CN110350128B - Preparation method of composite diaphragm for lithium-sulfur battery - Google Patents
Preparation method of composite diaphragm for lithium-sulfur battery Download PDFInfo
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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Abstract
The invention relates to a lithium-sulfur battery technology, and aims to provide a preparation method of a composite diaphragm for a lithium-sulfur battery. The method comprises the following steps: reacting diamine and dianhydride to obtain polyamic acid solution, taking the polyamic acid solution as spinning solution to carry out spinning film formation, and carrying out thermal imidization treatment to obtain a polyimide spinning basement membrane; mixing a polyamic acid solution with nitrogen-containing micromolecules and graphene oxide, then spinning to form a film, and performing thermal imidization and carbonization treatment to obtain self-supporting reduced graphene oxide/nitrogen-doped carbon nanofibers; and (3) taking the polyimide spinning base film and the reduced graphene oxide/nitrogen-doped carbon nanofiber, laminating the two layers, and then slicing to obtain the composite diaphragm for assembling the lithium-sulfur battery. The diaphragm has good heat resistance and flame retardant property, and can greatly improve the safety performance of the lithium-sulfur battery; the internal resistance of the battery is reduced, and the electrochemical performance of the battery is enhanced. The lithium-sulfur battery has high charge-discharge specific capacity, high cyclicity and high safety.
Description
Technical Field
The invention relates to a lithium-sulfur battery technology, in particular to a preparation method of a composite diaphragm for a lithium-sulfur battery.
Background
Lithium sulfur batteries are an ideal replacement for today's lithium ion batteries due to the high theoretical specific capacity of sulfur (about 1675mAh g)-1) And high energy density (2600Wh kg)-1) And sulfur is a cheap and easily-obtained material with rich natural reserves and environment-friendly, and becomes an ideal battery anode material, but the current lithium sulfur battery has a certain distance from industrialization, mainly has the problems of shuttling of soluble polysulfide, the safety of the battery and the like, and particularly the electrochemical performance of the lithium sulfur battery is seriously influenced by the shuttling effect of the soluble polysulfide.
At present, the separator used in the lithium sulfur battery is more a commercial PP or PE separator, and because the separator has a large pore size and polypropylene and polyethylene do not have an adsorption effect on soluble polysulfide, it is of great significance to find a separator capable of effectively promoting polysulfide to be converted into a low-valence compound.
Because the safety problem of the battery is one of the main problems of the lithium-sulfur battery at present, and the heat resistance and the flame retardant property of the diaphragm cannot be well improved because the diaphragm is generally coated on a commercial diaphragm or a PAN diaphragm in the modification of the diaphragm at present, the selection of a base film with flame retardant and heat resistance is also significant.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a preparation method of a composite diaphragm for a lithium-sulfur battery.
In order to solve the technical problem, the solution of the invention is as follows:
provided is a method for preparing a composite separator for a lithium-sulfur battery, including the steps of:
(1) reacting equimolar diamine and dianhydride to obtain a polyamic acid solution; taking a part of the polyamic acid solution as a spinning solution to carry out spinning film formation, and carrying out thermal imidization treatment to obtain a polyimide spinning base film;
(2) mixing the residual polyamic acid solution with nitrogen-containing micromolecules and graphene oxide, spinning to form a film, and performing thermal imidization and carbonization treatment to obtain self-supporting reduced graphene oxide/nitrogen-doped carbon nanofibers;
(3) and (3) taking the polyimide spinning base film and the reduced graphene oxide/nitrogen-doped carbon nanofiber, laminating the two layers, and then slicing to obtain the composite diaphragm for assembling the lithium-sulfur battery.
In the present invention, the step (1) specifically includes:
(1.1) adding diamine into a solvent, and stirring in a cold trap at-3 ℃ under the protection of nitrogen until the diamine is dissolved; then adding dianhydride into the diamine solution for four times; after reacting for 12h, obtaining a polyamic acid solution;
(1.2) carrying out electrostatic spinning on the polyamic acid solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, the distance between a spinning needle head and a receiver is 20cm, and spinning is carried out for 2 hours to obtain a polyamic acid non-woven fabric diaphragm;
(1.3) drying the polyamic acid non-woven fabric membrane at 60 ℃ overnight, and then carrying out thermal imidization treatment to obtain the polyimide spinning basement membrane.
