Positive active material, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to positive active material, a positive electrode and a lithium secondary battery comprising same, the positive electrode material comprising: first positive active material in the single-crystal form; and second positive active material having an average diameter (D50), which is larger than that of the first positive active material, wherein the first positive active material is a lithium-rich manganese-based layered oxide comprising both a Li2MnO3 phase and a LiMO2 (where M is an element including at least one selected from Ni, Co and Mn) phase, and the second positive active material is a lithium nickel-based layered oxide containing nickel in an amount of 50 mol% or more and less than 80 mol% on the basis of the total mole of metals that exclude lithium.

Description

Cathode material, cathode containing same, and lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0091824, filed July 14, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode material, a cathode comprising the same, and a lithium secondary battery, and more particularly, to a cathode material comprising a lithium-excess manganese oxide and a Mid-Ni lithium nickel oxide, and a cathode comprising the same, and a lithium secondary battery.

[0005]

[0006] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. For lithium secondary batteries to achieve high energy density, output, and lifespan, improving the performance of the cathode active material is essential. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0007] Recently, with the increasing use of lithium secondary batteries, active development is being conducted on high-nickel NCM cathode materials with increased nickel content to increase the energy density of the batteries, especially capacity. However, high-nickel NCM cathode materials have a high fire risk due to structural instability caused by the high nickel content. On the other hand, mid-nickel NCM cathode materials have a nickel content of around 60 mol%, and have the advantage of structural stability compared to high-nickel NCM cathode materials. However, the low nickel content reduces the capacity, which in turn reduces the energy density.

[0008] Therefore, there is a need to develop a cathode material that is structurally stable while also having improved energy density.

[0009]

[0010] The problem to be solved in the present invention is to improve the energy density and thermal stability of a cathode material, thereby improving the performance of a battery including the cathode material.

[0011] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery including the positive electrode material.

[0012]

[0013] To solve the above problem, the present invention provides a cathode material, a cathode, and a lithium secondary battery.

[0014]

[0015] (1) The present invention comprises a first positive electrode active material in the form of a single particle; and an average particle diameter (D) greater than that of the first positive electrode active material. 50 ) includes a second cathode active material; wherein the first cathode active material is a lithium-excess manganese oxide that simultaneously includes a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, and the second cathode active material is a lithium nickel oxide that includes nickel in an amount of 50 mol% or more and less than 80 mol% based on the total moles of metals other than lithium.

[0016] (2) In the present invention, in the above (1), the first positive electrode active material has an average particle diameter (D 50 ) provides a cathode material having a thickness of 0.1㎛ or more and less than 3.5㎛.

[0017] (3) In the present invention, in the above (1) or (2), the second positive electrode active material has an average particle diameter (D 50 ) provides a cathode material having a thickness of 3.5㎛ or more and 10.0㎛ or less.

[0018] (4) The present invention provides a cathode material in any one of the above (1) to (3), wherein the second cathode active material is in the form of a single particle or a secondary particle.

[0019] (5) The present invention provides a cathode material in any one of the above (1) to (4), wherein the first cathode active material has a composition represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li 1+x1 Ni a1 Mn b1 M 1 c1 O y1

[0022] In the above chemical formula 1,

[0023] M 1 is at least one selected from Co, Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B,

[0024] 0.05≤x1≤0.25, 0 <a1≤0.5, 0.5≤b1≤0.75, 0≤c1≤0.15, 0≤y1≤2.0이고,

[0025] x1+a1+b1+c1=1.0.

[0026] (6) The present invention provides a cathode material in any one of (1) to (5) above, wherein the second cathode active material has a composition represented by the following chemical formula 2.

[0027] [Chemical Formula 2]

[0028] Li 1+x2 Ni a2 Co b2 Mn c2 M 2 d2 O2

[0029] In the above chemical formula 2,

[0030] M 2is at least one selected from Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B,

[0031] 0.9≤1+x2≤1.1, 0.50≤a2<0.80, 0 <b2<0.50, 0<c2<0.50, 0≤d2≤0.1이고,

[0032] a2+b2+c2+d2=1.0.

[0033] (7) The present invention provides a cathode material in which the weight ratio of the first cathode active material and the second cathode active material is 1:0.5 to 4 in any one of the above (1) to (6).

