Battery cell and battery pack

Abstract

The invention relates to the technical field of batteries, and discloses a battery cell and a battery pack. Wherein the battery cell comprises a pole, one end of which is provided with a pole base; one end of the pole group is provided with a pole lug, and the pole lug is welded with one side, far away from the pole, of the pole base to form a welding mark; the effective overcurrent area of the welding mark is S, the unit of S is mm < 2 >, the overcurrent coefficient of the tab is gamma, the value range of gamma is that gamma is more than or equal to 8A / mm < 2 > and less than or equal to 15A / mm < 2 >, the rated current of the welding mark is I, the unit of I is A, S and gamma, and the condition that S is more than or equal to 1.2 * I / gamma is satisfied. According to the invention, the relationship among the effective overcurrent area S of the welding mark, the overcurrent coefficient gamma of the tab and the rated current I of the welding mark is limited to be greater than or equal to 1.2 * I / gamma, so that the sufficient effective overcurrent area of the welding mark can be ensured, the problems of overheating, resistance increase and the like caused by insufficient overcurrent area are avoided while stable overcurrent of the battery cell is ensured, and the service life of the battery cell is prolonged. The overcurrent capability and the safety performance of the battery cell are improved, the reliability and the stability of the battery cell in actual use are enhanced, and the service life of the battery cell is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell and a battery pack. Background Art

[0002] As power batteries become increasingly widely used in vehicles, users are demanding faster battery charging. Secondly, because batteries rely on tabs and terminals to channel current in and out of the battery, the design of the connection between the tabs and terminals is crucial. However, the weld area between the tabs and terminals currently doesn't match the rated current of the weld. As a result, when the battery is fast-charged at high currents, the temperature at the tab-terminal connection rises significantly, generating significant heat and impacting the safety of the battery cell. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell and a battery pack to solve the problem in the prior art that the weld area between the tab and the pole does not match the rated current of the weld, resulting in a high temperature rise at the connection between the tab and the pole.

[0004] In a first aspect, the present invention provides a battery cell, comprising:

[0005] A pole, one end of which is provided with a pole base;

[0006] A pole group, one end of which is provided with a pole ear, the pole ear being welded to a side of the pole base away from the pole to form a weld mark;

[0007] The effective flow area of ​​the weld mark is S, and the unit of S is mm 2 The current coefficient of the tab is γ, and the value range of γ is 8A / mm 2 ≤γ≤15A / mm 2 The rated current of the welding mark is I, the unit of I is A, and S, γ, and I satisfy: S≥1.2*I / γ.

[0008] Beneficial Effects: Compared to directly welding the pole and the tab, the present invention connects the pole and the tab with the help of the pole base, which can increase the welding contact area between the pole and the tab, ensuring that the effective flow area of ​​the weld print meets the design requirements, thereby reducing energy loss and heat generation during current transmission, and improving the charging and discharging efficiency and safety of the battery cell. Compared to increasing the size of the pole, the pole of the present invention connects the pole and the tab with the help of the pole base, which not only avoids the increase in material cost due to the increase in the cross-sectional area of ​​the pole itself, but also avoids the increase in space occupied by the cross-sectional area of ​​the pole itself. In addition, the present invention limits the relationship between the effective flow area S of the weld print, the flow coefficient γ of the tab, and the rated current I of the weld print to S≥1.2*I / γ, which can ensure that the weld print has sufficient effective flow area. While ensuring stable flow of the battery cell, it avoids problems such as overheating and increased resistance caused by insufficient flow area, thereby improving the flow capacity and safety performance of the battery cell, enhancing the reliability and stability of the battery cell in actual use, and extending the service life of the battery cell.

[0009] In an optional embodiment, the weld mark includes at least one sub-weld mark, the sub-weld mark is rectangular in shape, and the orthographic projection of the sub-weld mark along the height direction of the pole falls within the range of the pole base.

