CN115692620A - Method for preparing water-based positive plate and application - Google Patents
Method for preparing water-based positive plate and application Download PDFInfo
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- CN115692620A CN115692620A CN202211436358.XA CN202211436358A CN115692620A CN 115692620 A CN115692620 A CN 115692620A CN 202211436358 A CN202211436358 A CN 202211436358A CN 115692620 A CN115692620 A CN 115692620A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 35
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- 239000006185 dispersion Substances 0.000 claims abstract description 45
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- 238000001035 drying Methods 0.000 claims abstract description 38
- 239000000853 adhesive Substances 0.000 claims abstract description 37
- 238000002156 mixing Methods 0.000 claims abstract description 35
- 239000008367 deionised water Substances 0.000 claims abstract description 33
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 33
- 239000011248 coating agent Substances 0.000 claims abstract description 25
- 238000000576 coating method Methods 0.000 claims abstract description 25
- 239000003292 glue Substances 0.000 claims abstract description 25
- 239000006258 conductive agent Substances 0.000 claims abstract description 24
- 239000007774 positive electrode material Substances 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims description 39
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 20
- 229910001416 lithium ion Inorganic materials 0.000 claims description 20
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 19
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 18
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 18
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 18
- 239000011230 binding agent Substances 0.000 claims description 17
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 17
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 13
- 239000007787 solid Substances 0.000 claims description 12
- 239000002109 single walled nanotube Substances 0.000 claims description 11
- 229920000058 polyacrylate Polymers 0.000 claims description 10
- 239000006230 acetylene black Substances 0.000 claims description 6
- 239000003792 electrolyte Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000006232 furnace black Substances 0.000 claims description 2
- 239000002048 multi walled nanotube Substances 0.000 claims description 2
- 230000009467 reduction Effects 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 abstract description 11
- 230000000694 effects Effects 0.000 abstract description 10
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- 238000009776 industrial production Methods 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 15
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 14
- 238000012360 testing method Methods 0.000 description 9
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- 230000008569 process Effects 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 239000002033 PVDF binder Substances 0.000 description 4
- 239000007772 electrode material Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 238000007790 scraping Methods 0.000 description 4
- 239000013543 active substance Substances 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- 239000011267 electrode slurry Substances 0.000 description 3
- 108010010803 Gelatin Proteins 0.000 description 2
- 229920002125 Sokalan® Polymers 0.000 description 2
- 239000006256 anode slurry Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
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- 239000003125 aqueous solvent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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- 229910052799 carbon Inorganic materials 0.000 description 1
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a method for preparing a water-based positive plate and application thereof. The method comprises the following steps: (1) Mixing the water-based adhesive, the conductive agent and the deionized water, and sequentially carrying out primary mixing and primary dispersion to obtain a glue solution; (2) Sequentially carrying out secondary mixing and secondary dispersion on the glue solution and the positive active material obtained in the step (1), then adding deionized water to sequentially carry out tertiary mixing and tertiary dispersion, and carrying out quaternary mixing and quaternary dispersion after cooling to obtain slurry; (3) And (3) coating the slurry obtained in the step (2) on the surface of a current collector, and drying the slurry by adopting a sectional drying method to obtain the water-based positive plate. The invention provides the preparation method of the water-based positive plate, which has the advantages of simple homogenization step, good coating effect, low cost and easy industrial production.
Description
Technical Field
The invention belongs to the technical field of electrode materials, and particularly relates to a method for preparing a water-based positive plate and application of the water-based positive plate.
Background
The adhesive is used as an important component of an electrode material of a lithium ion battery, and has the main functions of bonding active substances, enhancing the electronic contact between the electrode active material and a conductive agent and between the active material and a current collector, and simultaneously improving the structural stability of a pole piece. In addition, the added adhesive can play a role in buffering volume expansion/contraction generated in the charge and discharge processes of the lithium ion battery electrode material, so that the proper adhesive is one of the key factors influencing the electrochemical performance of the lithium ion power battery.
Currently, in lithium ion batteries, polyvinylidene fluoride (PVDF) is mostly used as a binder, and an organic compound with strong polarity, N-dimethyl pyrrolidone (NMP), is used as a solvent for PVDF, that is, an organic solvent is used for coating and sheet-making. However, it still faces some problems in the application process, such as on one hand, the high price of the organic solvent NMP, the large amount used and the high recovery cost; on the other hand, NMP is toxic and harmful to the body of the operator.
