Battery cell and battery

Abstract

The utility model provides a battery cell and a battery, the battery cell comprises a roll core structure formed by sequentially laminating and winding a positive pole piece, a diaphragm and a negative pole piece, the negative pole piece further comprises an insulating coating, the insulating coating is coated on a second surface, at least part of the insulating coating is located on the outermost ring of the roll core structure, and the insulating coating is located on the outer ring of the roll core structure in the length direction of the negative pole piece. A first interval exists between the head end of the insulating coating and the tail end of the second negative active material layer; the roll core structure comprises a straight area and bending areas located at the two ends of the straight area, and at least part of the first interval is located in the bending areas. Therefore, the insulating coating can be prevented from covering the negative electrode active material layer and extending between the negative electrode active material layer and the negative electrode current collector, so that the poor conductivity of the region is avoided, the lithium ion embedding speed is reduced in the charging process, and the lithium precipitation of the region is slowed down or even avoided, and the safety performance of the battery in use is further improved; and the reduction of the energy density of the battery formed by the roll core structure due to the increase of the thickness of the region of the roll core structure can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery cell and a battery. BACKGROUND

[0002] With the rapid development of battery technology, lithium ion batteries are increasingly widely used. In a lithium ion battery in which a negative electrode sheet is located in the outermost winding layer of a winding core structure, an insulating coating is usually applied to the outer side of the negative electrode current collector in the outermost circle to avoid the negative electrode current collector of the negative electrode sheet from contacting the winding core shell. In order to improve the insulating effect, the insulating coating is continuously coated with the negative electrode active material layer coated on the side of the negative electrode current collector, which may cause the insulating coating to cover the negative electrode active material layer or the insulating coating to extend between the negative electrode active material layer and the negative electrode current collector, resulting in poor conductivity of the region, thereby causing the lithium ion insertion speed to slow down during the charging process, causing the lithium ion concentration in the region to increase to cause lithium precipitation, and even causing safety hazards. In addition, the overlap of the insulating coating and the active material layer in the region may increase the thickness of the region of the winding core structure, and even reduce the energy density of the battery formed by the winding core structure. SUMMARY

[0003] Therefore, the present application provides a battery cell to solve the problems of lithium precipitation of a negative electrode sheet and reduction of the energy density of a battery. The present application also provides a battery comprising the battery cell.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A battery cell, comprising a winding core structure formed by sequentially stacking and winding a positive electrode sheet, a separator and a negative electrode sheet, along the thickness direction of the winding core structure, the negative electrode sheet is located in the outermost circle of the winding core structure, the outermost circle is a layer farthest from the winding center of the winding core structure along the thickness direction of the winding core structure; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on both sides of the positive electrode current collector;

[0006] The negative electrode sheet comprises a negative electrode current collector, a first negative electrode active material layer and a second negative electrode active material layer, along the thickness direction of the negative electrode sheet, the negative electrode current collector comprises a first surface and a second surface, the first surface faces the winding center of the winding core structure, and the second surface faces away from the winding center of the winding core structure, wherein the first negative electrode active material layer is located on the first surface, and the second negative electrode active material layer is located on the second surface, in the length direction of the negative electrode sheet, the tail end of the first negative electrode active material layer exceeds the tail end of the second negative electrode active material layer;

[0007] The negative electrode sheet further comprises an insulating coating layer coated on the second surface, at least part of the insulating coating layer is located at the outermost circle of the core structure, and a head end of the insulating coating layer has a first interval with a tail end of the second negative electrode active material layer in the length direction of the negative electrode sheet.

[0008] The core structure comprises a flat area and bending areas located at both ends of the flat area, and at least part of the first interval is located in the bending area.

[0009] Optionally, the head end of the first interval is located at the head end of the bending area, and the size of the first interval is L1, the arc length of the bending area where the first interval is located is L2, and L1 and L2 satisfy: 0 < L1 ≤ 1.5 * L2 in the length direction of the negative electrode sheet.

[0010] Optionally, the size of the first interval is L1, and the size of the first negative electrode active material layer exceeding the second negative electrode active material layer is L3 in the length direction of the negative electrode sheet, and L1 and L3 satisfy: L3 ≥ 3 * L1.

