KR20220120468A - Sacrificial cathod meterials reduced gas generation, and preparation method thereof - Google Patents

Abstract

The present invention relates to a sacrificial positive electrode material with reduced gas generation and a method for manufacturing the same. The method for manufacturing a sacrificial positive electrode material can reduce the generation of gas, particularly oxygen (O_2) gas generated from an electrode assembly during battery charging by adjusting the electrical conductivity of the sacrificial positive electrode material within a specific range using lithium oxide that satisfies a specific size, thereby improving the stability and lifespan of a battery including the same.

Description

Sacrificial cathode material with reduced gas generation and manufacturing method thereof

The present invention relates to a method of manufacturing a sacrificial cathode material having reduced gas generation during charging and discharging by controlling the particle size of a lithium precursor to control the electrical conductivity of the sacrificial cathode material to a specific range, and to a sacrificial cathode material manufactured according to the method.

In recent years, as high-capacity electrode materials are more demanded, the 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, the conventional irreversible additive such as Li ₆ CoO ₄ is generally prepared by reacting cobalt oxide or the like with an excess of lithium oxide. At this time, by-products such as unreacted lithium oxide (Li ₂ O), which do not participate in the reaction, remain in the final manufactured irreversible additive, which may cause oxidation in the charging/discharging process to generate oxygen gas inside the battery. Oxygen gas thus generated may act as one of the main factors causing a decrease in battery performance by inducing volume expansion and the like.

Accordingly, there is a continuous demand for the development of a positive electrode additive having a higher irreversible capacity while a small amount of oxygen generated during the charging/discharging process of a battery is small due to a small residual amount of by-products such as lithium oxide.

Republic of Korea Patent Publication No. 10-2019-0012839

Accordingly, it is an object of the present invention to provide a positive electrode additive having a higher irreversible capacity while reducing the amount of oxygen generated during charging and discharging of a battery, and a positive electrode and a lithium secondary battery including the same.

In order to solve the above-mentioned problem,

The present invention in one embodiment,

Comprising the step of calcining a raw material mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) to prepare a lithium cobalt metal oxide represented by the following formula (1),

The average particle size (D50) of the lithium oxide (Li ₂ O) is 50㎛ or less,

Provided is a method for manufacturing a sacrificial cathode material having an electrical conductivity of 1 × 10 ⁻⁴ S/cm or more:

[Formula 1]

Li _x Co _(1-y) M _y O _4-z A _z

In 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 are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

Here, the electrical conductivity may be 1 × 10 ^-3 S/cm to 9 × 10 ^-3 S/cm.

In addition, the firing temperature may be 500 to 800 ℃.

In addition, the raw material mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) may be a mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) in a molar ratio of 2 to 4:1.

In addition, the lithium oxide (Li ₂ O) 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 (Li ₂ O) has a unimodal particle size distribution; 80 to 90% of the total particles may be present in a particle size range of 10 μm to 45 μm, and 65 to 75% of the total particles may be present in a particle size range of 15 μm to 35 μm.

In addition, the sacrificial cathode material manufactured by the above manufacturing method may satisfy Equation 1 below:

[Equation 1]

V _gas = -1.07 × D _Li2O + A

In Equation 1 above,

V _gas represents the amount of gas (unit: mL/g) generated by the positive electrode including the sacrificial positive electrode material,

D _Li2O represents the average particle size (D50, unit: μm) of lithium oxide (Li ₂ O), and

A is a constant, and 128≤A≤132.

In addition, the present invention in one embodiment,

positive electrode current collector; and

a positive electrode mixture layer containing a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material on the positive electrode current collector;

The sacrificial cathode material includes a lithium cobalt metal oxide represented by the following Chemical Formula 1, and provides a cathode having an electrical conductivity of 1 × 10 ⁻⁴ S/cm or more:

[Formula 1]

Li _x Co _(1-y) M _y O _4-z A _z

In 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 are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

Here, the cathode active material is nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr) and zirconium (Zr) It may be a lithium composite transition metal oxide containing two or more elements selected from the group consisting of.

In addition, the content of the sacrificial cathode material may be 0.001 to 5.0 parts by weight based on 100 parts by weight of the cathode active material.

Further, in one embodiment, the present invention provides an electrode assembly including the positive electrode.

Furthermore, in one embodiment, the present invention provides a lithium secondary battery including the electrode assembly.

