Reel and battery

Abstract

The utility model provides a winding core and a battery, the winding core comprises a first pole piece and a second pole piece, the first pole piece comprises a first current collector and a first active material layer coated on both sides of the first current collector, a first pole ear groove is provided on the first active material layer, the bottom wall of the first pole ear groove is the first current collector, the peripheral side is the first active material layer, the first pole ear groove extends to the edge of the first current collector along the second direction, and a first pole ear electrically connected to the first current collector is provided in the first pole ear groove; the second pole piece comprises a second current collector and a second active material layer coated on both sides of the second current collector, and a thinning groove is provided on the second active material layer opposite to the first pole ear groove. The utility model ensures that the battery can effectively dissipate heat during charging, improves the safety and performance of the battery, improves space utilization, and improves the endurance of electronic products.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a winding core and a battery. Background Art

[0002] With the advent of the 5G era and the rapid development of battery technology, people have put forward higher requirements on battery energy density, fast charging capability, and charge and discharge rate. Fast-charging lithium-ion batteries have become the development trend of consumer lithium-ion batteries.

[0003] At present, in high-rate charge and discharge conditions or under long-term full-load operation, the battery, especially the tab position, will face a more serious heating problem. Battery heat dissipation is an important issue that needs to be solved to ensure or extend battery life. How to improve the heat dissipation performance of the battery through a reasonable structure to reduce the temperature of the battery during operation and avoid reducing the battery life is a key research direction for technicians in this field. Utility Model Content

[0004] The embodiment of the utility model provides a winding core and a battery, which are mainly used to solve the problem of battery heating during high-rate charging and discharging in the prior art. The present application improves space utilization and ensures that the battery can effectively dissipate heat during the charging process, thereby improving the safety and performance of the battery.

[0005] The utility model provides a winding core, comprising a first pole piece and a second pole piece;

[0006] The first pole piece includes a first current collector and a first active material layer coated on both sides of the first current collector, a pole lug groove is provided on the first active material layer, the bottom wall of the pole lug groove is the first current collector, the surrounding side is the first active material layer, the pole lug groove extends to the edge of the first current collector along the second direction, and a first pole lug electrically connected to the first current collector is provided in the pole lug groove;

[0007] The second pole piece includes a second current collector and a second active material layer coated on both sides of the second current collector, a skived groove is provided on the second active material layer opposite to the pole ear groove, the thickness of the second active material layer in the skived groove is less than the thickness of the second active material layer in the non-skived groove area of ​​the second current collector, a first protective tape is provided in the skived groove, the projection of the first pole ear in the first direction is located within the projection of the first protective tape in the first direction, and the second current collector has a second edge in the second direction;

[0008] Among them, the thinning groove is located in the straight section of the winding core, the thinning groove and the second edge have a first gap, the projection of the first gap in the first direction at least partially overlaps with the projection of the first pole ear in the first direction, and the thinning groove and the nearest adjacent side winding core arc section have a second gap.

[0009] Through the above arrangement, that is, on the one hand, through the arrangement of the first gap, the second active material layer at the first gap can be closely abutted against the first pole ear, thereby improving the heat conduction efficiency on the pole piece. On the other hand, due to the arrangement of the second gap, a conduction channel is formed around the first pole ear, so that the heat of the pole piece surrounding the first pole ear can be evenly and quickly conducted to the surrounding of the first pole ear, thereby improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the core. In addition, through the arrangement of the thinning groove, on the one hand, since part of the active material is reserved in the thinning groove, and the weld mark of the first pole ear can be abutted against the active material of the thinning groove, and the active material in the thinning groove and the active material in the surrounding area are continuously arranged, the heat of the pole piece can also be quickly conducted out through the active material abutting against the weld mark of the first pole ear, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first pole ear is hidden in the thinning groove to reduce the overall thickness of the core, so that the space utilization of the core is improved, thereby improving the energy density.

[0010] In some optional embodiments, the width of the first gap in the second direction is A, and the width of the second gap in the third direction of the first current collector is B, wherein A and B satisfy: 2 mm < B and 0.8 ≤ A / B ≤ 1.2.

[0011] It should be noted that the ratio between the first gap A and the second gap B is greater than or equal to 0.8 and less than or equal to 1.2. This setting mainly takes into account the overlapping area between the extended area of ​​the first gap A and the extended area of ​​the second gap B to avoid excessive heat here and the inability to quickly export it.

[0012] In some optional embodiments, the first current collector in the pole lug groove is provided with a first notch, the first notch extends to the edge of the first current collector, and the distance between the bottom wall of the first notch and the second edge in the projection in the second direction is m, wherein m satisfies: m<A.

[0013] In some optional embodiments, along the second direction, the distance between the first protective tape and the edge of the skived groove is C, which satisfies: 0mm<C<5mm; and / or,

[0014] Along the length direction of the first current collector, the distance between the first protective tape and the edge of the skived groove is D, which satisfies: 0mm<D<5mm.

[0015] It should be noted that such a setting makes the first protective tape covering area in this region, the thinning groove and the normal thickness of the second active material layer present a stepped funnel shape, which is conducive to the storage of electrolyte here. The electrolyte absorbs the heat generated by the first electrode ear and reduces the temperature rise.

[0016] In some optional embodiments, a plurality of first grooves are further provided on the second active material layer, and the first grooves extend along the second direction;

[0017] The plurality of first grooves are arranged at intervals on at least one of the arc segment of the second active material layer and the straight segment of the second active material layer.

[0018] It should be noted that the setting of the first groove facilitates the dissipation of heat at the first pole ear to the outside of the winding core, that is, the heat at the first pole ear can be discharged in the direction facing the second active material layer and the direction of the arc segment of the second active material layer, and then dissipated through the first heat dissipation channel in the first groove, which is more conducive to heat dissipation.

[0019] In some optional embodiments, the relationship between the depth H of the first groove and the elongation at break e of the second current collector satisfies: 1 mm ≤ H / e ≤ 15 mm.

[0020] The second pole piece is also provided with a second pole ear, and the relationship between the depth H of the first groove, the width L of the first groove, the width E of the first pole ear and the second pole ear, and the thickness F of the first pole ear and the second pole ear satisfies: 2*10 -4 mm 4 ≤H*L*E*F≤2*10 -3 mm 4 .

