Electrode assembly and battery having the same

Abstract

The embodiment of the utility model provides an electrode assembly and a battery with the same. The electrode assembly comprises a positive plate, a diaphragm and a negative plate which are stacked and wound, the positive plate comprises a positive current collector and a positive active layer, the positive active layer comprises a first positive active layer and a second positive active layer which are arranged on the two opposite sides in the thickness direction of the positive current collector, and the first positive active layer is provided with a tab groove and at least one first concave part; the at least one first concave part is distributed in the first area of the first positive electrode active layer, a positive electrode lug is arranged in the lug groove and electrically connected with the positive electrode current collector, the positive plate is provided with a first plate edge and a second plate edge in the width direction, and the lug groove, the first area and the first plate edge are arranged on the same side in the width direction of the positive plate; the first region extends along the length direction of the positive plate, and a distance D1 is formed between the first region and the tab groove, and D1 is greater than or equal to 0.2 mm. According to the technical scheme provided by the embodiment of the utility model, the risk of lithium precipitation at the side edge of the tab can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model discloses an electrode assembly and battery with same, and belongs to the field of battery. BACKGROUND

[0002] The electrode assembly generally comprises positive electrode sheets and negative electrode sheets stacked and distributed through a separator. The positive electrode sheet generally comprises a current collector and active layers arranged on opposite sides of the thickness direction of the current collector. Some positive electrode sheets adopt a tab centering structure, that is, the active material layer is provided with a tab slot, and a tab is connected with a current collector part exposed by the tab slot. The battery with such a positive electrode sheet may have the problem of lithium precipitation at the side edge of the tab and the edge of the tab slot, affecting the safety performance of the battery. SUMMARY

[0003] Therefore, the utility model discloses an electrode assembly and battery with same, to reduce the risk of lithium precipitation at the side edge of the tab and improve the safety performance of the battery.

[0004] In one aspect, the utility model discloses an electrode assembly. The electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked and wound. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer. The positive electrode active layer comprises a first positive electrode active layer and a second positive electrode active layer arranged on opposite sides of the thickness direction of the positive electrode current collector. The first positive electrode active layer is provided with a tab slot and at least one first recess. The at least one first recess is arranged in a first region of the first positive electrode active layer. A positive tab is arranged in the tab slot, and the positive tab is electrically connected with the positive electrode current collector. The positive electrode sheet has a first sheet edge and a second sheet edge in the width direction of the positive electrode sheet, the tab slot, the first region and the first sheet edge are arranged on the same side in the width direction of the positive electrode sheet, the first region extends along the length direction of the positive electrode sheet and has a spacing D1 with the tab slot, and D1 is greater than or equal to 0.2mm.

[0005] In some embodiments, the second positive electrode active layer is provided with an exposed groove and at least one second recess, the at least one second recess is arranged in a second region of the second positive electrode active layer, the exposed groove, the second region and the first sheet edge are arranged on the same side in the width direction of the positive electrode sheet, the tab slot has two first slot edges in the length direction of the positive electrode sheet, the exposed groove has two second slot edges in the length direction of the positive electrode sheet, the orthographic projection of each second slot edge on the first positive electrode active layer is located on the outer side of the two first slot edges, and each second slot edge has a transition area between the orthographic projection on the first positive electrode active layer and the first slot edge on the same side of the tab slot.

[0006] In some embodiments, the transition area has a size D2 in the length direction of the positive electrode sheet, and D1 is greater than or equal to D2, and preferably 1.1≤D1 / D2≤10.

[0007] In some embodiments, there is a spacing D3 between the second region and the exposed groove, 0.5 mm≤D1≤15 mm, 0.5 mm≤D2≤5 mm, and 0.2 mm≤D3≤10 mm.

[0008] In some embodiments, the first groove edge on the first side of the tab slot in the length direction of the positive electrode sheet has a spacing D11 to the first region, and the first groove edge on the second side of the tab slot in the length direction of the positive electrode sheet has a spacing D12 to the first region, |D11-D12|≤10.

[0009] In some embodiments, the second groove edge on the first side of the exposed groove in the length direction of the positive electrode sheet has a spacing D31 to the second region, and the second groove edge on the second side of the exposed groove in the length direction of the positive electrode sheet has a spacing D32 to the second region, |D31-D32|≤10.

[0010] In some embodiments, 1 / 35≤W2 / W1≤1 / 2; and / or, 2 mm≤W2≤20 mm; and / or, 0.1 mm≤D4≤10 mm. Here, W1 is the dimension of the positive electrode sheet in its width direction, W2 is the dimension of the first region in the width direction of the positive electrode sheet, and D4 is the distance from the first region to the active layer edge of the first positive active layer, which is closer to the first tab edge than to the second tab edge.

[0011] In some embodiments, the positive tab is welded to the positive current collector and has a plurality of weld points, the at least one first recess includes a plurality of first recesses, and the plurality of weld points and the plurality of first recesses satisfy: 5 μm≤H1≤30 μm; and / or, 30 μm≤H2≤500 μm; and / or, 1≤H2 / H1≤100; and / or, 100 μm≤D5≤300 μm; and / or, τ1≥τ2; and / or, 9 / mm2≤τ1≤120 / mm2; and / or, 4 / mm2≤τ2≤64 / mm2. Here, H1 is the depth of the plurality of first recesses, H2 is the depth of the plurality of weld points, D5 is the spacing of the plurality of first recesses, τ1 is the distribution density of the plurality of first recesses, and τ2 is the distribution density of the plurality of weld points. 2 2 ; and / or, 4 / mm2≤τ2≤64 / mm2. Here, H1 is the depth of the plurality of first recesses, H2 is the depth of the plurality of weld points, D5 is the spacing of the plurality of first recesses, τ1 is the distribution density of the plurality of first recesses, and τ2 is the distribution density of the plurality of weld points.

[0012] In some embodiments, the electrode assembly further includes a first adhesive tape, the first adhesive tape covers the positive tab and part of the first region, the area of the first region covered by the first adhesive tape is S1, 0.1 mm 2 ≤S1≤500mm 2 .

[0013] ​In some embodiments, the negative tab includes a negative current collector and a negative active layer, the negative active layer contains a receiving recess, a positive projection of the positive tab on the negative tab at least partially overlaps the receiving recess, and a positive projection of the first region on the negative tab is located outside the receiving recess.

[0014] In some embodiments, the negative tab further includes a second adhesive tape, wherein the second adhesive tape is located within the receiving recess; or the second adhesive tape is partially located outside the receiving recess, and a positive projection of the part of the second adhesive tape located outside the receiving recess on the positive tab partially overlaps the first region and has an overlapping area S2, 0.1mm 2 ≤ S2≤ 500mm 2 .

[0015] In some embodiments, the positive tab further includes a third adhesive tape, a positive projection of the negative tab on the positive tab falls on the first region, the third adhesive tape is arranged at a position of the positive tab corresponding to the negative tab, a positive projection of the third adhesive tape on the positive tab overlaps a positive projection of the negative tab on the positive tab, and the overlapping part covers a part of the first region.

[0016] In some embodiments, the third adhesive tape has a first adhesive tape edge and a second adhesive tape edge along the width direction of the positive tab, the first adhesive tape edge exceeds the positive tab outward in the width direction of the positive tab, the second adhesive tape edge exceeds the corresponding region inward in the width direction of the positive tab, the second adhesive tape edge has a distance D6 from the corresponding region, and D6≤20mm.

[0017] In some embodiments, the first positive active layer is further provided with a third region, at least one third recess is arranged in the third region, the third region extends along the length direction of the positive tab, and the third region is closer to the second tab edge than to the first tab edge; and / or, the second positive active layer is further provided with a fourth region, at least one third recess is arranged in the fourth region, the fourth region extends along the length direction of the positive tab, and the fourth region is closer to the second tab edge than to the first tab edge.

[0018] In some embodiments, the electrode assembly has a flat part and a curved part, the positive tab includes a circular arc segment located in the curved part, the positive active layer is provided with a fifth region, at least one fifth recess is arranged in the fifth region, and the fifth region is at least partially provided in the circular arc segment.

[0019] In some embodiments, the positive tab further includes a straight segment located in the flat part, the two straight segments are respectively connected to two ends of the circular arc segment along the length direction of the positive tab, and two edges of the fifth region in the length direction of the positive tab are respectively located in the two straight segments.

[0020] In some embodiments, the at least one first recess is arranged non-linearly.

[0021] In some embodiments, the first region is divided into at least two sections arranged along the length direction of the positive electrode sheet by at least one first joint region; and / or, the fifth region is divided into at least two sections arranged along the width direction by at least one second joint region; and / or, the first region and the fifth region are divided by a third joint region.

[0022] In some embodiments, the first joint region has a size W3 along the length direction of the positive electrode sheet, 0.1mm≤W3≤20mm; and / or, the second joint region has a size W4 along the width direction of the positive electrode sheet, 0mm≤W4≤20mm; and / or, the third joint region has a size W5 along the width direction of the positive electrode sheet, 0mm≤W5≤20mm.

