CN117247751A - Natural polymer modified binder and preparation method and application thereof - Google Patents
Natural polymer modified binder and preparation method and application thereof Download PDFInfo
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- CN117247751A CN117247751A CN202311132859.3A CN202311132859A CN117247751A CN 117247751 A CN117247751 A CN 117247751A CN 202311132859 A CN202311132859 A CN 202311132859A CN 117247751 A CN117247751 A CN 117247751A
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- natural polymer
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- 239000011230 binding agent Substances 0.000 title claims abstract description 74
- 229920005615 natural polymer Polymers 0.000 title claims abstract description 35
- 238000002360 preparation method Methods 0.000 title claims abstract description 31
- 230000001070 adhesive effect Effects 0.000 claims abstract description 28
- 239000000853 adhesive Substances 0.000 claims abstract description 24
- 238000003756 stirring Methods 0.000 claims abstract description 24
- 229920001046 Nanocellulose Polymers 0.000 claims abstract description 23
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims abstract description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000008367 deionised water Substances 0.000 claims abstract description 17
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 17
- 229910001424 calcium ion Inorganic materials 0.000 claims abstract description 15
- 239000003999 initiator Substances 0.000 claims abstract description 14
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 13
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000004132 cross linking Methods 0.000 claims abstract description 11
- ZIUHHBKFKCYYJD-UHFFFAOYSA-N n,n'-methylenebisacrylamide Chemical compound C=CC(=O)NCNC(=O)C=C ZIUHHBKFKCYYJD-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000010526 radical polymerization reaction Methods 0.000 claims abstract description 10
- 239000012299 nitrogen atmosphere Substances 0.000 claims abstract description 9
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical group [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- OZAIFHULBGXAKX-UHFFFAOYSA-N 2-(2-cyanopropan-2-yldiazenyl)-2-methylpropanenitrile Chemical compound N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 claims description 8
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 8
- 239000002002 slurry Substances 0.000 claims description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 6
- 239000013543 active substance Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 238000001291 vacuum drying Methods 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000011149 active material Substances 0.000 claims description 4
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims description 4
- 239000011889 copper foil Substances 0.000 claims description 4
- 239000002931 mesocarbon microbead Substances 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- ZKQDCIXGCQPQNV-UHFFFAOYSA-N Calcium hypochlorite Chemical compound [Ca+2].Cl[O-].Cl[O-] ZKQDCIXGCQPQNV-UHFFFAOYSA-N 0.000 claims description 2
- YYRMJZQKEFZXMX-UHFFFAOYSA-L calcium bis(dihydrogenphosphate) Chemical compound [Ca+2].OP(O)([O-])=O.OP(O)([O-])=O YYRMJZQKEFZXMX-UHFFFAOYSA-L 0.000 claims description 2
- 239000001110 calcium chloride Substances 0.000 claims description 2
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 2
- 229940062672 calcium dihydrogen phosphate Drugs 0.000 claims description 2
- 229910000389 calcium phosphate Inorganic materials 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 235000019691 monocalcium phosphate Nutrition 0.000 claims description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 2
- 239000002491 polymer binding agent Substances 0.000 claims 1
- 239000003792 electrolyte Substances 0.000 abstract description 9
- 230000008961 swelling Effects 0.000 abstract description 8
- 150000002500 ions Chemical class 0.000 abstract description 5
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 230000001351 cycling effect Effects 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 239000002245 particle Substances 0.000 abstract description 3
- 230000003993 interaction Effects 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 17
- 238000012360 testing method Methods 0.000 description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 9
- 229910001416 lithium ion Inorganic materials 0.000 description 9
- 238000000576 coating method Methods 0.000 description 7
- 239000011575 calcium Substances 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 229920002401 polyacrylamide Polymers 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 229920003048 styrene butadiene rubber Polymers 0.000 description 5
- 239000002390 adhesive tape Substances 0.000 description 4
- 239000003431 cross linking reagent Substances 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000009477 glass transition Effects 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
- 239000002174 Styrene-butadiene Substances 0.000 description 2
- 150000001408 amides Chemical class 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- XMPZTFVPEKAKFH-UHFFFAOYSA-P ceric ammonium nitrate Chemical compound [NH4+].[NH4+].[Ce+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O XMPZTFVPEKAKFH-UHFFFAOYSA-P 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000002482 conductive additive Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000000113 differential scanning calorimetry Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 150000002148 esters Chemical class 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- -1 organic acid salt Chemical class 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000004971 Cross linker Substances 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 1
