High-performance lithium-sulfur battery and preparation method thereof
By modifying the separator with fluorine-doped CoSe2 nanoflower material, the problems of polysulfide shuttle effect and slow reaction kinetics were solved, and high-capacity and long-cycle-life lithium-sulfur battery performance was achieved.
Patent Information
- Application Number
- CN202511463227.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-13
AI Technical Summary
The problems of polysulfide shuttle effect, slow reaction kinetics and short cycle life during the charging and discharging process of lithium-sulfur batteries, especially the weak physical barrier ability of traditional separators against polysulfides and the poor conductivity and limited specific surface area of CoSe2 materials.
The membrane is modified with fluorine-doped CoSe2 nanoflower material. Through its high specific surface area and excellent electrolyte wettability, it serves as a physical barrier and catalytic platform, enhancing the adsorption and catalytic conversion of polysulfides and improving the ion transport efficiency and chemical activity of the battery.
This technology achieves high capacity and long cycle life in lithium-sulfur batteries, suppresses the shuttle effect of polysulfides, and improves the charge-discharge performance and cycle stability of the batteries.
Smart Images
Figure CN121331967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing lithium-sulfur batteries, and more particularly to a high-performance lithium-sulfur battery and its preparation method. Background Technology
[0002] Lithium-sulfur batteries (Li-S) are one of the most promising next-generation high-energy-density energy storage systems, with a theoretical specific energy of up to 2600 Wh kg. -1 Its efficiency is far higher than that of currently commercialized lithium-ion batteries. However, the commercialization of lithium-sulfur batteries has long been limited by inherent scientific problems and technological challenges. Among them, the most critical bottleneck lies in the soluble long-chain polysulfides (Li2S) generated during charging and discharging. n The "shuttle effect" between the positive and negative electrodes (4≤n≤8) leads to irreversible loss of active material, rapid capacity decay, and reduced coulombic efficiency. Simultaneously, the intrinsic insulating properties of sulfur and its discharge products, such as Li₂S₂ / Li₂S, and the slow kinetics of polysulfide conversion reactions result in high polarization overpotentials and low sulfur utilization, severely limiting the rate performance and cycle life of batteries. To suppress the shuttle effect, researchers are dedicated to developing novel membrane modification materials that aim to physically block polysulfides while chemically anchoring and catalyzing their conversion. In recent years, polar materials such as transition metal selenides (CoSe₂) have been widely explored due to their strong adsorption of polysulfides and certain catalytic activity. However, intrinsic CoSe₂ materials still suffer from poor conductivity, limited specific surface area, and insufficient exposure of active sites, resulting in significant room for improvement in their polysulfide binding capacity and catalytic conversion efficiency. Therefore, developing a multifunctional membrane modification material that combines a highly conductive network, abundant active interfaces, and efficient catalytic sites is of great significance for simultaneously solving the shuttle effect and slow kinetic problems of lithium-sulfur batteries and promoting their industrialization. Summary of the Invention
[0003] This application provides a method for preparing a high-performance lithium-sulfur battery, which solves the core problems of rapid capacity decay and short cycle life in existing lithium-sulfur batteries, and achieves the technical effects of high capacity and long cycle life in lithium-sulfur batteries.
[0004] This application provides a method for preparing a high-performance lithium-sulfur battery, characterized by the following steps:
[0005] Preparation of S01 positive electrode sheet: Sulfur / carbon composite positive electrode material, conductive agent and binder are mixed in a mass ratio of 8:1:1, solvent is added and ground to form a uniform slurry, which is then coated on aluminum foil current collector, dried, pressed and punched into positive electrode sheets of the required size.
[0006] Modification of SO2 membrane: The prepared F-CoSe2 nanoflower material, conductive agent and binder are mixed in a mass ratio of (7~8):(1~2):1, solvent is added and the mixture is ground to form a uniform slurry. Then, it is uniformly coated on the surface of a commercial polypropylene PP membrane by a scraping method. After drying, F-CoSe2@PP modified membrane is obtained.
