【Technical Field】
This application claims priority to and the benefits of
Korean Patent Application No. 10-2014-0118493, filed with the
Korean Intellectual Property Office on September 5, 2014, the
10 entire contents of which are incorporated herein by reference.
The present specification relates to a lithium electrode,
a lithium secondary battery including the same, a battery
module including the lithium secondary battery, and a method
for preparing the lithium electrode.
15 【Background Art】
With a recent trend of miniaturization and weight
lightening of electronic devices, miniaturization and weight
lightening of batteries used therein as a power supply have
been also required. Lithium secondary batteries are
20 commercialized as batteries that are small, light, and
chargeable and dischargeable with high capacity, and used in
portable electronic devices such as small video cameras, mobile
phones and laptops, communication devices and the like.
Lithium secondary batteries are an energy storage system
25 having high energy and power, and have excellent advantages of
3
having higher capacity or operating voltage compared to other
batteries. However, battery safety becomes a problem due to
such high energy, and there is a risk of explosion or fire.
Particularly, in hybrid vehicles and the like recently
5 receiving an attention, high energy and output properties are
required and accordingly, such safety is more important.
A lithium secondary battery is generally formed with a
cathode, an anode and an electrolyte, and charge and discharge
become possible since lithium ions perform a role of
10 transferring energy while travelling back and forth between
both electrodes such as lithium ions coming out of a cathode
active material being inserted into an anode active material,
that is, carbon particles, by first charge, and eliminated
again during discharge.
15 Meanwhile, with the development of portable electronic
devices, high capacity batteries have been continuously
required, and researches on high capacity lithium anode
materials having significantly higher capacity per unit weight
compared to carbon used as an existing anode material have been
20 actively conducted.
【Disclosure】
【Technical Problem】
The present specification is directed to providing a
lithium electrode, a lithium secondary battery including the
25 same, a battery module including the lithium secondary battery,
4
and a method for preparing a lithium electrode.
【Technical Solution】
One embodiment of the present specification provides a
lithium electrode including a lithium metal layer having a
5 hydroxyl group on a surface thereof; and a silicon layer
provided on the lithium metal layer and including a siliconbased
compound, wherein the silicon-based compound of the
silicon layer forms covalent bonds with a hydroxyl group of a
lower membrane that is in contact with the silicon layer.
10 Another embodiment of the present specification provides
a lithium secondary battery including the lithium electrode.
Still another embodiment of the present specification
provides a battery module including the lithium secondary
battery as a unit battery.
15 Yet another embodiment of the present specification
provides a method for preparing a lithium electrode including
forming a silicon layer including a silicon-based compound on a
lithium metal layer having a hydroxyl group on a surface
thereof, wherein the silicon-based compound of the silicon
20 layer forms covalent bonds to a hydroxyl group of a lower
membrane that is in contact with the silicon layer.
【Advantageous Effects】
A lithium electrode according to one embodiment of the
present specification has an advantage of having a long life.
25 A lithium electrode according to one embodiment of the
5
present specification can be efficiently blocked from moisture.
A lithium electrode according to one embodiment of the
present specification has low interfacial resistance and
therefore, is capable of enhancing charge and discharge
5 efficiency.
A lithium electrode according to one embodiment of the
present specification has an advantage of having smooth lithium
ion transfer by being blocked from moisture.
【Description of Drawings】
10 FIG. 1 is a structural diagram of a lithium electrode
according to one embodiment of the present specification.
FIG. 2 is a structural diagram of a lithium electrode
according to another embodiment of the present specification.
FIG. 3 is a diagram illustrating steps of preparing the
15 lithium electrode of FIG. 2.
FIG. 4 is a graph evaluating a cycle life of a lithium
electrode of Test Example 1.
FIG. 5 is a result showing moisture permeability of Test
Example 2.
20
100: Lithium Metal Layer
200: Silicon Layer
300: Buffer Layer
310: Lower Part of Buffer Layer
25 330: Upper Part of Buffer Layer
6
【Mode for Disclosure】
Hereinafter, the present specification will be described
in detail.
The present specification provides a lithium electrode
5 including a lithium metal layer having a hydroxyl group on a
surface thereof; and a silicon layer provided on the lithium
metal layer and including a silicon-based compound, wherein the
silicon-based compound of the silicon layer forms covalent
bonds with a hydroxyl group of a lower membrane that is in
10 contact with the silicon layer.
The lithium electrode may have a thickness of greater
than or equal to 10 μm and less than or equal to 200 μm.
Preferably, the lithium electrode may have a thickness of
greater than or equal to 10 μm and less than or equal to 100 μm.
15 In the present specification, the thickness of the
lithium electrode means a total thickness including the lithium
metal layer and the silicon layer. When the lithium electrode
further includes additional layers in addition to the lithium
metal layer and the silicon layer, the thickness of the lithium
20 electrode means a total thickness of the whole lithium
electrode with the thicknesses of the additional layers further
included therein. For example, when the lithium electrode
further includes a buffer layer to be described below, the
thickness of the lithium electrode means a total thickness
25 including the lithium metal layer, the silicon layer and the
7
buffer layer.
In the present specification, the lithium electrode may
be used in a battery, and the lithium electrode may be an
electrode exporting electrons when the battery is discharged.
5 Specifically, the lithium electrode may be used in a secondary
battery, and the lithium electrode may export electrons based
on when the battery is discharged, and may perform a role of a
cathode (reduction electrode) when the battery is charged.
