Homogenizing method of slurry with negative electrode containing liquid retention additive and lithium ion battery

Abstract

The method comprises the following steps: firstly, mixing and stirring silicon-based graphite, conductive carbon black and a CMC (Carboxy Methylated Cellulose) thickening agent for 1-3 hours, then adding conductive slurry, an acrylic acid adhesive and a solvent deionized water, then adding a liquid retaining agent SFC (Solution Factor Cellulose), and uniformly stirring, so as to obtain the slurry containing the liquid retaining additive for the negative electrode. And mixing and stirring for 2-4 hours, then adding an SBR styrene-butadiene latex adhesive and a solvent to adjust the viscosity of the slurry, mixing and stirring for 0.5-1 hour, and then reversing to remove bubbles in vacuum and sieving the slurry to obtain the negative electrode slurry to be prepared. According to the invention, the SFC liquid retaining agent is added into the conductive adhesive in advance, so that the liquid retaining agent SFC and the negative active material silicon-based graphite are fully and uniformly dispersed, and the cycle performance of the battery and the specific capacity per gram can be fully improved under the condition that the total slurry mixing time is not changed.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery preparation, and particularly relates to a method for homogenizing a negative electrode slurry containing a liquid-retaining additive and a lithium ion battery. Background Art

[0002] At present, the manufacturing process of lithium-ion battery production is generally divided into the front stage (homogenization, coating, rolling, slitting), the middle stage (sheet making, winding, assembly, baking, liquid injection and sealing), and the back stage (aging, formation, aging, capacity sorting) until the battery is shipped. The manufacturing process has many steps and the manufacturing process is relatively complicated, especially some key operation steps, such as homogenization, coating, winding, liquid injection, etc. Improper operation can easily lead to quality problems such as low battery capacity, high internal resistance, and high self-discharge. Severe cases can cause battery safety problems. Among the many production processes, the homogenization operation process is particularly important. In the lithium-ion battery slurry preparation process, it is more common to use a one-time homogenization process, that is, a one-step homogenization operation. Summary of the Invention

[0003] One object of the present invention is to provide a method for homogenizing a negative electrode slurry containing a liquid-retaining additive.

[0004] The above purpose can be achieved through the following technical solutions:

[0005] A method for homogenizing a slurry containing a liquid-retaining additive for a negative electrode comprises the following steps: firstly, silicon-based graphite, conductive carbon black, and a CMC thickener are mixed and stirred for 1 to 3 hours; then, conductive slurry, acrylic adhesive as a binder, and deionized water as a solvent are added; then, a liquid-retaining agent SFC is added and mixed and stirred for 2 to 4 hours; then, an SBR styrene-butadiene latex adhesive and a solvent are added to adjust the slurry viscosity; then, the mixture is mixed and stirred for 0.5 to 1 hour; then, the mixture is reversed and vacuumed to remove bubbles; and the slurry is sieved to obtain the negative electrode slurry to be prepared.

[0006] Silicon-based graphite generally refers to pre-lithiated silicon-oxygen graphite or silicon-carbon graphite.

[0007] Acrylic adhesive is an acrylic acid ester multipolymer with a solid content of about 15%. It has a -CC- bond as the main chain and side chains with strong polar functional groups such as -CN, which give the adhesive molecules a higher bonding strength. At the same time, the presence of strong polar side groups gives the adhesive molecules a higher cohesive strength, showing higher cohesive strength during the bonding process of the negative electrode material, and has a certain inhibitory effect on the expansion of the Si-C material.

[0008] The conductive paste refers to a single-arm or multi-arm carbon nanotube paste with a solid content of about 5%.

[0009] 55%-65% solvent deionized water refers to using 55%-65% of the total amount of the prepared solvent deionized water.

[0010] The liquid retaining agent SFC used is a functional polymer SFC, which is a large-particle high-molecular emulsion produced by Shanghai Daoying Company.

[0011] Furthermore: the method for homogenizing the negative electrode slurry containing a liquid retaining additive comprises the following steps: 95-100 parts of active material silicon-based graphite, 0.5-3 parts of conductive carbon powder, 0.5-3 parts of conductive slurry, 0.5-3 parts of thickener CMC sodium carboxymethyl cellulose, 1-3 parts of binder SBR styrene-butadiene rubber, 1-3 parts of binder acrylic glue, 0.5-3 parts of SFC liquid retaining agent and a certain amount of solvent deionized water are mixed in parts by mass, and dry powder stirring, mud stirring, high viscosity stirring, high-speed stirring, viscosity adjustment stirring and vacuum degassing are carried out in sequence.

