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

Abstract

The present invention relates to a positive electrode material, and relates to a positive electrode material, a positive electrode comprising same, and a lithium secondary battery, the positive electrode material comprising: a first positive electrode active material having an olivine structure; and a second positive electrode active material which is a lithium nickel-based oxide having a layered structure with an average particle diameter (D50) larger than the first positive electrode active material, wherein the first positive electrode active material has an average particle diameter (D50) of 0.5-10 ㎛, contains 2-3.5 wt% of carbon (C), and has an average crystal size of 100 nm or more and less than 160 nm.

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. 10-2024-0003005, filed January 8, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery, and more particularly, to a cathode material including a cathode active material having an olivine structure and a cathode active material that is a lithium nickel-based oxide having a layered structure, and a cathode including the same and a lithium secondary battery.

[0005]

[0006] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0007] 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. Currently used cathode active materials include NCM-based cathode active materials containing nickel, cobalt, manganese, and / or aluminum, and LFP (lithium iron phosphate)-based cathode active materials. Meanwhile, improving the performance of cathode active materials is essential for lithium secondary batteries to achieve high energy density, output, and lifespan. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0008] Recently, with the increasing use of lithium secondary batteries, active development of NCM-based cathode active materials with increased nickel content is being actively pursued to increase the energy density of the batteries, especially the capacity. However, NCM-based cathode active materials with increased nickel content suffer from the problem of reduced thermal stability due to structural instability caused by the high nickel content. On the other hand, LFP-based cathode active materials, which are olivine-structured cathode active materials, have the advantage of excellent thermal stability and price competitiveness, although they have lower capacity than NCM-based cathode active materials. However, batteries using 100% LFP-based cathode active materials have a lower operating voltage than batteries using NCM-based cathode active materials, resulting in lower battery energy density. Therefore, attempts have been made to utilize a mixture of NCM-based and LFP-based cathode active materials to realize the advantages of each material. However, LFP-based cathode active materials have problems with low electrical conductivity and slow lithium ion diffusion rate, and when mixed with NCM cathode active materials, there was a problem of acting as resistance.

[0009] Accordingly, there is a need to develop a cathode material that can prevent the resistance of the electrode from increasing even when using a mixture of NCM cathode active material and LFP-based cathode active material.

[0010]

[0011] The problem to be solved in the present invention is to provide a cathode material that can not only improve the energy density of the cathode material but also prevent the resistance of an electrode including the cathode material from increasing.

[0012] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery including the positive electrode material.

[0013]

[0014] To solve the above problem, the present invention provides a cathode material, a cathode, and a lithium secondary battery.

[0015]

[0016] (1) The present invention comprises a first positive electrode active material having an olivine structure; and an average particle diameter (D) greater than that of the first positive electrode active material. 50 ) includes a second cathode active material which is a lithium nickel oxide having a large layered structure; and the first cathode active material has an average particle diameter (D 50 ) is 0.5㎛ to 10㎛, contains 2 wt% to 3.5 wt% of carbon (C), and has an average crystal size of 100 nm or more and less than 160 nm.

[0017] (2) The present invention provides a cathode material according to (1), wherein the first cathode active material includes a lithium iron phosphate compound and a coating layer including carbon (C) formed on the lithium iron phosphate compound.

[0018] (3) The present invention provides a cathode material in the above (2), wherein the lithium iron phosphate compound has a composition represented by the following chemical formula 1.

[0019] [Chemical Formula 1]

[0020] Li 1+x Fe 1-a M a PO4

[0021] In the above chemical formula 1,

[0022] M is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y,

[0023] -0.2≤x≤0.2, 0≤a≤0.9.

[0024] (4) The present invention provides a cathode material in which the particle form of the first cathode active material is a secondary particle form, a single particle form, or a combination thereof, in any one of the above (1) to (3).

[0025] (5) The present invention provides a cathode material in any one of the above (1) to (4), wherein the second cathode active material contains nickel in an amount of 60 mol% or more relative to the total molar number of metals excluding lithium.

[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+y Ni b Co c M1 d M2 e O2

[0029] In the above chemical formula 2,

[0030] M1 is Mn, Al or a combination thereof,

[0031] M2 is one or more selected from W, Mo, Cr, Zr, Ti, Mg, Ta, B and Nb,

[0032] -0.05≤y≤0.3, 0.6≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e≤0.1, b+c+d+e=1이다.

[0033] (7) The present invention provides a cathode material in any one of the above (1) to (6), wherein the second cathode active material is in the form of secondary particles.

