阅读说明：本技术 一种锂离子电池负极及其制备方法 (Lithium ion battery cathode and preparation method thereof ) 是由 於志锋 彭冲 李俊义 徐延铭 于 2019-10-16 设计创作，主要内容包括：一种锂离子电池负极及其制备方法,属于锂离子电池技术领域；具体方案如下：一种锂离子电池负极,包括负极集流体和负极涂层,负极涂层包括涂层Ⅰ和涂层Ⅱ,涂层Ⅰ涂布在负极集流体的一个表面上,涂层Ⅱ涂布在负极集流体的另一个表面上,涂层Ⅰ包括混合物Ⅰ,混合物Ⅰ由负极主材、高比表面积导电剂、CMC和SBR组成,涂层Ⅱ由负极主材、低比表面积导电剂、CMC和SBR组成,涂层Ⅰ中负极主材的OI值记为OI<Sub>1</Sub>,涂层Ⅱ中负极主材的OI值记为OI<Sub>2</Sub>,OI<Sub>1</Sub>和OI<Sub>2</Sub>满足0.5≤OI<Sub>2</Sub>-OI<Sub>1</Sub>≤2.0。改善了负极长涂膏层与负极集流体间的极化效应,提高了高电压电池的循环性能。(A lithium ion battery cathode and a preparation method thereof belong to the technical field of lithium ion batteries; the specific scheme is as follows: a lithium ion battery negative electrode comprises a negative electrode current collector and a negative electrode coating, wherein the negative electrode coating comprises a coating I and a coating II, the coating I is coated on one surface of the negative electrode current collector, the coating II is coated on the other surface of the negative electrode current collector, the coating I comprises a mixture I, the mixture I comprises a negative electrode main material, a high specific surface area conductive agent, CMC and SBR, the coating II comprises a negative electrode main material, a low specific surface area conductive agent, CMC and SBR, and the OI value of the negative electrode main material in the coating I is marked as OI 1 And the OI value of the main material of the negative electrode in the coating II is marked as OI 2 ，OI 1 And OI 2 OI of 0.5 or more 2 ‑OI 1 Less than or equal to 2.0. Improves the polarization effect between the long coating layer of the negative electrode and the current collector of the negative electrode,the cycle performance of the high voltage battery is improved.)

1. The negative electrode of the lithium ion battery comprises a negative electrode current collector (3) and a negative electrode coating, wherein the negative electrode coating comprises a coating I (1) and a coating II (2), the coating I (1) is coated on one surface of the negative electrode current collector (3), and the coating II (2) is coated on the other surface of the negative electrode current collector (3)The method is characterized in that: the coating I (1) comprises a mixture I, the mixture I is composed of 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a high specific surface area conductive agent, 1.2-1.5% of sodium carboxymethylcellulose CMC and 1.0-1.4% of styrene butadiene rubber SBR in percentage by mass, the coating II (2) is composed of 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a low specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in percentage by mass, and the orientation degree OI value of crystals of the negative electrode main material in the coating I (1) is marked as OI₁The OI value of the main material of the negative electrode in the coating II (2) is marked as OI₂，OI₁And OI₂OI of 0.5 or more₂-OI₁≤2.0。

2. The lithium ion battery negative electrode of claim 1, wherein: the length of the coating I (1) is larger than that of the coating II (2).

3. The lithium ion battery negative electrode of claim 1, wherein: the specific surface area of the high specific surface area conductive agent is 150-800 m²/g。

4. The lithium ion battery negative electrode of claim 1, wherein: the specific surface area of the low specific surface area conductive agent is 50-100 m²/g。

5. The lithium ion battery negative electrode of claim 1, wherein: the thickness of the coating I (1) and the thickness of the coating II (2) are both 150-250 micrometers.

6. The lithium ion battery negative electrode of claim 1, wherein: the coating I (1) further comprises ethylene carbonate, and the ethylene carbonate accounts for 0.4-0.9% of the mixture I by mass.

