Electrode lug embossing device and embossing method

Abstract

The invention relates to the technical field of lithium batteries, in particular to a tab embossing device and an embossing method. Comprising a plurality of V-shaped embossing protrusions which are continuously arranged in the circumferential direction, and the second embossing section comprises a plurality of strip-shaped embossing protrusions which are arranged at intervals in the circumferential direction. The V-shaped embossing protrusions and the strip-shaped embossing protrusions are arranged on the outer surface of the first tab embossing roller in a protruding mode, the strip-shaped embossing protrusions extend in the axial direction of the first tab embossing roller, and the strip-shaped embossing protrusions and the V-shaped embossing protrusions are connected in a one-to-one correspondence mode. The strip-shaped embossed protrusions and the V-shaped embossed protrusions are connected in a one-to-one correspondence mode to form a point-line combined strengthening network. According to the structure, longitudinal support is provided for the middle part of the tab, so that collapse caused by uneven extension of the root part and the top part is prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, and in particular to an electrode tab embossing device and an embossing method. BACKGROUND

[0002] In the production process of lithium batteries, the cutting and stacking link is closely related to the core process of battery manufacturing, especially the stacking technology, which significantly improves the production efficiency and battery performance by integrating the cutting and stacking processes.

[0003] However, with the requirement for high-rate discharge of the battery, the electrode tab of the battery is getting larger and the current collector is getting thinner, so that the electrode tab after cutting and stacking presents a collapsed state. For ultrasonic welding, excessive electrode tab collapse will greatly increase the probability of electrode tab folding failure. The industry often introduces an electrode tab embossing process in the die-cutting machine to improve the bending strength of the electrode tab to reduce the collapse amount. However, the conventional electrode tab embossing in the die-cutting machine cannot meet the consistency and rapid production requirements of ultra-thin foils. SUMMARY

[0004] The present application provides an electrode tab embossing device and an embossing method to solve the technical problem that the improvement of electrode tab collapse in the die-cutting machine is small in the related art.

[0005] The first aspect of the present application provides an electrode tab embossing device, comprising a first electrode tab embossing roller and a first embossing section and a second embossing section arranged in sequence along the axial direction on the outer surface of the first electrode tab embossing roller, the first embossing section comprising a plurality of V-shaped embossing protrusions arranged continuously along the circumferential direction, the second embossing section comprising a plurality of strip-shaped embossing protrusions arranged at intervals along the circumferential direction, the V-shaped embossing protrusions and the strip-shaped embossing protrusions are both protruding on the outer surface of the first electrode tab embossing roller, and the strip-shaped embossing protrusions extend along the axial direction of the first electrode tab embossing roller, and the strip-shaped embossing protrusions are connected to the V-shaped embossing protrusions one by one.

[0006] In some embodiments, the V-shaped opening of the V-shaped embossing protrusion is arranged in a direction away from the strip-shaped embossing protrusion, and the corner of the V-shaped embossing protrusion is connected to the strip-shaped embossing protrusion.

[0007] In some embodiments, the corner of the V-shaped embossing protrusion is arranged as a first rounded corner away from one side of the strip-shaped embossing protrusion, and the radius of the first rounded corner is R1, 0.1mm≤R1≤0.3mm.

[0008] And / or, the included angle of the connection between two adjacent V-shaped embossing protrusions is α, 30°≤α≤60°.

[0009] And / or, the connection between two adjacent V-shaped embossing protrusions is smoothly transitioned, the side of the connection away from the strip-shaped embossing protrusion is provided with a second fillet with a radius R2, 0.3mm≤R2≤0.8mm, and the side of the connection close to the strip-shaped embossing protrusion is provided with a third fillet with a radius R3, 0.1mm≤R3≤0.3mm;

[0010] And / or, the diameter of the first tab embossing roller is D, 40mm≤D≤200mm, and the tooth depth of the V-shaped embossing protrusion and the strip-shaped embossing protrusion is h, 0.5mm≤h≤2.5mm.

[0011] In some embodiments, the width of the V-shaped embossing protrusion is d1, 0.5mm≤d1≤2.5mm; the two side edges of the V-shaped embossing protrusion in the width direction are provided with a fourth fillet with a radius R4, 0.05mm≤R4≤0.2mm; the width of the strip-shaped embossing protrusion is d2, 0.8mm≤d2≤1.8mm, and the distance between two adjacent strip-shaped embossing protrusions is d3, 1.3mm≤d3≤2.5mm.

