CN113224268A - Efficient and stable graphite negative electrode material slurry mixing process - Google Patents
Efficient and stable graphite negative electrode material slurry mixing process Download PDFInfo
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- 239000002002 slurry Substances 0.000 title claims abstract description 165
- 238000002156 mixing Methods 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 54
- 230000008569 process Effects 0.000 title claims abstract description 49
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 36
- 239000010439 graphite Substances 0.000 title claims abstract description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 239000007773 negative electrode material Substances 0.000 title claims description 6
- 238000003756 stirring Methods 0.000 claims abstract description 96
- 238000004898 kneading Methods 0.000 claims abstract description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000007787 solid Substances 0.000 claims abstract description 31
- 239000008367 deionised water Substances 0.000 claims abstract description 30
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 30
- 239000002270 dispersing agent Substances 0.000 claims abstract description 15
- 239000010406 cathode material Substances 0.000 claims abstract description 12
- 239000006258 conductive agent Substances 0.000 claims abstract description 12
- 238000007580 dry-mixing Methods 0.000 claims abstract description 10
- 238000007790 scraping Methods 0.000 claims description 22
- 239000006185 dispersion Substances 0.000 claims description 15
- 238000007599 discharging Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 5
- 239000011230 binding agent Substances 0.000 claims description 4
- 238000004537 pulping Methods 0.000 claims description 3
- 239000012046 mixed solvent Substances 0.000 claims description 2
- 239000010405 anode material Substances 0.000 claims 7
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 238000007873 sieving Methods 0.000 abstract description 5
- 238000002360 preparation method Methods 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 18
- 239000007770 graphite material Substances 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 8
- 238000000576 coating method Methods 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 6
- 230000008859 change Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000004062 sedimentation Methods 0.000 description 4
- 230000004580 weight loss Effects 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 230000008719 thickening Effects 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000009194 climbing Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a high-efficiency stable graphite cathode material slurry mixing process, which comprises the steps of firstly adding a graphite cathode material and a conductive agent for dry mixing, adding deionized water for kneading after the dry mixing is finished, adding a CMC dispersing agent and the deionized water for high-viscosity stirring after the kneading is finished, adding the deionized water for medium-speed stirring after the high-viscosity stirring is finished, adding the deionized water again for low-viscosity stirring after the stirring is finished, removing bubbles after the stirring is finished, and sieving by a 150-mesh sieve to finish slurry preparation. The slurry mixing process can avoid the problems that the CMC dispersing agent prepared by the dry method is invalid in the kneading stage and the slurry is difficult to open in a conglomerated manner, simultaneously improve the production efficiency and the solid content of the slurry, and optimize the dispersibility of the conductive agent SP in the slurry.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a high-efficiency stable graphite negative electrode material slurry mixing process.
Background
At present, lithium ion batteries are rapidly developed in the field of power, host factories continuously pursue batteries with high energy density, quick charge and low cost, batteries with high cost performance are required to be reformed on design and materials, but the manufacturing process of a battery core is the central importance, the battery quality is determined by the manufacturing process of more than 70 percent, but the manufacturing process is the most important front-stage manufacturing process and comprises a slurry mixing process, the conventional cathode graphite material slurry mixing process mainly adopts two modes of wet slurry mixing and dry slurry mixing, wherein the wet slurry mixing is the main mode, and the dry slurry mixing is used by a small number of manufacturers.
The two processes have advantages and disadvantages, the battery pole piece manufactured by the wet slurry mixing process has the problems of large internal resistance, poor dispersibility, low production efficiency, low solid content of slurry and the like, the dry slurry mixing efficiency is high, but the CMC kneading stage is easy to lose effectiveness, and the slurry viscosity is unstable, so that the later coating has a large risk. The two processes also make the battery easy to have the influences of lithium precipitation, poor rate performance of the battery core, fast attenuation of long-cycle capacity, poor high-temperature cycle and the like.
