High-performance room-temperature sodium-sulfur battery positive electrode material and preparation method thereof

Abstract

The invention discloses a high-performance room-temperature sodium-sulfur battery positive electrode material and a preparation method thereof. The positive electrode material is a sulfur / carbon supported catalyst composite material, metal salt containing lattice water and a compound containing an organic functional group are subjected to simple mechanical mixing and aging under the condition of no additional solvent, high-temperature calcination is performed, metal elements in the metal salt are partially reduced and are supported on the carbonized organic compound, and the positive electrode material is obtained. And forming the carbon / metal composite material. The carbon-loaded metal composite material is fused with pure sulfur powder to obtain the sodium-sulfur battery positive electrode material, the advantages of high specific surface area, good conductivity and the like of a porous carbon material can be effectively utilized, and meanwhile, the catalytic performance is fully played, so that the conversion rate of long-chain sodium polysulfide is increased, the retention time of the long-chain sodium polysulfide in electrolyte is shortened, the shuttle effect is greatly relieved, and the service life of the sodium-sulfur battery is prolonged. The stability of the sodium-sulfur battery in the cycle process is improved, so that the sodium-sulfur battery shows good cycle stability and relatively high specific capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-sulfur batteries, and in particular to a high-performance room-temperature sodium-sulfur battery cathode material and a preparation method thereof. Background Art

[0002] With the increasing depletion of global fossil energy and the environmental deterioration problems brought about by its use, the development and use of green and renewable energy have become one of the important strategies for sustainable development in countries around the world today. The development of large-scale energy storage technology is imminent. Although lithium-ion batteries have been widely used, there are problems such as safety hazards, and they are restricted by the shortage of lithium resources in large-scale applications. In this context, room-temperature sodium-sulfur batteries are considered to be one of the next-generation large-scale energy storage technologies with great development prospects because they avoid the disadvantages of insufficient lithium resources and have advantages such as high theoretical energy density, environmental friendliness, safety and reliability, and low cost. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a high-performance room-temperature sodium-sulfur battery cathode material and a preparation method thereof. The present invention further optimizes the structure and catalytic conversion process of the sodium-sulfur battery cathode material to improve kinetics. In addition, the present invention uses metal catalysis on the porous structure carrier in the cathode material to accelerate the conversion of polysodium sulfide, and also provides a method to shorten the residence time of long-chain polysodium sulfide in the electrolyte.

[0004] The first object of the present invention is to provide a high-performance room-temperature sodium-sulfur battery cathode material. The high-performance room-temperature sodium-sulfur battery cathode material is based on a porous carbon material, and the substrate contains rich pores and is loaded with metal atoms and heteroatoms to form a composite material; sulfur is loaded on the surface and pores of the composite material.

[0005] In some embodiments of the present invention, the metal atoms include one or more of Al, Na, Zn, Ni, Co, Fe, Ca, Mg, Cu, and Ga;

[0006] The heteroatoms include one or more of N, S, O, and P.

[0007] The second object of the present invention is to provide a preparation method of the high-performance room-temperature sodium-sulfur battery cathode material, including the following steps:

[0008] (1) Mechanically mix and age a hydrated metal salt and an organic compound containing multifunctional functional groups to obtain a mixture;

[0009] (2) Heat-treat the mixture obtained in step (1) in an inert gas atmosphere to obtain a carbon-supported metal composite material;

[0010] (3) The carbon-supported metal composite material in step (2) and sulfur powder are subjected to solid-liquid fusion in an inert gas environment, so that sulfur is loaded in the pores and on the surface of the composite material, and finally the high-performance room-temperature sodium-sulfur battery cathode material is obtained; wherein most of the molten sulfur at high temperature enters the pore structure of the material and a small amount is on the surface of the material.

[0011] In some embodiments of the present invention, in step (1), the metal of the hydrated metal salt is selected from one or more of Al, Na, Zn, Ni, Co, Fe, Ca, Mg, Cu, and Ga; the types of the hydrated metal salt include one or more combinations of nitrates, chlorides, and sulfates.