The lithium metal layer means a metal layer including a
10 lithium metal element. Materials of the lithium metal layer
may include lithium alloys, lithium metal, oxides of lithium
alloys or lithium oxides. Herein, a part of the lithium metal
layer may be degenerated due to oxygen or moisture, or may
include impurities.
15 The lithium metal layer may have a thickness of greater
than or equal to 10 μm and less than or equal to 200 μm.
Preferably, the lithium metal layer may have a thickness of
greater than or equal to 10 μm and less than or equal to 100 μm.
Based on the total thickness of the lithium electrode, a
20 percentage of the thickness of the lithium metal layer may be
from 90% to 99.99%. This has an advantage in that lithium ions
smoothly migrate due to a very thin organic protective layer.
The lithium metal layer may have a hydroxyl group on the
surface. The hydroxyl group on the surface of the lithium
25 metal layer is a hydroxyl group produced from a reaction
8
between lithium metal in the lithium metal layer and a small
amount of moisture without a separate artificial process, or a
hydroxyl group formed from surface modification through an
additional artificial process.
5 The artificial process forming a hydroxyl group on the
surface of the lithium metal layer is not particularly limited,
and examples thereof may include a method of polishing with a
film or sandpaper, a method of thinly oxidizing a surface of
the lithium metal layer by adding a small amount of water into
10 a solvent, and a method of polishing a surface of the lithium
metal layer with methanol or n-alkane such as pentane, however,
the method is not limited thereto.
The silicon layer is provided on the lithium metal layer
and may include a silicon-based compound forming covalent bonds
15 with a hydroxyl group of a lower membrane of the silicon layer.
The silicon layer is formed with a silicon-based compound
having a reactive group capable of forming covalent bonds with
a hydroxyl group, and when the lower membrane that is in direct
contact with the silicon layer is a lithium metal layer,
20 covalent bonds may be formed by the hydroxyl group of the
lithium metal layer reacting with substituents capable of
reacting with the hydroxyl group in the silicon-based compound
on the surface that the silicon layer is in contact with the
lithium metal layer.
25 The silicon-based compound may form covalent bonds by the
9
hydroxyl group on the surface of the lithium metal layer
reacting with reactive substituents of the silicon-based
compound while being self-assembled on the lithium metal
surface. Among the substituents of the silicon-based compound,
5 substituents that do not react with the hydroxyl group on the
surface of the lithium metal layer may form cross-linked bonds
with neighboring silicon-based compounds.
The silicon layer may be provided on at least a part of
the surface of the lithium metal layer, and specifically, the
10 silicon layer may be provided on at least one side surface of
the surface of the lithium metal layer, or the silicon layer
may be provided on the whole surface of the lithium metal layer.
When the silicon layer is provided on at least a part of
the surface of the lithium metal layer, formation of a solid
15 electrolyte interphase (SEI) layer formed while the lithium
metal layer and a liquid electrolyte react may be suppressed.
In other words, interfacial resistance may be reduced since
formation of a solid electrolyte interphase layer that induces
resistance is suppressed.
20 When the silicon layer is provided on the whole surface
of the lithium metal layer, a contact between the lithium metal
layer and moisture may be blocked while suppressing the
formation of a solid electrolyte interphase layer on the
surface of the lithium metal layer.
25 When a buffer layer is provided between the lithium metal
1 0
layer and the silicon layer, the silicon layer may include a
silicon-based compound forming covalent bonds with a hydroxyl
group of the buffer layer.
The silicon-based compound may be prepared with a
5 compound represented by the following Chemical Formula 1.
[Chemical Formula 1]
Si
R1
R2 R4
R3
In Chemical Formula 1, one or more of R1 to R4 are each
independently a halogen group, an amino group or an alkoxy
10 group, and the rest are each independently a C1 to C10 alkyl
group, a hydroxyl group, an aliphatic cyclic group having two
rings or less, an aromatic cyclic group having two rings or
less, or -L-(CF2)nCF3, L is a direct bond or a C1 to C10 alkylene
group, and n is an integer of 0 to 10.
15 A water contact angle of the silicon layer may be greater
than or equal to 100° and less than or equal to 160°. This has
an advantage in that moisture penetration into the silicon
layer, a protective layer, may be prevented since the surface
is extremely hydrophobic.
20 The silicon layer may have a thickness of greater than or
equal to 1 nm and less than or equal to 1 μm. The silicon
layer is formed from a self-assembly behavior of a silane-based
1 1
compound, and therefore, may form a uniform and even
hydrophobic surface on the lithium metal layer.
Specifically, the silicon layer may have a thickness of
greater than or equal to 1 nm and less than or equal to 10 nm.
5 The silicon layer is formed from a self-assembly behavior of a
silane-based compound, and therefore, may form a uniform and
even hydrophobic surface on the lithium metal layer, and has an
advantage in that lithium ions readily migrate since the
silicon layer is very thin.
10 In the present specification, the silicon layer may be
formed on the lithium metal layer by forming covalent bonds
with a hydroxyl group on the surface of the lithium metal layer
while molecules forming the silicon layer are arranged through
self-assembly as shown in FIG. 1. The thickness of the silicon
15 layer formed thereby may correspond to a length of one molecule
forming the silicon layer.
The silicon layer is capable of performing a role of a
relatively stably fixed protective layer despite its small
thickness since it forms covalent bonds on the lithium metal
20 layer.
