CN114220973A - Adhesive, preparation method and application thereof - Google Patents
Adhesive, preparation method and application thereof Download PDFInfo
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- CN114220973A CN114220973A CN202111531865.7A CN202111531865A CN114220973A CN 114220973 A CN114220973 A CN 114220973A CN 202111531865 A CN202111531865 A CN 202111531865A CN 114220973 A CN114220973 A CN 114220973A
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- polyvinyl alcohol
- sulfonic acid
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- 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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Abstract
The invention provides a binder and a preparation method and application thereof. Raw materials for preparing the binder comprise polyvinyl alcohol and polyfunctional group sulfonic acid; the mass ratio of the polyvinyl alcohol to the polyfunctional group sulfonic acid is 20 (1-6). The preparation method comprises the following steps: (1) mixing polyfunctional group sulfonic acid with a solvent to obtain polyfunctional group sulfonic acid solution; mixing polyvinyl alcohol with a solvent to obtain a polyvinyl alcohol solution; (2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution, and carrying out a crosslinking reaction to obtain the binder. The binder provided by the invention has better toughness and better electrical property, and is suitable for preparing a silicon cathode lithium ion battery.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a binder and a preparation method and application thereof.
Background
An effective energy storage system is needed in the current society, and a lithium ion battery is one of the most concerned energy storage devices at present and is mainly applied to the fields of electric automobiles, smart phones, tablet computers and the like. The performance of the electrode material is critical to the performance of the lithium ion battery, wherein the binder is used for binding the conductive agent particles and the active material and binding them on the surface of the metal current collector, and the performance of the binder is closely related to the cycle performance of the battery. If the performance of the binder is not good, the electrode is easy to be pulverized in the electrochemical circulation process, so that the electrode material falls off from the surface of the current collector, and the electrochemical energy storage performance is lost, so that the development of the high-performance binder is an important aspect of the performance of the high-lithium ion battery.
CN110336037A discloses an aqueous binder for a negative electrode material of a lithium ion battery and a preparation method thereof. The water-based binder comprises the following components in percentage by volume: the polyvinyl alcohol solution, the polydopamine solution and the PEDOT/PSS aqueous solution in a volume ratio of 25:5: 2-5; the preparation method comprises the following steps: and uniformly mixing the polyvinyl alcohol solution, the polydopamine solution and the PEDOT/PSS aqueous solution in proportion to obtain the water-based binder. The adhesive provided by the technical scheme has good adhesion, but poor toughness.
CN109273717A discloses a modified binder for a silicon-based negative electrode of a lithium ion battery and a preparation method of a battery containing the binder. The negative electrode modified binder comprises the following components in percentage by weight: 15-35% of a binder, 5-20% of graphene quantum dots GQDs and 50-70% of deionized water; the pH value of the mixed solution composed of the components is 4.5-8.5, and the viscosity of the mixed solution is 5-55 mPa & S; the preparation method comprises the following steps: firstly dispersing graphene quantum dots GQDs in deionized water, stirring at room temperature for 1-4 h to completely dissolve the graphene quantum dots GQDs uniformly, and marking as a solution A; adding deionized water into a dispersion pot, heating to 60-90 ℃, adding the binder under stirring, adding the solution A after the binder is uniformly dispersed, continuously stirring for 4 hours, and cooling to room temperature to obtain the cathode modified binder; the binder is selected from one or a mixture of any more of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), Polytetrafluoroethylene (PTFE), Polyimide (PI), polyvinyl alcohol (PVA) and Polyacrylonitrile (PAN). The negative electrode modified binder prepared by the technical scheme has good elasticity and swelling performance, but has poor toughness, so that the lithium ion battery prepared by the technical scheme has poor electrical properties.
