CN117525416A - Blending type binder - Google Patents
Blending type binder Download PDFInfo
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- CN117525416A CN117525416A CN202311582275.6A CN202311582275A CN117525416A CN 117525416 A CN117525416 A CN 117525416A CN 202311582275 A CN202311582275 A CN 202311582275A CN 117525416 A CN117525416 A CN 117525416A
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- Prior art keywords
- nanocellulose
- modified
- carboxymethyl cellulose
- hydroxyethyl acrylate
- mass ratio
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- 238000002156 mixing Methods 0.000 title claims abstract description 20
- 239000011230 binding agent Substances 0.000 title claims description 33
- 229920001046 Nanocellulose Polymers 0.000 claims abstract description 68
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims abstract description 40
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims abstract description 40
- 239000001768 carboxy methyl cellulose Substances 0.000 claims abstract description 33
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims abstract description 33
- 239000000853 adhesive Substances 0.000 claims abstract description 17
- 230000001070 adhesive effect Effects 0.000 claims abstract description 17
- OMIGHNLMNHATMP-UHFFFAOYSA-N 2-hydroxyethyl prop-2-enoate Chemical compound OCCOC(=O)C=C OMIGHNLMNHATMP-UHFFFAOYSA-N 0.000 claims description 52
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 50
- 239000002121 nanofiber Substances 0.000 claims description 20
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 18
- 229910001416 lithium ion Inorganic materials 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 15
- 239000000178 monomer Substances 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 239000011883 electrode binding agent Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 6
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 239000002244 precipitate Substances 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 239000011541 reaction mixture Substances 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 21
- 239000007773 negative electrode material Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 6
- 239000011856 silicon-based particle Substances 0.000 description 6
- 125000003368 amide group Chemical group 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 229920003048 styrene butadiene rubber Polymers 0.000 description 5
- 239000006258 conductive agent Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 230000001351 cycling effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 125000004185 ester group Chemical group 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229920000742 Cotton Polymers 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 239000002174 Styrene-butadiene Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 229920003169 water-soluble polymer Polymers 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical group 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 229920000578 graft copolymer Polymers 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920005596 polymer binder Polymers 0.000 description 1
- 239000002491 polymer binding agent Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 239000002562 thickening agent Substances 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
-
- 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
-
- 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
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 discloses a blending type adhesive, which comprises carboxymethyl cellulose and modified nano cellulose, wherein the mass ratio of the carboxymethyl cellulose to the modified nano cellulose is (4-7): 1.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a blending type binder.
Background
The lithium ion battery has been widely used in the fields of 3C consumer electronic products, electric traffic, large-scale energy storage and the like due to the characteristics of long service life, high safety and the like. In the prior art, various performances of the lithium ion battery are improved from different directions of a negative electrode, a positive electrode, a binder, an additive and the like.
Among them, the polymer binder plays a very important role with little content in the electrode. Firstly, the binder uniformly adheres electrode components such as active materials, conductive agents and the like to a current collector, so that the integrity of the electrode is maintained; secondly, in the first charge and discharge process of the liquid lithium ion battery, the liquid lithium ion battery is favorable for reacting on the interface of the electrode material and the electrolyte to form a passivation layer which covers the surface of the electrode material, namely a Solid Electrolyte Interface (SEI) film, and the active material is protected from being corroded by the electrolyte; finally, the volume expansion effect of silicon particles in the lithium intercalation/deintercalation of the electrode can be relieved, and the electrode is prevented from swelling, cracking and falling. The properties of the binder in the electrode directly affect the electrochemical properties of the cell.
