TECHNICAL FIELD
[0001] The present invention relates to a gel polymer
electrolyte including an additive capable of imparting
forming effects of the gel polymer electrolyte in an air
atmosphere and the reinforcing function of flame retardan5 cy,
and an electrochemical device including the gel polymer
electrolyte.
BACKGROUND ART
10 [0002] As an applying field of energy storage technique is
enlarged to a cellular phone, a camcorder, a laptop PC and an
electrical vehicle, efforts on studying and developing
batteries have been increasingly embodied.
[0003] In consideration of this aspect, an electrochemical
15 device receives the most attention. Particularly, according
to the trend of electric devices having small size and light
weight, efforts on developing a lithium secondary battery
having small size, light weight and capable of charging and
discharging in high capacity have been continued.
20 [0004] The lithium secondary battery is composed of a
cathode and an anode, which include an electrode active
material that may intercalate and deintercalate lithium ions,
a separator disposed therebetween and an electrolyte as a
delivering medium of the lithium ions.
25 [0005] As the electrolyte, an electrolyte of a liquid state,
3
particularly, an ion conductive organic liquid electrolyte
obtained by dissolving a salt in a non-aqueous organic
solvent has been widely used. However, with the liquid
electrolyte, leakage may be generated, and ignition and
explosion may be induced due to the high flammability 5 ity of the
non-aqueous organic solvent used. In addition, with the
liquid electrolyte, a carbonate organic solvent may be
decomposed during charging and discharging a lithium
secondary battery, or a side reaction with an electrode may
10 be carried out to generate a gas in a battery. The side
reaction may be further accelerated during storing at a high
temperature to increase the amount of the gas generated. The
gas consistently generated may induce the increase of the
inner pressure of the battery, leading the modification of
15 the battery including the expansion of the thickness of the
battery. In addition, the local difference of adhesiveness
may be generated on the surface of the electrode of the
battery, and electrode reaction may not be carried out
uniformly on the entire surface of the electrode.
20 [0006] Recently, a method of using a gel polymer electrolyte
causing no concern of leakage, etc. has been suggested to
overcome the safety problem of an electrolyte having a liquid
state. The gel polymer electrolyte is manufactured by
impregnating a polymer matrix formed by the polymerization
25 reaction of a polymerizable monomer and a polymer initiator
4
with an electrolyte including an electrolyte salt and a nonaqueous
organic solvent and then, gelling.
[0007] However, since the gel polymer electrolyte also
includes the non-aqueous organic solvent, defects concerning
thermal safety still are mentioned. In addition, 5 on, since
inferior battery performance is attainable when compared to a
battery using a liquid electrolyte, there are limits on
commercialization.
10 DISCLOSURE OF THE INVENTION
TECHNICAL PROBLEM
[0008] In order to improve the thermal safety of a gel
polymer electrolyte including a non-aqueous organic solvent,
a gel polymer electrolyte including a polymerizable monomer
15 containing a flame retardant functional group and a flame
retardant additive having gel polymer electrolyte forming
effects and imparting flame retardant performance in an air
atmosphere, is provided in the present invention.
[0009] In addition, an electrochemical device including the
20 gel polymer electrolyte is provided in the present invention.
TECHNICAL SOLUTION
[0010] According to an aspect of the present invention,
there is provided a gel polymer electrolyte obtained by
25 polymerizing and gelling a composition for a gel polymer
including a non-aqueous organic solvent, an electrolyte salt
5
and a first polymerizable monomer,
[0011] wherein the gel polymer electrolyte further includes
(a) a compound represented by the following Formula 1 as a
first additive.
5 [Formula 1]
where R1 to R3 are independently hydrogen, an alkyl
group having 1 to 5 carbon atoms, an aryl group having 5 to 7
carbon atoms, or a fluorine substituted alkyl group having 1
10 to 5 carbon atoms, or at least two substituents selected from
R1 to R3 are coupled or connected to each other to form a
cycle group having a ring atom composed of 2 to 6 carbon
atoms or a heterocyclic group having a ring atom composed of
2 to 8 carbon atoms and 1 to 3 oxygen hetero atoms.
15 [0012] In addition, the gel polymer electrolyte may further
include a (meth)acrylic acid ester compound, as a second
additive.
[0013] The gel polymer electrolyte of the present invention
may further include a compound represented by the following
20 Formula 2, as a third additive.
[Formula 2]
6
where R4 is hydrogen or an alkyl group having 1 to 5
carbon atoms, R5 to R7 are independently hydrogen, fluorine
or –O-CO-CH=CH2, and n is an integer from 1 to 5.
[0014] According to another aspect of the present invention5 ,
there is provided an electrochemical device including a
cathode, an anode, a separator disposed between the cathode
and the anode, and the gel polymer electrolyte.
10 ADVANTAGEOUS EFFECTS
[0015] According to the present invention, a polymerizable
monomer including a flame retardant functional group and a
flame retardant additive decreasing the effects of oxygen are
further added during preparing a gel polymer electrolyte,
15 thereby improving the forming effects of the gel polymer
electrolyte in an air atmosphere and securing the thermal
safety of an electrochemical device including the same.
