Preparation method and preparation device of electrode slurry

Abstract

The invention relates to the field of batteries, and discloses a preparation method and a preparation device of electrode slurry. The invention aims to utilize the corresponding relation between the dissolving time of the binder and the solid content of the binder to firstly form the binder mother liquor, and then the binder mother liquor is discharged to the electrode slurry stirring tank and the supplementary binder mother liquor tank in a proper amount for many times, so that the dissolving time of the binder mother liquor is always in a short time-consuming degree, and the service life of the binder mother liquor is prolonged. Therefore, the production time of the electrode slurry is shortened, particularly, the consumed time of the electrode slurry can be greatly shortened under continuous industrial production, and the solvent and the solution are added after discharging to continue stirring, so that the content of the binder in the stirring tank is kept unchanged. Therefore, the stirring time required by production is reduced.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a method and device for preparing electrode slurry. Background Art

[0002] Lithium battery slurry is a complex multiphase mixed non-Newtonian fluid. The negative electrode slurry is made of a mixture of multiphase materials such as active materials (graphite, etc.), conductive agents (carbon black, CNT, VGC, etc.), binders, thickeners and solvents such as deionized water. The positive electrode slurry is composed of active materials (ternary materials, lithium iron phosphate, lithium cobalt oxide, etc.), conductive agents, binders and solvents. Active materials, conductive agents and solvents have no adhesion to metal electrodes, so they cannot be made into pole pieces for the preparation of lithium batteries. The binder is an important component in the slurry. The binder bonds various particles together to form an adhesive slurry, which tightly bonds it to the metal foil. Although the binder is generally used in small amounts, it plays a very important role in lithium batteries.

[0003] Preparing lithium-ion battery slurry is a step in the process of making lithium-ion batteries. The slurry mixing process is usually used, that is, the positive / negative electrode active materials, thickeners, binders, and solvents are mixed in a certain proportion and stirred in a slurry mixing tank to obtain the positive / negative electrode slurry. The current slurry mixing process usually adds all the binders to the solvent at one time and stirs them, and then adds the conductive agent and active materials and stirs them, but the binder dissolves relatively slowly and takes a long time to dissolve. In order to shorten the preparation time of the electrode slurry, some processes use dispersants to shorten the slurry mixing process, but this will undoubtedly increase industrial costs. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a method for preparing an electrode slurry, so that the preparation method can significantly reduce the stirring time of the binder without using a dispersant, thereby shortening the preparation time of the electrode slurry as a whole;

[0005] Another object of the present application is to provide a device for preparing electrode slurry based on the above-mentioned preparation method.

[0006] In order to solve the above technical problem / achieve the above purpose or at least partially solve the above technical problem / achieve the above purpose, as a first aspect of the present application, a method for preparing an electrode slurry is provided, comprising:

[0007] S1. According to the type of solvent to be used in the electrode slurry and the expected solid content of the binder, a small amount of the same solvent and binder are stirred and dissolved to prepare binder solutions with different test solid contents, and the relationship between the dissolution time of the binder and its test solid content in the solvent is determined. The test solid content with the shortest dissolution time and higher than and closest to the expected solid content is selected as the solid content of the binder mother solution, and then the same solvent and binder are added to the binder mother solution tank and stirred to prepare the binder mother solution;

[0008] S2. A portion of the binder mother solution accounting for 15-25% of the binder mother solution by mass is sent to a stirring tank for stirring, and the same solvent and binder are added to the binder mother solution tank so that the binder solid content of the binder mother solution remains unchanged;

[0009] S3. Repeat S2 until the binder mother liquor in the stirring tank reaches the required amount, add a solvent to the stirring tank, adjust the solid content of the binder to its expected solid content in the electrode slurry, and then add a conductive agent and an active material and stir to obtain the electrode slurry.

[0010] Optionally, the number of the stirring tanks is one or more than two.

