Pole piece, battery cell and secondary battery
By designing grooves of varying depths and widths on the electrodes, the flow and wettability of the electrolyte are improved, solving the problem of the electrolyte's difficulty in penetrating the active material near the current collector, thus enhancing the battery's performance and lifespan.
Patent Information
- Application Number
- CN202422694333.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-05
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2034-11-05
AI Technical Summary
The electrolyte has difficulty penetrating into the active material near the current collector, resulting in insufficient electrochemical reaction and affecting battery performance and lifespan.
An electrode is designed, comprising a current collector and an active layer. The active layer has grooves, which include a main groove segment and an edge groove segment. The depth and width of the edge groove segment are greater than those of the main groove segment. The shape and distribution of the grooves are optimized to improve the flow and wettability of the electrolyte.
It improves the flow rate and uniformity of the electrolyte, enhances the lithium-ion transport path, reduces edge powder shedding, improves the electrolyte injection efficiency and cell rate performance, and extends battery life.
Smart Images
Figure CN223527264U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of battery, concretely relates to pole piece, electric core and secondary battery. BACKGROUND
[0002] In the field of battery manufacturing, lithium ion battery is a kind of rechargeable battery type, is widely used in portable electronic products (such as mobile phone, notebook computer) and electric vehicle and other fields, it is famous with its high energy density, long service life and low self-discharge rate and other characteristics.
[0003] In lithium ion battery, "pole piece" is a kind of key component inside battery, pole piece is used to store electric energy and transmit ions in the process of battery charging and discharging.Pole piece mainly includes current collector and active material layer, and the active material layer forms a dense layer on the surface of the current collector by rolling, and electrolyte is difficult to penetrate into the active material near the current collector, resulting in that full electrochemical reaction cannot be carried out. UTILITY MODEL CONTENTS
[0004] Therefore, the utility model provides a kind of pole piece, electric core and secondary battery to solve the problem that electrolyte is difficult to penetrate into the active material near the current collector, resulting in that full electrochemical reaction cannot be carried out.
[0005] In the first aspect, the utility model provides a kind of pole piece, including: negative pole piece, negative pole piece includes: current collector;Active layer is set on the surface of current collector, and the surface of active layer away from current collector has several line grooves, each line groove includes main groove section and edge groove section, along the first direction, at least one end of edge groove section is connected with main groove section, along the second direction, the depth of at least part edge groove section is greater than the depth of main groove section;And / or, along the third direction, the width of at least part edge groove section is greater than the width of main groove section.
[0006] Through the above-mentioned setting, it is favorable to improve the flow of electrolyte, improve the rate of electrolyte flowing from edge groove section to main groove section, improve the uniformity of electrolyte impregnation to active material and lithium ion transmission path and rate, improve liquid injection efficiency, improve electric core rate performance, in addition, along the second direction, the depth of edge groove section is greater than the depth of main groove section, and / or, along the third direction, the width of at least part edge groove section is greater than the width of main groove section, also can improve the self-discharge phenomenon caused by the edge of pole piece drop powder, it is favorable to improve the yield of battery.
[0007] In an alternative embodiment, the width of the edge groove section gradually increases from the end connected to the main groove section to the end away from the main groove section. The width of the edge groove section gradually decreases towards the main groove section, which can increase the penetration area of the electrolyte, thereby improving the contact efficiency between the electrolyte and the active material. As the width of the edge groove section gradually increases, it can better adapt to the diffusion needs of the electrolyte, especially during high-rate charging and discharging.
[0008] In an optional embodiment, the ratio of the depth of the edge groove segment to the depth of the main groove segment is 1.001-4; and / or, the ratio of the width of the edge groove segment to the width of the main groove segment is 1.001-2; and / or, the depth of the edge groove segment is greater than the depth of the main groove segment by 1-50 um; and / or, the width of the edge groove segment is greater than the width of the main groove segment by 1-150 um. Setting the ratio of the width of the edge groove segment to the width of the main groove segment and the ratio of the depth of the edge groove segment to the depth of the main groove segment within a reasonable range is conducive to the flow of electrolyte, improves the wettability of the edge electrolyte, ensures the total capacity of the battery, prolongs the service life of the battery, and can also alleviate the problem of thickening of the edge of the battery cell.
[0009] In an optional embodiment, the depth of the edge groove segment is in the range of 6-50 um; and / or, the depth of the main groove segment is in the range of 5-30 um; and / or, the width of the edge groove segment is in the range of 55-250 um; and / or, the width of the main groove segment is in the range of 50-200 um.
[0010] In an optional embodiment, the ratio of the projected area S1 of a single wire groove on the current collector to the projected area S2 of the edge groove segment of a single wire groove on the current collector is 500-15000. Setting the ratio of the projected area of a single wire groove on the current collector to the projected area of a single edge groove segment within a reasonable range not only improves the wettability of the electrolyte during liquid injection, but also improves the liquid retention of the battery cell, thereby maintaining the total capacity of the battery.
[0011] In an optional embodiment, in any two adjacent wire grooves, the distance L1 between the edge groove segments is 0.001-0.2 mm less than the distance L2 between the main groove segments; and / or, L1 is 1-2 mm; and / or, L2 is 0.8-2 mm. The edge wire groove has a high degree of density, which can improve the liquid retention of the edge region, supplement the electrolyte in the internal electrode sheet when the electrolyte is scarce, prevent lithium precipitation at the edge, and improve the uniformity of the electrolyte wettability of the battery cell.
