Roll core and battery

Abstract

The invention provides a roll core and a battery, the roll core comprises a first pole piece and a second pole piece, the first pole piece comprises a first current collector and first active material layers coated on two sides of the first current collector, a first tab groove is arranged on the first active material layer, the bottom wall of the first tab groove is the first current collector, and the peripheral side of the first tab groove is the first active material layer; the first tab groove extends to the edge of the first current collector along the second direction, and a first tab electrically connected with the first current collector is arranged in the first tab groove; the second pole piece comprises a second current collector and second active substance layers coated on the two sides of the second current collector; and a thinning groove is formed in the second active substance layer opposite to the first tab groove. Effective heat dissipation of the battery in the charging process is ensured, the safety and performance of the battery are improved, the space utilization rate is improved, and the cruising ability of an electronic product is improved.

Description

[0001] This application claims the priority of a Chinese patent application with the application number 202410250583.7 and the application title "Spool Core and Battery", which was filed with the Chinese Patent Office on March 5, 2024. The entire content thereof is incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of batteries, and particularly to a spool core and a battery. Background Art

[0004] With the advent of the 5G era and the rapid development of battery technology, people have put forward higher requirements for battery energy density, fast charging ability, and charge-discharge rate. Fast-charging lithium-ion batteries have become the development trend of consumer lithium-ion batteries.

[0005] Currently, in high-rate charge-discharge conditions or during long-term full-load operation, the battery, especially the position of the tab, will face relatively serious heating problems. The heat dissipation of the battery is an important problem that needs to be solved to ensure or extend the battery life. How to improve the battery heat dissipation performance through a reasonable structure to reduce the temperature of the battery during operation and avoid reducing the battery service life is the key research direction of those skilled in the art. Summary of the Invention

[0006] Embodiments of the present invention provide a spool core and a battery, which are mainly used to solve problems such as battery overheating during high-rate charge and discharge in the prior art. This application improves the space utilization rate, and in addition, ensures that the battery can effectively dissipate heat during charging, improving the safety and performance of the battery.

[0007] The present invention provides a spool core, which includes a first electrode tab and a second electrode tab;

[0008] The first electrode tab includes a first current collector and first active material layers coated on both sides of the first current collector. On the first active material layer, there is a tab groove. The bottom wall of the tab groove is the first current collector, and the peripheral side is the first active material layer. The tab groove extends to the edge of the first current collector in the second direction, and a first tab electrically connected to the first current collector is provided in the tab groove;

[0009] The second electrode tab includes a second current collector and second active material layers coated on both sides of the second current collector. On the second active material layer opposite to the tab groove, there is a thinning 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. Along the width direction of the first tab, both sides of the width of the first tab do not exceed both sides of the first protective adhesive tape. The second current collector has a second edge in the second direction;

[0010] Among them, the thinning groove is located in the straight section of the core. There is a first gap between the thinning groove and the second edge. The projection of the first gap in the first direction at least partially overlaps with the projection of the first tab in the first direction. There is a second gap between the thinning groove and the nearest arc section of the core adjacent to it.

[0011] Through the above settings, that is, on the one hand, through the setting of the first gap, the second active material layer at the first gap can be in close contact with the first tab, 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 tab, enabling the heat of the pole piece surrounding the first tab to be evenly and quickly conducted to the periphery of the first tab, thereby improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charge and discharge, 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 welding mark of the first tab can be in contact with the active material in 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 exported through the active material in contact with the welding mark of the first tab, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first tab and the like are hidden in the thinning groove to reduce the overall thickness of the core, improving the space utilization rate of the core, thereby enhancing the energy density. 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, where A and B satisfy: 2mm < B; and / or, 0.8 ≤ A / B ≤ 1.2.

[0012] 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. Such a 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 too much heat in this area and unable to be quickly exported.

[0013] In some optional embodiments, a first notch is opened on the first edge of the first current collector. The first notch communicates with the tab groove and extends to the edge of the first current collector. The distance from the bottom wall of the first notch to the second edge in the projection in the second direction is m, where m satisfies: m > A.

[0014] In some optional embodiments, along the second direction, the distance between the first protective adhesive tape and the edge of the thinning groove is C, satisfying: 0mm < C < 5mm; and / or,

[0015] Along the length direction of the first current collector, the distance between the first protective adhesive tape and the edge of the thinning groove is D, satisfying: 0mm < D < 5mm.

[0016] It should be noted that with such a setting, the first protective adhesive 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 the electrolyte here. The electrolyte absorbs the heat generated by the first tab, reducing the temperature rise.

[0017] In some alternative embodiments, a plurality of first grooves are further formed in the second active material layer, and the first grooves extend along the second direction;

[0018] The plurality of first grooves are arranged at intervals on at least one of the arc segment and the straight segment of the second active material layer.

[0019] It should be noted that the setting of the first grooves facilitates the dissipation of the heat at the first tab to the outside of the core. That is, the heat at the first tab can be conducted out in the direction facing the second active material layer and in the direction of the arc segment of the second active material layer, and then dissipated through the first heat dissipation channels in the first grooves, which is more conducive to heat dissipation.