In the present invention, the solvent in the step (1.1) is N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP).
In the present invention, the step (2) specifically includes:
(2.1) taking a certain amount of polyamic acid solution, nitrogen-containing micromolecules and graphene oxide according to the mass ratio of the polyamic acid to the nitrogen-containing micromolecules to the graphene oxide of 8:1: 1-9: 0.5:0.5, mixing and stirring for 3 hours; carrying out electrostatic spinning on the mixed solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, and the distance between a spinning needle head and a receiver is 20 cm; spinning for 2h to obtain a polyamide acid composite non-woven fabric diaphragm;
and (2.2) drying the polyamic acid composite non-woven fabric membrane obtained in the step (2.1) at 60 ℃ overnight, performing thermal imidization treatment, and then performing carbonization treatment to obtain the self-supported reduced graphene oxide/nitrogen-doped carbon nanofiber.
In the present invention, the thermal imidization means: in N2Under protection, heating at 5 deg.C/min, and keeping the temperature at 100 deg.C, 200 deg.C, and 300 deg.C for 1 h; the carbonization is as follows: in N2Under protection, heating to 500 ℃ at a speed of 3 ℃/min, and keeping the temperature for 1 h; then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is kept for 2 h.
In the invention, the diamine in the step (1) is any one or more of the following: p-phenylenediamine, 4 '-diaminodiphenyl ether, diphenylenediamine, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 4' -diaminodiphenyl sulfone, or 1, 6-hexanediamine; the dianhydride is any one or more of the following: 4,4' -diphenyl ether dianhydride, pyromellitic dianhydride, 3',4,4' -diphenyl tetracarboxylic dianhydride, hexafluoro dianhydride or triphendiether tetracarboxylic dianhydride.
In the invention, the nitrogen-containing small molecule in the step (2) is at least one of dicyandiamide or melamine.
Description of the inventive principles:
the diaphragm is obtained by laminating a polyimide spinning base film and a reduced graphene oxide/nitrogen-doped carbon nanofiber layer and then slicing the laminated layers. The nitrogen-doped carbonized film can effectively promote the polysulfide conversion and accelerate the electron transmission, and intercept the polysulfide, thereby promoting the polysulfide to be converted into low-price Li2S2And Li2S, inhibiting the polysulfide shuttling effect. The layer structure is also used as a current collector, promotes the transfer of electrons, accelerates the conversion of polysulfide and has better physical and chemical adsorption effects. The polyimide base film can greatly improve the heat resistance of the diaphragm. The compounding of the base film and the nitrogen-doped carbonization film compounded by the reduced graphene oxide can greatly improve the electrochemistry and safety performance of the lithium-sulfur battery.
Compared with the prior art, the invention has the beneficial effects that:
1. the base film of the diaphragm is the base film of the electrostatic spinning polyimide non-woven fabric, so that the diaphragm has good heat resistance and flame retardance, and the safety performance of the lithium-sulfur battery can be greatly improved; and the good electrostatic spinning fiber can also increase the liquid absorption rate of the electrolyte, thereby reducing the internal resistance of the battery and enhancing the electrochemical performance of the battery.
2. The composite interlayer of the diaphragm has strong physical and chemical adsorption effects on polysulfide. The spinning conductive fiber is not only used as a current collector to promote the transfer of electrons and accelerate the conversion of polysulfide, nitrogen-containing micromolecules and nitrogen elements in polyimide are changed into pyridine nitrogen or pyrrole nitrogen in the carbonization process, but the composite pyridine nitrogen also has stronger adsorption effect on lithium polysulfide, so that soluble polysulfide can keep higher concentration gradient in the battery and cannot pass through the diaphragm to reach a negative electrode. Through the physical and chemical adsorption, the probability of polysulfide penetrating through the diaphragm can be greatly reduced, and the electrochemical performance of the battery is improved.
