Carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, preparation method and application

Abstract

The present invention relates to the field of new energy technology, specifically a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, a preparation method, and applications thereof. The preparation method comprises the following steps: S1, ball-milling a template and sulfur powder to uniformly mix to form a mixed powder; S2, heating the mixed powder to a certain temperature to melt the sulfur, stirring it in the molten state for a period of time to allow the molten sulfur to fill the pores of the template, and cooling it to form a composite of porous sulfur and the template; removing the template to obtain porous sulfur; S3, impregnating a sulfide electrolyte solution into the pores of the porous sulfur, and drying to form a sulfide electrolyte coupled integrated 3D sulfur; S4, dispersing the sulfide electrolyte coupled integrated 3D sulfur with an organic solution, mixing it with a carbon source solution, and drying the mixed solution to carbonize it to form the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur. This system solves the problems of poor conductivity and severe volume expansion of sulfur positive electrodes.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, a preparation method and applications thereof. Background Art

[0002] Sulfur, as the cathode material for lithium-sulfur batteries, boasts a theoretical specific capacity of 1675 mAh / g and a theoretical energy density of 2600 Wh / kg, far exceeding existing lithium-ion battery cathode materials. However, sulfur cathodes face numerous challenges in practical applications, such as poor conductivity, large volume expansion, and the "shuttle effect" of polysulfides, which have severely hampered the commercialization of lithium-sulfur batteries.

[0003] To address the above issues, existing technologies mainly focus on three strategies:

[0004] 1. Porous structure construction: Porous sulfur frameworks are designed through template methods and self-assembly to increase active material loading, buffer volume strain, and shorten ion transport pathways. However, these methods often face problems such as uneven pore distribution, poor structural stability, and complex processes, making them difficult to scale up.

[0005] 2. Conductive / functional material composites: Sulfur is composited with conductive materials such as carbon nanotubes and graphene, or functional materials such as metal oxides and polymers, to enhance electrode conductivity and physically / chemically anchor LiPSs. However, the weak interfacial bonding between sulfur and the carrier easily leads to the shedding of active materials, and it is difficult to effectively inhibit the diffusion of LiPSs during long cycles.

[0006] 3. Interface engineering modification: Introducing polar coatings or solid electrolyte interfaces (SEI) to enhance the adsorption capacity of LiPSs. However, the introduction of additional interface layers may increase the internal resistance of the electrode, reduce the mobility of lithium ions, and even induce side reactions, deteriorating the battery kinetics.

[0007] Although the above research has made certain progress, the following bottlenecks still exist: the preparation of porous structures relies on complex template etching or high-temperature treatment, which is costly; the interface compatibility between the conductive / functional components and sulfur is poor, and the composite structure is prone to stress concentration and cracking during cycling; modification methods to suppress the "shuttle effect" often sacrifice ion / electron transmission efficiency, making it difficult to balance high capacity and long-cycle stability.

[0008] At present, research on the modification of sulfur cathodes mainly focuses on the following aspects:

[0009] 1. By constructing a porous structure, the specific surface area of the electrode is increased, the utilization rate of the active material is improved, and the volume expansion of sulfur during the charge and discharge process is buffered;

[0010] Second, compound sulfur 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 inhibiting the shuttling of polysulfides;

[0011] 3. Modify the interface of the sulfur positive electrode by introducing polar materials or surface coatings to adsorb polysulfides and reduce their dissolution and diffusion in the electrolyte.

[0012] Despite progress, existing sulfur cathode modification methods still have some shortcomings. For example, the preparation process for porous structures is complex and costly, and the uniformity and stability of the pore structure are difficult to control. During the preparation of composite materials, the bonding strength between sulfur and conductive or functional materials is insufficient, resulting in limited improvements in electrode conductivity and stability. In interfacial modification methods, the modified materials used may adversely affect other battery properties, such as increasing the battery's internal resistance and reducing its charge and discharge efficiency.