While for different anode materials the binder is not capable of exerting a favourable effect on it. Among them, silicon is considered as one of the most promising graphite negative electrode substitute materials in the lithium ion battery industry due to its higher theoretical capacity. However, si particles undergo large volume changes during insertion and extraction of lithium ions, and Si particles are pulverized and electrode cracked, resulting in poor electrochemical performance of the silicon-based negative electrode, including, for example, low Initial Coulombic Efficiency (ICE) and rapid capacity fade. Finally, the negative electrode is liable to be pulverized during the cycle, resulting in capacity fading, and the main reason for this phenomenon is that the binder is not sufficiently remarkable in the expansion inhibition of the negative electrode material containing Si element in charge and discharge, and the mechanical strength is low. Among the existing binders, water-soluble polymers are widely used as binders for silicon anodes because of their better adhesion properties than the conventional binder polyvinylidene fluoride (PVDF). These water-soluble polymers can form hydrogen bonds between their carboxylic acid functional groups and the surface functional groups of the Si negative electrode material, thereby providing better adhesion to the Si particles. However, these binders lack sufficient mechanical strength to accommodate the large volume changes of Si particles during cycling.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a blending type adhesive and application thereof, so as to solve the problem that the adhesive in the prior art lacks enough mechanical strength to adapt to a large amount of volume change of silicon particles in the circulating process.
In order to solve the technical problems, the invention adopts the following technical scheme:
a blending type adhesive comprises carboxymethyl cellulose and modified nano cellulose, wherein the mass ratio of the carboxymethyl cellulose to the modified nano cellulose is (4-7): 1.
Preferably, hydroxyethyl acrylate and acrylamide are grafted on the nanocellulose to obtain the modified nanocellulose; wherein, the molar ratio of the nanocellulose to the hydroxyethyl acrylate to the acrylamide monomer is 13: (1-9): (1-9).
Preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (4-6): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (5-7): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (5-6): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (4-5): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (6-7): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 4:1; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 5:1; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 6:1; preferably, the mass ratio of carboxymethyl cellulose to modified nanofiber is 7:1.
Preferably, the molar ratio of nanocellulose, hydroxyethyl acrylate and acrylamide monomers is 13: (1-5): (5-9); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13: (2-5): (5-8); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13:5:5.
the invention also provides a preparation method of the modified nanocellulose, which is used for preparing the modified nanocellulose in the blending adhesive and specifically comprises the following steps of:
step 1: preparing a nanocellulose aqueous solution:
dissolving nano cellulose in water, stirring in a room temperature environment until the nano cellulose is completely dispersed, introducing inert gas for gas washing, and then raising the temperature to maintain the nano cellulose water solution at 55-75 ℃;
step 2: adding a reaction monomer:
adding potassium persulfate into the nano cellulose aqueous solution obtained in the step 1 in an inert gas environment to generate free radicals, and then slowly adding monomers of hydroxyethyl acrylate and acrylamide; wherein, the molar ratio of the nanocellulose to the hydroxyethyl acrylate to the acrylamide monomer is 13: (1-9): (1-9); the addition amount of the potassium persulfate is 0.05-0.1% of the mass sum of the nano cellulose, the hydroxyl ethyl acrylate and the acrylamide;
step 3: the reaction process comprises the following steps:
keeping the temperature of the reaction system at 60-75 ℃ under the stirring state, and reacting for 1-5 h;
step 4: and (3) separating and purifying:
after the reaction of the step 3 is completed, pouring the reaction mixture into acetone to obtain a precipitate; and separating, vacuum drying and crushing the precipitate to obtain the modified nanocellulose.
Preferably, in step 2, the molar ratio of nanocellulose, hydroxyethyl acrylate and acrylamide monomers is 13: (1-5): (5-9); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13: (2-5): (5-8); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13:5:5.
the invention provides application of a blending type binder, and the blending type binder is used for a negative electrode binder of a lithium ion battery.
Preferably, the blended binder is used for a silicon carbon negative electrode binder.
The invention provides a lithium ion battery which is prepared from the negative electrode binder.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, the carboxymethyl cellulose and the modified nanocellulose are blended according to a specific proportion to obtain the blended adhesive, so that the blended adhesive has good mechanical properties; the method is particularly suitable for the lithium ion battery of a silicon-carbon system, can effectively improve the tensile strength of the negative electrode plate, reduce the problem of expansion of the negative electrode plate of the lithium ion battery mainly made of silicon-carbon negative electrode materials in the charge and discharge process, and effectively improve the cycle life of the lithium ion battery.
