CN113224314A - Three-dimensional grading porous current collector and preparation method thereof - Google Patents
Three-dimensional grading porous current collector and preparation method thereof Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
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- H01M10/052—Li-accumulators
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
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- H01M4/02—Electrodes composed of, or comprising, active material
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- H—ELECTRICITY
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/70—Carriers or collectors characterised by shape or form
- H01M4/80—Porous plates, e.g. sintered carriers
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Abstract
The invention provides a preparation method of a three-dimensional grading porous current collector, which comprises the following steps: s1) mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry; s2) coating the slurry on the surface of a current collector, drying, and removing a pore-forming agent to obtain a three-dimensional graded porous current collector; the decomposition temperature of the conductive polymer material is higher than that of the pore-forming agent. Compared with the prior art, the invention can realize the regulation and control of the three-dimensional structure shape and the pore size by changing the type of the pore-forming agent, thereby being beneficial to the lithium battery to be deposited in the pore cavity; the pore-forming agent modified by the conductive high polymer material can be used for in-situ synthesis of a pore in a three-dimensional current collector, has a defect chemical site, has electron-rich groups such as pyridine nitrogen and pyrrole nitrogen, and increases the affinity to lithium ions, so that the lithium ions can be further guided to be deposited in the three-dimensional pore, the pore-forming agent is beneficial to being applied to an actual battery system, and can be used for a lithium metal battery cathode and a lithium-free cathode.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a three-dimensional graded porous current collector and a preparation method thereof.
Background
Global energy crisis and environmental deterioration accelerate the development of green energy technologies, and further, people have attracted extensive attention to green energy storage technologies including Lithium Ion Batteries (LIBs). Since the 90 s of the last century, the commercialization of LIBs has greatly pushed the development and popularity of portable electronic products including notebooks, mobile phones, and the like. However, in recent years, with the rapid development of electric vehicles and other advanced portable electronic products, the current lithium ion battery has been gradually unable to meet the demand. In this context, high energy density batteries have become a current research hotspot field, and related research results are receiving wide attention. The lithium metal negative electrode is expected to be an ideal negative electrode material in a high-energy-density lithium battery due to the fact that the lithium metal negative electrode has high theoretical specific capacity and the lowest negative electrode electrochemical potential, however, dendrites are easily formed in the using process of the lithium metal negative electrode, and the practical application of the lithium metal negative electrode is seriously hindered due to the problems of battery safety and the like caused by the dendrites.
Nucleation and growth of lithium ion deposition behaviors generated by a negative electrode in the lithium metal battery are random in the deposition process, and a plane current collector is small in specific surface area and large in current density, so that the uniform deposition of lithium ions is not facilitated, and a huge volume expansion effect is caused. To solve this problem, three-dimensional current collectors have been used. The three-dimensional current collector has a higher specific surface area, can reduce current density, and can inhibit the formation of dendrites caused by uneven deposition of lithium metal in a circulation process to cause infinite volume expansion effect so that a lithium metal body is broken to lose good electric contact with a substrate, and lithium is changed into lithium without electrochemical activity prematurely. The principle benefits from the sand's time model, the specific surface area is large, the current density is small, and the deposition of lithium ions is more compact and uniform.
The traditional three-dimensional current collectors for lithium metal, such as foamed nickel, foamed copper and the like, are heavy in weight and are not beneficial to improving the energy density; the three-dimensional current collector can be constructed by growing copper oxide nanosheets or copper nanowires on a planar current collector such as a planar copper foil, but the preparation process is complicated and needs chemical treatment, particularly hydrogen reduction is needed in the preparation process of the copper nanowires, and large-scale preparation is not facilitated; the carbon-based three-dimensional current collector can also be made of a three-dimensional carbon skeleton, such as three-dimensional graphene, three-dimensional carbon foam and the like, but the preparation process is also complicated, high-temperature preparation is required, the preparation scale is small, the practical application is not facilitated, lithium deposition only occurs on the upper surface of the current collector of most three-dimensional skeleton current collectors, the three-dimensional skeleton is difficult to fully utilize, and meanwhile deposited lithium can directly contact with electrolyte to consume the electrolyte. Resulting in increased internal resistance and capacity degradation of the battery.