[0020] In some alternative embodiments, the relationship between the depth H of the first groove and the fracture elongation rate e of the second current collector satisfies: 1 mm ≤ H / e ≤ 15 mm;

[0021] The second pole piece is further provided with a second tab, and the relationship between the depth H of the first groove, the width L of the first groove, the tab width E of one of the first tab and the second tab, and the tab thickness F of one of the first tab and the second tab satisfies: 2×10 -4 mm 4 ≤ H×L×E×F ≤ 2×10 -3 mm 4 .

[0022] It should be noted that the larger the fracture elongation rate 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.

[0023] It should be noted that the thinner or thinner the tab of one of the first tab and the second tab, the more obvious the heat generation, and the larger the area of the heat conduction and gas conduction channels required.

[0024] In some alternative embodiments, a ceramic layer is coated on at least one 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;

[0025] The coating thickness of the ceramic layer is greater than or equal to 5 μm and less than or equal to 20 μm; and / or,

[0026] The ratio of the ceramic particle 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.

[0027] It should be noted that the ceramic layer is conducive to heat absorption and reduces the overall temperature rise of the entire battery.

[0028] In some alternative embodiments, a second groove is provided at the end of the first active material layer away from the winding center, and a part of the ceramic layer covers the second groove;

[0029] The depth of the second groove is greater than or equal to 0 um and less than or equal to 20 um.

[0030] It should be noted that the second groove is used to offset the thickness of the ceramic layer, facilitate reducing the thickness of the ceramic layer, prevent the overlapping area from thickening compared with other positions, affect the flatness of the battery cell, and the ceramic is conducive to heat absorption and reduces the overall temperature rise of the entire battery.

[0031] In some alternative embodiments, at least a part of the ceramic layer is projected into the thinning groove in the first direction.

[0032] It should be noted that such a setting reduces the heat conduction path and facilitates the heat conduction to the ceramic layer.

[0033] In some alternative 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 the side away from the second current collector.

[0034] In some alternative embodiments, at least one of the first material layer and the second material layer is made of a graphite doped with silicon material, wherein the particle size of the graphite particles in the first material layer is smaller than the particle size of the graphite particles in the second material layer;

[0035] The ratio between the thickness of the first material layer and the thickness of the second active material layer is greater than or equal to 20% and less than or equal to 60%.

[0036] It should be noted that the second active material layer is designed with a double-layer graphite structure, where the lower layer is large-particle graphite and the upper layer is small-particle graphite. The thickness of the upper small-particle graphite layer accounts for 20%-60% of the total thickness of the second active material layer. A linear first groove is formed on the second electrode plate by laser, and the depth h of the first groove is less than the thickness of the first material layer. The upper small-particle graphite layer has a larger porosity and is more beneficial to gas conduction and heat conduction.

[0037] In some alternative embodiments, 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, wherein the doping amount of the silicon-carbon material in the mixed material is greater than or equal to 2% and less than or equal to 15%; and / or,

[0038] The relationship between the width L of the first groove and the particle size M of the silicon-carbon material satisfies: L≥2M, where 50 um≤L≤100 um.

[0039] It should be noted that the second active material layer is a graphite-doped silicon-carbon material. During the charge and discharge process, the silicon-carbon particles will undergo significant expansion changes, and more side reactions will occur when silicon-carbon comes into contact with the electrolyte than graphite, generating heat. A linear first groove is formed on the second electrode plate by laser to provide sufficient space to accommodate the expansion of the silicon-carbon material during the cyclic charge and discharge process and ensure the smoothness of the first heat dissipation channel.

[0040] In some alternative embodiments, a lithium compensation layer is provided on the side of the second electrode plate, and the thickness of the lithium compensation layer is less than or equal to the depth of the first groove.

[0041] It should be noted that there is a lithium compensation layer on the surface of the second electrode plate, and the depth h of the first groove > the thickness of the lithium compensation layer, so that there is still a linear first groove channel on the surface of the electrode plate after lithium compensation, which is convenient for gas conduction and heat conduction.

[0042] In some alternative embodiments, a second protective adhesive tape is provided at the end of the first electrode plate, and the ratio of the width of the second protective adhesive tape to the width of the core is greater than or equal to 1 / 2 and less than or equal to 1; and / or,

[0043] The width of the second protective adhesive tape is greater than or equal to 10 mm and less than or equal to 40 mm.

[0044] It should be noted that to ensure that the second protective adhesive tape extends beyond the end empty foil (or the ceramic layer-coated part) after passing through the arc, the sticking relationship between the second protective adhesive tape and the end hot melt adhesive is that in the width direction of the core, the second protective adhesive tape extends beyond the hot melt adhesive, and the hot melt adhesive is pasted above the second protective adhesive tape, which can prevent the hot melt adhesive from tearing the first electrode plate.

