Preparation method of sulfur-selenium composite all-solid-state positive electrode and all-solid-state lithium-sulfur battery
By combining nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalysts with selenium sulfide, an all-solid-state lithium-sulfur battery cathode was constructed, solving the problem of poor conductivity of sulfur cathodes and realizing an all-solid-state lithium-sulfur battery with high rate performance and long cycle life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-09
AI Technical Summary
In all-solid-state lithium-sulfur batteries, the sulfur cathode has poor electronic and ionic conductivity, resulting in slow reaction kinetics, low capacity utilization, and poor cycle stability, especially at high rates, which limits its commercialization.
A nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst was combined with selenium sulfide and a hydrothermal reaction and three-dimensional ball milling to construct an asymmetric single-atom catalytic system, thereby improving the reaction kinetics and interfacial charge transfer characteristics of the sulfur-selenium cathode.
It significantly improves the capacity release and cycle stability of all-solid-state lithium-sulfur batteries at high rates, achieving high capacity and long cycle life, and expanding its applicability in practical application scenarios.
Smart Images
Figure CN122177835A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of sulfur-selenium composite cathode materials, specifically relating to a method for preparing a carbon-based asymmetric single-atom sulfur-selenium composite all-solid-state cathode material and an all-solid-state lithium-sulfur battery. Background Technology
[0002] All-solid-state lithium-sulfur batteries, employing both metallic lithium anode and sulfur-based cathode materials, exhibit high theoretical specific capacity and theoretical energy density, with a theoretical energy density reaching 2600 Wh·kg⁻¹. -1 However, in all-solid-state systems, sulfur itself possesses extremely low electronic and ionic conductivity, resulting in slow electrochemical reaction kinetics in solid-state electrodes. This severely limits the rate performance and cycle stability of all-solid-state lithium-sulfur batteries. Especially under high-rate charge-discharge conditions, the sulfur cathode struggles to achieve sufficient reaction, leading to low capacity utilization and becoming one of the key factors restricting the further development of all-solid-state lithium-sulfur batteries.
[0003] To improve the conductivity of sulfur cathode materials, researchers proposed introducing selenium to construct sulfur-selenium composite cathode materials. Compared to sulfur, selenium exhibits higher electronic conductivity, with a room temperature conductivity of approximately 10⁻⁶. -3 S·m -1 Sulfur has an electrical conductivity of only about 10. -28 S·m -1 Therefore, sulfur-selenium cathodes, composed of sulfur and selenium, are considered a type of cathode material that can balance high specific capacity and good conductivity, and are widely used in the research of all-solid-state lithium-sulfur batteries. Although all-solid-state sulfur-selenium cathodes improve electronic conductivity to some extent, existing all-solid-state sulfur-selenium batteries still exhibit significant electrochemical polarization at high charge-discharge rates, making it difficult to achieve high capacity output at high rates. The fundamental reason for this is the slow kinetics of the sulfur reduction reaction, which greatly limits the commercialization of all-solid-state sulfur-selenium batteries. Furthermore, in solid-state systems, the conversion reaction of sulfur-selenium compounds is often incomplete, resulting in the slow formation of lithium sulfide and lithium selenide. Reaction intermediates tend to accumulate at the cathode interface, further hindering subsequent reactions and severely affecting the cycle performance of the battery. Therefore, effectively reducing the reaction energy barrier of sulfur-selenium cathode materials in all-solid-state systems and accelerating the sulfur reduction reaction kinetics are urgent technical problems to be solved to improve the overall performance of all-solid-state sulfur-selenium batteries.
