Negative pole piece as well as preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a negative pole piece as well as a preparation method and application thereof, and provides a negative pole piece which comprises a negative current collector and negative active material areas arranged on the surface of the negative current collector at intervals, the negative electrode active material area comprises a first negative electrode active material area and a second negative electrode active material area which are alternately arranged in sequence, the cohesiveness of the first negative electrode active material area is higher than that of the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate. Due to the fact that the cohesiveness of the first negative electrode active material area arranged on the edge of the negative electrode piece is high, the stripping force of the edge position of the negative electrode piece is high, the problem of large-area powder falling caused by slitting of the negative electrode piece can be greatly solved, and wide application is facilitated.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a negative electrode plate and a preparation method and application thereof. Background Art

[0002] A battery is a cup, trough or other container or part of a composite container that contains electrolyte solution and metal electrodes to generate current. It is a device that can convert chemical energy into electrical energy. Using batteries as an energy source can produce current with stable voltage, stable current, long-term stable power supply, and little external influence. The battery has a simple structure, is easy to carry, and is easy to charge and discharge. It is not affected by external climate and temperature, and has stable and reliable performance. It plays a great role in all aspects of modern social life.

[0003] The structure of the battery is simple, including positive electrode, negative electrode, separator and electrolyte. In daily production, the negative electrode always has the problem of powder falling off, especially after die-cutting, the peeling effect is poor, and large areas of powder falling off are prone to occur at the edge, which greatly affects the yield and even has a great impact on the performance of the battery cell.

[0004] In view of the fact that the negative electrode plate is prone to powder shedding, the formulation of the plate is improved from the perspective of plate design. However, lowering the proportion of active materials will greatly reduce the capacity of the battery cell, and if the peeling force is not increased, the plate will shed powder, affecting the performance. Therefore, it is urgent to provide a negative electrode plate to solve the problem of powder shedding of the negative electrode plate. Summary of the invention

[0005] The purpose of the present application is to provide a negative electrode plate and a preparation method and application thereof, aiming to solve the problem of powder shedding of negative electrode plates in the prior art.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present application provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode active material region spaced apart on the surface of the negative electrode current collector, wherein the negative electrode active material region comprises a first negative electrode active material region and a second negative electrode active material region alternately arranged in sequence, the first negative electrode active material region has higher adhesion than the second negative electrode active material region, and the first negative electrode active material region is arranged at the edge of the negative electrode plate.

[0008] In some embodiments, the first negative electrode active material region is obtained by coating a first negative electrode slurry, wherein the first negative electrode slurry includes the following components in weight percentage, taking the total weight of the first negative electrode slurry as 100%:

[0009] Negative electrode active material 95% to 96%;

[0010] Dispersant 1.3%,

[0011] Binder 2.7%~3.7%.

[0012] In some embodiments, the second negative electrode active material region is obtained by coating the second negative electrode slurry, wherein the second negative electrode slurry includes the following components in weight percentage, taking the total weight of the second negative electrode slurry as 100%:

[0013] Negative electrode active material 96.5%~97%;

[0014] Dispersant 1.5%~2%,

[0015] Binder 2%.

[0016] In some embodiments, the negative electrode active material includes any one of graphite and silicon carbon.

[0017] In some embodiments, the dispersing agent comprises carboxymethyl cellulose.

[0018] In some embodiments, the adhesive includes at least one of a styrene-butadiene rubber adhesive and a polyacrylic acid adhesive.

[0019] In some embodiments, the width of the first negative electrode active material region is 3 to 6 mm.

[0020] In some embodiments, the width of the negative electrode active material region is 72-77 mm.

[0021] In some embodiments, the width of the negative electrode plate is 80-82 mm.

[0022] In some embodiments, the negative electrode current collector includes copper foil.

[0023] In a second aspect, the present application provides a method for preparing a negative electrode sheet, comprising the following steps:

[0024] A negative electrode current collector is provided, and the first negative electrode slurry and the second negative electrode slurry are sequentially coated on the surface of the negative electrode current collector and dried; and then the coating is repeated on the other surface of the negative electrode current collector and dried to obtain a negative electrode sheet.

