Protective device and welding method

Abstract

The invention discloses a protection device and a welding method. The protection device comprises an annular protection cover and a cover plate. The protective cover is provided with a first port and a second port. The cover plate covers the first port in a sealing manner and is connected with the protective cover, the cover plate and the protective cover jointly define a welding cavity, and the welding cavity is used for covering a to-be-welded area of a pole and a connecting piece in the top cover assembly of the battery. The protective cover is of a porous structure, the porosity phi of the porous structure is larger than or equal to 30% and smaller than or equal to 80%, and the aperture D is larger than or equal to 30 micrometers and smaller than or equal to 200 micrometers. In the application, the protective cover adopts the porous structure with the porosity of 30-80% and the pore diameter of 30-200 microns, and the porous structure can enable metal splashes which are generated by welding and have the particle size distributed in the range of 10-800 microns to effectively enter and be retained in a pore network, so that the metal splashes are prevented from flying into the battery shell; and the hidden danger of micro short circuit or thermal runaway of the battery caused by metal foreign matters is eliminated from the source.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a protective device and welding method. Background Technology

[0002] With the rapid development of the energy storage and new energy vehicle industries, the safety and reliability of batteries, as core power and energy storage units, have become key factors for industrial progress. In the battery's top cover assembly, the welding process between the connecting tabs and the terminals is a crucial step in the battery packaging process, directly affecting the integrity of the battery's internal structure and the stability of its electrical connections. The purpose of this welding process is to achieve an efficient and reliable connection between the top cover and the copper or aluminum connecting tabs. Currently, laser welding technology, due to its advantages such as high efficiency, concentrated heat input, and small heat-affected zone, has become the mainstream process for this welding procedure.

[0003] However, due to the extremely high energy density during laser welding, it is highly prone to causing violent vaporization and sputtering of copper and aluminum materials, generating a large amount of metal spatter. These spatter particles have a wide size distribution, typically between 10 μm and 800 μm. Among them, tiny particles of 10-50 μm are difficult to effectively capture and remove from the inner cavity of the battery casing due to their small size, light weight, and wide diffusion range. Once these metal foreign objects remain inside the battery casing, they can cause micro-short circuits, leading to an abnormally high self-discharge rate. In more serious cases, larger or sharp metal particles may pierce the separator, causing internal short circuits, reducing battery cycle life by 20%-30%, or even triggering thermal runaway, resulting in serious safety accidents. Summary of the Invention

[0004] In view of the above problems, this application provides a protective device and a welding method.

[0005] In a first aspect, this application provides a protective device. The protective device includes an annular protective cover and a cover plate. The protective cover has a first port and a second port. The cover plate seals the first port and is connected to the protective cover. The cover plate and the protective cover together form a welding cavity, which is used to cover the welding area between the terminal post and the connecting piece in the top cover assembly of the battery. The protective cover has a porous structure, and the porosity φ of the porous structure satisfies: 30% ≤ φ ≤ 80%, and the pore diameter D satisfies: 30 μm ≤ D ≤ 200 μm.

[0006] In some embodiments, the protective cover is made of porous ceramic fiber felt.

[0007] In some embodiments, the material of the protective cover comprises aluminum oxide and silicon dioxide, wherein the mass percentage W1 of the aluminum oxide in the material of the protective cover satisfies: 60% ≤ W1 ≤ 70%, and the mass percentage W2 of the silicon dioxide in the material of the protective cover satisfies: 25% ≤ W2 ≤ 35%.

[0008] In some embodiments, the roughness Ra of the inner surface of the protective cover satisfies: 2.5 μm ≤ Ra ≤ 4.2 μm.

[0009] In some embodiments, the cover plate is provided with a first through hole for the laser to pass through and enter the welding cavity.

[0010] In some embodiments, the flow-cutting area S1 of the first through hole and the area S0 of the cover plate satisfy: 0.2≤S1 / S0≤0.3.

[0011] In some embodiments, the cover plate is provided with a second through hole spaced apart from the first through hole. The second through hole is used to dissipate heat from the welding cavity to the outside of the welding cavity or to introduce protective gas into the welding cavity. The cross-sectional area S1 of the first through hole is larger than the cross-sectional area S2 of the second through hole.

[0012] In some embodiments, the first through hole is located at the center of the cover plate, and the second through hole includes a plurality of second through holes, which are evenly distributed around the first through hole.

[0013] In some embodiments, the flow-cutting area S2 of the second through hole and the flow-cutting area S1 of the first through hole satisfy the condition: 0.2≤S2 / S1≤0.3.

[0014] In some embodiments, the total intercepting area S2' of the second through hole and the area S0 of the cover plate satisfy: 0.02≤S2' / S0≤0.3.

[0015] In some embodiments, the protective device further includes a blocking portion housed in the welding cavity and connected to the protective cover and / or the cover plate. Each second through hole corresponds to one blocking portion. In the height direction of the protective cover, the blocking portion is spaced apart from the corresponding second through hole, and in a projection plane perpendicular to the height direction of the protective cover, the projection of the blocking portion at least partially overlaps with the projection of the second through hole.

[0016] In some embodiments, the height h of the protective cover satisfies: 100mm ≤ h ≤ 150mm.

[0017] In some embodiments, the light transmittance of the cover plate satisfies: 90% ≤ T.

[0018] In some embodiments, the cover plate is made of borosilicate glass.

[0019] In some embodiments, the thickness t of the cover plate satisfies: 2mm ≤ t ≤ 3mm.

[0020] In some embodiments, the protective cover and the cover plate are bonded together with ceramic adhesive.

[0021] Secondly, this application provides a welding method for the protective device described in any of the above embodiments, used for welding a connecting piece and an electrode post. The welding method includes: The protective device is placed on the platform and covered over the area to be welded between the connecting piece and the pole post, so that the area to be welded is located within the welding cavity; and A laser welding device is used to perform laser welding on the area to be welded of the connecting piece and the area to be welded of the pole through the cover plate.

[0022] In some embodiments, the welding power P of the welding device satisfies: 1500W ≤ P ≤ 2000W.

[0023] In some embodiments, the welding rate V of the welding apparatus satisfies: 8 mm / s ≤ V ≤ 10 mm / s.

[0024] In some embodiments, the focal offset δ of the welding device satisfies: -0.3mm≤V≤0mm.

[0025] In some embodiments, the process of laser welding the area to be welded of the connecting piece and the area to be welded of the pole piece through the cover plate using a laser welding device further includes: Protective gas is introduced into the welding cavity through the second through hole on the cover plate.

[0026] In some embodiments, the flow rate of the protective gas satisfies: 8 L / min ≤ Q ≤ 10 L / min.

[0027] In the protective device and welding method of this application, the protective cover adopts a porous structure with a porosity of 30% to 80% and a pore size of 30 micrometers to 200 micrometers. This porous structure enables metal spatter generated during welding, with a particle size distribution in the range of 10 micrometers to 800 micrometers, to effectively enter and remain in the pore network, thereby preventing it from flying into the battery casing and eliminating the potential danger of battery micro-short circuit or thermal runaway caused by metal foreign objects from the source.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0029] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein: Figure 1 This is a schematic diagram of the protective device, platform, and battery according to some embodiments of this application; Figure 2 These are schematic diagrams of the battery structure in some implementation methods; Figure 3 yes Figure 2 A schematic diagram of the planar structure of the top cover assembly of the battery shown; Figure 4 yes Figure 1 A top view of the cover plate of the protective device shown; Figure 5 This is a schematic diagram of the structure of the protective device according to other embodiments of this application; Figure 6 This is a schematic flowchart of a welding method according to some embodiments of this application; Figure 7 This is a schematic flowchart of a welding method according to some other embodiments of this application.

[0030] The reference numerals in the detailed embodiments are as follows: Protective device 10, protective cover 11, first port 111, second port 113, cover plate 13, welding cavity 110, first through hole 131, second through hole 133, blocking part 15; Battery 20, top cover assembly 21, terminal post 213, connecting piece 215; Stage 30; height direction Z. Detailed Implementation

[0031] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0032] With the rapid development of the energy storage and new energy vehicle industries, the safety and reliability of batteries, as core power and energy storage units, have become key factors for industrial progress. In the battery's top cover assembly, the welding process between the connecting tabs and the terminals is a crucial step in the battery packaging process, directly affecting the integrity of the battery's internal structure and the stability of its electrical connections. The purpose of this welding process is to achieve an efficient and reliable connection between the top cover and the copper or aluminum connecting tabs. Currently, laser welding technology, due to its advantages such as high efficiency, concentrated heat input, and small heat-affected zone, has become the mainstream process for this welding procedure.