Disclosure of Invention
In view of the above, the present invention provides a three-dimensional graded porous current collector and a method for preparing the same, which are simple to prepare and can induce uniform deposition of lithium.
The invention provides a preparation method of a three-dimensional grading porous current collector, which comprises the following steps:
s1) mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry;
s2) coating the slurry on the surface of a current collector, drying, and removing a pore-forming agent to obtain a three-dimensional graded porous current collector;
the decomposition temperature of the conductive polymer material is higher than that of the pore-forming agent.
Preferably, the conductive polymer material modified pore-forming agent is prepared by the following method:
and mixing the conductive polymer monomer, the pore-forming agent and an initiator in water to perform polymerization reaction, thereby obtaining the conductive polymer material modified pore-forming agent.
Preferably, the conductive polymer monomer is selected from one or more of pyrrole, aniline, thiophene and acetylene; the pore-forming agent is selected from one or more of benzoic acid, phenolic resin, polystyrene microspheres, polymethyl methacrylate micro powder and ammonium bicarbonate; the mass ratio of the conductive polymer monomer to the pore-forming agent is 1: (0.5-2).
Preferably, the particle size of the pore-forming agent is 1-10 μm; the mass ratio of the conductive polymer monomer to the pore-forming agent is 1: 1.
preferably, the initiator is a peroxide initiator; the molar ratio of the initiator to the conductive high molecular monomer is 1: (0.8 to 1.2); the temperature of the polymerization reaction is 0-5 ℃; the polymerization reaction time is 15-30 h.
Preferably, the conductive agent is selected from one or more of conductive carbon black, graphene, carbon nanotubes, copper powder and nickel powder; the adhesive is selected from polyacrylonitrile and/or polyamide-imide.
Preferably, the mass of the conductive agent is 20-30% of the mass of the solvent; the mass of the conductive polymer material modified pore-forming agent is 50-60% of the mass of the solvent; the mass of the adhesive is 20-30% of that of the solvent.
Preferably, the thickness of the slurry coating in the step S2) is 50-200 μm.
Preferably, the pore-forming agent is removed by heating in step S2); the heating rate is 1-10 ℃/min; the heating temperature is 80-400 ℃; the heating time is 0.5-1.5 h.
The invention also provides the three-dimensional graded porous current collector prepared by the preparation method; and the inner wall of the pore passage of the three-dimensional grading porous current collector is adhered with a conductive polymer material after heat treatment.
The invention provides a preparation method of a three-dimensional grading porous current collector, which comprises the following steps: s1) mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry; s2) coating the slurry on the surface of a current collector, drying, and removing a pore-forming agent to obtain a three-dimensional graded porous current collector; the decomposition temperature of the conductive polymer material is higher than that of the pore-forming agent. Compared with the prior art, the invention mixes the slurry to coat on the current collector through the conventional lithium battery slurry process, realizes the construction of the three-dimensional structure on the planar current collector through drying and removing the pore-forming agent, does not need a complicated process, can continuously prepare in large scale, and can disperse the current density through the constructed three-dimensional structure, thereby being beneficial to the uniform and compact deposition of lithium; meanwhile, the regulation and control of the three-dimensional structure shape and the pore size can be realized by changing the type of the pore-forming agent, and the thickness can be flexibly adjusted according to the coating process, so that lithium ion can be favorably deposited in the pore cavity; in addition, the invention adopts the pore-forming agent modified by the conductive polymer material, can synthesize a defect chemical site in the pore channel in the three-dimensional current collector in situ after removing the pore-forming agent, has electron-rich groups such as pyridine nitrogen and pyrrole nitrogen, and increases the affinity to lithium ions, thereby further guiding the lithium ions to deposit in the three-dimensional pore channel, being beneficial to being applied to an actual battery system, and being capable of being used for a lithium metal battery cathode and a lithium-free cathode.
