Carbon packaged sulfide electrolyte coupling integrated 3D porous sulfur, preparation method and application

Abstract

The invention relates to the technical field of new energy, in particular to carbon-packaged sulfide electrolyte coupled and integrated 3D porous sulfur, a preparation method and application. The preparation method comprises the following steps: S1, ball-milling and uniformly mixing a template and sulfur powder to form mixed powder; s2, heating the mixed powder to a certain temperature, melting sulfur, stirring for a period of time in a molten state, filling pores of the template with the molten sulfur, and cooling to form a complex of porous sulfur and the template; removing the template to obtain porous sulfur; s3, soaking the sulfide electrolyte solution into pores of the porous sulfur, and drying to form sulfide electrolyte coupled and integrated 3D sulfur; and S4, dispersing the sulfide electrolyte coupling integrated 3D sulfur by using an organic solution, mixing with a carbon source solution, drying the mixed solution, and carbonizing to form the carbon-encapsulated sulfide electrolyte coupling integrated 3D porous sulfur. The problems that a sulfur positive electrode is poor in conductivity and serious in volume expansion are solved.

Description

Technical Field

[0001] The present invention relates to the field of new energy technologies, and particularly relates to a carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur, a preparation method and an application thereof. Background Art

[0002] As a cathode material for lithium-sulfur batteries, sulfur has a theoretical specific capacity as high as 1675 mAh / g and a theoretical energy density of 2600 Wh / kg, far exceeding the existing cathode materials for lithium-ion batteries. However, the sulfur cathode faces many challenges in practical applications, such as poor conductivity, large volume expansion, and the "shuttle effect" of polysulfides, etc., which seriously restrict the commercialization process of lithium-sulfur batteries.

[0003] In response to the above problems, the existing technologies mainly focus on three major strategies: 1. Porous structure construction: Designing a porous sulfur framework through methods such as template method and self-assembly to improve the active material loading, buffer volume strain, and shorten the ion transport path. However, such methods often face problems such as uneven pore distribution, poor structural stability, and complex processes, making it difficult to achieve large-scale production.

[0004] 2. Conductive / functional material composite: Composites of sulfur with conductive materials such as carbon nanotubes and graphene or functional materials such as metal oxides and polymers are used to improve the electrode conductivity and physically / chemically anchor LiPSs. However, the weak interfacial binding between sulfur and the carrier easily leads to the shedding of active substances, and it is difficult to effectively inhibit the diffusion of LiPSs during long cycles.

[0005] 3. Interface engineering modification: Introducing a polar coating or a solid electrolyte interface (SEI) to enhance the adsorption ability of LiPSs. However, the introduction of an additional interfacial layer may increase the electrode internal resistance, reduce the lithium ion mobility, and even trigger side reactions, deteriorating the battery kinetic performance.

[0006] Although the above research has made certain progress, there are still the following bottlenecks: The preparation of porous structures relies on complex template etching or high-temperature treatment, with high costs; the interfacial compatibility between conductive / functional components and sulfur is poor, and the composite structure is prone to stress concentration and cracking during cycling; the modification means to inhibit the "shuttle effect" often come at the cost of sacrificing ion / electron transport efficiency, making it difficult to balance high capacity and long cycle stability.

[0007] Currently, the modification research on sulfur cathodes mainly focuses on the following aspects: I. By constructing a porous structure to increase the specific surface area of the electrode, improve the utilization rate of active substances, and buffer the volume expansion of sulfur during charge and discharge; II. Sulfur is combined with conductive materials (such as carbon nanotubes, graphene, etc.) or functional materials (such as metal oxides, polymers, etc.) to improve the conductivity and stability of the electrode while suppressing the shuttle of polysulfides. III. Interface modification of the sulfur cathode is carried out by introducing polar materials or surface coatings to adsorb polysulfides and reduce their dissolution and diffusion in the electrolyte.

[0008] Although certain progress has been made in existing research, there are still some deficiencies in the existing sulfur cathode modification methods. For example, the preparation process of the porous structure is complex, the cost is high, and it is difficult to control the uniformity and stability of the pore structure; in the preparation process of the composite material, the bonding strength between sulfur and the conductive material or functional material is insufficient, resulting in limited improvement in the conductivity and stability of the electrode; in the interface modification method, the modified materials used may have an adverse impact on other performance of the battery, such as increasing the internal resistance of the battery and reducing the charge-discharge efficiency of the battery.