7. A preparation method of a lithium ion battery cathode is characterized by comprising the following steps:

the method comprises the following steps: uniformly dispersing a mixture I consisting of 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a high specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in a solvent to prepare a negative electrode slurry A, and coating the negative electrode slurry A on one surface of a negative electrode current collector (3) to form a coating I (1);

step two: uniformly dispersing 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a low specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in a solvent to prepare a negative electrode slurry B, and coating the negative electrode slurry B on the other surface of a negative electrode current collector (3) to form a coating II (2);

step three: drying the negative current collector (3) coated with the negative slurry A and the negative slurry B to remove the solvent, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode;

wherein, the OI value of the main material of the negative electrode in the negative electrode slurry A is marked as OI₁The OI value of the main negative electrode material in the negative electrode slurry B is marked as OI₂，OI₁And OI₂OI of 0.5 or more₂-OI₁≤2.0。

8. The method for preparing the negative electrode of the lithium ion battery according to claim 7, wherein the method comprises the following steps: in the first step, the specific preparation method of the negative electrode slurry A comprises the following steps: step 1: mixing and uniformly dispersing 10-50% of the total mass of the CMC and all the high specific surface area conductive agents into a solvent; step 2: then adding 20-30% of the total mass of the negative main material and 20-30% of the total mass of the CMC, and uniformly dispersing; and step 3: adding 20-30% of the total mass of the main negative electrode material and 20-70% of the total mass of the CMC, and uniformly dispersing; and 4, step 4: adding 20-30% of the total mass of the main material of the negative electrode, and uniformly dispersing; and 5: adding 10-40% of the total mass of the main material of the negative electrode, and uniformly dispersing; step 6: and finally, completely adding the SBR, and uniformly dispersing to obtain the cathode slurry A.

9. The method for preparing the negative electrode of the lithium ion battery according to claim 7, wherein the method comprises the following steps: in the second step, the specific preparation method of the negative electrode slurry B comprises the following steps: step 1: mixing and uniformly dispersing 10-40% of the total mass of the CMC and all the low specific surface area conductive agents into a solvent; step 2: then adding 20-30% of the total mass of the negative main material and 20-30% of the total mass of the CMC, and uniformly dispersing; and step 3: adding 20-30% of the total mass of the main negative electrode material and 30-70% of the total mass of the CMC, and uniformly dispersing; and 4, step 4: adding 20-30% of the total mass of the main material of the negative electrode, and uniformly dispersing; and 5: adding 10-40% of the total mass of the main material of the negative electrode, and uniformly dispersing; step 6: and finally, completely adding the SBR, and uniformly dispersing to obtain the negative electrode slurry B.

10. The method for preparing the negative electrode of the lithium ion battery according to claim 7, wherein the method comprises the following steps: in the first step, ethylene carbonate is further added into the negative electrode slurry A, and the addition amount of the ethylene carbonate is 0.4-0.9% of the mass of the mixture I.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery cathode and a preparation method thereof.

Background

In the process of charging and discharging, the high-voltage lithium ion battery has the defects of fast capacity attenuation, short cycle life, large thickness expansion rate, especially the lithium ion battery with the voltage of more than or equal to 4.45V, the polarization effect of the long coating layer of the negative electrode is gradually enhanced along with the increase of the cycle times, lithium precipitation and the like are easy to occur, and the application of the high-voltage lithium ion battery is severely limited.

Disclosure of Invention

The invention aims to improve the cycle performance of a high-voltage lithium ion battery and improve the polarization effect between a long negative electrode paste coating and a negative electrode current collector.

The second purpose of the invention is to provide a preparation method of the lithium ion battery cathode.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the utility model provides a lithium ion battery negative pole, includes negative pole mass flow body and negative coating, the negative coating includes coating I and coating II, coating I coats on negative pole mass flow body's a surface, coating II coats on negative pole mass flow body's another surface, its characterized in that: the coating I comprises a mixture I, the mixture I comprises 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a high specific surface area conductive agent, 1.2-1.5% of sodium carboxymethyl cellulose (CMC) and 1.0-1.4% of Styrene Butadiene Rubber (SBR) in percentage by mass, the coating II comprises 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a low specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in percentage by mass, and the orientation degree OI value of crystals of the negative electrode main material in the coating I is marked as OI₁And the OI value of the main material of the negative electrode in the coating II is marked as OI₂，OI₁And OI₂OI of 0.5 or more₂-OI₁≤2.0。

Further, the length of the coating I is larger than that of the coating II.

