CN115939392A

CN115939392A - Negative electrode slurry, preparation method thereof and lithium ion battery

Info

Publication number: CN115939392A
Application number: CN202211536229.8A
Authority: CN
Inventors: 毛霏; 王理; 洪斯凡
Original assignee: Eve Energy Co Ltd
Current assignee: Eve Energy Co Ltd
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2023-04-07

Abstract

The invention relates to a negative electrode slurry, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps: (1) Mixing the aqueous binder and the synthetic fiber glue solution to obtain a dispersed glue solution; (2) Mixing a negative electrode material, a conductive agent and the dispersed glue solution obtained in the step (1) to obtain a mixed solution; (3) And (3) mixing the synthetic rubber and the mixed liquid obtained in the step (2) to obtain the negative electrode slurry. The invention provides a preparation method of cathode slurry, which adopts an aqueous binder with conductive performance, and reduces the solid content of the cathode slurry by improving the mixing process, thereby greatly improving the rate performance of the prepared battery, and improving the cycle performance and the high-temperature storage performance.

Description

Negative electrode slurry, preparation method thereof and lithium ion battery

Technical Field

The invention belongs to the technical field of lithium ion battery material manufacturing, relates to a preparation method of negative electrode slurry, and particularly relates to negative electrode slurry, a preparation method of the negative electrode slurry and a lithium ion battery.

Background

The aqueous binder material is a conductive adhesive which can be used for a high-energy-density and high-performance battery system such as 3C power and the like, and the aqueous binder in the current market is prepared into a CMC + conductive agent + SBR integrated aqueous binder product by combining a specific pretreatment process with an in-situ synthesis and dispersion blending process, so that the production efficiency can be greatly improved, the short-range of the battery is promoted, and the binding power of a pole piece is improved. However, the solid content in the slurry is reduced due to the addition of the aqueous binder, so that the phenomena of high viscosity, low solid content and the like occur in the preparation process of the slurry, and the pole piece has the phenomena of rolling and cracking at two sides, large-area powder falling or no drying in the middle and the like.

CN 106876656A provides a preparation method of a negative electrode slurry for a lithium ion battery, including: providing at least one negative electrode active material, a conductive agent, a polymer monomer or prepolymer and a solvent, adding the negative electrode active material, the conductive agent and the polymer monomer or prepolymer into the solvent for uniform dispersion, then adding an initiator to carry out polymerization reaction on the polymer monomer or prepolymer at a certain temperature, thereby preparing negative electrode slurry. In addition, the negative electrode slurry prepared by the method, the negative electrode sheet prepared by the negative electrode slurry and the lithium ion battery containing the negative electrode sheet are also provided.

CN 106169559A discloses a negative electrode slurry, a preparation method of the negative electrode slurry, a negative electrode sheet and a lithium ion battery which are made of the negative electrode slurry, and the negative electrode sheet and the lithium ion battery comprise the following components in parts by weight: 91-95% of hard carbon and graphite mixture, 1-3% of conductive carbon black, 4-6% of polyvinylidene fluoride and oxalic acid accounting for 0.1-0.3% of the total weight of the materials. The lithium ion battery prepared by adopting the cathode slurry of the technical scheme has the following technical effects: the battery can discharge at high rate of 10C-30C, the 20C/1C discharge capacity can reach 95%, and the 30C/1C discharge capacity can reach more than 90%; the battery can be rapidly charged at a large multiplying power, and after 5C rapid charging, the release rates of 10C and 20C high multiplying power discharge capacities are both as high as more than 98%.

CN 112713257A discloses a preparation method of a negative electrode slurry and the negative electrode slurry. The method comprises the following steps: (1) Mixing a negative electrode active material, conductive agent powder and water to obtain wetting slurry; (2) adding thickening agent powder in three steps; (3) Adding water, and stirring to obtain slurry with preset solid content; (4) And adding an aqueous solution of a binder, and stirring to obtain the cathode slurry. According to the method, a preparation process of glue solution is not needed before the preparation of the cathode slurry, the preparation effect of the slurry can be met, the slurry is proper in viscosity, good in stability, proper in fineness and smooth in filtration, the equipment cost and the occupied area of a slurry preparation system can be reduced, the total time for preparing the slurry can be greatly shortened, and the labor cost can be reduced.