[0012] In some embodiments, d2 / d3≤0.6.

[0013] In some embodiments, the first tab embossing roller comprises a hard roller and a soft roller coaxially arranged, the first embossing section and the second embossing section are both arranged on the hard roller, and the soft roller is arranged on the side of the first embossing section away from the second embossing section; the width of the soft roller in the axial direction is L, 5mm≤L≤30mm.

[0014] In some embodiments, a support roller is further included, which is arranged in parallel with the first tab embossing roller, and a gap is formed between the support roller and the first tab embossing roller for the tab to pass through.

[0015] The second aspect of the present application provides a tab embossing method, comprising:

[0016] The tab embossing device according to any one of the above is used to emboss the tab area;

[0017] Rolling;

[0018] Cutting and stacking.

[0019] In some embodiments,

[0020] The embossing on the tab area comprises:

[0021] Pre-embossing, pre-embossing the front and back of the tab area respectively to strengthen the tab area;

[0022] embossed on the front or back of the tab by the first tab embossing roller.

[0023] In some embodiments, the pre-embossing is performed by the second tab embossing roller and the third tab embossing roller on the front and back of the tab region respectively;

[0024] The second tab embossing roller is arranged upstream of the first tab embossing roller, and the second tab embossing roller comprises a roller and a point-shaped embossing protrusion, wherein the point-shaped embossing protrusion is protruded on the outer surface of the roller, the diameter of the point-shaped embossing protrusion is R5, 0.3mm≤R5≤1.2mm, the radius of the edge chamfer of the point-shaped embossing protrusion is R6, 0.05mm≤R6≤0.3mm, the longitudinal pitch of the point-shaped embossing protrusion is S2, 1mm≤S2≤3mm, the transverse pitch of the point-shaped embossing protrusion is S1, 0.8mm≤S1≤3.6mm; 1≤S2 / d2≤2; and the third tab embossing roller is a straight strip-shaped embossing roller.

[0025] Compared with the prior art, the technical scheme provided by the embodiments of the present application has the following advantages:

[0026] The tab embossing device provided by the embodiments of the present application is provided with a first embossing section and a second embossing section on the outer surface of the first tab embossing roller, and the V-shaped embossing protrusion forms a continuous wavy pattern at the tab root, thereby increasing the contact area of the tab and the current collector and improving the mechanical bonding force. This structure can effectively resist the shear stress generated when the tab is wound or bent, and reduce the risk of tab root breakage. The included angle of the V-shaped embossing protrusion can guide the stress to disperse along the inclined surface of the protrusion, avoiding local stress concentration. For example, when the tab is subjected to a vertical tensile force, the V-shaped embossing protrusion converts the stress into a component force along the inclined surface, reducing the probability of tab root tearing. The strip-shaped embossing protrusion is connected to the V-shaped embossing protrusion one by one to form a reinforced network of "point-line" combination. This structure provides longitudinal support in the middle of the tab, preventing the tab from collapsing due to uneven extension of the root and the top. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, those drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0029] Figure 1An expanded structure schematic view of part of the structure of the first tab embossing roller according to the embodiments of the present application;

[0030] Figure 2 A structure schematic view of the tab embossing device according to the embodiments of the present application;

[0031] Figure 3 An expanded structure schematic view of part of the structure of the second tab embossing roller according to the embodiments of the present application;

[0032] Figure 4 A flow chart of the tab embossing method according to the embodiments of the present application.

[0033] 1, the first tab embossing roller; 101, the V-shaped embossing protrusion; 102, the strip-shaped embossing protrusion;

[0034] 2, the soft roller;

[0035] 3, the pole piece;

[0036] 4, the tab area;

[0037] 5, the supporting roller;

[0038] 601, the roller; 602, the dot-shaped embossing protrusion. DETAILED DESCRIPTION

[0039] In order to enable the above-mentioned purposes, features and advantages of the present application to be more clearly understood, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0040] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein; obviously, the embodiments in the description are only some of the embodiments of the present application, not all the embodiments.