In order to solve the above problems, researchers developed an aqueous adhesive and applied the aqueous adhesive to a process of preparing a positive electrode sheet. For example, CN1824724A discloses an aqueous adhesive consisting of gelatin, latex, water-soluble polymer and water. Although gelatin is decomposed into amino acids, which can improve the adhesive force of the slurry, the preparation process of the aqueous binder is complicated, and the cycle life of the battery prepared is short. CN102185157A discloses a production process of an aqueous positive lithium ion battery, which comprises the following steps: preparing the positive and negative electrodes, coating the positive and negative electrodes, preparing the sheets, baking, preparing the battery cell, detecting short circuit, baking, putting down the gasket into the shell, pointing the bottom, putting the gasket on the shell, folding the positive lug, rolling the groove and detecting the short circuit. Injecting liquid, wiping the positive lug, welding the positive lug and the cover plate, folding the cover plate to close the cover, sealing, cleaning, shelving, forming, shelving and grading. In the method, more substances are added to prepare the anode slurry, the homogenization time is increased, and the operation is relatively complex.
The prior art uses water-based adhesives to prepare the positive pole piece, and has the following problems: on one hand, the types of materials added in the homogenization process are more, the homogenization time is long, and the operation is relatively complex; on the other hand, the process parameters of the process such as coating and the like are completely different from those of the traditional oily system due to the adoption of the aqueous solvent.
Therefore, it is necessary to provide a method for producing an aqueous positive electrode sheet having a simple homogenization step and a good coating effect.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for preparing an aqueous positive plate and application thereof. The invention provides the preparation method of the water-based positive plate, which has the advantages of simple homogenization step, good coating effect, low cost and easy industrial production.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing an aqueous positive electrode sheet, the method comprising the steps of:
(1) Mixing the water-based adhesive, the conductive agent and the deionized water, and sequentially carrying out primary mixing and primary dispersion to obtain a glue solution;
(2) Sequentially carrying out secondary mixing and secondary dispersion on the glue solution obtained in the step (1) and the positive active material, then adding deionized water to sequentially carry out tertiary mixing and tertiary dispersion, and carrying out quaternary mixing and quaternary dispersion after cooling to obtain slurry;
(3) And (3) coating the slurry obtained in the step (2) on the surface of a current collector, and drying the slurry by adopting a sectional drying method to obtain the water-based positive plate.
The invention provides a method for preparing a water-based positive plate, which comprises the steps of firstly mixing a water-based adhesive, a conductive agent and deionized water to prepare a glue solution, then adding a positive active substance to carry out multiple dispersion to prepare a uniformly dispersed slurry, and avoiding the phenomena of sedimentation and floating powder. In addition, the slurry is dried by adopting a sectional drying method, so that the active material layer and the current collector have a good bonding effect, and the problems of structural collapse and the like of the active material layer are prevented.
Preferably, the aqueous binder in step (1) comprises carboxymethyl cellulose grafted sodium polyacrylate copolymer and/or polyacrylate.
In the invention, polyacrylic acid is a commonly used water-based adhesive for the cathode material at present, and a molecular chain of polyacrylic acid and salts thereof has a plurality of oxygen-containing groups (such as-COOH), so that hydrogen bonds can be formed with the surface of the cathode active material, and a strong binding force is given between active particles and a current collector, thereby improving the cycle performance of the battery. The carboxymethyl cellulose can well disperse the active material and the conductive agent in the aqueous solution, so the carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive can simultaneously play the roles of the adhesive and the dispersant, thereby obtaining the aqueous anode slurry which can be compared with an oily system, and the coating effect is good and is easy to realize.
In addition, the polyacrylate adhesive has the advantages of small swelling and excellent cycle performance.
Preferably, the conductive agent in step (1) comprises any one of single-walled carbon nanotubes, multi-walled carbon nanotubes, acetylene black or furnace black.
Preferably, the one-time mixing in the step (1) includes one-time stirring and one-time revolution.
Preferably, the time of the one-time stirring is 30-60 min, for example, 30min, 35min, 40min, 45min, 50min, 55min, 60min, and for brevity, the numerical values in the above range are not listed.
Preferably, the revolution rate is 30-40 rpm, such as 30rpm, 32rpm, 35rpm, 38rpm, 40rpm, and for brevity, the above ranges are not enumerated.
