Pole piece, pole piece welding method and lithium ion battery thereof

Abstract

The pole piece, pole piece welding method and lithium ion battery of the present application, the pole piece includes a first current collector and a tab, one end of the first current collector is covered by a first coating area and coated with a coating on both sides, and the other end is a first tab welding area, the first extended light foil in the welding area is bent to form a first light foil part, a light foil bending part and a second light foil part; the tab includes a first welding metal strip, a second welding metal strip, an external metal strip connected to the two welding metal strips and a tab adhesive coated on the external metal strip, which are welded at the first light foil part and / or the second light foil part; the welding method bends the first extended light foil twice to form two light foil parts, and then integrates the two welding metal strips of the tab with the two light foil parts through a welding and pressing process; the positive pole piece and / or the negative pole piece of the lithium ion battery adopts the pole piece, and after winding with a separator, it is formed by casing and injecting electrolyte, the present application can disperse welding stress, form double conductive paths and reduce the risk of current collector fracture.

Description

Technical Field

[0001] This invention relates to the technical fields of electrode sheets, manufacturing processes, and batteries, and in particular to an electrode sheet, an electrode sheet welding method, and a lithium-ion battery thereof. Background Technology

[0002] In the preparation of electrode sheets for lithium-ion batteries, the positive and negative electrodes are generally made by coating both sides of a current collector (such as aluminum foil, copper foil, or other metal foil) with an active material coating. A section of bare foil on the current collector (i.e., the bare foil area) without coating is used to weld to the tabs to lead the current from the electrode to the external circuitry of the battery. The tabs typically include a welding metal strip directly welded to the bare foil area of ​​the current collector, and an external metal strip electrically connected to the external circuitry. The two are connected by integral molding or transfer welding. The welding metal strip is usually welded to one side of the single-layer bare foil area of ​​the current collector using ultrasonic welding, laser welding, or resistance welding, forming a conductive connection between the electrode and the tab. After the positive and negative electrodes with the above structure are wound together with a separator to form a wound structure, the battery undergoes processes such as encapsulation, electrolyte injection, formation, and capacity testing to produce a lithium-ion battery. As lithium-ion batteries develop towards higher energy density, the doping ratio of silicon-based materials as negative electrode active materials is constantly increasing, and they are becoming increasingly common in the development and application of 3C lithium-ion batteries.

[0003] However, in existing welding methods between the tab and the current collector foil area, the welding metal strip is usually only welded to one side of the single-layer foil area. On the one hand, the welding process itself, such as ultrasonic welding and laser welding, will cause certain mechanical damage to the current collector foil at this location, such as local foil melting, thinning, or the generation of micro-cracks, resulting in the mechanical strength of the current collector at the welding position being significantly lower than that of other unwelded areas. On the other hand, the welding metal strip and the current collector foil area only form a single welding connection interface. Once the foil at this location breaks, the conductive path between the electrode and the tab will be completely lost, and there is no other backup connection to maintain conductivity. As the doping ratio of silicon-based materials in the negative electrode increases, the volume expansion generated during charge-discharge cycles becomes more significant. Consequently, the circumferential and radial expansion stresses generated on the winding structure also increase. These stresses tend to concentrate at the electrode tab welding positions, where the mechanical strength is reduced due to welding. This makes the current collector at these positions highly susceptible to fracture under continuous stress impact. Once fracture occurs, since the existing welding structure only has a single conductive connection interface, the electrode will become completely non-conductive, resulting in battery failure. This makes it difficult to meet the reliability requirements of electrode structures for the industrial application of high-silicon content negative electrode systems in lithium-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide an electrode, an electrode welding method and a lithium-ion battery thereof. The invention involves bending the first extended optical foil of the first current collector to form a connected first optical foil portion, an optical foil bending portion and a second optical foil portion, and then connecting the first welding metal strip and the second welding metal strip to the double-layer optical foil portion and welding and pressing them together. This achieves the dispersion of mechanical stress at the electrode tab welding position and the redundancy guarantee of another conductive path after the single welding metal strip breaks. Therefore, when the negative electrode is a silicon-based negative electrode, the risk of the electrode breaking under the volume expansion stress of the silicon-based negative electrode can be reduced.

[0005] To achieve the above objectives, the present invention provides the following three aspects:

[0006] In a first aspect, the present invention provides an electrode sheet, comprising:

[0007] The first current collector has a first coating covering area at one end and a first tab welding area at the other end. A section of the first current collector extending from the first coating covering area to the first tab welding area is designated as a first extended foil.

[0008] In the first coating coverage area of ​​the first current collector, the first current collector is coated with a first coating on one side and a second coating on the other side;

[0009] In the first tab welding area of ​​the first current collector, one end of the first extended light foil is bent, so that the first extended light foil forms a first light foil portion, a light foil bent portion connected to the first light foil portion, and a second light foil portion connected to the light foil bent portion.

[0010] The electrode tab includes a first welding metal strip welded to a first foil portion and / or a second foil portion, a second welding metal strip welded to the first foil portion and / or the second foil portion, an external metal strip connected to the first welding metal strip and the second welding metal strip respectively, and an electrode tab adhesive coated on the external metal strip.

[0011] Preferably, the first welding metal strip is welded to the first foil portion and / or the second foil portion by a welding and pressing process, the second welding metal strip is welded to the first foil portion and / or the second foil portion, and one side of the second foil portion is bonded to the first foil portion.

[0012] Preferably, when one end of the first extended foil is bent, the bending angle between the first foil portion and the bent portion of the foil is 90 degrees, the bending angle between the bent portion of the foil and the second foil portion is 90 degrees, and the first foil portion and the second foil portion are arranged in parallel.

[0013] After the first welding metal strip is welded to the first foil portion and / or the second foil portion through a welding and pressing process, and the second welding metal strip is welded to the first foil portion and / or the second foil portion, one side of the inner side of the second foil portion is bonded to the inner side of the first foil portion.

[0014] Preferably, the first welding metal strip is connected between the inner side of the first foil portion and the inner side of the second foil portion, and the second welding metal strip is connected to the outer side of the second foil portion.

[0015] Preferably, the first welding metal strip is connected to the outer surface of the first foil portion, and the second welding metal strip is connected to the outer surface of the second foil portion.

[0016] Preferably, the first welding metal strip is connected between the inner side of the first foil portion and the inner side of the second foil portion, and the second welding metal strip is connected between the inner side of the first foil portion and the inner side of the second foil portion.

[0017] Preferably, the first welding metal strip is connected to the outer surface of the second foil portion, and the second welding metal strip is connected to the outer surface of the second foil portion.

[0018] Preferably, the inner surfaces of the first foil portion and the second foil portion are respectively coated with conductive adhesive.

[0019] Preferably, the first welded metal strip and the outer metal strip are integrally connected, or the first welded metal strip and the outer metal strip are connected together by an adapter weld.

[0020] The second welded metal strip and the outer metal strip are integrally connected, or the second welded metal strip and the outer metal strip are connected together by an adapter weld.

[0021] Preferably, both the first and second welding metal strips are located on one side of the outer metal strip, or the first welding metal strip is located on one side of the outer metal strip and the second welding metal strip is located on the other side of the outer metal strip.

[0022] Preferably, when the first welded metal strip and the outer metal strip are connected together by an adapter weld, the first welded metal strip is adapter welded to one end face of the outer metal strip, and when the second welded metal strip and the outer metal strip are connected together by an adapter weld, the second welded metal strip is adapter welded to the other end face of the outer metal strip.

[0023] Preferably, when the first welding metal strip is located on one side of the outer metal strip and the second welding metal strip is located on the other side of the outer metal strip, the width of the outer metal strip is set to W, the width of the first welding metal strip is set to W1, the width of the second welding metal strip is set to W2, and the distance between the first welding metal strip and the second welding metal strip is set to W3. The following relationship is satisfied between W, W1, W2, and W3:

[0024] W>W1;

[0025] W>W2;

[0026] 0.1mm <W3<W。

[0027] Preferably, the external metal strip, the first welding metal strip, and the second welding metal strip are made of one of aluminum strip, nickel strip, copper strip, or nickel-plated copper strip.

