U.S. patent application number 13/554120 was filed with the patent office on 2013-07-04 for method for making sulfur-graphene composite material.
This patent application is currently assigned to HON HAI PRECISION INDUSTRY CO., LTD.. The applicant listed for this patent is Jian-Wei GUO, Xiang-Ming HE, Jian-Jun LI, Jian-Guo REN, Wen-Ting SUN, Li WANG. Invention is credited to Jian-Wei GUO, Xiang-Ming HE, Jian-Jun LI, Jian-Guo REN, Wen-Ting SUN, Li WANG.
Application Number | 20130171355 13/554120 |
Document ID | / |
Family ID | 48678623 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130171355 |
Kind Code |
A1 |
WANG; Li ; et al. |
July 4, 2013 |
METHOD FOR MAKING SULFUR-GRAPHENE COMPOSITE MATERIAL
Abstract
A method for making a sulfur-graphene composite material is
provided. In the method, an elemental sulfur solution and a
graphene dispersion are provided. The elemental sulfur solution
includes a first solvent and an elemental sulfur dissolved in the
first solvent. The graphene dispersion includes a second solvent
and graphene sheets dispersed in the second solvent. The elemental
sulfur solution is added to the graphene dispersion, a number of
elemental sulfur particles are precipitated and attracted to a
surface of the graphene sheets to form the sulfur-graphene
composite material. The sulfur-graphene composite material is
separated from the mixture.
Inventors: |
WANG; Li; (Beijing, CN)
; HE; Xiang-Ming; (Beijing, CN) ; LI;
Jian-Jun; (Beijing, CN) ; GUO; Jian-Wei;
(Beijing, CN) ; SUN; Wen-Ting; (Beijing, CN)
; REN; Jian-Guo; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WANG; Li
HE; Xiang-Ming
LI; Jian-Jun
GUO; Jian-Wei
SUN; Wen-Ting
REN; Jian-Guo |
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing |
|
CN
CN
CN
CN
CN
CN |
|
|
Assignee: |
HON HAI PRECISION INDUSTRY CO.,
LTD.
Tu-Cheng
TW
Tsinghua University
Beijing
CN
|
Family ID: |
48678623 |
Appl. No.: |
13/554120 |
Filed: |
July 20, 2012 |
Current U.S.
Class: |
427/337 ;
427/372.2; 427/443.2; 977/734; 977/773 |
Current CPC
Class: |
H01M 4/382 20130101;
H01M 4/5815 20130101; H01M 10/0525 20130101; B05D 1/18 20130101;
H01M 4/38 20130101; H01M 4/625 20130101; Y02E 60/10 20130101; H01M
4/366 20130101; H01M 4/583 20130101; H01M 2004/026 20130101; B05D
3/107 20130101; H01M 4/587 20130101 |
Class at
Publication: |
427/337 ;
427/443.2; 427/372.2; 977/734; 977/773 |
International
Class: |
B05D 1/18 20060101
B05D001/18; B05D 3/04 20060101 B05D003/04; B05D 3/10 20060101
B05D003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2011 |
CN |
201110447288.3 |
Claims
1. A method for making a sulfur-graphene composite material
comprising: providing an elemental sulfur solution and a graphene
dispersion, the elemental sulfur solution comprising a first
solvent and an elemental sulfur dissolved in the first solvent, the
graphene dispersion comprising a second solvent and a plurality of
graphene sheets dispersed in the second solvent, the elemental
sulfur being insoluble in the second solvent; adding the elemental
sulfur solution in the graphene dispersion to form a mixture, a
plurality of elemental sulfur particles being precipitated from the
second solvent and attracted to a surface of the plurality of
graphene sheets to form the sulfur-graphene composite material; and
separating the sulfur-graphene composite material from the
mixture.
2. The method of claim 1, wherein the first solvent is selected
from the group consisting of carbon disulfide, carbon
tetrachloride, benzene, toluene, and any combination thereof.
3. The method of claim 1, wherein a concentration of the elemental
solution is about 20 grams per liter to about 80 grams per
liter.
