CN117393764A - Positive electrode binder, positive electrode slurry, positive electrode plate and sodium ion battery - Google Patents
Positive electrode binder, positive electrode slurry, positive electrode plate and sodium ion battery Download PDFInfo
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- CN117393764A CN117393764A CN202311458618.8A CN202311458618A CN117393764A CN 117393764 A CN117393764 A CN 117393764A CN 202311458618 A CN202311458618 A CN 202311458618A CN 117393764 A CN117393764 A CN 117393764A
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- positive electrode
- acrylic ester
- polyvinylidene fluoride
- modified acrylic
- binder
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- 239000011883 electrode binding agent Substances 0.000 title claims abstract description 42
- 239000011267 electrode slurry Substances 0.000 title claims abstract description 29
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 title claims abstract description 26
- 229910001415 sodium ion Inorganic materials 0.000 title claims abstract description 26
- 239000002033 PVDF binder Substances 0.000 claims abstract description 59
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims abstract description 59
- -1 modified acrylic ester Chemical class 0.000 claims abstract description 45
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 claims abstract description 20
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 17
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims abstract description 13
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000003999 initiator Substances 0.000 claims abstract description 12
- 239000000178 monomer Substances 0.000 claims abstract description 11
- DXPPIEDUBFUSEZ-UHFFFAOYSA-N 6-methylheptyl prop-2-enoate Chemical compound CC(C)CCCCCOC(=O)C=C DXPPIEDUBFUSEZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 claims abstract description 10
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000004132 cross linking Methods 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 7
- 150000001252 acrylic acid derivatives Chemical class 0.000 claims description 28
- 239000007774 positive electrode material Substances 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 7
- 238000000576 coating method Methods 0.000 claims description 7
- 239000006258 conductive agent Substances 0.000 claims description 7
- OMPJBNCRMGITSC-UHFFFAOYSA-N Benzoylperoxide Chemical group C=1C=CC=CC=1C(=O)OOC(=O)C1=CC=CC=C1 OMPJBNCRMGITSC-UHFFFAOYSA-N 0.000 claims description 6
- 235000019400 benzoyl peroxide Nutrition 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 239000006185 dispersion Substances 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 abstract description 18
- 230000001070 adhesive effect Effects 0.000 abstract description 14
- 239000000853 adhesive Substances 0.000 abstract description 12
- 230000008569 process Effects 0.000 abstract description 8
- 239000002002 slurry Substances 0.000 abstract description 5
- 238000012545 processing Methods 0.000 abstract description 4
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 31
- 239000011230 binding agent Substances 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 24
- 238000002360 preparation method Methods 0.000 description 14
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical group CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 12
- 239000003792 electrolyte Substances 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 239000002041 carbon nanotube Substances 0.000 description 9
- 229910021393 carbon nanotube Inorganic materials 0.000 description 9
- 239000003292 glue Substances 0.000 description 9
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 7
- 239000000843 powder Substances 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000013329 compounding Methods 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 230000008961 swelling Effects 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 125000005396 acrylic acid ester group Chemical group 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- 239000002390 adhesive tape Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 241001391944 Commicarpus scandens Species 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012983 electrochemical energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 229920000447 polyanionic polymer Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the technical field of sodium ion batteries and discloses a positive electrode binder, positive electrode slurry, a positive electrode plate and a sodium ion battery, wherein the positive electrode binder contains 50-90 wt% of modified acrylic ester and 10-50 wt% of PVDF; the modified acrylic ester is prepared by crosslinking polymerization reaction of a polymerization monomer and an initiator in an organic solvent, wherein the polymerization monomer contains acrylic acid, methyl methacrylate, butyl acrylate, isooctyl acrylate, styrene and isoprene. According to the invention, the modified acrylic ester and PVDF are compounded, and the modified acrylic ester and PVDF are synergistic, so that the adhesive property of the adhesive is ensured; by adding the modified acrylic ester, the problem of poor flexibility of polyvinylidene fluoride is solved, and the problems of brittleness, easy breakage and the like of the pole piece in the processing process are avoided; in addition, the modified acrylic ester is used for replacing part of polyvinylidene fluoride, so that the dosage of polyvinylidene fluoride in the pole piece adhesive is reduced, the introduction of F element in the slurry is reduced, and the performance of the battery is improved.
