Single battery and battery pack

Abstract

The invention relates to a single battery and a battery pack, and relates to the technical field of battery protection. Each single battery comprises an inner tab and an outer tab, the inner tab comprises a fixed base part and a welding extension part, the fixed base part comprises a first end part, a second end part and a folding position, the first end part is connected to the first side surface of the pole core and is adjacent to the top surface of the pole core, and the second end part is connected to the welding extension part; the welding extension part extends along the thickness direction of the pole core, the clamping groove is formed between the welding extension part and the first side surface of the pole core, and the outer pole lug extends into the clamping groove and is welded with the inner pole lug, so that the welding of the inner pole lug and the outer pole lug can be prevented from occupying too much space of the single battery, and the energy density of the single battery can be increased.

Description

Technical Field

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

[0002] Soft-pack lithium batteries usually refer to lithium batteries whose outer shells are encapsulated with aluminum-plastic film. Due to their many advantages such as light structure and weight, low mold cost, great structural flexibility, high energy density, and high core safety performance, they have been widely used in various fields such as electric vehicles, drones, smart homes, and mobile power supplies.

[0003] The existing soft-pack battery structure mainly consists of: aluminum-plastic film shell, pole group, outer pole ear, etc. The pole group includes a pole core and an inner pole ear, and the outer pole ear includes an electrode sheet and a pole ear insulating glue (injection molding integrated structure). The aluminum-plastic film is punched out of the cavity that accommodates the pole group by mold stamping. After the pole group is placed in the cavity, it is sealed by hot-pressing the edge of the aluminum-plastic film. At the same time, the insulating glue of the outer pole ear is hot-pressed and sealed during the sealing process of the aluminum-plastic film shell to achieve the sealing of the pole core. One end of the outer pole ear is fixed to the inner pole ear of the pole group by laser welding, and the other end is led to the outside of the aluminum-plastic film shell. The middle part is isolated from the aluminum-plastic film shell by the pole ear insulating glue, so as to lead out the current. The current inner pole ear extends along the length direction of the pole core and is fixed to the outer pole ear by laser welding, so as to lead the current out of the aluminum-plastic film shell. In this structure, the inner pole ear and the outer pole ear occupy more internal space of the soft-pack battery, resulting in a low overall energy density of the soft-pack battery. Summary of the invention

[0004] The embodiments of the present application provide a single cell and a battery pack, which can solve the technical problem that the inner pole ear stretches along the length direction of the pole core, the outer pole ear and the inner pole ear occupy more internal space of the single cell, resulting in low overall energy density of the single cell.

[0005] An embodiment of the present application provides a single cell battery, which includes an inner pole ear and an outer pole ear, one end of the inner pole ear is connected to the pole core, and the other end of the inner pole ear is connected to the outer pole ear; the pole core has a first side surface in its length direction, and the pole core has a top surface in its thickness direction, the inner pole ear includes a fixed base portion and a welding extension portion, the fixed base portion includes a first end, a second end and a folded position, the first end is connected to the first side surface of the pole core and is arranged adjacent to the top surface of the pole core, the second end is connected to the welding extension portion, the folded position is located between the first end and the second end, and a fifth spacing is provided between the vertex of the folded position in the thickness direction of the pole core and the top surface of the pole core, the ratio of the fifth spacing to the thickness of the pole core is 0.026-0.11, the welding extension portion extends along the thickness direction of the pole core, a clamping groove is formed between the welding extension portion and the first side surface of the pole core, and the outer pole ear extends into the clamping groove and is connected to the welding extension portion.

[0006] In some embodiments, the fifth spacing is 0.3 mm-0.6 mm, and the thickness of the pole core is 5.5 mm-11.5 mm.

[0007] In some embodiments, the outer tab includes a connected welding clamping portion and a current lead-out portion, the welding clamping portion at least partially extends into the clamping slot and is connected to the welding extension portion, and the current lead-out portion is located outside the clamping slot.

[0008] In some embodiments, the welding clamping portion extends along the thickness direction of the pole core, and the current lead-out portion extends along the length direction of the pole core.

[0009] In some embodiments, the welding clamping portion and the welding extension portion are welded by laser welding or ultrasonic welding. The welding clamping portion and the welding extension portion are welded to form a weld mark, and the weld mark is located in the middle of the welding extension portion.

[0010] In some embodiments, when the welding clamping portion extends into the clamping groove, a first distance is provided between the top of the welding clamping portion in the thickness direction of the pole core and the bottom of the clamping groove.