[0033] However, due to the extremely high energy density during laser welding, it is highly prone to causing violent vaporization and sputtering of copper and aluminum metal materials, generating a large amount of metal spatter. These spatter particles have a wide size distribution, typically between 10μm and 800μm. Among them, tiny particles of 10μm-50μm are difficult to effectively capture and remove from the inner cavity of the battery casing due to their small size, light weight, and wide diffusion range. Once these metal foreign objects remain inside the battery casing, they can cause micro-short circuits, leading to an abnormally high self-discharge rate. In more serious cases, larger or sharp metal particles may pierce the separator, causing internal short circuits, reducing battery cycle life by 20%-30%, or even triggering thermal runaway, resulting in serious safety accidents. To address this problem, this application provides a protective device 10 ( Figure 1 (as shown) and welding method ( Figure 6 and Figure 7 (As shown).

[0034] Please see Figures 1 to 3 In a first aspect, this application provides a protective device 10. The protective device 10 includes an annular protective cover 11 and a cover plate 13. The protective cover 11 is provided with a first port 111 and a second port 113. The cover plate 13 covers the first port 111 and is connected to the protective cover 11. The cover plate 13 and the protective cover 11 together form a welding cavity 110, which is used to cover the welding area between the terminal post 213 and the connecting piece 215 in the top cover assembly 21 of the battery 20. The protective cover 11 has a porous structure, and the porosity φ of the porous structure satisfies: 30%≤φ≤80%, and the pore diameter D satisfies: 30μm≤D≤200μm.

[0035] The protective cover 11 is a ring-shaped or cylindrical structural component in the protective device 10. The cross-sectional shape of the protective cover 11, obtained by a plane perpendicular to the height direction Z of the protective device 10, can be circular, square, or other polygonal to accommodate different shapes of welding areas or installation spaces. The ring-shaped protective cover 11 has a first port 111 and a second port 113, which are separated in the height direction Z. The second port 113 is an open end close to the workpiece to be welded (such as the top cover assembly 21 and connecting piece 215 of the battery 20), while the first port 111 is a closed end or an open end connecting to other structures (such as a support frame).

[0036] The cover plate 13 is a light-transmitting component that is basically plate-shaped and is sealed to the first port 111 by a connection method. The connection between the cover plate 13 and the protective cover 11 can be achieved by various methods such as adhesive bonding, snap fastening, threaded fastening, or flange docking.

[0037] The welding chamber 110 is a semi-enclosed space formed by the cover plate 13 and the side walls of the protective cover 11. Together with the stage 30, the welding chamber 110 can physically isolate the area to be welded from the external environment. During operation, the welding chamber 110 completely encloses the area to be welded of the electrode post 213 and the connecting piece 215, providing an operating space that isolates the area to be welded from the external environment for laser welding operations.

[0038] The protective cover 11 adopts a porous structure, where the porosity φ is the percentage of pore volume in the porous material relative to the total volume. The pore diameter D refers to the diameter of the pore channels in the porous material. In this embodiment, the porosity φ can be any one of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%, or any value between any two adjacent values. The pore diameter D can be any one of 30μm, 40μm, 50μm, 60μm, 80μm, 100μm, 120μm, 150μm, 180μm, and 200μm, or any value between any two adjacent values.

[0039] If the porosity φ is less than 30%, the porous material is too dense. Dense materials have poor air permeability, which is not conducive to the diffusion of high-temperature fumes and the release of instantaneous pressure in the welding cavity 110. This may affect the stability of the welding process or increase the pressure inside the protective cover 11.

[0040] If the porosity φ is higher than 80%, the porous material is too loose, and the mechanical strength and structural integrity of the protective cover 11 will decrease. Under the thermal shock generated by welding and the high-speed impact of metal particles, the porous structure is prone to local collapse, pulverization or fiber breakage, making it unsuitable for long-term use as a reliable protective cover 11, and it may introduce secondary pollution due to the debris it generates.

[0041] If the pore size D is less than 30 μm, the pores are too small. Although they may intercept some tiny particles, they will form a surface barrier for larger particles (such as those larger than 50 μm), making it difficult for them to enter the material and causing rebound problems. Moreover, an excessively small pore size will increase airflow resistance, hindering heat exchange and pressure balance within the welding cavity 110.

[0042] If the pore size D is greater than 200 μm, the pores are too large. For tiny splashes of 10 μm-50 μm, a large number of tiny particles may escape directly through the pores, rendering the protective shield 11 meaningless. At the same time, an excessively large pore size also reduces the specific surface area and fiber network complexity inside the porous material, weakening its ability to capture particles through surface adsorption and mechanical interlocking.

[0043] Therefore, limiting the porosity φ to between 30% and 80% and the pore size D to between 30 μm and 200 μm can balance high interception efficiency with sufficient structural robustness. When metal spatter with a particle size distribution of 10 μm-800 μm impacts this porous structure, larger particles (e.g., >50 μm) may embed themselves in the shallow surface layer or be initially intercepted by the surface fiber network at the moment of impact; small and medium-sized particles easily enter the interior of the pores and move in the complex and tortuous three-dimensional pore network. Due to multiple collisions and friction with the fibers, they rapidly dissipate kinetic energy and are eventually captured by the fiber surface or stuck at the pore intersections. In this way, the spatter is fixed inside the side wall of the protective cover 11, rather than remaining in the welding cavity 110 space or bouncing back to the area to be welded.

[0044] In the protective device 10 of this application, the protective cover 11 adopts a porous structure with a porosity of 30% to 80% and a pore size of 30 micrometers to 200 micrometers. This porous structure enables metal spatter generated during welding, with a particle size distribution in the range of 10 micrometers to 800 micrometers, to effectively enter and remain in the pore network, thereby preventing it from scattering into the battery 20 casing and eliminating the potential for micro-short circuits or thermal runaway of the battery 20 caused by metal foreign objects from the source.

[0045] Please continue reading. Figure 1 In some embodiments, the protective cover 11 is made of porous ceramic fiber felt.

[0046] Porous ceramic fiber felt is a flexible or semi-rigid felt-like material made primarily of ceramic fibers through web-forming, needle-punching, or bonding processes. The microstructure of porous ceramic fiber felt consists of a large number of randomly interwoven and stacked ceramic fibers with diameters in the micrometer range, forming a complex and interconnected three-dimensional pore network.

[0047] Ceramic fiber felt is typically composed of high-temperature resistant oxides such as alumina, silicon dioxide, and zirconium oxide, with a melting point above 1600℃ and a softening point far exceeding the instantaneous high temperature (usually below 800℃) that may be reached inside the welding cavity 110 during laser welding. Therefore, the protective cover 11 made of ceramic fiber felt can withstand long-term welding thermal cycling without melting or softening, thus maintaining the stability of its geometry and pore structure.

[0048] When molten or semi-molten metal splashes (such as copper or aluminum particles) impact the surface of ceramic fiber felt at high speed, the fiber network acts as a physical barrier, directly and mechanically intercepting larger particles. Secondly, a larger number of tiny particles enter the fiber network. Inside, the large specific surface area of ​​the fibers provides abundant adsorption sites. For metal particles still in a molten or softened state at high temperatures, slight wetting or adhesion may occur upon contact with the ceramic fibers, and they will firmly adhere to the fiber surface after cooling. For solidified particles, they lose kinetic energy through collisions and friction within the fiber labyrinth, eventually becoming stuck at fiber intersections or entangled in the fibers, thus being captured.

[0049] In this embodiment, the protective cover 11 is made of porous ceramic fiber felt. Porous ceramic fiber felt has high porosity and high temperature resistance, which can maintain structural stability at high welding temperatures. It also utilizes its fiber network to provide a large specific surface area, capturing metal spatter generated during welding through a dual mechanism of physical interception and surface adsorption.

[0050] Please continue reading. Figure 1 In some embodiments, the material of the protective cover 11 comprises aluminum oxide and silicon dioxide, wherein the mass percentage W1 of aluminum oxide in the material of the protective cover 11 satisfies: 60% ≤ W1 ≤ 70%, and the mass percentage W2 of silicon dioxide in the material of the protective cover 11 satisfies: 25% ≤ W2 ≤ 35%.

