A pole piece, electrode assembly and battery

Abstract

The application discloses a pole piece, an electrode assembly and a battery. The pole piece comprises a current collector and an active material layer arranged on the surface of the current collector; the active material layer comprises active material, and the particle size Dv90 of the active material satisfies 7 mu m<=Dv90<=40 mu m; part of the current collector of the pole piece and the active material layer on the surface thereof are protruded towards the same side to form a plurality of convex parts, and the height of the convex parts is H in the thickness direction of the pole piece, and H satisfies 3 mu m<=H<=80 mu m. By matching the particle size Dv90 of the active material and the height H of the convex part 311, the height H can play a supporting role to make the isolation film and the pole piece have a suitable gap, the electrolyte infiltration effect is improved, the convex part with a better form can be processed, the active material layer is not prone to abnormal conditions such as micro-cracks, powder falling or puncturing the isolation film, the yield in the winding process is improved, and when the pole piece is used in the battery, the battery has good use safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a tab, an electrode assembly and a battery. BACKGROUND

[0002] The charge-discharge cycle life is a key performance of a battery. In addition to optimizing and innovating the electrolyte of the battery to improve the charge-discharge cycle life, the charge-discharge cycle life can also be effectively improved by designing and improving the material and structure of the tab of the battery, which has more requirements for the design of the tab. SUMMARY

[0003] The inventor finds that extrusion exists between the layers of the electrode assembly, and the extrusion is further intensified due to the expansion and extrusion of the electrode assembly during the charge-discharge process of the battery, which leads to insufficient electrolyte between the layers of the electrode assembly, poor wetting, easy interface deterioration, and even poor wetting, cycle failure and other abnormal conditions.

[0004] The present application provides a tab, an electrode assembly and a battery, which can improve the problem of poor electrolyte wetting of the battery.

[0005] In a first aspect, the present application provides a tab, the tab comprising a current collector and an active material layer arranged on the surface of the current collector;

[0006] The active material layer comprises an active material, and the particle size Dv90 of the active material satisfies 7 μm≤Dv90≤40 μm.

[0007] Part of the current collector and part of the active material layer of the tab are protruded towards the same side to form a plurality of protrusions, and the height of the protrusions in the thickness direction of the tab is H, which satisfies 3 μm≤H≤80 μm.

[0008] Based on the tab of the present application, the particle size Dv90 of the active material is suitable in the range of 7 μm≤Dv90≤40 μm, which is beneficial to process the protrusions with good morphology. The height H of the protrusions is suitable in the range of 3 μm≤H≤80 μm, which can provide stable support for the separator, so that the tab and the separator have a suitable space for accommodating electrolyte, and the wetting effect of the electrolyte is improved.

[0009] In some embodiments, the tab satisfies one of the following conditions:

[0010] (1) 7 μm≤Dv90≤20 μm, 30 μm<H≤80 μm;

[0011] (2) 20 μm<Dv90≤40 μm, 3 μm≤H≤30 μm.

[0012] Based on the above embodiment, the particle size Dv90 of the active material and the height H of the convex part can be more matched, so that the active material layer is more stable, micro-cracks and powder falling are less likely to occur, and the side reaction at the convex part is less, effectively improving the use safety of the battery when the pole piece is applied in the battery.

[0013] In some embodiments, the coating weight per unit area of the active material layer is CW, CW satisfies: 150 mg / 1540.25 cm 2 ≤ CW ≤ 400 mg / 1540.25 cm 2 .

[0014] Based on the above embodiment, the pole piece has suitable electrolyte infiltration effect, and the thickness of the active material layer can be controlled in a suitable range, so that when the convex part of the pole piece is formed, the active material layer is less likely to produce micro-cracks, and the active material layer is less likely to have powder falling and abnormal conditions such as piercing the isolation film.

[0015] In some embodiments, the pole piece satisfies one of the following conditions:

[0016] (1) 150 mg / 1540.25 cm 2 ≤ CW ≤ 210 mg / 1540.25 cm 2 , 3 μm ≤ H1 ≤ 30 μm;

[0017] (2) 210 mg / 1540.25 cm 2 ≤ CW ≤ 270 mg / 1540.25 cm 2 , 30 μm < H1 ≤ 40 μm;

[0018] (3) 270 mg / 1540.25 cm 2 ≤ CW ≤ 400 mg / 1540.25 cm 2 , 40 μm < H1 ≤ 80 μm.

[0019] Based on the above embodiment, CW and the height of the convex part can be more matched, so that in the case of suitable coating weight CW, a convex part with suitable thickness H is selected, to prevent that when the coating weight CW is in a certain range, the height H of the convex part is too small, the supporting capacity of the convex part is insufficient, and it is difficult to meet the electrolyte infiltration requirement, and to prevent that when the coating weight CW is in a certain range, the height H of the convex part is too large, the elongation rate of the pole piece at the convex part is too large, which causes the active material layer surface to produce micro-cracks, powder falling, and the risk of piercing the diaphragm.

[0020] In some embodiments, the active material layer includes a binder, the weight percentage of the active material is La, and the weight percentage of the binder is Lb, based on the total weight of the active material layer, La satisfies: 94% ≤ La ≤ 98.6%, and Lb satisfies: 0.3% ≤ Lb ≤ 2%.

[0021] Based on the above embodiments, the adhesive can provide good adhesion, so that the active material particles and the active material and the current collector surface have good adhesion, and when part of the protrusions of the pole piece form protrusions, the active material layer at the protrusions is not prone to micro-cracks, and the active material layer is not prone to powdering.

[0022] In some embodiments, the pole piece satisfies at least one of the following conditions:

[0023] (1) 94%≤La≤97.6%, 0.5%<Lb≤2%, 40μm<H≤80μm;

[0024] (2) 94%≤La≤97.6%, 0.3%<Lb≤0.5%, 20μm<H≤40μm;

[0025] (3) 94%≤La≤97.6%, 0.1%≤Lb≤0.3%, 3μm≤H≤20μm;

[0026] (4) 97.6%<La≤98.6%, 0.7%<Lb≤1.2%, 40μm<H≤80μm;

[0027] (5) 97.6%<La≤98.6%, 0.5%<Lb≤0.7%, 20μm<H≤40μm;

[0028] (6) 97.6%<La≤98.6%, 0.3%≤Lb≤0.5%, 3μm≤H≤20μm;

[0029] (7) 98.6%<La≤99.2%, 0.6%≤Lb≤1.2%, 3μm≤H≤20μm.