[0034] (8) In any one of (1) to (7), the second positive electrode active material has an average particle diameter (D 50 ) provides a cathode material having a diameter of 3㎛ to 15㎛.

[0035] (9) The present invention provides a cathode material in which the first cathode active material is included in an amount of 35 wt% or more and less than 90 wt% based on the total weight of the first cathode active material and the second cathode active material in any one of the above (1) to (8).

[0036] (10) The present invention provides a cathode comprising a cathode material according to any one of (1) to (9).

[0037] (11) The present invention provides a lithium secondary battery including a positive electrode according to (10).

[0038]

[0039] The cathode material of the present invention has an average particle diameter (D 50 ) is 0.5㎛ to 10㎛, contains 2 wt% to 3.5 wt% of carbon (C), and has an olivine structure of small particles having an average crystal size of 100 nm to less than 160 nm; and contains a second cathode active material of a lithium nickel-based oxide, so that not only the energy density is excellent, but also the performance of the electrode and battery including the same, such as resistance performance and life performance, can be improved.

[0040]

[0041] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0042] 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.

[0043] In this specification, the term "single-particle positive electrode active material" refers to a positive electrode active material composed of 10 or fewer primary particles, in contrast to a spherical secondary particle positive electrode active material formed by the aggregation of tens to hundreds of primary particles. Specifically, in this specification, the single-particle positive electrode active material may be a single particle composed of one primary particle, or may be a secondary particle in which several primary particles are agglomerated. In this case, "primary particle" refers to the smallest particle unit recognized when the positive electrode active material is observed through a scanning electron microscope, and "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles.

[0044] 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., Mastersizer3000 from Malvern) and the particle size distribution is calculated by measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, and the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device is calculated, thereby D 50 can be measured.

[0045] In this specification, the 'average crystal size' can be quantitatively obtained using X-ray diffraction analysis (XRD) using Cu Kα X-rays. Specifically, the average crystal size can be obtained by obtaining XRD data of the positive active material using Bruker's D8 XRD equipment (Cu-target, voltage: 45 kV, current: 40 mA, 2θ: 10°~100°), and then using Malvern panalytical's Highscore software through the Rietveld refinement method. At this time, the Rietveld refinement method is a method of obtaining a diffraction pattern calculated from an initial structural model that the crystal structure of the materials can have, comparing it with the measured diffraction pattern of an actual synthetic material, and gradually and repeatedly adjusting by introducing various structural factors and changing the values ​​until the two patterns match. Among the structural factors that can be introduced in this process, the crystal size can be obtained using the peak full width at half maximum (FWHM) of each crystal plane appearing in the measured diffraction pattern.

[0046]

[0047] cathode material

[0048] The cathode material according to the present invention comprises a first cathode active material having an olivine structure; and an average particle diameter (D) greater than that of the first cathode active material. 50 ) includes a second cathode active material which is a lithium nickel-based oxide having a large layered structure. At this time, the first cathode average particle diameter (D 50 ) is 0.5㎛ to 10㎛, contains 2% to 3.5% by weight of carbon (C), and has an average crystal size of 100 nm or more and less than 160 nm.

[0049] The present inventors have determined that the cathode material has an average particle diameter (D 50) is 0.5㎛ to 10㎛, contains 2 wt% to 3.5 wt% of carbon (C), and has an olivine structure of small particles having an average crystal size of 100 nm to less than 160 nm; and a second cathode active material of a lithium nickel-based oxide; when the cathode material is applied to a cathode for a secondary battery and a secondary battery, it has been found that the resistance of the cathode and the battery can be lowered and the life performance can be improved, thereby completing the present invention.

[0050] In particular, the first positive electrode active material has an average particle diameter (D 50 ) is 0.5㎛ to 10㎛, contains 2 wt% to 3.5 wt% of carbon (C), and has an average crystal size of 100 nm to less than 160 nm, it was confirmed that an appropriate movement path of lithium ions within the crystal is provided, so that the resistance of the cathode and battery using the cathode material according to the present invention is reduced and the life performance is improved.

[0051] Meanwhile, as mentioned in the background technology of the above invention, as the scope of use of lithium secondary batteries has recently increased, there is a great demand for increased capacity and energy density. However, if only the first cathode active material is used as a cathode material, there is a problem of low energy density, and if only the second cathode active material is used as a cathode material, there is a problem of reduced thermal stability.

