CN110783543B - Cobalt/carbon nanotube/sulfur particle microcapsule composite material, preparation method thereof, lithium-sulfur battery positive electrode and lithium-sulfur battery - Google Patents
Cobalt/carbon nanotube/sulfur particle microcapsule composite material, preparation method thereof, lithium-sulfur battery positive electrode and lithium-sulfur battery Download PDFInfo
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Abstract
The invention discloses a cobalt/carbon nano tube/sulfur particle microcapsule composite material and a preparation method thereof, as well as a lithium sulfur battery anode and a lithium sulfur battery, wherein microcapsules coated with cobaltosic oxide nano particles are synthesized by an in-situ polymerization method, then cobalt/carbon nano tube microcapsules are obtained through carbonization-reduction, and then the cobalt/carbon nano tube microcapsules are subjected to sulfur fumigation to obtain the cobalt/carbon nano tube/sulfur particle microcapsule composite material.
Description
Technical Field
The invention belongs to the technical field of battery composite materials, and particularly relates to a cobalt/carbon nanotube/sulfur particle microcapsule composite material, a preparation method thereof, a lithium-sulfur battery anode and a lithium-sulfur battery.
Background
Since the 21 st century, global energy crisis and environmental problems have become more serious, and human beings need to reduce their dependence on fossil fuels, so that the development of new environmentally friendly energy sources and efficient energy storage systems is urgently needed. With the increase of energy consumption and global warming, a novel energy storage system, namely a lithium ion secondary battery, with high energy density, low cost, no pollution and long service life is produced. At present, the actual specific capacity of commercial lithium ion batteries is less than 200m Ah/g, the specific energy is less than 300Wh/kg, the development of industries such as electric automobiles, electronic products, smart grids and the like is severely restricted, and researchers are promoted to develop more reasonable and effective battery energy systems.
The lithium-sulfur battery (Li-S battery) has high theoretical specific energy (2600 W.h/kg) and high theoretical specific capacity (1675 mA.h/g), and the sulfur element has the advantages of rich content in the earth crust, low price, no toxicity, no pollution and the like, so the Li-S battery is considered to be one of novel energy storage batteries with the greatest prospect of improving the energy density.
The most commonly used positive electrode material in Li-S batteries is elemental sulfur, which is mainly cyclic S in nature8The molecule is present. Different from the lithium intercalation and deintercalation reaction of the traditional lithium ion battery, the lithium sulfur battery adopts sulfur or a sulfur-containing compound as a positive electrode and lithium as a negative electrode, and realizes the mutual conversion of electric energy and chemical energy through the fracture generation of a sulfur-sulfur bond. During discharge, lithium ions migrate from the negative electrode to the positive electrode, and the positive electrode active material is broken in a sulfur-sulfur bond and combined with lithium ions to produce Li2S; upon charging, Li2S is electrolyzed, and the released lithium ions are returned to be negativeAnd a pole, deposited as metallic lithium or intercalated into the negative electrode material. The chemical process of sulfur is complex and there is a series of reversible reactions and disproportionation reactions. During the discharge, the S-S bond starts to break and continues to react with Li+Combined, successively reduced to Li2S8、Li2S6、Li2S4Long-chain polysulfides that are equally soluble in organic electrolytes; as the reaction proceeds, these long-chain polysulfides are further reduced to short-chain polysulfides Li which are insoluble in the electrolyte2S2And Li2S, depositing on the surface of the positive electrode and precipitating in a solid form. When Li is present2When S covers the entire electrode, the voltage drops rapidly, resulting in termination of the discharge. During this kinetic process, a series of soluble polysulfide intermediates, LiS, are producedx(x>2)。
Although the lithium-sulfur battery has extremely high theoretical specific capacity and energy density, the utilization rate of active substances is low, the capacity attenuation is rapid, the cycle life is short, and a certain gap is left between the capacity theoretical value and the capacity theoretical value. The specific reasons are as follows: (1) during discharge, sulfur reacts with metallic lithium to form lithium polysulfide Li which is readily soluble in the electrolyte2Sx(2<x<8) And insoluble Li2S2With Li2And S. The dissolved lithium polysulfide generates redox shuttle reaction between the anode and the cathode to cause overcharge and corrosion and pulverization of the lithium cathode, so that the coulombic efficiency is low and the lithium loss is serious in the circulating process; insoluble Li2S2And Li2S is unevenly covered on the sulfur anode, so that the conductivity of the anode is deteriorated, and finally, the service life of the battery is reduced; (2) elemental sulfur and its final product have very poor conductivity. Elemental sulfur is an electronic and ionic insulator at room temperature and has a conductivity of only 5X 10-30S/cm, when used as an electrode material, the activated carbon is difficult to activate and the utilization rate is low; (3) volume expansion and contraction are carried out in the charging and discharging processes, and the volume expansion is about 80% after complete lithiation, so that sulfur is separated from a conductive framework, the battery structure is seriously damaged, and the capacity attenuation is serious; (4) the SEI layer is repeatedly formed-cracked, and the metallic lithium and the electrolyte are continuously consumed; (5) non-uniformity of the negative electrode lithium metal surface may cause lithium dendrites to pierce the separator, causing electricityThe short circuit in the pool is invalid, which brings serious potential safety hazard.