[0021] It should be noted that the greater the elongation at break of the current collector, the greater the stress it can withstand, the greater the laser intensity it can withstand, and the deeper the first groove.

[0022] It should be noted that the narrower or thinner the electrode ear of one of the first electrode ear and the second electrode ear is, the more obvious the heat generation is, and the larger the channel area required for heat and gas conduction is.

[0023] In some optional embodiments, a ceramic layer is coated on at least one side surface of the tail end of the first pole piece away from the winding center, and part of the ceramic layer covers the first active material layer;

[0024] The coating thickness of the ceramic layer is greater than or equal to 5um and less than or equal to 20um; and / or,

[0025] The ratio of the ceramic grain size of the ceramic layer to the width of the first groove is greater than or equal to 1 / 20 and less than or equal to 1 / 4.

[0026] It should be noted that the ceramic layer is conducive to absorbing heat and reducing the overall temperature rise of the entire battery.

[0027] In some optional embodiments, a second groove is provided at the tail end of the first active material layer away from the winding center, and part of the ceramic layer covers the second groove;

[0028] The depth of the second groove is greater than or equal to 0 um and less than or equal to 20 um.

[0029] It should be noted that the second groove is used to offset the thickness of the ceramic layer and facilitate reducing the thickness of the ceramic layer to prevent the overlapping area from being thicker than other positions and affecting the flatness of the battery cell. Ceramics are good at absorbing heat and reducing the overall temperature rise of the entire battery.

[0030] In some optional embodiments, a projection of at least a portion of the ceramic layer in the first direction is located within the thinning groove.

[0031] It should be noted that such a configuration reduces the heat conduction path and facilitates heat conduction to the ceramic layer.

[0032] In some optional embodiments, the second active material layer includes a first material layer and a second material layer, and the first material layer and the second material layer are stacked in sequence along the first direction, wherein the first material layer is located on a side away from the second current collector.

[0033] In some optional embodiments, a lithium replenishing layer is provided on the side of the second pole piece, and the thickness of the lithium replenishing layer is less than or equal to the depth of the first groove.

[0034] It should be noted that there is a lithium replenishment layer on the surface of the second pole piece, and the first groove depth h>the thickness of the lithium replenishment layer, so that there is still a linear first groove channel on the surface of the pole piece after lithium replenishment, which is convenient for air and heat conduction.

[0035] In some optional embodiments, a second protective tape is provided at the tail end of the first pole piece, and the ratio between the width of the second protective tape and the width of the winding core is greater than or equal to 1 / 2 and less than or equal to 1; and / or,

[0036] The width of the second protective tape is greater than or equal to 10 um and less than or equal to 40 um.

[0037] It should be noted that the second protective tape is ensured to exceed the finishing empty foil (or coated with a ceramic layer) after passing the arc. The gluing relationship between the second protective tape and the finishing hot melt adhesive is that the second protective tape exceeds the hot melt adhesive in the width direction of the core, and the hot melt adhesive is attached to the top of the second protective tape, which can prevent the hot melt adhesive from tearing the first pole piece.

[0038] In some optional embodiments, a third protective tape is provided on the pole lug groove located on one side of the first pole piece, and the third protective tape is used to cover the thinning groove.

[0039] It should be noted that the third protective tape can prevent the burrs at the welding point of the first pole ear from piercing the diaphragm and causing the risk of short circuit and fire.

[0040] The utility model also provides a battery, comprising the winding core as described above.

[0041] The utility model provides a winding core and a battery, the battery comprising a winding core; the winding core comprising a first pole piece and a second pole piece, the first pole piece comprising a first current collector and a first active material layer coated on both sides of the first current collector, a first pole ear groove is provided on the first active material layer, the bottom wall of the first pole ear groove is the first current collector, the surrounding side is the first active material layer, the first pole ear groove extends to the edge of the first current collector along the second direction, a first pole ear electrically connected to the first current collector is provided in the first pole ear groove; the second pole piece comprises a second current collector and a second active material layer coated on both sides of the second current collector, and a second active material layer opposite to the first pole ear groove is provided. A thinning groove is provided on the active material layer, the thickness of the second active material layer in the thinning groove is less than the thickness of the second active material layer in the non-thinning groove area of ​​the second current collector, a first protective tape is provided in the thinning groove, the projection of the first pole ear in the first direction is located within the projection of the first protective tape in the first direction, and the second current collector has a second edge in the second direction; wherein, the thinning groove is located in the straight section of the winding core, the thinning groove and the second edge have a first gap, the projection of the first gap in the first direction at least partially overlaps with the projection of the first pole ear in the first direction, and the thinning groove and the arc section of the winding core adjacent to the nearest side have a second gap.

[0042] Through the above arrangement, that is, on the one hand, through the arrangement of the first gap, the second active material layer at the first gap can be closely abutted against the first pole ear, thereby improving the heat conduction efficiency on the pole piece. On the other hand, due to the arrangement of the second gap, a conduction channel is formed around the first pole ear, so that the heat of the pole piece surrounding the first pole ear can be evenly and quickly conducted to the surrounding of the first pole ear, thereby improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the core. In addition, through the arrangement of the thinning groove, on the one hand, since part of the active material is reserved in the thinning groove, and the weld mark of the first pole ear can be abutted against the active material of the thinning groove, and the active material in the thinning groove and the active material in the surrounding area are continuously arranged, the heat of the pole piece can also be quickly conducted out through the active material abutting against the weld mark of the first pole ear, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first pole ear is hidden in the thinning groove to reduce the overall thickness of the core, so that the space utilization of the core is improved, thereby improving the energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1A schematic structural diagram of a winding core provided in an embodiment of the present application from a first perspective;

[0045] Figure 2 A schematic diagram of the structure of the first pole piece in the winding core provided in an embodiment of the present application;

[0046] Figure 3 A schematic diagram of the structure of the second pole piece in the winding core provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of the structure of the unfolded winding core provided in an embodiment of the present application;

[0048] Figure 5 A schematic structural diagram of a second viewing angle of a winding core provided in an embodiment of the present application;

[0049] Figure 6 A cross-sectional view of the second pole piece in the winding core provided in an embodiment of the present application;

[0050] Figure 7 A schematic diagram of the structure of the first pole ear in the winding core provided in an embodiment of the present application;

[0051] Figure 8 A schematic diagram of the structure of particles of silicon-carbon material in the winding core provided in an embodiment of the present application.