In the stirring process of the binder in the technical scheme, the binder is added after the mixed solution is qualified in viscosity adjustment and solid content, the material is demulsified due to overhigh stirring speed, the bonding force of a coated pole piece is worsened, the negative main material with small particle size and poor dispersibility is easy to agglomerate due to low stirring speed, the matching space between materials is small, the dispersibility of the modified water-based binder material is poor, and the requirement on production equipment is high.

Therefore, how to reasonably design the preparation method of the negative electrode slurry, so that the solid content and the normal pole piece coating process are not affected after the addition of the aqueous binder, and the effect of the lithium ion battery with high energy density can be favorably exerted is a technical problem which needs to be solved in the field of negative electrode slurry preparation.

Disclosure of Invention

In order to solve the technical problems, the invention provides the negative electrode slurry and the preparation method thereof and the lithium ion battery, and the addition of the aqueous binder does not affect the solid content and the normal pole piece coating process by optimizing the stirring and mixing process, and the effect of the lithium ion battery with high energy density can be favorably exerted.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a method for preparing a negative electrode slurry, the method comprising the steps of:

(1) Mixing the aqueous binder and the synthetic fiber glue solution to obtain a dispersed glue solution;

(2) Mixing a negative electrode material, a conductive agent and the dispersed glue solution obtained in the step (1) to obtain a mixed solution;

(3) And (3) mixing the synthetic rubber and the mixed liquid obtained in the step (2) to obtain the negative electrode slurry.

The invention provides a preparation method of cathode slurry, which adopts an aqueous binder with conductive performance, and reduces the solid content of the cathode slurry by improving the mixing process, thereby greatly improving the rate performance of the prepared battery, and improving the cycle performance and the high-temperature storage performance.

Preferably, the aqueous binder of step (1) comprises CMC, a conductive agent and SBR.

The aqueous binder provided by the invention contains a conductive agent, such as 0.15-0.25wt% of carbon nano tubes, and the conductive agent is effectively combined with the binder through a pretreatment process in combination with an in-situ synthesis and dispersion blending process to prepare the aqueous binder containing the conductive agent, so that the production efficiency can be greatly improved, and the shortening of the battery is promoted.

Preferably, the synthetic fiber glue solution in the step (1) comprises sodium carboxymethyl cellulose.

Preferably, the concentration of sodium carboxymethylcellulose in the synthetic viscose dope is 1.6-2.0%, for example 1.6%, 1.65%, 1.7%, 1.9% or 2%, but is not limited to the values recited, and other values not recited in the numerical ranges are equally applicable.

Preferably, the mass ratio of the sodium carboxymethylcellulose to the aqueous binder is 1 (75-80), and can be, for example, 1.

Preferably, the mixing method of step (1) comprises wet stirring.

Preferably, the method of mixing comprises stirring.

Preferably, the stirring revolution is 20-30rpm, for example 20rpm, 22rpm, 24rpm, 26rpm, 28rpm or 30rpm, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.

Preferably, the revolution time of the stirring is 30-60min, such as 30min, 35min, 40min, 50min, 55min or 60min, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the stirring speed is from 2500 to 3000rpm, which may be, for example, 2500rpm, 2600rpm, 2700rpm, 2800rpm, 2900rpm or 3000rpm, but is not limited to the values recited, and other values not recited within the range of values are equally applicable.

Preferably, the rotation time of the stirring is 250-350min, such as 250min, 270min, 290min, 310min, 330min or 350min, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.

Preferably, the negative electrode material in the step (2) comprises any one or a combination of at least two of graphite, silica or silicon carbon. Typical, but non-limiting, combinations include a combination of graphite and silica, a combination of silica and silicon carbon, a combination of graphite and silicon carbon, or a combination of graphite, silica, and silicon carbon.

Preferably, the conductive agent in step (2) comprises any one or a combination of at least two of conductive carbon black, carbon nanotubes or conductive graphite. Typical but non-limiting combinations include combinations of conductive carbon black and carbon nanotubes, carbon nanotubes and conductive graphite, conductive carbon black and conductive graphite, or conductive carbon black, carbon nanotubes and conductive graphite.

Preferably, the mass ratio of the negative electrode material, the conductive agent and the obtained dispersion glue solution in the step (2) is (100-96) to 1 (100-105), and the ratio can be, for example, 100.