Description
Technical Field
The invention relates to the technical field of sodium ion batteries, in particular to a positive electrode binder, positive electrode slurry and a sodium ion battery.
Background
Currently, electrochemical energy storage technology is an important link in developing new energy sources for environmental protection. The lithium ion battery has the advantages of good cycle performance, high energy density and the like, and is widely applied to the fields of electric automobiles, energy storage and the like. However, the development difficulty is great due to shortage of raw material resources of lithium batteries, resulting in higher and higher cost. Sodium ion batteries are next-generation low-cost and high-performance energy storage batteries, and compared with lithium ion batteries, sodium ion batteries have abundant resources as raw materials, and particularly in China, sodium reserves are more abundant than lithium resources.
Sodium and lithium belong to the same main group, have similar physical and chemical properties as lithium, and the reaction mechanism of a sodium ion battery and a lithium ion battery is similar, so that the sodium ion battery has good application prospect. Sodium ion batteries have many advantages. Compared with a lithium ion battery, the sodium ion battery has higher safety, lower cost, strong environmental adaptability, good low-temperature performance and good quick-charging performance.
The most commonly used positive electrode binder for sodium ion batteries today is polyvinylidene fluoride (PVDF). The PVDF has good adhesive property, thermal stability and electrochemical stability, and is easy to process and suitable for battery production. However, PVDF is relatively harsh in preparation conditions, resulting in relatively high prices; meanwhile, F element contained in the PVDF molecular structure possibly reacts with metal ions, so that metal impurities enter a battery system to influence a battery; in addition, PVDF has low elastic modulus and poor flexibility, so that the manufactured positive electrode plate is easy to break in the processing process.
Disclosure of Invention
The invention aims to solve the problems that PVDF used as a binder in the prior art is high in price, F element in PVDF is easy to affect a battery, and PVDF is low in elastic modulus and poor in flexibility, and provides a positive electrode binder, positive electrode slurry and a sodium ion battery.
In order to achieve the above object, according to one aspect of the present invention, there is provided a positive electrode binder comprising 50 to 90wt% of modified acrylate and 10 to 50wt% of polyvinylidene fluoride, based on the total weight of the positive electrode binder;
the modified acrylic ester is prepared by performing cross-linking polymerization reaction on a polymerization monomer and an initiator in an organic solvent, wherein the polymerization monomer contains acrylic acid, methyl methacrylate, butyl acrylate, isooctyl acrylate, styrene and isoprene.
Preferably, the content of the modified acrylic ester is 70 to 90wt% and the content of the polyvinylidene fluoride is 10 to 30wt% based on the total weight of the positive electrode binder.
Preferably, the weight ratio of the dosages of the acrylic acid, the methyl methacrylate, the butyl acrylate, the isooctyl acrylate, the styrene and the isoprene is 10: 6-20: 5-15: 5-15: 5-10: 5 to 10.
Preferably, the initiator is dibenzoyl peroxide.
Preferably, the weight ratio of the amount of the acrylic acid to the amount of the initiator is 10: 0.002-0.5.
Preferably, the viscosity of the modified acrylate is 500 to 4000mpa·s.
Preferably, the intrinsic viscosity of the polyvinylidene fluoride is 2 to 4dl/g.
Preferably, the polyvinylidene fluoride has a density of 1.6 to 1.8g/cc.
The second aspect of the present invention provides a positive electrode slurry containing the positive electrode binder as described above.
Preferably, the positive electrode slurry further contains a positive electrode active material, a conductive agent, and a dispersion solvent.
Preferably, the solid content of the positive electrode slurry is 30-80%, and the viscosity is 1000-7000 mPas.
Preferably, the content of the positive electrode binder is 1 to 5wt% based on the total weight of the positive electrode slurry.
The third aspect of the present invention provides a positive electrode sheet obtained by coating the positive electrode slurry described above onto a positive electrode current collector.
A fourth aspect of the invention provides a sodium ion battery comprising a positive electrode sheet as described above.
