Roll core and battery

Abstract

The utility model provides a roll core and a battery, relates to the technical field of batteries, and is used for solving the technical problem of low battery safety caused by easy lithium precipitation at the tail part of a negative electrode head of the roll core in the related art, the roll core comprises a first pole piece, a diaphragm and a second pole piece which are sequentially stacked; the first pole piece comprises a first current collector, and paste coating layers are arranged on the two surfaces of the first current collector; in the length direction of the pole piece, the head and / or the tail of the first pole piece comprises a combination area, at least one surface of the combination area comprises a first empty foil area and a first reserved pasting area, in the width direction of the pole piece, the first empty foil area is provided with a first edge, the first reserved pasting area is arranged on the first edge, and in the width direction of the pole piece, the first edge is provided with a second edge. The first empty foil area and the first reserved pasting area are arranged adjacently; the first reserved paste area is provided with first reserved paste, and the first reserved paste and the paste layer are adjacently arranged in the length direction of the pole piece. By removing the thinned areas at the head and the tail of the pole piece, lithium precipitation in the thinned areas is prevented, and the safety of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium electronic battery, and particularly to a winding core and a battery. BACKGROUND

[0002] The positive surface and the back surface of the negative plate of the lithium ion battery are provided with a coating. Due to the characteristics of the coating slurry, the end of the coating will form a casting area, so that the head and tail of the negative plate in the winding direction have a thinning area in the thickness direction. For the winding core, the thinning area is prone to cause the local capacity of the negative electrode to be less than the local capacity of the positive electrode after winding, and further cause the phenomenon of lithium precipitation at the head and tail of the negative electrode in the use process of the battery, thereby reducing the safety performance of the battery. CONTENT OF THE UTILITY MODEL

[0003] In view of the above problems, the present application provides a winding core and a battery to solve the problem that the head and tail of the negative electrode of the winding core in the related art are prone to lithium precipitation, thereby reducing the safety performance of the battery.

[0004] In order to achieve the above purpose, the present application provides the following technical scheme:

[0005] The present application provides a winding core, comprising: a first electrode plate, a diaphragm and a second electrode plate, the first electrode plate, the diaphragm and the second electrode plate are sequentially stacked, the polarity of the first electrode plate and the second electrode plate is opposite; the first electrode plate comprises a first current collector, the first current collector has opposite first and second surfaces in the thickness direction of the electrode plate, and the first and second surfaces are both provided with a coating layer; along the length direction of the electrode plate, the head of the first electrode plate and / or the tail of the first electrode plate comprises a combination area, at least one surface of the combination area comprises a first empty foil and a first reserved coating area, along the width direction of the electrode plate, the first empty foil has a first edge, the first reserved coating area is arranged at the first edge, and along the width direction of the electrode plate, the first empty foil area and the first reserved coating area are arranged adjacent to each other; the first reserved coating area is provided with a first reserved coating, and along the length direction of the electrode plate, the first reserved coating and the coating layer are arranged adjacent to each other.

[0006] In an embodiment of the present application, the combination area further comprises a second reserved coating area, the second reserved coating area is provided with the second reserved coating, the first empty foil area has a second edge which is perpendicular to the first edge, the second reserved coating is arranged close to the second edge, and the second reserved coating area and the first reserved coating area are at least partially in contact.

[0007] In an embodiment of the present application, the first empty foil area has a first width M1 along the length direction of the pole piece, 0mm < M1 < 10mm; and / or, the first reserved coating has a second width M2 along the width direction of the pole piece, 0.1mm < M2 < 1mm; and / or, the second reserved coating has a third width M3 along the length direction of the pole piece, 0.1mm < M3 < 1mm.

[0008] In an embodiment of the present application, the first pole piece further comprises a second empty foil area between the head of the first pole piece and the tail of the first pole piece; the second empty foil area comprises at least one first area and at least one second area connected in sequence, the first area has a first thickness H1 along the thickness direction of the pole piece, the second area has a second thickness H2 along the thickness direction of the pole piece, and the first thickness H1 is greater than the second thickness H2; optionally, H1 ≥ 0.7H2.

[0009] In an embodiment of the present application, the first area has a first surface roughness R1, the second area has a second surface roughness R2, and the two surfaces of the combined area have a first empty foil area arranged opposite along the thickness direction of the pole piece, the first empty foil area has a third surface roughness R3; wherein, R1 ≤ R2 ≤ R3; optionally, R2 = (1~1.25)R1; optionally, R3 = (1~2)R1.

[0010] In an embodiment of the present application, the first pole piece, the diaphragm and the second pole piece are wound around a first center surface, the surface of the first current collector facing the first center surface is the first surface, and the surface of the first current collector away from the first center surface is the second surface; the first current collector comprises a first flat section, and the combined area is on the first surface and the second surface of the first flat section; the diaphragm has a backfolding section, and the projection of at least part of the combined area of the first flat section along the thickness direction of the winding core coincides with the backfolding section.

