CA3234875A1 - Silica coated sulfur-carbon composite and lithium-sulfur battery comprising the same - Google Patents

Abstract

The present invention relates to a silica-coated sulfur-carbon composite, the silica-coated sulfur-carbon composite comprising a sulfur-carbon composite and silica particles coated on at least a portion of the surface of the sulfur-carbon composite . The silica-coated sulfur-carbon composite according to the present invention can be used as a positive electrode active material of a lithium-sulfur secondary battery as a non-limiting example.

Description

DESCRIPTION
TITLE OF INVENTION: SILICA COATED SULFUR-CARBON COMPOSITE
AND LITHIUM-SULFUR BATTERY COMPRISING THE SAME
TECHNICAL FIELD
The present disclosure relates to a sulfur-carbon composite and a lithium-sulfur battery comprising the same. This application claims priority from Korean application No.
10-2022-0065671 filed May 27, 2022, and No. 10-2022-0135073 filed Oct 19, 2022, the contents of which are incorporated for all intents and purposes as if fully set forth herein.
BACKGROUND ART
Secondary batteries are used as high-capacity energy storage batteries and high-performance energy sources for portable electronic devices including mobile phones, camcorders and laptops.
A type of secondary battery, a lithium-ion secondary battery, has higher energy density and larger capacity per area than a nickel-manganese battery or a nickel-cadmium battery, but despite these advantages, it has disadvantages such as stability reduction caused by overheating and low output characteristics.
In particular, as the application of secondary batteries has been expanded to electric vehicles (EVs) and energy storage systems (ESSs), attention is directed to Date Regue/Date Received 2024-04-09 lithium-sulfur battery technology due to its high theoretical energy storage density by weight (-2,600 Wh/kg) compared to lithium-ion secondary batteries with lower energy storage density by weight (-250 Wh/kg).
A lithium-sulfur battery refers to a battery system comprising a sulfur-containing material having a sulfur-sulfur (S-S) bond for a positive electrode active material and lithium metal for a negative electrode active material. Sulfur, the main component of the positive electrode active material, is plentiful and can be found all over the world, is non-toxic, and has low atomic weight.
Sulfur used in the lithium-sulfur battery has electrical conductivity of 5 x 10' S/cm, and thus it is a nonconductor which is not electrically conductive.
Electrons generated by electrochemical reactions cannot move in sulfur. Attempts have been made to combine the sulfur-containing material with a conductive material such as carbon capable of providing electrochemical reaction sites to form a sulfur-carbon composite for use as a positive electrode active material.
However, despite the above-described advantages, when the sulfur-containing material is used as an active material, the amount of sulfur that participates in the electrochemical oxidation-reduction reactions in the battery is low based on the total amount of sulfur used as the raw material, so the actual battery capacity is lower than the theoretical capacity.
Hence, currently, the potential of a lithium-sulfur battery containing a sulfur-containing material cannot be fully realized because the theoretical capacity cannot

2 Date Regue/Date Received 2024-04-09 be fully used in practice.
This problem may be caused by various factors, and for example, sulfur-agglomerates are formed by the non-uniform feeding of sulfur in the sulfur-carbon composite, or sulfur is not uniformly fed by the agglomeration of the sulfur-carbon composite itself in the electrode fabrication.
For example, when manufacturing the lithium-sulfur battery using dry electrodes, in the process of uniformly feeding the sulfur-carbon composite in powder state, spreading thin and flattening using a blade to fabricate the electrode, in case that the flowability of the sulfur-carbon composite is low, non-uniform feeding of sulfur leads to large variations of electrode loading, causing defects in the electrode.
Accordingly, for the practical use of lithium-sulfur batteries having good characteristics as described above, it is necessary to improve the flowability of the sulfur-carbon composite to solve the above problems.
Thus, when manufacturing dry electrodes for a lithium-sulfur battery, it is desired that a sulfur-carbon composite can be spread uniformly and flattened for the fabrication of an electrode, for example by the use of a blade, so that a uniform electrode loading and minimizing electrode defects can be achieved. To achieve these objectives, it is required that the formation of agglomerates of the sulfur-carbon composite be reduced.
DISCLOSURE
Technical Problem

3 Date Regue/Date Received 2024-04-09 The present invention is directed to solve the problems of the prior art, by providing lithium-sulfur batteries with improved performance and uniform quality.
Furthermore, such problems in the art can be solved by providing an electrode with improved performance, uniform quality and less defects to increase production yield.
Thereby, such problems can be solved by providing an electrode, for example a positive electrode, that can be more efficiently produced and which can be unifoimly loaded to minimize electrode defects.
Accordingly, for the practical use of lithium-sulfur batteries having good characteristics as described above, it may be necessary to improve the flowability of the sulfur-carbon composite to solve the above problems.
The present disclosure is designed to solve the above-described problems, and therefore, the present disclosure is directed to providing a silica coated sulfur-carbon composite with improved flowability and a method for manufacturing the same.
According to an aspect, the present disclosure is directed to providing a silica coated sulfur-carbon composite with reduced agglomeration of the sulfur-carbon composite, and a method for manufacturing the same.
According to another aspect, the present disclosure is directed to providing a method for improving the flowability of a silica coated sulfur-carbon composite by improving the surface roughness of the sulfur-carbon composite.
Technical Solution To solve the above-described problem, according to an aspect of the present

4 Date Regue/Date Received 2024-04-09 disclosure, there is provided a silica coated sulfur-carbon composite of the following embodiments.
The silica coated sulfur-carbon composite according to a first embodiment comprises a sulfur-carbon composite; and silica particles coated on at least part of a surface of the sulfur-carbon composite.
According to a second embodiment, in the first embodiment, an angle of repose of the silica coated sulfur-carbon composite may be equal to or less than 32 .
According to a third embodiment, in the first or second embodiment, an average particle size Dso of the silica particles may be 10 to 50 nm.
According to a fourth embodiment, in any one of the first to third embodiments, the silica particles may be nanoparticles represented by the following Formula 1:
[Formula 11 [Si021p[SiO(OH)211-p where p is a number of 0 <p < 1.
According to a fifth embodiment, in any one of the first to fourth embodiments, a coating thickness of the silica particles on at least part of the surface of the silica coated sulfur-carbon composite may be 20 nm to 5 gm.
According to a sixth embodiment, in any one of the first to fifth embodiments, the silica coated sulfur-carbon composite may have features of the following Formula 2:
[Formula 21

5 Date Regue/Date Received 2024-04-09 0.0001 --= [ _______________ (So/Sr) S 0.2 where Mp is a mass of the silica particles, Mc is a mass of the sulfur-carbon composite, So is a coating area of the silica particles, and St is a surface area of the silica coated sulfur-carbon composite.
According to a seventh embodiment, in any one of the first to sixth embodiments, the silica coated sulfur-carbon composite comprises the sulfur-carbon composite and the silica particles at a weight ratio of 99.9:0.1 to 80:20.
According to an eighth embodiment, in any one of the first to seventh embodiments, an average particle size D50 of the sulfur-carbon composite may be 20 gm to 50 gm.
According to a ninth embodiment, in any one of the first to eighth embodiments, the sulfur-carbon composite may comprise a porous carbon material; and a sulfur-containing compound supported on at least part of inner and outer surfaces of pores in the porous carbon material.
According to a tenth embodiment, in any one of the first to ninth embodiments, an average diameter of the pores present in the porous carbon material may be 1 to 200 nm.
According to an eleventh embodiment, in the ninth embodiment, the sulfur-containing compound may comprise at least one of inorganic sulfur (Ss), lithium