[0012] In some embodiments of the present invention, in step (1), the multifunctional functional groups include one or more of amino, hydroxyl, sulfonic acid group, mercapto, and methyl; the organic substances include 2-methylimidazole, 2-aminoterephthalic acid, mercaptoterephthalic acid, 2-hydroxyterephthalic acid, and 2-sulfoterephthalic acid. The multi-functional group organic substances provided in the present invention can be used to provide a coordination environment for metal ions and heteroatoms.

[0013] In some embodiments of the present invention, in step (1), the molar ratio of the hydrated metal salt to the organic substance containing multifunctional functional groups is (1-5):(6-20); the aging time is 0.5-12 hours.

[0014] In some embodiments of the present invention, in step (2), the inert non-reactive gas of the inert gas includes nitrogen and argon;

[0015] The heat treatment is instantaneous arc heating or slow heating.

[0016] In some embodiments of the present invention, the temperature of the instantaneous arc is controlled to be maintained at 900-1500 °C for 5-25 seconds; the heating rate of the slow heating is 1-20 °C / min, exemplarily, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 °C / min, or any interval value between any two values, and is maintained at 700-1200 °C for 0.5-15 h, exemplarily, it can be 700, 800, 900, 1000, 1100, 1200 °C, etc., and can be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 h, or any interval value between any two values.

[0017] In some embodiments of the present invention, in step (3), the mass ratio of the carbon-supported metal composite material to sulfur powder is (0.5-1):(0.5-5); further preferably, it is (1:0.5) to (1:1), (1:1) to (1:2), etc.

[0018] The fusion temperature is 100-400 °C, the time is 10-20 h, and the heating rate is 5-10 °C / min. Exemplarily, it can be 5, 6, 7, 8, 9, 10 °C / min, or any interval value between any two values.

[0019] The third object of the present invention is to provide a positive electrode sheet, including the positive electrode material of the high-performance room-temperature sodium-sulfur battery.

[0020] The fourth object of the present invention is to provide a battery, including the positive electrode sheet.

[0021] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0022] The present invention adopts a solvent-free mechanical grinding combined with high-temperature calcination synthesis method to synthesize a porous carbon-supported metal composite material, which is used as a sulfur storage material in the positive electrode of a room-temperature sodium-sulfur battery. The water and crystal water in the metal salt will produce a competitive coordination effect during the coordination of metal ions and organic compounds containing functional groups, causing the crystal water to escape, which is beneficial to the occurrence of the coordination reaction. The metal in the composite material is highly dispersed on the porous carbon, and the conversion rate of the room-temperature sodium-sulfur battery in the redox of sulfur can be improved by increasing the concentration of the metal, playing a role in improving the cycle stability and high rate of the composite material of the room-temperature sodium-sulfur battery. Then, through the coating of the metal by the porous carbon and the doping of the metal surface with heteroatoms derived from heteroorganic functional groups, the loss of the active substance sulfur on the surface during charge and discharge can be reduced, the deterioration of the environment and dendrite growth during the sodium deposition process on the negative electrode side can be inhibited, the cycle stability of the surface of the porous carbon-supported metal composite material can be improved, and at the same time, the conductivity of the metal-supported composite material can be improved, enhancing the electrochemical performance of the composite material. Description of the Drawings

[0023] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention and in combination with the drawings, where

[0024] Figure 1 is the SEM image of the carbon-supported metal composite material prepared in Example 1;

[0025] Figure 2 is the SEM image of the composite of carbon-supported metal and sulfur prepared in Example 1;

[0026] Figure 3 is the XRD pattern of the carbon-supported metal composite material prepared in Example 1;

[0027] Figure 4 XRD pattern of the carbon-supported metal and sulfur composite prepared in Example 1;

[0028] Figure 5 Cycling diagrams of the materials prepared from carbon-supported metal and sulfur composites in Example 1, Comparative Examples 1, 2, and 3 at a current of 1C;

[0029] Figure 6 Rate performance cycling diagram of the positive electrode material of the sodium-sulfur battery based on carbon-supported metal prepared in Example 1.