[0052] Description of reference numerals:

[0053] 100-coil core;

[0054] 110- first pole piece;

[0055] 111- first pole lug;

[0056] 112- first active material layer;

[0057] 120- second pole piece;

[0058] 121- second fluid collector;

[0059] 122- second active material layer;

[0060] 1221-thinning groove;

[0061] 1222-first groove;

[0062] 130-ear slot;

[0063] 140-first protective tape;

[0064] 150-second protective tape;

[0065] 160-Third protective tape. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a one-cavity embodiment of the utility model, not an embodiment of the whole cavity. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model. All other embodiments obtained are within the scope of protection of the utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0067] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0068] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication of the inner cavities of two components or the interaction relationship between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] It should be noted that in the description of the present utility model, the terms "first", "second", and "third" are only used to facilitate the description of different chambers, and cannot be understood as indicating or implying a sequential relationship, relative importance, or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include at least one of the features.

[0070] At present, batteries face serious heating problems in high-power conditions or when running at full load for a long time. Battery heat dissipation is an important issue that needs to be solved to ensure or extend battery life. How to improve the heat dissipation performance of batteries through reasonable structures to reduce the temperature of the batteries during operation and avoid reducing the battery life is a key research direction for technicians in this field.

[0071] In order to overcome the defects in the prior art, the winding core and the battery provided by the utility model, on the one hand, through the setting of the first gap, the second active material layer at the first gap can be closely abutted with the first pole ear, thereby improving the heat conduction efficiency on the pole piece, on the other hand, due to the setting of the second gap, a conduction channel is formed around the first pole ear, so that the heat of the pole piece surrounding the first pole ear can be evenly and quickly conducted to the surrounding of the first pole ear, thereby improving the heat dissipation efficiency of the winding core, ensuring that the winding core can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the winding core; in addition, through the setting of the thinning groove, on the one hand, since part of the active material is reserved in the thinning groove, and the weld mark of the first pole ear can be abutted with the active material of the thinning groove, and the active material in the thinning groove and the active material in the surrounding area are continuously arranged, the heat of the pole piece can also be quickly conducted out through the active material abutting with the weld mark of the first pole ear, further improving the heat dissipation efficiency of the winding core, on the other hand, the thickness of the first pole ear is hidden in the thinning groove to reduce the overall thickness of the winding core, so that the space utilization of the winding core is improved, thereby improving the energy density.

[0072] The content of the utility model will be described in detail below with reference to the accompanying drawings so that those skilled in the art can understand the content of the utility model more clearly and in detail.

[0073] Figure 1 This is a schematic structural diagram of a winding core from a first perspective provided in an embodiment of the present application. Figure 2 This is a schematic diagram of the structure of the first pole piece in the winding core provided in an embodiment of the present application. Figure 3 This is a schematic diagram of the structure of the second pole piece in the winding core provided in an embodiment of the present application. Figure 4 A schematic diagram of the structure of the unfolded roll core provided in an embodiment of the present application.

[0074] like Figures 1 to 4 As shown, the embodiment of the present application provides a winding core 100, including a wound first pole piece 110, a diaphragm and a second pole piece 120, the diaphragm is located between adjacent first pole pieces 110 and second pole pieces 120, and the first pole piece 110 and the second pole piece 120 have opposite polarities;

[0075] The first pole piece 110 includes a first current collector and a first active material layer 112 coated on both sides of the first current collector, a pole tab groove 130 is provided on the first active material layer 112, the bottom wall of the pole tab groove 130 is the first current collector, and the surrounding side is the first active material layer 112, the pole tab groove 130 extends to the edge of the first current collector along the second direction, and a first pole tab 111 electrically connected to the first current collector is provided in the pole tab groove 130;

[0076] The second pole piece 120 includes a second current collector 121 and a second active material layer 122 coated on both sides of the second current collector 121. A skived groove 1221 is provided on the second active material layer 122 opposite to the pole ear groove 130. The thickness of the second active material layer 122 in the skived groove 1221 is less than the thickness of the second active material layer 122 in the non-skived groove region of the second current collector 121. A first protective adhesive tape 140 is provided in the skived groove 1221. The projection of the first pole ear 111 in the first direction is located within the projection of the first protective adhesive tape 140 in the first direction. The second current collector 121 has a second edge in the second direction.

[0077] Among them, the thinning groove 1221 is located in the straight section of the winding core, and there is a first gap between the thinning groove 1221 and the second edge. The projection of the first gap in the first direction at least partially overlaps with the projection of the first pole ear 111 in the first direction. The thinning groove 1221 and the nearest adjacent winding core arc section have a second gap.

[0078] It should be noted that the projection of the first electrode tab 111 in the first direction is located within the projection of the first protective adhesive tape 140 in the first direction, that is, Figure 1 In the orthographic projection of the plane perpendicular to the first direction, that is, in the orthographic projection of the plane where the first protective tape 140 is located, along the width direction of the first pole ear 111 , the width of the first pole ear 111 on both sides does not exceed the width of the first protective tape 140 on both sides.

[0079] It should be noted that if Figure 1 As shown, the first direction e is the thickness direction of the winding core 100. Figure 2 , Figure 3 as well as Figure 4 As shown, the second direction b is the width direction of the pole piece, and the third direction d is the length direction of the pole piece.

[0080] It is understandable that part of the structure in the thickness direction of the first pole tab 111 can be located in the thinning groove 1221, which can offset part of the thickness of the first pole tab 111 and reduce the stacking thickness at the first pole tab 111. As a result, the flatness of the winding core is further improved, the thickness of the winding core can be reduced to a certain extent, and the space utilization and energy density of the battery can be improved.

[0081] It should be noted that during the battery charging and discharging process, the pole pieces of the winding core are prone to heat up due to the electrochemical reaction. In particular, the second pole piece is the negative pole piece, which is usually made of graphite, silicon and other materials, and generates more heat than the positive pole piece. During the high-rate charging and discharging process, the heat generated by the pole piece increases exponentially due to the more intense electrochemical reaction. On the one hand, the pole ear is usually made of metal or alloy such as nickel, copper or aluminum, and has excellent thermal conductivity. On the other hand, the pole ear usually extends to the outside of the pole piece and contacts the external air, so the pole piece can dissipate most of the heat through the pole ear.

