Electrode assembly and secondary battery
By setting concave and convex points on the lithium battery electrode to disperse stress and buffer the electrode expansion force, the problems of lithium battery deformation and poor wetting due to extrusion are solved, resulting in more stable battery performance and higher energy density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHUHAI COSMX BATTERY CO LTD
- Filing Date
- 2025-06-06
- Publication Date
- 2026-06-09
AI Technical Summary
Existing lithium batteries suffer from problems such as compression deformation, insufficient interlayer electrolyte, poor wetting, and interface deterioration caused by the expansion of positive and negative electrode sheets during charging and discharging. In particular, stress concentration is severe in the arc area of wound lithium-ion batteries, which affects cycle life and safety performance.
Raised and recessed points are set on the first electrode of the electrode assembly to disperse mechanical stress, buffer the expansion force of the electrode, enhance the support of the edge area, optimize the wetting and interface bonding between the electrodes, and reduce stress concentration by setting raised and recessed points in the arc area and edge area of the core, thereby improving structural strength and electrolyte wettability.
It effectively reduces the extrusion pressure between electrodes, improves interface adhesion, enhances electrolyte wettability, avoids lithium plating and interface deterioration, strengthens core stability, and improves battery energy density and cycle life.
Smart Images
Figure CN224342368U_ABST
Abstract
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 charging and discharging, the positive and negative electrodes of lithium batteries expand, causing interlayer compression, especially in wound lithium-ion batteries. Because the electrode components are formed by winding, significant stress accumulates in the arc (corner) areas of the winding structure. The winding structure itself already causes interlayer compression, which is exacerbated by the expansion of the positive and negative electrodes during charging and discharging. This compression extends beyond the arc areas to the planar areas. When the interlayer structure has poor support stability, this compression leads to insufficient electrolyte, poor wetting, and interface deterioration, potentially resulting in poor wetting and cycle failure. Simultaneously, in the height direction of the battery (i.e., the width direction of the electrode), edge effects and uneven pressure distribution during formation can cause poor adhesion between the top and bottom of the cell, leading to interface problems and ultimately lithium plating and failure during cycling. 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 deformation, lithium plating leading to interface deterioration, and poor adhesion between the top and bottom of the cell due to edge effects and uneven pressure distribution during formation, which in turn leads to cyclic lithium plating and lifespan degradation.
[0005] In a first aspect, this utility model provides an electrode assembly, comprising:
[0006] The first electrode, the second electrode, and the diaphragm are arranged between the first electrode and the second electrode, and the first electrode, the second electrode, and the diaphragm are wound together to form a core.
[0007] The first electrode plate has a first electrode tab on one side along the first direction, and the second electrode plate has a second electrode tab on one side along the first direction;
[0008] The core has a planar area and arc areas located on both sides of the planar area along the fourth direction;
[0009] The first electrode has a first target area and a second target area. The first target area and the second target area are alternately arranged on the first electrode along the second direction. The first target area corresponds to the planar area of the core, and the second target area corresponds to the arc area of the core.
[0010] The first electrode includes a main body region and edge regions located on both sides of the main body region along a first direction;
[0011] The edge area and the second target area are provided with concave and convex points, which include convex parts and concave parts corresponding to the convex parts.
[0012] Beneficial effects: The electrode assembly provided by this utility model, by setting concave and convex points in the second target area of the first electrode sheet, and making the second target area form the arc area of the core, disperses the mechanical stress in the arc area of the core through the concave and convex points, reducing stress concentration in the arc area. At the same time, the concave and convex points buffer and absorb the expansion force of the positive and negative electrodes during charging and discharging, effectively reducing the extrusion force between the electrodes and avoiding insufficient electrolyte and poor wetting between layers due to interlayer extrusion. By setting concave and convex points in the edge area, it is beneficial to increase the ineffective thickness of the edge area (the thickness of the concave and convex points). The concave and convex points play a supporting role between the electrodes. The concave and convex points on different planar layers partially overlap and partially do not overlap in the vertical direction of the stacking, which is more conducive to the support. Functions: During formation, the edge region thickens due to the support of the bumps and concave points, thus better bearing the force and improving interface adhesion. At the same time, the micro-gaps created by the bumps and concave points facilitate the wetting of the cell edge by the electrolyte, which can further improve the uniformity of lithium-ion distribution in this area during charging and discharging, and further avoid edge lithium plating problems. The simultaneous setting of bumps and concave points in the edge region and the second target region not only helps to increase the interlayer bonding force and improve the overall structural strength of the core, avoiding core loosening and deformation, making the core more stable during charge and discharge cycles, but also increases the specific surface area of the arc region and edge region of the core, which is conducive to optimizing electrolyte wetting, thereby better avoiding interface deterioration, poor wetting, and problems such as cycle lithium plating and failure.
