Sacrificial positive electrode material with reduced amount of gas generation and method of making same

Abstract

The present invention relates to a sacrificial cathode material having a reduced amount of gas generation and a method of preparing the same, and the method of preparing the sacrificial cathode material is capable of reducing gas, particularly oxygen (O2), generated in an electrode assembly during charging of a battery by adjusting the electrical conductivity of the sacrificial cathode material within a certain range using lithium oxide satisfying a certain size, thereby capable of effectively improving the stability and lifespan of a battery containing the same.

Description

Technical Field

[0001] The present invention relates to a method for preparing a sacrificial cathode material and the sacrificial cathode material thereby prepared, the method being to prepare the sacrificial cathode material having a reduced amount of gas generation during charging and discharging by adjusting the particle size of the lithium precursor to control the conductivity of the sacrificial cathode material within a specific range.

[0002] This application claims 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 8, 2022, the entire contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, the increasing demand for high-capacity electrode materials has also necessitated the development of irreversible additives with higher irreversible capacities. However, limitations do exist in the development of cathode additives with high irreversible capacities.

[0004] On the other hand, traditional irreversible additives such as Li6CoO4 are generally prepared by reacting cobalt oxide with an excess of lithium oxide. In this case, unreacted byproducts such as unreacted lithium oxide (Li2O) remain in the final irreversible additive, which can cause oxidation during charging / discharging, thereby generating oxygen inside the battery. The generated oxygen can lead to volume expansion, thus becoming one of the main factors causing battery performance degradation.

[0005] Therefore, there has been a need to develop a cathode additive that, due to its low residual amount of byproducts such as lithium oxide, reduces oxygen production during battery charging / discharging while maintaining high irreversible capacity.

[0006] Related technical documents

[0007] [Patent Literature]

[0008] Korean Patent Publication No. 10-2019-0012839 Summary of the Invention

[0009] [Technical Issues]

[0010] The purpose of this invention is to provide a positive electrode additive that reduces oxygen production during the charging / discharging process of a battery while having a high irreversible capacity, as well as a positive electrode and a lithium secondary battery containing the additive.

[0011] [Technical Solution]

[0012] One aspect of the present invention provides a method for preparing a sacrificial cathode material, the method comprising the steps of: calcining a 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 (D) of less than 50 μm. 50 Furthermore, the prepared sacrificial cathode material has a strength of 1×10⁻⁶. -4 Conductivity above S / cm

[0013] [Chemical Formula 1]

[0014] Li x Co (1-y) M y O 4-z A z

[0015] In chemical formula 1,

[0016] M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni.

[0017] A is a halogen that substitutes for oxygen, and

[0018] x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

[0019] Here, the conductivity can be 1×10 -3 S / cm up to 9×10 -3 Within the range of S / cm.

[0020] In addition, calcination can be carried out at 500°C to 800°C.

[0021] Furthermore, a mixture of lithium oxide (Li2O) and cobalt oxide (CoO) can be obtained by mixing lithium oxide (Li2O) and cobalt oxide (CoO) in a molar ratio of 2 to 4:1.

[0022] Furthermore, lithium oxide (Li₂O) can have an average particle size (D) of 15 μm to 35 μm. 50 ) and minimum particle size greater than 2μm (D min ).

[0023] Furthermore, lithium oxide (Li2O) can have a unimodal particle size distribution, with 80% to 90% of all particles in the particle size range of 10 μm to 45 μm, and 65% to 75% of all particles in the particle size range of 15 μm to 35 μm.

[0024] Furthermore, the sacrificial cathode material prepared by the method can satisfy the following formula 1:

[0025] [Formula 1]

[0026] V gas = -1.07 × D Li2O +A

[0027] In Formula 1,

[0028] V gas This indicates the amount of gas produced in a cathode containing sacrificial cathode material (unit: mL / g).

[0029] D Li2O The average particle size (D) of lithium oxide (Li2O) 50 (unit: μm), and

[0030] A is a constant and satisfies 128≤A≤132.

[0031] Another aspect of the present invention provides a positive electrode comprising: a positive electrode current collector; and a positive electrode mixture layer on the positive electrode current collector, the positive electrode mixture layer comprising a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material, wherein the sacrificial positive electrode material comprises a lithium cobalt metal oxide represented by the following chemical formula 1 and has a density of 1 × 10⁻⁶. -4 Conductivity above S / cm

[0032] [Chemical Formula 1]

[0033] Li x Co (1-y) M y O 4-z A z

[0034] In chemical formula 1,

[0035] M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni.

[0036] A is a halogen that substitutes for oxygen, and

[0037] x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

[0038] Here, the positive electrode active material can be a lithium composite transition metal oxide containing two or more elements selected from the following: nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr), and zirconium (Zr).

