Electrode assembly and secondary battery

Abstract

The utility model relates to the technical field of batteries, and discloses an electrode assembly and a secondary battery, the electrode assembly comprises a roll core formed by sequentially laminating and winding a first pole piece, a diaphragm and a second pole piece; wherein the first pole piece is provided with a first surface and a second surface which are oppositely arranged along a third direction; the first pole piece comprises a first area, a second area and a third area which are arranged in the first direction, the first area is located on the side close to the first tab, the third area is located on the side away from the first tab, and the second area is located between the first area and the third area; concave-convex structures are arranged in the first area and the second area, each concave-convex structure comprises a convex part and a concave part, the concave parts are formed by sinking the first face towards the direction close to the second face, the convex parts are formed by protruding the second face towards the direction away from the first face, and the convex parts and the concave parts are correspondingly arranged in the third direction. According to the electrode assembly provided by the utility model, the electrolyte infiltration effect can be optimized, the stress concentration condition and interface adhesion of the roll core are improved, and lithium precipitation at the edge is avoided.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to an electrode assembly and a secondary battery. Background Technology

[0002] With the rapid development of lithium-ion battery technology, higher demands have been placed on the energy density, cycle life, and safety performance of lithium-ion batteries. Cycle life and safety performance are key performance characteristics of lithium-ion batteries. Improving these performances can be achieved through optimization and innovation of materials such as the positive and negative electrode materials, electrolyte types, and separator types. However, due to limitations in material development and innovation, improvements in this area have reached a bottleneck. On the other hand, the design and optimization of the electrode structure are also crucial for performance enhancement. This design can effectively increase the residual electrolyte content of the lithium battery, providing sufficient electrolyte for a long cycle life. It can also provide microspace between the positive and negative electrodes, reserving internal space for the expansion of the negative electrode and preventing safety issues such as compression deformation and lithium plating caused by negative electrode expansion during long cycles.

[0003] During the charging and discharging process of lithium batteries, the positive and negative electrodes expand, and there is compression between the electrode layers. This is especially true for wound lithium-ion batteries, because their electrode components are formed by winding. As a result, a large amount of stress accumulates in the arc (also called corner) area of ​​the winding structure. The winding structure itself causes compression between the electrodes. In addition, the expansion of the positive and negative electrodes during charging and discharging intensifies the compression between the electrodes. This compression is not only in the arc area but also transmitted to the planar area. The presence of this compression force can lead to insufficient electrolyte between the layers when the support stability of the interlayer structure of the electrode is poor. This interlayer compression can result in poor wetting and interface deterioration, and even abnormal situations such as poor wetting and cycle failure. Meanwhile, if it is a multi-tab cell structure or a stacked cell structure, the positive electrode head will be 3μm to 20μm thinner than the electrode body after coating at a position of 1mm to 5mm due to the manufacturing process. The addition of multiple positive electrodes will result in the cell head being too thin. During formation, the formation pressure cannot be well balanced, leading to undervoltage at the cell head, poor interface, and problems such as lithium plating during cycling and lifespan degradation. Utility Model Content

[0004] In view of this, the present invention provides an electrode assembly and a secondary battery to solve the problems faced by existing lithium batteries, such as insufficient liquid retention, expansion and extrusion deformation and lithium plating leading to interface deterioration, and interface problems caused by undervoltage of the cell during cell formation due to electrode thinning at the core head, which in turn lead to lithium plating during cycling and lifespan degradation.

[0005] In a first aspect, this utility model provides an electrode assembly, comprising:

[0006] A core consisting of a first electrode, a diaphragm, and a second electrode stacked and wound in sequence, wherein the first electrode has a first surface and a second surface arranged opposite to each other along a third direction;

[0007] The first electrode plate has a first electrode tab on one side along the first direction, and the first electrode tab is electrically connected to the first electrode plate;

[0008] The first electrode includes a first region, a second region, and a third region arranged along a first direction. The first region is located on the side closer to the first electrode tab, the third region is located on the side farther from the first electrode tab, and the second region is located between the first region and the third region.

[0009] The first region and the second region are provided with concave and convex structures. Each concave and convex structure includes a convex part and a concave part. The concave part is formed by the first surface being recessed in the direction close to the second surface, and the convex part is formed by the second surface being protruded in the direction away from the first surface. The convex part and the concave part are arranged correspondingly along the third direction.