[0034] (8) The present invention is a method for producing a pellet having a density of 2.7 g / cm in any one of the above (1) to (7). 2 3.3g / cm 2 It provides a positive electrode material.

[0035] (9) The present invention provides a cathode comprising a cathode material according to any one of (1) to (8).

[0036] (10) The present invention provides a lithium secondary battery including a positive electrode according to (9).

[0037]

[0038] The cathode material of the present invention simultaneously includes a small particle lithium-rich manganese oxide in the form of a single particle and a large particle Mid-Ni lithium nickel oxide, and thus has excellent energy density and stability, and as a result, the performance of a battery including the cathode material, such as capacity and energy density, can be improved, and the cathode active material particles can be prevented from breaking during battery manufacturing or operation.

[0039] The cathode material of the present invention has a stable structure and can be used as a cathode material for high voltages of 4.4 V or higher.

[0040]

[0041] Figure 1 is a cross-sectional EPMA data of a cathode including the cathode material of Example 1.

[0042] Figure 2 is a cross-sectional EPMA data of a cathode including the cathode material of Example 2.

[0043] Figure 3 shows XRD data of the cathode materials of Examples 1 to 6 and Comparative Examples 1 and 3.

[0044]

[0045] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0046] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0047] In this specification, the term "single particle form" refers to a form composed of 10 or fewer primary particles, in contrast to the spherical secondary particle form formed by the agglomeration of tens to hundreds of primary particles. Specifically, the "single particle form" may be a single particle form composed of one primary particle, or a secondary particle form in which several primary particles are agglomerated.

[0048] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0049] In this specification, the average particle diameter (D 50 ) can be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve. The average particle size (D 50) can be measured, for example, using a laser diffraction method, and more specifically, after dispersing the positive active material in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac Bluewave) and irradiated with ultrasonic waves at an output of 40 W, and then the average particle diameter (D) corresponding to 50% of the particle size distribution in the measuring device is measured. 50 ) can be produced.

[0050] In this specification, the pellet density is a value calculated by Equation 2 below when a force equivalent to 2,000 kgf is applied to form a pellet using an automatic pellet press. Specifically, the pellet density is a value obtained according to (1) to (3) below.

[0051] (1) Using a universal testing machine (UTM: Universal Testing Machine, Instron, Model 5966), adjust the zero point for thickness using a cylindrical mold for a circular pellet holder.

[0052] (2) Place the positive electrode active material in the above circular pellet holder, apply force until a force equivalent to 2,000 kgf is reached, and measure the thickness of the formed pellet.

[0053] (3) Calculate the pellet volume using the following equation 1, and calculate the pellet density using the following equation 2.

[0054] [Formula 1]

[0055] Pellet volume (cm) 3 ) = π(radius of the circular pellet holder) 2 × Pellet thickness

[0056] [Formula 2]

[0057] Pellet density (g / cm) 3 ) = Positive active material weight (g) / Pellet volume (cm 3 )]]

[0058]

[0059] cathode material

[0060] The cathode material according to the present invention comprises a first cathode active material in the form of single particles; and an average particle diameter (D) greater than that of the first cathode active material. 50 ) includes a second cathode active material having a large mass. At this time, the first cathode active material is a lithium-excess manganese oxide including both a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, and the second cathode active material is a lithium nickel oxide including nickel in an amount of 50 mol% or more and less than 80 mol% based on the total moles of metals other than lithium.

[0061] The present inventors have found that when a cathode material simultaneously includes a small-particle lithium-rich manganese oxide in the form of a single particle and a large-particle Mid-Ni lithium nickel oxide, when the cathode material is applied to a cathode for a secondary battery, the electrode density can be improved, particle breakage can be minimized, when the cathode material is applied to a secondary battery, the capacity and energy density of the battery can be improved, and when the cathode material is applied to a secondary battery, the cathode active material particles can be prevented from breaking during battery manufacturing or operation, thereby suppressing gas generation, and the cathode material can be used as a cathode material for a high voltage of 4.4 V or higher, and have completed the present invention.

