Single battery and battery pack
By locally hardening the electrode ears of the lithium-ion battery, divided into hardened parts and main parts, the problem of easy bending of the electrode ears during winding is solved, and the yield and production efficiency of the battery cell are improved.
Patent Information
- Application Number
- CN202420807992.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-16
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2034-04-16
AI Technical Summary
Existing lithium-ion batteries are prone to bend during winding, resulting in low production efficiency and yield, and short-circuit safety hazards.
By hardening the pole ear part, it is divided into a hardened part and a main body part. The hardness of the hardened part is greater than the main body part, which improves the overall hardness of the pole ear, reduces the risk of bending, and improves the welding yield of the pole ear bundle through welding optimization.
It improves the bending resistance of the electrode ear, reduces the defective rate of the electrode ear welding, improves the yield rate of the battery cell, and reduces production costs.
Smart Images
Figure CN222995456U_ABST
Abstract
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] With the rapid development of new energy, power lithium-ion batteries as core components of new energy vehicles have also received great attention, so it is crucial to develop safer and more efficient lithium-ion batteries. In order to pursue higher energy density, thinner foils are used to prepare pole pieces to improve the energy density of the battery cell, but thinner pole tabs are more likely to be folded and damaged during winding, and even the pole tabs may be rolled into the battery cell, seriously affecting production efficiency and yield, and there is a safety hazard of piercing the diaphragm and causing internal short circuits in the battery.
[0003] Therefore, it is necessary to improve the existing technology. Utility Model Content
[0004] The utility model aims to solve at least one of the technical problems existing in the prior art and provides a single cell and a battery pack.
[0005] According to one aspect of the present application, the present application provides a single cell battery, comprising a shell, a cover body and a battery cell, the shell having a accommodating cavity; the cover body covers the shell to close the accommodating cavity; the battery cell is accommodated in the accommodating cavity, the battery cell comprises a battery cell body and a pole tab bundle, the pole tab bundle is connected to the battery cell body, the pole tab bundle comprises a plurality of pole tabs arranged in a stacked manner, and adjacent pole tabs in the same pole tab bundle are welded; the pole tab comprises a hardened portion and a main body portion connected to the hardened portion, and the main body portions of adjacent pole tabs in the same pole tab bundle are welded; the hardness of the hardened portion is greater than the hardness of the main body portion; in the thickness direction of the pole tab, the thickness of the hardened portion is less than the thickness of the main body portion.
[0006] Furthermore, along the thickness direction of the pole ear, the main body has a first surface and a second surface relative to each other, and the hardened portion has a third surface and a fourth surface relative to each other; one of the third surface and the fourth surface is coplanar with the first surface or the second surface, and the other is located between the first surface and the second surface.
[0007] Optionally, along the thickness direction of the tab, the main body has a first surface and a second surface opposite to each other, and the hardened portion has a third surface and a fourth surface opposite to each other; the third surface and the fourth surface are both located between the first surface and the second surface.
[0008] Furthermore, the shortest distance from the hardened portion to the outer edge of the tab is d mm, satisfying: 1≤d≤6.
[0009] Further, in the thickness direction of the tab, the size of the main body portion is H1 μm, and the size of the hardened portion is H2 μm, satisfying: 1 / 3 ≤ H2 / H1 ≤ 2 / 3.
[0010] Further, the hardness of the main body portion is Q1, and the hardness of the hardened portion is Q2, satisfying:
[0011] 1.5 ≤ Q2 / Q1 ≤ 3.
[0012] Further, in the thickness direction of the tab, the main body portion has opposite first and second surfaces, and the hardened portion has opposite third and fourth surfaces; in the flattened state of the same tab, the orthographic projection area of a single hardened portion on the plane where the first surface is located is S1 mm 2 , the total orthographic projection area of all the hardened portions on the plane where the first surface is located is S2 mm 2 , and the total orthographic projection area of the tab on the plane where the first surface is located is S mm 2 , satisfying: 1 / 15 ≤ S1 / S ≤ 1 / 3, 1 / 3 ≤ S2 / S ≤ 3 / 4.