[0030] Figure 7 Schematic diagram of the formation of the carbon-supported metal material prepared by the solvent-free method of the present invention. Detailed implementation mode

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.

[0032] Example 1

[0033] This example provides a preparation method for a high-performance room-temperature sodium-sulfur battery positive electrode material, which is specifically as follows:

[0034] (1) Mix 5.82 g of cobalt nitrate hexahydrate and 13.14 g of 2-methylimidazole in a corundum mortar and grind for 30 min to obtain a solid paste-like mixture.

[0035] (2) Pour the solid paste-like mixture in step (1) into a quartz boat, and then place it in a tube furnace for carbonization treatment in a high-purity Ar atmosphere environment. The temperature is 800 degrees Celsius, the heating rate is 5°C / min, and keep it warm for 3 hours to obtain a carbon-supported metal composite material. The obtained composite material is subjected to structure characterization, and the results are shown in Figure 1 and Figure 3 , Figure 1 SEM image of the carbon-supported metal composite material prepared in this example. As can be seen from the figure, the morphology of the carbon / metal composite material is irregularly porous, and sufficient space can be provided for the active substance sulfur between the pores. Figure 3 XRD pattern of the carbon / metal composite material prepared in this example. From Figure 3 it can be seen that the composite material has good crystallinity.

[0036] (3) The carbon-supported metal composite material in step (2) and pure sulfur powder are fused at a mass ratio of 1:1 in a high-purity Ar atmosphere. The heating rate is 5 °C / min, and it is maintained at 300 °C for 12 h. After cooling to room temperature, a sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur is obtained. The obtained sodium-sulfur battery cathode composite material is subjected to structural characterization, and the results are shown in Figure 2 and Figure 4 , Figure 2 Figure Figure 2 is the SEM image of the sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur prepared in this example. It can be seen from the figure that after fusing sulfur, the shape of the carbon-supported matrix does not change significantly. There is no structural collapse. At the same time, sulfur enters from the pores of the material, and most of it enters the macropores, mesopores and micropores, and a small amount is on its surface. Figure 4 Figure Figure 4 is the XRD pattern of the sodium-sulfur battery cathode material based on carbon-supported metal prepared in this example. It can be known from Figure 4 that the characteristic peaks of cobalt metal are masked after high-temperature sulfur fusion of the composite material, and several new characteristic peaks with higher intensities and some weak peaks appear. These peaks can coincide with the characteristic peaks of sulfur. This phenomenon indicates that sulfur is successfully and uniformly composite on the carbon-supported metal.

[0037] Example 2

[0038] This example provides a preparation method of a high-performance room-temperature sodium-sulfur battery cathode material, which is specifically as follows:

[0039] (1) 5.82 g of cobalt nitrate hexahydrate, 4.82 g of nickel nitrate hexahydrate, 13.14 g of 2-methylimidazole and 12.56 g of 2-aminoterephthalic acid are placed in a corundum mortar and mixed and ground for 30 min to obtain a solid paste mixture.

[0040] (2) The solid paste mixture in step (1) is poured into a quartz boat, and then placed in a tube furnace for carbonization treatment in a high-purity Ar atmosphere. The temperature is 900 °C, the heating rate is 10 °C / min, and it is kept for 5 hours to obtain a carbon-supported metal composite material.

[0041] (3) The carbon-supported metal composite material in step (2) and pure sulfur powder are fused at a mass ratio of 1:1 in a high-purity Ar atmosphere. The heating rate is 5 °C / min, and it is maintained at 300 °C for 12 h. After cooling to room temperature, a sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur is obtained.

[0042] Comparative Example 1

[0043] It is basically the same as Example 1, and the only difference is in step (3): the mass ratio of the carbon-supported metal composite material to pure sulfur powder is 1:3, and the others are all the same as in Example 1.