[0052]

[0053] The above cathode material is a first cathode active material having an olivine structure; and an average particle diameter (D) greater than that of the first cathode active material 50 ) including a second cathode active material which is a lithium nickel-based oxide having a large layered structure; and since the first cathode active material is filled between the second cathode active materials, the electrode density is high and the stress applied to the second cathode active material is distributed, so that particle breakage can be prevented during rolling for electrode manufacturing.

[0054]

[0055] The above first cathode active material can be manufactured through a process of drying a mixture of a lithium raw material (e.g., Li2CO3, LiOH, etc.), a transition metal raw material (e.g., FePO4), a carbon raw material (e.g., sucrose), etc., through a wet mixing process, and then firing the dried powder. However, the present invention is not limited thereto.

[0056] The above 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.

[0057]

[0058] According to the present invention, the first positive electrode active material has an average particle diameter (D 50 ) is 0.5㎛ to 10㎛. Specifically, when the first positive electrode active material is in the form of secondary particles formed by agglomeration of primary particles, the average particle diameter (D 50 ) may be 0.5 ㎛ or more, 1.0 ㎛ or more, 1.5 ㎛ or more, 2.0 ㎛ or more, 2.5 ㎛ or more, 3.0 ㎛ or more, 3.5 ㎛ or more, 4.0 ㎛ or more, 4.5 ㎛ or more, or 5.0 ㎛ or more, and may be 6.5 ㎛ or less, 7.0 ㎛ or less, 7.5 ㎛ or less, 8.0 ㎛ or less, 8.5 ㎛ or less, 9.0 ㎛ or less, 9.5 ㎛ or less, or 10 ㎛ or less. In addition, when the first positive electrode active material is in the form of a single particle, the average particle diameter (D 50) may be 0.5 ㎛ or more, 0.6 ㎛ or more, 0.7 ㎛ or more, 0.8 ㎛ or more, 0.9 ㎛ or more, 1.0 ㎛ or more, 1.1 ㎛ or more, 1.2 ㎛ or more, 1.3 ㎛ or more, 1.4 ㎛ or more, or 1.5 ㎛ or more, and may be 2.0 ㎛ or less, 2.5 ㎛ or less, 3.0 ㎛ or less, 3.5 ㎛ or less, 4.0 ㎛ or less, 4.5 ㎛ or less, 5.0 ㎛ or less, 5.5 ㎛ or less, 6.0 ㎛ or less, 6.5 ㎛ or less, 7.0 ㎛ or less, 7.5 ㎛ or less, 8.0 ㎛ or less, 8.5 ㎛ or less, 9.0 ㎛ or less, 9.5 ㎛ or less, or 10 ㎛ or less. The average particle diameter (D of the first positive electrode active material 50 ) is within the above range, the electrode density can be improved. Meanwhile, the average particle diameter (D of the first positive electrode active material 50 ) is less than 0.5㎛, the particles are too small to handle the powder, and there is a problem of poor electrode processability, and if it exceeds 10㎛, there is a problem of no improvement in electrode density.

[0059] According to the present invention, the first positive electrode active material contains 2 wt% to 3.5 wt% of carbon (C). Specifically, the first positive electrode active material may contain 2 wt% or more, 2.1 wt% or more, or 2.2 wt% or more, and 3.2 wt% or less, 3.3 wt% or less, 3.4 wt% or less, or 3.5 wt% or less of carbon (C). When the first positive electrode active material contains carbon (C) in the above-described content range, the positive electrode active material can have appropriate electron conductivity due to the carbon layer present on the surface. On the other hand, when the content of carbon (C) contained in the first positive electrode active material is less than 2 wt%, there is a problem that the positive electrode active material does not have appropriate electron conductivity, and when it exceeds 3.5 wt%, there is a problem that the reactivity of the positive electrode active material is lowered due to the excessive carbon.

[0060] According to the present invention, the first positive electrode active material has an average crystal size of 100 nm or more and less than 160 nm. Specifically, the average crystal size of the first positive electrode active material may be 100 nm or more, 101 nm or more, 102 nm or more, 103 nm or more, 104 nm or more, 105 nm or more, 106 nm or more, 107 nm or more, 108 nm or more, 109 nm or more, 110 nm or more, 111 nm or more, 112 nm or more, 113 nm or more, 114 nm or more, or 115 nm or more, and may be 151 nm or less, 152 nm or less, 153 nm or less, 154 nm or less, 155 nm or less, 156 nm or less, 157 nm or less, 158 nm or less, 159 nm or less, or less than 160 nm. When the average crystal size of the first positive electrode active material is within the above range, there is an advantage in that the resistance of the electrode is reduced.