Disclosure of Invention
In order to solve the technical problems, the invention provides a cobalt/carbon nano tube/sulfur particle microcapsule composite material and a preparation method thereof, urea, formaldehyde aqueous solution and n-hexadecane are utilized to synthesize a microcapsule wrapping cobaltosic oxide nano particles by an in-situ polymerization method in an acid solution environment, then the cobalt/carbon nano tube microcapsule is obtained by carbonization-reduction catalysis, so that the cobalt/carbon nano tube microcapsule has rich pores and larger specific surface area in the cobalt/carbon nano tube microcapsule, and then the cobalt/carbon nano tube microcapsule is subjected to sulfur fumigation to obtain the cobalt/carbon nano tube/sulfur particle microcapsule composite material, thereby obtaining the carbon nano tube composite material loaded with sulfur particles in the capsule.
The invention also provides a lithium-sulfur battery anode and a lithium-sulfur battery, wherein the lithium-sulfur battery anode is prepared by taking the cobalt/carbon nano tube/sulfur particle microcapsule composite material as an active material and assembled into the lithium-sulfur battery, and the cobalt/carbon nano tube/sulfur particle microcapsule composite material has rich void structures inside, so that the volume change can be buffered, the structural integrity of sulfur particles and cobalt/carbon nano tubes is greatly improved, the active mass loss in the charging/discharging process is reduced, and the electrochemical performance of the anode is improved.
The technical scheme adopted by the invention is as follows:
a preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
(1) ultrasonically dispersing cobaltosic oxide nanoparticles in n-hexadecane to obtain a mixed solution A;
(2) dissolving urea, resorcinol and ammonium chloride in water to obtain a mixed solution B;
(3) adding the mixed solution B into an aqueous solution of a methyl vinyl ether-maleic anhydride copolymer, adjusting the pH of the system to 3-4, stirring for dissolving, and heating for reaction for 0.5-1 h;
(4) continuously adding the mixed solution A into the step (3), and uniformly stirring; then dropwise adding a formaldehyde aqueous solution into the mixture, and continuously stirring the mixture to react to obtain a microcapsule coated with cobaltosic oxide nano particles;
(5) filtering the reaction liquid obtained in the step (4), drying a product obtained by filtering, and then carrying out carbonization reduction in the nitrogen environment;
(6) and (5) carrying out sulfur fumigation on the product obtained in the step (5) to obtain the cobalt/carbon nano tube/sulfur particle microcapsule composite material.
Further, in the step (1), the mass ratio of the cobaltosic oxide nanoparticles to the n-hexadecane is 0.1-0.5: 4.
in the step (2), the mass ratio of urea, resorcinol and ammonium chloride is (1.0-1.45): (0.15-0.35): (0.1 to 0.15), preferably 1.0: 0.2: 0.1; the concentration of the urea in the mixed solution B is 0.025-0.035 g/mL.
In the step (3), the mass concentration of the methyl vinyl ether-maleic anhydride copolymer in the aqueous solution of the methyl vinyl ether-maleic anhydride copolymer is 2.5-5%.
In the step (3), triethanolamine is used for adjusting the pH value of the system to 3.5; the temperature of the heating reaction is 40-60 ℃.