[0051] Porous ceramic fiber felt comprises alumina (Al₂O₃) and silicon dioxide (SiO₂). Alumina is a high-hardness, high-melting-point oxide that enhances the refractoriness and high-temperature strength of porous materials. Silicon dioxide can form a glassy phase or mullite crystals with alumina at high temperatures, which facilitates the bonding between fibers and improves the thermal stability and thermal shock resistance of porous materials.

[0052] The mass percentage W1 of alumina refers to the percentage of the mass of alumina, a single compound, in the total mass of the porous ceramic fiber felt. Specifically, the mass percentage W1 of alumina can be any value from 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, and 70%, or any value between any two adjacent values.

[0053] When the alumina content W1 is below 60%, the overall refractoriness and high-temperature strength of the porous material will be lower. Under the localized high temperatures that may occur inside the welding cavity 110, the porous material of the protective cover 11 is prone to softening, leading to collapse and deformation of the pore structure, thereby reducing the interception efficiency of the protective cover 11 against spatter and the structural integrity of the protective cover 11. At the same time, an excessively low alumina content may mean a relatively high content of silica or other impurities, making the porous material more prone to microcracks under repeated thermal cycling, thus shortening the service life of the protective device 10.

[0054] When the alumina content W1 is higher than 70%, the refractoriness of the protective cover 11 is higher, but the porous material becomes too hard and brittle. Under the continuous high-speed impact of metal spatter, the fibers are more prone to brittle fracture, generating dust. In addition, excessively high alumina content usually requires higher sintering temperatures, which may lead to reduced porosity of the fiber felt, excessive rigidity and insufficient flexibility, making it difficult to process into complex shapes.

[0055] The mass percentage of silicon dioxide, W2, refers to the percentage of the mass of silicon dioxide, a single compound, in the total mass of the porous ceramic fiber felt. Specifically, the mass percentage of silicon dioxide, W2, can be any value from 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%, or any value between any two adjacent values.

[0056] When the silica content W2 is less than 25%, the components in the porous material that serve as high-temperature bonding phases or glass phase forming agents are insufficient, which may lead to weak bonding between ceramic fibers, loose overall structure, easy disintegration of the fiber network under high temperature or mechanical action, insufficient structural strength, and difficulty in maintaining long-term stability of pore morphology.

[0057] When the silica content W2 is higher than 35%, the excessive silica content may cause the porous material to undergo too many crystal phase transformations within a specific temperature range, resulting in a large volume change, which in turn impairs its thermal shock resistance and makes it prone to cracking during the hot and cold cycles of welding.

[0058] Therefore, by controlling the alumina content W1 to 60% to 70% and the silica content W2 to 25% to 35%, the high-temperature strength and chemical inertness dominated by alumina are maintained, while an appropriate amount of silica is used to promote fiber bonding, optimize high-temperature toughness, and inhibit excessive sintering. This allows the protective cover 11 to withstand the high temperature of approximately 800°C in the welding cavity 110 without softening or deforming, nor to become brittle or powdery. Its pore structure can stably perform its interception function, thereby achieving long-term reliable protection.

[0059] Please continue reading. Figure 1In some embodiments, the roughness Ra of the inner surface of the protective cover 11 satisfies: 2.5μm≤Ra≤4.2μm.

[0060] Roughness Ra is a parameter characterizing the degree of microscopic unevenness on the inner surface of the protective cover 11. Specifically, it is the arithmetic mean of the average undulation height of an ideal smooth plane within the sampling length. Specifically, the roughness Ra of the inner surface of the protective cover 11 can be any one of the following values: 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, and 4.2μm, or any value between any two adjacent values.

[0061] When the roughness Ra of the inner surface of the protective cover 11 is less than 2.5 μm, the inner surface is too smooth. Metal spatter that impacts the inner surface at high speed, especially solidified or semi-solidified particles, easily converts its normal kinetic energy into tangential velocity, causing the particles to bounce back into the welding cavity 110 at a large reflection angle. These bounced particles may fly directly into the through-hole area (described below) on the cover plate 13, increasing the risk of metal foreign objects escaping, or they may eventually fall into the battery 20 casing after multiple bounces, reducing the safety of the battery 20.

[0062] When the roughness Ra of the inner surface of the protective cover 11 is greater than 4.2 μm, the inner surface is too rough. Although it increases the surface area, the excessive peaks and valleys can easily cause micro-scraping due to thermal stress concentration when repeatedly impacted by high-temperature molten metal particles, generating ceramic dust and contaminating the battery 20. Moreover, excessively deep rough valleys may trap splashes, making them difficult to clean. Long-term accumulation may affect the air permeability and thermal conductivity of the protective cover 11.

[0063] Therefore, by controlling the surface roughness Ra of the inner surface of the protective cover 11 between 2.5 μm and 4.2 μm, the surface area of ​​the inner surface of the protective cover 11 is increased. This allows for mechanical interlocking and increased friction, which helps the adhered parts impact the inner wall of the protective cover 11, reducing the rebound of metal splashes and preventing them from entering the battery 20 casing due to rebound. At the same time, it prevents the porous material from peeling off and contaminating the battery 20, and ensures the breathability and thermal conductivity of the protective cover 11.

[0064] Please refer to the following: Figure 1 and Figure 4 In some embodiments, the cover plate 13 is provided with a first through hole 131, which is used for the laser to pass through and enter the welding cavity 110.

[0065] The first through hole 131 is a through-hole that penetrates the cover plate 13 and serves as the main path for the laser beam to enter the welding cavity 110. In this application, the axis of the first through hole 131 is perpendicular to the surface of the cover plate 13 to ensure that the laser can accurately and vertically irradiate the area to be welded located at the bottom of the welding cavity 110 (i.e., the contact surface between the pole post 213 and the connecting piece 215).

[0066] The cross-sectional shape of the first through hole 131 can be circular, square, or other geometric shapes that match the shape of the laser spot. The size (diameter or side length) of the first through hole 131 is slightly larger than the diameter of the laser spot after focusing, so as to leave a safety margin for the focusing tolerance of the laser head, optical path jitter, and thermal deformation during the welding process.

[0067] The laser beam generated by the laser welding device passes sequentially through a focusing lens and the first through hole 131 of the cover plate 13 before finally acting on the area to be welded. The first through hole 131 allows the laser energy to penetrate the cover plate 13 (the main body of the cover plate 13 is transparent) with almost no attenuation, thus preserving the optical path conditions required for the laser welding process while maintaining the complete physical enclosure of the welding cavity 110 from spatter.

[0068] Please refer to the following: Figure 1 and Figure 4 In some embodiments, the flow-blocking area S1 of the first through hole 131 and the area S0 of the cover plate 13 satisfy: 0.2≤S1 / S0≤0.3.

[0069] Wherein, the intercepting area S1 refers to the projected area of ​​the first through hole 131 on the plane perpendicular to the laser beam axis, which for a circular hole is π*(d1 / 2)² (d1 is the diameter of the first through hole 131). The area S0 of the cover plate 13 is the effective working area of ​​the cover plate 13 covering the first port 111 of the protective cover 11, which is usually the area enclosed by its outer contour. This ratio (S1 / S0) measures the proportion of the laser channel area in the total window area of ​​the cover plate 13. Specifically, the ratio S1 / S0 can be any value among 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, and 0.30, or any value between any two adjacent values.

[0070] When the ratio S1 / S0 is less than 0.2, the relative area of ​​the first through-hole 131 is too small. This can cause the energy of the laser beam at its periphery to be blocked by the hole wall or to undergo severe diffraction when passing through the first through-hole 131, resulting in laser energy loss, a decrease in focal energy density, and affecting welding penetration and efficiency. Simultaneously, an excessively small first through-hole 131 also places higher demands on the alignment accuracy between the laser head and the workpiece to be welded. Even a small deviation can cause the laser beam to be partially or completely blocked by the cover plate 13, making welding impossible. Furthermore, an excessively small first through-hole 131 is also detrimental to the escape of some of the fumes generated during the welding process.

[0071] When the ratio S1 / S0 is greater than 0.3, the relative area of ​​the first through hole 131 is too large. Although this ensures that the laser beam can pass through smoothly, on the one hand, the excessively large first through hole 131 weakens the structural strength and rigidity of the cover plate 13. When the cover plate 13 is subjected to possible air pressure fluctuations or external mechanical forces in the welding cavity 110, it is prone to bending, vibration, or even cracking, affecting the sealing and stability. On the other hand, the excessively large first through hole 131 reduces the effective coverage area of ​​the cover plate 13 on the top of the welding cavity 110, causing spatter to fly upwards and escape from it, reducing the protective effect of the protective device 10.

