CN116445104A - Polymer binder, physical-chemical double-crosslinked conductive polymer network, and preparation method and application thereof - Google Patents

Polymer binder, physical-chemical double-crosslinked conductive polymer network, and preparation method and application thereof Download PDF

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CN116445104A
CN116445104A CN202310294534.9A CN202310294534A CN116445104A CN 116445104 A CN116445104 A CN 116445104A CN 202310294534 A CN202310294534 A CN 202310294534A CN 116445104 A CN116445104 A CN 116445104A
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polymer binder
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刘栋
张彪
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Beijing University of Chemical Technology
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    • 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
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
    • 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
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/06—Non-macromolecular additives organic
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • 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
    • 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
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
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  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a polymer binder, a physical-chemical double-crosslinked conductive polymer network, a preparation method and application thereof. The invention discloses a polymer binder and a preparation method thereof, wherein the polymer binder comprises the following components: dissolving polyacrylic acid and tannic acid in N-methyl pyrrolidone to obtain clear pale yellow solution; adding carboxyl-containing groupsStirring after the rubber to obtain suspension; filtering, evaporating, and drying. The invention further discloses a preparation method and application of the physical-chemical double-crosslinking conductive polymerization network. The invention obtains the polymer binder with high elasticity and multiple physical crosslinking rich in catechol groups through a polymer blending crosslinking process. In the electrode drying process, a brand new physical-chemical double-crosslinking three-dimensional conductive polymerization network is constructed by utilizing amidation reaction of a polymer binder and an aminated carbon nano tube, and the polymer binder has excellent mechanical property and energy dissipation capacity, so that micron silicon or SiO x The negative electrode still has excellent cycle stability at high loadings.

Description

Polymer binder, physical-chemical double-crosslinked conductive polymer network, and preparation method and application thereof
Technical Field
The invention relates to the technical field of high-capacity negative electrode materials of lithium ion batteries. More particularly, it relates to a polymer binder, a physical-chemical double cross-linked conductive polymer network, and a preparation method and application thereof.
Background
In recent years, development of lithium ion batteries with high energy density is needed for both 'life mileage anxiety' of new energy automobiles and 'low power anxiety' of 3C consumer electronic products. Silicon (Si) has been considered as a next-generation negative electrode material for realizing high-performance lithium ion batteries due to its high theoretical capacity, abundant natural reserves, and environmental friendliness. However, the volume of Si is greatly changed (about 400%) during the charge and discharge process, resulting in problems of Si particle breakage or pulverization, electrode structure collapse, and loss of electrical contact due to falling-off of the electrode material, and thus large-scale application of the silicon material is hindered. In addition, the large stresses created by the lithium silicon alloying reactions can lead to cracking and repeated formation of the Solid Electrolyte Interface (SEI), making the battery performance well below commercial standards. The development of high performance adhesives with simple synthesis processes is considered a simple and effective strategy to mitigate silicon volume expansion.
The binder serves as a bridge connecting the conductive agent and the Si particles, and plays an indispensable role in eliminating bad mechanical stress and maintaining structural integrity of the electrode during the cyclic process. However, conventional binders such as polyvinylidene fluoride (PVDF) and carboxymethyl cellulose (CMC) cannot accommodate the volume expansion of Si due to poor intermolecular interactions and brittle characteristics. Binders having groups of different polarity (hydroxyl, catechol, carboxylate and amino) may enhance the binding capacity with Si particles by covalent bonds and/or enhanced van der waals interactions. In addition, the novel adhesive with self-healing capability, host-guest interaction, multiple crosslinking and energy dissipation capability can be designed and prepared based on different polarity interactions in the adhesive. The binder is mostly applied to nano silicon cathodes, and has excellent mechanical properties and electrochemical stability; the micron silicon negative electrode is subjected to more serious stress damage in the charge-discharge process, so a brand new physical-chemical double-crosslinking conductive polymerization network needs to be designed, and the problems of the micron silicon negative electrode are solved fundamentally.
Disclosure of Invention
The invention aims to provide a polymer binder PTBR, a preparation method and application thereof, wherein the PTBR not only has excellent deformability, but also has excellent mechanical properties, and the PTBR can show stable long-cycle performance after being applied to a silicon-based negative electrode.
Another object of the present invention is to provide a physical-chemical double crosslinked conductive polymer network prepared by the above polymer binder and its application, wherein the physical-chemical double crosslinked conductive polymer network has high strength and high toughness, and can be used for silicon-based negative electrodes (micro silicon and SiO) by sliding of rubber segments and dynamic physical crosslinking formed by multiple hydrogen bonds to gradually crack and buffer larger volume expansion x Etc.) and other high capacity, high volume expansion electrode materials, to produce high energy density lithium ion batteries.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention firstly provides a preparation method of a polymer binder, which comprises the following steps:
dissolving a high molecular polymer containing carboxyl groups and tannic acid in N-methylpyrrolidone to obtain a clear pale yellow solution;
adding rubber containing carboxyl groups into the clarified light yellow solution, and stirring to obtain suspension;
and filtering, evaporating and drying the suspension to obtain the polymer binder, namely PTBR.