According to the technical scheme provided by the invention, the positive electrode binder contains the modified acrylic ester and the polyvinylidene fluoride, and the modified acrylic ester and the polyvinylidene fluoride are compounded to have synergistic effect, so that the binding performance of the binder is ensured, and the most basic capacity performance, short circuit problem and the like of the finally prepared battery are improved; meanwhile, the problem of poor flexibility of polyvinylidene fluoride is solved by adding the modified acrylic ester, and the problems of brittle pole piece, easy breakage and the like in the processing process are avoided; in addition, the modified acrylic ester is used for replacing part of polyvinylidene fluoride, so that the dosage of polyvinylidene fluoride in the pole piece adhesive is reduced, the introduction of F element in the slurry is reduced, the electrochemical performance of the battery is improved, and the cost is low.
Drawings
FIG. 1 is a graph showing the results of the flexibility test of the positive electrode sheet obtained in test example 2 by applying example 2;
FIG. 2 is a graph showing the results of the flexibility test of the positive electrode sheet prepared in test example 2 using comparative example 1;
FIG. 3 is a graph showing the results of the flexibility test of the positive electrode sheet prepared in test example 2 using comparative example 2;
FIG. 4 is an external view of the positive electrode sheet after being left on the shelf in test example 3;
FIG. 5 is an external view of the positive electrode sheet after formation in test example 3;
FIG. 6 is an external view of the positive electrode sheet after capacity division in test example 3;
fig. 7 is a graph showing the results of the cycle performance test of the full cell prepared in test example 3 using example 2 and using the positive electrode sheets of comparative examples 1 to 2.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The invention provides a positive electrode binder, which comprises 50-90 wt% of modified acrylic ester and 10-50 wt% of polyvinylidene fluoride based on the total weight of the positive electrode binder;
the modified acrylic ester is prepared by performing cross-linking polymerization reaction on a polymerization monomer and an initiator in an organic solvent, wherein the polymerization monomer contains acrylic acid, methyl methacrylate, butyl acrylate, isooctyl acrylate, styrene and isoprene.
The polymer monomer is selected, so that the prepared modified acrylic ester has strong cohesiveness, can increase the stripping force of the pole piece, reduces the internal resistance of the pole piece, and shows good electrochemical performance on the battery level; meanwhile, the modified acrylic ester has good flexibility. According to the invention, the modified acrylic ester is added on the basis of the traditional PVDF, and the modified acrylic ester act together, so that the bonding performance of the obtained positive electrode binder is ensured, the most basic capacity performance, the short circuit problem and the like of the finally prepared battery are improved, the problems that the pole piece is relatively fragile and easy to break and the like in the processing process are avoided, and the electrochemical performance of the finally prepared battery is improved.
In a preferred embodiment, the content of the modified acrylic ester is 70-90 wt% and the content of the polyvinylidene fluoride is 10-30 wt% based on the total weight of the positive electrode binder, so that the amount of the polyvinylidene fluoride is small, the cost is low, and the comprehensive performance of the binder is better.
The specific amount of each component in the polymerized monomer used for preparing the modified acrylic ester is not limited, and can be adaptively adjusted according to actual needs, and in a preferred embodiment, the weight ratio of the amounts of the acrylic acid, the methyl methacrylate, the butyl acrylate, the isooctyl acrylate, the styrene and the isoprene is 10: 6-20: 5-15: 5-15: 5-10: 5-10, and the prepared adhesive has better adhesion under the proportion.
The specific kind of the initiator used for preparing the modified acrylate is not limited, and may be an initiator commonly used in the art. In a specific embodiment, the initiator is dibenzoyl peroxide.
In a preferred embodiment, the weight ratio of acrylic acid to initiator is 10:0.002 to 0.5, specifically, for example, 10:0.002, 10:0.005, 10:0.01, 10:0.02, 10:0.05, 10:0.006, 10:0.007, 10:0.1, 10:0.2, 10:0.3, 10:0.4 or 10:0.5 may be used.
In order to make the performance of the positive electrode binder better, in a preferred embodiment, the viscosity of the modified acrylate is 500 to 4000mpa·s, specifically, the viscosity of a mixed solution of the modified acrylate and N-methylpyrrolidone (NMP) at 25 ℃ is tested, and the concentration of NMP in the mixed solution is 10wt%.
