Roll-wound and soft-pack batteries

Abstract

The present invention provides a roll core and soft-pack battery, relating to the field of lithium battery technology. The roll core includes a negative electrode sheet, the inner surface of the second bend of the negative electrode sheet along the winding direction is covered with a first adhesive tape layer. The projections of the two ends of the first adhesive tape layer along the thickness direction of the roll core are connected to or partially overlap with the projections of the winding head end of the negative electrode sheet along the thickness direction of the roll core. This improves the unevenness of the roll core surface, thereby improving the flatness of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a roll core and a soft-pack battery. Background Art

[0002] With the development of science and technology, lithium-ion battery technology has developed rapidly. At the same time, users have also put forward higher requirements for the fast charging capability and charge and discharge rate of lithium-ion batteries. Fast-charging lithium batteries have become the development trend of consumer lithium-ion batteries.

[0003] The good interfacial bonding of lithium-ion batteries during high-rate charging directly affects their long cycle life, expansion, and deformation. The key to good interfacial bonding in lithium-ion batteries lies in the uniformity of the pressure they withstand during the formation process. The key to uniform pressure during the formation process lies in the smoothness of the entire cell during cell design. Specifically, the smaller the difference between the highest and lowest points on the cell surface, the better the cell's smoothness. The cell consists of a coiled core and the outer shell that encapsulates the coiled core.

[0004] However, in the prior art, the surface of the winding core is seriously uneven, thereby affecting the flatness of the battery cell. Summary of the Invention

[0005] The present invention provides a roll core and a soft-pack battery, wherein the uneven surface of the roll core is improved, thereby facilitating the improvement of the flatness of the battery cell, and further facilitating the improvement of the interface bonding effect of the lithium-ion battery, thereby achieving the purpose of improving the long cycle life of the lithium-ion battery, and preventing expansion and deformation problems.

[0006] In a first aspect, the present invention provides a winding core, comprising a negative electrode sheet, wherein the inner surface of the second bending area of the negative electrode sheet along the winding direction is covered with a first adhesive paper layer, and the projections of the two ends of the first adhesive paper layer along the thickness direction of the winding core are connected to or partially overlapped with the projections of the winding head end of the negative electrode sheet along the thickness direction of the winding core.

[0007] The winding core provided by the present invention includes a negative electrode sheet. A first adhesive tape layer is applied to the inner surface of the second bend region of the negative electrode sheet along the winding direction, and the projections of the two ends of the first adhesive tape layer along the thickness direction of the winding core are aligned with or partially overlap the projections of the winding head end of the negative electrode sheet along the thickness direction of the winding core. This helps increase the thickness of the end of the winding core near the bend region, so that the thickness of the end of the winding core away from the bend region is substantially the same as the thickness of the end of the winding core near the bend region. This further helps improve the unevenness of the winding core surface, improves the flatness of the battery cell, and improves the interfacial bonding of the battery after formation, ultimately achieving the purpose of improving the battery's long cycle life, and reducing expansion and deformation issues.

[0008] The winding core as described above may optionally further include a negative electrode ear, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer, and the negative electrode active layer is coated on two opposite sides of the negative electrode current collector; the winding head end of the negative electrode current collector is exposed in sequence along the winding direction to form a negative electrode double-sided empty foil area and a negative electrode single-sided empty foil area, and the negative electrode ear is arranged in the negative electrode double-sided empty foil area; the first adhesive paper layer is located in the negative electrode single-sided empty foil area, and the two ends of the first adhesive paper layer are connected to one end of the negative electrode ear close to the bending area.

[0009] As for the winding core as described above, optionally, a recessed portion is provided on a side of the first adhesive paper layer facing away from the negative electrode single-sided empty foil area.

[0010] As for the winding core as described above, optionally, the thickness of the middle area of the recessed portion in the length direction of the negative electrode sheet is smaller than the thickness of other areas of the recessed portion; and the thickness of the recessed portion gradually increases from the middle area of the recessed portion to both sides.

[0011] For the winding core as described above, optionally, the thickness of the middle region of the recessed portion ranges from 3 μm to 8 μm.

[0012] In the winding core as described above, optionally, the size of the opening of the recessed portion in the length direction of the negative electrode sheet ranges from 1 mm to 5 mm.

[0013] For the winding core as described above, optionally, the middle area of the recessed portion corresponds to the middle area of the negative electrode single-sided empty foil area in the length direction of the negative electrode sheet.

[0014] The winding core as described above may optionally further include a negative electrode tab paper layer, wherein the negative electrode tab paper layer covers the surface of the negative electrode tab, the dimension of the negative electrode tab paper layer in the length direction of the negative electrode sheet is a first length, and the dimension of the negative electrode tab in the length direction of the negative electrode sheet is a second length; the first length is greater than or equal to the second length.

[0015] The winding core as described above may optionally further include a positive electrode sheet and a positive electrode ear assembly, wherein the positive electrode sheet includes a positive electrode collector and a positive electrode active layer, and the positive electrode active layer is coated on two opposite sides of the positive electrode collector; the winding head end of the positive electrode collector is exposed to form a positive electrode double-sided empty foil area, and the positive electrode ear assembly is arranged in the positive electrode double-sided empty foil area and has a preset distance between it and the negative electrode ear, and the negative electrode ear is located between the positive electrode ear assembly and the bending area; second adhesive paper layers are provided on two opposite sides of the positive electrode double-sided empty foil area, and the first ends of the two second adhesive paper layers are respectively overlapped on the first ends of the positive electrode active layers located on two opposite sides of the positive electrode collector, and the second ends of the two second adhesive paper layers are both connected to the end of the positive electrode ear assembly away from the negative electrode ear.

[0016] As described above, the winding core may optionally include a positive electrode ear assembly including a positive electrode ear, a first positive electrode ear adhesive paper layer and a second positive electrode ear adhesive paper layer, wherein the first positive electrode ear adhesive paper layer covers the surface of the positive electrode ear, and the second positive electrode ear adhesive paper layer covers the side of the positive electrode double-sided empty foil area away from the positive electrode ear, and the position of the second positive electrode ear adhesive paper layer is opposite to that of the first positive electrode ear adhesive paper layer; the second ends of the two second adhesive paper layers are respectively connected to the ends of the first positive electrode ear adhesive paper layer and the second positive electrode ear adhesive paper layer away from the negative electrode ear.