[0072] Therefore, the ratio of the intercepting area S1 of the first through hole 131 to the area S0 of the cover plate 13 is between 0.2 and 0.3, ensuring that the first through hole 131 is large enough to minimize the energy loss and optical path interference of the laser, while not excessively weakening the overall structural strength and coverage of the cover plate 13.

[0073] Please refer to [link / reference] Figure 1 and Figure 4 In some embodiments, the cover plate 13 is provided with a second through hole 133 spaced apart from the first through hole 131. The second through hole 133 is used to dissipate heat from the welding cavity 110 to the outside of the welding cavity 110 or to introduce protective gas into the welding cavity 110. The cross-sectional area of ​​the first through hole 131 is larger than the cross-sectional area of ​​the second through hole 133.

[0074] In addition to the first through-hole 131 for laser transmission, the cover plate 13 also has a second through-hole 133 physically spaced from it. The second through-hole 133 is a through-hole penetrating the cover plate 13 and is used to facilitate gas exchange or heat transfer between the inside of the welding cavity 110 and the external environment. In one working mode, the second through-hole 133 serves as a heat dissipation channel, allowing the high-temperature gas generated during welding inside the welding cavity 110 to exchange heat with the outside air through convection, thereby reducing the temperature inside the welding cavity 110. In another working mode, an external gas source (such as an argon cylinder) can be connected to the second through-hole 133 to actively introduce inert protective gas into the welding cavity 110 to drive away air, prevent weld oxidation, and help remove fumes. In yet another working mode, some of the second through-holes 133 serve as heat dissipation channels, while others are connected to the external gas source (such as an argon cylinder). In this way, both functions are achieved, and the second through-hole 133 can reuse both functions, saving design costs.

[0075] The cross-sectional area S1 of the first through hole 131 is larger than the cross-sectional area S2 of the second through hole 133. The second through hole 133 is used to dissipate the heat accumulated in the welding cavity 110 or to introduce protective gas into it. The larger area of ​​the first through hole 131 ensures the unobstructed flow of the main laser beam, while the second through hole 133 provides auxiliary heat dissipation and gas protection functions.

[0076] Please refer to [link / reference] Figure 1 and Figure 4 In some embodiments, the first through hole 131 is located at the center of the cover plate 13, and the second through hole 133 includes a plurality of second through holes 133, which are evenly distributed around the first through hole 131.

[0077] The first through hole 131 is located at the center of the cover plate 13. That is, when the cover plate 13 is installed at the first port 111 of the protective cover 11, the axis of the first through hole 131 coincides with or substantially coincides with the central axis of the annular protective cover 11. This central arrangement ensures that the laser beam emitted from the laser welding device can be incident perpendicularly along the axis of symmetry of the protective cover 11, minimizing unnecessary reflections and scattering caused by beam tilting or eccentricity, and making the welding energy distributed most symmetrically and concentrated in the area to be welded, which is conducive to forming a uniform and high-quality weld.

[0078] Multiple second through holes 133 are arranged in a ring around a central first through hole 131. "Randomly distributed" means that the centers of the second through holes 133 are arranged with equal angular spacing on the same circumference surrounding the first through hole 131. For example, four, six, or eight second through holes 133 can be provided, corresponding to angular spacings of 90 degrees, 60 degrees, or 45 degrees, respectively. This ring-symmetrical layout ensures that the spatial relationship of each second through hole 133 relative to the central first through hole 131 and relative to the center of the welding cavity 110 is identical.

[0079] The heat generated during welding diffuses outwards within the welding cavity 110. The multiple second through holes 133, evenly arranged around the cavity, provide multiple equal outlet channels for the rising and escaping of hot air. This prevents excessive heat accumulation on one side of the welding cavity 110, thus achieving uniformity of the temperature field within the welding cavity 110 and preventing local overheating from damaging the workpiece to be welded or the protective device 10 itself.

[0080] Therefore, the first through hole 131 is located at the center of the cover plate 13, and multiple second through holes 133 are evenly distributed around the first through hole 131. This arrangement puts the laser beam path in the optimal central position, while the multiple smaller second through holes 133 can evenly dissipate heat or exchange gas from all directions, avoiding the formation of local overheating or airflow dead zones in the welding cavity 110.

[0081] Please see Figure 4 In some embodiments, the flow-cutting area S2 of the second through hole 133 and the flow-cutting area S1 of the first through hole 131 satisfy: 0.2≤S2 / S1≤0.3.

[0082] The intercepting area S2 refers to the projected area of ​​any single second through-hole 133 on a plane perpendicular to the laser beam axis. For a circular hole, it is π*(d2 / 2)² (d2 is the diameter of the second through-hole 133). The intercepting area S1 of the first through-hole 131 is defined as described above. The ratio (S2 / S1) defines the scale of the size of a single heat dissipation / ventilation channel relative to the size of the main laser channel. Specifically, the ratio S2 / S1 can be any value among 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, and 0.30, or any value between any two adjacent values.

[0083] When the ratio S2 / S1 is less than 0.2, the size of a single second through-hole 133 is too small relative to the first through-hole 131. While this further reduces the probability of spatter escaping directly through the second through-hole 133, the excessively small second through-hole 133 increases the resistance to gas flow. This limits the effective flow rate, whether for heat dissipation relying on natural convection or for actively introduced shielding gas. This may lead to excessively rapid heat accumulation within the welding cavity 110, resulting in low heat dissipation efficiency, or the shielding gas failing to form a sufficient flow rate and coverage to effectively dissipate air, thus affecting weld quality. Simultaneously, the excessively small diameter of the second through-hole 133 makes it more susceptible to blockage by occasional spatter or condensate, increasing maintenance frequency.

[0084] When the ratio S2 / S1 is greater than 0.3, the size of a single second through-hole 133 is too large relative to the first through-hole 131. This increases the risk of metal spatter directly passing through the second through-hole 133 and sputtering outwards. During welding, some molten metal spatter has a high initial velocity and a certain spray angle, and an excessively large second through-hole 133 cannot effectively physically block these spatter. In addition, an excessively large second through-hole 133 will occupy more area on the cover plate 13, which may affect the local structural strength of the cover plate 13.

[0085] Therefore, limiting the ratio S2 / S1 to between 0.2 and 0.3 restricts the size of the heat dissipation / ventilation holes to be much smaller than the main laser path, thus minimizing the possibility of metal spatter being ejected through these small holes while achieving the auxiliary function (heat dissipation / protective gas passage).

[0086] Please refer to [link / reference] Figure 4 In some embodiments, the total intercepting area S2' of the second through hole 133 (heat dissipation hole) and the area S0 of the cover plate 13 satisfy: 0.02≤S2' / S0≤0.3.

[0087] The total flow area S2' refers to the sum of the individual flow areas (S2) of all the second through holes 133 on the cover plate 13, i.e., S2' = ΣS2. This parameter characterizes the total opening area on the cover plate 13 used for heat dissipation or ventilation. The area S0 of the cover plate 13 is defined as described above. The ratio (S2' / S0) measures the proportion of the heat dissipation / ventilation functional area in the entire working area of ​​the cover plate 13. Specifically, the ratio S2' / S0 can be any value among 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, and 0.30, or any value between any two adjacent values.

[0088] When the ratio S2' / S0 is less than 0.02, the total area of ​​all the second through holes 133 is too small, resulting in insufficient total channels for gas flow. Heat generated during welding cannot be effectively dissipated through natural convection, causing a continuous rise in temperature within the welding cavity 110. This may affect workpiece quality, accelerate the aging of the protective device 10, and even pose safety hazards. Simultaneously, when active introduction of protective gas is required, the small total through hole area creates significant flow resistance, increasing the gas pressure required to achieve the predetermined flow rate, or even preventing the establishment of an effective protective atmosphere, thus reducing welding quality.

[0089] When the ratio S2' / S0 is greater than 0.3, the total area of ​​all the second through holes 133 is too large. Although this can improve heat dissipation and ventilation, it weakens the structural rigidity and strength of the cover plate 13, making it more prone to deformation or damage under pressure fluctuations inside the welding cavity 110 or under external stress. Moreover, the excessively large total opening area of ​​the second through holes 133 increases the probability of metal spatter being directly ejected outwards. Even if the size (S2) of a single second through hole 133 is controlled, the excessively large total area leads to a large number of potential escape paths, reducing the overall reliability of protection.