Further, the mass ratio of the high molecular polymer containing carboxyl groups to the tannic acid is 2:1-5:1.
Further, the mass ratio of the high molecular polymer containing carboxyl groups to the rubber containing carboxyl groups is 2:1-5:1.
Further, the high molecular polymer containing carboxyl groups is one or more of polyacrylic acid and sodium polyacrylate.
Further, the rubber containing carboxyl groups is one or more of carboxyl butadiene rubber, carboxyl styrene-butadiene rubber and carboxyl nitrile rubber.
Further, the stirring is to stir at a low temperature of 80-100 ℃ for 8-12 hours to ensure that the carboxylated nitrile rubber is fully dissolved, and then to heat to 150-160 ℃ to continue stirring for 2-3 hours.
Further, the filtration is a hot filtration, and since the carboxyl group-containing rubber is less soluble in N-methylpyrrolidone, the suspension is filtered hot, such as vacuum filtration or natural filtration, to separate undissolved carboxyl group-containing rubber.
Further, the evaporation is to remove most of N-methylpyrrolidone by rotary evaporation of the liquid obtained by filtration at 100-120 ℃.
Further, the drying is performed in vacuum drying at 100-120 ℃ until drying.
The polymer binder prepared by the preparation method is also within the protection scope of the invention.
The invention further provides a preparation method of the polymer binder for preparing a physical-chemical double-crosslinked conductive polymer network and/or lithium ion battery micron silicon and/or SiO x Application on the negative electrode.
The invention provides a preparation method of a physical-chemical double-crosslinking conductive polymerization network, which comprises the following steps:
preparing the polymer binder into a polymer binder solution, uniformly mixing the polymer binder solution with the aminated carbon nanotubes, and synthesizing the physical-chemical double-crosslinking three-dimensional conductive polymer network by means of amidation reaction of the polymer binder and the aminated carbon nanotubes in the drying process.
Further, the aminated carbon nanotube is one of an aminated single-walled carbon nanotube and an aminated multi-walled carbon nanotube.
Further, the concentration of the polymer binder solution is 20-40mg mL -1 。
Further, the mass ratio of the aminated carbon nano tube to the polymer binder is 1:1-1:2.
Further, the amidation reaction of the polymer binder and the aminated carbon nanotubes in the drying process is performed by vacuum drying at 120-180 ℃ for 2-3 hours.
The physical-chemical double-crosslinking conductive polymer network prepared by the preparation method is also within the protection scope of the invention.
The invention further provides the physical-chemical double-crosslinked conductive polymer network for preparing micron silicon and/or SiO x The application of the cathode or the lithium ion battery.
The invention provides a lithium ion battery micron silicon and/or SiO x The preparation method of the negative electrode comprises the following steps:
preparing the polymer binder into polymer binder solution, and coating the solution with slurry to obtain micrometer silicon or SiO x Mixing polymer binder solution with aminated carbon nanotube, coating on copper foil, and synthesizing physical-chemical double-crosslinked conductive polymer network micron silicon or SiO via amidation reaction between polymer binder and aminated carbon nanotube during drying x Composite electrodes, i.e. lithium ion batteries, of microsilica and/or SiO x And a negative electrode.
Further, the aminated carbon nanotube is one of an aminated single-walled carbon nanotube and an aminated multi-walled carbon nanotube.
Further, the concentration of the polymer binder solution is 20-40mg mL -1 。
Further, the mass ratio of the aminated carbon nano tube to the polymer binder is 1:1-1:2; the aminated carbon nano tube and micron silicon or SiO x The mass ratio of (2) is 1:7-1:8.
Further, the amidation reaction of the polymer binder and the aminated carbon nanotubes in the drying process is performed by vacuum drying at 120-180 ℃ for 2-3 hours.
The lithium ion battery micron silicon and/or SiO prepared by the preparation method x The negative electrode is also within the scope of the present invention.
Aiming at the problems of local concentration of the stress, unstable interface and the like of the micron silicon-based negative electrode, novel stress dissipation is introducedAnd the unit is used for constructing a totally new physical-chemical double-crosslinking conductive polymerization network. This design can provide a strong three-dimensional conductive network by chemical crosslinking; meanwhile, the formed multiple physical crosslinking increases the crosslinking degree and the bonding sites between the silicon particles, and improves the mechanical properties. The physical-chemical double-crosslinked conductive polymer network has excellent mechanical properties, so that the micron silicon-based negative electrode has the highest load (2.337 mN), hardness (0.0765 GPa), modulus (1.45 GPa) and elastic recovery (43.93%) when the indentation depth is 1000 nm. The prepared mu Si/PTBR electrode is 0.6Ag -1 With 2Ag -1 The following both showed excellent cycle performance and was found to be 1.103mg cm -2 Under Si load of 0.6Ag -1 The current density is cycled 50 times with capacity retention up to 90.3%. Application of the physical-chemical double cross-linked polymer network to SiO x The negative electrode can also achieve excellent long-cycle performance.
