Single battery and battery pack

Abstract

The embodiment of the invention relates to the technical field of batteries, and particularly discloses a single battery and a battery pack. The electrode assembly is arranged in the shell; the end cover is arranged at one end, in the axial direction, of the shell; the current collecting element is arranged between the electrode assembly and the end cover, the current collecting element comprises a connecting part, a first-stage welding part and a second-stage welding part, the first-stage welding part and the second-stage welding part are both arranged on the connecting part, the first-stage welding part and the second-stage welding part are arranged at intervals in the circumferential direction, and the first-stage welding part and the second-stage welding part are both electrically connected with the electrode assembly; in the radial direction, the first-stage welding part and the second-stage welding part extend from the edge of the connecting part to the center of the current collecting element, and the size of the first-stage welding part in the radial direction is larger than that of the second-stage welding part in the radial direction. According to the invention, the overall over-current performance of the single battery is improved, the high-rate over-current capability of the single battery is improved, and finally the rate performance and the cycle performance of the single battery are improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a single cell and a battery pack. Background Art

[0002] The replacement of traditional fuel vehicles with new energy vehicles is crucial for addressing energy and pollution challenges facing the global transportation industry and represents an inevitable trend. With the rapid development of the new energy industry, there is an urgent need for batteries with greater capacity, increased durability, and longer battery life. As one of the core performance characteristics of batteries, improving their rate performance has become a pressing issue. Summary of the Invention

[0003] The embodiments of the present application provide a single cell battery and a battery pack to improve the rate performance of the single cell battery.

[0004] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0005] In one aspect, a single battery is provided, having a vertical axial direction and a radial direction, and a circumferential direction around the axial direction, comprising: a housing;

[0006] an electrode assembly, disposed in the housing;

[0007] an end cover, disposed at one axial end of the housing; and

[0008] A current collecting element is disposed between the electrode assembly and the end cap, and the current collecting element includes: a connecting portion, a primary welding portion, and a secondary welding portion, wherein the primary welding portion and the secondary welding portion are both disposed on the connecting portion, the primary welding portion and the secondary welding portion are spaced apart in the circumferential direction, and the primary welding portion and the secondary welding portion are both electrically connected to the electrode assembly;

[0009] In the radial direction, both the primary welding portion and the secondary welding portion extend from the edge of the connecting portion toward the center of the current collecting element, and the radial size of the primary welding portion is larger than the radial size of the secondary welding portion.

[0010] In addition to one or more features disclosed above, or as an alternative, a plurality of primary welding portions and a plurality of secondary welding portions are provided, and the plurality of primary welding portions and the plurality of secondary welding portions are arranged at intervals and alternately in the circumferential direction.

[0011] In addition to one or more features disclosed above, or as an alternative, the flow path between the secondary weld and its closest primary weld is T mm, satisfying: T = (2π × R0 × α) / 360°;

[0012] Wherein, R0 mm is the radius of the end of the primary weld close to the axis, α is the angle between two adjacent primary welds, and satisfies: 1≤R0≤10, and 0°<α≤180°.

[0013] In addition to one or more features disclosed above, or as an alternative, the angle α between two adjacent primary welding portions further satisfies: 18°≤α≤180°.

[0014] In addition to or as an alternative to one or more features disclosed above, the flow path between two adjacent primary welding portions is W mm, satisfying: W=T.

[0015] In addition to or as an alternative to one or more of the features disclosed above, the current collecting element further comprises: a tertiary welding portion provided on the connecting portion, and the tertiary welding portion is provided between the primary welding portion and the secondary welding portion adjacent thereto;

[0016] In the radial direction, the tertiary welding portion extends from the edge of the connecting portion toward the center of the current collecting element, and the radial size of the secondary welding portion is larger than the radial size of the tertiary welding portion.

[0017] In addition to one or more features disclosed above, or as an alternative, a plurality of tertiary welding portions are provided, and a tertiary welding portion is provided between each secondary welding portion and each adjacent primary welding portion.

[0018] In addition to or as an alternative to one or more features disclosed above, the current collecting element further includes: an n-1-level welding portion and an n-level welding portion, wherein both the n-1-level welding portion and the n-level welding portion are provided on the connecting portion, and the n-level welding portion is provided on both sides of the n-1-level welding portion in the circumferential direction (θ);

[0019] The angle between the first-level weld and its closest n-level weld is β n , satisfying: β n =α / 2 n-1 , n is an integer not less than 2 and satisfies: β n ≤90°.

[0020] In addition to one or more features disclosed above, or as an alternative, in the radial direction, the n-level welding portion extends from the edge toward the center of the connecting portion, and the maximum dimension of the n-level welding portion in the radial direction is L n mm, meet: L n =H+R0-T×360° / 2πβ n ;

[0021] Where H mm is the maximum radial dimension of the primary weld, n is an integer not less than 1, and satisfies: L n ≤18.

