 can support the inner ring of the electrode assembly 100, reducing the possibility of the electrode assembly 100 sinking inward, which in turn helps to improve the safety and cycle life of the cylindrical cell 10.

[0064] The center pin 300 can be made of high-strength materials, such as titanium alloys, stainless steel, or ceramic matrix composites such as zirconia ceramics and silicon nitride ceramics, or metal matrix composites such as aluminum-based silicon carbide and titanium-based composites. This can make the center pin 300 have higher support strength, reduce the risk of the inner ring of the electrode assembly 100 sinking, and improve the safety and cycle life of the cylindrical cell 10.

[0065] See Figures 3 to 6 , Figure 3 A cross-sectional view of the center pin of a cylindrical battery cell provided in some embodiments of this application; Figure 4 A schematic diagram of the structure of the center pin of a cylindrical battery cell provided in some embodiments of this application; Figure 5 for Figure 4 A cross-sectional view of the center pin of the cylindrical battery cell along the AA direction; Figure 6 for Figure 4 A cross-sectional view of the center pin of a cylindrical battery cell along the BB direction.

[0066] In some embodiments, the center needle 300 is a tubular structure. Along the axial direction X of the center needle, the center needle 300 includes a first part 310 and a second part 320. Both the first part 310 and the second part 320 include a base material 301. The first part 310 also includes a thermally conductive material 302 embedded in the base material 301. The thermal conductivity of the first part 310 is greater than that of the second part 320.

[0067] By including a base material 301 in both the first part 310 and the second part 320, and the first part 310 further including a thermally conductive material 302 embedded in the base material 301, the thermal conductivity of the first part 310 is greater than that of the second part 320. This results in better thermal conductivity of the first part 310, enabling faster conduction of heat from the electrode assembly 100 near the first part 310 to the second part 320. This also makes the heat distribution inside the electrode assembly 100 more uniform along the winding axis, reducing the accumulation of heat inside the electrode assembly 100 near the first part 310 and the problem of short circuits caused by indentation inside the electrode assembly 100. This reduces the risk of thermal runaway of the cylindrical cell 10 and improves the safety of the cylindrical cell 10.

[0068] The thermal conductivity of the center pin 300 can be tested using the laser flash method. The testing equipment and model are Linseis LFA 1000, manufactured by Linseis Germany. For details, please refer to the national standard GB / T 22588-2008.

[0069] In some embodiments, the thermal conductivity of the first portion 310 is P1, and the thermal conductivity of the second portion 320 is P2, where 3 ≤ P1 / P2 ≤ 15. For example, P1 / P2 can be 3, 5, 7, 9, 10, 11, 13, or 15, etc.

[0070] When P1 / P2 is greater than or equal to 3, P1 is prevented from being too small, resulting in better thermal conductivity in the first part 310. This allows for faster heat transfer from the electrode assembly 100 near the first part 310 to the second part 320, leading to a more uniform heat distribution along the winding axis within the electrode assembly 100. This reduces the accumulation of internal heat near the first part 310 and the risk of short circuits caused by indentation within the electrode assembly 100, thereby reducing the risk of thermal runaway in the cylindrical cell 10 and improving its safety. Since the thermally conductive material 302 embedded in the substrate material 301 affects the support force of the center pin 300, when P1 / When P2 is less than or equal to 15, the difference in thermal conductivity between the first part 310 and the second part 320 is not too large, reducing the problem of interface stress concentration caused by the large difference in the expansion of the first part 310 and the second part 320 when heated, and reducing the risk of cracking of the center pin 300. At the same time, since the thermally conductive material 302 embedded in the base material 301 reduces the strength of the first part 310, when P1 / P2 is less than or equal to 15, the strength of the first part 310 is also not too small, which can reduce the risk of the electrode assembly 100's electrode plates being misaligned in the winding axis direction due to insufficient support force of the center pin 300 on the electrode assembly 100, and improve the safety of the cylindrical cell 10; therefore, when 3≤P1 / P2≤15 can reduce the risk of thermal runaway of cylindrical cell 10 and improve the safety of cylindrical cell 10. It can also reduce the risk of cracking of center pin 300. At the same time, it can also reduce the risk of misalignment of electrode sheet of electrode assembly 100 in the winding axis direction due to insufficient support force of center pin 300 on electrode assembly 100, thus improving the safety of cylindrical cell 10.

[0071] In some embodiments, 4 ≤ P1 / P2 ≤ 10. For example, P1 / P2 can be 4, 5, 6, 7, 8, 9, or 10, etc.

[0072] When P1 / P2 is greater than or equal to 4, P1 is prevented from being too small, resulting in better thermal conductivity in the first part 310. This allows for faster heat transfer from the electrode assembly 100 near the first part 310 to the second part 320, leading to a more uniform heat distribution along the winding axis within the electrode assembly 100. This further reduces the accumulation of internal heat near the first part 310 and the risk of short circuits caused by indentation within the electrode assembly 100, thereby reducing the risk of thermal runaway in the cylindrical cell 10 and improving its safety. Since the thermally conductive material 302 embedded in the substrate material 301 affects the support force of the center pin 300, when P1 / When P2 is less than or equal to 10, the difference in thermal conductivity between the first part 310 and the second part 320 is not too large. This reduces the problem of interface stress concentration caused by the large difference in the expansion of the first part 310 and the second part 320 when heated, further reducing the risk of cracking of the center pin 300. Simultaneously, since the embedding of the thermally conductive material 302 into the base material 301 reduces the strength of the first part 310, when P1 / When P2 is less than or equal to 10, the strength of the first part 310 is not too small, which reduces the risk of the electrode plates of the electrode assembly 100 being misaligned in the winding axis direction due to insufficient support force of the center pin 300 on the electrode assembly 100, thus further improving the safety of the cylindrical cell 10. Therefore, when 4≤P1 / P2≤10, the risk of thermal runaway of the cylindrical cell 10 can be further reduced, improving the safety of the cylindrical cell 10. It can also further reduce the risk of cracking of the center pin 300, and at the same time reduce the risk of misalignment of the electrode plates of the electrode assembly 100 in the winding axis direction due to insufficient support force of the center pin 300 on the electrode assembly 100, thus further improving the safety of the cylindrical cell 10.

