Pole piece structure, laminated battery cell and secondary battery

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a pole piece structure, a laminated battery cell and a secondary battery. The pole piece structure comprises a current collector and an active material layer connected to at least one side surface of the current collector, a central region and an edge region are arranged on the active material layer; the edge area comprises a first subarea and a second subarea which are adjacently arranged; the first subarea is arranged between the edge of the surface of one side of the current collector and the central area; the second subarea is arranged between the edge of the surface of one side of the current collector and the central area; the active material layer is also provided with at least one accommodating structure; the containing structure is arranged in the first subarea and / or the second subarea. According to the utility model, the storage capacity of electrolyte can be increased, and the failure caused by premature lithium separation at the edge of the pole piece in the use process is effectively avoided; therefore, the wettability of the electrolyte and the use stability are improved.

Description

Technical Field

[0001] This utility model belongs to the field of battery technology, and in particular relates to an electrode structure, a stacked cell, and a secondary battery. Background Technology

[0002] Stacked battery technology is considered one of the most promising technologies in the lithium-ion battery field due to its high volume utilization, stable internal structure, high energy density, and high safety. For example, the popular "blade battery" uses stacked technology. Furthermore, incorporating high-capacity silicon-carbon materials into stacked cells can significantly improve fast charging and energy density performance.

[0003] In the current lithium-ion battery stacking manufacturing process, stacked cells are typically composed of two outermost positive single-sided electrodes and several inner positive and negative double-sided electrodes. Due to electron repulsion and tip discharge effects, the negative electrode edge of the stacked cell exhibits excessive polarization, resulting in low lithium-ion concentration in the electrolyte at the edge. This leads to weaker kinetic performance compared to other parts, making it prone to lithium plating during cycling, thus reducing stability. Furthermore, silicon-carbon system cells require a higher electrolyte level during cycling. Current stacked cells may experience electrolyte depletion during cycling, further reducing stability. Utility Model Content

[0004] The purpose of this invention is to provide an electrode structure that addresses the shortcomings of existing technologies and solves the problem of low stability in the use of existing technologies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An electrode structure includes a current collector and an active material layer connected to at least one surface of the current collector; the active material layer has a central region and an edge region; the edge region includes a first partition and a second partition disposed adjacent to each other; the first partition is disposed between the edge of one surface of the current collector and the central region; the second partition is disposed between the edge of one surface of the current collector and the central region; the active material layer further includes at least one receiving structure; the receiving structure is disposed within the first partition and / or the second partition.

[0007] Preferably, multiple receiving structures are provided; and the distance between two adjacent receiving structures is L; L satisfies: 1mm≤L≤10mm.

[0008] Preferably, the receiving structure is a receiving groove; the receiving groove is recessed from the active material layer toward the current collector.

[0009] Preferably, the relationship between the depth h2 of the receiving groove and the thickness h1 of the active material layer satisfies: h2 = h1 * (25% ~ 75%).

[0010] Preferably, there are two first partitions, which are located on both sides of the length direction of the central region; and there are two second partitions, which are located on both sides of the width direction of the central region.

[0011] Preferably, the receiving groove is a first etching groove; the first etching groove is distributed inside the first partition; and the relationship between the total coverage area S2 of all the first etching grooves and the coverage area S1 of the active material layer satisfies: S2 = S1 * (1 / 5 ~ 1 / 2).

[0012] Preferably, the receiving groove is a second etching groove; the second etching groove is distributed inside the second partition; and the relationship between the total coverage area S3 of all the second etching grooves and the coverage area S1 of the active material layer satisfies: S3 = S1 * (1 / 5 ~ 1 / 2).

[0013] Preferably, the receiving groove is a third etching groove and a fourth etching groove; the third etching groove is distributed inside the first partition; the fourth etching groove is distributed inside the second partition; and the relationship between the coverage area of ​​all the third etching grooves and the sum of the coverage areas of all the fourth etching grooves S4, and the coverage area S1 of the active material layer, satisfies: S4 = S1 * (1 / 5 ~ 1 / 2).

[0014] This utility model also discloses a stacked battery cell, including a positive electrode, a negative electrode, and a separator; the separator is disposed between the positive electrode and the negative electrode; and the positive electrode, the separator, and the electrode are stacked sequentially; the positive electrode and / or the negative electrode has the electrode structure described above.