4. The method of claim 1, wherein the plurality of graphene sheets
are uniformly dispersed in the graphene dispersion, and a mass
percentage of the plurality of graphene sheets in the graphene
dispersion is in a range from about 0.1 wt % to about 10 wt %.
5. The method of claim 1, wherein the second solvent is selected
from the group consisting of water, methanol, ethanol, ether, and
any combination thereof.
6. The method of claim 1 further comprising adding a surfactant in
the graphene dispersion before the elemental sulfur solution is
added.
7. The method of claim 6, wherein the surfactant is selected from
the group consisting of sorbitan oleate or sorbitan
(Z)-mono-9-octadecenoate,
octylphenolpoly(ethyleneglycolether).sub.x, x=9-10,
tetrahydrofuran, and any combination thereof.
8. The method of claim 1, wherein the elemental sulfur solution is
dripped in the graphene dispersion.
9. The method of claim 1, wherein the sulfur-graphene composite
material is separated by leaching.
10. The method of claim 1, wherein the sulfur-graphene composite
material separated is air-dried or freeze-dried.
11. The method of claim 1, wherein the plurality of elemental
sulfur particles in the sulfur-graphene composite material are
attracted to the surface of each graphene sheet
12. The method of claim 1, wherein a diameter of the plurality of
elemental sulfur particles is in a range from about 20 nanometers
to about 200 nanometers.
13. A method for making a sulfur-graphene composite material
comprising: providing an elemental sulfur solution and a graphene
oxide dispersion, the elemental sulfur solution comprising a first
solvent and an elemental sulfur dissolved in the first solvent, the
graphene dispersion comprising a second solvent and a plurality of
graphene oxide sheets dispersed in the second solvent; the
elemental sulfur being insoluble in the second solvent; adding the
elemental sulfur solution in the graphene oxide dispersion to form
a mixed solution, a plurality of elemental sulfur particles being
precipitated from the second solvent and attracted to a surface of
the plurality of graphene oxide sheets to form the sulfur-graphene
oxide composite material; adding a reducing agent to the mixed
solution to reduce the graphene oxide sheets to the graphene sheets
to form the sulfur-graphene composite material; and separating the
sulfur-graphene composite material from the mixed solution.
14. The method of claim 13, wherein the first solvent is selected
from the group consisting of carbon disulfide, carbon
tetrachloride, benzene, toluene, and any combination thereof.
15. The method of claim 13, wherein the second solvent is selected
from the group consisting of water, methanol, ethanol, aether, and
any combination thereof.
16. The method of claim 13, wherein the reducing agent is selected
from the group consisting of sodium borohydride, hydrazine hydrate,
ascorbic acid, formaldehyde, hydroiodic acid, hydrobromic acid, and
any combination thereof.
17. The method of claim 13, wherein a mass percentage of the
graphene oxide sheets in the graphene oxide dispersion is in a
range from about 1 wt % to about 20 wt %.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims all benefits accruing under 35
U.S.C. .sctn.119 from China Patent Application No. 201110447288.3,
filed on Dec. 28, 2011, in the China Intellectual Property Office,
the contents of which are hereby incorporated by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a method for making
sulfur-graphene composite materials.
[0004] 2. Description of Related Art
[0005] Sulfur is a promising cathode active material with a high
theoretical specific capacity, low cost, and environmental
benignity. Nevertheless, it is difficult to develop a practical
secondary battery without problems such as the low electrical
conductivity of sulfur, dissolution of polysulfides in electrolyte,
and volume expansion of sulfur during discharge. These problems
result in poor cycle life, low specific capacity, and low energy
efficiency.
[0006] Carbon materials, such as active carbon, carbon nanotubes,
mesoporous carbon, or graphene are combined with the sulfur to help
remedy some of the problems. However, there has been difficulty
uniformly combining sulfur and the carbon materials which limits
the cycle life of the secondary battery.
[0007] What is needed, therefore, is to provide a method for making
a sulfur-graphene composite material which can improve the cycle
life of the secondary battery having the sulfur-graphene composite
material used as a cathode active material.