[0041] As shown in Figure 1 and Figure 2 , the tab embossing device provided by the embodiments of the present application comprises a first tab embossing roller 1 and a first embossing section and a second embossing section arranged on the outer surface of the first tab embossing roller 1 in the axial direction, the first embossing section comprises a plurality of V-shaped embossing protrusions 101 arranged continuously in the circumferential direction, the second embossing section comprises a plurality of strip-shaped embossing protrusions 102 arranged in the circumferential direction at intervals, the V-shaped embossing protrusions 101 and the strip-shaped embossing protrusions 102 are protruded on the outer surface of the first tab embossing roller 1, and the strip-shaped embossing protrusions 102 extend in the axial direction of the first tab embossing roller 1, and the strip-shaped embossing protrusions 102 are connected one by one with the V-shaped embossing protrusions 101.

[0042] Specifically, when embossing the tab area 4, the first tab embossing roller 1 contacts with the front or back of the tab area 4, embossing is achieved by applying pressure to the tab area 4, and the first embossing section is arranged corresponding to the root of the tab. The V-shaped embossing protrusion 101 forms a continuous wavy pattern at the tab root, which increases the contact area between the tab and the current collector and improves the mechanical bonding force. This structure can effectively resist the shear stress generated when the tab is wound or bent, reducing the risk of tab root breakage. The included angle of the V-shaped embossing protrusion 101 can guide the stress to disperse along the inclined surface of the protrusion, avoiding local stress concentration. For example, when the tab is subjected to a vertical tensile force, the V-shaped embossing protrusion 101 converts the stress into a component force along the inclined surface, reducing the probability of tab root tearing. The strip-shaped embossing protrusion 102 is connected one by one with the V-shaped embossing protrusion 101, forming a reinforced network of "point-line" combination. This structure provides longitudinal support on the tab, preventing the tab from collapsing due to uneven extension of the root and top.

[0043] For example, if the number of V-shaped embossing protrusions 101 and strip-shaped embossing protrusions 102 is not equal, there are two cases:

[0044] In the first case, the number of V-shaped embossing protrusions 101 is greater than the number of strip-shaped embossing protrusions 102. Taking the case where the number of V-shaped embossing protrusions 101 is twice the number of strip-shaped embossing protrusions 102 as an example, when the adjacent strip-shaped embossing protrusions 102 are connected in one-to-one correspondence in the embodiment of the present application, the spacing between the two adjacent strip-shaped embossing protrusions 102 is equal, and the width of the strip-shaped embossing protrusions 102 is also equal, the length of the V-shaped embossing protrusions 101 along the circumference of the first tab embossing roller 1 is smaller than the length of the V-shaped embossing protrusions 101 along the circumference of the first tab embossing roller 1 in one-to-one correspondence in the embodiment of the present application, that is, the length of the V-shaped embossing protrusions 101 along the circumference is shorter than that in the embodiment of the present application, and thus the number of V-shaped embossing protrusions 101 formed on the first tab embossing roller 1 of the same radius is greater, and the wavy lines formed by the V-shaped embossing protrusions 101 at the tab root are relatively dense. Although the wavy lines at the tab root can disperse stress, when they are too dense, the concave-convex structures of adjacent lines will form a "extrusion-stretching" superposition effect. For example, when the tab is bent or the battery is cyclically expanded and contracted, the protrusions and depressions of the two adjacent wavy lines will simultaneously bear stress, causing the stress to be superimposed in the local area (such as the transition part of adjacent lines), thereby forming a new stress concentration point, and even causing the "micro-cracks" to spread in a chain (a crack in one line may quickly spread to adjacent lines), thereby accelerating the risk of tab root fracture. The tab needs to have a certain flexibility to adapt to the deformation during battery assembly (such as tab bending and shaping) and cycling. Too dense lines will make the metal material at the tab root "stiff" due to repeated plastic deformation (caused by embossing), and the dense concave-convex structure limits the free expansion space of the material. When repeatedly bent, the material between the lines is difficult to buffer stress through deformation, and is prone to brittle fracture due to "fatigue accumulation" (similar to repeatedly folded paper, too dense folds will tear faster). The tab is usually a metal foil (such as aluminum foil, copper foil), and the embossing process relies on plastic deformation of the material to form lines. Dense lines mean more local deformation points, and the protrusions / depressions of each line will cause the material to locally thin (especially at the sharp corner of the V-shaped embossing). When the deformation exceeds the material's bearing limit, micro-cracks may occur directly; even if it does not immediately break, in long-term use, it will also cause a vicious cycle of "thinning-strength reduction-further damage", leading to a decrease in the overall mechanical strength of the tab and weakening the stretch and tear resistance.

