CN102376940A - Lithium ion battery, cathode slurry and preparation method thereof - Google Patents

Abstract

The invention discloses a lithium ion battery, a negative electrode slurry and a preparation method thereof. The method comprises the following steps: (1) mixing the negative electrode active material and the negative electrode conductive agent in a stirrer, adding a lubricant and stirring evenly; (2) Add the additive sodium carboxymethyl cellulose CMC into the stirrer and stir; (3) add the above-mentioned substance in the stirrer to the mixed rubber material of the negative electrode solvent water and the negative electrode binder, mix and stir evenly, and make the negative electrode slurry. The lubricant is alcohol, ketone or a mixture of alcohol and ketone. Because the present invention mixes the wetting agent with the graphite and the conductive agent, the wetting time can be effectively shortened, the slurry preparation time can be shortened, and the uniformity and stability of the negative electrode slurry can be improved.

Description

Lithium ion battery, negative electrode slurry and preparation method thereof

technical field

The invention relates to the field of lithium ion battery manufacturing, in particular to a negative electrode slurry of a lithium ion battery and a preparation method thereof.

Background technique

Lithium-ion batteries were introduced to the market by Sony Corporation of Japan in the 1990s. Because of their high operating voltage, high energy density, and long cycle life, they are widely used in mobile phones, laptops and other small mobile power fields. With the further improvement of the energy density and power density of lithium-ion batteries, it has been regarded as an ideal power source for hybrid electric vehicles and electric vehicles, and it is a type of energy storage device with broad application prospects.

The first process of the lithium-ion battery preparation process is homogenization, which is to mix the active material with solvent, conductive agent, binder, etc. to obtain a slurry with a certain viscosity and solid content. The existing positive electrode slurry mostly uses NMP (nitromethylpyrrolidone) as a solvent (that is, oily slurry). The solvent of negative electrode slurry is changed from NMP to water under the pressure of cost reduction (that is, water-based slurry). Although using water as a solvent can significantly reduce the manufacturing cost of lithium-ion batteries, the stability of water-based slurry is not as good as that of oil-based slurry, and sedimentation is prone to occur, which affects the continuous and stable operation of production. In order to improve the stability of the water-based slurry, the Chinese patent document CN 101609882A proposes a process of mixing oil and water, that is, using a mixed solvent of oil and water in the glue preparation process, and this process can prepare a negative electrode slurry with better stability than the water-based slurry. However, this process takes a long time (14-20 hours), which seriously affects the improvement of production efficiency, and if the ratio of NMP is too high, it will have a limited effect on reducing costs.

Due to the high surface tension of graphite particles in water, although the density of graphite is greater than that of water, after the graphite powder is sprinkled on the water surface, the surface of graphite particles cannot be effectively wetted and floats on the water surface, which is not easy to disperse evenly in water. An anti-precipitation agent sodium carboxymethyl cellulose CMC is added in the existing production process of water-based graphite negative electrode slurry. CMC has a high viscosity, which is not conducive to the mixing of active substances and glue. In severe cases, even semi-dry materials will adhere to the stirring paddle of the mixer. The resistance of the stirring paddle is greater than the stirring force that the mixer can provide, causing the equipment to alarm. Production is greatly affected.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the above defects, propose a preparation method of lithium-ion battery negative electrode slurry, and improve the uniformity and stability of the aqueous negative electrode slurry.

The invention also proposes the lithium ion battery and its negative electrode slurry prepared by the preparation method.

The technical problem of the present invention is achieved through the following technical solutions.

The preparation method of this lithium-ion battery negative electrode slurry comprises the following steps: (1) mixing the negative electrode active material and the negative electrode conductive agent in a stirrer, adding lubricant and stirring evenly; (2) adding the additive sodium carboxymethylcellulose CMC Adding to a stirrer and stirring; (3) adding the above-mentioned substance in the stirrer to the mixed rubber material of the negative electrode solvent water and the negative electrode binder, and mixing and stirring evenly to prepare the negative electrode slurry.

The lubricant is alcohol, ketone or a mixture of alcohol and ketone.

The lubricant is one or more of NMP, methanol, ethanol and acetone.

The weight of the lubricant is 1/20-1/4 of the sum of the weight of the negative electrode active material and the negative electrode conductive agent powder.

In the step (1), the negative electrode active material, the negative electrode conductive agent, and the lubricant are stirred for 5 to 40 minutes, and the inside of the stirrer is evacuated during stirring.

In the step (2), the additive CMC is added in batches to the stirrer and stirred.

The negative electrode conductive agent is conductive carbon black, and the negative electrode binder is styrene-butadiene rubber SBR.