[0073] In some embodiments, the thermal conductivity of the first portion 310 is P1, where 0.7 W / m·K ≤ P1 ≤ 4.5 W / m·K. For example, P1 can be 0.7 W / m·K, 1 W / m·K, 2 W / m·K, 3 W / m·K, 4 W / m·K, or 4.5 W / m·K, etc.

[0074] When P1 is greater than or equal to 0.7 W / m·K, ensuring that P1 is not too small, the first part 310 has better thermal conductivity, enabling faster heat transfer from the electrode assembly 100 near the first part 310 to the second part 320. This results in a more uniform heat distribution within the electrode assembly 100 along the winding axis, reducing the accumulation of internal heat near the first part 310 and preventing short circuits caused by indentation within the electrode assembly 100. This reduces the risk of thermal runaway in the cylindrical cell 10 and improves its safety. When P1 is less than or equal to 4.5 W / m·K, ensuring that P1 is not too large, the strength of the first part 310 is not too weak. This reduces the risk of misalignment of the electrode plates in the winding axis due to insufficient support from the center pin 300, further improving the safety of the cylindrical cell 10. Therefore, when 0.7... W / m·K≤P1≤4.5W / m·K can reduce the risk of thermal runaway of the cylindrical cell 10 and improve the safety of the cylindrical cell 10. It can also reduce the risk of misalignment of the electrode plates of the electrode assembly 100 in the winding axis direction due to insufficient support force of the center pin 300 on the electrode assembly 100, thus improving the safety of the cylindrical cell 10.

[0075] In some embodiments, the thermal conductivity of the second portion 320 is P2, where 0.1 W / m·K ≤ P2 ≤ 0.3 W / m·K. For example, P2 can be 0.1 W / m·K, 0.15 W / m·K, 0.2 W / m·K, 0.25 W / m·K, or 0.3 W / m·K, etc.

[0076] When P2 is greater than or equal to 0.1 W / m·K, ensuring that P2 is not too small, the second part 320 can also play a role in heat conduction, reducing the accumulation of internal heat near the second part 320 of the electrode assembly 100 and the problem of short circuits caused by indentation inside the electrode assembly 100. This reduces the risk of thermal runaway of the cylindrical cell 10 and improves the safety of the cylindrical cell 10. When P2 is less than or equal to 0.3 W / m·K, ensuring that P2 is not too small, the second part 320 has greater strength, which allows the center pin 300 to provide better support for the electrode assembly 100, reducing the risk of thermal runaway of the cylindrical cell 100. The risk of indentation of the inner ring of the small electrode assembly 100 is reduced, which is beneficial to improving the safety and cycle life of the cylindrical cell 10. Therefore, when 0.1W / m·K≤P2≤0.3W / m·K, it can reduce the accumulation of internal heat of the electrode assembly 100 near the second part 320 and the problem of short circuit caused by indentation inside the electrode assembly 100, thereby reducing the risk of thermal runaway of the cylindrical cell 10 and improving the safety of the cylindrical cell 10. It can also reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10.

[0077] In some embodiments, along the axial direction X of the center needle, the height of the center needle 300 is H0, the height of the first portion 310 is H1, and 10% ≤ H1 / H0 ≤ 70%. For example, H1 / H0 can be 10%, 20%, 30%, 40%, 50%, 60%, or 70%, etc.

[0078] When H1 / H0 is greater than or equal to 10%, ensuring that H1 is not too small, the first part 310 can conduct heat further, resulting in a more uniform heat distribution along the winding axis inside the electrode assembly 100. This reduces the accumulation of internal heat near the first part 310 and the problem of short circuits caused by indentation within the electrode assembly 100, thereby reducing the risk of thermal runaway in the cylindrical cell 10 and improving its safety. And / or, if H0 is not too small, the center pin 300 provides a larger support area for the electrode assembly 100, resulting in a higher support effect and reducing the risk of thermal runaway in the electrode assembly 100. The risk of indentation of the inner ring of the electrode assembly 100 is reduced, which is beneficial to improving the safety and cycle life of the cylindrical cell 10; when H1 / H0 is less than or equal to 70%, H1 is not too large, and the overall strength of the center pin 300 is not too small, which can reduce the risk of indentation of the inner ring of the electrode assembly 100, thus improving the safety and cycle life of the cylindrical cell 10; and / or, H0 is not too large, which can reduce the risk of the center pin 300 detaching from the center hole 101, thus improving the safety of the cylindrical cell 10; therefore, when 10%≤H1 / H0≤70%, the cylindrical cell 10 has high safety and cycle life.

[0079] In some embodiments, 20% ≤ H1 / H0 ≤ 50%. For example, H1 / H0 can be 20%, 25%, 30%, 35%, 40%, 45%, or 50%, etc.

[0080] When H1 / H0 is greater than or equal to 20%, ensuring that H1 is not too small, the first part 310 can conduct heat further, resulting in a more uniform heat distribution within the electrode assembly 100 along the winding axis. This further reduces the accumulation of internal heat near the first part 310 and the problem of short circuits caused by indentation within the electrode assembly 100, thereby further reducing the risk of thermal runaway in the cylindrical cell 10 and improving its safety. And / or, if H0 is not too small, the center pin 300 provides a larger support area for the electrode assembly 100, resulting in a higher support effect and further reducing the risk of thermal runaway in the electrode assembly 100. The risk of indentation of the inner ring of the electrode assembly 100 is reduced, which helps to further improve the safety and cycle life of the cylindrical cell 10; when H1 / H0 is less than or equal to 50%, H1 is not too large, and the overall strength of the center pin 300 is not too small, which can further reduce the risk of indentation of the inner ring of the electrode assembly 100, which helps to improve the safety and cycle life of the cylindrical cell 10; and / or, H0 is not too large, which can reduce the risk of the center pin 300 detaching from the center hole 101, which further improves the safety of the cylindrical cell 10; therefore, when 20%≤H1 / H0≤50%, the cylindrical cell 10 has high safety and cycle life.