Disclosure of Invention
In view of the above, the invention aims to provide an efficient and stable graphite negative electrode material slurry mixing process to solve the problems of uneven dispersion, unstable viscosity and low solid content existing in negative electrode graphite material wet slurry mixing and dry slurry mixing.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a high-efficiency stable graphite cathode material slurry mixing process comprises the following steps:
(1) dry-mixing a conductive agent SP and graphite to obtain a dry mixture;
(2) adding deionized water into the dry mixture for kneading, and scraping pulp after kneading to obtain pre-pulping;
(3) adding a dispersing agent and deionized water into the prefabricated slurry for high-viscosity stirring to obtain a first slurry;
(4) adding deionized water into the first slurry, and stirring at a medium speed to obtain a second slurry;
(5) adding a mixed solvent of deionized water and NMP into the second slurry, and stirring at a low viscosity to obtain a third slurry;
(6) and adding a binder into the third slurry, stirring, and scraping to obtain the required slurry.
Preferably, the dry mixing in step (1) comprises the following specific operation steps: adding 50% of graphite into the stirrer, adding the conductive agent SP, and finally adding the rest graphite for stirring, wherein the revolution speed of the stirrer is 15-25rpm, the dispersion speed is 300-800rpm, and the stirring time is 20-40 min.
Preferably, the dry mixture obtained in the step (1) is kept still for 10min and then subjected to the step (2).
Preferably, the solid content of the pre-pulping is 68% -70%, and the specific operation steps of kneading in the step (2) are as follows: firstly kneading at low speed with the revolution speed of the stirrer of 10-20rpm for 10-20min, and then kneading at high speed with the revolution speed of the stirrer of 20-30rpm for 25-45 min.
Preferably, the solid content of the first slurry is 62-66%, the revolution speed of the stirrer during high-viscosity stirring in the step (3) is 10-30rpm, the high-viscosity stirring time is 40-70min, and the high-viscosity stirring temperature is less than or equal to 32 ℃.
Preferably, the solid content of the second slurry is 57% -60%, and the operation steps of medium-speed stirring in the step (4) are as follows: stirring for 20min to scrape slurry, and then stirring for 30-60min, wherein the revolution speed of the stirrer is 20-30rpm, the dispersion speed is 200-500rpm, and the medium-speed stirring temperature is less than or equal to 32 ℃.
Preferably, the solid content of the third slurry is 54-56%, the revolution speed of the stirrer during low-viscosity stirring in the step (5) is 25-35rpm, the dispersion speed is 1000-1500rpm, the low-viscosity stirring time is 60-90min, and the low-viscosity stirring temperature is less than or equal to 32 ℃.
Preferably, the revolution speed of the stirrer during stirring in the step (6) is 25-35rpm, the dispersion speed is 200-500rpm, the stirring time is 30-60min, and the stirring temperature is less than or equal to 32 ℃.
Preferably, the method further comprises the following steps:
stirring the required slurry, vacuumizing and removing bubbles, wherein the revolution speed of the stirrer is 15rpm, the time is 60min, the temperature is less than or equal to 32 ℃, the vacuum degree is-90 kpa, and then filtering and discharging the slurry by a 150-mesh screen.
Preferably, the dispersant is CMC and the binder is SBR.