[0011] Optionally, the negative electrode sheet further comprises an empty foil area where no negative electrode active material layer is arranged on both sides of the negative electrode current collector, and the second surface of the negative electrode current collector located in the empty foil area is coated with the insulating coating layer, wherein:

[0012] The size of the first interval is L1, and the size of the insulating coating layer located in the empty foil area is L4 in the length direction of the negative electrode sheet, and L1 and L4 satisfy: L4 ≥ L1.

[0013] Optionally, the insulating coating layer comprises a first area located on opposite sides of the first negative electrode active material layer, and a second area located in the empty foil area, the projection of the first area and the second area in the thickness direction of the core structure has an overlapping area, and the size W of the overlapping area in the width direction of the core structure satisfies: W ≥ 2 mm.

[0014] Optionally, the negative electrode sheet does not have an empty foil area, and the battery cell further comprises an insulating adhesive tape arranged outside the outermost circle of the core structure, and the insulating adhesive tape covers the first interval.

[0015] Optionally, the negative electrode sheet does not have an empty foil area, and the tail end of the insulating coating layer has a second interval with the tail end of the negative electrode sheet in the length direction of the negative electrode sheet, the second interval and the first interval are located on both sides of the insulating coating layer, and the size L5 of the second interval satisfies: L5 ≤ 5 mm.

[0016] Optionally, the battery cell further comprises an insulating tape arranged outside the outermost winding layer of the winding structure, and the insulating tape covers the second interval.

[0017] A battery comprising the battery cell described in any one of the preceding embodiments.

[0018] The battery cell provided in the present application is coated with an insulating coating on the second surface of the negative current collector away from the center of the winding structure, and at least part of the insulating coating is located in the outermost winding layer of the winding structure. In the length direction of the negative electrode sheet, the head end of the insulating coating and the tail end of the second negative active material layer have a first interval. In this way, the insulating coating can be prevented from covering the negative active material layer and extending into the space between the negative active material layer and the negative current collector, so as to avoid poor conductivity in this area, slow lithium ion insertion speed during charging, large lithium ion concentration in this area, and lithium precipitation in this area, thereby improving the safety performance of the battery during use. In addition, the thickness of this area of the winding structure can also be reduced, and the energy density of the battery formed by the winding structure can also be improved.

[0019] In addition, when the positive electrode sheet is arranged in the outermost winding layer of the winding structure, the positive current collector located at the junction between the single-sided area and the double-sided area of the positive electrode sheet may be broken due to the hard pressure of the roller. In addition, due to the large hardness of the particles of the positive active material layer, especially during the rolling process of the single-sided area of the positive electrode sheet, part of the positive active material layer may be embedded into the positive current collector, causing damage to the positive current collector located in the single-sided area of the positive electrode sheet. However, in the present application, the positive electrode sheet of the battery cell does not have a single-sided area. Compared with the scheme of arranging the positive electrode sheet in the outermost winding layer of the winding structure, the risk of breaking the positive current collector of the positive electrode sheet can be avoided, and the problem of damage to the positive current collector can also be avoided.

[0020] In addition, at least part of the first interval is located in the bending area, which can reduce the thickness of the insulating coating arranged in the bending area of the winding structure, so as to avoid the insulating coating overlapping in the area where the bending area is located during the winding process to form the winding structure, thereby reducing the width of the winding structure, and further reducing the size of the winding structure, that is, reducing the proportion of the non-active material layer structure in the winding structure, thereby improving the energy density of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without any creative labor.

[0022] Figure 1A structural schematic diagram of a winding core structure provided for the embodiment;

[0023] Figure 2 For Figure 1 A structural schematic diagram of a winding core structure provided for the embodiment; Figure 1

[0024] Figure 3 For Figure 1 A structural schematic diagram of a winding core structure provided for the embodiment; Figure 2

[0025] Figure 4 A structural schematic diagram of another winding core structure;

[0026] Figure 5 For Figure 4 A structural schematic diagram of a winding core structure provided for the embodiment;

[0027] Figure 6 A structural schematic diagram of a winding core structure provided for the embodiment;

[0028] In Figures 1-6 , the application provides a winding core structure.

