Winding core and battery

Abstract

The utility model provides a kind of roll core and battery, the embossed pole piece of this roll core includes current collector and respectively the first active material layer and the second active material layer coated on the two sides of current collector;Current collector is equipped with at least one embossed area, and embossed area is located in the arc region of roll core;Embossed area includes the embossed groove located in the winding outside of current collector, and the embossed protrusion located in the winding inside of current collector;Embossed protrusion and embossed groove are set on the two sides of current collector one by one;First active material layer covers embossed groove, and first active material layer has thickening area corresponding embossed groove;Second active material layer covers embossed protrusion, and second active material layer has thinning area corresponding embossed protrusion;So that the active material layer of the winding outside of embossed pole piece is locally thickened, the active material layer of the winding inside of embossed pole piece is locally thinned, try to make the NP ratio of arc region and the NP ratio of flat area keep consistent, to improve the lithium precipitation problem of roll core arc region.

Description

Technical Field

[0001] This utility model relates to the field of winding core technology, and in particular to a winding core and a battery. Background Technology

[0002] The core of a wound battery has a flat region and a curved region. In the flat region, the active material layers of the positive and negative electrodes are of uniform thickness, and the NP ratio (i.e., the capacity ratio of the negative electrode to the positive electrode) remains at the design value. In the curved region, due to the tensile and compressive stresses on the positive and negative electrodes (especially the negative electrode) at the bends during winding, the active material layer on the inner side of the electrode winding becomes thicker, while the active material layer on the outer side of the electrode winding becomes thinner (especially the active material layer). This leads to a difference between the NP ratio and the design value. In the curved region, the NP ratio of the area where the positive electrode covers the negative electrode is lower than the design value, and the NP ratio of the area where the negative electrode covers the positive electrode is higher than the design value. This makes the area where the positive electrode covers the negative electrode prone to lithium plating. The conventional approach is to increase the overall NP ratio to ensure that the area where the positive electrode covers the negative electrode does not plating lithium, but this leads to material waste and energy density loss. Summary of the Invention

[0003] This invention provides a winding core and a battery to solve the problem of lithium plating occurring in the arc region of existing winding cores.

[0004] A type of core includes a positive electrode sheet, a separator, and a negative electrode sheet; At least one of the positive electrode and the negative electrode is a knitted electrode, and the knitted electrode includes a current collector and a first active material layer and a second active material layer respectively coated on both sides of the current collector. The current collector is provided with at least one embossed area, which is located in the arc area of ​​the core; The embossed area includes an embossed groove located on the outer side of the current collector and an embossed protrusion located on the other side of the current collector; the embossed protrusion and the embossed groove are respectively disposed on both sides of the current collector. The first active material layer covers the embossing groove, and the first active material layer has a thickened area corresponding to the embossing groove. The thickness of the thickened area is greater than the thickness of the first active material layer in the remaining area of ​​the arc region. The second active material layer covers the embossed protrusion, and the second active material layer has a thinning area corresponding to the embossed protrusion, the thickness of the thinning area being less than the thickness of the second active material layer in the remaining area of ​​the arc region.

[0005] Preferably, the length of the embossed area is 2-10 mm.

[0006] Preferably, in the winding direction perpendicular to the core, the length of the embossed areas arranged from the inside to the outside gradually increases.

[0007] Preferably, the embossed area includes at least two embossed grooves, and the distance between two adjacent embossed grooves is 0.5-2mm.

[0008] Preferably, in the winding direction of the core, the width of each embossing groove is 0.5-2 mm.

[0009] Preferably, the depth of the embossing groove is 10%-40% of the total thickness of the first active material layer and the second active material layer.

[0010] Preferably, the two ends of the embossing groove extend to the edge of the current collector in the width direction.

[0011] Preferably, the cross-sectional shape of the embossing groove is any one of the following: arc, triangle, rectangle, and trapezoid.

[0012] Preferably, the positive electrode and the negative electrode are the embossed electrode; At least a portion of the embossed grooves of the negative electrode sheet are arranged opposite to or offset from the embossed protrusions of the positive electrode sheet on the opposite side; and / or, At least some of the embossed protrusions of the negative electrode sheet are arranged opposite to or offset from the embossed grooves of the positive electrode sheet on the opposite side.

