阅读说明：本技术 一种锂离子电池负极的制备方法 (Preparation method of lithium ion battery cathode ) 是由 朱虎 于 2020-05-12 设计创作，主要内容包括：本发明提供了一种锂离子电池负极的制备方法,所述负极包括集流体,以及位于集流体两侧的活性物质层,所述活性物质层中含有石墨颗粒和硅颗粒的混合物组成的活性物质,其中,所述石墨颗粒包括第一石墨颗粒和第二石墨颗粒,所述第一石墨颗粒的粒径D50为3.2-3.5微米,所述第二石墨颗粒的粒径D50为1.5-1.7微米,所述硅颗粒的粒径D50为1.2-1.5微米；所述制备方法包括配置第一石墨颗粒浆料,第二石墨颗粒浆料,和硅颗粒浆料,然后按照不同的配比配置底层浆料,中间层浆料和表层浆料,依次将底层浆料,中间层浆料和表层浆料涂覆在集流体上,并干燥,得到所述负极。本发明得到的负极,具有较高的能量密度和倍率性能,以及较优异的循环稳定性。(The invention provides a preparation method of a lithium ion battery negative electrode, which comprises a current collector and active material layers positioned on two sides of the current collector, wherein the active material layers contain active materials consisting of a mixture of graphite particles and silicon particles, the graphite particles comprise first graphite particles and second graphite particles, the particle size D50 of the first graphite particles is 3.2-3.5 micrometers, the particle size D50 of the second graphite particles is 1.5-1.7 micrometers, and the particle size D50 of the silicon particles is 1.2-1.5 micrometers; the preparation method comprises the steps of preparing first graphite particle slurry, second graphite particle slurry and silicon particle slurry, preparing bottom layer slurry, middle layer slurry and surface layer slurry according to different proportions, sequentially coating the bottom layer slurry, the middle layer slurry and the surface layer slurry on a current collector, and drying to obtain the negative electrode. The cathode obtained by the invention has higher energy density and rate capability and more excellent cycling stability.)

1. A preparation method of a lithium ion battery negative electrode comprises a current collector and active material layers positioned on two sides of the current collector, wherein the active material layers contain active materials composed of a mixture of graphite particles and silicon particles, the graphite particles comprise first graphite particles and second graphite particles, the particle size D50 of the first graphite particles is 3.2-3.5 micrometers, the particle size D50 of the second graphite particles is 1.5-1.7 micrometers, and the particle size D50 of the silicon particles is 1.2-1.5 micrometers; the preparation method comprises the following steps:

1) sequentially adding a binder and a conductive agent into a solvent, uniformly stirring, adding first graphite particles, and uniformly stirring to obtain first graphite particle slurry;

2) sequentially adding a binder and a conductive agent into the solvent, uniformly stirring, adding second graphite particles, and uniformly stirring to obtain second graphite particle slurry;

3) sequentially adding a binder and a conductive agent into a solvent, uniformly stirring, adding silicon particles, and uniformly stirring to obtain silicon particle slurry;

4) according to the first graphite particles: adding the first graphite particle slurry into the second graphite particle slurry according to the proportion of 1:9-3:7, and adding a solvent to adjust the solid content to obtain bottom layer slurry;

5) according to the first graphite particles: second graphite particles: adding the first graphite particle slurry into the second graphite particle slurry to be uniformly mixed, then adding the mixed slurry into the silicon particle slurry, and adding a solvent to adjust the solid content to obtain intermediate layer slurry;

6) according to the first graphite particles: adding the first graphite particle slurry into the second graphite particle slurry according to the proportion of 4:6-5:5, and adding a solvent to adjust the solid content to obtain surface layer slurry;

7) and sequentially coating the bottom layer slurry, the middle layer slurry and the surface layer slurry on a current collector, and drying to obtain the cathode.

2. The production method as claimed in the above claim, wherein the first graphite particle slurry has a solid content of 60 to 65%, the second graphite particle slurry has a solid content of 55 to 60%, and the silicon particle slurry has a solid content of 55 to 60%.

3. The method according to the preceding claim, wherein the solids contents of the primer slurry, the middle layer slurry and the surface layer slurry are each independently 50-55%.

4. The production method according to the preceding claim, wherein the mass ratio of the first graphite particles to the second graphite particles in the interlayer slurry satisfies the following relationship, b is 0.54 (a + c), where a is the mass fraction of the first graphite particles, b is the mass fraction of the second graphite particles, and c is the mass fraction of the silicon particles.

5. The method of claim, wherein the ratio of the thickness of each layer, bottom layer: an intermediate layer: the surface layer is 1-4:10: 1-2.

6. The method of claim, wherein the solvent is deionized water, the binder is SBR, and the conductive agent is super conductive carbon black.

7. A lithium ion battery negative electrode prepared by the method of any one of claims 1-6.

Technical Field

The invention relates to a preparation method of a lithium ion battery cathode.

Background

The lithium ion battery has the advantages of high energy density, long cycle life, small self-discharge, no memory effect, environmental friendliness and the like, is widely applied to the consumer electronics field such as smart phones, smart bracelets, digital cameras, notebook computers and the like, and has the largest consumption demand. Meanwhile, the electric vehicle is gradually popularized in the fields of pure electric vehicles, hybrid electric vehicles and extended-range electric vehicles, and the market share is the largest in increasing trend. The lithium ion battery mainly comprises a positive electrode, a negative electrode, electrolyte, a diaphragm and the like, wherein the selection of the negative electrode material is directly related to the energy density of the battery.