BRIEF DESCRIPTION OF THE DRAWINGS
20 [0016] Preferred embodiments of the invention will be
illustrated with reference to the accompanying drawings. The
drawings are illustrated for further understanding of the
7
technical spirit of present invention and the above-described
contents of the invention, and the present invention should
not be construed as limited to the disclosure in the drawings.
[0017] FIG. 1 is a photographic image illustrating the
experiments on forming reaction of a gel polymer 5 ymer electrolyte
according to Experimental Example 1 of the present invention;
and
[0018] FIG. 2 is a graph illustrating cell life properties
according to Experimental Example 2 of the present invention.
10
BEST MODE FOR CARRYING OUT THE INVENTION
[0019] Hereinafter, the present invention will be described
in more detail to assist the understanding of the present
invention. It will be understood that terms or words used in
15 the specification and claims, should not be interpreted as
having a meaning that is commonly used or defined in
dictionaries, but should be interpreted as having a meaning
that is consistent with their meaning in the context of the
present invention on the basis of the principle that the
20 concept of the terms may be appropriately defined by the
inventors for the best explanation of the invention.
[0020] A non-aqueous organic solvent used for the
preparation of a gel polymer electrolyte is decomposed and
burns while generating highly active radicals such as OH-, H+
25 when the temperature of an electrochemical device increases.
8
In this case, since the radical generating reaction is an
exothermic reaction, the combustion reaction of the organic
solvent may be a chain reaction, and explosion and ignition
of a device may be induced. Meanwhile, in the case that the
gel polymer electrolyte is prepared in the presence of th5 e
air or oxygen, the reactivity of polymerizable monomers may
decrease, and unreacted monomers may be present. Thus, the
forming effects of the gel polymer electrolyte may be
deteriorated, and battery performance may be decreased.
10 [0021] In an embodiment of the present invention, there is
provided a gel polymer electrolyte obtained by polymerizing
and gelling a composition for a gel polymer including a nonaqueous
organic solvent, an electrolyte salt and a first
polymerizable monomer, wherein the gel polymer electrolyte
15 further includes a compound represented by the following
Formula 1 as a first additive.
9
[Formula 1]
where R1 to R3 are independently hydrogen, an alkyl
group having 1 to 5 carbon atoms, an aryl group having 5 to 7
carbon atoms, or a fluorine substituted alkyl group 5 p having 1
to 5 carbon atoms, or at least two substituents selected from
R1 to R3 are coupled or connected to each other to form a
cycle group having a ring atom composed of 2 to 6 carbon
atoms or a heterocyclic group having a ring atom composed of
10 2 to 8 carbon atoms and 1 to 3 oxygen hetero atoms.
[0022] Meanwhile, when the radical reaction required during
the preparation of the gel polymer electrolyte is performed
in the presence of oxygen, a peroxide group may be stabilized
through quenching by the oxygen, and the efficiency of the
15 chain reaction is known to decrease.
[0023] In the present invention, the compound represented by
Formula 1 as the first additive is a flame retardant additive
component and decreases the effect of oxygen in an air
atmosphere, for example, performs a reaction with an active
20 oxygen to form a phosphate, consumes oxygen to increase
conversion ratio during reaction (the reactivity of
polymerizable monomers), and reinforces flame retardancy at
10
the same time.
[0024] In this case, a typical example of the compound
represented by Formula 1 as the first additive may be at
least one selected from the group consisting of trimethyl
phosphite, triethyl phosphite, tributyl phosphate (5 TBP),
triphenyl phosphite, ethyl ethylene phosphate (EEP) and
tris(2,2,2-trifluoroethyl)phosphite (TTFEP).
[0025] In addition, the amount of the compound represented
by Formula 1 as the first additive may be from 0.01 to 10
10 parts by weight based on 100 parts by weight of the total
amount of the gel polymer electrolyte. In the case that the
amount of the compound is less than 0.01 parts by weight, the
improving effect of flame retardancy may be insufficient, and
the mechanical properties of the electrolyte may be
15 deteriorated, and in the case that the amount exceeds 10
parts by weight, the ionic conductivity of the electrolyte
may decrease.
[0026] In addition, the gel polymer electrolyte of the
present invention may further include a second polymerizable
20 monomer as a second additive, for example, a (meth)acrylic
acid ester compound including at least two acrylate groups in
the molecule to form a polymer matrix more easily, which is a
basic skeleton, during preparing the gel polymer electrolyte.
[0027] Examples of the (meth)acrylic acid ester compound of
25 the second additive may include a monomer represented by the
11
following Formulae 3a to 3c or the oligomers thereof.