[0010] Beneficial effects: The rectangular sub-weld marks have a regular structure and high area utilization. Therefore, by setting a single or multiple sub-weld marks, the effective flow area can be flexibly adjusted to avoid space waste caused by the irregular shape of the sub-weld marks. Secondly, the orthographic projection of the sub-weld marks along the height direction of the pole falls within the range of the pole base, which can prevent the sub-weld marks from exceeding the edge of the pole base, causing interference with welding tooling or thermal deformation of the plastic under the battery cell. In addition, the rectangular sub-weld marks facilitate the unification of welding parameters and reduce process complexity. Especially in narrow cover plate scenarios such as blade batteries, by setting sub-weld marks along the length of the pole base, the limited space can be fully utilized, the utilization rate of the pole base material and the compactness of the battery cell structure can be improved, and the stability and safety of current transmission can be guaranteed.

[0011] In an optional embodiment, there are n sub-weld marks, where n is a positive integer greater than or equal to 2, and the n sub-weld marks are arranged side by side along the width direction of the tab, and the distance between two adjacent sub-weld marks is H; the length direction of the sub-weld marks is consistent with the length direction of the tab.

[0012] Beneficial Effects: This invention arranges n sub-weld prints in parallel. This increases the total effective flow area of ​​the weld prints, adapting to the rated current of high-capacity, high-rate cells and avoiding the risk of overheating due to insufficient weld print area. It also disperses welding stress, reducing the risk of cracking at a single weld point due to concentrated force, and enhancing the reliability of the connection between the tab and the pole base. Furthermore, in narrow-width applications such as blade cells, the horizontal arrangement of n sub-weld prints fully utilizes the space along the width of the tab, improving the compactness and flow performance of the cell structure.

[0013] In an optional embodiment, the length of the sub-weld print is L, the unit of L is mm, the width of the sub-weld print is W, the unit of W is mm, the surface area of ​​the weld print S1 = n*L*W, and S1 and S satisfy: S = σ*n*L*W, where n is the number of sub-weld prints, σ ​​is the effective overcurrent ratio of the weld print, the value range of σ is 0.55≤σ≤0.8, and the unit of S1 is mm 2 .

[0014] Beneficial Effects: The present invention accurately calculates the weld area using the formula S1 = n*L*W. This, combined with the effective overcurrent ratio σ, correlates the actual overcurrent with the theoretical area, making the design of the weld area more scientific and reasonable. When σ is between 0.55 and 0.8, it avoids both the material waste and increased costs associated with overly large weld areas and the overcurrent heating and reduced conductivity caused by insufficient area. This ensures the stability and reliability of the electrical connection and effectively improves the electrical and safety performance of the battery cell.

[0015] In an optional embodiment, the length L of the sub-weld mark is in the range of 15 mm ≤ L ≤ 22 mm, the width W of the sub-weld mark is in the range of 1.5 mm ≤ W ≤ 3.5 mm, and the distance H between two adjacent sub-weld marks is in the range of 0 mm ≤ H ≤ 2 mm.

[0016] Beneficial Effects: Setting the sub-weld print length between 15mm and 22mm and the width between 1.5mm and 3.5mm ensures sufficient solder contact area, enhances the mechanical strength and conductivity of the weld, and prevents problems such as cold solder joints, desoldering, and overheating caused by improper sub-weld print size. Controlling the distance H between adjacent sub-weld prints between 0mm and 2mm avoids both loose connections caused by excessive spacing and short circuit risks caused by too small spacing, thereby improving battery cell reliability.

[0017] In an optional embodiment, the cross-sectional shape of the pole base is rectangular, the length direction of the sub-weld mark is consistent with the length direction of the pole base, the distance between the side of the weld mark and the corresponding side of the pole base is a, the value range of a is 1.5mm≤a≤2.5mm, and the cross-sectional area of ​​the pole base S2=(L+2a)*[nW+(n-1)*H+2a], where S2 is in mm 2 .