[0013] A battery, comprising a casing and the said winding core; The core is installed inside the housing.

[0014] The winding core provided in this embodiment of the utility model achieves at least one embossed area on the current collector by performing embossing pretreatment on the current collector. The embossed area includes an embossed groove located on the outer side of the current collector winding and an embossed protrusion located on the inner side of the current collector winding. The embossed protrusions and embossed grooves are arranged on both sides of the current collector in a one-to-one correspondence. During manufacturing, a first active material layer and a second active material layer are respectively coated on both sides of the current collector, that is, the first active material layer covers the embossed groove. The first active material layer has a thickened area corresponding to the embossed groove, and the thickness of the thickened area is greater than the thickness of the first active material layer in the remaining area of ​​the arc region. The second active material layer covers the embossed protrusions, and the second active material layer... The active material layer has a thinning region corresponding to the embossed protrusions. The thickness of the thinning region is less than the thickness of the second active material layer in the remaining areas of the arc region. This allows the active material layer on the outer side of the embossed electrode to be locally thicker, while the active material layer on the inner side of the embossed electrode to be locally thinner. Compared with the unembossed electrode, this increases the NP ratio in the arc region where the positive electrode covers the negative electrode, bringing it closer to the design value. Conversely, it decreases the NP ratio in the region where the negative electrode covers the positive electrode, bringing it closer to the design value. This reduces the difference between the NP ratio and the design value, and strives to keep the NP ratio in the arc region consistent with the NP ratio in the flat region. In other words, the NP ratios in both the flat and arc regions are consistent with the design value, thereby improving the lithium plating problem in the arc region of the core. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a first sectional view of the core in one embodiment of the present invention; Figure 2 This is a second sectional view of the core in one embodiment of the present invention; Figure 3 This is a cross-sectional view of the negative electrode sheet in one embodiment of this utility model; Figure 4 This is a cross-sectional view of the positive electrode sheet in one embodiment of this utility model.

[0017] Among them, 1 is the embossed electrode sheet; 11 is the current collector; 12 is the first active material layer; 13 is the second active material layer; 14 is the embossed area; 141 is the embossed groove; and 142 is the embossed protrusion. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] In the description of this application, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] This utility model embodiment provides a winding core, as shown in the reference. Figures 1-4 The core includes a positive electrode sheet, a separator, and a negative electrode sheet; at least one of the positive and negative electrode sheets is an embossed electrode sheet 1, which includes a current collector 11 and a first active material layer 12 and a second active material layer 13 coated on both sides of the current collector 11 respectively; the current collector 11 is provided with at least one embossed region 14, which is located in the arc region of the core; the embossed region 14 includes an embossed groove 141 located on the outer side of the current collector 11 (the opening of the embossed groove 141 faces the outer side of the core), and an embossed protrusion located on the inner side of the current collector 11. 142; Embossed protrusions 142 and embossed grooves 141 are disposed on both sides of the current collector 11 in a one-to-one correspondence; a first active material layer 12 covers the embossed grooves 141, the first active material layer 12 has a thickened area corresponding to the embossed grooves 141, the thickness of the thickened area is greater than the thickness of the first active material layer 12 in the remaining area of ​​the arc region; a second active material layer 13 covers the embossed protrusions 142, the second active material layer 13 has a thinned area corresponding to the embossed protrusions 142, the thickness of the thinned area is less than the thickness of the second active material layer 13 in the remaining area of ​​the arc region.