[0028] In a second aspect, the present invention provides an electrode welding method for manufacturing an electrode as described in the first aspect, comprising the following steps:

[0029] A first current collector is provided, one end of which forms a first coating coverage area, and the other end forms a first tab welding area. A section of the first current collector extending from the first coating coverage area to the first tab welding area is designated as a first extended foil.

[0030] In the first coating coverage area, the first current collector is coated with a first coating on one side and a second coating on the other side;

[0031] Flip one end of the first extended light foil to the first angle, while keeping the end of the first extended light foil connected to the first coating coverage area fixed.

[0032] The end that has been flipped to the first angle is flipped to the second angle, so that the flip angle of the end reaches the sum of the first angle and the second angle, so that the first extended light foil forms a first light foil part, a light foil bending part connected to the first light foil part, and a second light foil part connected to the light foil bending part.

[0033] Provide a tab, the tab comprising an external metal strip, a first welded metal strip and a second welded metal strip respectively connected to the external metal strip, and tab adhesive coated on the external metal strip;

[0034] By means of a welding and pressing process, the first welding metal strip is welded to the first foil portion and / or the second foil portion, and the second welding metal strip is welded to the first foil portion and / or the second foil portion, so that one side of the second foil portion is bonded to the first foil portion.

[0035] Preferably, the first angle is 90 degrees, and the sum of the first angle and the second angle is 180 degrees.

[0036] Preferably, the end of the first extended foil to be folded is pulled by a mechanical gripper and flipped to a first angle, and the end connected to the first coating coverage area is pressed and fixed by a mechanical pressure handle.

[0037] The robotic arm pulls the end that has been flipped to the first angle to continue flipping it to the second angle;

[0038] The first and second welded metal strips of the electrode tabs are inserted into the first and / or second foil portions respectively by means of the robotic arm and the mechanical pressure handle.

[0039] Welding is completed by pressing down the first welding metal strip, the second welding metal strip, the first foil section, and the second foil section after they are inserted by a welding die.

[0040] Thirdly, the present invention provides a lithium-ion battery, including a housing and a positive electrode, a separator, and a negative electrode respectively disposed inside the housing. The positive electrode and / or the negative electrode is an electrode as described in the first aspect. The separator is located between the positive electrode and the negative electrode. The positive electrode, the separator, and the negative electrode are stacked in sequence and then wound along the same axial direction to form a wound structure. The wound structure is disposed inside the housing, and the housing is filled with electrolyte.

[0041] Preferably, when the positive electrode and / or negative electrode is one of the electrode types described in the first aspect...

[0042] Looking along the winding direction,

[0043] The shortest arc length distance between the first and second welded metal strips and the bent portion of the electrode foil is L, and L satisfies the following formula:

[0044] L = απR / 180;

[0045] Wherein, the first endpoint of the shortest arc length distance L is connected to the center of the winding structure to form a first straight line, the second endpoint of the shortest arc length distance L is connected to the center of the winding structure to form a second straight line, α is the angle between the first straight line and the second straight line, the value of the angle α is in the range of 15-30 degrees, and R is the radius of the winding structure.

[0046] Preferably, the negative electrode sheet of the wound structure is located on the outermost ring.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] 1. This invention bends one end of the first extended foil of the first current collector to form a connected first foil portion, a bent foil portion, and a second foil portion. This allows the first current collector to form a double-layered foil portion in the first tab welding area. A first welding metal strip and a second welding metal strip are used to connect the first foil portion and / or the second foil portion, respectively. A welding and pressing process is used to weld the first welding metal strip, the second welding metal strip, the first foil portion, and the second foil portion into a single unit, and to bond the second foil portion to the first foil portion. On one hand, the double-layered foil portion increases the effective thickness of the tab welding area, which can disperse the mechanical stress and silicon-based negative electrode expansion stress originally concentrated at the welding position of the single-layer bare foil, reducing the risk of the first current collector breaking due to stress impact caused by welding damage. On the other hand, the two relatively independent welding metal strips are welded to the double-layered foil portion respectively. Even if one welding metal strip fails or breaks due to stress, the other welding metal strip can still maintain the conductive path between the electrode and the tab, avoiding the problem of existing single-layer, single-weld interface structures completely losing conductivity due to local breakage.

[0049] 2. Furthermore, the first and second welding metal strips can be flexibly selected to connect to the inner or outer sides of the first and / or second foil portions according to actual welding needs. They can also be connected to the external metal strip using an integral connection structure or an adapter welding connection structure. This allows the electrode structure provided by the present invention to not only meet the requirements of stress dispersion and dual conductivity protection, but also to take into account the adaptability under different welding process conditions and material selection requirements. This helps to reduce the risk of heat accumulation at the electrode welding position due to poor contact or local overheating, and further improves the structural stability and service life of the electrode welding position under long-term charge and discharge cycles.

[0050] 3. In summary, the electrode sheet, electrode sheet welding method, and lithium-ion battery provided by this invention, without significantly increasing manufacturing complexity, take into account both the mechanical strength and conductivity reliability of the electrode tab welding position, providing an effective solution for the stability of lithium-ion battery electrode structure under the condition of silicon-based anode volume expansion, and helping to promote the industrial application of lithium-ion batteries with high silicon content anode system. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1This is a front cross-sectional view of an electrode sheet according to one of the first embodiments provided in Embodiment 1 of the present invention (the electrode sheet in this view is a front cross-sectional view before the first welding metal strip is welded to the second foil portion by a welding and pressing process after one end of the first extended optical foil is folded, and the second welding metal strip is welded to the first and second optical foil portions, and the electrode tab adhesive and external metal strip are omitted in this view).

[0053] Figure 2 This is a front cross-sectional view of another type of electrode sheet provided in the first embodiment of the present invention (the electrode sheet in this view is a front cross-sectional view before the first welding metal strip is welded to the first foil portion and the second foil portion by a welding and pressing process after one end of the first extended optical foil is folded, and the second welding metal strip is welded to the second foil portion, and the electrode tab adhesive and the external metal strip are omitted in this view).

[0054] Figure 3 This is a front cross-sectional view of an electrode sheet according to the second embodiment of the present invention (the electrode sheet in this view is folded at one end of the first extended optical foil, and the first welding metal strip is welded to the first optical foil portion by a welding and pressing process, and the second welding metal strip is welded to the second optical foil portion before the second welding metal strip is welded to the first optical foil portion, and the electrode tab adhesive and the external metal strip are omitted in this view).

[0055] Figure 4 This is a front cross-sectional view of an electrode sheet according to the third embodiment of the present invention (the electrode sheet in this view is folded at one end of the first extended optical foil, and the first welding metal strip is welded to the first optical foil portion and the second optical foil portion by a welding and pressing process, and the second welding metal strip is welded to the first optical foil portion and the second optical foil portion before the electrode sheet is folded at one end of the first extended optical foil portion, and the electrode tab adhesive and the external metal strip are omitted in this view).

[0056] Figure 5 This is a front cross-sectional view of an electrode sheet according to the fourth embodiment of the present invention (the electrode sheet in this view is folded at one end of the first extended optical foil, and the first welding metal strip is welded to the second optical foil part by a welding and pressing process, and the second welding metal strip is welded to the second optical foil part before the electrode sheet is folded at one end of the first extended optical foil part, and the electrode tab adhesive and the external metal strip are omitted in this view).

[0057] Figure 6 This is a front view of an electrode sheet provided in Embodiment 1 of the present invention (the electrode sheet in this view is a schematic diagram after the first welding metal strip is welded to the second foil portion by a welding and pressing process, and the second welding metal strip is welded to the first foil portion and the second foil portion, and the tab adhesive and the external metal strip are omitted in this schematic diagram).

[0058] Figure 7 yes Figure 6 A magnified view of the area pointed to by the letter A in the middle;

[0059] Figure 8 This is a front view of a first connection method of the tab of an electrode provided in Embodiment 1 of the present invention (the first current collector is omitted in this view).

[0060] Figure 9 This is a front view of a second connection method of the electrode tab of an electrode provided in Embodiment 1 of the present invention (the first current collector is omitted in this view).

[0061] Figure 10 This is a front view of a third connection method of the electrode tab of an electrode provided in Embodiment 1 of the present invention (the first current collector is omitted in this view).

