Jelly roll and battery

Abstract

The present disclosure provides a jelly roll and a battery. The jelly roll comprises an electrode assembly, a first adhesive tape and a second adhesive tape; the electrode assembly comprises a straight section, and a first arc bent section and a second arc bent section which are respectively located at two ends of the straight section; tabs are provided in the straight section, and the first arc bent section is away from a winding termination end of the electrode assembly in a winding direction; the first adhesive tape is provided on the outermost side of the first arc bent section, the orthographic projection of the second adhesive tape in the thickness direction of the jelly roll covers the tabs, and the second adhesive tape extends to the first arc bent section. The first adhesive tape and the second adhesive tape both extend beyond the edge of the electrode assembly in a first direction, and the first direction is the width direction of an electrode sheet. By means of cooperation of the first adhesive tape and the second adhesive tape, the problem of the jelly roll being prone to cracking and deformation after multiple cycles can be avoided.

Description

A winding core and a battery Technical Field

[0001] The present disclosure belongs to the technical field of batteries, and particularly relates to a winding core and a battery. Background Art

[0002] The rapid development of new energy vehicles and large-scale energy storage has led to higher demands on battery safety and energy density. Currently, increasing energy density is often achieved by reducing the gap between the aluminum-plastic film and the battery cell. However, as the battery cycles, heat accumulates within the battery as the number of charges increases, causing the electrode material and the cell thickness to expand. This expansion and elongation of the negative electrode sheet, in particular, can cause structural fractures in the cell. Furthermore, if the battery cell is loosely packaged in aluminum-plastic film, friction and vibration between the cell and the film during transportation can cause structural deformation.

[0003] Currently, most battery windings secure the core structure by coating the electrode assembly with a protective adhesive layer. However, this layer only protects the outer periphery of the electrode assembly, leaving the internal structure unprotected. Furthermore, the protective adhesive layer increases the thickness of the battery cell, hindering the improvement of the battery's energy density. Therefore, preventing the core from cracking and deforming after repeated cycles is a pressing technical challenge in this field. Summary of the Invention

[0004] The present disclosure provides a winding core, which is mainly used to solve the problem in the prior art that the winding core is easily broken and deformed after multiple cycles.

[0005] The present disclosure provides a battery, which includes the winding core, so that a flexible buffer body is formed between the electrode assembly and the aluminum-plastic film, thereby improving both the energy density and safety performance of the battery.

[0006] According to a first aspect of the present disclosure, a winding core is provided, which includes an electrode assembly, a first adhesive tape and a second adhesive tape; the electrode assembly includes a straight section and a first arc bending section and a second arc bending section respectively located at both ends of the straight section; a pole ear is provided in the straight section, and the winding tail end of the electrode assembly is located in the second arc bending section; the first adhesive tape is provided at the outermost side of the first arc bending section, and the second adhesive tape covers the pole ear in the orthographic projection along the thickness direction of the winding core, and the second adhesive tape extends to the first arc bending section; wherein, the first adhesive tape and the second adhesive tape both exceed the edge of the electrode assembly in the first direction, and the first direction is the width direction of the pole piece.

[0007] A second aspect of the present disclosure provides a battery, comprising the battery cell according to the first aspect and an aluminum-plastic film, wherein the aluminum-plastic film encloses a receiving cavity, and the battery cell is located in the receiving cavity.

[0008] The implementation of this disclosure has at least the following beneficial effects:

[0009] The present invention provides a first adhesive tape on the outermost side of the first arc bending section, which can effectively prevent the electrolyte from corroding the outermost aluminum layer, thereby causing the aluminum layer of the arc section to break first under the action of stress. Even if the aluminum layer of the arc section breaks, the first adhesive tape can effectively connect the two sides of the aluminum layer of the outermost aluminum layer at the broken part of the arc section, effectively avoiding the loosening of the winding core. In addition, since the second adhesive tape is provided on the pole ear and extends to the first arc bending section, when the outermost side of the first arc bending section of the winding core breaks and causes the inside of the winding core to loosen, the second adhesive tape can, on the one hand, effectively offset the gap formed by the loosening under the action of its own elastic deformation, reduce the loose displacement of the arc section near the pole ear groove, thereby reducing the displacement causing the active material particles in the area to scratch the diaphragm. On the other hand, the second adhesive tape covers the active material in the arc section, which further reduces the probability of the active material particles in the area scratching the diaphragm and reduces the risk of lithium plating. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 is a schematic diagram of the cross-sectional structure of a winding core in one embodiment of the present disclosure.

[0011] FIG2 is a partial enlarged view of the second adhesive tape in the roll core of FIG1 .

[0012] FIG3 is a schematic diagram of the cross-sectional structure of a winding core in another embodiment of the present disclosure.

[0013] FIG4 is a partial enlarged view of the second adhesive tape in the roll core of FIG3 .

[0014] FIG5 is a schematic diagram of a partial cross-sectional structure of the innermost side of an electrode assembly in one embodiment of the present disclosure.

[0015] FIG6 is a top view of the winding end of the winding core according to one embodiment of the present disclosure.

[0016] FIG7 is a schematic diagram of a partial cross-sectional structure of a tab in an electrode assembly according to an embodiment of the present disclosure.

[0017] FIG8 is a schematic diagram of the cross-sectional structure of a winding core in another embodiment of the present disclosure.

[0018] FIG9 is a schematic diagram of a top view of the structure of the negative electrode sheet in the electrode assembly before winding in one embodiment of the present disclosure.

[0019] FIG10 is a schematic side view of the structure of the negative electrode sheet in the electrode assembly before winding in one embodiment of the present disclosure.

[0020] Explanation of the accompanying drawings: 1-electrode assembly; 2-first adhesive tape; 3-second adhesive tape; 4-first termination adhesive; 5-second termination adhesive; 41-hot melt adhesive; 6-third adhesive tape; 11-straight section; 12-first arc bending section; 13-second arc bending section; 101-ear; 102-positive electrode sheet; 103-negative electrode sheet; 104-separator; 1031-negative electrode current collector; 1032-negative electrode active material layer; 1033-first groove; 1034-second groove; 1001-first negative electrode straight part; 1002-first negative electrode bending part; 1003-second negative electrode straight part; 1004-first positive electrode straight part; 1005-positive electrode single-sided empty foil area; 1006-positive electrode double-sided empty foil area; 1007-winding end. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present disclosure.

[0022] In Figures 1 to 10, it should be noted that X is the first direction, which is also the width direction of the electrode assembly and the width direction of the negative electrode sheet before winding; Y is the second direction, which is also the length direction of the electrode assembly and the length direction of the negative electrode sheet before winding; Z is the third direction, which is also the thickness direction of the electrode assembly and the thickness direction of the negative electrode sheet before winding.

[0023] It should be noted that the cell structure provided in the embodiments of the present disclosure is preferably applicable to lithium-ion batteries; of course, it is also applicable to wound cells such as sodium-ion batteries, and no further limitations are made here.

[0024] It should be noted that during the winding process of the core, in order to ensure the tightness of the internal film layers, the positive electrode sheet, separator, and negative electrode sheet need to be tightened during the winding process. As the winding radius increases, the stress of the arc segment of the film layer closer to the outside is more concentrated. The core in the disclosed embodiment is preferably wrapped with aluminum foil for the positive electrode sheet, that is, the outermost layer of the core is aluminum. As the number of cycles of the core increases, the electrolyte will gradually corrode the exposed outermost aluminum layer. Because the stress of the outermost arc segment of the core is the greatest, the outermost aluminum layer of the core is easily corroded and breaks first under the action of stress.

[0025] In addition, since the winding core in the embodiment of the present disclosure preferably adopts a tab-centered structure, that is, part of the active material is removed from the edge of the active layer located in the middle of the positive and negative electrode sheets to form a tab groove, and then the tab is welded in the tab groove; in the process of forming the tab groove, scraping or laser ablation is usually adopted, which will cause the active material in the area near the tab groove to become fluffy due to stress and splash part of the active material particles in the area near the tab groove. Therefore, after the outermost layer of the winding core breaks, the film layers inside the winding core will loosen to form a gap, and the active material particles in the area near the tab groove will be displaced under the action of the active material's fluffy recovery, and especially the arc segment near the tab groove has the largest loosening displacement, which may puncture the diaphragm of this arc segment and cause risks such as lithium precipitation or short circuit fire.

