WO2015135108A1

WO2015135108A1 - A boron-doped composite for lithium-sulfur battery, a process for preparing said composite, an electrode material and a lithium-sulfur battery comprising said composite

Info

Publication number: WO2015135108A1
Application number: PCT/CN2014/073123
Authority: WO
Inventors: Yuguo GUO; Chunpeng YANG; Yaxia YIN; Nahong ZHAO; Yvonne Chen; Lonqjie ZHOU
Original assignee: Institute of Chemistry CAS; Robert Bosch GmbH
Current assignee: Institute of Chemistry CAS; Robert Bosch GmbH
Priority date: 2014-03-10
Filing date: 2014-03-10
Publication date: 2015-09-17
Anticipated expiration: 2016-09-10
Also published as: CN106463703A

Abstract

The present invention relates to a composite for lithium-sulfur battery, containing a boron-doped carbon substrate and sulfur loaded; as well as a process for preparing said composite, an electrode material and a lithium-sulfur battery comprising said composite.

Description

A BORON-DOPED COMPOSITE FOR LITHIUM-SULFUR BATTERY,

A PROCESS FOR PREPARING SAID COMPOSITE, AN ELECTRODE MATERIAL AND A LITHIUM-SULFUR BATTERY

COMPRISING SAID COMPOSITE

Technical Field

Background Art

Lithium-Sulfur (Li-S) batteries have attracted considerable attention for their high energy density and low cost. However, the inherent insulating nature of sulfur and the issue of the dissolution of polysufide intermediates into the electrolyte lead to a low utilization rate of S and poor battery life of Li-S batteries, and therefore hinder the commercial application of Li-S batteries. Various carbon materials have been adopted as the substrate to host S to improve the electronic conductivity and meanwhile confine the polysulfides. While strategies tuning the textural characteristics are beneficial to addressing the above issues, methods modifying the intrinsic properties of the carbon substrate, such as interface chemical properties and electronic conductivity, should also contribute to build advanced Sulfur-Carbon (S-C) cathode. However, very few researches have been conducted focusing on this point.

To provide good electronic conductive network and confine polysulfide intermediates, porous carbon framework is often used as matrix to immobilize sulfur. Most recent researches are intended to design carbon structure, including pore volume and size, morphology, etc. Although sulfur in these carbon materials represents considerable progress in terms of capacity retain and battery life, we note that few researches have been carried on adjusting the intrinsic properties of the carbon substrate. The interface chemical properties and electronic conductivity of the matrix could significantly affect the performance of S-C cathode. Heteroatom doping is an effective method to modify interfacial properties and improve conductivity. Some researches show Nitrogen-doping (N-doping) is in favor of the S-C cathode. Nevertheless, considering the electron-rich system of N-doped carbon, polysulfide anions might not be confined in the substrate. Therefore, the cycling performance of the S/N-C cathode is still unsatisfactory.

Summary of Invention

It is therefore an object of the present invention to provide a novel composite which constrains the polysulfide anions to the positively charged interfaces, and improves the conductivity at the same time, so that a high cycling stability can be achieved. This object is achieved by a composite for lithium-sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded.

This object is also achieved by a process for preparing a composite for lithium- sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded, said process including the steps of :

1) providing a boron-doped carbon substrate; and

2) loading sulfur into said boron-doped carbon substrate.

According to another aspect of the invention, an electrode material is also provided, which comprises the composite according to the present invention.

According to another aspect of the invention, a lithium-sulfur battery is also provided, which comprises the composite according to the present invention.

Brief Description of Drawings

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein :

Figure 1(a) shows a TEM image of the BPC composite from Example 1;

Figure 1(b) shows the pore size distribution and the pore volume of the BPC composite from

Example 1;

Figure 2(a) shows the TG curve and the corresponding differential thermogravimetry analysis result of the S/BPC composite from Example 1 ;

Figure 2(b) shows an SEM image of the S/BPC composite from Example 1 ;

Figure 3(a) shows the XPS spectra of the BPC composite from Example 1;

Figure 3(b) shows a schematic illustration of the different B-containing functional groups in the carbon backbone based on the XPS analysis in Fig. 3(a);

Figure 3(c) shows the binding energy of C Is in the S/BPC and S/CMK-3 composites from