[0010] Beneficial effects: The electrode assembly provided by this utility model, by setting a concave-convex structure in the first region of the first electrode, can provide support between the electrodes. The concave-convex structures on different layers partially overlap and partially do not overlap in the stacking direction, which is more conducive to providing support. During formation, due to the support of the concave-convex structure, the first region will thicken, avoiding the thinness of the cell head, thus better bearing the force and improving interface adhesion, thereby solving the problems of lithium plating during cycles and lifespan degradation. At the same time, the micro gaps generated by the concave-convex structure support facilitate the wetting of the electrolyte to the cell edge, which can further improve the uniformity of lithium ion distribution in this region during charging and discharging, and further prevent edge lithium plating. The problem is that by setting a concave-convex structure in the second region of the first electrode, the second region can form the planar area and the arc area of ​​the core. This concave-convex structure disperses the mechanical stress in the arc area of ​​the core, reducing stress concentration in the arc area. At the same time, the concave-convex structure buffers and absorbs the expansion force of the positive and negative electrodes during charging and discharging. It can also alleviate the interlayer extrusion pressure in the planar area, effectively reducing the interlayer extrusion pressure and avoiding insufficient electrolyte and poor wetting due to interlayer extrusion. The third region does not have a concave-convex structure, thus reserving a flatter edge for the first electrode, which is beneficial for correction during winding, improving coverage yield, and thus improving production efficiency.

[0011] In one optional embodiment, the protrusion has a first target point P and a second target point Q, wherein the first target point P is the point on the protrusion that is farthest from the second surface along a third direction, and the second target point Q is the intersection point of the protrusion and the second surface.

[0012] Along the third direction, the orthographic projection of the first target point P on the second surface is O, and the angle between the line OQ and the line PQ is β, where β satisfies 3°≤β≤45°.

[0013] Beneficial effects: By ensuring that β satisfies 3°≤β≤45°, the excessively high slope of the convex part is avoided, which can cause the convex tip to puncture the diaphragm and prevent safety issues.

[0014] In one alternative embodiment, the electrode assembly further includes an insulating coating disposed on a first surface and a second surface, the insulating coating being located in a first region and extending to a first tab, the insulating coating being provided with an uneven structure.

[0015] Beneficial effects: By providing an insulating coating on the edge of the first electrode sheet along the first direction X near the first electrode tab, on the one hand, it can prevent sharp particles generated during the coating of the first electrode sheet from piercing the diaphragm, and the insulating coating can cover the burrs; on the other hand, it can prevent the first electrode tab from contacting the second electrode sheet when bent, which would cause a short circuit.

[0016] In one alternative implementation, the dimension of the first region along the first direction is W1 mm, where W1 satisfies 3≤W1≤5;

[0017] And / or, the dimension of the third region along the first direction is W2 mm, where W2 satisfies 3≤W2≤5.

[0018] Beneficial effects: By setting a concave-convex structure in the first region of the first electrode, with multiple concave-convex structures evenly spaced within the first region, and the dimension of the first region along the first direction X being W1 mm, and by ensuring that W1 satisfies 3≤W1≤5, the stress in the edge regions on both sides of the core along the third direction Z is more widely dispersed, thereby reducing stress concentration. This effectively avoids interface problems caused by poor adhesion at the top and bottom of the cell due to edge effects and uneven pressure distribution during formation, and also effectively prevents delamination in the edge regions of the cell during charge-discharge cycles. The third region of the first electrode does not have a concave-convex structure, and the dimension of the third region along the first direction X being W2 mm, with W2 satisfying 3≤W2≤5, thus reserving sufficient correction space during winding, ensuring coverage yield, and thereby improving production efficiency.

[0019] In one alternative embodiment, at least a portion of the individual convex-concave structure is located within the insulating coating at the edge position of the insulating coating along the first direction;

[0020] And / or, the first electrode tab includes a fourth region and a fifth region arranged along a first direction, the fourth region being located on the side of the first electrode tab closest to the first electrode plate; the fourth region is provided with a concave-convex structure; the dimension of the fourth region along the first direction is W3mm, where W3 satisfies 3≤W3≤5.

[0021] Beneficial effects: It allows for more micro-gaps in the insulating coating of the first region, facilitating the absorption of more electrolyte from the tab side into the cell, and improving the wetting effect of the electrode sheet;

[0022] The first electrode tab is led out from the first electrode plate. The fourth region is the area where the concave and convex structure of the first electrode tab is set. The dimension of the fourth region along the first direction X is W3 mm. W3 satisfies 3≤W3≤5, thereby increasing the friction when multiple first electrodes tabs are stacked together and avoiding the problem of poor contact caused by sliding between the first electrodes tabs.

[0023] In one optional embodiment, along a third direction, the recess in the first region has a recess depth of H4 μm relative to the first surface, and the recess in the second region has a recess depth of H3 μm relative to the first surface, wherein H4 and H3 satisfy 1.2 ≤ H4 / H3 ≤ 1.6.