[0004] Single-atom catalysts, which anchor transition metals in an atomically dispersed form on a specific support and modulate their coordination environment and valence state, are considered an effective technique for enhancing electrochemical reaction activity. Existing techniques have shown that disrupting the electronic symmetry of single-atom catalysts and constructing asymmetric coordination structures can significantly enhance the adsorption and activation capacity of active centers for reaction intermediates, thereby improving catalytic performance. However, these materials are primarily used as sulfur-based host materials in liquid lithium-sulfur batteries, mainly participating in the catalysis of soluble lithium polysulfides (Li₂S₂). n (n=4–8), while the reaction intermediates of the all-solid-state sulfur-selenium cathode system are only solid-phase Li₂S₂ and Li₂Se₂, which have electronic structures different from soluble lithium polysulfides. Therefore, the design and application of asymmetric single-atom catalysts in the all-solid-state sulfur-selenium cathode system in the realization of solid-state sulfur-selenium composite cathodes are still limited, and there is still a lack of technical solutions that can effectively promote the deep conversion of sulfur selenides in the all-solid-state system, accelerate reaction kinetics, and improve battery rate performance and cycle stability. Summary of the Invention
[0005] To address the problems existing in the background technology, the present invention aims to provide a method for preparing a sulfur-selenium composite all-solid-state cathode and an all-solid-state lithium-sulfur battery. This preparation method involves preparing a nitrogen- and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite all-solid-state cathode material and constructing a sulfur-doped asymmetric single-atom catalytic system. This fundamentally improves the reaction kinetics and interfacial charge transfer characteristics of the all-solid-state selenium sulfide cathode, achieving a synergistic improvement in high rate capability, high capacity, and long cycle life while ensuring battery safety. This effectively solves the problems of slow conversion reaction, insufficient capacity release, and poor cycle stability in all-solid-state lithium-sulfur batteries at high rate performance.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows:
[0007] A method for preparing a sulfur-selenium composite all-solid-state cathode includes the following steps:
[0008] Step 1: Prepare nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalysts;
[0009] Step 2: Prepare selenium sulfide powder;
[0010] Step 3: Mix selenium sulfide powder with conductive additives, and then carry out a hydrothermal reaction at a temperature of 155-300℃ for 8-12 hours to prepare selenium sulfide-conductive additive composite powder.
[0011] Step 4: Mix the nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst, selenium sulfide-conductive additive composite powder, and sulfide electrolyte, and then perform multiple three-dimensional oscillating ball milling processes to obtain the desired sulfur-selenium composite all-solid-state cathode material.
[0012] Furthermore, the specific process of step 1 is as follows:
[0013] Step 1.1. Weigh melamine, L-cysteine and metal hydrate and grind them in a mortar to form a uniform precursor powder A;
[0014] Step 1.2. Add precursor powder A to the mixed solution of ethanol and hydrochloric acid to obtain a slurry. Continue grinding the slurry until the ethanol is completely evaporated to form precursor slurry B.
[0015] Step 1.3. Place the precursor slurry B in an oven to dry, and then ball mill it again to obtain the precursor powder C;
[0016] Step 1.4. The precursor powder C is subjected to a two-stage pyrolysis carbonization treatment in an argon atmosphere. After cooling, a nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst is obtained.
[0017] Further, in step 1.1, the mass ratio of melamine, L-cysteine and metal hydrate is 2:1:(1~5).
[0018] The metal hydrate is any one of nickel nitrate hydrate, cobalt nitrate hydrate, iron nitrate hydrate, manganese nitrate hydrate, copper nitrate hydrate, and tungstate hydrate.
[0019] Furthermore, in the mixed solution of step 1.2, the volume ratio of ethanol to hydrochloric acid is (3~5):1; the mass ratio of the mixed solution to precursor powder A should be greater than 1:1.2.
[0020] Furthermore, in step 1.4, the specific process of the two-stage pyrolysis carbonization treatment is as follows:
[0021] The first stage involves raising the temperature from 25℃ to 450-600℃ and holding it for 120-150 minutes; the second stage involves further raising the temperature to 800-1000℃ and holding it for 120-150 minutes, with the overall heating rate set at 2-5℃ / minute.
[0022] Furthermore, in step 2, selenium sulfide is generated by mixing sulfur powder and selenium powder and then sintering at high temperature under vacuum. The sintering temperature is 400~600℃, the heating rate is 2~5℃ / min, and the sintering time is not less than 24 h. The mass ratio of sulfur powder to selenium powder should be greater than 1.