[0062] Figure 11 It is about Figure 10 A side view of the electrode tab (the first current collector is omitted in this view);

[0063] Figure 12 This is a schematic diagram of the structure of the first current collector formed by cutting and separating two adjacent coatings at a designated position with a cutter, as provided in Embodiments 1 and 2 of the present invention.

[0064] Figure 13 This is a schematic diagram of the structure provided in Embodiments 1 and 2 of the present invention, which shows how the end of the first extended optical foil to be folded is flipped to a first angle by a mechanical gripper.

[0065] Figure 14 These are schematic diagrams of the structures provided in Embodiments 1 and 2 of the present invention, showing how the end that has been flipped to the first angle is further flipped to the second angle by a robotic arm.

[0066] Figure 15 These are schematic diagrams of the structure provided in Embodiments 1 and 2 of the present invention when the first welding metal strip and the second welding metal strip of the electrode tab are respectively inserted into the first optical foil portion and / or the second optical foil portion;

[0067] Figure 16 This is a top view of the winding structure provided in Embodiment 3 of the present invention;

[0068] Figure 17 This is a front cross-sectional view of the electrode provided in Comparative Example 1 (the electrode provided in Comparative Example 1 is prior art).

[0069] Figure 18This is a front cross-sectional view of the electrode sheet provided in Comparative Example 2 (the electrode sheet prepared by welding the conventional electrode tab with the first current collector 1 provided by the present invention and the electrode tab).

[0070] Figure 19 This is a front cross-sectional schematic diagram of an electrode sheet provided in Comparative Example 3 (Comparative Example 3 is an electrode sheet prepared using a Y-shaped electrode tab structure, and the Y-shaped electrode tab structure is omitted in this schematic diagram).

[0071] Figure 20 This is a front cross-sectional schematic diagram of an electrode sheet provided in Comparative Example 4 (Comparative Example 4 is an electrode sheet prepared using a Y-shaped electrode tab structure, and the Y-shaped electrode tab structure is omitted in this schematic diagram).

[0072] Figure 21 The diagrams provided in Comparative Examples 3 and 4 are schematic diagrams of the Y-shaped tab structure (the first current collector is omitted in these diagrams).

[0073] The diagram includes:

[0074] 1. First current collector; 11. First coating coverage area; 12. First tab welding area; 13. First extended foil; 14. First coating; 15. Second coating; 16. First foil portion; 17. Foil bending portion; 18. Second foil portion; 21. First welding metal strip; 22. Second welding metal strip; 23. External metal strip; 24. Tab adhesive; 5. Positive electrode sheet; 6. Negative electrode sheet; 7. Separator; 8. Winding structure; 91. Conventional current collector; 92a. Tab metal strip; 92b. External metal strip for tab; 93. Welding metal strip; 94. Auxiliary welding metal strip. Detailed Implementation

[0075] The technical solution of this embodiment of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiment is one embodiment of the present invention, and not all embodiments thereof. Based on this embodiment of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0076] Example 1:

[0077] Please see Figures 1 to 15 Embodiment 1 of the present invention provides an electrode sheet, comprising:

[0078] The first current collector 1 has a first coating covering area 11 at one end and a first electrode welding area 12 at the other end. The section of the first current collector 1 extending from the first coating covering area 11 to the first electrode welding area 12 is designated as a first extended light foil 13.

[0079] In the first coating coverage area 11 of the first current collector 1, the first current collector 1 is coated with a first coating 14 on one side and a second coating 15 on the other side;

[0080] In the first electrode tab welding area 12 of the first current collector 1, one end of the first extended foil 13 is bent (the bending effect is as follows) Figures 1 to 5 As shown), the first extended foil 13 forms a first foil portion 16, a foil bending portion 17 connected to the first foil portion 16, and a second foil portion 18 connected to the foil bending portion 17.

[0081] Polar ears (such as) Figures 8 to 11 As shown), the tab includes a first welding metal strip 21 welded to the first foil portion 16 and / or the second foil portion 18, a second welding metal strip 22 welded to the first foil portion 16 and / or the second foil portion 18, an external metal strip 23 connected to the first welding metal strip 21 and the second welding metal strip 22 respectively, and tab adhesive 24 coated on the external metal strip 23.

[0082] Through a welding and pressing process, the first welding metal strip 21 is welded to the first foil portion 16 and / or the second foil portion 18 (e.g., Figure 7 As shown), the second welding metal strip 22 is welded to the first foil portion 16 and / or the second foil portion 18 (as shown). Figure 7 As shown), and so that one side of the second foil portion 18 is attached to the first foil portion 16 (as shown). Figure 7 (As shown).

[0083] In Embodiment 1 of the present invention, the first extended optical foil 13 of the first current collector 1 of the electrode sheet is first bent in two sections, then inserted into the designated parts of the two bends by two welding metal strips, and finally welded together by a welding and pressing process to form the electrode sheet of Embodiment 1 of the present invention. The process is specifically divided into the following two steps:

[0084] First: When one end of the first extended light foil 13 is bent, the bending angle between the first light foil portion 16 and the light foil bending portion 17 is 90 degrees, the bending angle between the light foil bending portion 17 and the second light foil portion 18 is 90 degrees, and the first light foil portion 16 and the second light foil portion 18 are arranged in parallel.

[0085] Second: After the first welding metal strip 21 is welded to the first foil portion 16 and / or the second foil portion 18 through a welding and pressing process, and the second welding metal strip 22 is welded to the first foil portion 16 and / or the second foil portion 18, and one side of the inner surface of the second foil portion 18 is bonded to the inner surface of the first foil portion 16 (e.g., Figure 7 (As shown).

[0086] By bending the first extended foil 13 twice at 90 degrees, the first foil portion 16 and the second foil portion 18 are arranged completely parallel with their inner surfaces facing each other. This allows the first foil portion 16 and the second foil portion 18 to achieve maximum overlap and bonding, forming a double-layer foil stacked structure with uniform thickness in the first tab welding area 12. This is beneficial for forming a uniform and reliable welding interface between the two welding metal strips and the two foil layers in the subsequent welding and pressing process, and avoids uneven local stress or welding gaps caused by inconsistent bending angles.

[0087] In the first coating coverage area 11 of the first current collector 1, a first coating 14 is coated on one side of the first current collector 1 and a second coating 15 is coated on the other side. In the horizontal direction, the first coating 14 and the second coating 15 can be aligned end to end, or their beginnings or ends are separated, or their beginnings and ends are doubly separated.

[0088] The first welding metal strip 21 is connected to the first foil portion 16 and / or the second foil portion 18, and the second welding metal strip 22 is connected to the first foil portion 16 and / or the second foil portion 18, which has the following four embodiments:

[0089] The first implementation method is as follows: Figure 1 or Figure 2 As shown, one of the welding metal strips (first welding metal strip 21 or second welding metal strip 22) is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18, while the other welding metal strip (first welding metal strip 21 or second welding metal strip 22) is connected to the outer side of the second foil portion 18.

[0090] That is, the first implementation method Figure 1 The second welding metal strip 22 is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18, and the first welding metal strip 21 is connected to the outer side of the second foil portion 18.

[0091] That is, the first implementation method Figure 2 The first welding metal strip 21 is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18, and the second welding metal strip 22 is connected to the outer side of the second foil portion 18.

[0092] Wherein, the inner side of the first light foil portion 16 is the side of the first light foil portion 16 facing the second light foil portion 18, the outer side of the first light foil portion 16 is the side of the first light foil portion 16 facing away from the second light foil portion 18, the inner side of the second light foil portion 18 is the side of the second light foil portion 18 facing the first light foil portion 16, and the outer side of the second light foil portion 18 is the side of the second light foil portion 18 facing away from the first light foil portion 16.

