A negative electrode current collector and a cylindrical secondary battery

Abstract

This utility model relates to the field of cylindrical battery technology, and proposes a negative electrode current collector and a cylindrical secondary battery, including a disk surface, a tail end, and an intermediate connecting part. The two ends of the intermediate connecting part are integrally formed on the disk surface and the tail end, respectively. The width of the intermediate connecting part is W, the maximum length of the disk surface along the width direction of the intermediate connecting part is D0, and the maximum length of the tail end along the width direction of the intermediate connecting part is W2, where W / D0 = 58.3%-72.3% and W / W2 = 71.8%-80%. By rationally setting the width of the disk surface, the tail end, and the intermediate connecting part, this utility model not only ensures the current carrying capacity of the negative electrode current collector and the safety performance of the battery, but also avoids interference and collision between the negative electrode current collector and the battery casing during assembly, improving the assembly efficiency and quality of the battery, thereby effectively improving the overall performance of the battery.

Description

Technical Field

[0001] This utility model relates to the field of cylindrical battery technology, and in particular to a negative electrode current collector and a cylindrical secondary battery. Background Technology

[0002] With the rapid development of technology, the demand for energy storage in various electronic devices, electric vehicles, and energy storage systems is increasing. Rechargeable batteries, due to their rechargeable nature, have become a key energy solution to meet these needs. Among them, cylindrical rechargeable batteries, with their compact structure, high energy density, and mature manufacturing processes, have been widely used in numerous application scenarios.

[0003] The negative electrode current collector is one of the key components in a cylindrical secondary battery. As a bridge for electron conduction, it efficiently collects the current generated by the active materials inside the cell and outputs it to the external circuit.

[0004] For example, the utility model disclosed in announcement number CN211305143U discloses a negative electrode bottom welding current collector device, which is provided with a cover plate and a tail body, and the cover plate and tail body are combined to form a structure that is thick at both ends and thin in the middle. However, this technical solution does not reasonably set the width of the current collector in the middle position. If the width is too small, the current carrying capacity of the current collector will be limited, and the current collector will easily heat up when the battery is charged and discharged at high rates, affecting the safety performance of the battery. If the width is too large, the current collector will interfere with the battery casing during the battery assembly process, affecting the assembly efficiency and assembly quality of the battery. Utility Model Content

[0005] In view of this, the present invention proposes a negative electrode current collector and a cylindrical secondary battery. By reasonably setting the width ratio of the negative electrode current collector, the current carrying capacity and assembly efficiency of the battery can be balanced, thereby effectively improving the overall performance of the battery.

[0006] The technical solution of this utility model is implemented as follows: On the one hand, this utility model provides a negative electrode current collector, including a plate surface, a tail end, and an intermediate connecting part. The two ends of the intermediate connecting part are integrally formed on the plate surface and the tail end, respectively. The width of the intermediate connecting part is W, the maximum length of the plate surface along the width direction of the intermediate connecting part is D0, and the maximum length of the tail end along the width direction of the intermediate connecting part is W2. W / D0 = 58.3%-72.3%, and W / W2 = 71.8%-80%.

[0007] Based on the above technical solution, preferably, the length of the negative electrode current collector along the length direction of the intermediate connecting part is L. 10 W / L 10 =26.5% - 32.8%.

[0008] Further optimized, W2 / L 10 =37.1% - 41.3%.

[0009] Further optimized, D0 / L 10 =41.2% - 49.7%.

[0010] Based on the above technical solutions, preferably, the intermediate connecting part includes a plate and a shrinking part. One end of the plate is integrally formed on the tail end, and the other end is connected to the disc surface through the shrinking part. The shrinking part is integrally formed with the plate and the disc surface. The minimum length of the shrinking part along the width direction of the intermediate connecting part is W1, where W1 / W = 89.3%-98.2%.

[0011] More preferably, the disc surface is a circular plate structure with a radius of R1, and the length of the contracted portion along the length direction of the intermediate connecting portion is L1, where L1 / R1 = 23.3%-32.6%.

[0012] More preferably, the length of the intermediate connecting portion is L. 12 L 12 / L 10 =39% - 47.4%.

[0013] Based on the above technical solutions, preferably, the maximum length of the disk surface along the length direction of the intermediate connecting portion is L. 13 L 13 =33.65-37.65mm.

[0014] Based on the above technical solutions, preferably, the maximum length of the tail end along the length direction of the intermediate connecting portion is L. 11 L 11 =17-21mm.

[0015] Secondly, this utility model provides a cylindrical secondary battery, including the aforementioned negative electrode current collector; the length of the negative electrode current collector along the length direction of the intermediate connecting portion is L. 10 L 10 =90.45-98.45mm.