[0023] Furthermore, the mass ratio of selenium sulfide to conductive additive is 1:(0.5~1.5); the mass fraction of nitrogen- and sulfur-doped carbon-based single-atom catalyst in the positive electrode mixed powder is no more than 10%; the mass ratio of the mixed powder of selenium sulfide and conductive additive to sulfide electrolyte is (1~3):1.
[0024] Furthermore, the conductive additive is conductive carbon black, carbon nanotubes, graphene, or vapor-grown carbon fibers; the sulfide electrolyte is Li 10 Sn2PS 12 Li3PS4, Li7P3S 11 Li 10 GeP2S 12 Or Li6PS5Cl.
[0025] Furthermore, in the three-dimensional oscillating ball mill, after each ball milling rest period, the ball milling direction is changed, switching between forward and reverse rotation to ensure uniform mixing and prevent powder agglomeration and wall adhesion caused by always milling in the same direction; the ball milling speed is 550 rpm each time, the ball milling time is 10~15 min, and the resting time is 10~20 min after each ball milling to prevent the ball milling from causing the temperature to be too high and the powder to stick to the inside of the ball mill jar wall;
[0026] Furthermore, the volume of the zirconia ball mill jar is 50~100ml, and the zirconia ball milling beads consist of at least three types of ball milling beads with diameters ranging from large to small, and the number of them decreases as the diameter of the ball milling beads increases. The total volume of the ball milling beads does not exceed two-thirds of the volume of the ball mill jar, and the volume of the mixed powder does not exceed one-half of the total volume of the ball milling beads. Ball milling will affect the size of the selenium sulfide cathode particles, as well as the contact between the three-phase interface of the selenium sulfide cathode, the solid electrolyte, and the conductive additives.
[0027] An all-solid-state lithium-sulfur battery is assembled from a sulfur-selenium composite all-solid-state cathode, a sulfide solid electrolyte, and a lithium-indium alloy anode; wherein the sulfide solid electrolyte used in the sulfur-selenium composite all-solid-state cathode is the same material.
[0028] The mechanism of this invention is as follows:
[0029] This invention synthesizes an asymmetric single-atom Ni-N3-S catalyst. This catalyst, leveraging the low electronegativity of sulfur, breaks the local electronic symmetry of the Ni-N4 symmetric single-atom catalyst, shifting the d-band center of the Ni-N3-S catalyst towards the Fermi level. When the Ni-N3-S catalyst adsorbs intermediate products (Li2S2, Li2Se2), the Ni center reaches a 3dz... 2 Strong dp hybridization occurs between the orbitals and the S 3p and Se 4p orbitals, thereby accelerating the charge transfer in the reduction reaction, effectively reducing the reaction energy barrier of the reduction reaction, enhancing the adsorption of the catalyst and the intermediate products of the selenium sulfide reduction reaction, and further reducing the polarization of the battery during the charging and discharging process.
[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:
[0031] (1) The nitrogen and sulfur doped carbon-based asymmetric single-atom catalyst prepared in this invention can effectively promote the deep conversion of selenium sulfide from intermediate product to final discharge product lithium sulfide and lithium selenide in a solid-state environment, reduce the accumulation of reaction intermediates, avoid polarization aggravation and capacity decay caused by incomplete conversion, and thus significantly improve the utilization rate of positive electrode active material.
[0032] (2) This invention employs a three-dimensional oscillating ball milling method, rationally selecting the size and ratio of the milling beads, as well as the milling speed and interval time. Furthermore, by using a forward and reverse rotation alternating method, nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalysts are successfully and uniformly dispersed in the all-solid-state selenium sulfide cathode composite material. This allows more of the active sites of the single-atom catalyst to be exposed at the three-phase interface under solid-phase catalytic conditions, constructing a highly efficient catalytic reaction interface. This facilitates the formation of a stable and efficient multiphase contact network between electrons, lithium ions, and active materials, thereby simultaneously improving electron transport capacity and lithium ion diffusion rate, and enhancing the rate performance and cycle stability of the all-solid-state lithium-sulfur battery. The prepared all-solid-state lithium-sulfur battery achieves 649 mAh / g at 1C rate and retains 76.6% of its capacity after 600 cycles at 2C rate.