[0030] Based on the above embodiments, it is convenient to select a suitable height of the protrusion under the corresponding content of the active material and the adhesive, increase the support capacity of the protrusion, for the process of processing the protrusion, it can realize higher protrusion height while improving the processing rate of the protrusion, prevent short circuit risk, significantly improve the battery rate and safety, and then reduce the influence of the protrusion existing in the pole piece on the thermal safety and mechanical safety performance of the battery.

[0031] In some embodiments, in the thickness direction of the pole piece, the radius of the orthogonal projection of the protrusion is R, wherein the protrusion has a sharpness S, S=H / R, and the pole piece satisfies at least one of the following conditions:

[0032] (1) R satisfies: 0μm<R≤133μm;

[0033] (2) S satisfies: 0.4≤S≤0.6.

[0034] Based on the above embodiment, the convex part has good support stability for the isolation film, the convex part is not easy to be bent or deformed by external force, and the convex part is not easy to damage the isolation film.

[0035] In some embodiments, along the thickness direction of the pole piece, the radius of the orthogonal projection of the convex part is R, and the pole piece satisfies at least one of the following conditions:

[0036] (1) The center distance between two adjacent convex parts is L, and 2≤L / R≤3;

[0037] (2) In a unit area of the pole piece, the total area ratio of the orthogonal projection of the convex part is M, and 40%≤M≤80%.

[0038] Based on the above embodiment, it is convenient to select the appropriate distribution density of the convex part to prevent the convex part from being too sparse to support the electrolyte and prevent the convex part from being too dense to hinder the flow of the electrolyte.

[0039] In a second aspect, the embodiments of the present application provide an electrode assembly, which comprises an isolation film and a plurality of pole pieces, the isolation film is arranged between two pole pieces with opposite polarities, and at least one of the plurality of pole pieces adopts the above-mentioned pole piece.

[0040] In a third aspect, the embodiments of the present application provide a battery, which comprises an outer package and the above-mentioned electrode assembly, and the electrode assembly is arranged in the inner space of the outer package.

[0041] Based on the pole piece, the electrode assembly and the battery of the embodiments of the present application, by selecting the particle size Dv90 of the active material to satisfy 7μm≤Dv90≤40μm and selecting the height H of the convex part to satisfy 3μm≤H≤80μm, the particle size Dv90 of the active material and the height H of the convex part 311 are matched, the height H can play a supporting role to make the isolation film and the pole piece have a suitable gap, improve the electrolyte infiltration effect, and process a convex part with a better form, the active material layer is not easy to have abnormal conditions such as micro-cracks, powder falling or puncturing the diaphragm, improve the yield rate in the winding process, and when the pole piece 300 is used in the battery, the battery can have good use safety. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0043] Figure 1 It is a front view structural schematic diagram of the pole piece of an embodiment of the present application in an unfolded state;

[0044] Figure 2 A cross-sectional structure schematic diagram of an electrode assembly of an embodiment of the present application;

[0045] Figure 3 A partial cross-sectional structure schematic diagram of a tab having a convex portion of an embodiment of the present application;

[0046] Figure 4 A front view structure schematic diagram of a tab having an end avoidance area of an embodiment of the present application;

[0047] Figure 5 A front view structure schematic diagram of a tab having a tab area of an embodiment of the present application;

[0048] Figure 6 A front view structure schematic diagram of a tab area of a tab penetrating through the tab of an embodiment of the present application.

[0049] Reference signs:

[0050] 20, electrode body; 21, flat section; 22, corner section; 100, tab; 40, tab assembly; 50, separator film;

[0051] 300, tab; 311, convex portion;

[0052] 410, positive tab; 420, negative tab;

[0053] 310, convex point area; 320, tab area; 330, end avoidance area; 331, head avoidance area; 332, tail avoidance area; 341, first area; 342, second area;

[0054] X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0056] 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 increases the thickness of the electrode assembly and causes 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. However, the improvement effect is limited and there are other side effects on battery performance; (3) Thickening the separator. The separator has a stronger ability to store electrolyte and improves the wetting effect of electrolyte. However, this method will make the battery thicker and greatly reduce the energy density.

[0057] 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.

[0058] 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 of opposite polarity and a separator, such as... Figure 1 The diagram shown is a front view of an embodiment of the electrode 300 in its unfolded state. The electrode 300 has two perpendicular length directions (X), width directions (Y), and thickness directions (Z). The length directions (X), width directions (Y), and thickness directions (Z) are aligned for two electrodes 300 with opposite polarities in the electrode assembly. Figure 2 As shown, the separator 50 is disposed in the thickness direction Z of the electrode 300 between two electrodes 300 with opposite polarities. 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 insulating 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.

[0059] At least one of the positive electrode tab 410 and the negative electrode tab 420 has a protrusion 311. Specifically, the tab includes a current collector and an active material layer stacked with the current collector in a thickness direction Z of the tab 300, and the active material layer is arranged on a surface of the current collector. The protrusion 311 is formed by a part of the current collector and a part of the active material layer protruding toward the same side of the tab 300 in the thickness direction Z of the tab 300. The protrusion 311 provides support for the separator 50, so that there is a gap between the separator 50 and the tab 300, improving the effect of electrolyte infiltration.

[0060] It can be understood that the part of the current collector and the part of the active material layer need to be deformed to form the protrusion 311. The active material layer includes active material, and when the active material layer is stretched, the particle size of the active material particles can easily affect the form stability of the active material layer at the protrusion 311. For example, if the particle size of the active material particles is too large, it can easily cause the active material layer at the protrusion 311 to crack, powder, or pierce the separator 50, affecting the yield during the battery winding process and the safety of the battery. In addition, 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 reaction. However, the diffusion path of ions in the solid particles is increased, reducing the kinetic performance of the tab. The smaller the particle size of the active material, the shorter the diffusion path of ions in the particles, but the specific surface area of the active material increases, resulting in an increase in the actual contact area between the active material and the electrolyte, which increases the side reaction on the surface of the positive or negative active material particles, which is not conducive to the cycle stability of the battery.