The beneficial effects of the invention are as follows:
the invention prepares a polymer binder (PTBR) with high elasticity and multiple physical crosslinking of catechol-rich groups through a simple polymer blending crosslinking process. PTBR and carbon-aminated nanotubes (SCNT-NH) are used in electrode drying process 2 ) Realizes the chemical crosslinking of the conductive agent and the binder by amidation reaction, and constructs a totally new physical-chemical double-crosslinked three-dimensional conductive polymer network (PTBR-SCNT-NH) 2 )。PTBR-SCNT-NH 2 Coupled with the high strength of polyacrylic acid and the high toughness of carboxylated nitrile rubber, has excellent mechanical property and energy dissipation capability, and ensures that silicon-based (micron silicon or SiO x ) The negative electrode has excellent cycling stability under high load, and can be used for preparing lithium ion batteries with high energy density.
The invention provides abundant and visual experience for designing and constructing high-efficiency stress dissipation polymer binders and conductive polymer networks to be applied to silicon-based cathodes of lithium ion batteries and other high-capacity cathodes with large volume expansion.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
FIG. 1 is a physical-chemical double crosslinked conductive polymeric network (PTBR-SCNT-NH) formed in examples 4 and 5 2 ) Is a chemical structure schematic diagram of the (c).
FIG. 2 (a) is the IR spectra of the polymer binders (PTBR, PT, PBR and TBR) prepared in example 1 and comparative examples 1-3, (b) is the IR fitting spectra of PTBR at 30, 90 and 150℃in examples 4 and 5, and (c) is the single physical/chemical double crosslinked conductive polymeric network (XNBR-SCNT-NH) in comparative examples 4-6 2 、TA-SCNT-NH 2 And PAA-SCNT-NH 2 ) High resolution N element XPS spectrum.
Fig. 3 shows mechanical properties of the polymer binders (PTBR and PT) of example 1 and comparative example 2, wherein (a) is a tensile stress-strain curve of the polymer binders (PTBR and PT) of example 1 and comparative example 2, and (b) is a stress-strain curve of the PTBR cyclic stretching experiment of example 1.
FIG. 4 shows the mechanical properties of the composite electrodes prepared in example 6 and comparative examples 1-3, wherein (a) the load-displacement curves of the electrodes in example 6 and comparative examples 1-3, and (b) and (c) are the modulus, hardness and elastic recovery calculated from the load-displacement curves, respectively.
FIG. 5 is a graph of electrochemical performance of a composite electrode half cell of example 6 and comparative examples 1-3; wherein (a), (b) and (d) are the first charge-discharge curves, 0.6Ag, of the composite electrodes of example 6 and comparative examples 1-3, respectively -1 2Ag -1 Cycling performance plot at current density, (c) is a cycling performance plot for the μsi/PTBR electrode of example 6 at different Si loads.
FIG. 6 is a graph showing electrochemical properties of half cells of the composite electrode prepared in example 7 and comparative example 7, wherein (a) is SiO x PTBR and SiO x First charge-discharge curve of/PAA, (b) is SiO x PTBR and SiO x Long cycle performance plot of PAA electrode.
Fig. 7 is an electrochemical performance graph of a full cell assembled with a ternary positive electrode for a commercial lithium battery in example 6, and (a) and (b) are respectively a charge-discharge curve and a cycle performance graph of the full cell.
Detailed Description
In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments and the accompanying drawings. Like parts in the drawings are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.
EXAMPLE 1 preparation of Polymer Binder PTBR
(1) 2.0g of polyacrylic acid and 1.0g of tannic acid are weighed and dissolved in N-methylpyrrolidone to obtain a clear light yellow solution;
(2) Adding 1.0g of carboxyl nitrile rubber (XNBR) into the clear pale yellow solution, placing the solution in an oil bath at 100 ℃ and stirring for 8 hours at low temperature, heating to 150 ℃ and stirring for 3 hours to obtain suspension;
(3) The suspension is naturally filtered while hot, subjected to rotary evaporation at 100 ℃, and then placed at 120 ℃ for vacuum drying overnight, so as to obtain the dark brown polymer binder PTBR.