[0062] Meanwhile, as mentioned in the background technology of the above invention, with the recent increase in the scope of use of lithium secondary batteries, there is a great demand for increased capacity and energy density. However, if only the second cathode active material is used as the cathode material, the nickel content is not high, so there are shortcomings in terms of capacity and energy density. On the other hand, if the nickel content in the lithium nickel-based oxide is 80 mol% or more, the battery capacity (discharge capacity) increases, but there is a problem of decreased thermal stability.

[0063]

[0064] The above cathode material is a first cathode active material in the form of a single particle; and an average particle diameter (D) greater than that of the first cathode active material 50 ) including a large second positive electrode active material; since the first positive electrode active material is filled between the second positive electrode active materials, the pellet density is high, and the stress applied to the second positive electrode active material is distributed, so that particle breakage can be prevented during rolling for electrode manufacturing.

[0065]

[0066] The above first cathode active material can be manufactured through a process of dry mixing lithium raw materials and transition metal raw materials, followed by sintering. However, the present invention is not limited thereto.

[0067] The second positive electrode active material can be obtained by preparing a precursor through co-precipitation in the same manner as in the prior art, mixing it with a lithium raw material, and calcining it, but is not limited thereto. Meanwhile, as described below, the second positive electrode active material may be in the form of secondary particles or single particles, and when the second positive electrode active material is in the form of single particles, the calcination temperature may be higher than when the second positive electrode active material is in the form of secondary particles. Additionally, when the second positive electrode active material is in the form of single particles, it may be prepared through a process of dry mixing a lithium raw material and a transition metal raw material, and then calcining them, similar to the first positive electrode active material.

[0068]

[0069] According to the present invention, the first positive electrode active material has an average particle diameter (D 50 ) may be 0.1㎛ or more and less than 3.5㎛. Specifically, the average particle diameter (D of the first positive electrode active material 50 ) can be 0.1㎛, 0.2㎛, 0.3㎛, 0.4㎛, 0.5㎛, 0.6㎛, 0.7㎛, 0.8㎛, 0.9㎛ or more, 2.0㎛, 2.5㎛, 3.0㎛ or less, or less than 3.5㎛. In this case, there is an advantage in terms of long-term life and capacity of the cathode material.

[0070] According to the present invention, the second positive electrode active material has an average particle diameter (D 50 ) may be 3.5㎛ or more and 10.0㎛ or less. Specifically, the average particle diameter (D of the second positive electrode active material 50 ) may be 3.5㎛, 4.0㎛ or more, 5.0㎛, 6.0㎛, 7.0㎛, 8.0㎛, 9.0㎛, or 10.0㎛ or less.

[0071] The average particle diameter (D) of the first positive electrode active material and the second positive electrode active material 50 ) is within the above range, the second positive electrode active material can be appropriately distributed between the first positive electrode active material, so that the filling rate can be excellent.

[0072]

[0073] According to the present invention, the second positive electrode active material may be in the form of a single particle or a secondary particle. If the second positive electrode active material is in the form of a single particle, it has the advantage of less particle breakage and a higher pellet density, and if it is in the form of a secondary particle, it has the advantage of improved capacity expression.

[0074]

[0075] According to the present invention, the first positive electrode active material may have a composition represented by the following chemical formula 1 to improve charge / discharge efficiency, initial charge / discharge efficiency (particularly, charge / discharge efficiency at 0.1 C) and discharge capacity in the activation process of the battery.

[0076] [Chemical Formula 1]

[0077] Li 1+x1 Ni a1 Mn b1 M 1 c1 O y1

[0078] In the above chemical formula 1,

[0079] M 1is at least one selected from Co, Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B, specifically at least one selected from Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B,

[0080] 0.05≤x1≤0.25, 0 <a1≤0.5, 0.5≤b1≤0.75, 0≤c1≤0.15, 0≤y1≤2.0이고,

[0081] x1+a1+b1+c1=1.0.

[0082] Meanwhile, the first positive electrode active material may not contain expensive cobalt, and may improve the performance of a lithium secondary battery without containing cobalt.

[0083] x1 can be more specifically 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, or less than or equal to 0.15, 0.20, or 0.25.

[0084] a1 can be more specifically greater than 0, 0.10, 0.15, 0.20 and less than or equal to 0.30, 0.40, 0.50.

[0085] b1 can be specifically greater than or equal to 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, or less than or equal to 0.60, 0.65, 0.70, or 0.75.

