Negative plate and battery cell comprising same

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a negative plate which comprises a current collector and a silicon-based layer coated on the surface of the current collector, and at least one protective layer for preventing the silicon-based layer from being burnt by laser is coated on the surface of the silicon-based layer; through the design that the protective layer is coated on the silicon-based layer, particles which are not easy to clean and are generated in the process of laser etching of the pole piece can be reduced, so that the stability of the performance of the battery cell is ensured. In addition, the utility model further discloses a battery cell comprising the negative plate.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and in particular relates to a negative electrode sheet and a battery core comprising the negative electrode sheet. Background Art

[0002] The rapid development of science and technology has put forward higher requirements for the performance and life standards of lithium batteries. Given the advantages of silicon materials in terms of capacity characteristics, it has become a key direction for the research and development of a new generation of negative electrode materials. At the same time, in addition to paying attention to the quality of the electrode and raw materials, it is also crucial to ensure that the silicon-based negative electrode is fully and evenly dispersed in the lithium and electrolyte.

[0003] The existing technology uses laser etching to burn powder by laser to build ion channels for lithium ion transfer in thick electrodes, thereby optimizing battery performance. However, during the laser etching process of silicon-based material pole pieces, silicon materials are often burned by lasers, producing a large number of particles with large particle sizes. These particles are difficult to be effectively removed by dust removal equipment, which leads to an increase in the proportion of poor K values ​​in the battery cells. However, the existing technology has not paid enough attention to this problem.

[0004] Based on this, there is an urgent need for a negative electrode sheet to solve the aforementioned technical problems. Utility Model Content

[0005] One of the purposes of the utility model of the present application is to provide a negative electrode sheet to address the deficiencies of the prior art, thereby solving the technical problem of poor K value of the battery cell.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A negative electrode sheet comprises a current collector and a silicon-based layer coated on the surface of the current collector, wherein the surface of the silicon-based layer is coated with at least one protective layer for preventing the silicon-based layer from being burned by laser.

[0008] The beneficial effects of the utility model are:

[0009] By coating a protective layer on the silicon-based material, the silicon-based negative electrode material can be fully protected from being etched during the laser etching process. By coating a protective layer on the silicon-based layer, the particles generated by the laser etching of the silicon-based layer during the laser etching of the electrode can be effectively suppressed, thereby eliminating the formation of large particles and the problem of cleaning, thereby achieving a reduction in the K value of the battery cell.

[0010] As an improvement to the negative electrode sheet of the utility model, the protective layer is laser etched with a concave portion, the depth of the concave portion is D1, and the thickness of the protective layer is D2, which satisfy: D1≤D2.

[0011] As an improvement to the negative electrode sheet of the utility model, the depth of the recess is D1, and the thickness of the protective layer is D2, which satisfy: D1≤1 / 2D2.

[0012] As an improvement to the negative electrode sheet of the utility model, the depth D1 of the recess satisfies: 9 μm≤D1≤12 μm, and the thickness D2 of the protective layer satisfies: 14 μm≤D2≤16 μm.

[0013] As an improvement to the negative electrode sheet of the utility model, the depth D1 of the recess satisfies: 9 μm≤D1≤16 μm, and the thickness D2 of the protective layer satisfies: 24 μm≤D2≤26 μm.

[0014] As an improvement to the negative electrode sheet of the utility model, the depth D1 of the recess satisfies: 27 μm≤D1≤33 μm, and the thickness D2 of the protective layer satisfies: 39 μm≤D2≤41 μm.

[0015] As an improvement to the negative electrode sheet of the utility model, the concave portion is arranged as a regular structure or an irregular structure, and the regular structure is a circular, square, elliptical or conical regular structure.

[0016] As an improvement to the negative electrode sheet of the utility model, there are multiple recesses, the multiple recesses are evenly arranged on the protective layer, and the distance D3 between two adjacent recesses is less than 2.5 mm.

[0017] As an improvement to the negative electrode sheet of the utility model, a graphite layer is bonded to the surface of the protective layer, a through hole is penetrated through the inside of the graphite layer, and the through hole is connected to the concave portion.

[0018] The second purpose of the utility model of the present application is to provide a battery cell including the above-mentioned negative electrode plate.