[0023] In some embodiments, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged in a stack, and the negative electrode active layer is provided with a plurality of grooves arranged at intervals.

[0024] In some embodiments, 5μm≤H3≤30μm; and / or, 0.5mm≤D7≤5mm,

[0025] Wherein, H3 is the groove depth of the plurality of grooves, and D7 is the groove spacing of the plurality of grooves.

[0026] In a possible implementation, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged in a stack; the material of the negative electrode active layer comprises one or more of graphite, a silicon-based material, and when the material of the negative electrode active layer is a silicon-based material, the silicon element content is 3-30wt%.

[0027] In another aspect, the embodiments of the utility model further provide a lithium ion secondary battery. The battery comprises the electrode assembly in the above aspect.

[0028] According to the implementation provided by the embodiments of the utility model, the plurality of recesses arranged in the first region on the positive electrode active layer can reduce the active material of the positive electrode active layer, reduce the amount of lithium ions received by the negative electrode sheet, thereby reducing the risk of lithium precipitation on the side edge of the tab and improving the safety performance of the battery. In addition, the recesses can increase the storage capacity of the electrolyte, which is conducive to the transmission of lithium ions. At the same time, since there is a large enough interval between each first region and the first groove edge located on the same side of the tab groove, the recesses can avoid the phenomenon of powder falling off the positive electrode active layer, which can cause short circuit caused by powder cutting through the diaphragm, and can avoid the powder falling into the welding area of the positive tab, which can affect the welding effect, thereby further improving the safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the battery according to an embodiment of the utility model.

[0030] Figure 2This is a schematic diagram of the structure of a battery according to another embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the structure of an electrode assembly according to a disclosed embodiment.

[0032] Figure 4 For along Figure 3 A cross-sectional view taken from the middle BB line.

[0033] Figure 5 It shows Figure 4 A schematic diagram of the structure on both sides of the positive electrode sheet in the thickness direction.

[0034] Figure 6A and 6B for Figure 5 A schematic diagram of a portion of the positive electrode.

[0035] Figure 7 for Figure 6A A magnified view of a portion of the positive electrode plate.

[0036] Figure 8 It shows Figure 5 A schematic diagram of the positive electrode tab of the positive electrode plate.

[0037] Figures 9A to 9C for Figure 4 A schematic diagram of a portion of the electrode assembly.

[0038] Figure 10 for Figure 5 A schematic diagram of a portion of the positive electrode.

[0039] Figure 11 for Figure 5 A schematic diagram of another part of the positive electrode.

[0040] Figure 12 for Figure 4 A schematic diagram of a portion of the middle electrode assembly.

[0041] Figure 13 for Figure 5 A schematic diagram of a portion of the positive electrode plate.

[0042] Figure 14 for Figure 5 A schematic diagram of the structure of the positive electrode.

[0043] Figure 15 for Figure 4 A schematic diagram of the negative electrode in the diagram.

[0044] Figure 16 for Figure 15 A cross-sectional view of the groove in the middle. Detailed Implementation

[0045] This document provides numerous specific details to offer a deep understanding of the overall structure, function, and purpose of the embodiments described and illustrated in the specification and figures. Well-known operations, components, and elements have not been described in detail to avoid making the description overly redundant. The reader will understand that the embodiments described and illustrated herein are non-limiting examples, and thus will recognize that the specific structural and functional details mentioned herein are representative and illustrative. Variations and changes may be made to these embodiments without departing from the scope of the claims.

[0046] <Example Battery>

[0047] In this embodiment of the invention, "battery" refers to an energy storage device capable of repeated charging and discharging, which can be interpreted as the concept of a "secondary battery." In this embodiment of the invention, the concept of "secondary battery" can include, but is not limited to, lithium-ion secondary batteries, sodium-ion secondary batteries, etc.

[0048] According to one embodiment of the present utility model, the battery 100 is in... Figure 1 It is shown in the image. (Reference) Figure 1 The battery 100 may include an electrode assembly 10 and a package 20. The package 20 may have a cavity, which may house one or more electrode assemblies 10.

[0049] like Figure 1 As shown, the packaging body 20 can be square. That is, the battery 100 can be a square battery. The material of the packaging body 20 can be the same as the materials used in the past, and there are no particular restrictions. For example, the packaging body 20 can be made of metal, specifically, it can be made of aluminum (alloy) or iron (alloy).

[0050] According to another embodiment of the present invention, the battery 100 is in... Figure 2 It is shown in the middle. For example... Figure 2 As shown, in this embodiment, the packaging body 20 is flat and made of a relatively soft material, such as aluminum-plastic film. That is, in this embodiment, the battery 100 can be a pouch battery.

[0051] It is foreseeable that in other examples of embodiments of this utility model, the battery 100 may also be implemented as other types besides prismatic batteries and pouch batteries, such as cylindrical batteries.

[0052] It should be noted that the structure of other aspects of the battery 100 can be the same as that of conventional batteries. For the sake of simplicity, this embodiment of the utility model will not be described in detail.

[0053] <Example Electrode Assembly>

[0054] refer to Figure 3 and Figure 4 The electrode assembly 10 may include a positive electrode 11, a negative electrode 12, and a separator 13 arranged in a stacked manner. The separator 13 is a component that insulates the positive electrode 11 and the negative electrode 12. The positive electrode 11 and the negative electrode 12 may be wound with the winding axis A as the winding center through the separator 13. For example, the electrode assembly 10 may be wound into a flat structure. In this document, flat means that the width is greater than the thickness. For example, the ratio B / C of the width B and the thickness C of the electrode assembly 10 may satisfy 1.1 ≤ A / B ≤ 200. The electrode assembly 10 may include two bent portions 181 and a flat portion 182, with the flat portion 182 located between the two bent portions 181. As in some examples, the electrode assembly 10 may also be wound into a cylindrical shape.

[0055] When the electrode assembly 10 is flat, for ease of explanation, the "width direction" and "thickness direction" of the electrode assembly 10 will be used in this embodiment of the invention. Here, the "width direction" refers to the direction from one bend to another, indicated by arrow U in the figure; the "thickness direction" refers to the thickness direction of the front electrode sheet, which is perpendicular to the "width direction", indicated by arrow V in the figure.

[0056] refer to Figure 4 The positive electrode 11 may include a positive current collector 14, a first positive active layer 151, and a second positive active layer 152, which can be collectively referred to as the positive active layer 15. The first positive active layer 151 and the second positive active layer 152 may be located on opposite sides of the current collector 14 in the thickness direction. The negative electrode 12 may include a stacked negative current collector 121 and two negative active layers 122, which may be located on opposite sides of the negative current collector 121 in the thickness direction.

[0057] By way of example only, the positive electrode current collector 14 can be a strip of metal foil, and the positive electrode active layer 15 can contain a positive electrode active material capable of reversibly absorbing and releasing charge carriers. Furthermore, they may further include conductive materials, binders, and various additives. By way of example only, the metal foil mentioned here can be aluminum foil, the positive electrode active material can be a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide, the conductive material can be a carbon-based material such as acetylene black, and the binder can be polyvinylidene fluoride, etc.

[0058] By way of example only, the negative electrode current collector 121 can be a strip of metal foil or a composite current collector, and the negative electrode active layer 122 can contain a negative electrode active material capable of reversibly absorbing and releasing charge carriers, a binder, a dispersant, and various additives. By way of example only, the metal foil mentioned here can be copper foil, the negative electrode active material can be a carbon-based material such as graphite, the binder can be a rubber such as styrene-butadiene rubber, and the dispersant can be a cellulose such as carboxymethyl cellulose.

[0059] It can be understood that when the electrode assembly is unfolded, the winding direction of a certain element is consistent with its length direction; in other words, the direction from its starting end to its ending end is its length direction. Therefore, in the unfolded view, arrow X also indicates the length direction of the positive electrode sheet. In the attached diagram of the unfolded electrode assembly, the width direction of elements such as the positive electrode sheet, negative electrode sheet, separator, current collector, and active layer is indicated by arrow Y, and the direction indicated by arrow Y is perpendicular to the direction indicated by arrow X.

[0060] refer to Figure 5 The positive electrode active layer 15 may have at least one first recess 16. As an example, the at least one first recess 16 may be implemented as a plurality of holes 16, which may be distributed in at least one region of the positive electrode active layer 15. For example, the plurality of holes 16 may be formed on the positive electrode active layer 15 by laser drilling. Due to the presence of the plurality of holes 16, the positive active material in at least one region will be reduced, and the amount of lithium ions accepted by the negative active material at the corresponding position will be reduced, thereby alleviating lithium plating. At the same time, the presence of the plurality of holes 16 will increase the electrolyte storage capacity, which is beneficial to lithium ion transport.

[0061] It is understood that in other embodiments, the recess on the positive electrode active layer 15 can also be implemented as a groove, and this disclosure does not impose any particular limitation on this.