[0090] Therefore, the ratio of the total intercepting area S2' of all the second through holes 133 to the area S0 of the cover plate 13 is between 0.02 and 0.3. This ratio limits the total capacity of the heat dissipation or ventilation channel, which can ensure the necessary heat exchange and ventilation efficiency, and avoid the problem of increased risk of splashes escaping from the protective cover 11 due to the excessively large total area of ​​the openings.

[0091] Please see Figure 5 In some embodiments, the protective device 10 further includes a blocking part 15, which is housed in the welding cavity 110 and connected to the protective cover 11 and / or the cover plate 13. Each second through hole 133 corresponds to a blocking part 15. In the height direction Z of the protective cover 11, the blocking part 15 is spaced apart from the corresponding second through hole 133, and in the projection plane perpendicular to the height direction Z of the protective cover 11, the projection of the blocking part 15 at least partially overlaps with the projection of the second through hole 133.

[0092] The blocking part 15 is an independent solid component in the protective device 10, and each second through hole 133 has at least one corresponding blocking part 15 that matches it in the welding cavity 110. The blocking part 15 obtains stable support by being fixedly connected to the inner side wall of the protective cover 11, or connected to the inner surface of the cover plate 13 facing the welding cavity 110, or connected to both at the same time.

[0093] Along the height direction Z of the protective cover 11, the blocking part 15 is not tightly attached to the cover plate 13, but maintains a certain vertical distance from the corresponding second through hole 133. This distance constitutes a buffer zone. When projected from the height direction Z of the protective cover 11, the projection area of ​​the blocking part 15 on the plane of the cover plate 13 and the projection area of ​​the corresponding second through hole 133 on the plane of the cover plate 13 have at least partial spatial overlap. That is, when viewed from directly above (along the axial direction of the second through hole 133), the blocking part 15 can partially or completely cover its corresponding second through hole 133.

[0094] The blocking part 15 can be plate-shaped, sheet-shaped, mesh-shaped, or have a specific flow-guiding surface. The material of the blocking part 15 can be the same as that of the protective cover 11 (such as porous ceramic fiber felt), or it can be other high-temperature resistant metals or ceramics. During laser welding, some metal spatter will splash upwards at a high speed and with a certain vertical component. Without the blocking part 15, these spatters have a certain probability of directly passing through the second through hole 133 directly above and escaping to the outside of the welding cavity 110. The blocking part 15, through its spatial positional relationship of overlapping projections with the second through hole 133, sets up a physical barrier on the upward path of the spatter. After the spatter impacts the blocking part 15, its kinetic energy is absorbed or dissipated, and the particles are intercepted or have their direction of movement changed by the surface of the blocking part 15 (if it is a porous or rough surface, it can also assist in adsorption), thereby confining them within the welding cavity 110. The vertical spacing between the blocking part 15 and the second through hole 133 serves two purposes: firstly, it prevents the blocking part 15 from blocking the ventilation channel, ensuring smooth gas flow; secondly, it provides space for the rebound or fall of splashes after hitting the blocking part 15, preventing them from accumulating between the blocking part 15 and the cover plate 13.

[0095] In the protective device 10 of this application embodiment, a blocking part 15 corresponding to the second through hole 133 is provided in the welding cavity 110. The blocking part 15 is located below the through hole and overlaps with its projection, which can physically block metal particles that sputter directly upward from the welding point and fly towards the second through hole 133, effectively preventing the spatter from escaping from the welding cavity 110 through the second through hole 133.

[0096] Please see Figure 5 In some embodiments, the height h of the protective cover 11 satisfies: 100mm≤h≤150mm.

[0097] The height h of the protective cover 11 is the vertical distance between the plane of its first port 111 (typically the inner surface of the cover plate 13) and the inner end face of its opposite second port 113 when the protective device 10 is installed in the working state. This distance is the effective internal height of the welding cavity 110. This parameter determines the available space dimension of the welding cavity 110 in the vertical direction. Specifically, the height h of the protective cover 11 can be any value among 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, and 150mm, or any value between any two adjacent values.

[0098] When the height h of the protective cover 11 is less than 100mm, the vertical space of the welding cavity 110 is too small, which may not provide enough installation and operation space for the workpiece, welding fixture and other process equipment, resulting in interference or failure to perform welding normally; moreover, the metal particles that splash out from the welding point will hit the cover plate 13 within a very short distance. At this time, the splash still has a high speed and kinetic energy, and after hitting the cover plate 13, it will bounce and enter the battery 20.

[0099] When the height h of the protective cover 11 is greater than 150mm, the vertical space of the welding cavity 110 is too large. Although the spatial interference problem is avoided, the excessive volume of the welding cavity 110 indicates that more protective gas is needed to establish an effective atmosphere environment, which increases gas consumption.

[0100] Therefore, the height h of the protective cover 11 is between 100 mm and 150 mm, providing ample internal space for the welding process. This space accommodates the welding fixture and the workpiece, and allows the spatter to be sufficiently attenuated before impacting the cover plate 13. This effectively reduces the risk of the spatter rebounding into the battery 20 due to high-speed collisions and also reduces the amount of protective gas used.

[0101] Please see Figure 1 In some embodiments, the light transmittance of the cover plate 13 satisfies: 90% ≤ T.

[0102] Transmittance T is the ratio of the laser radiation flux transmitted through the cover plate 13 to the laser radiation flux incident on the surface of the cover plate 13 at a given wavelength (usually the laser operating wavelength, such as 1064 nm), typically expressed as a percentage. This parameter characterizes the ability of the cover plate 13 material to transmit the operating laser. Specifically, transmittance T can be any value from 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, and 100%, or any value between any two adjacent values.

[0103] When the transmittance T of the cover plate 13 is less than 90%, the laser will experience significant energy loss during penetration. This energy loss is primarily converted into heat, causing the cover plate 13 to heat up. This not only reduces the effective welding power applied to the workpiece, potentially affecting the welding penetration and speed, requiring a higher power laser output to compensate, but also leads to thermal expansion and stress in the cover plate 13, causing the laser focus to drift and affecting welding quality. Furthermore, the lower transmittance reduces the clarity of the field of view when observing the welding process inside the cavity from outside the cover plate 13, hindering alignment, monitoring, and process adjustments by operators or vision systems.

[0104] The light transmittance T of the cover plate 13 is not less than 90%. The high light transmittance ensures that the laser energy loss when penetrating the cover plate 13 is less than 5%, which meets the power requirements of the welding process. At the same time, it allows operators or vision systems to observe the welding situation in the welding cavity 110 in real time.

[0105] Please see Figure 1 In some embodiments, the cover plate 13 is made of borosilicate glass.

[0106] High borosilicate glass is a special type of glass primarily composed of silicon dioxide (SiO2) and boron oxide (B2O3), with a typically high boron oxide content (e.g., greater than 13%). High borosilicate glass has a low coefficient of thermal expansion, typically around 3.3 × 10⁻⁶. -6 Around / K, far lower than ordinary glass (approximately 9×10). -6 / K), which makes the cover plate 13 made of it generate very little thermal stress when subjected to rapid temperature changes and possible temperature gradients in the welding cavity 110 during laser welding, thereby greatly reducing the risk of cracking or shattering due to thermal shock and ensuring structural integrity and reliability under thermal cycling.

[0107] Moreover, the strain point, annealing point, and softening point of high borosilicate glass are significantly higher than those of ordinary glass, enabling it to withstand high temperatures of 400℃-500℃ for extended periods and even higher instantaneous temperatures for short periods. This allows the cover plate 13 to directly withstand the heat radiation that may be generated by welding spatter and occasional molten droplet sputtering without softening, deformation, or surface damage, thus maintaining the precision of its optical plane over a long period.

[0108] Therefore, the cover plate 13 is made of high borosilicate glass. High borosilicate glass has a low coefficient of thermal expansion and high thermal stability, which can withstand the instantaneous high temperature in the welding cavity 110 without cracking. Moreover, high borosilicate glass has excellent optical properties, which can ensure the realization of high light transmittance.

[0109] Please see Figure 5 In some embodiments, the thickness t of the cover plate 13 satisfies: 2mm≤t≤3mm.