[0033] (3) The technical solution proposed in this invention can maintain stable capacity output and low capacity decay rate under harsh conditions such as high current density, high active material loading and high operating temperature, which significantly expands the application scope of all solid-state lithium-sulfur batteries in practical application scenarios and improves the reliability and service life of the battery system.
[0034] (4) The nitrogen and sulfur doped carbon-based asymmetric single-atom catalyst used in this invention has a relatively simple preparation process, the raw materials are widely available, it does not rely on complex or expensive preparation equipment, and it is easy to achieve large-scale preparation. At the same time, the catalyst is compatible with the existing all-solid-state lithium-sulfur battery cathode preparation process, and there is no need to make significant adjustments to the existing battery manufacturing process, which has good engineering application prospects. Attached Figure Description
[0035] Figure 1 This is a dark-field image of a carbon-based asymmetric single atom doped with nitrogen and sulfur in Example 1 of the present invention, obtained by spherical aberration electron microscopy.
[0036] Figure 2 This is a transmission electron microscope (TEM) image of nitrogen- and sulfur-doped carbon-based asymmetric single atoms in Example 1 of the present invention.
[0037] Figure 3 The image shows a scanning electron microscope image of the carbon-based asymmetric single-atom sulfur-selenium composite cathode obtained in Example 1.
[0038] Figure 4 The image shows a scanning electron microscope image of the sulfur-selenium composite cathode obtained in Comparative Example 3.
[0039] Figure 5 The adsorption energies of the nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst in Example 1 and the selenium sulfide discharge intermediates Li2S2 and Li2Se2 in Comparative Example 1 without the addition of an asymmetric single-atom catalyst were calculated.
[0040] Figure 6 The activation energy barrier of selenium sulfide reduction reaction in Example 1 was calculated under the action of nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst and in Comparative Example 1 without the addition of asymmetric single-atom catalyst.
[0041] Figure 7 Cyclic voltammetry curves of an all-solid-state lithium-sulfur battery based on nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst from Example 1 and a comparative example of an all-solid-state lithium-sulfur battery without asymmetric single-atom catalyst from Example 1.
[0042] Figure 8 The rate performance of an all-solid-state lithium-sulfur battery based on the nitrogen and sulfur doped carbon-based asymmetric single-atom sulfur-selenium composite material of Example 1 and the composite cathode material without asymmetric single atoms of Comparative Example 1 is compared.
[0043] Figure 9 The high-load charge-discharge curves of all-solid-state lithium-sulfur batteries based on the nitrogen and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite material of Example 1 and the composite cathode material without asymmetric single atoms of Comparative Example 1 are shown.
[0044] Figure 10 This is a cycle performance curve of the all-solid-state lithium-sulfur battery using nitrogen- and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite material as the positive electrode in Example 1 of the present invention. Detailed Implementation
[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.
[0046] Example 1
[0047] A method for preparing a nitrogen- and sulfur-doped carbon-based asymmetric single-atom-sulfur-selenium composite all-solid-state cathode includes the following steps:
[0048] Step 1: Weigh melamine, L-cysteine, and nickel nitrate hexahydrate in a mass ratio of 2:1:3 and grind them in a zirconium oxide mortar for 120 minutes to form a uniform precursor powder A;
[0049] Step 2: Add a mixed solution of ethanol and hydrochloric acid (volume ratio 5:1) that can submerge the mixed powder A, and continue grinding the slurry until the ethanol is completely evaporated to obtain precursor slurry B;
[0050] Step 3: Dry the precursor slurry B in an 80℃ oven, and then ball mill it again for 20 minutes to obtain the precursor powder C;
[0051] Step 4: The precursor powder C is subjected to a two-stage pyrolysis carbonization treatment in an argon atmosphere (first stage: heating from 25℃ to 550℃ and holding for 120 minutes; second stage: continuing to heat to 900℃ and holding for 120 minutes). The heating rate is set to 2℃ / minute throughout the process to obtain nitrogen and sulfur doped carbon-based asymmetric single atoms.