[0017] For the winding core as described above, optionally, the second adhesive paper layer located on the side of the positive electrode double-sided empty foil area facing away from the positive electrode tab is integrated with the second positive electrode tab adhesive paper layer.

[0018] For the winding core as described above, optionally, the second adhesive paper layer located on the side of the positive electrode double-sided empty foil area where the positive electrode tab is provided is integrated with the first positive electrode tab adhesive paper layer.

[0019] As described above, the winding core may optionally be provided with two third adhesive paper layers at the winding end of the positive electrode sheet, the first ends of the two third adhesive paper layers are respectively overlapped on the second ends of the positive electrode active layer located on the opposite sides of the positive electrode current collector, and the projections of the second ends of the two third adhesive paper layers along the thickness direction of the winding core are both connected to the projections of the end of the positive electrode ear away from the negative electrode ear along the thickness direction of the winding core.

[0020] For the winding core as described above, optionally, the sum of the thickness of the two second adhesive paper layers and the thickness of the two third adhesive paper layers is a first thickness value; the sum of the thickness of the positive electrode ear, the thickness of the first positive electrode ear adhesive paper layer and the thickness of the second positive electrode ear adhesive paper layer is a second thickness value; the difference between the first thickness value and the second thickness value ranges from 80% to 120%.

[0021] The winding core as described above may optionally further include a diaphragm, which is arranged between the positive electrode sheet and the negative electrode sheet; the sum of the thickness of the positive electrode ear, the thickness of the first positive electrode ear adhesive paper layer, the thickness of the second positive electrode ear adhesive paper layer, twice the thickness of the positive electrode collector and twice the thickness of the diaphragm is a third thickness value; twice the thickness of the first adhesive paper layer is a fourth thickness value; the difference between the third thickness value and the fourth thickness value ranges from 80% to 120%.

[0022] The winding core as described above may optionally further include a fourth adhesive paper layer, wherein the fourth adhesive paper layer is attached to at least one side of the outer surface of the winding core, and the fourth adhesive paper layer is located between the negative electrode tab and the positive electrode tab.

[0023] In a second aspect, the present invention provides a soft-pack battery, comprising a shell and a roll core as described above, wherein the roll core is encapsulated in the shell.

[0024] The soft-pack battery provided by the present invention includes a housing and a core, which is encapsulated within the housing. While the unevenness of the core surface is improved, the flatness of the soft-pack battery is also improved, which helps improve the interfacial bonding effect of the soft-pack battery after formation, ultimately achieving the goal of improving the soft-pack battery's long cycle life, reducing expansion and deformation issues.

[0025] The winding core includes a negative electrode sheet. A first adhesive tape layer is applied to the inner surface of the second bend of the negative electrode sheet along the winding direction, and the projections of the two ends of the first adhesive tape layer along the thickness direction of the winding core are aligned with or partially overlap the projections of the winding head of the negative electrode sheet along the thickness direction of the winding core. This helps increase the thickness of the end of the winding core near the bend, so that the thickness of the end of the winding core away from the bend is substantially the same as the thickness of the end of the winding core near the bend. This further helps improve the unevenness of the winding core surface, improves the flatness of the battery cell, and improves the interfacial bonding of the battery after formation, ultimately achieving the purpose of improving the battery's long cycle life, and reducing expansion and deformation issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A top view of a winding core provided in one embodiment of the present invention;

[0028] Figure 2 for Figure 1 A magnified view of the central area of the middle roll core;

[0029] Figure 3 A front view of a negative electrode sheet of a winding core provided in one embodiment of the present invention;

[0030] Figure 4 A top view of a negative electrode sheet of a winding core provided in one embodiment of the present invention;

[0031] Figure 5 for Figure 4 Enlarged view of point A in the middle;

[0032] Figure 6 A front view of a winding core provided in one embodiment of the present invention;

[0033] Figure 7 for Figure 6 Cross-sectional view at the middle BB.

[0034] Description of reference numerals:

[0035] 20-winding core; 21-negative electrode sheet; 211-negative electrode current collector; 2111-negative electrode double-sided empty foil area; 2112-negative electrode single-sided empty foil area; 21121-bending area; 212-negative electrode active layer; 22-negative electrode ear; 23-positive electrode sheet; 231-positive electrode current collector; 2311-positive electrode double-sided empty foil area; 232-positive electrode active layer; 24-positive electrode ear; 31-first adhesive tape layer; 311-recessed portion; 32-second adhesive tape layer; 33-third adhesive tape layer; 34-fourth adhesive tape layer; 35-protective adhesive tape layer; 36-sealing adhesive tape layer; 41-negative electrode ear adhesive tape layer; 42-negative electrode ear adhesive pad; 51-first positive electrode ear adhesive tape layer; 52-second positive electrode ear adhesive tape layer. DETAILED DESCRIPTION

[0036] In related technologies, the winding core mainly includes a negative electrode sheet, a positive electrode sheet, a separator, a negative electrode ear, and a positive electrode ear. The negative electrode ear is welded to the winding head end of the negative electrode sheet, and the positive electrode ear is welded to the winding head end of the positive electrode sheet. The negative electrode sheet, the positive electrode sheet, and the separator are stacked in a preset order and wound in the same direction starting from the winding head end to finally form the winding core. Due to factors such as the structure of the positive / negative electrode sheets, the structure of the positive / negative electrode ears, the welding position of the positive / negative electrode ears, and the setting method of the separator, the thickness of different parts of the winding core varies, resulting in poor flatness of the winding core, which in turn affects the interface bonding effect of the battery after formation, shortens the long cycle life of the battery, and aggravates the expansion and deformation problems of the battery.