[0015] The projection of the receiving groove on the positive electrode sheet toward the separator film partially overlaps with the projection of the receiving groove on the negative electrode sheet toward the separator film; and in the same thickness direction, the coverage area of ​​the receiving groove on the negative electrode sheet is greater than the coverage area of ​​the receiving groove on the positive electrode sheet.

[0016] This utility model also discloses a secondary battery, including the aforementioned stacked battery cells.

[0017] The beneficial effects of this utility model are that, by adding multiple containment structures in the first and / or second partitions of the edge region, the electrolyte storage capacity of the electrode structure is significantly increased, thereby significantly improving the electrolyte retention capacity of the electrode structure, improving the cycle performance during use, and effectively avoiding failure caused by premature lithium plating at the edge of the electrode during use. Therefore, it improves the wettability of the electrolyte and the stability of use, and is also conducive to improving the long-term cycle performance of silicon-carbon high-rate system cells at both room temperature and high temperature. Attached Figure Description

[0018] The following will refer to the appendix. Figures 1-5 This section describes the features, advantages, and technical effects of exemplary embodiments of the present invention.

[0019] Figure 1 This is a schematic diagram of the electrode structure according to an embodiment of the present invention;

[0020] Figure 2 This is a cross-sectional view of the electrode structure AA section according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the electrode structure of one embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the electrode structure according to another embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the electrode structure of another embodiment of the present invention.

[0024] In the figure: 11-Active material layer; 12-Current collector; 101-Electrode body; 2-Central region; 3-Edge region; 31-First partition; 32-Second partition; 4-Accommodation structure; 41-Accommodation groove; 401-First etching groove; 402-Second etching groove; 403-Third etching groove; 404-Fourth etching groove. Detailed Implementation

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or multiple situations existing alone. In addition, the character " / " in this document generally indicates that the related objects before and after are in an "or" relationship.

[0029] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0030] The following is in conjunction with the appendix Figures 1-5 The present invention will be described in further detail, but this is not intended to limit the scope of the present invention.

[0031] like Figure 1As shown, in one embodiment of this utility model, the electrode structure includes a current collector 12 and an active material layer 11 connected to at least one surface of the current collector 12. The active material layer 11 has a central region 2 and an edge region 3. The edge region 3 includes a first partition 31 and a second partition 32 disposed adjacent to each other. The first partition 31 is disposed between the edge of one surface of the current collector 12 and the central region 2. The second partition 32 is disposed between the edge of one surface of the current collector 12 and the central region 2. The active material layer 11 also has at least one receiving structure 4. The receiving structure 4 is disposed within the first partition 31 and / or the second partition 32. The active material layer 11 has an electrode tab groove. An electrode tab body 101 is disposed within the electrode tab groove and is connected to the current collector 12.

[0032] The technical solution of this utility model significantly increases the electrolyte storage capacity of the electrode structure by adding multiple containment structures in the first and / or second partitions of the edge region. This significantly improves the electrolyte retention capacity of the electrode structure, enhances the cycle performance during use, and effectively prevents failure caused by premature lithium plating at the edge of the electrode during use. Therefore, it improves the wettability of the electrolyte and the stability of use, and also helps to improve the long-term cycle performance of silicon-carbon high-rate system cells at both room temperature and high temperature.

[0033] The active material layer 11 can be a pure graphite system or a silicon-carbon system; it can be formed by single-layer coating or double-layer coating; no specific restrictions are made here.

[0034] Specifically, in some implementations, such as Figure 1 and 2 As shown, multiple receiving structures 4 are provided; and the distance between two adjacent receiving structures 4 is L; L satisfies: 1mm≤L≤10mm; further, 1mm≤L≤3mm; and can be 1mm, 1.5mm, 2mm, 3mm, etc.; preferably 2mm. That is to say, by forming a spacing of 1 to 3mm, this structure can effectively shorten the lithium-ion transport path distance, reduce or minimize the problem of poor dynamic performance of the electrode edge caused by polarization; thereby improving the wettability of the electrolyte and improving the stability of use.