[0018] Beneficial effects: On the one hand, the regular shape of the rectangular base is utilized so that the weld marks can be arranged neatly along the length direction, making full use of the longitudinal space of the base to match the current conduction requirements in the length direction of the tab. At the same time, the a value is used to reserve space for welding tooling operation to avoid tooling interference caused by the weld mark edge being too close to the side of the base, thereby ensuring the feasibility of the welding process. On the other hand, the value range of a can also meet the welding deviation tolerance (such as positioning error, thermal deformation allowance) while avoiding design redundancy due to excessive a in the base size, thereby reducing waste of raw materials.

[0019] In an optional embodiment, the capacity of the battery cell is U, the unit of U is Ah, the peak charge and discharge rate of the battery cell is C, the unit of C is 1 / h, the rated current I of the weld print is the rated current of the weld print, and the relationship between U, C, and I satisfies: I=U*C.

[0020] Beneficial effect: The present invention establishes a quantitative relationship I=U*C among the battery cell capacity U, the charge and discharge peak rate C and the rated current I of the weld mark. On the one hand, it can quickly calculate the matching maximum overcurrent value I of the weld mark according to the actual capacity and rate requirements in different application scenarios (such as fast charging and high power output scenarios of power batteries), thereby avoiding insufficient overcurrent capacity or redundant design caused by empirical estimation; on the other hand, the standardized formula provides the core input variable for the calculation of the effective overcurrent area of ​​the weld mark (S≥1.2UC / γ), so that the tab welding design (such as the number of weld marks n, size L, W, etc.) can be dynamically adjusted based on the physical characteristics of the battery cell, thereby improving design efficiency and consistency.

[0021] In an optional embodiment, the cross-section of the pole is in the shape of an athletic track.

[0022] Beneficial effects: The present invention designs the cross-sectional shape of the pole into a circular runway shape or an athletics track shape, which enables the pole to obtain a larger effective flow area in a limited space. Compared with the traditional shape (cylindrical), it can carry larger currents, which meets the fast charging requirements of the battery cell; at the same time, the shape of the athletics track optimizes the current distribution path, avoids the current from being concentrated in a local area, reduces the resistance increase and heat generation problems caused by uneven current density, and ensures that the temperature of the pole is stable during the charging and discharging process.

[0023] In an optional embodiment, the central axis of the pole is collinear with the central axis of the pole base.

[0024] Beneficial effect: In order to meet the welding requirements of the battery cell tabs, the eccentricity of the tabs cannot be large or small. Therefore, in the battery cells currently using a bipolar design, the portion of the pole base of one pole is usually unable to be welded to the tabs. Therefore, it is necessary to increase the length of the pole base of the other pole to ensure the overcurrent capacity of the battery cell. However, the unused portion of the pole base and the extended portion of the pole base will lead to a decrease in material utilization and an increase in production costs. In addition, since the two poles need to be separated by a distance from each other in the battery cells with a bipolar design, the poles must be an eccentric structure relative to the pole base. Based on this, the present invention arranges the central axis of the pole and the central axis of the pole base in a colinear manner, which not only optimizes the current conduction path and avoids performance loss and structural hidden dangers caused by eccentricity, but also the single-pole design does not require an additional extension of the pole base, thereby improving material utilization and reducing production costs. While meeting the overcurrent capacity and tab welding requirements of the battery cell, the overall safety, reliability and economy of the battery cell are improved.

[0025] In a second aspect, the present invention further provides a battery pack comprising: a plurality of the above-mentioned battery cells.

[0026] Beneficial effects: The battery pack of the present invention includes the battery cell as described above and has all the beneficial technical effects of the battery cell, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic diagram of a partial structure of a battery cell according to an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a partial structure of another battery cell according to an embodiment of the present invention;

[0030] Figure 3 This is a structural schematic diagram of a battery cell cover according to an embodiment of the present invention;

[0031] Figure 4 The figure is a schematic structural diagram of a pole according to an embodiment of the present invention.