The method for manufacturing a sacrificial cathode material according to the present invention uses a lithium precursor satisfying a specific size to adjust the electrical conductivity of the sacrificial cathode material to a specific range, thereby reducing the generation of gas, particularly oxygen (O ₂ ) gas, generated from the cathode during battery charging. Since it can be reduced, the effect of improving the stability and lifespan of a battery including the same is excellent.

1 is a graph showing the amount of gas generated by the positive electrode according to the number of times of charging and discharging at 45° C. for each average particle size of lithium oxide (Li ₂ O) used in the manufacture of a sacrificial positive electrode.
2 is a graph showing the amount of gas generated by the cathode according to the storage time (unit: weeks) at 60° C. for each average particle size of lithium oxide (Li ₂ O) used in the manufacture of the sacrificial cathode material.
3 is a graph showing the amount of gas generated by the positive electrode according to the average particle size of lithium oxide (Li ₂ O) used in the manufacture of the sacrificial positive electrode.
4 is a graph illustrating an initial charge/discharge curve of a sacrificial positive electrode material according to an average particle size of lithium oxide (Li ₂ O) used in manufacturing the sacrificial positive electrode material.

Since the present invention can have various changes and can have various embodiments, specific embodiments will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In the present invention, terms such as "comprising" or "having" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Also, in the present invention, when a part of a layer, film, region, plate, etc. is described as being “on” another part, this includes not only cases where it is “directly on” another part, but also a case where there is another part in between. . Conversely, when a part of a layer, film, region, plate, etc. is described as being “under” another part, this includes not only cases where the other part is “directly under” but also cases where another part is in between. In addition, in the present application, “on” may include the case of being disposed not only on the upper part but also on the lower part.

In addition, in the present invention, "D ₅₀ " is the particle size of the point reaching 50% of the volume percentage in the cumulative curve when obtaining the cumulative curve of the particle size distribution with the total volume being 100%, and the volume is accumulated from the smaller particle size. It means the particle size where it becomes 50%. The average particle size (D ₅₀ ) may be measured, for example, by using a laser diffraction method, and the laser diffraction method is generally used to measure a particle size of several mm from a submicron region. possible, and high reproducibility and high resolution results can be obtained.

Hereinafter, the present invention will be described in more detail.

Manufacturing method of sacrificial cathode material

In one embodiment, the present invention provides a method for manufacturing a sacrificial cathode material comprising the step of preparing a lithium cobalt metal oxide represented by the following Chemical Formula 1 by calcining a raw material mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) do:

[Formula 1]

Li _x Co _(1-y) M _y O _4-z A _z

In 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 are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

The method for manufacturing a sacrificial cathode material according to the present invention is to prepare a lithium cobalt metal oxide represented by Formula 1 as a sacrificial cathode material, wherein the lithium cobalt metal oxide represented by Formula 1 has an anti-fluorite structure. Li _x CoO _4-z A _z (provided that A is F or Cl, 5.4≤x≤6.8 and 0≤z≤0.0005), in some cases, the Li _x CoO _4-z A _z It may include a cobalt (Co) position doped with any one or more of Ti, Al, Zr, Mn, and Ni. Specifically, the lithium cobalt metal oxide is Li ₆ CoO ₄ , Li ₆ Co _(1-y) Ti _y O ₄ , Li ₆ Co _(1-y) Al _y O ₄ , Li ₆ Co _(1-y) Zn _y O ₄ , Li ₆ Co _(1-y) Zr _y O ₄ , Li ₆ Co _(1-y) Mn _y O ₄ , Li ₆ Co _(1-y) Ni _y O ₄ (where 0≤y≤0.4) And it may include one or more selected from the group consisting of mixtures thereof.

The sacrificial cathode material including such lithium cobalt metal oxide is mixed with lithium oxide (Li ₂ O) and oxide in a molar ratio of 2 to 4:1, for example, 2.5 to 3.5:1, or 2.95 to 3.1:1. It can be produced by calcining a raw material mixture of cobalt (CoO), and when one or more oxides of Ti, Al, Zr, Mn and Ni are added to the raw material mixture, Ti, Al, Zr, Mn and Ni are at least one Doped form of lithium cobalt metal oxide can be prepared.

In this case, the sintering is performed in an inert gas atmosphere containing a small amount of oxygen gas, for example, 0.01 to 0.1%; 0.02 to 0.09%; Alternatively, argon (Ar) gas or nitrogen (N ₂ ) gas containing oxygen gas at a partial pressure of 0.05 to 0.08% may be performed under an atmosphere.