[0009] Therefore, developing a simple, efficient, and low-cost sulfur cathode modification method to overcome the deficiencies of the existing technology and improve the conductivity, stability, and cycling performance of the sulfur cathode is of great significance for promoting the commercial application of lithium-sulfur batteries. Summary of the Invention

[0010] In view of this, the present invention proposes a carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur, a preparation method and an application thereof, which systematically solve the problems of poor conductivity and serious volume expansion of the sulfur cathode, slow ion transport caused by poor contact between the all-solid composite cathode particles prepared therefrom, and slow kinetics of all-solid-state lithium-sulfur batteries through multi-level structure design and material synergistic optimization.

[0011] The technical solution provided by the present invention is as follows: A preparation method of carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur, comprising the following steps: S1. The template and sulfur powder are ball-milled and mixed evenly to form a mixed powder; S2. The mixed powder is heated to melt sulfur, and stirred in the molten state to make the molten sulfur fill into the pores of the template, and cooled to form a composite of porous sulfur and the template; after removing the template, porous sulfur is obtained; (the treated porous sulfur is dried in an oven to obtain a dried porous sulfur product, drying temperature: 60-80 °C, time: 6-12 h); S3. The sulfide electrolyte solution is impregnated into the pores of the porous sulfur, and dried to form a sulfide electrolyte coupled with integrated 3D sulfur; S4. Carbon encapsulation: The sulfide electrolyte coupled with integrated 3D sulfur is dispersed with an organic solution, mixed with a carbon source solution, and the mixed solution is dried and carbonized to form carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur.

[0012] In S1, the template material is selected from at least one of alumina, silica, carbon materials, metal oxides, or polymer materials.

[0013] And / or, in S1, the mass ratio of the template to sulfur powder is 0.1 - 2:1.

[0014] And / or, in S1, the ball milling conditions are: ball-to-material ratio of 10 - 20:1, rotation speed of 400 - 500 rpm.

[0015] In S2, when removing the template, for alumina or silica templates, use hydrofluoric acid (HF) solution for soaking. The soaking time (12 - 24 h) is determined according to the thickness and pore size of the template. After soaking, rinse repeatedly with deionized water until the washing liquid is neutral to remove the residual acid solution.

[0016] In S2, the mixed powder is heated to 115 - 130 °C, and mechanical stirring is used. The stirring speed is 300 - 500 revolutions per minute, and the stirring time is 30 - 60 minutes.

[0017] In S2, the cooling is natural cooling.

[0018] In S3, the sulfide electrolyte is Li 6 PS 5 Cl, and the preparation method of the Li 6 PS 5 Cl includes the following steps: (1), Weigh LiCl, P 2 S 5 and Li 5 S according to the stoichiometric ratio, and ball mill to obtain LPSCl powder, denoted as M-LPSCl (2), Under vacuum, heat the M-LPSCl powder at a rate of 2 - 5 °C / min to 400 - 600 °C and sinter for 10 - 12 hours to obtain the sulfide electrolyte powder.

[0019] In step (1), weigh LiCl, P 2 S 5 and Li 5 S and seal them in a zirconium can, and use a high-energy planetary ball mill for ball milling. The ball milling conditions are 400 - 500 rpm and the ball milling time is 10 - 24 hours.

[0020] In step (2), place the M-LPSCl powder in a crucible with a glass carbon lid, vacuum seal it in a quartz tube for sintering and annealing to obtain the final Li 6 PS 5 Cl electrolyte powder.

[0021] S3 includes the following steps: S31. Dissolve the sulfide electrolyte powder in an organic solvent (such as anhydrous ethanol solution) to obtain a sulfide electrolyte solution, denoted as S-LPSCl; S32. Drop the sulfide electrolyte solution onto the porous sulfur prepared in S2, impregnate the sulfide electrolyte solution into the pores of the porous sulfur, and heat it at 140 - 180 °C for 3 - 5 hours under vacuum to make the sulfide electrolyte solution enter the pores of the porous sulfur to form a sulfide electrolyte-coupled integrated 3D sulfur.

[0022] All of the above processes are carried out in a glove box filled with argon.

[0023] Step S4 includes the following steps: S41. Disperse the sulfide electrolyte-coupled integrated 3D sulfur in an organic solvent (such as anhydrous ethanol solution) to prepare a sulfur precursor solution; dissolve the carbon source in an organic solvent (such as anhydrous ethanol solution) to prepare a carbon source solution; S42. Add the carbon source solution to the sulfur precursor solution, stir and mix evenly to form a mixed solution, and dry it to obtain a carbon source-sulfur composite; S43. Carbonize the carbon source-sulfur composite under an inert atmosphere to obtain carbon-encapsulated sulfide electrolyte-coupled integrated 3D porous sulfur (C@S-LPSCl).

[0024] In step S41, it is selected from sucrose or polyvinylpyrrolidone (PVP).

