Negative electrode slurry, negative electrode plate, preparation method of negative electrode slurry and negative electrode plate, and battery

Abstract

The invention relates to the technical field of energy storage batteries, in particular to negative electrode slurry, a negative electrode plate, a preparation method and a battery. And the negative electrode slurry comprises 97.0 to 98.0 parts of a negative electrode active material, 0.5 to 1.0 part of a thickening agent, 1.0 to 1.2 parts of a binder, 0.5 to 1 part of a conductive agent and a solvent. The invention provides a low-cost lithium ion battery negative electrode slurry formula. According to the formula, the proportion of main materials is increased, and meanwhile, the proportion of a thickening agent and a binding agent is reduced. Meanwhile, the invention provides a preparation method of the formula, according to the method, part of the negative electrode active material is added in the glue preparation stage, heat production is increased, dissolution of the thickening agent is promoted, the dissolution efficiency and the utilization rate of the thickening agent are improved, and the problems of non-uniform slurry dispersion, low viscosity, coating edge bulging and the like caused by reduction of the ratio of the thickening agent to the binding power are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage batteries, and in particular to a negative electrode slurry, a negative electrode sheet, a preparation method and a battery. Background Art

[0002] Currently, the negative electrode formulation for lithium-ion batteries mainly consists of a negative electrode active material, a conductive agent, a thickener, a binder, and other auxiliary materials. Sodium carboxymethyl cellulose (CMC) is commonly used as the thickener. CMC serves both the dispersing and bonding functions. Reducing the proportion of CMC in the formulation can lead to poor graphite dispersion and low slurry viscosity. This problem can prevent the slurry from being sieved, leading to slurry scrapping. It can also lead to poor coating rim and electrode uniformity, thus affecting the performance of the entire battery. The most common solution is to increase the proportion of CMC in the formulation or add acrylic acid resin (PAA). PAA can effectively enhance the dispersion between graphite particles and increase the adhesion between the electrode and the foil. Both CN 119581555 A and CN 116826055 A use this method. However, the addition of PAA increases the slurry cost. Moreover, the addition of PAA increases the proportion of graphite, which ultimately affects the energy density of the battery. This is inconsistent with the development trend of lithium-ion batteries. CN 118039904A does not use PAA, but the proportion of the main ingredient graphite is only 92-96%, and the battery energy density is low. The proportions of styrene-butadiene rubber (SBR) and CMC are 1.7% and 1.3% respectively. Excessive proportion of binder will also lead to increased costs. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies and defects of the prior art and to provide a negative electrode slurry, a negative electrode sheet, a preparation method and a battery.

[0004] In order to achieve the above objectives, this application adopts the following solutions:

[0005] A negative electrode slurry comprises 97.0-98.0 parts of a negative electrode active material, 0.5-1.0 parts of a thickener, 1.0-1.2 parts of a binder, 0.5-0.1 parts of a conductive agent and a solvent.

[0006] The negative electrode active material is artificial graphite made from petroleum coke or needle coke. 50 : 10-14μm, specific surface area: 1.0-2.0m 2 / g;

[0007] Preferably, the thickener is sodium carboxymethyl cellulose or lithium carboxymethyl cellulose, with a molecular weight of 100,000-200,000 g / mol;

[0008] Preferably, the binder is styrene-butadiene emulsion with a solid content of 40-50%;

[0009] Preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene.

[0010] Preferably, the solvent is water, more preferably deionized water.

[0011] The present invention also includes a method for preparing the negative electrode slurry, comprising the following steps:

[0012] S1, stirring and mixing a conductive agent, a thickener and part of the negative electrode active material to obtain a first mixture;

[0013] S2, adding deionized water into the circulating high-efficiency pulping system, and setting up a premixing bin to discharge materials, and mixing the first mixed material with the deionized water to obtain a second mixed material;

[0014] S3, adding the remaining negative electrode active material to the premixing bin of the circulating high-efficiency pulping system and discharging the material, and uniformly mixing the negative electrode active material with the second mixed material to obtain a third mixed material;

[0015] S4, adding an appropriate amount of deionized water to adjust the solid content, and performing high-speed dispersion to obtain a fourth mixture;

[0016] S5, adding a binder and mixing evenly, and then defoaming under negative pressure to obtain the lithium ion battery negative electrode slurry.