[0039] Furthermore, based on 100 parts by weight of positive electrode active material, the content of sacrificial positive electrode material can be from 0.001 to 5.0 parts by weight.

[0040] Another aspect of the present invention provides an electrode assembly including the positive electrode.

[0041] Another aspect of the present invention provides a lithium secondary battery comprising the electrode assembly.

[0042] [Beneficial Effects]

[0043] The method for preparing sacrificial cathode material according to the present invention can reduce the gases, especially oxygen (O2), generated in the cathode during battery charging by using lithium precursors of a specific size to adjust the conductivity of the sacrificial cathode material within a specific range, thereby effectively improving the stability and lifespan of the battery containing the sacrificial cathode material. Attached Figure Description

[0044] Figure 1 This is a graph showing the amount of gas generated in the cathode for each average particle size of lithium oxide (Li2O) used to prepare sacrificial cathode materials, based on the number of charge and discharge cycles at 45°C.

[0045] Figure 2 This is a graph showing the amount of gas generated in the cathode for each average particle size of lithium oxide (Li2O) used to prepare sacrificial cathode materials, based on storage time (in weeks) at 60°C.

[0046] Figure 3 This is a graph showing the amount of gas generated in the cathode based on the average particle size of lithium oxide (Li2O) used to prepare the sacrificial cathode material.

[0047] Figure 4 This is a graph showing the initial charge / discharge curves of the sacrificial cathode material based on the average particle size of lithium oxide (Li2O) used to prepare the sacrificial cathode material. Detailed Implementation

[0048] Because the present invention allows for various variations and implementations, specific implementations will be described in detail in the detailed description section.

[0049] However, this is not intended to limit the invention to specific embodiments, and it should be understood that all variations, equivalents or substitutions within the spirit and scope of the invention are included in the invention.

[0050] In this invention, it should be understood that the terms "comprising" or "having" are intended only to specify the presence of features, numbers, steps, operations, ingredients, parts or combinations thereof, but are not intended to exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, ingredients, parts or combinations thereof.

[0051] Furthermore, in this invention, when a portion of a layer, film, region, plate, etc., is described as being "on" another portion, this includes not only the case where the portion is "directly" "on" the other portion, but also the case where another portion is interposed therebetween. Conversely, when a portion of a layer, film, region, plate, etc., is described as being "below" another portion, this includes not only the case where the portion is "directly" "below" the other portion, but also the case where another portion is interposed therebetween. Additionally, in this document, the phrase "deposited on" can include not only being disposed on the upper part, but also being disposed on the lower part.

[0052] Furthermore, in this invention, "D" 50 "This refers to the particle size at the point where the cumulative curve of particle size distribution reaches 50% of the volume when the total volume is 100%, and specifically the particle size accumulated from the smallest particle size to 50% of the volume. Average particle size (D...)" 50 Particle sizes can be measured, for example, using laser diffraction, which is typically capable of measuring particle sizes from submicron to several millimeters and can yield highly reproducible and high-resolution results.

[0053] The invention will be described in more detail below.

[0054] Methods for preparing sacrificial cathode materials

[0055] One aspect of the present invention provides a method for preparing a sacrificial cathode material, the method comprising the steps of: calcining a mixture of lithium oxide (Li₂O) and cobalt oxide (CoO) to prepare a lithium cobalt metal oxide represented by the following chemical formula 1:

[0056] [Chemical Formula 1]

[0057] Li x Co (1-y) M y O 4-z A z

[0058] In chemical formula 1,

[0059] M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni.

[0060] A is a halogen that substitutes for oxygen, and

[0061] x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

[0062] The method for preparing sacrificial cathode materials according to the present invention aims to prepare lithium cobalt metal oxide represented by Chemical Formula 1 as a sacrificial cathode material, and the lithium cobalt metal oxide represented by Chemical Formula 1 may include Li having an antifluorite structure. x CoO 4-z A z (where A is F or Cl, and satisfies 5.4 ≤ x ≤ 6.8 and 0 ≤ z ≤ 0.0005), and in some cases may include Li doped at the cobalt (Co) sites by any one or more of Ti, Al, Zr, Mn and Ni. x CoO 4-z A z Specifically, the lithium cobalt metal oxide may include one or more selected from: Li6CoO4, Li6Co (1-y) Ti y O4, Li6Co (1-y) Al y O4, Li6Co (1-y) Zn y O4, Li6Co (1-y) Zr y O4, Li6Co (1-y) Mn y O4, Li6Co (1-y) Ni y O4 (where 0 ≤ y ≤ 0.4) and its mixtures.