[0026] As shown in Figures 1 to 10, the first aspect of the present disclosure provides a winding core, which includes an electrode assembly 1, a first adhesive tape 2 and a second adhesive tape 3; the electrode assembly 1 includes a pole piece; the electrode assembly 1 includes a straight section 11 and a first arc bending section 12 and a second arc bending section 13 respectively located at both ends of the straight section 11; a pole ear 101 is provided in the straight section 11, and the winding tail end 1007 of the electrode assembly is located in the second arc bending section 13; the first adhesive tape 2 is provided at the outermost side of the first arc bending section 12, and the second adhesive tape 3 covers the pole ear 101 along the orthographic projection in the thickness direction of the winding core, and the second adhesive tape 3 extends to the first arc bending section 12; wherein, the first adhesive tape 2 and the second adhesive tape 3 both exceed the edge of the electrode assembly 1 in the first direction, and the first direction is the width direction of the pole piece.

[0027] It should be noted that the winding tail end 1007 of the electrode assembly is located at the second arc bending section 13, as shown in Figure 1, that is, the electrode and / or diaphragm located at the outermost tail end of the winding core extends from the second arc bending section 13 or is located on the second arc bending section 13.

[0028] In the present disclosure, the electrode assembly 1 is a winding structure formed by stacking and winding electrode sheets and diaphragms 104 with opposite polarities. The electrode sheets and diaphragms 104 form arc bending portions and straight portions during the winding process. For example, each time the electrode sheets and diaphragms 104 are wound one circle, two arc bending portions and two straight portions are formed. The two arc bending portions are respectively located at the two ends of the two straight portions, and the two straight portions are connected by the two arc bending portions. Specifically, one end of the arc bending portion is connected to one straight portion, and the other end is connected to the other straight portion, thereby forming the first circle of the winding core. As the number of winding turns of the electrode sheet and the diaphragm 104 increases, multiple straight portions and multiple arc-shaped bent portions will be formed. At this time, the multiple straight portions are stacked in sequence to form a straight section of the electrode assembly; the multiple arc-shaped bent portions are stacked in sequence to form a first arc-shaped bent section 12 and a second arc-shaped bent section 13 that are relatively arranged at both ends of the straight section 11. At this time, the first arc-shaped bent section 12 is connected to one end of the straight section 11, and the second arc-shaped bent section 13 is connected to the other end of the straight section 11.

[0029] It should be noted that the direction from the first arc bent section 12 at one end of the electrode assembly 1 to the second arc bent section 13 at the other end thereof is the second direction of the electrode assembly (i.e., the length direction of the electrode assembly); on the first plane parallel to the straight section 11, the direction perpendicular to the second direction is the first direction of the electrode assembly (i.e., the width direction of the electrode assembly); the direction from one straight portion of the electrode assembly 1 to another straight portion thereof is the third direction of the electrode assembly (i.e., the thickness direction of the electrode assembly and the winding core).

[0030] The winding tail end 1007 of the electrode assembly is located in the second arc bending section 13 , that is, the winding tail end 1007 of the electrode assembly is partially or entirely located in the second arc bending section 13 .

[0031] Specifically, in the winding structure, winding begins with the winding start end of the electrode assembly 1 as the starting point and ends with the winding end 1007 of the electrode assembly 1 as the end point. Along the winding direction, based on the distance from the winding end 1007, the arc-shaped bend section can be divided into a first arc-shaped bend section 12 away from the winding end 1007 and a second arc-shaped bend section 13 close to the winding end 1007. The first arc-shaped bend section 12 is farther away from the winding end of the electrode assembly than the second arc-shaped bend section 13, and the second arc-shaped bend section 13 is closer to the winding end 1007 than the first arc-shaped bend section 12.

[0032] The outermost side of the first arc-shaped bending section 12 refers to the outermost side of the first arc-shaped bending section 12 away from the winding center of the electrode assembly 1, and can specifically be the inner and outer surfaces of the outermost electrode sheet or the inner and outer surfaces of the outermost diaphragm. For example, it can be the surface of the positive electrode collector (aluminum foil) of the positive electrode sheet or the surface of the diaphragm, which can be the outer surface and / or inner surface of the aluminum foil, or the outer surface and / or inner surface of the diaphragm; for example, referring to Figure 1, the first adhesive tape 2 is only wrapped around the outer surface of the aluminum foil.

[0033] The winding core also includes tabs 101, which are provided to guide the circuit inside the winding core to connect with the peripheral circuit. In the present disclosure, the tabs 101 are provided on the straight section 11, and specifically, can be provided on a current collector in a straight portion of the straight section 11.

[0034] The number of pole tabs 101 is usually two, and both are arranged in the pole tab groove of the straight section 11. The two pole tabs are arranged at intervals along the orthographic projection on the first plane. The first plane is a plane parallel to the collector surface of the straight section 11 in the electrode assembly 1, that is, line segments are emitted from each point on the pole tab in a direction perpendicular to the first plane, and these line segments are intersected with the first plane. The resulting projection is the orthographic projection of the pole tab. It can also be understood that the two pole tabs are arranged at intervals along the orthographic projection in the thickness direction of the core, and the thickness direction of the core is perpendicular to the first plane.

[0035] The second adhesive tape 3 covers the tab 101 along its orthographic projection in the thickness direction of the winding core, and the second adhesive tape 3 extends to the first arc-shaped bend section 12. In this case, the second adhesive tape 3 can be covered on the tab, or the second adhesive tape 3 can be set on the diaphragm or another pole piece on the opposite side of the tab. In this case, when the outermost side of the first arc-shaped bend section breaks and causes the inside of the winding core to loosen, the second adhesive tape can, on the one hand, effectively offset the gap formed by the loosening under the action of its own elastic deformation, reducing the loose displacement of the first arc section, thereby reducing the displacement that causes the active material particles in this area to scratch the diaphragm. On the other hand, the second adhesive tape covers the active material on the first arc section, which further reduces the probability of the active material particles in this area scratching the diaphragm and reduces the risk of lithium plating. When the second adhesive tape 3 is covered on the tab, the second adhesive tape 3 also plays the role of surface protection, insulation and fixation, preventing burrs from appearing on the tab 101 during cutting. If the second adhesive tape 3 is not pasted to cover, the burrs will easily pierce the diaphragm and cause a short circuit. At the same time, the position of the tab 101 is fixed to prevent the tab 101 from falling off and causing an increase in the internal resistance of the battery.

[0036] The number of the second adhesive tape 3 is one or two. When the number of the third adhesive tape is one, the third adhesive tape 3 can be placed on either side of the tab 101; when the number of the third adhesive tape is two, the two adhesive tapes are placed on both sides of the tab 101, and the two adhesive tapes are placed opposite each other.

[0037] In the electrode assembly disclosed herein, each of the positive and negative electrode sheets has at least one tab. Specifically, the positive electrode sheet is provided with a positive tab, with positive tab protective glue provided on both sides of the positive tab. Positive tab insulating glue is provided on the negative electrode sheets on opposite sides of the positive tab. The positive tab protective glue extends along the winding direction to the arc-shaped bend, and the orthographic projection of the positive tab protective glue on a first plane exceeds the edge of the orthographic projection of the positive tab insulating glue on the first plane. The negative electrode sheet is provided with a negative tab, with negative tab protective glue provided on both sides of the negative tab. Negative tab insulating glue is provided on the positive electrode sheet on opposite sides of the negative tab. The negative tab insulating glue extends along the winding direction to the arc-shaped bend, and the orthographic projection of the negative tab insulating glue on a first plane exceeds the edge of the orthographic projection of the negative tab protective glue on the first plane. Both the positive tab protective glue and the negative tab insulating glue are on the positive electrode sheet.