[0025] In S42, in the mixed solution, the mass ratio of the sulfide electrolyte-coupled integrated 3D sulfur to the carbon source is 0.5 - 1:1.

[0026] In step S43, the carbonization conditions are: heating rate: 5 - 10 °C / min, temperature: 600 - 900 °C, heat preservation time: 1 - 3 h.

[0027] <Second aspect> The present invention also provides a carbon-encapsulated sulfide electrolyte-coupled integrated 3D porous sulfur obtained by the preparation method as described above.

[0028] <Third aspect> The present invention provides a preparation method for a carbon-encapsulated sulfide electrolyte-coupled integrated 3D sulfur composite positive electrode, including the following steps: Step 1. Under a protective atmosphere, mix and grind the carbon-encapsulated sulfide electrolyte-coupled integrated 3D porous sulfur and the sulfide electrolyte according to a mass ratio of 40 - 60:10 - 20 (the ball-to-material ratio is 2:1 - 5:1, and the rotation speed is 300 - 400 rpm); after ball milling, separate the balls from the material; Step 2: Add conductive carbon to the material after removing the abrasive in Step 1 and grind it (the ball-to-material ratio is 2:1 - 5:1, and the rotation speed is 400 - 500 rpm) to obtain the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite cathode.

[0029] In Step 1 and Step 2, the grinding method is rolling grinding plus ball milling. Specifically, roll grind for 1 - 2 h; stop for 5 - 10 min, with a total of 3 - 6 cycles; then ball mill for 30 - 60 min; stop for 5 - 10 min; and ball mill for a total of 8 - 10 cycles.

[0030] The mass ratio of the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur (C@S-LPSCl), sulfide electrolyte, and conductive carbon is 40~60:10~20:30~40.

[0031] The sulfide electrolyte includes Li 5.5 PS 4.5 X 1.5 、Li 10 MP 2 S 12 、80Li 2 S·20P 2 S 5 、or at least one or more of them; where M is selected from at least one of Ge, Si, or Sn; and X is selected from at least one of F, Cl, Br, or I.

[0032] Preferably, the sulfide electrolyte is Li 5.5 P 4.5 Cl 1.5 with a conductivity of 8 - 10 mS / cm.

[0033] The protective gas is argon.

[0034] The conductive carbon includes at least one of vapor-grown carbon fiber (VGCF), carbon black, SuperP, conductive graphite, and carbon nanotubes.

[0035] The carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite cathode (C@S-LPSCl composite cathode) prepared by the preparation method as described above also belongs to the protection scope of the present invention.

[0036] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a composite material in which porous sulfur is filled with an electrolyte and then encapsulated in a carbon layer, and a preparation method thereof. Through the pore structure of the porous sulfur and the encapsulation of the carbon layer, the dispersion of the electrolyte is effectively improved, ensuring that the electrolyte is fully in contact with the inside and outside of sulfur, thereby significantly improving the ion transport efficiency. At the same time, the encapsulation of the carbon layer effectively inhibits the dissolution and diffusion of polysulfides, reduces the "shuttle effect", and further improves the cycle stability and capacity retention rate of the battery. In addition, the conductivity of the carbon layer is better than that of sulfur, significantly improving the overall conductivity, thereby enhancing the rate performance and charge-discharge efficiency of the battery. The pore structure of the porous sulfur can also buffer the volume expansion of sulfur during charge and discharge, reduce the mechanical stress of the electrode material, and improve the cycle life of the battery. The composite material also provides more active sites, improves the utilization rate of sulfur, and thus enhances the energy density of the battery. Finally, the encapsulation of the carbon layer enhances the structural stability of the porous sulfur, reduces the physical loss of sulfur during charge and discharge, and further improves the long-term cycle performance of the battery. This composite material has broad application prospects in the field of lithium-sulfur batteries, can effectively solve the problems existing in pure sulfur cathodes, and promote the development of lithium-sulfur battery technology.

[0037] 2. The present invention also provides a C@S-LPSCl composite cathode, which is mechanically ball-milled from C@S-LPSCl, a sulfide electrolyte, and conductive carbon. The addition of conductive carbon can improve the electronic conductivity of the composite material; the addition of the sulfide electrolyte can provide contact between particles and improve the ion transport inside the composite cathode to the cathode / electrolyte interface; the composite cathode prepared by the method of the present invention has an initial capacity of 1400 mAhg -1 and maintains a capacity of 508 mAhg at a high rate of 1C -1 and has excellent cycle stability with a capacity retention rate of 91%, and the rate performance is also improved.