[0037] In order to solve the above-mentioned technical problems, the present invention provides a winding core, which includes a negative electrode sheet. By covering the inner surface of the second bend area of the negative electrode sheet along the winding direction with a first adhesive paper layer, and making the projections of the two ends of the first adhesive paper layer along the thickness direction of the winding core connect or partially overlap with the projections of the winding head end of the negative electrode sheet along the thickness direction of the winding core, the winding core can be increased in thickness at the end near the bend area, so that the thickness of the end of the winding core away from the bend area is substantially the same as the thickness of the end near the bend area. This can further improve the unevenness of the winding core surface, improve the flatness of the battery cell, and improve the interfacial bonding effect of the battery after formation, ultimately achieving the purpose of improving the battery's long cycle life, swelling, and deformation.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1

[0040] Figure 1 A top view of a winding core provided in one embodiment of the present invention; Figure 2 for Figure 1 A magnified view of the central area of the middle roll core; Figure 3 A front view of a negative electrode sheet of a winding core provided in one embodiment of the present invention; Figure 4 A top view of a negative electrode sheet of a winding core provided in one embodiment of the present invention; Figure 5 for Figure 4 Enlarged view of point A in the middle; Figure 6 A front view of a winding core provided in one embodiment of the present invention; Figure 7 for Figure 6 Cross-sectional view at the middle BB.

[0041] Reference Figures 1 to 6 This embodiment provides a winding core, which includes a negative electrode sheet 21. The inner surface of the second bending area 21121 of the negative electrode sheet 21 along the winding direction is covered with a first adhesive paper layer 31. The projections of the two ends of the first adhesive paper layer 31 along the thickness direction of the winding core are connected to or partially overlapped with the projections of the winding head end of the negative electrode sheet 21 along the thickness direction of the winding core.

[0042] The winding core provided in this embodiment includes a negative electrode sheet. A first adhesive tape layer is applied to the inner surface of the second bend region of the negative electrode sheet along the winding direction, and the projections of the two ends of the first adhesive tape layer along the thickness direction of the winding core are aligned with or partially overlap the projections of the winding head end of the negative electrode sheet along the thickness direction of the winding core. This helps increase the thickness of the end of the winding core near the bend region, so that the thickness of the end of the winding core away from the bend region is substantially the same as the thickness of the end of the winding core near the bend region. This further helps improve the unevenness of the winding core surface, improves the flatness of the battery cell, and improves the interfacial bonding of the battery after formation, ultimately achieving the goal of improving the battery's long cycle life, preventing expansion and deformation.

[0043] Optionally, the winding core 20 further includes a negative electrode tab 22. The negative electrode sheet 21 includes a negative electrode current collector 211 and a negative electrode active layer 212. The negative electrode active layer 212 is coated on opposite sides of the negative electrode current collector 211. For example, the negative electrode current collector 211 is typically made of copper foil. Of course, other materials can also be used for the negative electrode current collector 211 as needed, as long as they meet the requirements of the winding core 20.

[0044] The winding leading end of the negative electrode current collector 211 is exposed along the winding direction, forming a negative electrode double-sided empty foil area 2111 and a negative electrode single-sided empty foil area 2112. The winding leading end refers to the end at which winding begins; the negative electrode double-sided empty foil area 2111 refers to the area on both opposing sides of the negative electrode current collector 211 that is not covered with the negative electrode active layer 212. When one of the opposing sides of the negative electrode current collector 211 is covered with the negative electrode active layer 212 and the other side is not covered with the negative electrode active layer 212, the side not covered with the negative electrode active layer 212 is the negative electrode single-sided empty foil area 2112. The negative electrode single-sided empty foil area 2112 is located on the side of the negative electrode current collector 211 facing the center of the winding core 20, and is connected between the negative electrode double-sided empty foil area 2111 and the negative electrode current collector 211, both opposing sides of which are coated with the negative electrode active layer 212. The negative electrode tab 22 is arranged in the negative electrode double-sided empty foil area 2111.

[0045] During the winding process, the second bend 21121 of the negative electrode sheet 21 along the winding direction is located within the negative electrode single-sided bare foil area 2112. That is, the first adhesive tape layer 31 is located within the negative electrode single-sided bare foil area 2112. The bend 21121 is opposite the end of the winding head of the negative electrode current collector 211. For example, the end of the winding head of the negative electrode current collector 211 can extend into the bend 21121 or can be located outside the bend 21121. The two ends of the first adhesive tape layer 31 are connected to the end of the negative electrode tab 22 closest to the bend 21121.

[0046] Illustratively, the first adhesive tape layer 31 may include a base material layer and a glue layer, with the first adhesive tape layer 31 being bonded to the surface of the bending region 21121 via the glue layer. The base material layer may be made of one or more of cast polypropylene, uniaxially oriented polypropylene, biaxially oriented polypropylene, polyethylene, polyester fiber, or polyvinyl chloride. The glue layer may be made of one or more of water-based adhesive, oil-based adhesive, hot-melt adhesive, natural rubber, or synthetic rubber. The glue layer may have a thickness of 2 μm, and the base material layer thickness may be adjusted based on actual needs. Illustratively, the dimension of the first adhesive tape layer along the length of the negative electrode sheet is 2 × the distance between the end of the negative electrode tab facing the bending region and the end of the bending region facing away from the negative electrode tab.

[0047] By covering the surface of the first bending area 21121 of the negative single-sided empty foil area 2112 along the winding direction with a first adhesive paper layer 31, and making the two ends of the first adhesive paper layer 31 connected to the end of the negative ear 22 close to the bending area 21121, it is beneficial to increase the thickness of the end of the core 20 located at the negative ear 22 facing the bending area 21121, so that the thickness of the end of the core 20 located at the negative ear 22 facing the bending area 21121 is basically consistent with the thickness of the area of the core 20 where the negative ear 22 is provided; it is beneficial to improve the unevenness of the surface of the core 20, improve the flatness of the battery cell, and at the same time, improve the interface bonding effect of the battery after formation, and ultimately achieve the purpose of improving the long cycle life of the battery, expansion problem and deformation problem.