[0032] Description of reference numerals:

[0033] 1. Pole; 101. Pole base; 2. Pole group; 201. Pole ear; 3. Welding mark; 301. Sub-welding mark; 4. Riveting block; 5. Top cover; 6. Lower plastic. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0035] To address the problem in the prior art that the weld area between the tab and the pole does not match the rated current of the weld, resulting in a high temperature rise at the connection between the tab and the pole, the present invention provides a battery cell and a battery pack.

[0036] The following combination Figures 1 to 4 , describing embodiments of the present invention.

[0037] According to an embodiment of the present invention, on the one hand, a battery cell is provided, such as Figure 1 、 Figure 2 and Figure 4 As shown, it includes: a pole 1 and a pole group 2.

[0038] Specifically, a pole base 101 is provided at one end of the pole 1; a pole lug 201 is provided at one end of the pole group 2, and the pole lug 201 is welded to the side of the pole base 101 away from the pole 1 to form a weld mark 3; the effective flow area of ​​the weld mark 3 is S, and the unit of S is mm 2 , the overflow coefficient of the tab 201 is γ, and the value range of γ is 8A / mm 2 ≤γ≤15 / mm 2 The rated current of weld mark 3 is I, the unit of I is A, and S, γ, and I satisfy: S ≥ 1.2*I / γ.

[0039] Compared to directly welding the pole 1 to the tab 201, the embodiment of the present invention connects the pole 1 to the tab 201 via the pole base 101. This increases the welding contact area between the pole 1 and the tab 201, ensuring that the effective flow area of ​​the weld mark 3 meets the design requirements, thereby reducing energy loss and heat generation during current transmission, and improving the charging and discharging efficiency and safety of the battery cell. Furthermore, compared to increasing the size of the pole 1, the embodiment of the present invention connects the pole 1 to the tab 201 via the pole base 101. This not only avoids the increase in material costs caused by the increased cross-sectional area of ​​the pole 1 itself, but also avoids the increased space occupied by the increased cross-sectional area of ​​the pole 1 itself. In addition, the embodiment of the present invention limits the relationship between the effective flow area S of the weld mark 3, the flow coefficient γ of the tab 201 and the rated current I of the weld mark 3 to S≥1.2*I / γ, which can ensure that the weld mark 3 has a sufficient effective flow area. While ensuring stable flow of the battery cell, it avoids problems such as overheating and increased resistance caused by insufficient flow area, improves the flow capacity and safety performance of the battery cell, enhances the reliability and stability of the battery cell in actual use, and extends the service life of the battery cell.

[0040] It should be noted that the reason why the current coefficient γ of the tab 201 in this embodiment is 8A / mm 2 Up to 15A / mm 2 , because the material of the lower tab 201 is generally aluminum foil. In addition, it is understood that the current coefficient γ of the tab 201 can be but is not limited to 8A / mm 2 , 8.5A / mm 2 , 9A / mm 2 , 9.5A / mm 2 , 10A / mm 2 , 10.5A / mm 2 , 11A / mm 2 , 11.5A / mm 2 , 12A / mm 2 , 12.5A / mm 2 , 13A / mm 2 , 13.5A / mm 2 , 14A / mm 2 , 14.5A / mm 2 , 15A / mm 2 .

[0041] It should be noted that γ is a physical parameter of the tab foil itself, and since the tab is usually made of aluminum foil, the γ calculation value in the industry is generally 8A / mm. 2 Up to 15A / mm 2 .