[0011] In one embodiment of the present application, the first current collector comprises a first flat section and a first circular arc section connected to the first flat section; the first empty-foil region is located on the first surface and the second surface of the first flat section; the first region comprises a first section (1211) and a second section (1212) connected to each other, the first section (1211) is located on the first surface and the second surface of the first flat section (103), and the second section (1212) is located on the first surface of the first flat section (103); the second region comprises a first sub-region and a second sub-region connected to each other, the first sub-region is located on the second surface of the first circular arc section, and the second sub-region is located on the second surface of the first flat section; the first section on the second surface of the first empty-foil region, the second sub-region and the first sub-region are sequentially connected in the winding direction of the winding core.

[0012] In one embodiment of the present application, the first current collector further comprises a first circular arc section connected to the first flat section; the first empty-foil region is located on the first surface and the second surface of the first flat section; the first region comprises a second section located on the first surface of the first flat section; the second region comprises a first sub-region and a second sub-region connected to each other, the first sub-region is located on the second surface of the first circular arc section, and the second sub-region is located on the second surface of the first flat section; the first empty-foil region on the second surface, the second sub-region and the first sub-region are sequentially connected in the winding direction of the winding core.

[0013] In one embodiment of the present application, the first current collector further comprises a second circular arc section, a second flat section and a third flat section, the second circular arc section is located on the side of the first circular arc section away from the first central surface, the second flat section and the third flat section are respectively connected to the two ends of the second circular arc section; the second region further comprises a third sub-region and a fourth sub-region connected to each other, the third sub-region is located on the first surface of the second circular arc section, and the second surface of the second circular arc section has the paste layer; the fourth sub-region is located on the first surface of the second flat section, and the second surface of the second flat section opposite to the fourth sub-region has the paste layer; the first region further comprises a third section, at least part of the third section is located on the first surface of the second flat section, the third sub-region is connected to the third section through the fourth sub-region, and the first surface and the second surface of the third flat section both have the paste layer.

[0014] In an embodiment of the present application, the first current collector further comprises a fourth flat section, the fourth flat section is located on a side of the third flat section away from the first central plane, the fourth flat section comprises a fourth section and a fifth section connected along the length direction of the pole piece; the first surface and the second surface of the fourth section are both provided with the paste layer; the combination area further comprises a fifth sub-area, the fifth sub-area is located on the first surface and / or the second surface of the fifth section; at least one surface of the fifth sub-area comprises the first reserved paste and / or the second reserved paste.

[0015] In an embodiment of the present application, the second pole piece comprises a second current collector and a tab, the tab is connected to the second current collector; along the thickness direction of the winding core, the projection of the second sub-area on the first central plane covers the projection of the tab.

[0016] In an embodiment of the present application, the winding core further comprises an insulating adhesive tape, the insulating adhesive tape is attached to the second pole piece, along the thickness direction of the winding core, the insulating adhesive tape is opposite to the fourth flat section, and the size of the insulating adhesive tape covering the second pole piece is 0 mm to 6 mm.

[0017] In an embodiment of the present application, the thickness tolerance of the paste layer is ±3 μm.

[0018] In an embodiment of the present application, along the winding direction of the winding core, the first pole piece comprises a first bending area located at the innermost circle of the winding core, and a first flat area connected to the first bending area, along the thickness direction of the winding core, the projection of the winding starting end of the second pole piece on the first central plane is between the intersection line between the first bending area and the first flat area of the first pole piece, the distance of the withdrawal area is 0 mm to 0.2 mm along the width direction of the winding core.

[0019] The embodiments of the present application further provide a battery comprising the winding core described above.

[0020] The winding core provided by the embodiments of the present application has the following technical effects:

[0021] By cleaning, the thinning area at the head and tail of the negative pole piece is eliminated, the phenomenon of lithium precipitation in the thinning area after winding of the negative pole piece is avoided, the risk of lithium precipitation of the lithium battery is reduced under the premise of ensuring the product quality and safety, and the safety of the lithium battery is improved. Meanwhile, the first reserved paste is arranged in the area needing cleaning, so that the perforation or breakage of the edge position of the first pole piece caused by cleaning in the cleaning process is avoided; meanwhile, after cleaning is completed, the existence of the first reserved paste can also ensure that the position of the pole piece is suitable when the pole piece is cut, so that the cutting efficiency of the pole piece and the yield of the pole piece after cutting are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0023] Figure 1 It is a schematic view of the front structure of the negative plate in the related art.

[0024] Figure 2 It is a schematic view of the top structure of the negative plate in the related art.

[0025] Figure 3 It is a schematic view of the bottom structure of the negative plate in the related art.

[0026] Figure 4 It is a schematic view of the front structure of the negative plate provided by the embodiments of the present application.

[0027] Figure 5 It is a schematic view of the top structure of the negative plate provided by the embodiments of the present application. Figure 1

[0028] Figure 6 It is a schematic view of the bottom structure of the negative plate provided by the embodiments of the present application.

[0029] Figure 7 It is a schematic view of the top structure of the negative plate provided by the embodiments of the present application. Figure 2

[0030] Figure 8 It is a schematic view of the structure of the winding core provided by the embodiments of the present application.