[0022] As an example, the core includes a positive electrode sheet, a separator, and a negative electrode sheet; at least one of the positive and negative electrode sheets is an embossed electrode sheet 1, which includes a current collector 11, a first active material layer 12, and a second active material layer 13. The current collector 11 includes, but is not limited to, foil; the current collector 11 of the positive electrode sheet is aluminum foil, and the current collector 11 of the negative electrode sheet is copper foil. During manufacturing, at least one embossed area 14 is provided on the current collector 11 using an embossing device. The embossed area 14 is located in the arc region of the core. For example, a portion of the embossed area 14 can be located in the arc region of the core, or each embossed area can be... All 14 are located in the arc area of ​​the core; with this arrangement, by performing embossing pretreatment on the current collector 11 of the embossed electrode sheet 1, at least one embossed area 14 is provided on the current collector 11. The embossed area 14 includes an embossed groove 141 located on the outer side of the current collector 11 (the opening of the embossed groove 141 faces the outer side of the core) and an embossed protrusion 142 located on the inner side of the current collector 11; the embossed protrusion 142 is arranged on both sides of the current collector 11 in a one-to-one correspondence with the embossed groove 141. During manufacturing, the first active material layer 12 and the second active material layer 13 are respectively coated on the current collector 11. On both sides, that is, the first active material layer 12 covers the embossing groove 141, and the first active material layer 12 has a thickened area corresponding to the embossing groove 141. The thickness of the thickened area is greater than the thickness of the first active material layer 12 in the remaining area of ​​the arc region. The second active material layer 13 covers the embossing protrusion 142, and the second active material layer 13 has a thinned area corresponding to the embossing protrusion 142. The thickness of the thinned area is less than the thickness of the second active material layer 13 in the remaining area of ​​the arc region. In this way, the active material layer on the outer side of the embossed electrode 1 can be locally thickened, while the active material layer on the inner side of the embossed electrode 1 can be thickened. The active material layer is locally thinned, which increases the NP ratio in the area where the positive electrode covers the negative electrode in the arc region compared to the unembossed electrode, making it closer to the design value; the NP ratio in the area where the negative electrode covers the positive electrode decreases, making it closer to the design value, reducing the difference between the NP ratio and the design value, and trying to keep the NP ratio in the arc region consistent with the NP ratio in the flat region. That is, the NP ratio in the flat region and the arc region are consistent with the design value, so as to ensure that lithium does not deposit in the arc region, especially in the area where the positive electrode covers the negative electrode, thereby improving the lithium deposition problem in the arc region of the core; and it can also avoid material waste and energy density loss.

[0023] Reference Figure 3Taking the negative electrode sheet as an example of the embossed electrode sheet 1, the current collector 11 of the negative electrode sheet is made of copper foil. The copper foil in the arc area is embossed, forming an embossing groove 141 on one side of the copper foil, and an embossing protrusion 142 on the back side of the embossing groove 141. After pretreatment, active material layers are coated on both sides of the copper foil. The first active material layer 12 and the second active material layer 13 are respectively coated on both sides of the current collector 11. The first active material layer 12 fills the embossing groove 141 and has a thickened area corresponding to the embossing groove 141. The second active material layer 13 covers the embossing protrusion 142 and has a thinned area corresponding to the embossing protrusion 142. The area of ​​the positive electrode sheet covering the negative electrode sheet has a first active material layer on the outside of the negative electrode sheet. The thickened area of ​​material layer 12 can increase the NP ratio between the active material layer on the side of the copper foil with the embossed groove 141 and the active material layer of the positive electrode covering that side. In the area where the negative electrode covers the positive electrode, since there is a thinned area of ​​the second active material layer 13 inside the negative electrode, the NP ratio between the active material layer on the side of the copper foil with the embossed protrusion 142 and the active material layer of the positive electrode covered by that side can be reduced. This reduces the difference between the NP ratio of adjacent layers in the arc region and the design value, and tries to keep the NP ratio of the arc region consistent with the NP ratio of the flat region, thereby increasing the liquid retention in this region and ensuring that lithium does not deposit in the arc region, especially in the area where the positive electrode covers the negative electrode, thus improving the problem of lithium deposition in the arc region.

[0024] Similarly, refer to Figure 4 Taking the positive electrode sheet as an embossed electrode sheet 1 as an example, the current collector 11 of the positive electrode sheet is made of aluminum foil. The aluminum foil in the arc area is embossed, and an embossing groove 141 is formed on one side of the aluminum foil. The back side of the embossing groove 141 is an embossing protrusion 142. After pretreatment, active material layers are coated on both sides of the aluminum foil. The first active material layer 12 and the second active material layer 13 are respectively coated on both sides of the current collector 11. The first active material layer 12 fills the embossing groove 141 and has a thickened area corresponding to the embossing groove 141. The second active material layer 13 covers the embossing protrusion 142 and has a thinned area corresponding to the embossing protrusion 142. In the region where the positive electrode sheet covers the negative electrode sheet, the thinning region of the second active material layer 13 on the inner side of the positive electrode sheet increases the NP ratio between the active material layer on the side of the aluminum foil with the embossed groove 141 and the active material layer of the negative electrode sheet covered by that side. In the region where the negative electrode sheet covers the positive electrode sheet, the thickening region of the first active material layer 12 on the outer side of the positive electrode sheet decreases the NP ratio between the active material layer on the side of the aluminum foil with the embossed protrusion 142 and the active material layer of the negative electrode sheet covering that side. This reduces the difference between the NP ratio of adjacent layers in the arc region and the design value, and makes the NP ratio of the arc region as consistent as possible with the NP ratio of the flat region, thereby increasing the liquid retention in this region and ensuring that lithium does not deposit in the arc region, especially in the region where the positive electrode sheet covers the negative electrode sheet, thus improving the problem of lithium deposition in the arc region.