[0013] Further, in the flattened state of the same tab, the edge of the hardened portion has a positioning edge close to the battery cell main body, a welding mark is formed on the surface of the main body portion, the extending direction of the welding mark is the same as the extending direction of the positioning edge, and the welding mark is arranged close to the positioning edge.
[0014] Further, the distance from any position of the positioning edge to the battery cell main body is L mm; in the thickness direction of the tab, the size of the battery cell main body is M mm, satisfying: 1 ≤ L - M ≤ 3 or 1 ≤ L - 0.5M ≤ 3.
[0015] Further, in the thickness direction of the tab, the main body portion has opposite first and second surfaces, and the hardened portion has opposite third and fourth surfaces; the orthographic projection of the hardened portion on the plane where the first surface is located is an equilateral triangle, and there are at least three, and two adjacent hardened portions are spaced apart; the orthographic projection of the tab on the plane where the first surface is located is an isosceles trapezoid or a square.
[0016] According to another aspect of the present application, there is provided a battery pack including any one of the above-mentioned single cells.
[0017] The beneficial effects of the present application are as follows: By locally hardening the tab, the tab is divided into a hardened part and a main body part, and the hardness of the hardened part is greater than that of the main body part, so as to improve the overall hardness of the tab, enhance the anti-bending ability of the tab, and since the thickness of the hardened part is less than that of the main body part, when multiple tabs with the same polarity are stacked, the gap between two adjacent stacked tabs is smaller, and the main body parts are in contact with each other. During the process of welding into a tab bundle, it is not easy to occur false soldering or tab explosion, effectively improving the qualified rate of tab welding, thereby improving the qualified rate of the battery cell and reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The following will, by describing in detail the specific embodiments of the present application in conjunction with the drawings, make the technical solutions and other beneficial effects of the present application obvious.
[0019] Figure 1 is a schematic diagram of a single battery provided by an embodiment of the present application.
[0020] Figure 2 is a schematic diagram of a battery cell provided by an embodiment of the present application.
[0021] Figure 3 is Figure 2 an enlarged view of part A in
[0022] Figure 4 is Figure 2 a side view of
[0023] Figure 5 is a cross-sectional view of a tab provided by an embodiment of the present application.
[0024] Figure 6 is a cross-sectional view of another tab provided by an embodiment of the present application.
[0025] Figure 7 is a cross-sectional view of another tab provided by an embodiment of the present application.
[0026] Figure 8 is a schematic diagram of another battery cell provided by an embodiment of the present application.
[0027] Figure 9 is a schematic diagram of another battery cell provided by an embodiment of the present application.
[0028] Figure 10 is a schematic diagram of another battery cell provided by an embodiment of the present application.
[0029] Figure 11 is a schematic diagram of another battery cell provided by an embodiment of the present application.
[0030] Figure 12 is a schematic diagram of a flattened state of a battery cell provided by an embodiment of the present application.
[0031] In the figure:
[0032] 10. Housing
[0033] 20. Battery cell; 21. Battery cell body; 22. Tab bundle; 221. Tab; 2211. Hardened part; 22111. Third surface; 22112. Fourth surface; 2212. Main body part; 22121. First surface; 22122. Second surface; 2213. Positioning edge
[0034] 30. Cover
[0035] 40. Welding mark Detailed implementation manners
[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.
[0037] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection, an electrical connection, or a communication with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0038] To solve the technical problem that the tabs of the battery cell are easily bent during winding in the prior art, an embodiment of the present application provides a single cell battery, including a housing, a cover, and a battery cell. The housing has a receiving cavity; the cover covers the housing to close the receiving cavity; the battery cell is received in the receiving cavity. The battery cell includes a battery cell body and a tab bundle. The tab bundle is connected to the battery cell body. The tab bundle includes a plurality of tabs stacked on top of each other, and adjacent tabs in the same tab bundle are welded to each other; each tab includes a hardened part and a main body part connected to the hardened part, and the main body parts of adjacent tabs in the same tab bundle are welded to each other; the hardness of the hardened part is greater than that of the main body part; in the thickness direction of the tab, the thickness of the hardened part is less than that of the main body part. The following is a detailed description.