[0024] And / or, the diameter of the circumcircle of the concave portion in the first region projected onto the first surface is R2 mm, and the diameter of the circumcircle of the concave portion in the second region projected onto the first surface is R1 mm, wherein R2 and R1 satisfy 1≤R2 / R1≤1.5.

[0025] Beneficial effects: By satisfying 1.2≤H4 / H3≤1.6 for H4 and H3, and / or 1.0≤R2 / R1≤1.5 for R2 and R1, the uneven structure of the first electrode in the first region after the winding battery is formed can play a supporting role, and supplement the thinning part of the first electrode during the production process, providing a point of force during formation, making the entire cell more uniformly stressed during formation, improving the adhesion of the cell head, and avoiding the problem of lithium plating caused by poor interface adhesion.

[0026] In one optional embodiment, the diameter of the circumcircle of the orthographic projection of the protrusion on the second surface is R3mm, and the value of R3 is in the range of 0.3≤R3≤8.

[0027] And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions on the second surface is D mm, where the value of D is 1 ≤ D ≤ 6;

[0028] And / or, along the third direction, the protrusion height of the convex part relative to the second surface is H5μm, where the value of H5 is 3≤H5≤80.

[0029] Beneficial effects: By satisfying 0.3≤R3≤8, the convex portion can avoid the tip effect, prevent electrode breakage, and ensure the span of the convex surface, thus ensuring effective support between the positive and negative electrodes; By satisfying 1≤D≤6, the convex portion can avoid electrode breakage caused by overlapping of the convex portion, and also ensure effective support between the positive and negative electrodes; By satisfying 3≤H5≤80, the convex portion can ensure effective support between the positive and negative electrodes, allow the electrolyte to sufficiently wet the cell, and effectively prevent delamination between the positive and negative electrodes, thus avoiding new interface problems.

[0030] In one alternative embodiment, the depth of the recess gradually decreases as the number of folds in the winding core increases; and / or,

[0031] The first electrode includes a first current collector and a first paste and a second paste disposed on both sides of the first current collector along a third direction. Along the second direction, the size of the first paste is larger than the size of the second paste. The first paste is located on the side of the first current collector closer to the winding center, and the second paste is located on the side of the first current collector away from the winding center. The first surface is the side of the first paste away from the first current collector, and the second surface is the side of the second paste away from the first current collector.

[0032] Beneficial effects: The depth of the concave part gradually becomes shallower as the number of folds in the winding core increases, which can reduce the width dimension of the arc area along the fifth direction V, improve the problem of ultra-wide battery cell, and increase the energy density of battery cell;

[0033] When a concave-convex structure is set on the first electrode, the concave-convex structure protrudes from the first surface to the second surface, thereby increasing the local lithium ion migration distance in the arc region, reducing the amount of lithium ions accumulating on the negative electrode surface per unit time, and thus improving the problem of lithium deposition in the arc region.

[0034] In one alternative embodiment, the core has a planar area and arcuate areas located on both sides of the planar area along a fourth direction;

[0035] The dimension of the arc region along the fourth direction is H1, and the dimension of the planar region along the fifth direction is H2. H1 and H2 satisfy 1.05≤H1 / (H2 / 2)≤1.5.

[0036] Beneficial effect: By satisfying 1.05≤H1 / (H2 / 2)≤1.5 for H1 and H2, the lithium plating problem in the arc region can be effectively improved.

[0037] Secondly, this utility model also provides a secondary battery, including: a membrane housing, and an electrode assembly as described above, wherein the electrode assembly is built into the membrane housing.

[0038] Beneficial effects: The secondary battery of the second aspect includes the electrode assembly of the first aspect, therefore, the secondary battery of the second aspect includes all the beneficial effects of the electrode assembly of the first aspect. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a three-dimensional structural schematic diagram of an electrode assembly according to an embodiment of the present utility model;

[0041] Figure 2 This is a schematic cross-sectional view of an electrode assembly according to an embodiment of the present invention;

[0042] Figure 3 This is a cross-sectional view of the first electrode, the second electrode, and the diaphragm of an electrode assembly according to an embodiment of the present invention, taken in a third direction at the leading edge of the winding.

[0043] Figure 4 This is a cross-sectional view of the first electrode sheet of an electrode assembly according to an embodiment of the present invention, taken in a third direction at the leading edge of the winding.