CN101393985A discloses a battery negative electrode material, a preparation method and a battery made of the negative electrode material. The battery negative electrode material comprises a carbonaceous negative electrode active material, a conductive agent, a thickening agent, a binder and a solvent, wherein the carbonaceous negative electrode active material comprises the following components in parts by weight: conductive agent: thickening agent: adhesive: the solvent is 110-140: 1-10: 80-200, wherein the carbonaceous negative active material is a mixture of natural graphite and artificial graphite in a ratio of 10: 1-4; the binder is PTFE, HPMC, SBR, PVA or PEO. The toughness of the binder in the technical scheme is poor.
Polyvinyl alcohol (PVA) is used as a silicon negative electrode material binder because of its advantages such as biodegradability, good biocompatibility, acid and alkali resistance, and chemical stability. Compared with the traditional binder such as sodium carboxymethylcellulose (CMC), sodium alginate, Guar Gum (GG) and the like, the PVA has lower price, the industrial production technology is more mature, and the production cost of the lithium ion battery can be obviously reduced. In addition, PVA contains a large number of hydroxyl groups, has good affinity with functional groups on the surface of the silicon, can effectively bond silicon and a conductive agent, and keeps the conductivity of the electrode. However, research finds that when polyvinyl alcohol is used as a binder, the polyvinyl alcohol has poor toughness after the electrode is dried, and cannot well meet the requirement of volume expansion of silicon particles.
With the development of scientific technology, silicon negative electrode materials are considered as one of the promising lithium ion battery negative electrode materials of the new generation due to the higher theoretical specific capacity (4200mAh/g), but the silicon negative electrode materials also have some problems: on one hand, the silicon can face larger volume expansion (about 300%) in the lithium-intercalation and lithium-deintercalation process, so that electrode materials are pulverized and detached, and lose electric contact with a current collector, so that the impedance of the battery is obviously improved, and the capacity is rapidly attenuated; on the other hand, the destruction and rearrangement of a solid electrolyte interface film (SEI) can also occur due to volume expansion, and a great amount of active lithium is lost, so that the battery can be rapidly failed, and further development of the silicon material in the lithium ion battery industry is restricted.
Therefore, how to enhance the toughness of PVA so that it can be used as a binder of silicon negative electrode material to maintain the integrity of silicon surface and structure has become a technical problem to be solved.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a bonding agent and a preparation method and application thereof. The invention takes polyfunctional group sulfonic acid and polyvinyl alcohol as the raw materials, and the prepared binder has better toughness and better electrical property, and is suitable for being used as the binder of a silicon cathode lithium ion battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a binder, which is prepared from raw materials including polyvinyl alcohol and multifunctional sulfonic acid;
the mass ratio of the polyvinyl alcohol to the polyfunctional group sulfonic acid is 20 (1-6).
In the present invention, the polyfunctional sulfonic acid means that it contains 1 or more of other functional groups (e.g., carboxyl group, amino group, hydroxyl group, etc.) that can react with hydroxyl group in addition to the sulfonic acid functional group.
On one hand, the binder with a three-dimensional network structure is prepared through the reaction of functional groups in polyfunctional sulfonic acid and hydroxyl groups in polyvinyl alcohol, so that the toughness of the binder is improved, and the effect of inhibiting the volume expansion of silicon particles is achieved; on the other hand, through the reaction of the multifunctional sulfonic acid and the polyvinyl alcohol, a sulfonic acid group is introduced in situ on the polyvinyl alcohol, the introduced sulfonic acid group can preferentially contact with the electrolyte and participate in forming a stable solid electrolyte interface film (SEI) on the silicon surface, the lithium consumption in the first charge-discharge process is inhibited, the first coulombic efficiency and the cycle stability of the battery are improved, and simultaneously the R-SO formed by the reduction of the sulfonic acid group on the silicon surface3Li/Li2SO3(R refers to a group except a sulfonic group in the multifunctional sulfonic acid, for example, if the multifunctional sulfonic acid is sulfoacetic acid, R is an acetate group) obviously improves the mobility of lithium ions, improves the dynamic performance of a silicon cathode and improves the rate capability of a battery.
In the present invention, the mass ratio of the polyvinyl alcohol to the polyfunctional sulfonic acid is 20 (1-6), and may be, for example, 20:1, 20:2, 20:3, 20:4, 20:5, or 20: 6.