[0045] In some alternative embodiments, a third protective adhesive tape is provided on the tab groove on one side of the first electrode plate, and the third protective adhesive tape is used to cover the thinning groove.

[0046] It should be noted that the third protective adhesive tape can prevent the burrs at the welding point of the first tab from piercing the diaphragm and causing the risk of short circuit and fire.

[0047] The present invention also provides a battery, including the core as described above.

[0048] The winding core and battery provided by the present invention include a winding core; the winding core 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, 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, 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, and the second active material layer opposite to the first pole ear groove A thinning groove is provided on the 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.

[0049] 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

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0051] Figure 1Structural schematic diagram of the bobbin from the first perspective provided by the embodiment of the present application;

[0052] Figure 2 Structural schematic diagram of the first pole piece in the bobbin provided by the embodiment of the present application;

[0053] Figure 3 Structural schematic diagram of the second pole piece in the bobbin provided by the embodiment of the present application;

[0054] Figure 4 Structural schematic diagram of the unfolded bobbin provided by the embodiment of the present application;

[0055] Figure 5 Structural schematic diagram of the bobbin from the second perspective provided by the embodiment of the present application;

[0056] Figure 6 Cross-sectional view of the second pole piece in the bobbin provided by the embodiment of the present application;

[0057] Figure 7 Structural schematic diagram of the first tab in the bobbin provided by the embodiment of the present application;

[0058] Figure 8 Structural schematic diagram of the particles of the silicon-carbon material in the bobbin provided by the embodiment of the present application.

[0059] Explanation of reference numerals:

[0060] 100 - Bobbin;

[0061] 110 - First pole piece;

[0062] 111 - First tab;

[0063] 112 - First active material layer;

[0064] 120 - Second pole piece;

[0065] 121 - Second current collector;

[0066] 122 - Second active material layer;

[0067] 1221 - Thinning groove;

[0068] 1222 - First groove;

[0069] 130 - Tab groove;

[0070] 140 - First protective adhesive tape;

[0071] 150 - Second protective adhesive tape;

[0072] 160 - Third protective adhesive tape. Detailed implementation manners

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. All other embodiments obtained fall within the scope of protection of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0074] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0075] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication of the inner cavities of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0076] It should be noted that in the description of the present invention, the terms "first", "second", "third" are only used for the convenience of describing different components and cannot be understood as indicating or implying a sequential relationship, relative importance, or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include at least one of such features.

[0077] Currently, in high-power operating conditions or during long-term full-load operation, the battery will face a relatively serious heat generation problem. The heat dissipation of the battery is an important problem that needs to be solved to ensure or extend the battery life. How to improve the battery heat dissipation performance through a reasonable structure to reduce the temperature of the battery during operation and avoid reducing the battery service life is the key research direction of those skilled in the art.

[0078] In order to overcome the deficiencies in the prior art, the present invention provides a core and a battery. On the one hand, through the setting of the first gap, the second active material layer at the first gap can be closely abutted against the first tab, thereby improving the heat conduction efficiency on the electrode sheet. On the other hand, due to the setting of the second gap, a conduction channel is formed around the first tab, enabling the heat of the electrode sheet surrounding the first tab to be evenly and quickly conducted to the periphery of the first tab, thus improving the heat dissipation efficiency of the core, ensuring that the core can effectively dissipate heat during high-rate charge and discharge, 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 welding mark of the first tab can be abutted against the active material in the thinning groove, and the active material in the thinning groove is continuously arranged with the active material in the surrounding area, the heat of the electrode sheet can also be quickly exported through the active material abutted against the welding mark of the first tab, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first tab and the like are hidden in the thinning groove to reduce the overall thickness of the core, improving the space utilization rate of the core, and thus enhancing the energy density.

[0079] The content of the present invention will be described in detail below in conjunction with the accompanying drawings, so that those skilled in the art can understand the content of the present invention more clearly and in detail.

[0080] Figure 1 It is a schematic structural diagram of the first perspective of the core provided by the embodiment of the present application. Figure 2 It is a schematic structural diagram of the first electrode sheet in the core provided by the embodiment of the present application. Figure 3 It is a schematic structural diagram of the second electrode sheet in the core provided by the embodiment of the present application. Figure 4 It is a schematic structural diagram of the unfolded core provided by the embodiment of the present application.

[0081] As Figures 1 to 4 shown, the embodiment of the present application provides a core 100, which includes a wound first electrode sheet 110, a separator, and a second electrode sheet 120. The separator is located between adjacent first electrode sheets 110 and second electrode sheets 120, and the first electrode sheet 110 and the second electrode sheet 120 have opposite polarities.

[0082] The first electrode sheet 110 includes a first current collector and first active material layers 112 coated on both sides of the first current collector. An ear groove 130 is provided on the first active material layer 112. The bottom wall of the ear groove 130 is the first current collector, and the peripheral side is the first active material layer 112. The ear groove 130 extends along the second direction to the edge of the first current collector, and a first tab 111 electrically connected to the first current collector is provided in the ear groove 130.

