阅读说明：本技术 一种梯次结构硅碳负极极片的制备方法及其产品 (Preparation method of silicon-carbon negative electrode plate with gradient structure and product thereof ) 是由 崔大祥 王金 张芳 卢玉英 葛美英 王亚坤 焦靖华 张放为 颜雪冬 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种梯次结构硅碳负极极片的制备方法及其产品,包括制备涂炭铜箔、制备不同比例的电极浆料和将浆料A和浆料B按照不同的顺序涂在涂炭铜箔上,形成炭层-浆料层这样的梯次结构。采用该方法得到的电池极片,减小了电池内阻,缓解了嵌锂过程中的体积膨胀,极大提升了电池的倍率性能和循环性能。操作简单易行,可控性高,适合产业化生产。(The invention discloses a preparation method of a silicon-carbon negative pole piece with a ladder structure and a product thereof. The battery pole piece obtained by the method reduces the internal resistance of the battery, relieves the volume expansion in the lithium embedding process, and greatly improves the rate capability and the cycle performance of the battery. The method is simple and easy to operate, high in controllability and suitable for industrial production.)

1. A preparation method of a silicon-carbon negative electrode plate with a echelon structure is characterized by comprising the following steps:

1) preparing carbon-coated copper foil: selecting a high-conductivity material as a conductive agent, mixing the conductive agent with a binder according to a certain proportion, mixing the mixture, and coating the mixture on a copper foil;

2) preparing electrode slurry with different proportions: mixing and pulping a silicon-carbon active material, a conductive agent and a binder according to different proportions to obtain two parts of slurry A and slurry B with different concentrations;

3) coating the sizing agent A and the sizing agent B on the carbon-coated copper foil according to different sequences to form a carbon layer-sizing agent layer ladder structure.

2. The method for preparing the silicon-carbon negative electrode plate with the ladder structure according to claim 1, wherein the thickness of the copper foil current collector is 6-12 um.

3. The preparation method of the silicon-carbon negative electrode plate with the echelon structure according to claim 1, wherein in the step 1), the mass ratio of the conductive agent to the binder is 1: 1.

4. the preparation method of the silicon-carbon negative electrode plate with the ladder structure as claimed in claim 1, wherein in the step 2), the mass ratio of the silicon-carbon active material, the conductive agent and the binder of the slurry A is 9: 0.5: 0.5; the mass ratio of the silicon-carbon active material, the conductive agent and the binder of the slurry B is 4: 2: 1.

5. the method for preparing the silicon-carbon negative electrode plate with the echelon structure as recited in claim 1, wherein in the step 1), the carbon coating thickness is 2 μm.

6. The method for preparing the silicon-carbon negative electrode plate with the ladder structure according to claim 1, wherein in the step 2), the thickness of the slurry A is 75 μm, and the thickness of the slurry B is 25 μm, or the thickness of the slurry A is 25 μm, and the thickness of the slurry B is 75 μm.

7. The preparation method of the silicon-carbon negative electrode plate with the echelon structure according to any one of claims 1 to 6, which is characterized by comprising the following steps:

1) preparing carbon-coated copper foil: selecting high-conductivity material graphene as a conductive agent, and mixing with a binder according to the ratio of 1: mixing and pulping at a ratio of 1, coating on a copper foil, wherein the thickness of a carbon layer is 2 mu m, and drying in vacuum at 110 ℃ for later use;

2) preparing electrode slurry with different proportions: silicon-carbon active material, conductive agent Super C and adhesive are mixed according to the weight ratio of 9: 0.5: 0.5 make-up slurry A and 4: 2: 1 preparing slurry B;

3) coating the slurry A on the carbon-coated copper foil to a thickness of 75 μm, drying, coating the slurry B to a thickness of 25 μm, and obtaining the electrode with the carbon layer-slurry A-slurry B echelon structure, which is named as electrode CAB.

8. The preparation method of the silicon-carbon negative electrode plate with the echelon structure according to any one of claims 1 to 6, which is characterized by comprising the following steps:

1) preparing carbon-coated copper foil: selecting high-conductivity material graphene oxide as a conductive agent, and mixing the conductive agent with a binder according to the ratio of 1: mixing and pulping at a ratio of 1, coating on a copper foil, wherein the thickness of a carbon layer is 2 mu m, and drying in vacuum at 110 ℃ for later use;

2) preparing electrode slurry with different proportions: respectively mixing a silicon-carbon active material, a conductive agent Super C and a binder according to the weight ratio of 9: 0.5: 0.5 make-up slurry A and 4: 2: 1 preparing slurry B;

3) coating the slurry B on the carbon-coated copper foil with the thickness of 25 mu m, drying, coating the slurry A with the thickness of 75 mu m, and obtaining the electrode with the carbon layer-slurry B-slurry A echelon structure, which is named as electrode CBA.