Drawings
Fig. 1 is a scanning electron microscope image of a three-dimensional graded porous current collector obtained in example 1 of the present invention;
fig. 2 is a scanning electron micrograph of a three-dimensional porous current collector obtained in comparative example 1 of the present invention;
fig. 3 is a scanning electron micrograph of a three-dimensional porous current collector obtained in comparative example 2 of the present invention;
fig. 4 is a graph comparing coulombic efficiencies of the three-dimensional graded porous current collectors obtained in example 1 and example 2 of the present invention and the three-dimensional porous current collector obtained in comparative example 1;
fig. 5 is a scanning electron microscope image of the three-dimensional graded porous current collector obtained in example 3 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a three-dimensional grading porous current collector, which comprises the following steps: s1) mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry; s2) coating the slurry on the surface of a current collector, drying, and removing a pore-forming agent to obtain a three-dimensional graded porous current collector; the decomposition temperature of the conductive polymer material is higher than that of the pore-forming agent.
According to the invention, the existing lithium battery slurry process is adopted, the pore-forming agent capable of volatilizing at low temperature is added, and the pore-forming agent volatilizes to leave holes, so that the construction of the three-dimensional current collector on the planar copper foil is realized, the effect of the traditional three-dimensional current collector can be realized, the coating can be carried out on a large scale, and the application of an actual battery system is facilitated; meanwhile, the method can be further optimized, the pore-forming agent is modified by some conductive polymers, and the steps are added, so that the structure containing defect functional groups is realized to induce the electrochemical deposition of lithium.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
In the invention, the conductive agent can be a carbon-based conductive material or a metal-based conductive material, preferably one or more of conductive carbon black, graphene, carbon nanotubes, copper powder and nickel powder; the conductive carbon black is zero-dimensional particles, the graphene is a two-dimensional conductive material, the carbon nano tube is a one-dimensional conductive material, and the two-dimensional conductive material and the one-dimensional conductive material are easier to form a good conductive path compared with the zero-dimensional particles.
The adhesive is preferably a high temperature resistant polymer adhesive, more preferably polyacrylonitrile and/or polyamideimide.
The conductive polymer material modified pore-forming agent is preferably a pore-forming agent with the surface coated with a conductive polymer material; the conductive polymer material is preferably one or more of polypyrrole, polyaniline, polythiophene and polyacetylene; in the present invention, the conductive polymer material modified pore-forming agent is preferably formed by in-situ polymerization using a solution method, and more preferably prepared according to the following method: and mixing the conductive polymer monomer, the pore-forming agent and an initiator in water to perform polymerization reaction, thereby obtaining the conductive polymer material modified pore-forming agent. The conductive polymer monomer is preferably one or more of pyrrole, aniline, thiophene and acetylene; the pore-forming agent is preferably one or more of benzoic acid, phenolic resin, polystyrene microspheres, polymethyl methacrylate micro powder and ammonium bicarbonate; the particle size of the pore-forming agent is preferably 1-10 mu m, and more preferably 5-10 mu m; the mass ratio of the conductive polymer monomer to the pore-forming agent is preferably 1: (0.5 to 2), more preferably 1: (0.5 to 1.5), and preferably 1: (0.8 to 1.2), more preferably 1: 1; the initiator is preferably a peroxide initiator, more preferably ammonium persulfate; the molar ratio of the initiator to the conductive polymer monomer is preferably 1: (0.8 to 1.2), more preferably 1: 1; in the invention, preferably, after mixing the conductive polymer monomer, the pore-forming agent and water, controlling the temperature to be the polymerization reaction temperature, then adding the initiator for mixing and carrying out polymerization reaction, and carrying out in-situ oxidation polymerization on the conductive polymer monomer on the surface of the pore-forming agent to obtain the pore-forming agent modified by the conductive polymer material; the concentration of the conductive polymer monomer in the reaction system is preferably 0.5-5 mg/ml, more preferably 0.5-3 mg/ml, and still more preferably 1-2 mg/ml; the temperature of the polymerization reaction is preferably 0-5 ℃; the time of the polymerization reaction is preferably 15-30 h, more preferably 20-26 h, and still more preferably 24-26 h. The conductive polymer material is modified on the surface of the pore-forming agent, so that the doping of the defect chemical functional groups in the internal hollow island can be realized.
Mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry; the solvent is preferably N-methylpyrrolidone; the mass of the conductive agent is preferably 20-30% of that of the solvent, and more preferably 20-25%; the mass of the adhesive is preferably 20-30% of that of the solvent, and more preferably 20-25%; the mass of the conductive polymer material modified pore-forming agent is preferably 50-60% of that of the solvent, and more preferably 55-60%; the mixing speed is preferably 300-800 r/min, more preferably 400-600 r/min, and still more preferably 500 r/min; the mixing time is preferably 5-10 h, more preferably 6-9 h, and still more preferably 7-8 h.
Coating the slurry on the surface of a current collector; the thickness of the slurry coating is preferably 50-200 μm, more preferably 80-150 μm, even more preferably 80-120 μm, and most preferably 100 μm; the current collector is preferably a metal foil, more preferably a copper foil or an aluminum foil.
Drying after coating; the drying is preferably drying; the drying temperature is preferably 60-80 ℃; the solvent was removed by drying.
After drying, removing the pore-forming agent to obtain a three-dimensional graded porous current collector; in the present invention, it is preferable that the pore-forming agent is removed by heating, and the pore-forming agent is removed by heating to gasify and decompose the pore-forming agent; the heating is preferably carried out in a vacuum or protective atmosphere; the protective atmosphere is preferably argon; the heating rate is preferably 1-10 ℃/min, more preferably 2-8 ℃/min, still more preferably 4-6 ℃/min, and most preferably 5 ℃/min; the heating temperature is preferably 80-400 ℃, and can be selected according to the type of the pore-forming agent, for example, the pore-forming agent is polymethyl methacrylate micro powder, the heating temperature is preferably 200-400 ℃, for example, the pore-forming agent is ammonium bicarbonate, and the heating temperature is preferably 80-100 ℃; the heating time, namely the heat preservation time is preferably 0.5-1.5 h, preferably 0.8-1.2 h, and preferably 1 h; the structure transformation of the conductive polymer material modified in situ can be realized in the process of removing the pore-forming agent in the protective atmosphere, so that a defect chemical site with pyrrole nitrogen and pyrrole nitrogen functional groups is formed on the inner wall of the pore channel.
According to the invention, the slurry prepared by the conventional lithium battery slurry process is coated on the current collector, and the three-dimensional structure is constructed on the planar current collector by drying and removing the pore-forming agent, so that the method does not need a complicated process, can be used for continuous large-scale preparation, and can disperse the current density due to the constructed three-dimensional structure, thereby being beneficial to uniform and compact deposition of lithium; meanwhile, the regulation and control of the three-dimensional structure shape and the pore size can be realized by changing the type of the pore-forming agent, and the thickness can be flexibly adjusted according to the coating process, so that lithium ion can be favorably deposited in the pore cavity; in addition, the invention adopts the pore-forming agent modified by the conductive polymer material, can synthesize a defect chemical site in the pore channel in the three-dimensional current collector in situ after removing the pore-forming agent, has electron-rich groups such as pyridine nitrogen and pyrrole nitrogen, and increases the affinity to lithium ions, thereby further guiding the lithium ions to deposit in the three-dimensional pore channel, being beneficial to being applied to an actual battery system, and being capable of being used for a lithium metal battery cathode and a lithium-free cathode.
The invention also provides the three-dimensional hierarchical porous current collector prepared by the method, wherein the inner wall of the pore passage of the three-dimensional hierarchical porous current collector is attached with a conductive high polymer material; the conductive polymer material is preferably one or more of polypyrrole, polyaniline, polythiophene and polyacetylene.
The invention also provides a lithium metal battery cathode, which comprises the three-dimensional hierarchical porous current collector prepared by the method.
In order to further illustrate the present invention, a three-dimensional graded porous current collector and a method for preparing the same according to the present invention will be described in detail with reference to the following examples.