[0029] 1-positive electrode sheet, 2-separator, 3-negative electrode sheet, 4-first interval, 5-second interval, 6-flat area, 7-bent area, 8-insulating adhesive tape;

[0030] 11-positive electrode current collector, 12-positive electrode active material layer, 31-negative electrode current collector, 32-first negative electrode active material layer, 33-second negative electrode active material layer, 34-insulating coating, 35-empty foil area. DETAILED DESCRIPTION

[0031] The application provides an electric core. The application also provides a battery comprising the electric core.

[0032] The technical solutions in the embodiments of the application will be clearly and completely described in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0033] As Figures 1-6 ​​As shown, the embodiment of the present application provides an electric core, which comprises a positive electrode sheet 1, a separator 2 and a negative electrode sheet 3, which are sequentially stacked and wound to form a winding core structure. In the thickness direction of the winding core structure, the negative electrode sheet 3 is located at the outermost layer of the winding core structure. The outermost layer is the layer farthest from the winding center of the winding core structure in the thickness direction of the winding core structure. The winding center of the winding core structure is the central region of the winding structure. For example, the winding center of the winding core structure is the region indicated by A in Figure 1 and Figure 4 . The thickness direction of the winding core structure is the direction indicated by the bidirectional arrow Y in Figure 1 and Figure 4 . The positive electrode sheet 1 comprises a positive electrode current collector 11 and a positive electrode active material layer 12 coated on both sides of the positive electrode current collector 11.

[0034] Specifically, the negative electrode sheet 3 comprises a negative electrode current collector 31, a first negative electrode active material layer 32 and a second negative electrode active material layer 33. The first negative electrode active material layer 32 and the second negative electrode active material layer 33 are respectively coated on both sides of the negative electrode current collector 31. In the unwound state of the negative electrode sheet 3 (as shown in Figure 2 , Figure 3 , Figure 5 and Figure 6 ), in the thickness direction of the negative electrode sheet 3, the negative electrode current collector 31 comprises a first surface and a second surface. In the wound state of the negative electrode sheet 3, the first surface faces the winding center of the winding core structure, and the second surface faces away from the winding center of the winding core structure. It should be noted that in the unwound state of the negative electrode sheet 3, as shown in Figure 2 , the first surface is the side surface of the negative electrode current collector 31 at D, and the second surface is the side surface of the negative electrode current collector 31 at E. The first negative electrode active material layer 32 is located at the first surface, and the second negative electrode active material layer 33 is located at the second surface. In the length direction of the negative electrode sheet 3, the tail end of the first negative electrode active material layer 32 exceeds the tail end of the second negative electrode active material layer 33. That is, the first negative electrode active material layer 32 is located on the side of the negative electrode current collector 31 facing the winding center, and the second negative electrode active material layer 33 is located on the side of the negative electrode current collector 31 facing away from the winding center. The negative electrode sheet 3 comprises a double-sided region coated with negative electrode active material on both sides and a single-sided region coated with negative electrode active material on one side. The second negative electrode active material layer 33 is located in the double-sided region, and part of the first negative electrode active material layer 32 is located in the single-sided region and part of the first negative electrode active material layer 32 is located in the double-sided region. In the unwound state of the negative electrode sheet 3, Figure 2 , the region indicated by B is the double-sided region of the negative electrode sheet 3, Figure 2 , and the region indicated by C is the single-sided region of the negative electrode sheet 3.

