CN113991118B - Silicon-carbon negative electrode material adhesive and preparation method and application thereof - Google Patents
Silicon-carbon negative electrode material adhesive and preparation method and application thereof Download PDFInfo
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- H01—ELECTRIC ELEMENTS
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- 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
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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Abstract
The invention discloses a silicon-carbon negative electrode material adhesive and a preparation method and application thereof, wherein the adhesive is an amphiphilic copolymer, and the organic unification of a hydrophobic polymer and a hydrophilic polymer is realized by copolymerizing polyvinyl acetate and polyacrylic acid and regulating and controlling the proportion of the polyvinyl acetate and the polyacrylic acid in the adhesive, and the prepared amphiphilic copolymer adhesive can be uniformly dispersed and dissolved in water, so that the adhesion of the polyvinyl acetate to carbon and the adhesion of the polyacrylic acid to silicon are respectively exerted; the adhesive has the characteristics of multifunction, polyvinyl acetate sticks carbon through hydrophobic interaction, polyacrylic acid sticks silicon through hydrogen bonding, and meanwhile, the pH of the polymer is regulated by introducing lithium hydroxide monohydrate, so that the problem of gas production of carboxyl groups is reduced.
Description
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a silicon-carbon negative electrode material adhesive, a preparation method and application thereof.
Background
Lithium ion batteries have been widely used in energy storage devices for electric vehicles, 3C products, and renewable energy and smart grids. The positive electrode material of the lithium ion battery is currently commercialized as an oxide positive electrode material such as LiCoO 2 、LiMn 2 O 4 And LiFePO 4 Wait for the main part; the negative electrode material is graphite and various carbon materials using graphite as a precursor. Although the carbon material has good reversible charge and discharge performance, the theoretical capacity is low (372 mAh/g), and the high-rate charge and discharge performance is poor. And when the battery is overcharged, lithium dendrites are easily formed on the surface of the carbon material, short circuit is caused, and potential safety hazards are generated. Because the carbon material is difficult to meet the requirements of rapid development of the current electronic information and energy technologies, development of a novel and reliable high-capacity lithium ion battery cathode material becomes a technical bottleneck of development of the high-performance lithium ion battery.
Silicon can be used as a negative electrode material of a lithium ion battery, and the silicon is more and more important because of the high mass specific capacity (4200 mAh/g), rich material, low price and the like. However, the silicon anode material generates huge volume change in the charge and discharge process, so that the electrode capacity is fast attenuated, the cycle performance is poor, and commercialization is difficult. The silicon-carbon material combines the advantages of two materials, namely silicon and carbon, has high specific capacity, ensures excellent mechanical properties in the charge and discharge process, and has wide commercial prospect.
A strong binder is a prerequisite for the application of the silicon carbon anode material. In a lithium ion battery, an adhesive is a high polymer material which bonds an active material and a conductive additive to a current collector to form an electronic guide path and ensure the normal operation of the battery. In the charge and discharge process, the binder effectively maintains the structural integrity of the electrode, ensures that the electrode material can repeatedly intercalate and deintercalate lithium, but in the aspect of binders, the current binder for the silicon-carbon material is less studied, and is mainly a pure silicon binder which is widely reported to realize the binding by establishing interaction with polar functional groups on the surface of pure silicon, but in the silicon-carbon material, the surface property of the silicon-carbon material is different from that of the pure silicon due to the introduction of carbon, the surface of the silicon is hydrophilic, and the surface of the carbon is hydrophobic, so that the binder suitable for the pure silicon material may not be suitable for the silicon-carbon material, and therefore, the binder suitable for the silicon-carbon composite material needs to be further developed on the basis of the pure silicon binder.