[0019] The beneficial effects of the battery provided by the utility model are:

[0020] This improvement not only ensures the stability of the battery cell performance and improves the yield rate, but also significantly extends the service life of the battery cell. In addition, the design of the protective layer also enhances the overall structural stability of the pole piece, further improving the reliability and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0022] Figure 1 It is a schematic diagram of the structure of the negative electrode sheet in the embodiment of the utility model;

[0023] Figure 2This is a schematic diagram of the structure of a negative electrode sheet with two protective layers in an embodiment of the utility model;

[0024] Figure 3 It is a schematic diagram of the structure of the negative electrode sheet with a concave portion in an embodiment of the utility model;

[0025] Figure 4 It is a schematic diagram of the concave portion in the embodiment of the utility model being a regular pattern;

[0026] Figure 5 It is a schematic diagram of an embodiment of the utility model in which the concave portion is an irregular shape;

[0027] Figure 6 It is a schematic diagram of the recess spacing in the utility model embodiment;

[0028] Figure 7 It is a schematic diagram of the structure of the negative electrode sheet with a graphite layer in the embodiment of the utility model;

[0029] in:

[0030] 1-current collector;

[0031] 2-Silicon-based layer;

[0032] 3- Protective layer;

[0033] 31-concave;

[0034] 32-graphite layer;

[0035] 321-through hole;

[0036] D1-Depth of concave part;

[0037] D2-protective layer thickness;

[0038] D3- The distance between two adjacent recesses. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0040] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any technical personnel in this field may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

[0041] The present invention will be described in further detail below in conjunction with specific implementations, but the implementations of the present invention are not limited thereto.

[0042] like Figure 1 As shown, a negative electrode sheet includes a current collector 1 and a silicon-based layer 2 coated on the surface of the current collector 1, and at least one protective layer 3 is coated on the surface of the silicon-based layer 2 to prevent the silicon-based layer 2 from being burned by laser. During the laser etching process of the electrode sheet, the protective layer 3 can effectively prevent the silicon-based layer from being burned and thus generating large particles, thereby improving the performance and yield rate of the battery cell.

[0043] In a further embodiment of the utility model, the protective layer 3 can be prepared by a variety of materials, which can not only fully contact with the electrolyte, but also will not produce particles that are difficult to clean due to the burning of the silicon base layer 3 during the laser etching process. Specifically, materials such as silicon nitride (SiNx), silicon carbide (SiC) or graphite can be selected. Since silicon nitride and silicon carbide are ceramic materials, they have extremely high hardness, chemical stability and thermal stability. During the laser etching process, they can resist the impact of high temperature and laser, and are not easy to peel off or decompose, so large particles will not be formed. In addition, these ceramic materials also have good insulation properties, which can effectively prevent current leakage and ensure the safe operation of the battery. During the laser etching process, a layer of dense graphite oxide will form on the surface of graphite, which can effectively prevent the laser from further eroding the graphite, thereby avoiding the generation of particles. In addition, graphite also has good lubricity, which can reduce friction and wear inside the battery cell and improve the life and performance stability of the battery cell. In the embodiments of the present application, the protective layer 3 will be described using graphite as an example. Other materials may also be used as the protective layer 3, which will not be discussed here.

[0044] In addition, if Figure 2 As shown, in order to further improve the conductivity of the battery cell, we can also coat another protective layer 3 on the surface of the protective layer 3, such as carbon black, graphite, etc. The coating of multiple protective layers 3 can not only further reduce the impact of laser etching on the silicon base layer 2, but also effectively improve the conductivity of the pole piece, reduce the internal resistance of the battery, and thus improve the charging and discharging efficiency and service life of the battery.

[0045] In some embodiments, Figure 3As shown, the protective layer 3 is laser etched with a concave portion 31, the depth of the concave portion 31 is D1, and the thickness of the protective layer 3 is D2, which satisfies: D1≤D2. By designing the concave portion 31 with a specific depth, the laser etching will only stay on the protective layer 3, so that the silicon base layer 2 will not be etched.

[0046] In some embodiments, the depth of the recess 31 is D1, and the thickness of the protective layer 3 is D2, which satisfy: D1≤1 / 2D2. With this design, the protective layer 3 can fully cover the recess 31, ensuring that the recess 31 is not directly corroded by the external environment, thereby improving the durability and stability of the product. Secondly, such a design also helps to maintain the structural integrity of the recess 31 and prevent the recess 31 from being deformed or damaged during use due to excessive depth. In actual applications, the specific values ​​of D1 and D2 may vary according to specific product needs and design requirements.

