【Technical Field】
The present disclosure relates to a method of preparing a sacrificial positive electrode
material with reduced gas generation during charging of a battery by controlling both
humidity and gas conditions in calcination of a raw material mixture, and a sacrificial positive
electrode material prepared according to the method.
10 The present application claims the benefit of priority based on Korean Patent
Application No. 10-2021-0024248 dated February 23, 2021 and Korean Patent Application
No. 10-2022-0007852 dated January 19, 2022, and all contents published in the literature of
the Korean patent applications are incorporated as part of this specification.
【Background Art】
15 In recent years, as high-capacity electrode materials are more required, an irreversible
additive is also required to have a higher irreversible capacity. However, it is true that there
is a limit to the development of a positive electrode additive having such a high irreversible
capacity.
Meanwhile, a conventional irreversible additive such as Li6CoO4 is generally
20 prepared by reacting cobalt oxide, etc. with an excess of lithium oxide. At this time, byproducts such as unreacted lithium oxide (Li2O), which did not participate in the reaction,
remain in the final prepared irreversible additive, which may cause oxidation in the
3
charging/discharging process to generate oxygen gas inside the battery. Oxygen gas thus
generated may cause volume expansion and the like, and may be one of the main factors
leading to deterioration of battery performance.
In addition, the by-products such as lithium oxide may react with a binder component
5 and the like when preparing a slurry composition for manufacturing an electrode, thereby
increasing the viscosity or causing gelation of the composition. As a result, it is difficult to
uniformly apply the electrode composition for forming the active material layer, and there is a
problem in that the characteristics of the battery are deteriorated.
Therefore, due to the above problems, the development of a positive electrode
10 additive having a higher irreversible capacity while the amount of oxygen generated in the
charging/discharging process of the battery is small due to a small amount of residual byproducts such as lithium oxide is continuously required.
[Related art literature]
Republic of Korea Patent Publication No. 2019-0078392
15 【Disclosure】
【Technical Problem】
Accordingly, an object of the present disclosure is to provide a positive electrode
additive having a higher irreversible capacity while an amount of oxygen generated in the
charging and discharging process of the battery is small due to a small residual amount of by20 products such as lithium oxide, and a positive electrode and a lithium secondary battery
including the same.
【Technical Solution】
In order to solve the above-described problems, in one embodiment, the present
4
disclosure provides a method of preparing a sacrificial positive electrode material, wherein the
method includes calcining a raw material mixture of lithium oxide (Li2O) and cobalt oxide
(CoO) under an atmosphere containing an inert gasand oxygen gas, wherein the oxygen gas is
at a partial pressure of 1% or less to prepare a lithium cobalt metal oxide represented by the
5 following Chemical Formula (1),
the relative humidity (RH) during calcination is 20% or less:
[Chemical Formula 1]
LixCo(1-y)MyO4-zAz
wherein,
10 M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni,
A is a halogen,
x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
Here, the calcining may be carried out in an inert gas atmosphere having a relative
humidity of 0.1% to 15% and including oxygen gas at a partial pressure of 0.1 to 1%.
15 In addition, the calcining temperature may be 500 to 800 °C.
In addition, the raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO)
may be a mixture in which lithium oxide (Li2O) and cobalt oxide (CoO) are mixed in a molar
ratio of 2 to 4 : 1.
In addition, the lithium oxide (Li2O) may have an average particle size (D50) of 10
20 µm to 30 µm.
In addition, the sacrificial positive electrode material prepared by the above
preparation method may satisfy at least one of Equations 1 and 2 below, as measured by Xray diffraction:
[Equation 1] A/B ≤ 0.1
5
[Equation 2] C/D ≤ 0.35
wherein,
A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
5 B represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=19.2±0.1°,
C represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
10 range of 2θ=47.9±0.1°.
The present disclosure also provides, in one embodiment, an electrode assembly
including a positive electrode comprising:
a positive electrode current collector; and
a positive electrode mixture layer including a positive electrode active material, a
15 conductive material, an organic binder polymer, and a sacrificial positive electrode material
on the positive electrode current collector;
the sacrificial positive electrode material includes lithium cobalt metal oxide
represented by Chemical Formula 1 below, and satisfies at least one of Equations 1 and 2, as
measured by X-ray diffraction:
20 [Chemical Formula 1]
LixCo(1-y)MyO4-zAz
wherein,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni,
A is a halogen,
6
x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001,
[Equation 1] A/B ≤ 0.1
[Equation 2] C/D ≤ 0.35
wherein,
5 A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
B represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=19.2±0.1°,
C represents the intensity of the strongest peak among the peaks appearing in the
10 range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=47.9±0.1°.
Here, the positive electrode active material may be a lithium composite transition
metal oxide containing two or more elements selected from the group consisting of nickel
15 (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium
(Mg), chromium (Cr) and zirconium (Zr).
In addition, the content of the sacrificial positive electrode material may be 0.001 to
5.0 parts by weight based on 100 parts by weight of the positive electrode active material.
Furthermore, in one embodiment, the present disclosure provides a lithium secondary
20 battery including the electrode assembly.