[0061] Meanwhile, if the average crystal size of the first cathode active material is less than 100 nm, there is a problem that the crystal size is too small and the performance of the battery decreases due to deterioration, and if it is more than 160 nm, there is a problem that the movement path of lithium ions within the crystal becomes long and the performance of the battery decreases.

[0062]

[0063] According to the present invention, the first positive electrode active material may include a lithium iron phosphate-based compound and a coating layer including carbon (C) formed on the lithium iron phosphate-based compound in order to improve electron conductivity. That is, the first positive electrode active material may be a lithium iron phosphate-based compound having a coating layer including carbon formed thereon. Specifically, it may be a lithium iron phosphate-based compound having a carbon coating layer formed on the surface of particles (particles recognized through an SEM image).

[0064] According to the present invention, the lithium iron phosphate compound may have a composition represented by chemical formula 1.

[0065] [Chemical Formula 1]

[0066] Li 1+x Fe 1-a M a PO4

[0067] In the above chemical formula 1,

[0068] M is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y,

[0069] -0.2≤x≤0.2, 0≤a≤0.9.

[0070] The above M is a doping element, and specifically, the above M may be at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y. The above M is not necessarily included, but when included in an appropriate amount, the stability of the crystal structure may be improved, and it may help improve the performance of the cathode material.

[0071] Meanwhile, the above x may be -0.2 or more, -0.1 or more, or 0 or more, and may be 0.1 or less, or 0.2 or less. When x satisfies the above range, structural stability may be improved.

[0072] The above a may be 0 or more, 0.1 or more, or 0.2 or more, and may be 0.3 or less, 0.4 or less, 0.5 or less, 0.6 or less, 0.7 or less, 0.8 or less, or 0.9 or less. When a satisfies the above range, high energy density is exhibited, and high capacity characteristics can be implemented.

[0073]

[0074] According to the present invention, the particle form of the first positive electrode active material is a secondary particle form, a single particle form, or a combination thereof. That is, the first positive electrode active material may exist only in the form of secondary particles formed by agglomeration of tens to hundreds of primary particles, or in the form of single particles composed of 10 or fewer primary particles, or may exist in a mixed state of the secondary particle form and the single particle form. Meanwhile, when the first positive electrode active material exists only in the form of secondary particles, the interface is less exposed, so the resistance characteristics can be further improved.

[0075]

[0076] According to the present invention, the second positive electrode active material, which is a lithium nickel-based oxide having a layered structure, may contain nickel in an amount of 60 mol% or more relative to the total molar number of metals excluding lithium in terms of improving the capacity of the battery.

[0077] Specifically, the first positive electrode active material may have a composition represented by chemical formula 2.

[0078] [Chemical Formula 2]

[0079] Li 1+y Ni b Co c M1 d M2 e O2

[0080] In the above chemical formula 2,

[0081] M1 is Mn, Al or a combination thereof,

[0082] M2 is one or more selected from W, Mo, Cr, Zr, Ti, Mg, Ta, B and Nb,

[0083] -0.05≤y≤0.3, 0.6≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e≤0.1, b+c+d+e=1이다.

[0084] y can be specifically greater than or equal to -0.05, greater than or equal to -0.04, greater than or equal to -0.03, greater than or equal to -0.02, greater than or equal to -0.01, or greater than or equal to 0, and less than or equal to 0.01, less than or equal to 0.02, less than or equal to 0.03, less than or equal to 0.04, less than or equal to 0.05, less than or equal to 0.06, less than or equal to 0.07, less than or equal to 0.08, less than or equal to 0.09, less than or equal to 0.10, less than or equal to 0.20, or less than or equal to 0.30.

[0085] a refers to the atomic fraction of nickel among the metal elements excluding lithium in the second positive electrode active material, and specifically, it may be 0.6 or more, 0.7 or more, 0.8 or more, or 0.85 or more, and may be 0.90 or less, 0.95 or less, or less than 1.0.

[0086] b refers to the atomic fraction of cobalt among metal elements other than lithium in the second positive electrode active material, and specifically, it may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be 0.10 or less, 0.20 or less, 0.30 or less, or less than 0.4.

[0087] c refers to the atomic fraction of the M1 element among the metal elements excluding lithium in the second positive electrode active material, and specifically, it may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be 0.10 or less, 0.20 or less, 0.30 or less, or less than 0.4.