[0039] Refer to Figure 1 and Figure 2, in one embodiment, the single cell includes a housing 10, a cover 30, and an electrode assembly 20. The housing 10 has a receiving cavity (not labeled in the figure), which is used to receive the electrode assembly 20. The cover 30 is closed on the housing 10 to close the receiving cavity. The electrode assembly 20 includes an electrode body 21 and an ear bundle 22. The ear bundle 22 is connected to the electrode body 21. The ear bundle 22 includes a plurality of stacked ears 221, and adjacent ears 221 are connected by welding.
[0040] It should be noted that the electrode assembly 20 includes a positive electrode plate, a negative electrode plate, and a separator. The separator is used to isolate the positive electrode plate and the negative electrode plate to prevent short circuit between the positive electrode plate and the negative electrode plate. The positive electrode plate, the negative electrode plate, and the separator form the electrode assembly 20 through a conventional winding process, or the positive electrode plate, the separator, and the negative electrode plate form the electrode assembly 20 through a conventional stacking process. The positive electrode plate includes a positive electrode plate body and a positive electrode tab connected to the edge of the positive electrode plate body. The negative electrode plate includes a negative electrode plate body and a negative electrode tab connected to the edge of the negative electrode plate body. In the wound or stacked electrode assembly 20 (as shown in Figure 2 and Figure 4 ), the positive electrode plate body, the separator, and the negative electrode plate body constitute the electrode body 21; the ear bundle 22 includes a positive ear bundle and a negative ear bundle. The positive ear bundle is the positive electrode tab on the positive electrode plate. After the positive electrode plate is wound or stacked, the positive electrode tabs are stacked, and then a plurality of stacked positive electrode tabs are welded to form a positive ear bundle; the negative ear bundle is the negative electrode tab on the negative electrode plate. After the negative electrode plate is wound or stacked, the negative electrode tabs are stacked, and then a plurality of stacked negative electrode tabs are welded to form a negative ear bundle. The description of the above ears 221 (positive electrode tabs or negative electrode tabs) in this application is in the state where the electrode assembly 20 is wound (as shown in Figure 2 and Figure 4 ) or the electrode assembly 20 is unfolded to a flat state (as shown in Figure 12 ), and at this time the ears 221 are in a flattened state; at the same time, the above single cell includes, but is not limited to, lithium-ion secondary batteries, sodium lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, etc., and the embodiments of the present disclosure do not limit this.
[0041] Referring to Figure 3 and Figure 5 , in one embodiment, the above ear 221 includes a hardening portion 2211 and a main body portion 2212. In the same ear bundle 22, adjacent ears 221 are welded between the main body portions 2212. The hardness of the hardening portion 2211 is greater than that of the main body portion 2212. By the difference in hardness between the hardening portion 2211 and the main body portion 2212, the overall anti-bending ability of the ear 221 is improved, and the ear 221 is prevented from being bent during the winding process of the electrode assembly 20; along the thickness direction of the ear 221, the size of the hardening portion 2211 is smaller than that of the main body portion 2212 (that is, Figure 5In a perspective view, the thickness of the hardened portion 2211 is less than that of the main body portion 2212). With such a setting, the centrifugal force of the tab 221 during the winding process of the battery cell 20 can be effectively reduced, further avoiding the bending of the tab 221, which is beneficial to improving the overall anti-bending ability of the tab 221. In some embodiments, the hardened portion 2211 is formed by laser treating a local area of the tab 221, so that a part of the tab 221 becomes denser and harder under the action of the laser compared to the un-laser-treated part. For example, one surface of the tab 221 is divided into several regions, and some of these regions are laser-treated. When laser-treating, spaced-apart regions among several regions are selected for treatment, so that the hardened portions 2211 are formed on the tab 221 at intervals, and the regions between the hardened portions 2211 arranged at intervals form the main body portion 2212 because they are not laser-treated. In addition, when two adjacent tabs 221 in the same tab bundle 22 are welded, the main body portions 2212 of the two adjacent tabs 221 are mutually bonded and welded. The above-mentioned main body portions 2212 are mutually abutted, and it is not easy to have poor soldering or the tab 221 exploding, effectively improving the qualified rate of tab 221 soldering.