BRIEF DESCRIPTION OF THE DRAWING
[0008] Many aspects of the present disclosure can be better
understood with reference to the following drawings. The components
in the drawings are not necessarily to scale, the emphasis instead
being placed upon clearly illustrating the principles of the
present embodiments.
[0009] FIG. 1 is a flow chart of one embodiment of a method for
making a sulfur-graphene composite material.
[0010] FIG. 2 is a flow chart of another embodiment of a method for
making the sulfur-graphene composite material.
[0011] FIG. 3 is a photo showing a scanning electron microscope
(SEM) image of the sulfur-graphene composite material of example
1.
[0012] FIG. 4 is a graph showing a charge-discharge curve of the
sulfur-graphene composite material of example 1.
DETAILED DESCRIPTION
[0013] The disclosure is illustrated by way of example and not by
way of limitation in the figures of the accompanying drawings. It
should be noted that references to "another," "an," or "one"
embodiment in this disclosure are not necessarily to the same
embodiment, and such references mean at least one.
[0014] FIG. 1, is one embodiment of a method for making a
sulfur-graphene composite material. The method includes the
following steps:
[0015] S1, providing an elemental sulfur solution and a graphene
dispersion, the elemental sulfur solution includes a first solvent
and an elemental sulfur dissolved in the first solvent, and the
graphene dispersion includes a plurality of graphene sheets and a
second solvent, wherein the elemental sulfur is insoluble in the
second solvent;
[0016] S2, adding the elemental sulfur solution in the graphene
dispersion to form a mixture, a plurality of elemental sulfur
particles are precipitated from the second solvent and attracted to
a surface of the plurality of graphene sheets to form the
sulfur-graphene composite material; and
[0017] S3, separating the sulfur-graphene composite material from
the mixture.
[0018] In step S1, the elemental sulfur is soluble in the first
solvent, forming a stable and uniform elemental sulfur solution.
The first solvent can be a liquid phase substance. In one
embodiment, the elemental sulfur particles are totally dissolved in
the first solvent. The elemental sulfur, as a raw material, can be
elemental sulfur particles or a sublimed sulfur. The first solvent
can be at least one of carbon disulfide (CS.sub.2), carbon
tetrachloride (CC1.sub.4), benzene, and toluene. In one embodiment,
the first solvent is CS.sub.2. A concentration of the elemental
sulfur solution can be in a range from about 20 grams per one liter
(20 g/L) to about 80 g/L.
[0019] The elemental sulfur can be made by the following
substeps:
[0020] S11, providing a thiosulfate solution;
[0021] S12, adding a hydrochloric acid in and reacting with the
thiosulfate solution to obtain the elemental sulfur; and
[0022] S13, separating the elemental sulfur from a mixing of the
hydrochloric acid and the thiosulfate solution.
[0023] The method is used to fabricate the elemental sulfur
particles. The thiosulfate can be at least one of sodium
thiosulfate and potassium thiosulfate. The step S11 can further
include a step of adding a first surfactant to the thiosulfate
solution to suppress a diameter of the elemental sulfur particles
to be formed. The surfactant can be at least one of octylphenolpoly
(ethyleneglycolether).sub.x, x=9-10 (also called Triton.RTM. X-100)
and tetrahydrofuran.
[0024] In step S13, the elemental sulfur particles can be filtered
out from the solvent and dried.
[0025] In step S1, the elemental sulfur is insoluble in the second
solvent such that the elemental sulfur can be precipitated from the
second solvent and combined to the surface of the plurality of
graphene sheets. The second solvent can be a liquid phase
substance, which can be at least one of water, methanol, ethanol,
and ether. In one embodiment, the second solvent is water.
[0026] The plurality of graphene sheets can be made by methods of
thermal expansion and reduction of graphite, chemical vapor
deposition, or epitaxial crystal growth. The plurality of graphene
sheets are uniformly dispersed in the second solvent by
ultrasonically vibrating the graphene dispersion. A mass percentage
of the plurality of graphene sheets in the graphene dispersion can
be in a range from about 0.1 wt % to about 10 wt %. In one
embodiment, the mass percentage is about 0.1 wt % to about 3 wt
%.