[0012] In one embodiment, the steps of homogenizing the negative electrode slurry containing the liquid retaining additive are as follows:

[0013] 1. Dry powder stirring: Silicon-based graphite and conductive carbon powder are stirred for 120 minutes at a dispersion speed of 500 rpm and a stirring speed of 25 rpm;

[0014] 2. Dry powder mixing: Add CMC sodium carboxymethyl cellulose into the blender at a dispersing speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes;

[0015] 3. Mud stirring: Add conductive paste, 55% solvent deionized water, and 0.5 parts of SFC liquid retaining agent into the blender at a dispersion speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes;

[0016] 4. High Viscosity Stirring: After step 3, add the acrylic adhesive and 10% deionized water to the blender. Stir for 10 minutes at a dispersion speed of 50 rpm and a stirring speed of 15 rpm. Then, stir for 30 minutes at a dispersion speed of 100 rpm and a stirring speed of 25 rpm.

[0017] 5. High-speed stirring: After step 4, add 10% solvent deionized water into the blender and stir at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 10 minutes; then stir at a dispersion speed of 1000 rpm and a stirring speed of 25 rpm for 30 minutes; and then stir at a dispersion speed of 1500 rpm and a stirring speed of 35 rpm for 30 minutes;

[0018] 6. Viscosity Adjustment and Stirring: After step 5, add the binder SBR and 10% deionized water to a blender and stir for 10 minutes at a dispersion speed of 500 rpm and a stirring speed of 20 rpm; then stir for 30 minutes at a dispersion speed of 1000 rpm and a stirring speed of 20 rpm; maintain the viscosity of the slurry composed of the active material silicon-based graphite, conductive carbon powder, conductive slurry, thickener sodium carboxymethyl cellulose (CMC), binder acrylic glue, binder SBR styrene-butadiene rubber, and solvent deionized water at 2000-5000 mPa·s;

[0019] 7. Vacuum degassing: After step 6, the mixture was stirred at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 30 minutes, and the slurry was sieved to obtain the molding slurry to be prepared.

[0020] Another object of the present invention is to provide a method for homogenizing a negative electrode slurry containing a liquid-retaining additive.

[0021] The above purpose can be achieved through the following technical solutions:

[0022] A lithium ion battery, wherein the forming slurry used for the negative electrode of the lithium ion battery is prepared by adopting the above-mentioned slurry homogenization method containing the liquid retaining additive for the negative electrode.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention adds the SFC solution retaining agent in advance during the mixing process of the conductive glue, so that the solution retaining agent SFC and the negative electrode active material silicon-based graphite are fully and evenly dispersed. Without changing the overall slurry mixing time, the battery cycle performance and gram-specific capacity can be fully improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] Figure 1 Schematic diagram showing the effect of adding the solution retaining agent SFC on ACIR in the present invention.

[0027] Figure 2 Schematic diagram showing the effect of adding the liquid retaining agent SFC on DCIR in the present invention. DETAILED DESCRIPTION

[0028] A method for homogenizing a negative electrode slurry containing a liquid-retaining additive comprises the following steps: first, silicon-based graphite, conductive carbon black, and a CMC thickener are mixed and stirred for 1 to 3 hours; then, a conductive slurry, an acrylic adhesive, and a solvent, deionized water, are added; then, a liquid-retaining agent, SFC, is added and mixed and stirred for 2 to 4 hours; then, an SBR styrene-butadiene latex adhesive and a solvent are added to adjust the slurry viscosity; then, the mixture is reversed and vacuum-defoamed, and the slurry is sieved to obtain the negative electrode slurry to be prepared.

[0029] The liquid retaining agent SFC is a functional polymer additive, hereinafter referred to as liquid retaining agent.

[0030] The present invention adds the liquid retaining agent SFC to fully and evenly disperse the liquid retaining agent SFC and the negative electrode active material silicon-based graphite, which can fully improve the cycle performance of the battery and increase the gram-specific capacity without changing the overall slurry mixing time.

[0031] A method for homogenizing a negative electrode slurry containing a liquid-retaining additive comprises the following steps: mixing, by mass, 95-100 parts of active material silicon-based graphite, 0.5-3 parts of conductive carbon powder, 0.5-3 parts of conductive paste, 0.5-3 parts of CMC sodium carboxymethyl cellulose (a thickener), 1-3 parts of SBR styrene-butadiene rubber (SBR) as a binder, 1-3 parts of acrylic adhesive as a binder, 0.5-3 parts of an SFC liquid-retaining agent, and a quantity of deionized water as a solvent, sequentially performing dry powder stirring, slurry stirring, high-viscosity stirring, high-speed stirring, viscosity-adjusting stirring, and vacuum degassing. The method adds the SFC liquid-retaining agent to the conductive adhesive mixing process in advance, ensuring that the liquid-retaining agent (SFC) and the negative electrode active material silicon-based graphite are fully and evenly dispersed. This significantly improves the battery's cycle performance and increases the gram-specific capacity without changing the overall slurry mixing time.