In the invention, by controlling the mass ratio of the polyvinyl alcohol to the polyfunctional group sulfonic acid within a specific proportion range, the prepared adhesive has good toughness and electrical properties, has proper crosslinking degree and is convenient to use. If the mass ratio of the polyvinyl alcohol to the polyfunctional group sulfonic acid is too small, namely the polyfunctional group sulfonic acid content is too large, the prepared binder has too large degree of crosslinking, is easy to form a 'jelly shape', and cannot be used; if the mass ratio of the polyvinyl alcohol to the polyfunctional sulfonic acid is too large, that is, the content of the polyfunctional sulfonic acid is too small, the crosslinking degree of the prepared binder is too small, the toughness of the prepared binder is poor, and the volume expansion of a silicon negative electrode cannot be well inhibited in the lithium intercalation and deintercalation process, so that the SEI film is cracked and rearranged, and a large amount of active lithium is lost, and the electrical performance of the prepared lithium ion battery is poor.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the object and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
In a preferred embodiment of the present invention, the multifunctional sulfonic acid is selected from one or a combination of at least two of sulfoacetic acid, sulfosuccinic acid, sulfosalicylic acid, sulfamic acid and isethionic acid.
As a preferable technical scheme of the invention, the raw materials for preparing the adhesive also comprise a solvent.
Preferably, the solvent is selected from any one of deionized water, ethanol, methanol, acetone, N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran or N-methylpyrrolidone or a combination of at least two of the above.
In a second aspect, the present invention provides a method for preparing the binder according to the first aspect, the method comprising the steps of:
(1) mixing polyfunctional group sulfonic acid with a solvent to obtain polyfunctional group sulfonic acid solution;
mixing polyvinyl alcohol with a solvent to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution, and carrying out a crosslinking reaction to obtain the binder.
In a preferred embodiment of the present invention, the content of the polyfunctional sulfonic acid in the polyfunctional sulfonic acid solution is 1 to 20% by mass, and may be, for example, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or the like.
In a preferred embodiment of the present invention, the temperature at which the polyvinyl alcohol and the solvent are mixed is 40 to 100 ℃, and may be, for example, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃.
Preferably, the mixing time is 1 to 3 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours.
In a preferred embodiment of the present invention, the polyvinyl alcohol solution may contain 5 to 20% by mass of polyvinyl alcohol, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or the like.
In a preferred embodiment of the present invention, the temperature of the crosslinking reaction is 80 to 100 ℃, and may be, for example, 80 ℃, 82 ℃, 84 ℃, 86 ℃, 88 ℃, 90 ℃, 92 ℃, 94 ℃, 96 ℃, 98 ℃ or 100 ℃.
Preferably, the time of the crosslinking reaction is 2-24 h, for example, 2h, 4h, 5h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, etc.
As a preferred technical scheme of the invention, the preparation method specifically comprises the following steps:
(1) uniformly mixing polyfunctional group sulfonic acid with a solvent to obtain a polyfunctional group sulfonic acid solution with the mass percentage of 1-20%;
mixing polyvinyl alcohol and a solvent for 1-3 hours at 40-100 ℃ to obtain a polyvinyl alcohol solution with the mass percentage of 5-20%;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution at the temperature of 80-100 ℃, and carrying out a crosslinking reaction for 2-24 hours to obtain the binder.
In a third aspect, the invention provides a use of the binder according to the first aspect in a lithium ion battery with a silicon negative electrode.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the binder with a three-dimensional network structure is prepared through the reaction of functional groups in polyfunctional sulfonic acid and hydroxyl groups in polyvinyl alcohol, so that the toughness of the binder is improved, the effect of inhibiting the volume expansion of silicon particles is achieved, and meanwhile, through the reaction of polyfunctional sulfonic acid and polyvinyl alcohol, sulfonic acid groups are introduced in situ on the polyvinyl alcohol, so that the electrical performance of the battery can be improved, the multiplying power performance is good, the reversible capacity is 2986.4-3192.2 mAh/g, the first coulombic efficiency is 88.31-90.50%, and the reversible capacity is 876.3-1842.3 mAh/g after 200 cycles.
