Technical Field
The. present invention relates to an electrolyte that
can prevent corrosion of metallic interior and exterior
materials of a battery, caused by abnormal conditions, such
as overcharge, overdischarge and high-temperature storage
conditions, to which the battery is exposed. The present
invention also relates to an electrochemical device,
preferably a lithium secondary battery, which comprises the
above electrolyte, and thus degradation in the quality,
caused by corrosion of metallic materials, is prevented.
Background Art
Recently, as electronic devices become smaller and
lighter, batteries used therein as power sources are
increasingly required to have a compact size and light
weight. As rechargeable batteries with a compact size, light
weight and high capacity, lithium secondary batteries have
been put to practical use and widely used in portable
electronic and communication devices such as compact
camcorders, portable phones, notebook PCs, or the like.
A lithium secondary battery comprises a cathode, an
anode and an electrolyte. Such lithium secondary batteries
are capable of repeated charge/discharge cycles, because
lithium ions deintercalated from a cathode active material
upon the first charge cycle are intercalated into an anode
active material (for example, carbon particles) and
deintercalated again during a discharge cycle, so that
lithium ions reciprocate between both electrodes while
transferring energy.

In general, metals and metal alloys, such as iron,
aluminum, copper, nickel, etc. are widely used as materials
for forming a can for housing a lithium secondary battery and
forming a collector of a lithium secondary battery. Such
metallic materials are not susceptible to corrosion
(oxidation) under the normal charge/discharge conditions of a
lithium secondary battery. However, under extreme conditions,
such as overcharge, overdischarge and high-temperature
storage conditions, such metallic materials tend to show a
greett possibility of corrosion. Particularly, when a battery
is overdischarged to a voltage of OV at low current or under
constant resistance, the voltage: of an anode having a high
irreversible capacity increases in advance of the voltage of
a cathode. Under these circumstances, when the anode voltage
reaches to a specific voltage range of about 3.6V or higher,
at which point copper foil used as an anode collector is
oxidized, copper dissolution (i.e. oxidation) occurs,
resulting in damages of the battery. In brief, corrosion of
metallic materials present inside of a battery under the
overcharge, overdischarge and high-temperature storage
conditions, causes the problems of self-discharge, a drop in
capacity, internal short circuit and an increase in internal
resistance of the battery, resulting in degradation in the
guality of a battery and damages of the battery.
Brief Description of the Drawings
The foregoing and other objects, features and
advantages of the present invention will become more apparent
from the following detailed description when taken in
conjunction with the accompanying drawing in which:
FIG. 1 is a graph showing the electrochemical oxidation
characteristics of the inner walls of the cylindrical cans,

in the batteries using the electrolyte according to Example 1
and the electrolyte according to Example 2, to which Li2MoO4
and Li2WO4 are added, respectively, as a multinary metal oxide
salt; and in the battery using a conventional electrolyte
according to Comparative Example 1, as a control.
Disclosure of the Invention
Therefore, the present invention has been made in view
of the above-mentioned problems. The present inventors have
found that when a metal oxide salt, which is dissolved and
dissociated in a non-aqueous electrolyte solvent to generate
oxyanions having an activity of inhibiting oxidation
(corrosion) of metallic materials, is used for forming an
electrolyte, it is possible to inhibit corrosion of metallic
materials forming an electrochemical device, such as a
metallic can and a collector, and to prevent the
electrochemical device from being degraded in its quality by
corrosion of metallic materials.
Therefore, it is an object of the present invention to
provide a non-aqueous electrolyte comprising the above-
mentioned metal oxide salt, and an electrochemical device,
preferably a lithium secondary battery, comprising the same
electrolyte.
According to an aspect of the present invention, there
is provided an electrolyte comprising: (a) an electrolyte
salt; (b) a non-aqueous electrolyte solvent; and (c) a binary
or multinary metal oxide salt. There is also provided an
electrochemical device, preferably a lithium secondary
battery, comprising the same electrolyte.
Hereinafter, the present invention will be explained in
more detail.
The present invention is characterized by using a