In a preferred embodiment, the modified acrylate has a viscosity of 500 to 1000 mPas.
The reaction temperature at the time of preparing the modified acrylic acid ester is not limited in the present invention, as long as the crosslinking polymerization reaction between the polymerization monomers can be performed. In a specific embodiment, the reaction temperature is 70 to 90℃and may be, for example, 70℃75℃77℃78℃80℃81℃83℃85℃or 90 ℃.
In a specific embodiment, the organic solvent used to prepare the modified acrylate is ethyl acetate.
The invention is not limited to the specific structure and properties of the polyvinylidene fluoride, and can be polyvinylidene fluoride commonly used in the art. In a specific embodiment, the polyvinylidene fluoride has an intrinsic viscosity of 2 to 4dl/g.
In a preferred embodiment, the polyvinylidene fluoride has a density of 1.6 to 1.8g/cc, more preferably 1.75 to 1.78g/cc.
The invention also provides positive electrode slurry, which contains the positive electrode binder. According to the embodiment, the positive electrode slurry is adopted, so that the slurry has good uniformity and excellent cohesiveness and flexibility after the pole piece is coated, and the electrochemical performance of the whole finally manufactured battery is improved.
In a preferred embodiment, the content of the positive electrode binder is 1 to 5wt% based on the total weight of the positive electrode slurry, and thus the final battery has good adhesion without affecting the electrochemical performance.
The present invention is not limited to the specific components of the positive electrode slurry, and may be components conventional in the art as long as the positive electrode binder described above is contained. In a specific embodiment, the positive electrode slurry further contains a positive electrode active material, a conductive agent, and a dispersion solvent.
In particular embodiments, the positive electrode active material may be a sodium ion layered oxide and/or a sodium ion polyanion oxide. More specifically, the sodium ion layered oxide is layered oxide sodium nickel iron manganate.
In a specific embodiment, the dispersing solvent is NMP.
In a specific embodiment, the conductive agent is a conductive Carbon Nanotube (CNT) and/or a conductive carbon black (SP), preferably a mixture of a conductive carbon nanotube and a conductive carbon black, and by compounding the conductive agent and the conductive carbon nanotube, the electrical property of the positive electrode slurry is better. More preferably, the conductive carbon black is in the form of powder.
In a preferred embodiment, the content of the positive electrode active material is 90 to 97.5wt%, the content of the binder is 1 to 5wt%, the content of the conductive carbon nanotube is 0.5 to 2wt%, and the content of the conductive carbon black is 1 to 3wt%, based on 100% of the total weight of the positive electrode active material, the binder, and the conductive agent.
The present invention is not limited to the amount of the dispersion solvent, and may be designed as needed. In a preferred embodiment, the positive electrode slurry has a solid content of 30 to 80% and a viscosity of 1000 to 7000mpa·s.
The invention also provides a positive electrode plate, which is obtained by coating the positive electrode slurry on a positive electrode current collector.
In the present invention, the positive electrode current collector may be of a type conventional in the art. In a specific embodiment, the current collector is aluminum foil, and the thickness of the current collector is 10-16 μm.
In a preferred embodiment, the positive electrode sheet has a thickness of 100 to 160 μm. That is, the coating thickness of the positive electrode slurry on the positive electrode current collector is 100 to 160 μm.
The invention is not limited to the specific type of the battery applied to the positive electrode plate, and can be applied to sodium ion batteries and lithium ion batteries.
At present, the comprehensive performance of the sodium ion battery is better, and based on the comprehensive performance, the invention also provides the sodium ion battery which comprises the positive electrode plate.
The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto. The reagents used in the following examples and comparative examples are commercially available products unless otherwise specified.
In the following preparation examples, the viscosity test method of the modified acrylic ester is as follows: the modified acrylate was mixed with N-methylpyrrolidone (NMP) in a weight ratio of 1:9, and the resulting mixed solution was tested for viscosity at 25℃using a viscometer.
In the following examples and comparative examples, the parameters of the PVDF used are shown in Table 1 below.