[0027] The step S1 can further include a step of adding a second
surfactant to the graphene dispersion. The second surfactant can
facilitate a dispersing of the plurality of graphene sheets in the
second solvent, coated on a surface of each elemental sulfur
particle to suppress the growth of the elemental sulfur particle
after the elemental sulfur particles are precipitated from the
solvent, and adhered on the surface of the plurality of graphene
sheets and chemically combined with the graphene sheets by chemical
groups of the surfactant. The elemental sulfur particles can
chemically combine with the plurality of graphene sheets via the
chemical groups of the second surfactant connected with the
graphene sheets. The second surfactant can be an ionic surfactant,
such as Triton.RTM. X-100, sorbitanoleate or sorbitan
(Z)-mono-9-octadecenoate (also called Span.RTM. 80), and
tetrahydrofuran. In one embodiment, the second surfactant is the
Triton.RTM. X-100.
[0028] In step S2, the elemental sulfur solution is a liquid phase
substance, but when added to the graphene dispersion, the elemental
sulfur particles will precipitate as solid phase substances from a
liquid environment. In addition, the precipitated elemental sulfur
particles are easily captured by the graphene sheets and attracted
to the surface of the plurality of graphene sheets for a large
specific surface energy of the graphene sheets. The precipitated
elemental sulfur particles can be attracted to the surface of each
graphene sheet and uniformly dispersed thereon. The elemental
sulfur particles can be attracted to the surface of each graphene
sheet by a strong interaction therebetween, such as a hydrogen
bonding. The step S2 is a phase transfer process. More
specifically, the elemental sulfur is transferred from a soluble
phase (i.e., the first solvent) to an insoluble phase (i.e., the
second solvent), thus the elemental sulfur is transformed from a
liquid state to a solid state.
[0029] The elemental sulfur solution can be added to the graphene
dispersion once or several times. In one embodiment, the elemental
sulfur solution is slowly dripped in the graphene dispersion to
cause the elemental sulfur particles to completely precipitate out
and disperse uniformly on the surface of each graphene sheet. A
diameter of the elemental sulfur particles in the sulfur-graphene
composite material can be in a range from about 20 nanometers to
about 200 nanometers.
[0030] In step S3, the sulfur-graphene composite material can be
separated from the liquid environment in a way which avoids
strongly disturbing the plurality of uniformly dispersed graphene
sheets. For example, heating and stirring may be avoided when
separating the sulfur-graphene composite material. In one
embodiment, the sulfur-graphene composite material can be separated
by a leaching process to remove the liquid solvent. The separated
sulfur-graphene composite material can be air dried or freeze
dried. Air drying does not involve heat and can be dried in an
inert atmosphere. Because there is no strong disturbance when
separating the sulfur-graphene composite material, the plurality of
graphene sheets can self-assemble as a stable layered sandwich
structure. An elemental sulfur layer is sandwiched by two graphene
sheets.
[0031] Referring to FIG. 2, another embodiment of a method for
making the sulfur-graphene composite material includes the
following steps:
[0032] B1, providing the elemental sulfur solution and a graphene
oxide dispersion, the graphene oxide dispersion includes a
plurality of graphene oxide sheets and the second solvent;
[0033] B2, adding the elemental sulfur solution to the graphene
oxide dispersion to form a mixed solution, a plurality of elemental
sulfur particles are precipitated from the second solvent and
attracted to a surface of the plurality of graphene oxide sheets to
form a sulfur-graphene oxide composite material;
[0034] B3, putting a reducing agent to the mixed solution to reduce
the graphene oxide sheets to the graphene sheets to form the
sulfur-graphene composite material; and
[0035] B4, separating the sulfur-graphene composite material.
[0036] The method in this embodiment is similar to the method
mentioned above. However, the graphene oxide sheets are used, and
the reducing step B3 is further processed.