[0047] In some embodiments, the depth D1 of the recess 31 satisfies: 9μm≤D1≤12μm, and the thickness D2 of the protective layer 3 satisfies: 14μm≤D2≤16μm. Specifically, the depth D1 of the recess 31 can be set to 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm; the thickness D2 of the protective layer 3 can be set to 14μm, 14.5μm, 15μm, 15.5μm, 16μm. These two sets of values ​​provide a good balance within the provided range, ensuring sufficient depth to accommodate the necessary structure without being too deep to affect the overall performance.

[0048] In some embodiments, the depth D1 of the recess 31 satisfies: 9μm≤D1≤16μm, and the thickness D2 of the protective layer 3 satisfies: 24μm≤D2≤26μm. Specifically, the depth D1 of the recess 31 can be set to 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm. The thickness D2 of the protective layer 3 can be set to 24μm, 24.5μm, 25μm, 25.5μm, 26μm. These two sets of values ​​provide a good balance within the provided range, ensuring sufficient depth to accommodate the necessary structure without being too deep to affect the overall performance.

[0049] Preferably, the depth D1 of the recess 31 satisfies: 27μm≤D1≤33μm, and the thickness D2 of the protective layer 3 satisfies: 39μm≤D2≤41μm. Specifically, the depth D1 of the recess 31 can be set to 27μm, 27.5μm, 28μm, 28.5μm, 29μm, 29.5μm, 30μm, 30.5μm, 31μm, 31.5μm, 32μm, 32.5μm, 33μm. The thickness D2 of the protective layer 3 can be set to 39μm, 39.5μm, 40μm, 40.5μm, 41μm. These two sets of values ​​provide a good balance within the provided range, ensuring sufficient depth to accommodate the necessary structure without being too deep to affect the overall performance.

[0050] Preferably, Figure 4 , Figure 5 As shown, the concave portion 31 is set to a regular structure or an irregular structure, and the regular structure is a regular structure of a circle, a square, an ellipse or a cone. Further, when the concave portion 31 is set to a regular structure as shown in Figure 4 As shown, such as circular, square, elliptical or conical shapes, these shapes can effectively adapt to and protect the silicon-based layer 2, and prevent particles generated during laser etching. These regularly shaped recesses 31 can be evenly distributed on the silicon-based layer 2, providing a stable protection effect. When the recesses 31 are set to an irregular structure, although the complexity of the production process may be increased, this structure can better adapt to the irregular surface of the silicon-based layer 2, and the recesses 31 with irregular structures can fit the silicon-based layer 2 more closely, reducing the generation of particles during laser etching, thereby further improving the performance and cycle life of the battery.

[0051] In addition, whether the concave portion 31 is a regular structure or an irregular structure, the optimization of its depth D1 is crucial. By adjusting the coating thickness of the graphite coating and the silicon-based layer 2, the depth D1 of the concave portion 31 can be accurately controlled, thereby ensuring that the protective layer 3 can fully protect the silicon-based layer 2, reduce the formation of large particles, reduce the K value, and improve the performance of the battery.

[0052] Preferably, Figure 6As shown, the number of recesses 31 is multiple, and the multiple recesses 31 are evenly arranged on the protective layer 3, and the spacing between two adjacent recesses 31 is less than 2.5 mm. When the number of recesses 31 is set to multiple and evenly arranged on the protective layer 3, a denser protective structure can be formed. The spacing between two adjacent recesses 31 is less than 2.5 mm, which ensures that the silicon-based layer 2 is fully protected during the laser etching process and reduces the generation of particles. This dense arrangement of recesses 31 not only improves the overall effect of the protective layer 3, but also helps to reduce the open-circuit voltage fluctuation of the battery cell during the static period, that is, to reduce the K value. At the same time, the setting of multiple recesses 31 also improves the structural stability of the battery cell. During the battery charging and discharging process, the silicon-based layer 2 may generate stress due to volume changes, and multiple evenly distributed recesses 31 can effectively disperse these stresses and reduce the deformation and damage of the silicon-based layer 2. This helps to extend the cycle life of the battery cell and improve the overall performance.

[0053] Preferably, Figure 7 As shown, a graphite layer 32 is bonded to the surface of the protective layer 3, and a through hole 321 is penetrated inside the graphite layer 32, and the through hole 321 is connected to the recess 31. By further improving the protective layer 3, that is, bonding a layer of graphite layer 32 to the surface of the protective layer 3, and etching a through hole through the inside of the graphite layer 32, and the through hole is connected to the recess 31, the performance of the battery cell can be further optimized. The advantage of this structural design is that the presence of the through hole can effectively improve the permeability and distribution uniformity of the electrolyte in the active material layer. When the electrolyte penetrates into the recess 31 through the through hole, it can more fully contact the silicon base layer 2, thereby improving the reaction efficiency and energy density of the battery cell.