[0042] In one embodiment, the electrode group 2 in this embodiment includes a plurality of alternating positive and negative electrode sheets and a separator provided between the positive and negative electrode sheets. Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material provided on at least one surface of the positive electrode current collector. As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material is provided on either or both of the two opposite surfaces of the positive electrode current collector. As an example, the positive electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum or stainless steel treated with silver, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphate, lithium transition metal oxide and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0043] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two surfaces opposing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the opposing surfaces of the negative electrode current collector. For example, the negative electrode current collector may be a metal foil, metal foam, or a composite current collector. For example, the metal foil may include silver-treated aluminum or stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium. The composite current collector may include a polymer base layer and a metal layer. The metal foam may include nickel foam, copper foam, aluminum foam, alloy foam, or carbon foam. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). For example, the negative electrode active material may be a negative electrode active material commonly known in the art for battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. In some embodiments, the separator is a separator. This application does not particularly limit the type of separator, and any well-known porous structure separator with good chemical and mechanical stability can be selected. As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0044] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transport ions and isolate the positive and negative electrodes.

[0045] It should be noted that the tabs 201 in this embodiment include positive and negative tabs. The positive tabs consist of the portion of the positive electrode sheet that does not contain active material, and the negative tabs consist of the portion of the negative electrode sheet that does not contain active material. The negative and positive tabs can be located together at one end of the electrode assembly 2 or separately at both ends of the electrode assembly 2.

[0046] According to one embodiment of the present invention, Figure 1As shown, the weld mark 3 includes at least one sub-weld mark 301, which is rectangular in shape. The orthographic projection of the sub-weld mark 301 along the height direction of the pole 1 falls within the range of the pole base 101. The rectangular sub-weld mark 301 has a regular structure and high area utilization. Therefore, by providing a single or multiple sub-weld marks 301, the effective flow area can be flexibly adjusted, avoiding space waste caused by the irregular shape of the sub-weld mark 301. Secondly, the orthographic projection of the sub-weld mark 301 along the height direction of the pole 1 falls within the range of the pole base 101, which can prevent the sub-weld mark 301 from exceeding the edge of the pole base 101, causing interference with welding tooling or thermal deformation of the plastic under the battery cell. In addition, the rectangular sub-weld mark 301 facilitates the unification of welding parameters and reduces process complexity, especially in narrow cover scenarios such as blade cells. By setting the sub-weld mark 301 along the length direction of the pole base 101, the limited space can be fully utilized, the material utilization rate of the pole base 101 and the compactness of the cell structure can be improved, and the stability and safety of current transmission can be ensured.

[0047] It should be noted that if Figure 3 As shown, a battery cell generally has a cell cover. The cell cover includes a terminal 1 and a rivet block 4, an upper plastic, a top cover 5, and a lower plastic 6 stacked in sequence. The rivet block 2 is provided with a through hole for the terminal 1 to pass through. One end of the terminal 1 passes through the lower plastic 6, the top cover 5, the upper plastic, and the through hole in sequence, and is fixed to the rivet block 4 by riveting.

[0048] According to one embodiment of the present invention, Figure 2 As shown, there are n sub-weld marks 301, where n is a positive integer greater than or equal to 2. The n sub-weld marks 301 are arranged side by side along the width direction of the tab 201, and the distance between two adjacent sub-weld marks 301 is H; the length direction of the sub-weld mark 301 is consistent with the length direction of the tab 201. In the embodiment of the present invention, the n sub-weld marks 301 are arranged side by side. On the one hand, it can increase the total effective flow area of ​​the weld mark 3 and avoid the risk of overheating of the weld mark 3 due to insufficient area; on the other hand, it can disperse the welding stress, reduce the risk of cracking of a single weld point due to concentrated force, and enhance the reliability of the connection between the tab 201 and the pole base 101. In addition, in narrow width scenarios such as blade cells, by arranging n sub-weld marks 301 side by side horizontally, the space in the width direction of the tab 201 can be fully utilized, thereby improving the compactness and flow performance of the cell structure.