[0082] It should also be noted that the reference Figures 1 to 3 The core includes a straight section and two arc sections, and the two arc sections are located on both sides of the straight section of the core. The core is formed by winding the positive electrode sheet, the separator and the negative electrode sheet in sequence along its head, so correspondingly, each layer of the electrode sheet has a corresponding straight section and at least one arc section. From the winding center of the core to the outside, the straight sections and arc sections of the multiple layers of electrode sheets are stacked in sequence to form a straight section of the core and two arc sections of the core.

[0083] In addition, since the thickness of the positive and negative electrodes and the separator is relatively thin, both in the micron (um) scale, and in order to increase the unit energy density of the battery cell, they are tightly wound, so that the positive and negative electrodes and the separator are closely attached; therefore, the diameter of the circular arc segment of the winding core is relatively small, especially the electrode piece closer to the winding center, the winding radius is closer to zero, and the arc segment of the electrode piece closer to the winding center is more likely to have the active layer on the surface of the electrode piece thinning or even breaking due to large-angle bending and stretching, that is, the active layer on the surface of the electrode piece in the circular arc segment may be discontinuous. At this time, if the pole ear is set close to the circular arc segment, the active layer between the pole piece where the pole ear is located and the circular arc segment and the second gap on the pole piece set opposite to the pole ear approach zero. In addition, referring to the above phenomenon of the active layer breaking or thinning on the surface of the circular arc segment, the heat of the active layer close to the circular arc segment cannot be effectively conducted to the pole ear, such as Figure 3 As shown, the heat conduction from the second active material layer 122 to the first electrode tab 111 in the d direction is blocked, thereby affecting the heat dissipation of the electrode piece.

[0084] After the first electrode tab 111 is wound, the straight section facing the second active material layer 122, that is, Figure 3 In directions a and b, the blank areas of the first pole ear 111 in directions a and b are larger, so the effects of heat transfer to the pole ear in these two directions are better; however, in the prior art, no active layer is reserved for the first pole ear 111 in directions c and / or d, so the second active material layer transfers less heat to the first pole ear 111 in directions a and b, reducing the heat dissipation efficiency of the pole piece.

[0085] Therefore, the present application adds a blank area to the first pole ear 111 in the direction c and the direction d, that is, there is a first gap between the top of the thinning groove 1221 and the edge of the second active material layer 122, so that in the direction c, the first pole ear 111 can abut against the second active material layer 122, and then the heat generated by the second active material layer 122 can be transferred to the first pole ear 111 through heat conduction to quickly dissipate the heat; at the same time, in the direction d, there is a second gap between the side wall of the thinning groove 1221 and the arc segment of the second active material layer 122, and at the same time The two ends of the second gap are respectively connected to the first gap and the large active layer at the bottom, and the two ends of the first gap are respectively connected to the second gap and the large active layer on the right, so that an annular conduction channel is formed around the thinning groove 1221 and the first pole ear 111, so that the heat generated by the second active material layer 122 of the first pole ear 111 in direction a and direction b can be further transferred to the first gap and the second gap, so that the heat generated by the pole piece can be conducted around the first pole ear 111, thereby improving the thermal conductivity and heat dissipation efficiency of the first pole ear 111.

[0086] Through the above arrangement, that is, on the one hand, through the arrangement of the first gap, the second active material layer 122 at the first gap can be in close contact with the first pole ear 111, thereby improving the heat conduction efficiency on the pole piece. On the other hand, due to the arrangement of the second gap, a conduction channel is formed around the first pole ear 111, so that the heat of the pole piece surrounding the first pole ear 111 can be evenly and quickly conducted to the surrounding of the first pole ear 111, thereby improving the heat dissipation efficiency of the core 100, ensuring that the core 100 can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the core 100; in addition, By setting the thinning groove 1221, on the one hand, since part of the active material is reserved in the thinning groove 1221, and the weld mark of the first pole ear 111 can abut against the active material in the thinning groove 1221, and the active material in the thinning groove 1221 and the active material in the surrounding area are arranged continuously, the heat of the pole piece can also be quickly discharged through the active material abutting against the weld mark of the first pole ear 111, thereby further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first pole ear 111 is hidden in the thinning groove 1221 to reduce the overall thickness of the core 100, so that the space utilization of the core 100 is improved, thereby improving the energy density.

[0087] It should be noted that the second current collector 121 is a high-strength copper foil current collector with a tensile strength of 300MPa-700MPa, an elongation of 2.0%-11%, and a surface density of 30g / m2-65g / m2. The purpose is to effectively improve the problem of the second current collector 121 breaking due to the stress difference generated during the welding process; at the same time, it can also effectively reduce the burrs on the solder joints and reduce the risk of puncture. At the same time, it can also increase the tensile force value at the welding point, reduce the contact impedance, and reduce the internal resistance of the core.

[0088] Preferably, the first electrode sheet 110 in the embodiment of the present application may be a positive electrode sheet, wherein the first current collector is a positive electrode current collector, the first active material layer 112 is a positive electrode active material layer, and the first electrode tab 111 is a positive electrode tab.

[0089] The second electrode sheet 120 may be a negative electrode sheet, wherein the second current collector 121 is a negative electrode current collector, the second active material layer 122 is a negative electrode active material layer, and the second electrode tab is a negative electrode tab.

[0090] Correspondingly, in other embodiments, the first pole piece 110 may also be a negative pole piece, and the second pole piece 120 may also be a positive pole piece. The principles are the same or similar to those described above and will not be elaborated on herein.

[0091] like Figures 1 to 4 As shown, in some optional embodiments, the width of the first gap in the second direction is A, and the width of the second gap in the third direction of the first current collector is B, wherein A and B satisfy: 2mm<B and 0.8≤A / B≤1.2.

[0092] It should be noted that the second gap can be 2.5 mm, 3 mm, 3.5 mm, 4 mm, etc., and there are no specific restrictions.

[0093] In addition, the ratio between the first gap A and the second gap B is greater than or equal to 0.8 and less than or equal to 1.2. This setting mainly takes into account the overlapping area between the extended area of ​​the first gap A and the extended area of ​​the second gap B to avoid excessive heat here and the inability to quickly export it.