[0054] At the same time, the introduction of the graphite layer 32 also plays a role in enhancing conductivity. As an excellent conductive material, graphite can effectively improve the conductivity of the battery cell and reduce the internal resistance, thereby improving the energy output and cycle stability of the battery cell.

[0055] The negative electrode sheet was prepared according to the actual situation to obtain the following examples and comparative examples: Example 1

[0056] Coating of silicon-based materials: The coating process adopts double-layer coating. For the coating of silicon-based materials of the lower dry film, the thickness of the lower dry film is required to meet the specification of 60μm. If it is found that the thickness of the lower dry film does not meet the specification requirement of 60μm, the pump speed of the lower layer is adjusted and the coating is repeated. After the coating is completed, the pole piece is baked to remove moisture.

[0057] Coating graphite layer 32: Since the coating process adopts double-layer coating, the upper and lower layers are coated at the same time. The thickness of the upper and lower dry film layer materials is required to meet the 75μm specification. If the dry film thickness does not reach the 75μm specification, readjust the upper layer pump speed, re-coat, bake and dry, and measure the electrode thickness until the dry film thickness reaches the 75μm specification (that is, the upper graphite dry film thickness reaches the 15μm specification).

[0058] Laser etching: adjust the laser etching equipment parameters, laser etch to form a recess 31 on the pole piece, use a 3D profiler to detect the depth of the hole. If the depth of the recess 31 is not within the 12μm specification, continue to adjust the equipment parameters and adjust the drilling depth until the average hole depth is detected to be around 12μm.

[0059] Example 2

[0060] The difference from Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. A 3D profiler is used to detect the depth of the hole. If the depth of the recess 31 is not within the specification of 11 μm, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 11 μm.

[0061] The rest is the same as that of Example 1 and will not be described again here.

[0062] Example 3

[0063] The difference from Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. A 3D profiler is used to detect the depth of the hole. If the depth of the recess 31 is not within the specification of 10 μm, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 10 μm.

[0064] The rest is the same as that of Example 1 and will not be described again here.

[0065] Example 4

[0066] The difference from Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. A 3D profiler is used to detect the depth of the hole. If the depth of the recess 31 is not within the specification of 10.5 μm, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 10.5 μm.

[0067] The rest is the same as that of Example 1 and will not be described again here.

[0068] Example 5

[0069] The difference from Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. A 3D profiler is used to detect the depth of the hole. If the depth of the recess 31 is not within the specification of 9 μm, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 9 μm.

[0070] The rest is the same as that of Example 1 and will not be described again here.

[0071] Example 6

[0072] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 85μm. If the dry film thickness does not reach the specification of 85μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 25μm).

[0073] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 12 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 12 μm.

[0074] The rest is the same as that of Example 1 and will not be described again here.

[0075] Example 7

[0076] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 85μm. If the dry film thickness does not reach the specification of 85μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 25μm).

[0077] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 13μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 13μm.

[0078] The rest is the same as that of Example 1 and will not be described again here.

[0079] Example 8

[0080] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 85μm. If the dry film thickness does not reach the specification of 85μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 25μm).

[0081] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 14 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 14 μm.

[0082] The rest is the same as that of Example 1 and will not be described again here.

[0083] Example 9

[0084] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 85μm. If the dry film thickness does not reach the specification of 85μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 25μm).

[0085] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 15 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 15 μm.

[0086] The rest is the same as that of Example 1 and will not be described again here.

[0087] Example 10

[0088] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 85μm. If the dry film thickness does not reach the specification of 85μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 25μm).

[0089] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 16 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 16 μm.

[0090] The rest is the same as that of Example 1 and will not be described again here.

[0091] Embodiment 11

[0092] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 100μm. If the dry film thickness does not reach the specification of 100μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 40μm).

[0093] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 27 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 27 μm.

[0094] The rest is the same as Example 11 and will not be described again here.

[0095] Example 12

[0096] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 100μm. If the dry film thickness does not reach the specification of 100μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 40μm).

[0097] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 28μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 28μm.

[0098] The rest is the same as that of Example 1 and will not be described again here.

[0099] Example 13

[0100] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 100μm. If the dry film thickness does not reach the specification of 100μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 40μm).

[0101] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 30 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 30 μm.