Examples 1 and 2;

Figure 3(d) shows the binding energy of S 2p_3/2 in the S/BPC and S/CMK-3 composites from

Examples 1 and 2;

Figure 4(a) shows the discharge/charge curves of the S/BPC composite from Example 1

(sulfur content: 53 wt.%) at C/4;

Figure 4(b) shows the electrochemical impedance spectroscopy of the S/BPC and S/CMK-3 composites from Examples 1 and 2 before charge and discharge;

Figure 4(c) shows the discharge capacities and efficiency of the S/BPC and S/CMK-3 composites from Examples 1 and 2 at C/4 for the first 50 cycles;

Figure 4(d) shows the discharge/charge capacities of the S/BPC composite from Example 1 at different current densities (0.1 C, 0.2 C, 0.5 C, 1 C, 2 C and recovers to 0.1 C). Detailed Description of Preferred Embodiments

The present invention relates to a composite for lithium-sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded.

In an embodiment of the composite according to the present invention, the carbon substrate has a porous structure, namely a boron-doped porous carbon substrate (BPC).

In the composite according to the present invention, the substrate preferably has a BET specific surface area of 200 - 3000 m²/g, preferably 500 - 2000 m²/g, and more preferably 800 - 1500 m²/g; a pore volume of 0.2 - 3.0 cm³/g, preferably 0.5 - 3.0 cm³/g, and more preferably 0.8 - 3.0 cm³/g; and an average pore diameter of 0.3 - 50 nm, preferably 0.3 - 10 nm.

In the composite according to the present invention, the pore structure of the boron-doped carbon substrate is not particularly limited. In an embodiment of the composite according to the present invention, the boron-doped carbon substrate can have for example an ordered or disordered pore structure or their combination, preferably an ordered pore structure. However, it should be understood for a person skilled in the art that no matter whether the boron-doped carbon substrate has an ordered or disordered pore structure, a good confinement effect for polysulfide anions can be achieved by boron-doping, which will be discussed in the theoretic assumptions below in detail.

In an embodiment of the composite according to the present invention, the content of boron in the boron-doped carbon substrate can be in a range of 0.3 - 8.0 wt.%, preferably 0.5 - 3.0 wt.%, more preferably 0.5 - 2.0 wt.%, in each case based on the weight of the boron-doped carbon substrate.

The shape of the substrate used here is not particularly limited, and can be for example short-rod, rod, sphere, near- sphere, polyhedron, or any other shapes.

In an embodiment of the composite according to the present invention, the composite preferably has a sulfur load amount of 20 - 90 wt.%, preferably 30 - 80 wt.%>, and more preferably 40 - 60 wt.%, in each case based on the total weight of the composite.

The inventors have found that as electron-deficiency is introduced to the carbon system by heteroatom doping, a boron-doped carbon system shows a good confinement effect for polysulfide anions.

Boron-doped carbon is proposed based on two assumptions. On one hand, boron atom, with an s²p electronic configuration, can introduce electron vacancy into the carbon energy band, so as to increase carrier concentration and improve the conductivity. On the other hand, the electron-deficient system is able to constrain the polysulfide anions to lessen the dissolution issue. B atoms are positively polarized, leading to chemisorption of negative species on the surface of BPC. As S and polysulfide anions are electron-abundant, they can be attracted by the slightly positive B and BPC. XPS results confirm the interaction between S and BPC (Fig. 3). For polysulfide S_x ^2~ (x = 4 - 8) anions, the Coulombic interaction would be even stronger and polysulfide anions can therefore be entrapped within the cathode. Due to the high electronic conductivity and interaction between boron-doped carbon and sulfur, the S-C composite shows a high specific capacity, a low resistance, an excellent cycling stability, and a favorable rate performance.

The present invention further relates to a process for preparing a composite for lithium-sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded, said process including the steps of :

1) providing a boron-doped carbon substrate; and

2) loading sulfur into said boron-doped carbon substrate.

1) Providing a boron-doped carbon substrate :

In an embodiment of the process according to the present invention, said boron-doped carbon substrate can be prepared by the carbonization of one or more carbon sources together with one or more boron sources.

In an embodiment of the process according to the present invention, said carbon substrate preferably has a porous structure.

