Electrode sheet, electrode assembly and battery

Abstract

Disclosed in the present application are an electrode sheet, an electrode assembly and a battery. The electrode sheet comprises a current collector and an active material layer provided on the surface of the current collector; the active material layer comprises an active material, and the particle size Dv90 of the active material satisfies: 7 μm≤Dv90≤40 μm; a portion of the current collector of the electrode sheet as well as the active material layer on the surface thereof protrude towards a same side, so as to form a plurality of protrusions; in the thickness direction of the electrode sheet, the height of the protrusions is H, H satisfying: 3 μm≤H≤80 μm. In the present application, by means of matching the particle size Dv90 of the active material with the height H of the protrusions, the height H can provide a supporting function to allow a suitable gap to be formed between a separator and the electrode sheet, so as to improve the electrolyte infiltration effect, and on this basis, protrusions having better morphology can be formed, and the active material layer is not prone to abnormal conditions such as micro-cracks, powder shedding or separator puncture, thereby improving the yield during winding. Thus, when the electrode sheet is used in a battery, the battery has good use safety.

Description

An electrode, an electrode assembly, and a battery

[0001] This application claims priority to Chinese Patent Application No. 202510031017.1, filed on January 8, 2025, entitled "An Electrode, Electrode Assembly and Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to an electrode, an electrode assembly, and a battery. Background Technology

[0003] Charge-discharge cycle life is a key performance indicator for batteries. In addition to optimizing and innovating the battery electrolyte to improve charge-discharge cycle life, designing and improving the materials and structure of the battery electrodes can also effectively contribute to improving charge-discharge cycle life. This places higher demands on electrode design. Summary of the Invention

[0004] The inventors discovered that there is compression between the layers of the electrode assembly. Especially during the charging and discharging process of the battery, the expansion and compression of the electrode assembly will be further aggravated, resulting in insufficient electrolyte between the layers of the electrode assembly, poor wetting, and easy interface deterioration, or even abnormal situations such as poor wetting and cycle failure.

[0005] This application provides an electrode sheet, an electrode assembly, and a battery, which can improve the problem of poor electrolyte wetting in batteries.

[0006] In a first aspect, embodiments of this application provide an electrode sheet, which includes a current collector and an active material layer disposed on the surface of the current collector;

[0007] The active material layer includes active materials, and the particle size Dv90 of the active materials satisfies: 7μm≤Dv90≤40μm;

[0008] A portion of the current collector and a portion of the active material layer of the electrode protrude toward the same side to form multiple protrusions. In the thickness direction of the electrode, the height of the protrusion is H, which satisfies: 3μm≤H≤80μm.

[0009] Based on the electrode of this application embodiment, the particle size Dv90 of the active material is suitable in the range of 7μm≤Dv90≤40μm, which is conducive to processing the protrusions with good morphology. In the range of 3μm≤H≤80μm, the height H of the protrusion is suitable, which can provide stable support for the separator, so that there is a suitable space between the electrode and the separator to accommodate the electrolyte and improve the electrolyte wetting effect.

[0010] In some embodiments, the electrode satisfies one of the following conditions:

[0011] (1)7μm≤Dv90≤20μm, 30μm <H≤80μm;

[0012] (2) 20μm <Dv90≤40μm, 3μm≤H≤30μm。

[0013] Based on the above embodiments, the particle size Dv90 of the active material and the height H of the protrusion can be better matched, making the active material layer more stable, less prone to microcracks and powder shedding, and with fewer side reactions at the protrusion, effectively improving the battery's safety when the electrode is used in the battery.

[0014] In some embodiments, the coating weight per unit area of ​​the active material layer is CW, where CW satisfies: 150 mg / 1540.25 cm². 2 ≤CW≤400mg / 1540.25cm 2 .

[0015] Based on the above embodiments, the electrode has a suitable electrolyte wetting effect and it is easy to control the thickness of the active material layer within a suitable range. Therefore, when the electrode protrudes to form a protrusion, the active material layer is less likely to generate microcracks, and the active material layer is less likely to experience abnormalities such as powder shedding or puncture of the separator.

[0016] In some embodiments, the electrode satisfies one of the following conditions:

[0017] (1) 150 mg / 1540.25 cm 2 ≤CW≤210mg / 1540.25cm 2 3μm≤H1≤30μm;

[0018] (2) 210 mg / 1540.25cm 2 <CW≤270mg / 1540.25cm 2 30μm

[0019] (3) 270 mg / 1540.25 cm 2 <CW≤400mg / 1540.25cm 2 40μm

[0020] ​​Based on the above embodiments, the heights of CW and the protrusions can be better matched, so that a protrusion with an appropriate thickness H can be selected when the coating weight CW is appropriate. This prevents the height H of the protrusion from being too small when the coating weight CW is within a certain range, resulting in insufficient support capacity of the protrusion and difficulty in meeting the electrolyte wetting requirements. It also prevents the height H of the protrusion from being too large when the coating weight CW is within a certain range, resulting in excessive elongation of the electrode at the protrusion, which could lead to microcracks on the surface of the active material layer, powder shedding, and puncture of the diaphragm.

[0021] In some embodiments, the active material layer includes an adhesive, and based on the total weight of the active material layer, the weight percentage of the active material is La, and the weight percentage of the adhesive is Lb, wherein La satisfies: 94%≤La≤98.6%, and Lb satisfies: 0.3%≤Lb≤2%.

[0022] Based on the above embodiments, the adhesive can provide good adhesion, so that the active material particles and the surface of the active material and the current collector have good adhesion. Therefore, when a part of the electrode protrudes to form a protrusion, the active material layer at the protrusion is not prone to microcracks, and the active material layer is not prone to powder shedding.

[0023] In some embodiments, the electrode satisfies at least one of the following conditions:

[0024] (1) 94%≤La≤97.6%, 0.5% <Lb≤2 %, 40μm<H≤80μm;

[0025] (2) 94%≤La≤97.6%, 0.3% <Lb≤0.5%, 20μm<H≤40μm;

[0026] (3) 94%≤La≤97.6%, 0.1%≤Lb≤0.3%, 3μm≤H≤20μm;

[0027] (4) 97.6% <La≤98.6%, 0.7 %<Lb≤1.2 %, 40μm<H≤80μm;

[0028] (5) 97.6% <La≤98.6%, 0.5%<Lb≤0.7%, 20μm<H≤40μm;

[0029] (6) 97.6% <La≤98.6%,0.3%≤Lb≤0.5%, 3μm≤H≤20μm;

[0030] (7) 98.6% <La≤99.2%, 0.6 %≤Lb≤1.2 %, 3μm≤H≤20μm。

[0031] Based on the above embodiments, it is convenient to select a suitable height of protrusion under the corresponding active material and binder content, thereby increasing the support capacity of the protrusion. For the processing of the protrusion, it is possible to achieve a higher protrusion height while improving the processing yield of the protrusion, preventing short circuit risks, significantly improving the battery yield and safety, and thus reducing the impact of the protrusions on the battery's thermal and mechanical safety performance.

[0032] In some embodiments, the radius of the orthographic projection of the protrusion in the thickness direction of the electrode is R, wherein the protrusion has a sharpness S, S=H / R, and the electrode satisfies at least one of the following conditions:

[0033] (1) R satisfies: 0μm <R≤133μm;

[0034] (2) S satisfies: 0.4≤S≤0.6.

