Preparation method of bimetallic nanoparticles and application thereof in lithium-sulfur battery

Abstract

The application discloses a preparation method of bimetallic nanoparticles and application of the bimetallic nanoparticles in lithium-sulfur batteries. The preparation method of the bimetallic nanoparticles comprises the following steps: configuring ZIF-8 seeds, configuring ZIF-8@ZIF-67 powder, and obtaining Co3ZnC nanoparticle carbon derivatives by using a joule heat rapid sintering technology. The Co3ZnC nanoparticle carbon derivatives prepared by the application have a stable framework provided by ZIF-8@ZIF-67 precursors, and can inhibit the diffusion of polysulfides; the Co3ZnC nanoparticle carbon derivatives have active sites of Co ZnC, and can accelerate the catalytic conversion of polysulfides; and therefore, the Co3ZnC nanoparticle carbon derivatives have high conductivity, excellent catalytic performance and strong chemical adsorption capacity for polysulfides. The Co3ZnC nanoparticle carbon derivatives have good prospects when applied in lithium-sulfur batteries.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic functional material synthesis, and particularly relates to a preparation method of bimetallic nanoparticles and application thereof in lithium-sulfur batteries. BACKGROUND

[0002] Lithium-sulfur batteries (Li-S batteries) have become an important research direction for next-generation battery technology due to their high theoretical energy density (about 500 Wh / kg). Compared with traditional lithium-ion batteries, lithium-sulfur batteries have significant advantages, especially in terms of high energy density and lower cost, which makes them have wide application potential in electric vehicles, portable electronic devices and other fields. However, lithium-sulfur batteries still face many technical challenges in practical application, mainly including low conductivity of sulfur, dissolution of lithium polysulfides and poor cycle performance of the battery, etc. First, sulfur as the active material of the battery has low conductivity, which limits its effective utilization in the battery. Secondly, during the charging and discharging process, sulfur will be converted into soluble lithium polysulfides (Li S), which may dissolve in the electrolyte, leading to the capacity decay phenomenon of the battery, further affecting the efficiency and stability of the battery. Therefore, how to improve the electrical conductivity of sulfur and inhibit the dissolution of lithium polysulfides has become the key to improving the performance of lithium-sulfur batteries. In order to solve these problems, researchers have proposed various strategies, one of which is to introduce catalysts to improve the electrochemical performance of lithium-sulfur batteries.

[0003] Chinese patent CN118978146A (publication date: November 19, 2024) discloses a Co 0.5 Ni 0.5 Te2 nanoparticle / three-dimensional carbon sheet composite material and application thereof in lithium-sulfur batteries. The nanoparticles in the composite material are uniformly distributed on the surface of the carbon sheet, chemically adsorbed and catalyze the kinetic conversion of polysulfide ions; at the same time, the three-dimensional carbon sheet with cross-linked network structure provides a continuous electron transport channel to ensure the rapid transmission of electric charge. The synthesis method provided in the application is simple, universal and has good repeatability; when used as a lithium-sulfur battery separator coating material, it can effectively improve the specific capacity and cycle stability of the battery.

[0004] Chinese patent CN115832312A (publication date: March 21, 2023) discloses a preparation method of a lithium-sulfur battery catalyst material. The lithium-sulfur battery catalyst material is prepared by atomically dispersing Ni Co bimetallic series sites, coordinating with nitrogen, and embedding in porous carbon. The preparation method comprises the following steps: step S1, dissolving Zn(NO3)2·6H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in methanol to form a mixed solution, adding 2-methylimidazole and methanol to the mixed solution, stirring and then aging, collecting the precipitate by suction filtration, and obtaining ZnCoNi ZIF after washing and vacuum drying; step S2, placing the ZnCoNi ZIF in a tube furnace to obtain a pyrolysis product, selectively removing the metal particles on the surface of the pyrolysis product after soaking treatment, and obtaining the lithium-sulfur battery catalyst material CoNi NC after vacuum drying.