[0110] The thickness t of the cover plate 13 is between 2 mm and 3 mm, which ensures that the cover plate 13 has sufficient rigidity to maintain structural stability and resist pressure fluctuations in the welding cavity 110, while avoiding excessive laser refraction deviation or increased energy absorption caused by excessive glass thickness.

[0111] Thickness t is the dimension of cover plate 13 in the direction perpendicular to its surface. Specifically, thickness t can be any value among 2.0mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm and 3.0mm, or any value between any two adjacent values.

[0112] When the thickness t of the cover plate 13 is less than 2 mm, the mechanical rigidity of the cover plate 13 may be insufficient. During laser welding, slight pressure fluctuations may occur within the welding cavity 110 due to the expansion of high-temperature gas, the introduction of protective gas, or the action of evacuation. An excessively thin cover plate 13 is more prone to micro-deformation or vibration invisible to the naked eye under the influence of internal and external pressure differences. This micro-deformation can cause changes in the optical flatness of the cover plate 13, leading to unexpected refraction or optical path deflection of the laser beam passing through it, affecting the stability of the focal position and welding accuracy. Furthermore, an excessively thin cover plate 13 is more susceptible to damage during installation, cleaning, or exposure to accidental mechanical impacts.

[0113] When the thickness t of the cover plate 13 is greater than 3 mm, the optical path length of the cover plate 13 increases significantly. While this enhances mechanical strength, the lateral displacement (parallel offset) of the laser beam will be greater when passing through a thicker glass medium due to the difference in refractive index between glass and air. If the laser beam is not incident perpendicularly, this offset will be amplified, causing the actual spot position on the workpiece to deviate from the theoretical position, affecting alignment accuracy. Moreover, thicker glass means a longer path for the laser to propagate within it. Even if the material itself has a low absorptivity, the cumulative total absorption loss will increase, resulting in more laser energy being converted into heat within the cover plate 13 itself, exacerbating its temperature rise stress, which is also detrimental to the stability of the optical path and energy transmission efficiency.

[0114] Therefore, the thickness t of the cover plate 13 is limited to between 2 mm and 3 mm to ensure that the cover plate 13 has sufficient rigidity to withstand pressure fluctuations and maintain shape stability, thereby providing a reliable optical window for the laser beam. At the same time, it can minimize unnecessary lateral deviation and energy absorption of the laser beam caused by passing through the glass medium, ensuring that the laser energy is transmitted to the welding area efficiently and accurately, and maintaining the precision and stability of the focal position.

[0115] Please see Figure 1 or Figure 5 In some embodiments, the protective cover 11 and the cover plate 13 are bonded together with ceramic adhesive.

[0116] The protective cover 11 and the cover plate 13 are bonded with ceramic adhesive. The ceramic adhesive is resistant to high temperature and can maintain the bonding strength in the high temperature environment of welding, so as to achieve a reliable sealing connection between the protective cover 11 and the cover plate 13. Moreover, the composition of the ceramic adhesive is stable and will not pollute the welding environment.

[0117] Ceramic adhesive is a special adhesive formulated with inorganic ceramic powders (such as alumina, silica, zirconium oxide, etc.) as a base material, combined with high-temperature resistant binders (such as phosphates, silicates, etc.). The adhesive layer formed after curing possesses ceramic-like high-temperature resistance, aging resistance, and chemical stability, capable of withstanding temperatures above 800℃ for extended periods and above 1000℃ for short periods. This matches the potentially instantaneous high-temperature environment (usually below 800℃) that may occur within the laser welding cavity 110. When the heat generated during welding is conducted to the connection interface, the ceramic adhesive layer does not soften, melt, or thermally decompose, maintaining its original adhesive strength and sealing performance, thus ensuring the long-term reliability of the connection between the protective cover 11 and the cover plate 13 under thermal cycling.

[0118] Please see Figure 1 and Figure 6 Secondly, this application provides a welding method for the protective device 10 employing any of the above embodiments, used for welding the connecting piece 215 and the pole post 213. The welding method includes: The protective device 10 is placed on the stage 30 and covers the area to be welded between the connecting piece 215 and the pole post 213, so that the area to be welded is located within the welding cavity 110; and A laser welding device is used to perform laser welding on the welding area of ​​the connecting piece 215 and the welding area of ​​the pole post 213 through the cover plate 13.

[0119] The term "covering" refers to: directing the first port 111 of the protective device 10 (i.e. the end with the cover plate 13) toward and covering the area to be welded, so that the mating part of the pole post 213 and the connecting piece 215 is completely contained within the welding cavity 110 formed by the side wall of the protective cover 11 and the cover plate 13.

[0120] After the protective device 10 is in place, the laser welding device is activated. A laser beam is emitted from the welding device, passing sequentially through the first through-hole 131 of the cover plate 13 and the space within the welding cavity 110, ultimately focusing precisely on the surface of the area to be welded. The welding process proceeds according to preset path, power, and speed parameters. During this process, the protective device 10 remains stationary, and the sidewalls of the porous protective shield 11 surround the welding area, completely enclosing the laser molten pool that generates metal spatter within a closed or semi-closed space with active adsorption capabilities. When welding begins, metal spatter is ejected from the molten pool, its movement confined within the welding cavity 110. Regardless of the angle at which the spatter is ejected, the vast majority will impact the inner wall of the porous protective shield 11. As mentioned earlier, this porous structure has optimized porosity and pore size, effectively capturing and retaining these spatter particles, especially difficult-to-handle microparticles. Simultaneously, the second through-hole 133 on the cover plate 13 has auxiliary functions for heat dissipation or providing protective gas to optimize the welding environment.

[0121] The welding method of this application uses the aforementioned protective device 10 and covers the area to be welded for laser welding. By enclosing the welding area in the welding cavity 110 with a porous adsorption protective cover 11, the metal spatter generated during the welding process is intercepted and captured, eliminating the need for subsequent cleaning and improving the safety and production quality of the battery 20.

[0122] In some implementations, the welding power P of the welding apparatus satisfies: 1500W ≤ P ≤ 2000W.

[0123] Welding power P refers to the average power of the continuous or pulsed laser output from the laser of a laser welding device during the welding process, which ultimately acts on the surface of the workpiece. It is an important parameter for controlling the weld penetration. Specifically, the welding power P can be any value from 1500W, 1550W, 1600W, 1650W, 1700W, 1750W, 1800W, 1850W, 1900W, 1950W, and 2000W, or any value between any two adjacent values.

[0124] When the welding power P is less than 1500W, the energy density of the laser acting on the pole post 213 and the connecting piece 215 may be insufficient, which will result in shallow penetration and difficulty in forming a reliable full penetration weld, and the connection strength cannot be guaranteed; or the welding speed needs to be significantly reduced to compensate for the energy, thereby reducing production efficiency.

[0125] When the welding power P is greater than 2000W, although sufficient penetration can be easily obtained, excessive power will generate extremely violent and large amounts of metal vapor and spatter. The number, particle size and initial kinetic energy of the spatter may exceed the processing capacity of the porous structure of the protective cover 11, resulting in a decrease in interception efficiency, and there is even a risk that the spatter will break through the adsorption layer or escape from the gaps.

[0126] Therefore, limiting the welding power P to between 1500W and 2000W can ensure that the weld has sufficient penetration depth while keeping the generated metal spatter within the efficient processing range of the porous structure of the protective cover 11, thereby achieving the best balance between welding quality and spatter control.

[0127] In some embodiments, the welding rate V of the welding apparatus satisfies: 8 mm / s ≤ V ≤ 10 mm / s.

[0128] Welding rate V refers to the linear velocity of the laser spot relative to the workpiece along the predetermined welding path. This parameter, together with the welding power P, determines the linear energy (heat input) input per unit length of weld, and is a key parameter for controlling weld width, depth, and the width of the heat-affected zone. Specifically, the welding rate V can be any value from 8.0 mm / s, 8.2 mm / s, 8.4 mm / s, 8.6 mm / s, 8.8 mm / s, 9.0 mm / s, 9.2 mm / s, 9.4 mm / s, 9.6 mm / s, 9.8 mm / s, and 10.0 mm / s, or any value between any two adjacent values.

[0129] When the welding rate V is less than 8 mm / s, the dwell time per unit length of the weld is too long, which leads to excessively high heat input, potentially causing overheating in the weld area, an excessively large molten pool volume, and prolonged residence time. This not only exacerbates metal evaporation and spatter, potentially exceeding the adsorption capacity and instantaneous impact resistance of the protective cover 11, but may also cause weld collapse and increased workpiece thermal deformation. Moreover, an excessively slow welding rate also reduces welding efficiency.