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000001938 differential scanning calorimetry curve Methods 0.000 description 1
- 239000011883 electrode binding agent Substances 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011115 styrene butadiene Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002522 swelling effect Effects 0.000 description 1
- 238000010257 thawing Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
- C09J151/02—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to polysaccharides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
- C08F251/02—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof on to cellulose or derivatives thereof
-
- 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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the technical field of lithium batteries, and particularly discloses a preparation method of a natural polymer modified binder, which comprises the following steps: dispersing nano cellulose in deionized water, adding an acrylamide solution, uniformly stirring in a nitrogen atmosphere, and adding an initiator to perform free radical polymerization for 2-4 hours; and then adding methylene bisacrylamide for crosslinking for 1-2 hours, and finally adding a calcium ion-containing solution and stirring for 15-60 minutes to obtain the natural polymer modified binder. The natural polymer modified adhesive prepared by the preparation method of the natural polymer modified adhesive has good adhesive property, is used for preparing pole pieces, has no particle stripping phenomenon, and has good pole piece integrity; the mechanical property of the binder maintains the stability of the pole piece structure, and the pole piece structure has good cycling stability when applied to the negative electrode, can well resist the electrolyte environment, has little interaction with the electrolyte, has proper swelling degree, is beneficial to ion transmission, and reduces impedance.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a natural polymer modified binder and a preparation method and application thereof.
Background
In commercial lithium ion battery electrodes, the binder is an important component, and properties of the binder such as viscosity, mechanical properties, alkali resistance and the like have a great influence on the performance of the lithium ion battery. The binder with excellent performance is adopted, so that the lithium ion battery can exert larger capacity and longer cycle life; the method has the promotion effects of improving the quick charge and discharge capacity of the battery and reducing the internal pressure of the battery so as to meet the strict requirements on the performance of the battery due to continuous development of society. However, PVDF and CMC binders commonly used in industry show increasingly more problems, and it has been difficult to meet the requirements of modern high energy density battery development. Therefore, development of a novel adhesive excellent in performance, friendly to the environment and inexpensive is a necessary trend.
The binder is generally a high polymer material, and has the main effects of uniformly and stably binding the active material, the conductive additive and the current collector, avoiding the phenomena of powder falling and glass falling of the pole piece, forming good electronic contact so as to ensure an effective electronic loop and reducing the impedance of the battery. In addition, the binder can play a role in inhibiting and buffering huge volume expansion of the negative electrode in the repeated charge and discharge process, so that the phenomenon that the pole piece structure is damaged due to larger stress of the pole piece in the battery cycle process is prevented, and the capacity attenuation of the battery is slowed down; meanwhile, stable SEI films with deformable structures can be formed on the surfaces of graphite, battery capacity loss is reduced, and coulombic efficiency and energy density of the battery are improved. However, the binder should not be used too much, generally 1% -10% of the total amount of the electrode, if the binder is used too much, the electrochemical inertness of the electrode material will increase, the internal resistance and polarization of the battery will be enhanced, the conductivity will be reduced, and a series of safety problems such as reduction of the electrochemical platform or increase of the heat generation amount will occur. Currently, the main negative electrode binders are polyvinylidene fluoride (PVDF), styrene-butadiene emulsion (SBR), polyacrylic acid (PAA), modified materials thereof, and the like. Compared with pure styrene-butadiene rubber, the styrene-butadiene rubber can improve the adhesive property and the ion conductivity of the negative electrode plate prepared by the styrene-butadiene rubber, but can increase the swelling property of the adhesive to electrolyte, and the adhesive strength is reduced, so that the problem of increasing the expansion rate of the negative electrode plate is caused, the SEI film is formed unevenly due to the change of the volume, uneven lithium deposition on the electrode is caused, and the growth of lithium dendrites is promoted. In the circulation process, the larger volume change can cause degradation of active materials and electrodes, the cycle life of the battery is shortened, and even the problems of potential safety hazards caused by battery bulge and the like can occur.
