CN116914146A - Supermolecule composite binder for silicon-based negative electrode of lithium ion battery and preparation method and application thereof - Google Patents
Supermolecule composite binder for silicon-based negative electrode of lithium ion battery and preparation method and application thereof Download PDFInfo
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- CN116914146A CN116914146A CN202311039589.1A CN202311039589A CN116914146A CN 116914146 A CN116914146 A CN 116914146A CN 202311039589 A CN202311039589 A CN 202311039589A CN 116914146 A CN116914146 A CN 116914146A
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- 239000011230 binding agent Substances 0.000 title claims abstract description 37
- 239000002131 composite material Substances 0.000 title claims abstract description 34
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 24
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 20
- 239000010703 silicon Substances 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 230000001070 adhesive effect Effects 0.000 claims abstract description 16
- 239000000853 adhesive Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 11
- 229920002125 Sokalan® Polymers 0.000 claims description 23
- 239000004584 polyacrylic acid Substances 0.000 claims description 23
- 238000003756 stirring Methods 0.000 claims description 14
- TUSDEZXZIZRFGC-UHFFFAOYSA-N 1-O-galloyl-3,6-(R)-HHDP-beta-D-glucose Natural products OC1C(O2)COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC1C(O)C2OC(=O)C1=CC(O)=C(O)C(O)=C1 TUSDEZXZIZRFGC-UHFFFAOYSA-N 0.000 claims description 13
- 239000001263 FEMA 3042 Substances 0.000 claims description 13
- LRBQNJMCXXYXIU-PPKXGCFTSA-N Penta-digallate-beta-D-glucose Natural products OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-PPKXGCFTSA-N 0.000 claims description 13
- AGBQKNBQESQNJD-UHFFFAOYSA-M lipoate Chemical compound [O-]C(=O)CCCCC1CCSS1 AGBQKNBQESQNJD-UHFFFAOYSA-M 0.000 claims description 13
- 235000019136 lipoic acid Nutrition 0.000 claims description 13
- LRBQNJMCXXYXIU-NRMVVENXSA-N tannic acid Chemical compound OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-NRMVVENXSA-N 0.000 claims description 13
- 229940033123 tannic acid Drugs 0.000 claims description 13
- 235000015523 tannic acid Nutrition 0.000 claims description 13
- 229920002258 tannic acid Polymers 0.000 claims description 13
- 229960002663 thioctic acid Drugs 0.000 claims description 13
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000004132 cross linking Methods 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 239000006258 conductive agent Substances 0.000 claims description 9
- 239000011267 electrode slurry Substances 0.000 claims description 9
- 238000001291 vacuum drying Methods 0.000 claims description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 239000013543 active substance Substances 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 5
- 239000011259 mixed solution Substances 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 239000011149 active material Substances 0.000 claims description 2
- 239000007773 negative electrode material Substances 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 5
- 239000010405 anode material Substances 0.000 abstract description 5
- 229910052744 lithium Inorganic materials 0.000 abstract description 5
- 230000008569 process Effects 0.000 abstract description 5
- 238000007599 discharging Methods 0.000 abstract description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 229910013872 LiPF Inorganic materials 0.000 description 3
- 101150058243 Lipf gene Proteins 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- YCIMNLLNPGFGHC-UHFFFAOYSA-N catechol Chemical compound OC1=CC=CC=C1O YCIMNLLNPGFGHC-UHFFFAOYSA-N 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000003760 magnetic stirring Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000007342 radical addition reaction Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012620 biological material Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000035876 healing Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 150000008442 polyphenolic compounds Chemical class 0.000 description 1
- 235000013824 polyphenols Nutrition 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- WQGWDDDVZFFDIG-UHFFFAOYSA-N pyrogallyl group Chemical group C1(=C(C(=CC=C1)O)O)O WQGWDDDVZFFDIG-UHFFFAOYSA-N 0.000 description 1
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 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
-
- 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
- H01M4/134—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
- 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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- 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 belongs to the technical field of lithium batteries, and discloses a supermolecule composite binder for a silicon-based negative electrode of a lithium ion battery, and a preparation method and application thereof. The adhesive has the advantages of good dispersibility, self-healing property, strong adhesion and the like, and can effectively inhibit SiO in the process of charging and discharging electrodes x Volume expansion of the anode material to cause SiO x The negative electrode exhibits good cycle stability. The adhesive has the advantages of simple preparation process and low cost, and the adhesive prepared by the method obviously improves the electrochemical performance of the silicon-based negative electrode of the lithium ion battery.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a supermolecule composite binder for a silicon-based negative electrode of a lithium ion battery, and a preparation method and application thereof.