[0042] Further, along the thickness direction of the tab 221, the main body portion 2212 has opposite first surface 22121 and second surface 22122, and the hardened portion 2211 has opposite third surface 22111 and fourth surface 22112. In this embodiment, when the tab 221 is in a flattened state, the fourth surface 22112 and the second surface 22122 are coplanar, and the third surface 22111 is located between the first surface 22121 and the second surface 22122 (as Figure 5 shown). With such a setting, it is ensured that the hardened portion 2211 does not protrude from the main body portion 2212, ensuring the flatness of the first surface 22121 and the second surface 22122 of the main body portion 2212, which is beneficial to the close fitting between adjacent tabs 221 during the soldering of the tabs 221. During the process of welding the tabs into a tab bundle, it is not easy to have poor soldering or the tab exploding, improving the finished product quality.
[0043] It should be noted that in some embodiments (when the tab 221 is in a flattened state), it is also possible that the third surface 22111 and the first surface 22121 are coplanar, and the fourth surface 22112 is located between the first surface 22121 and the second surface 22122 (no schematic diagram is given). Such a setting can also ensure the flatness of the tab 221, ensure the tight fit between adjacent tabs 221, improve the flatness of the tab bundle 22, and it is not easy to have false soldering or tab explosion during the process of welding into a tab bundle, thus improving the product quality. The main body portion 2212 surrounds the hardened portion 2211, ensuring the integrity of the tab 221. In this embodiment, the positive projection of the hardened portion 2211 on the plane where the first surface 22121 is located is in an equilateral triangle shape. The equilateral triangle structure is stable, further improving the anti-bending ability of the tab 221, and the structure is more stable. And in order for the hardened portion 2211 to cover the tab 221 as much as possible, at least three hardened portions 2211 are provided, and five are set in this embodiment (as Figure 2 shown), and the adjacent hardened portions 2211 are arranged at intervals. In other embodiments, the hardened portion 2211 can be set in other quantities and other arrangement forms (as Figures 8 - 11 shown), the quantity can be three, six, etc., which will not be elaborated here. In addition, the positive projection of the tab 221 on the plane where the first surface 22121 is located is in an isosceles trapezoid shape, which can further improve the anti-bending ability of the tab 221. In some embodiments, the positive projection of the tab 221 on the plane where the first surface 22121 is located can also be any other shape, which can be set according to actual use requirements. For example, the positive projection of the tab 221 on the plane where the first surface 22121 is located can be a square (such as the rectangle shown in Figure 8 and Figure 9 ), etc., which will not be elaborated here.
[0044] Refer to Figure 6 , in an embodiment, both the third surface 22111 and the fourth surface 22112 are located between the first surface 22121 and the second surface 22122. Such a setting can ensure that when adjacent tabs 221 are welded, the tabs 221 fit more tightly, and it is not easy to have false soldering or tab explosion during the process of welding into a tab bundle, reducing the occurrence of welding defects.
[0045] It should be noted that in the embodiment shown in Figure 6 , the hardened portion 2211 of the tab 221 can be hardened by laser. In actual production, there will be slight wrinkles in the hardened part (that is, there will be slight wrinkles on the surface of the hardened portion 2211). Through Figure 6In the illustrated embodiment, laser treatment is performed on both the first surface 22121 and the second surface 22122 of the tab 221 to form a hardened portion 2211 in a local area of the tab 221, which can avoid adverse effects of wrinkles on the surface of the hardened portion 2211 on the adhesion between adjacent tabs 221. At the same time, this setting can ensure that the stress difference on both sides of the tab 221 is small, further improving the anti-bending ability of the tab 221. In some embodiments, the hardened portion 2211 can be formed by other production methods, which will not be elaborated here; in addition, in some embodiments, the above-mentioned third surface 22111 can also protrude from the first surface 22121 ( Figure 7 viewing angle), and the above-mentioned fourth surface 22112 is located between the above-mentioned first surface 22121 and the second surface 22122. As in the Figure 7 illustrated embodiment, it will not be elaborated here.