[0062] refer to Figure 5 and Figure 6AThe positive electrode 11 has two opposing edges in its width direction, namely a first electrode edge 111 and a second electrode edge 112. The first electrode edge 111 can be referred to as the tab side edge because the positive tab 19a of the positive electrode 11 is located at the first electrode edge 111. At least one region may include a first region 161, which is disposed on the first positive electrode active layer 151, extends along the length direction of the positive electrode 11, and is close to the first electrode edge 111. That is, the first region 161 is closer to the first electrode edge 111 than the second electrode edge 112. At least one recess 16 may include a plurality of first recesses 16, which are disposed in the first region 161. This can reduce the active material of the positive electrode active layer near the first electrode edge 111, reduce the amount of lithium ions received by the negative electrode, and thus reduce the risk of lithium plating near the first electrode edge 111.

[0063] Continue to refer to Figure 5 and Figure 6A The first positive electrode active layer 151 may have a tab groove 1511. The tab groove 1511, the first region 161, and the first electrode edge 111 are arranged on the same side in the width direction of the positive electrode 11, that is, the tab groove 1511 is closer to the first electrode edge 111 than the second electrode edge 112. The positive electrode tab 19a can be connected to the portion of the positive electrode current collector 14 exposed by the tab groove 1511, for example, by welding. Figure 5 and Figure 6A As shown, the first region 161 extends beyond the tab groove 1511 and is divided into two parts by the tab groove 1511, namely, into two first region portions 161a and 161b. The tab groove 1511 has two first groove edges 1512a and 1512b along the length of the positive electrode 11. Along the length of the positive electrode 11, the first region portion 161a and the first groove edge 1512a are located on the same side of the tab groove 1511, and the first region portion 161b and the first groove edge 1512b are located on the same side of the tab groove 1511.

[0064] After the first positive electrode active layer 151 is deposited on the positive electrode current collector 14, a portion of the active material in the first positive electrode active layer 151 can be removed to form a tab groove 1511. For example, a portion of the active material in the first positive electrode active layer 151 can be scraped off using a scraper. Before removing this portion of the active material, an adhesion weakening agent, such as N-methylpyrrolidone (NMP) solvent, can be applied to it, making the adhesion of the active material in the applied area lower than that in the unapplied area. Subsequently, the applied area can be scraped off or otherwise processed to form the tab groove 1511.

[0065] After the tab groove 1511 is formed, the active material near the tab groove 1511 has weaker adhesion than other areas due to the action of the adhesive weakening agent. If the two first regions 161a and 161b are too close to the two first groove edges 1512a and 1512b of the tab groove 1511, some holes 16 will fall into the area with poor adhesion, resulting in powder shedding from the positive electrode active layer 15. On the one hand, the falling powder may puncture the separator 13 and cause a short circuit; on the other hand, the falling powder may fall into the welding area of ​​the positive tab 19a, degrading the welding effect. Both of these aspects will reduce the safety performance of the battery 100.

[0066] In view of the above, and based on the embodiments of this utility model, reference continues to be made. Figure 5 and Figure 6A Each first region portion has a spacing D1 with the edge of the first groove on the same side of the tab groove 1511, and the spacing D1 is greater than or equal to 0.2 mm. In this way, since there is a sufficiently large spacing between each first region portion and the edge of the first groove on the same side of the tab groove 1511, it is possible to avoid powder shedding from the positive electrode active layer 15 during drilling, which would cause powder debris to puncture the separator and cause a short circuit, and to prevent powder debris from falling into the positive electrode tab welding area and affecting the welding effect, thereby improving the safety performance of the battery 100.

[0067] It should be noted that the spacing D1 can be the shortest distance between the first region portion and the edge of the first groove located on the same side of the tab groove 1511.

[0068] refer to Figure 5 and Figure 6B The second positive electrode active layer 152 may have an exposure groove 1521, and at least one region may include a second region 162 disposed on the second positive electrode active layer 152. A plurality of recesses 16 may include at least one second recess disposed on the second region. The exposure groove 1521 and the second region 162 are close to the first edge 111. That is, the exposure groove 1521 and the second region 162 are closer to the first electrode edge 111 than the second electrode edge 112. The second region 162 may extend along the length direction of the positive electrode 11 and be divided into two second region portions 162a and 162b by the exposure groove 1521. The exposure groove 1521 may have two second groove edges 1522a and 1522b along the length direction of the positive electrode 11. The second region portion 162a and the second groove edge 1522a are located on the same side of the exposed groove 1521 along the length of the positive electrode 11, and the second region portion 162b and the second groove edge 1522b are located on the same side of the exposed groove 1521 along the length of the positive electrode 11.

[0069] Because the first positive electrode active layer 151 has a tab groove 1511 and the second positive electrode active layer 152 has an exposure groove 1521, during the formation of the tab groove, the active material of the first positive electrode active layer 151 can be scraped off first to form the tab groove 1511, and then the active material of the second positive electrode active layer 152 can be scraped off to form the exposure groove 1521. Furthermore, the scraped area of ​​the second positive electrode active layer 152 is larger than the scraped area of ​​the first positive electrode active layer 151. This results in the orthographic projections of the two second groove edges 1522a and 1522b onto the first positive electrode active layer 151 being located outside the two first groove edges 1512a and 1512b, respectively. Figure 7 As shown. Because the areas scraped off on both sides of the positive current collector 14 are different, it is possible to avoid the positive current collector 14 being repeatedly subjected to force at the same location, which could cause it to crack.

[0070] refer to Figure 7 Each second trench edge has a transition region between its orthographic projection on the first positive electrode active layer 151 and the first trench edge located on the same side of the tab trench 1511. Specifically, a transition region 153a is formed between the orthographic projection of the second trench edge 1522a on the first positive electrode active layer 151 and the first trench edge 1512a, and a transition region 153b is formed between the orthographic projection of the second trench edge 1522b on the first positive electrode active layer 151 and the first trench edge 1512b. Each transition region has a dimension D2 in the length direction of the positive electrode sheet 11. (Reference) Figure 6B Each second region portion may have a spacing D3 with the edge of the second groove located on the same side of the exposed groove 1521.

[0071] Drilling holes in transition zones 153a and 153b is not advisable, as it may increase the risk of powder shedding and thus reduce the safety performance of battery 100. Therefore, size D1 can be greater than or equal to size D2 to prevent the hole 16 in the first region 161 from falling into transition zones 153a and 153b, thereby reducing the risk of powder shedding and improving the safety performance of battery 100.

[0072] The relationship between dimensions D1 and D2 can satisfy: 1.1 ≤ D1 / D2 ≤ 10, preferably 1.13 ≤ D1 / D2 ≤ 5. Alternatively, D1 / D2 can be 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5, or 10. The ratio of D1 / D2 should not be too small. If D1 / D2 is less than 1.1, the hole 16 in the first region 161 will fall into the transition regions 153a and 153b, or be too close to the transition regions 153a and 153b, both of which will increase the risk of powder shedding. The ratio of D1 / D2 should also not be too large. If D1 / D2 is greater than 10, it will increase the risk of lithium plating at the edge of the tab. Selecting the ratio of D1 / D2 as 1.1 ≤ D1 / D2 ≤ 10 can achieve both a low risk of powder shedding and a low risk of lithium plating at the edge of the tab.

[0073] More preferably, dimensions D1, D2, and D3 can satisfy the following conditions: 0.5mm ≤ D1 ≤ 15mm, 0.5mm ≤ D2 ≤ 5mm, and 0.2mm ≤ D3 ≤ 10mm. Preferably, 0.5mm ≤ D1 ≤ 7.5mm, 0.5mm ≤ D2 ≤ 1.5mm, and 0.2mm ≤ D3 ≤ 5mm. Alternatively, D2 can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm, and D3 can be 0.5mm, 1mm, 3mm, 5mm, 7mm, 9mm, or 10mm. It has been proven that when dimensions D1, D2, and D3 meet the above conditions, the risk of powder shedding and the risk of lithium plating at the tab edge are relatively low, and the safety performance of battery 100 is relatively high.

[0074] refer to Figure 6A and Figure 7 The first groove edge 1512a and the first region portion 161a located on the first side of the tab groove 1511 along the length direction of the positive electrode plate 11 have a spacing D11, and the first groove edge 1512b and the first region portion 161b located on the second side of the tab groove 1511 along the length direction of the positive electrode plate 11 have a spacing D12. The spacings D11 and D12 can satisfy: |D11-D12|≤10, preferably, |D11-D12|≤3. That is, the spacings D11 and D12 are not required to be equal, and they can have a difference of ±10mm. (Reference) Figure 6BThe second groove edge 1522a and the second region portion 162a located on the first side of the exposed groove 1521 along the length direction of the positive electrode sheet 11 have a spacing D31, and the second groove edge 1522b and the second region portion 162b located on the second side of the exposed groove 1521 along the length direction of the positive electrode sheet 11 have a spacing D32. The spacings D31 and D32 can satisfy: |D31-D32|≤10, preferably, |D31-D32|≤5. That is, the spacings D31 and D32 are not required to be equal; they can have a difference of ±10mm. The difference between spacings D11 and D12, and between spacings D31 and D32, should not be too large or too small. If the difference is too small, higher manufacturing precision will be required, which will increase manufacturing costs. If the difference is too large, it will cause one side of the groove edge to be too far from the corresponding region, while the other side's groove edge will be too close to the corresponding region. As mentioned earlier, if the edge of the groove is too close to the corresponding area, it will increase the risk of powder shedding, thereby reducing the safety performance of the battery.