[0012] In an optional embodiment, the surface of the pole piece is taken as a reference surface, a plane perpendicular to the extension direction of the linear slot is taken as a second reference surface, the main slot section has a first cross section perpendicular to the first direction, the intersection of the first profile line of the first cross section and the reference surface is a first intersection t1 and a second intersection t2, the lowest point of the first profile line is a first lowest point z1, the included angle between the line connecting the first intersection t1 and the first lowest point z1 and the line connecting the second intersection t2 and the first lowest point z1 is a first included angle θ1, the edge slot section has a second cross section perpendicular to the first direction, the intersection of the second profile line of the second cross section and the reference surface is a third intersection t3 and a fourth intersection t4, the lowest point of the second profile line is a second lowest point z2, the included angle between the line connecting the third intersection t3 and the second lowest point z2 and the line connecting the fourth intersection t4 and the second lowest point z2 is a second included angle θ2, and the ratio of the first included angle θ1 and the second included angle θ2 is 0.3-0.8. By setting the ratio of the first included angle and the second included angle within a reasonable range, not only the flow speed of the electrolyte in the linear slot can be improved, but also the total capacity of the battery can be ensured, and the service life of the battery can be prolonged.
[0013] In an optional embodiment, along the second direction, the pole piece has oppositely arranged first and second surfaces, the linear slots on the first surface are arranged staggered with the linear slots on the second surface, and the staggered distance between the center line of the linear slot on the first surface and the projection of the center line of the adjacent linear slot on the second surface on the first surface is 0.001 mm-1.999 mm; or, the linear slots on the first surface are arranged coincident with the linear slots on the second surface. By arranging the linear slots on the front and back surfaces of the pole piece staggered, the damage to the current collector can be reduced, and the conductivity reduction, capacity reduction and structural instability caused by the damage to the current collector can be avoided.
[0014] In an optional embodiment, the region of the exposed part of the current collector on the first surface of the pole piece forms a tab welding region for welding the tab, and along the third direction, at least one end of the current collector has a blank region, and the ratio of the roughness of the tab welding region to the roughness of the blank region is 1.1-3. After the linear slot is opened on the active layer, part of the active layer is removed to expose the current collector, thereby forming the tab welding region, and at this time, the tab welding region has a striped structure, which can increase the surface roughness of the tab welding region and improve the tab welding strength.
[0015] In an optional embodiment, the region of the exposed portion of the current collector on the first surface of the tab forms a tab welding region of a welding tab, and after the welding tab is welded, a plurality of welding protrusions are formed on the second surface of the tab, and the welding protrusions closest to the edge groove segment form edge protrusions, and the distance between the side of the edge protrusion closest to the edge groove segment and the end of the edge groove segment away from the main groove segment is 1mm-5mm. By setting the distance between the side of the edge protrusion closest to the edge groove segment and the end of the edge groove segment away from the main groove segment within a reasonable range, not only can the heat diffusion during welding be improved, but also the area of the tab welding region and the welding tab can be controlled.
[0016] In an optional embodiment, the tab is a negative tab.
[0017] In a second aspect, the utility model also provides an electric core, the electric core includes negative tab, the negative tab is the tab, the electric core also includes positive tab and diaphragm, the negative tab is stacked with diaphragm and positive tab, along the first direction, the negative tab has coincident area with positive tab and non-coincident area beyond the edge of positive tab, and the edge groove segment is located in the non-coincident area. In the battery charging and discharging process, the edge region is easy to produce uneven lithium deposition or extraction, resulting in local overheating or dendrite growth. By the width of the positive tab being less than the width of the negative tab, the negative effects of these edge effects can be reduced, thereby prolonging the service life of the battery.
[0018] In an optional embodiment, the ratio of the projected area S2 of the single edge groove segment on the current collector to the area of the non-coincident area is less than or equal to 0.1; and / or, along the first direction, the width of the non-coincident area is 0.01mm-1.5mm. By the above settings, the lithium ion of the negative active material at the edge of the non-coincident area 104 can be strengthened to be inserted and extracted, and the possibility of lithium precipitation can be reduced.
[0019] In a third aspect, the utility model also provides a secondary battery, which comprises the electric core described above. BRIEF DESCRIPTION OF DRAWINGS
[0020] In order to more clearly illustrate the specific embodiments of the utility model or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.
[0021] Figure 1 It is a top view of the negative tab of the utility model embodiment;
[0022] Figure 2 It is a top view of the negative tab of the utility model embodiment; Figure 1 It is a top view of the negative tab of the utility model embodiment;
[0023] Figure 3 Fig. 1 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 2 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0024] Figure 4 Fig. 3 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 4 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0025] Figure 5 Fig. 5 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 6 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0026] Figure 6 Fig. 7 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 8 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0027] Figure 7 Fig. 9 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 10 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0028] Figure 8 Fig. 11 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 12 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0029] Figure 9 Fig. 13 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 8 Fig. 14 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0030] Figure 10 Fig. 15 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 8 Fig. 16 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0031] Figure 11 Fig. 17 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 8 Fig. 18 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0032] Figure 12 Fig. 19 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 20 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application;
[0033] Figure 13 Fig. 21 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 1 Fig. 22 is a structural schematic diagram of a negative electrode sheet according to an embodiment of the present application.