[0061] In the embodiments of the present application, the particle size Dv90 of the active material satisfies: 7 μm≤Dv90≤40 μm, for example, Dv90 can be 7 μm, 12 μm, 18 μm, 22 μm, 28 μm, 32 μm, 40 μm, or any range of the above two. In the above particle size range, the particle size of the active material Dv90 is suitable, which is beneficial to the processing of the protrusion 311 with good form. In the thickness direction Z of the tab 300, the protrusion 311 is formed by the part of the current collector and the part of the active material layer protruding toward the same side of the tab 300 in the thickness direction Z of the tab 300. Figure 3As shown, the height of the protrusion 311 is H, which satisfies the condition: 3μm ≤ H ≤ 80μm. For example, H can be 3μm, 7μm, 12μm, 18μm, 22μm, 28μm, 32μm, 40μm, or any range of the above. Within the above height range, the height H of the protrusion 311 is suitable, providing stable support for the separator 50 and ensuring a suitable space between the electrode 300 and the separator 50 for accommodating the electrolyte, thus improving the electrolyte wetting effect. 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 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. 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 300 is used in a battery, the battery can have good safety in use. When the particle size Dv90 of the active material is less than 7 μm, the particle size is too small, which easily increases the generation of side reactions. When the particle size Dv90 of the active material is greater than 40 μm, the particle size is too large, which is not conducive to the formation of the protrusion 311. Microcracks, powdering, or punctures of the separator 50 are likely to occur on the surface of the active material layer. When H is higher than the upper limit of 80 μm, the height of the protrusion 311 is too high, which is easily deformed by external forces. Moreover, the elongation of the protrusion 311 is too large, which easily leads to abnormalities such as microcracks and powdering on the surface of the active material layer. When H is lower than the lower limit of 3 μm, the height of the protrusion 311 is too low, which also makes it difficult to provide stable support for the separator 50. It is impossible to have a suitable space between the electrode 300 and the separator 50 to accommodate the electrolyte, and it cannot play a role in improving electrolyte wetting.

[0062] The electrode 300 includes a first surface perpendicular to the thickness direction Z of the electrode 300. Please refer to [further details]. Figure 1 The first surface includes a raised area 310, and multiple protrusions 311 are disposed in the raised area 310. There is a gap between the raised area 310 and the edge of the first surface. After the two electrode sheets 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 sheet 300 corresponding to the raised area 310 and the separator 50 to accommodate the electrolyte. This prevents abnormal situations such as insufficient electrolyte or poor wetting between the electrode sheet 300 and the separator 50 due to expansion and compression.

[0063] like Figure 2As shown, the isolation film 50 and the two pole pieces 300 are wound along the length direction X of the pole pieces 300 to form the electrode main body 20, and the length direction X of the pole pieces 300 is the direction in which the pole pieces 300 are wound. The electrode main body 20 is flat, and the electrode main body 20 includes a flat portion 201 and two corner portions 202 arranged at opposite ends of the flat portion 201. Specifically, each turn of the pole pieces 300 of the electrode main body 20 includes two flat segments 21 arranged side by side in a direction perpendicular to the plate surface of the flat segments 21 and two corner segments 22 arranged opposite to each other in a direction parallel to the plate surface of the flat segments 21, that is, the two flat segments 21 and the two corner segments 22 are sequentially connected end to end. The electrode main body 20 has a tail end formed by a part of the flat segments 21 of the outermost turn of the pole pieces 300. All the flat segments 21 arranged in a direction perpendicular to the plate surface of the flat segments 21, the tail end, and the isolation film 50 arranged between adjacent two flat segments 21 together form the flat portion 201, and all the corner segments 22 located on the same side of the flat segments 21 in a direction parallel to the plate surface of the flat segments 21 and the isolation film 50 arranged between adjacent two corner segments 22 together form the corner portion 202.

[0064] The pole pieces 300 have a plurality of protrusions 311, and at least one of the flat segments 21 and the corner segments 22 has the protrusions 311. Optionally, all the protrusions 311 provided on a single pole piece 300 protrude toward the same side of the pole piece 300 in the thickness direction Z of the pole piece 300, for example, when the flat segments 21 and the corner segments 22 both have the protrusions 311, the protrusions 311 provided on the flat segments 21 and the protrusions 311 provided on the corner segments 22 both protrude toward one side of the winding center of the electrode main body 20, or the protrusions 311 provided on the flat segments 21 and the protrusions 311 provided on the corner segments 22 both protrude away from one side of the winding center of the electrode main body 20. Optionally, part of the protrusions 311 provided on a single pole piece 300 protrude toward one side of the pole piece 300 in the thickness direction Z of the pole piece 300, and the other part of the protrusions 311 protrude toward the other side of the pole piece 300 in the thickness direction Z of the pole piece 300, for example, the protrusions 311 provided on the flat segments 21 protrude toward one side of the winding center of the electrode main body 20, and the protrusions 311 provided on the corner segments 22 protrude away from one side of the winding center of the electrode main body 20, or the protrusions 311 provided on the flat segments 21 protrude away from one side of the winding center of the electrode main body 20, and the protrusions 311 provided on the corner segments 22 protrude toward one side of the winding center of the electrode main body 20.

[0065] The above is only an exemplary introduction, and the application does not limit the direction of the protrusions 311 of each pole piece 300, which can be selected according to actual needs.

[0066] Due to the internal stress in the electrode body 20 and the expansion of the electrode body 20 during charging and discharging of the battery, the adjacent two turns of the electrode tab 300 are prone to extrusion, especially the extrusion of the corner section 22 of the adjacent two turns of the electrode tab 300 is relatively strong, and the electrolyte is prone to poor wetting due to insufficient gap, and under the action of the extrusion force and the internal stress, when the corner section 22 has the protrusion 311, the protrusion 311 at the corner section 22 is prone to deformation and the active material layer is prone to cracking, thereby affecting the cycle performance of the battery. By selecting the particle size Dv90 of the active material to satisfy 7 μm≤Dv90≤40 μm and selecting the height H of the protrusion to satisfy 3 μm≤H≤80 μm, during the winding of the electrode tab 300 and when the protrusion 311 is subjected to the extrusion force and the internal stress, the protrusion 311 at the corner section 22 can maintain good support stability, and the active material layer at the corner section 22 can still maintain good morphological stability and is not prone to micro-cracks or powdering.

[0067] In some embodiments, the electrode tab 300 satisfies one of the following conditions:

[0068] (1) 7 μm≤Dv90≤12 μm, 40 μm<H≤80 μm;

[0069] (2) 12 μm<Dv90≤20 μm, 30 μm<H≤60 μm;

[0070] (3) 20 μm<Dv90≤30 μm, 20 μm<H≤40 μm;

[0071] (4) 30 μm<Dv90≤40 μm, 3 μm≤H≤20 μm.

[0072] By selecting the particle size Dv90 of the active material and the height H of the protrusion 311 to satisfy the above ranges, the particle size Dv90 of the active material and the height H of the protrusion 311 can be more matched, so that the active material layer is more stable and is not prone to micro-cracks and powdering, and the side reaction at the protrusion 311 is less, thereby effectively improving the use safety of the battery when the electrode tab 300 is applied to the battery.