[0013] In one alternative embodiment, 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.
[0014] The dimension of the first current collector along the second direction is L1 mm, the dimension of the first paste along the second direction is L2 mm, and the dimension of the second paste along the second direction is L3 mm. L1, L2 and L3 satisfy L1>L2>L3;
[0015] Along the second direction, the electrode length corresponding to the overlapping dimension L3 of the first current collector, the first paste, and the second paste is the double-sided region of the first electrode. The electrode length corresponding to the dimension L2-L3 where the first current collector and the first paste overlap but do not overlap with the second paste is the single-sided region of the first electrode. The electrode length corresponding to the dimension L1-L2 where the first current collector extends beyond the first paste is the empty foil region of the first electrode.
[0016] Beneficial effects: By setting up a double-sided area, the first electrode can maximize the utilization of active materials, which is conducive to improving the energy density of the battery cell. By setting up a single-sided area and an empty foil area, the outer surface of the single-sided area does not need to be coated with paste, and the inner and outer surfaces of the empty foil area do not need to be coated with paste, thereby improving the space utilization of the core along the fifth direction.
[0017] In one alternative embodiment, along a first direction, the first coating and / or the second coating includes a first sub-coating and a second sub-coating, with the first sub-coating located on the side of the second sub-coating closer to the first tab.
[0018] The thickness of the first sub-coating is less than or equal to that of the second sub-coating, and in the third direction, the projection of the first sub-coating and the projection of the edge region do not overlap.
[0019] Beneficial effect: No bumps or depressions are set in the thinning area of the first coat (i.e., the first sub-coat), to avoid the problem of powder falling off the coat.
[0020] In one alternative embodiment, 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 farther from the winding center.
[0021] And / or, the first electrode has a first surface and a second surface disposed opposite to each other along a third direction; the first surface is the side with the first paste away from the first current collector, and the second surface is the side with the second paste away from the first current collector;
[0022] For the concave and convex points in the second target area, the first electrode plate is recessed from the first surface along the third direction towards the second surface to form a concave part, and protrudes from the second surface along the third direction away from the first surface to form a convex part, with the convex part and the concave part being correspondingly arranged along the third direction;
[0023] And / or, for the concave and convex points in the edge region, the first electrode plate is recessed from the first surface along the third direction toward the second surface to form a concave portion, and protrudes from the second surface along the third direction toward the distance from the first surface to form a convex portion, with the convex portion and the concave portion being correspondingly arranged along the third direction.
[0024] Beneficial effects: When the bumps and dents are set on the first electrode, by making the bumps and dents bulge from the first surface to the second surface, the local lithium ion migration distance in the arc area is increased, the amount of lithium ions accumulating on the negative electrode surface per unit time is reduced, and thus the problem of lithium plating in the arc area is improved.
[0025] The protrusions in the edge area and the protrusions in the second target area have the same orientation, which helps to reduce manufacturing difficulty and improve production efficiency.
[0026] In one optional implementation, the dimension of the second target area along the second direction is greater than or equal to the arc length of the arc area of the core, and / or the dimension of the edge area along the first direction is W1 mm, where the value of W1 is 0 < W1 ≤ 10.
[0027] Beneficial effects: Ensure that the dimension of the second target area along the second direction is not less than the arc length of the arc area, and prevent powder from falling off at the junction of the arc area and the planar area due to the different thicknesses formed after setting the concave and convex points, which would cause different forces on the left and right sides of the junction during the winding process.
[0028] W1, by satisfying 0 < W1 ≤ 10, more widely disperses the stress in the edge areas on both sides of the core along the third direction Z, thereby reducing stress concentration and effectively avoiding interface problems caused by poor bonding at the top and bottom of the cell due to edge effects and uneven pressure distribution during formation. At the same time, it effectively prevents delamination in the edge areas of the cell during charge and discharge cycles.
[0029] 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.
[0030] 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°.
[0031] Beneficial effect: By satisfying 3°≤β≤45°, β avoids the problem of excessively high slope of the convex part causing the convex tip to puncture the diaphragm, thereby preventing the convex part from causing safety problems.
[0032] In one optional implementation, the diameter of the circumcircle of the orthographic projection of the protrusion in the second target area on the second surface is R1 mm, and the value of R1 is in the range of 0.3≤R1≤8.