【Advantageous Effects】
In the method of preparing the sacrificial positive electrode material according to the
present disclosure, the calcination of the raw material mixture is carried out under an
atmosphere containing an inert gas and a small amount of oxygen (O2) gas and a humidity
7
satisfying a specific range, whereby the generation of gas, particularly oxygen (O2) gas,
generated in the electrode assembly at the time of charging the battery can be reduced, and
thus the effect of improving the stability and life of the battery containing the same is
excellent.
5 【Brief Description of the Drawings】
FIG. 1 is a graph showing X-ray diffraction of a sacrificial positive electrode material
according to a humidity condition in calcination of a raw material mixture.
FIG. 2 is a graph showing X-ray diffraction of a sacrificial positive electrode material
according to an oxygen partial pressure in calcination of a raw material mixture.
10 FIG. 3 is a graph showing the amount of gas generated according to the number of
times of charging/discharging at 45 °C for each oxygen partial pressure in calcination of the
raw material mixture.
FIG. 4 is a graph showing the amount of gas generated according to the storage time
(units: week) at 60 °C for each oxygen partial pressure in calcination of the raw material
15 mixture.
FIG. 5 is a graph showing an initial charging/discharging curve of a positive electrode
including a sacrificial positive electrode material according to a humidity condition in
calcination of a raw material mixture.
FIG. 6 is a graph showing an initial charging/discharging curve of a positive electrode
20 including a sacrificial positive electrode material according to an oxygen partial pressure in
calcination of a raw material mixture.
【Detailed Description of the Preferred Embodiments】
Since the present disclosure can have various changes and can have various
embodiments, specific embodiments will be described in detail in the detailed description.
8
However, this is not intended to limit the present disclosure to specific embodiments,
and it should be understood to include all modifications, equivalents and substitutes included
in the spirit and scope of the present disclosure.
In the present disclosure, it is to be understood that the terms “include(s)” or
5 “have(has)” and the like are intended to specify the presence of stated features, numbers,
steps, operations, components, components or combinations thereof, but do not preclude the
presence or addition of one or more other features or numbers, steps, operations, components
and combinations thereof.
Further, in the present disclosure, when a portion of a layer, film, region, plate, etc. is
10 described as being “on” another portion, it includes not only the case where the other portion
is “directly on” but also the case where there is another portion therebetween. Conversely,
where a portion of a layer, film, region, plate, etc. is described as being “under” another
portion, this includes the case where there is another portion therebetween as well as “directly
under” the other portion. Also, herein, what is referred to as being disposed “on” may
15 include being disposed not only on an upper part but also on a lower part.
In addition, in the present disclosure, "relative humidity (RH)" is expressed as a
percentage (%) and is the ratio of the amount of water vapor currently contained in the air to
the maximum saturated water vapor pressure that a constant volume of air can hold, and it
may be expressed as a percentage of the humidity inside the electric furnace in which the raw
20 material mixture is calcined.
In addition, in the present disclosure, "D50" is the particle size of the point that
reaches 50% of the volume percentage in the cumulative curve when calculating the
cumulative curve of the particle size distribution with the total volume being 100%, and it
means the particle size where the volume is 50% by accumulating from the smallest particle
9
size. The average particle size (D50) can be measured, for example, by using a laser
diffraction method, and the laser diffraction method can generally measure a particle size of
from a submicron region to several mm, and high reproducibility and high resolution results
can be obtained.
5
Hereinafter, the present disclosure will be described in more detail.
Method of Preparing a Sacrificial Positive Electrode Material
In one embodiment, the present disclosure provides a method of preparing a
10 sacrificial positive electrode material, wherein the method includes calcining a raw material
mixture of lithium oxide (Li2O) and cobalt oxide (CoO) under an atmosphere containing inert
gas and oxygen gas, wherein the oxygen gas is at a partial pressure of 1% or less to prepare a
lithium cobalt metal oxide represented by the following Chemical Formula (1),
[Chemical Formula 1]
15 LixCo(1-y)MyO4-zAz
wherein,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni,
A is a halogen,
x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
20 The method of preparing a sacrificial positive electrode material according to the
present disclosure relates to a method of preparing a lithium cobalt metal oxide represented by
Chemical Formula 1 as a sacrificial positive electrode material, wherein the lithium cobalt
metal oxide represented by Chemical Formula 1 has an anti-fluorite structure LixCoO4-zAz
(provided that A is F or Cl, 5.4≤x≤6.8 and 0≤z≤0.0005), and in some cases, any one or more
10
of Ti, Al, Zn, Zr, Mn and Ni may doped at the cobalt (Co) position of LixCoO4-zAz.
Specifically, the lithium cobalt metal oxide may include at least one selected from the group
consisting of Li6CoO4, Li6Co(1-y)TiyO4, Li6Co(1-y)AlyO4, Li6Co(1-y)ZnyO4, Li6Co(1-y)ZryO4,
Li6Co(1-y)MnyO4, Li6Co(1-y)NiyO4 (provided that 0≤y≤0.4) and mixtures thereof.