[0035] The negative electrode sheet 3 further comprises an insulating coating 34 coated on the second surface, and at least part of the insulating coating 34 is located at the outermost circle of the winding core structure, that is, the insulating coating 34 is coated on the negative electrode current collector 31 located in the single-face area, and the insulating coating 34 and the first negative electrode active material layer 32 are located at opposite sides of the negative electrode sheet 3. When the winding core structure is in a winding state, part of the insulating coating 34 is located at the outermost circle of the winding core structure, which is arranged to avoid the negative electrode current collector 31 of the negative electrode sheet 3 from contacting the outside of the winding core structure. Further, in the length direction of the negative electrode sheet 3, the head end of the insulating coating 34 and the tail end of the second negative electrode active material layer 33 are separated by a first interval 4, that is, the insulating coating 34 and the second negative electrode active material layer 33 are arranged in an interval, or in other words, the insulating coating 34 and the second negative electrode active material layer 33 are not continuously coated in this application, so that the insulating coating 34 does not cover the second negative electrode active material layer 33 or extend into the negative electrode active material layer and the negative electrode current collector 31, thereby avoiding poor conductivity of the area of the battery, further avoiding slow lithium ion intercalation speed during charging, avoiding large lithium ion concentration in the area, thereby avoiding lithium precipitation, and improving the safety performance of the battery composed of the winding core structure.

[0036] On the basis of the above-mentioned embodiments, further Figures 1-3 , the winding core structure comprises a flat area 6 and a bending area 7 located at both ends of the flat area 6, and at least part of the first interval 4 is located in the bending area 7. That is, part of the first interval 4 is located in the bending area 7, or the first interval 4 is entirely located in the bending area 7. By arranging in this way, the thickness of the insulating coating 34 in the bending area 7 can be reduced to avoid the insulating coating 34 overlapping in the area where the bending area 7 is located during winding to form the winding core structure, thereby reducing the width of the winding core structure and further reducing the size of the winding core structure, that is, reducing the proportion of the non-active material layer structure in the winding core structure, thereby improving the energy density of the battery.

[0037] It should be noted that the head end and the tail end of the above-mentioned components refer to the head end and the tail end indicated by the arrows Figure 3 . Specifically, when the negative electrode sheet 3 is in an unfolded state as shown in Figure 2 , the left end of the negative electrode sheet 3 is the head end of the negative electrode sheet 3, and the right end of the negative electrode sheet 3 is the tail end of the negative electrode sheet 3. In addition, when the winding core structure is in a winding state, the end of the negative electrode sheet 3 located at the center of the winding is the head end of the negative electrode sheet 3, and the end located at the outermost circle of the winding core structure is the tail end of the negative electrode sheet 3.

[0038] For example, the thickness direction of the negative electrode sheet 3 is the direction indicated by the double-headed arrow F in Figure 3 ; and the length direction of the negative electrode sheet 3 is the direction indicated by the double-headed arrow G in Figure 3 .

[0039] The battery cell provided by the application is coated with the insulating coating 34 on the second surface of the negative current collector 31 away from the center of the winding core structure, and at least part of the insulating coating 34 is located at the outermost circle of the winding core structure. In the length direction of the negative electrode sheet 3, the head end of the insulating coating 34 is spaced apart from the tail end of the second negative active material layer 33 by a first interval 4. In this way, the insulating coating 34 can be prevented from covering the negative active material layer and extending into the negative active material layer and the negative current collector 31, so as to avoid poor conductivity in this area, slow lithium ion insertion speed in the charging process, large lithium ion concentration in this area, and lithium precipitation in this area, thereby improving the safety performance of the battery during use. In addition, the thickness of the winding core structure in this area can also be prevented from increasing, and the energy density of the battery formed by the winding core structure can also be prevented from decreasing. Moreover, when the positive electrode sheet 1 is arranged at the outermost winding layer of the winding core structure, the positive current collector 11 located at the junction area between the single-face area and the double-face area of the positive electrode sheet 1 can be broken due to the hard pressure of the roller. In addition, due to the large hardness of the positive active material layer 12, especially during the roller pressing process in the single-face area of the positive electrode sheet 1, part of the positive active material layer 12 can be embedded into the positive current collector 11, causing damage to the positive current collector 11 located in the single-face area of the positive electrode sheet 1. However, in the application, the positive electrode sheet 1 is not provided with a single-face area, which can avoid the risk of breaking the positive current collector 11 of the positive electrode sheet 1 compared with the scheme of arranging the positive electrode sheet 1 at the outermost winding layer of the winding core structure, and can also avoid the damage to the positive current collector 11. Moreover, locating at least part of the first interval 4 at the bending area 7 can reduce the proportion of the insulating coating 34 arranged in the bending area 7, so as to reduce the size of the winding core structure, thereby reducing the proportion of the non-active material layer structure in the winding core structure, and further improving the energy density of the battery.