[0081] In some embodiments, along the axial direction X of the center needle, the height of the center needle 300 is H0, the height of the second portion 320 is H2, and 30% ≤ H2 / H0 ≤ 90%. For example, H2 / H0 can be 30%, 40%, 50%, 60%, 70%, 80%, or 90%, etc.

[0082] When H2 / H0 is greater than or equal to 30%, H2 is not too small, and the overall strength of the center pin 300 is not too small, reducing the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10; and / or, H0 is not too small, the center pin 300 has a larger support area for the electrode assembly 100, and the support effect is higher, further reducing the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to further improving the safety and cycle life of the cylindrical cell 10; when H2 / H0 is less than or equal to 90%, H2 is not too large, and the heat conduction effect of the center pin 300 is better, making... The heat distribution inside the electrode assembly 100 along the winding axis is more uniform, which can further reduce the accumulation of internal heat near the first part 310 and the problem of short circuit caused by indentation inside the electrode assembly 100. This can further reduce the risk of thermal runaway of the cylindrical cell 10 and further improve the safety of the cylindrical cell 10; and / or, so that H0 is not too large, which can reduce the risk of the center pin 300 detaching from the center hole 101 and further improve the safety of the cylindrical cell 10; therefore, when 30%≤H2 / H0≤90%, the cylindrical cell 10 has high safety and cycle life.

[0083] See Figure 1 and Figure 7 , Figure 7 for Figure 1 A magnified schematic diagram of a portion of the cylindrical battery cell at point C.

[0084] In some embodiments, the electrode assembly 100 includes a main body portion 100a, a positive electrode tab 140, and a negative electrode tab 150, which are respectively disposed at both ends of the main body portion 100a along the winding axis of the electrode assembly 100. Along the winding axis, the first portion 310 is closer to the positive electrode tab 140 than the second portion 320.

[0085] Since the positive electrode tab 140 generates more heat than the negative electrode tab 150, by making the first part 310 closer to the positive electrode tab 140 than the second part 320 along the winding axis, the heat generated at the positive electrode tab 140 can be conducted to the second part 320 more quickly through the first part 310. This makes the heat distribution inside the electrode assembly 100 along the winding axis more uniform, which can reduce the accumulation of heat inside the electrode assembly 100 near the positive electrode tab 140 and the problem of short circuits caused by indentation inside the electrode assembly 100. This can reduce the risk of thermal runaway of the cylindrical cell 10 and improve the safety of the cylindrical cell 10.

[0086] See Figure 1 , Figure 2 and Figure 8 , Figure 8 This is a schematic diagram of the negative electrode of a cylindrical battery cell provided in some embodiments of this application.

[0087] In some embodiments, the electrode assembly 100 includes a negative electrode sheet 120, which includes a negative current collector 121 and a negative active material layer 122. The negative active material layer 122 is disposed on at least one side of the negative current collector 121 along its thickness direction Y. The negative active material layer 122 includes a negative active material, which is a silicon-based material. Based on the total mass of the negative active material layer 122, the mass content percentage of silicon element in the silicon-based material is Csi. The cross-sectional area of ​​the central hole 101 is S1, and the cross-sectional area of ​​the central pin 300 is S2, where q×Csi≤S2 / S1≤0.98, and 0.1≤q≤1.0. The cross-section is perpendicular to the winding axis direction of the electrode assembly 100.

[0088] When S2 / S1 is greater than or equal to q×Csi, the volume ratio of the center pin 300 within the center hole 101 is not too small, reducing the risk that the center pin 300's supporting role is too delayed (e.g., the electrode assembly 100 is recessed a certain distance before the center pin 300 provides support). This reduces the risk of the inner ring of the electrode assembly 100 being recessed, which is beneficial to improving the safety and cycle life of the cylindrical cell 10. When S2 / S1 is less than or equal to 0.98, it reduces the risk of the center pin 300 excessively compressing the electrode assembly. The risk of stress not being released in the electrode assembly 100 caused by component 100 is reduced, resulting in better wetting of the electrolyte between the electrodes of the electrode assembly 100 and better cycle performance of the cylindrical cell 10. Therefore, when q×Csi≤S2 / S1≤0.98, it can reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10, and also make the wetting effect of the electrolyte between the electrodes of the electrode assembly 100 better, resulting in better cycle performance of the cylindrical cell 10.

[0089] The test method for the percentage of silicon content (Csi) in silicon-based materials based on the total mass of the negative electrode active material layer includes: (1) discharging the cylindrical cell 10 to the cutoff voltage of 2.5V using a 0.2C capacity, disassembling the cylindrical cell 10, and immersing the disassembled negative electrode 120 in dimethyl carbonate solvent for 10 minutes; (2) obtaining the silicon-based material in the negative electrode; (3) taking the silicon-based material and digesting it with aqua regia and hydrofluoric acid HF. Since the digestion time is positively correlated with the depth of silicon dissolution in silicon carbon particles, the solutions with different digestion times in this experiment were tested by gradient inductively coupled plasma spectrometry (ICP), and the silicon content in the completely digested solution was measured by inductively coupled plasma spectrometry (ICP-OES), corresponding to the silicon content of the silicon-based material; (4) calculating the percentage of silicon content (Csi) in silicon-based materials based on the total mass of the negative electrode active material layer by the content of silicon-based material in the silicon-based material.

[0090] In this application, the central hole 101 of the electrode assembly 100 may be an irregular circle. The central hole 101 is simplified to a circle for calculation.