[0025] In some embodiments, the first negative electrode slurry is directly coated by placing a discharge port above the negative electrode current collector.

[0026] In some embodiments, the second negative electrode slurry is coated using a transfer coater.

[0027] In a third aspect, the present application provides a battery, comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein the negative electrode plate is such as the negative electrode plate described above.

[0028] The first aspect of the present application provides a negative electrode plate, which includes a negative electrode collector and a negative electrode active material area spaced apart on the surface of the negative electrode collector, wherein the negative electrode active material area includes a first negative electrode active material area and a second negative electrode active material area alternately arranged in sequence, the first negative electrode active material area has higher adhesion than the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate; due to the high adhesion of the first negative electrode active material area arranged at the edge of the negative electrode plate, the peeling force at the edge of the plate is relatively high, which can greatly improve the problem of large-area powder falling caused by the plate when cutting, which is conducive to wide application.

[0029] The second aspect of the present application provides a method for preparing a negative electrode sheet, which only requires coating the first negative electrode slurry and the second negative electrode slurry in sequence and then drying them to obtain a negative electrode sheet. The preparation method is simple and is conducive to wide application.

[0030] The battery provided in the third aspect of the present application includes the above-mentioned negative electrode plate. Therefore, there will be no problem of large-scale powder loss during the slitting process in the process of preparing the plate, which ensures that the battery cell performance can be exerted normally, greatly reduces the production defective rate, and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a peeling force test diagram provided in an embodiment of the present application.

[0033] Figure 2 This is the situation of the pole piece in comparative example 1 of the present application.

[0034] Figure 3 This is the pole piece situation of Example 2 of the present application.

[0035] Figure 4 It is a comparison chart of the cycle curves of Example 3 of the present application and Comparative Example 1.

[0036] Figure 5 It is a schematic diagram of the structure of the negative electrode plate provided in this application. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0038] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0039] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0040] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0041] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0042] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass in the embodiment description of the present application can be μg, mg, g, kg and other mass units known in the chemical industry.

[0043] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0044] In a first aspect, an embodiment of the present application provides a negative electrode sheet, such as Figure 5 As shown, the negative electrode plate includes a negative electrode current collector 1 and a negative electrode active material area 2 arranged at intervals on the surface of the negative electrode current collector, wherein the negative electrode active material area includes a first negative electrode active material area 3 and a second negative electrode active material area 4 arranged alternately in sequence, the first negative electrode active material area 3 has higher adhesion than the second negative electrode active material area 4, and the first negative electrode active material area 3 is arranged at the edge of the negative electrode plate.

[0045] The first aspect of the embodiment of the present application provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode active material area spaced apart on the surface of the negative electrode current collector, wherein the negative electrode active material area includes a first negative electrode active material area and a second negative electrode active material area alternately arranged in sequence, the first negative electrode active material area has higher adhesion than the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate; since the first negative electrode active material area arranged at the edge of the negative electrode plate has high adhesion, the peeling force at the edge of the plate is relatively high, which can greatly improve the problem of large-area powder falling caused by the plate when cutting, which is conducive to wide application.

[0046] The negative electrode sheet includes a negative electrode current collector 1 and a negative electrode active material region 2 spaced apart on the surface of the negative electrode current collector.

[0047] In some embodiments, the negative electrode current collector includes copper foil.

[0048] In some embodiments, the tab region is disposed between the negative electrode active material regions 2 on the surface of the negative electrode current collector.

[0049] In some embodiments, the first negative electrode active material region is obtained by coating a first negative electrode slurry, wherein the first negative electrode slurry includes the following components in weight percentage, taking the total weight of the first negative electrode slurry as 100%:

[0050] Negative electrode active material 95% to 96%;

[0051] Dispersant 1.3%,

[0052] Binder 2.7%~3.7%.