6 Date Regue/Date Received 2024-04-09 polysulfide (Li2Sn, 1 < n < 8) or carbon sulfur polymer (C2Sx)., 2.5 < x < 50, 2 < m).
According to a twelfth embodiment, in any one of the ninth to eleventh embodiments, the sulfur-carbon composite may comprise the porous carbon material and the sulfur-containing compound at a weight ratio of 1:9 to 5:5.
According to a thirteenth embodiment, in any one of the first to twelfth embodiments, the ratio of the maximum average particle diameter (D50) of the sulfur-carbon composite to the maximum thickness of the coating layer formed of the silica particles may be 100:1 to 1000:1.
According to a fourteenth embodiment, in any one of the first to thirteenth embodiments, based on the total weight of the silica-coated sulfur-carbon composite, 0.01 to 20% by weight of the silica particles and 80% to 99.99% by weight of the sulfur-carbon composite may be included.
According to a fifteenth embodiment, in any one of the first to fourtennth embodiments, 60% to 100% of the surface area of the sulfur-carbon composite may be coated with the silica particles.
According to another aspect of the present disclosure, there is provided a method for manufacturing a silica coated sulfur-carbon composite of the following embodiment.
The method for manufacturing a silica coated sulfur-carbon composite according to a sixteenth embodiment comprises coating silica particles on at least part of a surface of a sulfur-carbon composite.

7 Date Regue/Date Received 2024-04-09 According to a seventeenth embodiment, in the sixteenth embodiment, the method for manufacturing a silica coated sulfur-carbon composite may further comprise, before the coating step: manufacturing the sulfur-carbon composite, and the step of manufacturing the sulfur-carbon composite may comprise mixing a sulfur-containing compound with a porous carbon material.
According to a eighteenth embodiment, in any one of the sixteenth and seventeenth embodiments, after the coating step, a step of separating the sulfur-carbon composite coated with the silica particles may be further included.
According to a nineteenth embodiment, in any one of the sixteenth to eighteenth embodiments, the coating step may comprise mixing the sulfur-carbon composite with the silica particles in solid state.
According to a twelfth embodiment, in any one of the sixteenth to nineteenth embodiments, in the coating step, a weight ratio of the sulfur-carbon composite and the silica particles may be 99.9:0.1 to 80:20.
According to another aspect of the present disclosure, there are provided a positive electrode active material, an electrode and a lithium-sulfur battery of the following embodiments.
According to a twenty-first embodiment, there is provided the positive electrode active material comprising the silica coated sulfur-carbon composite according to any one of the first to fifteenth embodiments.

8 Date Regue/Date Received 2024-04-09 According to a twenty-second embodiment, there is provided the electrode comprising the silica coated sulfur-carbon composite according to any one of the first to fifteenth embodiments.
According to a twenty-third embodiment, there is provided the lithium-sulfur battery comprising a positive electrode comprising the silica coated sulfur-carbon composite according to any one of the first to fifteenth embodiments; a negative electrode comprising a negative electrode active material; and an electrolyte solution.
Advantageous Effects The silica coated sulfur-carbon composite according to an embodiment of the present disclosure has the improved flowability on surface. Due to the increased fluidity of the sulfur-carbon composite, aggregation of the silica-coated sulfur-carbon composite may be reduced. As a result, the silica coated sulfur-carbon composite is unifolinly coated on the electrode support, thereby improving the performance of the battery.
Specifically, when compared with the conventional sulfur-carbon composite having high surface roughness, the silica coated sulfur-carbon composite according to an embodiment of the present disclosure includes silica particles coated on at least part of the surface of the sulfur-carbon composite, so the silica particles are inserted into the surface of the sulfur-carbon composite having high surface roughness, thereby reducing the surface roughness of the sulfur-carbon composite and providing good particle flowability to the sulfur-carbon composite.
Accordingly, the silica coated sulfur-carbon composite

9 Date Regue/Date Received 2024-04-09 according to an embodiment of the present disclosure reduces agglomerates and is uniformly coated on the electrode support, thereby manufacturing the electrode with uniform loading.
In addition, an electrode manufactured using the same, for example, a positive electrode, can be more effectively manufactured due to the improved fluidity of the silica-coated sulfur-carbon composite, and as a result, the productivity of the lithium-sulfur battery can be improved.
DESCRIPTION OF DRAWINGS
The accompanying drawings illustrate an exemplary embodiment of the present disclosure, and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus the present disclosure is not construed as being limited to the drawings.
FIG. 1 shows scanning electron microscopy (SEM) images of sulfur-carbon composite according to Comparative Example 1 and silica coated sulfur-carbon composite according to Examples 1 and 2 of the present disclosure. The upper row SEM
images have a 15 000 times magnification, and the lower row SEM images have a 2000 times magnification.
FIG. 2 shows the results of measuring the angle of repose of sulfur-carbon composite according to Comparative Example 1 and silica coated sulfur-carbon composite according to Examples 1 and 2 of the present disclosure.
Date Regue/Date Received 2024-04-09 FIG. 3 is an image showing the flowability of sulfur-carbon composite according to Comparative Example 1 and silica coated sulfur-carbon composite according to Examples 1 and 2 of the present disclosure.
FIG. 4 shows SEM images of sulfur-carbon composite according to Comparative Example 2 and zinc oxide (ZnO) coated sulfur-carbon composite according to Comparative Examples 3 and 4. The upper row SEM images have a 10 000 times magnification, and the lower row SEM images have a 2000 times magnification.
FIG. 5 shows the results of measuring the angle of repose of sulfur-carbon composite according to Comparative Example 2 and zinc oxide (ZnO) coated sulfur-carbon composite according to Comparative Examples 3 and 4.
BEST MODE
Hereinafter, the present disclosure is described in detail. However, the present disclosure is not limited to the following description, and each element may be variously adapted or modified or selectively interchangeably used, if necessary.
Accordingly, it should be understood that the present disclosure covers all modifications, equivalents or alternatives included in the technical features and aspects of the present disclosure.
In the present specification, the term including specifies the presence of stated elements, but does not preclude the presence or addition of one or more other elements unless expressly stated otherwise.
In the present specification, A and/or B refers to either A or B or both.

Date Regue/Date Received 2024-04-09 In the present disclosure, the term composite refers to a material which is produced by combining at least two materials to form a physically and chemically different phase and exhibit a more effective function.
An aspect of the present disclosure provides a silica coated sulfur-carbon composite for use as a carrier for supporting a positive electrode active material in a positive electrode of a lithium-sulfur battery, a positive electrode active material itself or a conductive material. However, the use of the silica coated sulfur-carbon composite according to an aspect of the present disclosure is not limited thereto.
Silica coated sulfur-carbon composite The silica coated sulfur-carbon composite according to an aspect of the present disclosure comprises a sulfur-carbon composite and silica particles coated on at least part of the surface of the sulfur-carbon composite.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may comprise a sulfur-carbon composite having an outer surface on which silica particles are at least partly coated, preferably in which the outer surface is fully coated with silica particles.
After coating a sulfur-carbon composite with silica particles, the silica particles themselves may not be distinguishable as particles anymore, but may form a coating layer on the surface of the sulfur-carbon composite. Hence, the particle size of a sulfur-carbon composite, and also of a carbon composite, may be bigger than the particle size of a silica Date Regue/Date Received 2024-04-09 particle. The particle size may correspond to the average particle size (D50) according to ISO 13320:2020 as it is known by the person skilled in the art. However, the method for measuring the particle size is not limited thereto.
In an embodiment of the present disclosure, the silica particles may be nanoparticles according to the following Formula 1:
[Formula 11 [Si021p[SiO(OH)211-p wherein p is a number of 0 < p < 1.
In an embodiment of the present disclosure, p may be 0.3 < p < 1.
In an embodiment of the present disclosure, p may be 0.5 < p < 1.
In an embodiment of the present disclosure, p may be 0.6 < p < 1.
In an embodiment of the present disclosure, p may be 0.7 < p < 1.
In an embodiment of the present disclosure, p may be 0.8 < p < 1.
In an embodiment of the present disclosure, p may be 0.9 < p < 1.
In another embodiment of the present disclosure, p may be 1.
The silica coated sulfur-carbon composite according to an embodiment of the present disclosure comprises the sulfur-carbon composite and the silica particles coated on at least part of the surface of the sulfur-carbon composite.
In an embodiment of the present disclosure, the silica particles coated on at least part of the surface of the sulfur-carbon composite may impart a hydroxyl group (-OH) to the surface of the sulfur-carbon composite through reaction with the surrounding moisture Date Regue/Date Received 2024-04-09 (H20). That is, Formula 1 may vary depending on the amount of moisture around.

