U.S. patent application number 13/943754 was filed with the patent office on 2013-11-14 for fibrous separation membrane for secondary battery and manufacturiing method thereof.
The applicant listed for this patent is SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Sun Ok Kim, Jin Wook Na, Young Seuck Yoo.
Application Number | 20130300033 13/943754 |
Document ID | / |
Family ID | 44656852 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130300033 |
Kind Code |
A1 |
Kim; Sun Ok ; et
al. |
November 14, 2013 |
FIBROUS SEPARATION MEMBRANE FOR SECONDARY BATTERY AND
MANUFACTURIING METHOD THEREOF
Abstract
Disclosed herein is a fibrous separation membrane for secondary
batteries, comprising: a support layer containing cellulose fiber;
and a first heat-resistant resin layer applied on one side of the
support layer.
Inventors: |
Kim; Sun Ok; (Seoul, KR)
; Yoo; Young Seuck; (Seoul, KR) ; Na; Jin
Wook; (Suwon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRO-MECHANICS CO., LTD. |
Suwon |
|
KR |
|
|
Family ID: |
44656852 |
Appl. No.: |
13/943754 |
Filed: |
July 16, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13155366 |
Jun 7, 2011 |
|
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13943754 |
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Current U.S.
Class: |
264/465 |
Current CPC
Class: |
H01M 2/162 20130101;
H01M 2/1686 20130101; D01D 11/06 20130101; B29L 2031/3468 20130101;
B29L 2009/00 20130101; Y02E 60/10 20130101 |
Class at
Publication: |
264/465 |
International
Class: |
D01D 11/06 20060101
D01D011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2010 |
KR |
10-2011-0027783 |
Claims
1.-8. (canceled)
9. A method of manufacturing a fibrous separation membrane for
secondary batteries, comprising: forming a support layer containing
cellulose fiber; and electrospinning a heat-resistant resin
solution onto one side of the support layer to form a first
ultrafine-fibrous heat-resistant resin layer.
10. The method according to claim 9, further comprising:
electrospinning a first polymer solution onto one side of the
support layer to form a first ultrafine-fibrous polymer layer
between the forming the support layer and the forming the first
ultrafine-fibrous heat-resistant resin layer.
11. The method according to claim 10, wherein the first polymer
layer is made of a polymer material having a melting point of
100.about.180.degree. C.
12. The method according to claim 9, further comprising:
electrospinning a heat-resistant resin solution onto the other side
of the support layer to form a second ultrafine-fibrous
heat-resistant resin layer.
13. The method according to claim 12, further comprising:
electrospinning a second polymer solution onto the other side of
the support layer to form a second ultrafine-fibrous polymer layer
between the forming the support layer and the forming the second
ultrafine-fibrous heat-resistant resin layer.
14. The method according to claim 13, wherein the second polymer
layer is made of a polymer material having a melting point of
100.about.180.degree. C.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2011-0027783, filed Mar. 28, 2011, entitled
"Secondary battery fibrous separation membrane and method thereof",
which is hereby incorporated by reference in its entirety into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to a fibrous separation
membrane for secondary batteries, and a method of manufacturing the
same.
[0004] 2. Description of the Related Art
[0005] A secondary battery is a battery which can be reused because
it can be recharged using external energy and returned to an
original state after being discharged.
[0006] Such a secondary battery is characterized in that it has
high power density, it can do high-power discharge, and it is only
slightly influenced by temperature.
[0007] Recently, green energy has attracted considerable attention,
and thus secondary batteries have expanded their fields to IT, EV,
ESS, and the like.
[0008] The demand for secondary batteries is rapidly increasing,
and the function of secondary batteries is also becoming highly
functionalized.
[0009] Such a secondary battery includes the four major components
of a cathode active material, an anode active material, an
electrolyte and a separation membrane. Among them, a separation
membrane serves to separate a cathode active material and an anode
active material, and is used as an ion transfer passage. As such,
since a separation membrane serves to provide an ion transfer
passage and prevent foreign matter from moving, it must have pores
having a size of several micrometers or less.
[0010] Conventional separation membranes are mostly formed by a wet
process or a dry process.
[0011] The wet process is a process of forming pores by
phase-separating a solution containing a polymer, a solvent and
other components and then stretching the phase-separated product,
and the dry process is a process of forming pores by extruding a
polymer and then stretching the extruded polymer.