In an embodiment of the process according to the present invention, the not-yet-doped substrate can be a carbon substrate having an ordered or disordered pore structure or their combination, preferably an ordered pore structure, and more preferably can be selected from the group consisting of CMK-3 and CMK-5. These not-yet-doped substrates are commercially available or can be obtained by known methods.

In an embodiment of the process according to the present invention, the step 1) includes the substeps of :

a) providing a template;

b) impregnating or applying carbon and boron into or onto said template from a solution or suspension containing one or more carbon sources and one or more boron sources by a hydrothermal reaction;

c) annealing the product from b); and

d) optionally removing said template. a) Providing a template :

The template used here can be sulfonated polystyrene (SPS) nanospheres or silica nanospheres. The preparation method of sulfonated polystyrene (SPS) nanospheres can be carried out according to WO 2013/078605 Al, which is herein incorporated by reference in its entirety. Silica nanospheres are commercially available or can be obtained by known methods.

The template used here can also be a template having an ordered pore structure or a zeolite template, for example mesoporous silica template, such as SBA-15 and MCM-41. These templates are commercially available or can be obtained by known methods.

For example, SBA-15 can be synthesized by a method reported by Dong- Yuan Zhao, et al., Triblock Copolymer Syntheses of Mesoporous Silica with Periodic 50 to 300 Angstrom Pores, Science, 1998, 279, 548, and MCM-41 can be synthesized by a method reported by C. T. Kresge, et al., Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism, Nature, 1992, 359, 710 - 712. b) Hydrothermal reaction :

In the step of "b) Hydrothermal reaction", carbon and boron can be impregnated into or applied onto the template from a solution or suspension containing one or more carbon sources and one or more boron sources by a hydrothermal reaction.

The carbon source can be one or more carbohydrates, preferably selected from the group consisting of sucrose, D-glucose, fructose, and any combinations thereof.

The boron source can be selected from the group consisting of boric acid; boric acid esters, such as trimethyl borate; boric acid salts, such as lithium borate; boron oxides; organoboron compounds; boranes; borohydrides; and any combinations thereof.

The content of the one or more carbon sources in said solution or suspension is not particularly limited. For example 2 - 8 parts by weight of carbohydrates can be dissolved in 20 - 60 parts by weight of water.

The one or more boron sources can be used in an amount, such that the content of boron in the boron-doped carbon substrate is in a range of 0.3 - 8.0 wt.%, preferably 0.5 - 3.0 wt.%, more preferably 0.5 - 2.0 wt.%, in each case based on the weight of the boron-doped carbon substrate.

The solvent of said solution or suspension is not particularly limited, and can be for example water, preferably deionized water.

Said solution or suspension can also contain H₂S0₄ to facilitate the hydrothermal reaction. The content of H₂S0₄ is not particularly limited, and can be for example 0.015 - 0.03 g/mL, preferably 0.018 - 0.028 g/mL.

The template can be dispersed in said solution or suspension under sonication for 1 h. The amount of the template used is not particularly limited. For example the weight ratio of the template to the carbon sources can be 3 : 7 - 7 : 3, preferably 4 : 6 - 6 : 4, more preferably about 1 : 1.

The hydrothermal reaction can be carried out in an autoclave at 100 - 200°C for 12 - 24 h. Alternatively the hydrothermal reaction can be carried out in an autoclave firstly at 100 - 150°C for 6 - 12 h and then at 150 - 200°C for another 6 - 12 h. Preferably the product as prepared can be subjected to another hydrothermal reaction with another solution or suspension containing said one or more carbon sources and said one or more boron sources. c) Annealing :

The product as prepared in b) can be further carbonized at 800 - 1000°C for 5 - 10 h in an inert gas flow, such as an Ar flow. In case of a SPS template, which can be vaporized during the step of "c) Annealing", the subsequent step of "d) Removing the template" can be dispensed with. d) Removing the template :

The template can be removed by any chemical agent which can dissolve the template but can not dissolve the boron-doped carbon substrate.

In case of a silica template, hydrofluoric acid or a sodium hydroxide solution can be used for removing the template. For example the product from b) can be stirred in a 5 - 20 wt.% HF solution or a 1 - 6 mol/L, preferably 2 - 4 mol/L sodium hydroxide solution for 2 - 6 h.