[0022] On the other hand, a battery pack is further disclosed. In addition to or as an alternative to one or more of the features disclosed above, the battery pack includes a box body; and a single cell as described in any one of the above items, wherein the single cell is arranged in the box body.

[0023] One of the above technical solutions has the following advantages or beneficial effects: the present application sets a primary welding part and a secondary welding part in the current collecting element, and uses the primary welding part and the secondary welding part to electrically connect with the electrode assembly, and the radial size of the primary welding part is larger than the radial size of the secondary welding part. In this way, the length of the electronic conduction path from the inner coil electrode of the battery core to the nearest welding part is more consistent with the length of the electronic conduction path from the outer coil electrode of the core to the nearest welding part, and the internal resistance of the inner coil electrode and the outer coil electrode also tends to be consistent, so as to reasonably design the electrical connection structure between the current collecting element and the electrode assembly, optimize the electronic conduction path in the single cell, ensure that the overcurrent path between the electrode sheets of different levels in the single cell and the current collecting element is consistent, improve the overcurrent uniformity of the single cell, improve the overall overcurrent performance of the single cell, improve the high-rate overcurrent capability of the single cell, and ultimately improve the rate performance and cycle performance of the single cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0025] Figure 1 is an exploded structural view of a single cell provided according to an embodiment of the present application;

[0026] Figure 2 This is a top view of a current collecting element provided according to an embodiment of the present application.

[0027] Description of reference numerals:

[0028] 100. Single cell; 110. Housing; 120. Electrode assembly; 130. End cap; 140. Current collecting element; 141. Connecting portion; 142. Primary welding portion; 143. Secondary welding portion; 144. Tertiary welding portion. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and beneficial effects of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described in this specification are only for the purpose of explaining this application and are not intended to limit this application.

[0030] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, the meaning of "multiple" refers to two or more, unless otherwise clearly and specifically defined.

[0031] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, direct connections, or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0032] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0033] In order to improve the rate performance of secondary batteries, a full-tab design is usually adopted in secondary batteries to reduce the current path. The tabs can be formed into tab end faces using two processes: flattening or cutting, stacking and flattening. The tab end faces are then connected to the current collecting disk to achieve current conduction. Therefore, the connection track between the tab end faces and the current collecting disk is the bottleneck of the rate performance of secondary batteries. The existing connection tracks between the current collecting disk and the tab end faces are uniformly distributed along the radial direction of the battery, and each connection track has the same structure. Since the electrode assembly in the secondary battery is a wound structure, as the winding diameter gradually increases, the length of the pole piece of each circle also gradually increases. However, since the existing connection tracks between the current collecting disk and the tab end faces are uniformly distributed along the radial direction of the battery, and each connection track has the same structure, the overcurrent path of each circle of pole pieces in the secondary battery is different, which in turn leads to different overcurrent capacity of each circle of pole pieces, and the overcurrent uniformity of the secondary battery deteriorates, which seriously affects the high-rate overcurrent capacity of the secondary battery, and thus affects the rate performance of the secondary battery.

[0034] In order to solve the above problems, in the embodiments of the present application, referring to Figures 1 to 2 The present application provides a single battery 100, which has an axial direction Z and a radial direction X that are perpendicular to each other, and a circumferential direction θ surrounding the axial direction Z. The axial direction Z, the radial direction X, and the circumferential direction θ are perpendicular to each other.

[0035] It should be noted that in all embodiments of this application, the axial direction Z refers to the direction indicated by the arrows in the accompanying drawings; it should be understood that the axial direction Z is the direction indicated by a line perpendicular to the outer surface of the pressure relief member 200. A cylindrical coordinate system is constructed with a line passing through the center of the current collecting element 140 and parallel to the axial direction Z as the axis (which can be considered the axis of the single cell). The circumferential direction θ refers to the direction of a tangent to a circle on a plane perpendicular to the axial direction Z, centered at the intersection of the axis and the plane. The radial direction X refers to the direction of a ray originating from the axis and within the plane.

[0036] It should be understood that in all embodiments of the present application, the concepts of axial Z, radial X, and circumferential θ are introduced only for the convenience of describing the spatial position relationship and should not be understood as limiting the scope of the embodiments of the present application; therefore, the axial Z, radial X, and circumferential θ are perpendicular to each other. Such a position relationship can be reasonably interpreted as a nearly relatively perpendicular directional relationship between the axial Z, radial X, and circumferential θ according to actual technical scenarios, for example, the angle between the axial Z, radial X, and circumferential θ is in the range of 85°-95°... As long as it conforms to the spirit of the present invention or achieves the technical effect described in the present invention, the technical solution can be considered to fall within the scope defined by the appended claims.

[0037] Specifically, refer to Figures 1 to 2The single cell 100 includes: a shell 110 , an electrode assembly 120 , an end cap 130 and a current collecting element 140 .