[0025] Similarly, if both the positive and negative electrode sheets are embossed electrode sheets 1, it can also reduce the difference between the NP ratio and the design value between adjacent layers in the arc region, and try to keep the NP ratio of the arc region consistent with the NP ratio of the flat region, thereby increasing the liquid retention in this region and ensuring that the arc region, especially the area where the positive electrode sheet covers the negative electrode sheet, does not have lithium deposition, thus improving the problem of lithium deposition in the arc region.

[0026] In one embodiment, reference is made to Figure 1 , Figure 2 , Figure 3 and Figure 4 The length of the embossed area 14 is 2-10mm.

[0027] As an example, when embossing the current collector 11, if the embossed area 14 is too small, it is close to no embossing and has no obvious effect; if the embossed area 14 is too long, it will extend into the non-circular area of ​​the core, increasing the core thickness and reducing the battery energy density. Therefore, the embossed area 14 is limited to a length of 2-10mm. This setting ensures that the current collector 11 has an embossing effect, increases the local thickness of the active material layer on the side of the current collector 11 with the embossed groove 141, and decreases the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This allows for local adjustment of the NP ratio in the circular area, making the NP ratio in the circular area closer to the design value, reducing the difference between the NP ratio and the design value, and keeping the NP ratio in the circular area consistent with that in the flat area. This improves the liquid retention in this area, ensuring that the circular area, especially the area where the positive electrode covers the negative electrode, does not experience lithium deposition, thereby improving the problem of lithium deposition in the circular area. The length of each embossed area 14 is 2-10mm, which can better improve the problem of lithium plating in the arc area.

[0028] In one embodiment, reference is made to Figure 1 and Figure 2 In the winding direction perpendicular to the core, the length of the embossed area 14 arranged from the inside to the outside gradually increases.

[0029] As an example, the embossed electrode 1 has multiple layers in the arc region of the core. In the winding direction perpendicular to the core, the length of the embossed region 14 arranged from the inside to the outside gradually increases. This ensures that the embossed electrode 1 has a balanced embossing effect on the current collector 11 in the arc region of the core, and makes the NP ratio of the arc region as consistent as possible with that of the straight region, thereby increasing the liquid retention in this region and ensuring that the arc region, especially the area where the positive electrode covers the negative electrode, does not have lithium deposition, thus improving the problem of lithium deposition in the arc region.

[0030] In one embodiment, reference is made to Figure 3 and Figure 4The embossed area 14 includes at least two embossed grooves 141, and the distance between two adjacent embossed grooves 141 is 0.5-2mm.

[0031] As an example, when embossing the current collector 11, the embossing area 14 includes at least two embossing grooves 141. If the distance between two adjacent embossing grooves 141 is too small, it is impossible to form a single tank for storing electrolyte, resulting in no significant effect; if the distance between two adjacent embossing grooves 141 is too large, the storage of electrolyte is limited, also resulting in no significant effect. Therefore, the distance between two adjacent embossing grooves 141 is limited to 0.5-2mm. This setting ensures that a single tank can be formed on the current collector 11 to store electrolyte, avoiding limited electrolyte storage and improving the efficiency of the area. The liquid retention capacity improves the dynamic performance of the current collector 11 on the side with the embossed groove 141. It can also increase the local thickness of the active material layer on the side of the current collector 11 with the embossed groove 141 and decrease the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This allows for local adjustment of the NP ratio in the arc region, making the NP ratio in the arc region closer to the design value, reducing the difference between the NP ratio and the design value, and keeping the NP ratio in the arc region consistent with the NP ratio in the straight region as much as possible. This ensures that lithium does not deposit in the arc region, especially in the area where the positive electrode covers the negative electrode, thereby improving the problem of lithium deposition in the arc region.