[0045] In the second case, the number of V-shaped embossing protrusions 101 is less than the number of strip-shaped embossing protrusions 102. Taking the case where the number of strip-shaped embossing protrusions 102 is twice the number of V-shaped embossing protrusions 101, when the adjacent strip-shaped embossing protrusions 102 are connected in one-to-one correspondence in the embodiment, the spacing between the two adjacent strip-shaped embossing protrusions 102 is equal, and the width of the strip-shaped embossing protrusions 102 is also equal, the length of the V-shaped embossing protrusions 102 along the circumference of the first lug embossing roller 1 is greater than the length of the V-shaped embossing protrusions 101 along the circumference of the first lug embossing roller 1 in one-to-one correspondence in the embodiment, that is, the length of the V-shaped embossing protrusions 101 along the circumference is longer, and thus the number of V-shaped embossing protrusions 101 formed on the first lug embossing roller 1 with the same radius is less, and the wave-shaped lines formed by the V-shaped embossing protrusions 101 at the lug root are relatively sparse. One of the core roles of the wave-shaped lines (formed by the V-shaped embossing protrusions 101) at the lug root is to reduce local stress concentration by dispersing stress. When the lines are sparse, stress cannot be evenly dispersed through the dense wave structure, but is concentrated in a few line areas. When the battery is charged and discharged (accompanied by volume expansion and contraction), the lug is bent or subjected to external impact, and the local stress is too large, which causes the lug root to be more prone to cracking, and even directly breaks, seriously affecting the safety and service life of the battery. The sparse wave-shaped lines weaken the "enhanced support" effect on the lug root. Dense lines can form "cooperative stress" through the concave-convex structure of multiple nodes, improving the tensile and bending resistance of the lug root; when the lines are sparse, this cooperative effect disappears, and the lug root lacks sufficient structural support when subjected to tensile or bending deformation, and is prone to deformation failure (such as permanent deformation and wrinkling).

[0046] Since the number of strip-shaped embossing protrusions 101 is twice the number of V-shaped embossing protrusions 102, each V-shaped embossing protrusion 101 needs to be connected to two strip-shaped embossing protrusions 102. This "one-to-many" connection method can cause uneven stress transmission between the V-shaped embossing protrusions 101 and the strip-shaped embossing protrusions 102: the stress of the strip-shaped embossing protrusions 102 cannot be effectively dispersed through the V-shaped embossing protrusions 101, which can make the connection (the joint between the V-shaped embossing protrusions 101 and the strip-shaped embossing protrusions 102) a weak point, which is prone to peeling or damage after long-term stress, reducing the stability of the overall structure of the lug.

[0047] Therefore, in the first two cases, when the number of V-shaped embossing protrusions 101 is less than that of strip-shaped embossing protrusions 102, the lines are sparse, and the stress cannot be effectively dispersed (concentrated in a few areas); when the number of V-shaped embossing protrusions 101 is more than that of strip-shaped embossing protrusions 102, the lines are too dense, and the stresses of adjacent lines are superimposed (forming new concentration points). In the embodiments of the present application, the V-shaped embossing protrusions 101 correspond to the strip-shaped embossing protrusions 102 one by one, and the number is equal, so that the wave-shaped lines formed by the V-shaped embossing protrusions 101 have moderate density, neither stress concentration due to sparseness nor stress superposition due to denseness.

[0048] At the same time, the length of the V-shaped embossing protrusions 101 in the circumferential direction matches the spacing and width of the strip-shaped embossing protrusions 102 (because they are connected one by one), the "concave-convex nodes" of the wave-shaped lines are uniformly distributed, the stress of the tab root during charging and discharging cycles, bending or impact can be uniformly dispersed to multiple nodes through the arc transition structure of each V-shaped line, avoiding excessive local stress, and fundamentally reducing the risk of crack generation and rupture. The plastic deformation amount of the material during embossing is moderate (neither excessively thinned nor lacking effective lines), avoiding the weakness caused by insufficient deformation or embrittlement caused by excessive deformation, so that the tab is not prone to fatigue failure during repeated bending or cyclic deformation, prolonging the service life.

[0049] In some embodiments of the present application, the V-shaped opening of the V-shaped embossing protrusion 101 is arranged in a direction away from the strip-shaped embossing protrusion 102, and the corner of the V-shaped embossing protrusion 101 is connected with the strip-shaped embossing protrusion 102. Specifically, as shown in Figure 1 one V-shaped embossing protrusion 101 and one strip-shaped protrusion form a "Y" shape structure, and a plurality of "Y" shape structures are arranged in a circle around the circumference of the first tab embossing roller 1. When embossing the tab area 4, the V-shaped embossing protrusion 101 is pressed against the root of the tab.