[0038] Specifically, the electrode assembly 120 is arranged in the shell 110; the end cover 130 is arranged at one end of the shell 110 in the axial direction Z to seal the shell 110; the current collecting element 140 is arranged between the electrode assembly 120 and the end cover 130, and the current collecting element 140 includes: a connecting portion 141, a primary welding portion 142 and a secondary welding portion 143, the primary welding portion 142 and the secondary welding portion 143 are both arranged on the connecting portion 141, the primary welding portion 142 and the secondary welding portion 143 are spaced apart in the circumferential direction θ, and the primary welding portion 142 and the secondary welding portion 143 are both electrically connected to the electrode assembly 120.

[0039] The single cell 100 may be a secondary battery, which refers to a single cell that can be recharged to activate the active material after discharge and continue to be used. For example, the single cell 100 may be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery, but is not limited thereto.

[0040] The single battery 100 may be a prismatic battery, a soft-pack battery, or a battery of other shapes. For example, in the present application, the single battery 100 is a cylindrical battery.

[0041] The single cell 100 also includes an electrolyte, a pole and other functional components. The electrolyte can be a conventional electrolyte or a special electrolyte with additives. The electrolyte is used to soak the electrode assembly 120. Among them, the electrode assembly 120 is a component where the electrochemical reaction occurs in the single cell 100, and there can be one or more electrode assemblies. The electrode assembly 120 is mainly formed by winding or stacking a positive electrode sheet, a separator and a negative electrode sheet. The parts of the positive electrode sheet and the negative electrode sheet with active substances constitute the main body of the electrode assembly 120, and the parts of the positive electrode sheet and the negative electrode sheet without active substances constitute the tabs. During the charge and discharge process of the single cell 100, the positive electrode active substance and the negative electrode active substance react with the electrolyte, and the tabs are electrically connected to the poles through the current collecting element 140 to form a current loop, so that the single cell 100 can be used normally.

[0042] The end cap 130 can be integrally formed with the housing 110, i.e., the end cap 130 can be the outer wall of the housing 110. The end cap 130 can also be fixedly connected to the housing 110, for example, by welding or other processes to one end of the housing 110 in the axial direction Z. This is not specifically limited in this application and can be specifically configured according to actual circumstances. For example, in this application, the end cap 130 is provided separately from the housing 110 and is fixedly welded to the housing 110.

[0043] The current collecting element 140 may be a positive electrode current collecting element or a negative electrode current collecting element, which is not specifically limited in this application and may be specifically configured according to actual circumstances.

[0044] The electrode assembly 120 is welded to the current collecting element 140 to form a primary welding portion 142 and a secondary welding portion 143. Specifically, the tabs in the electrode assembly 120 are welded to the current collecting element 140 to form a primary welding portion 142 and a secondary welding portion 143.

[0045] The primary welding portion 142 and the secondary welding portion 143 may be formed by laser welding, ultrasonic welding, or resistance welding.

[0046] The primary welding portion 142 and the secondary welding portion 143 may be in a straight line shape or a spiral line shape, but are not limited thereto.

[0047] Specifically, in the radial direction X, both the primary welding portion 142 and the secondary welding portion 143 extend from the edge of the connecting portion 141 toward the center of the current collecting element 140 , and the size of the primary welding portion 142 in the radial direction X is larger than the size of the secondary welding portion 143 in the radial direction X. In each embodiment of the present application, the center of the current collecting element 140 can be considered as the centroid of the current collecting element 140, that is, the position where the axis intersects the current collecting element 140. The advantage of doing so is that the length of the electronic conduction path from the inner coil electrode of the battery core to the nearest welding part can be made more consistent with the length of the electronic conduction path from the outer coil electrode to the nearest welding part, and the internal resistance of the inner coil electrode and the outer coil electrode also tends to be consistent, thereby realizing a reasonable design of the electrical connection structure between the current collecting element 140 and the electrode assembly 120, optimizing the electronic conduction path in the single cell 100, ensuring that the flow path between the electrodes of different levels in the single cell 100 and the current collecting element 140 is consistent, improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0048] In some embodiments, reference Figure 2 There are multiple first-level welding parts 142 and multiple second-level welding parts 143, and the multiple first-level welding parts 142 and the multiple second-level welding parts 143 are arranged at intervals and alternately in the circumferential direction θ. That is, in the circumferential direction θ, each second-level welding part 143 is arranged between two adjacent first-level welding parts 142.

[0049] Specifically, the plurality of primary welding portions 142 are centrosymmetric about the center point of the connecting portion 141 , and the plurality of secondary welding portions 143 are centrosymmetric about the center point of the connecting portion 141 .

[0050] The present application sets multiple primary welding parts 142 and secondary welding parts 143, and multiple secondary welding parts 143 are respectively set between two adjacent primary welding parts 142, so as to further rationally design the electrical connection structure between the current collecting element 140 and the electrode assembly 120, optimize the electron conduction path in the single cell 100, ensure that the flow paths between the pole pieces of different levels in the single cell 100 and the current collecting element 140 are consistent, improve the flow uniformity of the single cell 100, improve the overall flow performance of the single cell, improve the high-rate flow capability of the single cell 100, and ultimately improve the rate performance and cycle performance of the single cell 100.

