阅读说明：本技术 一种锂离子电池用混合正极的制备方法 (Preparation method of mixed anode for lithium ion battery ) 是由 朱虎 于 2019-10-17 设计创作，主要内容包括：本发明提供了一种锂离子电池用混合正极的制备方法,所述正极的活性材料包括磷酸铁锂和镍钴锰酸锂三元材料,所述方法包括,将磷酸铁锂材料和三元材料分别过筛,将筛过的部分材料混合制成混合材料,然后再将其余材料分别制浆,得到磷酸铁锂浆料,三元材料浆料和混合浆料,然后按顺序将三元材料浆料,混合浆料,和磷酸铁锂浆料依次涂布在集流体上并干燥,得到正极。由本发明的制备方法得到的正极结构稳定,面密度高,并且循环寿命好。(The invention provides a preparation method of a mixed anode for a lithium ion battery, wherein an active material of the anode comprises a ternary material of lithium iron phosphate and nickel cobalt lithium manganate, the method comprises the steps of respectively sieving the lithium iron phosphate material and the ternary material, mixing the sieved materials to prepare a mixed material, then respectively pulping the rest materials to obtain a lithium iron phosphate slurry, the ternary material slurry and a mixed slurry, and then sequentially coating the ternary material slurry, the mixed slurry and the lithium iron phosphate slurry on a current collector and drying to obtain the anode. The positive electrode prepared by the preparation method provided by the invention has the advantages of stable structure, high surface density and long cycle life.)

1. A preparation method of a mixed anode for a lithium ion battery is provided, wherein the active material of the anode comprises a ternary material of lithium iron phosphate and nickel cobalt lithium manganate, the D50 of the lithium iron phosphate material is 1.8-2.2 μm, the D50 of the ternary material is 5-10 μm, and the preparation method is characterized in that: the preparation method comprises the following steps:

1) sieving the lithium iron phosphate material, wherein the aperture of a sieve mesh is 2.2-2.5 mu m, and collecting the material on the sieve mesh as a first material; collecting the material below the screen and sieving again, wherein the aperture of the screen is 0.5-0.8 μm, collecting the material on the screen as a second material, and mixing the material below the screen and the first material to obtain a lithium iron phosphate mixed material;

2) sieving the ternary material, wherein the aperture of a sieve mesh is 4-4.5 mu m, and collecting the material on the sieve mesh as a first material; collecting the material below the screen and sieving again, wherein the aperture of the screen is 2.5-3 μm, collecting the material on the screen as a second material, and mixing the material below the screen and the first material to obtain a ternary material mixed material;

3) placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and the ternary material mixed material in the step 2, vacuumizing and uniformly stirring to obtain a first slurry, wherein the slurry contains the ternary material: conductive agent: binder 100:3-4: 3-5;

4) and (3) mixing the second material obtained in the step (1) and the second material obtained in the step (2) to obtain a mixed material, wherein the mass ratio of lithium iron phosphate: placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and a mixed material, vacuumizing and uniformly stirring to obtain a second slurry, wherein the ternary material is 2-5:10, and the mixed material is prepared by mixing the following components in the slurry in a mass ratio: conductive agent: binder 100:4-5: 3-5;

5) and (3) mixing the second material obtained in the step (1) and the second material obtained in the step (2) to obtain a mixed material, wherein the mass ratio of lithium iron phosphate: placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and a mixed material, vacuumizing and uniformly stirring to obtain a third slurry, wherein the ternary material is 10:1-3, and the mixed material comprises the following components in percentage by mass: conductive agent: binder 100:5-8: 3-5;

6) placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and the lithium iron phosphate mixed material obtained in the step 1, vacuumizing and uniformly stirring to obtain a fourth slurry, wherein the slurry contains the following components in percentage by mass: conductive agent: binder 100:8-12: 5-7;

7) and sequentially coating and drying the first slurry, the second slurry, the third slurry and the fourth slurry on a current collector to obtain a first layer, a second layer, a third layer and a fourth layer, and carrying out hot pressing to obtain the anode.

2. The method of claim 1, wherein said lithium iron phosphate material is selected from the group consisting of pure lithium iron phosphate, carbon-coated lithium iron phosphate, metal-modified lithium iron phosphate, and combinations thereof.

3. The method of claim 1, wherein the ternary material is selected from a pure nickel cobalt manganese ternary material or a modified nickel cobalt manganese ternary material.

4. The method of claims 1-2, wherein the first layer, the second layer, the third layer, and the fourth layer have a thickness ratio of 100:10 to 20:5 to 10.

5. The method of claims 1-3, wherein the lithium iron phosphate material has a D10 of 0.3-0.5 μm and a D90 of 2.5-3 μm.

6. The method of claims 1-4, wherein the ternary material has a D10 of 1.5-2 μm and a D90 of 15-20 μm.

7. A mixed positive electrode for a lithium ion battery, which is prepared by the preparation method of 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 of a mixed anode for a lithium ion battery.

Background

The ternary material is a mainstream material of a power lithium ion battery due to a high discharge platform and high energy density, but the cyclicity of the ternary material is poor, and the main reason is the problems of decomposition of electrolyte on the surface of an electrode, dissolution of Ni, Mn and Co elements and the like under high potential; the lithium iron phosphate has the advantages of low price, good cyclicity, good safety and the like, and is widely used in the anode material of the lithium ion battery, but the tap density of the lithium iron phosphate is low, so that the ternary material and the lithium iron phosphate material are generally mixed together in the prior art, so that the stacking density of the anode active material layer is improved, but the process parameters from material mixing to coating processing of slurry mixed with different particle sizes are difficult to control, and the quality of the electrode is uneven.