Meanwhile, aiming at the commercial electrode, the energy density is required to be improved, the consumption of the adhesive is less than about 5 percent, the electrode plate is subjected to the processing procedures of rolling and the like, the powder falling and cracking condition often occurs in the process, the integrity of the electrode plate is seriously influenced, and therefore, the improvement of the flexibility and the adhesive force of the electrode plate is significant, and the adhesive is increasingly important as the electrode stability is maintained.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a silicon-carbon negative electrode material adhesive, a preparation method and application thereof, so as to solve the problem of the prior art that the adhesive is suitable for silicon-carbon negative electrode materials.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
a silicon-carbon negative electrode material adhesive is polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid, and the molecular structural formula is as follows:
wherein: x: y: z=30 (10 to 20) to (50 to 60).
The preparation method of the silicon-carbon negative electrode material adhesive comprises the following steps:
step 2, sequentially dissolving acrylic acid, lithium hydroxide monohydrate and vinyl acetate in a solution A, bubbling the solution into the mixed solution, adding an initiator to form a reaction system B, heating the reaction system B, and reacting to generate a copolymer C, wherein the copolymer C is polyvinyl acetate-co-polyacrylic acid;
and 3, adding a lithium hydroxide monohydrate aqueous solution into the copolymer C, and heating to react to obtain polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid.
The invention further improves that:
preferably, in the step 1, the heating temperature is 80-90 ℃ and the heating time is 20-40 min.
Preferably, in the step 2, the reaction temperature is 65-75 ℃ and the reaction time is 30-60 min.
Preferably, in the step 1 and the step 2, the mixing ratio of the polyvinyl alcohol, the emulsifier, the acrylic acid, the lithium hydroxide monohydrate, the vinyl acetate and the initiator is 5:5 by mass: (30-70): (0-70): (30-70): 1.
Preferably, in step 2, the concentration of copolymer C in the product system is 20wt.%.
Preferably, in the step 3, the reaction temperature is 50-65 ℃ and the reaction time is 60-90 min.
Preferably, in the step 1, the emulsifier is OP-10, and in the step 2, the initiator is ammonium persulfate.
The silicon-carbon negative electrode material adhesive is applied to a lithium battery.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a silicon-carbon negative electrode material adhesive, which is an amphiphilic copolymer, wherein the adhesive realizes the organic unification of a hydrophobic polymer and a hydrophilic polymer by copolymerizing polyvinyl acetate and polyacrylic acid and regulating and controlling the proportion of the polyvinyl acetate and the polyacrylic acid, and the prepared amphiphilic copolymer adhesive can be uniformly dispersed and dissolved in water, so that the adhesion of the polyvinyl acetate to carbon and the adhesion of the polyacrylic acid to silicon are respectively exerted; the adhesive has the characteristics of multifunction, polyvinyl acetate sticks carbon through hydrophobic interaction, polyacrylic acid sticks silicon through hydrogen bonding, and meanwhile, the pH of the polymer is regulated by introducing lithium hydroxide monohydrate, so that the problem of gas production of carboxyl groups is reduced. Meanwhile, due to the introduction of vinyl acetate monomer with low glass transition temperature, the glass transition temperature of the final integral polymer is reduced, the mechanical property of the polymer can be regulated and controlled, the flexibility of the polymer is enhanced, and the processability of the pole piece is improved. The adhesive realizes effective adhesion to the silicon-carbon negative electrode, and effectively improves the circulation stability of the silicon-carbon negative electrode. Meanwhile, deionized water is adopted as a solvent in the whole synthesis process of the adhesive, so that the adhesive is environment-friendly.
The invention also discloses a preparation method of the silicon-carbon negative electrode material adhesive, wherein in the preparation process, the adhesive is prepared by a three-step method, firstly, polyvinyl alcohol and an emulsifying agent are dissolved under the heating condition, then, a polyvinyl acetate-co-polyacrylic acid copolymer is prepared, finally, the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer is prepared by lithiation, the whole preparation process adopts the traditional free radical polymerization, the whole reaction process is easy to control, and the preparation of the amphiphilic copolymer and the application of the polymer as the adhesive can be realized. The simple polyvinyl acetate polymer has better flexibility and can interact with carbon with hydrophobic surface, but is insoluble in water and can not be used as an aqueous adhesive. According to the invention, the organic unification of the hydrophobic polymer and the hydrophilic polymer is realized by copolymerizing the polyvinyl acetate and the polyacrylic acid and regulating and controlling the proportion of the polyvinyl acetate and the polyacrylic acid, and the prepared amphiphilic copolymer adhesive can be uniformly dispersed and dissolved in water, so that the bonding effect of the polyvinyl acetate on carbon and the bonding effect of the polyacrylic acid on silicon are respectively exerted.