[0013] Therefore, developing a simple, efficient and low-cost sulfur cathode modification method to overcome the shortcomings of existing technologies and improve the conductivity, stability and cycle performance of the sulfur cathode is of great significance for promoting the commercial application of lithium-sulfur batteries. Summary of the Invention

[0014] In view of this, the present invention proposes a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur, a preparation method and an application. Through multi-level structural design and material coordinated optimization, the system solves the problems of poor conductivity and severe volume expansion of the sulfur positive electrode, slow ion transfer caused by poor contact between the particles of the all-solid-state composite positive electrode prepared thereby, and slow kinetics of the all-solid-state lithium-sulfur battery.

[0015] The technical solutions provided by the present invention are as follows:

[0016] A method for preparing carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur comprises the following steps:

[0017] S1. Mix the template and sulfur powder by ball milling to form a mixed powder;

[0018] S2. The mixed powder is heated to melt the sulfur, stirred in a molten state to allow the molten sulfur to fill the pores of the template, and cooled to form a complex of porous sulfur and the template; the template is removed to obtain porous sulfur; (the treated porous sulfur is dried in an oven to obtain a dry porous sulfur product, the drying temperature is: 60-80 ° C, the time is: 6-12 hours); S3. A sulfide electrolyte solution is impregnated into the pores of the porous sulfur, and after drying, a sulfide electrolyte coupled integrated 3D sulfur is formed; S4. Carbon encapsulation: The sulfide electrolyte coupled 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 a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur.

[0019] In S1, the template material is selected from at least one of aluminum oxide, silicon oxide, carbon materials, metal oxides or polymer materials.

[0020] And / or, in S1, the mass ratio of the template to the sulfur powder is 0.1-2:1.

[0021] And / or, in S1, the ball milling conditions are: ball-to-material ratio 10-20:1, rotation speed 400-500 rpm.

[0022] In S2, when removing the template, for aluminum oxide or silicon oxide templates, soak them in hydrofluoric acid (HF) solution for a period of 12-24 hours, depending on the thickness and pore size of the template. After soaking, rinse repeatedly with deionized water until the solution is neutral to remove any residual acid.

[0023] In S2, the mixed powder is heated to 115-130° C. and stirred mechanically at a speed of 300-500 rpm for 30-60 minutes.

[0024] In S2, the cooling is natural cooling.

[0025] In S3, the sulfide electrolyte is Li6PS5Cl, and the preparation method of Li6PS5Cl comprises the following steps:

[0026] (1) LiCl, P2S5 and Li5S were weighed according to the stoichiometric ratio and ball milled to obtain LPSCl powder, which was recorded as M-LPSCl.

[0027] (2) The M-LPSCl powder is heated to 400-600°C at a rate of 2-5°C / min under vacuum and sintered for 10-12 hours to obtain sulfide electrolyte powder.

[0028] In step (1), LiCl, P2S5 and Li5S are weighed according to the stoichiometric ratio, sealed in a zirconium can, and ball milled using a high-energy planetary ball mill at 400-500 rpm for 10-24 hours.

[0029] In step (2), the M-LPSCl powder is placed in a crucible covered with a glassy carbon lid, vacuum-sealed in a quartz tube, sintered, and annealed to obtain the final Li6PS5Cl electrolyte powder.

[0030] S3 includes the following steps:

[0031] S31, dissolving the sulfide electrolyte powder in an organic solvent (such as an anhydrous ethanol solution) to obtain a sulfide electrolyte solution, which is recorded as S-LPSCl;

[0032] 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, and heat at 140-180° C. under vacuum for 3-5 hours to allow the sulfide electrolyte solution to enter the pores of the porous sulfur to form sulfide electrolyte-coupled integrated 3D sulfur.

[0033] All the above processes were carried out in a glove box filled with argon.