2. The modified nano-cellulose provided by the invention simultaneously introduces hydroxyethyl acrylate and acrylamide. The modified nano-cellulose has more polar groups, such as hydroxyl groups and amide groups, and the polar groups can form a crosslinked network structure with the carboxymethyl cellulose by the action of hydrogen bond force, so that the tensile strength of the modified nano-cellulose is enhanced. Meanwhile, the amide groups can be effectively combined with Styrene Butadiene Rubber (SBR) in the anode pole piece slurry, and the amide groups and the SBR cooperate to further improve the bonding effect on anode materials.
3. In the invention, the carboxymethyl cellulose gum has certain viscosity and can help the modified nano cellulose to be better dispersed. In addition, the amide group and the hydroxyl in the hydroxyethyl acrylate have stronger hydrophilicity; the ester group in the hydroxyethyl acrylate has certain lipophilicity, and the dispersibility of the effective materials in the negative electrode plate slurry can be improved under a specific proportion.
4. The preparation method of the adhesive is simple and has less environmental pollution; meanwhile, the adhesive has wide application range, can be used for preparing the silicon-carbon system negative plate, and has application prospect of large-scale industrial production.
Drawings
FIG. 1 is a graph showing cyclic thickness changes of examples 5 and comparative examples 3 to 4.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention fall within the scope of the present invention.
Unless otherwise indicated in the context of a specific instance, the numerical ranges set forth herein include upper and lower limits, as well as all integers and fractions within the range, and are not limited to the specific values set forth in the defined range.
In the present invention, the reference to the letter abbreviations is as follows:
NCs: nanocellulose;
HEA: hydroxy ethyl acrylate;
AM: an acrylamide;
NCs-g-P (HEA-AM): modified nanocellulose;
KPS: potassium persulfate;
CMC: carboxymethyl cellulose;
ar: argon;
SBR: styrene-butadiene rubber;
SP: and a conductive agent.
1. Blending type binder
The binder comprises carboxymethyl cellulose and nano cellulose, wherein the mass ratio of the carboxymethyl cellulose to the modified nano fiber is (4-7): 1.
In some embodiments, the mass ratio of carboxymethyl cellulose to modified nanofibers can be controlled to be (4-6): 1. (5-7): 1. (5-6): 1. (4-5): 1. (6-7): 1. 4:1, 5:1, 6:1, 7:1, etc., as well as all ranges and subranges therebetween. It is to be understood that any of the above ranges may be combined with any of the other ranges in embodiments.
In some embodiments, nanocellulose is used as a main chain structure, and the lateral group is hydroxyethyl acrylate (HEA) and Acrylamide (AM) are introduced into the main chain through a grafting modification method. Wherein, the molar ratio of the nanocellulose to the hydroxyethyl acrylate to the acrylamide monomer is 13: (1-9): (1-9). HEA and AM are grafted on nanocellulose simultaneously, so that the binder has the effects of HEA and AM simultaneously, and NCs-g-P (HEA-AM) polymers grafted with HEA and AM simultaneously can have more polar groups, such as hydroxyl groups, amide groups and the like, and the polar groups can form a crosslinked network with carboxymethyl cellulose in the form of hydrogen bond acting force, so that the tensile strength of the negative electrode plate is further enhanced; meanwhile, the carboxymethyl cellulose gum solution has certain viscosity, and can help NCs-g-P (HEA-AM) polymer to be better dispersed in the negative electrode plate slurry. Thus, the molar ratio of nanocellulose, HEA and AM may be 13: (1-9): (1-9), 13:
(1-5): (5-9), 13: (2-5): (5-8), 13:5:5, etc., as well as all ranges and subranges therebetween. It is to be understood that any of the above ranges may be combined with any of the other ranges in embodiments.