[0034] BRIEF DESCRIPTION OF THE DRAWINGS
[0035] 1. A negative electrode sheet; 101. a current collector; 1011. a tab welding area; 1012. a blank area; 102. an active layer; 1021. a slot; 1022. a main slot section; 1023. an edge slot section; 104. a non-coincidence area; 105. a welding protrusion;
[0036] 2. A positive electrode sheet;
[0037] 4. tab. DETAILED DESCRIPTION
[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.
[0039] The embodiments of the present application will be described below with reference to the drawings. Figures 1 to 13
[0040] According to the embodiments of the present application, on the one hand, a tab is provided, which comprises: a negative tab 1, the negative tab 1 comprising: a current collector 101 and an active layer 102, the active layer 102 being arranged on the surface of the current collector 101, the active layer 102 having a plurality of linear grooves 1021, each linear groove 1021 comprising a main groove section 1022 and an edge groove section 1023, along a first direction X, the edge groove section 1023 being connected with at least one end of the main groove section 1022, along a second direction Z, the depth d1 of at least part of the edge groove section 1023 being greater than the depth d2 of the main groove section 1022; along a third direction Y, the width w1 of at least part of the edge groove section 1023 being greater than the width w2 of the main groove section 1022.
[0041] The tab of the present embodiment is provided with the linear grooves 1021 in the active layer 102, when the tab with the linear grooves 1021 is used to manufacture a battery, the electrolyte can enter the active material close to the current collector 101, which is conducive to improving the flow of the electrolyte, improving the rate of the electrolyte flowing from the edge groove section to the main groove section, improving the uniformity of the electrolyte wetting the active material and the transmission path and rate of lithium ions, improving the liquid injection efficiency, and improving the rate capability of the battery cell. In addition, along the second direction, the depth of the edge groove section 1023 is greater than the depth of the main groove section 1022, and along the third direction, the width of at least part of the edge groove section 1023 is greater than the width of the main groove section 1022, which can also improve the self-discharge phenomenon caused by the edge powder falling of the tab, and is conducive to improving the yield of the battery.
[0042] It should be noted that if the edge part is not properly processed, such as polishing or cleaning, during the cutting or other processing steps, tiny cracks or damages may be left, thereby affecting the adhesion strength of the active layer 102, and the physical and chemical properties of the active material itself may also affect its stability at different positions. If the adhesion between the active material and the current collector 101 is insufficient, especially at the edge, powder falling may occur, and due to the edge effect, the active layer at the edge of the pole piece may be relatively loose, which may cause the edge active layer to fall after the wire slot 1021, thereby making the edge region of the active layer 102 more prone to falling than the middle region. By increasing the width and depth of the edge slot segment 1023 relative to the main slot segment 1022, the amount of active material at the edge of the pole piece is reduced, thereby reducing the edge region falling, and effectively solving the self-discharge and other phenomena caused by the edge region falling.
[0043] The pole piece is formed by cutting, and the edge of the pole piece has burrs. When the wire slot 1021 is opened in the active layer 102, the burrs at the edge can be removed together, which can avoid the internal short circuit caused by the burrs possibly piercing the diaphragm to cause the positive and negative pole pieces to directly contact, thereby effectively improving the safety performance of the battery.
[0044] It should be noted that the first direction refers to the width direction of the pole piece, the second direction refers to the thickness direction of the pole piece, and the third direction refers to the length direction of the pole piece.
[0045] In one embodiment, the width of the edge slot segment 1023 gradually increases from one end adjacent to the main slot segment 1022 to the other end away from the main slot segment 1022. The width of the edge slot segment 1023 gradually decreases towards the main slot segment 1022, which can increase the penetration area of the electrolyte, thereby improving the contact efficiency between the electrolyte and the active material. As the width of the edge slot segment 1023 gradually increases, it can better adapt to the diffusion needs of the electrolyte, especially during high-rate charging and discharging.
[0046] In one embodiment, as shown in Figure 2 and Figure 3 , the depth ratio of the edge slot segment 1023 to the main slot segment 1022 is 1.001-4, and the width ratio of the edge slot segment 1023 to the main slot segment 1022 is 1.001-2. The width of the edge slot segment 1023 is 1um-150um larger than the width of the main slot segment 1022, and the depth of the edge slot segment 1023 is 1um-50um larger than the depth of the main slot segment 1022.
[0047] wherein the width of the main slot segment 1022 is the vertical dimension of the main slot segment 1022 in Figure 3 , and the width of the edge slot segment 1023 is the vertical dimension of the edge slot segment 1023 in Figure 3The vertical dimension of the edge groove section 1023, the ratio of the width of the edge groove section 1023 to the width of the main groove section 1022, and the ratio of the depth of the edge groove section 1023 to the depth of the main groove section 1022 cannot be too large or too small. If the ratio of the width of the edge groove section 1023 to the width of the main groove section 1022 and the ratio of the depth of the edge groove section 1023 to the depth of the main groove section 1022 are too large, it means that the width of the edge groove section 1023 is too wide and the depth is too deep, which will reduce the area of the active layer 102, thereby reducing the total capacity of the battery, reducing the efficiency of the battery, and shortening the cycle life of the battery. If the ratio of the width of the edge groove section 1023 to the width of the main groove section 1022 and the ratio of the depth of the edge groove section 1023 to the depth of the main groove section 1022 are too small, it means that the width of the edge groove section 1023 is almost the same as the width of the main groove section 1022, which is not conducive to the flow of electrolyte and affects the efficiency of liquid injection.
