A sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material and its preparation method and application

Abstract

The present invention discloses a sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material and a preparation method and application thereof, and the present invention relates to the technical field of preparation of positive electrode materials for lithium-sulfur batteries. The composite material comprises a three-dimensional carbon skeleton derived from mold hyphae and a carbon-based material uniformly doped therein; the composite material also comprises sulfur and a metal catalyst; the sulfur is uniformly distributed on the surface of the mold hyphae-derived carbon, the surface of the carbon-based material and the graded pores of the three-dimensional skeleton, and the metal catalyst is loaded on the surface of the carbon-based material. When the composite material of the present invention is used as a positive electrode material for a self-supporting lithium-sulfur battery, it has the advantages of high sulfur loading, good electrical conductivity and effective adsorption of polysulfides; the assembled lithium-sulfur battery has the advantages of high specific capacity, high rate performance and long cycle life. The present invention solves the problem in the prior art that the macropores outside the hyphae cannot achieve effective sulfur loading and the overall sulfur loading of the material is low.

Description

Technical Field

[0001] The invention relates to the technical field of lithium-sulfur battery positive electrode material preparation, and in particular to a sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material and a preparation method and application thereof. Background Art

[0002] In recent years, as energy and environmental issues have become increasingly severe, people are in urgent need of developing environmentally friendly, safe and high-energy-density energy storage devices. Lithium-sulfur batteries have a high theoretical specific capacity (1675 mA hg -1 ) and theoretical energy density (2600W h kg -1 ) has received great attention and is expected to become a high-density energy storage device for the next generation of hybrid and all electric vehicles. However, the inherent challenges of lithium-sulfur battery cathodes hinder their practical application, such as: (i) the insulating properties of elemental sulfur lead to insufficient utilization of active materials, limiting the high-power performance of the battery; (ii) the generation of soluble lithium polysulfide intermediates during the reaction will cause serious loss of active materials, reduce Coulomb efficiency, and lead to poor cycle stability; (iii) sulfur has a volume expansion of nearly 80% before and after the reaction, which makes the electrode structure easy to collapse during the cycle and has a low cycle life. Therefore, in the preparation process of lithium-sulfur battery cathode materials, it is often necessary to compound sulfur and other conductive carrier materials to improve its conductivity and provide space for the volume expansion of sulfur. In addition, the physical barrier, physical adsorption or chemical adsorption of polysulfides by the conductive carrier can be used to inhibit the "shuttle effect", thereby improving the electrochemical performance of lithium-sulfur batteries and increasing the cycle life.

[0003] At present, the strategy of adding porous carbon-based materials to lithium-sulfur batteries has been proven to effectively alleviate the above problems. Porous carbon-based materials have high conductivity, adjustable porous structure and light weight. They can improve the conductivity of sulfur and reduce the "shuttle effect" by increasing the affinity between carbon and polysulfides, thereby achieving a longer cycle life. Among them, biomass carbon materials often retain the skeleton morphology of the biomass itself, have a good hierarchical structure, and are in-situ doped with heterogeneous elements such as nitrogen and phosphorus. They have both physical barrier and chemical adsorption effects on polysulfides, and are ideal sulfur carrier materials. However, the three-dimensional configuration and hierarchical structure of most biomass-derived carbon materials themselves are fixed. For example, mold hyphae carbon presents a three-dimensional filamentous spatial configuration. The sulfur loading is mainly concentrated in the pores on the surface of hyphae carbon and the internal space of hyphae. The large pores outside the hyphae cannot effectively realize the sulfur loading, which reduces the overall sulfur loading of the material and reduces the compaction density of the positive electrode material itself. Therefore, it is necessary to construct a new type of high sulfur loading multi-dimensional spatial configuration and hierarchical structure carrier material based on biomass-derived carbon. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a sulfur-alginate gel-filled mold mycelium-derived carbon-based composite material and its preparation method and application, so as to solve the problems in the prior art that the large pores outside the mycelium cannot achieve effective sulfur loading and the overall sulfur loading of the material is low.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a sulfur-alginate gel-filled fungal hyphae-derived carbon-based composite material is provided, wherein the composite material comprises a fungal hyphae-derived carbon three-dimensional skeleton and a carbon-based material uniformly doped therein; the composite material also comprises sulfur and a metal catalyst; the sulfur is uniformly distributed on the surface of the fungal hyphae-derived carbon, the surface of the carbon-based material and in the hierarchical pores of the three-dimensional skeleton, and the metal catalyst is loaded on the surface of the carbon-based material.