Preferably the product as prepared can be centrifuged and washed with water and ethanol for several times, and then further dried in an oven.

In another embodiment of the process according to the present invention, the step 1) includes the substeps of :

a') subjecting a solution or suspension containing one or more carbon sources and one or more boron sources to a hydrothermal reaction;

b') activating the product from a'). a') Hydrothermal reaction

The hydrothermal reaction can be carried out in an autoclave at 100 - 200°C, preferably 150 - 200°C for 2 - 24 h, preferably 2 - 12 h to obtain boron-doped microporous carbon spheres.

The solvent of said solution or suspension is not particularly limited, and can be for example water, preferably deionized water. b') Activation

The boron-doped microporous carbon spheres obtained from a') can be activated by :

i) dispersing the boron-doped microporous carbon spheres in a 0.1 - 10 mol/L aqueous solution of potassium hydroxide (KOH) preferably under sonication;

ii) standing for 10 - 48 h to adsorb KOH in the micropores of the boron-doped microporous carbon spheres;

iii) filtrating the boron-doped microporous carbon spheres; iv) annealing the boron-doped microporous carbon spheres at 700 - 1000°C in an inert gas atmosphere, such as nitrogen or argon, for 2 - 4 h with a heating rate of 2 - 10°C/min; v) removing KOH by washing the boron-doped microporous carbon spheres with water, preferably deionized water.

2) Load of sulfur :

In the step of "2) load of sulfur", sulfur and the substrate to be loaded with sulfur can be mixed in a weight ratio of 1 : 4 - 9 : 1 , preferably 3 : 7 - 4 : 1, and more preferably 2 : 3 - 3 : 2, to yield a homogeneous mixture. And then the mixture can be sealed and heated at 150 - 600°C, preferably 400 - 600°C for 5 - 15 h, so that sulfur is dispersed into the substrate.

The step of "2) load of sulfur" can be carried out to achieve a sulfur load amount of 20 - 90 wt.%, preferably 30 - 80 wt.%, and more preferably 40 - 60 wt.%, in each case based on the total weight of the composite.

The present invention further relates to an electrode material, which comprises the composite according to the present invention.

The present invention further relates to a lithium-sulfur battery, which comprises the composite according to the present invention.

The following non-limiting examples illustrate various features and characteristics of the present invention, which is not to be construed as limited thereto.

Example 1 : Preparation of S/BPC

1) Providing a boron-doped carbon substrate :

a) Providing a template SBA-15 as reported by Zhao :

SBA-15 was prepared by a procedure described previously. First, 4 g of Pluronic PI 23 (EO20PO70EO20) was dissolved in 120 mL of hydrochloric acid (2 M) at 38°C. Then 9 mL of tetraethylorthosilicate was added into the solution. The mixture was vigorously stirred at 38°C for 8 min and remained quiescent for 24 h, followed by hydrothermal treatment at 100°C for another 24 h in an autoclave. The white product was filtered, washed, dried, and finally calcined at 550°C in air for 4 h to get SBA-15 without surfactant. b) Preparation of BPC :

Firstly 1 g of boric acid was dissolved in 5 mL of water under sonication and heat at 70°C for 1 h. Then 1 g of fructose, 0.14 g concentrated H₂S0₄ and 1.0 g of SBA-15 were successively added into the above solution, and sonicated for 1 h. The mixture was heated at 100°C for 12 h and at 160°C for another 12 h, followed by repetition of this impregnation process with another 5 mL aqueous solution containing 0.8 g of boric acid, 0.8 g of frucrose, and 0.09 g of H₂S0₄. c) Annealing :

The intermediate product was completely carbonized at 900°C for 5 h in an Ar flow. d) Removing the template :

The product from c) was stirred in a HF solution (10 wt.%) for 2 h. The product was centrifuged, washed with water and ethanol for several times, and further dried in an oven to obtain BPC. The content of boron in BPC was about 0.93% as determined by XPS. BPC had an ordered pore structure and a hierarchical pore size distribution (see Fig. 1).

2) Load of sulfur :

A mixture of sulfur and BPC with a weight ratio of 7 : 3 was sealed in a glass tube filled with Ar, and then calcined at 400°C in a tube furnace for 6 h to obtain a composite (S/BPC) for lithium-sulfur battery, wherein said composite contains a boron-doped porous carbon substrate (BPC) and sulfur loaded. The residual sulfur on the surface of S/BPC was removed at 220°C for 6 h to obtain the final product S/BPC.

