阅读说明：本技术 一种用于锂离子电池正极的制备方法 (Preparation method for positive electrode of lithium ion battery ) 是由 陆晨杰 于 2019-10-18 设计创作，主要内容包括：本发明提供了一种用于锂离子电池正极的制备方法,所述正极包括集流体、位于集流体表面依次设置的第一活性物质层、第二活性物质层和第三活性物质层；所述负极由以下方法制备得到,将平均粒径为50-200nm的活性物质颗粒,石墨烯以及甲基萘磺酸钠分散在有机溶剂中得到第一浆料,平均粒径为5-8μm的活性物质颗粒,线状导电碳材料以及聚丙烯酰胺分散在有机溶剂中得到第二浆料,将平均粒径为0.5-2μm的活性物质颗粒,金属氧化物、膨胀石墨,和甲基萘磺酸钠分散在有机溶剂中得到第三浆料,依次涂布在所述集流体表面干燥得到所述正极。由本发明的制备方法得到的正极倍率性能好,能量密度高,循环寿命高。(The invention provides a preparation method for a lithium ion battery anode, wherein the anode comprises a current collector, and a first active material layer, a second active material layer and a third active material layer which are sequentially arranged on the surface of the current collector; the negative electrode is prepared by dispersing active substance particles with the average particle size of 50-200nm, graphene and sodium methylnaphthalenesulfonate in an organic solvent to obtain a first slurry, dispersing active substance particles with the average particle size of 5-8 mu m, a linear conductive carbon material and polyacrylamide in the organic solvent to obtain a second slurry, dispersing active substance particles with the average particle size of 0.5-2 mu m, metal oxide, expanded graphite and sodium methylnaphthalenesulfonate in the organic solvent to obtain a third slurry, and sequentially coating the third slurry on the surface of a current collector and drying to obtain the positive electrode. The positive electrode prepared by the preparation method provided by the invention has the advantages of good rate capability, high energy density and long cycle life.)

1. The preparation method for the positive electrode of the lithium ion battery comprises a current collector, and a first active material layer, a second active material layer and a third active material layer which are sequentially arranged on the surface of the current collector, wherein the first active material layer comprises active material particles with the average particle size of 50-200nm, graphene and sodium methylnaphthalenesulfonate; the second active material layer includes active material particles having an average particle diameter of 5 to 8 μm, a linear conductive carbon material, and polyacrylamide, and the third active material layer includes active material particles having an average particle diameter of 0.5 to 2 μm, a metal oxide, expanded graphite, and sodium methylnaphthalenesulfonate, characterized in that: the preparation method comprises the following steps:

1) adding a binder and sodium methyl naphthalene sulfonate into an organic solvent, uniformly stirring, then ball-milling graphene and active substance particles with the average particle size of 50-200nm at a high speed for 10-20h, putting into a glue solution, vacuumizing and stirring to obtain first slurry, wherein in the first slurry, the active substance particles: graphene: sodium methylnaphthalenesulfonate: binder 50:40-70:5-8: 4-6;

2) adding a binder and polyacrylamide into an organic solvent, uniformly stirring, sequentially putting active substance particles with the average particle size of 5-8 mu m and a linear conductive carbon material into a glue solution, and vacuumizing and stirring to obtain a second slurry, wherein in the second slurry, the active substance particles: linear conductive carbon material: polyacrylamide: binder 100:4-8:5-8: 3-5;

3) adding a binder and sodium methyl naphthalene sulfonate into an organic solvent, uniformly stirring, then carrying out high-speed ball milling on metal oxide and expanded graphite, and active substance particles with the average particle size of 0.5-2 mu m for 10-20h, then putting into a glue solution, vacuumizing and stirring to obtain a third slurry, wherein in the third slurry, the active substance particles: metal oxide(s): expanded graphite: sodium methylnaphthalenesulfonate: the binder is 50:30-50:20-40:5-8: 4-6;

4) coating the first slurry on a current collector, and drying to obtain a first active material layer; continuously coating the second slurry, and drying to obtain a second active material layer; continuously coating the third slurry, and drying to obtain a third active material layer; and carrying out hot pressing to obtain the anode.

2. The method of claim 1, wherein the active material is LiCo_0.6Ni_0.25Mn_0.15O₂。

3. The method according to claims 1-2, wherein the linear conductive carbon material is selected from carbon nanotubes or carbon nanofibers.