Compared with the prior art, the efficient and stable graphite cathode material slurry mixing process has the following advantages:
(1) the efficient and stable graphite cathode material slurry mixing process can avoid the problems that a dry-method slurry mixing CMC dispersing agent is ineffective in a kneading stage and slurry is difficult to open in a conglomerated manner, simultaneously improves the slurry mixing production efficiency and solid content, and optimizes the dispersibility of a conductive agent SP in the slurry;
(2) the efficient stable graphite cathode material slurry mixing process can shorten the slurry mixing time, and compared with wet slurry mixing for 10 hours, the slurry mixing process can complete discharging within about 5 hours;
(3) in the efficient stable graphite cathode material slurry mixing process, the main material and the conductive agent are subjected to dry mixing and kneading procedures, so that the problems that the conductive agent SP in the wet process cannot be sufficiently and uniformly dispersed in a glue solution and is easy to agglomerate are solved;
(4) the efficient and stable graphite cathode material slurry mixing process can avoid the failure problem of the CMC dispersing agent, and greatly reduce the sedimentation probability of slurry mixing;
(5) the slurry prepared by the efficient and stable graphite cathode material slurry mixing process has high solid content, reduces the addition amount of a solvent and the energy consumption of coating and drying equipment, and has the advantages of short time and low internal resistance of a pole piece.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic view of a pulp mixing process flow according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the fineness of the slurry prepared in example 2 of the present invention;
FIG. 3 is a schematic diagram of the slurry discharge state of the slurry prepared in example 2 of the present invention;
FIG. 4 is a schematic view showing a 150 mesh screen of a slurry obtained in example 2 of the present invention;
FIG. 5 is a graph showing the viscosity and solid content change curves of the slurry prepared in example 2 of the present invention at 25 ℃ for 48 hours;
FIG. 6 is a schematic diagram of the coating adhesion and weight loss rate change curves of the slurry electrode plate prepared in example 2 of the present invention;
FIG. 7 is a schematic diagram of the state of slurry at the kneading stage of the slurry mixing process according to the embodiment of the invention;
FIG. 8 is a schematic diagram of a slurry state after low viscosity stirring in a slurry mixing process according to an embodiment of the invention;
FIG. 9 is a schematic diagram of a dry slurry mixing process in the prior art;
FIG. 10 is a schematic diagram showing the state of slurry at the kneading stage of the dry mixing process in the prior art;
FIG. 11 is a diagram illustrating a low viscosity stirred slurry state of a dry slurry mixing process in the prior art;
fig. 12 is a schematic diagram of a 150-mesh screen of slurry prepared by a dry-method slurry mixing process in the prior art.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
The invention is described in detail below with reference to the following embodiments and accompanying drawings, fig. 1 is a slurry mixing process flow diagram related to the invention, the process flow is for manufacturing a graphite cathode material, and the mass ratio of the cathode system of the invention is as follows: mGraphite cathode:MConductive agent SP:MCMC dispersant:MSBR95.9:1: 1.3: 1.8; and in the slurry mixing stage, if the temperature is less than or equal to 32 ℃, the cooling water is closed, otherwise, the cooling water is opened for cooling. Adding mixed water, wherein an N-methyl pyrrolidone (NMP) solvent is required to be added, the addition amount of the solvent is 2% of the total mass of the graphite main material, and the main purpose is to prevent the pole piece from being cracked in a coating stage.
Example 1
1. Conducting agent SP and graphite material are dry-mixed, 50% of graphite material is added firstly, then conducting agent SP is added, and 50% of graphite material is added again to be mixed (revolution (inversion) 15rpm, dispersion 300rpm, time 20 min).
2. And standing for 10min after mixing is finished, adding deionized water for kneading, controlling the solid content of kneading to be 68%, firstly kneading at a low speed (revolution at 10rpm for 10min), scraping pulp after the low speed kneading is finished, then continuously stirring and kneading (revolution at 20rpm for 25min), and scraping pulp after the kneading is finished.
3. Adding CMC dispersant and deionized water, performing high-viscosity stirring, controlling the solid content of the slurry at 62%, revolving at 10rpm for 40min, and scraping the slurry after the high-viscosity stirring is finished to obtain the slurry 1.
4. Adding deionized water, stirring at medium speed, controlling the solid content of the slurry at 57%, revolving at 20rpm, dispersing at 200rpm, stirring for 50min at the temperature of less than or equal to 32 ℃, stirring for 20min first, scraping the slurry, stirring for the rest of time, and scraping the slurry after the medium-speed stirring is finished to obtain slurry 2.
5. Adding mixed water (deionized water and NMP solvent) to carry out low-viscosity stirring, controlling the solid content of the slurry to be 54 percent, revolving at 25rpm, dispersing at 1000rpm for 60min, and scraping the slurry to obtain slurry 3 after the low-viscosity stirring is finished.
6. Adding SBR, then continuing stirring, revolving at 25rpm, dispersing at 200rpm for 30min, and obtaining the required slurry after stirring at the temperature of less than or equal to 32 ℃.