Accordingly, the sulfur-carbon composite coated with silica particles on at least part of the surface may have the reduced roughness and improved flowability due to the inserted silica particles, but the mechanism of the present disclosure is not limited thereto.
The flowability may be determined by the angle of repose as described below.
The roughness of the silica coated sulfur-carbon composite may be measured according to ISO-25718:2016 as it is known by the person skilled in the art. However, the measurement of the roughness may not be limited thereto.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may have a lower angle of repose by the improved flowability compared to the sulfur-carbon composite not coated with silica particles.
In an embodiment of the present disclosure, the angle of repose of the silica coated sulfur-carbon composite may be lower by 5% or more than the sulfur-carbon composite before silica particle coating. More specifically, the angle of repose of the silica coated sulfur-carbon composite may be lower by 6% or more, 6.5% or more, 7% or more, 8% or more, 9% or more, 10% or more, 15% or more, 20% or more, 25% or more or 30% or more than the sulfur-carbon composite before silica particles coating. A
phenomenon in which the angle of repose of the silica-coated sulfur-carbon composite is lower than that of the sulfur-carbon composite before coating may reflect improved fluidity of the sulfur-carbon composite. In one embodiment of the present invention, the angle of repose may vary depending on the specific sulfur-carbon composite used.

Date Regue/Date Received 2024-04-09 In the specification, the reduction in the angle of repose may be calculated according to the following Formula 3.
[Formula 31 Change in angle of repose (%) = [(Ra-Rb)/Rb] X 100 Rb is the angle of repose of the sulfur-carbon composite before coating, and Ra is the angle of repose of the silica coated sulfur-carbon composite.
In an embodiment of the present disclosure, the angle of repose of the silica coated sulfur-carbon composite may be equal to or less than 32 by the improved flowability.
In the present specification, the "angle of repose" may indicate a value measured by the method commonly used to measure the angle of repose of a sample, and the method for measuring the angle of repose may be, for example, the Angle of Repose Method described in US Pharmacopoeia 1174 and EP Pharmacopoeia 2.9.76. In an embodiment of the present disclosure, the angle of repose may be measured, for example, by the following method. First, the funnel is placed at the height of 7.5 cm from the ground, and fixed with the center aligned using a horizontal leveler, and the lower portion of the funnel is closed to prevent the fed sample from sliding down. 100 g of the sample to be measured is poured into the funnel, and the lower portion of the funnel is opened to cause the sample to fall freely into a pile on a disk (diameter 13 cm) on the base.
Subsequently, the angle of repose (0) of the sample pile is measured.
In an embodiment of the present disclosure, the angle of repose may be, for example, 5 to 32 , 5 to 31.5 , 5 to 31 , 10 to 31 , 5 to 30.5 , 5 to 30 , 10 to 30 , 15 Date Regue/Date Received 2024-04-09 to 28 , 15.5 to 27 , 200 to 26.5 , or 23 to 26 , or 5 to 30.3 , or 5 to 25.5 , or 5 to 23 , or 23 to 30.3 , or 23 to 25.5 , or 25.5 to 30.3 .
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may fulfill the following formula 4:
[foimula 4]
¨316 In (Nil, 1- 0.2) + 31> U> ¨ 3.16 ]h(Nly +0.2) 1- 25 wherein, Mp * 100 -1-mcr NiY =
Mp = mass of silica particles Mc = mass of sulfur-carbon composite 0 = angle of repose in degree of the silica coated sulfur-carbon composite determined according to <1174>, "Powder Flow" in US Pharmacopeia 36.
Thus, the angle of repose (0) may depend on the amount of silica particles used for a certain amount of sulfur-carbon composite for obtaining a silica coated sulfur-carbon composite. A silica coated sulfur-carbon composite which fulfills the above formula 4 may have the ideal balance between good flowability and low density of the silica coated sulfur-carbon composite. Furthermore, a silica coated sulfur-carbon composite which fulfills the above formula 4 may also provide an ideal balance between good flowability of Date Regue/Date Received 2024-04-09 the silica coated sulfur-carbon composite and high-capacity and/or performance of an electrode, like a positive electrode, and/ or a lithium-sulfur battery. Thus, it may be beneficial for the user of a silica coated sulfur-carbon composite to have a minimum amount of silica particles that is good enough for improving the flowability, but that is not too high so that the capacity and/ or performance of an electrode, like a positive electrode, and/ or a lithium-sulfur battery may be notably affected.
Preferably, the silica coated sulfur-carbon composite may fulfill the following formula 5A:
[formula 5A1 < 7.41n(S3p8,) ¨ 40 wherein, mp * 100 -1-Mc NlY =
Mp = mass of silica particles Mc = mass of sulfur-carbon composite Sspec ¨ specific surface area of the porous carbon material.
Thus, the weight amount of silica particles based on the sulfur-carbon composite may depend on the specific surface area of the porous carbon material. A
larger specific surface area of the porous carbon material may correspond to a larger outer surface area of Date Regue/Date Received 2024-04-09 the porous carbon material and thus also of the resulting sulfur-carbon composite. The coating of a larger outer surface area of a sulfur-carbon composite may make it necessary that a larger amount of silica particles is used. Consequently, a larger specific surface area of the porous carbon material may make the use of more silica particles necessary, compared to a porous carbon material with a smaller specific surface area of the porous carbon material. Hence, a silica coated sulfur-carbon composite which may fulfill the above formula 5A, may have the ideal balance between flowability and density of the silica coated sulfur-carbon composite. The specific surface area of the porous carbon material may be determined by BET according to ISO 9277:2010 as it is known by the skilled person in the art, in which mostly none, preferably none, of the sulfur-containing compound is remained in the silica coated sulfur-carbon composite, when measured. Thus, most preferably the specific surface area of the porous carbon material in the silica coated sulfur-carbon composite may be highly similar, preferably about the same, as the corresponding porous carbon material which may not have been used for the formation of a sulfur-carbon composite and/ or a silica coated sulfur-carbon composite.
More preferably, the silica coated sulfur-carbon composite may fulfill the following formula 5B;
[formula 5B1 6.5 iii( ssp ¨41 < 7.31452p ¨ 40 , Date Regue/Date Received 2024-04-09 wherein Mp * 100 Mp-i-Mcr NlY =
Mp = mass of silica particles Mc = mass of sulfur-carbon composite Sspec ¨ specific surface area of the porous carbon material.
Thus, the weight amount of silica particles based on the sulfur-carbon composite may depend on the specific surface area of the porous carbon material.
Thereby, the amount of silica particles may have a lower limit for silica coated sulfur-carbon composite comprising porous carbon material with higher specific surface areas which may be determined by BET according to ISO 9277:2010 as it is known by the skilled person in the art, for providing a silica coated sulfur-carbon composite with improved flowability. Thus, a silica coated sulfur-carbon composite which may fulfill the above formula 5B
may have an improved balanced between good flowability and low density.
In an embodiment of the present disclosure, the average particle size Dso of the silica particles coated on at least part of the surface of the sulfur-carbon composite may be, for example, 10 to 50 nm, or 10 to 40 nm or 15 to 40 nm, or 10 to 15 nm. When the average particle size D50 of the silica particles satisfies the above-described range, it is possible to improve the coating uniformity of the silica particles and reduce the agglomeration of the sulfur-carbon composite.