[0088] d refers to the atomic fraction of the M2 element among the metal elements excluding lithium in the second positive electrode active material, and specifically, it may be 0 or more, or 0.01 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less.

[0089]

[0090] According to the present invention, the second positive electrode active material may be in the form of secondary particles. That is, it may be in the form of secondary particles formed by agglomeration of tens to hundreds of primary particles.

[0091] According to the present invention, the second positive electrode active material has an average particle diameter (D 50 ) may be 3㎛ to 15㎛. Specifically, the average particle diameter (D) of the second positive electrode active material 50 ) may be 3.0 ㎛ or more, 4.0 ㎛ or more, 5.0 ㎛ or more, 6.0 ㎛ or more, 7.0 ㎛ or more, 8.0 ㎛ or more, or 9.0 ㎛ or more, and may be 10.0 ㎛ or less, 11.0 ㎛ or less, 12.0 ㎛ or less, 13.0 ㎛ or less, 14.0 ㎛ or less, or 15.0 ㎛ or less. The average particle diameter (D of the second positive electrode active material 50 ) is within the above range, the electrode density improvement effect can be maximized when mixed with the first positive electrode active material.

[0092] In addition, 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.

[0093]

[0094] According to the present invention, the first positive electrode active material may be included in an amount of 35 wt% or more and less than 90 wt% based on the total weight of the first positive electrode active material and the second positive electrode active material. Specifically, the first positive electrode active material may be included in an amount of 35 wt% or more, or 40 wt% or more, and 55 wt% or less, 60 wt% or less, 65 wt% or less, 70 wt% or less, 75 wt% or less, 80 wt% or less, 85 wt% or less, or less than 90 wt% based on the total weight of the first positive electrode active material and the second positive electrode active material. When the first positive electrode active material is included in the above-described content range, there is an advantage in that the characteristics resulting from the structural stability of the first positive electrode active material can be utilized.

[0095]

[0096] anode

[0097] The present invention provides a cathode comprising the above cathode material.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105]

[0106] lithium secondary battery

[0107] The present invention provides a lithium secondary battery including the positive electrode.

[0108]

[0109] 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.

[0110] 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.

[0111] 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.

[0112] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122]

[0123] A lithium secondary battery including a cathode material according to the present invention stably exhibits excellent resistance 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).

[0124] 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.

[0125] 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.

[0126] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0127] 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.

[0128]

[0129] 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.

[0130]

[0131] Manufacturing example

[0132] Manufacturing Example 1

[0133] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 12 wt% based on the total weight of the solid content present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry. At this time, the average particle diameter (D) of the entire raw materials (Li2CO3, FePO4, sucrose) present in the slurry 50 ) was 200 nm.

[0134] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 750°C for 6.5 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 5.7㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0135]

[0136] Manufacturing Example 2

[0137] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 12 wt% based on the total weight of the solid content present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry. At this time, the average particle diameter (D) of the entire raw materials (Li2CO3, FePO4, sucrose) present in the slurry 50 ) was 200 nm.

[0138] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 5.5㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0139]

[0140] Manufacturing Example 3

[0141] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 10 wt% based on the total weight of the solid content present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry. At this time, the average particle diameter (D) of the entire raw materials (Li2CO3, FePO4, sucrose) present in the slurry 50 ) was 200 nm.

[0142] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 6.3㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0143]

[0144] Manufacturing Example 4

[0145] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 8 wt% based on the total weight of the solid content present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry. At this time, the average particle diameter (D) of all raw materials (Li2CO3, FePO4, sucrose) present in the slurry 50 ) was 200 nm.

[0146] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 6.1㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0147]

[0148] Manufacturing Example 5

[0149] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 15 wt% based on the total weight of solids present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry.

[0150] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 5.5㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0151]

[0152] Manufacturing Example 6

[0153] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 16.5 wt% based on the total weight of solids present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry.

[0154] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 5.7㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0155]

[0156] Manufacturing Example 7

[0157] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 12 wt% based on the total weight of solids present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry.

[0158] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 700°C for 6.5 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 5.5㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0159]

[0160] Manufacturing Example 8

[0161] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 9 wt% based on the total weight of solids present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry.

[0162] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 750°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50 ): 6.2㎛) was manufactured. At this time, the positive electrode active material is in the form of secondary particles.