The invention also discloses application of the silicon-carbon negative electrode material adhesive, which shows good adhesive effect when applied to the silicon-carbon negative electrode material, and the silicon-carbon negative electrode shows good electrochemical stability.
Drawings
FIG. 1 is an infrared spectrum of a polyvinyl acetate-polyacrylic acid polymer prepared in examples 1 and 2 and comparative example 1 of the present invention.
FIG. 2 shows DSC test results of examples 1, 2 and 3.
FIG. 3 is a graph showing the peel strength of the adhesives of application examples 1, 2, and 3 and comparative example 1.
FIG. 4 is a graph showing the comparison of the adhesive cycle properties in application examples 1, 2, 3 and comparative example 1.
Detailed Description
The invention is described in further detail below with reference to the attached drawing figures:
the invention discloses an adhesive for a silicon-carbon negative electrode material of a lithium ion battery and a preparation method thereof, wherein the adhesive polymer is polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA) and is an amphiphilic copolymer. The adhesive is prepared by conventional free radical polymerization. The adhesive shows water solubility, is green and environment-friendly, polyvinyl acetate can adhere carbon through hydrophobic interaction, lithium polyacrylate can reduce the problem of gas production of carboxyl in a battery, meanwhile, the peeling strength is improved, polyacrylic acid can adhere silicon through hydrogen bonding, meanwhile, the glass transition temperature of a polymer is reduced by introducing vinyl acetate, the flexibility of the polymer is improved, the three parts cooperate together, the structural integrity of a silicon-carbon cathode in the circulation process is ensured, the flexibility of the polymer is improved, and the processability of a pole piece in the battery is improved. The molecular structural formula of the compound is as follows:
wherein: x: y: z=30 (10 to 20) to (50 to 60).
The preparation method of the device is a traditional free radical polymerization method, and comprises the following steps:
Step 2, sequentially dissolving acrylic acid, lithium hydroxide monohydrate and vinyl acetate in a solution A to form a reaction system B, wherein the acrylic acid and the lithium hydroxide monohydrate can provide a salt environment for dissolution of the vinyl acetate, so that the solubility of the vinyl acetate in the whole system is improved, oxygen in the reaction system B is removed by bubbling for 30min, and finally an initiator is added, the bubbling deoxidization time is ensured to be 30min, and the initiator is reacted due to insufficient deoxidization time; the mixing ratio of polyvinyl alcohol, emulsifier, acrylic acid, total lithium hydroxide monohydrate, vinyl acetate and initiator is 5:5 by mass: (30-70): (0-70): (30-70) 1, the reaction temperature is 65-75 ℃ and the reaction time is 30-60 min; after the reaction, a copolymer C, polyvinyl acetate-co-polyacrylic acid, was produced, the concentration of copolymer C being 20% by weight.
Step 3, synthesizing polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), adding a lithium hydroxide monohydrate aqueous solution into the copolymer C, wherein the concentration is changed from 20% wt to 10% wt, so as to ensure that the viscosity can meet the reaction requirement; the reaction temperature is 50-65 ℃ and the reaction time is 60-90 min, forming a reaction system D; copolymer C: the mixing proportion of the lithium hydroxide monohydrate is (70-90): (30-50), and obtaining polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA) after the reaction, thereby completing the preparation of the adhesive.