Structural and electrochemical evaluation :

Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were employed to characterize the size and structure of the products (see Figs. 1(a) and 2(b)).

The content of sulfur in the composite S/BPC was 53% according to thermogravimetry (TG) curve (see Fig. 2(a)). There was no bulk sulfur outside the BPC (see Fig. 2(b)).

The XPS result of BPC verified that boron was doped into the carbon framework in different forms, such as BC₃, BC₂0, and BC0₂, as shown in Fig. 3(a). B₂0₃ from raw material H₃B0₃ was also identified. This proved that B was incorporated into the backbone of carbon, as illustrated in Fig. 3(b). The binding energy of the C Is was shifted to the high energy along with B doping, indicating the doping effect of the electron deficiency status, as shown in Fig. 3(c). B-doping would introduce electron vacancy into the carbon energy band, which could attract S element and make it anchored onto the surface of the carbon matrix. From the S 2p_3/2 XPS spectra (Fig. 3(d)), we can see that the binding energy of S in S/BPC was higher than that of S/CMK-3. This means the electron of S slightly transferred to the carbon framework, forming an interaction between S and BPC. For polysulfide S_x ^2~ (x = 4 - 8) anions, the Coulombic interaction would be even stronger and the polysulfide anions can therefore be entrapped within the cathode.

Electrochemical measurements were performed with coin cells assembled in an argon-filled glovebox. For preparing working electrodes, a mixture of active material, carbon black, and poly-(vinyl difluoride) (PVDF) at a weight ratio of 80 : 10 : 10 was pasted on an Aluminium foil. Lithium foil was used as the counter electrode. A glass fiber sheet (GF/D, Whatman) was used as a separator. An electrolyte (Zhangjiagang Guotai-Huarong New Chemical Materials Co., Ltd.) consisting of a solution of 1 M LiN(CF₃S0₂)₂ (LiTFSI) salt in a mixture of 1,3-dioxolane (DOL) and 1 ,2-dimethoxyethane (DME) (1 : 1, v/v). Galvanostatic cycling of the assembled cells was carried out by using a battery testing system in the voltage range of 1 - 3 V (vs. Li⁺/Li).

When discharged at C/4, the S/BPC composite demonstrated a first discharge capacity of ca. 1300 mA h g^"1 (based on the mass of S), indicating the high activity of S in BPC. After charging to 2.7 V, the Coulombic efficiency was approaching 100% and the shuttle effect was obviously alleviated. A high capacity was stabilized to about 1000 mA h g^"1 after 50 cycles. The S/BPC composite also exhibited a low charge-transfer resistance and an excellent rate performance (see Fig. 4). The specific capacity was calculated based on the weight of sulfur.

Example 2: Preparation of S/CMK-3

1) Providing a non-doped carbon substrate :

a) Preparation of SBA-15 :

The operation of the step a) in Example 1 was repeated. b) Preparation of CMK-3 :

A nano casting method was also employed to prepare CMK-3 as Example 1. 1.25 g of fructose was dissolved in 5.0 mL of water containing 0.14 g of concentrated H₂S0₄. Then 1.0 g of SBA-15 was dispersed in the solution and sonicated for 1 h. The mixture was heated at 100°C for 12 h and at 160°C for another 12 h, followed by repetition of impregnation process once with another 5 mL aqueous solution containing 0.8 g of fructose and 0.09 g of H₂S0₄. c) Annealing :

The obtained dark brown intermediate product was completely carbonized at 900°C for 5 h in an Ar flow. d) Removing the template :

To remove the SBA-15 template, the carbonized product was stirred in a 10 wt.% HF solution for 4 h. The as-prepared CMK-3 was collected by centrifugation, repeatedly washed by distilled water and finally dried at 80°C.

2) Load of sulfur :

The operation of the step 2) in Example 1 was repeated, except that BPC and S/BPC were substitute by CMK-3 and S/CMK-3 respectively. Structural and electrochemical evaluation

Electrochemical measurements were performed in the same way as Example 1. The electrochemical impedance spectroscopy, discharge capacity and efficiency of S/CMK-3 were shown in Figs. 4(b) and 4(c).