7. Vacuumizing the slurry to remove bubbles, revolving at 15rpm (rotating the stirring paddle in reverse), standing for 60min at the temperature of less than or equal to 32 ℃ and the vacuum degree of-90 kpa, and filtering and discharging by using a 150-mesh screen.
Example 2
1. Conducting agent SP and graphite material are dry-mixed, 50% of graphite material is added firstly, then conducting agent SP is added, and 50% of graphite material is added again to be mixed (revolution (reverse rotation) is carried out at 20rpm, dispersion is carried out at 500rpm, and time is 30 min).
2. And standing for 10min after mixing is finished, adding deionized water for kneading, controlling the solid content of kneading to be 69.1%, firstly kneading at a low speed (revolution at 15rpm for 15min), scraping pulp after the low speed kneading is finished, then continuously stirring and kneading (revolution at 20rpm for 30min), and scraping pulp after the kneading is finished.
3. Adding CMC dispersant and deionized water, stirring at high viscosity, controlling the solid content of the slurry at 64%, revolving at 20rpm for 60min, and scraping the slurry after the stirring at high viscosity is finished to obtain slurry 1.
4. Adding deionized water, stirring at medium speed, controlling the solid content of the slurry at 58.6%, revolving at 25rpm, dispersing at 305rpm, keeping the time at 60min and the temperature at less than or equal to 32 ℃, stirring for 20min first, scraping the slurry, then stirring for the rest of time, and scraping the slurry after the medium-speed stirring is finished to obtain slurry 2.
5. Adding mixed water (deionized water and NMP solvent) to carry out low-viscosity stirring, controlling the solid content of the slurry to be 55 percent, revolving at 30rpm, dispersing at 1200rpm for 60min, and scraping the slurry to obtain slurry 3 after the low-viscosity stirring is finished.
6. And adding SBR, then continuing stirring, revolving at 30rpm, dispersing at 305rpm for 45min at the temperature of less than or equal to 32 ℃, and obtaining the required slurry after stirring.
7. Vacuumizing the slurry to remove bubbles, revolving at 15rpm (rotating the stirring paddle in reverse), standing for 60min at the temperature of less than or equal to 32 ℃ and the vacuum degree of-90 kpa, and filtering and discharging by using a 150-mesh screen.
Example 3
1. Conducting agent SP and graphite material are dry-mixed, 50% of graphite material is added firstly, then conducting agent SP is added, and 50% of graphite material is added again to be mixed (revolution (reverse rotation) is 25rpm, dispersion is 800rpm, and time is 40 min).
2. And standing for 10min after mixing is finished, adding deionized water for kneading, controlling the solid content of kneading to be 70%, firstly kneading at a low speed (revolution at 20rpm for 20min), scraping pulp after the low speed kneading is finished, then continuously stirring and kneading (revolution at 30rpm for 45min), and scraping pulp after the kneading is finished.
3. Adding CMC dispersant and deionized water, performing high-viscosity stirring, controlling the solid content of the slurry at 66%, revolving at 30rpm for 70min, and scraping the slurry after the high-viscosity stirring is finished to obtain the slurry 1.
4. Adding deionized water, stirring at medium speed, controlling the solid content of the slurry at 60%, revolving at 30rpm, dispersing at 500rpm, stirring for 90min at the temperature of less than or equal to 32 ℃, stirring for 20min, scraping the slurry, stirring for the rest of time, and scraping the slurry after the medium-speed stirring is finished to obtain slurry 2.
5. Adding mixed water (deionized water and NMP solvent) to carry out low-viscosity stirring, controlling the solid content of the slurry to be 56 percent, revolving at 35rpm, dispersing at 1500rpm for 90min, and scraping the slurry to obtain slurry 3 after the low-viscosity stirring is finished.
6. Adding SBR, then continuing stirring, revolving at 35rpm, dispersing at 500rpm for 60min, and obtaining the required slurry after stirring at the temperature of less than or equal to 32 ℃.
7. Vacuumizing the slurry to remove bubbles, revolving at 15rpm (rotating the stirring paddle in reverse), standing for 60min at the temperature of less than or equal to 32 ℃ and the vacuum degree of-90 kpa, and filtering and discharging by using a 150-mesh screen.