[0075] It should be noted that the spacing D11 can be the shortest distance between the first groove edge 1512a and the first region portion 161a, and the spacing D11 can be the shortest distance between the first groove edge 1512b and the first region portion 161b. Similarly, D31 is the shortest distance between the second groove edge 1522a and the second region portion 162a, and D32 is the shortest distance between the second groove edge 1522b and the second region portion 162b.

[0076] refer to Figure 5 and Figure 6A The positive electrode 11 has a dimension W1 in the width direction, and the first region 161 has a dimension W2 in the width direction of the positive electrode 11. The value of dimension W2 can be in the range of 2mm ≤ W2 ≤ 20mm, and dimensions W1 and W2 can satisfy 1 / 35 ≤ W2 / W1 ≤ 1 / 2. Alternatively, W2 can be 2mm, 4mm, 7mm, 10mm, 15mm, or 20mm, and W2 / W1 can be 1 / 35, 1 / 30, 1 / 20, 1 / 10, 1 / 5, or 1 / 2. If dimension W2 and the ratio W2 / W1 are too large, the active material of the positive electrode active layer 15 will be excessively reduced, which is detrimental to the energy density of the battery 100. If dimension W2 and the ratio W2 / W1 are too small, it will be difficult to effectively improve the lithium plating problem at the edge of the tab side. By selecting the value of dimension W2 and the W2 / W1 ratio within the above range, lithium deposition at the tab edge can be improved without excessively reducing the energy density of battery 100.

[0077] Continue to refer to Figure 6AThe first region 161 has a dimension W2 in the width direction of the positive electrode 11, and the distance from the first region 161 to the edge of the active layer of the first positive electrode active layer 151 is D4. The value of the distance D4 can be in the range of 0.1mm≤D4≤10mm, preferably 0.1mm≤D4≤5mm. Alternatively, D4 can be 0.5mm, 2mm, 4mm, or 7mm. Here, the edge of the active layer is closer to the edge of the first electrode 111 than the edge of the second electrode 112. This ensures that the electrode edge is avoided when drilling holes in the first positive electrode active layer 151, preventing the electrode edge from being damaged and forming burrs, as well as the problem of the positive electrode breaking during the subsequent winding process. Furthermore, drilling according to the above implementation method allows the area to cover the positive electrode edge corresponding to the area of ​​easy lithium deposition at the negative electrode edge, thus reducing the risk of lithium deposition at the negative electrode edge.

[0078] refer to Figure 8 The positive electrode tab 19a can be welded to the positive electrode current collector 14 to form at least one solder joint 191. Multiple first recesses can have a depth H1 (not shown in the figure), and a spacing D5 exists between the multiple first recesses. Multiple solder joints 191 can have a solder joint depth H2 (not shown in the figure). It is understood that the depths of the multiple first recesses can be the same; in this case, H1 is the depth of any one of the first recesses. The depths of the multiple first recesses can also be different; in this case, H1 can be the average depth. When calculating the average depth of the multiple first recesses, only the average depth of a portion of the multiple first recesses can be considered, without including all the first recesses in the calculation. For example, H1 can be 10 cm near the welding area. 2 The average depth H1 of the first recess 16 in the region can also be the average depth of 10 adjacent first recesses 16. Similarly, when calculating the solder joint depth H2 of multiple solder joints, only a portion of the multiple solder joints 191 can be considered. For example, H2 can be the average depth of 6 cm in the soldering area. 2The average depth H2 of solder joints 191 in the region can also be the average depth of 10 adjacent solder joints 191. The value range of depth H1 can be: 5μm ≤ H1 ≤ 30μm. Alternatively, H1 can be 10μm, 15μm, 20μm, or 25μm. The value range of solder joint depth H2 can be: 30μm ≤ H2 ≤ 500μm. Alternatively, H2 can be 40μm, 60μm, 90μm, 100μm, 200μm, 300μm, or 400μm. Depths H1 and H2 can satisfy: 1 ​​≤ H2 / H1 ≤ 100. The value range of hole spacing D5 can be 100μm ≤ D5 ≤ 300μm. Alternatively, D5 can be 120μm, 150μm, 200μm, or 250μm. The welding performed according to the above parameters is beneficial to the bonding between the electrode tab and the current collector, as well as the conductivity of the metal, and can avoid excessive internal resistance at the weld joint, which would cause heat accumulation during charging and discharging. In addition, according to the above implementation method, it is not necessary to scrape off too much paste on the first positive electrode active layer 151, so while meeting the welding conditions, the capacity of the battery and the strength of the positive electrode sheet can also be guaranteed.

[0079] Continue to refer to Figure 8 τ1 refers to the number of the first recesses 16 per unit area. τ2 refers to the number of weld points 191 per unit area. The distribution densities τ1 and τ2 can satisfy: τ1 ≥ τ2. The value range of the distribution density τ1 can be: 9 points / mm. 2 ≤τ1≤120 pieces / mm 2 Alternatively, τ1 can be 20 pieces / mm. 2 40 pieces / mm 2 60 pieces / mm 2 80 pieces / mm 2 100 pieces / mm 2 The distribution density τ2 can range from 4 units / mm. 2 ≤τ2≤64 pieces / mm 2 Alternatively, τ1 can be 10 pieces / mm. 2 20 pieces / mm 2 40 pieces / mm 2 60 pieces / mm 2 The density of the tab solder bumps can differ from the density of the first recess 16; for example, the density of the solder bumps can be less than the density of the first recess 16. A higher density in the first recess 16 results in a more uniform stress distribution in the positive electrode active layer after the formation of the first recess 16. Simultaneously, because more electrolyte can be stored in the first recess 16, the smoothness of lithium-ion transport is improved, enhancing the battery's fast-charging performance and long-cycle performance.

[0080] refer to Figure 10The electrode assembly 10 may further include a first adhesive tape 171 adhered to the positive electrode sheet 11, and the positive electrode tab 19a and the first region 161 may be partially covered by the first adhesive tape 171. The area of ​​the portion of the first region 161 covered by the first adhesive tape 171 is S1. The area S1 can satisfy: 0.1 mm. 2 ≤S1≤500mm 2 Alternatively, S1 can be 5mm. 2 40mm 2 60mm 2 120mm 2 150mm 2 250mm 2 300mm 2 400mm 2 450mm 2 According to the above implementation method, the risk of short circuit between the positive and negative electrodes after the metal burrs at the positive electrode tab puncture the separator can be reduced, ensuring the safety performance of the battery. In addition, after the electrode assembly 10 is hot-pressed, the first adhesive tape 171 covering the first recess 16 will be embedded in the first recess 16, thereby increasing the bonding strength between the positive electrode 11 and the negative electrode 12, while improving space utilization, and thus increasing the volumetric energy density.

[0081] It should be noted that the first tape 171 should cover the positive electrode as little as possible to ensure the amount of active lithium ions available to the positive electrode and to guarantee the battery capacity.

[0082] refer to Figure 9A The negative electrode active layer 122 may have a receiving recess, which can be implemented as a receiving recess 123. The orthogonal projection of the positive electrode tab 19a of the positive electrode 11 onto the negative electrode 12 can fall into the receiving recess 123, and the orthogonal projection of the first region 161 onto the negative electrode 12 can fall outside the receiving recess 123. In this way, when the electrode assembly 10 is pressed in the width direction, the negative electrode active layer 122 can support the first positive electrode active layer 151, preventing the paste on the first positive electrode active layer 151 from falling off, thereby affecting the adhesion of the first adhesive tape 171 of the electrode tab.

[0083] The electrode assembly 10 may also include a second adhesive tape 172 adhered to the negative electrode 12 to further reduce the risk of short circuit between the positive and negative electrodes after a metal burr punctures the separator 13, thus ensuring the safety performance of the battery.

[0084] As one implementation method, refer to Figure 9A The second tape 172 can be completely located within the receiving recess 123. In this way, the orthogonal projection of the second tape 172 onto the positive electrode 11 will not cover the first region 161, thus preventing additional capacity loss.