Table 1 shows the content of heteroatoms in carbon materials and electric conductivity of BPC and CMK-3 from Examples 1 and 2. Even though with only 0.93 at.% B, the electronic conductivity was also increased compared with undoped CMK-3. Such increase of the conductivity was in favor of the activity of S.

Table 1

CMK-3 BPC

Heteroatom content (at.% by XPS) 0 0.93

Conductivity (S cm^"1) 0.13 0.42

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. The attached claims and their equivalents are intended to cover all the modifications, substitutions and changes as would fall within the scope and spirit of the invention.

Claims

A composite for lithium-sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded.

The composite of claim 1, wherein said carbon substrate has a porous structure.

The composite of claim 1 or 2, wherein said carbon substrate has an ordered or disordered pore structure or their combination.

The composite of any one of claims 1 to 3, wherein said boron-doped carbon substrate has an average pore diameter of 0.3 - 50 nm, preferably 0.3 - 10 nm.

The composite of any one of claims 1 to 3, wherein said boron-doped carbon substrate has a BET specific surface area of 200 - 3000 m²/g, preferably 500 - 2000 m²/g, and more preferably 800 - 1500 m²/g.

The composite of any one of claims 1 to 4, wherein said boron-doped carbon substrate has a pore volume of 0.2 - 3.0 cm³/g, preferably 0.5 - 3.0 cm³/g, and more preferably 0.8 - 3.0 cm³/g.

The composite of any one of claims 1 to 5, wherein the content of boron in said boron-doped carbon substrate is in a range of 0.3 - 8.0 wt.%, preferably 0.5 - 3.0 wt.%, more preferably 0.5 - 2.0 wt.%, in each case based on the weight of said boron-doped carbon substrate.

The composite of any one of claims 1 to 6, wherein said composite has a sulfur load amount of 20 - 90 wt.%, preferably 30 - 80 wt.%>, and more preferably 40 - 60 wt.%>, in each case based on the total weight of said composite.

A process for preparing a composite for lithium-sulfur battery, wherein said composite contains a boron-doped carbon substrate and sulfur loaded, said process including the steps of :

1) providing a boron-doped carbon substrate; and

2) loading sulfur into said boron-doped carbon substrate.

The process of claim 9, wherein in step 1) said boron-doped carbon substrate is prepared by the carbonization of one or more carbon sources together with one or more boron sources.

11. The process of claim 9 or 10, wherein step 1) including the substeps of : a) providing a template;

c) annealing the product from b); and

d) optionally removing said template.

12. The process of claim 9 or 10, wherein step 1) including the substeps of :

b') activating the product from a').

13. The process of any one of claims 9 to 11, wherein said template has an ordered or disordered pore structure or their combination.

14. The process of any one of claims 9 to 11, wherein said template is sulfonated polystyrene nanospheres or silica nanospheres.

15. The process of any one of claims 9 to 14, wherein said carbon source is one or more carbohydrates, preferably selected from the group consisting of sucrose, D-glucose, fructose, and any combinations thereof.

16. The process of any one of claims 9 to 15, wherein said boron source is selected from the group consisting of boric acid, boric acid esters, boric acid salts, boron oxides, organoboron compounds, boranes, borohydrides, and any combinations thereof.

17. The process of any one of claims 9 to 16, wherein said one or more boron sources is used in an amount, such that the content of boron in said boron-doped carbon substrate is in a range of 0.3 - 8.0 wt.%, preferably 0.5 - 3.0 wt.%, more preferably 0.5 - 2.0 wt.%, in each case based on the weight of said boron-doped carbon substrate.

18. The process of any one of claims 9 to 17, wherein step 2) is carried out so that said composite has a sulfur load amount of 20 - 90 wt.%, preferably 30 - 80 wt.%, and more preferably 40 - 60 wt.%>, in each case based on the total weight of said composite.

19. The process of any one of claims 9 to 18, wherein said carbon substrate has a porous structure.

20. An electrode material, comprising the composite of any one of claims 1 to 8 or the composite prepared by the process of any one of claims 9 to 19.

1. A lithium-sulfur battery, comprising the composite of any one of claims 1 to 8 or the composite prepared by the process of any one of claims 9 to 19.