Battery cell

Abstract

A battery cell. At least one end of a battery cell casing (100) forms an opening, and the inner wall surface of the battery cell casing (100) comprises an interlocking section (111) located on the side close to the opening. The interlocking section (111) is welded to the body (210) of a cover plate (200), the depth of the interlocking section (111) is d, and the thickness L2 of the body (210) satisfies: L2-0.5≤d≤L2+0.5, wherein L2≥0.5 mm. By using the described assembly size relationship, the matching degree between the body (210) of the cover plate (200) and the battery cell casing (100) is high, and the welding strength and the welding yield are high.

Description

battery cells

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 31, 2024, with application number 202410129583.1, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, for example, to a battery cell. Background Art

[0003] Currently, battery cells generally consist of internal and external structures. The internal structure primarily comprises the electrode group, while the external structure primarily comprises a cover plate and a cell housing. The cell housing provides space for the electrode group, and the cover plate and cell housing are welded together to form an enclosed space, which is then assembled to form a complete battery cell. The cell housing is typically formed using continuous stamping and stretching. One side of the cell housing has an opening. After the electrode group is installed within the cell housing through the opening, the opening is welded to the cover plate, sealing the opening. The cover plate is then welded to the opening of the cell housing using a laser-assisted seam welding process, achieving a seal between the cover plate and the cell housing. Summary of the Invention

[0004] The present application provides a battery cell with a high degree of fit between the battery cell shell and the cover plate, which is beneficial to improving the welding strength and welding yield between the battery cell shell and the cover plate, ensuring the sealing performance after welding, and having high safety.

[0005] An embodiment of the present application provides a battery cell, including:

[0006] The battery cell shell has an open end at least at one end, and the inner wall surface of the battery cell shell includes an embedding section, a shielding section and a pole group accommodating section;

[0007] The cover plate includes a body embedded in the opening, wherein the four corners of the body are interference-fitted with the embedding section, the remaining portion of the body is clearance-fitted with the embedding section, and the body and the embedding section are welded;

[0008] When the cover plate and the cell housing are assembled, the depth of the engaging section is d, and the thickness L2 of the body satisfies: L2-0.5≤d≤L2+0.5, L2≥0.5 mm.

[0009] In some embodiments, the wall thickness of the splice section is a, and the wall thickness a of the splice section satisfies: 0.3 mm ≤ a ≤ 1 mm.

[0010] In some embodiments, the electrode group accommodating section has a wall thickness of f, the shielding section has an inclined step surface, the width of the projection of the step surface on the cover plate along the height direction of the battery cell housing is c, and a first seam is formed between the embedded section and the body, and the width of the first seam is b;

[0011] Among them, 2b≤c≤0.5 mm;

[0012] The width b of the first seam satisfies: 0≤b≤0.2 mm.

[0013] In some embodiments, the battery cell housing includes two first side panels and two second side panels that are oppositely disposed, the first side panels and the second side panels being sequentially connected, the first side panels and the second side panels being arranged at the same end to form the opening, the body including a first side edge and a second side edge, a first seam being formed between the first side panel and the first side edge, and a second seam being formed between the second side panel and the second side edge, and the width of the second seam is g;

[0014] The width g of the second seam satisfies: 0≤g≤0.5 mm.

[0015] In some embodiments, the first side plate includes an inlay section, a shielding section, and a pole group accommodating section arranged in sequence, and the inlay section is located on an end of the inner wall surface of the first side plate close to the opening.

[0016] In some embodiments, the first side panel and the second side panel are connected by an inner fillet transition, and the radius of the inner fillet is R1;

[0017] The first side edge and the second side edge are transitionally connected via an outer fillet, and the radius of the outer fillet is R2;

[0018] Wherein, the radius R1 of the inner fillet satisfies: 1.5 mm ≤ R1 ≤ 5 mm;

[0019] The radius R2 of the outer fillet satisfies: 0≤R1-R2≤0.5 mm.

[0020] In some embodiments, a boss is further provided on a side of the body facing the battery cell housing, the boss has a guide portion in a circumferential direction, and the boss extends from the opening into the battery cell housing;

[0021] Wherein, the thickness of the cover plate is L1, the thickness of the boss is L3, L1=L2+L3;

[0022] The thickness L1 of the cover plate satisfies: 0.7 mm ≤ L1 ≤ 5 mm;

[0023] The thickness L3 of the boss satisfies: L3 ≥ 0.2 mm.