[0034] Step S4 includes the following steps:

[0035] S41, dispersing the sulfide electrolyte coupled integrated 3D sulfur in an organic solvent (such as an anhydrous ethanol solution) to prepare a sulfur precursor solution; dissolving a carbon source in an organic solvent (such as an anhydrous ethanol solution) to prepare a carbon source solution;

[0036] S42, adding the carbon source solution to the sulfur precursor solution, stirring and mixing to form a mixed solution, and drying to obtain a carbon source-sulfur complex;

[0037] S43. The carbon source-sulfur complex is carbonized under an inert atmosphere to obtain carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur (C@S-LPSCl).

[0038] Step S41: Select from sucrose or polyvinylpyrrolidone (PVP).

[0039] 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.

[0040] In step S43, the carbonization conditions are: heating rate: 5-10°C / min, temperature: 600-900°C, and holding time: 1-3h.

[0041] <Second Aspect>

[0042] The present invention also provides a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur prepared by the preparation method described above.

[0043] <Third Aspect>

[0044] The present invention provides a method for preparing a carbon-encapsulated sulfide electrolyte coupled integrated 3D sulfur composite positive electrode, comprising the following steps:

[0045] Step 1: Under a protective atmosphere, the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur and the sulfide electrolyte are mixed and ground in a mass ratio of 40-60:10-20 (ball-to-material ratio of 2:1-5:1, rotation speed of 300-400 rpm); after the ball milling, the ball and material are separated;

[0046] Step 2: Add conductive carbon to the material after removing the abrasive in step 1 and grind (ball-to-material ratio of 2:1-5:1, rotation speed of 400-500 rpm) to obtain the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite positive electrode.

[0047] In step 1 and step 2, the grinding method is roller milling plus ball milling, specifically, roller milling for 1-2 hours; stopping for 5-10 minutes, for a total of 3-6 cycles; then ball milling for 30-60 minutes; stopping for 5-10 minutes; and ball milling for a total of 8-10 cycles.

[0048] The carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur (C@S-LPSCl), sulfide electrolyte, and conductive carbon have a mass ratio of 40~60:10~20:30~40.

[0049] The sulfide electrolyte includes Li 5.5 PS 4.5 X 1.5 、Li 10 MP2S 12 , 80Li2S·20P2S5, at least one or more thereof; wherein, 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.

[0050] Preferably, the sulfide electrolyte is Li 5.5 P 4.5 Cl 1.5 The conductivity is 8-10 mS / cm.

[0051] The shielding gas is argon.

[0052] The conductive carbon includes at least one of nano-carbon fiber (VGCF), carbon black, SuperP, conductive graphite, and carbon nanotubes.

[0053] The carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite positive electrode (C@S-LPSCl composite positive electrode) prepared by the preparation method described above also falls within the scope of protection of the present invention.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention provides a composite material composed of porous sulfur filled with electrolyte and then encapsulated in a carbon layer, and its preparation method. The porous sulfur's pore structure and the carbon layer's encapsulation effectively enhance the electrolyte's dispersion, ensuring sufficient contact between the electrolyte and the sulfur's interior and exterior, thereby significantly improving ion transport efficiency. Furthermore, the carbon layer's encapsulation effectively inhibits the dissolution and diffusion of polysulfides, reducing the "shuttle effect," thereby enhancing the battery's cycling stability and capacity retention. Furthermore, the carbon layer's superior conductivity compared to sulfur significantly improves the overall conductivity, thereby enhancing the battery's rate capability and charge-discharge efficiency. The porous sulfur's pore structure also buffers sulfur volume expansion during charge and discharge, reducing mechanical stress in the electrode material and extending the battery's cycle life. The composite material also provides more active sites, increasing sulfur utilization and thus improving the battery's energy density. Finally, the carbon layer's encapsulation enhances the porous sulfur's structural stability, reduces physical loss of sulfur during charge and discharge, and further improves the battery's long-term cycling performance. This composite material has broad application prospects in lithium-sulfur batteries, effectively addressing the challenges associated with pure sulfur cathodes and promoting the development of lithium-sulfur battery technology.