According to the invention, the (PVAc-co-PAALi-co-PAA) copolymer is prepared by traditional free radical polymerization, the reaction process is easy to control, the characteristic of multifunctional polymerization can be realized, polyvinyl acetate can adhere carbon through hydrophobic interaction, lithium polyacrylate can reduce the problem of gas generation of carboxyl in a battery, meanwhile, the peeling strength is improved, polyacrylic acid can adhere silicon through hydrogen bonding, and meanwhile, vinyl acetate is introduced to reduce the glass transition temperature of the polymer, the flexibility of the polymer is improved, the three parts cooperate together, the structural integrity of a silicon-carbon negative electrode in the circulation process is ensured, the flexibility of the polymer is improved, and the processability of a pole piece in the battery is improved.
Based on the above functions, when the binder is applied in a silicon carbon anode, it can exhibit good adhesion to an electrode material and can improve cycle stability, flexibility, and processability of a battery.
The silicon-carbon negative electrode of the lithium ion battery comprises a current collector and silicon-carbon negative electrode slurry attached to the current collector; the silicon-carbon negative electrode slurry comprises a silicon-carbon active material, a conductive additive and a binder, wherein the mass ratio of the silicon-carbon negative electrode slurry is as follows: conductive additive: binder= (70-95): (3.5-15): (1.5-15); the silicon-carbon anode active material comprises silicon with the mass ratio of silicon to carbon: carbon=2:3, 1:4 and 1:32, the conductive additives including Super P, acetylene black and ketjen black; the adhesive is the polyethylene acetate adhesive vinyl ester-lithium polyacrylate-polyacrylic acid.
The adhesive can be used for preparing silicon-carbon cathodes of lithium ion batteries and lithium ion batteries containing the silicon-carbon cathodes, and comprises the following steps:
(1) The silicon-carbon anode material, the conductive additive and the adhesive are mixed according to (70-95): (3.5-15): (1.5-15) uniformly dispersing the silicon-carbon anode slurry in deionized water by ball milling to obtain the uniformly mixed silicon-carbon anode slurry.
(2) The slurry in (1) was uniformly coated on a copper foil of 12 μm thickness with an automatic film coater to a thickness of 180 μm, and then dried in a vacuum oven to remove the solvent. And after the drying is finished, cutting into a silicon-carbon negative electrode plate with the diameter of 12 mm.
(3) Transferring the electrode plate prepared in the step (2) into a glove box filled with argon, and assembling the electrode plate into a 2032 button half cell. Pure lithium sheets were used as counter electrodes and Celgard2325 polypropylene-polyethylene-polypropylene (PP-PE-PP) films were used as separators. The electrolyte was a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) containing 1M lithium hexafluorophosphate (LiPF 6), and fluoroethylene carbonate (FEC) was added at a volume fraction of 10%.
(4) The assembled button cell of (3) was allowed to stand for 8 hours, and then was cycled at a rate of 0.1C for one week in a voltage range of 0.01 to 1.50V, followed by charge and discharge cycles at a rate of 0.3C. Wherein 1C is 500mAh/g.
Example 1
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 85deg.C for 30min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction at 75 ℃ for 30min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), adding 0.8g of lithium hydroxide monohydrate to copolymer C, and adding water to change the concentration from 20% by weight to 10% by weight, wherein the reaction temperature is 60 ℃, the reaction time is 60min, and obtaining polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) after the reaction, the preparation of adhesive A1 is completed, and the adhesive A1 is prepared by the following steps of: lithium acrylate: acrylic = 30:52.5:17.5.
The mixing ratio of the polyvinyl alcohol, the emulsifier, the acrylic acid, the total lithium hydroxide monohydrate, the vinyl acetate and the initiator is 5:5:70:52.5:30:1 preparing a silicon-carbon negative electrode of a lithium ion battery by using an adhesive A1 according to the method, and assembling the silicon-carbon negative electrode into the lithium ion battery to test performance, wherein the silicon-carbon negative electrode material, the conductive additive and the adhesive are prepared according to the mass ratio of 80:10:10, and the conductive additive is Super P.
Example 2
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:50:37.5:50:1, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 50:37.5:12.5, the preparation of adhesive A2 was completed.