[0032] In one embodiment, reference is made to Figure 3 and Figure 4 In the winding direction of the core, the width of each embossing groove 141 is 0.5-2mm.

[0033] As an example, when embossing the current collector 11, if the width of each embossing groove 141 is too small or too large, the electrolyte storage is limited and there is no obvious effect. Therefore, it is necessary to limit the width of each embossing groove 141. In the winding direction of the core, the width of each embossing groove 141 is 0.5-2mm. This setting can avoid limited electrolyte storage, increase the electrolyte retention in this area, improve the dynamic performance of the side of the current collector 11 with the embossing groove 141, and also increase the local thickness of the active material layer on the side of the current collector 11 with the embossing groove 141 and decrease the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This allows for local adjustment of the NP ratio in the arc region, so that the NP ratio in the arc region is close to the design value, reducing the difference between the NP ratio and the design value, and keeping the NP ratio in the arc region consistent with the NP ratio in the straight region as much as possible. This ensures that the arc region, especially the area where the positive electrode covers the negative electrode, does not experience lithium deposition, thereby improving the problem of lithium deposition in the arc region.

[0034] In one embodiment, reference is made to Figure 3 and Figure 4The depth of each embossing groove 141 is 10%-40% of the total thickness of the first active material layer 12 and the second active material layer 13.

[0035] As an example, when embossing the current collector 11, if the depth of the embossing groove 141 is too small, it is close to no embossing and has no obvious effect. If the depth of the embossing groove 141 is too large, the embossing protrusion 142 will be too large, increasing the cell width and reducing the battery energy density. Therefore, it is necessary to limit the depth of each embossing groove 141. The depth of each embossing groove 141 should be 10%-40% of the total thickness of the first active material layer 12 and the second active material layer 13. This setting can ensure that the current collector 11 has an embossing effect and can increase the current collector's capacity. The local thickness of the active material layer on the side of the fluid 11 with the embossed groove 141 is reduced, thereby reducing the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This locally adjusts the NP ratio in the arc region, making the NP ratio in the arc region closer to the design value, reducing the difference between the NP ratio and the design value, and trying to keep the NP ratio in the arc region consistent with the NP ratio in the straight region. This increases the liquid retention in the region, ensuring that lithium does not deposit in the arc region, especially in the area where the positive electrode covers the negative electrode, thereby improving the problem of lithium deposition in the arc region.

[0036] In one embodiment, reference is made to Figure 3 and Figure 4 The two ends of the embossing groove 141 extend to the edge of the collector 11 in the width direction.

[0037] As an example, after embossing the current collector 11, the two ends of the embossing groove 141 extend to the edge of the current collector 11 in the width direction. This is beneficial for the electrolyte to wet the active material layer in the arc area, improve the dynamic performance of the arc area, ensure that the active material can also be fully embedded in the edge area of ​​the current collector 11, and avoid the active material from falling off or peeling off due to insufficient bonding force at the edge. It can also disperse stress, improve the edge anti-peeling ability, and extend the battery life. It can also enhance the mechanical strength of the current collector 11, prevent the current collector 11 from deforming or breaking due to external force during battery assembly or use, limit the expansion direction of the active material, and reduce the risk of structural deformation. It can also reduce additional processing steps (such as edge treatment or reinforcement), simplify the production process, and improve production efficiency.

[0038] In one embodiment, reference is made to Figure 3 and Figure 4 The cross-sectional shape of the embossed groove 141 can be any one of the following: arc, triangle, rectangle and trapezoid.

[0039] As an example, the shape of the embossing groove 141 is introduced. The shape of the embossing groove 141 can be set to any one of arc, triangle, rectangle and trapezoid according to actual needs, which is convenient for embossing, conducive to electrolyte wetting of the active material layer in the arc region, and improves the dynamic performance of the arc region, so as to make local adjustment of the NP ratio in the arc region, thereby improving the lithium plating problem in the arc region of the core.