[0063] Sacrificial cathode materials containing lithium cobalt metal oxides can be prepared by calcining a mixture of lithium oxide (Li₂O) and cobalt oxide (CoO) in a molar ratio of 2 to 4:1, for example 2.5 to 3.5:1 or 2.95 to 3.1:1. Lithium cobalt metal oxides doped with one or more of Ti, Al, Zr, Mn, and Ni can be prepared by adding one or more oxides of Ti, Al, Zr, Mn, and Ni to the raw material mixture.

[0064] In this case, calcination can be carried out in an inert gas atmosphere containing a small amount of oxygen, such as in an argon (Ar) or nitrogen (N2) atmosphere containing oxygen at a partial pressure of 0.01% to 0.1%, 0.02% to 0.09%, or 0.05% to 0.08%.

[0065] Furthermore, there are no particular restrictions on the calcination temperature, as long as it is within the temperature range that allows the mixed metal oxides to transform into lithium cobalt metal oxide represented by chemical formula 1. Specifically, the calcination temperature can be 500°C to 800°C, more specifically 500°C to 700°C, 600°C to 800°C, 600°C to 750°C, 650°C to 800°C, 630°C to 770°C, or 660°C to 740°C.

[0066] As an example, calcination can be carried out at 670°C to 730°C for 2 to 20 hours in an argon (Ar) atmosphere containing oxygen at a partial pressure of 0.04% to 0.07%. In this case, the proportion of lithium cobalt metal oxide represented by chemical formula 1 in the prepared sacrificial cathode material can be increased, thus reducing the amount of gas generated during battery charging and discharging.

[0067] Furthermore, in the method for preparing the sacrificial cathode material according to the present invention, lithium oxide (Li2O) with a particle size adjusted within a specific range can be used as a raw material, without particular limitation on its shape. Specifically, in the method for preparing the sacrificial cathode material, an average particle size (D) can be used. 50 The lithium oxide (Li₂O) is less than 50 μm; more specifically, the average particle size (D) can be used. 50 Lithium oxide (Li₂O) with a diameter 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, or 15 μm to 20 μm.

[0068] In this case, the minimum particle size (D) of lithium oxide (Li2O) min The value can be 2μm or larger, more specifically 2.5μm or larger, 3μm or larger, 5μm or larger, 2μm to 25μm, 2μm to 20μm, 2μm to 10μm, 2μm to 7μm, 2μm to 4.5μm, 4μm to 10μm, 15μm to 25μm or 18μm to 22μm.

[0069] Furthermore, lithium oxide (Li2O) can have a unimodal particle size distribution. In the case of lithium oxide (Li2O) having a unimodal particle size distribution, 80% to 90% of all particles are in the particle size range of 10 μm to 45 μm, and 65% to 75% of all particles are in the particle size range of 15 μm to 35 μm.

[0070] As an example, lithium oxide (Li₂O) can have a unimodal particle size distribution and an average particle size (D) of 25 μm to 30 μm. 50 ) and minimum particle size of 4μm to 6μm (D min Furthermore, 80% to 90% of all particles are within the particle size range of 12 μm to 40 μm, and 65% to 75% of all particles are within the particle size range of 20 μm to 35 μm.

[0071] By adjusting the particle size of lithium oxide (LiO2) as a raw material as described above, the method for preparing sacrificial cathode materials according to the present invention can prevent the deterioration of processability during preparation due to the easy floating of small-particle-size lithium oxide, and prevent the decrease in the yield of sacrificial cathode materials due to the decreased reactivity of large-particle-size lithium oxide. Furthermore, conventionally, sacrificial cathode materials containing lithium cobalt metal oxide represented by Chemical Formula 1 have an antifluorite structure through a calcination process, and even after initial charging and discharging, the sacrificial cathode material generates gases containing oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), etc., during charging and discharging at high temperatures. However, when lithium oxide (Li2O) with a particle size adjusted within the above-mentioned range is used in the present invention, the conductivity of the prepared sacrificial cathode material can be controlled to meet a specific range, thus reducing the amount of gas generated during charging and discharging of the battery containing the sacrificial cathode material.

[0072] As an example, the sacrificial cathode material prepared according to the present invention can have a 1×10⁻⁶ ohm diameter. -4 Powder conductivity above S / cm, specifically, its upper limit can be 9×10 -3 S / cm or less, 8×10 -3 S / cm or less, 7×10 -3 S / cm or below or 6×10 -3 Below S / cm, and its lower limit can be 5×10 -4 S / cm or higher, 8×10 -4 S / cm or higher, 1×10 -3 S / cm or higher or 2×10 -3 S / cm or higher. More specifically, the sacrificial cathode material can have a strength of 1×10⁻⁶. -3 S / cm up to 9×10 -3 S / cm, 2×10 -3 S / cm up to 9×10 -3 S / cm, 4×10 -3 S / cm up to 8.5×10 -3 S / cm, 4×10 -3 S / cm up to 6.5×10 -3 S / cm or 5×10 -3 S / cm up to 8.2×10 -3 Powder conductivity in S / cm.