[0094] In addition, since the connection between the first gap A and the second gap B is close to the edge corner of the pole piece, by setting 0.8≤A / B≤1.2, that is, the widths of the first gap A and the second gap B are similar, the poor heat conduction at the connection between the first gap A and the second gap B is effectively avoided, and the high heat generation caused by the heat accumulation at the connection between the first gap A and the second gap B is effectively avoided, thereby effectively avoiding the melting and rupture of the aluminum-plastic film at the top corner of the battery cell near the pole ear due to abnormal heat increase, that is, corner cracking.

[0095] In some optional embodiments, the first current collector in the tab groove 130 is provided with a first notch, the first notch extends to the edge of the first current collector, and the distance between the bottom wall of the first notch and the second edge in the projection in the second direction is m, wherein m satisfies: m<A.

[0096] It should be noted that the first notch is the arc-shaped punching area of ​​the first pole ear 111, the bottom wall of the first notch is the deepest part of the notch into the first current collector, and m is the size of the bottom wall of the first notch from the edge of the second active material layer 122 in the projection of the second active material layer 122. The purpose of such a setting is to avoid the overlap between the first pole ear 111 and the aluminum foil, thereby reducing the thickness here, and then reducing the ineffective thickness of the core, thereby improving the energy density of lithium-ion batteries, improving space utilization, and improving the endurance of electronic products.

[0097] like Figures 1 to 4 As shown, in some optional embodiments, along the second direction, the distance between the first protective tape 140 and the edge of the thinning groove 1221 is C, which satisfies: 0mm<C<5mm; and / or,

[0098] Along the length direction of the first current collector, the distance between the first protective tape 140 and the edge of the thinning groove 1221 is D, which satisfies: 0 mm<D<5 mm.

[0099] It should be noted that such a configuration makes the first protective tape 140 covering the area, the skived groove 1221 and the normal thickness of the second active material layer 122 present a stepped funnel shape, which is conducive to the storage of electrolyte here, and the electrolyte absorbs the heat generated by the first pole ear 111 to reduce the temperature rise. In particular, the electrolyte can effectively fill the gap between the skived groove 1221 and the first protective tape 140, so that the heat on the first protective tape 140 abutting against the first pole ear 111 can be continuously conducted to the first gap and the second gap through the electrolyte, thereby improving the heat conduction efficiency.

[0100] It should be noted that the distance between the first protective tape 140 and the edge of the thinning groove 1221 can be 1 mm, 2 mm, 3 mm or 4 mm, or other values.

[0101] Figure 5 This is a schematic diagram of the structure of the winding core provided by the embodiment of the present application from a second perspective. Figure 6 A cross-sectional view of the second pole piece in the winding core provided in an embodiment of the present application.

[0102] like Figures 1 to 6 As shown, in some optional embodiments, a plurality of first grooves 1222 are further provided on the second active material layer 122, and the first grooves extend along the second direction;

[0103] The plurality of first grooves 1222 are disposed at intervals on at least one of the arc segment of the second active material layer 122 and the straight segment of the second active material layer 122 .

[0104] It should be noted that the setting of the first groove 1222 facilitates the dissipation of heat at the first pole ear 111 to the outside of the winding core, that is, the heat at the first pole ear 111 can be discharged in the direction facing the second active material layer 122 and in the direction of the arc segment of the second active material layer 122, and then dissipated through the first heat dissipation channel in the first groove 1222, which is more conducive to heat dissipation.

[0105] In some embodiments, the first groove 1222 can be a complete linear first groove 1222 made by laser, or a linear first groove 1222 made by splicing multiple segments of laser lines. This mainly depends on the size of the laser equipment. The width of the wire is related to the size of the equipment. If the pole piece is too wide, splicing wires is required. Figure 3 The at least partially linear first groove 1222 connects the edge of the pole piece and the thinning groove 1221 , which is more conducive to the electrolyte to quickly and fully penetrate into the gap between the first protective tape 140 and the thinning groove 1221 , thereby improving the thermal conductivity and heat dissipation efficiency at the first pole ear 111 .

[0106] In some embodiments, the length direction of the first groove 1222 can be consistent with the width direction of the thinning groove 1221, or can be consistent with the length direction of the thinning groove 1221, or can be any direction as long as it can dissipate heat.

[0107] In other embodiments, the cross-sectional shape of the first groove 1222 is any one of a rectangle, a trapezoid, a cone, an arc and a column. In specific implementation, the first groove 1222 can be formed by at least one of laser burning, tool cutting, stamping and the like, and the cross-sectional shape of the formed first heat dissipation channel can be a square, a trapezoid, a triangle and the like, which is not limited in this embodiment.

[0108] In some optional embodiments, a gap is provided between the first pole piece 110 and the second pole piece 120 of the arc segment of the second active material layer 122 , and the gap has a second heat dissipation channel.

[0109] It should be noted that the adhesion between the interfaces of the arc region of the winding core 100 is worse than that of the straight region. Since the winding core is pressed downward along the thickness direction of the winding core, the straight region is compressed at this time, and thus a gap is provided between the first pole piece 110 and the second pole piece 120 of the arc segment. The gap has a second heat dissipation channel, and thus the heat at the first pole ear 111 is dissipated to the outside of the winding core.

[0110] In addition, there are pores in the arc area, which is convenient for releasing the stress of the arc area and providing a second heat dissipation channel. There is a second gap between the thinned groove 1221 and the arc area, that is, the second heat dissipation channel is not blocked and the heat and gas conduction effect of this area is not affected.

[0111] like Figures 1 to 6As shown, in some optional embodiments, the relationship between the depth H of the first groove 1222 and the elongation at break e of the second current collector 121 satisfies: 1 mm ≤ H / e ≤ 15 mm.

[0112] It should be noted that the greater the elongation at break of the current collector, the greater the stress it can withstand, the greater the laser intensity it can withstand, and the deeper the first groove 1222.

[0113] Figure 7 A schematic diagram of the structure of the first pole ear in the winding core provided in an embodiment of the present application, such as Figures 1 to 7 As shown, in some optional embodiments, the relationship between the depth H of the first groove 1222, the width L of the first groove 1222, the width E of the first pole ear 111 or the second pole ear, and the thickness F of the first pole ear 111 or the second pole ear satisfies: 2*10 -4 mm 4 ≤H*L*E*F≤2*10 -3 mm 4 .

[0114] It should be noted that the narrower or thinner the electrode ear of one of the first electrode ear 111 and the second electrode ear is, the more obvious the heat generation is, and the larger the channel area required for heat and gas conduction is.