In the step (3), the stirring speed is 700-1000 rpm.
The ratio of the mixed solution A to the mixed solution B to the aqueous solution of the methyl vinyl ether-maleic anhydride copolymer to the formaldehyde solution is 4.5-5.0 g: 40-50 mL: 20-30 mL: 3.0 to 3.5 g.
In the step (4), the stirring reaction time is 2-6 h, preferably 3-5 h; the mass concentration of the formaldehyde aqueous solution is 35-40%.
In the step (5), the carbonization-reduction is carried out for 5-10 hours at 500-800 ℃.
In the step (6), mixing the product obtained in the step (5) and sulfur powder in an argon atmosphere for sulfuration, wherein the mass ratio of the product to the sulfur powder is 1: 1-5; the sulfuring condition is that the sulfuring is carried out at the temperature of 135-160 ℃ for 12-16 h.
The invention also provides the cobalt/carbon nanotube/sulfur particle microcapsule composite material prepared by the preparation method, the cobalt/carbon nanotube/sulfur particle microcapsule composite material is spherical with the average diameter of 15-50 mu m, and the carbon nanotube material loaded with sulfur particles is wrapped inside the spherical capsule.
The invention also provides a lithium-sulfur battery anode which is prepared by taking the cobalt/carbon nano tube/sulfur particle microcapsule composite material as a raw material.
The invention also provides a lithium-sulfur battery which is obtained by taking the positive electrode of the lithium-sulfur battery as the positive electrode, has good cycle stability, and the battery capacity is still stabilized to be more than 440mAh/g after 80 times of cycle.
In the preparation method of the cobalt/carbon nanotube/sulfur particle microcapsule composite material, cobaltosic oxide nanoparticles are ultrasonically dispersed in n-hexadecane to obtain an oil phase; mixing an aqueous solution containing urea, resorcinol and ammonium chloride with an aqueous solution of a methyl vinyl ether-maleic anhydride copolymer to form a water phase, and respectively adjusting the acidity, viscosity and dispersibility of the water phase through the ammonium chloride, the resorcinol and the methyl vinyl ether-maleic anhydride copolymer to enable the urea to be better coated on the surfaces of the nanoparticles in an oil-in-water mode; adding the oil phase into the water phase to form an oil-in-water emulsification system, and continuously dropwise adding formaldehyde to form a microcapsule wrapping cobaltosic oxide nanoparticles outside the oil phase; after the microcapsules wrapped with the cobaltosic oxide nano particles are subjected to high-temperature carbonization reduction under the protection of nitrogen, the cobaltosic oxide nano particles are reduced into cobalt, and simultaneously the cobalt catalyzes carbon in the capsules into carbon nano tubes so as to obtain a cobalt/carbon nano tube microcapsule composite material; after the step of fumigating the obtained cobalt/carbon nano tube microcapsule composite material, sulfur particles are loaded on the tube wall of the nano tube in the microcapsule, thereby forming the cobalt/carbon nano tube/sulfur particle microcapsule composite material.
The cobalt/carbon nanotube/sulfur particle microcapsule composite material provided by the invention has a large specific surface area due to the fact that a large number of carbon nanotubes are wrapped, the improvement of sulfur loading capacity and the acceleration of electron transmission are facilitated, meanwhile, the microcapsule structure of the cobalt/carbon nanotube/sulfur particle composite material plays a role in slowing down the shuttle effect of polysulfide, the loss of active substances in the charging and discharging processes is reduced, and therefore the electrochemical performance of the anode material is improved. Meanwhile, the capsule structure can well accommodate the volume change of sulfur particles in the charging and discharging processes, the structural integrity of sulfur is greatly improved, and the material is used as the positive electrode of the lithium-sulfur battery and has the characteristics of high capacity and stable cycle performance.
Compared with the prior art, the cobalt/carbon nano tube/sulfur particle microcapsule composite material prepared by the chemical synthesis method has good controllability; the experimental process is simple, the raw materials are cheap and easy to obtain, and the cost is low.