Background
The lithium ion battery has the advantages of high capacity, no memory effect, quick reversible charge and discharge, high coulombic efficiency and the like. Lithium ion batteries are widely used in commercial products such as mobile phones, notebook computers, digital cameras, new energy automobiles, and the like. Silicon is considered as the most promising new generation of negative electrode materials in lithium ion battery applications, with theoretical specification capacities up to 4200mAh/g, far exceeding the unit capacities of 372mAh/g of commercial graphite. However, commercialization of silicon-based anode materials is severely hampered due to the large volume change (about 300%). SiO with better cycle performance x (0<x<2) The material is a hot spot of current research, but the non-negligible volume change (100-200%) still faces the defects of rapid decay of battery capacity, poor rate capability and the like.
At present solve SiO x The volume expansion problem of the cathode mainly comprises methods of nanocrystallization, structuring, compounding and the like, and the commercialization is difficult to realize due to complex synthesis process, complicated steps and high cost. Through research investigation, the optimization of the binder is to solve SiO x One of the most cost-effective methods for anode volume expansion problems is due to its combination with SiO x The weak van der Waals interactions between the material and the copper current collector make conventional polyvinylidene fluoride binders difficult to withstand SiO x Stresses resulting from volumetric expansion of particles during cycling are not applicable to SiO x And a negative electrode. In recent years, researchers have made great efforts in designing and preparing silicon-based binders to enhance SiO by synthesizing high-performance composite binders x Electrochemical performance of the negative electrode.
Disclosure of Invention
The invention aims to solve the defects and the shortcomings of the prior art, and the primary aim is to provide a supermolecule composite binder for a silicon-based negative electrode of a lithium ion battery. The adhesive has good dispersibility and self-adhesionHas the advantages of strong healing property and cohesiveness, and the like, and can effectively inhibit SiO in the process of charging and discharging electrodes x Volume expansion of the anode material to cause SiO x The negative electrode exhibits good cycle stability.
The invention also aims to provide a preparation method of the supermolecule composite binder for the silicon-based negative electrode of the lithium ion battery. The adhesive is prepared by heating lipoic acid to initiate ring-opening polymerization to form linear polythiooctanoic acid, then carrying out polyphenol-sulfur radical addition reaction with tannic acid, and then carrying out hydrogen bond crosslinking with polyacrylic acid to synthesize the supermolecule composite adhesive. The adhesive prepared by the method obviously improves the electrochemical performance of the silicon-based negative electrode of the lithium ion battery. In addition, the adhesive has simple preparation process and low cost.
It is still another object of the present invention to provide the use of the above-described supramolecular composite binders for silicon-based cathodes of lithium ion batteries.
The aim of the invention is achieved by the following technical scheme:
a supermolecule composite binder for silicon-based negative electrode of lithium ion battery is prepared through heating lipoic acid at 120-150 deg.C, stirring, adding tannic acid for cross-linking reaction, cooling, and adding polyacrylic acid solution.
Preferably, the mass ratio of the lipoic acid to the tannic acid to the polyacrylic acid in the polyacrylic acid solution is 1 (0.04-0.12) to 4-11.
Preferably, the solvent in the polyacrylic acid solution is N-methyl pyrrolidone; the mass ratio of the polyacrylic acid to the N-methyl pyrrolidone is 1 (9-19); the molecular weight of the polyacrylic acid is 24-300 ten thousand.