[0040] On the basis of the above-mentioned embodiments, please refer to Figures 1-3The head end of the first interval 4 is located at the head end of the bending area 7, and the size of the first interval 4 in the length direction of the negative electrode tab 3 is L1, the arc length of the bending area 7 where the first interval 4 is located is L2 (not shown in the figure), and L1 and L2 satisfy: 0 < L1 < 1.5 * L2. That is, after the negative electrode tab 3 is wound into a core structure, the head end of the first interval 4 is located at the junction position of the bending area 7 and the flat area 4 in the winding direction of the core structure. When the size of the first interval 4 is less than the arc length of the bending area 7 where the first interval 4 is located, the first interval 4 is entirely located in the bending area 7 of the core structure; when the size of the first interval 4 is greater than the arc length of the bending area 7 where the first interval 4 is located, part of the structure of the first interval 4 is located in the bending area 7 of the core structure, and the remaining structure of the first interval 4 is located in the flat area 6 of the core structure. By ensuring that the size of the first interval 4 and the arc length of the bending area 7 where the first interval 4 is located satisfy the above relationship, the width of the bending area 7 of the core structure can be further reduced, thereby reducing the width and thickness of the core structure, and reducing the size of the core structure to further improve the energy density of the battery composed of the core structure.

[0041] For example, the relationship between the size L1 of the first interval 4 and the arc length L2 of the bending area 7 where the first interval 4 is located can be: L1 = 0.1 * L2, L1 = 0.2 * L2, L1 = 0.3 * L2, L1 = 0.5 * L2, L1 = 0.8 * L2, L1 = L2, L1 = 1.1 * L2, L1 = 1.3 * L2, L1 = 1.5 * L2.

[0042] In some embodiments, referring to Figures 1-3 The size of the first interval 4 in the length direction of the negative electrode tab 3 is L1, the size of the first negative electrode active material layer 32 exceeding the second negative electrode active material layer is L3, and L1 and L3 satisfy: L3 > 3 * L1. By ensuring that the size of the first negative electrode active material layer 32 exceeding the second negative electrode active material layer 33 is greater than or equal to 3 times the size of the first interval 4, the setting position of the first interval 4 is limited, and the first interval 4 of the core structure in the wound state is ensured not to be located in the outermost circle of the core structure, thereby ensuring that the negative electrode current collector 31 is not in contact with the shell of the battery cell, achieving the insulation of the negative electrode current collector 31, and reducing the risk of corrosion between the negative electrode tab 3 and the shell of the battery cell due to contact.

[0043] It should be noted that the part of the first negative electrode active material layer 32 exceeding the second negative electrode active material layer 33 refers to the part of the first negative electrode active material layer 32 located in the single-face area of the negative electrode tab 3.

[0044] For example, the relationship between the size of the first negative active material layer 32 exceeding the size of the second negative active material layer 33 and the size of the first interval 4 can be: L3 = 3*L1, L3 = 3.1*L1, L3 = 3.5*L1, L3 = 4*L1, L3 = 5*L1, L3 = 8*L1, L3 = 10*L1, L3 = 15*L1, L3 = 20*L1, and the like.

[0045] In some embodiments, referring to Figures 2-3 , the negative electrode tab 3 further includes an empty foil area 35 where no negative active material layer is arranged on both sides of the negative current collector 31, and the second surface of the negative current collector 31 located in the empty foil area 35 is coated with an insulating coating 34. In the length direction of the negative electrode tab 3, the size of the first interval 4 is L1, the size of the insulating coating 34 located in the empty foil area 35 is L4, and L1 and L4 satisfy: L4≥L1. Specifically, according to the manufacturing process of the winding core structure, under the premise that the positive electrode tab 1 only includes a double-sided area, and the negative electrode tab 3 includes both a single-sided area and a double-sided area, and the negative electrode tab 3 is located in the outermost circle of the winding core structure, the single-sided area of the negative electrode tab 3 forms a complete winding circle in the winding core structure, and the empty foil area 35 of the negative electrode tab 3 is located on the side of the single-sided area of the negative electrode tab 3 away from the double-sided area of the negative electrode tab 3, so that the head end of the single-sided area of the negative electrode tab 3 and the head end of the empty foil area 35 are located at the same winding position in the circumferential direction of the winding structure. Therefore, by ensuring that the size of the insulating coating 34 located in the empty foil area 35 and the size of the first interval 4 satisfy the above relationship, it can be ensured that the insulating coating 34 covers the first interval 4, so that the negative current collector 31 in the area of the first interval 4 cannot leak out, and the risk of corrosion between the negative electrode tab 3 and the cell membrane shell due to contact is reduced.