[0073] In some embodiments, the coating weight per unit area of the active material layer is CW, and CW satisfies: 150 mg / 1540.25 cm 2 ≤CW≤400 mg / 1540.25 cm 2 For example, CW can be 150 mg / 1540.25 cm 2 , 200 mg / 1540.25 cm 2 , 280 mg / 1540.25 cm 2 , 350 mg / 1540.25 cm 2, 400 mg / 1540.25 cm 2 or any range of the above two. By selecting the coating weight per unit area CW of the active material layer in the above range, the pole piece 300 has a suitable electrolyte infiltration effect, and it is convenient to control the thickness of the active material layer in a suitable range, so that when the pole piece 300 is protruded to form the convex portion 311, the active material layer is not prone to micro-cracks, and the active material layer is also not prone to abnormal conditions such as powder falling and piercing the separator film 50.

[0074] It can be understood that for different coating weights per unit area CW, the required electrolyte infiltration capacity is different. For a pole piece 300 with a low CW, the thickness of the pole piece 300 is small, and the required electrolyte is less. At this time, a smaller convex portion 311 height can meet the battery infiltration requirements. For a pole piece 300 with a higher CW, the thickness of the pole piece 300 increases significantly, and the amount of required electrolyte increases greatly. If a smaller convex portion 311 design is still used, it cannot meet the actual demand for electrolyte infiltration, and still causes uneven internal infiltration of the battery, thereby leading to battery purple stains, lithium precipitation and other problems. Similarly, for a pole piece 300 with a low CW, if a larger convex portion 311 height is used, although it can meet the electrolyte infiltration requirements, the convex portion 311 structure generates stress and plastic deformation to the pole piece 300. At this time, the pole piece 300 is elongated, and the higher the convex portion 311 height H, the greater the elongation rate, and the greater the damage to the pole piece 300. It is more likely to produce micro-cracks on the surface of the active material layer, and it is more likely to cause powder falling and piercing the separator. The risk affects the winding process and the safety of the battery. Therefore, different CWs need to be matched with different convex portion 311 heights to achieve the best infiltration while not affecting the battery process and safety. Based on this, the embodiments of the present application select the pole piece 300 to satisfy one of the following conditions:

[0075] (1) 150 mg / 1540.25 cm 2 ≤ CW≤ 210 mg / 1540.25 cm 2 , 3 μm≤ H1≤ 30 μm;

[0076] (2) 210 mg / 1540.25 cm 2 ≤ CW≤ 270 mg / 1540.25 cm 2 , 30 μm<H1≤ 40 μm;

[0077] (3) 270 mg / 1540.25 cm 2 ≤ CW≤ 400 mg / 1540.25 cm 2 , 40 μm<H1≤ 80 μm.

[0078] By selecting the coating weight per unit area CW of the active material layer and the height of the convex portion 311 to satisfy the range of the above condition formula, CW and the height of the convex portion 311 can be more matched, so as to select a suitable thickness H of the convex portion 311 in the case of a suitable coating weight CW, prevent the height H of the convex portion 311 from being too small when the coating weight CW is in a certain range, the supporting capacity of the convex portion 311 is insufficient, it is difficult to meet the electrolyte infiltration requirement, causing uneven internal infiltration of the battery, and prevent the height H of the convex portion 311 from being too large when the coating weight CW is in a certain range, the elongation rate of the tab 300 at the convex portion 311 is too large, which may cause micro-cracks on the surface of the active material layer, powder falling and the risk of piercing the separator.

[0079] In some embodiments, the active material mainly plays a role of providing ions or storing ions in the charging and discharging process, and the active material layer further includes a binder. The binder plays a role of bonding and fixing all the active materials, so that all the active material layers become a whole and are bonded to the surface of the current collector. 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 binder 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 between any two of the above, and Lb can be 0.3%, 0.8%, 1.2%, 1.5%, 1.8%, 2.0%, or any range between any two of the above. By selecting the weight percentage La of the active material and the weight percentage Lb of the binder to satisfy the range of the above condition formula, the binder can provide good bonding force, so that the active material particles and the surface of the current collector have good adhesion, and thus when part of the tab 300 is raised to form the convex portion 311, the active material layer at the convex portion 311 is not prone to micro-cracks and powder falling.

[0080] It can be understood that different contents of active materials or different contents of binders have different effects on the stress and plastic deformation capacity of the tab 300. The higher the content Lb of the active material, the lower the content of the binder, and the more prone the active material is to powder falling risk during the manufacturing of the convex portion 311. Different tabs 300 need to use different heights of the convex portion 311 according to the content La of the active material and the content Lb of the binder. Based on this, the embodiments of the present application select the tab 300 to satisfy one of the following conditions:

[0081] (1) 94%≤La≤97.6%, 0.5%<Lb≤2%, 40μm<H≤80μm;

[0082] (2) 94%≤La≤97.6%, 0.3%<Lb≤0.5%, 20μm<H≤40μm;

[0083] (3) 94% ≤ La ≤ 97.6%, 0.1% ≤ Lb ≤ 0.3%, 3 μm ≤ H ≤ 20 μm;

[0084] (4) 97.6% < La ≤ 98.6%, 0.7% < Lb ≤ 1.2%, 40 μm < H ≤ 80 μm;

[0085] (5) 97.6% < La ≤ 98.6%, 0.5% < Lb ≤ 0.7%, 20 μm < H ≤ 40 μm;

[0086] (6) 97.6% < La ≤ 98.6%, 0.3% ≤ Lb ≤ 0.5%, 3 μm ≤ H ≤ 20 μm;

[0087] (7) 98.6% < La ≤ 99.2%, 0.6% ≤ Lb ≤ 1.2%, 3 μm ≤ H ≤ 20 μm.

[0088] By selecting the weight percentage La of the active material and the weight percentage Lb of the binder to satisfy the ranges of 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, thereby reducing the influence of the convex portion 311 existing on the electrode sheet 300 on the thermal safety and mechanical safety performance of the battery, and at the same time improving the battery wetting and the charge-discharge cycle performance of the battery.

[0089] In some embodiments, as Figure 3 shown, in the thickness direction of the electrode sheet 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 radius R of the orthographic projection of the convex portion 311 to satisfy the range of 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 electrode sheet 300, which can provide more sufficient support for the separator 50.