[0052] Step 5: Weigh sulfur powder and selenium powder in a molar ratio of 2:1, grind them in an agate mortar for 30 minutes, seal them in a glass tube, and calcine them in a tube furnace at 450°C for 24 hours in a vacuum atmosphere. The heating rate is set to 5°C / minute throughout the process to obtain selenium sulfide powder D.
[0053] Step 6: Grind selenium sulfide powder D and vapor-grown carbon fiber in an agate mortar for 30 minutes at a mass ratio of 3:4, pour into a hydrothermal reactor, and sinter in a high-temperature oven at 155°C for 12 hours to prepare selenium sulfide-conductive additive composite powder.
[0054] Step 7: Mix the selenium sulfide-conductive additive composite powder with Li6PS5Cl solid electrolyte and nitrogen and sulfur doped carbon-based asymmetric single atoms at a mass ratio of 2:1:0.05. Use a vibrating ball mill to ball mill at a speed of 550 rpm. After every 15 minutes of ball milling, let it stand for 10 minutes. When restarting, change the direction of ball milling (forward or reverse). The standing time is negligible. Ball mill for 10 hours. Finally, nitrogen and sulfur doped carbon-based asymmetric single atom-sulfur selenium composite all-solid-state cathode material is obtained.
[0055] Example 2
[0056] The sulfur-selenium composite all-solid-state cathode was prepared according to the steps of Example 1, except that the mass ratio of selenium sulfide to vapor-grown carbon fiber in step 6 was adjusted to 1:1, while the other steps remained unchanged.
[0057] Example 3
[0058] The sulfur-selenium composite all-solid-state cathode was prepared according to the steps in Example 1, except that the carbon fibers grown in the vapor phase in step 6 were changed to carbon nanotubes, while the other steps remained unchanged.
[0059] Comparative Example 1
[0060] The sulfur-selenium composite all-solid-state cathode was prepared according to the steps in Example 1. In step 7, no nitrogen or sulfur-doped carbon-based asymmetric single atoms were added, and the remaining steps remained unchanged.
[0061] Comparative Example 2
[0062] The sulfur-selenium composite all-solid-state cathode was prepared according to the steps in Example 1, except that L-cysteine in step 1 was replaced with L-alanine, while the other steps remained unchanged.
[0063] The comparative example yielded a Ni-N4 symmetric single-atom catalyst.
[0064] Comparative Example 3
[0065] The sulfur-selenium composite all-solid-state cathode was prepared according to the steps in Example 1, except that the oscillating ball mill in step 7 was changed to a planetary ball mill, while the other steps remained unchanged.
[0066] All the sulfur-selenium composite solid-state cathodes, sulfide solid electrolytes, and lithium-indium alloy anodes prepared in all the examples and comparative examples were assembled to obtain a solid-state lithium-sulfur battery; wherein the sulfide solid electrolyte and the sulfide solid electrolyte used in the synthesized nitrogen- and sulfur-doped carbon-based single-atom-sulfur-selenium composite solid-state cathode are the same material.
[0067] Performance testing:
[0068] Morphological characterization: The morphology of the nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst prepared in Example 1 was observed. Its dark-field electron microscopy (DEM) and transmission electron microscopy (TEM) images are shown below. Figure 1 and Figure 2 As shown, from Figure 1 It can be seen that the dots within the circles are nickel atoms, and the isolated bright spots dispersed on the support in the image are relatively uniform, with no obvious clustering characteristics observed. This indicates that nickel has not aggregated, suggesting that nickel is anchored on the catalyst support surface in a highly dispersed single-atom form. Figure 2 It can be seen that the nitrogen and sulfur-doped carbon-based asymmetric single-atom catalysts are mainly composed of folded and rolled sheet structures. The sheets interweave and stack with each other to form loose flocculent aggregates with a size at the nanoscale.