Preferably, the rate of the primary dispersion in step (1) is 1000 to 3000rpm, for example 1000rpm, 1200rpm, 1500rpm, 1800rpm, 2000rpm, 2200rpm, 2500rpm, 2800rpm, 3000rpm, and for brevity of the description, the values in the above ranges are not enumerated.
In the invention, the rate of primary mixing and primary dispersing in the step (1) is adjusted to fully dissolve the aqueous adhesive and the conductive agent to obtain uniform conductive glue solution.
Preferably, the secondary mixing in step (2) includes secondary stirring and secondary revolution.
Preferably, the time of the second stirring is 10-20 min, for example, 10min, 15min, 20min, and the values in the above range are not listed for brevity.
Preferably, the second revolution is at a rate of 30-40 rpm, such as 30rpm, 32rpm, 35rpm, 38rpm, 40rpm, and for brevity, the above ranges are not enumerated.
Preferably, the rate of the secondary dispersion in step (2) is 500-1000 rpm, such as 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, and for brevity, the above ranges are not listed.
In the invention, the conductive glue solution and the main material are fully mixed by adjusting the rate of secondary mixing and secondary dispersion in the step (2), so as to obtain the uniformly dispersed slurry.
Preferably, the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is (65-75%): 25-35%), and may be, for example, 65%:35%, 68%:32%, 70%:30%, 72%:28%, 75%:25%, and for brevity, the numerical values in the above range are not listed.
Preferably, the three times of mixing in the step (2) includes three times of stirring and three times of revolution.
Preferably, the time of the three times of stirring is 90 to 140min, for example, 90min, 100min, 110min, 120min, 130min, 140min, and the values in the above range are not listed for brevity.
Preferably, the speed of the three revolutions is 30-40 rpm, for example, 30rpm, 32rpm, 35rpm, 38rpm, 40rpm, and for brevity, the values in the above range are not listed.
Preferably, the rate of the tertiary dispersion in step (2) is 1000 to 3000rpm, for example 1000rpm, 1200rpm, 1500rpm, 1800rpm, 2000rpm, 2200rpm, 2500rpm, 2800rpm, 3000rpm, and for brevity, no more than one of the values in the above ranges is enumerated.
Preferably, the temperature in the step (2) is reduced to 20-30 ℃.
Preferably, the temperature reduction in step (2) is performed under stirring.
Preferably, the four mixing events in step (2) comprise four revolutions.
Preferably, the four revolutions are at a rate of 20 to 30rpm, such as 20rpm, 22rpm, 25rpm, 28rpm, 30rpm, and the values in the above ranges are not listed for brevity.
Preferably, the rate of the quartic dispersion in step (2) is 500 to 1000rpm, for example 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, and for brevity of disclosure, no numerical values in the above ranges are enumerated.
Preferably, the solid content of the slurry in the step (2) is 50% to 70%, preferably 55% to 65%, for example, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 70%, and for brevity, the numerical values in the above ranges are not listed.
In the invention, the viscosity of the slurry meets the coating requirement by regulating and controlling the solid content of the slurry in the step (2), so that the coating is conveniently and smoothly carried out.
Preferably, the viscosity of the slurry in step (2) is 5000 to 20000 mPas, preferably 5000 to 15000 mPas, for example 5000 to 8000 mPas, 10000 to 12000, 15000 to 20000 mPas, and the values in the above range are not listed for brevity.
In the invention, the viscosity of the slurry in the step (2) is regulated and controlled, so that the viscosity of the slurry is suitable for a coating window of a coating machine, and the coating is smoothly carried out.
Preferably, the step (3) of drying in a segmented manner specifically comprises drying at 60-80 ℃, drying at 65-85 ℃ and then drying at 60-80 ℃.
Preferably, the areal density of the coating in step (3) is from 120 to 140g/m 2 It may be, for example, 120g/m 2 、125g/m 2 、130g/m 2 、135g/m 2 、140g/m 2 For brevity, the above-described ranges are not intended to be exhaustive.
In the invention, the C.B. value of the battery meets the use requirement by controlling the surface density coated in the step (3).
Preferably, the mass ratio of the positive electrode active material, the conductive agent and the aqueous binder in the aqueous positive electrode sheet is (95-99%): 1-3%), and may be, for example, 95%:2%:3%, 96%:2%:2%, 97%:1%:2%, 98%:1%:1% and 1%, and the numerical values in the above ranges are not listed for brevity.
In the present invention, the positive electrode active material includes, but is not limited to, any one of lithium iron phosphate, lithium cobaltate, lithium manganate, or lithium nickel cobalt manganate.