Date Regue/Date Received 2024-04-09 In the present specification, the average particle size D50 refers to the particle size at 50% of the cumulative particle size distribution. The particle size may be, for example, a value obtained by measuring the silica coated sulfur-carbon composite coated with silica particles through a particle size analyzer (PSA), but the method for measuring the particle size is not limited thereto. The particle size may correspond to the average particle size (D50) according to ISO 13320:2020 as it is known by the person skilled in the art. However, the method for measuring the particle size is not limited thereto.
In an embodiment of the present disclosure, the coating thickness of the silica particles on at least part of the surface of the silica coated sulfur-carbon composite may be, for example, 20 nm to 5 gm, 40 nm to 5 gm, or 40 nm to 1 gm. When the coating thickness of the silica particles is in the above-described range, it is possible to achieve the low density of the silica coated sulfur-carbon composite and improving the flowability, but the present disclosure is not limited thereto. In other words, the silica-coated sulfur-carbon composite may have an optimal balance between excellent fluidity and low density when the coating thickness is within the above-mentioned range. The coating thickness of silica particles may be determined through scanning electron microscopy (SEM), but the measurement method is not limited thereto.
In an embodiment of the present disclosure, the ratio of the average particle size diameter (1)50) of the silica coated sulfur-carbon composite to the maximum thickness of the coating layer may be between 100:1 to 1000:1. A silica coated sulfur-carbon composite fulfilling this ratio may have an optimal balance between good flowability and low density.
Date Regue/Date Received 2024-04-09 The average particle size diameter of the silica coated sulfur-carbon composite may be measured as it is described above, and the thickness of the coating layer may be measured as it is described above. The ratio may be a dimensionless value.
In one embodiment of the present invention, 60% to 100% of the surface area of the sulfur-carbon composite may be coated with the silica particles.
Specifically, the surface area of the sulfur-carbon composite coated by the silica particles is 65% to 100%, 70% to 100%, 75% to 100%, 80% to 100%, 85% to 100%, 90% to 100%, 95% to 100%, or 95% to 99%, but the present invention is not limited thereto.
Specifically, the sulfur-carbon composite may have an external surface and a specific surface area, and the surface area of the sulfur-carbon composite coated with the silica particles is measured based on 100% of the entire external surface of the sulfur-carbon composite by SEM image analysis.
In an embodiment of the present disclosure, the sulfur-carbon composite contains an outer surface and a specific surface, wherein between 60% and 100% of the outer surface of the sulfur-carbon composite is coated with silica particles determined by SEM
analysis in which the surface of the silica coated sulfur-carbon composite is magnified by 15,000 times and a surface area of 10 gm x 10 gm is analyzed. The specific surface may be similar to the inner surface. The specific surface may be determined by BET
according to ISO 9277:2010 as it is known by the person skilled in the art. However, the method for the measurement of the specific surface may not be limited thereto.
In an embodiment of the present disclosure, the coating thickness of the silica Date Regue/Date Received 2024-04-09 particles in the silica coated sulfur-carbon composite may be estimated from a correlation between a ratio of the weight of the silica particles to the total weight of the silica coated sulfur-carbon composite and a ratio of the coating area of the silica particles to the total surface area of the silica coated sulfur-carbon composite.
For example, in an embodiment of the present disclosure, the silica coated sulfur-carbon composite may have features of the following Formula 2.
[Formula 21 0.00101 [ 1/(So/St) 0.2 iMp+Arc where Mp is the mass of the silica particles, Mc is the mass of the sulfur-carbon composite, So is the coating area of the silica particles, and St is the surface area of the silica coated sulfur-carbon composite.
In the specification, the "coating area of the silica particles" may be measured by a method for measuring the coating area of the silica particles on the surface of the sulfur-carbon composite, and for example, may be measured using scanning electron microscopy (SEM).
In the specification, the "surface area of the silica coated sulfur-carbon composite"
may be, for example, a specific surface area value measured by the BET method.
For example, the surface area of the silica coated sulfur-carbon composite may be a value calculated from the volume of adsorbed nitrogen gas using BEL Japan BELSORP-mino II

Date Regue/Date Received 2024-04-09 under the liquid nitrogen temperature (77K). The specific surface may be determined by BET according to ISO 9277:2010 as it is known by the person skilled in the art. However, the method for the measurement of the specific surface may not be limited thereto.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may comprise 0.01 to 20 wt.%, preferably 0.01 to 10 wt.%, more preferably 1 to wt.%, even more preferably 1 to 5 wt.%, most preferably 1 to 3 wt.% silica particles, with respect to the total weight of the silica coated sulfur-carbon composite, respectively.
Preferably, the silica coated sulfur-carbon composite may comprise 99.99 to 80 wt.%, preferably 99.99 to 90 wt.%, more preferably 99 to 90 wt.%, even more preferably 99 to 95