Drawings
FIG. 1 is an SEM image of cobaltosic oxide nanoparticles;
FIG. 2 is an SEM image of the cobalt/carbon nanotube microcapsule composite prepared in step 5) of example 1;
FIG. 3 is a TEM image of the cobalt/carbon nanotube microcapsule composite prepared in step 5) of example 1;
FIG. 4 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 1;
FIG. 5 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 1;
FIG. 6 is an XRD pattern of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 1;
FIG. 7 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 2;
FIG. 8 is an SEM image of a cobalt/carbon nanotube microcapsule composite prepared in step 5) of example 3;
FIG. 9 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 3;
FIG. 10 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 4;
FIG. 11 is an SEM image of a cobalt/carbon nanotube microcapsule composite prepared in step 5) of example 5;
FIG. 12 is an SEM image of a cobalt/carbon nanotube/sulfur particle microcapsule composite prepared in example 5;
fig. 13 is a charge/discharge capacity test chart of a lithium-sulfur battery assembled by the positive electrode of the lithium-sulfur battery prepared from the cobalt/carbon nanotube/sulfur particle microcapsule composite material prepared in example 3 at a current density of 0.1C;
fig. 14 is a test chart of the charge and discharge curves of the lithium-sulfur battery assembled by the positive electrode of the lithium-sulfur battery prepared from the cobalt/carbon nanotube/sulfur particle microcapsule composite material prepared in example 3 at a current density of 0.1C.
Detailed Description
The present invention will be described in detail with reference to examples.
The preparation method of the cobaltosic oxide nano-particles comprises the following steps: 0.58g of Co (NO)3)2·6H2O and 0.5g polyvinylpyrrolidone (PVP) were dissolved in 20mL of a 1:1, stirring for 30min, slowly adding 20mL of 0.4mol/L sodium hydroxide aqueous solution under the condition of continuous stirring to change the mixture from red to blue, then quickly transferring the reaction suspension into an autoclave with a polytetrafluoroethylene lining, heating and reacting for 12 hours at 200 ℃, cooling to room temperature, filtering, washing and drying to obtain cobaltosic oxide nanoparticles, wherein the SEM of the cobaltosic oxide nanoparticles is shown in figure 1, and the cobaltosic oxide nanoparticles are nanosheets with the average particle size of 40 nm.
Example 1
A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
1) mixing 0.1g of cobaltosic oxide nanoparticles with 4g of n-hexadecane, and ultrasonically dispersing for 20min at room temperature to obtain a mixed solution A;
2) dissolving 1.25g of urea, 0.25g of resorcinol and 0.125g of ammonium chloride in 45mL of distilled water to obtain a mixed solution B;
3) adding the mixed solution B into 25mL of aqueous solution of methyl vinyl ether-maleic anhydride copolymer with the mass concentration of 2.5%, mechanically stirring, adjusting the pH to 3.5 by using triethanolamine, stirring for dissolving, and reacting for 1h at 40 ℃;
4) adding the mixed solution A into the step 3), mechanically stirring for 0.5h under the condition that the stirring speed is 800rpm, then dropwise adding 3.1g of formaldehyde solution with the mass concentration of 35%, and continuously stirring for 2 hours to obtain a capsule coated with cobaltosic oxide nanoparticles;
5) filtering and drying the reaction liquid obtained in the step 4), and carbonizing the reaction liquid for 5 hours at 500 ℃ in a nitrogen environment to reduce cobaltosic oxide into cobalt and catalyze the inner wall of the capsule to obtain a carbon nanotube structure so as to obtain a cobalt/carbon nanotube microcapsule composite material; the SEM image is shown in 2, and the composite material is spherical and forms carbon nanotubes inside the spherical capsule wall; a TEM image of the carbon nanotubes inside the spherical capsule wall is shown in fig. 3, and the morphology of the carbon nanotubes in a hollow nanotube shape can be seen from the TEM image;
6) mixing the cobalt/carbon nano tube microcapsule composite material prepared in the step 5) with sulfur powder according to the mass ratio of 1:1, uniformly mixing, and fumigating at 135 ℃ for 12h in an argon atmosphere to obtain the cobalt/carbon nanotube/sulfur particle microcapsule composite material, wherein SEM images are shown in figures 4 and 5, the cobalt/carbon nanotube/sulfur particle microcapsule composite material is in a spherical shape with an average size of about 50 mu m, and sulfur particles are successfully loaded on the carbon nanotubes on the inner wall of the microcapsule. The XRD pattern is shown in figure 6, and all characteristic diffraction peaks are consistent with those of standard card JCPDS No.08-0247 of sulfur, which indicates that the sulfur particles are successfully loaded on the cobalt/carbon nanotube microcapsule composite material by the sulfur fumigation.