[0085] As one possible implementation, refer to Figure 9B The second adhesive tape 172 may also be partially located outside the receiving recess 123. In this case, the orthographic projection of the portion of the second adhesive tape 172 outside the receiving recess 123 onto the positive electrode 11 partially overlaps with the first region 161, having an overlap area S2. The overlap area S2 ranges from 0.1 mm. 2 ≤S2≤500mm 2 Alternatively, S2 can be 5mm. 2 40mm 2 60mm 2 120mm 2 150mm 2 250mm 2 300mm 2 400mm 2 450mm 2 Within this range, the second tape 172 will not cause excessive energy loss, and the presence of the receiving recess 123 can compensate for the energy loss caused by the positive electrode tab 19a.

[0086] Back Figure 5 At least one region may further include a third region 163 disposed on the first positive electrode active layer 151 and a fourth region 164 disposed on the second positive electrode active layer 152. The third region 163 may extend along the length direction of the positive electrode 11, and the third region 163 may be close to the edge 112 of the second electrode, that is, the third region 163 is closer to the edge 112 of the second electrode than the edge 111 of the first electrode. The fourth region 164 may extend along the length direction of the positive electrode 11, and the fourth region 164 may be close to the edge 112 of the second electrode, that is, the fourth region 164 is closer to the edge 112 of the second electrode than the edge 111 of the first electrode. The plurality of recesses 16 may also include at least one third recess and at least one fourth recess, wherein at least one third recess is located in a third region and at least one fourth recess is located in a fourth region. Since the regions near the first electrode edge 111 and the second electrode edge 112 are provided with recesses 16, and the recesses 16 can store a portion of the electrolyte, this can increase the residual electrolyte amount of the battery (i.e., the amount of electrolyte in the final battery), improve the cycle performance of the battery, and at the same time help lithium ion migration, making it less likely to accumulate on the surface of the negative electrode, thereby reducing the risk of lithium plating.

[0087] refer to Figure 9C and Figure 11The electrode assembly 10 may further include a third adhesive tape 173 adhered to the positive electrode 11. The orthographic projection of the negative electrode tab 19b of the negative electrode 12 onto the positive electrode 11 falls on a corresponding region extending along the length of the positive electrode 11. This corresponding region may be one of a first region 161, a second region 162, a third region 163, and a fourth region 164. The third adhesive tape 173 may be positioned between the positive electrode 11 and the negative electrode tab 19b, with the orthographic projection of the third adhesive tape 173 onto the positive electrode 11 overlapping with the orthographic projection of the negative electrode tab 19b onto the positive electrode 11, and the overlapping portion covering a portion of the corresponding receiving recess 123. This prevents the metal burrs of the negative electrode tab 19b from piercing the separator 13 and directly short-circuiting with the positive electrode 11, thus affecting the safety performance of the battery. Furthermore, since the third tape 173 covers a portion of the first recess 16 on the first positive electrode active layer 151, after the electrode assembly 10 is hot-pressed, a portion of the third tape 173 will be embedded in the first recess 16, thereby increasing the bonding strength, improving space utilization and volumetric energy density.

[0088] Continue to refer to Figure 9C and Figure 11 The third adhesive tape 173 may have a first tape edge 173a and a second tape edge 173b along the width direction of the positive electrode sheet 11. The first tape edge 173a may extend outward beyond the positive electrode sheet 11 in the width direction, and the second tape edge 173b may extend inward beyond the edge of the corresponding area in the width direction of the positive electrode sheet 11. The second tape edge 173b and the edge of the corresponding area have a distance D6. The value of the distance D6 may satisfy: D6≤20mm, preferably, D6≤5mm. Alternatively, D6 may be 18mm, 16mm, 14mm, 12mm, 10mm, 8mm, 6mm, 4mm, 2mm, or 1mm. In this way, the third adhesive tape 173 can cover the positive electrode sheet 11 as little as possible, ensuring the amount of active lithium ions that the positive electrode sheet 11 can utilize, and ensuring the battery capacity.

[0089] It should be noted that the spacing D6 is the shortest distance between the edge 173b of the second tape and the edge of the corresponding area.

[0090] refer to Figure 5 and Figure 12The positive electrode 11 may further include an arcuate segment located in the bend 181, and at least one region further includes a fifth region 165, which is at least partially located within the arcuate segment. The plurality of recesses 16 may also include at least one fifth recess located within the fifth region. In the arcuate segment, the active material located inside the positive electrode 11 is compressed, resulting in a concentration of active lithium. According to the implementation provided by this embodiment, perforating the arcuate segment of the positive electrode 11 can prevent the accumulation of active lithium ions in the arcuate segment, thereby reducing the risk of lithium plating. Furthermore, due to the presence of the fifth region 165, the stress inside the positive electrode 11 can be released during winding, preventing excessive stress concentration that could cause powder shedding and thus localized short circuits.

[0091] refer to Figure 12 Along the length of the positive electrode 11, two straight segments (the portions located in the flat portion 182) of the positive electrode 11 are respectively connected to the two ends of the arc segment (the portion located in the curved portion 181). The two edges of the fifth region 165 along the length of the positive electrode 11 are located in the two straight segments, that is, in the flat portion 182. The fifth region 165 on each arc segment is at least partially located in the straight segment 182, and the closer the arc segment is to the outer ring, the less the portion of the fifth region 165 on it is located in the straight segment 182. In this way, the amount of active lithium near the inner ring is less than the number of lithium intercalation sites provided by the negative electrode, thereby reducing the risk of lithium plating.

[0092] In some examples, reference Figure 13 The holes 16 in the same region can be arranged non-linearly, meaning that the holes 16 are neither in rows nor columns along the width and length directions of the positive electrode 11, i.e., they are not arranged in a straight line. Reducing the requirements for the arrangement of the holes 16 can improve the process yield and avoid resource waste. At the same time, by misaligning the holes 16, the capillary effect between different rows and columns of holes 16 can be increased, thereby increasing the wettability of the electrolyte to the positive electrode 11. This is beneficial to the uniformity of lithium-ion transport rate and avoids the local accumulation of large amounts of lithium ions that cause lithium plating.

[0093] It should be noted that the spacing between adjacent rows or columns should not be too large, as this will weaken the capillary effect. As an example, the misalignment distance can be less than 300 μm.

[0094] refer to Figure 14The region extending along the length of the positive electrode 11, namely any one of the first region 161, the second region 162, the third region 163, and the fourth region 164, is divided into at least two segments arranged along the length of the positive electrode 11 by at least one first splicing region 166. The region extending along the width of the positive electrode 11, namely the fifth region 165, is divided into at least two segments arranged along the width of the positive electrode 11 by at least one second splicing region 167. The regions extending along the length of the positive electrode 11 and the regions extending along the width of the positive electrode 11 are separated by a third splicing region 168. By way of example only, the first splicing region 166 may have a dimension W3 along the length of the positive electrode 11, the second splicing region may have a dimension W4 along the width of the positive electrode 11, and the third splicing region may have a dimension W5 along the width of the positive electrode 11, where 0.1 mm ≤ W3 ≤ 10 mm, 0 mm ≤ W4 ≤ 10 mm, and 0 mm ≤ W5 ≤ 10 mm. Preferably, 0.1mm ≤ W3 ≤ 3mm, 0mm ≤ W4 ≤ 3mm, and 0mm ≤ W5 ≤ 3mm. Alternatively, W3 can be 0.5mm, 1mm, 3mm, 5mm, 7mm, or 10mm; W4 can be 0.5mm, 1mm, 3mm, 5mm, 7mm, or 10mm; and W5 can be 0.5mm, 1mm, 3mm, 5mm, 7mm, or 10mm. After winding, the paste on the outer side of the arc segment in the negative electrode 12 is stretched, making the paste layer thickness lower than the inner side, while the paste on the inner side of the arc segment in the positive electrode 11 is compressed, causing active lithium ions to accumulate. According to the implementation method provided by this utility model embodiment, drilling holes in the arc segment of the positive electrode 11 can prevent the accumulation of active lithium ions, thus reducing the risk of lithium plating. Furthermore, due to the existence of the splicing area, the stress on the inner side of the positive electrode 11 can be released during winding, preventing excessive stress concentration that could cause powder shedding and thus local short circuits.

[0095] refer to Figure 15 The negative electrode active layer 122 may have a plurality of grooves 124 arranged at intervals. For example, the plurality of grooves 124 may extend along the length direction of the negative electrode sheet 12 and be spaced apart in the width direction of the negative electrode sheet 12. Alternatively, the plurality of grooves 124 may extend along the width direction of the negative electrode sheet 12 and be spaced apart in the length direction of the negative electrode sheet 12. By providing a plurality of grooves 124 on the negative electrode active layer 122, the content of residual electrolyte can be increased, thereby increasing the long-cycle performance of the battery 100.

[0096] refer to Figure 15 and Figure 16For example, each groove 124 can have a groove depth H3, and adjacent grooves 124 can have a spacing D7. The groove depth H3 can range from 5μm to 30μm. The spacing D7 can range from 0.5mm to 5mm, preferably 0.5mm to 1.5mm. Alternatively, D7 can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm, where H3 is the groove depth of the multiple grooves 124 and D7 is the groove spacing of the multiple grooves 124. By satisfying the above-mentioned groove depth H3 and spacing D7, it is possible to ensure that lithium ions can be transported quickly, while ensuring the number of lithium insertion sites on the negative electrode 12 and avoiding lithium plating.