multinary metal oxide salt, capable of ionization upon
dissolution, in a non-aqueous electrolyte solvent.
Unlike conventional oxides (US Patent No. 5,168,019),
which are comprised of covalent bonds and thus are not
dissociated in an electrolyte solvent, the above-mentioned
metal oxide salt is comprised of ionic bonds, and thus is
dissociated with ease when it is dissolved in an electrolyte
solvent currently used in a battery. Moreover, the metal
oxide salt can generate oxyanions, after the dissociation,
and such oxyanions can improve the corrosion resistance of
metals. The oxyanions significantly reduce the possibility of
corrosion of metallic materials,, which otherwise increases
under abnormal conditions, such as overcharge, overdischarge
and high-temperature storage conditions. Therefore, the
oxyanions generated from the metal oxide ' salt can prevent
degradation in the quality of an electrochemical device,
caused by corrosion of metallic materials present inside the
device.
One component forming the electrolyte according to the
present invention is a binary or multinary metal oxide salt.
There; is no particular limitation in the metal oxide salt, as
long as it is comprised of ionic bonds and is ionizable in
water and/or organic solvents. As described above, the metal
oxide salt is dissociated into oxyanions when it is dissolved
in an electrolyte solvent currently used in a battery, and
such oxyanions are adsorbed on a protection film generally
formed on the surface of a metallic can and/or collector. For
example, such oxyanions are adsorbed on defects present on an
oxide film. It is thought that such adsorbed oxyanions
prevent any oxidation generated from the defects. Therefore,
it is possible to solve the problems caused by corrosion of
the metallic materials. Such problems include self-discharge,

a drop in capacity, internal short circuit and an increase in
internal resistance of an electrochemical device, preferably
of a battery. Further, it is possible to prevent degradation
in the battery quality and damages of the battery.
According to a preferred embodiment of the present
invention, the metal oxide salt is represented by the
following formula 1, but is not limited thereto:
[Formula 1]

wherein A is at least one element selected from the
group consisting of alkali metals and alkaline earth metals;
M is at least one element selected from the group
consisting of non-metals, metalloids and transition metals;

Non-limiting examples of the multinary metal oxide salt
represented by formula 1 include: Li4SiO4, Li2B4O7, Li2MoO4,
Li2WO4, Li2CrO4, Li2TiO3, Li2ZrO3, LiTaO3, LiNbO3, Na4SiO4, Na2B4O7,
Na2MoO4, Na2WO4, Na2CrO4, Na2TiO3, Na2ZrO3, NaTaO3, NaNbO3, Cs4SiO4,
Cs2B4O7, Cs2MoO4, Cs2WO4, Cs2CrO4, Cs2TiO3, Cs2ZrO3, CsTaO3, CsNbO3,
Mg2SiO4, MgB4O7, MgMoO4, MgWO4, MgCrO4, MgTiO3, MgZrO3, Ba4SiO4,
BaB4O7, BaMoO4, BaWO4, BaCrO4, BaTiO3, BaZrO3 and mixtures
thereof. Particularly, when a lithium-containing metal oxide
salt is used as the multinary metal oxide salt, it is
possible to minimize degradation in the quality of a battery,
caused by using the additive for electrolyte, because a
higher concentration of lithium ions is available for
electrochemical reactions occurring in the battery. In
addition to the above-described salts, any compounds may be
used in the scope of the present invention regardless of
their elements or configurations, as long as they are

