Method for measuring viscosity of lithium iron phosphate

Abstract

The invention discloses a lithium iron phosphate viscosity measurement method, and belongs to the technical field of lithium ion batteries, the measurement method comprises the following steps: 1, drying lithium iron phosphate with different particle size distributions for later use; drying the conductive agent and polyvinylidene fluoride for later use; step 2, weighing the dried conductive agent and dispersant, adding the weighed conductive agent and dispersant into an organic solvent, and stirring and dispersing to obtain a mixed solution; step 3, weighing dried polyvinylidene fluoride, adding the dried polyvinylidene fluoride into the mixed solution obtained in the step 2, and stirring and dispersing to obtain a conductive adhesive solution; step 4, weighing lithium iron phosphate, adding the lithium iron phosphate into the conductive adhesive solution obtained in the step 3, and continuously stirring to obtain slurry; and step 5, measuring the slurry mixed in the step 4 by adopting a viscometer to finish measurement. The method for measuring the viscosity of the lithium iron phosphate, provided by the invention, can be used for rapidly and accurately detecting the viscosity of the lithium iron phosphate slurry, is simple to operate and is suitable for large-scale process production.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for measuring the viscosity of lithium iron phosphate. Background Art

[0002] By 2023, the cumulative installed capacity of lithium iron phosphate power batteries in China will reach 261.0GWh, accounting for 67.3% of the total installed capacity of power batteries. Based on the economic and safety of lithium iron phosphate, the proportion of lithium iron phosphate in the lithium battery industry will continue to rise. In the lithium battery processing process, pole piece manufacturing is related to the core performance of the battery, and the viscosity of lithium iron phosphate slurry has a crucial impact on pole piece manufacturing.

[0003] During the slurry mixing and coating process, the slurry needs to have a stable and appropriate viscosity. Too high or too low viscosity is not conducive to electrode coating: slurry with high viscosity is not easy to precipitate and has better dispersibility, but too high viscosity is not conducive to leveling effect and coating; too low viscosity is also not good. When the viscosity is low, the slurry has good fluidity, but it is difficult to dry, the drying efficiency of coating decreases, and problems such as coating cracking, slurry particle agglomeration, and poor surface density consistency may occur. Therefore, pre-judging the viscosity of lithium iron phosphate has a guiding role in the production and processing of lithium iron phosphate. Summary of the invention

[0004] In order to realize how to quickly and accurately detect the viscosity of lithium iron phosphate slurry during processing, the present invention provides a method for measuring the viscosity of lithium iron phosphate.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for measuring the viscosity of lithium iron phosphate comprises the following steps:

[0007] Step 1, drying lithium iron phosphate with different particle size distributions at 100° C. for 2-12 hours for standby use;

[0008] The conductive agent and polyvinylidene fluoride (PVDF) are dried at 50-100° C. for 8 h-12 h respectively for later use;

[0009] Step 2, weighing the dried conductive agent and dispersant, adding them to an organic solvent, stirring and dispersing at 500-1500 rpm for 10-30 minutes to obtain a mixed solution;

[0010] Step 3, weigh the dried polyvinylidene fluoride and add it to the mixed solution obtained in step 2, and stir and disperse it at 500-1500 rpm for 10-30 minutes to obtain a conductive adhesive solution;

[0011] Step 4, weigh lithium iron phosphate, add it to the conductive glue obtained in step 3, and continue stirring at 1000-2000 rpm for 10-30 minutes to obtain a slurry;

[0012] Step 5: Use a viscometer to measure the slurry mixed in step 4, and the measurement is completed.

[0013] As a further embodiment of the present invention, the amount ratio of the conductive agent, the dispersant, the organic solvent, the polyvinylidene fluoride and the lithium iron phosphate is 0.5-1.5 g: 0.005-0.03 g: 100-150 g: 2-4 g: 50-150 g.

[0014] As a further embodiment of the present invention, the conductive agent is at least one of graphite, carbon black, carbon nanotubes, and graphene.

[0015] As a further solution of the present invention, the PVDF is at least one of PVDF5130, PVDF900, and PVDF9100.