[0093] The advantage of the first embodiment is that: one of the welded metal strips forms a welding interface with the inner side of the first foil portion 16 and the inner side of the second foil portion 18 through a welding and pressing process, thereby forming an additional bridging connection path between the first foil portion 16 and the second foil portion 18 outside the foil bending portion 17. Even if the foil bending portion 17 develops fatigue cracks or even breaks due to cyclic stress, the bridging path can still maintain the conductive connection between the first foil portion 16 and the second foil portion 18. Although the other welded metal strip only directly contacts the outer side of the second foil portion 18, since the other welded metal strip, the first foil portion 16, and the second foil portion 18 are welded together in the same welding and pressing process, its weld point also plays a bridging and fixing role for the two foil portions, thus forming a double conductive guarantee together with the bridging path of the one welded metal strip: even if one of the welded metal strips fails first due to cyclic stress, the other welded metal strip can still maintain the conductive connection between the first current collector 1 and the tab. Meanwhile, the superposition of the double-layer foil increases the effective thickness of the first tab welding area 12, disperses the mechanical stress concentrated on the single-layer bare foil in the prior art, and significantly reduces the risk of strip breakage at the tab welding point.

[0094] The second implementation method is as follows: Figure 3 As shown, the first welding metal strip 21 is connected to the outer surface of the first foil portion 16, and the second welding metal strip 22 is connected to the outer surface of the second foil portion 18.

[0095] The advantage of the second implementation is that, although the second implementation does not form a double-layer conductive path as well as the first implementation to ensure the redundancy effect of the connection, the second implementation still benefits from the fact that the first welding metal strip 21 is connected to the outer surface of the first foil portion 16, which increases the thickness of the first foil portion 16, and the second welding metal strip 22 is connected to the outer surface of the second foil portion 18, which increases the thickness of the second foil portion 18. This arrangement can also disperse the mechanical / impact stress that was originally concentrated on the single-layer bare foil. Compared with the folded single-layer structure of the prior art, it can still significantly reduce the risk of strip breakage. At the same time, it provides more room for the process tolerance of the welding position.

[0096] The third implementation method is as follows: Figure 4 As shown, the first welding metal strip 21 is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18, and the second welding metal strip 22 is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18.

[0097] The advantage of the third implementation is that the third implementation is equivalent to forming two independent bridging conductive paths between the first foil section 16 and the second foil section 18. Even if one of the bridging conductive paths fails first due to long-term cyclic stress, the other bridging conductive path can still maintain conductive connection independently. It has a higher redundancy guarantee capability than the first implementation and is suitable for application scenarios with higher reliability requirements.

[0098] The fourth implementation method is as follows: Figure 5 As shown, the first welding metal strip 21 is connected to the outer surface of the second foil portion 18, and the second welding metal strip 22 is connected to the outer surface of the second foil portion 18.

[0099] The advantage of the fourth embodiment is that the first welding metal strip 21 and the second welding metal strip 22 are both connected to the same surface of the second foil portion 18. In terms of process, only two welding operations need to be completed on the same side, without the need to weld on different sides of the first foil portion 16 and the second foil portion 18 respectively. This simplifies the design of the welding die and the welding process. At the same time, this welding method also allows the second foil portion 18 to be thickened while the stress dispersion effect is still retained.

[0100] In the first electrode welding area 12 of the first current collector 1, after one end of the first extended light foil 13 is bent to form a first light foil portion 16, a light foil bending portion 17 connected to the first light foil portion 16, and a second light foil portion 18 connected to the light foil bending portion 17, conductive adhesive is applied to the inner surface of the first light foil portion 16 and the inner surface of the second light foil portion 18, respectively. After the conductive adhesive is applied, the first welding metal strip 21, the second welding metal strip 22, the first light foil portion 16 and the second light foil portion 18 are welded together by a welding and pressing process. By applying conductive adhesive before welding and pressing, the reliability of the conductive connection and the structural integrity between the two layers of optical foil can be further enhanced in areas other than the welding positions of the first optical foil section 16 and the second optical foil section 18. Even if the electrode is subjected to expansion stress during charge and discharge cycles, or if local misalignment or gaps occur between the two layers of optical foil in non-welded areas, the conductive adhesive can maintain the conductive continuity and bonding strength in that area, thereby further reducing the risk of strip breakage and improving the overall structural stability of the optical foil bending section 17 area.

[0101] The connection between the first welded metal strip 21 and the outer metal strip 23 has the following two implementation methods: the first welded metal strip 21 and the outer metal strip 23 are integrally connected structures, or the first welded metal strip 21 and the outer metal strip 23 are connected together by an adapter weld.

[0102] The connection between the second welded metal strip 22 and the external metal strip 23 has the following two implementation methods: the second welded metal strip 22 and the external metal strip 23 are integrally connected structures, or the second welded metal strip 22 and the external metal strip 23 are connected together by an adapter weld.

[0103] The aforementioned integrated connection structure can be formed in one step by stamping, cutting, etching and other processes on the same metal sheet / strip. There are no seams or welds between the external metal strip 23 and the first welded metal strip 21 and the second welded metal strip 22, respectively. They are different sections of the same continuous metal material. This structure is beneficial to improving the mechanical strength and electrical conductivity of the connection interface.

[0104] The aforementioned transition welding can be one of the metal welding methods such as laser welding, ultrasonic welding, or resistance welding. The external metal strip 23 and the first welding metal strip 21 and the second welding metal strip 22 can be made of the same material or different materials. This transition welding setting facilitates the selection of materials for the external metal strip 23, the first welding metal strip 21, and the second welding metal strip 22, thereby enabling targeted performance optimization.

[0105] Among them, such as Figure 10 As shown, when the first welding metal strip 21 and the outer metal strip 23 are connected together by an adapter weld, the first welding metal strip 21 is adapter welded to one end face of the outer metal strip 23. When the second welding metal strip 22 and the outer metal strip 23 are connected together by an adapter weld, the second welding metal strip 22 is adapter welded to the other end face of the outer metal strip 23. The advantage of this structure is that, since the first welding metal strip 21 and the second welding metal strip 22 need to extend to different positions of the first electrode welding area 12 in the electrode structure, by staggering the welding of the two welding metal strips on the outer metal strip, the two welding metal strips can extend to the corresponding welding positions along their respective required paths, avoiding intersections or interference between them on the extension paths. This facilitates the implementation of the adapter weld process and the design of the operating space of the welding equipment. At the same time, the two adapter welds are located on the two end faces of the outer metal strip 23, which also helps to disperse the stress concentration at the connection between the outer metal strip 23 and the two welding metal strips, improving the overall mechanical reliability of the adapter weld joint.

[0106] like Figure 10 As shown, when the first welding metal strip 21 is located on one side of the outer metal strip 23 and the second welding metal strip 22 is located on the other side of the outer metal strip 23, the width of the outer metal strip 23 is set to W, the width of the first welding metal strip 21 is set to W1, the width of the second welding metal strip 22 is set to W2, and the distance between the first welding metal strip 21 and the second welding metal strip 22 is set to W3. W, W1, W2 and W3 satisfy the following relationship:

[0107] W>W1;

[0108] W>W2;

[0109] 0.1mm<W3<W.

[0110] The thickness of the first welded metal strip 21 is set as H1, the thickness of the second welded metal strip 22 is set as H2, W1=W2 or W1≠W2, and H1=H2 or H1≠H2.

[0111] The above arrangement of W>W1 and W>W2 is to ensure that the width of the external metal strip 23 is greater than the widths of the two welded metal strips, so that the external metal strip 23 can cover, gather and reliably connect the two welded metal strips; the arrangement of 0.1mm<W3<W ensures that a certain distance is maintained between the first welded metal strip 21 and the second welded metal strip 22, avoiding short circuit or mutual interference between the two during welding and use, while the distance does not exceed the width of the external metal strip 23, ensuring structural compactness. The widths W1, W2 and thicknesses H1, H2 of the first welded metal strip 21 and the second welded metal strip 22 may be equal or different, and can be designed differentially according to the stress distribution and conductive requirements at the actual welding position. For example, one of the welded metal strips can be designed to have a larger width and a thinner thickness to reduce stress concentration during welding and use of this welded metal strip and lower the risk of fracture; the other welded metal strip can be designed to have a smaller width and a larger thickness to increase its conductive cross-sectional area and conductive capacity, so as to give consideration to stress dispersion and enhanced conductivity. The materials of the external metal strip 23, the first welded metal strip 21 and the second welded metal strip 22 are one of aluminum strip, nickel strip, copper strip or nickel-plated copper strip.