[0130] When the welding rate V is greater than 10 mm / s, the dwell time on the weld per unit length is too short, which will result in insufficient heat input and may prevent the formation of a continuous molten pool, causing discontinuous welds, insufficient penetration or incomplete penetration, which seriously affects the connection strength and conductivity.

[0131] Therefore, welding at a welding rate V in the range of 8 mm / s to 10 mm / s can ensure the formation of a continuous and reliable weld while controlling the state of the molten pool and the behavior of spatter generation within a suitable and stable range. This, in conjunction with the protective device 10, ensures both welding quality and spatter protection.

[0132] In some implementations, the focal offset δ of the welding apparatus satisfies: -0.3mm ≤ V ≤ 0mm.

[0133] The focal offset δ is a parameter characterizing the vertical distance between the laser focal plane and the workpiece surface. δ is negative when the focal plane is below the workpiece surface; positive when the focal plane is above the workpiece surface; and 0 mm when the focal plane is on the workpiece surface. Specifically, the focal offset δ can be any value from -0.30 mm, -0.27 mm, -0.24 mm, -0.21 mm, -0.18 mm, -0.15 mm, -0.12 mm, -0.09 mm, -0.06 mm, -0.03 mm, and 0.00 mm, or any value between any two adjacent values.

[0134] When the focal offset δ is less than -0.3mm, the laser beam has not yet converged to the minimum spot size when it reaches the workpiece surface. This results in an increased spot area on the surface and a significant decrease in power density. This can cause instability in the welding process, requiring higher power to ignite the arc and maintain the molten pool, or leading to insufficient penetration and excessively wide welds. In this under-focused state, the molten pool is often flatter and more unstable, making it more prone to spattering. Furthermore, the spatter may be more dispersed, increasing the difficulty of all-around interception by the protective shield 11.

[0135] When the focal offset δ is greater than 0mm, it is in an over-focused state. Although the power density on the workpiece surface is very high, which is beneficial for initiation, the molten pool will become narrow and deep, and very unstable.

[0136] Therefore, welding within the range of -0.3mm to 0mm of the focal offset δ helps to form a stable and moderate molten pool, thereby ensuring the welding penetration depth while effectively suppressing the generation of violent spatter, making the spatter easier to be reliably intercepted by the protective device 10, and improving the overall stability and protective effect of the welding process.

[0137] Please see Figure 1 and Figure 7 In some embodiments, during the laser welding process of the area to be welded of the connecting piece 215 and the area to be welded of the pole post 213 through the cover plate 13 using a laser welding device, the process further includes: Protective gas is introduced into the welding cavity 110 through the second through hole 133 on the cover plate 13.

[0138] While laser welding is in progress, a shielding gas is continuously or pulsedly introduced into the welding chamber 110 through the second through-hole 133 on the cover plate 13. The shielding gas is typically an inert gas, such as argon (Ar), nitrogen (N2), or helium (He), or a mixture thereof. The shielding gas replaces and isolates the air, especially oxygen (O2) and nitrogen (N2), within the welding chamber 110. At the high temperatures generated by the laser, molten metals such as copper and aluminum undergo severe oxidation upon contact with oxygen, generating oxide slag. This not only contaminates the molten pool, leading to weld inclusions and porosity, but also severely weakens the weld's conductivity and mechanical strength. Nitrogen entrapment can cause nitride embrittlement. By forming an inert atmosphere barrier around the welding area, the shielding gas effectively prevents the contact of these harmful gases, resulting in a clean, dense, and high-performance weld.

[0139] In addition to its protective function, the introduced protective gas also assists in heat dissipation and dust removal. The continuously flowing gas passes through the high-temperature welding area and weld surface, carrying away some heat through convection, which helps control the overall temperature rise within the welding cavity 110 and prevents damage to the workpiece and protective device 10 due to overheating. At the same time, the airflow can carry away the metal fumes and fine particles generated during the welding process, preventing them from spreading within the welding cavity 110, depositing on the inner surface of the cover plate 13 (affecting light transmittance and observation), or falling back into the molten pool to form inclusions.

[0140] Therefore, during the welding process, a protective gas is introduced into the welding cavity 110 through the second through hole 133. The protective gas (such as argon) can dissipate the air in the welding area, prevent the metal from oxidizing at high temperatures, improve the weld quality, and at the same time help reduce the temperature inside the cavity and promote the discharge of fumes.

[0141] In some implementations, the flow rate of the protective gas satisfies: 8 L / min ≤ Q ≤ 10 L / min.

[0142] The flow rate Q refers to the volume of shielding gas flowing into the welding chamber 110 through the second through-hole 133 per unit time under standard conditions (e.g., 0°C, 1 atmosphere). Specifically, the flow rate Q can be any value among 8.0 L / min, 8.2 L / min, 8.4 L / min, 8.6 L / min, 8.8 L / min, 9.0 L / min, 9.2 L / min, 9.4 L / min, 9.6 L / min, 9.8 L / min, and 10.0 L / min, or any value between any two adjacent values.

[0143] When the flow rate Q is less than 8 L / min, the gas flow rate is too low to form a sufficiently thick inert gas layer in the welding area to effectively remove air. Oxygen may seep in from the surrounding area, resulting in incomplete protection and leaving the weld at risk of oxidation. Simultaneously, the low gas flow lacks sufficient force to disperse welding fumes, which tend to linger within the welding chamber 110, polluting the environment and potentially affecting laser transmission and the field of view. Furthermore, the auxiliary cooling effect of the gas flow on the welding area is also weakened.

[0144] When the flow rate Q is greater than 10 L / min, the gas flow rate is too high. Although the protection is more thorough, the excessively strong airflow will directly impact the surface of the molten pool, interfering with the stability of the molten pool, potentially altering the flow pattern of the molten pool, leading to uneven weld formation, or even defects such as spatter. Moreover, the high-speed airflow may blow tiny metal particles that have just splashed out of the molten pool, which are not yet fully solidified or are in a semi-molten state, away from their original trajectory and out of the effective capture range of the protective cover 11.

[0145] Therefore, controlling the flow rate Q of the protective gas between 8 L / min and 10 L / min can create a stable and moderate protective gas atmosphere, effectively isolating oxygen, while avoiding excessive airflow that could interfere with the stability of the molten pool or blow uncooled small splashes out of the effective capture range of the protective cover 11.

[0146] Several specific embodiments are described below. Example 1: 1. Protective device structural parameters: The protective cover is cylindrical and made of porous ceramic fiber felt with a porosity of 60%, a pore size of 100μm, and a bulk density of 0.4g / cm³; the roughness Ra of the inner surface after sandblasting is 3.2μm; the cover plate is made of 2mm thick high borosilicate glass (92% light transmittance), and the cover plate has 4 small heat dissipation holes (second through holes) with a diameter of 2mm, which are distributed in an equilateral cross shape. The protective cover and the cover plate are bonded together with high temperature ceramic adhesive.

[0147] 2. Welding process parameters: Copper and aluminum connecting pieces and battery terminals to be welded. Welding parameters: Welding power P is 2000W, welding speed V is 10mm / s, focal point offset of welding device is 0mm, flow rate of shielding gas argon is 8L / min; post-treatment delay for cooling is 8s, and compressed air purging pressure is 0.4MPa.

[0148] 3. Performance test results: The highest temperature inside the welding cavity during the welding process was 720℃, and the heat dissipation rate was 16℃ / s; the slag interception efficiency was 96.8%, and the residual amount of metal foreign matter inside the battery cell was 0.21mg / m³. 2 The welding pull force between the connecting piece and the pole is 152N, which meets the standard.

[0149] Example 2: Protective device with a rectangular prism-shaped protective cover 1. Protective device structural parameters: The protective cover is a rectangular column, made of porous ceramic fiber felt with a porosity of 50%, a pore size of 80μm, and a bulk density of 0.5g / cm³; the roughness Ra of the inner surface after sandblasting is 4.0μm; the cover plate is made of 3mm thick high borosilicate glass (91% light transmittance), with 4 small heat dissipation holes (second through holes) with a diameter of 1.5mm, arranged in a rectangular pattern.

[0150] 2. Welding process parameters: Copper and aluminum connecting pieces and battery terminals to be welded; Welding parameters: Welding power P is 1500W, welding speed V is 8mm / s, focal point offset of welding device is -0.3mm, and the flow rate of protective gas argon is 6L / min; Other processes are the same as in Example 1.