[0035] Based on the above embodiments, the protrusion provides good support stability for the separator membrane, and the protrusion is not easily bent or deformed by external forces, nor is it easy for the protrusion to damage the separator membrane.

[0036] In some embodiments, the radius of the orthographic projection of the protrusion along the thickness direction of the electrode is R, and the electrode satisfies at least one of the following conditions:

[0037] (1) The center-to-center distance between two adjacent protrusions is L, and 2≤L / R≤3;

[0038] (2) Within a unit area of ​​the electrode, the total area of ​​the orthographic projection of the convex part is M, and 40%≤M≤80%.

[0039] Based on the above embodiments, it is convenient to select an appropriate distribution density of the protrusions, to prevent the protrusions from being too sparse and having insufficient support, and to prevent the protrusions from being too dense and obstructing the flow of electrolyte.

[0040] Secondly, embodiments of this application provide an electrode assembly, which includes a separator and a plurality of electrodes. The separator is sandwiched between two electrodes of opposite polarity, and at least one of the plurality of electrodes is an electrode as described above.

[0041] Thirdly, embodiments of this application provide a battery, including an outer packaging and the aforementioned electrode assembly, wherein the electrode assembly is disposed within the internal space of the outer packaging.

[0042] Based on the electrode sheet, electrode assembly, and battery of the embodiments of this application, by selecting the particle size Dv90 of the active material to satisfy 7μm≤Dv90≤40μm, and selecting the height H of the protrusion to satisfy 3μm≤H≤80μm, the particle size Dv90 of the active material and the height H of the protrusion 311 are matched. With the height H playing a supporting role to ensure a suitable gap between the separator and the electrode sheet, and improving the electrolyte wetting effect, a protrusion with a better shape can be processed. The active material layer is less prone to abnormalities such as microcracks, powder shedding, or puncture of the separator, improving the yield during the winding process. When the electrode sheet 300 is used in the battery, the battery can have good safety in use. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 is a front view of a schematic diagram of the electrode sheet in an unfolded state according to an embodiment of this application;

[0045] Figure 2 is a cross-sectional view of an electrode assembly according to an embodiment of this application;

[0046] Figure 3 is a partial cross-sectional view of an embodiment of the present application showing a electrode sheet with a protrusion.

[0047] Figure 4 is a front view schematic diagram of an embodiment of the present application of an electrode sheet having an end clearance area;

[0048] Figure 5 is a front view schematic diagram of the electrode sheet having an electrode tab region according to an embodiment of this application;

[0049] Figure 6 is a schematic diagram of the front view of the electrode tab region penetrating the electrode sheet according to an embodiment of this application.

[0050] Figure label:

[0051] 20. Electrode body; 21. Straight section; 22. Corner section; 100. Electrode tab; 40. Electrode tab assembly; 50. Separating membrane;

[0052] 300, pole piece; 311, convex part;

[0053] 410. Positive electrode plate; 420. Negative electrode plate;

[0054] 310. Protrusion area; 320. Electrode area; 330. End clearance area; 331. Head clearance area; 332. Tail clearance area; 341. First region; 342. Second region;

[0055] X: length direction; Y: width direction; Z: thickness direction. Embodiments of the present invention

[0056] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0057] The inventors discovered that the electrode assembly inside the secondary battery adopts a wound structure, which requires hot pressing after the electrode sheet and separator are alternately stacked and wound. There is internal stress inside the electrode assembly, resulting in poor electrolyte wettability. Furthermore, the electrode assembly expands during charging and discharging, further exacerbating the interlayer compression of the electrode assembly, leading to insufficient electrolyte, poor wettability, and ultimately, interface deterioration at weak points, and even lithium plating. To solve the above problems, gaps need to be created between battery layers. Currently, there are the following methods for creating gaps: (1) Applying adhesive paper to specific positions on the electrode to form gaps. This method currently improves the wetting ability, but the presence of adhesive paper occupies thickness, increasing the thickness of the electrode assembly and causing a certain loss in the energy density of the battery; (2) Applying soluble chemical substances to form gaps by uniformly applying some adhesive that is soluble in electrolyte to the electrode, but the improvement effect is limited and there are other side effects on battery performance; (3) Thickening the separator membrane. The separator membrane has a stronger ability to store electrolyte and improves the wetting effect of electrolyte, but this method will thicken the battery and greatly reduce the energy density.

[0058] The inventors also discovered that by machining protrusions on the electrode sheet, which provide support during winding, gaps are formed between the electrode layers of the electrode assembly, thereby improving the electrolyte transport capacity within the electrode assembly and enhancing the battery's cycle performance. Based on this, embodiments of this application provide an electrode sheet, an electrode assembly, and a battery, with the protrusions on the electrode sheet designed to effectively improve electrolytic wetting and electrode interface problems.

[0059] The battery provided in this application includes an outer packaging and an electrode assembly disposed within the inner space of the outer packaging, as well as an electrolyte filling the inner space of the outer packaging. The electrode assembly includes two electrodes with opposite polarities and a separator. As shown in FIG1, which is a front view of an embodiment of the present application with the electrode 300 in an unfolded state, the electrode 300 has a length direction X, a width direction Y, and a thickness direction Z that are perpendicular to each other. The length direction X, width direction Y, and thickness direction Z of the two electrodes 300 with opposite polarities of the electrode assembly are consistent. As shown in FIG2, the separator 50 is disposed between the two electrodes 300 with opposite polarities in the thickness direction Z of the electrode 300. One of the two electrodes 300 with opposite polarities is a positive electrode 410 and the other is a negative electrode 420. The separator 50 has insulation properties to separate the positive electrode 410 and the negative electrode 420 to prevent the positive electrode 410 and the negative electrode 420 from short-circuiting.

[0060] At least one of the positive electrode 410 and the negative electrode 420 has a protrusion 311. Specifically, the electrode includes a current collector and an active material layer, which are stacked together along the thickness direction Z of the electrode 300, and the active material layer is disposed on the surface of the current collector. The protrusion 311 is formed by a portion of the current collector and a portion of the active material layer protruding along the thickness direction Z of the electrode 300 towards the same side of the electrode 300. The protrusion 311 provides support for the separator 50, creating a gap between the separator 50 and the electrode 300, thereby improving the electrolyte wetting effect.

[0061] It is understandable that a portion of the current collector and a portion of the active material layer need to be extended and deformed to form the protrusion 311. The active material layer includes the active material. When the active material layer extends, the particle size of the active material particles can easily affect the morphological stability of the active material layer at the protrusion 311. For example, if the particle size of the active material is too large, it can easily lead to risks such as microcracks, powder shedding, or puncture of the separator 50 at the active material layer at the protrusion 311, affecting the yield rate and battery safety during battery winding. Furthermore, the larger the particle size of the active material, the smaller the contact area between the active material and the electrolyte, and the smaller the side reactions. However, this increases the diffusion path of ions within the solid particles, reducing the electrode kinetic performance. Conversely, the smaller the particle size of the active material, the shorter the diffusion path of ions within the particles. However, this increases the specific surface area of ​​the active material, leading to a larger actual contact area between the active material and the electrolyte, which increases the side reactions on the surface of the positive or negative electrode active material particles, negatively impacting the battery's cycle stability.