[0005] Chinese patent CN112670669A (publication date: April 16, 2021) discloses an application of a nitrogen-doped carbon-coated Co and / or Co3ZnC composite material in the preparation of a lithium-sulfur battery separator. First, Pluronic F127 is dissolved in water, a carbon source dicyandiamide is added, and then a divalent cobalt salt and a divalent zinc salt are added. After further stirring, the water is evaporated to obtain a solid composite. Then, high-temperature carbonization is carried out under N2 gas protection. In this process, dicyandiamide is carbonized to obtain N-doped carbon, and the reducing substances such as carbon monoxide, carbon dioxide, nitrogen monoxide and carbon produced during the carbonization process can reduce and carbonize cobalt and zinc to obtain Co or Co3ZnC. After the reaction is completed, the target product is obtained. The N-doped carbon-coated Co and / or Co3ZnC composite material is used as a separator modification material and is coated on a commercial separator by a doctor blade method. When applied in a lithium-sulfur battery, the electrochemical performance of the lithium-sulfur battery can be effectively improved.

[0006] Through retrieval analysis, it is found that the bimetallic nanoparticles as catalysts for improving the performance of lithium-sulfur batteries need to be further developed. Most of the current positive electrode materials only contain a single metal, and the catalytic efficiency is limited. In addition, the traditional catalyst preparation method usually requires a long time and high energy consumption, which will result in large particle size and poor dispersibility of the catalyst, and may reduce the activity of the catalyst. In order to solve the above problems, there is an urgent need to invent a new synthetic bimetallic nanoparticle as a lithium-sulfur battery catalyst. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a preparation method of bimetallic nanoparticles and its application in lithium-sulfur batteries.

[0008] A preparation method of bimetallic nanoparticles comprises the following steps:

[0009] Step S1: proportioning ZIF-8 seeds;

[0010] Step S2: proportioning ZIF-8@ZIF-67 solution and obtaining ZIF-8@ZIF-67 powder;

[0011] Step S3: using Joule heat rapid sintering technology to sinter ZIF-8@ZIF-67 powder to obtain Co3ZnC nanoparticle carbon derivative.

[0012] Further, the step S1 comprises the following steps:

[0013] Step S101: adding 2-methylimidazole into distilled water and ultrasonic dispersion to obtain solution A;

[0014] Step S102: adding zinc acetate dihydrate into distilled water and ultrasonic dispersion to obtain solution B;

[0015] Step S103: adding solution B into stirring solution A, stirring for 10-30s, and standing at room temperature for 24-36h to obtain mixed solution A;

[0016] Step S104: taking supernatant of mixed solution A, centrifuging the remaining mixed solution A precipitate in a centrifuge at 8000-10000rpm / min for 5-10min, repeating the cleaning for 2-3 times, and then cleaning with anhydrous ethanol for 1-2 times to obtain precipitate A;

[0017] Step S105: placing the obtained precipitate A into an oven at 70-80℃ and drying for 8-12h to obtain ZIF-8 seeds.

[0018] Further, the step S2 comprises the following steps:

[0019] Step S201: adding ZIF-8 seeds into distilled water and ultrasonic dispersion to obtain ZIF-8 suspension;

[0020] Step S202: adding 2-methylimidazole into distilled water and ultrasonic dispersion to obtain solution C;

[0021] Step S203: adding cobalt acetate tetrahydrate into distilled water and ultrasonic dispersion to obtain solution D;

[0022] Step S204: adding solution D into ZIF-8 suspension and ultrasonic dispersion to obtain purple suspension E;

[0023] Step S205: adding suspension E into stirring solution C, stirring for 10-30s, and standing at room temperature for 24-36h to obtain mixed solution B;

[0024] Step S206: Take the supernatant in the mixed solution B, centrifuge the remaining precipitate of the mixed solution B in a centrifuge at 8000-10000 rpm / min for 5-10 min, repeat the cleaning for 2-3 times, and then clean with anhydrous ethanol for 1-2 times to obtain a precipitate B;

[0025] Step S207: Dry the precipitate B in an oven at 70-80°C for 8-12 h to obtain a ZIF-8@ZIF-67 powder.

[0026] Further, the step S3 comprises the following steps:

[0027] Step S301: Put the obtained ZIF-8@ZIF-67 powder into a joule heat rapid sintering device;

[0028] Step S302: Sinter at 700-900°C for 20-40 s in an argon environment to obtain a Co3ZnC nanoparticle carbon derivative.

[0029] Further, the content of 2-methylimidazole in each 5 ml of solution A is 1-2 g; the content of zinc acetate dihydrate in each 5 ml of solution B is 0.15-0.45 g; the content of 2-methylimidazole in each 5 ml of solution C is 0.5-1 g; and the content of cobalt acetate tetrahydrate in each 5 ml of solution D is 0.1-0.3 g.