[0007] S03 Assembly of high-performance lithium-sulfur battery: In an inert atmosphere glove box, using a lithium metal sheet as the negative electrode, the positive electrode sheet prepared in step S01 as the positive electrode, and the F-CoSe2@PP modified separator prepared in step S02 as the separator, the battery is assembled into a button cell or pouch cell according to conventional processes, and an appropriate amount of ether electrolyte containing lithium salt is injected. After standing, the high-performance lithium-sulfur battery can be obtained.
[0008] The F-CoSe2 nanoflower material is prepared by a method comprising the following steps:
[0009] ① First, prepare C / Co / CoO composite material, then load selenium powder and the C / Co / CoO composite material into a ceramic boat at a mass ratio of 4~6:1, and place them in the downstream and upstream of a tube furnace respectively. After high-temperature calcination in an argon-hydrogen mixture for 5~7 hours, obtain CoSe2 / C material.
[0010] ② The prepared CoSe2 / C material and ammonium fluoride were placed downstream and upstream of a ceramic boat at a mass ratio of 2~4:1. Under an argon atmosphere, the temperature was increased to 170-210℃ at a heating rate of 1-3℃ / min, held for 1-3 hours, and then naturally cooled to obtain F-CoSe2 nanoflower material.
[0011] Preferably, in step S01, the mass percentage of sulfur in the sulfur / carbon composite cathode material is 60% to 80%.
[0012] Preferably, in step S02, the areal density of the F-CoSe2 nanoflower material coating on the diaphragm is 0.2~1.0 mg cm⁻¹. -2 .
[0013] Preferably, in step ② of the preparation method of the F-CoSe2 nanoflower material, the mass ratio of CoSe2 / C material to ammonium fluoride is 3:1.
[0014] Preferably, in step ② of the method for preparing the F-CoSe2 nanoflower material, the heating rate is 2℃ / min.
[0015] Preferably, in step S02, the conductive agent is Super P and the binder is polyvinylidene fluoride.
[0016] This invention also provides a high-performance lithium-sulfur battery, which is prepared by any of the above-described preparation methods.
[0017] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:
[0018] 1. The embodiments of the present invention effectively solve the problems of low ion / electron transport efficiency and poor interface wettability in batteries by utilizing the carbon composite conductive network of F-CoSe2@PP separator and its excellent electrolyte wettability, thereby achieving uniform deposition and rapid transport of lithium ions, suppressing the growth of lithium dendrites, and improving the utilization rate of active materials and high-rate charge and discharge performance.
[0019] 2. In this embodiment of the invention, the membrane is modified with F-CoSe2 nanoflower material. The unique flower-like structure of F-CoSe2 nanoflower material provides a high specific surface area and abundant pores, which effectively solves the problem of weak physical barrier ability of traditional membranes against polysulfides. This achieves efficient physical confinement and adsorption of polysulfides and significantly alleviates the shuttle effect.
[0020] 3. The F-CoSe2 nanoflower material of this invention effectively solves the problem of the need to improve the intrinsic catalytic activity of CoSe2 by introducing fluorine atoms to dope CoSe2. F doping optimizes the electronic structure of Co material, increases the positive charge of Co sites, and thus achieves stronger chemical adsorption of polysulfide anions and faster liquid-to-solid phase conversion reaction kinetics, while reducing reaction polarization. Attached Figure Description
[0021] Figure 1 (ab) are potentiostatic intermittent titration (GITT) diagrams of batteries modified with F-CoSe2@PP membrane and batteries modified with CoSe2@PP membrane; Figure 1 (c) Potential difference at the nucleation and activation points of Li2S in different cells.
[0022] Figure 2 (a) Battery cycle performance test at 0.2 C charge / discharge rate for the F-CoSe2@PP separator modified battery, the CoSe2@PP separator modified battery and the original PP separator modified battery of Example 1; Figure 2 (b) Constant current charge-discharge curves of the F-CoSe2@PP separator modified battery, the CoSe2@PP separator modified battery and the original PP separator modified battery at 0.2 C.