5 The sacrificial positive electrode material including this lithium cobalt metal oxide
may be prepared by calcining a raw material mixture of lithium oxide (Li2O) and cobalt oxide
(CoO) mixed in a molar ratio of 2 to 4:1, for example 2.5 to 3.5:1, or 2.95 to 3.1:1, and when
one or more oxides of Ti, Al, Zn, Zr, Mn and Ni are added to the raw material mixture, a
lithium cobalt metal oxide doped with one or more of Ti, Al, Zn, Zr, Mn and Ni may be
10 prepared.
Here, the temperature at which the calcining is carried out is not particularly limited
and may be applied as long as the mixed metal oxides can be transformed into the lithium
cobalt metal oxide represented by Chemical Formula 1. Specifically, the calcining
temperature may be 500 to 800 °C, more specifically 500 to 700 °C; 600 to 800 °C; 600 to
15 750 °C; 650 to 800 °C; 630 to 770 °C; or 660 to 740 °C.
In addition, the calcination may be carried out under an atmosphere containing an
inert gas and a small amount of oxygen gas, for example, an atmosphere containing an argon
(Ar) gas or nitrogen (N2) gas and oxygen gas, wherein the oxygen gas is at a partial pressure
of 1% or less; 0.1 to 1%; 0.5 to 1%; 0.2 to 0.8%; 0.5 to 0.9%; or 0.2 to 0.6%.
20 In the present disclosure, by controlling the content of the oxygen gas contained in
the inert gas during calcination of a raw material mixture to the above-mentioned range, it is
possible to prevent an increase in the amount of gas generated during charging and
discharging of the battery because partial pressure of oxygen gas is too low, and it is possible
to prevent the initial charging capacity of the batteries from being lowered due to excess
11
oxygen gas.
In addition, the humidity during calcination may be a relative humidity (RH) of 20%
or less, specifically, 0.1% to 20%; 0.1% to 18%; 0.1% to 15%; 1% to 15%; 0.5% to 12%; 1%
to 12%; 4% to 12%; 7% to 12%; 0.5% to 10%; 0.5% to 7%; or 3% to 8%.
5 The present disclosure can prevent the fraction of the lithium cobalt metal oxide
represented by Chemical Formula 1 included in the prepared sacrificial positive electrode
material from being lowered due to the remarkably low humidity of less than 0.01% by
controlling the humidity in the calcining of the raw material mixture to such a range, and can
overcome the problem that the initial charging capacity of the battery is reduced due to excess
10 humidity.
As an example, in the method of preparing a sacrificial positive electrode material
according to the present disclosure, calcining may be carried out under a relative humidity
(RH) of 4 - 6%; and an aomosphere containing argon (Ar) gas or nitrogen (N2) gas
atmosphere and oxygen gas, wherein the oxygen gas is at a partial pressure 0.2 to 0.8%, at a
15 temperature of 670 to 730 °C for 2 to 20 hours.
Conventionally, a sacrificial positive electrode material including lithium cobalt
metal oxide represented by Chemical Formula 1 has an anti-fluorite structure by a calcining
process, and the sacrificial positive electrode material having the anti-fluorite structure has a
problem of generating a large amount of gas containing oxygen (O2), carbon monoxide (CO),
20 carbon dioxide (CO2), hydrogen (H2), etc. during charging/discharging.
However, the sacrificial positive electrode material prepared according to the present
disclosure may prevent the highly reactive lithium oxide (Li2O) from remaining by calcining a
raw material mixture containing lithium oxide (Li2O) and cobalt oxide (CoO) under a
condition of mixing a small amount of oxygen gas with an inert gas and a relative humidity
12
(RH) satisfying the above-mentioned range, so it is possible to increase the fraction of lithium
cobalt metal oxide represented by Chemical Formula 1 in the synthesized sacrificial positive
electrode material, and further reduce the amount of gas generated at the time of using the
battery while maintaining or increasing the charge/discharge capacity of the battery.
5 As an example, in the sacrificial positive electrode material prepared according to the
present disclosure, the fraction of lithium cobalt metal oxide represented by Chemical
Formula 1 increases, so that at least one of Equations 1 and 2 below may be satisfied when Xray diffraction measurement is performed:
[Equation 1] A/B ≤ 0.1
10 [Equation 2] C/D ≤ 0.35
wherein,
A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
B represents the intensity of the strongest peak among the peaks appearing in the
15 range of 2θ=19.2±0.1°,
C represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=47.9±0.1°.
20 In Equations 1 and 2, the peaks (B and D) appearing in the ranges of 2θ=19.2±0.1°
and 47.9±0.1° are realized by the crystal of lithium cobalt metal oxide represented by
Chemical Formula 1, and the peaks (A and C) appearing in the ranges of 2θ=18.9±0.1° and 2θ
= 38.5 ± 0.1 ° are realized by impurities. The lower the intensity ratio of these peaks, i.e.,
"A/B" and "C/D", means that the fraction of lithium cobalt metal oxide represented by
13
Chemical Formula 1 is high. In the sacrificial positive electrode material prepared according
to the present disclosure, the fraction of lithium cobalt metal oxide represented by Chemical
Formula 1 is improved to 98% or more, and thus A/B may be satisfied by 0.15 or less,
specifically 0.12 or less, 0.1 or less, or 0.05 or less in X-ray diffraction measurement; and C/D
5 may be satisfied by 0.3 or less, 0.25 or less, or 0.1 or less. In some cases, A/B and C/D may
be satisfied by 0 when the lithium cobalt metal oxide represented by Chemical Formula 1
accounts for 100% of the sacrificial positive electrode.
