Preparation and application of lithium-sulfur battery organic-inorganic composite cathode material

Abstract

This invention belongs to the field of lithium-sulfur battery electrode material preparation, and specifically relates to the preparation and application of an organic-inorganic composite cathode material for lithium-sulfur batteries. It provides the application of compound 6,12-dihydroxyperylene-1,7-dione in the preparation of lithium-sulfur battery cathode materials, and a method for preparing an organic-inorganic composite cathode material for lithium-sulfur batteries, and studies its performance as a lithium-sulfur battery cathode material. This material exhibits excellent electrochemical performance, with a smaller potential difference, higher catalytic ability for sulfur reduction, larger overpotential, and promotes Li2S nucleation, deposition, and catalytic conversion kinetics. The discharge specific capacity is improved at different current densities; when the current density is switched back to 0.2C, the battery can still achieve 832.1 mAh g⁻¹. ‑1 It exhibits a discharge specific capacity with 88.5% capacity retention, retaining 691.2 mAh g⁻¹ after 100 cycles at 0.2C. ‑1 The reversible capacity is achieved. The organic-inorganic composite cathode material for lithium-sulfur batteries provided by this invention is simple to prepare, improves the cycle performance of lithium-sulfur batteries, and has commercial application potential.

Description

[Technical Field]

[0001] This invention belongs to the field of lithium-sulfur battery electrode material preparation, and specifically relates to the preparation and application of an organic-inorganic composite cathode material for lithium-sulfur batteries. [Background Technology]

[0002] Lithium-sulfur batteries are considered one of the most promising candidates for next-generation energy storage systems due to their high theoretical energy density and low cost. However, lithium-sulfur batteries suffer from inherent material defects, including low conductivity of sulfur and discharge products, slow reaction kinetics, shuttle effect caused by polysulfide dissolution, volume expansion during charge and discharge, and lithium anode dendrite formation. These problems further limit the commercial development of lithium-sulfur batteries. Among these, the shuttle effect caused by polysulfide dissolution is a significant factor contributing to poor cycle stability and short lifespan.

[0003] In recent years, researchers have proposed improvement strategies for different components of lithium-sulfur batteries to suppress the shuttle effect and improve cycle stability. Among these, loading transition metals and their compounds onto porous carbon as sulfur supports has shown some effectiveness in suppressing the shuttle effect through adsorption-catalysis synergy. However, further improving sulfur utilization and approaching the theoretical capacity remains extremely difficult. Organic compounds, containing one or more redox-active free radicals, undergo multi-electron reversible reactions during electrochemical processes, making them a new favorite for energy storage materials. However, due to their poor electronic conductivity and ability to dissolve instantaneously in liquid electrolytes, organic electrode materials still lack the high cycle stability and rate performance found in transition metal-based electrode materials. In recent years, the condensation of organic molecules or their salting out has achieved some effect in suppressing dissolution and improving cycle stability, but this approach undoubtedly reduces the overall energy density of the electrode.

[0004] In summary, the electrode materials for lithium-sulfur batteries still suffer from defects such as unstable conductivity and electrochemical performance in the existing technology. [Summary of the Invention]

[0005] Therefore, this invention provides an organic-inorganic composite cathode material for lithium-sulfur batteries, as well as its preparation and application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] 1. This invention provides an organic-inorganic composite cathode material for lithium-sulfur batteries. The organic-inorganic composite cathode material for lithium-sulfur batteries comprises the compound 6,12-dihydroxyperylene-1,7-dione and a cobalt-containing carbon material. The structure of 6,12-dihydroxyperylene-1,7-dione is shown in formula (I):

[0008]

[0009] 2. A method for preparing organic-inorganic composite cathode materials for lithium-sulfur batteries, comprising the following steps:

[0010] (1) Dissolve 6,12-dihydroxyperylene-1,7-dione in anhydrous ethanol to prepare a solution, disperse the cobalt-containing carbon material in the above solution, stir for 1 hour, and centrifuge to obtain the solid.

[0011] (2) The solid from step (1) and sublimed sulfur were ground in a mortar for 30 min, and then kept at 155°C for 12 h under an argon atmosphere to obtain an organic-inorganic hybrid lithium-sulfur battery cathode material.

[0012] 3. In step (2), the mass ratio of the solid in step (1) to sublimed sulfur is 1 to 2:1, preferably 1:1.5.

[0013] 4. Application of compound 6,12-dihydroxyperylene-1,7-dione in the preparation of cathode materials for lithium-sulfur batteries.

[0014] Advantages of this invention:

[0015] The organic-inorganic composite cathode material for lithium-sulfur batteries, prepared from 6,12-dihydroxyperylene-1,7-dione, exhibits excellent electrochemical performance, with a smaller potential difference, higher catalytic activity for sulfur reduction, larger overpotential, and a promoting effect on Li₂S nucleation, deposition, and catalytic conversion kinetics. The discharge specific capacity increases under different current densities; when the current density is switched back to 0.2C, the battery can still achieve a specific capacity of 832.1 mAh g⁻¹. -1 It exhibits a discharge specific capacity with 88.5% capacity retention, retaining 691.2 mAh g⁻¹ after 100 cycles at 0.2C. -1 The reversible capacity is achieved. The organic-inorganic composite cathode material for lithium-sulfur batteries provided by this invention is simple to prepare, improves the cycle performance of lithium-sulfur batteries, and has commercial application potential. [Attached Image Description]

[0016] Figure 1 These are charge-discharge curves of lithium-sulfur batteries made with electrode materials from Example 1 and Comparative Example 1.