[0011] Optionally, the electrode slurry is a positive / negative electrode slurry for a lithium-ion battery, comprising a positive / negative electrode active material, a conductive agent, a binder and a solvent. Further optionally, the solvent comprises N-methylpyrrolidone, the binder comprises polyvinylidene fluoride, the positive electrode active material comprises lithium iron phosphate, lithium cobalt oxide and a ternary positive electrode material, the negative electrode active material comprises lithium titanate, and the conductive agent comprises conductive carbon black.

[0012] As a second aspect of the present application, a device for preparing electrode slurry is provided, comprising: a binder feeding tank, a solvent feeding tank, a binder mother liquid tank, a conductive agent feeding tank, an active material feeding tank and a stirring tank;

[0013] The binder feeding tank and the solvent feeding tank are connected to the binder mother liquid tank through pipelines respectively; the binder mother liquid tank is connected to the stirring tank through pipelines; the solvent feeding tank, the conductive agent feeding tank and the active material feeding tank are connected to the stirring tank through pipelines respectively.

[0014] Optionally, a solid content detection device is provided on a pipeline connecting the binder mother liquid tank with the stirring tank through a pipeline.

[0015] Optionally, each communicating pipeline is provided with a flow control valve and / or a pump.

[0016] The present application aims to utilize the corresponding relationship between the dissolution time of the binder and the solid content of the binder, firstly form a binder mother liquor, and then discharge the material to the electrode slurry stirring tank and the binder mother liquor tank for replenishment in appropriate amounts multiple times, so as to ensure that the dissolution time of the binder mother liquor is always at a relatively short level, thereby reducing the production time of the electrode slurry, especially in continuous industrial production, which can greatly reduce the time consumption of the electrode slurry, and add solvents and solutions after discharging to continue stirring, so as to ensure that the binder content in the stirring tank remains unchanged. Thus, the stirring time required for production is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application.

[0018] Figure 1 Shown is a schematic diagram of the structure of the preparation device of the present application;

[0019] Figure 2 The figure shows the relationship between the solid content of the binder in the solvent and the dissolution time; Binder 1 and Binder 2 represent two brands of PVDF respectively;

[0020] Figure numerals: 1. Binder feeding tank; 2. Solvent feeding tank; 3. Binder mother liquid tank; 4. Stirring tank; 5. Conductive agent feeding tank; 6. Active material feeding tank; 7. Solid content detection device; 8. Flow control valve. DETAILED DESCRIPTION

[0021] The present application discloses a method and a device for preparing an electrode slurry. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in this application. The products, processes and applications described in this application have been described through preferred embodiments. Relevant personnel can obviously modify or appropriately change and combine the products, processes and applications described in this article without departing from the content, spirit and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0022] It should be noted that, in this article, if relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" appear, they are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements. At the same time, the embodiments in this application and the features in the embodiments may be combined with each other without conflict.

[0023] In the first aspect of the present application, a method for preparing an electrode slurry is provided, wherein the binder mother liquid tank is discharged multiple times into a stirring tank, and a solvent and a binder are added after the binder mother liquid tank is discharged and the stirring is continued, so as to ensure that the binder mother liquid tank is always in a high viscosity state and reduce the stirring time of the binder. The preparation method specifically comprises:

[0024] S1. According to the type of solvent to be used in the electrode slurry and the expected solid content of the binder, a small amount of the same solvent and binder are stirred and dissolved to prepare binder solutions with different test solid contents, and the relationship between the dissolution time of the binder and its test solid content in the solvent is determined. The test solid content with the shortest dissolution time and higher than and closest to the expected solid content is selected as the solid content of the binder mother solution, and then the same solvent and binder are added to the binder mother solution tank and stirred to prepare the binder mother solution;

[0025] S2. A portion of the binder mother solution accounting for 15-25% of the binder mother solution by mass is sent to a stirring tank for stirring, and the same solvent and binder are added to the binder mother solution tank so that the binder solid content of the binder mother solution remains unchanged;

[0026] S3. Repeat S2 until the binder mother liquor in the stirring tank reaches the required amount, add a solvent to the stirring tank, adjust the solid content of the binder to its expected solid content in the electrode slurry, and then add a conductive agent and an active material and stir to obtain the electrode slurry.