[0038] 3. When preparing the C@S-LPSCl composite cathode, a combination of ball milling and rolling milling is adopted. The rolling milling method can ensure that S and the sulfide electrolyte are in contact with the ball milling medium, the milling beads, to the greatest extent, improving the mixing efficiency and scale of the two. Ball milling can effectively provide high-energy impacts to break the gradient distribution of the three components caused by physical aggregation. This rolling milling method may result in the uneven distribution of conductive carbon inside and outside. The combination of the two can make the conductive carbon fully distributed inside and outside the composite material. Generally speaking, the pre-mixing and then mixing with conductive carbon are more sufficient, which is conducive to the uniform distribution of the electrolyte and conductive carbon in the active material, ensuring the effective transport of ions and electrons inside the composite cathode. At the same time, the step-by-step mixing provides an opportunity to controllably monitor the particle size change and mixing degree, facilitating the full-process evaluation and design of the composite cathode. In the process of large-scale production practice, the output of the materials obtained in different ball milling stages can be efficiently controlled, improving the production efficiency. Brief Description of the Drawings

[0039] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non - limiting embodiments read in conjunction with the accompanying drawings: Figure 1 It is the XRD pattern of raw materials S and carbon C required for preparing the C@S - LPSCl material in Preparation Example 1; Figure 2 It is the Raman spectrum of the S / C material and pure S material prepared in Comparative Preparation Example 1; Figure 3 It is the LSV curve of the S / C material and pure S material prepared in Comparative Preparation Example 1; Figure 4 It is the cyclic voltammetry (CV) pattern of the full cell assembled with the material prepared in Example 1; Figure 5 It is the in - situ impedance test during the discharge process of the full cell assembled with the material prepared in Example 1; where the abscissa: Z′ / ohm means the real part of impedance / ohm; the ordinate: means the imaginary part of impedance (negative value) / ohm; Figure 6 It is the full - cell impedance test of the full cells assembled with the materials prepared in Example 1 and Comparative Example 2; where the abscissa: Z′ / ohm means the real part of impedance / ohm; the ordinate: means the imaginary part of impedance (negative value) / ohm; Figure 7 It is the rate performance pattern of Example 1, Comparative Example 1, and Comparative Example 2; Figure 8 It is the comparison pattern of the long - cycle performance of the full cells assembled with the composite positive electrodes of Example 1, Comparative Examples 1 - 6; Figure 9 It is the first - cycle charge - discharge curve pattern of the full cell assembled with the composite positive electrodes of Example 1 and Comparative Example 4. Detailed Description of the Embodiments

[0040] The present invention will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several adjustments and improvements can still be made. These all fall within the protection scope of the present invention.

[0041] In the following embodiments and comparative examples: The conductive agent used is SuperP; the electrolyte is Li 5.5 P 4.5 Cl 1.5 ; the protective gas is argon.

[0042] Figure 1is the XRD pattern of raw material sulfur powder and sucrose carbonization; this pattern shows that the raw material is pure in phase and has good crystallinity.

[0043] Sucrose carbonization conditions: Preparation of C@S-LPSCl material in Preparation Example 1 1. Preparation of porous sulfur (1) Mixing of template and sulfur powder: Weigh 0.5 g of alumina template material (pore size 50 - 200 nm, purity ≥99%) and 1.0 g of sulfur powder, place them in a planetary ball mill, and ball mill at room temperature for 2 hours with a ball-to-material ratio to make the template and sulfur powder fully mixed and uniform. Among them, zirconia ball mill beads are used; the diameter of the ball mill beads is 1 mm - 10 mm, and the ball-to-material ratio is 10:1. (2) Melting and filling: Place the powder after mixing in step (1) in a crucible, heat it to 120°C at a heating rate of 5°C / min to melt the sulfur. In the molten state, stir mechanically at 400 revolutions per minute for 40 minutes to ensure that the sulfur is fully filled into the pores of the template.

[0044] (3) Cooling and solidification: Take out the template filled with sulfur from the molten state and cool it naturally to room temperature to solidify the sulfur in the pores of the template, forming a composite of porous sulfur and the template.

[0045] (4) Removal of template: Immerse the composite in 10% (molar concentration) HF solution for 16 hours. After immersion, rinse repeatedly with deionized water until the washing liquid is neutral to remove the residual acid solution.

[0046] (5) Drying treatment: Dry the material processed in step (4) in an oven at 60°C for 10 hours to obtain a dry porous sulfur product.

[0047] 2. Preparation of sulfide electrolyte Li6PS5Cl (1) Mechanical ball milling: Weigh LiCl, P 2 S 5 and Li 2 S according to the stoichiometric ratio, seal them in a zirconium can, and use a high-energy planetary ball mill to ball mill at 450 rpm for 16 hours to obtain LPSCl powder, denoted as M-LPSCl; among them, zirconia ball mill beads are used; the diameter of the ball mill beads is 1 mm - 10 mm, and the ball-to-material ratio is 10:1.