[0023] Figure 3The graph shows the cycle performance of the battery modified with F-CoSe2@PP separator, the battery modified with CoSe2@PP separator, and the battery modified with the original PP separator at a charge-discharge rate of 1 C. Detailed Implementation
[0024] This application provides a high-performance lithium-sulfur battery and its preparation method, aiming to solve the technical problems of polysulfides in existing lithium-sulfur batteries, such as the shuttle effect, slow reaction kinetics, and short cycle life. The overall approach to solving these problems is as follows:
[0025] A fluorine-doped CoSe2 nanoflower material (F-CoSe2) was designed and prepared to enhance the physical adsorption capacity of polysulfides by utilizing its high specific surface area. Simultaneously, fluorine doping was used to modulate the electronic structure, thereby improving its chemisorption and catalytic conversion activity. This material was then used as a functional coating to modify a commercial polypropylene (PP) membrane, resulting in an F-CoSe2@PP composite membrane. This membrane plays multiple roles in the battery: on the one hand, it acts as a physical barrier to efficiently anchor polysulfides; on the other hand, it serves as a catalytic platform to accelerate the conversion kinetics of polysulfides; and its excellent hydrophilicity ensures a good ion transport channel. Finally, by assembling this composite membrane with a conventional sulfur cathode and lithium anode to form a battery, a high-performance lithium-sulfur battery with high capacity and long cycle life was obtained.
[0026] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.
[0027] Example 1
[0028] Step 1: Preparation of the positive electrode sheet: Mix sulfur / carbon composite positive electrode material, conductive agent and binder at a mass ratio of 8:1:1. The sulfur content in the sulfur / carbon composite positive electrode material is 50% by mass. Add an appropriate amount of N-methylpyrrolidone solvent and stir at high speed in a planetary mixer for 4-8 hours to form a uniform and viscous positive electrode slurry. Use a coating machine to evenly coat the slurry onto the aluminum foil current collector. Place the coated electrode sheet in a vacuum oven at 60-80℃ and dry for 12 hours to completely remove the solvent. Finally, use a roller press to press the electrode sheet and punch it into positive electrode sheets of the required diameter.
[0029] Step 2: Preparation of F-CoSe2@PP membrane:
[0030] (1) Preparation of polyimide precursor: First, prepare 1.8 g benzidine, 3.6 g 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and 60 mL dimethylformamide (DMF). Dissolve benzidine in 30 mL of DMF and stir magnetically until completely dissolved to obtain solution A. Then, dissolve 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride in another 30 mL of DMF to obtain solution B. Under continuous stirring, slowly add solution B to solution A and react at room temperature for 4-6 h to obtain a viscous polyimide acid solution. Subsequently, transfer the polyimide acid solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and heat-treat at 180 °C for 10 h to complete the imidization reaction. After the reaction, cool naturally to room temperature and wash the obtained solid product three times with anhydrous ethanol and deionized water to thoroughly remove residual solvent and byproducts. Finally, the product was dried in a vacuum drying oven at 80°C for 12 hours, and then ground to obtain a brownish-yellow polyimide powder.
[0031] (2) Preparation and selenization of C / Co / CoO composite material: Weigh 100 mg of polyimide powder from step (1), 10 mg of cobalt nitrate, and 10 mg of polyvinylpyrrolidone, mix them, add the mixture to 100 mL of ultrapure water, and sonicate at room temperature for 1 hour to form a uniform suspension, so that cobalt ions and polyvinylpyrrolidone are uniformly dispersed on the surface of nanospheres. Then, heat the suspension at 80 °C and stir magnetically for 6 hours to completely evaporate the solvent and obtain a solid mixture. Grind the solid mixture thoroughly in an agate mortar, and then transfer it to a quartz boat in a tube furnace. Heat to 600 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, and sinter at this temperature for 6 hours. After natural cooling, the C / Co / CoO composite material is obtained.
[0032] 100 mg of the C / Co / CoO composite material and 500 mg of selenium powder were respectively loaded into two ceramic boats. The ceramic boat containing the selenium powder was placed in the upstream zone of a tube furnace, and the ceramic boat containing the C / Co / CoO composite material was placed in the downstream zone. Argon gas was first introduced to purge air, and then switched to an argon-hydrogen mixture (V(H2) / V(Ar) = 10 / 90, total gas flow rate 100 sccm). The temperature was increased to 400℃ at a heating rate of 5℃ / min, and calcined at this temperature for 6 hours for selenization. After the reaction was completed, the mixture was cooled to room temperature under argon protection to obtain the CoSe2 / C nanoflower material.