Preferably, the time of the crosslinking reaction is 0.5 to 2 hours.
The preparation method of the supermolecule composite binder for the silicon-based negative electrode of the lithium ion battery comprises the following steps:
s1, heating and stirring lipoic acid at 120-150 ℃, then adding tannic acid to carry out a crosslinking reaction, and cooling at room temperature to obtain a mixed solution;
s2, adding the polyacrylic acid solution into the mixed solution, and uniformly stirring to obtain the supermolecule composite adhesive.
A negative electrode comprising an active material SiO x Mixing the conductive agent with the supermolecule composite binder according to any one of claims 1-4, adding N-methyl pyrrolidone, stirring to obtain uniformly dispersed electrode slurry, coating the electrode slurry on copper foil, and vacuum drying.
Preferably, the conductive agent is conductive carbon black, carbon nanotubes, super conductive carbon black or conductive graphite; the active substance SiO x The mass ratio of the conductive agent to the supermolecule composite binder is (7-8): 1-2): 1.
Preferably, the stirring time is 6-8h, the temperature of the vacuum drying is 100-120 ℃, and the time of the vacuum drying is 12-36 h.
The negative electrode is applied to a lithium ion battery.
Preferably, the anode material of the lithium ion battery is SiO x ，0<x<2。
The tannic acid is a common plant polyphenol, has rich catechol and pyrogallol groups, and has good biocompatibility and strong cohesiveness; lipoic acid is a biological molecule with a specific structure, comprising two types of dynamic bonds: dynamic covalent disulfide bonds in five-membered rings and non-covalent hydrogen bonds of carboxyl groups; polyacrylic acid is of a linear structure with rich carboxyl groups, and has good adhesive property; the supermolecule composite adhesive realizes high-efficiency bonding effect by utilizing non-covalent interactions among molecules, such as hydrogen bonds, van der Waals forces, ionic interactions and the like. Based on the above, the supermolecule composite binder is synthesized by the addition reaction of the lipoic acid and tannic acid with polyphenol-sulfur radical free radicals and then hydrogen bond crosslinking with polyacrylic acid. The mechanical strength of the adhesive is improved by modifying the modified supermolecule composite adhesive with biological materials, so that the cycling stability of the silicon-based negative electrode is realized.
The invention uses active substance SiO x Conductive agent (conductive carbon black, carbon nanotube, and specific conductivity)Carbon black or conductive graphite) and a binder according to the mass ratio of (7-8) (1-2) (1), adding a proper amount of N-methyl pyrrolidone, mixing and stirring for 6-8 hours to obtain uniformly dispersed slurry, coating the obtained slurry on a copper foil, and vacuum drying at 120 ℃ for 12 hours, and then cutting into round pole pieces with the diameter of 12 mm. And transferring the dried pole piece into a glove box filled with argon gas for battery assembly. Wherein the lithium sheet in the battery is used as a counter electrode, and 1.0mmol/L LiPF is used as electrolyte 6 As solutes, solvents were EC and DEC in a volume ratio of 1:1, with 10wt% fec and 1wt% vc as additives, assembled using CR2032 button cell.
Compared with the prior art, the invention has the following beneficial effects:
1. the supermolecule composite binder is prepared by carrying out a polyphenol-sulfur radical addition reaction on natural biological micromolecule lipoic acid and tannic acid under the condition of no solvent and then carrying out hydrogen bond crosslinking on the natural biological micromolecule lipoic acid and tannic acid, has a three-dimensional network structure, is favorable for the transmission of electrons and ions, and greatly improves the mechanical property of the binder, so that the electrode keeps good integrity in the circulating process.
2. The supermolecule composite binder and SiO of the invention x The particles have rich binding sites, so that the binder is bonded with SiO x The particles have stronger interfacial bonding capability, siO x The negative electrode can better bear the volume change during the charge and discharge of the electrode, so the SiO adopting the binder is based on good binding capacity and mechanical strength x The negative electrode realizes stable long-cycle performance.