3. According to the invention, the designed composite diaphragm can greatly improve the electrochemistry and safety performance of the lithium-sulfur battery, so that the high charge-discharge specific capacity, high cyclicity and safety of the lithium-sulfur battery are realized.
Drawings
Fig. 1 is a graph of voltage capacity of the first turn of the composite separator prepared in example 1 and PP at 0.5c rate during charge and discharge.
Fig. 2 is a graph of the charge and discharge cycle performance of the composite separator prepared in example 1 and PP at a rate of 0.5 c.
Detailed Description
The preparation method of the composite diaphragm provided by the invention comprises the following steps:
(1) reacting equimolar diamine and dianhydride to obtain a polyamic acid solution; taking a part of the polyamic acid solution as a spinning solution to carry out spinning film formation, and carrying out thermal imidization treatment to obtain a polyimide spinning base film; the method specifically comprises the following steps:
(1.1) adding diamine into a solvent, and stirring in a cold trap at-3 ℃ under the protection of nitrogen until the diamine is dissolved; then adding dianhydride into the diamine solution for four times; after reacting for 12h, obtaining a polyamic acid solution; the solvent is N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP);
the diamine is any one or more of the following: p-phenylenediamine, 4 '-diaminodiphenyl ether, diphenylenediamine, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 4' -diaminodiphenyl sulfone, or 1, 6-hexanediamine; the dianhydride is any one or more of the following: 4,4' -diphenyl ether dianhydride, pyromellitic dianhydride, 3',4,4' -diphenyl tetracarboxylic dianhydride, hexafluoro dianhydride or triphendiether tetracarboxylic dianhydride.
(1.2) carrying out electrostatic spinning on the polyamic acid solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, the distance between a spinning needle head and a receiver is 20cm, and spinning is carried out for 2 hours to obtain a polyamic acid non-woven fabric diaphragm;
(1.3) drying the polyamic acid non-woven fabric membrane at 60 ℃ overnight, and then carrying out thermal imidization treatment to obtain the polyimide spinning basement membrane.
The thermal imidization refers to: in N2Under protection, heating at 5 deg.C/min, and keeping the temperature at 100 deg.C, 200 deg.C, and 300 deg.C for 1 h; the carbonization is as follows: in N2Under protection, heating to 500 ℃ at a speed of 3 ℃/min, and keeping the temperature for 1 h; then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is kept for 2 h.
(2) Mixing the residual polyamic acid solution with nitrogen-containing micromolecules and graphene oxide, spinning to form a film, and performing thermal imidization and carbonization treatment to obtain reduced graphene oxide/nitrogen-doped carbon nanofibers; the method specifically comprises the following steps:
(2.1) taking a certain amount of polyamic acid solution, nitrogen-containing micromolecules and graphene oxide according to the mass ratio of the polyamic acid to the nitrogen-containing micromolecules to the graphene oxide of 8:1: 1-9: 0.5:0.5, mixing and stirring for 3 hours; carrying out electrostatic spinning on the mixed solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, and the distance between a spinning needle head and a receiver is 20 cm; spinning for 2h to obtain a polyamide acid composite non-woven fabric diaphragm; the nitrogen-containing small molecule is at least one of dicyandiamide or melamine.
And (2.2) drying the polyamic acid composite non-woven fabric membrane obtained in the step (2.1) at 60 ℃ overnight, performing thermal imidization treatment, and then performing carbonization treatment to obtain the reduced graphene oxide/nitrogen-doped carbon nanofiber.
(3) And (3) laminating the polyimide spinning base film and the reduced graphene oxide/nitrogen-doped carbon nanofiber, and then slicing to obtain the composite diaphragm for assembling the lithium-sulfur battery.
Examples 1
Preparation example of a diaphragm sandwiched by a nitrogen-doped carbonized film.