[0033] (3) Fluoride doping: Weigh 100 mg of the CoSe2 / C nanoflower material obtained in step (2) and 500 mg of ammonium fluoride, and place them in two ceramic boats respectively. Place the ceramic boat containing ammonium fluoride in the upstream zone of the tube furnace and the ceramic boat containing the CoSe2 / C nanoflower material in the downstream zone. In an argon atmosphere, heat the material to 180°C at a heating rate of 2°C / min, heat-treat for 2 h, and hold at this temperature for 2 h to perform fluoride doping. After the reaction is complete, allow it to cool naturally to room temperature, wash the product three times with anhydrous ethanol to remove residual fluoride salts, and finally vacuum dry at 60°C for 6 h to obtain F-CoSe2 nanoflower material. The F-CoSe2 nanoflower material prepared above was mixed and ground in an agate mortar with conductive agent Super P and binder PVDF at a mass ratio of (7~8):(1~2):1 for 30 minutes. Then, N-methylpyrrolidone (NMP) solution was slowly added dropwise, and grinding continued to form a slurry with moderate viscosity and uniform dispersion. The slurry was then uniformly coated onto one or both sides of a commercial polypropylene (PP) separator using a doctor blade coating method. The coated separator was then dried in a vacuum oven at 60-80℃ for 12 hours to obtain the modified F-CoSe2@PP separator. The areal density of the coating is usually controlled between 0.2 and 1.0 mg / cm³. -2 The effect of fluorine atom doping on the wettability of CoSe2 / C with the electrolyte was evaluated by contact angle testing. After adding the electrolyte, the contact angle of CoSe2 / C@PP was 19.3°, while that of F-CoSe2 / C@PP was close to 0°, indicating that F-CoSe2 / C@PP has superior wettability. This characteristic means that F-CoSe2 / C@PP can more effectively promote the uniform distribution of electrolyte inside the battery and the rapid transport of lithium ions during charge and discharge, thereby improving the battery's charge and discharge efficiency and cycle stability.
[0034] Step 3: Battery Assembly
[0035] In an inert atmosphere glove box, using a lithium metal sheet as the negative electrode and the positive electrode sheet prepared in step one as the positive electrode, the F-CoSe2@PP modified separator prepared in step two is placed between the positive and negative electrodes. The cells are assembled into button cells or pouch cells using conventional processes, and an appropriate amount of lithium salt-containing ether electrolyte is injected to ensure that the electrolyte-to-sulfur mass ratio (E / S) is 5–15 μL mg. -1 Within the specified range, a high-performance lithium-sulfur battery can be obtained after standing.
[0036] For CR2032 button batteries, the electrolyte volume is typically 15-30 μL, preferably 20 μL.
[0037] In other embodiments, the preparation method of the ether electrolyte is as follows: The electrolyte is prepared in an argon-filled glove box by dissolving lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in a mixed solvent composed of 1,3-dioxolane DOL and ethylene glycol dimethyl ether (DME) in a 1:1 volume ratio, with 1-3 wt% lithium nitrate (LiNO3) added as an additive. The concentration of LiTFSI is typically 1 mol / L. -1 .
[0038] CoSe2@PP membranes were prepared using the same method described above.
[0039] After the assembled high-performance lithium-sulfur battery has been left to stand for 8 hours, electrochemical tests are performed. Please refer to [reference needed]. Figures 1-3 , Figure 1 By comparing the nucleation and activation potential differences of F-CoSe2@PP and CoSe2@PP separators, their charge transfer efficiencies can be directly reflected. During Li2S nucleation and activation, the potential differences of F-CoSe2@PP (36.4 mV and 32.4 mV) are lower than those of CoSe2@PP (46.1 mV and 50.4 mV), indicating that the F-CoSe2 nanoflower material has lower charge transfer resistance and superior electrochemical performance. The low ΔiR indicates that the battery modified with the F-CoSe2@PP separator exhibits significantly improved reaction kinetics in the reversible reaction between soluble long-chain lithium polysulfides and insoluble Li2S, effectively mitigating polarization and kinetic limitation.