In addition, the temperature at which the sintering is performed is not particularly limited as long as the mixed metal oxides can be transformed into the lithium cobalt metal oxide represented by Chemical Formula 1, and may be applied. Specifically, the firing temperature may be 500 to 800 ℃, more specifically 500 to 700 ℃; 600 to 800°C; 600 to 750° C.; 650 to 800°C; 630 to 770°C; or 660 to 740°C.

As an example, the firing may be performed at 670 to 730° C. for 2 to 20 hours under an argon (Ar) gas atmosphere containing oxygen gas at a partial pressure of 0.04 to 0.07%, in which case the sacrificial cathode material manufactured It is possible to increase the fraction of lithium cobalt metal tetraoxide represented by the chemical formula 1, thereby reducing the amount of gas generated during charging and discharging of the battery.

In addition, the form of the method for manufacturing the sacrificial cathode material according to the present invention is not particularly limited, but lithium oxide (Li ₂ O) whose size is adjusted to a specific range may be used as a raw material. Specifically, in the method of manufacturing the sacrificial cathode material, lithium oxide (Li ₂ O) having an average particle size (D ₅₀ ) of 50 μm or less may be used, and more specifically, an average particle size (D ₅₀ ) of 10 μm to 50 μm; 10 μm to 40 μm; 10 μm to 30 μm; 10 μm to 20 μm; 20 μm to 50 μm; 25 μm to 50 μm; 15 μm to 40 μm; 15 μm to 35 μm; 15 μm to 25 μm; 20 μm to 40 μm; 25 μm to 35 μm; Alternatively, 15 μm to 20 μm of lithium oxide (Li ₂ O) may be used.

Here, the minimum particle size (D _min ) of the lithium oxide (Li ₂ O) may be 2 μm or more, more specifically 2.5 μm or more; 3 μm or more; 5 μm or more; 2 μm to 25 μm; 2 μm to 20 μm; 2 μm to 10 μm; 2 μm to 7 μm; 2 μm to 4.5 μm; 4 μm to 10 μm; 15 μm to 25 μm; or 18 μm to 22 μm.

In addition, the lithium oxide (Li ₂ O) may have a particle size distribution of a unimodal distribution, and 80 to 90% of the total particles of the lithium oxide (Li ₂ O) having a unimodal distribution are in a particle size range of 10 μm to 45 μm. and 65 to 75% of the total particles may be present in a particle size range of 15 μm to 35 μm.

As an example, the lithium oxide (Li ₂ O) has a particle size distribution of a unimodal distribution, and the average particle size (D ₅₀ ) and the minimum particle size (D _min ) are 25 μm to 30 μm and 4 μm to 6 μm, respectively, 80 to 90% of the total particles may be present in a particle size range of 12 μm to 40 μm, and 65 to 75% of the total particles may be present in a particle size range of 20 μm to 35 μm.

In the method of manufacturing a sacrificial cathode material according to the present invention, by controlling the particle size of lithium oxide (LiO ₂ ), which is a raw material, as described above, lithium oxide having a small particle size is easily floated, so that workability is deteriorated during the manufacturing process, and lithium oxide having a large particle size It is possible to prevent a decrease in the yield of the sacrificial cathode material due to a decrease in the reactivity of the sacrificial cathode material. In addition, conventionally, a sacrificial cathode material including lithium cobalt metal oxide represented by Chemical Formula 1 has an anti-fluorite structure by a firing process. There is a problem of generating a gas containing oxygen (O ₂ ), carbon monoxide (CO), carbon dioxide (CO ₂ ), hydrogen (H ₂ ), and the like. However, when lithium oxide (Li ₂ O) whose particle size is controlled within the above-described range as in the present invention is used, the electrical conductivity of the manufactured sacrificial cathode material may be controlled to satisfy a specific range, and thus the sacrificial cathode material may be The amount of oxygen gas generated during charging and discharging of the included battery may be reduced.