[0062] In this embodiment, the particle size Dv90 of the active material satisfies: 7μm ≤ Dv90 ≤ 40μm. For example, Dv90 can be 7μm, 12μm, 18μm, 22μm, 28μm, 32μm, 40μm, or any range thereof. Within the above particle size range, the particle size Dv90 of the active material is suitable, which is beneficial for processing the well-shaped protrusion 311. In the thickness direction Z of the electrode 300, as shown in Figure 3, the height of the protrusion 311 is H, which satisfies: 3μm ≤ H ≤ 80μm. For example, H can be 3μm, 7μm, 12μm, 18μm, 22μm, 28μm, 32μm, 40μm, or any range thereof. Within the aforementioned height range, the height H of the protrusion 311 is suitable, providing stable support for the separator 50 and ensuring adequate space between the electrode 300 and the separator 50 to accommodate the electrolyte, thus improving electrolyte wetting. In this embodiment, by selecting the particle size Dv90 of the active material and the height H of the protrusion 311 to satisfy the above-mentioned conditions, the particle size Dv90 of the active material and the height H of the protrusion 311 are matched, enabling the processing of a protrusion 311 with a better morphology. This reduces the likelihood of microcracks, powder shedding, or punctures in the separator layer, improving the yield during winding. When the electrode 300 is used in a battery, the battery exhibits good safety. When the particle size Dv90 of the active material is below 7 μm, the particle size is too small, easily increasing the generation of side reactions. When the particle size Dv90 of the active material is above 40 μm, the particle size is too large, which is detrimental to the formation of the protrusion 311, and microcracks, powder shedding, or punctures in the separator 50 easily appear on the surface of the active material layer. When H is higher than the upper limit of 80μm, the height of the protrusion 311 is too high, making it easy to deform under external force. In addition, the elongation of the protrusion 311 is too large, which can easily lead to abnormalities such as microcracks and powder shedding on the surface of the active material layer. When H is lower than the lower limit of 3μm, the height of the protrusion 311 is too low, making it difficult to provide stable support for the separator 50. It is impossible to provide a suitable space between the electrode 300 and the separator 50 to accommodate the electrolyte, and thus it cannot improve the electrolyte wetting effect.

[0063] The electrode 300 includes a first surface perpendicular to the thickness direction Z of the electrode 300. Referring again to Figure 1, the first surface includes a protrusion area 310, and multiple protrusions 311 are disposed in the protrusion area 310. There is a gap between the protrusion area 310 and the edge of the first surface. After the two electrodes 300 and the separator 50 are wound multiple times to form the electrode body 20, the protrusions 311 contact the separator 50 and provide support for the separator 50. When the electrode body 20 expands, the protrusions 311 can still support the separator 50. The contact area between the protrusions 311 and the separator 50 is small, so that there is space between the part of the electrode 300 corresponding to the protrusion area 310 and the separator 50 to accommodate the electrolyte. This prevents abnormal situations such as insufficient electrolyte or poor wetting between the electrode 300 and the separator 50 due to expansion and compression.

[0064] As shown in Figure 2, the separator 50 and two electrode plates 300 are wound multiple times along the length direction X of the electrode plates 300 to form the electrode body 20. The length direction X of the electrode plates 300 is the direction in which the electrode plates 300 are wound. The electrode body 20 is flat and includes a straight portion 201 and two corner portions 202. The two corner portions 202 are respectively located at opposite ends of the straight portion 201. Specifically, each turn of the electrode plate 300 in the electrode body 20 includes two straight sections 21 and two corner sections 22. The two straight sections 21 are arranged side by side in a direction perpendicular to the surface of the straight section 21, and the two corner sections 22 are arranged opposite each other along the surface of the straight section 21. That is, the two straight sections 21 and the two corner sections 22 are connected end to end. The electrode body 20 has a terminal end, which is formed by a portion of the straight section 21 of the outermost electrode plate 300. All the straight sections 21, the end points, and the isolation membrane 50 sandwiched between two adjacent straight sections 21 are stacked in a direction perpendicular to the surface of the straight section 21 to form a straight portion 201; all the corner sections 22 located on the same side of the straight section 21 in a direction parallel to the surface of the straight section 21 and the isolation membrane 50 sandwiched between two adjacent corner sections 22 together form a corner portion 202.

[0065] The electrode 300 has a plurality of protrusions 311, and at least one of the straight section 21 and the corner section 22 has a protrusion 311. Optionally, all the protrusions 311 provided on a single electrode 300 protrude toward the same side of the electrode 300 in the thickness direction Z of the electrode 300. For example, when both the straight section 21 and the corner section 22 have protrusions 311, the protrusions 311 provided on the straight section 21 and the protrusions 311 provided on the corner section 22 both protrude toward the side of the winding center of the electrode body 20; or, the protrusions 311 provided on the straight section 21 and the protrusions 311 provided on the corner section 22 both protrude toward the side away from the winding center of the electrode body 20. Optionally, a portion of the protrusions 311 on a single electrode 300 protrude toward one side of the electrode 300 in the thickness direction Z, and another portion of the protrusions 311 protrude toward the other side of the electrode 300 in the thickness direction Z. For example, the protrusions 311 on the straight section 21 protrude toward the side facing the winding center of the electrode body 20, and the protrusions 311 on the corner section 22 protrude toward the side away from the winding center of the electrode body 20; or, the protrusions 311 on the straight section 21 protrude toward the side away from the winding center of the electrode body 20, and the protrusions 311 on the corner section 22 protrude toward the side facing the winding center of the electrode body 20.

[0066] The above is merely an illustrative description. This application does not limit the orientation of the protrusions 311 of each electrode 300, and the orientation can be selected according to actual needs.

[0067] Due to internal stress within the electrode body 20 and its expansion during battery charging and discharging, adjacent electrode rings 300 are prone to compression, especially at the corner section 22. This compression can lead to insufficient gaps and poor electrolyte wetting. Furthermore, under the influence of compression and internal stress, when the corner section 22 has a protrusion 311, this protrusion is prone to deformation, and the active material layer is susceptible to cracking, thus affecting the battery's cycle performance. By selecting an active material particle size Dv90 that satisfies 7μm≤Dv90≤40μm and a protrusion height H that satisfies 3μm≤H≤80μm, the protrusion 311 at the corner section 22 can maintain good support stability during electrode ring winding and under the influence of compression and internal stress, while the active material layer at the corner section 22 can also maintain good morphological stability, preventing microcracks or powder shedding.

[0068] In some embodiments, the electrode 300 satisfies one of the following conditions:

[0069] (1)7μm≤Dv90≤12μm, 40μm <H≤80μm;

[0070] (2) 12μm <Dv90≤20μm, 30μm<H≤60μm;

[0071] (3) 20μm <Dv90≤30μm, 20μm<H≤40μm;

[0072] (4) 30μm <Dv90≤40μm, 3μm≤H≤20μm。

[0073] By selecting the particle size Dv90 of the active material and the height H of the protrusion 311 to meet the above range, the particle size Dv90 of the active material and the height H of the protrusion 311 can be better matched, making the active material layer more stable, less prone to microcracks and powder shedding, and with fewer side reactions at the protrusion 311, effectively improving the battery's safety when the electrode 300 is used in the battery.