[0035] Specifically, in some implementations, such as Figure 1 and 2As shown, the receiving structure 4 is a receiving groove 41; the receiving groove 41 is recessed from the active material layer 11 toward the current collector 12. That is, the distance between two adjacent receiving grooves 41 is L; L satisfies: 1mm≤L≤10mm; further, 1mm≤L≤3mm. This structure, by adding multiple receiving grooves 41 in the first and / or second partitions of the edge region, can increase the lithium ion concentration in the edge electrolyte; and effectively reduce edge polarization; thereby improving the wettability of the electrolyte and improving the stability of use. The receiving groove 41 can be a long rectangle, a lattice rectangle, a rhombus, or other shapes or combinations thereof; no specific limitation is made here.

[0036] Specifically, in some implementations, such as Figure 1 and 2 As shown, the relationship between the depth h2 of the receiving groove 41 and the thickness h1 of the active material layer 11 satisfies: h2 = h1 * (25% ~ 75%). Specifically, h2 can be h1 * 25%; h2 = h1 * 35%; h2 = h1 * 45%; h2 = h1 * 55%; h2 = h1 * 65%; h2 = h1 * 75%, etc. In other words, a receiving groove 41 of appropriate depth can store as much electrolyte as possible, thereby increasing the electrolyte retention capacity of the battery cell; at the same time, it shortens the electrolyte transport distance, improves the electrolyte wettability, and thus helps to improve the room temperature and high temperature long-cycle performance of the silicon-carbon high-rate system battery cell. Both the thickness direction and the depth direction are along the 0Y axis.

[0037] Specifically, in some implementations, such as Figure 1 and 2 As shown, when the active material layer 11 is the active material layer of the negative electrode, the thickness h1 of the active material layer 11 satisfies: 80μm≤h1≤120μm. Where h1 can be 80μm, 90μm, 100μm, 110μm, 120μm, etc. When the active material layer 11 is the active material layer of the positive electrode, the thickness h1 of the active material layer 11 satisfies: 90μm≤h1≤200μm. Where h1 can be 90μm, 95μm, 100μm, 110μm, 200μm, etc. This structure, with a suitable thickness h1 of the active material layer 11, ensures the normal and stable use of the electrode and guarantees that the receiving groove 41 can store as much electrolyte as possible.

[0038] In some implementation methods, such as Figure 1As shown, there are two first partitions 31, located on both sides of the length of the central region 2; there are two second partitions 32, located on both sides of the width of the central region 2. That is, the first partitions 31 and the second partitions 32 are arranged alternately around the central region 2. The length of the central region 2 corresponds to the 0X axis, and the width of the central region 2 corresponds to the 0Z axis.

[0039] Specifically, in some of its implementations, such as Figure 2 and 3 As shown, the receiving groove 41 is a first etching groove 401; the first etching grooves 401 are distributed inside the first partition 31; and the relationship between the total coverage area S2 of all the first etching grooves 401 and the coverage area S1 of the active material layer 11 satisfies: S2 = S1 * (1 / 5 ~ 1 / 2). This structure, through the relatively large coverage area of ​​the etching region in the width direction, can effectively reduce the edge polarization in the width direction, increase the lithium ion concentration in the electrolyte at the edge in the width direction; and can shorten the lithium ion transport path distance, eliminating the problem of poor dynamic performance at the electrode edge caused by polarization. In addition, the first etching grooves 401 can store electrolyte, improving the electrolyte retention of the cell.

[0040] Specifically, in other implementations, such as Figure 2 and 4 As shown, the receiving groove 41 is a second etching groove 402; the second etching grooves 402 are distributed inside the second partition 32; and the relationship between the total coverage area S3 of all the second etching grooves 402 and the coverage area S1 of the active material layer 11 satisfies: S3 = S1 * (1 / 5 ~ 1 / 2). This structure, through the relatively large coverage area of ​​the etching region in the length direction, can effectively reduce the edge polarization in the width direction and increase the lithium ion concentration in the electrolyte in the length direction; it can also shorten the lithium ion transport path distance in the length direction, eliminating the problem of poor dynamic performance of the electrode edge caused by polarization. In addition, the second etching grooves 402 can store electrolyte, improving the electrolyte retention of the cell.