The water-based binder commonly used in the current lithium ion battery market is CMC binder, and the CMC binder is firstly applied to the lithium ion battery cathode material by Jernej Drofenik and the like for research , so that the lithium ion battery cathode material has good electrochemical performance, and has the advantages of high solubility in water, stable viscosity, high product purity and the like, and is in great charge of the market. However, the CMC binder has a decreased viscosity with increasing temperature, is easily absorbed with moisture, has poor mechanical properties, and is unfavorable for the stable cycle of the battery, so that it is very necessary to develop a novel binder by adopting different measures. Chinese patent publication No. CN 112159638A discloses a dendritic aqueous binder, the main chain is nanocellulose, the side chain is chemical grafting, and the polymer contains at least one group of ester, organic acid, amide, and organic acid salt; in an acidic aqueous solution, hydroxyl groups in the nanocellulose are initiated by ceric ammonium nitrate, and one or more unsaturated olefin monomers in water-soluble esters, organic acids, amides and organic acid salts containing carbon-carbon double bonds are initiated at side chains. The main chain in the binder is a nano cellulose material, and has the properties of high length-diameter ratio, high toughness and high modulus, and the nano cellulose can be used for extending and bonding different anode particles, but the binder is applied to a battery anode in a line-surface contact bonding effect, is unfavorable for maintaining the stability of a pole piece structure in the battery cycle process, and has no excellent electrochemical performance.
Disclosure of Invention
Aiming at the defects, the invention provides a natural polymer modified binder and a preparation method thereof, which can improve the mechanical property of the binder, maintain the stability of a pole piece structure, and show good cycling stability when applied to a negative electrode, and the specific technical scheme is as follows:
the preparation method of the natural polymer modified binder comprises the following steps:
(1) Dispersing nano cellulose in deionized water, adding an acrylamide solution, uniformly stirring under a nitrogen atmosphere, and adding an initiator to perform free radical polymerization for 2-4 h;
(2) Then adding methylene bisacrylamide for crosslinking for 1-2 h, and finally adding calcium ion-containing solution and stirring for 15-60 min to obtain the natural polymer modified binder.
Preferably, in the preparation method of the natural polymer modified binder, the mass ratio of the nanocellulose, the acrylamide, the initiator and the subunit bisacrylamide to the calcium ion solution is 1:1-4:0.001-0.01:0.1-1:1-5.
Preferably, in the preparation method of the natural polymer modified binder, the mass ratio of the nanocellulose to the deionized water is 1:25-100, and the mass fraction of the acrylamide solution is 10-25%.
Preferably, in the preparation method of the natural polymer modified binder, the free radical polymerization temperature is 40-60 ℃, and the crosslinking reaction temperature is 40-60 ℃.
Preferably, in the preparation method of the natural polymer modified binder, the initiator is ammonium persulfate, potassium persulfate, hydrogen peroxide, azobisisobutyronitrile or azobisisobutyronitrile.
Preferably, in the preparation method of the natural polymer modified binder, the calcium ion solution is calcium hypochlorite, calcium chloride, calcium nitrate or calcium dihydrogen phosphate solution, and the mass fraction of the calcium ion solution is 1-2%.
The natural polymer modified adhesive is prepared by the preparation method of the natural polymer modified adhesive.
The natural polymer modified binder is applied to the preparation of lithium batteries.
Preferably, in the application, the binder, the active substance and the SuperC65 obtained in the step (1) are uniformly mixed in deionized water according to a certain proportion to prepare slurry, the slurry is coated on copper foil, and the pole piece is placed in a vacuum drying oven to be dried and cooled to obtain the lithium battery pole piece.