Preferably, the mixing sequence in the step (2) includes mixing the conductive agent and the negative electrode material, and then mixing the conductive agent and the negative electrode material with the dispersion glue solution;

preferably, the mixing method of step (2) comprises dry stirring;

preferably, the method of mixing comprises stirring.

Preferably, the revolution speed of the stirring is 15-25rpm, for example, 15rpm, 18rpm, 20rpm, 22rpm or 25rpm, but is not limited to the enumerated values, and other unrecited values in the numerical range are also applicable.

Preferably, the revolution time of the stirring is 10-20min, for example, 10min, 12min, 14min, 16min, 28min or 20min, but is not limited to the values listed, and other values not listed in the range of values are also applicable.

Preferably, the rotation speed of the stirring is 1500-2500rpm, for example 1500rpm, 1800rpm, 2000rpm, 2200rpm, 2300rpm or 2500rpm, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the rotation time of the stirring is 60-90min, for example, 60min, 65min, 70min, 80min, 85min or 90min, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the synthetic rubber of step (3) comprises styrene butadiene rubber.

Preferably, the mass ratio of the synthetic rubber and the mixed solution in the step (3) is 1 (160-180), and can be, for example, 1.

Preferably, the mixing method of step (3) comprises dry stirring.

Preferably, the mixing further comprises post-mixing agitation.

Preferably, the revolution speed of the stirring is 10-20rpm, for example, 10rpm, 12rpm, 15rpm, 18rpm or 20rpm, but is not limited to the enumerated values, and other unrecited values in the numerical range are also applicable.

Preferably, the revolution time of the stirring is 30-60min, for example, 30min, 35min, 40min, 50min, 55min or 60min, but is not limited to the values listed, and other values not listed in the range of values are also applicable.

Preferably, the rotational speed of the stirring is 1500-2000rpm, for example 1500rpm, 1600rpm, 1700rpm, 1800rpm, 1900rpm or 2000rpm, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.

Preferably, the spinning time of the stirring is 250-350min, for example 250min, 280min, 300min, 320min or 350min, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

As a preferable technical solution of the preparation method of the first aspect of the present invention, the preparation method comprises the steps of:

(1) Mixing the aqueous binder and the synthetic fiber glue solution in a mass ratio of (75-80): 1, and stirring the mixture after mixing, wherein the revolution speed is 20-30rpm, the revolution time is 30-60min, the rotation speed is 2500-3000rpm, and the rotation time is 250-350min to obtain a dispersed glue solution; the synthetic fiber glue solution comprises sodium carboxymethylcellulose and water, and the liquid-solid ratio is 1.6-2.0%;

(2) Mixing the negative electrode material, the conductive agent and the obtained dispersion glue solution in a mass ratio of (100-96) to (1) (100-105), stirring after mixing, wherein the revolution speed is 15-25rpm, the revolution time is 10-20min, the rotation speed is 1500-2500rpm, and the rotation time is 60-90min to obtain a mixed solution;

(3) And (2) mixing the synthetic rubber with the obtained mixed solution in the mass ratio of 1 (160-180), stirring the mixture, and obtaining the cathode slurry, wherein the revolution speed is 10-20rpm, the revolution time is 30-60min, the rotation speed is 1500-2000rpm, and the rotation time is 250-350min.

In a second aspect, the present invention provides an anode slurry obtained according to the preparation method of the first aspect.

In a third aspect, the invention provides a lithium ion battery comprising the negative electrode slurry of the second aspect.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) The invention provides a preparation method of cathode slurry, which adopts a water-based binder with conductive performance, and reduces the solid content of the cathode slurry by improving the mixing process, thereby greatly improving the rate capability of the prepared battery, and improving the cycle performance and the high-temperature storage performance.

(2) According to the invention, by improving the mixing process, the solid content and the normal pole piece coating process are not influenced after the addition of the aqueous binder, and the prepared negative electrode slurry can be beneficial to exerting the effect of the lithium ion battery with high energy density.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a negative electrode slurry, and a preparation method of the negative electrode slurry comprises the following steps:

(1) Mixing an aqueous binder and a synthetic fiber glue solution in a mass ratio of 78;

the aqueous binder comprises CMC, carbon nano tubes and SBR, wherein the mass percent of the carbon nano tubes is 0.2wt%;

the synthetic fiber glue solution comprises sodium carboxymethylcellulose and water, and the liquid-solid ratio is 1.8%;

(2) Mixing a silica-graphite negative electrode material, conductive carbon black and the obtained dispersion glue solution in a mass ratio of 98;

(3) And mixing styrene butadiene rubber and the obtained mixed solution in a mass ratio of 1.