The reagents used in the following examples are all commercially available; in the conventional ether electrolyte used in the embodiment, LiTFSI is used as lithium salt with the concentration of 1 mol/L; DME (dimethyl ether) (DOL) 1:1, and LiNO 1% by mass of the electrolyte3。
Example 1
The pore-forming agent is PMMA powder, wherein 0.1g of pore-forming agent PMMA spherical powder (with the average particle size of 10 mu m) is dispersed in deionized water to prepare 1mg/ml solution, 0.1g of pyrrole monomer is added, the mixture is uniformly stirred, and the stirring temperature is controlled at 5 ℃. And after fully and uniformly mixing, adding ammonium persulfate which is in equimolar with pyrrole, fully stirring for 24h to realize in-situ oxidative polymerization of pyrrole on the surface of the pore-forming agent PMMA material to form polypyrrole, and collecting the polypyrrole-modified pore-forming agent PMMA material by vacuum filtration.
Step 2, preparing slurry
Mixing the polypyrrole-modified PMMA powder obtained in step 1: two-dimensional conductive material graphene: high temperature resistant adhesive PAN: mixing PMMA powder (6: 2: 2) and NMP (the mass of the high-temperature-resistant adhesive is 5 percent of the mass of the solvent) to form slurry, and fully stirring at room temperature for 8 hours at 500r/min to form uniform slurry.
Step 3, current collector preparation
The slurry prepared in step 2 was uniformly coated on a copper foil (thickness 12 μm) with a thickness of 100 μm by a doctor blade, and then placed in an oven at 80 ℃ to primarily remove the solvent NMP.
Step 4, removing the pore-forming agent
And (3) heating the current collector obtained in the step (3) in an argon protective atmosphere at a heating rate of 5 ℃/min, keeping the temperature at 400 ℃ for heat treatment for 1h, completely removing the pore-forming agent, forming a three-dimensional porous structure, and obtaining the three-dimensional graded porous current collector, wherein the pore channel contains lithium-philic sites with defect chemical functional groups such as pyridine nitrogen, pyrrole nitrogen and the like.
The three-dimensional graded porous current collector obtained in example 1 was analyzed by a scanning electron microscope, and a scanning electron micrograph thereof is shown in fig. 1.
A500 μm lithium sheet was used as a counter electrode, the three-dimensional graded porous current collector obtained in example 1 was used as a working electrode, and a conventional ether electrolyte (LiTFSI, lithium salt concentration 1 mol/L; DME: DOL ═ 1: 1; LiNO, 1% by mass of electrolyte was added3) Assembled into a button cell with the power of 1mA/cm2Current density, deposition 1mAh/cm2Coulomb efficiency measurements were made on the electricity quantities and a comparative graph was obtained as shown in fig. 4. Wherein the blank comparison is that common copper foil is used as a working electrode, a 500 μm lithium sheet is used as a counter electrode, conventional ether electrolyte is adopted, and the concentration of the electrolyte is 1mA/cm2Current density, deposition 1mAh/cm2And measuring coulomb efficiency by using the electric quantity.
Example 2
The pore-forming agent is PMMA powder, wherein 0.1g of the pore-forming agent PMMA (with the average particle size of 10 mu M) is dispersed in deionized water to prepare a solution of 1mg/ml, hydrochloric acid is added to enable the concentration of the hydrochloric acid to be 1M, 0.1g of aniline monomer is added, the mixture is uniformly stirred, and the stirring temperature is controlled to be 5 ℃. And after fully and uniformly mixing, adding ammonium persulfate with the same mol as aniline, fully stirring for 24 hours to realize in-situ oxidation polymerization of aniline on the surface of the pore-forming agent PMMA material to form polyaniline, and collecting the polyaniline-modified pore-forming agent PMMA material by suction filtration.
Step 2, preparing slurry
In the implementation 2, PAN is selected as a binder, polyaniline-modified PMMA powder is selected as a pore-forming agent, and the conductive phase is selected from two-dimensional graphene, the binder PAN: two-dimensional graphene material: and (3) preparing slurry by using a pore-forming agent PMMA with the mass ratio of (2: 2: 6), selecting NMP (the mass of the binder is 5% of the mass of the solvent) as a solvent, mixing the slurry, and fully stirring the slurry at room temperature for 8 hours at 500r/min to obtain the slurry.
