CN-122025578-A - Preparation and application of starch-based material for sulfur anode of magnesium-sulfur battery

CN122025578ACN 122025578 ACN122025578 ACN 122025578ACN-122025578-A

Abstract

The invention discloses a preparation and application of a sulfur anode for a magnesium-sulfur battery based on starch materials, which is characterized in that the starch materials from different sources are sequentially subjected to gelatinization, freeze drying and carbonization treatment to obtain powdery carbon materials with the particle size of 0.5-3 mu m; and mixing the anode with sulfur powder, performing heat treatment, uniformly mixing the anode with a conductive agent, a binder and the like, and coating the mixture on a copper-containing current collector to obtain the sulfur anode. In a specific magnesium-lithium mixed electrolyte system, the positive electrode has electrochemical performance superior to or equivalent to that of a commercial sulfur-carbon composite positive electrode in a magnesium-sulfur battery, has reversible discharge specific capacity of more than 1000mAh/g and good cycle stability. The method has simple process and low cost, is suitable for starch with various biomass sources, and the prepared sulfur anode has consistent excellent performance and strong universality, is suitable for large-scale production, can be used as a substitute material of the existing commercial sulfur-carbon composite anode, and has wide application prospect in the field of magnesium-sulfur batteries.

Inventors

CAO LIUYUE
LIAO HONGQING
ZHANG BINWEI
WANG JINGFENG
PAN FUSHENG

Assignees

重庆大学

Dates

Publication Date: 20260512
Application Date: 20260124

Claims (9)