[0033] And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions in the second target area on the second surface is D1 mm, and the value of D1 is 1≤D1≤6;
[0034] And / or, the protrusion height of the convex part in the second target area relative to the second surface along the third direction is H3μm, and the value of H3 is in the range of 3≤H3≤80.
[0035] Beneficial effects: For the protrusions in the second target area, by satisfying 0.3≤R1≤8, it is possible to avoid the tip effect and prevent electrode breakage, while ensuring the span of the protrusion surface, thus ensuring effective support between the positive and negative electrodes; by satisfying 1≤D1≤6, it is possible to avoid the situation where the protrusions overlap and cause electrode breakage, while also ensuring effective support between the positive and negative electrodes; by satisfying 3≤H3≤80, it is possible to ensure 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.
[0036] In one alternative embodiment, the diameter of the circumcircle of the orthographic projection of the protrusion in the edge region onto the second surface is R2 mm, where R2 satisfies 0.6≤R2 / R1≤0.9.
[0037] And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions on the second surface within the edge region is D2 mm, where D2 satisfies 1.1≤D2 / D1≤1.5;
[0038] And / or, the protrusion height of the convex portion within the edge region relative to the second surface along the third direction is H4μm, where H4 satisfies 0.6≤H4 / H3≤0.9.
[0039] Beneficial effects: On the one hand, it helps to balance the formation pressure during formation; on the other hand, it can control the gap in the edge area within a reasonable range and avoid causing interface defects.
[0040] In one alternative implementation, the recess depth of the concave portion within the second target area gradually decreases as the number of folds in the winding core increases;
[0041] And / or, the depth of the recess in the edge area gradually decreases as the number of folds in the winding core increases.
[0042] Beneficial effects: The depth of the concave portion in the second target area gradually decreases with the increase of the number of folds in the winding core, thereby reducing the width dimension of the arc area along the fifth direction V, improving the problem of ultra-wide cells, and increasing the energy density of the cells. The depth of the concave portion in the edge area gradually decreases with the increase of the number of folds in the winding core, thereby avoiding excessive thickness of the cells in the edge area and avoiding affecting the energy density of the cells.
[0043] In one alternative implementation, 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 H1=H2 / 2×K3, 1.05≤K3≤1.5.
[0044] Beneficial effects: By satisfying H1=H2 / 2×K3 and 1.05≤K3≤1.5, the lithium plating problem in the arc region can be effectively improved.
[0045] 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.
[0046] 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
[0047] 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.
[0048] Figure 1 This is a three-dimensional structural schematic diagram of an electrode assembly according to an embodiment of the present utility model;
[0049] Figure 2 This is a schematic cross-sectional view of an electrode assembly according to an embodiment of the present invention;
[0050] 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.
[0051] Figure 4 This is a front view of the first electrode sheet of an electrode assembly according to an embodiment of the present invention before winding;
[0052] Figure 5 This is a schematic diagram of the structure of the first sub-coating and the second sub-coating according to an embodiment of the present invention;
[0053] 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.
[0054] Figure 7 This is a cross-sectional view along a third direction of the concave and convex points of the first electrode plate of an electrode assembly according to an embodiment of the present invention.
[0055] Figure 8 for Figure 7 The diagram shows the dimension annotations for the raised and recessed points.
[0056] Figure 9 This is a cross-sectional view along a third direction of two adjacent concave and convex points of the first electrode plate of an electrode assembly according to an embodiment of the present invention.
[0057] Explanation of reference numerals in the attached figures:
[0058] 10. First electrode; 101. First current collector; 102. First paste; 103. Second paste; 104. Double-sided area; 105. Single-sided area; 106. Empty foil area; 107. First side; 108. Second side; 109. First sub-paste; 110. Second sub-paste; 11. First target area; 12. Second target area; 13. Main body area; 14. Edge area; 15. Concave and convex points; 151. Convex part; 152. Concave part;
[0059] 20. First pole ear;
[0060] 30. Second electrode;
[0061] 40. Diaphragm;
[0062] 60. Core; 61. Flat area; 62. Arc area;
[0063] X—First direction; Y—Second direction; Z—Third direction; U—Fourth direction; V—Fifth direction. Detailed Implementation
[0064] 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.
[0065] 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 battery 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, because the flat area undergoes hot pressing during production, it is compressed very tightly, resulting in poor electrolyte wetting. Furthermore, the wound core structure in related technologies often suffers from poor edge adhesion within a 3mm to 10mm range at the top and bottom of the cell, easily leading to lithium plating at the cell edges.