[0031] Figure 9 It is a schematic view of the local structure of the winding core provided by the embodiments of the present application. Figure 1

[0032] Figure 10 It is a schematic view of the local structure of the winding core provided by the embodiments of the present application. Figure 2

[0033] Figure 11 It is a schematic view of the local structure of the winding core provided by the embodiments of the present application. Figure 3

[0034] Figure 12 It is a schematic view of the local structure of the winding core provided by the embodiments of the present application. Figure 4

[0035] Reference signs:

[0036] 100 - first current collector​​​​​​

[0037] 200 - First coating layer; 201 - First end; 202 - Second end;

[0038] 300 - Second coating layer; 301 - Third end; 302 - Fourth end;

[0039] 101-First reserved paste; 102-Second reserved paste; 103-First straight section; 104-First arc section; 105-Second arc section; 106-Second straight section; 107-Third straight section; 108-Fourth straight section; 150-Fifth sub-region;

[0040] 110 - First empty foil area; 120 - Second empty foil area; 130 - Winding tail end; 140 - Winding start end; 210 - Negative electrode current collector;

[0041] 121 - Zone 1; 122 - Zone 2;

[0042] 1211 - First paragraph; 1212 - Second paragraph; 1213 - Third paragraph; 1221 - First sub-section; 1222 - Second sub-section; 1223 - Third sub-section; 1224 - Fourth sub-section; 1081 - Fourth paragraph; 1082 - Fifth paragraph;

[0043] S-combination region;

[0044] 400 - First central plane;

[0045] 500-return section;

[0046] 600-diaphragm;

[0047] 700 - Second electrode;

[0048] 800 - Remove ointment area. Detailed Implementation

[0049] refer to Figures 1 to 3 The core in the related technology includes a negative electrode sheet, a separator, and a positive electrode sheet, which are stacked sequentially. The negative electrode sheet includes a negative current collector 210, which has a front and a back side along the thickness direction of the electrode sheet (z-axis shown in the figure), and both the front and back sides are provided with a paste layer; along the length direction of the electrode sheet (x-axis shown in the figure), the paste layer on the front side has a first end 201 and a second end 202, and the paste layer on the back side has a third end 301 and a fourth end 302.

[0050] The first end 201 and the third end 301 are both located at the head or tail of the negative electrode, and the second end 202 and the fourth end 302 are both located between the head and tail of the negative electrode.

[0051] Due to the characteristics of the paste and electrode foil (i.e., current collector), during coating, the end positions of the paste: the first end 201, the second end 202, the third end 301 and the fourth end 302 will experience paste flow to form a flow area. This results in thinning areas at the first end 201, the second end 202, the third end 301 and the fourth end 302 in the thickness direction of the electrode (z-axis shown in the figure). The thinning area will affect the energy density of the battery and thus lead to the risk of lithium plating.

[0052] This application embodiment cleans the areas containing the first end 201, the second end 202, the third end 301, and the fourth end 302, so that the negative electrode sheet corresponding to the casting area forms an empty foil area after cleaning. This removes the thinned area and avoids lithium plating in the thinned area after the electrode sheet is wound. While ensuring product quality and safety, it reduces the risk of lithium plating in lithium batteries and improves the safety of lithium batteries. The cleaning method in this application can be scraper cleaning or laser cleaning, which is not limited here. To ensure cleaning effect and efficiency, laser cleaning is preferred.

[0053] To make the above-mentioned objectives, features, and advantages of the embodiments of this application more apparent and understandable, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0054] In this embodiment of the application, the thickness direction of the electrode is the z-axis shown in the figure; the length direction of the electrode is the x-axis shown in the figure; and the width direction of the electrode is the y-axis shown in the figure.

[0055] refer to Figures 4 to 6 The core provided in this application includes: a first electrode, a diaphragm, and a second electrode. The first electrode, the diaphragm, and the second electrode are stacked sequentially. The polarities of the first electrode and the second electrode are opposite. The first electrode can be a negative electrode, and the second electrode can be a positive electrode.

[0056] The first electrode includes a first current collector 100, which has a first surface and a second surface opposite to each other along the thickness direction of the electrode (z-axis shown in the figure). The first surface is provided with a first paste layer 200, and the second surface is provided with a second paste layer 300.

[0057] Along the length direction of the electrode (x-axis shown in the figure), the head and / or tail of the first electrode includes a combination region S, and the first surface and / or the second surface of the combination region S includes a first empty foil region 110. The first empty foil region 110 refers to an empty foil area on at least one surface of the head and / or tail of the first electrode where no paste layer is provided.

[0058] In other words, after the cast area is removed by laser cleaning, the first empty foil area 110 is formed, thereby removing the thinned area and avoiding the phenomenon of lithium plating in the thinned area after the electrode is wound. Under the premise of ensuring product quality and safety, the risk of lithium plating in lithium batteries is reduced and the safety of lithium batteries is improved.