[0011] In some embodiments, the welding clamping portion includes an inner clamping portion, an outer clamping portion and a connecting portion, the inner clamping portion and the outer clamping portion both extend along the thickness direction of the pole core, and the connecting portion is connected between the inner clamping portion and the outer clamping portion.

[0012] In some embodiments, the inner snap-fitting portion, the outer snap-fitting portion and the connecting portion are all located in the snap-fitting slot, the connecting portion is connected to one end of the inner snap-fitting portion close to the bottom of the snap-fitting slot, and the surface of the connecting portion close to the bottom of the snap-fitting slot is a curved surface.

[0013] In some embodiments, the welding extension portion is located between the inner clamping portion and the outer clamping portion, the inner clamping portion is located in the clamping groove, and the connecting portion is located outside the clamping groove and connected to an end of the inner clamping portion away from the bottom of the clamping groove.

[0014] An embodiment of the present application also provides a battery pack, which includes the single cell of the present application.

[0015] The single cell and battery pack provided in the embodiments of the present application, the inner pole ear includes a fixed base portion and a welding extension portion, the fixed base portion includes a first end portion, a second end portion and a folded position, the first end portion is connected to the first side surface of the pole core and is arranged adjacent to the top surface of the pole core, the second end portion is connected to the welding extension portion, the welding extension portion extends along the thickness direction of the pole core, and a snap-in groove is formed between the welding extension portion and the first side surface of the pole core, the outer pole ear extends into the snap-in groove and is welded to the inner pole ear, thereby avoiding the welding of the inner pole ear and the outer pole ear from occupying too much space of the single cell, which is beneficial to increasing the energy density of the single cell.

[0016] The folded position of the inner pole ear in the embodiment of the present application is located between the first end and the second end, and a fifth spacing is provided between the vertex of the folded position in the thickness direction of the pole core and the top surface of the pole core, and the ratio of the fifth spacing to the thickness of the pole core is 0.026-0.11, thereby avoiding the top of the welding clamping part of the outer pole ear from contacting with the fixed base part, avoiding the burrs of the welding clamping part of the outer pole ear from cutting the diaphragm and pole piece of the pole core, and avoiding causing a short circuit in the pole core. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 It is a structural schematic diagram of a single cell in the prior art;

[0019] Figure 2 A schematic diagram of the overall structure of a single cell provided in Example 1 of the present application;

[0020] Figure 3 A schematic diagram of the structure of the pole core and the inner pole ear provided in Example 1 of the present application;

[0021] Figure 4 A schematic diagram of the structure of the outer tab and the tab insulation portion provided in Example 1 of the present application;

[0022] Figure 5 Partial structural cross section of a single cell provided in Example 1 of the present application Figure 1 ;

[0023] Figure 6 Partial structural cross section of a single cell provided in Example 1 of the present application Figure 2 ;

[0024] Figure 7 A partial structural cross-sectional view of a single cell provided in Example 2 of the present application;

[0025] Figure 8 This is a cross-sectional view of the local structure of a single cell provided in Example 3 of the present application.

[0026] The markings in the figure are as follows:

[0027] 90. Single cell; 91. Pole core; 92. Inner pole ear; 93. Outer pole ear; 94. Aluminum-plastic film shell;

[0028] 1. Inner pole ear; 2. Outer pole ear; 3. Pole core; 4. Welding mark; 5. Insulation;

[0029] 11. fixed base portion; 12. welding extension portion; 111. first end portion; 112. second end portion; 113. folded position; 21. welding clamping portion; 22. current lead-out portion; 211. inner clamping portion; 212. outer clamping portion; 213. connection portion;

[0030] 31. First side surface; 32. Top surface. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present application are described in detail below in conjunction with the drawings in the specification, so as to fully introduce the technical content of the present application to those skilled in the art, to illustrate that the present application can be implemented, to make the technical content disclosed in the present application clearer, and to make it easier for those skilled in the art to understand how to implement the present application. However, the present application can be embodied through many different forms of embodiments, and the protection scope of the present application is not limited to the embodiments mentioned in the text, and the description of the embodiments below is not intended to limit the scope of the present application.

[0032] The directional terms mentioned in this application, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "side", etc., are only directions in the drawings. The directional terms used in this article are used to explain and illustrate this application, and are not used to limit the scope of protection of this application.