[0090] In some embodiments, the protrusions 311 have a sharpness S, S = H / R, 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 between the two. By selecting the sharpness S of the protrusions 311 to satisfy the range of the above condition formula, the support stability of the protrusions 311 to the isolation film 50 is good, the protrusions 311 are not easy to be bent or pressed deformed by external force, the protrusions 311 are not easy to cause damage to the isolation film 50, and in the case that the particle size Dv90 of the active material satisfies 7μm≤Dv90≤40μm, the processing yield of the protrusions 311 can be improved, and the active material layer is not easy to produce micro-cracks and is not easy to fall off.

[0091] In some embodiments, the center distance between two adjacent protrusions 311 is L, 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 between the two. By selecting the center distance L between two adjacent protrusions 311 and the radius R of the protrusions 311 to satisfy the range of the above condition formula, it is convenient to select the appropriate distribution density of the protrusions 311, prevent the protrusions 311 from being too sparse to support, and prevent the protrusions 311 from being too dense to hinder the flow of electrolyte.

[0092] In some embodiments, in a unit area of the pole piece 300, the total area ratio of the protrusions 311 is M, 40%≤M≤80%, for example, M can be 40%, 44%, 50%, 55%, 60%, 80% or any range between the two. By selecting the total area ratio M of the protrusions 311 to satisfy the range of the above condition formula, the protrusions 311 can provide more sufficient support for the isolation film 50, and in the case that the particle size Dv90 of the active material satisfies 7μm≤Dv90≤40μm, the protrusions 311 are formed in a complete shape, and the active material layer is not easy to produce micro-cracks and is not easy to fall off.

[0093] 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.

[0094] An end clearance region 330 is provided at 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, and the end clearance region 330 also extends to the edge of the electrode 300 in the width direction Y of the electrode 300. For example... Figure 4 As shown, 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.

[0095] 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.

[0096] 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.

[0097] Optionally, one of the first region 341 and the second region 342 is used for mounting the tab assembly 40 of the electrode assembly, such as Figure 4 As shown, for example, the second region 342 is used to mount the tab assembly 40 of the electrode assembly, and the protrusion region 310 is spaced apart from the tab assembly 40.

[0098] Optionally, such as Figure 5 As shown, the first surface also includes a tab region 320, extending along the width direction Y of the electrode 300 from one edge of the first surface to the opposite edge, 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, such as Figure 6 As shown, the tab region 320 extends through the protrusion region 310 along the width direction Y of the electrode 300. Each tab region 320 is used to provide at least one tab assembly 40. For example, the tab assembly 40 includes a tab and a protective adhesive, and the tab and the protective adhesive can be installed in the same tab region 320; or, the tab is installed in one tab region 320 and the protective adhesive is installed in another tab region 320.

[0099] 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.

[0100] Exemplarily, the negative current collector can adopt at least one of a copper foil, an aluminum foil, a nickel foil or a carbon-based current collector; the thickness of the negative current collector can be 1 μm to 200 μm. The negative active material layer can be arranged on one surface or opposite two surfaces of the negative current collector, further, in the thickness direction Z of the negative electrode tab 420, the negative active material layer can be coated only on a partial area of the negative current collector. Exemplarily, the thickness of the negative active material layer can be 10 μm to 500 μm.

[0101] Exemplarily, the negative active material includes at least one of lithium metal, natural graphite, artificial graphite or a silicon-based material, the silicon-based material includes at least one of silicon, silicon oxide compound, silicon carbon compound or silicon alloy. The negative active material layer can further include a conductive agent, exemplarily, the conductive agent in the negative active material layer can include at least one of carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotube, carbon fiber or carbon nanowire. Wherein, the negative active material layer can further include a binder, the binder can include at least one of carboxymethyl cellulose CMC, polyacrylate, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin or polyfluorene.

[0102] Exemplarily, the positive current collector can adopt an aluminum foil, of course, other positive current collectors commonly used in the art can also be adopted, the thickness of the positive current collector can be 1 μm to 200 μm. The positive active material layer can be arranged on one surface or opposite two surfaces of the positive current collector, further, in the thickness direction Z of the positive electrode tab 410, the positive active material layer can be coated only on a partial area of the positive current collector, the thickness of the positive active material layer can be 10 μm to 500 μm.

[0103] Exemplarily, the positive active material includes LiCoO2, LiNiO2, LiMn2O4, 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 active material can include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese phosphate, lithium nickel cobalt aluminate or lithium nickel manganese phosphate, and the positive active material can be subjected to a doping and / or coating treatment. The positive active material layer further includes a conductive agent, and exemplarily, the conductive agent in the positive active material layer can include at least one of conductive carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotube or carbon fiber. The positive active material layer can further include a binder, and the binder can include at least one of a copolymer of vinylidene fluoride-hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, a polyamide, a polyacrylonitrile, a polyacrylate, a polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.

[0104] The isolation film 50 is not particularly limited in the embodiments of the present application, and various materials known in the art that can be used as the isolation film 50 are suitable for use in the present application. Exemplarily, the isolation film 50 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid. For example, the polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene or ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have good effects on preventing short circuit and can improve the stability of the electrode assembly through the shutdown effect. The thickness of the isolation film 50 is in the range of about 3 μm to 500 μm. The positive and negative tabs are made of a metal conductive material.

[0105] The tabs in the embodiments of the present application include positive and negative tabs, and the positive tab is arranged on the positive tab piece and the negative tab is arranged on the negative tab piece. The positive and negative tabs and the protective adhesive are not particularly limited in the embodiments of the present application, and various materials known in the art that can be used as the positive and negative tabs and the protective adhesive are suitable for use in the present application.

[0106] The electrolyte is also not particularly limited in the embodiments of the present application, and various materials known in the art that can be used as the electrolyte are suitable for use in the present application. The electrolyte includes a lithium salt and a non-aqueous organic solvent.

[0107] Exemplarily, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis-trifluoromethanesulfonimide, lithium bis-fluorosulfonimide, lithium nitrate or lithium methyl sulfite.

[0108] Exemplarily, the non-aqueous organic solvent can further comprise at least one of a carbonic ester compound, an ether compound, or other organic solvents. The carbonic ester compound can include, but is not limited to, at least one of a chain carbonic ester compound and a cyclic carbonic ester compound. The chain carbonic ester compound can include, but is not limited to, at least one of dipropyl carbonate (DPC) or ethyl methyl carbonate (EMC). The cyclic carbonic ester compound can include, but is not limited to, at least one of butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The carboxylic ester compound can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The ether compound can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents can include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphoric ester. The mass percentage of the non-aqueous organic solvent in the electrolyte is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the mass percentage of the non-aqueous organic solvent is 10% to 70% based on the total mass of the electrolyte.