In some embodiments, nanocellulose may be modified with conventional nanocellulose, specifically prepared as follows:
28g of purified cotton wool was weighed into a three-necked flask. 600ml of mixed acid was added to the three-necked flask. Soaking refined absorbent cotton in mixed acid at 25+ -2deg.C for 30min. The temperature of the constant-temperature water bath kettle is set to 55 ℃, and then the three-neck flask is placed in the water bath kettle to react for 2-3h under the constant-temperature condition. After the reaction is stopped, the three-neck flask is placed in an ultrasonic oscillator for ultrasonic treatment for 1.5 hours, and 1L of deionized water is added into the three-neck flask after the reaction is finished. Separating the reaction product in batches by using a centrifugal machine, setting the rotating speed to be 8000r/min, centrifuging for 15min, pouring out supernatant, collecting white precipitate at the bottom layer, and repeatedly washing with distilled water for several times until the p H value is 7, wherein the obtained product is short-chain nanocellulose suspension. This method is illustrated by way of example only.
2. Preparation method of modified nanocellulose
The preparation method of the modified nanocellulose specifically comprises the following steps:
step 1: preparation of aqueous nanocellulose solutions
Dissolving the NCs with certain mass in a proper amount of water, stirring in a room temperature environment until the NCs are completely dispersed, and introducing Ar gas for gas washing.
Step 2: adding the reaction monomers
In Ar gas atmosphere, raising the temperature to 55-75 ℃, adding a proper amount of KPS (potassium persulfate) to generate free radicals, slowly adding monomer HEA and monomer AM, and continuously introducing Ar gas in the process. Wherein, the molar ratio of the nanocellulose to HEA to AM is 13: (1-9): (1-9). The addition amount of KPS is 0.05% -0.1%.
Step 3: reaction procedure
The temperature of the reaction system is kept at 60-75 ℃ under the stirring state, and the reaction is carried out for 1-5 h.
Step 4: separation and purification
And 3, after the reaction of the step 3 is finished, pouring the obtained substance into acetone for precipitation to obtain a graft polymer NCs-g-P (HEA-AM), and then, carrying out vacuum drying and crushing to obtain the modified nanocellulose.
3. Application of blending type binder
The blending type binder can be used as a negative electrode binder of a lithium ion battery. The blending type binder can be uniformly mixed with active substances, thickening agents and conductive agents in the anode material to obtain anode slurry.
4. Lithium ion battery
The lithium ion battery is prepared by adopting the negative electrode binder. In an embodiment of the present invention, the binder of the present invention is used in the prior art to make lithium ion batteries.
5. Detection method
(1) Impedance test (1 s DCR test): test condition SOC:50% temperature: 25+ -2 DEG C
The DCR electrical performance test was performed first using a low current activated battery and then as follows:
1、Rest 10min
2、1C DC to 3.3V
3、Rest 60min
4、05C CC to 4.4V,CV to 0.05C
5、Rest 60min
6. 02C DC to 3.3V (where the actual capacity is obtained)
7、Rest 60min
8. 0.5C actual CC to 4.4V, CV to 0.05C (actual capacity definition obtained in sixth step is used here to charge actual multiplying power)
9、Rest 60min
10. 02C actual DC to 2.5h
11. Rest 60min (standing voltage V1)
12. 1C DC to 1s (taking the voltage V2 recorded after 1s ended)
13、Rest 60min
1s DCR calculation formula R= (V1-V2)/I
(2) The cycle test was stopped when the battery cycle capacity decayed to 70% of the initial capacity, or the maximum cycle number 300, using 05C for both charge and discharge.
(3) And (3) pole piece adhesive force test: according to GB/T2792-2014 Experimental method for adhesive tape peel strength, a spline with the width of 24mm and the length of 300mm is cut, a 180-degree peeling method is adopted, the peeling speed is 50mm/min, and the average value is obtained by three times of measurement in each group.
It should be noted that: in the above test expressions, the meaning of the unexplained letter abbreviations is understood according to common general knowledge in the art.
6. Examples and comparative examples
The invention adopts the proportion in table 1 to prepare the binder, and prepares the binder prepared in the example into the negative electrode material. The content of negative electrode active substances in the negative electrode material is 92.0-99.0%, the content of Styrene Butadiene Rubber (SBR) in the negative electrode material is 0.5-3.0%, the content of blending binder in the negative electrode material is 0.5-3.0%, and the content of conductive agent (SP) in the negative electrode material is 0-2.0% of the total weight of the negative electrode material.