[0102] The rest is the same as that of Example 1 and will not be described again here.

[0103] Embodiment 14

[0104] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 100μm. If the dry film thickness does not reach the specification of 100μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 40μm).

[0105] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 31 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 31 μm.

[0106] The rest is the same as Example 11 and will not be described again here.

[0107] Embodiment 15

[0108] The difference from Example 1 is that during the coating process of the graphite layer 32, the thickness of the upper and lower dry film layer materials is required to meet the specification of 100μm. If the dry film thickness does not reach the specification of 100μm, the upper layer pump speed is readjusted, re-coated, and the electrode thickness is measured after baking and drying until the dry film thickness reaches the specification of 85μm (that is, the upper graphite dry film thickness reaches the specification of 40μm).

[0109] In the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed on the pole piece by laser etching. The depth of the hole is detected using a 3D profiler. If the depth of the recess 31 is not within the 33 μm specification, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 33 μm.

[0110] The rest is the same as that of Example 1 and will not be described again here.

[0111] Comparative Example 1

[0112] Coating of silicon-based materials: The coating process adopts double-layer coating. For the coating of silicon-based materials of the lower dry film, the thickness of the lower dry film is required to meet the specification of 60μm. If it is found that the thickness of the lower dry film does not meet the specification requirement of 60μm, the pump speed of the lower layer is adjusted and the coating is repeated. After the coating is completed, the pole piece is baked to remove moisture.

[0113] Laser etching: adjust the laser etching equipment parameters, laser etch the electrode to form a recess 31, and use a 3D profiler to detect the depth of the hole. If the drilling depth of the silicon-based material is not within the 1μm specification, continue to adjust the equipment parameters and adjust the drilling depth until the average hole depth is detected to be around 1μm.

[0114] Comparative Example 2

[0115] What is different from Comparative Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted to form a recess 31 on the pole piece by laser etching, and the depth of the hole is detected using a 3D profiler. If the drilling depth of the silicon-based material is not within the specification of 10μm, the equipment parameters are continued to be adjusted to adjust the drilling depth until the average hole depth is detected to be around 10μm.

[0116] The rest is the same as Comparative Example 1 and will not be described again.

[0117] Comparative Example 3

[0118] What is different from Comparative Example 1 is that in the laser etching step, the laser etching equipment parameters are adjusted, and a recess 31 is formed by laser etching on the pole piece. A 3D profiler is used to detect the depth of the hole. If the drilling depth of the silicon-based material is not within the specification of 20μm, the equipment parameters are further adjusted to adjust the drilling depth until the average hole depth is detected to be around 20μm.

[0119] The rest is the same as Comparative Example 1 and will not be described again.

[0120] In summary, the K value test was performed on the same type of lithium-ion batteries prepared by laser etching the pole pieces in Examples 1-15 and Comparative Examples 1-3, and the test results are recorded in Table 1.

[0121] Test method: Make the above electrodes into battery cells normally, and measure the K value of the battery cells at OCV. The K value calculation formula is K = (OCV1 cut-off voltage - OCV2 cut-off voltage) / standing time t, where the standing time is always defaulted to 168h.

[0122] Table 1

[0123]

[0124] The negative electrode sheets made by the embodiments and comparative examples are assembled into battery cells, and then the K value of the battery cells is tested, and the fluctuation of the open circuit voltage of the battery during the static period can be observed. This observation provides a basis for evaluating whether there are large particles in the electrode sheets and the electrolyte base of the battery cell. The K value represents the rate of change of the open circuit voltage of the battery during static period, that is, the rate of change of the battery voltage from the OCV1 cut-off voltage to the OCV2 cut-off voltage. If there are large particles in the electrode sheets or the electrolyte base of the battery cell, these particles may cause non-uniform reactions inside the battery, thereby affecting the performance of the battery. This effect will be reflected in an increase in the rate of change of the open circuit voltage, which will cause an increase in the K value. In addition, large particles may also cause local concentration or accumulation of substances inside the battery, resulting in an increase in internal resistance, which in turn causes an increase in energy loss and a shortened cycle life during the charge and discharge process. These potential problems will be reflected in the changes in the K value of the battery cell. Therefore, by monitoring the K value, it is possible to indirectly gain insight into the changes in the internal structure of the battery.