dissolved in a non-aqueous electrolyte solvent and generate
oxyanions so as to serve to i.nhibit corrosion of metallic
materials.
Preferably, the multinary metal oxide salt is used in
an amount of 0.01—10 wt% per 100 parts by weight of the
electrolyte, but the content of the metal oxide salt is not
limited thereto. If the content of the metal oxide salt is
less than 0.01 wt%, it is not possible to obtain the effect
of preventing corrosion of metallic materials to a sufficient
degree. On the other hand, if the content of the metal oxide
salt is greater than 10 wt%, the metal oxide salt may not be
dissolved in the electrolyte completely.
The electrolyte, to which the metal oxide salt is
added, may comprise conventional electrolyte components known
to one skilled in the art, for example an electrolyte salt
and a non-aqueous electrolyte solvent.
The electrolyte salt that may be used in the present
invention includes a salt represented by the formula of A+Ef,
wherein A+ represents an alkali metal cation selected from the
group consisting of Li+, Na+, K+ and combinations thereof, and
B- represents an anion selected from the group consisting of
PF6-, BF4-, CI-, Br-, I-, ClO4-, AsF6-, CH3CO2-, CF3SO3-, N(CF3SO2)2-
, C(CF2SO2)3- and combinations thereof. Non-limiting examples
of the non-aqueous electrolyte solvent include propylene
carbonate (PC), ethylene carbonate (EC), diethyl carbonate
(DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC),
dimethyl sulfoxide, acetonitrile, dimethoxyethane,
diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone
(NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (GBL) '
and mixtures thereof.
According to another aspect of the present invention,
there is provided an electrochemical device, which comprises

a cathode, an anode and an electrolyte, wherein the
electrolyte comprises the above-described multinary metal
oxide salt.
Such electrochemical devices include any devices in
which electrochemical reactions occur, and particular
examples thereof include all kinds of primary batteries,
secondary batteries, fuel cells,, solar cells or capacitors.
Particularly, the electrochemical device is a lithium
secondary battery including a lithium metal secondary
battery, lithium ion secondary battery, lithium polymer
secondary battery or lithium ion polymer secondary battery.
The electrochemical device may be manufactured by a
conventional method known to one skilled in the art. In one
embodiment of the method for manufacturing the
electrochemical device, a separator is interposed between a
cathode and anode to provide an assembly, and then an
electrolyte, containing the metal oxide salt added thereto,
is injected.
There is no particular limitation in the electrode that
may be applied together with the electrolyte according to the
present invention. The electrode may be formed by applying an
electrode active material on a current collector according to
a method known to one skilled in the art.
More particularly, cathode active materials may include
any conventional cathode active materials currently used in a
cathode of a conventional electrochemical device. Particular
non-Limiting examples of the cathode active materials
include: lithium transition metal composite oxides, such as a
composite oxide represented by the formula of LiMxOy, wherein
M= Co, Ni, Mn, CoaNibMnc (e.g. lithium manganese composite
oxides; lithium nickel oxides; lithium cobalt oxides; lithium
iron oxides; other composite oxides thereof, in which

manganese, nickel, cobalt and iron present in the above
oxides are partially substituted with other transition
metals; and lithium-containing vanadium oxides); chalcogen
compounds (e.g. manganese dioxide, titanium dioxide,
molybdenum dioxide, etc.); and mixtures thereof.
Additionally, anode active materials may include any
conventional anode active materials currently used in an
anode of a conventional electrochemical device. Particular
non-limiting examples of the anode active materials include:
lithium metal; lithium alloys; carbon; petroleum coke;
activated carbon; graphite; other carbonaceous materials; and
lithium intercalation materials capable of lithium
intercalation/ deintercalation and having a potential of less
than 2V based on lithium, for example T1O2 and SnO2.
Non-limiting examples of a cathode current collector
include foil formed of aluminum, nickel or a combination
thereof. Non-limiting examples of an anode current collector
include foil formed of copper, gold, nickel, copper alloys or
a combination thereof.
There is no particular limitation in the separator that
may be used in the present invention, as long as it is a
porous material that interrupts an internal short circuit
between both electrodes and is impregnated with the
electrolyte. Particular non-limiting examples of porous
separators include polypropylene-based, polyethylene-based,
polyolefin-based porous separators, and composite porous
separators comprising the above porous separators, to which
inorganic materials are added.
There is no particular limitation in the shape of the
electrochemical device according to the present invention.
The electrochemical device may be a cylindrical can-type,
prismatic, pouch-type or a coin-type electrochemical device.

