High-loading composite sulfur cathode, preparation method thereof and lithium-sulfur battery

Abstract

The application discloses a high-load composite sulfur positive electrode, a preparation method thereof and a lithium-sulfur battery, and belongs to the technical field of lithium batteries. The high-load composite sulfur positive electrode comprises a current collector, a carbon / sulfur positive electrode layer located on the current collector, the carbon / sulfur positive electrode layer comprising a carbon-sulfur composite material, and a functional polymer layer located on the carbon / sulfur positive electrode layer, the functional polymer layer being formed by a polymer containing an electron-deficient group. The application uses a polymer with a strong electron-deficient group as a positive electrode protective coating, uses the inherent electron-deficient center of the polymer to adsorb anions and repel cations. The effect of adsorbing anions can prevent active substances from passing through the polymer layer to shuttle to the negative electrode, causing capacity loss. On the other hand, the effect of repelling cations can promote the dissociation of lithium ions from anions in the polymer layer, which is beneficial to lithium ion conduction. Compared with the prior art, the application solves the problem of cracking of the high-load composite sulfur positive electrode while still maintaining good ion conductivity and battery capacity.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, and specifically relates to a high-load composite sulfur cathode, its preparation method, and a lithium-sulfur battery. Background Technology

[0002] Lithium-sulfur batteries, with a theoretical energy density of 2600 Wh / kg, are considered one of the most promising high-energy-density batteries. However, current research uses low sulfur cathode loading, resulting in a high proportion of inactive materials in the overall battery weight and consequently, lower actual energy density. To advance lithium-sulfur battery technology from basic laboratory research to practical application, it is necessary to increase the sulfur loading per unit area on the surface of a single current collector, increase the proportion of active materials in the battery, and reduce the weight of inactive materials, thereby unlocking the battery's energy density.

[0003] Due to the insulating properties of elemental sulfur, the proportion of conductive carbon required in sulfur cathodes is typically higher than in traditional lithium-ion batteries. Furthermore, the high specific surface area and poor compaction of conductive carbon make the dried electrode prone to cracking when increasing the cathode load (i.e., increasing the cathode coating thickness). This negatively impacts battery uniformity, stability, and structural integrity. A common approach to address this is to add more binder. However, due to the insulating properties of binders, excessive binder coating on the carbon-sulfur composite particles hinders electron conduction between particles, preventing the formation of a conductive network in the thick electrode. In some areas, especially those far from the current collector in the thick sulfur cathode, the active material cannot gain or lose electrons through the network formed by the conductive agent, resulting in low utilization of the active material, insufficient capacity release, and a failure to improve battery energy density.

[0004] In existing technologies, researchers have proposed a self-supporting porous current collector scheme, using a self-supporting porous current collector (such as a carbonized porous fiber membrane) and then forming a composite self-supporting cathode through sulfur melt loading, thereby achieving high loading without the use of binders. However, this scheme suffers from small synthesis area, incompatibility with existing commercial battery assembly equipment, complex preparation process, inability to scale up, and low compaction density of the loose porous structure, resulting in excessively large battery volume. Another approach involves adding a polymer coating containing inorganic fillers to the cathode surface. However, existing polymer coatings have limited effectiveness in blocking the shuttle effect of active materials, requiring the addition of inorganic fillers as Lewis acid sites to adsorb polysulfide compounds, which increases process difficulty and cost. Furthermore, existing polymer coatings may hinder lithium-ion transport; therefore, conventional methods involve adding lithium salts to the polymer precursor to improve ionic conductivity. However, lithium salts are hygroscopic and expensive, hindering practical production, processing, and application.

[0005] Therefore, there is an urgent need in this field to develop a technical solution that can ensure the structural integrity of the high-load sulfur cathode, promote ion transport, effectively suppress the shuttle effect, and be compatible with existing commercial battery manufacturing processes. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the main objective of this invention is to provide a high-load composite sulfur cathode, its preparation method and lithium-sulfur battery. The high-load composite sulfur cathode can effectively solve problems such as electrode cracking, ion transport obstruction and shuttle effect under high sulfur load.