[0032] Example 1

[0033] This embodiment is a method for homogenizing a negative electrode slurry containing a liquid retaining agent SFC.

[0034] Prepare 95 parts by mass of active material silicon-based graphite, 0.5 parts of conductive carbon powder, 0.5 parts of conductive slurry, 0.5 parts of thickener CMC sodium carboxymethyl cellulose, 1 part of binder SBR styrene-butadiene rubber, 1 part of binder acrylic glue, 0.5 parts of liquid retaining agent SFC and some solvent deionized water.

[0035] The specific steps of the method for homogenizing the negative electrode slurry containing the liquid retaining additive are as follows:

[0036] 1. Dry powder stirring: Silicon-based graphite and conductive carbon powder are stirred for 120 minutes at a dispersion speed of 500 rpm and a stirring speed of 25 rpm;

[0037] 2. Dry powder mixing: Add CMC sodium carboxymethyl cellulose into the blender at a dispersing speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes;

[0038] 3. Mud stirring: Add conductive paste, 55% solvent deionized water, and 0.5 parts of SFC liquid retaining agent into the blender at a dispersion speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes;

[0039] 4. High Viscosity Stirring: After step 3, add the acrylic adhesive and 10% deionized water to the blender. Stir for 10 minutes at a dispersion speed of 50 rpm and a stirring speed of 15 rpm. Then, stir for 30 minutes at a dispersion speed of 100 rpm and a stirring speed of 25 rpm.

[0040] 5. High-speed stirring: After step 4, add 10% solvent deionized water into the blender and stir at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 10 minutes; then stir at a dispersion speed of 1000 rpm and a stirring speed of 25 rpm for 30 minutes; and then stir at a dispersion speed of 1500 rpm and a stirring speed of 35 rpm for 30 minutes;

[0041] 6. Viscosity Adjustment and Stirring: After step 5, add the binder SBR and 10% deionized water to a blender and stir for 10 minutes at a dispersion speed of 500 rpm and a stirring speed of 20 rpm; then stir for 30 minutes at a dispersion speed of 1000 rpm and a stirring speed of 20 rpm; maintain the viscosity of the slurry composed of the active material silicon-based graphite, conductive carbon powder, conductive slurry, thickener sodium carboxymethyl cellulose (CMC), binder acrylic glue, binder SBR styrene-butadiene rubber, and solvent deionized water at 2000-5000 mPa·s;

[0042] 7. Vacuum degassing: After step 6, the mixture was stirred at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 30 minutes, and the slurry was sieved to obtain the shaped negative electrode slurry to be prepared.

[0043] Comparative Example 1

[0044] This comparative example is a negative electrode slurry homogenization method without adding the liquid retaining agent SFC.

[0045] Prepare 95 parts by mass of active material silicon-based graphite, 0.5 parts of conductive carbon powder, 0.5 parts of conductive slurry, 0.5 parts of thickener CMC sodium carboxymethyl cellulose, 1 part of binder SBR styrene-butadiene rubber, 1 part of binder acrylic glue and some solvent deionized water.

[0046] The specific steps of the method for homogenizing the negative electrode slurry containing the liquid retaining additive are as follows:

[0047] 1. Dry mix silicon-based graphite and conductive carbon powder in a blender, then add conductive slurry, thickener CMC sodium carboxymethyl cellulose, binder acrylic acid glue, binder SBR styrene-butadiene rubber and solvent deionized water and continue to stir evenly to make a shaped negative electrode slurry.

[0048] Example 3

[0049] The shaped slurries prepared in Example 1 and Comparative Example 1 were used to prepare negative electrodes, and the obtained negative electrodes were used to prepare lithium-ion batteries. The lithium-ion batteries were tested for battery AC internal resistance and DC internal resistance. The test results are as follows: Figure 1 and Figure 2 As shown, through Figure 1 and Figure 2 It can be seen that the addition of SFC to the negative electrode sheet significantly affects the battery's AC and DC internal resistances. The battery with SFC has lower AC and DC internal resistances.