[0050] In some embodiments of the present application, the diameter of the first tab embossing roller 1 is D, and 40mm≤D≤200mm; the tooth depth of the strip-shaped embossing protrusion 102 and the V-shaped embossing protrusion 101 is h, and 0.5mm≤h≤2.5mm; the tooth depth of the strip-shaped embossing protrusion 102 and the V-shaped embossing protrusion 101 is the distance between the side of the strip-shaped embossing protrusion 102 or the V-shaped embossing protrusion 101 away from the first tab embossing roller 1 and the outer surface of the first tab embossing roller 1.

[0051] The side of the V-shaped corner of the V-shaped embossing protrusion 101 away from the strip-shaped embossing protrusion 102 is provided with a first rounded corner, and the radius of the first rounded corner is R1, and 0.1mm≤R1≤0.3mm.

[0052] An included angle of a joint of two adjacent V-shaped embossing protrusions 101 is a, 30°≤a≤60°, and an included angle of a corner of a single V-shaped embossing protrusion 101 is β, β=a.

[0053] The joint of the two adjacent V-shaped embossing protrusions 101 is smoothly transitioned, a second fillet is arranged on a side of the joint away from the strip-shaped embossing protrusion 102, a radius of the second fillet is R2, 0.3mm≤R2≤0.8mm; a third fillet is arranged on a side of the joint close to the strip-shaped embossing protrusion 102, a radius of the third fillet is R3, 0.1mm≤R3≤0.3mm, and in some embodiments, R3=R1.

[0054] A width of the V-shaped embossing protrusion 101 is d1, 0.5mm≤d1≤2.5mm, a fourth fillet is arranged at both side edges of the V-shaped embossing protrusion 101 in the width direction, a radius of the fourth fillet is R4, 0.05mm≤R4≤0.2mm, a width of the strip-shaped embossing protrusion 102 is d2, 0.8mm≤d2≤1.8mm, a distance between two adjacent strip-shaped embossing protrusions 102 is d3, 1.3mm≤d3≤2.5mm, and d2 / d3≤0.6.

[0055] Simulation results show that the first tab embossing roller 1 with the above dimensions can control the foil tab collapse of 5μm to within 1mm, has good tab collapse suppression effect, and can meet the tab embossing of ultra-thin foil of 4μm to 5μm. The depth of embossing on the tab is shallow, and the risk of tab breakage is low. The stiffness of the tab in the transverse and longitudinal directions is significantly enhanced, and the stress in the high stress area of the tab root is significantly reduced, further reducing the risk of tab breakage and tab 3 dropping.

[0056] The width of the coating from the root of the tab in the related art is controlled within the range of 2mm to 3mm, the embossing process is affected by the embossing roller, the outer free surface of the tab is prone to contract earlier than the inner side, wrinkles and deformations occur in the tab root area, and the internal stress in the wrinkled area is released after the embossing process is completed, which seriously affects the tab collapse.

[0057] As Figure 2As shown, in order to solve this technical problem, in some embodiments of the present application, the first lug embossing roller 1 comprises a hard roller and a soft roller 2 arranged coaxially, the first embossing section and the second embossing section are arranged on the hard roller, and the soft roller 2 is arranged on the side of the first embossing roller away from the second embossing roller. The diameter of the soft roller 2 is substantially the same as that of the hard roller. When embossing the lug area 4, the soft roller 2 is pressed against the coating area of the pole piece 3, and the hard roller is pressed against the lug area 4. The soft roller 2 makes the lug root and the edge of the coating of the pole piece 3 be pressed flat by the soft roller 2 during the embossing process, limits the air of the lug root, reduces the risk of breakage of the lug root, and strictly limits the deformation of the coating area of the pole piece 3, further reducing the risk of material falling. Simulation results show that the same embossing pattern is used to process the lugs of the same specification, and the embossing effect is better with the cooperation of the soft roller 2, which can obviously inhibit the collapse of the lug.

[0058] Further, in some embodiments of the present application, the width of the soft roller 2 in the axial direction is L, and 5mm≤L≤30mm. The soft roller 2 can completely cover the coating area of the pole piece 3 during the embossing process, avoiding the bulging of the lug root.

