CN112713265A - Composite conductive binder suitable for silicon-based negative electrode, preparation method and application - Google Patents
Composite conductive binder suitable for silicon-based negative electrode, preparation method and application Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- 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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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention discloses a composite conductive binder suitable for a silicon-based negative electrode, and a preparation method and application thereof. The method comprises the following steps: 1) adding the single-wall nanotube and the carbon fiber into an aqueous solution of an acrylic polymer binder, and infiltrating to obtain a mixed system; 2) dispersing the mixed system in the step 1) to obtain the composite conductive adhesive. According to the method, the single-walled carbon nanotube and the carbon fiber are compounded with the conductive agent and matched with the acrylic polymer binder, and after the composite conductive binder is soaked and dispersed, the composite conductive binder has excellent conductivity and good dispersibility, has good binding power when being applied to a silicon-based negative electrode, avoids the use of a small molecular dispersant, and solves the problem of incompatibility of the conductive agent and the binder.
Description
Technical Field
The invention relates to the technical field of new energy, and relates to a composite conductive binder suitable for a silicon-based negative electrode, a preparation method and application.
Background
The silicon-based anode material has the following two problems: (1) in the charge-discharge cycle process of the silicon material, active substances are easy to break and pulverize due to large volume expansion (about 300%), and in addition, the expansion and shrinkage of silicon particles cause continuous breakage and generation of a surface SEI film, so that limited electrolyte and lithium in a positive electrode are consumed, the SEI film is thickened, the internal resistance of a battery is increased, and the cycle performance of the battery is finally rapidly degraded; (2) silicon is used as a semiconductor, has much poorer conductivity than graphite, and has larger polarization and slower dynamic process in the charge and discharge process.
For the above problems, the existing methods, on one hand, design and optimize the structure of the silicon-based material, reduce the size of the silicon particles, regulate and control the micro-morphology to reduce and inhibit the volume expansion, and improve the cycle life, for example, CN111180712A adopts the spray drying technology to prepare the carbon nanotube microspheres, then uses the carbon nanotube microspheres as the hard template, and deposits the nano-silicon particles in the interior and on the surface by the chemical vapor deposition method. For another example, CN111883760A provides a composite nano-silicon negative electrode material, in which nano-silicon is uniformly dispersed in a three-dimensional electron conducting skeleton and a polymer, and the polymer wraps the nano-silicon and the conductive material, so as to reduce the shedding caused by the volume expansion of silicon. However, this reduces the material compaction density and energy density and complicates the manufacturing process; and on the other hand, the silicon-based materials are optimally designed and matched with auxiliary materials, such as a binder and a conductive agent. The common binder comprises sodium carboxymethylcellulose, styrene butadiene rubber, polyacrylic acid, sodium alginate and the like, and when the binder is designed and matched, the binder is required to have certain dispersibility and binding power, and the binder is expected to have better flexibility. The commonly used conductive agents comprise carbon nano tubes, carbon black, graphene, carbon fibers and composite conductive agents thereof, and the like, so that a three-dimensional conductive network is formed, and better electronic and ionic conductivity, long-range conductivity and short-range conductivity are ensured. However, the adhesive and the conductive agent in the market are various in types, and the matching of the adhesive and the conductive agent leads to a plurality of problems: 1) the conductive agent mainly comprising CNT is likely to introduce a small-molecule unstable dispersant to promote the cyclic gas generation of the battery; 2) some binders are incompatible with conductive agents and use together can present difficulties in homogenization and dispersion.
Therefore, there is a need for a new composite conductive binder, which is important for promoting the development of silicon-based negative electrode systems.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a composite conductive adhesive suitable for a silicon-based negative electrode, a preparation method and application thereof, and particularly provides a composite conductive adhesive suitable for a silicon-based negative electrode, a preparation method and a preparation method of a silicon-based negative electrode piece.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a composite conductive binder suitable for a silicon-based anode, the method comprising the steps of:
(1) adding the single-wall nanotube and the carbon fiber into an aqueous solution of an acrylic polymer binder, and infiltrating to obtain a mixed system;
(2) dispersing the mixed system in the step (1) to obtain a composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotube in the mixed system is 0.2-0.6%.