[0051] For example, in the present application, there are two primary welding parts 142 and two secondary welding parts 143 , the two primary welding parts 142 are symmetrical about the center point of the connecting part 141 , and the two secondary welding parts 143 are symmetrical about the center point of the connecting part 141 .

[0052] In some embodiments, reference Figure 2 The current path between the secondary weld 143 and its closest primary weld 142 is T mm, satisfying the following: T = (2π × R0 × α) / 360°, where R0 mm is the radius of the primary weld 142's end closest to the axis, and α is the angle between two adjacent primary welds 142, satisfying the following: 0° < α ≤ 180°. It should be noted that the axis is a straight line parallel to the axial direction Z and passing through the center of the current collecting element 140, i.e., the axis of the single cell. The radius of the primary weld 142's end closest to the axis is the distance from the primary weld 142's end closest to the axis to the intersection of the axis and the current collecting element 140. The current path T mm between the secondary weld 143 and its closest primary weld 142 is only related to, and affected by, the radius R0 mm of the primary weld 142's end closest to the axis and the angle α between two adjacent primary welds 142.

[0053] The current path T mm between the secondary weld 143 and its closest primary weld 142 can be determined by disassembling the actual single battery 100, capturing image information of the current collecting element 140 using an image acquisition device, processing the image information to generate auxiliary lines for the current path between the secondary weld 143 and its closest primary weld 142, and then measuring the length of the auxiliary lines multiple times with a measuring tool and calculating the average value. The measuring tool can be any one of, but is not limited to, a ruler, a vernier caliper, or other dimensional measuring instrument.

[0054] The radius R0 mm of the end of the primary weld 142 close to the axis can be obtained by disassembling the actual single battery 100, measuring the radius of the primary weld 142 at different locations on the current collecting element 140 multiple times using a measuring tool, and calculating the average value. The measuring tool can be any one of, but is not limited to, a ruler, a vernier caliper, or other dimensional measuring instruments.

[0055] The angle α between two adjacent primary welding portions 142 can be obtained by disassembling the actual single battery 100, measuring the angle between any two adjacent primary welding portions 142 on the current collecting element 140 multiple times with a measuring tool, and calculating the average value. The measuring tool can be a protractor, but is not limited thereto.

[0056] This application optimizes the electron conduction path in the single cell 100 by limiting the overcurrent path Tmm between the secondary welding portion 143 and its closest primary welding portion 142 to satisfy: T = (2π×R0×α) / 360°, ensuring that the overcurrent paths between the pole pieces at different levels in the single cell 100 and the current collecting element 140 are consistent, thereby improving the overcurrent uniformity of the single cell 100, improving the overall overcurrent performance of the single cell, improving the high-rate overcurrent capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0057] For example, in this application, the flow path T mm between the secondary weld 143 and its closest primary weld 142 also satisfies the following: 3.14 mm ≤ T ≤ 94.2 mm. That is, the flow path T mm between the secondary weld 143 and its closest primary weld 142 can be controlled within the range of 3.14 mm to 94.2 mm. For example, the flow path T mm between the secondary weld 143 and its closest primary weld 142 can be within the range of 3.14 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, or 94.2 mm, or any two of these. The above specific values ​​for the flow path T mm are provided for example only; any value within the range of 3.14 mm to 94.2 mm is within the scope of this application. When these ranges are met, the single cell 100 exhibits superior performance.

[0058] In some embodiments, reference Figure 2, the radius R mm of the connection portion 141 also satisfies: 10≤R≤30. That is, the radius R mm of the connection portion 141 can be controlled within the range of 10 mm to 30 mm. For example, the radius R mm of the connection portion 141 can be 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, or 30 mm, or a range consisting of any two of them. The above specific values ​​of R mm are given for example only, and any value within the range of 10 mm to 30 mm is within the scope of protection of this application.

[0059] In some embodiments, reference Figure 2 , the radius R0 mm of the end of the primary welding portion 142 close to the axis also satisfies: 1≤R0≤10. That is, the radius R0 mm of the end of the primary welding portion 142 close to the axis can be controlled within the range of 1mm to 10mm. Exemplarily, the radius R0 mm of the end of the primary welding portion 142 close to the axis can be one of 1mm, 2mm, 3mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 7mm, 8mm, 9mm or 10mm, or a range consisting of any two of them. The above specific numerical values ​​of R0 mm are given for example only, and any value within the range of 1mm to 10mm is within the protection scope of this application.

[0060] This application limits the radius R0 mm of the end of the primary weld 142 near the axis to a range of 2 mm to 10 mm, thereby further rationally designing the structural dimensions of the current collecting element 140, improving the current uniformity of the cell 100, improving the overall current flow performance of the cell, improving the high-rate current flow capability of the cell 100, and ultimately improving the rate performance and cycle performance of the cell 100. More preferably, the radius R0 mm of the end of the primary weld 142 near the axis also satisfies the following: 2 ≤ R0 ≤ 6.