[0048] Optionally, a recessed portion 311 is provided on the side of the first adhesive paper layer 31 facing away from the negative electrode single-sided empty foil area 2112. The provision of the recessed portion 311 can prevent the side of the first adhesive paper layer 31 facing away from the negative electrode single-sided empty foil area 2112 from being squeezed against each other at the bending position after the first adhesive paper layer 31 is bent along the bending area 21121, resulting in an increase in the thickness of the winding core 20 corresponding to the bending position, thereby helping to improve the uneven surface of the winding core 20.

[0049] Optionally, the thickness of the middle region of the recessed portion 311 along the length of the negative electrode sheet 21 is less than the thickness of other regions of the recessed portion 311; and the thickness of the recessed portion 311 gradually increases from the middle region toward both sides of the recessed portion 311. For example, the cross-sectional profile of the recessed portion 311 can be angular or arcuate. This helps ensure that the thickness of the first adhesive tape layer 31 remains uniform along the middle region after being bent, thereby improving the unevenness of the surface of the winding core 20.

[0050] Optionally, the thickness of the middle region of the recessed portion 311 ranges from 3 μm to 8 μm. For example, the thickness of the middle region of the recessed portion 311 can be set to 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any value between 3 μm and 8 μm, depending on actual needs. This helps ensure a uniform thickness of the first adhesive tape layer 31 after bending, thereby improving the unevenness of the surface of the winding core 20.

[0051] Optionally, the opening of the recessed portion 311 has a dimension ranging from 1 mm to 5 mm along the length of the negative electrode sheet 21. For example, the dimension of the opening of the recessed portion 311 along the length of the negative electrode sheet 21 can be set to 1 mm, 2 mm, 4 mm, 5 mm, or any value between 1 mm and 5 mm, depending on actual needs. Preferably, the opening of the recessed portion 311 has a dimension of 3 mm along the length of the negative electrode sheet 21. This helps ensure a uniform thickness of the first adhesive tape layer 31 after bending, thereby improving the unevenness of the surface of the winding core 20.

[0052] Optionally, the middle area of the recessed portion 311 corresponds to the middle area of the negative electrode single-sided empty foil area 2112 in the longitudinal direction of the negative electrode sheet 21. Typically, the negative electrode single-sided empty foil area 2112 is bent in the middle area in the longitudinal direction of the negative electrode sheet 21 to form a bending area 21121. By aligning the middle area of the recessed portion 311 of the first adhesive tape layer 31 with the middle area of the negative electrode single-sided empty foil area 2112 in the longitudinal direction of the negative electrode sheet 21, the middle area of the recessed portion 311 is ensured to bend along with the bending area 21121, thereby facilitating uniform thickness of the first adhesive tape layer 31 after bending, thereby facilitating improvement of unevenness on the surface of the winding core 20.

[0053] Optionally, the winding core 20 further includes a negative tab tape layer 41, which covers the surface of the negative tab 22 to prevent burrs on the surface of the negative tab 22 from piercing the separator between the negative electrode sheet 21 and the positive electrode sheet 23, causing a short circuit within the winding core 20. The dimension of the negative tab tape layer 41 in the longitudinal direction of the negative electrode sheet 21 is greater than or equal to the dimension of the negative tab 22 in the longitudinal direction of the negative electrode sheet 21. The dimension of the negative tab 22 in the longitudinal direction of the negative electrode sheet 21 can range from 5 mm to 10 mm; the thickness of the negative tab 22 can range from 45 μm to 110 μm; the dimension of the negative tab tape layer 41 in the longitudinal direction of the negative electrode sheet 21 can range from 10 mm to 20 mm; and the thickness of the negative tab tape layer 41 can range from 5 μm to 16 μm. Illustratively, when the size of the negative tab paper layer 41 in the length direction of the negative electrode sheet 21 is larger than the size of the negative tab 22 in the length direction of the negative electrode sheet 21, the size of the negative tab paper layer 41 extending from both sides of the negative tab 22 along the length direction of the negative electrode sheet 21 may be equal or unequal.

[0054] Optionally, the winding core 20 further includes a positive electrode sheet 23 and a positive electrode tab assembly. The positive electrode sheet 23 includes a positive electrode current collector 231 and a positive electrode active layer 232. The positive electrode active layer 232 is coated on opposite sides of the positive electrode current collector 231. For example, the positive electrode current collector 231 is typically made of aluminum foil. Of course, other materials can also be used as needed, as long as they meet the requirements of the winding core 20.

[0055] The first end of the positive electrode current collector 231 is exposed, forming a positive electrode double-sided hollow foil region 2311. The "first end" refers to the end where the winding begins. The positive electrode double-sided hollow foil region 2311 refers to the area where the positive electrode current collector 231 is not covered with the positive electrode active layer 232 on both opposing sides. The positive electrode tab assembly is disposed within the positive electrode double-sided hollow foil region 2311 and has a preset spacing with the negative electrode tab 22. The negative electrode tab 22 is located between the positive electrode tab assembly and the folding region 21121. The positive electrode tab assembly includes a positive electrode tab 24. The preset spacing between the positive electrode tab 24 and the negative electrode tab 22 can be set according to actual needs and is not specifically limited here.

[0056] Optionally, the end of the winding head end of the positive current collector 231 extends between the positive electrode ear 24 and the negative electrode ear 22, and a protective tape layer 35 is provided on both opposite sides of the part of the positive electrode collector 231 located between the positive electrode ear 24 and the negative electrode ear 22. The protective tape layer 35 can be affixed to the negative electrode collector 211 located on the opposite sides of the positive electrode collector 231, or on the positive electrode collector 231, or on the diaphragm located on the opposite sides of the positive electrode collector 231. The first end of the protective paper layer 35 can be connected to the end of the negative electrode ear 22 facing the positive electrode ear 24, and the second end of the protective paper layer 35 can be connected to the end of the positive electrode ear 24 facing the negative electrode ear 22; on the one hand, the protective paper layer 35 prevents the burrs on the positive electrode current collector 231 from piercing the diaphragm and causing an internal short circuit in the core 20; on the other hand, it is used to increase the thickness of the core 20 between the positive electrode ear 24 and the negative electrode ear 22, so as to improve the unevenness of the surface of the core 20.