Fig. 2 is data of the fineness of the slurry prepared in example 2 of the present invention, and it can be seen that the discharge fineness of the slurry is about 25 μm, which corresponds to the discharge fineness of the slurry for a graphite negative electrode. The fineness is determined by the particle size of the material, and the process has good dispersibility and does not have obvious aggregates and hard blocks.
Fig. 9 is a schematic diagram of a process flow of dry slurry mixing in the prior art, in which graphite, a conductive agent SP, and a dispersant CMC are premixed and then added with deionized water to be kneaded, fig. 10 is a schematic diagram of a slurry state at a kneading stage of the dry slurry mixing process in the prior art, fig. 11 is a schematic diagram of a slurry state after low-viscosity stirring of the dry slurry mixing process in the prior art, and fig. 12 is a schematic diagram of a sieving state of a 150-mesh screen of slurry prepared by the dry slurry mixing process in the prior art. As can be seen from fig. 10, in the kneading stage, the slurry is agglomerated into blocks in a large area, the agglomerates are still not opened along with kneading, so that the kneading effect is not obvious, and meanwhile, the slurry after dispersion is started and is in direct contact with CMC to rub to generate a higher temperature, so that the CMC has a failure risk; as shown in FIG. 11, the slurry was not too viscous and was not stringingly drawn, as shown in FIG. 12, the 150 mesh screen was found to fail to properly screen, and the slurry was sedimented due to the fact that CMC may be lost during kneading and did not perform significant dispersing and thickening effects, resulting in sedimentation of the slurry.
Fig. 1 is a schematic diagram of a slurry mixing process flow according to an embodiment of the present invention, in which a graphite negative electrode material and a conductive agent are added to perform dry mixing, deionized water is added to perform kneading after the dry mixing is finished, a CMC dispersant and deionized water are added to perform high viscosity stirring, deionized water is added to perform medium speed stirring after the high viscosity stirring is finished, deionized water is added again to perform low viscosity stirring after the stirring is finished, and a 150-mesh sieve is used to perform defoaming after the stirring is finished to complete slurry preparation. Fig. 7 is a schematic diagram of a state of slurry at a kneading stage of a slurry mixing process according to an embodiment of the present invention, fig. 8 is a schematic diagram of a state of slurry after low-viscosity stirring and stirring in the slurry mixing process according to the embodiment of the present invention, and fig. 4 is a schematic diagram of a state of a 150-mesh screen for sieving the slurry obtained in example 2 of the present invention. As shown in figure 8, no large-area aggregate appears in the kneading stage, the phenomenon of rod climbing along the stirring paddle does not occur in the slurry, and the kneading process does not add a CMC dispersing agent for kneading, so that the CMC is mainly prevented from losing efficacy and the slurry aggregate appears, as shown in figure 8, the phenomenon of wire drawing appears after the stirring is finished by low-speed stirring (adding mixed water), which indicates that the problem of losing efficacy does not occur in the later-stage addition of the CMC and the thickening effect is achieved, as shown in figure 4, the slurry can be normally sieved by using a 150-mesh sieve, and the slurry has good fluidity and does not have the phenomenon of sedimentation.
Fig. 3 shows the discharge state of the slurry prepared in example 2 of the present invention, and fig. 4 shows the sieving data of the slurry prepared in example 2 of the present invention with a 150-mesh sieve, and the 150-mesh normal sieving indicates that the slurry has good fluidity, no obvious dispersion unevenness, agglomeration and sedimentation risks, and good dispersion effect.
FIG. 5 shows the data of the change of the viscosity and solid content of the slurry prepared in example 2 at 25 ℃ for 48h, and it can be seen from the data that the viscosity rises by 938mpa.s and the solid content rises by 0.24% after the slurry is discharged and is kept still for 48h, and because the slurry is kept still in a beaker, deionized water is gradually volatilized after being kept for a long time, the solvent is reduced, the viscosity is gradually increased, and the solid content correspondingly rises. The stability of viscosity and solid content is beneficial to smooth coating, and the large fluctuation of surface density and thickness can not occur.