[Formula 3a]
where R8, R9, R10 and R13 are independently hydrogen, a
substituted or unsubstituted alkyl group 5 roup having 1 to 4 carbon
atoms, R11 and R12 are independently hydrogen, oxygen or an
alkyl group having 1 to 4 carbon atoms, where in the case
that R11 and R12 are oxygen, a double bond is formed with a
combined carbon, m is an integer from 1 to 20, and o is an
10 integer of 0 or 1 to 3,
[Formula 3b]
where R14 is an alkyl group having 1 to 5 carbon atoms
12
or , where R18 is an alkylene group having 1
to 5 carbon atoms, R19 is an alkyl group having 1 to 5 carbon
atoms, an alkyl group including a hydroxyl terminal group and
having 1 to 5 carbon atoms or –C-O-CO-CH=CH2, and R20 and R21
are –R22-O-CO-CH=CH2, where R22 is an alkylene group having 5 ng 1
to 5 carbon atoms, R15 and R16 are an alkylene group having 1
to 10 carbon atoms or an alkylene group including at least
one ether group and having 1 to 10 carbon atoms, R17 is –C-O-
(R24)y-O-CO-CH=CH2 or –(R24)y-O-CO-CH=CH2, where R24 is an
10 alkylene group having 1 to 5 carbon atoms, y is an integer
from 0 to 5, and P is an integer from 0 to 5,
[Formula 3c]
where R25 is an alkyl group having 1 to 5 carbon atoms,
15 R26 and R27 are –O-(R23)y-O-CO-CH=CH2 or –(R26)y-O-CO-CH=CH2,
where R23 and R26 are an alkylene group having 1 to 5 carbon
atoms, and y is an integer from 0 to 5.
[0028] Particularly, typical examples of the (meth)acrylic
acid ester compound as the second additive may include a
20 single material or a mixture of at least two selected from
13
the group consisting of ethoxylated trimethylolpropane
triacrylate (ETPTA), di(trimethylolpropane)tetraacrylate,
di(ethylene glycol) diacrylate (Di(EG)DA), di(ethylene
glycol) dimethacrylate (Di(EG)DM), ethylene glycol
dimethacrylate (EGDM), dipropylene glycol 5 lycol diacrylate
(Di(PG)DA), dipropylene glycol dimethacrylate (Di(PG)DM),
ethylene glycol divinyl ether (EGDVE), diethylene glycol
divinyl ether (Di(EG)DVE), triethylene glycol dimethacrylate
(Tri(EG)DM), dipentaerythritol pentaacrylate (DPentA),
10 trimethylolpropane triacrylate (TMPTA), trimethylolpropane
trimethacrylate (TMPTM), propoxylated(3) trimethylolpropane
triacrylate (PO(3)TMPTA), propoxylated(6) trimethylolpropane
triacrylate (PO(6)TMPTA), poly(ethylene glycol) diacrylate
(PAI) and polyethylene glycol dimethacrylate. However, the
15 present invention is not limited thereto, and a multiacrylate
may be mixed thereto.
[0029] The amount of the (meth)acrylic acid ester compound
of the second additive is not specifically limited, however
may be from about 0.1 to about 20 parts by weight based on
20 100 parts by weight of the total amount of the gel polymer
electrolyte to improve the forming effects of the polymer
matrix, which is the basic skeleton of the gel polymer
electrolyte.
[0030] In addition, the gel polymer electrolyte of the
25 present invention may further include a compound represented
14
by the following Formula 2, as a third additive to
additionally impart flame retardancy improving effects.
[Formula 2]
where R4 is hydrogen or an alkyl group having 5 ving 1 to 5
carbon atoms, R5 to R7 are independently hydrogen, fluorine
or –O-CO-CH=CH2, and n is an integer from 1 to 5.
[0031] The compound (oligomer) represented by Formula 2 as
the third additive is a flame retardant additive component
10 and may improve the flame retardancy and impart the
decreasing effects of battery resistance. Typical examples
may include the following Formulae 2a and 2b.
[Formula 2a]
15
15
[Formula 2b]
[0032] Generally, a fluorine atom has strong electron
withdrawing properties, and a compound including the fluorine
atom and represented by the above Formula 2 is known to bloc5 k
continuous combustion reaction during the burning of an
organic solvent by the elevation of the temperature of a
device, or block the inflow of oxygen into the electrolyte,
thereby restraining the burning any longer. That is, the
10 compound represented by Formula 2 may be decomposed when the
temperature of an electrochemical device increases to easily
form radicals (X-). In this case, the radicals (X-) may
capture radicals (OH-, H+) generated from the decomposition
of the organic solvent and produce stable and incombustible
15 HX, thereby restraining the continuous combustion of the
organic solvent. Particularly, since a compound including a
C-F bond as in the compound of the above Formula 2, has a
quite strong bonding force and has very high structural
safety, the flame retardancy of the gel polymer electrolyte
20 may be further improved.
[0033] The amount of the compound represented by Formula 2,
16
as the third additive may be from 0.5 to 20 parts by weight
based on 100 parts by weight of the total amount of the gel
polymer electrolyte, without limitation. In the case that
the amount is less than 0.5 parts by weight, the flame
retardant effects may be insufficient, 5 ent, and the mechanical
properties of the electrolyte may be deteriorated. In the
case that the amount exceeds 20 parts by weight, the ionic
conductivity of the electrolyte may be decreased.