[0048] (2) Heat treatment: Place the obtained M-LPSCl powder in a crucible with a glass carbon lid, vacuum-seal it in a quartz tube, heat it to 500°C at a heating rate of 2°C / min for sintering and annealing for 10 hours, and further ball mill (where zirconia ball mill beads are used; the diameter of the ball mill beads is 1 mm - 10 mm, and the ball-to-material ratio is 10:1) to refine to obtain the final powder, which is Li 6 PS 5Cl electrolyte powder.

[0049] 3. Sulfide electrolyte coupled with integrated 3D sulfur (1)Prepare the solution: Disperse 0.2 g of Li 6 PS 5 Cl powder in 2 mL of absolute ethanol to obtain a sulfide electrolyte solution, denoted as S-LPSCl solution.

[0050] (2)Impregnate the electrolyte solution: Drop the S-LPSCl solution onto the porous sulfur prepared in step 1, and through vacuum-assisted capillary action, make the solution fully enter the pores. (The mass ratio of S-LPSCl to porous sulfur is 1:1) (3)Drying treatment: Heat at 150 °C for 4 hours under vacuum to evaporate the solvent, so that S-LPSCl fills the pores of the porous sulfur evenly and tightly, forming a sulfide electrolyte coupled with integrated 3D sulfur.

[0051] All processes are carried out in a glove box filled with argon.

[0052] 4. Carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur (1)Prepare the sulfur precursor solution: Weigh 600 mg of the carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur powder, add an appropriate amount of ethanol (the concentration of the carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur powder is 0.1 g / mL), and stir it mechanically at 500 revolutions per minute at room temperature to make it fully dispersed, forming a uniform sulfur precursor solution.

[0053] (2)Prepare the carbon source solution: Weigh 600 mg of sucrose, dissolve it in an appropriate amount of ethanol to make a carbon source solution (in this solution, the concentration of sucrose is 0.05 g / mL).

[0054] (3)Prepare the carbon source-sulfur composite: Slowly add the carbon source solution to the sulfur precursor solution, stirring while adding to ensure that the two are fully mixed evenly (in the mixed solution, the mass ratio of the carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur powder to sucrose is 1:1). Dry the mixed solution in an oven at 60 °C for 8 hours until the solvent completely evaporates to obtain a carbon source-sulfur composite.

[0055] (4)Carbonization: Place the dried carbon source-sulfur composite in a tube furnace and carry out carbonization treatment under nitrogen protection. Raise the temperature to 800 °C at a heating rate of 5 °C / min and keep this temperature for 2 hours to make the carbon source fully carbonize to form a carbon layer. After carbonization is completed, wait for the furnace temperature to cool naturally to room temperature, take out the product, and obtain the carbon-encapsulated sulfide electrolyte coupled with integrated 3D porous sulfur (C@S-LPSCl).

[0056] Comparative Preparation Example 1 The difference between this comparative preparation example and preparation example 1 is that sulfide electrolyte is directly used for carbon encapsulation.

[0057] The specific steps are as follows: (1) Preparation of sulfur precursor solution: Weigh 600 mg of sulfide electrolyte Li 6 PS 5 Cl, add an appropriate amount of anhydrous ethanol (sulfide electrolyte Li 6 PS 5 Cl concentration is 0.1 g / mL), and the mixture is fully dispersed by mechanical stirring at 500 rpm at room temperature to form a uniform sulfur precursor solution; (2) Preparation of carbon source solution: same as Preparation Example 1; (3) Preparation of carbon source-sulfur complex: Slowly add the carbon source solution to the sulfur precursor solution, stirring while adding to ensure that the two are fully mixed (the mass ratio of sulfur to sucrose in the mixed solution is 1:1). Dry the mixed solution in an oven at 60°C for 8 hours until the solvent is completely evaporated to obtain a dry carbon source-sulfur complex (S / C material).

[0058] (4) Carbonization: Same as Preparation Example 1.

[0059] Figure 2 is a Raman spectrum of the carbon source-sulfur composite S / C material and the pure S material prepared in Comparative Preparation Example 1; Figure 2 It shows that the carbon source-sulfur composite material prepared in this preparation example retains the characteristic displacement peak of sulfur, but due to the encapsulation of carbon, part of the displacement peak of sulfur disappears and is replaced by the characteristic peak of carbon.