[0059] The first and / or second surfaces of the combination area S may further include a first reserved paste area. Along the width direction of the electrode sheet (y-axis shown in the figure), the first empty foil area 110 has a first edge, and the first reserved paste area is disposed at the first edge. Along the width direction of the electrode sheet, the first empty foil area 110 and the first reserved paste area are disposed adjacent to each other. The first reserved paste area is provided with a first reserved paste 101. Along the length direction of the electrode sheet (x-axis shown in the figure), the first reserved paste 101 and the first paste layer 200 are disposed adjacent to each other, or the first reserved paste 101 and the second paste layer 300 are disposed adjacent to each other.

[0060] In other words, by reserving a portion of the coating during the cleaning of the first end 201 and the third end 301, and performing laser cleaning on both sides of the same location at the head or tail of the first electrode, perforation or breakage of the first electrode can be avoided. This effectively prevents electrode perforation or breakage without affecting the cell thickness. Furthermore, when the electrode needs to be slit after cleaning, the reserved coating ensures slitting efficiency and electrode yield after slitting.

[0061] Continue to refer to Figures 4 to 6 In this embodiment of the application, the combination area S further includes a second reserved paste area, which is provided with a second reserved paste 102. The first empty foil area 110 has a second edge that intersects the first edge perpendicularly. The second reserved paste 102 is disposed close to the second edge, and the second reserved paste area and the first reserved paste area are at least partially in contact.

[0062] The second reserved paste 102 setting can further prevent the first electrode from being perforated or broken.

[0063] It should be noted that the composition of the first reserved coating 101 and the second reserved coating 102 is the same as that of the first coating layer 200 and the second coating layer 300.

[0064] refer to Figure 7 , Figure 7The first electrode sheet is a complete first electrode sheet, which includes a winding start end 140 and a winding end 130. The first electrode sheet is wound starting from the winding start end 140. In one embodiment of this application, the head and tail of the first electrode sheet are provided with a combination area S. The combination area S at the head of the first electrode sheet includes a first empty foil area 110 and a first reserved paste area. The first reserved paste area is provided with a first reserved paste 101. The combination area S at the tail of the first electrode sheet includes a first empty foil area 110, a first reserved paste area and a second reserved paste area. The first reserved paste area is provided with a first reserved paste 101 and the second reserved paste area is provided with a second reserved paste 102.

[0065] In another embodiment of this application, the head and tail of the first electrode are provided with a combination area S. The combination area S of the head and tail of the first electrode includes a first empty foil area 110, a first reserved paste area and a second reserved paste area. The first reserved paste area is provided with a first reserved paste 101 and the second reserved paste area is provided with a second reserved paste 102.

[0066] In another embodiment of this application, the first electrode sheet has a combination area S at both the head and tail. The combination area S at the head of the first electrode sheet includes a first empty foil area 110 and a first reserved paste area, and the first reserved paste area is provided with a first reserved paste 101. The combination area S at the tail of the first electrode sheet includes a first empty foil area 110 and a second reserved paste area, and the second reserved paste area is provided with a second reserved paste 102.

[0067] In another embodiment of this application, the head of the first electrode is provided with a combination area S, and the tail of the first electrode is an empty foil without a combination area S; wherein, the combination area S at the head of the first electrode includes a first empty foil area 110 and a first reserved paste area, and the first reserved paste area is provided with a first reserved paste 101.

[0068] In another embodiment of this application, the head of the first electrode is provided with a combination area S, and the tail of the first electrode is an empty foil without a combination area S; wherein, the combination area S at the head of the first electrode includes a first empty foil area 110, a first reserved paste area and a second reserved paste area, the first reserved paste area is provided with a first reserved paste 101, and the second reserved paste area is provided with a second reserved paste 102.

[0069] In another embodiment of this application, the head of the first electrode has a paste layer and no assembly area S is provided; the tail of the first electrode is provided with an assembly area S, wherein the assembly area S at the tail of the first electrode includes a first empty foil area 110, a first reserved paste area and a second reserved paste area, the first reserved paste area is provided with a first reserved paste 101, and the second reserved paste area is provided with a second reserved paste 102.

[0070] In another embodiment of the present application, the head of the first pole piece has a pasted layer, and the combined area S is not provided; the combined area S is provided at the tail of the first pole piece. Among them, the combined area S at the tail of the first pole piece includes a first empty foil area 110 and a second reserved pasted area, and the second reserved pasted area is provided with a second reserved paste 102.

[0071] Reference Figure 5 and Figure 6 , in the embodiment of the present application, the first empty foil area 110 has a first width M1 along the length direction of the pole piece (the x-axis shown in the figure), 0 mm < M1 < 10 mm; while ensuring that the thinned area is completely cleaned, the waste of active materials is reduced, and the battery capacity is maximally improved.

[0072] When the first width M1 is less than 10 mm, it cannot be ensured that the thinned area is completely cleaned; when the first width M1 is greater than 10 mm, the waste of active materials will be caused.

[0073] The first reserved paste 101 has a second width M2 along the width direction of the pole piece (the y-axis shown in the figure), 0.1 mm < M2 < 1 mm; on the premise of not affecting the thickness of the battery cell, the first reserved paste 101 with the second width M2 can effectively avoid perforation or breakage of the first pole piece during laser cleaning.