[0030] Further, the diameter of the Co3ZnC nanoparticle carbon derivative is 600-1500 nm.

[0031] A preparation method of a Co3ZnC nanoparticle carbon derivative positive electrode sheet, comprising the following steps:

[0032] Step 1: Grind and mix the Co3ZnC nanoparticle carbon derivative powder and the sulfur powder to obtain a mixed powder A;

[0033] Step 2: Put the mixed powder A into a sealed titanium tube, heat at 155°C for 12-24 h in a tube furnace, and then cool to room temperature;

[0034] Step 3: Grind the cooled mixed powder A thoroughly, put it into a tube furnace, heat at 200°C for 1-2 h in an argon atmosphere, and then cool to room temperature to obtain a Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur;

[0035] Step 4: Add the Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur, a conductive agent, and a binder into a ball mill jar;

[0036] Step 5: Add a solvent E into the ball mill jar, and then grind and uniformly mix to form an electrode slurry with fluidity.

[0037] Step 6: use a doctor to evenly spread the electrode slurry on the surface of the aluminum foil, then put the aluminum foil into a 70-80℃ air drying oven for 8-12h, and after complete drying, obtain the Co3ZnC nanoparticle carbon derivative positive electrode sheet.

[0038] Further, the mass ratio of the Co3ZnC nanoparticle carbon derivative powder and the sublimed sulfur powder is 3:7;

[0039] Further, the mass ratio of the Co3ZnC nanoparticle carbon derivative after loading elemental sulfur, the conductive agent and the binder is 7:2:1.

[0040] Further, the conductive agent includes Ketjen black; the binder includes polyvinylidene fluoride; and the solvent E includes N-methyl pyrrolidone.

[0041] A Co3ZnC nanoparticle carbon derivative positive electrode sheet in the preparation of a lithium-sulfur battery.

[0042] Compared with the prior art, the advantages and effects of the present application are as follows:

[0043] 1、The present application can obtain Co3ZnC nanoparticle carbon derivatives with a porous structure in a short time by using Joule heat rapid sintering technology, which can effectively avoid the problems of larger particle size and poor dispersibility, thereby improving the catalytic activity; and the Co3ZnC nanoparticle carbon derivatives exhibit excellent long cycle stability and rate performance in lithium-sulfur batteries.

[0044] 2、The present application solves the problems of capacity decay of sulfur positive electrode and polysulfide shuttle effect in lithium-sulfur batteries by using Co3ZnC nanoparticle carbon derivatives to prepare lithium-sulfur batteries.

[0045] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, so as to be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following will be described in detail with the preferred embodiments of the present application and the accompanying drawings as follows.

[0046] According to the detailed description of the specific embodiments of the present application in the following combined with the drawings, those skilled in the art will be more clear about the above and other purposes, advantages and features of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual proportion.

[0048] Wherein:

[0049] Figure 1 Flow chart of the preparation method of the bimetallic nanoparticles of the present application;

[0050] Figure 2 TEM image of the Co3ZnC nanoparticle carbon derivative described in the present application;

[0051] Figure 2 (a) TEM image of the Co3ZnC nanoparticle carbon derivative described in the present application with a scale of 500 nm;

[0052] Figure 2 (b) TEM image of the Co3ZnC nanoparticle carbon derivative described in the present application with a scale of 20 nm;

[0053] Figure 2 (c) TEM image of the Co3ZnC nanoparticle carbon derivative described in the present application with a scale of 10 nm;

[0054] Figure 3 XRD image of the secondary battery described in the present application;

[0055] Figure 4 Cycle image and rate image of the secondary battery described in the present application at different current densities;

[0056] Figure 4 (a) Cycle image of the secondary battery of the control group and experimental group 3 described in the present application at a current density of 0.5C;

[0057] Figure 4 (b) Cycle image of the secondary battery of the control group and experimental group 3 described in the present application at a current density of 1C;

[0058] Figure 4 (c) Cycle image of the secondary battery of the control group and experimental group 3 described in the present application at a current density of 2C;

[0059] Figure 4 (d) Rate image of the secondary battery of the control group and experimental group 3 described in the present application at a cut-off voltage of 2.8V. DETAILED DESCRIPTION

[0060] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. In the following description, specific details such as specific configurations and components are provided only for helping to understand the embodiments of the present application. Therefore, one of ordinary skill in the art should clearly understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, in the embodiments, the description of known functions and structures is omitted for clarity and conciseness.