Preparing a diaphragm: 2.0024g of 4,4 '-diaminodiphenyl ether is weighed, 4' -diaminodiphenyl ether is dissolved in 40mL of DMF under the nitrogen atmosphere in a cold trap at-3 ℃, equimolar amount of pyromellitic dianhydride is added to the solution four times at half minute intervals, specifically, 0.7271g is added to each of the first and second times, 0.3635g is added to each of the third and fourth times, and the reaction is carried out for 12 hours, thus obtaining a polyamic acid solution. Then, carrying out electrostatic spinning on the polyamic acid solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, the distance between a spinning needle head and a receiver is 20cm, spinning for 2h, drying the polyamic acid non-woven fabric diaphragm obtained by spinning in an oven at 60 ℃ overnight, and then placing the polyamic acid non-woven fabric diaphragm in N2Under protection, heating at the speed of 5 ℃/min, and preserving heat for 1h at the temperature of 100 ℃, 200 ℃ and 300 ℃ respectively to finish thermal imidization to obtain the polyimide spinning basement membrane with the thickness of 20-30 mu m. 4.0241g of polyamic acid solution is taken, 0.05g of dicyandiamide and 0.05g of graphene oxide are added (the mass ratio of the polyamic acid, the dicyandiamide and the graphene oxide in the solution is 8:1:1), the mixture is stirred for 3 hours to be uniformly mixed, and then electrostatic spinning and thermal imidization are carried out under the same conditions. Then continue at N2Under protection, the temperature is raised to 500 ℃ at the speed of 3 ℃/min, the temperature is maintained for 1h, then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is maintained for 2 h. And after carbonization is completed, taking out the nitrogen-doped carbonized film with the thickness of 10-15 microns, then overlapping the nitrogen-doped carbonized film with the polyimide spinning base film, and cutting the nitrogen-doped carbonized film into 19mm wafers to obtain the composite diaphragm.
Preparing an electrode slice: the Super-P and sulfur powder are mixed according to the mass ratio of 2:7, putting the mixture into a polytetrafluoroethylene reaction kettle, putting the polytetrafluoroethylene reaction kettle into an oven at 155 ℃ for 3 hours, and mixing the taken-out sulfur-carbon composite with the polyvinylidene fluoride serving as the binder according to a mass ratio of 9:1, adding the mixture into a mortar, uniformly mixing, adding a proper amount of solvent NMP, and grinding for 30min to obtain slurry. And uniformly coating the slurry on a carbon-coated aluminum foil by using a scraper method, drying in an oven at 60 ℃ overnight, and cutting the dried positive plate into a 14mm circular pole piece to finish the preparation of the positive plate.
Assembling the lithium-sulfur battery: and assembling the button 2025 battery, namely, taking the metal lithium sheet as a lithium cathode and taking the foamed nickel as a gasket to complete the assembly of the sulfur anode/composite diaphragm/lithium sheet/foamed nickel button battery.
And (3) testing and comparing the composite diaphragm and the commercial PP diaphragm, and comparing the first-circle voltage capacity of the two batteries at 0.5c and the charge-discharge cycle performance of the two batteries at 0.5c respectively.
From the voltage capacity diagram of fig. 1, it can be seen that the charge and discharge platform of the GNP/PI membrane prepared in this example is longer, and the voltage lag between the charge and discharge curves is narrower, indicating that the GNP/PI membrane has high specific discharge capacity and better electrochemical reversibility during charge and discharge.
As can be seen from FIG. 2, the first-pass discharge capacity of the GNP/PI separator prepared in this example is 884.6mAh/g, while that of the PP separator is only 530.1 mAh/g; the GNP/PI diaphragm can still maintain high specific discharge capacity of 881.4mAh/g after 100 circles, the capacity decay rate is only 0.36%, and the capacity is hardly reduced, while the PP diaphragm has the capacity of 422.1mAh/g after 100 circles, the capacity decay rate reaches 20.4%, and is much higher than that of the GNP/PI diaphragm, which shows that the GNP/PI diaphragm has better capacity retention rate and higher capacity.
