Core

Abstract

The present invention belongs to the technical field of battery processing, and discloses a winding core. The winding core is formed by winding a positive electrode sheet, a diaphragm, a negative electrode sheet and a diaphragm stacked in sequence to form a through hole in the center of the winding core. The positive electrode foil of the positive electrode sheet has a positive electrode active material layer and a blank foil located at the axial end of the winding core. The blank foil of the positive electrode sheet is flattened to form a flat surface. An insulating layer is provided on the inner side of at least one circle of the negative electrode sheet closest to the through hole. The insulating layer is used to prevent the blank foil of the positive electrode sheet from piercing the diaphragm and connecting with the negative electrode sheet. The winding core can prevent the blank foil of the positive electrode sheet from penetrating the diaphragm and contacting the negative electrode sheet, thereby avoiding the occurrence of a short circuit and improving the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery processing, and in particular to a winding core. Background Art

[0002] Full-ear cylindrical batteries have greatly improved the battery's overcurrent capability, reduced the battery's heat generation, and broken through the bottleneck of cylindrical batteries, so they have attracted much attention. Leveling is a key process in the manufacturing process of cylindrical full-ear batteries. In high-rate discharge, due to the large current flowing through, the internal resistance of the battery becomes a problem. Cylindrical batteries currently use a full-ear method to reduce the internal resistance of the battery.

[0003] The full-ear cylindrical battery includes a winding core and two current collecting sheets. The winding core is formed by stacking the positive electrode sheet, diaphragm, negative electrode sheet and diaphragm in sequence from the outside to the inside to form a through hole in the center of the winding core. The two ends of the winding core need to be flattened and welded to the two current collecting sheets. During the flattening process, a positioning pin is inserted into the through hole. After the blank foil on the top of the positive electrode sheet is flattened, the blank foil of the positive electrode sheet closer to the inside is easy to press against the positioning pin. Under the action of a large external force, the blank foil of the positive electrode sheet is easy to extend into the through hole through the gap between the positioning pin and the through hole wall. There is a certain probability that the edge of the blank foil of the positive electrode sheet will pierce the innermost diaphragm and contact the negative electrode sheet, causing a short circuit and causing safety problems.

[0004] Therefore, it is urgent to design a winding core to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a winding core that can prevent the blank foil of the positive electrode sheet from penetrating the diaphragm and contacting the negative electrode sheet, thereby avoiding the occurrence of a short circuit and improving the safety performance of the battery.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The winding core is formed by winding the positive electrode sheet, the separator, the negative electrode sheet and the separator stacked in sequence, and a through hole is formed in the center of the winding core.

[0008] The positive electrode foil of the positive electrode sheet has a positive electrode active material layer and a first blank foil located at the axial end of the winding core; the negative electrode foil of the negative electrode sheet has a negative electrode active material layer and a second blank foil located at the axial end of the winding core;

[0009] At least the first blank foil is bent toward the center of the winding core and overlapped to form a flat surface;

[0010] The negative electrode sheet has an insulating layer at the corner position of the outer edge of the side away from the second blank foil and the winding start edge, the insulating layer at least partially overlaps with the projection of the negative electrode active material layer, the insulating layer faces the center of the winding core, and the insulating layer is used to prevent the first blank foil from piercing the separator and connecting with the negative electrode sheet;

[0011] The length of the insulating layer extending from the winding start end of the negative electrode sheet to the extending direction of the negative electrode sheet is L1, the diameter of the inner circumference of the negative electrode sheet is D, and L1≥πD.

[0012] As an optional solution, the negative electrode sheet located at the winding starting end is wound inwards by a preset distance L4 more than the positive electrode sheet, πD≤L1≤πD+L4.

[0013] As an optional scheme, the above-mentioned insulating layer extends axially from the edge of the above-mentioned negative electrode sheet close to the above-mentioned first blank foil, and has a height of L2, L2≥W1-W2-L3, and a bending zone is formed at the outermost side of the above-mentioned first blank foil, W1 is the bending width of the above-mentioned bending zone, W2 is the distance between the innermost above-mentioned positive electrode sheet and the innermost above-mentioned diaphragm, and L3 is the axial distance between the above-mentioned flat surface and the edge of the above-mentioned negative electrode sheet.

[0014] As an optional solution, the insulating layer is an insulating tape or an insulating ceramic layer.

[0015] As an optional solution, the winding core is a winding core prepared by a flattening method, and the flat surface is a whole single plane.

[0016] As an optional solution, the above-mentioned winding core is prepared by a flattening method, and the above-mentioned flat surface also has grooves. The above-mentioned grooves are radially spaced from the inner periphery to the outer periphery of the above-mentioned winding core on the above-mentioned flat surface, and the above-mentioned flat surface is divided into several independent welding areas by the above-mentioned grooves.

[0017] As an optional solution, the diaphragm pre-wound with the through hole is provided with at least two layers.