[0083] The second pole piece 120 includes a second current collector 121 and second active material layers 122 coated on both sides of the second current collector 121. A thinning groove 1221 is provided on the second active material layer 122 opposite to the pole tab groove 130. The thickness of the second active material layer 122 in the thinning groove 1221 is less than the thickness of the second active material layer 122 in the non-thinning groove area of the second current collector 121. A first protective adhesive tape 140 is provided in the thinning groove 1221. The projection of the first pole tab 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;

[0084] Wherein, the thinning groove 1221 is located in the straight section of the core. The thinning groove 1221 and the second edge have a first gap. The projection of the first gap in the first direction and the projection of the first pole tab 111 in the first direction at least partially overlap. The thinning groove 1221 and the nearest arc section of the core adjacent to it have a second gap.

[0085] It should be noted that the projection of the first pole tab 111 in the first direction is located within the projection of the first protective adhesive tape 140 in the first direction, that is, referring to Figure 1 , in the orthographic projection perpendicular to the plane where the first direction is located, that is, in the orthographic projection of the plane where the first protective adhesive tape 140 is located, along the width direction of the first pole tab 111, both sides of the width of the first pole tab 11 do not exceed both sides of the first protective adhesive tape 140.

[0086] It should be noted that as Figure 1 shown, the first direction e is the thickness direction of the core 100. As Figure 2 , Figure 3 and Figure 4 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.

[0087] It can be understood that part of the structure of the first pole tab 111 in the thickness direction can be located in the thinning groove 1221, which can offset a part of the thickness of the first pole tab 111 and reduce the stacking thickness at the first pole tab 111. Thus, the flatness of the core is further improved, the thickness of the core can be reduced to a certain extent, and the space utilization rate and energy density of the battery are improved.

[0088] It should be noted that during the charge and discharge process of the battery, the pole pieces of the core are prone to heat due to electrochemical reactions. Especially when the second pole piece is the negative pole piece, which is usually made of materials such as graphite and silicon, the heat generation is greater than that of the positive pole piece. During the high-rate charge and discharge process, the heat generation of the pole piece increases exponentially due to the more intense electrochemical reactions. On the one hand, the pole tabs are usually made of metals or alloys such as nickel, copper, or aluminum, and their thermal conductivity is relatively excellent. On the other hand, the pole tabs usually extend to the outside of the pole piece and are in contact with the external air. Therefore, the pole piece can dissipate most of the heat through the pole tabs.

[0089] It should be further noted that, referring to Figures 1 to 3 , the core includes a flat section of the core and two arc sections of the core. The two arc sections of the core are respectively located on both sides of the flat section of the core; the core is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet in sequence along its head. Therefore, correspondingly, each layer of the electrode sheet has a corresponding flat section and at least one arc section. From the winding center of the core outwards, the flat sections and arc sections of multiple layers of electrode sheets are stacked in sequence to form the flat section of the core and the two arc sections of the core.

[0090] In addition, since the thicknesses of the positive and negative electrode sheets and the separator are relatively thin, all in the micrometer (μm) scale, and are tightly wound in order to improve the unit energy density of the battery cell, the positive and negative electrode sheets and the separator are closely attached to each other; therefore, the diameter of the arc section of the core is relatively small. Especially for the electrode sheet closer to the winding center, its winding radius approaches zero. And for the electrode sheet of the arc section closer to the winding center, due to large-angle bending and stretching, the active layer on the surface of the electrode sheet is more likely to become thinner or even break, that is, the active layer on the surface of the electrode sheet in the arc section may be discontinuous. At this time, if the tab is arranged close to the arc section, the active layer between the electrode sheet where the tab is located and the arc section and the second gap on the electrode sheet opposite to the tab approach zero. Referring to the above-mentioned phenomenon that the active layer on the surface of the arc section breaks or becomes thinner, the heat of the active layer close to the arc section cannot be effectively conducted to the tab, as Figure 3 shown, the heat conduction of the second active material layer 122 to the first tab 111 in the d direction is blocked, thereby affecting the heat dissipation of the electrode sheet.

[0091] Since after winding, in the flat section of the first tab 111 facing the second active material layer 122, that is, Figure 3 in directions a and b, the blank areas of the first tab 111 towards directions a and b are relatively large. Therefore, the heat transfer effect through these two directions to the tab is relatively good; however, in the prior art, there is no reserved active layer for the first tab 111 towards direction c and / or direction d. Therefore, the heat transferred from the second active material layer to the first tab 111 in directions a and b is less, reducing the heat dissipation efficiency of the electrode sheet.

[0092] Therefore, in the present application, a blank area is increased in the first tab 111 in the directions c and 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 tab 111 can be in contact with the second active material layer 122, and then the heat generated by the second active material layer 122 can be transferred to the first tab 111 through heat conduction for rapid heat dissipation; 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 both ends of the second gap are respectively communicated with the first gap and the active layer with a large area at the bottom, and both ends of the first gap are respectively communicated with the second gap and the active layer with a large area on the right, so that an annular conduction channel is formed around the thinning groove 1221 and the first tab 111, so that the heat generated by the second active material layer 122 in the directions a and b of the first tab 111 can be further transferred to the first gap and the second gap, so that the heat generated by the electrode sheet can be conducted around the first tab 111, improving the heat conduction and heat dissipation efficiency of the first tab 111.