[0007] To achieve the above objectives, the present invention provides a high-loaded composite sulfur cathode, comprising:

[0008] current collector;

[0009] A carbon / sulfur cathode layer located on the current collector, the carbon / sulfur cathode layer comprising a carbon-sulfur composite material;

[0010] And a functional polymer layer located on the carbon / sulfur cathode layer, the functional polymer layer being formed of a polymer containing electron-deficient groups.

[0011] Furthermore, the polymer containing electron-deficient groups is selected from one or more of polypentafluorostyrene, poly(ethylene-alt-maleic anhydride), poly(4-chlorostyrene), or poly(4-bromostyrene).

[0012] Furthermore, the thickness of the functional polymer layer is 30~70μm.

[0013] Furthermore, the sulfur loading of the carbon / sulfur cathode layer is 6~12 mg / cm³. 2 .

[0014] In another aspect, the present invention provides a method for preparing the aforementioned high-loaded composite sulfur cathode, comprising the following steps:

[0015] A slurry is prepared by mixing carbon-sulfur composite material, conductive agent, binder and first solvent;

[0016] The slurry is coated onto the current collector, dried to form a carbon / sulfur positive electrode layer, and then rolled to obtain a carbon / sulfur positive electrode sheet.

[0017] A polymer solution is prepared by dissolving a polymer containing electron-deficient groups in a second solvent.

[0018] The polymer solution is coated onto the surface of the carbon / sulfur cathode sheet, and then dried to form a functional polymer layer, thus obtaining the high-load composite sulfur cathode.

[0019] Furthermore, in the polymer solution, the mass concentration of the polymer containing electron-deficient groups is 25-50%.

[0020] Furthermore, the second solvent is selected from chlorobenzene and / or chloroform.

[0021] Furthermore, the pressure of the rolling process is 4~8 MPa.

[0022] Furthermore, the drying process is carried out at a temperature of 90~110℃ for a time of 6~24h.

[0023] Furthermore, the carbon-sulfur composite material is prepared using a method comprising the following steps:

[0024] Elemental sulfur was mixed with conductive carbon material and then subjected to a first ball milling process.

[0025] The material after the first ball milling treatment is sintered under sealed conditions;

[0026] The sintered material is subjected to a second ball milling process to obtain the carbon-sulfur composite material.

[0027] Furthermore, the mass ratio of elemental sulfur to conductive carbon material is 1:0.2~0.4.

[0028] Furthermore, the sintering treatment is performed at a temperature of 155~180℃ for 15~20h.

[0029] In another aspect, the present invention provides a lithium-sulfur battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the aforementioned high-load composite sulfur positive electrode.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) This invention solves the cracking problem of high-load sulfur cathodes by introducing a functional polymer layer with high lithium-ion conductivity and anion anchoring properties to reinforce the surface. A polymer with strong electron-deficient groups is used as the cathode protective coating. The inherent electron-deficient centers of the polymer adsorb anions and repel cations. The anion adsorption prevents active materials from shuttling through the polymer layer to the negative electrode, thus preventing capacity loss. On the other hand, the cation repulsion promotes the dissociation of lithium ions from anions in the polymer layer, which is beneficial for lithium-ion conduction. Compared with existing technologies, this invention solves the cracking problem of high-load sulfur cathodes while maintaining good ion conductivity and battery capacity.

[0032] (2) The present invention does not require the use of modified binders that are complex to prepare and expensive, nor does it require the use of self-supporting conductive skeletons that are difficult to prepare on a large scale, thus maintaining compatibility with existing lithium battery manufacturing equipment and processes.

[0033] (3) This invention not only ensures the integrity of the high-load sulfur cathode, but also improves the stability during the processing and charge / discharge process. By utilizing the void structure in the high-load sulfur cathode, the addition of polymers with electron-deficient groups with high ion conductivity increases the ion transport and electrolyte wetting uniformity throughout the electrode, while also playing a role in retaining the electrolyte in the cathode. Attached Figure Description

[0034] Figure 1 A scanning electron microscope image of the surface of the carbon / sulfur positive electrode sheet prepared in Example 1 of the present invention is shown;

[0035] Figure 2 A scanning electron microscope image of the surface of the high-load composite sulfur cathode prepared in Example 1 of the present invention is shown;

[0036] Figure 3 The cycle performance curves of the lithium-sulfur batteries prepared in Example 1 and Comparative Example 1 of the present invention are shown. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; and the reagents and materials described are commercially available unless otherwise specified.