[0040] The following are the parameters for the example: Example 1: The copper foil is pre-treated by embossing. The length of the embossing area 14 is 6 mm, the width of the embossing groove 141 is 1.0 mm, the depth of the embossing groove 141 is 25% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 1.0 mm. Example 2: The copper foil is pre-treated by embossing. The length of the embossing area 14 is 2 mm, the width of the embossing groove 141 is 0.5 mm, the depth of the embossing groove 141 is 25% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 0.5 mm. Example 3: The copper foil is pre-treated by embossing. The length of the embossing area 14 is 10 mm, the width of the embossing groove 141 is 2.0 mm, the depth of the embossing groove 141 is 25% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 2.0 mm. Example 4: The copper foil is pre-treated by embossing. The length of the embossing area 14 is 6 mm, the width of the embossing groove 141 is 1.0 mm, the depth of the embossing groove 141 is 10% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 1.0 mm. Example 5: The copper foil is pre-treated by embossing. The length of the embossing area 14 is 6 mm, the width of the embossing groove 141 is 1.0 mm, the depth of the embossing groove 141 is 40% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 1.0 mm. Example 6: The aluminum foil is pre-treated by embossing. The length of the embossing area 14 is 6 mm, the width of the embossing groove 141 is 1.0 mm, the depth of the embossing groove 141 is 25% of the total thickness of the first active material layer 12 and the second active material layer 13, and the distance between two adjacent embossing grooves 141 is 1.0 mm. Comparative Example 1: No pre-treatment for flower pressing.

[0041] The battery cell was charged at 3C constant current and constant voltage to 4.5V, cut off at 0.05C, and discharged at 0.5C. After 1000 cycles, the battery was disassembled to check the lithium plating on the electrode arcs, and classified as no lithium plating, slight lithium plating, moderate lithium plating, and severe lithium plating.

[0042] Comparison of battery cell test performance: Example 1: Energy density of 750.2 Wh / L, cycle count of 1000, no lithium deposition at the arc; Example 2: Energy density of 750.3 Wh / L, cycle count of 1000, no lithium deposition at the arc; Example 3: Energy density was 749.8 Wh / L, cycle count was 1000, and there was no lithium deposition at the arc. Example 4: Energy density of 750.2 Wh / L, cycle count of 1000, no lithium deposition at the arc; Example 5: Energy density was 749.7 Wh / L, cycle count was 1000, and there was no lithium deposition at the arc. Example 6: Energy density of 750.2 Wh / L, cycle count of 1000, no lithium deposition at the arc; Comparative Example 1: Energy density of 750.0 Wh / L, cycle count of 600, and severe lithium deposition at the arc.

[0043] In one embodiment, during the fabrication of the core, the positive electrode sheet, separator, and negative electrode sheet are arranged alternately, with the separator located between the positive and negative electrode sheets. In the winding direction, the length of the separator is greater than the length of the negative electrode sheet. The longer separator can better wrap the electrode sheet, making the winding process smoother and reducing problems such as misalignment and wrinkles of the electrode sheet during the winding process, thereby improving the consistency and production efficiency of the battery. The length of the negative electrode sheet is greater than the length of the positive electrode sheet, which can increase the effective area of ​​the negative electrode and the lithium-ion insertion sites, thereby improving the charge and discharge efficiency and cycle life of the battery.

[0044] In one embodiment, reference is made to Figure 1 , Figure 2 , Figure 3 and Figure 4 The positive electrode and the negative electrode are the embossed electrode 1 in the above embodiment; at least a portion of the embossed groove 141 of the negative electrode is disposed opposite to or offset from the embossed protrusion 142 of the positive electrode on the opposite side; and / or, at least a portion of the embossed protrusion 142 of the negative electrode is disposed opposite to or offset from the embossed groove 141 of the positive electrode on the opposite side.