Example 2

(1) Mixing the aqueous binder and the synthetic fiber glue solution in a mass ratio of 75; the synthetic fiber glue solution comprises sodium carboxymethylcellulose and water, and the liquid-solid ratio is 1.6%;

the aqueous binder comprises CMC, carbon nano tubes and SBR, wherein the mass percent of the carbon nano tubes is 0.15wt%;

(2) Mixing a silica-graphite negative electrode material with a mass ratio of 100;

(3) And mixing styrene butadiene rubber and the obtained mixed solution in a mass ratio of 1 to 160, and stirring the mixture after mixing, wherein the revolution speed is 10rpm, the revolution time is 60min, the rotation speed is 1500rpm, and the rotation time is 350min to obtain the negative electrode slurry.

Example 3

(1) Mixing the aqueous binder and the synthetic fiber glue solution in a mass ratio of 80 to 1, stirring the mixture after mixing, wherein the revolution speed is 30rpm, the revolution time is 30min, the rotation speed is 3000rpm, and the rotation time is 250min to obtain a dispersion glue solution; the synthetic fiber glue solution comprises sodium carboxymethylcellulose and water, and the liquid-solid ratio is 2.0%;

the aqueous binder comprises CMC, carbon nano tubes and SBR, wherein the mass percent of the carbon nano tubes is 0.25wt%;

(2) Mixing a silica + graphite negative electrode material, conductive graphite and the obtained dispersion glue solution in a mass ratio of 96;

Example 4

This example provides a negative electrode slurry prepared in the same manner as in example 1, except that the aqueous binder in step (1) does not contain carbon nanotubes.

Example 5

This example provides a negative electrode slurry, which was prepared in the same manner as in example 1, except that the revolution speed of stirring in step (1) was 10 rpm.

Example 6

This example provides a negative electrode slurry, which was prepared in the same manner as in example 1, except that the revolution speed of stirring in step (1) was 40 rpm.

Example 7

This example provides a negative electrode slurry, which was prepared in the same manner as in example 1, except that the revolution speed of stirring in step (2) was 5 rpm.

Example 8

This example provides a negative electrode slurry prepared in the same manner as in example 1, except that the revolution speed of stirring in step (2) was 35 rpm.

Example 9

This example provides a negative electrode slurry, which was prepared in the same manner as in example 1, except that the revolution speed of stirring in step (3) was 5 rpm.

Example 10

This example provides a negative electrode slurry prepared in the same manner as in example 1, except that the revolution speed of stirring in step (3) was 25 rpm.

Comparative example 1

The present comparative example provides a negative electrode slurry, the method of preparing the negative electrode slurry comprising the steps of:

(1) Mixing silica-graphite negative electrode material, conductive carbon black and synthetic fiber glue solution in a mass ratio of 98;

(2) Mixing an aqueous binder and the obtained mixed solution in a mass ratio of 78;

the water-based binder comprises CMC, carbon nano tubes and SBR, wherein the mass percent of the carbon nano tubes is 0.2wt%.

After coating the negative electrode pastes obtained in examples 1 to 10 and comparative example 1, a lithium ion battery was prepared and tested, and the results are shown in table 1 below.

TABLE 1

The following conclusions are drawn from table 1:

(1) From examples 1 to 3, it can be seen that the present invention provides a method for preparing a negative electrode slurry, in which an aqueous binder having a conductive property is used, and a mixing process is improved to reduce a solid content of the negative electrode slurry, thereby greatly improving a rate capability, a cycle performance, and a high temperature storage performance of a battery prepared by the method.

(2) As is clear from comparison between example 4 and example 1, when the conductive agent is added to the water-in binder, the production efficiency can be greatly improved, the battery can be shortened, the rate capability of the battery can be improved, and the cycle performance and the high-temperature storage performance can be improved.

(3) As can be seen from the comparison between examples 5, 7 and 9 and example 1, when the stirring speed is too low, the particle size is small, the dispersibility is poor, the viscosity of the negative electrode slurry is reduced, and the rate capability of the battery is not improved, and the cycle performance and the high-temperature storage performance are improved.