[0041] Specifically, in some other implementations, such as Figure 2 and 5As shown, the receiving groove 41 comprises a third etching groove 403 and a fourth etching groove 404; the third etching groove 403 is distributed inside the first partition 31; the fourth etching groove 404 is distributed inside the second partition 32; and the relationship between the coverage area of ​​all the third etching grooves 403 and the sum of the coverage areas of all the fourth etching grooves 404, S4, and the coverage area S1 of the active material layer 11, satisfies: S4 = S1 * (1 / 5 ~ 1 / 2). This structure, through the relatively small coverage area of ​​the etching region in the length and width directions, can effectively reduce the edge polarization in the length and width directions, increase the lithium ion concentration in the electrolyte at the edges in the length and width directions; and can shorten the lithium ion transport path distance in the length and width directions, eliminating the problem of poor dynamic performance at the electrode edges caused by polarization. In addition, the third etching groove 403 and the fourth etching groove 404 can store electrolyte, improving the electrolyte retention of the battery cell.

[0042] This utility model also proposes a stacked battery cell, which includes a positive electrode, a negative electrode, and a separator; the separator is disposed between the positive electrode and the negative electrode; and the positive electrode, the separator, and the electrode are stacked sequentially; the positive electrode and / or the negative electrode are electrode structures; the specific structure of the electrode structure is as described in the above embodiments. Since this stacked battery cell adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0043] In some embodiments, the projection of the receiving groove 4 on the positive electrode sheet toward the separator film partially overlaps with the projection of the receiving groove 4 on the negative electrode sheet toward the separator film; and in the same thickness direction, the coverage area of ​​the receiving groove 4 on the negative electrode sheet is greater than the coverage area of ​​the receiving groove 4 on the positive electrode sheet.

[0044] In other words, when the receiving groove 41 is the first etching groove 401; the first etching groove 401 is distributed inside the first partition 31 of the negative electrode sheet (including the second edge and the fourth edge that are arranged opposite to each other); the first etching groove 401 is distributed inside the first partition 31 of the positive electrode sheet (including the sixth edge and the eighth edge that are arranged opposite to each other), the etching area of ​​the first etching groove 401 on the second edge is ≥ the etching area of ​​the first etching groove 401 on the sixth edge; the etching area of ​​the first etching groove 401 on the fourth edge is ≥ the etching area of ​​the first etching groove 401 on the eighth edge.

[0045] When the receiving groove 41 is the second etching groove 402; the second etching groove 402 is distributed inside the second partition 32 (including the first edge and the third edge that are arranged opposite each other); and the first etching groove 401 is distributed inside the second partition 32 of the positive electrode sheet (including the fifth edge and the seventh edge that are arranged opposite each other); the etching area of ​​the second etching groove 401 on the first edge is ≥ the etching area of ​​the first etching groove 401 on the fifth edge; the etching area of ​​the first etching groove 401 on the third edge is ≥ the etching area of ​​the seventh etching groove 401 on the eighth edge.

[0046] When the receiving groove 41 is a third etching groove 403 and a fourth etching groove 404; the third etching groove 403 is distributed inside the first partition 31 (including the second edge and the fourth edge that are arranged opposite each other); the first etching groove 401 is distributed inside the first partition 31 of the positive electrode sheet (including the sixth edge and the eighth edge that are arranged opposite each other); the fourth etching groove 404 is distributed inside the second partition 32 (including the first edge and the third edge that are arranged opposite each other); and the first etching groove 401 is distributed inside the second partition 32 of the positive electrode sheet (including the fifth edge and the seventh edge that are arranged opposite each other); the etching area of ​​the first etching groove 401 on the second edge is ≥ the etching area of ​​the first etching groove 401 on the sixth edge; the etching area of ​​the first etching groove 401 on the fourth edge is ≥ the etching area of ​​the first etching groove 401 on the eighth edge; the etching area of ​​the second etching groove 401 on the first edge is ≥ the etching area of ​​the first etching groove 401 on the fifth edge; and the etching area of ​​the first etching groove 401 on the third edge is ≥ the etching area of ​​the seventh etching groove 401 on the eighth edge.

[0047] The positive electrode includes a positive current collector and a positive active material layer, the latter being coated on the surface of the current collector. The current collector can be made of aluminum, and the active material layer includes a positive active material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode includes a negative current collector and a negative active material layer, the latter being coated on the surface of the current collector. The current collector can be made of copper, and the active material layer includes a negative active material, such as carbon or silicon. The separator is made of, but is not limited to, polyethylene, polypropylene, polyvinylidene fluoride, and their multilayer composite films, one or more of these materials.