[0060] Figure 3 The LSV curves of the carbon source-sulfur composite S / C material and the pure S material prepared in Preparation Example 1 are compared, and the electronic conductivity of the two materials is obtained by calculation; Figure 3 This shows that sulfur itself is an insulator, and carbon encapsulation can greatly improve the electronic conductivity of the material, which is more than 20 orders of magnitude higher than that of sulfur alone. This is of great help to the rate and effective utilization of sulfur positive electrodes.

[0061] Comparative Preparation Example 2 The difference between this comparative preparation example and preparation example 1 lies in the step of coupling the sulfide-free electrolyte with the porous sulfur; the specific steps are as follows: 1. Preparation of porous sulfur: same as Preparation Example 1; 2. Sulfide electrolyte Li 6 PS 5 Preparation of Cl: Same as Preparation Example 1; 3. Carbon encapsulation of porous sulfur; (1) Preparation of sulfur precursor solution: weigh 600 mg Li 6 PS5 Cl electrolyte powder was added with an appropriate amount of ethanol to obtain a sulfide electrolyte solution, denoted as S-LPSCl solution (electrolyte powder concentration: 0.1 g / mL). It was mechanically stirred at 500 revolutions per minute at room temperature to disperse it sufficiently to form a uniform sulfur precursor solution.

[0062] (2) Preparation of carbon source solution: 600 mg of sucrose was weighed and dissolved in an appropriate amount of ethanol to prepare a carbon source solution (in this solution, the sucrose concentration was 0.05 g / mL).

[0063] (3) Preparation of carbon source-sulfur composite: The carbon source solution was slowly added to the sulfur precursor solution while stirring to ensure thorough mixing of the two (in the mixed solution, the mass ratio of Li 6 PS 5 Cl electrolyte powder to sucrose was 1:1). The mixed solution was dropped onto the porous sulfur, and through vacuum-assisted capillary action, the solution fully entered the pores. It was dried in an oven at 60°C for 8 hours until the solvent completely evaporated to obtain a dry carbon source-sulfur composite.

[0064] (4) Carbonization: The same as Preparation Example 1.

[0065] Comparative Preparation Example 3 The difference between this comparative preparation example and Preparation Example 1 was that there was only the step of coupling porous sulfur with the sulfide electrolyte, and there was no carbon encapsulation step. The product of this preparation example was a sulfide electrolyte-coupled integrated 3D porous sulfur powder.

[0066] Example 1 Preparation of C@S-LPSCl Composite Cathode for Sulfide-Based All-Solid-State Lithium Batteries Step 1: According to a ball-to-material ratio of 20:1, zirconia beads (10 of 5 mm, 20 of 3 mm, and the rest all 1 mm) were weighed and placed in a zirconia ball mill jar. After drying in an oven at 60°C for four hours, it was transferred to an argon glove box (the water content of argon in the glove box was less than 1 ppm, and the oxygen content was less than 1 ppm); 400 mg of C@S-LPSCl (prepared in Preparation Example 1) and 50 mg of Li 5.5 PS 4.5 Cl 1.5 were added to the ball mill jar, sealed with insulating tape; it was intermittently ball milled at a speed of 200 rpm for 8 h (where the intermittent ball milling method was: ball milling for 30 min; stopping for 5 min); after ball milling was completed, the ball mill jar was transferred to the glove box and the balls and materials were separated; Step 2: Add 57 mg of Super P to the material separated in Step 1 for premixing, and then transfer it to a ball milling jar. Perform intermittent ball milling at a ball (zirconia beads) to material ratio of 5:1 for 10 h at a rotation speed of 500 rpm (where the intermittent ball milling method is: ball milling for 30 min; stopping for 5 min). After ball milling is completed, perform ball-material separation to obtain the C@S-LPSCl composite cathode.

[0067] Comparative Example 1 The difference between this comparative example and Example 1 is that: the C@S-LPSCl in Step 1 is replaced with the material prepared in Comparative Preparation Example 1. Other steps are the same as those in Example 1.

[0068] Comparative Example 2 The difference between this comparative example and Example 1 is that: the C@S-LPSCl in Step 1 is replaced with the material prepared in Comparative Preparation Example 2. Other steps are the same as those in Example 1.

[0069] Comparative Example 3 The difference between this comparative example and Example 1 is that: the C@S-LPSCl in Step 1 is replaced with the material prepared in Comparative Preparation Example 3. Other steps are the same as those in Example 1.

[0070] Comparative Example 4 The difference between this comparative example and Example 1 is that: the C@S-LPSCl in Step 1 is replaced with pure sulfur without any treatment. Other steps are the same as those in Example 1.