[0049] According to one embodiment of the present invention, Figure 2 As shown, the length of the sub-weld mark 301 is L, the unit of L is mm, the width of the sub-weld mark 301 is W, the unit of W is mm, the surface area of ​​the weld mark 3 S1 = n*L*W, and S1 and S satisfy: S = σ*n*L*W, where n is the number of sub-weld marks, σ is the effective overcurrent ratio of the weld mark 3, the value range of σ is 0.55≤σ≤0.8, and the unit of S1 is mm2 This embodiment uses the formula S1 = n*L*W to accurately calculate the area of ​​weld mark 3. Combined with the effective overcurrent ratio σ, the actual overcurrent situation is correlated with the theoretical area, making the design of the weld mark 3 area more scientific and reasonable. When σ is between 0.55 and 0.8, it avoids the material waste and cost increase caused by overly large weld mark 3 area, while also preventing problems such as overcurrent heating and reduced conductivity caused by insufficient area. This ensures the stability and reliability of the electrical connection and effectively improves the electrical performance and safety of the battery cell.

[0050] It should be noted that, in this embodiment, the tab 201 and the pole base 101 are connected by ultrasonic welding. Figure 1 and Figure 2 , Figure 1 and Figure 2 The shaded area in the middle shows the weld mark 3 area on the outer surface of the weld. Figure 2 It can be seen that for the rectangular weld mark 3, the area of ​​the weld mark 3 on the outer surface of the weld is S1. The actual weld area is typically measured in the following manner in actual production: the pole base 101 is peeled off the tab 201, and the area of ​​the pole base 101 remaining on the tab 201 is used as the actual weld area. Furthermore, the actual weld area can be calculated by counting the number of pits on the tab 201 where the pole base 101 remains, or the number of pits where no tab 201 remains. It is understood that the value of σ can be, but is not limited to, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8.

[0051] It can be understood that, since S≥1.2*I / γ, it can be deduced that σ*n*L*W≥1.2*I / γ.

[0052] According to one embodiment of the present invention, the length L of the sub-weld mark 301 ranges from 15 mm ≤ L ≤ 22 mm, the width W of the sub-weld mark 301 ranges from 1.5 mm ≤ W ≤ 3.5 mm, and the distance H between two adjacent sub-weld marks 301 ranges from 0 mm ≤ H ≤ 2 mm. Setting the sub-weld mark 301 length between 15 mm and 22 mm and the width between 1.5 mm and 3.5 mm ensures sufficient welding contact area, enhances the mechanical strength and conductivity of the weld, and prevents problems such as cold solder joints, desoldering, and overheating caused by improperly sized sub-weld marks 301. Controlling the distance H between adjacent sub-weld marks 301 between 0 mm and 2 mm avoids both loose connections caused by excessive spacing and short circuit risks caused by too small spacing, thereby improving the reliability of the battery cell.

[0053] It should be noted that the length L of the sub-weld mark 301 in this embodiment may be, but is not limited to, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, or 22 mm. The width W of the sub-weld mark 301 in this embodiment may be, but is not limited to, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, or 3.5 mm. In this embodiment, the distance H between two adjacent sub-weld marks 301 can be, but is not limited to, 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2 mm.

[0054] According to one embodiment of the present invention, Figure 1 and Figure 2 As shown, the cross-sectional shape of the pole base 101 is rectangular, the length direction of the weld mark 3 is consistent with the length direction of the pole base 101, the distance between the side of the weld mark 3 and the corresponding side of the pole base 101 is a, and the value range of a is 1.5mm≤a≤2.5mm. The cross-sectional area S2 of the pole base 101 is (L+2a)*[nW+(n-1)*H+2a], and the unit of S2 is mm 2 On the one hand, the regular shape of the rectangular base allows the weld marks 3 to be neatly arranged along the length direction, making full use of the longitudinal space of the base to match the current conduction requirements of the tab 201 in the length direction. At the same time, the value of a reserves space for welding tooling operation, avoiding tooling interference caused by the edge of the weld mark 3 being too close to the side of the base, thereby ensuring the feasibility of the welding process. On the other hand, the value range of a can also meet the welding deviation tolerance (such as positioning error and thermal deformation allowance) while avoiding design redundancy caused by the base size being too large due to a, thereby reducing raw material waste.