[0048] Example 1

[0049] Positive electrode sheet: The active material LiCoO2, conductive agent superconducting carbon, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and uniformly coated onto an aluminum current collector in an N-methylpyrrolidone solvent system at a weight ratio of 97.6:0.6:0.5:1.3. Then, the positive electrode sheet is obtained by cold pressing, slitting, and die cutting.

[0050] Negative electrode sheet: Negative electrode active material, conductive agent, and binder are mixed in a weight ratio of 97.6:1.1:1.3 to prepare a negative electrode active material slurry, which is then coated, cold-pressed, laser-etched, and die-cut to obtain the negative electrode sheet. The negative electrode sheet includes a negative electrode current collector, the surface of which is coated with an active material layer. A central region 2, two first partitions 31, and two second partitions 32 are provided on the first surface of the coating of the negative electrode current collector; and the two first partitions 31 and two second partitions 32 are respectively located around the central region 2.

[0051] Positive electrode sheet: The active material LiCoO2, conductive agent superconducting carbon, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and uniformly coated onto an aluminum current collector in an N-methylpyrrolidone solvent system at a weight ratio of 97.6:0.6:0.5:1.3. The coating is then cold-pressed, slit, laser-etched, and die-cut to obtain the positive electrode sheet. The positive electrode sheet includes a positive current collector, the surface of which is coated with an active material layer. A central region 2, two first partitions 31, and two second partitions 32 are formed on the first surface of the coating of the positive current collector; the two first partitions 31 and two second partitions 32 are located around the central region 2.

[0052] The first to fourth edge coatings of the negative electrode sheet are all provided with etched areas and the central area is not etched, and the fifth to eighth edge coatings of the positive electrode sheet are all provided with etched areas and the central area is not etched. Simultaneously, the total etching area of ​​the coatings at the first, second, third, and fourth edges is 1 / 2 of the surface area of ​​the negative electrode sheet; the total etching area of ​​the coatings at the fifth, sixth, seventh, and eighth edges is 2 / 5 of the surface area of ​​the positive electrode sheet; and the etching area of ​​the first etching groove 401 on the second edge is greater than or equal to the etching area of ​​the first etching groove 401 on the sixth edge; the etching area of ​​the first etching groove 401 on the fourth edge is greater than or equal to the etching area of ​​the first etching groove 401 on the eighth edge; the etching area of ​​the second etching groove 401 on the first edge is greater than or equal to the etching area of ​​the first etching groove 401 on the fifth edge; the etching area of ​​the first etching groove 401 on the third edge is greater than or equal to the etching area of ​​the seventh etching groove 401 on the eighth edge; the etching depth of the etching area on the positive electrode sheet is 50% of the thickness of the positive electrode sheet, and the distance between two adjacent etching areas is 0.2 mm; the etching depth of the etching area on the negative electrode sheet is 50% of the thickness of the negative electrode sheet, and the distance between two adjacent etching areas is 0.2 mm.

[0053] Separator: A ceramic mixture is coated on the PE surface to serve as a separator.

[0054] Electrolyte: Ethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1:1:4:4. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.

[0055] Full cell preparation: The above-mentioned positive electrode, separator and negative electrode are stacked to make a bare cell, which is then packaged and injected with electrolyte to make a finished lithium-ion battery.

[0056] The electrolyte retention coefficient is calculated based on the electrolyte retention amount after the cell is sealed twice / the cell discharge capacity.

[0057] Cycle retention rate is the percentage of the cell's remaining capacity relative to its initial capacity after 800 cycles of a 4.0C step-charged cell to 4.35V and a 2.5C speed-charged cell to 4.55V.

[0058] The lithium plating interface is obtained by disassembling the battery cell after 800 cycles.

[0059] Energy density: Calculated according to the following formula: discharge capacity / (cell width × cell thickness × cell length), unit Wh / L.