According to the method of preparing a sacrificial positive electrode material
according to the present disclosure, the raw material mixture is calcining under an inert gas
10 atmosphere including an inert gas and a small amount of oxygen (O2) gas and a relative
humidity (RH) that satisfies a specific range, whereby the generation of gas, particularly
oxygen (O2) gas, generated in the electrode assembly at the time of charging the battery can
be reduced, and thus the effect of improving the stability and life of the battery containing the
same is excellent.
15
Positive Electrode
In one embodiment, the present disclosure provides a positive electrode including:
a positive electrode current collector; and
a positive electrode mixture layer containing a positive electrode active material, a
20 conductive material, an organic binder polymer, and a sacrificial positive electrode material
on the positive electrode current collector;
the sacrificial positive electrode material is prepared according to the preparation
method, includes a lithium cobalt metal oxide represented by Chemical Formula 1 below, and
satisfies at least one of Equations 1 and 2, as measured in X-ray diffraction analysis:
14
[Chemical Formula 1]
LixCo(1-y)MyO4-zAz
wherein,
M is at least one selected from the group consisting of Ti, Mg, Al, Zn, Zr, Mn and Ni,
5 A is a halogen,
x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001,
[Equation 1] A/B ≤ 0.1
[Equation 2] C/D ≤ 0.35
wherein,
10 A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
B represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=19.2±0.1°,
C represents the intensity of the strongest peak among the peaks appearing in the
15 range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=47.9±0.1°.
The positive electrode according to the present disclosure has a structure in which a
positive electrode mixture layer is formed on a positive electrode current collector, wherein
20 the positive electrode mixture layer includes a sacrificial positive electrode material prepared
according to the preparation method of the present disclosure and containing lithium cobalt
metal oxide represented by Chemical Formula 1 together with a positive electrode active
material; conductive material; and the organic binder polymer, and thus the effect of reducing
gas, particularly oxygen (O2) gas, generated during charging/discharging of the battery is
15
excellent.
Here, the positive electrode active material may be a lithium composite transition
metal oxide containing two or more elements selected from the group consisting of nickel
(Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium
5 (Mg), chromium (Cr) and zirconium (Zr). For example, the positive electrode active
material may include a layered compound such as lithium cobalt oxide (LiCoO2) and lithium
nickel oxide (LiNiO2), or a layered compound substituted with one or more transition metals;
lithium manganese oxides of the formula Li1+xMn2-xO4 (wherein x is 0 to 0.33), LiMnO3,
LiMn2O3, LiMnO2, etc.; lithium copper oxides such as Li2CuO2; vanadium oxides such as
10 LiV3O8, LiFe3O4, V2O5, Cu2V2O7; Ni site-type lithium nickel oxide represented by the
formula LiNi1-xMxO2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3);
lithium manganese composite oxide represented by the formula LiMn2-xMxO2 (where M = Co,
Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn);
lithium manganese composite oxide having a spinel structure represented by LiNixMn2-xO4;
15 LiMn2O4 in which a part of Li in the formula is substituted with an alkaline earth metal ion;
disulfide compounds; Fe2(MoO4)3 etc.
In addition, the positive electrode mixture layer may include 0.001 to 5.0 parts by
weight of the sacrificial positive electrode material prepared by the preparation method
according to the present disclosure based on 100 parts by weight of the positive electrode
20 active material. More specifically, the sacrificial positive electrode material may be
included in an amount of 0.001 to 4.0 parts by weight; 0.001 to 3.0 parts by weight; 0.001 to
2.0 parts by weight; 0.001 to 1.0 parts by weight; 0.01 to 2.0 parts by weight; 0.05 to 2.0 parts
by weight; 0.1 to 2.0 parts by weight; or 0.1 to 1.5 parts by weight, based on 100 parts by
weight of the positive electrode active material.
16
In addition, the conductive material may be included in an amount of 1 to 20 parts by
weight, specifically, 1 to 10 parts by weight; 1 to 5 parts by weight; 3 to 8 parts by weight; or
2 to 5 parts by weight, based on 100 parts by weight of the positive electrode active material.
In addition, the conductive material is not particularly limited as long as it has
5 conductivity without causing a chemical change in the battery. For example, graphite such
as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black,
channel black, furnace black, lamp black, and themal black; conductive fibers such as carbon
fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder;
conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such
10 as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.
In addition, the organic binder polymer is a component that assists in bonding of the
active material and the conductive material and bonding to the current collector, and it may be
included in an amount of 1 to 20 parts by weight, specifically, 1 to 10 parts by weight; 1 to 5
parts by weight; 3 to 8 parts by weight; or 2 to 5 parts by weight, based on 100 parts by
15 weight of the positive electrode active material.
In addition, examples of the organic binder polymer include polyvinylidene fluoride
(PVdF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose,
regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene,
an ethylene-propylene-diether polymer (EPDM), a sulfonated EPDM, styrene-butyrene
20 rubber, fluororubber, various copolymers, etc.