[0163]

[0164] Manufacturing Example 9

[0165] The positive electrode active material in the form of secondary particles manufactured in Manufacturing Example 1 (average particle diameter (D 50 ): 6.1㎛) through a jet mill to obtain an average particle diameter (D 50 ) was crushed to 1.9㎛ to form a coating layer containing carbon, LiFePO4 positive electrode active material (average particle diameter (D 50 ): 1.9㎛) was manufactured. At this time, the final manufactured positive electrode active material is in the form of a single particle.

[0166]

[0167] Manufacturing Example 10

[0168] The positive electrode active material in the form of secondary particles manufactured in Manufacturing Example 4 (average particle diameter (D 50 ): 5.5㎛) through a jet mill to obtain an average particle diameter (D 50 ) is crushed to 1.0㎛, and a LiFePO4 positive electrode active material (average particle diameter (D)) is formed with a coating layer containing carbon. 50 ): 1.0㎛) was manufactured. At this time, the final manufactured positive electrode active material is in the form of a single particle.

[0169]

[0170] Manufacturing Example 11

[0171] Li2CO3 and FePO4 were mixed with water in an amount such that the molar ratio of lithium:iron (Li:Fe) was 1.05:1 (mixed so that the total content of Li2CO3 and FePO4 was 40 wt% of the solution), and then sucrose was additionally added in an amount of 8 wt% based on the total weight of solids present in the mixed solution to prepare a mixed solution, and the mixed solution was wet-ground with a bead mill to obtain a slurry.

[0172] After the above slurry was dried through spray drying (inlet temperature: 230°C, outlet temperature: 95°C), the dried powder was heat-treated at 750°C for 10 hours under a nitrogen atmosphere to form a LiFePO4 positive electrode active material (average particle diameter (D 50): 6.2㎛) was manufactured. The LiFePO4 positive electrode active material (average particle diameter (D) on which the coating layer including the carbon was formed 50 ): 6.2㎛) (secondary particle form) through a jet mill to obtain an average particle diameter (D 50 ) was crushed to 1.2㎛, and the LiFePO4 positive electrode active material (average particle diameter (D 50 ): 1.2㎛) was manufactured. At this time, the final manufactured positive electrode active material is in the form of a single particle.

[0173]

[0174] Manufacturing Example 12

[0175] The positive electrode active material in the form of secondary particles manufactured in Manufacturing Example 7 (average particle diameter (D 50 ): 5.5㎛) with an average particle diameter (D 50 ) is crushed to 1.1㎛, and a LiFePO4 positive electrode active material (average particle diameter (D)) is formed with a coating layer containing carbon. 50 ): 1.1㎛) was manufactured. At this time, the final manufactured positive electrode active material is in the form of a single particle.

[0176]

[0177] Examples and Comparative Examples

[0178] Example 1

[0179] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 1 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0180]

[0181] Example 2

[0182] LiFePO4 positive electrode active material with a coating layer including carbon manufactured in Manufacturing Example 2 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0183]

[0184] Example 3

[0185] LiFePO4 positive electrode active material with a coating layer including carbon manufactured in Manufacturing Example 3 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0186]

[0187] Example 4

[0188] LiFePO4 positive electrode active material and secondary particle LiNi having a coating layer including carbon manufactured in Manufacturing Example 5 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0189]

[0190] Example 5

[0191] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 9 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0192]

[0193] Example 6

[0194] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 9 and LiNi in the form of secondary particles0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 5:5 to manufacture a cathode material.

[0195]

[0196] Example 7

[0197] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 9 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 6:4 to manufacture a cathode material.

[0198]

[0199] Example 8

[0200] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 9 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 7:3 to manufacture a cathode material.

[0201]

[0202] Example 9

[0203] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 9 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 8:2 to manufacture a cathode material.

[0204]

[0205] Example 10

[0206] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 1 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 9:1 to manufacture a cathode material.

[0207]

[0208] Comparative Example 1

[0209] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 4 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0210]

[0211] Comparative Example 2

[0212] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 6 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0213]

[0214] Comparative Example 3

[0215] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 7 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0216]

[0217] Comparative Example 4

[0218] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 8 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0219]

[0220] Comparative Example 5

[0221] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 10 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0222]

[0223] Comparative Example 6

[0224] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 11 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50 ): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0225]

[0226] Comparative Example 7

[0227] LiFePO4 positive electrode active material having a coating layer including carbon manufactured in Manufacturing Example 12 and LiNi in the form of secondary particles 0.86 Co 0.05 Mn 0.07 Al 0.02 O2 positive electrode active material (average particle diameter (D 50): 10㎛) was mixed in a weight ratio of 4:6 to manufacture a cathode material.