[0012] Since biaxial stretching must be conducted in the wet
process, the wet process is advantageous in that pores are
non-oriented, but is disadvantageous in that manufacturing costs
are high. In contrast, since uniaxial stretching must be conducted
in the dry process, the dry process is disadvantageous in that
pores are oriented, but is advantageous in that manufacturing costs
are low.
[0013] All of the separation membranes formed by the wet process or
the dry process are made of polyolefin-based resins. Since both the
wet process and the dry process include a stretching process, there
is a problem in that the raw materials of the separation membranes
cannot be freely selected.
[0014] The separation membrane is generally made of two kinds of
resins of polyethylene and polypropylene. The separation membrane
is produced by mixing the two kinds of resins or laminating
them.
[0015] Like this, since the conventional separation membrane is
made of a polyolefin-based resin, its heat resistance is low, so
that it is greatly constricted at high temperature, with the result
that it is not suitable for EV.
[0016] Further, the conventional separation membrane is problematic
in that its raw material is limited to polyolefin-based resins, so
that the range of selection of raw materials is very narrow, with
the result that it is not suitable for the realization of high
functionality.
SUMMARY OF THE INVENTION
[0017] Accordingly, the present invention has been devised to solve
the above-mentioned problems, and the present invention intends to
provide a fibrous separation membrane for secondary batteries,
which can expand the range of selection of raw materials because it
is manufactured by electrospinning, and which can maintain high
strength because paper is used as a support layer, and a method of
manufacturing the same.
[0018] An aspect of the present invention provides a fibrous
separation membrane for secondary batteries, including: a support
layer containing cellulose fiber; and a first heat-resistant resin
layer applied on one side of the support layer.
[0019] Here, the first heat-resistant resin layer may be made of
any one selected from the group consisting of aromatic polyesters,
polyphosphazenes, polyurethane, polyurethane copolymers including
polyetherurethane, cellulose acetate, cellulose acetate butylate,
cellulose acetate propionate, polyvinylidene fluoride,
perfluoropolymers, polyvinylchloride, polyvinylidene chloride,
polyethyleneglycol derivatives, polyoxide, polyvinyl acetate,
polystyrene, polyacrylonitrile, and polymethacrylate.
[0020] Further, the fibrous separation membrane may further
include: a first polymer layer applied between the support layer
and the first heat-resistant resin layer.
[0021] Further, the first polymer layer may be made of a polymer
material having a melting point of 100.about.180.degree. C.
[0022] Further, the fibrous separation membrane may further
include: a second heat-resistant resin layer applied on the other
side of the support layer.
[0023] Further, the second heat-resistant resin layer may be made
of any one selected from the group consisting of aromatic
polyesters, polyphosphazenes, polyurethane, polyurethane copolymers
including polyetherurethane, cellulose acetate, cellulose acetate
butylate, cellulose acetate propionate, polyvinylidene fluoride,
perfluoropolymers, polyvinylchloride, polyvinylidene chloride,
polyethyleneglycol derivatives, polyoxide, polyvinyl acetate,
polystyrene, polyacrylonitrile, and polymethacrylate.
[0024] Further, the fibrous separation membrane may further
include: a second polymer layer applied between the support layer
and the second heat-resistant resin layer.
[0025] Further, the second polymer layer may be made of a polymer
material having a melting point of 100.about.180.degree. C.
[0026] Another aspect of the present invention provides a method of
manufacturing a fibrous separation membrane for secondary
batteries, including: forming a support layer containing cellulose
fiber; and electrospinning a heat-resistant resin solution onto one
side of the support layer to form a first ultrafine-fibrous
heat-resistant resin layer.
[0027] Here, the method may further include: electrospinning a
first polymer solution onto one side of the support layer to form a
first ultrafine-fibrous polymer layer between the forming the
support layer and the forming the first ultrafine-fibrous
heat-resistant resin layer.
[0028] Further, the first polymer layer may be made of a polymer
material having a melting point of 100.about.180.degree. C.
[0029] Further, the method may further include: electrospinning a
heat-resistant resin solution onto the other side of the support
layer to form a second ultrafine-fibrous heat-resistant resin
layer.
[0030] Further, the method may further include: electrospinning a
second polymer solution onto the other side of the support layer to
form a second ultrafine-fibrous polymer layer between the forming
the support layer and the forming the second ultrafine-fibrous
heat-resistant resin layer.
[0031] Further, the second polymer layer may be made of a polymer
material having a melting point of 100.about.180.degree. C.