[0017] Figure 2 The graph shows the rate performance of lithium-sulfur batteries made with the electrode materials of Example 1 and Comparative Example 1.

[0018] Figure 3 The graph shows the cycle performance of lithium-sulfur batteries made with the electrode materials of Example 1 and Comparative Example 1.

Detailed Implementation Methods

[0019] To better understand the present invention, specific embodiments are described below. These embodiments are only for explaining the present invention and do not constitute any limitation on the present invention.

[0020]

Example 1

[0021] DPD powder was dissolved in anhydrous ethanol to prepare a 0.1 mM DPD solution. Cobalt-containing carbon substrate (Co-NC) was dispersed in the DPD solution, stirred for 1 h, and the solid was collected by centrifugation. This solid was the DPD-loaded cobalt-containing carbon material (DPD / Co-NC).

[0022] DPD / Co-NC and sublimed sulfur were ground in a mortar at a mass ratio of 2:3 for 30 min, and then kept at 155℃ for 12 h under an argon atmosphere to obtain an organic-inorganic hybrid lithium-sulfur battery cathode material (S@DPD / Co-NC).

[0023] S@DPD / Co-NC (20wt%) and binder PVDF (10wt%) were mixed and ground, dissolved in NMP, and then coated onto aluminum foil current collectors. The mixture was then dried in a vacuum oven at 60°C for 12 hours to remove the solvent, thus obtaining the positive electrode for lithium-sulfur batteries.

[0024] Ethylene glycol dimethyl ether and 1,3-dioxapentane were mixed in a 1:1 ratio and then dehydrated. Under a helium atmosphere at room temperature, lithium bis(trifluoromethanesulfonyl)imide and lithium nitrate were weighed at ratios of 1 mol / L and 0.1 mol / L, respectively, and dissolved in the above solvent. The mixture was stirred until homogeneous to obtain the electrolyte.

[0025] Using Celgard-2400 as the separator and lithium metal as the anode, button cells were assembled in an argon-filled glove box using a stainless steel battery case type 2032 for battery testing.

[0026] Comparative Example 1

[0027] Co-NC and sublimed sulfur were ground in a mortar at a mass ratio of 2:3 for 30 min, and then kept at 155 °C for 12 h under an argon atmosphere to obtain a comparative material (S@Co-NC) without DPD loading.

[0028] S@Co-NC (20wt%) and binder PVDF (10wt%) were mixed and ground, dissolved in NMP, and then coated onto aluminum foil current collectors. The mixture was then dried in a vacuum oven at 60°C for 12 hours to remove the solvent, thus obtaining the positive electrode for lithium-sulfur batteries.

[0029] Ethylene glycol dimethyl ether and 1,3-dioxapentane were mixed in a 1:1 ratio and then dehydrated. Under a helium atmosphere at room temperature, lithium bis(trifluoromethanesulfonyl)imide and lithium nitrate were weighed at ratios of 1 mol / L and 0.1 mol / L, respectively, and dissolved in the above solvent. The mixture was stirred until homogeneous to obtain the electrolyte.

[0030] Button cells were assembled using Celgard-2400 as the separator and lithium metal as the anode in an argon-filled glove box using a 2032 stainless steel battery casing. Battery testing was conducted using cells assembled without added DPD (Dielectric Power Distribution Device) cathode material.

[0031] from Figure 1 It can be seen that, at a current density of 0.1C, the S@DPD / Co-NC exhibits a smaller potential difference (172mV), indicating a higher catalytic activity for sulfur reduction. The larger overpotential of S@DPD / Co-NC suggests a greater amount of Li2S deposition during discharge, indicating that DPD / Co-NC promotes Li2S nucleation, deposition, and catalytic conversion kinetics. Figure 2 It can be seen that the discharge specific capacity of the S@DPD / Co-NC electrode increases under different current densities. When the current density is switched back to 0.2C, the battery can still reach 832.1 mAh g⁻¹. -1 The discharge specific capacity has a capacity retention rate of 88.5%. From Figure 3 It can be seen that the S@DPD / Co-NC composite material exhibits excellent electrochemical performance during lithium-sulfur battery cycling. After 100 cycles at 0.2C, the S@DPD / Co-NC composite still retains 691.2 mAh g⁻¹. -1 The reversible capacity of covalent and chemical sulfur fixation shows a significant effect compared to metal-based materials that only use chemical sulfur fixation.

Claims

The application of 1,6,12-dihydroxyperylene-1,7-dione in the preparation of an organic-inorganic composite cathode for lithium-sulfur batteries, characterized in that, The positive electrode comprises the organic compound 6,12-dihydroxyperylene-1,7-dione and the inorganic cobalt-containing carbon material Co-NC. The structure of the 6,12-dihydroxyperylene-1,7-dione is shown in formula (I). Formula (1).

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