[0034] Meanwhile, in the gel polymer electrolyte of the
10 present invention, non-aqueous organic solvents used for the
preparation of a common electrolyte may be used, without
limitation. Typical examples of the non-aqueous organic
solvent may include a cyclic carbonate, a linear carbonate, a
lactone, an ether, an ester, a sulfoxide, an acetonitrile, a
15 lactam and a ketone.
[0035] The cyclic carbonate may include ethylene carbonate
(EC), propylene carbonate (PC), butylene carbonate (BC),
fluoroethylene carbonate (FEC), etc., and the linear
carbonate may include diethyl carbonate (DEC), dimethyl
20 carbonate (DMC), dipropyl carbonate (DPC), ethyl methyl
carbonate (EMC), methyl propyl carbonate (MPC), etc. The
lactone may include gamma butyrolactone (GBL), and the ether
may include dibutyl ether, tetrahydrofuran, 2-methyl
tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-
25 diethoxyethane, etc. The ester may include methyl formate,
17
ethyl formate, propyl formate, methyl acetate, ethyl acetate,
propyl acetate, methyl propionate, ethyl propionate, butyl
propionate, methyl pivalate, etc. In addition, the sulfoxide
may include dimethylsulfoxide, etc., and the lactam may
include N-methyl-2-pyrrolidone (NMP), etc. In 5 addition, the
ketone may include polymethyl vinyl ketone. In addition, a
halogen derivative of the organic solvent may be used. These
solvents may be used alone or as a mixture thereof.
[0036] Particularly, the organic solvent in the gel polymer
10 electrolyte of the present invention may further include an
organic solvent containing fluorine to maximize flame
retardancy.
[0037] In addition, in the gel polymer electrolyte of the
present invention, the electrolyte salt may be an electrolyte
15 salt for a common electrochemical device, and may be a
combination of (i) at least one cation selected from the
group consisting of Li+, Na+ and K+ and (ii) at least one
anion selected from the group consisting of PF6-, BF4-, Cl-,
Br-, I-, ClO4-, AsF6-, CH3CO2-, CF3SO3-, N(CF3SO2)2- and
20 C(CF2SO2)3-, without limitation. These electrolyte salts may
be used alone or as a mixture thereof. The amount of the
electrolyte salt is not specifically limited. The
electrolyte salt may particularly include a lithium salt or a
lithium imide salt.
25 [0038] In addition, in the gel polymer electrolyte of the
18
present invention, the first polymerizable monomer may be any
polyfunctional acrylate compounds used for the preparation of
a common gel polymer electrolyte, without limitation.
Particularly, a phosphate compound or a pyrophosphate
compound, known to be used as a flame retardant 5 nt agent may be
included. Typical example of the phosphate compound may
include a phosphate acrylate monomer represented by the
following Formula 4.
[Formula 4]
10
where R30 to R32 are independently hydrogen or an alkyl
group having 1 to 3 carbon atoms, and q is an integer from 1
to 3.
[0039] Typical examples of the first polymerizable monomer
15 may include a phosphate acrylate represented by the following
Formula 4a.
19
[Formula 4a]
[0040] That is, the phosphate compound of the first
polymerizable monomer may be oxidized by the burning when the
temperature of a device increases to form 5 orm a cross-linking
compound having a three dimensional network structure. For
example, the phosphate compound is thermally decomposed to
form a phosphoric acid, and a dehydration reaction is carried
out between the transformed phosphoric acid molecules to form
10 a cross-linking bond. Thus, the electrolyte including the
phosphate compound may block the inflow of oxygen into the
electrolyte to restrain the burning of the organic solvent.
[0041] Since the first polymerizable monomer of the present
invention includes a phosphate part, which is a flame
15 retardant functional group and an acrylate group, a polymer
matrix, which is a basic skeleton of the gel polymer
electrolyte, may be formed through a polymerization reaction.
Thus, flowing properties are not illustrated in the
20
electrolyte, and the gel polymer electrolyte of the present
invention may accomplish electrochemical safety and thermal
safety, particularly, improving effects of flame retardancy.
[0042] The amount of the first polymerizable monomer may be
from 0.5 to 20 parts by weight based on 100 parts by weigh5 t
of the total amount of the gel polymer electrolyte, without
limitation. In the case that the amount is less than 0.5
parts by weight, effects as a cross-linking agent is
insufficient, the gellation of the polymer may be difficult,
10 and the mechanical properties of the electrolyte may be
deteriorated. In the case that the amount exceeds 20 parts
by weight, the monomer may remain in the electrolyte, and
battery performance, for example, ionic conductivity may
decrease.
15 [0043] In addition, the gel polymer electrolyte of the
present invention may further include a polymerization
initiator.
[0044] The polymerization initiator may be included in an
amount ratio of 0.01 to 5 parts by weight based on 100 parts
20 by weight of the total amount of the polymerizable monomer.