[0228]

[0229] Experimental example

[0230] Experimental Example 1: Confirmation of the carbon (C) content in the first cathode active material.

[0231] The carbon content present in each of the LiFePO4 positive electrode active materials having a carbon-containing coating layer formed thereon used in Examples 1 to 10 and Comparative Examples 1 to 7 was measured using a carbon-sulfur analyzer (LECO, CS844), and the results are shown in Table 1 below.

[0232]

[0233] Experimental Example 2: Confirmation of the average crystal size of the first cathode active material.

[0234] XRD diffraction data of each LiFePO4 positive electrode active material having a carbon-containing coating layer formed thereon used in Examples 1 to 10 and Comparative Examples 1 to 7 were obtained using XRD (Bruker, D8 ENDEAVOR), and the average crystal size was derived using the Rietveld refinement method, which is shown in Table 1 below.

[0235]

[0236] Classification Carbon content (wt%) Average crystal size (nm) of the first positive electrode active material Content of the first positive electrode active material relative to the total weight of the positive electrode active material (wt%) Example 12.6 15 0.940 Example 22.6 13 5.940 Example 32.2 11 5.140 Example 43.2 10 2.040 Example 52.6 15 0.940 Example 62.6 15 0.950 Example 72.6 15 0.960 Example 82.6 15 0.970 Example 92.6 15 0.980 Example 102.6 15 0.990 Comparative example 11.4 17 0.740 Comparative example 23.9 0.640 Comparative example 32.6 9 8.140 Comparative example 42.0164.240Comparative example 51.4170.740Comparative example 61.4174.140Comparative example 72.698.140

[0237] Referring to Table 1 above, it can be confirmed that the cathode materials of Examples 1 to 10 simultaneously include a first cathode active material of small particles having an olivine structure containing 2 to 3.5 wt% of carbon (C) and a second cathode active material of large particles that is a lithium nickel-based oxide, and that the average crystal size of the first cathode active material satisfies 100 nm or more and less than 160 nm, whereas the cathode materials of Comparative Examples 1 to 7 do not satisfy this.

[0238]

[0239] Experimental Example 3: Battery Resistance Evaluation

[0240] Examples 1 to 5 and Comparative Examples 1 to 7 each contained a cathode material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder, in a weight ratio of 96:2:2 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 prepare a cathode.

[0241] 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 a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0242] Using the coin-type half-cell manufactured as described above, the initial charge-discharge process was performed by charging to 4.25 V using the CC (0.1 C)-CV (Cut-off current: 0.05 C) method at 25°C, followed by a 20-minute rest period, and then discharging to 2.5 V using the CC (0.1 C) method. At this time, the resistance was measured through the voltage change for 60 seconds during the discharge, and the measured resistance is shown in Table 2 below.

[0243] Resistance (Ω) Example 131.9 Example 232.5 Example 333.2 Example 433.8 Example 538.9 Comparative Example 138 Comparative Example 236.9 Comparative Example 335.2 Comparative Example 447.9 Comparative Example 553.1 Comparative Example 640.1 Comparative Example 748.2

[0244]

[0245] Experimental Example 4: Battery Performance Evaluation

[0246] Examples 1 to 10 and Comparative Examples 1 to 7 each contained a cathode material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 97.5:1:1.5 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 prepare a cathode.

[0247] Graphite as a negative active material, carbon black as a conductive agent, and PVDF as a binder were mixed in a weight ratio of 96:0.5:3.5 in distilled water to prepare a negative electrode slurry (solid content: 50 wt%). The prepared negative electrode slurry was applied to a copper thin film as a negative electrode current collector, and then dried and rolled to prepare a negative electrode.

[0248] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3 was injected, and sealed to manufacture a pouch-type lithium secondary battery (battery capacity: 40 mAh).

[0249] Using the pouch-type lithium secondary batteries containing the positive electrode materials of Examples 1 to 10 and Comparative Examples 1 to 7, respectively, the batteries were charged to 4.25 V in the CC (0.1 C)-CV (Cut-off current: 0.05 C) mode at 25°C, and then discharged to 3.0 V at 0.1 C to perform an activation process (formation). Subsequently, the batteries were charged to 4.25 V in the CC (0.33 C)-CV (Cut-off current: 0.05 C) mode at 45°C, and then discharged to 3.0 V at 0.33 C, which is considered one cycle, for 100 cycles, and the discharge capacity and resistance were measured.