Example 2
A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
1) mixing 0.2g of cobaltosic oxide nanoparticles with 4.5g of n-hexadecane, and ultrasonically dispersing for 20min at room temperature to obtain a mixed solution A;
2) dissolving 1.25g of urea, 0.25g of resorcinol and 0.125g of ammonium chloride in 45mL of distilled water to obtain a mixed solution B;
3) adding the mixed solution B into 25mL of aqueous solution of methyl vinyl ether-maleic anhydride copolymer with the mass concentration of 3%, mechanically stirring, adjusting the pH to 3.5 by using triethanolamine, stirring for dissolving, and reacting at 45 ℃ for 1.5 h;
4) adding the mixed solution A into the step 3), mechanically stirring for 0.5h under the condition that the stirring speed is 850rpm, then dropwise adding 3.2g of formaldehyde solution with the mass concentration of 40%, and continuously stirring and mechanically stirring for 3h to obtain a capsule coated with cobaltosic oxide nanoparticles;
5) filtering and drying the reaction liquid obtained in the step 4), and then carbonizing the reaction liquid for 6 hours at 550 ℃ in a nitrogen environment, namely reducing cobaltosic oxide into cobalt and catalyzing the inner wall of the capsule to obtain a carbon nanotube structure to obtain a cobalt/carbon nanotube microcapsule composite material;
6) mixing the cobalt/carbon nano tube microcapsule composite material prepared in the step 5) with sulfur powder according to the mass ratio of 1: 2, uniformly mixing, and fumigating at 140 ℃ for 13h in an argon atmosphere to obtain the cobalt/carbon nano tube/sulfur particle microcapsule composite material. The SEM image is shown in FIG. 7, which shows that the particles are spherical and have an average size of about 15 μm.
Example 3
A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
1) mixing 0.3g of cobaltosic oxide nanoparticles with 5g of n-hexadecane, and ultrasonically dispersing for 20min at room temperature to obtain a mixed solution A;
2) dissolving 1.25g of urea, 0.25g of resorcinol and 0.125g of ammonium chloride in 45mL of distilled water to obtain a mixed solution B;
3) adding the mixed solution B into 25mL of aqueous solution of methyl vinyl ether-maleic anhydride copolymer with the mass concentration of 3.5%, mechanically stirring, adjusting the pH to 3.5 by using triethanolamine, stirring for dissolving, and reacting for 2 hours at 50 ℃;
4) adding the mixed solution A into the step 3), mechanically stirring for 0.5h under the condition that the stirring speed is 900rpm, then dropwise adding 3.3g of formaldehyde solution with the mass concentration of 35%, and continuously mechanically stirring for 4h to obtain a capsule coated with cobaltosic oxide nanoparticles;
5) filtering and drying the reaction liquid obtained in the step 4), and carbonizing the reaction liquid for 7 hours at 600 ℃ in a nitrogen environment, namely reducing cobaltosic oxide into cobalt and catalyzing the inner wall of the capsule to obtain a carbon nanotube structure to obtain a cobalt/carbon nanotube microcapsule composite material; the SEM image is shown in FIG. 8;
6) mixing the cobalt/carbon nano tube microcapsule composite material prepared in the step 5) with sulfur powder according to the mass ratio of 1: 3, uniformly mixing, and fumigating at 145 ℃ for 14h in argon atmosphere to obtain the cobalt carbide/carbon nanotube capsule/sulfur particle material cobalt @ carbon nanotube/sulfur particle microcapsule composite material, wherein an SEM picture of the composite material is shown in figure 9, and the composite material is spherical and has an average size of about 15 mu m.