[0109] The packaging bag of the battery is not particularly limited in the present application, and can be a packaging bag known in the art, as long as the purpose of the present application can be achieved.

[0110] The type of the battery is not particularly limited in the present application, and can include any device that generates an electrochemical reaction. In the present application, the battery can include, but is not limited to, a lithium metal battery, a lithium ion battery, a lithium polymer battery, a lithium ion polymer battery, or the like.

[0111] The preparation process of the battery of the present application is well known to those skilled in the art, and the present application is not particularly limited, for example, can include but is not limited to the following steps: after installing the positive electrode tab on the positive electrode tab and installing the negative electrode tab on the negative electrode tab, stacking the positive electrode tab, the separator and the negative electrode tab in order, and winding, folding, etc. according to the need to obtain a wound electrode assembly of the structure, placing the electrode assembly into the packaging bag, injecting the electrolyte into the packaging bag and sealing to obtain the battery; or, stacking the positive electrode tab, the separator and the negative electrode tab in order, then fixing the four corners of the entire stack structure with adhesive tape to obtain an electrode assembly of the stack structure, placing the electrode assembly into the packaging bag, injecting the electrolyte into the packaging bag and sealing to obtain the battery.

[0112] The battery of the present application can be used in an electric device, and the present application does not particularly limit the type of the electric device, which can be used in any electric device known in the art. In some embodiments, the electric device can include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, an electric tool, a flash, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0113] The present application will be further described below by taking lithium ion batteries as examples and in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0114] The performance of the lithium ion batteries in the embodiments and comparative examples of the present application is tested by using the following methods:

[0115] (1) Test method for cycle capacity retention rate at 25℃ / 45℃ 5C charge / 0.7C discharge

[0116] The lithium ion battery is charged at a constant current to the full charge voltage (4.5V, the maximum voltage designed for the lithium ion battery) at a charge current of 5C in an environment of 25℃ / 45℃, then charged at a constant voltage until the current is 0.02C at the maximum voltage, and then discharged at a constant current until the final voltage is 3.0V at a discharge current of 0.7C, and the discharge capacity of the first cycle is recorded. After that, the above steps are repeated to perform the charge and discharge cycles, and the discharge capacity of the lithium ion battery in each charge and discharge cycle is recorded.

[0117] Cycle capacity retention rate at 25℃ / 45℃ 5C charge / 0.7C discharge = (discharge capacity of the Nth cycle / discharge capacity of the first cycle) x 100%.

[0118] The cycle number of the lithium ion battery at 25℃ / 45℃ 5C cycle capacity ≤80% is the cycle number of charge and discharge at which the cycle capacity retention rate is 80%.

[0119] (2) Test method for liquid retention amount

[0120] In the assembly process of the lithium ion battery, the weight of the dry battery before liquid injection is counted after drying for 12h in a vacuum oven at 85℃ to remove water, and is recorded as w1; after vacuum packaging, standing, formation, capacity, degassing, edge cutting and other processes, the weight of the lithium ion battery is counted, and is recorded as w2.

[0121] Liquid retention amount = (w2-w1) / w1 x 100%.

[0122] (3) Infiltration improvement effect test method

[0123] The pole piece 300 is cut into a standard size of 10 mm x 10 mm, 5 μL of electrolyte is added dropwise on the surface of the pole piece 300, the diffusion speed and wetting area of the electrolyte are observed, a contact angle measuring instrument is used to measure the contact angle of the electrolyte on the surface of the pole piece 300, and the wettability of the pole piece 300 is evaluated according to the diffusion speed and contact angle of the electrolyte. The faster the diffusion speed, the smaller the contact angle, and the better the wettability.

[0124] Wherein, the contact angle range is 15°-25°, the surface infiltration effect is "good", and the contact angle range is 5°-15°, the surface infiltration effect is "poor".

[0125] (4) Active material layer morphology test method

[0126] The pole piece 300 is cut into a standard size of 10 mm x 10 mm, and is placed in the sample chamber of a scanning electron microscope (SEM), and the surface morphology of the pole piece 300 is observed by a scanning electron microscope (SEM).

[0127] If the surface of the pole piece 300 is smooth, complete, and has no cracks, there is no powder falling; if the number of pits per square centimeter on the surface of the pole piece 300 is less than or equal to 3, it means that the integrity of the pole piece 300 is damaged, which belongs to slight powder falling; if the number of pits per square centimeter on the surface of the pole piece 300 is greater than 3, it means that the pole piece 300 is damaged to a greater extent, which belongs to serious powder falling.

[0128] (5) Height H test method of convex part 311

[0129] The pole piece 300 at the corner part of the battery is taken for testing the height of the convex part 311.

[0130] (6) Particle size Dv90 test method of active material

[0131] The particle size Dv90 test is measured by a particle size analyzer. Dv90 represents the particle size of 90% of the particle volume. A representative sample is taken from the material to be tested, and a suitable dispersion medium (such as water, ethanol, etc.) is selected to ensure that the sample can be fully dispersed in the medium. Then use the ultrasonic dispersing instrument to process the sample to disperse the agglomerated particles. The dispersed sample is injected into the sample cell of the particle size analyzer. Start the instrument to measure, the instrument will measure the particle size distribution by laser diffraction or dynamic light scattering method and automatically collect data and generate particle size distribution curve. Read the Dv90 value from the particle size distribution curve, which is the particle size of 90% of the particle volume. According to the need, multiple measurements are carried out to ensure the repeatability and accuracy of the results.

[0132] (7) Test method for coating weight per unit area of active material layer

[0133] Take a certain area of the electrode sheet, cut it into a circular sheet with an area of 15.4025 cm2using a sheet cutting machine, and then deduct the weight of the current collector to obtain the coating weight per unit area of the active material layer;

[0134] Example 1-1

[0135] (1) Preparation of positive electrode sheet

[0136] The positive electrode active material LiCoO2, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride (PVDF, Mw=7x10 6 ) were mixed in a mass ratio of 97.5:1:1.5, N-methyl pyrrolidone (NMP) was added as a solvent, and the mixture was stirred uniformly under the action of a vacuum stirrer to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, dried at 85°C, and cold-pressed to obtain a positive electrode sheet with a single-side coated positive electrode active material layer with a thickness of 50 μm. Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-side coated positive electrode active material layer. The positive electrode sheet with a size of 74 mm x 851 mm was obtained by cutting and was ready for use.