Step 3, current collector preparation
The slurry prepared in step 2 was uniformly coated on a copper foil (thickness 12 μm) with a thickness of 100 μm by a doctor blade, and then placed in an oven at 80 ℃ to primarily remove the solvent NMP.
Step 4, removing the pore-forming agent
And (3) heating the current collector obtained in the step (3) in an argon protective atmosphere at a heating rate of 5 ℃/min, keeping the temperature at 400 ℃ for heat treatment for 1h, completely removing the pore-forming agent, forming a three-dimensional porous structure, and obtaining the three-dimensional graded porous current collector, wherein the pore channel contains lithium-philic sites with defect chemical functional groups such as pyridine nitrogen, pyrrole nitrogen and the like.
A button cell is assembled by using a 500-micron lithium sheet as a counter electrode and the three-dimensional graded porous current collector obtained in the example 2 as a working electrode and adopting a conventional ether electrolyte, wherein the total amount of electrolyte is 1mA/cm2Current density, deposition 1mAh/cm2Coulomb efficiency measurements were made on the electricity quantities and a comparative graph was obtained as shown in fig. 4.
Example 3
The pore-forming agent is PMMA powder, wherein 0.1g of the pore-forming agent PMMA (with the average particle size of 5 mu M) is dispersed in deionized water to prepare a solution of 1mg/ml, hydrochloric acid is added to enable the concentration of the hydrochloric acid to be 1M, 0.1g of aniline monomer is added, the mixture is uniformly stirred, and the stirring temperature is controlled to be 5 ℃. And after fully and uniformly mixing, adding ammonium persulfate with the same mol as aniline, fully stirring for 24 hours to realize in-situ oxidation polymerization of aniline on the surface of the pore-forming agent PMMA material to form polyaniline, and collecting the polyaniline-modified pore-forming agent PMMA material by suction filtration.
Step 2, preparing slurry
In the implementation 2, PAN is selected as a binder, polyaniline-modified PMMA powder is selected as a pore-forming agent, and the conductive phase is selected from two-dimensional graphene, the binder PAN: two-dimensional graphene material: preparing slurry with the pore-forming agent PMMA in a mass ratio of (3: 2: 5), selecting NMP (the mass of the binder is 5% of the mass of the solvent) as a solvent, mixing the slurry, and fully stirring the slurry at room temperature for 8 hours at 500r/min to obtain the slurry.
Step 3, current collector preparation
The slurry prepared in step 2 was uniformly coated on a copper foil (thickness 12 μm) with a thickness of 100 μm by a doctor blade, and then placed in an oven at 80 ℃ to primarily remove the solvent NMP.
Step 4, removing the pore-forming agent
And (3) heating the current collector obtained in the step (3) in an argon protective atmosphere at a heating rate of 5 ℃/min, keeping the temperature at 400 ℃ for heat treatment for 1h, completely removing the pore-forming agent, forming a three-dimensional porous structure, and obtaining the three-dimensional graded porous current collector, wherein the pore channel contains lithium-philic sites with defect chemical functional groups such as pyridine nitrogen, pyrrole nitrogen and the like.
The three-dimensional graded porous current collector obtained in example 3 was analyzed by a scanning electron microscope, and a scanning electron micrograph thereof is shown in fig. 5.
Comparative example 1
Step 2, preparing the slurry,
in the implementation 2, PAN is selected as a binder, PMMA powder is selected as a pore former (average particle size is 10 μm), and carbon black is selected as a conductive phase, wherein the binder PAN: carbon black: and (3) preparing slurry by using a pore-forming agent PMMA with the mass ratio of (2: 2: 6), selecting NMP (the mass of the binder is 5% of the mass of the solvent) as a solvent, mixing the slurry, and fully stirring the slurry at room temperature for 8 hours at 500r/min to obtain the slurry.