[0066] The following is combined Figures 1 to 9 The following describes embodiments of the present invention.
[0067] According to an embodiment of the present invention, in one aspect, an electrode assembly is provided, comprising:
[0068] For the first electrode 10, the second electrode 30, and the diaphragm 40, please refer to [link / reference]. 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 second electrode 30, and the diaphragm 40 are wound together to form a core 60;
[0069] Please see below. Figure 2 As shown, the core 60 has a planar area 61 and an arcuate area 62 located on both sides of the planar area 61 along the fourth direction U;
[0070] Please see Figure 4 As shown, the first electrode 10 is provided with a first target area 11 and a second target area 12. The first target area 11 and the second target area 12 are alternately arranged on the first electrode 10 along the second direction Y. The first target area 11 corresponds to the planar area 61 of the core 60, and the second target area 12 corresponds to the arc area 62 of the core 60.
[0071] The first electrode 10 includes a main body region 13 and edge regions 14 located on both sides of the main body region 13 along the first direction X;
[0072] The edge area 14 and the second target area 12 are provided with concave and convex points 15.
[0073] Furthermore, multiple protrusions 15 are evenly spaced within the edge region 14 and the second target region 12.
[0074] 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.
[0075] The electrode assembly provided by this utility model, by setting concave and convex points 15 in the second target area 12 of the first electrode 10, and making the second target area 12 form the arc area 62 of the core 60, disperses the mechanical stress of the arc area 62 of the core 60 through the concave and convex points 15, reducing stress concentration in the arc area 62. At the same time, the concave and convex points 15 buffer and absorb the expansion force of the positive and negative electrodes during charging and discharging, effectively reducing the extrusion force between the electrodes and avoiding insufficient electrolyte and poor wetting between layers due to interlayer extrusion. By setting concave and convex points 15 in the edge area 14, it is beneficial to increase the ineffective thickness of the edge area 14 (the thickness manufactured by the concave and convex points 15). The concave and convex points 15 play a supporting role between the electrodes. The concave and convex points 15 on different planar layers partially overlap and partially do not overlap in the vertical direction of the stacking, which is more conducive to the function of... The supporting function of the protrusions 15 during formation allows the edge region 14 to thicken, thus better bearing the force and improving interface adhesion. Simultaneously, the micro-gaps created by the protrusions 15 facilitate electrolyte wetting of the cell edge, further improving the uniformity of lithium-ion distribution during charging and discharging, and further preventing edge lithium plating. The simultaneous placement of protrusions 15 in both the edge region 14 and the second target region 12 not only increases the interlayer bonding force and enhances the overall structural strength of the core 60, preventing loosening and deformation and making the core 60 more stable during charge-discharge cycles, but also increases the specific surface area of the arc region 62 and the edge region 14 of the core 60, optimizing electrolyte wetting and thus better preventing interface deterioration, poor wetting, and cycle lithium plating and failure.
[0076] It should be noted that the shape of the bumps 15 can be circular, elliptical, island-shaped, rhomboid, irregular polygon, etc. Since the sharp edges of the bumps 15 can easily pierce the coating, causing cracks and powder shedding, which can easily lead to short circuits and fire risks caused by particles, the bumps 15 are preferably round without sharp corners to avoid powder shedding at the edges of the bumps 15 during the manufacturing process.
[0077] In some embodiments, see Figure 4 As shown, the dimension of the edge region 14 along the first direction X is W1 mm, and the value of W1 is in the range of 0 < W1 ≤ 10.
[0078] By setting concave and convex points 15 in the edge region 14 of the first electrode 10, and the multiple concave and convex points 15 are evenly spaced in the edge region 14, the dimension of the edge region 14 along the first direction X is W1 mm. W1 satisfies 0 < W1 ≤ 10, so as to more widely disperse the stress in the edge region 14 on both sides of the third direction Z of the core 60, thereby reducing stress concentration, effectively avoiding interface problems caused by poor bonding at the top and bottom of the cell due to edge effect and uneven pressure distribution during formation, and effectively preventing delamination in the edge region 14 of the cell during charge and discharge cycles.
[0079] In some embodiments, see Figure 6 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.
[0080] The first current collector 101 has a dimension of L1 mm along the second direction Y, the first paste 102 has a dimension of L2 mm along the second direction Y, and the second paste 103 has a dimension of L3 mm along the second direction Y. L1, L2 and L3 satisfy L1>L2>L3;
[0081] Along the second direction Y, the electrode length corresponding to the overlapping dimension L3 of the first current collector 101, the first paste 102, and the second paste 103 is the double-sided region 104 of the first electrode 10. The electrode length corresponding to the dimension L2-L3 where the first current collector 101 and the first paste 102 overlap but do not overlap with the second paste 103 is the single-sided region 105 of the first electrode 10. The electrode length corresponding to the dimension L1-L2 where the first current collector 101 extends out of the first paste 102 is the empty foil region 106 of the first electrode 10.