[0074] In some embodiments, the coating weight per unit area of ​​the active material layer is CW, where CW satisfies: 150 mg / 1540.25 cm². 2 ≤CW≤400mg / 1540.25cm 2 For example, CW can be 150 mg / 1540.25 cm. 2 200 mg / 1540.25cm 2 280 mg / 1540.25cm 2 350 mg / 1540.25cm 2 400 mg / 1540.25cm 2 Or any range of the two mentioned above. By selecting the coating weight CW per unit area of ​​the active material layer within the above range, the electrode 300 has a suitable electrolyte wetting effect and it is easy to control the thickness of the active material layer within a suitable range. As a result, when the electrode 300 protrudes to form the protrusion 311, the active material layer is less likely to generate microcracks, and the active material layer is less likely to experience abnormalities such as powder shedding or puncture of the separator 50.

[0075] Understandably, the required electrolyte wetting capacity varies depending on the coating weight (CW) per unit area. For electrode 300 with low CW, the electrode 300 thickness is smaller, requiring less electrolyte. In this case, a smaller protrusion 311 height is sufficient to meet the battery wetting requirements. For electrode 300 with higher CW, the electrode 300 thickness increases significantly, requiring a much larger amount of electrolyte. If a smaller protrusion 311 design is still used, it cannot meet the actual electrolyte wetting needs, resulting in uneven wetting inside the battery and leading to problems such as purple spots and lithium plating. Similarly, for an electrode 300 with a lower CW, using a larger protrusion 311 height can meet the electrolyte wetting requirements, but the formation of the protrusion 311 structure causes stress and plastic deformation in the electrode 300. This leads to electrode elongation; the higher the protrusion 311 height H, the greater the elongation, and the greater the damage to the electrode 300. This makes it easier for microcracks to form on the surface of the active material layer, leading to risks such as powder shedding and separator puncture, affecting the yield during winding and battery safety. Therefore, different CWs require different protrusion 311 heights to achieve optimal wetting without affecting the battery manufacturing process and safety. Based on this, the embodiments of this application select an electrode 300 that meets one of the following conditions:

[0076] (1) 150 mg / 1540.25 cm 2 ≤CW≤210mg / 1540.25cm 2 3μm≤H1≤30μm;

[0077] (2) 210 mg / 1540.25cm 2 <CW≤270mg / 1540.25cm 2 30μm

[0078] (3) 270 mg / 1540.25 cm 2 <CW≤400mg / 1540.25cm 2 40μm

[0079] ​​By selecting a coating weight CW per unit area of ​​the active material layer and a height of the protrusion 311 that satisfy the above-mentioned conditions, the CW and the height of the protrusion 311 are better matched. This allows for the selection of a protrusion 311 with a suitable thickness H when the coating weight CW is appropriate. This prevents the height H of the protrusion 311 from being too small when the coating weight CW is within a certain range, resulting in insufficient support capacity of the protrusion 311 and difficulty in meeting the electrolyte wetting requirements, which would cause uneven wetting inside the battery. It also prevents the height H of the protrusion 311 from being too large when the coating weight CW is within a certain range, which would lead to excessive elongation of the electrode 300 at the protrusion 311, resulting in risks such as microcracks on the surface of the active material layer, powder shedding, and puncture of the separator.

[0080] In some embodiments, the active material primarily functions to provide or store ions during charging and discharging. The active material layer also includes an adhesive, which serves to bond and fix all the active materials together, making all the active material layers a single unit and adhering to the current collector surface. Based on the total weight of the active material layers, the weight percentage of the active material is La, and the weight percentage of the adhesive is Lb, wherein La satisfies: 94% ≤ La ≤ 98.6%, and Lb satisfies: 0.3% ≤ Lb ≤ 2.0%. For example, La can be 94%, 94.5%, 95.0%, 96.3%, 97.4%, 98.6%, or any range thereof, and Lb can be 0.3%, 0.8%, 1.2%, 1.5%, 1.8%, 2.0%, or any range thereof. By selecting the weight percentage of active material La and the weight percentage of adhesive Lb to satisfy the above conditions, the adhesive can provide good adhesion, so that there is good adhesion between the active material particles and between the active material and the current collector surface. As a result, when a portion of the electrode 300 protrudes to form a protrusion 311, the active material layer at the protrusion 311 is less prone to microcracks and the active material layer is less prone to powder shedding.

[0081] It is understandable that different contents of active material or binder will affect the stress and plastic deformation capacity of the electrode 300. The higher the content of active material Lb, the lower the content of binder, and the more likely the active material will shed powder during the manufacturing process of the protrusion 311. Different electrodes 300 require different heights of the protrusion 311 based on the content of active material La and the content of binder Lb. Based on this, the embodiments of this application select an electrode 300 that meets one of the following conditions:

[0082] (1) 94%≤La≤97.6%, 0.5% <Lb≤2 %, 40μm<H≤80μm;

[0083] (2) 94%≤La≤97.6%, 0.3% <Lb≤0.5%, 20μm<H≤40μm;

[0084] (3) 94% ≤ La ≤ 97.6%, 0.1% ≤ Lb ≤ 0.3%, 3 μm ≤ H ≤ 20 μm;

[0085] (4) 97.6% < La ≤ 98.6%, 0.7% < Lb ≤ 1.2%, 40 μm < H ≤ 80 μm;

[0086] (5) 97.6% < La ≤ 98.6%, 0.5% < Lb ≤ 0.7%, 20 μm < H ≤ 40 μm;

[0087] (6) 97.6% < La ≤ 98.6%, 0.3% ≤ Lb ≤ 0.5%, 3 μm ≤ H ≤ 20 μm;

[0088] (7) 98.6% < La ≤ 99.2%, 0.6% ≤ Lb ≤ 1.2%, 3 μm ≤ H ≤ 20 μm.

[0089] By selecting the ranges of the weight percentage La of the active material and the weight percentage Lb of the binder that satisfy the above conditional expressions, it is convenient to select the convex portion 311 with a suitable height under the corresponding contents of the active material and the binder, increase the supporting ability of the convex portion 311. For the process of machining the convex portion 311, it is possible to achieve a higher height of the convex portion 311 while improving the machining yield rate of the convex portion 311, preventing the risk of short circuit, significantly improving the battery yield rate and safety, and further reducing the influence of the convex portion 311 existing on the pole piece 300 on the thermal safety and mechanical safety performance of the battery. At the same time, it improves the battery wetting and the charge-discharge cycle performance of the battery.

[0090] In some embodiments, as shown in FIG. 3, in the thickness direction of the pole piece 300, the radius of the orthographic projection of the convex portion 311 is R, and R satisfies: 0 μm < R ≤ 133 μm. For example, R can be 20 μm, 45 μm, 83 μm, 103 μm, 120 μm, 133 μm or any range between the two. By selecting the range of the orthographic projection radius R of the convex portion 311 that satisfies the above conditional expression, it is convenient to select the size of the convex portion 311 within a suitable range. The convex portion 311 has a good supporting effect and is not easily deformed. At the same time, it is convenient to select a suitable area ratio of the convex portion 311 relative to the pole piece 300, which can provide more sufficient support for the separator 50.