[0137] (2) Preparation of negative electrode sheet

[0138] The negative electrode active material artificial graphite, the negative electrode conductive agent conductive carbon black (Super P), the thickening agent carboxymethyl cellulose (CMC-Na, Mw=7x10 5 ), the negative electrode binder styrene-butadiene rubber (SBR, Mw=5x10 6 ) were mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent, and the mixture was stirred uniformly under the action of a vacuum stirrer to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 8 μm, dried at 85°C, and cold-pressed to obtain a negative electrode sheet with a single-side coated negative electrode active material layer with a thickness of 60 μm. Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-side coated negative electrode active material layer. The negative electrode sheet with a size of 76 mm x 867 mm was obtained by cutting and was ready for use, the tap density of the negative electrode active material layer was 1.75 g / cm 3 , the coating weight per unit area of the negative electrode active material layer CW was 230 mg / 1540.25 cm 2 , and the particle size Dv90 of the negative electrode active material was 45 μm.

[0139] (3) Preparation of the separator film

[0140] A polyethylene (PE) porous film having a thickness of 5 μm was used.

[0141] (4) Preparation of the electrolyte

[0142] In an argon atmosphere 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, and then lithium hexafluorophosphate (LiPF6) was dissolved in the base solvent to obtain an electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5% based on the total mass of the electrolyte.

[0143] (5) Assembly of the lithium ion battery

[0144] The positive tab aluminum tab was installed on the edge area of the positive electrode sheet 410 in a rolling manner, the protective adhesive was pasted on the edge area of the positive electrode sheet 410, and the negative nickel tab was installed on the edge area of the negative electrode sheet 420 in a rolling manner.

[0145] The positive electrode sheet 410 with the positive tab, the separator film 50, and the negative electrode sheet 420 with the negative tab were sequentially stacked in order, with the separator film 50 in the middle of the positive electrode sheet 410 and the negative electrode sheet 420 to play a separating role, and the electrode main body 20 was obtained by winding. The electrode assembly was placed in an outer packaging aluminum plastic film, dried in a vacuum oven at 85°C for 12h to remove water, then electrolyte was injected, and the lithium ion battery was obtained after vacuum packaging, standing, formation (0.2°C constant current charging to 3.5V, then 1C constant current charging to 3.9V), capacity, degassing, and edge cutting processes.

[0146] In Example 1-1, the negative electrode sheet had a protrusion 311, which was rolled out of the negative electrode sheet in a rolling manner, and the electrode sheet 300 shown in FIG. 3 was used as the negative electrode sheet, and in the electrode main body 20 formed by winding, the corner segment 22 and the straight segment 21 of each coil of the electrode sheet 300 had the protrusion 311, and the parameters of the lithium ion battery were as shown in Table I. Figure 4

[0147] Table I

[0148] Parameter Value Parameter Value H 10 μm R 80 μm CW 230 mg / 1540.25 cm 2 ]] L 160 μm S 0.13 M 60％ L / R 2.0 Lb 1.0％ La 97.5％

[0149] Examples 1-2 to 1-25 and Comparative Examples 1-1 to 1-7 were the same as Example 1-1 except that in the preparation of the positive electrode sheet, the height of the protrusion 311 and the particle size Dv90 of the positive active material were adjusted according to Table 1.

[0150] ​The parameters of the lithium ion batteries of Example 1-1 to Example 1-25, Comparative Example 1-1 to Comparative Example 1-7 and the performance test results of the lithium ion batteries are shown in Table 1.

[0151] Table 1

[0152]

[0153]

[0154] The greater the number of charge-discharge cycles and the greater the liquid retention amount, the better the performance of the battery.

[0155] As can be seen from Example 1-1 to Example 1-25, Comparative Example 1-1 to Comparative Example 1-7 in Table 1, when the particle size Dv90 of the active material satisfies 7 μm≤Dv90≤40 μm and the height of the convex portion 311 satisfies 3 μm≤H≤80 μm, the lithium ion battery has good charge-discharge cycle performance.

[0156] As can be seen from Example 1-1 to Example 1-25, Comparative Example 1-1 to Comparative Example 1-7 in Table 1, within a certain range, although increasing the height of the convex portion 311 can improve wettability and increase the liquid retention amount, when the limit value is exceeded, problems such as powder falling, cracking or wrinkling of the pole piece 300 can occur. At this time, although the wettability of the pole piece 300 is still improved, the problems of powder falling and cracking of the pole piece 300 can cause the cycle performance to deteriorate.

[0157] When the height of the convex portion 311 is kept constant, the Dv90 of the active material cannot be too large. If the Dv90 is too large, the active material itself can be subjected to excessive stress and strain during the preparation of the convex portion 311, so that the interaction force with other particles in the pole piece 300 is too large, causing the active particles to fall off from the pole piece 300 or even break, at which time the wettability of the pole piece 300 is still greatly improved, but the cycle of the pole piece 300 is very unfavorable.

[0158] Example 2-1 to Example 2-18 are the same as Example 1-7 except that the height H of the convex portion 311 and the convex portion weight per unit area CW of the positive active material layer are adjusted according to Table 1 during the preparation of the positive pole piece.

[0159] The parameters of the lithium ion batteries of Example 2-1 to Example 2-18 and the performance test results of the lithium ion batteries are shown in Table 2.

[0160] Table 2

[0161]

[0162]

[0163] As can be seen from Examples 2-1 to 2-3 in Table 2, the convex portion weight CW per unit area of the active material layer and the height H of the convex portion 311 satisfy 150 mg / 1540.25 cm 2 ≤ CW≤ 210 mg / 1540.25 cm 2 , 3 μm≤ H1≤ 30 μm; As can be seen from Examples 2-4 to 2-9 in Table 2, the convex portion weight CW per unit area of the active material layer and the height H of the convex portion 311 satisfy 210 mg / 1540.25 cm 2 ≤ CW≤ 270 mg / 1540.25 cm 2 , 30 μm<H1≤ 40 μm; As can be seen from Examples 2-8 to 2-15 in Table 2, the convex portion weight CW per unit area of the active material layer and the height H of the convex portion 311 satisfy 270 mg / 1540.25 cm 2 ≤ CW≤ 400 mg / 1540.25 cm 2 , 40 μm<H1≤ 80 μm, within a certain CW range, the height H of the convex portion 311 should be increased with the increase of CW, if only CW is increased without increasing the height H of the convex portion 311, it will lead to the decrease of the gap during the heat pressing process of the battery, the liquid retention amount is insufficient, the wettability is poor, and it is not conducive to the improvement of the cycle performance. However, within a certain CW, the height H of the convex portion 311 should not exceed a certain limited value, because it will lead to the damage of the pole piece 300 during the convex portion 311 process, and micro-cracks will be generated on the pole piece 300, which will have side effects on the processing process, and will affect the safety performance of the battery level, and is not conducive to the improvement of the cycle performance of the battery.