In addition, the positive electrode may further include a filler for suppressing the
expansion of the positive electrode in addition to the positive electrode active material, the
conductive material, and the organic binder polymer in the positive electrode mixture layer,
and the filler is not particularly limited when it is fibrous material that does not cause a
17
chemical change in the battery. Specifically, as the filler, an olefin-based polymer such as
polyethylene or polypropylene; a fibrous material such as glass fiber or carbon fiber may be
used.
In addition, the positive electrode current collector is not particularly limited as long
5 as it has high conductivity without causing a chemical change in the battery, and for example,
stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and in the case
of aluminum or stainless steel, a surface treated with carbon, nickel, titanium, silver, etc. may
be used. In addition, fine irregularities may be formed on the surface of the positive
electrode current collector to increase the adhesion of the positive electrode active material,
10 and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven
body are possible. In addition, the average thickness of the positive electrode current
collector may be appropriately applied in a range of 3 to 500 µm in consideration of the
conductivity and total thickness of the positive electrode to be manufactured.
15 Electrode Assembly
Also, in one embodiment, the present disclosure provides an electrode assembly
including the above-described positive electrode.
The electrode assembly according to the present disclosure may have a structure
including the above-described positive electrode, a negative electrode, and a separation
20 membrane interposed between the positive electrode and the negative electrode, and in some
cases, the separation membrane may be excluded.
Here, the negative electrode is manufactured by coating, drying and pressing a
negative electrode active material on the negative electrode current collector, and if necessary,
the conductive material, organic binder polymer, filler, etc. as described above may be
18
optionally further included.
In addition, as the negative electrode active material, for example, graphite having a
completely layered crystal structure such as natural graphite, and soft carbon having a low
crystallinity layered crystal structure (graphene structure; a structure in which hexagonal
5 honeycomb planes of carbon are arranged in layers) and graphite materials such as hard
carbon, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon
black, carbon nanotubes, fullerenes, activated carbon, etc. in which carbon and these
structures are mixed with amorphous parts; LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), SnxMe1-
xMe'yOz (Me: Mn, Fe, Pb, Ge; Me', Al, B, P, Si, Group 1 of the periodic table, metal complex
10 oxides such as Group 2 and Group 3 elements and halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8);
lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO,
SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5;
conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxide;
lithium titanium oxide and the like, may be used.
15 In addition, the negative electrode current collector is not particularly limited as long
as it has high conductivity without causing a chemical change in the battery, and for example,
copper, stainless steel, nickel, titanium, calcined carbon, etc. may be used, and in the case of
copper or stainless steel, a surface treated with carbon, nickel, titanium, silver, etc. may be
used. In addition, like the positive electrode current collector, fine irregularities may be
20 formed on the surface of the negative electrode current collector to strengthen the adhesion
with the negative electrode active material, and various forms such as films, sheets, foils, nets,
porous materials, foams, non-woven materials, etc. are possible. In addition, the average
thickness of the negative electrode current collector may be appropriately applied in a range
of 3 to 500 µm in consideration of the conductivity and total thickness of the negative
19
electrode to be manufactured.
In addition, the separation membrane is interposed between the negative electrode
and the positive electrode, and an insulating thin film having high ion permeability and
mechanical strength is used. The separation membrane is not particularly limited as long as
5 it is conventionally used in the art, but specifically, a sheet or nonwoven fabric made of
chemical resistant and hydrophobic polypropylene, glass fiber, polyethylene or the like may
be used, and in some cases, a composite separation membrane in which inorganic
particles/organic particles are coated with an organic binder polymer on a porous polymer
substrate such as a sheet or nonwoven fabric may be used. When a solid electrolyte such as
10 a polymer is used as the electrolyte, the solid electrolyte may also serve as a separation
membrane. In addition, the separation membrane may have an average pore diameter of
0.01 to 10 µm, and an average thickness of 5 to 300 µm.
Meanwhile, the electrode assembly may be wound in the form of a jelly roll and
stored in a cylindrical battery, a prismatic battery, or a pouch-type battery, or may be stored in
15 a pouch-type battery in a folding or stack-and-folding form, but is not limited thereto.
Lithium Secondary Battery
Furthermore, in one embodiment, the present disclosure provides a lithium secondary
battery including the above-mentioned electrode assembly.
20 The lithium secondary battery according to the present disclosure may have a
structure in which the electrode assembly is impregnated with a lithium salt-containing
electrolyte.
In this case, the lithium salt-containing electrolyte may consist of an electrolyte and a
lithium salt, and as the electrolyte, a non-aqueous organic solvent, an organic solid electrolyte,
20
an inorganic solid electrolyte, and the like may be used.
As the non-aqueous organic solvent, for example, an aprotic organic solvent such as
N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate,
dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane,
5 tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide,
dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate,
phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl
sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran
derivatives, ether, propionic methyl or propionic ethyl, may be used.
10 As the organic solid electrolyte, for example, polyethylene derivatives, polyethylene
oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly
agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymeric
material including an ionic dissociating group and the like may be used.