[0038] To achieve the above objectives, a first aspect of the present invention provides a high-loaded composite sulfur cathode, comprising: a current collector;

[0039] A carbon / sulfur cathode layer located on the current collector, the carbon / sulfur cathode layer comprising a carbon-sulfur composite material;

[0040] And a functional polymer layer located on the carbon / sulfur cathode layer, the functional polymer layer being formed of a polymer containing electron-deficient groups.

[0041] This invention uses a functional polymer layer as a protective coating for the positive electrode layer to reinforce the positive electrode surface, ensuring that the structure is not damaged during the processing and cycling of the high-load composite sulfur positive electrode, solving the problem of cracking in the high-load sulfur positive electrode, reducing the amount of binder used during the carbon / sulfur positive electrode layer coating process, and preventing the conductive skeleton path formed by conductive carbon contact from being damaged.

[0042] Furthermore, the functional polymer layer of this invention is formed using a polymer containing electron-deficient groups. By utilizing the inherent electron-deficient centers of the polymer, it adsorbs anions and repels cations. The effect of adsorbing anions can prevent the active substance (S...) from... x 2-Lithium ions shuttle through the functional polymer layer to the negative electrode, causing capacity loss. On the other hand, the cation repulsion effect can promote lithium ion exchange (Li₂O₃). + The dissociation of anions in the functional polymer layer facilitates lithium-ion conduction, achieving a balance between "blocking" and "conducting".

[0043] Meanwhile, the polymer containing electron-deficient groups of the present invention can fill the voids in the high-load composite sulfur cathode. After the battery is filled with electrolyte, the polymer can absorb the electrolyte and swell to form a three-dimensional ion transport channel, which greatly improves the ion conduction inside the thick electrode and the uniformity of electrolyte wetting, and plays the role of retaining the electrolyte in the cathode.

[0044] In a preferred embodiment of the present invention, the polymer containing electron-deficient groups is selected from one or more of polypentafluorostyrene, poly(ethylene-alt-maleic anhydride), poly(4-chlorostyrene), or poly(4-bromostyrene). These polymers with electron-deficient groups exhibit significant electron-deficient characteristics, enabling strong electron-withdrawing properties. Their electron-deficient benzene ring groups and maleic anhydride groups can adsorb polysulfide anions, preventing their shuttle movement, while simultaneously repelling lithium ions and promoting their dissociation and transport. Furthermore, this polymer has a swelling effect on the electrolyte solvent, absorbing the electrolyte and promoting its wetting in high-load, thick electrodes, while also providing a certain degree of positive electrode electrolyte retention.

[0045] To further balance the mechanical properties and ionic conductivity of the high-load composite sulfur cathode, in a preferred embodiment of the present invention, the thickness of the functional polymer layer is 30~70μm.

[0046] In a preferred embodiment of the present invention, the sulfur loading of the carbon / sulfur cathode layer is 6~12 mg / cm³. 2 Based on this invention, by setting a functional polymer layer on the carbon / sulfur cathode layer, the composite sulfur cathode can still ensure that the electrode is not prone to cracking during subsequent processing even under high load conditions.

[0047] A second aspect of the present invention also provides a method for preparing the aforementioned high-loaded composite sulfur cathode, comprising the following steps:

[0048] A slurry is prepared by mixing carbon-sulfur composite material, conductive agent, binder and first solvent;

[0049] The slurry is coated onto the current collector, dried to form a carbon / sulfur positive electrode layer, and then rolled to obtain a carbon / sulfur positive electrode sheet.

[0050] A polymer solution is prepared by dissolving a polymer containing electron-deficient groups in a second solvent.

[0051] The polymer solution is coated onto the surface of the carbon / sulfur cathode sheet, and then dried to form a functional polymer layer, thus obtaining the high-load composite sulfur cathode.

[0052] To further improve the overall performance of the functional polymer layer, in some preferred embodiments of the present invention, the mass concentration of the polymer containing electron-deficient groups in the polymer solution is 25-50%. The second solvent may be selected, for example, from chlorobenzene and / or chloroform. The coating thickness of the polymer containing electron-deficient groups is 50-100 μm. The drying treatment temperature is 90-110°C, and the time is 6-24 h. The molecular weight of the polymer containing electron-deficient groups is greater than 50,000.