[0038] The second adhesive tape 3 extends along the winding direction to the first arc bending section 12. In one embodiment, as shown in Figures 1 and 2, the electrode tab closest to the first arc segment 12 is the positive electrode tab, and the second adhesive tape 3 can be a positive electrode tab protective adhesive, that is, it covers the electrode tab 101. At this time, the positive electrode tab protective adhesive extends to the first arc bending section 12; or, in another embodiment, as shown in Figures 3, 4 and 6, the electrode tab closest to the first arc segment is the negative electrode tab, and the second adhesive tape 3 can also be a negative electrode tab insulating adhesive, that is, it is relatively arranged on the positive electrode sheet opposite to the negative electrode tab. At this time, the negative electrode tab insulating adhesive extends to the first arc bending section 12.

[0039] In the first direction, both the first adhesive tape 2 and the second adhesive tape 3 extend beyond the upper edge of the electrode assembly 1. Specifically, the first adhesive tape 2, the second adhesive tape 3, and the electrode assembly 1 each have two oppositely disposed edges along the second direction, with both edges of the first adhesive tape 2 protruding beyond the edge of the electrode assembly 1, and the edge of the second adhesive tape 3 near the tab 101 protruding beyond the electrode assembly 1, thereby ensuring that both the first adhesive tape 2 and the second adhesive tape 3 extend beyond the edge of the electrode assembly in the first direction.

[0040] The embodiment of the present disclosure sets a first adhesive tape on the outermost side of the first arc bending section, which can effectively prevent the electrolyte from corroding the outermost aluminum layer, thereby causing the aluminum layer of the arc section to break first under the action of stress, and even if the aluminum layer of the arc section breaks, the first adhesive tape can effectively connect the two sides of the aluminum layer of the outermost aluminum layer at the broken part of the arc section, effectively avoiding the loosening of the winding core; in addition, since the second adhesive tape is set on the pole ear and extends to the first arc bending section, when the outermost side of the first arc bending section of the winding core breaks and causes the inside of the winding core to loosen, the second adhesive tape can, on the one hand, effectively offset the gap formed by the loosening under the action of its own elastic deformation, reduce the loose displacement of the arc section near the pole ear groove, thereby reducing the displacement causing the active material particles in this area to scratch the diaphragm; on the other hand, the second adhesive tape covers the active material in the arc section, which further reduces the probability of the active material particles in this area scratching the diaphragm and reduces the risk of lithium plating.

[0041] In particular, the winding core of the present disclosure can reduce corner damage of the aluminum-plastic film without increasing the thickness. This is because, by making the first adhesive tape 2 and the second adhesive tape 3 protrude beyond the edge of the electrode assembly 1, when the aluminum-plastic film is used for packaging, the portions of the first adhesive tape 2 and the second adhesive tape 3 that extend beyond the edge of the electrode assembly 1 can directly contact the aluminum-plastic film, forming a flexible buffer between the electrode assembly 1 and the aluminum-plastic film. In particular, a flexible buffer is formed outside the first arc-shaped bend section 12 and the tab 101. This buffer serves to fix the electrode assembly 1, preventing it from shaking. It also provides sufficient space for the electrode assembly 1 to expand and extend, preventing the electrode assembly 1 from expanding and extending during the cyclic charge and discharge process and directly puncturing the aluminum-plastic film, thereby avoiding corner damage. In addition, since the first adhesive tape 2 is only provided on the first arc-shaped bend section 12 away from the winding end, it helps to avoid increasing the overall thickness of the winding core. Therefore, the winding core of the present disclosure can reduce corner damage of the aluminum-plastic film without increasing the thickness, thereby facilitating both improving the energy density and safety performance of the battery.

[0042] In some embodiments, along the winding center of the winding core pointing to the outside of the winding core, the winding core includes multiple folded pole pieces, and the pole ear is provided on the pole piece between the front quarter folded pole piece and the rear quarter folded pole piece.

[0043] That is to say, the pole ear of the pole piece in the winding core is arranged in the middle of the pole piece. At this time, the second adhesive tape 3 is located in the middle of the winding core, and can alternately cooperate with the first adhesive tape 2 to reduce the further loosening of the winding core caused by the winding stress, thereby reducing the loosening and deformation of the winding core inside the second adhesive tape 3, avoiding the further increase of the gap in the inner arc bending section of the winding core, thereby reducing the lithium plating phenomenon in the arc bending section of the winding core.

[0044] The present disclosure does not limit the size of the first and second adhesive tapes 2 and 3 protruding from the edge of the electrode assembly 1, and the specific size can be adjusted according to actual needs. For example, in some embodiments, the size of the first adhesive tape 2 protruding from the edge of the electrode assembly 1 in the first direction is A, and the size of the second adhesive tape 3 protruding from the edge of the electrode assembly 1 in the first direction is B; A and B satisfy the following relationship: A and B satisfy the following relationship: 0≤BA≤2mm (for example, 0mm, 0.5mm, 1mm, 1.5mm, or 2mm), 0<A≤3mm (for example, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, or 3mm), 0<B≤3mm (for example, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, or 3mm). In this way, the second adhesive tape 3 protrudes from the edge of the electrode assembly in the first direction by an equivalent or longer size relative to the first adhesive tape 2, thereby reducing the problem of bulging or wrinkling of the appearance caused by the folding of the second adhesive tape 3.

[0045] Here, A refers to the dimension by which any edge of the first adhesive tape 2 protrudes from the electrode assembly in the first direction, and B refers to the dimension by which the edge of the second adhesive tape 3 protrudes from the electrode assembly on the side closest to the tab 101. In the present disclosure, the second adhesive tape 3 is located within the straight section 11, and the first adhesive tape 2 is located on the first arc-shaped section 12. The projection of the first adhesive tape 2 on a first plane is spaced apart from the tab 101. The first plane is a plane parallel to the straight section 11 of the electrode assembly. This ensures that the first adhesive tape 2 and the tab 101 do not overlap in thickness along the winding core, further ensuring that the winding core thickness is not increased. In some embodiments, the distance between the orthographic projection of the first adhesive tape 3 on the first plane and the orthographic projection of the tab 101 on the first plane is J, where J satisfies 0 < J < 60 mm (e.g., 0.1 mm, 0.5 mm, 1 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, or 59 mm).

[0046] In some embodiments, the extended dimension of the first adhesive tape 2 is E (in mm), the thickness of the winding core is H (in mm), and the maximum dimension in the second direction between the end of the tab 101 closest to the first arcuate bend 12 and the side of the first adhesive tape 2 away from the first arcuate bend 12 is F (in mm). The second direction is perpendicular to the first direction. E, H, and F satisfy the following relationship: 2F + (π - 1) × H > E > π × H. In the above relationship, only the numerical value of each parameter is used in the calculation; the unit value is not involved in the calculation.

[0047] The extended dimension E of the first adhesive tape 2 refers to the actual dimension of the first adhesive tape 2 extending from one end of the first arcuate bend 12 to the other end. As shown in Figures 1 and 3, the extended dimension E of the first adhesive tape 2 is the sum of the distances E1, E2, and E3. Based on the distance between the tab 101 and the first arcuate bend 12 in the second direction, the tab 101 can be divided into a tab close to the first arcuate bend 12 and a tab far from the first arcuate bend 12. The tab close to the first arcuate bend 12 is the subject of study. This tab has two opposing ends in the second direction. The end of the tab closest to the first arcuate bend 12 is the starting point of F. The side of the first adhesive tape 2 far from the first arcuate bend 12 is in an arc shape. The vertex of the arc is the end point of F, and the distance in the second direction from the starting point to the end point is F.

[0048] By limiting E, H and F to satisfy the above relationship, not only can the first adhesive tape 2 located at the outermost layer be prevented from wrinkling and aggravating the corner damage, but it can also ensure that the projections of the first adhesive tape and the second adhesive tape do not overlap with the projections of the positive and negative electrode ears, thereby avoiding the energy density loss caused by thickness superposition.

[0049] In the present disclosure, the electrode assembly 1 is formed by stacking and winding a negative electrode sheet 103, a separator 104, and a positive electrode sheet 102. The negative electrode sheet 103 includes at least a negative electrode current collector 1031 and a negative electrode active material layer 1032 disposed on at least one functional surface of the negative electrode current collector 1031. The tensile strength s of the negative electrode current collector 1031 in the longitudinal direction satisfies 50 MPa ≤ s ≤ 500 MPa (e.g., 50 MPa, 100 MPa, 150 MPa, 200 MPa, 250 MPa, 300 MPa, 350 MPa, 400 MPa, 450 MPa, or 500 MPa). The higher the tensile strength of the negative electrode current collector 1031, the lower its elongation (elongation). By limiting the tensile strength of the negative electrode current collector 1031 to within this range, the ductility of the negative electrode sheet itself can be improved, preventing corner cracking. Without the first and second adhesive tapes 2 and 3 , and only limiting the tensile strength of the negative electrode current collector 1031 , the corner breakage problem still exists. The present disclosure further improves the corner breakage problem by limiting the tensile strength of the negative electrode current collector 1031 and combining the first and second adhesive tapes 2 and 3 .