[0046] Please continue to refer to Figure 2 and Figure 3 . In some embodiments, in the flattened state of the same tab 221, the edge of the hardened portion 2211 has a positioning edge 2213 close to the cell main body 21, and a welding mark 40 is formed on the surface of the main body portion 2212. The extending direction of the welding mark 40 is the same as the extending direction of the positioning edge 2213, and at the same time, the welding mark 40 is arranged close to the positioning edge 2213. Through the positioning edge 2213 formed by the edge of the hardened portion 2211, the welding mark 40 can be positioned, and welding can be performed according to the positioning edge 2213 during the welding operation.
[0047] It should be noted that according to different design requirements of the cell 20, the position of the above-mentioned positioning edge 2213 is uncertain. After the tabs 221 with the same polarity are welded to form a tab bundle 22, during the subsequent installation of the cell 20, the above-mentioned tab bundle 22 will not be redundant; in actual production, the welding position between the tabs 221 with the same polarity cannot be determined. After the tabs 221 with the same polarity are welded to form a tab bundle 22, the distance from the welding mark 40 to the cell main body 21 is uncontrollable. After the tab bundle 22 is connected to the cover 30, the tab bundle 22 needs to be bent. During the bending process, due to the uncertainty of the position of the above-mentioned welding mark 40, the above-mentioned tab bundle 22 will be redundant (when the distance from the welding mark 40 to the cell main body 21 is too large, the tab 221 will be inserted reversely into the cell main body 21) or the tab bundle 22 will be torn and damaged after bending (when the distance from the welding mark 40 to the cell main body 21 is too small, the tab bundle 22 is subjected to tension). Through the setting of the above-mentioned positioning edge 2213, the position of the welding mark 40 can be determined to meet the use requirements of the cell 20, improving the welding efficiency and ensuring the safe use of the cell 20 at the same time.
[0048] In one embodiment, in the flattened state of the same tab 221, the shortest distance from the hardened portion 2211 to the outer edge of the tab 221 is d mm, where d satisfies: 1 ≤ d ≤ 6, such as 1, 2, 3, 4, 5, 6, etc.; in the thickness direction of the tab 221, the thickness dimension of the main body portion 2212 is H1 μm, and the thickness dimension of the hardened portion 2211 is H2 μm, satisfying: 1 / 3 ≤ H2 / H1 ≤ 2 / 3, such as 1 / 3, 5 / 9, 2 / 3, etc.; the hardness of the main body portion 2212 is Q1 Hv, and the hardness of the hardened portion 2211 is Q2 Hv, where Hv is the Vickers hardness unit, satisfying: 1.5 ≤ Q2 / Q1 ≤ 3, such as: 1.5, 2, 3, etc.; the orthographic projection area of a single hardened portion 2211 on the plane where the first surface 22121 is located is S1 mm 2 , the total orthographic projection area of all the hardened portions 2211 in one tab 221 on the plane where the first surface 22121 is located is S2 mm 2 , the total orthographic projection area of the tab 221 on the plane where the first surface 22121 is located is S mm 2 , satisfying: 1 / 15 ≤ S1 / S ≤ 1 / 3, 1 / 3 ≤ S2 / S ≤ 3 / 4, S1 / S such as 1 / 15, 1 / 12, 2 / 9, 5 / 36, 3 / 20, 5 / 18, 1 / 3, etc., S2 / S such as 1 / 3, 5 / 12, 5 / 9, 25 / 36, 3 / 4, etc.; in this way, in this embodiment, by reasonably setting the dimensions and parameters of the main body portion 2212 and the hardened portion 2211, it is possible to ensure that the tab 221 has sufficient anti-bending ability and prevent the tab 221 from being folded over during the winding of the battery cell 20, affecting the yield and use safety of the battery cell 20.
[0049] In one embodiment, the distance from any position of the positioning edge 2213 to the battery cell main body 21 is L mm, and along the thickness direction of the tab 221, the dimension of the battery cell main body 21 is M mm, satisfying: 1 ≤ L - M ≤ 3 or 1 ≤ L - 0.5M ≤ 3, L - M such as 1, 2, 3, etc., L - 0.5M such as 1, 2, 3, etc.; in this way, in this embodiment, by reasonably setting the position of the positioning edge 2213 (i.e., the welding mark 40), it is effectively avoided that the tab 221 is too long or the tab 221 is torn after being bent.