Based on the total thickness of the lithium electrode, a
percentage of the thickness of the silicon layer may be from
0.0001% to 10%. In this case, due to the silicon layer that is
a thin organic protective layer, the lithium metal layer may be
25 blocked from moisture while lithium ions smoothly migrate.
1 2
Specifically, based on the total thickness of the lithium
electrode, a percentage of the thickness of the silicon layer
may be from 0.0005% to 1% and more specifically from 0.0005% to
0.1%.
5 The buffer layer may be provided between the lithium
metal layer and the silicon layer, and is a layer having a
hydroxyl group on the surface.
The buffer layer may be prepared with a material having a
hydroxyl group to have a hydroxyl group on the surface.
10 The buffer layer may be prepared with a material of which
surface is readily modified so as to have a hydroxyl group
through an additional process.
Materials of the buffer layer are not particularly
limited as long as they have a hydroxyl group on the surface
15 and capable of being coated on the lithium metal layer, and for
example, the buffer layer may include a siloxane-based compound.
This has an advantage in that the surface is readily modified
to have a hydroxyl group and coating is favorably carried out
on the surface of the lithium metal layer. In addition, the
20 siloxane-based compound is expanded in an electrolyte making
lithium ion migration possible.
Specifically, the buffer layer may include
polydimethylsiloxane. This has an advantage in that the
polydimethylsiloxane is expanded in an electrolyte making
25 lithium ion migration smooth.
1 3
The hydroxyl group on the surface of the buffer layer may
react with a reactive group of the silicon-based compound to
form covalent bonds with the silicon layer.
The buffer layer may be provided on at least a part of
5 the surface of the lithium metal layer, and specifically, the
buffer layer may be provided on at least one side surface of
the surface of the lithium metal layer, or the silicon layer
may be provided on the whole surface of the lithium metal layer.
The buffer layer may be provided on 90% or higher of the
10 whole surface area of the lithium metal layer, and specifically,
the buffer layer is preferably provided on the whole surface of
the lithium metal layer. This has an advantage in that the
lithium metal layer is protected from moisture, and the silicon
layer forming covalent bonds with a hydroxyl group on the
15 surface of the protective layer is readily formed.
The buffer layer may have a thickness of greater than or
equal to 10 nm and less than or equal to 10 μm. In this case,
the buffer layer assists the role of a protective layer
blocking moisture, and is expanded enabling the migration of
20 lithium ions without inhibiting the lithium ion migration.
Preferably, the buffer layer may have a thickness of
greater than or equal to 10 nm and less than or equal to 1 μm,
and more preferably, the buffer layer may have a thickness of
greater than or equal to 10 nm and less than or equal to 100 nm.
25 Based on the total thickness of the lithium electrode, a
1 4
percentage of the thickness of the buffer layer may be from
0.001% to 10%. This may provide an environment for smooth
lithium ion migration as well as providing an expansion
phenomenon.
5 Specifically, based on the total thickness of the lithium
electrode, a percentage of the thickness of the buffer layer
may be from 0.005% to 5% and more specifically from 0.005% to
1%.
The present specification provides a lithium secondary
10 battery including the lithium electrode. Specifically, the
present specification provides a lithium secondary battery
including the lithium electrode; a cathode, and an electrolyte
provided between the lithium electrode and the cathode.
A shape of the lithium secondary battery is not limited,
15 and examples thereof may include a coin-type, a plate-type, a
cylinder-type, a horn-type, a button-type, a sheet-type or a
layered-type.
The lithium secondary battery may be a lithium air
battery. Specifically, the cathode of the lithium secondary
20 battery may be an air electrode.
The lithium secondary battery may further include tanks
each storing the cathode liquid electrolyte and the lithium
electrode liquid electrolyte, and a pump transporting the each
liquid electrolyte to an electrode cell, and may be
25 manufactured to a flow battery.
1 5
The electrolyte may be an electrolyte liquid into which
the lithium electrode and the cathode are immersed.
The lithium secondary battery may further include a
separator provided between the lithium electrode and the
5 cathode. The separator placed between the lithium electrode
and the cathode separates or insulates the lithium electrode
and the cathode, and any material may be used as long as it
allows ion transport between the lithium electrode and the
cathode. Examples thereof may include a non-conducting porous
10 membrane or an insulating porous membrane. More specifically,
polymer non-woven fabric such as non-woven fabric made of
polypropylene materials or non-woven fabric made of
polyphenylene sulfide materials; or porous films of olefinbased
resins such as polyethylene or polypropylene may be
15 included as examples, and these may be used as a combination of
two or more types.
The lithium secondary battery may further include a
cathode-side cathode liquid electrolyte and a lithium
electrode-side lithium electrode liquid electrolyte divided by
20 the separator. The cathode liquid electrolyte and the lithium
electrode liquid electrolyte may each include a solvent and an
electrolytic salt. The cathode liquid electrolyte and the
lithium electrode liquid electrolyte may be the same as or
different from each other.
25 The liquid electrolyte may be an aqueous liquid
1 6
electrolyte or a non-aqueous liquid electrolyte. The aqueous
liquid electrolyte may include water as a solvent, and the nonaqueous
liquid electrolyte may include a non-aqueous solvent as
a solvent.