10 wt.%, most preferably 99 to 97 wt.%, sulfur-carbon composite, with respect to the total weight of the silica coated sulfur-carbon composite, respectively. A silica coated sulfur-carbon composite which fulfills the above requirements, may have improved flowability balanced with improved density. Furthermore, an electrode and particularly a lithium-sulfur battery may be provided with improved performance, capacity and/or long lifetime.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may comprise the sulfur-carbon composite and the silica particles at a weight ratio of 99.9:0.1 to 80:20. That is, the weight ratio of the sulfur-carbon composite to the silica particles may be in the range of, for example, 99.9:0.1 to 80:20. For example, the weight ratio of the sulfur-carbon composite and the silica particles may be 99.9:0.1 to 90:10 or 99:1 to 90:10, or 99:1 to 95:5, or 97:3 to 90:10, or 99:1 to 97:3.
When the Date Regue/Date Received 2024-04-09 weight ratio of the sulfur-carbon composite and the silica particles is in the above-described range, it is possible to achieve the low density of the silica coated sulfur-carbon composite and improve the flowability, but the present disclosure is not limited thereto.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite has technical significance in that the silica particles are inserted into the surface of the sulfur-carbon composite commonly used in positive electrodes of lithium-sulfur batteries to reduce the roughness. Accordingly, the sulfur-carbon composite are not limited to a particular type and shape. The roughness may be measured according to the method described above.
In an embodiment of the present disclosure, the average particle size Dso of the sulfur-carbon composite may be 20 gm to 50 gm, but the present disclosure is not limited thereto. For the method for measuring the average particle size D50, reference is made to the description of the average particle size of the silica particles.
In an embodiment of the present disclosure, the sulfur-carbon composite may refer to a composite comprising a sulfur-containing compound supported on at least part of inner and outer surfaces of pores in a porous carbon material.
In one embodiment of the present invention, the sulfur-containing compound may be located on at least a part of the inner surface of the pores of the porous carbon material.
The inner surface of the pores of the porous carbon material may be a specific surface of the porous carbon material. In another embodiment of the present invention, the Date Regue/Date Received 2024-04-09 sulfur-containing compound may be located on at least a part of the outer surface of the porous carbon material.
In an embodiment of the present disclosure, the porous carbon material provides the skeleton for uniform and stable fixing of the sulfur-containing compound which is a positive electrode active material, and supplements the electrical conductivity of the sulfur-containing compound for smooth electrochemical reactions. Therefore, the sulfur-containing compound can directly contact the surface of the porous carbon material, that is, the outer surface of the pores of the porous carbon material and/or the specific surface of the porous carbon material, such as the inner surface of the pores of the porous carbon material. The sulfur-containing compound in direct contact with the porous carbon material may have a technical effect in which an electrochemical reaction may occur, which is suitable for the silica-coated sulfur-carbon composite to be used in an electrode such as an anode, for example. and to be used in lithium-sulfur batteries.
In an embodiment of the present disclosure, in general, the porous carbon material may be made by carbonizing precursors of various carbon materials. In addition, the porous carbon material may include irregular pores, and the average diameter of the pores may be in the range of 1 to 200 nm, for example, 1 to 100 nm, 10 to 80 nm, or 20 to 50 nm.
The average diameter of the pores may be determined according to ISO
15901:2019 as it is known by the person skilled in the art. However, determining the average diameter may not be limited thereto.
Additionally, in an embodiment of the present disclosure, the porosity (or referred Date Regue/Date Received 2024-04-09 to as void fraction) of the porous carbon material may be in the range of 10 to 90% of the total volume of the porous carbon material. The porosity of the porous carbon material may be determined according to ISO 15901:2019 as it is known by the person skilled in the art.
When the average pore size and porosity of the porous carbon material is in the above-described range, it is possible to improve the impregnation of the sulfur-containing compound and ensure the mechanical strength of the sulfur-carbon composite, allowing the use in the electrode fabrication process, but the present disclosure is not limited thereto.
In an embodiment of the present disclosure, the shape of the porous carbon material may include, without limitation, any shape that is commonly used in positive electrodes of lithium-sulfur batteries, for example, a spherical shape, a rod shape, a scaly shape, a platy shape, a tubular shape or a bulk shape.
In an embodiment of the present disclosure, the porous carbon material may include, without limitation, any type of common carbon material having a porous structure.
For example, the porous carbon material may include, but is not limited to, at least one of graphene; carbon black such as denim black, acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); carbon fiber such as graphite nanofiber (GNF), carbon nanofiber (CNF), and activated carbon fiber (ACF); and graphite such as natural graphite, artificial graphite, expandable graphite; or activated carbon.

Date Regue/Date Received 2024-04-09 The porous carbon material may have a specific surface between 300 and 2000 m2/g, preferably between 400 and 1800 m2/g, more preferably between 450 and 1500 m2/g, even more preferably between 500 and 1200 m2/g. The specific surface area may be determined by BET method according to ISO 15901:2019 as it is known by the person skilled in the art. However, determining the specific surface may not be limited thereto. A
porous carbon material which may have a higher specific surface may have the effect that the density of the silica coated sulfur-carbon composite can be reduced and the electrochemical reaction of the sulfur-containing compound can be improved.
However, a porous carbon material which may have a specific surface that is above the above named ranges may have inferior mechanical properties so that their use in an electrode, or lithium-sulfur battery, may not be suitable anymore.
In an embodiment of the present disclosure, the sulfur-containing compound supported on the porous carbon material is not limited to a particular type and includes any type of material that may be used as positive electrode active materials of lithium-sulfur batteries. For example, the sulfur-containing compound may include, but is not limited to, inorganic sulfur (Ss), lithium polysulfide (Li25n, 1 < n < 8) or carbon sulfur polymer (C25x). (2.5<x<50, 2<m).
In another embodiment of the present disclosure, the sulfur-containing compound may be inorganic sulfur (Ss).
In an embodiment of the present disclosure, the sulfur-carbon composite may comprise the porous carbon material and the sulfur-containing compound at a weight ratio Date Regue/Date Received 2024-04-09 of 1:9 to 1:1. For example, the weight ratio of the porous carbon material and the sulfur-containing compound in the sulfur-carbon composite may be 1:1.5 to 1:7, 1:2 to 1:5, 1:2.5 to 1:4, 1:2.7 to 1:3.5, 1:2.8 to 1:3.5 or 1:3. When the weight ratio of the porous carbon material and the sulfur-containing compound is in the above-described range, it is possible to reduce the resistance of the positive electrode active material layer and improve the battery performance, but the present disclosure is not limited thereto.
In an embodiment of the present disclosure, the concentration of silica may be higher at the outer surface compared to the specific surface of the porous carbon material.
The inner surface of the pore of the porous carbon material may be mostly filled with a sulfur -containing compound. Consequently, the concentration of silica that may enter the specific surface (inner surface of the pore) of the porous carbon material may be lower compared to the concentration of silica at the outer surface of the silica coated sulfur-carbon composite. It may be advantageous, if the silica particles mostly, preferably only, coat the outer surface of a silica coated sulfur-carbon composite. As a consequence, the silica coated sulfur-carbon composite may have a good balance between high flowability and density.
The concentration of silica particles may be determined by the weight of silica particles divided by the respective surface. Thus, the concentration of the silica particles in the inner surface of the pore of the porous carbon material may be determined by the weight amount of silica particles divided by the specific surface of the porous carbon material. The concentration of the silica particles in the outer surface of the porous carbon Date Regue/Date Received 2024-04-09 material may be determined by the weight amount of silica particles divided by the outer surface of the porous carbon material.
In one embodiment, the surface of the porous carbon material of a silica coated sulfur-carbon composite may be estimated by subtracting the amount of a sulfur-containing compound in the silica coated sulfur-carbon composite. The specific surface may be determined by BET according to ISO 9277:2010 as it is known by the person skilled in the art. However, the method for the measurement of the specific surface may not be limited thereto.
Preparation method of silica coated sulfur-carbon composite According to another aspect of the present disclosure, there is provided a method for manufacturing the above-described silica coated sulfur-carbon composite.
The method for manufacturing the silica coated sulfur-carbon composite includes the step of coating the silica particles on at least part of the surface of the sulfur-carbon composite.
In an embodiment of the present disclosure, the coating step may be performed by uniformly mixing the sulfur-carbon composite with the silica particles.
In an embodiment of the present disclosure, the mixing for the coating may be the mixing of the sulfur-carbon composite and the silica particles at a weight ratio of 99.9:0.1 to 80:20. For example, the sulfur-carbon composite and the silica particles may be mixed at a weight ratio of 99.9:0.1 to 90:10, or 99:1 to 90:10, or 99:1 to 95:5, or 97:3 to 90:10, or Date Regue/Date Received 2024-04-09 99:1 to 97:3. When the mixing weight ratio of the sulfur-carbon composite and the silica particles is in the above-described range, it is possible to achieve the low density of the silica coated sulfur-carbon composite and improve the flowability, but the present disclosure is not limited thereto.
In an embodiment of the present disclosure, the mixing for the coating may be performed for the uniform distribution of the sulfur-carbon composite and the silica particles.
In an embodiment of the present disclosure, the coating step may include the step of mixing the sulfur-carbon composite with the silica particles in solid state. For example, the sulfur-carbon composite and the silica particles are in a powder phase, and the mixing in solid state may be performed by feeding the sulfur-carbon composite and the silica particles into a powder mixer.
In an embodiment of the present disclosure, since the sulfur-carbon composite and the silica particles are mixed in solid state, any method for simple mixing of them may be used without limitation.
In an embodiment of the present disclosure, the mixing for the coating may be performed by feeding the materials into a mixer such as a bead mill or an acoustic mixer.
In an embodiment of the present disclosure, the mixing for the coating may be performed, for example, for 60 seconds to 60 minutes while stirring at 1,000 rpm to 2,000 rpm in the mixer, to be specific, for 15 minutes to 60 minutes, or 15 minutes to 30 minutes, or 60 seconds to 30 minutes, or 30 minutes to 60 minutes while stirring at 1,300 rpm to Date Regue/Date Received 2024-04-09 2,000 rpm or 1,400 rpm to 2,000 rpm or 1,500 rpm to 2,000 rpm, or 1,000 rpm to 1,500 rpm, to ensure uniformity of the silica coating. However, the mixing time may change depending on the amounts of the materials, and the present disclosure is not limited thereto.
In one embodiment of the present invention, mixing for the coating may be performed for, for example, 60 seconds to 60 minutes, specifically 15 minutes to 60 minutes, and more specifically 15 minutes to 30 minutes. In another embodiment of the present invention, mixing for the coating may be performed for, for example, 60 seconds to 30 minutes, or 30 minutes to 60 minutes, but is not limited thereto.
In one embodiment of the present invention, mixing for the coating is performed at 1,000 rpm to 2,000 rpm, specifically 1,400 rpm to 2,000 rpm, 1,500 rpm to 2,000 rpm or 1,000 rpm to 1,000 rpm in a mixer for uniform mixing. It may be performed at 1,500 rpm, but is not limited thereto.
In an embodiment of the present disclosure, the mixing for the coating may be performed, for example, at room temperature (25 1 C) to minimize the shape deformation of the sulfur-carbon composite and unifointly coat the silica particles, but the present disclosure is not limited thereto.
In an embodiment of the present disclosure, for details of the sulfur-carbon composite and the silica particles, reference is made to the above description of the silica coated sulfur-carbon composite.
In an embodiment of the present disclosure, the method for manufacturing the Date Regue/Date Received 2024-04-09 silica coated sulfur-carbon composite may further include the step of manufacturing the sulfur-carbon composite before the step of coating the silica particles.
In an embodiment of the present disclosure, the step of manufacturing the sulfur-carbon composite may include the step of mixing the porous carbon material with the sulfur-containing compound.
In an embodiment of the present disclosure, the step of manufacturing the sulfur-carbon composite may include the step of mixing the porous carbon material with the sulfur-containing compound and molding them.
In an embodiment of the present disclosure, the mixing of the porous carbon material and the sulfur-containing compound may be performed using a mixer commonly used, and in this instance, the mixing time, temperature and speed may be selectively adjusted according to the amounts and conditions of the raw materials.
In an embodiment of the present disclosure, the step of molding the porous carbon material and the sulfur-containing compound mixed as described above may include heating their mixture. The heating is not limited to a particular temperature and may be performed at any temperature at which the sulfur-containing compound melts, and for example, 110 C to 180 C, to be specific, 115 C to 180 C.
In one embodiment of the present invention, after the coating step, a step of separating the sulfur-carbon composite coated with the silica particles may be further included.