[0073] As another example, the sacrificial cathode material prepared according to the present invention can satisfy the following formula 1 by significantly reducing the amount of gas generated during the initial discharge of the battery:

[0074] [Formula 1]

[0075] V gas = -1.07 × D Li2O +A

[0076] In Formula 1,

[0077] V gas This indicates the amount of gas produced in a cathode containing sacrificial cathode material (unit: mL / g).

[0078] D Li2O The average particle size (D) of lithium oxide (Li2O) 50 (unit: μm), and

[0079] A is a constant and satisfies 128≤A≤132.

[0080] Formula 1 represents the amount of gas generated in the cathode during the initial discharge of a battery manufactured using the sacrificial cathode material prepared according to the present invention, and the average particle size (D) of the lithium oxide (LiO2) used to prepare the sacrificial cathode material. 50 The relationship between ) and the average particle size (D) of the sacrificial cathode material prepared according to the present invention. 50 The cathode is prepared using lithium oxide (Li₂O) with a particle size of less than 50 μm, and the cathode made from it generates a gas concentration of less than 70 mL / g, specifically between 70 mL / g and 130 mL / g, during the initial discharge. Therefore, Formula 1 can be satisfied.

[0081] The method for preparing sacrificial cathode materials according to the present invention uses a specific average particle size (D) to achieve the desired particle size. 50 Lithium oxide in the range of ) can control the conductivity of the sacrificial cathode material within a specific range, thereby reducing the gases generated in the cathode during battery charging, especially oxygen (O2), which can effectively improve the stability and lifespan of the battery containing the sacrificial cathode material.

[0082] positive electrode

[0083] Another aspect of the present invention provides a positive electrode comprising: a positive electrode current collector; and a positive electrode mixture layer on the positive electrode current collector, the positive electrode mixture layer comprising a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material, wherein the sacrificial positive electrode material comprises a lithium cobalt metal oxide represented by the following chemical formula 1 and has a density of 1 × 10⁻⁶. -4 Conductivity above S / cm

[0084] [Chemical Formula 1]

[0085] Li x Co (1-y) M y O 4-z Az

[0086] In chemical formula 1,

[0087] M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni.

[0088] A is a halogen that substitutes for oxygen, and

[0089] x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001.

[0090] The positive electrode according to the 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 comprises a sacrificial positive electrode material as well as a positive electrode active material, a conductive material and an organic binder polymer, the sacrificial positive electrode material being prepared by the method of the invention and comprising a lithium cobalt metal oxide represented by chemical formula 1, thereby effectively reducing the gases, particularly oxygen (O2), generated during charging and discharging of the battery and / or during high-temperature storage after activation.

[0091] As an example, when the battery undergoes 50 charge / discharge cycles after activation (at 45°C and 4.5C / 0.3C), the positive electrode can exhibit gas production levels of less than 15 mL / g, specifically less than 13 mL / g, less than 10 mL / g, or less than 5 mL / g.

[0092] As another example, when the cathode is stored at 60°C for 4 weeks after activation, it can exhibit gas production of less than 5 mL / g, specifically less than 3 mL / g, less than 2 mL / g, or less than 1.8 mL / g.

[0093] In this case, the positive electrode active material can be a lithium composite transition metal oxide containing two or more elements selected from the following: nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), zinc (Zn), titanium (Ti), magnesium (Mg), chromium (Cr), and zirconium (Zr). For example, the positive electrode active material can be a layered compound, such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), etc., or a layered compound replaced by one or more transition metals; or a compound with the chemical formula Li... 1+x Mn 2-x Lithium manganese oxides represented by O4 (where x is 0 to 0.33), such as LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxides, such as Li2CuO2, etc.; vanadium oxides, such as LiV3O8, Li3VO4, V2O5, Cu2V2O7, etc.; and those represented by the chemical formula LiNi. 1-x M xNi-site type lithium nickel oxides represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); and those with the chemical formula LiMn 2-x M x Lithium manganese composite oxides represented by O2 (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); and LiNi x Mn 2-x O4 represents lithium manganese composite oxides with a spinel structure; LiMn2O4, in which some of the Li ions in the chemical formula are replaced by alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc.