[0045] As an example, the positive and negative electrode sheets are the embossed electrode sheets 1 in the above embodiments. Thus, when embossing the current collector 11, embossing can be performed only on the current collector 11 of the positive electrode sheet, only on the current collector 11 of the negative electrode sheet, or on both. When embossed areas 14 exist on both the current collector 11 of the positive and negative electrode sheets, the core structure has eight possible arrangements. The first is that at least a portion of the embossed groove 141 of the negative electrode sheet is opposite to the embossed protrusion 142 of the positive electrode sheet on the opposite side; the second is that at least a portion of the embossed groove 141 of the negative electrode sheet is offset from the embossed protrusion 142 of the positive electrode sheet on the opposite side; the third is that at least a portion of the embossed protrusion 142 of the negative electrode sheet is opposite to the embossed groove 141 of the positive electrode sheet on the opposite side; the fourth is that the negative electrode sheet... The fifth type has at least a portion of the embossed protrusion 142 of the negative electrode sheet, which is offset from the embossed groove 141 of the positive electrode sheet on the opposite side; the sixth type has at least a portion of the embossed groove 141 of the negative electrode sheet, which is offset from the embossed protrusion 142 of the positive electrode sheet on the opposite side; the at least a portion of the embossed protrusion 142 of the negative electrode sheet is offset from the embossed groove 141 of the positive electrode sheet on the opposite side. The embossing grooves 141 are arranged opposite to each other; the seventh type has at least a portion of the embossing groove 141 of the negative electrode sheet opposite to the embossing protrusion 142 of the positive electrode sheet on the opposite side, and at least a portion of the embossing protrusion 142 of the negative electrode sheet is offset from the embossing groove 141 of the positive electrode sheet on the opposite side; the eighth type has at least a portion of the embossing groove 141 of the negative electrode sheet offset from the embossing protrusion 142 of the positive electrode sheet on the opposite side, and at least a portion of the embossing protrusion 142 of the negative electrode sheet is offset from the embossing groove 141 of the positive electrode sheet on the opposite side; this can increase the current collector. The local thickness of the active material layer on the side of the current collector 11 with the embossed groove 141 is reduced, thereby reducing the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This allows for local adjustment of the NP ratio in the arc region, making the NP ratio in the arc region closer to the design value, reducing the difference between the NP ratio and the design value, and making the NP ratio in the arc region as consistent as possible with the NP ratio in the straight region. This increases the liquid retention in the region, ensuring that lithium does not deposit in the arc region, especially in the area where the positive electrode covers the negative electrode, thereby improving the problem of lithium deposition in the arc region.

[0046] In addition, the number of embossed regions 14 on the positive electrode sheet can be the same as the number of embossed regions 14 on the negative electrode sheet. One embossed groove 141 on the negative electrode sheet corresponds to multiple embossed protrusions 142 on the positive electrode sheet, and multiple embossed grooves 141 on the negative electrode sheet correspond to one embossed protrusion 142 on the positive electrode sheet. This can increase the local thickness of the active material layer on the side of the current collector 11 with the embossed groove 141 and decrease the local thickness of the active material layer on the side of the current collector 11 with the embossed protrusion 142. This allows for local adjustment of the NP ratio in the arc region, making the NP ratio in the arc region closer to the design value, reducing the difference between the NP ratio and the design value, and keeping the NP ratio in the arc region consistent with the NP ratio in the flat region as much as possible. This increases the liquid retention in the region and ensures that lithium does not deposit in the arc region, especially in the area where the positive electrode sheet covers the negative electrode sheet, thereby improving the problem of lithium deposition in the arc region.

[0047] This utility model provides a battery, including a casing and a winding core; the winding core is installed inside the casing.