9. A silicon-carbon negative electrode plate with a ladder structure, which is characterized by being prepared according to any one of the methods of claims 1 to 8.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a silicon-carbon negative electrode plate with a gradient structure and a product thereof.

Background

The lithium ion battery has the advantages of high energy density, convenient use and the like, and is widely applied to the fields of portable electronic equipment, electric tools, hybrid electric/full electric automobiles and the like. With the expansion of the application fields and the increase of the requirements, the lithium ion batteries are being developed in the direction of pursuing light weight and miniaturization. At present, the theoretical capacity of a commercial graphite negative electrode is 372mAh/g, and the gram capacity in a full battery reaches 355mAh/g, which is basically the limit value of application. Therefore, high capacity electrode materials are receiving increasing attention. Among them, the silicon carbon negative electrode material is becoming the preferred of battery enterprises due to the reserve capacity and the ultrahigh specific capacity.

However, silicon carbon materials have significant disadvantages, mainly in the following areas: 1) during the charging and discharging process, lithium is inserted and removed to cause silicon volume expansion, and the volume effect seriously influences the electrochemical performance of the battery; 2) the silicon material has poor conductivity, so that the first efficiency of the battery is very low, and the exertion of the battery capacity is limited.

Therefore, it is crucial to relieve the volume expansion during charging and discharging and to improve the conductivity of the material and the electrode plate.

Disclosure of Invention

Based on the problems in the prior art, the invention aims to provide a preparation method of a silicon-carbon negative electrode plate with a echelon structure.

Yet another object of the present invention is to: the silicon-carbon negative electrode plate product with the echelon structure prepared by the method is provided.

The purpose of the invention is realized by the following scheme: a preparation method of a silicon-carbon negative pole piece with a echelon structure comprises the following process steps:

1) preparing carbon-coated copper foil: selecting a high-conductivity material as a conductive agent, mixing the conductive agent with a binder according to a certain proportion, mixing the mixture, and coating the mixture on a copper foil;

2) preparing electrode slurry with different proportions: mixing and pulping a silicon-carbon active material, a conductive agent and a binder according to different proportions to obtain two parts of slurry A and slurry B with different concentrations;

3) and coating the sizing agent A and the sizing agent on the carbon-coated copper foil according to different sequences to form a carbon layer-sizing agent layer ladder structure.

Wherein, the binder can be selected from CMC and the like commonly used by battery dyes.

Preferably, the thickness of the copper foil current collector is 6-12 um.

Preferably, the mass ratio of the conductive agent to the binder in the step 1) is 1: 1.

preferably, the mass ratio of the slurry A, the silicon-carbon active material, the conductive agent and the binder in the step 2) is 9: 0.5: 0.5; the mass ratio of the slurry B silicon-carbon active material to the conductive agent to the binder is 4: 2: 1.

preferably, in the step 1), the thickness of the carbon coating is 2 um.

Preferably, in step 2), the thickness of slurry a is 75um, and the thickness of slurry B is 25um, or the thickness of slurry a is 25um, and the thickness of slurry B is 75 um.

The invention also provides a silicon-carbon negative electrode plate with a echelon structure, which is prepared according to the method.

According to the invention, the contact area of the active material and the current collector is increased through the carbon layer, the conductivity is improved to a certain extent, and the internal resistance is reduced. The electrode structures with different proportion gradients relieve the volume expansion of the battery in the circulating process, thereby well improving the electrochemical performance of the battery. The method has the advantages of simple operation of steps, easily controlled conditions, convenient large-scale production, saving a large amount of cost and time, and greatly improving the electrochemical performance of the battery.

Drawings

FIG. 1 is a flow chart of the electrode preparation of the present invention;

fig. 2 is a graph comparing the cycle performance of the battery of the present invention.