[0093] Through the above settings, that is, on the one hand, through the setting of the first gap, the second active material layer 122 at the first gap can be in close contact with the first tab 111, thereby improving the heat conduction efficiency of the heat on the electrode sheet. On the other hand, due to the setting of the second gap, an conduction channel is formed around the first tab 111, so that the heat of the electrode sheet surrounding the first tab 111 can be evenly and quickly conducted to the periphery of the first tab 111, thereby improving the heat dissipation efficiency of the core 100, ensuring that the core 100 can effectively dissipate heat during high-rate charge and discharge, and improving the safety and performance of the core 100; in addition, through the setting of the thinning groove 1221, on the one hand, since some active materials are reserved in the thinning groove 1221, and the welding mark of the first tab 111 can be in contact with the active materials in the thinning groove 1221, and the active materials in the thinning groove 1221 and the active materials in the surrounding area are continuously arranged, so that the heat of the electrode sheet can also be quickly exported through the active materials in contact with the welding mark of the first tab 111, further improving the heat dissipation efficiency of the core. On the other hand, the thickness of the first tab 111 and the like are hidden in the thinning groove 1221 to reduce the overall thickness of the core 100, improving the space utilization rate of the core 100, thereby enhancing the energy density.

[0094] It should be noted that the second current collector 121 is a high-strength copper foil current collector with a tensile strength of 300 MPa - 700 MPa, an elongation rate of 2.0% - 11%, and a surface density of 30 g / m2 - 65 g / m2, which can effectively improve the problem of the fracture of the second current collector 121 caused by the stress difference generated during welding melting; at the same time, it can also effectively reduce the burrs at the welding points, reduce the piercing risk, and at the same time increase the tensile value at the welding point, reduce the contact impedance, and reduce the internal resistance of the core.

[0095] Preferably, the first electrode tab 110 in the embodiments of the present application may be a positive electrode tab, wherein the first current collector is a positive current collector, the first active material layer 112 is a positive active material layer, and the first tab 111 is a positive electrode tab.

[0096] The second electrode tab 120 may be a negative electrode tab, wherein the second current collector 121 is a negative current collector, the second active material layer 122 is a negative active material layer, and the second tab is a negative electrode tab.

[0097] Correspondingly, in some other embodiments, the first electrode tab 110 may also be a negative electrode tab, and the second electrode tab 120 may also be a positive electrode tab. The principle is the same as or similar to that described above, and will not be elaborated here.

[0098] As Figures 1 to 4 shown, in some alternative 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, where A and B satisfy: 2 mm < B; and / or, 0.8 ≤ A / B ≤ 1.2.

[0099] It should be noted that the second gap may be 2.5 mm, 3 mm, 3.5 mm, 4 mm, etc., and there is no specific limitation.

[0100] 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. Such a setting mainly considers the overlapping area between the extended area of the first gap A and the extended area of the second gap B, to avoid too much heat here and ensure that the heat cannot be quickly dissipated.

[0101] In addition, since the connection between the first gap A and the second gap B is close to the corner of the electrode tab, by setting 0.8 ≤ A / B ≤ 1.2, that is, the widths of the first gap A and the second gap B are similar, it effectively avoids the poor heat conduction at the connection between the first gap A and the second gap B, and further effectively avoids the heat accumulation at the connection between the first gap A and the second gap B, which may cause a large amount of heat generation, and thus effectively avoids the phenomenon of melting and rupture of the aluminum-plastic film at the top corner of the battery cell near the tab, that is, corner cracking.

[0102] In some alternative embodiments, a first notch is provided in the first current collector located in the tab groove 130. Specifically, a first notch is provided at the first edge of the first current collector. The first notch communicates with the tab groove 130 and extends to the edge of the first current collector. The distance from the bottom wall of the first notch to the second edge in the projection in the second direction is m, where m satisfies: m > A.

[0103] It should be noted that the first notch is the arc-shaped punching area of the first tab 111. The bottom wall of the first notch is the deepest part where the notch penetrates into the first current collector. And m is the dimension of the bottom wall of the first notch from the edge of the second active material layer 122 in the projection on the second active material layer 122. Such a setting aims to avoid the superposition between the first tab 111 and the aluminum foil, thereby reducing the thickness here, further reducing the ineffective thickness of the core, improving the energy density of the lithium-ion battery, increasing the space utilization rate, and enhancing the battery life of electronic products.

[0104] As Figures 1 to 4 shown, in some alternative embodiments, along the second direction, the distance between the first protective tape 140 and the edge of the thinning groove 1221 is C, satisfying: 0 mm < C < 5 mm; and / or,

[0105] 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, satisfying: 0 mm < D < 5 mm.