[0091] In some embodiments, the protrusion 311 has a sharpness S, where S = H / R, and S satisfies: 0.4 ≤ S ≤ 0.6. For example, S can be 0.40, 0.45, 0.48, 0.50, 0.54, 0.60, or any range thereof. By selecting a range where the sharpness S of the protrusion 311 satisfies the above condition, the protrusion 311 provides good support stability for the separator 50. The protrusion 311 is not easily bent or deformed by external forces, and it is also less likely to damage the separator 311. Furthermore, when the particle size Dv90 of the active material satisfies 7 μm ≤ Dv90 ≤ 40 μm, the processing yield of the protrusion 311 can be improved, making the active material layer less prone to microcracks and less prone to powder shedding.

[0092] In some embodiments, the center-to-center distance between two adjacent protrusions 311 is L, where 2 ≤ L / R ≤ 3. For example, L / R can be 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, or any range thereof. By selecting a range where the center-to-center distance L between two adjacent protrusions 311 and the radius R of the orthographic projection of the protrusion 311 satisfy the above condition, it is convenient to select a suitable distribution density of the protrusions 311, preventing the protrusions 311 from being too sparse and lacking sufficient support, and preventing the protrusions 311 from being too dense and obstructing the flow of electrolyte.

[0093] In some embodiments, within a unit area of ​​the electrode 300, the total area of ​​the orthographic projection of the protrusion 311 accounts for M, where 40% ≤ M ≤ 80%. For example, M can be 40%, 44%, 50%, 55%, 60%, 80%, or any range thereof. By selecting a range where the total area of ​​the orthographic projection of the protrusion 311 satisfies the above condition, the protrusion 311 can provide more sufficient support for the separator 50. Simultaneously, when the particle size Dv90 of the active material satisfies 7μm ≤ Dv90 ≤ 40μm, the processed protrusion 311 has a complete shape, and the active material layer is less prone to microcracks and powder shedding.

[0094] In some embodiments, the surface of the active material layer facing away from the current collector forms a first surface. A protrusion 311 is disposed on the protrusion region 310 of the first surface. The protrusion region 310 is defined by a protrusion boundary line. The protrusion 311 of the protrusion region 310 may be located within the area defined by the protrusion boundary line, or the protrusion 311 may be internally connected to the protrusion boundary line. The first surface also includes an end clearance region 330 and an edge clearance region. The end clearance region 330 is connected to the end of the protrusion region 310 in the length direction X of the electrode 300 and extends to the edge of the electrode 300. The edge clearance region is disposed on one side of the protrusion region 310 in the width direction Y of the electrode 300 and extends to the edge of the electrode 300. Neither the edge clearance region nor the end clearance region 330 has a protrusion 311. After the two electrodes 300 and the separator 50 are wound together, the surfaces of the electrodes 300 corresponding to the edge clearance region and the end clearance region 330 may be spaced apart from the separator 50.

[0095] The end clearance area 330 is located at the end of the protrusion area 310 in the length direction X of the electrode 300 and extends to the edge of the electrode 300. The end clearance area 330 also extends to the edge of the electrode 300 in the width direction Y of the electrode 300. As shown in FIG4, the end clearance area 330 includes at least one of the head clearance area 331 and the tail clearance area 332. Preferably, the end clearance area 330 includes both the head clearance area 331 and the tail clearance area 332. In the length direction X of the electrode 300, the head clearance area 331 is located at one end of the protrusion area 310 and the tail clearance area 332 is located at the other end of the protrusion area 310.

[0096] After the two electrodes 300 and the separator 50 are wound, the head clearance area 331 can be located in the innermost few turns of the electrode body 20, which facilitates the winding and forming of the electrode body 20 and helps to improve the structural stability of the central area of ​​the electrode body 20. The tail clearance area 332 can be located in the outermost few turns of the electrode body 20. The tail clearance area 332 can serve as a buffer area between the protrusion 311 and the tail end of the electrode body 20, so that the portion of the clearance area 330 at the corresponding end of the electrode 300 can more smoothly bind the inner layer structure of the electrode body 20, which helps to improve the encapsulation stability of the electrode body 20. Especially when the electrode body 20 has a tendency to expand, using the tail clearance area 332 without the protrusion 311 to finish can prevent the tail end of the electrode body 20 from slipping due to expansion stress, thereby improving the structural stability of the electrode body 20.

[0097] The edge clearance area includes a first region 341 and a second region 342. In the width direction Y of the electrode 300, the first region 341 is connected to one side of the protrusion region 310, and the second region 342 is connected to the other side of the protrusion region 310. The first region 341 extends to the edge of the electrode 300 in a direction away from the second region 342, and the second region 342 extends to the edge of the electrode 300 in a direction away from the first region 341. That is, the two opposite boundaries of the protrusion region 310 in the width direction Y of the electrode 300 are respectively spaced from the corresponding edge of the electrode 300, so as to prevent the deformation stress when the protrusion 311 is processed in the protrusion region 310 from causing abnormal deformation such as wavy edges or wrinkles on the edge of the electrode 300.

[0098] Optionally, one of the first region 341 and the second region 342 is used to mount the electrode assembly tab 40, as shown in FIG4. For example, the second region 342 is used to mount the electrode assembly tab 40, and the protrusion region 310 is spaced apart from the tab assembly 40.

[0099] Optionally, as shown in FIG. 5, the first surface further includes a tab region 320 extending from one edge of the first surface to the opposite edge along the width direction Y of the electrode 300, and not penetrating the protrusion region 310. The tab region 320 is used to mount the tab assembly 40 of the electrode assembly, and the tab assembly 40 is spaced apart from the protrusion region 310. In some other embodiments, as shown in FIG. 6, the tab region 320 penetrates the protrusion region 310 along the width direction Y of the electrode 300. Each tab region 320 is used to mount at least one tab assembly 40. For example, the tab assembly 40 includes a tab and a protective adhesive, which can be mounted in the same tab region 320; or, the tab is mounted in one tab region 320, and the protective adhesive is mounted in another tab region 320.

[0100] The electrode 300 in this embodiment can form at least one of a positive electrode 410 and a negative electrode 420. The current collector of the negative electrode 420 is a negative current collector, and the active material layer is a negative active material layer. The current collector of the positive electrode 410 is a positive current collector, and the active material layer is a positive active material layer. This embodiment does not impose any particular limitations on the materials used for the positive active material, positive current collector, negative active material, and negative current collector. Various materials known in the art that can be used as positive active materials, positive current collectors, negative active materials, and negative current collectors are applicable to this application.

[0101] Exemplarily, the negative electrode current collector can be at least one of copper foil, aluminum foil, nickel foil, or carbon-based current collector; the thickness of the negative electrode current collector can be from 1 μm to 200 μm. The negative electrode active material layer can be disposed on one or both opposing surfaces of the negative electrode current collector. Further, in the thickness direction Z of the negative electrode sheet 420, the negative electrode active material layer can be coated only on a portion of the negative electrode current collector. Exemplarily, the thickness of the negative electrode active material layer can be from 10 μm to 500 μm.