[0060] Cyclic expansion rate: The percentage of the cell thickness after 800 cycles of charging the cell from 4.0C to 4.35V in a stepwise manner and charging it from 2.5C to 4.55V. The difference between the cell thickness and the initial half-cell thickness (i.e., the cell thickness at half-cell voltage of 3.9V) is relative to the initial half-cell thickness.

[0061] Example 2

[0062] The difference between Example 2 and Example 1 is that the second and fourth edges on the negative electrode are not etched, and the sixth and eighth edges on the positive electrode are not etched.

[0063] Example 3

[0064] The difference between Example 3 and Example 1 is that the first and third edges of the negative electrode are not etched, and the fifth and seventh edges of the positive electrode are not etched.

[0065] Example 4

[0066] The difference between Example 4 and Example 1 is that the second and fourth edges on the negative electrode are not etched, and the fifth and seventh edges on the positive electrode are not etched.

[0067] Example 5

[0068] The difference between Example 5 and Example 1 is that the first and third edges of the negative electrode are not etched, and the sixth and eighth edges of the positive electrode are not etched.

[0069] Example 6

[0070] The difference between Example 6 and Example 1 is that the etching depth of the etched area on the positive electrode is 25% of the thickness of the positive electrode; the etching depth of the etched area on the negative electrode is 25% of the thickness of the negative electrode.

[0071] Example 7

[0072] The difference between Example 7 and Example 1 is that the etching depth of the etched area on the positive electrode sheet is 75% of the thickness of the positive electrode sheet; the etching depth of the etched area on the negative electrode sheet is 75% of the thickness of the negative electrode sheet.

[0073] Comparative Example 1

[0074] The difference between Comparative Example 1 and Example 1 is that neither the positive nor negative electrode sheet is etched.

[0075] Comparative Example 2

[0076] The difference between Comparative Example 2 and Example 1 is that the central region 2 of the positive and negative electrode structures is also etched to form a fully etched surface of the active material layer 11.

[0077] Comparative Example 3

[0078] The difference between Comparative Example 3 and Example 1 is that the coating on the first to fourth edges of the negative electrode is etched, while the coating on the positive electrode is not etched.

[0079] Comparative Example 4

[0080] The difference between Comparative Example 4 and Example 1 is that the coating at the fifth to eighth edges of the positive electrode is etched, while the coating at the negative electrode is not etched.

[0081] Comparative Example 5

[0082] The difference between Comparative Example 5 and Example 1 is that the second etching groove 402 is 20% of the thickness of the active material layer 11.

[0083] Comparative Example 6

[0084] The difference between Comparative Example 6 and Example 1 is that the second etching groove 402 is 80% of the thickness of the active material layer 11.

[0085] Table 1 Performance parameters for all embodiments and comparative examples

[0086]

[0087]

[0088] Therefore, as shown in the table above: 1. By comparing Example 1 with Examples 2 and 3, it can be seen that when the coatings of the first, second, third, and fourth edges of the negative electrode and the fifth, sixth, seventh, and eighth edges of the positive electrode are simultaneously laser-etched, although the energy density is reduced due to the loss of active material in the negative electrode, the liquid retention coefficient of the cell has a significant advantage. At the same time, the expansion during cycling is small, the retention rate is high, and the edge lithium plating problem is improved. This is mainly because laser etching around the edges of the negative electrode can effectively shorten the lithium ion insertion channel distance at the edge of the negative electrode, reduce the tortuosity of the voids at the edge of the negative electrode, improve the dynamic performance, and avoid the lithium plating problem caused by the slow insertion speed of lithium ions at the edge. At the same time, laser etching is also performed on the corresponding edges of the positive electrode, which can reduce the active material of the corresponding positive electrode at the edge of the negative electrode, reduce the concentration of lithium ions extracted from the edge of the positive electrode and transferred to the negative electrode during charging, thereby reducing the charging current density at the edge of the negative electrode and further improving the edge lithium plating problem.

[0089] 2. By comparing Examples 2 and 3 with Examples 4 and 5, it can be concluded that when the positive and negative electrode etching regions are mismatched, there is no significant advantage in energy density, liquid retention coefficient, cycle expansion, and lithium plating interface.

[0090] 3. By comparing Example 1 with Comparative Examples 1 to 4, it can be found that: if no etching area is provided on the positive and negative electrode sheets, or if etching areas are provided on both the positive and negative electrode sheets, or if etching areas are provided only on the edge of the positive electrode, or if etching areas are provided only on the edge of the negative electrode, the liquid retention coefficient, cycle expansion and lithium plating interface are all deteriorated to varying degrees.