[0055] According to one embodiment of the present invention, the capacity of the battery cell is U, where U is measured in A·h; the peak charge and discharge rate of the battery cell is C, where C is measured in 1 / h; and the relationship between U, C, and I satisfies the following: I=U*C. This embodiment of the present invention establishes a quantitative relationship, I=U*C, between the battery cell capacity U, the peak charge and discharge rate C, and the rated current I of the weld mark 3. On the one hand, the maximum overcurrent value I of the weld mark 3 can be quickly calculated based on the actual capacity and rate requirements in different application scenarios (such as fast charging and high-power output scenarios of power batteries), thereby avoiding insufficient overcurrent capacity or redundant design caused by empirical estimation. On the other hand, the standardized formula provides the core input variable for the calculation of the effective overcurrent area of ​​the weld mark 3 (S≥1.2UC / γ), allowing the tab 201 welding design (such as the number n, dimensions L, W, etc. of the weld marks 3) to be dynamically adjusted based on the physical characteristics of the battery cell, thereby improving design efficiency and consistency.

[0056] It should be noted that the battery charge and discharge rate refers to the current required for the battery to discharge its rated capacity within a specified time, that is, charge and discharge rate = charge and discharge current / rated capacity. For example, when a battery with a rated capacity of 100Ah is discharged at 20A, its discharge rate is 0.2C. In addition, in this embodiment, A·h is the unit used to measure charge capacity in electricity, usually expressed as ampere-hour, abbreviated as "ampere-hour". It is mainly used to describe the storage capacity of energy storage devices such as batteries and capacitors, or the continuous transmission capacity of charge in a circuit.

[0057] According to one embodiment of the present invention, Figure 4 As shown, the cross-sectional shape of the pole 1 is in the shape of an athletic track. In the embodiment of the present invention, the cross-sectional shape of the pole 1 is designed to be in the shape of an annular track, so that the pole 1 can obtain a larger effective flow area in a limited space. Compared with the traditional shape (cylindrical), it can carry a larger current, which meets the fast charging requirements of the battery cell. At the same time, the shape of the athletic track optimizes the current distribution path, avoids the current from being concentrated in a local area, reduces the resistance increase and heat generation problems caused by uneven current density, and ensures that the temperature of the pole 1 is stable during the charging and discharging process.

[0058] According to one embodiment of the present invention, Figure 4As shown, the central axis of the pole 1 is arranged in a collinear manner with the central axis of the pole base 101. In order to meet the welding requirements of the battery cell tab 201, the eccentricity of the tab 201 cannot be large or small. Therefore, in the battery cell currently using a bipolar design, the portion of the pole base of one of the poles is usually unable to be welded to the tab. Therefore, it is necessary to increase the length of the pole base of the other pole to ensure the current capacity of the battery cell. However, the unused portion of the pole base and the extended portion of the pole base will lead to a decrease in material utilization and an increase in production costs. In addition, since the two poles need to be separated by a distance from each other in the battery cell with a bipolar design, the pole must be an eccentric structure relative to the pole base. Based on this, the present invention sets the central axis of the pole 1 and the central axis of the pole base 101 in a collinear manner, which not only optimizes the current conduction path and avoids performance loss and structural hidden dangers caused by eccentricity, but also the single-pole design does not require additional lengthening of the pole base 101, thereby improving material utilization and reducing production costs. While meeting the battery cell's overcurrent capacity and the tab 201 welding requirements, it also improves the overall safety, reliability and economy of the battery cell.

[0059] According to an embodiment of the present invention, on the other hand, a battery pack is provided, comprising: a plurality of the above-mentioned battery cells.

[0060] The battery pack of the embodiment of the present invention includes the battery cell as described above and has all the beneficial technical effects of the battery cell, which will not be described in detail here.