Disclosure of Invention

The invention provides a preparation method of a lithium ion battery negative electrode, which comprises a current collector and active material layers positioned on two sides of the current collector, wherein the active material layers contain active materials consisting of a mixture of graphite particles and silicon particles, the graphite particles comprise first graphite particles and second graphite particles, the particle size D50 of the first graphite particles is 3.2-3.5 micrometers, the particle size D50 of the second graphite particles is 1.5-1.7 micrometers, and the particle size D50 of the silicon particles is 1.2-1.5 micrometers; the active material layer sequentially comprises a bottom layer, a middle layer and a surface layer from a current collector to the surface of the active material layer, the active materials of the bottom layer and the surface layer are composed of first graphite particles and second graphite particles, and the active materials of the middle layer comprise the first graphite particles, the second graphite particles and silicon particles. The preparation method comprises the steps of preparing first graphite particle slurry, second graphite particle slurry and silicon particle slurry, preparing bottom layer slurry, middle layer slurry and surface layer slurry according to different proportions, sequentially coating the bottom layer slurry, the middle layer slurry and the surface layer slurry on a current collector, and drying to obtain the negative electrode. The cathode obtained by the invention has higher energy density and rate capability and more excellent cycling stability.

The specific scheme is as follows:

a preparation method of a lithium ion battery negative electrode comprises a current collector and active material layers positioned on two sides of the current collector, wherein the active material layers contain active materials composed of a mixture of graphite particles and silicon particles, the graphite particles comprise first graphite particles and second graphite particles, the particle size D50 of the first graphite particles is 3.2-3.5 micrometers, the particle size D50 of the second graphite particles is 1.5-1.7 micrometers, and the particle size D50 of the silicon particles is 1.2-1.5 micrometers; the preparation method comprises the following steps:

1) sequentially adding a binder and a conductive agent into a solvent, uniformly stirring, adding first graphite particles, and uniformly stirring to obtain first graphite particle slurry;

2) sequentially adding a binder and a conductive agent into the solvent, uniformly stirring, adding second graphite particles, and uniformly stirring to obtain second graphite particle slurry;

3) sequentially adding a binder and a conductive agent into a solvent, uniformly stirring, adding silicon particles, and uniformly stirring to obtain silicon particle slurry;

4) according to the first graphite particles: adding the first graphite particle slurry into the second graphite particle slurry according to the proportion of 1:9-3:7, and adding a solvent to adjust the solid content to obtain bottom layer slurry;

5) according to the first graphite particles: second graphite particles: adding the first graphite particle slurry into the second graphite particle slurry to be uniformly mixed, then adding the mixed slurry into the silicon particle slurry, and adding a solvent to adjust the solid content to obtain intermediate layer slurry;

6) according to the first graphite particles: adding the first graphite particle slurry into the second graphite particle slurry according to the proportion of 4:6-5:5, and adding a solvent to adjust the solid content to obtain surface layer slurry;

7) and sequentially coating the bottom layer slurry, the middle layer slurry and the surface layer slurry on a current collector, and drying to obtain the cathode.

Further, the solid content of the first graphite particle slurry is 60-65%, the solid content of the second graphite particle slurry is 55-60%, and the solid content of the silicon particle slurry is 55-60%.

Further, the solid contents of the bottom layer slurry, the middle layer slurry and the surface layer slurry are respectively 50-55% independently.

Further, in the interlayer slurry, the mass ratio of the first graphite particles to the second graphite particles to the silicon particles satisfies the following relationship, b is 0.54 (a + c), where a is the mass fraction of the first graphite particles, b is the mass fraction of the second graphite particles, and c is the mass fraction of the silicon particles.

Further, wherein the thickness ratio of each layer, bottom layer: an intermediate layer: the surface layer is 1-4:10: 1-2.

Further, the solvent is deionized water, the binder is SBR, and the conductive agent is superconducting carbon black.

Further, the lithium ion battery cathode is prepared by the method.

The invention has the following beneficial effects:

1) the inventor finds that the energy density and the cycle performance of the negative electrode can be improved by arranging slurry of the bottom layer, the middle layer and the surface layer in the negative electrode, and the volume effect of silicon can be effectively relieved by clamping the graphite-silicon mixed layer by the two graphite layers, so that the cycle performance is improved, and the rate performance of the negative electrode is improved.

2) In the intermediate layer, when the mass ratio of the first graphite particles, the second graphite particles, and the silicon particles satisfies the following relational expression, and b is 0.54 (a + c), the stability of the intermediate layer can be greatly improved, and the cycle performance of the electrode can be improved;

3) the bottom layer slurry has high conductivity and porosity, the multiplying power performance of the electrode is improved, and the surface layer slurry has low specific surface area per unit mass, so that the stability of the surface of the negative electrode to electrolyte is improved.

Detailed Description

The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples. The negative electrode of the present invention includes a current collector, and an active material layer on both sides of the current collector, the active material layer containing an active material composed of a mixture of graphite particles and silicon particles, wherein the graphite particles include first graphite particles and second graphite particles.