According to the invention, the content of the water-based adhesive is controlled, so that the pole piece has both adhesive force and flexibility, and thus better rate performance and cycle performance are achieved, and the pole piece has poor adhesive property and poor cycle performance if the content is too low, otherwise, the internal resistance is increased, and the rate performance is poor.
In a second aspect, the present invention provides an aqueous positive electrode sheet prepared by the method according to the first aspect.
In a third aspect, the invention provides a lithium ion battery, which comprises a positive plate, a negative plate, electrolyte and a diaphragm, wherein the positive plate comprises the aqueous positive plate according to the second aspect.
The active material layer and the current collector in the prepared water-based positive plate have good adhesive force, are not easy to fall off, and further the cycle life of the lithium ion battery is prolonged.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a method for preparing a water-based positive plate, which comprises the steps of firstly mixing a water-based adhesive, a conductive agent and deionized water to prepare a glue solution, then adding a positive active substance to carry out multiple dispersion to prepare a uniformly dispersed slurry, and avoiding the phenomena of sedimentation and floating powder. In addition, the slurry is dried by adopting a sectional drying method, so that the active material layer and the current collector have a good bonding effect, and the problems of structural collapse and the like of the active material layer are prevented.
In the present invention, a carboxymethyl cellulose grafted sodium polyacrylate copolymer and/or a polyacrylate aqueous binder are preferably used, and these binders and dispersants can simultaneously function as a binder, so that an aqueous positive electrode slurry comparable to an oily system can be obtained, and the coating effect is good and easy to implement.
Drawings
Fig. 1 is a performance comparison diagram of lithium ion batteries provided in application example 1 and comparative application example 1 under different multiplying power;
fig. 2 is a graph comparing the cycle performance at 25 ℃ of the lithium ion batteries provided in application example 1 and comparative application example 1.
Detailed Description
The technical solution of the present invention is further explained by combining the drawings and the detailed description. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a water-based positive plate and a preparation method thereof, wherein the mass ratio of a lithium iron phosphate positive active material, a single-wall carbon nanotube conductive agent and a carboxymethyl cellulose grafted sodium polyacrylate copolymer water-based adhesive (purchased from Xianqiyue bioscience, co., ltd.) in the water-based positive plate is 97% to 1.5%, and the method comprises the following steps:
(1) Mixing a carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive, a single-walled carbon nanotube conductive agent and deionized water, and sequentially stirring for 45min once, wherein the speed of revolution for one time is 35rpm, and the speed of dispersion for one time is 2000rpm to obtain a glue solution;
(2) Sequentially carrying out secondary stirring on the glue solution obtained in the step (1) and the lithium iron phosphate positive electrode active material for 15min, wherein the secondary revolution speed is 35rpm, the secondary dispersion speed is 700rpm, then adding deionized water, sequentially carrying out tertiary stirring for 110min, the tertiary revolution speed is 35rpm, the tertiary dispersion speed is 2000rpm, cooling to 25 ℃, and then carrying out four-revolution speed is 25rpm and four-dispersion speed is 700rpm, wherein the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is 70: 30%, so as to obtain slurry with the solid content of 60% and the viscosity of 10000mPa & s;
(3) Coating the slurry obtained in the step (2) on the surface of an aluminum current collector, drying at 70 ℃ for 10min, drying at 75 ℃ for 10min, and drying at 70 ℃ for 10min to obtain the slurry, wherein the surface density is 130g/m 2 The aqueous positive electrode sheet according to (1).
Example 2
The embodiment provides a water-based positive plate and a preparation method thereof, wherein the mass ratio of a lithium iron phosphate positive active material, a single-walled carbon nanotube conductive agent and a carboxymethyl cellulose grafted sodium polyacrylate copolymer water-based adhesive (purchased from seian qi bioscience limited) in the water-based positive plate is 97% to 1.5%, and the method comprises the following steps:
(1) Mixing a carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive, a single-walled carbon nanotube conductive agent and deionized water, and sequentially stirring for 35min once, wherein the speed of revolution for one time is 32rpm, and the speed of dispersion for one time is 1500rpm to obtain a glue solution;
(2) Sequentially carrying out secondary stirring on the glue solution obtained in the step (1) and the lithium iron phosphate positive electrode active material for 12min, wherein the secondary revolution speed is 32rpm, the secondary dispersion speed is 600rpm, then adding deionized water, sequentially carrying out tertiary stirring for 100min, the tertiary revolution speed is 32rpm, the tertiary dispersion speed is 1500rpm, and after cooling to 25 ℃, carrying out four-revolution speed is 22rpm and four-dispersion speed is 600rpm, wherein the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is 70: 30%, so as to obtain slurry with the solid content of 55% and the viscosity of 8000mPa & s;
(3) Coating the slurry obtained in the step (2) on the surface of an aluminum current collector, drying at 70 ℃ for 10min, drying at 75 ℃ for 10min, and drying at 70 ℃ for 10min to obtain the slurry, wherein the surface density is 130g/m 2 The aqueous positive electrode sheet according to (1).