[0057] Optionally, the end of the winding tail of the positive electrode current collector 231 extends between the positive electrode tab 24 and the negative electrode tab 22, and a sealing tape layer 36 is provided at the winding tail of the positive electrode current collector 231. The sealing tape layer 36 not only secures the winding tail of the positive electrode current collector 231 to the outer surface of the winding core 20 to ensure the stability and reliability of the wound core 20, but also increases the thickness of the winding core 20 between the positive electrode tab 24 and the negative electrode tab 22 to improve the unevenness of the winding core 20 surface.

[0058] Second adhesive paper layers 32 are provided on opposite sides of the positive electrode double-sided hollow foil area 2311. The first ends of the two second adhesive paper layers 32 are respectively overlapped with the first ends of the positive electrode active layer 232 located on opposite sides of the positive electrode current collector 231. The second ends of the two second adhesive paper layers 32 are both connected to the end of the positive electrode tab assembly away from the negative electrode tab 22. On the one hand, because burrs are generally formed at the starting and ending ends of the positive electrode active layer 232 coated on the positive electrode current collector 231, overlapping the first end of the second adhesive paper layer 32 with the first end of the positive electrode active layer 232 helps prevent burrs on the first end of the positive electrode active layer 232 from piercing the separator between the positive electrode sheet 23 and the negative electrode sheet 21, causing an internal short circuit in the winding core 20. On the other hand, the second end of the second adhesive tape layer 32 is connected to the end of the positive electrode tab assembly away from the negative electrode tab 22, so that the thickness of the end of the core 20 located at the positive electrode tab assembly away from the negative electrode tab 22 is basically consistent with the thickness of the area of the core 20 where the positive electrode tab assembly is provided; thereby facilitating improvement of the uneven surface of the core 20.

[0059] In a specific implementation, the thickness of the two second adhesive paper layers 32 can be set to be equal or unequal, depending on actual needs. The dimensions of the two second adhesive paper layers 32 along the length of the positive electrode sheet 23 can also be set to be equal or unequal, depending on actual needs. In an optional implementation, the dimensions of the two second adhesive paper layers 32 along the length of the positive electrode sheet 23 can be set to be equal. For example, the dimension of the second adhesive paper layer along the length of the positive electrode sheet is equal to the distance from the end of the positive electrode tab away from the negative electrode tab to the first end of the positive electrode active layer.

[0060] Optionally, the positive electrode ear assembly includes a positive electrode ear 24, a first positive electrode ear adhesive paper layer 51 and a second positive electrode ear adhesive layer 52, the first positive electrode ear adhesive paper layer 51 covers the surface of the positive electrode ear 24 to prevent burrs on the surface of the positive electrode ear 24 from piercing the diaphragm and causing a short circuit inside the roll core 20; the second positive electrode ear adhesive paper layer 52 covers the side of the positive electrode double-sided empty foil area 2311 facing away from the positive electrode ear 24, and the position of the second positive electrode ear adhesive paper layer 52 is opposite to that of the first positive electrode ear adhesive paper layer 51 to prevent welding burrs formed on the side of the positive electrode double-sided empty foil area 2311 facing away from the positive electrode ear 24 during welding of the positive electrode ear 24 from piercing the diaphragm and causing a short circuit inside the roll core 20.

[0061] The dimension of the first positive tab tape layer 51 in the longitudinal direction of the positive electrode sheet 23 may be greater than or equal to the dimension of the positive tab 24 in the longitudinal direction of the positive electrode sheet 23. The dimension of the second positive tab tape layer 52 in the longitudinal direction of the positive electrode sheet 23 may be greater than or equal to the dimension of the positive tab 24 in the longitudinal direction of the positive electrode sheet 23. Specifically, the dimension of the positive tab 24 in the longitudinal direction of the positive electrode sheet 23 may range from 5 mm to 10 mm; the thickness of the positive tab 24 may range from 45 μm to 110 μm; the dimension of the first positive tab tape layer 51 and the second positive tab tape layer 52 in the longitudinal direction of the positive electrode sheet 23 may range from 10 mm to 20 mm; and the thickness of the first positive tab tape layer 51 and the second positive tab tape layer 52 may range from 5 μm to 16 μm.

[0062] Illustratively, when the dimensions of the first positive electrode tab adhesive paper layer 51 and the second positive electrode tab adhesive paper layer 52 in the length direction of the positive electrode sheet 23 are greater than the dimensions of the positive electrode tab 24 in the length direction of the positive electrode sheet 23, the dimensions of the first positive electrode tab adhesive paper layer 51 extending out on both sides of the positive electrode tab 24 along the length direction of the positive electrode sheet 23 may be equal or unequal; the dimensions of the second positive electrode tab adhesive paper layer 52 extending out on both sides of the positive electrode tab 24 along the length direction of the positive electrode sheet 23 may be equal or unequal.

[0063] In an optional implementation, the second ends of the two second adhesive paper layers 32 are respectively connected to the ends of the first positive electrode ear adhesive paper layer 51 and the second positive electrode ear adhesive paper layer 52 away from the negative electrode ear 22, so that the thickness of the end of the positive electrode ear 24 of the winding core 20 away from the negative electrode ear 22 remains uniform, which is beneficial to improving the uneven surface of the winding core 20.

[0064] In another optional implementation, the second adhesive paper layer 32 and the second positive electrode ear adhesive paper layer 52 located on the side of the positive electrode double-sided empty foil area 2311 facing away from the positive electrode ear 24 can be an integrated piece, which is beneficial to further maintain the thickness of the end of the core 20 located on the positive electrode ear 24 away from the negative electrode ear 22 uniform, and further beneficial to improve the uneven surface of the core 20.