[0059] In some embodiments of the present application, a support roller 5 is further included, which is arranged in parallel with the first lug embossing roller 1, and a gap is formed between the support roller 5 and the first lug embossing roller 1 for the lug to pass through. The support roller 5 is used to support the pole piece 3 on the other side of the pole piece 3, and is usually made of rubber material. The support roller 5 and the first lug embossing roller 1 are pressed against each other to generate a pressing force on the lug, thereby realizing embossing of the lug.

[0060] In some embodiments of the present application, the lug embossing device further comprises three embossing rollers, namely a second lug embossing roller, a third lug embossing roller and a fourth lug embossing roller. One of the second lug embossing roller, the third lug embossing roller and the fourth lug embossing roller is a standby roller, which does not participate in the embossing process when the other two embossing rollers participate in the embossing process.

[0061] As shown in FIG. 6, the lug embossing device comprises a first lug embossing roller 1, a second lug embossing roller 2, a third lug embossing roller 3 and a fourth lug embossing roller 4. The first lug embossing roller 1 comprises a first embossing section and a second embossing section arranged on the same roller. The second lug embossing roller 2 is arranged on the side of the first lug embossing roller 1 away from the second lug embossing roller 2. The third lug embossing roller 3 is arranged on the side of the second lug embossing roller 2 away from the first lug embossing roller 1. The fourth lug embossing roller 4 is arranged on the side of the third lug embossing roller 3 away from the second lug embossing roller 2. Figure 3As shown, taking the fourth lug embossing roller as a standby roller as an example, in some embodiments of the present application, the second lug embossing roller includes a roller 601 and a point-shaped embossing protrusion 602, wherein the point-shaped embossing protrusion 602 is protruded on the outer surface of the roller 601, the diameter of the point-shaped embossing protrusion 602 is R5, 0.3mm≤R5≤1.2mm, the radius of the edge chamfer of the point-shaped embossing is R6, 0.05mm≤R6≤0.3mm, the longitudinal pitch S2 of the point-shaped embossing protrusion 602, 1mm≤S2≤3mm, the longitudinal pitch refers to the distance between two adjacent point-shaped embossing protrusions 602 in the same column in the axial direction. The transverse pitch S1 of the point-shaped embossing protrusion 602 is 0.8mm≤S1≤3.6mm, and the ratio of the transverse pitch of the point-shaped embossing protrusion 602 to the width of the strip-shaped embossing protrusion 102 is greater than or equal to 1 and less than or equal to 2. The third lug embossing roller includes a third roller and a straight strip-shaped embossing protrusion protruded on the outer surface of the third roller, and the straight strip-shaped embossing protrusion is matched with the strip-shaped embossing protrusion on the first lug embossing roller 1.

[0062] The second lug embossing roller and the third lug embossing roller are located upstream of the first lug embossing roller 1, in order to avoid the collapse of the lug during embossing, the second lug embossing roller, the third lug embossing roller and the first lug embossing roller 1 are substantially the same in other structures except for the shape and size of the embossing protrusions.

[0063] Before the first lug embossing roller 1 is used to emboss the lug area 4, the second lug embossing roller and the third lug embossing roller are used to emboss the lug area 4, so that the foil of the lug area 4 realizes the stages of elasticity, plasticity and finally strengthening. In the elastic stage, the pressure applied by the embossing roller to the lug needs to be controlled within the elastic limit to avoid premature plastic deformation leading to blurred embossing pattern. In the plastic stage, by controlling the plastic deformation amount, stable embossing lines are formed on the surface of the lug, while avoiding excessive deformation to cause cracks. In the strengthening stage, it is necessary to avoid excessive pressure of the embossing roller to cause the lug to break, and at the same time, to utilize the strengthening effect to improve the bending stiffness of the lug. The first lug embossing roller 1 and the second lug embossing roller respectively pre-press the lug area 4 on the front and back surfaces of the lug, and then the first lug embossing roller 1 is used to emboss and form the lug area 4, so that the depth of the formed indentation is deeper, and the shape of the embossing protrusion on the first lug embossing roller 1 is used to form a lug with stronger bending strength, which greatly reduces the collapse of the lug.

[0064] In the traditional embossing process, the shape of the embossing protrusion on the embossing roller is generally diamond-shaped, and the embossing roller can only perform one embossing on the lug area 4 in the cutting and stacking machine. Before the cutting and stacking process and after the rolling process, the rolling process is used to change the internal stress of the lug piece 3, which will cause uneven stress of the lug piece 3 itself and further cause the lug piece 3 to be warped.