[0164] Examples 3-1 to 3-37 are the same as Example 2-5 except that the height H of the convex portion 311, the weight percentage content Lb of the positive active material and the weight percentage content Lb of the binder are adjusted according to Table 1 during the preparation of the positive pole piece.

[0165] The parameters of the lithium ion batteries of Examples 3-1 to 3-37 and the performance test results of the lithium ion batteries are shown in Table 3.

[0166] Table 3

[0167]

[0168]

[0169] It can be seen from Examples 3-15, 3-20 to 3-49 in Table 3 that when the proportion of low-activity materials is low and the binder content is low, it is very easy for particles to fall off and the electrode sheet 300 to rupture during the preparation of the convex portion 311, which is not conducive to improving the cycle stability. Therefore, when the content of low-activity materials 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 shedding, 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 this will not affect the manufacturing process of the convex portion 311. If the active material content remains at a 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. At this time, if a relatively high height of the convex portion 311 is still maintained, it will cause the active particles to fall off due to poor adhesion and the electrode sheet 300 to rupture 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.

[0170] 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 as shown in Table 1.

[0171] The parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries in Examples 4-1 to 4-14 are shown in Table 4.

[0172] Table 4

[0173]

[0174] 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 greatly 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, and thus to enhancing the cycle performance. Therefore, when the design of the battery convex portion 311 satisfies at least one of 0μm < R ≤ 133μm, 0.4 ≤ S ≤ 0.6, and 2 ≤ L / R ≤ 3, while maintaining no powder shedding and no rupture of the electrode sheet 300, increasing the size of the positive projection radius R of the convex portion 311 and reducing the center distance between two adjacent convex portions 300 as much as possible will have a better effect on improving the performance of the lithium-ion battery.

[0175] Embodiment 5-1 to Embodiment 5-6 are the same as Embodiment 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 in unit area are adjusted according to Table 1 in the preparation of the positive electrode plate.

[0176] The parameters of the lithium ion batteries of Embodiment 5-1 to Embodiment 5-6 and the performance test results of the lithium ion batteries are shown in Table 5.

[0177] Table 5

[0178]

[0179] As can be seen from Embodiment 5-1 to Embodiment 5-6 and Embodiment 1-7 in Table 5, when the height H of the protrusion 311 is the same, the total area ratio M of the orthographic projection of the protrusion 311 in unit area satisfies 40%≤M≤80%, and as M increases, the charge-discharge cycle performance of the lithium ion battery gradually increases, and the performance improvement effect of the lithium ion battery is better.

[0180] The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms “upper”, “lower”, “left”, “right” and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore the terms describing the positional relationships in the drawings are only used for exemplary illustration, and cannot be understood as limiting the present patent, and for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0181] The above only describes the preferred embodiments of the present application and does not limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An electrode sheet, characterized in that, The electrode tab includes a current collector and an active material layer provided on the surface of the current collector; The active material layer includes active materials, and the particle size Dv90 of the active materials satisfies: 7 μm ≤ Dv90 ≤ 40 μm; Part of the current collector of the electrode tab and the active material layer on its surface bulge toward the same side to form a plurality of convex portions. Along the thickness direction of the electrode tab, the height of the convex portion is H, and H satisfies: 3 μm ≤ H ≤ 80 μm.

2. The electrode sheet according to claim 1, characterized in that, 7 μm ≤ Dv90 ≤ 20 μm, 30 μm < H ≤ 80 μm; or 20 μm < Dv90 ≤ 40 μm, 3 μm ≤ H ≤ 30 μm.

3. The electrode sheet according to claim 1, characterized in that, The coating weight per unit area of ​​the active material layer is CW, and CW satisfies: 150mg / 1540.25cm². 2 ≤CW≤400mg / 1540.25cm 2 .

4. The electrode sheet according to claim 3, characterized in that, The electrode tab satisfies one of the following conditions: (1)150mg / 1540.25cm 2 ≤CW≤210mg / 1540.25cm 2 ,3μm≤H1≤30μm; (2)210mg / 1540.25cm 2 <CW≤270mg / 1540.25cm 2 ,30μm<H1≤40μm; (3)270mg / 1540.25cm 2 <CW≤400mg / 1540.25cm 2 ,40μm<H1≤80μm。 5. The electrode sheet according to claim 1, characterized in that, The active material layer includes a binder. 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 binder is Lb. La satisfies: 94% ≤ La ≤ 98.6%, and Lb satisfies: 0.3% ≤ Lb ≤ 2%.

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

7. The electrode sheet according to claim 5, characterized in that, The electrode tab satisfies one of the following conditions: (a) 97.6% < La ≤ 98.6%, 0.7% < Lb ≤ 1.2%, 40 μm < H ≤ 80 μm; (b) 97.6% < La ≤ 98.6%, 0.5% < Lb ≤ 0.7%, 20 μm < H ≤ 40 μm; (c) 97.6% < La ≤ 98.6%, 0.3% ≤ Lb ≤ 0.5%, 3 μm ≤ H ≤ 20 μm; (d) 98.6% < La ≤ 99.2%, 0.6% ≤ Lb ≤ 1.2%, 3 μm ≤ H ≤ 20 μm.

8. The electrode sheet according to claim 1, characterized in that, Along the thickness direction of the electrode tab, the radius of the orthographic projection of the convex portion is R. Among them, the convex portion has a sharpness S, S = H / R, and the electrode tab satisfies at least one of the following conditions: (1) 0 μm < R ≤ 133 μm; (2)0.4≤S≤0.6。 9. The electrode sheet according to claim 1, characterized in that, Along the thickness direction of the electrode tab, the radius of the orthographic projection of the convex portion is R, and the electrode tab satisfies at least one of the following conditions: (1) The center-to-center distance between two adjacent convex portions is L, 2 ≤ L / R ≤ 3; (2) In the unit area of the electrode tab, the total area ratio of the orthographic projections of the convex portions is M, 40% ≤ M ≤ 80%.

10. An electrode assembly, characterized in that, The electrode assembly includes a separator and a plurality of electrode tabs. The separator is sandwiched between two electrode tabs with opposite polarities, and at least one of the plurality of electrode tabs uses the electrode tab described in any one of claims 1-9.

11. A battery, characterized in that, Including: A housing; And the electrode assembly described in claim 10, and the electrode assembly is provided in the internal space of the housing.

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