TABLE 1
| Name of the name | Polyvinylidene fluoride |
| Density (g/cc) | 1.75-1.78 |
| Water content (%) (Time 24 hr) | ＜0.20 |
| Intrinsic viscosity (dl/g) | 2.7-3.7 |
| Rotational viscosity (cps) | 490-510 |
| Melting point (. Degree. C.) | 160-168 |
| Melting Point (. Degree. C.) of actual sample | 158-166 |
| Crystallization temperature (DSC penk) (. Degree.C.) | 135 to 140 |
| Glass transition temperature Tg (. Degree. C.) | -40 |
| Heat of fusion (J/g) | 40 to 48 |
| Surface resistance (ohm) | ＞1.0E+14 |
| Volume resistivity (ohm. Cm) | ＞1.0E+14 |
Preparation example 1
10 parts by weight of acrylic acid, 10 parts by weight of methyl methacrylate, 8 parts by weight of butyl acrylate, 8 parts by weight of isooctyl acrylate, 7 parts by weight of styrene, 7 parts by weight of isoprene and 0.05 part by weight of dibenzoyl peroxide are added to 90 parts by weight of ethyl acetate, and a crosslinking polymerization reaction is carried out at 80 ℃ to obtain modified acrylate, wherein the viscosity of the modified acrylate is 560 mPa.s.
Preparation example 2
10 parts by weight of acrylic acid, 12 parts by weight of methyl methacrylate, 10 parts by weight of butyl acrylate, 10 parts by weight of isooctyl acrylate, 9 parts by weight of styrene, 9 parts by weight of isoprene and 0.1 part by weight of dibenzoyl peroxide are added to 125 parts by weight of ethyl acetate, and a crosslinking polymerization reaction is carried out at 85 ℃ to obtain modified acrylate, wherein the viscosity of the modified acrylate is 520 mPa.s.
Preparation example 3
10 parts by weight of acrylic acid, 15 parts by weight of methyl methacrylate, 12 parts by weight of butyl acrylate, 13 parts by weight of isooctyl acrylate, 6 parts by weight of styrene, 6 parts by weight of isoprene and 0.2 part by weight of dibenzoyl peroxide are added to 130 parts by weight of ethyl acetate, and a crosslinking polymerization reaction is carried out at 80 ℃ to obtain modified acrylate, wherein the viscosity of the modified acrylate is 570 mPa.s.
Example 1
This example is for illustrating the positive electrode binder according to the present invention.
The positive electrode binder is a mixture of modified acrylic ester and polyvinylidene fluoride;
wherein, the content of the modified acrylic ester is 90wt percent and the content of the polyvinylidene fluoride is 10wt percent based on the total weight of the positive electrode binder;
the modified acrylic ester is the modified acrylic ester prepared in preparation example 1.
Example 2
The positive electrode binder is a mixture of modified acrylic ester and polyvinylidene fluoride;
wherein, the content of the modified acrylic ester is 80wt percent and the content of the polyvinylidene fluoride is 20wt percent based on the total weight of the positive electrode binder;
the modified acrylic ester is the modified acrylic ester prepared in preparation example 1.
Example 3
The positive electrode binder is a mixture of modified acrylic ester and polyvinylidene fluoride;
wherein the content of the modified acrylic ester is 70wt% and the content of the polyvinylidene fluoride is 30wt% based on the total weight of the positive electrode binder;
the modified acrylic ester is the modified acrylic ester prepared in preparation example 1.
Example 4
The positive electrode binder is a mixture of modified acrylic ester and polyvinylidene fluoride;
wherein, the content of the modified acrylic ester is 60wt percent and the content of the polyvinylidene fluoride is 40wt percent based on the total weight of the positive electrode binder;
the modified acrylic ester is the modified acrylic ester prepared in preparation example 1.
Example 5
The procedure of example 2 was followed, except that the modified acrylate was the modified acrylate prepared in preparation example 2.
Example 6
The procedure of example 2 was followed, except that the modified acrylate was the modified acrylate prepared in preparation example 3.
Comparative example 1
The positive electrode binder was only the modified acrylate prepared in preparation example 1.
Comparative example 2
The positive electrode binder is only polyvinylidene fluoride.