According to the method, the single-walled carbon nanotube and the carbon fiber are compounded with the conductive agent and matched with the acrylic polymer binder, and after infiltration and dispersion, the obtained composite conductive binder has excellent conductivity and good dispersibility, has good binding power when being applied to a silicon-based negative electrode, avoids the use of small molecular dispersibility, and solves the problem of incompatibility of the conductive agent and the binder. The technical principle is as follows: firstly, because the single-walled carbon nanotube has ultrahigh conductivity and very high length-diameter ratio, the addition of the single-walled carbon nanotube is beneficial to coating and inhibiting the cyclic expansion of a silicon-based negative electrode active material; the carbon fiber with a lower specific surface area is matched with the single-walled carbon nanotube, so that the consumption of the adhesive can be reduced, the high adhesive force of the adhesive during the subsequent preparation of the silicon-based negative electrode is ensured, the porosity of a pole piece is increased, and the silicon-based negative electrode has good cycle performance and rate capability. And the acrylic acid polymer binder has good dispersion effect on the carbon nano tubes and the carbon fibers, ensures the exertion of the beneficial effects of the carbon nano tubes and the carbon fibers, and has good binding effect on silicon-based negative active substances.
The preparation method is simple, large-scale production is easy to realize, the viscosity of the prepared conductive paste is proper and generally ranges from 3000 mPa.s to 20000 mPa.s, the stability is good, and the negative electrode paste prepared by the conductive paste is favorable for obtaining good coating performance.
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 technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
Generally, single-walled carbon nanotubes have a very high aspect ratio, for example in the range of 5000 to 100000.
Preferably, the mass ratio of the single-walled carbon nanotubes in the step (1) in the mixed system is 0.2-0.6%, such as 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%.
The method can ensure good dispersibility, conductivity and good compounding effect with carbon fibers under the condition of adding a small amount of single-walled carbon nanotubes, thereby enabling the silicon-based negative electrode to obtain excellent electrochemical performance.
Preferably, the carbon fiber of step (1) is Vapor Grown Carbon Fiber (VGCF).
Preferably, the pipe diameter of the carbon fiber in the step (1) is 150-200 nm. The specific manufacturer and grade of the carbon fiber are not particularly limited, and the manufacturer may be, for example, Showa, Jiangxi Kai carbon nanocarbon Co., Ltd. The carbon fiber has the characteristics of large size and small specific surface area, is beneficial to reducing the consumption of the adhesive, increasing the porosity and the adhesive force of a pole piece and improving the electrochemical performance of the silicon-based negative electrode.
Preferably, the mass ratio of the single-walled carbon nanotubes to the carbon fibers in the step (1) is (0.04-0.08): (0.3-0.7), such as 0.02:0.3, 0.04:0.5 or 0.02: 0.5.
Preferably, the acrylic polymer binder in step (1) is an acrylic polymer binder. For example, LA136D from Chengdingle Power technology, Inc., S66 from Shenzhen research New materials, Inc., BA1810 from Taiwan Changxing chemical industry, Inc., etc., can be used.
Preferably, the mass fraction of the aqueous solution of the acrylic polymer binder in the step (1) is 0.4 to 5%, for example, 0.4%, 0.5%, 0.8%, 1%, 1.5%, 1.7%, 2%, 2.5%, or 3%, and preferably 0.5 to 3%.
Preferably, the mixed system in the step (1) is prepared according to the following mode:
(a) mixing an acrylic high-molecular binder with water, stirring at a low speed of 100-300 r/min to obtain an aqueous solution of the acrylic high-molecular binder;
(b) and (b) increasing the stirring speed of the aqueous solution obtained in the step (a) to 800-1500 r/min, and adding the single-walled carbon nanotubes and the carbon fibers to fully mix and wet the mixture for 0.5-2 h (for example, 0.5h, 1h, 1.2h, 1.5h or 2 h).
In the present invention, the dispersing means in step (2) is not particularly limited, and may be homogenization treatment, sanding treatment, or treatment with an ultrasonic oscillator.