Drawings
Fig. 1 is a graph of the first charge and discharge of silicon half cells provided in application examples 1-3 and comparative application example 1;
fig. 2 is a graph of cycling curves for the silicon half-cells provided in application examples 1-3 and comparative application example 1;
FIG. 3 is a graph of the post-cycling impedance of the silicon half-cells provided in application examples 1-3 and comparative application example 1;
fig. 4 is a cycle chart of a full cell in which a silicon electrode sheet made of the binder provided in examples 1 to 3 and comparative example 1 was used as a negative electrode and lithium iron phosphate was used as a positive electrode.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Some of the component sources in the following examples and comparative examples are as follows:
polyvinyl alcohol: beijing Vocko Biotech, Inc., 1799.
Example 1
The embodiment provides a binder and a preparation method thereof, wherein raw materials for preparing the binder comprise polyvinyl alcohol, sulfoacetic acid and deionized water.
The preparation method of the adhesive comprises the following steps:
(1) uniformly mixing sulfoacetic acid (5g) and deionized water (75g) to obtain a polyfunctional group sulfonic acid solution;
mixing polyvinyl alcohol (50g) with deionized water (950g) for 2h at 80 ℃ to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a sulfoacetic acid solution at 90 ℃, and carrying out a crosslinking reaction for 12h to obtain the adhesive.
Example 2
The embodiment provides a binder and a preparation method thereof, wherein raw materials for preparing the binder comprise polyvinyl alcohol, polyfunctional sulfonic acid and deionized water.
The preparation method of the adhesive comprises the following steps:
(1) uniformly mixing multifunctional sulfonic acid (10g) and deionized water (75g) to obtain a multifunctional sulfonic acid solution;
mixing polyvinyl alcohol (50g) with deionized water (450g) at 90 ℃ for 3h to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution at 90 ℃, and carrying out a crosslinking reaction for 12h to obtain the binder.
Example 3
This example provides a binder and a method for preparing the same, differing from example 1 only in that the mass of sulfoacetic acid in step (1) is 15g, and the other conditions are the same as example 1.
Example 4
This example provides a binder and a method for preparing the same, differing from example 1 only in that the mass of sulfoacetic acid in step (1) is 2.5g, and the other conditions are the same as example 1.
Example 5
The embodiment provides a binder and a preparation method thereof, wherein raw materials for preparing the binder comprise polyvinyl alcohol, sulfosuccinic acid and deionized water.
The preparation method of the adhesive comprises the following steps:
(1) evenly mixing 10g of sulfosuccinic acid with 75g of deionized water to obtain a solution of the sulfosuccinic acid;
mixing polyvinyl alcohol (50g) with deionized water (1000g) at 90 ℃ for 2h to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a sulfosuccinic acid solution at 90 ℃, and carrying out a crosslinking reaction for 2h to obtain the binder.
Example 6
The embodiment provides a binder and a preparation method thereof, wherein raw materials for preparing the binder comprise polyvinyl alcohol, sulfosalicylic acid and deionized water.
The preparation method of the adhesive comprises the following steps:
(1) evenly mixing sulfosalicylic acid (10g) with deionized water (75g) to obtain a sulfosalicylic acid solution;
mixing polyvinyl alcohol (50g) with deionized water (1000g) at 90 ℃ for 2h to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a sulfosalicylic acid solution at 90 ℃, and carrying out a crosslinking reaction for 24 hours to obtain the adhesive.
Example 7
This example provides a binder and a method of making the same, differing from example 2 only in that sulfoacetic acid is replaced with sulfamic acid, otherwise the conditions are the same as in example 2.
Example 8
This example provides a binder and a method of preparing the same, differing from example 2 only in that sulfoacetic acid is replaced with glycolic acid, and the other conditions are the same as example 2.