[0027] In certain embodiments of the present application, the different test solid contents include 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% ... and other values, according to the solid content, the corresponding binder and solvent are weighed for stirring and dissolving, and the solution viscosity no longer changes as the dissolution end point, and the stirring and dissolving of other links in the subsequent actual production is also determined by reference to this standard; the preparation of binder solutions with different test solid contents needs to be consistent with the types of binders and solvents to be used in the actual electrode slurry, such as polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are used in the electrode slurry, and the binder solutions with different test solid contents also need to use PVDF and NMP; since S1 only needs to test the test solid content with the least dissolution time and higher than and closest to the expected solid content, only a small amount of binder and solvent is needed to avoid increasing the operation time. In the actual production process, if the batch and brand of the binder and solvent used remain unchanged, then S1 only needs to be performed once.

[0028] In certain embodiments of the present application, the number of the stirring tanks is one or more than two, so that the electrode slurry can be prepared in parallel, but it is necessary to ensure that the one-time discharge of the binder mother liquid tank does not exceed 25%. Too high a discharge will increase the stirring time after the binder mother liquid tank is refilled, and a one-time discharge of less than 15% will increase the number of discharges, making the process more complicated. In some other embodiments of the present application, the one-time discharge accounts for 20% of the mass of the binder mother liquid, that is, part of the binder mother liquid that accounts for 20% of the mass of the binder mother liquid is sent to the stirring tank for stirring. After discharging, the binder mother liquid tank is refilled with the binder and solvent required for the one-time discharge, and the viscosity is continuously stirred to keep the binder solid content of the binder mother liquid unchanged.

[0029] In certain embodiments of the present application, after the binder mother liquor in the stirring tank reaches the required amount by continuously repeating S2, a solvent is added to the stirring tank, and the solid content of the binder is adjusted to its expected solid content in the electrode slurry by continuously stirring until the viscosity is constant. Since the present application requires that the solid content of the binder mother liquor be higher than the expected solid content, the solid content can be reduced to the expected solid content by adding a solvent. Compared with adjusting the solid content by adding a binder, this method requires a shorter stirring time. After the expected binder solid content is adjusted, the conductive agent and the active substance are then added and stirred. The conductive agent and the active substance can be added and stirred at the same time, or they can be added and stirred one after another until the viscosity is constant to obtain the electrode slurry. The electrode slurry is transported to the electrode coating stage for use, and the stirring tank can be used to prepare the electrode slurry for the next cycle.

[0030] In certain embodiments of the present application, the electrode slurry is a positive / negative electrode slurry of a lithium-ion battery, comprising a positive / negative electrode active material, a conductive agent, a binder, and a solvent. Further optionally, the solvent comprises N-methylpyrrolidone, the binder comprises polyvinylidene fluoride, the positive electrode active material comprises lithium iron phosphate, lithium cobalt oxide, and a ternary positive electrode material, the negative electrode active material comprises lithium titanate, and the conductive agent comprises conductive carbon black.

[0031] In the second aspect of the present application, based on the preparation process provided in the first aspect, the present application further provides an electrode slurry preparation device, comprising: a binder feed tank, a solvent feed tank, a binder mother liquid tank, a conductive agent feed tank, an active material feed tank and a stirring tank;

[0032] The binder feed tank and the solvent feed tank are connected to the binder mother liquid tank through pipelines; the binder mother liquid tank is connected to the stirring tank through pipelines; the solvent feed tank, the conductive agent feed tank and the active material feed tank are connected to the stirring tank through pipelines, respectively. The result schematic diagram is shown in Figure 2 .