Fig. 6 is the coating adhesion and weight loss rate change data of the pole piece in example 2, and it can be seen from the data that the coating adhesion of the pole piece is maintained above 1N/30mm, and the weight loss rate is below 0.3%, which meets the specification requirements of the negative graphite pole piece, which indicates that the slurry prepared by the invention has good process feasibility, and the higher the adhesion of the pole piece, the better the adhesion of the slurry and the current collector, and is beneficial to improving the cycle performance and the rate capability of the battery cell at the later stage. The lower the weight loss rate is, the less the solvent used by the slurry is, the solid content is correspondingly improved, the coating thickness of the pole piece is correspondingly reduced, and the charging and discharging performance of the battery cell is facilitated.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A high-efficiency stable graphite cathode material slurry mixing process is characterized by comprising the following steps:
(1) dry-mixing a conductive agent SP and graphite to obtain a dry mixture;
(2) adding deionized water into the dry mixture for kneading, and scraping pulp after kneading to obtain pre-pulping;
(3) adding a dispersing agent and deionized water into the prefabricated slurry for high-viscosity stirring to obtain a first slurry;
(4) adding deionized water into the first slurry, and stirring at a medium speed to obtain a second slurry;
(5) adding a mixed solvent of deionized water and NMP into the second slurry, and stirring at a low viscosity to obtain a third slurry;
(6) and adding a binder into the third slurry, stirring, and scraping to obtain the required slurry.
2. The slurry mixing process for the high-efficiency stable graphite negative electrode material according to claim 1, wherein the dry mixing in the step (1) comprises the following specific operation steps: adding 50% of graphite into the stirrer, adding the conductive agent SP, and finally adding the rest graphite for stirring, wherein the revolution speed of the stirrer is 15-25rpm, the dispersion speed is 300-800rpm, and the stirring time is 20-40 min.
3. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, characterized in that: and (3) standing the dry mixture obtained in the step (1) for 10min, and then performing the step (2).
4. The high-efficiency stable graphite cathode material slurry mixing process as claimed in claim 1, wherein the solid content of the pre-slurrying is 68% -70%, and the specific operation steps of kneading in the step (2) are as follows: firstly kneading at low speed with the revolution speed of the stirrer of 10-20rpm for 10-20min, and then kneading at high speed with the revolution speed of the stirrer of 20-30rpm for 25-45 min.
5. The slurry mixing process of the high-efficiency stable graphite anode material as claimed in claim 1, wherein the solid content of the first slurry is 62% -66%, the revolution speed of the stirrer during high-viscosity stirring in step (3) is 10-30rpm, the high-viscosity stirring time is 40-70min, and the high-viscosity stirring temperature is less than or equal to 32 ℃.
6. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, wherein the solid content of the second slurry is 57% -60%, and the specific operation steps of medium-speed stirring in the step (4) are as follows: stirring for 20min to scrape slurry, and then stirring for 30-60min, wherein the revolution speed of the stirrer is 20-30rpm, the dispersion speed is 200-500rpm, and the medium-speed stirring temperature is less than or equal to 32 ℃.
7. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, characterized in that: the solid content of the third slurry is 54-56%, the revolution speed of the stirrer during low-viscosity stirring in the step (5) is 25-35rpm, the dispersion speed is 1000-1500rpm, the low-viscosity stirring time is 60-90min, and the low-viscosity stirring temperature is less than or equal to 32 ℃.
8. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, characterized in that: in the step (6), the revolution speed of the stirrer is 25-35rpm, the dispersion speed is 200-500rpm, the stirring time is 30-60min, and the stirring temperature is less than or equal to 32 ℃.
9. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, characterized by further comprising the following steps:
stirring the required slurry, vacuumizing and removing bubbles, wherein the revolution speed of the stirrer is 15rpm, the time is 60min, the temperature is less than or equal to 32 ℃, the vacuum degree is-90 kpa, and then filtering and discharging the slurry by a 150-mesh screen.
10. The high-efficiency stable graphite anode material slurry mixing process according to claim 1, characterized in that: the dispersant is CMC, and the binder is SBR.
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