[0006] The beneficial effects of the present invention are as follows: the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite electrode material prepared by the present invention has excellent electrical conductivity, effectively promoting ion and electron transmission in the reaction process; has a rich three-dimensional hierarchical pore structure, which can provide space for the volume expansion of sulfur; has a complex pore structure and rich heterogeneous element doping, which can intercept polysulfides through physical barrier, physical adsorption and chemical adsorption, inhibit the "shuttle effect", and improve the specific capacity and cycle life of lithium-sulfur batteries; has a uniformly dispersed metal catalyst load, which can significantly improve the catalytic conversion kinetics of polysulfides.

[0007] When the composite material of the present invention is used as a positive electrode material for a self-supporting lithium-sulfur battery, it has the advantages of high sulfur loading, good conductivity and effective adsorption of polysulfides; the assembled lithium-sulfur battery has the advantages of high specific capacity, high rate performance and long cycle life, and has broad application prospects in energy storage fields such as electric vehicles and smart grids, and is expected to become a high-density energy storage device for the next generation of hybrid and electric vehicles.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows:

[0009] Furthermore, the mass fraction of sulfur in the composite material is 70-90%.

[0010] Furthermore, the diameter of the mold hyphae-derived carbon is 3-5 μm, the size of the carbon-based material is 0.05-200 μm, and the particle size of the metal catalyst is 1-15 nm.

[0011] The beneficial effects of adopting the above further technical solution are: the micro-nano size of the composite material enables the material to have a large specific surface area and more active sites, high electrical conductivity and short ion diffusion channels.

[0012] The present invention also provides a method for preparing the above-mentioned sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material, comprising the following steps:

[0013] (1) taking out the fungal pellets cultured in the liquid culture medium, washing them, and freeze-drying them to obtain mycelial pellets;

[0014] (2) soaking the mycelium ball obtained in step (1) in a sodium alginate solution, and then soaking it in a multivalent cation salt solution for curing, then washing and drying, heating it to 700-900° C., keeping it warm for 1-3 hours, and cooling it to obtain an alginate gel-filled mold mycelium-derived carbon-based composite material;

[0015] (3) Evenly mixing the alginate gel-filled fungus mycelium-derived carbon-based composite material obtained in step (2) and sulfur, reacting at 150-180° C. for 5-16 hours, and cooling to obtain a sulfur-alginate gel-filled fungus mycelium-derived carbon-based composite material.

[0016] Furthermore, in step (1), the liquid culture medium is SDB culture medium.

[0017] Furthermore, in step (1), deionized water is used for washing.

[0018] Further, in step (1), freeze-drying is performed for 2-3.

[0019] Furthermore, in step (2), the concentration of the sodium alginate solution is 0.3-2 g / L.

[0020] Furthermore, in step (2), the concentration of the multivalent cation salt solution is 0.02-0.5 mol / L.

[0021] Furthermore, in step (2), the multivalent cation salt is at least one of vanadium chloride, cobalt chloride and manganese chloride.

[0022] Furthermore, in step (2), curing is performed for 2-6 hours.

[0023] Furthermore, in step (2), deionized water is used for washing.

[0024] Furthermore, in step (2), freeze drying is used.

[0025] Furthermore, in step (2), heating is performed under an argon atmosphere.

[0026] The present invention also provides the use of the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material in the preparation of a self-supporting lithium-sulfur battery positive electrode material.

[0027] The present invention has the following beneficial effects:

[0028] 1. The present invention realizes in-situ gelation in the three-dimensional space of fungal mycelium by infusing liquid sodium alginate polysaccharide and subsequent multivalent cation replacement process in the mold mycelium skeleton, and obtains a carbon-based composite material derived from fungal mycelium by subsequent drying and carbon heat treatment. The micro-nano size of the composite material enables the material to have a large specific surface area and more active sites, high electrical conductivity and short ion diffusion channels. The composite material has excellent electrical conductivity, effectively promotes ion and electron transmission during the reaction process; has a rich three-dimensional hierarchical pore structure, which can provide space for the volume expansion of sulfur; has a complex pore structure and rich heterogeneous element doping, can intercept polysulfides through physical barrier, physical adsorption and chemical adsorption, inhibit the "shuttle effect", and improve the specific capacity and cycle life of lithium-sulfur batteries; has a uniformly dispersed metal element or metal compound load of a few nanometers, which can significantly improve the catalytic conversion kinetics of polysulfide. Finally, after sulfurization by melt diffusion method, a sulfur-alginate gel-filled mold mycelium-derived carbon-based composite material was obtained, which can be used as a self-supporting lithium-sulfur battery positive electrode material. Compared with the ordinary slurry coating method to prepare electrodes, it reduces the use of binders and conductive agents, effectively increases the proportion of active substances, achieves a high sulfur loading, and thus improves the overall energy density of the lithium-sulfur battery.