[0091] The measurement method for S2 / S1 includes: charging the cylindrical cell 10 at a constant current of 2C to 4.2V at 25℃, then charging it at a constant voltage of 4.2V to 0.05C, letting it stand for 5 minutes, and then using industrial computed tomography (industrial CT, Zeiss Xradia 620) technology. Versa), along the radial direction of the electrode assembly, a CT scan is performed on the wound structure electrode assembly 100; the diameter of the central hole is measured 10 times at equal angles along the winding axis Z of the electrode assembly (i.e., the diameter measured for the first time is 0°, the second time is 36°, the third time is 72°, and so on, until the tenth measurement is 324°), and the average value is taken as the diameter D1 of the central hole 101; the outer diameter of the central pin 300 is measured 10 times at equal angles along the winding axis Z of the electrode assembly, and the average value is taken as the outer diameter D2 of the central pin 300; the inner diameter of the central pin 300 is measured 10 times at equal angles along the winding axis Z of the electrode assembly, and the average value is taken as the inner diameter D3 of the central pin 300; calculate S2 / S1 = (D2 2 - D3 2 ) / D1 2 .

[0092] In some embodiments, 0.4 ≤ S2 / S1 ≤ 0.7. For example, S2 / S1 can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, or 0.7, etc.

[0093] When S2 / S1 is greater than or equal to 0.4, the volume ratio of the center pin 300 within the center hole 101 is not too small, reducing the risk that the center pin 300's supporting role is too delayed (e.g., the electrode assembly 100 is recessed a certain distance before the center pin 300 provides support). This further reduces the risk of the inner ring of the electrode assembly 100 being recessed, which is beneficial for further improving the safety and cycle life of the cylindrical cell 10. When S2 / S1 is less than or equal to 0.7, it reduces the risk of the center pin 300 excessively compressing the electrode assembly 10. The risk of stress not being released in the electrode assembly 100 is reduced by 0, which further improves the wetting effect of the electrolyte between the electrodes of the electrode assembly 100 and the cycle performance of the cylindrical cell 10. Therefore, when 0.4≤S2 / S1≤0.7, the risk of indentation of the inner ring of the electrode assembly 100 can be further reduced, which is conducive to further improving the safety and cycle life of the cylindrical cell 10. It can also further improve the wetting effect of the electrolyte between the electrodes of the electrode assembly 100 and the cycle performance of the cylindrical cell 10.

[0094] In some embodiments, 1% ≤ Csi ≤ 40%. For example, Csi can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%, etc.

[0095] When Csi is greater than or equal to 1%, it prevents Csi from being too small, resulting in a higher specific capacity of the negative electrode 120, which is beneficial to improving the energy density of the cylindrical cell 10. When Csi is less than or equal to 40%, it prevents Csi from being too large, preventing the deformation of the negative electrode 120 during the cyclic charging and discharging of the cylindrical cell 10 from being too large, which can slow down the pulverization and delamination process of the negative electrode 120 and slow down the capacity decay of the cylindrical cell 10. Therefore, when 1%≤Csi≤40%, it can not only result in a higher specific capacity of the negative electrode 120, which is beneficial to improving the energy density of the cylindrical cell 10, but also slow down the pulverization and delamination process of the negative electrode 120 and slow down the capacity decay of the cylindrical cell 10.

[0096] In some embodiments, 5% ≤ Csi ≤ 20%. For example, Csi can be 5%, 7%, 9%, 10%, 12%, 25%, 18%, or 20%, etc.

[0097] When Csi is greater than or equal to 5%, it prevents Csi from being too small, resulting in a higher specific capacity of the negative electrode 120, which is beneficial for further improving the energy density of the cylindrical cell 10. When Csi is less than or equal to 20%, it prevents Csi from being too large, preventing the deformation of the negative electrode 120 during the cyclic charging and discharging of the cylindrical cell 10 from being too large, which can further slow down the pulverization and delamination process of the negative electrode 120, and further slow down the capacity decay of the cylindrical cell 10. Therefore, when 5%≤Csi≤20%, it can not only further improve the specific capacity of the negative electrode 120, which is beneficial for further improving the energy density of the cylindrical cell 10, but also further slow down the pulverization and delamination process of the negative electrode 120, and further slow down the capacity decay of the cylindrical cell 10.

[0098] In some embodiments, the compressive strength of the center pin 300 is F, where 200N≤F≤1800N. For example, F can be 200N, 300N, 500N, 800N, 1000N, 1200N, 1500N, or 1800N, etc.

[0099] When F is greater than or equal to 200N, it prevents F from being too small, reducing the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10. Since the center pin 300 generally improves its pressure resistance by increasing its wall thickness, when F is less than or equal to 1800N, it prevents F from being too large, allowing the inner hole of the center pin 300 to have a larger space to accommodate gas, reducing the risk of premature opening of the pressure relief valve and causing failure of the cylindrical cell 10 in the event of thermal runaway. Therefore, when 200N≤F≤1800N, it can both reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10, and allow the inner hole of the center pin 300 to have a larger space to accommodate gas, reducing the risk of premature opening of the pressure relief valve and causing failure of the cylindrical cell 10 in the event of thermal runaway.

[0100] The test method for the compressive strength F of the center pin 300 includes: applying vertical pressure (pressure perpendicular to the axial direction X of the center pin) to the center pin 300 using the New Sansi CMT universal testing machine, and recording the load value when the center pin 300 deforms by 0.2 mm. For details, please refer to the standard: GB / T 1041-2008 "Determination of Compressive Properties of Plastics" (Chinese National Standard).

[0101] In some embodiments, 500N ≤ F ≤ 1000N. For example, F can be 500N, 600N, 700N, 800N, 900N, or 1000N, etc.