As an example, the electrical conductivity of the powder of the sacrificial cathode material prepared according to the present invention may be 1 × 10 ^-4 S/cm or more, specifically, the upper limit is 9 × 10 ^-3 S/cm or less, 8 × 10 ^-3 S /cm or less, 7 × 10 ^-3 S/cm or less, or 6 × 10 ^-3 S/cm or less, and the lower limit is 5 × 10 ^-4 S/cm or more, 8 × 10 ^-4 S/cm or more, 1 × It may be 10 ^-3 S/cm or more or 2 × 10 ^-3 S/cm or more. More specifically, the electrical conductivity of the powder of the sacrificial positive electrode is 1 × 10 ^-3 S/cm to 9 × 10 ^-3 S/cm; 2×10 ^-3 S/cm to 9×10 ^-3 S/cm; 4×10 ^-3 S/cm to 8.5×10 ^-3 S/cm; 4 × 10 ^-3 S/cm to 6.5 × 10 ^-3 S/cm; or 5 × 10 ^-3 S/cm to 8.2 × 10 ^-3 S/cm.

As another example, in the sacrificial cathode material manufactured according to the present invention, the amount of gas generated during the initial discharge of the battery is significantly reduced, and thus Equation 1 may be satisfied:

[Equation 1]

V _gas = -1.07 × D _Li2O + A

In Equation 1 above,

V _gas represents the amount of gas (unit: mL/g) generated by the positive electrode including the sacrificial positive electrode material,

D _Li2O represents the average particle size (D ₅₀ , unit: μm) of lithium oxide (Li ₂ O), and

A is a constant, and 128≤A≤132.

Equation 1 is the average particle size (D 50 ) of the amount of gas generated from the positive electrode and the lithium oxide (LiO ₂ ) used in the preparation of the sacrificial positive electrode material during initial discharge of a battery manufactured using the sacrificial positive electrode material prepared according to the present invention (D ₅₀ ) As an indication _of the correlation _of mL/g or less, specifically, since a gas of 70 mL/g to 130 mL/g is generated, Equation 1 may be satisfied.

The method for manufacturing a sacrificial cathode material according to the present invention uses lithium oxide that satisfies the average particle size (D ₅₀ ) of a specific range to control the electrical conductivity of the sacrificial cathode material to a specific range, thereby generating gas, particularly oxygen ( O ₂ ) Since it is possible to significantly reduce the generation of gas, there is an advantage in that it is excellent in the effect of improving the stability and lifespan of the battery including the same.

anode

In addition, the present invention in one embodiment,

positive electrode current collector; and

a positive electrode mixture layer containing a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material on the positive electrode current collector;

The sacrificial cathode material includes a lithium cobalt metal oxide represented by the following Chemical Formula 1, and provides a cathode having an electrical conductivity of 1 × 10 ⁻⁴ S/cm or more:

[Formula 1]

Li _x Co _(1-y) M _y O _4-z A _z

In Formula 1,

M is at least one selected from the group consisting of Ti, Mg, 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.

The positive electrode according to the present invention has a structure in which a positive electrode mixture layer is formed on a positive electrode current collector, wherein the positive electrode mixture layer includes a positive electrode active material; conductive material; and a sacrificial cathode material prepared according to the manufacturing method of the present invention and containing lithium cobalt metal oxide represented by Chemical Formula 1 together with an organic binder polymer, gas generated during charging and discharging of the battery and/or high temperature storage after activation , in particular, the effect of reducing oxygen (O ₂ ) gas is excellent.

As an example, when the positive electrode is charged and discharged 50 times (45°C, 4.5C/0.3C conditions) after activation, the gas generation amount may be 15 mL/g or less, specifically 13 mL/g or less, It may be 10 mL/g or less or 5 mL/g or less.

As another example, when the positive electrode is stored at 60° C. for 4 weeks after activation, the gas generation amount may be 5 mL/g or less, specifically 3 mL/g or less, 2 mL/g or less, or 1.8 mL/g may be below.

Here, the cathode active material is nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr) and zirconium (Zr) It may be a lithium composite transition metal oxide containing two or more elements selected from the group consisting of. For example, the cathode active material may include a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a layered compound substituted with one or more transition metals; Lithium manganese oxide, such as Formula Li _1+x Mn _2-x O ₄ (here, x is 0-0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; lithium copper oxides such as Li ₂ CuO ₂ ; vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x M _x O ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, lithium manganese composite oxide represented by Ni, Cu or Zn; LiNi _x Mn _2-x O ₄ A lithium manganese composite oxide having a spinel structure; LiMn ₂ O ₄ in which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. are mentioned.