Date Regue/Date Received 2024-04-09 The silica coated sulfur-carbon composite comprises the sulfur-carbon composite with reduced agglomeration by the silica-coating on at least part of the surface, thereby improving the flowability.
According to another aspect of the present disclosure, there is provided a method for improving the flowability of the silica coated sulfur-carbon composite.
The method for improving the flowability of the silica coated sulfur-carbon composite includes the step of coating the silica particles on at least part of the surface of the sulfur-carbon composite.
For details of the step of coating the silica particles on at least part of the surface of the sulfur-carbon composite, reference is made to the above description for the method for manufacturing the silica coated sulfur-carbon composite.
Positive active material and electrode According to another aspect of the present disclosure, there is provided a positive electrode active material comprising the silica coated sulfur-carbon composite.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite itself may be used as the positive electrode active material.
In another embodiment of the present disclosure, the silica coated sulfur-carbon composite may be used as the positive electrode active material together with the sulfur-containing compound where necessary.

Date Regue/Date Received 2024-04-09 According to another aspect of the present disclosure, there is provided an electrode comprising the silica coated sulfur-carbon composite.
Specifically, the electrode may include a porous carbon material, and each porous carbon material may be coated with silica particles. In addition, the porous carbon material may be derived from the silica-coated sulfur-carbon composite.
In one embodiment of the present invention, the electrode may include a silica-coated sulfur-carbon composite, wherein the silica-coated sulfur-carbon composite may include a porous carbon material coated with silica particles. In this case, the silica particles may form a silica coating layer between the porous carbon material and/or the sulfur-carbon composite. The presence of the sulfur-carbon composite or porous carbon material in the silica-coated sulfur-carbon composite may vary depending on whether the electrode is in a charged state or a discharged state when used in a lithium-sulfur battery.
In an embodiment of the present disclosure, the electrode may comprise a current collector; and an electrode active material layer comprising a plurality of silica coated sulfur-carbon composites on at least one surface of the current collector.
In an embodiment of the present disclosure, the electrode may be used as at least one of a negative electrode or a positive electrode for use in lithium secondary batteries.
For example, the electrode may be used as a positive electrode for use in lithium-sulfur batteries, but the use of the present disclosure is not limited thereto.
According to another aspect of the present disclosure, there is provided a Date Regue/Date Received 2024-04-09 lithium-sulfur battery comprising the silica coated sulfur-carbon composite.
The lithium-sulfur battery comprises a positive electrode comprising the above-described silica coated sulfur-carbon composite, a negative electrode comprising a negative electrode active material, and an electrolyte solution.
In an embodiment of the present disclosure, the silica coated sulfur-carbon composite may be included as a carrier for supporting a positive electrode active material of a positive electrode, a positive electrode active material itself, or a conductive material.
In one embodiment of the present invention, a lithium-sulfur battery including the silica-coated sulfur-carbon composite described above may have improved performance. A
lithium-sulfur battery comprising a silica-coated sulfur composite according to the present invention may have improved capacity. Thus, the lithium-sulfur battery according to the present invention can have improved performance and capacity. Without being bound by any theory, the silica-coated sulfur-carbon composite can improve the dispersibility of the silica-coated sulfur-carbon composite in an electrode, such as a positive electrode, and thus a lithium-sulfur battery using the same may indicate an advantageous effect in terms of performance and capacity. In addition, since the formation of agglomerates of the silica-coated sulfur-carbon composite on the electrode, for example, the anode, is minimized, the above-described effect may be exhibited.
Performance improvement can be measured by comparing a lithium-sulfur battery comprising a silica-coated sulfur-carbon composite as described above to a lithium-sulfur battery comprising a sulfur-carbon composite not coated with silica particles.
Date Regue/Date Received 2024-04-09 In an embodiment of the present disclosure, the positive electrode, the negative electrode, the positive electrode active material, the negative electrode active material, and the electrolyte solution may include, without limitation, those used in lithium-sulfur batteries without departing from the present disclosure.
For example, the positive electrode may comprise a positive electrode current collector and a positive electrode active material layer coated on one or two surfaces of the positive electrode current collector, and the negative electrode may comprise a negative electrode current collector and a negative electrode active material layer coated on one or two surfaces of the negative electrode current collector.
In this instance, the positive electrode current collector may include any type of material that supports the positive electrode active material and is highly conductive without causing chemical changes in the corresponding battery, and the negative electrode current collector may include any type of material that supports the negative electrode active material, and is highly conductive without causing chemical changes in the corresponding battery.
In an embodiment of the present disclosure, the negative electrode active material may include, without limitation, any type of material that can reversibly intercalate or deintercalate lithium (Lit), or react with lithium ions to reversibly form a lithium-containing compound. For example, the negative electrode active material may include at least one of lithium metal or a lithium alloy. The lithium alloy may be, for Date Regue/Date Received 2024-04-09 example, an alloy of lithium (Li) and at least one of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) or tin (Sn).
In an embodiment of the present disclosure, the electrolyte solution may include, without limitation, any type of electrolyte solution that may be used in lithium-sulfur batteries, and the electrolyte solution may comprise, for example, a lithium salt and a solvent. The solvent may include, for example, at least one of an ether-based compound or a carbonate-based compound, but is not limited thereto. In addition, the lithium salt includes any type of lithium salt that may be used in electrolyte solutions for lithium-sulfur batteries, and for example, at least one of LiSCN, LiBr, LiI, LiPF6, LiBEI, LiBioClio, LiSO3CF3, LiC1, LiC104, LiSO3CH3, LiB(Ph)4, LiC(502CF3)3, LiN(502CF3)2, LiCF3CO2, LiAsF6, LiSbF6, LiA1C14, LiFSI, chloroborane lithium or lower aliphatic lithium carboxylate, but is not limited thereto.
In an embodiment of the present disclosure, the lithium-sulfur battery may further comprise a separator interposed between the positive electrode and the negative electrode.
The separator separates or insulates the positive electrode from the negative electrode, and may be made of a porous non-conductive or insulating material to transport lithium ions between the positive electrode and the negative electrode. The separator may be an independent member such as a film, or may be a coating layer added to the positive electrode and/or the negative electrode.
In an embodiment of the present disclosure, the material of the separator may Date Regue/Date Received 2024-04-09 include, for example, at least one of polyolefin such as polyethylene and polypropylene, a glass fiber filter paper or a silica material, but is not limited thereto.
In an embodiment of the present disclosure, the shape of the lithium-sulfur battery is not limited to a particular shape, and may come in various shapes such as a cylindrical shape, a stack shape and a coin shape.