Disclosure of Invention

On the basis, the invention provides a preparation method of a mixed anode for a lithium ion battery, wherein an active material of the anode comprises a ternary material of lithium iron phosphate and nickel cobalt lithium manganate, the method comprises the steps of sieving the lithium iron phosphate material and the ternary material respectively, mixing the sieved materials to prepare a mixed material, pulping the rest materials respectively to obtain lithium iron phosphate slurry, the ternary material slurry and mixed slurry, and sequentially coating the ternary material slurry, the mixed slurry and the lithium iron phosphate slurry on a current collector and drying to obtain the anode. The positive electrode prepared by the preparation method provided by the invention has the advantages of stable structure, high surface density and long cycle life.

The specific scheme is as follows:

a preparation method of a mixed anode for a lithium ion battery is provided, wherein the active material of the anode comprises a ternary material of lithium iron phosphate and nickel cobalt lithium manganate, the D50 of the lithium iron phosphate material is 1.8-2.2 μm, the D50 of the ternary material is 5-10 μm, and the preparation method is characterized in that: the preparation method comprises the following steps:

1) sieving the lithium iron phosphate material, wherein the aperture of a sieve mesh is 2.2-2.5 mu m, and collecting the material on the sieve mesh as a first material; collecting the material below the screen and sieving again, wherein the aperture of the screen is 0.5-0.8 μm, collecting the material on the screen as a second material, and mixing the material below the screen and the first material to obtain a lithium iron phosphate mixed material;

2) sieving the ternary material, wherein the aperture of a sieve mesh is 4-4.5 mu m, and collecting the material on the sieve mesh as a first material; collecting the material below the screen and sieving again, wherein the aperture of the screen is 2.5-3 μm, collecting the material on the screen as a second material, and mixing the material below the screen and the first material to obtain a ternary material mixed material;

3) placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and the ternary material mixed material in the step 2, vacuumizing and uniformly stirring to obtain a first slurry, wherein the slurry contains the ternary material: conductive agent: binder 100:3-4: 3-5;

4) and (3) mixing the second material obtained in the step (1) and the second material obtained in the step (2) to obtain a mixed material, wherein the mass ratio of lithium iron phosphate: placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and a mixed material, vacuumizing and uniformly stirring to obtain a second slurry, wherein the ternary material is 2-5:10, and the mixed material is prepared by mixing the following components in the slurry in a mass ratio: conductive agent: binder 100:4-5: 3-5;

5) and (3) mixing the second material obtained in the step (1) and the second material obtained in the step (2) to obtain a mixed material, wherein the mass ratio of lithium iron phosphate: placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and a mixed material, vacuumizing and uniformly stirring to obtain a third slurry, wherein the ternary material is 10:1-3, and the mixed material comprises the following components in percentage by mass: conductive agent: binder 100:5-8: 3-5;

6) placing an organic solvent in a vacuum stirring kettle, sequentially adding a binder, a conductive agent and the lithium iron phosphate mixed material obtained in the step 1, vacuumizing and uniformly stirring to obtain a fourth slurry, wherein the slurry contains the following components in percentage by mass: conductive agent: binder 100:8-12: 5-7;

7) and sequentially coating and drying the first slurry, the second slurry, the third slurry and the fourth slurry on a current collector to obtain a first layer, a second layer, a third layer and a fourth layer, and carrying out hot pressing to obtain the anode.

Further, the lithium iron phosphate material is selected from pure lithium iron phosphate, carbon-coated lithium iron phosphate, metal-modified lithium iron phosphate and a combination thereof.

Further, the ternary material is selected from a pure nickel-cobalt-manganese ternary material or a modified nickel-cobalt-manganese ternary material.

Furthermore, the thickness ratio of the first layer, the second layer, the third layer and the fourth layer is 100:10-20:10-20: 5-10.

Furthermore, the D10 of the lithium iron phosphate material is 0.3-0.5 μm, and the D90 is 2.5-3 μm.

Further, the D10 of the ternary material is 1.5-2 μm, and the D90 is 15-20 μm.

7. The mixed positive electrode is prepared by the preparation method.

The invention has the following beneficial effects:

1) through a plurality of tests, the applicant finds that the lithium iron phosphate and the ternary material are sieved under the size of the screen, the small-particle-size particle material and the large-particle-size particle material are collected and mixed, and the small particles can be just filled in gaps of the large particles due to relatively differentiated particle size distribution, so that the stacking density of the anode material layer is improved;

2) the lithium iron phosphate is mixed with medium particles of a ternary material, and the particle size distribution of the lithium iron phosphate can enable small particles to fill gaps of large particles, so that the stacking density of the anode material layer is improved; (ii) a

3) The ternary material is used as a main material as an inner layer, and the lithium iron phosphate material is used as a surface layer, so that the cycle performance of the anode with the ternary material as a main body can be improved on the premise of ensuring the energy density;

4) two layers of transition layers, so that the volume change between layers is more uniform, and the phenomenon that the separation between layers is caused due to the overlarge volume change difference between layers to influence the cycle life is prevented.

Detailed Description

The invention will now be described in more detail by means of specific examples, without limiting the scope of the invention theretoExamples are given. The lithium iron phosphate particles used in the examples and comparative examples of the present invention were LiFePO₄The ternary material is LiNi (2%)/C_0.4Mn_0.3Co_0.3O₂。