The silicon carbon negative electrode of the lithium ion battery is prepared by using the adhesive A2 according to the method and assembled into the lithium ion battery for testing performance.
Example 3
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:30:22.5:70:1, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 70:22.5:7.5, the preparation of adhesive A3 was completed.
The silicon carbon negative electrode of the lithium ion battery is prepared by using the adhesive A3 according to the method and assembled into the lithium ion battery for testing performance.
Comparative example 1
4g of acrylic acid monomer is taken and dissolved in water, a bubbling deoxidization method is used for deoxidizing the reaction system, then nitrogen is filled in, an ammonium persulfate initiator is added, the ammonium persulfate accounts for 0.6 wt% of the mass of the acrylic acid monomer, the concentration of the monomer is 20 wt%, and the reaction is carried out for 40min at 70 ℃ and then the cooling is carried out, so that the preparation of the adhesive B1 is completed.
The silicon-carbon negative electrode of the lithium ion battery is prepared by using the adhesive B1 according to the method and assembled into the lithium ion battery for testing the performance.
FIG. 1 is an infrared spectrum of a polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer prepared in this example, from which it can be seen that in the spectrum of PAA, PAA is in the range of 3300-2500cm -1 ，1720cm -1 And 1132cm -1 Characteristic peaks are shown corresponding to O-H stretch, C=O stretch and C-O stretch, respectively, whereas PVAc-PAA is 1250cm compared to PAA -1 And 1032cm -1 There appears a new peak corresponding to C- (C=O) -O and C-O-C stretching vibrations in PVAc, where PVAc-PAA=5-5 compared to PVAc-PAA=3-7, 1250cm with increasing vinyl acetate monomer -1 And 1032cm -1 The absorption peak was more intense, demonstrating successful synthesis of PVAc-PAA at both ratios.
Fig. 2 shows the DSC test results of the adhesives A1, A2, A3 prepared in examples 1, 2, 3, with the gradual decrease in the glass transition temperature of the adhesives of the invention as the amount of vinyl acetate introduced increases, demonstrating that the introduction of vinyl acetate helps to lower the glass transition temperature of the polymer.
Fig. 3 shows the results of the peel property test of the adhesives A1, A2, A3 and comparative example 1 prepared in examples 1, 2, 3, in which the adhesive of the present invention exhibits a tendency to increase and decrease in peel strength with increasing amounts of vinyl acetate, and the adhesive A2 has the highest peel strength (77N/m) than comparative example 1 (50N/m), demonstrating good adhesion to silicon carbon negative electrodes.
Table 1 and fig. 4 show the charge-discharge cycle test results of the lithium ion battery prepared by the silicon-carbon negative electrode according to the examples and comparative examples of the present invention:
| numbering device | First week efficiency (%) | Capacity retention after 200 weeks (%) |
| Example 1 | 84.3 | 81.2 |
| Example 2 | 85.7 | 84.2 |
| Example 3 | 83.3 | 80.5 |
| Comparative example 1 | 81.8 | 68.2 |
From the results shown in table 1, the silicon-carbon negative electrode binder provided by the invention has a coulombic efficiency of 83% or more at the first week and a capacity retention rate of 80% or more after 200 weeks of cycle, but the comparative binder has a coulombic efficiency of 82% or so at the first week and a capacity retention rate of 68.2% after 200 weeks of cycle. Therefore, the binder of the invention significantly improves the cycle stability of the silicon-carbon anode material.
Example 4
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:50:0:50:1, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 50:0:50, the preparation of adhesive A4 was completed.
The silicon carbon negative electrode of the lithium ion battery is prepared by using the adhesive A4 according to the method and assembled into the lithium ion battery for testing performance.
Example 5
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:50:12.5:50:1, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 50:12.5:37.5, the preparation of adhesive A5 was completed.
The silicon carbon negative electrode of the lithium ion battery is prepared by using the adhesive A5 according to the method and assembled into the lithium ion battery for testing performance.
Example 6
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:50:25:50:1, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 50:25:25, preparation of adhesive A6 was completed.