[0016] As a further embodiment of the present invention, the dispersant is at least one of polyvinyl pyrrolidone (PVP) and sodium lignin sulfonate (SLS).

[0017] As a further embodiment of the present invention, the organic solvent is one of N-methylpyrrolidone (NMP), pinitol, and dimethylformamide (DMF).

[0018] As a further embodiment of the present invention, the different particle size distributions include D10, D50, D90 and Dmax.

[0019] As a further solution of the present invention, the particle size of D10 in the particle size distribution is 0.35-0.50 μm.

[0020] As a further embodiment of the present invention, the particle size D50 in the particle size distribution is 1.0-1.3 μm.

[0021] As a further embodiment of the present invention, the particle size D90 in the particle size distribution is 3.0-5.0 μm.

[0022] As a further embodiment of the present invention, the particle size Dmax in the particle size distribution is 7.0-10.0 μm.

[0023] Beneficial effects of the present invention:

[0024] The present invention first adds modified carbon black, polyvinylidene fluoride and a dispersant to an organic solvent, stirs and disperses them uniformly, obtains a uniformly dispersed conductive glue, then adds lithium iron phosphate particles with different particle size distributions and continues to stir and mix them, obtains a highly dispersed lithium iron phosphate slurry, and then uses a viscometer to measure the viscosity, and the measured viscosity data has high accuracy and small error. By adding and mixing the conductive agent, dispersant, PVDF and lithium iron phosphate in steps, the conductive agent, PVDF and lithium iron phosphate are mixed and dispersed more uniformly, and the conductive agent and lithium iron phosphate absorb the organic solvent more fully during the slurrying process, thereby making the lithium iron phosphate slurry more stable in the subsequent viscosity detection process.

[0025] In addition, lithium iron phosphate with different particle size distributions is mixed into slurry. After mixing particles of different sizes, the porosity is reduced, and it helps to prevent particles from embedding into each other, improves the dispersion stability of lithium iron phosphate slurry, and avoids the slurry sedimentation caused by agglomeration, so that the viscosity of lithium iron phosphate slurry can be measured quickly and accurately. Furthermore, by accurately and quickly measuring the viscosity of lithium iron phosphate, the overall performance and quality of the battery are improved, which helps to improve production efficiency and economic costs. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] This embodiment provides a method for measuring the viscosity of lithium iron phosphate, comprising the following steps:

[0029] Step 1, drying lithium iron phosphate with different particle size distributions (specific particle size distributions are shown in Table 1) at 100° C. for 2 h for standby use;

[0030] Carbon black and PVDF5130 were dried at 50°C for 12 h respectively and set aside;

[0031] Step 2, weigh 0.5 g of dried carbon black and 0.005 g of polyvinyl pyrrolidone, slowly add them into 100 g of N-methyl pyrrolidone, and stir and disperse them at 500 rpm for 30 min to obtain a mixed solution;

[0032] Step 3, weigh 2 g of dried PVDF5130, slowly add it to the mixed solution obtained in step 2, and stir and disperse at 500 rpm for 30 minutes to obtain a conductive adhesive solution;

[0033] Step 4: Weigh 50 g of lithium iron phosphate and add it to the conductive glue obtained in step 3, and continue stirring at 1000 rpm for 30 min to obtain a slurry;

[0034] Step 5: Use NDJ rotational viscometer to measure the slurry mixed in step 4, and the measurement is completed.

[0035] The different particle size distributions used above are shown in Table 1:

[0036] Table 1

[0037]

[0038] The lithium iron phosphate slurries obtained by using different particle size distributions were tested, and the test results are shown in Table 2 and Table 3:

[0039] Table 2

[0040]

[0041]

[0042] Table 3

[0043]

[0044] Example 2

[0045] This embodiment provides a method for measuring the viscosity of lithium iron phosphate, comprising the following steps:

[0046] Step 1, drying lithium iron phosphate with different particle size distributions (specific particle size distributions are shown in Table 4) at 100° C. for 2 h for standby use;

[0047] Carbon black and PVDF5130 were dried at 50°C for 12 h respectively and set aside;