[0082] It should be noted that "double-sided area 104" in the text refers to the paste being applied to both sides of the current collector in the third direction Z. Double-sided area 104 is usually located in the middle part of the core 60 and is also the main area for energy generation. "Single-sided area 105" in the text refers to the paste being applied only to the side of the current collector in the third direction Z. "Empty foil area 106" in the text refers to the area where neither side of the current collector in the third direction Z is coated with paste.
[0083] The first electrode 10 maximizes the utilization of active materials by setting a double-sided region 104, which is beneficial to improving the energy density of the battery cell. By setting a single-sided region 105 and an empty foil region 106, the outer surface of the single-sided region 105 does not need to be coated with paste, and the inner and outer surfaces of the empty foil region 106 do not need to be coated with paste, thereby improving the space utilization of the core 60 along the fifth direction V.
[0084] In some embodiments, such as Figure 5As shown, along the first direction X, the first coating 102 and / or the second coating 103 include a first sub-coating 109 and a second sub-coating 110, with the first sub-coating 109 located on the side of the second sub-coating 110 close to the first tab 20;
[0085] The thickness of the first sub-coating 109 is less than or equal to that of the second sub-coating 110. In the third direction Z, the projection of the first sub-coating 109 and the projection of the edge region 14 do not overlap.
[0086] With this setting, no bumps 15 are provided in the thinning area of the first coating 102 (i.e., the first sub-coating 109), to avoid the problem of powder falling off the coating.
[0087] In some embodiments, the first paste 102 is located on the side of the first current collector 101 closer to the winding center, and the second paste 103 is located on the side of the first current collector 101 away from the winding center;
[0088] And / or, please see Figure 6 As shown, the first electrode 10 has a first surface 107 and a second surface 108 disposed opposite to each other along the third direction Z; the first surface 107 is the side of the first paste 102 away from the first current collector 101, and the second surface 108 is the side of the second paste 103 away from the first current collector 101.
[0089] Please see Figure 7 As shown, the concave-convex point 15 includes a convex part 151 and a concave part 152 corresponding to the convex part 151; for the concave-convex point 15 in the second target area 12, the first electrode 10 is recessed from the first surface 107 along the third direction Z towards the second surface 108 to form the concave part 152, and protrudes from the second surface 108 along the third direction Z away from the first surface 107 to form the convex part 151, and the convex part 151 and the concave part 152 are correspondingly arranged along the third direction Z.
[0090] It should be noted that when forming the winding structure, the first surface 107 is located on the side closer to the inner side of the core 60, and the second surface 108 is located on the side closer to the outer side of the core 60. Due to the curvature of the arc region 62, when the arc formed by the first surface 107 wraps around the second electrode 30, the circumference of the arc of the first surface 107 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 a decrease in NP and lead to the risk of lithium plating.
[0091] When the protrusions 15 are provided on the first electrode 10, the protrusions 15 are made to bulge from the first surface 107 to the second surface 108, thereby increasing the local lithium ion migration distance in the arc region 62, 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 62.
[0092] In some embodiments, the dimension of the second target area 12 along the second direction Y is greater than or equal to the arc length of the arc area 62 of the core 60. This ensures that the dimension of the second target area 12 along the second direction Y is not less than the arc length of the arc area 62, preventing powder shedding at the junction of the arc area 62 and the planar area 61 due to the different thicknesses formed after setting the protrusions 15, which could result in different forces on the left and right sides of the junction during winding.
[0093] There are two settings for the size of the second target area 12 along the second direction Y. The first is that the size of the second target area 12 along the second direction Y increases with the increase of the number of folds of the core 60. That is, the size of the second target area 12 along the second direction Y of each fold is the arc length of the actual arc area 62 of the core 60. Each fold of the second target area 12 is provided with concave and convex points 15, thereby ensuring that the concave and convex points 15 do not fall on the plane area 61 of the core 60 during the manufacturing process, which helps to reduce the ineffective thickness of the cell and improve the energy density of the battery. The second is that the size of the second target area 12 along the second direction Y of each fold is the arc length of the outermost arc area 62 of the core 60. This design can effectively improve production efficiency and reduce manufacturing difficulty.