Example 4
A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
1) mixing 0.4g of cobaltosic oxide nano particles with 5.5 hexadecane, and ultrasonically dispersing for 20min at room temperature to obtain a mixed solution A;
2) dissolving 1.25g of urea, 0.25g of resorcinol and 0.125g of ammonium chloride in 45mL of distilled water to obtain a mixed solution B;
3) adding the mixed solution B into 25mL of aqueous solution of methyl vinyl ether-maleic anhydride copolymer with the mass concentration of 4%, mechanically stirring, adjusting the pH to 3.5 by using triethanolamine, stirring for dissolving, and reacting at 55 ℃ for 2.5 h;
4) adding the mixed solution A into the step 3), mechanically stirring for 0.5h under the condition that the stirring speed is 950rpm, then dropwise adding 3.4g of formaldehyde solution with the mass concentration of 35%, and continuously stirring and mechanically stirring for 5h to obtain a capsule coated with cobaltosic oxide nanoparticles;
5) filtering and drying the reaction liquid obtained in the step 4), and carbonizing for 8 hours at 650 ℃ in a nitrogen environment, namely reducing cobaltosic oxide into cobalt and catalyzing the inner wall of the capsule to obtain a carbon nanotube structure to obtain a cobalt/carbon nanotube microcapsule composite material;
6) mixing the cobalt/carbon nano tube microcapsule composite material prepared in the step 5) with sulfur powder according to the mass ratio of 1: 4, uniformly mixing, and fumigating at 150 ℃ for 15h in an argon atmosphere to obtain the cobalt/carbon nanotube/sulfur particle microcapsule composite material, wherein an SEM picture is shown in figure 10, and the cobalt/carbon nanotube/sulfur particle microcapsule composite material is spherical and has an average size of about 25 mu m.
Example 5
A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material comprises the following steps:
1) mixing 0.5g of cobaltosic oxide nanoparticles with 6g of n-hexadecane, and ultrasonically dispersing for 20min at room temperature to obtain a mixed solution A;
2) dissolving 1.25g of urea, 0.25g of resorcinol and 0.125g of ammonium chloride in 45mL of distilled water to obtain a mixed solution B;
3) adding the mixed solution B into 25mL of aqueous solution of methyl vinyl ether-maleic anhydride copolymer with the mass concentration of 4.5%, mechanically stirring, adjusting the pH to 3.5 by using triethanolamine, stirring for dissolving, and reacting for 3h at 60 ℃;
4) adding the mixed solution A into the step 3), mechanically stirring for 0.5h under the condition that the stirring speed is 1000rpm, then dropwise adding 3.5g of formaldehyde solution with the mass concentration of 35%, and continuously stirring and mechanically stirring for 6h to obtain a capsule coated with cobaltosic oxide nanoparticles;
5) filtering and drying the reaction liquid obtained in the step 4), and carbonizing the reaction liquid at 700 ℃ for 9 hours in a nitrogen environment, namely reducing cobaltosic oxide into cobalt and catalyzing the inner wall of the capsule to obtain a carbon nanotube structure, so as to obtain the cobalt/carbon nanotube microcapsule composite material, wherein an SEM image of the cobalt/carbon nanotube microcapsule composite material is shown in figure 11;
6) mixing the cobalt/carbon nano tube microcapsule composite material prepared in the step 5) with sulfur powder according to the mass ratio of 1: 5, uniformly mixing, and fumigating at 155 ℃ for 16h in an argon atmosphere to obtain the cobalt/carbon nanotube/sulfur particle microcapsule composite material, wherein an SEM picture is shown in figure 12, and the cobalt/carbon nanotube/sulfur particle microcapsule composite material is spherical and has an average size of about 30 mu m.
Example 6
A positive electrode of a lithium sulfur battery was fabricated using the cobalt/carbon nanotube/sulfur particle microcapsule composite material prepared in example 3 above:
the lithium-sulfur battery is assembled by taking the positive electrode of the lithium-sulfur battery as a positive electrode.
The method specifically comprises the following steps:
the final product cobalt/carbon nanotube/sulfur particle microcapsule composite material obtained in example 3 was used as a positive electrode active material of a lithium sulfur battery, and the obtained active material was mixed with superconducting carbon black and PVDF in a ratio of 65: 25: 10, preparing the mixture into uniform slurry by using an N-methyl pyrrolidone (NMP) solvent, coating the uniform slurry on an aluminum foil, uniformly coating the uniform slurry into a film sheet by using a scraper, and uniformly adhering the film sheet to the surface of the aluminum foil. Then the prepared coating is put in a drying oven and dried for 12 hours at the temperature of 60 ℃; after drying, moving the mixture into a vacuum drying oven, and carrying out vacuum drying for 10 hours at the temperature of 60 ℃; and cutting an electrode plate of the dried composite material coating by adopting a mechanical cutting machine, taking a lithium plate as a counter electrode, and assembling the electrolyte which is a commercially available 1mol/L LiTFSI/DME + DOL solution to obtain the lithium-sulfur battery.