[0016] The negative electrode current collector and cylindrical secondary battery of this utility model have the following advantages over the prior art:

[0017] Beneficial effects:

[0018] (1) By reasonably setting the width of the disk, the width of the tail end and the width of the middle connection, not only can the current carrying capacity of the negative current collector be guaranteed and the safety performance of the battery be guaranteed, but also interference and collision between the negative current collector and the battery casing during the assembly process can be avoided, thereby improving the assembly efficiency and assembly quality of the battery and effectively improving the overall performance of the battery.

[0019] (2) By setting the intermediate connecting part to include a plate and a shrinking part, and limiting the specifications of the shrinking part, not only can the structural strength of the negative electrode current collector be guaranteed, but the bending effect of the negative electrode current collector can also be improved, thereby further improving the assembly efficiency of the negative electrode current collector. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a top view of a negative electrode current collector according to the present invention.

[0022] Figure 2 This is a top view of the middle connecting part of a negative electrode current collector according to this utility model.

[0023] Figure 3 This is a perspective view of a negative electrode current collector of this utility model in a folded state.

[0024] Among them: 1. Plate surface; 2. Tail end; 3. Middle connecting part; 31. Plate body; 32. Shrinking part. Detailed Implementation

[0025] The technical solutions of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0026] The present invention relates to a cylindrical secondary battery, comprising a casing, a core, and a negative electrode current collector. The core is disposed inside the casing and is composed of a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.

[0027] The positive electrode is made by coating positive active materials (such as lithium cobalt oxide, lithium iron phosphate, etc.) onto an aluminum foil current collector. These active materials release lithium ions during charging and absorb lithium ions during discharging. The negative electrode is made by coating negative active materials (such as graphite) onto a copper foil current collector. During battery charging and discharging, the negative electrode is responsible for accepting and releasing lithium ions. The separator is a porous insulating material, usually made of polymers such as polypropylene (PP) and polyethylene (PE). It is located between the positive and negative electrodes, acting as an interlayer to isolate the positive and negative electrodes, prevent short circuits, and allow lithium ions to pass through, ensuring ion conduction within the battery. The electrolyte is the lithium ion transport medium, made by dissolving lithium salts (such as lithium hexafluorophosphate) in an organic solvent. It provides channels for the movement of lithium ions between the positive and negative electrodes, enabling the battery to charge and discharge normally.

[0028] The negative current collector is the electrical connection medium of the battery, used to connect the negative terminal of the winding core to the casing, or to connect the negative terminal of the winding core to the negative terminal cap assembly on the casing.

[0029] The negative electrode current collector has high conductivity. It quickly collects electrons generated by the negative electrode active material and transmits the current to the external circuit with low resistance. This can effectively reduce the internal resistance of the battery, reduce energy loss during transmission, and improve the charging and discharging efficiency of the battery.

[0030] The negative electrode current collector ensures that the current is evenly distributed in the negative electrode area, avoiding situations where the local current is too large or too small. The uniform current distribution helps to improve the consistency of the internal chemical reaction of the battery, reduce the risk of local overheating and overcharging / over-discharging, thereby improving the overall performance and safety of the battery.

[0031] Meanwhile, the negative electrode current collector provides physical support for the negative electrode material, helping to maintain the stability of the negative electrode structure. During battery charging and discharging, the negative electrode active material expands and contracts. The negative electrode current collector can withstand this mechanical stress, preventing the negative electrode material from falling off or deforming, ensuring the integrity of the battery structure. Especially after multiple charge-discharge cycles of lithium-ion batteries, it can still maintain the stable structure of the negative electrode, which is beneficial to extending the battery's cycle life.

[0032] The present invention provides a negative electrode current collector, comprising a plate surface 1, a tail end 2, and an intermediate connecting part 3. The plate surface 1, the intermediate connecting part 3, and the tail end 2 are arranged sequentially. The two ends of the intermediate connecting part 3 are integrally formed on the plate surface 1 and the tail end 2, respectively, and the two ends of the intermediate connecting part 3 are continuously arranged with the plate surface 1 and the tail end 2, respectively.

[0033] The intermediate connecting part 3 is a long strip structure. The lengths of the negative electrode current collector, the disk surface 1 and the tail end 2 along the length direction of the intermediate connecting part 3 are respectively represented as the length of the negative electrode current collector, the length of the disk surface 1 and the length of the tail end 2. The lengths of the negative electrode current collector, the disk surface 1 and the tail end 2 along the width direction of the intermediate connecting part 3 are respectively represented as the width of the negative electrode current collector, the width of the disk surface 1 and the width of the tail end 2.