[0017] The mass ratio of the negative electrode active material in step S1) to that in step S3 is 1:(1-6); preferably 1:(2-3).

[0018] The amount of deionized water added in step S2 is 1-4 times the amount of the negative electrode active material in step S1; the solid content in step S4 is 55-60%; and the viscosity is 3000-6000 CP.

[0019] The stirring speed in S1 is 100-300 rpm, and the stirring time is 10-30 min.

[0020] Preferably, the mixing parameters in the circulating high-efficiency pulping system in S2 are: pre-mixing chamber screw feeding speed 40-60 rpm / min; dispersion linear speed 20-25 m / s; flow rate 40-60 L / min; time 30-90 min;

[0021] Preferably, the mixing parameters in the circulating high-efficiency pulping system in S3 are: feeding speed 40-60 rpm / min; dispersion linear speed 20-25 m / s; flow rate 40-60 L / min; time 30-90 min;

[0022] Preferably, the mixing parameters in the circulating high-efficiency pulping system in S4 are: dispersion linear speed 20-25 m / s; flow rate 40-60 L / min; time 30-90 min;

[0023] Preferably, the mixing parameters in the circulating high-efficiency pulping system described in S5 are: dispersion line speed 5-15m / s; flow rate 20-40L / min; time 10-20min, and the negative pressure defoaming stage parameters are set to dispersion line speed 5-15m / s; negative pressure -90kPa.

[0024] The present invention also includes a method for preparing a negative electrode sheet, comprising the following steps: applying the negative electrode slurry to a negative electrode current collector.

[0025] The present invention also includes a negative electrode sheet obtained by the preparation method.

[0026] The present invention also includes a battery comprising the negative electrode sheet.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention proposes a low-cost lithium-ion battery negative electrode slurry formula that increases the proportion of the main ingredients while reducing the proportions of thickener and binder, aiming to reduce lithium-ion battery production costs and improve battery energy density, thereby enhancing product competitiveness. A preparation method for this formula is also provided. This method adds a portion of the negative electrode active material during the slurry preparation stage to increase heat generation and promote the dissolution of the thickener, improving the dissolution efficiency and utilization rate of the thickener. This eliminates problems such as uneven slurry dispersion, low viscosity, and bulging edges caused by a reduced ratio of thickener to binder. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The temperature changes during the pulping process of the embodiment of the present invention and the comparative example;

[0030] Figure 2 This is a viscosity comparison chart of the embodiments of the present invention and the comparative examples;

[0031] Figure 3 The solid content change diagram of the embodiment of the present invention and the comparative example over 72 hours;

[0032] Figure 4 Graph showing energy density of cells according to embodiments of the present invention and a comparative example. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1:

[0035] The negative electrode slurry includes the negative electrode active material artificial graphite (D 50 : 12μm, specific surface area: 1.4m 2 / g,) 97.0 parts, thickener CMC (solid content 93%, molecular weight 186000 g / mol) 0.56 parts, binder (styrene-butadiene emulsion, solid content 40%) 1.16 parts, conductive agent 0.97 parts and deionized water;

[0036] The method for preparing the negative electrode slurry comprises the following steps:

[0037] S1, adding 0.6 kg of conductive carbon black, 0.6 kg of thickener and 15.0 kg of artificial graphite into the premixing bin of the circulating high-efficiency pulping system, setting the stirring speed to 200 rpm / min and the stirring time to 15 minutes to obtain a first mixture;

[0038] S2, adding 40.4 kg of deionized water to the circulation tank of the circulating high-efficiency pulping system, and at the same time starting to feed the first mixture, setting the screw feeding speed to 50 rpm / min, the dispersion linear speed in the circulation tank to 20 m / s, the flow rate to 40 L / min, and the time to 40 min to obtain the second mixture;

[0039] S3, adding the remaining 45.0 kg of artificial graphite to the premixing bin, setting the screw feeding speed to 50 rpm / min, adding the artificial graphite to the circulating high-efficiency pulping system with the following parameters: dispersion linear speed 20 m / s, flow rate 40 L / min, time 40 min, and mixing with the second mixture to obtain a third mixture;

[0040] The mass ratio of the negative electrode active material in step S1) to that in step S3 is 1:3;

