【Technical Field】 5
The present invention relates to a method of preparing a sacrificial positive electrode material with a reduced gas generation amount during charging and discharging by controlling the electrical conductivity of a sacrificial positive electrode material within a specific range by adjusting the particle size of a lithium precursor, and a sacrificial positive electrode material prepared thereby. 10
This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0024251, filed on February 23, 2021, and Korean Patent Application No. 10-2022-0016374, filed on February 08, 2022, and the entire contents of the Korean patent applications are incorporated herein by reference.
【Background Art】 15
As demand for high-capacity electrode materials has increased in recent years, irreversible additives are required to have a higher irreversible capacity. However, it is true that there is a limitation in developing positive electrode additives having a high irreversible capacity.
Meanwhile, a conventional irreversible additive such as Li6CoO4 is generally prepared 20
3
by allowing cobalt oxide and the like to react with an excessive amount of lithium oxide. In this case, by-products such as unreacted lithium oxide (Li2O) and the like, which did not participate in the reaction, remain in the finally prepared irreversible additive, and this may cause oxidation in a charging/discharging process to generate oxygen gas inside a battery. The generated oxygen gas may cause volume expansion and the like and thus acts as one of the main 5 factors leading to degradation of battery performance.
Therefore, there is a continuous demand for the development of a positive electrode additive having a higher irreversible capacity while generating a small amount of oxygen in a charging/discharging process of a battery due to a small residual amount of by-products such as lithium oxide and the like. 10
[Related-Art Documents]
[Patent Documents]
Korean Laid-Open Patent Publication No. 10-2019-0012839
【Disclosure】
【Technical Problem】 15
An object of the present invention is to provide a positive electrode additive having a higher irreversible capacity while generating a small amount of oxygen in a charging/discharging process of a battery, and a positive electrode and lithium secondary battery including the same.
【Technical Solution】 20
One aspect of the present invention provides a method of preparing a sacrificial positive
4
electrode material, which includes a step of calcinating a raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO) to prepare a lithium cobalt metal oxide represented by the following Chemical Formula 1, wherein the lithium oxide (Li2O) has an average particle size (D50) of 50 μm or less, and the resulting sacrificial positive electrode material has an electrical conductivity of 1 × 10-4 S/cm or more: 5
[Chemical Formula 1]
LixCo(1-y)MyO4-zAz
in Chemical Formula 1,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn, and Ni,
A is an oxygen-substituted halogen, and 10
x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
Here, the electrical conductivity may range from 1 × 10-3 S/cm to 9 × 10-3 S/cm.
In addition, the calcinating may be performed at 500°C to 800°C.
In addition, the raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO) may be obtained by mixing lithium oxide (Li2O) and cobalt oxide (CoO) at a molar ratio of 2 15 to 4:1.
In addition, the lithium oxide (Li2O) may have an average particle size (D50) of 15 μm to 35 μm and a minimum particle size (Dmin) of 2 μm or more.
In addition, the lithium oxide (Li2O) may have a unimodal particle size distribution, 80 to 90% of all particles may be in a particle size range of 10 μm to 45 μm, and 65 to 75% of all 20 particles may be in a particle size range of 15 μm to 35 μm.
In addition, the sacrificial positive electrode material prepared by the method may
5
satisfy the following Equation 1:
[Equation 1]
Vgas = -1.07 × DLi2O + A
in Equation 1,
Vgas represents an amount (units: mL/g) of gas generated in a positive electrode 5 including a sacrificial positive electrode material,
DLi2O represents an average particle size (D50, units: μm) of lithium oxide (Li2O), and
A is a constant and satisfies 128≤A≤132.
Another aspect of the present invention provides a positive electrode which includes: a positive electrode current collector; and a positive electrode mixture layer including a positive 10 electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material on the positive electrode current collector, wherein the sacrificial positive electrode material includes a lithium cobalt metal oxide represented by the following Chemical Formula 1 and has an electrical conductivity of 1 × 10-4 S/cm or more:
[Chemical Formula 1] 15
LixCo(1-y)MyO4-zAz
in Chemical Formula 1,
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 satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001. 20
Here, the positive electrode active material may be a lithium composite transition metal oxide including two or more elements selected from the group consisting of nickel (Ni), cobalt
6
(Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr), and zirconium (Zr).
In addition, the sacrificial positive electrode material may be included in an amount of 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the positive electrode active material. 5
Still another aspect of the present invention provides an electrode assembly including the positive electrode.