[0061] Reference Figure 2 , the angle α between two adjacent primary welding parts also satisfies: 18°≤α≤180°. That is, the angle α between two adjacent primary welding parts can be controlled within the range of 18° to 180°. For example, α can be one of 18°, 20°, 40°, 45°, 60°, 72°, 80°, 90°, 100°, 120°, 140°, 160° or 180°, or a range consisting of any two of them. The above specific numerical values ​​of α are given for example only, and any value within the range of 18° to 180° is within the scope of protection of this application.

[0062] The present application limits the angle α between two adjacent primary welding portions to be within the range of 18° to 180°, so as to further rationally design the overall structural dimensions of the current collecting element 140, thereby improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0063] Accordingly, refer to Figure 2 , the angle β2 between the adjacent primary welds 142 and the secondary welds 143 also satisfies: 9°≤β2≤90°. The angle β2 between the primary weld 142 and the secondary weld 143 can be controlled within the range of 9° to 90°. Exemplarily, α can be one of 9°, 10°, 20°, 22.5°, 30°, 36°, 40°, 45°, 50°, 60°, 70°, 80° or 90°, or a range consisting of any two of them. The above specific values ​​of β2 are only given as examples, and any value within the range of 9° to 90° is within the protection scope of this application. The angle β3 between the adjacent tertiary welds 144 and the secondary welds 143, and between the adjacent tertiary welds 144 and the primary welds 142 is half of β2. It is only necessary to follow β n =α / 2 n-1 Just set the rules.

[0064] In some embodiments, the current path between two adjacent primary welds 142 is W mm, satisfying the following: W = T. That is, the current path W mm between two adjacent primary welds 142 is equal to the current path T mm between a secondary weld 143 and its closest primary weld 142. This further optimizes the electron conduction path in the cell 100, ensures that the current paths between the electrode sheets and the current collecting element 140 at different levels in the cell 100 are consistent, improves the current uniformity of the cell 100, improves the overall current performance of the cell, improves the high-rate current capability of the cell 100, and ultimately improves the rate performance and cycle performance of the cell 100.

[0065] Among them, the measurement method of the flow path W mm between two adjacent first-level welding parts 142 is the same as the measurement method of the flow path T mm between the second-level welding part 143 and its closest first-level welding part 142. It will not be elaborated here and can refer to the above description.

[0066] In some embodiments, reference Figure 2 The current collecting element 140 further includes a tertiary welding portion 144 , which is disposed on the connecting portion 141 and between the primary welding portion 142 and the secondary welding portion 143 adjacent thereto.

[0067] The tertiary welding portion 144 may be formed by laser welding, ultrasonic welding, or resistance welding.

[0068] Specifically, in the radial direction X, the tertiary welding portion 144 extends from the outer edge of the connecting portion 141 toward the center of the current collecting element 140, and the size of the secondary welding portion 143 in the radial direction X is larger than the size of the tertiary welding portion 144 in the radial direction X, so as to further rationally design the electrical connection structure between the current collecting element 140 and the electrode assembly 120, optimize the electron conduction path in the single cell 100, ensure that the flow paths between the pole pieces of different levels in the single cell 100 and the current collecting element 140 are consistent, improve the flow uniformity of the single cell 100, improve the overall flow performance of the single cell, improve the high-rate flow capability of the single cell 100, and ultimately improve the rate performance and cycle performance of the single cell 100.

[0069] In some embodiments, a plurality of tertiary welding portions 144 are provided, and a tertiary welding portion 144 is provided between each secondary welding portion 143 and each adjacent primary welding portion 142; specifically, the plurality of tertiary welding portions 144 are centrally symmetrical about the center point of the connecting portion 141, so as to further rationally design the electrical connection structure between the current collecting element 140 and the electrode assembly 120, optimize the electron conduction path in the single cell 100, ensure that the flow paths between the pole pieces of different levels in the single cell 100 and the current collecting element 140 are consistent, improve the flow uniformity of the single cell 100, improve the overall flow performance of the single cell, improve the high-rate flow capability of the single cell 100, and ultimately improve the rate performance and cycle performance of the single cell 100.

[0070] Illustratively, in the present application, four tertiary welding portions 144 are provided, and the four tertiary welding portions 144 are centrally symmetrical about the center point of the connecting portion 141 .

[0071] In some embodiments, the flow path between the tertiary weld 144 and its closest primary weld 142 is T3 mm, satisfying T3 = (2π × R0 × α) / 360°. Parameters R0 and α have been previously described in detail and are therefore not further described here. Reference is made to the previous description.

[0072] Among them, the measurement method of the flow path T3 mm between the tertiary welding part 144 and its closest primary welding part 142 is the same as the measurement method of the flow path Tmm between the secondary welding part 143 and its closest primary welding part 142. It will not be elaborated here and can refer to the above description.