[0074] When the second width M2 is less than 1 mm, the content of the first reserved paste 101 is less, and it cannot play a role in protecting the first pole piece; when the second width M2 is greater than 1 mm, there will be too much paste residue in the casting area, and the effect of improving lithium deposition in the thinned area is not obvious.

[0075] The second reserved paste 102 has a third width M3 along the length direction of the pole piece (the x-axis shown in the figure), 0.1 mm < M3 < 1 mm; on the premise of not affecting the thickness of the battery cell, the second reserved paste 102 with the third width M3 can effectively avoid perforation or breakage of the first pole piece during laser cleaning.

[0076] When the third width M3 is less than 1 mm, the content of the second reserved paste 102 is less, and it cannot play a role in protecting the first pole piece; when the third width M3 is greater than 1 mm, there will be too much paste residue in the casting area, and the effect of improving lithium deposition in the thinned area is not obvious.

[0077] Continue to refer to Figures 4 to 6In this embodiment of the application, a second empty foil area 120 is further included between the head and tail of the first electrode. The second empty foil area 120 refers to an empty foil area where at least one surface is not coated with a paste layer. The second empty foil area 120 includes at least one first area 121 and at least one second area 122 connected together. The first area 121 refers to the empty foil area that has not been laser cleaned, and the second area 122 refers to the empty foil area formed after laser cleaning. The second area 122 after laser cleaning will show oxidation. Compared with the first area 121 that has not been laser cleaned, the color of the second area 122 is darker. Therefore, the second area 122 can also be called the dark area, and the first area 121 can also be called the bright area. The first area 121 and the second area 122 have obvious differences in color.

[0078] The thickness of the first region 121 along the thickness direction of the electrode (z-axis shown in the figure) is the first thickness H1, and the thickness of the second region 122 along the thickness direction of the electrode is the second thickness H2. The first thickness H1 is greater than the second thickness H2; H1≥0.7H2.

[0079] Because the second end 202 and the fourth end 302 between the head and tail of the first electrode are not aligned, the side opposite to the second end 202 is not laser-processed when cleaning the second end 202; the side opposite to the fourth end 302 is not laser-processed when cleaning the fourth end 302. Therefore, the second end 202 and the fourth end 302 do not experience the breakage or perforation caused by laser processing.

[0080] Meanwhile, under laser shock, the thickness of the second zone 122 after cleaning is less than the thickness of the uncleaned first zone 121, which reduces the thickness and weight of the battery cell without affecting subsequent battery processes.

[0081] In this embodiment, the first region 121 has a first surface roughness R1, the second region 122 has a second surface roughness R2, and when the two surfaces of the combined region S have a first empty foil region 110 facing each other along the thickness direction of the electrode sheet (z-axis shown in the figure), the first empty foil region 110 has a third surface roughness R3; wherein, R1≤R2≤R3; R2=(1~1.25)R1; R3=(1~2)R1.

[0082] The larger surface roughness of the cleaning area effectively increases the electrode surface area, improves the contact area between the electrode and the electrolyte, enhances the electrode reactivity, and increases the battery capacity and energy density. Simultaneously, the larger roughness improves the uniformity of the electrode tip, reduces stress concentration during charging and discharging, helps slow down electrode degradation, and increases electrolyte storage capacity. It also enhances the composite strength between the electrode and the separator, preventing the electrode tip from detaching from the separator during winding, avoiding contact between the first and second electrodes, and improving battery safety.

[0083] It should be noted that in this embodiment, a roughness tester (model SJ-310) is used to test the surface roughness of the area to be tested. The test method is as follows: flatten the area to be tested, align the test probe with the area to be tested, trigger the device test switch to start the test, and the test instrument sweeps across the area to be tested for a fixed distance (e.g., 1 mm) to obtain the surface roughness of the area to be tested.

[0084] refer to Figure 8 The positive and negative electrode plates of the core are wound from the inside out. The innermost circle of the core is the first circle where the positive and negative electrode plates begin to be wound. The heads of the positive and negative electrode plates are located on the innermost circle of the core, and the tails of the positive and negative electrode plates are located on the outer circle of the core.

[0085] refer to Figure 8 and Figure 9 In this embodiment, the first electrode, the separator 600, and the second electrode 700 are wound around the first center surface 400. The surface of the first current collector 100 facing the first center surface 400 is the first surface, and the surface of the first current collector 100 away from the first center surface 400 is the second surface. The first current collector 100 includes a first straight section 103, which is located at the innermost loop of the core. The combined region S is located on the first surface and the second surface of the first straight section 103. The separator 600 has a folded section 500, and the projection of at least a portion of the combined region S along the thickness direction of the core coincides with the folded section. This increases the composite strength of the combined region S and the separator 600. At the same time, the folded section 500 is a relatively thick area within the cell, and the projection of at least a portion of the combined region S along the thickness direction of the core coincides with the folded section, which can disperse the stress in this area and prevent electrode breakage.