[0024] In some embodiments, the guide portion is a chamfered surface that cooperates with the step surface, and an angle x is formed between the step surface and the extended surface of the engaging section;

[0025] The body includes an outer end surface and a side surface, the side surface is located in the circumferential direction of the outer end surface and connected to the outer end surface, the side surface cooperates with the engaging section, an angle z is formed between the chamfered surface and the extended surface of the side surface, and the angle z is greater than or equal to the angle x;

[0026] Wherein, the angle x satisfies: x ≥ 30 degrees;

[0027] The angle z satisfies: z≤60 degrees.

[0028] In some embodiments, the weld width after welding the main body and the scarf section is w, and the weld depth is h;

[0029] Wherein, the weld width w satisfies: w ≥ 0.6 mm;

[0030] The penetration depth h satisfies: 0.5 mm ≤ h ≤ 1.0 mm.

[0031] In some embodiments, the battery cell further includes a pole group, and the pole group is disposed inside the battery cell shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a top view of a battery cell provided in an embodiment of the present application;

[0033] FIG2 is a partial enlarged view of point A in FIG1 ;

[0034] FIG3 is a cross-sectional view of the BB section in FIG1 ;

[0035] FIG4 is a partial enlarged view of point C in FIG3 ;

[0036] FIG5 is a cross-sectional view of the DD section in FIG3 ;

[0037] FIG6 is a partial enlarged view of point E in FIG5 ;

[0038] FIG7 is an exploded view of a battery cell provided in an embodiment of the present application;

[0039] FIG8 is an enlarged view of the metallographic structure of the weld position of the battery cell housing and the cover plate after welding provided in an embodiment of the present application (unqualified product);

[0040] FIG9 is a second enlarged view of the metallographic structure of the weld position after welding the battery cell housing and the cover plate provided in an embodiment of the present application (qualified product).

[0041] In the figure: 10, molten bead; 100, battery cell shell; 110, first side plate; 111, embedded section; 112, shielding section; 113, pole group accommodating section; 114, step surface; 120, second side plate; 130, inner fillet; 200, cover plate; 210, body; 211, first side edge; 212, second side edge; 213, outer fillet; 220, boss; 214, outer end face; 215, side surface; 221, guide portion; 300, pole group. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present application in conjunction with the accompanying drawings. The embodiments described are some sub-embodiments related to the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] In the description of this application, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this 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 operate in a specific orientation. In addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or indicates that the first feature is at a higher level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or indicates that the first feature is at a lower level than the second feature.

[0044] In the description of this application, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. A person of ordinary skill in the art will understand the meaning of these terms in this application as appropriate.

[0045] The following describes embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application.

[0046] In the related art, sealing welding methods lack constraints on the matching dimensions and structure of the cell housing and cover plate, resulting in a weak weld connection between the cover plate and the cell housing, a low welding yield, and a high risk of cracking and breakage at the weld seam between the cover plate and the cell housing. This increases production costs and reduces production efficiency. In particular, when the cell generates gas during charging and discharging, the gas pressure inside the cell housing creates shear forces at the weld seam, which can easily crack the weld. This poor sealing can lead to leakage, cell failure, and even serious safety accidents.

[0047] This embodiment provides a battery cell, as shown in Figures 1 to 4, which includes a battery cell shell 100 and a cover plate 200. The battery cell shell 100 and the cover plate 200 have a high degree of fit, high welding strength and high welding yield, and good sealing after welding the battery cell shell 100 and the cover plate 200.

[0048] At least one end of the battery cell shell 100 forms an opening, and the inner wall surface of the battery cell shell 100 includes an embedding section 111, a shielding section 112 and a pole group accommodating section 113, wherein the embedding section 111 is located on the side close to the opening, and the pole group accommodating section 113 is enclosed to form an installation space for placing the pole group 300, so that the pole group 300 can pass through the opening into the installation space inside the battery cell shell 100, thereby accommodating the pole group 300, and the shielding section 112 is located between the embedding section 111 and the pole group accommodating section 113. The cover plate 200 includes a main body 210, which is embedded in the opening of the battery cell housing 100. The four corners of the main body 210 are interference-fitted with the splicing section 111 so that when the cover plate 200 is assembled with the battery cell housing 100, the cover plate 200 can be supported at the opening and will not fall into the installation space. The remaining part of the main body 210 is clearance-fitted with the splicing section 111, and then the main body 210 and the splicing section 111 (at one end of the opening) are connected by welding. Laser welding is used between the battery cell housing 100 and the cover plate 200. The setting of the shielding section 112 can prevent the laser from entering the installation space in the battery cell housing 100 during welding, thereby preventing the pole group 300 from being burned.