Preferably, in the application, the active substance is one or more of MCMB, graphene, silicon and silicon-based oxide, and the mass ratio of the active substance to the SuperC65 to the binder is 8-9:0.5-1:0.2-1.
Preferably, in the above application, the drying temperature is 90 ℃ to 120 ℃ and the drying time is 10 hours to 16 hours.
Compared with the prior art, the invention has the beneficial effects that:
1. the natural polymer modified adhesive prepared by the preparation method of the natural polymer modified adhesive has good adhesive property, is used for preparing pole pieces, has no particle stripping phenomenon, and has good pole piece integrity; the mechanical property of the binder can maintain the stability of the pole piece structure, and the binder has good cycling stability when applied to a negative electrode, can well resist the environment of electrolyte, has little interaction with the electrolyte, has proper swelling degree, is beneficial to ion transmission, and reduces impedance.
2. According to the preparation method of the natural polymer modified binder, the nano Cellulose (CNF) is adopted as a base material, the nano cellulose is subjected to graft copolymerization with acrylamide, an amide bond is introduced to enhance the binding capacity of the binder, and then the methylene bisacrylamide is used for forming crosslinking among macromolecular chains to synthesize the binder with a three-dimensional crosslinking network structure.
3. The preparation method of the natural polymer modified binder uses Ca 2+ And the modification is carried out, so that an ionic bond effect is formed between ungrafted CNF, the mechanical property of the binder is enhanced, the stability of the pole piece structure is maintained, and the pole piece structure has good cycle stability when applied to a battery cathode.
4. The preparation method of the natural polymer modified binder has the advantages that the source of raw materials of the synthesized binder is wide, the cost is low, and the synthesized binder is a water-based binder, so that the problems of environmental pollution, high cost and the like caused by the traditional oil-based binder are solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the description of the embodiments will be briefly described below. It will be apparent to those of ordinary skill in the art that the drawings in the following description are of some embodiments of the invention and that other drawings may be derived from them without undue effort.
FIG. 1 is a graph of electrochemical impedance testing of a battery assembled from pole pieces according to example 2 of the present invention;
FIG. 2 is a graph showing the cycle performance of the assembled battery of example 2 of the present invention at a charge/discharge rate of 0.1C;
fig. 3 is a first charge-discharge curve of the assembled battery of example 2.
Detailed Description
The following detailed description of specific embodiments of the invention is, but it should be understood that the invention is not limited to specific embodiments. Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention. Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
Example 1
The preparation method of the natural polymer modified binder comprises the following steps:
(1) Dispersing 1g of nanocellulose powder (CNF, diameter 5-50 nm, length 1-10 um) in 50g of deionized water, uniformly stirring, adding 12g of 10wt% Acrylamide (AM) aqueous solution, uniformly stirring under nitrogen atmosphere, and carrying out free radical polymerization at 50 ℃ for 2h by taking 0.2g of 2.5wt% ammonium persulfate solution as an initiator;
(2) Then adding 12g of 5wt% methylene bisacrylamide, performing crosslinking for 1h at 50 ℃, adopting absolute ethanol for precipitation, washing the precipitate with deionized water, vacuum drying at 80 ℃ for 12h, dispersing the dried product in the deionized water to prepare a solution with the mass fraction of 2%, finally adding 2g of 1wt% calcium chloride solution, and stirring for 30min; the obtained nano cellulose grafted polyacrylamide binder modified by calcium ions is a natural polymer modified binder, and is marked as CNF-10% PAM-Ca2+.
The adhesive prepared in the embodiment is used for preparing a negative plate of a lithium ion battery, and the specific preparation method comprises the following steps:
mixing MCMB, superC65 and a binder according to a mass ratio of 9:0.6:0.4, adding a certain amount of deionized water to adjust the solid content to 55%, and preparing into slurry by using a magnetic stirrer, wherein the stirring time is 1h. Then coating the slurry on the copper foil by using a push rod, and coating pole pieces with different loading capacities according to different groove depths of the push rod, wherein the coating thickness of the pole pieces is 50um in the embodiment; and (3) drying the pole piece in a vacuum drying oven at 100 ℃ for 12 hours, naturally cooling to room temperature, cutting the pole piece into a round pole piece with the diameter of 16mm by a cutting machine, and storing the round pole piece in a glove box for standby.