In an embodiment of the present disclosure, the method for manufacturing the lithium-sulfur battery may use a winding process commonly used to fabricate electrodes as well as a lamination and stacking process or a folding process of the separator and the electrode, but is not limited thereto.
Hereinafter, the present disclosure will be described in more detail through examples, but the following examples are for illustrative purposes only, and the scope of the present disclosure is not limited thereto.
Experimental example 1. Manufacture of silica coated sulfur-carbon composite Example 1 99 parts by weight of sulfur (SO-carbon (CNT) composite (sulfur (Ss) raw material: H sulfur corp., carbon (CNT) raw material: Nano C corp, S8 70 wt%, wt%) and 1 part by weight of silica particles ([Si021x[SiO(OH)211,, 0.5 < x <
1, D50 15 nm) are put into a mixer (Hanchel mixer), and unifolinly mixed at 1,500 rpm, room temperature Date Regue/Date Received 2024-04-09 for 30 minutes to manufacture a silica coated sulfur-carbon composite with silica particles coated on at least part of the surface of the sulfur-carbon composite.
In this instance, the coating thickness of the silica particles is 40 nm to 5 gm (2.5 gm on average).
Example 2 A silica coated sulfur-carbon composite is manufactured by the same method as Example 1, except that 97 parts by weight of the sulfur-carbon composite and 3 parts by weight of the silica particles ([Si021[SiO(OH)211, 0.5<x<1, D50 15 nm) are mixed.
Example 3 A silica coated sulfur-carbon composite is manufactured by the same method as Example 1, except that 90 parts by weight of the sulfur-carbon composite and 10 parts by weight of the silica particles ([Si021[SiO(OH)211, 0.5<x<1, D50 15 nm) are mixed.
Comparative Example 1 The sulfur-carbon composite itself used in Example 1 is prepared for Comparative Example 1 without the step of mixing silica particles with the sulfur-carbon composite to coat the silica particles on at least part of the surface of the sulfur-carbon composite.
[Measurement of average particle size D50 of silica particles]

Date Regue/Date Received 2024-04-09 The average particle size Dso of the silica particles is measured by a particle size at 50% of the cumulative particle size distribution using a particle size analyzer (PSA).
[Measurement of coating thickness of silica particles]
The coating thickness of the silica particles is measured through a scanning electron microscope (SEM).
[Determination of structure of silica coated sulfur-carbon composite]
To determine the structures of the silica coated sulfur-carbon composites according to Examples 1 and 2 and the sulfur-carbon composite according to Comparative Example 1, the observation results using a scanning electron microscope (SEM, available from JEOL Ltd.) are shown in FIG. 1.
In FIG. 1, an image at 15k magnification is at the upper part, and an image at 2k magnification is at the lower part.
According to FIG. 1, it is found that the sulfur-carbon composite according to Comparative Example 1 without silica particle coating has a rough surface due to the porosity of the sulfur-carbon composite, while in Examples 1 and 2, the silica particles are coated on the surface of the sulfur-carbon composite to form a smooth surface.
Among the silica coated sulfur-carbon composites according to Examples 1 and 2, it is found that the surface of Example 2 with a larger coating amount of silica particles is smoother.
Date Regue/Date Received 2024-04-09 [Determination of flowability of silica coated sulfur-carbon composites]
To determine the flowability of the silica coated sulfur-carbon composites according to Examples 1, 2 and 3 and Comparative Example 1, the angle of repose is measured according to the following angle of repose test, and the results are shown in Table 1 and FIGS. 2 and 3 below. First, a funnel is placed at the height of 7.5 cm from the ground, and fixed with the center aligned using a horizontal leveler, and the lower portion of the funnel is closed to prevent the fed sample from sliding down.
100 g of the sample to be measured is poured into the funnel, the lower portion of the funnel is opened to cause the sample to fall freely into a pile on a disk (diameter 13 cm) on the base.
Subsequently, the angle of repose (0) of the sample pile is measured.
The results also present the result of the sulfur-carbon composite according to Comparative Example 1 without silica particle coating.
Change in angle of repose (%) = [(Ra-Rb)/Rb] X 100 Rb is the angle of repose of the sulfur-carbon composite before coating, and Ra is the angle of repose of the silica coated sulfur-carbon composite.
[Table 1]
Comparative Classification Example 1 Example 2 Example 3 Example 1 Angle of Repose ( ) 32.6 30.3 25.5 23 Change in angle of 0 - 7% - 22% - 30%
repose According to Table 1 and FIGS. 2 and 3, it is found that the angle of repose of the Date Regue/Date Received 2024-04-09 silica coated sulfur-carbon composite according to Examples 1 to 3 with silica coating is lower than Comparative Example 1, showing that flowability is improved.
In particular, according to the results of Table 1, it is found that according to Examples 2 and 3 with larger amounts of silica particles, the angle of repose is lower.
Experimental example 2. Manufacture of zinc oxide (ZnO) coated sulfur-carbon composite For comparative evaluation, to determine if ceramic particles used to coat a sulfur-carbon composite reduce the agglomeration of the sulfur-carbon composite and improve flowability, the following experiments using zinc oxide (ZnO) are conducted.
Comparative Example 2 For the experimental example 2, sulfur (SO-carbon (CNT) composite (sulfur (Ss) raw material: H sulfur corp., carbon (CNT) raw material: Nano C corp, S8 75 wt%, CNT
25 wt%) is prepared.
Comparative Example 3 99 parts by weight of the sulfur-carbon composite prepared in Comparative Example 2 and 1 part by weight of zinc oxide (ZnO, Sigma Aldrich) are put into a mixer (Hanchel mixer) and uniformly mixed at 1,500 rpm, room temperature for 30 minutes to manufacture a sulfur-carbon composite with zinc oxide coated on at least part of the Date Regue/Date Received 2024-04-09 surface of the sulfur-carbon composite.
Comparative Example 4 A sulfur-carbon composite coated with zinc oxide is manufactured by the same method as Comparative Example 3, except that 95 parts by weight of the sulfur-carbon composite and 5 parts by weight of ZnO are mixed.
[Determination of structure of zinc oxide coated sulfur-carbon composite]
To determine the structures of the sulfur-carbon composites according to Comparative Examples 2 to 4, the observation results using a scanning electron microscope (SEM, Jeol) are shown in FIG. 4.
In FIG. 4, an image at 10k magnification is at the upper part and an image at 2k magnification is at the lower part.
According to FIG. 4, it is found that the sulfur-carbon composite according to Comparative Example 2 without zinc oxide coating has a rough surface due to the porosity of the sulfur-carbon composite. In the case of Comparative Examples 3 and 4, it is found that some of zinc oxide is inserted into the surface of the sulfur-carbon composite due to the mixing with zinc oxide, but it is observed that zinc oxide is not unifofinly coated on the surface and the majority of zinc oxide agglomerates and sticks together.
It is observed that the surface roughness of Comparative Examples 3 and 4 is reduced to some extent compared to Comparative Example 2, but how much the surface Date Regue/Date Received 2024-04-09 roughness is reduced compared to Comparative Example 2 is not significant.
[Determination of flowability of zinc oxide coated sulfur-carbon composite]
To determine the flowability of the sulfur-carbon composite according to Comparative Examples 2 to 4, the angle of repose is measured by the same method as the experimental example 1 and the results are shown in the following Table 2 and FIG. 5.
[Table 2[
Classification Comparative Comparative Comparative Example 2 Example 3 Example 4 Angle of repose( ) 22.0 23.5 23.0 Change in angle of repose 0 + 6.8% + 4.5%
(%) According to the results of Table 2 and FIG. 5, as opposed to silica particles, it is found that zinc oxide does not reduce the agglomeration on the surface of the sulfur-carbon composite and improve the flowability, and rather, zinc oxide makes the agglomeration of the sulfur-carbon composite worse. Additionally, it is found that zinc oxide has no influence on the reduction of agglomeration of the sulfur-carbon composite at varying amounts of zinc oxide.