EXAMPLES example 2
Preparing a diaphragm: weighing 2.0024g of 4,4 '-diaminodiphenyl ether, dissolving 4,4' -diaminodiphenyl ether in DMF (dimethyl formamide) in a cold trap at the temperature of-3 ℃ under the atmosphere of nitrogen, adding 3,3',4,4' -biphenyltetracarboxylic dianhydride with equal molar quantity into the solution at intervals of half a minute four times, specifically, adding 0.9807g into the solution at the first time and adding 0.4904g into the solution at the third time and the fourth time respectively, reacting for 12 hours to obtain polyamic acid solution, then carrying out electrostatic spinning on the polyamic acid solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, the distance between a spinning needle and a receiver is 20cm, spinning for 2 hours, drying a non-woven fabric diaphragm obtained by spinning in an oven at the temperature of 60 ℃ for overnight, and then drying the non-woven fabric diaphragm in an N drying oven2Under protection, heating at the stage of 5 ℃/min, and preserving heat for 1h at the temperature of 100 ℃, 200 ℃ and 300 ℃ respectively to finish thermal imidization to obtain the polyimide spinning base film with the thickness of 30-40 mu m. 7.3627g of polyamide acid are dissolvedAdding 0.1g of melamine and 0.05g of graphene oxide (the mass ratio of the polyamic acid to the melamine to the graphene oxide in the solution is 8.5:1:0.5), stirring for 3h to mix uniformly, performing electrostatic spinning and thermal imidization under the same conditions, and then continuing to perform N2Under protection, the temperature is raised to 500 ℃ at the speed of 3 ℃/min, the temperature is maintained for 1h, then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is maintained for 2 h. And (3) finishing carbonization, taking out the nitrogen-doped carbonized film with the thickness of 15-20 microns, overlapping the nitrogen-doped carbonized film with the polyimide base film, and cutting the polyimide base film into 19mm wafers to obtain the composite diaphragm.
Preparing an electrode slice: the Super-P and sulfur powder are mixed according to the mass ratio of 2:7, placing the mixture into a polytetrafluoroethylene reaction kettle, placing the reaction kettle into an oven at 155 ℃ for 3 hours, adding the taken-out sulfur-carbon composite and the adhesive polyvinylidene fluoride into a mortar according to the mass ratio of 9:1, uniformly mixing, adding a proper amount of solvent NMP, and grinding for 30min to prepare slurry. And uniformly coating the slurry on a carbon-coated aluminum foil by using a scraper method, drying in an oven at 60 ℃ overnight, and cutting the dried positive plate into 14mm round pieces to finish the preparation of the positive plate.
Assembling the lithium-sulfur battery: and assembling the button 2025 battery, namely, taking the metal lithium sheet as a lithium cathode and taking the foamed nickel as a gasket to complete the assembly of the sulfur anode/composite diaphragm/lithium sheet/foamed nickel button battery.
EXAMPLE 3
Preparing a diaphragm: weighing 1.0814g of p-phenylenediamine, dissolving the p-phenylenediamine in 40mLDMAc in a cold trap at the temperature of-3 ℃ under the nitrogen atmosphere, adding equimolar amounts of 3,3',4,4' -biphenyltetracarboxylic dianhydride into the solution at intervals of half a minute four times, specifically, adding 0.9807g into the solution for the first time and adding 0.4904g into the solution for the third time and the fourth time respectively, reacting for 12 hours to obtain a polyamic acid solution, then carrying out electrostatic spinning on the polyamic acid solution at the temperature of 32 ℃, the spinning voltage of 17KV, the distance between a spinning needle and a receiver of 20cm and the spinning time of 2 hours, drying the polyamic acid non-woven fabric diaphragm obtained by spinning in an oven at the temperature of 60 ℃ overnight, and then drying in an N-N (N-N) oven for 2 hours2Under protection, heating at 5 deg.C/min, and keeping at 100 deg.C, 200 deg.C and 300 deg.C for 1 hr to complete thermal imidization to obtain polyimide spinning base film with thickness of40 to 50 μm. Adding 0.075g of dicyandiamide and 0.075g of graphene oxide into 8.7629g of polyamic acid solution (the mass ratio of polyamic acid to dicyandiamide to graphene oxide in the solution is 8.5:0.75:0.75), stirring for 3h to uniformly mix, carrying out electrostatic spinning and thermal imidization under the same conditions, and then continuing to carry out N-phase2Under protection, the temperature is raised to 500 ℃ at the speed of 3 ℃/min, the temperature is maintained for 1h, then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is maintained for 2 h. And (3) finishing carbonization, taking out the nitrogen-doped carbonized film with the thickness of 20-25 mu m, then overlapping the film with the polyimide base film, and cutting the film into 19mm wafers to obtain the composite diaphragm.