[0044] (1) Mix 5.82 g of cobalt nitrate hexahydrate and 13.14 g of 2-methylimidazole in a corundum mortar and grind for 30 min to obtain a solid paste-like mixture.

[0045] (2) Pour the solid paste-like mixture in step (1) into a quartz boat, and then place it in a tube furnace for carbonization treatment in a high-purity Ar atmosphere environment at a temperature of 800 °C, with a heating rate of 5 °C / min, and hold for 3 hours to obtain a carbon-supported metal composite material.

[0046] (3) Mix the carbon-supported metal composite material in step (2) with pure sulfur powder at a mass ratio of 1:3, and fuse it in a high-purity Ar atmosphere environment. Among them, the heating rate is 5 °C / min, hold at 300 °C for 12 h, and cool to room temperature to obtain a sodium-sulfur battery positive electrode material based on the composite of carbon-supported metal and sulfur.

[0047] Comparative Example 2

[0048] Basically the same as Example 1, the difference is only that cobalt nitrate hexahydrate in step (1) is replaced by anhydrous cobalt nitrate, and the others are all the same as Example 1.

[0049] (1) Heat 5.82 g of cobalt nitrate to 110 °C for dehydration, then mix it with 13.14 g of 2-methylimidazole in a corundum mortar and grind for 30 min to obtain a solid paste-like mixture. (2) Pour the solid paste-like mixture in step (1) into a quartz boat, and then place it in a tube furnace for carbonization treatment in a high-purity Ar atmosphere environment at a temperature of 800 °C, with a heating rate of 5 °C / min, and hold for 3 hours to obtain a carbon-supported metal composite material. (3) Mix the carbon-supported metal composite material in step (2) with pure sulfur powder at a mass ratio of 1:1, and fuse it in a high-purity Ar atmosphere environment. Among them, the heating rate is 5 °C / min, hold at 300 °C for 12 h, and cool to room temperature to obtain a sodium-sulfur battery positive electrode material based on the composite of carbon-supported metal and sulfur.

[0050] Comparative Example 3

[0051] Basically the same as Example 1, the difference is only that 2-methylimidazole in step (1) is equally replaced by imidazole, and the others are all the same as Example 1.

[0052] (1) Mix 5.82 g of cobalt nitrate hexahydrate and 13.14 g of imidazole in a corundum mortar and grind for 30 min to obtain a solid mixture.

[0053] (2) Pour the solid paste mixture in step (1) into a quartz boat, and then place it in a tube furnace for carbonization treatment in a high-purity Ar atmosphere environment at a temperature of 800 °C, a heating rate of 5 °C / min, and hold for 3 hours to obtain a carbon-supported metal composite material.

[0054] (3) Mix the carbon-supported metal composite material in step (2) with pure sulfur powder at a mass ratio of 1:1, and fuse it in a high-purity Ar atmosphere environment. Among them, the heating rate is 5 °C / min, hold at 300 °C for 12 h, and cool to room temperature to obtain a sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur.

[0055] Performance Test

[0056] Mix the sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur prepared in Example 1, the carbon / metal sodium-sulfur battery cathode materials obtained in Comparative Examples 1-3, binder carboxymethyl cellulose (CMC) and acetylene black in a ratio of 7:2:1, and add an appropriate amount of distilled water, and stir and mix them into a uniform slurry in a quartz mortar; evenly coat the slurry on a cut copper foil with a diameter of 12 mm, and dry it in a vacuum drying oven at 60 °C for 12 h to prepare a positive electrode sheet of a sodium-sulfur battery. Assemble the obtained positive electrode sheets with sodium negative electrodes into button cells respectively, and conduct cyclic performance and rate performance cyclic tests. The experimental results are shown in Figures 5 - 6 .