Preferably, the particle size distribution of the slurry after homogenization treatment satisfies: d50 is 0.5-5 μm, for example, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 2 μm, 3 μm, 4 μm or 5 μm, preferably 0.5-1.5 μm.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
s1 dilution:
mixing an acrylic high-molecular binder with water, stirring at a low speed, wherein the rotating speed is 100-300 r/min, and obtaining an aqueous solution of the acrylic high-molecular binder, wherein the mass fraction of the aqueous solution of the acrylic high-molecular binder is 0.5-3%;
s2 predispersion:
increasing the stirring speed of the aqueous solution obtained in the step S1 to 800-1500 r/min, adding the single-walled carbon nanotube and VGCF (VGCF), and fully mixing and wetting the mixture for 0.5-2 h to obtain a mixed system;
s3 dispersing:
and S2, homogenizing the mixed system, wherein the homogenizing pressure is 10-80 Mpa, and the homogenizing circulation is performed for 5-20 times, so that the particle size distribution of the slurry after homogenizing treatment meets the following requirements: d50 is 0.5-1.5 mu m to obtain the composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotube in the mixed system is 0.2-0.6%.
In a second aspect, the present invention provides a composite conductive adhesive prepared according to the method of the first aspect.
In a third aspect, the invention provides a preparation method of a silicon-based negative electrode plate, which comprises the following steps:
and mixing the silicon-based negative electrode, the composite conductive binder in the second aspect, SP and polyacrylic acid to prepare negative electrode slurry with the solid content of 40-50%, coating the negative electrode slurry on a negative electrode current collector, and drying to obtain the silicon-based negative electrode.
Preferably, the mass ratio of the silicon-based negative electrode active material, the single-walled carbon nanotube, the carbon fiber, the acrylic polymer binder and the SP is (95% -97%) to (0.04% -0.08) to (0.3% -0.7) to (2% -3.5) to (0.5% -1), for example, 95.74% to 0.06% to 0.5% to 2.95% to 0.7% or 96.50% to 0.05% to 0.45% to 2.5% to 0.5%, based on 100% of the mass of the negative electrode slurry.
In a fourth aspect, the invention provides a silicon-based negative electrode plate prepared by the method in the third aspect.
In a fifth aspect, the present invention provides a lithium ion battery, where the lithium ion battery includes the silicon-based negative electrode plate of the fourth aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the method, the single-walled carbon nanotube and the carbon fiber are compounded with the conductive agent, and the conductive agent is matched with the acrylic polymer binder, and after infiltration and homogenization treatment, the obtained composite conductive binder has excellent conductivity and good dispersibility, has good binding power when being applied to a silicon-based negative electrode, avoids the use of a small molecular dispersant, and solves the problem of incompatibility of the conductive agent and the binder.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
In the embodiment of the invention, the single-walled carbon nanotubes are selected from Russian OCSIAL, VGCF is selected from Japanese Zhao and electrician, and the acrylic polymer binder is Japanese Sumitomo AQC.
Example 1
The embodiment provides a preparation method of a composite conductive binder suitable for a silicon-based negative electrode, which comprises the following steps:
s1 dilution:
mixing an acrylic high-molecular binder with water, stirring at a low speed, wherein the rotating speed is 150r/min, and obtaining an aqueous solution of the acrylic high-molecular binder, wherein the mass fraction of the aqueous solution of the acrylic high-molecular binder is 2%;
s2 predispersion:
increasing the stirring speed of the aqueous solution obtained in the step (a) to 1000r/min, adding the single-walled carbon nanotube and VGCF (VGCF), and fully mixing and wetting the mixture for 1h to obtain a mixed system;
s3 dispersing:
and (5) homogenizing the mixed system in the step (S2), wherein the homogenizing pressure is 30Mpa, and the homogenizing circulation is carried out for 10 times, so that the particle size distribution of the slurry after the homogenizing treatment meets the following requirements: d50 is 1.0 mu m to obtain the composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotube in the mixed system is 0.2%, and the mass ratio of the single-walled carbon nanotube to the carbon fiber is 0.06: 0.5.
The embodiment also provides a preparation method of the negative pole piece, which comprises the following steps: preparing a negative electrode slurry with solid content of 48% by adopting 450mAh/g of silicon-carbon negative electrode active substance, a composite conductive binder, SP and PAA, wherein the mass ratio of the silicon-based negative electrode active substance, the single-walled carbon nanotube, VGCF, the acrylic polymer binder and the SP in the negative electrode slurry is 95.74%, 0.06%, 0.5%, 3%, 0.7%, coating the negative electrode slurry on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate.