EXAMPLE 2 preparation of Polymer Binder PTBR
(1) Weighing 5.0g of sodium polyacrylate and 1.0g of tannic acid to dissolve in N-methylpyrrolidone to obtain a clear light yellow solution;
(2) Adding 1.0g of carboxyl styrene-butadiene rubber into the clarified light yellow solution, placing the solution in an oil bath at 80 ℃ and stirring for 12 hours at low temperature, heating to 160 ℃ and stirring for 2 hours to obtain suspension;
(3) The suspension is naturally filtered while hot, subjected to rotary evaporation at 120 ℃, and then placed at 100 ℃ for vacuum drying overnight, so as to obtain the dark brown polymer binder PTBR.
EXAMPLE 3 preparation of Polymer Binder PTBR
(1) 2.0g of polyacrylic acid and 1.0g of tannic acid are weighed and dissolved in N-methylpyrrolidone to obtain a clear light yellow solution;
(2) Adding 0.5g of carboxyl butadiene rubber into the clear pale yellow solution, placing the solution in an oil bath at 100 ℃ and stirring for 8 hours at low temperature, heating to 150 ℃ and stirring for 3 hours to obtain suspension;
(3) The suspension is naturally filtered while hot, subjected to rotary evaporation at 100 ℃, and then placed at 120 ℃ for vacuum drying overnight, so as to obtain the dark brown polymer binder PTBR.
Example 4 preparation of a physical-chemical Dual Cross-Linked three-dimensional conductive Polymer network for micron silicon cathodes
The polymeric binder PTBR prepared in example 1 was formulated to 30mg mL -1 PTBR solution and aminated single-walled carbon nanotubes (SCNT-NH) 2 ) (PTBR and SCNT-NH) 2 The mass ratio of (2:1) is evenly mixed, and is placed at 150 ℃ for vacuum drying for 3 hours, thus synthesizing the physical-chemical double cross-linked three-dimensional conductive polymer network (PTBR-SCNT-NH) 2 ) The chemical structure of the catalyst is schematically shown in figure 1. The double-crosslinked conductive polymer network is divided into two parts, namely a three-dimensional conductive polymer network with chemical crosslinking and a stress dissipation unit formed by multiple physical crosslinking, the chemical crosslinking realizes the chemical bonding of a conductive agent and a binder by means of formed amide bonds, a firm conductive network is provided for micrometer Si particles, and the stress dissipation unit with multiple physical crosslinking can buffer severe stress generated by Si expansion through sliding of folded molecular chains in rubber and gradual splitting of graded hydrogen bonds.
Example 5 for SiO x Preparation of physical-chemical double-crosslinking three-dimensional conductive polymeric network of negative electrode
The polymeric binder PTBR prepared in example 3 was formulated to 40mg mL -1 PTBR solution and aminated multi-walled carbon nanotubes (PTBR and SCNT-NH) 2 The mass ratio of (1:1) is uniformly mixed, and vacuum drying is carried out for 2 hours at 180 ℃, so that the physical-chemical double-crosslinking three-dimensional conductive polymer network can be synthesized.
Example 6 preparation of a physical-chemical Dual crosslinked three-dimensional conductive polymeric network micro silicon composite electrode
The polymeric binder PTBR prepared in example 1 was formulated to 30mg mL -1 Adopts a slurry coating process to mix the micron silicon powder, the PTBR solution and SCNT-NH 2 (micron silica powder, PTBR and SCNT-NH) 2 The mass ratio of (1) is 7:2:1), and the mixture is coated on copper foil, and is dried for 3 hours in vacuum at 150 ℃ to synthesize a physical-chemical double-crosslinked three-dimensional conductive polymeric network micron silicon composite electrode (mu Si/PTBR), namely a lithium ion battery micron silicon negative electrode.
Example 7 physical-chemical Dual Cross-Linked three-dimensional conductive polymeric networks SiO x Preparation of composite electrode
The polymeric binder PTBR prepared in example 3 was formulated to 20mg mL -1 In (2) by a slurry coating process, siO x Powder, PTBR solution and SCNT-NH 2 (SiO x Powder, PTBR and SCNT-NH 2 The mass ratio of (1) is 8:1), and the mixture is uniformly mixed and coated on a copper foil, and is dried for 2 hours in vacuum at 180 ℃ to synthesize the physical-chemical double-crosslinked three-dimensional conductive polymeric network SiO x Composite electrode (SiO) x PTBR), i.e. lithium ion battery SiO x And a negative electrode.
Comparative example 1
(1) 2.0g of polyacrylic acid is weighed and dissolved in N-methyl pyrrolidone to obtain a clear solution;
(2) Adding 1.0g of carboxylated nitrile rubber into the clear solution, placing the solution in an oil bath at 100 ℃ and stirring for 8 hours at low temperature, heating to 150 ℃ and stirring for 3 hours to obtain suspension;
(3) Naturally filtering the suspension while the suspension is hot, rotationally evaporating at 100 ℃, and vacuum drying at 120 ℃ overnight to obtain a polymer binder PBR;
(4) PBR was formulated as 30mg mL -1 Adopts a slurry coating process to mix the micron silicon powder, the PBR solution and SCNT-NH 2 (micron silica powder, PBR and SCNT-NH) 2 The mass ratio of (2) to (1) is 7:2), and the mixture is coated on copper foil, and vacuum drying is carried out for 3 hours at 150 ℃ to synthesize the micron silicon composite electrode (mu Si/PBR).