1. The preparation method of the sulfur anode for the magnesium-sulfur battery based on the starch material is characterized by comprising the following steps of: s1, gelatinizing and dissolving starch, namely mixing the starch with ultrapure water according to a liquid/solid mass ratio of 8-25, stirring for 10-30min at a rotating speed of 400-800rmp, and then magnetically stirring and gelatinizing for 1-3h at 70-95 ℃ to form a semitransparent colloid; S2, freeze drying, namely pre-freezing the colloid obtained in the step S1 at the temperature of-50 ℃ to liquid nitrogen, and then freeze drying in vacuum for 24-96 hours to obtain a white porous solid; S3, carbonizing at a low temperature, namely placing the product obtained in the step S2 in an inert atmosphere, heating to 300-700 ℃ at 1-20 ℃ per min, preserving heat for 1-3 hours, and cooling to obtain a first-stage carbon material; S4, high-temperature carbonization, namely grinding the carbon material in the first stage until the grain diameter is less than or equal to 60 mu m, heating to 800-1200 ℃ at 1-10 ℃ per min under protective atmosphere, preserving heat for 1-3 hours, and grinding until the grain diameter is less than or equal to 50 mu m after cooling to obtain the carbon material in the second stage; S5, sulfur-carbon compounding, namely mixing the carbon material of the second stage with sulfur powder according to the mass ratio of 1:1.5-4, and ball-milling for 4-7 hours in an inert atmosphere or vacuum with the oxygen content less than or equal to 0.1% at the material mass ratio of 10-40 and the rotating speed of 350-900 rmp; S6, sulfur melting treatment, namely placing the ball-milling product in a closed container, vacuumizing or introducing inert gas, and preserving heat for 12-48 hours at 110-200 ℃ to obtain the sulfur-carbon composite material.
2. The method for preparing the sulfur cathode of the magnesium-sulfur battery based on the starch material according to claim 1, wherein the starch in the step S1 is at least one selected from sweet potato starch, pea starch, mung bean starch, potato starch, wheat starch, corn starch and tapioca starch, and the difference of the proportion of the straight chain to the branched chain is converted into uniform colloid through pasting, so that the influence of the natural structure difference on carbonization is eliminated.
3. The preparation method of the sulfur anode for the magnesium-sulfur battery based on the starch material, which is disclosed in claim 1, is characterized in that the inert atmosphere is nitrogen or argon with the purity of more than or equal to 99.9%, the flow is 10-300ml/min, the temperature rising rate is controlled to be less than or equal to 10 ℃ per min in the low-temperature carbonization stage so as to avoid foaming, a high-conductivity carbon skeleton is formed in the high-temperature carbonization stage at the temperature of more than or equal to 1000 ℃, the specific surface area of the material is cooperatively improved to 100-300m 2 /g by double-stage carbonization, the mesoporous pore size is concentrated to 2-5 nm, and the polysulfide domain limiting capacity is enhanced.
4. The preparation method of the sulfur anode for the magnesium-sulfur battery based on the starch material, which is disclosed in claim 1, is characterized in that in the step S5, the mass ratio of sulfur to carbon is preferably 3:1-3.5:1, so that sulfur is uniformly embedded into carbon pores, the particle size of a composite is less than or equal to 20 mu m, and the improvement of the bulk density and the sulfur loading of the anode is facilitated.
5. The preparation method of the sulfur anode for the magnesium-sulfur battery based on the starch material, which is disclosed in claim 1, is characterized in that the sulfur melting treatment in the step S6 is carried out in a closed container, the temperature is kept constant for 12-24 hours at 155+/-5 ℃, the atmosphere can be inert gas (such as argon or nitrogen) or vacuum environment, the residual amount of oxygen is less than or equal to 50ppm, the molten sulfur is completely filled with carbon material, and the sulfur load rate is more than or equal to 70wt%.
6. The preparation method of the sulfur anode for the magnesium-sulfur battery based on the starch material, which is disclosed in claim 1, is characterized in that the second-stage carbon material has a hierarchical porous structure, wherein micropores are 40-60% in proportion to 2nm and 30-50% in proportion to 2-50nm, and can be used for matching polysulfides with different chain lengths, so that polysulfide shuttling is inhibited through physical confinement.
7. Use of a sulfur/starch-based carbon composite material in a magnesium sulfur battery, the sulfur/starch-based carbon composite material being prepared by the method of any one of claims 1-6, characterized in that (a) the preparation of a positive plate of the sulfur/starch-based carbon composite material: Firstly, mixing and grinding a composite material, a binder and a conductive agent, then adding a solvent, stirring uniformly to slurry or paste, coating on a copper-containing current collector, drying the copper-containing current collector in a drying oven at 40-80 ℃ for 12-24 hours, and then cutting the copper-containing current collector into a positive plate to obtain a positive plate of the sulfur/starch-based carbon composite material, wherein the sulfur/starch-based carbon composite material, the conductive agent and the binder are 70-99% by mass of the sulfur/starch-based carbon composite material, 0.5-15% by mass of the conductive agent and 0.5-15% by mass of the binder; (b) Magnesium-sulfur battery assembly of sulfur/starch-based carbon composite: and (c) sequentially assembling the positive plate obtained in the step (a) according to the positive plate, the diaphragm and the negative plate, and sealing the battery after the electrolyte is dripped.
8. The application of the sulfur/starch-based carbon composite material in the magnesium-sulfur battery is characterized in that the conductive agent is one or two of conductive carbon black, graphite, carbon nano tubes and ketjen black, the binder is one or more of polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, sodium alginate, styrene-butadiene rubber emulsion and styrene-butadiene rubber emulsion, the solvent is one of N-methyl pyrrolidone, water and ethanol, and the current collector is a porous net-shaped, foil-shaped or fabric-shaped conductor material, and relates to one or more of copper net, copper foil, foam copper and composite copper material.
9. The application of the sulfur/starch-based carbon composite material in a magnesium sulfur battery according to claim 7, wherein the electrolyte is a mixed solution containing magnesium salt and lithium salt, the magnesium salt is magnesium chloride (MgCl 2 ), a magnesium chloride-aluminum chloride mixture (MgCl 2 -AlCl 3 ), bis (magnesium triflimide) (Mg (NO 4 S 2 C 2 F 6 ) 2 , magnesium triflate (Mg (CF 3 SO 3 ) 2 ), a phenyl magnesium chloride-aluminum trichloride mixture (PhMgCl-AlCl 3 ) and the concentration of the magnesium salt is 0.1-3mol/L, the lithium salt is lithium chloride (LiCl), lithium triflimide (LiNO 4 S 2 C 2 F 6 ) and the concentration of the lithium triflate (LiCF 3 SO 3 ) is 0.1-3mol/L, the organic solvent is Tetrahydrofuran (THF), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), tetraethylene glycol dimethyl ether (G4) and other ethers as main solvents, the negative electrode is magnesium, magnesium alloy, magnesium titanate, magnesium silicate, one of metal sulfide, polypropylene, cellulose, polytetrafluoroethylene, a membrane or a composite membrane of the polypropylene, a fiber, a polytetrafluoroethylene membrane or a membrane.