Detailed Description

Example 1

A silicon-carbon negative electrode plate with a echelon structure is prepared by the following steps as shown in figure 1:

1) preparing carbon-coated copper foil: selecting high-conductivity material graphene as a conductive agent, and mixing with a binder according to the ratio of 1: mixing and pulping at a ratio of 1, coating on a copper foil, wherein the thickness of a carbon layer is 2 mu m, and drying in vacuum at 110 ℃ for later use;

2) preparing electrode slurry with different proportions: silicon-carbon active material, conductive agent Super C and adhesive are mixed according to the weight ratio of 9: 0.5: 0.5 make-up slurry A and 4: 2: 1 preparing slurry B;

3) coating the slurry A on the carbon-coated copper foil to a thickness of 75 μm, drying, coating the slurry B to a thickness of 25 μm, and obtaining the electrode with the carbon layer-slurry A-slurry B echelon structure, which is named as electrode CAB.

The charge and discharge capacity performance of the corresponding battery of the embodiment is measured in the voltage range of 0.01-1.5V, the first effect is 75.6%, and the first discharge specific capacity is 1500 mAh g^-1After 200 cycles, the specific discharge capacity is 1180 mAh g^-1As shown in fig. 2.

Example 2

A silicon-carbon negative electrode pole piece with a echelon structure is similar to the step of the embodiment 1, and is prepared by the following steps:

1) preparing carbon-coated copper foil: selecting high-conductivity material graphene oxide as a conductive agent, and mixing the conductive agent with a binder according to the ratio of 1: mixing and pulping at a ratio of 1, coating on a copper foil, wherein the thickness of a carbon layer is 2 mu m, and drying in vacuum at 110 ℃ for later use;

2) preparing electrode slurry with different proportions: respectively mixing a silicon-carbon active material, a conductive agent Super C and a binder according to the weight ratio of 9: 0.5: 0.5 make-up slurry A and 4: 2: 1 preparing slurry B;

3) coating the slurry B on the carbon-coated copper foil with the thickness of 25 mu m, drying, coating the slurry A with the thickness of 75 mu m, and obtaining the electrode with the carbon layer-slurry B-slurry A echelon structure, which is named as electrode CBA.

The charge-discharge capacity performance of the corresponding battery of the embodiment is measured in the voltage range of 0.01-1.5V, the first effect is 74.2%, and the first discharge specific capacity is 1556 mAh g^-1After 200 cycles, the specific discharge capacity is 1130 mAh g^-1As shown in fig. 2.

Comparative example 1

A silicon-carbon negative pole piece with a echelon structure is prepared by the following steps:

1) preparing carbon-coated copper foil: selecting high-conductivity material graphene oxide as a conductive agent, and mixing the conductive agent with a binder according to the ratio of 1: mixing and pulping at a ratio of 1, coating on a copper foil with a carbon layer thickness of 2 mu m, and drying in vacuum at 110 ℃ for later use;

2) preparing electrode slurry: respectively mixing a silicon-carbon active material, a conductive agent Super C and a binder according to the weight ratio of 9: 0.5: 0.5 preparing slurry A;

3) the slurry A is coated on the carbon-coated copper foil, the thickness is 100 mu m, and the electrode with the carbon layer-slurry A echelon structure is obtained and named as electrode CA.

The charge and discharge capacity performance of the corresponding battery of the comparative example is measured in the voltage range of 0.01-1.5V, the first effect is 71.8 percent, and the first discharge specific capacity is 1453 mAh g^-1 After 200 cycles, the specific discharge capacity is 1025 mAh g^-1As shown in fig. 2.

Comparative example 2

A silicon-carbon negative pole piece with a echelon structure is prepared by the following steps:

1) preparing electrode slurry with different proportions: respectively mixing a silicon-carbon active material, a conductive agent Super C and a binder according to the weight ratio of 9: 0.5: 0.5 make-up slurry A and 4: 2: 1 preparing slurry B;

2) and coating the slurry A on a copper foil to a thickness of 75 microns, and after drying, coating the slurry B to a thickness of 25 microns to obtain the electrode with the slurry A-slurry B echelon structure, which is named as an electrode AB.

The charge and discharge capacity performance of the battery corresponding to the comparative example is measured in the voltage range of 0.01-1.5V, the first effect is 73.6 percent, and the first discharge specific capacity is 1470 mAh g^-1 After 200 cycles, the specific discharge capacity is 1150 mAh g^-1As shown in fig. 2.