[0094] Furthermore, the sacrificial cathode material is prepared by the method for preparing sacrificial cathode materials according to the present invention described above, and can be used to meet a specific average particle size (D). 50 Lithium oxide is used in the range of ) to control the conductivity of the sacrificial cathode material within a specific range. Therefore, the cathode containing this sacrificial cathode material can exhibit significantly less gas, especially oxygen (O2), generated during activation.

[0095] Specifically, the sacrificial cathode material can have a 1×10 -4 Powder conductivity above S / cm, specifically, its upper limit can be 9×10 -3 S / cm or less, 8×10 -3 S / cm or less, 7×10 -3 S / cm or below or 6×10 -3 Below S / cm, and its lower limit can be 5×10 -4 S / cm or higher, 8×10 -4 S / cm or higher, 1×10 -3 S / cm or higher or 2×10 -3 S / cm or higher. More specifically, the sacrificial cathode material can have a strength of 1×10⁻⁶. -3 S / cm up to 9×10 -3 S / cm, 2×10 -3 S / cm up to 9×10 -3 S / cm, 4×10 -3 S / cm up to 8.5×10 -3 S / cm, 4×10 -3 S / cm up to 6.5×10 -3 S / cm or 5×10 -3 S / cm up to 8.2×10 -3 Powder conductivity in S / cm.

[0096] The content of the sacrificial cathode material can be from 0.001 to 5.0 parts by weight relative to 100 parts by weight of the positive electrode active material. More specifically, the content of the sacrificial cathode material can be from 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 relative to 100 parts by weight of the positive electrode active material.

[0097] The amount of conductive material added can be 1 to 20 parts by weight relative to 100 parts by weight of positive electrode active material, 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.

[0098] Furthermore, there are no particular limitations on the conductive material, as long as it does not cause chemical changes in the battery and is conductive. For example, the following can be used: graphite, such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fiber and metal fiber; fluorinated carbon; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; or conductive materials, such as polyphenylene derivatives.

[0099] The organic binder polymer is a component that helps active materials, conductive materials, etc. to bond together and to current collectors. The amount of the organic binder polymer added relative to 100 parts by weight of positive electrode active material can be 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.

[0100] In addition, examples of organic adhesive polymers include: polyvinylidene fluoride (PVdF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber and various copolymers thereof.

[0101] In addition to the positive electrode active material, conductive material, and organic binder polymer, the positive electrode can also contain fillers to suppress positive electrode expansion. There are no particular restrictions on the fillers, as long as they are fibrous materials that do not cause chemical changes in the battery. Specifically, fillers can be: olefin polymers, such as polyethylene and polypropylene; and fibrous materials, such as glass fiber and carbon fiber.

[0102] There is no particular limitation on the positive electrode current collector as long as it does not cause chemical changes in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, the surface of the aluminum or stainless steel has been treated with carbon, nickel, titanium, silver, etc. In addition, fine concavities and convexities can be formed on the surface of the positive electrode current collector to improve the adhesion of the positive electrode active material, and various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabric bodies are possible. In addition, considering the conductivity and total thickness of the positive electrode to be manufactured, the average thickness of the positive electrode current collector can be appropriately applied within the range of 3 μm to 500 μm.

[0103] Electrode assembly

[0104] Another aspect of the present invention provides an electrode assembly including the above positive electrode.

[0105] The electrode assembly according to the present invention may include the above positive electrode, negative electrode, and a separator interposed between the positive electrode and the negative electrode. In some cases, the separator may not be included.

[0106] In this case, the negative electrode can be manufactured by coating the negative electrode active material on the negative electrode current collector, followed by drying and pressing, and if necessary, the negative electrode may optionally further include conductive materials, organic binder polymers, fillers, etc. as in the positive electrode.

[0107] As the negative electrode active material, for example, the following can be used: carbon and graphite materials, such as graphite having a completely layered crystal structure (such as natural graphite), soft carbon having a layered crystal structure with low crystallinity (graphene structure; a structure in which the hexagonal honeycomb planes of carbon are arranged in layers), hard carbon in which these structures are mixed with an amorphous part, artificial graphite, expanded graphite, carbon fiber, non-graphitized carbon, carbon black, carbon nanotubes, fullerenes, activated carbon, etc.; metal composite oxides, such as Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2 (0 ≤ x ≤ 1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Group 1, Group 2, and Group 3 of the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides, such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers, such as polyacetylene, etc.; Li-Co-Ni-based materials; titanium oxide; lithium titanium oxide, etc.

[0108] The following materials can be used: graphite, such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers, such as carbon fiber and metal fiber; fluorinated carbon; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; or conductive materials, such as polyphenylene derivatives.