Preparing an electrode slice: the Super-P and sulfur powder are mixed according to the mass ratio of 2:7, placing the mixture into a polytetrafluoroethylene reaction kettle, placing the reaction kettle into an oven at 155 ℃ for 12 hours, adding the taken-out sulfur-carbon composite and the adhesive polyvinylidene fluoride into a mortar according to the mass ratio of 9:1, uniformly mixing, adding a proper amount of solvent NMP, and grinding for 30min to obtain slurry. Uniformly coating the slurry on a carbon-coated aluminum foil by a scraper method, drying in an oven at 60 ℃ overnight, and cutting the dried positive plate into 14mm round pieces to finish the preparation of the positive plate
Assembling the lithium-sulfur battery: and assembling the button 2025 battery, namely, taking the metal lithium sheet as a lithium cathode and taking the foamed nickel as a gasket to complete the assembly of the sulfur anode/composite diaphragm/lithium sheet/foamed nickel button battery.
EXAMPLE 4
Preparing a diaphragm: weighing 2.0024g of 4,4 '-diaminodiphenyl ether, dissolving the 4,4' -diaminodiphenyl ether in 40mLNMP in a cold trap at the temperature of-3 ℃ under the nitrogen atmosphere, adding equal molar amount of pyromellitic dianhydride into the solution four times at intervals of half a minute, specifically, respectively adding 0.7271g for the first time and 0.3635g for the third time and four times, reacting for 12 hours to obtain polyamic acid solution, then carrying out electrostatic spinning on the polyamic acid solution at the temperature of 32 ℃, the spinning voltage of 17KV, the distance between a spinning needle and a receiver of 20cm and the spinning time of 2 hours, drying the polyamic acid non-woven fabric diaphragm obtained by spinning in an oven at the temperature of 60 ℃ overnight, and then drying in an N-N cold trap at the temperature of 17KV2Under protection, heating at 5 deg.C/min, and maintaining at 100 deg.C, 200 deg.C, and 300 deg.C for 1 hrAnd performing thermal imidization to obtain the polyimide spinning base film with the thickness of 50-60 mu m. Adding 0.05g of melamine and 0.05g of graphene oxide into 9.7402g of polyamic acid solution (the mass ratio of the polyamic acid to the melamine to the graphene oxide in the solution is 9:0.5:0.5), stirring for 3h to uniformly mix, carrying out electrostatic spinning and thermal imidization under the same conditions, and then continuing to perform N-phase spinning2Under protection, the temperature is raised to 500 ℃ at the speed of 3 ℃/min, the temperature is maintained for 1h, then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is maintained for 2 h. And (3) finishing carbonization, taking out the nitrogen-doped carbonized film with the thickness of 25-30 microns, overlapping the carbonized film with the polyimide base film, and cutting into 19mm wafers to obtain the composite diaphragm.
Preparing an electrode slice: mixing and stirring Super-P and sulfur powder uniformly according to the mass ratio of 2:7, putting the mixture into a polytetrafluoroethylene reaction kettle, putting the polytetrafluoroethylene reaction kettle into an oven at 155 ℃ for 3 hours, adding the taken-out sulfur-carbon composite and a binder polyvinylidene fluoride into a mortar according to the mass ratio of 9:1, mixing uniformly, adding a proper amount of solvent NMP, and grinding for 30min to prepare slurry. And uniformly coating the slurry on a carbon-coated aluminum foil by using a scraper method, drying in an oven at 60 ℃ overnight, and cutting the dried positive plate into 14mm round pieces to finish the preparation of the positive plate.
Assembling the lithium-sulfur battery: and assembling the button 2025 battery, namely, taking the metal lithium sheet as a lithium cathode and taking the foamed nickel as a gasket to complete the assembly of the sulfur anode/composite diaphragm/lithium sheet/foamed nickel button battery.