The modified nanocellulose of examples 1 to 12 was prepared according to the ratios and conditions of table 1 using the preparation method of the modified nanocellulose of the present invention.
TABLE 1
Table 1 illustrates: comparative example 1 synthesis procedure, grafting only HEA monomer; comparative example 2 Synthesis procedure, only AM monomer was grafted.
According to the proportions shown in table 2, the modified nanocellulose obtained in examples and comparative examples was used to prepare corresponding negative electrode sheet slurries, which were then prepared into corresponding negative electrode sheets by conventional techniques for detection.
TABLE 2
Table 2 illustrates:
comparative example 1 is modified NCs grafted with HEA monomer alone;
comparative example 2 is modified NCs grafted with AM monomer only;
the blend binder in comparative example 3 was only CMC;
the blend binders in comparative example 4 were CMC and unmodified NCs; according to the mass ratio, CMC: unmodified ncs=5:1.
The blended binders of examples 11 and 12 were identical to the synthesis of example 5, except that the blending ratio of CMC and NCs-g-P (HEA-AM) was not identical.
The impedance performance test results are shown in table 3:
TABLE 3 Table 3
As can be seen from table 3, the 1s DCR of examples 1 to 12 was reduced compared to comparative examples 1 to 4, and the modified chemical nanocellulose was reduced in electrochemical polarization due to electrolyte affinity caused by its ester group, which can effectively reduce impedance and improve the partial kinetics of lithium battery, demonstrating that the blending binder EHA is effective. Example 5 compared to comparative example 1 and comparative example 2, both HEA alone and AM alone have a 1s DCR value greater than 1:1 HEA and AM grafted, which indicates that HEA and AM have a synergistic effect. Example 5 shows that the internal resistance of the resulting cell is lower than the other examples, indicating that the synergy of HEA and AM is further enhanced, so that the preferred grafting ratio is 1 for HEA and AM moles: 1. example 5 compared to examples 11-12 demonstrates that the optimum electrical performance results are obtained with the appropriate blend ratio (CMC: NCs-g-P (HEA-AM) =5:1 in the blended adhesive).
The cycle performance test results were as follows:
TABLE 4 Table 4
From the capacity retention of the cycling data in table 4 and fig. 1, the maximum cycle number in all examples was increased compared to comparative examples 1 to 4, which demonstrates that the blended binders provided in the examples of the present invention are effective in increasing the cycling performance of the battery. The inventors speculate that the reason is that: after HEA and AM are grafted at the same time, the self-healing network (amide bond in acrylamide and hydrogen bond in hydroxyethyl acrylate are mutually crosslinked and wound) is formed after the HEA and AM are blended with CMC, so that the silicon-carbon negative electrode can well resist the huge deformation generated in the charge-discharge process, and the cycle performance of the battery is improved.
The pole piece adhesion test results are shown in the following table:
TABLE 5
| Sample of | Adhesive force (N/M) |
| Comparative example 1 | 6.8 |
| Comparative example 2 | 7.1 |
| Comparative example 3 | 5.9 |
| Comparative example 4 | 6.3 |
| Example 1 | 7.2 |
| Example 2 | 7.3 |
| Example 3 | 7.4 |
| Example 4 | 7.8 |
| Example 5 | 8.4 |
| Example 6 | 7.9 |
| Example 7 | 7.7 |
| Example 8 | 7.8 |
| Example 9 | 7.6 |
| Example 10 | 7.7 |
| Example 11 | 7.6 |
| Example 12 | 7.4 |
As can be seen from Table 5, comparative examples 1 and 2 are comparable to examples 1 to 12, in which either HEA or AM alone has less pole piece peel force than HEA and AM are graft copolymerized simultaneously. Examples 11-12 are compared to example 5, and the pole piece peel force for either too low or too high a doping ratio is lower than for the optimal set of example 5, so example five is the most preferred set. In other examples, compared to example 5, when the grafted HEA ratio is too high or the AM ratio is too low, the high HEA content can cause too high electrolyte swelling or dissolution, resulting in pole piece peel force loss; when the HEA proportion is too low and the AM proportion is too high, the content of ester groups is too low, so that the affinity of the binder to the electrolyte is insufficient, and the internal resistance of the prepared battery is increased. Comparative example 4 was compared with comparative example 3 and it was found that the addition of a certain proportion of unmodified nanocellulose alone was very limited in improvement of the adhesion to the pole piece. In the invention, after modifying the nanocellulose, HEA and AM are introduced through chemical grafting, the adhesion force of the embodiment 5 is improved by 42.37% compared with that of the comparative example 3, and the reason is presumed to be that the strong polarity amide bond in the acrylamide provides stronger polarity, so that the adhesion force of the nanocellulose after copolymerization is ensured.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the technical solution, and those skilled in the art should understand that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the present invention, and all such modifications and equivalents are included in the scope of the claims.