[0018] As an optional solution, at the end away from the second blank foil, the edge of the negative electrode active material layer is flush with the edge of the negative electrode sheet.

[0019] As an optional solution, the winding start end of the negative electrode sheet is flush with the winding start end of the negative electrode active material layer.

[0020] As an optional solution, a third blank foil is provided between the winding start end of the negative electrode sheet and the winding start end of the negative electrode active material layer, and the width of the third blank foil is L3, where L3<L1.

[0021] The beneficial effects of the present invention are:

[0022] The present invention provides a winding core, wherein an insulating layer is arranged on a side of a negative electrode sheet facing a through hole, such that the top of an innermost first blank foil abuts against a positioning pin and is inserted into a gap between the positioning pin and the through hole, and its edge punctures a diaphragm and pierces the insulating layer. The insulating layer negative electrode sheet plays a protective role, preventing the first blank foil from contacting the negative electrode sheet and causing a short circuit, thereby improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is an exploded view of the flattened winding core and two current collecting sheets welded together according to an embodiment of the present invention;

[0024] Figure 2 is an exploded view of the welding of a flattened winding core and two current collecting sheets provided by an embodiment of the present invention;

[0025] Figure 3 is a layered diagram of the interior of a winding core provided by an embodiment of the present invention;

[0026] Figure 4 is a schematic cross-sectional view of a winding core provided by an embodiment of the present invention;

[0027] Figure 5 This is a stacking diagram of the positive electrode sheet and the negative electrode sheet of the winding core at the starting end of the winding when the positive electrode sheet and the negative electrode sheet are unfolded in one embodiment of the present invention (back side);

[0028] Figure 6 It is a stacking diagram (front) of the core positive electrode sheet, separator, negative electrode sheet, and separator provided in an embodiment of the present invention when they are unfolded at the starting end of winding;

[0029] Figure 7 is a stacking diagram (back side) of the positive electrode sheet and the negative electrode sheet of the winding core at the starting end of the winding when the positive electrode sheet and the negative electrode sheet are unfolded in another embodiment of the present invention;

[0030] Figure 8 is a schematic diagram of partitioning of a flat surface of a winding core provided by an embodiment of the present invention;

[0031] Fig. 9 is a working principle diagram of the electric screwdriver provided by an embodiment of the present invention;

[0032] Fig.10 It is a working principle diagram of an electric vehicle provided by an embodiment of the present invention.

[0033] In the figure:

[0034] 10. Roll core;

[0035] 11. flat surface; 111. welding area; 1111. welding line; 112. groove;

[0036] 13. positive electrode sheet; 131. positive electrode active material layer; 132. first blank foil; 14. negative electrode sheet; 141. insulating layer; 142. negative electrode active material layer; 143. second blank foil; 144. third blank foil; 15. separator;

[0037] 16. positive electrode flat surface; 17. negative electrode flat surface; 18. through hole;

[0038] 20. Current collector; 21. Positive electrode current collector; 22. Negative electrode current collector; 30. Winding start end;

[0039] 430, battery pack; 431, electric screwdriver; 432, trigger switch; 433, motor; 434, shaft; 435, motor control unit;

[0040] 600, hybrid vehicle; 601, engine; 602, generator; 603, electric driving force conversion device; 6041, first drive wheel; 6042, second drive wheel; 6051, first wheel; 6052, second wheel; 608, battery; 609, vehicle control device; 610, various sensors; 611, charging port. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0042] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0044] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0045] Figure 1 The structure of a full-ear cylindrical battery according to an embodiment of the present invention (only the winding core 10 and two current collectors 20 are shown), and see Figure 3 The core 10 is formed by winding the positive electrode sheet 13, the separator 15, the negative electrode sheet 14 and the separator 15 stacked in sequence, and the whole is cylindrical. The core 10 in the present invention also has a battery shell on the outside, and the battery shell is a cylindrical metal shell, preferably a steel shell or an aluminum shell (the shell is not shown). The model of the cylindrical battery assembled into the battery cell in the present invention can be selected from any model of cylindrical battery, preferably a 21700 model or a 18650 model cylindrical battery. Figure 3 As shown, in an optional embodiment, the positive electrode active material layer 131 covers most of the positive electrode foil, and the negative electrode active material layer 142 covers most of the negative electrode foil. In the unfolded state, both ends of the positive electrode sheet 13 and the negative electrode sheet 14 in the width direction (i.e., the positions where the active material is not coated) form blank foils. Figure 3 As shown, taking the positive electrode sheet 13 as an example, the position on the positive electrode foil where the positive electrode active material layer 131 is not coated forms a first blank foil 132. Of course, see Figure 3 The portion of the negative electrode foil not coated with the negative electrode active material layer 142 forms a second blank foil 143. Figure 3 As shown, when the core 10 is wound, the positive electrode active material layer 131 and the negative electrode active material layer 142 are staggered in the axial direction so that the first blank foil 132 and the second blank foil 143 are wound into the core 10 in opposite directions, and the upper and lower end surfaces are flattened into a flat surface 11.