[0044] Figure 5 This is a front view of the first electrode sheet of an electrode assembly according to an embodiment of the present invention before winding;

[0045] Figure 6 This is a cross-sectional view of the first electrode sheet of an electrode assembly according to an embodiment of the present invention, taken in a third direction at the leading edge of the winding.

[0046] Figure 7 This is a cross-sectional view along a third direction of the concave-convex structure of the first electrode plate of an electrode assembly according to an embodiment of the present invention.

[0047] Figure 8 for Figure 7 The diagram shows the dimensioning of the concave and convex structure.

[0048] Figure 9 This is a cross-sectional view along a third direction of two adjacent concave and convex structures of the first electrode plate of an electrode assembly according to an embodiment of the present invention.

[0049] Explanation of reference numerals in the attached figures:

[0050] 10. First electrode; 101. First current collector; 102. First paste; 103. Second paste; 104. First surface; 105. Second surface; 11. Uneven structure; 111. Protrusion; 112. Recess; 12. First region; 13. Second region; 14. Third region; 15. Thinning region;

[0051] 20. First pole ear; 21. Fourth region; 22. Fifth region;

[0052] 30. Second electrode;

[0053] 40. Diaphragm;

[0054] 50. Insulating coating;

[0055] 60. Core; 61. Flat area; 62. Arc area;

[0056] X—First direction; Y—Second direction; Z—Third direction; U—Fourth direction; V—Fifth direction. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0058] The wound core structure of related technologies for lithium-ion batteries has a flat elliptical cross-section, with arc-shaped areas on both sides and a flat area in the middle. The electrode components are layered and wound to form the cell. Due to the special nature of the arc areas, the stress in these areas is relatively high, easily leading to compression and core deformation. Simultaneously, the flat area undergoes hot pressing during production, resulting in very tight compression and poor electrolyte wetting. Furthermore, in the wound core structure of related technologies, during the coating of multi-tab positive electrode sheets, the head of the positive electrode sheet is 3μm to 20μm thinner than the electrode body at a position of 1mm to 5mm due to manufacturing process limitations. The combined effect of multiple positive electrode layers results in a thinner cell head, which, during formation, cannot effectively balance the formation pressure, leading to undervoltage at the cell head, poor interface, and lithium plating during cycling.

[0059] The following is combined with Figures 1 to 9 The following describes embodiments of the present invention.

[0060] According to an embodiment of the present invention, in one aspect, an electrode assembly is provided, comprising:

[0061] A core 60 is formed by sequentially stacking and winding the first electrode 10, the diaphragm 40, and the second electrode 30. For details, please refer to [link to documentation]. Figure 3 As shown, the diaphragm 40 is disposed between the first electrode 10 and the second electrode 30. Please refer to [link / reference]. Figure 1 As shown, the first electrode 10, the diaphragm 40, and the second electrode 30 are wound together to form a core 60;

[0062] Please see below. Figure 4 As shown, the first electrode 10 has a first surface 104 and a second surface 105 disposed opposite to each other along the third direction Z;

[0063] Please see Figure 5 As shown, the first electrode 10 has a first electrode tab 20 on one side along the first direction X, and the first electrode tab 20 is electrically connected to the first electrode 10;

[0064] See also Figure 5 As shown, the first electrode 10 includes a first region 12, a second region 13 and a third region 14 arranged along the first direction X. The first region 12 is located on the side closer to the first electrode tab 20, the third region 14 is located on the side away from the first electrode tab 20, and the second region 13 is located between the first region 12 and the third region 14.

[0065] Please see Figure 5 As shown, the first region 12 and the second region 13 are provided with concave and convex structures 11. Please refer to [link / reference]. Figure 7 As shown, each concave-convex structure 11 includes a protrusion 111 and a concave portion 112; wherein, the concave portion 112 is formed by recessing from the first surface 104 toward the direction close to the second surface 105, and the protrusion 111 is formed by protruding from the second surface 105 toward the direction away from the first surface 104, and the protrusion 111 and the concave portion 112 are correspondingly arranged along the third direction Z.

[0066] It should be noted that, regarding the electrode layer, "first direction X" refers to the width direction of the electrode and / or the direction of its second largest dimension; "second direction Y" refers to the length direction of the electrode and / or the direction of its largest dimension; and "third direction Z" refers to the thickness direction of the electrode and / or the direction of its smallest dimension. The first direction X, second direction Y, and third direction Z are mutually perpendicular. Regarding the core 60 layer, "first direction X" refers to the height direction of the core 60; "fourth direction U" refers to the width direction of the core 60; and "fifth direction V" refers to the thickness direction of the core 60. The first direction X, fourth direction U, and fifth direction V are mutually perpendicular. In the text, "planar region 61" refers to the portion of the first electrode 10, the second electrode 30, and the diaphragm 40 that does not bend during the winding process to form the core 60; "arc region 62" refers to the non-linear portion formed by the first electrode 10, the second electrode 30, and the diaphragm 40 during the winding process to form the core 60. The first electrode 10 is the positive electrode, and the second electrode 30 is the negative electrode.