Example 9
This example provides a binder and a method for preparing the same, wherein the raw materials for preparing the binder include polyvinyl alcohol, sulfoacetic acid and N-methyl pyrrolidone.
The preparation method of the adhesive comprises the following steps:
(1) sulfoacetic acid (5g) and N-methyl pyrrolidone (60g) are mixed uniformly to obtain a sulfoacetic acid solution;
mixing polyvinyl alcohol (50g) and N-methyl pyrrolidone (200g) at 100 ℃ for 1h to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a sulfoacetic acid solution at 100 ℃, and carrying out a crosslinking reaction for 8h to obtain the adhesive.
Comparative example 1
This comparative example provides a binder and a method for preparing the same, which are different from example 1 only in that sulfoacetic acid is not contained in the raw materials for preparing the binder, and the other conditions are the same as example 1.
Comparative example 2
This comparative example provides a binder and a method for preparing the same, differing from example 1 only in that the mass of sulfoacetic acid in step (1) is 20g, and the other conditions are the same as example 1.
Comparative example 3
This comparative example provides a binder and a method for preparing the same, differing from example 1 only in that the mass of sulfoacetic acid in step (1) is 1g, and the other conditions are the same as example 1.
Comparative example 4
This comparative example provides a binder and a method for preparing the same, differing from example 1 only in that sulfoacetic acid is replaced with ethylsulfonic acid, and the other conditions are the same as example 1.
Application examples 1 to 9
Application examples 1 to 9 respectively provide a silicon half cell, and a preparation method of the silicon half cell is as follows:
the binders provided in examples 1 to 9 were uniformly mixed with silicon and acetylene black at a mass ratio of 15:70:15 to prepare electrode pastes, which were coated on copper foil current collectors (816 mm. times.6 μm, Kyunjiand, Fuke technologies Co., Ltd.), dried and used at 2MPa/cm2Pressing under the pressure, cutting, drying at 120 deg.C under vacuum for 16h to obtain silicon electrode slice, assembling the silicon electrode slice with lithium metal as counter electrode to obtain half cell,and obtaining the silicon half cell.
Comparative application examples 1 to 4
Comparative application examples 1 to 4 each provide a silicon half cell, differing from application example 1 only in that the adhesive provided in example 1 was replaced with the adhesive provided in comparative examples 1 to 4, respectively, and the other conditions were the same as in application example 1.
Fig. 1 shows the first charge and discharge curves of the silicon half cells provided in application examples 1 to 3 and comparative application example 1. As can be seen from fig. 1, if only polyvinyl alcohol is selected as a raw material for preparing the binder (comparative application example 1), the first coulombic efficiency of the prepared silicon half-cell is only 87.6%, the specific charge capacity is 3328.6mAh/g, and the discharge capacity is 2918.9 mAh/g; and polyvinyl alcohol crosslinked by sulfoacetic acid is selected as a binder (application examples 1-3), and the first coulombic efficiency and the charge-discharge capacity of the prepared silicon half-cell are improved. When the mass ratio of the sulfoacetic acid to the PVA is (application example 1), the first coulombic efficiency of the silicon reaches up to 90.5%, the specific charge capacity is 3527.1mAh/g, the discharge capacity reaches 3192.2mAh/g, and the PVA subjected to sulfoacetic acid crosslinking on the surface can participate in the formation of an SEI film and inhibit lithium consumption in the first charge-discharge process.
The cycling profiles for the silicon half-cells provided in application examples 1-3 and comparative application example 1 are shown in fig. 2. As can be seen from fig. 2, when only polyvinyl alcohol was selected as a raw material for preparing the binder (comparative application example 1), the capacity of the prepared silicon half cell began to rapidly decay after about 50 electrochemical cycles; and the polyvinyl alcohol crosslinked by sulfoacetic acid is selected as a binder (application examples 1-3), the cycling stability of the prepared silicon half cell is obviously improved, and the sulfoacetic acid can obviously improve the toughness of the polyvinyl alcohol, effectively inhibit the expansion of silicon particles, prevent the electrode pulverization cycle attenuation and achieve the purpose of prolonging the cycle life of the cell.