3. The polythiooctanoic acid of the supermolecule composite adhesive contains reversible dynamic covalent disulfide bonds, can be reformed after fracture, is a three-dimensional network structure constructed by hydrogen bond crosslinking, can furthest improve the self-healing property of the adhesive, and can effectively inhibit SiO in the electrode charging and discharging process x Volume expansion of the anode material to cause SiO x The negative electrode exhibits good cycle stability.
Drawings
Fig. 1 is a cycle performance chart of the button cell prepared in application example 1.
Fig. 2 is a graph showing the cycle performance of the button cell prepared in application example 1 and comparative example 1.
Detailed Description
The present invention is further illustrated below in conjunction with specific examples, but should not be construed as limiting the invention. The technical means used in the examples are conventional means well known to those skilled in the art unless otherwise indicated. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.
Example 1
1.25g of lipoic acid was added to a three-necked flask while introducing nitrogen to remove oxygen. After heating to 150 ℃, magnetic stirring was started, followed by a further reaction for 10min to obtain a yellow transparent liquid, and 0.05g of tannic acid was added to crosslink for 0.5h, and then the liquid mixture was poured into a glass dish and cooled to room temperature. Adding 5% of polyacrylic acid (with the molecular weight of 24-300 ten thousand) into the mixture, and stirring for 1h, wherein the mass ratio of the mixed liquid to the polyacrylic acid in the polyacrylic acid N-methylpyrrolidone solution is 1:8, so as to obtain the supermolecule composite binder (PLT).
Example 2
4g of lipoic acid was added to a three-necked flask while introducing nitrogen to remove oxygen. After heating to 120 ℃, magnetic stirring was started, followed by a further reaction for 10min to obtain a yellow transparent liquid, and 0.24g of tannic acid was added for crosslinking reaction for 1h, and then the liquid mixture was poured into a glass dish and cooled to room temperature. Adding 5% of polyacrylic acid (with the molecular weight of 24-300 ten thousand) into the mixture, and stirring for 1h, wherein the mass ratio of the mixed liquid to the polyacrylic acid in the polyacrylic acid N-methylpyrrolidone solution is 1:6, so as to obtain the supermolecule composite binder (PLT).
Application example 1
1. To active substance SiO x Mixing the conductive agent Super P and the supermolecule composite binder solution prepared in the embodiment 1 according to the mass ratio of 7:2:1, adding a proper amount of N-methyl pyrrolidone, then placing the mixture into a defoaming stirrer for stirring to obtain uniformly dispersed electrode slurry, and mixing the uniformly dispersed electrode slurry with the N-methyl pyrrolidoneThe electrode slurry is coated on copper foil, dried in vacuum at 120 ℃ for 12 hours, and cut into round negative electrode plates with the diameter of 12 mm.
2. Transferring the dried negative electrode plate into a glove box filled with argon, taking a lithium plate as a counter electrode, and using LiPF with solute of 1.0mmol/L as electrolyte 6 The solvents were Ethylene Carbonate (EC) EC and diethyl carbonate (DEC) in a volume ratio of 1:1, with 10wt% fluoroethylene carbonate (FEC) and 1wt% ethylene carbonate (VC) as additives. Assembled using CR2032 button cell, the assembled button cell was left to stand for 10h. And carrying out constant current test on the electrochemical performance of the static battery in a Xinwei test system.
FIG. 1 is a graph showing the cycle performance of a button cell prepared in accordance with application example 1. As can be seen from FIG. 1, siO is composed of a supermolecule composite binder (PLT) x The electrode has a specific capacity of 1900mAh/g or more for the first discharge under a current density of 400mA/g, a coulombic efficiency of 60% or more for the first discharge, and the capacity of 1055mAh/g after 200 cycles, and the electrode shows excellent cycle stability.
Comparative example 1
1. 0.5g of polyacrylic acid powder having a molecular weight of 45W was added to 9.5g of N-methylpyrrolidone to obtain a 5% by mass of a binder.