[0106] It should be noted that such a setting makes the thickness of the thinning groove 1221 and the normal second active material layer 122 present a stepped funnel shape in the area covered by the first protective tape 140, which is beneficial to storing the electrolyte here. The electrolyte absorbs the heat generated by the first tab 111 and reduces the temperature rise. In particular, the electrolyte can effectively fill the gap between the thinning groove 1221 and the first protective tape 140, so that the heat on the first protective tape 140 in contact with the first tab 111 can be continuously conducted to the first gap and the second gap through the electrolyte, improving the heat conduction efficiency.

[0107] 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.

[0108] Figure 5 It is a schematic structural diagram of the second perspective of the core provided by the embodiment of the present application. Figure 6 It is a cross-sectional view of the second pole piece in the core provided by the embodiment of the present application.

[0109] As Figures 1 to 6 shown, in some alternative embodiments, a plurality of first grooves 1222 are further formed on the second active material layer 122, and the first grooves extend along the second direction;

[0110] The plurality of first grooves 1222 are arranged at intervals on at least one of the arc segment and the straight segment of the second active material layer 122.

[0111] It should be noted that the provision of the first groove 1222 facilitates the dissipation of heat at the first tab 111 to the outside of the core, that is, the heat at the first tab 111 can be conducted out in the direction facing the second active material layer 122 and in the direction of the arc section 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.

[0112] In some embodiments, the first groove 1222 can be a complete linear first groove 1222 formed by laser, or a linear first groove 1222 formed by splicing multiple laser lines. This mainly depends on the size of the laser device. The width of each laser line is related to the device size. If the pole piece is too wide, splicing of the laser lines is required. In addition, referring to Figure 3 , at least part of the linear first groove 1222 communicates with the edge of the pole piece and the thinning groove 1221, which is more conducive to the rapid and sufficient immersion of the electrolyte into the gap between the first protective adhesive paper 140 and the thinning groove 1221, improving the heat conduction and dissipation efficiency at the first tab 111.

[0113] In some embodiments, the length direction of the first groove 1222 can be the same as the width direction of the thinning groove 1221, or the same as the length direction of the thinning groove 1221, or can be in any direction as long as heat dissipation can be achieved.

[0114] In some 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 cylinder. In specific implementation, the first groove 1222 can be formed by at least one of laser burning, tool cutting, stamping, etc. The cross-sectional shape of the formed first heat dissipation channel can be a square, a trapezoid, a triangle, etc., and this embodiment does not make any limitations in this regard.

[0115] In some alternative embodiments, there is a pore between the first pole piece 110 and the second pole piece 120 in the arc section of the second active material layer 122, and the pore has a second heat dissipation channel.

[0116] It should be noted that for the core 100, the adhesion between the interfaces of its arc regions is poorer than that of the flat regions. Since the core is pressed down along the thickness direction of the core, the flat regions are tightly pressed at this time, and thus there is a pore between the first pole piece 110 and the second pole piece 120 in the arc section. This pore has a second heat dissipation channel, which further dissipates the heat at the first tab 111 to the outside of the core.

[0117] In addition, the presence of pores in the arc region facilitates the release of stress in the arc region and at the same time provides a second heat dissipation channel. There is a second gap between the thinning groove 1221 and the arc region, that is, the second heat dissipation channel is not blocked, and the heat conduction and gas conduction effects in this region are not affected.

[0118] Such as Figures 1 to 6As shown, in some alternative embodiments, the relationship between the depth H of the first groove 1222 and the fracture elongation rate e of the second current collector 121 satisfies: 1 mm ≤ H / e ≤ 15 mm.

[0119] It should be noted that the larger the fracture elongation rate 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.

[0120] Figure 7 Schematic diagram of the structure of the first tab in the core provided by the embodiment of the present application, as Figures 1 to 7 shown, in some alternative embodiments, the relationship between the depth H of the first groove 1222, the width L of the first groove 1222, the tab width E of one of the first tab 111 and the second tab, and the tab thickness F of one of the first tab 111 and the second tab satisfies: 2×10 -4 mm 4 ≤ H×L×E×F ≤ 2×10 -3 mm 4 .

[0121] It should be noted that the narrower or thinner the tab of one of the first tab 111 and the second tab, the more obvious the heat generation, and the larger the channel area required for heat conduction and gas conduction.

[0122] Specifically: the resistance value R of the tab metal strip = ρL / S, where L represents the length and S represents the area; when the charge and discharge current remains unchanged, the smaller S is, the larger the resistance value is, and the more serious the heat generation is due to the larger resistance.

[0123] As Figures 1 to 7 shown, in some alternative embodiments, a ceramic layer is coated on at least one side of the end of the first electrode sheet 110 away from the winding center, and part of the ceramic layer covers the first active material layer 112;

[0124] The coating thickness of the ceramic layer is greater than or equal to 5 μm and less than or equal to 20 μm; and / or,

[0125] The ratio of the ceramic particle 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.