[0069] Characterization of nitrogen- and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite cathodes as follows: Figure 3 It can be seen that selenium sulfide and solid electrolyte particles are uniformly distributed on the surface of conductive fibers, and no obvious agglomeration is formed between the particles. Instead, they are connected together by conductive fibers, and the phases of the positive electrode are uniformly mixed. Selenium sulfide, conductive additives, and solid electrolyte form a good three-phase interface. The morphology of the sulfur-selenium composite positive electrode obtained by planetary ball milling in Comparative Example 3 is as follows: Figure 4 As shown, selenium sulfide particles are clearly agglomerated and encapsulate the conductive fibers, resulting in no effective connection between the conductive fibers. Therefore, the three-phase interface formed cannot achieve efficient transport of ions and electrons.
[0070] Theoretical calculations: Density functional theory was used to investigate the interaction mechanism of nitrogen- and sulfur-doped carbon-based asymmetric single atoms with the sulfur-selenium composite cathode. Calculations revealed that, compared to ordinary carbon materials, nitrogen- and sulfur-doped carbon-based asymmetric single atoms exhibit stronger adsorption energies for the intermediate products Li₂S₂ and Li₂Se₂ from the reduction reaction of selenium sulfide. Figure 5 As shown, the increase in adsorption energy leads to faster charge transfer and a lower conversion reaction energy barrier (1.19 eV). The calculation shows the reduction in the reaction energy barrier as follows. Figure 6 As shown, this invention can effectively promote the transformation of Li2S2+Li2Se2 to Li2S and Li2Se in the solid-phase reduction reaction of the sulfur-selenium composite cathode.
[0071] Electrochemical testing: Cyclic voltammetry curves of the all-solid-state lithium-sulfur batteries in Example 1 and Comparative Example 1 are shown below. Figure 7 The peak current density of the nitrogen- and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite cathode was significantly improved at different scan rates; in particular, at a scan rate of 0.5 mV / s, the peak discharge current density increased from 1.01 mA·cm⁻¹. -2 Increased to 1.41 mA·cm -2 This demonstrates that the electrode reaction rate of the battery is improved.
[0072] The rate performance of the all-solid-state lithium-sulfur batteries prepared in Example 1 and Comparative Example 1 is shown in [reference]. Figure 8 Nitrogen and sulfur doped carbon-based asymmetric single atoms effectively improved the battery's capacity release at different rates from 0.1 to 1C. Specifically, the battery capacity increased from 788.7 mAh / g to 1212.8 mAh / g at 0.1C, from 742 mAh / g to 1205 mAh / g at 0.2C, from 642 mAh / g to 902 mAh / g at 0.5C, and from 543 mAh / g to 649 mAh / g at 1C.
[0073] Figure 9 The charge-discharge curves of Example 1 and Comparative Example 1 under high positive electrode load are shown. As can be seen from the figure, the specific capacity of the all-solid-state lithium-sulfur battery obtained in Comparative Example 1 is 565 mAh / g, while the specific capacity of the all-solid-state lithium-sulfur battery obtained in Example 1 is 1053 mAh / g. It can be seen that the all-solid-state lithium-sulfur battery with nitrogen and sulfur doped carbon-based asymmetric single-atom catalyst has a significantly increased capacity release under high load.
[0074] Figure 10This is a cycle performance curve of the all-solid-state lithium-sulfur battery using a nitrogen- and sulfur-doped carbon-based asymmetric single-atom sulfur-selenium composite material as the positive electrode in Example 1 of this invention. As can be seen from the figure, the battery obtained in Example 1 can stably cycle for more than 600 times at a high rate of 2C, which demonstrates the excellent cycle performance and practicality of the positive electrode material and the all-solid-state lithium-sulfur battery.
[0075] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.
Claims
1. A method for preparing a sulfur-selenium composite all-solid-state cathode, characterized in that, Includes the following steps: Step 1: Prepare nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalysts; Step 2: Prepare selenium sulfide powder; Step 3: Mix selenium sulfide powder with conductive additives, and then carry out a hydrothermal reaction at a temperature of 155-300℃ for 8-12 hours to prepare selenium sulfide-conductive additive composite powder. Step 4: Mix the nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst, selenium sulfide-conductive additive composite powder, and sulfide electrolyte, and then perform multiple three-dimensional oscillating ball milling processes to obtain the desired sulfur-selenium composite all-solid-state cathode material.