[0048] Therefore, by setting the ratio of the width of the edge groove section 1023 to the width of the main groove section 1022 and the ratio of the depth of the edge groove section 1023 to the depth of the main groove section 1022 within a reasonable range, it is beneficial to the flow of electrolyte, improves the wettability of the edge electrolyte, ensures the total capacity of the battery, prolongs the service life of the battery, and can also alleviate the problem of thickening of the cell edge.
[0049] Preferably, the depth of the edge groove section 1023 is in the range of 6um-50um, the depth of the main groove section 1022 is in the range of 5um-30um, the width of the edge groove section 1023 is in the range of 55um-250um, and the width of the main groove section 1022 is in the range of 50um-200um.
[0050] In one embodiment, the ratio of the projected area S1 of a single wire groove 1021 on the current collector 101 to the projected area S2 of the edge groove section 1023 of the single wire groove 1021 is 500-15000.
[0051] The ratio of the projected area of the single wire groove 1021 on the current collector 101 to the projected area of the edge groove section 1023 of the single wire groove 1021 cannot be too large or too small. If the ratio of the projected area of the single wire groove 1021 on the current collector 101 to the projected area of the edge groove section 1023 of the single wire groove 1021 is too large, it means that the projected area of the edge groove section 1023 is smaller, the width and length of the edge groove section 1023 are smaller, and the wettability of the battery liquid is slower. If the ratio of the projected area of the single wire groove 1021 on the current collector 101 to the projected area of the edge groove section 1023 of the single wire groove 1021 is too small, it means that the projected area of the edge groove section 1023 is larger, the width and length of the edge groove section 1023 are larger, and the electrolyte is more. The area of the active layer 102 will be smaller, thereby reducing the total capacity of the battery, reducing the efficiency of the battery, and shortening the cycle life of the battery.
[0052] Therefore, the ratio of the projected area of the single linear groove 1021 on the current collector 101 to the projected area of the edge groove section 1023 of the single linear groove 1021 is set within a reasonable range, which not only improves the infiltration speed of the electrolyte during the liquid injection process, but also improves the liquid retention amount of the battery cell, thereby maintaining the total capacity of the battery.
[0053] It should be noted that S1 is the area of one black region, and S2 is the area of the edge groove section 1023 of the left or right cone. Figure 2
[0054] In one embodiment, as shown in FIG. 1, in any two adjacent linear grooves 1021, the spacing L1 between the edge groove sections 1023 is 0.001 mm-0.2 mm smaller than the spacing L2 between the main groove sections 1022, at which time the edge linear groove 1021 has a high degree of density, which can improve the liquid retention amount of the edge region, the electrolyte in the inner part of the pole piece can be supplemented from the edge when the electrolyte is insufficient, which prevents lithium precipitation at the edge, and at the same time improves the uniformity of the electrolyte infiltration of the battery cell. Figure 2
[0055] Preferably, L1 is 1 mm-2 mm, and L2 is 0.8 mm-2 mm.
[0056] In one embodiment, as shown in FIG. 1, in any two adjacent linear grooves 1021, the spacing L1 between the edge groove sections 1023 is 0.001 mm-0.2 mm smaller than the spacing L2 between the main groove sections 1022, at which time the edge linear groove 1021 has a high degree of density, which can improve the liquid retention amount of the edge region, the electrolyte in the inner part of the pole piece can be supplemented from the edge when the electrolyte is insufficient, which prevents lithium precipitation at the edge, and at the same time improves the uniformity of the electrolyte infiltration of the battery cell. Figure 6 Figure 7 As shown in FIG. 1, with the surface of the pole piece as the reference surface, the main groove section 1022 has a first cross section perpendicular to the first direction, the intersection of the first profile line of the first cross section and the reference surface is the first intersection t1 and the second intersection t2, the lowest point of the first profile line is the first lowest point z1, the included angle between the line connecting the first intersection t1 and the first lowest point z1 and the line connecting the second intersection t2 and the first lowest point z1 is the first included angle θ1, the edge groove section 1023 has a second cross section perpendicular to the first direction, the intersection of the second profile line of the second cross section and the reference surface is the third intersection t3 and the fourth intersection t4, the lowest point of the second profile line is the second lowest point z2, the included angle between the line connecting the third intersection t3 and the second lowest point z2 and the line connecting the fourth intersection t4 and the second lowest point z2 is the second included angle θ2, and the ratio of the first included angle θ1 to the second included angle θ2 is 0.3-0.8.
[0057] The ratio of the first included angle θ1 to the second included angle θ2 should be neither too small nor too large. The larger the ratio of the first included angle θ1 to the second included angle θ2, the closer the second included angle is to the first included angle. That is, the width and depth of the edge groove segment 1023 are closer to the width and depth of the main groove segment 1022, which is not conducive to the flow of electrolyte and affects the electrolyte injection efficiency. If the ratio of the first included angle θ1 to the second included angle θ2 is smaller, the second included angle is larger than the first included angle. That is, the depth and width of the edge groove segment 1023 are wider than the depth and width of the main groove segment 1022. The area of the active layer 102 will be reduced, which will lead to a decrease in the total capacity of the battery, reduce the efficiency of the battery, and shorten the cycle life of the battery.
[0058] Therefore, setting the ratio of the first included angle and the second included angle within a reasonable range can not only increase the flow rate of the electrolyte in the online tank 1021, but also ensure the total capacity of the battery and extend its service life.