[0086] c1 can be specifically greater than or equal to 0, 0.05, 0.10, or 0.15.

[0087] y1 can be specifically 0, 0.5, 1.0, 1.5 or greater, 2.0 or less, and more specifically 2.0.

[0088]

[0089] According to the present invention, the second positive electrode active material may have a composition represented by the following chemical formula 2 in order to realize a positive electrode material having a stable structure and high battery capacity.

[0090] [Chemical Formula 2]

[0091] Li 1+x2 Ni a2 Co b2 Mn c2 M 2 d2 O2

[0092] In the above chemical formula 2,

[0093] M 2 is at least one selected from Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B,

[0094] 0.9≤1+x2≤1.1, 0.50≤a2<0.80, 0 <b2<0.50, 0<c2<0.50, 0≤d2≤0.1이고,

[0095] a2+b2+c2+d2=1.0.

[0096] 1+x2 can be more specifically 0.9, 0.95 or greater, 1.05, 1.10 or less, or even 0.

[0097] a2 refers to the atomic fraction of nickel among the metal elements excluding lithium in the second positive electrode active material, and may be 0.50, 0.55, 0.60 or more, 0.70, 0.75 or less, or less than 0.80.

[0098] b2 refers to the atomic fraction of cobalt among the metal elements excluding lithium in the second positive electrode active material, and may be greater than 0, 0.05 or more, 0.20, 0.30, 0.40 or less, or less than 0.50.

[0099] c2 refers to the atomic fraction of manganese among the metal elements excluding lithium in the second positive electrode active material, and may be greater than 0, 0.05, 0.10, 0.15 or more, 0.35, 0.40, 0.45 or less, or less than 0.50.

[0100] d2 refers to the atomic fraction of the M2 element among the metal elements excluding lithium in the second positive electrode active material, and can be 0 or more, 0.05, or 0.10 or less.

[0101]

[0102] The weight ratio of the first positive electrode active material and the second positive electrode active material may be 1:0.5 to 4. Specifically, the weight ratio of the first positive electrode active material and the second positive electrode active material may be 1:0.5 to 4, 1:0.7 to 4, 1:0.7 to 3, and 1:0.7 to 2.5. When the weight ratio of the first positive electrode active material and the second positive electrode active material is within the above range, the packing density of the particles can be increased, and as a result, when applied to a battery, the capacity and energy density of the battery can be increased.

[0103]

[0104] According to the present invention, the cathode material has a pellet density of 2.7 g / cm 2 3.3g / cm 2 It can be. Specifically, the pellet density of the above cathode material is 2.7 g / cm 2 , 2.8g / cm 2 , 2.9g / cm 2 More than 3.2g / cm 2 , 3.3g / cm 2 It may be as follows. When the pellet density of the positive electrode material is within the above range, the capacity and energy density can be improved, and the positive electrode active material particles can be prevented from breaking during battery manufacturing or operation.

[0105]

[0106] anode

[0107] The present invention provides a cathode comprising the above cathode material.

[0108] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode material.

[0109] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and does not react within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0110] The above-mentioned positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode material, as needed. In this case, the positive electrode material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0111] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0112] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0113] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode material is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer (positive electrode slurry) prepared by dissolving or dispersing the above positive electrode material and optionally a binder, a conductive material, and a dispersant in a solvent as needed, and then drying and rolling the composition, or by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support onto a positive electrode current collector.

[0114] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0115]

[0116] lithium secondary battery

[0117] The present invention provides a lithium secondary battery including the positive electrode.

[0118]

[0119] The lithium secondary battery may include the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0120] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0121] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0122] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0123] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical or fibrous shapes, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0124] The binder of the above-described negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0125] The conductive material of the above-described negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0126] The above negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer (negative electrode slurry) prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0127] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0128] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0129] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0130] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0131] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0132]

[0133] A lithium secondary battery including a cathode material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0134] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0135] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0136] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0137] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0138]

[0139] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0140]

[0141] Manufacturing example

[0142] Manufacturing Example 1

[0143] Li2CO3, NiCO3, and MnCO3 were dry mixed in amounts such that the molar ratio of lithium:nickel:manganese (Li:Ni:Mn) was 1.143:0.287:0.57, and pulverized using a High Energy Ball milling device (Zoz) at 1600 rpm for 30 minutes, and then sintered at 1000°C for 9 hours in an air atmosphere to produce a sintered product. The sintered product was pulverized using a Jet mill device under 3.5 bar conditions, and Li 1.143 Ni 0.287 Mn 0.57 It has a composition represented by O2 and an average particle size (D 50 ) was prepared as a single particle lithium-excess manganese oxide (A1) having a particle size of 0.93 μm.