Non-limiting examples of the polymerization initiator may
include an organic peroxide or hydroperoxide such as benzoyl
peroxide, acetyl peroxide, dilauryl peroxide, di-tertbutylperoxide,
t-butyl peroxy-2-ethyl-hexanoate, cumyl
25 hydroperoxide, hydrogen peroxide, etc., and an azo compound
21
such as 2,2-azobis(2-cyanobutane), 2,2-
azobis(methylbutyronitrile), azobis(isobutyronitrile) (AIBN),
azobisdimethyl-valeronitrile (AMVN), etc. The abovedescribed
polymerization initiator may be thermally
decomposed to form radicals and may react with 5 ith the
polymerizable monomer by a free radical polymerization to
form a gel polymer electrolyte.
[0045] In addition, the gelling method of the gel polymer
electrolyte of the present invention is not specifically
10 limited, and may be performed according to common methods
known in this field.
[0046] Particularly, a gel type may be formed by
i) adding a first polymerizable monomer and a first
additive, and selectively at least one additive of second and
15 third additives in an electrochemical device and performing a
polymerization reaction in the presence of a polymerization
initiator to form a polymer matrix, and then, gelling by
impregnating the polymer matrix with an electrolyte including
an electrolyte salt and an organic solvent; or
20 ii) preparing a precursor solution of a gel polymer
electrolyte including a first additive, selectively at least
one additive of second and third additives, a polymerizable
monomer, a polymerization initiator, an electrolyte salt and
an organic solvent, and performing a polymerization reaction.
25 [0047] In this case, the polymerization reaction may be
22
performed through a heating, e-beam, gamma ray and aging at
room temperature/high temperature process. In the case that
the polymerization reaction is a thermal polymerization,
about 1 to 8 hours may be consumed, and the reaction
temperature may be in a range 5 ge of 50 to 100°C.
[0048] Meanwhile, a common polymerization reaction is
inconvenient because is necessary to be performed in inert
conditions so as to basically block the reaction of the
radical with oxygen that is a radical scavenger in the air.
10 [0049] However, by providing a gel polymer electrolyte
including a polymerizable monomer including a flame retardant
functional group and a flame retardant additive imparting
flame retardancy reinforcing performance in the present
invention, the flame retardancy reinforcing effects of the
15 gel polymer electrolyte may be imparted, and further, a
polymerization reaction for preparing a gel polymer
electrolyte in the presence of the air or oxygen may be
performed. That is, the additive may decrease the influence
of oxygen during performing the polymerization reaction, and
20 the reactivity of the polymerizable monomers may be improved.
In addition, the extent of reaction may be increased so that
unreacted monomers are hardly present. As a result, defects
such as the deterioration of charge and discharge performance
induced by the remaining unreacted monomers in the battery,
25 may be improved.
23
[0050] In addition, in an embodiment of the present
invention, an electrochemical device including a cathode, an
anode, a separator disposed between the cathode and the anode
and the gel polymer electrolyte of the present invention is
5 provided.
[0051] In this case, the electrochemical device includes all
devices in which an electrochemical reaction is performed.
Particularly, all kinds of primary batteries, secondary
batteries, fuel cells, solar cells, capacitors, etc. may be
10 included. The secondary battery may be a lithium secondary
battery, and non-limiting examples of the lithium secondary
battery may include a lithium metal secondary battery, a
lithium ion secondary battery, a lithium polymer secondary
battery or a lithium ion polymer secondary battery.
15 [0052] The electrochemical device of the present invention
may be manufactured by a common method known in this field.
According to a preferred embodiment, the electrochemical
device may be manufactured by a method including (a)
inserting an electrode assembly formed by wrapping a cathode,
20 an anode and a separator disposed between the cathode and the
anode in a case of an electrochemical device; and (b)
inserting the precursor solution of a gel polymer electrolyte
in the case and polymerizing to form a gel polymer
electrolyte.
25 [0053] The electrode of the electrochemical device may be
24
manufactured by a common method known in this field. For
example, a slurry is prepared by mixing and stirring an
electrode active material, a solvent, and a binder, a
conductive material and a dispersing agent, as occasion
demands, spreading (coating) the slurry on a cu5 rrent
collector of a metal material, compressing and drying.
[0054] The electrode active material may use a cathode
active material or an anode active material.
[0055] The cathode active material may include a lithium
10 nickel manganese composite oxide (LNMO) and other materials,
for example, a layer structured compound such as lithium
cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), etc.; a
lithium transition metal composite oxide substituted with a
transition metal such as Li(NiaCobMnc)O2 (0＜a＜1, 0＜b＜1, 0＜c
15 ＜1, a+b+c=1); a lithium manganese oxide such as LiMnO3,
LiMn2O4, LiMnO2, etc.; a lithium copper oxide (Li2CuO2); a
vanadium oxide such as LiV3O8, V2O5, Cu2V2O7, etc.; LiFe3O4; a
lithium phosphate such as LiFePO4, LiCoPO4, LiFexMn1-xPO4,
etc.; a Ni site type lithium nickel oxide represented by a
20 Formula of LiNi1-xMxO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or
Ga, and x = 0.01 to 0.3); a lithium manganese composite oxide
represented by a Formula of LiMn2-xMxO2 (where M =Co, Ni, Fe,
Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe,
Co, Ni, Cu or Zn), etc., without limitation.
25 [0056] The anode active material may be a common anode
25
active material used in an anode of a common electrochemical
device, without specific limitation. Typical examples of the
anode active material used may include a lithium titanium
oxide (LTO), and other materials, for example, carbon such as
hard carbon, graphite-based carbon, etc.; LixFe2O3 (0≤x≤5 1),
LixWO2 (0≤x≤1), a lithium metal; a lithium alloy; a silicon
alloy; a tin alloy; a metal oxide such as SnO, SnO2, PbO,
PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4,
and Bi2O5; a conductive polymer such as polyacetylene, etc.;
10 a Li-Co-Ni-based material; titanium oxide, etc.
[0057] In addition, a metal oxide such as TiO2, SnO2, etc.,
that may intercalate and deintercalate lithium and has a
potential less than 2 V with respect to lithium may be used,
without limitation. Particularly, a carbon material such as
15 graphite, a carbon fiber, active carbon, etc. may be
preferably used.
[0058] The current collector of a metal material is a metal
having high conductivity and a metal to which the slurry of
the electrode active material may easily attach. Any metals
20 may be used only when the metal has no reactivity in a
voltage range of a battery. Non-limiting examples of a
cathode collector may include aluminum, nickel, or a foil
formed by the combination thereof, and non-limiting examples
of an anode collector may include copper, gold, nickel, a
25 copper alloy or a foil formed by the combination thereof.
26
[0059] The separator is not specifically limited, however, a
porous separator may preferably be used. Non-limiting
examples of the separator may include polypropylene,
polyethylene or polyolefin-based porous separator. In
addition, methods for applying the separator in a 5 battery may
include a common winding method, a lamination (stacking)
method or a folding method of a separator and an electrode,
etc.
[0060] The appearance of the electrochemical device of the
10 present invention is not limited, and may have a cylindrical
type using a can, a prismatic type, a pouch type or a coin
type, etc.
MODE FOR CARRYING OUT THE INVENTION
15 [0061] Hereinafter, the present invention will be described
in more detail referring to embodiments and comparative
embodiments. However, the following embodiments are for
illustrating the present invention, and the scope of the
present invention is not limited to the embodiments set forth
20 herein.
Examples
(Example 1)
[0062] In an organic solvent having a weight ratio of
25 EC:PC:EMC = 1:1:1, LiPF6 was dissolved in the air so that the
27
concentration thereof was 1 M. Then, 5 parts by weight of
the phosphate acrylate of the above Formula 4a as a first
polymerizable monomer, 0.25 parts by weight of AIBN as a
polymerization initiator, and 3 parts by weight of TTFEP as a
first additive based on 100 parts by weight of a gel polyme5 r
electrolyte were added thereto to prepare a precursor
solution of the gel polymer electrolyte.
(Example 2)
10 [0063] In an organic solvent having a weight ratio of
EC:PC:EMC = 1:1:1, LiPF6 was dissolved in the air so that the
concentration thereof was 1 M. Then, 3 parts by weight of
the phosphate acrylate of the above Formula 4a as a
polymerizable monomer, 0.25 parts by weight of AIBN as a
15 polymerization initiator, 3 parts by weight of TTFEP as a
first additive and 2 parts by weight of ethoxylated
trimethylolpropane triacrylate as a second additive based on
100 parts by weight of a gel polymer electrolyte were added
thereto to prepare a precursor solution of the gel polymer
20 electrolyte.
(Example 3)
[0064] In an organic solvent having a weight ratio of
EC:PC:EMC = 1:1:1, LiPF6 was dissolved in the air so that the
25 concentration thereof was 1 M. Then, 2 parts by weight of
28
the phosphate acrylate of the above Formula 4a as a
polymerizable monomer, 0.25 parts by weight of AIBN as a
polymerization initiator, 3 parts by weight of TTFEP as a
first additive, 2 parts by weight of ethoxylated
trimethylolpropane triacrylate as a second additive, 5 and 2
parts by weight of a compound having the above Formula 2a as
a third additive based on 100 parts by weight of a gel
polymer electrolyte were added thereto to prepare a precursor
solution of the gel polymer electrolyte.
10
(Comparative Example 1)
[0065] A precursor solution of a gel polymer electrolyte was
prepared by performing the same procedure described in
Example 2 except for adding 5 parts by weight of the
15 ethoxylated trimethylolpropane triacrylate as the second
additive while excluding the first additive.
(Experimental Example 1: Experiment on the formation of gel
polymer electrolyte)
20 [0066] The precursor solution of the gel polymer electrolyte
of Example 1 (c), the precursor solution of the gel polymer
electrolyte of Example 2 (d), and the precursor solutions of
the gel polymer electrolytes of Comparative Example 1 (a and
b) prepared in a glove box were put in vials, respectively,
25 in a dry room. Oxygen was inserted in the vial and mixed.
29
Then, a polymerization reaction was performed in a chamber at
50 to 80°C, and the formation of gel (the amount of free
liquid) was observed with naked eyes. From the results, the
formation of the gel was easy in the precursor solutions of
the gel polymer electrolytes of Examples 1 5 and 2 of the
present invention when compared to precursor solution of the
gel polymer electrolyte of Comparative Example 1 even with
the oxygen (see FIG. 1).
10 (Experimental Example 2: Experiment on flame retardancy of
gel polymer electrolyte)
[0067] After forming gel using a precursor solution of the
gel polymer electrolyte prepared in Examples 1 to 3 and
Comparative Example 1, the gel was fired and time until the
15 gel burns completely (combustion time) and self-extinguishing
time were measured. The results are illustrated in the
following Table 1.
[Table 1]
Initial
weight
Combustion
time
Self-extinguishing
time (SET)
Example 1 4.7 g 190 sec 40.4 sec/g
Example 2 4.9 g 200 sec 40.8 sec/g
Example 3 4.5 g 400 sec 89.0 sec/g
Comparative
Example 1
4.6 g 130 sec 28.3 sec/g
20 [0068] From the results of the experiments, it would be
secured that the combustion time and the self-extinguishing
30
time of the gels according to Examples 1 to 3 including an
additive containing a flame retardant functional group, etc.
according to the present invention were markedly long when
compared to those of the gel according to Comparative Example
1. Therefore, the gel polymer electrolyte of the 5 present
invention is able to secure the safety and the flame
retardancy.
(Experimental Example 3: Experiment on cycle life properties)
10 [0069] An electrode assembly was formed by disposing a
separator of a polyethylene material between a cathode
including a LCO and an anode including graphite according to
a common method, and the precursor solutions of the gel
polymer electrolytes of Example 3 and Comparative Example 1
15 and a common liquid electrolyte were injected, respectively.
After performing reaction at 70°C for 5 hours, lithium
secondary batteries were manufactured. Then, charging and
discharging were performed at 0.5 C for 50 times to measure
the cycle life properties of secondary batteries.
20 [0070] As shown in FIG. 2, the secondary battery using the
gel polymer electrolyte of Example 3 of the present invention
has improved cycle life properties when compared to a battery
using the gel polymer electrolyte of Comparative Example 1
and has similar cycle properties to that of a battery using
25 the liquid electrolyte.
[0071] While this invention has been particularly shown and described with reference to preferred embodiments thereof and drawings, it will be understood by those skilled in the art
that various changes in form and details may be made therein without departing from the spirit and scope 5 ope of the invention as defined by the appended claims.

I/We Claim:
1. A gel polymer electrolyte obtained by polymerizing and
gelling a composition for a gel polymer comprising an organic
solvent, an electrolyte salt and a first polymerizable
5 monomer,
wherein the gel polymer electrolyte further comprises a
compound represented by the following Formula 1 as a first
additive:
[Formula 1]
10
where R1 to R3 are independently hydrogen, an alkyl
group having 1 to 5 carbon atoms, an aryl group having 5 to 7
carbon atoms, or a fluorine substituted alkyl group having 1
to 5 carbon atoms, or at least two substituents selected from
15 R1 to R3 are coupled or connected to each other to form a
cycle group having a ring atom composed of 2 to 6 carbon
atoms or a heterocyclic group having a ring atom composed of
2 to 8 carbon atoms and 1 to 3 oxygen hetero atoms.
20 2. The gel polymer electrolyte of claim 1, wherein the
first additive comprises at least one selected from the group
consisting of trimethyl phosphite, triethyl phosphite,
33
tributyl phosphite, triphenyl phosphite, ethyl ethylene
phosphite and tris(2,2,2-trifluoroethyl)phosphite.
3. The gel polymer electrolyte of claim 1, wherein an
amount of the first additive is 0.01 to 10 5 parts by weight
based on 100 parts by weight of a total amount of the gel
polymer electrolyte.
4. The gel polymer electrolyte of claim 1, further
10 comprising a (meth)acrylic acid ester compound containing at
least two acrylate groups in a molecule, as a second additive.
5. The gel polymer electrolyte of claim 4, wherein the
second additive is at least one selected from the group
15 consisting of compounds represented by the following Formulae
3a to 3c:
[Formula 3a]
where R8, R9, R10 and R13 are independently hydrogen, a
20 substituted or unsubstituted alkyl group having 1 to 4 carbon
34
atoms, R11 and R12 are independently hydrogen, oxygen or an
alkyl group having 1 to 4 carbon atoms, where in the case
that R11 and R12 are oxygen, a double bond is formed with a
combined carbon, m is an integer from 1 to 20, and o is an
integer 5 of 0 or 1 to 3,
[Formula 3b]
where R14 is an alkyl group having 1 to 5 carbon atoms,
or , where R18 is an alkylene group having 1
10 to 5 carbon atoms, R19 is an alkyl group having 1 to 5 carbon
atoms, an alkyl group including a hydroxyl terminal group and
having 1 to 5 carbon atoms, or –C-O-CO-CH=CH2, and R20 and R21
are –R22-O-CO-CH=CH2, where R22 is an alkylene group having 1
to 5 carbon atoms, R15 and R16 are an alkylene group having 1
15 to 10 carbon atoms or an alkylene group including at least
one ether group and having 1 to 10 carbon atoms, R17 is –C-O-
(R24)y-O-CO-CH=CH2 or –(R24)y-O-CO-CH=CH2, where R24 is an
alkylene group having 1 to 5 carbon atoms, y is an integer
35
from 0 to 5, and P is an integer from 0 to 5,
[Formula 3c]
where R25 is an alkyl group having 1 to 5 carbon atoms,
R26 and R27 are –O-(R23)y-O-CO-CH=CH2 or –(R26)y-O-CO-5 O-CH=CH2,
where R23 and R26 are an alkylene group having 1 to 5 carbon
atoms, and y is an integer from 0 to 5.
6. The gel polymer electrolyte of claim 4, wherein the
10 second additive is a single material or a mixture of at least
two selected from the group consisting of ethoxylated
trimethylolpropane triacrylate,
di(trimethylolpropane)tetraacrylate, diethylene glycol
diacrylate, diethylene glycol dimethacrylate, ethylene glycol
15 dimethacrylate, dipropylene glycol diacrylate, dipropylene
glycol dimethacrylate, ethylene glycol divinyl ether,
diethylene glycol divinyl ether, triethylene glycol
dimethacrylate, dipentaerythritol pentaacrylate,
teimethylolpropane triacrylate, trimethylolpropane
20 trimethacrylate, propoxylated(3) trimethylolpropane
triacrylate, propoxylated(6) trimethylolpropane triacrylate,
36
polyethylene glycol diacrylate and polyethylene glycol
dimethacrylate.
7. The gel polymer electrolyte of claim 4, wherein the
second additive is comprised in an amount 5 unt ratio of 0.1 to 20
parts by weight based on 100 parts by weight of a total
amount of the gel polymer electrolyte.
8. The gel polymer electrolyte of claim 1, further
10 comprising a compound represented by the following Formula 2,
as a third additive:
[Formula 2]
where R4 is hydrogen or an alkyl group having 1 to 5
15 carbon atoms, R5 to R7 are independently hydrogen, fluorine
or –O-CO-CH=CH2, and n is an integer from 1 to 5.
9. The gel polymer electrolyte of claim 8, wherein the
third additive is represented by the following Formula 2a or
20 2b:
[Formula 2a]
37
[Formula 2b]
.
10. The gel polymer electrolyte 5 of claim 1, wherein an
amount of the third additive is 0.5 to 20 parts by weight
based on 100 parts by weight of a total amount of the gel
polymer electrolyte.
10 11. The gel polymer electrolyte of claim 1, wherein the
non-aqueous organic solvent is selected from the group
consisting of a cyclic carbonate, a linear carbonate, a
lactone, an ether, an ester, a sulfoxide, an acetonitrile, a
lactam and a ketone.
15
12. The gel polymer electrolyte of claim 1, wherein the
electrolyte salt comprises a combination of (i) at least one
cation selected from the group consisting of Li+, Na+ and K+
38
and (ii) at least one anion selected from the group
consisting of PF6-, BF4-, Cl-, Br-, I-, ClO4-, AsF6-, CH3CO2-,
CF3SO3-, N(CF3SO2)2- and C(CF2SO2)3-.
13. The gel polymer electrolyte 5 lyte of claim 1, wherein the
first polymerizable monomer is a polyfunctional acrylate
compound.
14. The gel polymer electrolyte of claim 1, wherein the
10 first polymerizable monomer comprises a phosphate compound or
a pyrophosphate compound.
15. The gel polymer electrolyte of claim 14, wherein the
first polymerizable monomer is represented by the following
15 Formula 4:
39
[Formula 4]
where R30 to R32 are independently hydrogen or an alkyl
group having 1 to 3 carbon atoms, and q is an integer from 1
5 to 3.
16. The gel polymer electrolyte of claim 1, wherein the
first polymerizable monomer is comprised in an amount ratio
of 0.5 to 20 parts by weight based on 100 parts by weight of
10 a total amount of the gel polymer electrolyte.
17. The gel polymer electrolyte of claim 1, wherein the
composition for a gel polymer electrolyte further comprises a
polymerization initiator.
15
18. The gel polymer electrolyte of claim 17, wherein the
polymerization initiator is comprised in an amount ratio of
0.01 to 5 parts by weight based on 100 parts by weight of a
40
total amount of a polymerizable monomer.
19. The gel polymer electrolyte of claim 17, wherein the
polymerization initiator is selected from the group
consisting of benzoyl peroxide, acetyl peroxide, dilaury5 l
peroxide, di-tert-butylperoxide, t-butyl peroxy-2-ethylhexanoate,
cumyl hydroperoxide, hydrogen peroxide, 2,2-
azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile),
azobis(isobutyronitrile) and azobisdimethyl-valeronitrile.
10
20. An electrochemical device comprising:
a cathode, an anode, a separator disposed between the
cathode and the anode, and the gel polymer electrolyte
described in claim 1.
15
21. The electrochemical device of claim 20, wherein the
electrochemical device is a lithium secondary battery.