Example 3
The embodiment provides a water-based positive plate and a preparation method thereof, wherein the mass ratio of a lithium iron phosphate positive active material, a single-walled carbon nanotube conductive agent and a carboxymethyl cellulose grafted sodium polyacrylate copolymer water-based adhesive (purchased from seian qi bioscience limited) in the water-based positive plate is 97% to 1.5%, and the method comprises the following steps:
(1) Mixing a carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive, a single-walled carbon nanotube conductive agent and deionized water, and sequentially stirring for 55min once, wherein the speed of revolution once is 38rpm, and the speed of dispersion once is 2500rpm to obtain a glue solution;
(2) Sequentially carrying out secondary stirring on the glue solution obtained in the step (1) and the lithium iron phosphate positive electrode active material for 18min, wherein the secondary revolution speed is 38rpm, the secondary dispersion speed is 800rpm, then adding deionized water, sequentially carrying out tertiary stirring for 120min, the tertiary revolution speed is 38rpm, the tertiary dispersion speed is 2500rpm, cooling to 25 ℃, then carrying out four-revolution speed is 28rpm, and the four-dispersion speed is 800rpm, wherein the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is 70%:30%, and thus obtaining slurry with the solid content of 65% and the viscosity of 15000 mPas;
(3) Coating the slurry obtained in the step (2) on the surface of an aluminum current collector, drying at 70 ℃ for 10min, drying at 75 ℃ for 10min, drying at 70 ℃ for 10min, and drying the slurry at 70 ℃ for 10min to obtain the surface density of 130g/m 2 The aqueous positive electrode sheet according to (1).
Example 4
The embodiment provides a water-based positive plate and a preparation method thereof, wherein the mass ratio of a lithium iron phosphate positive active material, an acetylene black conductive agent and a polyacrylate water-based adhesive in the water-based positive plate is 95% to 2% to 3%, and the method comprises the following steps:
(1) Mixing a polyacrylate water-based adhesive, an acetylene black conductive agent and deionized water, and sequentially stirring for 30min once, wherein the revolution rate is 30rpm and the dispersion rate is 1000rpm to obtain a glue solution;
(2) Sequentially carrying out secondary stirring on the glue solution obtained in the step (1) and the lithium iron phosphate positive active material for 10min, wherein the secondary revolution speed is 30rpm, the secondary dispersion speed is 500rpm, then adding deionized water, sequentially carrying out tertiary stirring for 90min, the tertiary revolution speed is 30rpm, the tertiary dispersion speed is 1000rpm, cooling to 25 ℃, and then carrying out four-revolution speed is 20rpm and four-dispersion speed is 500rpm, wherein the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is 65: 35%, so as to obtain slurry with the solid content of 50% and the viscosity of 5000mPa & s;
(3) Coating the slurry obtained in the step (2) on the surface of an aluminum current collector, drying at 60 ℃ for 10min, at 65 ℃ for 10min, and then drying at 60 ℃ for 10min to obtain the slurry with the surface density of 120g/m 2 The aqueous positive electrode sheet according to (1).