[0041] S4, adding 5.4 kg of deionized water to adjust the solid content to 58%, performing high-speed dispersion, and setting the parameters of the circulating high-efficiency pulping system: dispersion line speed 20 m / s, flow rate 40 L / min, time 30 min, to obtain a fourth mixture;

[0042] In step S5, 1.8 kg of binder was added to the circulating high-efficiency pulping system. The mixing parameters were set as follows: dispersion speed of 10 m / s, flow rate of 30 L / min, and mixing time of 20 min. The negative pressure defoaming stage parameters were set as follows: dispersion speed of 5 m / s, negative pressure of -90 kPa, and mixing time of 40 min. After negative pressure defoaming, the lithium-ion battery negative electrode slurry was obtained.

[0043] Example 2:

[0044] The negative electrode slurry includes the negative electrode active material artificial graphite (D 50 : 12μm, specific surface area: 1.4m2 / g) 97.96 parts, thickener CMC (solid content 93%, molecular weight 186000g / mol) 0.55 parts, binder (styrene-butadiene emulsion, solid content 40%) 1 part, conductive agent 0.5 parts and deionized water;

[0045] The method for preparing the negative electrode slurry comprises the following steps:

[0046] S1, adding 0.31 kg of conductive carbon black, 0.35 kg of thickener and 20.0 kg of artificial graphite into the premixing bin of the circulating high-efficiency pulping system, setting the stirring speed to 200 rpm / min and the stirring time to 15 minutes to obtain a first mixture;

[0047] S2, adding 40.4 kg of deionized water to the circulation tank of the circulating high-efficiency pulping system, and at the same time starting to feed the first mixture, setting the screw feeding speed to 50 rpm / min, the dispersion linear speed in the circulation tank to 20 m / s, the flow rate to 40 L / min, and the time to 40 min to obtain the second mixture;

[0048] S3, adding the remaining 40.0 kg of artificial graphite to the premixing bin, setting the screw feeding speed to 50 rpm / min, adding the artificial graphite to the circulating high-efficiency pulping system with the following parameters: dispersion linear speed 20 m / s, flow rate 40 L / min, time 40 min, and mixing with the second mixture to obtain a third mixture;

[0049] The mass ratio of the negative electrode active material in step S1) to that in step S3 is 1:2;

[0050] S4, adding 0.8 kg of deionized water to adjust the solid content to 60%, performing high-speed dispersion, and setting the parameters of the circulating high-efficiency pulping system: dispersion line speed 20 m / s, flow rate 40 L / min, time 30 min, to obtain a fourth mixture;

[0051] In step S5, 1.53 kg of binder was added to the circulating high-efficiency pulping system. The mixing parameters were set to: dispersion speed of 10 m / s, flow rate of 30 L / min, and mixing time of 20 min. The negative pressure defoaming stage parameters were set to: dispersion speed of 5 m / s, negative pressure of -90 kPa, and mixing time of 40 min. After negative pressure defoaming, the lithium-ion battery negative electrode slurry was obtained.

[0052] Comparative Example 1:

[0053] The negative electrode slurry includes the negative electrode active material artificial graphite (D 50 : 12μm, specific surface area: 1.4m 2 / g) 96.99 parts, thickener CMC (solid content 93%, molecular weight 186000g / mol) 0.89 parts, binder (styrene-butadiene emulsion, solid content 40%) 1.15 parts, conductive agent 0.96 parts and deionized water;

[0054] The method for preparing the negative electrode slurry comprises the following steps:

[0055] S1, adding 0.6 kg of conductive carbon black and 0.6 kg of thickener into the premixing bin of the circulating high-efficiency pulping system, setting the stirring speed to 200 rpm / min and the stirring time to 15 minutes to obtain a first mixture;

[0056] S2, adding 40.4 kg of deionized water to the circulation tank of the circulating high-efficiency pulping system, and at the same time starting to feed the first mixture, setting the screw feeding speed to 50 rpm / min, the dispersion linear speed in the circulation tank to 20 m / s, the flow rate to 40 L / min, and the time to 40 min to obtain the second mixture;

[0057] S3, adding 60.0 kg of artificial graphite to the premixing bin, setting the screw feeding speed to 50 rpm / min, adding the artificial graphite to the circulating high-efficiency pulping system with the following parameters: dispersion linear speed 20 m / s, flow rate 40 L / min, time 40 min, and mixing with the second mixed material to obtain a third mixed material;