[0086] Continue to refer to Figures 8 to 9 In this embodiment, the first current collector 100 further includes a first arc segment 104, which is the initial bending segment of the first electrode, and the first arc segment 104 is connected to the first straight segment 103; the first empty foil area 110 is located on the first surface and the second surface of the first straight segment 103; the first area 121 includes a first segment 1211 and a second segment 1212 connected to each other, the first segment 1211 is located on the first surface and the second surface of the first straight segment 103, and the second segment 1212 is located on the first surface of the first straight segment 103; the second area 122 includes a first sub-area 1221 and a second sub-area 1222 connected to each other, the first sub-area 1221 is located on the second surface of the first arc segment 104, and the second sub-area 1222 is located on the second surface of the first straight segment 103.

[0087] Along the winding direction of the core, the first empty foil area 110 located on the second surface is sequentially connected to the first segment 1211, the second sub-area 1222 and the first sub-area 1221, thereby dispersing the stress on the electrode head, preventing stress concentration, and thus avoiding electrode head breakage.

[0088] refer to Figure 8 and Figure 10 In this embodiment of the application, the first current collector 100 further includes a first arc segment 104 which is the initial bending segment of the first electrode, and the first arc segment 104 is connected to the first straight segment 103; the first empty foil area 110 is located on the first surface and the second surface of the first straight segment 103, the first area 121 includes a second segment 1212 located on the first surface of the first straight segment 103; the second area 122 includes a first sub-area 1221 and a second sub-area 1222 connected to each other, the first sub-area 1221 is located on the second surface of the first arc segment 104, and the second sub-area 1222 is located on the second surface of the first straight segment 103.

[0089] Along the winding direction of the core, the first empty foil area 110 on the second surface is sequentially connected to the second sub-area 1222 and the first sub-area 1221, thereby dispersing the stress on the electrode head, preventing stress concentration, and thus avoiding electrode head breakage; at the same time, maximizing battery capacity.

[0090] refer to Figure 8 and Figure 11 In this embodiment of the application, the first current collector 100 further includes a second arc segment 105, a second straight segment 106 and a third straight segment 107. The second arc segment 105 is located on the side of the first arc segment 104 away from the first center plane 400. The second straight segment 106 and the third straight segment 107 are respectively connected to the two ends of the second arc segment 105.

[0091] The second region 122 also includes a third sub-region 1223 and a fourth sub-region 1224 connected to each other. The third sub-region 1223 is located on the first surface of the second arc segment 105, and the second surface of the second arc segment 105 has a paste layer. The fourth sub-region 1224 is located on the first surface of the second straight segment 106, and the second surface of the second straight segment 106, which is disposed opposite to the fourth sub-region 1224, has a paste layer.

[0092] The first region 121 also includes a third segment 1213, at least part of which is located on the first surface of the second straight segment 106. The third sub-region 1223 is connected to the third segment 1213 via a fourth sub-region 1224. Both the first and second surfaces of the third straight segment 107 have a coating layer.

[0093] refer to Figure 8 and Figure 12In this embodiment of the application, the first current collector 100 further includes a fourth straight section 108, which is located on the side of the third straight section 107 away from the first center surface 400. The fourth straight section 108 may be the end section of the electrode sheet. The fourth straight section 108 includes a fourth segment 1081 and a fifth segment 1082 connected along the length direction of the electrode sheet. The first and second surfaces of the fourth segment 1081 are both provided with a paste layer.

[0094] The combination area S also includes a fifth sub-area 150, which is located on the first surface and / or the second surface of the fifth segment 1082; at least one surface of the fifth sub-area 150 includes a first reserved paste 101 and / or a second reserved paste 102.

[0095] When cutting the electrode sheets that are connected end to end, the fifth sub-region 150 of the fourth straight section 108 can avoid cutting the paste part during cutting, which would cause powder to fall off and affect the cell; at the same time, the thickness of the head and tail is reduced, the energy density per unit volume of the battery is increased, the cell head and tail are sealed more smoothly, and the safety is improved.

[0096] In this embodiment, the second electrode includes a second current collector and an electrode tab, with the electrode tab connected to the second current collector; along the thickness direction of the core, the projection of the second sub-region 1222 on the first center plane 400 covers the projection of the electrode tab.

[0097] In this embodiment, the core also includes insulating tape, which is attached to the second electrode sheet. Along the thickness direction of the core, the insulating tape is opposite to the fourth straight section 108, and the size of the insulating tape covering the second electrode sheet is 0mm to 6mm.

[0098] In other words, the size of the insulating tape required for the positive electrode is reduced, saving tape material and increasing energy density; at the same time, since there is no casting area at this location, there is no insufficient site for active particles to accommodate lithium ions, thus avoiding the risk of lithium plating.

[0099] For example, the length of the insulating tape is 0.5 mm, 1 mm, or 3 mm.

[0100] In this embodiment, the thickness tolerance of the paste layer is ±3μm. For example, the thickness tolerance of the paste layer is -3μm, or the thickness tolerance of the paste layer is 3μm. It can be understood that by cleaning the casting area of ​​the electrode, the overall thickness of the first electrode tends to be uniform, reducing the probability that lithium ions are easily accumulated in a certain place in the paste layer, resulting in lithium plating problems.