[0059] In one embodiment, such as Figure 4 As shown, along the second direction, the electrode has a first surface and a second surface arranged opposite to each other. The grooves 1021 on the first surface and the grooves 1021 on the second surface are staggered. The distance between the projection of the center line of the groove 1021 on the first surface and the center line of the groove 1021 on the adjacent second surface onto the first surface is 0.001mm-1.999mm. Staggering the grooves 1021 on the front and back sides of the electrode can reduce damage to the current collector 101, thereby avoiding the decrease in conductivity, capacity reduction, and structural instability caused by damage to the current collector 101.
[0060] It is understood that, in another embodiment, such as Figure 5 As shown, the projections of the groove 1021 on the first surface and the groove 1021 on the second surface on the first surface coincide. When the groove 1021 is processed at the same position on the front and back of the electrode, the current collector 101 is greatly damaged.
[0061] It should be noted that, in Figure 4 and Figure 5 In the diagram, the black area refers to the groove 1021 on the first surface, and the white dashed line refers to the groove 1021 on the second surface.
[0062] In one embodiment, the groove 1021 can be formed by laser etching. Laser energy is used to etch the groove 1021 onto the surface of the negative electrode 1. Laser etching offers advantages such as high precision, high flexibility, and high speed. It is understood that the groove 1021 can also be formed using other methods and is not limited to laser etching.
[0063] In one embodiment, the exposed part of the current collector on the first surface of the pole piece forms the tab welding area 1011 of the welding tab 4, and at least one end of the current collector has a blank area 1012 along the third direction. The ratio of the roughness Ra1 of the tab welding area to the roughness Ra2 of the blank area is 1.1-3. After the line groove 1021 is opened on the active layer 102, part of the active layer is removed to expose part of the current collector 101, thereby forming the tab welding area. At this time, the tab welding area has a striped structure, which can increase the surface roughness of the welding area of the tab 4 and improve the welding strength of the tab 4.
[0064] In one embodiment, as shown in Figures 8 to 11 , the exposed part of the current collector on the first surface of the pole piece forms the tab welding area 1011 of the welding tab 4. After the tab welding area welds the tab 4, a plurality of welding protrusions 105 are formed on the second surface of the pole piece. The welding protrusion 105 closest to the edge groove section 1023 forms an edge protrusion. The distance h2 between the side of the edge protrusion close to the edge groove section 1023 and the end of the edge groove section 1023 away from the main groove section 1022 is 1mm-5mm.
[0065] The distance between the side of the edge protrusion close to the edge groove section 1023 and the end of the edge groove section 1023 away from the main groove section 1022 cannot be too large or too small. If the distance between the side of the edge protrusion close to the edge groove section 1023 and the end of the edge groove section 1023 away from the main groove section 1022 is too large, in order to ensure the welding strength between the current collector 101 and the tab, the area of the tab welding area 1011 is large, which reduces the area of the active layer 102. At the same time, the area of the tab is also large, and the required material of the tab is more, and the cost is higher. If the distance between the side of the edge protrusion close to the edge groove section 1023 and the end of the edge groove section 1023 away from the main groove section 1022 is too small, it is not conducive to heat diffusion during welding of the tab 4.
[0066] Therefore, the distance between the side of the edge protrusion close to the edge groove section 1023 and the end of the edge groove section 1023 away from the main groove section 1022 is set within a reasonable range, which not only improves heat diffusion during welding, but also controls the area of the tab welding area 1011 and the tab.
[0067] It should be noted that, as shown in Figure 8 and Figure 9As shown, after etching the line groove 1021 on the active layer 102, the active layer 102 in the region where the current collector 101 is welded with the tab 4 is cleaned away, thereby exposing part of the current collector 101, the exposed current collector 101 forms a tab welding area 1011, and then part of the tab 4 is placed on the tab welding area 1011, and then the tab is welded on the tab by laser. The material of the current collector 101 is a foil. When the tab is a negative tab 1, the material of the current collector is a copper foil.
[0068] It is worth noting that in Figure 1 , Figure 2 , Figure 4 , Figure 5 , the light gray area refers to the active layer 102, and the black area refers to the line groove 1021; in Figure 12 , the light gray area refers to the negative tab 1, the dark gray area refers to the positive tab 2, and the black area refers to the line groove 1021; in Figures 8 to 10 , the gold area refers to the tab welding area 1011.
[0069] Specifically, the tab is a negative tab 1, and the width of the negative tab 1 is 30mm-150mm.
[0070] According to the embodiment of the utility model, on the other hand, another kind of battery cell, the battery cell includes a negative tab 1, the negative tab 1 is the tab described above, and the battery cell further includes a positive tab 2 and a separator, the negative tab 1 is stacked with the separator and the positive tab 2, along the first direction, the negative tab 1 has a coincident area coinciding with the positive tab 2 and a non-coincident area 104 exceeding the edge of the positive tab 2, and the edge groove section 1023 is located in the non-coincident area 104.
[0071] In the process of charging and discharging the battery, the edge area is prone to uneven lithium deposition or extraction, causing local overheating or dendrite growth. By making the width of the positive tab 2 less than the width of the negative tab 1, the negative effects of these edge effects can be reduced, thereby prolonging the service life of the battery.
[0072] In one embodiment, the ratio of the projected area S2 of the single edge groove section 1023 on the current collector 101 to the area S3 of the non-coincident area 104 is less than or equal to 0.1, which can enhance the lithium ion insertion and extraction of the negative active material at the edge of the non-coincident area 104, and reduce the possibility of lithium precipitation.