5 The non-aqueous solvent is not particularly limited, and
those generally used in the art may be selected, and for
example, may be selected from the group consisting of
carbonate-based solvents, ester-based solvents, ether-based
solvents, ketone-based solvents, organosulfur-based solvents,
10 organophosphorous-based solvents, nonprotonic solvents and
combinations thereof.
The electrolytic salt refers to those dissociated into
cations and anions in water or non-aqueous organic solvents,
and is not particularly limited as long as it is capable of
15 transferring lithium ions in a lithium secondary battery, and
those generally used in the art may be selected.
In the liquid electrolyte, the electrolytic salt may have
a concentration of greater than or equal to 0.1 M and less than
or equal to 3 M. In this case, charge and discharge properties
20 of a lithium secondary battery may be effectively exhibited.
The electrolyte may be a solid electrolyte membrane or a
polymer electrolyte membrane.
Materials of the solid electrolyte membrane and the
polymer electrolyte membrane are not particularly limited, and
25 those generally used in the art may be employed. For example,
1 7
the solid electrolyte membrane may include composite metal
oxides, and the polymer electrolyte membrane may be a membrane
having a conducting polymer provided inside a porous substrate.
The cathode means an electrode accepting electrons and
5 reducing lithium-containing ions when a battery is discharged
in a lithium secondary battery. On the contrary, the cathode
performs a role of a lithium electrode (oxidation electrode)
exporting electrons and losing lithium-containing ions with an
oxidation of a cathode active material when a battery is
10 charged.
The cathode may include a cathode collector and a cathode
active material layer formed on the cathode collector.
In the present specification, materials of the cathode
active material of the cathode active material layer are not
15 particularly limited as long as lithium-containing ions are
reduced when the battery is discharged and oxidized when
charged when the cathode active material is used in a lithium
secondary battery with the lithium electrode. For example, the
material may be transition metal oxides or composites based on
20 sulfur (S), and specifically, may include at least one of LiCoO2,
LiNiO2, LiFePO4, LiMn2O4, LiNixCoyMnzO2 (herein, x+y+z=1),
Li2FeSiO4, Li2FePO4F and Li2MnO3.
In addition, when the cathode is a composite based on
sulfur (S), the lithium secondary battery may be a lithium
25 sulfur battery. The composite based on sulfur (S) is not
1 8
particularly limited, and cathode materials generally used in
the art may be selected and used.
The present specification provides a battery module
including the lithium secondary battery as a unit battery.
5 The battery module may be formed by stacking with bipolar
plates provided between the two or more lithium secondary
batteries according to one embodiment of the present
specification.
When the lithium secondary battery is a lithium air
10 battery, the bipolar plate may be porous so as to supply air
supplied from the outside to a cathode included in each lithium
air battery. Examples thereof may include porous stainless
steel or porous ceramic.
Specifically, the battery module may be used as a power
15 supply of electric vehicles, hybrid electric vehicles, plug-in
hybrid electric vehicles or power storage systems.
The present specification provides a method for preparing
a lithium electrode including forming a silicon layer including
a silicon-based compound on a lithium metal layer having a
20 hydroxyl group on a surface thereof, wherein the silicon-based
compound of the silicon layer forms covalent bonds with a
hydroxyl group of a lower membrane that is in contact with the
silicon layer.
The forming of a silicon layer may include preparing a
25 solution including a silicon-based compound having a
1 9
substituent capable of reacting with a hydroxyl group; and
coating the solution on at least a part of the surface of the
lithium metal layer.
The forming of a silicon layer may include preparing a
5 solution including a silicon-based compound having a
substituent capable of reacting with a hydroxyl group; and
immersing the lithium metal layer into the solution.
Based on FIG. 1, a silicon layer 200 may be formed by
coating a silicon-based compound (R3SiCl) having a chloride
10 group, a substituent capable of reacting with a hydroxyl group,
on a lithium metal layer 100 having a hydroxyl group. The
silicon-based compound is arranged while being self-assembled
on the surface of the lithium metal layer, and the lithium
metal layer and the silicon layer may form covalent bonds as
15 the hydroxyl group on the surface of the lithium metal layer
and the chloride group of the silicon-based compound react and
produce hydrochloric acid (HCl). In the R3SiCl, Rs are each
independently a halogen group, an amino group, an alkoxy group,
a C1 to C10 alkyl group, a hydroxyl group, an aliphatic cyclic
20 group having two rings or less, an aromatic cyclic group having
two rings or less, or -L-(CF2)nCF3, L is a direct bond or a C1 to
C10 alkylene group, and n is an integer of 0 to 10.
The silicon-based compound having a substituent capable
of reacting with a hydroxyl group may be represented by the
25 following Chemical Formula 1.
2 0
[Chemical Formula 1]
Si
R1
R2 R4
R3
In Chemical Formula 1, one or more of R1 to R4 are each
independently a halogen group, an amino group or an alkoxy
5 group, the rest are each independently a C1 to C10 alkyl group,
a hydroxyl group, an aliphatic cyclic group having two rings or
less, an aromatic cyclic group having two rings or less, or -L-
(CF2)nCF3, L is a direct bond or a C1 to C10 alkylene group, and
n is an integer of 0 to 10.
10 In Chemical Formula 1, one or more of R1 to R3 are each
independently a halogen group, an amino group or an alkoxy
group, and the rest are each independently a C1 to C10 alkyl
group, a hydroxyl group, an aliphatic cyclic group having two
rings or less, an aromatic cyclic group having two rings or
15 less, or -L-(CF2)nCF3,
R4 is a C1 to C10 alkyl group, a hydroxyl group, an
aliphatic cyclic group having two rings or less, an aromatic
cyclic group having two rings or less, or -L-(CF2)nCF3, L is a
direct bond or a C1 to C10 alkylene group, and n is an integer
20 of 0 to 10.