[0050] The negative electrode sheet 103 includes at least a negative current collector 1031 and a negative active material layer 1032 disposed on at least one functional surface of the negative current collector 1031. The positive electrode sheet 102 includes at least a positive current collector and a positive active material layer disposed on at least one functional surface of the positive current collector. The materials of the current collector and active material layer are determined by the specific choice of electrode sheet. For example, when the electrode sheet is a negative electrode sheet, the current collector is copper foil, and the active material layer can contain graphite or other negative electrode active materials such as silicon-based materials. When the electrode sheet is a positive electrode sheet 102, the current collector is aluminum foil, and the active material layer contains positive electrode active materials such as ternary materials or lithium iron phosphate.

[0051] As shown in FIG9 and FIG10 , in some embodiments, a first groove 1033 is provided on the negative electrode active material layer 1032 at least in the first arc bending segment 12 . The depth of the first groove 1033 is not greater than the thickness of the negative electrode active material layer 1032 .

[0052] In this way, the first groove 1033 at least provides a buffer space for the expansion of the first arc bending section 12, solves the problem of excessive extension of the pole piece along the first direction, avoids the winding core from loosening, and also prevents the corner of the aluminum-plastic film from being damaged.

[0053] The first groove 1033 can be provided on the active material layer on one side of the negative electrode current collector 1031, or can be provided on the active material layers on both sides of the negative electrode current collector 1031. In some embodiments, at the first arc-bent segment 12, the ratio of the orthographic projection area of ​​the first groove 1033 on the negative electrode current collector 1031 to the orthographic projection area of ​​the negative electrode active material layer 1032 on the negative electrode current collector 1031 is (0.04-0.13):1, for example, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, or 0.13:1.

[0054] In some embodiments, the negative electrode active material layer 1032 of the straight section 11 is provided with a first groove 1033. The first groove 1033 is a strip-shaped groove or a dot-shaped groove. Providing the first groove 1033 in the negative electrode active material layer 1032 of the straight section 11 increases the exposed sites of the negative electrode active material layer 1032, thereby increasing the contact area between the electrolyte and the negative electrode sheet. This helps increase the electrolyte infiltration rate of the negative electrode sheet, improves the ion and electron transmission rate, and helps improve the kinetic performance of the negative electrode sheet, thereby improving the electrochemical performance of the battery. The depth of the first groove 1033 refers to the dimension of the first groove 1033 in the thickness direction of the negative electrode current collector.

[0055] The shape of the first groove 1033 on the side of the negative active material layer 1032 away from the negative current collector 1031 can be at least one of a circle and a rectangle. The first groove 1033 can extend along the length direction or the width direction of the negative current collector. In some embodiments, the shape of the first groove 1033 on the side of the negative active material layer 1032 away from the negative current collector 1031 is a strip (i.e., a narrow and long rectangle), and there are multiple first grooves 1033; multiple first grooves 1033 are spaced apart along the length direction of the negative current collector 1031, and each first groove 1033 extends along the width direction of the negative current collector 1031; the concave size of the first groove 1033 in the thickness direction of the negative current collector 1031 is h, and the size of the first groove 1033 in the length direction of the negative current collector 1031 is L, both in μm; wherein h, L and s satisfy the following relationship: 0.03MPa / μm 2 ≤s / (h×L)≤0.75MPa / μm 2 , for example 0.03MPa / μm 2 , 0.05MPa / μm 2 , 0.1MPa / μm 2 , 0.15MPa / μm 2 , 0.2MPa / μm 2 , 0.25MPa / μm 2 , 0.3MPa / μm 2 , 0.35MPa / μm 2 , 0.4MPa / μm 2 , 0.45MPa / μm 2 , 0.5MPa / μm 2 , 0.55MPa / μm 2 , 0.6MPa / μm 2 , 0.65MPa / μm 2 , 0.7MPa / μm 2 or 0.75MPa / μm 2 The first groove 1033 provides space for the expansion of the negative electrode active material, thereby reducing the elongation of the negative electrode sheet. At the same time, the higher the tensile strength of the negative electrode current collector 1031, the smaller its elongation. During the expansion process, the negative electrode active material drives the elongation of the negative electrode sheet to gradually decrease. By limiting h, L, and s to meet the above relationship, the relationship between the elongation of the negative electrode sheet and the space provided by the first groove 1033 can be balanced, thereby further preventing the winding of the core from loosening and reducing corner damage.

[0056] In the present disclosure, as shown in Figure 5, at the innermost side of the electrode assembly 1, the negative electrode sheet 103 includes a first negative electrode straight portion 1001 located in the straight section 11, a second negative electrode straight portion 1003 and a first negative electrode bent portion 1002 located in the second arc bent section 13; the first negative electrode straight portion 1001, the first negative electrode bent portion 1002 and the second negative electrode straight portion 1003 are connected in sequence; the positive electrode sheet 102 includes a first positive electrode straight portion 1004 located in the straight section 11; the first positive electrode straight portion 1004 is located on the outside of the second negative electrode straight portion 1003; the maximum dimension of the head of the negative electrode active material layer 1032 on the first negative electrode straight portion 1001 and the first negative electrode bent portion 1002 in the second direction is m1, and the maximum dimension of the head of the positive electrode active material layer on the first positive electrode straight portion 1004 and the first negative electrode bent portion 1002 in the second direction is m2, where 0<m1≤m2.

[0057] At the innermost side of the winding structure of the electrode assembly 1, along the winding direction, the negative electrode sheet 103 has a first negative electrode straight portion 1001, a first negative electrode bent portion 1002 and a second negative electrode straight portion 1003 connected in sequence; the positive electrode sheet 102 has a first positive electrode straight portion 1004. At this time, the first positive electrode straight portion 1004 is located on the outside of the second negative electrode straight portion 1003. It can also be understood that the head of the first positive electrode straight portion 1004 is the starting end of the winding of the positive electrode sheet 102, and the head of the first negative electrode straight portion 1001 is the starting end of the winding of the negative electrode sheet 103 (which is also the starting end of the winding of the electrode assembly 1).

[0058] The maximum size of the head of the negative electrode active material layer 1032 on the first negative electrode straight portion 1001 and the first negative electrode bent portion 1002 in the second direction refers to the plane where the head of the negative electrode active material layer 1032 on the first negative electrode straight portion 1001 is located is surface a, and the plane where the arc-shaped top surface of the first negative electrode bent portion 1002 is located is surface b, and the distance from surface a to surface b in the second direction is m1; similarly, the maximum size of the head of the positive electrode active material layer on the first positive electrode straight portion 1004 and the first negative electrode bent portion 1002 in the second direction is m2. When 0<m1≤m2 is satisfied, that is, the negative electrode active material layer on the first negative electrode straight portion 1001 is The positive electrode active material layer 1032 and the positive electrode active material layer on the first positive electrode straight portion 1004 are spaced apart on the first plane, which avoids the thickness step generated in the innermost area and ensures the uniformity of the core thickness. In addition, if there are long thickness steps at different positions of the core, in order to make the step area bond more tightly, it is necessary to apply greater pressure during hot pressing and forming of the core. Excessive pressure can easily cause the extension of the electrode in all directions, resulting in loosening and deformation of the core and cracking of the aluminum-plastic film. Therefore, the present disclosure can ensure the uniformity of the core thickness and balance the thickness by limiting 0<m1≤m2, further avoiding problems such as loosening and deformation of the core and damage to the corners of the aluminum-plastic film.