[0094] In some embodiments, for the concave and convex points 15 in the edge region 14, the first electrode 10 is recessed from the first surface 107 along the third direction Z toward the direction close to the second surface 108 to form a concave portion 152, and protrudes from the second surface 108 along the third direction Z toward the direction away from the first surface 107 to form a convex portion 151, and the convex portion 151 and the concave portion 152 are correspondingly arranged along the third direction Z.
[0095] It should be noted that the orientation of the protrusions 15 within the edge area 14 is not limited. They can be the first surface 107 facing the second surface 108 or the second surface 108 facing the first surface 107. Both have the same technical effect.
[0096] In this embodiment, the protrusions of the concave and convex points 15 in the edge region 14 and the protrusions of the concave and convex points 15 in the second target region 12 are aligned, which helps to reduce manufacturing difficulty and improve production efficiency.
[0097] In some embodiments, see Figure 7 As shown, the protrusion 151 has a first target point P and a second target point Q, wherein the first target point P is the point on the protrusion 151 that is farthest from the second surface 108 along the third direction Z, and the second target point Q is the intersection point of the protrusion 151 and the second surface 108.
[0098] Along the third direction Z, the orthographic projection of the first target point P onto the second surface 108 is O, and the angle between the line OQ and the line PQ is β, where β satisfies 3°≤β≤45°.
[0099] By satisfying 3°≤β≤45°, β avoids the problem of excessively high slope of the protrusion 151 causing a protruding tip, thereby preventing the protrusion 151 from piercing the diaphragm 40 and avoiding safety issues.
[0100] Preferably, β satisfies 5°≤β≤25°.
[0101] The structure of the protrusions 15 on the first electrode 10 is preferably a near-circular shape without sharp corners. In the specific implementation process, by using a 3D profilometer to test the state of the first electrode 10, it can be clearly detected that the edges of its protrusions 151 or concave parts 152 are near-circular, thereby avoiding the problem of powder falling off the edges of the protrusions 15 during the manufacturing process.
[0102] In some embodiments, such as Figure 8 As shown, the diameter of the circumcircle of the protrusion 151 in the second target area 12 projected onto the second surface 108 is R1 mm, and the value of R1 is 0.3≤R1≤8.
[0103] And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions 151 on the second surface 108 within the second target area 12 is D1 mm, and the value of D1 is 1≤D1≤6.
[0104] And / or, the protrusion height of the protrusion 151 in the second target area 12 relative to the second surface 108 along the third direction Z is H3μm, and the value of H3 is in the range of 3≤H3≤80.
[0105] It should be noted that for the circumcircle diameter R1 mm of the orthographic projection of the protrusion 151 in the second target area 12 onto the second surface 108, if R1 is too small, it is easy to cause a tip effect, leading to electrode breakage. Therefore, R1 must satisfy R1≥0.3; if R1 is too large, the span of its protruding surface is too large, which is not conducive to providing support between the positive and negative electrodes. Therefore, R1 must also satisfy R1≤8. For the distance D1 mm between the centers of the circumcircles of the orthographic projections of two adjacent protrusions 151 on the second surface 108 in the second target area 12, if D1 is too small, it is easy to cause the protrusions 151 to overlap, leading to electrode breakage. Therefore, D1 must satisfy D1≥1; if the distance between the centers is too large, the two protrusions 151 cannot provide support. Therefore, D1 must also satisfy D1≤6. For the protrusion 151 in the second target area 12, the dimension (i.e. the protrusion height) along the third direction Z is H3μm. If H3 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, H3 needs to satisfy H3≥3. When H3 is too large, it will cause severe delamination between the positive and negative electrodes and cause new interface problems. Therefore, H3 also needs to satisfy H3≤80.
[0106] For the protrusion 151 within the second target region 12, by satisfying 0.3≤R1≤8, it is possible to avoid the tip effect and prevent electrode breakage, while also ensuring the span of the protrusion surface, thereby guaranteeing effective support between the positive and negative electrodes. By satisfying 1≤D1≤6, it is possible to avoid the situation where the protrusion 151 overlaps and causes electrode breakage, while also guaranteeing effective support between the positive and negative electrodes. By satisfying 3≤H3≤80, it is possible to 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.
[0107] Preferably, 1≤R1≤3; and / or, 1.5≤D1≤4.