[0033] In certain embodiments of the present application, a solid content detection device is provided on the pipe connecting the binder mother liquid tank and the stirring tank through the pipe, and whether the stirring is completed is quickly determined by detecting whether the solid content here reaches the solid content required by the binder mother liquid. In addition, a viscosity monitoring device can also be provided inside the binder mother liquid tank and the stirring tank to monitor the viscosity in real time.

[0034] In certain embodiments of the present application, each connecting pipeline is provided with a flow control valve and / or a pump, which can adjust the speed and amount of material discharge and material replenishment.

[0035] In each group of comparative experiments provided in this application, unless otherwise specified, other experimental conditions, materials, etc. are kept consistent except for the differences indicated in each group, so as to provide comparability. The experimental materials and reagents used in the examples can be obtained from commercial channels unless otherwise specified.

[0036] The following is a further description of a method and device for preparing an electrode slurry provided in the present application.

[0037] Embodiment 1:

[0038] 1. Taking the preparation of ternary nickel cobalt lithium manganese oxide positive electrode slurry as an example (PVDF is used as the binder, and the expected solid content is 6%), the relationship between the dissolution time of the PVDF to be used and its solid content in the solvent NMP is first tested, such as Figure 1 As shown in the middle binder 1, it is judged that it is higher than and closest to the expected solid content of 6% and the test solid content with the shortest dissolution time is 7%.

[0039] according to Figure 2The device shown in the figure is used for preparation, 4650g NMP and 350g PVDF are added into the binder mother liquid tank 3 with a capacity of 60L, and stirred until the viscosity no longer changes. During this period, the solid content detection device 7 can be used to quickly monitor whether the solid content reaches 7%, and the viscosity detection equipment can also be used for detection.

[0040] 2. Open the flow control valve 8, and introduce 1000 g of part of the binder mother liquid in the binder mother liquid tank 3 into the stirring tank 4 through the connecting pipe to start stirring.

[0041] 3. Start the feeding system, add 930g NMP and 70g PVDF into the binder mother liquid tank 3 through the binder feeding tank 1 and the solvent feeding tank 2, and stir to the solid content and total amount before discharging.

[0042] 4. Repeat steps 2 and 3 until the total weight in the mixing tank 4 reaches 5000 g.

[0043] 5. First, add 883 g of NMP to the stirring tank 4 through the solvent feeding tank 2 to reach the expected solid content of 6% required by the formula, and then add the conductive agent SP and lithium nickel cobalt manganese oxide in sequence through the conductive agent feeding tank 5 and the active material feeding tank 6, and stir until the viscosity no longer changes to obtain the nickel cobalt manganese oxide positive electrode slurry.

[0044] Embodiment 2:

[0045] 1. Taking the preparation of lithium titanate negative electrode slurry as an example (PVDF is used as the binder, and the expected solid content is 5%), first test the relationship between the dissolution time of the PVDF to be used and its solid content in the solvent NMP, such as Figure 1 As shown in the middle binder 2, it is judged that it is higher than and closest to the expected solid content of 5% and the test solid content with the shortest dissolution time is 6%.

[0046] according to Figure 2 The device shown is used for preparation, 4700g NMP and 300g PVDF are added into the binder mother liquid tank 3 with a capacity of 60L, and stirred for about 8 hours until the viscosity no longer changes. During this period, the solid content detection device 7 can be used to quickly monitor whether 6% solid content is reached, and the viscosity detection equipment can also be used for detection.

[0047] 2. Open the flow control valve 8, and introduce 1000 g of part of the binder mother liquid in the binder mother liquid tank 3 into the stirring tank 4 through the connecting pipe to start stirring.

[0048] 3. Start the feeding system, add 940g NMP and 60g PVDF into the binder mother liquid tank 3 through the binder feeding tank 1 and the solvent feeding tank 2, and stir to the solid content and total amount before discharging.