[0033] In the drawings, components with the same structure are represented by the same numerical labels, and components with similar structures or functions are represented by similar numerical labels. In addition, for the convenience of understanding and description, the size and thickness of each component shown in the drawings are arbitrarily shown, and the present application does not limit the size and thickness of each component.

[0034] See also Figure 1 The single cell 90 in the prior art includes a pole core 91, an inner pole ear 92 and an outer pole ear 93. The inner pole ear 92 is arranged on both sides of the pole core 91 in the length direction, and the inner pole ear 92 extends along the length direction of the pole core 91. The inner pole ear 92 and the outer pole ear 93 are fixed by laser welding to achieve the connection between the inner pole ear 92 and the outer pole ear 93, so as to lead the current to the outside of the aluminum-plastic film shell 94. The inner pole ear 92 extends along the length direction of the pole core 91 and is fixed to the outer pole ear 93 by laser welding, so as to lead the current to the outside of the shell. In this structure, the inner pole ear 92 and the outer pole ear 93 occupy more internal space of the soft-pack battery, resulting in a low overall energy density of the soft-pack battery.

[0035] Example 1

[0036] See also Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6In embodiment 1 of the present application, a single cell is provided, and the single cell includes an inner pole ear 1, an outer pole ear 2, a pole core 3 and an insulating member 5.

[0037] Wherein, the pole core 3 is located in the aluminum-plastic film shell (not shown). The pole core 3 has a first side surface 61 in its length direction, and the pole core 3 has a top surface 32 in its thickness direction. The inner pole ear 1 is located in the aluminum-plastic film shell (not shown). One end of the inner pole ear 1 is connected to the pole core 3, and the other end of the inner pole ear 1 is connected to the outer pole ear 2. A part of the outer pole ear 2 is located in the aluminum-plastic film shell (not shown) and welded to the inner pole ear 1, and the other part of the outer pole ear 2 extends out of the aluminum-plastic film shell (not shown).

[0038] The inner pole ear 1 includes a fixed base portion 11 and a welding extension portion 12. The fixed base portion 11 is conical or wedge-shaped, which can achieve a more stable structure. The fixed base portion 11 includes a first end 111, a second end 112 and a folded position 113. The first end 111 is connected to the first side surface 31 of the pole core 3 and is arranged adjacent to the top surface 32 of the pole core 3, the second end 112 is connected to the welding extension portion 12, and the folded position 113 is located between the first end 111 and the second end 112. It is worth noting that the folded position 113 refers to the position where multiple inner pole ears are folded by welding.

[0039] Among them, the welding extension part 12 extends along the thickness direction of the pole core 3, and a snap-in groove 13 is formed between the welding extension part 12 and the first side surface 31 of the pole core 3. The outer pole ear 2 extends into the snap-in groove 13 and is connected to the welding extension part 12. This can avoid the welding of the inner pole ear 1 and the outer pole ear 2 occupying too much space of the single cell, which is beneficial to increase the energy density of the single cell.

[0040] Among them, a fifth spacing A is provided between the vertex of the folded position 113 in the thickness direction of the pole core 3 and the top surface 32 of the pole core 3, and the ratio of the fifth spacing A to the thickness B of the pole core 3 is 0.03-0.15. Specifically, the fifth spacing A is 0.3mm-0.6mm, and the thickness B of the pole core 3 is 5.5mm-11.5mm. In this embodiment, the ratio of the fifth spacing A to the thickness B of the pole core 3 is 0.05. Specifically, the fifth spacing A is 0.4mm, and the thickness B of the pole core 3 is 8mm. In this way, the top of the welding clamping portion 21 of the outer pole ear 2 can be prevented from contacting with the fixed base portion 11, and the burrs of the welding clamping portion 21 of the outer pole ear 2 can be prevented from cutting the diaphragm and pole piece of the pole core 3, thereby preventing the pole core 3 from short-circuiting.