[0049] When the cover plate 200 and the cell shell 100 are assembled, the depth of the embedded section 111 is d, that is, the distance between the end of the shielding section 112 close to the embedded section 111 and the opening of the cell shell 100 is d, and the thickness L2 of the body 210 satisfies: L2-0.5≤d≤L2+0.5. By adopting the above-mentioned assembly dimension relationship, the fit between the body 210 of the cover plate 200 and the cell shell 100 is relatively high. After the body 210 of the cover plate 200 is inserted into the shell, the end face of the body 210 facing away from the installation space will not be too much higher than the end of the cell shell 100. At the same time, the size of the body 210 sunk into the cell shell 100 will not be too large, thereby ensuring good welding quality, and is less likely to cause problems such as blowholes and cold welds, and having high welding strength and welding yield. By controlling the value range of L2 to L2 ≥ 0.5 millimeters (mm), sufficient penetration is achieved during welding, molten beads 10 are unlikely to be generated, welding quality is guaranteed, and molten beads 10 are prevented from falling on the electrode assembly 300 and burning the electrode assembly 300 (see Figures 8 and 9). For example, the value of L2 can be 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, or 1.5 mm.

[0050] In some embodiments, the wall thickness of the scarf section 111 is a, and the wall thickness a of the scarf section 111 satisfies the following: 0.3 mm ≤ a ≤ 1 mm. This ensures that the wall thickness of the scarf section 111 is within an appropriate range, preventing it from being too thick, which is beneficial for weight reduction and material conservation. At the same time, the wall thickness of the scarf section 111 is also not too thin, which would result in a narrow weld width and affect welding quality. For example, the value of a can be 0.3 mm, 0.6 mm, 0.8 mm, or 1.0 mm, etc.

[0051] In some embodiments, the weld width w and the depth h after welding the body 210 of the cover plate 200 and the interlocking section 111 of the cell housing 100 (see FIG9 ) are achieved. By adopting the aforementioned dimension ranges of L2 ≥ 0.5 mm and 0.3 mm ≤ a ≤ 1 mm, the weld width w satisfies the following conditions: w ≥ 0.6 mm; and the depth h satisfies the following conditions: 0.5 mm ≤ h ≤ 1.0 mm. This ensures sufficient weld width and depth, high weld strength, and high weld quality, ensuring a good seal between the cover plate 200 and the cell housing 100 after welding, and preventing leakage.

[0052] In some embodiments, the electrode assembly accommodating section 113 of the cell housing 100 has a wall thickness of f. The shielding section 112 has an inclined stepped surface 114. The width of the projection of the stepped surface 114 on the cover plate 200 along the height direction of the cell housing 100 is c. A first seam is defined between the interlocking section 111 and the body 210. The width of the first seam is b. The width b of the first seam must satisfy the following requirement: 2b ≤ c ≤ 0.5 mm to prevent the cover plate 200 from being biased to one side during assembly, which could cause laser light to leak into the installation space of the cell housing 100 through the first seam.

[0053] Continuing with Figures 1 and 2 , the cell housing 100 in this embodiment includes two first side panels 110 and two second side panels 120 disposed opposite each other. The first side panels 110 and the second side panels 120 are sequentially connected, and the aforementioned opening is formed by enclosing the same end of the two first side panels 110 and the two second side panels 120. In this embodiment, the cell housing 100 has an opening on only one side. That is, the ends of the first and second side panels 110, 120 of the cell housing 100 facing away from the opening are connected to a bottom panel, so that the first and second side panels 110, 120, and the bottom panel collectively enclose an installation space for accommodating the electrode assembly 300. Optionally, the area of ​​the first side panel 110 is smaller than that of the second side panel 120, that is, the second side panel 120 is the larger surface of the cell housing 100.

[0054] In some embodiments, referring to Figures 5 and 6 , the inner wall surface of the first side panel 110 in this embodiment includes a sequentially arranged interlocking section 111, a shielding section 112, and a pole group accommodating section 113. The interlocking section 111 is located on the inner wall surface of the first side panel 110, near the open end. The inner wall surface of the second side panel 120 is a plane. The shielding section 112 is not provided on the second side panel 120. The wall thickness of the second side panel 120 is equal to the wall thickness of the interlocking section 111 of the first side panel 110, that is, the wall thickness of the second side panel 120 is also a, 0.3mm≤a≤1mm. This arrangement can reduce the overall weight of the battery cell housing 100 and save material.