Claims (9)
1. The blending type adhesive is characterized by comprising carboxymethyl cellulose and modified nano cellulose, wherein the mass ratio of the carboxymethyl cellulose to the modified nano cellulose is (4-7): 1.
2. The blending adhesive according to claim 1, wherein the modified nanocellulose is obtained by grafting hydroxyethyl acrylate and acrylamide on nanocellulose; wherein, the molar ratio of the nanocellulose to the hydroxyethyl acrylate to the acrylamide monomer is 13: (1-9): (1-9).
3. The blending adhesive according to claim 2, wherein the mass ratio of carboxymethyl cellulose to modified nanofiber is (4-6): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (5-7): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (5-6): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (4-5): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is (6-7): 1, a step of; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 4:1; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 5:1; preferably, the mass ratio of the carboxymethyl cellulose to the modified nanofiber is 6:1; preferably, the mass ratio of carboxymethyl cellulose to modified nanofiber is 7:1.
4. The blended adhesive according to claim 2 wherein the nanocellulose, hydroxyethyl acrylate and acrylamide monomers are present in a molar ratio of 13: (1-5): (5-9); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13: (2-5): (5-8); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13:5:5.
5. a method for preparing modified nanocellulose, which is characterized by preparing the modified nanocellulose in the blending adhesive according to any one of claims 1-4, specifically comprising the following steps:
step 1: preparing a nanocellulose aqueous solution:
dissolving nano cellulose in water, stirring in a room temperature environment until the nano cellulose is completely dispersed, introducing inert gas for gas washing, and then raising the temperature to maintain the nano cellulose water solution at 55-75 ℃;
step 2: adding a reaction monomer:
adding potassium persulfate into the nano cellulose aqueous solution obtained in the step 1 in an inert gas environment to generate free radicals, and then slowly adding monomers of hydroxyethyl acrylate and acrylamide; wherein, the molar ratio of the nanocellulose to the hydroxyethyl acrylate to the acrylamide monomer is 13: (1-9): (1-9); the addition amount of the potassium persulfate is 0.05-0.1% of the mass sum of the nano cellulose, the hydroxyl ethyl acrylate and the acrylamide;
step 3: the reaction process comprises the following steps:
keeping the temperature of the reaction system at 60-75 ℃ under the stirring state, and reacting for 1-5 h;
step 4: and (3) separating and purifying:
after the reaction of the step 3 is completed, pouring the reaction mixture into acetone to obtain a precipitate; and separating, vacuum drying and crushing the precipitate to obtain the modified nanocellulose.
6. The method according to claim 5, wherein in step 2, the molar ratio of nanocellulose, hydroxyethyl acrylate and acrylamide monomers is 13: (1-5): (5-9); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13: (2-5): (5-8); preferably, the molar ratio of the nanocellulose, the hydroxyethyl acrylate and the acrylamide monomer is 13:5:5.
7. use of a blended binder according to any of claims 1-4 for a negative electrode binder of a lithium ion battery.
8. Use of a blended binder according to claim 7 for silicon carbon negative electrode binders.
9. A lithium ion battery, characterized in that it is made of the negative electrode binder according to any of claims 7 to 8.
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