Application example 1
Coating the positive electrode slurry on a positive electrode current collector, and drying to obtain a positive electrode plate;
wherein the positive electrode slurry contains a positive electrode active material, a binder, conductive Carbon Nanotubes (CNT), conductive carbon black (SP), and a dispersion solvent (NMP), the binder being the binder described in example 1;
based on the total weight of the positive electrode active material, the binder, the conductive carbon nano tube and the conductive carbon black, wherein the content of the positive electrode active material is 96.5wt%, the content of the binder is 1.3wt%, the content of the conductive carbon nano tube is 0.6wt%, and the content of the conductive carbon black is 1.6wt%; the solid content of the positive electrode slurry is 56.8%, and the viscosity of the slurry is 4300 mPa.s;
the positive electrode active material is layered oxide sodium nickel iron manganate;
the positive electrode current collector adopts aluminum foil with the thickness of 13 mu m and the coating thickness of the pole piece of 116 mu m.
Application example 2
The procedure described in application example 1 was followed, except that the adhesive described in example 2 was used.
Application example 3
The procedure described in application example 1 was followed, except that the adhesive described in example 3 was used.
Application example 4
The procedure described in application example 1 was followed, except that the adhesive described in example 4 was used.
Application example 5
The procedure described in application example 1 was followed, except that the adhesive described in example 5 was used.
Application example 6
The procedure described in application example 1 was followed, except that the adhesive described in example 6 was used.
Comparative example 1 was used
The procedure was followed as described in application example 1, except that the binder used was only the modified acrylate prepared in preparation example 1.
Comparative example 2 was used
The procedure of application example 1 was followed, except that the binder used was polyvinylidene fluoride alone.
Test example 1
The binders described in examples 1 to 6 and comparative example 1 were glued to NMP in a mass ratio of 1:11.5 to give glues.
(1) The viscosity of the glue was measured using a viscometer using a number 3 rotor with a speed of 12rpm for 90 seconds and the results are shown in table 2 below.
TABLE 2
As can be seen from table 2, the viscosities of the glues prepared in examples 1-6 are all within a suitable range, and can be used for the subsequent preparation of positive electrode slurry.
(2) The glues prepared in examples 1 to 4 and comparative example 1 were coated on a glass slide, and then dried in an oven at 90 ℃ for 4 hours, and the dried glues were taken off with tweezers, weighed with an electronic balance, and recorded. Then the different glue films are subjected to electrolyte soaking (sodium ion electrolyte is adopted, wherein the mass ratio of organic solvents is EC: EMC: PC=15:80:5, and sodium electrolyte salt adopts NaPF) 6 Sodium salt concentration of 1 mol/L), sealing with an aluminum plastic film, recording the change of glue quality from the first day to the tenth day, and sucking free electrolyte on the surface by dust-free paper before weighing each time, thereby calculating the swelling rate of the glue films with different proportions on the electrolyte. Coating film is initially coatedThe initial mass is denoted as m 0 The mass on the first to tenth days is denoted as m respectively dx (x=1, 2,3,.,. 10) the swell ratio calculation formula is:
(m dx -m 0 )/m 0 *100％。
the results of the glue electrolyte swelling ratio experiments are shown in table 3 below.
TABLE 3 Table 3
As can be seen from Table 3, the adhesive (the ratio of the acrylic acid ester to PVDF is 8:2) provided in examples 1-4 has a proper swelling ratio of electrolyte, so that the ionic conductivity of the prepared positive electrode plate can be ensured, and the falling of the active material of the plate is not caused in the later period of battery circulation. The electrolyte swelling ratio of the binder provided in comparative example 1 is too high, which may reduce the binding strength of the binder, thereby causing the active material, the conductive agent, etc. to fall off from the surface of the current collector, further causing damage to the positive electrode sheet, and affecting the cycle stability of the battery.
Test example 2
The positive electrode sheet prepared in the application example and the application comparative example was subjected to peel force, resistance and flexibility test.
(1) Positive pole piece stripping force test
Cutting a pole piece to be tested into a strip-shaped pole piece, sticking the pole piece on a stainless steel plate by using double-sided adhesive tape, ensuring that no bubble exists between adhesive tape and the steel plate in the process of sticking paper, flatly sticking the pole piece with powder on the stainless steel plate, rolling the pole piece back and forth for 3 times by using a double-sided adhesive tape cylinder, placing a prepared sample on a test frame of a peeling tester for testing, clamping the stainless steel plate at one end of the tester, clamping the pole piece at the other end of the tester, testing at a speed of 50mm/min, testing a load of 50N for 90-degree peeling force test, separating the powder from a current collector, measuring the maximum peeling force and the minimum peeling force in a test stroke, and calculating the average peeling force. The test results are shown in table 4 below.