[0057] Figure 5 is the cyclic spectrum diagram of the sulfur-carbon composite materials obtained in Example 1 and Comparative Examples 1, 2 and 3 at a current of 1C, indicating that the sodium-sulfur battery cathode material based on the composite of carbon-supported metal and sulfur prepared by the solvent-free method enables the sodium-sulfur battery to exhibit good cyclic stability and high specific capacity. It can be seen that the specific capacity of Comparative Example 1 is much lower than that of Example 1. The reason is that the sulfur melting ratio of Comparative Example 1 is 1:3, far exceeding the 1:1 sulfur melting ratio of Example 1. The electronic conductivity and ionic conductivity of elemental sulfur are poor, the conductivity of sulfur materials at room temperature is extremely low, and the final product of the reaction is also an electronic insulator, which is not conducive to the catalytic performance of electrode materials.

[0058] Figure 6 is the rate performance cyclic diagram of the sodium-sulfur battery cathode material based on carbon-supported metal prepared in Example 1. It can be seen from the figure that the composite material of Example 1 not only exhibits a high specific capacity at a low current density, but also has excellent reversibility at a high current density.

[0059] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A high-performance cathode material for room-temperature sodium-sulfur batteries, characterized in that, The positive electrode material of the high-performance room-temperature sodium-sulfur battery uses a porous carbon material as the substrate. The substrate contains abundant pores and is loaded with metal atoms and heteroatoms to form a composite material; sulfur is loaded on the surface and in the pores of the composite material.

2. The high-performance room-temperature sodium-sulfur battery cathode material according to claim 1, wherein The metal atoms include one or more of Al, Na, Zn, Ni, Co, Fe, Ca, Mg, Cu, and Ga; The heteroatoms include one or more of N, S, O, and P.

3. A method for preparing a high-performance cathode material for a room-temperature sodium-sulfur battery as described in claim 1 or 2, characterized in that, It includes the following steps: (1) Mechanically mix and age a hydrated metal salt and an organic compound containing multifunctional functional groups to obtain a mixture; (2) Heat-treat the mixture obtained in step (1) in an inert gas atmosphere to obtain a carbon-supported metal composite material; (3) Fuse the carbon-supported metal composite material in step (2) with sulfur powder in an inert gas environment so that sulfur is loaded in the pores and on the surface of the composite material, and finally obtain the positive electrode material of the high-performance room-temperature sodium-sulfur battery.

4. The preparation method according to claim 3, characterized in that, In step (1), the metal of the hydrated metal salt is selected from one or more of Al, Na, Zn, Ni, Co, Fe, Ca, Mg, Cu, and Ga; The hydrated metal salt includes one or more mixtures of nitrates, chlorides, and sulfates; The multifunctional functional groups include one or more of amino, hydroxyl, sulfonic acid group, mercapto, and methyl; The organic compounds include 2-methylimidazole, 2-aminoterephthalic acid, mercaptoterephthalic acid, 2-hydroxyterephthalic acid, and 2-sulfoterephthalic acid.

5. The preparation method according to claim 3, characterized in that, In step (1), the molar ratio of the hydrated metal salt to the organic compound containing multifunctional functional groups is (1-5):(6-20); the aging time is 0.5-12 hours.

6. The preparation method according to claim 3, wherein, In step (2), the inert non-reactive gas of the inert gas includes nitrogen and argon; The heat treatment is instantaneous arc heating or slow heating.

7. The preparation method according to claim 6, wherein, The temperature of the instantaneous arc is controlled to be maintained at 900-1500 °C for 5-25 seconds; the heating rate of the slow heating is 1-20 °C / min, and it is maintained at 700-1200 °C for 0.5-15 h.

8. The preparation method according to claim 3, characterized in that, In step (3), the mass ratio of the carbon-supported metal composite material to the sulfur powder is (0.5-1):(0.5-5); The fusion temperature is 100-400 °C, the time is 10-20 h, and the heating rate is 5-10 °C / min.

9. A positive electrode sheet, characterized in that, It includes the positive electrode material of the high-performance room-temperature sodium-sulfur battery described in claim 1 or 2.

10. A battery, characterized in that, It includes the positive electrode plate described in claim 9.

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