[0034] The disc 1 and the tail end 2 are used to connect with the negative electrode tab and the housing. For this purpose, the surface area of ​​the disc 1 and the tail end 2 is appropriately increased, so that the width of the middle connecting part 3 is slightly narrower than the width of the disc 1 and the tail end 2. In order to facilitate the connection between the disc 1 and the relevant components, increase the contact area between the disc 1 and the relevant components, and improve the connection reliability between the disc 1 and the relevant components, the disc 1 is preferably set as a circular plate structure or an arc-shaped plate structure. Similarly, the tail end 2 can also be set as a circular plate structure or an arc-shaped plate structure.

[0035] The negative electrode tab is parallel to the bottom of the casing or the negative electrode cap assembly on the bottom of the casing. Therefore, after the battery is assembled, the disc 1 needs to be parallel to the tail end 2. That is, during the battery assembly process, the middle connecting part 3 needs to be bent.

[0036] Therefore, the intermediate connecting part 3 is configured to include a plate 31 and a contraction part 32. One end of the plate 31 is integrally formed on the tail end 2, and the other end is connected to the disk surface 1 through the contraction part 32. The contraction part 32 is integrally formed with the plate 31 and the disk surface 1, and the tail end 2, plate 31, contraction part 32 and disk surface 1 are continuously arranged. The contraction part 32 is the bending position of the intermediate connecting part 3. Therefore, in order to facilitate bending of the contraction part 32, the structural strength of the contraction part 32 should be reduced.

[0037] In a preferred embodiment, the length of the contraction portion 32 along the width direction of the intermediate connecting portion 3 is reduced, such as... Figure 1 and Figure 2 As shown, a corresponding groove is opened at the connection between the disc surface 1 and the middle connecting part 3, which reduces the width of that position.

[0038] To ensure the overcurrent stability of the negative electrode current collector, the plate 31 is preferably a long strip structure of equal width.

[0039] At the same time, the position of the shrinkage part 32 is relatively obvious. During the battery assembly process, the operator can accurately judge the position of the shrinkage part 32, that is, accurately grasp the bending position of the negative electrode current collector, which helps to improve the assembly efficiency of the battery and the consistency of the finished battery.

[0040] like Figure 1 and Figure 2As shown, the radius of disk 1 is R1, the width of the intermediate connecting part 3 is W, the maximum length of disk 1 along the width direction of the intermediate connecting part 3 is D0, the minimum length of the contraction part 32 along the width direction of the intermediate connecting part 3 is W1, the maximum length of the tail end 2 along the width direction of the intermediate connecting part 3 is W2, and the length of the negative electrode current collector along the length direction of the intermediate connecting part 3 is L. 10 The maximum length of the tail end 2 along the length direction of the intermediate connecting part 3 is L. 11 The length of the intermediate connecting part 3 is L 12 The maximum length of disk 1 along the length direction of the intermediate connecting part 3 is L. 13 The length of the contraction portion 32 along the length direction of the intermediate connecting portion 3 is L1.

[0041] In some embodiments, L 10 =90.45-98.45mm, that is, the length of the negative electrode current collector is 90.45mm, 94.45mm or 98.45mm, etc.

[0042] In some embodiments, W / D0 = 58.3%-72.3%, meaning the width of the intermediate connecting portion 3 is 58.3%, 65%, or 72.3% of the maximum width of the disk surface 1, etc. If W / D0 < 58.3%, the width of the intermediate connecting portion 3 is too small, which limits the current carrying capacity of the negative electrode current collector. During high-rate charging and discharging, the tail end 2 is more prone to overheating, affecting the battery's safety performance. If W / D0 > 72.3%, the width of the intermediate connecting portion 3 is too large. When bending and assembling the negative electrode current collector, the bending position of the negative electrode current collector will interfere with the casing, affecting the battery assembly.

[0043] In some embodiments, W / W2 = 71.8%-80%, meaning the width of the intermediate connecting portion 3 is 71.8%, 76%, or 80% of the maximum width of the tail end 2. If W / W2 < 71.8%, the width of the intermediate connecting portion 3 is too small, which limits the current carrying capacity of the negative electrode current collector. During high-rate charging and discharging, the tail end 2 is more prone to overheating, affecting the battery's safety performance. If W / W2 > 80%, the width of the intermediate connecting portion 3 is too large. When bending and assembling the negative electrode current collector, the bending position of the negative electrode current collector will interfere with the casing, affecting the battery assembly.