[0101] In this embodiment of the application, along the winding direction of the core, the first electrode includes a first bending area located on the innermost ring of the core, and a first straight area connected to the first bending area.

[0102] Along the thickness direction of the core ( Figure 8The first bending region of the first electrode 700 has a projection on the first straight region (z-axis in the diagram), and the first bending region of the first electrode has a boundary line with the first straight region. The distance between the projection and the boundary line is the desizing region 800.

[0103] Along the width direction of the core ( Figure 8 (x-axis in the figure), the size of the degreasing zone 800 is 0mm~0.2mm.

[0104] In summary, this application provides a winding core and a battery. The winding core includes a first electrode, a separator, and a second electrode, which are sequentially stacked. The first electrode and the second electrode have opposite polarities. The first electrode includes a first current collector 100, which has opposing first and second surfaces along the thickness direction of the electrode (z-axis shown in the figure). The first surface is provided with a first paste layer 200, and the second surface is provided with a second paste layer 300. Along the length direction of the electrode (x-axis shown in the figure), the head and / or tail of the first electrode include a combination region S, and the first and / or second surfaces of the combination region S include a first empty foil region. 110, the first empty foil area 110 refers to at least one surface of the empty foil area that is not provided with a paste layer; the first surface and / or the second surface of the combined area S may also include a first reserved paste area, along the width direction of the electrode sheet (y-axis shown in the figure), the first empty foil area 110 has a first edge, the first reserved paste area is disposed at the first edge, and along the width direction of the electrode sheet, the first empty foil area 110 and the first reserved paste area are disposed adjacent to each other; the first reserved paste area is provided with a first reserved paste 101, along the length direction of the electrode sheet (x-axis shown in the figure), the first reserved paste 101 and the first paste layer 200 are disposed adjacent to each other, or the first reserved paste 101 and the second paste layer 300 are disposed adjacent to each other.

[0105] Laser cleaning eliminates the thinning areas at the beginning and end of the electrode, preventing lithium plating in the thinned areas after the negative electrode is wound. This reduces the risk of lithium plating in lithium batteries while ensuring product quality and safety, thus improving the safety of lithium batteries.

[0106] Pre-applied paste is placed in the area that needs to be cleaned to prevent perforation or breakage of the first electrode after cleaning. At the same time, when the electrode needs to be slit after cleaning, the pre-applied paste can also ensure the slitting efficiency and the yield of the electrode after slitting.

[0107] The various embodiments or embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

[0108] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0109] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0110] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0111] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A type of winding core, characterized in that, include: A first electrode, a diaphragm, and a second electrode are stacked sequentially, with the first electrode and the second electrode having opposite polarities. The first electrode includes a first current collector (100), the first current collector (100) has a first surface and a second surface opposite to each other along the thickness direction Z of the electrode, and both the first surface and the second surface are provided with a paste layer; Along the length direction X of the electrode sheet, the head and / or tail of the first electrode sheet includes a combination region (S), at least one surface of the combination region (S) includes a first empty foil region (110) and a first reserved paste region. Along the width direction of the electrode sheet, the first empty foil region (110) has a first edge, and the first reserved paste region is disposed at the first edge. Along the width direction Y of the electrode sheet, the first empty foil region (110) and the first reserved paste region are disposed adjacent to each other. The first reserved coating area is provided with a first reserved coating (101). The size of the first reserved coating along the width direction of the electrode is smaller than the size of the coating layer along the width direction of the electrode. Along the length direction of the electrode, the first reserved coating (101) and the coating layer are arranged adjacent to each other; and / or the first reserved coating (101) and the coating layer are arranged at intervals.

2. The winding core according to claim 1, characterized in that, The combination area (S) further includes a second reserved paste area, which is provided with the second reserved paste (102). The first empty foil area (110) has a second edge that intersects the first edge perpendicularly. The second reserved paste (102) is disposed near the second edge. The end of the second reserved paste area near the first edge is at least partially in contact with the first reserved paste area.

3. The winding core according to claim 2, characterized in that, The first empty foil region (110) has a first width M1,0 mm along the length direction X of the electrode sheet. <M1<10mm; And / or, the first pre-reserved paste (101) has a second width M2, 0.1 mm, along the width direction Y of the electrode. <M2<1mm; And / or, the second reserved paste (102) has a third width M3, 0.1 mm, along the length direction X of the electrode. <M3<1mm。 4. The winding core according to claim 2, characterized in that, The first electrode also includes a second empty foil region (120) located between the head and tail of the first electrode. The second empty foil region (120) includes at least one first region (121) and at least one second region (122) connected together. The thickness of the first region (121) along the thickness direction of the electrode sheet is a first thickness H1, and the thickness of the second region (122) along the thickness direction of the electrode sheet is a second thickness H2. The first thickness H1 is greater than the second thickness H2.

5. The winding core according to claim 4, characterized in that, The first region (121) has a first surface roughness R1, the second region (122) has a second surface roughness R2, and when the two surfaces of the combined region (S) have a first empty foil region (110) facing each other along the thickness direction of the electrode, the first empty foil region (110) has a third surface roughness R3. Where R1≤R2≤R3.