[0046] like Figure 3 As shown, the winding core 10 is contained in the battery case in a state of being impregnated with electrolyte. The first blank foil 132 can be a metal foil made of aluminum or aluminum alloy, and the material of the second blank foil 143 can be a metal foil made of copper or copper alloy.

[0047] like Figure 1 As shown, in an optional embodiment, there is a through hole 18 on the central axis of the winding core 10, and the through hole 18 is used to insert a positioning pin (not shown in the figure), and the positioning pin is used for welding the negative electrode collector 22 and the bottom of the battery casing.

[0048] like Figure 1 and Figure 3 As shown, in an optional embodiment, the current collector 20 is divided into a positive current collector 21 and a negative current collector 22. The positive current collector 21 is welded to the flat surface 11 formed by the first blank foil 132. The positive current collector 21 can be a metal plate or metal sheet made of a single body or composite material of aluminum or aluminum alloy. The negative current collector 22 is welded to the flat surface 11 formed by the second blank foil 143. The negative current collector 22 can be a metal plate or metal sheet made of a single body or composite material of nickel, nickel alloy, copper, or copper alloy. A hole is opened near the center of the positive current collector 21, and the position of the hole is the position corresponding to the through hole 18. The negative current collector 22 can be a whole circular current collector, or a circular current collector with a circular protrusion in the center. The center position of the current collector 20 at one end of the negative electrode is further welded to the bottom of the battery shell through an external positioning pin.

[0049] It is understandable that the present invention Figures 1 to 8 They are only schematic diagrams. For example, the actual number of layers of the core 10 is subject to actual conditions. In an optional embodiment, the positive electrode active material layer 131 includes any one or more of the positive electrode materials capable of embedding and de-embedding lithium. The positive electrode active material layer 131 may also further include any one or more of other materials such as a positive electrode binder and a positive electrode conductor. The positive electrode material can be lithium iron phosphate or nickel-cobalt-manganese system, nickel-cobalt-aluminum system ternary materials and other lithium-ion battery positive electrode materials already available in the prior art.

[0050] In an optional embodiment, the negative electrode material can be a carbon material, such as artificial graphite and natural graphite, or a graphite composite negative electrode material doped with a certain amount of silicon oxygen or silicon carbon, as well as other lithium-ion battery negative electrode materials available in the prior art.

[0051] In an optional embodiment, the diaphragm 15 can be a single-layer PP, a single-layer PE, a double-layer PP / PE, a double-layer PP / PP, and a triple-layer PP / PE / PP. The diaphragm 15 can also be a porous membrane coated with ceramic particles, and the ceramic is preferably Al 2 O 3Or boehmite; the diaphragm 15 can also be other lithium-ion battery diaphragm materials available in the prior art.

[0052] In an optional embodiment, the electrolyte includes a solvent and an electrolyte salt. In addition, the electrolyte may further include any one or more of other materials such as additives.

[0053] In an optional embodiment, the solvent includes any one or more non-aqueous solvents such as organic solvents. The electrolyte of the non-aqueous solvent is a so-called non-aqueous electrolyte, and the non-aqueous solvent can be, for example, cyclic carbonate, chain carbonate, lactone, chain carboxylic acid ester, nitrile (mononitrile), etc.

[0054] In an optional embodiment, the electrolyte salt may include any one or more of lithium salts, etc. In addition, the electrolyte salt may also include salts other than lithium salts, etc. The salts other than lithium salts may be light metal salts other than lithium, etc.

[0055] In one embodiment, the battery shell is a metal shell, which may be a steel shell or an aluminum shell, and is more preferably a steel shell.

[0056] In an optional embodiment, the lithium salt is, for example, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), lithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl) and lithium bromide (LiBr). Among them, the lithium salt can be any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoroarsenate; the lithium salt more preferably includes lithium hexafluorophosphate. The content of the electrolyte salt is not particularly limited, and preferably 0.3 mol / kg to 3 mol / kg relative to the solvent.

[0057] Among them, the preparation method for forming the flat surface 11 is generally divided into flattening or pressing. The flattening method is to directly contact the flattening head of the flattening machine on the full-pole ear, and then as the flattening head rotates close to the full-pole ear, it will roll and drive the full-pole ear to be flattened at the end of the wound battery cell, such as Figure 2 As shown, the core is prepared by the flattening method, and the flat surfaces at both ends are a whole single plane. Figure 1 ), taking the positive electrode flat surface 16 as an example, the flat surface 11 is formed by bending and overlapping the multiple layers of the first blank foil 132 toward the central axis of the winding core 10 by a flattening device, and the groove 112 on the flat surface 11 is realized by pressing down the ribs. Figure 1As shown, the first blank foil 132 and the second blank foil 143 are bent into the flat surface 11 , and the bending direction is from the outer periphery of the winding core 10 toward the through hole 18 , and the adjacent blank foils of the positive electrode sheet 13 or the negative electrode sheet 14 are bent so as to overlap each other.