Example 2
The preparation method of the natural polymer modified binder comprises the following steps:
(1) Dispersing 1g of nanocellulose (CNF, the diameter is 5-50 nm, the length is 1-10 um) in 50g of deionized water, adding 12g of 15wt% Acrylamide (AM) solution after uniformly stirring, uniformly stirring under nitrogen atmosphere, and carrying out free radical polymerization at 50 ℃ for 2h by taking 0.2g of 2.5wt% ammonium persulfate solution as an initiator;
(2) Then adding 12g of 5wt% methylene bisacrylamide to crosslink for 1h at 50 ℃, finally adding 2g of 1wt% calcium chloride solution, stirring for 30min to obtain the calcium ion modified nano cellulose grafted polyacrylamide binder, namely the natural polymer modified binder, which is marked as CNF-15% PAM-Ca2+.
The pole piece preparation process is the same as in example 1.
Example 3
The preparation method of the natural polymer modified binder comprises the following steps:
(1) Dispersing 1g of nano Cellulose (CNF) in 50g of deionized water, uniformly stirring, adding 12g of 20wt% Acrylamide (AM) solution, uniformly stirring under a nitrogen atmosphere, and carrying out free radical polymerization by taking 0.2g of 2.5wt% ammonium persulfate solution as an initiator for 2h;
(2) Then 6g of 5wt% methylenebisacrylamide was added for crosslinking for 1h, and finally 2g of 1wt% calcium chloride solution was added and stirred for 30min. The obtained calcium ion modified nano cellulose grafted polyacrylamide binder is marked as CNF-20% PAM-Ca2+.
The pole piece preparation process is the same as in example 1.
Comparative example 1
Mixing MCMB, superC65 and CNF according to the mass ratio of 9:0.6:0.4, adding a certain amount of deionized water, and using a magnetic stirrer to prepare slurry, wherein the stirring time is 1h. Then coating the slurry on the copper foil by using a push rod, and coating pole pieces with different loading amounts according to different groove depths of the push rod, wherein the coating thickness of the pole pieces in the comparative example is 50um; and (3) drying the pole piece in a vacuum drying oven at 100 ℃ for 12 hours, naturally cooling to room temperature, cutting the pole piece into a round pole piece with the diameter of 16mm by a cutting machine, and storing the round pole piece in a glove box.
Comparative example 2
The preparation method of the adhesive of the comparative example comprises the following steps: dispersing 1g of nanocellulose (CNF) in 50g of deionized water, uniformly stirring, adding 12g of 15wt% Acrylamide (AM) solution, uniformly stirring under a nitrogen atmosphere, and performing free radical polymerization at 50 ℃ for 2h by taking 0.2g of 2.5wt% ammonium persulfate solution as an initiator to obtain the binder. This comparative example differs from example 2 in that: no crosslinker and Ca are added 2+ A solution. The pole piece preparation process is the same as in example 1.
Comparative example 3
The preparation method of the adhesive of the comparative example comprises the following steps: dispersing 1g of nanocellulose (CNF) in 50g of deionized water, uniformly stirring, adding 12g of 15wt% Acrylamide (AM) solution, uniformly stirring under nitrogen atmosphere, and adding 0.2g of 2.5wt%The ammonium persulfate solution was subjected to radical polymerization at 50℃for 2 hours as an initiator, followed by crosslinking at 50℃for 1 hour by adding 12g of 5wt% methylenebisacrylamide, and this comparative example differs from example 2 in that: finally, no Ca is added 2+ The solution was used to obtain a polyacrylamide grafted nanocellulose binder, designated CNF-15% pam. The pole piece preparation process is the same as in example 1.