[0061] It should be understood that the “one embodiment” or “the embodiment” mentioned throughout the specification means that a specific feature, structure or property related to the embodiment is included in at least one embodiment of the present application. Therefore, “one embodiment” or “the embodiment” appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or properties can be combined in one or more embodiments in any suitable manner.

[0062] In addition, reference numerals and / or letters can be repeated in different examples in the present application. Such repetition is for the purpose of simplification and clarity, and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0063] The term “and / or” herein is only used to describe an association relationship of associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, B exists alone, and A and B exist together. The term “ / and” herein is used to describe another association relationship of associated objects, which means that there can be two relationships, for example, A / and B can mean that A exists alone and A and B exist together. In addition, the character “ / ” herein generally means that the associated objects before and after the character “ / ” are in an “or” relationship.

[0064] The term “at least one” herein is only used to describe an association relationship of associated objects, which means that there can be three relationships, for example, at least one of A and B can mean that A exists alone, A and B exist together, and B exists alone.

[0065] It should also be noted that the relationship terms such as first and second and the like used herein are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms “include”, “contain” or any other variants thereof are intended to cover non-exclusive inclusion.

[0066] Embodiment 1

[0067] The embodiment is a preparation method of bimetallic nanoparticles.

[0068] Referring to Figure 1 , a flow chart of the preparation method of bimetallic nanoparticles of the present application. The preparation method of bimetallic nanoparticles comprises the following steps:

[0069] Step S1: configuring ZIF-8 seeds in proportion;

[0070] Step S2: configuring ZIF-8@ZIF-67 solution in proportion, and obtaining ZIF-8@ZIF-67 powder;

[0071] Step S3: using Joule heat rapid sintering technology to sinter the ZIF-8@ZIF-67 powder to obtain Co3ZnC nanoparticle carbon derivatives.

[0072] Further, the step S1 comprises the following steps:

[0073] Step S101: adding 2-methylimidazole into distilled water to ultrasonically disperse to obtain solution A;

[0074] Step S102: adding zinc acetate dihydrate into distilled water to ultrasonically disperse to obtain solution B;

[0075] Step S103: adding the B solution into the solution A, stirring for 10-30 s, and standing at room temperature for 24-36 h to obtain a mixed solution A;

[0076] Step S104: taking the supernatant in the mixed solution A, centrifuging the remaining mixed solution A in a centrifuge at 8000-10000 rpm / min for 5-10 min, repeating the cleaning for 2-3 times, and then cleaning with anhydrous ethanol for 1-2 times to obtain a precipitate A;

[0077] Step S105: placing the obtained precipitate A into an oven at 70-80℃ to dry for 8-12 h to obtain ZIF-8 seeds.

[0078] Further, the step S2 comprises the following steps:

[0079] Step S201: adding ZIF-8 seeds into distilled water to ultrasonically disperse to obtain a ZIF-8 suspension;

[0080] Step S202: adding 2-methylimidazole into distilled water to ultrasonically disperse to obtain solution C;

[0081] Step S203: adding cobalt acetate tetrahydrate into distilled water to ultrasonically disperse to obtain solution D;

[0082] Step S204: Solution D is added to the ZIF-8 suspension for ultrasonic dispersion, and a purple suspension E is obtained.

[0083] Step S205: Suspension E is added to solution C, stirred for 10-30 s, and left to stand at room temperature for 24-36 h to obtain a mixed solution B.

[0084] Step S206: The supernatant in the mixed solution B is removed, and the remaining precipitate of the mixed solution B is centrifuged at 8000-10000 rpm / min in a centrifuge for 5-10 min. The washing is repeated 2-3 times, and then the precipitate is washed with anhydrous ethanol 1-2 times to obtain a precipitate B.

[0085] Step S207: The precipitate B is placed in an oven at 70-80°C for drying for 8-12 h to obtain a ZIF-8@ZIF-67 powder.

[0086] Further, the step S3 comprises the following steps:

[0087] Step S301: The obtained ZIF-8@ZIF-67 powder is placed in a joule heat rapid sintering device.

[0088] Step S302: Sintering is performed at 700-900°C for 20-40 s in an argon environment to obtain a Co3ZnC nanoparticle carbon derivative.