[0055] Continuing with Figure 2 , the body 210 includes a first side 211 and a second side 212. The first side panel 110 and the first side 211 form the aforementioned first seam, while the second side panel 120 and the second side 212 form a second seam. The width of the first seam is b, and the width of the second seam is g. It should be noted that the width g of the second seam satisfies the following condition: 0 ≤ g ≤ 0.5 mm, resulting in a relatively small assembly clearance. When the body 210 of the cover plate 200 is inserted into the opening of the cell housing 100 for welding, a clamping fixture can be used to clamp the second side 212 of the body 210 and the second side panel 120 of the cell housing 100 to zero the second seam g, thereby preventing laser light from leaking into the electrode assembly 300 during welding. The clamping fixture is commonly used in the related art. For example, the value of g can be 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm.

[0056] In some embodiments, in order to ensure that the laser does not leak into the first side plate 110, the width b of the first seam in this embodiment needs to satisfy the following requirements: 2b≤c≤0.5mm. At this time, even in the extreme case where the cover plate 200 deviates to one side when the battery cell housing 100 and the cover plate 200 are assembled, the laser can be blocked by the step surface 114 of the shielding section 112 on the inner wall surface of the first side plate 110, and the laser will not leak into the battery cell housing 100, thereby ensuring that the electrode group 300 is not damaged. The extreme case where the cover plate 200 deviates to one side refers to the case where there is no gap between the main body 210 of the cover plate 200 and the splicing section 111 of the first side plate 110 on one side, and there is a fitting gap between the main body 210 of the cover plate 200 and the splicing section 111 of the first side plate 110 on the other side. Therefore, it is necessary to ensure that c≥2b to prevent the laser from being blocked by the shielding section 112 and leaking during welding. Of course, the value of c should also be minimal. If c is excessively large, the wall thickness f of the electrode assembly housing section 113 of the first side plate 110 will be excessively large, wasting material and cost. Therefore, in this embodiment, the width b of the first seam satisfies the following: 0 ≤ b ≤ 0.2 mm. This range of values ​​ensures easy assembly of the cover plate 200 and the cell housing 100 while preventing laser leakage into the housing and burning the electrode assembly 300 due to an excessively large first seam. For example, the value of b can be 0 mm, 0.1 mm, or 0.2 mm. The value of c can be 0 mm, 0.2 mm, 0.25 mm, 0.3 mm, or 0.4 mm.

[0057] Optionally, in this embodiment, the first side panel 110 and the second side panel 120 of the cell shell 100 are transitionally connected via an inner fillet 130. The first side edge 211 and the second side edge 212 of the body 210 are transitionally connected via an outer fillet 213. It should be noted that the shielding section 112 is only provided on the inner wall surface of the first side panel 110 of the cell shell 100, and not on the inner wall surface of the second side panel 120. The inner fillet 130 serves as the transition surface between the first side panel 110 and the second side panel 120. The setting size of the shielding section 112 is relatively small, so the value of the width b of the first seam needs to be relatively small (0≤b≤0.2) to avoid the gap being too large to cause the laser to leak in.

[0058] In some embodiments, in order to prevent the cover plate 200 from falling into the battery cell housing 100 when the cover plate 200 is assembled with the battery cell housing 100, the inner fillet 130 and the outer fillet 213 in this embodiment are fitted with an interference fit or a small clearance, so that the four corners of the body 210 of the cover plate 200 can be supported at the four corners of the battery cell housing 100, that is, the outer fillet 213 is supported at the inner fillet 130 where the first side plate 110 and the second side plate 120 are transitionally connected.

[0059] For example, in this embodiment, the radius of the inner fillet 130 is R1, and the radius of the outer fillet 213 is R2. The radius R1 of the inner fillet 130 satisfies: 1.5mm≤R1≤5mm. On the one hand, it avoids the situation where the inner fillet 130 is too small, the welding trajectory is stuck at the joint of the inner fillet 130 and the outer fillet 213, the welding is not smooth, and then leads to a cold weld or a broken weld. On the other hand, it avoids the situation where the inner fillet 130 is too large, resulting in a waste of installation space of the battery cell housing 100 and easy crushing of the electrode group 300. By adopting the above-mentioned value range, the welding quality at the joint of the inner fillet 130 and the outer fillet 213 is good, the welding strength is high, and the sealing of the weld is good. For example, the value of R1 can be 1.5mm, 1.8mm, 2.0mm, 2.5mm, 3mm, 4mm or 5mm, etc.