[0032] The terms and words used in the present specification and
claims should not be interpreted as being limited to typical
meanings or dictionary definitions, but should be interpreted as
having meanings and concepts relevant to the technical scope of the
present invention based on the rule that an inventor can
appropriately define the concept of the term to describe the best
method he or she knows for carrying out the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0034] FIG. 1 is a sectional view showing a fibrous separation
membrane for secondary batteries according to a first embodiment of
the present invention;
[0035] FIG. 2 is a sectional view showing a fibrous separation
membrane for secondary batteries according to a second embodiment
of the present invention;
[0036] FIG. 3 is a schematic view showing an electrospinning
apparatus which can be used to manufacture the fibrous separation
membrane for secondary batteries according to the present
invention;
[0037] FIG. 4 is a flowchart showing a method of manufacturing the
fibrous membrane for secondary batteries according to the first
embodiment of the present invention; and
[0038] FIG. 5 is a scanning electron microscope (SEM) photograph
showing a polymer layer formed on the surface of a support layer in
the fibrous separation membrane according to the first embodiment
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] The objects, features and advantages of the present
invention will be more clearly understood from the following
detailed description of preferred embodiments taken in conjunction
with the accompanying drawings. Throughout the accompanying
drawings, the same reference numerals are used to designate the
same or similar components, and redundant descriptions thereof are
omitted. Further, in the description of the present invention, when
it is determined that the detailed description of the related art
would obscure the gist of the present invention, the description
thereof will be omitted.
[0040] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the attached
drawings.
[0041] FIG. 1 is a sectional view showing a fibrous separation
membrane for secondary batteries according to a first embodiment of
the present invention.
[0042] As shown in FIG. 1, the fibrous separation membrane for
secondary batteries according to the first embodiment of the
present invention includes a support layer 10, a polymer layer 22
applied on the support layer 10, and a heat-resistant resin layer
24 applied on the polymer layer 22. Here, if necessary, the polymer
layer 22 may not be provided.
[0043] The support layer 10, which serves to provide strength to
the polymer layer 22 and the heat-resistance resin layer 24, is
made of cellulose fiber, and has a weight of 5.about.500 g/m.sup.2,
preferably 100-300 g/m.sup.2.
[0044] Meanwhile, the support layer 10 may be formed of paper, and
the paper may be transparent or translucent. In particular, the
paper for forming the support layer 10 may be tracing paper. The
"tracing paper" is referred to as paper certified according to ISO
4046-1978, 6.94.
[0045] Particularly, the tracing paper is obtained by hardening
cellulose fiber.
[0046] Here, when paper is used as the support layer 10, pores
having a size of several micrometers (.mu.m), which is a
requirement of a separation membrane, can be obtained as well
guaranteeing strength.
[0047] The polymer layer 22 functions to shut down a secondary
battery when the secondary battery reaches a high temperature.
[0048] The heat-resistant resin layer 24 prevents the meltdown of a
separation membrane when the secondary battery is further heated
after the secondary battery was shut down, thus preventing the
short and explosion of the secondary battery.
[0049] The polymer layer 22 and the heat-resistant resin layer 24
may have a molecular weight which enables electrospinning to be
carried out, and, particularly, may have a molecular weight of
10,000 or more. When the polymer layer 22 and the heat-resistant
resin layer 24 have a molecular weight of 10,000 or more, fiber can
be easily made by electrospinning, and the physical properties
thereof are excellent. Further, as the molecular weight thereof
increases, the diameter of the nanofiber obtained by
electrospinning decreases, thus forming a large number of junctions
of nanofibers.
[0050] Further, the polymer layer 22 and the heat-resistant resin
layer 24 can be made of a polymer having a molecular weight of
2,000 or more in terms of workability and physical properties
depending on mass production. In particularly, the polymer layer 22
and the heat-resistant resin layer 24 can be made of ultra-high
molecular weight polyethylene having a molecular weight of
1,000,000.about.5,000,000.
[0051] If the solvent used to form the polymer layer 22 and the
heat-resistant resin layer 24 can suitably dissolve a polymer and
disperse solid particles, the solvent may be selectively used
depending on the kind of polymer and solid particles by those
skilled in the art.
[0052] The polymer layer 22 is made of a polyolefin resin or a
polymer having a melt index of 1.about.25 g/min and a relatively
low melting point, such as polyethylene (PE), polypropylene (PP),
polymethylpentene, an ethylene-propylene copolymer or the like.
[0053] Further, for the purpose of shutdown function, the polymer
layer 22 may be made of a polymer material having a melting point
of 100.about.180.degree. C., preferably 120.about.150.degree.
C.
[0054] Here, a polyolefin resin or a polymer is used to make the
polymer layer 22, but the present invention is not limited thereto.