[0058] S4, adding 5.4 kg of deionized water to adjust the solid content to 57%, performing high-speed dispersion, and setting the parameters of the circulating high-efficiency pulping system: dispersion line speed 20 m / s, flow rate 40 L / min, time 30 min, to obtain a fourth mixture;

[0059] In step S5, 1.8 kg of binder was added to the circulating high-efficiency pulping system. The mixing parameters were set to: dispersion speed of 10 m / s, flow rate of 30 L / min, and mixing time of 20 minutes. The negative pressure defoaming stage parameters were set to: dispersion speed of 5 m / s, negative pressure of -90 kPa, and mixing time of 40 minutes. After negative pressure defoaming, the lithium-ion battery negative electrode slurry was obtained.

[0060] Comparative Example 2:

[0061] The negative electrode slurry includes the negative electrode active material artificial graphite (D 50 : 12μm, specific surface area: 1.4m 2 / g) 96.42 parts, thickener CMC (solid content 93%, molecular weight 186000g / mol) 1.48 parts, binder (styrene-butadiene emulsion, solid content 40%) 1.15 parts, conductive agent 0.96 parts and deionized water;

[0062] The method for preparing the negative electrode slurry comprises the following steps:

[0063] S1, adding 0.6 kg of conductive carbon black and 1.0 kg of thickener into the premixing bin of the circulating high-efficiency pulping system, setting the stirring speed to 200 rpm / min and the stirring time to 15 minutes to obtain a first mixture;

[0064] S2, adding 40.4 kg of deionized water to the circulation tank of the circulating high-efficiency pulping system, and at the same time starting to feed the first mixture, setting the screw feeding speed to 50 rpm / min, the dispersion linear speed in the circulation tank to 20 m / s, the flow rate to 40 L / min, and the time to 40 min to obtain the second mixture;

[0065] S3, adding 60.0 kg of artificial graphite to the premixing bin, setting the screw feeding speed to 50 rpm / min, adding the artificial graphite to the circulating high-efficiency pulping system with the following parameters: dispersion linear speed 20 m / s, flow rate 40 L / min, time 40 min, and mixing with the second mixed material to obtain a third mixed material;

[0066] S4, adding 5.4 kg of deionized water to adjust the solid content to 56%, performing high-speed dispersion, and setting the parameters of the circulating high-efficiency pulping system: dispersion line speed 20 m / s, flow rate 40 L / min, time 30 min, to obtain a fourth mixture;

[0067] In step S5, 1.8 kg of binder was added to the circulating high-efficiency pulping system. The mixing parameters were set to: dispersion speed of 10 m / s, flow rate of 30 L / min, and mixing time of 20 minutes. The negative pressure defoaming stage parameters were set to: dispersion speed of 5 m / s, negative pressure of -90 kPa, and mixing time of 40 minutes. After negative pressure defoaming, the lithium-ion battery negative electrode slurry was obtained.

[0068] The mass fractions of the components in Example 1 and Comparative Example 1 are the same, except that artificial graphite is added in the S1 stage of the embodiment, and the temperature when making the first mixture is increased. Figure 1 , thereby promoting the dissolution of the thickener and increasing the viscosity of the slurry, such as Figure 2 , Comparative Example 1 settled after 40 hours, while Example 1 did not settle. Figure 3 .

[0069] In Example 2, the proportion of the main material is further increased, and the amount of the main material added in S1 is increased. The pulping temperature is slightly increased compared to Example 1. Figure 1 , the viscosity is slightly lower, such as Figure 2 , the slurry is stable and no sedimentation occurs, such as Figure 3 , the highest energy density, such as Figure 4 .

[0070] Compared with Example 1, Comparative Example 2 increases the mass fraction of the thickener while reducing the mass fraction of the negative electrode active material. Comparative Example 2 can discharge the material normally without adding part of the main material in the S1 stage, and the viscosity is normal. However, the proportion of negative electrode active material in this system is small, and the battery energy density is low. Figure 4 .

[0071] The present invention also includes a method for preparing a negative electrode sheet, comprising the following steps: applying the negative electrode slurry obtained in Example 1 or 2 to a negative electrode current collector, and the negative electrode sheet can be used to prepare a battery.