[0151] 3. Performance test results: The highest temperature inside the welding cavity during the welding process was 680℃, and the heat dissipation rate was 14℃ / s; the slag interception efficiency was 95.3%, and the residual amount of metal foreign matter inside the battery cell was 0.27mg / m³. 2 The welding tensile strength between the connecting piece and the cover plate is 150N, which meets the standard.

[0152] As can be seen from Examples 1 and 2, when using the protective device of this application for laser welding, the slag interception efficiency is higher than 95.3%, and the residual amount of metal foreign matter inside the battery cell is less than or equal to 0.27 mg / m³. 2 The welding tensile force between the connecting piece and the cover plate is greater than or equal to 150N, which meets the standard.

[0153] Table 1

[0154] Table 1 above is a comparison table of product tests after laser welding of the connecting piece and the pole using the process of Example 1 and laser welding using the conventional process. The welding process parameters of the conventional process are the same as those in Example 1. The difference is that the conventional process does not use the protective device of this application, while Example 1 uses the protective device of this application.

[0155] The metal foreign matter residue rate is a proportional parameter characterizing the content of metal spatter introduced by laser welding inside the battery. It is usually expressed in mass concentration units, that is, the total mass of metal spatter (such as copper and aluminum particles) remaining inside the battery casing after the welding process, divided by the total mass of the battery in parts per million (ppm). The metal foreign matter residue rate can be tested by ICP-MS (inductively coupled plasma mass spectrometry) to dissolve and sample the battery cell, detecting the total content of copper and aluminum elements. As shown in Table 1, the metal foreign matter residue rate inside the battery after laser welding using the traditional process is 450 ppm, while the metal foreign matter residue rate after laser welding using the process in Example 1 is 8 ppb, a difference of more than four orders of magnitude. This demonstrates that the protective device of this application has extremely high interception efficiency for metal spatter.

[0156] The self-discharge failure rate is the percentage of batteries in a batch whose voltage drops beyond a specified threshold due to abnormal losses such as internal micro-short circuits caused by metal spatter introduced during laser welding during static storage. The detection method involves charging the batteries to a specified voltage (e.g., fully charged) in their initial state, and then allowing them to stand at a standard ambient temperature for a specified period (e.g., 28 days). The battery terminal voltage is then measured. If the voltage decay exceeds a preset standard (e.g., 50mV), the battery is deemed "self-discharge defective." The self-discharge failure rate is the ratio of the number of batteries deemed "self-discharge defective" in that batch to the total number of tested batteries. Table 1 shows that the self-discharge failure rate of batteries using the traditional laser welding process is 3.8%, while the self-discharge failure rate of batteries using the process described in Example 1 is 0.09%, a difference of 42 times. This demonstrates that the protective device of this application effectively solves the self-discharge problem caused by micro-short circuits after intercepting metal spatter.

[0157] The separator puncture rate is a parameter used to quantify the probability of physical perforation of the separator due to the presence of sharp or large-sized metal spatter inside the battery. The specific detection method involves randomly selecting samples from a batch of welded batteries, disassembling the cells, and using an optical microscope or scanning electron microscope to inspect the entire surface or key areas of the separator. The number of separators with mechanical puncture or embedding damage caused by metal foreign objects (such as metal spatter from the welding process) is statistically analyzed. The separator puncture rate is the percentage of such damaged separators out of the total number of inspected separators. As shown in Table 1, the separator puncture rate of batteries using traditional laser welding processes is 0.12%, while the separator puncture rate of batteries using the process in Example 1 is less than 0.001%, a difference of more than 120 times. This indicates that large-sized or sharp spatter capable of puncturing the separator is successfully blocked outside the battery, almost eliminating the risk of internal short circuits that could lead to thermal runaway caused by the welding process, thus greatly improving battery safety.

[0158] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. At the same time, other embodiments can be derived from the above embodiments, so that structural and logical substitutions and changes can be made without departing from the scope of this disclosure.

[0159] The embodiments described above are merely illustrative of several implementations of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the appended claims.

Claims

1. A protective device, characterized in that, include: The ring-shaped protective cover has a first port and a second port; and A cover plate, sealing the first port and connected to the protective cover, together with the protective cover, forms a welding cavity. The welding cavity is used to cover the welding area between the terminal post and the connecting piece in the top cover assembly of the battery, wherein: The protective cover has a porous structure, and the porosity φ of the porous structure satisfies: 30%≤φ≤80%, and the pore diameter D satisfies: 30μm≤D≤200μm.

2. The protective device according to claim 1, characterized in that, The protective cover is made of porous ceramic fiber felt.

3. The protective device according to claim 1, characterized in that, The protective cover is made of aluminum oxide and silicon dioxide, wherein the mass percentage W1 of aluminum oxide in the material of the protective cover satisfies: 60% ≤ W1 ≤ 70%, and the mass percentage W2 of silicon dioxide in the material of the protective cover satisfies: 25% ≤ W2 ≤ 35%.

4. The protective device according to claim 1, characterized in that, The surface roughness Ra of the inner surface of the protective cover satisfies: 2.5μm≤Ra≤4.2μm.

5. The protective device according to any one of claims 1-4, characterized in that, The cover plate is provided with a first through hole, which is used to allow the laser to pass through and enter the welding cavity.

6. The protective device according to claim 5, characterized in that, The flow-cutting area S1 of the first through hole and the area S0 of the cover plate satisfy: 0.2≤S1 / S0≤0.

3.

7. The protective device according to claim 5, characterized in that, The cover plate is provided with a second through hole spaced apart from the first through hole. The second through hole is used to dissipate heat from the welding cavity to the outside of the welding cavity or to introduce protective gas into the welding cavity. The cross-sectional area S1 of the first through hole is greater than the cross-sectional area S2 of the second through hole.

8. The protective device according to claim 7, characterized in that, The first through hole is located at the center of the cover plate, and the second through hole includes multiple second through holes, which are evenly distributed around the first through hole.

9. The protective device according to claim 7, characterized in that, The flow-cutting area S2 of the second through hole and the flow-cutting area S1 of the first through hole satisfy the condition: 0.2≤S2 / S1≤0.

3.

10. The protective device according to claim 7, characterized in that, The total intercepting area S2' of the second through hole and the area S0 of the cover plate satisfy: 0.02≤S2' / S0≤0.

3.

11. The protective device according to claim 7, characterized in that, The protective device also includes: A blocking part is housed in the welding cavity and connected to the protective cover and / or the cover plate. Each second through hole corresponds to one blocking part. In the height direction of the protective cover, the blocking part is spaced apart from the corresponding second through hole, and in a projection plane perpendicular to the height direction of the protective cover, the projection of the blocking part at least partially overlaps with the projection of the second through hole.

12. The protective device according to claim 7, characterized in that, The height h of the protective cover satisfies: 100mm≤h≤150mm.

13. The protective device according to claim 1, characterized in that, The light transmittance of the cover plate satisfies: 90% ≤ T.

14. The protective device according to claim 1, characterized in that, The cover plate is made of borosilicate glass.

15. The protective device according to claim 1, characterized in that, The thickness t of the cover plate satisfies: 2mm≤t≤3mm.

16. The protective device according to claim 1, characterized in that, The protective cover and the cover plate are bonded together with ceramic adhesive.

17. A welding method for the protective device according to any one of claims 1-16, used for welding connecting pieces and pole posts, characterized in that, The welding method includes: The protective device is placed on the platform and covered over the area to be welded between the connecting piece and the pole post, so that the area to be welded is located within the welding cavity; and A laser welding device is used to perform laser welding on the area to be welded of the connecting piece and the area to be welded of the pole through the cover plate.

18. The welding method according to claim 17, characterized in that, The welding power P of the welding device satisfies: 1500W ≤ P ≤ 2000W; and / or, The welding rate V of the welding device satisfies: 8 mm / s ≤ V ≤ 10 mm / s; and / or, The focal offset δ of the welding device satisfies: -0.3mm≤V≤0mm.

19. The welding method according to claim 17, characterized in that, The process of laser welding the area to be welded of the connecting piece and the area to be welded of the pole post through the cover plate using a laser welding device also includes: Protective gas is introduced into the welding cavity through the second through hole on the cover plate.

20. The welding method according to claim 19, characterized in that, The flow rate of the protective gas satisfies: 8L / min≤Q≤10L / min.

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