[0089] Further, the content of 2-methylimidazole in 5 ml of solution A is 1-2 g; the content of zinc acetate dihydrate in 5 ml of solution B is 0.15-0.45 g; the content of 2-methylimidazole added in 5 ml of solution C is 0.5-1 g; and the content of cobalt acetate tetrahydrate in 5 ml of solution D is 0.1-0.3 g.

[0090] Please refer to Figure 2 The TEM image of the Co3ZnC nanoparticle carbon derivative described in the present application; further, the diameter of the Co3ZnC nanoparticle carbon derivative is 600-1500 nm.

[0091] Technical effects of the embodiment: The traditional catalyst synthesis method often needs a long time and high temperature treatment, resulting in larger catalyst particle size and poorer dispersibility, thereby affecting its activity. The carbonization treatment of the ZIF-8@ZIF-67 precursor by the Joule heat sintering technology can quickly synthesize a catalyst containing bimetallic alloy Co3ZnC nanoparticles. During the sintering process, the ZIF-8@ZIF-67 precursor provides a stable skeleton to inhibit the diffusion of polysulfides, while the active sites of Co3ZnC accelerate the catalytic conversion of polysulfides, and finally the formed Co3ZnC has high electrical conductivity, excellent catalytic performance and strong chemical adsorption capacity for polysulfides.

[0092] Embodiment 2

[0093] Based on embodiment 1, a preparation method of a Co3ZnC nanoparticle carbon derivative positive electrode sheet.

[0094] A preparation method of a Co3ZnC nanoparticle carbon derivative positive electrode sheet, comprising the following steps:

[0095] Step 1: The Co3ZnC nanoparticle carbon derivative powder and the sublimed sulfur powder are fully ground and mixed to obtain a mixed powder A;

[0096] Step 2: The mixed powder A is placed in a sealed titanium tube, and is kept at 155℃ for 12h-24h in a tube furnace, and then is cooled to room temperature along with the furnace;

[0097] Step 3: The cooled mixed powder A is fully ground and placed in a tube furnace, and is kept at 200℃ for 1h-2h under an argon atmosphere, and then is cooled to room temperature along with the furnace to obtain a Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur;

[0098] Step 4: The Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur, a conductive agent and a binder are added to a ball mill jar;

[0099] Step 5: A solvent E is added to the ball mill jar, and then is ground and uniformly mixed to form an electrode slurry with fluidity;

[0100] Step 6: The electrode slurry is uniformly scraped on the surface of an aluminum foil using a doctor blade, and then the aluminum foil is placed in a forced air drying oven at 70℃-80℃ for drying for 8-12h, and after complete drying, a Co3ZnC nanoparticle carbon derivative positive electrode sheet is obtained.

[0101] Further, the mass ratio of the Co3ZnC nanoparticle carbon derivative powder and the sublimed sulfur powder is 3:7;

[0102] Further, the mass ratio of the Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur, the conductive agent and the binder is 7:2:1.

[0103] Further, the conductive agent includes Ketjen black; the binder includes polyvinylidene fluoride; and the solvent E includes N-methyl pyrrolidone.

[0104] Technical effects of the embodiment: By loading elemental sulfur on the Co3ZnC nanoparticle carbon derivative to prepare the positive electrode sheet, the electrical conductivity of sulfur can be improved and the dissolution of lithium polysulfide can be inhibited, thereby improving the performance of lithium-sulfur batteries.

[0105] Embodiment 3

[0106] Based on embodiment 2, the present embodiment is a preparation method of a lithium-sulfur battery using a Co3ZnC nanoparticle carbon derivative positive electrode sheet.

[0107] A preparation method of a lithium-sulfur battery using a Co3ZnC nanoparticle carbon derivative positive electrode sheet, comprising the following steps:

[0108] Step SS1: using a roller press to compact the Co3ZnC nanoparticle carbon derivative positive electrode sheet, and using a punching machine to cut the Co3ZnC nanoparticle carbon derivative positive electrode sheet into positive electrode round sheets with a diameter of 14 mm, and the cut positive electrode round sheets are placed in a 60℃ vacuum drying oven for drying for 12h for standby;

[0109] Step SS2: under room temperature conditions, 1mol / L of LITFSI is added to a solution containing 2% LiNO3 in ethylene glycol dimethyl ether:1,3-dioxolane with a volume ratio of 1:1, and after mixing, it is placed for 24h to obtain an electrolyte;

[0110] Step SS3: the polyethylene separator is punched into a round sheet with a diameter of 16mm, and is transferred to a 55℃ vacuum drying oven, and is vacuum dried for 24h to obtain a separator;

[0111] Step SS4: in a glove box with a water and oxygen content of less than 0.1ppm, a lithium sheet is used as a counter electrode, and is assembled with the electrolyte obtained in step S502, the positive electrode round sheet, and the separator to form a secondary battery.