Comparative example 4
Dispersing 1g of nanocellulose (CNF) in 50g of deionized water, uniformly stirring, adding 12g of 15wt% Acrylamide (AM) solution, uniformly stirring under a nitrogen atmosphere, sequentially adding 0.2g of 2.5wt% ammonium persulfate solution and 12g of 5wt% methylenebisacrylamide, continuously stirring at 50 ℃ for 3 hours, finally adding 2g of 1wt% calcium chloride solution, and stirring for 30 minutes to obtain the binder. This comparative example differs from example 2 in that: the crosslinking agent and initiator are added simultaneously. The pole piece preparation process is the same as in example 1.
Assembling a battery:
the whole assembly process of the lithium ion battery is completed in a glove box. The battery is assembled into a button battery, wherein the model of a battery shell is CR2025, and the lithium ion half battery is assembled by adopting a flip-chip method: firstly taking out the lithium battery cathode shell, pouring the lithium battery cathode shell, placing a spring piece, a gasket and a lithium piece into the lithium battery cathode shell, and soaking the diaphragm and the electrode piece in EC/PC in advance. Care should be taken when placing the electrode pads to face down the active material coated face. Finally, the lithium battery shell is covered and sealed by a sealing machine under the pressure of 6 MPa. The assembled battery was placed in an oven and allowed to stand at 60 ℃ for 10 hours to allow the separator to fully contact the electrode material. The electrode sheets prepared in examples 1 to 3 and comparative examples 1 to 4 were used as negative electrode sheets of batteries, respectively, and the other parts were the same, and assembled into batteries.
The binders prepared in examples 1 to 3 and comparative examples 1 to 4, the pole pieces, and the assembled batteries were tested for their related properties as follows:
(1) DSC analysis
Differential Scanning Calorimetry (DSC), a function of temperature or time that characterizes the difference in flow heat between a sample and a reference, can be used to determine the binderThe phase transition temperature, glass transition temperature, specific heat capacity or purity and other properties were analyzed. The characterization is performed herein using the American TA company TA-Q500. Ca by DSC thermogram 2+ The adhesive before and after modification is characterized, the testing temperature range is 20-200 ℃, and the heating rate is 10 ℃/min.
(2) Swelling Performance test
The swelling ratio can be used for characterizing the stability of the adhesive in the electrolyte environment, and the operation method is that the mass of the adhesive before the adhesive is soaked in the electrolyte is recorded as m 0 After being soaked in the electrolyte for 48 hours, the electrolyte which is wiped off the surface of the adhesive is taken out, and the weighing is recorded as m 1 The swelling ratio can be controlled by (m 1 -m 0 )*100％/m 0 And calculating to obtain the swelling rate of the adhesive.
(3) Peel test
The peeling test can evaluate the bonding strength among the adhesive, the active substance and the conductive additive, a layer of 3M double faced adhesive tape is firstly stuck on a glass slide, then the prepared pole piece is cut into the same size as the 3M double faced adhesive tape and stuck on the 3M double faced adhesive tape, then a layer of 3M transparent adhesive tape is stuck on the pole piece, the peeling test is carried out by a universal material tester, and the peeling rate is 5mm/min.
(4) Electrochemical impedance testing
The cell samples were tested for ac impedance (amplitude 5mV, test frequency 0.1-100 Hz) using a CHI660E electrochemical workstation.
(5) Cycle performance test
CR2025 button cell was clamped in a BST-4800 type 8-channel cell analyzer (5V, 50 mA) for testing, and charge and discharge cycles were performed in constant current mode, and cycle test was performed at room temperature at 0.1C charge and discharge rate, with a voltage of 0.005-2.00V, and a capacity retention rate after 100 cycles was tested.
Analysis of detection results:
the glass transition temperature Tg of the CNF-15% PAM binder (comparative example 3) was 105.3℃at Ca addition 2+ The Tg of the modified binder (example 2) was raised to 129.2℃and the glass transition temperature was characterized by the temperature at which the polymer macromolecular segments began to move freely as a result of thawing, CNF-15% PAM-Ca 2+ The Tg of the binder (example 2) increased because the ionic bonds formed therein made free movement of the polymer segments more difficult, demonstrating Ca 2+ Ionic bonding of the modified binder.