[0073] Further, in the first direction, the width h1 of the non-overlapping area 104 is 0.01mm-1.5mm. Wherein, the width of the non-overlapping area 104 cannot be too large or too small, if the width of the non-overlapping area 104 is too large, it means that the width of the negative plate 1 is too wide, which leads to occupying a large space, increasing the weight, rising the cost, and increasing the difficulty of production; if the width of the non-overlapping area 104 is too small, it means that the negative plate 1 is too narrow, which may lead to that the lithium ions extracted from the positive electrode cannot be completely embedded in the negative electrode, but form lithium dendrites on the surface of the negative plate 1, and once the lithium dendrites grow too long, they may penetrate the separator, leading to short circuit of the positive and negative plates 1, and further causing battery failure and even safety accidents.
[0074] Therefore, by setting the width of the non-overlapping area 104 within a reasonable range, that is, the distance between the edge of the positive plate 2 and the edge of the linear groove 1021 is within a reasonable range, the lithium precipitation phenomenon caused by the mass of the positive material being greater than the mass of the negative material can be avoided, and the size of the plate can be ensured not to be too large and the weight not to be too heavy, thereby reducing the cost and the difficulty of production.
[0075] It should be noted that the width of the non-overlapping area 104 is the distance between the edge of the positive plate 2 in the width direction and the end of the corresponding edge groove segment 1023 away from the main groove segment 1022.
[0076] According to the embodiments of the present application, on the other hand, a secondary battery is also provided, comprising the above-mentioned battery cell.
[0077] By constructing the linear groove 1021 on the surface of the negative plate 1, the wettability of the electrolyte to the active material and the transmission path of the lithium ion are improved, and the rate performance of the battery cell is improved. Specifically, the linear groove 1021 is etched on the active material of the negative plate 1 by using a laser, and the negative plate 1 with the linear groove 1021 is used to make a battery, which can improve the wettability of the electrolyte, widen the lithium precipitation window of the material, and improve the fast charging performance of the battery.
[0078] The application will be further described in detail below in conjunction with specific examples, which cannot be understood as limiting the scope of the application claimed. If the specific experimental steps or conditions are not specified in the examples and comparative examples, the operations or conditions can be carried out according to the conventional experimental steps described in the literature in the art. In all examples and comparative examples of the present application, the unit % represents the mass percentage.
[0079] The method for preparing the battery comprises:
[0080] Step one: disperse the silicon-doped 7% silicon-carbon negative electrode material, sodium carboxymethyl cellulose, butadiene rubber and conductive carbon black in a solvent deionized water according to a mass ratio of 93:2.5:1.5:3, mix uniformly to obtain a slurry; uniformly coat the prepared slurry on a copper foil, dry at 100℃, and roll and cut to obtain a negative plate;
[0081] The positive electrode lithium cobaltate material, polyvinylidene fluoride, and conductive carbon black are mixed in a mass ratio of 90:5:5, an appropriate amount of N-methyl pyrrolidone is added as a solvent, and stirring is performed to obtain an electrode slurry. The prepared electrode slurry is uniformly coated on an aluminum foil to form a positive electrode sheet.
[0082] Step two: laser etching line groove treatment is performed on the negative electrode sheet.
[0083] Step three: the treated negative electrode sheet, the positive electrode sheet, and the separator are wound to prepare a wound lithium ion battery according to a conventional winding structure, and the battery is prepared through packaging, liquid injection, formation, second sealing, and capacity testing.
[0084] The batteries prepared in each example and the comparative examples are subjected to electrical performance testing: a charge-discharge device is used to charge the battery at a rate of 2C, and discharge the battery at a rate of 2C. In this way, the capacity retention rate of the battery is tested after 300 cycles.
[0085] After the disassembled battery is washed clean with an organic solution and dried, a standard contact angle measuring instrument (water droplet angle measuring instrument) is used to test the time taken for the electrolyte to drop from the liquid bead to the treated electrode sheet until the liquid bead is completely absorbed by the electrode sheet, and the wetting time is recorded.
[0086] Table 1
[0087]
[0088]
[0089]
[0090] From Table 1, it can be seen that:
[0091] When d1 in Examples 1-3 takes an intermediate value, the capacity retention rate of the battery is higher than when d1 in Examples 1-1 and 1-2 takes the minimum and maximum values, and the capacity retention rate of the battery in Comparative Examples 1 and 2 is also lower when d1 takes a smaller and larger value.
[0092] When d2 in Example 2-3 takes an intermediate value, the capacity retention rate of the battery is higher than when d2 in Examples 2-1 and 2-2 takes the minimum and maximum values, and the capacity retention rate of the battery in Comparative Examples 3 and 4 is also lower when d2 takes a smaller and larger value.
[0093] When w1 in Example 3-4 takes an intermediate value, the capacity retention rate of the battery is higher than when w1 in Examples 3-2 and 3-3 takes the minimum and maximum values, and the capacity retention rate of the battery in Comparative Examples 5 and 6 is also lower when w1 takes a smaller and larger value.
[0094] When d2 and w1 of Example 3-1 and Example 3-2 have the same value, d1 of Example 3-1 is greater than d1 of Example 3-2, w2 of Example 3-1 is smaller than w2 of Example 3-2, the electrolyte immersion time of Example 3-1 is longer, and the capacity retention rate of the battery is lower.
[0095] When w2 in Example 4-3 has an intermediate value, the capacity retention rate of the battery is higher than when w1 has the minimum and maximum values in Example 4-1 and Example 4-2, and the capacity retention rate of the battery is also lower when w2 has a smaller and larger value in Comparative Example 7 and Comparative Example 8.