[0112] Technical effects of the embodiment: In the lithium-sulfur battery, by using the Co3ZnC nanoparticle carbon derivative positive electrode sheet, not only the reduction reaction of lithium polysulfide can be promoted, but also more active sites can be provided and the electrical conductivity can be improved, thereby improving the overall performance of the battery.

[0113] Embodiment 4

[0114] Based on the above embodiments 1-3, the present embodiment mainly introduces an effect verification of a lithium-sulfur battery using a Co3ZnC nanoparticle carbon derivative positive electrode sheet.

[0115] In the process of preparing the lithium-sulfur battery, other conditions are controlled to remain unchanged, the sintering temperature and time in step S302 are changed, different secondary batteries are obtained, and are named as a control group, an experimental group 1, an experimental group 2, an experimental group 3, an experimental group 4, and an experimental group 5 respectively; the corresponding sintering temperature and sintering time are shown in Table 1 as follows.

[0116] Table 1: Sintering temperature and sintering time control table

[0117]

[0118] The secondary batteries of the control group and the experimental groups are tested by using an Arbin BT2000 test system, the charge and discharge voltage range is 1.7-2.8 V, and the cycle performance is obtained under 0.5 C, 1 C and 2 C corresponding cycles (25 DEG C) for 500 cycles, and the test results are shown in Table 2.

[0119] Table 2: Test results of the secondary battery tested by the Arbin BT2000 test system

[0120]

[0121] Please refer to Figure 3 , the XRD image of the secondary battery described in the present application; please refer to Figure 4 , the different current density cycle and rate images of the secondary battery described in the present application. It can be seen from Figures 3-4 and Table 2 that after 500 cycles of super-long cycles, the experimental groups 1-5 can all maintain a relatively high specific capacity, especially the experimental group 3, the specific capacity can still be maintained at 556.51 mAh / g under a current density of 2 C, while the control group cannot cycle for 500 cycles under a current density of 2 C at all. And the overall capacity is also higher than that of the battery containing CoZnC.

[0122] Technical effects of the present embodiment: CoZnC is prepared by high-temperature sintering of the double-layer structure of ZIF-8@ZIF-67 precursor, and the double-layer porous structure of ZIF-8@ZIF-67 precursor and the high catalytic activity of CoZnC are utilized to realize the optimization of structure and function. In the sintering process, the ZIF-8@ZIF-67 precursor provides a stable skeleton to inhibit the diffusion of polysulfides, and the active sites of CoZnC accelerate the catalytic conversion of polysulfides, and finally the CoZnC has high conductivity, excellent catalytic performance and strong chemical adsorption capacity for polysulfides.

[0123] In summary, the application provides a preparation method of bimetallic nanoparticles and its application in lithium-sulfur batteries. The Co3ZnC nanoparticle carbon derivative with porous structure can be obtained in a short time by using the joule heat rapid sintering technology, which can effectively avoid the problems of large particle size and poor dispersibility, thereby improving the catalytic activity. The Co3ZnC nanoparticle carbon derivative exhibits excellent long cycle stability and rate performance in lithium-sulfur batteries. By using the Co3ZnC nanoparticle carbon derivative to prepare lithium-sulfur batteries, the problems of sulfur positive electrode capacity attenuation and polysulfide shuttle effect in lithium-sulfur batteries are solved. The application has innovation.