Example 2
The embodiment provides a preparation method of a composite conductive binder suitable for a silicon-based negative electrode, which comprises the following steps:
s1 dilution:
mixing an acrylic high-molecular binder with water, stirring at a low speed, wherein the rotating speed is 150r/min, and obtaining an aqueous solution of the acrylic high-molecular binder, wherein the mass fraction of the aqueous solution of the acrylic high-molecular binder is 1%;
s2 predispersion:
increasing the stirring speed of the aqueous solution obtained in the step (a) to 1000r/min, adding the single-walled carbon nanotube and VGCF (VGCF), and fully mixing and wetting the mixture for 1h to obtain a mixed system;
s3 dispersing:
and (5) homogenizing the mixed system in the step (S2), wherein the homogenizing pressure is 30Mpa, and the homogenizing circulation is carried out for 10 times, so that the particle size distribution of the slurry after the homogenizing treatment meets the following requirements: d50 is 1.0 mu m to obtain the composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotube in the mixed system is 0.4%, and the mass ratio of the single-walled carbon nanotube to the carbon fiber is 0.06: 0.3.
The embodiment also provides a preparation method of the negative pole piece, which comprises the following steps: preparing a negative electrode slurry with solid content of 48% by adopting 450mAh/g of silicon-carbon negative electrode active substance, a composite conductive binder, SP and PAA, wherein the mass ratio of the silicon-based negative electrode active substance, the single-walled carbon nanotube, VGCF, the acrylic polymer binder and the SP in the negative electrode slurry is 95.74%, 0.06%, 0.3%, 3%, 0.9%, coating the negative electrode slurry on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate.
Example 3
The embodiment provides a preparation method of a composite conductive binder suitable for a silicon-based negative electrode, which comprises the following steps:
s1 dilution:
mixing an acrylic high-molecular binder with water, stirring at a low speed, wherein the rotating speed is 150r/min, and obtaining an aqueous solution of the acrylic high-molecular binder, wherein the mass fraction of the aqueous solution of the acrylic high-molecular binder is 0.5%;
s2 predispersion:
increasing the stirring speed of the aqueous solution obtained in the step (a) to 1000r/min, adding the single-walled carbon nanotube and VGCF (VGCF), and fully mixing and wetting the mixture for 1h to obtain a mixed system;
s3 dispersing:
and (5) homogenizing the mixed system in the step (S2), wherein the homogenizing pressure is 30Mpa, and the homogenizing circulation is carried out for 10 times, so that the particle size distribution of the slurry after the homogenizing treatment meets the following requirements: d50 is 1.0 mu m to obtain the composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotubes in the mixed system is 0.6%, and the mass ratio of the single-walled carbon nanotubes to the carbon fibers is 0.04: 0.5.
The embodiment also provides a preparation method of the negative pole piece, which comprises the following steps: preparing a negative electrode slurry with solid content of 48% by adopting 450mAh/g of silicon-carbon negative electrode active substance, a composite conductive binder, SP and PAA, wherein the mass ratio of the silicon-based negative electrode active substance, the single-walled carbon nanotube, VGCF, the acrylic polymer binder and the SP is 95.76%, 0.04%, 0.5%, 3%, 0.7% in the negative electrode slurry, coating the negative electrode slurry on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate.
Comparative example 1
The method of preparing the negative electrode sheet was the same as in example 1 except that VGCF was not contained and the SP content was 1.2%.
And (3) detection:
firstly, rate performance testing:
the negative pole pieces of the above examples and comparative examples, lithium cobaltate positive pole pieces (the positive active material is lithium cobaltate LCO) prepared by the traditional mature process, and 1mol/L LiPF6An electrolyte solution of/EC + DMC + EMC (v/v ═ 1:1:1), a Celgard2400 separator, and a 432729 wound pack were prepared.
The rate performance of the battery was tested under the 432729 wound pouch battery test conditions, and the charge and discharge voltage was limited to 3.0V to 4.4V when tested on a LAND battery test system at ambient temperature (25 ℃), with the results shown in table 1.
II, testing cycle performance:
the battery manufactured by the method is at 25 ℃, 0.5C/0.5C and 3-4.4 v of voltage, and the current is cut off to 0.02C cycle.