4. The process according to claims 1-3, wherein the metal oxide is selected from the group consisting of titanium dioxide, zirconium dioxide, titanium dioxide, aluminum oxide, silicon dioxide; preference is given to silicon dioxide, wherein the average particle diameter of the silicon dioxide is from 30 to 100 nm.

5. The method according to claims 1 to 4, wherein the first active material layer has a thickness of 1 to 3 μm, the second active material layer has a thickness of 20 to 80 μm, and the third active material layer has a thickness of 3 to 5 μm.

6. The method of claims 1-5, wherein the high-speed ball milling is performed at a speed of 200 r/min.

7. A positive electrode for a lithium ion battery, which is produced by the production method according to any one of claims 1 to 6.

Technical Field

The invention relates to the technical field of lithium ion battery production, in particular to a preparation method for a lithium ion battery anode.

Background

The lithium ion battery has the characteristics of high energy density, wide working temperature range, environmental friendliness and the like, and is widely applied to the fields of electric automobiles, energy storage and the like. Particularly in the field of electric automobiles, has higher requirements on the voltage platform, the energy density and the cyclicity of batteries, and the ternary material LiCo_0.6Ni_0.25Mn_0.15O₂The lithium ion battery positive electrode material has a high voltage platform and good high-temperature safety performance, and is widely applied to a lithium ion battery in the field, in order to pursue higher energy density, researchers hope that the particle size of the material is as large as possible, but the negative effects brought by the large particle size are poor in adhesion performance with a current collector, low in rate capability and obvious in volume effect in the using process, so that the material is separated from the surface of the positive electrode, the cycle capacity is rapidly attenuated, and particularly the cycle performance of working under large current is poor.

Disclosure of Invention

On the basis, the invention provides a preparation method for a lithium ion battery anode, wherein the anode comprises a current collector, a first active material layer, a second active material layer and a third active material layer which are sequentially arranged on the surface of the current collector, and the first active material layer comprises active material particles with the average particle size of 50-200nm, graphene and sodium methylnaphthalenesulfonate; the second active material layer comprises active material particles with an average particle size of 5-8 μm, a linear conductive carbon material and polyacrylamide, and the third active material layer comprises active material particles with an average particle size of 0.5-2 μm, a metal oxide, expanded graphite and sodium methylnaphthalenesulfonate; the negative electrode is prepared by dispersing active substance particles with the average particle size of 50-200nm, graphene and sodium methylnaphthalenesulfonate in an organic solvent to obtain a first slurry, dispersing active substance particles with the average particle size of 5-8 mu m, a linear conductive carbon material and polyacrylamide in the organic solvent to obtain a second slurry, dispersing active substance particles with the average particle size of 0.5-2 mu m, metal oxide, expanded graphite and sodium methylnaphthalenesulfonate in the organic solvent to obtain a third slurry, and sequentially coating the third slurry on the surface of a current collector and drying to obtain the positive electrode. The positive electrode prepared by the preparation method provided by the invention has the advantages of good rate capability, high energy density and long cycle life.

The first active material layer is arranged between the current collector and the second active material layer as a conductive layer and a transition layer, the first active material layer contains conductive material graphene with a high proportion and active materials with small particle sizes, the transition layer can be effectively arranged between the current collector and the second active material layer, the electrode conductive performance is improved, and the adhesion force between the active material layer and the current collector is improved; the second active material layer adopts linear conductive carbon to form a conductive network, so that the stability of active material particles with large particle size is improved; the third active material layer contains metal oxide with higher content, so that the passivation performance of the electrode surface is improved, the electrolyte is prevented from being decomposed on the surface of the positive electrode under high voltage, and meanwhile, the expanded graphite and the active material with small particle size are contained, so that the adsorption capacity of the third active material layer can be improved, the wetting performance of the electrolyte is improved, the volume effect of active material particles can be effectively relieved, and the active material is prevented from falling off from the surface of the positive electrode; sodium methylnaphthalenesulfonate as anionic dispersant can improve the dispersibility of metal oxide, graphene, expanded graphite and other substances and improve the coating uniformity of the active material layer, polyacrylamide as cationic dispersant is used for the second active material layer, due to the electrostatic adsorption of the anions and cations, the binding force among the first, second and third active material layers can be improved, the overall structural stability of the active material layers is improved, therefore, active particles with larger size can be used in the second active material layer, the energy density of the electrode is improved, the defects of rate performance and cycle performance reduction are avoided, the structural stability of the whole active material layer is improved, therefore, the active particles of the second active material layer can use active particles with larger sizes, the energy density of the electrode is improved, and the defects of rate performance and cycle performance reduction are avoided.