6. The winding core according to claim 4, characterized in that, The first electrode, the diaphragm, and the second electrode are wound around the first central surface. The surface of the first current collector facing the first central surface is the first surface, and the surface of the first current collector away from the first central surface is the second surface. The first current collector (100) includes a first straight section (103), and the combined region (S) is located on the first surface and the second surface of the first straight section (103); The diaphragm has a folded section, and at least a portion of the combined area (S) located in the first straight section (103) has its projection along the thickness direction of the core coinciding with the folded section.

7. The winding core according to claim 6, characterized in that, The first current collector (100) further includes a first arc segment (104), which is connected to the first straight segment (103). The first empty foil area (110) is located on the first surface and the second surface of the first straight section (103). The first area (121) includes a first segment (1211) and a second segment (1212) connected to each other. The first segment (1211) is located on the first surface and the second surface of the first straight section (103), and the second segment (1212) is located on the first surface of the first straight section (103). The second region (122) includes a first sub-region (1221) and a second sub-region (1222) connected to each other. The first sub-region (1221) is located on the second surface of the first arc segment (104), and the second sub-region (1222) is located on the second surface of the first straight segment (103). Along the winding direction of the core, the first empty foil area (110) located on the second surface is sequentially connected to the first segment (1211), the second sub-area (1222), and the first sub-area (1221).

8. The winding core according to claim 6, characterized in that, The first current collector (100) further includes a first arc segment (104), which is connected to the first straight segment (103). The first empty foil area (110) is located on the first surface and the second surface of the first straight section (103), and the first area (121) includes a second section (1212) located on the first surface of the first straight section (103). The second region (122) includes a first sub-region (1221) and a second sub-region (1222) connected to each other. The first sub-region (1221) is located on the second surface of the first arc segment (104), and the second sub-region (1222) is located on the second surface of the first straight segment (103). Along the winding direction of the core, the first empty foil area (110) located on the second surface is sequentially connected to the second sub-area (1222) and the first sub-area (1221).

9. The winding core according to claim 8, characterized in that, The first current collector (100) further includes a second arc segment (105), a second straight segment (106), and a third straight segment (107). The second arc segment (105) is located on the side of the first arc segment (104) away from the first center plane. The second straight segment (106) and the third straight segment (107) are respectively connected to the two ends of the second arc segment (105). The second region (122) further includes a third sub-region (1223) and a fourth sub-region (1224) connected to each other. The third sub-region (1223) is located on the first surface of the second arc segment (105), and the second surface of the second arc segment (105) has the paste layer. The fourth sub-region (1224) is located on the first surface of the second straight segment (106), and the second surface of the second straight segment (106) opposite to the fourth sub-region (1224) has the paste layer. The first region (121) further includes a third segment, at least a portion of which is located on the first surface of the second straight segment (106). The third sub-region (1223) is connected to the third segment (1213) via the fourth sub-region (1224). The first and second surfaces of the third straight segment (107) both have the coating layer.

10. The winding core according to claim 9, characterized in that, The first current collector (100) further includes a fourth straight section (108), which is located on the side of the third straight section (107) away from the first center plane. The fourth straight section (108) includes a fourth segment (1081) and a fifth segment (1082) connected along the length direction of the electrode. The first and second surfaces of the fourth segment (1081) are both provided with the paste layer; The combined region (S) further includes a fifth sub-region (150), which is located on the first surface and / or the second surface of the fifth segment (1082); At least one surface of the fifth sub-region (150) includes the first reserved paste (101) and / or the second reserved paste (102).

11. The winding core according to claim 7 or 8, characterized in that, The second electrode includes a second current collector and a tab, wherein the tab is connected to the second current collector; Along the thickness direction of the core, the projection of the second sub-region (1222) onto the first center plane covers the projection of the tab.

12. The winding core according to claim 10, characterized in that, The core also includes insulating tape, which is attached to the second electrode sheet. Along the thickness direction of the core, the insulating tape is opposite to the fourth straight section (108), and the insulating tape covers the second electrode sheet by a size of 0mm to 6mm.

13. The winding core according to any one of claims 1-5, characterized in that, The thickness tolerance of the coating layer is ±3μm.

14. The winding core according to claim 1, characterized in that, Along the winding direction of the core, the first electrode includes a first bending area located on the innermost ring of the core, and a first straight area connected to the first bending area. Along the thickness direction of the core, the distance between the projection of the winding start end of the second electrode onto the first straight area and the boundary line between the first bending area and the first straight area of ​​the first electrode is the degreasing area. Along the width direction of the core, the size of the degreasing area is 0mm to 0.2mm.

15. The winding core according to claim 4, characterized in that, The first thickness H1 and the second thickness H2 have the following relationship: H1 ≥ 0.7H2.

16. The winding core according to claim 5, characterized in that, The first surface roughness R1, the second surface roughness R2, and the third surface roughness R3 have the following relationship: R2 = (1~1.25)R1; R3 = (1~2)R1.

17. A battery, characterized in that, Includes the core as described in any one of claims 1-16.

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