[0060] The radius R2 of the outer fillet 213 satisfies the following: 0≤R1-R2≤0.5mm. This arrangement ensures that when the body 210 of the cover plate 200 is assembled with the cell housing 100, the body 210 of the cover plate 200 is located in the middle of the opening of the cell housing 100. In other words, the first seam b between the two first side edges 211 of the body 210 and the engaging sections 111 of the two first side panels 110 of the cell housing 100 is relatively close in size. This prevents the first seam on one side from being too large, which could easily leak in laser light and burn the electrode assembly 300 during welding. It also prevents the gap between the inner fillet 130 and the outer fillet 213 from being too large, which could cause laser light to leak into the cell housing 100.

[0061] Continuing with Figure 4 , in this embodiment, the body 210 of the cover plate 200 is further provided with a boss 220 on the side facing the cell housing 100. The boss 220 has a circumferential guide 221 extending from the opening into the cell housing 100. The guide 221 on the boss 220 facilitates installation of the cover plate 200 into the opening of the cell housing 100. The thickness of the cover plate 200 is L1, where L1 = L2 + L3. The thickness L1 of the cover plate 200 satisfies the following conditions: 0.7 mm ≤ L1 ≤ 5 mm; the thickness L3 of the boss 220 satisfies the following conditions: L3 ≥ 0.2 mm. By controlling the thickness L1 of the cover plate 200 and the thickness L3 of the boss 220 within the aforementioned ranges, the material used for the cover plate 200 can be reduced, preventing increased costs due to excessive thickness of the cover plate 200. Furthermore, interference with the electrode assembly 300 within the cell casing 100 due to excessive thickness of the boss 220 on the cover plate 200 can be avoided. For example, the value of L1 can be 0.7 mm, 1.0 mm, 2.0 mm, 2.5 mm, 3 mm, 4 mm, or 5 mm.

[0062] In some embodiments, the stepped surface 114 of the shielding segment 112 is an inclined plane, and an angle x is formed between the stepped surface 114 of the shielding segment 112 and the extended surface of the interlocking segment 111. The body 210 includes an outer end surface 214 and a side surface 215. The outer end surface 214 is the end surface of the body 210 facing away from the battery cell housing 100 and is located outside the installation space of the battery cell housing 100. The side surface 215 is located circumferentially of the outer end surface 214 and is connected to the outer end surface 214. The side surface 215 is used to mate with the interlocking segment 111 and be welded to the interlocking segment 111. The value range of the angle x satisfies: x ≥ 30°, so as to increase the surface area of ​​the step surface 114 of the shielding segment 112 facing the cover plate 200, thereby helping to block laser radiation. At the same time, when one end of the cover plate 200 (the end where the first side 211 is located) continues to slide downward into the cell housing 100 relative to the opening of the battery cell housing 100, the step surface 114 of the shielding segment 112 can fully abut against the cover plate 200, providing support for the cover plate 200 and improving the stability of the battery cell. For example, the value of the angle x can be 30°, 35°, 40°, 45°, 50°, or 55°, etc.

[0063] In some embodiments, the circumferential guide portion 221 of the boss 220 is generally in the form of a closed ring. The guide portion 221 is a chamfered surface that mates with the stepped surface 114 of the shielding section 112. In other words, the chamfered surface is also generally in the form of a closed ring. An angle z is formed between the chamfered surface and the extended surface of the side surface 215 of the body 210. The angle z is greater than or equal to the angle x, and the angle z satisfies: z ≤ 60°. This prevents interference between the boss 220 and the shielding section 112 of the cell housing 100, and the chamfered surface can provide a good guide when the cover plate 200 is inserted into the housing. For example, the value of the angle z can be 35°, 40°, 45°, 50°, 55°, or 60°, etc.

[0064] In some embodiments, when the cell housing 100 and the cover plate 200 are assembled and welded, the main body 210 of the cover plate 200 and the splicing section 111 of the cell housing 100 are pre-spot welded before the welding process, so that the cover plate 200 can be pre-fixed on the cell housing 100. The pre-weld spot will fix the height difference between the end face of the cover plate 200 facing away from the installation space and the end of the splicing section 111 of the cell housing 100. When L2-0.5≤d≤L2+0.5, the height difference between the two is small, which prepares for the subsequent full-circle welding between the cover plate 200 and the cell housing 100, ensuring that the compressive strength of the cell after full-circle welding is greater than 1.2 MPa and there is no leakage at the weld seam, resulting in high welding strength. In addition, the helium leak rate of the cell after full-circle welding is less than 1*10 -7 Pascal cubic meter per second (Pa·m 3 / s) to ensure good sealing.