[0071] Comparative Example 5 According to a ball to material ratio of 20:1, weigh zirconia beads (10 of 5 mm, 20 of 3 mm and the rest all 1 mm) into a zirconia ball milling jar, dry in an oven at 60 °C for four hours and then transfer to an argon glove box (the water content of argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm); add 400 mg of C@S-LPSCl (prepared in Preparation Example 1), 50 mg of Li 5.5 PS 4.5 Cl 1.5 and 57 mg of Super P into the ball milling jar, seal with insulating tape; perform intermittent rolling milling at a rotation speed of 200 rpm for 8 h (where the intermittent ball milling method is: rolling milling for 30 min; stopping for 5 min); after rolling milling is completed, transfer the ball milling jar to the glove box and perform ball-material separation to obtain the C@S-LPSCl composite cathode.

[0072] Comparative Example 6 Weigh zirconia beads (10 of 5 mm, 20 of 3 mm, and the rest all 1 mm) in a zirconia ball mill jar according to a ball-to-material ratio of 5:1, dry them in an oven at 60 °C for four hours, and then transfer them to an argon glove box (the water content of the argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm); put 400 mg of C@S-LPSCl (prepared in Preparation Example 1) and 50 mg of Li 5.5 PS 4.5 Cl 1.5 and 57 mg of Super P into the ball mill jar together, seal it with insulating tape; perform intermittent ball milling at a rotation speed of 500 rpm for 10 h (the intermittent ball milling method: ball mill for 30 min; stop for 5 min); after ball milling is completed, transfer the ball mill jar to the glove box and perform ball-material separation to obtain the C@S-LPSCl composite cathode.

[0073] Performance Test Test method: In the argon glove box, press 10 mg of the composite cathode prepared in Example 1 and 100 mg of the electrolyte (Li 5.5 PS 4.5 Cl 1.5 ) into tablets in a pressure mold, and assemble them with a lithium-silicon alloy anode (indium foil, thickness 200 μm, lithium foil, thickness 50 μm). The anode electrode sheet is 8 cm wide and 10 cm long, and is attached to the anode current collector. The anode current collector is 10-μm copper foil) to assemble a full cell. The charge-discharge rate tested is 0.1 C - 2 C, and the charge-discharge cut-off voltage is 1 V - 2.8 V relative to Li-Si / Li + . The charge and discharge capacities described in the present invention both refer to the specific capacity calculated based on the S-based composite active material of the cathode.

[0074] Figure 4 is the cyclic voltammetry (CV) diagram of the full cell assembled with the materials prepared in Example 1; Figure 4 It shows clear oxidation-reduction peaks and corresponding oxidation-reduction potentials of the lithium-sulfur battery.

[0075] Figure 5 is the in-situ impedance test during the discharge process of the full cell assembled with the materials prepared in Example 1; It can be proved from the figure that the formation of polysulfide during the discharge process (1.7 V → 1 V) will increase the resistance of the battery, but due to the porous sulfur coupling electrolyte and carbon encapsulation, when volume expansion occurs at the cathode, it triggers the contact between carbon, electrolyte and polysulfide, thereby improving the electron / ion conduction between the inside of the composite cathode and the electrolyte and reducing the battery resistance.

[0076] Figure 6 is the full cell impedance test of the full cells assembled with the materials prepared in Example 1 and Comparative Example 2; Figure 6It is shown that the positive electrode impedance and ion diffusion of the full cell in Example 1 are significantly better than those in Comparative Example 2. The main reason is attributed to the fact that the C@S-LPSCl material can improve the contact between the electrolyte and sulfur by coupling the electrolyte inside the porous sulfur, establish a more efficient ion transport path, and thus optimize ion transport. Therefore, the composite positive electrode shows a small bulk impedance and a high ion diffusion ability.

[0077] Figure 7 Figure 4 shows the rate performance graphs of Example 1, Comparative Example 1, and Comparative Example 2; the results show that the sulfur positive electrode with porous sulfur structure design, sulfide electrolyte coupling, and carbon encapsulation in Example 1 exhibits higher capacity and rate performance. The performances of Comparative Example 1 (without porous sulfur preparation and electrolyte coupling) and Comparative Example 2 (without electrolyte coupling) are lower, which is attributed to the lack of coupling between the sulfide electrolyte and sulfur, resulting in insufficient ion transport paths.

[0078] Figure 8 Figure 5 is a comparative graph of the long cycle performance of the full cells assembled with the composite positive electrodes of Example 1 and Comparative Examples 1-6. It can be seen from this figure that the composite positive electrode prepared by the optimized ball milling method with porous design, electrolyte coupling, and carbon encapsulation of the sulfur positive electrode has higher capacity and cycle stability. This is because the porous design and carbon encapsulation can relieve the volume expansion of sulfur and stabilize the structure of the positive electrode during cycling. Electrolyte coupling can improve lithium ion transport and contribute to the capacity by improving the utilization rate of sulfur. Finally, the preparation method of the composite positive electrode by rolling milling plus ball milling can make the solid particles in the composite positive electrode contact more fully and disperse more evenly, ensuring the establishment of an efficient ion / electron transport path.