[0144]

[0145] Manufacturing Example 2

[0146] Ni 0.65 Co 0.15 Mn 0.2(OH)2 and Li2CO3 were dry mixed in an amount such that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and calcined at 835℃ for 8 hours in an air atmosphere to obtain LiNi 0.65 Co 0.15 Mn 0.2 It has a composition represented by O2 and an average particle size (D 50 ) was prepared as a secondary particle of lithium nickel oxide (B1) having a size of 4.13 μm.

[0147]

[0148] Manufacturing Example 3

[0149] Ni 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 were dry mixed in an amount such that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and then calcined for the first time at 940℃ for 6 hours in an air atmosphere, and then calcined for the second time at 810℃ for 9 hours to obtain LiNi 0.6 Co 0.1 Mn 0.3 It has a composition represented by O2 and an average particle size (D 50 ) was prepared as a single particle lithium nickel oxide (B2) having a particle size of 4.40 μm.

[0150]

[0151] Manufacturing Example 4

[0152] Li2CO3, Ni(OH)2, and MnCO3 were mixed in pure water in an amount such that the molar ratio of lithium:nickel:manganese (Li:Ni:Mn) was 1.15:0.30:0.55 (solid content: 20 wt%), and wet mixing was performed in a ball mill using zirconia balls for 1 hour. Afterwards, the zirconia balls were removed, and the solids were pulverized using wet grinding equipment (NETZCH, MiniCer) to obtain the average particle diameter (D) of the solids. 50) was prepared as a slurry having a particle size of 0.2 μm. Afterwards, the slurry was spray-dried using a spray drying device (Buchi, B-290) at an inlet hot air temperature of 200°C and an exhaust hot air temperature of 90°C or higher to obtain a dried product. The dried product was fired at 1000°C for 12 hours in an air atmosphere to produce a fired product. The fired product was pulverized using a jet-mill device (Isac E&C, Micron-master air jetmill, 3.5 bar), and Li 1.15 Ni 0.30 Mn 0.55 It has a composition represented by O2 and an average particle size (D 50 ) was prepared as a single particle of lithium-excess manganese oxide (A2) having a particle size of 1.24 μm.

[0153]

[0154] Examples and Comparative Examples

[0155] Example 1

[0156] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A1) in the form of a single particle manufactured in Manufacturing Example 1 and the lithium nickel oxide (B1) in the form of a secondary particle manufactured in Manufacturing Example 2 at a weight ratio of 4:6.

[0157]

[0158] Example 2

[0159] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A1) in the form of single particles manufactured in Manufacturing Example 1 and the lithium nickel oxide (B2) in the form of single particles manufactured in Manufacturing Example 3 in a weight ratio of 4:6.

[0160]

[0161] Example 3

[0162] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A2) in the form of a single particle manufactured in Manufacturing Example 4 and the lithium nickel oxide (B1) in the form of a secondary particle manufactured in Manufacturing Example 2 at a weight ratio of 1:0.7.

[0163]

[0164] Example 4

[0165] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A2) in the form of a single particle manufactured in Manufacturing Example 4 and the lithium nickel oxide (B1) in the form of a secondary particle manufactured in Manufacturing Example 2 at a weight ratio of 1:1.

[0166]

[0167] Example 5

[0168] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A2) in the form of a single particle manufactured in Manufacturing Example 4 and the lithium nickel oxide (B1) in the form of a secondary particle manufactured in Manufacturing Example 2 at a weight ratio of 1:1.5.

[0169]

[0170] Example 6

[0171] A cathode material was manufactured by mixing the lithium-excess manganese oxide (A2) in the form of a single particle manufactured in Manufacturing Example 4 and the lithium nickel oxide (B1) in the form of a secondary particle manufactured in Manufacturing Example 2 at a weight ratio of 1:2.3.