Comparative example 2
(1) 2.0g of polyacrylic acid and 1.0g of tannic acid are weighed and dissolved in N-methylpyrrolidone to obtain a clear light yellow solution;
(2) Placing the clarified pale yellow solution in an oil bath at 100 ℃ and stirring for 8 hours at low temperature, heating to 150 ℃ and stirring for 3 hours to obtain a suspension;
(3) Naturally filtering the suspension while the suspension is hot, rotationally evaporating the suspension at 100 ℃, and vacuum drying the suspension at 120 ℃ overnight to obtain a polymer binder PT;
(4) PT was formulated as 30mg mL -1 Adopts a slurry coating process to mix the micron silicon powder, the PT solution and the SCNT-NH 2 (micron silica powder, PT and SCNT-NH) 2 The mass ratio of (1) is 7:2:1), and the mixture is evenly mixed and coatedThe mixture was spread on a copper foil and dried in vacuo at 150℃for 3 hours to synthesize a micrometer silicon composite electrode (. Mu.Si/PT).
Comparative example 3
(1) 1.0g of tannic acid is weighed and dissolved in N-methyl pyrrolidone to obtain a clear light yellow solution;
(2) Adding 1.0g of carboxylated nitrile rubber into the clarified yellowish solution, placing the solution in an oil bath at 100 ℃ and stirring for 8 hours at low temperature, heating to 150 ℃ and stirring for 3 hours to obtain suspension;
(3) Naturally filtering the suspension while the suspension is hot, rotationally evaporating the suspension at 100 ℃, and vacuum drying the suspension at 120 ℃ overnight to obtain a polymer binder TBR;
(4) TBR was formulated as 30mg mL -1 Adopts slurry coating technology to mix micron silicon powder, TBR solution and SCNT-NH 2 (micron silica powder, TBR and SCNT-NH) 2 The mass ratio of (2) to (1) is 7:2), and the mixture is coated on copper foil, and vacuum drying is carried out for 3 hours at 150 ℃ to synthesize the micron silicon composite electrode (mu Si/TBR).
Comparative example 4
(1) 1.0g of carboxylated nitrile rubber (XNBR) is weighed in N-methyl pyrrolidone and is placed in an oil bath at 100 ℃ to be stirred for 8 hours at low temperature, so as to obtain a suspension;
(2) The suspension is naturally filtered while hot to obtain a pale yellow clear solution, and 1mL of the solution is taken and dried to calculate the solid content.
(3) The pale yellow clear solution was reacted with aminated single-walled carbon nanotubes (SCNT-NH) 2 ) Uniformly mixed (XNBR and SCNT-NH) 2 The mass ratio of (B) is 2:1), and is dried in vacuum for 3 hours at 150 ℃ to obtain a chemically crosslinked three-dimensional conductive polymer network (XNBR-SCNT-NH) 2 )。
Comparative example 5
(1) 1.0g of Tannic Acid (TA) is weighed and dissolved in N-methylpyrrolidone to obtain 30mg mL -1 Clarifying the solution;
(2) Mixing the clarified solution with an aminated single-walled carbon nanotube (SCNT-NH) 2 ) (TA and SCNT-NH) 2 The mass ratio of (2:1) are evenly mixed, and are placed at 150 ℃ for vacuum drying for 3 hours to obtain a physical cross-linked three-dimensional conductive polymer network (TA-SCNT-NH) 2 )
Comparative example 6
(1) 2.0g of polyacrylic acid (PAA) was weighed out and dissolved in N-methylpyrrolidone, 30mg mL was obtained -1 Clarifying the solution;
(2) Mixing the clarified solution with an aminated single-walled carbon nanotube (SCNT-NH) 2 ) (PAA and SCNT-NH) 2 Is evenly mixed according to the mass ratio of 2:1), and is placed at 150 ℃ for vacuum drying for 3 hours to obtain the three-dimensional conductive polymer network (PAA-SCNT-NH) with chemical crosslinking 2 )。
Comparative example 7
(1) 2.0g of polyacrylic acid is weighed and dissolved in N-methyl pyrrolidone to obtain a clear solution;
(2) Placing the clarified solution in an oil bath at 80 ℃ and stirring for 12 hours at low temperature, heating to 160 ℃ and stirring for 2 hours to obtain a suspension;
(3) Naturally filtering the suspension while the suspension is hot, rotationally evaporating the suspension at 120 ℃, and vacuum drying the suspension at 100 ℃ overnight to obtain a polymer binder PAA;
(4) PAA was formulated as 30mg mL -1 The PAA solution of (2) adopts a slurry coating process to coat SiO x Powder, PAA and SCNT-NH 2 (SiO x Powder, PAA and SCNT-NH 2 The mass ratio of (1) is 8:1), and is evenly mixed and coated on copper foil, and is dried for 2 hours in vacuum at 180 ℃ to synthesize SiO x Composite electrode (SiO) x /PAA)。