[0046] For example, the size of the insulating coating 34 located in the empty foil area 35 and the size of the first interval 4 can be: L4 = L1, L4 = 1.1L1, L4 = 1.2L1, L4 = 1.3L1, L4 = 1.5L1, L4 = 2L1, and the like.

[0047] In some embodiments, referring to Figures 1-3 , the insulating coating 34 includes a first area located on the opposite side of the first negative active material layer, and a second area located in the empty foil area 35. It should be noted that the first area refers to the part of the insulating coating 34 located on the opposite side of the first negative active material layer, i.e., the single-sided area of the negative electrode tab 3 Figure 2The insulation coating 34 is provided with a first region and a second region. The first region is provided on the head portion of the insulation coating 34, and the second region is provided on the tail portion of the insulation coating 34. The first region and the second region are provided on the insulation coating 34 in the same way as the first region and the second region shown in the area C in FIG. 6. In the thickness direction of the winding core structure, the projection of the first region and the projection of the second region overlap each other, that is, in the winding direction of the winding core structure, the tail portion of the insulation coating 34 is beyond the head portion of the insulation coating 34, so that the insulation coating 34 in the empty foil area 35 can cover the first interval 4, so that the negative current collector 31 in the first interval 4 area cannot be exposed, and the risk of corrosion between the negative electrode sheet 3 and the cell film shell due to contact is reduced.

[0048] In the width direction of the winding core structure, the size W of the overlapping region satisfies: W≥2 mm. In this way, the size of the overlapping region is avoided to be too small, so that the first interval 4 cannot be covered when there is a winding error, and the stability of the winding core structure is improved; and the size of the overlapping region is avoided to be too large, so that the energy density of the battery provided with the winding core structure is reduced.

[0049] For example, the size W of the overlapping region can be: 2 mm, 2.2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 8 mm, 10 mm, 20 mm, and the like.

[0050] In some embodiments, referring to Figure 4 and Figure 5 The negative electrode sheet 3 is not provided with the empty foil area 35, that is, the negative electrode sheet 3 only includes the double-sided area and the single-sided area, and the cell further includes the insulating tape 8 provided outside the outermost circle of the winding core structure. The insulating tape 8 is used for the insulation of the winding core structure and the cell shell and the like, and the insulating tape 8 covers the first interval 4. In this way, the scheme that the negative electrode sheet 3 is not provided with the empty foil area 35 ensures that the negative current collector 31 corresponding to the first interval 4 will not be exposed by providing the insulating tape 8, and the risk of corrosion with the cell film shell is avoided. It should be noted that this setting method can reduce the setting of the empty foil area 35, and can reduce the setting length of the insulation coating 34, can reduce the size of the winding core structure, and can improve the energy density of the battery provided with the winding core structure.