[0172]

[0173] Comparative Example 1

[0174] The lithium nickel oxide (B1) in the form of the above secondary particles was used as the positive electrode active material of Comparative Example 1.

[0175]

[0176] Comparative Example 2

[0177] The lithium nickel oxide (B2) in the form of single particles was used as the positive electrode active material of Comparative Example 2.

[0178]

[0179] Comparative Example 3

[0180] The lithium-excess manganese oxide (A1) in the form of single particles was used as the positive electrode active material of Comparative Example 3.

[0181]

[0182] Comparative Example 4

[0183] The lithium-excess manganese oxide (A2) in the form of single particles was used as the positive electrode active material of Comparative Example 4.

[0184]

[0185] Experimental example

[0186] Experimental Example 1: Analysis of positive electrode active material

[0187] (EPMA)

[0188] For each of the above examples and comparative examples, a cathode material or cathode active material, Super P as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 92.5:3:4.5 in an N-methylpyrrolidone (NMP) solvent to prepare a cathode slurry. The prepared cathode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to a porosity of 22% to prepare a cathode.

[0189] To create a flat surface for EPMA cross-sectional analysis, the anode was subjected to Ar-ion milling to obtain a cross-section of the anode sample, and the cross-sectional image of the anode sample was observed using JEOL JXA-iHP200F equipment.

[0190] Figures 1 and 2 are EPMA data of Examples 1 and 2, respectively. From Figures 1 and 2, it was confirmed that the cathode materials of Examples 1 and 2 contained a well-mixed lithium-excess manganese oxide (A1) in the form of single particles and a lithium nickel oxide (B1) in the form of secondary particles or a lithium nickel oxide (B2) in the form of single particles.

[0191] (XRD)

[0192] Using XRD (Bruker, D8 endeavor), the XRD spectra of the positive electrode materials or positive electrode active materials of each of the examples and comparative examples were obtained, and are shown in Fig. 3. Fig. 3 shows XRD data of the positive electrode materials of Examples 1 to 6 and Comparative Examples 1 and 3.

[0193] Referring to FIG. 3, it can be confirmed that a super-structure peak (A region), which is a characteristic of lithium-excess manganese oxide, is observed in the cathode materials of Examples 1 to 6.

[0194]

[0195] Experimental Example 2: Evaluation of Pellet Density (Press Density)

[0196] Using a UTM (Universal Testing Machine, Instron 5966) equipment, a cylindrical mold was used to adjust the zero point for thickness on a circular pellet holder with a diameter of 4 mm. Then, 40 mg each of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 2 to 3 was placed into the circular pellet holder, and a force was applied until a force corresponding to 2,000 kgf was reached, and the thickness of the formed pellet was measured. Then, the pellet volume was calculated using the following Equation 1, and the pellet density was calculated using the following Equation 2, and the results are shown in Table 1.

[0197] Using a compression density meter (Hantech, HPRM-A1), the zero point for thickness was adjusted using a cylindrical mold for a circular pellet holder with a diameter of 22 mm. Then, 2.5 g each of the positive electrode active materials manufactured in Examples 3 to 6 and Comparative Examples 1 and 4 was placed into the circular pellet holder, and a force was applied until a force corresponding to 2,000 kgf was reached, and the thickness of the formed pellet was measured. Then, the pellet volume was calculated using the following Equation 1, and the pellet density was calculated using the following Equation 2, and the results are shown in Table 1.

[0198] [Formula 1]

[0199] Pellet volume (cm) 3 ) = π(radius of the circular pellet holder) 2 × Pellet thickness

[0200] [Formula 2]

[0201] Pellet density (g / cm) 3 ) = Positive active material weight (g) / Pellet volume (cm 3 )

[0202]

[0203] Experimental Example 3: Battery Characteristics Evaluation

[0204] For each of the above examples and comparative examples, the positive electrode active material, Super P as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 92.5:3:4.5 in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to a porosity of 22% to prepare a positive electrode.

[0205] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case and an electrolyte solution (additives: LiBF 42%, FEC 5%) containing 1 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 was injected to manufacture a coin-type half-cell.