[0041] Table 1 Parameters and test results of Examples 1 to 11

[0042]

[0043]

[0044] It can be seen from the data in Table 1 that: in Examples 8 to 11, the ratio A / B of the fifth spacing A to the thickness B of the pole core 3 exceeds the parameter range of this application. Specifically, the fifth spacing A of Example 8 is too small, and the ratio of the fifth spacing A to the thickness B of the pole core 3 is too small, resulting in that after the inner pole ear 1 is bent and welded during CT detection, the outermost layer of the root of the inner pole ear 1 is easy to exceed the upper end surface of the pole core 3 and reach the middle of the pole core 3 and the aluminum-plastic film shell, and the risk of damaging the inner pole ear 1 when the pole core 3 is squeezed by external force during use increases. The fifth spacing A of Example 9 is too large, and the ratio of the fifth spacing A to the thickness B of the pole core 3 is too large, resulting in a smaller first spacing E value between the top of the welding clamping portion 21 in the thickness direction of the pole core 3 and the bottom of the clamping groove 13, and the risk of the inner pole ear 1 being cut by the outer pole ear 2 increases. Among them, the thickness B of the pole core 3 of Example 10 is too large, and the ratio of the fifth spacing A to the thickness B of the pole core 3 is too small. After the inner pole ear 1 is bent and welded, the outermost layer of the root of the inner pole ear 1 is easy to exceed the upper end surface of the pole core 3 and reach the middle of the pole core 3 and the aluminum-plastic film shell. The risk of damaging the inner pole ear 1 when the pole core 3 is squeezed by external force during use increases. The thickness B of the pole core 3 of Example 11 is too small, and the ratio of the fifth spacing A to the thickness B of the pole core 3 is too large, resulting in a small first spacing E value between the top of the welding clamping portion 21 in the thickness direction of the pole core 3 and the bottom of the clamping groove 13, and the risk of the inner pole ear 1 being cut by the outer pole ear 2 increases.

[0045] It can be seen from the data in Table 1 that in Examples 1 to 7, the fifth spacing A, the thickness B of the pole core 3, and the ratio of the fifth spacing A to the thickness B of the pole core 3 do not exceed the parameter range of the present application, and the internal structure of the pole core 3 after CT detection is normal.

[0046] It is worth noting that CT testing refers to computed tomography (CT), which is an imaging method that combines X-rays and computer technology to obtain three-dimensional images of the interior of an object.

[0047] The outer pole ear 2 includes a connected welding clamping portion 21 and a current lead-out portion 22. The outer pole ear 2 can be a plane or a 90° bent structure; if the outer pole ear 2 is a plane structure, it is welded with the inner pole ear 1 and then bent to a 90° bent structure by a fixture to form the welding clamping portion 21 and the current lead-out portion 22; if the outer pole ear 2 is a 90° bent structure, the welding clamping portion 21 can be directly welded to the inner pole ear 1.

[0048] Among them, the welding clamping part 21 at least partially extends into the clamping groove 13 and is connected to the welding extension part 12, and the welding clamping part 21 extends along the thickness direction of the pole core 3. In this embodiment, the welding clamping part 21 and the welding extension part 12 are welded by laser welding or ultrasonic welding. The welding clamping part 21 and the welding extension part 12 are welded to form a weld mark 4, and the weld mark 4 is located in the middle of the welding extension part 12. The width w of the weld mark 4 is 1.0mm-1.5mm, thereby ensuring the strength and stability of the welding part between the welding clamping part 21 and the welding extension part 12, and avoiding the welding being too narrow or the material waste caused by the width of the weld mark 4 being too wide. In this embodiment, the width w of the weld mark 4 is preferably 1.2mm, and the weld mark 4 is set in the center.

[0049] There is a third spacing t between the top of the weld mark 4 and the top of the welding clamping portion 21, and the third spacing t is 0.7mm-1.0mm, which can help evenly distribute the thermal stress at the weld mark 4, reduce the risk of cracking at the weld mark 4, promote the cooling efficiency at the weld mark 4, reduce welding deformation, reduce defects such as pores and slag inclusions that may occur during welding, and thus improve the reliability of welding. In this embodiment, the third spacing t is 0.8mm.

[0050] There is a fourth spacing m between the bottom of the weld mark 4 and the bottom of the weld extension 12, and the fourth spacing m is 0.7 mm-1.0 mm, which can help evenly distribute the thermal stress at the weld mark 4, reduce the risk of cracking at the weld mark 4, promote the cooling efficiency at the weld mark 4, reduce welding deformation, reduce defects such as pores and slag inclusions that may occur during welding, and thus improve the reliability of welding. In this embodiment, the fourth spacing m is 0.75 mm.

[0051] When the welding clamping part 21 extends into the clamping groove 13, a first spacing E is provided between the top of the welding clamping part 21 in the thickness direction of the pole core 3 and the bottom of the clamping groove 13. The first spacing E is between 1 mm and 1.5 mm, thereby preventing the burrs of the welding clamping part 21 of the outer pole ear 2 from cutting the diaphragm and pole piece of the pole core 3 and causing a short circuit of the pole core 3 due to the first spacing E being too small, and preventing the thickness of the single battery from increasing due to the first spacing E being too large.