The impedance plots after cycling for the silicon half cells provided in application examples 1-3 of the present invention and comparative application example 1 are shown in fig. 3. As can be seen from FIG. 3, the impedance of the polyvinyl alcohol silicon half cell after the multifunctional crosslinking was significantly reduced (application examples 1 to 3). This is based on the conversion of the sulfonic acid groups to form R-SO3Li/Li2SO3The lithium ion conductive coating has high lithium conductivity, and polyvinyl alcohol formed by crosslinking has better toughness, can effectively relieve the expansion and pulverization of silicon particles, and inhibits the impedance rise in the battery circulation process.
In addition, according to the method of application example 1, the invention uses the silicon electrode plates made of the binders provided in examples 1 to 3 and comparative example 1 as negative electrodes and lithium iron phosphate as positive electrodes to assemble full cells, which are respectively marked as full cell 1, full cell 2, full cell 3 and comparative full cell 1, and the cycle curve chart is shown in fig. 4. As can be seen from fig. 4, if multifunctional sulfonic acid and polyvinyl alcohol are used as the raw materials for preparing the binder, the prepared silicon-based full cells (full cell 1, full cell 2, and full cell 3) have better cycling stability, and after 100 cycles of cycling, the reversible capacities thereof are 75.1mAh/g, 105.9mAh/g, and 97.9mAh/g, respectively; whereas the reversible capacity of the full cell (comparative full cell 1) prepared using only polyvinyl alcohol as a binder was only 68.2 mAh/g. The result shows that the bonding agent prepared by the reaction of the polyfunctional group sulfonic acid and the polyvinyl alcohol can improve the cycle life of the silicon-based full cell.
Carrying out charge and discharge performance tests on the silicon half-cell provided by the application example and the comparative application example, wherein the test conditions of the first reversible capacity and the first coulombic efficiency are 0.05C; the test condition of the reversible capacity after 200 cycles of circulation is 0.5C; the test conditions of the rate capability are as follows: and (3) carrying out a charging test under the condition of 0.2C, carrying out a discharging test under the condition of 0.1-20C, if the ratio of the test result to the reversible capacity is more than or equal to 70%, marking as 'excellent', if the ratio of the test result to the reversible capacity is more than or equal to 50%, marking as 'good', and if the ratio of the test result to the reversible capacity is less than 50%, marking as 'poor'. The results of the above tests are shown in table 1 below:
TABLE 1
As can be seen from Table 1, the prepared binder has good toughness and achieves the effect of inhibiting the volume expansion of silicon particles by the reaction of functional groups in the multifunctional sulfonic acid and hydroxyl groups in polyvinyl alcohol and controlling the mass ratio of the functional groups in the multifunctional sulfonic acid to the polyvinyl alcohol within a specific proportion range; meanwhile, through the reaction of the multifunctional sulfonic acid and the polyvinyl alcohol, a sulfonic acid group is introduced in situ on the polyvinyl alcohol, so that the electrical performance of the battery can be improved, the multiplying power performance is good, the reversible capacity is 2986.4-3192.2 mAh/g, the first coulombic efficiency is 88.31-90.50%, and the reversible capacity is 876.3-1842.3 mAh/g after 200 cycles.
Compared with example 1, if the raw materials for preparing the binding agent do not contain multifunctional sulfonic acid (comparative example 1), the prepared binding agent has poor toughness, the rate capability of the prepared silicon half-cell is poor, and the reversible capacity, the first coulomb efficiency and the reversible capacity after 200 cycles are all low.