[0250] And, the percentage of the discharge capacity of the 100th cycle to the discharge capacity of the first cycle is the capacity retention rate (%), and the percentage of the resistance measured in the 100th cycle to the resistance measured in the first cycle is the resistance increase rate (%), which are shown in Table 3 below.

[0251] Capacity retention rate (%) Resistance increase rate (%) Example 194.56 18.94 Example 294.48 20.58 Example 394.41 21.01 Example 494.52 21.32 Example 594.45 22.11 Example 695.22 24.57 Example 795.39 24.61 Example 895.81 24.96 Example 995.89 25.27 Example 1096.28 24.31 Comparative example 193.85 31.82 Comparative example 294.02 30.46 Comparative example 394.24 27.52 Comparative example 494.15 36.79 Comparative example 594.89 35.63 Comparative example 694.4238.48Comparative example 793.8232.87

[0252] And, except that the weight ratio of cathode material:conductive material:binder was changed from 97.5:1:1.5 to 97.72:0.8:1.48 for some of the examples and comparative examples, the capacity retention rate and resistance increase rate were evaluated in the same manner as described above, and are shown in Table 4 below.

[0253] Capacity retention rate (%) Resistance increase rate (%) Example 194.66 20.07 Example 294.44 21.55 Example 594.29 23.98 Example 995.53 27.11 Comparative example 693.78 85.70

[0254] Referring to Tables 2 and 3 above, it can be confirmed that in the case of a battery including a positive electrode material according to the present invention, not only is the resistance low at 38.9Ω or less, but the capacity retention rate is high at 94.41% or more, and the resistance increase rate is low at 25.27% or less. In contrast, in the case of the batteries including the positive electrode materials of Comparative Examples 1 to 9, there were problems such as high resistance, low capacity retention rate, or high resistance increase rate.

[0255] That is, in the case of a battery including a cathode material according to the present invention, it can be confirmed that the resistance is low and the life performance is excellent, whereas in the case of a battery including a cathode material of a comparative example, problems occurred in the resistance performance or life performance.

[0256]

[0257] And, referring to Tables 3 and 4 above, in the case of a battery including a cathode material according to the present invention, it can be confirmed that the performance of the battery does not deteriorate significantly even though the content of the conductive material is reduced. In contrast, in the case of a battery including a cathode material of the comparative example, it can be seen that when the content of the conductive material is reduced, the conductivity decreases, causing the resistance increase rate of the battery to significantly increase.

[0258]

[0259] In conclusion, the cathode material according to the present invention has an average particle diameter (D 50) is 0.5㎛ to 10㎛, contains 2 wt% to 3.5 wt% of carbon (C), and has an olivine structure of small particles having an average crystal size of 100 nm to less than 160 nm; and contains a second cathode active material of a lithium nickel-based oxide, so that not only the energy density is excellent, but also the performance of the electrode and battery including the same, such as resistance performance and life performance, can be improved.

Claims

1. A first cathode active material having an olivine structure; and an average particle diameter (D) greater than that of the first cathode active material. 50 ) includes a second cathode active material which is a lithium nickel oxide having a large layered structure; The above first cathode active material has an average particle diameter (D 50 ) is 0.5㎛ to 10㎛, contains 2 to 3.5 wt% of carbon (C), and has an average crystal size of 100 nm to less than 160 nm.

2. In claim 1, A cathode material, wherein the first cathode active material comprises a lithium iron phosphate-based compound and a coating layer including carbon (C) formed on the lithium iron phosphate-based compound.

3. In claim 2, The above lithium iron phosphate compound is a cathode material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Fe 1-a M a PO4 In the above chemical formula 1, M is at least one selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, -0.2≤x≤0.2, 0≤a≤0.

9.

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

5. In claim 1, A cathode material wherein the second cathode active material contains nickel in an amount of 60 mol% or more relative to the total mole number of metals excluding lithium.

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] The 1+y Nor b Co c M1 d M2 e O2 In the above chemical formula 2, M1 is Mn, Al or a combination of these, M2 is at least one selected from W, Mo, Cr, Zr, Ti, Mg, Ta, B and Nb, -0.05≤y≤0.3, 0.6≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e≤0.1, b+c+d+e=1이다.

7. In claim 1, A cathode material wherein the second cathode active material is in the form of secondary particles.

8. 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㎛ to 15㎛.

9. In claim 1, A cathode material in which the first cathode active material is included in an amount of 35 wt% or more and less than 90 wt% based on the total weight of the first cathode active material and the second cathode active material.

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

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