[0097] In some possible examples, the material of the positive electrode active layer may include one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium titanate, ternary materials (lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide), lithium manganese iron phosphate, and lithium-rich manganese-based materials. The material of the negative electrode active layer includes one or more of graphite and silicon-based materials. Graphite may include one or more of artificial graphite and natural graphite. Silicon-based materials may include one or more of silicon-carbon, silicon-oxygen, elemental silicon, and silicon alloys. When the material of the negative electrode active layer contains silicon, the silicon content may be 3–30 wt%. Doping with silicon can increase the number of active sites on the negative electrode that can intercalate lithium ions, thereby increasing battery capacity. Simultaneously, by incorporating a recessed portion in the positive electrode, the lithium plating problem caused by the silicon negative electrode can be reduced.

[0098] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0099] Example 1

[0100] (1) Preparation of positive electrode sheet

[0101] Lithium cobalt oxide powder, polyvinylidene fluoride, acetylene black, and carbon nanotubes were added to a vacuum mixer in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a uniform and fluid positive electrode slurry with a solid content of 55 wt% was formed. The positive electrode slurry was uniformly coated onto a 12 μm thick carbon-coated aluminum foil with a single-sided surface density of 11 mg / cm2. After drying, the active material thickness was controlled to 70 μm after rolling, slitting, scraping, and laser drilling to obtain the positive electrode sheet.

[0102] (2) Preparation of negative electrode sheet

[0103] The negative electrode materials (graphite, silicon carbide), styrene-butadiene rubber, sodium carboxymethyl cellulose, and acetylene black were added to a vacuum mixer in a mass ratio of 96.5:1:1:1.5. Deionized water was added, and the mixture was thoroughly mixed under vacuum to form a uniform, free-flowing negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was then uniformly coated onto a 6 μm thick copper foil with a single-sided surface density of 5 mg / cm². 2 After drying, rolling, controlling the thickness of the active material to 35μm, slitting, and laser cleaning, the negative electrode sheet is obtained, with a silicon-based material content of 3.03wt%.

[0104] (3) Preparation of electrolyte

[0105] In an argon-filled glove box with a water content of <0.1ppm and an oxygen content of <0.1ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and ethyl propionate (EP) are mixed uniformly at a mass ratio of 2:9:9. Fully dried lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI) are added and stirred to dissolve. Based on the total mass of the electrolyte, the mass percentages of LiPF6 and LiFSI are 6.5% and 10%, respectively. 2.5% of ethylene carbonate (VC) based on the total mass of the electrolyte is added, along with 0.5% of ethylene sulfite (ES), 0.5% of thiophene, and 0.5% of ethylene sulfate (DTD) based on the total mass of the electrolyte. Finally, 1.0% of lithium difluorophosphate (LiPO2F2) based on the total mass of the electrolyte is added. The mixture is stirred until homogeneous, and after passing physical property testing, the electrolyte is obtained.

[0106] (4) Battery fabrication

[0107] The positive electrode obtained in step (2), the negative electrode obtained in step (3), and the separator (PP) are wound together to obtain a bare cell; the bare cell is welded with tabs and placed in the battery casing; the electrolyte prepared in step (3) is injected into the dried and qualified cell; and the battery is obtained through processes such as standing, aging, formation, venting, aging, and sorting.

[0108] The first region extends along the length of the positive electrode 11 and has a spacing D1 of 0.79 mm between it and the tab groove. The transition area between the orthographic projection of each second groove edge onto the first positive electrode active layer and the first groove edge located on the same side of the tab groove has a dimension D2 of 0.51 mm along the length of the positive electrode 11, and the ratio D1 / D2 is 1.549. The spacing D3 between the second region of the second positive electrode active layer and the exposed groove is 0.28 mm. The distance D4 from the first region to the edge of the active layer of the first positive electrode active layer is 2.63 mm. The dimension W1 of the positive electrode in its width direction is 63 mm. The dimension W2 of the first region in the width direction of the positive electrode is 7.89 mm, and the ratio W2 / W1 is 1 / 8. The depth H1 of the first recess is 15.1 μm, and the distribution density τ1 of the recesses is 65 recesses / mm. 2 The solder joint depth H2 is 279 μm, the H2 / H1 ratio is 18.48, and the solder joint density τ2 is 31 joints / mm. 2 The area S1 of the first region covered by the first tape is 249.76 mm². 2 The overlapping area S2 of the portion of the second tape located outside the receiving recess on the positive electrode sheet with the first region is 250.78 mm². 2 The distance D6 between the edge of the second tape and its corresponding area on the positive electrode sheet is 3.4 mm. The dimension W3 of the splicing area between the first areas along the length direction of the positive electrode sheet 11 is 0.17 mm. The dimension W4 of the second splicing area between the fifth areas along the width direction of the positive electrode sheet 11 is 0.17 mm. The dimension W5 of the third splicing area between the first and fifth areas along the width direction of the positive electrode sheet 11 is 0.17 mm. The trench depth H3 of the groove on the negative electrode active layer is 5.3 μm, and the trench spacing D7 is 0.5 mm.

[0109] (5) Test the battery

[0110] (i) Short-term anatomy

[0111] The battery is subjected to charge-discharge cycles using a battery cycle tester. The specific steps are as follows:

[0112] ① Let stand for 10 minutes;

[0113] ② Discharge at 0.2C to 3V, then let stand for 10 minutes;

[0114] ③ Fully charge at 1C, stop at 0.05C, and let stand for 10 minutes;

[0115] ④ Discharge at 1C to 3V and let stand for 10 minutes;

[0116] ⑤ Repeat steps ③ and ④ 20 times;

[0117] ⑥ Fully charged at 1C, until the cutoff current is 0.05C.

[0118] After completing the above charge-discharge cycles, dissect the battery. If the surface of the negative electrode is golden yellow, without black spots or obvious color unevenness, it indicates that lithium has not been deposited. If there are obvious black spots on the surface of the negative electrode, it indicates that lithium has been deposited.

[0119] (ii) Battery capacity test

[0120] The battery is charged and discharged using a battery capacity tester (charged and discharged at 0.2C with a cutoff voltage of 4.4V). The final result of the test is the battery capacity obtained by the instrument.

[0121] (iii) Welding tensile test

[0122] The welding tensile strength test of the electrode tabs and electrode sheets was performed using a universal mechanical testing machine. The specific steps are as follows:

[0123] ① Remove the welded positive electrode sheet without protective adhesive at the welding station, cut the positive electrode sheet with ceramic scissors, and cut the sample into a square with a width greater than 24mm, and keep the positive electrode tab intact in the sample;

[0124] ② On the side where the positive electrode tab has not been welded, attach 24±1mm transparent tape to the position where the projection of the positive electrode tab is located. The tape width is 24±1mm. Align the tape with the positive electrode tab on the side away from the edge of the positive electrode plate to prevent the positive electrode plate from being pulled off before the solder joint on the positive electrode tab groove during the test.

[0125] ③ Set the instrument's lifting speed to 400 mm / min;

[0126] ④ The universal testing machine's fixing frame clamps one end of the exposed positive electrode tab and the other end onto the positive electrode plate to ensure that the sample surface is flat;

[0127] ⑤ Begin the test. Stop once the positive electrode tab and positive electrode plate are completely separated. The maximum tensile force displayed is the welding tensile force. If the tensile force test result is: welding tensile force ≥ 15N, the battery is qualified.

[0128] Examples 1-2

[0129] The difference from Embodiment 1-1 is that the first region extends along the length of the positive electrode 11 and the distance D1 between it and the tab groove is 3.98 mm; the dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode 11 is 1.45 mm, and the D1 / D2 ratio is 2.745; the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 2.53 mm; the dimension W3 of the splicing area between the first regions along the length direction of the positive electrode 11 is 1.45 mm; the dimension W4 of the second splicing area between the fifth regions along the width direction of the positive electrode 11 is 1.45 mm; and the dimension W5 of the third splicing area between the first and fifth regions along the width direction of the positive electrode 11 is 1.45 mm. The groove depth H3 of the groove on the negative electrode active layer is 16.4 μm, and the groove spacing D7 is 2.6 mm. The content of silicon-based material is 9.67 wt%.

[0130] Examples 1-3

[0131] The difference from Embodiment 1-1 is that the first region extends along the length of the positive electrode 11 and the distance D1 between it and the tab groove is 7.47 mm; the dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode 11 is 2.50 mm, and D1 / D2 is 2.988; the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 4.97 mm; the dimension W3 of the splicing area between the first regions along the length direction of the positive electrode 11 is 2.98 mm; the dimension W4 of the second splicing area between the fifth regions along the width direction of the positive electrode 11 is 2.98 mm; and the dimension W5 of the third splicing area between the first and fifth regions along the width direction of the positive electrode 11 is 2.98 mm. The groove depth H3 of the groove on the negative electrode active layer is 29.7 μm, and the groove spacing D7 is 4.9 mm. The content of silicon-based material is 29.95 wt%.