[0102] When F is greater than or equal to 500N, it prevents F from being too small, further reducing the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to further improving the safety and cycle life of the cylindrical cell 10. Since the center pin 300 generally improves its pressure resistance by increasing its wall thickness, when F is less than or equal to 1000N, it prevents F from being too large, allowing the inner hole of the center pin 300 to have a larger space to accommodate gas, further reducing the risk of premature opening of the pressure relief valve and causing failure of the cylindrical cell 10 in the event of thermal runaway. Therefore, when 500N≤F≤1000N, it can both further reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to further improving the safety and cycle life of the cylindrical cell 10, and allow the inner hole of the center pin 300 to have a larger space to accommodate gas, further reducing the risk of premature opening of the pressure relief valve and causing failure of the cylindrical cell 10 in the event of thermal runaway.

[0103] See Figures 3 to 6In some embodiments, the thermally conductive material 302 includes a plurality of first thermally conductive particles 3021 and a plurality of second thermally conductive particles 3022. The plurality of first thermally conductive particles 3021 are arranged at intervals along the circumference of the central needle 300, and the plurality of second thermally conductive particles 3022 are arranged at intervals along the circumference of the central needle 300. The first thermally conductive particles 3021 and the second thermally conductive particles 3022 are arranged alternately at intervals along the axial direction X of the central needle.

[0104] By arranging multiple first thermally conductive particles 3021 and multiple second thermally conductive particles 3022 at intervals along the circumference of the center pin 300, and by alternating the arrangement of the first thermally conductive particles 3021 and the second thermally conductive particles 3022 along the axial direction X of the center pin, the distribution of the first thermally conductive particles 3021 and the second thermally conductive particles 3022 within the first part 310 becomes more uniform. This results in better overall thermal conductivity of the first part 310, enabling faster heat transfer from the electrode assembly 100 near the first part 310 to the second part 320. Furthermore, this leads to a more uniform heat distribution within the electrode assembly 100 along the winding axis, further reducing the accumulation of internal heat near the first part 310 and the risk of short circuits caused by indentation within the electrode assembly 100. This further reduces the risk of thermal runaway in the cylindrical cell 10 and improves its safety.

[0105] In some embodiments, the matrix material 301 includes polypropylene and / or polyvinyl chloride.

[0106] By including polypropylene and / or polyvinyl chloride in the matrix material 301, the strength of the matrix material can be increased, resulting in better support of the center pin 300 for the electrode assembly 100, reducing the risk of indentation of the inner ring of the electrode assembly 100, and improving the safety and cycle life of the cylindrical cell 10.

[0107] In some embodiments, the first thermally conductive particle 3021 includes at least one of aluminum oxide, silicon carbide, and silicon nitride.

[0108] By including at least one of aluminum oxide, silicon carbide, and silicon nitride in the first thermally conductive particle 3021, the thermal conductivity of the first thermally conductive particle 3021 is improved, and the heat of the electrode assembly 100 near the first part 310 can be conducted to the second part 320 more quickly. This makes the heat distribution inside the electrode assembly 100 along the winding axis more uniform, which can reduce the problem of heat accumulation inside the electrode assembly 100 near the first part 310 and the problem of short circuit caused by indentation inside the electrode assembly 100. This can reduce the risk of thermal runaway of the cylindrical cell 10 and improve the safety of the cylindrical cell 10.

[0109] In some embodiments, the second thermally conductive particle 3022 includes at least one of boron nitride, beryllium oxide, and diamond.

[0110] By including at least one of boron nitride, beryllium oxide, and diamond in the second thermally conductive particle 3022, the thermal conductivity of the second thermally conductive particle 3022 is improved, and the heat of the electrode assembly 100 near the first part 310 can be conducted to the second part 320 more quickly. This makes the heat distribution inside the electrode assembly 100 along the winding axis more uniform, which can reduce the problem of heat accumulation inside the electrode assembly 100 near the first part 310 and the problem of short circuit caused by indentation inside the electrode assembly 100. This can reduce the risk of thermal runaway of the cylindrical cell 10 and improve the safety of the cylindrical cell 10.

[0111] In some embodiments, the volume percentage of the first thermally conductive particles 3021 in the first portion 310 is 40%-70%. For example, the volume percentage of the first thermally conductive particles 3021 in the first portion 310 can be 40%, 45%, 50%, 55%, 60%, 65%, or 70%, etc.

[0112] When the volume percentage of the first thermally conductive particles 3021 in the first part 310 is greater than or equal to 40%, ensuring that the volume percentage of the first thermally conductive particles 3021 in the first part 310 is not too small, the thermal conductivity of the first part 310 is better. This allows for faster heat conduction from the electrode assembly 100 near the first part 310 to the second part 320, resulting in a more uniform heat distribution along the winding axis inside the electrode assembly 100. This reduces the accumulation of internal heat near the first part 310 and the problem of short circuits caused by indentation within the electrode assembly 100, thereby reducing the risk of thermal runaway in the cylindrical cell 10 and improving the safety of the cylindrical cell 10. When the volume percentage of the first thermally conductive particles 3021 in the first part 310 is greater than or equal to 40%, the thermal conductivity of the first part 310 is better. This allows for faster heat conduction from the electrode assembly 100 near the first part 310. The volume percentage of the thermally conductive particles 3021 is less than or equal to 70%, ensuring that the volume percentage of the first thermally conductive particles 3021 in the first part 310 is not too large, the support strength of the first part 310 is not too small, and the overall support strength of the center pin 300 is relatively large. This reduces the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10. Therefore, when the volume percentage of the first thermally conductive particles 3021 in the first part 310 is 40%-70%, it can reduce the risk of thermal runaway of the cylindrical cell 10, improve the safety of the cylindrical cell 10, and reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10.

[0113] In some embodiments, the volume percentage of the second thermally conductive particle 3022 in the first part 310 is 5%-30%. For example, 5%, 8%, 10%, 15%, 20%, 25%, or 30%.