[0108] In some embodiments, such as Figure 8 As shown, the diameter of the circumcircle of the protrusion 151 in the edge region 14 projected onto the second surface 108 is R2 mm, and R2 satisfies 0.6≤R2 / R1≤0.9;
[0109] And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions 151 on the second surface 108 within the edge region 14 is D2 mm, where D2 satisfies 1.1≤D2 / D1≤1.5;
[0110] And / or, the protrusion height of the protrusion 151 in the edge region 14 relative to the second surface 108 along the third direction Z is H4μm, where H4 satisfies 0.6≤H4 / H3≤0.9.
[0111] It should be noted that, compared to the protrusion 151 set in the second target area 12, the edge area 14 requires more stacked and staggered support points. These points need to provide support to balance the formation pressure during formation, but they also need to avoid creating too many gaps to prevent interface defects. Therefore, both aspects need to be considered.
[0112] For the protrusion 151 in the edge region 14, by satisfying 0.6≤R2 / R1≤0.9, and / or 1.1≤D2 / D1≤1.5, and / or 0.6≤H4 / H3≤0.9, it has the beneficial effects of the protrusion 151 in the second target region 12, which is conducive to balancing the formation pressure during formation, which will not be elaborated here; on the other hand, it can control the gap in the edge region 14 within a reasonable range and avoid causing interface defects.
[0113] In some embodiments, 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 second electrode 30 has a second electrode tab on one side along the first direction X.
[0114] In some embodiments, the recess depth of the recess 152 in the second target area 12 gradually decreases as the number of folds of the winding core 60 increases;
[0115] And / or, the depth of the recess 152 within the edge region 14 gradually decreases as the number of folds in the winding core 60 increases.
[0116] It should be noted that since the compression of the arc region 62 mainly occurs in the interlayer near the inner ring of the core 60, the compression force is smaller closer to the outer ring, the electrolyte shortage is less, and the risk of lithium plating is lower. The depth of the recess 152 in the second target region 12 gradually decreases with the increase of the number of folds in the core 60 winding, thereby reducing the width of the arc region 62 along the fifth direction V, improving the problem of the cell being too wide, and increasing the cell's energy density. Since the area near the outer surface of the core 60 is well wetted and not prone to delamination, deeper concave and convex points 15 are not needed near the outer ring. The depth of the recess 152 in the edge region 14 gradually decreases with the increase of the number of folds in the core 60 winding, thereby avoiding the cell being too thick in the edge region 14 and avoiding affecting the cell's energy density.
[0117] In some embodiments, the size of the arc region 62 along the fourth direction U is H1, and the size of the planar region 61 along the fifth direction V is H2. H1 and H2 satisfy H1=H2 / 2×K3, 1.05≤K3≤1.5.
[0118] It should be noted that by setting the concave and convex points 15 in the arc region 62 of the core 60, a certain support is provided between the positive electrode, separator 40, 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 H1 = H2 / 2 × K3, and 1.05 ≤ K3 ≤ 1.5, the lithium plating problem in the arc region 62 can be effectively improved.
[0119] Preferably, 1.08≤K3≤1.3.
[0120] 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.
[0121] 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.
[0122] 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 first electrode (10), a second electrode (30), and a diaphragm (40) are provided, wherein the diaphragm (40) is disposed between the first electrode (10) and the second electrode (30), and the first electrode (10), the second electrode (30), and the diaphragm (40) are wound together to form a core (60); The first electrode (10) is provided with a first electrode tab (20) on one side along the first direction (X), and the second electrode (30) is provided with a second electrode tab on one side along the first direction (X); The core (60) has a planar area (61) and an arc area (62) located on both sides of the planar area (61) along the fourth direction (U); The first electrode (10) is provided with a first target area (11) and a second target area (12). The first target area (11) and the second target area (12) are alternately arranged on the first electrode (10) along the second direction (Y). The first target area (11) corresponds to the planar area (61) of the core (60), and the second target area (12) corresponds to the arc area (62) of the core (60). The first electrode (10) includes a main body region (13) and edge regions (14) located on both sides of the main body region (13) along a first direction (X); The edge area (14) and the second target area (12) are provided with concave and convex points (15), the concave and convex points (15) include a convex part (151) and a concave part (152) corresponding to the convex part (151).
2. The electrode assembly according to claim 1, characterized in that, 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 a third direction (Z); The first current collector (101) has a dimension of L1 mm along the second direction (Y), the first paste (102) has a dimension of L2 mm along the second direction (Y), and the second paste (103) has a dimension of L3 mm along the second direction (Y). L1, L2 and L3 satisfy L1 > L2 > L3. Along the second direction (Y), the electrode length corresponding to the overlapping dimension L3 of the first current collector (101), the first paste (102) and the second paste (103) is the double-sided region (104) of the first electrode (10), the electrode length corresponding to the overlapping dimension L2-L3 of the first current collector (101) and the first paste (102) but not the second paste (103) is the single-sided region (105) of the first electrode (10), and the electrode length corresponding to the dimension L1-L2 of the first current collector (101) extending beyond the first paste (102) is the empty foil region (106) of the first electrode (10).