[0132] Examples 1-4

[0133] The difference from Embodiment 1-1 is that the first region extends along the length of the positive electrode 11 and the distance D1 between it and the tab groove is 14.97 mm; the dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode 11 is 4.99 mm, and D1 / D2 is 3.0; the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 9.97 mm; the dimension W3 of the splicing area between the first regions along the length direction of the positive electrode 11 is 9.97 mm; the dimension W4 of the second splicing area between the fifth regions along the width direction of the positive electrode 11 is 9.97 mm; and the dimension W5 of the third splicing area between the first and fifth regions along the width direction of the positive electrode 11 is 9.97 mm. The groove depth H3 of the groove on the negative electrode active layer is 7.8 μm, and the groove spacing D7 is 1.1 mm. The content of silicon-based material is 17.89 wt%.

[0134] Examples 1-5

[0135] The difference from Embodiment 1-1 is that the first region extends along the length of the positive electrode 11 and the distance D1 between it and the tab groove is 12.86 mm; the dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode 11 is 2.89 mm, and D1 / D2 is 4.45; the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 9.97 mm; the dimension W3 of the splicing area between the first regions along the length direction of the positive electrode 11 is 19.78 mm; the dimension W4 of the second splicing area between the fifth regions along the width direction of the positive electrode 11 is 19.78 mm; and the dimension W5 of the third splicing area between the first and fifth regions along the width direction of the positive electrode 11 is 19.78 mm. The groove depth H3 of the groove on the negative electrode active layer is 24.6 μm, and the groove spacing D7 is 4.1 mm. The content of silicon-based material is 24.46 wt%.

[0136] Example 2-1

[0137] The difference from Embodiments 1-2 is that the first region extends along the length direction of the positive electrode 11 and the distance D1 between it and the tab groove is 0.33 mm. The dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode 11 is 0.15 mm, D1 / D2 is 2.2, and the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 0.18 mm.

[0138] Example 3-1

[0139] The difference from Embodiments 1-2 is that the dimension D2 of the transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove in the length direction of the positive electrode sheet 11 is 0.41 mm, D1 / D2 is 9.707, and the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 3.57 mm.

[0140] Example 3-2

[0141] The difference from Examples 1-2 is that D2 is 6.97 mm, D1 / D2 is 2.148, and the distance D3 between the second region of the second positive electrode active layer and the exposed groove is 8.0 mm.

[0142] Example 4-1

[0143] The difference from Examples 1-2 is that D4 is 0.01 mm.

[0144] Example 4-2

[0145] The difference from Examples 1-2 is that D4 is 0.17 mm.

[0146] Example 4-3

[0147] The difference from Examples 1-2 is that D4 is 4.98 mm.

[0148] Example 4-4

[0149] The difference from Examples 1-2 is that D4 is 7.15 mm.

[0150] Examples 4-5

[0151] The difference from Examples 1-2 is that D4 is 9.83 mm.

[0152] Examples 4-6

[0153] The difference from Examples 1-2 is that D4 is 11.07 mm.

[0154] Example 5-1

[0155] The difference from Examples 1-2 is that W2 is 1.83 mm and W2 / W1 is 2 / 69.

[0156] Example 5-2

[0157] The difference from Examples 1-2 is that W2 is 2.12 mm and W2 / W1 is 3 / 89.

[0158] Example 5-3

[0159] The difference from Examples 1-2 is that W2 is 19.97 mm and W2 / W1 is 13 / 41.

[0160] Example 5-4

[0161] The difference from Examples 1-2 is that W2 is 21.06 mm and W2 / W1 is 1 / 3.

[0162] Example 6-1

[0163] The difference from Examples 1-2 is that H1 is 4.67 μm.

[0164] Example 6-2

[0165] The difference from Examples 1-2 is that H1 is 5.01 μm.

[0166] Example 6-3

[0167] The difference from Examples 1-2 is that H1 is 29.6 μm.

[0168] Example 6-4

[0169] The difference from Examples 1-2 is that H1 is 31.4 μm.

[0170] Example 7-1

[0171] The difference from Examples 1-2 is that H2 is 27.5 μm.

[0172] Example 7-2

[0173] The difference from Examples 1-2 is that H2 is 30.4 μm.

[0174] Example 7-3

[0175] The difference from Examples 1-2 is that H2 is 150 μm.

[0176] Example 7-4

[0177] The difference from Examples 1-2 is that H2 is 499.6 μm.

[0178] Example 7-5

[0179] The difference from Examples 1-2 is that H2 is 510.7 μm.

[0180] Example 8-1

[0181] The difference from Examples 1-2 is that τ1 is 8 per mm. 2 .

[0182] Example 8-2

[0183] The difference from Examples 1-2 is that τ1 is 10 pieces / mm. 2 .

[0184] Example 8-3

[0185] The difference from Examples 1-2 is that τ1 is 119 pieces / mm. 2 .

[0186] Example 8-4

[0187] The difference from Examples 1-2 is that τ1 is 134 pieces / mm. 2 .

[0188] Example 9-1

[0189] The difference from Examples 1-2 is that τ2 is 3 per mm. 2 .

[0190] Example 9-2

[0191] The difference from Examples 1-2 is that τ2 is 5 per mm. 2 .

[0192] Example 9-3

[0193] The difference from Examples 1-2 is that τ2 is 63 pieces / mm. 2 .

[0194] Example 9-4

[0195] The difference from Examples 1-2 is that τ2 is 71 pieces / mm. 2 .

[0196] Example 10-1

[0197] The difference from Examples 1-2 is that D5 is 98.1 μm.

[0198] Example 10-2

[0199] The difference from Examples 1-2 is that D5 is 101.3 μm.

[0200] Example 10-3

[0201] The difference from Examples 1-2 is that D5 is 299.7 μm.

[0202] Example 10-4

[0203] The difference from Examples 1-2 is that D5 is 320.4 μm.

[0204] Example 11-1

[0205] The difference from Examples 1-2 is that S1 is 499.84 mm. 2 .

[0206] Example 11-2

[0207] The difference from Examples 1-2 is that S1 is 510.7 mm. 2 .

[0208] Examples 11-3

[0209] The difference from Examples 1-2 is that S1 is 0.01 mm. 2 .

[0210] Example 12-1

[0211] The difference from Examples 1-2 is that S2 is 0.03 mm. 2 .

[0212] Example 12-2

[0213] The difference from Examples 1-2 is that S2 is 499.65 mm. 2 .

[0214] Example 12-3

[0215] The difference from Examples 1-2 is that S2 is 520.11 mm. 2 .

[0216] Example 13-1

[0217] The difference from Examples 1-2 is that D6 is 4.97 mm.

[0218] Example 13-2

[0219] The difference from Examples 1-2 is that D6 is 9.89 mm.

[0220] Example 13-3

[0221] The difference from Examples 1-2 is that D6 is 19.69 mm.

[0222] Examples 13-4

[0223] The difference from Examples 1-2 is that D6 is 23.11 mm.

[0224] Comparative Example 1

[0225] The difference from Embodiments 1-2 is that the first recess is not provided.

[0226] Comparative Example 2

[0227] The difference from Examples 1-2 is that D1 is 0.03mm, D2 is 0.01mm, D1 / D2 is 3, and D3 is 0.02mm.

[0228] Table 1 shows the test results of the electrode assemblies in the embodiments.

[0229]

[0230]

[0231] It should be noted that before conducting short-term dissection and battery capacity testing, it is necessary to ensure that the batteries involved in the test are qualified batteries. If the batteries involved in the test do not meet this condition, short-term dissection and battery capacity testing will not be conducted, which will be reflected in Table 1 as no data, indicated by " / ".

[0232] The following examples provide specific details: In Example 2-1, the battery's tab groove area is prone to cracking, therefore the battery is defective; in Example 4-1, the positive electrode sheet is severely broken, therefore the battery is defective; in Example 7-1, the battery's welding tensile strength test result is unqualified, therefore the battery is defective; in Example 7-5, the tab is broken during welding, therefore the battery is defective; in Example 9-1, the battery's welding tensile strength test result is unqualified, therefore the battery is defective; in Example 9-4, the tab is broken during welding, therefore the battery is defective; in Example 11-3, the adhesive on some of the battery cells' tabs falls off; in Example 12-1, the battery cell experiences a short circuit, therefore the battery is defective; in Comparative Example 2, the battery's welding tensile strength test result is unqualified, therefore the battery is defective.

[0233] It should be understood that the term "comprising" and its variations used in the embodiments of this utility model are open-ended, meaning "including but not limited to". The term "according to" means "at least in part according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least another embodiment". The term "a plurality of" means "more than one", which implies covering two, three or more cases.