The infrared spectra of the polymer binders (PTBR, PT, PBR and TBR) of example 1 and comparative examples 1-3 were examined, and the results are shown in FIG. 2 (a), with PT at 1717cm -1 Is 1720cm in PBR and the absorption peak of (C) -1 1711cm in PTBR -1 The absorption peak of (C) can be ascribed to the stretching vibration of c=o in the carboxyl group. As can be seen from the figure, the PBR was at 1720cm after introduction of TA -1 C=o absorption peak at 1711cm -1 It is shown that hydrogen bonds are formed between-OH of TA and-COOH of PBR, so that the absorption peak shifts to low wavenumbers. To further reveal the type of hydrogen bonding present in PTBR, the change in FT-IR spectra during the temperature increase of PTBR from 30℃to 150℃was employed. As can be seen from figure 2 (b), the C=O deformation vibration region at room temperature can be divided into 1595, 1647 and 1735cm by infrared peak-splitting fitting -1 Three peaks at 1647 and 1735cm -1 The c=o characteristic peak at corresponds to c=o in PAA/XNBR and TA formed of catechol groups hydrogen bonding (c=o····h-O-Ph, I). In addition, 1647 and 1735cm -1 The c=o characteristic peak at this point gradually shifted to higher wavenumbers with increasing temperature, indicating that c=o··h-O-Ph gradually breaks. And at 150℃at 1653 and 1743cm -1 The characteristic peaks of (a) can be respectively attributed to intramolecular hydrogen bonds (C=O.H-OOC, II) of carboxyl groups per se and free C=O exposed by cleavage of C=O.H-O-Ph in the PAA/XNBR. Thus, the polymeric binder PTBR has physical crosslinks with multiple hydrogen bond formation, at normal temperature, predominantly c=o··h-O-Ph, and as the temperature increases, this type of hydrogen bond breaks, gradually changing to predominantly intramolecular hydrogen bonds (c=o·h-OOC) and free c=o.
Single physical/chemical double crosslinked conductive polymeric network (XNBR-SCNT-NH) in comparative examples 4-6 was examined 2 、TA-SCNT-NH 2 And PAA-SCNT-NH 2 ) The interaction between the conductive agent and the binder was evaluated based on the photoelectron spectrum, and the result is shown in fig. 2 (c). As can be seen from the figure, XNBR-SCNT-NH 2 And PAA-SCNT-NH 2 The characteristic peak of O=C-N appears at 401.8eV in the crosslinked network of (C), which indicates that the-COOH group of PAA/XNBR and SCNT-NH 2 Of (2) NH 2 Amidation reaction between groups occurs at 150C, but due to the incompleteness of the reaction, A hydrogen bond (C=O. Cndot. H-NH-Ph) is also present in the complex. In addition, SCNT-NH 2 After mixing with TA, SCNT-NH 2 The only C-N peak in the (C) is shifted to a higher binding energy, indicating the presence of hydrogen bonds (Ph-OH. Cndot. H-NH-Ph) between the two. In summary, PTBR-SCNT-NH in examples 4-5 2 Chemical crosslinking and physical crosslinking exist, so that the polymer is a novel physical-chemical double-crosslinking three-dimensional conductive polymer network.
The results of examining the mechanical properties of the polymer binders (PTBR and PT) in example 1 and comparative example 2 are shown in FIG. 3. The tensile stress-strain curves of the polymer binders (PTBR and PT) of example 1 and comparative example 2 are shown in fig. 3 (a), and it can be seen that the stress-strain curve of the PTBR spline is a non-hook type curve, the young's modulus thereof is 5.7MPa, the strain before fracture can reach more than 560%, indicating that the PTBR has higher strength and good toughness, and its higher strain can fully withstand the nearly-400% volume change of the silicon negative electrode during the cycling. In contrast, PT splines have a hook stress-strain curve with a strain at break of only 8.2% and a large young's modulus (17 MPa), indicating a high PT friability. In addition, the invention independently performs a cyclic tensile test on PTBR splines, and further explores the energy dissipation capacity through the change of a sample hysteresis curve. The stress-strain curve of the PTBR loop tensile test of example 1 is shown in FIG. 3 (b), which shows that PTBR retains 65% strain after undergoing the first load-unload cycle. After 15min of rest, the subsequent load-unload cycle test was performed, and it can be seen that the samples exhibited a significant hysteresis, indicating a slight reduction in energy dissipation capacity, and a residual strain of up to 93.8% compared to the strain after the first cycle, indicating good recovery capacity and energy dissipation capacity in the subsequent cycles.