[0058] Regardless of whether the flat surface 11 is formed by kneading or pressing, during the flattening process, since the blank foil on the top of the positive electrode sheet 13 is flattened, the first blank foil 132 closer to the inside is easy to press against the positioning pin. Under the action of a large external force, the first blank foil 132 is easy to extend into the through hole 18 through the gap between the positioning pin and the wall of the through hole 18. There is a certain probability that the edge of the first blank foil 132 will pierce the innermost diaphragm 15 and contact the negative electrode sheet 14, causing a short circuit and causing safety problems.

[0059] In order to solve the above problems, this embodiment provides a winding core, such as Figure 3 , Figure 4 and Figure 5 As shown, the negative electrode sheet 14 has an insulating layer 141 at the outer edge of the side away from the second blank foil 143 and the corner position of the winding start edge. The insulating layer 141 at least partially overlaps with the projection of the negative electrode active material layer 142. The insulating layer 141 faces the center of the winding core 10 and covers the negative electrode active material layer 142 for more than one circle. The insulating layer 141 is used to prevent the first blank foil 132 from piercing the separator 15 and connecting with the negative electrode sheet 14. The winding core 10 is provided with an insulating layer 141 on the side of the negative electrode sheet 14 facing the through hole 18, such as the top of the innermost first blank foil 132 abuts against the positioning pin and then is inserted into the gap between the positioning pin and the through hole 18 (see Figure 3 ), the edge of which pierces the diaphragm 15 and pierces the insulating layer 141. The insulating layer 141 plays a protective role, preventing the first blank foil 132 from contacting the negative electrode sheet 14 and causing a short circuit, thereby improving the safety performance of the battery.

[0060] At the end away from the second blank foil 143 , the edge of the negative electrode active material layer 142 is flush with the edge of the negative electrode sheet 14 .

[0061] See also Figure 3 , Figure 4-Figure 6, the end close to the through hole 18 is defined as the winding starting end 30, and the negative electrode sheet 14 at the winding starting end 30 is wound inwardly by a preset distance L4 more than the positive electrode sheet 13. It can be understood that when the positive electrode sheet 13, the separator 15, the negative electrode sheet 14 and the separator 15 are in a flattened state, the winding starting end 30 is not flush, and the winding starting end 30 of the separator 15 inside the negative electrode sheet 14 is ahead of the winding starting end 30 of the positive electrode sheet 13, and the negative electrode sheet The winding starting end 30 of the separator 15 on the inner side of 14 is closer to the front than the winding starting end 30 of the negative electrode sheet 14. The winding starting ends 30 of the two separators 15 can be flush or staggered. What is more important is that in order to ensure that the positive electrode active material layer 131 of the positive electrode sheet 13 falls entirely inside the negative electrode sheet 14 and to ensure that the coverage area of ​​the two is maximized, it is necessary to ensure that the winding starting end 30 of the negative electrode sheet 14 is closer to the front than the winding starting end 30 of the positive electrode sheet 13.

[0062] The insulating layer 141 extends from the winding start end 30 of the negative electrode sheet 14 to the extension direction of the negative electrode sheet 14, the length of the insulating layer 141 is L1, the diameter of the through hole 18 is D, and L1 ≥ πD. That is, see Figure 4 If L1<πD, the insulating layer 141 does not form a complete circle of protection around the positioning pin, and there is a gap between the beginning and the end. The first blank foil 132 may still pass through the diaphragm 15 from the gap and contact the negative electrode sheet 14 to short-circuit. Therefore, L1≥πD is set to ensure that the protection area of ​​the insulating layer 141 is sufficient.

[0063] In a preferred embodiment, L1≤πD+L4, so set, see Figure 4 It can be understood that if the length of the insulating layer 141 is too long, so that it extends between the second circle of negative electrode sheets 14 and the first circle of positive electrode sheets 13, this will affect the ion or electron exchange rate between the positive electrode sheets 13 and the negative electrode sheets 14, and affect the battery capacity and interlayer thickness, etc. Therefore, L1≤πD+L4 is set to ensure sufficient protection for the innermost circle of negative electrode sheets 14 without affecting the battery capacity and interlayer thickness.

[0064] In an optional embodiment, if Figure 5 As shown, the winding start end 30 of the negative electrode active material layer 142 is flush with the winding start end 30 of the negative electrode sheet 14 .

[0065] In another embodiment, Figure 7 As shown, there is a third blank foil 144 between the winding start end 30 of the negative electrode sheet 14 , and the width of the third blank foil 144 is L7 , where L7 < L1 .