[0056] 2. The present invention also provides a C@S-LPSCl composite cathode, which is prepared by mechanically ball-milling 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 this method has an initial cycle capacity of 1400 mAhg -1 The capacity and high rate are maintained at 508mAhg at 1C -1 It also has super cycle stability with a capacity retention rate of 91%, and its rate performance is also improved.

[0057] 3. A combination of ball milling and tumble milling was employed to prepare the C@S-LPSCl composite cathode. Tumble milling ensures maximum contact between the sulfur and sulfide electrolyte and the milling media beads, improving mixing efficiency and scalability. Ball milling provides high-energy impact, disrupting the gradient distribution caused by physical aggregation of the three components. Tumble milling, however, can result in uneven distribution of the conductive carbon within and outside the composite. Combining the two ensures that the conductive carbon is fully distributed throughout the composite. In general, pre-mixing followed by mixing with the conductive carbon promotes more complete distribution of the electrolyte and conductive carbon within the active material, ensuring efficient ion and electron transport within the composite cathode. Furthermore, step-by-step mixing provides the opportunity to monitor particle size changes and mixing levels, facilitating comprehensive evaluation and design of the composite cathode. In large-scale production, the yield of material from each ball milling stage can be effectively controlled, improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0059] Figure 1 This is the XRD pattern of the raw materials S and carbon C required for preparing C@S-LPSCl material in Preparation Example 1;

[0060] Figure 2 is a Raman spectrum of the S / C material and pure S material prepared in comparative preparation example 1;

[0061] Figure 3 is the LSV curve of the S / C material and pure S material prepared in comparative preparation example 1;

[0062] Figure 4 is a cyclic voltammetry (CV) graph of a full battery assembled with the materials prepared in Example 1;

[0063] Figure 5 This is an in-situ impedance test of the discharge process of a full battery assembled with the materials prepared in Example 1; wherein the horizontal axis: Z' / ohm means the real part of the impedance / ohm; the vertical axis: It means the imaginary (negative) part of impedance / ohm;

[0064] Figure 6 The full-cell impedance test is performed on the full-cell assembled with the materials prepared in Example 1 and Comparative Example 2; wherein the horizontal axis: Z' / ohm means the real part of the impedance / ohm; the vertical axis: It means the imaginary (negative) part of impedance / ohm;

[0065] Figure 7 1 is a rate performance diagram of Example 1, Comparative Example 1 and Comparative Example 2;

[0066] Figure 8 This is a comparison chart of the long cycle performance of full batteries assembled with the composite positive electrodes of Example 1 and Comparative Examples 1-6;

[0067] Figure 9 It is a first cycle charge and discharge curve diagram of the full battery assembled with the composite positive electrode of Example 1 and Comparative Example 4. DETAILED DESCRIPTION

[0068] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0069] In the following examples 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.

[0070] Figure 1 The XRD patterns of the carbonized raw materials sulfur powder and sucrose show that the raw materials are phase pure and have good crystallinity.

[0071] Sucrose carbonization conditions:

[0072] Preparation Example 1 Preparation of C@S-LPSCl material

[0073] 1. Preparation of porous sulfur

[0074] (1) Mixing the template and sulfur powder: Weigh 0.5g of alumina template material (pore size 50-200nm, purity ≥99%) and 1.0g of sulfur powder, place them in a planetary ball mill, and ball mill them at room temperature for 2 hours at a ball-to-material ratio to fully mix the template and sulfur powder. The ball milling beads are zirconium oxide ball milling beads; the ball milling beads have a diameter of 1mm-10mm and the ball-to-material ratio is 10:1. (2) Melting and filling: Place the powder mixed in step (1) in a crucible and 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 rpm for 40 minutes to ensure that the sulfur is fully filled into the pores of the template.

[0075] (3) Cooling and solidification: The template filled with sulfur is taken out from the molten state and naturally cooled to room temperature, so that the sulfur solidifies in the pores of the template to form a composite of porous sulfur and the template.