All of the polymer materials having a melting point of
100.about.180.degree. C. can be used.
[0055] The heat-resistant resin layer is made of a polymer having a
melting point of 180.degree. C. or having no melting point.
Examples of the polymer having a melting point of 180.degree. C. or
having no melting point may include: aromatic polyesters, such as
polyamide, polyimide, polyamideimide,
poly(meta-phenyleneisophthalamide), ploysulfone, polyether ketone,
polyether imide, polyethylene terephthalate, polytrimethylene
terephthalate, polyethylene naphthalate, and the like;
polyphosphazenes, such as polytetrafluoroethylene,
polydiphenoxyphosphazene,
poly{bis[2-(2-methoxyethoxy)phosphazene]}, and the like;
polyurethane; polyurethane copolymers, such as polyetherurethane,
and the like; cellulose acetate; cellulose acetate butylate;
cellulose acetate propionate; polyvinylidene fluoride;
perfluoropolymers; polyvinylchloride; polyvinylidene chloride;
polyethyleneglycol derivatives; polyoxide; polyvinyl acetate;
polystyrene; polyacrylonitrile; polymethacrylate; and the like.
[0056] Here, the polymer having no melting point is referred to as
a polymer that bums without melting even at 180.degree. C. or
higher.
[0057] Both the polymer layer 22 and the heat-resistant resin layer
24 may have a thickness of 1.about.50 .mu.m, preferably 1.about.20
.mu.m, more preferably 5.about.10 .mu.m. When the thickness thereof
is excessively small, sufficient effects cannot be exhibited.
Further, when the thickness thereof is excessively large, it is
economically disadvantageous and is not especially profitable.
[0058] As described above, the fibrous separation membrane for
secondary batteries is formed by sequentially electrospinning a
polymer solution (including a melt solution) onto the support layer
10, and is formed therein with pores that are micrometers in
size.
[0059] It was ascertained that the matrix of the fibrous separation
membrane for secondary batteries has a structure in which ultrafine
polymer fibers having a diameter of 1.about.3000 nm are irregularly
and three-dimensionally laminated, so that the ratio of surface
area to volume of the matrix thereof is higher than that of a
conventional matrix, and the porosity thereof is higher than that
of the conventional matrix.
[0060] Therefore, since the porosity of the matrix of the
separation membrane is high, the amount of an electrolyte
impregnated into the matrix thereof increases, thus increasing the
ion conductivity of the separation membrane. Further, since the
surface area of the matrix of the separation membrane is large
regardless of the high porosity thereof, the contact area of an
electrolyte to the matrix of the separation membrane can be
increased, thus minimizing the leakage of the electrolyte.
[0061] Meanwhile, when a porous polymer matrix is formed by
electrospinning, there is an advantage in that the porous polymer
matrix is directly formed in the form of membrane.
[0062] The diameter of the fibrous polymer forming the porous
polymer matrix may be adjusted to within a range of 1.about.3000
nm, preferably 10.about.1000 nm, more preferably 50.about.500 nm.
When the diameter of the fibrous polymer is excessively small, it
is difficult to form a separation membrane. Further, when the
diameter thereof is excessively large, the impregnation rate of an
electrolyte is decreased.
[0063] Further, the porosity of the polymer layer 22 applied on the
support layer 10 is about 20.about.90%, and the pore size thereof
is about 10 nm.about.10 .mu.m.
[0064] FIG. 2 is a sectional view showing a fibrous separation
membrane for secondary batteries according to a second embodiment
of the present invention.
[0065] As shown in FIG. 2, the fibrous separation membrane for
secondary batteries according to the second embodiment of the
present invention includes a support layer 10, a pair of polymer
layers 22 and 22' applied on both sides of the support layer 10,
and a pair of heat-resistant resin layers 24 and 24' respectively
applied on the polymer layers 22 and 22'. Here, if necessary, the
polymer layers 22 and 22' may not be provided.
[0066] The configuration of the fibrous separation membrane for
secondary batteries according to the second embodiment of the
present invention is the same as that of the fibrous separation
membrane for secondary batteries according to the first embodiment
of the present invention, except that the polymer layers 22 and 22'
and the heat-resistant resin layers 24 and 24' are sequentially
formed on both sides of the support layer 10. Therefore, detailed
descriptions thereof will be omitted.
[0067] Hereinafter, a method of manufacturing the fibrous membrane
for secondary batteries according to the first embodiment will be
described with reference to FIG. 3.