[0066] In an alternative embodiment, see Figure 3 and Figure 5The insulating layer 141 extends axially from the edge of the negative electrode sheet 14 close to the first blank foil 132, and the height is L2, L2 ≥ W1-W2-L3, and a bending area is formed on the outermost side of the first blank foil 132, W1 is the bending width of the bending area, W2 is the distance between the innermost positive electrode sheet 13 and the innermost separator 15, and L3 is the distance between the flat surface 11 and the edge of the negative electrode sheet 14 in the axial direction. Figure 3 and Figure 4 To further explain the bending area, flattening is used as an example. The flattening is similar. The blank foil of the positive electrode foil extends along the axial direction of the winding core 10. The top of the blank foil of the positive electrode foil (that is, the first blank foil 132) is flattened by the pressing tool (part of the first blank foil 132) to form a positive electrode flat surface 16 (the flat surface 11 at the other end of the winding core 10 is the negative electrode flat surface 17). The flattened portion is the bending portion, and the length of the bending portion bent inward is W1. It can be understood that, see also Figure 3 For the innermost first blank foil 132, after the length W1 is bent, the length W2 is first planed off to be the length that may be squeezed between the positioning pin and the side wall of the through hole 18, and the remaining length is planed down to a distance of L3 to contact the negative electrode sheet 14. Considering the most extreme case, the farthest position that can be contacted in a straight line downward is the lowest position of the insulating layer 141. If the bottom edge of the insulating layer 141 is higher than this position, the edge of the first blank foil 132 may pierce the diaphragm 15 inwardly and the insulating layer 141 cannot block it. Therefore, L2 ≥ W1-W2-L3 is set to ensure that the first blank foil 132 and the negative electrode sheet 14 are completely blocked in the axial direction of the winding core 10.

[0067] Among them, Figure 3As shown, the first blank foil 132 and the second blank foil 143, due to the different flattening structures, we discuss them separately for positive and negative electrodes. The first blank foil 132 can be divided into a vertical area and a bending area L+W1, wherein the width of the vertical area is L, and the width of the bending area is W1. Due to the design of the electrode structure, the negative electrode sheet 14 will be larger than the positive electrode sheet 13 in the width direction, and the entire negative electrode sheet 14 will cover the positive electrode sheet 13. Therefore, in the width direction of the electrode sheet (i.e., the length direction of the winding core 10), the vertical area L can be further divided into an outer vertical area L5 and an inner vertical area L6, L=L5+L6, and the entire first blank foil 132 is L+W1. Generally speaking, since the physical rigidity requirements of L5 and L6 are much greater than those of W1, in the actual coil design, L6 will be coated with ceramic slurry or insulating glue and other materials to increase the rigidity of L6 to resist bending. At the same time, its insulating coating can effectively alleviate the internal short of the positive electrode sheet 13 and the negative electrode sheet 14. For the L5 part, as needed, we will also apply ceramic slurry or insulating glue and other materials on most or all of L5 to increase the rigidity of L5 to resist bending. The coating on L5 and the coating on L6 are continuous coatings, and the materials of the two can be the same and applied at the same time. It can be understood that the vertical area L has stronger physical rigidity than the bending area, ensuring that the vertical area L maintains a substantially vertical direction during the flattening process to prevent excessive interference with the negative electrode sheet 14.

[0068] Through long-term practical exploration by technicians, when L5 / L6<0.2, the ratio is too small to effectively protect the negative electrode sheet 14, and it also affects the alignment accuracy of the winding (this part mostly considers the use of glue coating). When L5 / L6>2, the ratio is too large, the battery energy density will be affected, and the battery capacity will be reduced by about 2.5%-5%. In an optional embodiment, 0.2≤L5 / L6≤2 is adopted. Through this setting method, the negative electrode sheet 14 can be protected at the same time, the winding alignment accuracy is ensured, and the battery energy density will not be affected.

[0069] For the negative electrode, its structure is basically the same as that of the positive electrode. The main difference is that: on the positive electrode side, there is a situation where the negative electrode sheet 14 is larger than the positive electrode sheet 13 in the width direction. On the negative electrode side, the above structure does not exist, and the entire negative electrode protrudes from the positive electrode sheet 13. Of course, we can also divide the blank foil on the negative electrode side into the form of L+W (not shown in the figure), but L does not need to be further divided into L5 and L6. For the L part on the negative electrode side, we can also choose to apply ceramic slurry or insulating glue and other materials to increase the rigidity of L, but considering the flattening process, if the L part of the negative electrode itself can meet the rigidity requirements of flattening, it is also possible not to apply ceramic slurry or insulating glue and other materials. The core reason is that the negative electrode side does not need to consider the problem of internal short caused by the negative electrode sheet 14 and the positive electrode touching each other, so the ceramic slurry or insulating glue coating on the negative electrode side is an option, which can be selected according to actual needs.

[0070] It should be noted that in actual products, the vertical area L and the bending area can be directly connected or smoothly transitioned through a transition structure. In the present invention, a direct connection method is adopted.

[0071] In an optional embodiment, the insulating layer 141 is an insulating tape, that is, the insulating layer 141 is directly bonded to the inner side of the negative electrode sheet 14 (specifically, the negative electrode active material layer 142), which is more convenient to operate. The insulating tape, preferably PI tape, and other existing insulating tapes in the prior art are used in the present invention.