[0065] To solve the problem that the pole piece 3 is easy to be buckled, the application embodiment improves the process of the ear embossing.

[0066] Specifically, as Figure 4 shown, in some embodiments of the application, the ear embossing method comprises:

[0067] S1, pulping;

[0068] S2, coating;

[0069] S3, drying;

[0070] S4, embossing;

[0071] S5, rolling;

[0072] S6, cutting and stacking.

[0073] Placing the embossing process upstream of the rolling process avoids the influence of the rolling process on the embossing process, thereby solving the problem of ear collapse.

[0074] The traditional ear embossing process sequence is: pulping → coating → drying → rolling → embossing (implemented in a cutting and stacking machine)

[0075] Rolling applies vertical pressure to the pole piece 3 by rigid rollers, making the pole piece 3 thickness uniform (thickness tolerance is usually controlled within ±1μm). But this process will cause the following stress problems:

[0076] Biaxial tensile stress: the pole piece 3 produces elastic stretching in the rolling direction (MD) and the width direction (TD) at the same time, forming residual tensile stress.

[0077] Stress gradient: the edge of the pole piece 3 deforms more than the center area due to smaller friction, resulting in stress concentration at the edge.

[0078] Anisotropy: coating particles (such as graphite, NCM) are oriented in the MD direction under the rolling pressure, forming stress anisotropy (MD direction strength > TD direction).

[0079] Stress interference in the embossing stage:

[0080] When embossing is performed after rolling, the embossing protrusions exert local plastic deformation on the pole piece 3 which already has residual stress, resulting in:

[0081] Stress superposition: the compressive stress generated by embossing is superimposed with the residual tensile stress from rolling, forming an irregular stress field on the surface of the pole piece 3.

[0082] Edge effect: embossing protrusions are more likely to cause local buckling at the edge of the pole piece 3 due to stress concentration, resulting in buckling.

[0083] Collapse risk: after embossing, the residual stress of the tab 3 is released, causing irreversible deformation during subsequent slitting or winding, which is manifested as the collapse of the tab root.

[0084] The sequence of the tab embossing method provided by the embodiment of the application is: pulp preparation, coating, drying, embossing, rolling, and cutting.

[0085] The embossing is performed when the tab 3 has not undergone rolling, and the stress distribution is optimized by using the following mechanisms:

[0086] Plastic deformation dominated: embossing introduces a compressive stress field through local plastic deformation, which offsets the tensile stress that may be generated during subsequent rolling.

[0087] Stress homogenization: the first tab embossing roller 1 forms a "stress groove" on the surface of the tab 3, guiding the rolling stress to diffuse along the direction of the lines, and reducing the stress concentration at the edge.

[0088] Isotropy enhancement: the embossing protrusions destroy the directional arrangement of the coating particles, reducing the stress anisotropy after rolling.

[0089] Further, the problem of tab collapse can be solved.

[0090] Further, in some embodiments of the application, S4 specifically comprises:

[0091] S41, two pre-embossing processes are performed on the front and back of the tab area 4 by using the second tab embossing roller and the third tab embossing roller, so as to strengthen the tab area 4.

[0092] S42, embossing forming, the first tab embossing roller 1 is used to form an embossing mark on the front or back of the tab.

[0093] The tab embossing device provided by the embodiment of the application is integrated in the rolling mechanism, which can effectively reduce the cost of the equipment. The rolling device can be quickly adjusted horizontally to meet the production needs of various types of batteries. The tab 3 area with the dressing is not consistent in ductility with the tab area 4 of the foil, and a large stress concentration and deformation incoordination occurs at the edge of the tab 3, i.e., the tab root, which causes wrinkles. The V-shaped embossing protrusion 101 and the strip-shaped embossing protrusion 102 are combined in the embodiment of the application, which can reduce the stress in this area to a certain extent, inhibit the generation of wrinkles, improve the yield, and reduce the risk of tab breakage.

[0094] It has to be noted that, in the present document, relational terms are intended only to convey a possible relationship between elements or

[0095] The above description is merely that of a specific implementation to enable a person skilled in the art to understand or implement the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tab embossing device, characterized in that, The device includes a first tab embossing roller and a first embossing section and a second embossing section sequentially disposed on the outer surface of the first tab embossing roller along the axial direction. The first embossing section includes a plurality of V-shaped embossing protrusions continuously disposed along the circumferential direction, and the second embossing section includes a plurality of strip-shaped embossing protrusions spaced apart along the circumferential direction. Both the V-shaped embossing protrusions and the strip-shaped embossing protrusions are protruding on the outer surface of the first tab embossing roller, and the strip-shaped embossing protrusions extend along the axial direction of the first tab embossing roller. The strip-shaped embossing protrusions and the V-shaped embossing protrusions are connected in a one-to-one correspondence.