[0053] In a preferred embodiment of the invention, the rolling process is carried out at a pressure of 4-8 MPa. High-load carbon / sulfur positive electrode sheets exhibit higher loading (typically above 6 mg / cm³). 2 After drying, cracks may appear on the electrode sheets. If the polymer solution is applied directly without rolling, a large amount of polymer filling will be required, reducing the effective mass ratio of the battery. This invention uses a specifically designed rolling pressure to make the electrode structure more compact and smaller in volume. However, the rolling pressure cannot be too high; a certain gap must be left to allow polymer injection. After the battery is assembled and absorbs the electrolyte, it can serve as an ion transport channel, increasing the release of battery performance.

[0054] In some optional embodiments of the present invention, the conductive agent may be Ketjen Black, or other conventional conductive agents in the art, without particular limitation. The binder may be polyvinylidene fluoride, or other conventional binders in the art, without particular limitation. The first solvent may be N-methylpyrrolidone or other conventional solvents.

[0055] In some preferred embodiments of the present invention, the mass ratio of the carbon-sulfur composite material, the conductive agent, the binder, and the first solvent is 7~9:0.3~1:1:1.5~2.5. The coating thickness of the slurry is 200~500μm. The drying temperature of the slurry is 75~90℃, and the drying time is 10~15h.

[0056] In a preferred embodiment of the present invention, the carbon-sulfur composite material is prepared by a method comprising the following steps:

[0057] Elemental sulfur was mixed with conductive carbon material and then subjected to a first ball milling process.

[0058] The material after the first ball milling treatment is sintered under sealed conditions;

[0059] The sintered material is subjected to a second ball milling process to obtain the carbon-sulfur composite material.

[0060] In a preferred embodiment of the present invention, the mass ratio of elemental sulfur to conductive carbon material is 1:0.2~0.4. Since elemental sulfur is an insulating material, too low a carbon content will lead to reduced sulfur utilization and incomplete capacity release. Since carbon has a high specific surface area, is porous, and has a low density, too high a carbon content will cause high-load electrodes to crack easily and reduce the overall energy density. Controlling the carbon content within the above range can achieve better mechanical and electrical properties.

[0061] In some preferred embodiments of the present invention, the first ball milling treatment is performed at a rotation speed of 20-40 r / min for 3-10 min. The second ball milling treatment is performed at a rotation speed of 10-30 r / min for 5-10 min. The sintering treatment is performed at a temperature of 155-180°C for 15-20 h.

[0062] In a third aspect of the present invention, a lithium-sulfur battery is also provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the aforementioned high-load composite sulfur positive electrode.

[0063] In some preferred embodiments of the present invention, the negative electrode of the lithium-sulfur battery is made of lithium foil or lithium-copper composite strip with a diameter of 50-200 μm, the separator can be made of PP, PE or other materials, and the electrolyte can be ether-based or ester-based electrolyte.

[0064] Furthermore, the present invention also provides an assembly method for the aforementioned lithium-sulfur battery, comprising the following steps:

[0065] Step 1: Stack or wind the high-load composite sulfur cathode, separator, and anode, and then install them into the battery casing;

[0066] Step 2: Inject electrolyte;

[0067] Step 3: Let stand in a vacuum environment for 0.5~3 hours;

[0068] Step 4: Seal the battery and store it at 40~60℃ for 6~48 hours.

[0069] This invention utilizes vacuum settling to expel gases from the porous, high-load positive electrode and polymer coating, promoting electrolyte wetting. After battery sealing, thermal settling is required to promote electrolyte absorption by the polymer layer, accelerating the diffusion of solvent and lithium ions through the polymer chains to achieve a uniform distribution.

[0070] In a preferred embodiment of the present invention, the amount of electrolyte added is 2~5g / Ah.

[0071] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0072] Example 1

[0073] A high-loaded composite sulfur cathode is prepared by the following method:

[0074] Step 1: Preparation of carbon-sulfur composite materials:

[0075] (1) Mix elemental sulfur with Ketjen black and ball mill for 5 min at a ball mill speed of 30 rpm. After removing the mixture, seal and sinter it at a sintering temperature of 165℃ for 18 h. The mass ratio of sulfur to Ketjen black is 1:4.