TABLE 4 Table 4
| Project | Average peel force/N |
| Application example 1 | 2.9081 |
| Application example 2 | 2.7396 |
| Application example 3 | 2.6661 |
| Application example 4 | 2.6277 |
| Application example 5 | 2.7031 |
| Application example 6 | 2.6958 |
| Comparative example 1 was used | 3.0546 |
| Comparative example 2 was used | 2.3201 |
As can be seen from table 4, the average stripping force of the positive electrode plate prepared by applying examples 1-6 is superior to that of the positive electrode plate prepared by applying comparative example 2, the binder used by applying examples 1-6 is a compound of modified acrylic ester and PVDF, and the binder used by applying comparative example 2 is only PVDF, which shows that the stripping force of the positive electrode plate can be obviously enhanced by adding the modified acrylic ester, the bonding strength of the positive electrode plate in the subsequent manufacturing and battery testing processes is ensured, and the full battery performance is facilitated to be improved.
(2) Positive pole piece resistance test
The rolled positive electrode plate is striped according to the width of the positive electrode of the 18650 cylindrical battery, is placed on a clamping plate for measuring the resistance of the electrode plate, is tested by an internal resistance meter, and has the length of 10cm and the width of 5.75cm, and the test results are shown in the following table 5.
TABLE 5
As can be seen from table 5, the internal resistance of the positive electrode sheets prepared by applying examples 1 to 6 of the present invention is lower than that of the positive electrode sheet prepared by applying comparative example 2, which indicates that the internal resistance of the positive electrode sheet can be reduced by adding the modified acrylic acid ester.
Meanwhile, as can be seen from application examples 1-6, the positive electrode plate prepared by application example 2 (the ratio of the modified acrylic ester to the PVDF is 8:2) has the lowest resistance, and is beneficial to the capacity and other performances of the finally prepared full battery.
(3) Positive pole piece flexibility test
The positive electrode sheets prepared in application example 2 and application comparative examples 1-2 were rolled and subjected to a flexibility test, the sheet was folded in half perpendicular to the winding direction and then folded in reverse along the same fold, the sheet was unfolded, and the fold positions were observed by light, and the results are shown in fig. 1-3.
As can be seen from fig. 1, the crease of the positive electrode sheet prepared in application example 2 has no light transmission, and the surface of the sheet has no powder falling and foil exposing, which indicates that the positive electrode sheet prepared from the adhesive obtained by compounding the modified acrylic ester and the PVDF has good flexibility.
As can be seen from fig. 2, the positive electrode sheet prepared by comparative example 1 (the binder is only modified acrylate) did not show light transmission at the folds of the sheet, but had slight powder drop at the folds of the sheet.
As can be seen from fig. 3, the positive electrode sheet prepared in comparative example 2 (the binder is PVDF only) was partially transparent at the crease, and a current collector was observed, indicating poor sheet toughness.
Test example 3
(1) The positive electrode plate prepared in application example 2 and conventional materials (negative electrode plate, positive and negative electrode lugs, diaphragm, steel shell, cap, electrolyte and the like) are prepared into a sodium ion cylindrical battery according to a conventional method in the field; placing the battery after the liquid injection is completed at a low temperature (45 ℃) and a high temperature (45 ℃), and then performing formation and capacity division; and (4) respectively carrying out battery disassembly after the storage, the formation and the capacity division, observing the condition of the positive pole piece, and judging whether the slurry layer falls off from the current collector, wherein the result is shown in figures 4-6.
As can be seen from fig. 4 to 6, the positive electrode sheet prepared in application example 2 has no powder falling after being placed and formed and separated, which indicates that the adhesive provided by the invention has good adhesion, and can ensure that the active material does not fall off during the battery test process, thereby ensuring the capacity performance and the cycle performance of the battery.