Example 5
The embodiment provides a water-based positive plate and a preparation method thereof, wherein the mass ratio of a lithium iron phosphate positive active material, an acetylene black conductive agent and a polyacrylate water-based adhesive in the water-based positive plate is 98% to 1%, and the method comprises the following steps:
(1) Mixing a polyacrylate water-based adhesive, an acetylene black conductive agent and deionized water, and sequentially stirring for 60min for one time at a revolution speed of 40rpm and a dispersion speed of 3000rpm to obtain a glue solution;
(2) Sequentially carrying out secondary stirring on the glue solution obtained in the step (1) and the lithium iron phosphate positive electrode active material for 20min, wherein the secondary revolution speed is 40rpm, the secondary dispersion speed is 1000rpm, then adding deionized water, sequentially carrying out tertiary stirring for 140min, the tertiary revolution speed is 40rpm, the tertiary dispersion speed is 3000rpm, and after cooling to 25 ℃, carrying out four-revolution speed is 30rpm and four-dispersion speed is 1000rpm, wherein the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is 75: 25%, so as to obtain slurry with the solid content of 70% and the viscosity of 20000mPa s;
(3) Coating the slurry obtained in the step (2) on the surface of an aluminum current collector, drying at 80 ℃ for 10min, at 85 ℃ for 10min, and drying at 80 ℃ for 10min to obtain the slurry, wherein the surface density is 140g/m 2 The aqueous positive electrode sheet according to (1).
Example 6
This example is different from example 1 in that the aqueous binder in step (1) is polyacrylate, and the rest is the same as example 1.
Example 7
This example is different from example 1 in that the aqueous binder in step (1) is a combination of a carboxymethyl cellulose grafted sodium polyacrylate copolymer and polyacrylate in a mass ratio of 0.7% to 0.8%, and the rest is the same as example 1.
Example 8
This example is different from example 1 in that the aqueous adhesive in step (1) is sodium polyacrylate, and the rest is the same as example 1.
Example 9
This example is different from example 1 in that the aqueous binder in step (1) is carboxymethyl cellulose, and the rest is the same as example 1.
Example 10
The difference between the present example and example 1 is that the mass ratio of the lithium iron phosphate positive electrode active material, the single-wall carbon nanotube conductive agent and the carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous binder in the aqueous positive electrode sheet is 97% to 2.5% to 0.5%, and the rest is the same as example 1.
Example 11
The difference between the present example and example 1 is that the mass ratio of the lithium iron phosphate positive electrode active material, the single-walled carbon nanotube conductive agent and the carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous binder in the aqueous positive electrode sheet is 92.5%:1.5%:6%, and the rest is the same as example 1.
Example 12
This example is different from example 1 in that the solid content of the slurry in step (2) is 40%, and the rest is the same as example 1.
Example 13
This example is different from example 1 in that the solid content of the slurry in step (2) is 80%, and the rest is the same as example 1.
Comparative example 1
The comparative example provides an oily positive plate, and the preparation method comprises the following steps:
firstly, mixing PVDF and NMP according to a certain proportion to prepare a glue solution, firstly stirring for 20min, revolving at 25rpm, dispersing at 2000rpm, and then scraping a cylinder; then stirring for 20min, revolving at 25rpm, dispersing at 2000rpm, and scraping the cylinder; stirring for 45min, revolving at 35rpm, dispersing at 2000rpm, and scraping cylinder; stirring for 200min, revolving at 35rpm, dispersing at 2000rpm, and maintaining the vacuum degree at-0.090 Mpa; then cooling, adjusting revolution at 25rpm, dispersion at 800rpm, and vacuum degree at-0.090 Mpa; stirring the prepared glue solution at a low speed for later use;
secondly, mixing the carbon nano tube, the conductive carbon black, the prepared glue solution and NMP according to a certain proportion, stirring for 60min, revolving at 35rpm and dispersing at 2000rpm; then adding the positive electrode main material, stirring for 15min, revolving at 35rpm, dispersing at 800rpm, and scraping the cylinder; adding a certain amount of NMP, stirring for 120min, revolving at 35rpm, dispersing at 2000rpm, and maintaining the vacuum degree at-0.090 Mpa; then cooling, adjusting revolution at 25rpm, dispersion at 800rpm, and vacuum degree at-0.090 Mpa; stirring the prepared slurry at a low speed for later use;
finally, coating the prepared slurry on a carbon-coated aluminum foil, and then drying by using an air-blast drying oven; drying at 110 deg.C for 10min, at 120 deg.C for 10min, at 110 deg.C for 10min, and completely evaporating solvent NMP to obtain an oily positive plate.
Comparative example 2
The comparative example provides a preparation method of a water-based positive plate, which comprises the following steps:
stirring lithium iron phosphate, a single-walled carbon nanotube, a carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive and deionized water, uniformly dispersing to obtain slurry, sequentially drying at 70 ℃ for 10min, at 75 ℃ for 10min, and then drying at 70 ℃ for 10min to obtain the slurry, and thus obtaining the aqueous positive plate.