The lithium-sulfur battery obtained by assembling is tested for charge and discharge performance by using a battery tester, and the result of the cycling stability test under the current density of 0.1C is shown in figures 13 and 14, so that the cycling stability of the battery is good, and the battery capacity is still stable at 440mAh/g after 80 cycles.
The above detailed description of a cobalt/carbon nanotube/sulfur particle microcapsule composite material, a method for preparing the same, and a lithium sulfur battery positive electrode and a lithium sulfur battery, with reference to examples, is illustrative and not restrictive, and several examples may be cited within the scope of the present invention, so that variations and modifications may be made without departing from the general inventive concept within the scope of the present invention.
Claims (10)
1. A preparation method of a cobalt/carbon nanotube/sulfur particle microcapsule composite material is characterized by comprising the following steps:
(1) ultrasonically dispersing cobaltosic oxide nanoparticles in n-hexadecane to obtain a mixed solution A;
(2) dissolving urea, resorcinol and ammonium chloride in water to obtain a mixed solution B;
(3) adding the mixed solution B into an aqueous solution of a methyl vinyl ether-maleic anhydride copolymer, adjusting the pH of the system to 3-4, stirring for dissolving, and heating for reaction for 0.5-1 h;
(4) continuously adding the mixed solution A into the step (3), and uniformly stirring; then dropwise adding a formaldehyde aqueous solution into the mixture, and continuously stirring the mixture to react to obtain a microcapsule coated with cobaltosic oxide nano particles;
(5) filtering the reaction liquid obtained in the step (4), drying a product obtained by filtering, and then carrying out carbonization reduction in the nitrogen environment;
(6) and (5) carrying out sulfur fumigation on the product obtained in the step (5) to obtain the cobalt/carbon nano tube/sulfur particle microcapsule composite material.
2. The method according to claim 1, wherein in the step (1), the mass ratio of the cobaltosic oxide nanoparticles to the n-hexadecane is 0.1-0.5: 4.
3. the method according to claim 1, wherein in the step (2), the mass ratio of urea, resorcinol and ammonium chloride is (1.05-1.45): (0.15-0.35): (0.1 to 0.15); the concentration of the urea in the mixed solution B is 0.025-0.035 g/mL.
4. The preparation method according to claim 1, wherein in the step (3), the mass concentration of the methyl vinyl ether-maleic anhydride copolymer in the aqueous solution of the methyl vinyl ether-maleic anhydride copolymer is 2.5-5%; regulating the pH value of the system by using triethanolamine; the temperature of the heating reaction is 40-60 ℃.
5. The preparation method according to claim 1, wherein the ratio of the mixed solution A to the mixed solution B to the aqueous solution of the methyl vinyl ether-maleic anhydride copolymer to the formaldehyde solution is 4.5 to 5.0 g: 40-50 mL: 20-30 mL: 3.0 to 3.5 g.
6. The preparation method according to claim 1, wherein in the step (4), the stirring reaction time is 2-6 h; the mass concentration of the formaldehyde aqueous solution is 35-40%.
7. The preparation method according to claim 1, wherein in the step (5), the carbonization and reduction conditions are 500-800 ℃ for 5-10 h.
8. The cobalt/carbon nanotube/sulfur particle microcapsule composite material prepared by the preparation method according to any one of claims 1 to 7, wherein the cobalt/carbon nanotube/sulfur particle microcapsule composite material is spherical with an average diameter of 15 to 50 μm, and a carbon nanotube material loaded with sulfur particles is wrapped inside the spherical capsule.
9. A lithium-sulfur battery positive electrode, characterized in that, the cobalt/carbon nanotube/sulfur particle microcapsule composite material of claim 8 is used as a raw material.
10. A lithium-sulfur battery, characterized in that it is obtained by using the positive electrode of the lithium-sulfur battery according to claim 9 as a positive electrode.
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