As the inorganic solid electrolyte, nitrides, halides, sulfates, etc. of Li, such as Li3N,
15 LiI, Li5Ni2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH,
Li3PO4-Li2S-SiS2, may be used.
The lithium salt is a material easily soluble in the non-aqueous electrolyte, and for
example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6,
LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, chloroborane lithium, lithium lower aliphatic
20 carboxylates, lithium 4-phenylboronate, imide and the like may be used.
In addition, for the purpose of improving charging/discharging characteristics, flame
retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether,
ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone
imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol
21
dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride and the like
may be added to the electrolyte. In some cases, in order to impart incombustibility, a
halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride may be
further included, and carbon dioxide gas may be further included to improve high temperature
5 storage characteristics, and fluoro-ethylene carbonate (FEC), propene sultone (PRS), etc. may
be further included.
Further, in one embodiment, the present disclosure provides a battery module
including the above-described secondary battery as a unit cell, and provides a battery pack
including the battery module.
10 The battery pack may be used as a power source for a medium or large device that
requires high temperature stability, long cycle characteristics, and high rate characteristics,
and specific examples of the medium or large device include a power tool that is powered by
an omnipresent motor; electric vehicles including electric vehicles (EVs), hybrid electric
vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric two-wheeled
15 vehicles including electric bicycles (E-bikes) and electric scooters (E-scooter); electric golf
carts; and a system for storing power, and more specifically, a hybrid electric vehicle (HEV),
but is not limited thereto.
Hereinafter, the present disclosure will be described in detail by way of Examples.
20 However, the following Examples and Experimental Examples are merely illustrative
of the present disclosure, and the content of the present disclosure is not limited to the
following Examples and Experimental Examples.
Examples 1-6 and Comparative Examples 1-2. Preparation of Sacrificial Positive
22
Electrode Material
Lithium oxide (Li2O, unimodal distribution, D50 = 10 to 30 µm) and cobalt oxide
(CoO) were input into a reactor to have a molar ratio of 3.0 to 3.03:1, and uniformly drymixed for about 30 minutes using a mixer. Then, the prepared raw material mixture was put
5 into an electric furnace and calcined for 10 hours at about 700 °C under argon gas (Ar)
conditions to obtain lithium cobalt oxide (Li6CoO4). At this time, the relative humidity (RH)
in the electric furnace during calcination and the partial pressure of oxygen gas (O2) contained
in argon gas are shown in Table 1 below.
[Table 1]
RH [%] O2 partial pressure
[%]
Example 1 1 0.1 to 1.0
Example 2 5 0.1 to 1.0
Example 3 10 0.1 to 1.0
Example 4 15 0.1 to 1.0
Example 5 0 0.1 to 1.0
Example 6 10 ≤0.08
Comparative
Example 1
25 0.1 to 1.0
Comparative
Example 2
10 1.01 to 1.5
10
Experimental Example 1.
X-ray diffraction was measured for the sacrificial positive electrode materials
prepared in Examples 1 to 6 and Comparative Examples 1 to 2 in order to confirm the change
according to the partial pressure of oxygen gas in the inert gas in calcination of the raw
15 material mixture, and the fractions of components included in each sacrificial positive
electrode material were calculated from the measured X-ray diffraction. At this time, the Xray diffraction was carried out using Rigaku's X-ray diffraction analyzer, and 1.5406 Å
wavelength (Cu Ka radiation, 40 kV, 100 mA) was scanned, and an X-ray diffraction pattern
23
was obtained in the range of 15° to 64° at 2θ and a scanning speed of 5°/sec. Fractions of
components contained in the prepared sacrificial positive electrode material were calculated
from the obtained X-ray diffraction pattern, and the results are shown in Table 2 and FIGS. 1
and 2.
5 [Table 2]
Calcining Conditions Component fraction [mol%]
RH [%] O2 partial
pressure
[%]
Li6CoO4 CoO LiOH Li2CO3 Li2O LiCoO2
Example 1 1 0.1 to 1.0 97.8 2.2 - - - -
Example 2 5 0.1 to 1.0 98.7 1.3 - - - -
Example 3 10 0.1 to 1.0 98.7 1.3 - - - -
Example 4 15 0.1 to 1.0 90.5 1.6 1.6 6.4 - -
Example 5 0 0.1 to 1.0 98.8 1.8 - - - -
Example 6 10 ≤0.08% 100 - - - - -
Comparative
Example 1
25 0.1 to 1.0 85.0 2.4 2.3 8.1 0.7 1.5
Comparative
Example 2
10 1.05 - 1.5 95.4 1.3 - - - 3.3
As shown in Table 2, in the sacrificial positive electrode material prepared according
to the present disclosure, the relative humidity and partial pressure of oxygen gas in the inert
gas were controlled within certain ranges in calcining of the raw material mixture, thus it can
10 be seen that the fraction of lithium cobalt metal oxide represented by Chemical Formula 1 was
increased to 90% or more, specifically 97% or more.