[0067] The electrode assembly provided by this utility model features a concave-convex structure 11 within the first region 12 of the first electrode 10. This structure 11 provides support between the electrodes. The concave-convex structures 11 on different layers partially overlap and partially do not overlap in the stacking direction, further enhancing their support function. During formation, the first region 12 thickens due to the support of the concave-convex structure 11, preventing the cell head from being too thin and thus improving stress resistance and interface adhesion, thereby solving the problems of cycle lithium plating and lifespan degradation. Simultaneously, the micro-gaps created by the concave-convex structure 11 facilitate electrolyte wetting of the cell edges, further improving the uniformity of lithium ion distribution during charging and discharging in this region, and further preventing edge lithium plating. Through the first electrode 10... The second region 13 is provided with a concave-convex structure 11, which can form the planar region 61 and the arc region 62 of the core 60. The concave-convex structure 11 disperses the mechanical stress of the arc region 62 of the core 60, reduces the stress concentration of the arc region 62, and at the same time buffers and absorbs the expansion force of the positive and negative electrode sheets during charging and discharging. The concave-convex structure 11 can also relieve the interlayer extrusion pressure of the electrode sheets in the planar region 61, effectively reducing the interlayer extrusion pressure and avoiding insufficient electrolyte and poor wetting due to interlayer extrusion. The third region 14 does not have a concave-convex structure 11, thus reserving a flatter edge for the first electrode sheet 10, which is conducive to correction during winding, improves the coverage yield, and thus improves production efficiency.

[0068] In some embodiments, see Figure 7As shown, the protrusion 111 has a first target point P and a second target point Q, wherein the first target point P is the point on the protrusion 111 that is farthest from the second surface 105 along the third direction Z, and the second target point Q is the intersection point of the protrusion 111 and the second surface 105.

[0069] Along the third direction Z, the orthographic projection of the first target point P onto the second surface 105 is O, and the angle between the line OQ and the line PQ is β, where β satisfies 3°≤β≤45°.

[0070] This setting ensures that β satisfies 3°≤β≤45°, thereby avoiding the problem of excessively high slope of the protrusion 111 causing a protruding tip, and thus preventing the protrusion 111 from piercing the diaphragm 40, avoiding safety issues.

[0071] Preferably, β satisfies 5°≤β≤25°.

[0072] In some embodiments, see Figure 4 As shown, the first electrode 10 includes a first current collector 101 and a first paste 102 and a second paste 103 disposed on both sides of the first current collector 101 along the third direction Z.

[0073] Along the second direction Y, the size of the first paste 102 is larger than the size of the second paste 103; the first paste 102 is located on the side of the first current collector 101 near the winding center, and the second paste 103 is located on the side of the first current collector 101 away from the winding center; the first surface 104 is the side of the first paste 102 away from the first current collector 101, and the second surface 105 is the side of the second paste 103 away from the first current collector 101.

[0074] It should be noted that when forming the winding structure, the first surface 104 is located on the side closer to the winding center of the core 60, and the second surface 105 is located on the side farther from the winding center of the core 60. Due to the curvature of the arc region 62, when the arc formed by the first surface 104 wraps around the second electrode 30, the circumference of the arc of the first surface 104 of the first electrode 10 will be greater than the circumference of the second electrode 30 in the arc region 62. This results in the amount of positive electrode active material in this region being greater than the amount of positive electrode active material in this region as designed; that is, the negative electrode surface capacity / positive electrode surface capacity in this region will decrease, which can easily cause NP to decrease and lead to the risk of lithium plating.

[0075] Therefore, when the concave-convex structure 11 is provided on the first electrode 10, by making the concave-convex structure 11 protrude from the first surface 104 to the second surface 105, the local lithium ion migration distance in the arc region 62 is increased, the amount of lithium ions accumulating on the negative electrode surface per unit time is reduced, thereby improving the problem of lithium deposition in the arc region 62.

[0076] In some embodiments, please combine Figure 6As shown, the electrode assembly also includes an insulating coating 50, which is disposed on the first surface 104 and the second surface 105. The insulating coating 50 is located in the first region 12 and extends to the first electrode tab 20. The insulating coating 50 is provided with a concave-convex structure 11.