[0050] The following evaluates the technical solutions provided in the embodiments of the present application in combination with specific embodiments.
[0051] Embodiments 1 to 33 are provided. It should be noted that the provided embodiments use a copper foil with H1 = 4.5 μm, S = 180 mm 2Verification was carried out on the trapezoidal tab 221 with [specific condition not provided] and on the core with M = 23 mm. In Examples 1 to 6 and Examples 9 to 33, 1 ≤ d ≤ 6 is satisfied, while in Examples 7 and 8, 1 ≤ d ≤ 6 is not satisfied. In Examples 1 to 13 and Examples 15 to 33, 1 / 15 ≤ S1 / S ≤ 1 / 3 is satisfied, while in Example 14, 1 / 15 ≤ S1 / S ≤ 1 / 3 is not satisfied; in Examples 1 to 13 and Examples 16 to 33, 1 / 3 ≤ S2 / S ≤ 3 / 4 is satisfied, while in Examples 14 and 15, 1 / 3 ≤ S2 / S ≤ 3 / 4 is not satisfied. In Examples 1 to 21 and Examples 24 to 33, 1 / 3 ≤ H2 / H1 ≤ 2 / 3 is satisfied, while in Examples 22 and 23, 1 / 3 ≤ H2 / H1 ≤ 2 / 3 is not satisfied. In Examples 1 to 26, 1 ≤ L - M ≤ 3 is satisfied, while in Examples 27 and 28, 1 ≤ L - M ≤ 3 is not satisfied. In Examples 29 to 31, 1 ≤ L - 0.5M ≤ 3 is satisfied, while in Examples 32 and 33, 1 ≤ L - 0.5M ≤ 3 is not satisfied. In Examples 1 to 21 and Examples 24 to 33, 1.5 ≤ Q2 / Q1 ≤ 3 is satisfied, while in Examples 22 and 23, 1.5 ≤ Q2 / Q1 ≤ 3 is not satisfied. For specific parameters, see Table 1, and for specific test results, see Table 2.
[0052] Table 1
[0053]
[0054]
[0055]
[0056] Table 2
[0057]
[0058]
[0059] Combined with the analysis of Table 1 and Table 2, it can be seen that by setting the position of the positioning edge 2213 (i.e., the welding mark 40), the elongation of the tab 221 or the tearing after the tab 221 is bent is effectively avoided, and by setting the dimensions and parameters of the main body part 2212 and the hardening part 2211, it is possible to ensure that the tab 221 has sufficient anti-bending ability to prevent the tab 221 from being folded and damaged during the winding of the battery cell 20. The data in Table 2 can intuitively show that through reasonable settings, the yield rate is improved and the production cost is reduced.
[0060] It should be noted that the number of hardening parts 2211 in Examples 1 to 15 and Examples 19 to 33 is 5. In Example 15, S2 = 150 mm 2, it does not satisfy 1 / 3 ≤ S2 / S ≤ 3 / 4. Therefore, overall, the value of S1 in Example 15 also does not meet the usage requirements; the number of hardening parts 2211 in Examples 16 to 18 is 2; in addition, when 1 ≤ L - M ≤ 3, it is a full tab Figure 4 (in the perspective, when the tabs 221 cover the battery cell main body 21 from left to right, it is a full tab) the examples of battery cells. Therefore, Examples 1 to 28 are all the example data of full tab battery cells. When 1 ≤ L - 0.5M ≤ 3, it is a half tab Figure 4 (in the perspective, when the tabs 221 cover half of the battery cell main body 21 from left to right, it is a half tab, and no schematic diagram is given) the examples of battery cells. Therefore, Examples 29 to 33 are all the example data of half tab battery cells. From Examples 19 to 23, it can be seen that the smaller the value of H2, the denser the hardening part 2211 is laser-treated, and the higher the hardness of the hardening part 2211. If H2 is too small, the hardening part 2211 is prone to becoming brittle, resulting in the risk of tab cracking and damage. Therefore, when the relationship between H2 and H1 is 1 / 3 ≤ H2 / H1 ≤ 2 / 3, the yield rate of the tabs of the single battery is relatively high. In some embodiments, other treatment methods can also be used for hardening, not limited to this. In addition, it should be noted that Examples 1 to 33 in Table 1 correspond to Examples 1 to 33 in Table 2 one by one. For example, the specific parameters of Example 1 in Table 1 correspond to the test results of Example 1 in Table 2, and the same is true for Examples 2 to 33, which will not be elaborated here.