[0072] In summary, the present invention proposes a low-cost lithium-ion battery negative electrode slurry formula that increases the proportion of the main ingredients while reducing the proportions of the thickener and binder, aiming to reduce the production cost of lithium-ion batteries and improve the battery's energy density, thereby enhancing product competitiveness. A preparation method for this formula is also provided. This method adds a portion of the negative electrode active material during the gelling stage to increase heat generation and promote the dissolution of the thickener, improving the dissolution efficiency and utilization rate of the thickener, and eliminating problems such as uneven slurry dispersion, low viscosity, and bulging edges caused by a reduced ratio of thickener to binder.

[0073] The basic principles, main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0074] The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are therefore intended to be embraced therein.

[0075] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A negative electrode slurry, characterized in that: The invention comprises 97.0-98.0 parts of negative electrode active material, 0.5-1.0 parts of thickener, 1.0-1.2 parts of binder, 0.5-1 parts of conductive agent and solvent.

2. The negative electrode slurry according to claim 1, characterized in that The negative electrode active material is artificial graphite made from petroleum coke or needle coke. 50 : 10-14μm, specific surface area: 1.0-2.0m 2 / g; Preferably, the thickener is sodium carboxymethyl cellulose or lithium carboxymethyl cellulose, with a molecular weight of 100,000-200,000 g / mol; Preferably, the binder is styrene-butadiene emulsion with a solid content of 40-50%; Preferably, the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; Preferably, the solvent is water, more preferably deionized water.

3. A method for preparing the negative electrode slurry according to claim 1 or 2, characterized in that: The steps include: S1, stirring and mixing a conductive agent, a thickener and part of the negative electrode active material to obtain a first mixture; S2, adding deionized water into the circulating high-efficiency pulping system, and setting up a premixing bin to discharge materials, and mixing the first mixed material with the deionized water to obtain a second mixed material; S3, adding the remaining negative electrode active material to the premixing bin of the circulating high-efficiency pulping system and discharging the material, and uniformly mixing the negative electrode active material with the second mixed material to obtain a third mixed material; S4, adding an appropriate amount of deionized water to adjust the solid content, and performing high-speed dispersion to obtain a fourth mixture; S5, adding a binder and mixing evenly, and then defoaming under negative pressure to obtain the lithium ion battery negative electrode slurry.

4. The method for preparing the negative electrode slurry according to claim 3, wherein: The mass ratio of the negative electrode active material in step S1) to that in step S3 is 1:(1-6); preferably 1:(2-3).

5. The method for preparing the negative electrode slurry according to claim 3, wherein: The amount of deionized water added in step S2 is 1-4 times the amount of the negative electrode active material in step S1; the solid content in step S4 is 55-60%; and the viscosity is 3000-6000 CP.

6. The method for preparing the negative electrode slurry according to claim 3, wherein: The stirring speed in S1 is 100-300 rpm, and the stirring time is 10-30 min. Preferably, the mixing parameters in the circulating high-efficiency pulping system in S2 are: pre-mixing chamber screw feeding speed 40-60 rpm / min; dispersion line speed 20-25 m / s; Flow rate 40-60L / min; time 30-90min.

7. The method for preparing the negative electrode slurry according to claim 3, wherein: The mixing parameters in the circulating high-efficiency pulping system described in S3 are: feeding speed 40-60 rpm / min; dispersion line speed 20-25 m / s; Flow rate 40-60L / min; time 30-90min; Preferably, the mixing parameters in the circulating high-efficiency pulping system in S4 are: dispersion line speed 20-25 m / s; Flow rate 40-60L / min; time 30-90min; Preferably, the mixing parameters in the circulating high-efficiency pulping system described in S5 are: dispersion line speed 5-15m / s; flow rate 20-40L / min; time 10-20min, and the negative pressure defoaming stage parameters are set to dispersion line speed 5-15m / s; negative pressure -90kPa.

8. A method for preparing a negative electrode sheet, characterized in that: The method comprises the following steps: applying the negative electrode slurry according to claim 1 or 2 to a negative electrode current collector.

9. A negative electrode sheet obtained by the preparation method according to claim 9.

10. A battery, characterized in that: Including the negative electrode sheet according to claim 9.

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