3. The electrode assembly according to claim 2, characterized in that, Along the first direction (X), the first coating (102) and / or the second coating (103) include a first sub-coating (109) and a second sub-coating (110), wherein the first sub-coating (109) is located on the side of the second sub-coating (110) near the first tab (20); The thickness of the first sub-paint (109) is less than or equal to that of the second sub-paint (110), and the projection of the first sub-paint (109) and the projection of the edge region (14) do not overlap in the third direction (Z) of (10).
4. The electrode assembly according to claim 3, characterized in that, The first paste (102) is located on the side of the first current collector (101) closer to the winding center, and the second paste (103) is located on the side of the first current collector (101) away from the winding center; And / or, the first electrode (10) has a first surface (107) and a second surface (108) disposed opposite each other in a third direction (Z); the first surface (107) is the side of the first paste (102) away from the first current collector (101), and the second surface (108) is the side of the second paste (103) away from the first current collector (101); For the concave and convex points (15) in the second target area (12), the first electrode (10) is recessed from the first surface (107) in a direction close to the second surface (108) along the third direction (Z) to form the concave portion (152), and protrudes from the second surface (108) in a direction away from the first surface (107) along the third direction (Z) to form the convex portion (151). The convex portion (151) and the concave portion (152) are correspondingly arranged along the third direction (Z). And / or, for the concave and convex points (15) in the edge region (14), the first electrode (10) is recessed from the first surface (107) in a direction close to the second surface (108) along the third direction (Z) to form the concave portion (152), and protrudes from the second surface (108) in a direction away from the first surface (107) along the third direction (Z) to form the convex portion (151), and the convex portion (151) and the concave portion (152) are correspondingly arranged along the third direction (Z).
5. The electrode assembly according to claim 1, characterized in that, The second target area (12) has a size along the second direction (Y) that is greater than or equal to the arc length of the arc area (62) of the core (60), and / or the edge area (14) has a size along the first direction (X) that is W1 mm, where the value of W1 is 0 < W1 ≤ 10.
6. The electrode assembly according to claim 4, characterized in that, The protrusion (151) has a first target point P and a second target point Q, wherein the first target point P is the point on the protrusion (151) that is farthest from the second surface (108) along the third direction (Z), and the second target point Q is the intersection point of the protrusion (151) and the second surface (108). Along the third direction (Z), the orthographic projection of the first target point P on the second surface (108) is O, and the angle between the line OQ and the line PQ is β, where β satisfies 3°≤β≤45°.
7. The electrode assembly according to claim 4, characterized in that, The diameter of the circumcircle of the orthographic projection of the protrusion (151) in the second target area (12) onto the second surface (108) is R1 mm, and the value of R1 is 0.3≤R1≤8; And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions (151) in the second target area (12) onto the second surface (108) is D1 mm, and the value of D1 is 1≤D1≤6; And / or, the protrusion height of the protrusion (151) in the second target area (12) relative to the second surface (108) along the third direction (Z) is H3μm, and the value of H3 is 3≤H3≤80.
8. The electrode assembly according to claim 7, characterized in that, The diameter of the circumcircle of the orthographic projection of the protrusion (151) in the edge region (14) onto the second surface (108) is R2 mm, where R2 satisfies 0.6≤R2 / R1≤0.9; And / or, the distance between the centers of the circumcircles of the orthographic projections of two adjacent protrusions (151) in the edge region (14) onto the second surface (108) is D2 mm, where D2 satisfies 1.1≤D2 / D1≤1.5; And / or, the protrusion height of the protrusion (151) in the edge region (14) relative to the second surface (108) along the third direction (Z) is H4μm, where H4 satisfies 0.6≤H4 / H3≤0.
9.
9. The electrode assembly according to any one of claims 1 to 4, characterized in that, The depth of the recess (152) in the second target area (12) gradually decreases as the number of folds of the core (60) increases; And / or, the depth of the recess (152) in the edge region (14) gradually decreases as the number of folds of the winding core (60) increases; And / or, the size of the arc region (62) along the fourth direction (U) is H1, and the size of the planar region (61) along the fifth direction (V) is H2, and H1 and H2 satisfy H1=H2 / 2×K3, 1.05≤K3≤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.