[0076] (4) Template removal: Soak the complex in a 10% (molar concentration) HF solution for 16 hours. After soaking, rinse repeatedly with deionized water until the washing solution becomes neutral to remove residual acid.

[0077] (5) Drying treatment: The material treated in step (4) was dried in an oven at 60°C for 10 hours to obtain a dry porous sulfur product.

[0078] 2. Preparation of sulfide electrolyte Li6PS5Cl

[0079] (1) Mechanical ball milling: LiCl, P2S5, and Li2S were weighed according to the stoichiometric ratio, sealed in a zirconium can, and ball milled at 450 rpm for 16 h using a high-energy planetary ball mill to obtain LPSCl powder, which was designated as M-LPSCl. The ball milling beads used were zirconia ball milling beads with a diameter of 1 mm to 10 mm, and the ball-to-material ratio was 10:1.

[0080] (2) Heat treatment: The obtained M-LPSCl powder was placed in a crucible with a glassy carbon lid, vacuum-sealed in a quartz tube, and sintered and annealed at 500°C at a rate of 2°C / min for 10 h. The powder was further refined by ball milling (zirconia balls were used; the diameter of the balls was 1 mm to 10 mm, and the ball-to-material ratio was 10:1) to obtain the final powder, namely, Li6PS5Cl electrolyte powder.

[0081] 3. Sulfide electrolyte coupled integrated 3D sulfur

[0082] (1) Solution preparation: Disperse 0.2 g of Li6PS5Cl powder in 2 mL of anhydrous ethanol to obtain a sulfide electrolyte solution, which is recorded as S-LPSCl solution.

[0083] (2) Electrolyte solution impregnation: Add the S-LPSCl solution dropwise onto the porous sulfur prepared in step 1, and allow the solution to fully enter the pores through vacuum-assisted capillary action. (The mass ratio of S-LPSCl to porous sulfur is 1:1)

[0084] (3) Drying treatment: The solvent was evaporated by heating at 150 °C for 4 h under vacuum, so that S-LPSCl was uniformly and tightly filled in the porous sulfur pores, forming a sulfide electrolyte coupled integrated 3D sulfur.

[0085] All processes were carried out in an argon-filled glove box.

[0086] 4. Carbon encapsulated sulfide electrolyte coupled integrated 3D porous sulfur

[0087] (1) Preparation of sulfur precursor solution: Weigh 600 mg of sulfide electrolyte coupled integrated 3D porous sulfur powder, add an appropriate amount of ethanol (the concentration of sulfide electrolyte coupled integrated 3D porous sulfur powder is 0.1 g / mL), and mechanically stir it at 500 rpm at room temperature to fully disperse it to form a uniform sulfur precursor solution.

[0088] (2) Preparation of carbon source solution: Weigh 600 mg of sucrose and dissolve it in an appropriate amount of ethanol to prepare a carbon source solution (the sucrose concentration in this solution is 0.05 g / mL).

[0089] (3) Preparation of carbon source-sulfur complex: The carbon source solution was slowly added to the sulfur precursor solution while stirring to ensure that the two were thoroughly mixed (the mass ratio of sulfide electrolyte coupled integrated 3D porous sulfur powder and sucrose in the mixed solution was 1:1). The mixed solution was dried in an oven at 60°C for 8 hours until the solvent was completely evaporated to obtain a carbon source-sulfur complex.

[0090] (4) Carbonization: The dried carbon source-sulfur composite was placed in a tube furnace and carbonized under nitrogen protection. The temperature was raised to 800°C at a heating rate of 5°C / min and maintained at this temperature for 2 hours to allow the carbon source to be fully carbonized to form a carbon layer. After carbonization, the furnace temperature was allowed to cool naturally to room temperature, and the product was removed to obtain carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur (C@S-LPSCl).

[0091] Comparative Preparation Example 1

[0092] The difference between this comparative preparation example and Preparation Example 1 is that sulfide electrolyte is directly used for carbon encapsulation.