[0044] In some embodiments, W / L 10 =26.5%-32.8%, meaning the width of the intermediate connecting part 3 is 26.5%, 29.6%, or 32.8% of the overall length of the negative electrode current collector, etc. If W / L 10 If the W / L is less than 26.5%, the width of the intermediate connection part 3 is too small, which limits the current carrying capacity of the negative electrode current collector. During high-rate charging and discharging, the tail end 2 is more prone to overheating, affecting the battery's safety performance.10 If the width of the intermediate connecting part 3 is greater than 32.8%, the bending position of the negative current collector will interfere with the casing when the negative current collector is bent and assembled, affecting the assembly of the battery.

[0045] In some embodiments, W2 / L 10 =37.1%-41.3%, meaning the maximum width of tail end 2 is 37.1%, 39.2%, or 41.3% of the overall length of the negative electrode current collector, etc. If W2 / L 10 If the width of tail end 2 is less than 37.1%, then the maximum width of tail end 2 is too small. When tail end 2 is welded to the cap, the area of ​​its weldable region becomes smaller, resulting in a reduction in the effective area of ​​the welding position, a decrease in current carrying capacity, and heat generation at the welding point, affecting battery performance. If W2 / L 10 If the width is greater than 41.3%, the maximum width of the tail end 2 is too large, which limits the adjustment range of the tail end 2 and the cap during welding. When the tail end 2 is bent into the shell, it will interfere with the shell, which will restrict the assembly of the battery.

[0046] In some embodiments, D0 / L 10 =41.2%-49.7%, meaning the maximum width of panel 1 is 41.2%, 45.4%, or 49.7% of the overall length of the negative electrode current collector, etc. If D0 / L 10 If the ratio is less than 41.2%, the maximum width of panel 1 is too small, resulting in a reduction in the area of ​​the solderable region of panel 1. This leads to a decrease in the current carrying capacity and an increase in temperature at the soldering position of panel 1, affecting battery performance. If D0 / L 10 If the maximum width of the disk 1 is greater than 49.7%, then the maximum width of the disk 1 is too large. When assembling the battery, the disk 1 is prone to interference with the casing. At the same time, the excessive maximum width of the disk 1 will also increase the weight of the battery and the production cost.

[0047] In some embodiments, W1 / W = 89.3%-98.2%, meaning the minimum width of the contraction portion 32 is 89.3%, 96.4%, or 98.2% of the width of the intermediate connecting portion 3, etc. If W1 / W < 89.3%, the minimum width of the contraction portion 32 is too small. During normal use, the contraction portion 32 is prone to overheating and melting, leading to battery failure. Simultaneously, a small minimum width of the contraction portion 32 also weakens its structural strength, making it prone to deformation during production and transportation, and affecting battery performance. For example, when the battery is used in vibrating conditions such as with power tools, high-frequency vibrations can cause cracks or even breakage in the contraction portion 32. Cracks in the contraction portion 32 can also produce metallic foreign objects, easily leading to battery failure. Short circuits can occur, affecting battery safety. If W1 / W > 98.2%, the minimum width of the shrinkage section 32 is too large. This not only makes it difficult for operators to quickly identify the shrinkage section 32, but also makes it difficult to bend, affecting battery assembly efficiency. At the same time, the excessive minimum width of the shrinkage section 32 makes it difficult to control the bending position. It will occupy a larger length during bending, and the stress and deformation force during bending are also relatively large. This can easily pull on the welding position between the disc 1 and the core, causing the welding position between the disc 1 and the core to separate, resulting in battery failure.

[0048] In some embodiments, L1 / R1 = 23.3%-32.6%, meaning the length of the contraction portion 32 is 23.3%, 28%, or 32.6% of the radius of the disk surface 1, etc. If L1 / R1 < 23.3%, the length of the contraction portion 32 is too small, which not only makes it difficult for operators to quickly identify the contraction portion 32, affecting assembly efficiency, but also affects the bending effect of the contraction portion 32. If L1 / R1 > 32.6%, the length of the contraction portion 32 is too large, which will affect the strength of the negative electrode current collector. During the production, transportation, and assembly of the negative electrode current collector, cracking or even breakage can easily occur at the contraction portion 32. Cracks in the contraction portion 32 can also generate metal foreign objects, which can easily lead to short circuits in the battery and affect the battery's safety performance.