[0053] Wherein, the total mass of the first negative electrode slurry is 100%, and the weight percentage of the negative electrode active material is 95% to 96%. In some specific embodiments, the total mass of the first negative electrode slurry is 100%, and the weight percentage of the negative electrode active material includes but is not limited to 95%, 95.1%, 95.2%, 95.3%, 95.4%, 95.5%, 95.6%, 95.7%, 95.8%, 95.9%, 96%.

[0054] The total mass of the first negative electrode slurry is 100%, and the weight percentage of the dispersant is 1.3%.

[0055] Wherein, the total mass of the first negative electrode slurry is 100%, and the weight percentage of the binder is 2.7% to 3.7%. In some specific embodiments, the total mass of the first negative electrode slurry is 100%, and the weight percentage of the binder includes but is not limited to 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%.

[0056] In some embodiments, the second negative electrode slurry region is obtained by coating the second negative electrode slurry, wherein the second negative electrode slurry includes the following components in weight percentage, taking the total weight of the second negative electrode slurry as 100%:

[0057] Negative electrode active material 96.5%~97%;

[0058] Dispersant 1.5%~2%,

[0059] Binder 2%.

[0060] Wherein, the total mass of the second negative electrode slurry is 100%, and the weight percentage of the negative electrode active material is 96.5% to 97%. In some specific embodiments, the total mass of the second negative electrode slurry is 100%, and the weight percentage of the negative electrode active material includes but is not limited to 96.5%, 96.6%, 96.7%, 96.8%, 96.9%, and 97%.

[0061] Wherein, the total mass of the first negative electrode slurry is 100%, and the weight percentage of the dispersant is 1.5% to 2%. In some specific embodiments, the total mass of the first negative electrode active material is 100%, and the weight percentage of the dispersant includes but is not limited to 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2%.

[0062] The total mass of the second negative electrode slurry is 100%, including 2% by weight of the binder.

[0063] In some embodiments, the negative electrode active material includes any one of graphite and silicon carbon.

[0064] In some embodiments, the dispersing agent comprises carboxymethyl cellulose.

[0065] In some embodiments, the adhesive includes at least one of a styrene-butadiene rubber adhesive and a polyacrylic acid adhesive.

[0066] In some embodiments, the width of the first negative electrode active material area is 3 to 6 mm. In some specific embodiments, the width of the first negative electrode active material area includes but is not limited to 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, and 6 mm. Among them, the first negative electrode active material area has a high degree of adhesion and is arranged at the edge of the negative electrode pole piece, which is conducive to making the peeling force at the edge of the pole piece higher, and can also greatly improve the problem of large-area powder loss caused by the pole piece when cutting. If the width of the first negative electrode active material area is too large, it will affect the capacity of the battery cell. If the width of the first negative electrode active material area is too small, it will not play a role in improving the edge adhesion.

[0067] In some embodiments, the width of the negative electrode active material region is 72-77 mm. In some specific embodiments, the width of the negative electrode active material region includes but is not limited to 72 mm, 73 mm, 74 mm, 75 mm, 76 mm, and 77 mm.

[0068] In some embodiments, the width of the negative electrode plate is 80-82 mm. In some specific embodiments, the width of the negative electrode plate includes but is not limited to 80 mm, 80.5 mm, 81 mm, 81.5 mm, and 82 mm.

[0069] A second aspect of the embodiment of the present application provides a method for preparing a negative electrode sheet, comprising the following steps:

[0070] A negative electrode current collector is provided, and the first negative electrode slurry and the second negative electrode slurry are sequentially coated on the surface of the negative electrode current collector and dried; and then the coating is repeated on the other surface of the negative electrode current collector and dried to obtain a negative electrode sheet.

[0071] The method for preparing the negative electrode sheet provided in the second aspect of the embodiment of the present application only requires coating the first negative electrode slurry and the second negative electrode slurry in sequence and then drying them to obtain the negative electrode sheet. The preparation method is simple and is conducive to wide application.

[0072] In some embodiments, the first negative electrode slurry is directly coated by placing a discharge port above the negative electrode current collector.

[0073] In some embodiments, the second negative electrode slurry is coated using a transfer coater.