[0065] Similarly, the second adhesive paper layer 32 and the first positive electrode ear adhesive paper layer 51 on the side of the positive electrode double-sided empty foil area 2311 where the positive electrode ear 24 is set can be an integrated part, which is conducive to further maintaining the thickness of the end of the core 20 located at the positive electrode ear 24 away from the negative electrode ear 22 uniform, and further helps to improve the uneven surface of the core 20.

[0066] Optionally, two third adhesive paper layers 33 are provided at the winding end of the positive electrode sheet 23. The first ends of the two third adhesive paper layers 33 are respectively overlapped with the second ends of the positive electrode active layer 232 located on opposite sides of the positive electrode current collector 231. The second ends of the two third adhesive paper layers 33, as projected along the thickness direction of the winding core, are both connected to the projection of the end of the positive electrode tab 24 away from the negative electrode tab 22, as projected along the thickness direction of the winding core. On the one hand, because burrs are generally formed at the starting and ending ends of the positive electrode active layer 232 coated on the positive electrode current collector 231, overlapping the first end of the third adhesive paper layer 33 with the second end of the positive electrode active layer 232 helps prevent the burrs at the second end of the positive electrode active layer 232 from piercing the separator between the positive electrode sheet 23 and the negative electrode sheet 21, causing an internal short circuit in the winding core 20. On the other hand, the projection of the second end of the third adhesive tape layer 33 along the thickness direction of the core is connected to the projection of the end of the positive electrode ear 24 away from the negative electrode ear 22 along the thickness direction of the core, so as to further ensure that the thickness of the end of the core 20 located at the positive electrode ear 24 away from the negative electrode ear 22 is basically consistent with the thickness of the area of the core 20 where the positive electrode ear 24 is provided; thereby helping to improve the unevenness of the surface of the core 20.

[0067] In a specific implementation, the thicknesses of the two third adhesive paper layers 33 can be set to be equal or unequal based on actual needs; the dimensions of the two third adhesive paper layers 33 along the length of the positive electrode sheet 23 can also be set to be equal or unequal based on actual needs. In an optional implementation, the dimensions of the two third adhesive paper layers 33 along the length of the positive electrode sheet 23 can be set to be equal. For example, the dimension of the third adhesive paper layer along the length of the positive electrode sheet = the winding core thickness × 3.14 ÷ 2 + the winding core thickness ÷ 2 + the horizontal distance between the end of the positive electrode tab away from the negative electrode tab and the first end of the positive electrode active layer + δ, where δ is a tolerance, 2mm≤δ≤3mm.

[0068] Optionally, the sum of the thicknesses of the two second adhesive tape layers 32 and the two third adhesive tape layers 33 is a first thickness value; the sum of the thicknesses of the positive tab 24, the first positive tab adhesive tape layer 51, and the second positive tab adhesive tape layer 52 is a second thickness value, and the difference between the first and second thickness values ranges from 80% to 120%. For example, the first thickness value can be equal to the second thickness value, or the first thickness value can be less than the second thickness value, or the first thickness value can be greater than the second thickness value, as long as the difference between the first and second thickness values ranges from 80% to 120%. This ensures that the thickness of the end of the core 20 located on the positive tab 24 away from the negative tab 22 is consistent with the thickness of the region of the core 20 where the positive tab 24 is located, thereby improving the unevenness of the core 20 surface.

[0069] The winding core 20 also includes a separator (not shown), which is disposed between the positive electrode sheet 23 and the negative electrode sheet 21 to insulate the positive electrode sheet 23 from the negative electrode sheet 21. Optionally, the sum of the thickness of the positive electrode tab 24, the thickness of the first positive electrode tab adhesive layer 51, the thickness of the second positive electrode tab adhesive layer 52, twice the thickness of the positive electrode current collector 231, and twice the thickness of the separator is a third thickness value; twice the thickness of the first adhesive layer 31 is a fourth thickness value; the difference between the third thickness value and the fourth thickness value ranges from 80% to 120%. Exemplarily, the third thickness value can be equal to the fourth thickness value, or the third thickness value can be less than the fourth thickness value, or the third thickness value can be greater than the fourth thickness value, as long as the difference between the third thickness value and the fourth thickness value ranges from 80% to 120%. When the thickness of the positive tab 24 is equal to that of the negative tab 22, and the thickness of the negative tab paper layer 41 is equal to that of the first positive tab paper layer 51, the above relationship can also be expressed as follows: the sum of the thickness of the negative tab 22, the thickness of the negative tab paper layer 41, the thickness of the second positive tab paper layer 52, twice the thickness of the positive current collector 231, and twice the thickness of the separator is equal to twice the thickness of the first paper layer 31. This ensures that the thickness of the winding core 20 at the end of the negative tab 22 away from the positive tab 24 is consistent with the thickness of the region of the winding core 20 where the positive tab 24 is located, thereby improving the unevenness of the winding core 20 surface.

[0070] Optionally, the negative electrode tab 22 includes a connected negative electrode tab welding section and a negative electrode tab free section. The negative electrode tab welding section extends along the width of the negative electrode sheet 21 and is welded within the negative electrode double-sided hollow foil area 2111, while the negative electrode tab free section extends outside the negative electrode double-sided hollow foil area 2111. The length of the negative electrode tab welding section is greater than or equal to the width of the negative electrode sheet 21 to ensure that the thickness of the winding core 20 along the width of the negative electrode sheet 21 remains uniform, thereby improving the unevenness of the winding core 20 surface.

[0071] Furthermore, a negative tab rubber pad 42 is provided at one end of the negative tab free section near the negative tab welding section. This pad 42 seals the gap between the negative tab 22 and the outer casing when the winding core 20 is packaged in the outer casing. When the length of the negative tab welding section is greater than the width of the negative electrode sheet 21, the portion of the negative tab welding section that extends beyond the negative electrode sheet 21—that is, the portion where the length of the negative tab welding section differs from the width of the negative electrode sheet 21—can be positioned between the negative electrode sheet 21 and the negative tab rubber pad 42. This allows for thermal expansion of the negative tab rubber pad 42 to prevent it from melting and becoming embedded between the positive and negative electrode sheets 23 and 21 during packaging. Furthermore, it allows for bending and adjustment of the negative tab 22 near the negative electrode sheet 21 to prevent it from directly adhering to the end surface formed by the winding of the positive and negative electrode sheets 23 and 21 when the negative tab 22 is bent and adjusted. Exemplarily, the difference between the length of the negative electrode ear welding section and the width of the negative electrode sheet 21 is between 0.5 mm and 1.5 mm. In specific implementation, the difference between the length of the negative electrode ear welding section and the width of the negative electrode sheet 21 can be set to 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.3 mm, 1.5 mm or any value between 0.5 mm and 1.5 mm according to actual needs.