The silicon carbon negative electrode of the lithium ion battery is prepared by the method and assembled into the lithium ion battery test performance by using the adhesive A6.
Example 7
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:50:50:50:1, but the feed ratio is different, wherein the mass ratio of the three blocks is vinyl acetate: lithium acrylate: acrylic = 50:50:0, the preparation of adhesive A7 was completed.
The silicon carbon negative electrode of the lithium ion battery was prepared by the method described above using the adhesive A7 and assembled into the lithium ion battery test performance.
Table 2 shows the results of peel property tests for the adhesives prepared in inventive examples 2, 4, 5, 6, 7 and comparative example 1.
From the results in Table 1, the adhesive provided by the present invention was higher than the peel strength of the comparative examples, both before and after rolling, and the optimum ratio was when the ratio of PAALi to total AA was 75%, namely PAALi: paa=3:1, the peel strength was optimal. From this, it is understood that the adhesive of the present invention contributes not only to improvement of peel strength before rolling but also to reduction of peel strength by rolling. The adhesive of the invention has proved to obviously improve the processability of the silicon-carbon anode material.
Example 8
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:70:70:30:1.
example 9
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:40:30:35:1.
example 10
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:60:40:50:1.
example 11
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:35:35:45:1.
example 12
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:45:45:45:1.
example 13
The preparation method and the reaction conditions of the polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid copolymer are the same as in example 1, the charging ratio is polyvinyl alcohol, an emulsifying agent, acrylic acid, total lithium hydroxide monohydrate, and the mixing ratio of the vinyl acetate and an initiator is 5:5:55:20:30:1.
example 14
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 85deg.C for 25min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction at 65 ℃ for 60min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% by weight from 20% by weight, the reaction temperature was 65℃and the reaction time was 65 minutes, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
Example 15
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 82 deg.C for 38min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction for 55min at 68 ℃ for standby.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% by weight from 20% by weight, the reaction temperature was 62℃and the reaction time was 70 minutes, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
Example 16
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 85deg.C for 35min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% wt, and the copolymer solution C is obtained after reaction at 70 ℃ for 50min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% by weight from 20% by weight, the reaction temperature was 60℃and the reaction time was 75 minutes, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
Example 17
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 87deg.C for 30min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction at 72 ℃ for 40min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% by weight from 20% by weight, the reaction temperature was 58℃and the reaction time was 80 minutes, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
Example 18
(1) Dissolving 0.2g polyvinyl alcohol and 0.2. 0.2gOP-10 in water, heating at 89 deg.C for 25min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction at 73 ℃ for 35min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% wt from 20% wt, the reaction temperature was 55℃and the reaction time was 85min, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
Example 19
(1) Dissolving 0.2g polyvinyl alcohol and 0.2-gOP-10 in water, heating at 90deg.C for 20min to dissolve the above materials, and cooling to obtain solution A.
(2) 2.8g of acrylic acid, 0.4g of lithium hydroxide monohydrate and 1.2g of vinyl acetate are sequentially dissolved in the solution A to form a reaction system B, oxygen in the reaction system B is removed by bubbling for 30min, finally 0.04g of ammonium persulfate is added as an initiator, the concentration of the monomer is 20% by weight, and the copolymer solution C is obtained after reaction at 75 ℃ for 30min and is reserved for use.
(3) Synthesis of polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid (PVAc-co-PAALi-co-PAA), 0.8g of lithium hydroxide monohydrate was added to copolymer C, and water was added so that the concentration became 10% by weight from 20% by weight, the reaction temperature was 50℃and the reaction time was 90 minutes, and polyvinyl acetate-lithium polyacrylate-polyacrylic acid (PVAc-co-PAALi-co-PAA) was obtained after the reaction.