[0061] In addition, it should be noted that the detection methods and purposes of the technical parameters in Table 2 are as follows: Detect the number of folded tab ears 221. After the winding of the battery cell 20 is completed, visual inspection is carried out. When the hardening strength and hardening area of the hardening part 2211 are insufficient, it is easy to cause the tab ear 221 to sag and fold; Detect the number of damaged tab ears 221. Still, after the winding of the battery cell 20 is completed, visual inspection is carried out. When the hardening strength and hardening area of the tab ear 221 exceed the upper and lower limits, the tab ear 221 is prone to damage; Detect the number of redundant tab ears 221. After ultrasonic welding (welding multiple tab ears 221 of the same polarity into a tab ear bundle 22), detect whether the root of the tab ear 221 is loose. The welding mark 40 is far from the root of the tab ear 221 (the connection between the tab ear 221 and the battery cell body 21, the same below). After assembling into a battery, it causes the tab ear 221 to be redundant; Detect the number of cracked tab ears 221. Detect by using CT. When the distance between the welding mark 40 and the root of the tab ear 221 exceeds the upper and lower limits, it is easy to cause the tab ear 221 to crack; Detect the number of tab ears 221 with Hi-pot failure. The battery cell 20 after hot pressing has a certain voltage. Measure its resistance. If the resistance is less than 1 MΩ, it is determined as Hi-pot failure. The resistance can be detected by measuring tools such as a resistance meter, which will not be elaborated here. Metal chips from the folded or damaged tab ear 221 enter the core. After hot pressing, it is easy to pierce the diaphragm and cause Hi-pot failure; Detect the number of purple spots on the tab ear 221. After fully charging the battery cell 20, check the state of the electrode sheet. The folded tab ear 221 is inserted into the core, hindering the conduction of lithium ions and causing purple spots; K value. After the battery cell 20 stands for a period of time, measure the ratio of the voltage drop to the time. The voltage drop and time can be measured by a voltage meter and a stopwatch, which will not be elaborated here. The folded tab ear 221 will enter the core. The folded tab ear 221 contacts the electrode sheet of the opposite electric property (for example, the negative tab ear contacts the positive electrode sheet after folding), resulting in internal short circuit, accelerated self-discharge, and an increase in the k value. The redundant tab ear 221 being inserted into the core and contacting the electrode sheet will also cause an increase in the K value (Note: The K value requirement is K ≤ 0.02 mV / h). The specific steps are as follows: After the winding of the battery cell 20 is completed, observe the number of folded and damaged tab ears 221 through visual inspection. After hot pressing, pick out the battery cell cores with Hi-pot failure. The remaining battery cell cores continue with ultrasonic welding, and visually inspect the battery cell cores with redundant tab ears 221. Subsequently, assemble them into the battery cell 20 (except for the battery cell cores with Hi-pot failure, the others are normally assembled into the battery cell 20), measure the K value, use CT to detect the cracking of the tab ear 221, and disassemble the battery cell 20 to observe the purple spots.
[0062] On the other hand, the present application also provides a battery pack, including any one of the foregoing single cells.
[0063] The above has provided a detailed introduction to the single battery and battery pack of the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.