[0076] (2) The sintered material was ball-milled again for 8 minutes at a speed of 20 rpm to obtain carbon-sulfur composite material (C / S).

[0077] Step 2: Mix the C / S, Ketjenblack, PVDF, and NMP obtained in Step 1, and stir for 6 hours to obtain a slurry. The mass ratio of C / S: Ketjenblack: PVDF: NMP is 8.5:0.5:1:2.

[0078] Step 3: The slurry obtained in Step 2 is coated onto the surface of aluminum foil and then dried in an oven to form a carbon / sulfur cathode layer with a coating thickness of 300 μm, a drying temperature of 80℃, and a drying time of 12 h.

[0079] Step 4: Then, the aluminum foil containing the carbon / sulfur positive electrode layer is rolled to obtain a carbon / sulfur positive electrode sheet. The rolling pressure is 6 MPa.

[0080] Step 5: Mix PFS (polypentafluorostyrene) and CB (chlorobenzene), stir until homogeneous to obtain a polymer solution, coat it onto the surface of the above carbon / sulfur cathode sheet, and vacuum dry to form a functional polymer layer (thickness of 30 μm), obtaining a high-load composite sulfur cathode (7 mg). The mass ratio of PFS to CB is 1:2, the coating thickness is 50 μm, the drying temperature is 95℃, and the drying time is 18 h.

[0081] Step Six: Assemble a soft-pack battery using the high-load composite sulfur cathode, lithium foil, PP separator, and ether-based electrolyte prepared above. The lithium foil thickness is 100 μm. The electrolyte is a mixture of 287 g of lithium bis(trifluoromethanesulfonyl)imide and 20 g of lithium nitrate in 1 L of solvent, specifically 0.5 LDME (ethylene glycol dimethyl ether) and 0.5 L DOL (1,3-dioxane). The electrolyte addition rate is 3 g / Ah. After adding the electrolyte, the battery is allowed to stand under vacuum for 1.5 hours. The battery is then sealed and stored at 45°C for 24 hours to obtain the lithium-sulfur battery.

[0082] Example 2

[0083] A high-load composite sulfur cathode differs from Example 1 only in that the thickness of the functional polymer layer is 70 μm. Following the lithium-sulfur battery preparation method of Example 1, the high-load composite sulfur cathode of Example 1 is replaced with the high-load composite sulfur cathode of this example to prepare a lithium-sulfur battery.

[0084] Example 3

[0085] A method for preparing a high-load composite sulfur cathode differs from Example 1 only in that the rolling pressure is 8 MPa. Referring to the lithium-sulfur battery preparation method of Example 1, the high-load composite sulfur cathode of Example 1 is replaced with the high-load composite sulfur cathode of this example to prepare a lithium-sulfur battery.

[0086] Example 4

[0087] A method for preparing a high-load composite sulfur cathode differs from Example 1 only in that the rolling pressure is 12 MPa. Referring to the lithium-sulfur battery preparation method of Example 1, the high-load composite sulfur cathode of Example 1 is replaced with the high-load composite sulfur cathode of this example to prepare a lithium-sulfur battery.

[0088] Comparative Example 1

[0089] A composite sulfur cathode differs from Example 1 only in that the carbon / sulfur cathode layer on the current collector does not have the functional polymer layer of the present invention.

[0090] Referring to the lithium-sulfur battery preparation method of Example 1, the high-load composite sulfur cathode of Example 1 was replaced with the composite sulfur cathode of this comparative example to prepare a lithium-sulfur battery.

[0091] Comparative Example 2

[0092] A composite sulfur cathode differs from Example 1 in that polypentafluorostyrene is replaced with PEO (polyethylene oxide).

[0093] Referring to the lithium-sulfur battery preparation method of Example 1, the high-load composite sulfur cathode of Example 1 was replaced with the composite sulfur cathode of this comparative example to prepare a lithium-sulfur battery.