[0050] The characteristic of the slurry homogenization method of the negative electrode containing liquid retaining additive of the present invention is that the amount of solvent is added in batches. For example, the above process, by adding the liquid retaining agent SFC and adding the solvent in multiple steps, has a great effect on adjusting the viscosity, dynamic viscoelasticity, and fluidity, reducing the internal resistance of the battery and improving the cycle performance and rate performance.

[0051] The unique core-shell structure of the liquid-retaining agent (SFC) prevents the negative electrode from swelling after absorbing electrolyte, reducing its internal impedance while minimizing changes in the polymer particle morphology, thereby maintaining a strong bond to the negative electrode. The gelation of the SFC improves the interface when used for negative electrode bonding, effectively suppressing negative electrode expansion during charge and discharge, and extending the battery's electrolyte consumption time, significantly improving the battery's cycle life.

Claims

1. A method for homogenizing a negative electrode slurry containing a liquid-retaining additive, characterized in that: The following steps are involved: First, silicon-based graphite, conductive carbon black, and CMC thickener are mixed and stirred for 1 to 3 hours, and then conductive slurry, acrylic adhesive, and solvent deionized water are added, and then liquid retaining agent SFC is added and mixed and stirred for 2 to 4 hours, and then SBR styrene-butadiene latex adhesive and solvent are added to adjust the slurry viscosity, and the mixing time is 0.5 to 1 hour. Then, vacuum degassing is performed, and the slurry is sieved to obtain the negative electrode slurry to be prepared.

2. The method for homogenizing the negative electrode slurry containing the liquid-retaining additive according to claim 1, characterized in that: The method comprises the following steps: mixing 95-100 parts of active material silicon-based graphite, 0.5-3 parts of conductive carbon powder, 0.5-3 parts of conductive slurry, 0.5-3 parts of thickener CMC sodium carboxymethyl cellulose, 1-3 parts of binder SBR styrene-butadiene rubber, 1-3 parts of binder acrylic glue, 0.5-3 parts of SFC liquid retaining agent and some solvent deionized water in parts by mass, and sequentially performing dry powder stirring, mud stirring, high viscosity stirring, high-speed stirring, viscosity adjustment stirring and vacuum degassing.

3. The method for homogenizing the negative electrode slurry containing the liquid-retaining additive according to claim 2, characterized in that: The specific steps of the method for homogenizing the negative electrode slurry containing the liquid retaining additive are as follows:

1. Dry powder stirring: Silicon-based graphite and conductive carbon powder are stirred for 120 minutes at a dispersion speed of 500 rpm and a stirring speed of 25 rpm; 2. Dry powder mixing: Add CMC sodium carboxymethyl cellulose into the blender at a dispersing speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes; 3. Mud stirring: Add conductive paste, 55% solvent deionized water, and 0.5 parts of SFC liquid retaining agent into the blender at a dispersion speed of 100 rpm and a stirring speed of 25 rpm, and stir for 30 minutes; 4. High Viscosity Stirring: After step 3, add the acrylic adhesive and 10% deionized water to the blender. Stir for 10 minutes at a dispersion speed of 50 rpm and a stirring speed of 15 rpm. Then, stir for 30 minutes at a dispersion speed of 100 rpm and a stirring speed of 25 rpm.

5. High-speed stirring: After step 4, add 10% solvent deionized water into the blender and stir at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 10 minutes; then stir at a dispersion speed of 1000 rpm and a stirring speed of 25 rpm for 30 minutes; and then stir at a dispersion speed of 1500 rpm and a stirring speed of 35 rpm for 30 minutes; 6. Viscosity Adjustment and Stirring: After step 5, add the binder SBR and 10% deionized water to a blender and stir for 10 minutes at a dispersion speed of 500 rpm and a stirring speed of 20 rpm; then stir for 30 minutes at a dispersion speed of 1000 rpm and a stirring speed of 20 rpm; maintain the viscosity of the slurry composed of the active material silicon-based graphite, conductive carbon powder, conductive slurry, thickener sodium carboxymethyl cellulose (CMC), binder acrylic glue, binder SBR styrene-butadiene rubber, and solvent deionized water at 2000-5000 mPa·s; 7. Vacuum degassing: After step 6, the mixture was stirred at a dispersion speed of 500 rpm and a stirring speed of 20 rpm for 30 minutes, and the slurry was sieved to obtain the molding slurry to be prepared.

4. A lithium-ion battery, characterized in that: The forming slurry used for the negative electrode of the lithium-ion battery is prepared by the slurry homogenization method of the negative electrode containing liquid-retaining additive according to any one of claims 1 to 3.

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