[0073] In some embodiments, the current collecting element 140 further includes: an n-1 level welding portion and an n-level welding portion, both of which are disposed on the connecting portion 141 , and the n-level welding portion is disposed on both sides of the n-1 level welding portion in the circumferential direction θ.

[0074] Specifically, the angle between the first-level welding portion 142 and the nearest n-level welding portion is β n , satisfying: β n =α / 2 n -1 , n is an integer not less than 2, so as to further reasonably design the structural dimensions of the welding parts at all levels on the current collecting element 140, thereby further optimizing the electron conduction path in the single cell 100, ensuring that the flow paths between the pole pieces at different levels in the single cell 100 and the current collecting element 140 are consistent, improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0075] For example, in this application, the flow path between the n-level welding portion and the first-level welding portion 142 closest thereto is T n mm, satisfying: T n =(2π×R0×α) / 360°, that is, the flow path T between the n-level welding portion and the first-level welding portion 142 closest to it n mm is only related to the radius R0 mm of one end of the primary welding portion 142 close to the axis and the angle α between two adjacent primary welding portions 142, and is only affected by the radius R0 mm of one end of the primary welding portion 142 close to the axis and the angle α between two adjacent primary welding portions 142, thereby ensuring that the flow paths between the pole pieces and the current collecting elements 140 at different levels in the single battery 100 are consistent, improving the flow uniformity of the single battery 100, improving the overall flow performance of the single battery, improving the high-rate flow capability of the single battery 100, and ultimately improving the rate performance and cycle performance of the single battery 100.

[0076] The parameters R and α have been described in detail in the previous text, so they will not be described here. Please refer to the description in the previous text.

[0077] In some embodiments, in the radial direction X, the n-level welding portion extends from the edge of the connecting portion 141 toward the center, and the maximum size of the n-level welding portion in the radial direction X is L n mm, meet: L n =H+R0-T×360° / 2πβ n ; H mm is the maximum dimension of the primary welding portion 142 in the radial direction X, and n is an integer not less than 2.

[0078] Among them, the maximum size L of the n-level weld in the radial direction X is n The mm can be obtained by disassembling the actual single battery 100, measuring the distance between two ends of the n-level welding portion on the current collecting element 140 that are opposite to each other in the radial direction X multiple times using a measuring tool, and calculating the average value. The measuring tool can be any one of a ruler, a vernier caliper, or other dimensional measuring instrument, but is not limited thereto.

[0079] The maximum dimension H mm of the primary welding portion 142 in the radial direction X can be obtained by disassembling the actual single battery 100, measuring the distance between two opposite ends of the primary welding portion 142 on the current collecting element 140 in the radial direction X multiple times using a measuring tool, and calculating the average value. The measuring tool can be any one of a ruler, a vernier caliper, or other dimension measuring instrument, but is not limited thereto.

[0080] The present application defines the maximum size L of the n-level welding portion in the radial direction X. n mm meets L n =H+R0-T×360° / 2πβ n The maximum dimensions of the welding parts at each level in the radial direction X are reasonably designed to ensure that the flow paths between the pole pieces at different levels in the single cell 100 and the current collecting element 140 are consistent, thereby improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0081] In one embodiment, referring to Figure 2 The maximum dimension of the primary weld portion 142 in the radial direction X is H mm, satisfying the following: 0.5 ≤ H / R ≤ 1. That is, the ratio of the maximum dimension H mm of the primary weld portion 142 in the radial direction X to the radius R mm of the connecting portion 141 can be controlled within the range of 0.5 to 1. For example, H / R can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1, or a range consisting of any two of these. The above specific values ​​of H / R are given for example only; any value within the range of 0.5 to 1 is within the scope of protection of this application.

[0082] The present application limits the ratio of the maximum dimension H mm of the primary welding portion 142 in the radial direction X to the radius R mm of the connecting portion 141 to be controlled within the range of 0.5 to 1, so as to rationally design the structural dimensions of the primary welding portion 142, thereby ensuring that the flow paths between the pole pieces and the current collecting element 140 at different levels in the single cell 100 are consistent, thereby improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0083] In one embodiment, referring to Figure 2 The maximum dimension H mm of the primary weld portion 142 in the radial direction X also satisfies the following: 5 mm ≤ H ≤ 30 mm. That is, the maximum dimension H mm of the primary weld portion 142 in the radial direction X can be controlled within the range of 5 mm to 30 mm. For example, the maximum dimension H mm of the primary weld portion 142 in the radial direction X can be 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15 mm, 17.5 mm, 20 mm, 22.5 mm, 25 mm, 27.5 mm, or 30 mm, or a range consisting of any two of these. The above specific values ​​of H mm are provided for illustrative purposes only; any value within the range of 5 mm to 30 mm is within the scope of protection of this application.