[0065] The following experiments were conducted to test the welding quality and airtightness of the battery cells in this embodiment. The battery cell housings 100 of the same dimensions were assembled with lids, bodies 210, and bosses 220 of varying thicknesses, and then laser butt welded. The experimental dimensions are shown in Table 1 below:

[0066] Table 1

[0067] Note: NG means the sample is unqualified; OK means the sample is qualified

[0068] Among them, L2, b, c, d, R1, and R2 of samples 2#, 5#, and 6# are all within the required ranges of the above dimensions. After the cover plate 200 and the cell shell 100 are laser welded, no laser light leaks into the cell shell 100. The welding quality of the joint between the cell shell 100 and the cover plate 200 is good, and the welding strength is high. Samples 2#, 5#, and 6# are all qualified.

[0069] Comparing samples 1#, 2#, 5#, and 6#, except for the thickness L2 of the body 210 of sample 1# being 0.4mm, which is not within the range of the size requirement L2 ≥ 0.5mm, the other b, c, d, R1, and R2 all meet the design requirements. After the cover plate 200 and the cell housing 100 are laser welded, the size of L2 is too small, resulting in the formation of a molten bead 10 (see Figure 8) in the melted portion after laser welding. The compressive strength of the cell after welding is lower than 1.2Mpa, or even lower than 1.0Mpa. Sample 1# fails the test.

[0070] Comparing samples 2#, 3#, 5#, and 6#, except for the height difference c=0.1mm at both ends of the shielding section 112 of sample 3#, which is not within the size requirement 2b≤c≤0.5mm, the remaining L2, b, d, R1, and R2 all meet the design requirements. After the cover plate 200 and the battery cell shell 100 are laser welded, the laser leaks into the inside of the battery cell shell 100, and the shielding section 112 cannot block the laser, resulting in the pole group 300 being burned. Sample 3# is unqualified.

[0071] Comparing samples 2#, 4#, 5#, and 6#, except for the depth d=0.6mm of the scarf section 111 of sample 4#, which is not within the range of the dimensional requirement L2-0.5≤d≤L2+0.5, the remaining L2, b, c, R1, and R2 all meet the design requirements. After the cover plate 200 and the battery cell housing 100 are laser welded, the depth d of the scarf section 111 is too small, resulting in problems such as cold welding and holes in the weld. At the same time, the end surface of the cover plate 200 facing away from the installation space protrudes from the end of the scarf section 111 of the battery cell housing 100 by more than 0.5mm, resulting in poor welding. The helium leak test rate does not meet the requirements, and sample 4# fails.

[0072] Comparing samples 2#, 5#, 6#, and 7#, except for the depth d=1.8mm of the scarf section 111 of sample 7#, which is not within the dimensional requirement L2-0.5≤d≤L2+0.5, the remaining L2, b, c, R1, and R2 all meet the design requirements. After the cover plate 200 and the battery cell housing 100 are laser welded, the depth d of the scarf section 111 is too large, resulting in problems such as cold welding and blowout holes at the welding site. The end surface of the cover plate 200 facing away from the installation space sinks into the end of the scarf section 111 of the battery cell housing 100 by more than 0.5mm, resulting in poor welding. The helium leak test rate does not meet the requirements, and sample 7# fails.

[0073] Comparing samples 2#, 5#, 6#, and 8#, except for the width b of the first seam of sample 8#, which is 0.3mm and is not within the size requirement range of 0≤b≤0.2, the remaining L2, c, d, R1, and R2 all meet the design requirements. After the cover plate 200 and the battery cell housing 100 are laser welded, the laser leaks into the position corresponding to the inner fillet 130 inside the battery cell housing 100, and the laser burns the four corners of the electrode group 300. Since the shielding section 112 is set on the first side plate 110, the inner wall surface of the second side plate 120 is a plane (no shielding section 112 is provided), and the inner fillet 130 serves as the transition surface between the first side plate 110 and the second side plate 120, the shielding section 112 is not obvious. Therefore, when the gap size of the first seam b is too large, it will also cause laser leakage, and sample 8# fails.