In addition, referring to FIGS. 1 and 2, when a raw material mixture of lithium oxide
(Li2O) and cobalt oxide (CoO) is calcinated at about 700 °C under an inert gas atmosphere,
lithium cobalt metal oxide (Li6CoO4) represented by Chemical Formula 1 is produced as a
15 product. In addition, when the relative humidity (RH) during calcination of the raw material
mixture is 15% or less and the partial pressure of oxygen gas is 0.1 to 1.0%, the fraction of
lithium cobalt metal oxide represented by Chemical Formula 1 increased, a peak (A≒0)
24
showing an impurity in the range of θ=18.9±0.1° was not confirmed, and a peak (C≒0)
appearing in the region of θ=38.5±0.3° was confirmed to have insignificant intensity. On the
other hand, when the partial pressure of oxygen gas during calcination is 0.2% or more, since
the fraction of impurities is high, the intensity of these peaks (A and C) is high, and
5 accordingly, it was confirmed that the ratios (A/B and C/D) of the intensities (B and D) of the
peaks representing the lithium cobalt metal oxide represented by Chemical Formula 1 were
0.174 or more and 0.37 or more, respectively. This means that the increased moisture and
oxygen gas in the inert gas inhibit the synthesis of the lithium cobalt metal oxide represented
by Chemical Formula 1, thereby reducing the yield.
10 From these results, it can be seen that, during calcination, the relative humidity and
the partial pressure of oxygen gas in the inert gas affect the fraction of metal oxide included in
the sacrificial positive electrode material.
Experimental Example 2.
15 In order to evaluate the performance of the sacrificial cathode material prepared in the
present disclosure, the following experiment was performed.
A) Measurement of gas emission
N-methylpyrrolidone solvent was input into a homo mixer, and each of the sacrificial
20 positive electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 2, an
acetylene black conductive material, a modified silanol binder, and a dispersant were added in
a weight ratio of 95:3:1.7:0.3 and then mixed at 3,000 rpm for 60 minutes to prepare a predispersion.
The prepared pre-dispersion was mixed with the positive electrode active material so
25
that the content of the sacrificial positive electrode material was 2 parts by weight based on
100 parts by weight of the positive electrode active material (LiNi0.6Co0.2Mn0.2O2), and the
positive electrode active material mixed in an N-methylpyrrolidone solvent, PVdF as a binder
and carbon black as a conductive material were put into a homo mixer so as to have a weight
5 ratio of 96:1:3, and then dispersed at 3,000 rpm for 80 minutes to prepare a slurry for a
positive electrode. The prepared positive electrode slurry was applied to one surface of an
aluminum current collector, dried at 100° C, and rolled to manufacture a positive electrode.
A 2032 type cell was manufactured using the positive electrode and a lithium metal
counter electrode. A separator (thickness: about 16 µm) made of a porous polyethylene (PE)
10 film was interposed between the positive electrode and the lithium metal counter electrode,
and an electrolyte was injected to manufacture a half-cell type cell.
At this time, as the electrolyte, a mixed solution of ethylene carbonate (EC): ethyl
methyl carbonate (EMC) = 3:7 (volume ratio), lithium hexafluoro phosphate (LiPF6, 0.7 M),
lithium bis(fluorosulfonyl) imide (LiFSI, 0.5M), lithium tetrafluoroborate (LiBF4, 0.2 wt%),
15 vinyl carbonate (VC, 2 wt%), 1,3-propane sultone (PS, 0.5 wt%), and ethylene sulfate (Esa, 1
wt%), was used.
The manufactured cell was charged/discharged once under the condition of 4.5 C/0.3
C to carry out formation. And then the manufactured cell was analyzed the amount and
component of gas generated respectively during each charge and discharge which were
20 repeatedly performed 50 times at 45°C under 0.3C condition and during storage at 60°C for 4
weeks. The results are shown in Table 3 below and FIGS. 3 and 4.
[Table 3]
Units: mL/g Example Comparative
Example
1 2 3 4 5 6 1 2
initial 78.1 80.7 99.6 106 100.3 111 119.5 82
26
charging/discharging
(formation)
As shown in Table 3 and FIGS. 3 and 4, in the case of the sacrificial positive
electrode material prepared according to the present disclosure, the amount of gas generated
during charging/discharging was found to be reduced. It can be confirmed that such a
5 tendency occurs when the relative humidity (RH) in the electric furnace and the oxygen gas
(O2) in the inert gas in calcination of the raw material mixture satisfy specific ranges as in the
present disclosure.
B) Evaluation of Initial Charging/Discharging
10 A half-cell type cell was manufactured in the same manner as in the measurement of
gas emission, except that a mixed solution of ethyl methyl carbonate (EMC): dimethyl
carbonate (DMC): diethyl carbonate (DEC) = 1:2:1 (volume ratio), lithium
hexafluorophosphate (LiPF6, 1.0M) and vinyl carbonate (VC, 2 wt%) was used as the
electrolyte.
15 The initial charging capacity and the irreversible capacity were measured by
performing charging/discharging (formation) for each manufactured cell. At this time, the
charging/discharging (formation) was carried out under the conditions of 70 mAh/3 mAh, and
the results are shown in Table 4 and FIGS. 5 and 6 below.