2. The preparation method according to claim 1, characterized in that, The specific process of step 1 is as follows: Step 1.
1. Weigh melamine, L-cysteine and metal hydrate and grind them in a mortar to form a uniform precursor powder A; Step 1.
2. Add precursor powder A to the mixed solution of ethanol and hydrochloric acid to obtain a slurry. Continue grinding the slurry until the ethanol is completely evaporated to form precursor slurry B. Step 1.
3. Place the precursor slurry B in an oven to dry, and then ball mill it again to obtain the precursor powder C; Step 1.
4. The precursor powder C is subjected to a two-stage pyrolysis carbonization treatment in an argon atmosphere. After cooling, a nitrogen- and sulfur-doped carbon-based asymmetric single-atom catalyst is obtained.
3. The preparation method according to claim 2, characterized in that, In step 1.1, the mass ratio of melamine, L-cysteine, and metal hydrate is 2:1:(1~5). The metal hydrate is any one of nickel nitrate hydrate, cobalt nitrate hydrate, iron nitrate hydrate, manganese nitrate hydrate, copper nitrate hydrate, and tungstate hydrate.
4. The preparation method according to claim 1, characterized in that, In the mixed solution of step 1.2, the volume ratio of ethanol to hydrochloric acid is (3~5):1; the mass ratio of the mixed solution to precursor powder A should be greater than 1:1.
2.
5. The preparation method according to claim 1, characterized in that, In step 1.4, the specific process of the two-stage pyrolysis carbonization treatment is as follows: The first stage involves raising the temperature from 25℃ to 450-600℃ and holding it for 120-150 minutes; the second stage involves further raising the temperature to 800-1000℃ and holding it for 120-150 minutes, with the overall heating rate set at 2-5℃ / minute.
6. The preparation method according to claim 1, characterized in that, In step 2, selenium sulfide is generated by mixing sulfur powder and selenium powder and sintering at high temperature under vacuum. The sintering temperature is 400~600℃, the heating rate is 2~5℃ / min, and the sintering time is not less than 24 h. The mass ratio of sulfur powder to selenium powder should be greater than 1.
7. The preparation method according to claim 1, characterized in that, In step 3, the mass ratio of selenium sulfide to conductive additive is 1:(0.5~1.5); the nitrogen- and sulfur-doped carbon-based single-atom catalyst accounts for no more than 10% of the mass fraction of the cathode mixed powder; the mass ratio of the mixed powder of selenium sulfide and conductive additive to the sulfide electrolyte is (1~3):1; the conductive additive is conductive carbon black, carbon nanotubes, graphene, or vapor-grown carbon fiber; the sulfide electrolyte is Li 10 Sn2PS 12 Li3PS4, Li7P3S 11 Li 10 GeP2S 12 Or Li6PS5Cl.
8. The preparation method according to claim 1, characterized in that, In the three-dimensional oscillating ball mill, after each ball milling rest period, the ball milling direction is changed, switching between forward and reverse rotation to ensure uniform mixing and prevent powder agglomeration and wall adhesion caused by always milling in the same direction; the ball milling speed is 550 rpm each time, the ball milling time is 10~15 min, and the resting time is 10~20 min after each ball milling.
9. The preparation method according to claim 8, characterized in that, The volume of the zirconia ball mill jar is 50~100ml. The zirconia ball milling beads consist of at least three types of ball milling beads with diameters ranging from large to small, and the number of them decreases as the diameter of the ball milling beads increases. The total volume of the ball milling beads does not exceed two-thirds of the volume of the ball mill jar, and the volume of the mixed powder does not exceed one-half of the total volume of the ball milling beads.
10. An all-solid-state lithium-sulfur battery, characterized in that, The process involves assembling a sulfur-selenium composite all-solid-state cathode, a sulfide solid electrolyte, and a lithium-indium alloy anode prepared by any one of the preparation methods of claims 1-9; wherein the sulfide solid electrolyte and the sulfur-selenium composite all-solid-state cathode use the same sulfide solid electrolyte material.