[0037] Each graphene oxide sheet has hydrophilic oxygen functional
groups to increase the dispersibility in the second solvent. Thus,
a uniform and stable graphene oxide dispersion can be formed. The
oxygen functional groups can be at least one of a carboxyl group,
hydroxyl group, carbonyl group, ester group, and epoxy group. A
mass percentage of the graphene oxide sheets in the graphene oxide
dispersion can be in a range from about 1 wt % to about 20 wt %. In
one embodiment, the mass percentage is about 3 wt %.
[0038] In step B3, the reducing agent can be slowly dripped in the
mixed solution to react with the graphene oxide sheets thoroughly.
The reducing agent can be sodium borohydride, hydrazine hydrate,
ascorbic acid, formaldehyde, hydroiodic acid, hydrobromic acid, or
a combination thereof.
[0039] In present disclosure, a phase transfer method is used to
make the sulfur-graphene composite material. The elemental sulfur
particles can be phase transferred from a soluble solvent to an
insoluble solvent which causes a uniform precipitation on the
surface of the graphene sheets or graphene oxide sheets. A
morphology of the elemental sulfur particles precipitated can be
well controlled by the method. In addition, the method is simple
and low cost. The sulfur-graphene composite material fabricated has
a good conductivity. The sulfur-graphene composite material is
separated from the liquid environment, and the graphene sheets has
the large specific surface energy, Therefore, the separated
sulfur-graphene composite material can self-assemble as a sandwich
structure with a plurality of layers stacked. Dissolution of the
sulfur in an electrolyte of the secondary battery can be minimized
if the sulfur-graphene composite material is used as the cathode
active material of the second battery. Therefore, a
charge-discharge cycle performance of the secondary battery can be
improved.
Example 1
[0040] The elemental sulfur solution having a concentration of
about 40 g/L, is prepared by having the sublimed sulfur dissolved
in the CS.sub.2 solvent. The graphene sheets are added to the
ethanol and then ultrasonically vibrated to prepare the graphene
dispersion. A power of the ultrasonically vibrating is about 150
watt. The mass percentage of the graphene sheets in the graphene
dispersion is about 1 wt %. The elemental sulfur solution is added
to the graphene dispersion to form a mixture. A plurality of
elemental sulfur particles are precipitated and combine to the
surface of the graphene sheets. The mixture is leached to remove
the liquid substances and air-dried to obtain the sulfur-graphene
composite material. Referring to FIG. 3, in the SEM image, the
diameter of the elemental sulfur particles is uniform and small.
Referring to FIG. 4, the sulfur-graphene composite material is used
as the cathode active material for the Li--S battery. The result
shows that the Li--S battery has a good capacity retention and
charge-discharge efficiency.
Example 2
[0041] The process is the same as in the Example 1, except that the
concentration of the elemental sulfur solution is about 60 g/L, the
mass percentage of the graphene sheets in the graphene dispersion
is about 0.5 wt %. The elemental sulfur particles in the
sulfur-graphene composite material appear like stubs or needles.
The diameter of the elemental sulfur particles is in a range from
about 50 nm to about 200 nm.
Example 3
[0042] The process is the same as in the example 1, except that
graphene oxide dispersion is added to the elemental sulfur
solution. The graphene oxide is prepared by Hummers method. A
plurality of elemental sulfur particles are precipitated and
combined to the surface of the graphene oxide. Hydrazine hydrate
water solution is added to the mixture to reduce the graphene oxide
to the graphene. The diameter of the elemental sulfur particles is
about 50 nm to about 80 nm.
[0043] Depending on the embodiment, certain steps of methods
described may be removed, others may be added, and the sequence of
steps may be altered. It is also to be understood that the
description and the claims drawn to a method may include some
indication in reference to certain steps. However, the indication
used is only to be viewed for identification purposes and not as a
suggestion as to an order for the steps.
[0044] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
present disclosure. Variations may be made to the embodiments
without departing from the spirit of the present disclosure as
claimed. Elements associated with any of the above embodiments are
envisioned to be associated with any other embodiments. The
above-described embodiments illustrate the scope of the present
disclosure but do not restrict the scope of the present
disclosure.
* * * * *