Fig. 1 to 3 show electrochemical impedance test patterns, cycle performance curves and first charge and discharge curves of the battery obtained in example 2 of the present invention, and it is known from the figures that example 2 has small interface impedance, is favorable for ion transmission, circulates for 100 circles at a current density of 0.1C, has a capacity retention rate of 99.02%, and a first circle coulomb efficiency of 99.37%, shows excellent long cycle performance, and has excellent electrochemical cycle stability.
The performance data of each example and comparative example are shown in Table 1, and it can be seen from the table that the adhesive of the example of the invention has proper swelling degree, is favorable for ion transmission and reduces impedance, and the peel strength of the pole piece of example 2 is 15.8N/m at maximum, which is higher than that of other examples and comparative examples, so that the adhesive has the strongest adhesive property and mechanical property, can well maintain the stability of the pole piece structure, and has excellent electrochemical cycling stability when applied to the cathode of a battery.
As is clear from comparison between example 2 and comparative examples 1 to 4, the addition of the crosslinking agent can synthesize the binder having a three-dimensional crosslinked network structure, but the addition of the crosslinking agent may affect the performance of the binder, and the simultaneous addition of the crosslinking agent and the initiator (comparative example 4) directly allows the simultaneous polymerization and crosslinking, and the molecular chain length may be shorter than that of example 2, and a denser structure is formed, which is disadvantageous for the subsequent coating process step, and results in an excessively low swelling rate of the binder, a significant increase in interface resistance, and poor cycle stability of the battery.
TABLE 1 Performance data for binders, pole pieces and batteries
The foregoing descriptions of specific exemplary embodiments of the present invention are presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application to thereby enable one skilled in the art to make and utilize the invention in various exemplary embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (10)
1. The preparation method of the natural polymer modified binder is characterized by comprising the following steps of:
(1) Dispersing nano cellulose in deionized water, adding an acrylamide solution, uniformly stirring in a nitrogen atmosphere, and adding an initiator to perform free radical polymerization for 2-4 hours;
(2) And then adding methylene bisacrylamide to carry out crosslinking reaction for 1-2 hours, and finally adding a calcium ion-containing solution and stirring for 15-60 minutes to obtain the natural polymer modified binder.
2. The method for preparing the natural polymer modified adhesive according to claim 1, wherein the mass ratio of the nanocellulose, the acrylamide, the initiator, the methylenebisacrylamide and the calcium ion solution is 1:1-4:0.001-0.01:0.1-1:1-5.
3. The preparation method of the natural polymer modified binder according to claim 1, wherein the mass ratio of the nanocellulose to the deionized water is 1:25-100, and the mass fraction of the acrylamide solution is 10-25%.
4. The method for preparing a natural polymer modified binder according to claim 1, wherein the free radical polymerization temperature is 40-60 ℃, and the crosslinking reaction temperature is 40-60 ℃.
5. The method for preparing a natural polymer modified binder according to claim 1, wherein the initiator is ammonium persulfate, potassium persulfate, hydrogen peroxide, azobisisobutyronitrile or azobisisobutyronitrile; the calcium ion solution is calcium hypochlorite, calcium chloride, calcium nitrate or calcium dihydrogen phosphate solution, and the mass fraction of the calcium ion solution is 1-2%.
6. A natural polymer-modified adhesive prepared by the method for preparing a natural polymer-modified adhesive according to any one of claims 1 to 5.
7. The use of the modified natural polymer binder according to claim 6 for preparing lithium batteries.
8. The method according to claim 7, wherein the binder, the active material and the SuperC65 obtained in the step (1) are uniformly mixed in deionized water according to a certain proportion to prepare slurry, the slurry is coated on copper foil, and the pole piece is dried in a vacuum drying oven and cooled to obtain the lithium battery pole piece.
9. The use according to claim 8, wherein the active substance is one or more of MCMB, graphene, silicon and silicon-based oxide, and the mass ratio of the active substance to SuperC65 to the binder is 8-9:0.5-1:0.2-1.
10. The use according to claim 8, wherein the drying temperature is between 90 ℃ and 120 ℃ and the drying time is between 10h and 16h.
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