[0102] Exemplarily, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite, or silicon-based materials, wherein the silicon-based material includes at least one of silicon, silicon oxide, silicon carbide, or silicon alloy. The negative electrode active material layer may also include a conductive agent; exemplaryly, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, sheet graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. The negative electrode active material layer may also include a binder, which may include at least one of carboxymethyl cellulose (CMC), polyacrylate, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0103] For example, the positive current collector can be aluminum foil, or other positive current collectors commonly used in the art can be used. The thickness of the positive current collector can be from 1 μm to 200 μm. The positive active material layer can be disposed on one or both opposite surfaces of the positive current collector. Furthermore, in the thickness direction Z of the positive electrode 410, the positive active material layer can be coated only on a portion of the positive current collector, and the thickness of the positive active material layer can be from 10 μm to 500 μm.

[0104] For example, the positive electrode active material includes LiCoO2, LiNiO2, LiMn2O4, and LiCo. 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, LiNi x Co y Mn z M 1-x-y-zO2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1. Exemplarily, the positive electrode active material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese oxide, and the above positive electrode active material may be doped and / or coated. The positive electrode active material layer also includes a conductive agent; exemplaryly, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, sheet graphite, graphene, carbon nanotubes, or carbon fibers. The positive electrode active material layer may also include an adhesive, which may include at least one of the following: a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of styrene and acrylate, a copolymer of styrene and butadiene, polyamide, polyacrylonitrile, polyacrylate, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0105] This application does not impose any particular limitation on the separator 50, and various materials known in the art that can be used as the separator 50 are applicable to this application. Exemplarily, the separator 50 includes at least one selected from polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene, in particular, have good short-circuit prevention properties and can improve the stability of the electrode assembly through a turn-off effect. The thickness of the separator 50 is in the range of about 3 μm to 500 μm. The positive and negative tabs are made of a metallic conductive material.

[0106] The tabs in this application embodiment include positive tabs and negative tabs. The positive tab is disposed on the positive electrode plate, and the negative tab is disposed on the negative electrode plate. This application embodiment does not have any particular limitations on the positive tab, negative tab and protective adhesive. Various materials known in the art that can be used as positive tabs, negative tabs and protective adhesives are applicable to this application.

[0107] This application does not impose any particular limitation on the electrolyte. Various materials known in the art that can be used as electrolytes are applicable to this application. Electrolytes include lithium salts and non-aqueous organic solvents.

[0108] For example, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium methyl sulfite.

[0109] By way of example, the non-aqueous organic solvent may also contain at least one of a carboxylic acid ester compound, an ether compound, or other organic solvent. The aforementioned carbonate compound may include, but is not limited to, at least one of a chain carbonate compound and a cyclic carbonate compound. The aforementioned chain carbonate compound may include, but is not limited to, at least one of dipropyl carbonate (DPC) or ethyl methyl carbonate (EMC). The aforementioned cyclic carbonate compound may include, but is not limited to, at least one of butyl carbonate (BC) or vinyl ethylene carbonate (VEC). The aforementioned carboxylic acid ester compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The aforementioned ether compound may include, but is not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents mentioned above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the mass percentage of non-aqueous organic solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage of non-aqueous organic solvents may be from 10% to 70%.

[0110] This application does not impose any particular restrictions on the packaging bag for the battery; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0111] This application does not impose any particular limitation on the type of battery, which may include any device in which an electrochemical reaction occurs. In this application, the battery may include, but is not limited to, lithium metal batteries, lithium-ion batteries, lithium polymer batteries, or lithium-ion polymer batteries.

[0112] The battery manufacturing process described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: after installing the positive electrode tab on the positive electrode sheet and the negative electrode tab on the negative electrode sheet, stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a battery; or, stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a battery.

[0113] The battery described in this application can be used in electrical devices. This application does not specifically limit the type of electrical device; it can be any electrical device known in the prior art. In some embodiments, the electrical device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0114] The present application will be further illustrated below using a lithium-ion battery as an example and with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0115] The performance of lithium-ion batteries in the embodiments and comparative examples of this application is tested using the following methods:

[0116] (1) Test method for cycle capacity retention at 25℃ / 45℃ 5C charging / 0.7C discharging

[0117] In an environment of 25℃ / 45℃, the lithium-ion battery was charged at a constant current of 5C to its full charge voltage (the maximum designed voltage of the lithium-ion battery is 4.5V). Then, it was charged at the maximum voltage at a constant voltage until the current reached 0.02C. Finally, it was discharged at a constant current of 0.7C until the final voltage reached 3.0V. The discharge capacity of the first cycle was recorded. The above steps were then repeated for charge and discharge cycles, and the discharge capacity of the lithium-ion battery in each charge and discharge cycle was recorded.

[0118] The cycle capacity retention rate at 25℃ / 45℃ with 5C charging and 0.7C discharging is calculated as (discharge capacity of the Nth cycle / discharge capacity of the first cycle) × 100%.

[0119] The number of charge-discharge cycles when the 5C cycle capacity is ≤80% at 25℃ / 45℃ is: the number of charge-discharge cycles when the cycle capacity retention rate is 80%.

[0120] (2) Liquid retention test method

[0121] During the assembly of lithium-ion batteries, after drying in a vacuum oven at 85°C for 12 hours to remove moisture, the weight of the dry cell before liquid injection is recorded as w1. After vacuum sealing, settling, formation, capacity testing, degassing, and edge trimming, the weight of the lithium-ion battery is recorded as w2.

[0122] Liquid retention capacity = (w2-w1) / w1×100%.

[0123] (3) Test method for improving the effect of infiltration

[0124] The electrode 300 was cut into a standard size of 10mm × 10mm. 5μL of electrolyte was dropped onto the surface of the electrode 300, and the diffusion rate and wetting area of ​​the electrolyte were observed. The contact angle of the electrolyte on the surface of the electrode 300 was measured using a contact angle meter. Based on the diffusion rate and contact angle, the wettability of the electrode 300 was evaluated. A faster diffusion rate and a smaller contact angle indicate better wettability.

[0125] Among them, a contact angle range of 15°~25° indicates "good" surface wetting effect, while a contact angle range of 5°~15° indicates "poor" surface wetting effect.

[0126] (4) Methods for testing the morphology of active material layers

[0127] The electrode 300 was cut into a standard size of 10mm×10mm and placed in the sample chamber of a scanning electron microscope (SEM). The surface morphology of the electrode 300 was observed using a scanning electron microscope (SEM).

[0128] If the surface of electrode 300 is smooth, intact, and without cracks, there is no powder shedding. If the number of pits per square centimeter on the surface of electrode 300 is less than or equal to 3, it indicates that the integrity of electrode 300 has been damaged, which is considered slight powder shedding. If the number of pits per square centimeter on the surface of electrode 300 is greater than 3, it indicates that electrode 300 has been significantly damaged, which is considered severe powder shedding.

[0129] (5) Test method for the height H of the protrusion 311

[0130] The height of the protrusion 311 is tested on the electrode 300 at the corner of the battery.