[0048] Step 2, weigh 0.5 g of dried carbon black and 0.005 g of polyvinyl pyrrolidone, slowly add them into 100 g of N-methyl pyrrolidone, and stir and disperse them at 500 rpm for 30 min to obtain a mixed solution;

[0049] Step 3, weigh 2 g of dried PVDF5130, slowly add it to the mixed solution obtained in step 2, and stir and disperse at 500 rpm for 30 minutes to obtain a conductive adhesive solution;

[0050] Step 4, weigh 60g of lithium iron phosphate, add it to the conductive glue obtained in step 3, and continue stirring at 1000rpm for 30min to obtain a slurry;

[0051] Step 5: Use NDJ rotational viscometer to measure the slurry mixed in step 4, and the measurement is completed.

[0052] The different particle size distributions used above are shown in Table 4:

[0053] Table 4

[0054]

[0055]

[0056] The lithium iron phosphate slurry obtained by using different particle size distributions was tested, and the test results are shown in Table 5:

[0057] Table 5

[0058]

[0059] It can be seen from Tables 1-5 that the method for measuring the viscosity of lithium iron phosphate provided by the present invention can quickly and accurately detect the viscosity of lithium iron phosphate slurry, and is simple to operate and suitable for large-scale process production.

[0060] It should be noted that, in this article, relational terms such as first and second, etc. 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 "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device 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 device.

[0061] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the viscosity of lithium iron phosphate, characterized in that: The following steps are involved: Step 1, drying lithium iron phosphate with different particle size distributions at 100° C. for 2-12 hours for standby use; Dry the conductive agent and polyvinylidene fluoride at 50-100°C for 8h-12h respectively and set aside; Step 2, weighing the dried conductive agent and dispersant, adding them to an organic solvent, stirring and dispersing at 500-1500 rpm for 10-30 minutes to obtain a mixed solution; Step 3, weigh the dried polyvinylidene fluoride and add it to the mixed solution obtained in step 2, and stir and disperse it at 500-1500 rpm for 10-30 minutes to obtain a conductive adhesive solution; Step 4, weigh lithium iron phosphate, add it to the conductive glue obtained in step 3, and continue stirring at 1000-2000 rpm for 10-30 minutes to obtain a slurry; Step 5: Use a viscometer to measure the slurry mixed in step 4, and the measurement is completed.

2. The method for measuring the viscosity of lithium iron phosphate according to claim 1, characterized in that: The usage ratio of the conductive agent, the dispersant, the organic solvent, the polyvinylidene fluoride and the lithium iron phosphate is 0.5-1.5g: 0.005-0.03g: 100-150g: 2-4g: 50-150g.

3. The method for measuring the viscosity of lithium iron phosphate according to claim 1, characterized in that: The conductive agent is at least one of graphite, carbon black, carbon nanotubes, and graphene; the PVDF is at least one of PVDF5130, PVDF900, and PVDF9100.

4. The method for measuring the viscosity of lithium iron phosphate according to claim 1, characterized in that: The dispersant is at least one of polyvinyl pyrrolidone and sodium lignin sulfonate.

5. The method for measuring the viscosity of lithium iron phosphate according to claim 1, characterized in that: The organic solvent is one of N-methylpyrrolidone, pinol and dimethylformamide.

6. The method for measuring the viscosity of lithium iron phosphate according to claim 1, characterized in that: The different particle size distributions include D10, D50, D90 and Dmax.

7. The method for measuring the viscosity of lithium iron phosphate according to claim 6, characterized in that: The particle size of D10 in the particle size distribution is 0.35-0.50 μm.

8. The method for measuring the viscosity of lithium iron phosphate according to claim 6, characterized in that: The particle size D50 in the particle size distribution is 1.0-1.3 μm.

9. The method for measuring the viscosity of lithium iron phosphate according to claim 6, characterized in that: The particle size D90 in the particle size distribution is 3.0-5.0 μm.

10. The method for measuring the viscosity of lithium iron phosphate according to claim 6, characterized in that: The particle size Dmax in the particle size distribution is 7.0-10.0 μm.

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