The lithium ion battery negative electrode slurry proposed by the present invention is prepared by the above-mentioned preparation method of the lithium ion battery negative electrode slurry.

The preparation method of the lithium ion battery that the present invention proposes comprises the preparation step of negative electrode slurry, and the preparation step of described negative electrode slurry comprises the following steps: (1) after mixing negative electrode active material and negative electrode conductive agent in agitator, add lubrication (2) Add the additive CMC to the stirrer and stir; (3) Add the above-mentioned substance in the stirrer to the mixed rubber material of the negative electrode solvent water and the negative electrode binder, mix and stir evenly, and make the negative electrode slurry.

The lithium-ion battery proposed by the present invention is prepared by the above-mentioned preparation method of the lithium-ion battery.

The beneficial effect that the present invention has compared with prior art is:

1) Improve production efficiency. Due to the use of wetting agent mixed with graphite and conductive agent, when the surface of graphite and conductive agent is well wetted, the glue can reach the wet particle surface more smoothly, which can effectively shorten the wetting time and shorten the slurry preparation time .

2) Improve the uniformity and stability of the negative electrode slurry. Use an organic liquid that has a good wetting effect on graphite to wet the graphite, which can fully wet the graphite surface, facilitate the uniform dispersion of graphite particles in the glue, promote the uniform mixing of the glue and active substances, and improve the uniformity of the slurry and stability.

Detailed ways

Example 1

A negative electrode slurry for a lithium ion battery is prepared, and the process includes the following steps.

(101) Mix 2000 g of negative active material natural graphite and 50 g of negative conductive agent carbon black in a stirred tank, add lubricant methanol 15 g, and stir for 5 to 40 minutes until uniformly mixed;

(102) The additive sodium carboxymethylcellulose CMC30g is added in the stirrer and stirred;

(103) Mix 2000 g of negative electrode solvent deionized water and 60 g of negative electrode binder SBR to make a rubber compound, add the material in the above-mentioned agitator to the rubber compound, and mix and stir for 8 hours to make a negative electrode slurry.

Example 2

A negative electrode slurry for a lithium ion battery is prepared, and the process includes the following steps.

(201) 2000 g of natural graphite, a negative electrode active material, and 50 g of negative electrode conductive agent carbon black are mixed in a stirred tank, and a total of 200 g of lubricant nitrogen methyl pyrrolidone NMP and acetone are added, and stirred for 5 to 40 minutes until uniformly mixed;

(202) The additive sodium carboxymethylcellulose CMC30g is added in the stirrer and stirred;

(203) Mix 2000 g of negative electrode solvent deionized water and 60 g of negative electrode binder SBR to make a rubber compound, add the material in the above-mentioned agitator to the rubber compound, and mix and stir for 7.5 hours to make a negative electrode slurry.

Example 3

A negative electrode slurry for a lithium ion battery is prepared, and the process includes the following steps.

(301) 2000g of natural graphite, the negative electrode active material, and 50g of the negative electrode conductive agent, carbon black, are mixed in a stirred tank, and a total of 600g of lubricant methanol and ethanol are added, stirred for 5 to 40 minutes until uniformly mixed;

(302) The additive sodium carboxymethyl cellulose CMC30g is added in the stirrer and stirred;

(303) Mix 2000 g of negative electrode solvent distilled water and 60 g of negative electrode binder SBR to make a rubber compound, add the material in the above-mentioned agitator to the rubber compound, and mix and stir for 7 hours to make a negative electrode slurry.

Comparative example 4

A negative electrode slurry for a lithium ion battery is prepared, and the process includes the following steps.

(401) negative electrode active material natural graphite 2000g and negative electrode conductive agent carbon black 50g are mixed in stirred tank;

(402) The additive sodium carboxymethylcellulose CMC30g is added in the stirrer and stirred;

(403) Mix 2000 g of negative electrode solvent deionized water and 60 g of negative electrode binder SBR to make a rubber compound, add the above-mentioned material in the agitator to the rubber compound, and mix and stir for 10 hours to make a negative electrode slurry.

The data of the preparation process of the above-mentioned Examples 1-3 and Comparative Example 4 were compared, the viscosity of the slurry during the preparation process was measured, and the stability of the slurry was observed after standing for 8 hours. As shown in Table 1.

Table 1

Example 5

To prepare a lithium-ion battery with a model number of 423048AH and a nominal capacity of 650mAh, the steps for preparing the battery cell are as follows.

501) Positive electrode ingredients. The positive electrode active material lithium cobaltate LiCoO ₂ , the positive electrode conductive agent acetylene black (cabot CABOT superconducting carbon black BP2000), the positive electrode binder PVDF (model RC10214) and the solvent NMP were mixed and stirred evenly to prepare the positive electrode slurry.