Step 3, current collector preparation
The slurry prepared in step 2 was uniformly coated on a copper foil (thickness 12 μm) with a thickness of 100 μm by a doctor blade, and then placed in an oven at 80 ℃ to primarily remove the solvent NMP.
Step 4, removing the pore-forming agent
And (4) heating the current collector obtained in the step (3) at a heating rate of 5 ℃/min in an argon protective atmosphere, keeping the temperature at 400 ℃ for heat treatment for 1h, completely removing the pore-forming agent, and forming the three-dimensional porous current collector.
The three-dimensional porous current collector obtained in comparative example 1 was analyzed by a scanning electron microscope, and a scanning electron micrograph thereof is shown in fig. 2.
A button cell is assembled by using a 500-micron lithium sheet as a counter electrode and the three-dimensional porous current collector obtained in the comparative example 1 as a working electrode and adopting a conventional ether electrolyte, wherein the mA/cm of the current collector is 1mA/cm2Current density, deposition 1mAh/cm2Coulomb efficiency measurements were made on the electricity quantities and a comparative graph was obtained as shown in fig. 4.
Comparative example 2
Different from the comparative example 1, the method is characterized in that the size of the pore-forming agent is different, spherical PMMA particles with the size of about 5 mu m are selected as the pore-forming agent, and other operations are the same as those in the comparative example 1.
The three-dimensional porous current collector obtained in comparative example 2 was analyzed by a scanning electron microscope, and a scanning electron micrograph thereof is shown in fig. 3.
Claims (10)
1. A method for preparing a three-dimensional graded porous current collector is characterized by comprising the following steps:
s1) mixing a conductive agent, an adhesive, a conductive polymer material modified pore-forming agent and a solvent to obtain slurry;
s2) coating the slurry on the surface of a current collector, drying, and removing a pore-forming agent to obtain a three-dimensional graded porous current collector;
the decomposition temperature of the conductive polymer material is higher than that of the pore-forming agent.
2. The preparation method of claim 1, wherein the conductive polymer material modified pore-forming agent is prepared by the following method:
and mixing the conductive polymer monomer, the pore-forming agent and an initiator in water to perform polymerization reaction, thereby obtaining the conductive polymer material modified pore-forming agent.
3. The preparation method according to claim 2, wherein the conductive polymer monomer is selected from one or more of pyrrole, aniline, thiophene and acetylene; the pore-forming agent is selected from one or more of benzoic acid, phenolic resin, polystyrene microspheres, polymethyl methacrylate micro powder and ammonium bicarbonate; the mass ratio of the conductive polymer monomer to the pore-forming agent is 1: (0.5-2).
4. The preparation method according to claim 2, wherein the pore-forming agent has a particle size of 1 to 10 μm; the mass ratio of the conductive polymer monomer to the pore-forming agent is 1: 1.
5. the method of claim 2, wherein the initiator is a peroxide initiator; the molar ratio of the initiator to the conductive high molecular monomer is 1: (0.8 to 1.2); the temperature of the polymerization reaction is 0-5 ℃; the polymerization reaction time is 15-30 h.
6. The method according to claim 1, wherein the conductive agent is selected from one or more of conductive carbon black, graphene, carbon nanotubes, copper powder and nickel powder; the adhesive is selected from polyacrylonitrile and/or polyamide-imide.
7. The preparation method according to claim 1, wherein the mass of the conductive agent is 20-30% of the mass of the solvent; the mass of the conductive polymer material modified pore-forming agent is 50-60% of the mass of the solvent; the mass of the adhesive is 20-30% of that of the solvent.
8. The method according to claim 1, wherein the slurry is applied to a thickness of 50 to 200 μm in step S2).
9. The production method according to claim 1, wherein the pore-forming agent is removed by heating in step S2); the heating rate is 1-10 ℃/min; the heating temperature is 80-400 ℃; the heating time is 0.5-1.5 h.
10. A three-dimensional graded porous current collector prepared by the preparation method of any one of claims 1 to 9; and the inner wall of the pore passage of the three-dimensional grading porous current collector is adhered with a conductive polymer material after heat treatment.
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