2. To active substance SiO x Mixing the conductive agent supplier P and 5% of binder according to the mass ratio of 7:2:1, adding a proper amount of N-methyl pyrrolidone, mixing and stirring for 6-8 hours to obtain uniformly dispersed electrode slurry, coating the electrode slurry on a copper foil, vacuum-drying at 120 ℃ for 12 hours, and cutting into round pole pieces with the diameter of 12 mm.
3. And transferring the pole piece into a glove box filled with argon gas for battery assembly. Lithium sheet in battery as counter electrode, electrolyte with LiPF of 1.0mmol/L 6 As solutes, ethylene Carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 were used as solvents, wherein 10wt% fluoroethylene carbonate (FEC) and 1wt% ethylene carbonate (VC) were used as additives for assembly with a CR2032 button cell.
The CR2032 coin cells assembled in application example 1 and comparative example 1 were allowed to stand at 28 ℃ for 10 hours, and then subjected to constant current test for electrochemical performance in a new power test system. MeasuringThe test conditions are as follows: the current density is 400mA/g; the voltage window is 0.01-1.5V. Fig. 2 is a graph showing the cycle performance of the CR2032 button cell prepared in application example 1 and comparative example 1. As shown in FIG. 2, the button cell prepared in comparative example 1 had a capacity fade of 922mAh/g after 100 cycles at a current density of 400mA/g, and the button cell prepared in application example 1 had a capacity kept at 1065mAh/g, and had a higher discharge capacity and a better cycle stability, and the supramolecular composite binder (PLT) enabled SiO x The negative electrode exhibits good cycle stability.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. The supermolecule composite binder for the silicon-based negative electrode of the lithium ion battery is characterized in that the supermolecule composite binder is abbreviated as PLT, lipoic acid is heated and stirred at 120-150 ℃, tannic acid is added to carry out crosslinking reaction, and the obtained mixed solution is cooled at room temperature and then added with polyacrylic acid solution to be compounded.
2. The supermolecule composite binder for the silicon-based negative electrode of the lithium ion battery according to claim 1, wherein the mass ratio of the lipoic acid, the tannic acid and the polyacrylic acid solution is 1 (0.04-0.12): 4-11.
3. The supramolecular composite binder for silicon-based negative electrodes of lithium ion batteries according to claim 1, wherein the solvent in the polyacrylic acid solution is N-methylpyrrolidone; the mass ratio of the polyacrylic acid to the N-methyl pyrrolidone is 1 (9-19); the molecular weight of the polyacrylic acid is 24-300 ten thousand.
4. The supramolecular composite binder for silicon-based negative electrode of lithium ion battery according to claim 1, wherein the time of the crosslinking reaction is 0.5-2 h.
5. The method for preparing the supramolecular composite binder for silicon-based negative electrode of lithium ion battery according to any one of claims 1 to 4, comprising the steps of:
s1, heating and stirring lipoic acid at 120-150 ℃, then adding tannic acid to carry out a crosslinking reaction, and cooling at room temperature to obtain a mixed solution;
s2, adding the polyacrylic acid solution into the mixed solution, and uniformly stirring to obtain the supermolecule composite adhesive.
6. A negative electrode comprising an active material SiO x Mixing the conductive agent with the supermolecule composite binder according to any one of claims 1-4, adding N-methyl pyrrolidone, stirring to obtain uniformly dispersed electrode slurry, coating the electrode slurry on copper foil, and vacuum drying.
7. The negative electrode according to claim 6, wherein the conductive agent is conductive carbon black, carbon nanotubes, extra conductive carbon black or conductive graphite; the active substance SiO x The mass ratio of the conductive agent to the supermolecule composite binder is (7-8): 1-2): 1.
8. The negative electrode according to claim 6, wherein the stirring time is 6 to 8 hours, the vacuum drying temperature is 100 to 120 ℃, and the vacuum drying time is 12 to 36 hours.
9. Use of the negative electrode of any one of claims 6-8 in a lithium ion battery.
10. The use of the negative electrode according to claim 9 in a lithium ion battery, wherein the negative electrode material of the lithium ion battery is SiO x ，0<x<2。
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