[0115] Specifically: the resistance value of the metal strip of the pole ear R = ρL / S, L represents the length, S represents the area; the charging and discharging current remains unchanged, the smaller S is, the larger the resistance value is, and the larger the resistance is, the more serious the heat generation is.

[0116] like Figures 1 to 7 As shown, in some optional embodiments, a ceramic layer is coated on at least one side surface of the tail end of the first pole piece 110 away from the winding center, and part of the ceramic layer covers the first active material layer 112;

[0117] The coating thickness of the ceramic layer is greater than or equal to 5um and less than or equal to 20um; and / or,

[0118] The ratio of the ceramic grain size of the ceramic layer to the width of the first groove 1222 is greater than or equal to 1 / 20 and less than or equal to 1 / 4.

[0119] It should be noted that the ceramic layer is conducive to absorbing heat and reducing the overall temperature rise of the entire battery.

[0120] In some embodiments, a ceramic layer is coated on the aluminum foil at the tail end of the first pole piece 110 , wherein the ceramic layer may be coated on both sides or on only one side.

[0121] In addition, the setting of the above values ​​can effectively prevent the ceramic from detaching and blocking the first groove 1222, thereby affecting the heat conduction of the battery cell.

[0122] In some embodiments, the coating thickness of the ceramic layer can be 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um or 20um, or any value therein.

[0123] In some embodiments, the ratio of the ceramic grain size of the ceramic layer to the width of the first groove 1222 may be 0.05, 0.1, 0.15, 0.2, 0.25, or any value therein.

[0124] In some optional embodiments, a second groove is provided at the tail end of the first active material layer 112 away from the winding center, and part of the ceramic layer covers the second groove;

[0125] The depth of the second groove is greater than or equal to 0 um and less than or equal to 20 um.

[0126] It should be noted that the second groove is used to offset the thickness of the ceramic layer and facilitate reducing the thickness of the ceramic layer to prevent the overlapping area from being thicker than other positions and affecting the flatness of the battery cell. Ceramics are good at absorbing heat and reducing the overall temperature rise of the entire battery.

[0127] In some embodiments, the thickness of the second groove may be 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um or 20um, or any value therein.

[0128] In some optional embodiments, the projection of at least part of the ceramic layer in the thickness direction of the winding core 100 is located within the thinning groove 1221 .

[0129] It should be noted that, with such a configuration, the heat generated by the first pole ear 111 is vertically conducted to the ceramic layer along the thickness direction of the winding core 100 , which reduces the heat conduction path and improves the thermal conductivity and heat dissipation efficiency of the winding core 100 .

[0130] In some optional embodiments, the second active material layer 122 includes a first material layer and a second material layer, which are stacked in sequence along a first direction, wherein the first material layer is located on a side away from the second current collector 121 .

[0131] It should be noted that this means that the second active material layer 122 has a double-layer structure, wherein the materials used for the first material layer and the second material layer may be the same or different.

[0132] In some optional embodiments, at least one of the first material layer and the second material layer is made of graphite doped with silicon, wherein the particle size of graphite particles in the first material layer is smaller than the particle size of graphite particles in the second material layer;

[0133] The ratio of the thickness of the first material layer to the thickness of the second active material layer 122 is greater than or equal to 20% and less than or equal to 60%;

[0134] The thickness of the second active material layer 122 is greater than the depth of the first groove 1222 .

[0135] In some embodiments, the thickness of the first material layer may be greater than, less than, or equal to the depth of the first groove 1222 .

[0136] It should be noted that the second active material layer 122 is a double-layer graphite design, in which the lower layer is large-particle graphite and the upper layer is small-particle graphite. The thickness of the upper layer of small-particle graphite accounts for 20%-60% of the total thickness of the second active material layer 122. A linear first groove 1222 is punched on the second pole piece 120 using a laser. The depth h of the first groove 1222 is less than the thickness of the first material layer. The upper layer of small-particle graphite has a larger porosity and is more conducive to air and heat conduction.

[0137] It should be noted that the silicon materials doped in the first material layer and the second material layer can be the same silicon material or different silicon materials. There is no requirement for the particle size of different silicon materials in upper and lower mass production. Only the particle size of the graphite particles is required here. The particle size of the graphite particles in the first material layer is smaller than that of the graphite particles in the second material layer.

[0138] Figure 8 A schematic diagram of the structure of the silicon-carbon material particles in the winding core provided in the embodiment of the present application, such as Figures 1 to 8 As shown, in some optional embodiments, at least one of the first material layer and the second material layer is a mixed material including at least one of a graphite material and a silicon-carbon material, wherein the ratio of the doping amount of the silicon-carbon material to the mixed material is greater than or equal to 2% and less than or equal to 15%; and / or,

[0139] The relationship between the width L of the first groove 1222 and the particle size M of the silicon-carbon material satisfies: L≥2M, wherein 50 um≤L≤100 um.

[0140] The second active material layer 122 is a double-layer structure, that is, at least one of the first material layer and the second material layer is made of a mixed material including at least one of a graphite material and a silicon-carbon material.

[0141] It should be noted that the second active material layer 122 is a graphite-doped silicon-carbon material. The silicon-carbon particles will undergo a large expansion change during the charge and discharge process, and silicon-carbon will produce more side reactions and heat when in contact with the electrolyte than graphite. A linear first groove 1222 is punched out on the second pole piece 120 using a laser to provide sufficient space to accommodate the expansion of the silicon-carbon material during the cyclic charge and discharge process and to ensure that the first heat dissipation channel is unobstructed.

[0142] In some optional embodiments, a lithium replenishing layer is disposed on the side of the second pole piece 120 , and the thickness of the lithium replenishing layer is less than or equal to the depth of the first groove 1222 .

[0143] It should be noted that there is a lithium replenishment layer on the surface of the second electrode 120, and the depth h of the first groove 1222 is greater than the thickness of the lithium replenishment layer, so that there is still a linear first groove 1222 channel on the surface of the electrode after lithium replenishment, which is convenient for air and heat conduction.