[0109] As an example, as a negative electrode active material, a mixture of carbon and graphite materials (80% to 95% by weight) and SiO2 (5% to 20% by weight) can be used, and the carbon and graphite materials can be a mixture of graphite and / or acetylene black and carbon nanotubes in a weight ratio of 1:0.05 to 0.5.

[0110] Furthermore, there are no particular restrictions on the negative electrode current collector, as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, nickel, titanium, calcined carbon, etc., can be used, and copper or stainless steel with surface treatments of carbon, nickel, titanium, silver, etc., can also be used. In addition, similar to the positive electrode current collector, the negative electrode current collector can have fine irregularities formed on its surface to improve the adhesion of the negative electrode active material, and various forms such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics are possible. Furthermore, considering the conductivity and total thickness of the negative electrode to be manufactured, the average thickness of the negative electrode current collector can be appropriately applied in the range of 3 μm to 500 μm.

[0111] Furthermore, the separator is positioned between the positive and negative electrodes and is an insulating film with high ion permeability and mechanical strength. While there are no particular limitations on the separator, as long as it is commonly used in the art, specifically, sheets or nonwoven fabrics made of chemically resistant and hydrophobic polypropylene, glass fiber, polyethylene, etc., can be used. In some cases, composite separators can be used where inorganic / organic particles are coated onto a porous polymer substrate (such as sheets or nonwoven fabrics) using an organic binder polymer. When a solid electrolyte, such as a polymer, is used as the electrolyte, the solid electrolyte can also serve as the separator. Furthermore, the average pore size of the separator can be from 0.01 μm to 10 μm, and the average thickness can be from 5 μm to 300 μm.

[0112] On the other hand, the electrode assembly can be housed in a cylindrical, prismatic, or pouch cell while being wound in a roll, or it can be housed in a pouch cell in a folded or stacked-folded form.

[0113] As an example, electrode assemblies can be housed in cylindrical or pouch cells while being wound in a roll.

[0114] Lithium secondary batteries

[0115] Another aspect of the present invention provides a lithium secondary battery comprising the above-described electrode assembly.

[0116] The lithium secondary battery according to the present invention can have a structure in which the electrode components are impregnated with a liquid electrolyte containing lithium salt.

[0117] In this case, a lithium-containing liquid electrolyte can be composed of a liquid electrolyte and a lithium salt. Non-aqueous organic solvents, organic solid electrolytes, and inorganic solid electrolytes can be used as liquid electrolytes.

[0118] As non-aqueous organic solvents, aprotic organic solvents such as N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, etc., can be used.

[0119] As organic solid electrolytes, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyalginate lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ion-dissociating groups, etc.

[0120] As an inorganic solid electrolyte, for example, nitrides, halides or sulfates of Li can be used, such as Li3N, LiI, Li5Ni2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2, etc.

[0121] Lithium salts are substances that are readily soluble in non-aqueous electrolytes, and can be used in applications such as LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB. 10 Cl 10 LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylic acids, lithium tetraphenylborate, lithium imide, etc.

[0122] In addition, to improve charge / discharge characteristics, flame retardancy, etc., the following can be added to the liquid electrolyte: pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, (condensed) glycol dimethyl ethers, hexamethylphosphoryltriamine, nitrobenzene derivatives, sulfur, quinone imine dyes, and N-substituted compounds. Examples of suitable solvents include azole ketones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, and aluminum trichloride. In some cases, to impart non-flammability, halogenated solvents such as carbon tetrachloride and trifluoroethylene may be further included. Carbon dioxide gas may also be included to improve high-temperature storage properties. Furthermore, fluoroethylene carbonate (FEC) and propylene sulfonate lactone (PRS) may be further included.

[0123] On the other hand, another aspect of the present invention provides a battery module comprising the above-mentioned secondary battery as a unit battery, and also provides a battery pack comprising the battery module.

[0124] The battery pack can be used as a power source for medium to large-sized devices that require high-temperature stability, high-rate characteristics, and long-cycle characteristics. Specific examples of such medium to large-sized devices include: power tools powered by electric motors; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled vehicles, including electric bicycles (E-bicycles) and electric scooters (E-scooters); electric golf carts; and power storage systems, etc. More specific examples include HEVs, but the present invention is not limited thereto.

[0125] Preferred implementation scheme

[0126] The invention will be described in more detail below with reference to embodiments and experimental examples.

[0127] However, it should be understood that the following embodiments and experimental examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0128] Preparation of sacrificial cathode materials in Examples 1 to 5 and Comparative Examples 1 and 2.