[Table 4]
RH [%] O2 partial pressure [%] Initial charging capacity
[mAh]
Example 1 1 0.1 to 1.0 810.8
Example 2 5 0.1 to 1.0 802.7
Example 3 10 0.1 to 1.0 792.4
Example 4 15 0.1 to 1.0 749.5
Example 5 0 0.1 to 1.0 788.1
Example 6 10 to 0.08 817
27
Comparative
Example 1
25 0.1 to 1.0 723.5
Comparative
Example 2
10 1.01 to 1.5 682
As shown in Table 4 and FIGS. 5 and 6, it can be seen that the sacrificial positive
electrode material prepared according to the present disclosure has an effect of improving the
performance of the battery. Specifically, the sacrificial positive electrode material of the
5 examples was found to have a higher initial charge capacity as the relative humidity (RH) in
the electric furnace was high and the oxygen gas (O2) in the inert gas had a lower partial
pressure when the raw material mixture was calcined. This means that when the relative
humidity (RH) in the electric furnace is high when the raw material mixture is calcinated, the
initial charging capacity is increased, but the amount of gas generated during
10 charging/discharging is increased.
From these results, the sacrificial positive electrode material prepared according to
the present disclosure has an excellent effect of improving the performance of the battery by
adjusting the relative humidity (RH) and the partial pressure of the oxygen (O2) gas in the
inert gas in calcination of the raw material mixture to specific ranges, and is capable of
15 reducing the generation of gas, in particular, oxygen (O2) gas, generated in the electrode
assembly during battery charging, and thus an effect for improving the stability and life of the
battery containing the same is excellent.
While the foregoing has been described with reference to preferred embodiments of
20 the present disclosure, it should be understood by those skilled in the art or by those of
ordinary skill in the art that various changes and modifications can be made therein without
departing from the spirit and scope of the disclosure as set forth in the claims that follow.
28
Accordingly, the technical scope of the present disclosure should not be limited to the
content described in the detailed description of the specification, but should be defined by the
claims.

【Claims】
【Claim 1】
A method of preparing a sacrificial positive electrode material, comprising:
calcining a raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO)
5 under atmosphere containing an inert gas and oxygen gas, wherein the oxygen gas is at a
partial pressure of 1% or less to prepare a lithium cobalt metal oxide represented by the
following Chemical Formula (1),
wherein the atmosphere has a relative humidity (RH) of 20% or less:
[Chemical Formula 1]
10 LixCo(1-y)MyO4-zAz
wherein,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni,
A is an oxygen-substituted halogen,
x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
15
【Claim 2】
The method of claim 1, wherein RH is in a range of 0.1% to 15%.
【Claim 3】
20 The method of claim 1, wherein the partial pressure of oxygen gas is 0.1 to 1%.
【Claim 4】
30
The method of claim 1, wherein the calcining is performed at a temperature of 500 to
800 °C.
【Claim 5】
5 The method according to claim 1, wherein the lithium oxide (Li2O) and the cobalt
oxide (CoO) are in a molar ratio of 2 to 4 : 1.
【Claim 6】
The method of claim 1, wherein the average particle size (D50) of lithium oxide
10 (Li2O) is in a range of 10 µm to 30 µm.
【Claim 7】
The method of claim 1, wherein the sacrificial positive electrode material satisfies
one or more of Equations 1 and 2 below, as measured by X-ray diffraction:
15 [Equation 1]
A/B ≤ 0.1
[Equation 2]
C/D ≤ 0.35
wherein,
20 A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
B represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=19.2±0.1°,
31
C represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=47.9±0.1°.
5
【Claim 8】
A positive electrode comprising:
a positive electrode current collector; and
a positive electrode mixture layer containing a positive electrode active material, a
10 conductive material, an organic binder polymer, and a sacrificial positive electrode material
on the positive electrode current collector;
the sacrificial positive electrode material comprises lithium cobalt metal oxide
represented by Chemical Formula 1 below, and satisfies one or more of Equations 1 and 2, as
measured by X-ray diffraction:
15 [Chemical Formula 1]
LixCo(1-y)MyO4-zAz
wherein,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni,
A is a halogen,
20 x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001,
[Equation 1]
A/B ≤ 0.1
[Equation 2]
C/D ≤ 0.35
32
wherein,
A represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=18.9±0.1°,
B represents the intensity of the strongest peak among the peaks appearing in the
5 range of 2θ=19.2±0.1°,
C represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=38.5±0.1°, and
D represents the intensity of the strongest peak among the peaks appearing in the
range of 2θ=47.9±0.1°.
10
【Claim 9】
The positive electrode of claim 8, wherein the positive electrode active material is a
lithium composite transition metal oxide containing two or more elements selected from the
group consisting of nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn),
15 titanium (Ti), magnesium (Mg), chromium (Cr) and zirconium (Zr).
【Claim 10】
The positive electrode of claim 8, wherein the content of the sacrificial positive
electrode material is 0.001 to 5.0 parts by weight based on 100 parts by weight of the positive
20 electrode active material.
【Claim 11】
An electrode assembly comprising the positive electrode of claim 8.
33
【Claim 12】
A lithium secondary battery comprising the electrode assembly of claim 11.