[0114] When the volume percentage of the second thermally conductive particles 3022 in the first part 310 is greater than or equal to 5%, ensuring that the volume percentage of the second thermally conductive particles 3022 in the first part 310 is not too small, the thermal conductivity of the first part 310 is better. This allows for faster heat conduction from the electrode assembly 100 near the first part 310 to the second part 320, resulting in a more uniform heat distribution along the winding axis inside the electrode assembly 100. This reduces the accumulation of internal heat near the first part 310 and the problem of short circuits caused by indentation within the electrode assembly 100, thereby reducing the risk of thermal runaway in the cylindrical cell 10 and improving the safety of the cylindrical cell 10. When the volume percentage of the second thermally conductive particles 3022 in the first part 310 is greater than or equal to 5%, the thermal conductivity of the first part 310 is better, allowing for faster heat conduction from the electrode assembly 100 near the first part 310 to the second part 320. The volume percentage of the thermally conductive particles 3022 is less than or equal to 30%, ensuring that the volume percentage of the second thermally conductive particles 3022 in the first part 310 is not too large, the support strength of the first part 310 is not too small, and the overall support strength of the center pin 300 is relatively large. This reduces the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10. Therefore, when the volume percentage of the second thermally conductive particles 3022 in the first part 310 is 5%-30%, it can reduce the risk of thermal runaway of the cylindrical cell 10, improve the safety of the cylindrical cell 10, and reduce the risk of indentation of the inner ring of the electrode assembly 100, which is beneficial to improving the safety and cycle life of the cylindrical cell 10.

[0115] In some embodiments, the electrode assembly 100 includes a negative electrode 120, which includes a negative current collector 121 and a negative active material layer 122. The negative active material layer 122 is disposed on at least one side of the negative current collector 121 along its thickness direction Y. The negative active material layer 122 includes a silicon-based material, and the coefficient of thermal expansion of the negative electrode 120 is k, where 0.1 ≤ k ≤ 1.0. For example, k can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0, etc.

[0116] Since the expansion coefficient of the negative electrode 120 is positively correlated with the percentage of silicon (Csi) in the negative electrode active material, when k is greater than or equal to 0.1, k is not too small, resulting in a higher specific capacity of the negative electrode 120, which is beneficial to improving the energy density of the cylindrical cell 10. When k is less than or equal to 1, k is not too large, and the deformation of the negative electrode 120 during the cyclic charging and discharging of the cylindrical cell 10 is not too large, which can slow down the pulverization and delamination process of the negative electrode 120 and slow down the capacity decay of the cylindrical cell 10. Therefore, when 0.1≤k≤1.0, the specific capacity of the negative electrode 120 is higher, which is beneficial to improving the energy density of the cylindrical cell 10, and the pulverization and delamination process of the negative electrode 120 is slowed down, which slows down the capacity decay of the cylindrical cell 10.

[0117] The test method for the expansion coefficient k of the negative electrode 120 includes: charging one cylindrical cell 10 to 4.2V with a constant current of 2C in a 25℃ constant temperature chamber, then charging it to 0.05C with a constant voltage of 4.2V, and letting it stand for 5 minutes (i.e., full charge); charging another cylindrical cell 10 from the same batch to 4.2V with a constant current of 2C in a 25℃ constant temperature chamber, then charging it to 0.05C with a constant voltage of 4.2V, letting it stand for 5 minutes, and then discharging it to 2V with a constant current of 6C. 0.5V, stand for 5 minutes (i.e., fully discharged); disassemble the two cylindrical cells 10 respectively, and soak the negative electrode 120 in dimethyl carbonate solvent for 10 minutes. Measure the thickness of the negative electrode 120, and take the average value of 15 points. Measure the thickness of the negative electrode 120 of the fully charged cylindrical cell 10 as T1, and measure the thickness of the negative electrode 120 of the fully discharged cylindrical cell 10 as T2. The expansion coefficient of the negative electrode 120 is k = T2 / T1.

[0118] See Figure 1 In some embodiments, the cylindrical cell 10 further includes a first current collector 410, and the housing 200 is provided with a terminal post 210, which is insulated from the housing 200. The first current collector 410 can be connected to the positive electrode tab 140, so that the positive electrode tab 140 is electrically connected to the terminal post 210 through the first current collector 410.

[0119] In some embodiments, the cylindrical cell 10 further includes a second current collector 420, through which the negative electrode tab 150 is electrically connected to the housing 200.

[0120] This application provides an electrical device including a cylindrical battery cell 10 provided in any of the above embodiments, the cylindrical battery cell 10 being used to provide electrical energy.

[0121] Manufacturing method of cylindrical battery cells: <Preparation of the positive electrode> The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.91 Co 0.045 Mn 0.045 O2), polyvinylidene fluoride (PVDF) binder, and conductive carbon black were dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.1:1.6:1.3 and thoroughly mixed to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated on one surface of a 13 μm thick aluminum foil for the positive electrode current collector and dried at 105 °C to obtain a positive electrode sheet with a first positive electrode material layer coated on one side. The above steps were then repeated on the other surface of the same aluminum foil to obtain a positive electrode sheet with both a first and a second positive electrode material layer coated.

[0122] The positive electrode sheet has dimensions of 66.5mm × 1688mm, and the coating weight of the first and second positive electrode material layers is 196.5mg / 1540.25mm. 2 The first positive electrode material layer has a size of 60mm × 1688mm, the second positive electrode material layer has the same size as the first positive electrode material layer, and the width of the empty foil area of ​​the positive electrode sheet is 4.5mm.

[0123] <Preparation of Negative Electrode Sheets> Artificial graphite (anode active material), silicon carbide (SiC) (anode active material), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 82.45:14.55:1.7:1.3. Deionized water was then added as a solvent, and the mixture was stirred until homogeneous, yielding a cathode slurry with a solid content of 50 wt%. This cathode slurry was uniformly coated onto one surface of an 8 μm thick copper foil current collector and dried at 105 °C to obtain a cathode sheet with a single-sided coating of the first cathode material layer. The above steps were then repeated on the other surface of the same copper foil to obtain a cathode sheet coated with both the first and second cathode material layers.