[0093] The specific steps are as follows:

[0094] (1) Preparation of sulfur precursor solution: Weigh 600 mg of sulfide electrolyte Li6PS5Cl, add an appropriate amount of anhydrous ethanol (the concentration of sulfide electrolyte Li6PS5Cl is 0.1 g / mL), and fully disperse it by mechanical stirring at 500 rpm at room temperature to form a uniform sulfur precursor solution;

[0095] (2) Preparation of carbon source solution: same as in Preparation Example 1;

[0096] (3) Preparation of carbon source-sulfur complex: Slowly add the carbon source solution to the sulfur precursor solution while stirring to ensure that the two are thoroughly mixed (the mass ratio of sulfur to sucrose in the mixed solution is 1:1). The mixed solution is dried 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).

[0097] (4) Carbonization: Same as Preparation Example 1.

[0098] Figure 2 This is a Raman spectrum of the carbon source-sulfur composite S / C material and 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 shift peak of sulfur, but due to the encapsulation of carbon, part of the shift peak of sulfur disappears and is replaced by the characteristic peak of carbon.

[0099] 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 indicates that sulfur itself is an insulator, but carbon encapsulation can significantly improve the material's electronic conductivity, by more than 20 orders of magnitude compared to elemental sulfur. This is of great benefit to the rate capability and effective utilization of sulfur cathodes.

[0100] Comparative Preparation Example 2

[0101] 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:

[0102] 1. Preparation of porous sulfur: same as Preparation Example 1;

[0103] 2. Preparation of sulfide electrolyte Li6PS5Cl: same as Preparation Example 1;

[0104] 3. Carbon encapsulation of porous sulfur;

[0105] (1) Preparation of sulfur precursor solution: Weigh 600 mg of Li6PS5Cl electrolyte powder and add an appropriate amount of ethanol to obtain a sulfide electrolyte solution, which is recorded as S-LPSCl solution (electrolyte powder concentration is 0.1 g / mL). Mechanical stirring is carried out at room temperature at 500 rpm to fully disperse it and form a uniform sulfur precursor solution.

[0106] (2) Preparation of carbon source solution: Weigh 600 mg of sucrose and dissolve it in an appropriate amount of ethanol to prepare a carbon source solution (the sucrose concentration in this solution is 0.05 g / mL).

[0107] (3) Preparation of carbon source-sulfur complex: The carbon source solution was slowly added to the sulfur precursor solution, stirring while adding to ensure that the two were thoroughly mixed (the mass ratio of Li6PS5Cl electrolyte powder to sucrose in the mixed solution was 1:1). The mixed solution was dropped onto the porous sulfur and the solution was fully absorbed into the pores by vacuum-assisted capillary action. The mixture was dried in an oven at 60°C for 8 hours until the solvent was completely evaporated, obtaining a dry carbon source-sulfur complex.

[0108] (4) Carbonization: Same as Preparation Example 1.

[0109] Comparative Preparation Example 3

[0110] The difference between this comparative preparation example and Preparation Example 1 is that there is only the step of coupling porous sulfur and sulfide electrolysis, and no carbon encapsulation step. The product of this preparation example is sulfide electrolyte coupled integrated 3D porous sulfur powder.

[0111] Example 1 Preparation of C@S-LPSCl composite cathode for sulfide-based all-solid-state lithium batteries

[0112] Step 1: According to the ball-to-material ratio of 20:1, weigh zirconia beads (10 5mm, 20 3mm and the rest 1mm) in a zirconia ball mill, dry them in a 60℃ oven 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 1ppm and the oxygen content is less than 1ppm); 400mg C@S-LPSCl (prepared in Preparation Example 1) and 50mg Li 5.5 PS 4.5 Cl 1.5 Add the mixture to a ball mill and seal it with insulating tape; intermittently roll mill at 200 rpm for 8 h (intermittent milling method: roll mill for 30 min and rest for 5 min); after rolling, transfer the ball mill to a glove box and separate the ball and material;

[0113] Step 2: Add 57 mg of Super P to a mortar and premix with the material separated in Step 1. The mixture is then transferred to a ball mill and intermittently milled at 500 rpm for 10 hours (intermittent milling: mill for 30 minutes followed by a 5-minute rest period). After milling, separate the ball material to obtain a C@S-LPSCl composite cathode.