Comparative example 3
This comparative example is different from example 1 in that the aqueous positive electrode sheet was obtained by drying at 75 ℃ for 8 hours in step (3) as it is, and the others were the same as example 1.
Application example 1 to application example 13 and comparative application example 1 to comparative application example 3
The lithium ion batteries are prepared by the aqueous positive electrode sheets provided in examples 1 to 13 and comparative examples 1 to 3, and the preparation method comprises the following steps:
preparing a positive plate: as described above;
preparing a negative plate: mixing graphite, sodium carboxymethylcellulose and styrene butadiene rubber according to a ratio of 96% to 2% to prepare negative electrode slurry, and performing stepped drying through a transfer coater to obtain a negative electrode sheet;
preparing a lithium ion battery: the coated positive plate and the coated negative plate are cold-pressed to a specific thickness, then the plates are cut and stamped to a specific size, then the plates are baked, then the diaphragms with fixed sizes (widths) are laminated, the positive and negative minimum plates are isolated, a wound electric core body is obtained, a bare electric core body is obtained through welding, gluing and assembling, then electrolyte is injected, formation, secondary packaging and capacity grading are carried out, and an open-circuit voltage 1 and an open-circuit voltage 2 are tested, so that the lithium ion battery is obtained.
Test conditions
The lithium ion batteries provided in application examples 1 to 13 and comparative application examples 1 to 3 were subjected to performance tests, the test methods were as follows:
and (3) rate performance test: using a charging and discharging device and a constant humidity and heat test box;
the testing steps are as follows: standing at 25 + -2 deg.C for 10min; the battery is cycled for 13 weeks; charging with 0.5C (A) current at constant current and constant voltage until the battery voltage reaches 3.65V, stopping current at 0.05C, and standing for 10min; respectively changing the discharge current to 0.1C, 0.2C, 0.5C, 1C, 2C and 3C (A), repeating the steps, and carrying out the multiple continuous discharge test; and recording the discharge capacity and the temperature rise of the battery cell during discharge of each multiplying power.
And (3) testing the cycle performance: using a charge and discharge device and a voltage internal resistance instrument;
the testing steps are as follows: standing at 25 + -2 deg.C for 10min; setting current 01C (A), standing for 5min, and performing cycle test with cycle number of 3000; if the discharge capacity is less than 80% of the rated capacity, the test is terminated.
The test results are shown in table 1:
TABLE 1
As shown in fig. 1-2, the active material layer and the current collector in the aqueous positive electrode sheet prepared according to the present invention have good adhesion, and are not easily detached, so that the rate capability and cycle life of the lithium ion battery are improved.
Application examples 6 to 7 are types of alternative adhesives, and the lithium ion batteries provided in application examples 6 to 7 are inferior to the batteries provided in application example 1 in overall performance compared to application example 1, because the carboxymethyl cellulose grafted sodium polyacrylate copolymer aqueous adhesive can function as both an adhesive and a dispersant, and thus an aqueous positive electrode slurry comparable to an oily system can be obtained, and the coating effect is good and easy to implement. In addition, the effect of the combination of the two binders in application example 7 is not as good as that of the carboxymethyl cellulose grafted sodium polyacrylate copolymer provided in application example 1, because the solubility of the glue solution prepared in application example 7 is not as good as that of application example 1 under the condition that the glue making process condition is not changed, the stability of the pulp is not as good as that of application example 1, and the effect is not as good as that of application example 1; application examples 8-9 are aqueous adhesives in the prior art, and the obtained lithium ion battery has poor performance; the application examples 10 to 11 are the cases where the content of the binder exceeds the range, and the application examples 12 to 13 are the cases where the solid content of the slurry exceeds the range, which shows that the slurry using the binder with a specific content and the solid content has superior performance.
The comparative application example 1 is an oily positive plate; comparative application example 2 was prepared by direct mixing; the comparative application example 3 is one-time drying, and the comprehensive performance of the lithium ion battery obtained by assembling the lithium ion battery is not the same as that of the lithium ion battery provided by the application example 1.
The applicant states that the process of the present invention is illustrated by the above examples, but the present invention is not limited to the above process steps, i.e. it is not meant to imply that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modifications to the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific forms, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A method of making an aqueous positive electrode sheet, comprising the steps of:
(1) Mixing the water-based adhesive, the conductive agent and the deionized water, and sequentially carrying out primary mixing and primary dispersion to obtain a glue solution;
(2) Sequentially carrying out secondary mixing and secondary dispersion on the glue solution and the positive active material obtained in the step (1), then adding deionized water to sequentially carry out tertiary mixing and tertiary dispersion, and carrying out quaternary mixing and quaternary dispersion after cooling to obtain slurry;
(3) And (3) coating the slurry obtained in the step (2) on the surface of a current collector, and drying the slurry by adopting a sectional drying method to obtain the water-based positive plate.