[0124] The negative electrode sheet has dimensions of 67.45mm × 1730mm, and the coating weight of the first and second negative electrode material layers is 78mg / 1540.25mm. 2 The first negative electrode material layer has a size of 62mm × 1730mm, the second negative electrode material layer has the same size as the first negative electrode material layer, the sum of the thickness of the first negative electrode material layer and the negative electrode current collector is 40μm, and the width of the empty foil area of ​​the negative electrode sheet is 5.45mm.

[0125] <Isolation membrane> A polyethylene (PE) film with a thickness of 12μm was used as the separator.

[0126] <Preparation of Electrolyte> In a dry argon-atmospheric glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain a base solvent. Lithium hexafluorophosphate (LiPF6) was then added to the base solvent and mixed thoroughly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, with the remainder being the base solvent.

[0127] <Preparation of Cylindrical Cells> The separator, negative electrode, separator, and positive electrode prepared above are stacked sequentially and pre-wound, with the separator positioned between the negative and positive electrode sheets. Simultaneously, the first positive electrode material layer is positioned away from the center of the pre-wound electrode assembly, and the starting end of the first positive electrode material layer is located close to the center of the pre-wound electrode assembly. Next, an electrode assembly with a central hole is formed by winding with a 3.0 mm diameter needle. After removing the needle, a central needle with an outer diameter of 2.4 mm, a wall thickness of 0.5 mm, and a height of 60 mm is inserted into the central hole. The base material of the central needle is polypropylene, and the first part of the central needle is embedded with 60% aluminum oxide particles and 8% boron nitride particles by volume.

[0128] After the electrode assembly is installed in the casing, electrolyte is injected, it is sealed, and then subjected to high-temperature settling and formation, a cylindrical battery cell can be obtained. The upper limit voltage for formation is 3.6V, and the formation temperature is 45℃.

[0129] Refer to Table 1, where P1 represents the thermal conductivity of the first part and P2 represents the thermal conductivity of the second part. In Comparative Example 1, the center pin is not embedded with thermally conductive material. In Examples 1-12, the first part of the center pin is embedded with thermally conductive material.

[0130] Table 1

[0131] Test method for the indentation distance of electrode assembly: (1) Cyclic cells are charged and discharged at an ambient temperature of 25±2℃. The charging and discharging voltage range is 2.5V to 4.2V. They are charged to 4.2V with a constant current of 3C, then charged to 0.05C with a constant voltage of 4.2V and left to stand for 5 minutes. Then they are discharged to 2.5V with a constant current of 6C. The above charging and discharging process is repeated 600 times.

[0132] (2) After the cylindrical battery cell is fully charged, industrial computed tomography (industrial CT, Zeiss Xradia620 Versa) is used to perform CT scans on the wound electrode assembly along the radial direction of the electrode assembly.

[0133] (3) See Figure 9 , Figure 9 The scan image of the electrode assembly after 600 cycles of charging and discharging of the cylindrical battery cell provided in some embodiments of this application is defined as point E, the maximum indentation position of the electrode assembly (the point where the indentation is closest to the winding axis) is defined as point E, and the indentation position of the electrode assembly (the electrode plate with a height greater than or equal to 0.2 mm protruding towards the winding axis is defined as point F) is defined as point F. The distance between point E and point F is the indentation distance of the electrode assembly.

[0134] Cycle capacity retention test of cylindrical cells: (1) Cyclic cells are charged and discharged in a constant temperature chamber at 25°C. They are charged to 4.2V with a constant current of 3C and charged to 0.05C with a constant voltage of 4.2V. After standing for 5 minutes, they are discharged to 2.5V with a constant current of 6C. This is the first cycle. The discharge capacity C1 of the first cycle is recorded.

[0135] (2) After 600 cycles of the above cycle process, record the discharge capacity C600 of the cylindrical cell. Then the capacity retention rate (%) of the 600th cycle is C600 / C1×100%.

[0136] Thermal runaway testing of cylindrical cells can refer to the "Thermal Abuse Test" in GB 31241-2022 "Safety Technical Specifications for Lithium-ion Batteries and Battery Packs for Portable Electronic Products". Each group tests 20 cylindrical cell samples, and the number of cylindrical cells that pass the test is Q. The thermal runaway test pass rate = Q / 20.

[0137] Based on Table 1, the following conclusions can be drawn: (1) Referring to Comparative Example 1 and Examples 1-12, the center pin is not embedded with thermally conductive material, resulting in poor thermal conductivity. Heat accumulates locally inside the electrode assembly, making it prone to short circuits due to indentation. This increases the risk of thermal runaway in cylindrical cells and affects their cycle life. In this application, the first part of the center pin is embedded with thermally conductive material, which can more quickly conduct heat from the electrode assembly near the first part to the second part. This makes the heat distribution along the winding axis of the electrode assembly more uniform, reducing the accumulation of heat near the first part and the short circuits caused by indentation. Consequently, the indentation distance of the electrode assembly is smaller, the risk of thermal runaway in cylindrical cells is lower, and the safety and cycle life of cylindrical cells are improved.

[0138] (2) Referring to Comparative Example 1 and Examples 1-6, when P1 / P2 is less than 3, P1 is small, and the internal heat of the electrode assembly accumulates in the first part. The electrode assembly is prone to indentation, which can lead to short circuits. The risk of thermal runaway of the cylindrical cell is high, affecting the cycle life of the cylindrical cell. When P1 / P2 is greater than 15, the thermally conductive material will weaken the support force of the center pin, resulting in a lower support strength of the center pin for the electrode assembly. The indentation distance of the electrode assembly is large, which affects the cycle life of the cylindrical cell. Furthermore, the large indentation distance of the electrode assembly will cause lithium plating in the electrode assembly, affecting the thermal stability of the cylindrical cell and leading to a higher risk of thermal runaway of the cylindrical cell. When 3≤P1 / P2≤15, the temperature of the electrode assembly in the winding axis direction can be more uniform, reducing the risk of thermal runaway of the cylindrical cell and improving the safety and cycle life of the cylindrical cell. At the same time, the support force of the center pin for the electrode assembly can be increased, the indentation distance of the electrode assembly can be reduced, and the cycle life of the cylindrical cell can be improved. When 4≤P1 / P2≤10, the risk of thermal runaway in cylindrical cells can be further reduced, and the safety and cycle life of cylindrical cells can be improved.