[0077] By providing an insulating coating 50 on the edge of the first electrode 10 along the first direction X near the first electrode tab 20, on the one hand, it can prevent sharp particles generated during the coating of the edge of the first electrode 10 from piercing the diaphragm 40, and the insulating coating 50 can cover the burrs; on the other hand, it can prevent the first electrode tab 20 from contacting the second electrode 30 when bent, which would cause a short circuit.

[0078] Further, please see Figure 6 As shown, the first electrode 10 has a thinning region 15 on one side edge near the first electrode tab 20 along the first direction X. The size of the thinning region 15 along the third direction Z is smaller than the size of the first electrode 10 along the third direction Z. The thinning region 15 is used to offset the extra thickness brought by the insulating coating 50.

[0079] In some embodiments, see Figure 5 As shown, the size of the first region 12 along the first direction X is W1 mm, where W1 satisfies 3≤W1≤5;

[0080] And / or, the dimension of the third region 14 along the first direction X is W2 mm, where W2 satisfies 3≤W2≤5.

[0081] It should be noted that the second region 13 is the main body of the first electrode 10; the size of the second region 13 along the first direction X can be adjusted according to actual production needs, and no specific limitation is made here.

[0082] By providing a concave-convex structure 11 in the first region 12 of the first electrode 10, with multiple concave-convex structures 11 evenly spaced within the first region 12, and the dimension of the first region 12 along the first direction X being W1 mm, where W1 satisfies 3≤W1≤5, the stress in the edge regions of the core 60 along the third direction Z is more widely dispersed, thereby reducing stress concentration and effectively avoiding interface problems caused by poor adhesion between the top and bottom of the cell due to edge effects and uneven pressure distribution during formation. Simultaneously, it effectively prevents delamination in the edge regions of the cell during charge-discharge cycles. The third region 14 of the first electrode 10 does not have a concave-convex structure 11, and the dimension of the third region 14 along the first direction X being W2 mm, where W2 satisfies 3≤W2≤5, thus reserving sufficient correction space during winding, ensuring coverage yield, and thereby improving production efficiency.

[0083] In some embodiments, see Figure 5As shown, at the edge position of the insulating coating 50 along the first direction X, a single convex-concave structure 11 is at least partially located in the insulating coating 50.

[0084] This design allows for more micro-gaps in the insulating coating 50 within the first region 12, facilitating the absorption of more electrolyte from the tab side into the cell and improving the wetting effect of the electrode sheets.

[0085] It is worth noting that the convex-concave structure 11 is formed by rolling a convex roller onto the insulating coating 50. Therefore, at the edge of the insulating coating 50, it is possible that the convex-concave structure 11 is not a complete convex-concave structure 11. Furthermore, at the edge of the insulating coating 50 along the first direction X, the area of ​​the recess 112 projected onto the first surface 104 is at least 1 / 3 of the area of ​​the complete recess 112 projected onto the first surface 104.

[0086] In some embodiments, see Figure 5 As shown, the first electrode tab 20 includes a fourth region 21 and a fifth region 22 arranged along the first direction X, with the fourth region 21 located on the side of the first electrode tab 20 closer to the first electrode plate 10.

[0087] The fourth region 21 is provided with a concave-convex structure 11; the dimension of the fourth region 21 along the first direction X is W3mm, where W3 satisfies 3≤W3≤5.

[0088] The first electrode tab 20 is led out from the first electrode plate 10. The fourth region 21 is the area where the concave and convex structure 11 of the first electrode tab 20 is set. The size of the fourth region 21 along the first direction X is W3 mm. W3 satisfies 3≤W3≤5, thereby increasing the friction when multiple first electrodes tabs 20 are stacked together, and avoiding the problem of poor contact caused by sliding between the first electrodes tabs 20.

[0089] In some embodiments, please refer to Figure 8 Along the third direction Z, the recess 112 in the first region 12 has a recess depth of H4μm relative to the first surface 104, and the recess 112 in the second region 13 has a recess depth of H3μm relative to the first surface 104. H4 and H3 satisfy 1.2≤H4 / H3≤1.6.

[0090] And / or, the diameter of the circumcircle of the recess 112 in the first region 12 projected onto the first surface 104 is R2 mm, and the diameter of the circumcircle of the recess 112 in the second region 13 projected onto the first surface 104 is R1 mm, and R2 and R1 satisfy 1.0≤R2 / R1≤1.5.