[0112] The advantages of the structural arrangement of the electrode plate in Embodiment 1 of the present invention are as follows: by bending the first extended bare foil 13 to form the connected first bare foil portion 16, bare foil bent portion 17 and second bare foil portion 18, a double-layer bare foil structure is formed in the first tab welding region 12 of the first current collector 1, and the first welded metal strip 21 and the second welded metal strip 22 are respectively connected to the first bare foil portion 16 and / or the second bare foil portion 18, and the two welded metal strips and the double-layer bare foil are welded into a whole through a welding and pressing process: on the one hand, the double-layer bare foil increases the effective thickness of the tab welding region, which can disperse the mechanical stress concentrated at this position during welding and subsequent charge-discharge cycles, and reduce the risk of fracture of the first current collector 1 caused by welding damage and expansion stress impact; on the other hand, the two relatively independent welded metal strips are respectively welded and connected to the double-layer bare foil. Even if one of the welded metal strips fails due to stress, the other welded metal strip can still maintain the conductive path between the first current collector 1 and the tab, thereby reducing the risk of electrode plate strip breakage and improving the conductive reliability after strip breakage at the tab welding position.

[0113] Example 2:

[0114] Please see Figures 11 to 15 Embodiment 2 of the present invention provides an electrode welding method for fabricating an electrode as described in Embodiment 1, comprising the following steps:

[0115] A current collector mother tape is provided, and multiple coatings are applied to the upper and lower surfaces of the current collector mother tape at intervals. Two adjacent coatings in the horizontal direction of the current collector mother tape are clamped by a mold clamp, and the two adjacent coatings are cut and separated by a cutter at a designated position to form a first current collector 1.

[0116] A first current collector 1 is provided, one end of the first current collector 1 forms a first coating coverage area 11, and the other end forms a first electrode welding area 12. A section of the first current collector 1 extending from the first coating coverage area 11 to the first electrode welding area 12 is designated as a first extended light foil 13.

[0117] In the first coating coverage area 11, the first current collector 1 is coated with the first coating 14 on one side and the second coating 15 on the other side;

[0118] Flip one end of the first extended light foil 13 to the first angle, while keeping the end of the first extended light foil 13 connected to the first coating coverage area 11 fixed.

[0119] The end that has been flipped to the first angle is flipped to the second angle, so that the flip angle of the end reaches the sum of the first angle and the second angle, so that the first extended light foil 13 forms a first light foil part 16, a light foil bending part 17 connected to the first light foil part 16, and a second light foil part 18 connected to the light foil bending part 17.

[0120] Provides a tab, the tab includes an external metal strip 23, a first welded metal strip 21 and a second welded metal strip 22 respectively connected to the external metal strip 23, and tab adhesive 24 applied to the external metal strip 23;

[0121] By means of a welding and pressing process, the first welding metal strip 21 is welded to the first foil portion 16 and / or the second foil portion 18, and the second welding metal strip 22 is welded to the first foil portion 16 and / or the second foil portion 18, so that one side of the second foil portion 18 is attached to the first foil portion 16.

[0122] The first angle is 90 degrees. The sum of the first and second angles is 180 degrees.

[0123] The mechanical gripper pulls the end of the first extended light foil 13 to be folded and flips it to the first angle, and the mechanical pressure handle presses and fixes the end connected to the first coating coverage area 11.

[0124] The robotic arm pulls the end that has been flipped to the first angle to continue flipping it to the second angle;

[0125] With the cooperation of a robotic arm and a mechanical pressure handle, the first welding metal strip 21 and the second welding metal strip 22 of the electrode tab are respectively inserted into the first foil section 16 and / or the second foil section 18.

[0126] Welding is completed by pressing down the first welding metal strip 21, the second welding metal strip 22, the first foil section 16 and the second foil section 18 after they are inserted by a welding die.

[0127] Example 3:

[0128] Please see Figure 16 Embodiment 3 of the present invention provides a lithium-ion battery, including a housing and a positive electrode 5, a separator 7 and a negative electrode 6 respectively installed inside the housing. The positive electrode 5 and / or the negative electrode 6 are electrodes of Embodiment 1. The separator 7 is located between the positive electrode 5 and the negative electrode 6. The positive electrode 5, the separator 7 and the negative electrode 6 are stacked in sequence and then wound along the same axial direction to form a winding structure 8. The winding structure 8 is installed inside the housing, and the housing is filled with electrolyte.

[0129] Wherein, when the positive electrode 5 and / or the negative electrode 6 are one of the electrodes of Example 1,

[0130] Looking along the winding direction,

[0131] The shortest arc length distance between the first weld metal strip 21 and the second weld metal strip 22 and the foil bending portion 17 of the electrode sheet is L, and L satisfies the following formula:

[0132] L = απR / 180;

[0133] Wherein, the first endpoint of the shortest arc length distance L is connected to the center of the winding structure to form a first straight line, and the second endpoint of the shortest arc length distance L is connected to the center of the winding structure to form a second straight line. α is the angle between the first straight line and the second straight line, and the value of the angle α is in the range of 15-30 degrees. Setting the angle α within 15-30 degrees effectively avoids poor stress conduction effect due to too short an angle α and easy deviation and displacement of the winding end foil due to too long an angle α. R is the radius of the winding structure.

[0134] By setting the shortest arc length distance L=απR / 180, an extension section satisfying the relationship L=απR / 180 is retained in the outer winding direction outside the welding position of the two welding metal strips along the winding direction. This allows the circumferential stress generated by the charge and discharge cycle to continue to be conducted and dispersed in the outer winding direction through this extension section after being conducted to the welding position of the two welding metal strips. This avoids the stress being completely concentrated at the welding position and the foil bending part 17. This is a further stress management design for the electrode structure of Embodiment 1 at the overall winding direction level.

[0135] Furthermore, in the aforementioned winding structure 8, the negative electrode 6 is located at the outermost ring. This arrangement has the advantage that the tensile strength and elongation of the negative electrode 6 foil are superior to those of the positive electrode 5 foil. The superior elasticity and plasticity of the negative electrode 6 foil can better conduct stress transmission, and the expansion stress on the entire winding structure 8 mainly originates from the negative electrode 6. Therefore, the negative electrode 6 is the primary stress transmission medium. If the positive electrode were to terminate at the outermost layer, the circumferential and radial stresses of the negative electrode 6 would accelerate the fracture of the positive electrode 5.

[0136] In addition, the lithium-ion battery can be a pouch-style prismatic battery.

[0137] Example 4:

[0138] Example 4 of the present invention provides nine experimental examples and four comparative examples of an electrode sheet, an electrode sheet welding method, and a lithium-ion battery related to Examples 1-3. Statistical experiments were conducted on the negative electrode sheet breakage rate of the lithium-ion batteries prepared in the nine experimental examples and four comparative examples at different stages of formation, capacity testing, and cycling to verify the technical effectiveness of the electrode sheet included in Examples 1-3 of the present invention. The specific details are as follows:

[0139] The positive electrode 5, negative electrode 6, and lithium-ion battery preparation process of Embodiments 1-3 of the present invention are as follows: the positive electrode 5 and negative electrode 6 after coating and rolling are slit into the required width, and one end of the first extended light foil 13 on the positive electrode 5 and negative electrode 6 is folded 180° to form a first light foil portion 16, a light foil bending portion 17 connected to the first light foil portion 16, and a second light foil portion 18 connected to the light foil bending portion 17. The first welding metal strip 21 and the second welding metal strip 22 of the electrode tab are respectively connected to the first light foil portion 16 and / or the second light foil portion 18. The obtained positive electrode 5 and negative electrode 6 are wound together with the separator 7 to form the winding structure 8 of Embodiment 3, and the winding structure 8 is sequentially encapsulated, injected with liquid, formed, and capacity tested to obtain a lithium-ion battery.

[0140] Since the risk of electrode breakage in the winding structure 8 of a lithium-ion battery is mainly affected by the silicon doping content of the negative electrode 6, generally, under the same winding structure 8 and winding structure 8 size, the higher the silicon doping content, the higher the risk of breakage of the negative electrode 6 on the winding structure 8. Different degrees of negative electrode 6 breakage occur at silicon doping ratios of 7%, 10%, 15%, 20%, 30%, and 50%. When the silicon doping content is 15% or less, the negative electrode 6 generally does not break during the initial charge-discharge stages such as formation and capacity testing, but only after a certain number of cycles. When the silicon doping content is 20% or more, the negative electrode 6 may break during the formation and capacity testing stages, and the breakage frequency and breakage period are higher during cycling. To quickly and comprehensively verify the effectiveness of the technical solutions in Examples 1-3 of this invention, the silicon doping content of the negative electrode 6 in the following 9 experimental examples and 4 comparative examples is designed to be 50%.