[0051] In some embodiments, referring to Figure 6, the negative electrode sheet 3 is not provided with the empty foil area 35, that is, the negative electrode sheet 3 is only provided with the single-face area and the double-face area. In the processing of the negative electrode sheet 3, the negative electrode sheet 3 is cut from a long material belt. If the negative electrode sheet 3 without the empty foil area 35 in the embodiment is cut, the negative electrode active material layer and the insulating coating layer 34 need to be coated on the second surface of the negative electrode current collector 31 in sequence, and in the length direction of the material belt, the first section of the negative electrode active material layer and the first section of the insulating coating layer 34 have the first interval 4, and the second section of the negative electrode active material layer and the second section of the insulating coating layer 34 also have the first interval 4, but there is no interval between the first section of the insulating coating layer 34 and the second section of the negative electrode active material layer, that is, part of the negative electrode active material layer and the insulating coating layer 34 on the second surface of the negative electrode current collector 31 have no interval, which may cause the insulating coating layer 34 to be located on the upside of the negative electrode active material layer or between the negative electrode current collector 31 and the negative electrode active material layer during the rolling process, and may cause the battery made of the cut electrode sheet to have the lithium precipitation problem mentioned in the background art. Therefore, in the length direction of the negative electrode sheet 3, the tail end of the insulating coating layer 34 and the tail end of the negative electrode sheet 3 have the second interval 5, and the second interval 5 and the first interval 4 are located on both sides of the insulating coating layer 34. In this way, the insulating coating layer 34 of the single-face area of the cut negative electrode sheet 3 can be prevented from overlapping the negative electrode active material layer of the double-face area of the next negative electrode sheet 3 to be cut, so as to prevent the battery made of the next negative electrode sheet 3 from precipitating lithium and reduce the energy density of the battery made of the next negative electrode sheet 3.

[0052] Further in some embodiments, referring to Figure 6 The size L5 of the second interval 5 satisfies: L5≤5mm. In this way, the size of the second interval 5 is ensured to satisfy the above range, so as to prevent the second interval 5 from being too large and prevent the size of the insulating coating layer 34 from being reduced too much to improve the insulation effect of the insulating coating layer 34.

[0053] For example, the size of the second interval 5 can be 5mm, 4.9mm, 4.8mm, 4.5mm, 4mm, 3mm, 2mm, 1mm, 0.5mm, 0.2mm, 0.1mm, etc.

[0054] As can be seen from the above embodiments, the scheme that the negative electrode sheet 3 is not provided with the empty foil area 35 ensures that the negative electrode current collector 31 corresponding to the first interval 4 will not leak out by setting the insulating adhesive tape 8, so as to prevent the risk of corrosion with the cell film shell. In some embodiments, the cell further comprises the insulating adhesive tape 8 arranged outside the outermost circle of the winding core structure, and the insulating adhesive tape 8 covers the second interval 5. In this way, the scheme that the negative electrode sheet 3 is not provided with the empty foil area 35 ensures that the negative electrode current collector 31 corresponding to the second interval 5 will not leak out by setting the insulating adhesive tape 8, so as to prevent the risk of corrosion with the cell film shell.

[0055] Correspondingly, such arrangement can reduce the arrangement of the empty foil area 35, and can reduce the length of the arrangement of the insulating adhesive layer, can reduce the size of the core structure, and improve the energy density of the battery arranged with the core structure.

[0056] In some embodiments, the insulating coating 34 comprises an inorganic material and a binder, the inorganic material being at least one of alumina, boehmite, magnesium oxide, magnesium hydroxide.

[0057] A battery comprises the above-mentioned battery core, since the battery comprises the battery core, the beneficial effects brought by the battery core are described above, and will not be repeated here.

[0058] The basic principles of the present application are described above in combination with specific embodiments, but it should be pointed out that the advantages, advantages, effects and the like mentioned in the present application are only examples and not limitations, and these advantages, advantages, effects and the like cannot be considered as the necessary possession of each embodiment of the present application. In addition, the above-mentioned specific details are only for the purpose of example and for the purpose of understanding, and are not limited to the above-mentioned specific details.

[0059] The block diagram of the device, apparatus, equipment, system involved in the present application is only an illustrative example and is not intended to require or imply the connection, arrangement, configuration shown in the block diagram. As those skilled in the art will recognize, these devices, apparatus, equipment, system can be connected, arranged, configured in any way. Words such as "include", "contain", "have" and the like are open-ended words, which mean "include but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably, unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

[0060] It should also be noted that in the device, equipment and method of the present application, each component or each step can be decomposed and / or recombined. These decompositions and / or recombination should be considered as equivalent solutions of the present application.

[0061] The above description of the disclosed aspects is provided so that any person skilled in the art can make or use the present application. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but is intended to be consistent with the widest scope consistent with the principles and novel features disclosed herein.