[0091] By satisfying 1.2≤H4 / H3≤1.6 for H4 and H3, and / or 1.0≤R2 / R1≤1.5 for R2 and R1, the uneven structure 11 of the first electrode 10 in the first region 12 can play a supporting role after the first electrode 10 is formed into a wound battery, and supplement the thinned part of the first electrode 10 during the production process, providing a force point during formation, making the entire cell more uniformly stressed during formation, improving the adhesion of the cell head, and avoiding the problem of lithium plating caused by poor interface adhesion.

[0092] In some embodiments, please refer to Figure 8 The diameter of the circumcircle of the orthographic projection of the protrusion 111 onto the second surface 105 is R3mm, and the value of R3 is 0.3≤R3≤8.

[0093] And / or, please see Figure 9 The distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions 111 onto the second surface 105 is D mm, and the value of D is 1≤D≤6.

[0094] And / or, please see Figure 8 Along the third direction Z, the protrusion height of the convex part 111 relative to the second surface 105 is H5μm, and the value of H5 is in the range of 3≤H5≤80.

[0095] It should be noted that the diameter of the circumcircle of the orthographic projection of the protrusion 111 onto the second surface 105 is R3 mm. When R3 is too small, it is easy to cause a tip effect, leading to electrode breakage. Therefore, R3 must satisfy R3≥0.3. When R3 is too large, its protruding surface span is too large, which is not conducive to supporting the positive and negative electrodes. Therefore, R3 must also satisfy R3≤8. The distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions 111 onto the second surface 105 is D mm. When D is too small, it is easy to cause the protrusions 111 to overlap, leading to electrode breakage. Therefore, D must satisfy D≥1. When D is too large, the two protrusions 111 cannot provide support. Therefore, D must also satisfy D≤6. The dimension of the protrusion 111 along the third direction Z is H5μm. If H5 is too small, it will not provide support between the positive and negative electrodes and will be an ineffective protrusion. It will also not allow the electrolyte to wet the cell sufficiently. Therefore, H5 needs to satisfy H5≥3. When H5 is too large, it will cause severe delamination between the positive and negative electrodes and cause new interface problems. Therefore, H5 also needs to satisfy H5≤80.

[0096] The convex portion 111, by satisfying 0.3≤R3≤8, can avoid the tip effect and prevent electrode breakage, while also ensuring the span of the convex surface, thus guaranteeing effective support between the positive and negative electrodes. The convex portion 111, by satisfying 1≤D≤6, can avoid the electrode breakage caused by the overlap of the convex portions 111, while also guaranteeing effective support between the positive and negative electrodes. The convex portion 111, by satisfying 3≤H5≤80, can guarantee effective support between the positive and negative electrodes, ensure sufficient wetting of the cell by the electrolyte, and effectively prevent delamination between the positive and negative electrodes, thus avoiding new interface problems.

[0097] Preferably, 1 ≤ R3 ≤ 3; and / or, 1.5 ≤ D ≤ 4.

[0098] In some embodiments, the recess depth of the recess 112 gradually decreases as the number of folds of the winding core 60 increases.

[0099] It should be noted that since the compression of the arc region 62 mainly occurs in the interlayer of the core 60 near the inner ring, the compression force is smaller closer to the outer ring, the electrolyte shortage is smaller, and the risk of lithium plating is lower. This makes the depth of the recess 112 gradually shallower as the number of folds of the core 60 increases, thereby reducing the width dimension of the arc region 62 along the fifth direction V, improving the problem of the cell being too wide, and increasing the cell energy density.

[0100] In some embodiments, see Figure 2 As shown, the core 60 has a planar region 61 and an arcuate region 62 located on both sides of the planar region 61 along the fourth direction U;

[0101] The arc region 62 has a dimension of H1 along the fourth direction U, and the planar region 61 has a dimension of H2 along the fifth direction V. H1 and H2 satisfy 1.05≤H1 / (H2 / 2)≤1.5.

[0102] It should be noted that by setting the concave-convex structure 11 in the arc region 62 of the core 60, a certain support is provided between the positive electrode, separator, and negative electrode in the arc region 62, increasing the micro-spacing between the electrode assemblies. When the lithium battery is charging and discharging, the negative electrode expands. The planar region 61 of the core 60 can expand freely upwards or downwards, but due to its structural characteristics and stress accumulation, the outward expansion of the arc region 62 is constrained. This ultimately leads to interlayer compression between the electrodes, causing the separator 40 to become clogged, resulting in electrolyte loss and lithium plating in the arc region 62. By satisfying 1.05 ≤ H1 / (H2 / 2) ≤ 1.5, the lithium plating problem in the arc region 62 can be effectively improved.

[0103] Preferably, 1.08≤H1 / (H2 / 2)≤1.3.