Particularly, a cylindrical device comprising a metallic can
connected with an anode of a battery is preferred, a
cylindrical lithium secondary battery being more preferred.
In the latter case, the effect of preventing corrosion of the
metallic can, derived from the multinary metal oxide when the
battery is exposed to overcharge, overdischarge or high-
temperature storage conditions, is more significant compared
to other batteries having different shapes.
Best Mode for Carrying Out the Invention
Reference will now be made in detail to the preferred
embodiments of the present invention. It is to be understood
that the following examples are illustrative only and the
present invention is not limited thereto.
[Examples 1~2] Manufacture of Lithium Secondary
Batteries
Example 1
LiCo02 was provided as a cathode active material. Next,
90 wt% of LiCo02, 5 wt% of Super-? as a conductive agent and 5
wt% of PVDF (polyvinylidene difluoride) as a binder were
mixed, and then the resultant mixture was added to NMP (N-
methyl-2-pyrrolidone) as a solvent to form cathode slurry.
The slurry was applied on an aluminum (Al) collector to form
a cathode. Then, lithium metal as an anode and the cathode
formed as described above were used to manufacture a
cylindrical battery. As an electrolyte, EC/EMC solution
containing 1M LiPF6 was used, and 0.5 wt% of Li2MoO4 was added
to the electrolyte.
Example 2
Example 1 was repeated to manufacture a cylindrical
lithium secondary battery, except that Li2WO4 was used instead
of Li2MoO4.

Comparative Example 1
Example 1 was repeated to manufacture a cylindrical
lithium secondary battery, except that no additive was added
to the electrolyte.
Experimental Example 1. Evaluation for Oxidation
Oxidation characteristics of metallic materials were
evaluated by using the electrolyte, to which a metal oxide
salt was added according to the present invention.
The electrolytes according to Examples 1 and 2, which
contain Li2MoO4 and IA2WO4, respectively, as a multinary metal
oxide salt, were used. As a control, a conventional
electrolyte according to Comparative Example 1 was used.
The inner wall of a can currently used in a cylindrical
battery was used as a work electrode, lithium metal was used
as a reference electrode, and a platinum (Pt) wire electrode
was used as a counter electrode, in order to carry out linear
sweep voltammetry. By doing so, each of the electrolytes
according to Examples 1 and 2 and Comparative Example 1 was
evaluated for its effect upon the electrochemical oxidation
characteristics of the inner wall of the can for a
cylindrical battery. The results are shown in FIG. 1. During
the evaluation, a scanning rate of 10 mV/s was used, and
oxidation characteristics were determined in a glove box
under the argon atmosphere containing at most 10 ppm of
moisture and oxygen.
After the test, the electrolytes according to Examples
1 and 2, to which Li2MoO4 and Li2WO4 are added, respectively,
showed an oxidation initiation voltage increased by about
0.4V, as compared to the conventional electrolyte according
to Comparative Example 1. Additionally, the electrolytes
according to Examples 1 and 2 showed a significantly
decreased oxidation current (see FIG. 1) . This indicates that

the multinary metal oxide salt added to the electrolytes
improve the oxidation resistance of the cylindrical can.
Therefore, the electrolyte according to the present
invention, comprising a metal oxide salt as an additive, can
improve the oxidation resistance of metallic materials used
in a battery.
Industrial Applicability
As can be seen from the foregoing, the electrolyte
according to the present invention, which comprises a
multinary metal oxide salt that is dissolved in a non-aqueous
electrolyte solvent and generates oxyanions capable of
improving the oxidation resistance of metals, can prevent
corrosion of metallic materials present in an electrochemical
device, such as a collector and a metallic can, and can
minimize degradation in the quality of the device, caused by
corrosion of metallic materials.
While this invention has been described in connection
with what is presently considered to be the most practical
and preferred embodiment, it is to be understood that the
invention is not limited to the disclosed embodiment and the
drawings. On the contrary, it is intended to cover various
modifications and variations within the spirit and scope of
the appended claims.