The specific scheme is as follows:

the preparation method for the positive electrode of the lithium ion battery comprises a current collector, and a first active material layer, a second active material layer and a third active material layer which are sequentially arranged on the surface of the current collector, wherein the first active material layer comprises active material particles with the average particle size of 50-200nm, graphene and sodium methylnaphthalenesulfonate; the second active material layer includes active material particles having an average particle diameter of 5 to 8 μm, a linear conductive carbon material, and polyacrylamide, and the third active material layer includes active material particles having an average particle diameter of 0.5 to 2 μm, a metal oxide, expanded graphite, and sodium methylnaphthalenesulfonate, characterized in that: the preparation method comprises the following steps:

1) adding a binder and sodium methyl naphthalene sulfonate into an organic solvent, uniformly stirring, then ball-milling graphene and active substance particles with the average particle size of 50-200nm at a high speed for 10-20h, putting into a glue solution, vacuumizing and stirring to obtain first slurry, wherein in the first slurry, the active substance particles: graphene: sodium methylnaphthalenesulfonate: binder 50:40-70:5-8: 4-6;

2) adding a binder and polyacrylamide into an organic solvent, uniformly stirring, sequentially putting active substance particles with the average particle size of 5-8 mu m and a linear conductive carbon material into a glue solution, and vacuumizing and stirring to obtain a second slurry, wherein in the second slurry, the active substance particles: linear conductive carbon material: polyacrylamide: binder 100:4-8:5-8: 3-5;

3) adding a binder and sodium methyl naphthalene sulfonate into an organic solvent, uniformly stirring, then carrying out high-speed ball milling on metal oxide and expanded graphite, and active substance particles with the average particle size of 0.5-2 mu m for 10-20h, then putting into a glue solution, vacuumizing and stirring to obtain a third slurry, wherein in the third slurry, the active substance particles: metal oxide(s): expanded graphite: sodium methylnaphthalenesulfonate: the binder is 50:30-50:20-40:5-8: 4-6;

4) coating the first slurry on a current collector, and drying to obtain a first active material layer; continuously coating the second slurry, and drying to obtain a second active material layer; continuously coating the third slurry, and drying to obtain a third active material layer; and carrying out hot pressing to obtain the anode.

Further, the active material is LiCo_0.6Ni_0.25Mn_0.15O₂。

Further, the linear conductive carbon material is selected from carbon nanotubes or carbon nanofibers.

Further, the metal oxide is selected from titanium dioxide, zirconium dioxide, titanium dioxide, aluminum oxide, silicon dioxide; silica having an average particle diameter of 30 to 100nm is preferable.

Further, the thickness of the first active material layer is 1-3 μm, the thickness of the second active material layer is 20-80 μm, and the thickness of the third active material layer is 3-5 μm.

Further, the rotating speed of the high-speed ball milling is 200 r/min.

The invention has the following beneficial effects:

1) the first active material layer is arranged between the current collector and the second active material layer as a conducting layer and a transition layer, so that the adhesion between the layers can be improved;

2) the first active material layer contains a conductive material graphene with a high proportion and an active material with a small particle size, so that the effect of a transition layer between the current collector and the second active material layer can be effectively achieved, the electrode conductivity is improved, and the adhesion between the active material layer and the current collector is improved;

3) the second active material layer adopts linear conductive carbon to form a conductive network, so that the stability of active material particles with large particle size is improved;

4) the third active material layer contains metal oxide with higher content, so that the passivation performance of the electrode surface is improved, the electrolyte is prevented from being decomposed on the surface of the positive electrode under high voltage, and meanwhile, the expanded graphite and the active material with small particle size are contained, so that the adsorption capacity of the third active material layer can be improved, the wetting performance of the electrolyte is improved, the volume effect of active material particles can be effectively relieved, and the active material is prevented from falling off from the surface of the positive electrode;

5) the sodium methylnaphthalenesulfonate is used as anionic dispersant, can improve the dispersibility of metal oxide, graphene, expanded graphite and other substances, improves the coating uniformity of the active material layer, and the polyacrylamide is used as cationic dispersant for the second active material layer.

6) Graphene or metal oxide and expanded graphite are compounded with active substances through high-speed ball milling, so that the conductivity of the active substances is improved, or the stability of the active substances to electrolyte is improved, and the volume effect is relieved.

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 positive electrode active materials used in the examples and comparative examples of the present invention were all LiCo_0.6Ni_0.25Mn_0.15O₂。