[0096] When d1 / d2 in Example 5-3 has an intermediate value, the capacity retention rate of the battery is higher than when d1 / d2 has the minimum and maximum values in Example 5-1 and Example 5-2, and the capacity retention rate of the battery is also lower when d1 / d2 has a smaller and larger value in Comparative Example 9 and Comparative Example 10.
[0097] When w1 / w2 in Example 6-3 has an intermediate value, the capacity retention rate of the battery is higher than when w1 / w2 has the minimum and maximum values in Example 6-1 and Example 6-2, and the capacity retention rate of the battery is also lower when w1 / w2 has a smaller and larger value in Comparative Example 11 and Comparative Example 12.
[0098] When d1 is greater than d2 in Example 7-3 has an intermediate value, the capacity retention rate of the battery is higher than when d1 is greater than d2 has the minimum and maximum values in Example 7-1 and Example 7-2, and the capacity retention rate of the battery is also lower when d1 is greater than d2 has a smaller and larger value in Comparative Example 13 and Comparative Example 14.
[0099] When w1 is greater than w2 in Example 8-3 has an intermediate value, the capacity retention rate of the battery is higher than when w1 is greater than w2 has the minimum and maximum values in Example 8-1 and Example 8-2, and the capacity retention rate of the battery is also lower when w1 is greater than w2 has a smaller and larger value in Comparative Example 15 and Comparative Example 16.
[0100] It should be noted that the distance between the tab plane and the lowest point of the bottom of the linear groove is the depth of the linear groove, and the distance between the left and right edges of the linear groove profile is the width of the linear groove.
[0101] The negative tab was prepared according to the area of the linear groove shown in Table 2, and then the battery was prepared, and the electrolyte retention amount of the battery was tested. Among them, when the linear groove on the negative tab was laser etched, the area of the linear groove at different positions was controlled by controlling the action time of the laser scribe at the beginning and end on the negative tab; the electrolyte retention amount of the battery refers to the weight gain of the battery before and after liquid injection.
[0102] Table 2
[0103] [S1(mm 2 )]]> [S2(mm 2 )]]> S1 / S2 Electrolyte solution retention amount (g) Example 9-1 8.00 0.01600000 500.0 8.27 Example 9-2 8.00 0.00053333 15000.0 8.25 Example 9-3 8.00 0.00100000 8000.0 8.32 Comparative Example 17 8.00 0.02000000 400.0 8.20 Comparative Example 18 8.00 0.00044444 18000.0 8.19
[0104] From Table 2, it can be seen that:
[0105] When S1 / S2 takes an intermediate value in Example 9-3, the electrolyte retention amount of the electrolyte is larger than that when S1 / S2 takes the minimum value and the maximum value in Example 9-1 and Example 9-2, and the electrolyte retention amount of the electrolyte when S1 / S2 takes a smaller value and a larger value in Comparative Example 17 and Comparative Example 18 is also smaller.
[0106] The negative pole piece was prepared according to the staggered distance of the wire slot shown in Table 3, and then the battery was prepared, and the damage degree of the current collector was tested. Among them, when preparing the negative pole piece, when setting the position of the first wire slot of the second surface, the position of the first wire slot of the first surface of the pole piece was added according to the staggered distance.
[0107] It should be noted that the damage degree of the current collector refers to the oxidation degree of the copper foil. The specific method for judging the damage degree of the current collector is: by disassembling the battery and cleaning the area of the active layer on the pole piece, observing the color difference of the copper foil, the color of the oxidized copper foil becomes gray, and the color becomes dark, then it is determined that the current collector is damaged, and when the proportion of the dark area of the current collector to the total area of the current collector is greater than 10%, it is determined that the current collector is severely damaged.
[0108] Table 3
[0109] Misalignment distance Degree of damage to current collector Example 10-1 0.001 Current collector not damaged Example 10-2 1.999 Current collector not damaged Example 10-3 1.00 Current collector not damaged Example 10-4 0.00 Current collector severely damaged
[0110] From Table 3, it can be seen that:
[0111] When the staggered distance in Example 10-1, Example 10-2 and Example 10-3 is not zero, the current collector is not damaged, and when the staggered distance in Example 10-4 is zero, the current collector is severely damaged.
[0112] After the negative pole piece is prepared, the roughness of the copper foil in the tab welding area and the roughness of the copper foil in the blank area are measured, and the welding stress is also tested, and then the specific values of Ra1, Ra2 and welding pressure are obtained. Among them, the roughness is measured by using the roughness detection function of the Keyence 3D microscope.
[0113] Table 4
[0114] Ra1 Ra2 Ra1 / Ra2 Welding tension (N) Example 11-1 0.33 0.30 1.10 15.00 Example 11-2 0.90 0.30 3.00 15.20 Example 11-3 0.60 0.30 2.00 18.10 Comparative Example 19 0.15 0.30 0.50 13.80 Comparative Example 20 1.20 0.30 4.00 12.60
[0115] From Table 4, it can be seen that:
[0116] The weld pull force in Example 11-3, where Ra1 / Ra2 takes an intermediate value, is greater than in Examples 11-1 and 11-2, where Ra1 / Ra2 takes a minimum and maximum value, respectively. In Comparative Examples 19 and 20, where Ra1 / Ra2 takes a smaller and larger value, respectively, the weld pull force is smaller.