[0144] In addition, it should be noted that the lithium replenishment method is to heat and melt lithium metal, cast or coat it on the electrode material coating to form a lithium replenishment layer, or oscillate the powdered lithium metal to the electrode sheet and roll it to form a lithium replenishment layer, or directly extrude solid metal lithium on the surface of the electrode sheet to form a lithium replenishment layer, but the above-mentioned lithium replenishment methods all generate a lot of heat during the lithium replenishment process that is difficult to discharge, resulting in the inability to guarantee the safety performance of the lithium battery. Therefore, through the first groove 1222, a linear first groove 1222 channel still exists on the surface of the electrode sheet after lithium replenishment, which is convenient for air and heat conduction.

[0145] like Figures 1 to 8 As shown, in some optional embodiments, a second protective tape 150 is provided at the tail end of the first pole piece 110, and the ratio between the width of the second protective tape 150 and the width of the winding core 100 is greater than or equal to 1 / 2 and less than or equal to 1; and / or,

[0146] The width of the second protective tape 150 is greater than or equal to 10 um and less than or equal to 40 um.

[0147] It should be noted that, to ensure that the second protective tape 150 exceeds the finishing empty foil (or coated with a ceramic layer) after passing the arc, the gluing relationship between the second protective tape 150 and the finishing hot melt adhesive is that in the width direction of the core, the second protective tape 150 exceeds the hot melt adhesive, and the hot melt adhesive is attached above the second protective tape 150, which can prevent the hot melt adhesive from tearing the first pole piece 110.

[0148] In some embodiments, the width of the second protective film 150 may be 15 um, 20 um, 25 um, 30 um, 35 um or 40 um, or any other value.

[0149] like Figures 1 to 8As shown, in some optional embodiments, a third protective tape 160 is disposed on the pole lug groove 130 located on one side of the first pole piece 110 , and the third protective tape 160 is used to cover the thinning groove 1221 .

[0150] It should be noted that the third protective tape 160 can prevent the burrs at the welding point of the first electrode tab 111 from piercing the diaphragm and causing the risk of short circuit and fire.

[0151] It should be noted that the following is a table for comparing multiple groups of example data.

[0152] Table 1 is a table of temperature rise data for multiple groups of examples and comparative examples

[0153]

[0154]

[0155] The difference between the comparative example and the embodiment 1 is that the second pole piece 120 of the comparative example has no thinning groove 1221 .

[0156] The difference between Example 2 and Example 1 is that the distance A between the thinning groove 1221 and the edge of the pole piece is 0.

[0157] The difference between the third embodiment and the first embodiment is that there is no linear first groove 1222 formed by laser marking on the surface of the second pole piece 120 .

[0158] The difference between Example 4 and Example 1 is that the specification of the tab is 4mm*0.08mm.

[0159] The difference between Example 5 and Example 1 is that the depth of the linear first groove 1222 laser-marked on the surface of the second pole piece 120 is 30 um.

[0160] The difference between Example 6 and Example 1 is that the width of the linear first groove 1222 laser-marked on the surface of the second pole piece 120 is 20 um.

[0161] The difference between Example 7 and Example 1 is that there is no ceramic layer at the tail of the first pole piece 110 .

[0162] The difference between Example 8 and Example 1 is that the width of the second protective tape 150 on the short side of the first pole piece 110 is 10 mm.

[0163] The winding core provided in the embodiment of the present application includes a first pole piece and a second pole piece, the first pole piece includes a first current collector and a first active material layer coated on both sides of the first current collector, a first pole ear groove is provided on the first active material layer, the bottom wall of the first pole ear groove is the first current collector, and the surrounding side is the first active material layer, the first pole ear groove extends along the second direction to the edge of the first current collector, and a first pole ear electrically connected to the first current collector is provided in the first pole ear groove; the second pole piece includes a second current collector and a second active material layer coated on both sides of the second current collector, a thinning groove is provided on the second active material layer opposite to the first pole ear groove, the thickness of the second active material layer in the thinning groove is less than the thickness of the second active material layer in the non-thinning groove area of ​​the second current collector, a first protective tape is provided in the thinning groove, the projection of the first pole ear in the first direction is located within the projection of the first protective tape in the first direction, and the second current collector has a second edge in the second direction; wherein the thinning groove is located in the straight section of the winding core, the thinning groove and the second edge have a first gap, the projection of the first gap in the first direction overlaps at least partially with the projection of the first pole ear in the first direction, and the thinning groove and the nearest side of the winding core arc section adjacent to the thinning groove have a second gap.

[0164] On the one hand, by setting the first gap, the second active material layer at the first gap can be closely abutted against the first pole ear, thereby improving the heat conduction efficiency on the pole piece. On the other hand, due to the setting of the second gap, a conduction channel is formed around the first pole ear, so that the heat of the pole piece surrounding the first pole ear can be evenly and quickly conducted to the surrounding of the first pole ear, thereby improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the core. In addition, by setting the thinning groove, on the one hand, since part of the active material is reserved in the thinning groove, and the weld mark of the first pole ear can be abutted against the active material of the thinning groove, and the active material in the thinning groove and the active material in the surrounding area are continuously arranged, the heat of the pole piece can also be quickly discharged through the active material abutting against the weld mark of the first pole ear, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first pole ear is hidden in the thinning groove to reduce the overall thickness of the core, so that the space utilization of the core is improved, thereby improving the energy density.

[0165] In addition, an embodiment of the present application further provides a battery, including a winding core 100 .

[0166] The battery is not limited to lithium batteries, and in the future this technology may be applied to sodium batteries, etc. In the present application, lithium-ion batteries are preferred.

[0167] The specific structure, working principle and function of the winding core 100 have been described in detail in the above embodiments and will not be repeated here. It should be noted that the preparation process of the lithium-ion battery is as follows:

[0168] Step 1: Preparation of positive electrode sheet: prepare positive electrode active layer slurry, apply positive electrode active material slurry and ceramic slurry on the surface of current collector by gravure coating or skip coating, and obtain positive electrode sheet after baking and roller pressing. A certain position of the positive electrode sheet has a slot of fixed size, and a 6mm*0.08mm nickel pole ear is welded in this slot by laser or ultrasonic welding, and the width of the second protective tape on the short side of the positive electrode is 35mm;

[0169] Step 2: prepare two different negative electrode active layer slurries, apply them on carbon-coated copper foil at the same time, and obtain negative electrode sheets after baking and rolling. The bottom layer paste thickness is 50um, and the upper layer paste thickness is 20um. A certain position of the negative electrode sheet has a slot with a fixed size, and a 6mm*0.08mm copper-plated nickel-plated pole ear is welded in this slot by laser or ultrasonic welding; in addition, a thinning groove 1221 is cleaned out at the position where the positive pole ear welding area is projected on the negative electrode sheet, and the thinning groove 1221 has a depth of 25um, and the distance A between the thinning groove 1221 and the edge of the pole sheet is 2mm, and the distance from the arc area is 1mm; a uniform linear first groove 1222 is punched on the surface of the negative electrode sheet using a laser of a certain intensity, and the depth h of the first groove 1222 is 15um and the width L is 80um;

[0170] Step 3: The positive and negative electrode sheets are cut, sliced ​​and wound with the separator to obtain a winding core;

[0171] Step 4: After packaging, baking, liquid injection, formation, secondary sealing, sorting and OCV, the lithium-ion battery is obtained.