Compared with example 1, if the mass ratio of polyvinyl alcohol to multifunctional sulfonic acid is too small (comparative example 2), i.e. the content of multifunctional sulfonic acid is too large, the prepared binder has too large degree of crosslinking to form a 'jelly shape' and cannot be used; if the mass ratio of polyvinyl alcohol to multifunctional sulfonic acid is too large (comparative example 3), i.e. the content of multifunctional sulfonic acid is too small, the prepared binder has a low degree of crosslinking and poor toughness, and the electrical properties of the silicon half cell prepared therefrom are poor.
Compared to example 1, if the binder is prepared using monofunctional sulfonic acid (comparative example 4), the binder having a three-dimensional cross-linked network structure cannot be formed, and thus the electrical properties of the silicon half cell prepared therefrom are poor.
In conclusion, the prepared adhesive has better toughness and achieves the effect of inhibiting the volume expansion of silicon particles by the reaction of the functional groups in the multifunctional sulfonic acid and the hydroxyl groups in the polyvinyl alcohol and controlling the mass ratio of the functional groups in the multifunctional sulfonic acid to the polyvinyl alcohol within a specific proportion range; meanwhile, through the reaction of the multifunctional sulfonic acid and the polyvinyl alcohol, sulfonic acid groups are introduced in situ on the polyvinyl alcohol, so that the electrical property of the battery can be improved.
The applicant states that the present invention is illustrated by the detailed process flow of the present invention through the above examples, but the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The adhesive is characterized in that raw materials for preparing the adhesive comprise polyvinyl alcohol and multifunctional sulfonic acid;
the mass ratio of the polyvinyl alcohol to the polyfunctional group sulfonic acid is 20 (1-6).
2. The binder of claim 1 wherein the multifunctional sulfonic acid is selected from the group consisting of sulfoacetic acid, sulfosuccinic acid, sulfosalicylic acid, sulfamic acid, and isethionic acid, either alone or in combination with at least two thereof.
3. The binder as claimed in claim 1 or 2, wherein the raw materials for preparing the binder further comprise a solvent;
preferably, the solvent is selected from any one of deionized water, ethanol, methanol, acetone, N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran or N-methylpyrrolidone or a combination of at least two of the above.
4. A method for preparing a binder as claimed in any one of claims 1 to 3, characterized in that it comprises the following steps:
(1) mixing polyfunctional group sulfonic acid with a solvent to obtain polyfunctional group sulfonic acid solution;
mixing polyvinyl alcohol with a solvent to obtain a polyvinyl alcohol solution;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution, and carrying out a crosslinking reaction to obtain the binder.
5. The method according to claim 4, wherein the polyfunctional sulfonic acid solution contains 1 to 20% by mass of polyfunctional sulfonic acid.
6. The method according to claim 4 or 5, wherein the polyvinyl alcohol is mixed with the solvent at a temperature of 40 to 100 ℃;
preferably, the mixing time is 1-3 h.
7. The preparation method according to any one of claims 4 to 6, wherein the polyvinyl alcohol solution contains 5 to 20% by mass of polyvinyl alcohol.
8. The method according to any one of claims 4 to 7, wherein the temperature of the crosslinking reaction is 80 to 100 ℃;
preferably, the time of the crosslinking reaction is 2-24 h.
9. The method according to any one of claims 4 to 8, comprising in particular the steps of:
(1) uniformly mixing polyfunctional group sulfonic acid with a solvent to obtain a polyfunctional group sulfonic acid solution with the mass percentage of 1-20%;
mixing polyvinyl alcohol and a solvent for 1-3 hours at 40-100 ℃ to obtain a polyvinyl alcohol solution with the mass percentage of 5-20%;
(2) and (2) mixing the polyvinyl alcohol solution obtained in the step (1) with a polyfunctional group sulfonic acid solution at the temperature of 80-100 ℃, and carrying out a crosslinking reaction for 2-24 hours to obtain the binder.
10. Use of a binder according to any one of claims 1 to 3 in a silicon negative electrode lithium ion battery.
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| CN113563531A (en) * | 2020-04-28 | 2021-10-29 | 成都翊昂科技有限公司 | Graft copolymer aqueous adhesive, preparation method and application in silicon-carbon negative electrode |
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