In Chemical Formula 1, R1 may be a halogen group, an
amino group or an alkoxy group.
2 1
In Chemical Formula 1, R2 and R3 are each independently a
halogen group, a hydroxyl group or an alkoxy group.
In Chemical Formula 1, R4 is a C1 to C10 alkyl group, an
aliphatic cyclic group having two rings or less, an aromatic
5 cyclic group having two rings or less, or -L-(CF2)nCF3, L is a
direct bond or a C1 to C10 alkylene group, and n is an integer
of 0 to 10.
In Chemical Formula 1, R1 is a halogen group, an amino
group or an alkoxy group, R2 and R3 are each independently a
10 halogen group, a hydroxyl group or an alkoxy group, R4 is a C1
to C10 alkyl group, an aliphatic cyclic group having two rings
or less, an aromatic cyclic group having two rings or less, or
-L-(CF2)nCF3, L is a direct bond or a C1 to C10 alkylene group,
and n is an integer of 0 to 10.
15 In Chemical Formula 1, at least one of R1 to R3 may be a
halogen group. Specifically, at least one of R1 to R3 may be a
chloride group.
In Chemical Formula 1, at least one of the remaining
substituents among R1 to R3, and R4 may be a C1 to C10 alkyl
20 group or -L-(CF2)nCF3, and herein, L is a direct bond or a C1 to
C10 alkylene group, and n is an integer of 0 to 10. In this
case, hydrophobicity on the surface of the silicon layer
increases and the lithium metal layer may be readily blocked
from moisture.
25 In Chemical Formula 1, at least one of R1 to R3 is a
2 2
halogen group, and the remaining substituents among R1 to R3,
and R4 are each independently a C1 to C10 alkyl group or -L-
(CF2)nCF3, and herein, L is a direct bond or a C1 to C10 alkylene
group, and n is an integer of 0 to 10.
5 The silicon-based compound having a substituent capable
of reacting with a hydroxyl group may be represented by at
least one of the following Chemical Formulae 2 to 4.
[Chemical Formula 2]
Si Cl
CH3
CH3
L
F3C
10 [Chemical Formula 3]
Si Cl
Cl
Cl
L
F3C
[Chemical Formula 4]
Si Cl
Cl
Cl
L
(CF2)n
F3C
In Chemical Formulae 2 to 4,
15 L is a direct bond or a C1 to C10 alkylene group, and n is
an integer of 0 to 10.
2 3
In Chemical Formula 2, L may be an ethylene group.
In Chemical Formula 3, L may be an ethylene group.
In Chemical Formula 4, n is 5, and L may be an ethylene
group.
5 In the present specification, examples of the halogen
group may include fluorine, chlorine, bromine or iodine.
In the present specification, the alkyl group may be
linear or branched, and the number of carbon atoms is not
particularly limited, but is preferably from 1 to 10. Specific
10 examples thereof may include methyl, ethyl, propyl, n-propyl,
isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-
methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl,
neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-
methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-
15 ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl,
cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl,
2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-
ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-
methylhexyl, 5-methylhexyl or the like, but are not limited
20 thereto.
In the present specification, the aliphatic cyclic group
is not particularly limited, but preferably has 3 to 60 carbon
atoms, and specific examples thereof may include cyclopropyl,
cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-
25 dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-
2 4
methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-
trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl,
cyclooctyl, adamantly or the like, but are not limited thereto.
In the present specification, the aromatic cyclic group
5 may include a heterocyclic group and a non-heterocyclic group.
The heterocyclic group may be a heterocyclic group having
2 to 60 carbon atoms including one or more of O, N and S as a
heteroatom, and may include a monocyclic heterocyclic group or
a multicyclic heterocyclic group. Examples of the heterocyclic
10 group may include a thiophene group, a furan group, a pyrrole
group, an imidazole group, a thiazole group, an oxazole group,
an oxadiazole group, a triazole group, a pyridyl group, a
bipyridyl group, a pyrimidyl group, a triazine group, a
triazole group, an acridyl group, a pyridazine group, a
15 pyrazinyl group, a qinolinyl group, a quinazoline group, a
quinoxalinyl group, a phthalazinyl group, a pyridopyrimidinyl
group, a pyridopyrazinyl group, a pyrazinopyrazinyl group, an
isoquinoline group, an indole group, a carbazole group, a
benzoxazole group, a benzimidazole group, a benzothiazole group,
20 a benzocarbazole group, a benzothiophene group, a
dibenzothiophene group, a benzofuranyl group, a phenanthroline
group, a thiazolyl group, an isoxazolyl group, an oxadiazolyl
group, a thiadiazolyl group, a benzothiazolyl group, a
phenothiazinyl group, a dibenzofuranyl group or the like, but
25 are not limited thereto.
2 5
The non-heterocyclic group means an aromatic cyclic group
formed with carbon and hydrogen, and may be a monocyclic aryl
group or a multicyclic aryl group.
When the non-heterocyclic group is a monocyclic aryl
5 group, the number of carbon atoms is not particularly limited,
but is preferably from 6 to 25. Specific examples of the
monocyclic aryl group may include a phenyl group, a biphenyl
group, a terphenyl group or the like, but are not limited
thereto.