Yet another aspect of the present invention provides a lithium secondary battery including the electrode assembly.
【Advantageous Effects】 10
A method of preparing a sacrificial positive electrode material according to the present invention can reduce the generation of gas, particularly, oxygen (O2) gas, in a positive electrode during charging of a battery by adjusting the electrical conductivity of a sacrificial positive electrode material within a specific range using a lithium precursor that satisfies a specific size, and thus the stability and lifespan of a battery including the same can be effectively enhanced. 15
【Brief Description of the Drawings】
FIG. 1 is a graph showing a gas generation amount in a positive electrode according to the number of charging and discharging cycles at 45 °C for each average particle size of lithium oxide (Li2O) used in preparation of a sacrificial positive electrode material.
FIG. 2 is a graph showing a gas generation amount in a positive electrode according to 20 a storage time (units: weeks) at 60 °C for each average particle size of lithium oxide (Li2O)
7
used in preparation of a sacrificial positive electrode material.
FIG. 3 is a graph showing a gas generation amount in a positive electrode according to an average particle size of lithium oxide (Li2O) used in preparation of a sacrificial positive electrode material.

【Claim 1】
A method of preparing a sacrificial positive electrode material, comprising:
calcinating a raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO) to prepare a lithium cobalt metal oxide represented by the following Chemical Formula 1, 5
wherein the lithium oxide (Li2O) has an average particle size (D50) of 50 μm or less, and
the resulting sacrificial positive electrode material has an electrical conductivity of 1 × 10-4 S/cm or more:
[Chemical Formula 1] 10
LixCo(1-y)MyO4-zAz
in Chemical Formula 1,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn, and Ni,
A is an oxygen-substituted halogen, and
x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001. 15
【Claim 2】
The method of claim 1, wherein the electrical conductivity ranges from 1 × 10-3 S/cm to 9 × 10-3 S/cm.
20
【Claim 3】
30
The method of claim 1, wherein the calcinating is performed at 500 to 800 °C.
【Claim 4】
The method of claim 1, wherein the raw material mixture of lithium oxide (Li2O) and cobalt oxide (CoO) is obtained by mixing lithium oxide (Li2O) and cobalt oxide (CoO) at a 5 molar ratio of 2 to 4:1.
【Claim 5】
The method of claim 1, wherein the lithium oxide (Li2O) has an average particle size (D50) of 15 μm to 35 μm. 10
【Claim 6】
The method of claim 1, wherein the lithium oxide (Li2O) has a minimum particle size (Dmin) of 2 μm or more.
15
【Claim 7】
The method of claim 1, wherein the lithium oxide (Li2O) has a unimodal particle size distribution,
80 to 90% of all particles are in a particle size range of 10 μm to 45 μm, and
65 to 75% of all particles are in a particle size range of 15 μm to 35 μm. 20
31
【Claim 8】
The method of claim 1, wherein the sacrificial positive electrode material satisfies the following Equation 1:
[Equation 1] 5
Vgas = -1.07 × DLi2O + A
in Equation 1,
Vgas represents an amount (units: mL/g) of gas generated in an electrode assembly including a sacrificial positive electrode material,
DLi2O represents an average particle size (D50, units: μm) of lithium oxide (Li2O), and 10
A is a constant and satisfies 128≤A≤132.
【Claim 9】
A positive electrode comprising:
a positive electrode current collector; and 15
a positive electrode mixture layer including a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material on the positive electrode current collector,
wherein the sacrificial positive electrode material includes a lithium cobalt metal oxide represented by the following Chemical Formula 1 and has an electrical conductivity of 1 × 10-20 4 S/cm or more:
32
[Chemical Formula 1]
LixCo(1-y)MyO4-zAz
in Chemical Formula 1,
M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn, and Ni,
A is an oxygen-substituted halogen, 5
x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
【Claim 10】
The positive electrode of claim 9, wherein the positive electrode active material is a lithium composite transition metal oxide including two or more elements selected from the 10 group consisting of nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr), and zirconium (Zr).
【Claim 11】
The positive electrode of claim 9, wherein the sacrificial positive electrode material is 15 included in an amount of 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the positive electrode active material.
【Claim 12】
An electrode assembly comprising the positive electrode of claim 9. 20
33
【Claim 13】
A lithium secondary battery comprising the electrode assembly of claim 12.