In addition, the sacrificial cathode material is manufactured by the method for manufacturing the sacrificial cathode material according to the present invention described above, and the electrical conductivity of the sacrificial cathode material is controlled to a specific range by using lithium oxide satisfying the average particle size (D ₅₀ ) in a specific range. The amount of gas generated during activation of the anode including the same, in particular oxygen (O ₂ ) gas, may be significantly less.

Specifically, the powder electrical conductivity of the sacrificial cathode material may be 1 × 10 ^-4 S/cm or more, and specifically, the upper limit is 9 × 10 ^-3 S/cm or less, 8 × 10 ^-3 S/cm or less, 7 × 10 ^-3 S/cm or less or 6 × 10 ^-3 S/cm or less, and the lower limit is 5 × 10 ^-4 S/cm or more, 8 × 10 ^-4 S/cm or more, 1 × 10 ^-3 S/cm or more Or 2 × 10 ^-3 S/cm or more. More specifically, the electrical conductivity of the powder of the sacrificial positive electrode is 1 × 10 ^-3 S/cm to 9 × 10 ^-3 S/cm; 2×10 ^-3 S/cm to 9×10 ^-3 S/cm; 4×10 ^-3 S/cm to 8.5×10 ^-3 S/cm; 4 × 10 ^-3 S/cm to 6.5 × 10 ^-3 S/cm; or 5 × 10 ^-3 S/cm to 8.2 × 10 ^-3 S/cm.

In addition, the sacrificial cathode material may be included in an amount of 0.001 to 5.0 parts by weight based on 100 parts by weight of the cathode active material. More specifically, the sacrificial cathode material may include 0.001 to 4.0 parts by weight based on 100 parts by weight of the positive electrode active material; 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 may be included.

In addition, the conductive material may be added in an amount of 1 to 20 parts by weight based on 100 parts by weight of the positive electrode active material, specifically, 1 to 10 parts by weight based on 100 parts by weight of the positive electrode active material; 1 to 5 parts by weight; 3 to 8 parts by weight; Or 2 to 5 parts by weight may be added.

In addition, the conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

In addition, the organic binder polymer is a component that assists in bonding between the active material and the conductive material and bonding to the current collector, and may be added in an amount of 1 to 20% by weight based on 100 parts by weight of the positive electrode active material, specifically, 100 parts by weight of the positive electrode active material. 1 to 10 parts by weight based on parts by weight; 1 to 5 parts by weight; 3 to 8 parts by weight; Or 2 to 5 parts by weight may be added.

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, ethylene-propylene-diether polymer (EPDM), sulfonated EPDM, styrene-butyrene rubber, fluororubber, various copolymers, and the like.

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, and the filler is a fibrous material without causing a chemical change in the battery. it's not going to be 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 as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, etc. may be used, and aluminum However, in the case of stainless steel, a surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface, 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.

electrode assembly

Further, in one embodiment, the present invention provides an electrode assembly including the above-described positive electrode.

The electrode assembly according to the present invention may have a structure including the above-described positive electrode, the negative electrode, and a separator interposed between the positive electrode and the negative electrode, and in some cases, the separator may be excluded.

Here, the negative electrode is manufactured by coating, drying and pressing the negative electrode active material on the negative electrode current collector, and if necessary, the same conductive material as in the positive electrode, an organic binder polymer, a filler, and the like may be optionally further included.

In addition, the negative active material is, 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 honeycomb planes of carbon are arranged in layers). and carbon and graphite materials, such as hard carbon, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, etc., in which these structures are mixed with amorphous parts; LixFe ₂ O ₃ (0≤x≤1), LixWO ₂ (0≤x≤1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me', Al, B, P, Si, periodic table metal complex oxides such as Group 1, Group 2, and Group 3 elements, halogen, 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloys; tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and metal oxides such as Bi ₂ O ₅ ; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxide; Lithium titanium oxide and the like can be used.

graphite such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

As an example, the anode active material may be a mixture of 80 to 95% by weight of carbon and graphite material and 5 to 20% by weight of SiO ₂ , and the carbon and graphite material is graphite and/or acetylene black and carbon nanotubes. It may be mixed in a weight ratio of 1:0.05 to 0.5.