[0072] In an optional embodiment, the insulating layer 141 is formed by coating an insulating ceramic layer, which is not limited here. The insulating ceramic layer preferably uses a mixed coating of Al2O3 / boehmite and PVDF, as well as other insulating ceramic layers available in the prior art.

[0073] In another optional embodiment, if Figure 3 and Figure 4 As shown, the innermost diaphragm 15 can be provided with at least two layers, which can further increase the thickness of the insulation and provide a better anti-puncture effect. In principle, due to the presence of the insulating layer 141 of the present invention, the innermost diaphragm 15 can be a single layer, or even no diaphragm 15 is provided, which can prevent the occurrence of a short circuit in the battery. However, in order to achieve the effect of double insurance, the diaphragm 15 of the present invention is provided with more than two layers. At the very least, the insulating layer 141 of the present invention can effectively reduce the number of layers of the required diaphragm.

[0074] In an optional embodiment, if Figure 8As shown, when the winding core is prepared by a flattening method, grooves 112 are formed on the flat surface 11, and the grooves 112 are radially spaced from the inner circumference to the outer circumference of the winding core on the flat surface 11, and the flat surface 11 is divided into a plurality of independent welding areas 111 by the grooves 112. The grooves 112 can absorb the wrinkles generated when the multiple layers of the first blank foil 132 or the multiple layers of the second blank foil 143 are stacked and pressed inwardly, so as to reduce the flatness of the flat surface 11, thereby improving the welding stability with the current collector 20.

[0075] Combination Figure 8 The flatness of the flat surface 11 is obtained as follows: Figure 8 As shown, in the experiment, a 3D profilometer is used to test the flatness of the flat surface 11 of the core 10. The plane to be measured is selected, and the machine identifies the highest point and the lowest point of the selected area, and automatically calculates the difference between the high and low points, that is, the flatness.

[0076] The calculation formula for flatness is as follows:

[0077] F=H1-H2;

[0078] Among them, F is the flatness of the test area of ​​the flat surface 11 of the core 10, H1 is the height of the highest point of the test area of ​​the flat surface 11 of the core 10, and H2 is the height of the lowest point of the test area of ​​the flat surface 11 of the core 10. Figure 6 The shaded area in the middle is the eight overall plane areas measured. In a specific embodiment, the flatness measured by the present invention is the flatness of the entire battery cell end face (including the eight welding areas).

[0079] For example, Figure 8 The shaded part is the eight measured welding areas 111 , which are used for welding with the corresponding current collecting pieces 20 . Those skilled in the art can measure the flatness of the entire flat surface 11 or measure the flatness of each welding area 111 separately as needed.

[0080] In an optional embodiment, if Figure 8 As shown, for the number M of the grooves 112, generally a symmetrical number or a number that can equally divide the circumference can be selected. Generally speaking, the number M should be greater than or equal to 4. M can be selected as 4, 5, 6, 8, 9, 10, 12, etc. All point values ​​or ranges greater than or equal to 4 and less than or equal to 12 are within the protection scope of this optional embodiment. Among them, based on the size of the commonly used model of the winding core 10, the number M of this optional embodiment can be selected as 6 or 8.

[0081] In an optional embodiment, if Figure 8As shown, the grooves 112 on the flat surface 11 can be evenly arranged in the entire circumferential area, and the angles of the grooves 112 are the same, so as to ensure the uniformity of the overall strength and hardness of the flat surface 11 and the overall flatness, and ensure the stable welding effect between the flat surface 11 and the current collecting sheet 20. Of course, in other optional embodiments, it is not ruled out that some areas may not be arranged with grooves 112, or the grooves 112 may also be arranged in the form of unequal spacing, and the arrangement of different grooves 112 is within the protection scope of the present application.

[0082] In an optional embodiment, if Figure 8 As shown, the arrangement of the grooves 112 should extend from the inner periphery of the winding core 10 to the outer periphery and run through the entire winding core 10. This design divides the flat surface 11 into several independent fan-shaped areas, which are used to weld with the current collector 20. These fan-shaped areas are called welding areas 111. This welding area 111 can be the same fan-shaped area, which is the same and independent and not connected to each other. For example, in this embodiment, the preferred scheme is to be divided into eight fan-shaped welding areas 111 with equal areas by eight grooves 112 spaced at the same angle of 45°.

[0083] Alternatively, if Figure 8 As shown, the welding area 111 is welded to the corresponding position of the current collecting sheet 20 by a welding wire 1111, and the welding wire 1111 is a straight spiral welding, which has a simple shape and is convenient for welding. It should be noted that since the flat surface obtained by the present invention has a high flatness, the selection of welding wire is not limited to a straight spiral welding, and existing welding wires can be used.