[0079] Figure 9 Figure 6 is the first charge-discharge curve graph of the full cell assembled with the composite positive electrodes of Example 1 and Comparative Example 4. This figure shows that the untreated S has greater polarization and lower sulfur utilization rate compared with the modified C@S-LPSCl. This is because the untreated sulfur in the composite positive electrode has only solid-solid contact with the conductive carbon and electrolyte, without the strong coupling effect between the porous sulfur and the electrolyte inside and the stable encapsulation by carbon like the modified sulfur. Therefore, the volume expansion during cycling will deteriorate the unstable solid-solid contact, resulting in a huge impedance between sulfur and the electrolyte, increasing polarization. And it leads to the ineffective utilization of the sulfur positive electrode, manifested as low charge-discharge capacity.

[0080] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A method for preparing carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, characterized in that: The following steps are involved: S1, ball-milling the template and sulfur powder to form a mixed powder; S2, heating the mixed powder until the sulfur is melted, stirring in a molten state to allow the molten sulfur to fill the pores of the template, and cooling to form a composite of porous sulfur and the template; and removing the template to obtain porous sulfur; S3, impregnating the sulfide electrolyte solution into the pores of the porous sulfur, and forming a sulfide electrolyte coupled integrated 3D sulfur after drying; S4. Sulfide electrolyte coupled integrated 3D sulfur is dispersed in an organic solution and mixed with a carbon source solution. The mixed solution is dried and carbonized to form a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur.

2. The preparation method according to claim 1, characterized in that: In S1, The template material is selected from at least one of aluminum oxide, silicon oxide, carbon material, metal oxide, and polymer material; and / or, the mass ratio of template to sulfur powder is 0.1-2:1; And / or, ball milling conditions: ball to material ratio 10-20:1; rotation speed 400-500 rpm.

3. The preparation method according to claim 1, characterized in that: In S2, when removing the template, the aluminum oxide or silicon oxide template is soaked in a hydrofluoric acid solution for 12-24 hours; after soaking, it is repeatedly rinsed with deionized water until the washing solution is neutral to remove the residual acid solution.

4. The preparation method according to claim 1, characterized in that: S3 includes the following steps: S31, dissolving sulfide electrolyte powder in an organic solvent to obtain a sulfide electrolyte solution; S32. Add the sulfide electrolyte solution dropwise onto the porous sulfur prepared in S2, impregnate the sulfide electrolyte solution into the pores of the porous sulfur, heat at 140-180° C. for 3-5 hours under vacuum, so that the sulfide electrolyte solution enters the pores of the porous sulfur to form sulfide electrolyte-coupled integrated 3D sulfur.

5. The preparation method according to claim 1, characterized in that: Step S4 includes the following steps: S41, dispersing the sulfide electrolyte coupled integrated 3D sulfur in an organic solvent to prepare a sulfur precursor solution; dissolving a carbon source in an organic solvent to prepare a carbon source solution; S42, mixing the carbon source solution and the sulfur precursor solution uniformly, and drying to obtain a carbon source-sulfur complex; S43. Carbonizing the carbon source-sulfur complex under an inert atmosphere to obtain carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur.

6. A carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing a carbon-encapsulated sulfide electrolyte coupled integrated 3D sulfur composite positive electrode, characterized in that: The steps include: Step 1, under a protective atmosphere, mixing and grinding the carbon encapsulated sulfide electrolyte coupled integrated 3D porous sulfur and the sulfide electrolyte according to claim 6 in a mass ratio of 40-60:10-20; separating the ball milling material after the ball milling is completed; Step 2: Add conductive carbon to the material after removing the abrasive in step 1 and grind it to obtain the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite positive electrode.

8. The preparation method according to claim 7, characterized in that: In step 1 and step 2, the grinding method is roller milling plus ball milling, specifically, roller milling for 1-2 hours; stop for 5-10 minutes, a total of 3-6 cycles; then ball milling for 30-60 minutes; stop for 5-10 minutes; ball milling for a total of 8-10 cycles.

9. The preparation method according to claim 7, characterized in that: The mass ratio of the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, sulfide electrolyte, and conductive carbon is: 40~60:10~20:30~40.

10. A carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite positive electrode prepared by the preparation method according to any one of claims 7 to 9.

Images