[0117] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be suggested by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes are intended to fall within the scope of the appended claims.
Claims
1. A pole piece, characterized in that, It comprises: a current collector (101); an active layer (102) disposed on the surface of the current collector (101), the active layer (102) having a plurality of line grooves (1021) on the surface away from the current collector (101), each of the line grooves (1021) comprising a main groove section (1022) and an edge groove section (1023), the edge groove section (1023) being connected with at least one end of the main groove section (1022) along a first direction (X), the depth of at least part of the edge groove section (1023) being greater than the depth of the main groove section (1022) along a second direction (Z); and / or, the width of at least part of the edge groove section (1023) being greater than the width of the main groove section (1022) along a third direction (Y).
2. The pole piece of claim 1, wherein The width of the edge groove section (1023) gradually increases from the end connected with the main groove section (1022) to the end away from the main groove section (1022).
3. The pole piece of claim 1, wherein The ratio of the depth of the edge groove section (1023) to the depth of the main groove section (1022) is 1.001-4; and / or, the ratio of the width of the edge groove section (1023) to the width of the main groove section (1022) is 1.001-2; and / or, the depth of the edge groove section (1023) is greater than the depth of the main groove section (1022) by 1um-50um; and / or, the width of the edge groove section (1023) is greater than the width of the main groove section (1022) by 1um-150um.
4. The pole piece of claim 1, wherein The depth of the edge groove section (1023) ranges from 6um to 50um; and / or, the depth of the main groove section (1022) ranges from 5um to 30um; and / or, the width of the edge groove section (1023) ranges from 55um to 250um; and / or, the width of the main groove section (1022) ranges from 50um to 200um.
5. The pole piece of claim 1, wherein The ratio of the projection area S1 of a single line groove (1021) on the current collector (101) to the projection area S2 of the edge groove section (1023) of a single line groove (1021) on the current collector (101) is 500-15000.
6. The pole piece of claim 1, wherein In any two adjacent line grooves (1021), the distance L1 between the edge groove sections (1023) is 0.001mm-0.2m less than the distance L2 between the main groove sections (1022); and / or, the distance L1 between the edge groove sections (1023) is 1mm-2mm; and / or, the distance L2 between the main groove sections (1022) is 0.8mm-2mm.
7. The pole piece of claim 1, wherein The main groove section (1022) has a first cross section perpendicular to the first direction, and the intersection of the first cross section and the reference surface is a first intersection t1 and a second intersection t2, the lowest point of the first cross section is a first lowest point z1, the included angle between the line connecting the first intersection t1 and the first lowest point z1 and the line connecting the second intersection t2 and the first lowest point z1 is a first included angle θ1, the edge groove section (1023) has a second cross section perpendicular to the first direction, and the intersection of the second cross section and the reference surface is a third intersection t3 and a fourth intersection t4, the lowest point of the second cross section is a second lowest point z2, the included angle between the line connecting the third intersection t3 and the second lowest point z2 and the line connecting the fourth intersection t4 and the second lowest point z2 is a second included angle θ2, and the ratio of the first included angle θ1 to the second included angle θ2 is 0.3-0.
8.
8. The pole piece of claim 1, wherein Along the second direction, the pole piece has oppositely arranged first and second surfaces, the linear grooves (1021) on the first surface are arranged staggered with the linear grooves (1021) on the second surface, and the staggered distance between the center line of the linear groove (1021) on the first surface and the projection of the center line of the adjacent linear groove (1021) on the second surface on the first surface is 0.001mm-1.999mm. Alternatively, the linear grooves (1021) on the first surface are arranged coincident with the projection of the linear grooves (1021) on the second surface on the first surface.
9. The pole piece of claim 1, wherein, The area of the exposed part of the current collector on the first surface of the pole piece forms a tab welding area (1011) for welding the tab (4), and along the third direction, at least one end of the current collector (101) has a blank area (1012), and the ratio of the roughness of the tab welding area (1011) to the roughness of the blank area (1012) is 1.1-3.
10. The pole piece of claim 1, wherein The area of the exposed part of the current collector on the first surface of the pole piece forms a tab welding area for welding the tab (4), and after welding the tab (4), a plurality of welding protrusions (105) are formed on the second surface of the pole piece, the welding protrusion (105) closest to the edge groove section (1023) forms an edge protrusion, and the distance h2 between the side of the edge protrusion close to the edge groove section (1023) and the end of the edge groove section (1023) away from the main groove section (1022) is 1mm-5mm.
11. The pole piece of claim 1, wherein The pole piece is a negative pole piece (1).
12. An electric cell characterized by The battery cell comprises a negative electrode sheet (1), the negative electrode sheet (1) is the electrode sheet as claimed in any one of claims 1-11, the battery cell further comprises a positive electrode sheet (2) and a separator, the negative electrode sheet (1), the separator and the positive electrode sheet (2) are stacked, along the first direction, the negative electrode sheet (1) has a coincident area coinciding with the positive electrode sheet (2) and a non-coincident area (104) beyond the edge of the positive electrode sheet (2), and the edge groove section (1023) is located in the non-coincident area (104).
13. The electric cell of claim 12, wherein, The ratio of the projection area S2 of a single edge groove section (1023) on the current collector (101) to the area of the non-coincident area (104) is less than or equal to 0.1; And / or, along the first direction, the width of the non-coincident area (104) is 0.01mm-1.5mm.
14. A secondary battery characterized by comprising: Comprise: The battery cell as claimed in any one of claims 12-13.