2. The method of claim 1, wherein the aqueous binder in step (1) comprises a carboxymethyl cellulose grafted sodium polyacrylate copolymer and/or polyacrylate;
preferably, the conductive agent in step (1) comprises any one of single-walled carbon nanotubes, multi-walled carbon nanotubes, acetylene black or furnace black.
3. The method according to claim 1 or 2, wherein the one mixing in step (1) comprises one stirring and one revolution;
preferably, the time for the primary stirring is 30-60 min;
preferably, the speed of one revolution is 30-40 rpm;
preferably, the rate of the primary dispersion in step (1) is 1000 to 3000rpm.
4. The method according to any one of claims 1 to 3, wherein the secondary mixing in step (2) comprises secondary stirring and secondary revolution;
preferably, the time of the secondary stirring is 10-20 min;
preferably, the speed of the secondary revolution is 30-40 rpm;
preferably, the rate of the secondary dispersion in the step (2) is 500 to 1000rpm;
preferably, the mass ratio of the deionized water in the step (1) to the deionized water in the step (2) is (65-75%): 25-35%.
5. The method according to any one of claims 1 to 4, wherein the three times of mixing in step (2) comprises three times of stirring and three times of revolution;
preferably, the time for stirring for three times is 90-140 min;
preferably, the speed of the three times of revolution is 30-40 rpm;
preferably, the rate of the tertiary dispersion in step (2) is 1000 to 3000rpm.
6. The method according to any one of claims 1 to 5, wherein the temperature is reduced to 20 ℃ to 30 ℃ in the step (2);
preferably, the temperature reduction in step (2) is performed under stirring.
7. The method of any one of claims 1-6, wherein the four mixes in step (2) comprise four revolutions;
preferably, the rate of the four revolutions is 20-30 rpm;
preferably, the rate of said quartic dispersion in step (2) is 500 to 1000rpm;
preferably, the solid content of the slurry in the step (2) is 50-70%, preferably 55-65%;
preferably, the viscosity of the slurry in step (2) is from 5000 to 20000 mPas, preferably from 5000 to 15000 mPas.
8. The method according to any one of claims 1 to 7, wherein the step (3) of step-wise drying specifically comprises drying at 60 to 80 ℃, drying at 65 to 85 ℃ and then drying at 60 to 80 ℃ in sequence;
preferably, the areal density of the coating in step (3) is 120 to 140g/m 2 ；
Preferably, the mass ratio of the positive electrode active material, the conductive agent and the aqueous binder in the aqueous positive electrode sheet is (95-99%).
9. An aqueous positive electrode sheet, characterized in that it is produced by the method according to any one of claims 1 to 8.
10. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, wherein the positive electrode sheet comprises the aqueous positive electrode sheet according to claim 9.
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| CN103579579A (en) * | 2012-08-06 | 2014-02-12 | 万向电动汽车有限公司 | Lithium ion battery aqueous anode slurry and preparation method thereof |
| CN105504169A (en) * | 2016-01-07 | 2016-04-20 | 上海交通大学 | Adhesive for lithium ion battery |
| CN106207129A (en) * | 2016-08-31 | 2016-12-07 | 中航锂电（洛阳）有限公司 | A kind of preparation method of anode slurry of high-rate |
| KR20220100240A (en) * | 2021-01-08 | 2022-07-15 | 현대자동차주식회사 | Dry binder and Electrode for lithium secondary battery including same and Method for manufacturing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103579579A (en) * | 2012-08-06 | 2014-02-12 | 万向电动汽车有限公司 | Lithium ion battery aqueous anode slurry and preparation method thereof |
| CN105504169A (en) * | 2016-01-07 | 2016-04-20 | 上海交通大学 | Adhesive for lithium ion battery |
| CN106207129A (en) * | 2016-08-31 | 2016-12-07 | 中航锂电（洛阳）有限公司 | A kind of preparation method of anode slurry of high-rate |
| KR20220100240A (en) * | 2021-01-08 | 2022-07-15 | 현대자동차주식회사 | Dry binder and Electrode for lithium secondary battery including same and Method for manufacturing the same |
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