[0062] It should be understood that the limiting words "first", "second", "third", "fourth", "fifth" and "sixth" used in the embodiments of the present application are only used for more clearly explaining the technical solutions, and cannot be used to limit the protection scope of the present application.

[0063] The above description is given for the purpose of illustration and description. Furthermore, this description does not intend to limit the embodiments of the present application to the forms disclosed herein. Although several example aspects and embodiments have been discussed above, those of ordinary skill in the art will appreciate a variety of modifications, alternatives, permutations, additions, and sub-combinations of the described aspects and embodiments.

Claims

1. An electric cell, characterized by, The winding core structure is formed by stacking and winding a positive electrode sheet, a separator and a negative electrode sheet in sequence, and the negative electrode sheet is located at the outermost layer of the winding core structure in the thickness direction of the winding core structure, and the outermost layer is the layer farthest from the winding center of the winding core structure in the thickness direction of the winding core structure; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on both sides of the positive electrode current collector; The negative electrode sheet comprises a negative electrode current collector, a first negative electrode active material layer and a second negative electrode active material layer, and the negative electrode current collector comprises a first surface and a second surface in the thickness direction of the negative electrode sheet, the first surface faces the winding center of the winding core structure, and the second surface faces away from the winding center of the winding core structure, wherein the first negative electrode active material layer is located on the first surface, and the second negative electrode active material layer is located on the second surface, and the tail end of the first negative electrode active material layer exceeds the tail end of the second negative electrode active material layer in the length direction of the negative electrode sheet; The negative electrode sheet further comprises an insulating coating layer, the insulating coating layer is coated on the second surface, at least part of the insulating coating layer is located at the outermost layer of the winding core structure, and the head end of the insulating coating layer is spaced apart from the tail end of the second negative electrode active material layer in the length direction of the negative electrode sheet; The winding core structure comprises a flat area and a bending area at both ends of the flat area, and at least part of the first interval is located in the bending area.

2. The electric cell of claim 1, wherein, The head end of the first interval is located at the head end of the bending area, and the size of the first interval is L1 in the length direction of the negative electrode sheet, the arc length of the bending area where the first interval is located is L2, and L1 and L2 satisfy: 0 3. The electric cell of claim 1, wherein, The size of the first interval is L1 in the length direction of the negative electrode sheet, the size of the first negative electrode active material layer exceeding the second negative electrode active material layer is L3, and L1 and L3 satisfy: L3≥3*L1.

4. The electric cell of claim 1, wherein, The negative electrode sheet further comprises an empty foil area where no negative electrode active material layer is arranged on both sides of the negative electrode current collector, and the second surface of the negative electrode current collector located in the empty foil area is coated with the insulating coating layer, wherein: The size of the first interval is L1 in the length direction of the negative electrode sheet, the size of the insulating coating layer located in the empty foil area is L4, and L1 and L4 satisfy: L4≥L1.

5. The electric cell of claim 4, wherein, The insulating coating layer comprises a first area located on the opposite side of the first negative electrode active material layer and a second area located in the empty foil area, the projection of the first area and the second area in the thickness direction of the winding core structure has an overlapping area, and the size W of the overlapping area in the width direction of the winding core structure satisfies: W≥2mm.

6. The electric cell of claim 1, wherein, The negative electrode sheet is not provided with an empty foil area, and the battery cell further comprises an insulating adhesive tape arranged outside the outermost layer of the winding core structure, and the insulating adhesive tape covers the first interval.

7. The electric cell of claim 1, wherein, The negative pole piece is not provided with an empty foil area, and the tail end of the insulating coating and the tail end of the negative pole piece have a second interval in the length direction of the negative pole piece, the second interval and the first interval are located on two sides of the insulating coating, and the size L5 of the second interval satisfies: L5≤5 mm.

8. The electric cell of claim 7, wherein, The electric core further comprises an insulating adhesive paper arranged outside the outermost coil structure, and the insulating adhesive paper covers the second interval.

9. A battery, characterized by The electric core comprises the electric core as claimed in any one of claims 1-8.

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