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. For example, copper, stainless steel, nickel, titanium, sintered carbon, etc. may be used, and copper In the case of stainless steel, a surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the negative electrode current collector, like the positive electrode current collector, may form fine irregularities on the surface to strengthen the bonding force with the negative electrode active material, and may have various forms such as films, sheets, foils, nets, porous bodies, foams, nonwovens, etc. It is possible. In addition, the average thickness of the negative electrode current collector may be appropriately applied in the range of 3 to 500 μm in consideration of the conductivity and total thickness of the negative electrode to be manufactured.

Furthermore, the separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The separation membrane is not particularly limited as long as it is conventionally used in the art, and specifically, chemical resistance and hydrophobic polypropylene; glass fiber; Alternatively, a sheet or non-woven fabric made of polyethylene may be used, and in some cases, a composite separator in which inorganic particles/organic particles are coated with an organic binder polymer on a porous polymer substrate such as the sheet or non-woven fabric may be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator. In addition, the 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 accommodated in a cylindrical battery, a prismatic battery, or a pouch-type battery, or may be accommodated in a pouch-type battery in a folding or stack-and-folding form.

As an example, the electrode assembly may be wound in the form of a jelly roll and accommodated in a cylindrical battery or a pouch-type battery.

lithium secondary battery

Furthermore, in one embodiment, the present invention provides a lithium secondary battery including the above-mentioned electrode assembly.

The lithium secondary battery according to the present invention 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 be composed of an electrolyte and a lithium salt, and a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like may be used as the electrolyte.

As the non-aqueous organic solvent, for example, N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dime ethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, pyropion An aprotic organic solvent such as methyl acid or ethyl propionate may be used.

In addition, as the organic solid electrolyte, for example, polyethylene derivative, polyethylene oxide derivative, polypropylene oxide derivative, phosphoric acid ester polymer, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride , a polymerization agent containing an ionic dissociation group, etc. may be used.

In addition, as the inorganic solid electrolyte, for example, Li ₃ N, LiI, Li ₅ Ni ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ Nitride, halide, sulfate, etc. of Li may be used.

In addition, lithium salt is a material that is easily dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB10Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylboronate, imide, and the like may be used.

In addition, for the purpose of improving charge/discharge characteristics, flame retardancy, etc. in the electrolyte solution, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitro Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added. have. In some cases, in order to impart incombustibility, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate) ), PRS (propene sultone), and the like may be further included.

Meanwhile, in one embodiment, the present invention provides a battery module including the above-described secondary battery as a unit cell, and provides a battery pack including the battery module.

The battery pack may be used as a power source for a medium or large device requiring 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 omniscient motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooter); electric golf carts; and a power storage system, and more specifically, a hybrid electric vehicle (HEV), but is not limited thereto.

Hereinafter, the present invention will be described in more detail by way of Examples and Experimental Examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following Examples and Experimental Examples.

Examples 1-5 and Comparative Examples 1-2. Preparation of sacrificial cathode material

Lithium oxide (Li ₂ O, unimodal distribution) and cobalt oxide (CoO) were put into the reactor to have a molar ratio of 3.0 to 3.03, and uniformly dry-mixed for about 30 minutes using a mixer. Then, the prepared raw material mixture was put in an electric furnace, and calcined at about 700° C. for 10 hours under argon gas (Ar) conditions to obtain lithium cobalt oxide (Li ₆ CoO ₄ ). At this time, the average particle size (D ₅₀ ) and the minimum particle size (D _min ) of lithium oxide (Li ₂ O) and the partial pressure of oxygen gas (O ₂ ) contained in argon gas during firing are shown in Table 1 below.

Lithium oxide particle size [㎛] O ₂ partial pressure [%] D ₅₀ D _min Example 1 17.5±0.5 2.75±0.01 0.01~0.08 Example 2 28.1±0.5 5.01±0.05 0.01~0.08 Example 3 49.5±0.5 20.4±0.5 0.01~0.08 Example 4 28.1±0.5 5.01±0.05 0 Example 5 28.1±0.5 5.01±0.05 1.01~1.5 Comparative Example 1 5.0±0.1 0.8±0.05 0.01~0.08 Comparative Example 2 70.0±0.5 31.2±0.5 0.01~0.08

Experimental Example 1.

In order to evaluate the electrical conductivity of the sacrificial positive electrode material prepared according to the present invention, the electrical conductivity of the sacrificial positive electrode material prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was measured. In this case, the measurement is performed by measuring the sheet resistance according to the volume and pressure change of each sacrificial cathode material by a 4-point probe method using a powder resistance characteristic measuring instrument, and using the measured volume and the input mass to measure the sheet resistance Electrical conductivity was calculated, and the results are shown in Table 2 below.