[0059] At the outermost side of the electrode assembly 1, the positive electrode sheet 102 includes a positive electrode single-sided empty foil area 1005 and a positive electrode double-sided empty foil area 1006, which are partially located in the second arc bending section 13. The positive electrode double-sided empty foil area 1006 is located on the outside of the positive electrode single-sided empty foil area 1005; the surface of the positive electrode single-sided empty foil area 1005 is provided with a first termination glue 4; the first termination glue 4 exceeds the edge of the electrode assembly 1 in the first direction, and the first termination glue 4 extends out of the edge of the winding tail end 1007 in the second direction.

[0060] Empty foil refers to the current collector where the active material layer has been removed to expose the current collector surface. Single-sided empty foil refers to the current collector where the active material layer has been removed from one functional surface, while double-sided empty foil refers to the current collector where the active material layer has been removed from both functional surfaces.

[0061] At the outermost side of the wound structure of the electrode assembly 1, the positive electrode sheet 102 includes a positive electrode single-sided empty foil area 1005 and a positive electrode double-sided empty foil area 1006, which are partially located in the second arc bend section 13. It can also be understood that the positive electrode single-sided empty foil area 1005 and the positive electrode double-sided empty foil area 1006 are partially located in the second arc bend section 13, and the remaining portion extends to the straight section 11. At this time, the positive electrode double-sided empty foil area 1006 is located outside the positive electrode single-sided empty foil area 1005, and the side of the positive electrode double-sided empty foil area 1006 away from the positive electrode single-sided empty foil area 1005 is the outermost surface of the electrode assembly 1. It can also be understood that the portion of the positive electrode double-sided empty foil area 1006 extending to the straight section 11 is the winding end of the positive electrode sheet 102 (which is also the winding end 1007 of the electrode assembly 1).

[0062] The surface of the positive electrode single-sided empty foil area 1005 is located away from the winding center of the winding structure. A first stopper glue 4 is provided on this surface for insulation and securing the winding core. The first stopper glue 4 and the electrode assembly 1 have two edges disposed opposite each other along the second direction. Both edges of the first stopper glue 4 extend beyond the edge of the electrode assembly 1. This ensures that the first stopper glue 4 extends beyond the edge of the electrode assembly 1 in the first direction. This allows the portion of the first stopper glue 4 that extends beyond the electrode assembly 1 to cooperate with the first adhesive tape 2 and the second adhesive tape 3 to form a flexible buffer between the electrode assembly 1 and the aluminum-plastic film, further improving the safety performance of the battery.

[0063] The first termination glue 4 extends beyond the edge of the electrode assembly 1 in the first direction, and extends beyond the edge of the winding end 1007 in the second direction. The first termination glue 4 and the winding end 1007 each have an edge along the first direction, and the edge of the first termination glue 4 extends beyond the edge of the winding end 1007, so that the first termination glue 4 extends beyond the edge of the winding end 1007 in the second direction. This allows the portion of the first termination glue 4 that extends beyond the winding end 1007 to secure the winding core and the aluminum-plastic film, preventing the winding core from shifting within the aluminum-plastic film, thereby avoiding cracking and deformation of the winding core and damage to the aluminum-plastic film.

[0064] The present disclosure does not limit the size of the first end glue 4. In some embodiments, the orthographic projection of the first end glue 4 on the first plane in the second direction is P, and the size of the winding core in the second direction is W. P and W satisfy the following relationship: P = (0.5-1)W, where 10mm < P < 40mm (for example, 11mm, 15mm, 20mm, 25mm, 30mm, 35mm, or 39mm). By limiting the size of the first end glue 4, it is ensured that the first end glue 4 extends beyond the edge of the winding end 1007 after crossing the second arc bend section 13.

[0065] In some embodiments, a second termination glue 5 is provided on one surface of the positive electrode double-sided empty foil area 1006 close to the positive electrode single-sided empty foil area 1005; the second termination glue 5 exceeds the edge of the electrode assembly 1 in the first direction.

[0066] The positive electrode double-sided empty foil area 1006 has two opposing surfaces, with a second stopper 5 disposed on the surface near the winding center for insulation and securing the winding core. The second stopper 5 and the electrode assembly 1 have two opposing edges along the second direction, with both edges of the second stopper 5 extending beyond the edge of the electrode assembly 1. This ensures that the second stopper 5 extends beyond the edge of the electrode assembly 1 in the first direction, allowing the portion of the second stopper 5 extending beyond the electrode assembly 1 to cooperate with the first tape 2, the second tape 3, and the first stopper 4 to form a flexible buffer between the electrode assembly 1 and the aluminum-plastic film, further enhancing the safety performance of the battery.

[0067] As shown in Figure 8, in some embodiments, a hot melt adhesive 41 is provided on the outermost side of the winding tail end 1007 of the electrode assembly 1, a part of the hot melt adhesive 41 is located on the side surface of the positive electrode double-sided empty foil area away from the positive electrode single-sided empty foil area, and the other part is located on the positive electrode single-sided empty foil area; the orthographic projection of the first termination adhesive 4 on the first plane covers the orthographic projection of the hot melt adhesive 41 on the first plane; the ratio of the orthographic projection area of ​​the hot melt adhesive 41 on the first plane to the orthographic projection area of ​​the core on the first plane is G, 30% <G <70%, for example, 31%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 69%.

[0068] As shown in Figure 6, the orthographic projection of the first stop glue 4 on the first plane overlaps the orthographic projection of the hot melt adhesive 41 on the first plane. The main function of the hot melt adhesive 41 is to fix the tail end of the electrode assembly and to fix the position of the winding core and the aluminum-plastic film to prevent displacement. In addition, when the above-mentioned projection relationship is satisfied, the orthographic projection of the hot melt adhesive 41 on the first plane can be ensured to not exceed the orthographic projection of the first stop glue 4 on the first plane. This prevents the hot melt adhesive from directly contacting the positive electrode current collector provided with the positive electrode active material layer and causing the positive electrode sheet 102 to tear.

[0069] The orthographic projection area of ​​the hot melt adhesive 41 on the first plane is 30% to 70% of the orthographic projection area of ​​the core on the first plane. By limiting the coverage area of ​​the hot melt adhesive, the thickness of the core is prevented from being superimposed due to a large hot melt adhesive application area.

[0070] As shown in Figures 7 and 8, to prevent the core thickness from overlapping due to the orthographic projection of the hot melt adhesive 41 on the first plane overlapping with the area where the tab 101 is located, in some embodiments, as shown in Figure 7, a second groove 1034 is provided on the active material layer located opposite the tab 101. The depth of the second groove 1034 does not exceed that of the active material layer. A third adhesive tape 6 is provided on the second groove 1034. The orthographic projection of the third adhesive tape 6 on the first plane is flush with the orthographic projection of the second groove 1034 on the first plane. The following relationship is satisfied: the thickness of a single active material layer > the depth of the second groove 1034 ≥ the sum of the thicknesses of the second adhesive tape 3, the third adhesive tape 6, and the hot melt adhesive. By providing the second groove 1034 in the tab area, the core thickness from overlapping due to the orthographic projection of the hot melt adhesive 41 on the first plane overlapping with the area where the tab is located can be prevented.

[0071] There are typically two tabs 101, each located in the tab region of the straight section 11. The second groove 1034 is located in the active material layer of the other electrode sheet located opposite the tab region, and the size of the second groove 1034 is substantially the same as that of the tab region. In one embodiment, as shown in Figures 7 and 8 , a positive electrode sheet is provided with a positive tab, with positive tab protective adhesive applied on both sides of the positive tab. The negative electrode sheets on opposite sides of the positive tab are provided with positive tab insulating adhesive, and the second adhesive tape 3 is the positive tab protective adhesive. A negative electrode sheet is provided with a negative tab, with negative tab protective adhesive applied on both sides of the negative tab. The positive electrode sheets on opposite sides of the negative tab are provided with negative tab insulating adhesive. The second groove 1034 is provided in the negative active material layer on both sides of the positive tab, and the third adhesive tape 6 is the positive tab insulating adhesive.

[0072] Among them, the thickness of the single-layer active material layer refers to the coating thickness of the active material layer on one side of the current collector; the depth of the second groove 1034 refers to the concave size of the second groove 1034 in the thickness direction of the current collector, the thickness of the second adhesive tape 3 refers to the size of the second adhesive tape 3 in the thickness direction of the current collector, the thickness of the third adhesive tape 6 refers to the size of the third adhesive tape 6 in the thickness direction of the current collector, and the thickness of the hot melt adhesive 41 refers to the size of the hot melt adhesive 41 in the thickness direction of the current collector.