The mechanical properties of the composite electrodes of example 6 and comparative examples 1 to 3 were examined, and the results are shown in FIG. 4, in which (a), (b) and (c) in FIG. 4 are load-displacement curves, modulus, hardness and elastic recovery graphs of the composite electrodes (μSi/PTBR, μSi/PBR, μSi/PT and μSi/TBR), respectively. As can be seen from FIG. 4 (a), the μSi/PTBR electrode exhibited the highest load (2.337 mN) at a controlled indentation depth of 1000nm, significantly higher than the μSi/PT (1.048 mN), μSi/TBR (1.213 mN) and μSi/PBR electrodes (0.822 mN), indicating that the μSi/PTBR had the strongest stress tolerance. In addition, the modulus and hardness of the μSi/PTBR in FIGS. 4 (b) and (c) are 1.4507GPa and 0.0765GPa, respectively, which are higher than those of the other composite electrodes, again indicating that the μSi/PTBR has the strongest deformation resistance. The indentation depth after removal of the load from 1011.01nm to 566.91nm corresponds to an elastic recovery of 43.93%, whereas the elastic recovery of the μSi/PT, μSi/TBR and μSi/PBR electrodes were 27.56%, 34.97% and 31.18%, respectively. The μsi/PTBR has the highest elastic recovery, consistent with its higher strain results in fig. 3 (a), which is beneficial to withstand the huge stresses generated during the micron silicon negative cycle, thus maintaining the electrode integrity.
Detection of the composite electrode halves in example 6, example 7, comparative examples 1-3 and comparative example 7The electrochemical properties of the cells are shown in FIGS. 5 and 6, wherein (a), (b) and (d) in FIG. 5 are the initial charge-discharge curves of the composite electrode μSi/PTBR in example 6 and the composite electrodes (μSi/PBR, μSi/PT and μSi/TBR, respectively) in comparative examples 1 to 3, respectively, 0.6A g -1 2A g -1 As can be seen from FIG. 5 (a), the cycle performance at current density is shown for mu Si/PTBR at 100mA g -1 The lower part is 3807.2mAh g -1 And is higher than mu Si/PT (3197 mAh g -1 )、μSi/PBR(3474.9mAh g -1 ) And mu Si/TBR (3542.9 mAh g -1 ). The mu Si/PTBR electrode in FIG. 5 (b) is at 0.6A g -1 After 50 times of lower circulation, the specific discharge capacity is 3449mAh g -1 Decaying to 3173.6mAh g -1 Corresponding to a capacity retention of 92%. In contrast, the μSi/PT electrode was measured from 3105.1mAh g under the same conditions -1 Decaying to 2756.2mAh g -1 The capacity retention rate is 88.76%; the specific discharge capacity of mu Si/PBR is 2840.1mAh g -1 Decaying to 2336.5mAh g -1 The capacity retention was-82.2%. When the test current rises to 2.0Ag -1 When, as shown in FIG. 5 (d), the μSi/PTBR still exhibited the optimal electrochemical performance, and the discharge capacity was measured from 2027mAh g at the 19 th cycle -1 After 180 cycles, only the attenuation is 1968mAh g -1 (cycle 200) with capacity retention up to 97%, whereas μSi/PT remains only 1220.3mAh g after 160 cycles under this condition -1 The capacity retention was only 59.67%. In addition, the mu Si/PBR and mu Si/TBR electrodes are at 2.0Ag -1 Lower capacity fade is severe and cycling performance is poor. FIG. 5 (c) is a graph showing the cycle performance of the composite electrode μSi/PTBR of example 6 under various Si loads, wherein the Si loading is 0.675mg cm -2 When mu Si/PTBR is 0.6A g -1 The area capacity is maintained to be 2.0mAh cm after 50 times of circulation -2 Has excellent cycle stability. Si loading was increased to 1.103mg cm -2 The initial area capacity of the electrode was 3.265mAh cm -2 The circulation time is reduced to 2.949mAh cm for 50 times -2 The capacity retention was about 90.3%; further increase Si loading to 1.438mg cm -2 When the circulation stability of the. Mu. Si/PTBR is reduced, however, it isThe area capacity can still be kept at 3.6mAh cm after 50 cycles -2 . FIG. 6 (a) shows the composite electrode SiOx/PTBR of example 7 and the composite electrode SiO of comparative example 7 x First charge-discharge curve of/PAA, as can be seen from the figure, siO x The specific capacity of the PTBR for the first discharge can reach 2450.4mAh g -1 The first coulomb efficiency is 68.8%, which is obviously better than SiO x Electrochemical performance of PAA. In FIG. 6 (b) is SiO x PTBR and SiO x Long cycle performance of the PAA electrode, from which it can be seen that SiO x PTBR at 1.5A g -1 After 1000 cycles, the capacity loss per cycle is about 0.012% (from 25 th cycle to 1000 cycles); and SiO x The capacity retention of the/PAA electrode after 1000 cycles was only 41.04%, the capacity loss per cycle was about 0.059%, and the rate of capacity decay was SiO x 5 times that of PTBR.