10 When the non-heterocyclic group is a multicyclic aryl
group, the number of carbon atoms is not particularly limited,
but is preferably from 10 to 24. Specific examples of the
multicyclic aryl group may include a naphthyl group, an
anthracenyl group, a phenanthryl group, a pyrenyl group, a
15 perylenyl group, a crycenyl group, a fluorenyl group or the
like, but are not limited thereto.
In the present specification, the amine group may include
an alkylamine group, an arylamine group, a diarylamine group, a
dialkylamine group and an alkylarylamine group. The number of
20 carbon atoms is not particularly limited, but is preferably
from 1 to 30. Specific examples of the amine group may include
a methylamine group, a dimethylamine group, an ethylamine group,
a diethylamine group, a phenylamine group, a naphthylamine
group, a biphenylamine group, an anthracenylamine group, a 9-
25 methyl-anthracenylamine group, a diphenylamine group, a
2 6
phenylnaphthylamine group, a ditolylamine group, a
phenyltolylamine group, a triphenylamine group or the like, but
are not limited thereto.
In the present specification, the alkoxy group is -OR,
5 and R is an alkyl group. Herein, the alkyl group may cite the
descriptions provided above.
The silicon-based compound having a substituent capable
of reacting with a hydroxyl group may be any one of the
following compounds.
Si Cl
CH3
CH3
F3C
10
Si Cl
Cl
Cl
F3C
Si Cl
Cl
Cl
CF3(CF2)5
The method for preparing a lithium electrode may include
forming a buffer layer having a hydroxyl group on the surface
15 of the lithium metal layer; and forming a silicon layer
including a silicon-based compound forming covalent bonds with
2 7
the hydroxyl group on the buffer layer.
Based on FIG. 2, a buffer layer 300 having a hydroxyl
group on the surface is formed on a lithium metal layer 100,
and a silicon layer 200 may be formed by coating a silicon5
based compound (R3SiCl) having a chloride group, a substituent
capable of reacting with a hydroxyl group, on the buffer layer
300. The silicon-based compound is arranged while being selfassembled
on the surface of the buffer layer, and the buffer
layer and the silicon layer may form covalent bonds as the
10 hydroxyl group on the surface of the buffer layer and the
chloride group of the silicon-based compound react and produce
hydrochloric acid (HCl). In the R3SiCl, Rs are each
independently a halogen group, an amino group, an alkoxy group,
a C1 to C10 alkyl group, a hydroxyl group, an aliphatic cyclic
15 group having two rings or less, an aromatic cyclic group having
two rings or less, or -L-(CF2)nCF3, L is a direct bond or a C1 to
C10 alkylene group, and n is an integer of 0 to 10.
The forming of a buffer layer may include forming a
buffer layer on the lithium metal layer; and introducing a
20 hydroxyl group on a surface of the buffer layer by oxygen
plasma treating or ultraviolet/ozone treating the buffer layer.
Based on FIG. 3, a buffer layer 300 is formed on a
lithium metal layer 100, and by oxygen plasma treating or
ultraviolet/ozone treating a surface of the buffer layer, a
25 hydroxyl group may be introduced to the surface of the buffer
2 8
layer. Herein, an upper part 330 of the oxygen plasma treated
or ultraviolet/ozone treated buffer layer is modified to a
layer formed with silicon oxide (SiOx, herein, x is an
oxidation number.), and the upper part 330 of the buffer layer
5 may have a hydroxyl group on the surface. In addition, in the
buffer layer 300, a lower part 310 of the buffer layer that is
not oxygen plasma treated or ultraviolet/ozone treated is not
modified, and its original material may be maintained.
The forming of a buffer layer may include forming a
10 buffer layer on a release substrate; and laminating the buffer
layer on the lithium metal layer.
The method for preparing a lithium electrode may include
forming a buffer layer having a hydroxyl group on a surface of
a release substrate; forming a silicon layer including a
15 silicon-based compound forming covalent bonds with the hydroxyl
group on the buffer layer; and removing the release substrate
and laminating the result on the lithium metal layer.
The forming of a buffer layer may include forming a
buffer layer on a surface of a release substrate; and
20 introducing a hydroxyl group on a surface of the buffer layer
by oxygen plasma treating or ultraviolet/ozone treating the
buffer layer.
In the method for preparing a lithium electrode,
descriptions on the lithium metal layer, the silicon layer, the
25 buffer layer and the like may use the descriptions provided
2 9
above.
A composition for a buffer layer for forming the buffer
layer may include a PDMS precursor and a curing agent, and
herein, the curing agent may be added in a ratio of 10:1 to
5 10:5 with respect to the PDMS precursor. As the amount of the
curing agent increases, curing time decreases. A curing
temperature after applying the composition for a buffer layer
is from 50C to 100C, and as the curing temperature increases,
curing time decreases.
10 Hereinafter, the present specification will be described
in more detail with reference to examples. However, the
following examples are for illustrative purposes only, and the
present specification is not limited thereto.
[Example]
15 [Example 1]
A lithium electrode layer was prepared with lithium foil
each having a thickness of 20 μm, 40 μm and 150 μm or by
further attaching copper foil to lithium foil each having a
thickness of 20 μm, 40 μm and 150 μm. The lithium electrode
20 layer was immersed in an anhydrous alkane-based solvent for 1
hour, taken out, and vacuum dried for 30 minutes.