[0052] The current lead-out portion 22 is located outside the clamping groove 13 , and extends along the length direction of the pole core 3 .

[0053] The single cell further includes an insulating member 5. The insulating member 5 is disposed around the outer periphery of the outer pole ear 2, and specifically, the insulating member 5 is disposed around the outer periphery of the current lead-out portion 22. When the thickness of the pole core 3 is greater than 6.5 mm, the bottom of the insulating member 5 and the bottom of the pole core 3 have a second spacing F, and the second spacing F is 6.5-B. At this time, the bottom of the insulating member 5 is higher than the bottom of the pole core 3; when the thickness of the pole core 3 is less than 6.5 mm, the bottom of the insulating member 5 is flush with the bottom of the pole core 3.

[0054] Table 2 Comparison of space occupied by welding of inner and outer tabs of the pole core

[0055]

[0056] Please refer to Table 2. In the embodiment of the present application, the welding extension portion 12 extends along the thickness direction of the pole core 3, and a snap-in groove 13 is formed between the welding extension portion 12 and the first side surface 31 of the pole core 3. The outer pole ear 2 extends into the snap-in groove 13 and is connected to the welding extension portion 12. This can avoid the welding of the inner pole ear 1 and the outer pole ear 2 occupying too much space of the single cell, which is beneficial to increase the energy density of the single cell.

[0057] Example 2

[0058] See also Figure 7 In the second embodiment of the present application, a single cell is provided, which includes most of the technical features of the first embodiment, and the difference lies in the structure of the welding clamping part 21. The welding clamping part 21 includes an inner clamping part 211, an outer clamping part 212 and a connecting part 213. The inner clamping part 211 and the outer clamping part 212 both extend along the thickness direction of the pole core 3, and the connecting part 213 is connected between the inner clamping part 211 and the outer clamping part 212.

[0059] See also Figure 7 In this embodiment, the inner clamping part 211, the outer clamping part 212 and the connecting part 213 are all located in the clamping groove 13, and the connecting part 213 is connected to one end of the inner clamping part 211 close to the bottom of the clamping groove 13. The surface of the connecting part 213 close to the bottom of the clamping groove 13 is a curved surface, that is, the welding clamping part 21 of this embodiment is in an inverted U shape. By setting the surface of the connecting part 213 close to the bottom of the clamping groove 13 as a curved surface, the burrs of the welding clamping part 21 of the outer pole ear 2 are prevented from cutting the diaphragm and pole piece of the pole core 3, and preventing the pole core 3 from short-circuiting.

[0060] In the embodiment of the present application, the welding extension portion 12 extends along the thickness direction of the pole core 3, and a snap-in groove 13 is formed between the welding extension portion 12 and the first side surface 31 of the pole core 3. The outer pole ear 2 extends into the snap-in groove 13 and is connected to the welding extension portion 12. This can avoid the welding of the inner pole ear 1 and the outer pole ear 2 occupying too much space of the single cell, which is beneficial to increase the energy density of the single cell.

[0061] Example 3

[0062] See also Figure 8 In the third embodiment of the present application, a single cell is provided, which includes most of the technical features of the first embodiment, and the difference lies in the structure of the welding clamping part 21. The welding clamping part 21 includes an inner clamping part 211, an outer clamping part 212 and a connecting part 213. The inner clamping part 211 and the outer clamping part 212 both extend along the thickness direction of the pole core 3, and the connecting part 213 is connected between the inner clamping part 211 and the outer clamping part 212.

[0063] See also Figure 8 In this embodiment, the welding extension part 12 is located between the inner clamping part 211 and the outer clamping part 212, the inner clamping part 211 is located in the clamping groove 13, and the connecting part 213 is located outside the clamping groove 13 and connected to an end of the inner clamping part 211 away from the groove bottom of the clamping groove 13. That is, the welding clamping part 21 is U-shaped, and thus, by welding the welding extension part 12 between the inner clamping part 211 and the outer clamping part 212, the connection stability of the welding extension part 12 and the welding clamping part 21 is improved.