[0040] Figure 2 , Figure 3 Electrochemical data of assembled F-CoSe2 / C@PP membrane-modified and CoSe2 / C@PP membrane-modified coin cells at different charge-discharge rates are shown. The functional membrane coated with composite material effectively improves the electrochemical performance of lithium-sulfur batteries. The comparison shows that F-CoSe2 nanoflower material has a significant catalytic effect on the conversion of polysulfides in lithium-sulfur batteries, thereby improving the lifespan of lithium-sulfur batteries.
[0041] Among them, F-CoSe2 / C@PP exhibited superior electrochemical performance at a C rate of 0.2, with an initial specific capacity as high as 1309 mAh g⁻¹. -1 After 100 cycles, it still maintains 946.4 mAh g. -1 The capacity of CoSe2 / C@PP was only 822.2 mAh g after 100 cycles under the same conditions; while CoSe2 / C@PP had a capacity of only 822.2 mAh g after 100 cycles. -1 At a 1 C rate, F-CoSe2 / C@PP maintains excellent cycling stability and specific capacity retention. After 500 cycles, its capacity decay per cycle is only 0.0939%.
[0042] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.
[0043] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for preparing a high-performance lithium-sulfur battery, characterized in that, Includes the following steps: Preparation of S01 positive electrode sheet: Sulfur / carbon composite positive electrode material, conductive agent and binder are mixed in a mass ratio of 8:1:1, solvent is added and ground to form a uniform slurry, which is then coated on aluminum foil current collector, dried, pressed and punched into positive electrode sheets of the required size. Modification of SO2 membrane: The prepared F-CoSe2 nanoflower material, conductive agent and binder are mixed in a mass ratio of (7~8):(1~2):1, solvent is added and the mixture is ground to form a uniform slurry. Then, it is uniformly coated on the surface of a commercial polypropylene PP membrane by a scraping method. After drying, F-CoSe2@PP modified membrane is obtained. S03 Assembly of high-performance lithium-sulfur battery: In an inert atmosphere glove box, using a lithium metal sheet as the negative electrode, the positive electrode sheet prepared in step S01 as the positive electrode, and the F-CoSe2@PP modified separator prepared in step S02 as the separator, the battery is assembled into a button cell or pouch cell according to conventional processes, and an appropriate amount of ether electrolyte containing lithium salt is injected. After standing, the high-performance lithium-sulfur battery can be obtained. The F-CoSe2 nanoflower material is prepared by a method comprising the following steps: ① First, prepare C / Co / CoO composite material, then load selenium powder and the C / Co / CoO composite material into a ceramic boat at a mass ratio of 4~6:1, and place them in the downstream and upstream of a tube furnace respectively. After high-temperature calcination in an argon-hydrogen mixture for 5~7 hours, obtain CoSe2 / C material. ② The prepared CoSe2 / C material and ammonium fluoride were placed downstream and upstream of a ceramic boat at a mass ratio of 2~4:
1. Under an argon atmosphere, the temperature was increased to 170-210℃ at a heating rate of 1-3℃ / min, held for 1-3 hours, and then naturally cooled to obtain F-CoSe2 nanoflower material.
2. The method for preparing a high-performance lithium-sulfur battery according to claim 1, characterized in that, In step S01, the sulfur / carbon composite cathode material has a sulfur content of 60% to 80% by mass.
3. The method for preparing a high-performance lithium-sulfur battery according to claim 1, characterized in that, In step S02, the areal density of the F-CoSe2 nanoflower material coating on the diaphragm is 0.2 ~ 1.0 mg cm⁻¹. -2 .
4. The method for preparing a high-performance lithium-sulfur battery according to claim 1, characterized in that, In step ② of the preparation method of the F-CoSe2 nanoflower material, the mass ratio of CoSe2 / C material to ammonium fluoride is 3:
1.
5. The method for preparing a high-performance lithium-sulfur battery according to claim 1, characterized in that, In step ② of the preparation method of the F-CoSe2 nanoflower material, the heating rate is 2℃ / min.
6. The method for preparing a high-performance lithium-sulfur battery according to claim 1, characterized in that, In step S02, the conductive agent is Super P and the binder is polyvinylidene fluoride.
7. A high-performance lithium-sulfur battery, characterized in that, The high-performance lithium-sulfur battery is prepared by the preparation method described in any one of claims 1 to 6.