[0049] 4. Repeat steps 2 and 3 until the total weight in the mixing tank 4 reaches 5000 g.

[0050] 5. First, add 1000 g of NMP to the stirring tank 4 through the solvent adding tank 2 to reach the expected solid content of 5% required by the formula, and then add the conductive agent SP and lithium titanate in sequence through the conductive agent adding tank 5 and the active material adding tank 6, and stir until the viscosity no longer changes to obtain lithium titanate negative electrode slurry.

[0051] Experimental example:

[0052] Taking the preparation of 23532g of ternary nickel cobalt lithium manganese oxide positive electrode slurry as an example, the formula is the same as that of Example 1;

[0053] Control group: conventional method, i.e., adding 1400g PVDF and 22132g NMP at one time and stirring, adding conductive agent SP and lithium nickel cobalt manganese oxide in sequence after the viscosity remains unchanged, stirring until the viscosity no longer changes, and obtaining lithium nickel cobalt manganese oxide positive electrode slurry;

[0054] Experimental group: the method of Example 1;

[0055] The time taken to complete the final preparation of the above two treatment groups was counted, and the results are shown in Table 1 below;

[0056] Table 1

[0057] Preparation time Example 1 17h Control group 13h

[0058] It can be clearly seen from Table 1 that the process of the present application can significantly shorten the preparation time and improve the production efficiency in actual continuous slurry production.

[0059] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing an electrode slurry, characterized in that: include: S1. According to the type of solvent to be used in the electrode slurry and the expected solid content of the binder, a small amount of the same solvent and binder are stirred and dissolved to prepare binder solutions with different test solid contents, and the relationship between the dissolution time of the binder and its test solid content in the solvent is determined. The test solid content with the shortest dissolution time and higher than and closest to the expected solid content is selected as the solid content of the binder mother solution, and then the same solvent and binder are added to the binder mother solution tank and stirred to prepare the binder mother solution; S2. A portion of the binder mother solution accounting for 15-25% of the binder mother solution by mass is sent to a stirring tank for stirring, and the same solvent and binder are added to the binder mother solution tank so that the binder solid content of the binder mother solution remains unchanged; S3. Repeat S2 until the binder mother liquor in the stirring tank reaches the required amount, add a solvent to the stirring tank, adjust the solid content of the binder to its expected solid content in the electrode slurry, and then add a conductive agent and an active material and stir to obtain the electrode slurry.

2. The preparation method according to claim 1, characterized in that: The number of the stirring tanks is one or more than two.

3. The preparation method according to claim 1, characterized in that: The electrode slurry is positive / negative electrode slurry of a lithium ion battery, comprising positive / negative electrode active materials, a conductive agent, a binder and a solvent.

4. The preparation method according to claim 3, characterized in that: The solvent includes N-methylpyrrolidone, and the binder includes polyvinylidene fluoride.

5. The preparation method according to claim 3, characterized in that: The positive electrode active material includes lithium iron phosphate, lithium cobalt oxide and a ternary positive electrode material, the negative electrode active material includes lithium titanate, and the conductive agent includes conductive carbon black.

6. A device for preparing electrode slurry, characterized in that: include: Binder feeding tank, solvent feeding tank, binder mother liquid tank, conductive agent feeding tank, active material feeding tank and stirring tank; The binder feeding tank and the solvent feeding tank are connected to the binder mother liquid tank through pipelines respectively; the binder mother liquid tank is connected to the stirring tank through pipelines; the solvent feeding tank, the conductive agent feeding tank and the active material feeding tank are connected to the stirring tank through pipelines respectively.

7. The preparation device according to claim 6, characterized in that: A solid content detection device is arranged on the pipeline connecting the binder mother liquid tank with the stirring tank through the pipeline.

8. The preparation device according to claim 6, characterized in that: Each communicating pipeline is provided with a flow control valve and / or a pump.

Images