[0206] Coin-type half-cells containing the positive electrode active materials of each of the above examples and comparative examples were charged to 4.65 V in CC (0.1 C)-CV (Cut-off current: 0.05 C) mode at 45°C, and then discharged to 2.0 V at 0.1 C to perform an activation process (formation). Subsequently, they were charged to 4.4 V in CC (0.1 C)-CV (Cut-off current: 0.05 C) mode at 25°C, and then discharged to 2.5 V at 0.1 C to measure the initial discharge capacity, which is shown in Table 1 below.

[0207] Separation Pellet Density (g / cm) 3)Discharge capacity (mAh / g)Example 13.060203.59Example 23.181196.06Example 32.858189.22Example 42.884191.79Example 52.916193.96Example 62.830195.35Comparative example 12.574199.64Comparative example 23.132188.15Comparative example 31.823209.57Comparative example 42.708187.30

[0208] Referring to Table 1 above, it can be confirmed that the cathode materials of Examples 1 and 2 according to the present invention have significantly higher pellet densities than the cathode active materials of Comparative Examples 1 and 2, respectively, and have excellent discharge capacity under high voltage conditions. In addition, it can be confirmed that the cathode materials of Examples 1 and 2 have significantly higher pellet densities than the cathode active material of Comparative Example 3.

[0209] In addition, it can be confirmed that the cathode materials of Examples 3 to 6 according to the present invention have a significantly higher pellet density than the cathode active material of Comparative Example 1. In addition, it can be confirmed that the cathode materials of Examples 3 to 6 have a significantly higher pellet density than the cathode active material of Comparative Example 4, and have excellent discharge capacity under high voltage conditions.

[0210] In conclusion, it can be seen that the cathode material according to the present invention simultaneously comprises a small-particle lithium-rich manganese oxide in the form of a single particle and a large-particle mid-Ni lithium nickel oxide, thereby exhibiting excellent energy density and stability, and consequently improving the capacity characteristics of a battery comprising it. In addition, it can be seen that the cathode material according to the present invention can be used as a cathode material for high voltages of 4.4 V or higher.

Claims

1. A first positive electrode active material in the form of a single particle; and an average particle diameter (D) greater than that of the first positive electrode active material 50 ) contains a large second positive electrode active material; The above first cathode active material is a lithium-excess manganese oxide that simultaneously includes a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase, A cathode material wherein the second cathode active material is a lithium nickel-based oxide containing nickel in an amount of 50 mol% or more and less than 80 mol% based on the total moles of metals other than lithium.

2. In claim 1, The above first positive electrode active material has an average particle diameter (D 50 ) is a cathode material having a thickness of 0.1㎛ or more and less than 3.5㎛.

3. In claim 1, The above second positive electrode active material has an average particle diameter (D 50 ) A cathode material having a thickness of 3.5㎛ or more and 10.0㎛ or less.

4. In claim 1, A cathode material wherein the second cathode active material is in the form of a single particle or a secondary particle.

5. In claim 1, The above first positive electrode active material is a positive electrode material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x1 Ni a1 Mr b1 M 1 c1 O y1 In the above chemical formula 1, M 1 is at least one selected from Co, Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B, 0.05≤x1≤0.25, 0 <a1≤0.5, 0.5≤b1≤0.75, 0≤c1≤0.15, 0≤y1≤2.0이고, x1+a1+b1+c1=1.

0.

6. In claim 1, The above second positive electrode active material is a positive electrode material having a composition represented by the following chemical formula 2: [Chemical Formula 2] Li 1+x2 Ni a2 Co b2 Mr c2 M 2 d2 O2 In the above chemical formula 2, M 2 is at least one selected from Mo, W, V, Zr, Al, Nb, Ti, Y, Ta, Sn and B, 0.9≤1+x2≤1.1, 0.50≤a2<0.80, 0 <b2<0.50, 0<c2<0.50, 0≤d2≤0.1이고, a2+b2+c2+d2=1.

0.

7. In claim 1, A cathode material in which the weight ratio of the first cathode active material and the second cathode active material is 1:0.5 to 4.

8. In claim 1, Pellet density is 2.7g / cm 2 3.3g / cm 2 Bipolar material.

9. A cathode comprising a cathode material according to any one of claims 1 to 8.

10. A lithium secondary battery comprising a positive electrode according to claim 9.

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