[0129] Lithium oxide (Li₂O, unimodal distribution) and cobalt oxide (CoO) were added to a reactor at a molar ratio of 3.0 to 3.03 and dry-mixed uniformly using a mixer for approximately 30 minutes. The prepared raw material mixture was then placed in an electric furnace and calcined at approximately 700°C for 10 hours under an argon (Ar) atmosphere to obtain lithium cobalt oxide (Li₆CoO₄). In this case, the average particle size (D) of the lithium oxide (Li₂O) was... 50 ) and minimum granularity (D min The partial pressures of oxygen (O2) contained in argon during calcination are shown in Table 1 below.

[0130] [Table 1]

[0131]

[0132] Experimental Example 1.

[0133] To evaluate the conductivity of the sacrificial cathode material prepared according to the present invention, the conductivity of the sacrificial cathode materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was measured. In this case, the measurement was performed by using a powder resistivity meter to measure the volume and sheet resistance as a function of pressure for each sacrificial cathode material using a four-point probe method, and the powder conductivity was calculated using the measured volume and the mass placed in the sample, and the results are shown in Table 2 below.

[0134] [Table 2]

[0135]

[0136] As shown in Table 2, it can be seen that the sacrificial cathode material prepared in the examples exhibits a 1×10⁻⁶ Ω·cm²·d⁻¹ ... -3 S / cm up to 8.5×10 -3 The conductivity S / cm thus satisfies the powder conductivity according to the present invention.

[0137] Experimental Example 2.

[0138] To evaluate the performance of the sacrificial cathode material prepared according to the present invention, experiments were conducted as follows.

[0139] A) Measurement of gas emissions

[0140] N-methylpyrrolidone solvent was placed in a homogenizer and each of the sacrificial cathode materials, acetylene black conductive materials, modified silanol binders and dispersants prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were added in a weight ratio of 95:3:1.7:0.3. The mixture was then mixed at 3000 rpm for 60 minutes to prepare a pre-dispersion.

[0141] The prepared pre-dispersion was combined with the positive electrode active material (LiNi). 0.6 Co 0.2 Mn 0.2 O2) is mixed so that the content of sacrificial cathode material is 2 parts by weight relative to 100 parts by weight of positive electrode active material. The positive electrode active material, PVdF binder, and carbon black conductive material, mixed in N-methylpyrrolidone solvent, are placed in a homogenizer at a weight ratio of 96:1:3 and then dispersed at 3000 rpm for 80 minutes to prepare a positive electrode slurry. The prepared positive electrode slurry is coated onto one surface of an aluminum current collector, dried at 100°C, and then rolled to manufacture the positive electrode.

[0142] The positive electrode and lithium metal counter electrode are used to manufacture a 2032-type battery. A separator made of porous polyethylene (PE) membrane (thickness: about 16 μm) is placed between the positive electrode and the lithium metal counter electrode, and a liquid electrolyte is injected to manufacture a half-cell battery.

[0143] In this case, as the liquid electrolyte, a solution obtained by mixing ethylene carbonate (EC): ethyl methyl carbonate (EMC) (volume ratio = 3:7), lithium hexafluorophosphate (LiPF6, 0.7M), lithium bis(fluorosulfonyl)imide (LiFSI, 0.5M), lithium tetrafluoroborate (LiBF4, 0.2 wt%), ethylene carbonate (VC, 2 wt%), 1,3-propanesulfonyl lactone (PS, 0.5 wt%), and ethylene sulfate (Esa, 1 wt%) is used.

[0144] The manufactured batteries were charged and discharged once at 4.5C / 0.3C for formation. Then, the amount of gas produced by the manufactured batteries was analyzed during each of 50 charge / discharge cycles at 45°C under 0.3C / 0.3C conditions, and during storage at 60°C for 4 weeks. The results are shown in Table 3 below. Figure 1 and Figure 2 middle.

[0145] [Table 3]

[0146]

[0147] As shown in Table 3 and Figure 1 and Figure 2 As shown, the sacrificial cathode material prepared according to the present invention exhibits a reduced amount of gas generated during the charging / discharging process. This is because the average particle size (D) of the lithium precursor (i.e., lithium oxide (Li₂O)) used to prepare the sacrificial cathode material is significantly reduced. 50 The fact that the oxygen (O2) in the inert gas used for calcination is relatively large and at a lower partial pressure allows us to confirm this trend.

[0148] B) Evaluation of initial charge and discharge

[0149] In addition to using a solution obtained by mixing EMC: dimethyl carbonate (DMC): diethyl carbonate (DEC) (volume ratio = 1:2:1), lithium hexafluorophosphate (LiPF6, 1.0M), and VC (2% by weight) as the liquid electrolyte, a half-cell type battery was manufactured in the same manner as that used in measuring gas emissions.