[0074] In some specific embodiments, during the coating process, the first negative electrode slurry is coated by placing a discharge port above the electrode sheet; the second negative electrode slurry is coated by a transfer coater, and the two slurries are coated simultaneously, which does not affect the time waste of the process. Drying is performed after single-sided coating, and drying is performed after double-sided coating, and the process is changed from the original process.

[0075] A third aspect of an embodiment of the present application provides a battery, comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein the negative electrode plate is such as the negative electrode plate described above.

[0076] The battery provided in the third aspect of the embodiment of the present application includes the above-mentioned negative electrode plate. Therefore, there will be no problem of large-scale powder loss during the slitting process in the process of preparing the plate, ensuring that the battery cell performance can be exerted normally, greatly reducing the production defective rate and reducing the production cost.

[0077] The following describes the invention in conjunction with specific embodiments.

[0078] Example 1

[0079] Negative electrode sheet and preparation method thereof

[0080] The negative electrode plate includes a negative electrode collector and a negative electrode active material area spaced apart on the surface of the negative electrode collector, wherein the negative electrode active material area includes a first negative electrode active material area and a second negative electrode active material area alternately arranged in sequence, the first negative electrode active material area has higher adhesion than the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate.

[0081] The first negative electrode active material area is obtained by coating the first negative electrode slurry, wherein the total mass of the first negative electrode slurry is 100%, and includes the following components in weight percentage:

[0082] Negative electrode active material 95%;

[0083] CMC dispersant 1.3%;

[0084] SBR binder 3.7%.

[0085] The second negative electrode active material area is obtained by coating the second negative electrode slurry, wherein the total mass of the second negative electrode slurry is 100%, and includes the following components in weight percentage:

[0086] Negative electrode active material 96.5%;

[0087] CMC dispersant 1.5%;

[0088] SBR binder 2%.

[0089] Method for preparing negative electrode sheet

[0090] A negative electrode current collector is provided, and a first negative electrode slurry and a second negative electrode slurry are sequentially coated on the surface of the negative electrode current collector and dried; the coating is repeated on the other surface of the negative electrode current collector and dried to obtain a negative electrode plate; during the coating process, the first negative electrode slurry is coated by placing a discharge port above the plate; the second negative electrode slurry is coated by a transfer coater, and the two slurries are coated simultaneously.

[0091] Example 2

[0092] Negative electrode sheet and preparation method thereof

[0093] Compared with Example 1, in the first negative electrode slurry, the addition amount of the "active material" is modified to "95.5%", the addition amount of the "SBR binder" is modified to "3.2%", and the others are consistent with Example 1.

[0094] Example 3

[0095] Negative electrode sheet and preparation method thereof

[0096] Compared with Example 1, in the first negative electrode slurry, the addition amount of the "active material" is modified to "96%", the addition amount of the "SBR binder" is modified to "2.7%", and the others are consistent with Example 1.

[0097] Comparative Example 1

[0098] Negative electrode sheet and preparation method thereof

[0099] Compared with Example 1, “first negative electrode slurry” is deleted, and the rest is consistent with Example 1.

[0100] The components of the first negative electrode slurry and the second negative electrode slurry of each embodiment and comparative example and the addition amount of each component are summarized in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] Performance testing and result analysis

[0105] (1) Figure 1 As shown in Table 2, the peeling force test of the first negative electrode slurry is a single-sided peeling force test result. As the proportion of SBR increases, the peeling force also increases.

[0106] Table 2

[0107]

[0108] (2) Analysis of electrode powder loss

[0109] Comparative Example 2 ( Figure 3 ) and Comparative Example 1 ( Figure 2 ) it can be observed that the edge of the pole piece of comparative example 1 is prone to powder loss after die-cutting, which greatly affects the performance of the battery cell; the pole piece of embodiment 2 has almost no powder loss and the die-cutting is not affected.

[0110] (3) Electrochemical performance

[0111] The 2Ah soft-pack battery cell uses a ternary positive electrode material and graphite system, a winding method, and a voltage range of 3.0-4.2V.