[0125] It can be concluded from the above Table 1 that the utility model can effectively suppress the particles generated by the laser etching of the silicon base layer 2 during the laser etching of the pole piece by coating the protective layer 3 on the silicon base layer 2, thereby eliminating the formation of large particles and the problem of cleaning. By comparing Examples 1-5 with Comparative Examples 1-3, it can be concluded that, under the premise of the same silicon-based coating thickness, the pole piece protected by the protective layer 3 on the pole piece silicon base layer 2 is lower than the pole piece not protected by the protective layer 3 on the pole piece silicon base layer 2 in the OCV detected K value and is below 0.06. Specifically, the battery cell pole piece in Comparative Example 1 is not designed with a protective layer 3 as shown in Examples 1-5 of the present application and has been laser etched, and the K value of its battery cell happens to be around 0.06. On the other hand, the K values ​​of the battery cell pole pieces in Comparative Examples 2 and 3 have exceeded 0.06. This means that after the pole piece prepared by the above method of the present application is prepared into a battery cell, the number of large particles between the active material layer and the electrolyte is significantly reduced.

[0126] It can be seen from the experimental data of Examples 6-10 that, under the premise of maintaining the same active material surface density of the battery electrode, the change in the K value detected by OCV is more obvious when the coating thickness of the graphite coating and the silicon-based layer 2 is increased. By improving the depth D1 of the recess 31 of Examples 6-10 of the utility model, the protective layer 3 can fully protect the silicon-based material.

[0127] It can be seen from the experimental data of Examples 11-15 that when the graphite coating is thicker and the laser-etched gap is deeper, the large particles of the pole piece are more difficult to clean and the K value of the prepared battery cell is more difficult to adjust. However, by improving the depth D1 of the recess 31 in Examples 11-15, the K value is also reduced, thereby optimizing the performance of the battery cell.

[0128] In summary, the present invention successfully reduces the fluctuation of the open circuit voltage of the battery cell during the static period, that is, reduces the K value, by coating the protective layer 3 on the silicon-based layer 2 and optimizing the depth D1 of the protective layer 3 through the coating thickness of the graphite layer 32. This improvement not only reduces the formation and cleaning problems of large particles inside the battery, but also improves the performance and cycle life of the battery.

[0129] It should be noted that: any of the above embodiments 1-15 can be used to prepare corresponding battery cells, and the prepared battery cells have the characteristics of good stability, high yield rate, long service life, etc.

[0130] According to the disclosure and teaching of the above description, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the above specific implementation, and any obvious improvement, replacement or modification made by the technicians in this field on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the utility model.

Claims

1. A negative electrode sheet, characterized in that: It comprises a current collector (1) and a silicon-based layer (2) coated on the surface of the current collector (1), wherein the surface of the silicon-based layer (2) is coated with at least one protective layer (3) for preventing the silicon-based layer (2) from being burned by laser; The protective layer (3) is laser etched to form a concave portion (31), the depth of the concave portion (31) is D1, and the thickness of the protective layer (3) is D2, which satisfies: D1≤D2.

2. The negative electrode sheet according to claim 1, characterized in that: The depth of the recess (31) is D1, and the thickness of the protective layer (3) is D2, which satisfy: D1≤1 / 2D2.

3. The negative electrode sheet according to claim 1, characterized in that: The depth D1 of the recess (31) satisfies: 9 μm≤D1≤12 μm, and the thickness D2 of the protective layer (3) satisfies: 14 μm≤D2≤16 μm.

4. The negative electrode sheet according to claim 1, characterized in that: The depth D1 of the recess (31) satisfies: 9 μm≤D1≤16 μm, and the thickness D2 of the protective layer (3) satisfies: 24 μm≤D2≤26 μm.

5. The negative electrode sheet according to claim 1, characterized in that: The depth D1 of the recess (31) satisfies: 27 μm ≤ D1 ≤ 33 μm, and the thickness D2 of the protective layer (3) satisfies: 39 μm ≤ D2 ≤ 41 μm.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The recess (31) is configured as a regular structure or an irregular structure, and the regular structure is a circular, square, elliptical or conical regular structure.

7. The negative electrode sheet according to claim 5, characterized in that: The number of the recesses (31) is multiple, the multiple recesses (31) are evenly arranged on the protective layer (3), and the distance D3 between two adjacent recesses (31) is less than 2.5 mm.

8. The negative electrode sheet according to claim 1, characterized in that: A graphite layer (32) is bonded to the surface of the protective layer (3), a through hole (321) penetrates the interior of the graphite layer (32), and the through hole (321) is connected to the recess (31).

9. A battery cell, characterized in that: A negative electrode sheet comprising any one of claims 1 to 8.

Images