502) Negative electrode ingredients. The steps in Example 1 were used to prepare negative electrode slurry.

503) Coating. The positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil with a thickness of 16 μm, dried and rolled to form a positive electrode sheet, and the positive electrode sheet was cut into positive electrode pieces of a certain size, and an aluminum strip was welded on the positive electrode sheet. The negative electrode slurry is coated on a negative electrode current collector copper foil with a thickness of 10 μm, dried and rolled to form a negative electrode sheet, the negative electrode sheet is cut into a certain size of negative electrode small pieces, and a nickel strip is welded on the negative electrode small pieces.

504) prepare electrolyte. The lithium salt LiPF ₆ is dissolved in a lithium salt solvent, and the solvent is a mixed solvent of EC, EMC, and DMC, and the mass ratio of the three is EC:EMC:DMC=1:1:1.

505) Assembly. The cut positive electrode pieces, separators and negative electrode pieces are stacked or wound into an aluminum metal battery case, the battery case and the cap assembly are welded and sealed, and the prepared electrolyte is injected into the aluminum case.

506) Battery formation and capacity division.

Example 6

It differs from Example 5 in that, in step 502) in the negative electrode ingredients, the steps in Example 2 are used to prepare the negative electrode slurry.

Example 7

It differs from Example 5 in that, in step 502) in the negative electrode ingredients, the steps in Example 3 are used to prepare the negative electrode slurry.

Comparative example 8

It differs from Example 5 in that in step 502) in the negative electrode ingredients, the steps in Comparative Example 4 are used to prepare the negative electrode slurry.

Take 50 batteries obtained in Examples 5-7 and Comparative Example 8 to test the cycle performance. The test steps are as follows: first charge the formed batteries to 4.2V at a constant current of 0.5C, and then charge at a constant voltage of 4.2V to the cut-off Current 0.02C. Then discharge to 3.7V with 1C current. Repeat the above process, record the discharge capacity each time, and calculate the capacity retention rate after 300 cycles. The results are shown in Table 2.

Table 2

It can be seen from Tables 1 and 2 that after adding alcohol and ketone organic lubricants to the negative electrode slurry, the battery has good cycle performance, and because the preparation time of the negative electrode slurry is shortened, the production efficiency of the battery is improved and the cost is reduced. .

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. a preparation method of lithium ion battery negative electrode slurry, is characterized in that, comprises the following steps: (1) After mixing the negative electrode active material and the negative electrode conductive agent in the stirrer, add lubricant and stir evenly; (2) The additive sodium carboxymethylcellulose CMC is added in the stirrer and stirred; (3) Add the material in the above-mentioned agitator to the mixed compound of the negative electrode solvent water and the negative electrode binder, mix and stir evenly, and make the negative electrode slurry. 2. The preparation method of lithium ion battery as claimed in claim 1, characterized in that: the lubricant is alcohol, ketone or a mixture of alcohol and ketone. 3. The preparation method of lithium ion battery as claimed in claim 2, characterized in that: the lubricant is a mixture of one or more of NMP, methanol, ethanol, and acetone. 4. The preparation method of lithium ion battery as claimed in claim 1, 2 or 3, characterized in that: the weight of the lubricant is 1/20 to 1/4 of the sum of the weight of the negative electrode active material and the negative electrode conductive agent powder . 5. the preparation method of lithium-ion battery as claimed in claim 4 is characterized in that: in described step (1), negative electrode active material and negative electrode conductive agent, lubricant are stirred for 5～40 minutes, and when stirring, stir Vacuum the interior of the device. 6. The preparation method of the lithium ion battery as claimed in claim 5, characterized in that: in the step (2), the additive CMC is added in batches to the stirrer and stirred. 7. The preparation method of lithium ion battery as claimed in claim 4, characterized in that: the negative electrode conductive agent is conductive carbon black, and the negative electrode binder is styrene-butadiene rubber (SBR). 8. A negative electrode slurry for a lithium ion battery, prepared by any one of the preparation methods for the negative electrode slurry for a lithium ion battery in claims 1-7. 9. A preparation method for lithium ion battery, comprising the preparation step of negative electrode slurry, characterized in that, the preparation step of negative electrode slurry comprises the following steps: (1) After mixing the negative electrode active material and the negative electrode conductive agent in the stirrer, add lubricant and stir evenly; (2) Add the additive CMC to the stirrer and stir; (3) Add the material in the above-mentioned agitator to the mixed compound of the negative electrode solvent water and the negative electrode binder, mix and stir evenly, and make the negative electrode slurry. 10. The lithium ion battery prepared by the preparation method of lithium ion battery according to claim 9.