[0124] The above specific embodiments further illustrate the purposes, technical solutions and beneficial effects of the application, and it should be understood that the above description is only a specific embodiment of the application and is not used to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A method for preparing a Co3ZnC nanoparticle carbon derivative positive electrode sheet, characterized by, The method comprises the following steps: Step 1: Co3ZnC nanoparticle carbon derivative powder and sublimed sulfur powder are mixed by grinding in a mass ratio of 2.5-3.5:6.5-7.5 to obtain mixed powder A; Step 2: The mixed powder A is placed in a sealed titanium tube, and is kept at 155 DEG C for 12-24 hours in a tube furnace, and then is cooled to room temperature along with the furnace; Step 3: The cooled mixed powder A is ground thoroughly, and is placed in a tube furnace, and is kept at 200 DEG C for 1-2 hours in an argon atmosphere, and then is cooled to room temperature along with the furnace to obtain Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur; Step 4: The Co3ZnC nanoparticle carbon derivative loaded with elemental sulfur, a conductive agent and a binder are added to a ball mill jar in a mass ratio of 7:2:1; Step 5: A solvent E is added to the ball mill jar, and then is ground and uniformly mixed to form an electrode slurry with fluidity; Step 6: The electrode slurry is uniformly scraped on the surface of an aluminum foil using a doctor blade, and then the aluminum foil is placed in a blast drying oven at 70-80 DEG C for drying for 8-12 hours, and then the Co3ZnC nanoparticle carbon derivative positive electrode sheet is obtained after complete drying. The preparation method of the Co3ZnC nanoparticle carbon derivative comprises the following steps: Step S11: ZIF-8 seeds are prepared according to a proportion; Step S12: ZIF-8@ZIF-67 solution is prepared according to a proportion, and ZIF-8@ZIF-67 powder is obtained; Step S13: The ZIF-8@ZIF-67 powder is sintered by using a joule heat rapid sintering technology, and Co3ZnC nanoparticle carbon derivative is obtained by sintering at 700-900 DEG C for 20-40 seconds in an argon environment, wherein the diameter of the Co3ZnC nanoparticle carbon derivative is 600-1500 nm.

2. The method according to claim 1, wherein the method for preparing a positive electrode sheet of a Co3ZnC nanoparticle carbon derivative is characterized by, The step S11 comprises the following steps: Step S111: 2-methylimidazole is added to distilled water to obtain solution A by ultrasonic dispersion; Step S112: Zinc acetate dihydrate is added to distilled water to obtain solution B by ultrasonic dispersion; Step S113: Solution B is added to solution A, and stirring is performed for 10-30 seconds, and the mixture is left to stand at room temperature for 24-36 hours to obtain mixed solution A; Step S114: The supernatant in the mixed solution A is taken out, and the remaining mixed solution A is centrifuged at 8000-10000 rpm / min in a centrifuge for 5-10 minutes, and the precipitate is washed repeatedly for 2-3 times with distilled water, and then is washed for 1-2 times with anhydrous ethanol to obtain precipitate A; Step S115: The obtained precipitate A is dried in an oven at 70-80 DEG C for 8-12 hours to obtain ZIF-8 seeds.

3. The method according to claim 2, wherein the method is characterized by, The step S12 comprises the following steps: Step S121: The ZIF-8 seeds are added to distilled water to obtain ZIF-8 suspension by ultrasonic dispersion; Step S122: 2-methylimidazole is added to distilled water to obtain solution C by ultrasonic dispersion; Step S123: Cobalt acetate tetrahydrate is added to distilled water to obtain solution D by ultrasonic dispersion; Step S124: Solution D is added to the ZIF-8 suspension to obtain purple suspension E by ultrasonic dispersion; Step S125: add the suspension E to the solution C, stir for 10-30s, stand for 24-36h at room temperature, to obtain a mixed solution B; Step S126: take the supernatant in the mixed solution B, centrifuge the remaining precipitate in the mixed solution B at 8000-10000rpm / min for 5-10min using distilled water in a centrifuge, repeat the washing for 2-3 times, and then wash with anhydrous ethanol for 1-2 times, to obtain a precipitate B; Step S127: dry the precipitate B in an oven at 70-80℃ for 8-12h, to obtain a ZIF-8@ZIF-67 powder.

4. The method of claim 1, wherein the method is characterized by, The optimal sintering temperature in the step S13 is 800℃, and the sintering time is 60s.

5. The method of claim 4, wherein the method is characterized by: The content of 2-methylimidazole in 5ml of the solution A is 1-2g; The content of zinc acetate dihydrate in 5ml of the solution B is 0.15-0.45g; The content of 2-methylimidazole in 5ml of the solution C is 0.5-1g; The content of cobalt acetate tetrahydrate in 5ml of the solution D is 0.1-0.3g.

6. The method of claim 1, wherein the method is characterized by: The conductive agent includes Ketjen black; The binder includes polyvinylidene fluoride; The solvent E includes N-methylpyrrolidone.

7. Application of the Co3ZnC nanoparticle carbon derivative positive electrode plate prepared by the preparation method of any one of claims 1-6 in preparation of a lithium-sulfur battery.

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