[0074] Comparing 2#, 5#, 6#, and 9#, except that the radius R1 of the inner fillet 130 of sample 9# is not within the size requirement range of 1.5mm≤R1≤5mm, and the radius R2 of the outer fillet 213 of sample 9# is not within the size requirement range of 0≤R1-R2≤0.5mm, the remaining L2, b, c, and d all meet the design requirements. After the cover plate 200 and the battery cell shell 100 are laser welded, the radius R1 of the inner fillet 130 is too small, the welding trajectory is discontinuous, and cold welds and broken welds occur. The helium leak test rate does not meet the requirements, and sample 9# fails.

[0075] For sample 10#, the thickness of its body 210 is L2 = 0.5mm, which is at the minimum boundary of the aforementioned value range of L2 ≥ 0.5mm. The width of the first seam is b = 0.2mm, which is at the maximum boundary of the aforementioned value range of 0 ≤ b ≤ 0.2. The remaining values ​​c, d, R1, and R2 all meet the design requirements. During the laser welding of the cover plate 200 and the cell housing 100, no laser light leaks into the installation space of the cell housing 100, and the electrode group 300 is not damaged. The weld quality at the joint between the cell housing 100 and the cover plate 200 is good, with high weld strength. Sample 10# passes the test.

[0076] For sample 11#, the radius R1 of its inner fillet 130 is 1.5mm, which is at the minimum boundary of the value range of the size requirement 1.5mm≤R1≤5mm, and d=L2+0.5, which is at the maximum boundary of the value range of L2-0.5≤d≤L2+0.5. The remaining L2, b, c, and R2 all meet the design requirements. When the cover plate 200 and the battery cell housing 100 are laser welded, the welding trajectory is continuous, and there are no cold welds or broken welds. The welding quality of the matching part between the battery cell housing 100 and the cover plate 200 is good, the welding strength is high, the helium leak rate meets the requirements, and no laser leaks into the installation space of the battery cell housing 100, and will not damage the electrode group 300. Sample 11# is qualified;

[0077] For sample 12#, the width c of the projection of the step surface 114 of the shielding section 112 on the cover plate 200 along the height direction of the cell shell 100 is 0.5mm, which is at the maximum boundary of the value range of 2b≤c≤0.5mm, d=L2-0.5, which is at the minimum boundary of the value range of L2-0.5≤d≤L2+0.5, the radius R1 of the inner fillet 130 is 5mm, which is at the maximum boundary of the value range of the size requirement 1.5mm≤R1≤5mm, and the radius R2 of the outer fillet 213 is 5mm. 2=4.5mm, which is at the maximum boundary of the value range of the size requirement 0≤R1-R2≤0.5mm. The rest of L2 and b meet the design requirements. When the cover 200 and the battery cell shell 100 are laser welded, the welding trajectory is continuous, there are no cold welds or broken welds, the welding quality of the matching point between the battery cell shell 100 and the cover 200 is good, the welding strength is high, the helium leak detection rate meets the requirements, and no laser leaks into the installation space of the battery cell shell 100, and will not damage the electrode group 300. Sample 12# is qualified.

[0078] In summary, when the battery cell meets the above-mentioned values ​​of L2, b, c, d, R1, and R2, as well as the dimensional matching relationship between L2, b, c, d, R1, and R2 and other parameters, the welding quality and welding airtightness can be guaranteed to be good, and at the same time, no laser leaks into the installation space of the battery cell shell 100.

[0079] Referring to Figure 7 , the battery cell in this embodiment further includes an electrode group 300, which is disposed within the cell housing 100. The aforementioned mating structure between the cell housing 100 and the cover plate 200 ensures a good seal between the cover plate 200 and the cell housing 100. Furthermore, the weld strength and quality between the cover plate 200 and the cell housing 100 are high, making leakage less likely and preventing the electrode from being burned during welding, resulting in excellent overall safety.

[0080] As an optional solution, in this embodiment, the battery cell housing 100 is provided with an opening on only one side, that is, the first side plate 110 and the second side plate 120 of the battery cell housing 100 are connected to the bottom plate at one end facing away from the opening, and one end of the first side plate 110 and the second side plate 120 are assembled with the cover plate 200 using the above-mentioned matching structure.