The dried lithium electrode layer was immersed in a
trichloro(1H,1H,2H,2H-perfluorooctyl)silane/toluene solution (1
wt%) for 1 hour, taken out, and washed with an anhydrous alkane
25 solvent. Herein, immersing in an approximately 2 mL of
3 0
solution per cm2 area unit of the lithium electrode layer is
common.
The result obtained as above may be used as a
trichloro(1H,1H,2H,2H-perfluorooctyl)silane-coated lithium
5 electrode. As a structure of a battery, various shapes such as
a coin cell and a pouch cell may be used.
[Example 2]
A lithium electrode layer was prepared with lithium foil
each having a thickness of 20 μm, 40 μm and 150 μm or by
10 further attaching copper foil to lithium foil each having a
thickness of 20 μm, 40 μm and 150 μm.
As a buffer layer on the lithium electrode layer,
polydimethylsiloxane (PDMS) was used. A PDMS precursor and a
curing agent were added to a solvent in a weight ratio of 10:1
15 to prepare a composition, and the composition was coated on the
electrode foil using drop-casting or spin-coating to form a
PDMS layer, and an electrode was prepared. The electrode was
heat treated for 2 hours at 80C to cure the PDMS layer. The
cured PDMS was UV ozone treated or oxygen plasma treated to
20 form a polar hydroxyl group on the PDMS surface (produced SiOx
phase).
After that, the treated electrode foil was immersed in a
trichloro(1H,1H,2H,2H-perfluorooctyl)silane/toluene solution (1
wt%) for 1 hour, taken out, and washed with an anhydrous alkane
25 solvent. Herein, immersing in an approximately 2 mL of
3 1
solution per cm2 area unit of the foil is common.
The result obtained as above may be used as a
trichloro(1H,1H,2H,2H-perfluorooctyl)silane-coated lithium
electrode. As a structure of a battery, various shapes such as
5 a coin cell and a pouch cell may be used.
[Comparative Example 1]
Lithium foil or lithium/copper foil without forming a
silicon layer in Example 1 was used as Comparative Example 1.
[Test Example 1]
10 Life of Lithium Electrode
Cycle life of the lithium electrodes of Examples 1 and 2
and Comparative Example 1 was evaluated. Specifically, Li/Li
symmetric cell was prepared and measured with reference to an
Aurbach method, and the results are shown in FIG. 4.
15 Liquid electrolyte composition: 1 M LiPF6 in EC:EMC (1:1
v/v)
[Test Example 2]
Moisture Permeability
States after exposing Examples 1 and 2 and Comparative
20 Example 1 to air (RH 50%) for 10 minutes and states after
dropping water drops on Examples 1 and 2 and Comparative
Example 1 were compared, and each image is shown in FIG. 5.
As shown in FIG. 5, LiCl having a very strong moisture
absorbing property was produced as a byproduct in Example 1
25 leading to a result exhibiting a declined moisture blocking
3 2
property compared to Comparative Example 1. Meanwhile, Example
2 exhibited an improved moisture blocking property compared to
Comparative Example 1.
[Test Example 3]
5 Water Contact Angle
Results or measuring water contact angles of Examples 1
and 2 and Comparative Example 1 are shown in the following
Table 1.
[Table 1]
Water Contact Angle ()
Comparative Example 1 Impossible to Measure (Reacted with Water)
Example 1 Impossible to Measure (Reacted with Water)
PDMS/Li, intermediate
of Example 2
110
Example 2 130 to 150

WE CLAIM:
【Claim 1】
A lithium electrode comprising:
a lithium metal layer having a hydroxyl group on a
5 surface thereof; and
a silicon layer provided on the lithium metal layer and
including a silicon-based compound,
wherein the silicon-based compound of the silicon layer
forms covalent bonds with a hydroxyl group of a lower membrane
10 that is in contact with the silicon layer.
【Claim 2】
The lithium electrode of Claim 1, further comprising a
buffer layer provided between the lithium metal layer and the
silicon layer and having a hydroxyl group on a surface thereof,
15 wherein the silicon layer includes a silicon-based
compound forming covalent bonds with the hydroxyl group of the
buffer layer.
【Claim 3】
The lithium electrode of Claim 1, wherein the silicon20
based compound is prepared with a compound represented by the
following Chemical Formula 1:
[Chemical Formula 1]
3 4
Si
R1
R2 R4
R3
wherein, in Chemical Formula 1,
one or more of R1 to R4 are each independently a halogen
group, an amino group or an alkoxy group, and the rest are each
5 independently a C1 to C10 alkyl group, a hydroxyl group, an
aliphatic cyclic group having two rings or less, an aromatic
cyclic group having two rings or less, or -L-(CF2)nCF3, L is a
direct bond or a C1 to C10 alkylene group, and n is an integer
of 0 to 10.
10 【Claim 4】
The lithium electrode of Claim 3, wherein the siliconbased
compound is prepared with a compound represented by at
least one of the following Chemical Formulae 2 to 4:
[Chemical Formula 2]
Si Cl
CH3
CH3
L
F3C
15
[Chemical Formula 3]
3 5
Si Cl
Cl
Cl
L
F3C
[Chemical Formula 4]
Si Cl
Cl
Cl
L
(CF2)n
F3C
wherein, in Chemical Formulae 2 to 4,
5 L is a direct bond or a C1 to C10 alkylene group, and n is
an integer of 0 to 10.