[0114] Comparative Example 1

[0115] The difference between this comparative example and Example 1 is that the C@S-LPSCl in step 1 is replaced by the substance prepared in Comparative Preparation Example 1. The other steps are consistent with Example 1.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 1 is that the C@S-LPSCl in step 1 is replaced by the substance prepared in Comparative Preparation Example 2. The other steps are consistent with Example 1.

[0118] Comparative Example 3

[0119] The difference between this comparative example and Example 1 is that the C@S-LPSCl in step 1 is replaced by the substance prepared in Comparative Preparation Example 3. The other steps are consistent with Example 1.

[0120] Comparative Example 4

[0121] The difference between this comparative example and Example 1 is that the C@S-LPSCl in step 1 is replaced by pure sulfur without any treatment. The other steps are the same as those in Example 1.

[0122] Comparative Example 5

[0123] According to the ball-to-material ratio of 20:1, zirconia beads (10 5 mm, 20 3 mm and the rest 1 mm) were weighed and placed in a zirconia ball mill. After drying in a 60 °C oven for four hours, the beads were transferred to an argon glove box (the water content and oxygen content of the glove box argon were less than 1 ppm and less than 1 ppm respectively). 400 mg C@S-LPSCl (prepared in Preparation Example 1) and 50 mg Li 5.5 PS 4.5 Cl 1.5 The mixture was added together with 57 mg of Super P into a ball mill jar and sealed with insulating tape. The mixture was intermittently milled at a speed of 200 rpm for 8 h (intermittent ball milling method: milling for 30 min and resting for 5 min). After the milling was completed, the ball mill jar was transferred to a glove box and the ball material was separated to obtain a C@S-LPSCl composite positive electrode.

[0124] Comparative Example 6

[0125] According to the ball-to-material ratio of 5:1, zirconia beads (10 5mm, 20 3mm and the rest 1mm) were weighed and placed in a zirconia ball mill. After drying in a 60°C oven for four hours, the beads were transferred to an argon glove box (the water content and oxygen content of the glove box argon were less than 1 ppm and less than 1 ppm respectively). 400 mg C@S-LPSCl (prepared in Preparation Example 1) and 50 mg Li 5.5 PS 4.5 Cl 1.5 The mixture was added together with 57 mg of Super P into a ball milling jar and sealed with insulating tape; the mixture was intermittently ball milled at a speed of 500 rpm for 10 h (intermittent ball milling method: ball milling for 30 min and rest for 5 min). After the ball milling was completed, the ball milling jar was transferred to a glove box and the ball material was separated to obtain a C@S-LPSCl composite positive electrode.

[0126] Performance Testing

[0127] Test method: 10 mg of the composite positive electrode and 100 mg of the electrolyte (Li 5.5 PS 4.5 Cl 1.5) were pressed into sheets in a pressure mold and assembled into a full battery with a lithium-silicon alloy negative electrode (indium foil, thickness 200μm, lithium foil, thickness 50μm), the negative electrode sheet was 8cm wide and 10cm long, and was attached to the negative electrode collector, which was a 10μm copper foil. The charge and discharge rate tested was 0.1C-2C, and the charge and discharge cut-off voltage was relative to the Li-Si / Li + The charge and discharge capacities mentioned in the present invention are all specific capacities calculated based on the positive electrode S-based composite active material.

[0128] Figure 4 is a cyclic voltammetry (CV) graph of a full battery assembled with the materials prepared in Example 1; Figure 4 Showing the clear redox peaks and corresponding redox potentials of lithium-sulfur batteries.