[0131] (6) Test method for particle size Dv90 of active materials

[0132] Particle size Dv90 testing is performed using a particle size analyzer. Dv90 represents the particle size at which 90% of the particles are smaller than this value. A representative sample must be taken from the material to be tested, and a suitable dispersion medium (such as water, ethanol, etc.) must be selected to ensure the sample is fully dispersed in the medium. Then, an ultrasonic disperser is used to treat the sample to break up any aggregated particles. The dispersed sample is then injected into the sample cell of the particle size analyzer. The instrument is started for measurement; it determines the particle size distribution using methods such as laser diffraction or dynamic light scattering, automatically collects data, and generates a particle size distribution curve. The Dv90 value is read from the particle size distribution curve, representing the particle size at which 90% of the particles are smaller than this value.

[0133] Perform multiple measurements as needed to ensure the repeatability and accuracy of the results.

[0134] (7) Test method for coating weight per unit area of ​​active material layer

[0135] A certain area of ​​electrode sheet is taken and cut into pieces with an area of ​​15.4025 cm² using a stamping machine. 2 The weight of the active material layer per unit area can be obtained by deducting the weight of the current collector from the circular disc.

[0136] Example 1-1

[0137] (1) Preparation of positive electrode sheet

[0138] The positive electrode active material is LiCoO2, the positive electrode conductive agent is conductive carbon black (Super P), and the positive electrode binder is polyvinylidene fluoride (PVDF, Mw=7×10). 6 The materials were mixed at a mass ratio of 97.5:1:1.5, with N-methylpyrrolidone (NMP) added as a solvent. The mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil for the positive electrode current collector. The foil was then dried at 85°C and cold-pressed to obtain a positive electrode sheet with a single-sided coating of 50 μm thick positive electrode active material. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode active material. The sheets were then cut to a size of 74 mm × 851 mm for later use.

[0139] (2) Preparation of negative electrode sheet

[0140] Artificial graphite as the negative electrode active material, conductive carbon black (Super P) as the negative electrode conductive agent, and carboxymethyl cellulose (CMC-Na, Mw=7×10) as the thickener are used. 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10), 6 The materials were mixed at a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent. The mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry was uniformly coated onto one surface of an 8 μm thick copper foil current collector. The foil was then dried at 85°C and cold-pressed to obtain a negative electrode sheet with a single-sided coating of 60 μm thick negative electrode active material. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode active material. The sheets were then cut to a size of 76 mm × 867 mm for later use. The compaction density of the negative electrode active material layer was 1.75 g / cm³. 3 The coating weight per unit area (CW) of the negative electrode active material layer is 230 mg / 1540.25 cm². 2The particle size Dv90 of the negative electrode active material is 45 μm.

[0141] (3) Preparation of the separating membrane

[0142] A porous polyethylene (PE) membrane with a thickness of 5 μm was used.

[0143] (4) Preparation of electrolyte

[0144] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:2 to obtain a base solvent. Lithium hexafluorophosphate (LiPF6) was then dissolved in the base solvent to obtain the electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5%.

[0145] (5) Assembly of lithium-ion batteries

[0146] The positive electrode aluminum tab is installed on the edge area of ​​the positive electrode sheet 410 by rolling, and the protective adhesive is pasted on the edge area of ​​the positive electrode sheet 410. The negative electrode nickel tab is installed on the edge area of ​​the negative electrode sheet 420 by rolling.

[0147] The positive electrode 410 with positive tabs, the separator 50, and the negative electrode 420 with negative tabs are stacked sequentially, with the separator 50 positioned between the positive electrode 410 and the negative electrode 420 to provide insulation. The electrode assembly is then wound to form the electrode body 20. The electrode assembly is placed in an outer aluminum-plastic film package and dried in an 85°C vacuum oven for 12 hours to remove moisture. Electrolyte is then injected, and the battery undergoes vacuum sealing, settling, formation (constant current charging at 0.2°C to 3.5V, followed by constant current charging at 1C to 3.9V), capacity testing, degassing, and edge trimming to obtain the lithium-ion battery.

[0148] In Example 1-1, the negative electrode sheet has a protrusion 311. The protrusion is rolled out on the negative electrode sheet by rolling. The electrode sheet 300 shown in Figure 4 is used as the negative electrode sheet. In the electrode body 20 formed by winding, each turn of the electrode sheet 300 has a protrusion 311 at the corner section 21 and the straight section 22. The parameters of the lithium-ion battery are shown in Table I.

[0149] Table I

[0150]

[0151] Examples 1-2 to 1-25 and Comparative Examples 1-1 to 1-7 are the same as in Example 1-1, except that the height of the protrusion 311 and the particle size Dv90 of the positive electrode active material are adjusted according to Table 1 in the preparation of the positive electrode sheet.

[0152] The parameters and performance test results of the lithium-ion batteries of Examples 1-1 to 1-25 and Comparative Examples 1-1 to 1-7 are shown in Table 1.

[0153] Table 1

[0154]

[0155]

[0156] Among them, the higher the number of charge-discharge cycles and the greater the liquid retention, the better the battery performance.

[0157] As can be seen from Examples 1-1 to 1-25 and Comparative Examples 1-1 to 1-7 in Table 1, the particle size Dv90 of the active material satisfies 7μm≤Dv90≤40μm, and the height of the protrusion 311 satisfies 3μm≤H≤80μm, indicating that the lithium-ion battery has good charge-discharge cycle performance.

[0158] As can be seen from Examples 1-1 to 1-25 and Comparative Examples 1-1 to 1-7 in Table 1, within a certain range, although increasing the height of the protrusion 311 can improve wettability and increase liquid retention, when the limit value is exceeded, it will lead to problems such as powder shedding, cracking or wrinkling of the electrode 300. At this time, although the wettability of the electrode 300 is still improved, the problems of powder shedding and cracking of the electrode 300 will lead to the deterioration of cycle performance.

[0159] While keeping the height of the protrusion 311 constant, the Dv90 of the active material cannot be too large. An excessively large Dv90 will cause the active material itself to be subjected to excessive stress and strain during the preparation of the protrusion 311, resulting in excessive interaction force with other particles in the electrode 300, causing it to detach from the electrode 300, or even break the active particles themselves. Although the wettability of the electrode 300 is still greatly improved, it is very detrimental to the cycling of the electrode 300.

[0160] Examples 2-1 to 2-18 are the same as those in Examples 1-7, except that the height H of the protrusion 311 and the protrusion weight CW per unit area of ​​the positive electrode active material layer are adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0161] The parameters and performance test results of the lithium-ion batteries in Examples 2-1 to 2-18 are shown in Table 2.

[0162] Table 2

[0163]

[0164] As can be seen from Examples 2-1 to 2-3 in Table 2, the weight CW of the protrusion per unit area of ​​the active material layer and the height H of the protrusion 311 satisfy 150 mg / 1540.25 cm. 2 ≤CW≤210mg / 1540.25cm 2 3μm≤H1≤30μm; as can be seen from Examples 2-4 to 2-9 in Table 2, the weight CW of the protrusion per unit area of ​​the active material layer and the height H of the protrusion 311 satisfy 210mg / 1540.25cm. 2 <CW≤270mg / 1540.25cm 2 30μm 2 <CW≤400mg / 1540.25cm 2 40μm

[0165] Examples 3-1 to 3-49 are the same as those in Examples 2-5, except that the height H of the protrusion 311, the weight percentage Lb of the positive electrode active material, and the weight percentage Lb of the binder are adjusted according to Table 1 in the preparation of the positive electrode sheet.