Description

Preparation and application of starch-based material for sulfur anode of magnesium-sulfur battery Technical Field The invention belongs to the field of electrochemical energy storage magnesium-sulfur batteries, and particularly relates to a preparation method for a sulfur anode of a magnesium-sulfur battery based on a starch material. Meanwhile, the invention also relates to application of the starch-based material. Background Magnesium ion batteries are considered as one of ideal candidate systems for next-generation high-energy-density rechargeable batteries due to the characteristics of rich resource reserves, high theoretical specific capacity, small ion radius and the like. Meanwhile, the metal magnesium cathode has high reversibility and low dendrite growth tendency in the charge and discharge process, and the practical prospect of the magnesium battery is further improved. The sulfur cathode material exhibits significant advantages in its extremely high theoretical energy density (mass energy density up to 1700Wh/kg, volumetric energy density up to 3200 Wh/L). Based on the above, the magnesium-sulfur battery system is widely focused, the theoretical specific discharge capacity of the magnesium-sulfur battery system can reach 1675mAh/g, and the actual specific discharge capacity reported at present is 300-1200 mAh/g. However, the sulfur anode has poor conductivity, and has problems of polysulfide shuttle effect, remarkable volume expansion, slow reaction kinetics and the like in the circulating process, so that the working voltage is low and the circulating stability is poor. In order to improve the electrochemical performance of the sulfur positive electrode, the current mainstream strategy is to select a proper sulfur carrier material, and by means of the high conductivity and good mechanical performance of the carrier, the conductive capacity of the positive electrode is enhanced, the shuttle effect is inhibited, and the volume change is relieved. Carbon materials are considered ideal sulfur carriers because of their excellent electrical conductivity, suitable mechanical strength and structural adjustability. However, factors such as the microscopic morphology, pore structure, cost and source of the carbon support have important effects on the overall performance of the battery. Biomass materials are considered as ideal precursors for preparing functional carbon materials because of their wide sources, strong reproducibility, environmental friendliness, rich carbon content and natural fine multi-stage structure. The starch is one of renewable biomass resources with the most abundant reserves in the plant kingdom, has the advantages of unique particle morphology, uniform particle size distribution, easy acquisition, low cost, short regeneration period and the like, and becomes a carbon precursor with great development potential. However, starch is easy to melt and foam in the high-temperature carbonization process, and usually needs to be subjected to stabilization treatment such as oxidation, esterification or crosslinking in advance, meanwhile, the proportion of straight chains and branched chains in different varieties of starch is different, so that the structure and the performance of a final carbon material are different, and in addition, the varieties and the contents of natural doping atoms (such as nitrogen, phosphorus and the like) in different sources of starch are different, so that the charging and discharging behaviors of a battery are possibly affected differently. More importantly, the treatment method optimized for certain starch is difficult to be directly applied to other starches, and the battery performance is easy to be reduced if the starch is forcibly applied. Therefore, if a high-performance electrode material needs to be developed based on multiple starches, an independent preparation process is usually required to be established for different starches, which clearly increases the development cost and time. In order to solve the problems, the preparation and the application of the starch-based material to the sulfur anode of the magnesium-sulfur battery are proposed. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a preparation and application of a starch-based material for a sulfur anode of a magnesium-sulfur battery, which is characterized in that different types of starch raw materials are converted into carbon substrates with similar morphology structures in a mode of combining dissolution, freeze drying and multi-step sintering, and uniform compounding of the starch raw materials and sulfur is further realized through processes such as ball milling and sulfur melting. In order to achieve the above purpose, the present invention provides the following technical solutions: a preparation method for a sulfur positive electrode of a magnesium-sulfur battery based on a starch material comprises the following steps: s1, gelatiniz