2. The electrode tab embossing device according to claim 1, characterized in that, The V-shaped opening of the V-shaped embossed protrusion is oriented away from the strip-shaped embossed protrusion, and the corner of the V-shape of the V-shaped embossed protrusion is connected to the strip-shaped embossed protrusion.

3. The electrode tab embossing device according to claim 1, characterized in that, The corner of the V-shaped embossed protrusion, away from the strip-shaped embossed protrusion, is set as a first rounded corner, and the radius of the first rounded corner is R1, 0.1mm≤R1≤0.3mm; And / or, the included angle at the connection point of two adjacent V-shaped embossed protrusions is α, 30°≤α≤60°; And / or, the connection between two adjacent V-shaped embossed protrusions is smoothly transitioned, the side of the connection away from the strip embossed protrusion is set as a second rounded corner, the radius of the second rounded corner is R2, 0.3mm≤R2≤0.8mm, and the side of the connection closer to the strip embossed protrusion is set as a third rounded corner, the radius of the third rounded corner is R3, 0.1mm≤R3≤0.3mm; And / or, the diameter of the first electrode embossing roller is D, 40mm≤D≤200mm, and the tooth depth of the V-shaped embossing protrusion and the strip-shaped embossing protrusion is h, 0.5mm≤h≤2.5mm.

4. The electrode tab embossing device according to claim 1, characterized in that, The width of the V-shaped embossed protrusion is d1, 0.5mm≤d1≤2.5mm; the two sides of the V-shaped embossed protrusion along the width direction are set with a fourth rounded corner, the radius of the fourth rounded corner is R4, 0.05mm≤R4≤0.2mm; the width of the strip embossed protrusion is d2, 0.8mm≤d2≤1.8mm, and the distance between two adjacent strip embossed protrusions is d3, 1.3mm≤d3≤2.5mm.

5. The electrode embossing device according to claim 4, characterized in that, d2 / d3≤0.

6.

6. The electrode tab embossing device according to claim 1, characterized in that, The first tab embossing roller includes a hard roller and a soft roller arranged coaxially. The first embossing section and the second embossing section are both disposed on the hard roller, and the soft roller is disposed on the side of the first embossing section away from the second embossing section. The width of the soft roller along the axial direction is L, 5mm≤L≤30mm.

7. The electrode tab embossing device according to claim 1, characterized in that, It also includes a support roller, which is arranged parallel to the first tab embossing roller, and a gap is formed between the support roller and the first tab embossing roller for the tab to pass through.

8. A method for embossing electrode ears, characterized in that, include: The electrode tab area is embossed using the electrode tab embossing device as described in any one of claims 1-7; Rolling; Cut and stack.

9. The electrode embossing method as described in claim 8, characterized in that, The embossing in the electrode area includes: Pre-compression involves pre-compressing both sides of the tab region to strengthen it. Embossing is performed by using a first electrode embossing roller to create indentations on the front or back of the electrode.

10. The electrode embossing method according to claim 9, characterized in that, The pre-pressing is performed by using a second tab embossing roller and a third tab embossing roller to pre-press the front and back sides of the tab area, respectively. The second electrode embossing roller is disposed upstream of the first electrode embossing roller, and the second electrode embossing roller includes a roller and dot-shaped embossing protrusions. The dot-shaped embossing protrusions are provided on the outer surface of the roller. The diameter of the dot-shaped embossing protrusions is R5, between 0.3mm ≤ R5 ≤ 1.2mm. The radius of the chamfer of the edge of the dot-shaped embossing protrusions is R6, between 0.05mm ≤ R6 ≤ 0.3mm. The longitudinal tooth pitch of the dot-shaped embossing protrusions is S2, between 1mm ≤ S2 ≤ 3mm. The transverse tooth pitch of the dot-shaped embossing protrusions is S1, between 0.8mm ≤ S1 ≤ 3.6mm; 1 ≤ S2 / d2 ≤ 2. The third electrode embossing roller is a straight strip embossing roller.

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