[0104] According to an embodiment of the present invention, another aspect provides a secondary battery, comprising: a membrane housing, and an electrode assembly as described above, wherein the electrode assembly is embedded within the membrane housing.

[0105] The secondary battery in this embodiment includes the electrode assembly described above. Therefore, the secondary battery in this embodiment includes all the beneficial effects of the electrode assembly described above.

[0106] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electrode assembly, characterized in that, include: A core is formed by sequentially stacking and winding a first electrode, a diaphragm, and a second electrode, wherein the first electrode has a first surface and a second surface that are arranged opposite to each other along a third direction; The first electrode plate has a first tab on one side along the first direction, and the first tab is electrically connected to the first electrode plate; The first electrode includes a first region, a second region, and a third region arranged along a first direction. The first region is located on the side closer to the first electrode tab, the third region is located on the side farther from the first electrode tab, and the second region is located between the first region and the third region. The first region and the second region are provided with concave and convex structures. Each concave and convex structure includes a convex part and a concave part. The concave part is formed by the first surface being recessed in a direction close to the second surface, and the convex part is formed by the second surface being protruded in a direction away from the first surface. The convex part and the concave part are arranged correspondingly in a third direction.

2. The electrode assembly according to claim 1, characterized in that, The protrusion has a first target point P and a second target point Q, wherein the first target point P is the point on the protrusion that is farthest from the second surface along a third direction, and the second target point Q is the intersection point of the protrusion and the second surface. Along the third direction, the orthographic projection of the first target point P onto the second surface is O, and the angle between the line OQ and the line PQ is β, where β satisfies 3°≤β≤45°.

3. The electrode assembly according to claim 1 or 2, characterized in that, The electrode assembly further includes an insulating coating disposed on the first surface and the second surface, the insulating coating being located in the first region and extending to the first electrode tab, and the insulating coating having the aforementioned uneven structure.

4. The electrode assembly according to claim 1 or 2, characterized in that, The first region has a dimension of W1 mm ​​along the first direction, where W1 satisfies 3≤W1≤5; And / or, the dimension of the third region along the first direction is W2 mm, where W2 satisfies 3≤W2≤5.

5. The electrode assembly according to claim 3, characterized in that, At the edge location of the insulating coating along the first direction, at least a portion of the individual said uneven structure is located within the insulating coating; And / or, the first electrode tab includes a fourth region and a fifth region arranged along a first direction, the fourth region being located on the side of the first electrode tab close to the first electrode sheet; the fourth region is provided with the concave-convex structure; the dimension of the fourth region along the first direction is W3 mm, where W3 satisfies 3≤W3≤5.

6. The electrode assembly according to claim 1 or 2, characterized in that, Along the third direction, the recess depth of the concave portion in the first region is H4μm, and the recess depth of the concave portion in the second region is H3μm, where H4 and H3 satisfy 1.2≤H4 / H3≤1.6; And / or, the circumcircle diameter of the concave portion in the first region projected onto the first surface is R2 mm, the circumcircle diameter of the concave portion in the second region projected onto the first surface is R1 mm, and R2 and R1 satisfy 1 ≤ R2 / R1 ≤ 1.

5.

7. The electrode assembly according to claim 1 or 2, characterized in that, The diameter of the circumcircle of the orthographic projection of the protrusion on the second surface is R3 mm, and the value of R3 is in the range of 0.3≤R3≤8. And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions onto the second surface is D mm, where the value of D is 1 ≤ D ≤ 6; And / or, along a third direction, the protrusion height of the protrusion relative to the second surface is H5μm, where the value of H5 is in the range of 3≤H5≤80.

8. The electrode assembly according to claim 1 or 2, characterized in that, The depth of the recess gradually decreases as the number of folds in the winding core increases; and / or, The first electrode includes a first current collector and a first paste and a second paste disposed on both sides of the first current collector along a third direction. Along the second direction, the size of the first paste is larger than the size of the second paste. The first paste is located on the side of the first current collector closer to the winding center, and the second paste is located on the side of the first current collector away from the winding center. The first surface is the side of the first paste away from the first current collector, and the second surface is the side of the second paste away from the first current collector.

9. The electrode assembly according to claim 1 or 2, characterized in that, The core has a planar area and arcuate areas located on both sides of the planar area along a fourth direction; The arc region has a dimension of H1 along the fourth direction, and the planar region has a dimension of H2 along the fifth direction. H1 and H2 satisfy 1.05≤H1 / (H2 / 2)≤1.

5.

10. A secondary battery, characterized in that, include: A membrane housing, and an electrode assembly as described in any one of claims 1 to 9, wherein the electrode assembly is embedded within the membrane housing.

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