(2) The positive electrode plate and the negative electrode plate (hard carbon), the positive electrode lug, the diaphragm (ceramic diaphragm with the diameter of 12+2 μm), the steel shell, the cap and the electrolyte (sodium ion electrolyte is adopted, wherein the mass ratio of organic solvents is EC: PC=15:80:5, and sodium electrolyte adopts NaPF) are prepared in application example 2 6 Sodium salt concentration 1 mol/L) was prepared into a sodium ion cylindrical battery according to a conventional method in the art, and then the positive electrode sheet prepared by using comparative examples 1-2 was prepared into a cylindrical battery according to the same method; and (3) placing the battery after the liquid injection is completed at a low temperature (45 ℃) and then performing formation and capacity division.
The test shows that the design capacity of the prepared cylindrical battery is 1.1Ah, and the battery capacity of application example 2, in which the binder is compounded by using the modified acrylate and PVDF, is 1.025Ah. Application comparative example 1, in which only the modified acrylate was used as the binder, exhibited a battery capacity of 0.997Ah, and application comparative example 2, in which only PVDF was used as the binder, exhibited a battery capacity of 0.983Ah.
Meanwhile, one battery after capacity division is selected for normal temperature 1C1C cycle test, cycle data of the battery after 500 weeks are calculated, and FIG. 7 is drawn according to test results.
As can be seen from the cycle data, the battery prepared by compounding the modified acrylate and PVDF as the binder (i.e., application example 2) is excellent in cycle effect, and has a capacity retention of 95.75% after 500 cycles, which is superior to the battery prepared by using only the modified acrylate as the binder and only PVDF as the binder, indicating that the cycle performance of the finally prepared battery can be improved by compounding the modified acrylate and PVDF as the binder.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (10)
1. The positive electrode binder is characterized by comprising 50-90 wt% of modified acrylic ester and 10-50 wt% of polyvinylidene fluoride based on the total weight of the positive electrode binder;
the modified acrylic ester is prepared by performing cross-linking polymerization reaction on a polymerization monomer and an initiator in an organic solvent, wherein the polymerization monomer contains acrylic acid, methyl methacrylate, butyl acrylate, isooctyl acrylate, styrene and isoprene.
2. The positive electrode binder according to claim 1, wherein the content of the modified acrylate is 70 to 90wt% and the content of the polyvinylidene fluoride is 10 to 30wt%, based on the total weight of the positive electrode binder.
3. The positive electrode binder according to claim 1, wherein the amounts of acrylic acid, methyl methacrylate, butyl acrylate, isooctyl acrylate, styrene and isoprene are 10% by weight: 6-20: 5-15: 5-15: 5-10: 5 to 10.
4. A positive electrode binder according to claim 1 or 3, wherein the initiator is dibenzoyl peroxide;
preferably, the weight ratio of the amount of the acrylic acid to the amount of the initiator is 10: 0.002-0.5.
5. The positive electrode binder according to claim 1, wherein the modified acrylate has a viscosity of 500 to 4000 mPa-s.
6. The positive electrode binder according to claim 1, wherein the intrinsic viscosity of polyvinylidene fluoride is 2 to 4dl/g;
preferably, the polyvinylidene fluoride has a density of 1.6 to 1.8g/cc.
7. A positive electrode slurry, characterized in that the positive electrode slurry contains the positive electrode binder according to any one of claims 1 to 6.
8. The positive electrode slurry according to claim 7, further comprising a positive electrode active material, a conductive agent, and a dispersion solvent;
preferably, the solid content of the positive electrode slurry is 30-80%, and the viscosity is 1000-7000 mPa.s;
preferably, the content of the positive electrode binder is 1 to 5wt% based on the total weight of the positive electrode slurry.
9. A positive electrode sheet, characterized in that the positive electrode sheet is obtained by coating the positive electrode slurry according to claim 7 or 8 onto a positive electrode current collector.
10. A sodium ion battery comprising the positive electrode sheet of claim 9.
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| CN202311458618.8A CN117393764A (en) | 2023-11-02 | 2023-11-02 | Positive electrode binder, positive electrode slurry, positive electrode plate and sodium ion battery |
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| CN202311458618.8A CN117393764A (en) | 2023-11-02 | 2023-11-02 | Positive electrode binder, positive electrode slurry, positive electrode plate and sodium ion battery |
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