Unit: S/cm Example comparative example One 2 3 One 2 electrical conductivity 8.02×10 ^-3 6.42×10 ^-3 5.31×10 ^-3 7.84×10 ^-5 4.32×10 ^-5

As shown in Table 2 above, it can be seen that the sacrificial cathode material prepared in Examples has electrical conductivity of 1 × 10 ^-3 S/cm to 8.5 × 10 ^-3 S/cm, which satisfies the powder electrical conductivity according to the present invention. have.

Experimental Example 2.

In order to evaluate the performance of the sacrificial cathode material prepared according to the present invention, the following experiment was performed.

A) Measurement of gas emission

N-methylpyrrolidone solvent was injected into a homo mixer, and each of the sacrificial cathode materials prepared in Examples 1 to 5 and Comparative Examples 1 and 2, an acetylene black conductive material, a modified silanol binder, and The dispersant was added in a weight ratio of 95:3:1.7:0.3 and mixed at 3,000 rpm for 60 minutes to prepare a pre-dispersion.

The content of the sacrificial cathode material is mixed with the cathode active material so that 2 parts by weight based on 100 parts by weight of the cathode active material (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) is mixed with the cathode active material, and the cathode active material mixed in N-methylpyrrolidone solvent, a binder Phosphorus PVdF and carbon black as a conductive material were put into a homo mixer in a weight 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 prepare a positive electrode.

A 2032 type cell was manufactured using the positive electrode and the lithium metal counter electrode. A separator (thickness: about 16 μm) made of a porous polyethylene (PE) film was interposed between the positive electrode and the lithium metal counter electrode, and electrolyte was injected to prepare a half-cell type cell.

At this time, the electrolyte is ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 (volume ratio), lithium hexafluoro phosphate (LiPF ₆ , 0.7M), lithium bis (fluorosulfonyl) imide (LiFSI) , 0.5M), lithium tetrafluoroborate (LiBF ₄ , 0.2 wt%), vinyl carbonate (VC, 2 wt%), 1,3-propane sultone (PS, 0.5 wt%), and ethylene sulfate (Esa, 1 % by weight) was used.

Formation is carried out by charging and discharging one time at 4.5C/0.3C condition for the fabricated cell, and then ① repeating charging and discharging 50 times at 45°C under 0.3C/0.3C condition to charge and discharge each charge/discharge. The amount of gas generated during storage and the amount of gas generated during storage at 60°C for 4 weeks were measured. The results are shown in Table 3 and FIGS. 1 and 2 below.

Unit: mL/g Example comparative example One 2 3 4 5 One 2 initial charge/discharge
gas generation 111 99.89 75.5 111.5 120.4 101.7 114.5

As shown in Table 3 and FIGS. 1 and 2, the amount of gas generated in the charge/discharge process of the sacrificial cathode material prepared according to the present invention is reduced. This tendency shows that the average particle size (D ₅₀ ) of a lithium precursor used in manufacturing the sacrificial cathode material, for example, lithium oxide (Li ₂ O) is large, and the oxygen gas (O ₂ ) in the inert gas used during firing is used at a low partial pressure. You can see it grows.

B) Initial charge/discharge evaluation

A half-cell type cell was manufactured in the same manner as in the measurement of gas emission, except that the electrolyte was ethylmethyl carbonate (EMC): dimethyl carbonate (DMC): diethyl carbonate (DEC) = 1:2:1 (volume ratio). , a solution of lithium hexafluorophosphate (LiPF ₆ , 1.0M) and vinyl carbonate (VC, 2 wt%) was used.

The initial charging capacity was measured by performing charging and discharging (formation) for each manufactured cell. At this time, the charging/discharging (formation) was performed under the conditions of 25°C and 70mah/3mAh, and the results are shown in Table 4 and FIG. 3 below.

Average particle size of Li ₂ O (D ₅₀ )
[μm] O ₂ partial pressure
[%] initial charge capacity
[mAh] Example 1 17.5±0.5 0.01~0.08 817 Example 2 28.1±0.5 0.01~0.08 764.7 Example 3 49.5±0.5 0.01~0.08 654.8 Example 4 28.1±0.5 0 643.9 Example 5 28.1±0.5 1.01~1.5 682 Comparative Example 1 5.0±0.1 0.01~0.08 520.2 Comparative Example 2 70.0±0.5 0.01~0.08 594.1

As shown in Table 4 and FIG. 3, it can be seen that the sacrificial cathode material prepared according to the present invention has an effect of improving battery performance.