[0073] The present disclosure does not limit the specific type of negative electrode active material layer 1032. For example, in some embodiments, the negative electrode active material layer 1032 includes a graphite-doped silicon-carbon material, where the doping amount of the silicon-carbon material is K, 1% ≤ K ≤ 30%, for example, 1%, 5%, 10%, 15%, 20%, 25%, or 30%. By limiting the above materials, the energy density of the battery can be effectively improved. Combined with the arrangement of the first and second adhesive tapes 2 and 3, both the energy density and safety performance of the battery can be improved.

[0074] In the above embodiment, the silicon-carbon material undergoes significant expansion during the charge and discharge process, causing significant lateral and longitudinal expansion of the electrode. In some embodiments, the silicon-carbon material has a particle size of D1; h, L, and D1 satisfy the following relationship: L ≥ 2D1, h ≥ D1. By defining this relationship, sufficient space is provided for the negative electrode material to release, preventing excessive expansion of the electrode and the resulting cracking of the aluminum-plastic film.

[0075] In some embodiments, 100 μm ≥ L ≥ 50 μm (for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm) ensures that there is sufficient space to accommodate the expansion of the silicon-carbon material during the cyclic charge and discharge process, reduces the elongation of the negative electrode sheet in the first direction, and prevents the electrode sheet from extending too much and breaking the aluminum-plastic film, causing corner cracks.

[0076] In some embodiments, 5 μm≤D1≤15 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.

[0077] In some embodiments, the silicon-carbon material includes a porous carbon matrix and nano-silicon materials located in the pores of the porous carbon matrix.

[0078] In some embodiments, 20 μm ≥ L ≥ 10 μm, to prevent the silicon-carbon material from becoming too hard after expansion and being exposed, thereby puncturing the diaphragm and avoiding a short circuit.

[0079] In the present disclosure, the negative electrode active material layer 1032 further includes a negative electrode additive, such as at least one of a negative electrode conductor, a negative electrode binder, and a negative electrode dispersant. The material selection and amount of the negative electrode additive are conventionally selected in the art. The positive electrode active material layer further includes a positive electrode additive, such as a positive electrode conductor and / or a positive electrode binder. The material selection and amount of the positive electrode additive are conventionally selected in the art.

[0080] A second aspect of the present disclosure provides a battery, comprising the winding core of the first aspect and an aluminum-plastic film, wherein the aluminum-plastic film encloses a receiving cavity, and the winding core is located in the receiving cavity.

[0081] By installing the winding core and protective circuitry inside the aluminum-plastic film, a battery for charge and discharge is formed. The quality of the winding core directly determines the quality of the battery. Due to the use of the aforementioned electrode sheet, the battery disclosed herein exhibits excellent resistance to corner breakage and other issues.

[0082] The present disclosure is further illustrated below through specific examples and comparative examples.

[0083] Example 1

[0084] 1. Preparation of negative electrode sheet

[0085] (1) Graphite doped with 10% silicon-carbon material by mass (the total mass ratio of silicon-carbon material and graphite is 97.2%), 0.05% negative electrode conductive agent (carbon nanotubes), 0.35% negative electrode dispersant (lithium carboxymethyl cellulose) and 2.4% negative electrode binder (polyacrylic acid) are dissolved in deionized water to obtain a negative electrode slurry; the negative electrode slurry is coated on both surfaces of a negative electrode current collector (copper foil) with a thickness of 5 μm, and a negative electrode sheet with a thickness of 100 μm is obtained after rolling; wherein the particle size D1 of the silicon-carbon material is 10 μm, and the tensile strength s of the negative electrode current collector in the longitudinal direction is 300 MPa;

[0086] (2) The active material layer on the negative electrode sheet on both sides of the negative electrode current collector is punched by laser to form a first strip-shaped groove 1033, wherein on one side of the negative electrode current collector, the ratio of the orthographic projection area of ​​the first groove 1033 on the negative electrode current collector to the orthographic projection area of ​​the active material layer on the negative electrode current collector is 0.07:1. Specifically, the active material layer is grooved every 1.2 mm along the length direction of the negative electrode current collector. The dimension h of the first groove 1033 in the thickness direction of the current collector is 15 μm, and the dimension L of the first groove 1033 in the length direction of the current collector is 80 μm.

[0087] (3) A slot of fixed size is set at a certain position of the negative electrode sheet, and the copper-nickel-plated electrode tab (negative electrode tab) is welded in this slot by laser or ultrasonic welding, and a second adhesive tape 3 is affixed to the electrode tab; in addition, a second groove 1034 is cleaned in the welding area of ​​the positive electrode tab at the position of the positive projection of the adjacent negative electrode sheet. The size of the second groove 1034 in the third direction is 30 μm, and a third adhesive tape 6 is affixed to the second groove 1034.

[0088] 2. Preparation of positive electrode

[0089] (1) 97.6% by mass of lithium cobalt oxide, 1% of a positive electrode conductive agent (conductive carbon black), and 1.4% of a positive electrode binder (polyvinylidene fluoride) are dissolved in N-methylpyrrolidone to obtain a positive electrode slurry; the positive electrode slurry is coated on both surfaces of an 8 μm thick aluminum foil, and rolled to obtain a positive electrode sheet with a thickness of 70 μm. A slot of a fixed size is set at a certain position of the positive electrode sheet as a positive electrode tab welding area, and the positive electrode tab is welded in the slot by laser or ultrasonic welding, and a second adhesive tape 3 is affixed to the tab;

[0090] A first termination glue 4 and a second termination glue 5 are respectively affixed to the empty foil area of ​​the positive electrode sheet; the dimension P of the orthographic projection of the first termination glue 4 on the first plane in the second direction is 35 mm, and the thickness of the first termination glue 4 is 12 μm; the dimension P of the orthographic projection of the second termination glue 5 on the first plane in the second direction is 15 mm, and the thickness of the second termination glue 5 is 12 μm;

[0091] 3. Preparation of batteries

[0092] (1) Using a polyethylene (PE) porous polymer film as a diaphragm, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order and wound to form an electrode assembly 1 as shown in Figures 3, 4, and 8; a first adhesive tape 2 is affixed to the first arc bending section 12, wherein the extension dimension E of the first adhesive tape is 10 mm, and the two edges of the first adhesive tape 2 respectively exceed the edge of the electrode assembly by a dimension A of 0.5 mm in the first direction, and the second adhesive tape 3 exceeds the edge of the electrode assembly by a dimension B of 0.5 mm in the first direction, and the positive projection of the first adhesive tape 2 on the first plane is spaced from the positive projection of the electrode ear 101 on the first plane, and hot melt adhesive is affixed. 41 is obtained after winding a core having a certain size; and during the winding process, a negative electrode active material layer is present on the first negative electrode straight portion 1001, the first negative electrode bent portion 1002, and the second negative electrode straight portion at the first fold of the negative electrode sheet, and m1=2mm is satisfied on the first negative electrode straight portion 1001; a positive electrode active material layer is present on the first positive electrode straight portion 1004 at the first fold of the positive electrode sheet, and m2=4mm is satisfied; the orthographic projection area of ​​the hot melt adhesive 41 on the first plane is 50% of the orthographic projection area of ​​the core on the first plane; the size of the hot melt adhesive 41 in the second direction is 20mm, and the size in the first direction is 60mm;

[0093] (2) Preparation of electrolyte: In a dry argon environment, lithium hexafluorophosphate (LiPF6) was added to a solvent solution of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1, and the mixture was uniformly mixed, wherein the concentration of LiPF6 was 1.12 mol / L, and then 10 wt% of fluoroethylene carbonate (FEC) was added and mixed uniformly to obtain an electrolyte;

[0094] (3) The core is encapsulated in the punched hole of the aluminum-plastic film (the aluminum-plastic film comprises an outer layer of nylon, a middle layer of Al, and an inner layer of PP). After the core is dried, the electrolyte is injected and encapsulated. After formation, secondary sealing, sorting, and OCV, a battery is obtained, and the electrical performance of the battery is tested.