[0172] The electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0173] The battery provided in the embodiment of the present application, on the one hand, through the setting of the first gap, the second active material layer at the first gap can be closely abutted with the first pole ear, thereby improving the heat conduction efficiency on the pole piece. On the other hand, due to the setting of the second gap, a conduction channel is formed around the first pole ear, so that the heat of the pole piece surrounding the first pole ear can be evenly and quickly conducted to the surrounding of the first pole ear, thereby improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charging and discharging, and improving the safety and performance of the core. In addition, through the setting of the thinning groove, on the one hand, since part of the active material is reserved in the thinning groove, and the weld mark of the first pole ear can be abutted with the active material of the thinning groove, and the active material in the thinning groove and the active material in the surrounding area are continuously arranged, the heat of the pole piece can also be quickly conducted out through the active material abutting with the weld mark of the first pole ear, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first pole ear is hidden in the thinning groove to reduce the overall thickness of the core, so that the space utilization of the core is improved, thereby improving the energy density.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A winding core, comprising a first pole piece and a second pole piece, characterized in that: The first pole piece includes a first current collector and a first active material layer coated on both sides of the first current collector, a pole lug groove is provided on the first active material layer, the bottom wall of the pole lug groove is the first current collector, and the surrounding side is the first active material layer, the pole lug groove extends along the second direction to the edge of the first current collector, and a first pole lug electrically connected to the first current collector is provided in the pole lug groove; The second pole piece includes a second current collector and a second active material layer coated on both sides of the second current collector, a thinning groove is provided on the second active material layer opposite to the electrode tab groove, the thickness of the second active material layer in the thinning groove is less than the thickness of the second active material layer in the non-thinning groove area of ​​the second current collector, a first protective adhesive tape is provided in the thinning groove, the projection of the first electrode tab in the first direction is located within the projection of the first protective adhesive tape in the first direction, and the second current collector has a second edge in the second direction; Among them, the thinning groove is located in the straight section of the winding core, the thinning groove and the second edge have a first gap, the projection of the first gap in the first direction at least partially overlaps with the projection of the first pole ear in the first direction, and the thinning groove and the nearest adjacent winding core arc section have a second gap.

2. The winding core according to claim 1, characterized in that: The width of the first gap in the second direction is A, and the width of the second gap in the third direction of the first current collector is B, wherein A and B satisfy: 2 mm < B and 0.8 ≤ A / B ≤ 1.

2.

3. The winding core according to claim 2, characterized in that: The first current collector in the tab groove is provided with a first notch, the first notch extends to the edge of the first current collector, and the distance between the bottom wall of the first notch and the second edge in the projection in the second direction is m, wherein m satisfies: m<A.

4. The winding core according to claim 1, characterized in that: Along the second direction, the distance between the first protective tape and the edge of the skived groove is C, which satisfies: 0mm<C<5mm; and / or, Along the length direction of the first current collector, the distance between the first protective tape and the edge of the skived groove is D, satisfying: 0mm<D<5mm.

5. The winding core according to any one of claims 1 to 4, characterized in that: A plurality of first grooves are also formed on the second active material layer, and the first grooves extend along the second direction; A plurality of the first grooves are arranged at intervals in the arc segment of the second active material layer and / or the straight segment of the second active material layer.

6. The winding core according to claim 5, characterized in that: The relationship between the depth H of the first groove and the elongation at break e of the second current collector satisfies: 1 mm ≤ H / e ≤ 15 mm; The second pole piece is further provided with a second pole ear, and the relationship between the depth H of the first groove, the width L of the first groove, the width E of the first pole ear and the second pole ear, and the thickness F of the first pole ear and the second pole ear satisfies: 2*10 -4 mm 4 ≤H*L*E*F≤2*10 -3 mm 4 .

7. The winding core according to claim 5, characterized in that: A ceramic layer is coated on at least one side of the tail end of the first pole piece away from the winding center, and part of the ceramic layer covers the first active material layer; The coating thickness of the ceramic layer is greater than or equal to 5um and less than or equal to 20um; and / or, The ratio of the ceramic grain size of the ceramic layer to the width of the first groove is greater than or equal to 1 / 20 and less than or equal to 1 / 4.

8. The winding core according to claim 7, characterized in that: A second groove is provided at the tail end of the first active material layer away from the winding center, and part of the ceramic layer covers the second groove; The depth of the second groove is greater than or equal to 0 um and less than or equal to 20 um.

9. The winding core according to claim 8, characterized in that: A projection of at least a portion of the ceramic layer in the first direction is located within the thinning groove.

10. The winding core according to claim 5, characterized in that: The second active material layer includes a first material layer and a second material layer, and the first material layer and the second material layer are sequentially stacked along the first direction, wherein the first material layer is located on a side away from the second current collector.

11. The winding core according to claim 5, characterized in that: A lithium replenishing layer is provided on the second pole piece, and the thickness of the lithium replenishing layer is less than or equal to the depth of the first groove.

12. The winding core according to any one of claims 1 to 4, characterized in that: A second protective tape is provided at the tail end of the first pole piece, and the ratio between the width of the second protective tape and the width of the winding core is greater than or equal to 1 / 2 and less than or equal to 1; and / or, The width of the second protective tape is greater than or equal to 10 um and less than or equal to 40 um.

13. The winding core according to any one of claims 1 to 3, characterized in that: A third protective adhesive tape is arranged on the pole lug groove located on one side of the first pole piece, and the third protective adhesive tape covers the thinning groove.

14. A battery, characterized in that: Comprising the winding core as described in any one of claims 1-13.

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