[0029] 2. The present invention uses mold mycelium balls as carriers, introduces an in-situ solidified gel system into the three-dimensional space of natural mold mycelium, and then obtains a three-dimensionally restructured alginate gel-filled mold mycelium-derived carbon-based composite material through subsequent heat treatment, that is, a three-dimensional self-supporting sulfur carrier material with a multi-dimensional spatial configuration and a hierarchical structure, and then prepares a sulfur-alginate gel-filled mold mycelium-derived carbon-based composite electrode material through a sulfurization method to achieve good sulfur fixation and polysulfide adsorption, and finally improves the electrochemical performance of lithium-sulfur batteries. The preparation method is simple and convenient, easy to control, and conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope image of the alginate gel-filled mold hyphae-derived carbon-based composite material prepared in Example 1;

[0031] Figure 2 This is a transmission electron microscopy image of the mold hyphae-derived carbon-based composite material filled with alginate gel prepared in Example 1;

[0032] Figure 3 This is a scanning electron microscope image of the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material prepared in Example 1;

[0033] Figure 4 This is a rate performance diagram of a lithium-sulfur battery assembled with the composite material prepared in Example 1. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0035] Embodiment 1:

[0036] A sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material, the preparation method of which comprises the following steps:

[0037] (1) taking out the fungal pellets cultured in SDB liquid medium, washing them three times with deionized water, and freeze-drying them for 2 days to obtain mycelial pellets;

[0038] (2) soaking the mycelium pellet obtained in step (1) in a sodium alginate solution until the mycelium pellet is fully soaked by the sodium alginate solution, and then soaking the mycelium pellet soaked in the sodium alginate solution in a vanadium chloride solution (with a concentration of 0.5 mol / L), in situ gel curing for 5 hours, then washing with deionized water and freeze drying, heating to 800° C. in an argon atmosphere, keeping the temperature for 2 hours, and cooling to obtain an alginate gel-filled mold mycelium-derived carbon-based composite material;

[0039] (3) The alginate gel-filled fungus mycelium-derived carbon-based composite material obtained in step (2) and elemental sulfur are evenly mixed, placed in a reactor, reacted at 155° C. for 10 hours, and the reactor is cooled to obtain a sulfur-alginate gel-filled fungus mycelium-derived carbon-based composite material.

[0040] Embodiment 2:

[0041] A sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material, the preparation method of which comprises the following steps:

[0042] (1) taking out the fungal pellets cultured in SDB liquid medium, washing them three times with deionized water, and freeze-drying them for 2 days to obtain mycelial pellets;

[0043] (2) soaking the mycelium pellet obtained in step (1) in a sodium alginate solution until the mycelium pellet is fully soaked by the sodium alginate solution, and then soaking the mycelium pellet soaked in the sodium alginate solution in a cobalt chloride solution (with a concentration of 0.02 mol / L), in situ gel curing for 6 hours, then washing with deionized water and freeze drying, heating to 700° C. in an argon atmosphere, keeping warm for 3 hours, and cooling to obtain an alginate gel-filled mold mycelium-derived carbon-based composite material;

[0044] (3) The alginate gel-filled fungus mycelium-derived carbon-based composite material obtained in step (2) and elemental sulfur are evenly mixed, placed in a reactor, reacted at 150° C. for 16 hours, and the reactor is cooled to obtain a sulfur-alginate gel-filled fungus mycelium-derived carbon-based composite material.

[0045] Embodiment 3:

[0046] A sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material, the preparation method of which comprises the following steps:

[0047] (1) taking out the fungal pellets cultured in SDB liquid medium, washing them three times with deionized water, and freeze-drying them for 2 days to obtain mycelial pellets;

[0048] (2) soaking the mycelium ball obtained in step (1) in a sodium alginate solution until the mycelium ball is fully soaked by the sodium alginate solution, and then soaking the mycelium ball soaked in the sodium alginate solution in a manganese chloride solution (with a concentration of 0.4 mol / L), in situ gel curing for 2 hours, and then washing with deionized water and freeze drying, heating to 900° C. in an argon atmosphere, keeping warm for 1 hour, and cooling to obtain an alginate gel-filled mold mycelium-derived carbon-based composite material;

[0049] (3) The alginate gel-filled fungus mycelium-derived carbon-based composite material obtained in step (2) and elemental sulfur are evenly mixed, placed in a reactor, reacted at 180° C. for 5 hours, and the reactor is cooled to obtain a sulfur-alginate gel-filled fungus mycelium-derived carbon-based composite material.

[0050] Test example

[0051] 1. The alginate gel-filled mold hyphae-derived carbon-based composite material obtained in step (2) of Example 1 was subjected to scanning electron microscopy and transmission electron microscopy. The results are shown in Figure 1-2 .