The electrochemical performance of the assembled full cell (NCM 811// μSi/PTBR) of ternary positive electrode of commercial lithium battery in example 6 was examined, and the results are shown in FIG. 7, wherein (a) and (b) in FIG. 7 are respectively a charge-discharge curve and a cycle performance chart of the full cell, and it can be seen from the graph that NCM811// μSi/PTBR is 20mAg -1 And 40mA g -1 Exhibits a similar specific discharge capacity (197 mAh g -1 ) The battery was charged at 40mA g -1 The capacity retention rate after 50 cycles of current density was 88.4%, indicating good full cell cycling stability. In conclusion, the NCM811// mu Si/PTBR full battery has excellent capacity output and cycle stability, and the physical-chemical double-crosslinked conductive polymer network is proved to be applicable to the research of commercial high-performance lithium ion batteries, and has extremely high practical value.
It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (10)

1. A method of preparing a polymeric binder comprising the steps of:
dissolving a high molecular polymer containing carboxyl groups and tannic acid in N-methylpyrrolidone to obtain a clear pale yellow solution;
adding rubber containing carboxyl groups into the clarified light yellow solution, and stirring to obtain suspension;
and filtering, evaporating and drying the suspension to obtain the polymer binder.
2. The preparation method according to claim 1, wherein the mass ratio of the high molecular polymer containing carboxyl groups to tannic acid is 2:1-5:1; preferably, the mass ratio of the high molecular polymer containing carboxyl groups to the rubber containing carboxyl groups is 2:1-5:1; more preferably, the high molecular polymer containing carboxyl groups is one or more of polyacrylic acid and sodium polyacrylate; more preferably, the rubber containing carboxyl groups is one or more of carboxyl butadiene rubber, carboxyl styrene-butadiene rubber and carboxyl nitrile rubber.
3. The preparation method according to claim 1, wherein the stirring is carried out for 8-12 hours at a low temperature of 80-100 ℃, and then the temperature is raised to 150-160 ℃ and stirring is continued for 2-3 hours;
preferably, the evaporation is rotary evaporation at 100-120 ℃ of the liquid obtained by filtration;
more preferably, the drying is from 100 to 120 ℃ vacuum drying to drying.
4. A polymer binder prepared by the preparation method of any one of claims 1 to 3.
5. The polymer binder of claim 4 for preparing physical-chemical double cross-linked conductive polymer network and/or lithium ion battery micron silicon and/or SiO x Application on the negative electrode.
6. The preparation method of the physical-chemical double-crosslinking conductive polymerization network is characterized by comprising the following steps of:
the polymer binder of claim 4 is prepared into a polymer binder solution, and after the polymer binder solution is uniformly mixed with the aminated carbon nanotubes, the physical-chemical double-crosslinked three-dimensional conductive polymer network is synthesized by means of amidation reaction of the polymer binder and the aminated carbon nanotubes.
7. The physical-chemical double-crosslinking conductive polymer network prepared by the preparation method of claim 6.
8. The physical-chemical double cross-linked conductive polymer network of claim 7 in the preparation of micron silicon and/or SiO x The application of the cathode or the lithium ion battery.
9. Lithium ion battery micron silicon and/or SiO x The preparation method of the negative electrode is characterized by comprising the following steps:
the polymer binder of claim 4 is prepared into a polymer binder solution, and the micrometer silicon or SiO is coated by a slurry coating process x Mixing polymer binder solution with aminated carbon nanotube, coating on copper foil, and synthesizing physical-chemical double-crosslinked conductive polymer network micron silicon or SiO via amidation reaction between polymer binder and aminated carbon nanotube during drying x Composite electrodes, i.e. lithium ion batteries, of microsilica or SiO x And a negative electrode.
10. The method according to claim 6 or 9, wherein the aminated carbon nanotube is one of an aminated single-walled carbon nanotube and an aminated multi-walled carbon nanotube;
preferably, the concentration of the polymer binder solution is 20-40mg mL -1 ；
More preferably, the mass ratio of the aminated carbon nano tube to the polymer binder is 1:1-1:2; the aminated carbon nano tube and the micronSilicon or SiO x The mass ratio of (2) is 1:7-1:8;
most preferably, the amidation reaction of the polymer binder with the aminated carbon nanotubes by means of the drying process is vacuum-dried at 120-180℃for 2-3 hours.
CN202310294534.9A 2023-03-23 2023-03-23 Polymer binder, physical-chemical double-crosslinked conductive polymer network, and preparation method and application thereof Pending CN116445104A (en)

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