[0064] In addition, in order to facilitate the welding of the welding extension part 12 and the welding clamping part 21, welding through holes can be set on the external clamping part 212 and the welding extension part 12. During welding, the welding rod passes through the welding through hole to realize the welding of the welding extension part 12 and the internal clamping part 211, and even the welding rod passes through the welding through hole to realize the welding of the welding extension part 12, the external clamping part 212 and the internal clamping part 211 together.

[0065] In the embodiment of the present application, the welding extension portion 12 extends along the thickness direction of the pole core 3, and a snap-in groove 13 is formed between the welding extension portion 12 and the first side surface 31 of the pole core 3. The outer pole ear 2 extends into the snap-in groove 13 and is connected to the welding extension portion 12. This can avoid the welding of the inner pole ear 1 and the outer pole ear 2 occupying too much space of the single cell, which is beneficial to increase the energy density of the single cell.

[0066] Example 4

[0067] In the fourth embodiment of the present application, a battery pack is also provided, and the battery pack includes the above-mentioned single cell. The single cell and the battery pack provided in the embodiment of the present application extend along the thickness direction of the pole core 3 through the welding extension 12, and a clamping groove 13 is formed between the welding extension 12 and the first side surface 31 of the pole core 3, and the outer pole ear 2 extends into the clamping groove 13 and is connected to the welding extension 12, thereby avoiding that the welding of the inner pole ear 1 and the outer pole ear 2 occupies too much space of the single cell, which is conducive to increasing the energy density of the single cell.

[0068] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0069] The above is a detailed introduction to a single cell and a battery pack provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A single cell battery, characterized in that: It comprises an inner pole ear and an outer pole ear, one end of the inner pole ear is connected to the pole core, and the other end of the inner pole ear is connected to the outer pole ear; The pole core has a first side surface in its length direction, and the pole core has a top surface in its thickness direction. The inner pole ear includes a fixed base portion and a welding extension portion. The fixed base portion includes a first end, a second end, and a retracted position. The first end is connected to the first side surface of the pole core and is arranged adjacent to the top surface of the pole core. The second end is connected to the welding extension portion. The retracted position is located between the first end and the second end. A fifth spacing is provided between the vertex of the retracted position in the thickness direction of the pole core and the top surface of the pole core. The ratio of the fifth spacing to the thickness of the pole core is 0.026-0. .

11. The welding extension portion extends along the thickness direction of the pole core, and a clamping groove is formed between the welding extension portion and the first side surface of the pole core. The outer pole ear extends into the clamping groove and is connected to the welding extension portion.

2. The single cell according to claim 1, characterized in that: The fifth spacing is 0.3mm-0.6mm, and the thickness of the pole core is 5.5mm-11.5mm.

3. The single cell according to claim 1, characterized in that: The outer pole ear comprises a connected welding clamping portion and a current lead-out portion, wherein the welding clamping portion at least partially extends into the clamping slot and is connected to the welding extension portion, and the current lead-out portion is located outside the clamping slot.

4. The single cell according to claim 3, characterized in that: The welding clamping portion extends along the thickness direction of the pole core, and the current lead-out portion extends along the length direction of the pole core.

5. The single cell according to claim 3, characterized in that: The welding method of the welding clamping part and the welding extension part is laser welding or ultrasonic welding. The welding clamping part and the welding extension part are welded to form a welding mark, and the welding mark is located in the middle of the welding extension part.

6. The single cell according to claim 3, characterized in that: When the welding clamping portion extends into the clamping groove, a first distance is provided between the top of the welding clamping portion in the thickness direction of the pole core and the bottom of the clamping groove.

7. The single cell according to claim 3, characterized in that: The welding clamping part comprises an inner clamping part, an outer clamping part and a connecting part. The inner clamping part and the outer clamping part both extend along the thickness direction of the pole core. The connecting part is connected between the inner clamping part and the outer clamping part.

8. The single cell according to claim 7, characterized in that: The inner clamping part, the outer clamping part and the connecting part are all located in the clamping groove, the connecting part is connected to one end of the inner clamping part close to the bottom of the clamping groove, and the surface of the connecting part close to the bottom of the clamping groove is a curved surface.

9. The single cell according to claim 7, characterized in that: The welding extension portion is located between the inner clamping portion and the outer clamping portion, the inner clamping portion is located in the clamping groove, and the connecting portion is located outside the clamping groove and connected to an end of the inner clamping portion away from the bottom of the clamping groove.

10. A battery pack, characterized in that: A single cell comprising any one of claims 1 to 9.

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