[0126] It should be noted that the ceramic layer is conducive to heat absorption and reduces the overall temperature rise of the entire battery.

[0127] In some embodiments, a ceramic layer is coated on the aluminum foil at the end of the first electrode sheet 110, and the ceramic can be coated on both sides or one side.

[0128] 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 core.

[0129] 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 therebetween.

[0130] In some embodiments, the ratio of the ceramic particle size of the ceramic layer to the width of the first groove 1222 can be 0.05, 0.1, 0.15, 0.2, 0.25 or any value therebetween.

[0131] In some alternative embodiments, a second groove is provided at the end of the first active material layer 112 away from the winding center, and part of the ceramic layer covers the second groove;

[0132] The depth of the second groove is greater than or equal to 0um and less than or equal to 20um.

[0133] 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, preventing the overlapping area from thickening compared to other positions and affecting the flatness of the battery cell. The ceramic is conducive to heat absorption and reduces the overall temperature rise of the entire battery.

[0134] In some embodiments, the thickness of the second groove can 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 therebetween.

[0135] In some alternative embodiments, at least part of the projection of the ceramic layer in the thickness direction of the core 100 is located within the thinning groove 1221.

[0136] It should be noted that with such a setting, in the thickness direction of the core 100, the heat generated by the first tab 111 is vertically conducted to the ceramic layer, which shortens the heat conduction path and improves the heat conduction and heat dissipation efficiency of the core 100.

[0137] In some alternative embodiments, the second active material layer 122 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 the side away from the second current collector 121.

[0138] It should be noted that this means that the second active material layer 122 is a double-layer structure, and the materials used for the first material layer and the second material layer can be the same or different.

[0139] In some alternative embodiments, at least one of the first material layer and the second material layer is made of a silicon-doped graphite material, wherein 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;

[0140] 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%;

[0141] The thickness of the second active material layer 122 is greater than the depth of the first groove 1222.

[0142] Wherein, 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.

[0143] It should be noted that the second active material layer 122 is designed with a double-layer graphite structure, where the lower layer is large-particle graphite and the upper layer is small-particle graphite. The thickness of the upper small-particle graphite layer accounts for 20%-60% of the total thickness of the second active material layer 122. A linear first groove 1222 is formed on the second electrode sheet 120 by laser. The depth h of the first groove 1222 is less than the thickness of the first material layer. The upper small-particle graphite layer has a larger porosity, which is more beneficial for gas and heat conduction.

[0144] 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. For different silicon materials, there is no requirement for the particle size in mass production. Here, only the particle size of the graphite particles is required, and 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.

[0145] Figure 8 This is a schematic structural diagram of the particles of the silicon-carbon material in the core provided by the embodiments of the present application. As Figures 1 to 8 shown, in some alternative embodiments, 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. Wherein, the doping amount of the silicon-carbon material in the mixed material is greater than or equal to 2% and less than or equal to 15%; and / or,

[0146] The relationship between the width L of the first groove 1222 and the particle size M of the silicon-carbon material satisfies: L≥2M, where 50um≤L≤100um.

[0147] Wherein, the second active material layer 122 has 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.

[0148] It should be noted that the second active material layer 122 is a graphite-doped silicon-carbon material. During the charge and discharge process, the silicon-carbon particles will undergo significant expansion changes, and more side reactions will occur between the silicon-carbon and the electrolyte to generate heat. A linear first groove 1222 is formed on the second electrode sheet 120 by laser to have enough space to accommodate the expansion of the silicon-carbon material during the cyclic charge and discharge process and ensure the smoothness of the first heat dissipation channel.

[0149] In some alternative embodiments, a lithium supplement layer is provided on the side of the second electrode sheet 120, and the thickness of the lithium supplement layer is less than or equal to the depth of the first groove 1222.

[0150] It should be noted that there is a lithium supplement layer on the surface of the second electrode sheet 120, and the depth h of the first groove 1222 > the thickness of the lithium supplement layer, so that there is still a linear first groove 1222 channel on the surface of the electrode sheet after lithium supplementation, which is convenient for gas conduction and heat conduction.

[0151] In addition, it should be noted that the lithium supplementation method is to heat and melt lithium metal, and cast or coat it on the electrode material coating to form a lithium supplement layer, or oscillate the powdered lithium metal to the electrode sheet for rolling to form a lithium supplement layer, or directly extrude solid lithium metal on the surface of the electrode sheet to form one or a mixture of lithium supplement layers. However, more heat is generated during the lithium supplementation process of the above lithium supplementation methods and is difficult to discharge, resulting in the inability to guarantee the safety performance of the lithium battery. Therefore, through the first groove 1222, there is still a linear first groove 1222 channel on the surface of the electrode sheet after lithium supplementation, which is convenient for gas conduction and heat conduction.