[0084] The present application limits the maximum dimension H mm of the primary welding portion 142 in the radial direction X to be within the range of 5 mm to 30 mm, so as to further rationally design the structural dimensions of the primary welding portion 142, thereby ensuring that the flow paths between the pole pieces at different levels in the single cell 100 and the current collecting element 140 are consistent, thereby improving the flow uniformity of the single cell 100, improving the overall flow performance of the single cell, improving the high-rate flow capability of the single cell 100, and ultimately improving the rate performance and cycle performance of the single cell 100.

[0085] Accordingly, refer to Figure 2 The maximum dimension L2 mm of the secondary welding portion 143 in the radial direction X also satisfies: L2≤18, thereby satisfying L n ≤18. That is, the maximum dimension L2 mm of the secondary welding portion 143 in the radial direction X can be controlled within the range of 0 mm to 18 mm. For example, the maximum dimension L2 mm of the secondary welding portion 143 in the radial direction X can be 1.5 mm, 2.5 mm, 3.0 mm, 3.8 mm, 5.5 mm, 6.1 mm, 8.0 mm, 8.4 mm, 10.7 mm, 13.0 mm or 18.0 mm, or a range consisting of any two of them. The above specific values ​​of L2 mm are given for example only. As long as L2 mm is met, n =H+R0-T×360° / 2πβ nGenerally speaking, L2 can be any value in the range of 0mm to 18mm, but as long as L2 meets the above numerical relationship, it is within the protection scope of this application.

[0086] On the other hand, in an embodiment of the present application, the present application also provides a battery pack, comprising: a box body, a single cell 100 as in any of the above embodiments, and a box cover, wherein the single cell 100 is arranged in the box body, the box cover is connected to the box body, and the box cover seals the box body.

[0087] The battery pack can be a three-layer battery pack consisting of single cells 100, battery modules, and battery packs, whereby the single cells 100 are first grouped into battery modules, which are then placed in a box to form a battery pack. Alternatively, the battery pack can be a two-layer battery pack consisting of single cells 100 and battery packs, whereby the single cells 100 are directly placed in a box to form a battery pack. This is not specifically limited in this application and can be configured based on actual circumstances, as long as it does not affect the effectiveness of this application.

[0088] On the other hand, in an embodiment of the present application, the present application further provides an electrical device, including: a battery pack as in the above embodiment, the battery pack serving as a power supply for the electrical device.

[0089] Among them, electrical devices can be but are not limited to mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0090] To better understand the technical solution of the present application, a lithium-ion battery with two primary welding portions 142 is taken as an example for further explanation.

[0091] Test Example 1

[0092] This test example provides a method for preparing a lithium-ion battery. The specific process is as follows:

[0093] 1. Preparation of positive electrode

[0094] The positive electrode active material is lithium iron phosphate, the conductive agent is conductive carbon black (SP), and the binder is polyvinylidene fluoride (PVDF) in a mass ratio of 96:2:2. Then, N-methylpyrrolidone (NMP) is added as a solvent to mix, and stirred under vacuum until the system becomes uniform to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, and then transferred to a 120°C oven for drying, and then rolled, slit, and cut into pieces to obtain a positive electrode sheet.

[0095] 2. Preparation of negative electrode sheet

[0096] The negative electrode active material graphite, the conductive agent conductive carbon black (SP), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96.2:1.2:1.2:1.4, and then deionized water is added as a solvent to mix. The mixture is stirred under vacuum until the system becomes uniform to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on both sides of the negative electrode current collector copper foil, and then transferred to a 110°C oven for drying, and then rolled, slit, and cut into pieces to obtain a negative electrode sheet.

[0097] 3. Preparation of electrolyte

[0098] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:4:3 to obtain an organic solvent, 1 mQl / L of LiPF6 was added and mixed evenly, and then vinylene carbonate, vinyl sulfate, and lithium difluorophosphate were added to prepare an electrolyte.

[0099] 4. Preparation of diaphragm

[0100] PP film is used as the separator.

[0101] 5. Preparation of lithium-ion batteries

[0102] After drying, the negative and positive electrode sheets prepared by the above steps are wound together with the separator using a winding machine to prepare a wound electrode roll. The positive and negative electrode tabs are welded to the end caps, and the welded electrode assembly with the top cover is placed in an aluminum shell for packaging. The lithium-ion battery is obtained by pouring electrolyte and forming a constant capacity.

[0103] The lithium-ion batteries prepared in the above test examples and comparative examples were subjected to performance tests. The specific test items were as follows:

[0104] 1. Test method for DC internal resistance of lithium-ion batteries

[0105] At 25°C, use 1C constant current and constant voltage to charge to the upper limit voltage, let it stand for 30 minutes, then discharge at 1C constant current to 50% SQC, let it stand for 60 minutes, then discharge at 3C constant current for 10 seconds, let it stand for 30 minutes, and calculate the DC internal resistance of the lithium-ion battery.

[0106] 2. Test method for rate performance of lithium-ion batteries

[0107] At 25°C, the lithium-ion battery was left to stand for 30 minutes, then discharged at a constant current rate of 4C, left to stand for 10 minutes, and then charged at a constant current and constant voltage rate of 4C. After 10 cycles of charge and discharge, the temperature difference between the inner and outer layers of the lithium-ion battery core was tested.