[0072] Optionally, the positive tab 24 includes a connected positive tab welding section and a positive tab free section. The positive tab welding section extends along the width of the positive electrode sheet 23 and is welded within the positive electrode double-sided hollow foil area 2311, while the positive tab free section extends outside the positive electrode double-sided hollow foil area 2311. The length of the positive tab welding section is greater than or equal to the width of the positive electrode sheet 23 to ensure that the thickness of the winding core 20 along the width of the positive electrode sheet 23 remains uniform, thereby improving the unevenness of the winding core 20 surface.

[0073] Typically, the width of the positive electrode sheet 23 is greater than the width of the negative electrode sheet 21, and the difference between the widths of the positive electrode sheet 23 and the negative electrode sheet 21 is in the range of 0.5 mm to 2 mm. For example, the difference between the widths of the positive electrode sheet 23 and the negative electrode sheet 21 can be set to 0.5 mm, 1 mm, 1.5 mm, 2 mm, or any value between 0.5 mm and 2 mm according to actual needs.

[0074] Furthermore, a positive tab rubber pad (not shown) is provided at one end of the free section of the positive tab, near the positive tab welding section. This pad seals the gap between the positive tab 24 and the outer casing when the winding core 20 is enclosed in the outer casing. If the length of the positive tab welding section is greater than the width of the positive electrode sheet 23, the portion of the positive tab welding section that extends beyond the positive electrode sheet 23—that is, the difference between the length of the positive tab welding section and the width of the positive electrode sheet 23—can be positioned between the positive electrode sheet 23 and the pad. This allows for the pad to extend through the heat-melt process, preventing it from melting and becoming embedded between the positive and negative electrode sheets 23 and 21 during packaging. Furthermore, it allows for flexing and adjustment near the end of the positive tab 24, preventing the pad from directly adhering to the end surface formed by the winding of the positive and negative electrode sheets 23 and 21 when the tab 24 is bent and adjusted. Exemplarily, the difference between the length of the positive electrode tab welding section and the width of the positive electrode sheet 23 is between 0.5 mm and 1.5 mm. In specific implementation, the difference between the length of the positive electrode tab welding section and the width of the positive electrode sheet 23 can be set to 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.3 mm, 1.5 mm or any value between 0.5 mm and 1.5 mm according to actual needs.

[0075] Optionally, the core further includes a fourth adhesive paper layer 34, which is affixed to at least one side of the outer surface of the core, and the fourth adhesive paper layer 34 is located between the negative electrode tab 22 and the positive electrode tab 24. Specifically, the fourth adhesive paper layer 34 can be affixed to any side of the outer surface of the core, or the fourth adhesive paper layer 34 can be affixed to the opposite side of the outer surface of the core. Exemplarily, the fourth adhesive paper layer 34 can surround the outer surface of the core, or can be affixed only to two opposite sides of the core. On the one hand, the fourth adhesive paper layer 34 can make the thickness of the portion of the core located between the negative electrode tab 22 and the positive electrode tab 24 substantially consistent with the thickness of the portion of the core where the negative electrode tab 22 and the positive electrode tab 24 are provided, thereby improving the flatness of the core and improving the interfacial bonding effect of the core after formation, ultimately achieving the purpose of improving the long cycle life of the battery, and preventing expansion problems and deformation problems. On the other hand, the fourth adhesive tape layer 34 can play a buffering role when the roll core falls or is impacted, thereby helping to improve the falling performance of the roll core.

[0076] Optionally, the width of the fourth adhesive paper layer 34 is less than or equal to the width between the negative electrode tab 22 and the positive electrode tab 24 to ensure that the fourth adhesive paper layer 34 is disposed between the negative electrode tab 22 and the positive electrode tab 24 , thereby facilitating improvement in the flatness of the winding core.

[0077] Optionally, twice the thickness of the fourth adhesive tape layer 34 is equal to the thickness of the negative electrode tab 22, or twice the thickness of the fourth adhesive tape layer 34 is equal to the thickness of the positive electrode tab 24. The fourth adhesive tape layer 34 can increase the thickness of the portion of the winding core located between the negative electrode tab 22 and the positive electrode tab 24, so that the thickness of the portion of the winding core located between the negative electrode tab 22 and the positive electrode tab 24 is substantially consistent with the thickness of the portion of the winding core where the negative electrode tab 22 and the positive electrode tab 24 are located, thereby facilitating improved flatness of the winding core. The thickness of the negative electrode tab 22 can be equal to the thickness of the positive electrode tab 24.

[0078] Example 2

[0079] Based on the first embodiment, this embodiment provides a soft-pack battery, which includes a shell and a roll core, wherein the roll core is encapsulated in the shell. Exemplarily, the shell can be an aluminum-plastic film shell.

[0080] The winding core provided in this embodiment has the same structure as the winding core in the first embodiment and can bring the same or similar technical effects. Please refer to the first embodiment for details.

[0081] The soft-pack battery provided in this embodiment includes a housing and a core, which is encapsulated within the housing. While the unevenness of the core surface is improved, the flatness of the soft-pack battery is also improved, which helps improve the interfacial bonding of the soft-pack battery after formation, ultimately achieving the goal of improving the soft-pack battery's long cycle life, reducing expansion and deformation issues.