[0094] Performance testing:

[0095] Morphological characterization: The surfaces of the carbon / sulfur positive electrode sheet prepared in Example 1 and the carbon / sulfur positive electrode sheet coated with the functional polymer layer were observed, and their scanning electron microscope images are shown below. Figure 1 and Figure 2 ,from Figure 1 It can be seen that the carbon / sulfur positive electrode has a large number of voids. Figure 2 It can be seen that the voids in the carbon / sulfur cathode are filled by functional polymers.

[0096] The lithium-sulfur batteries prepared in the above examples and comparative examples were subjected to capacity retention tests: the voltage range was 1.7~2.7V, and the current rate was 0.5C. The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] The cycle performance (cycle rate of 1C) of the lithium-sulfur batteries prepared in Example 1 and Comparative Example 1 can be found in [reference]. Figure 3 It can be observed that the cycle performance of the lithium-sulfur battery in Example 1 is significantly improved compared to that of the lithium-sulfur battery in Comparative Example 1. It maintains a superior specific capacity even after 300 cycles, while the specific capacity of the lithium-sulfur battery in Comparative Example 1 drops significantly after 50 cycles. This is because the polymer coating of this embodiment can protect the stability of the high-load carbon / sulfur cathode during cycling, resulting in higher capacity retention. In contrast, the cathode in the comparative example lacks polymer coating protection, causing the cathode structure to collapse and crack during cycling, leading to a rapid decrease in cycle capacity. Furthermore, the functional polymer layer acts as a liquid absorber and retainer, increasing the wettability and liquid content of the high-load cathode, thereby improving the cathode capacity of the battery.

[0100] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. The present invention can also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of the present invention should be defined by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A high-load composite sulfur cathode, characterized in that, include: current collector; A carbon / sulfur cathode layer located on the current collector, the carbon / sulfur cathode layer comprising a carbon-sulfur composite material; And a functional polymer layer located on the carbon / sulfur cathode layer, the functional polymer layer being formed of a polymer containing electron-deficient groups; The polymer containing electron-deficient groups is selected from one or more of polypentafluorostyrene, poly(ethylene-alt-maleic anhydride), poly(4-chlorostyrene), or poly(4-bromostyrene).

2. The high-load composite sulfur cathode according to claim 1, characterized in that, The thickness of the functional polymer layer is 30~70μm.

3. The high-load composite sulfur cathode according to claim 1 or 2, characterized in that, The sulfur loading of the carbon / sulfur cathode layer is 6~12 mg / cm³. 2 .

4. A method for preparing a high-loaded composite sulfur cathode as described in any one of claims 1 to 3, characterized in that, Includes the following steps: A slurry is prepared by mixing carbon-sulfur composite material, conductive agent, binder and first solvent; The slurry is coated onto the current collector, dried to form a carbon / sulfur positive electrode layer, and then rolled to obtain a carbon / sulfur positive electrode sheet. A polymer solution is prepared by dissolving a polymer containing electron-deficient groups in a second solvent. The polymer solution is coated onto the surface of the carbon / sulfur cathode sheet, and then dried to form a functional polymer layer, thus obtaining the high-load composite sulfur cathode.

5. The method for preparing a high-loaded composite sulfur cathode according to claim 4, characterized in that, In the polymer solution, the mass concentration of the polymer containing electron-deficient groups is 25-50%; And / or, the second solvent is selected from chlorobenzene and / or chloroform.

6. The method for preparing a high-loaded composite sulfur cathode according to claim 4, characterized in that, The pressure of the roller pressing process is 4~8MPa; And / or, the drying process is carried out at a temperature of 90~110℃ for a time of 6~24h.

7. The method for preparing a high-loaded composite sulfur cathode according to claim 4, characterized in that, The carbon-sulfur composite material is prepared using a method comprising the following steps: Elemental sulfur was mixed with conductive carbon material and then subjected to a first ball milling process. The material after the first ball milling treatment is sintered under sealed conditions; The sintered material is subjected to a second ball milling process to obtain the carbon-sulfur composite material.

8. The method for preparing a high-loaded composite sulfur cathode according to claim 7, characterized in that, The mass ratio of elemental sulfur to conductive carbon material is 1:0.2~0.4; And / or, the sintering treatment is performed at a temperature of 155~180℃ for a time of 15~20h.

9. A lithium-sulfur battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode is a high-load composite sulfur positive electrode as described in any one of claims 1 to 3.

Images