Specifically, in the battery including the sacrificial cathode material of the embodiment, the initial charge capacity tends to increase as the average particle size (D ₅₀ ) of the lithium precursor, for example, lithium oxide (Li ₂ O) decreases. This means that when the average particle size (D ₅₀ ) of lithium oxide (Li ₂ O) is decreased, the charging capacity is improved, but the amount of gas generated during charging/discharging and/or storage after the activation step is increased.

From these results, the sacrificial cathode material prepared according to the present invention has an excellent effect of improving the performance of the battery by adjusting the electrical conductivity of the sacrificial cathode material to a specific range using a lithium precursor satisfying a specific size during manufacture, and when charging and discharging the battery Since the generation of gas, particularly oxygen (O ₂ ) gas, generated from the electrode assembly can be reduced, it can be seen that the effect of improving the stability and lifespan of a battery including the same is excellent.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art or those having ordinary knowledge in the technical field do not depart from the spirit and technical scope of the present invention described in the claims to be described later. It will be understood that various modifications and variations of the present invention may be made within the scope thereof.

Accordingly, the technical scope of the present invention is not limited to the content described in the detailed description of the specification, but should be defined by the claims.

Claims (13)

Comprising the step of calcining a raw material mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) to prepare a lithium cobalt metal oxide represented by the following formula (1),
The average particle size (D50) of the lithium oxide (Li ₂ O) is 50㎛ or less,
The sacrificial cathode material has an electrical conductivity of 1 × 10 ^-4 S/cm or more. Method for producing a sacrificial cathode material:
[Formula 1]
Li _x Co _(1-y) M _y O _4-z A _z
In 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 are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.
According to claim 1,
Electrical conductivity is 1 × 10 ^-3 S/cm to 9 × 10 ^-3 S/cm A method of manufacturing a sacrificial cathode material.
According to claim 1,
A method of manufacturing a sacrificial cathode material wherein the firing is performed at a temperature of 500 to 800°C.
According to claim 1,
A raw material mixture of lithium oxide (Li ₂ O) and cobalt oxide (CoO) is a method of manufacturing a sacrificial cathode material in which lithium oxide (Li ₂ O) and cobalt oxide (CoO) are mixed in a molar ratio of 2 to 4:1.
According to claim 1,
A method of manufacturing a sacrificial cathode material having an average particle size (D50) of lithium oxide (Li ₂ O) of 15 μm to 35 μm.
According to claim 1,
A method of manufacturing a sacrificial cathode material having a minimum particle size (Dmin) of lithium oxide (Li ₂ O) of 2 μm or more.
According to claim 1,
Lithium oxide (Li ₂ O) has a unimodal particle size distribution; and
80-90% of the total particles are present in the particle size range of 10㎛ to 45㎛,
A method of manufacturing a sacrificial cathode material in which 65 to 75% of the total particles are present in a particle size range of 15 μm to 35 μm.
According to claim 1,
The sacrificial cathode material is a method of manufacturing a sacrificial cathode material satisfying Equation 1:
[Equation 1]
V _gas = -1.07 × D _Li2O + A
In Equation 1 above,
V _gas represents the amount of gas (unit: mL/g) generated by the electrode assembly including the sacrificial cathode material,
D _Li2O represents the average particle size (D50, unit: μm) of lithium oxide (Li ₂ O), and
A is a constant, and 128≤A≤132.
positive electrode current collector; and
a positive electrode mixture layer containing a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material on the positive electrode current collector;
The sacrificial cathode 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:
[Formula 1]
Li _x Co _(1-y) M _y O _4-z A _z
In Formula 1,
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.
10. The method of claim 9,
The cathode active material is a group consisting of nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr) and zirconium (Zr). A positive electrode comprising a lithium composite transition metal oxide comprising two or more elements selected from
10. The method of claim 9,
The content of the sacrificial cathode material is 0.001 to 5.0 parts by weight based on 100 parts by weight of the cathode active material.
An electrode assembly comprising the positive electrode according to claim 9 .
A lithium secondary battery comprising the electrode assembly according to claim 12 .

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