[0095] Example 2

[0096] The preparation process is basically the same as that of Example 1, except that the extended dimension E of the first adhesive tape 2 is 18 mm, and the first adhesive tape 2 partially overlaps with the orthographic projection of the tab 101 on the first plane. Other conditions remain unchanged to obtain the battery of this embodiment.

[0097] Example 3

[0098] The preparation process is basically the same as that of Example 1, except that in this embodiment, no active material layer is set on the first negative electrode straight portion 1001 and the first negative electrode bent portion 1002 (i.e., m1=0), and they are empty copper foils. Other conditions remain unchanged to obtain the battery of this embodiment.

[0099] Example 4

[0100] The preparation process is basically the same as that of Example 1, except that the tensile strength s of the negative electrode current collector in the length direction of this embodiment is 50 MPa, the dimension h of the first groove 1033 in the thickness direction is 5 μm, and other conditions remain unchanged to obtain the battery of this embodiment.

[0101] Example 5

[0102] The preparation process is basically the same as that of Example 1, except that the negative electrode sheet is not provided with the second groove 1034. Other conditions remain unchanged to obtain the battery of this embodiment.

[0103] Example 6

[0104] The preparation process is basically the same as that of Example 1, with the difference that, during the preparation process of the battery, the first fold of the negative electrode sheet in this embodiment, the first negative electrode straight portion 1001 and the first negative electrode bent portion 1002 are not provided with an active material layer, but are empty copper foils, and the maximum dimension of the head of the negative electrode active material layer on the second negative electrode straight portion 1003 and the side of the first negative electrode bent portion 1002 away from the winding center is 2 mm, that is, m1 = -2 mm. Other conditions remain unchanged, and the battery of this embodiment is obtained.

[0105] Example 7

[0106] The preparation process is basically the same as that of Example 1, except that, during the preparation of the battery, the dimension P of the orthographic projection of the first termination glue 4 of this embodiment on the first plane in the second direction is 15 mm, and other conditions remain unchanged to obtain the battery of this embodiment.

[0107] Example 8

[0108] The preparation process is basically the same as that of Example 1, except that, during the preparation process of the battery, the orthographic projection area of ​​the hot melt adhesive 41 of this embodiment on the first plane is 10% of the orthographic projection area of ​​the core on the first plane. Other conditions remain unchanged, and the battery of this embodiment is obtained.

[0109] Example 9

[0110] The preparation process is basically the same as that of Example 1, except that, during the preparation of the negative electrode sheet, the tensile strength s of the negative electrode current collector in the length direction of this embodiment is 50 MPa, the depth h of the first groove 1033 on the negative electrode sheet is 5 μm, and the dimension L of the first groove 1033 in the first direction is 15 μm; other conditions remain unchanged, and the battery of this embodiment is obtained.

[0111] Example 10

[0112] The preparation process is basically the same as that of Example 1, except that during the preparation of the negative electrode sheet, graphite is directly dissolved in deionized water to obtain the negative electrode slurry of this embodiment. Other conditions remain unchanged to obtain the battery of this embodiment.

[0113] Example 11

[0114] The preparation process is basically the same as that of Example 1, except that, during the preparation process of the battery, the dimension A of the first adhesive tape 2 protruding from the electrode assembly set in the first arc bending section 12 of this embodiment is 4 mm, and other conditions remain unchanged to obtain the battery of this embodiment.

[0115] Example 12 Group

[0116] The preparation process of this group of examples is basically the same as that of Example 1, except that the particle size of the silicon-carbon material is changed during the preparation of the battery, while the other conditions remain unchanged, as follows:

[0117] In Example 12a, the particle size D1 of the silicon-carbon material is 5 μm;

[0118] In Example 12b, the particle size D1 of the silicon-carbon material is 15 μm.

[0119] Example 13 Group

[0120] The preparation process of this group of examples is basically the same as that of Example 1. The difference is that, during the preparation of the battery, the depth h of the first groove 1033 on the negative electrode sheet and the dimension L of the first groove 1033 in the first direction are changed to control s / (h×L), as follows:

[0121] Example 13a, h is 7 mm, L is 60 mm; s / (h×L) is 0.714;

[0122] In Example 13b, h is 35 mm, L is 200 mm, and s / (h×L) is 0.04.

[0123] The above embodiments all satisfy: 0<J<60mm, 2F+(π-1)×H>E>π×H, and P=(0.5~1)W.

[0124] Comparative Example 1

[0125] The preparation process is basically the same as that of Example 1, except that the tensile strength s of the negative electrode current collector in the longitudinal direction of this comparative example is 50 MPa, and the first groove 1033 is not provided on the surface of the negative electrode sheet of this comparative example; during the preparation process of the battery, the first arc bending section 12 of this comparative example is not provided with the first adhesive tape 2, and other conditions remain unchanged to obtain the battery of this comparative example.

[0126] Comparative Example 2

[0127] The preparation process is basically the same as that of Example 1, except that in this comparative example, the first adhesive tape 2 does not extend beyond the edge of the electrode assembly in the first direction, that is, A=0.

[0128] Comparative Example 3

[0129] The preparation process is basically the same as that of Example 1, except that in this comparative example, the second adhesive tape 3 does not extend beyond the edge of the electrode assembly in the first direction, that is, B=0.

[0130] The main parameters in the above embodiments and comparative examples can be seen in Table 1.

[0131] Test example

[0132] Tensile strength test: Use a fixed-size cutter to cut the negative electrode current collector into samples with a width of 15 mm and a length of more than 50 mm. Use a WD-D3 electronic universal testing machine (precision of 0.5 level, accuracy of ±1% of the indicated value) with a gauge length of 50 mm and a speed of 50 mm / min to perform the tensile strength test.

[0133] Appearance test during the cycle: In a constant temperature room at 45°C, use 0.5C constant current and constant voltage to the upper limit voltage (4.53V), 0.05C cut-off, stand for 5 minutes, 0.5C discharge to 3.0V, cycle 500 times, and observe whether there are any corner damage (corner cracks) at the four corners of the deep pit surface of the aluminum-plastic film opposite to the four corners of the core.

[0134] Elongation test: The coils after 500 cycles were disassembled, and fixed-size cutters were used to cut the negative electrode sheets after the cycles into samples with a width of 15 mm and a length of more than 50 mm. The elongation test was performed using a WD-D3 electronic universal testing machine (with a precision of 0.5 and an accuracy of ±1% of the indicated value) with a gauge length of 50 mm and a speed of 50 mm / min.

[0135] After the battery was dropped 10 times from a height of 1 meter, the core was disassembled and the structural integrity of the core was observed. The test results are shown in Table 2.

[0136] Table 1

[0137] Table 2

[0138] According to Table 1 and Table 2, the battery of the embodiment has a lower pole piece elongation after cycling, and can ensure the integrity of the core structure, and the aluminum-plastic film has lower corner cracks. This is because the present disclosure sets a first adhesive tape on the first arc bending section of the electrode assembly, sets a second adhesive tape on the pole ear, and makes the first adhesive tape and the second adhesive tape protrude from the edge of the electrode assembly. In this way, the setting of the first adhesive tape can effectively prevent the electrolyte from corroding the outermost aluminum layer and causing the aluminum layer of the arc section to break first under the action of stress, and even if the aluminum layer of the arc section breaks, the first adhesive tape can effectively connect the two sides of the aluminum layer at the break, effectively avoiding the loosening of the core winding; secondly, when the outermost side of the first arc bending section of the core breaks and causes the inside of the core to loosen, the second adhesive tape can, on the one hand, Under the action of its own elastic deformation, it effectively offsets the gap formed by loosening, reduces the loose displacement of the arc section near the tab groove, and thus reduces the displacement that causes the active material particles in this area to scratch the diaphragm. On the other hand, the second adhesive tape covers the active material in the arc section, which further reduces the probability of the active material particles in this area scratching the diaphragm, thereby ensuring the integrity of the core structure. In addition, when aluminum-plastic film packaging is used, the parts of the first and second adhesive tapes that extend beyond the edge of the electrode assembly can directly contact the aluminum-plastic film, forming a flexible buffer between the electrode assembly and the aluminum-plastic film to avoid corner damage.