[0129] Figure 5 This is an in-situ impedance test of the discharge process of a full battery assembled with the materials prepared in Example 1. The figure shows that the formation of lithium polysulfide during the discharge process (1.7V→1V) increases the resistance of the battery. However, due to the porous sulfur-coupled electrolyte and carbon encapsulation, the volume expansion of the positive electrode triggers contact between the carbon and electrolyte with the polysulfide, thereby improving the electron / ion conduction between the interior of the composite positive electrode and the electrolyte and reducing the battery resistance.

[0130] Figure 6 This is a full-cell impedance test performed on full cells assembled with materials prepared in Example 1 and Comparative Example 2; Figure 6 The full-cell cathode impedance and ion diffusion of Example 1 are significantly superior to those of Comparative Example 2. This is primarily due to the C@S-LPSCl material coupling the electrolyte through the porous sulfur interior, which improves contact between the electrolyte and sulfur, establishes a more efficient ion transport path, and thus optimizes ion transport. Consequently, the composite cathode exhibits low bulk impedance and high ion diffusion capacity.

[0131] Figure 7 Figure 1 shows the rate performance of Example 1, Comparative Example 1, and Comparative Example 2. The results show that the sulfur cathode in Example 1, through its porous sulfur structure design, sulfide electrolyte coupling, and carbon encapsulation, exhibits higher capacity and rate performance. However, the performance of Comparative Example 1 (without porous sulfur preparation and electrolyte coupling) and Comparative Example 2 (without electrolyte coupling) is lower. This is attributed to the lack of coupling between the sulfide electrolyte and sulfur, resulting in insufficient ion transport pathways.

[0132] Figure 8This figure compares the long-cycle performance of full batteries assembled with the composite cathodes of Example 1 and Comparative Examples 1-6. This figure shows that the composite cathode prepared by optimized ball milling with a porous design, electrolyte coupling, and carbon encapsulation exhibits higher capacity and cycling stability. This is because the porous design and carbon encapsulation mitigate sulfur volume expansion and stabilize the cathode structure during cycling. Electrolyte coupling enhances lithium ion transport and increases sulfur utilization and capacity contribution. Finally, the combined roller milling and ball milling method allows for more complete contact and uniform dispersion of solid particles within the composite cathode, ensuring efficient ion / electron transport pathways.

[0133] Figure 9 The first cycle charge-discharge curves for full cells assembled with the composite cathodes of Example 1 and Comparative Example 4 are shown. This graph shows that the untreated sulfur phase has greater polarization and lower sulfur utilization than the modified C@S-LPSCl. This is because the untreated sulfur in the composite cathode has only solid-solid contact with the conductive carbon and electrolyte. It lacks the strong coupling between the porous sulfur and the electrolyte and the stable encapsulation by the carbon, as seen in the modified sulfur. Therefore, volume expansion during cycling exacerbates the unstable solid-solid contact, leading to significant impedance between the sulfur and the electrolyte and increased polarization. This results in ineffective utilization of the sulfur cathode, manifested as low charge-discharge capacity.

[0134] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite cathode, characterized in that: The steps include: Step 1: Under a protective atmosphere, the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur and the sulfide electrolyte are mixed and ground in a mass ratio of 40-60:10-20; after the ball milling, the balls and materials are separated; Step 2: Adding conductive carbon to the material after removing the abrasive in step 1 and grinding it to obtain the carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur composite positive electrode; In step 1 and step 2, the grinding method is roller milling plus ball milling, specifically, roller milling for 1-2 hours, resting for 5-10 minutes, for a total of 3-6 cycles; then ball milling for 30-60 minutes, resting for 5-10 minutes, for a total of 8-10 cycles; The carbon-encapsulated sulfide electrolyte coupled integrated 3D porous sulfur is prepared by a method comprising the following steps: S1. Mix the template and sulfur powder by ball milling to form a mixed powder; S2, heating the mixed powder until the sulfur is melted, stirring in the 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; 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 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, 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 2, 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 becomes neutral to remove residual acid.

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, and heat at 140-180° C. under vacuum for 3-5 hours to allow the sulfide electrolyte solution to enter 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. The preparation method according to claim 1, 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.

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

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