Claims
1. A single cell battery, characterized in that: include: A housing (10) having a receiving cavity; A cover body (30) is covered on the housing (10) to close the accommodating cavity; and A battery cell (20) is accommodated in the accommodation cavity, the battery cell (20) comprising a battery cell body (21) and a pole lug bundle (22), the pole lug bundle (22) being connected to the battery cell body (21), the pole lug bundle (22) comprising a plurality of pole lugs (221) stacked in layers, and adjacent pole lugs (221) in the same pole lug bundle (22) being welded; The pole lug (221) comprises a hardened portion (2211) and a main portion (2212) connected to the hardened portion (2211); the main portions (2212) of adjacent pole lugs (221) in the same pole lug bundle (22) are welded; the hardness of the hardened portion (2211) is greater than the hardness of the main portion (2212); and in the thickness direction of the pole lug (221), the thickness of the hardened portion (2211) is less than the thickness of the main portion (2212).
2. The single cell according to claim 1, characterized in that: Along the thickness direction of the pole ear (221), the main body (2212) has a first surface (22121) and a second surface (22122) that are opposite to each other, and the hardened portion (2211) has a third surface (22111) and a fourth surface (22112) that are opposite to each other; One of the third surface (22111) and the fourth surface (22112) is coplanar with the first surface (22121) or the second surface (22122), and the other is located between the first surface (22121) and the second surface (22122).
3. The single cell according to claim 1, characterized in that: Along the thickness direction of the pole ear (221), the main body (2212) has a first surface (22121) and a second surface (22122) that are opposite to each other, and the hardened portion (2211) has a third surface (22111) and a fourth surface (22112) that are opposite to each other; The third surface (22111) and the fourth surface (22112) are both located between the first surface (22121) and the second surface (22122).
4. The single cell according to claim 1, characterized in that: The shortest distance from the hardened portion (2211) to the outer edge of the tab (221) is d mm, satisfying: 1≤d≤6.
5. The single cell according to claim 1, characterized in that: Along the thickness direction of the pole lug (221), the size of the main body (2212) is H1 μm, and the size of the hardened portion (2211) is H2 μm, satisfying the following: 1 / 3≤H2 / H1≤2 / 3.
6. The single cell according to claim 1, characterized in that: The hardness of the main body (2212) is Q1, and the hardness of the hardened portion (2211) is Q2, satisfying: 1.5≤Q2 / Q1≤3.
7. The single cell according to claim 1, characterized in that: Along the thickness direction of the pole ear (221), the main body (2212) has a first surface (22121) and a second surface (22122) that are opposite to each other, and the hardened portion (2211) has a third surface (22111) and a fourth surface (22112) that are opposite to each other; When the same pole lug (221) is in a flattened state, the orthographic projection area of a single hardened portion (2211) on the plane where the first surface (22121) is located is S1 mm 2 The total area of the orthographic projections of all the hardened portions (2211) on the plane where the first surface (22121) is located is S2 mm 2 The total area of the positive projection of the tab (221) on the plane where the first surface (22121) is located is S mm 2 , satisfying: 1 / 15≤S1 / S≤1 / 3, 1 / 3≤S2 / S≤3 / 4.
8. The single cell according to claim 1, characterized in that: When the same pole lug (221) is in a flattened state, the edge of the hardened portion (2211) has a positioning edge (2213) close to the battery cell body (21), and a weld mark (40) is formed on the surface of the main body (2212), the extension direction of the weld mark (40) is the same as the extension direction of the positioning edge (2213), and the weld mark (40) is arranged close to the positioning edge (2213).
9. The single cell according to claim 8, characterized in that: The distance from any position of the positioning edge (2213) to the battery cell body (21) is L mm; along the thickness direction of the pole ear (221), the size of the battery cell body (21) is M mm, satisfying: 1≤LM≤3 or 1≤L-0.5M≤3.
10. The single cell according to claim 1, characterized in that: Along the thickness direction of the pole ear (221), the main body (2212) has a first surface (22121) and a second surface (22122) that are opposite to each other, and the hardened portion (2211) has a third surface (22111) and a fourth surface (22112) that are opposite to each other; The positive projection of the hardened portion (2211) on the plane where the first surface (22121) is located is an equilateral triangle, and at least three hardened portions (2211) are provided, and the hardened portions (2211) are arranged at intervals in pairs; The orthographic projection of the pole ear (221) on the plane where the first surface (22121) is located is in the shape of an isosceles trapezoid or a square.
11. A battery pack, characterized in that: The method comprises a single cell as claimed in any one of claims 1 to 10.