[0141] Furthermore, the cycling tests in the following experiments all adopted a high-temperature cycling mode, with direct charging at a 3C rate and discharging at a 1C rate. The upper limit of the charging voltage was 4.55V, and the lower limit of the discharging voltage was 2.8V. This is because the lithium-ion battery has a higher charge and discharge capacity and more severe volume expansion and contraction under the high-temperature cycling mode, which makes it more likely to cause the negative electrode 6 to break. It also makes it easier to verify the improvement effect brought by embodiments 1-3 of the present invention. At the same time, the stress acceleration generated during the charging and discharging process of the battery under the 3C / 1C fast charge and discharge mode is greater, which also makes it easier to accelerate the occurrence of the negative electrode 6 breakage, thereby more fully verifying the technical effect. It should be noted that for lithium-ion batteries with different silicon doping amounts of negative electrode 6, different battery winding structures 8, or different battery capacities, as well as different cycling modes and cycle life requirements, the improvement effect of negative electrode 6 breakage will be affected by different preconditions. Therefore, the complete elimination of breakage should not be used as the final evaluation criterion.

[0142] In this embodiment 4, the confirmation of the breakage of the negative electrode 6 is mainly based on direct observation by dissecting the winding structure 8 of the lithium-ion battery and CT imaging inspection of the winding structure 8 of the lithium-ion battery: For the winding structure 8 of the lithium-ion battery in the process stage, if formation or capacity failure occurs, the negative electrode 6 is directly disassembled to check for breakage; For lithium-ion batteries in the cycling process, test data is observed first. If the test data shows a sudden drop in capacity or voltage to 0 or other abnormalities, the abnormal battery is first subjected to CT imaging to confirm whether the negative electrode 6 is broken. Lithium-ion batteries with obvious breakage shown by CT imaging are directly disassembled for observation and confirmation. Batteries without obvious breakage shown by CT imaging are subjected to other tests and analyses, and the cycling test is continued by changing the cycling mode, etc., until the lithium-ion battery can no longer be charged or discharged, and then it is disassembled for observation and confirmation.

[0143] The statistical counts of lithium-ion batteries in the following experimental examples and comparative examples are all 100 pieces of good batteries after encapsulation and electrolyte filling. The defect rate of negative electrode 6 breakage at each stage is calculated by dividing the number of batteries with negative electrode 6 breakage at each stage by the total number of good batteries (100 pieces). The sum of the defect rates at each stage is the total defect rate.

[0144] 1. Experimental Example 1, wherein an electrode sheet according to Example 1 and an electrode sheet welding method according to Example 2 were used for preparation, and the specific parameters are as follows:

[0145] like Figure 10 The electrode structure shown and Figure 1 The first current collector 1 and the electrode tab welding structure shown have the following characteristics: the outer metal strip 23 has a thickness of 0.08 mm and a width of W = 1.5 mm; the second welding metal strip 22 has a thickness of H2 = 0.06 mm and a width of W2 = 1 mm; the first welding metal strip 21 has a thickness of H1 = 0.06 mm and a width of W1 = 1 mm; the first welding metal strip 21 and the second welding metal strip 22 are connected to the outer metal strip 23 by an adapter weld, with one adapter weld point for each; the distance between the first welding metal strip 21 and the second welding metal strip 22 is W3 = 0.5 mm. The electrode tab adhesive 24 has a shoulder width of 2 mm, an adhesive height of 3 mm, and an adhesive thickness of 0.1 mm. The above electrode tabs are then assembled... Figure 1 After welding as shown, follow the instructions. Figure 16 The shown winding structure 8 is used to wind, encapsulate, inject electrolyte, form, and quantify lithium-ion batteries.

[0146] 2. Experimental Example 2

[0147] The difference from Experimental Example 1 is that the thickness of the first welded metal strip 21 is adjusted to H1=0.04mm and the width is adjusted to W1=1.5mm, while the other parameters and battery manufacturing steps are the same as in Experimental Example 1.

[0148] 3. Experimental Example 3

[0149] The difference from Experimental Example 1 is that the thickness of the first welded metal strip 21 is adjusted to H1=0.08mm, while the other parameters and battery manufacturing steps are the same as in Experimental Example 1.

[0150] Experiments 4 to 7 respectively used the following methods: Figures 2 to 5 The welding structure between the first current collector 1 and the electrode tab shown, i.e., Experimental Examples 4 to 7, differs only in the connection position relationship between the first welding metal strip 21, the second welding metal strip 22, and the first foil portion 16 and the second foil portion 18 (see Appendix for details). Figures 2 to 5 The remaining tab specifications and battery manufacturing steps are the same as in Experiment 1, as follows:

[0151] 4. Experimental Example 4

[0152] The welding structure between the first current collector 1 and the electrode tab is as follows: Figure 2 As shown, the remaining parameters and battery manufacturing steps are the same as in Experiment 1.

[0153] 5. Experimental Example 5

[0154] The welding structure between the first current collector 1 and the electrode tab is as follows: Figure 3 As shown, the remaining parameters and battery manufacturing steps are the same as in Experiment 1.

[0155] 6. Experimental Example 6

[0156] The welding structure between the first current collector 1 and the electrode tab is as follows: Figure 4 As shown, the remaining parameters and battery manufacturing steps are the same as in Experiment 1.

[0157] 7. Experimental Example 7

[0158] The welding structure between the first current collector 1 and the electrode tab is as follows: Figure 5 As shown, the remaining parameters and battery manufacturing steps are the same as in Experiment 1.

[0159] 8. Experimental Example 8

[0160] The only difference between Experiment 8 and Experiment 1 is that Experiment 8 uses the following... Figure 9 The electrode structure shown is as follows: the first welded metal strip 21 and the outer metal strip 23 are connected by an adapter weld. The thickness of the first welded metal strip 21 is H1=0.06mm and the width is W1=1mm. The second welded metal strip 22 and the outer metal strip 23 are integrally formed, with a thickness of H2=0.08mm and a width of W2=0.5mm. The distance between the first welded metal strip 21 and the second welded metal strip 22 is W3=0.5mm. The remaining parameters (including the welding structure between the first current collector 1 and the electrode) and the battery manufacturing steps are the same as in Experimental Example 1.

[0161] 9. Experimental Example 9

[0162] The only difference between Experiment 9 and Experiment 1 is that Experiment 9 uses the following... Figure 8 The electrode structure shown: the first welded metal strip 21 and the second welded metal strip 22 are both integrally formed with the outer metal strip 23. The thickness of the first welded metal strip 21 and the second welded metal strip 22 are both H1=H2=0.08mm, and the width is both W1=W2=0.5mm. The distance between the first welded metal strip 21 and the second welded metal strip 22 is W3=0.5mm. The remaining parameters (including the welding structure between the first current collector 1 and the electrode) and the battery manufacturing steps are the same as in Experimental Example 1.

[0163] 10. Comparative Example 1

[0164] like Figure 17 As shown, Comparative Example 1 uses conventional tabs and conventional welding methods to prepare the electrode sheet. The electrode sheet of Comparative Example 1 includes a conventional current collector 91 and a tab metal strip 92a welded to one side of the conventional current collector 91 using conventional welding methods. The tab metal strip 92a is coated with tab adhesive 24. The tab metal strip 92a has a thickness of 0.08 mm and a width of 1.5 mm. The tab adhesive 24 has a shoulder width of 2 mm, an adhesive height of 3 mm, and an adhesive thickness of 0.1 mm. The remaining battery manufacturing steps are the same as those in Experimental Example 1.

[0165] 11. Comparative Example 2

[0166] The difference between Comparative Example 2 and Comparative Example 1 is that, for example... Figure 18 As shown, Comparative Example 2 uses conventional tabs to prepare the electrode sheet. Specifically, the electrode sheet of Comparative Example 2 includes a first current collector 1. One end of the first current collector 1 is bent to form a first foil portion 16, a foil bending portion 17 connected to the first foil portion 16, and a second foil portion 18 connected to the foil bending portion 17. The tab metal strip 92a is welded between the first foil portion 16 and the second foil portion 18. The tab metal strip 92a is coated with tab adhesive 24. The parameters of the tab metal strip 92a and the tab adhesive 24 are the same as those of Comparative Example 1. The remaining battery manufacturing steps are the same as those of Experimental Example 1.