[0091] 4. By comparing the ratios of Example 1 with Example 6 and Example 7, and Comparative Example 5 with Comparative Example 6, it can be concluded that: when the laser etching depth is too deep, although the liquid retention increases, the mass loss of the negative electrode active material is too large, resulting in a mismatch between the positive and negative electrode CB values ​​and a deterioration of the cycle interface; when the laser etching depth is too small, the liquid retention coefficient, cycle expansion, and lithium plating interface all deteriorate to varying degrees.

[0092] This utility model also proposes a secondary battery, which includes a stacked cell. The specific structure of the stacked cell is as described in the above embodiments. Since this secondary battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0093] A rechargeable battery, also known as a secondary battery or accumulator battery, is a battery that can be recharged after discharge to reactivate its active materials and continue to be used. Utilizing the reversibility of chemical reactions, a new battery can be constructed; that is, after a chemical reaction converts into electrical energy, the electrical energy can be used to repair the chemical system, and then the chemical reaction can be converted back into electrical energy. Therefore, it is called a secondary battery (rechargeable battery). The main types of rechargeable batteries on the market include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid) batteries, lithium-ion batteries, and polymer lithium-ion batteries.

[0094] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0095] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this utility model are within the protection scope of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A pole piece structure, characterized by: The active material layer is provided with a center region and an edge region; the edge region comprises adjacently arranged first and second sub-regions; the first sub-region is arranged between the edge of one side surface of the current collector and the center region; the second sub-region is arranged between the edge of one side surface of the current collector and the center region; the active material layer is further provided with at least one accommodation structure; the accommodation structure is arranged in the first sub-region and / or the second sub-region.

2. The pole piece structure of claim 1, wherein: The accommodation structures are arranged in plurality; and the distance between two adjacent accommodation structures is L; L satisfies: 1mm≤L≤10mm.

3. The pole piece structure of claim 1 or 2, wherein: The accommodation structure is an accommodation groove; the accommodation groove is arranged in a recessed manner from the active material layer towards the current collector.

4. The pole piece structure of claim 3, wherein: The relationship between the depth h2 of the accommodation groove and the thickness h1 of the active material layer satisfies: h2=h1*(25%~75%).

5. The pole piece structure of claim 3, wherein: The number of the first sub-regions is two, and the first sub-regions are arranged on both sides of the length direction of the center region; the number of the second sub-regions is two, and the second sub-regions are arranged on both sides of the width direction of the center region.

6. The pole piece structure of claim 5, wherein: The accommodation groove is a first etching groove; the first etching grooves are arranged in the interior of the first sub-region; and the relationship between the total area S2 covered by all the first etching grooves and the covered area S1 of the active material layer satisfies: S2=S1*(1 / 5~1 / 2).

7. The pole structure of claim 5, wherein: The accommodation groove is a second etching groove; the second etching grooves are arranged in the interior of the second sub-region; and the relationship between the total area S3 covered by all the second etching grooves and the covered area S1 of the active material layer satisfies: S3=S1*(1 / 5~1 / 2).

8. The pole structure of claim 5, wherein: The accommodation groove is a third etching groove and a fourth etching groove; the third etching grooves are arranged in the interior of the first sub-region; the fourth etching grooves are arranged in the interior of the second sub-region; and the relationship between the sum S4 of the covered areas of all the third etching grooves and all the fourth etching grooves and the covered area S1 of the active material layer satisfies: S4=S1*(1 / 5~1 / 2).

9. A jelly-roll cell characterized by: The positive electrode tab, the negative electrode tab and the separator film are arranged in sequence; the positive electrode tab and / or the negative electrode tab is the tab structure of any one of claims 1 to 8. The projection of the accommodation groove on the positive electrode tab towards the separator film partially overlaps with the projection of the accommodation groove on the negative electrode tab towards the separator film. In the same thickness direction, the covered area of the accommodation groove on the negative electrode tab is greater than the covered area of the accommodation groove on the positive electrode tab.

10. A secondary battery characterized by comprising: The laminated battery cell of claim 9 is provided.

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