[0166] The parameters and performance test results of the lithium-ion batteries in Examples 3-1 to 3-49 are shown in Table 3.

[0167] Table 3

[0168]

[0169]

[0170] ​​It can be seen from Examples 3-15, 3-20 to 3-49 in Table 3 that when the proportion of low-activity material is low and the content of the binder is low, it is very easy for particles to fall off and the electrode sheet 300 to crack during the preparation of the convex portion 311, which is not conducive to improving the cycle stability. Therefore, when the content of the low-activity material is low, a relatively high binder content should be maintained to facilitate maintaining the integrity of the electrode sheet 300 during the preparation of the relatively high convex portion 311, preventing particle detachment, thus facilitating the improvement of wettability and cycle stability. When the proportion of the active material content further increases and reaches a medium level, the binder content can be appropriately reduced, and the process conditions of the convex portion 311 will not be affected at this time. If the active material content remains at a relatively high level, the height of the convex portion 311 should be minimized as much as possible because an increase in the proportion of the active material content means a relatively small binder content. If a relatively high height of the convex portion 311 is still maintained at this time, it will cause the active particles to fall off due to weak bonding and the electrode sheet 300 to crack during the preparation of the convex portion 311. Therefore, the active material content, the binder content, and the height of the convex portion 311 should be designed within the ranges defined by the above conditional expressions.

[0171] Examples 4-1 to 4-14 are the same as Examples 1-7 except that in the preparation of the positive electrode sheet, the height H of the convex portion 311, the positive projection radius R of the convex portion 311, and the center distance L between two adjacent convex portions 311 are adjusted according to Table 1.

[0172] The parameters of the lithium-ion batteries of Examples 4-1 to 4-14 and the performance test results of the lithium-ion batteries are shown in Table 4.

[0173] Table 4

[0174]

[0175] It can be seen from Examples 4-1 to 4-14 and Examples 1-7 in Table 4 that when the height H of the convex portion 311 is the same, the larger the positive projection radius R, the higher the liquid retention amount of the electrolyte and the better the wettability, indicating that a larger positive projection radius can significantly improve the electrochemical performance of the battery and further enhance the cycle performance. In addition, when the height H of the convex portion 311 is the same, the smaller the center distance L between two adjacent convex portions 311, the more conducive it is to improving the wettability and liquid retention amount of the electrolyte, thereby facilitating the improvement of the cycle performance. Therefore, when the design of the convex portion 311 of the battery satisfies at least one of 0μm < R ≤ 133μm, 0.4 ≤ S ≤ 0.6, and 2 ≤ L / R ≤ 3, while maintaining no powder loss and no cracking of the electrode sheet 300, increasing the size of the positive projection radius R of the convex portion 311 as much as possible and reducing the center distance between two adjacent convex portions 300 will have a better effect on improving the performance of the lithium-ion battery.

[0176] Examples 5-1 to 5-6 are the same as Examples 1-7, except that the height H of the protrusion 311 and the total area ratio M of the orthographic projection of the protrusion 311 per unit area are adjusted according to Table 1 in the preparation of the positive electrode sheet.

[0177] The parameters and performance test results of the lithium-ion batteries in Examples 5-1 to 5-6 are shown in Table 5.

[0178] Table 5

[0179]

[0180] As can be seen from Examples 5-1 to 5-6 and Examples 1-7 in Table 5, when the height H of the protrusion 311 is the same, the proportion M of the total area of ​​the orthographic projection of the protrusion 311 per unit area satisfies 40%≤M≤80%. As M increases, the liquid retention of each charge-discharge cycle performance of the lithium-ion battery gradually increases, resulting in a better performance improvement effect on the lithium-ion battery.

[0181] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0182] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrode sheet, wherein, The electrode includes a current collector and an active material layer disposed on the surface of the current collector; The active material layer includes an active material, and the particle size Dv90 of the active material satisfies: 7μm≤Dv90≤40μm; A portion of the current collector and the active material layer on its surface of the electrode sheet protrude toward the same side to form a plurality of protrusions. The height of the protrusions along the thickness direction of the electrode sheet is H, where H satisfies: 3μm≤H≤80μm.

2. The electrode according to claim 1, wherein, The electrode sheet satisfies one of the following conditions: (1)7μm≤Dv90≤20μm, 30μm <H≤80μm; (2) 20μm <Dv90≤40μm,3μm≤H≤30μm。 3. The electrode according to claim 1, wherein, The coating weight per unit area of ​​the active material layer is CW, and CW satisfies: 150 mg / 1540.25 cm². 2 ≤CW≤400mg / 1540.25cm 2 .

4. The electrode according to claim 3, wherein, The electrode sheet satisfies one of the following conditions: 。。 5. The electrode according to claim 1, wherein, The active material layer includes an adhesive. Based on the total weight of the active material layer, the weight percentage of the active material is La, and the weight percentage of the adhesive is Lb. La satisfies: 94%≤La≤98.6%, and Lb satisfies: 0.3%≤Lb≤2%.

6. The electrode according to claim 5, wherein, The electrode sheet satisfies one of the following conditions: (1) 94%≤La≤97.6%, 0.5% <Lb≤2 %, 40μm<H≤80μm; (2) 94%≤La≤97.6%, 0.3% <Lb≤0.5%, 20μm<H≤40μm; (3) 94%≤La≤97.6%, 0.1%≤Lb≤0.3%, 3μm≤H≤20μm.

7. The electrode according to claim 5, wherein, The electrode sheet satisfies one of the following conditions: (a) 97.6% <La≤98.6%, 0.7 %<Lb≤1.2 %, 40μm<H≤80μm; (b) 97.6% <La≤98.6%, 0.5%<Lb≤0.7%, 20μm<H≤40μm; (c) 97.6% <La≤98.6%, 0.3%≤Lb≤0.5%, 3μm≤H≤20μm; (d) 98.6% <La≤99.2%, 0.6 %≤Lb≤1.2 %, 3μm≤H≤20μm。 8. The electrode according to claim 1, wherein, Along the thickness direction of the electrode sheet, the radius of the orthographic projection of the protrusion is R, wherein the protrusion has a sharpness S, S=H / R, and the electrode sheet satisfies at least one of the following conditions: (1) 0μm <R≤133μm; （2）0.4≤S≤0.6。 9. The electrode according to claim 1, wherein, Along the thickness direction of the electrode sheet, the radius of the orthographic projection of the protrusion is R, and the electrode sheet satisfies at least one of the following conditions: (1) The center-to-center distance between two adjacent protrusions is L, where 2 ≤ L / R ≤ 3; (2) Within the unit area of ​​the electrode, the total area of ​​the orthographic projection of the protrusion accounts for M, 40%≤M≤80%.

10. An electrode assembly, wherein, The electrode assembly includes a separator and a plurality of electrodes, the separator being sandwiched between two electrodes of opposite polarity, and at least one of the plurality of electrodes being an electrode as described in any one of claims 1-9.

11. A battery, wherein, include: shell; And, the electrode assembly of claim 10, wherein the electrode assembly is disposed in the interior space of the housing.

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