[0112] The first stage is charged to 3.0-3.1V, which is 1% of the total battery capacity; the second stage is charged to 3.6-3.65V, which is 9% of the total battery capacity; the third stage is charged to 3.9-3.95V, which is 30% of the total battery capacity. The temperature of the formation stage is room temperature formation, and the formation pressure is 1MPa.

[0113] As shown in Table 3, by adopting the method of the embodiment of the present application, the capacity of the battery cell will be improved to a certain extent, mainly because the NP ratio of the negative electrode is smaller and the formation loss is less.

[0114] From the perspective of Example 1, the cycle is worse because the formula ratio will cause the negative electrode to be unable to fully accept the lithium ions migrated from the positive electrode, resulting in lithium deposition, while Examples 2 and 3 can match the positive electrode and have good cycles. The poor cycle of Comparative Example 1 is caused by powder falling off the edge, resulting in lithium deposition in some positions ( Figure 4 ).

[0115] Table 3

[0116] Example / Comparative Example Capacity / mAh 100 cycles capacity retention rate / % Comparative Example 1 2063 96.3 Example 1 2075 97.5 Example 2 2068 98.2 Example 3 2070 98.4

[0117] In summary, the negative electrode plate provided in the embodiment of the present application includes a negative electrode current collector and a negative electrode active material area spaced apart on the surface of the negative electrode current collector, wherein the negative electrode active material area includes a first negative electrode active material area and a second negative electrode active material area alternately arranged in sequence, the first negative electrode active material area has higher adhesion than the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate; since the first negative electrode active material area arranged at the edge of the negative electrode plate has high adhesion, the peeling force at the edge of the plate is relatively high, which can greatly improve the problem of large-area powder falling caused by the plate when cutting, which is conducive to wide application.

[0118] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate includes a negative electrode collector and a negative electrode active material area spaced apart on the surface of the negative electrode collector, wherein the negative electrode active material area includes a first negative electrode active material area and a second negative electrode active material area alternately arranged in sequence, the first negative electrode active material area has higher adhesion than the second negative electrode active material area, and the first negative electrode active material area is arranged at the edge of the negative electrode plate.

2. The negative electrode sheet according to claim 1, characterized in that: The first negative electrode active material area is obtained by coating the first negative electrode slurry, wherein the first negative electrode slurry includes the following components in weight percentage, taking the total weight of the first negative electrode slurry as 100%: Negative electrode active material 95% to 96%; Dispersant 1.3%, Binder 2.7%~3.7%.

3. The negative electrode sheet according to claim 1, characterized in that: The second negative electrode active material area is obtained by coating the second negative electrode slurry, wherein the second negative electrode slurry includes the following components in weight percentage, taking the total weight of the second negative electrode slurry as 100%: Negative electrode active material 96.5%~97%; Dispersant 1.5%~2%, Binder 2%.

4. The negative electrode sheet according to claim 2 or 3, characterized in that: The negative electrode active material includes any one of graphite and silicon carbon; and / or, The dispersant comprises carboxymethyl cellulose; and / or, The adhesive includes at least one of a styrene-butadiene rubber adhesive and a polyacrylic acid adhesive.

5. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The width of the first negative electrode active material region is 3 to 6 mm; and / or, The width of the negative electrode active material area is 72 to 77 mm; and / or, The width of the negative electrode plate is 80-82 mm.

6. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The negative electrode current collector includes copper foil.

7. A method for preparing a negative electrode sheet according to any one of claims 1 to 6, characterized in that: The steps include: A negative electrode current collector is provided, and a first negative electrode slurry and a second negative electrode slurry are sequentially coated on the surface of the negative electrode current collector and dried; and then the coating is repeated on another surface of the negative electrode current collector and dried to obtain a negative electrode sheet.

8. The method for preparing a negative electrode sheet according to claim 7, characterized in that: The first negative electrode slurry is directly coated by placing a discharge port above the negative electrode current collector.

9. The method for preparing a negative electrode sheet according to claim 7, characterized in that: The second negative electrode slurry is coated by using a transfer coater.

10. A battery, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the negative electrode sheet is the negative electrode sheet as claimed in any one of claims 1 to 6.

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