WE CLAIM:
1. An electrolyte comprising:
(a) an electrolyte salt;
(b) a non-aqueous electrolyte solvent; and
(c) a binary or multinary metal oxide salt,
wherein the metal oxide salt is represented by the following formula 1:
[Formula 1]
AxMyOz
wherein A is at least one element selected from the group consisting of alkali metals
and alkaline earth metals;
M is at least one element selected from the group consisting of non-matals, metalloids
and transition metals;
1≤x≤6:
1≤y≤7; and
2≤z≤24.
2. The electrolyte as claimed in claim 1, wherein the metal oxide salt is an ionically
bonded salt of oxide.
3. The electrolyte as claimed in claim 1, wherein the metal oxide salt is dissociated to
generate oxyanions, when it is dissolved in a non-aqueous electrolyte solvent.
4. The electrolyte as claimed in claim 1, wherein the metal oxide salt is at least one salt
selected from the group consisting of: Li4SiO4, Li2B4O7, Li2MoO4, Li2WO4, Li2CrO4,
Li2TiO3, Li2ZrO3, LiTaO3, LiNbO3, Na4SiO4, Na2B4O7; Na2MoO4, Na2WO4, Na2CrO4,
Na2TiO3, Na2ZrO3, NaTaO3, NaNbO,, Cs4SiO4, Cs2B4O7, Cs2MoO4, Cs2WO4, Cs2CrO4,
Cs2TiO3, Cs2ZrO3, CsTaO3, CsNbO3, Mg2SiO4, MgB4O7, MgMoO4, MgWO4, MgCrO4,
MgTiO3, MgZrO3, Ba4SiO4, BaB4O7, BaMoO4, BaWO4, BaCrO4, BaTiO3, and BaZrO3.
5. The electrolyte as claimed in claim 1, wherein the metal oxide salt is used in an
amount of 0.01~10 wt % per 100 wt % of the electrolyte.

6. The electrolyte as claimed in claim 1, wherein the electrolyte salt is a salt represented
by the formula of A+B-, wherein A+ represents an alkali metal cation selected from the
group consisting of Li+, Na+ and I+, and B- represents an anion selected from the group
consisting of PF6-, BF4-, CI-, Br, I-, CIO4-, AsF6-, CH3Co2-, CF3SO3-, N(CF3So2)2- and
C(CF2SO2)3-; and the non-aqueous electrolyte solvent is at least one solvent selected from
the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl
carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl
sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-
pyrrolidone (NMP), ethylmethyl carbonate (EMC) and gamma-butyrolactone (GBL).
7. An electrochemical device comprising a cathode, an anode and an electrolyte as
claimed in any one of claims 1 to 6.
8. The electrochemical device as claimed in claim 7, which is a lithium secondary
battery. / /

ABSTRACT

NONAQUEOUS ELECTROLYTE COMPRISING OXYANION AND LITHIUM
SECONDARY BATTERY USING THE SAME
Disclosed is an electrolyte comprising: (a) an electrolyte salt; (b) a non-aqueous
electrolyte solvent; and (c) a binary or multinary metal oxide salt. An electrochemical
device comprising the same electrolyte is also disclosed, wherein the metal oxide salt is
represented by the following formula 1: [Formula 1] AxMyOz, wherein A is at least one
element selected from the group consisting of alkali metals and alkaline earth metals, M
is at least one element selected from the group consisting of non-matals, metalloids and
transition metals, 1≤x≤6; 1≤y≤7; and 2≤z≤24. The metal oxide salt used in the electrolyte
is dissolved in a non-aqueous solvent and generates oxyanions capable of improving
corrosion resistance of metals. Therefore, the electrolyte prevents corrosion of metallic
materials present in an electrochemical device, caused by extreme conditions, such as
overcharge, overdischarge and high-temperature storage conditions, to which the device
is exposed. Further, the electrolyte prevents degradation in the quality of an
electrochemical device, caused by corrosion of metallic materials.