【Claim 5】
The lithium electrode of Claim 1, wherein a water contact
angle of the silicon layer is 100 or more and 160 or less.
10 【Claim 6】
The lithium electrode of Claim 1, wherein a thickness of
the silicon layer is 1 nm or more and 1 μm or less.
【Claim 7】
The lithium electrode of Claim 2, wherein the buffer
15 layer includes a siloxane-based compound.
【Claim 8】
The lithium electrode of Claim 2, wherein the buffer
layer includes polydimethylsiloxane.
【Claim 9】
3 6
The lithium electrode of Claim 2, wherein a thickness of
the buffer layer is 10 nm or more and 10 μm or less.
【Claim 10】
A lithium secondary battery comprising the lithium
5 electrode of any one of Claims 1 to 9.
【Claim 11】
The lithium secondary battery of Claim 10, wherein the
lithium electrode is a lithium electrode of the lithium
secondary battery.
10 【Claim 12】
The lithium secondary battery of Claim 10, wherein the
lithium electrode is a lithium electrode of the lithium
secondary battery, the battery comprising:
a cathode; and
15 an electrolyte provided between the lithium electrode and
the cathode.
【Claim 13】
The lithium secondary battery of Claim 12, wherein the
electrolyte is an electrolyte liquid into which the lithium
20 electrode and the cathode are immersed.
【Claim 14】
The lithium secondary battery of Claim 12, further
comprising a separator provided between the lithium electrode
and the cathode.
25 【Claim 15】
3 7
The lithium secondary battery of Claim 12, wherein the
electrolyte is a solid electrolyte membrane or a polymer
electrolyte membrane.
【Claim 16】
5 A battery module comprising the lithium secondary battery
of Claim 10 as a unit battery.
【Claim 17】
A method for preparing a lithium electrode comprising
forming a silicon layer including a silicon-based compound on a
10 lithium metal layer having a hydroxyl group on a surface
thereof,
wherein the silicon-based compound of the silicon layer
forms covalent bonds to a hydroxyl group of a lower membrane
that is in contact with the silicon layer.
15 【Claim 18】
The method for preparing a lithium electrode of Claim 17,
wherein the forming of a silicon layer includes preparing a
solution including a silicon-based compound having a
substituent capable of reacting with a hydroxyl group; and
20 coating the solution on at least a part of the surface of the
lithium metal layer.
【Claim 19】
The method for preparing a lithium electrode of Claim 17,
wherein the forming of a silicon layer includes preparing a
25 solution including a silicon-based compound having a
3 8
substituent capable of reacting with a hydroxyl group; and
immersing the lithium metal layer into the solution.
【Claim 20】
The method for preparing a lithium electrode of Claim 18
5 or 19, wherein the silicon-based compound having a substituent
capable of reacting with a hydroxyl group is represented by the
following Chemical Formula 1:
[Chemical Formula 1]
Si
R1
R2 R4
R3
10 wherein, in Chemical Formula 1,
one or more of R1 to R4 are each independently a halogen
group, an amino group or an alkoxy group, and the rest are each
independently a C1 to C10 alkyl group, a hydroxyl group, an
aliphatic cyclic group having two rings or less, an aromatic
15 cyclic group having two rings or less, or -L-(CF2)nCF3, L is a
direct bond or a C1 to C10 alkylene group, and n is an integer
of 0 to 10.
【Claim 21】
The method for preparing a lithium electrode of Claim 18
20 or 19, wherein the silicon-based compound having a substituent
capable of reacting with a hydroxyl group is represented by at
least one of the following Chemical Formulae 2 to 4:
3 9
[Chemical Formula 2]
Si Cl
CH3
CH3
L
F3C
[Chemical Formula 3]
Si Cl
Cl
Cl
L
F3C
5 [Chemical Formula 4]
Si Cl
Cl
Cl
L
(CF2)n
F3C
wherein, in Chemical Formulae 2 to 4,
L is a direct bond or a C1 to C10 alkylene group, and n is
an integer of 0 to 10.
10 【Claim 22】
The method for preparing a lithium electrode of Claim 17,
comprising:
forming a buffer layer having a hydroxyl group on the
surface of the lithium metal layer; and
15 forming a silicon layer including a silicon-based
compound forming covalent bonds with the hydroxyl group of the
4 0
buffer layer on the buffer layer.
【Claim 23】
The method for preparing a lithium electrode of Claim 22,
wherein the forming of a buffer layer includes forming a buffer
5 layer on the lithium metal layer; and introducing a hydroxyl
group on a surface of the buffer layer by oxygen plasma
treating or ultraviolet/ozone treating the buffer layer.
【Claim 24】
The method for preparing a lithium electrode of Claim 22,
10 wherein the forming of a buffer layer includes forming a buffer
layer on a release substrate; and laminating the buffer layer
on the lithium metal layer.
【Claim 25】
The method for preparing a lithium electrode of Claim 17,
15 comprising:
forming a buffer layer having a hydroxyl group on a
surface of a release substrate;
forming a silicon layer including a silicon-based
compound forming covalent bonds with the hydroxyl group on the
20 buffer layer; and
removing the release substrate and laminating the result
on the lithium metal layer.
【Claim 26】
The method for preparing a lithium electrode of Claim 25,
25 wherein the forming of a buffer layer includes forming a buffer
4 1