[0049] In some embodiments, L 12 / L 10 =39%-47.4%, meaning the length of the intermediate connecting part 3 is 39%, 43.2%, or 47.4% of the overall length of the negative electrode current collector, etc. If L 12 / L 10If the length of the intermediate connecting part 3 is less than 39%, then the length of the disc 1 or the tail end 2 is too large. If the diameter of the disc 1 is too large, it will not only cause interference between the disc 1 and the shell during assembly, increasing the assembly difficulty, but also increase the weight and manufacturing cost of the disc 1. If the length of the tail end 2 is too large, when the tail end 2 is welded to the cap assembly, it will block the explosion-proof valve on the cap. When the battery experiences thermal runaway, the gas will not be able to escape quickly, which will affect the safety performance of the battery. If L 12 / L 10 If the length of the intermediate connecting part 3 is greater than 47.4%, the length of the disk 1 or the tail end 2 is too small, which reduces the weldable area of ​​the disk 1 or the tail end 2, decreases the current carrying capacity, increases the temperature rise at the welding position, and affects the performance of the battery.

[0050] In some embodiments, L 13 =33.65-37.65mm, meaning the maximum length of disk 1 is 33.65mm, 35.65mm, or 37.65mm, etc. If L 13 If the length is less than 33.65mm, the maximum length of the disk surface 1 is too small, causing the contraction section 32 to shift towards the disk surface 1, occupying the solderable area of ​​the disk surface 1. This reduces the current carrying capacity at the soldering position of the disk surface 1, increases the temperature rise, and affects the battery performance. If L 13 If the length is greater than 37.65mm, the maximum length of the disc 1 is too large. This will not only make the disc 1 easily interfere with the shell during assembly, but also increase the weight and manufacturing cost of the disc 1.

[0051] In some embodiments, L 11 =17-21mm, meaning the maximum length of tail end 2 is 17mm, 19mm, or 21mm, etc. If L 11 If the length is less than 17mm, the maximum length of tail end 2 is too small, reducing the weldable area and weakening its current-carrying capacity, thus increasing the temperature and affecting battery performance. 11 If the length of the tail end 2 is greater than 21mm, the maximum length of the tail end 2 is too large. When inserting the negative current collector into the casing, the tail end 2 is prone to interference with the casing, affecting the battery assembly effect. At the same time, if the maximum length of the tail end 2 is too large, there is no room for position adjustment when welding the tail end 2 to the cap. When the negative current collector is bent into the casing, the tail end 2 will interfere with the opening of the casing, affecting the insertion of the cap into the casing, leading to an increase in the battery assembly failure rate.

[0052] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A negative electrode current collector, characterized in that: It includes a disc surface (1), a tail end (2) and a middle connecting part (3), wherein the two ends of the middle connecting part (3) are integrally formed on the disc surface (1) and the tail end (2), respectively; The width of the intermediate connecting part (3) is W, the maximum length of the disk surface (1) along the width direction of the intermediate connecting part (3) is D0, the maximum length of the tail end (2) along the width direction of the intermediate connecting part (3) is W2, W / D0 = 58.3%-72.3%, and W / W2 = 71.8%-80%.

2. The negative electrode current collector as described in claim 1, characterized in that: The length of the negative current collector along the length direction of the intermediate connecting part (3) is L. 10 W / L 10 =26.5% - 32.8%.

3. A negative electrode current collector as described in claim 2, characterized in that: W2 / L 10 =37.1%-41.3%.

4. A negative electrode current collector as described in claim 3, characterized in that: D0 / L 10 <41.2%-49.7% 5. A negative electrode current collector as described in claim 1, characterized in that: The intermediate connecting part (3) includes a plate (31) and a shrinking part (32). One end of the plate (31) is integrally formed on the tail end (2), and the other end is connected to the disk surface (1) through the shrinking part (32). The shrinking part (32) is integrally formed with the plate (31) and the disk surface (1). The minimum length of the contraction portion (32) along the width direction of the intermediate connecting portion (3) is W1, where W1 / W = 89.3%-98.2%.

6. A negative electrode current collector as described in claim 5, characterized in that: The disk surface (1) is a circular plate structure with a radius of R1. The length of the contraction part (32) along the length direction of the intermediate connecting part (3) is L1, and L1 / R1 = 23.3%-32.6%.

7. A negative electrode current collector as described in claim 2, characterized in that: The length of the intermediate connecting part (3) is L 12 L 12 / L 10 =39% - 47.4%.

8. A negative current collector as described in any one of claims 1-7, characterized in that: The maximum length of the disk surface (1) along the length direction of the intermediate connecting part (3) is L. 13 L 13 =33.65-37.65mm.

9. A negative current collector as described in any one of claims 1-7, characterized in that: The maximum length of the tail end (2) along the length direction of the intermediate connecting part (3) is L. 11 L 11 =17-21mm.

10. A cylindrical secondary battery, characterized in that: Includes the negative current collector as described in any one of claims 1-9; The length of the negative electrode current collector along the length direction of the intermediate connecting part (3) is L. 10 L 10 =90.45-98.45mm.

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