[0234] It should be understood that although terms such as "first" or "second" may be used in embodiments of the present invention to describe various elements, such as the first positive electrode active layer and the second positive electrode active layer, these elements are not defined by these terms, which are only used to distinguish one element from another.

[0235] The protection scope of this utility model embodiment is not limited to the above embodiments. Any variations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in this utility model embodiment should be included within the protection scope of this utility model embodiment. Therefore, the protection scope of this utility model embodiment should be determined by the protection scope of the claims.

Claims

1. An electrode assembly, characterized in that, The device includes a positive electrode sheet, a separator, and a negative electrode sheet stacked and wound together. The positive electrode sheet includes a positive current collector and a positive active layer. The positive active layer includes a first positive active layer and a second positive active layer disposed on opposite sides of the thickness direction of the positive current collector. The first positive active layer has a tab groove and at least one first recess. The at least one first recess is distributed in a first region of the first positive active layer. A positive tab is disposed in the tab groove and is electrically connected to the positive current collector. The positive electrode sheet has a first electrode edge and a second electrode edge in its width direction. The tab groove, the first region, and the first electrode edge are arranged on the same side in the width direction of the positive electrode sheet. The first region extends along the length direction of the positive electrode sheet and has a distance D1 between it and the tab groove, where D1 ≥ 0.2 mm.

2. The electrode assembly according to claim 1, characterized in that, The second positive electrode active layer is provided with an exposure groove and at least one second recess. The at least one second recess is distributed in a second region of the second positive electrode active layer. The exposure groove, the second region, and the edge of the first electrode sheet are arranged on the same side in the width direction of the positive electrode sheet. The tab groove has two first groove edges in the length direction of the positive electrode sheet. The exposure groove has two second groove edges in the length direction of the positive electrode sheet. The orthographic projections of the two second groove edges on the first positive electrode active layer are respectively located outside the two first groove edges. There is a transition area between the orthographic projection of each second groove edge on the first positive electrode active layer and the first groove edge located on the same side of the tab groove.

3. The electrode assembly according to claim 2, characterized in that, The transition region has a dimension D2 along the length of the positive electrode, wherein D1 ≥ D2.

4. The electrode assembly according to claim 3, characterized in that, 1.1≤D1 / D2≤10.

5. The electrode assembly according to claim 3 or 4, characterized in that, There is a distance D3 between the second region and the exposed groove, where 0.5 mm ≤ D1 ≤ 15 mm, 0.5 mm ≤ D2 ≤ 5 mm, and 0.2 mm ≤ D3 ≤ 10 mm.

6. The electrode assembly according to claim 2, characterized in that, The first groove edge of the tab groove located on the first side of the positive electrode sheet along the length direction has a distance D11 from the first region, and the first groove edge of the tab groove located on the second side of the positive electrode sheet along the length direction has a distance D12 from the first region, |D11-D12|≤10; and / or The second groove edge located on the first side of the exposed groove in the length direction of the positive electrode sheet has a distance D31 with the second region, and the second groove edge located on the second side of the exposed groove in the length direction of the positive electrode sheet has a distance D32 with the second region, |D31-D32|≤10.

7. The electrode assembly according to claim 1, characterized in that: 1 / 35≤W2 / W1≤1 / 2; and / or 2 mm ≤ W2 ≤ 20 mm; and / or 0.1 mm ≤ D4 ≤ 10 mm, Wherein, W1 is the dimension of the positive electrode in its width direction, W2 is the dimension of the first region in the width direction of the positive electrode, and D4 is the distance from the first region to the edge of the active layer of the first positive electrode active layer, wherein the edge of the active layer is closer to the edge of the first electrode than the edge of the second electrode.

8. The electrode assembly according to claim 7, characterized in that, The positive electrode tab is welded to the positive electrode current collector and has multiple solder joints. The at least one first recess includes multiple first recesses, and the multiple solder joints and the multiple first recesses satisfy the following: 5 μm ≤ H1 ≤ 30 μm; and / or 30 μm≤H2≤500 μm; and / or 1≤H2 / H1≤100; and / or 100 μm≤D5≤300 μm; and / or τ1≥τ2; and / or 9 pieces / mm 2 ≤τ1≤120 pieces / mm 2 ; and / or 4 pieces / mm 2 ≤τ2≤64 pieces / mm 2 ; Wherein, H1 is the depth of the plurality of first recesses, H2 is the depth of the plurality of solder joints, D5 is the spacing between the plurality of first recesses, τ1 is the distribution density of the plurality of first recesses, and τ2 is the distribution density of the plurality of solder joints.

9. The electrode assembly according to claim 8, characterized in that, It also includes a first adhesive tape, which covers the positive electrode tab and a portion of the first region, wherein the area of ​​the portion of the first region covered by the first adhesive tape is S1, 0.1 mm. 2 ≤S1≤500 mm 2 .

10. The electrode assembly according to claim 9, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer. The negative electrode active layer contains a receiving recess. The orthographic projection of the positive electrode tab on the negative electrode sheet at least partially coincides with the receiving recess. The orthogonal projection of the first region onto the negative electrode sheet is located outside the receiving recess.

11. The electrode assembly according to claim 10, characterized in that, The negative electrode sheet further includes a second adhesive tape, wherein... The second tape is located within the receiving recess; or The second tape is partially located outside the receiving recess. The orthographic projection of the portion of the second tape outside the receiving recess onto the positive electrode partially overlaps with the first region, and the overlap area is S2, 0.1 mm. 2 ≤S2≤500 mm 2 .

12. The electrode assembly according to claim 1, characterized in that, The positive electrode sheet also includes a third adhesive tape. The orthogonal projection of the negative electrode tab of the negative electrode sheet onto the positive electrode sheet falls on a first region. The third adhesive tape is disposed on the positive electrode sheet at a position corresponding to the negative electrode tab. The orthogonal projection of the third adhesive tape onto the positive electrode sheet overlaps with the orthogonal projection of the negative electrode tab onto the positive electrode sheet, and the overlapping portion covers a part of the first region.

13. The electrode assembly according to claim 12, characterized in that, The third tape has a first tape edge and a second tape edge along the width direction of the positive electrode sheet. The first tape edge extends outward beyond the positive electrode sheet in the width direction of the positive electrode sheet, and the second tape edge extends inward beyond the corresponding area in the width direction of the positive electrode sheet. The second tape edge and the corresponding area have a distance D6, where D6 ≤ 20 mm.

14. The electrode assembly according to claim 1, characterized in that... ； The first positive electrode active layer further comprises a third region, wherein the third region has at least one third recess, the third region extends along the length direction of the positive electrode sheet, and the third region is closer to the edge of the second electrode sheet than the edge of the first electrode sheet; and / or The second positive electrode active layer is further provided with a fourth region, the fourth region having at least one third recess, the fourth region extending along the length direction of the positive electrode sheet, and the fourth region being closer to the edge of the second electrode sheet than the edge of the first electrode sheet.

15. The electrode assembly according to claim 1, characterized in that, The electrode assembly has a flat portion and a curved portion, the positive electrode sheet includes an arc segment located in the curved portion, the positive electrode active layer has a fifth region, the fifth region has at least one fifth recess, and the fifth region is at least partially located in the arc segment.

16. The electrode assembly according to claim 15, characterized in that, The positive electrode sheet also includes a straight section located in the flat portion, and two straight sections along the length direction of the positive electrode sheet are respectively connected to the two ends of the arc segment. The two edges of the fifth region along the length direction of the positive electrode sheet are respectively located in the two straight sections.

17. The electrode assembly according to claim 15, characterized in that: The first region is divided into at least two segments arranged along the length of the positive electrode by at least one first splicing region; and / or The fifth region is divided into at least two segments arranged along the width direction of the positive electrode by at least one second splicing region; and / or The first region and the fifth region are separated by a third splicing region.

18. The electrode assembly according to claim 17, characterized in that: The first splicing area has a dimension W3 along the length direction of the positive electrode sheet, where 0.1 mm ≤ W3 ≤ 20 mm; and / or The second splicing area has a dimension W4 along the width direction of the positive electrode sheet, where 0 mm ≤ W4 ≤ 20 mm; and / or The third splicing area has a dimension W5 along the width direction of the positive electrode sheet, where 0 mm ≤ W5 ≤ 20 mm.

19. The electrode assembly according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer arranged in layers, and the negative electrode active layer has a plurality of slots arranged at intervals.

20. The electrode assembly according to claim 19, characterized in that: 5 μm ≤ H3 ≤ 30 μm; and / or 0.5 mm ≤ D7 ≤ 5 mm Where H3 is the depth of the multiple slots, and D7 is the spacing between the multiple slots.

21. The electrode assembly according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer arranged in layers; the negative electrode active layer includes a negative electrode active material, which includes one of graphite and silicon-based materials.

22. A lithium-ion secondary battery, characterized in that, The battery includes an electrode assembly according to any one of claims 1 to 21.

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