[0081] In other embodiments, it is also applicable to the case where both ends of the battery cell housing 100 have openings. In this case, there are two cover plates 200, one of which is a positive electrode cover plate and the other is a negative electrode cover plate. The positive electrode cover plate and the negative electrode cover plate are assembled with the two openings respectively. The top and bottom ends of the first side plate 110 of the battery cell housing 100 are provided with an interlocking section 111 and a shielding section 112, and the pole group accommodating section 113 is located in the middle, that is, along the height direction of the battery cell housing 100, the interlocking section 111, the shielding section 112, the pole group accommodating section 113, another shielding section 112 and another interlocking section 111 are connected in sequence. The positive electrode cover plate and one interlocking section 111 of the battery cell housing 100, as well as the negative electrode cover plate and the other interlocking section 111 of the battery cell housing 100 are connected using the above-mentioned matching structure between the battery cell housing 100 and the cover plate 200.

Claims

1. A battery cell comprising: The battery cell shell has an open end at least at one end, and the inner wall surface of the battery cell shell includes an embedding section, a shielding section and a pole group accommodating section; The cover plate includes a body embedded in the opening, wherein the four corners of the body are interference-fitted with the embedding section, the remaining portion of the body is clearance-fitted with the embedding section, and the body and the embedding section are welded; When the cover plate and the cell housing are assembled, the depth of the engaging section is d, and the thickness L2 of the body satisfies: L2-0.5≤d≤L2+0.5, L2≥0.5 mm.

2. The battery cell according to claim 1, wherein: The wall thickness of the splice section is a, and the wall thickness a of the splice section satisfies: 0.3 mm ≤ a ≤ 1 mm.

3. The battery cell according to claim 2, wherein: The wall thickness of the electrode group accommodating section is f, the shielding section has an inclined step surface, the width of the projection of the step surface on the cover plate along the height direction of the battery cell housing is c, and a first seam is formed between the embedded section and the body, the width of the first seam is b; Among them, 2b≤c≤0.5 mm; The width b of the first seam satisfies: 0≤b≤0.2 mm.

4. The battery cell according to claim 3, wherein: The battery cell housing includes two first side panels and two second side panels that are oppositely arranged, the first side panels and the second side panels are sequentially connected, and the same end of the first side panels and the second side panels is surrounded to form the opening. The body includes a first side edge and a second side edge, a first seam is formed between the first side panel and the first side edge, and a second seam is formed between the second side panel and the second side edge, and the width of the second seam is g; The width g of the second seam satisfies: 0≤g≤0.5 mm.

5. The battery cell according to claim 4, wherein: The first side plate includes an embedding section, a shielding section and a pole group accommodating section arranged in sequence, and the embedding section is located on an end of the inner wall surface of the first side plate close to the opening.

6. The battery cell according to claim 4, wherein: The first side panel and the second side panel are connected by an inner fillet transition, and the radius of the inner fillet is R1; The first side edge and the second side edge are transitionally connected via an outer fillet, and the radius of the outer fillet is R2; The radius R1 of the inner fillet satisfies: 1.5 mm ≤ R1 ≤ 5 mm; The radius R2 of the outer fillet satisfies: 0≤R1-R2≤0.5 mm.

7. The battery cell according to claim 3, wherein: A boss is further provided on one side of the body facing the cell shell, the boss has a guide portion in the circumference, and the boss extends into the cell shell from the opening; Wherein, the thickness of the cover plate is L1, the thickness of the boss is L3, L1=L2+L3; The thickness L1 of the cover plate satisfies: 0.7 mm ≤ L1 ≤ 5 mm; The thickness L3 of the boss satisfies: L3 ≥ 0.2 mm.

8. The battery cell according to claim 7, wherein: The guide portion is a chamfered surface that matches the step surface, and an angle x is formed between the step surface and the extended surface of the engaging section; The body includes an outer end surface and a side surface, the side surface is located in the circumferential direction of the outer end surface and connected to the outer end surface, the side surface cooperates with the engaging section, an angle z is formed between the chamfered surface and the extended surface of the side surface, and the angle z is greater than or equal to the angle x; Wherein, the angle x satisfies: x ≥ 30 degrees; The angle z satisfies: z≤60 degrees.

9. The battery cell according to claim 1, wherein: The weld width after welding the main body and the scarfing section is w, and the weld depth is h; Wherein, the weld width w satisfies: w ≥ 0.6 mm; The penetration depth h satisfies: 0.5 mm ≤ h ≤ 1.0 mm. 10 . The battery cell according to claim 1 , further comprising a pole group, wherein the pole group is disposed inside the battery cell shell.

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