[0139] (3) Referring to Examples 4 and 7-12, when P1 is less than 0.7 W / m·K and P2 is less than 0.1 W / m·K, the thermal conductivity of the center pin is poor, the internal heat of the electrode assembly accumulates near the first part, and the electrode assembly is prone to indentation leading to short circuits. The risk of thermal runaway of the cylindrical cell is high, affecting the safety and cycle life of the cylindrical cell. When P1 is greater than 4.5 W / m·K, the amount of thermally conductive material added is large, affecting the support strength of the first part. When P2 is greater than 0.3 W / m·K, that is, the thermal conductivity of the base material is high, which will make the strength of the base material low, affecting the support strength of the second part. Both of these will result in a large indentation distance of the electrode assembly, a short cycle life of the cylindrical cell, and a large indentation distance of the electrode assembly will cause lithium plating in the electrode assembly, affecting the thermal stability of the cylindrical cell and leading to a high risk of thermal runaway of the cylindrical cell. When 0.7W / m·K≤P1≤4.5W / m·K and 0.1W / m·K≤P2≤0.3W / m·K, the thermal conductivity of the first part is better, reducing the risk of thermal runaway in the cylindrical cell and improving the safety and cycle life of the cylindrical cell. At the same time, the support strength of the center pin is higher, reducing the indentation distance of the electrode assembly and improving the cycle life of the cylindrical cell.

[0140] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0141] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A cylindrical battery cell, characterized in that, include: An electrode assembly having a wound structure, the electrode assembly having a central hole; A center pin is disposed within the center hole. The center pin is a tubular structure. Along the axial direction of the center pin, the center pin includes a first part and a second part. Both the first part and the second part include a base material. The first part also includes a thermally conductive material embedded in the base material. The thermal conductivity of the first part is greater than that of the second part.

2. The cylindrical battery cell according to claim 1, characterized in that, The thermal conductivity of the first part is P1, and the thermal conductivity of the second part is P2, where 3 ≤ P1 / P2 ≤ 15, preferably 4 ≤ P1 / P2 ≤ 10.

3. The cylindrical battery cell according to claim 1, characterized in that, The thermal conductivity of the first part is P1, 0.7 W / m·K ≤ P1 ≤ 4.5 W / m·K; and / or, The thermal conductivity of the second part is P2, 0.1 W / m·K ≤ P2 ≤ 0.3 W / m·K.

4. The cylindrical battery cell according to claim 1, characterized in that, Along the axial direction of the center needle, the height of the center needle is H0, and the height of the first part is H1, 10%≤H1 / H0≤70%, preferably, 20%≤H1 / H0≤50%.

5. The cylindrical battery cell according to claim 1, characterized in that, Along the axial direction of the central needle, the height of the central needle is H0, the height of the second part is H2, and 30%≤H2 / H0≤90%.

6. The cylindrical battery cell according to claim 1, characterized in that, The electrode assembly includes a main body, a positive electrode tab, and a negative electrode tab, wherein the positive electrode tab and the negative electrode tab are respectively disposed at both ends of the main body along the winding axis of the electrode assembly; Along the winding axis, the first portion is closer to the positive electrode tab than the second portion.

7. The cylindrical battery cell according to claim 1, characterized in that, The electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative active material layer, the negative active material layer is disposed on at least one side of the negative current collector along its thickness direction, the negative active material layer includes a negative active material, the negative active material includes a silicon-based material, and based on the total mass of the negative active material layer, the mass content percentage of silicon element in the silicon-based material is Csi. The cross-sectional area of ​​the central hole is S1, the cross-sectional area of ​​the central needle is S2, q×Csi≤S2 / S1≤0.98, where 0.1≤q≤1.0, and the cross-section is perpendicular to the winding axis of the electrode assembly.

8. The cylindrical battery cell according to claim 7, characterized in that, 0.4≤S2 / S1≤0.

7.

9. The cylindrical battery cell according to claim 7, characterized in that, 1%≤Csi≤40%, preferably 5%≤Csi≤20%.

10. The cylindrical battery cell according to claim 1, characterized in that, The compressive strength of the center pin is F, where 200N≤F≤1800N, preferably 500N≤F≤1000N.

11. The cylindrical battery cell according to claim 1, characterized in that, The thermally conductive material includes a plurality of first thermally conductive particles and a plurality of second thermally conductive particles. The plurality of first thermally conductive particles are arranged at intervals along the circumference of the central needle, and the plurality of second thermally conductive particles are arranged at intervals along the circumference of the central needle. The first thermally conductive particles and the second thermally conductive particles are arranged alternately at intervals along the axial direction of the central needle.

12. The cylindrical battery cell according to claim 11, characterized in that, The matrix material includes polypropylene and / or polyvinyl chloride; and / or, The first thermally conductive particles comprise at least one of aluminum oxide, silicon carbide, and silicon nitride; and / or, The second heat-conducting particle includes at least one of boron nitride, beryllium oxide, and diamond.

13. The cylindrical battery cell according to claim 11, characterized in that, In the first part, the volume percentage of the first thermally conductive particles is 40%-70%; and / or, The volume percentage of the second heat-conducting particles in the first part is 5%-30%.

14. The cylindrical battery cell according to claim 1, characterized in that, The electrode assembly includes a negative electrode sheet, which includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector along its thickness direction. The negative active material layer includes a silicon-based material. The coefficient of thermal expansion of the negative electrode sheet is k, where 0.1 ≤ k ≤ 1.

0.

15. An electrical appliance, characterized in that, Includes a cylindrical battery cell as described in any one of claims 1-14, the cylindrical battery cell being used to provide electrical energy.

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