Date Regue/Date Received 2024-04-09

Claims (23)

WHAT IS CLAIMED IS:

1. A silica coated sulfur-carbon composite, comprising:
a sulfur-carbon composite; and silica particles coated on at least part of a surface of the sulfur-carbon composite.

2. The silica coated sulfur-carbon composite according to claim 1, wherein an angle of repose of the silica coated sulfur-carbon composite is equal to or less than 32 .

3. The silica coated sulfur-carbon composite according to claim 1, wherein an average particle size (D50) of the silica particles is 10 to 50 nm.

4. The silica coated sulfur-carbon composite according to claim 1, wherein the silica particles are nanoparticles represented by the following Formula 1:
[Formula 11 [Si021p[SiO(OH)211-p where p is a number of 0 < p < 1.

5. The silica coated sulfur-carbon composite according to claim 1, wherein a coating thickness of the silica particles on at least part of the surface of the silica coated sulfur-carbon composite is 20 nm to 5 gm.
Date Regue/Date Received 2024-04-09

6. The silica coated sulfur-carbon composite according to claim 1, wherein the silica coated sulfur-carbon composite has features of the following Formula 2:
[Formula 21 _ ____ 0.0001- -[ 1/ (So/Sr) 0.2 ¨
where Mp is a mass of the silica particles, Mc is a mass of the sulfur-carbon composite, So is a coating area of the silica particles, and St is a surface area of the silica coated sulfur-carbon composite.

7. The silica coated sulfur-carbon composite according to claim 1, wherein a weight ratio of the sulfur-carbon composite and the silica particles in 99.9:0.1 to 80:20.

8. The silica coated sulfur-carbon composite according to claim 1, wherein an average particle size (D50) of the sulfur-carbon composite is 20 gm to 50 gm.

9. The silica coated sulfur-carbon composite according to claim 1, wherein the sulfur-carbon composite comprises a porous carbon material; and a sulfur-containing compound supported on at least part of inner and outer surfaces of pores in the porous Date Regue/Date Received 2024-04-09 carbon material.

10. The silica coated sulfur-carbon composite according to claim 9, wherein an average diameter of the pores present in the porous carbon material is 1 to 200 nm.

11. The silica coated sulfur-carbon composite according to claim 9, wherein the sulfur-containing compound comprises at least one of inorganic sulfur (Ss), lithium polysulfide (Li2Sn, 1 <= n <= 8) or carbon sulfur polymer (C2Sx)m, 2.5 <= x <= 50, 2 <= m).

12. The silica coated sulfur-carbon composite according to claim 9, wherein the sulfur-carbon composite comprises the porous carbon material and the sulfur-containing compound at a weight ratio of 1:9 to 5:5.

13. The silica coated sulfur-carbon composite according to claim 1, wherein the ratio of the maximum average particle diameter (D50) of the sulfur-carbon composite to the maximum thickness of the coating layer formed by the silica particles is 100:1 to 1000:1.

14. The silica coated sulfur-carbon composite according to claim 1, wherein 0.01 weight% to 20 weight% of the silica particles, and 80 weight% to 99.99 weight% of the sulfur-carbon composite are comprised, based on a total weight of the silica-coated sulfur-carbon composite.

15. The silica coated sulfur-carbon composite according to claim 1, wherein 60% to 100% of the surface area of the sulfur-carbon composite is coated by the silica particles.

16. A method for manufacturing a silica coated sulfur-carbon composite, comprising: coating silica particles on at least part of a surface of a sulfur-carbon composite.

17. The method for manufacturing a silica coated sulfur-carbon composite according to claim 16, further comprising, before the coating step:
manufacturing the sulfur-carbon composite, wherein the step of manufacturing the sulfur-carbon composite comprises mixing a sulfur-containing compound with a porous carbon material.

18. The method for manufacturing a silica coated sulfur-carbon composite according to claim 16, further comprises separating the sulfur-carbon composite coated by the silica particle after the coating.

19. The method for manufacturing a silica coated sulfur-carbon composite according to claim 16, wherein the coating step comprises mixing the sulfur-carbon Date Regue/Date Received 2024-04-09 composite with the silica particles in solid state.

20. The method for manufacturing a silica coated sulfur-carbon composite according to claim 16, wherein in the coating step, a weight ratio of the sulfur-carbon composite and the silica particles is 99.9:0.1 to 80:20.

21. A positive electrode active material comprising the silica coated sulfur-carbon composite according to any one of claims 1 to 15.

22. An electrode comprising the silica coated sulfur-carbon composite according to any one of claims 1 to 15.

23. A lithium-sulfur battery, comprising:
a positive electrode comprising the silica coated sulfur-carbon composite according to any one of claims 1 to 15;
a negative electrode comprising a negative electrode active material; and an electrolyte solution.

Date Regue/Date Received 2024-04-09