[0084] In an optional embodiment, if Figure 8 As shown, a plurality of welding wires 1111 are evenly distributed radially from the center of the winding core 10. Through the above arrangement, the uniformity of welding between the flat surface 11 and the corresponding current collecting sheet 20 is improved. Figure 8 As shown, the number of welding wires 1111 and slots 112 is set to eight. In other embodiments, it can be understood that the present invention does not require all welding areas 111 to be welded, and the number of welding wires 1111 can also be less than the number of welding areas 111, and can also be 3, 4, 5, 6 or 7, etc., which is not limited here.

[0085] This embodiment also provides a full-ear tab cylindrical battery, comprising the winding core 10 and two current collecting sheets 20, wherein the two current collecting sheets 20 and the two flat surfaces 11 are arranged in a one-to-one correspondence and connected by welding. The full-ear tab cylindrical battery adopts the winding core 10, which can reduce the probability of short circuit and improve the safety performance of the battery.

[0086] Optionally, the full-tab cylindrical battery provided in this embodiment can be applied to an electrical device, which includes the full-tab cylindrical battery and an electrical component, and the full-tab cylindrical battery is used to power the electrical component. The electrical device improves the electrical safety of the electrical device by using the full-tab cylindrical battery.

[0087] In an optional embodiment, the electrical component may be an electronic device, such as a notebook personal computer, a smart phone, a tablet terminal, a PDA (portable information terminal), a mobile phone, a wearable terminal, a cordless phone handset, a camcorder, a digital camera, an electronic book, an electronic dictionary, a music player, a radio, a headset, a game console, a navigation system, a memory card, a pacemaker, a hearing aid, an electric tool, an electric shaver, a refrigerator, an air conditioner, a television, a stereo, a water heater, a microwave oven, a dishwasher, a washing machine, a dryer, lighting equipment, toys, medical equipment, a robot, a load regulator, a signal machine, etc.

[0088] Reference Fig. 9 , an example of an electric tool, such as an electric screwdriver, to which the present invention can be applied is briefly described. The electric screwdriver 431 has a motor 433 such as a DC motor housed in the main body. The rotation of the motor 433 is transmitted to a shaft 434, and the screw is screwed into the object through the shaft 434. The electric screwdriver 431 is provided with a trigger switch 432 operated by the user.

[0089] A battery pack 430 (the battery pack 430 may be composed of a plurality of full-ear cylindrical batteries) and a motor control unit 435 are housed in the lower frame of the handle of the electric screwdriver 431. The motor control unit 435 controls the motor 433. The various parts of the electric screwdriver 431 other than the motor 433 may also be controlled by the motor control unit 435. Although not shown in the figure, the battery pack 430 and the electric screwdriver 431 are engaged by engaging parts provided in each. As described later, the battery pack 430 and the motor control unit 435 each have a microcomputer. Battery power is supplied from the battery pack 430 to the motor control unit 435, and information about the battery pack 430 is communicated between the microcomputers of both.

[0090] The battery pack 430 can be freely attached and detached from the electric screwdriver 431, for example. The battery pack 430 can also be built into the electric screwdriver 431. The battery pack 430 is installed in the charging device when charging. It should be noted that when the battery pack 430 is installed in the electric screwdriver 431, a part of the battery pack 430 is exposed to the outside of the electric screwdriver 431, and the user can visually identify the exposed part. For example, an LED can also be provided on the exposed part of the battery pack 430 so that the user can confirm whether the LED is lit or not.

[0091] The motor control unit 435 controls, for example, the rotation, stop, and rotation direction of the motor 433. Furthermore, the power supply to the load is cut off in the event of overdischarge. The trigger switch 432 is inserted between the motor 433 and the motor control unit 435, for example. When the user presses the trigger switch 432, the motor 433 is powered and rotates. When the user returns the trigger switch 432, the rotation of the motor 433 stops.

[0092] In an optional embodiment, the electric component may be an electric vehicle. Examples of electric vehicles include railway vehicles, golf carts, electric carts, electric vehicles (including hybrid electric vehicles), etc., and the electric component may be used as a driving power source or auxiliary power source for the electric components. Examples of power storage devices include power sources for buildings such as residences or power generation equipment.

[0093] Reference Fig.10 An example in which the present invention is applied to a power storage system for an electric vehicle will be described. Fig.10 An example of the structure of a hybrid vehicle using a series hybrid system to which the present invention is applied is schematically shown. The series hybrid system is a vehicle that runs using electric power generated by a generator driven by an engine or electric power temporarily stored in a battery using an electric driving force conversion device.

[0094] The hybrid vehicle 600 is equipped with an engine 601, a generator 602, an electric power conversion device 603, a first drive wheel 6041, a second drive wheel 6042, a first wheel 6051, a second wheel 6052, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. The battery pack 430 of the present invention is applied to the battery 608.