[0139] Comparing the examples and comparative examples shows that, when the tensile strength of the negative electrode current collector is consistent, the use of the first and second adhesive tapes can significantly reduce the probability of corner cracks and ensure the integrity of the core structure. Comparing Example 4 with Comparative Example 1 shows that due to the low tensile strength of the negative electrode current collector and the fact that the first groove is only 5μm in the thickness direction, the final electrode sheet elongation is 2.2%. Without the first adhesive tape as a side tape, Comparative Example 1 has 100% corner cracks, while Example 4, with the first adhesive tape as a side tape, reduces the corner cracks to 50%.

[0140] The above describes in detail the preferred embodiments and experimental verifications of the present disclosure. It should be understood that ordinary technicians in this field can make many modifications and variations based on the concepts of this disclosure without creative effort. Therefore, any technical solutions that can be obtained by those skilled in the art based on the concepts of this disclosure through logical analysis, reasoning, or limited experimentation on the basis of existing technologies should be within the scope of protection of this disclosure.

Claims

1. A winding core, characterized in that: It includes an electrode assembly, a first adhesive tape and a second adhesive tape; The electrode assembly includes a straight section and a first arc bent section and a second arc bent section respectively located at both ends of the straight section; a tab is provided in the straight section, and the winding end of the electrode assembly is located in the second arc bent section; The first adhesive tape is arranged at the outermost side of the first arc bending section, and the second adhesive tape covers the tab along the orthographic projection of the second adhesive tape in the thickness direction of the winding core, and extends to the first arc bending section; Wherein, the first adhesive tape and the second adhesive tape both extend beyond the edge of the electrode assembly in a first direction, and the first direction is the width direction of the electrode sheet.

2. The winding core according to claim 1, characterized in that Along the winding center of the winding core pointing to the outer side of the winding core, the winding core includes multiple folded pole pieces, and the pole ear is provided on the pole piece between the first quarter folded pole piece and the second quarter folded pole piece.

3. The winding core according to claim 1 or 2, characterized in that: The first adhesive tape extends beyond the edge of the electrode assembly by a dimension A in the first direction, and the second adhesive tape extends beyond the edge of the electrode assembly by a dimension B in the first direction; A and B satisfy the following relationship: 0≤BA≤2mm; Preferably, 0<A≤3mm, 0<B≤3mm.

4. The winding core according to any one of claims 1 to 3, characterized in that The distance between the orthographic projection of the first adhesive tape on the first plane and the orthographic projection of the electrode tab on the first plane is J, J satisfies 0<J<60mm, and the first plane is a plane parallel to the straight section in the electrode assembly.

5. The winding core according to any one of claims 1 to 4, characterized in that: The extended dimension of the first adhesive tape is E, in mm; the thickness of the winding core is H, in mm; and the maximum dimension in the second direction between the end of the tab closest to the first arc-shaped section and the side of the first adhesive tape away from the first arc-shaped section is F, in mm; wherein the second direction is perpendicular to the first direction; E, H and F satisfy the following relationship: 2F+(π-1)×H>E>π×H.

6. The winding core according to any one of claims 1 to 5, characterized in that The electrode assembly is formed by stacking and winding a negative electrode sheet, a separator and a positive electrode sheet; The negative electrode sheet at least comprises a negative electrode current collector and a negative electrode active material layer provided on at least one functional surface of the negative electrode current collector; The tensile strength s of the negative electrode current collector in the length direction satisfies 50 MPa≤s≤500 MPa.

7. The winding core according to claim 6, characterized in that A first groove is provided on the negative electrode active material layer at least in the first arc bending section, and the depth of the first groove is not greater than the thickness of the negative electrode active material layer; Preferably, the ratio of the orthogonal projection area of ​​the first groove on the negative electrode current collector to the orthogonal projection area of ​​the negative electrode active material layer on the negative electrode current collector is (0.04-0.13):1; Preferably, the first groove is provided on the negative electrode active material layer of the straight section, and the first groove is a strip-shaped groove or a dot-shaped groove.

8. The winding core according to claim 7, characterized in that The first groove is in a strip shape on the side of the negative electrode active material layer away from the negative electrode current collector, and there are a plurality of the first grooves; A plurality of first grooves are arranged at intervals along the length direction of the negative electrode current collector, and each first groove extends along the width direction of the negative electrode current collector; The concave dimension of the first groove in the thickness direction of the negative electrode current collector is h, and the dimension of the first groove in the length direction of the negative electrode current collector is L, both in μm; Among them, h, L and s satisfy the following relationship: 0.03MPa / μm 2 ≤s / (h×L)≤0.75MPa / μm 2 .

9. The winding core according to claim 6, characterized in that At the innermost side of the electrode assembly, the negative electrode sheet includes a first negative straight portion located in the straight section, a second negative straight portion, and a first negative bent portion located in the second arc bent section; the first negative straight portion, the first negative bent portion, and the second negative straight portion are sequentially connected; The positive electrode sheet includes a first positive straight portion located in the straight section; the first positive straight portion is located outside the second negative straight portion; The maximum dimension between the head of the negative electrode active material layer on the first negative electrode straight portion and the first negative electrode bent portion in the second direction is m1, and the maximum dimension between the head of the positive electrode active material layer on the first positive electrode straight portion and the first negative electrode bent portion in the second direction is m2; Where 0<m1≤m2.

10. The winding core according to claim 9, characterized in that At the outermost side of the electrode assembly, the positive electrode sheet includes a positive electrode single-sided empty foil area and a positive electrode double-sided empty foil area partially located in the second arc bending section, and the positive electrode double-sided empty foil area is located outside the positive electrode single-sided empty foil area; A first termination glue is provided on the surface of the single-sided empty foil area of ​​the positive electrode; The first termination glue exceeds the edge of the electrode assembly in the first direction, and the first termination glue extends beyond the edge of the winding tail end in the second direction.

11. The winding core according to claim 10, characterized in that The size of the orthographic projection of the first terminating adhesive on the first plane in the second direction is P, and the size of the winding core in the second direction is W, and P and W satisfy the following relationship: P = (0.5-1) W, where 10 mm < P < 40 mm; Preferably, a second stopper glue is provided on the surface of the positive electrode double-sided empty foil area close to the positive electrode single-sided empty foil area; The second termination glue exceeds the edge of the electrode assembly in the first direction.

12. The winding core according to claim 11, characterized in that A hot melt adhesive is provided on the outermost side of the winding tail end of the electrode assembly, a portion of the hot melt adhesive is located on a surface of the positive electrode double-sided empty foil area facing away from the positive electrode single-sided empty foil area, and another portion is located on the positive electrode single-sided empty foil area; the orthographic projection of the first termination adhesive on the first plane covers the orthographic projection of the hot melt adhesive on the first plane; The ratio of the orthographic projection area of ​​the hot melt adhesive on the first plane to the orthographic projection area of ​​the core on the first plane is G, and 30%<G<70%.

13. The winding core according to claim 12, characterized in that A second groove is provided on the active material layer arranged opposite to the tab; the depth of the second groove is no greater than the thickness of the active material layer, and a third adhesive tape is provided on the second groove, and the orthographic projection of the third adhesive tape on the first plane is flush with the orthographic projection of the second groove on the first plane; The following relationship is satisfied: the thickness of the single active material layer>the depth of the second groove≥the sum of the thicknesses of the second adhesive tape, the third adhesive tape and the hot melt adhesive.

14. The winding core according to any one of claims 6 to 13, characterized in that: The negative electrode active material layer comprises graphite doped with silicon-carbon material, wherein the doping amount of the silicon-carbon material is K, 1%≤K≤30%; The particle size of the silicon-carbon material is D1; ​​h, L, and D1 satisfy the following relationship: L ≥ 2D1, 100 μm ≥ L ≥ 50 μm, h ≥ D1; or, 20 μm ≥ L ≥ 10 μm; Preferably, 5 μm ≤ D1 ≤ 15 μm; Preferably, the silicon-carbon material comprises a porous carbon matrix and nano-silicon material located in the pores of the porous carbon matrix.

15. A battery, characterized in that: The winding core comprises the winding core and the aluminum-plastic film according to any one of claims 1 to 14, wherein the aluminum-plastic film encloses a receiving cavity, and the winding core is located in the receiving cavity.

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