TABLE 1
And (3) analysis:
by comparing example 1 with comparative example 1, it can be seen that the cycle performance and rate performance of the battery can be improved by equivalently replacing SP with a small amount of VGCF.
It is seen by comparing example 1 with example 3 that reducing the amount of single wall tube is detrimental to rate performance.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. 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. A preparation method of a composite conductive adhesive suitable for a silicon-based negative electrode is characterized by comprising the following steps:
(1) adding the single-wall nanotube and the carbon fiber into an aqueous solution of an acrylic polymer binder, and infiltrating to obtain a mixed system;
(2) and (2) dispersing the mixed system in the step (1) to obtain the composite conductive adhesive.
2. The method of claim 1, wherein the mass ratio of the single-walled carbon nanotubes in the step (1) in the mixed system is 0.2-0.6%;
preferably, the carbon fiber of step (1) is vapor grown carbon fiber VGCF;
preferably, the pipe diameter of the carbon fiber in the step (1) is 150-200 nm;
preferably, the mass ratio of the single-walled carbon nanotubes to the carbon fibers in the step (1) is (0.04-0.08): (0.3-0.7);
preferably, the mass fraction of the aqueous solution of the acrylic polymer binder in the step (1) is 0.4-5%, preferably 0.5-3%.
3. The method according to claim 1 or 2, wherein the mixed system of step (1) is prepared in the following manner:
(a) mixing an acrylic high-molecular binder with water, stirring at a low speed of 100-300 r/min to obtain an aqueous solution of the acrylic high-molecular binder;
(b) and (b) increasing the stirring rotating speed of the aqueous solution obtained in the step (a) to 800-1500 r/min, and adding the single-walled carbon nanotube and the carbon fiber to fully mix and wet the mixture for 0.5-2 h.
4. The method of any one of claims 1-3, wherein said dispersing of step (2) comprises at least one of homogenizing, sanding, and ultrasonic treatment.
5. The method according to any one of claims 1 to 4, wherein the size distribution of the homogenized slurry is such that: d50 is 0.5 to 5 μm, preferably 0.5 to 1.5 μm.
6. The method according to any one of claims 1-5, characterized in that the method comprises the steps of:
s1 dilution:
mixing an acrylic high-molecular binder with water, stirring at a low speed, wherein the rotating speed is 100-300 r/min, and obtaining an aqueous solution of the acrylic high-molecular binder, wherein the mass fraction of the aqueous solution of the acrylic high-molecular binder is 0.5-3%;
s2 predispersion:
increasing the stirring speed of the aqueous solution obtained in the step S1 to 800-1500 r/min, adding the single-walled carbon nanotube and VGCF (VGCF), and fully mixing and wetting the mixture for 0.5-2 h to obtain a mixed system;
s3 dispersing:
and S2, homogenizing the mixed system, wherein the homogenizing pressure is 10-80 Mpa, and the homogenizing circulation is performed for 5-20 times, so that the particle size distribution of the slurry after homogenizing treatment meets the following requirements: d50 is 0.5-1.5 mu m to obtain the composite conductive adhesive;
wherein the mass ratio of the single-walled carbon nanotube in the mixed system is 0.2-0.6%.
7. A composite conductive adhesive prepared according to the method of any one of claims 1-6.
8. A preparation method of a silicon-based negative electrode plate is characterized by comprising the following steps:
preparing negative electrode slurry with the solid content of 40-50% by adopting a silicon-based negative electrode, the composite conductive adhesive as claimed in claim 7, SP and polyacrylic acid, coating the negative electrode slurry on a negative electrode current collector, and drying to obtain a silicon-based negative electrode piece;
preferably, the mass ratio of the silicon-based negative electrode active material, the single-walled carbon nanotube, the carbon fiber, the acrylic polymer binder and the SP is (95% -97%) to (0.04% -0.08) to (0.3% -0.7) to (2% -3.5) to (0.5% -1) based on 100% of the negative electrode slurry.
9. A silicon-based negative electrode plate prepared according to the method of claim 8.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the silicon-based negative electrode plate of claim 8.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113745519A (en) * | 2021-08-30 | 2021-12-03 | 惠州亿纬锂能股份有限公司 | Silicon-based negative electrode material with artificial SEI film and preparation method and application thereof |
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