[0048] As an example, the battery includes a casing and a core, with the core installed inside the casing. The core includes a positive electrode sheet, a separator, and a negative electrode sheet; at least one of the positive and negative electrode sheets is an embossed electrode sheet 1, which includes a current collector 11, a first active material layer 12, and a second active material layer 13. The current collector 11 includes, but is not limited to, foil; the current collector 11 for the positive electrode sheet is aluminum foil, and the current collector 11 for the negative electrode sheet is copper foil. During manufacturing, at least one embossed area 14 is provided on the current collector 11 using an embossing device. The embossed area 14 is located in the arc region of the core. For example, a portion of the embossed area 14 can be located in the arc region of the core, or all embossed areas 14 can be located in the arc region of the core. With this configuration, by performing an embossing pretreatment on the current collector 11, at least one embossed area 14 is provided on the current collector 11. The embossed area 14 includes an embossed groove 141 located on the outer side of the current collector 11 (the opening of the embossed groove 141 faces the outer side of the core), and an embossed protrusion 142 located on the inner side of the current collector 11. The embossed protrusions 142 and the embossed grooves 141 are respectively disposed on both sides of the current collector 11. During manufacturing, the first active material layer 12 and the second active material layer 13 are respectively coated on both sides of the current collector 11. That is, the first active material layer 12 covers the embossed groove 141. The first active material layer 12 has a thickened area corresponding to the embossed groove 141, and the thickness of the thickened area is greater than the thickness of the first active material layer 12 in the remaining area of ​​the arc region. The second active material layer 13 covers the embossed protrusions 142. The second active material layer 13 has a thinned area corresponding to the embossed protrusions 142, and the thickness of the thinned area is less than the thickness of the second active material layer 13 in the remaining area of ​​the arc region. The thickness of the region allows for a localized thickening of the active material layer on the outer side of the embossed electrode 1 and a localized thinning of the active material layer on the inner side of the embossed electrode 1. Compared to an unembossed electrode, this increases the NP ratio in the arc region where the positive electrode covers the negative electrode, bringing it closer to the design value. Conversely, it decreases the NP ratio in the region where the negative electrode covers the positive electrode, reducing the difference between the NP ratio and the design value. This aims to keep the NP ratio in the arc region consistent with the NP ratio in the flat region, ensuring that the NP ratios in both the flat and arc regions are consistent with the design value. Furthermore, the embossing groove 141 increases the electrolyte wetting amount on the current collector 11 side, which is beneficial for improving the dynamic performance of the embossed electrode 1 on the outer side of the arc region. This ensures that lithium does not deposit in the arc region, especially in the region where the positive electrode covers the negative electrode, thus improving the lithium deposition problem in the arc region of the core. It also avoids material waste and energy density loss.

[0049] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A type of winding core, characterized in that, Includes positive electrode, separator, and negative electrode; At least one of the positive electrode and the negative electrode is a knitted electrode, and the knitted electrode includes a current collector and a first active material layer and a second active material layer respectively coated on both sides of the current collector. The current collector is provided with at least one embossed area, which is located in the arc area of ​​the core; The embossed area includes an embossed groove located on the outer side of the winding of the current collector and an embossed protrusion located on the inner side of the winding of the current collector; the embossed protrusion and the embossed groove are respectively arranged on both sides of the current collector. The first active material layer covers the embossing groove, and the first active material layer has a thickened area corresponding to the embossing groove. The thickness of the thickened area is greater than the thickness of the first active material layer in the remaining area of ​​the arc region. The second active material layer covers the embossed protrusion, and the second active material layer has a thinning area corresponding to the embossed protrusion, the thickness of the thinning area being less than the thickness of the second active material layer in the remaining area of ​​the arc region.

2. The winding core according to claim 1, characterized in that, The length of the embossed area is 2-10mm.

3. The winding core according to claim 1, characterized in that, In the winding direction perpendicular to the core, the length of the embossed areas arranged from the inside to the outside gradually increases.

4. The winding core according to claim 1, characterized in that, The embossed area includes at least two embossed grooves, and the distance between two adjacent embossed grooves is 0.5-2mm.

5. The winding core according to claim 1, characterized in that, In the winding direction of the core, the width of each embossed groove is 0.5-2 mm.

6. The winding core according to claim 1, characterized in that, The depth of the embossing groove is 10%-40% of the total thickness of the first active material layer and the second active material layer.

7. The winding core according to claim 1, characterized in that, The two ends of the embossing groove extend to the edge of the current collector in the width direction.

8. The winding core according to claim 1, characterized in that, The cross-sectional shape of the embossing groove can be any one of the following: arc, triangle, rectangle, and trapezoid.

9. The winding core according to claim 1, characterized in that, The positive electrode and the negative electrode are the embossed electrode; At least a portion of the embossed grooves of the negative electrode sheet are arranged opposite to or offset from the embossed protrusions of the positive electrode sheet on the opposite side; and / or, At least some of the embossed protrusions of the negative electrode sheet are arranged opposite to or offset from the embossed grooves of the positive electrode sheet on the opposite side.

10. A battery, characterized in that, Includes the outer casing and the winding core as described in any one of claims 1-9; The core is installed inside the housing.

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