[0108] 3. Test method for lithium-ion battery cycle performance

[0109] At 25°C, the prepared lithium-ion battery was charged to 4.2V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C, and discharged to 2.8V at a constant current of 1C. The cycle test was performed until the capacity of the lithium-ion battery decayed to 80% of the initial capacity, and the number of full-life cycles was recorded.

[0110] Table 1 Parameters and test results of test cases 1 to 21

[0111]

[0112] As can be seen from the above test examples 1-15, the solutions provided by the embodiments of the present application provide a first-level weld and a second-level weld on the current collecting element, which are electrically connected to the electrode assembly using the first-level weld and the second-level weld. The radial size of the first-level weld is larger than the radial size of the second-level weld, so as to rationally design the electrical connection structure between the current collecting element and the electrode assembly, optimize the electron conduction path in the single cell, ensure the consistency of the flow path between the electrode sheets and the current collecting element at different levels in the single cell, improve the flow uniformity of the single cell, improve the overall flow performance of the single cell, improve the high-rate flow capacity of the single cell, and ultimately improve the rate performance and cycle performance of the single cell. In contrast, the dimensions of the fourth-level weld, fifth-level weld, sixth-level weld, seventh-level weld, and eighth-level weld in test examples 16-20 are significantly too large. Although they can reduce the DC internal resistance, the temperature difference between the inner and outer layers of the winding core is significantly increased, resulting in a significant reduction in the number of full-life cycle cycles.

[0113] The above steps are merely provided to help understand the method, structure, and core concept of the present application. A person skilled in the art may make several improvements and modifications to the present application without departing from the principles of the present application, and such improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A single battery, characterized in that: The single cell has an axial direction and a radial direction perpendicular to each other, and a circumferential direction around the axial direction, and the single cell includes: case; an electrode assembly, disposed in the housing; an end cover, disposed at one end of the housing in the axial direction; and a current collecting element disposed between the electrode assembly and the end cap, the current collecting element comprising: a connecting portion, a primary welding portion, and a secondary welding portion, the primary welding portion and the secondary welding portion both being disposed on the connecting portion, the primary welding portion and the secondary welding portion being spaced apart in the circumferential direction, and both being electrically connected to the electrode assembly; In the radial direction, both the primary welding portion and the secondary welding portion extend from the edge of the connecting portion toward the center of the current collecting element, and a size of the primary welding portion in the radial direction is larger than a size of the secondary welding portion in the radial direction.

2. The single cell according to claim 1, wherein: A plurality of the first-level welding parts and a plurality of the second-level welding parts are provided, and the plurality of the first-level welding parts and the plurality of the second-level welding parts are arranged at intervals and alternately in the circumferential direction.

3. The single cell according to claim 1, wherein: The flow path between the secondary welding part and the primary welding part closest to it is T mm, which satisfies: T = (2π × R0 × α) / 360°; Wherein, R0 mm is the radius of one end of the primary welding portion close to the axis, α is the angle between two adjacent primary welding portions, and satisfies: 1≤R0≤10, and 0°<α≤180°.

4. The single cell according to claim 3, wherein: The included angle α between two adjacent primary welding portions further satisfies: 18°≤α≤180°.

5. The single cell according to claim 3, wherein: The flow path between two adjacent primary welding portions is W mm, satisfying: W=T.

6. The single cell according to claim 3, wherein: The current collecting element further includes: a third-level welding portion, which is provided on the connecting portion, and the third-level welding portion is provided between the first-level welding portion and the second-level welding portion adjacent thereto; In the radial direction, the tertiary welding portion extends from the edge of the connecting portion toward the center of the current collecting element, and a size of the secondary welding portion in the radial direction is larger than a size of the tertiary welding portion in the radial direction.

7. The single cell according to claim 6, wherein: There are multiple tertiary welding parts, and a tertiary welding part is provided between each of the secondary welding parts and each of the adjacent primary welding parts.

8. The single cell according to claim 7, wherein: The current collecting element further includes: an n-1 level welding portion and an n-level welding portion, wherein the n-1 level welding portion and the n-level welding portion are both provided on the connecting portion, and the n-level welding portion is provided on both sides of the n-1 level welding portion in the circumferential direction; The angle between the first-level welding part and the n-level welding part closest to it is β n , satisfying: β n =α / 2 n-1 , n is an integer not less than 2 and satisfies: β n ≤90°.

9. The single cell according to claim 8, wherein: In the radial direction, the n-level welding portion extends from the edge of the connecting portion toward the center, and the maximum size of the n-level welding portion in the radial direction is L n mm, meet: L n =H+R0-T×360° / 2πβ n ; Wherein, H mm is the maximum dimension of the primary weld in the radial direction and satisfies: L n ≤18.

10. A battery pack, characterized in that: include: Cabinet: and The single cell according to any one of claims 1 to 9, wherein the single cell is arranged in a box.

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