[0167] 12. Comparative Example 3

[0168] The difference between Comparative Example 3 and Comparative Example 2 is as follows: Figure 19 and 21 As shown, Comparative Example 3 uses a Y-shaped tab structure to prepare the electrode sheet. Specifically, the electrode sheet of Comparative Example 3 includes a first current collector 1. One end of the first current collector 1 is bent to form a first foil portion 16, a bent foil portion 17 connected to the first foil portion 16, and a second foil portion 18 connected to the bent foil portion 17. A welding metal strip 93 is welded between the first foil portion 16 and the second foil portion 18, and an auxiliary welding metal strip 94 is welded onto the first foil portion 16. In the horizontal direction, the welding metal strip 93 and the auxiliary welding metal strip 94 are aligned. The electrode sheet of Comparative Example 3 also includes an external metal strip 92b for the tab, and the welding metal strip 93... The external metal strip 92b of the electrode tab is integrally connected to the structure, or the welded metal strip 93 is welded together with the external metal strip 92b of the electrode tab, and the auxiliary welded metal strip 94 is welded together with the external metal strip 92b of the electrode tab. The external metal strip 92b of the electrode tab, the welded metal strip 93 and the auxiliary welded metal strip 94 form a Y-shaped electrode tab structure. The thickness of the external metal strip 92b of the electrode tab is 0.08mm and the width is 1.5mm. The thickness of the welded metal strip 93 and the auxiliary welded metal strip 94 are both 0.06mm and the width is both 1.5mm. The electrode tab adhesive 24 has a shoulder width of 2mm, an adhesive height of 3mm and an adhesive thickness of 0.1mm. The rest of the battery manufacturing steps are the same as in Experimental Example 1.

[0169] 13. Comparative Example 4

[0170] like Figure 20 and 21 As shown, Comparative Example 4 includes the structure of Comparative Example 3. The only difference between Comparative Example 4 and Comparative Example 3 is the welding position of the auxiliary welding metal strip 94. That is, the auxiliary welding metal strip 94 of Comparative Example 4 is welded to the second foil part 18. Other structures, the positional relationship of other structures, the connection relationship of other structures, the size of the external metal strip 92b of the electrode tab, the size of the welding metal strip 93, the size of the auxiliary welding metal strip 94, and the size of the electrode tab adhesive 24 are all the same as those of Comparative Example 3. The remaining battery manufacturing steps are the same as those of Experimental Example 1.

[0171] In summary, the dimensional parameters of the above 9 experimental examples and 4 comparative examples are shown in Table 1 below:

[0172] Table 1: Dimensional parameters of Experimental Examples 1-9 and Comparative Examples 1-4

[0173]

[0174] In summary, the lithium-ion batteries prepared in the above 9 experimental examples and 4 comparative examples were subjected to electrode breakage rate tests at each stage of formation, capacity testing, and cycling under the same experimental environment and conditions. The experimental results are shown in Table 2 below:

[0175] Table 2: Test results of tape breakage rate for Experimental Examples 1-9 and Comparative Examples 1-4

[0176]

[0177] Therefore, the analysis of the experimental data in Table 2 shows that, compared with Comparative Examples 1-4, the total defect rate of Experimental Examples 1-9 (which decreased from 100%, 100%, 100%, and 94% in Comparative Examples 1-4 to 7%, 2%, 6%, 12%, 27%, 20%, 13%, 9%, and 9% in Experimental Examples 1-9, respectively, with a minimum reduction of 2%) has been significantly and consistently reduced. The structural mechanism behind the improved data is as follows: This invention bends the first extended foil 13 by 180 degrees to form two layers of foil: a first foil portion 16 and a second foil portion 18. Two relatively independent conductive paths are formed between the two foil layers via a first welding metal strip 21 and a second welding metal strip 22. On one hand, the superposition of the two foil layers increases the effective thickness of the welding area, dispersing the mechanical stress concentrated on a single bare foil layer in the prior art. On the other hand, even if one welding path develops fatigue cracks or even breaks due to cyclic stress, the other welding path can still maintain conductive continuity, thus significantly reducing the risk of electrode breakage under high silicon expansion stress. In contrast, the conventional electrode tabs and conventional welding methods in Comparative Example 1, because the current collector is not folded and thickened, and there is only a single conductive path, result in 5% breakage during the formation and capacity testing stages. In Comparative Example 1, 27% of the strip breaks occurred, reaching 59% within 200 cycles, and ultimately 100% of the strip breaks occurred. Although Comparative Example 2 delayed the fracture process by forming a cladding weld with the conventional tab (i.e., tab metal strip 92a) through bending the first current collector 1 (18% in the capacity testing stage and 44% within 200 cycles), the fracture process was further delayed in Comparative Examples 3 and 4 after adopting a Y-type tab structure (only 3% in the capacity testing stage in Comparative Example 3, and even more so in Comparative Example 4, where 2% of the strip breaks occurred only after 800-1200 cycles, with a total defect rate of 94%). However, Comparative Examples 2 and 3 still ultimately all experienced 100% strip breaks, and the total defect rate of 94% in Comparative Example 4 was also much higher than any of the experimental examples. It can be seen that although the improved schemes of Comparative Examples 2-4 can delay the fracture to a certain extent, they cannot significantly improve the strip breakage problem in a high silicon doping system.

[0178] Further comparison shows that Experiment 2 has the lowest overall defect rate (2%). The only difference is that the thickness of the first weld metal strip 21 was adjusted to 0.04 mm and the width to 1.5 mm. This makes the width of the first weld metal strip 21 greater than the width of the second weld metal strip 22, and the thickness less than the thickness of the second weld metal strip 22. This indicates that designing the outer first weld metal strip 21 as a wider and thinner structure directly reduces the welding stress concentration of the first weld metal strip 21 and reduces the probability of its own solder joint failure. It also indirectly improves the reliability of the first weld metal strip 21 as a redundant conductive path. This is the most outstanding technical solution in terms of improving the interruption band effect among the many experimental examples of this invention. Furthermore, Experiments 1, 2, 3, 8, and 9 all adopted... Figure 1The welding structure of the first current collector 1 and the electrode tab shown (i.e., the first welding metal strip 21 is connected between the inner side of the first foil portion 16 and the inner side of the second foil portion 18, and the second welding metal strip 22 is connected to the outer side of the second foil portion 18) has a total defect rate between 2% and 9%, which is better than other experimental examples 4 to 7 (total defect rate 12%-27%) that use the welding structure of the first current collector 1 and the electrode tab. Figures 2 to 5 ), which indicates Figure 1 The welding structure between the first current collector 1 and the electrode tab shown is the optimal solution among the various optional connection methods of this invention. Meanwhile, Experiments 8 and 9, using a hybrid connection of integral molding and transfer welding, and an integrally molded external metal strip 23 connection method respectively, both had a total defect rate of 9%, which is at the same low level as Experiments 1 (7%) and 3 (6%), which used all transfer welding connections. This indicates that the external metal strip 23, whether using an integral molding structure or a transfer welding structure, can achieve good strip breakage suppression. The above experimental data 1-9 fully demonstrate that this invention, through the cross-welding design of the bimetallic welding strip and the folded foil current collector, can effectively disperse the stress concentration caused by the huge expansion force of the high-silicon anode system, and avoids the complete open circuit problem caused by the failure of a single welding position through dual conductive paths. This significantly improves the fracture resistance of the electrode under harsh cycling conditions such as high silicon content and high-temperature fast charging and discharging, achieving the invention's objective.