(4) As can be seen from comparison of examples 6, 8 and 10 with example 1, when the stirring speed is too high, the material may be broken, the viscosity of the negative electrode slurry may be reduced, and it is not favorable for improving the rate capability of the battery, and improving the cycle performance and high-temperature storage performance.

(5) As can be seen from comparison of comparative example 1 with example 1, when the conventional preparation process of the negative electrode slurry was followed, the slurry viscosity was low and the rate performance of the battery was poor, which was not favorable for improving cycle performance and high-temperature storage performance.

The present invention is illustrated by the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, i.e. it is not meant to imply that the present invention must rely on the above-mentioned detailed process equipment and process flow to be practiced. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A preparation method of negative electrode slurry is characterized by comprising the following steps:

2. The method of claim 1, wherein the aqueous binder of step (1) comprises CMC, conductive agent and SBR;

preferably, the synthetic fiber glue solution in the step (1) comprises sodium carboxymethyl cellulose;

preferably, the concentration of the sodium carboxymethylcellulose in the synthetic fiber glue solution is 1.6-2.0%;

preferably, the mass ratio of the sodium carboxymethyl cellulose to the aqueous binder is 1 (75-80).

3. The method of producing as claimed in claim 1 or 2, wherein the mixing of step (1) comprises wet stirring;

preferably, the method of mixing comprises stirring;

preferably, the stirring revolution speed is 20-30rpm;

preferably, the revolution time of the stirring is 30-60min;

preferably, the self-rotating speed of the stirring is 2500-3000rpm;

preferably, the rotation time of the stirring is 250-350min.

4. The production method according to any one of claims 1 to 3, wherein the negative electrode material of step (2) comprises any one of graphite, silica or silicon carbon or a combination of at least two thereof;

preferably, the conductive agent in step (2) comprises any one or a combination of at least two of conductive carbon black, carbon nanotubes or conductive graphite;

preferably, the mass ratio of the negative electrode material, the conductive agent and the obtained dispersion glue solution in the step (2) is (100-96): 1 (100-105).

5. The preparation method according to any one of claims 1 to 4, wherein the mixing sequence of step (2) comprises mixing the conductive agent and the negative electrode material, and then mixing with the dispersion glue solution;

preferably, the mixing method of step (2) comprises dry stirring;

preferably, the method of mixing comprises stirring;

preferably, the revolution speed of the stirring is 15-25rpm;

preferably, the revolution time of the stirring is 10-20min;

preferably, the rotation speed of the stirring is 1500-2500rpm;

preferably, the rotation time of the stirring is 60-90min.

6. The production method according to any one of claims 1 to 5, wherein the synthetic rubber of step (3) comprises styrene-butadiene rubber;

preferably, the mass ratio of the synthetic rubber in the step (3) to the mixed solution is 1 (160-180).

7. The production method according to any one of claims 1 to 6, wherein the mixing in step (3) comprises dry stirring;

preferably, the mixing further comprises post-mixing agitation;

preferably, the revolution speed of the stirring is 10-20rpm;

preferably, the revolution time of the stirring is 30-60min;

preferably, the rotation speed of the stirring is 1500-2000rpm;

preferably, the rotation time of the stirring is 250-350min.

8. The production method according to any one of claims 1 to 7, characterized by comprising the steps of:

(1) Mixing the aqueous binder and the synthetic fiber glue solution in a mass ratio of (75-80): 1, stirring after mixing, wherein the revolution speed is 20-30rpm, the revolution time is 30-60min, the rotation speed is 2500-3000rpm, and the rotation time is 250-350min to obtain a dispersion glue solution; the synthetic fiber glue solution comprises sodium carboxymethylcellulose and water, and the liquid-solid ratio is 1.6-2.0%;

(3) And (2) mixing the synthetic rubber with the obtained mixed solution according to the mass ratio of 1 (160-180), stirring the mixture, and obtaining the cathode slurry, wherein the revolution speed is 10-20rpm, the revolution time is 30-60min, the rotation speed is 1500-2000rpm, and the rotation time is 250-350min.

9. A negative electrode slurry obtained by the production method according to any one of claims 1 to 8.

10. A lithium ion battery comprising the negative electrode slurry according to claim 9.