Further, the specific surface area of the high specific surface area conductive agent is 150-800 m²/g。

Further, the low specific surface areaThe specific surface area of the conductive agent is 50-100 m²/g。

Furthermore, the thickness of the coating I (1) and the thickness of the coating II (2) are both 150-250 micrometers.

Further, the coating I also comprises ethylene carbonate, and the ethylene carbonate accounts for 0.4-0.9% of the mixture I by mass.

A preparation method of a lithium ion battery cathode comprises the following steps:

the method comprises the following steps: uniformly dispersing a mixture I consisting of 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a high specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in a solvent to prepare a negative electrode slurry A, and coating the negative electrode slurry A on one surface of a negative electrode current collector to form a coating I;

step two: uniformly dispersing 96.1-97.3% of a negative electrode main material, 0.5-1.0% of a low specific surface area conductive agent, 1.2-1.5% of CMC and 1.0-1.4% of SBR in a solvent to prepare a negative electrode slurry B, and coating the negative electrode slurry B on the other surface of the negative electrode current collector to form a coating II;

step three: drying the negative current collector coated with the negative slurry A and the negative slurry B to remove the solvent, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode;

wherein, the OI value of the main material of the negative electrode in the negative electrode slurry A is marked as OI₁The OI value of the main negative electrode material in the negative electrode slurry B is marked as OI₂，OI₁And OI₂OI of 0.5 or more₂-OI₁≤2.0。

Further, in the step one, a specific preparation method of the negative electrode slurry a is as follows: step 1: mixing and uniformly dispersing 10-50% of the total mass of the CMC and all the high specific surface area conductive agents into a solvent; step 2: then adding 20-30% of the total mass of the negative main material and 20-30% of the total mass of the CMC, and uniformly dispersing; and step 3: adding 20-30% of the total mass of the main negative electrode material and 20-70% of the total mass of the CMC, and uniformly dispersing; and 4, step 4: adding 20-30% of the total mass of the main material of the negative electrode, and uniformly dispersing; and 5: adding 10-40% of the total mass of the main material of the negative electrode, and uniformly dispersing; step 6: and finally, completely adding the SBR, and uniformly dispersing to obtain the cathode slurry A.

Further, in the second step, a specific preparation method of the negative electrode slurry B is as follows: step 1: mixing and uniformly dispersing 10-40% of the total mass of the CMC and all the low specific surface area conductive agents into a solvent; step 2: then adding 20-30% of the total mass of the negative main material and 20-30% of the total mass of the CMC, and uniformly dispersing; and step 3: adding 20-30% of the total mass of the main negative electrode material and 30-70% of the total mass of the CMC, and uniformly dispersing; and 4, step 4: adding 20-30% of the total mass of the main material of the negative electrode, and uniformly dispersing; and 5: adding 10-40% of the total mass of the main material of the negative electrode, and uniformly dispersing; step 6: and finally, completely adding the SBR, and uniformly dispersing to obtain the negative electrode slurry B.

Further, in the first step, ethylene carbonate is added into the negative electrode slurry A, and the addition amount of the ethylene carbonate is 0.4-0.9% of the mass of the mixture I.

Compared with the prior art, the invention has the following advantages and beneficial effects:

according to the invention, through two coating processes, different types of negative electrode slurry are respectively coated on two sides of the negative electrode current collector to improve the liquid absorption performance and the dynamic performance of the negative electrode pole piece of the high-voltage battery, and particularly, the polarization effect between the negative electrode long paste coating layer and the negative electrode current collector is improved, so that the cycle performance of the high-voltage battery is improved.

Drawings

FIG. 1: a schematic structural diagram of a negative pole piece;

in the figure: 1. coating I, 2, coating II, 3, negative current collector 3.

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and modifications and equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit of the technical solutions of the present invention, and the technical solutions of the present invention are covered by the protection scope of the present invention.

The negative electrode main material and the conductive agent referred to in the following specific embodiments are all conventional materials in lithium ion batteries; the related 'drying, rolling, slitting and flaking' are all conventional technical means for preparing the lithium ion battery in the field.