[0150] The manufactured batteries were charged and discharged (formed) to measure the initial charge capacity. In this case, charging and discharging (formation) were performed at 25°C under conditions of 70mAh / 3mAh, and the results are shown in Table 4 below. Figure 3 middle.

[0151] [Table 4]

[0152]

[0153] As shown in Table 4 and Figure 3 As shown, it can be seen that the sacrificial cathode material prepared according to the present invention is effective in improving battery performance.

[0154] Specifically, the battery incorporating the sacrificial cathode material of the embodiment exhibits an initial charge capacity that increases with the average particle size (D) of the lithium precursor (i.e., lithium oxide (Li2O)). 50 The trend of decreasing and increasing particle size (D) of lithium oxide (Li₂O) indicates that as the average particle size (D) of lithium oxide (Li₂O) decreases, the particle size increases. 50 The smaller the charge capacity, the higher the gas production during activation, charging / discharging, and / or storage.

[0155] These results demonstrate that by using lithium precursors of specific sizes during preparation to adjust the conductivity of the sacrificial cathode material within a specific range, the sacrificial cathode material prepared according to the present invention is effective in enhancing battery performance and can reduce the gases, particularly oxygen (O2), generated in the electrode assembly during battery charging and discharging, thereby effectively improving the stability and lifespan of batteries containing the sacrificial cathode material.

[0156] Although the invention has been described above with reference to exemplary embodiments, those skilled in the art will understand that various variations and changes can be made without departing from the spirit and scope of the invention as set forth in the appended claims.

[0157] Therefore, the scope of the present invention should be defined by the appended claims, and not by the detailed description in the specification.

Claims

1. A method for preparing a sacrificial cathode material, the method comprising the following steps: A mixture of Li₂O and CoO raw materials was calcined to prepare a lithium cobalt metal oxide represented by the following chemical formula 1. in, The Li₂O has an average particle size D of 10 μm to 50 μm. 50 ,and The prepared sacrificial cathode material has a density of 5 × 10⁻⁶. -4 Conductivity above S / cm [Chemical Formula 1] Li x Co (1-y) M y O 4-z A z In chemical formula 1, M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni. A is a halogen that substitutes for oxygen, and x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.

001.

2. The method according to claim 1, wherein, The conductivity is 1×10 -3 S / cm up to 9×10 -3 Within the range of S / cm.

3. The method according to claim 1, wherein, The calcination is carried out at 500°C to 800°C.

4. The method according to claim 1, wherein, The raw material mixture of Li2O and CoO is obtained by mixing Li2O and CoO in a molar ratio of 2 to 4:

1.

5. The method according to claim 1, wherein, The Li₂O has an average particle size D of 15 μm to 35 μm. 50 .

6. The method according to claim 1, wherein, The Li₂O has a minimum particle size D of 2 μm or more. min .

7. The method according to claim 1, wherein, The Li₂O has a unimodal particle size distribution. 80% to 90% of all particles are in the particle size range of 10 μm to 45 μm, and 65% to 75% of all particles are in the particle size range of 15 μm to 35 μm.

8. The method according to claim 1, wherein, The sacrificial cathode material satisfies the following formula 1: [Formula 1] V gas = -1.07 × D Li2O + A In Formula 1, V gas V represents the amount of gas generated in an electrode assembly containing sacrificial cathode material. gas The unit is mL / g. D Li2O The average particle size D of Li₂O is represented by... 50 D Li2O The unit is μm, and A is a constant, and satisfies 128≤A≤132.

9. A positive electrode, said positive electrode comprising: Positive current collector; and The positive electrode mixture layer on the positive current collector comprises a positive electrode active material, a conductive material, an organic binder polymer, and a sacrificial positive electrode material. in, The sacrificial cathode material is prepared by the method described in claim 1. The sacrificial cathode material comprises a lithium cobalt metal oxide represented by the following chemical formula 1, and has a density of 5 × 10⁻⁶. -4 Conductivity above S / cm [Chemical Formula 1] Li x Co (1-y) M y O 4-z A z In chemical formula 1, M is selected from at least one of the following: Ti, Al, Zn, Zr, Mn, and Ni. A is a halogen that substitutes for oxygen, and x, y, and z satisfy 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.

001.

10. The positive electrode according to claim 9, wherein, The positive electrode active material is a lithium composite transition metal oxide containing two or more elements selected from the following: Ni, Co, Mn, Al, Zn, Ti, Mg, Cr and Zr.

11. The positive electrode according to claim 9, wherein, The content of the sacrificial cathode material is 0.001 to 5.0 parts by weight relative to 100 parts by weight of the positive electrode active material.

12. An electrode assembly comprising the positive electrode of claim 9.

13. A lithium secondary battery comprising the electrode assembly of claim 12.

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