[0068] FIG. 3 is a schematic view showing an electrospinning
apparatus which can be used to manufacture the fibrous separation
membrane for secondary batteries according to the present
invention.
[0069] As shown in FIG. 3, the electrospinning apparatus includes a
barrel 100 for storing a polymer solution or a heat-resistant resin
solution, a proportioning pump 110 for discharging the polymer
solution or heat-resistant resin solution, a high-voltage generator
120, and a spinning nozzle 130 connected to the high-voltage
generator 120.
[0070] The polymer solution or heat-resistant resin solution
discharged through the proportioning pump 110 passes through the
spinning nozzle 130 electrically charged by the high-voltage
generator 120 to be formed into ultrafine fiber, and the ultrafine
fiber is collected on the support layer 10 disposed on a collecting
plate 140 grounded in the form of a conveyor moving at a
predetermined speed.
[0071] FIG. 4 is a flowchart showing a method of manufacturing the
fibrous membrane for secondary batteries according to the first
embodiment.
[0072] As shown in FIG. 4, in the method of manufacturing the
fibrous membrane for secondary batteries according to the first
embodiment, first, paper to be used as a support layer is prepared
and provided (S100).
[0073] The paper is made of cellulose fiber, and has a weight of
5.about.500 g/m.sup.2, preferably 100.about.300 g/m.sup.2. In
particular, the paper is a tracing paper obtained by hardening
cellulose fiber.
[0074] Subsequently, a polymer solution is put into a barrel of an
electrospinning apparatus, the polymer solution is discharged using
a proportioning pump, and then a spinning nozzle is electrically
charged using a high-voltage generator, thus forming a polymer
layer on the paper disposed on a collecting plate grounded in the
form of a conveyor moving at a predetermined speed (S200).
[0075] For example, as the polymer solution, a polyethylene (PE)
solution is prepared and then put into a barrel of an
electrospinning apparatus, and then the polyethylene (PE) solution
is discharged using a proportioning pump.
[0076] In this case, a spinning nozzle is electrically charged
using a high-voltage generator to form a polymer layer having a
thickness of 50 .mu.m on a support layer.
[0077] Here, if necessary, the procedure of forming the polymer
layer may be omitted.
[0078] Subsequently, a heat-resistant resin solution, for example a
polyethylene terephthalate (PET) solution, is electrospun in the
same manner as the polymer solution to form a heat-resistant resin
layer on the polymer layer, thereby manufacturing an
ultrafine-fibrous porous polymer separation membrane (S300).
[0079] FIG. 5 shows a scanning electron microscope (SEM) photograph
of the polymer layer applied on the surface of the support
layer.
[0080] Subsequently, in order to increase adhesion between the
support layer and the polymer layer and adhesion between the
polymer layer and the heat-resistant resin layer and to adjust the
porosity and thickness of the heat-resistant resin layer, press
lamination is conducted at a predetermined temperature or lower
after the polymer layer is disposed on the support layer, or is
conducted at a predetermined temperature or lower after the
separation membrane of the present invention is disposed between a
cathode and an anode (S400).
[0081] Meanwhile, in a method of manufacturing the fibrous membrane
for secondary batteries according to the second embodiment of the
present invention, a pair of polymer layers 22 and 22' and a pair
of heat-resistant resin layers 24 and 24' can be sequentially
formed on both sides of a support layer in the same manner as the
above-mentioned method of manufacturing the fibrous membrane for
secondary batteries according to the first embodiment of the
present invention. Therefore, detailed descriptions thereof will be
omitted.
[0082] Here, if necessary, the procedure of forming the pair of
polymer layers 22 and 22' may be omitted.
[0083] As described above, according to the present invention, a
separation membrane can assure sufficient strength because it is
manufactured by electrospinning a polymer solution on paper used as
a support layer.
[0084] Further, according to the present invention, micropores can
be formed in a separation membrane because the separation membrane
is manufactured by electrospinning a polymer solution on paper used
as a support layer.
[0085] Further, according to the present invention, a separation
membrane having heat resistance, which is not constricted even at
high temperature, can be obtained because paper and several polymer
resins are used.
[0086] Further, according to the present invention, owing to the
post-treatment using a thermal pressing process, the adhesion
between the fiber and the paper can be improved, the strength of a
separation membrane can be improved, and a thin fibrous separation
membrane can be obtained.
[0087] Furthermore, according to the present invention, a thin
separation membrane can be obtained, so that a secondary battery
generates high power, thereby improving the performance of a
secondary battery.
[0088] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *