LITHIUM ELECTRODE AND LITHIUM SECONDARY BATTERY
COMPRISING SAME
[Technical Field]
This application claims priority to and the benefit
of Korean Patent Application Nos. 10-2014-0072205, 10-2014-
0072201, and 10-2014-0072249 filed in the Korean
Intellectual Property Office on June 13, 2014, the entire
contents of which are incorporated herein by reference.
The present application relates to a lithium
electrode and a lithium secondary battery including the
same.
[Background Art]
Recently, interests in energy storage technology
have been gradually increased. As the application field of
energy storage technology is enlarged to energy for
cellular phones, camcorders, notebook computers and
electric vehicles, efforts on the research and development
of electrochemical devices are increasingly embodied. In
this aspect, the field of electrochemical devices have
received the majority of attention, and among them,
interests in the development of chargeable/dischargeable
secondary batteries are focused. Recently, in order to
increase the capacity density and specific energy in
- 3 -
developing such batteries, research and development for the
design of new electrodes and batteries have been conducted.
Among secondary batteries which are currently
applied, lithium secondary batteries developed in the early
1990s are in the spotlight due to the advantages of higher
operation voltages and far greater energy densities than
those of conventional batteries, such as Ni-MH, Ni-Cd and
sulfuric acid-lead batteries, which use an aqueous
electrolyte solution.
In general, lithium secondary batteries are
constructed by embedding an electrode assembly including a
positive electrode, a negative electrode, and a separator
interposed between the positive electrode and the negative
electrode in the form of a stacked or wound structure in a
battery case and injecting an electrolyte therein.
In this case, when a lithium electrode is used as
the negative electrode, the lithium electrode formed by
attaching a lithium foil on a planar current collector has
been generally used.
FIG. 1 is a view illustrating electron transfer
pathways in a lithium electrode prepared by attaching a
lithium foil on a planar current collector in the related
art.
If the above-described general lithium electrode 10
is described with reference to FIG. 1, when a battery is
- 4 -
driven, electrons being transferred to a lithium foil 12
through a current collector 11 are transferred in a
unidirectional flow. For this reason, electron density on
lithium surface becomes non-uniform, and accordingly,
lithium dendrites may be formed.
These lithium dendrites may finally cause damage to
the separator and may generate a short circuit in the
lithium secondary battery, and as a result, there may occur
a problem in that the safety of the lithium battery
deteriorates.
[Detailed Description of the Invention]
[Technical Problem]
The present application has been made in an effort
to provide a lithium electrode and a lithium secondary
battery including the same.
[Technical Solution]
In order to solve the problem, the present
application provides a lithium electrode including: a
porous carbon body; and a lithium metal inserted into pores
of the porous carbon body.
Further, the present application provides a lithium
secondary battery including a positive electrode, a
negative electrode, and an electrolyte, in which the
negative electrode is the lithium electrode.
[Advantageous Effects]
- 5 -
According to an exemplary embodiment of the present
application, a contact surface area between a lithium metal
and a porous carbon body may be increased to improve the
performance of a lithium secondary battery.
According to an exemplary embodiment of the present
application, the performance of the lithium secondary
battery may be improved by a porous carbon body, which is
lightweight and has a high energy density per unit weight.
According to an exemplary embodiment of the present
application, the safety of a lithium secondary battery may
be improved by having a porous carbon body to prevent
lithium dendrites from being grown through the
uniformization of electron distribution in the lithium
electrode when the lithium secondary battery is driven.
According to an exemplary embodiment of the present
application, even when a lithium ion conductive protective
layer, which prevents lithium dendrites from being formed
by the porous carbon body, is provided on the surface of
the electrode, it is possible to prevent a phenomenon in
which the protective layer is peeled off during the charge
and discharge of the battery.
[Brief Description of Drawings]
FIG. 1 illustrates electron transfer pathways in a
lithium electrode in the related art.
FIG. 2 illustrates electron transfer pathways in a
- 6 -
lithium electrode according to an exemplary embodiment of
the present application.
FIG. 3 is a view schematically illustrating the
states before and after discharge of a lithium electrode
including a protective layer in the related art.
FIG. 4 is a view schematically illustrating the
states before and after discharge of a lithium electrode
including a protective layer according to an exemplary
embodiment of the present application.
FIG. 5 is a view schematically illustrating the
states before and after discharge of a lithium electrode
including a protective layer according to an exemplary
embodiment of the present application.
[Best Mode]
Hereinafter, the present application will be
described in detail.
The present application provides a lithium electrode
including: a porous carbon body; and a lithium metal
inserted into pores of the porous carbon body.
For example, FIG. 2 illustrates electron transfer
pathways in a lithium electrode prepared according to an
exemplary embodiment of the present application. According
to FIG. 2, a lithium electrode 100 includes: a porous
carbon body 110; and a lithium metal 120 inserted into
pores of the carbon body 110.
- 7 -
A lithium electrode in the related art is prepared
by attaching a lithium foil on a planar current collector.
In this case, since electrons being transferred to the
lithium foil through the planar current collector are
transferred in a unidirectional flow when a battery is
driven, the electron density may be non-uniform on the
surface of the lithium foil, and accordingly, lithium
dendrites may be formed. These lithium dendrites may cause
damage to a separator and may generate a short circuit in a
battery, which is problematic. For example, FIG. 1
illustrates electron transfer pathways in a lithium
electrode in the related art. According to FIG. 1, a
lithium foil 12 is attached on a current collector 11 to
form a lithium electrode 10. Accordingly, electrons are
transferred from the current collector 11 to the lithium
foil 12 in a unidirectional flow.
However, the lithium electrode 100 according to an
exemplary embodiment of the present application has a
structure in which the lithium metal 120 is inserted into
pores of the porous carbon body 100, and a contact area
between the lithium metal acting as an electrode active
material and the porous carbon body is increased to make
the electron distribution on the surface of the lithium
metal uniform. From this, the performance of the lithium
secondary battery may be improved, and the safety of the
- 8 -
lithium secondary battery may be improved by preventing
lithium dendrites from being grown.
According to an exemplary embodiment of the present
application, as a method of inserting the lithium metal
into pores of the porous carbon body, it is possible to use
a method of placing a lithium foil on the porous carbon
body, and then applying pressure by a roll press and the
like to insert the lithium foil into pores, or a method of
melting the lithium metal, and then injecting the molten
metal between pores. Furthermore, the lithium electrode
may be prepared by preparing a slurry using a mixture of a
carbon powder, which forms the porous carbon body, and a
lithium metal powder, and then coating the slurry on a base
material. In this case, in the coating, comma coating, bar
coating, slot die coating, and the like may be used.
However, the method of inserting the lithium metal into
pores of the porous carbon body may be modified or added
depending on the need of the person skilled in the art, and
is not limited thereto.
According to an exemplary embodiment of the present
application, the content of the lithium metal may be 1 to
80 wt%, specifically 40 to 60 wt%, based on the total
weight of the porous carbon body and the lithium metal.
When the content of the lithium metal is within the range,
lithium dendrites may be suppressed from being grown to
- 9 -
prevent a short circuit from being generated even though
continuous charge and discharge of 100 cycles or more are
performed.
According to an exemplary embodiment of the present
application, the porous carbon body may include at least
one selected from activated carbon, graphite, graphene,
carbon nanotubes (CNTs), carbon fiber, carbon black, and
carbon aerosol, but may be used without being limited
depending on the need of the person skilled in the art as
long as the porous carbon body is a porous carbon-based
material.
According to an exemplary embodiment of the present
application, the porous carbon body may be in the form of
mesh, foam, paper, and the like, but the form is not
limited thereto.
Since a carbon-based material is lighter in weight
than typical metals, in a lithium metal according to an
exemplary embodiment of the present application, the
performance of the lithium secondary battery may be
improved by a porous carbon body, which has a high energy
density per unit weight.
The higher porosity the carbon body has and the
smaller the size of pores is, the better the effect of
suppressing lithium dendrite from being grown is.
According to an exemplary embodiment of the present
- 10 -
application, the porous carbon body may have a porosity of
50 to 99%, specifically 60 to 90%. When the porosity of
the porous carbon body is within the range, the surface
area of lithium to be inserted may be maximized while
having high durability and processability of the porous
carbon body.
According to an exemplary embodiment of the present
application, the porosity may be calculated by (the actual
weight of a porous carbon body)/(the measured
volume*theoretical density of the porous carbon body).
In the present specification, the ‘porosity’ of the
porous carbon body means a ratio of a volume occupied by
pores to a total volume of the porous carbon body, and may
also be expressed as a ‘pore rate’.
According to an exemplary embodiment of the present
application, the pores of the porous carbon body may have
an average particle diameter of 5 to 500 μm, specifically
10 to 100 μm. When the average particle diameter of the
pores of the porous carbon body is within the range, the
surface area of lithium to be inserted may be maximized
while having high durability and processability of the
porous carbon body.
According to an exemplary embodiment of the present
application, the porous carbon body may have a thickness of
200 μm or less. Specifically, the porous carbon body may
- 11 -
have a thickness of 150 μm or less.
According to an exemplary embodiment of the present
application, the porous carbon body may have a thickness of
10 μm or more. Specifically, the porous carbon body may
have a thickness of 50 μm or more.
When the thickness of the porous carbon body is
within the range, there is an effect of improving the
performance of the battery because the energy density per
the volume of the battery is increased, and it is
appropriate to apply to the battery.
When a lightweight porous carbon body is used, there
is an effect of increasing the energy density per weight in
the battery because the weight of a current collector is
decreased by about 70% than the weight of another metal
current collector generally used. Further, since a porous
carbon body is more advantageous than another metal current
collector when a thickness of 250 μm or less is formed in
the process, there is an effect of enhancing the efficiency
on the process.
An exemplary embodiment of the present application
may further include a lithium ion conductive protective
layer formed on at least one surface of the lithium
electrode.
A lithium electrode including a protective layer in
the related art was prepared by attaching a lithium foil on
- 12 -
a planar current collector, and a protective layer was
formed on the lithium foil in order to prevent lithium
dendrites. However, there was a problem in that the
protective layer was peeled off depending on the change in
volume of an electrode during the charge and discharge.
For example, FIG. 3 is a view schematically
illustrating the states before and after discharge of a
lithium electrode prepared by attaching a lithium foil on a
current collector in the related art. According to FIG. 3,
in the lithium electrode 10 including a protective layer in
the related art, the lithium foil 12 was attached on the
current collector 11, and a lithium ion conductive
protective layer 13 was formed on the upper surface of the
lithium foil 12 in order to prevent lithium dendrites from
being formed. However, there was a problem in that the
volume of the electrode is changed depending on the
decrease or increase in lithium during the charge and
discharge of the battery, and accordingly, the lithium ion
conductive protective layer 13 is peeled off.
FIG. 4 is a view schematically illustrating the
states before and after discharge of a lithium electrode
including a protective layer according to an exemplary
embodiment of the present application. In order to solve
the problem, the present application uses a porous carbon
body as a current collector. According to FIG. 4, a
- 13 -
lithium electrode 101 including a protective layer
according to an exemplary embodiment of the present
application includes: an electrode composite including a
porous carbon body 110 and a lithium metal 120 inserted
into pores of the porous carbon body 110; and a lithium ion
conductive protective layer 130 formed on at least one
surface of the electrode composite.
The lithium electrode 101 including the protective
layer according to an exemplary embodiment of the present
application has a structure in which the lithium metal 120
is inserted into pores of the porous carbon body 100, and a
contact area between the lithium metal acting as an
electrode active material and the porous carbon body is
increased to make the electron distribution on the surface
of the lithium metal uniform, and lithium dendrites may be
suppressed from being grown by the protective layer. In
addition, the lithium electrode 101 including the
protective layer according to an exemplary embodiment of
the present application has little change in volume of the
electrode depending on the decrease or increase of lithium
during the charge and discharge of the battery because the
porous carbon body 110 is brought into direct contact with
the lithium ion conductive protective layer 130, and
accordingly, there does not occur a peeling-off phenomenon
of the protective layer which has been a problem when a
- 14 -
protective layer is formed, and the safety and performance
of the lithium secondary battery may be further improved.
Further, FIG. 5 is a view schematically illustrating
the states before and after discharge of a lithium
electrode including a protective layer according to an
exemplary embodiment of the present application.
According to FIG. 5, it can be confirmed that even
though the lithium is located on only the lower portion of
the porous carbon body due to the decrease in lithium
during the discharge, the protective layer is attached to
the porous carbon body. Therefore, the lithium electrode
according to an exemplary embodiment of the present
application may prevent the peeling-off of the protective
layer according to the discharge.
Further, the lithium ion conductive protective layer
may take the place of a role of a separation membrane.
According to an exemplary embodiment of the present
application, the lithium ion conductive protective layer
may use a material having a lithium ion conductivity of 10-
7 S/cm or more.
According to an exemplary embodiment of the present
application, the lithium ion conductive protective layer
may include at least one selected from inorganic compounds
and organic compounds.
According to an exemplary embodiment of the present
- 15 -
application, the inorganic compound may be any one or a
mixture of two or more selected from a group consisting of
LiPON, hydride-based compounds, thio-LISICON-based
compounds, NASICON-based compounds, LISICON-based compounds,
and Perovskite-based compounds.
According to an exemplary embodiment of the present
application, the hydride-based compound may be LiBH4-LI,
Li3N, Li2NH, Li2BNH6, Li1.8N0.4Cl0.6, LiBH4, Li3P-LiCl, Li4SiO4,
Li3PS4, or Li3SiS4, but is not limited thereto.
According to an exemplary embodiment of the present
application, the thio-LISICON-based compound may be
Li10GeP2S12, Li3.25Ge0.25P0.75S4, or Li2S-GeS-Ga2S3, but is not
limited thereto.
According to an exemplary embodiment of the present
application, the NASICON-based compound may be
Li1.3Al0.3Ge1.7(PO4)3, Li1.3Al0.3Ti1.7(PO4)3, or LiTi0.5Zr1.5(PO4)3,
but is not limited thereto.
According to an exemplary embodiment of the present
application, the LISICON-based compound may be Li14Zn(GeO4)4,
but is not limited thereto.
According to an exemplary embodiment of the present
application, the Perovskite-based compound may be LixLa1-
xTiO3(0 < x < 1) or Li7La3Zr2O12, and specifically, may be
Li0.35La0.55TiO3, Li0.5La0.5TiO3, or Li7La3Zr2O12, but is not
limited thereto.
- 16 -
According to an exemplary embodiment of the present
application, the organic compound may be selected from
polyethylene oxide (PEO); polyacrylonitrile (PAN);
polymethylmethacrylate (PMMA); polyvinylidene fluoride
(PVDF); and a polymer including -SO3Li, -COOLi, or –OLi.
According to an exemplary embodiment of the present
application, the polymer including -SO3Li, -COOLi, or –OLi
is a polymer which may transfer lithium ions, and may
include a copolymer including a repeating unit of the
following Chemical Formula A and a repeating unit of the
following Chemical Formula B.
[Chemical Formula A]
[Chemical Formula B]
In Chemical Formulae A and B,
m and n mean the number of repeating units,
1 ≤ m ≤ 500, and 1 ≤ n ≤ 500,
X1, X2, and X3 are the same as or different from each
other, and are each independently represented by any one of
the following Chemical Formulae 1 to 3,
- 17 -
[Chemical Formula 1]
[Chemical Formula 2]
[Chemical Formula 3]
In Chemical Formulae 1 to 3,
L1 is a direct bond, or any one of -CZ2Z3-, -CO-, -O-,
-S-, -SO2-, -SiZ2Z3-, and a substituted or unsubstituted
divalent fluorene group,
Z2 and Z3 are the same as or different from each
other, and are each independently any one of hydrogen, an
alkyl group, a trifluoromethyl group (-CF3), and a phenyl
group,
S1 to S5 are the same as or different from each other,
and are each independently hydrogen; deuterium; a halogen
- 18 -
group; a cyano group; a nitrile group; a nitro group; a
hydroxy group; a substituted or unsubstituted alkyl group;
a substituted or unsubstituted cycloalkyl group; a
substituted or unsubstituted alkoxy group; a substituted or
unsubstituted alkenyl group; a substituted or unsubstituted
silyl group; a substituted or unsubstituted boron group; a
substituted or unsubstituted amine group; a substituted or
unsubstituted aryl group; or a substituted or unsubstituted
heteroaryl group,
a, b, c, p, and q are the same as or different from
each other, and are each independently an integer of 0 or
more and 4 or less,
p + q ≤ 6,
a' is an integer of 1 or more and 5 or less,
in Chemical Formula B, Y1 is represented by any one
of the following Chemical Formulae 4 to 6,
[Chemical Formula 4]
[Chemical Formula 5]
- 19 -
[Chemical Formula 6]
in Chemical Formulae 4 to 6,
L2 is a direct bond, or any one selected from -CO-,
-SO2-, and a substituted or unsubstituted divalent fluorene
group,
d, e, f, g, and h are the same as or different from
each other, and are each independently an integer of 0 or
more and 4 or less,
f + g ≤ 6 and b' is an integer of 1 or more and 5 or
less, and
T1 to T5 are the same as or different from each other,
and each independently, at least one is -SO3Li, -COOLi, or
–OLi, and the others are the same as or different from each
other, and are each independently hydrogen; deuterium; a
halogen group; a cyano group; a nitrile group; a nitro
group; a hydroxy group; a substituted or unsubstituted
alkyl group; a substituted or unsubstituted cycloalkyl
- 20 -
group; a substituted or unsubstituted alkoxy group; a
substituted or unsubstituted alkenyl group; a substituted
or unsubstituted silyl group; a substituted or
unsubstituted boron group; a substituted or unsubstituted
amine group; a substituted or unsubstituted aryl group; or
a substituted or unsubstituted heteroaryl group.
In the present specification, " " represents a
position which may be bonded to an adjacent substituent.
Examples of the substituents will be described below,
but are not limited thereto.
In the present specification, examples of the
halogen group include fluorine, chlorine, bromine or iodine.
In the present specification, the alkyl group may be
straight-chained or branch-chained, and the number of
carbon atoms thereof is not particularly limited, but it is
preferred that the number is 1 to 60, specifically 1 to 40,
and more specifically 1 to 20. Specific examples thereof
include a methyl group, an ethyl group, a propyl group, an
isopropyl group, a butyl group, a t-butyl group, a pentyl
group, a hexyl group, a heptyl group, and the like, but are
not limited thereto.
In the present specification, the alkenyl group may
be straight-chained or branch-chained, and the number of
carbon atoms thereof is not particularly limited, but it is
- 21 -
preferred that the number is 2 to 60, specifically 2 to 40,
and more specifically 2 to 20.
In the present specification, the alkoxy group may
be straight-chained or branch-chained, and the number of
carbon atoms thereof is not particularly limited, but it is
preferred that the number is 1 to 60, specifically 1 to 40,
and more specifically 1 to 20.
In the present specification, the cycloalkyl group
is not particularly limited, but it is preferred that the
number of carbon atoms thereof is 3 to 60, specifically 3
to 40, and more specifically 5 to 20, and particularly, a
cyclopentyl group and a cyclohexyl group are preferred.
In the present specification, the heterocycloalkyl
group includes one or more of S, O, and N and is not
particularly limited, but it is preferred that the number
of carbon atoms thereof is 2 to 60, specifically 2 to 40,
and more specifically 3 to 20, and particularly, a
cyclopentyl group and a cyclohexyl group are preferred.
In the present specification, the number of carbon
atoms of the amine group is not particularly limited, but
it is preferred that the number is 1 to 60, specifically 1
to 40, and more specifically 1 to 20. Specific examples of
the amine group include a methylamine group, a
dimethylamine group, an ethylamine group, a diethylamine
group, a phenylamine group, a naphthylamine group, a
- 22 -
biphenylamine group, an anthracenylamine group, a 9-methylanthracenylamine
group, a diphenylamine group, a
phenylnaphthylamine group, a ditolylamine group, a
phenyltolylamine group, a triphenylamine group, and the
like, but are not limited thereto.
In the present specification, the aryl group may be
monocyclic or polycyclic, and the number of carbon atoms
thereof is not particularly limited, but it is preferred
that the number is 6 to 60, specifically 6 to 40, and more
specifically 6 to 20. Specific examples of the aryl group
include a monocyclic aromatic group, such as a phenyl group,
a biphenyl group, a triphenyl group, a terphenyl group, and
a stilbene group, and a polycyclic aromatic group, such as
a naphthyl group, a binaphthyl group, an anthracenyl group,
a phenanthrenyl group, a pyrenyl group, a perylenyl group,
a tetracenyl group, a chrysenyl group, a fluorenyl group,
an acenaphthacenyl group, a triphenylene group, and a
fluoranthene group, and the like, but are not limited
thereto.
In the present specification, the heteroaryl group
includes one or more of S, O, and N as a heteroatom, and
the number of carbon atoms thereof is not particularly
limited, and it is preferred that the number is 2 to 60,
specifically 2 to 40, and more specifically 3 to 20.
Specific examples of the heteroaryl include pyridyl,
- 23 -
pyrrolyl, pyrimidyl, pyridazinyl, furanyl, thienyl,
imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl,
isothiazolyl, triazolyl , furazanyl, oxadiazolyl,
thiadiazolyl, dithiazolyl, tetrazolyl, pyranyl, thiopyranyl,
diazinyl, oxazinyl, thiazinyl, dioxynyl, triazinyl,
tetrazinyl, quinolyl, isoquinolyl, quinazolinyl,
isoquinazolinyl, acridinyl, phenanthridinyl,
imidazopyridinyl, diazanaphthalenyl, triazaindene, indolyl,
benzothiazolyl, benzoxazolyl, benzoimidazolyl, a
benzothiophene group, a benzofuran group, a
dibenzothiophene group, a dibenzofuran group, carbazolyl,
benzocarbazolyl, phenazinyl, and the like, or fused rings
thereof, but are not limited thereto.
In the present specification, the fluorenyl group
may be substituted with another substituent, and
substituents may combine with each other to form a ring.
Examples thereof include
, and
the like.
In the present specification, the term “substituted
or unsubstituted” means being unsubstituted or substituted
with one or more substituents selected from a group
- 24 -
consisting of deuterium; a halogen group; a nitrile group;
a nitro group; a hydroxy group; a cyano group; straightchained
or branch-chained C1 to C60 alkyl; straight-chained
or branch-chained C2 to C60 alkenyl; straight-chained or
branch-chained C2 to C60 alkynyl; C3 to C60 monocyclic or
polycyclic cycloalkyl; C2 to C60 monocyclic or polycyclic
heterocycloalkyl; C6 to C60 monocyclic or polycyclic aryl;
and C2 to C60 monocyclic or polycyclic heteroaryl, or being
unsubstituted or substituted with a substituent having a
structure in which two or more selected from a group
consisting of the substituents above exemplified are linked.
As described above, when the substituent has a structure in
which two or more substituents are linked, the two or more
substituents may be the same as or different from each
other.
According to an exemplary embodiment of the present
application, m and n may be 2 ≤ m ≤ 500 and 2 ≤ n ≤ 500.
According to an exemplary embodiment of the present
application, the copolymer may be a block copolymer.
In an exemplary embodiment of the present
application, the ratio of m and n may be 1 : 9 to 7 : 3.
That is, when m + n is 1, n may have a ratio of 0.3 to 0.9.
In an exemplary embodiment of the present
application, the ratio of m and n may be 2 : 8 to 6 : 4.
That is, when m + n is 1, n may have a ratio of 0.4 to 0.8.
- 25 -
According to an exemplary embodiment of the present
application, Chemical Formula 1 may be represented by the
following Chemical Formula 1-1.
[Chemical Formula 1-1]
In Chemical Formula 1-1, S1, S2, a, b, and L1 are the
same as those defined in Chemical Formula 1.
According to an exemplary embodiment of the present
application, Chemical Formula 4 may be represented by the
following Chemical Formula 4-1.
[Chemical Formula 4-1]
In Chemical Formula 4-1, T1, T2, d, e, and L2 are the
same as those defined in Chemical Formula 4.
According to an exemplary embodiment of the present
application, in Chemical Formulae A and B, X1, X2, and X3
are the same as or different from each other, and may be
each independently any one selected from the following
structural formulae.
- 26 -
Here, R and R' are the same as or different from
each other, and are each independently –NO2 or –CF3.
According to an exemplary embodiment of the present
- 27 -
application, in Chemical Formulae A and B, at least one of
X1, X2, and X3 may be represented by the following Chemical
Formula 11.
[Chemical Formula 11]
In Chemical Formula 11,
S6 to S8 are the same as or different from each other,
and are each independently hydrogen; deuterium; a halogen
group; a cyano group; a nitrile group; a nitro group; a
hydroxy group; a substituted or unsubstituted alkyl group;
a substituted or unsubstituted cycloalkyl group; a
substituted or unsubstituted alkoxy group; a substituted or
unsubstituted alkenyl group; a substituted or unsubstituted
silyl group; a substituted or unsubstituted boron group; a
substituted or unsubstituted amine group; a substituted or
unsubstituted aryl group; or a substituted or unsubstituted
heteroaryl group,
s and t are the same as or different from each other,
and are each independently an integer of 0 or more and 4 or
less, and
- 28 -
r is an integer of 0 or more and 8 or less.
When the copolymer includes Chemical Formula 11
including a bulky fluorene group, the copolymer may improve
the durability while having heat resistance and strong
physical properties by a rigid aromatic skeleton, and may
exhibit an effect in that lithium ions are easily
transferred due to the increase in hydrodynamic volume
during the entanglement of polymer chains.
According to an exemplary embodiment of the present
application, in Chemical Formulae A and B, at least one of
X1 and X2 may be represented by Chemical Formula 11.
According to an exemplary embodiment of the present
application, in Chemical Formulae A and B, at least one of
X1, X2, and X3 may be or
.
According to an exemplary embodiment of the present
application, in Chemical Formula B, Y1 may be any one
selected from the following structural formulae.
- 29 -
Here, Q is -SO3Li, -COOLi, or -OLi, and Q' is
hydrogen, -SO3Li, -COOLi, or –OLi.
According to an exemplary embodiment of the present
application, the copolymer may further include a repeating
unit of the following Chemical Formula C.
[Chemical Formula C]
- 30 -
According to an exemplary embodiment of the present
application, in Chemical Formula C, Z is a trivalent
organic group.
According to an exemplary embodiment of the present
application, the repeating unit of Chemical Formula C
serves to link or cross-link polymer chains as a brancher.
Depending on the number of repeating units of Chemical
Formula C, a branch may be formed on the chain, or the
chains may be cross-linked to each other to form a networktype
structure.
According to an exemplary embodiment of the present
application, in Chemical Formula C, Z is a trivalent
organic group, and may be bonded to additional repeating
units in each three directions to elongate the polymer
chain.
According to an exemplary embodiment of the present
application, the number, molecular weight, and the like of
an ion transfer functional group may be adjusted and
mechanical properties may be strengthened by using a
brancher which is the repeating unit of Chemical Formula C.
According to an exemplary embodiment of the present
application, when the number of repeating units in the
- 31 -
repeating unit of Chemical Formula C is denoted as k, k may
be an integer of 1 to 300.
According to an exemplary embodiment of the present
application, the repeating unit of Chemical Formula C may
be a polymer repeating unit constituting a main chain. For
example, Z may be linked to at least one selected from X1,
X2, X3, and Y1 to form one repeating unit. The one
repeating unit formed as described above may constitute the
main chain. In this case, the number of repeating units is
the same as that of the above-described k.
In the present specification, when any two or more
selected from Z, X1, X2, X3, and Y1 are bonded to each other,
the resulting bonds each have a linking group of oxygen (-
O-). The oxygen linking group is a linking group that
remains in the chain after the compound evades therefrom by
a condensation polymerization. For example, when a
dihalogen-based monomer and a diol-based monomer are
polymerized, the oxygen linking group may be a case where
HF evades and only oxygen (-O-) remains in the chain.
According to an exemplary embodiment of the present
application, in Chemical Formula C, Z is represented by the
following Chemical Formula C-1 or C-2.
[Chemical Formula C-1]
- 32 -
[Chemical Formula C-2]
In Chemical Formulae C-1 and C-2,
Z1 may be represented by any one of the following
Chemical Formulae 7 to 9.
[Chemical Formula 7]
[Chemical Formula 8]
- 33 -
[Chemical Formula 9]
In Chemical Formulae 7 to 9,
L3 to L6 are the same as or different from each other,
and are each independently a direct bond, or -O-, -CO-, or
-SO2-.
E1 to E7 are the same as or different from each other,
and are each independently hydrogen; deuterium; a halogen
group; a cyano group; a nitrile group; a nitro group; a
hydroxy group; a substituted or unsubstituted alkyl group;
a substituted or unsubstituted cycloalkyl group; a
substituted or unsubstituted alkoxy group; a substituted or
unsubstituted alkenyl group; a substituted or unsubstituted
silyl group; a substituted or unsubstituted boron group; a
substituted or unsubstituted amine group; a substituted or
unsubstituted aryl group; or a substituted or unsubstituted
heteroaryl group,
c', d', e', and h' are the same as or different from
- 34 -
each other, and are each independently an integer of 0 or
more and 4 or less,
f', g', and i' are the same as or different from
each other, and are each independently an integer of 0 or
more and 3 or less, and
X4 and X5 are the same as or different from each
other, and are each independently the same as the
definition of X3 or Y1 of Chemical Formula B.
According to an exemplary embodiment of the present
application, in Chemical Formula C, Z may be any one
selected from the following structural formulae.
- 35 -
According to an exemplary embodiment of the present
application, the repeating unit of Chemical Formula A may
be represented by the following structural formula.
In the structural formula, m is the same as that as
- 36 -
described above.
According to an exemplary embodiment of the present
application, the repeating unit of Chemical Formula B may
be represented by the following structural formulae.
In the structural formulae, n is the same as that as
described above.
According to an exemplary embodiment of the present
specification, the copolymer may have a weight average
molecular weight of 100,000 or more and 1,000,000 or less.
When the weight average molecular weight of the copolymer
is within the range, an appropriate solubility of the
copolymer may be maintained while having mechanical
properties as a protective layer.
According to an exemplary embodiment of the present
specification, the lithium ion conductive protective layer
may have a thickness of 0.01 to 50 μm, specifically 0.1 to
10 μm. The smaller the thickness of the lithium ion
conductive protective layer is, the more advantageous
output characteristics of the battery are, but dendrites
may be blocked from being grown only when the lithium ion
- 37 -
conductive protective layer is formed to have a
predetermined thickness or more. When the thickness of the
lithium ion conductive protective layer is within the range,
lithium dendrites may be blocked from being grown while
preventing output characteristics of the battery from
excessively deteriorating.
According to an exemplary embodiment of the present
specification, method typically used in the art may be used
without limitation as a method of forming the lithium ion
conductive protective layer. For example, it is possible
to use a general method of forming a layer, such as a tape
casting method, a dip coating method, a spray coating
method, spin coating, a sputtering method of physical vapor
deposition (PVD), and an atomic layer deposition (ALD)
method of chemical vapor deposition (CVD).
According to an exemplary embodiment of the present
application, the lithium electrode may have a thickness of
250 μm or less. Specifically, the lithium electrode may
have a thickness of 200 μm or less.
According to an exemplary embodiment of the present
application, the lithium electrode may have a thickness of
10 μm or more. Specifically, the lithium electrode may
have a thickness of 50 μm or more.
When the thickness of the lithium electrode is
within the range, there is an effect of improving the
- 38 -
performance of the battery because the energy density per
the volume of the battery is increased, and it is
appropriate to apply to the battery.
In the present specification, when the lithium
electrode does not include a protective layer, the
‘thickness’ of the porous carbon body may mean a thickness
of the lithium electrode. That is, since the electrode has
a structure in which lithium is inserted into the porous
carbon body, the thickness of the porous carbon body
including pores of the porous carbon body and lithium may
be the thickness of the lithium electrode.
According to an exemplary embodiment of the present
application, when the lithium electrode does not include a
protective layer, the lithium electrode may have a
thickness of 200 μm or less. Specifically, the lithium
electrode may have a thickness of 150 μm or less.
Further, the present application provides a lithium
secondary battery including a positive electrode, a
negative electrode, and an electrolyte, in which the
negative electrode is the above-described lithium electrode.
According to an exemplary embodiment of the present
application, the positive electrode may be composed of a
positive electrode current collector and a positive
electrode active material layer applied on one surface or
both surfaces thereof. Here, non-limiting examples of the
- 39 -
positive electrode current collector include a foil
prepared by aluminum, nickel or a combination thereof, and
the like.
According to an exemplary embodiment of the present
application, a positive electrode active material included
in the positive electrode active material layer may be any
one or a mixture of two or more selected from a group
consisting of LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4,
LiNiMnCoO2, and LiNi1-x-y-zCoxM1yM2zO2 (M1 and M2 are each
independently any one selected from a group consisting of
Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg, and Mo, and x, y,
and z are each independently an atomic fraction of oxide
composition elements, and 0 ≤ x < 0.5, 0 ≤ y < 0.5, 0 ≤ z <
0.5, and x+y+z ≤ 1).
According to an exemplary embodiment of the present
application, the lithium secondary battery may further
include a separation membrane between the positive
electrode and the negative electrode.
The separation membrane may be formed of a porous
base material, and the porous base material may be used
without limitation as long as the porous base material is a
porous base material typically used in the electrochemical
device, and for example, a polyolefin-based porous membrane
or a nonwoven fabric may be used, but the separation
membrane is not particularly limited thereto.
- 40 -
The polyolefin-based porous membrane may be a
membrane formed by using polyethylene such as high density
polyethylene, linear low density polyethylene, low density
polyethylene, and ultrahigh molecular weight polyethylene,
and a polyolefin-based polymer such as polypropylene,
polybutylene, and polypentene, either alone or a polymer
prepared from a mixture thereof.
Examples of the nonwoven fabric include a nonwoven
fabric formed by using each of polyethyleneterephthalate,
polybutyleneterephthalate, polyester, polyacetal, polyamide,
polycarbonate, polyimide, polyetheretherketone,
polyethersulfone, polyphenyleneoxide, polyphenylenesulfide,
and polyethylenenaphthalene, and the like either alone, or
a polymer prepared from a mixture thereof. The structure
of the nonwoven fabric may be a spunbond nonwoven fabric
composed of long fibers or a melt-blown nonwoven fabric.
According to an exemplary embodiment of the present
application, the thickness of the porous base material is
not particularly limited, but may be 1 μm to 100 μm or 5 μm
to 50 μm.
According to an exemplary embodiment of the present
application, the size and porosity of pores present in the
porous base material are also not particularly limited, but
may be 0.001 μm to 50 μm and 10% to 95%, respectively.
According to an exemplary embodiment of the present
- 41 -
application, the electrolyte may include an organic solvent
and an electrolyte salt.
The electrolyte salt may be a lithium salt. As the
lithium salt, those typically used in an electrolyte for a
lithium secondary battery may be used without limitation.
For example, an anion of the lithium salt may be any one
selected from a group consisting of F-, Cl-, Br-, I-, NO3
-,
N(CN)2
-, BF4
-, ClO4
-, PF6
-, (CF3)2PF4
-, (CF3)3PF3
-, (CF3)4PF2
-,
(CF3)5PF-, (CF3)6P-, CF3SO3
-, CF3CF2SO3
-, (CF3SO2)2N-, (FSO2)2N-,
CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-,
CF3(CF2)7SO3
-, CF3CO2
-, CH3CO2
-, SCN-, and (CF3CF2SO2)2N-.
As the organic solvent, those typically used in the
electrolyte for a lithium secondary battery may be used
without limitation, and for example, ether, ester, amide,
linear carbonate, cyclic carbonate, and the like may be
each used either alone or in combination of two or more
thereof. Specifically, the organic solvent may include
cyclic carbonate, linear carbonate, or a carbonate compound
which is a mixture thereof.
As an ether among the organic solvents, it is
possible to use any one or a mixture of two or more
selected from a group consisting of dimethyl ether, diethyl
ether, dipropyl ether, methyl ethyl ether, methyl propyl
ether, and ethyl propyl ether, but the ether is not limited
thereto.
- 42 -
As an ester among the organic solvents, it is
possible to use any one or a mixture of two or more
selected from a group consisting of methyl acetate, ethyl
acetate, propyl acetate, methyl propionate, ethyl
propionate, propyl propionate, γ-butyrolactone, γ-
valerolactone, γ-caprolactone, σ-valerolactone, and ε-
caprolactone, but the ester is not limited thereto.
Specific example of the cyclic carbonate compound
include any one or a mixture of two or more selected from a
group consisting of ethylene carbonate (EC), propylene
carbonate (PC), 1,2-butylene carbonate, 2,3-butylene
carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate,
vinylene carbonate, vinyl ethylene carbonate, and
halogenides thereof. Examples of the halogenides thereof
include fluoroethylene carbonate (FEC), and the like, and
are not limited thereto.
In particular, ethylene carbonate and propylene
carbonate, which are a cyclic carbonate among the
carbonate-based organic solvents, are a high-viscosity
organic solvent, and may even more dissociate a lithium
salt in the electrolyte due to high permittivity, and when
a low-viscosity and low permittivity linear carbonate such
as dimethyl carbonate and diethyl carbonate is mixed with
the cyclic carbonate at a suitable ratio and a mixture is
used, an electrolyte having a much higher electric
- 43 -
conductivity may be made.
As a specific example of the linear carbonate
compound, it is possible to representatively use any one or
a mixture of two or more selected from a group consisting
of dimethyl carbonate (DMC), diethyl carbonate (DEC),
dipropyl carbonate, ethyl methyl carbonate (EMC), methyl
propyl carbonate, and ethyl propyl carbonate, but the
example is not limited thereto.
[Mode for Invention]
Hereinafter, the present application will be
described in more detail through Examples. However, the
following Examples are provided for exemplifying the
present application, and the scope of the present
application is not limited thereby.

A battery was prepared by using a positive electrode
including 95 wt.% of LiCoO2 as a positive electrode active
material, 2.5 wt.% of Super-P as a conductive material, and
2.5 wt.% of polyvinylidene fluoride (PVDF) as a binder;
a negative electrode which is a lithium electrode in
which a lithium metal (40 wt.% compared to the total
content of a carbon paper and a lithium metal) is inserted
into the carbon paper (thickness 100 μm, porosity 90%,
manufactured by Toray Co., Ltd.) which is a porous carbon
body; and
- 44 -
an electrolytic solution of 1 M LiPF6, EC/EMC = 3 :
7 (vol. ratio).

A battery was prepared in the same manner as in
Example 1, except that a lithium ion conductive protective
layer was formed to have a thickness of 5 μm on a lithium
electrode by using a lithiated polyarylene ether copolymer
having a sulfonic acid group including the structural
formula in Example 1.

A battery was prepared in the same manner as in
Example 2, except that the content of the lithium metal was
made to be 90 wt.% compared to the total content of the
carbon paper and the lithium metal in Example 2.

A battery was prepared in the same manner as in
Example 2, except that a carbon paper having a porosity of
50% was used in Example 2.

A battery was prepared in the same manner as in
Example 2, except that a carbon paper having a thickness of
- 45 -
200 μm was used in Example 2.

A battery was prepared in the same manner as in
Example 1, except that a lithium ion conductive protective
layer was formed to have a thickness of 5 μm on a lithium
electrode by using poly(vinylidene fluoride-cohexafluoropropylene)
(PVDF-HFP) in Example 1.

A battery was prepared in the same manner as in
Example 2, except that a thickness of a lithiated
polyarylene ether copolymer having a sulfonic acid group
was made to be 20 μm in Example 2.

A battery was prepared in the same manner as in
Example 2, except that a thickness of a lithiated
polyarylene ether copolymer having a sulfonic acid group
was made to be 1 μm in Example 2.

A battery was prepared in the same manner as in
Example 1, except that a lithium metal foil was used as a
negative electrode in Example 1.

A battery was prepared in the same manner as in
Comparative Example 1, except that a lithium ion conductive
protective layer was formed to have a thickness of 5 μm on
- 46 -
a lithium metal foil by using a lithiated polyarylene ether
copolymer having a sulfonic acid group in Comparative
Example 1.

The battery short-circuit time points were measured
by 0.5C/0.5C charging/discharging the batteries prepared in
Examples 1 to 8 and Comparative Examples 1 and 2, and the
results are shown in the following Table 1.
[Table 1]
Number of Battery Short-Circuit
Cycles
Example 1 220
Example 2 312
Example 3 205
Example 4 155
Example 5 157
Example 6 230
Example 7 110
Example 8 249
Comparative Example 1 134
Comparative Example 2 151
As shown in Table 1, it can be confirmed that
Example 1 in which the lithium electrode according to an
exemplary embodiment of the present application was used
had a more delayed battery short-circuit time point than
- 47 -
Comparative Example 1 where the lithium metal foil was used
as the negative electrode and Comparative Example 2 where
the lithium electrode in which the lithium ion conductive
protective layer was formed on the lithium metal foil was
used as the negative electrode. In particular, in the case
of Example 2 where the lithium electrode further including
the lithium ion conductive protective layer was used, a
high performance may be exhibited because a battery shortcircuit
time point was further delayed. This is because
the lithium electrode including the protective layer
according to an exemplary embodiment of the present
application prevents a phenomenon in which the protective
layer was peeled off even when the battery was driven,
thereby blocking the short circuit of the battery.
Further, it can be confirmed that when the porosity
of the porous carbon body is too low or the thickness
thereof is large, the balance between lithium active
materials is not established, and accordingly, it is
difficult to increase the efficiency, and when the
thickness of the protective layer is large, the efficiency
is reduced by cell resistance.
Therefore, the lithium battery including the lithium
electrode according to an exemplary embodiment of the
present application may prevent lithium dendrites and
prevent a short circuit of the battery, thereby exhibiting
- 48 -
high efficiency.
[Explanation of Reference Numerals and Symbols]
10, 100, 101: Lithium electrode
11: Current collector
12: Lithium foil
13, 130: Lithium ion conductive protective layer
110: Porous carbon body
120: Lithium metal
- 49 -

[CLAIMS]
[Claim 1]
A lithium electrode comprising: a porous carbon
body; and
a lithium metal inserted into pores of the porous
carbon body.
[Claim 2]
The lithium electrode of claim 1, further
comprising:
a lithium ion conductive protective layer formed on
at least one surface of the lithium electrode.
[Claim 3]
The lithium electrode of claim 1, wherein a content
of the lithium metal is 1 to 80 wt% based on a total weight
of the porous carbon body and the lithium metal.
[Claim 4]
The lithium electrode of claim 1, wherein the porous
carbon body comprises at least one selected from activated
carbon, graphite, graphene, carbon nanotubes (CNTs), carbon
fiber, carbon black, and carbon aerosol.
[Claim 5]
The lithium electrode of claim 1, wherein the porous
carbon body has a porosity of 50 to 99%.
[Claim 6]
The lithium electrode of claim 1, wherein the pores
- 50 -
have an average particle diameter of 5 to 500 μm.
[Claim 7]
The lithium electrode of claim 1, wherein the porous
carbon body has a thickness of 200 μm or less.
[Claim 8]
The lithium electrode of claim 1, wherein the porous
carbon body is in a form of mesh, foam, or paper.
[Claim 9]
The lithium electrode of claim 2, wherein the
lithium ion conductive protective layer comprises a
material having a lithium ion conductivity of 10-7 S/cm or
more.
[Claim 10]
The lithium electrode of claim 2, wherein the
lithium ion conductive protective layer comprises at least
one selected from inorganic compounds and organic compounds.
[Claim 11]
The lithium electrode of claim 10, wherein the
inorganic compound is any one or a mixture of two or more
selected from a group consisting of LiPON, hydride-based
compounds, thio-LISICON-based compounds, NASICON-based
compounds, LISICON-based compounds, and Perovskite-based
compounds.
[Claim 12]
The lithium electrode of claim 10, wherein the
- 51 -
organic compound is selected from polyethylene oxide (PEO);
polyacrylonitrile (PAN); polymethylmethacrylate (PMMA);
polyvinylidene fluoride (PVDF); and a polymer comprising -
SO3Li, -COOLi, or –OLi.
[Claim 13]
The lithium electrode of claim 2, wherein the
lithium ion conductive protective layer has a thickness of
0.01 μm to 5 μm.
[Claim 14]
The lithium electrode of claim 1, wherein the
lithium electrode has a thickness of 250 μm or less.
[Claim 15]
A lithium secondary battery comprising:
a positive electrode;
a negative electrode; and
an electrolyte,
wherein the negative electrode is the lithium
electrode of any one of claims 1 to 14.
[Claim 16]
The lithium secondary battery of claim 15, wherein
the positive electrode comprises a positive electrode
active material which is any one or a mixture of two or
more selected from a group consisting of LiCoO2, LiNiO2,
LiMn2O4, LiCoPO4, LiFePO4, LiNiMnCoO2, and LiNi1-x-yzCoxM1yM2zO2
(M1 and M2 are each independently any one
- 52 -
selected from a group consisting of Al, Ni, Co, Fe, Mn, V,
Cr, Ti, W, Ta, Mg, and Mo, and x, y, and z are each
independently an atomic fraction of oxide composition
elements, and 0 ≤ x < 0.5, 0 ≤ y < 0.5, 0 ≤ z < 0.5, and
x+y+z ≤ 1).
[Claim 17]
The lithium secondary battery of claim 15, wherein
the electrolyte comprises an organic solvent and an
electrolyte salt.
[Claim 18]
The lithium secondary battery of claim 17, wherein
the organic solvent is any one or a mixture of two or more
selected from a group consisting of ethylene carbonate (EC),
propylene carbonate (PC), 1,2-butylene carbonate, 2,3-
butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene
carbonate, vinylene carbonate, vinyl ethylene carbonate,
fluoroethylene carbonate (FEC), dimethyl carbonate (DMC),
diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl
carbonate (EMC), methyl propyl carbonate, ethyl propyl
carbonate, dimethyl ether, diethyl ether, dipropyl ether,
methyl ethyl ether, methyl propyl ether, ethyl propyl ether,
methyl acetate, ethyl acetate, propyl acetate, methyl
propionate, ethyl propionate, propyl propionate, γ-
butyrolactone, γ-valerolactone, γ-caprolactone, σ-
valerolactone, and ε-caprolactone.
[Claim 19]
The lithium secondary battery of claim 17, wherein
the electrolyte salt comprises any one or two or more
selected from a group consisting of F-, Cl-, Br-, I-, NO3
-,
N(CN)2
-, BF4
-, ClO4
-, PF6
-, (CF3)2PF4
-, (CF3)3PF3
-, (CF3)4PF2
-,
(CF3)5PF-, (CF3)6P-, CF3SO3
-, CF3CF2SO3
-, (CF3SO2)2N-, (FSO2)2N-,
CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-,
CF3(CF2)7SO3
-, CF3CO2
-, CH3CO2
-, SCN-, and (CF3CF2SO2)2N-.