[0152] As Figures 1 to 8 shown, in some alternative embodiments, a second protective adhesive tape 150 is provided at the tail end of the first electrode sheet 110, and the ratio of the width of the second protective adhesive tape 150 to the width of the core 100 is greater than or equal to 1 / 2 and less than or equal to 1; and / or,

[0153] The width of the second protective adhesive tape 150 is greater than or equal to 10 mm and less than or equal to 40 mm.

[0154] It should be noted that to ensure that the second protective adhesive tape 150 extends beyond the end empty foil (or the ceramic layer is coated) after passing through the arc, the bonding relationship between the second protective adhesive tape 150 and the end heat-melt adhesive is that in the width direction of the core, the second protective adhesive tape 150 extends beyond the heat-melt adhesive, and the heat-melt adhesive is attached above the second protective adhesive tape 150, which can prevent the heat-melt adhesive from tearing the first electrode sheet 110.

[0155] In some embodiments, the width of the second protective adhesive tape 150 can be 15 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm, or any one value.

[0156] As Figures 1 to 8As shown, in some alternative embodiments, a third protective adhesive tape 160 is provided on the tab groove 130 on one side of the first electrode tab 110, and the third protective adhesive tape 160 is used to cover the thinning groove 1221.

[0157] It should be noted that the third protective adhesive tape 160 can prevent the burrs at the welding point of the first tab 111 from piercing the diaphragm and causing the risk of short - circuit fire.

[0158] It should be noted that the following is a table for comparing multiple groups of example data.

[0159] Table 1 is a data table of temperature rise for multiple groups of examples and comparative examples.

[0160] Cell thickness mm Temperature rise at tab end ℃ Temperature rise of cell body ℃ Comparative example 5.689 16.53 15.98 Example 1 5.665 16.14 15.55 Example 2 5.665 18.8 17.99 Example 3 5.665 17.74 16.32 Example 4 5.665 20.77 19.56 Example 5 5.665 18.84 18.22 Example 6 5.665 17.75 16.32 Example 7 5.645 16.15 14.37 Example 8 5.645 16.16 14.39

[0161] Among them, the difference between the comparative example and Example 1 is that there is no thinning groove 1221 on the second electrode tab 120 in the comparative example.

[0162] The difference between Example 2 and Example 1 is that the distance A from the thinning groove 1221 to the edge of the electrode tab is 0.

[0163] The difference between Example 3 and Example 1 is that there is no linear first groove 1222 formed by laser scribing on the surface of the second electrode tab 120.

[0164] The difference between Example 4 and Example 1 is that the tab specification is 4mm * 0.08mm.

[0165] The difference between Example 5 and Example 1 is that the depth of the linear first groove 1222 formed by laser scribing on the surface of the second electrode tab 120 is 30um.

[0166] The difference between Example 6 and Example 1 is that the width of the linear first groove 1222 formed by laser scribing on the surface of the second electrode tab 120 is 20um.

[0167] The difference between Example 7 and Example 1 is that there is no ceramic layer at the tail of the first electrode tab 110.

[0168] The difference between Example 8 and Example 1 is that the width of the second protective adhesive tape 150 on the short side of the first electrode tab 110 is 10mm.

[0169] 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.

[0170] 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.

[0171] In addition, an embodiment of the present application further provides a battery, including a winding core 100 .

[0172] 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.

[0173] 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:

[0174] 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;

[0175] 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;

[0176] Step 3: The positive and negative electrode sheets are cut, sliced ​​and wound with the separator to obtain a winding core;

[0177] Step 4: After packaging, baking, liquid injection, formation, secondary sealing, sorting and OCV, the lithium-ion battery is obtained.

[0178] The electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0179] 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.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A winding core, 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 tab groove is provided on the first active material layer, the bottom wall of the pole tab groove is the first current collector, the surrounding side is the first active material layer, and a first pole tab electrically connected to the first current collector is provided in the pole tab 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 pole 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 tape is provided in the thinning groove, along the width direction of the first pole tab, the two sides of the first pole tab width do not exceed the two sides of the first protective tape, and the second current collector has a second edge in the second direction; 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 segment 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 / or, 0.8 ≤ A / B ≤ 1.

2.

3. The winding core according to claim 2, characterized in that: A first notch is provided at the first edge of the first current collector, the first notch is connected to the pole ear groove, the first notch extends to the edge of the first current collector, and the distance from the bottom wall of the first notch to 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 10, characterized in that: 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 the graphite particles in the first material layer is smaller than the particle size of the graphite particles in the second material layer; A ratio between a thickness of the first material layer and a thickness of the second active material layer is greater than or equal to 20% and less than or equal to 60%.

12. The winding core according to claim 10, characterized in that: 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 a ratio of a doping amount of the silicon-carbon material to that of the mixed material is greater than or equal to 2% and less than or equal to 15%; and / or, The relationship between the width L of the first groove and the particle size M of the silicon-carbon material satisfies: L≥2M, wherein 50um≤L≤100um.

13. 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.

14. 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 mm and less than or equal to 40 mm.

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

16. A battery, characterized in that: Comprising the winding core as described in any one of claims 1-15.

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