Claims (6)
1. A method for preparing a composite separator for a lithium-sulfur battery, comprising the steps of:
(1) reacting equimolar diamine and dianhydride to obtain a polyamic acid solution; taking a part of the polyamic acid solution as a spinning solution to carry out spinning film formation, and carrying out thermal imidization treatment to obtain a polyimide spinning base film;
(2) mixing the residual polyamic acid solution with nitrogen-containing micromolecules and graphene oxide, spinning to form a film, and performing thermal imidization and carbonization treatment to obtain self-supporting reduced graphene oxide/nitrogen-doped carbon nanofibers; the nitrogen-containing small molecule is at least one of dicyandiamide or melamine;
(3) and (3) taking the polyimide spinning base film and the reduced graphene oxide/nitrogen-doped carbon nanofiber, laminating the two layers, and then slicing to obtain the composite diaphragm for assembling the lithium-sulfur battery.
2. The method according to claim 1, characterized in that said step (1) comprises in particular:
(1.1) adding diamine into a solvent, and stirring in a cold trap at-3 ℃ under the protection of nitrogen until the diamine is dissolved; then adding dianhydride into the diamine solution for four times; after reacting for 12h, obtaining a polyamic acid solution;
(1.2) carrying out electrostatic spinning on the polyamic acid solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, the distance between a spinning needle head and a receiver is 20cm, and spinning is carried out for 2 hours to obtain a polyamic acid non-woven fabric diaphragm;
(1.3) drying the polyamic acid non-woven fabric membrane at 60 ℃ overnight, and then carrying out thermal imidization treatment to obtain the polyimide spinning basement membrane.
3. The method according to claim 2, wherein the solvent in step (1.1) is N, N-dimethylformamide, N-dimethylacetamide or N-methylpyrrolidone.
4. The method according to claim 1, wherein the step (2) comprises in particular:
(2.1) mixing and stirring polyamic acid solution, nitrogen-containing micromolecules and graphene oxide for 3 hours according to the mass ratio of the polyamic acid to the nitrogen-containing micromolecules to the graphene oxide of 8:1: 1-9: 0.5: 0.5; carrying out electrostatic spinning on the mixed solution, wherein the electrostatic spinning temperature is 32 ℃, the spinning voltage is 17KV, and the distance between a spinning needle head and a receiver is 20 cm; spinning for 2h to obtain a polyamide acid composite non-woven fabric diaphragm;
and (2.2) drying the polyamic acid composite non-woven fabric membrane obtained in the step (2.1) at 60 ℃ overnight, performing thermal imidization treatment, and then performing carbonization treatment to obtain the reduced graphene oxide/nitrogen-doped carbon nanofiber.
5. The method according to claim 1, wherein the thermal imidization is: in N2Under protection, heating at 5 deg.C/min, and keeping the temperature at 100 deg.C, 200 deg.C, and 300 deg.C for 1 h; the carbonization is as follows: in N2Under protection, heating to 500 ℃ at a speed of 3 ℃/min, and keeping the temperature for 1 h; then the temperature is raised to 800 ℃ at the speed of 3 ℃/min, and the temperature is kept for 2 h.
6. The method according to any one of claims 1 to 5, wherein the diamine in step (1) is any one or more of: p-phenylenediamine, 4 '-diaminodiphenyl ether, diphenylenediamine, 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 4' -diaminodiphenyl sulfone, or 1, 6-hexanediamine; the dianhydride is any one or more of the following: 4,4' -diphenyl ether dianhydride, pyromellitic dianhydride, 3',4,4' -diphenyl tetracarboxylic dianhydride, hexafluoro dianhydride or triphendiether tetracarboxylic dianhydride.
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| CN114583386B (en) * | 2022-03-22 | 2023-08-22 | 中国石油大学(华东) | Lithium-sulfur battery composite integrated diaphragm, preparation method thereof and lithium-sulfur battery |
| CN116272917B (en) * | 2023-03-16 | 2024-09-27 | 山东圳谷新材料科技有限公司 | Electrostatic spinning membrane material for adsorbing lithium ions and preparation method and application thereof |
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