[0095] The hybrid vehicle 600 travels using an electric driving force conversion device 603 as a power source. An example of the electric driving force conversion device 603 is a motor. The electric driving force conversion device 603 operates with the power of a battery 608, and the rotational force of the electric driving force conversion device 603 is transmitted to a first drive wheel 6041 and a second drive wheel 6042. It should be noted that the electric driving force conversion device 603 can be applied to an AC motor or a DC motor by using direct current-alternating current (DC-AC) or reverse conversion (AC-DC conversion) at necessary positions. Various sensors 610 control the engine speed via a vehicle control device 609, or control the opening of a throttle valve (throttle opening) not shown. Various sensors 610 include a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

[0096] The rotational force of the engine 601 is transmitted to the generator 602 , and the electric power generated by the generator 602 can be stored in the battery 608 by the rotational force.

[0097] When the hybrid vehicle 600 is decelerated by a brake mechanism (not shown), the resistance during deceleration is applied to the electric driving force conversion device 603 as a rotational force, and the regenerative electric power generated by the electric driving force conversion device 603 by the rotational force is stored in the battery 608 .

[0098] Battery 608 is connected to a power source external to hybrid vehicle 600 , and can receive power from the external power source using charging port 611 as an input port, and can store the received power.

[0099] Although not shown, an information processing device that performs vehicle control based on information about the secondary battery may be provided. Examples of such an information processing device include an information processing device that displays the remaining battery level based on information about the remaining battery level.

[0100] It should be noted that the above description is based on a series hybrid vehicle that uses the power generated by the generator driven by the engine or the power temporarily stored in the battery and is driven by a motor. However, the present invention can also be effectively applied to a parallel hybrid vehicle that uses the output of both the engine and the motor as a driving source and appropriately switches between three modes of driving only by the engine, driving only by the motor, and driving by the engine and the motor. Furthermore, the present invention can also be effectively applied to so-called electric vehicles that are driven only by the drive motor without using an engine.

[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A winding core, wherein the winding core is formed by winding a positive electrode sheet (13), a separator (15), a negative electrode sheet (14) and a separator (15) stacked in sequence, and a through hole (18) is formed at the center of the winding core, characterized in that: The positive electrode foil of the positive electrode sheet (13) has a positive electrode active material layer (131) and a first blank foil (132) located at the axial end of the winding core; the negative electrode foil of the negative electrode sheet (14) has a negative electrode active material layer (142) and a second blank foil (143) located at the axial end of the winding core; At least the first blank foil (132) is bent toward the center of the winding core and overlapped to form a flat surface (11); The negative electrode sheet (14) has an insulating layer (141) at the outer edge of the side away from the second blank foil (143) and at the corner position of the winding start edge, the insulating layer (141) at least partially overlaps with the projection of the negative electrode active material layer (142), the insulating layer (141) faces the center of the winding core, and the insulating layer (141) is used to prevent the first blank foil (132) from piercing the separator (15) and connecting with the negative electrode sheet (14); The length of the insulating layer (141) extending from the winding start end (30) of the negative electrode sheet (14) to the extension direction of the negative electrode sheet (14) is L1, the diameter of the inner circumference of the negative electrode sheet (14) is D, and L1≥πD; The insulating layer (141) extends axially from the edge of the negative electrode sheet (14) close to the first blank foil (132), and has a height of L2, L2 ≥ W1-W2-L3, a bending zone is formed on the outermost side of the first blank foil (132), W1 is the bending width of the bending zone, W2 is the distance between the innermost positive electrode sheet (13) and the innermost separator (15), and L3 is the distance between the flat surface (11) and the edge of the negative electrode sheet (14) in the axial direction; The negative electrode sheet (14) located at the winding starting end (30) is wound inwards by a preset distance L4 more than the positive electrode sheet (13), πD≤L1≤πD+L4.

2. The winding core according to claim 1, characterized in that: The insulating layer (141) is an insulating tape or an insulating ceramic layer.

3. The winding core according to any one of claims 1 to 2, characterized in that: The winding core is a winding core prepared by a flattening method, and the flat surface (11) is a whole single plane.

4. The winding core according to any one of claims 1 to 2, characterized in that: The winding core is prepared by a flattening method, and the flat surface (11) is also provided with grooves (112). The grooves (112) are radially spaced from the inner circumference to the outer circumference of the winding core on the flat surface (11), and the flat surface (11) is divided into a plurality of independent welding areas (111) by the grooves (112).

5. The winding core according to any one of claims 1 to 2, characterized in that: The diaphragm (15) pre-wound around the through hole (18) is provided with at least two layers.

6. The winding core according to any one of claims 1 to 2, characterized in that: At the end away from the second blank foil (143), the edge of the negative electrode active material layer (142) is flush with the edge of the negative electrode sheet (14).

7. The winding core according to any one of claims 1 to 2, characterized in that: The winding start end (30) of the negative electrode sheet (14) is flush with the winding start end (30) of the negative electrode active material layer (142).

8. The winding core according to any one of claims 1 to 2, characterized in that: A third blank foil (144) is provided between the winding start end (30) of the negative electrode sheet (14) and the winding start end (30) of the negative electrode active material layer (142), and the width of the third blank foil (144) is L7, where L7<L1.

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