[0082] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed or detachable connections; they can be in contact with each other or be integral; they can be mechanical or electrical connections; they can be directly connected or indirectly connected through an intermediate medium, or they can be internally connected between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0083] The terms "first" and "second" in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the application described herein can, for example, be implemented in an order other than that illustrated or described herein.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A winding core, characterized in that: The invention comprises a negative electrode sheet and a positive electrode sheet, wherein the positive electrode sheet and the negative electrode sheet are wound in the same direction; the inner surface of the second bending area of the negative electrode sheet along the winding direction is covered with a first adhesive paper layer, and the projections of the two ends of the first adhesive paper layer along the thickness direction of the winding core are connected to or partially overlapped with the projection of the winding head end of the negative electrode sheet along the thickness direction of the winding core; the projections of the two ends of the first adhesive paper layer along the thickness direction of the winding core do not overlap with the projection of the winding head end of the positive electrode sheet along the thickness direction of the winding core; A concave portion is provided on a side of the first adhesive paper layer facing away from the second bending area of the negative electrode sheet.

2. The winding core according to claim 1, characterized in that The negative electrode sheet further comprises a negative electrode tab, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer, wherein the negative electrode active layer is coated on two opposite sides of the negative electrode current collector; the winding head end of the negative electrode current collector is exposed in sequence along the winding direction to form a negative electrode double-sided empty foil area and a negative electrode single-sided empty foil area, and the negative electrode tab is arranged in the negative electrode double-sided empty foil area; The first adhesive paper layer is located in the single-sided empty foil area of the negative electrode, and the projections of the two ends of the first adhesive paper layer along the thickness direction of the winding core are connected to the projection of one end of the negative electrode ear close to the bending area along the thickness direction of the winding core.

3. The winding core according to claim 2, characterized in that A recessed portion is provided on a side of the first adhesive paper layer facing away from the negative electrode single-sided empty foil area.

4. The winding core according to claim 3, characterized in that The thickness of the middle region of the recessed portion in the longitudinal direction of the negative electrode sheet is smaller than the thickness of other regions of the recessed portion; and the thickness of the recessed portion gradually increases from the middle region to both sides of the recessed portion.

5. The winding core according to claim 4, characterized in that The thickness of the middle region of the recessed portion is in a range of 3 μm to 8 μm; and / or, The opening of the recessed portion has a size ranging from 1 mm to 5 mm in the longitudinal direction of the negative electrode sheet; and / or The middle area of the recessed portion corresponds to the middle area of the negative electrode single-sided empty foil area in the length direction of the negative electrode sheet.

6. The winding core according to claim 2, characterized in that The positive electrode sheet further comprises a positive electrode tab assembly, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer, wherein the positive electrode active layer is coated on two opposite sides of the positive electrode current collector; the winding head end of the positive electrode current collector is exposed to form a positive electrode double-sided empty foil area; the positive electrode tab assembly is disposed in the positive electrode double-sided empty foil area and has a preset distance between the positive electrode tab and the negative electrode tab; the negative electrode tab is located between the positive electrode tab assembly and the bending area; A second adhesive paper layer is provided on the opposite sides of the positive electrode double-sided empty foil area, and the first ends of the two second adhesive paper layers are respectively overlapped on the first ends of the positive electrode active layer located on the opposite sides of the positive electrode current collector, and the second ends of the two second adhesive paper layers are both connected to the end of the positive electrode ear assembly away from the negative electrode ear.

7. The winding core according to claim 6, characterized in that The positive electrode tab assembly includes a positive electrode tab, a first positive electrode tab adhesive paper layer and a second positive electrode tab adhesive paper layer, wherein the first positive electrode tab adhesive paper layer covers the surface of the positive electrode tab, and the second positive electrode tab adhesive paper layer covers the side of the positive electrode double-sided blank foil area away from the positive electrode tab, and the position of the second positive electrode tab adhesive paper layer is opposite to that of the first positive electrode tab adhesive paper layer; The second ends of the two second adhesive paper layers are respectively connected to the ends of the first positive electrode tab adhesive paper layer and the second positive electrode tab adhesive paper layer away from the negative electrode tab; and / or, The second adhesive paper layer located on the side of the positive electrode double-sided empty foil area away from the positive electrode tab and the second positive electrode tab adhesive paper layer are integrally formed; and / or, The second adhesive paper layer located on one side of the positive electrode double-sided empty foil area where the positive electrode tab is arranged is integrated with the first positive electrode tab adhesive paper layer.

8. The winding core according to claim 7, characterized in that Two third adhesive paper layers are provided at the winding end of the positive electrode sheet, and the first ends of the two third adhesive paper layers are respectively overlapped on the second ends of the positive electrode active layer located on the opposite sides of the positive electrode current collector, and the projections of the second ends of the two third adhesive paper layers along the thickness direction of the winding core are both connected to the projection of the end of the positive electrode ear away from the negative electrode ear along the thickness direction of the winding core.

9. The winding core according to claim 8, characterized in that The sum of the thickness of the two second adhesive paper layers and the thickness of the two third adhesive paper layers is a first thickness value; the sum of the thickness of the positive electrode tab, the thickness of the first positive electrode tab adhesive paper layer, and the thickness of the second positive electrode tab adhesive paper layer is a second thickness value; The difference between the first thickness value and the second thickness value ranges from 80% to 120%.

10. The winding core according to claim 7, characterized in that Also included is a separator, which is disposed between the positive electrode sheet and the negative electrode sheet; The sum of the thickness of the positive electrode tab, the thickness of the first positive electrode tab paper layer, the thickness of the second positive electrode tab paper layer, twice the thickness of the positive electrode current collector, and twice the thickness of the separator is a third thickness value; twice the thickness of the first paper layer is a fourth thickness value; The difference between the third thickness value and the fourth thickness value ranges from 80% to 120%; And / or, it further includes a fourth adhesive paper layer, wherein the fourth adhesive paper layer is attached to at least one side of the outer surface of the winding core, and the fourth adhesive paper layer is located between the negative electrode tab and the positive electrode tab.

11. A soft pack battery, characterized in that: The invention comprises a shell and a winding core according to any one of claims 1 to 10, wherein the winding core is encapsulated in the shell.

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