The invention provides a preparation method and application of a lithium ion battery silicon-carbon negative electrode material adhesive for improving flexibility of a pole piece. The organic unification of the hydrophobic polymer and the hydrophilic polymer is realized by copolymerizing the polyvinyl acetate and the polyacrylic acid and regulating and controlling the proportion of the polyvinyl acetate and the polyacrylic acid, and the prepared amphiphilic copolymer adhesive can be uniformly dispersed and dissolved in water, so that the bonding effect of the polyvinyl acetate on carbon and the bonding effect of the polyacrylic acid on silicon are respectively exerted; the adhesive has the characteristics of multifunction, polyvinyl acetate sticks carbon through hydrophobic interaction, polyacrylic acid sticks silicon through hydrogen bonding, and meanwhile, the pH of the polymer is regulated by introducing lithium hydroxide monohydrate, so that the problem of gas production of carboxyl groups is reduced. Meanwhile, due to the introduction of vinyl acetate monomer with low glass transition temperature, the glass transition temperature of the final integral polymer is reduced, the mechanical property of the polymer can be regulated and controlled, the flexibility of the polymer is enhanced, and the processability of the pole piece is improved. When applied in a silicon carbon anode, exhibits good adhesion and electrochemical stability. Meanwhile, deionized water is adopted as a solvent in the whole synthesis process of the adhesive, so that the adhesive is environment-friendly.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (7)
1. The preparation method of the silicon-carbon negative electrode material adhesive is characterized by comprising the following steps of:
step 1, sequentially adding polyvinyl alcohol and an emulsifier into water, heating and dissolving, and cooling for standby to obtain a solution A;
step 2, sequentially dissolving acrylic acid, lithium hydroxide monohydrate and vinyl acetate in a solution A, bubbling the solution into the mixed solution, adding an initiator to form a reaction system B, heating the reaction system B, and reacting to generate a copolymer C, wherein the copolymer C is polyvinyl acetate-co-polyacrylic acid; copolymer C was at a concentration of 20 wt% in the product system;
step 3, adding a lithium hydroxide monohydrate aqueous solution into the copolymer C, and heating to react to obtain polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid; the molecular structural formula is as follows:
wherein: x: y: z=30 (10-20): 50-60;
the mixing ratio of polyvinyl alcohol, an emulsifying agent, acrylic acid, lithium hydroxide monohydrate, vinyl acetate and an initiator is 5:5 by mass: (30-70): (12.5-70): (30-70) 1; the lithium hydroxide monohydrate is the sum of the lithium hydroxide monohydrate amount in the step 2 and the step 3.
2. The method for preparing the silicon-carbon anode material adhesive according to claim 1, wherein in the step 1, the heating temperature is 80-90 ℃ and the heating time is 20-40 min.
3. The method for preparing the silicon-carbon anode material adhesive according to claim 1, wherein in the step 2, the reaction temperature is 65-75 ℃ and the reaction time is 30-60 min.
4. The preparation method of the silicon-carbon anode material adhesive according to claim 1, wherein in the step 3, the reaction temperature is 50-65 ℃ and the reaction time is 60-90 min.
5. The method for preparing a silicon-carbon anode material binder according to any one of claims 1 to 4, wherein in step 1, the emulsifier is OP-10, and in step 2, the initiator is ammonium persulfate.
6. A silicon carbon negative electrode material binder prepared by the preparation method of claim 1, wherein the binder is polyvinyl acetate-co-lithium polyacrylate-co-polyacrylic acid, and has a molecular structural formula:
wherein: x: y: z=30 (10-20): 50-60.
7. Use of the silicon-carbon negative electrode material binder of claim 6 in a lithium battery.
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| CN112457805A (en) * | 2020-10-27 | 2021-03-09 | 西安交通大学 | Adhesive, preparation method thereof, silicon-carbon negative electrode material and lithium battery |
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| CN106207184B (en) * | 2016-08-03 | 2019-03-01 | 宣城研一新能源科技有限公司 | A kind of water adhesive for lithium ion battery and its preparation method and application |
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| CN110423301A (en) * | 2019-07-30 | 2019-11-08 | 中航锂电（洛阳）有限公司 | A kind of binder waterborne polymeric and preparation method thereof, aqueous binders and silicon cathode lithium ion battery |
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