[0052] Depend on Figure 1-2 It can be seen that the alginate gel-filled mold hyphae-derived carbon-based composite material presents a composite three-dimensional hierarchical structure with hyphae carbon as the skeleton and alginate gel-derived carbon sheets doped therein, wherein vanadium oxide nanoparticles are uniformly loaded in the alginate-derived sheet structure.

[0053] 2. The sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material prepared in Example 1 was subjected to scanning electron microscopy. The results are shown in Figure 3 .

[0054] Depend on Figure 3It can be seen that the composite material prepared by the present invention includes a three-dimensional mycelium carbon skeleton, a carbon-based material uniformly doped therein, a metal element or metal compound catalyst loaded on the surface of the carbon-based material, and sulfur entering the carbon-based composite material through a melt diffusion method; the sulfur is covered on the mold mycelium carbon and the in-situ grown carbon-based material and is uniformly dispersed in the three-dimensional hierarchical pores.

[0055] 3. The sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material prepared in Example 1 was subjected to elemental analysis. The results showed that the content of elemental sulfur in the composite material was 82wt%, the content of carbon was 10wt%, and the content of vanadium oxide nanoparticles was 7wt%.

[0056] 4. Performance Testing

[0057] The sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material prepared in Example 1 was assembled into a lithium-sulfur battery, and the specific method was as follows: the composite material was used as the positive electrode, the metal lithium was used as the negative electrode, and the polypropylene microporous membrane (Celgard 2400) was used as the diaphragm, and the CR2025 button battery was assembled in a closed glove box with argon as the protective gas and the water and oxygen partial pressures less than 0.1ppm. Lithium bistrifluoromethanesulfonyl imide (LiTFSI) was dissolved in a mixed solution of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) configured in a volume ratio of 1:1, and 1wt% of lithium nitrate (LiNO3) was added thereto as an electrolyte.

[0058] After the battery was left to stand for 12 hours, the electrochemical performance test was carried out at room temperature.

[0059] The rate performance of the assembled lithium-sulfur battery was tested under different current density conditions (0.1C-5C). Figure 4 .Depend on Figure 4 It can be seen that under 0.1C conditions, the first cycle discharge capacity is 1325.9mA hg -1 Even at a high current density of 5C, the assembled lithium-sulfur battery exhibited a current density of 578 mA hg -1 The discharge specific capacity shows that it has excellent rate performance.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material, characterized in that: The following steps are involved: (1) taking out the fungal pellets cultured in the liquid culture medium, washing them, and freeze-drying them to obtain mycelial pellets; (2) soaking the mycelium ball obtained in step (1) in a sodium alginate solution, and then soaking it in a multivalent cation salt solution for curing, then washing and drying, heating it to 700-900° C., keeping it warm for 1-3 hours, and cooling it to obtain an alginate gel-filled mold mycelium-derived carbon-based composite material; (3) uniformly mixing the alginate gel-filled fungus mycelium-derived carbon-based composite material obtained in step (2) and sulfur, reacting at 150-180° C. for 5-16 hours, and cooling to obtain a sulfur-alginate gel-filled fungus mycelium-derived carbon-based composite material; In step (2), the multivalent cation salt is at least one of vanadium chloride, cobalt chloride and manganese chloride.

2. The method for preparing the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 1, characterized in that: In step (1), the liquid culture medium is SDB culture medium.

3. The method for preparing the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 1, characterized in that: In step (2), the concentration of the sodium alginate solution is 0.3-2 g / L.

4. The method for preparing the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 1, characterized in that: In step (2), the concentration of the multivalent cation salt solution is 0.02-0.5 mol / L.

5. The method for preparing the sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 1, characterized in that: In step (2), the curing time is 2-6 hours.

6. A sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material prepared according to the preparation method according to any one of claims 1 to 5, characterized in that: The composite material comprises a three-dimensional carbon skeleton derived from mold hyphae and a carbon-based material uniformly doped therein; the composite material also comprises sulfur and a metal catalyst; the sulfur is uniformly distributed on the surface of the mold hyphae derived carbon, the surface of the carbon-based material and the hierarchical pores of the three-dimensional skeleton, and the metal catalyst is loaded on the surface of the carbon-based material.

7. The sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 6, characterized in that: The mass fraction of sulfur in the composite material is 70-90%.

8. The sulfur-alginate gel-filled mold hyphae-derived carbon-based composite material according to claim 6, characterized in that: The diameter of the mold hyphae-derived carbon is 3-5 μm, the size of the carbon-based material is 0.05-200 μm, and the particle size of the metal catalyst is 1-15 nm.

9. Use of the sulfur-alginate gel filled mold hyphae derived carbon-based composite material according to any one of claims 6 to 8 in the preparation of a self-supporting lithium-sulfur battery positive electrode material.

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