[0179] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrode sheet, characterized in that, include: The first current collector (1) has a first coating covering area (11) at one end and a first electrode welding area (12) at the other end. A section of the first current collector (1) extending from the first coating covering area (11) to the first electrode welding area (12) is designated as a first extended foil (13). In the first coating coverage area (11) of the first current collector (1), a first coating (14) is applied to one side of the first current collector (1) and a second coating (15) is applied to the other side; In the first tab welding area (12) of the first current collector (1), one end of the first extended light foil (13) is bent, so that the first extended light foil (13) forms a first light foil part (16), a light foil bending part (17) connected to the first light foil part (16), and a second light foil part (18) connected to the light foil bending part (17). The electrode tab includes a first welding metal strip (21) welded to a first foil portion (16) and / or a second foil portion (18), a second welding metal strip (22) welded to a first foil portion (16) and / or a second foil portion (18), an external metal strip (23) connected to the first welding metal strip (21) and the second welding metal strip (22) respectively, and an electrode tab adhesive (24) coated on the external metal strip (23).

2. The electrode sheet according to claim 1, characterized in that, Through a welding and pressing process, the first welding metal strip (21) is welded to the first foil portion (16) and / or the second foil portion (18), the second welding metal strip (22) is welded to the first foil portion (16) and / or the second foil portion (18), and one side of the second foil portion (18) is bonded to the first foil portion (16).

3. The electrode sheet according to claim 2, characterized in that, When one end of the first extended light foil (13) is bent, the bending angle between the first light foil part (16) and the light foil bending part (17) is 90 degrees, the bending angle between the light foil bending part (17) and the second light foil part (18) is 90 degrees, and the first light foil part (16) and the second light foil part (18) are arranged in parallel. After the first welding metal strip (21) is welded to the first foil portion (16) and / or the second foil portion (18) by welding and pressing process, and the second welding metal strip (22) is welded to the first foil portion (16) and / or the second foil portion (18), and one side of the inner side of the second foil portion (18) is attached to the inner side of the first foil portion (16).

4. An electrode sheet according to claim 1, characterized in that, The first welding metal strip (21) is connected between the inner side of the first foil portion (16) and the inner side of the second foil portion (18), and the second welding metal strip (22) is connected to the outer side of the second foil portion (18).

5. An electrode sheet according to claim 1, characterized in that, The first welding metal strip (21) is connected to the outer side of the first foil portion (16), and the second welding metal strip (22) is connected to the outer side of the second foil portion (18).

6. An electrode sheet according to claim 1, characterized in that, The first welding metal strip (21) is connected between the inner side of the first foil portion (16) and the inner side of the second foil portion (18), and the second welding metal strip (22) is connected between the inner side of the first foil portion (16) and the inner side of the second foil portion (18).

7. An electrode sheet according to claim 1, characterized in that, The first welding metal strip (21) is connected to the outer side of the second foil portion (18), and the second welding metal strip (22) is connected to the outer side of the second foil portion (18).

8. An electrode sheet according to claim 1, characterized in that, The inner surface of the first foil portion (16) and the inner surface of the second foil portion (18) are respectively coated with conductive adhesive.

9. An electrode sheet according to claim 1, characterized in that, The first welded metal strip (21) and the outer metal strip (23) are integrally connected, or the first welded metal strip (21) and the outer metal strip (23) are connected together by an adapter weld; The second welded metal strip (22) and the outer metal strip (23) are integrally connected, or the second welded metal strip (22) and the outer metal strip (23) are connected together by an adapter weld.

10. An electrode sheet according to claim 9, characterized in that, The first welding metal strip (21) and the second welding metal strip (22) are both located on one side of the outer metal strip (23), or the first welding metal strip (21) is located on one side of the outer metal strip (23) and the second welding metal strip (22) is located on the other side of the outer metal strip (23).

11. An electrode sheet according to claim 10, characterized in that, When the first welded metal strip (21) and the outer metal strip (23) are connected together by an adapter weld, the first welded metal strip (21) is adapted to one end face of the outer metal strip (23). When the second welded metal strip (22) and the outer metal strip (23) are connected together by an adapter weld, the second welded metal strip (22) is adapted to the other end face of the outer metal strip (23).

12. An electrode sheet according to claim 10, characterized in that, When the first welding metal strip (21) is located on one side of the outer metal strip (23) and the second welding metal strip (22) is located on the other side of the outer metal strip (23), the width of the outer metal strip (23) is set to W, the width of the first welding metal strip (21) is set to W1, the width of the second welding metal strip (22) is set to W2, and the distance between the first welding metal strip (21) and the second welding metal strip (22) is set to W3. The following relationship is satisfied between W, W1, W2 and W3: W>W1; W>W2; 0.1mm <W3<W。 13. An electrode sheet according to claim 1, characterized in that, The outer metal strip (23), the first welding metal strip (21), and the second welding metal strip (22) are made of one of the following materials: aluminum strip, nickel strip, copper strip, or nickel-plated copper strip.

14. A method for welding electrode sheets, characterized in that, Its use in manufacturing an electrode sheet as described in any one of claims 1 to 13 includes the following steps: A first current collector (1) is provided, one end of which forms a first coating coverage area (11) and the other end forms a first tab welding area (12). A section of the first current collector (1) extending from the first coating coverage area (11) to the first tab welding area (12) is designated as a first extended foil (13). In the first coating coverage area (11), the first current collector (1) is coated with a first coating (14) on one side and a second coating (15) on the other side; Flip one end of the first extended light foil (13) to the first angle, while keeping the end of the first extended light foil (13) connected to the first coating coverage area (11) fixed. The end that has been flipped to the first angle is flipped to the second angle, so that the flipping angle of the end reaches the sum of the first angle and the second angle, so that the first extended light foil (13) forms a first light foil part (16), a light foil bending part (17) connected to the first light foil part (16), and a second light foil part (18) connected to the light foil bending part (17). Provide a tab, the tab including an external metal strip (23), a first welded metal strip (21) and a second welded metal strip (22) respectively connected to the external metal strip (23), and tab adhesive (24) applied to the external metal strip (23); By means of a welding and pressing process, the first welding metal strip (21) is welded to the first foil portion (16) and / or the second foil portion (18), and the second welding metal strip (22) is welded to the first foil portion (16) and / or the second foil portion (18), so that one side of the second foil portion (18) is attached to the first foil portion (16).

15. The electrode welding method according to claim 14, characterized in that, The first angle is 90 degrees, and the sum of the first angle and the second angle is 180 degrees.

16. The electrode welding method according to claim 14, characterized in that, The first extended light foil (13) is flipped to the first angle by pulling the folding end of the first extended light foil (13) with a mechanical gripper, and the end connected to the first coating coverage area (11) is pressed and fixed by a mechanical pressure handle. The robotic arm pulls the end that has been flipped to the first angle to continue flipping it to the second angle; The first welded metal strip (21) and the second welded metal strip (22) of the electrode tab are inserted into the first foil portion (16) and / or the second foil portion (18) respectively by means of the cooperation of the robotic arm and the mechanical pressure handle. Welding is completed by pressing down the first welding metal strip (21), the second welding metal strip (22), the first foil part (16), and the second foil part (18) after insertion by the welding die head.

17. A lithium-ion battery, comprising a casing and a positive electrode (5), a separator (7), and a negative electrode (6) respectively disposed inside the casing, characterized in that, The positive electrode (5) and / or negative electrode (6) are electrodes according to any one of claims 1 to 14. The diaphragm (7) is located between the positive electrode (5) and the negative electrode (6). The positive electrode (5), the diaphragm (7) and the negative electrode (6) are stacked in sequence and then wound along the same axial direction to form a winding structure (8). The winding structure (8) is installed inside the housing, and the housing is filled with electrolyte.

18. A lithium-ion battery according to claim 17, characterized in that, When the positive electrode (5) and / or the negative electrode (6) is an electrode as described in any one of claims 1 to 13, Looking along the winding direction, The shortest arc length distance between the first weld metal strip (21) and the second weld metal strip (22) and the foil bending portion (17) of the electrode sheet is L, and L satisfies the following formula: L = απR / 180; Wherein, the first endpoint of the shortest arc length distance L is connected to the center of the winding structure (8) to form a first straight line, the second endpoint of the shortest arc length distance L is connected to the center of the winding structure (8) to form a second straight line, α is the angle between the first straight line and the second straight line, the value of the angle α is 15-30 degrees, and R is the radius of the winding structure (8).

19. A lithium-ion battery according to claim 18, characterized in that, The negative electrode (6) of the winding structure (8) is located on the outermost ring.

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