[0061] The solution of this application is described below with reference to some embodiments and comparative examples.

[0062] Cells with different overcurrent requirements were selected, different welding parameters and pole base sizes were designed, and the overcurrent temperature rise results of the cells were simulated and analyzed as shown in Table 1.

[0063] Table 1

[0064]

[0065] It can be seen that when the following conditions are met: σ*n*L*W ≥ 1.2*I / γ, the maximum overcurrent requirements of each cell can be met. Otherwise, the overcurrent temperature rise at the cell tab 2 is high, exceeding the design requirements. Furthermore, when the length of the pole base 101 is L+2a and the width of the pole base 101 is (L+2a)*[nW+(n-1)*H+2a], the welding requirements can be met. If the length or width of the pole base 101 is too large, it will cause design redundancy and increase the production cost of the pole 1. If the length or width of the pole base 101 is too small, welding may cause interference with welding tooling or affect the appearance of the lower plastic 6, resulting in quality issues.

[0066] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: A pole, one end of which is provided with a pole base; A pole group, one end of which is provided with a pole ear, the pole ear being welded to a side of the pole base away from the pole to form a weld mark; The effective flow area of ​​the weld mark is S, and the unit of S is mm 2 The current coefficient of the tab is γ, and the value range of γ is 8A / mm 2 ≤γ≤15A / mm 2 The rated current of the welding mark is I, the unit of I is A, and S, γ, and I satisfy: S≥1.2*I / γ.

2. The battery cell according to claim 1, characterized in that The weld mark includes at least one sub-weld mark, the sub-weld mark is rectangular in shape, and the orthographic projection of the sub-weld mark along the height direction of the pole falls within the range of the pole base.

3. The battery cell according to claim 2, characterized in that There are n sub-weld marks, where n is a positive integer greater than or equal to 2, and the n sub-weld marks are arranged side by side along the width direction of the tab, and the distance between two adjacent sub-weld marks is H; the length direction of the sub-weld marks is consistent with the length direction of the tab.

4. The battery cell according to claim 3, characterized in that The length of the sub-weld print is L, the unit of L is mm, the width of the sub-weld print is W, the unit of W is mm, the surface area of ​​the weld print S1 = n*L*W, and S1 and S satisfy: S = σ*n*L*W, where n is the number of sub-weld prints, σ ​​is the effective overcurrent ratio of the weld print, the value range of σ is 0.55≤σ≤0.8, and the unit of S1 is mm 2 .

5. The battery cell according to claim 4, characterized in that: The length L of the sub-weld mark is in the range of 15 mm ≤ L ≤ 22 mm, the width W of the sub-weld mark is in the range of 1.5 mm ≤ W ≤ 3.5 mm, and the distance H between two adjacent sub-weld marks is in the range of 0 mm ≤ H ≤ 2 mm.

6. The battery cell according to claim 5, characterized in that The cross-sectional shape of the pole base is rectangular, the length direction of the sub-weld mark is consistent with the length direction of the pole base, the distance between the side of the weld mark and the corresponding side of the pole base is a, and the value range of a is 1.5mm≤a≤2.5mm. The cross-sectional area of ​​the pole base S2 = (L+2a)*[nW+(n-1)*H+2a], and the unit of S2 is mm 2 .

7. The battery cell according to any one of claims 1 to 6, characterized in that: The capacity of the battery cell is U, where the unit of U is A·h; the charge and discharge peak rate of the battery cell is C, where the unit of C is 1 / h; and the relationship among U, C, and I satisfies: I=U*C.

8. The battery cell according to any one of claims 1 to 6, characterized in that: The cross section of the pole is in the shape of an athletic track.

9. The battery cell according to any one of claims 1 to 6, characterized in that: The central axis of the pole is collinear with the central axis of the pole base.

10. A battery pack, characterized in that: include: A plurality of battery cells according to any one of claims 1 to 9.

Images